RU2257189C2 - Hygienic absorbing layer - Google Patents

Abstract

FIELD: medicine, in particular, hygienic liquid absorbing articles.

SUBSTANCE: hygienic absorbing article of laminated structure has first liquid permeable sheet layer, second liquid permeable sheet layer arranged in the vicinity of first layer, and liquid absorbing member arranged in the vicinity of second layer. Second sheet is arranged so as to receive liquid released onto first sheet and transmit liquid to liquid absorbing member. In dry state, absorbing article has thickness less than or equal to 5 mm and liquid penetration rate less than 25 s.

EFFECT: reduced thickness and decreased risk of leakage.

37 cl, 7 dwg, 1 tbl

Description

Field of Invention

The present invention relates generally to hygienic absorbent articles and, in particular, to feminine hygienic absorbent pads that are thin and yet highly absorbent.

BACKGROUND OF THE INVENTION

Hygienic absorbent pads for outdoor wear are one of the many types of feminine protective products currently on the market. The creation of materials having a high ability to absorb liquid per unit volume makes it possible to reduce the necessary overall thickness of sanitary napkins, thereby obtaining a product that is more comfortable and less protruding when worn. Thin sanitary pads are usually made of many layers of material, each of which has a specific purpose, as, for example, described in US patent No. 5575786 in the name of T.W. Osborne III. The sanitary napkin described herein contains a top sheet, a receptive or transfer sheet, an absorbent core, and a barrier sheet. The top sheet serves as the initial layer onto which the liquid is first released and consists of a material that is permeable to liquids but does not absorb them to ensure that the contact surface with the user remains dry. A sensing sheet located between the top sheet and the absorbent core distributes the fluid from a specific location on the top sheet over a wider area so that the fluid flows to the absorbent core over a relatively large portion of its surface area. Therefore, the receiving layer is made of a material that has good lateral absorption. The sensing layer also serves as an intermediate buffer providing initial absorption and temporary retention of the liquid, to allow time for the liquid to be drawn into the absorbent core after it is first released onto the top sheet.

The absorbent core serves as the main reservoir for the liquid released on the sanitary napkin, and therefore has a high ability to absorb liquid. Materials used for the absorbent core include wood pulp, creped cellulose wool, absorbent foams and sponges, polymer fibers, and polymer gels. In addition, the material must be able to hold the fluid under pressure to prevent re-wetting of the receiving layer and the top sheet.

The barrier sheet is made of a material that is impervious to liquid absorbed into the absorbent core and serves as a protective barrier between the absorbent core material and the wearer's clothes.

In the above construction, the sensing or transfer layer is designed to facilitate the transverse propagation of the fluid, so that the absorbent core allows for quick and efficient absorption of fluid from the sensing layer. However, the disadvantage of this known design is that the liquid can pass too close to the edge of the receiving layer and wet the top sheet, which leads to undesirable leakage of liquid from the gasket, inconvenience to the user and soiling of her clothes.

Therefore, there is a need for a thin sanitary pad that reduces the risk of leakage.

According to the present invention, there is provided a sanitary towel adapted to be worn in the crotch of an undergarment and comprising a first liquid-permeable sheet of material, a second liquid-permeable sheet of material located near the first sheet, an absorbent element for absorbing liquid located near the second sheet wherein said second sheet is disposed to receive fluid released to said first sheet and to transfer fluid to said absorbent element entent, the specified gasket in the dry state has a thickness of approximately 5 mm or less, and the penetration time is less than 15 seconds.

“Penetration time" is defined as the time taken for the gasket to absorb a predetermined amount of a particular liquid in the test procedure described in detail below. As established by the inventors, when using a design that provides a penetration time of less than 15 seconds, the spread of fluid to the edges of the transfer layer is prevented, thereby eliminating the risk of leakage through the edge of the top sheet. It has been found that, in contrast, known thin sanitary absorbent pads that tend to leak fluid according to the above mechanism have a penetration time of about 25 seconds.

The first liquid-permeable sheet preferably has an open-pore structure and a small absorption capacity so that liquid can be quickly diverted from the upper body-facing surface to an adjacent second liquid-permeable sheet.

In a preferred embodiment, the second liquid-permeable sheet is made of a material that has a relatively open pore structure for efficient absorption of liquid from the first sheet. The second sheet may be made of a material having a bulk density ranging from about 0.04 to 0.05 g / cm ³ , a surface density between about 80 and 110 g / m ^2, and a thickness ranging from about 2 to 3 mm.

In a preferred embodiment of the invention, the gasket has at least one, and preferably a plurality of spaced apart channels, elongated channels made to guide the fluid along them for subsequent absorption into the second sheet. The channel (s) extend essentially in the plane of the gasket, i.e. transversely, for example, substantially parallel to the surface of the first and / or second sheets. Channels may be formed in the first and / or second sheets and / or between them. The channel (s) may extend obliquely to the longitudinal axis and may be rectilinear or curved. As established by the inventors, the presence of channels affects the reduction of penetration time, determined by the test method described below. The channel (s) can be successfully formed by applying pressure in certain places of the gasket, for example, by embossing, which at the same time provides a seal of the material at the bottom of the channel, allowing the liquid to flow further along the channel before its absorption. The second sheet may preferably contain fusible fibers, such as thermoplastic fibers. It has been found that thermoplastic fibers favorably create the necessary combination of liquid permeability and absorption properties and at the same time contribute to the formation of channels by embossing and maintaining the shape of the channels over time.

In a preferred embodiment, the absorbent element comprises superabsorbent material and may contain a mixture of cellulosic fibers and superabsorbent material.

The absorbent element preferably contains an absorbent material that has a surface density of from about 100 g / m ² to about 700 g / m ² and which can be pneumatically laid in the form of a lower layer of fibrous mass, a middle layer of fibrous mass and a superabsorbent polymer located in the fibrous the mass, and the upper layer containing at least some amount of pulp.

In a preferred embodiment, the absorbent element has a bulk density of greater than about 0.25 g / cm ³ , and more preferably, from about 0.3 to about 0.4 g / cm ³ .

The absorbent element contains a superabsorbent polymer, preferably from about 5 wt.% To about 60 wt.% And more preferably in the range of from about 30 to 40 wt.%.

In a preferred embodiment, the absorbent material has a surface density in the range of from about 150 g / m ² to about 350 g / m ^2, and more preferably in the range of from about 200 g / m ² to about 300 g / m ² .

Brief Description of the Drawings

Now will be described examples of embodiments of the present invention with reference to the drawings, in which:

Figure 1 is a top view of a sanitary napkin according to one embodiment of the present invention, while partially removing the cover layer of the sanitary napkin to show an absorbent system,

figure 2 is a perspective view of the sanitary towel in figure 1, depicted in the position achieved when placing the sanitary towel in the subject of underwear of the user,

figure 3 is a bottom view of the sanitary napkins shown in figure 1,

FIG. 4 is a sectional view along the longitudinal center line of the sanitary napkin shown in FIG. 3,

5 is a schematic illustration of a device for pneumatically laying absorbent material for manufacturing, for example, an absorbent core of a sanitary napkin according to one embodiment of the present invention using four pneumatic laying heads followed by a device for sealing pneumatically laid material,

6 shows three- and four-layer embodiments of an absorbent core that can be used in a sanitary towel according to one embodiment of the invention, and

7 shows a top view of a test plate used in measuring penetration time.

Description of preferred embodiments of the invention

1 and 2 show a feminine sanitary napkin 20 according to one embodiment of the present invention.

The sanitary napkin 20 has a main part 22 with a first transverse edge 26 defining its front part and a second transverse edge 28 defining its rear part. Each of these edges is made curved. In addition, the main part has two longitudinal edges, namely the longitudinal edge 30 and the longitudinal edge 32. The sanitary towel 20 has a thickness not exceeding approximately 5 mm. The thickness is preferably less than 3.5 mm, more preferably less than 3 mm, and most preferably about 2.8 mm.

The sanitary napkin 20 has a longitudinal center line 34, which is an imaginary line dividing the sanitary napkin 20 into two identical halves.

Outward from each of the longitudinal edges 30, 32, the wing 38, 40 protrudes laterally (respectively). The wings 38, 40 have the shape of an isosceles trapezoid, in which the top is adjacent to the longitudinal edge, and the base is located at the distal end. The main part 22, in addition, has an imaginary transverse center line 36, perpendicular to the longitudinal center line 34 and at the same time halving the wings 38, 40.

As shown in FIG. 4, the main part 22 is layered and preferably comprises a liquid permeable cover layer 42, an absorbent system 44 and a liquid impermeable barrier layer 50. The absorbent system preferably has two components, namely a first absorbent layer 46 (typically known as the “transfer layer”) and a second absorbent layer 48 (commonly known as the “absorbent core”). On the other hand, the absorbent system 44 may form a single layer, namely the second absorbent layer 48. Each of these layers will be described below.

The main part is the coating layer

The cover layer 42 may consist of a bulk, very loose nonwoven material with a relatively low density. The coating layer 42 may consist of fibers of only one kind, for example polyester or polypropylene fibers, or of bicomponent fibers having a component with a low melting point and a component with a high melting point. The fibers can be selected from a number of natural or synthetic fibers, for example nylon, polyester, cellulose hydrate (in combination with other fibers), cotton, acrylic fibers, etc. and their combinations. An example is a nonwoven cover layer of sanitary napkins sold by Johnson & Johnson, Inc., Montreal, Canada under the trademark “Stephrey Ultra-Tin Cotton Dry Cover”.

Bicomponent fibers can be made with a polyester layer and a polyethylene sheath. Using appropriate bicomponent materials, a fusible non-woven fabric is obtained. Examples of such fusible fabrics are described in US Pat. No. 4,555,446, issued November 20, 1985 to Mays. The use of fusible fabric facilitates the fastening of the coating layer to the adjacent first absorbent layer and / or to the barrier layer.

The coating layer 42 preferably has a relatively high degree of wettability, although the individual fibers constituting the coating layer may not be particularly hydrophilic. In addition, the material of the coating layer must contain a large number of relatively large pores. This is necessary because the cover layer 42 is intended for the rapid perception of body fluid and its movement from the body and the point of selection. Therefore, the coating layer takes a small part in the time spent on the absorption of a given amount of liquid (time

penetration). Preferably, the fibers forming the coating layer 42 do not lose their physical properties upon wetting. In other words, they should not flatten or lose their elasticity when exposed to water or body fluids. The coating layer 42 can be treated so that the fluid can easily pass through it. In addition, the function of the cover layer 42 is to quickly transfer fluid to other layers of the absorbent system 44. Thus, the cover layer 42 is advantageously wettable, hydrophilic and porous. When the coating layer 42 is composed of synthetic hydrophobic fibers, such as polyester or bicomponent fibers, it can be treated with a surfactant to give it the desired degree of wettability.

Alternatively, the coating layer 42 may also be made of a polymer film having large pores. Due to such a high porosity, the film performs the function of rapidly transferring body fluid to the inner layers of the absorbent system. Perforated, coextruded films, such as those described in US Pat. No. 4,690,679 and available on sanitary napkins sold by Johnson & Johnson Inc., Montreal, Canada, could be useful as coating layers in accordance with the present invention.

To promote hydrophilicity, the cover layer 42 can be pressed into the rest of the absorbent system 44 by fusing the cover layer with the next layer.

Such fusion can be carried out locally, at a plurality of points, or over the entire contact area of the cover layer 42 with the absorbent system 44. Alternatively, the cover layer 42 can be attached to the absorbent system 44 in other ways, for example by gluing.

The main part is the absorbent system - the first absorbent layer

Near the cover layer 42, a first absorbent layer 46 is bonded to it and forms a part of the absorbent system 44. The first absorbent layer 46 provides a means for receiving body fluid from the cover layer 42 and hold it until the underlying second absorbent layer will not be able to absorb liquid, and therefore, it serves as a layer for the transmission or perception of liquid.

The first absorbent layer 46 is preferably denser and has a larger fraction of smaller pores than the cover layer 42. These properties enable the first absorbent layer 46 to contain body fluid and divert it from the outside of the cover layer 42, thereby preventing re-wetting of the coating liquid. layer 42 and its surface. However, the first absorbent layer 46 is not so dense as to prevent the passage of fluid through the layer 46 into the underlying second absorbent layer 48.

The first absorbent layer 46 may consist of fibrous materials, such as wood pulp, polyester and hydrated cellulose fibers, flexible foam, and the like. or from combinations thereof. In addition, the first absorbent layer 46 may contain thermoplastic fibers to stabilize the layer and maintain its structural integrity. To increase the wettability of the first absorbent layer 46, it can be treated with a surfactant on one or both sides, although usually the first absorbent layer 46 is relatively hydrophilic and may not need to be processed. The first absorbent layer 46 is preferably bonded on both sides to adjacent layers, i.e. with a cover layer 42 and an underlying second absorbent layer 48.

Materials especially suitable for use in the first absorbent layer 46, which, as established by the inventors, provide a reduction in penetration time, have a bulk density in the range of about 0.04 to 0.05 g / cm ^{3 and a} surface density in the range of about 80 to 110 g / m ² and a thickness ranging from about 2 to 3 mm, in particular 2.6 mm An example of materials suitable for the first absorbent layer is hot air bonded cellulose sold by Buckey, Memphis, Tenn., USA under the designation “WIZORB 3008” and with a surface density of 110 g / m ² and also designation "VIZORB 3010" and with a surface density of 90 g / m ² .

The main part is the absorbent system - the second absorbent layer

The second absorbent layer 48 bonded thereto is directly adjacent to the first absorbent layer 46.

In one embodiment, the first absorbent layer 46 has a central width that is at least almost the same as the central width of the second absorbent layer 48. In a particular embodiment, the central width is greater than about 64 mm. In another embodiment, the first absorbent layer 46 has a central width that exceeds the central width of the second absorbent layer 48. The term “central width” refers to a specific portion of a layer, such as an absorbent layer, and is defined as follows. When wearing a sanitary pad, the reference point on the layer in question is located under the center of the vaginal opening. One plane is parallel to the transverse center line 36 and 3.75 cm forward from the reference point towards the pubic elevation of the user. Another plane is also parallel to the transverse center line 36 and 5.0 cm back from the reference point in the direction of the buttocks of the user. The largest transverse width of an even, uncompressed and unexposed portion of the layer under consideration between two planes is the width of the absorbent portion of the layer in question.

When the absorbent system comprises a plurality of absorbent layers, the central width of the absorbent system is the central width of the layer of the absorbent system having the largest central width. In a specific example, the central width of the absorbent system exceeds 64 mm.

In one embodiment of the invention, the second absorbent layer 48 is made of a mixture of cellulosic fibers and superabsorbent located between these cellulosic fibers.

In a specific example, the second absorbent layer 48 is made of a material containing from about 40 wt.% To about 90 wt.% Cellulose fibers and from about 5 wt.% To about 60 wt.% SAP (superabsorbent polymers). This material has a moisture content of less than about 10 wt.%. The expression “weight percent” (wt.%) As used herein refers to the ratio of the weight of a substance to the weight of the finished material. For example, 10 wt.% SAP means 10 g / m ² SAP per 100 g / m ² surface density of the material.

Cellulosic fibers that can be used in the second absorbent layer 48 are well known in the art and can be made from wood pulp, cotton, flax and peat moss. Wood pulp is preferred. As the pulp can be used mechanical or chemical-mechanical pulp, sulphite pulp, kraft pulp, waste converted into pulp, pulp obtained using an organic solvent, etc. Useful wood is both soft and hard. Pulps of softwood are preferred. For use in this material, it is not necessary to treat cellulose fibers with chemical disintegrants, crosslinking agents, and the like.

The second absorbent layer 48 may comprise any superabsorbent polymer (SAP), and these superabsorbent polymers are well known in the art. As used herein, the term “superabsorbent polymer” (or “SAP”) refers to materials that, at an overpressure of 0.5 psi, are capable of absorbing and retaining body fluids in an amount of at least about 10 times their own weight . The particles of the superabsorbent polymer according to the invention can be from inorganic or organic hydrophilic crosslinked polymers, such as, for example, polyvinyl alcohols, polyethylene oxides, crosslinked starches, guar gum, xanthan gum, etc. Particles can be in the form of powder, grains, granules or fibers. Particles of superabsorbent polymer consisting of crosslinked polyacrylates are preferred for use in the present invention, such as, for example, the product sold by Sumitomo Seika Camichles Co., Ltd., Osaka, Japan under the designation “SA60N type II,” and the product offered by the company “ Camdal International, Inc. ”, Palatine, Illinois, USA under the brand name“ 2100A. ”

In a specific example, the second absorbent layer 48 is made of a material containing from about 50 to about 90 wt.% Cellulosic fibers, and more particularly from about 60 to about 80 wt.% Of cellulosic fibers. Such material may contain from about 5 to about 60 wt.% SAP, preferably from about 20 to about 55 wt.% SAP, even more preferably from about 30 to about 45 wt.% SAP and most preferably about 40 wt.% SAP.

The second absorbent layer 48 may be fabricated by a pneumatic stacking method well known in the art (see FIG. 5). According to FIG. 5, cellulosic fibers (e.g., wood pulp) are processed in a hammer mill to separate into individual fibers. Separated fibers are mixed with SAP granules in the mixing system 1 and pneumatically transported to a number of molding heads 2. The mixing and distribution of fibers and SAP granules can be controlled separately for each molding head. Controlled air circulation and paddle mixers in each chamber ensure a homogeneous mixture and distribution of cellulose and SAP. SAP can be thoroughly and evenly mixed in all the material or only in its specific layers by distributing it to the selected molding heads. Fibers (or SAPs) from each forming head under the influence of rarefaction are deposited on the forming mesh 3, thus forming a layered absorbent non-woven material. This material is then densified using calendars 4 to achieve the desired density. The densified non-woven material is wound into a roll 5 using conventional winding equipment. To reduce material loss, the forming mesh 3 can be coated with tissue paper. A layer of tissue paper may be removed prior to calendering or incorporated into the molded material. In a possible embodiment, the first absorbent layer 46 may be formed integrally with the second absorbent layer 48 to form an absorbent system 44. This can be achieved by providing the device shown in FIG. 5 with an additional molding head (not shown in the drawings) so that before by calendering, lay the pneumatic stack on a second absorbent layer 48 with a material layer to form a first absorbent layer 46.

The second absorbent layer 48 according to the present invention has a high density, and in a specific example, the density is greater than about 0.25 g / cm ³ . Specifically, the second absorbent layer 48 may have a density in the range of from about 0.30 g / cm ³ to about 0.50 g / cm ³ . More specifically, the density is from about 0.30 g / cm ³ to about 0.45 g / cm ³ and even more specifically from about 0.35 g / cm ³ to about 0.40 g / cm ³ .

Air-laid absorbents are usually made with low density. In order to achieve higher density values, such as in the examples with the second absorbent layer 48, the air-laid material is densified using the calendars shown in FIG. 5. Compaction is carried out using means well known in the art. Typically, such a seal is carried out at a temperature of approximately 100 ° C. and a load of approximately 130 N / mm. The upper pressure roll is typically made of steel, while the lower pressure roll is a flexible roll having a Shore D hardness of approximately 85. It is preferred that both the upper and lower pressure rolls are smooth, although the upper roll may be engraved.

In one embodiment, the second absorbent layer has a Harley stiffness ratio measured in milligrams (mg) to a density measured in grams per cubic centimeter (g / cm ³ ) less than about 3700. In a specific example, this stiffness ratio is Harley's density is less than about 3200, and more specifically less than about 3000.

Harley stiffness is one of many indicators of softness. Harley stiffness is a measure of the bendability or flexibility of absorbent materials. The lower the Harley stiffness value, the greater the flexibility of the material. Harley stiffness values are measured using a Harley stiffness tester (Model No. 4171E) manufactured by Harley Precision Instruments. Troy, NY, USA. This device allows you to measure the externally applied moment necessary to create this deflection of the experimental strip of certain sizes, fixed at one end and having a concentrated load applied to the other end. When determining the “Harley stiffness” values, the results are obtained in units of milligrams.

The second absorbent layer 48 is strong when soft. The integrity of the cushion is a well-known measure of the strength of an absorbent material. In a particular embodiment, the second absorbent layer 48 exhibits strength (high pad integrity) over a wide range of densities. In a specific example, the second absorbent layer 48 has a ratio of pillow integrity, measured in Newtons (N), to a density (g / cm ³ ) of greater than about 25.0. In a more specific example, this ratio is greater than about 30.0, and could even be greater than about 35.0. The pillow integrity test is carried out on an Instron universal testing machine. During the test, the load necessary to pierce the prototype is essentially measured, as described in the PFI method of 1981. The prototype, measuring 50 mm × 50 mm, is clamped in an Instron machine using a suitable mounting device. A plunger with a diameter of 20 mm, moving at a speed of 50 mm / min, punches a stationary sample. The force required to pierce a sample is measured in Newtons (N).

The second absorbent layer 48 can be made with a wide range of surface density values. The second absorbent layer 48 may have a surface density ranging from about 100 g / m ² to about 700 g / m ² . In a specific example, the surface density is from about 150 g / m ² to about 350 g / m ² . The surface density is preferably from about 200 g / m ² to about 300 g / m ² , more preferably about 250 g / m ² .

The second absorbent layer 48 acts synergistically with the first absorbent layer to reduce penetration time. The first absorbent layer having a relatively open structure allows the liquid to relatively easily pass to the second absorbent layer, which has a large capillarity and, therefore, the ability to draw fluid from the first absorbent layer into its volume. In a specific embodiment, the second absorbent layer contains 30-40 wt.% Superabsorbent material, such as a superabsorbent polymer, has a surface density in the range of from about 200 to 300 g / m ² and bulk density in the range of from about 0.2 to 0.4 g / cm ³ .

The second absorbent layer 48 may be formed of three or four thin layers or interlayers. These interlayers are the lower interlayer, one or two middle interlayers and the upper interlayer. The following are specific examples of materials with three and four layers. SAP can be contained in any of the layers or in all layers. The concentration (weight percent) of SAP in each layer can vary depending on the nature of a particular SAP.

An interesting property of the second absorbent layer 48 is its ability to retain SAP when it is subjected to mechanical stress. After 10 minutes of vigorous shaking, the second absorbent layer 48 retained over 85% by weight of the SAP therein. Specifically, the material according to this invention, subjected to these mechanical stresses, retains over 90%, more precisely over 95%, and more precisely over 99% of the SAP contained therein. The percentage of retained SAP was determined by shaking the material in a Ro-Tap shaker manufactured by US Tyler Co., Cleveland, Ohio, USA. More specifically, the sample was placed in a sieve with a mesh size of 28 mesh (Tyler series). Additional sieves with mesh sizes of 35 mesh and 150 mesh were attached to the first sieve, forming a column of increasingly smaller sieves. A sieve column at each end was covered with a lid to prevent loss of fibers and / or SAP. A column of sieves was placed in a vibrator and shaken for 10 minutes. By combining the residue contained on each of the sieves and separating the cellulose fibers from the SAP, the number of SAP granules shaken from the samples was determined — “free SAP”.

Even in the case of the formation of many interlayers, the second absorbent layer 48 has a small final thickness. The thickness may vary from about 0.5 mm to about 2.5 mm. In a specific example, the thickness is from about 1.0 mm to about 2.0 mm, more specifically from about 1.25 mm to about 1.75 mm.

6 depicts one embodiment of a second absorbent layer 48, particularly well suited for use in a sanitary towel 20. Such a second absorbent layer 48 has a surface density of from about 200 g / m ² to about 350 g / m ² and a bulk density between about 0.3 g / cm ³ and 0.5 g / cm ³ . In a specific example, the bulk density is from about 0.3 g / cm ³ to about 0.45 g / cm ³ and more precisely about 0.4 g / cm ³ .

The second absorbent layer 48, shown in Fig.6, has three pneumo-laid layers: the lower layer of cellulose (without superabsorbent) with a surface density of approximately 25 g / m ² ; an average interlayer with a surface density of about 150 g / m ² that contains from about 10 to about 30 g / m ² superabsorbent and from about 120 g / m ² to about 140 g / m ² cellulose; and an upper layer of cellulose (without superabsorbent) with a surface density of approximately 25 g / m ² . Relative to the total surface density of the second absorbent layer 48, the content of superabsorbent is from about 5 to about 15 wt.% (G / m ² superabsorbent per g / m ^{2 of} material). In a specific example, the content of superabsorbent is from about 7.5 wt.% To about 12.5 wt.% Material. More specifically, the material contains about 10 wt.% Superabsorbent. Thus, the middle layer of material could contain from about 15 g / m ² to about 25 g / m ² superabsorbent and from about 125 g / m ² to about 135 g / m ² cellulose, and more specifically about 20 g / m ² superabsorbent and approximately 130 g / m ² cellulose. The middle layer containing cellulose and superabsorbent can be laid in the form of a homogeneous mixture or a heterogeneous mixture, in which the content of superabsorbent changes with approaching the lower layer.

In another embodiment, the second absorbent layer 48 has four air-laid interlayers. In this embodiment, the aforementioned middle layer is replaced by two middle layers: the first middle layer adjacent to the upper layer and the second middle layer adjacent to the upper layer. Each of the first and second middle layers contains individually from about 10 to about 30 g / m ² superabsorbent and from about 40 g / m ² to about 65 g / m ² cellulose. If it is desired to keep the absorbed liquid away from the cover layer 42, the amount of superabsorbent in the first and second middle layers is controlled so that more superabsorbent is contained in the second middle layer. The first and second middle layers may have the same or different superabsorbent contents.

In one embodiment of the invention, wood pulp is used as the cellulosic fibers in the second absorbent layer 48. Pulp has certain properties that make it particularly suitable for this application. In most wood pulp pulps, cellulose has a crystalline form known as cellulose I, which can be converted into a form known as cellulose II. In the second absorbent layer 48, wood pulp with a significant proportion of cellulose in the form of cellulose II could be used. In addition, useful pulp having an increased rate of crimp fibers. Finally, pulps with reduced hemicellulose content are preferred. Methods for treating pulp to optimize their properties are well known in the art. For example, a method is known for treating wood pulp with liquid ammonia to convert cellulose to cellulose structure II and to increase the crimp index of the fibers. A known method of spray drying under vacuum to increase the rate of crimp of the pulp fibers. During cold alkaline treatment of pulp, the hemicellulose content decreases, the crimp of the fibers increases, and cellulose is converted to cellulose II. Thus, it could be useful that the cellulosic fibers used to make the material according to this invention contain at least a portion of the pulp subjected to cold alkaline treatment.

A description of the cold alkaline extraction process can be found in US Patent Application No. 08/370571, filed January 18, 1995, and pending as ongoing patent application US No. 08/184377, filed January 21, 1994 and is currently canceled. The descriptions of these two applications are provided for reference.

In short, alkaline treatment is usually carried out at a temperature of less than about 60 ° C, but preferably less than 50 ° C, and more preferably at a temperature between about 10 ° C and 40 ° C. A preferred alkali metal salt solution is sodium hydroxide solution, freshly prepared or used as a by-product of pulp or paper production, hemicaustic white liquor, oxidized white liquor, and the like. Other alkali metal salts, such as, for example, ammonium hydroxide, potassium hydroxide, and the like, can be used. However, in terms of cost, the preferred salt is sodium hydroxide. The concentration of alkali metal salts is usually from about 2 to about 25 wt.% The solution and preferably from about 6 to about 18 wt.%. Cellulosic pulp intended for use in fast absorption at high speed are preferably treated at alkali metal salt concentrations of from about 10 to about 18% by weight.

For further details on the structure and method of manufacturing the second absorbent layer 48, see US Pat. No. 5,866,242 issued February 2, 1999 to Teng et al. The contents of this document are incorporated herein by reference.

The main part is the barrier layer

Underneath the absorbent system 44 is a barrier layer 50 consisting of a liquid impervious film material to ensure that liquid entrapped in the absorbent system 44 does not exit the sanitary napkin and does not stain the user's underwear. The barrier layer 50 is preferably made of a polymer film, although it may be made of liquid impermeable, breathable material, such as, for example, repellent-treated non-woven materials, microporous films or foams.

The cover layer 42 and the barrier layer 50 are joined together at their extreme parts to form a sealing or bead seam that keeps the absorbent system 44 insulated. This connection can be made by gluing, heat sealing, ultrasonic or high-frequency welding, mechanical corrugation, etc. or combinations thereof. 1, the line of the peripheral seam is indicated by 52.

Wings

The wings 38 and 40 are preferably made in the form of integral protrusions of the cover layer 42 and the barrier layer 50. These integral protrusions are connected to each other along their extreme sealing parts by gluing, heat sealing, ultrasonic or high-frequency welding, mechanical corrugation, etc. .P. or combinations thereof. Such a connection is most preferably done at the same time as the cover layer 42 and the barrier layer 50 are connected to each other to isolate the absorbent system 44. On the other hand, the wings may contain absorbent material between the protrusions of the cover layer and the barrier layer. Such absorbent material may be a continuation of the first absorbent layer 46, the second absorbent layer 48, or both. The wings are optional and may have any other suitable shape than that shown. Other fasteners may be used, for example adhesive fasteners placed on the barrier layer, as described below.

Adhesive system

Turning to FIGS. 2 and 3, where, to enhance the stability of the sanitary napkin, the surface of the barrier layer facing the garment is provided with a mounting adhesive 58, usually a hot-melt adhesive, capable of temporary adhesion to the material of the underwear. A suitable substance is a composition labeled HL-1491 XZP, commercially available from H.B. Fuller Caneda, Toronto, Ontario, Canada. Installation adhesive 58 can be applied to the clothing-facing surface of the barrier layer 50 in the form of various patterns, including continuous adhesive coating, adhesive application in the form of parallel longitudinal strips, strips around the perimeter of the structure, transverse strips, etc.

Prior to use of the gasket, the installation adhesive 58 is coated with ordinary gasket paper 82 (shown only in FIG. 3) to prevent the gasket from undesirably sticking to itself or to foreign objects. Laying paper has the usual structure (for example, wet-laid silicone coated kraft pulp), and suitable papers are commercially available from Tekkote Corporation (Leonia, NJ, USA) with the designation “FRAZER 30/61629” .

Channels

In a preferred embodiment of the invention, the sanitary napkin is provided with at least one and preferably more than one channel arranged to direct fluid along the channel (or channels) for subsequent absorption into the first absorbent layer. As established by the inventors, the presence of one or more channels helps to reduce the penetration time. The gasket preferably has a plurality of elongated channels formed therein, which are located at a distance from each other and are designed to spread liquid on the surface of the gasket facing the body or near its surface facing the body from the initial discharge.

The presence of one or more channels near the coating layer allows the fluid to quickly move along the pad so that different portions of the first absorbent layer act together to absorb the fluid over a larger surface area. This ensures that the liquid immediately provides a large part of the surface area of the second absorbent layer.

The gasket may be provided with one channel or many channels, for example, extending along or parallel to the longitudinal axis along the length of the gasket, inclined to the longitudinal axis, for example, from one edge of the gasket to another edge or essentially perpendicular to the longitudinal axis. The channel (s) may have any shape that can be selected in accordance with a particular application, for example, the channel (s) may be straight, curved or have a serpentine configuration, or a combination of these, as well as other forms, including spiral and zigzag configurations.

In one embodiment, the gasket has many individual channels that are spaced apart from one another and intersect with each other. Figure 1 shows an example of such a channel. In figure 1, the gasket 20 is provided with a plurality of curved channels 10 that extend substantially obliquely to the longitudinal center line 34 from one extreme part 12 to the opposite extreme part 14. This arrangement provides effective transmission of fluid along the length and across the gasket. The channel (s) may be formed in the coating layer and / or in the first absorbent layer. The channels can be successfully formed by applying local pressure to the material, for example, used for embossing. Applied pressure leads to compaction of the material, which forms the bottom of the channel, which extends to a distance by which the liquid could move before absorption. The second absorbent layer is preferably relatively thick compared to the other layers of the gasket, which makes it possible to form relatively deep channels. It is useful that the parts of the transfer layer adjacent to the side of the channel remain relatively thick and retain their original structure with comparatively open pores to allow efficient retraction of fluid from the channel. It is useful that the transfer layer contains thermoplastic fibers. The presence of thermoplastic fibers contributes to the formation of a stable and constant channel when thermoplastic fibers are heated. When heated, thermoplastic fibers tend to fuse with each other with the formation of a more rigid structure, so that when using gaskets and over time, the original structure of the channels is preserved. Heating can be conveniently applied in the embossing process.

Preparation method

The sanitary napkin 20 according to the above described embodiment is manufactured in the usual manner by conventional technology. More specifically, they form a layered structure, which is sometimes called a web in this technical field. The layered structure contains layers of materials from which the gasket will be formed. The layered structure contains the following layers of materials in a downward direction: the material of the coating layer, the material of the first absorbent layer, the material of the second absorbent layer (made as described above), and finally, the barrier layer. Some of these materials are not necessarily continuous in the layered structure, and if this is the case, they are precisely positioned relative to each other with the mutual arrangement that they will occupy in the finished products. The material of the coating layer and the material of the barrier layer are then bonded together by applying pressure in appropriate places to form a peripheral seam. (The seam can also be made by heat sealing, ultrasonic or high-frequency welding, mechanical corrugation, etc., or combinations thereof). Thereafter, by conventional methods (i.e., die cutting, liquid jet cutting, or laser cutting), the sealed structure is cut out of the web to form a separate article.

As mentioned above, one or more channels can be formed near the body surface of the gasket, and this channel (s) can be formed by embossing. The channel (s) can be formed by other methods, including cutting, hollowing, etching, molding and burning, as well as other methods known to specialists in this field. If embossing is used, this method may include passing a sanitary towel between two rolls, of which one roll has protrusions corresponding in shape to the desired embossing pattern. The protrusions squeeze and compact the material in certain places and can be applied to the coating layer, the absorbent system (in particular, to the first absorbent layer), or to a combination thereof. The amount of pressure applied during the embossing operation depends on the type of material and its physical integrity. The creation of an optimal process mode in accordance with a specific application is within the competence of a specialist in this field. In general, the pressure for embossing should be selected so that it provides sufficient compaction of the material in certain places for the formation of channels, but is not too high so that the material is cut. As mentioned above, the material may also be heated, and this can conveniently be done by heating by means of embossing rolls. Ultrasonic embossing can also be used to form the channel (s).

Embossing advantageously helps to hold the various layers of the sanitary napkin together and reduces the likelihood of the cover layer or barrier layer separating from adjacent layers or peeling off when the sanitary napkin is bent. The embossing of the gasket is preferably carried out at regular intervals over most and preferably over its entire surface.

An adhesive is then applied to be installed at appropriate locations in the barrier layer and the adhesive is covered with cushioning paper. On the other hand, glue or glue and cushioning paper can be applied to the canvas before cutting individual products from it.

Method for measuring the thickness of a sanitary napkin

дюйма и обеспечивающий точность показания 0,001 дюйма при собственном весе 2 унции. Предпочитается устройство цифрового типа. Если образец гигиенической прокладки отдельно загнут и свернут, то его необходимо развернуть и тщательно разгладить рукой. Снимают прокладочную бумагу с образца и вновь осторожно укладывают ее поперек полосок клея для установки, не сдавливая образец и обеспечивая при этом, чтобы прокладочная бумага ровно лежала поперек образца. Перед снятием показания о толщине в центре образца крылышки (если они имеются) загибают назад под образец.As previously indicated, the sanitary napkin 20 has a thickness of about 5 mm or less. The device needed to measure the thickness of the sanitary napkin is a dial-type thickness gauge with a foot, commercially available from Ames, equipped with a foot with a diameter

inches and providing an accuracy of 0.001 inches with a dead weight of 2 ounces. A digital type device is preferred. If the sanitary napkin sample is separately bent and folded, then it must be deployed and carefully smoothed by hand. Remove the cushion paper from the sample and carefully re-lay it across the strips of adhesive for installation, without squeezing the sample and ensuring that the cushion paper lies evenly across the sample. Before taking a reading about the thickness in the center of the sample, the wings (if any) are bent back under the sample.

Raise the leg of the thickness gauge and place the sample on a support so that the leg of the thickness gauge is approximately in the center of the sample (or in the place of interest of the sample of interest). When lowering the foot, care must be taken to avoid dropping the foot on the sample or applying excessive force. After lowering the legs, it is necessary to allow the sample to stabilize for 5 seconds, after which the thickness reading is taken.

Liquid Penetration Test Procedure

The following test procedure is used to measure and determine the liquid penetration time of a sanitary absorbent pad. “Penetration time" is a parameter associated with the time elapsed between the moment when 7 ml of liquid first comes into contact with the sample (the liquid is used with the device described below) and the moment when the coating layer first appears through the upper surface of the liquid. This time is measured to the nearest 0.1 second. The test is carried out on five samples, and the average value for five samples is recorded as “penetration time”.

The device required for the test includes a stopwatch with an accuracy of 0.1 sec, a glass graduated measuring vessel with a capacity of 10 ml, having an internal diameter of approximately 12 mm and containing a certain amount of synthetic menstrual fluid, and a plate with an opening for conducting a liquid penetration test shown in Fig.7. Turning to FIG. 7, the experimental plate is rectangular in shape, made of Lexan, and has a length of 25.4 cm (10.0 inches), a width of 7.6 cm (3.0 inches), and a thickness of 1.27 cm ( 0.5 inch). A concentric, elliptical hole is formed through the plate, having a large axis 3.8 cm long along the length of the plate and a small axis 1.9 cm long along the width of the plate.

In addition, the device comprises an elastic pad to support the sanitary napkin during the penetration test, which improves contact between the plate and the cover layer. The pillow is made of non-woven fabric, consisting of fusible fibers (made, for example, from Enka fibers) and having a low density (0.03-0.5 g / cm ³ ), measured at 0.24 kPa (0.35 lb / sq.inch). The nonwoven fabric is cut into rectangular sheets 32 × 14 × 0.3 cm in size, and these sheets are stacked until the stack reaches a free height of about 5 cm. Then, the stack is wrapped with one layer of 0.1 mm (0.004 inch) polyurethane elastomeric film. as, for example, Tuftein film from BF Goodrich. The film wrapper is sealed at the back with a double-sided transparent tape to form an elastic pad. An elastic cushion should respond to the formation of a load, for example, when using a Fraser Compressometer No. 255 equipped with a foot with a diameter of 12.7 cm (5 inches); The thickness of the pillow varies as follows:

Table 1 Pressure applied Thickness (after wrapping film) 0 pressure 42.0 mm 0.069 kPa (0.70 g / cm ² , 0.01 psi) 38.5 mm 0.207 kPa (2.1 g / cm ² , 0.03 psi) 31.0 mm 0.345 kPa (3.52 g / cm ² , 0.05 psi) 27.0 mm 0.483 kPa (4.9 g / cm ² , 0.07 psi) 24.0 mm

Sample preparation

Before the test, the hygienic absorbent pad (exempted from any packaging), the test fluid, the plate with the hole, and graduated vessels with divisions are kept at a temperature of 21 ± 1 ° С and relative humidity 65 ± 2% for at least 8 hours. If the gasket has folds, then folds are removed if possible, straightening it, and if the gasket is bent, the side assemblies are cut several times so that the sample can be flat.

Test method

A pre-seasoned sanitary napkin without removing the liner paper is placed on the horizontal surface of the elastic pad so that the cover layer is facing up.

A cleaned plate with a hole is placed on the sample so that the hole is in the center of the surface of the gasket, and the major axis of the elliptical hole coincides with the longitudinal axis of the gasket. If the gasket has at least one channel, then the plate should be positioned so that at least one channel is located in the hole or near its edge.

Then the measuring vessel with divisions is filled with 7 ml of synthetic menstrual test fluid. A suitable synthetic menstrual fluid has a viscosity of 30 centipoise (cP).

Holding the neck of the graduated vessel approximately 1–3 inches above the plate with the holes, the test liquid is poured into the hole and the stopwatch is started when the liquid first reaches the sample. Stop the stopwatch when the coating layer first appears through the upper surface of the liquid, regardless of where the coating layer becomes visible in the hole. The liquid should be poured into the hole so that the hole is filled as far as possible without overflow on the surface of the plate.

When performing the above method, it is important that the tests are carried out at a temperature of 21 ± 1 ° C and a relative humidity of 65 ± 2%. In addition, it is important that prior to testing the sample, all parts of the device and the test fluid are kept under the above conditions for a minimum of eight hours. Between the sample tests, the plate with holes must be thoroughly cleaned. In addition, the test fluid vessel should not be left open between sample tests, since evaporation will result in a fluid change. It is also important that the correct end moment is used in determining the penetration time. If any of the above conditions is not met, then this may adversely affect the test results.

A sanitary napkin embodying the present invention has excellent absorbent characteristics, and in particular, a unique combination of the properties of the transfer layer and the absorbent core, significantly reduce the time spent by the napkin on the fluid perception, and at the same time allow the napkin to remain thin with a relatively high absorption capacity. The gasket significantly reduces the penetration time compared to known gaskets of the same thickness and successfully eliminates essentially the risk of fluid leakage from the edge of the transverse layer.

The product and methods according to the present invention for hygiene and other areas of health can be used by methods and procedures that are used for hygiene, urinary incontinence, medicine and absorption, which are currently known to specialists in these fields or will become known to them in the future . Thus, it is intended that this application cover the modifications and variations of this invention provided they come within the scope of the claims in the appended claims and their equivalents.

Claims (37)

1. Hygienic pad made with the possibility of wearing in the crotch of the underwear, containing a first liquid permeable sheet of material, a second liquid-permeable sheet of material located near the first sheet, an absorbent element for absorbing liquid adjacent to the second sheet, said second sheet is disposed to receive a liquid released on said first sheet and to transfer liquid to said absorbent element, wherein said gasket has a dry thickness of 5 mm or less and a penetration time of less than 15 s. 2. The sanitary napkin of claim 1, wherein said absorbent element comprises superabsorbent material. 3. The sanitary napkin of claim 2, wherein said absorbent element comprises a mixture of cellulosic fibers and superabsorbent material. 4. The sanitary napkin according to claim 3, wherein said absorbent element comprises an absorbent material having a surface density of 100 to 700 g / m ² and which is pneumatically laid in the form of a lower layer of fibrous mass, a middle layer of fibrous mass and a superabsorbent polymer located in the pulp, and the upper layer containing at least some amount of pulp. 5. The sanitary napkin of claim 4, wherein said absorbent material has a density greater than 0.25 g / cm ³ . 6. The sanitary napkin of claim 4, wherein said absorbent material contains from 5 to 60 wt.% Superabsorbent polymer. 7. The sanitary napkin of claim 4, wherein said absorbent material has a surface density ranging from 150 to 350 g / m ² . 8. The sanitary napkin of claim 7, wherein said absorbent material has a surface density ranging from 200 to 300 g / m ² . 9. The sanitary napkin of claim 7, wherein said absorbent material has a surface density of 250 g / m ² . 10. The sanitary napkin of claim 7, wherein said absorbent material has a density in the range of 0.3 to 0.5 g / cm ³ . 11. The sanitary napkin of claim 10, wherein said absorbent material has a density in the range of 0.3 to 0.45 g / cm ³ . 12. The sanitary napkin of claim 4, wherein the middle layer comprises a first middle layer adjacent to the lower layer and a second middle layer adjacent to the upper layer. 13. The sanitary napkin of claim 6, wherein said absorbent material comprises from 20 to 55 wt.% Superabsorbent polymer. 14. The sanitary napkin of claim 13, wherein said absorbent material comprises from 30 to 45% by weight of a superabsorbent polymer. 15. The sanitary napkin of claim 14, wherein said absorbent material contains 40 wt.% Superabsorbent polymer. 16. The sanitary napkin of claim 15, wherein said second sheet is pneumatically laid over said upper layer of said absorbent element. 17. The sanitary towel according to claim 1, in which, in addition, contains another sheet of material located near the specified absorbent element and made essentially impermeable to liquid. 18. The sanitary napkin of claim 1, wherein the thickness is less than 3 mm. 19. The sanitary napkin of claim 18, wherein the thickness is 2.8 mm. 20. The sanitary napkin of claim 1, wherein said second sheet of material contains thermoplastic fibers. 21. The sanitary napkin according to claim 1, in which, in addition, contains fastening means for attaching the specified pads to the user's clothing. 22. The sanitary napkin of claim 21, wherein said fastener means is in the form of an adhesive fastener. 23. The sanitary napkin of claim 22, further comprising a wing carrying said adhesive fastener. 24. The sanitary napkin according to claim 1, in which there is an elongated channel made to guide the liquid for subsequent absorption in the specified second sheet. 25. Sanitary pad according to paragraph 24, in which, in addition, contains many of these elongated channels located at a distance from each other. 26. The sanitary napkin of claim 25, wherein said elongated channels are configured to intersect each other. 27. The sanitary napkin of claim 24, wherein said elongated channel is made curved in a plane parallel to said second sheet. 28. The sanitary napkin of claim 24, wherein said elongated channel is formed in at least one of said first and second sheets. 29. The sanitary napkin of claim 24, wherein said elongated channel is formed by applying pressure in at least one of said first and second sheets. 30. The sanitary napkin of claim 29, wherein said elongated channel is formed by applying heat to at least one of said first and second sheets. 31. The sanitary napkin of claim 24, wherein the material near the bottom of said channel has a higher density than the material on at least one side of said channel. 32. The sanitary napkin of claim 24, wherein said gasket has a longitudinal axis and two opposite longitudinal side sections, wherein said channel extends obliquely to said longitudinal axis from one said longitudinal side section to an opposite longitudinal side section, crossing said longitudinal axis. 33. The sanitary napkin according to claim 1, in which at the junction of said first and second sheets in said second sheet, a recessed elongated section is made having a higher density than the second section adjacent to it. 34. The sanitary napkin of claim 32, wherein, in addition, there are a plurality of said elongated sections. 35. A sanitary napkin according to claim 1, wherein said second sheet is made of a material having a density between 0.04 and 0.05 g / cm ³ . 36. The sanitary napkin according to claim 1, wherein said second sheet is made of a material having a surface density of from 80 to 110 g / m ² . 37. The sanitary napkin of claim 1, wherein said second sheet has a thickness ranging from 2 to 3 mm.

Images