RU2184516C2 - Absorbing articles having outer enclosure with reduced moisture content - Google Patents

Abstract

FIELD: individual hygiene articles. SUBSTANCE: absorbing articles have filamentary blocking layer arranged between absorbing middle part and moisture-impermeable breathing outer enclosure. Blocking layer may contain one or several layers of material formed from filaments produced by aerodynamic method from melt and having thickness of at least 0.03 cm and hydraulic load value of at least 18 bar. Water vapor penetration extent of absorbing articles exceeds 1,500 g/sq.m/day in dry state, however it reaches 15,000 g/sq. m/day in wet state. Absorbing article of such structure allows increased condensation induced outer moisture content to be reduced or eliminated. EFFECT: simplified structure, increased efficiency and convenient use. 22 cl, 3 dwg, 1 tbl, 6 ex

Description

 The technical field to which the invention relates.

 The invention relates to absorbent articles. In particular, this invention relates to absorbent articles, such as personal care products, which have a reduced moisture content of the outer shell.

State of the art
Absorbent products such as baby diapers, clothing for adults with incontinence, sanitary napkins, bedding, panty liners, incontinence pads, etc. well known in the art. Such products are not expensive, often for single use, but are able to absorb and retain liquids and other bodily secretions. Typically, such absorbent articles have an outer shell having a plastic film that does not allow liquid to pass through, such as polypropylene and / or polyethylene film, to prevent leakage of retained discharge from the product and contamination of clothing, bedding, furniture, and the like. However, until recently, a film was used in an impermeable outer shell that did not pass water vapor or liquid. Due to the fact that the outer shell was impervious to liquids and water vapor, absorbent articles were often hot and sticky to the user, even before the absorption of bodily secretions. In addition, the lack of water vapor permeability often caused skin irritation and, in some cases, led to serious dermatological problems. For example, absorbent products, such as diapers, can cause a rash in a child if worn for a long time. In addition to the problems associated with well-being of the skin, liquid-impermeable plastic films used as the outer shell often had low aesthetic and tactile qualities that are necessary for personal care products, such as disposable diapers.

 To eliminate the above problems, breathable, tissue-like, liquid-tight outer shells have been developed. Such structures, which are usually laminated from several different layers, remain impervious to liquids, but they "breathe" in the sense that water vapor passes through the outer shell. Breathable outer shells have become increasingly popular and have been increasingly used commercially in absorbent personal care products, in particular disposable diapers. However, although a healthier and more comfortable product has been provided from the user's point of view, breathable, liquid-impervious outer shells often have a lack of undesirable and unpleasant moisture in the outer shell. Continued use of the absorbent article after the liquid is isolated and absorbed by the article, even for a short time, makes the outer shell feel wet or damp. However, this unpleasant sensation of dampness is not caused by the passage of liquid through a liquid-tight enclosure or leakage from the product, but only by the condensation of water vapor on the outer shell due to too much water vapor passing through the outer shell.

 Thus, there is a need for an absorbent product that provides sufficient water vapor permeability so that the absorbent products remain healthy and comfortable products for the user, but which do not allow too much water vapor permeability after the liquid is released into the product, so that the outer shell does not become wet or wet to the touch.

SUMMARY OF THE INVENTION
This invention is directed to eliminating the difficulties and problems mentioned above, as well as the problems experienced by specialists in this field of technology when creating an absorbent product containing: (a) a breathable, liquid-impermeable outer shell; (b) a liquid permeable top layer; (c) an absorbent core between the outer shell and the top layer; and (d) a hydrophobic barrier layer located between the breathable outer shell and the absorbent core.

The hydrophobic barrier layer may contain one or more layers of porous material having a withstand hydraulic load of more than 18 cm and a thickness of at least 0.012 inches (0.03 cm), in which the outer shell and the barrier layer together have an inverted water vapor transmission rate (WVTR) less than 15000 g / m ² / day. In another embodiment, the absorbent material of the barrier layer may comprise a cotton pad having a Fraser air permeability of more than 40 cubic feet per minute (850 dm ³ / min). In one embodiment, the barrier layer may comprise one or more nonwoven meltblown fibers, together having a surface weight of more than 16 g / m ² , in particular, the hydrophobic barrier layer may contain fiber material having a thickness of 0.045 cm or more up to about 0.05 cm. In another embodiment, the barrier layer may comprise a plurality of layers, including a layer of meltblown fibers that can be adjacent to an absorbent the middle part in which the plurality of layers together has a surface weight of more than 20 g / m ² , preferably from about 25 to about 40 g / m ² . In another embodiment, the barrier layer comprises at least one nonwoven layer having a hydraulic load of at least 30 mbar and a combined surface unit weight of more than 20 g / m ² . In another embodiment, the hydrophobic barrier layer may comprise at least one layer of nonwoven fabric made by a spinneret method and one layer of material from fibers melt-blown.

 In another embodiment, the absorbent article includes a hydrophobic barrier layer that extends substantially beneath the entire absorbent core. For example: a hydrophobic barrier layer may extend beyond the outer edges of the absorbent body or only extend along the length of the central part of the absorbent article. In yet another embodiment, the barrier layer may comprise at least partially a wrapping layer around the absorbent body. For example, the wrapping layer may comprise a hydrophobic barrier layer above the first side of the absorbent core adjacent to the outer shell and a hydrophilic non-woven layer above the opposite side of the absorbent core adjacent to the upper layer. Alternatively, the wrapping layer may comprise a continuous layer having a hydrophobic portion adjacent to the liquid-tight outer shell and a hydrophilic portion above the opposite side of the absorbent core portion adjacent to the upper layer, so that the hydrophobic portion of the wrapper layer contains at least a portion locking layer.

In yet another embodiment, the hydrophobic barrier layer comprises a plurality of fiber webs obtained by the aerodynamic method from a polyolefin melt, together having a surface unit weight of at least about 20 g / m ² and a hydraulic load of at least about 30 mbar, wherein said breathable, impermeable liquid outer shell and said barrier layer has a water vapor transmission rate exceeding 1500 g / ^m2 / day, preferably at least 3000 g / ^m2 / day and an inverted degree of water vapor transmission enee 12000 g / ^m2 / day. In another embodiment, the hydrophobic barrier layer has a hydraulic load of at least about 30 mbar and a surface unit weight of at least about 25 g / m ² , wherein said breathable, liquid-impervious outer shell and said barrier layer have a water vapor transmission rate of over 3500 g / m ² / day and an inverted water vapor transmission rate of less than about 11000 g / m ² / day.

List of drawings
The figures depict:
FIG. 1 is a plan view, partially in section, of a diaper according to the invention in a flat, non-contact state.

 FIG. 2 is a cross-sectional side view of an absorbent core and a wrapping layer.

 FIG. 3 is a cross-sectional side view of an absorbent core and a wrapping layer.

Definitions
As used herein, the term “fleece web” or “non-woven fabric” means a web having a structure of individual fibers or threads that are interleaved, however indefinitely, as in a knitted fabric. Non-woven materials are made using various methods, such as, for example, an aerodynamic method for producing fibers from a melt, a spunbond method for manufacturing a non-woven material, a hydrointerleaving method and a method for producing a non-woven cord fabric.

 The term “spunbond fiber” as used herein refers to small diameter fibers that are obtained by extruding a molten thermoplastic material in the form of a filament from a plurality of thin, usually round capillaries of a multichannel extruder mouthpiece, wherein the diameter of the extruded filaments is quickly reduced as described for example, in U.S. Patent 4,340,563 issued to Appel et al., in U.S. Patent 3,692,618 issued to Dorschner et al. in U.S. Patents 3,338,992 and 3,341,394 to Kinney, in U.S. Patent 35 02763, issued to Hartman, in US Pat. No. 3,542,615, issued to Dobo et al., In US Pat. No. 5,336,552, issued to Strack and others, and in US Pat. No. 5,382,400, issued to Pike et al. Fiber-made fibers generally are not sticky when arranged on a common surface. Thus, nonwovens made from spunbond fibers are typically processed to provide additional integrity to the material, as described, for example, in U.S. Patent Application 08/362328, filed by Arnold et al. December 22, 1994, U.S. Patent 4,374,888 to Bornsleger; and U.S. Patent 3,855,046 to Hansen and Pennings. Spunbond fibers are typically continuous and often have an average diameter (at least in a sample of 10 fibers) of more than 7 microns, in particular between about 10 and 50 microns. However, thin non-woven materials can be made from fibers made by the spinneret method, which, as used herein, include fibers having (denier) a fiber titer of 2 or lower.

 As used herein, “meltblown fibers” means fibers obtained by extruding molten thermoplastic material through a variety of thin, usually round, capillaries of an extruder head in the form of filaments or filaments into convergent streams of a gas moving at high speed, usually hot ( for example, air), which lead to a decrease in the diameter of filaments of molten thermoplastic material, which can be of the order of several m calf. After this, the fibers obtained by the aerodynamic method from the melt are transferred by a high-speed gas stream and deposited on the collecting surface to form a web with randomly distributed fibers obtained by the aerodynamic method from the melt. Such a method is disclosed in various patents and publications, for example, in US Pat. No. 3,849,241 to Butin et al. Wendta, E.L. Buna and K. O. Fluharti, Production of Ultrafine Organic Fibers, NRL Report 4364; K.D. Lawrence, R.T. Lucas and J. A. Young, An Advanced Device for Producing Ultra-Thin Thermoplastic Fibers, NRL Report 5265. Melt-derived fibers are typically microfibers that can be continuous or of finite length and generally have an average diameter of less than 10 microns.

 As used herein, the term “polymer” typically includes, but is not limited to, homopolymers, copolymers, such as, for example, block copolymers, grafted, random and random copolymers, ternary copolymers, etc., mixtures and modifications thereof. In addition, unless otherwise indicated by way of limitation, the term "polymer" should include all possible geometric configurations of the molecules. These configurations include, but are not limited to, isotactic, syndiotactic, or randomly symmetric.

 As used herein, the term "multilayer material" means a material in which some layers are made of nonwoven fabric made by a spinneret method and some layers of material are made of fibers obtained by melt aerodynamic method, such as a multilayer material (SMS) with a first layer made by a spinneret method , with a second layer made by the aerodynamic method, and with a third layer obtained by a spinneret method, and other layered materials disclosed in US patent 4041203, issued to Brock and others, in US patent 4,374,888 to Bornsleger, U.S. Patent 5,169,706 to Collier et al., U.S. Patent 5,145,727. To Potts et al. U.S. Patent 5,178,931 to Perkins et al. And U.S. Patent 5,188,885 to Timmons et al. the material can be made by sequentially applying to the moving molding tape a first layer of nonwoven fabric made by the spinneret method, then a layer of material obtained by the aerodynamic method from the melt, and then another layer of nonwoven material made by the spinneret method, compound of the laminate in the manner described in the above sources. Alternatively, the layers of material can be manufactured individually, rolled up, and combined at a separate joining stage. The multilayer materials may also have a different number of layers of meltblown fibers or several layers of a nonwoven fabric made by a spinneret method in various configurations and may include other materials such as films (F) or coform materials, for example, SMMS , SFS, etc.

 As used herein, the term "coform" refers to a process in which at least one extruder head for fibers melt-blown is located near a tray through which additional materials are fed into the web during formation. Such other materials may be, for example, pulp, superabsorbent particles, cellulosic or staple fiber. The conformal processes are described in US Pat. No. 4,818,464 to Lau, and US Pat. No. 4,100,324 to Anderson et al.

 As used herein, the term “point connection” refers to the connection of one or more layers of material at a number of separate connection points. For example, thermal point bonding typically involves passing one or more layers to be bonded between heated rollers, such as, for example, profiled pattern rollers or smooth calender rollers. Profiled rollers give such a relief that all the material does not connect over the entire surface, the support roller is usually smooth. Various patterns have been developed for profiled rollers based on functional and aesthetic considerations. One example of such a pattern has dots and is a Hansen-Pennings pattern or “H & P” cure, where the connection area in the new state is about 30% with about 200 compounds per square inch, as described in US patent 3855046, issued to Hansen and Pennings. Another typical point connection has connecting areas with square pins in which each pin has a lateral size of 0.023 inches (0.584 mm), the distance between the pins is 0.062 inches (1.575 mm) and the connection depth is 0.033 inches (0.838 mm). The resulting pattern has a joint area of about 15% in the new state. Another common pattern is the C-star pattern, which has a joining area of about 16.9% in the new state. The C-star pattern has transverse stripes or a "velveteen" pattern interrupted by diverging stars. Another common pattern includes a diamond-shaped pattern with repeating and slightly offset diamonds, which has a joint area of about 16%. Typically, the percentage of the area of the compound does not exceed 50% and preferably ranges from about 10% to about 30% of the area of the multilayer material.

 As used herein, the term “superabsorbent” or “superabsorbent material” refers to a water-swellable, water-soluble organic or inorganic material capable of absorbing its 20-fold weight, preferably at least its 30-fold weight, of an aqueous solution containing 0 9 wt.% Sodium chloride. Organic materials suitable for use as superabsorbent materials in accordance with this invention include, but are not limited to, natural materials such as kieselguhr resin, agar, pectin, and the like; as well as synthetic materials such as synthetic hydrogel polymers. Such hydrogel polymers include, for example, alkali metal salts of polyacrylic acid, polyacrylamides, polyvinyl alcohol, copolymers of ethylene and maleic anhydride, polyvinyl esters, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl polymers, polyacrylamides, polymers . Other suitable polymers include hydrolyzed acrylonitrile grafted starch, acrylic acid grafted starch, and copolymers of isobutylene and maleic anhydride and mixtures thereof. Hydrogel polymers are preferably slightly crosslinked to render the material substantially water insoluble. Crosslinking can occur, for example, due to the breaking of a covalent, ionic bond, a van der Waals bond, or a hydrogen bond. Superabsorbent materials can be in any form suitable for use in absorbent composite materials, including particles, fibers, flakes, spheres, and the like. Typically, the superabsorbent material is present inside the absorbent core in an amount of from about 5 to about 95% by weight relative to the total weight of the absorbent core. Superabsorbent materials typically have a particle size in the range of from about 20 to about 1000 microns. An example of a suitable, commercially available superabsorbent material is SANWET IM 3900, available from Hoechst Celanese, Portsmouth, Virginia, and DRYTECH 2035. available from Dow Chemical Co., Midland, MI.

As used herein, “breathable material” means a water vapor permeable material according to the water vapor transmission test described below having a water vapor transmission (WVTR) of at least 1500 g / m ² / day.

 As used herein, the term “personal care product” refers to diapers, sweatpants, absorbent underwear, products for adults with incontinence, feminine hygiene products, and the like.

Information confirming the possibility of carrying out the invention
Absorbent articles typically include a liquid permeable top layer that faces the user, and a liquid impermeable lower layer or outer shell. An absorbent middle part is located between the upper layer and the outer shell, often the upper layer and the upper shell are hermetically connected to enclose the inside of the absorbent middle part. Although the following detailed description is made regarding a disposable diaper, one skilled in the art will appreciate that the idea of the present invention is suitable for use in other types of absorbent articles, in particular in other personal care products. In addition, although the invention has been described in the context of several specific configurations, it is understood that other combinations and specific configurations are possible for those skilled in the art, in addition to the following, which are also within the scope and scope of the invention.

 As shown in FIG. 1, the diaper 10 may include a liquid-impermeable, breathable outer shell 12, a liquid-permeable top layer 14 located opposite the outer shell 12, and an absorbent middle portion 16 between the outer shell 12 and the upper layer 14. Between the absorbent middle part 16 and the breathable outer shell 12 is a hydrophobic, breathable locking layer 18.

 The diaper 10 may have various shapes, such as, for example, a fully rectangular shape, a T-shape or an hourglass shape. Usually, the top layer 14 has the same shape as the outer shell 12, however, it can optionally occupy a larger or smaller area than the outer shell 12, if desired. Parts of the diaper 10, such as the edge of the outer shell 12, may extend beyond the outer edge of the absorbent middle portion 16. In the illustrated embodiment, for example, the outer shell 12 may extend outside the outer side edges of the absorbent middle portion 16 to form side edges 22 and end edges 24 diapers 10.

 As shown by way of illustration in FIG. 1, the top layer 14 preferably has a surface facing the body that is supple, soft to the touch and does not irritate the skin of the user. The top layer 14 is configured to isolate the skin of the user from the fluid held in the absorbent middle portion 16. In order to provide a drier surface for the user, the top layer 14 may be less hydrophilic than the absorbent middle part 16, and also sufficiently porous to providing permeability to liquids. The upper layers are well known in the art and can be made of various materials such as polystyrene, mesh foams, perforated plastic films, natural fibers (e.g., wool or cotton fibers), synthetic fibers (e.g., polyesters, polypropylene, polyethylene, etc.). .d.), or a combination of natural and synthetic fibers. For example, the top layer may comprise a web of polyolefin fibers obtained by the aerodynamic method from a melt or a spinneret method, or a knit-cord fabric composed of natural and / or synthetic fibers. From this point of view, the top layer may consist of a mainly hydrophobic material treated with a surfactant or in another way to achieve the desired level of wettability and permeability. As an example, a surfactant may be used in such an amount as to provide the desired degree of hydrophilicity using conventional means such as spraying, printing, or coating with a brush device. In a preferred embodiment, the top layer may comprise a fleece of nonwoven polypropylene material made by a spinneret method, or of polyethylene / propylene multicomponent fibers made by a spinneret method and treated with a surfactant octylphenoxypolyethoxyethanol commercially available from Union Carbide, Danbut, Conn. trade name Triton X-102.

 The backsheet or outer shell 12 may comprise a breathable, liquid-impermeable structure and often may comprise a multilayer material. In the particular embodiment shown in FIG. 1, the outer shell comprises a breathable, liquid-impermeable film 26 and one or more additional nonwoven layers 28 (shown in FIG. 1 as a single layer). The particular structure and composition of the outer shell may be selected from various combinations of films and / or nonwoven materials; nonwoven layers are generally selected to provide the desired strength, resistance to abrasion, pleasant to the touch and / or aesthetics of the appearance. In particular, it is preferable that the outermost part of the outer shell 12, such as the nonwoven layer 28 shown in FIG. 1, contains a wear resistant material that is perceived to be touch like fabric and has good abrasion resistance, such as SMS laminate. Liquid-tight outer shells contain multilayer materials having thin, non-porous films, such as polyvinyl alcohol, which allows water vapor to migrate through the film, which are themselves known in the art. In addition, films that are breathable but remain impervious to liquids by forming microporous voids that are sized to allow water vapor to pass through are also known in the art. In general, multilayer materials including the last named type of breathable films are preferred. These films can be made vapor-permeable by adding filler particles to the film and by rolling or stretching the film to form tears in which the filler particles are located. The amount of filler inside the film and the degree of stretching and / or rolling are adjusted to provide the desired degree of vapor permeability. Typically, such films are made of a polyolefin film, for example, polyethylene or polypropylene. Examples of breathable, liquid-impermeable films and liquid-impermeable multilayer materials are disclosed in US Pat. No. 4,777,073 to Ches, US Pat. US 08/929562, filed September 15, 1997 by McCormack et al., The entire contents of which are incorporated herein by reference. A particularly desirable material for use in liquid impermeable, breathable multilayer materials is a biaxially oriented polyethylene microporous film material, which is approximately 50% by weight calcium carbonate and which is commercially available from Exxon Chemical Co., Inc., Linden, New Jersey under the trade name EXXAIRE.

 Between the breathable, liquid-impermeable outer shell 12 and the liquid-permeable topsheet 14, there is an absorbent core 16, which typically includes superabsorbent particles, such as absorbent fibers, including, but not limited to, pulp fibers, synthetic wood fibers masses, synthetic fibers and their combinations. However, a common drawback of whipped wood pulp is the lack of integrity and the tendency to deteriorate when wet. Therefore, it is often preferable to add a stiffening agent that reinforces the fiber, such as fibers obtained aerodynamically from a polyolefin melt, or a staple fiber of short length, usually supplied in the form of a material of the same shape. For example, as already mentioned above, superabsorbent particles and / or staple fiber, such as made from wood pulp, can be injected into the stream of fibers obtained by the aerodynamic method from the melt, so that they are captured or bonded by fibers obtained by the aerodynamic method from the melt. Superabsorbent materials can be substantially homogeneously mixed with the hydrophilic fiber or can be selectively placed in the desired areas of the absorbent body to better retain and absorb bodily secretions. The concentration of the superabsorbent material may also vary along the thickness of the absorbent core. Alternatively, the absorbent core may comprise laminate of fiber webs and superabsorbent materials or other suitable means for holding the superabsorbent material in localized places.

 The absorbent middle portion may take many forms. For example, the absorbent core may be rectangular, I-shaped, and T-shaped. In general, it is preferable that the absorbent middle portion is somewhat narrower in the perineal region than in the front or back of the diaper. The size of the absorbent middle part and the choice of material for it depends on the desired loading capacity, the purpose of the absorbent product and other factors known to specialists in this field.

 The absorbent middle portion 16 may optionally have a wrapping layer of hydrophilic thin light tissue (not shown in FIG. 1). A wrap layer of lightweight thin fabric helps maintain the integrity of some absorbent structures, such as air-laid fiber structures. In addition, the wrapping layer of light thin fabric allows you to distribute the liquid throughout the entire mass of the absorbent middle part, in particular when using materials with an increased flow property, such as absorbent cellulosic materials. Examples of conventional wrapping materials from light, thin fabrics are crepe padding or high-strength, wet-damped fabrics. In addition, hydrophilic nonwovens may also be used as a wrapping layer for the absorbent core, as disclosed in US Pat. No. 5,485,592 to Abuto et al., The entire contents of which are incorporated herein by reference. The absorbent middle portion 16 and the breathable outer shell 12 are separated by a breathable hydrophobic barrier layer 18. In this regard, it was unexpectedly found that some materials do not noticeably limit the degree of transmittance of the diaper water vapor in the dry state, but significantly reduce the transmittance of the diaper water vapor after absorbing the absorbent liquid. middle part. Thus, the hydrophobic barrier layer according to this invention provides a sufficient degree of water vapor transmission when the absorbent article is in a dry state, so that the water vapor transmission of the diaper does not decrease appreciably and the diaper remains breathable. However, if the absorbent middle part has absorbed body fluid, the hydrophobic barrier layer significantly reduces the water vapor transmission rate of the absorbent article (with respect to the same absorbent article without a hydrophobic barrier layer), thereby reducing or eliminating the sensation of dampness or moisture that may occur on the outside of the back layer due to condensation.

The breathable, liquid-tight outer shell 12 together with the barrier layer 18 have an inverted water vapor transmission rate of less than 15,000 g / m ² / day, preferably less than 12,000 g / m ² / day, and more preferably less than 11,000 g / m ² / day. However, the outer shell 12 and the barrier layer 18 have a water vapor transmission rate (WVTR) of more than 1500 g / m ² / day, preferably more than 4000 g / m ² / day. Although the hydrophobic barrier layer 18 does not have to have the same liquid locking properties as the impermeable outer shells described above, it must have certain “barrier” properties to selectively control the degree of transmission of water vapor and limit the moisture content of the outer shell. From this point of view, suitable materials are those which are hydrophobic with a hydraulic load of at least 18 cm, preferably from about 30 to about 50 cm. In addition, the hydrophobic barrier layer should have a thickness of at least 0.012 inches (0.03 cm), preferably between about 0.018 and about 0.048 inches (0.046-0.122 cm). The non-woven barrier layer should preferably also have a Fraser air permeability of at least 20 cubic feet per square foot per minute (about 6095 l / m ² / min) and more preferably over 40 cubic meters. ft per sq. ft per minute (about 12192 l / m ² / min).

The barrier layer may contain breathable fiber materials, such as a woven or nonwoven fabric having the above properties, including, but not limited to, meltblown fibers, thin nonwovens made from spunbond fibers, such as having a titer fiber about 2 or less, non-woven or cord fabric, hydro-mixed fabric and other materials having similar properties. Suitable polymeric materials for the manufacture of the barrier layer include those materials from which the fiber web can be made; examples include, but are not limited to, polyamides, polyesters and polyolefins, such as polyethylene and / or polypropylenes. In a preferred embodiment, the barrier layer may comprise aerodynamic fibers made from polypropylene melt having a surface weight of 16 to about 64 g / m ² , more preferably in the range of over 20 g / cm ² to about 40 g / m ² . The fiber barrier layer 18 may contain one layer or several layers, which together have the desired characteristics. However, when using multilayer layers, it is preferable that they overlap each other without a point connection on the main surface of the layers or without another connection, which would significantly limit the breathing ability of the layers. Similarly, in a preferred embodiment, the barrier layer is not connected by a thermal point connection or in any other way to a liquid-tight outer sheath that would impair the breathability of the article.

 From this point of view, it may be desirable for the breathable hydrophobic barrier layer to be attached to the absorbent article primarily around the perimeter of the barrier layer. The multilayer layers can be connected thermally, by ultrasound, using glue or other methods known in the art.

 In one embodiment, as shown in FIG. 1, the barrier layer 18 may be located between the absorbent core portion 16, which optionally includes a hydrophilic wrapping layer (not shown), and the outer shell. The barrier layer should extend beneath at least those areas of the absorbent middle portion 16 that typically trap most bodily secretions. The locking layer 18 preferably also extends beneath substantially the entire absorbent middle portion 16 and may extend beyond its edges. As shown in FIG. 1, the barrier layer 18 may extend along the length of the central portion of the diaper 10 under the absorbent middle portion 16. Diaper configurations in which the barrier layer extends under the entire absorbent middle portion are particularly preferred if the absorbent core 16 includes a hydrophilic wrapping a layer with good flow characteristics, such as light fabric layers used to wrap the middle portion.

 In another embodiment, the barrier layer may comprise at least a portion of the wrapping layer of the absorbent core. The locking layer can be wide enough so that it can be folded over and then hermetically connected using glue, heat, ultrasound and / or pressure in the upper, lower and lateral parts of the wrapping layer. The folding of the locking layer can be carried out using conventional means of folding the layers, such as curved plates, which bend the locking layer onto itself. However, if a continuous web of locking material is used to encapsulate the absorbent middle portion 16, for example, the wrapping web 30, then the individual parts of the web are preferably treated so that it becomes hydrophilic in areas adjacent to the liquid-permeable topsheet 14. This can be achieved by zoning the barrier layer with a surfactant to impart wettability to certain areas.

 Thus, as shown in FIG. 2, the wrapping layer 30 of the absorbent middle part may comprise a continuous layer having hydrophilic regions 32 on the first side of the absorbent middle part 16 and hydrophobic regions 34 on the opposite side of the absorbent middle part 16. When included in the diaper, as this is shown in FIG. 1, the hydrophilic regions face the liquid permeable top layer 14, and the opposite hydrophobic region contains at least a portion of the barrier layer.

 In an alternative embodiment, the absorbent core may have a wrapping layer 30 comprising two or more strips connected together. For example, as shown in FIG. 3, the wrapping layer 30 may comprise a hydrophilic, liquid-permeable strip 36 on the side of the absorbent middle portion 12 adjacent to the user side, i.e. adjacent to the upper layer 14 of FIG. 1, and a hydrophobic barrier layer 38 adjacent to the opposite side of the absorbent middle portion 16. Both strips 36 and 38 together form a wrapping layer 30 and can be connected by one of many prior art methods, for example using adhesive, thermal, ultrasonic and / or pressure bonding.

 In addition, as shown in FIG. 1, the diaper 10 may further include a pair of fasteners 40 that are used to fasten the diaper 10 at the user's waist (not shown). Suitable fasteners include hook and loop fasteners, duct tape fasteners, button fasteners, snap fasteners, fungus and loop fasteners, and the like. In addition, although not discussed above, however, additional components that can be integrated into the diaper without deviating from the idea and scope of the invention are obvious to the skilled person. For example, diapers typically include elastic leg bands (not shown) that help secure the diaper to the wearer and thereby help prevent leakage from the diaper. Similarly, it is known to include in the diaper a pair of elastic, longitudinally extending closing wings (not shown) that are shaped to maintain a generally vertical, perpendicular arrangement along the central part of the diaper in order to provide an additional barrier to the lateral flow of bodily secretions. In addition, it is customary to include a layer for controlling the rapid rise in liquid level located between the upper layer 14 and the absorbent middle part 16, in order to prevent fluid collection on the part of the diaper adjacent to the skin of the user. These and other components are well known, and methods for their use in an absorbent article according to this invention are well known to those skilled in the art.

 The various components of the diaper are joined together using various bonding agents known to those skilled in the art, such as, for example, adhesive bonding, ultrasonic bonding, thermal bonding, and combinations thereof.

Test procedure
Material thickness measurement. The thickness of the material was measured according to the standard method for measuring the thickness of non-woven materials ASTM D 5729-95 using a three-inch acrylic plate, which provides a load of 0.05 psi. inch (3.447 kPa).

 The measurement of the properties of the barrier layer is reduced to the measurement of hydraulic load. Using a hydraulic load measurement, the height of the water or the amount of water pressure (in millibars) that the layer material can withstand before the water passes through it is determined. A material with a higher hydraulic load is a stronger barrier to liquid penetration than a material with a lower hydraulic load. Measurement of the hydraulic load can be carried out according to the federal test standard 191A, method 5514. The data on the hydraulic load given here were obtained using a test similar to the specified federal test standard, with the exception of the modification below. The hydraulic load was determined using a static hydraulic load measuring device offered by Marlo Enterprises, Inc. , Concord, North Carolina. The sample is subjected to standard water pressure, which is increased at a constant rate to the first signs of leakage on the surface of the material in three different areas (leakage at the edge adjacent to the clamps was neglected). Materials such as thin films can prevent premature sample rupture.

 The measurement of material permeability to air (Fraser permeability) was carried out according to the federal standard for testing 191A, method 5450 of July 20, 1978, and was recorded as the average measurement value of 3 samples. Fraser permeability is determined by measuring air flow through a material in cubic feet of air through a square foot of material per minute (CFM). Converting CFM to liters per square meter per minute (LMM) is done by multiplying the value in CFM by 304.8.

Water vapor transmission rate (WVTR) of a material sample was calculated according to ASTM E96-80. Round samples with a diameter of 3 inches (76.2 mm) were cut from each test material, as well as from the control material, which was a piece of CELGUARD ^TM 2500 film from Hoechst Celanese Corporation, Sommerville, NJ. CELGUARD ^TM 2500 is a microporous polypropylene film. For each material, 3 samples were prepared. The test bath was a Vapometer 60-1 cup, available from Thwing-Albert Instrument Company, Philadelphia, PA. 100 ml of water was poured into each Vapometer cup and separate samples of the test material were placed over the open top of the individual cups. Screw flanges were tightened to seal along the edges of the cups, leaving the test material or control material under the influence of the surrounding atmosphere on a circular surface with a diameter of 6.5 cm, which is an area of approximately 33.17 square meters. see. Cups were placed in an oven with forced ventilation at a temperature of 100 ^o F (32 ^o C) for 1 hour to achieve equilibrium. The furnace was kept at a constant temperature with external air circulation to prevent the accumulation of water vapor inside it. A suitable forced-air oven may be, for example, a Blue M Power-O-Matic 60 furnace, available from Blue M. Electric Company, Blue Island, Illinois. After reaching equilibrium, the plates were removed from the oven, weighed, and immediately returned to the oven. After 24 hours, the plates were removed from the oven and weighed again. A preliminary value of the degree of transmission of water vapor was calculated using the formula (I) below:
(I) The measured WVTR = (weight loss over 24 hours in grams) • 315,5 g / m ^2/24 h
Moreover, the relative humidity inside the furnace was not specifically regulated.

For given conditions of 100 ^o F (32 ^o C) and ambient relative humidity, it was assumed that measured for the control film CELGUARD ^TM 2500 transmission rate of water vapor is 5000 g / m ^2/24 hours. Accordingly, in each test, and the control film, and the preliminary measured values were reduced to the specified conditions using the formula (II):
(II) WVTR = (measured WVTR / WVTR control film) • (5000 g / m ^2/24 hours)
Inverted water vapor transmission rate (inverted WVTR): the test is carried out similarly to the test described above to determine the water vapor transmission rate with the exception that the cup is turned upside down so that the water is in contact with the test material. Furthermore, since the water vapor transmission rate for CELGUARD ^TM 2500 for an inverted test is not equal to 5000 g / ^m2 / 24 hours, then the control film and the correction is not used in the measurement of the degree of the inverted water vapor transmission. It was assumed that such a test more accurately reflects the passage of steam in a loaded absorbent article.

Example 1
A web was made from fibers obtained aerodynamically from a propylene melt using Himont PF-015 polypropylene polymer from Himont, Wilmington, Delaware, USA. A web of meltblown fibers was manufactured according to the method described in US Pat. No. 5,458,592 using aerodynamic parallel extrusion apparatus. Polypropylene was extruded through a die with a flow rate of 2.5 pounds per inch per hour (PIH). The extruded molten polymer flows were reduced in diameter by primary air supplied at a speed of about 1700 and 2000 cubic feet per minute (48140-56630 dm ³ / min) at a temperature of 530 ^° F. (287.8 ^{° C.} ). The resulting meltblown fiber web had a surface unit weight of 8.0 g / m ² and a thickness of 0.006 inches (0.015 cm). The average pore size of the sample was about 25 μm with a maximum pore size of 47 μm, while 0.5% of all pores had pore sizes in excess of 50 μm. The canvas had a sustained hydraulic load of 17.6 mbar, an unsustainable hydraulic load of 19.5 mbar, and a Fraser air permeability of 287 cubic feet per square foot per minute (CFM). A CELGUARD ^TM 2500 film with a thickness of 0.0025 cm was applied to a sample of the fabric obtained without any combination of both materials. The breathable, liquid-impermeable film and the web of fibers melt-blown aerodynamically had a water vapor transmission rate (WVTR) of 5154 g / m ² / day and an inverted water vapor transmission rate of 19396 g / m ² / day. The indicated results are also shown in table I.

Example 2
We used a cotton fleece made of fibers obtained by the aerodynamic method from a polypropylene melt, as in Example 1. Three layers of cotton fleece were laid on top of each other without any connection of the layers, and a total thickness of 0.012 inches (0.03 cm) was obtained, withstanding the hydraulic load 37 , 7 mbar, 37,4 mbar unresponsive hydraulic load and Fraser air permeability of 81.4 CFM. Then, a breathable, liquid tight barrier layer of CELGUARD ^TM 2500 film with a thickness of 0.0025 cm was applied to 3 layers of a cotton web. The breathable film and a cotton web layer had a combined water vapor transmission rate (WVTR) of about 5154 g / m ² / day and inverted the degree of transmission of water vapor 10367 g / m ² / day. These data are also shown in table I.

Example 3
We used a cotton fleece made of fibers obtained by the aerodynamic method from a polypropylene melt, as in Example 1. Five layers of cotton fleece were laid on top of each other without any connection of the layers, and a total thickness of 0.017 inches (0.04 cm) was obtained, withstand hydraulic load 50 , 5 mbar, 46.1 mbar unresponsive hydraulic load and Fraser air permeability of 81.4 CFM. Then, a breathable, liquid tight barrier layer of CELGUARD ^TM 2500 film with a thickness of 0.0025 cm was applied to 5 layers of a cotton canvas without any connection of the corresponding layers. The breathable film and the fleece layer had a combined water vapor transmission rate (WVTR) of about 4528 g / m ² / day and an inverted water vapor transmission rate of 12055 g / m ² / day. These data are also shown in table I.

Example 4
A nonwoven fabric was produced by the spinneret method according to the method described above, to produce a web of continuous fibers made by a spinneret method with a surface unit weight of 17.8 g / m ² . On a layer of nonwoven fabric made by a spinneret method, a meltblown fiber web was applied on both sides of the melt according to Example 1, so that a layer of nonwoven fabric made by a spinneret turned out to be located between the layers of the web of fibers obtained by the aerodynamic melt (MB / SB / MB). These layers were not connected in any way to each other. The three-layer fleece web had a total thickness of 0.016 inches (0.04 cm), withstand hydraulic loading of 38.0 mbar, not withstand hydraulic loading of 39.7 mbar, and Frazier air permeability of 112.4 CFM. Then, a breathable, liquid tight barrier layer of CELGUARD ^TM 2500 film with a thickness of 0.0025 cm was applied to 3 layers of a cotton web without any connection of the corresponding layers. The breathable, liquid-impermeable film and the fleece layers together had a water vapor transmission rate (WVTR) of about 4609 g / m ² / day and an inverted water vapor transmission rate of 10739 g / m ² / day. These data are also shown in table I.

Example 5
According to Example 4, layers of a nonwoven fabric made by a spinneret method were applied on both sides to a web of fibers obtained by the aerodynamic method from the melt, according to Example 1, so that the layer of the web of fibers obtained by the aerodynamic method from the melt was located between the layers of nonwoven material made by spinneret method (SB / MB / SB). The three-layer fleece web had a total thickness of 0.019 inches (0.05 cm), withstand hydraulic loading of 27.4 mbar, unresponsive hydraulic loading of 29.3 mbar and air permeability according to Fraser 181 CFM. Then, a layer of CELGUARD ^™ 2500 film with a thickness of 0.0025 cm was applied to 3 layers of a cotton fleece without any connection of the corresponding layers. The breathable, liquid-impermeable film and 3 layers of cotton fleece had a combined water vapor transmission (WVTR) of 4415 g / m ² / day and an inverted water vapor transmission of 11486 g / m ² / day. These data are also shown in table I.

Example 6
On a CELGUARD ^TM 2500 film with a thickness of 0.0025 cm, layers of a web of fibers obtained from the melt-blown aerodynamic method according to Example 4 were applied on both sides, so that the breathable film was located between the layers of nonwoven fabric made by the spinneret method (SB / film / SB) . The three-layer material had a total thickness of 0.018 inches (0.046 cm), withstand 206.8 mbar hydraulic load, 190.9 mbar withstand hydraulic load, and Fraser air permeability of 0.172 CFM. Then a layer of CELGUARD ^™ 2500 film with a thickness of 0.0025 cm was applied to the three-layer material without any connection of the corresponding layers. The breathable film and the three-layer material together had a water vapor transmission rate (WVTR) of 4652 g / m ² / day and an inverted water vapor transmission rate of 12315 g / m ² / day. These data are also shown in table I.

As graphically shown in Table I, it was unexpectedly found that certain materials have little effect on the degree of transmission of water vapor of the absorbent article if they are in a dry state, but significantly reduce the degree of transmission of water vapor of the absorbent article if it is loaded. According to Example 1, a material made of meltblown fibers with a thickness of 0.006 combined with CELGUARD ^™ 2500 has an excellent water vapor transmission rate of 5153 CFM and a correspondingly high inverted water vapor transmission rate in 19396 CFM. However, the multilayer fiber meltblown material having a thickness of about 0.012 inches (0.03 cm) also has a good water vapor transmission rate of 4807 CFM. However, the inverted water vapor transmission rate of Example 2 was only 10376 CFM. Thus, the thicker material from the fibers obtained by the aerodynamic method from the melt, slightly limiting the degree of transmission of water vapor, greatly reduces the inverted transmission of water vapor, namely, compared with the control film and example 1 by about 50%. Accordingly, an absorbent article using such a barrier layer will have the desired dry breathability, but will have a reduced degree of water vapor transmission if the article is loaded, thereby reducing or eliminating the increased external humidity caused by condensation. Comparative results were obtained with other layer materials with the required functional characteristics described above. In addition, as shown in Example 6, these results are comparable to the results when a second breathable, liquid-impermeable layer is used. However, as one skilled in the art understands, the high cost associated with breathable, liquid-impermeable membranes, such as microporous films, with absorbent articles according to the invention can be avoided.

 Although the invention has been particularly shown and described in relation to preferred embodiments, it will be understood by those skilled in the art that other changes in form and detail can be made without departing from the spirit and scope of the invention.

Claims (22)

1. An absorbent hygiene product comprising a breathable, liquid-impervious outer shell comprising a liquid-impervious film; liquid permeable top layer; an absorbent body between said outer shell and said upper layer and a hydrophobic barrier layer located between said breathable outer shell and said absorbent core, the barrier layer comprising a fiber material having a hydraulic load of at least 18 mbar and a thickness of at least 0, 03 cm, in which the specified outer shell and the locking layer together have an inverted degree of transmission of water vapor less than about 15,000 g / m ² / day. 2. The absorbent product according to claim 1, wherein said outer shell contains a liquid-tight microporous film, and said barrier layer comprises several layers of nonwoven material, including one or more layers of meltblown fibers, said layers of nonwoven material together have a surface unit weight of over 16 g / m ² . 3. The absorbent product according to claim 1, in which the locking layer contains a non-woven material from fibers obtained by the aerodynamic method from the melt, having a surface unit weight of more than 20 g / m ² . 4. The absorbent product according to claim 1, in which the locking layer contains several layers of non-woven material, including one or more layers of fibers obtained by aerodynamic method from the melt, and in which several layers of non-woven material have a surface weight of more than 20 and less than 40 g / m ² . 5. The absorbent article of claim 2, wherein said hydrophobic barrier layer has a surface unit weight of about 25 g / m ² .  6. The absorbent article of claim 1, wherein said hydrophobic barrier layer comprises a fiber material having a thickness of from 0.045 to about 0.05 cm.  7. The absorbent article according to claim 1, wherein said hydrophobic barrier layer comprises at least one layer of meltblown fibers, said layer of meltblown fibers adjacent to said absorbent core.  8. An absorbent article according to claim 1, wherein said hydrophobic barrier layer extends substantially beneath the entire specified absorbent core.  9. The absorbent article of claim 1, wherein the hydrophobic barrier layer extends beyond the outer edges of the absorbent body.  10. The absorbent article of claim 1, wherein the hydrophobic barrier layer extends along the length of the central portion of the absorbent article.  11. An absorbent article according to claim 2, further comprising a wrapping layer around said absorbent body. 12. The absorbent product according to claim 11, wherein said barrier layer comprises at least one layer of nonwoven material having a hydraulic load of at least 30 mbar and a combined surface unit weight of more than 20 g / m ² .  13. The absorbent article of claim 11, wherein the wrapping layer comprises a barrier layer above the first side of said absorbent core and a hydrophilic layer of nonwoven material above the opposite side of said absorbent core.  14. The absorbent article of claim 11, wherein the wrapping layer comprises a continuous layer having a hydrophilic portion adjacent to a first side of said absorbent core, and a hydrophobic portion adjacent to an opposite side of said absorbent core, and wherein said hydrophilic a portion of said wrapping layer is adjacent to said upper layer. 15. An absorbent product according to claim 1, wherein said hydrophobic barrier layer comprises a plurality of fiber webs obtained by the aerodynamic method from a polyolefin melt, together having a surface unit weight of at least about 20 g / m ² and a hydraulic load of at least about 30 mbar, wherein said breathable, liquid-impervious outer shell and said barrier layer have a water vapor transmission rate of more than 1,500 g / m ² / day and an inverted water vapor transmission degree of less than 12,000 g / m ² / day. 16. The absorbent product of claim 15, wherein said barrier layer has a water vapor transmission rate of at least 3000 g / m ² / day. 17. The absorbent product according to claim 1, wherein said hydrophobic barrier layer has a hydraulic load of at least about 30 mbar and a surface unit weight of at least about 25 g / m ² , wherein said breathable, liquid-impervious outer shell and the specified locking layer have a degree of transmission of water vapor over 3500 g / m ² / day and an inverted degree of transmission of water vapor is less than about 11000 g / m ² / day. 18. An absorbent product according to claim 1, wherein said hydrophobic barrier layer comprises a layer of material made of fibers aerodynamically obtained from a polyolefin melt, and a layer of nonwoven fabric made by a spinneret method in which said breathable, liquid-impermeable outer shell and the specified locking layer have a degree of transmission of water vapor over 4000 g / m ² / day and an inverted degree of transmission of water vapor less than about 12000 g / m ² / day. 19. The absorbent article of claim 1, wherein said barrier layer has a surface unit weight of at least about 25 g / m ² .  20. The absorbent product according to claim 1, wherein said product includes a personal care product.  21. The absorbent product according to claim 1, wherein said product includes a baby diaper.  22. The absorbent article of claim 1, wherein said article includes clothing for adults with incontinence.

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