JPH01156578A - Production of water absorbable composite - Google Patents

Abstract

PURPOSE: To produce an excellent water absorbent composite having a high mechanical strength by fusing a water-soluble resin powder to the other surface of a low-melting layer such as a tapelike laminate comprising a high-melting and a low-melting synthetic resin layers and then carrying out a cross-linking treatment of the water-soluble resin. CONSTITUTION: A tapelike laminate comprising a layer 2 of, e.g. a high-melting synthetic resin (e.g. a crystalline polypropylene) and a layer 3 of a low-melting synthetic resin (e.g. a polyolefin graft modified with an unsaturated carboxylic acid) and exposing the low-melting layer to the surface e.g. laminated three layers of the low-melting/high-melting/low-melting layers or an opened yarn or a composite fiber material prepared by splitting the laminate is prepared and heated at a temperature in the vicinity of the melting point of the low- melting resin to fuse a water-soluble resin fine powder (e.g. polyacrylic acid and its copolymer) to the outer surface of the low-melting layer exposed to the surface with an electrostatic charge coating machine. The water-soluble resin is subsequently subjected to a cross-linking reaction with a cross-linking agent (e.g. sorbitol polyglycidyl ether) to afford a water absorbent composite having high water absorbing performances.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing a water-absorbing composite mainly composed of a thermoplastic synthetic resin, and more particularly to a method for producing a water-absorbing composite composed of a thermoplastic synthetic resin. A water-absorbing composite material that has important uses as a waterproof coating material for conductive cables, water-retaining sheets for agriculture and horticulture, various water-stopping materials for civil engineering and construction, dehydration materials for various industries, sanitary materials, medical materials, etc. Relating to a manufacturing method.

[Conventional technology]

Waterproof covering materials using water-absorbing or water-retaining materials have been used in many fields.

For example, in so-called conductive cables such as telecommunication cables and original communication cables, the 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. There is.

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 polypropylene split fibers impregnated with polyethylene glycol and paper impregnated with diethylene glycol.

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

In addition, the surface of a single-layer polyolefin fibrillated yarn is melted, 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 do not lose their stretching effect when the stretched fibers are melted, cannot withstand stress such as tension during cable facility work, and are easily damaged. There is also a problem with the amount of fusion.

On the other hand, we also tried a method of melting the surface of a multilayer polyolefin fibrillated yarn and then passing it through a container filled with fine powder of a polymeric water absorbing agent to fuse the fine powder of the polymeric water absorbing agent. It is being However, while this method has good tensile strength and water absorption capacity, it has the disadvantage that it is difficult to control the amount of fused fine powder of the polymeric water absorbing agent.

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

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for producing a water-absorbing composite that has higher water-absorbing performance and good mechanical strength than ever before.

[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, the layer of low melting point synthetic resin is on at least a part of the surface. The exposed tape-like laminate or a defibrated yarn or composite fiber body obtained by splitting the exposed tape-like laminate is produced, and the laminate, defibrated yarn, or composite fiber body is heated to near the melting point of the low-melting point synthetic resin. Then, the water-soluble resin powder is fused to the outer surface of the exposed low-melting point synthetic resin layer using a charging coating machine, or the water-soluble resin powder is applied to the laminate, fibrillated yarn, or composite fiber body using a charging coating machine. After adhering, the laminate, fibrillated yarn or composite fiber body is heated to near the melting point of the low melting point synthetic resin to fuse the water-soluble resin powder to the outer surface of the exposed low melting point synthetic resin layer, Next, the fused water-soluble resin is brought into contact with a crosslinking agent to crosslink the water-soluble resin, and is further dried.

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

In the present invention, first, the tape-shaped laminate is made 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 is exposed on at least a portion of the surface. It is necessary to produce a fiber body or a fibrillated yarn or a composite fiber body obtained by splitting the fiber body.

The tape-like laminate can be produced by co-extruding a high-melting point synthetic resin and a low-melting point synthetic resin to form a film-like laminate, or by a lamination method using a high-melting point synthetic resin and a low-melting point synthetic resin. Then, the film-like laminate is slit into a predetermined narrow width and stretched in the longitudinal direction, or the film-like laminate is stretched in the longitudinal direction and then slit into a predetermined narrow width, and the thickness of the tape is 500-10. 000 denier, particularly in the range of 1,000 to 4,000 denier.

The fibrillated yarn is made by applying the above tape-like laminate to a net shape by applying it to a splint roll, and making it completely fibrous.
The single yarn width is preferably 0.03 to 0.2 cm, more preferably 0.03 to 0.11 cm, and most preferably 0.603 cm.
~0.07■. If the splitting width of the single filament of the fibrillated yarn exceeds 0.2 square centimeters, the amount of adhesion or fusion of the water-soluble resin powder described below will be small, and the resulting water-absorbing composite will have poor texture.

Moreover, if the splitting width is less than 0.03 square meters, it is difficult to split.

The fibrillated yarn has a denier of 500 to IO,000, especially 1,0
It is possible to use the yarn bundle with a thickness of 0.4,000 denier as it is.

In addition, as a preferable example of the film-like laminate used for manufacturing the tape-like laminate and the defibrated yarn, a two-layer laminate of a high melting point synthetic resin layer/low melting point synthetic resin layer (hereinafter abbreviated as high/low) is preferred. , a low/high/low three-layer laminate and a low/high/low/high/low five-layer laminate.

Next, the composite fiber body is a side-pie-side type conjugate fiber of a high-melting point synthetic resin and a low-melting point synthetic resin, or a cis-core conjugate fiber with a high-melting point synthetic resin as a core and a low-melting point synthetic resin as a sheath. υ is created by spinning and drawing it. The fineness of the single yarn is preferably in the range of 10 to 60 deniers.

The number of synthetic resin layers in the tape-like laminate, 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. It is preferable that the difference in melting point between the synthetic resin and the low melting point synthetic resin be large, and it is generally desirable that the difference is 10° C. or higher.

However, for synthetic resins whose melting points appear sharply, the difference in melting points may be small.

In the present invention, thermoplastic resins such as crystalline polypropylene, high density polyethylene, polyester, nylon 6 and nylon 66 are generally used as the high melting point synthetic resin.

Furthermore, as the low melting point synthetic resin, one that exhibits good bonding properties with the high melting point synthetic resin is used. Specific examples include polyolefins such as low-density polyethylene, linear low-density polyethylene, high-density polyethylene, and polypropylene; unsaturated carmenic acids such as maleic acid, fumaric acid, itaconic acid, maleic anhydride, and itaconic anhydride; Polyolefins graft-modified with anhydride (ER resins, particularly graft-modified products of high-density polyethylene and linear low-density polyethylene are preferred, the grafting ratio is 0.3
~0.36 weight coefficient is preferable); ethylene-maleic anhydride-methyl methacrylate terpolymer (ET resin)
, ethylene-7 acrylate or methacrylate copolymers, such as ethylene-acrylic acid copolymer (FAA resin), ethylene-ethyl acrylate copolymer (IJA resin);
Examples include thermoplastic resins (ionomer resins) partially neutralized with metals such as zinc. Among these low melting point synthetic resins, thermoplastic resins having a carbonyl group or a xyl group are particularly preferred. This is because if such a low melting point synthetic resin is used, when crosslinking the water soluble resin described below, the crosslinking agent will react with the water soluble resin and also react with the above functional groups in the low melting point synthetic resin. This is because the bond between the crosslinked water-soluble resin and the low-melting point synthetic resin can be strengthened and the crosslinked product can be prevented from falling off.

A preferred combination of high melting point synthetic resin and low melting point synthetic resin in the present invention is as follows.

Combination of crystalline polypropylene and acid-grafted linear low-density ethylene, combination of crystalline polyzolopylene and acid-grafted modified high-density ethylene, crystalline polypropylene and ethylene-maleic anhydride-methyl methacrylate terpolymer and combinations of crystalline polypropylene and ionomer resins.

Now, after manufacturing the tape-like laminate or the fibrillated yarn or composite fibrous body obtained by splitting the tape-like laminate as described above,
Next, a water-soluble resin powder is fused to the outer surface of the low-melting point synthetic resin layer exposed on the surface of the tape-like laminate, defibrated yarn, or composite fiber. There are two ways to do this.

One method is to first heat the tape-shaped laminate, fibrillated yarn, or composite fiber body to near the melting point of the low-melting synthetic resin, and then use a charging coating machine to expose the water-soluble resin powder on the surface of the low-melting synthetic resin. One method is to fuse it to the outer surface of the layer, and the other is to apply water-soluble resin powder to the tape-like laminate, defibrated yarn, or composite fiber using a charged coating machine, and then apply the water-soluble resin powder to the laminate or composite fiber. This is a method in which the fibrillated yarn or composite fiber body is heated to near the melting point of the low-melting synthetic resin, and the water-soluble resin is fused to the outer surface of the exposed low-melting synthetic resin layer. No matter which method is used, the water-soluble resin powder is uniformly fused to the outer surface of the low-melting point synthetic resin layer exposed on the surface of the tape-like laminate, defibrated yarn, or composite fiber, and the water-soluble resin powder is simply fused. The bond between the two becomes stronger than when they are attached or fused together.

However, in the above two methods, only the low melting point synthetic resin is melted by heating, and the high melting point synthetic resin does not undergo much change due to heating, so the stretched tape-shaped laminate , fibrillated yarns, and composite fibers do not lose their blended state and can maintain good tensile strength.

The water-soluble resin powder used in the present invention has a xyl group,
Powders of water-soluble polymers having sulfonic acid groups or their salts, specific examples include polyacrylic acid and its copolymers, polyacrylates, polyacrylamide partial hydrolysates, polystyrene sulfonic acids, polystyrene, etc. It is a powder of acrylamide propane sulfonic acid and its copolymer.

The average particle diameter is preferably as small as possible so that the exposed surface of the low melting point synthetic resin layer of the tape-shaped laminate, defibrated yarn or composite fiber can be coated as densely as possible. Generally the average particle size is lO~500μ, preferably lO~3
00μ, preferably in the range of 10 to 50μ. If the average particle size exceeds 500μ, not only will the water-soluble resin powder not form a dense coating, but the surface texture of the target water-absorbing composite will deteriorate. Furthermore, if the average particle size is less than 104, it is difficult to produce and handle the water-soluble resin powder, and the price is high. The amount of the water-soluble resin powder adhered or fused is suitably 10 to 60% by weight relative to the weight of the tape-like laminate, fibrillated yarn, or composite fiber. If the amount of adhesion or fusion is less than the 1O weight ratio, sufficient water absorption cannot be obtained, and if it exceeds 60 weight range, the surface is not a bad stain, and when rubbed, the water-soluble resin is removed. There is a problem with it falling off.

In the present invention, as described above, a charged coating machine is used for adhering or fusing the water-soluble resin powder.

This has the function of generating a corona discharge in a space, positively or negatively charging water-soluble resin powder in that space, and injecting it onto a tape-shaped laminate, defibrated yarn, or composite fiber body using pressurized air. Among them, 70k
An electrostatic powder coating machine that has a gun that uses a high voltage around V, has two or more electrodes inside the gun and at the outlet, and uses the voltage difference between these electrodes to generate an electric field to charge water-soluble resin powder. is preferred. The charged coating machine not only automatically attaches the water-soluble resin powder, but also allows the powder to be applied very uniformly onto the tape-shaped laminate, defibrated yarn, or composite fiber by the Coulomb suction force. It has the advantage that it can be attached or fused to the surface of the substrate, and that the amount of attachment or fusion can be freely controlled.

The tape-shaped laminate, defibrated yarn or composite fiber body to which water-soluble resin powder has been fused in the previous process is then sent to a crosslinking process,
The fused water-soluble resin is crosslinked.

In this crosslinking treatment, an aqueous solution of a crosslinking agent is usually used. This aqueous solution may be brought into contact with the water-soluble resin, but
As a method for carrying out this method, for example, an oiling method using an oiling roll is preferred.

The crosslinking agent used in the present invention must have 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 must be water-soluble. You can use any of them if you have them. Typical examples of such crosslinking agents include polyfunctional crosslinkers such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, etc. Examples include epoxy compounds. These crosslinking agents are preferably used in the form of an aqueous solution in order to facilitate the reaction with carboxyl groups, sulfonic acid groups, or their salts in the water-soluble resin and to make the crosslinking density uniform.

The amount of crosslinking agent to be used is 0.0% based on the weight of the water-soluble resin.
It is preferable that the weight ratio is 01 to 2. If the amount of the crosslinking agent used is less than 0.01 weight range, the degree of crosslinking will be low, and sufficient water absorption performance will not be obtained, resulting in dissolution.

Furthermore, if the amount of crosslinking agent used is more than 2 parts by weight, the degree of crosslinking will be too high and the water absorption capacity will be insufficient.

The crosslinked tape-like laminate, defibrated yarn or composite fiber body is then sent to a drying process.

In this drying step or before being transferred to the drying step, the carboxyl groups, sulfonic acid groups, or their salts in the water-soluble resin react with the functional groups in the crosslinking agent to form a tape-like laminate, defibrated yarn, or A crosslinked product of water-soluble resin is formed on the composite fiber body.

At this time, if a low melting point synthetic resin having a cartenyl group or a carboxyl group is used, these functional groups and the functional group in the crosslinking agent will react simultaneously, resulting in a crosslinked product of the water-soluble resin and a low melting point synthetic resin. The bond with the melting point synthetic resin becomes very strong and the crosslinked product is prevented from falling off.

The drying temperature is not limited unless it is particularly high, and generally depends on the type of tape-shaped laminate, defibrated yarn or composite fiber, the type and amount of water-soluble resin attached, the type and amount of crosslinking agent added, etc. Although it cannot be determined, if the drying time is particularly long, such as 1 hour or more, the temperature is preferably 120° C. or lower.

Further, when the drying temperature is relatively high, such as around 200° C., the drying time may be shortened.

As described above, the drying time also varies depending on the drying temperature, etc., but generally the passage time in the dryer is in the range of 4 to 10 minutes, preferably 6 to 9 minutes.

The drying method is not limited to a continuous drying method, and a patch drying method can also be adopted.

A water-absorbing composite is obtained through the above steps, and this water-absorbing composite is used, for example, in the production of nonwoven fabrics.

First, the tape-like laminate to which the cross-linked product is attached is passed through a split roll or the like to form fibrillated yarns.

The defibrated yarn or composite fiber body to which the cross-linked material has been adhered is made into short fibers by 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 placed on a hot roll, etc. A sheet-like nonwoven fabric is obtained by thermocompression bonding. This nonwoven fabric has high water absorption, elasticity, and mechanical strength, and is suitable, for example, as a variety of water supply materials for civil engineering and construction, and as a water retaining sheet for agriculture and horticulture.

〔Example〕

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

The water absorption capacity of the obtained water-absorbing composite was measured using Il
1 of the water-absorbing composite was immersed in 150 d of distilled water for 5 minutes,
After that, the 21st wire mesh and JK Kwai 150-8
Pour it on top of (Terash) and drain for 10 minutes,
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, this film was slit as shown below, stretched with a hot roll, and split with a sugerite roll to obtain a fibrillated yarn. Ta.

Outermost layer screw diameter 40■φ Cylinder temperature C1: 170℃ C2: 190℃ C,: 200℃ L-LDPE (Linear low density polyethylene, density 0
．． 92011/cm3, MFR 3.0y/lO min, melting point 120''C) base ER resin (maleic anhydride graft ratio 0.35 weight ratio, melting point 122°C) was melt extruded.

Intermediate layer screw diameter 65+wφ Cylinder temperature C1: 180℃ C,: 200℃ C3: 210℃ pp (crystalline polypropylene, density 0.90177cm
”, MFR 3.0#/10 minutes, melting point 160°C) was melt extruded.

innermost layer Screw diameter 40wmφ Other conditions are the same as for the outermost layer.

The die ridge was 1.2 wm, the take-up speed was 31.5 m/min, and the thickness was ER resin layer (20μ)/PP layer (10μ)/
After taking the three-layer blown film of the ER tree JIIi layer (20 μ), the film was slit into a tape width of 40 m, stretched in the longitudinal direction at a stretching roll temperature of 103°C and a stretching ratio of 5 times (3012 denier), and split with a split roll. It was defibrated to a width of 0.07 m5. The defibrated yarn had a denier of 3012.

The cross-sectional structure is schematically shown in Figure 2.
It is a composite structure consisting of an ER resin layer 3, a pp layer 2, and an ER resin layer 3.

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

That is, the defibrated yarn 1 was first sent to a charging coating machine (electrostatic powder coating machine, 721AP unit, manufactured by Nippon Landsparg Co., Ltd.) 5. This charging coating machine 5 is equipped with a coating tank 6, a gun 7, and a water-soluble resin powder storage tank 8, and has a function of charging the water-soluble resin powder by corona discharge and injecting it onto the defibrated yarn 1 using pressurized air. are doing.

The charging coating machine 5 was operated under conditions of a gun generation voltage of 70 kV and an air flow rate of 10 Nm'/hour, and the gun 7 applied sodium polyacrylate powder with an average particle size of about 50 μm as a water-soluble resin powder onto the fibrillated yarn 1. It erupted.

Note that the traveling speed of the defibrated yarn 1 was 3 m and 7 minutes.

With this operation, the surface of the KR resin layer of the defibrated yarn 1 was brought into a state where the sodium polyacrylate powder was adhered. The adhesion amount is 45
He was in charge of weight. Next, the defibrated thread l′ to which the powder has adhered is
was sent to a heating device 9 in which heated air at 130° C. was circulated. This operation brings the surface of the ER resin layer into a molten state, and the sodium polyacrylate powder is more firmly fused thereto.

Next, a fibrillated yarn I to which polyacrylic acid soda powder was fused
N is sent to the crosslinking treatment device 10, and the concentration is 0. An aqueous solution of ethylene glycol diglycidyl ether having a weight ratio of O1 was oiled onto the defibrated yarn l'' while maintaining the rotational speed of the oiling roll 11 at lrpm.

The amount of oiling is 0.0% based on the weight of sodium polyacrylate. I was in charge of O1 weight.

This cross-linked defibrated yarn 1'' was then heated to a temperature of 200°C.
(to a dryer 12) and rolls 13 for 8 minutes in a zigzag pattern for drying, and finally wound onto a bobbin 14.

The schematic cross-sectional structure of the obtained water-absorbent composite is shown in FIG. It was done. The properties of the water absorbent composite are shown in Table 1.

Example 2 A water-absorbing composite was produced in the same manner as in Example 1, except that the amount of air in the charging coating machine was 5 Nm37, and the amount of sodium polyacrylate powder deposited was 20 weight range. Its characteristics are shown in Table 1.

Example 3 A two-layer conjugate fiber body of side-pie-side disk was spun with the following composition and treatment.

Side 1 Screw diameter 40mm Cylinder temperature at 170℃, 24
0℃ Cs 230℃ L-LDPE (linear low density polyethylene, density 0.9
18117cm3, MFR9,0,9/10min, melting point
120℃）Page, ERm n (Maleic anhydride graft ratio 0.35 weight ratio, melting point 122℃) Side 2 Screw diameter 40■φ Cylinder temperature CI 180℃c, 24
0℃ cs 270℃ pp (crystalline polypropylene, density 0.901/cr
m", MFR10II/10 minutes, melting point 162℃) ER resin and PP were subjected to draft 100 from a nozzle with a hole diameter of 1.0mm.
Composite spinning was performed. The ratio of ER resin and pp is 50:50 (
weight ratio). Next, the stretching roll temperature was 130°C,
Stretching was carried out at a stretching ratio of 2 to obtain 760 composite fibers having a fineness of 3020 denier.

This composite fiber body was supplied to the apparatus shown in FIG. 1, and a water-absorbing composite was obtained in the same manner as in Example 1, except that the amount of sodium polyacrylate powder attached was 35% by weight.

Its characteristics are shown in Table 1.

*rf! Amount of sodium lyacrylate attached*Amount of ethylene glycol diglycidyl ether added [Effects of the invention] As described above, the water-absorbing composite produced by the method of the present invention has a superior water absorption ratio compared to the conventional one. It also has good tensile strength and is easier to handle than impregnated ones. Moreover, it has the advantage that the crosslinked material of the water-soluble resin can be uniformly adhered by a simple means, there is little wastage of the water-soluble resin during production, and costs can be reduced.

Therefore, this water-absorbing composite is extremely useful as a waterproof covering material for conductive cables, and is also an important material for water-retaining sheets for agriculture and horticulture, water-stopping materials for civil engineering and construction, dewatering materials for various industries, sanitary materials, etc. It has a purpose.

[Brief explanation of the drawing]

FIG. 1 is a flowchart adopted in one embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of a defibrated yarn used in the same embodiment,
FIG. 3 is a schematic cross-sectional view of a water-absorbing composite obtained by the same example. DESCRIPTION OF SYMBOLS 1... Defibrated yarn, 2... PP layer, 3... ER resin layer, 4... Crosslinked product, 5... Charged coating machine, 7
... gun, 9 ... heating device, 10 ... crosslinking treatment device, 11 ... oiling roll, 12 ... dryer,
l 4...Bohin.

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, or the same. The laminate, the fibrillated yarn, or the composite fiber body is heated to near the melting point of the low-melting point synthetic resin, and then a water-soluble resin powder is coated with a charged coating machine. Either by fusing the outer surface of the low melting point synthetic resin layer exposed on the surface, or by attaching water-soluble resin powder to the laminate, fibrillated yarn or composite fiber body using a charged coating machine, and then applying the laminate or fibrillation. The thread or composite fiber body is heated to near the melting point of the low melting point synthetic resin to fuse the water soluble resin powder to the outer surface of the exposed low melting point synthetic resin layer, and then a crosslinking agent is applied to the fused water soluble resin. 1. A method for producing a water-absorbing composite, which comprises cross-linking a water-soluble resin by contacting with a water-soluble resin, and further drying the water-soluble resin. (2) The charging coating machine has a function of positively or negatively charging water-soluble resin powder by corona discharge, and spraying it onto a tape-shaped laminate, defibrated yarn, or composite fiber body using pressurized air. A method for producing a water-absorbing composite according to scope (1).