Patent Application
20230381033
The present disclosure relates to absorbent articles, and more particularly, to absorbent articles with absorbent core structure perimeter seal arrangements that seal a portion of the inner core layer yet still sufficiently contains the liquid absorbent material and maintains the conforming features of the absorbent articles.
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. Historically, absorbent core structures for menstrual pad applications utilize cellulose fibers in various ways to manage the complex and varied rheological properties of menstrual fluid and vaginal discharge.
The first approach included cellulose (also known as “fluff” or “pulp”) based thick absorbent cores that can be stiff, bulky, and suffer from structural collapse due to the short fiber lengths of cellulose (<2.5 mm), particularly when loaded with fluid due to cellulose fiber softening when wet. Over time, these thick cellulose rich absorbent cores have been made thinner with the inclusion of absorbent polymer materials, such as absorbent gelling material (“AGM”), to further boost their absorption properties. However, these absorbent core structures are less mechanically strong and even less able to retain their shape, particularly when loaded with liquid exudate. These absorbent core structures can form cracks and tears while in-use and bunch (a permanent deformed shape). These thinner structures tend to be even more densified (thus stiffer) and are often wrapped in a simple cellulose tissue or thin nonwoven layer to keep the AGM inside and reduce core tearing and undesirable bunching while in use.
Other approaches combine these wrapped cellulose and AGM cores with an additional fluid acquisition-distribution layer (above the fluid storage core) to further improve the performance of these simple wrapped cores. This additional acquisition-distribution layer further serves to improve integrity and to some degree tearing and bunching of the wrapped core. These acquisition-distribution layers, however, are not ideal for complex viscous fluids which need to move over the boundary between these layers. To better facilitate fluid partitioning from the acquisition-distribution system to the fluid storage wrapped cellulose and AGM core, the core can be densified to increase capillarity and the ability to pull fluid effectively from the acquisition-distribution layer above. However, densifying this absorbent system comes at the cost of comfort (stiffness) and the ability of the absorbent core structure and/or absorbent article to readily conform to the wearer's unique anatomical geometry.
Another material used in absorbent core structure includes an airlaid core. Airlaid cores are typically composed of cellulose, AGM, and synthetic binder fibers to enhance wet integrity and often a surface coating of a polymer (such as latex) to reduce dust during product manufacture. Because these materials are manufactured at a separate supplier offline and need to be transported and introduced into a fast-moving production line, they are highly densified and stiff. The densification and synthetic binder fibers provide a higher wet integrity in-use and can help facilitate fluid transport from the acquisition-distribution layer to the airlaid core due to higher capillarity. However, this again can be at the cost of comfort (stiffness) and the ability to readily conform to the wearer's unique anatomical geometry due to high bending stiffness.
It is known that absorbent core structures which are shaped to follow (fit within) the user's underwear and inner thigh dimensions may help to provide a comfortable fit that can conform to the body and protect from leaks. Absorbent articles that are centrally narrow while being wider at the front and/or back regions may offer the best combination of comfort and protection. However, the narrow, central portion of these absorbent core structures experience the highest mechanical stress between the thighs during wear. As such, it is difficult to maintain the integrity and resiliency of the absorbent core structure and/or absorbent article in this region. If absorbent materials escape from or shift within the absorbent core structure, the absorbent article may become uncomfortable to wear and may not provide effective fluid handling. Current absorbent articles generally have a full perimeter seal surrounding the absorbent material in order to maintain product integrity and avoid bunching issues. One method of creating such a full perimeter seal is to sandwich the absorbent material between materials which have a substantially greater width than the entire absorbent material and then to cut the material out to follow the shape of the absorbent material. This requires more materials and/or additional manufacturing steps which increases the cost and complexity of manufacturing and may result in increased waste as excess materials are trimmed during manufacturing.
There is a need for improved absorbent articles that provide a comfortable, conformable fit that requires less materials and that can be made without undesirable cost and complexity while still delivering sufficient resiliency and fluid handling.
The present disclosure solves the problem of the complex and costly manufacturing of absorbent articles with conforming features. The absorbent articles of the present disclosure comprise upper and lower nonwoven layers that sandwich an inner core layer comprising a liquid absorbent material. A portion of the inner core layer in the middle region of the absorbent core structure and/or absorbent article is contained within the upper and lower nonwoven layers by sealing a portion of the upper and lower nonwoven layer side regions to define a lateral perimeter seal where adhesive is positioned between the upper nonwoven layer with the lower nonwoven layer and bonds the layers together. This lateral perimeter seal enables the use of narrow upper and/or lower nonwoven layers to partially seal the inner core layer with less material usage and enables a simpler manufacturing process and provides an economic benefit.
A disposable absorbent article comprises a front end region, a middle region, and a back end region; a topsheet; a backsheet; and an absorbent core structure disposed between the topsheet and backsheet. The absorbent core structure comprises (a) an upper nonwoven layer comprising polymer fibers and having a basis weight of from about 30 gsm to about 65 gsm; wherein the upper nonwoven layer comprises a first side region, a laterally opposing second side region, and a first nonwoven lateral width; (b) a lower nonwoven layer comprising polymer fibers and having a basis weight of from about 10 gsm to about 40 gsm; wherein the lower nonwoven layer comprises a first side region, a laterally opposing second side region, and a nonwoven second lateral width; and (c) an inner core layer having a longitudinal inner core length, a first inner core layer lateral width, and a second inner core lateral width. A portion of the inner core layer is disposed between the upper nonwoven layer and the lower nonwoven layer. The inner core layer comprises a liquid absorbent material comprising from about 50% to about 85% cellulosic fibers, by weight of the inner core layer, and from about 15% to about 50% superabsorbent particles, by weight of the inner core layer. The absorbent core structure has an average density of between about 0.045 g/cm3 and about 0.15 g/cm3. The portion of the inner core layer is contained within the upper nonwoven layer and the lower nonwoven layer by sealing a portion of the first side region and the second side region of the upper nonwoven layer with a portion of the first side region and the second side region of the lower nonwoven layer at a lateral perimeter seal, wherein an adhesive is positioned between the upper nonwoven layer and the lower nonwoven layer in the perimeter seal. The lateral perimeter seal is positioned in the middle region and has a longitudinal seal length that is from about 45% to about 90% of the longitudinal inner core length.
A disposable absorbent article comprises a front end region, a middle region, and a back end region; a topsheet; a backsheet; and an absorbent core structure disposed between the topsheet and backsheet. The absorbent core structure comprises (a) an upper nonwoven layer comprising polymer fibers and having a basis weight of from about 30 gsm to about 65 gsm; wherein the upper nonwoven layer comprises a first side region and a laterally opposing second side region; (b) a lower nonwoven layer comprising polymer fibers and having a basis weight of from about 10 gsm to about 40 gsm; wherein the lower nonwoven layer comprises a first side region and a laterally opposing second side region; (c) an inner core layer comprising a first side edge and a laterally opposing second side edge and having a longitudinal inner core length; wherein the inner core layer is positioned between the upper nonwoven layer and the lower nonwoven layer; and (d) an adhesive zone disposed intermediate a portion of at least one of the upper nonwoven layer and the lower nonwoven layer and the inner core layer. The inner core layer comprises a liquid absorbent material comprising a cellulosic fiber and a superabsorbent particle, and wherein the absorbent core structure has an average density of between about 0.045 g/cm3 and about 0.15 g/cm3. The upper nonwoven layer and the lower nonwoven layer substantially surrounds the adhesive zone and the inner core layer. A portion of the adhesive zone extends laterally outboard of the first and second side edges of the inner core layer and bonds the upper nonwoven layer to the lower nonwoven layer at a lateral perimeter seal. A portion of the inner core layer extends laterally outboard of the adhesive zone to define an unsealed portion; wherein the unsealed portion is positioned longitudinally outboard of the lateral perimeter seal.
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 “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, the term “filament” refers to any type of continuous strand produced through a spinning process, a meltblowing process, a melt fibrillation or film fibrillation process, or an electrospinning production process, or any other suitable process to make filaments. The term “continuous” within the context of filaments are distinguishable from staple length fibers in that staple length fibers are cut to a specific target length. In contrast, “continuous filaments” are not cut to a predetermined length, instead, they can break at random lengths but are usually much longer than staple length fibers.
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, 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, may be referred to as “CD”.
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 disposable absorbent articles described herein comprise a topsheet, a backsheet, and an absorbent core structure which comprises an upper nonwoven layer, a lower nonwoven layer, and an inner core layer positioned intermediate the upper and lower nonwoven layers. A portion of the inner core layer in the middle region of the absorbent core structure and/or absorbent article is contained within the upper and lower nonwoven layers by sealing a portion of the upper and lower nonwoven layer side regions to define a lateral perimeter seal where adhesive is positioned between the upper nonwoven layer with the lower nonwoven layer and bond the layers together.
In some configurations, the disposable absorbent article may comprise the following structure (from a wearer-facing surface to an outward-facing surface): a topsheet, an upper nonwoven layer, an inner core layer, a lower nonwoven layer, and a backsheet. In some aspects, the topsheet may be in direct contact with the upper nonwoven layer, the upper nonwoven layer may be in direct contact with the inner core layer, and/or the inner core layer may be in direct contact with the lower nonwoven layer. 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.
Referring to
The flexibility and/or resiliency of the absorbent core structure results in an absorbent article that comfortably conforms 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 fluff/AGM matrix of the inner core layer. This absorbent core structure is 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.
It is believed that wet integrity/shape stability in a cellulose rich absorbent core structure without substantial densification and stiffening results when select resilient upper and lower nonwovens are positioned above and below the fluff/AGM matrix of the inner core layer and joined to and around the fluff/AGM matrix. The upper and lower nonwovens require sufficient recovery force to carry the fluff/AGM matrix back to the original state 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 was surprisingly found that an absorbent core structure could be created without the need for a full perimeter seal surrounding the inner core layer. In particular, it was found that by using substantially straight-sided upper and/or lower nonwoven layers, material usage and waste may be reduced as compared to nonwoven layers that are cut out from a wider web into a shape that follows the inner core layer shape. It was surprisingly found that nonwoven layers which are wider than at least the narrowest, central inner core layer width allows for the creation of a lateral perimeter seal in the middle region (that corresponds to the region that experiences the highest mechanical stress during use) that can effectively contain the liquid absorbent material of the inner core layer and preserve the integrity and fit of the absorbent article. As a result, portions of the inner core layer in the front region and/or back region (which are subject to less mechanical stress) may be left unsealed by a perimeter seal without significantly impacting product integrity, resiliency, and/or performance.
Referring to
The upper nonwoven layer 210 may have a first nonwoven lateral width WN1, and the lower nonwoven layer 220 may have a second nonwoven lateral width WN2. In some configurations, the first and second nonwoven lateral widths WN1,WN2 may be substantially the same. In some configurations, the first and second nonwoven lateral width WN1, WN2 may be different. The first nonwoven lateral width WN1 and/or the second nonwoven lateral width WN2 may be from about 40 mm to about 110 mm, or from 45 mm to about 90 mm, or from about 50 mm to about 80 mm. The upper and/or lower nonwoven layers 210, 220 may have a longitudinal length of from about 100 mm to about 450 mm, or from about 150 mm to about 375 mm. In some configurations, the upper and/or lower nonwoven layers 210, 220 may extend from the front article edge 30 to the back article edge 32. In some configurations, the upper and/or lower nonwoven layers 210, 220 may not extend from the front article edge 30 to the back article edge 32. In some configurations, the upper and/or lower nonwoven layers 210, 220 may have a longitudinal length that is less than a longitudinal inner core length, LC.
The upper and lower nonwoven layers 210, 220 may be generally rectangular, however, in some configurations, the upper and lower nonwoven layers 210, 220 may be shaped, meaning that it is non-rectangular. In some configurations, the upper nonwoven layers 210 may be shaped and the lower nonwoven layer 220 may be rectangular, or vice versa. In some configurations, the upper and/or lower nonwoven layers 210, 220 may have a shaped front and/or back region while the middle region may be substantially straight.
At least a portion of the inner core layer 200 may be disposed between the upper nonwoven layer 210 and the lower nonwoven layer 210. In some configurations, the entire inner core layer 200 may be disposed between the upper nonwoven layer 210 and the lower nonwoven layer 220. The inner core layer 200 extends longitudinally between an inner core layer front edge 424 and an inner core layer back edge 426 and extends laterally from a first side edge 250 and to a second side edge 252. In some configurations, the inner core layer 200 may be shaped. As shown in
An adhesive zone 525 may be disposed intermediate at least one of the upper nonwoven layer 210 and the lower nonwoven layer 220 and the inner core layer 200. The adhesive zone 525 may comprise an adhesive 528 that extends from the first side region 400 of the upper nonwoven layer 210 to the second side region 402 of the upper nonwoven layer 210 and/or from the first side region 406 of the lower nonwoven layer 220 to the second side region 407 of the lower nonwoven layer 220. As shown in
In some configurations, a portion of the inner core layer 200 may be contained within the upper nonwoven layer 210 and the lower nonwoven layer 220 by sealing a portion of the first side region 400 and the second side region 402 of the upper nonwoven layer 210 with a portion of the first side region 406 and the second side region 407 of the lower nonwoven layer 220 to define a lateral perimeter seal 230 where adhesive 528 is positioned between the upper nonwoven layer 210 and the lower nonwoven layer 220. As such, adhesive 528 may bond the upper nonwoven layer 210 with the lower nonwoven layer 220. The lateral perimeter seal 230 may be positioned in the middle region 22 and may have a longitudinal seal length, LS, that is from about 45% to about 90% of a longitudinal inner core length, LC, or from about 50% to about 85%. Lateral perimeter seal 230 may have a maximum seal width, WS, of from about 1 mm to about 15 mm, or from about 2 mm to about 10 mm, or from about 3 mm to about 8 mm.
Without being limited by theory, it is believed that upper and lower nonwoven layers comprising polymer fibers may hold their shape and resist plasticizing when wet when at least partially attached to the liquid absorbent material via a core construction adhesive (applied either directly to the liquid absorbent material or the nonwoven) chosen to achieve a bond but not disrupt the flow of fluid into the liquid absorbent material. It was further found that a lateral perimeter seal having a longitudinal seal length LS of from about 45% to about 90% of the longitudinal inner core length LC and being positioned in the middle region is able to sufficiently contain the liquid absorbent material of the inner core layer during manufacturing and in use and allows the upper and lower nonwoven layers to maintain structural function during physical deformation between the wearer's thighs without separating. This may provide for more efficient manufacturing processes by substantially avoiding contamination of manufacturing lines with liquid absorbent material that may escape from the inner core during processing and may limit potential product integrity or bunching issues during use. In addition, creating a lateral perimeter seal may enable an absorbent core structure to be shaped to conform to inner thigh geometry and to reduce the cost of manufacturing by using less materials, using less complex manufacturing steps, and creating less waste.
With continued reference to
The absorbent core structure 10 may comprise a first unsealed portion 423a where a portion of the inner core layer 200 extends laterally outboard of the adhesive zone 525. In some configurations, the absorbent core structure 10 may comprise a second unsealed portion 423b where a second portion of the inner core layer 200 extends laterally outboard of the adhesive zone 525. Second unsealed portion 423b may be laterally separated from first unsealed portion 423a by a sealed portion 410. In some configurations, the first and second unsealed portions 423a, 423b may be positioned in the back region 23 and may extend longitudinally into a portion of the middle region 22. The absorbent core structure 10 may further comprise a third unsealed portion 421a where a third portion of the inner core layer 200 extends laterally outboard of the adhesive zone 525. In some configurations, the absorbent core structure 10 may comprise a fourth unsealed portion 421b where a fourth portion of the inner core layer 200 extends laterally outboard of the adhesive zone 525. Fourth unsealed portion 421b may be laterally separated from third unsealed portion 421a by a sealed portion 410. In some configurations, the third and fourth unsealed portions 421a, 421b may be positioned in the front region 21 and may extend longitudinally into the middle region 22. It is to be understood that an unsealed portion 420 may also be formed in configurations wherein a portion of the inner core layer perimeter 200a is coterminous with a first or second edge 525a, 525b of the adhesive zone 525, such as shown for example in
The first and second unsealed portions 423a, 423b may have an unsealed longitudinal length L1U that is about 5% to about 30%, or from about 8% to about 25%, of the longitudinal inner core length, LC. The third and fourth unsealed portions 421a, 421b may have an unsealed longitudinal length L2U that is about 5% to about 30%, or from about 8% to about 25%, of the longitudinal inner core length, LC. In some configurations, the unsealed longitudinal length L1U of the first or second unsealed portions 423a, 423b may be greater than the unsealed longitudinal length L2U of the third or fourth unsealed portions 421a, 421b.
Referring to
As discussed herein and as illustrated in the accompanying figures, the absorbent core structure 10 may comprise different configurations with respect to sealing the inner core layer within the upper and lower nonwoven layers.
As shown in
Referring to
While the figures show the upper and lower nonwoven layers 210, 220 extending to the front and back article edges 30, 32, it is to be appreciated that the front and/or back edges of the upper and/or lower nonwoven layers may be positioned inboard of the front and back article edges 30, 32. In some configurations, the front and/or back edges of the upper and lower nonwoven layers may be positioned between the crimp seal 500 and the inner core layer perimeter 200a.
Suitable upper nonwoven layers may have a basis weight of from about 30 gsm to about 85 gsm, or from about 30 to about 65 gsm, or from about 40 to about 55 gsm. The upper nonwoven layer may have a Tensile Stiffness of from about 0.3 N/mm to about 1.6 N/mm. 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%. 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.
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 1.6 N/mm. 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%. The lower nonwoven layer may have a Permanent Strain of about 0.005 to about 0.013 mm/mm.
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% regenerated cellulosic fibers, such as rayon and/or viscose.
The upper nonwoven layer may comprise fibers having a staple length of greater than about 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 DTex, alternatively from about 1.3 DTex to about 6.0 DTex, alternatively from about 2.0 DTex to about 5.0 DTex. In some configurations, the upper nonwoven layer may comprise fibers, wherein the fibers are a blend of staple fibers having a fiber diameter of from about 2.0 DTex to about 10 DTex.
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, alternatively from about 1.3 DTex to about 3.3 DTex, alternatively from about 1.3 DTex to about 2.2 DTex, alternatively 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, suitable fiber combinations may include upper nonwoven polymer fibers having a diameter of from about 2.0 DTex to about 10 DTex and lower nonwoven polymer fibers having a diameter of from about 1.7 DTex to about 5 DTex. In some configurations, suitable fiber combinations may include upper nonwoven polymer fibers having a diameter of from about 1.3 DTex to about 2.2 DTex and lower nonwoven polymer fibers having a diameter of from about 1.7 DTex to about 5 DTex.
Suitable upper and 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.
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 is 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 also 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 fibers (less than about 10 mm) then they 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 dissipate the tensile/compressive forces typical of bodily motions along the fiber length and across the structure. As a result, the imparted forces are available to recover the structure to its original state. Longer fiber networks composed of finer fibers (less than about 15 to about 20 microns and about 2.0 DTex) 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 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 this results in polymer chains within the fiber permanently rearranging and as a result the fibers themselves potentially remaining permanently elongated (permanently strained) and 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.
Suitable nonwoven materials examples 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. The material basis weight is 40 gsm and its caliper (under 7 KPa) is about 0.9 mm 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 N*mm) in the Wet and 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. As such 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 Wet and 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% DTex BiCo (PE/PET), 20% 3.3 DTex tri-lobal ‘structural’ rayon, and 20% 1.3 DTex rayon. As such 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 Wet and 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 fiber and AGM 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 AGM into the pocket in a laydown station. This shaped pocket provides the actual physical shape of the absorbent core structure. The upper or lower nonwoven may be first introduced onto the forming drum and under the vacuum the upper or lower nonwoven are drawn into the 3-dimensional pocket shape. In this case, the cellulose and AGM material stream is deposited on the upper (or lower nonwoven material) 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 AGM to the nonwoven layer. On exiting the laydown section, the second remaining nonwoven layer is combined with the nonwoven carrying the cellulose and AGM layer exiting the laydown section. This second remaining nonwoven (either upper or lower nonwoven depending on what nonwoven is run through the laydown section) is precoated with adhesive to enable a perimeter seal and to better integrate the cellulose and AGM without hindering the flow of liquid into the cellulose and AGM matrix. In another approach, a nonwoven is not first introduced into the forming station and the cellulose and AGM mass is held on the forming drum under vacuum until it is ejected onto either the upper or lower nonwoven layer that has an adhesive applied as detailed above and then sealed with the second remaining nonwoven to create the absorbent core structure. The width of the upper and lower nonwoven webs are typically chosen to be wider than the maximum width of the shaped cellulose and AGM matrix so as to enable an effective perimeter seal where the two nonwovens connect, at least on the left and right most sides of the absorbent core structure.
In yet another approach, neither the upper or lower nonwovens are drawn into the 3-dimensional pocket but rather the cellulose and AGM are deposited directly onto a 3-dimensional forming screen. The upper or lower nonwoven is coated with an adhesive to provide a stronger connection of the cellulose and AGM to the nonwoven layer and the cellulose/AGM matrix is directly deposited onto the nonwoven near the outlet of the forming drum so as to minimize material loss before the second nonwoven is combined with the first nonwoven and the accompanying fluff/AGM matrix.
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. Preferably, the inner core layer may comprise from about 125 gsm to about 400 gsm cellulosic fibers.
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. The resulting absorbent core structure may have an average density of between about 0.045 g/cm3 and about 0.15 g·cm3, and/or between 0.045 g/cm3 and 0.12 g/cm3. The absorbent article may have an average density of between about 0.045 g/cm3 and about 0.16 g/cm3.
The absorbent core structures may compress and recover their original shape following the compression step. Suitable absorbent core structures require 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 sustains sufficient recovery energy following multiple cyclic compressions. Without sufficient recovery energy the structure remains in a compressed bunched state with insufficient force (stored energy) to recover.
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 and/or absorbent core structure. In some configurations, the middle region 22 of the absorbent article and/or absorbent core structure may be free from structural bond sites and may be surrounded by an area of structural bond sites and/or embossing. 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.
In some configurations, the absorbent article and/or absorbent core structure may be free of structural bond sites.
Suitable absorbent articles and/or absorbent core structures may comprise an upper nonwoven layer and lower nonwoven layer that are closer together in the Z direction at the structural bond sites 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 may be substantially free of fusion bonds.
Referring to
In some configurations, side edges 120 and 125 of the absorbent article may follow the general contour of the inner core layer 200. However, forms are contemplated where the side edges 120 and 125 are generally straight or slightly curved such that they do not follow the contour of the inner core layer 200. The absorbent article 20 may be symmetric about the longitudinal centerline 80 or asymmetric about the longitudinal centerline 80. Similarly, the absorbent article may be symmetric about the lateral centerline 90 or asymmetric about the lateral centerline 90. The absorbent article 20 may be resilient and conformable and may deliver a superior in-use experience without substantially bunching and/or compressing. The absorbent article may be exposed to bodily forces and may recover to its original state. The absorbent article may have a CD Dry Modulus of between about 0.07 and 0.30 N/mm2 as measured in the Wet and Dry CD and MD 3 Point Bend Method, or from about 0.10 to about 0.25 N/mm2, or from about 0.10 to about 0.20 N/mm2.
The absorbent article may have a of Dry Caliper between about 2.0 mm and about 6.0 mm, or from about 2.0 mm and about 4.5 mm, or from about 2.5 mm to about 4.0 mm, or from about 2.75 mm to about 3.5 mm, as measured according to the Wet and Dry CD and MD 3-Point Method. In some configurations, the absorbent article may have a CD Dry Modulus of between about 0.07 and 0.30 N/mm2 and a Dry Caliper between about 2.0 mm and about 4.5 mm as measured according to the Wet and Dry CD and MD 3-Point Method, or a CD Dry Modulus of between from about to about 0.25 N/mm2 and a Dry Caliper of from about 2.50 mm to about 4.0 mm, or a CD Dry Modulus of between about from about 0.10 to about 0.20 N/mm2 and a Dry Caliper of from about 2.75 mm to about 3.5 mm. The absorbent article may have a CD Dry Bending Stiffness of between about 10.0 to about 30.0 N*mm2 as measured in the Wet and Dry CD and MD 3 Point Bend Method, or about 10.0 and about 25.0 N*mm2, or about 10 to about 20 N*mm2, or about 13 to about 20 N*mm2. Particularly suitable absorbent articles include those having a CD Dry Bending Stiffness of between about 10.0 and about 30.0 N*mm2 and a Dry Caliper of from about 2.5 mm to about 4.0 mm as measured according to the Wet and Dry CD and MD 3-Point Method, or a CD Dry Bending Stiffness of about 10 to about 25 N*mm2 and a Dry Caliper of between about 2.5 and 4.0 mm, or a CD Dry Bending Stiffness about 13 to about 30 N*mm2 and a Dry Caliper of from about 2.75 mm to about 3.5 mm.
The absorbent article may have a 5th Cycle Wet Energy of Recovery of from about 1.0 to 3.5 N*mm, or about 1.5 to about 3.0 N*mm, or about 1.5 to about 2.8 N*mm Particularly suitable absorbent articles may have a 5th Cycle Wet Energy of Recovery of between about 1.0 and 3.5 N*mm and a 5th Cycle Wet % Recovery of from about 29% to about 40%, or a 5th Cycle Wet Energy of Recovery of from about 1.5 to about 3.0 N*mm and a 5th Cycle Wet % Recovery of from about 29% to about 40%, or a 5th Cycle Wet Energy of Recovery from about 1.5 to about 2.75 N*mm and a 5th Cycle Wet % Recovery of from about 29% to about 40%.
Absorbent articles comprising the absorbent core structures as disclosed herein may also need to deliver a dry touch to the consumer following the addition of fluid as measured by the light touch rewet method. Absorbent core structures and absorbent articles meeting the above characteristics are designed to comfortably and gently conform more closely and more completely to the wearer's complex anatomical genital shape. Such absorbent articles therefore may also need to be dry to the touch following discharge so as not to irritate the sensitive genital tissues. As such absorbent articles described herein may also maintain a Light Touch Rewet value of less than about 0.15 grams, or less about 0.12 grams, or from about 0 to about 0.15 grams, or from about 0 to about grams.
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; US 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 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. applications. 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. 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 be provided with adhesive deposits to provide a mechanism for the user to adhere the absorbent article to the inside of her underpants in the crotch region thereof. When the absorbent article 20 is packaged for shipping, handling and storage prior to use, adhesive deposits may be covered by one or more sheets of release film or paper (not shown) 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.
In some configurations, the absorbent article 20 may include opposing wing portions 140, 150 on each side, extending laterally beyond longitudinal edges of the absorbent portions of the absorbent article by a comparatively greater width dimension than that of the forward and rearward portions 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.±3C° 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.
The test specimen is prepared as follows. Obtain the test material by excising it from an absorbent article, if necessary. When excising the test material, do not impart any contamination or distortion to the material layer during the process. 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.
% Strain to Break=((Lf−Li)/Li)*100
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 bending properties of an absorbent article test sample are 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 test is executed on dry test specimens as well as wet test specimens. 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.
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 moved 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 if 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.
Set the gap (“Span”) between the bars of the lower fixture to 25 mm±0.5 mm (center of bar to center of bar) with the upper bar centered at the midpoint between the lower bars. Set the gage (bottom of top bar to top of lower bars) to 1.0 cm.
The thickness (“caliper”) of the test specimen is measured 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 caliper to the nearest 0.01 mm.
The test fluid used to dose the wet test specimens is prepared by adding 100.0 grams of sodium chloride (reagent grade, any convenient source) to 900 grams of deionized water in a 1-liter Erlenmeyer flask. Agitate until the sodium chloride is completely dissolved.
The absorbent article samples are conditioned at 23° C.±3° C. and 50%±2% relative humidity two hours prior to testing. Dry test specimens are taken from an area of the sample that is free from any seams and residua of folds or wrinkles, and ideally from the center of absorbent article (intersection of longitudinal and lateral midlines). The dry specimens are prepared for MD (machine direction) bending by cutting them to a width of 50.8 mm along the CD (cross direction; parallel to the lateral axis of the sample) and a length of 50.8 mm along the MD (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). The dry specimens are prepared for CD (machine direction) bending by cutting them to a width of 50.8 mm along the MD (cross direction; parallel to the lateral axis of the sample) and a length of 50.8 mm along the CD (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). Measure the thickness of the test specimen, as described herein, and record as dry specimen caliper to the nearest 0.01 mm Now measure the mass of the test specimen and record as dry mass to the nearest 0.001 grams. Calculate the basis weight of the specimen by dividing the mass (g) by the area (0.002581 m2) and record as dry specimen basis weight to the nearest 0.01 g/m2. Calculate the bulk density of the specimen by dividing the specimen basis weight (g/m2) by the specimen thickness (mm), then dividing the quotient by 1000, and record as dry specimen density to the nearest 0.01 g/cm3. In like fashion, five replicate dry test specimens are prepared.
Wet test specimens are initially prepared in the exact manner as for the dry test specimen, followed by the addition of test fluid just prior to testing, as follows. First, the thickness and mass of the dry specimen is measured, as described herein, and recorded as initial thickness to the nearest mm and initial mass to the nearest 0.001 g. Next, the dry specimen is fully submersed in the test fluid for 60 seconds. After 60 seconds elapse, the specimen is removed from the test fluid and oriented vertically for 30 seconds to allow any excess fluid to drip off. Now the thickness and mass of the wet specimen are measured, as described herein, and recorded as wet specimen caliper to the nearest 0.01 mm and wet specimen mass to the nearest 0.001 g. If desired, the mass of test fluid in the test specimen is calculated by subtracting the initial mass (g) from the wet specimen mass (g) and recording as test specimen fluid amount to the nearest 0.001 g. After the wet test specimen is removed from the test fluid, it must be tested within 10 minutes. In like fashion, five replicate wet test specimens are prepared.
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/sec until the upper bar touches the top surface of the specimen with a nominal force of 0.02 N, then continue for an additional 12 mm. 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 100 Hz throughout the test.
Load a dry test specimen such that it spans the two lower bars and is centered under the upper bar, with its sides parallel to the bars. For MD bending, the MD direction of the test specimen is perpendicular to the length of the 3 bars. Start the test and continuously collect force and displacement data.
Construct a graph of force (N) versus displacement (mm). From the graph, determine the maximum peak force and record as dry MD peak load to the nearest 0.01 N. Now calculate the maximum slope of the curve between initial force and maximum force (during the loading portion of the curve) and record to the nearest 0.1 unit. Calculate the modulus as follows, and record as dry MD modulus to the nearest 0.001 N/mm2.
CD or MD Dry or Wet Bending Modulus(N/mm2)=(Slope×(Span3))/(4×specimen width×
(specimen caliper3))
CD or MD Dry or Wet Bending Stiffness (N mm2)=Modulus×Moment of Inertia
where Moment of Inertia (mm4)=(specimen width×(specimen caliper3))/12
In like fashion, the procedure is repeated for all five replicates of the dry test specimens. The arithmetic mean among the five replicate dry test specimens is calculated for each of the parameters and reported as Dry Specimen ‘Caliper’ to the nearest 0.01 mm, Dry Specimen Basis Weight to the nearest 0.01 g/m2, Dry Specimen Density to the nearest 0.001 g/cm3, Dry CD or MD Peak Load to the nearest 0.01 N, Dry CD or MD Bending Modulus to the nearest 0.001 N/mm2, and Dry CD or MD Bending Stiffness to the nearest N mm2.
The overall procedure is now repeated for all five replicates of the wet test specimens, reporting results as Wet CD or MD Peak Load to the nearest 0.01 N, Wet CD or MD Bending Modulus to the nearest 0.001 N/mm2, and Wet CD or MD Bending Stiffness to the nearest N mm2.
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 test is executed on dry test specimens as well as wet test specimens. 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.
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
The test fluid used to dose the wet test specimens is prepared by adding 100.0 grams of sodium chloride (reagent grade, any convenient source) to 900 grams of deionized water in a 1-liter Erlenmeyer flask. Agitate until the sodium chloride is completely dissolved.
Samples are conditioned at 23° C.±3° C. and 50%±2% relative humidity two hours prior to testing. Dry test specimens are taken from an area of the sample that is free from any seams and residua of 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.
Wet test specimens are initially prepared in the exact manner as for the dry test specimen, followed by the addition of test fluid just prior to testing, as follows. The dry specimen is fully submersed in the test fluid for 60 seconds. After 60 seconds elapse, the specimen is removed from the test fluid and oriented vertically for 30 seconds to allow any excess fluid to drip off. After the wet test specimen is removed from the test fluid, it must be tested within 10 minutes. In like fashion, five replicate wet 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 type (dry and wet), 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 and Wet Peak load, respectively. For each test specimen type (dry and wet), the arithmetic mean of bending energy among like specimens is calculated to the nearest 0.001 N-mm and reported as Dry Bending Energy and Wet Bending Energy, respectively. For each test specimen type (dry and wet), the arithmetic mean of recovery energy among like specimens is calculated to the nearest 0.001 N-mm and reported as Dry Recovery Energy and Wet Recovery Energy, respectively.
The bunched compression test method measures the force versus displacement behavior across five cycles of load application (“compression”) and load removal (“recovery”) of an absorbent article test sample that has been intentionally “bunched”, using 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 test is executed on dry test specimens as well as wet test specimens that are dosed with a specified amount of test fluid. The intention of this method is to mimic the deformation created in the z-plane of the crotch region of an absorbent article, or components thereof, as it is worn by the wearer during sit-stand movements. All testing is performed in a room controlled at 23° C.±3C° and 50%±2% relative humidity.
The test apparatus is depicted in
Test samples are conditioned at 23° C.±3C° and 50%±2% relative humidity for at least 2 hours before testing. Prepare the test specimen as follows. When testing an intact absorbent article, remove the release paper from any panty fastening adhesive on the garment facing side of the article, if present. Lightly apply talc powder to the adhesive to mitigate any tackiness. If there are cuffs, excise them with scissors so as not to disturb the topsheet or any other underlying layers of the article. Place the article, body facing surface up, on a benchtop. On the article, mark the intersection of the longitudinal midline and the lateral midline. Using a rectangular cutting die or equivalent cutting means, cut a specimen 100 mm in the longitudinal direction by 80 mm in the lateral direction, centered at the intersection of the midlines. When testing a material layer or layered components from an absorbent article, place the material layer or layered components on a benchtop and orient as it would be integrated into a finished article, i.e., identify the body facing surface and the lateral and longitudinal axis. Using a rectangular cutting die, or equivalent cutting means, cut a specimen 100 mm in the longitudinal direction by 80 mm in the lateral direction, centered at the intersection of the midlines. Measure the mass of the specimen and record to the nearest 0.001 grams. Calculate the basis weight of the specimen by dividing the mass (g) by the area (0.008 m2) and record as basis weight to the nearest 1 g/m2.
The specimen can be analyzed both wet and dry. The dry specimen requires no further preparation. The test fluid used to dose the wet test specimens is prepared by adding 100.0 grams of sodium chloride (reagent grade, any convenient source) to 900 grams of deionized water in a 1-liter Erlenmeyer flask. Agitate until the sodium chloride is completely dissolved. The wet specimen is dosed with total of 7 ml of the test solution as detailed below
The liquid dose is added using a calibrated Eppendorf-type pipettor, spreading the fluid over the complete body facing surface of the specimen within a period of approximately 3 sec. The wet specimen is tested 10.0 min±0.1 min after the dose is applied.
Program the tensile tester to zero the load cell, then lower the upper fixture at 2.00 mm/sec until the contact surface of the plunger touches the specimen and 0.02 N is read at the load cell. Zero the crosshead. Program the system to lower the crosshead 15.00 mm at 2.00 mm/sec then immediately raise the crosshead 15.00 mm at 2.00 mm/sec. This cycle is repeated for a total of five cycles, with no delay between cycles. Data is collected at 50 Hz during all compression/decompression cycles.
Position the left platform 3002a 2.5 mm from the side of the upper plunger (distance 3005). Lock the left platform into place. This platform 3002a will remain stationary throughout the experiment. Align the right platform 3002b 50.0 mm from the stationary clamp (distance 3006). Raise the upper probe 2001 such that it will not interfere with loading the specimen. Open both clamps 3001. Referring to
Start the test and continuously collect force (N) versus displacement (mm) data for all five cycles. Construct a graph of force (N) versus displacement (mm) separately for all cycles. A representative curve is shown in
The overall procedure is now repeated for a total of five replicate wet test specimens, reporting results for each of the five cycles as the arithmetic mean among the five wet replicates for Wet Maximum Compression Force to the nearest 1 gram-force for each cycle, Wet Energy of Compression to the nearest 0.1 N-mm for each cycle, Wet Energy Loss to the nearest 0.1 N-mm for each cycle, Wet Energy of Recovery to the nearest 0.1 N-mm for each cycle and Wet % recovery for each cycle. Of particular importance is the 5th cycle wet energy of recovery and 5th cycle wet % recovery properties from this test method.
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.
The test specimen is prepared as follows. Obtain the test material by excising it from an absorbent article, if necessary. When excising the test material, do not impart any contamination or distortion to the material layer during the process. 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 (AL) 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 (AL) 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 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 (G) 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), 6=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/mm 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 0.01 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.
Light Touch Rewet method is a quantitative measure of the mass of liquid that emerges from an absorbent article test sample that has been dosed with a specified volume of Artificial Menstrual Fluid (AMF; as described herein) when a weight is applied for a specified length of time. All measurements are performed in a laboratory maintained at 23° C.±2 C.° and 50%±2% relative humidity.
A syringe pump equipped with a disposable syringe is utilized to dose the test sample. A suitable pump is the Perfusor® Compact S (available from B. Braun), or equivalent, and must be able to accurately dispense the AMF at a rate of 42 ml/min. The disposable syringe is of ample volume (e.g., BD Plastipak 20 mL) and is connected to flexible tubing that has an inner diameter of 3/16″ (e.g., Original Perfusor® Line, available from Braun, or equivalent). The AMF is prepared, as described herein, and is brought to room temperature (23° C.±2 C.°) prior to using for this test. Prior to the commencement of the measurement, the syringe is filled with AMF and the flexible tubing is primed with the liquid, and the dispensing rate (42 ml/min) and dosing volume (4.0 mL+0.05 mL) are verified according to the manufacturer's instructions. The flexible tubing is then mounted such that it is oriented vertically above the test sample, and the distance between the tip of the tubing and the surface of the test sample is 19 mm. To note, the AMF must be removed from the syringe and thoroughly mixed every 15 minutes.
The rewet weight assembly consists of an acrylic plate and a stainless steel weight. The acrylic plate has dimensions of 65 mm by 80 mm with a thickness of about 5 mm. The stainless steel weight along with the acrylic plate have a combined mass of 2 pounds (907.19 g), to impart a pressure of 0.25 psi beneath the surface of the acrylic plate.
For each test sample, five sheets of filter paper with dimensions of 4 inch by 4 inch are used as the rewet substrate. The filter paper is conditioned at 23° C.±2 C.° and 50%±2% relative humidity for at least 2 hours prior to testing. A suitable filter paper has a basis weight of about 139 gsm, a thickness of about 700 microns with an absorption rate of about 1.7 seconds, and is available from Ahlstrom-Munksjo North America LLC, Alpharetta, GA VWR International as Ahlstrom grade 989, or equivalent.
Prepare the test sample as follows. The test samples are conditioned at 23° C.±2 C.° and 50%±2% relative humidity for at least 2 hours prior to testing. Test samples are removed from all packaging using care not to press down or pull on the products while handling. Lay the test sample on a horizontally rigid flat surface and gently smooth out any folds. Determine the test location as follows. For symmetrical samples (i.e., the front of the sample is the same shape and size as the back of the sample when divided laterally along the midpoint of the longitudinal axis of the sample), the test location is the intersection of the midpoints of the longitudinal axis and lateral axis of the sample. For asymmetrical samples (i.e., the front of the sample is not the same shape and size as the back of the sample when divided laterally along the midpoint of the longitudinal axis of the sample), the test location is the intersection of the midpoint of the longitudinal axis of the sample and a lateral axis positioned at the midpoint of the sample's wings. A total of three test samples are prepared.
Place the test sample on a horizontally flat rigid surface, with the previously identified test location centered directly below the tip of the flexible tubing. Adjust the height of the tubing such that it is 19.0 mm above the surface of the test sample. Start the pump to dispense 4.0 mL+0.05 mL of AMF at a rate of 42 ml/min. As soon as the AMF has been fully dispensed, start a 10 minute timer. Now obtain the mass of 5 sheets of the filter paper and record as dry mass to the nearest grams. When 10 minutes have elapsed, place the five sheets of pre-weighed filter papers onto the test sample, centering the stack over the dosing location. Now place the acrylic plate centered over the top of the filter papers such that the long side of the plate is parallel with the longitudinal axis of the test sample. Now carefully lower the stainless steel weight centered over the acrylic plate and immediately start a 30 second timer. After 30 seconds have elapsed, gently remove the rewet weight and acrylic plate and set aside. Obtain the mass of the five sheets of filter paper and record as wet mass to the nearest 0.001 grams. Subtract the dry mass from the wet mass of the filter papers, and record as rewet to the nearest 0.001 grams. Wipe off any residual test liquid from the bottom face of the acrylic plate prior to testing the next sample. In like fashion, repeat for a total of three replicate test samples.
The arithmetic mean of the rewet among the three replicate test samples is calculated and reported as the ‘Light Touch Rewet’ to the nearest 0.001 g.
The Artificial Menstrual Fluid (AMF) is composed of a mixture of defibrinated sheep blood, a phosphate buffered saline solution and a mucous component. The AMF is prepared such that it has a viscosity between 7.15 to 8.65 centistokes at 23° C.
Viscosity of the AMF is performed using a low viscosity rotary viscometer (a suitable instrument is the Cannon LV-2020 Rotary Viscometer with UL adapter, Cannon Instrument Co., State College, PA, or equivalent). The appropriate size spindle for the viscosity range is selected, and instrument is operated and calibrated as per the manufacturer. Measurements are taken at 23° C.±1 C.° and at 60 rpm. Results are reported to the nearest 0.01 centistokes.
Reagents needed for the AMF preparation include: defibrinated sheep blood with a packed cell volume of 38% or greater (collected under sterile conditions, available from Cleveland Scientific, Inc., Bath, OH, or equivalent), gastric mucin with a viscosity target of 3-4 centistokes when prepared as a 2% aqueous solution (crude form, sterilized, available from American Laboratories, Inc., Omaha, NE, or equivalent), 10% v/v lactic acid aqueous solution, 10% w/v potassium hydroxide aqueous solution, sodium phosphate dibasic anhydrous (reagent grade), sodium chloride (reagent grade), sodium phosphate monobasic monohydrate (reagent grade) and distilled water, each available from VWR International or equivalent source.
The phosphate buffered saline solution consists of two individually prepared solutions (Solution A and Solution B). To prepare 1 L of Solution A, add 1.38±0.005 g of sodium phosphate monobasic monohydrate and 8.50±0.005 g of sodium chloride to a 1000 mL volumetric flask and add distilled water to volume. Mix thoroughly. To prepare 1 L of Solution B, add 1.42±0.005 g of sodium phosphate dibasic anhydrous and 8.50±0.005 g of sodium chloride to a 1000 mL volumetric flask and add distilled water to volume. Mix thoroughly. To prepare the phosphate buffered saline solution, add 450±10 mL of Solution B to a 1000 mL beaker and stir at low speed on a stir plate. Insert a calibrated pH probe (accurate to 0.1) into the beaker of Solution B and add enough Solution A, while stirring, to bring the pH to 7.2±0.1.
The mucous component is a mixture of the phosphate buffered saline solution, potassium hydroxide aqueous solution, gastric mucin and lactic acid aqueous solution. The amount of gastric mucin added to the mucous component directly affects the final viscosity of the prepared AMF. To determine the amount of gastric mucin needed to achieve AMF within the target viscosity range (7.15-8.65 centistokes at 23° C.) prepare 3 batches of AMF with varying amounts of gastric mucin in the mucous component, and then interpolate the exact amount needed from a concentration versus viscosity curve with a least squares linear fit through the three points. A successful range of gastric mucin is usually between 38 to 50 grams.
To prepare about 500 mL of the mucous component, add 460±10 mL of the previously prepared phosphate buffered saline solution and 7.5±0.5 mL of the 10% w/v potassium hydroxide aqueous solution to a 1000 mL heavy duty glass beaker. Place this beaker onto a stirring hot plate and while stirring, bring the temperature to 45° C.±5 C°. Weigh the pre-determined amount of gastric mucin (±0.50 g) and slowly sprinkle it, without clumping, into the previously prepared liquid that has been brought to 45° C. Cover the beaker and continue mixing. Over a period of 15 minutes bring the temperature of this mixture to above 50° C. but not to exceed 80° C. Continue heating with gentle stirring for 2.5 hours while maintaining this temperature range. After the 2.5 hours has elapsed, remove the beaker from the hot plate and cool to below 40° C. Next add 1.8±mL of the 10% v/v lactic acid aqueous solution and mix thoroughly. Autoclave the mucous component mixture at 121° C. for 15 minutes and allow 5 minutes for cool down. Remove the mixture of mucous component from the autoclave and stir until the temperature reaches 23° C.±1 C°.
Allow the temperature of the sheep blood and mucous component to come to 23° C.±1 C°. Using a 500 mL graduated cylinder, measure the volume of the entire batch of the previously prepared mucous component and add it to a 1200 mL beaker. Add an equal volume of sheep blood to the beaker and mix thoroughly. Using the viscosity method previously described, ensure the viscosity of the AMF is between 7.15-8.65 centistokes. If not the batch is disposed and another batch is made adjusting the mucous component as appropriate.
The qualified AMF should be refrigerated at 4° C. unless intended for immediate use. AMF may be stored in an air-tight container at 4° C. for up to 48 hours after preparation. Prior to testing, the AMF must be brought to 23° C.±1 C°. Any unused portion is discarded after testing is complete.
The following data and examples, including comparative examples, are provided to help illustrate the upper and lower nonwoven layers, absorbent core structures 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.
Nonwoven layer materials are tested to assess the ability of the nonwoven material to strain (elongate) with a balanced stretch and to recover to their original state (simulating in-use physical deformation). Samples F-H are comparative examples. The test is performed according to the CD Cyclic Elongation to 3% Strain Method and the Strain to Break Method described herein. The results are shown in Table 1.
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 18G 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 found that suitable nonwoven layer materials strain (elongate) with a balanced stretch vs. recovery behavior. If the nonwoven layer material elongates plastically (i.e., stretches but does not recover) as the fluff/AGM matrix in the inner core layer elongates, there will be insufficient recovery energy to return to the initial, pre-stretched state and the nonwoven layer material will become permanently strained (stretched). The upper nonwoven layers of the present disclosure can have a Permanent Strain value of less than about 0.013. At the same time, if the nonwoven layer material is strained aggressively, for example greater than 5%, the nonwoven layer material needs to retain its integrity and not tear or break (see, for example, Sample H which tears and has a Strain to Break of less than 5%). Nonwoven layers of the present disclosure can have a Strain to Break of greater than about 10%.
The nonwoven layer materials described above are also tested to assess the ability of nonwoven materials to bend and deform and to recover to their original state. The test is performed according to the Wet and Dry CD Ultra Sensitive 3 Point Bending Method described herein. The results are shown in Table 2.
During walking, an absorbent article is compressed and bent side-to-side in a cyclic pattern as the gap between her legs narrows and then expands with her leg motions. Without being limited by theory, it is believed that a nonwoven layer material having a Dry Bending Energy of less than about 2 N*mm will allow this bending compression to occur readily yet will not be so stiff as to hinder the bending compression. At the same time, following the bending compression, the nonwoven layer needs to be able to sustain sufficient dry recovery energy to return the nonwoven layer and the fluff/AGM matrix in the inner core layer back to its initial, pre-bent state. The upper nonwoven layers of the present disclosure can have a Dry Recovery Energy value of greater than about 0.03 N*mm.
Samples A-E exhibit a Dry Peak Load of from 0.03 N to 0.38 N and a Dry Recovery Energy of from 0.032 to 0.092 N*mm, demonstrating that these materials readily bend and have sufficient dry recovery energy to recover their initial, pre-bent state. Samples F and G, which are comparative examples, exhibit a Dry Peak Load of 0.01 N and 0.03 N, respectively, and a Dry Recovery Energy of 0.005 N*mm and 0.019 N*mm, respectively, demonstrating that while these materials readily bend, they do not have sufficient recovery energy to recover their initial, pre-bent state after compression. Sample H (comparative example) exhibits a Dry Peak Load of 0.04 N and a Dry Recovery Energy of 0.031 N*mm. However, it is found that Sample H tears when it becomes wet, making it insufficient to function as an upper and/or lower nonwoven layer of the present disclosure.
Without being limited by theory, it is believed that nonwoven layer materials comprising thick fibers (from about 2.0 Dtex to about 10 Dtex) that are arranged within a network structure are able to carry the mechanical load within the fiber network and return the absorbent core structure and/or absorbent article to its initial shape following bending compression. Samples F and G comprise relatively fine fibers (less than about 2.0 Dtex), while Samples A-E comprise fiber blends having a fiber thickness of from about 2.2 Dtex to about 10 Dtex.
Absorbent cores structures are tested to assess the ability of the absorbent core structure to compress (simulating the compressions experienced between a wearer's legs) and to recover to their original state. Examples 1-3 in Table 3 illustrate absorbent core structures described herein. Comp. Ex. A-C are comparative examples. A description of Ex. 1-3 and Comp. Ex. A-C are listed in Table 3. The absorbent core structures are prepared as described hereafter. The absorbent core structures are evaluated according to the Wet and Dry Bunched Compression Method as described herein. The results are shown in Table 4.
1Available as ATB Z87G-40 from Xiamen Yanjan New Material Co. (China)
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 18G BICO8020 PHI 6 from dPFNonwovens Czech S.R.O (Czech Republic)
8Available as 3028 from DunnPaper (USA)
9Available as Favor SXM9745 from Evonik (Germany)
10Available as Item 9E3-COOSABSORB S from Resolute Alabama (USA)
11Available as Article 4004416 (MR 3585374) from Fitesa (Germany)
The absorbent core structures listed in Table 3 are produced as detailed within the specification. 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 fluff (cellulose) and AGM 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 fluff (cellulose) and AGM to the upper nonwoven layer without hindering the flow of liquid into the fluff/AGM matrix. On exiting the laydown section, the lower nonwoven web is combined with the nonwoven carrying the homogeneous blend of fluff/AGM. 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 fluff/AGM matrix.
Ex. 1 through 3 and Comp. Ex. A and B also have the structural bonds shown in
Ex. 1-3 and Comp. Ex. A-C also have flex bond channel regions applied with the pattern shown in
It is found that absorbent core structures comprising nonwoven layer materials that have sufficient resiliency and recovery energy are able to recover to the original, pre-compression absorbent core structure shape. Ex. 1-3 exhibit a 5th Cycle Wet Energy of Recovery of greater than 1.0 N*mm and a 5th Cycle Wet Maximum Compression Force of from 207 gf to 213 gf. These structures exhibit a low force to compress (less resistance so it feels soft and flexible), yet are still able to recover their shape as the structure is compressed and released in a cyclic fashion. However, Comp. Ex. A-C exhibit a 5th Cycle Wet Energy of Recovery of from 0.26 to 0.59 N*mm Without sufficient recovery energy after five cycles of compression, Comp. Ex. A-C remain in a compressed, bunched state with insufficient force (stored energy) to recover its original, pre-compression shape.
Absorbent core structures and/or absorbent articles of the present disclosure can have a 5th Cycle Wet Energy of Recovery of greater than about 1.0 N*mm, or from about 1.0 to about 3.5 N*mm Absorbent core structures and/or absorbent articles of the present disclosure can have a 5th Cycle Wet Maximum Compression Force of greater than about 150 gf, preferably greater than about 200 gf, or from about 150 gf to about 225 gf.
It is found that while an individual nonwoven material may have sufficient % Strain to Break in the Strain to Break Method, once combined into an absorbent core structure, the nonwoven material may not be capable of providing sufficient recovery energy for the full absorbent core structure (such as, for example in Comp. Ex. A) to return to its original, pre-compression shape. For instance, in Comp. Ex. A, the basis weight and thickness of the fibers of the upper nonwoven material when combined with the thin lower nonwoven material provides a 5th Cycle Wet Energy of Recovery of less than 1.0 N*mm.
Absorbent articles are tested to assess the ability of a wrapped absorbent core structure to compress (simulating the compressions experienced between a wearer's legs) and to recover to their original state. Ex. 4-7 illustrate absorbent articles described herein. Comp. Ex. D and E are comparative examples. Comp. Ex. F-L are in-market finished products. A description of Ex. 4-7 and Comp. Ex. D-E are listed in Table 5a. A description of Comp. Ex. F-L is listed in Tables 5b and 5c. Ex. 4-7 and Comp. Ex. D and E are prepared as described hereafter. The absorbent articles in Table 5a and 5b are evaluated according to the Wet and Dry CD and MD 3 Point Bend Method, the Wet and Dry Bunched Compression Method, and the Light Touch Rewet Method as described herein. The results are shown in in Table 6.
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 18G BICO8020 PHI 6 from dPFNonwovens Czech S.R.O (Czech Republic)
8Available as 3028 from DunnPaper (USA)
9Available as Favor SXM9745 from Evonik (Germany)
10Available as Item 9E3-COOSABSORB S from Resolute Alabama (USA)
12The nonwoven topsheet “Nonwoven SG” is a nonwoven web according to U.S. Patent Publication No. 2019/0380887.
Ex. 4 through 7 and Comp. Ex. D and E include structures as detailed for the Ex. 1 through 3 in Table 3 with the same adhesive designs and same 32 mm×16 mm structural bond pattern (a total structural bond site area of 1.38% of the total area of the absorbent core structure) in the absorbent core structure. Additionally, the absorbent articles include a nonwoven topsheet web as detailed in US Patent Publication No. 2019/0380887 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, 150 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, 150 mm long).
Ex. 4-7 and Comp. Ex. D and E also have the structural bonds shown in
Prior to bonding the backsheet, flex bond channel regions are applied to Ex. 4-7 and Comp. Ex. D and E with the pattern shown in
It is believed that in order to provide high bodily conformability, the absorbent article of the present disclosure can exhibit a low CD Dry Bending Stiffness (i.e., high flexibility) of from about 10 to about 30 N·mm2, or from about 10 to about 25 N·mm2. Also, it is believed that in order to provide an absorbent article that can compress with bodily motion and recover to its original, pre-compressed state against the user's body, the absorbent article of the present disclosure can have a 5th Cycle Wet Energy of Recovery of from about 1.0 to about 3.5 N·mm and/or a 5th Cycle Wet % Recovery of from about 29% to about 40%. Absorbent articles of the present disclosure can also maintain good fluid handling that delivers a low light touch rewet of from about 0 to about 0.15 g.
Ex. 4-7 exhibit a CD Dry Bending Stiffness of from 13.0 to 18.7 N mm2 and a 5th Cycle Wet % Recovery in the Wet and Dry Bunched Compression Method of from 29 to 36%, demonstrating that these structures will be able to sustain their shape in use. Comp. Ex. D and E exhibit a CD Dry Bending Stiffness of 9.1 and 13.0 N mm2, respectively. However, Comp. Ex. D and E exhibit a 5th Cycle Wet % Recovery in the Wet and Dry Bunched Compression Method that is less than 29%, demonstrating that these structures will be unable to sustain their shape in use and will remain bunched. Comp. Ex. F-L, which are in-market finished products, exhibit a CD Dry Bending Stiffness of 29 to 47.5 N·mm2, demonstrating that the structures are less flexible and less able to conform.
Without being limited by theory, it is believed that in order to sustain a comfortable shape recovery after compression, sufficient recovery energy is needed to push the absorbent article on the panty back to its pre-compression shape. At the same time, the absorbent article (via the absorbent core structure) needs to recover along the same path as the compression to return to its pre-compression location. If the 5th Cycle Wet Energy of Recovery is less than about 1.0 N·mm the absorbent article may not have the recovery energy needed to recover its shape. If the 5th Cycle Wet Energy of Recovery value is too high, the recovery may be too forceful, leaving the wearer to feel like the absorbent article is not staying in place. If the 5th Cycle Wet % Recovery value is low (less than about 29%), the absorbent article may not return to its pre-compression shape and may remain deformed and bunched. If the 5th Cycle Wet % Recovery value is excessively high (greater than about 40%), it suggests that the absorbent article may recover too strongly to the flat shape when it is first applied to the wearer's panty as opposed to the shape against her body.
Absorbent cores structures are tested to assess the impact of structural bond areas on flexibility and bending stiffness. Ex. 8 does not feature any structural bonds within the absorbent core structure. Ex. 9 and Ex. 10 have the structural bonds shown in
3Available as Sawasoft ® 553FC041005 (option 82) from Sandler GmbH (Germany)
9Available as Favor SXM9745 from Evonik (Germany)
10Available as Item 9E3-COOSABSORB S from Resolute Alabama (USA)
13Available as 10 SMS PHILIC from Union Industries SpA. (Italy)
Table 7 demonstrates the impact of the total structural bond site area and spacing amount. The asymmetric structural bond shape as shown in
The absorbent core structures listed in Table 7 are produced as detailed within the specification. Specifically, the 50 gsm Resilient Spunlace 6 upper nonwoven 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 fluff (cellulose) and AGM material is deposited onto the upper nonwoven material 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 fluff (cellulose) and AGM to the upper nonwoven layer without hindering the flow of liquid into the fluff/AGM mass. On exiting the laydown section, the 10 gsm SMS lower nonwoven web is combined with the nonwoven carrying the homogeneous blend of fluff (cellulose) and AGM layer. 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 is applied to better integrate the fluff/AGM mass. Structural bonds as shown in
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 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 of U.S. Provisional Application No. 63/345,582, filed May 25, 2022, and U.S. Provisional Application No. 63/413,634, filed Oct. 6, 2022, and U.S. Provisional Application No. 63/480,335, filed Jan. 18, 2023, the entire disclosures of which are fully incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 63345582 | May 2022 | US | |
| 63413634 | Oct 2022 | US | |
| 63480335 | Jan 2023 | US |
