FI71873B - FOERFARANDE FOER FAESTANDET AV SUPER-ABSORBERANDE PRODUKTER VI ETT FIBERUNDERLAG - Google Patents

Abstract

Insertion process of pulverulent products (3) so called "super absorbing" in a fiber structure. The powder of the super absorbing product (3) is deposited on a fiber layer (1), a fiber mat (2) comes on top for covering and the fiber mat is bound to said fiber layer, according to cohesion lines and/or points (4), so as to define between said layer and said mat spaces in which a certain amount of powder of super absorbing product (3) is trapped. Application to absorbing fiber structures, particularly sanitary towels.

Description

rn, ANNOUNCEMENT _ ^ (11) UTLÄGGNINGSSKRIFT 718 73 5¾¾ C - Patent granted ®p · --j · .-> 1+ '' • '' r '-' t O1 3 1087 (51) Kv.lk.7int. CI.4 A 61 F 13/18 (21) Patent application - Patentansökning 800048 (22) Filing date - Ansökningsdag 07.01 .80 (En) (23) Starting date - Giltighetsdag 07.01 .80 (41) Published Public - Blivit offentlig 1 3.0 7.80

National Board of Patents and Registration / 44 ^ Date of publication and publication on display. - 28.11.86

Patent and registration authorities '' Ansökan utlagd och utl.skriften publicerad (86) Kv. application - Int. ansökan (32) (33) (31) Privilege claimed — Begärd priority 12.01.79

France-France (FR) 7900717 Proven-Styrkt (71) Beghin-Say, Thumeries, France-France (FR) (72) Marcel Holvoet, Louvier, France-France (FR) (74) Oy Roister Ab (54) Method super The present invention relates to a method for incorporating "super-absorbent" powder products into a fibrous structure, which method consists of a combination of the following steps: a) applying a superabsorbent powder product to at least one fiber base; the width depends on the product to be manufactured, b) this is all covered with a fibrous sheet.

"Super-absorbent" products are compounds that swell in the presence of the liquid to be absorbed but are insoluble: the absorption of the liquid thus occurs quasi-irreversibly. In general, they are cellulose ethers, alginates or modified polyacrylates.

Numerous studies have been performed on their use, and thus numerous methods are known for incorporating them into a fibrous substrate.

In most known techniques, a product acting as a super-absorbent is attached to the surface of a substrate or incorporated into the mass of said substrate, and the terms "fix" and "incorporate" mean that there is a fixed bond between the substrate and the generally powdered product. This fixed connection is due to the presence of a specific fixing additive.

According to a group of known methods, this additive can be water: in this case it is said to fix the superabsorbent by wetting.

Thus, according to the method described in French Patent 2,319,434, the substrate is moistened, after which modified cellulose ether is applied to its surface in the form of particles. The particles swell and adhere to the substrate, after which the liquid is removed by drying. U.S. Patent 3,919,042 describes a similar alternative method of electrostatically applying starch-flour particles to a surface of a cellulosic fibrous sheet containing at least 25% water.

In methods other than those mentioned above, the product used as a "super-absorbent" is moistened. For example, in the method described in French Patent No. 2,122,432, a water-swollen gel (reticulated polyacrylamide) is applied to a cellulosic fibrous substrate, after which the resulting gel is dried. The method described in German Patent 489,308 wets a layer of starch powder (or a layer of dextrin or gelatin powder) to attach it.

There are still other methods in which water is used as the superabsorbent fixing agent by simultaneously adding it to both the substrate and the absorbent article. Thus, in the process described in British Patent 1,354,406, cationic-impregnated and unsaturated cellulose wadding sheets are coated with a water-absorbing polymer, assembled into stacks and treated with steam.

According to French Patent No. 2,066,234, the combination of the fibrous substrate and the absorbent powder is also moistened by steam treatment.

Wetting by attachment generally has the advantage of low cost and simplicity of technology, not to mention the drying involved in some of the methods described above. However, it has the inconvenience of swelling the absorbent particles before drying. This causes the surface of the absorbing 3 71873 particles to change and this results in a decrease in absorbency.

In addition, several particles may adhere to each other and this results in the formation of a film in the most common case, i.e. when only one layer of absorbent is applied. In order to avoid the unavoidable "partial gelation" in the application by wetting methods, some methods have resorted to other fixing agents instead of water.

Thus, according to U.S. Patent No. 3,903,889, the surface of a fibrous structure is coated with an adhesive layer and then "particles" of liquid absorbing product are "sprinkled" onto said adhesive layer.

Another example is French Patent Application No. 77 27569 in the name of the applicant, in which the order of the steps is reversed; a binder, preferably an aqueous solution of polyvinyl alcohol, is applied to the surface obtained by spraying or otherwise transferring the product used as a superabsorbent onto the substrate.

All methods of attaching a water-absorbent article that use a binder other than water have the advantages of simplicity and low cost, but the disadvantage is that the solid on some of the granular surface of the absorbent article impairs the absorbency of the agent.

For this reason, attempts have been made to keep the powder in a fibrous structure without the use of any binder.

U.S. Pat. No. 4,055,180 discloses a layered fiber structure, particularly for sanitary napkins and diapers, comprising a fibrous substrate and a wadding fabric placed on both sides thereof to which a powdered hydrocolloid compound has been applied without any attachment. The combination thus obtained is coated with a polyethylene film in which a plurality of cavities, for example hemispherical, are made, into which closed spaces the gel can expand. In this implementation, the powder is not "attached", i.e. glued to its substrate. Conversely, each cavity formed encloses a certain amount of powder. In order for the absorbent liquid to come into contact with the absorbent powder, a plurality of small holes are made in the polyethylene film.

4 71873 Such a structure only partially eliminates the above-mentioned difficulties associated with gluing with a binder or wetting the powder and / or substrate. In fact, the product used as a super-absorbent binds liquids by significantly expanding its volume. Due to the necessarily limited volume of the preformed cavities, the amount of absorbent product that can be added to them is also limited. If this amount is very large, the walls of the cavities formed in the polyethylene film form an obstacle to the expansion of the gel and thus impair the absorbency of the structure.

On the other hand, the polyethylene film is preformed, which makes it even more difficult to use the method of providing layered products. In addition, the numerous small holes made in the polyethylene film are easily blocked and the passage of liquid through them is quite unstable.

Also known is the method of the NATIONAL STARCH COMPANY, in which a net made of a heat-adhesive material is placed between two sheets of cotton fabric, in the eyes of which the powder to be used as a super-absorbent is placed and in which the layers of cotton fabric on both sides are glued by heating. This method avoids pre-shaping numerous cavities.

But just as in the method of U.S. Patent 4,055,180 already mentioned, the amount of powder used as a "super-absorbent" that can be placed between the layers of pads is limited. In this solution, it is limited by the relatively high inelasticity of the cotton fabric layer.

Thus, although the powder is not attached in any way, the inextensible walls of the cavity containing it limit the expansion of the gel.

The object of the present invention is to obviate all the above-mentioned drawbacks by providing a new method for incorporating a powdered product used as a superabsorbent into a fibrous substrate, so that large quantities of said product can be used, thus completely fulfilling their function as an absorbent, in a simple continuous manner at low cost.

5 71873 To achieve this purpose, the fibrous sheet is bonded to the fibrous substrate by cold forging along gripping lines and / or points so as to form spaces between the substrate and the sheet within which a predetermined amount of superabsorbent powder product is enclosed.

According to a first embodiment of the invention, the fibrous substrate and the fibrous web are both a thin shredded pulp. The shredded pulp web used as a coating is preferably narrower than the underlay on which the powder is placed so that only the area covered by the powder is covered.

The combination is cold-formed by a cylinder in which the ridges of the engraved mesh mold delimit a certain amount of powdered product used as a super-absorbent in each mesh of the mesh without, however, firmly binding it.

Such a fibrous structure containing a powdered product to be used as a super-absorbent can be used in many products intended to be absorbent, such as diapers, sanitary napkins, hospital sheets, etc.

In addition to the following non-limiting examples illustrating the practice of the invention, an example of the preparation of a sanitary napkin is provided in which the absorbent portion of the product is obtained directly by the method of the invention.

This description is supplemented by the following drawings:

Figure 1 is a cross-sectional view illustrating a product obtained according to a first embodiment of the invention.

Figure 2 is a perspective view of the product of Figure 1.

Figure 3 is a diagram illustrating various steps of a first embodiment of the invention.

Figure 4 is a schematic section of a sanitary napkin having an absorbent portion obtained by the method of the invention.

Figure 5 is a perspective view of the sanitary napkin of Figure 4.

According to the embodiment of the first invention shown in Figures 1, 2 and 3, the powdered product 3 used as a super-absorbent is placed on a thin shredded pulp web 1 having a thickness of less than 5 mm, preferably about 1 mm.

Such a shredded pulp cloth is also known as a "fluff" cloth. It is a cellulosic fibrous substrate obtained by the dry process 71873 by a very well known technique today: a simple fiberization of the cellulosic pulp sheet is carried out dry, after which the fibers are sucked onto a solid substrate or a transfer belt.

The application of the super-absorbent powder can take place continuously at a relatively high rate in order to achieve high productivity.

The resulting combination is then covered with a second thin shredded pulp web 2, preferably having a thickness equal to that of the web 1. The powder thus remains between the two shredded pulp webs 1 and 2.

Finally, to encapsulate the powdered super-absorbent between the upper and lower wipes and to provide some adhesion between them, forging (cold) of the resulting fibrous structure is performed by passing it between the forging cylinders, with the longitudinal ridges at their outer edges forming both tear webs.

It is recommended to use cylinders in which the engraving forms a pattern of diamond-shaped cells. By way of example only, these diamonds may measure 11 mm x 7 mm and 1.5 mm deep.

The forging mold lines of Figures 1 and 2 are schematically shown at 4.

They are found to form a reticulated pattern, and each mesh of the mesh encloses a certain amount of powdered super-absorbent.

Figure 3 schematically shows the different steps of the first embodiment of the method.

5, the fibers dry pulp fiberizing 6, after which the cellulose fibers are sucked by vacuum of the arrow d in the direction of the conveyor belt runs.

The powder 3 is applied to the formed cloth 1 by means of a feeding and spreading device schematically shown in step 8. The second shredded cloth 2 covers the cloth 1 and the powder is enclosed inside the combination thus formed. The assembly is cold forged by passing it between cylinders 9 engraved into a mesh surface.

7 71873

The tear web is elastic enough to allow the gel formed after absorption to expand well. In this way, of course, a fibrous structure of any length or width can be formed, it can have one or more strips of superabsorbent product of any width, and the absorbent product is not applied near the edges of the substrate to avoid spilling over the powder.

Alternatively, very well, as can be seen from the drawing of Figure 2, two parallel forging lines 4a can be formed along the edges of the strip formed by the super-absorbent product.

In this way, the powder closes precisely to the area to which it is applied.

Fiber constructions containing the superabsorbent product made from the above-described method are very useful in the manufacture of sanitary napkins.

Figures 4 and 5 show, by way of example, a sanitary napkin made of the fiber structure thus obtained.

As is known per se, the sanitary napkin consists of an absorbent core 20 obtained from the method described above, the side of which which is not against the wearer's skin is covered by a layer 21 made of polyethylene or the like. This layer, called -, r layer, also covers the absorbent V_y the edges of the core to prevent leakage to the side.

The entire combination is surrounded by a nonwoven layer 22, which may be secured with an adhesive tape 23. On the side of the sanitary napkin covered by the polyethylene film, one or more adhesive tapes 24 (e.g., "hot-melt" adhesive) are attached to the center portion to secure the dressing.

Prior to use, the adhesive is protected by a silicone paper tape 26 known per se. For a 230 mm long and 65 mm wide sanitary napkin, two shredding cloths with a total weight of 5 g and an amount of about 0.5-3 grams of powdered super-absorbent product are required.

The absorbent core 20 may, if desired, be joined to a cotton ball support plate 25 to maintain "fluff".

It is self-evident that the absorbent core can be obtained by any of the alternatives to the method described above.

Claims (7)

8 71873 A method for incorporating powdered "superabsorbent" products into a fibrous structure, which method comprises a combination of the following steps: a) placing the superabsorbent powder product (3) on a fibrous substrate (1) in at least one strip, the width of which depends on the product to be manufactured; (2), c) characterized in that the fibrous sheet (2) is cold-bonded to the fibrous substrate (1) along gripping lines and / or points so as to form spaces between the substrate and the sheet into which a predetermined amount of superabsorbent powder product (3) is enclosed. . Method according to Claim 1, characterized in that the cold forging is carried out in the form of a net, each eye of the net enclosing a predetermined amount of super-absorbent and powder product (3). A method according to claim 1 or 2, characterized in that the cold forging is performed by means of engraved cylinders, the cells formed by said engravings being diamond-shaped. Method according to Claim 1, characterized in that the thickness of the fibrous sheet (2) is between 0.5 and 5 mm, preferably about 1 mm. Method according to Claim 1, characterized in that the fibrous substrate (1) is also a thin fibrous sheet, preferably as thin as the first fibrous sheet (2). Method according to Claim 1, characterized in that the fibrous sheet (2) is narrower than the fibrous substrate (1), so that it is formed only on the superabsorbent product strip of the protective sheet. Use of a fibrous sheet bound to a fibrous substrate in a sanitary napkin according to any one of the preceding claims.