Patent Application
20240189161
The present invention relates to nonwoven, and an absorbent article comprising the nonwoven.
Absorbent articles have been used as personal hygiene products, such as sanitary napkins, infant disposable diapers, training pants for toddlers, adult incontinence undergarments, and the like. Such absorbent articles are designed to absorb and contain body exudates, in particularly large quantities of urine, runny BM, and/or menses (together the “fluids”). These absorbent articles may comprise several layers providing different functions, for example, a topsheet, a backsheet, and an absorbent core disposed therebetween, among other layers (e.g., acquisition layer, distribution layer, etc.) as desired.
Nonwovens are widely used as components such as topsheets constituting absorbent articles such as sanitary napkins, infant disposable diapers, personal care disposable diapers, and the like. Various nonwovens have been suggested for use as topsheets for absorbent articles from the standpoints of skin sensation, a feeling of dryness, comfort, absorption of expelled bodily fluids, and/or prevention of fluid flow-back.
One of design criteria of topsheets in absorbent articles is to reduce the amount of time the fluids spend on the topsheets prior to being absorbed by the absorbent article. If the fluids remain on the surfaces of the topsheets for too long of a period of time, wearers may feel unpleasant wetness and discomfort may increase. Another desirable quality of topsheets is prevention of fluid flow-back through a topsheet and provision of dryness feel. Meanwhile, topsheets acquire and retain some fluid in small capillaries that might exist between fibers which may be visually perceptible to the user of the product as an undesirable stain. It is also a desirable characteristic of absorbent article to present a clean user contacting surface with less stain.
It has been known that a hydrophilic topsheet exhibits a faster acquisition speed compared to a hydrophobic topsheet, however, it tends to cause unpleasant wetness sensation as it traps or retains the fluid, and/or the fluid flows back through the topsheet due to high affiliation of constituting fibers to the fluid. Therefore, absorbent articles having hydrophobic topsheets may be preferred by some consumers because they provide dryness feel and good blurring and stain masking benefits regarding menses/urine staining. However, hydrophobic topsheets absorb the fluid only via capillary force which leads to slower acquisition speed and causes fluid leakage problems. Nonwoven topsheets having a hydrophobic upper layer and a hydrophilic bottom layer were suggested for enhancing transfer of the body fluid from the top surface toward the bottom surface of the topsheet and eventually to the absorbent core. WO2018/167883 discloses an absorbent article comprising a laminate nonwoven which comprises a first surface facing the skin of the wearer, the first surface comprising a hydrophobic first layer, and a second surface comprising a hydrophilic second layer. The first and second layers are heat fused together at heat-bonded points where the laminate nonwoven has a thickness smaller than that of peripheral portions, and the first layer has inter-fiber fusion bonded points where constituent fibers of the first layer are fused together, and have a thickness smaller than that of peripheral portions. US20160067118A discloses an apertured nonwoven laminate for use in an absorbent article, the nonwoven laminate comprising a hydrophobic first nonwoven layer and a hydrophilic second nonwoven layer.
There is a continuous need for a topsheet of absorbent articles providing a rapid fluid acquisition speed at the same time to alleviate back flow of the body fluid and reduce the unpleasant rewet.
There is also a need for a topsheet of absorbent articles providing improved stain masking so that it can provide a clean user contacting surface without compromising fluid handling properties such as a rapid fluid acquisition speed and mitigated rewet.
There is a continuous need for a topsheet of absorbent articles providing smooth and soft sensation without comprising fluid handling properties such as a rapid fluid acquisition speed and mitigated rewet.
The present disclosure provides a nonwoven substrate having a top surface and an opposite bottom surface, and comprising a plurality of apertures, wherein the top surface has a first contact angle of no lower than about 90 degrees as measured according to Contact Angle Test, wherein the bottom surface has a second contact angle of lower than about 90 degrees as measured according to Contact Angle Test, and wherein the plurality of apertures comprise at least one aperture having at least three adjacent apertures that are spaced apart from by an edge-to-edge space no greater than about 2.5 mm.
The present disclosure also provides an absorbent article comprising a wearer facing surface, a garment facing surface, a liquid permeable topsheet, a liquid impermeable backsheet, and an absorbent core disposed between the topsheet and the backsheet, wherein the topsheet comprises a nonwoven substrate of the present disclosure, the topsheet being disposed in such a way that the first layer of the nonwoven substrate forms at least part of the wearer facing surface.
These and other features, aspects, and advantages of the present invention will become evident to those skilled in the art from a reading of the present disclosure.
All ranges are inclusive and combinable. The number of significant digits conveys neither limitations on the indicated amounts nor on the accuracy of the measurements. All numerical amounts are understood to be modified by the word “about” unless otherwise specifically indicated.
The term “absorbent articles”, as used herein, include disposable diapers, sanitary napkins, panty liners, incontinence pads, interlabial pads, breast-milk pads, sweat sheets, animal-use excreta handling articles, animal-use diapers, and the like.
The term “carded” as used herein is used to describe structural features of the fluid management layers described herein. A carded nonwoven utilizes fibers which are cut to a specific length, otherwise known as “staple length fibers.” Staple length fibers may be any suitable length. For example, staple length fibers may have a length of up to 120 mm or may have a length as short as 10 mm. However, if a particular group of fibers are staple length fibers, for example viscose fibers, then the length of each of the viscose fibers in the carded nonwoven is predominantly the same, i.e., the staple length. It is worth noting that where additional staple fiber length fiber types are included, for example, polypropylene fibers, the length of each of the polypropylene fibers in the carded nonwoven is also predominantly the same. But the staple length of the viscose and the staple length of the polypropylene may be different.
In contrast, continuous filaments such as by spunbonding or meltblowing processes, do not create staple length fibers. Instead, these filaments are of an indeterminate length and are not cut to a specific length as noted regarding their staple fiber length counterparts.
The “longitudinal” direction is a direction running parallel to the maximum linear dimension, typically the longitudinal axis, of the article and includes directions within 45° of the longitudinal direction. “Length” of the article or component thereof, when used herein, generally refers to the size/distance of the maximum linear dimension, or typically to the size/distance of the longitudinal axis, of an article or part thereof.
The “lateral” or “transverse” direction is orthogonal to the longitudinal direction, i.e., in the same plane of the majority of the article and the longitudinal axis, and the transverse direction is parallel to the transverse axis. “Width” of the article or of a component thereof, when used herein, refers to the size/distance of the dimension orthogonal to the longitudinal direction of the article or component thereof, i.e., orthogonal to the length of the article or component thereof, and typically it refers to the distance/size of the dimension parallel of the transverse axis of the article or component.
As used herein, the terms “hydrophilic” and “hydrophobic” have meanings that are 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° as measured by Contact Angle Test is considered hydrophobic, and a material having a water contact angle of less than about 90° as measured by Contact Angle Test is considered hydrophilic.
The nonwoven of the present disclosure comprises a top surface, an opposite bottom surface, and comprising a plurality of apertures. The top surface of the nonwoven has a first contact angle of no lower than about 90 degrees as measured according to Contact Angle Test, and the bottom surface of the nonwoven has a second contact angle of lower than about 90 degrees as measured according to Contact Angle Test. The plurality of apertures comprise at least one aperture having at least three adjacent apertures that are spaced apart from by an edge-to-edge space no greater than about 2.5 mm.
Advantageously, the nonwoven of the present disclosure when it is used as a topsheet of an absorbent article provides a fast fluid acquisition speed while maintaining preferable low rewet. The nonwoven of the present disclosure may provide improved stain masking so that it can present a clean user contacting surface. In addition, the nonwoven of the present disclosure may provide a soft and smooth skin feel by employing fine denier fibers at least for the first layer.
The advantageous properties of the nonwoven of the present disclosure, without being bound by theory, may be achieved by introducing surface energy difference by the top surface having a first contact angle of no lower than about 90 degrees as measured according to Contact Angle Test, and the bottom surface of the nonwoven having a second contact angle of lower than about 90 degrees as measured according to Contact Angle Test.
The nonwoven of the present disclosure may comprise a first layer comprising a first surface forming the top surface of the nonwoven, and a second surface forming the bottom surface of the nonwoven.
The nonwoven of the present disclosure may comprise a first layer which forms the top surface of the nonwoven and comprises hydrophobic fibers, and a second layer which forms the bottom surface of the nonwoven and comprises hydrophilic fibers.
Hereinafter, the fiber constituting the nonwoven substrate of the present disclosure, the configurations of the first and the optional second layer, and a method for manufacturing the nonwoven, and an absorbent article having the nonwoven substrate are described.
When the nonwoven of the present disclosure comprises a first layer and a second layer, the first layer and the second layer may form a unitary structure, or may remain as discrete layers which may be attached at least partially to each other by, for example, thermal bonding, adhesive bonding or a combination thereof. A unitary structure herein intends to mean that although it may be formed by several sub-layers that have distinct properties and/or compositions from one another, they are somehow intermixed at the boundary region so that, instead of a definite boundary between sub-layers, it would be possible to identify a region where the different sub-layers transition one into the other. Such a unitary structure is typically built by forming the various sub-layers one on top of the other in a continuous manner, for example using air laid or wet laid deposition. Or each of sub-layer is produced in a separate step and the sub-layers are combined together in a face to face relationship. The sub-layers combined can be integrated via a known integration or bonding process such as spunlacing processes, hydroentangling, calendar bonding, through-air bonding and resin bonding.
Typically, there is no adhesive used between the sub-layers of the unitary material. However, in some cases, adhesives and/or binders can be present.
When the nonwoven of the present disclosure is described herein, terms of layer (layers), sub-layer(s), and stratum (strata) are used interchangeably. Relating to descriptions of unitary structure nonwovens, the terms of layer(s) and stratum(s) are used interchangeably.
The nonwoven of the present disclosure may have various structures.
Referring to
Referring to
Referring to
Referring to
The plurality of the protrusions 9 may be uniformly distributed on the top surface 32 of the nonwoven 30. The plurality of the protrusions 9 may be unevenly distributed and form a shape or a pattern on the top surface 32 of the nonwoven 30. The majority of the protrusions 9 may be surrounded by at least one land area 8 and/or a plurality of apertures 5. The land area 8, apertures 5 and protrusion 9 may form a three-dimensional surface on the top surface 32 the nonwoven 30.
In some configurations, the majority of the protrusions 9 may be hollow. When viewing from the first surface 3 of the first layer 1, the protrusions 9 may protrude from the land area 8 of the first layer 1 in the same direction and the first layer 1 and the second layer 2 are spaced away. The hollow between the first layer 1 and the second layer 2 may improve breathability of the nonwoven. When the nonwoven described herein is incorporated into an absorbent article, the plurality of protrusions may protrude toward the skin of the wearer when the article is in use and away from the absorbent core of the absorbent article.
This three-dimensional structure of the nonwoven provides better softness to the nonwoven. When the nonwoven described herein is used as a topsheet in an absorbent article, it also helps maintain the skin of the wearer away from body fluids in the land area as the protrusions essentially create a space between the skin of the wearer and the body fluids.
The nonwoven 30 may comprise a plurality of non-aperture areas each of which has substantially no aperture. Referring to
Referring to
The non-aperture area may be a flat land area or a protrusion.
The nonwoven according to the present disclosure may have at least 2.5% of open area, or at least 3% of open area. The apertures of the nonwoven may have an open area no greater than about 10%, or no greater than 8%.
In some configurations, the hydrophobic fibers constituting the first layer has a denier no greater than 1.5 denier. With small denier fibers on the first layer forming the top surface of the nonwoven, the nonwoven can provide superior softness and smoothness. In some configurations, the hydrophobic fibers constituting the first layer may have a denier no greater than a denier of the hydrophilic fibers constituting the second layer.
Capillarity energy is one common consideration in nonwoven topsheets for better absorbing performance. In order to leverage capillarity energy in the absorbent article design context, nonwoven topsheet can be described to have a capillarity gradient from a top surface to a bottom surface to enlarge the capillarity energy. A common nonwoven design to create a capillarity gradient is to make a lower portion of the nonwoven topsheet more condensed with smaller pore size or more fine denier fiber than an upper portion of the nonwoven topsheet. Meanwhile, it can be preferred that an upper portion of the nonwoven is formed by fine denier fibers which can endow a soft and smooth touch feel. However, use of fine denier fibers in an upper portion in the topsheet limits choices of fibers for a layer underneath which enables the underneath layer to have a more condensed structure. In addition, if a lower portion of a nonwoven topsheet has a very condensed structure, it is difficult to find an absorbent material with strong suction capability disposed below the topsheet. Without being bound by theory, it is the nonwoven of the present disclosure can overcome this contradiction by introducing a surface energy gradient, that is by introducing a high hydrophilicity gradient from top to bottom, and getting the top layer and the bottom layer fully integrated together. Apertures comprising at least one aperture having at least three adjacent apertures that are spaced apart from by an edge-to-edge space no greater than about 2.5 mm may also play a critical role to overcome the contradiction.
In some configurations, the nonwoven of the present disclosure is a through-air bonded nonwoven having a unitary structure. The feature that the first layer and the second layers are fully and evenly integrated in a fiber level may contribute to the advantageous properties of the nonwoven of the present disclosure. In some embodiments, the nonwoven of the present disclosure is a carded air-through nonwoven having a unitary structure. In other configurations, the nonwoven of the present disclosure is a spunbond nonwoven.
A basis weight of the nonwoven of the present disclosure may be appropriately selected depending on the nonwoven application. The nonwoven may have the integral basis weight of the first layer and the second layer of the nonwoven from about 10 g/m2 to about 100 g/m2, or from about 35 g/m2 to about 70 g/m2. For the use of the nonwoven as a topsheet of an absorbent article, in one form, the integral basis weight of the nonwoven may be in the range of from about 30 g/m2 to about 70 g/m2, or from about 15 g/m2 to about 40 g/m2, or from about 12 g/m2 to about 35 g/m2.
In some configurations, the nonwoven comprises a first layer forming the top surface of the nonwoven and a second layer forming the bottom surface of the nonwoven. In some configurations, the nonwoven may include at least one intermediate layer between the first layer and the second layer.
The first layer of the nonwoven of the present disclosure may comprise hydrophobic fibers. The first layer may consist essentially of hydrophobic fibers.
Constituting fibers of the first layer may be natural fibers, synthetic fibers or a combination of natural and synthetic fibers. In some configurations, the first layer comprises thermoplastic fibers.
The hydrophobic fibers may be thermoplastic fibers which can selected from the group consisting of polyesters, polypropylenes, polyethylenes, polyethers, polyamides, polyhydroxyalkanoates, polysaccharides, and combinations thereof. Additionally, other synthetic fibers such as rayon, polyethylene, and polypropylene fibers can be used within the scope of the present disclosure. Thermoplastic fibers may be single component fibers (i.e., single synthetic material or a mixture to make up the entire fiber), multicomponent fibers, such as bicomponent fibers (i.e., the fiber is divided into regions, the regions including two or more different synthetic materials or mixtures thereof), and combinations thereof.
Hydrophilic fibers may be rendered hydrophobic by treatment with a hydrophobic treatment such as a hydrophobic surfactant, e.g., by spraying or kiss roll coating hydrophilic fibers with a hydrophobic treatment, by dipping fibers into a hydrophobic treatment or by including a hydrophobic treatment as part of the polymer melt in producing thermoplastic fibers. Upon melting and resolidification, the treatment will tend to remain at the surfaces of the fiber.
The first layer may comprise semi-synthetic fibers made from polymers, specifically hydroxyl polymers. The topsheet may also comprise semi-synthetic fibers made from polymers, specifically hydroxyl polymers. Non-limiting examples of suitable hydroxyl polymers include polyvinyl alcohol, starch, starch derivatives, chitosan, chitosan derivatives, cellulose derivatives such as viscose, gums, arabinans, galactans, Lyocell (Tencel®), and combinations thereof.
The first layer may also comprise absorbent fibers. Some examples of absorbent fibers include cotton, pulp, rayon or regenerated cellulose or combinations thereof. The first layer may also comprise cellulose-based fibers which may be selected from the group consisting of wheat straw fibers, rice straw fibers, flax fibers, bamboo fibers, cotton fibers, jute fibers, hemp fibers, sisal fibers, bagasse fibers, hesperaloe fibers, and combinations thereof.
Several examples of the first layer may include, but are not limited to: spunbonded nonwovens; carded nonwovens; carded air through nonwovens; spunlace nonwovens, needle punched nonwovens and nonwovens with relatively specific properties to be able to be readily deformed.
The first layer can be formed from many processes, such as, for example, air laying processes, wetlaid processes, meltblowing processes, spunbonding processes, needle punching processes and carding processes.
In some configurations, the first layer is a carded air through nonwoven. In another configuration, the first layer is a spunbond nonwoven.
Hydrophobic fibers constituting the first layer 1 may have a contact angle no lower than about 95 degrees, or no lower than about 100 degrees. The constituent fibers of the first layer 1 may have a contact angle no greater than 150 degrees, or no greater than 130 degrees, according to Contact Angle Test. The hydrophobicity of the constituent fibers can be adjusted by appropriately adjusting the degree of hydrophobilization treatment of the thermoplastic fibers, for example, the type and content of the hydrophobic treatment.
Hydrophobic fibers constituting the first layer may have a fiber fineness no greater than 4 denier, or no greater than 2.5 denier, or no greater than 2 denier, or no greater than 1.5 denier, or no greater than 1.2 denier.
The first layer may have a basis weight from about 5 g/m2 to about 50 g/m2, or from about from about 8 g/m2 to about 30 g/m2, or from about 8 g/m2 to about 25 g/m2.
The optional second layer of the nonwoven of the present disclosure may comprise hydrophilic fibers. The second layer may consist essentially of hydrophilic fibers.
Constituting fibers of the second layer may be natural fibers, synthetic fibers or a combination of natural and synthetic fibers. In one embodiment, the second layer comprises thermoplastic fibers.
The list of synthetic fibers corresponds to the list disclosed above for the topsheet and the first layer.
Hydrophobic fibers may be rendered hydrophilic by treatment with a hydrophilic treatment such as a hydrophilic surfactant, e.g., by spraying hydrophobic thermoplastic with a hydrophilic treatment, by dipping the fiber into a treatment or by including a hydrophilic treatment as part of the polymer melt in producing thermoplastic fibers. Upon melting and resolidification, the treatment will tend to remain at the surfaces of the fiber.
Hydrophilic fibers constituting the second layer may have a fiber fineness no greater than 6 denier, or no greater than 4 denier, or no greater than 2 denier.
Hydrophilic fibers constituting the second layer may have a contact angle no greater than about 90 degrees, or no greater than about 30 degrees, or no greater than about 10 degrees, or zero degree, according to the Contact Angle Test.
The second layer may have a basis weight from about 5 to about 70 g/m2, or from about 10 to about 60 g/m2, or about 10 to about 25 g/m2.
All aspects described above for the first layer, except for the second layer comprising hydrophilic fibers, are equally applicable to the first layer in a topsheet comprising a first and a second layers.
The nonwoven of the present disclosure may comprise a plurality of apertures in a clustered aperture pattern. The term “clustered apertures” herein intends to mean an aperture pattern wherein at least one aperture having at least three adjacent apertures, wherein the one aperture and each of the at least three adjacent apertures have an edge-to-edge space S (shortest space between an edge of one aperture to an edge of an adjacent aperture) no greater than about 2.5 mm, preferably no greater than 2 mm.
In one form, the nonwoven of the present disclosure may comprise a plurality of apertures having a clustered aperture pattern, the clustered aperture pattern comprises a first unit comprising an aperture having at least three adjacent aperture where the aperture and each of the at least three adjacent aperture have an edge-to-edge space S (shortest space between an edge of one aperture to an edge of an adjacent aperture) no greater than about 2.5 mm; and a second unit comprising an aperture having at least three adjacent aperture wherein the aperture and each of the at least three adjacent aperture have an edge-to-edge space S no greater than about 2.5 mm, wherein one aperture in the first unit and one aperture in the second unit have an edge-to-edge space S no greater than about 10 mm.
Meanwhile, the aperture pattern in
The apertures may vary in shape. For example, the shape of the apertures as seen from the first surface of the first layer may be circular, elliptic, rectangular or polygonal. In some configurations, the apertures have a circular shape, an elliptic shape or a polygonal shape.
The tridimensional shape of the apertures may be cylindrical (e.g., with a circular or elliptic base), prismatic (e.g., with a polygonal base) or truncated cone or pyramidal.
Referring to
The apertures may be tapered and take a conical shape such that the diameter of the aperture is larger at a part of the aperture proximate to the top surface of the nonwoven than the diameter of the aperture at the bottom edge of the aperture. Such tapered configurations may help to reduce the risk of rewet, i.e., of body fluids passing back from components underneath the topsheet (such as the absorbent core) into and through the topsheet. For apertured hydrophobic topsheets, rewet occurs predominantly through the apertures. The tapered shape of the apertures can help to reduce rewet, as the diameter of the aperture towards the absorbent core is smaller than the diameter of the aperture in the first layer.
The plurality of apertures may also vary in width.
The size of apertures may be determined to achieve the desired fluid and/or air penetration performance and other performances expected by wearers. If the apertures are too small, the fluids may not pass through the apertures, either due to poor alignment of the fluid source and the aperture location or due to runny fecal masses, for example, having a diameter greater than the apertures. If the apertures are too large, the area of skin that may be contaminated by “rewet” from the article is increased.
Each of the plurality of apertures may have a size ranging from 0.2 mm2 to 1.5 mm2, from 0.2 mm2 to 1.0 mm2, or from 0.25 mm2 to 0.5 mm2, and/or a diameter ranging from 0.3 mm to 1.5 mm, or from 0.3 mm to 1 mm, or from 0.4 mm to 0.8 mm. The plurality of apertures may have regular shapes selected from the group consisting of circle, oval, triangle, square, rectangle, parallelogram, trapezoid, polygon, hourglass, star, and any combinations thereof.
Without wishing to be bound by theory, it is believed that clustered apertures enable fluid to penetrate faster than non-clustered apertures due to two reasons. Firstly, apertures adjacent to each other with an edge-to-edge space S no more than 2.5 mm, preferably no more than 2 mm can drive more amount of fluid or high density fluid to penetrate a nonwoven topsheet than non-clustered apertures. Secondly, clustered apertures may make the nonwoven between aperture areas more condensed compared with no aperture areas or nonwoven in non-clustered apertures, and this condensation contrast may drive fluid to be absorbed on the clustered aperture area.
The nonwoven of the present disclosure exhibits a rapid acquisition of body fluid and/or maintains dryness of the top surface as the nonwoven can inhibit body fluid from flowing back to the top surface under pressures.
As such, the nonwoven of the present disclosure can be preferably used in applications in which the nonwoven is in contact with the skin, specifically applications in which the first layer constitutes the surface that is in contact with the skin in absorbent articles.
Absorbent articles will now be generally discussed and further illustrated in the form of a sanitary napkin 100 as exemplarily represented in
Referring to
The backsheet 26 and the topsheet 24 can be secured together in a variety of ways. The topsheet 24 and the backsheet 26 can be joined to each other by using an adhesive, heat bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or a crimp seal. A fluid impermeable crimp seal can resist lateral migration (“wicking”) of fluid through the edges of the product, inhibiting side soiling of the user's undergarments.
When the absorbent article is a sanitary napkin as shown in
An absorbent article according to the present disclosure comprises a topsheet and a liquid impermeable backsheet, and an absorbent core disposed between the topsheet and the backsheet, wherein the topsheet comprises the nonwoven as described herein.
The absorbent articles of the present disclosure may be produced industrially by any suitable means. The different layers may thus be assembled using standard means such as embossing, thermal bonding, gluing or any combination thereof.
The nonwoven according to the present invention may be manufactured via various process known in the industry.
The first layer and the second layer may be produced separately and bonded or integrated together for example, via thermal and/or glue application. Each of the first layer and the second layer may be from a carded web, air-laid web, wet-laid web, and spunbond web, and the like.
The nonwoven according to the present disclosure may be manufactured in a continuous process. For example, the nonwoven may be produced by laying a first fibrous web comprising hydrophobic fibers on a conveyor belt, overlaying a second fibrous web comprising hydrophilic fibers on the first fibrous web to obtain a composite fibrous web, and subjecting the composite fibrous web to thermal treatment in order to thermal bond at least a portion of the hydrophobic fibers and hydrophilic fibers. In other examples, the nonwoven may be produced using parallel carding machines via a process comprising the steps of forming a first fibrous web comprising hydrophobic fibers, forming a second fibrous web comprising hydrophilic fibers, forming a composite fibrous web by overlaying the second fibrous web on the first fibrous web; and subjecting the composite fibrous web to thermal treatment in order to thermal bond at least a portion of the hydrophobic fibers and hydrophilic fibers.
The bonding treatment of a composite fibrous web can be conducted using any conventionally known fiber bonding method. Examples of such a bonding method include hot air through-type thermal bonding and ultrasonic bonding.
Aperture of precursor nonwoven can be conducted using any conventionally known nonwoven aperture method. An exemplary aperture equipment is a pair of rolls comprising a pair of rolls.
All measurements are performed in a laboratory maintained at 23° C.±2° C. and 50%±2% relative humidity.
A rectangular specimen measuring 10 mm×50 mm is cut from a law material nonwoven or a topsheet of a disposable absorbent product taking care not to touch the surface of the specimen or to disturb the structure of the material. The specimen has a length of (5 cm) aligned with a longitudinal centerline of the article. The specimen is handled gently by the edges using forceps and is mounted flat in the view of a microscope such as Keyence VHX 5000 or equivalent. An appropriate magnification and light source of the equipment can be adjusted to make the specimen shown clearly.
One water droplet with a volume of approximately 0.05 ml is gently deposited onto the specimen from in a close distance no longer than 1 cm above tested surface of the specimen. Keyence VHX 5000 or equivalent instrument is used to obtain a high-resolution image of a water droplet on the tested surface of the nonwoven specimen. These steps are repeated to obtain multiple water droplet images. Suitable water droplet images where each water droplet is oriented such that the projection of the water droplet extending from the nonwoven surface is approximately maximized. The contact angle between the water droplet and the specimen is measured to the nearest 0.1 degree directly from the image taken as is shown via lines 3700 in
The measurement is performed on an area of a test nonwoven where no aperture exists. Five separate droplets are imaged from which ten contact angles, i.e., one on each side of each imaged droplet are measured. The arithmetic mean of the ten contact angle values is calculated to the nearest 0.1 degree and reported as the surface contact angle.
AMF is composed of a mixture of defibrinated sheep blood, a phosphate buffered saline solution and a mucous component, and has a viscosity between 7.15 cSt to 8.65 cSt at 23±1° C.
Viscosity on the AMF is performed using a low viscosity rotary viscometer such as Cannon LV-2020 Rotary Viscometer with UL adapter (Cannon Instrument Co., State College, US) 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±1° C. and at 60 rpm. Results are reported to the nearest 0.01 cSt.
Defibrinated sheep blood with a packed cell volume of 38% or greater collected under sterile conditions (available from Cleveland Scientific, Inc., Bath, OH, US) or equivalent is used.
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. 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. 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, then remove the beaker from the hot plate and cool to below 40° C. Next add 1.8±0.2 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 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 cSt. 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.
Rewet is measured for an absorbent article loaded with Artificial Menstrual Fluid (“AMF”) as described herein.
The fluid amounts left on a topsheet, i.e., rewet, under pressure of 0.1 psi and 0.5 psi are measured after 3.0 ml, 6.0 ml, 9.0 ml and 12.0 ml AMF are dispensed. All measurements are performed in a laboratory maintained at 23° C.±2° C. and 50%±2% relative humidity.
Test products are removed from all packaging using care not to press down or pull on the products while handling. No attempt is made to smooth out wrinkles. The test products are conditioned at 23° C.±2° C. and 50%±2% relative humidity for at least 2 hours prior to testing.
Place the test product onto a flat, horizontal surface with the body side facing up and load a strikethrough plate on the center of the test product to apply a pressure of 0.25 psi on the test product.
Referring to
Use a pipette to carefully dispense 3.0 ml of AMF through the open hole of the strikethrough plate onto the center of the test articles within 2 seconds. Once the gush fluid is acquired, remove the plate and start the timer for 3 minutes. After removing the plate, quickly acquire an image of a topsheet of the test product using a color scanner HP Scanjet G4010 or equivalent, and clean the scanner surface after each scan. The image will be analyzed to measure a stain size on a topsheet under Stain Size Test described below. At the end of 3 minutes, place 5 pieces of filter paper (a typical lab filter paper, for example, Ahlstrom #632 12.7 cm×12.7 cm filter papers) that are pre-weighed (termed as “dry weight”) are placed on top of an approximate center of an area stained with the fluid. Apply the required mass to generate 0.1 psi pressure on the top of the test product, and keep it under pressure for 5 seconds. Weigh the filter papers again (termed as “wet weight”). The difference between the wet weight and dry weight of the filter paper is the light pressure rewet at the added amount of fluid.
Repeat the step above till total 12.0 ml of fluid is dispensed on the test product. Report the rewet values to the nearest 0.001 gram for the gush level of 3.0 ml, 6.0 ml, 9.0 ml and 12.0 ml.
In like fashion, a total of three replicate samples are tested for each test product to be evaluated. Report the arithmetic mean of the replicates to the nearest 0.001 gram as rewet at 0.1 psi.
The same test is conducted by applying the required mass to generate 0.5 psi pressure on the top of the test product and obtain rewet at 0.5 psi.
The area of a stain visible on a topsheet of an absorbent article due to the fluid left on the topsheet is measured on topsheet images of test products acquired in Rewet Test above for the gush level of 3.0 ml, 6.0 ml, 9.0 ml and 12.0 ml.
Image analysis is performed using image analysis program such as Image J software (version 1.52p or above, National Institute of Health, USA) or equivalent. The image needs to be distance calibrated with an image of a ruler to give an image resolution, i.e., 7.95 pixels per mm.
Open a topsheet image in Image J. Set the scale according to the image resolution. Crop the image in the center area to make a minimum bounding rectangular selection around the total stain region visible across multiple pad layers. Convert the image type to 8 bit. Apply a Gaussian blur filter to smooth the image by a Gaussian function with a Sigma (radius) of 2. The filtered 8-bit grayscale image is then converted to a binary image using the “Minimum” thresholding method to find the boundary of the stain region on the topsheet (as a result of fluid left on the topsheet) against the lighter-colored stain region from the subsequent layers.
The area of the selected stain region on the topsheet is obtained and recorded as topsheet Stain Size to the nearest 0.01 cm2. This entire procedure is repeated on three substantially similar replicate articles. The reported value is the average of the three individual recorded measurements for topsheet Stain Size to the nearest 0.01 cm2.
Stain redness is indicated as redness saturation integral which is calculated based on the HSB color model using a color representation by three parameters: Hue, saturation and brightness. Hue range 240-45 is selected for representative total red stain hue range on a topsheet of the test product. For selected 240-45 hue red stain area, saturation range is between 0-100. Pixels for each saturation from 0-100 is counted where saturation level 35-100 is defined as TS stain saturation range similar as human visual judgement. Stain Saturation Integral is calculated using the equation below.
TS Stain Saturation Integral=35*P35+36*P36+37*P37+ . . . +100*P100
Acquisition time is measured for an absorbent article loaded with AMF as described herein, using a strikethrough plate and an electronic circuit interval timer. The time required for the absorbent article to acquire a dose of AMF is recorded. All measurements are performed in a laboratory maintained at 23° C.±2° C. and 50%±2% relative humidity.
Referring to
Test products are removed from all packaging using care not to press down or pull on the products while handling. No attempt is made to smooth out wrinkles. The test samples are conditioned at 23° C.±2° C. and 50%±2% relative humidity for at least 2 hours prior to testing.
The required mass of the strikethrough plate must be calculated for the specific dimensions of the test article such that a confining pressure of 1.72 kPa is applied. Determine the longitudinal and lateral midpoint of the article's absorbent core. Measure and record the lateral width of the core to the nearest 0.1 cm. The required mass of the strikethrough plate is calculated as the core width multiplied by strikethrough plate length (10.2 cm) multiplied by 17.6 gf/cm2 and recorded to the nearest 0.1 g. Add lead shot to the plate to achieve the calculated mass.
Connect the electronic circuit interval timer to the strikethrough plate 9001 and zero the timer. Place the test product onto a flat, horizontal surface with the body side facing up. Gently place the strikethrough plate 9001 onto the center of the test product ensuring that the “H” shaped reservoir 9003 is centered over the test area.
Using a mechanical pipette, accurately pipette 3.00 mL±0.05 mL of AMF into the test fluid reservoir 9003. The fluid is dispensed, without splashing, along the molded lip of the bottom of the reservoir 9003 within a period of 3 seconds or less. After the fluid has been acquired, record the acquisition time to the nearest 0.01 second. Thoroughly clean the electrodes 9004 before each test.
In like fashion, a total of three replicate samples are tested for each test product to be evaluated. Report the Acquisition Time (sec) as the mean of the replicates to the nearest 0.01 sec.
When a nonwoven is available in a raw material form, a specimen with a size of 55 mm×55 mm is cut from the raw material. When a nonwoven is a component of a finished product, the nonwoven is removed from the finished product using a razor blade to excise the nonwoven from other components of the finished product to provide a nonwoven specimen with a size of 55 mm×55 mm. A cryogenic spray (such as Cyto-Freeze, Control Company, Houston TX) may be used to remove the nonwoven specimen from other components of the finished product, if necessary.
The nonwoven specimen is placed flat against a dark background under uniform surface lighting conditions. The entire area of the specimen is scanned using an optical microscope such as Keyence 3D Measurement System VR-3200 or equivalent. The analysis such as area ratio measurement is performed using image analysis program such as ImageJ software (version 1.52p or above, National Institutes of Health, USA) and equivalent. The images need to be distance calibrated with an image of a ruler to give an image resolution. Set the scale according to the image resolution and select the field of view size of 55 mm×55 mm for the nonwoven specimen.
Open a specimen image in ImageJ. Convert the image type to 8 bits. The 8-bit grayscale image is then converted to a binary image (with “black” foreground pixels corresponding to the apertures) using the “Minimum” thresholding method: If the histogram of gray level (GL) values (ranging from 0 to 255, one bin with propensity Pi per gray level i) has exactly two local maxima, the threshold gray level value t is defined as that value for which Pt−1>Pt and Pt≤ Pt+1. If the histogram has greater than two local maxima, the histogram is iteratively smoothed using a windowed arithmetic mean of size 3, and this smoothing is performed iteratively until exactly two local maxima exist. The threshold gray level value t is defined as that value for which Pt−1>Pt and Pt≤Pt+1. This procedure identifies the gray level (GL) value for the minimum population located between the dark pixel peak of apertures and the lighter pixel peak of the specimen material. If the histogram contains either zero or one local maximum, the method cannot proceed further, and no output parameters are defined.
Create a filtered image by removing small openings or defects in the binary image using an outlier removing median filter, which replaces a pixel with median of the surrounding area of e.g., 5 pixels in radius if the pixel is darker than the surrounding. Create a reversed image so that discreate non-aperture zones have pixel values of 255.
An ImageJ plugin “Local Thickness” is applied to the image. The local thickness analysis measures the diameter of the largest sphere that fits inside the object and contains the point for each point, i.e., foreground pixel in an image. (reference: “New algorithms for Euclidean distance transformation on an n-dimensional digitized picture with applications”, T. Saito and J. Toriwaki, Pattern Recognition 27, 1994, 1551-1565). Convert the image type of local thickness map to 16 bits.
An ImageJ plugin “k-means Clustering” is applied to the image obtained above, which segments the image in the defined number of clusters with similar intensity. The options for k-means clustering used in this analysis are: 5 clusters (i.e., 5 segments image will be divided into); cluster center tolerance of 0.0001; enable randomization seed (randomization seed: 48); show clusters as centroid value. Use the image of clusters represented by centroid value and segment it via centroid value thresholding to only select the discrete non-aperture zones. The histogram data of the binary image is used to calculate the area ratio (%) of discrete non-aperture zones by dividing the counts of foreground pixels (corresponding to the discrete non-aperture zones) with the total pixel counts of the entire area of the image, and multiplying it by 100%. The value is reported to the nearest 1%. The same image is also used for the size/area analysis. Set the scale according to the image resolution. Use watershed segmentation if necessary to separate the discrete non-aperture zones that touch each other. Measure the area (mm2) of each of the discrete non-aperture zones, when excluding the incomplete ones on the edge of the image. The size/area of discrete non-aperture zones is the arithmetic mean of the area values and reported to the nearest 1 mm2.
Various nonwoven substrates having configurations as indicated in Table 1 were produced using a parallel carding machine and heat treatment.
Substrate 1: 11 gsm first fibrous web of was fabricated by laying down 1.5 denier hydrophobic PE/PET bicomponent fibers constituting the first layer on a conveyer belt. 13 gsm second fibrous web was fabricated by laying down 2 denier hydrophilic PE/PP bicomponent fibers constituting the second layer on a conveyer belt. The second fibrous web was overlaid on the first fibrous web, and the overlaid web was subjected to thermal treatment at the temperatures 130° C.-140° C. The thermal treatment was performed using a hot air through-type thermal treatment apparatus with a breathable conveyor belt. In the heat treatment, the overlaid web was placed on the breathable conveyor belt of the thermal treatment apparatus in such a way that the surface of the first fibrous web was in contact with the breathable conveyor belt. The 1.5 denier hydrophobic PE/PET bicomponent fibers have a fiber contact angle of 116.0°, and the 2 denier hydrophilic PE/PET bicomponent fibers have a fiber contact angle of 62.3°.
Substrate 2: Substrate 2 was produced using Substrate 1 by forming apertures in a pattern shown in
Substrate 3: Substrate 3 was produced using Substrate 1 by forming apertures in a pattern shown in
Substrate 4: Substrate 4 was produced according to the process disclosed with respect to Substrate 1 using 21 gsm 1.5 denier hydrophobic PE/PET bicomponent fibers for the first layer and 13 gsm 2 denier hydrophilic PE/PP bicomponent fibers for the second layer.
Substrate 5: Substrate 5 was produced using Substrate 4 by forming apertures in a pattern shown in
Substrate 6: Substrate 6 was produced using Substrate 4 by forming apertures in a pattern shown in
Substrate 7: 24 gsm of a mixture of 60% 1.5 denier hydrophobic PE/PET bicomponent fibers and 40% 1.5 denier hydrophilic PE/PET bicomponent fibers were laid down on a conveyer belt to obtain a fibrous web. The fibrous web was subjected to thermal treatment at the temperatures 130° C.-140° ° C. to obtain nonwoven. The thermal treatment was performed using a hot air through-type thermal treatment apparatus with a breathable conveyor belt. Apertures in a pattern shown in
Substrate 8: 24 gsm carded air-through nonwoven was fabricated using 1.5 denier hydrophobic PE/PEP sheath/core bicomponent fibers (fiber contact angle of 116.0°). Apertures having a pattern shown in
Substrates 9 and 10: Substrates 9 and 10 were produced using Substrate 1 by forming apertures in patterns shown in
Substrate 9, referring to
Substrate 10, referring to
Contact angles on a top surface and an opposite bottom surface in nonwovens were measured according to the Contact Angle Test, and indicated in Table 1 below. Contact angles of Substrates 2, 3, 5, 6, 9 and 10 were not tested given Substrates 2, 3, 9 and 10 are the same as Substrate 1, and Substrates 5 and 6 are the same as Substrate 4 in nonwoven composition and structure except having apertures.
Sanitary napkins 1-10 as exemplary absorbent articles having topsheets made by nonwoven substrates in Example 1 above were fabricated using a common secondary topsheet, absorbent core and backsheet.
Acquisition speed, and rewet at 0.1 psi/g and 0.5 psi/g of each of the sanitary napkins were tested according to Acquisition Speed Test and Rewet Test disclosed herein. Rewet at 0.1 psi/g represents rewet when the wearer is standing or walking, and rewet at 0.5 psi/g represents rewet when the wearer is sitting. Stain size and stain redness of the sanitary napkins were tested according to Stain Size and Redness Test disclosed herein. Table 2 below includes the measurement results.
Sanitary napkin 3 differs from Sanitary napkins 1 and 2 only in the topsheet in such a way that Substrate 3 has clustered apertures while Substrates 1 and 2 do not. Sanitary napkin 3 compared to Sanitary napkins 1 and 2 exhibits significantly improvement in acquisition time and rewet in both a light pressure and an increased pressure. In addition, Sanitary napkin 3 compared to Sanitary napkins 1 and 2 has a significant small stain area and stain redness.
Sanitary napkin 3, compared to Sanitary napkin 7 which comprises a topsheet made by a nonwoven substrate from a mixture of hydrophobic fibers and hydrophilic fibers, exhibits parity acquisition time, and significant small values in rewet in both a light pressure and an increased pressure. In addition, Sanitary napkin 3 compared to Sanitary napkin 7 has a significant small stain area and a stain redness.
Sanitary napkin 3, compared to Sanitary napkin 8 which comprises a topsheet made by a nonwoven substrate from 100% hydrophobic fibers, exhibits dramatic improvement in acquisition time while still having satisfactory rewet values in both a light pressure and an increased pressure, and a stain area.
Sanitary napkin 6 differs from Sanitary napkins 4 and 5 only in the topsheet where Substrate 6 differs from Substrates 4 and 5 only in aperture pattern. Sanitary napkin 6 compared to Sanitary napkins 4 and 5 exhibits significant improvement in acquisition time and rewet in both a light pressure and an increased pressure. In addition, Sanitary napkin 6 compared to Sanitary napkins 4 and 5 has a significantly small stain area and stain redness.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/137843 | Dec 2022 | WO | international |
This application claims foreign priority under 35 U.S.C. § 119 to Chinese Patent Application No. PCT/CN2022/137843, filed on Dec. 9, 2022, which is herein incorporated by reference in its entirety.
