JPH01162874A - Production of water absorbable composite - Google Patents

Abstract

PURPOSE: To produce an excellent water-absorbing complex having high strength by fusing together a water-soluble resin powder on the outer surface of a low-melting layer of a tape-like laminate or the like comprising high-melting and low-melting synthetic resin layers and then by subjecting the water-soluble resin powder to crosslinking treatment with a foaming crosslinking agent. CONSTITUTION: This water-absorbing complex is produced by the following steps: (1) the formation of a tape-like laminate (or its split fiber or conjugated fiber) where the laminate comprises a high-melting synthetic resin layer 1 and a low-melting synthetic resin layer 2 and the low-melting layer is disclosed from the surface; (2) heating the laminate up to the vicinity of the melting point of the low-melting resin and fusing together a water-soluble resin (e.g. polyacrylic acid or its copolymer or the like) on the outer surface of the low-melting layer discolored from the surface; (3) making the water-soluble resin contact with a foaming aqueous solution comprising a crosslinking agent (e.g. sorbitol polyglycidyl ether or the like) and a foaming agent such as a surfactant and applying crosslinking treatment. The high-melting synthetic resin is e.g. a crystalline polypropylene or the like. The low-melting synthetic resin is e.g. an unsaturated carboxylic acid-grafted modified polyolefin or the like. The laminate may have three layers e.g. consisting of the layer 2, the layer 1 and the layer 2 as the tape-like laminate.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for producing a water-absorbing composite mainly composed of a thermoplastic synthetic resin, and from a usage perspective,
In particular, it is used as a waterproof covering material for telecommunication cables, optical fiber communication cables, etc., as well as water-retaining sheets for agriculture and horticulture, various water-stopping materials for civil engineering and construction, water-absorbing materials for various industries, sanitary materials, medical materials, etc. The present invention relates to a method for producing a sexual complex.

[Conventional technology]

Waterproof coverings using water-absorbing or hygroscopic materials have been used in many fields.

For example, in so-called conductive cables such as telecommunication cables and optical fiber communication cables, ingress of water or moisture from the outside is absolutely not allowed, so the joints between the cables are particularly carefully coated with waterproof coatings.

This waterproof coating is obtained by further wrapping a water-absorbing material and a moisture-absorbing material around the outer surface of the waterproof coating material applied to the connection part, and coating the waterproof material such as rubber on top of the water-absorbing material. Moisture or the like that has passed through the waterproof material on the outermost surface and entered the coating layer is absorbed by the water-absorbing material and the moisture-absorbing material, and is prevented from reaching the cable.

Examples of water-absorbing materials and moisture-absorbing materials used here include split ethylene glycol-impregnated polypropylene fibers and diethylene glycol-impregnated paper.

However, since these water-absorbing materials and moisture-absorbing materials have wettability, they are complicated to handle, and since they contain fluid, there are problems in that the reproducibility of coating is difficult.

On the other hand, the surface of a single-layer polyolefin fibrillated yarn is brought to a molten state, and fine powder of a polymeric water absorbing agent such as crosslinked polysodium acrylate or acrylic acid-vinyl acetate copolymer is sprinkled onto it and fused. Attempts have been made to use dampened water-absorbing materials and moisture-absorbing materials.

However, these water-absorbing materials and moisture-absorbing materials are either fragile or polymeric water-absorbing materials, which do not lose their stretching effect due to melting of the stretched fibers, cannot withstand stress such as tension during cable facility work, and are easily damaged. There is also a problem with the amount of fusion.

As a means to solve these problems, a powdered polymeric water absorbing agent is added and kneaded into the resin during polyolefin extrusion, and the extruded film is subjected to split fiber treatment after stretching to impart waterproof properties. However, in general, polymeric water absorbing agents are sensitive to heat, and if left in that state for a long time before extrusion molding, even if the temperature is below the melting temperature of polyolefin, the water absorbing ability will only decrease. First, most of the polymeric water-absorbing agent after extrusion molding is buried in the resin, and only a very small amount is exposed on the surface, so there is a drawback that the water-absorbing effect cannot be fully exerted.

In addition, attempts have been made to create water-absorbing materials in which a water-soluble resin is fused to a fibrous material, such as a multilayered polyolefin fibrillated yarn, which is brought into contact with an aqueous solution of a crosslinking agent and then dried, but this requires high heat to dry. However, there is a drawback that it requires a long time.

[Problem that the invention seeks to solve]

The purpose of the present invention is to provide a method for fusing a water-soluble resin to a fibrous or tape-like laminate and crosslinking it, which enables short-time low-temperature drying, is easy to manufacture and handle, and has a higher υ than conventional methods. It is an object of the present invention to provide a manufacturing method for obtaining a water-absorbing composite having water-absorbing performance and good tensile strength.

[Means for solving problems]

The method for producing a water absorbent composite of the present invention comprises at least one layer of high melting point synthetic resin and at least one layer of low melting point synthetic resin, and the layer of low melting point synthetic resin is exposed on at least a part of the surface. It is composed of a tape-like laminate or a fibrillated yarn or a composite fiber obtained by splitting the tape-like laminate,
and a tape-like laminate in which a water-soluble resin powder is fused to the outer surface of a low-melting synthetic resin layer exposed on the surface, or a fibrillated yarn or a composite fiber obtained by splitting the tape-shaped laminate, or a composite fiber body of the water-soluble resin. The method is characterized in that a water-soluble resin is crosslinked by contacting an aqueous solution containing a crosslinking agent, a foaming agent, and water as main components in a foamed state, and then dried.

The manufacturing method of the present invention will be explained in more detail below.

In the present invention, the substrate of the water-absorbing composite consists of at least one layer of high melting point synthetic resin and at least one layer of low melting point synthetic resin, and the layer of low melting point synthetic resin covers at least a part of the surface. This is a tape-like laminate exposed to the laminate, or a fibrillated yarn or composite fiber obtained by splitting the laminate.

The tape-like laminate is obtained by coextruding a high-melting point synthetic resin and a low-melting point synthetic resin to form a film-like laminate, or by obtaining a film-like laminate from a high-melting point synthetic resin and a low-melting point synthetic resin by a lamination method, Next, the film-like laminate is stretched and then slit into a narrow width, or a tape-like product obtained by slitting the film-like laminate into a narrow width and then stretching it, the thickness of which is 500 to 10.0007" = - #, particularly preferably 1.ooo to 4.000 deniers.

Further, the fibrillated yarn refers to a tape-like laminate that is split by applying a split roll to make it into a net shape or a complete fiber shape, and the single yarn width is preferably 0.
It is in the range of 0.03 to 0.2 meters, more preferably 0.03 to 0.11 meters, most preferably 0.03 to 0.07 meters.

FIG. 2 shows an example of this, in which a high melting point synthetic resin layer 1 is used as an intermediate layer, and a low melting point synthetic resin layer 2 is located on the outside thereof.

Preferred examples of film-like laminates used for producing tape-like laminates and defibrated yarns include a high melting point base resin layer/
Examples include a low melting point synthetic resin layer (hereinafter abbreviated as high/low), a three-layer laminate of low/high/low, and a five-layer laminate of low/high/low/high/low.

Next, as a composite fiber body as a base material, a side pipe and
Used are drawn side-type composite fibers and drawn cis-core type composite fibers consisting of a low-melting point synthetic resin sheath and a high-melting point synthetic resin core. The fineness of the composite fiber body is preferably 10 to 60 deniers in single yarn form.

The number of layers in the tape-shaped & layered body, defibrated yarn, and composite fiber body is not particularly limited, but it is preferable that the high melting point synthetic resin constitutes the inner layer and the low melting point synthetic resin constitutes the outer layer. The larger the difference in melting point between the high melting point synthetic resin and the low melting point synthetic resin, the more preferable it is, and generally it is preferably 10° C. or higher. However, in the case of synthetic resins whose melting points appear sharply, the difference in melting points may be small.

Generally, the high melting point synthetic resin is selected from crystalline polypropylene, high density polyethylene, polyester, thermoplastic synthetic resins such as nylon 6 and nylon 66.

Further, as the low melting point synthetic resin, a low melting point thermoplastic resin that exhibits good bonding properties with the high melting point synthetic resin used is used. Examples include polyolefins such as low density polyethylene, linear low density polyethylene, high density polyethylene; ethylene-vinyl acetate copolymers; maleic acid,
Polyolefins (ER resin, Particularly preferred are graft-modified products of high-density polyethylene and linear low-density polyethylene,
The grafting rate is preferably 0.3 to 0.36% by weight); ethylene-maleic anhydride-methyl methacrylate terpolymer (ET resin), ethylene-acrylic acid copolymer (
FAA resins), ethylene-acrylate or methacrylate copolymers such as ethylene-ethyl acrylate copolymers (EEA resins); and ethylene-methacrylic acid copolymers partially neutralized with metals such as sodium and zinc. thermoplastic resin (i.e., ionomer resin)
can be given.

Among these low melting point synthetic resins, it is particularly preferable to use a low melting point thermoplastic resin having a carbonyl group or a carboxyl group. If such a low melting point thermoplastic resin is used,
When the water-soluble resin is completely cross-linked as described below, the cross-linking agent reacts with the water-soluble resin and also reacts with the above-mentioned functional groups in the low-melting point synthetic resin, so that the cross-linked product of the water bath resin and the low-melting point synthetic resin are combined. This makes the bond even stronger and prevents the crosslinked product from falling off.

A specific example of a preferable combination of a high melting point synthetic resin and a low melting point synthetic resin is as follows.

Combinations of crystalline polypropylene and acid-grafted modified linear low-density polyethylene, combinations of crystalline propylene and acid-grafted modified high-density polyethylene, combinations of crystalline polypropylene and ethylene-maleic anhydride/methyl methacrylate terpolymer combinations, and combinations of crystalline polypropylene and ionomer resins.

In the present invention, water-soluble resin powder is first fused to the outer surface of the low-melting point synthetic resin layer that is formed on the surface of the tape-shaped laminate, its defibrated yarn, or composite fiber.

In order to completely fuse the water-soluble resin powder to the low melting point synthetic resin layer, for example, the tape-like laminate, defibrated yarn, or composite fiber body is heated to near the melting point of the low-melting point synthetic resin, and the heated tape-like laminate or A method in which the water-soluble resin powder is fully brought into contact with the defibrated yarn or the composite fiber body, and the water-soluble resin powder is fused to the outer surface of the exposed low-melting point synthetic resin layer; Low-melting point synthesis involves heating the composite fiber body to near the melting point of the low-melting point synthetic resin, and exposing the water-soluble resin powder to the surface of the heated tape-shaped laminate, defibrated yarn, or composite fiber body using a charged coating machine. Method of fusing to a resin layer: After adhering water-soluble resin powder to a tape-shaped laminate, defibrated yarn, or composite fiber body using a charging coating machine, the tape-shaped laminate, defibrated yarn, or composite fiber body Examples include a method in which the water-soluble resin powder is heated to near the melting point of the low-melting synthetic resin layer exposed on the surface, and the water-soluble resin powder is fused to the outer surface of the low-melting synthetic resin layer exposed on the surface.

The water-soluble resin powder used in the present invention is a water-soluble polymer powder having a carboxyl group, a sulfonic acid group, or a salt thereof, and specific examples include polyacrylic acid and its copolymer, polyacrylic acid Examples include salts, polyacrylamide partial hydrolysates, polystyrene sulfonic acids, polyacrylamide propane sulfonic acids, and copolymers thereof. The average particle diameter of the water-soluble resin powder is preferably as small as possible so that the low melting point synthetic resin layer exposed on the outer surface of the tape-shaped laminate, defibrated yarn, or composite fiber body can be covered as densely as possible. Generally, the average particle size is 10-500μ, preferably 10-300μ, more preferably 10-5
It is 0μ. If the average particle size exceeds 500μ, the water-soluble resin will not form a dense coating, and the surface lines of the resulting water-absorbing composite will be poor.

Furthermore, water-soluble resins with an average particle size of less than 10 μm are difficult to manufacture and handle, and are expensive.

The amount of water-soluble resin attached or fused is 10% of the weight of the unattached tape-like laminate, fibrillated yarn or composite fiber.
It is preferably 60% by weight. If the amount of adhesion or fusion is 10% by weight without grooves, sufficient water absorption will not be obtained, and if it exceeds 60% by weight, the surface texture will not be bad and will become water soluble when rubbed. There is a problem that the resin falls off.

As mentioned above, when attaching or fusing the water-soluble resin powder, the tape-like laminate, fibrillated yarn, or composite fiber body is heated to near the melting point of the low-melting synthetic resin, but The melting point of synthetic resins does not change significantly even when heated, so it can be used for tape-shaped laminates, defibrated yarns, etc. The composite fiber maintains good tensile strength without losing its orientation due to stretching.

In the next step, the water-soluble resin fused to the tape-like laminate, fiber thread, or composite fiber is crosslinked by contacting it with foam from an aqueous solution mainly consisting of a crosslinking agent, a foaming agent, and water. .

The crosslinking agent used in the present invention has two or more functional groups capable of reacting with the carboxyl group, sulfonic acid group, or a salt thereof in the water-soluble resin, and is water-soluble. can be used for anything.

Typical examples of such crosslinking agents include sorbitol polyglycidyl ether, polydarycerol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, ethylene glycol & glycol dinor ether, and ethylene glycol noglycinole ether. Polyfunctional epoxy compounds such as

In addition, as the foaming agent, a water-soluble foaming agent is used.

Typical examples include anionic surfactants such as aliphatic alkyl sulfates and alkylaryl sulfonates, lower alkyl (1 to 4 carbon atoms) or phenyl ethers of polypropylene glycol or propylene dalicol, alkylphenol-based, -grade or secondary long chain Examples include nonionic surfactants such as alcohol sulfates, cellulose ethers, alcohol ethers, and aliphatic jetanolamide surfactants.

The crosslinking agent and foaming agent mentioned above are carboxyl groups in the water-soluble resin,
In order to facilitate the reaction with a sulfonic acid group or a salt thereof and to make the crosslinking density uniform, it is used as an aqueous solution, preferably as a diluted aqueous solution, as described below. The ratio of water, crosslinking agent, and foaming agent in an aqueous solution is generally 0.005 to 2 parts of crosslinking agent to 100 nfflt parts of water.
The foaming agent is preferably 0.1 to 5 parts by weight.

The foaming agents and crosslinking agents mentioned above are used in the form of aqueous solutions, and it is necessary to form these foams. The amount of crosslinking agent used is 0.0 based on the weight of the fused water-soluble resin.
It is preferably 1 to 2% by weight. The usage amount is 0.
If the amount is less than 0.01% by weight, the degree of crosslinking of the water-soluble resin will be low, and sufficient water absorption performance will not be obtained and it will dissolve in water. If the amount used is more than 2% by weight, the degree of crosslinking will be too high and the water absorption capacity will be insufficient.

Further, the amount of the foaming agent used is preferably 0.25 to 2% by weight based on the weight of the fused water-soluble resin. If the amount used is less than 0.255% by weight, foaming becomes unstable and the crosslinking density becomes non-uniform. In addition, if the amount used exceeds 2% by weight, excessive foaming will result, and the amount of crosslinking agent added to the water-soluble resin will decrease, resulting in a low degree of crosslinking, resulting in insufficient water absorption performance and dissolution in water. It ends up.

Note that with foam from an aqueous solution consisting of two components, a foaming agent and a crosslinking agent, the resulting water-absorbing composite may become hard when brought into contact with the fused water-soluble resin. A small amount of a softening agent represented by the following may be added to the above aqueous solution. The amount of the softener added is 0.01 to 2 times the weight of the fused water-soluble resin! -% range is preferred.

In the present invention, foam is formed from an aqueous solution containing the foaming agent, crosslinking agent, and water as essential components, and is brought into contact with the fused water-soluble resin for crosslinking treatment.

The reason for using foam instead of the aqueous solution is that with an aqueous solution, the drying temperature must be raised to a high temperature in the subsequent drying process, which is disadvantageous in terms of cost, whereas foam can be dried at low temperatures. This is because it has the advantage of not only being able to reduce costs, but also being able to suppress changes in the shape of the fibrillated yarn, etc., and maintain its texture.

Methods for creating foam from the aqueous solution include open systems such as the horizontal butter method, knife coating method, doctor roll method, Kuester method, Senfort method, and Mitzter method, and closed systems such as the FFT method, rotary screen method, and printnear method. There are several systems available, but the latter closed system, which allows foam to be created without exposure to the outside air, is preferred from the standpoint of foam stability. In particular, the FFT method is preferable because it is a method in which the aqueous solution is stirred at high speed with a foaming machine while blowing air into the aqueous solution. Although the foaming ratio is determined by the concentration of the foaming agent, the main factors are the amount of aqueous solution and the amount of air blown into the foam.

The expansion ratio of the foam obtained from the aqueous solution cannot be determined generally, but is generally 5 to 18 times, since the type and conveyance speed of the tape-like laminate, defibrated yarn, and composite fiber differ. Preferably, 8 to 13 times is appropriate. The reason for this is that if the expansion ratio is less than 5 times, the water content will increase and drying will take a long time, but the degree of crosslinking will increase and the water absorption capacity will decrease. This is because if the expansion ratio exceeds 18 times, the concentration of the crosslinking agent becomes diluted and the degree of crosslinking becomes low, which is not preferable. The tape-like laminate, fibrillated yarn, or composite fiber body to which the water-soluble resin is fused is brought into contact with the foam and then dried.

When the water-soluble resin comes into contact with the foam, the functional groups of the crosslinking agent in the foam react with carboxyl groups, sulfonic acid groups, or their salts in the water-soluble resin, resulting in a tape-like laminate, defibrated yarn, or composite fiber. A crosslinked product of the water-soluble resin is formed on the body, and this reaction is further promoted by the drying process.

At this time, when a low melting point synthetic resin having a carbinyl group or a carboxyl group is used, the reaction between these groups and the functional group in the crosslinking agent occurs simultaneously.

FIG. 3 shows an example of a yarn in which the crosslinked product is fused, and the crosslinked product 3 is attached to the surface of the low melting point synthetic resin layer 2.

Note that the temperature of the drying process varies depending on the type of tape-like layer, defibrated yarn or composite fiber used, the type and amount of water-soluble resin attached, the expansion ratio, the amount of crosslinking agent added, etc. Considering the characteristic values of the water-absorbing composite, the temperature may generally be lower than 120°C. Although the drying time cannot be determined unconditionally depending on the temperature, etc., generally 1 to 10 minutes, preferably 2 to 6 minutes, is sufficient since the amount of moisture attached is small. In addition to the continuous drying method, a patch drying method can also be used as the drying process.

The water-absorbing composite obtained through the above-mentioned processes is used, for example, in the production of nonwoven fabrics.

First, a fibrillated yarn is produced from a tape-like laminate in which the crosslinked product is fused using a splint roll or the like. The fused fibrillated yarns and composite fibers of this cross-linked product are made into short fibers using a combing roll, etc., and the short fibers are deposited on a screen net by suction using a pacuum to form a web, and this web is heated and rolled. A sheet-like nonwoven fabric can be obtained by heat-compression bonding by passing it through a cloth or the like.

This nonwoven fabric has high water absorption performance and elasticity, and is suitable for use as water retaining sheets for agriculture and horticulture, dewatering materials for civil engineering and various industries, sanitary materials, and other uses.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

In addition, the water absorption capacity of the obtained water absorbent composite was measured at 11
Immerse 1150d of the water-absorbent composite of No. 1 in distilled water for 5 minutes,
Thereafter, the mixture was poured onto the second wire mesh and JK Wynomer 150-8 (Terash), drained for 10 minutes, and the amount of water flowing out was calculated using the formula below.

Example 1 After forming a three-layer blown film with the following composition and treatment, the film was slit as shown below, stretched with a hot roll, and split with a splint roll to obtain a fibrillated yarn.

Outermost layer screw diameter 40■φ Cylinder temperature C4: 170℃C2: 190
°C CS: 200 °C L-LDPE (linear low density, j? IJ ethylene, density 0, 920 g 7cm5, MFR3, O,!i'
/10 minutes, melting point 120°C) PACE ER resin (maleic anhydride grafting rate 0.35% by weight, melting point 122°C) was melt extruded.

Intermediate layer screw diameter 65+m++φ Cylinder temperature C1: 180℃C2: 200℃ C5: 210℃ PP (crystalline polypropylene, density 0.901/cm'
, MFR 3.0g 710 minutes, melting point 160°C) was melt extruded.

Innermost layer Screw diameter 40mm φ Other conditions are the same as for the outermost layer.

After taking off a three-layer blown film with thicknesses of ER resin layer (20μ)/PP layer (10μ)/ER resin layer (20μ) at a grip of 1.21 and a take-up speed of 31.5m/min, the film was rolled to the tape width. After slitting it into 40 pieces and stretching it in the longitudinal direction at a stretching roll temperature of 103°C and a stretching magnification of 5 times, (
3012 denier) Split width 0.07 with splint roll
It was defibrated to 11111. The defibrated yarn had a denier of 3012.

A water-soluble resin powder was applied to the resulting fibrillated yarn using the apparatus shown in FIG. 1, and then crosslinked.

That is, the defibrated yarn 4 was first coated with a charging coating machine (electrostatic powder coating machine, manufactured by Nippon Landspurg ■, 721AP unit).
Sent to 5th. This charging coating machine 5 has a footing tank 6.
It consists of a coating gun 8 that uniformly sprays the water-soluble resin powder 7 and a storage tank 9 for the water-soluble resin powder 7. Acid soda powder was used.

This charging coating machine 5 was operated under the conditions of a gun generation voltage of 70 kV and an air flow rate of 10 Nm3/hour, and the coating gun 8 sprayed and adhered the sodium polyacrylate powder onto the fibrillated yarn 4. The amount of adhesion is 4% relative to the weight of the defibrated yarn.
It was 5% by weight. Note that the traveling speed of the defibrated yarn 4 is 3 m.
It was 7 minutes. With this operation, the surface of the ER resin layer of the defibrated yarn 4 is brought into a state where the sodium polyacrylate powder is attached (because the powder itself is electrically charged).

The defibrated yarn 4' to which the sodium polyacrylate powder was adhered was then sent via a roll 10 to a heating device 11 where the heating air temperature was 130°C. This operation brings the surface of the ER resin layer into a molten state, and the sodium polyacrylate powder is more firmly fused to the surface of the gR resin layer.

Next, 4"
is a foam processing machine (FFT machine manufactured by Gaston and Calanti) 12
Sent to. This foam processing machine 12 sends a mixed aqueous solution 13 of a crosslinking agent, a foaming agent, a softening agent, and water to a foaming machine 15 via a liquid feed pump 14, and also sends air to the foaming machine 15 via a compressor 16. The foam 17 comes out from the foaming machine 15 through a hose 18 onto a trumpet-shaped device 19.

The above mixed aqueous solution contains 100 parts by weight of water, ethylene glycol diglycidyl ether (crosslinking agent, Dinacol EX-3),
13) It was prepared by mixing 0.01 part by weight, 0.5 part by weight of a foaming agent (nonionic surfactant, Mayforma F210, manufactured by Meiho Kagaku Co., Ltd.), and 0.1 part by weight of glycerin. Further, the operating conditions for the foam processing machine 12 are as follows: the rotation speed of the foaming machine 15 is 90;
Orpm, liquid feeding amount 75 g/min, air amount 1.011 min, and foaming ratio 11.6 times.

The foam processing machine 12 brings the sodium polyacrylate powder on the ER resin layer into contact with the foam 17, and the crosslinking process begins. The defibrated yarn 4'' in this state is then placed in a dryer 20 at a temperature of 120°C.
The defibrated yarn 4'' was guided in a zigzag manner by the guide roll 21, dried for 3 minutes in the dryer, and finally wound around the depin 22.

Table 1 shows the properties of the obtained water absorbent composite.

Example 2 The three-layer blown film obtained in Example 1 (E
R resin layer 20μ/PP layer 10μ/ER resin layer 20μ) were slit to make a tape with a width of 40mm, and this tape was stretched 5 times in the longitudinal direction at a stretching roll temperature of 103°C to obtain 3012
Got denier tape. This tape was opened to a split width of 0.07 using a slit roll. The defibrated yarn had a denier of 3012. Next, the fiber was applied to a gold crimper machine (OKK Turbo DC crimper manufactured by Osaka Kiko) at a speed of 12 m.
It was operated under the conditions of 0.4'Q/min and a pressure of 0.4'Q/cm to obtain a Clinnota defibrated yarn having 13 defibrated yarns/inch. This defibrated yarn was sent to the charging coating machine 5 in the same manner as in Example 1, and sodium polyacrylate powder was adhered to the surface of the ER resin layer (adhesion amount: 40% by weight). Foam processing and drying were performed. The obtained water-absorbent composite had an excellent texture, and its characteristic values are shown in Table 1.

Example 3 The amount of air in the foam processing machine 12 is 0.81! /min, liquid flow rate 150
．． A water-absorbing composite was obtained in the same manner as in Example 1, except that the foaming rate was 9/min, the foaming ratio was 8 times, and the drying time in the final step was 5 minutes. Its characteristic values are shown in Table 1.

Comparative example 1 Foam processing 8! The defibrated yarn with sodium acrylate fused to it is added to the unfoamed mixed aqueous solution without using it at all, and the fused yarn is fused as described above. A water-absorbing composite was obtained in the same manner as in Example 1, except that the sodium acrylate was crosslinked and the drying was performed at 120° C. for 60 minutes. The results are shown in Table 1.

In addition, when drying was carried out at 120° C. for 3 minutes in the above, water remained in the obtained water absorbent composite and the surface thereof was sticky.

〔Effect of the invention〕

As described above, the water-absorbent composite produced by the production method of the present invention not only has superior water-absorption performance and tensile strength compared to conventional ones, but also is easy to handle and manufacture, and is made using water-soluble resin. There is also less waste. Since foam of an aqueous solution containing a crosslinking agent is used for the crosslinking treatment of the water-soluble resin, drying can be carried out at a low temperature for a short period of time, and costs can be reduced.

Therefore, the water-absorbing composite according to the present invention is useful as a waterproof coating material for conductive cables, water retaining trunks for agriculture and horticulture, various water-stopping materials for civil engineering and construction, dewatering materials for various industries, sanitary materials, and other materials. be.

[Brief explanation of the drawing]

FIG. 1 is a flowchart adopted in an embodiment of the present invention, FIG. 2 is a cross-sectional view showing an example of a composite defibrated yarn, and FIG. 3 is a cross-sectional view showing an example of a composite defibrated yarn obtained by the present invention. It is a front view. DESCRIPTION OF SYMBOLS 1...High melting point synthetic resin layer, 2...Low melting point synthetic resin bump, 3...Crosslinked product, 4...Fibrated thread, 5...Charging coating machine, 7...Water-soluble Resin powder, 11... Heating device, 12... Foam processing machine, 13... Mixed aqueous solution,
15... Foaming machine, 20... Dryer.

Claims (2)

[Claims] (1) A tape-shaped laminate consisting of at least one layer of high-melting point synthetic resin and at least one layer of low-melting point synthetic resin, in which the layer of low-melting point synthetic resin is exposed on at least a part of the surface; A tape-shaped laminate consisting of fibrillated yarn or composite fibers obtained by splitting a laminate, in which a water-soluble resin powder is fused to the outer surface of a low-melting synthetic resin layer exposed on the surface, or a tape-shaped laminate obtained by splitting the same. The water-soluble resin of the defibrated yarn or composite fiber body obtained by this process is brought into contact with an aqueous solution containing a crosslinking agent, a foaming agent, and water as main components in a foamed state, and the water-soluble resin is crosslinked, and then dried. A method for producing a water-absorbing composite, characterized by: (2) Claim No. 1, wherein the aqueous solution containing the crosslinking agent, foaming agent, and water as main components has a foaming ratio of 5 to 18 times.
2. Method for producing a water-absorbing composite as described in Section 1. (3) The method for producing a water-absorbing composite according to claim (1) or (2), wherein the foaming agent is an anionic or nonionic surfactant.