HK1032084A - Absorbent article comprising flocked fibers - Google Patents

Description

Absorbent article containing flocked fibers

The present invention relates to an absorbent article such as sanitary napkins and panty liners comprising a topsheet, an absorbent core and a backing. The absorbent article contains flocked fibers. The flocking fibers are bonded to the inner surface thereof, such as the surface of the cover facing the absorbent core, or the surface of the backing facing the absorbent core.

Absorbent articles come in a variety of forms, such as sanitary napkins, panty liners, diapers, incontinence pads, and interlabial products. In these articles, the addition of fibers is often required for a variety of applications. For example, superabsorbent polymer fibers may be added to improve the absorbent properties of the article. Unfortunately, superabsorbent polymer fibers are often brittle and it is often difficult to incorporate superabsorbent polymer fibers into absorbent articles using known manufacturing techniques. Particularly when special processing equipment is used to disperse the superabsorbent polymer fibers in an airlaid type matrix, they can be overwhelmed by adjacent superabsorbent polymer fibers and other fibers within the matrix. When overwhelmed, superabsorbent polymer fibers do not swell sufficiently to absorb liquid and their absorbent capacity is not fully utilized.

Flocking is a technique for securing fibers perpendicularly to a substrate, and is used primarily in the textile industry. However, EP 0, 737, 462 a1 discloses a laminate material which covers the surface of an absorbent article, characterized in that at least a part of the surface of the laminate material is provided with a layer of fibres which have been applied by flocking. Thus, flocking fibers to the outer surface of the absorbent article provides an absorbent article having improved tactile feel over products that utilize skin-friendly plastic films.

The applicant has now found that flocked fibres may advantageously be applied to one or more inner surfaces of an absorbent article. In an absorbent article comprising, for example, a skin, an absorbent core, and a backing, the flocking fibers may be applied to the surface of the skin facing the absorbent core, the surface of the absorbent core facing the skin, the surface of the absorbent core facing the backing, or the surface of the backing facing the absorbent core. The fibers are preferably selected from the group consisting of superabsorbent polymers and other hydrophilic materials, hydrophobic materials, and mixtures thereof, in order to provide absorbent articles with improved absorbent capacity and physical integrity.

The present invention provides an absorbent article having a body-facing surface and an undergarment-facing surface and comprising, in order, a skin layer, an absorbent core, and a backing, wherein the absorbent article comprises flocked fibers that are not bonded to the body-facing surface or the undergarment-facing surface of the absorbent article.

Figure 1 shows an absorbent article (panty liner) of the invention.

Fig. 2 is an enlarged view of an absorbent core according to the present invention with flocking fibers bonded to its surface.

The absorbent article may for example be a sanitary napkin, panty liner, diaper, incontinence pad, interlabial article or other similar article intended to absorb bodily discharges such as menses, urine or feces. Preferred absorbent articles are sanitary napkins or panty liners. Such sanitary napkins or panty liners can have an approximately rectangular, oval, dumbbell, or peanut shape. The size of the absorbent article may vary depending on its properties. For example, sanitary napkins generally have a thickness of about 1.4 to 5 millimeters, a length of about 3 to 16 inches, and a width of about 1 to 5 inches. The panty liner generally has a thickness of less than about 0.2 inches, a length of less than about 8 inches, and a width of less than about 3 inches.

Fig. 1 shows such a panty liner of the invention for the following description. The panty liner shown in figure 1 comprises, in order from its body facing surface 1 to its undergarment facing surface 2, a liquid permeable topsheet 3, an absorbent core 4, and a liquid impermeable backsheet 5. The top sheet 3 of the absorbent article can be formed of any liquid-permeable material which is comfortable against the skin and which allows liquid to penetrate the absorbent core which retains the liquid. The topsheet should retain little or no liquid to provide a relatively dry surface, since its outer surface forms the body-facing surface 1 of the article. A variety of materials are known to produce the skin layer, any of which may be used. For example, the skin layer may be a fibrous nonwoven fabric made of fibers or filaments of a polymer such as polyethylene, polypropylene, polyester, or cellulose. In addition, the skin layer may also be formed of a perforated polymer film, and the thickness of the skin layer may vary from about 0.001 inch to 0.062 inch, depending on the material selected.

Typically, the topsheet 3 is a single sheet of material having a width sufficient to form the body-facing surface 1 of the article. The cover layer may be the same length as the absorbent core or optionally longer than the absorbent core so as to form the lateral edges. Such transverse edges may be sealed with other layers to completely enclose the absorbent core.

The absorbent core 4 may comprise loosely associated hydrophilic absorbent materials such as cellulosic fibers, including wood pulp, regenerated cellulosic fibers, or cotton fibers, or other absorbent materials commonly known in the art, including acrylonitrile fibers, polyvinyl alcohol fibers, peat moss, and superabsorbent polymers.

The absorbent article further comprises a liquid impermeable backing 5, the outer surface of which forms the undergarment-facing surface 2 of the article. The backing may comprise any thin and flexible liquid impervious material, for example a polymeric film such as polyethylene, polypropylene or cellulose film. Alternatively, the backing may be a conventional liquid-permeable material that is treated to be impermeable to liquids, such as liquid-repellent impregnated paper, or a nonwoven material, or a flexible foam material such as polyurethane or crosslinked polyethylene. When made from a polymeric film, the backing typically has a thickness of about 0.001 to 0.002 inches. A variety of materials known in the art may be used as the backing, any of which may be employed.

Typically, the backing 5 is a single sheet of material that is wide enough to form the undergarment-facing surface 2 of the absorbent article. The backing may surround the side edges of the absorbent core in a C-shaped configuration with portions of the backing adjacent the longitudinal edges thereof extending from the garment-facing surface of the article toward the body-facing surface of the article. The preferred backing is breathable, i.e., a film that blocks a liquid layer but allows gas to pass through. Materials for this purpose include polyurethane films and microporous films in which micropores are formed by ionizing radiation or by filtering out solubles with a water-soluble or non-water-soluble solvent. Single or multiple permeable films, fabrics, and combinations thereof that provide a liquid surface that is resistant to liquid penetration by the labyrinth and/or its surface characteristics may also be used to provide a breathable backing.

The absorbent article may be applied to the crotch of the underpants by placing the garment-facing surface 2 of the absorbent article against the inner surface of the crotch of the underpants. A strip of pressure sensitive adhesive 6 may be applied to the undergarment-facing surface 2 of the absorbent article to help secure it in place. As used herein, the term "pressure sensitive adhesive" refers to any releasable adhesive or releasable adhesive device. Suitable pressure sensitive adhesives include, for example, water-based adhesives such as acrylate adhesives. In addition, the adhesive may comprise a fast setting thermoplastic "hot melt" rubber adhesive or a double sided adhesive tape.

Prior to use, a paper release strip 7 coated on one side may be applied to protect the strip of adhesive 6. Coating with, for example, silicone reduces the adhesion of the coated side of the release strip to the adhesive. The release strip may be formed from any suitable sheet material that can be bonded to the adhesive with sufficient tack to remain in place before use, after the sheet material is applied, but can be easily removed when the absorbent article is used.

The absorbent article may contain other known materials, layers and additives such as transfer layers, foam layers, mesh layers, odour control agents, fragrances, medicaments, moisturizers etc., many of which are known in the industry. However, as will be further described below, it is advantageous that the absorbent article does not contain, inter alia, a transfer layer. Decorative motifs may be pressed onto the absorbent article using conventional techniques.

According to the present invention, the absorbent article contains flocked fibers on one or more of its interior surfaces. The flocking fibers may be hydrophilic, hydrophobic, or a combination of both. Hydrophilic fibers include wettable fibers, i.e., hydrophobic fibers, absorbent fibers, and superabsorbent polymer fibers that have been treated with a wetting agent to render them hydrophilic. Examples of wettable fibers include, for example, bicomponent fibers, polypropylene fibers, and polyester fibers treated with a surfactant. A preferred wettable fiber is a polyester fiber such as DuPont-Akra PolyesterType 11A Bright fiber from DuPont Company treated with Tween 20 surfactant from ICI Americas Inc.

The absorbent fibers are hydrophilic materials having affinity for and absorbing liquid, and may contain rayon fibers, acrylonitrile fibers, nylon fibers, polyvinyl alcohol fibers, and natural or regenerated cellulose fibers. A preferred type of absorbent fiber is rayon.

Superabsorbent polymer fibers are hydrophilic fibers that swell and are capable of absorbing more than about 5 grams per gram (fiber weight) of a 1% saline solution. Examples of superabsorbent polymer fibers are polyacrylate fibers, grafted cellulose fibers and maleic acid fibers. Preferred types of superabsorbent polymer fibers include OASIS Type 101 available from Technical Absorbents Limited, and CAMELOT available from Camelot, Alberta, Canada.

Hydrophobic fibers include certain polyolefin fibers and large denier polyester fibers, preferably having a denier of at least 3, more preferably at least 6. The preferred hydrophobic fiber is a 15 denier polyester fiber available from DuPont Company.

Regardless of the flocking fibers used, the length should be less than about 1 mm, preferably less than about 0.8 mm. The denier of the flocking fibers should be in the range of about 1.2 to about 15 denier, preferably about 1.8 to about 6 denier. Fibers that do not collapse when wet are also preferred.

The flocking fibers may be bonded to any inner surface of all or part of the absorbent article. This includes the surface of the cover facing the absorbent core, the surface of the absorbent core facing the cover, the surface of the absorbent core facing the backing, and the surface of the backing facing the absorbent core. In fig. 1, flocked superabsorbent polymer fibers 8 are bonded to the surface of the absorbent core facing the cover. The flocking fibers may be on one or both sides of a particular layer within the absorbent article. The same or different flocking fibers may be on two or more different inner surfaces. The flocking fibers may also be bonded to any other inner layer surface optionally used in absorbent articles, such as a transfer layer, a mesh layer, an additional absorbent layer, and the like.

Methods of flocking fibers to a surface are known in the art of fabric manufacture. See, for example, U.S. patent nos. 2, 527, 501, 2, 691, 611, 3, 436, 442, 3, 672, 929. Generally, a substrate such as a skin layer is coated over all or part of its surface with an adhesive. The coated substrate is then passed through a fiber metering station, using, for example, electrodes positioned above and below the substrate, to maintain an electrostatic field around the substrate. The fibers are applied to the binder on the substrate in the presence of an electrostatic field that orients the fibers perpendicular to the substrate when the fibers contact the binder. The substrate is then heated to polymerize the binder and anchor the fibers. The unbonded fibers can be removed by vacuum.

Preferably, the adhesive used to bond the fibers to the interior surface is a polymerizable resin, such as modified acrylic water-based compounds, such as FLEXBOND 974, 977, 983, and 986 from Air Products, CARBOTAC Adhesives (PSAs) from BF Goodrich, and CARBOBAND Adhesives (non-PSAs) also from BFGoodrich.

Fig. 2 is an enlarged photograph of an airlaid slurry typically used as an absorbent core in an absorbent article. It contains high-absorption polymer fiber, artificial silk and polyester flocked fiber.

In a particularly preferred embodiment of the invention, the flock fibers contain one or more superabsorbent polymer fibers. Superabsorbent polymers in both particulate and fibrous forms are known to improve the fluid handling properties of absorbent articles, such as fluid containment and retention properties. However, according to the present invention, when the superabsorbent polymer flock fibres are applied to the substrate, they stand upright on the surface in a vertical manner. This orientation allows the flocked fibers of superabsorbent polymer to absorb more liquid than non-flocked fibers of superabsorbent polymer, i.e., fibers that are pressed down horizontally.

Preferably, the flocked superabsorbent polymer fibers are bonded to the surface of the absorbent core facing the topsheet. The superabsorbent polymer fibers are bonded to the surface of the absorbent core facing the topsheet to efficiently draw liquid into the absorbent core. If desired, the absorbent core may be densified according to this embodiment in order to wick liquid laterally once it has entered the absorbent core.

The absorbent article contains a total amount of superabsorbent polymer of from about 0.1 to about 5 grams, preferably from about 0.2 to about 2.5 grams, and more preferably from about 0.3 to about 1 gram. Wherein the flocking fibers may be up to 100%. The remainder, if any, being material that is present in the absorbent core as particles, fibers, or both.

In another embodiment of the present invention, the flocking fibers contain superabsorbent polymer fibers and other hydrophilic fibers (i.e., wettable fibers, absorbent fibers, or a combination of both). In this embodiment, the liquid is rapidly absorbed by the other hydrophilic fibers and then transferred to the superabsorbent polymer fibers. Although superabsorbent polymer fibers absorb slower than other hydrophilic fibers, superabsorbent polymer fibers have a higher total capacity and higher liquid retention.

In this embodiment, the amount of superabsorbent polymer in the combined superabsorbent polymer fiber/other hydrophilic fiber is generally from about 5 to about 95 weight percent, and preferably from about 30 to about 70 weight percent. The flocked superabsorbent polymer fibers can be uniformly dispersed in the other hydrophilic fibers or the superabsorbent polymer fibers can be bonded to the inner surface in a pattern with the other hydrophilic fibers.

In a particularly preferred embodiment of the invention, the flock fibers contain a combination of superabsorbent polymer fibers, other hydrophilic fibers and hydrophobic fibers. Similarly, liquid is rapidly absorbed by other hydrophilic fibers and transported to the superabsorbent polymer fibers, which have a higher capacity to retain liquid. The hydrophobic fibers absorb little or no liquid and thus advantageously retain their physical integrity to minimize wet collapse. The hydrophobic fibers support the superabsorbent polymer fibers and other hydrophilic fibers as the hydrophilic fibers absorb liquid and lose rigidity. In addition, due to the upward support of the hydrophobic fibers, lower pressure is generated on the inner layer of the absorbent product, and the absorption capacity of the absorbent product is also improved. In this way, the overall structural and physical integrity of the absorbent article is maintained.

The use of flocked hydrophobic fibers in absorbent articles also has other advantages, such as addressing the need for a transfer layer or secondary cover layer that is often used in sanitary napkins. The transfer layer is generally hydrophobic and is located between the cover and the absorbent core of the absorbent article. During use, they separate the absorbent core from external pressures acting on the absorbent article. This function can be accomplished by the hydrophobic flock fibres being thin and of relatively simple construction. In addition, the absorbent core is subjected to less pressure than the transfer layer by the hydrophobic flocking fibers because the former are oriented perpendicular to the surface of the absorbent core.

In this embodiment, the amount of superabsorbent polymer in the combined superabsorbent polymer fibers/other hydrophilic fibers/hydrophobic fibers is generally from about 5 to about 95 weight percent, and preferably from about 30 to about 70 weight percent. The superabsorbent polymer fibers may be uniformly dispersed within the other hydrophilic fibers, the hydrophobic fibers, or different fibers may be bonded to the inner surface in a pattern.

The following non-limiting examples further illustrate the invention.

An absorbent core containing superabsorbent polymer flocking fibers was prepared as follows.

A1 oz/yd 2 100% polyester substrate was used as the carrier fabric. The polymerizable resin was applied to the polyester fabric in various patterns. A fiber mixture consisting of 30% superabsorbent polymer fibers, 40% rayon fibers and 30% polyester fibers was metered onto a polyester fabric. The fibers are oriented in a vertical state by an electrostatic field. The fibers are bonded to the location where the resin is applied. The substrate is then passed through an oven to polymerize the resin and anchor the fibers to the polyester fabric. Excess fiber is drawn off by vacuum.

A panty liner was manufactured using the absorbent core of example 1 in the following manner. A liquid-permeable nonwoven surface layer is placed over the absorbent core with the surface of the absorbent core containing the flocked fibers facing the surface layer. A liquid impermeable backing is positioned beneath the absorbent core on the surface of the absorbent core free of the flocking fibers.

Claims (13)

1. An absorbent article comprising a body-facing surface and an undergarment-facing surface and comprising, in order, a cover, an absorbent core, and a backing, wherein said absorbent article comprises flocked fibers, said flocked fibers being unbonded to the body-facing surface or the undergarment-facing surface of the absorbent article.

2. The absorbent article of claim 1, wherein said fibers are bonded to a surface layer on the surface facing the absorbent core.

3. The absorbent article of claim 1, wherein the fibers are bonded to the absorbent core on the surface facing the topsheet.

4. The absorbent article of claim 1, wherein the fibers are bonded to the absorbent core on the backing-facing surface.

5. The absorbent article of claim 1 wherein said fibers are bonded to a backing on the surface facing the absorbent core.

6. The absorbent article of claim 5 wherein said backing is breathable.

7. The absorbent article of claim 1, wherein said fibers comprise hydrophilic fibers.

8. The absorbent article of claim 7, wherein said hydrophilic fibers are selected from the group consisting of wettable fibers, absorbent fibers, superabsorbent polymer fibers, and mixtures thereof.

9. The absorbent article of claim 8, wherein said fibers comprise one or more superabsorbent polymer fibers.

10. The absorbent article of claim 8, wherein said fibers comprise a combination of wettable fibers, absorbent fibers and superabsorbent polymer fibers.

11. The absorbent article of claim 1, wherein said fibers comprise hydrophobic fibers.

12. The absorbent article of claim 11, wherein said fibers further comprise a composition of hydrophilic fibers.

13. The absorbent article of claim 12, wherein said hydrophilic fibers are selected from the group consisting of wettable fibers, absorbent fibers, superabsorbent polymer fibers, and mixtures thereof.