Women's hygiene pads with a non-woven fabric top sheet for improved skin feel

Abstract

A feminine hygiene pad is disclosed having a topsheet comprising a fibrous nonwoven web material having hydrophilic fibers and an absorbent layer comprising an open-cell foam formed by polymerization of a high internal phase emulsion (HIPE). The topsheet and absorbent layer are disposed in a direct face-to-face relationship and attached to each other within a bonded region. Within the bonded region, each first identifiable attachment point between the topsheet and absorbent layer has an adjacent second identifiable attachment point between the topsheet and absorbent layer within a 6 mm radius of the first identifiable attachment point.

Description

[Background technology]

[0001] Experience and consumer research have shown that users of feminine hygiene pads have developed a number of diverse expectations and preferences regarding such products as the products themselves have evolved. These expectations and preferences include (in no particular order) (1) that the pad is soft, breathable, and comfortable against the skin when dry before menstrual fluid discharge; (2) that the pad does not feel excessively wet against the skin after fluid discharge (i.e., maintains a somewhat or substantially dry feel); (3) that the pad has suitable absorbency to easily receive, absorb, contain, isolate, and effectively retain discharged menstrual fluid without separating it from the user's skin and without leakage during normal use / wearing time; and (4) the outward-facing surface (5) The pad should not present an excessively dark coloration that could be visible through outer clothing, and should at least partially conceal the absorbed fluid on the surface facing the wearer, providing a visual indication that the absorbed fluid is contained and isolated from the wearer's skin; (6) For the purposes of comfort, adaptation to the wearer's body movements, and inconspicuous wear under clothing, the pad should be as thin (not bulky), flexible, and pliable as possible; and (7) the pad should not substantially support the presence or growth of microorganisms on the skin or near the genital area during use / wear. With respect to currently known product designs and materials currently known and used as components of these products, it is not possible to fully satisfy all of these expectations and preferences at the same time. In order to provide products that fully satisfy the user / consumer market, manufacturers must carefully balance priorities and provide product features that more or less address each of these expectations and preferences, under competitive cost / price constraints.

[0002] Many commercially available feminine hygiene pads have a top sheet formed from a perforated film. Polymer films (often polyethylene-based films) are found to be suitable as top sheet materials for many consumers because they are substantially non-absorbent and therefore do not retain deposited fluid. Polymer films tend to maintain a somewhat dry feel after the fluid is drained and subsequently absorbed by the absorbent components below. A typical film top sheet is provided with a pattern of openings that penetrate the film and have a size, geometric density, and numerical density per unit surface area to provide sufficient passage through the film, allowing the drained fluid to pass through this pattern of openings to the absorbent material beneath the top sheet. In some examples, the openings may be formed via a vacuum forming process that imparts a small, flexible funnel-shaped structure to each opening, causing the opening to function in a manner similar to a one-way check valve. However, some consumers may negatively perceive the "plastic" feel against the skin.

[0003] Nonwoven fabrics of a suitable basis weight, formed from polymer fibers, may offer a more preferable feel than films when dry for some users, but unless treated to be hydrophilic, they do not readily accept aqueous fluids or carry them by capillary action so that they can be absorbed by the underlying absorbent structure. To address this problem, such nonwoven fabrics may be given openings by various processes. However, perforated nonwoven fabrics may have mechanical weaknesses or dimensional instability (adversely affecting processability on the production line) and / or may not provide the desired level of visual concealment of absorbed fluids. Furthermore, the relatively larger openings required in such nonwoven fabrics may allow loose fragments of absorbent material in the underlying absorbent structure to sieve out through the openings, which can contribute to a negative consumer perception of quality.

[0004] Typically, hydrophobic polymer fibers can be treated to impart hydrophilicity and used to form nonwoven webs for topsheet materials without requiring openings to receive fluid and facilitate fluid movement through the interior. Hydrophilic fibers (e.g., suitably processed cotton and rayon fibers) can typically be used to form nonwoven webs for topsheet materials without requiring openings. Compared to perforated films, these may have a more pleasant feel against the skin for some consumers when dry. Furthermore, materials such as cotton or other plant fibers are considered natural products, making their use as components of skin-contact materials attractive to some consumers. A suitably manufactured nonwoven fabric formed from hydrophilic fibers can readily receive and disperse menstrual fluid (which is aqueous) discharged via suction. However, because nonwoven fabrics formed from hydrophilic fibers retain all discharged fluid, they may not allow that fluid to pass through to the absorbent material below, or they may tend to re-wet (re-capture fluid from the absorbent material below). Because the constituent fibers are hydrophilic, nonwoven fabrics tend to attract and / or retain some of the discharged fluid. That is, the nonwoven fabric is a functional part of the absorbent structure rather than more preferably functioning as a barrier between the wearer and the absorbed fluid, having a unidirectional passage to contain the discharged fluid and guide it through to the absorbent structure below. Therefore, a top sheet formed of hydrophilic fibers may, undesirably, leave a feeling of dampness on the wearer's skin after fluid discharge and may not provide substantial concealment of the absorbed fluid because it retains some of the fluid itself. Furthermore, a damp top sheet may provide a medium that supports the presence or growth of microorganisms in close proximity to the wearer's skin and genital area, which is generally considered undesirable.

[0005] Therefore, there remains room for improvement in the combination of top sheet materials, absorbent materials, and pad structures, enabling manufacturers to better satisfy the expectations and preferences of more users / consumers than are currently known. [Brief explanation of the drawing]

[0006] [Figure 1] This is a plan view of a women's hygiene pad with the top sheet facing the observer. [Figure 2A] Figure 1 is a schematic cross-sectional view of a women's hygiene pad. [Figure 2B] This is an enlarged portion 2B of the drawing in Figure 2A, which has been enlarged to depict the sublayer of the absorbent layer. [Figure 3A] This is a plan view of several examples of adhesive deposition patterns within bonding regions where the top sheet can be bonded to the absorbent layer. [Figure 3B] This is a plan view of several examples of adhesive deposition patterns within bonding regions where the top sheet can be bonded to the absorbent layer. [Figure 3C] This is a plan view of several examples of adhesive deposition patterns within bonding regions where the top sheet can be bonded to the absorbent layer. [Figure 4] The following is a schematic diagram of the equipment used in the capillary action potential measurement method described below. [Modes for carrying out the invention]

[0007] definition With respect to a female hygiene pad that is opened and laid flat on a horizontal surface, "lateral direction" refers to a direction that is perpendicular to the longitudinal direction and parallel to the horizontal plane.

[0008] With respect to a women's hygiene pad that is laid flat on a horizontal plane and has a length measured from the front end to the rear end, "longitudinal direction" refers to the direction parallel to the line along which the length is measured and also parallel to the horizontal plane. "Length" refers to the dimension measured in the longitudinal direction.

[0009] With regard to women's hygiene pads, the terms “front,” “back,” “forward,” and “rear” refer to the position where the pad is typically worn by the user, as well as the characteristics or areas of the pad corresponding to the front and back of the user’s body when standing upright.

[0010] Regarding a feminine hygiene pad that is opened on a horizontal plane and laid flat, or a non-woven web material laid flat on a horizontal plane, the "z-direction" refers to the direction perpendicular to the horizontal plane, and any plane parallel to the horizontal plane may be referred to as the "x-y plane". When the pad is being worn by a user (and thus biased into a curved configuration), the "z-direction" at any given point location on the pad refers to the direction perpendicular to the surface of the pad facing the wearer at that given point location. Regarding the non-woven web during manufacturing, the "z-direction" refers to the direction perpendicular to both the machine direction and the cross-machine direction of the product, and any plane parallel to the machine direction and the cross-machine direction may be referred to as the "x-y plane".

[0011] Regarding a feminine hygiene pad, "facing the wearer" is a relative positional term that refers to a feature of a component or structure of the pad that is closer to the wearer than another feature of a component or structure located along the same z-direction during use. For example, the topsheet has a surface facing the wearer that is located closer to the wearer than the outer-facing surface on the opposite side of the topsheet.

[0012] Regarding a feminine hygiene pad, "outer-facing" is a relative positional term that refers to a feature of a component or structure of the pad that is farther from the wearer than another feature of a component or structure located along the same z-direction during use. For example, the topsheet has an outer-facing surface that is located farther from the wearer than the surface facing the wearer on the opposite side of the topsheet.

[0013] Explanation Referring to FIGS. 1 and 2A, the feminine hygiene pad 10 can include a liquid-permeable topsheet 20, a liquid-impermeable backsheet 30, and an absorbent layer 40 disposed between the topsheet and the backsheet. This absorbent layer has an outer peripheral portion 41. In the region outside the outer peripheral portion 41, the topsheet and the backsheet may be joined together in a laminated manner by any suitable mechanism including, but not limited to, adhesive bonding, thermal bonding, pressure bonding, etc., whereby the absorbent layer 40 can be maintained and held in place between the topsheet 20 and the backsheet 30. The pad 10 may include opposing wing portions 15 that extend laterally outwardly beyond the outer peripheral portion 41 by a relatively large width dimension compared to the main portion of the pad. The outer surface of the backsheet that forms the lower surfaces of the main portion and the wing portions may have a deposit of adhesive 35 thereon. The adhesive deposit 35 is provided to allow the user to adhere the pad to the inside of the pants within the crotch region, wrap the wing portions through the inner edge of the leg opening of the underwear and adhere them to the outside / lower side of the underwear in the crotch region, provide an auxiliary holding support, and help protect against soiling the leg edges of the underwear. When the pad 10 is packaged, the adhesive deposit 35 may be covered by one or more sheets of release film or paper (not shown). The release film or paper covers / shields the adhesive deposit 35 so as not to contact other surfaces until the user removes the release film or paper and positions the pad for use.

[0014] Topsheet The topsheet 20 can be formed from any suitable hydrophilic nonwoven web material. Referring to the figures again, the topsheet 20 is positioned adjacent to the surface of the absorbent layer 40 facing the wearer and can be joined thereto and to the backsheet 30 by any suitable attachment or bonding method. The topsheet 20 and the backsheet 30 can be joined directly to each other in the peripheral region outside the outer peripheral portion 41 of the absorbent layer, or indirectly by joining directly to the surface of the absorbent layer facing the wearer and the surface facing outward, or to additional optional layers included in the pad.

[0015] Pad 10 may have any known or other effective top sheet, such as one that conforms to the wearer's skin, is soft to the touch, and is non-irritating. Suitable top sheet materials include liquid-permeable materials that are comfortable when in contact with the wearer's skin and allow discharged menstrual fluid to pass through quickly. Suitable top sheets may be made from a variety of materials, such as woven fabrics and nonwoven web materials.

[0016] Non-limiting examples of nonwoven web materials that may be suitable for use as a top sheet include fibrous materials made from natural fibers, modified natural fibers, synthetic fibers, or combinations thereof. Some suitable examples are described in U.S. Patents No. 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.

[0017] In some embodiments, the top sheet may include tufts as described in U.S. Patents No. 8,728,049, 7,553,532, 7,172,801, 8,440,286, 7,648,752, and 7,410,683. The top sheet may have a pattern of individual hair-like fibrils as described in U.S. Patent No. 7,655,176 or 7,402,723. Additional examples of preferred top sheet materials are described in U.S. Patents No. 8,614,365, 8,704,036, 6,025,535, and U.S. Patent Application Publication 2015 / 041640. Another preferred top sheet may be formed from a three-dimensional substrate as detailed in U.S. Patent Application Publication 2017 / 0258647. The top sheet may have one or more layers, as described in U.S. Patent Application Publications 2016 / 0167334, 2016 / 0166443, and 2017 / 0258651.

[0018] As intended herein, the nonwoven web material of the components from which the top sheet 20 can be cut may include, or consist mainly (by weight) of, or entirely of, cellulosic plant fibers such as cotton, flax, hemp, jute, or mixtures thereof, which are either naturally hydrophilic or suitably processed to be hydrophilic (or have increased hydrophilicity) and treated to have a suitably soft feel against the skin. Plant fibers may be preferred to appeal to consumer preferences for natural products. In other embodiments, semi-synthetic fibers derived from cellulosic materials such as rayon (including viscose, liocell, MODAL (product of Lenzing AG, Lenzing, Austria) and copper ammonia rayon) may be used.

[0019] The nonwoven web may be formed by any preferred process in which finite-length fibers are distributed and accumulated on a forming belt in a controlled manner, and a bat with a desired fiber distribution is formed to a desired basis weight. Preferred processes include carding, air laminating, and wet lamination. The bat may be treated to compact the fibers and entangle them in the z direction by processes that may include calendering, needle punching, and water entanglement.

[0020] In some embodiments, a top sheet cut from a nonwoven fabric containing, or mainly (by weight), plant fibers such as cotton fibers, or entirely composed of them, may be preferred. In some embodiments, the nonwoven web material may be formed by a carding process. In other embodiments, the nonwoven web material may be formed by air laminating or a wet lamination process. In yet another embodiment, the nonwoven web material is formed by physically blending or mixing finite-length plant fibers with a stream of long but indeterminate-length spun fibers spun from a polymer resin and arranging them on a forming belt to form the web, e.g., U.S. Patent No. 8,017,534, U.S. Patent No. 4,100,324, U.S. Patent Application Publication No. 2003 / 0200991, U.S. Patent No. 5,508,102, U.S. Patent Application Publication No. They may be formed by co-formation processes as described in Patent No. 2003 / 0211802, European Patent No. 0333228, International Publication No. 2009 / 10938, U.S. Patent Publication No. 2017 / 0000695, U.S. Patent Publication No. 2017 / 0002486, U.S. Patent No. 9,944,047, U.S. Patent Publication No. 2017 / 0022643, and U.S. Patent Publication No. 2018 / 0002848.

[0021] To ensure that the fluid in contact with the upper (wearer-facing) surface of the hydrophilic top sheet moves suitably and rapidly to the bottom (outward-facing) surface of the top sheet by capillary action in the z direction, and there can be drawn into the absorbent layer, it may be important to ensure that the nonwoven web material forming the top sheet has an appropriate weight / volume density, thereby reflecting the suitable presence of void passages in and between the constituent fibers through which the fluid can move within the nonwoven material. Nonwovens with fibers that are too densely packed will have insufficient number and volume of void passages, and the nonwoven will hinder rather than facilitate rapid z-direction fluid movement. On the other hand, nonwovens with fibers that are not densely packed enough to provide sufficient inter-fiber contact and / or sufficiently small void passages may offer insufficient potential for z-direction suction by capillary action. In embodiments where the nonwoven web material contains cotton fibers, or is composed mainly or entirely of cotton fibers, the web is made of 20 gsm (wherein "gsm" means grams / m²) for the purpose of balancing the priority between the properties of shielding absorbed fluids and mechanical strength (required for processing) and limiting the amount of top sheet material that must pass through and move in the z direction for the liquid to reach the underlying absorbent layer. 2 It is desirable to have a basis weight of ~50gsm, more preferably 25gsm~45gsm, and even more preferably 30gsm~40gsm. In addition, the web should be 74kg / m². 3 ~110 kg / m 3 , more preferably 83 kg / m 3 ~101 kg / m 3It may be desirable to have a density such that the density is calculated as basis weight divided by caliper (thickness in the z direction measured using the caliper measurement method described below). Alternatively, or in combination with controlling the above values, the caliper of the top sheet material may be controlled to balance the conflicting needs of opacity and loft (requiring a higher caliper) and the limitation of the z-direction distance that the discharged fluid must travel through the top sheet from the surface facing the wearer to the surface facing outward in order to reach the absorbent layer below. Therefore, it may be desirable that the manufacture of the top sheet material be controlled to produce a top sheet material having a caliper of 0.20 mm to 0.60 mm, more preferably 0.25 mm to 0.55 mm, and even more preferably 0.30 mm to 0.45 mm. For the purposes of this specification, the caliper is measured using the caliper measurement method described below.

[0022] Immediately after separation from the pod, cotton fibers are naturally hydrophobic due to the presence of natural waxes and oily compounds on the fiber surface. After ginning to separate the cotton fibers from the seeds, the raw cotton fiber mass (stored and transported as a bale) typically contains a considerable amount of impurities (particles, plant fragments, etc.) trapped within the fiber matrix and / or attached to the waxes and oils, which discolors the cotton fibers and makes them unsuitable for many applications. To make raw cotton fibers commercially acceptable for most applications, the fibers must first be treated in several steps to remove impurities. Typical processes also remove natural waxes and oils, making the cotton fibers hydrophilic. While it is possible to reintroduce hydrophobic agents such as oils, waxes, or silicones to make cotton fibers and cotton-based fiber structures hydrophobic and non-absorbent, for the purposes of this specification, non-porous hydrophobic cotton-based topsheets are unsuitable because they cannot adequately receive and absorb fluid discharges.

[0023] Following treatment to remove impurities, the cotton fiber mass is further mechanically processed to transform it into its intended end-use conditions and structure. Because the fibers are hydrophilic, any mass of processed cotton fibers (whether appearing as a component of a fabric / cloth, paper product, nonwoven web product, or absorbent product) will absorb aqueous fluids to some extent and exhibit capillary suction properties.

[0024] Rayon fibers (including viscose, liocell, tencel, and copper ammonia rayon) are manufactured from regenerated cellulose. At the molecular level, they are chemically similar to cotton fibers. At the fiber level, rayon fibers can be given complex surface shapes and substantial curl or crimp, and are naturally hydrophilic. A mass of rayon fibers typically has absorbent properties that exceed those of a mass of cotton fibers.

[0025] Absorbency and wicking performance may vary depending on the further processing of the fibers, and may be manipulated accordingly. Factors such as the level of densification (i.e., high density) of the fiber mass in the final structure, and the orientation of individual fibers within the final structure, may affect absorbency and wicking performance.

[0026] Therefore, for the purposes intended herein, in combination with imparting suitable basis weight, density, and / or caliper as discussed above, it may be desirable that the cotton and / or rayon nonwoven webs used to produce the top sheet be formed via a nonwoven web manufacturing process in which a considerable number of fibers are given directional orientation, including some z-direction orientation, rather than the fiber orientation being primarily biased along the mechanical direction or xy-plane of the web structure formation. Following any suitable process (e.g., air laminating, wet lamination, carding, etc.) in which the fibers are distributed and laid in bats on a horizontal forming belt, additional process steps may be employed to force some or a portion of the fibers to be reoriented in the z-direction. Suitable process steps may include needle punching and water entanglement. An array of fine, high-speed water jets directed at the bat as it is carried over this array of water jets on a perforated belt or drum may be desirable due to its effectiveness in reorienting the fibers with less fiber breakage and less formation of fibrous fuzz and surface fuzz (free fiber ends extending from the main structure of the web). A vacuum water removal system (in which air is drawn in the z-direction through the web and through a pattern of orifices or pores on the drum or belt carrying the bat, pulling the water jetted water) may be desirable because it tends to form, add, open, and / or pass through small z-direction passages of approximately the pattern of orifices or pores within the fiber matrix of the web. While not intended to be bound by theory, it is thought that an increase in the number of z-direction oriented fibers (or portions thereof) and the number of z-direction passages increases the web's ability and tendency to draw up aqueous fluid in the z-direction. In the case of the top sheet, this means that the material can transport fluid directly downwards by capillary action from the surface of the top sheet facing the wearer to the surface facing the outside of the top sheet, i.e., down to the absorbent layer below, thereby reducing the amount of fluid transported by capillary action along the xy plane (which causes the discharged fluid to spread laterally and / or longitudinally, resulting in stains).

[0027] absorbent layer In some embodiments, the absorbent layer 40 may be formed from or include layers of absorbent open-cell foam material. In some embodiments, the foam material may include at least first and second sublayers 40a, 40b (Figure 2B) of absorbent open-cell foam material, the sublayers being in direct contact with each other. In such embodiments, for purposes described in more detail below, the sublayer facing the wearer may be made of relatively larger open-cell foam material, and the sublayer facing outwards may be made of relatively smaller open-cell foam material.

[0028] The open-cell foam material may also be a foam material produced by polymerization of the continuous oil phase of a water-in-oil high internal phase emulsion (HIPE).

[0029] A water-in-oil HIPE has two phases. One phase is a continuous oil phase containing monomers to be polymerized and emulsifiers that help stabilize the HIPE. The oil phase may also contain one or more photoinitiators. The monomer components may be present in the oil phase in an amount of about 80% to about 99% by weight, and in certain examples in an amount of about 85% to about 95% by weight. An emulsifier component that is soluble in the oil phase and suitable for forming a stable water-in-oil emulsion may be present in the oil phase in an amount of about 1% to about 20% by weight. The emulsion may be formed at emulsification temperatures of about 20°C to about 130°C, and in certain examples in an amount of about 50°C to about 100°C.

[0030] Generally, monomers may be present in an amount of about 20% to about 97% by weight of the oil phase and may include at least one substantially water-insoluble monofunctional alkyl acrylate or alkyl methacrylate. For example, this type of monomer may include C4-C18 alkyl acrylates and C2-C18 methacrylates such as ethylhexyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, isodecyl acrylate, tetradecyl acrylate, benzyl acrylate, nonylphenyl acrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, tetradecyl methacrylate, and octadecyl methacrylate.

[0031] The oil phase may also contain approximately 2% to 40% by weight, and in certain embodiments approximately 10% to 30% by weight, of substantially water-insoluble polyfunctional crosslinked alkyl acrylates or methacrylates. The addition of these crosslinked comonomers or crosslinking agents imparts strength and elasticity to the resulting HIPE foam. Examples of this type of crosslinked monomer include monomers containing two or more activated acrylate, methacrylate groups, or combinations thereof. Non-limiting examples of these groups include 1,6-hexanediol diacrylate, 1,4-butanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,12-dodecyl dimethacrylate, 1,14-tetradecanediol dimethacrylate, ethylene glycol dimethacrylate, neopentyl glycol diacrylate (2,2-dimethylpropanediol diacrylate), hexanediol acrylate methacrylate, glucose pentaacrylate, sorbitan pentaacrylate, and the like. Other examples of crosslinking agents include mixtures of acrylate and methacrylate moieties, such as ethylene glycol acrylate-methacrylate and neopentyl glycol acrylate-methacrylate. The ratio of methacrylate to acrylate groups in the mixed crosslinking agent may vary from 50:50 to any other ratio as needed.

[0032] The properties of the HIPE foam can be modified by adding any third substantially water-insoluble comonomer to the oil phase in a weight percentage of about 0% to about 15% by weight, and in certain embodiments, about 2% to about 8% by weight. In certain cases, “toughening” monomers that impart toughness to the resulting HIPE foam may be desired. These include monomers such as styrene, vinyl chloride, vinylidene chloride, isoprene, and chloroprene. While not limited to theory, such monomers are thought to help stabilize HIPE during polymerization (also known as “curing”), resulting in a more homogeneous and better formed HIPE foam with superior toughness, tensile strength, abrasion resistance, etc. Monomers can also be added to impart flame retardancy, as disclosed in U.S. Patent No. 6,160,028. Monomers can be added to impart color (e.g., vinylferrocene), fluorescence properties, radiation resistance, radiopaqueness (e.g., lead tetraacrylate), charge dispersion, reflection of incident infrared light, absorption of radio waves, wetting of the surface of HIPE foam struts or bubble walls, or any other desired properties in HIPE foam. In some cases, these additional monomers may slow down the overall conversion process of HIPE to HIPE foam, but this trade-off is necessary if the desired properties must be imparted. Thus, such monomers can also be used to slow down the polymerization rate of HIPE. Examples of this type of monomer include styrene and vinyl chloride.

[0033] The oil phase may further contain emulsifiers to stabilize HIPE. Emulsifiers used in HIPE include (a) sorbitan monoesters of branched-chain C16-C24 fatty acids; linear-chain unsaturated C16-C22 fatty acids; and linear-chain saturated C12-C14 fatty acids, such as sorbitan monooleate, sorbitan monomyristate, and sorbitan monoesters, sorbitan monolaurate diglycerol monooleate (DGMO), polyglycerol monoisostearate (PGMIS), and polyglycerol monomyristate (polyglycerol (b) monomyristate (PGMM); (c) polyglycerol monoesters of branched-chain C16-C24 fatty acids, linear unsaturated C16-C22 fatty acids, or linear saturated C12-C14 fatty acids, e.g., diglycerol monooleates (e.g., diglycerol monoesters of C18:1 fatty acids), diglycerol monomyristate, diglycerol monoisostearate, and diglycerol monoesters; (d) diglycerol monoaliphatic ethers of branched-chain C16-C24 alcohols, linear unsaturated C16-C22 alcohols, and linear saturated C12-C14 alcohols, as well as mixtures of these emulsifiers. See U.S. Patents No. 5,287,207 and No. 5,500,451. Another emulsifier that can be used is polyglycerol succinate (PGS), formed from alkyl succinate, glycerol, and triglycerol.

[0034] Such emulsifiers, and combinations thereof, may be added to the oil phase in such a manner that they constitute about 1% to about 20% by weight of the oil phase, about 2% to about 15% by weight in certain embodiments, and about 3% to about 12% by weight in certain other embodiments. In certain embodiments, co-emulsifiers may also be used to provide further control over bubble size, bubble size distribution, and emulsion stability, particularly at higher temperatures, for example, above about 65°C. Examples of coemulsifiers include phosphatidylcholine and phosphatidylcholine-containing compositions, aliphatic betaine, long-chain C12-C22 divalent aliphatic quaternary ammonium salts, short-chain C1-C4 divalent aliphatic quaternary ammonium salts, long-chain C12-C22 dialcoyl(alkenoyl)-2-hydroxyethyl, short-chain C1-C4 divalent aliphatic quaternary ammonium salts, long-chain C12-C22 divalent aliphatic imidazolinium quaternary ammonium salts, short-chain C1-C4 divalent aliphatic imidazolinium quaternary ammonium salts, long-chain C12-C22 monovalent aliphatic benzyl quaternary ammonium salts, long-chain C12-C22 dialcoyl(alkenoyl)-2-aminoethyl, short-chain C1-C4 monovalent aliphatic benzyl quaternary ammonium salts, and short-chain C1-C4 monohydroxyaliphatic quaternary ammonium salts. In certain examples, ditallow dimethyl ammonium methyl sulfate (DTDMAMS) may be used as an auxiliary emulsifier.

[0035] Any photoinitiator included may be present in an amount of about 0.05% to about 10% by weight of the oil phase, and in some examples, about 0.2% to about 10% by weight. Small amounts of photoinitiator can allow light to pass through the HIPE foam well, thereby leading to polymerization deeper within the HIPE foam. However, if polymerization is carried out in an oxygen-containing environment, it may be desirable to have enough photoinitiator to initiate polymerization and overcome oxygen inhibition. Photoinitiators can respond quickly and efficiently to a light source, with the generation of radicals, cations, and other types that can initiate polymerization reactions. Photoinitiators selected for use in foam formation within the scope conceivable of this disclosure can absorb ultraviolet light with wavelengths of about 200 nanometers (nm) to about 800 nm, and in certain examples, about 250 nm to about 450 nm. When the photoinitiator is present in the oil phase, suitable types of oil-soluble photoinitiators include benzyl ketal, α-hydroxyalkylphenone, α-aminoalkylphenone, and acylphosphine oxide.Examples of photoinitiators include 2,4,6-[trimethylbenzoyldiphosphine]oxide combined with 2-hydroxy-2-methyl-1-phenylpropan-1-one (a 50:50 blend of these two is marketed by Ciba Speciality Chemicals (Ludwigshafen, Germany) as DAROCUR® 4265); benzyldimethyl ketal (marketed by Ciba Geigy as IRGACURE 651); α-,α-dimethoxy-α-hydroxyacetophenone (marketed by Ciba Speciality Chemicals as DAROCUR® 1173); 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one (marketed by Ciba Speciality Chemicals as IRGACURE® 907); and 1-hydroxycyclohexyl phenyl ketone (Ciba Speciality Examples include: IRGACURE® 184 (sold by Ciba Speciality Chemicals); bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (sold by Ciba Speciality Chemicals as IRGACURE 819); diethoxyacetophenone and 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone (sold by Ciba Speciality Chemicals as IRGACURE® 2959); and oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] (sold by Lamberti spa (Gallarate, Italy) as ESACURE® KIP EM).

[0036] The dispersed aqueous phase of HIPE contains water and may also contain one or more components such as initiators, photoinitiators, or electrolytes, and in certain embodiments, these one or more components are at least partially water-soluble.

[0037] One component in the aqueous phase may be a water-soluble electrolyte. The aqueous phase may contain about 0.2% to about 40% by weight, and in certain examples, about 2% to about 20% by weight, of the water-soluble electrolyte. The electrolyte minimizes the tendency of monomers, comonomers, and crosslinking agents, which are mainly oil-soluble, to dissolve in the aqueous phase. Examples of electrolytes include chlorides or sulfides of alkaline earth metals such as calcium or magnesium, and chlorides or sulfides of alkaline earth metals such as sodium. Such electrolytes may include buffers for controlling pH during polymerization, including inorganic counterions such as phosphates, borates, and carbonates, and mixtures thereof. Water-soluble monomers may also be used in the aqueous phase, examples of which are acrylic acid and vinyl acetate.

[0038] Another component that may be present in the aqueous phase is a water-soluble free radical initiator. The initiator may be present in up to about 20 mol% based on the total number of moles of polymerizable monomers present in the oil phase. In certain embodiments, the initiator may be present in the oil phase in an amount of about 0.001 to about 10 mol% based on the total moles of polymerizable monomers. Suitable initiators include ammonium persulfate, sodium persulfate, potassium persulfate, 2,2'-azobis(N,N'-dimethylene isobutylamidine) dihydrochloride, azo initiators, redox pairs such as persulfate-disulfate, persulfate-ascorbic acid, and other suitable redox initiators. In certain embodiments, to reduce the possibility of premature polymerization that may interfere with the emulsion system, the addition of the initiator to the monomer phase may be performed near the end of the emulsification step or immediately after emulsification.

[0039] When present in the aqueous phase, the photoinitiator may be at least partially water-soluble and may constitute about 0.05% to about 10% by weight of the oil phase, and in certain embodiments, about 0.2% to about 10% by weight. Small amounts of photoinitiator can allow light to pass through the HIPE foam well, thereby leading to polymerization deeper within the HIPE foam. However, if polymerization is carried out in an oxygen-containing environment, there should be enough photoinitiator to initiate polymerization and overcome oxygen inhibition. Photoinitiators can respond quickly and efficiently to a light source, with the generation of radicals, cations, and other species that can initiate polymerization reactions. Photoinitiators for use in foam formation within the scope conceivable of this disclosure can absorb ultraviolet light with wavelengths of about 200 nanometers (nm) to about 800 nm, in certain embodiments, about 200 nm to about 350 nm, and in certain embodiments, about 350 nm to about 450 nm. When the photoinitiator is contained in the aqueous phase, suitable water-soluble photoinitiators include benzophenone, benzyl, and thioxanthone. Examples of photoinitiators include 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate dehydrate, 2,2'-azobis(1-imino-1-pyrrolidino-2-ethylpropane)dihydrochloride, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2-methylpropionamidine)dihydrochloride, 2,2'-dicarboxymethoxydibenzalacetone, 4,4'-dicarboxymethoxydibenzalacetone, 4,4'-dicarboxymethoxydibenzalcyclohexanone, 4-dimethylamino-4'-carboxymethoxydibenzalacetone, and 4,4'-disulfoxymethoxydibenzalacetone. Other suitable photoinitiators are described in U.S. Patent No. 4,824,765.

[0040] In addition to the foregoing components, other components may be included in either the aqueous phase or the oil phase of the HIPE. Examples include antioxidants such as hindered phenols, hindered amine light stabilizers; plasticizers such as dioctyl phthalate, dinonyl sebacate; flame retardants such as halogenated hydrocarbons, phosphates, borates, inorganic salts such as antimony trioxide or ammonium phosphate or magnesium hydroxide; dyes and pigments; fluorescent agents; filler particles such as starch, titanium dioxide, carbon black, or calcium carbonate; fibers; chain transfer agents; odor absorbers such as activated carbon microparticles; dissolved polymers; dissolved oligomers; and the like.

[0041] The HIPE foam is produced from the polymerization of monomers containing the continuous oil phase of the HIPE. In certain embodiments, the HIPE foam layer may have one or more sub-layers and may be either a homogeneous or heterogeneous polymer continuous cellular foam. Homogeneity and heterogeneity relate to different layers within the same HIPE foam, which are similar in the case of a homogeneous HIPE foam and different in the case of a heterogeneous HIPE foam. A heterogeneous HIPE foam may contain at least two different sub-layers that differ in chemical composition, physical properties, or both. For example, these sub-layers may differ with respect to one or more of foam density, polymer composition, specific surface area, or pore size (also called cell size). For example, in the case of a HIPE foam that differs with respect to pore size, the average pore size of each sub-layer may differ by at least about 20%, in certain embodiments at least about 35%, and in other embodiments at least about 50%. In another embodiment, where the difference in the sub-layers of the HIPE foam layer relates to density, the density of the layers may differ by at least about 20%, in certain embodiments at least about 35%, and in other embodiments at least about 50%. For example, if one layer of the HIPE foam has a density of 0.020 g / cm 3 then another layer may have a density of at least 0.024 g / cm 3 or less than about 0.016 g / cm 3 in certain embodiments at least about 0.027 g / cm 3 or less than about 0.013 g / cm 3Less than, and in other embodiments, at least about 0.030 g / cm³ 3 Or approximately 0.010 g / cm³ 3 It may have a density of less than . If the difference between layers relates to the chemical composition of HIPE or HIPE foam, the difference may reflect a difference in the relative amount of at least one monomer component, for example, at least about 20%, at least about 35% in certain examples, and at least about 50% in further examples. For example, if one sublayer of HIPE or HIPE foam contains about 10% styrene in its formulation, another sublayer of HIPE or HIPE foam may contain at least about 12%, and at least about 15% in certain examples.

[0042] A HIPE foam layer structured to have separate sublayers formed from different HIPE can provide a HIPE foam layer having a range of desired performance characteristics. For example, a HIPE foam including first and second foam sublayers, where the first foam sublayer has a relatively larger pore size or bubble size than the second foam sublayer, can absorb incoming fluid more quickly than the second sublayer when used in absorbent articles. For example, when using a HIPE foam layer to form the absorbent layer of a feminine hygiene pad, the first foam sublayer can be overlaid on a second foam sublayer having a relatively smaller pore size compared to the first foam sublayer, thereby restoring the ability of the first foam sublayer to exert greater capillary pressure, draw the acquired fluid out of the first foam sublayer, and acquire more fluid from above. The pore size of the HIPE foam may be in the range of 1 to 200 μm, and in certain embodiments, may be less than 100 μm. The HIPE foam layer of this disclosure having two main parallel surfaces may have a thickness of about 0.5 to about 10 mm, and in certain embodiments, a thickness of about 2 to about 10 mm. The desired thickness of the HIPE foam layer depends on the material used to form the HIPE foam layer, the rate at which the HIPE is deposited on the belt, and the intended use of the resulting HIPE foam layer.

[0043] The HIPE foam layer of this disclosure is relatively continuous. This means that individual bubbles or pores in the HIPE foam layer are in communication with adjacent bubbles without substantially obstruction. Bubbles in such substantially continuous HIPE foam structures have internal openings or windows of sufficient size to allow fluid to move rapidly from one bubble to another within the HIPE foam structure. For the purposes of this disclosure, a HIPE foam is considered "continuous" if at least about 80% of the bubbles in a HIPE foam of at least 1 μm in size are in fluid communication with at least one adjacent bubble.

[0044] In addition to being open-cell, in certain embodiments, the HIPE foam is adapted to be sufficiently hydrophilic to the extent that it can absorb aqueous liquids. In some embodiments, the inner surface of the HIPE foam may be made hydrophilic by residual hydrophilic surfactants or salts remaining in the HIPE foam after polymerization, or by selected post-polymerization HIPE foam treatment procedures, such as those described in the references cited herein.

[0045] In certain embodiments, the HIPE foam layer may be flexible and exhibit a suitable glass transition temperature (Tg), for example, when used to form the absorbent layer of a feminine hygiene pad. Tg represents the midpoint of the transition between the glassy and rubbery states of the polymer. Generally, HIPE foams with a Tg higher than the operating temperature may have high strength but are also relatively rigid and potentially prone to fracturing (brittle). In certain embodiments, the regions of the HIPE foam of this disclosure that exhibit either a relatively high Tg or excessive brittleness are discontinuous. These discontinuous regions also generally exhibit high strength, so they can be prepared at low density without compromising the overall strength of the HIPE foam.

[0046] HIPE foams intended for applications requiring flexibility should include at least one continuous region having the lowest possible Tg, as long as the HIPE foam as a whole has acceptable strength at the temperature of use. In certain embodiments, the Tg of this region is less than about 40°C for foams used under approximately ambient temperature conditions, and in other specific embodiments, the Tg is less than about 30°C. For HIPE foams used in applications where the operating temperature is higher or lower than the ambient temperature, the Tg of the continuous region may be less than 10°C higher than the operating temperature, in certain embodiments it may be the same as the operating temperature, and in further embodiments it may be about 10°C lower than the operating temperature if flexibility is desired. Therefore, monomers are selected to provide the corresponding polymer having the lowest possible Tg.

[0047] HIPE foams useful for forming absorbent layers and / or sublayers within the scope conceivable of this disclosure, as well as materials and methods for their manufacture, are incorporated herein by reference to the extent not inconsistent with this specification, U.S. Patents 10,045,890, 9,056,412, 8,629,192, 8,257,787, 7,393,878, 6,551,295, 6,525,106, 6,550,960, and 6,406,6 No. 48, No. 6,376,565, No. 6,372,953, No. 6,369,121, No. 6,365,642, No. 6,207,724, No. 6,204,298, No. 6,158,144, No. 6,107,538 No. 6,107,356, No. 6,083,211, No. 6,013,589, No. 5,899,893, No. 5,873,869, No. 5,863,958, No. 5,849,805, No. 5,827,909, No. No. 5,827,253, No. 5,817,704, No. 5,817,081, No. 5,795,921, No. 5,741,581, No. 5,652,194, No. 5,650,222, No. 5,632,737, No. 5 ,563,179, 5,550,167, 5,500,451, 5,387,207, 5,352,711, 5,397,316, 5,331,015, 5,292,777, 5,26 Other examples include, but are not limited to, the foams and methods described in U.S. Patent Publications No. 8,224, No. 5,260,345, No. 5,250,576, No. 5,149,720, No. 5,147,345, and U.S. Patent Publications No. 2005 / 0197414, No. 2005 / 0197415, No. 2011 / 0160326, No. 2011 / 0159135, No. 2011 / 0159206, No. 2011 / 0160321, and No. 2011 / 0160689.

[0048] As reflected in Figure 1, the absorbent layer formed from the HIPE foam may include one or more perforations 42 in patterns, including at least one pattern disposed within the expected discharge location (coinciding with and / or located in the same place as the binding area 25) that overlaps with the intersection of the longitudinal axis 100 and the transverse axis 200 of the pad. The perforations 42 may be formed by perforating, cutting, or otherwise, penetrating through the entire z-depth of the HIPE foam absorbent layer, or penetrating only the layer facing the wearer, or partially penetrating the portion facing the wearer. When the HIPE foam absorbent layer is disposed in direct contact with the top sheet without an intervening trapping layer formed of another material, as described herein, the perforations 42 may function as a group of reservoirs to receive, temporarily hold, and assist in distributing relatively small amounts of rapid menstrual fluid discharge until the HIPE foam has sufficient time to distribute and absorb the fluid by capillary action. In addition, such perforations help to reduce the bending stiffness of the absorbent layer, which can help increase the comfort of the pad for the wearer. For example, the area occupied by the bonding region 25 may include a pattern of perforations having an average radius of 1.0 mm to 4.0 mm, and more preferably 1.5 mm to 3.5 mm, or other maximum dimensions. The pattern may be 1 cm 2 3.0 to 9.0 holes per unit, more preferably 1 cm 2 The perforations may be included at a numerical density of 4.0 to 8.0 perforations per unit. When selecting an appropriate average size, numerical density, and surface area occupied by the perforation pattern, the manufacturer may want to balance the desired “reservoir” volume with the need to retain the absorbent material in close proximity to and near the expected discharge point. Further details regarding such perforation configurations combined with examples of suitable absorbent layers can be found in U.S. Patent No. 8,211,078.

[0049] The absorbent layer formed from HIPE foam should be endowed with sufficient CWPA (described below) to have the ability to effectively absorb fluid discharged from the top sheet for the standard and expected duration of use / wear of a pad during menstruation, e.g., 4–8 hours, for a women's hygiene pad. As described below, the CWPA of a material is partially influenced by its volume. Therefore, it may be desirable for the absorbent layer 40 formed from HIPE foam to have a caliper (before wetting) that provides a satisfactory volume for a standard-sized pad. Naturally, it is possible to manufacture relatively thick pads, but this is considered undesirable for daytime use, given that flexibility / suppleness and thinness are desired for comfort and inconspicuousness under clothing. Manufacturers need to balance these competing objectives. Therefore, in the feminine hygiene pads having a HIPE foam absorbent layer intended herein, it may be desirable for the layer to have a caliper of 1 mm to 5 mm, more preferably 1.5 mm to 3.5 mm, or even more preferably 2.0 mm to 3.0 mm (before wetting) within the majority of the surface area facing the wearer (the caliper of the HIPE foam layer may be visually measured to the extent deemed useful with the assistance of magnification / microscopic observation and / or photography, or other facilitating techniques and equipment). If the absorbent layer 40 includes two sublayers 40a and 40b as described herein, it is desirable that the upper sublayer 40a has calipers (before wetting) of 0.64 mm to 3.2 mm, preferably 0.96 mm to 2.24 mm, or even more preferably 1.28 mm to 1.92 mm, and that the lower sublayer 40b has calipers (before wetting) of 0.16 mm to 0.80 mm, more preferably 0.24 mm to 0.56 mm, or even more preferably 0.32 mm to 0.48 mm.

[0050] Absorption properties and the interface between the top sheet and the absorbent layer The affinity and absorption of aqueous fluids in hydrophilic structures can be characterized in part by their capillary absorption pressure. Capillary absorption pressure (CAP) can be measured according to the steps of the capillary action potential measurement method described below. This value reflects the degree of the structure's tendency to draw in aqueous fluids. A plot of CAP versus saturation level for an absorbent structure will show that it has an initial maximum value (at the beginning of fluid absorption) and decreases as the structure is drawn into the fluid and approaches its full absorption capacity, i.e., complete saturation.

[0051] The resistance of an absorbent / hydrophilic structure to desorption, or its tendency to retain absorbed fluids, can be characterized in part by its capillary desorption pressure (CDP). CDP, which can also be measured according to the steps in the capillary action potential measurement method described below, is a value that reflects the magnitude of the pressure (or pressure difference) required to drive (or draw in) the aqueous fluid absorbed and retained by the structure. A plot of CDP versus saturation level for a structure will be seen to have an initial minimum (before any fluid leaves the structure) and increase as the fluid leaves the structure.

[0052] The CAP and CDP of a given structure are functions of the degree of hydrophilicity of the solid surfaces within the structure, the average size of the voids or air spaces, bubbles or pores within the structure in / between the solid surfaces, and the number of voids, bubbles or pores within the structure per unit volume of the structure.

[0053] In addition to the other conditions described herein, the capillary absorption pressure of the absorbent layer must be greater than the capillary desorption pressure of the top sheet at a selected level, preferably a relatively low level, so that the laminated top sheet / absorbent layer combination can effectively move the discharged fluid away from the wearer in the z direction away from the top sheet. In order that the laminated top sheet / absorbent layer combination can move the discharged fluid away from the wearer at an acceptable rate, i.e., so that the top sheet does not have time to excessively absorb the discharged fluid and thereby distribute (i.e., spread) the discharged fluid along the flat direction (forming an undesirably large stain on the top sheet), and so that the wearer does not feel excessively wet immediately after the fluid is discharged onto the top sheet, for example, the capillary absorption pressure of the absorbent layer at a saturation of 20 percent must be greater than the capillary desorption pressure of the top sheet at the same saturation. In this case, percentage saturation is the percentage of the total pore volume of the material occupied by the fluid, and the test fluid is physiological saline as specified in the Capillary Work Potential measurement method described below.

[0054] The total absorbency of a given material structure can be further characterized by the capillary work potential in absorption (CWPA) and the capillary work potential in drainage or desorption (CWPD), when measured using the capillary work potential measurement method described below. CWPA is a measure of the action performed by an absorbent material when drawing in a certain amount of aqueous fluid under the conditions of the described method. CWPD is a measure of the action required to drain or draw in the aqueous fluid absorbed and retained by the structure under the conditions of the described method. For a given structure that is hydrophilic and absorbent of aqueous fluid, the CWPD is greater than the CWPA because the properties of the absorbent structure (hydrophilicity; bubble / pore size and volume) tend to cause the absorbent structure to retain fluid. The CWPA and CWPD of a given structure are influenced by the features and properties that affect CAP and CDP, and are also influenced by the total volume of interstitial spaces or voids, bubbles or pores in the structure. Therefore, it will be understood that the CWPA and CWPD of a structure are partially influenced by the total volume (i.e., dimensions) of the structure.

[0055] To ensure that the absorbent layer 40 drains the fluid absorbed by the top sheet from the top sheet 20 to a sufficient extent that the absorbent layer 40 and the top sheet 20 provide a satisfactory pad, the absorbent layer should have a CWPA greater than the CWPD of the top sheet. If this condition is not met, the absorbent layer shall not drain the fluid from the top sheet to a sufficient extent that (1) the top sheet does not retain an unacceptable level of wetness after drainage, and (2) the top sheet remains drained and has the capacity to accept continuous drainage of fluid over a reasonable service life of the pad 10.

[0056] It has been found that an absorbent layer formed from HIPE foam as described herein can be manufactured to have a capillary absorption pressure large enough to draw fluid from the absorbent cotton top sheet at an acceptable rate over repeated discharges, i.e., over a reasonable lifespan of the pad.

[0057] In embodiments in which the top sheet is formed from a hydrophilic and absorbent web material, as described above, the top sheet material may tend to retain fluid on its wearer-facing and outward-facing surfaces, and in the voids between and along the fiber surfaces of the web material, unless the underlying material has a higher absorption pressure than the absorbent capacity and desorption pressure of the top sheet, and unless sufficient direct contact is maintained between the top sheet and the underlying absorbent layer, allowing the fluid to move directly from the fiber surfaces in the top sheet structure to the material surfaces in the underlying absorbent layer structure, and as a result the underlying absorbent layer cannot draw the fluid from the top sheet. The absorbent material will not release the absorbed fluid unless an adjacent material with a greater affinity for the fluid comes into sufficient direct contact with it before the absorbent material is completely saturated. Therefore, it is important to provide a structure that is sufficient to maintain sufficient contact without hindering fluid movement. At least one intervening layer or structure of a material, or a material that is less absorbent than the top sheet or more absorbent than the absorbent layer, should not be interposed between the material of the top sheet 20 and the material of the absorbent layer 40, at least within the bonding region 25, more preferably over most of the surface area of ​​the absorbent layer 40 facing the wearer, and even more preferably over the entire surface area of ​​the absorbent layer 40 facing the wearer. This differs from the systems provided in many current women's hygiene pads, which include a separate fluid acquisition / distribution material layer between the top sheet and the absorbent material of the absorbent core.

[0058] In some embodiments, sufficient direct contact between the top sheet 20 and the absorbent layer 40 may be provided by adhesive deposits between the top sheet and the absorbent layer, which bond them together in close proximity in the z direction. The adhesive may be applied in a pattern or arrangement of adhesive deposits with interspersed areas where no adhesive is present (non-bonding areas), so that the adhesive holds the two layers in close proximity in the z direction while maintaining areas where no adhesive is present that would obstruct fluid movement between the layers in the z direction.

[0059] Referring to Figures 1 and 3A-3C, it may be desirable to position a bonding region 25 at the intersection of the longitudinal axis 100 and the transverse axis 200 on the pad to ensure that the top sheet and the absorbent layer are held in close proximity in the z direction, at least within the area of ​​the top sheet where fluid discharge is expected. The bonding region 25 should be large enough to be reliably located below the expected discharge location during use of the pad, but since there will be reasonable slight variations in placement within the wearer's underwear, the bonding region should be at least 15 cm. 2 , more preferably at least 30 cm 2 It may be desirable for the bonded area to have an area equal to at least half of the total surface area of ​​the absorbent layer facing the wearer. (Note: Figures 3A to 3C are not presented herein as depictions of actual dimensions or scale.)

[0060] To ensure that the top sheet 20 and the absorbent layer remain sufficiently close in the z-direction during use, it may be desirable that a second point location where the top sheet is bonded to the absorbent layer exists within a radius of 10 mm, more preferably 6 mm, 5 mm, 4 mm, and even more preferably 3 mm radius r of any identifiable first point location 27 within the bonding region where the top sheet is bonded to the absorbent layer. Referring to Figures 3A to 3C, which show three non-limiting examples, it can be seen that various patterns or arrangements of bonding regions (by adhesive deposits 26 or other bonding mechanisms) may be employed to impart this feature. Within the radius r of each point location 27, there are numerous additional point locations present in the embodiments where bonding between the top sheet and the absorbent layer is shown.

[0061] While continuous deposits of adhesive can be applied to bond the top sheet and the absorbent layer within the entire bonding region 25, it will be understood that such continuous adhesive deposits may form a barrier that hinders fluid movement from the top sheet to the absorbent layer. Therefore, in embodiments where the bonding mechanism is adhesive deposits, it is preferable that the deposits be arranged in a discontinuous or intermittent pattern or arrangement such that they form a bonding region with unbonded regions interspersed between the top sheet and the absorbent layer. In addition, when the absorbent layer is formed of an open-cell foam (such as the HIPE foam intended herein), it may be desirable that the selected adhesive does not result in adhesion to the absorbent layer via chemical, dispersive, or diffusive adhesion with the foam layer at the adhesive deposit site, but rather mechanically results in adhesion to the foam layer by flowing specifically into the bubbles, at least partially taking shape, and solidifying at such locations, thereby forming a mechanical interlock with the cellular structure, allowing the adhesive to hold the top sheet relative to the absorbent layer. Such adhesives may be preferable because they do not alter the molecular structure or composition of the foam material and do not potentially adversely affect its fluid absorption properties or mechanical strength. For example, a suitable adhesive for use with HIPE foam may be the H1750 hot melt adhesive provided by Bostik (Wauwatosa, Wisconsin) (now a subsidiary of Arkema (Columbes, France)).

[0062] Non-porous top sheets for feminine hygiene pads, formed from nonwoven web materials and containing or primarily consisting of hydrophilic fibers (such as cotton fibers), are known and have been included in several feminine hygiene products to date. (In this specification, “non-porous” nonwoven top sheets are nonwoven top sheets whose surface area is not subjected to any process that forms holes or arrays of pores that completely penetrate them, maintaining an average size (maximum dimension) greater than 0.5 mm along the xy plane before wetting of the top sheet). While their natural / plant-based material origins are preferred by some consumers, cotton top sheets are not preferred by others because, due to their considerable absorbency, i.e., capillary absorption and desorption pressure, they become resistant to drainage by conventionally included capture / distribute and absorbent layer structures. After menstrual fluid discharge, pads with cotton top sheets superimposed on conventional absorbent structures may give users a feeling of a damp cloth being held against the skin for extended periods, which many users find undesirable. This dilemma has existed for many years and, to the best of the inventor's knowledge, has not been satisfactorily addressed until now.

[0063] However, a non-porous hydrophilic fiber top sheet (such as a cotton top sheet) fitted / manufactured to have sufficient capillary absorption capacity to draw fluid from the top sheet, and superimposed in a direct, sufficiently facing relationship with a HIPE foam absorbent layer or other layer, has been found to substantially drain the fluid by the absorbent layer and restore a much drier feel to the skin after drainage, without the need for any intervening absorbent layer and in combination with other structural features as described herein. A HIPE foam absorbent layer suitably configured and manufactured as described herein has been found to have a greater affinity for menstrual fluid than, for example, such a top sheet, and thereby has the ability to draw and retain fluid from the top sheet when the two are arranged and held in a sufficiently effective close contact relationship with each other. When the absorbent layer has sufficient volume, it can perform this function over a reasonably suitable usage time of the pad.

[0064] Back seat The backsheet 30 can be positioned adjacent to the surface facing outward of the absorbent layer 40 and can be bonded to this surface by any preferred mounting method. For example, the backsheet 30 may be fixed to the absorbent layer 40 by a uniform continuous adhesive layer, a patterned adhesive layer, or an arrangement of independent adhesive lines, spirals, or dots. Alternatively, the mounting method may include thermal bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or any other preferred mounting mechanism, or a combination thereof. In other embodiments, it is intended that the absorbent layer 40 is not directly bonded to the backsheet 30.

[0065] The backsheet 30 may be impermeable to or substantially impermeable to liquids (e.g., urine, menstrual fluid) and may be manufactured from a thin plastic film, but other flexible liquid-impermeable materials may also be used. As used herein, the term “flexible” refers to a material that is adaptable and readily conforms to the general shape and contours of the human body. The backsheet 30 can prevent, or at least substantially prevent, the fluid absorbed and contained within the absorbent layer 40 from escaping and reaching articles of the wearer’s clothing, such as underwear and other clothing, that may come into contact with the pad 10. However, in some examples, the backsheet 30 may be manufactured and / or adapted to allow vapor to escape from the absorbent layer 40 (i.e., the backsheet is made to be breathable), while in other examples, the backsheet 30 may be manufactured not to allow vapor to escape (i.e., it may be made to be non-breathable). Thus, the backsheet 30 may include a polymer film, such as a polyethylene or polypropylene thermoplastic film. Suitable materials for the backsheet 30 are, for example, thermoplastic films having a thickness of about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mil). Any suitable backsheet known in the art may be used in conjunction with the present invention.

[0066] Some preferred examples of backsheets are described in U.S. Patents No. 5,885,265, No. 4,342,314, and No. 4,463,045. Suitable single-layer breathable backsheets for use herein include, for example, those described in British Patents No. A2184389, A2184390, A2184391, U.S. Patents No. 4,591,523, No. 3,989,867, No. 3,156,242, International Publication No. 97 / 24097, U.S. Patents No. 6,623,464, No. 6,664,439, and U.S. Patent No. 6,436,508.

[0067] The backsheet may have two layers, namely a first layer comprising a vapor-permeable perforated film layer and a second layer comprising a breathable microporous film layer, as described in U.S. Patent No. 6,462,251. Other suitable examples of two-layer or multi-layer breathable backsheets for use herein include those described in U.S. Patents No. 3,881,489, 4,341,216, 4,713,068, 4,818,600, European Patent No. 203821, European Patent No. 710471, European Patent No. 710472, and European Patent No. 0793952.

[0068] Test / Measurement Methods Capillary action potential via pore volume distribution The pore volume distribution is determined by measuring the fluid movement in and out of the sample when a stepped, controlled differential pressure is applied to the sample within the sample chamber, thereby determining the estimated porosity of the effective pores in the porous sample. The incremental and cumulative amounts of fluid absorbed / discharged by the porous sample at each pressure are then determined. Next, the action performed by the porous sample, normalized by the sample's area, is calculated as the capillary action potential.

[0069] Principles of the method For a uniform cylindrical pore, the pore radius is related to the differential pressure required to fill or empty the pore, according to the following equation: Differential pressure = [2γ cosθ)] / r In the formula, γ = liquid surface tension, θ = contact angle, and r = pore radius.

[0070] Pores contained in natural and manufactured porous materials are often considered in terms of voids, holes, or conduits, and these pores are generally not perfectly cylindrical or uniform. Nevertheless, the distribution of effective pore radius in such porous materials can be characterized by relating the differential pressure to the effective pore radius and monitoring the movement of liquid in and out of the material as a function of the differential pressure using the equation described above. (This general methodology may not produce results that precisely match those obtained by measuring void dimensions using other methods such as microscopy, because non-uniform pores are approximated uniformly by the use of the effective pore radius.)

[0071] The pore volume distribution method is implemented using the apparatus and techniques described in "Liquid Porosimetry: New Methodologies and Applications" by B. Miller and I. Tyomkin, published in The Journal of Colloid and Interface Science (1994), volume 162, pages 163-170, which is incorporated herein by reference and uses the principle described above. This method relies on measuring the increment of liquid volume entering and leaving a porous sample as the air pressure difference between the ambient ("lab") air pressure and the slightly elevated air pressure (positive differential pressure) surrounding the sample in the sample test chamber changes. The sample is introduced into the sample chamber for drying, and the sample chamber is controlled with a sufficient positive differential pressure (relative to the laboratory) to prevent fluid from being taken into the sample after the fluid bridge is opened. After the fluid bridge is opened, the air pressure difference is gradually reduced to 0, in which case a subgroup of pores in the sample captures the liquid according to their effective pore radius. After reaching the minimum differential pressure where the mass of fluid in the sample is maximum, the differential pressure is again gradually increased toward the starting pressure, and the liquid is discharged from the sample. The absorption portion of the stepwise sequence begins at the maximum differential pressure (minimum corresponding effective pore radius) and ends at the minimum differential pressure (maximum corresponding effective pore radius). The drainage portion of the sequence begins at the minimum pressure difference and ends at the maximum pressure difference. After correcting for any fluid movement for each specific pressure step measured on the chamber while emptying for the entire absorption / drainage sequence, the fluid intake by the sample (mg) at each differential pressure, as well as the cumulative volume (mm) are measured. 3 The / mg) is determined.

[0072] Sample conditioning and sample preparation The pore volume distribution method is performed on samples that have been prepared for at least 2 hours in a room maintained at a temperature of 23°C ± 2.0°C and a relative humidity of 50% ± 2%, and all tests are performed under the same environmental conditions and in such a prepared room. Damaged products or samples with defects such as wrinkles, tears, or holes are not tested. Samples prepared as described herein are considered dry for the purposes of this invention. Determine which side of the sample is intended to face the wearer during use, and then cut it into a 55 mm x 55 mm piece. Measure the mass of the sample and record it in units of 0.1 mg. Three samples are measured for any given test material, and the results of these three repeated experiments are averaged to obtain the final reported value.

[0073] Device Appropriate apparatus for this method is described in "Liquid Porosimetry: New Methodology and Applications" by B. Miller and I. Tyomkin, published in The Journal of Colloid and Interface Science (1994), volume 162, pages 163-170. Furthermore, any pressure control scheme capable of controlling the sample chamber pressure differential of 0 mmH2O to 1098 mmH2O may be used instead of the pressure control subsystem described in this reference. An example of a suitable overall instrument and software is the TRI / Autoporosimeter (Textile Research Institute, TRI) / Princeton Inc. (Princeton, NJ, USA). The TRI / Autoporosimeter is an automated computer-controlled instrument for measuring the pore volume distribution of porous materials (e.g., pore volumes of different sizes within the effective pore radius range of 5 μm to 1200 μm). Computer programs such as Automated Instrument Software Releases 2000.1 or 2003.1 / 2005.1 or 2006.2, or Data Treatment Software Release 2000.1 (available from TRI Princeton Inc.), and spreadsheet programs may be used to collect and analyze the measured data.

[0074] A schematic diagram of a suitable apparatus is shown in Figure 4. The apparatus consists of a balance 800 having a fluid reservoir 802 that is in direct fluid communication with a sample 805 located in a sealed air-pressurized sample chamber 810. Fluid communication between the reservoir 802 and the sample chamber 810 is controlled by a valve 815. A sealing pressure of 0.25 psi is applied to the test sample using a weight 803 placed on top of a plexiglass plate 804 (55 mm long × 55 mm wide) to ensure good contact between the sample and the fluid-saturated membrane 806 throughout the test. The membrane 806 (90 mm in diameter, 150 μm thick, pore size 1.2 μm; mixed cellulose ester filter RAWP09024; available from Millipore Corporation (Bedford, MA)) is mounted on a macroporous frit 807 (a Monel plate with a diameter of 90 mm and a thickness of 60 mm; available from Mott Corporation (Farmington, CT), or an equivalent) as follows: Use Krylon® spray paint (Gloss White Spray Paint #1501, available from FilmTools, or equivalent) as an adhesive to bond film 806 to frit 807. Allow the prepared film / frit assembly to dry before use.

[0075] To prepare the test equipment, the inner base 812 of the sample chamber 810 is filled with the test fluid. The test fluid is reagent-grade NaCl (liquid density 1.0 g / cm³) per liter of deionized water. 3This is a degassed 0.9% physiological saline solution prepared by adding a solution with a surface tension γ of 72.3 ± 1 mN / m and a contact angle cosθ = 0.37. The membrane / frit assembly is placed on the inner base 812 of the sample chamber 810 with the membrane 806 side facing upward and secured in place with the locking collar 809. The reservoir 802 and connecting tube 816 are filled with the test fluid. The valve 815 is opened to ensure that no air bubbles are trapped in the connecting tube or in the pores of the membrane / frit assembly. The legs 811 of the sample chamber 810 are used to level the sample chamber as needed, adjusting the height of the sample chamber (and / or the amount of fluid in the reservoir 802) so that the top surface of the membrane 806 is level with the top surface of the fluid in the reservoir 802.

[0076] Program the system to proceed through a sequence of stepped differential pressures (in mmH2O units) as follows: 1098, 549, 366, 275, 220, 183, 137, 110, 92, 78, 69, 61, 55, 50, 46, 42, 39, 37, 34, 32, 31, 29, 27, 24, 22, 20, 18, 14, 9.2, 6.9, 5.5, 4.6, 5.5, 6.9, 9.2, 14, 18, 20, 22, 24, 27, 29, 31, 32, 34, 37, 39, 42, 46, 50, 55, 61, 69, 78, 92, 110, 137, 183, 220, 275, 366, 549, 1098. These pressures correlate with effective pore radii ranging from 5 μm (1098 mmH2O) to 1200 μm (4.6 mmH2O). The criterion for moving from one pressure stage to the next is that the fluid intake into / out of the sample, as measured by the 800 scale, is less than 10 mg / min for 15 seconds.

[0077] Method and Procedure The system is checked for leaks to ensure that the maximum test pressure is reached as follows: Open the liquid valve 815 to position the top 808 of the sample chamber 810 and seal the chamber. Apply sufficient air pressure to the chamber 810 (via the connector 814) to achieve a differential pressure of 1098 mmH2O (effective pore radius of 5 μm). After closing the liquid valve 815, open the sample chamber. Place the sample 805 directly on the membrane 806 (with the wearer side facing down), and then place the cover plate 804 and restraining weight 803 in the center on top of the sample. Replace the top 808 and reseal the sample chamber 810. Open the liquid valve 815 to allow fluid movement between the liquid reservoir 802 and the sample and proceed with the test through the predetermined differential pressure sequence. The amount of fluid absorbed (or discharged) by the sample at each pressure stage throughout the sequence is recorded as the intake amount in units of 0.1 mg.

[0078] A separate “blank” measurement is performed on an empty sample chamber without the sample 805, cover plate 804, or restraining weight 803 present on the membrane / frit assembly, following the same method procedure (the same stepwise sequence of differential pressure). Any fluid movement observed is recorded (mg) at each pressure step. The fluid uptake data of the sample is corrected for any fluid movement associated with the empty sample chamber by subtracting the fluid uptake value of this “blank” measurement from the corresponding value in the sample measurement, and is recorded in units of 0.1 mg as the blank-corrected sample uptake.

[0079] Determination of capillary pressure, cumulative volume, and capillary action potential The percentage saturation of the sample at each pressure stage in both the absorption and drainage portions of the test sequence can be calculated by dividing the maximum blank-corrected sample uptake (mg) by the blank-corrected sample uptake (mg), and then multiplying by 100. From the data collected throughout the sequence, a person skilled in the art can then determine the percentage saturation at any given capillary absorption pressure (CAP) or capillary desorption (drainage) pressure (CDP). CAP and CDP are reported in units of 0.1 mmH2O for any specified percentage saturation.

[0080] The cumulative volume is calculated from each pressure stage using the following equation: Cumulative volume (mm 3 (mg) = Blank-corrected sample intake (mg) / Fluid density (g / cm³) 3 ) / Mass of the sample (mg)

[0081] The capillary action potential (CWP) is the action performed by a sample, normalized by the sample area. The trapezoidal rule is used to integrate the i-th pressure as a function of the cumulative volume over n data points for the absorption and drainage portions of the cycle.

[0082]

number

[0083] CWP, CWPA, and CWPD at 0.1 mJ / m 2 Report in units, where CWPA represents the absorption portion of the pressure sequence and CWPD represents the drain portion of the pressure sequence.

[0084] Caliper measurement of nonwoven webs The caliper, or thickness, of a test specimen of nonwoven web material is measured as the distance between a reference platform on which the specimen is placed and a press that applies a specific amount of pressure to the specimen over a specific period of time. All measurements are performed in a laboratory maintained at 23°C ± 2°C and 50% ± 2% relative humidity, and the test specimens are conditioned in this environment for at least two hours prior to testing.

[0085] The caliper is measured with a manual micrometer equipped with a clamp capable of applying a steady pressure of 2.0 kPa ± 0.01 kPa to the test specimen. The manually operated micrometer is a gravity-type instrument with accurate readings to 0.001 mm. A preferred instrument is the Mitutoyo Series 543 ID-C Digimatic, available from VWR International, or an equivalent. The clamp is a flat, grounded, circular movable surface with a diameter smaller than the test specimen and capable of applying the required pressure. A preferred clamp has a diameter of 25.4 mm, but a smaller or larger clamp can be used depending on the size of the specimen being measured. The test specimen is supported by a horizontal, flat reference platform that is larger than the surface of the clamp and parallel to the surface of the clamp. The system is calibrated and operated according to the manufacturer's instructions.

[0086] Remove the test specimen from the absorbent material as necessary. When removing the test specimen from the absorbent material, take care not to impart any contamination or dimensional deformation to the specimen. The test specimen must be obtained from an area free of folds or wrinkles and must be larger than the presser foot.

[0087] To measure the caliper, first zero the micrometer against a horizontal, flat reference platform. Place the test specimen on the platform with the test position centered under the pressure foot. Gently lower the clamp at a rate of 3.0 mm ± 1.0 mm / sec until the full pressure is applied to the test specimen. After waiting 5 seconds, record the caliper measurement of the test specimen in 0.01 mm increments. Repeat the same process for a total of five duplicate test specimens. Calculate the arithmetic mean of all caliper measurements and report it in 0.01 mm increments.

[0088] In light of the aforementioned disclosures, the following non-limiting embodiments can be conceived. 1. A women's hygiene pad comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent layer disposed between the top sheet and the back sheet, The top sheet includes a fibrous nonwoven web material containing hydrophilic fibers, The absorbent layer contains an open-cell foam formed by polymerization of HIPE. The top sheet and the absorbent layer are arranged facing each other directly, and at least 15 cm apart. 2 , more preferably at least 30 cm 2 More preferably, a feminine hygiene pad, wherein the absorbent layers are attached to each other within a bonding region of at least half the surface area of ​​the surface of the absorbent layer facing the wearer, and within the bonding region, each first identifiable attachment point between the top sheet and the absorbent layer has an adjacent second identifiable attachment point between the top sheet and the absorbent layer within a radius of 6 mm from the first identifiable attachment point.

[0089] 2. A women's hygiene pad comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent layer disposed between the top sheet and the back sheet, The top sheet comprises a fibrous nonwoven web material containing cotton fibers and having CWPD, The absorbent layer has a CWPA larger than the CWPD, and has a caliper (before wetting) of 1 mm to 5 mm, more preferably 1.5 mm to 3.5 mm, or even more preferably 2.0 mm to 3.0 mm. The top sheet and the absorbent layer are arranged facing each other directly, and at least 15 cm apart. 2 , more preferably at least 30 cm 2 More preferably, a feminine hygiene pad, wherein the absorbent layers are attached to each other within a bonding region of at least half the surface area of ​​the surface of the absorbent layer facing the wearer, and within the bonding region, each first identifiable attachment point between the top sheet and the absorbent layer has an adjacent second identifiable attachment point between the top sheet and the absorbent layer within a radius of 6 mm from the first identifiable attachment point.

[0090] 3. A feminine hygiene pad according to Example 1 or 2, wherein the attachment between the top sheet and the absorbent layer is achieved by an adhesive deposited discontinuously or intermittently to form a bonding region, leaving non-bonding regions scattered between the top sheet and the absorbent layer within the bonding region.

[0091] 4. A feminine hygiene pad according to any of Examples 1 to 3, wherein the nonwoven web material contains plant fibers.

[0092] 5. A feminine hygiene pad according to any of Examples 1 to 4, wherein the nonwoven web material contains cotton fibers.

[0093] 6. A feminine hygiene pad according to any of Examples 1 to 5, wherein the nonwoven web material contains rayon fibers.

[0094] 7. A feminine hygiene pad according to Example 4, wherein the nonwoven web material mainly consists of plant fibers, preferably substantially entirely of plant fibers.

[0095] 8. A feminine hygiene pad according to Example 5, wherein the nonwoven web material mainly consists of cotton fibers, preferably substantially entirely cotton fibers.

[0096] 9. A women's hygiene pad according to Example 6, wherein the nonwoven web material mainly comprises rayon fibers, preferably substantially entirely rayon fibers.

[0097] 10. A feminine hygiene pad according to any of Examples 4 to 9, wherein the nonwoven web material also includes fibers spun from a thermoplastic polymer resin.

[0098] 11. A feminine hygiene pad according to any of Examples 4 to 10, wherein the nonwoven web material is entangled in water flow.

[0099] 12. A women's hygiene pad according to any one of Examples 1 to 11, comprising at least two absorbent sublayers, each including a wearer-facing sublayer with relatively larger bubbles, wherein the absorbent layer is disposed in contact with a sublayer facing the outward side of the relatively smaller bubbles.

[0100] 13. A feminine hygiene pad according to any one of Examples 1 to 12, wherein the fibrous nonwoven web material has CWPD, the absorbent layer has CWPA, the CWPA is larger than the CWPD, and the absorbent layer has a caliper (before wetting) of 1 mm to 5 mm, more preferably 1.5 mm to 3.5 mm, or even more preferably 2.0 mm to 3.0 mm.

[0101] 14. CWPA is at least 40 mJ / m³ 2 , more preferably at least 45 mJ / m³ 2 More preferably, at least 50 mJ / m³ 2 The women's hygiene pad described in Example 13 is larger than the CWPD.

[0102] 15. A feminine hygiene pad according to any one of Examples 1 to 14, wherein the fibrous nonwoven web material has a basis weight of 20 gsm to 50 gsm, more preferably 25 gsm to 45 gsm, and even more preferably 30 gsm to 40 gsm.

[0103] 16. A feminine hygiene pad according to Example 15, wherein the fibrous nonwoven web material has calipers of 0.20 mm to 0.60 mm, more preferably 0.25 mm to 0.55 mm, and even more preferably 0.30 mm to 0.45 mm.

[0104] 17. The fibrous nonwoven web material contains cotton fibers and has a density of 74 kg / m². 3 ~110 kg / m 3 , more preferably 83 kg / m 3 ~101 kg / m 3 A women's hygiene pad having the density of either Example 15 or 16.

[0105] 18. A feminine hygiene pad according to any one of Examples 1 to 17, wherein the absorbent layer includes an array of perforations present at least within the binding region. ***

[0106] The dimensions and values ​​disclosed herein should not be understood as being strictly limited to the exact numerical values ​​listed. Instead, unless otherwise indicated, each such dimension is intended to mean both the listed value and the functionally equivalent range encompassing that value. For example, a dimension disclosed as "40 mm" is intended to mean "approximately 40 mm."

[0107] All documents referenced in this Application, including all cross-referenced or related patents or patent applications, and any patent applications or patents for which this Application claims priority or benefit thereof, are incorporated herein by reference in their entirety, to the extent that they do not conflict with this Application and unless explicitly stated to exclude or limit them. No document reference shall be deemed prior art to any invention disclosed or claimed herein, nor shall it be deemed to teach, suggest or disclose any such invention, either alone or in combination with any other reference(s). Furthermore, if any meaning or definition of a term in this Document conflicts with any meaning or definition of the same term in any document incorporated by reference, the meaning or definition given to the term in this Document shall prevail.

[0108] While specific embodiments of the present invention have been illustrated and described, it will be apparent 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. Therefore, it is intended that all such changes and modifications within the scope of the invention be covered in the appended claims.

Claims

1. A women's hygiene pad comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent layer disposed between the top sheet and the back sheet, The top sheet comprises a fibrous nonwoven web material containing cotton fibers and having CWPD, The absorbent layer has a CWPA that is larger than the CWPD, The top sheet and the absorbent layer are arranged facing each other directly, and at least 15 cm apart. ２ They are attached to each other within a bonding region, and within the bonding region, each first identifiable attachment point between the top sheet and the absorbent layer has an adjacent second identifiable attachment point between the top sheet and the absorbent layer within a radius of 6 mm of the first identifiable attachment point. The attachment between the top sheet and the absorbent layer is achieved by an adhesive deposited discontinuously or intermittently, such that it forms a bonding region while leaving unbonded regions scattered between the top sheet and the absorbent layer within the bonding region. A women's hygiene pad in which the absorbent layer is formed of open-cell foam.

2. The women's hygiene pad according to claim 1, wherein the nonwoven web material includes rayon fibers.

3. The women's hygiene pad according to claim 1, wherein the nonwoven web material comprises cotton fibers entirely.

4. The women's hygiene pad according to claim 1, wherein the nonwoven web material also includes fibers spun from a thermoplastic polymer resin.

5. A women's hygiene pad according to any one of claims 1 to 4, wherein the nonwoven web material is entangled in water flow.

6. A women's hygiene pad according to any one of claims 1 to 5, comprising at least two absorbent sublayers, each sublayer having a relatively larger bubble facing the wearer, and the absorbent layer being disposed in contact with a sublayer facing the outward side of a relatively smaller bubble.

7. The feminine hygiene pad according to any one of claims 1 to 6, wherein the absorbent layer has a caliper of 1 mm to 5 mm before wetting.

8. The CWPA is at least 40 mJ / m ２ A women's hygiene pad according to any one of claims 1 to 7, which is larger than the CWPD.

9. The feminine hygiene pad according to any one of claims 1 to 8, wherein the fibrous nonwoven web material has a basis weight of 20 gsm to 50 gsm.

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