JPH07278342A - Production of water-absorbing composite material - Google Patents

Abstract

PURPOSE:To provide a water-absorbing composite material resistant to the change of dimension, feeling, color, etc., with time and having soft texture, low residual monomer content and high quality by a specific method from raw materials consisting of a foamed material and an aqueous solution of a monomer containing an acid group-containing monomer as an essential monomer component. CONSTITUTION:This composite material is produced by preparing an aqueous solution of a monomer component containing an acid-group containing monomer [preferably acrylic acid(salt)] as essential component, adjusting the pH of the solution to 6-8, applying the solution to a foamed material (preferably a spongy substrate such as polyurethane sponge) preferably at a ratio of 1-1,000 pts.wt. of the monomer component based on 100 pts.wt. of the foamed material, in terms of solid and finally polymerizing the monomer component. The polymerization is carried out preferably by adding a polymerization initiator to the aqueous solution of the monomer component and thermally polymerizing the monomer. The polymerization initiator is preferably a combination of an oxidative polymerization initiator such as sodium persulfate and an azo-type polymerization initiator such as 2,2'-azobis(2-amidinopropane) dihydrochloride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-absorbent composite, and more specifically, it is a high-quality water-absorbing material which is small in changes in size, texture, and color over time, is flexible, and has little residual monomer. The present invention relates to a method for producing a sexual complex.

[0002]

2. Description of the Related Art In recent years, water-absorbing polymers having a high water-absorbing ability have been widely used in paper diapers for sanitary goods, sanitary napkins, meat and seafood drip absorbers for food, water retention agents in the field of agriculture and horticulture. It has also come to be used as a civil engineering material or a building material. However, these conventionally used water-absorbing polymers have a problem in handling because the shape of the water-absorbing polymer has a high water-absorbing property and is in the form of powder. There was a problem of lowering it.

In order to solve these problems, various methods for producing a water-absorbent composite in which a water-absorbent polymer and a base material such as a nonwoven fabric are integrated have been proposed so far. For example, Japanese Patent Application Laid-Open No. 62-22810 discloses a method for producing a water-absorbing complex, which comprises subjecting a fibrous substrate to an aqueous solution of acrylic acid or an acrylic acid monomer and then thermally polymerizing the same with a radical polymerization initiator. There is. Also, JP-A-63-10
Japanese Patent No. 5044 discloses a method for producing a water-absorbing composite material in which a mixed aqueous solution of acrylic acid and an acrylic acid salt that is converted into a water-absorbing polymer by polymerization is applied to a flexible sheet and then polymerized and cured by electron beam irradiation. .

However, in particular, in a water-absorbent composite obtained by polymerizing the monomer after applying an aqueous solution of the monomer to the base material, the water-absorbent composite obtained yellows with time and changes its color. There was a problem that the size also shrinks, the initial soft texture becomes stiff and brittle, and the quality is remarkably deteriorated. For example, in the example of JP-A-63-105044, a mixed aqueous solution of acrylic acid monomer and sodium acrylate monomer in a molar ratio of 20:80 (neutralization rate 80 mol%; pH value of aqueous monomer solution) is used. 5.
A water-absorbent composite obtained by impregnating 6) into a polyurethane sponge and then polymerizing and curing it by irradiating with an electron beam is shown. The water-absorbing composite obtained by this method deteriorates with time as described above. Was caused, and the quality was remarkably deteriorated, which was not preferable when applied to various applications.

[0005]

The present invention is to solve the above problems. Therefore, an object of the present invention is to provide a method for producing a high-quality water-absorbent composite which is less likely to change in size, texture, and color with time, is flexible, and has less residual monomer.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors on a method for solving the above-mentioned problems, it has been found that an aqueous solution of a monomer component containing an acid group-containing monomer as an essential component has a specific pH value. After adjusting to, and applying this to the foam,
The inventors have found that a water-absorbent composite obtained by polymerizing the monomer component can solve the above-mentioned problems, and arrived at the present invention. That is, according to the present invention, an aqueous solution of a monomer component containing an acid group-containing monomer as an essential component is adjusted to have a pH value of 6 to 8, and this is applied to a foam, and then the monomer component is polymerized. The present invention provides a method for producing a characteristic water-absorbent composite.

The present invention will be described in detail below.

The method for producing a water-absorbing composite of the present invention is carried out by adjusting the pH of an aqueous solution of a monomer component which essentially contains an acid group-containing monomer.
It requires that the value be in the range 6-8. pH value is 6
A flexible polymer which is less likely to change in size, texture and color over time by polymerizing the monomer after polymerizing the aqueous solution of the monomer component, which essentially contains the acid group-containing monomer controlled to the range of 8 to 8. That is, a water-absorbent composite is obtained. or,
It is preferable to preliminarily include a polymerization initiator in the aqueous solution of the monomer component, and particularly to polymerize a monomer component containing an acid group-containing monomer as an essential component in combination with an oxidative polymerization initiator and an azo polymerization initiator. Thus, the amount of unpolymerized residual monomer can be significantly reduced.

The acid group-containing monomer used in the present invention is not particularly limited as long as it can be converted into a water absorbing polymer by polymerization. For example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid and their alkali metal salts or ammonium salts; 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropane Sulfonic acid,
Examples thereof include 2- (meth) acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, (meth) allylsulfonic acid, and alkali metal salts and ammonium salts thereof, and one or more of these may be mentioned. Can be used. Acrylic acid (salt) is preferred.

Further, the pH value of the aqueous solution of the monomer component is 6
It is also possible to use a monomer having no acid group such as acrylamide in an amount of 50 mol% or less with respect to the total monomer components as long as it is within the range of 8 to 8.

A compound having two or more ethylenically unsaturated groups in one molecule represented by methylenebisacrylamide, polyethylene glycol diacrylate, trimethylolpropane triacrylate and the like as a cross-linking agent in the above monomer. Can be added. The combined use of a cross-linking agent is preferable because it can improve the durability and shape retention of the resulting water-absorbent composite. The amount of the cross-linking agent used can be appropriately selected depending on the type of the above monomers and the polymerization conditions, but is generally in the range of 0.001 to 10 mol% (monomer containing an acid group), preferably 0.01 to 5 It is in the range of mol% (to the acid group-containing monomer).

If necessary, a polymerization initiator, a thickener, and other additives may be added to the above-mentioned aqueous solution of the monomer. Examples of other additives include ultraviolet absorbers, antifungal agents, flame retardants, moisture absorbents, and the like, which can impart new functions.

In the present invention, it is extremely necessary to adjust the pH value of the aqueous solution of the monomer component containing the above-mentioned acid group-containing monomer to the range of 6 to 8 in order to improve the quality of the water-absorbent composite obtained. is important.

When the pH value of the aqueous solution of the monomer component is out of the range of 6 to 8, deterioration of the sponge base material or the polymer is promoted at the time of polymerization or during storage / use of the product, the size of the product shrinks, and the texture becomes hard. It is not preferable because it becomes brittle and the color is yellowed. For example, p of the aqueous solution of the monomer component
When the H value exceeds 9, the resulting water-absorbent composite has a problem that the dimensional change is large and the quality of the water-absorbent composite is greatly deteriorated in terms of texture and color. Another advantage in the method for producing the water absorbent composite of the present invention is:
Since the pH value of the aqueous solution of the monomer component used is in the range of 6 to 8, the risk of chemical injury due to acid or alkali during the production of the water-absorbing complex can be reduced, and further the water-absorbing complex in the obtained water-absorbing complex can It is preferable because the amount of residual monomer can be reduced. In the present invention, the concentration of the acid group-containing monomer is preferably in the range of usually 10% by weight to the saturated concentration with respect to the aqueous solution of the monomer component containing the acid group-containing monomer as an essential component. From the viewpoint of the productivity of the composite, it is more preferably in the range of 30% by weight to the saturated aqueous solution concentration.

In the present invention, for example, when a 37% by weight aqueous solution of acrylic acid (sodium) is used as the monomer component, the neutralization ratio of the monomer is about 85 mol% in order to adjust the pH value of the aqueous monomer solution to 6-8. To 99.5 mol% must be prepared in a very narrow range. pH
It is not preferable that the value deviates from this range for the above reason. In the present invention, if the pH value falls within this range, citric acid, phosphoric acid and other pH adjusting agents can be added to the aqueous monomer solution.

The foam to which the aqueous solution of the monomer component of the present invention is applied is not particularly limited as long as it is a substrate to which the aqueous solution of the monomer component can be adhered, and it is an aggregate such as pumice stone, expanded styrene or expanded phenol. Examples thereof include foams such as resin and various sponge-like base materials. Above all, a sponge-like base material having an open cell structure having a high cushioning property and a large surface area is preferable. As the material forming the sponge-like base material of the present invention, either hydrophilic or hydrophobic can be used. For example,
Examples thereof include polyurethane sponge, polyethylene foam, polypropylene foam, rubber sponge, polyvinyl acetal-based sponge, and viscose sponge, and a composite of two or more of these may also be used. Further, the sponge-like base material colored or flame-retarded can also be used.

The method of applying the aqueous solution of the monomer component to the foam of the present invention is not particularly limited, but for example, a method of coating / printing, spraying or impregnating the aqueous solution of the monomer component on the foam in an aqueous solution state, etc. Allows the monomer to adhere to the substrate. If necessary, the amount of adhering monomer can be controlled by squeezing with a roller or the like after spraying / impregnation. Further, the amount of the aqueous solution of the monomer component attached to the foam is preferably in the range of 1 to 1000 parts by weight of the monomer component with respect to 100 parts by weight of the foam in terms of solid content.

The aqueous solution of the monomer component applied to the foam in this manner can be polymerized by a known means to obtain the water-absorbent composite of the present invention in which the water-absorbent polymer is directly fixed to the foam. As a method of polymerizing, for example,
A method using heat, light, radiation, ultraviolet rays, microwaves or the like can be adopted. Of these, thermal polymerization using a polymerization initiator is preferable from the characteristics of the water-absorbent composite obtained, and in this case, the polymerization can be further improved by including a polymerization initiator in the aqueous solution of the monomer component in advance. After the polymerization, if necessary, post-treatment such as heating, normal temperature or reduced pressure drying, high-humidity drying, rehydration drying, irradiation with electron beams, gamma rays, etc., addition treatment of oxidizing or reducing substances to remove residual monomers, etc. The quality may be further reduced to further improve the quality.

As the polymerization initiator contained in the aqueous solution of the monomer component of the present invention, a water-soluble or oxidizable or azo radical polymerization initiator which can be mixed and dispersed with water is preferable. Examples of the oxidative polymerization initiator include persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate; hydrogen peroxide; organic peroxides such as ditertiary butyl peroxide and acetyl peroxide. As the system polymerization initiator, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (N, N ′)
Dimethyleneisobutylamidine) dihydrochloride, 4,4'-
Examples thereof include azo compounds such as azobis (4-cyanovaleric acid).

In particular, it is preferable to use an oxidative polymerization initiator and an azo polymerization initiator in combination as the polymerization initiator, because the residual monomers in the obtained water-absorbing complex can be significantly reduced. By using the azo-based polymerization initiator and the oxidative polymerization initiator together, the polymerization in the initial stage of the polymerization can be rapidly started and the polymerization rate in the latter stage of the polymerization can be remarkably increased.

The amount of the oxidative polymerization initiator and the amount of the azo polymerization initiator used is 0.001 to 10 g / mole of each monomer.
The molar ratio is 0.01 to 0.01 from the viewpoint of polymerizability and safety.
5 g / mol is preferred. The amount of polymerization initiator is 0.001 each
When it is less than g / mol, the polymerizability of the monomer is lowered, and when it exceeds 10 g / mol, the polymerization initiator remains after the polymerization, which causes a problem in safety. Further, when the oxidizing polymerization initiator and the azo polymerization initiator are used in combination, the mixing ratio is 100 parts by weight of the oxidizing polymerization initiator and 100 parts by weight of the azo polymerization initiator.
The range of 1 part by weight to 1 part by weight is preferable, and when the proportion of the azo-based polymerization initiator is higher than this range, the resulting water-absorbent composite is not preferable because it becomes slimy when absorbing water.

If necessary, in addition to the combined use of these oxidative polymerization initiators and azo-based polymerization initiators, a plurality of the above-mentioned polymerization initiators may be used in combination or a reducing substance such as sulfite or L-ascorbic acid may be added. Redox polymerization may be performed.

The foam has an absorbing ability to rapidly absorb the liquid to be absorbed and a high heat insulating property in an open cell structure having a large surface area, and the water-absorbing polymer is directly fixed to the foam by polymerization. The water-absorbent composite of the present invention has both the water-absorbing and moisture-absorbing properties of the water-absorbing polymer and the properties of the foam. In particular, when a sponge-like base material is used as the foam, it is possible to obtain a water-absorbent composite having excellent cushioning properties, flexibility and texture. Therefore, even a liquid that is difficult to be absorbed by only a water-absorbing polymer such as blood can be quickly and abundantly absorbed, and is suitable for use in the field of hygiene and food. In addition, it is also used as a liquid leakage prevention material or packaging material that requires cushioning and water absorption,
From the viewpoint of heat insulation, it is also effective as an anti-condensation material for windows, press fits, containers, etc.

The water-absorbent composite obtained by the above-mentioned production method of the present invention can be further composited with a hydrophobic film or a heat insulating material or provided with a pressure-sensitive adhesive layer by a bonding agent, fusion bonding or the like,
You can design products according to your application.

[0025]

According to the production method of the present invention, by adjusting the pH value of the aqueous solution of the monomer component, which essentially contains the acid group-containing monomer, within the range of 6 to 8, it is possible to prevent acid generation during polymerization or during storage and use of the product. Or it can prevent the deterioration of the foam or polymer due to alkali, and there is no dimensional change of the product over time,
It is possible to obtain a high-quality water-absorbent composite which retains a soft texture and is excellent in storage stability without discoloration.

Further, the foamed product obtained by applying the aqueous solution of the monomer has characteristics such as absorption performance and high heat insulating property for rapidly absorbing the liquid to be absorbed in the open cell structure having high cushioning property and large surface area, The water-absorbent composite of the present invention, in which the foam and the water-absorbent polymer are directly adhered and integrated, has both the water-absorbing and moisture-absorbing characteristics of the water-absorbing polymer and the characteristics of the foam. In particular, when a sponge-like base material is used as the foam, it is possible to obtain a water-absorbent composite having excellent cushioning properties, flexibility and texture. Therefore, due to its heat insulating and absorbing effects, the water-absorbent composite can prevent dew condensation and can quickly absorb even a liquid that is difficult to absorb only with water-absorbing polymers such as blood.

Furthermore, the combined use of an oxidative polymerization initiator and an azo polymerization initiator as the polymerization initiator contained in the aqueous monomer solution can significantly reduce the residual monomers in the obtained water-absorbing complex. It is possible to provide a water absorbent composite having excellent stability over time.

[0028]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

The water absorption amount, residual monomer amount and dimensional change rate described in the examples were measured by the following methods.

(Water absorption amount) A dry sample of the water-absorbent composite cut into 5 * 5 cm was added to 100 ml of ion-exchanged water.
It was placed in a 20 ml beaker and immersed for 1 hour. Then, suction was carried out for 20 seconds on the filter paper to remove excess water, and the sample weight was measured. The amount of water absorption was calculated according to the following formula.

Water absorption (g / m ² ) = (weight after water absorption−initial dry weight) / sample size (amount of residual monomer) A sample of the water-absorbing composite having a dry polymer amount of 0.5 g was finely chopped. After dispersing and stirring in 1 L of ion-exchanged water for 2 hours, the dispersion was filtered through Whatman filter paper, and the amount of residual monomer in the filtrate was measured by HPLC. The amount of residual monomer in the water-absorbent polymer was determined from the measured value.

(Dimensional change rate) The dimensions of four sides of a 100 mm * 100 mm sample of the water-absorbent composite were measured accurately and left for 2 months in the room. Then, the four sides of the sample were measured and the dimensional change was calculated according to the following formula. The measured value is 4
It is an average value of the dimensional change rate of each side expressed as a percentage.

Dimensional change rate = (initial size-size after 2 months) / initial size (Example 1) N, N in a partially neutralized sodium acrylate aqueous solution in which 99 mol% was neutralized with sodium hydroxide. '
1.0 mol% methylenebisacrylamide (vs. sodium acrylate monomer) and sodium persulfate 1.
5 g / mol (to sodium acrylate monomer) was dissolved to prepare a 36 wt% monomer aqueous solution. The pH value of this monomer aqueous solution was 7.0. Next, a polyurethane sponge having a basis weight of 80 g / m ² was dipped in the aqueous monomer solution to impregnate the aqueous solution, and then the excess aqueous monomer solution was squeezed with a roller. The impregnated material was heated to carry out radical polymerization to obtain a water absorbent composite (1) in which 92 g / m ² of the water absorbent polymer was directly adhered to the substrate. The water absorption capacity of the obtained water absorbent composite was 3900 g / m ² , and the amount of residual monomer was 900 ppm. Further, the water-absorbent composite (1) had a thick open-cell structure and was excellent in the dew condensation preventing effect due to its heat insulating property and absorbing effect, and was able to rapidly absorb an aqueous solution, body fluid, blood and the like.

Next, when the dimensional change of the water-absorbent composite (1) was examined, the dimensional change rate was 0% and no shrinkage occurred. As for the texture, the same soft texture and cushioning property as before the dimensional change test were maintained, and the color tone was only slightly changed to that of the polyurethane sponge base material itself.

Example 2 1.5 g / mol of sodium persulfate, which is the polymerization initiator of Example 1, was added with 1.0 g / mol of sodium persulfate and 2,2'-azobis (N, N'dimethyleneisobutylamidine). ) An aqueous monomer solution was prepared under the same conditions as in Example 1 except that the dihydrochloride was changed to 0.5 g / mol and an oxidizing polymerization initiator and an azo polymerization initiator were used in combination (pH value 7.0). . Next, a polyurethane sponge having a basis weight of 80 g / m ² was dipped in the aqueous monomer solution to impregnate the aqueous solution, and then the excess aqueous monomer solution was squeezed with a roller. The impregnated material was heated to carry out radical polymerization to obtain a water-absorbent composite (2) in which 95 g / m ² of the water-absorbent polymer was directly adhered to the substrate.

The water absorption capacity of the resulting water-absorbent composite was 4000.
The amount of residual monomer was 200 ppm in g / m ² . When only the oxidative polymerization initiator was used as the polymerization initiator, the amount of the residual monomer was reduced by using the azo polymerization initiator together as compared with Example 1. Further, the water-absorbent composite (2) had a thick open-cell structure and was excellent in dew condensation preventing effect due to its heat insulating property and absorbing effect, and was capable of rapidly absorbing aqueous solution, body fluid, blood and the like.

Next, when the dimensional change of the water-absorbent composite (2) was examined, the dimensional change rate was 0% and no shrinkage occurred. As for the texture, the same soft texture and cushioning property as before the dimensional change test were maintained, and the color tone was only slightly changed to that of the polyurethane sponge base material itself.

(Comparative Example 1) 1.0 mol% of N, N'-methylenebisacrylamide (to a sodium acrylate monomer) and a peroxide were added to a partially neutralized sodium acrylate aqueous solution in which 80 mol% was neutralized with sodium hydroxide. Sodium sulfate (1.5 g / mol (versus sodium acrylate monomer)) was dissolved to prepare a 37% by weight aqueous monomer solution.
The PH value of this monomer aqueous solution was 5.6. Next, a polyurethane sponge having a basis weight of 80 g / m ² was dipped in the aqueous monomer solution to impregnate the aqueous solution, and then the excess aqueous monomer solution was squeezed with a roller. This impregnated product was heated to carry out radical polymerization to obtain a comparative water-absorbent composite (1) in which 85 g / m ² of the water-absorbent polymer was directly adhered to the substrate. The comparative water absorbent composite (1) thus obtained had a water absorption of 34.
The amount of residual monomer was 1100 ppm at 00 g / m ² .

Next, when the dimensional change of this comparative water-absorbent composite (1) was examined, the dimensional change rate was 3%, and considerable dimensional shrinkage was clearly recognized. Also, the texture was considerably brittle and tougher than that before the dimensional change test, and the degree of yellowing was remarkable as compared with the discoloration of the polyurethane sponge itself. Also, an odor of nasal smell was observed when handling the monomer.

(Comparative Example 2) 1.0 mol% of N, N'-methylenebisacrylamide (based on sodium acrylate monomer) and peroxide were added to a partially neutralized sodium acrylate aqueous solution in which 60 mol% was neutralized with sodium hydroxide. Sodium sulfate (1.5 g / mol (based on sodium acrylate monomer)) was dissolved to prepare a 46% by weight aqueous monomer solution.
The pH value of this aqueous monomer solution was 5.1. Next, a polyurethane sponge having a basis weight of 80 g / m ² was dipped in the aqueous monomer solution to impregnate the aqueous solution, and then the excess aqueous monomer solution was squeezed with a roller. This impregnated product was heated to carry out radical polymerization, and 110 g / m ² of the water-absorbent polymer was directly adhered to the substrate. Comparative water-absorbent composite (2)
Got The water absorption of the obtained comparative water-absorbing composite (2) was 4
At 500 g / m ² , the amount of residual monomer was 950 ppm.

Next, when the dimensional change of the comparative water-absorbent composite (2) was examined, the dimensional change rate was 4%, and considerable dimensional shrinkage was clearly recognized. Further, the texture was considerably brittle and tougher than before the dimensional change test, and the degree of yellowing was remarkable as compared with the discoloration of the polyurethane sponge base material itself. Also, an odor of nasal smell was observed when handling the monomer.

Comparative Example 3 1.0 mol% of N, N'-methylenebisacrylamide (relative to sodium acrylate monomer) and a peroxide were added to a partially neutralized sodium acrylate aqueous solution in which 100 mol% was neutralized with sodium hydroxide. Sodium sulfate (1.5 g / mol (versus sodium acrylate monomer)) was dissolved to prepare a 36 wt% monomer aqueous solution. The pH value of this monomer aqueous solution was 9.1. Next, a polyurethane sponge having a basis weight of 80 g / m ² was dipped in the aqueous monomer solution to impregnate the aqueous solution, and then the excess aqueous monomer solution was squeezed with a roller. This impregnated product was heated to carry out radical polymerization to obtain a comparative water-absorbing composite (3) in which 80 g / m ² of the water-absorbing polymer was directly adhered to the substrate. The comparative water absorbent composite (3) thus obtained had a water absorption of 3200 g / m ² and a residual monomer content of 960 ppm.
Met.

Next, when the dimensional change of this comparative water-absorbent composite (3) was examined, the dimensional change rate was 2%, and considerable dimensional shrinkage was clearly observed. Further, the texture was considerably brittle and tougher than before the dimensional change test, and the degree of yellowing was remarkable as compared with the discoloration of the polyurethane sponge base material itself.

Example 3 1.5 g / mol of sodium persulfate, which is the polymerization initiator of Example 1, was added to 2,2′-azobis (N, N′-dimethyleneisobutylamidine) 2 which was an azo-based polymerization initiator. An aqueous monomer solution was prepared under the same conditions as in Example 1 except that the hydrochloride was changed to 1.5 g / mol. Next, in this monomer aqueous solution (pH value 7.0), the basis weight is 80 g /
The polyurethane sponge of m ² was dipped and impregnated with the aqueous solution, and then the excess monomer aqueous solution was squeezed with a roller. This impregnated material is heated to carry out radical polymerization to give 91 g.
A water-absorbent composite (3) in which the water-absorbent polymer of / m ² was directly adhered to the substrate was obtained. The water absorption capacity of the obtained water absorbent composite (3) was 3800 g / m ² , and the amount of residual monomers was 850.
It was ppm. The dimensional change rate of the water absorbent composite (3) is 0.
%, The soft texture and cushioning property were maintained as in the case before the dimensional change test, and the color tone was slightly discolored to the same extent as the discoloration of the polyurethane sponge base material itself.

[0045]

EFFECTS OF THE INVENTION According to the method for producing a water-absorbent composite of the present invention, it is possible to obtain a water-absorbent composite that has little change in size and color with time, retains flexibility, and has less residual monomer.

Therefore, since the water-absorbent composite having extremely high quality and safety can be obtained, the water-absorbent composite of the present invention is used for absorbing drip of paper diapers for sanitary products, sanitary napkins, etc. and meat / seafood for food. It can be used as a water absorbing agent for the body and the like. Besides, it is also suitable as a liquid leakage prevention material and packaging material, and can also be used as a dew condensation prevention material for air conditioners, windows, push-ins, containers, building materials, etc., a water content removing material in oil, a lubricant for extracting piles, and an evaporator. .

[0047]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nobuyuki Harada 1 992 Nishikioki, Kamahama, Aboshi-ku, Himeji-shi, Hyogo Japan Catalytic Polymer Research Institute Co., Ltd.

Claims (5)

[Claims] 1. A monomer in which an acid group-containing monomer is essential.
A method for producing a water-absorbing complex, which comprises adjusting an aqueous solution of components to a pH value of 6 to 8, applying this to a foam, and then polymerizing the monomer component. 2. The method for producing a water absorbent composite according to claim 1, wherein the acid group-containing monomer is acrylic acid. 3. A monomer in which an acid group-containing monomer is essential.
The method for producing a water absorbent composite according to claim 1, wherein the aqueous solution of the components contains a polymerization initiator. 4. The method for producing a water-absorbing composite according to claim 3, wherein an oxidative polymerization initiator and an azo polymerization initiator are used together as the polymerization initiator. 5. The method for producing a water absorbent composite according to claim 4, wherein the amount of the azo-based polymerization initiator is in the range of 1 to 100 parts by weight relative to 100 parts by weight of the oxidizing polymerization initiator.