MXPA97002716A - An absorbent article, such as a diaper, an incontinence protector, a sanitary towel or a semile article - Google Patents

Abstract

The invention is related to an absorbent article, such as a diaper, an incontinence protector or a sanitary napkin that includes an external canvas permeable to liquid, a lower waterproof canvas, an absorbent body placed between them. The external canvas and the absorbent body, at least partially joined together by means of a hydrophobic gum

Description

"AN ABSORBENT ARTICLE, SUCH AS A DIAPER, AN INCONTINENCE PROTECTOR, A SANITARY TOWEL OR A SIMILAR ITEM" BACKGROUND The present invention relates to an absorbent article, such as a diaper, an incontinence protector or a sanitary napkin and also with the use of a hydrophilic gum in the manufacture of an absorbent article. Hydrophilic gums are previously known from Patent Number EP-A 1,297,769, for example. This document describes a hydrophilic gum composition that can be conveniently used in products that are to be attached to the skin, such as dressings. US Pat. No. 4,875,030 discloses a latex composition which, when the liquid phase is removed, forms a film whose surface is hydrophobic. The latex composition can be used as a rubber for cloth-like paper products. A surface canvas of an absorbent article, such as a diaper, an incontinence protector or a sanitary napkin typically comprises nonwoven material that is usually hydrophobic. In order to allow fluid, such as urine or menstrual fluid to pass through this outer layer, the non-woven layer is treated with a surfactant in order to make it hydrophilic. For a material to be considered as being hydrophilic, it must have a wetting angle of less than 90 °. Repeated wetting of the material will wash off the surfactant and the surface material will then become hydrophobic. This makes it difficult for the liquid to pass down through the surface layer.

OBJECT OF THE INVENTION The external canvas is usually fixed to the absorbent body by means of a hot melt gum. This gum is hydrophobic. An object of the present invention is to solve the problem that the surfactants are washed away from the external canvas and in this way prevent the liquid from passing through it. It has surprisingly been found that this problem can be solved by joining the outer canvas in the absorbent body with a hydrophilic gum, such as to retain a hydrophilic surface which will continue to allow the liquid to pass through it despite repeated wetting.

Another object of the present invention is to prevent the hydrophobic barrier that is formed by hydrophobic hot melt gums, in the current absorbent products. A typical problem with absorbent articles is that the outer canvas is loosened from the absorbent body after it has been moistened only once. In these cases, hydrophilic gum is the connecting link that makes a continuous liquid transport possible.

EXHIBITION OF THE INVENTION In accordance with the present invention, either a hydrophilic gum, for example, a dispersion gum or a hydrophobic gum, for example, a hot melt which has been rendered hydrophilic by modification, is used. An advantage in using a modified hot melt is that it avoids a step of evaporating the water in the dispersion gum in the manufacturing process of the absorbent article. The hot melt can be modified by inserting an otherwise hydrophobic polymer, or adding a surfactant to an otherwise hydrophobic hot melt, or using starch as the base in the hot melt.

The hot melt gum based on a grafted polymer will preferably include from 75 percent to 85 percent by weight of a graft copolymer and from 15 percent to 25 percent by weight of an adhesive agent. The graft copolymer consists of 40 percent to 80 percent by weight of a vinyl monomer and from 20 percent to 60 percent by weight of a polyalkylene oxide Le or soluble in water. The vinyl monomer is preferably vinyl acetate or an alkyl substituted acrylate, such as methyl acrylate or ethyl acrylate. The polyalkene oxide is preferably selected from the group including ethylene oxide homopolymers, copolymers of ethene oxide and propene oxide, and mixtures thereof. The adhesive agent can be a synthetic or natural resin. A hot melt that has been made hydrophilic by adding a surfactant can be based on a thermoplastic elastomer or an atactic poly-alpha-olefin, such as atactic polypropylene. The added surfactant is preferably nonionic. The nonionic surfactant can be an alcohol, an alkanolamide, an amino oxide, an ester or an ether. A starch-based hydrophilic hot melt includes modified starch ester. The ester can be based on natural starch, for example, corn, potato, wheat, rice or a synthetically produced starch. Examples: the modified starch is starch propionate and starch acetate. In addition to containing the starch ester, the hot melt also includes an organic solvent that imparts the properties of a hot melt gum to the composition. The solvent, for example, can be a sulfonamide, a carboxylic acid, a carboxylic acid ester, an amide, a phosphate ester, an alcohol or an ester. The solvent will preferably be a sulfonamide, an alcohol, an amide or an ester. The hydrophilic gum can be applied to the surface of a non-woven canvas that has been pretreated with a surfactant. This will result in a more permanent hydrophilic surface than that which could be obtained by treating the non-woven canvas solely with a surfactant. The hydrophilic gum can also be used in a hydrophobic nonwoven material that has not been pretreated with surfactants. In this case, the hydrophilic gum has the important function of penetrating the non-woven material and reducing the resistance to liquid transport, this strength being relatively high in the case of thick non-woven materials. Hydrophilic gum can be applied in different ways. The gum can be dispersed over the entire surface to be joined. In addition, hydrophilic gum can only be applied at the wetting point. The point of wetting is in the area in which the absorbent body initially receives the fluid fluid discharged by the user. As will be understood, the point of wetting will be placed in different places depending on the type of related article and also on the sex of the user. The remaining surface to be joined can be gummed with a hydrophobic gum, such as a conventional hot melt gum. The advantage with this method is that re-wetting is prevented in those parts that are covered with hydrophobic gum. Another method of gumming that will prevent re-wetting involves distributing the hydrophilic gum in a pattern, such as in a strip pattern, a checkered pattern or a punctate pattern, on the surface to be gummed. The material that remains between the rubber pattern, therefore, will be hydrophobic and will prevent re-wetting. The rubber strips may extend either longitudinally or transversely over the related article. The gum can be applied, for example, by spraying, full coating or silk spreading printing techniques.

The absorbent body includes a conventional absorbent material, for example, cellulose fibers, viscose fibers or synthetic superabsorbent polymers, such as polyacrylates. The use of mixtures of different absorbent materials is also conceivable of course. The outer canvas consists of a non-woven material. This may be a conventional non-woven material, for example, a non-woven material bonded by spinning or a nonwoven webbed material. Of course, a hydrophilic gum can also be used to stick an external canvas that is made of a plastic film. Both the outer canvas and the absorbent body may comprise more than one layer. The invention will now be described in greater detail with reference to exemplary embodiments thereof and also with reference to the accompanying drawings. It will be understood that the invention is not restricted to the exemplary embodiments described and illustrated, since these modalities are only intended to explain and illustrate the invention. Figure 1 illustrates an experimental shift test. Figure 2 illustrates a penetration plate used to determine the permeability.

Figure 3 illustrates an example of how the hydrophilic gum can be applied to a diaper in a punctate pattern. Figure 4 illustrates an example of how the hydrophilic gum can be applied to a diaper in a strip pattern. Figure 5 illustrates an example of how the rubber can be applied at the wetting point of a diaper. Figures 6 and 7 show the result of a shifting test that is carried out on a nonwoven material that has been pretreated as a surfactant. Figures 8 and 9 show the result of a shifting test carried out on a nonwoven material that has not been pretreated with a surfactant. Figures 10 and 11 show the results obtained with repeated penetration tests on a nonwoven material that has been pretreated with a surfactant. Figures 12 and 13 show the results obtained with repeated penetration tests on a nonwoven material that has not been pretreated with a surfactant. Figure 14 illustrates the results obtained when measuring rubber contact angles.

EXEMPLARY MODALITIES EXAMPLE 1 Determination running tests on non-woven material Principle Measuring the amount of liquid that remains unabsorbed when a known amount of test liquid is emptied onto the filter / non-woven paper placed on an inclined surface. The shift is measured three times in succession in one and the same non-woven sample even when the filter paper is changed between each measurement occasion.

Equipment Measurement table with adjustable table tilt; see Figure 1. Stile. - Regulated supply pump connected to the hose and the outlet pipe or burette. Filter paper FF3 W / S (Holling orth &Vose Co. Ltd.), 140 x 280 mm, long side in the machine direction. - Absorbent paper.

Test liquid, 0.9 percent solution of NaCl produced with deionized water.

Sample preparation The non-woven samples were cut to 140 x 285 millimeters, with the long side in the length direction. The measurement box was tilted at an angle of 25 °. The distance between the exit orifice of the outlet pipe and the sample was adjusted to 25 millimeters. The regulated supply pump was graduated to measure a dosing amount of 25 milliliters as the measurement rate of 7 milliliters per second. The absorbent paper was weighed to an accuracy of 0.1 gram.

Procedure Two filter papers were placed on the inclined surface with the smooth sides facing upwards. The non-woven paper was placed on top of the filter papers with 5 mm overshoot on the bottom edge. Filter papers and material Nonwoven were secured with a metal clamp. The measuring equipment was graduated to discharge the liquid to a point of 25 millimeters from the upper edge of the sample. The liquid measurement was carried out. The absorbent paper with the overflow fluid was weighed. The wet filter papers were removed after a waiting time of four minutes and the same non-woven sample was placed on the two new filter papers. The running test was repeated four additional times using 25 milliliters of test liquid on each measurement occasion.

The bleed tests were carried out with the following materials.

Rubber: 1) No rubber was applied. 2) Hydrophilic dispersion gum based on polyvinyl acetate, stabilized with polyvinyl alcohol. 3) Hydrophilic dispersion gum based on a copolymer of ethylene and vinyl acetate. 4) Hydrophilic dispersion rubber based on a partially crosslinked ethylene vinyl acetate copolymer. 5) Hydrophobic hot melt based on an atactic poly-alpha-olefin. 6) Hydrophobic hot melt based on a starch ester. 7) Hydrophobic hot melt based on a graft copolymer of vinyl acetate and polyethylene oxide. 8) Hydrophobic hot melt based on atactic polypropylene and a nonionic surfactant.

Nonwoven material; Holmestra B9 (fiber mesh), 20 grams per square meter pretreated with a surfactant. - Holmestra N9 (fiber mesh), 17 grams per square meter not pretreated with a surfactant. Holmestra B7 (fiber mesh), 20 grams per square meter pretreated with a surfactant. - Holmestra N7 (fiber mesh), 20 grams per square meter not pretreated with a surfactant.

Test Results See Figures 6 to 9. These figures show the degree to which the applied liquid runs. The different columns within the same groups show the results obtained with different liquid dosages on the same non-woven sample. The figures above the columns represent the amount of rubber that was applied. Figures 6 and 7 show the results obtained with a nonwoven material treated with a surfactant. Figures 8 and 9 show the results obtained with a nonwoven material that had not been treated with a surfactant.

Example 2 Repeated penetration of determination in non-woven material.

Principle Measuring the time required for a specific amount of liquid (synthetic urine) to pass through a nonwoven material and then be absorbed by the absorbent core. The time was measured five times in sequence in one and the same non-woven sample, but with a change of filter paper between each measurement occasion.

Equipment Penetration plate (see Figure 2) and instruments to measure penetration time: LISTER Lenzing AG.

Bottom plate of plexiglass, 125 x 125 mm. Synchronizer, with accuracy up to 0.1 second. - Cylinder of measurement: of 5 and 50 milliliters or a digital burette. Absorbent Core: 100 x 200 mm FF3 W / S filter paper (Holling orth &Vose Co. Ltd.). Synthetic urine, 9 grams of NaCl / 1000 milliliters of distilled gauze. Laboratory scales, accurate to 0.01 gram.

Sample preparation Samples measuring 125 x 125 millimeters of the test material were cut out. The samples and the filter paper were conditioned in a 65 percent atmospheric unit for four hours at 20 ° C.

Procedure Five layers of filter paper were placed on the lower plate with its smooth sides facing upwards. A non-woven sample was placed on top of the filter papers. The penetration plate was placed in the upper part of the sample well centered in relation to it. The instrument was adjusted vertically so that the distance between the outlet orifice of the outlet pipe and the top of the plate was 5 millimeters, in other words, 30 millimeters above the sample. 5 milliliters of synthetic urine was measured and emptied into the liquid container of the measuring instrument. The liquid measurement was started and the penetration time was observed to an accuracy of 0.1 s. The synchronizer was started and the penetration plate was removed after a period of four minutes. The wet filter papers were removed. The same non-woven sample was placed on five new filter papers. The penetration or wetting procedure was repeated twice more.

A permeability test was carried out with the following materials: Rubber: 1) No rubber was applied. 2) Hydrophilic dispersion rubber based on polyvinyl acetate stabilized with polyvinyl alcohol. 3) Hydrophilic dispersion rubber based on an erc copolymer of ethylene and vinyl acetate. 4) Hydrophilic dispersion gum based on a partially crosslinked ethylene vinyl acetate copolymate. 5) Hydrophilic hot melt based on an atactic poly-alpha-olefin. 6) Hydrophobic hot melt based on a starch ester. 7) Hydrophilic hot melt based on a graft copolymer of vinyl acetate and polyethylene oxide. 8) Hot hiodrofóbica fusion based on an atactic polypropylene and a nonionic surfactant.

Non-woven material: - Holmestra B9W (fiber mesh), 20 grams per square meter, pretreated with a surfactant. Holmestra N9 (fiber mesh), 17 grams per square meter, not pretreated with a surfactant. - Holmestra B7W (fiber mesh), 20 grams per square meter, pretreated with a surfactant. Holmestra N7W (fiber mesh), 20 grams per square meter, not pretreated with a surfactant.

Results of the test: See Figures 10 to 13. The different columns within the same group show results obtained when the liquid was dosed to the same non-woven sample with different dosages. The Figures above the columns represent the amount of rubber applied. Figures 10 and 11 show the results obtained with the nonwoven material treated with the surfactant. Figures 12 and 13 show the results obtained with the nonwoven material that was not treated with a surfactant.

Example 3 Measurement of rubber contact angle Principle In order for a rubber to be considered hydrophilic, the contact angle T between a water droplet and the material to be measured will be smaller than 90 °. Equipment - The contact angle was measured in a DAT (dynamic absorption tester). Distilled water. Paper, surface weight of 80 grams per square meter. - lí Procedure Three different gums were applied to the paper. The strips measuring 25 millimeters wide were then cut from the sample. Two different tests were carried out: one test involves measuring during 0.1, 1.0 and 10.0 seconds and another test involves measuring during 10.0, 30.0 and 60.0 seconds. The measurements were carried out only at 0.1, 1.0 and 10.0 seconds in sample 5). The measurements were carried out only at 0.1 second in sample 8). Contact angle measurements that were made in the following gums 2) Hydrophilic dispersion gum based on polyvinyl acetate stabilized with polyvinyl alcohol. 4) Hydrophilic dispersion rubber based on a partially crosslinked ethylene vinyl acetate copolymer. 5) Hydrophobic hot melt based on an atactic poly-alpha-olefin. The hydrophobic hot melt based on an atactic poly-alpha-olefin. 8) Hydrophobic hot melt based on an atactic polypropylene and a nonionic surfactant. Results of the test See Figure 11.

Claims (11)

R E I V I N D I C A C I O N E S:

1. An absorbent article, such as a diaper, an incontinence protector or a sanitary napkin comprising a liquid-permeable outer sheet, a water-impermeable backing sheet and an absorbent body placed therebetween, characterized by the outer canvas and the body Absorbent are mutually joined at least partially by means of a hydrophilic gum.

2. An absorbent article according to claim 1, characterized in that the external canvas and the absorbent body are joined to each other by a continuous layer of hydrophilic rubber.

3. An absorbent article according to claim 1, characterized in that the external canvas and the absorbent body are mutually joined by a hydrophilic gum distributed in a pattern.

4. An absorbent article according to claim 3, characterized in that the pattern is a pure pattern.

5. An absorbent article according to claim 3, characterized in that the pattern is in a striped pattern or a checkered pattern.

6. An absorbent article according to claims 1 to 5, characterized in that the hydrophilic gum is applied only at the moisture point.

7. An absorbent article according to claim 1, characterized in that the hydrophilic gum is an original hydrophilic gum which has been modified to become hydrophilic.

8. An absorbent article according to claim 1, characterized in that the hydrophilic gum is a dispersion gum.

9. An absorbent article according to claim 7, characterized in that the hydrophilic gum is a hot melt gum which has been modified by adding a surfactant.

10. An absorbent article according to claim 7, characterized in that the hydrophilic gum has been modified by grafting a hydrophilic group into an otherwise hydrophobic polymer.

11. An absorbent article according to claim 1, characterized in that the hydrophilic gum is a starch-based hot melt gum.