JPH01121307A - Production of water absorbing complex - Google Patents

Abstract

PURPOSE:To readily obtain a water absorbing complex having improved water absorbing performance without any residual monomer under mild condition, by applying an aqueous solution containing an acrylic acid based monomer, polyoxyethylene alkyl ether, etc., to a fibrous substrate and reducing the resultant substrate. CONSTITUTION:An aqueous solution containing (A) a polymerizable monomer consisting essentially of acrylic acid having >=20% carboxyl groups neutralized with an alkaline metallic salt or ammonium salt, (B) a crosslinking agent [e.g. ethylene glycol di(meth)acrylate or polyglycidyl ether], (C) a polyoxyethylene alkyl ether having >=7HLB and (D) an oxidizing radical polymerization initiator (e.g. hydrogen peroxide) is applied to a molded fibrous substrate and then a reducing agent (e.g. ascorbic acid) is applied to polymerize the polymerizable monomer and form the aimed complex of a polymer derived from the polymerizable monomer and the fibrous substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION Industrial Field of Application The present invention relates to a method for producing a water-absorbing composite comprising a water-absorbing polymer and a shaped fibrous substrate. More specifically, the present invention uses an acrylic acid monomer with an HLB of 7.
An aqueous solution containing the above polyoxyethylene alkyl ether, a crosslinking agent, and an oxidative radical polymerization initiator is applied to a molded fibrous substrate, and then a reducing agent is added to carry out polymerization in a short time at room temperature, The present invention relates to a method for producing a water-absorbing composite in which a super-absorbent polymer is fixed to a molded fibrous substrate.

The water-absorbent composite obtained by the production method of the present invention has excellent water absorption, has an extremely low content of unpolymerized monomers, and has a highly water-absorbent polymer stably fixed to a fibrous base, so it can be used for various purposes. It can be advantageously used in the production of water-absorbing materials.

BACKGROUND ART Conventionally, paper, valves, nonwoven fabrics, sponge-like urethane resins, and the like have been used as water-retaining agents in various sanitary materials such as sanitary napkins and paper diapers, and in various agricultural feeds. However, these materials absorb only 10 to 50 times their own weight of water, so in order to absorb or retain a large amount of water, a large amount of material is required, which not only makes them extremely bulky. In addition, there was a drawback that when a material that had absorbed water was pressurized, water was released rapidly.

In order to improve the above-mentioned drawbacks of this type of water-absorbing material, various highly water-absorbing polymeric materials have been proposed in recent years. For example, starch graft polymer (Japanese Patent Publication No. 53-46199
Publications, etc.), modified cellulose (Japanese Patent Application Laid-open No. 50-8037)
6, etc.), crosslinked products of water-soluble polymers (Japanese Patent Publication No. 43-2)
3462, etc.), self-crosslinking type acrylic acid alkali metal salt polymers (Japanese Patent Publication No. 54-30710, etc.), and the like have been proposed.

However, although these superabsorbent polymer materials have a fairly high level of water absorption performance, most of them are obtained in the form of powder, so they cannot be used for example in sanitary napkins,
Tissues to be used as sanitary materials such as paper diapers, etc.
It is necessary to disperse it evenly on a substrate such as nonwoven fabric or cotton. However, it is difficult to stably fix polymer powder dispersed by such a method on a substrate.
After dispersion, the gel often aggregates locally, and the swollen gel after water absorption is not stably fixed on the substrate and moves from the substrate to the container. For this reason, when this material is used, for example, in a paper diaper, the water-absorbent material becomes "stiff" after urinating, making it extremely uncomfortable to wear. In addition, the method of obtaining an absorbent material by dispersing a powdered polymer in a base material as described above has high costs due to the complexity associated with handling the powder and process problems in achieving uniform dispersion efficiently. It is also extremely expensive.

One method to solve these problems is to manufacture a composite by applying an aqueous solution of acrylic acid monomer to a molded fibrous substrate in a predetermined pattern, and then irradiating this with electromagnetic radiation or particulate ionizing radiation. , a method for producing a water-absorbing composite by converting an acrylic acid monomer into a superabsorbent polymer has been reported (Japanese Patent Publication No. 57-500546).
Duke? the law of nature. Although this method shows considerable improvement in terms of uniform dispersion and stable immobilization on the substrate when handling the above powder, it is difficult to convert it into a superabsorbent polymer. , due to the use of electromagnetic radiation or particulate ionizing radiation, the highly water-absorbing polymer inherent in this particular monomer is susceptible to excessive cross-linking reactions, so that the resulting composite has poor performance as an absorber. There seems to be a drawback in that the performance, particularly the water absorption capacity, is extremely low and is less than half that of the case where the above-mentioned powdered superabsorbent polymer is used. In addition, it is difficult to say that this is an inexpensive method in terms of the safety and cost involved in handling the radiation generating device as described above.

Recently, Japanese Patent Application Laid-open No. 60-149609 discloses that after impregnating a water-absorbing material with an aqueous solution of acrylate monomer in advance, a water-soluble radical polymerization initiator or a water-soluble radical polymerization initiator and a water-soluble A method for producing a water-absorbing composite material is proposed, in which a reducing agent is added in the form of a mist and polymerized. However, in this method, the water-soluble polymerization initiator is added after the water-absorbing organic material is impregnated with the acrylic acid monomer, so even if the polymerization initiator is atomized, "uneven polymerization" occurs. It is extremely difficult to completely polymerize the monomers, and as a result, a large amount of residual sludge remains, which poses many safety problems and seems to have drawbacks in terms of performance, particularly in terms of water absorption capacity. It will be done.

Possible Solutions Against this background, the inventors have already filed a patent application in 1986-23.
No. 8421 describes that after uniformly mixing an acrylic acid monomer aqueous solution containing a small amount of crosslinking agent and an oxidizing radical polymerization initiator, the mixture is applied to a fibrous substrate, and then an amine or a reducing agent is applied to polymerize. We proposed a method for producing a water-absorbing composite consisting of a super-absorbent polymer and a molded fibrous substrate. It has been found that by this method, a product with almost no "uneven polymerization", easy polymerization, and high water absorption capacity can be obtained. Although the water-absorbing composite aged by this method has a sufficiently good water-absorbing ability,
Needless to say, a water-absorbing composite having a water-absorbing capacity higher than this is more preferable.

[Summary of the invention]

Purpose of the Invention The present invention is based on the aforementioned Japanese Patent Application No. 60-238421, Japanese Patent Publication No. 57-500546, and Japanese Patent Application Laid-Open No. 60-149.
The present invention aims to improve the method for producing a water-absorbing composite described in Publication No. 609 to provide a method for easily producing a water-absorbing composite with no residual monomer and even better water-absorbing performance under mild conditions. It is something.

Structure of the Invention As a result of various studies aimed at solving the above-mentioned problems, the present inventors discovered that the acrylic acid monomer has an HLB of 7.
By applying an aqueous solution containing the above polyoxyethylene alkyl ether, a crosslinking agent, and an oxidative radical polymerization initiator to a molded fibrous substrate, and then adding a reducing agent in the form of a mist, polymerization occurs in an extremely short time. However, the present inventors have discovered that it is possible to easily obtain a water-absorbing composite with almost no residual monomer, particularly excellent water-absorbing performance, and in which a super-absorbent polymer is stably fixed to a fibrous substrate, and the present invention has been achieved. It is.

That is, the method for producing a water-absorbing composite with improved water-absorbing ability according to the present invention is characterized by comprising the combination of the following steps (A) and (B).

(A) A step of applying an aqueous solution containing the following components (a) to (d) to a molded fibrous substrate.

(a) A polymerizable monomer mainly composed of acrylic acid in which 2096 or more of the carboxyl groups are neutralized with an alkali metal salt or ammonium salt, (b) a crosslinking agent, (c) a polyoxy having an HLB of 7 or more ethylene alkyl ether, (d) oxidizing radical polymerization initiator, (B) applying a reducing agent to the polymerizable monomer applied to this fibrous substrate to polymerize the polymerizable monomer; A step of forming a composite of a monomer-derived polymer and a fibrous substrate.

Effects of the Invention The method for producing a water absorbent composite of the present invention has remarkable features in the following points.

(a) By coexisting polyoxyethylene alkyl ether with an HLB of 7 or more in the acrylic acid monomer, a polymer with extremely high water absorption ability can be obtained.

and (b) the remaining monomers in the polymer are dissolved by dissolving the oxidizing radical polymerization initiator in advance in the polyoxyethylene alkyl ether and acrylic acid monomer aqueous solution, and then spraying the reducing agent thereto to polymerize the monomers. The point is that a very small amount of polymer can be obtained in an extremely short time by a simple polymerization operation and under mild conditions at around room temperature.

Therefore, the water-absorbing composite obtained by the production method of the present invention is similar to the above-mentioned Japanese Patent Application No. 60-238421, Japanese Patent Publication No. 57-500546, and The water absorption performance is particularly higher than that of the method disclosed in JP-A-60-149609, and there is almost no residual monomer, making it highly safe. Furthermore, since it is in sheet form, it is easier to handle and cheaper than the powdered superabsorbent resin that has been used in the past, making it suitable for the production of various sanitary materials such as sanitary napkins and paper diapers. can be used advantageously. In addition, by utilizing its excellent water absorption performance and ease of handling, it can be used to manufacture various materials for horticultural and agricultural purposes, including soil conditioners, water retention agents, etc., which have recently attracted attention.

[Detailed description of the invention]

Step (A) Polymerizable monomer The polymerizable monomer used in the present invention has acrylic acid as a main component, and 20% or more, preferably 50% or more of the carboxyl group is an alkali metal. It is neutralized with salt or ammonium salt. If the degree of partial neutralization of the acrylic acid monomer is less than 20%, the water absorption capacity of the resulting polymer will be significantly reduced.

Furthermore, in the present invention, one or more types of second monomers copolymerizable with the above-mentioned acrylic acid monomer can also be used within a range that does not impair the water absorbency of the resulting polymer. Examples of such monomers include (a) methacrylic acid, itaconic acid, maleic acid, fumaric acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-acryloylethanesulfonic acid, 2-acryloylpropanesulfonic acid, and salts thereof; , (b) vinylpyridines and their salts such as 2-vinylpyridine and 4-vinylpyridine, (c) alkyl or alkoxy esters of dicarboxylic acids such as itaconic acid, maleic acid, and fumaric acid, (
d) Vinyl sulfonic acid, (e) acrylic acid methyl ester, acrylic acid ethyl ester, etc., (f) (meth) acrylic acid hydroxyethyl ester, (meth) acrylic acid hydroxypropyl ester, (g) polyethylene glycol mono(meth) Examples include acrylate.

Alkali metal hydroxides, bicarbonates, or ammonium hydroxide can be used to neutralize acrylic acid monomers and the above-mentioned acid monomers, but alkali metal hydroxides are preferred. Specific examples include sodium hydroxide, potassium hydroxide and lithium hydroxide. In terms of industrial availability, price, safety, etc.
Sodium hydroxide or potassium hydroxide is preferred.

The concentration of the aqueous solution containing such an acrylic acid monomer or the second heptamer used as necessary may be any value suitable for the purpose. Specifically, it is, for example, 20% by weight or more, preferably 30% by weight or more. It can be said that the higher the concentration, the better.

That is, by increasing the monomer concentration, the amount of superabsorbent polymer filled per unit surface area of the molded fibrous base increases, making it possible to obtain a composite with excellent water absorption performance.
In addition, by increasing the monomer concentration, conversely speaking, the water concentration can be decreased, which allows energy consumption during drying to be reduced, which is advantageous in terms of cost.

Crosslinking agent The crosslinking agent used in the production method of the present invention has two or more double bonds in the molecule and is copolymerizable with the acrylic acid monomer and/or the second monomer, or One that has two or more H functional groups in its molecule that can react with a functional group in the acrylic acid monomer and/or the second monomer, such as a carboxyl group, during polymerization or during drying after polymerization. , is. Any of these can be used as long as it exhibits some degree of water solubility.

An example of the former crosslinking agent is ethylene glycol di(
meth)acrylate, diethylene glycol di(meth)
Acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, glycerin tri(meth)acrylate, N, N'
- Methylene bis(meth)acrylamide, diallyl phthalate, diallyl maleate, diallyl terephthalate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, di Examples include pentaerythritol hexaacrylate.

Examples of the latter crosslinking agents include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and di- or polyglycidyl ether of aliphatic polyhydric alcohol.

Furthermore, as a device that has both the former and latter functions, for example, N
- Compounds such as methylol acrylamide, glycidyl methacrylate, etc. can also be used in the method of the invention.

Among these, particularly preferred in the present invention are:
It is preferable to have two or more double bonds in the molecule and exhibit copolymerizability with the acrylic acid monomer and/or the second monomer.

Such crosslinking agents may be used alone or in combination with 2F! It can also be used as a mixture of the above.

The amount of these crosslinking agents used is 0.001 to 10% by weight, preferably 0.01 to 2% by weight, based on the acrylic acid monomer. If it is less than 0.001% by weight, the water absorption capacity will be extremely large, but the gel strength of the superabsorbent polymer upon water absorption will be extremely weak.If it exceeds 10% by weight, the water absorption gel strength will be particularly improved, but the water absorption capacity will be This results in a considerably small size, which poses a practical problem.

Polyoxyethylene alkyl ether The polyoxyethylene alkyl ether used in the production method of the present invention has an HLB of 7 or more, preferably 10 or more (the upper limit is about 20), and is substantially soluble in the aqueous acrylic acid monomer solution. Preferably. It is also preferable to determine the degree of condensation of ethylene oxide and the number of carbon atoms of the alkyl group from this viewpoint. Regarding the number of carbon atoms in the alkyl group, it is preferably about 10 to 20. Given that the preferred method for producing this ether consists of the addition of ethylene oxide to the corresponding alkanol (typically a monohydric alcohol having an alkyl group as described above), the preferred ether in the present invention is an ether alcohol. I can say that. "Polyoxyethylene" may contain small amounts of oxypropylene groups. Specific examples of such polyoxyethylene alkyl ether include polyoxyethylene octyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether,
Examples include polyoxyethylene stearyl ether and polyoxyethylene oleyl ether. In addition, H.L.B.
is measured according to the Atlas method.

Such polyoxyethylene alkyl ethers can be used alone or as a mixture of two or more.

The amount of these polyoxyethylene alkyl ethers used is 0.001 to 10% by weight, preferably 0.01 to 1% by weight, based on the acrylic acid monomer. If the amount added is less than 0.001% by weight, the effect of the addition will be extremely small, while if the amount added exceeds 10% by weight, the water absorption capacity will actually decrease, which is not preferable.

Oxidizing radical polymerization initiator The polymerization initiator used in the production method of the present invention forms a redox system with the reducing agent, and must be a radical generator that exhibits a certain degree of water solubility and oxidizing properties. . Such oxidizing agents include (a) peroxides such as hydrogen peroxide, persulfates such as ammonium persulfate and potassium persulfate, hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; , (b) Others include ceric salts, permanganates, chlorites, hypochlorites, etc. Among these, hydrogen peroxide is particularly preferred.

Other water-soluble radical polymerization initiators that do not exhibit oxidizing properties, such as azo compounds such as 2.2'-azobis(2-amidinobroban) dihydrochloride, do not form a redox system of reducing agents. , is not used in the present invention.

The amount of these radical polymerization initiators used is 0.01 to 10% by weight, preferably 0.1% by weight based on the acrylic acid monomer.
~2% by weight.

Molded Fibrous Substrate The molded fibrous substrate used in the present invention is specifically formed of loosely formed fibers, such as pads, carded or air-laid webs, tissue paper, cotton gauze, etc. various woven fabrics, knitted fabrics,
Or non-woven fabric.

A "formed" fibrous substrate is defined here as a web-forming process, even if it is already a web and may require cutting, splicing, shaping, etc. to incorporate the fibrous substrate into an article. means that there is no need to apply further.

It is generally preferred to use a fibrous substrate based on absorbent fibers such as wood pulp, rayon, cotton, other cellulosic fibers, or polyester fibers. However, other types of fibers, such as polyethylene, polypropylene, polystyrene, polyamide, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyurea, polyurethane, polyfluoroethylene It is also possible to incorporate fibers such as polycyanide, vinylidene polycyanide, etc. into the molded fibrous substrate.

Application Method The aqueous solution containing a small amount of crosslinking agent, polyoxyethylene alkyl ether with HLB of 7 or higher, and acrylic acid monomer as described above is mixed uniformly with an oxidizing radical polymerization initiator and then applied to a formed fibrous substrate. be done. At this time, it is preferable to form a periodic pattern in the form of small dots or lines. This pattern can be used to create so-called "wicking channels" in the absorbent composite produced by the method of the invention, which can be used, for example, from absorbent polymers cross-linked around the edges of the absorbent pad portion of a diaper. The continuous linear shape of the diaper has the advantage that leakage around the edges is extremely reduced.

In general, it is preferred to employ a pattern of very finely divided, discrete sections in order to maximize the ratio of polymer surface area to mass. The method for applying the liquid mixture to the fibrous substrate may be any suitable means or mode.

For example, printing (pr'inting), spraying (s
(praying), pouring (f'l) through a nozzle
owing), kiss eoatin
g), saturating, etc. Further, if desired, the mixture may be applied to the fibrous substrate in an all-over pattern, whereupon the mixture may be applied in an amount sufficient to simply coat one side of the fibrous substrate; or It can also be used in an amount sufficient to penetrate the thickness of the fibrous substrate.

The mixed liquid is kept at around room temperature, specifically 20 to 60°C, and is applied to the fibrous substrate, and adjusted to a predetermined temperature (details will be described later) in a reaction tank.

Note that this liquid mixture may contain various substances other than those mentioned above, as long as they do not contradict the purpose of the present invention. The "mixed liquid" herein is basically an aqueous solution, but if desired, this aqueous solution may contain a small amount of a water-soluble organic solvent dissolved therein.

The amount of the liquid mixture to be impregnated into the fibrous substrate is not particularly limited, and can be varied over a wide range depending on the product use of the water-absorbing composite. - In the shell, 0.1 to 1000 parts by weight, usually 0.5 to 5 parts by weight, per 1 part by weight of the fibrous substrate.
0 parts by weight is adopted.

Step (B) Reducing Agent The reducing agent used in the production method of the present invention is capable of forming a redox system with the oxidative radical polymerization initiator, and exhibits a certain degree of water solubility. Such a reducing agent can be any one, but specifically includes sulfites such as sodium sulfite and sodium bisulfite, sodium thiosulfate, cobalt acetate, copper sulfate, ferrous sulfate, and L-ascorbic acid. or L-ascorbic acid alkali metal salts, etc. Among them, ascorbic acid or L-ascorbic acid alkali metal salts are particularly preferred.

The amount of these reducing agents used is 0.001 to 10% by weight, preferably 0.01 to 2 ff196, based on the acrylic acid monomer.

Application of reducing agent and polymerization conditions A mixed solution in which an oxidative radical polymerization initiator and an aqueous solution of an acrylic acid monomer containing a small amount of a crosslinking agent and a polyoxyethylene alkyl ether with an HLB of 7 or more are mixed in advance is first applied to a molded fibrous substrate. Next, the above-mentioned reducing agent is applied to the fibrous substrate coated with this mixed solution at room temperature or, if necessary, at a predetermined temperature to cause a polymerization reaction. The method of applying the reducing agent at this time is as follows:
For example, there is a method of adding it in the form of a mist using a spray nozzle or the like, and by using such an application method, excellent results can be obtained in terms of polymerization reaction efficiency and operability.

Furthermore, when the reducing agent is particularly solid at room temperature, it is preferable to apply it as an aqueous solution.

The temperature in the reaction tank and the reducing agent is, for example, room temperature to 60°C.
°C, usually room temperature to 40 °C.

Further, the reaction tank and reaction method are not particularly limited and may be of any type. Examples include a batch method in an oven-type box-type reaction tank, or a continuous method on an endless belt.

In addition, the polymerization time varies depending on the polymerization temperature, etc.
- The period of time in the shell is from several seconds to 2 hours, preferably from several seconds to 10 minutes.

After completion of the polymerization, if necessary, the composite may be dried, for example by passing it through a series of drying baths or using a forced draft oven, to effect the crosslinking reaction and to remove moisture.

[Experiment example]

Hereinafter, the present invention will be further explained in detail by giving Examples and Comparative Examples. In addition, the physiological saline water absorption capacity described in these examples refers to the numerical value measured by the following test method.

Approximately 1.0 m of the water-absorbing complex was placed in a beaker with a physiological saline water absorption capacity of 300 m1. 0 g and 200 g of sodium chloride solution having a concentration of 0.9% by weight were weighed and added, and the polymer was left to stand for about 4 hours to sufficiently swell the polymer with the saline solution. Next, after draining the water with 100 mesh yugushi, that? Weigh the amount of filtered saline, and calculate the physiological saline water absorption capacity according to the formula below.

Physiological saline water absorption capacity - Example 1 30g of acrylic acid was placed in a 100cc conical flask, and 17°Og of pure water and polyoxyethylene stearyl ether (HLB-13) (1.032g-
was added and dissolved. This was cooled with water, potassium hydroxide (
About 95% by weight) 18.3g was gradually added to neutralize the mixture. The degree of neutralization is about 75%-0, in addition to which N and N' are added as crosslinking agents.
-0.0 methylene bisacrylamide. o5g collection,
31 as a radical polymerization initiator.
0.8 g of 96 hydrogen peroxide solution was taken and dissolved.

Separately, 2.58 g of polyester nonwoven fabric was taken, and the above-mentioned raw material was coated and impregnated on the entire surface of the nonwoven fabric, and the temperature was maintained at 40°C in a constant temperature reaction tank. The amount of impregnated 7-mer was 6.3 times that of the nonwoven fabric.

Next, a 5% by weight aqueous L-ascorbic acid solution as a reducing agent was sprayed over the entire surface of the nonwoven fabric from a spray nozzle.

Polymerization occurred immediately, and a water-absorbent composite in which the superabsorbent polymer was stably fixed to the polyester nonwoven fabric was obtained.

The physiological saline water absorption capacity of the water-absorbing composite is 73.3,
Almost no residual monomer was observed.

Example 2 13.14 ml of sodium hydroxide (purity approximately 95% by weight) was placed in a 100 cc conical flask, and 3.14 ml of water-cooled pure water was added to it.
9g was added and dissolved. Add 30% acrylic acid to this under water cooling.
g was gradually added to neutralize the mixture.

The degree of neutralization was approximately 75%.

This is added to polyoxyethylene stearyl ether (HLB).
-13) 0.032 g, N as crosslinker.

N'-methylenebisacrylamide at 0.05K.

Furthermore, 3196 hydrogen peroxide solution 0 as a radical polymerization initiator
．． 8g of each was taken and dissolved.

Separately, 2.86g of polyester nonwoven fabric was taken, and the above raw material was coated and impregnated on the entire surface of the nonwoven fabric, and the mixture was heated in a constant temperature reaction tank for 4 hours.
It was kept at 0°C. The amount of monomer impregnated was 4.6 times the weight of the nonwoven fabric.

Next, an aqueous solution of 596L-ascorbic acid as a reducing agent was sprayed over the entire surface of the nonwoven fabric from a spray nozzle.

Polymerization occurred immediately, and a water-absorbent composite in which the superabsorbent polymer was stably fixed to the polyester nonwoven fabric was obtained.

The physiological saline water absorption capacity of the water-absorbing composite is 76.5,
Almost no residual monomer was observed.

Example 3 26.9 g of 25% by weight ammonia water was placed in a 100 cc conical flask, and 30.9 g of acrylic acid was added while cooling with water.
was added dropwise to neutralize it. The degree of neutralization of acrylic acid was approximately 95%.

This is added to polyoxyethylene stearyl ether (HLB).
-13) 0.032 g, N as crosslinker.

0.05 g of N'-methylenebisacrylamide.

Furthermore, 0.8 g of 31% hydrogen peroxide solution was added and dissolved as a polymerization initiator. - Separately, 4.62g of polyester nonwoven fabric was taken, and the above raw material was coated on the entire surface of the nonwoven fabric to impregnate it, and the mixture was heated in a constant temperature reaction tank for 4.62g.
It was kept at 0°C. The amount of monomer impregnated was 7.6 times the weight of the nonwoven fabric.

Next, a 5 weight 96 L aqueous ascorbic acid solution as a reducing agent was sprayed onto the entire surface of the nonwoven fabric from a spray nozzle.

Polymerization occurred immediately, and a water-absorbent composite in which the superabsorbent polymer was stably fixed to the polyester nonwoven fabric was obtained.

Results of measuring the physiological saline water absorption capacity of the above water-absorbing composite 71
．． 5, and almost no residual monomer was observed.

Example 4 A water-absorbing composite was obtained in the same manner as in Example 1 except that the nonwoven fabric was a rayon nonwoven fabric and the amount of raw material monomer impregnated was 5.5 times the weight of the nonwoven fabric.

The physiological saline water absorption capacity of the water-absorbing composite is 71.5,
Almost no residual monomer was observed.

Example 5 The amount of pure water to be added to acrylic acid in Example 1 was 18.
A water-absorbing composite was obtained in the same manner except that the amount of potassium hydroxide was 14.7 g (the degree of neutralization was approximately 60%).

The physiological saline water absorption capacity of the water-absorbing composite is 73.8,
Almost no residual monomer was observed.

Example 6 A water-absorbing composite was obtained in the same manner as in Example 2, except that 0.2 g of potassium persulfate was used as the radical polymerization initiator and 5% aqueous sodium bisulfite solution was used as the reducing agent.

The physiological saline water absorption capacity of the water-absorbing composite is 68.8,
Almost no residual monomer was observed.

Example 7 In Example 1, the crosslinking agent was polyethylene glycol (
A water-absorbing composite was obtained in the same manner except that 0.1 g of PEG600) diacrylate was used.

The physiological saline water absorption capacity of this water-absorbing composite is 81.5,
Almost no residual Mozumah was observed.

Example 8 In Example 2, 0.032 g of polyoxyethylene lauryl ether (HLB-14) was used instead of 0.032 g of polyoxyethylene stearyl ether (HLB-13).
A water-absorbing composite was obtained in the same manner except that g was changed.

The physiological saline water absorption capacity of this water-absorbing composite is 75.8,
Almost no residual monomer was observed.

Example 9 In Example 1, polyoxyethylene lauryl ether (HLB-1
4) A water-absorbing composite was obtained by the same operation except that the amount was changed to 0.032 g.

The physiological saline water absorption capacity of this water-absorbing composite is 72.5,
Almost no residual monomer was observed.

Example 10 Partially neutralized potassium acrylate aqueous solution in Example 1,
When applying a mixture of polyoxyethylene stearyl ether, a crosslinking agent, and a polymerization initiator to a polyester nonwoven fabric, the mixture is sprayed from a spray nozzle and impregnated onto the fibers in dots, so that the amount of impregnation is 7% relative to the nonwoven fabric. , a water-absorbing composite was obtained by the same operation except that the weight was increased by 5 times.

The physiological saline water absorption capacity of this water-absorbing composite is 75.6,
Almost no residual monomer was observed.

In addition, the above-mentioned water-absorbent composite has extremely finely divided super-absorbent polymers fixed on the fibers with good stability, and is extremely soft to the touch, making it suitable for sanitary materials such as sanitary napkins and paper diapers. Ta.

Example 11 Partially neutralized potassium acrylate aqueous solution in Example 1,
When applying a mixture of polyoxyethylene stearyl ether, a crosslinking agent, and a polymerization initiator to a polyester nonwoven yarn, the mixture is coated and impregnated with a roll coater to form a continuous striped pattern along the fibers, A water absorbent composite was obtained in the same manner except that the amount of impregnation was 4.8 times the weight of the nonwoven fabric.

The physiological saline water absorption capacity of this water-absorbing composite is 7862,
Almost no residual monomer was observed.

In addition, in the above-mentioned water-absorbing composite, the super-absorbent polymer is continuously fixed in thin stripes along the fibers and fixed with good stability.
It also had a high water absorption rate, making it suitable not only as a sanitary material for sanitary napkins, paper diapers, etc., but also as a water retention agent for agricultural use.

Comparative Example 1 A water-absorbing composite was obtained in the same manner as in Example 1, except that polyoxyethylene stearyl ether was not added.

The physiological saline water absorption capacity of the water-absorbing composite was 48.5.

Comparative Example 2 A water-absorbing composite was obtained in the same manner as in Example 2, except that polyoxyethylene stearyl ether was not added.

The physiological saline water absorption capacity of the upper AT water absorption complex is 45.8.

Comparative Example 3 A water-absorbing composite was obtained in the same manner as in Example 3, except that polyoxyethylene stearyl ether was not added.

The physiological saline water absorption capacity of the water-absorbing composite was 41.2.

Comparative Example 4 A water-absorbing composite was obtained in the same manner as in Example 5, except that polyoxyethylene stearyl ether was not added.

The physiological saline water absorption capacity of the water-absorbing composite was 48.6.

Comparative Example 5 A partially neutralized potassium acrylate aqueous solution was prepared with a degree of neutralization of 75% and a monomer concentration in the aqueous solution of about 65% by weight. This was applied and impregnated onto the entire surface of the polyester nonwoven fabric. The amount of monomer impregnated was about 10 times the weight of the nonwoven fabric. The nonwoven fabric impregnated with this partially neutralized potassium acrylate monomer aqueous solution was irradiated with an electron beam at a dose of 10 megarads from an electron beam device equivalent to a dynamidron accelerator. Polymerization occurred immediately, and a water-absorbing composite in which a super-absorbent polymer made of a self-crosslinked partially neutralized potassium polyacrylate was stably fixed to a polyester nonwoven fabric was obtained.

Results of measuring the physiological saline water absorption capacity of the above water-absorbing composite 18
．． It was quite small at 5.

Comparative Example 6 A partially neutralized sodium acrylate aqueous solution with a degree of neutralization of 75% and a concentration of 75% by weight in the aqueous solution:
J8 match. This was applied and impregnated onto the entire surface of the polyester nonwoven fabric. The amount of monomer impregnated was 13 times that of the nonwoven fabric. The nonwoven fabric impregnated with this partially neutralized aqueous sodium acrylate solution was irradiated with an electron beam at a dose of 10 megarads from an electron beam device equipped with a dynamidron accelerator.

Polymerization occurred immediately, and a water-absorbing composite in which a super-absorbent polymer made of a self-crosslinked partially neutralized sodium polyacrylate was stably fixed to a polyester nonwoven fabric was obtained.

Although almost no residual monomer was observed in this water-absorbing composite, its physiological saline water absorption capacity was quite low at 25.0.

Comparative Example 7 A partially neutralized sodium acrylate aqueous solution was prepared with a degree of neutralization of 75% and a monomer concentration in the aqueous solution of about 45% by weight. N was used as a crosslinking agent.

0.0085 g of N'-methylenebisacrylamide was taken and dissolved. This monomer aqueous solution was applied and impregnated onto a polyester nonwoven fabric at 70°C. The amount of monomer impregnated was 11 times the weight of the nonwoven fabric. 16.7ffi for this
When the m% 2.2-azobis(2-amidinobroban) dihydrochloride aqueous solution was sprayed from a spray nozzle, polymerization started immediately.

However, in the obtained water absorbent composite, only the upper layer of the nonwoven fabric was polymerized, and it had a strong odor. (The remaining monomer amount was about 15% by weight.) Then, an additional 7
The above initiator solution was sprayed from a spray nozzle at 0°C and held for about 30 minutes, but polymerization hardly progressed. The water-absorbing composite thus obtained was further dried under reduced pressure at 90°C, and its physiological saline water absorption capacity was measured, and it was found to be extremely small at 16.5.

Comparative Example 8 Neutralization degree 7596, monomer concentration in aqueous solution approximately 65
A partially neutralized potassium acrylate aqueous solution containing % by weight was prepared. N was added to this as a crosslinking agent.

0.010 g of N'-methylenebisacrylamide was taken and dissolved. This monomer aqueous solution was applied and impregnated onto a polyester nonwoven fabric and maintained at 70°C. The amount of impregnated 7-mer was 10 times the weight of the nonwoven fabric. When a 16.7% by weight aqueous solution of 2.2-azobis(2-amidinopropane) dihydrochloride was sprayed onto this from a spray nozzle, polymerization started immediately.

However, as in Comparative Example 7, only the upper layer of the nonwoven fabric was polymerized in the resulting water-absorbing composite, and it had a strong odor (the amount of residual monomer was about 12.1% by weight).

Therefore, the temperature was maintained at 90° C. for an additional 30 minutes, and the mixture was dried under reduced pressure at the same temperature. The physiological saline water absorption capacity of this water-absorbing composite is 14
．． 2, which was extremely small.

Applicant's representative: Mr. Sato

Claims (1)

[Scope of Claims] 1. A method for producing a water-absorbing composite with improved water-absorbing ability, which comprises combining the following steps (A) to (B). (A) An aqueous solution containing the following components (a) to (d),
A process applied to a formed fibrous base. (a) A polymerizable monomer whose main component is acrylic acid in which 20% or more of the carboxyl groups are neutralized with an alkali metal salt or ammonium salt, (b) a crosslinking agent, (c) a polyester having an HLB of 7 or more. Oxyethylene alkyl ether, (d) oxidizing radical polymerization initiator, (B) applying a reducing agent to the polymerizable monomer applied to this fibrous substrate to polymerize the polymerizable monomer; A step of forming a composite of a polymer derived from a monomer and a fibrous substrate. 2. The method according to claim 1, wherein the oxidative radical polymerization initiator is hydrogen peroxide, and the reducing agent is L-ascorbic acid and/or an alkali metal salt of L-ascorbic acid. 3. Claims 1 to 3, wherein the fibrous substrate is mainly composed of cellulose fibers or polyester fibers.
The method according to any one of Item 2. 4. The method according to any one of claims 1 to 3, wherein the fibrous substrate is a loose pad of fibers, a carded web, an air-laid web, paper, a nonwoven fabric, a woven fabric, or a knitted fabric. .