Patent Application
20250057704
The present disclosure relates to absorbent articles comprising an absorbent core structure having a shaped inner core layer. The present disclosure further relates to absorbent articles having flex bond channel regions yet are still flexible and conform closely to the body.
Absorbent articles are widely used among consumers, e.g., diapers, training pants, feminine pads, adult incontinence pads, etc. Generally, absorbent articles such as these comprise a topsheet and a backsheet, with an absorbent core structure disposed therebetween. These absorbent articles are designed to absorb and retain liquids and other discharges from the human body to prevent body and garment soiling. To absorb fluid effectively without leakage, absorbent articles for menstrual applications should conform closely to a women's genital anatomical shape such that the absorbent article can capture fluid as it exits the labial structure. A common complaint from users of current absorbent articles is the sensation of fluid moving along the body or escaping the article during heavier discharge events. In the case of panty-applied products, the panty and absorbent article often do not fit sufficiently close to the body to address these consumer concerns. Historically, absorbent articles have tried to address this problem by adding more bulk (i.e., absorbent material) to attempt to fill the space between the user's legs. Other approaches have added more absorbent material to the center of the absorbent article (commonly referred to as “more in the middle”) in order to increase the caliper in the central region. This is often accomplished by profiling the cellulose absorbent material in the longitudinal direction or by adding an additional, discrete ellipsoid-shaped absorbent layer.
However, these traditional approaches do not adequately solve the problem of reducing or eliminating the spread of fluid on the body because the additional absorbent material is invariably bulky, stiff, and not shaped to closely and comfortably conform to the wearer's intimate anatomy. In the case of female genitalia, fluid first exits the body internally within the labial vestibule, in particular within the labial minora, prior to exiting through the labial majora. Fluid can exit the labial structure at the top, the bottom, and/or at the sides. Since the labial vestibule is curved, there typically exists a gap between the labia majora such that fluid exiting the labial minora is not captured by simply adding more absorbent material in the central region. Traditional “more in the middle” shapes rest atop of the labial structure and thus forms a bridge across the gap between the labial majora without actually capturing the fluid that resides and is moving from within the labial vestibule outwards. Additionally, typical bulky central regions may actually push the non-raised portions of the absorbent article away from her body, thus causing more gapping on the sides for fluid to spread and be felt by the consumer.
In addition, channels created by embossing have historically been leveraged to create bending lines in thicker and/or stiffer products to provide specific in-use pad shapes and to help improve the fit to the body. In traditional cellulose based absorbent core structures, channels are formed by applying a high compressive force in order to densify the cellulose to a point where the cellulose is irreversibly compressed. While such channels may provide a preferential bending location within the absorbent article, the high compression force (i.e., densification) needed to create the channel (and keep the channel in place) creates stiffness that can hinder the ability of the absorbent article to conform to the wearer's body. As such, these products are not believed to conform or fit to the body of the wearer as closely as possible, particularly at the portions that are adjacent to the discharge portion of body fluids in use, and thus, leakage is possible.
There is a need for an absorbent article that more effectively captures fluid as it exits the labial minora, within the labia majora, across the diverse range of female genitalia shapes and sizes without being stiff and bulky. There is also need for an absorbent article that comprises channels yet can still be conformable to the body and flexible in both the longitudinal and lateral direction.
The present disclosure solves the problem of fluid spreading on the body by providing an absorbent core structure comprising an inner core layer that is shaped to closely fit within and between the upper spaces between the labial majora and to fit in the perinium and at the base of the pubis mons. As described herein, the absorbent article comprises an absorbent core structure comprising a profiled inner core layer which is highly compressible and moldable without being bulky, allowing the absorbent article to comfortably adapt and fit closely to a wide range of female anatomical shapes.
The present disclosure also solves the problem of absorbent articles having channels that are stiff and nonconformable by providing an absorbent core structure that can sandwich a liquid-absorbent material between two nonwoven layers that can plastically deform to form a flex bond channel region without high densification of the absorbent core structure and/or inner core layer.
As disclosed herein, a disposable absorbent article comprises a topsheet; a backsheet; an absorbent core structure disposed between the topsheet and the backsheet, and a flex bond channel region. The absorbent core structure comprises: (i) an upper nonwoven layer comprising polymer fibers and having a basis weight of from about 30 gsm to about 85 gsm; (ii) a lower nonwoven layer comprising polymer fibers; and (iii) an inner core layer disposed between the upper nonwoven layer and the lower nonwoven layer, wherein the inner core layer comprises cellulosic fibers and superabsorbent particles. The flex bond channel region has a dry channel depth of from about 1.0 mm to about 4.5 mm and a channel width of from about 1.0 mm to about 3.0 mm. The flex bond channel region has a Dry MD Bending Resistance of less than about 0.04 N/mm as measured according to Flex Bond Channel MD Bending Resistance Method. The inner core layer further comprises a central absorbent zone having a first basis weight and an outer absorbent zone having a second basis weight, wherein the outer absorbent zone substantially surrounds the central absorbent zone, and wherein the first basis weight is greater than the second basis weight.
As disclosed herein, a disposable absorbent article comprises a topsheet; a backsheet; an absorbent core structure disposed between the topsheet and the backsheet; wherein the topsheet forms a wearer facing surface of the absorbent article and the backsheet forms an outward facing surface of the absorbent article. The absorbent core structure comprises: (i) an upper nonwoven layer comprising polymer fibers having a basis weight of from about 35 gsm to about 85 gsm; (ii) a lower nonwoven layer comprising polymer fibers; and (iii) an inner core layer disposed between the upper nonwoven layer and the lower nonwoven layer, wherein the inner core layer comprises cellulosic fibers and superabsorbent particles. The wearer facing surface of the absorbent article comprises a flex bond channel region having a Dry MD Bending Resistance of less than about 0.04 N/mm as measured according to Flex Bond Channel MD Bending Resistance Method. The inner core layer further comprises a central absorbent zone and an outer absorbent zone substantially surrounding the central absorbent zone, wherein the central absorbent zone has a first basis weight and the outer absorbent zone has a second basis weight, wherein the first basis weight is about 20% to about 100% greater than the second basis weight. The flex bond channel region separates the central absorbent zone from the outer absorbent zone. The inner core layer is a unitary structure.
As used herein “disposable absorbent article” or “absorbent article” shall be used in reference to articles such as diapers, training pants, diaper pants, refastenable pants, adult incontinence pads, adult incontinence pants, feminine hygiene pads, cleaning pads, and the like, each of which are intended to be discarded after use.
As used herein “absorbent core structure” shall be used in reference to the upper nonwoven layer, the lower nonwoven layer, and the inner core layer disposed between the upper nonwoven layer and the lower nonwoven layer. As used herein, “absorbent core structure” does not include any secondary topsheet, topsheet, secondary backsheet, or backsheet of the absorbent article.
As used herein “hydrophilic” and “hydrophobic” have meanings as well established in the art with respect to the contact angle of water on the surface of a material. Thus, a material having a water contact angle of greater than about 90 degrees is considered hydrophobic, and a material having a water contact angle of less than about 90 degrees is considered hydrophilic. Compositions which are hydrophobic, will increase the contact angle of water on the surface of a material while compositions which are hydrophilic will decrease the contact angle of water on the surface of a material. Notwithstanding the foregoing, reference to relative hydrophobicity or hydrophilicity between a material and a composition, between two materials, and/or between two compositions, does not imply that the materials or compositions are hydrophobic or hydrophilic. For example, a composition may be more hydrophobic than a material. In such a case neither the composition nor the material may be hydrophobic; however, the contact angle exhibited by the composition is greater than that of the material. As another example, a composition may be more hydrophilic than a material. In such a case, neither the composition nor the material may be hydrophilic; however, the contact angle exhibited by the composition may be less than that exhibited by the material.
As used herein, “machine direction” refers to the direction in which a web flows through an absorbent article converting process. For the sake of brevity, “machine direction” may be referred to as “MD”.
As used herein, “cross machine direction” refers to the direction which is perpendicular to the MD. For the sake of brevity, “cross machine direction” may be referred to as “CD”.
Decitex” also known as Dtex is a measurement used in the textile industry used for measuring yarns or filaments. 1 Decitex=1 gram per 10,000 meters. In other words, if 10,000 linear meters of a yarn or filament weights 500 grams that yarn or filament would have a decitex of 500.
As used herein, “resilient” refers to a material that tends to retain its shape both in the dry and wet states and when subjected to a compression force tends to recover its original, pre-compression shape when such force is removed. In some aspects, the upper and/or lower nonwoven layers described herein may be resilient.
As used herein, “wearer-facing” (sometimes referred to herein as body-facing) and “outward-facing” (sometimes referred to herein as garment-facing) refer respectively to the relative location of an element or a surface of an element or group of elements. “Wearer-facing” implies the element or surface is nearer to the wearer during wear than some other element or surface. “Outward-facing” implies the element or surface is more remote from the wearer during wear than some other element or surface (i.e., element or surface is proximate to the wearer's garments that may be worn over the absorbent article).
“Inboard,” with respect to a first feature of an article and its position relative a second feature or location on the article, means that the first feature lies closer to a respective axis of the article than the second feature or location, along a horizontal x-y plane approximately occupied by the article when laid out flat, extended to the full longitudinal and lateral dimensions of its component web materials against any contraction induced by any included pre-strained elastomeric material, on a horizontal surface. Laterally inboard means the first feature is closer to the longitudinal axis, and longitudinally inboard means the first feature is closer to the lateral axis. Conversely, “outboard,” with respect to a first feature of an article and its position relative a second feature or location on the article, means that the first feature lies farther from the respective axis of the article than the second feature or location.
It should be understood that every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.
The present disclosure relates to disposable absorbent articles comprising a topsheet, a backsheet, and an absorbent core structure which comprises an upper nonwoven layer and a lower nonwoven layer, with an inner core layer comprising a liquid-absorbent material disposed between the upper and lower nonwoven layers. The liquid-absorbent material may comprise a matrix comprising cellulosic fibers and superabsorbent particles, sometimes referred to herein as “fluff/AGM”. The inner core layer may be contained within the nonwoven layers by substantially sealing at least the left side and the right side regions of the upper and lower nonwoven layers at a perimeter seal.
The absorbent core structure described herein is configured to compress and recover its original shape (dry or wet) across a range of bodily movements and compressions. The flexibility and/or resiliency of the absorbent core structure results in an absorbent article that can comfortably conform to the wearer's anatomical geometry while efficiently managing the fluid as it exits the body. This can, unexpectedly, be achieved without typical densification stiffening (for wet integrity) by leveraging resilient upper and lower nonwoven layers composed of resilient polymers located above and below the loosely packed liquid-absorbent material of the inner core layer. The absorbent core structure is surprisingly able to carry the structural load and recover shape without physically being stiff or losing the desired structural properties when the absorbent core structure becomes wet. Without being limited by theory, it is believed that wet integrity/shape stability in a cellulose rich absorbent core structure without substantial densification and stiffening may be achieved when select resilient upper and lower nonwovens are positioned above and below the liquid-absorbent material of the inner core layer and are joined to and around the liquid-absorbent material. The upper and lower nonwovens may have sufficient recovery force to carry the liquid-absorbent material back to the original state and/or a stable fiber orientation state following compression. Wrapping or encapsulating a cellulose rich fluff core with a simple cellulose tissue or less resilient nonwoven material may not exhibit sufficient recovery energy to recover shape in-use and particularly when wetted. Structural, wet resilient nonwovens detailed herein may exhibit recovery energies following compression that are sufficient to recover the cellulose rich fiber matrix and are chosen to deliver high compression recovery, with relatively low stiffness, in both dry and wet states. It is believed that suitable absorbent core structures have a low force to compress (less resistance) and the structure is able to recover its shape as the user, in a cyclic fashion, compresses and releases the compressive force with various body movements. To achieve this, the structure should sustain sufficient recovery energy following multiple cyclic compressions. Without sufficient recovery energy, the structure will remain in a compressed bunched state with insufficient force (stored energy) to recover.
The absorbent article described herein further comprises a profiled inner core layer comprising a central absorbent zone and an outer absorbent zone substantially surrounding the central absorbent zone. The central absorbent zone has a basis weight that is greater than the outer absorbent zone, creating a raised 3-dimensional (3D) structure in the middle region of the absorbent article. As described below, the shape of the inner core layer and/or the central absorbent zone is such that the central absorbent zone may fit and gently conform within and between the upper spaces between the labial majora. The central absorbent zone and the outer absorbent zone are highly compressible without being bulky and thus can fit closely to a wide range of intimate body shapes without discomfort.
The absorbent article further comprises one or more flex bond channel regions comprising closely spaced flex bond embossments. It was surprisingly found that an absorbent article comprising flex bond channel regions could be created while maintaining flexibility of the absorbent article in both the lateral and longitudinal direction, allowing the absorbent article to better conform to the body. Without being limited by theory, it is believed that the upper nonwoven can plastically deform and maintain the channel structure without the need to permanently compress (densify) the fluff/AGM of the inner core layer. As used herein, “flex bond channel region” refers to a generally elongated depression formed in at least a portion of an absorbent article, partially or entirely extending through the z-direction thickness of the absorbent article. Flex bond channel regions can reduce the thickness of the absorbent article in the z-direction and can act as preferential bending lines in the absorbent article, allowing the article to bend in particular directions so as to fit more closely to the wearer's body. Flex bond channel regions may also act as fluid wicking or fluid transport barriers that can reduce the potential for fluid to migrate to the absorbent article perimeter and cause a leak.
The absorbent article may be resilient and conformable and may deliver a superior in use experience without bunching and/or compressing. The absorbent article may be exposed to bodily forces and can recover to its original state.
An exemplary absorbent article 20 of the present disclosure is represented in
Referring to
The absorbent core structure 10 may comprise an upper nonwoven layer 210 and a lower nonwoven layer 220 (also referred to herein collectively as upper and lower nonwoven layers or upper and lower nonwovens) and an inner core layer 200 disposed between the upper nonwoven layer 210 and the lower nonwoven layer 220. The inner core layer 200 may comprise a liquid-absorbent material, such as, for example, cellulosic fibers and superabsorbent particles. In some configurations, the liquid-absorbent material may be uniformly distributed. In some configurations, the liquid-absorbent material may be present discontinuously within the absorbent core structure 10, for example, as individual pockets or stripes of liquid-absorbent material separated from each other by material-free areas. In some configurations, the absorbent core structure 10 may have a non-rectangular perimeter. In particular, the absorbent core may be shaped to define a tapering along its width towards the middle region of the absorbent core structure. The absorbent core structure may conform to a wearer's inner thigh geometry, such as, for example, an hourglass shape, an offset hourglass shape (one end is wider than an opposite end and a narrowed mid-section between the ends), a bicycle seat shape (one end and central portion are narrower than the second end), an oval, or a trapezoid shape.
The inner core layer 200 may comprise a central absorbent zone 306 that extends in the longitudinal direction of the absorbent article from the front region 21 to the rear region 23, and an outer absorbent zone 325 that substantially surrounds the central absorbent zone 306. The central absorbent zone may comprise a transition zone 330 that extends around the periphery of the central absorbent zone where the basis weight of the inner core layer gradually decreases. The inner core layer 200 may be profiled in the longitudinal and lateral direction such that the basis weight of the inner core layer is greater in the central absorbent zone 306 than in the outer absorbent zone 325.
In some configurations, the absorbent article 20 may comprise the following structure (from a wearer-facing surface to an outward-facing surface): a topsheet 110, an upper nonwoven layer 210, an inner core layer 200, a lower nonwoven layer 220, and a backsheet 130. In some aspects, the topsheet 110 may be in direct contact with the upper nonwoven layer 210, the upper nonwoven layer 210 may be in direct contact with the inner core layer 200, and/or the inner core layer 200 may be in direct contact with the lower nonwoven layer 220. By “direct contact”, it is meant that there is no further intermediate component layer between the respective layer in direct contact thereto. It is however not excluded that an adhesive material may be disposed between at least a portion of the layers described above.
Upper nonwoven layer 210 may comprise a left side region 210a and a right side region 210b, and lower nonwoven layer 220 may comprise a left side region 220a and a right side region 220b. The upper and lower nonwoven layers 210, 220 may extend outwardly from an inner core layer perimeter 200a and may be joined together with glue or other conventional bonding methods including, but not limited to, ultrasonic bonding, fusion bonding, crimping, and combinations thereof, to form a perimeter seal 230. In some configurations, the entire inner core layer 200 may be located inboard of the perimeter seal 230. The perimeter seal 230 may help to seal the liquid-absorbent material of the inner core layer 200 inside the upper and lower nonwoven layers 210, 220. Perimeter seal 230 may comprise at least a first lateral seal region 231 and a second lateral seal region 231′. In some configurations, perimeter seal 230 may further comprise a front perimeter seal region 232 and/or a back perimeter seal region 233. In some configurations, the perimeter seal 230 may extend around the entire inner core layer perimeter 200a. In some configurations, the perimeter seal 230 may extend partially around the inner core layer perimeter 200a.
In some configurations, the inner core layer 200 may be contained within the upper nonwoven layer 210 and the lower nonwoven layer 220 by substantially sealing at least a left side region 210a, 220a and a right side region 210b, 220b of the upper nonwoven layer 210 and the lower nonwoven layer 220. In some configurations, the inner core layer 200 may be contained within the upper nonwoven layer 210 and the lower nonwoven layer 220 by sealing at least a portion of the left side region 210a, 220a and the right side region 210b, 220b of the upper nonwoven layer 210 and the lower nonwoven layer 220. Without being limited by theory, it is believed that resilient nonwoven layers comprising polymer fibers may hold their shape and resist plasticizing when wet when attached to the inner core layer through the application of a core construction adhesive that is applied either directly to the inner core layer or the resilient nonwoven layer(s) via a conventional spray coating application chosen to achieve a bond but not disrupt the flow of fluid to the inner core layer. The perimeter seal 230 may be positioned in at least the middle region 22 of the absorbent article 20 and/or the absorbent core structure 10. It is believed that the middle region 22 (located between the wearer's thighs during use) may be subjected to the most frequent and/or highest forces during use. It was found that the presence of at least a partial perimeter seal at a left side region and a right side region of the upper nonwoven layer and the lower nonwoven layer external to the inner core layer may help to ensure the upper and lower nonwovens maintain their structural function during physical deformations without separating, limiting any potential integrity and bunching issues. In addition, a perimeter seal may allow for any excess nonwoven material to be removed in order to enable an absorbent core structure to be shaped to conform to inner thigh geometry.
The perimeter seal 230 may have a seal width WS of between about 1 mm and about 10 mm, or between about 2 mm and about 8 mm, or between about 3 mm and 6 mm. The seal width WS may be uniform or may vary about the perimeter of the inner core layer. In some configurations, the absorbent article 20 may also comprise a front end seal 234 positioned in the front region 21 of the absorbent article and a back end seal 235 positioned in a rear region 23 of the absorbent article. The front end seal 234 and/or back end seal 235 may seal the topsheet, upper nonwoven layer, lower nonwoven layer, and the backsheet together. In some configuration, the front end seal 234 and/or the back end seal 235 may seal the topsheet and the backsheet. In some configurations, the front end seal 234 and/or the back end seal 235 may be a crimp seal.
In some configurations, the upper and lower nonwoven layers 210, 220 may be discrete materials that can be cut to approximately the size and shape of the inner core layer 200 so as to fit between the topsheet 110 and backsheet 130 but may not extend substantially into either the front end seal 234 or the back end seal 235. In some configurations, the inner core layer 200, upper nonwoven layer 210 and/or lower nonwoven layer 220 may be shaped, meaning it is non-rectangular. In some configurations, the upper and/or lower nonwoven layers 210, 220 may extend from the front edge of the absorbent article, through the front end seal 234 and the back end seal 235, to the back edge of the absorbent article.
As shown in
As previously mentioned, the absorbent article 20 may comprise an inner core layer 200 having a profiled distribution of liquid-absorbent material in the longitudinal and lateral direction.
It is to be appreciated that the increase in basis weight in the central absorbent zone 306 is due to additional liquid-absorbent material in the inner core layer 200 positioned in the central absorbent zone 306 relative to the outer absorbent zone 325. The inner core layer 200 described herein may be a unitary structure. As used herein, “unitary structure” means that the inner core layer 200 is continuous and is constructed from essentially one type of material, this being essentially the same material, or essentially the same combination of two or more materials throughout the inner core layer 200. Variations in density and concentration of the material may occur, but these are limited to those which may be obtained without incorporation of regions which have been formed separately and then physically joined together. For example, when the inner core layer 200 comprises a liquid absorbent material, e.g., cellulosic fibers and superabsorbent polymers, the relative concentrations of superabsorbent particles and cellulosic fibers may be different in different parts of the inner core layer 200. However, when the construction is unitary, the inner core layer 200 does not, for instance, include layers or laminates of a different composition. Likewise, variations in the density or concentration of various components across the longitudinal direction, the lateral direction, or the thickness direction of the inner core layer 200 may occur, yet the inner core layer 200 should not include areas or layers of different composition which are formed separately and later joined together or areas of the same or different material that are physically separated by areas of substantially no basis weight of liquid absorbent material.
The absorbent article 20 may have varying caliper in the longitudinal and lateral directions (e.g., profiled so as to have a higher caliper in the center). In some configurations, the absorbent article 20 may have a first caliper measured in the central absorbent zone 306, and a second caliper measured in the outer absorbent zone 325. In some configurations, the first caliper may be from about 2.5 mm to about 6 mm, and the second caliper may be from about 1.0 mm to about 3.0 mm, as measured according to the Absorbent Article Caliper, Basis Weight and Density Method. In some configurations, the ratio of the first caliper to the second caliper may be from about 1.2 to about 2.5.
As described in more detail below, the inner core layer may have a non-rectangular perimeter. In particular, the inner core layer 200 be shaped such that the liquid-absorbent material in the central absorbent zone may define a tapering along its width towards the middle region such that it creates a 3D shape that is better able to fit within and between the upper spaces between the labial majora and to fit in the perinium and at the base of the pubis mons.
As shown in
As shown in
In some configurations, the central absorbent zone 306 may define a perimeter comprising a pair of inwardly concave longitudinal side edges 308a, 308b, an outwardly convex front edge 310, and an outwardly convex rear edge 312. The central absorbent zone 306 may comprise a front region 314 having a first lateral width W1, a rear region 318 having a third lateral width W3, and a middle region 316 positioned therebetween having a second lateral width W2. In some configurations, the second lateral width W2 may be less than the first lateral width W1 and/or the third lateral width W3. In some configurations, the third lateral width W3 may be greater than the first lateral width W1 and the second lateral width W2. The first lateral width W1 may be from about 20 mm to about 35 mm, or from about 22 mm to about 30 mm, as measured from the outer most point of the first inwardly concave longitudinal side edge to the outer most point of the second inwardly concave longitudinal side edge in front region 314. The second lateral width W2 is from about 10 mm to about 20 mm, or from about 12 mm to about 15 mm, as measured from the inner most point of the first inwardly concave longitudinal side edge to the inner most point of the second inwardly concave longitudinal side edge in middle region 316. The third lateral width W3 may be from about 30 mm to about 45 mm, or from about 32 mm to about 40 mm, as measured from the outer most point of the first inwardly concave longitudinal side edge to the outer most point of the second inwardly concave longitudinal side edge in rear region 318. In some configurations, the second lateral width W2 is from about 20% to about 40% of a minimum lateral width of the inner core layer.
In some configurations, the central absorbent zone 306 may have a longitudinal length LC of from about 115 mm to about 200 mm, or from about 125 mm to about 195 mm, as measured from the outermost point of the outwardly convex front edge 310 to the outermost point of the outwardly convex rear edge 312. In some configurations, the central absorbent zone 306 may have a longitudinal length LC of from about 50% to about 75% of an inner core layer longitudinal length LT.
Without being limited by theory, it is believed that the shape of the central absorbent zone allows the central absorbent zone to more effectively capture fluid as it exits the labial minora, within the labia majora across a wide range of female genitalia shapes and sizes. It is believed that in order to effectively fit and gently conform within and between the upper spaces between the labial majora, the shape of the central absorbent zone should be narrow, e.g., a lateral width in the 10-20 mm range, and the narrow portion should be of a corresponding narrowed length, e.g., around 50-80 mm long. In addition, the central absorbent zone should be of a generally concave shape that allows for intimate contact with the body to avoid fluid spreading in a lateral direction, but also be wider in both the front and rear regions so as to gently fit in the perinium and at the base of the pubis mons where natural depressions of the body can allow fluid to bypass a pad and spread on the body.
In some configurations, the outwardly convex front edge 310 of the central absorbent zone 306 may be positioned a distance of from about 25 mm to about 45 mm from a front edge 424 of the inner core layer 200. In some configurations, the outwardly convex rear edge 312 of the central absorbent zone 306 may be positioned a distance of from about 25 mm to about 85 mm from a rear edge 426 of the inner core layer 200.
It may also be described that the shape of the central absorbent zone 306 may taper as it extends from the front region of the absorbent article to the middle region, defining a narrow portion 350 between the inwardly concave longitudinal side edges. The narrow portion 350 of the central absorbent zone may have a width at its narrowest point that is positioned forward of or coterminous with a lateral centerline 91 of the first and second wing portions 140, 150. The narrow portion 350 of the central absorbent zone 306 may be positioned in the middle region 22 of the absorbent article 20. The narrow portion may have a lateral width of from about 10 mm to about 20 mm. The narrow portion may have a lateral width that is from about 20% to about 40% of a minimum lateral width of the inner core layer WC.
In some configurations, the absorbent core structure 10 and/or the inner core layer 200 may be shaped to substantially follow the shape of the central absorbent zone 306.
Although the central absorbent zone 306, outer absorbent zone 325, and the transition zone 330 have been discussed with reference to the inner core layer 200, the description for the different zones may also apply to the absorbent article 20. The basis weight of the absorbent article in the central absorbent zone may be from about 300 gsm to about 500 gsm, as measured according to the Absorbent Article Caliper, Basis Weight and Density Method. The basis weight of the absorbent article in the outer absorbent zone may be from about 200 gsm to about 400 gsm, as measured according to the Absorbent Article Caliper, Basis Weight and Density Method.
The average density of the absorbent article measured in the central absorbent zone 306 and the outer absorbent zone 325 may be from about 0.045 g/cm3 and about 0.150 g/cm3 as measured according to the Absorbent Article Caliper, Basis Weight, and Density Method. In some configurations, the average density of the absorbent article measured in the central absorbent zone 306 and the outer absorbent zone 325 may be substantially similar. In some configurations, the average density of the absorbent article measured in the outer absorbent zone 325 may be within about 0 to about 20%, or about 0 to about 18%, or about 0 to about 10%, or about 0 to about 5%, of the average density measured in the central absorbent zone.
In some configurations, as shown in
In some configurations, the structural bond sites may be distributed across the absorbent article and/or absorbent core structure or they may be clustered in regions of the absorbent article and/or absorbent core structure. In some configurations, the structural bond sites may be clustered in the middle region 22 of the absorbent article 20 and/or absorbent core structure 10. In some configurations, the middle region 22 of the absorbent article 20 and/or absorbent core structure 10 may be substantially free from structural bond sites and may be surrounded by an area of structural bond sites and/or embossing. In some configurations, as shown in
In some configurations, the structural bond sites 15 may join the topsheet 110, the upper nonwoven layer 210, the absorbent core structure 10, and the lower nonwoven layer 220. In some configurations, the structural bond sites 15 may join the upper nonwoven layer 210, the absorbent core structure 10, and the lower nonwoven layer 220. Absorbent articles 20 and/or absorbent core structures 10 may comprise an upper nonwoven layer 210 and a lower nonwoven layer 220 that are closer together in the Z-direction at the structural bond sites 15 but are not melted together. Since these structural bond sites are not melted together, they may not be permanent in nature and rather may intermingle the materials within the structural bond site. In some configurations, the structural bond sites 15 may be substantially free of fusion bonds.
In some configurations, the absorbent article 20 may also comprise one or more flex bond channel regions 160. At least some or all of the flex bond channel regions 160 may be permanent channels, meaning their integrity is at least partially maintained both in the dry state and in the wet state. The flex bond channel regions 160 may be a continuous depression and/or may comprise a series of individually compressed, closely spaced flex bond embossments.
The flex bond channel regions 160 may have any configuration, e.g., one or more straight line-like shape extending along the longitudinal centerline 80, one or more curved shape generally along the longitudinal centerline 80, an oval shape, a rectangle shape, a triangle shape, a polygonal shape, or any other shape. In some configurations, the flex bond channel regions 160 may extend substantially longitudinally, which means that each flex bond channel region extends more in the longitudinal direction than in the lateral direction, or at least twice as much in the longitudinal direction than in the lateral direction (as measured after projection on the respective axis). In some configurations, the flex bond channel regions 160 may extend substantially laterally, which means that each flex bond channel region extends more in the lateral direction than in the longitudinal direction, or at least twice as much in the lateral direction than in the longitudinal direction (as measured after projection on the respective axis).
In some configurations, flex bond channel region 160 may comprise an inner flex bond channel region 161 and an outer flex bond channel region 162. The inner and outer flex bond channel regions 161, 162 may serve as a hinge structure in the absorbent article, which may help enable the absorbent article to flex both longitudinally and laterally and thereby better conform to the wearer's anatomy. The inner and outer flex bond channel regions 161, 162 may also serve as a visual signal of a fluid barrier.
The inner flex bond channel region 161 may be curved and/or arcuate, and may run substantially parallel to the longitudinal centerline 80 of the absorbent article. In other configurations, the inner flex bond channel region 161 may be substantially straight. In some configurations, the inner flex bond channel region 161 may be concave towards the longitudinal centerline 80 as, for example, represented in
As previously mentioned, the absorbent article 20 and the absorbent core structure 10 each include a front end region 21, a back end region 23, and a middle region 22 disposed intermediate the front end and the back end regions. The inner flex bond channel region 161 may be present in the middle region 22, or part thereof, and part of the front end region 21 and/or back end region 23. In some configurations, the inner flex bond channel region 161 may extend longitudinally from the front end region 21 to the back end region 23. The absorbent article 20 may comprise one or more inner flex bond channel regions 161, such as two, three, four, five or six.
In some configurations, the inner flex bond channel region 161 may be positioned in at least the middle region 22 of the absorbent article and may form a closed loop substantially surrounding the central absorbent zone 306, as for example, represented in
In some configurations, the inner flex bond region 161 may be positioned between the central absorbent zone 306 and the outer absorbent zone 325. Without being limited by theory, it is believed that by having the flex bond channel region adjacent to the central absorbent zone enables the absorbent article to bend at a location that can allow the central absorbent zone to come up close to the body. In addition, the flex bond channel region can help the central absorbent zone be more visually perceptible to the user without the need for adding more mass (and stiffness).
The absorbent article may comprise structural bond sites 15 and flex bond channel regions 160. In some configurations, the central absorbent zone 306 may be substantially free from structural bond sites 15 and may be at least partially surrounded by an area of structural bond sites and/or flex bond channel regions, such as shown in
As shown in
In some configurations, the outer flex bond channel region 162 may comprise a closed loop surrounding the inner flex bond channel region 161. In such a configuration, as shown in
As shown in
Still referring to
The flex bond channel region 160 may be continuous or discontinuous. Herein, “discontinuous” means the flex bond channel region can be separated by a non-channel region (i.e., a region where no channel is formed). The distance between the two succeeding flex bond channel regions (i.e., the length of the non-channel portion) may be changed depending on the product design. Without being limited by theory, it is believed that by having a non-channel region between, for example, the ends of the front flex bond channel region 190 and the outer flex bond channel 162 or between the inner flex bond channel region 161 and the outer flex bond channel region 162 may help to avoid creating an undesirable stiffness and may help to provide improved flexibility and fit of the absorbent article.
In some configurations, the inner flex bond channel region 161 and/or the outer flex bond channel region 162 may be continuous. In some configurations, the inner flex bond channel region 161 may be discontinuous and the outer flex bond channel region 162 may be continuous. Flex bond channel region 160 may have a minimum channel length of about 50 mm, as measured from a first end of the flex bond channel region to a second end of the flex bond channel region following the curve of the flex bond channel region. Without being limited by theory, it is believed that if the flex bond channel region is less than about 50 mm there may be insufficient length in the flex bond channel region to provide sufficient multi-direction flexibility to create a desired bend in the absorbent article to allow the absorbent article to fit closely to the body. It is believed that a flex bond channel region having a channel length of at least 50 mm can sufficiently affect adjacent non-channeled regions such that the absorbent article may conform and fit closely to the body. Flex bond channel region 160 may have a length of from about 50 mm to about 400 mm, or from about 60 mm to about 350 mm, or from about 75 mm to about 300 mm, or from about 100 mm to about 200 mm.
In some configurations, the flex bond channel regions 160 may have a channel area of from about 10 to about 20% of the inner core layer area.
In some configurations, the flex bond embossments 160a may extend substantially parallel to the longitudinal centerline 80 of the absorbent article. In other configurations, the flex bond embossments 160a may extend substantially parallel to the lateral centerline 90 of the absorbent article.
In some configurations, the flex bond embossments 160a may be evenly spaced. In some configurations, at least a portion of the flex bond embossments 160a may be grouped in clusters of two, three, or four or more flex bond embossments, such as shown in
In contrast to the flex bond channel regions described herein, current absorbent articles for menstrual applications may comprise a series of point-like depressions whereby the material between the z-direction depression points recovers to a predominant degree to the uncompressed thickness of the non-channeled areas. In such structures, the channel depth between the depression points may be less than about 10% to about 25% of the channel depth at emboss points. Without being limited by theory, it is believed that such point-like depressions may not create an effective bending line to allow the article to conform closely to the body. Other current absorbent articles may comprise small physical bonding points with relatively large spacings between the bonding points. Without being limited by theory, it is believed that if the physical bonding points are relatively small (e.g., width less than about 0.5 mm) and spaced well apart (e.g., greater than about 1-4 mm), these physical bonding points will be insufficient to reproducibly drive a fit/bending direction of the absorbent article. To establish a reproducible, effective fit/bending direction, it is believed that sufficient mass should be displaced into the z-direction and there should be consistent thinning through a substantial portion of the channel region to effectively drive a preferred and consistent bending feature.
Typically, flex bond channel regions 160 may be formed by applying a compressive force to the topsheet 110, upper nonwoven layer 210, inner core layer 200, and lower nonwoven layer 220. The topsheet at the flex bond channel region is pushed down into the absorbent core structure, and the materials of the topsheet and the absorbent core structure are compressed at and below the bottom of the flex bond channel region. By this operation (which is often called “embossing process”), the flex bond channel region of the absorbent article has a relatively higher density than the non-channeled regions. As a result of compression, a flex bond channel region 160 may be formed to have an elongated depression such as a modified gutter-like shape having a pair of opposing side walls and a bottom surface.
In some configurations, the compressive force is applied to the topsheet 110, upper nonwoven layer 210, and lower nonwoven layer 220, creating a flex bond channel region 160 in an area with no inner core layer. The flex bond channel regions of the present disclosure can be formed by any structures and processes known in the art.
The flex bond channel regions 160 may be formed by applying a uniform (or a single level of) compression force. In some configurations, the flex bond channel region 160 can be formed by applying two or more levels of compression forces, thereby forming a stage channel structure, as disclosed for example in U.S. Pat. No. 6,563,013. In a stage channel configuration, the flex bond channel region may comprise opposing sidewalls, a first portion forming a first bottom surface and a second portion forming a second bottom surface, wherein the second bottom surface is subjacent the first bottom surface, and the second portion may be discrete and may be surrounded by the first portion.
In some configurations, the inner flex bond region 161 may be positioned in the transition zone 330 or in the outer absorbent zone 325. In some configurations, the inner flex bond channel region 161 may be positioned adjacent to the transition zone 330 in the outer absorbent zone 325. In some configurations, the inner flex bond channel region 161 may be positioned about 1 mm to about 10 mm, or from about 3 mm to about 6 mm, outboard of the outermost edge of the transition zone 330. In some configurations, the inner flex bond channel region 161 may be positioned about 1 mm to about 10 mm longitudinally outboard of the outermost point of the outwardly convex front edge and/or outwardly convex rear edge. In some configurations, the inner flex bond channel region 161 may be positioned about 3 mm to about 6 mm laterally outboard of the outermost point of the inwardly concave longitudinal side edges.
As shown in
Flex bond channel region 160 may have a channel thickness “T1” of less than about 2.5 mm, or from about 0.5 mm to about 2.5 mm, or from about 1.0 mm to about 2.0 mm.
Flex bond channel region 160 may have a channel width “A” at the base of the channel, as measured according to the Flex Bond Channel Width Method, of between about 1.0 mm to about 3.0 mm, or from about 1.25 to about 2.5 mm, or from about 1.5 to about 2.0 mm. Flex bond depression regions 164 may have a lateral channel width “A′” at the base of the depression of between about 1.0 mm to about 3.0 mm, or from about 1.25 to about 2.5 mm, or from about 1.5 to about 2.0 mm.
In some configurations, the maximum width of structural bond site 15 may be greater than the channel width “A” of flex bond channel region 160. Without being limited by theory, it is believed that if the channel width “A” of the flex bond channel region 160 is greater than the maximum width of structural bond site 15 it may create a stiffness that may hinder the ability of the absorbent core structure and/or absorbent article to closely conform to the body.
Flex bond channel region 160 may have a channel density of less than about 0.30 g/cm3, or from about 0.05 g/cm3 to about 0.3 g/cm3, or from about 0.10 g/cm3 to about 0.25 g/cm3. Without being limited by theory, it is believed that a channel density of less than about 0.30 g/cm3 plastically deforms the inner core layer such that the flex bond channel region stays in a compressed state yet still allows the flex bond channel region to bend in both the lateral and longitudinal direction. Flex bond channel region 160 may have a Dry MD Bending Resistance of less than about 0.040 N/mm as measured according to the Flex Bond Channel MD Bending Resistance Method, or from about 0.005 to about 0.035 N/mm, or from about 0.1 to about 0.030 N/mm. Without being limited by theory, it is believed that a flex bond channel region having a Dry MD Bending Resistance of greater than about 0.04 N/mm may create a stiffness that may hinder the ability of the absorbent core structure and/or absorbent article to closely conform to the body in both the longitudinal and lateral directions simultaneously.
It is to be appreciated that the dimensions of flex bond channel regions 160 described above also apply to inner flex bond channel regions 161, outer flex bond channel regions 162, front flex bond channel regions 190, back flex bond channel regions 192, and lateral secondary flex bond channel regions 170.
Suitable upper nonwoven layers may have a basis weight of from about 30 gsm to about 85 gsm, or from about 35 gsm to about 70 gsm, or from about 40 to about 60 gsm. The upper nonwoven layer may have a Tensile Stiffness of from about 0.1 N/mm to about 2.2 N/mm, or from about 0.3 N/mm to about 1.6 N/mm as measured according to the CD Cyclic Elongation to 3% Strain Method. The upper nonwoven layer may have a Strain to Break of greater than about 10%, or from about 10% to about 50%, or from about 20% to about 40%, as measured according to the Strain to Break Method. The upper nonwoven layer may have a Permanent Strain of about 0.005 to about 0.013 mm/mm, or from 0.005 to about 0.0090 mm/mm, as measured according to the CD Cyclic Elongation to 3% Strain Method. The upper nonwoven layer may have Thickness at 7 g/cm2 pressure of from about 0.3 mm to about 1.3 mm and/or a Thickness at 70 g/cm2 pressure of from about 0.2 mm to about 0.7 mm, as measured according to the Nonwoven Thickness-Pressure Method.
Suitable lower nonwoven layers may have a basis weight of from about 10 to about 40 gsm, or from about 15 to about 20 gsm. The lower nonwoven layer may have a Tensile Stiffness of from about 0.2 N/mm to about 2.0 N/mm, as measured according to the CD Cyclic Elongation to 3% Strain Method. The lower nonwoven layer may have a Strain to Break of greater than about 10%, or from about 10% to about 50%, or from about 20% to about 40%, as measured according to the Strain to Break Method. The lower nonwoven layer may have a Permanent Strain of about 0.005 to about 0.018 mm/mm, as measured according to the CD Cyclic Elongation to 3% Strain Method. The lower nonwoven layer may have a Thickness at 7 g/cm2 pressure of from about 0.1 mm to about 1.3 mm, as measured according to the Nonwoven Thickness-Pressure Method.
The upper and lower nonwoven layers may comprise polymer fibers. Suitable upper and lower nonwoven fibers may be selected from PET (polyethylene terephthalate), PP (polypropylene), a BiCo (Bicomponent fiber) selected from PE/PP (PE sheath and PP core) and/or PE/PET (PE sheath PET core), PLA (polylactic acid), and combinations thereof.
Suitable upper nonwovens may comprise from about 60 to about 100%, or from about 70% to about 100% synthetic fibers, or from about 0 to about 40%, or from about 0 to about 30% regenerated cellulosic fibers, such as rayon and/or viscose.
The upper nonwoven layer may comprise fibers having a staple length of greater than about 10 mm, or greater than about 25 mm, or from about 10 mm to about 100 mm, or from about 20 mm to about 75 mm, or from about 25 mm to about 50 mm. The upper nonwoven layer may comprise fibers having a fiber diameter of from about 1.3 DTex to about 10.0 DTex, alternatively from about 1.3 DTex to about 6.0 DTex, alternatively from about 2.0 DTex to about 5.0 DTex. Without being limited by theory, it is believed that if the fibers of the upper nonwoven layer are less than about 1.3 Dtex, there may be insufficient air flow through the material during manufacturing.
In some configurations, the upper nonwoven layer may comprise a blend of staple fibers. When the upper nonwoven layer comprises a blend of staple fibers, the blend of fibers preferably comprises 30% or less of fibers having a fiber diameter of 1.3 Dtex and/or 30% or less of fibers having a fiber diameter of 10.0 Dtex. In some configurations, the upper nonwoven layer may comprise fibers, wherein the fibers are a blend of staple fibers having an average fiber diameter of from about 2.0 DTex to about 8.0 DTex. Without being limited by theory, it is believed that fibers having an average fiber diameter of from about 2.0 Dtex to about 8.0 Dtex will help to enable sufficient air flow through the material during manufacturing of the absorbent core structure.
The lower nonwoven layer may comprise fibers having a length of greater than about 10 mm, or greater than about 25 mm, or from about 10 mm to about 100 mm, or from about 20 mm to about 75 mm, or from about 25 mm to about 50 mm. In some configurations, the lower nonwoven layer may comprise continuous fibers. The lower nonwoven layer may comprise fibers having a fiber diameter of from about 1.3 DTex to about 5.0 DTex, or from about 1.3 DTex to about 3.3 DTex, or from about 1.3 DTex to about 2.2 DTex, or from about 2.0 DTex to about 10 DTex. In some configurations, the lower nonwoven layer may comprise fibers, wherein the fibers are a blend of fibers having a fiber diameter of from about 0.1 DTex to about 6.0 DTex.
In some configurations, upper nonwoven layer may comprise a blend of fibers, wherein at least a portion of the fibers have a diameter of from about 2.0 DTex to about 10 DTex and the lower nonwoven layer may comprise a blend of fibers, wherein at least a portion of the fibers have a diameter of from about 1.3 DTex to about 5 DTex. In some configurations, the upper nonwoven layer may comprise a blend of fibers, wherein at least a portion of the fibers have a diameter of from about 1.3 DTex to about 2.2 DTex and the lower nonwoven layer may comprise a blend of fibers, wherein the blend of fibers have a diameter of from about 1.3 DTex to about 5 DTex.
Suitable upper and/or lower nonwoven layer materials may bend and recover their original shape following the bending force. Flimsy or highly flexible materials readily bend at low peak force (load) and with low bending energy. Unsuitable materials, while readily bending, do not have sufficient recovery energy and so retain a deformed, bent state because of insufficient recovery energy. Suitable materials have sufficient energy to recover their initial pre-bent state. The materials with sufficient bending recovery energy may be considered resilient upper and lower nonwoven layers. Particularly suitable upper nonwoven layers may have a Dry Recovery Energy of greater than about 0.03 N*mmm, or from about 0.03 N*mm to about 1 N*mm, or from about 0.04 N*mm to about 0.5 N*mm. Particularly suitable upper nonwoven layers may have a Dry Bending Energy of less than about 1.6 N*mm, or less than about 1.1 N*mm.
As noted above, the upper and lower nonwovens may include polymer fibers. Polymer fibers may be included to help provide structural integrity to the upper and lower nonwovens. The polymer fibers may help increase structural integrity of the upper and lower nonwovens in both a machine direction (MD) and in a cross-machine direction (CD), which may facilitate web manipulation during processing of the upper and lower nonwovens for incorporation into a pad.
Polymer fibers of any suitable composition may be selected. Some examples of suitable polymer fibers may include bi-component fibers comprising polyethylene (PE) and polyethylene terephthalate (PET) components or polyethylene terephthalate and co-polyethylene terephthalate components. The components of the bi-component fiber may be arranged in a sheath-core configuration, a side-by-side configuration, an eccentric sheath-core configuration, a trilobal arrangement, or any other desired configuration. In some configurations, the polymer fibers may include bi-component fibers having PE/PET components arranged in a concentric, sheath-core configuration, wherein the polyethylene component forms the sheath.
While other materials may be useful in creating a resilient structure, it is believed that the stiffness of a PET core component in a sheath-core fiber configuration may be useful for imparting resilience to the upper and lower nonwovens. In synergistic combination, a PE sheath component, having a lower melting temperature than the PET core component, may be utilized to provide inter-fiber melt/fusion bonding, effected via heat treatment of the precursor batt. This can help provide tensile strength to the web in both the MD and CD. Such inter-fiber bonds may serve to reduce fiber-to-fiber sliding, and thereby further contribute to imparting shape stability and resiliency to the material even when it is wetted.
Where a relatively higher weight fraction of polymer fibers is included, more connections within the structure may be created via heat treatment. However, too many connection points may impart greater stiffness to the upper and lower nonwovens than may be desirable. For this reason, selecting the weight fraction of the polymer fibers may involve prioritizing and balancing competing needs for stiffness and softness in the upper and lower nonwovens.
As noted above, the upper and lower nonwovens may additionally include polymer fibers which increase resiliency of the upper and lower nonwovens. The resilient polymer fibers may help the upper and lower nonwovens maintain permeability and compression recovery. In some configurations, the upper and lower nonwovens may comprise resilient polymer fibers having varying cross sections, e.g., round and hollow spiral, and/or may comprise resilient fibers having varying sizes.
The polymer fibers may be resilient and may be spun from any suitable thermoplastic resin, such as polypropylene (PP), polyethylene terephthalate (PET), or other suitable thermoplastics known in the art. The average staple length of the resilient polymer fibers may be selected to be in the range of greater than about 10 mm, from about 20 mm to about 100 mm, or about 30 mm to about 50 mm, or about 35 mm to about 50 mm. The resilient polymer fibers may have any suitable structure or shape. For example, the resilient polymer fibers may be round or have other shapes, such as spiral, scalloped oval, trilobal, scalloped ribbon, and so forth. Further, the resilient polymer fibers may be solid, hollow, or multi-hollow. The resilient polymer fibers may be solid and round in shape. In other suitable examples, resilient polymer fibers may include polyester/co-extruded polyester fibers. Other suitable examples of resilient polymer fibers may include bi-component fibers such as polyethylene/polypropylene, polyethylene/polyethylene terephthalate, polypropylene/polyethylene terephthalate bicomponent fibers. These bi-component fibers may have a sheath/core configuration.
The resilient polymer fibers may be polyethylene terephthalate (PET) fibers, or other suitable non-cellulosic fibers known in the art. PET fibers may be imparted with any suitable structure or shape. For example, the PET fibers may be round or have other shapes, such as spiral, scalloped oval, trilobal, scalloped ribbon, hollow spiral, and so forth. The PET fibers may be solid, hollow or multi-hollow. In one particular example, PET fibers may be hollow in cross section and have a curl or spiral configuration along their lengths. Optionally, the resilient polymer fibers may be spiral-crimped or flat-crimped. The resilient polymer fibers may have an average crimp count of about 4 to about 12 crimps per inch (cpi), or about 4 to about 8 cpi, or about 5 to about 7 cpi, or about 9 to about 10 cpi. Particular non-limiting examples of resilient polymer fibers may be obtained from Wellman, Inc. (Ireland) under the trade designations H1311 and T5974. Other examples of suitable resilient polymer fibers are disclosed in U.S. Pat. No. 7,767,598.
The stiffening polymer fibers and resilient polymer fibers should be carefully selected. For example, while the constituent polymers forming the stiffening polymer fibers and the resilient polymer fibers may have similarities, resilient polymer fiber composition should be selected such that their constituents' melting temperature(s) is/are higher than that of the bondable components of the stiffening polymer fibers. Otherwise, during heat treatment, resilient polymer fibers could bond to stiffening polymer fibers and vice versa, and thereby an overly rigid structure. To avoid this risk where the stiffening polymer fibers include bicomponent fibers, e.g., core-sheath configuration fibers with a sheath component of relatively lower melting temperature at which fusion bonding will occur, the resilient polymer fibers may comprise the constituent chemistry of only the core, which may be a polymer having a relatively higher melting temperature.
Nonwoven performance can be impacted by a combination of the nonwoven fiber polymer choice, fiber properties, and how the fibers are arranged or connected. Nonwoven selection can impact the absorbent article's ability to recover its shape following compression, bending and extension (stretching) forces present in-use with body motion. If the fibers are short (less than about 10 mm), the fibers are likely to irreversibly rearrange under extension and compressive forces. The rearranging (changing their orientation/state) of fibers in a fiber matrix dissipates the tensile (elongation) or compressive forces so that the energy used to affect the deformation is no longer available for recovery to the original shape. Longer fiber networks (typically greater than about 10 mm but less than about 100 mm) can absorb the tensile/compressive forces typical of bodily motions along the fiber length and across the structure. As a result, the absorbed forces are available to recover the structure to its original state. Longer fiber networks composed of finer fibers (typically less than about 15 to about 20 microns) more readily elongate and compress. As a result, the fluff/AGM structure can deform more readily (and to a higher degree) but the energy associated with these deformations is relatively small and insufficient to carry the structure back to its original state. Thicker fiber, such as greater than about 20 microns or about 2.0 DTex to about 10 DTex, are both flexible under bodily forces but provide sufficient fiber and web recovery energy to return the structure to its original state.
The fiber arrangement in a long fiber network from a structural standpoint can impact the performance of the absorbent articles containing these nonwovens. Long fiber webs of thicker fibers are typically loftier than a conventional thin spunbond nonwoven web composed of continuous fine fibers that are closely spaced and physically bonded together. Creating a web of thicker fibers arranged in a more randomized orientation such as those that can be achieved via carding, hydro-entangling, and needling are able to elongate and compress, whereby the fibers only temporary adjust their arrangement (space between the fibers exist for these arrangements) and are able to carry/store the deformation forces and this energy is available for recovering the structural shape.
Additionally, finer (less than about 2.0 DTex) synthetic fibers such as BiCo and PP fibers commonly found in spunbond are closely spaced, relatively parallel aligned and closely bonded together. The bonded fibers within these spunbond webs are so interconnected (with closely spaced point bonds) that in tensile (elongation) the fibers at the polymer level are forced to stretch, resulting in polymer chains within the fiber permanently rearranging. As a result, the fibers themselves potentially remain permanently elongated (permanently strained) and are no longer able to recover to their initial state.
In some configurations, the polymer fibers in the upper nonwoven layer and the polymer fibers of the lower nonwoven layer may be different. In some configurations, the polymer fibers of the upper nonwoven layer and the polymer fibers of the lower nonwoven layer may be the same. In some configurations, the upper nonwoven layer may be carded nonwoven. In some configurations, the upper nonwoven layer may be air through bonded or hydroentangled. In some configurations, the upper nonwoven layer is not a spunbond material.
Suitable nonwoven materials examples may include, but are not limited to, the following materials: (i) a 40 gsm carded resilient nonwoven material produced by Yanjan China (material code; ATB Z87G-40-90) which is a carded nonwoven composed of a blend of 60% 2 DTex and 40% 4 DTex BiCo (PE/PET) fibers. The fibers are bonded (ATB=Through ‘hot’ Air Bonded) to create a wet resilient network. Without being limited by theory, it is believed that because of the presence of the 4 DTex BiCo fibers and the fiber-to-fiber bonded BiCo network, the material has a low Permanent Strain (less than about 0.013 mm/mm) and a sufficient Dry Recovery Energy (greater than about 0.03 N*mm) in the Dry CD Ultra Sensitive 3 Point Bending Method; (ii) a 55 gsm resilient spunlace material produced by Sandler Germany (material code: 53FC041001), which is a hydro-entangled nonwoven that is produced via a carding step (like the nonwoven described above) followed by hydro-entangling with an elevated drying step (as described in U.S. Patent Publication No. 2020/0315873A1) that creates both an entangled and BiCo bonded resilient network. It comprises a fiber blend of 30% 10 DTex HS-PET, 50% 2.2 DTex BiCo (PE/PET), and 20% 1.3 DTex rayon. The material has a low Permanent Strain (less than about 0.013 mm/mm) and a sufficient Dry Recovery Energy (greater than about 0.03 N*mm) in the Dry CD Ultra Sensitive 3 Point Bending Method; and (iii) a 50 gsm resilient spunlace material produced by Sandler Germany (material code: 53FC041005 opt82), which is a hydro-entangled nonwoven that is produced via a carding step (like the nonwoven described above) followed by hydro-entangling with an elevated drying step (as described in U.S. Patent Publication No. 2020/0315873A1) that creates both an entangled and BiCo bonded resilient network. It comprises a fiber blend of 60% 5.8 DTex BiCo (PE/PET), 20% 3.3 DTex tri-lobal ‘structural’ rayon, and 20% 1.3 DTex rayon. The material has a low Permanent Strain (less than about 0.013 mm/mm) and a sufficient Dry Recovery Energy (greater than about 0.03 N*mm) in the Dry CD Ultra Sensitive 3 Point Bending Method. While this material has 40% rayon that can soften when wet, the use of structural tri-lobal rayon fibers helps structural stability in the wet state.
In combination with adjustment of pore size, volume, and number via selection of appropriate fiber size, basis weight, and extent of consolidation, the manufacturer may wish to select fiber constituents for having particular surface chemistry (ies), e.g., fibers with hydrophobic surfaces, hydrophilic surfaces, or a blend of differing fibers and/or z-direction stratification or gradient thereof. Fibers having hydrophilic surfaces will tend to attract and move aqueous components of menstrual fluid there along in a manner conducive to wicking and rapid fluid acquisition following discharge. At the same time, however, a predominance of hydrophilic fibers surfaces within the topsheet may increase a tendency of the topsheet to reacquire fluid from absorbent components beneath (rewet), which can cause an undesirable wet feel for the user. On the other hand, fibers having hydrophobic surfaces will tend to repel aqueous components of menstrual fluid and/or resist movement of fluid along their surfaces, thereby tending to resist wicking—but also to resist rewetting. The manufacturer may wish to seek an appropriate balance in selecting constituent fibers having hydrophilic surfaces, fibers having hydrophobic surfaces, or a blend and/or z-direction stratification thereof, in combination with fiber size, fiber consolidation level, and resulting topsheet pore size, volume and number, for any particular product design.
The inner core layer is produced in an airlaying process. Streams of cellulose and superabsorbent polymer are carried on a fast moving airstream and deposited into a three dimensionally shaped pocket on a rotating forming drum with a vacuum below to draw the cellulose and superabsorbent polymer into the pocket in a laydown station. This shaped pocket provides the actual physical shape of the absorbent core structure. The upper nonwoven layer may be first introduced onto the forming drum and under the vacuum the upper nonwoven layer is drawn into the 3-dimensional pocket shape. In this case, the cellulose and superabsorbent polymer material stream is deposited on the upper nonwoven layer directly in the forming station. Prior to entering the forming station, the nonwoven is coated with an adhesive to provide a stronger connection of the cellulose and superabsorbent polymer to the nonwoven layer. On exiting the laydown section, the lower nonwoven layer is combined with the upper nonwoven layer carrying the cellulose and superabsorbent polymer layer exiting the laydown section. This lower nonwoven is precoated with adhesive to enable a perimeter seal and to better integrate the cellulose and superabsorbent polymer without hindering the flow of liquid into the cellulose and superabsorbent polymer matrix. These adhesives are not represented in the Figures for simplicity.
The inner core layer may comprise any of a wide variety of liquid-absorbent materials commonly used in absorbent articles, such as comminuted wood pulp, which is generally referred to as airfelt. One suitable absorbent core material is an airfelt material which is available from Weyerhaeuser Company, Washington, USA, under Code No. FR516. Examples of other suitable liquid-absorbent materials for use in the absorbent core may include creped cellulose wadding; meltblown polymers including coform; chemically stiffened, modified or cross-linked cellulosic fibers; synthetic fibers such as crimped polyester fibers; peat moss; cotton, bamboo; absorbent polymer materials; or any equivalent material or combinations of materials, or mixtures of these.
Absorbent polymer materials for use in absorbent articles typically comprise water-insoluble, water-swellable, hydrogel-forming crosslinked absorbent polymers which are capable of absorbing large quantities of liquids and of retaining such absorbed liquids under moderate pressure.
The absorbent polymer material for the absorbent cores according to the present disclosure may comprise superabsorbent particles, also known as “superabsorbent materials” or as “absorbent gelling materials”. Absorbent polymer materials, typically in particle form, may be selected among polyacrylates and polyacrylate based materials, such as for example partially neutralized, crosslinked polyacrylates. The term “particles” refers to granules, fibers, flakes, spheres, powders, platelets and other shapes and forms known to persons skilled in the art of superabsorbent particles. In some aspects, the superabsorbent particles may be in the shape of fibers, i.e., elongated, acicular superabsorbent particles.
In some configurations, the inner core layer may comprise cellulosic fibers and superabsorbent particles. The inner core layer may comprise from about 50% to about 85% cellulosic fibers, or from about 55% to about 80%, or from about 60% to about 75%, all by weight of the inner core layer. The inner core layer may comprise from about 10% to about 50% superabsorbent particles, or from about 15% to about 50%, or from about 20% to about 40%, or from about 25% to about 35%, all by weight of the inner core layer. In some configurations, the inner core layer may comprise from about 125 gsm to about 500 gsm cellulosic fibers. In some configurations, the inner core layer may comprise from about 125 gsm to about 300 gsm superabsorbent particles.
In some configurations, the inner core layer may comprise from about 50% to about 85% cellulosic fibers and from about 15% to about 50% superabsorbent particles.
Topsheet 110 may be formed of any suitable nonwoven web or formed film material. Referring back to the figures, the topsheet 110 is positioned adjacent a wearer-facing surface of the absorbent article 20 and may be joined thereto and to the backsheet 130 by any suitable attachment or bonding method. The topsheet 110 and the backsheet 130 may be joined directly to each other in the peripheral regions outside the perimeter of the absorbent core structure and may be indirectly joined by directly joining them respectively to wearer-facing and outward-facing surfaces of the absorbent article or additional optional layers included with the absorbent article.
The absorbent article 20 may have any known or otherwise effective topsheet 110, such as one which is compliant, soft feeling, and non-irritating to the wearer's skin. A suitable topsheet material will include a liquid pervious material that is comfortable when in contact with the wearer's skin and permits discharged menstrual fluid to rapidly penetrate through it. Some suitable examples of topsheet materials include films, nonwovens, laminate structures including film/nonwoven layers, film/film layers, and nonwoven/nonwoven layers.
Nonlimiting examples of nonwoven web materials that may be suitable for use to form the topsheet 110 include fibrous materials made from natural fibers, modified natural fibers, synthetic fibers, or combinations thereof. Some suitable examples are described in U.S. Pat. Nos. 4,950,264; 4,988,344; 4,988,345; 3,978,185; 7,785,690; 7,838,099; 5,792,404; and 5,665,452.
The topsheet 110 may be compliant, soft feeling, and non-irritating to the wearer's skin. Further, the topsheet 110 may be liquid pervious permitting liquids (e.g., urine, menses) to readily penetrate through its thickness. Some suitable examples of topsheet materials include films, nonwovens, laminate structures including film/nonwoven layers, film/film layers, and nonwoven/nonwoven layers. Other exemplary topsheet materials and designs are disclosed in U.S. Patent Application Publication Nos. 2016/0129661, 2016/0167334, and 2016/0278986.
In some examples, the topsheet 110 may include tufts as described in U.S. Pat. Nos. 8,728,049; 7,553,532; 7,172,801; 8,440,286; 7,648,752; and 7,410,683. The topsheet 20 may have a pattern of discrete hair-like fibrils as described in U.S. Pat. No. 7,655,176 or U.S. Pat. No. 7,402,723. Additional examples of suitable topsheet materials include those described in U.S. Pat. Nos. 8,614,365; 8,704,036; 6,025,535; and US Patent Publication No. 2015/041640. Another suitable topsheet may be formed from a three-dimensional substrate as detailed in US 2017/0258647. The topsheet may have one or more layers, as described in US Patent Publication Nos. 2016/0167334; 2016/0166443; and US 2017/0258651.
In some examples a topsheet 110 may be formed of a nonwoven web material of a spunbond web including single-component continuous fibers, or alternatively, bi-component or multi-component fibers, or a blend of single-component fibers spun of differing polymer resins, or any combination thereof. The topsheet may also be a formed nonwoven topsheet as disclosed in US Patent Publication No. 2019/0380887.
In order to ensure that fluid contacting the top (wearer-facing) surface of a topsheet will move suitably rapidly in a z-direction to the bottom (outward-facing) surface of the topsheet where it can be drawn into the absorbent article, it may be important to ensure that the nonwoven web material forming the topsheet has an appropriate weight/volume density, reflecting suitable presence of interstitial passageways (sometimes known as “pores”) among and between the constituent fibers, through which fluid may move within the nonwoven material. In some circumstances a nonwoven material with fibers that are consolidated too densely may have insufficient numbers and/or volumes and/or sizes of pores, and the nonwoven will obstruct rather than facilitate rapid downward z-direction fluid movement. On the other hand, a nonwoven with fibers that are too large and/or not consolidated enough to provide a certain level of opacity (for purposes of concealing absorbed fluid in the layers beneath) and a substantial appearance may be negatively perceived by users.
The caliper of the topsheet material may be controlled, to balance competing needs for opacity and loft (which call for a higher caliper) vs. a limitation on the z-direction distance that discharged fluid travels through the topsheet from the wearer-facing surface to the outward-facing surface, to reach the absorbent core components below. Thus, it may be desired that the manufacture of the topsheet material be controlled to produce a topsheet material having a caliper of from about 0.20 mm to about 1.0 mm, or from about 0.25 mm to about 0.80 mm, or from about 0.30 mm to about 0.60 mm.
An STS layer may be included, in some circumstances, between the topsheet and the absorbent core structure to enable the absorbent core structure to readily receive a sudden discharge of fluid, and after receipt, to wick it along x- and y-directions to distribute it across the underlying absorbent core structure.
If included, an STS may be a nonwoven fibrous structure which may include cellulosic fibers, non-cellulosic fibers (e.g., fibers spun from polymer resin(s)), or a blend thereof. To accommodate the folding and lateral gathering of the absorbent article 20, and of the absorbent core structure 10, as described herein, the STS may be formed of a material that is relatively pliable (i.e., has relatively low bending stiffness).
A number of particular examples of suitable STS compositions and structures, as well as combinations thereof with suitable topsheet compositions and structures, are further described in U.S. application Ser. Nos. 16/831,862; 16/831,854; 16/832,270; 16/831,865; 16/831,868; 16/831,870; and Ser. No. 16/831,879; and U.S. Provisional Apps. Ser. Nos. 63/086,610 and 63/086,701. Additional suitable examples are described in U.S. Pat. No. 9,504,613; WO 2012/040315; and US 2019/0021917.
In some configurations, the absorbent article may be free of a secondary topsheet.
The backsheet 130 may be positioned beneath or subjacent an outward-facing surface of the absorbent core structure 10 and may be joined thereto by any suitable attachment methods. For example, the backsheet 130 may be secured to the absorbent core structure 10 by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines, spirals, or spots of adhesive. Alternatively, the attachment method may include heat bonds, pressure bonds, ultrasonic bonds, dynamic mechanical bonds, or any other suitable attachment mechanisms or combinations thereof. In other examples, it is contemplated that the absorbent core structure 10 is not joined directly to the backsheet 130.
The backsheet 130 may be impermeable or substantially impermeable by aqueous liquids (e.g., urine, menstrual fluid) and may be manufactured from a thin plastic film, although other flexible liquid impermeable materials may also be used. As used herein, the term “flexible” refers to materials which are compliant and will readily conform to the general shape and contours of the human body. The backsheet 130 may prevent, or at least substantially inhibit, fluids absorbed and contained within the absorbent core structure 10 from escaping and reaching articles of the wearer's clothing which may contact the absorbent article 20, such as underpants and outer clothing. However, in some instances, the backsheet 130 may be made and/or adapted to permit vapor to escape from the absorbent core structure 10 (i.e., the backsheet is made to be breathable), while in other instances the backsheet 130 may be made so as not to permit vapors to escape (i.e., it is made to be non-breathable). Thus, the backsheet 130 may comprise a polymeric film such as thermoplastic films of polyethylene or polypropylene. A suitable material for the backsheet 130 is a thermoplastic film having a thickness of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils), for example. Any suitable backsheet known in the art may be utilized with the present invention.
Some suitable examples of materials suitable for forming a backsheet are described in U.S. Pat. Nos. 5,885,265; 4,342,314; and 4,463,045. Suitable single layer breathable backsheets for use herein include those described for example in GB A 2184 389; GB A 2184 390; GB A 2184 391; U.S. Pat. Nos. 4,591,523; 3,989,867; 3,156,242; WO 97/24097; U.S. Pat. Nos. 6,623,464; 6,664,439; and 6,436,508.
The backsheet 130 may have two layers: a first layer comprising a vapor permeable aperture-formed film layer and a second layer comprising a breathable microporous film layer, as described in U.S. Pat. No. 6,462,251. Other suitable examples of dual or multi-layer breathable backsheets for use herein include those described in U.S. Pat. Nos. 3,881,489; 4,341,216; 4,713,068; 4,818,600; EP 203 821; EP 710 471; EP 710 472; and EP 0 793 952.
In some configurations, the absorbent article 20 may comprise a panty fastening component, such as a panty fastening adhesive or components of a hook and-loop fastening system (such as VELCRO®).
In some configurations, the absorbent article 20 may be provided with a panty fastening adhesive disposed on the garment-facing side of the backsheet 130 in order to provide a mechanism for the user to adhere the absorbent article to the inside of her underpants in the crotch region thereof. The panty fastening adhesive may comprise any adhesive or glue used in the art for such purposes. These adhesives typically are pressure sensitive and remain tacky well below their application temperature. In some configurations, the panty fastening adhesive may be a pressure sensitive hot melt adhesive. When the absorbent article 20 is packaged for shipping, handling and storage prior to use, the panty fastening adhesive may be covered by one or more sheets of release film or paper that covers/shields the adhesive deposits from contact with other surfaces until the user is ready to remove the release film or paper and place the absorbent article in her underpants for wear/use. The release film or paper may also function as an individualized packaging for the article or provide a disposal function as known in the art. Any commercially available release paper or film may be used. Suitable examples include BL 30 MG-A SILOX EI/O, BL 30 MG-A SILOX 4 P/O available from Akrosil Corporation, and M&W films available from Gronau in Germany, under the code X-5432. In some configurations, the absorbent article may be packaged in a bi-folded or tri-folded state.
In some configurations, the absorbent article 20 may include opposing wing portions 140, 150 on each side, extending laterally outward from a first longitudinal side 141 and a second longitudinal side 151 of the absorbent article. Wings are currently commonly provided with feminine hygiene absorbent articles. As provided, they typically have deposits of adhesive applied to their outward-facing surfaces (surface are outward-facing prior to placement of the absorbent article within the user's underwear and application of the wings). The wing portions may also include deposits of adhesive as described above, which enable the user to wrap the wing portions through the leg openings of the underpants and around the inside edges thereof, and adhere the wing portions to the outward-facing surface/underside of the underpants in the crotch region, providing supplemental holding support for the absorbent article and helping guard the underpants proximate the leg edges thereof against soiling.
For any of the methods below in which all the component layers of an article will not be tested, the layers of interest may be separated using cryo-spray as needed from layers which will not be tested.
The force versus displacement behavior of a sample is measured on a universal constant rate of extension test frame (a suitable instrument is the MTS Alliance using TestSuite Software, as available from MTS Systems Corp., Eden Prairie, MN, or equivalent) equipped with a load cell for which the forces measured are within 1% to 99% of the limit of the cell. The sample is subjected to tensile elongation at a constant rate (mm/sec) until it breaks, and the percent strain to break is measured. All testing is performed in a room controlled at 23° C.±3 C° and 50%±2% relative humidity and test samples are conditioned in this environment for at least 2 hours prior to testing.
The fixtures used to grip the test specimen are lightweight (<80 grams), vise action clamps with half cylinder steel versus rubber coated steel grip faces that are at least 40 mm wide. The fixtures are installed on the universal test frame and mounted such that they are horizontally and vertically aligned with one another.
Measurements are made on test specimens taken from rolls or sheets of the raw material, or test specimens obtained from a material layer removed from an absorbent article. When excising the material layer from an absorbent article, use care to not impart any contamination or distortion to the layer during the process. The excised layer should be free from residual adhesive and any fibers that may have transferred from underlying layers. To ensure that all adhesive and any transferred fibers are removed, soak the layer in a suitable solvent that will dissolve the adhesive and release any transferred fibers present without adversely affecting the material itself. One such solvent is THF (tetrahydrofuran, CAS 109-99-9, for general use, available from any convenient source). After the solvent soak, the material layer is allowed to thoroughly air dry in such a way that prevents undue stretching or other deformation of the material. After the material has dried, a test specimen is prepared as follows. The test specimen is cut from an area on the test material that is free of any folds or wrinkles. The test specimen is 100 mm long (parallel to the lateral axis, or intended lateral axis of the article) and 25.4 mm wide (parallel to the longitudinal axis, or intended longitudinal axis of the article). In like fashion, five replicate test specimens are prepared.
Prepare the universal test frame as follows. Set the initial grip to grip separation distance to a nominal gage length of 80 mm, then zero the crosshead. Program the test frame to move the grips closer together by an intentional slack of 1 mm to ensure no pretension force exists on the test specimen at the onset of the test. (During this motion, the specimen will become slack between the grips.) Next, the grips will move apart at a slack speed of 1 mm/s until the slack preload of 0.05 N is exceeded. (At this point, the crosshead position signal is used to compute the sample slack, the adjusted gage length, and the strain is defined at zero, 0.0). The grips will then move apart at a speed of 1 mm/s until the sample breaks or the extension limit of the instrument is exceeded.
The test is executed by inserting the test specimen into the grips such that the long axis of the specimen is parallel and centered with the motion of the crosshead. Start the test and continuously collect force (“load”) and displacement data at a data acquisition rate of 100 Hz.
Construct a graph of load (N) versus displacement (mm). Determine the peak load from the curve, then determine the break sensitivity as follows. Determine the crosshead position at which the load signal decreases by 75% after the peak load is reached, and record as specimen final length (Lf) to the nearest 0.01 mm. The initial length of the specimen is defined by the crosshead position when the slack preload of 0.05 N is exceeded, and this value is recorded as specimen initial length (Li) to the nearest 0.01 mm. Calculate the percent strain to break as follows, and record to the nearest 1 percent.
In like fashion, the procedure is repeated for all five replicate test specimens. The arithmetic mean of % strain to break among the five replicate test specimens is calculated and reported as % Strain to Break to the nearest 1 percent.
The CD (cross-direction) bending properties of a test sample are measured using an ultra sensitive 3 point bend test on a universal constant rate of extension test frame (a suitable instrument is the MTS Alliance using TestSuite Software, as available from MTS Systems Corp., Eden Prairie, MN, or equivalent) equipped with a load cell appropriate for the forces being measured. The intention of this method is to mimic deformation created in the x-y plane by a wearer of an absorbent article during normal use. All testing is performed in a room controlled at 23° C.±3° C. and 50%±2% relative humidity and test samples are conditioned in this environment for at least 2 hours prior to testing.
The ultra sensitive 3 point bend method is designed to maximize the force signal to noise ratio when testing materials with very low bending forces. The force signal is maximized by using a high sensitivity load cell (e.g., 5N), using a small span (load is proportional to the span cubed) and using a wide specimen width (total measured load is directly proportional to width). The fixture is designed such that the bending measurement is performed in tension, allowing the fixture mass to be kept to a minimum. Noise in the force signal is minimized by holding the load cell stationary to reduce mechanical vibration and inertial effect and by making the mass of the fixture attached to the load cell as low as possible.
Referring to
Measurements are made on test specimens taken from rolls or sheets of the raw material, or test specimens obtained from a material layer removed from an absorbent article. When excising the material layer from an absorbent article, use care to not impart any contamination or distortion to the layer during the process. The excised layer should be free from residual adhesive and any fibers that may have transferred from underlying layers. To ensure that all adhesive and any transferred fibers are removed, soak the layer in a suitable solvent that will dissolve the adhesive and release any transferred fibers present without adversely affecting the material itself. One such solvent is THF (tetrahydrofuran, CAS 109-99-9, for general use, available from any convenient source). After the solvent soak, the material layer is allowed to thoroughly air dry in such a way that prevents undue stretching or other deformation of the material. After the material has dried, a test specimen is obtained as follows. The test specimen is cut from an area on the test material that is free of any folds or wrinkles. The dry specimens are prepared for CD bending (i.e., bending normal to the lateral axis of the sample) by cutting them to a width of 50.0 mm along the CD (cross direction; parallel to the lateral axis of the sample) and a length of 100.0 mm along the MD (machine direction; parallel to the longitudinal axis of the sample), maintaining their orientation after they are cut and marking the body-facing surface (or the surface intended to face the body of a finished article). In like fashion, five replicate dry test specimens are prepared.
The universal test frame is programmed such that the moveable crosshead is set to move in a direction opposite of the stationary crosshead at a rate of 1.0 mm/s. Crosshead movement begins with the specimen 1006 lying flat and undeflected on the outer blades 1003a and 1003b, continues with the inner horizontal edge of cavity 1005 in the central blade 1002 coming into contact with the top surface of the specimen 1006, and further continues for an additional 4 mm of crosshead movement. The crosshead stops at 4 mm and then immediately returns to zero at a speed of 1.0 mm/s. Force (N) and displacement (mm) are collected at 50 Hz throughout.
Prior to loading the test specimen 1006, the outside blades 1003a and 1003b are moved towards and then past central blade 1002 until there is approximately a 3 mm clearance, C, between the inner horizontal edges of cavities 1004a and 1004b in the outside blades 1003a and 1003b and the inner horizontal edge of cavity 1005 in the central blade 1002 (see
Force (N) is plotted versus displacement (mm). The maximum peak force is recorded to the nearest 0.001 N. The area under the curve from load onset up to the maximum peak force is calculated and recorded as bending energy to the nearest 0.001 N*mm. The recovery energy is calculated as the area under the curve where the force is unloaded from the maximum peak to 0.0 N and recorded as recovery energy to the nearest 0.001 N*mm. In like fashion, repeat the entire test sequence for a total of five dry test specimens and five wet test specimens.
For each test specimen, the arithmetic mean of the maximum peak force among like specimens is calculated to the nearest 0.001 N and recorded as Dry Peak Load. For each test specimen, the arithmetic mean of bending energy among like specimens is calculated to the nearest 0.001 N*mm and reported as Dry Bending Energy. For each test specimen, the arithmetic mean of recovery energy among like specimens is calculated to the nearest 0.001 N*mm and reported as Dry Recovery Energy.
The cyclic tensile and recovery response of absorbent article specimens are measured for ten cycles of load application (“elongation”) and load removal (“recovery”) using a universal constant rate of extension test frame. The test specimen is cycled ten times to 3% engineering strain, then back to zero engineering strain. For each cycle, stiffness, peak load, normalized energy to peak, normalized recovery energy, strain at start of cycle, and strain at end of cycle (i.e., “permanent strain”) are calculated and reported. The intention of this method is to understand the ability of samples to stretch in the x-y plane as a result of bodily forces, and then recover to their original state. All measurements are performed in a laboratory maintained at 23° C.±2 C.° and 50%±2% relative humidity and test specimens are conditioned in this environment for at least 2 hours prior to testing.
A suitable universal constant rate of extension test frame is the MTS Alliance interfaced to a computer running TestSuite control software (available from MTS Systems Corp, Eden Prairie, MN), or equivalent. The universal test frame is equipped with a load cell for which forces measured are within 1% to 99% of the limit of the cell. The fixtures used to grip the test specimen are lightweight (<80 grams), vise action clamps with knife or serrated edge grip faces that are at least 40 mm wide. The fixtures are installed on the universal test frame and mounted such that they are horizontally and vertically aligned with one another.
Measurements are made on test specimens taken from rolls or sheets of the raw material, or test specimens obtained from a material layer removed from an absorbent article. When excising the material layer from an absorbent article, use care to not impart any contamination or distortion to the layer during the process. The excised layer should be free from residual adhesive and any fibers that may have transferred from underlying layers. To ensure that all adhesive and any transferred fibers are removed, soak the layer in a suitable solvent that will dissolve the adhesive and release any transferred fibers present without adversely affecting the material itself. One such solvent is THF (tetrahydrofuran, CAS 109-99-9, for general use, available from any convenient source). After the solvent soak, the material layer is allowed to thoroughly air dry in such a way that prevents undue stretching or other deformation of the material. After the material has dried, a test specimen is obtained. The test specimen is cut from an area on the test material that is free of any residual of folds or wrinkles. The test specimen is as long as the lateral length of the article (parallel to the lateral axis of the article, or the intended lateral axis of the article). When excising specimens from absorbent articles of different sizes and widths, the total specimen length (Ltotal) may vary from product to product, thus the results will be normalized to compensate for this variation. The test specimen has a width of 25.4 mm wide (parallel to the longitudinal axis, or intended longitudinal axis of the article). Specimen width (w)=25.4 mm. Measure and record the total specimen length (Ltotal) to the nearest 0.1 mm. In like fashion, five replicate test specimens are prepared.
Measure the thickness (t) of the test specimen using a manually-operated micrometer equipped with a pressure foot capable of exerting a steady pressure of 0.1 psi±0.01 psi. The manually-operated micrometer is a dead-weight type instrument with readings accurate to 0.01 mm. A suitable instrument is Mitutoyo Series 543 ID-C Digimatic, available from VWR International, or equivalent. The pressure foot is a flat circular moveable face with a diameter no greater than 25.4 mm. The test specimen is supported by a horizontal flat reference platform that is larger than and parallel to the surface of the pressure foot. Zero the micrometer against the horizontal flat reference platform. Place the test specimen onto the platform, centered beneath the pressure foot. The pressure foot is lowered by hand with a descent rate of 3±1 mm/s until the full weight of the pressure is exerted onto the specimen. After 5 seconds elapse, the thickness is recorded as specimen thickness (t) to the nearest 0.01 mm.
Prepare the universal test frame as follows. Set the initial grip to grip separation distance to a nominal gage length (Lnominal) that is shorter than the total specimen length and such that the specimen can be gripped securely at both ends (i.e., Lnominal<Ltotal). Then zero the crosshead. Program the test frame to move the grips closer together by an intentional slack of 1 mm to ensure no pretension force exists on the test specimen at the onset of the test. (During this motion, the specimen will become slack between the tensile grips.) Next, the grips will move apart at a slack speed of 1 mm/s until the slack preload of 0.05 N is exceeded. At this point, the following are true. 1) The crosshead position signal (mm) is defined as the specimen slack (Lslack). 2) The initial specimen gage length (L0) is calculated as the nominal gage length plus the slack L0=Lnominal+Lslack, where units are in millimeters. 3) The crosshead extension (ΔL) is set to zero (0.0 mm). 4) The crosshead displacement (mm) is set to zero (0.0 mm). At this position the engineering strain is zero, 0.0. Engineering strain is calculated as the change in length (ΔL) divided by the initial length (L0). Engineering strain=ΔL/L0. For one test cycle, the grips move apart at the initial speed of 1 mm/s until the engineering strain endpoint of 0.03 mm/mm is exceeded, immediately followed by the grips moving toward each other at the initial speed of 1 mm/s until the crosshead signal becomes less than the crosshead return position of 0 mm. The test cycle is repeated until a total of 10 cycles is complete.
The test is executed by inserting the test specimen into the grips such that the long axis of the specimen is parallel and centered with the motion of the crosshead. Start the test and continuously collect time, force and displacement data at a data acquisition rate of 100 Hz.
Construct a graph of load (N) versus displacement for all ten cycles. For each cycle, perform the following. Record peak load to the nearest 0.01 N. Calculate the energy to peak (Epeak) as the area under the load versus displacement curve from the cycle start to the strain endpoint of 0.03 mm/mm (during the loading portion of the cycle) and record to the nearest 0.01 N*mm. Calculate the return energy (Ereturn) as the area under the load versus displacement curve from the strain endpoint of 0.03 mm/mm to the crosshead return of 0 mm (during the unloading portion of the cycle) and record as recovery energy to the nearest 0.01 N*mm. Calculate the normalized energy to peak (NEpeak) as the energy to peak divided by the initial length, where NEpeak=Epeak/L0, and record to the nearest 0.01 mN. Calculate the normalized return energy (NEreturn) as the return energy divided by the initial length (NEreturn=Ereturn/L0), and record to the nearest 0.01 mN. Units of NEpeak and NEreturn are milliNewtons (mN).
Now construct a graph of engineering stress (o) versus engineering strain for all ten cycles, and for each cycle perform the following. Engineering stress, in units of N/mm2, is the load divided by the cross sectional area of the specimen, where the cross sectional area is the specimen width (w) multiplied by the thickness (t), σ=Load/(w*t). Determine the modulus, or slope of the stress versus strain curve for a line between the point that occurs at the minimum force and the point that occurs at the maximum force (during the loading portion of the cycle) and record as modulus to the nearest 0.01 N/mm2. Calculate stiffness by multiplying the modulus by the specimen thickness and record as tensile stiffness to the nearest 0.01 N/mm. The strain of the test specimen at the beginning of the cycle is defined by the strain when the slack preload of 0.05 N is exceeded for that cycle (during the loading portion of the cycle), and is recorded as cycle initial strain to the nearest 0.01 mm/mm. The strain of the test specimen at the end of the cycle is defined by the strain when the load becomes less than the preload of 0.05 N for that cycle (during the unloading portion of the cycle), and is recorded as permanent strain to the nearest 0.01 mm/mm. In like fashion, the overall procedure is now repeated for all five replicates.
The arithmetic mean among the five replicate test specimens is calculated for each of the parameters, for each of the ten cycles, and reported as Peak Load to the nearest 0.01 N, Normalized Energy to Peak to the nearest 0.01 mN, Normalized Recovery Energy to the nearest 0.01 mN, Tensile Stiffness to the nearest 0.01 N/mm, Cycle Initial Strain to the nearest 0.01 mm/mm, and Permanent Strain to the nearest 0.001 mm/mm.
The spacing between the discreet structural bond sites that are used to create a quilt-like pattern on absorbent article samples, and the overall area taken up by the sum of those elements in a specified region of the sample are measured on images of the absorbent article sample acquired using a flatbed scanner. The scanner is capable of scanning in reflectance mode at a resolution of 2400 dpi and 8 bit grayscale. A suitable scanner is an Epson Perfection V750 Pro from Epson America Inc., Long Beach CA, or equivalent. The scanner is interfaced with a computer running an image analysis program. A suitable program is ImageJ v. 1.52, National Institute of Health, USA, or equivalent. The sample images are distance calibrated against an acquired image of a ruler certified by NIST. To enable maximum contrast, the specimen is backed with an opaque, black background of uniform color prior to acquiring the image. All testing is performed in a conditioned room maintained at about 23±2° C. and about 50±2% relative humidity.
The test sample is prepared as follows. Remove the absorbent article from any wrapper present. If the article is folded, gently unfold it and smooth out any wrinkles. If wings are present, extend them but leave the release paper intact. The test samples are conditioned at about 23° C.±2 C.° and about 50%+2% relative humidity for 2 hours prior to testing.
Images are obtained as follows. The ruler is placed on the scanner bed such that it is oriented parallel to the sides of the scanner glass. An image of the ruler (the calibration image) is acquired in reflectance mode at a resolution of 2400 dpi (approximately 94 pixels per mm) and in 8-bit grayscale. The calibration image is saved as an uncompressed TIFF format file. After obtaining the calibration image, the ruler is removed from the scanner glass and the test sample is scanned under the same scanning conditions as follows. Place the test sample onto the center of the scanner glass and secure, if necessary, such that it lies flat with the body-facing surface of the sample facing the scanner's glass surface. The sample is oriented in such a way that the entire sample is within the glass surface. The black background is placed on top of the specimen, the scanner lid is closed, and a scanned image of the entire sample is acquired with the same settings as used for the calibration image. The sample image is saved as an uncompressed TIFF format file.
The sample image is analyzed as follows. Open the calibration image file in the image analysis program, and calibrate the image resolution using the imaged ruler to determine the number of pixels per millimeter. Now open the sample image in the image analysis program, and set the distance scale using the image resolution determined from the calibration image. Now visually inspect the pattern of emboss elements present on the sample in the image and identify the zones of the pattern that are to be analyzed. For example the absorbent article can be divided into three equal lengths zones in the machine direction such as the front one third zone, zone 1, the central one third zone, zone 2 and the end one third zone, zone 3 as example. Use the image analysis tools to draw a shape along the outer perimeter of the first discreet zone to be analyzed. Measure the area of this first zone and record as Zone 1 Total Area to the nearest 0.01 mm2. Now measure the area of each individual, discreet emboss element that lies inside of the zone 1 perimeter as follows. Draw a minimum bounding circle around an individual emboss element such that no portion of the emboss element lies outside of the bounding circle. Now measure the area of the bounding circle for that emboss element and record the emboss element area to the nearest 0.01 mm2. In like fashion, measure the area of every emboss element, including portions of emboss elements, that lie inside zone 1 and record each to the nearest 0.01 mm2. Now sum the areas of all of the emboss elements inside of zone 1 and record as Zone 1 Total Emboss Element Area to the nearest 0.01 mm2. Divide the Zone 1 Total Emboss Element Area by the Zone 1 Total Area then multiply by 100 and record as Zone 1% Total Area Represented by Emboss Elements. The spacing between each discreet emboss element inside of zone 1 is measured as follows. Measure the distance from the center of the minimum bounding circle drawn around a discreet emboss element inside of zone 1, as described herein, to the center of the minimum bounding circle drawn around the nearest neighboring discreet emboss element inside of zone 1, and record this distance as emboss spacing to the nearest 0.01 mm. In like fashion, repeat for all neighboring emboss elements inside of zone 1, and record each distance to the nearest 0.01 mm. Now calculate the arithmetic mean among all measured emboss spacings measured between nearest neighbors inside of zone 1, and record as Zone 1 Emboss Spacing to the nearest 0.01 mm.
In like fashion, the entire procedure is repeated for each additional zone containing emboss elements that is present on the test sample and label accordingly as Zone 2, Zone 3, etc.
The thickness of a test specimen is measured as the distance between a reference platform on which the specimen rests and a pressure foot that exerts a specified amount of pressure onto the specimen over a specified amount of time. For purposes herein, thickness is measured and reported at two different confining pressures (7 g/cm2 and 70 g/cm2). All measurements are performed in a laboratory maintained at 23° C.±2 C.° and 50%±2% relative humidity and test specimens are conditioned in this environment for at least 2 hours prior to testing.
Thickness is measured with a manually-operated micrometer equipped with a pressure foot capable of exerting a steady pressure (7 g/cm2 and 70 g/cm2) onto the test specimen. The manually-operated micrometer is a dead-weight type instrument with readings accurate to 0.01 mm. A suitable instrument is Mitutoyo Series 543 ID-C Digimatic, available from VWR International, or equivalent. The pressure foot is a flat ground circular movable face with a diameter that is smaller than the test specimen and capable of exerting the required pressure. A suitable pressure foot has a diameter of 25.4 mm, however a smaller or larger foot can be used depending on the size of the specimen being measured. The test specimen is supported by a horizontal flat reference platform that is larger than and parallel to the surface of the pressure foot. The system is calibrated and operated per the manufacturer's instructions.
Measurements are made on test specimens taken from rolls or sheets of the raw material, or test specimens obtained from a material layer removed from an absorbent article. When excising the material layer from an absorbent article, use care to not impart any contamination or distortion to the layer during the process. The excised layer should be free from residual adhesive and any fibers that may have transferred from underlying layers. To ensure that all adhesive and any transferred fibers are removed, soak the layer in a suitable solvent that will dissolve the adhesive and release any transferred fibers present without adversely affecting the material itself. One such solvent is THF (tetrahydrofuran, CAS 109-99-9, for general use, available from any convenient source). After the solvent soak, the material layer is allowed to thoroughly air dry in such a way that prevents undue stretching or other deformation of the material. After the material has dried, a test specimen is obtained from an area free of folds or wrinkles, and it must be larger than the pressure foot.
To measure thickness at a confining pressure of 7 g/cm2, first zero the micrometer against the horizontal flat reference platform. Place the test specimen on the platform with the test location centered below the pressure foot. Gently lower the pressure foot with a descent rate of 3.0 mm+1.0 mm per second until the full pressure is exerted onto the test specimen. Wait 5 seconds and then record the thickness of the test specimen to the nearest 0.01 mm. In like fashion, repeat for a total of ten replicate test specimens. Calculate the arithmetic mean for all thickness measurements obtained at a confining pressure of 7 g/cm2 and report as Thickness at 7 g/cm2 to the nearest 0.01 mm.
To measure thickness at a confining pressure of 70 g/cm2, first zero the micrometer against the horizontal flat reference platform. Place the test specimen on the platform with the test location centered below the pressure foot. Gently lower the pressure foot with a descent rate of 3.0 mm+1.0 mm per second until the full pressure is exerted onto the test specimen. Wait 5 seconds and then record the thickness of the test specimen to the nearest 0.01 mm. In like fashion, repeat for a total of ten replicate test specimens. Calculate the arithmetic mean for all thickness measurements obtained at a confining pressure of 70 g/cm2 and report as Thickness at 70 g/cm2 to the nearest 0.01 mm.
The flex bond embossment length, flex bond land area length between two adjacent flex bond embossments, the flex bond channel width, and the flex bond channel depth of the flex bond channel regions formed near the middle region 22 of an absorbent article test sample are measured using optical profilometry to obtain the areal surface topography of the body facing side of the test sample. The flex bond embossment length, flex bond land area length between two adjacent embossments, and the flex bond channel width of the flex bond channel are measured at the base of the depressions, and the depth of the flex bond channel is measured relative to an adjacent, non-channeled region located within the central absorbent zone 306. Additionally, the bending resistance properties of prepared test specimens of the flex bond channel regions are measured on a universal constant rate of extension test frame. All testing is performed in a room controlled at 23° C.±3° C. and 50%±2% relative humidity, and test samples and specimens are conditioned in this environment for at least 2 hours prior to testing.
For the flex bond embossment length, length of the land area between flex bond embossments, channel width and channel depth methods, three-dimensional (3D) surface topography images of the body-facing side of the test sample are recorded using an optical 3D surface topography measurement system. A suitable optical 3D surface topography measurement system is the MikroCAD Premium instrument commercially available from LMI Technologies Inc., Vancouver, Canada, or equivalent. The system includes the following main components: a) a Digital Light Processing (DLP) projector with direct digital controlled micro-mirrors; b) a CCD camera with at least a 1600×1200 pixel resolution; c) projection optics adapted to a measuring area of at least 140 mm×105 mm; d) recording optics adapted to a measuring area of 140 mm×105 mm; c) a table tripod based on a small hard stone plate; f) a blue LED light source; g) a measuring, control, and evaluation computer running surface texture analysis software (a suitable software is MikroCAD software with MountainsMap® technology, or equivalent); and h) calibration plates for lateral (XY) and vertical (Z) calibration available from the vendor. The optical 3D surface topography measurement system measures the surface height of a sample using the digital micro-mirror pattern fringe projection technique. The result of the measurement is a 3D image of surface height (defined as the Z axis) versus displacement in the horizontal (XY) plane. The system has a field of view of 140×105 mm with an XY pixel resolution of approximately 85 microns. The height resolution is set to 0.5 micron/count, with a height range of +/−10 mm. Prior to testing, the instrument is calibrated according to manufacturer's specifications using the calibration plates for lateral (XY plane) and vertical (Z axis) available from the vendor.
Prepare the absorbent article test sample for surface topography measurements, and subsequent channel MD bending resistance measurements, as follows. Unfold the absorbent article if necessary but keep the protective covering over the panty fastening adhesive (i.e., wrapper or release paper) in place. Identify and label the front and rear of the article. Additionally, identify and label the left and right sides of the article, with respect to the wearer's left and right. If the article was previously folded, use scissors or an equivalent sharp cutting device to make a cut along the width of the article at a location that is about 1 cm inboard and parallel to the front fold line such that any residua of folded or creased material is removed and discarded from the front portion of the article. In like fashion, make a cut along the width of the article at a location that is about 1 cm inboard and parallel to the rear fold line to remove and discard any residua of folded or creased material from the rear portion of the article. After making the cuts, the remaining central portion of the absorbent article is retained as the test sample with a length of about 60 mm but not less than 40 mm. With the residua of folded material removed, the test sample will lie flat against a horizontal rigid surface. Now remove the protective covering from the panty fastening adhesive and apply a light dusting of talc powder to the adhesive to mitigate tackiness. In like fashion, prepare a total of five replicate test samples.
Acquire a 3D surface topography image of the test sample as follows. Transfer the test sample onto the MikroCAD (or equivalent) table beneath the camera. Orient the test sample such that the longitudinal axes of the left and right flex bond channel regions are perpendicular to the long axis (X axis) of the instrument's field of view. A 3D surface topography image of the test sample is collected following the instrument manufacturer's recommended measurement procedures, which may include focusing the measurement system and performing a brightness adjustment. No pre-filtering options are used. The collected height image file is saved to the evaluation computer running the surface texture analysis software.
The 3D surface topography image is opened in the surface texture analysis software. The following filtering procedure is then performed on the image: 1) removal of invalid points; 2) a 3×3 pixel median filter to remove noise; and 3) a 3×3 pixel mean filter to smooth the surface.
To measure the flex bond embossment length, “L”, a two-dimensional (2D) line profile (a subsampling of the 3D surface image) is extracted from a location within one of the individual depressed regions within the flex bond channel regions that is perpendicular to the short side of the depression (i.e., the line traverses the longitudinal axis of the depression). This line profile extends across the entire length of the individual channel depression along its central longitudinal axis and includes non-depressed regions directly adjacent to both ends of the channel. One of skill in the art knows if the resulting line profile is not generally representative of the general contour of the flex bond channel region, owing to measurement noise or the presence of local wrinkling or a malformed channel (i.e. a channel that has a depth less than 1 mm as determined by the Flex Bond Channel Depth Method described herein), that another test location at a separate depressed region of the flex bond channel should be measured such that no such artifacts exist. Now create the height profile of the line (height (mm) versus line length (mm)). It will be obvious to one of skill in the art where the flex bond channel region (minimum Z value) and the non-channeled regions (maximum Z values adjacent to the channel) are located on the height profile, for example as depicted in
The five replicate test samples are retained and used for the subsequent flex bond land area length measurements.
To measure the length of the land area “S” between two individual, adjacent depressed regions (embossments) within a flex bond channel, a two-dimensional (2D) line profile (a subsampling of the 3D surface image) is extracted as follows. This line profile includes the entire lengths of two individual, adjacent channel depressions along their central longitudinal axes and additionally includes non-depressed regions directly adjacent to both the leading edge of the first depressed region and the trailing edge of the second, adjacent depressed region. One of skill in the art knows if the resulting line profile is not generally representative of the general contour of the flex bond channel region, owing to measurement noise or the presence of local wrinkling or a malformed channel (i.e. a channel that has a depth less than 1 mm as determined by the Flex Bond Channel Depth Method described herein), that another test location that includes a different set of two adjacent depressed regions of the flex bond channel should be measured such that no such artifacts exist. Now create the height profile of the line (height (mm) versus line length (mm)). It will be obvious to one of skill in the art where the flex bond channel regions (minimum Z values) and the non-channeled regions (maximum Z values adjacent to the channel) are located on the height profile, for example as depicted in
The five replicate test samples are retained and used for the subsequent flex bond channel width measurements.
To measure the flex bond channel width, “A”, a two-dimensional (2D) line profile (a subsampling of the 3D surface image) is extracted from a location within one of the individual depressed regions within the flex bond channel regions that is perpendicular to the long side of the depression (i.e., the line traverses the width of the depression). This line profile extends across the entire width of the individual channel depression along its central lateral axis and includes non-depressed regions directly adjacent to both sides of the channel. One of skill in the art knows if the resulting line profile is not generally representative of the general contour of the flex bond channel region, owing to measurement noise or the presence of local wrinkling or a malformed channel (i.e., a channel that has a depth less than 1 mm as determined by the Flex Bond Channel Depth Method described herein), that another test location at a separate depressed region of the flex bond channel should be measured such that no such artifacts exist. Now create the height profile of the line (height (mm) versus line length (mm)). It will be obvious to one of skill in the art where the flex bond channel region (minimum Z value) and the non-channeled regions (maximum Z values adjacent to the channel) are located on the height profile, for example as depicted in
The five replicate test samples are retained and used for the subsequent flex bond channel depth measurements.
The test samples from the flex bond channel width method are further prepared for the channel depth measurement as follows. Draw a line that is roughly 35 mm long on the body facing surface of the test sample within each of the flex bond channel regions (left and right) to depict the location where the flex bond channel region depth will be measured and the test specimen for the bending resistance test will be subsequently taken. The left and right flex bond channel regions are those that have a longitudinal direction that is generally parallel to the longitudinal axis of the absorbent article. In like fashion, prepare the remaining four replicate test samples such that a total of ten flex bond channel regions (5 right and 5 left) can be analyzed. Numerically label each test sample (i.e., i-v) such that the test samples can be tracked throughout each subsequent measurement.
Acquire a 3D surface topography image of the first test sample, i, as follows. Transfer the test sample onto the MikroCAD (or equivalent) table beneath the camera. Orient the test sample such that the longitudinal axes of the left and right flex bond channel regions are perpendicular to the long axis (X axis) of the instrument's field of view. A 3D surface topography image of the test sample is collected following the instrument manufacturer's recommended measurement procedures, which may include focusing the measurement system and performing a brightness adjustment. No pre-filtering options are used. The collected height image file is saved to the evaluation computer running the surface texture analysis software.
The 3D surface topography image is opened in the surface texture analysis software. The following filtering procedure is then performed on the image: 1) removal of invalid points; 2) a 3×3 pixel median filter to remove noise; and 3) a 3×3 pixel mean filter to smooth the surface. A two-dimensional (2D) line profile (a subsampling of the 3D surface image) is extracted from a location that is perpendicular to the direction of the flex bond channel regions. This line profile extends across the entire width (left to right) of the test sample and intersects both the left and right flex bond channel regions on the test sample at 90 degrees. The line profile is drawn such that it intersects a portion of the channels where the 35 mm line was previously drawn during sample prep. One of skill in the art knows if the resulting line profile is not generally representative of the general contour of the flex bond channel regions, owing to measurement noise or the presence of local wrinkling or a malformed channel, that another test sample should be prepared and measured such that no such artifacts exist. Now create the height profile of the line (height (mm) versus line length (mm)). It will be obvious to one of skill in the art where the flex bond channel regions (minimum Z values) and the non-channeled region (maximum Z values between the channels) are located on the height profile, for example as depicted in
The line height profile raw data is imported and processed in a spreadsheet program, such as Excel, or equivalent. Determine the Z minimum value for the flex bond channel region on the left side of test sample i, and record as ZminiL, to the nearest 0.1 mm. In like fashion, determine the Z minimum value for the flex bond channel region on the right side of test sample i, and record as ZminiR to the nearest 0.1 mm. The height of the non-channeled region along the portion of the line that lies between the left and right flex bond channel regions is Zmaxi. Zmaxi is the calculated arithmetic mean of all of the height values located along a 10 mm path length that is centered over the midpoint distance between the left and right flex bond channel regions along the line. To note, Zmaxi is located within the central absorbent zone 306. If, however, the non-channeled region between the left and right flex bond channel regions is too narrow and thus has some level of compression due to the close proximity of the channel regions, a more suitable non-channeled region is chosen as Zmaxi, such that Zmaxi most represents the intended height of a non-channeled region of the article within central absorbent zone 306 of the test sample. Calculate the depth of the flex bond channel region on the left side of test sample i by subtracting ZminiL from Zmaxi, and record as left channel depth, DiL, to the nearest 0.1 mm. In like fashion, calculate the depth of the flex bond channel region on the right side of test sample i by subtracting ZminiR from Zmaxi, and record as right channel depth, DiR, to the nearest 0.1 mm. Now calculate the arithmetic mean of the DiL and DiR values measured for test sample i, and record as channel depth, Di, to the nearest 0.1 mm. In like fashion, repeat the channel depth measurement for all five replicate test samples, i-v, such that a total of ten flex bond channel regions (5 right and 5 left) are analyzed, and channel depth is recorded for each test sample to the nearest 0.01 mm (i.e., Di-Dv). Now calculate the arithmetic mean across the five channel depths (Di-Dv) calculated for the five replicate test samples, and report as Dry Channel Depth, D, to the nearest 0.01 mm.
Each numerically labeled replicate test sample is retained for the subsequent Flex Bond Channel MD Bending Resistance Method.
MD bending resistance of the prepared test specimens is measured on a universal constant rate of extension (CRE) test frame, such as the MTS Alliance using TestSuite Software, as available from MTS Systems Corp., Eden Prairie, MN, or equivalent. The CRE test frame is equipped with a 3 point bend fixture and a load cell for which the forces measured are within 1% to 99% of the limit of the cell (preferably a 10 N load cell). The bottom stationary fixture consists of two cylindrical bars 3.175 mm in diameter by 110 mm in length, made of polished stainless steel each mounted on each end with frictionless roller bearings. These 2 bars are mounted horizontally, aligned front to back and parallel to each other, with top radii of the bars vertically aligned and are free to rotate around the diameter of the cylinder by the frictionless bearings. Furthermore, the fixture allows for the two bars to be move horizontally away from each other on a track so that a gap can be set between them while maintaining their orientation. The top fixture consists of a third cylinder bar also 3.175 mm in diameter by 110 mm in length, made of polished stainless steel mounted on each end with frictionless roller bearings. When in place the bar of the top fixture is parallel to and aligned front to back with the bars of the bottom fixture and is centered between the bars of the bottom fixture. Both fixtures include an integral adapter appropriate to fit the respective position on the universal test frame and lock into position such that the bars are orthogonal to the motion of the crossbeam of the test frame.
Prepare the test specimens for the bending resistance measurement from the numerically labeled test samples previously prepared for the flex bond channel depth measurement as follows. Each individually prepared test specimen is 5.3 mm wide and has a length of at least 35 mm. The width of the test specimen is centered over the width of the flex bond channel region, and the length of the test specimen is parallel to the longitudinal direction of the channel. The test specimen includes the channel region where the 35 mm line was previously drawn within the channel during sample prep. From each of the numerically labeled test samples, two test specimens are prepared; one from the flex bond channel region on the left side of the test sample and one from the flex bond channel region on the right side of the test sample. Each test specimen is obtained from the same region of the flex bond channel region that was previously analyzed for channel depth, denoted by the 35 mm line drawn during sample prep. A total of ten flex bond channel region test specimens are prepared (5 left and 5 right) and numerically labeled (i.e., iL-vL and iR-vR).
Set the gap (“span”) between the bars of the lower fixture to 20 mm+0.5 mm (center of bar to center of bar) with the upper bar centered at the midpoint between the lower bars. Load the first test specimen, it, such that its long side is perpendicular to and resting on the two lower bars of the fixture, and ensure it is centered under the upper bar with the body-facing surface of the test specimen facing the upper bar. Move the vertical position of the upper bar until the bottom edge of the upper bar is 1 mm above the surface of the test specimen and then zero the crosshead position.
Program the universal test frame for a flexural bend test, to move the crosshead such that the top fixture moves down with respect to the lower fixture at a rate of 1.0 mm/see for a total distance of 12 mm from the zero position. The crosshead is then immediately returned to the original gage at a rate of 1.0 mm/s. Force (N) and displacement (mm) data are continuously collected at 50 Hz throughout the test. The test specimen width is recorded as 5.3 mm. Start the test and continuously collect time, force and displacement data.
Construct a graph of force (N) versus displacement (mm) for test specimen iL. From the graph, determine the maximum peak force and record as flex bond channel MD peak load, MD peakiL, to the nearest 0.01 N. The slope of the initial linear portion of the curve, prior to the peak, is calculated and recorded as flex bond channel MD bending resistanceiL, to the nearest 0.005 N/mm. Calculate the energy to peak as the area under the force versus displacement curve from the initial point to the peak force and record as flex bond channel MD energy to peak, MD PEiL, to the nearest 0.01 N*mm. In like fashion, repeat the entire procedure for test specimen iR, taken from the right channel of test sample i. Now calculate the arithmetic mean for each parameter across the values obtained for the left, iL, and right, iR, test specimens, and record as Dry MD peaki, to the nearest 0.01 N; Dry MD bending resistancei, to the nearest 0.005 N/mm; and Dry MD PEi, to the nearest 0.01 N*mm. In like fashion, the procedure is repeated for all ten flex bond channel region test specimens (iL-vL and iR-vR) taken from test samples i-v. Calculate the arithmetic mean for each parameter across the values obtained for test samples i-v, and report as Dry MD Peak to the nearest 0.01 N; Dry MD Bending Resistance to the nearest 0.005 N/mm; and Dry MD Energy to Peak, PE, to the nearest 0.001 N*mm.
Simple dimensions like width, length, and area of specified locations (described herein) on the surface of an absorbent article are measured on images of the absorbent article sample (or prepared test specimen of a given zone) acquired using a flatbed scanner. The scanner is capable of scanning in reflectance mode at a resolution of 2400 dpi and 8 bit grayscale. A suitable scanner is an Epson Perfection V750 Pro from Epson America Inc., Long Beach CA, or equivalent. The scanner is interfaced with a computer running an image analysis program. A suitable program is ImageJ v. 1.52, National Institute of Health, USA, or equivalent. The sample images are distance calibrated against an acquired image of a ruler certified by NIST. To enable maximum contrast, the specimen is backed with an opaque, black background of uniform color prior to acquiring the image. All testing is performed in a conditioned room maintained at about 23±2° C. and about 50±2% relative humidity.
The test sample is prepared as follows. Remove the absorbent article from any wrapper present. If the article is folded, gently unfold it and smooth out any wrinkles. If wings are present, extend them but leave the release paper intact. In like fashion, a total of five replicate intact test samples are prepared. The test samples are conditioned at about 23° C.±2 C.° and about 50%±2% relative humidity for 2 hours prior to testing. To note, the area of test specimens prepared as specified in the basis weight section of the Absorbent Article Caliper, Basis Weight, and Density Method, described herein, is also measured using this imaging technique, and no further preparation of those test specimens is required.
Images are obtained as follows. The ruler is placed on the scanner bed such that it is oriented parallel to the sides of the scanner glass. An image of the ruler (the calibration image) is acquired in reflectance mode at a resolution of 2400 dpi (approximately 94 pixels per mm) and in 8-bit grayscale. The calibration image is saved as an uncompressed TIFF format file. After obtaining the calibration image, the ruler is removed from the scanner glass and the test sample, or test specimen, is scanned as follows. Place the test sample, or prepared test specimen, onto the center of the scanner glass and secure, if necessary, such that it lies flat with the body-facing surface of the test sample, or prepared test specimen, facing the scanner's glass surface. The test sample, or prepared test specimen, is oriented in such a way that the entire test sample, or prepared test specimen, is within the glass surface. The black background is placed on top of the test sample, or prepared test specimen, the scanner lid is closed, and a scanned image of the entire test sample, or prepared test specimen, is acquired with the same settings as used for the calibration image. The test sample, or prepared test specimen image is saved as an uncompressed TIFF format file.
The test sample image is analyzed to make width and length measurements as follows. Open the calibration image file in the image analysis program, and calibrate the image resolution using the imaged ruler to determine the number of pixels per millimeter. Now open the test sample image in the image analysis program, and set the distance scale using the image resolution determined from the calibration image. Linear measurements are made using the line measurement tool within the image analysis software. As depicted in
The test specimen images of the central absorbent zone and outer absorbent zone are analyzed as follows. Open the calibration image file in the image analysis program, and calibrate the image resolution using the imaged ruler to determine the number of pixels per millimeter. Now open the test specimen image in the image analysis program, and set the distance scale using the image resolution determined from the calibration image. Area measurements are made using the freehand selection tool, or equivalent, within the image analysis software to draw a shape that runs along the outer perimeter of the prepared test specimen. Now measure the area of the drawn shape and record as area to the nearest 0.01 mm2, denoting the zone as either central or outer absorbent zone, and also denoting the corresponding sample number. In like fashion, repeat until the area of each of the five replicate test specimens from each zone (central and outer absorbent zones) is measured and recorded, denoting the corresponding sample number for each replicate. Now proceed back to the basis weight portion of the Absorbent Article Caliper, Basis Weight, and Density Method.
The caliper, basis weight, and density method specifies how these parameters are measured for two different test locations on an absorbent article sample. Referring to
The absorbent article test samples are conditioned at 23° C.±3° C. and 50%±2% relative humidity two hours prior to testing. Remove the test sample from its outer wrapper, then remove the protective cover/release paper from the panty fastening adhesive on the garment facing side of the sample. Lightly dust the panty fastening adhesive with talc powder to mitigate any tackiness. In like fashion, a total of five replicate test samples are prepared. The test samples are labeled consecutively as sample 1 through sample 5 by marking a small number on the backsheet/garment side of each sample.
Caliper (or “thickness”) is measured at specified test locations on the absorbent article sample using a manually-operated micrometer equipped with a pressure foot capable of exerting a steady pressure of 7 g/cm2. The manually-operated micrometer is a dead-weight type instrument with readings accurate to 0.01 mm. A suitable instrument is Mitutoyo Series 543 ID-C Digimatic, available from VWR International, or equivalent. The pressure foot is a flat circular moveable face with a diameter no greater than 25.4 mm. The test sample is supported by a horizontal flat reference platform that is larger than and parallel to the surface of the pressure foot. Zero the micrometer against the horizontal flat reference platform. Place the test sample onto the platform, with the test location centered beneath the pressure foot. The pressure foot is lowered by hand with a descent rate of 3±1 mm/s until the full weight of the pressure is exerted onto the sample. After 5 seconds elapse, the thickness is recorded as absorbent article caliper to the nearest 0.01 mm, denoting the test location as either central or outer absorbent zone, and also denoting the sample number, as previously marked. As specified, the caliper is measured at three separate, non-overlapping regions within the central absorbent zone 306 of each intact absorbent article sample. The arithmetic mean of the caliper values collected for the central absorbent zone 306 across all five replicate samples is calculated and reported as Absorbent Article Caliper in the Central Absorbent Zone (or “T”) to the nearest 0.01 mm. Now the caliper is measured at three separate, non-overlapping regions within the outer absorbent zone 325 of each intact absorbent article sample. The arithmetic mean of the caliper values collected for the outer absorbent zone 325 across all five replicate samples is calculated and reported as Absorbent Article Caliper in the Outer Absorbent Zone to the nearest 0.01 mm. Proceed to the basis weight measurement using the same prepared and numbered test samples.
The basis weight of the central absorbent zone 306 and the outer absorbent zone 325 are measured separately for each prepared test sample using specially machined cutting dies. A first cutting die in the exact shape of the outer absorbent zone is prepared such that the cutting line of the die is aligned with the exact perimeter of the entire region designated as the outer absorbent zone 325, as depicted in
The density of the central absorbent zone 306 and the outer absorbent zone 325 are calculated as follows. For the central absorbent zone test specimen from Sample 1, divide the basis weight in g/m2 (absorbent article basis weight, central absorbent zone, sample 1) by the caliper, mm (absorbent article caliper, central absorbent zone, sample 1), then divide the quotient by 1000 and record as absorbent article density of the central absorbent zone to the nearest 0.001 g/m3. In like fashion, calculate density of the central absorbent zone for all five replicate test specimens. Now calculate the arithmetic mean of density across all five test specimens of the central absorbent zone, and report as Absorbent Article Density of the Central Absorbent Zone to the nearest 0.001 g/m3. For the outer absorbent zone test specimen from Sample 1, divide the basis weight in g/m2 (absorbent article basis weight, outer absorbent zone, sample 1) by the caliper, mm (absorbent article caliper, outer absorbent zone, sample 1), then divide the quotient by 1000 and record as absorbent article density of the outer absorbent zone to the nearest 0.001 g/m3. In like fashion, calculate density of the outer absorbent zone for all five replicate test specimens. Now calculate the arithmetic mean of density across all five test specimens of the outer absorbent zone, and report as Absorbent Article Density of the Outer Absorbent Zone to the nearest 0.001 g/m3.
The basis weight of the inner core layer, at the points in the central absorbent zone and the outer absorbent zone will typically be known by the manufacturer from the product making specification. However, if the basis weight is not known for a given article, the basis weight can be measured in the following manner.
The basis weight of the inner core layer within the central absorbent zone 306 and the outer absorbent zone 325 are measured separately for each of the retained absorbent article test specimens that were prepared in the basis weight section of the Absorbent Article Caliper, Basis Weight, and Density Method, as described herein. There will be five absorbent article test specimens that are the central absorbent zone (labeled as samples 1-5) and five absorbent article test specimens that are the outer absorbent zone (also labeled as samples 1-5). To note, the measured area values for each test specimens that were previously recorded to calculate the basis weight of the absorbent article central and outer absorbent zones in the basis weight section of the Absorbent Article Caliper, Basis Weight, and Density Method will also be used to calculate the basis weight of the inner core layer from each of these zones.
The inner core layer is removed from the test specimens, the mass recorded, and the basis weight calculated as follows. Begin with the absorbent article test specimen of the central absorbent zone from sample 1. Carefully remove the topsheet layer, backsheet film, the upper nonwoven layer and the lower nonwoven layer from the inner core layer of the test specimen, ensuring that in the process no particles or fibers are lost from the inner core layer. It is understood that, depending on the unique structure of the absorbent article, additional layers may need to be removed from the absorbent article test specimen in order to obtain a final test specimen that comprises only the inner core layer. Record the mass of the inner core layer test specimen to the nearest 0.001 g, denoting central absorbent zone, sample 1. Divide the mass of the inner core layer from the central absorbent zone of sample 1 by the area of the absorbent article central absorbent zone of sample 1 (previously measured), and record as basis weight of the inner core layer, denoting central absorbent zone, sample 1, to the nearest 0.1 g/m2. In like fashion, repeat the procedure until the basis weight of the inner core layer from the central absorbent zone is measured and recorded for each of the five central absorbent zone test specimen replicates from samples 1 through 5. Calculate the arithmetic mean across the basis weight values obtained for all five central absorbent zone replicates, and report as Inner Core Layer Basis Weight of the Central Absorbent Zone to the nearest 0.1 g/m2. In like fashion, this entire procedure is repeated for the five absorbent article test specimens from the outer absorbent zone of samples 1 through 5, and the arithmetic mean across the five basis weight values is calculated and reported as Inner Core Layer Basis Weight of the Outer Absorbent Zone to the nearest 0.1 g/m2.
The micro-CT measurement method is used to obtain images of the cross-section of a test specimen to enable visualization of the microstructure of an absorbent article, including the interconnectivity of layers within the article in specific regions of interest. These images enable qualitative and quantitative assessments to be made related to the proximity of adjacent layers within the test specimen, and the resultant size and shape of specified zones located within the test specimen. This method is based on analysis of a 3D x-ray sample image obtained on a micro-CT instrument (a suitable instrument is the Scanco μCT 50 available from Scanco Medical AG, Switzerland, or equivalent). The micro-CT instrument is a cone beam microtomograph with a shielded cabinet. A maintenance free x-ray tube is used as the source with an adjustable diameter focal spot. The x-ray beam passes through the sample, where some of the x-rays are attenuated by the sample. The extent of attenuation correlates to the mass of material the x-rays have to pass through. The transmitted x-rays continue on to the digital detector array and generate a 2D projection image of the sample. A 3D image of the sample is generated by collecting several individual projection images of the sample as it is rotated, which are then reconstructed into a single 3D image. The instrument is interfaced with a computer running software to control the image acquisition and reconstruction of the raw data into a 3D image. The 3D image is then analyzed using image analysis software (suitable image analysis software are MATLAB available from The Mathworks, Inc., Natick, MA, and Avizo 2022.2 available from Visualization Sciences Group/FEI Company, Burlington, MA, or equivalents) to identify specified zones with the test specimen, measure the distances between individual layers and zones, thickness of zones as well as any angle created as one zone transitions to another within the test specimen.
A test specimen is excised from the test sample using a very sharp blade as follows. The test specimen is taken from an area free of folds or wrinkles using care to not impart any contamination or distortion to the specimen during the preparation process. The test specimen is excised from a region of the test sample in such a way that it comprises a portion of both the central absorbent zone and the outer absorbent zone, including any transition zone that may be present. The test specimen is roughly 90 mm in diameter. In like fashion, a total of 3 replicate test specimens are prepared from three different test samples. The test specimens are conditioned at about 23° C.±2 C.° and about 50%±2% relative humidity for 2 hours prior to testing.
The micro-CT instrument is set up and calibrated according to the manufacturer's specifications. The test specimen is placed on a low density foam and placed into the appropriate holder. This will allow the test specimen to lay horizontal and be scanned with minimal attenuation from any surrounding material. A single 3D dataset of contiguous 13 μm (microns) isotropic voxels is collected. The 3D data set has dimensions of 96.7 mm on each side in the XY-plane and a sufficient number of slices to fully include the entire Z-direction of the test specimen. Images are acquired with the source at 70 kev and 114 μA with no additional low energy filter. These current and voltage settings may be optimized to produce the maximum contrast in the projection data with sufficient x-ray penetration through the test specimen, but once optimized held constant for all substantially similar test specimens. A total of 3000 projection images are obtained with a total integration of 500 msec integration time and 4 averages per projection. The projection images are reconstructed into a 3D dataset having an isotropic spatial resolution of 13 μm (microns), and saved in 16-bit RAW format to preserve the full detector output signal for analysis. For optimal visualization purposes, the data was scaled to 8 bit using a scale factor of 0.4 and subsampled to 26 micron resolution.
The 3D dataset is loaded into the image analysis software and trimmed (cropped) to a rectangular prism 3D image of the analysis region by removing the surrounding holder and the low density mounting material from the 3D dataset. Trimming is performed such that the maximum amount of the test specimen in the analysis region is retained in the 3D image, and the empty space above and below the test specimen is minimized. Within the 3D image, every 10 cross sectional slices are averaged together to create less noise. This averaging creates a thicker slice representing a 260 micron thick slab along the viewing direction. In-plane resolution is 26 microns.
The 3D image is oriented so that the upper surface (topsheet, or body size of the test specimen) is as close to parallel with the XY-plane as possible. Now qualitative observations can be made regarding the proximity of adjacent layers present in the test specimen including interconnectivity between said layers and the overall shape of the various zones present (i.e., central and outer absorbent zones and the transition between said zones). In addition to the qualitative observations, simple quantitative measures (e.g., thickness of zones, distance between zones, the angle formed as one zone transitions to the other, etc.) are possible using measurement tools available within the image analysis software.
The following data and examples, including comparative examples, are provided to help illustrate the upper and lower nonwoven layers and/or absorbent articles described herein. The exemplified structures are given solely for the purpose of illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the invention.
A series of measurements were performed on nonwoven materials to assess the ability of the material to function as an upper nonwoven layer and/or a lower nonwoven layer in the absorbent core structure described herein. Samples A-G are examples in accordance with the present disclosure. Comparative Sample H is a comparative example. Samples A-G and Comparative Sample H are described in Table 1 below.
Samples A-G and Comparative Sample H were evaluated according to the CD Cyclic Elongation to 3% Strain Method, the Strain to Break Method, Dry CD Ultra Sensitive 3 Point Bending Method, and the Nonwoven Thickness-Pressure Method. The results are shown in Table 2.
1Available as ATB Z87G-40 from Xiamen Yanjan New Material Co. (China)
2Available as Sawasoft ® 53FC041001 from Sandler GmbH (Germany)
3Available as Sawasoft ® 553FC041005 (option 82) from Sandler GmbH (Germany)
4Available as Aura 20 from Xiamen Yanjan New Material Co. (China)
5Available as S25000541R01 from Jacob Holms Industries (Germany)
6Available as PFNZN 18 G BICO8020 PHI 6 from dPFNonwovens Czech S.R.O (Czech Republic)
7Available as PEGZN25 BICO7030 Phobic from dPFNonwovens Czech S.R.O (Czech Republic)
8Available as 3028 from DunnPaper (USA)
It is believed that nonwoven materials suitable for upper and/or lower nonwoven layers can strain (elongate) with a balanced stretch and recover to their original state, thus helping to enable the absorbent core structure and/or absorbent article to recover from deformation during bodily motions. The 3D inner core layer shape described herein is configured to fit closely to the wearer's intimate genitalia and rest between the labial majora. As such, particularly suitable nonwoven materials of the upper nonwoven layer can provide fluid handling performance that can effectively transport fluid deep into the inner core layer to help provide a close and comfortable fit to the body that feels dry. To achieve this, suitable nonwoven materials of the upper nonwoven layer exhibit a relatively low density (e.g., from 0.03 to 0.07 g/cm3 under a pressure of 7 g/cm2) in order to allow fluid to efficiently drain from the upper nonwoven layer into the inner core layer below. In addition, suitable nonwoven materials of the upper nonwoven layer can maintain a relatively lofty thickness even under high bodily compressive forces (i.e., a pressure of 70 g/cm2) so that fluid residing within the inner core layer is not expelled back out of the absorbent core structure which can create a wet feeling on the body. Nonwoven materials suitable for upper and/or lower nonwoven layer may also need to be able to follow and assume the complex 3D inner core layer shapes described herein.
It was found that Samples A-C and E are suitable materials for upper and/or lower nonwoven layers. In particular, Samples A-C and E had a Permanent Strain of 0.013 mm/mm or less, demonstrating that the materials can elongate and recover, and had a Strain to Break of greater than 10% before tearing. Samples A-C and E also required less energy to bend (demonstrated by a Dry Bending Energy of less than 1.6 N*mm) while recovering from bending with a Dry Recovery Energy of greater than 0.03 N*mm. Samples A-C and E exhibited a relatively low density of from 0.03 to 0.07 g/cm3 under a pressure of 7 g/cm2 and a Thickness at 7 g/cm2 of pressure of from 0.80 to 1.21 mm, demonstrating that these materials are both lofty and have a more open fiber network structure that can help with efficient fluid handling performance.
It was found that Sample D had a Permanent Strain of 0.016 mm/mm, demonstrating that the material will likely elongate strongly during manufacture and/or in-use without recovering to its initial state. As such, it is believed that the material may not be capable of maintaining the structural stability and shape of the inner core layer. At the same time, Sample D was found to be highly compressible under bodily pressures, as demonstrated by a Thickness at 70 g/cm2 of 0.19 mm, illustrating that the material will become more dense under bodily compression and likely will not be sufficiently drained of fluid by the inner core layer. Samples F and G exhibited a Dry Recovery Energy of less than 0.03 N*mm, demonstrating that the materials will not recover from deformation, making the material insufficient to function as an upper nonwoven layer. However, when combined with an upper nonwoven layer described herein, Samples D, F, and G are suitable materials for a lower nonwoven layer.
Comparative Sample H exhibited a Strain to Break of less than 5% and a Thickness at 70 g/cm2 of less than 0.2 mm. In addition, it was found that Comparative Sample H tears when wet. As such, Comparative Sample H is insufficient to function as an upper or lower nonwoven layer.
Table 3 is provided for the convenience of the reader. Table 3 includes a non-exhaustive list of properties as well as a non-exhaustive list of corresponding values for each of the properties that particularly suitable upper nonwoven layers of the present disclosure may exhibit.
Absorbent articles were tested to assess the impact of flex bond channel regions on MD dry bending resistance. In particular, the absorbent articles were tested to assess the ability of the flex bond channel region to bend in the MD, that is longitudinal (or front to back) direction. Ex. 1-3 illustrate absorbent articles described herein. A description of Ex. 1-3 are listed in Table 4a. Ex. 1-3 are prepared as described hereafter. Comparative Ex. 4 and Comparative Ex 5 are in-market finished products which have embossed channels and a higher basis weight in the central region. A description of Comparative Ex. 4-5 are listed in Table 4b. Ex. 1-3 and Comparative Ex. 4-5 were evaluated according to the Flex Bond Channel Depth Method and Flex Bond Channel MD Bending Resistance Method, with the results shown in Table 5.
1Available as ATB Z87G-40 from Xiamen Yanjan New Material Co. (China)
6Available as PFNZN 18 G BICO8020 PHI 6 from PFNonwovens Czech S.R.O (Czech Republic)
9Available as R73B from Xiamen Yanjan New Material Co. (China)
10Available as Z73P-24 from Xiamen Yanjan New Material Co. (China)
11Available as Item 9E3-COOSABSORB S from Resolute Alabama (USA)
12Available as Acqualic L705 from Nippon Shokubai (Japan)
The absorbent articles listed in Table 4a were produced as detailed within the specification. Ex. 1-3 have the central absorbent zone and outer absorbent zone as shown and described in
Specifically, the upper nonwoven layer is first introduced onto the forming drum within the laydown section, and under vacuum it is drawn into the 3 dimensional pocket shape. A homogeneous stream of the cellulose and superabsorbent particle material is deposited onto the upper nonwoven layer directly within the forming station. Prior to entering the forming station, the upper nonwoven is coated with a spray adhesive (Technomelt DM 9036U available from Henkel, (Germany), 6 gsm continuous meltblown spirals, 50 mm wide) to provide a stronger connection of the cellulose and superabsorbent particle material to the upper nonwoven layer without hindering the flow of liquid into the cellulose/AGM matrix. On exiting the laydown section, the lower nonwoven web is combined with the nonwoven carrying the homogeneous blend of cellulose and superabsorbent particle material. This lower nonwoven is precoated with adhesive (Technomelt DM 9036U available from Henkel (Germany)) to enable a perimeter seal (10 gsm meltblown spirals, 20 mm wide on the sides) and in the center a 6 gsm, 50 mm wide continuous meltblown spiral adhesive (Technomelt DM 9036U available from Henkel (Germany)) is applied to better integrate the cellulose and superabsorbent particle material. Excess nonwoven material beyond the perimeter seal is removed prior to addition of the topsheet and the backsheet. The topsheet is bonded to the absorbent core structure with a spray adhesive application (Technomelt DM 9036U available from Henkel (Germany), 3 gsm continuous meltblown spirals, 50 mm wide, 250 mm long). In addition, a 12 gsm polypropylene backsheet is bonded to the outward-facing surface of the lower nonwoven with a spray adhesive application (Technomelt DM 9036U available from Henkel (Germany), 3 gsm continuous meltblown spirals, 50 mm wide, 250 mm long).
Ex. 1-3 also have the structural bonds as shown in
Prior to bonding the backsheet, flex bond channel regions are applied to Ex. 1-3 with the pattern shown in
It is found that Ex. 1-3 have a well defined flex bond channel region that are distinct, relatively narrow (as demonstrated by a Dry Channel Width of from 2.1 mm to 2.2 mm) with good depth (as demonstrated by a Dry Channel Depth of 2.6 mm to 3.8 mm). Ex. 1-3 also exhibited a low Dry MD Bending Resistance of 0.013 N/mm to 0.019 N/mm. In contrast, Comp. Ex. 4 & 5 have thicker, stiffer channels that exhibit a high Dry MD Bending Resistance of 0.084 N/mm and 0.131 N/mm, respectively, demonstrating that the channel-like structures in these products have a significantly higher resistance to bending (i.e., are less flexible). Without being limited by theory, it is believed that a consumer wearing the absorbent article depicted in Ex. 1-3 will experience the product conforming to her body with less resistance and pressure on her body, and as a result, will experience a closer more comfortable conforming absorbent article.
Paragraph A. A disposable absorbent article comprising:
Paragraph B. The disposable absorbent article of Paragraph A, wherein the central absorbent zone comprises transition zone, wherein the flex bond channel region is positioned outboard of the transition zone.
Paragraph C. The disposable absorbent article of Paragraph B, wherein flex bond channel region is positioned from about 1 mm to about 10 mm outboard of the transition zone.
Paragraph D. The disposable absorbent article of any of Paragraphs A-C, wherein the absorbent article has a first caliper measured in the central absorbent zone and a second caliper measured in the outer absorbent zone, wherein a ratio of the first caliper to the second caliper is from about 1.2 to about 2.5.
Paragraph E. The disposable absorbent article any of Paragraphs A-D, wherein the absorbent article has a first average density measured in the central absorbent zone and a second average density measured in the outer absorbent zone, wherein the second average density is within about 0 to about 20% of the first density.
Paragraph F. The disposable absorbent article of any of Paragraphs A-E, wherein the absorbent article has a first average density measured in the central absorbent zone and a second average density measured in the outer absorbent zone, wherein the first and second average density are between about 0.045 g/cm3 and about 0.150 g/cm3.
Paragraph G. The disposable absorbent article of any of Paragraphs A-F, wherein the lower nonwoven has a basis weight of from about 10 gsm to about 40 gsm.
Paragraph H. The disposable absorbent article of any of Paragraphs A-G, wherein absorbent article has a caliper measured in the central absorbent zone of from about 2.5 mm to about 6 mm.
Paragraph I. The disposable absorbent article of any of Paragraphs A-H, wherein the polymer fibers of the upper nonwoven layer have a fiber diameter of from about 2.0 Dtex to about 10 Dtex.
Paragraph J. The disposable absorbent article of any of Paragraphs A-I, wherein the polymer fibers of the lower nonwoven layer have a fiber diameter of from about 1.7 Dtex to about 5 Dtex.
Paragraph K. The disposable absorbent article of any of Paragraphs A-J, wherein the flex bond channel region separates the central absorbent zone from the outer absorbent zone.
Paragraph L. The disposable absorbent article of any of Paragraphs A-K, wherein the flex bond channel region has a minimum channel length of about 50 mm.
Paragraph M. The disposable absorbent article of any of Paragraphs A-L, wherein the first basis weight is about 20% to about 100% greater than the second basis weight.
Paragraph N. The disposable absorbent article of any of Paragraphs A-M, wherein the inner core layer is a unitary structure.
Paragraph O. The disposable absorbent article of any of Paragraphs A-N, wherein the absorbent core structure is shaped to substantially follow the shape of the central absorbent zone.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
This application claims the benefit, under 35 USC 119 (c), to U.S. Provisional Patent Application No. 63/519,345 filed on Aug. 14, 2023, which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63519345 | Aug 2023 | US |
