JPH08120012A - Production of highly water-absorbing resin - Google Patents

Abstract

PURPOSE: To obtain highly water-absorbing resin particles which suffer little from the deposition of polymer scales during their production and have a suitable mean particle diameter and a sharp particle diameter distribution by subjecting a partially neutralized salt of (meth)acrylic acid to a reversed-phase suspension polymerization reaction and drying the obtained resin particles in a specified manner. CONSTITUTION: An aqueous solution of (meth)acrylic acid or a water-soluble unsaturated monomer based on a water-soluble salt of (meth)acrylic acid is subjected to a reversed-phase suspension polymerization reaction in the presence of a β-1,3-glucan and a free-radical polymerization initiator in the presence of absence of a crosslinking agent in a hydrocarbon solvent to obtain highly water-absorbing resin particles. A polyfunctional compound having at least two COOH-reactive functional groups in the molecule is adhered to the surfaces of these particles, and the treated particles are treated with a water-soluble carboxylic polymer to obtain the objective highly water-absorbing resin. According to this process, the obtained resin has high strengths of a swollen gel, resistance to the formation of agglomerates of insufficiently wetted particles, an improved water-absorbing capacity, and an improved water absorption rate.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has a moderate average particle size and a sharp particle size distribution which are less likely to cause scaling in a reactor or a stirring blade during polymerization, suppress the generation of fine particles, and are easy to handle. Relates to a method for producing a highly water-absorbent resin in which the strength of a swollen gel is high, it has mamaco prevention properties, and the water absorption capacity and water absorption rate are improved.

[0002]

BACKGROUND OF THE INVENTION Super absorbent polymers having the property of absorbing a large amount of water are useful as a body fluid absorbent that absorbs body fluids and prevents leakage in sanitary and sanitary products. It is also used in applications such as seed coating agents, waterstops, thickeners, anti-condensation agents, sludge coagulants, desiccants, and humidity control agents.

As the super absorbent polymer, various kinds of starch-acrylonitrile graft polymer partially hydrolyzate, polyacrylic acid partially neutralized salt, polyethylene oxide system, polyacrylonitrile system, polyvinyl alcohol system, or cross-linking system thereof are used. Among them, from the viewpoint of quality and performance, among them, (meth) acrylic acid and (meth) acrylic acid water-soluble salt were obtained by reverse phase suspension polymerization in a hydrocarbon solvent. Partially neutralized salts of polyacrylic acid are particularly useful.

When reverse phase suspension polymerization of (meth) acrylic acid and a water-soluble salt of (meth) acrylic acid in a hydrocarbon solvent is carried out in the presence of a surfactant as a dispersion stabilizer. Is normal. As the surfactant for this purpose, sorbitan fatty acid ester, sucrose fatty acid ester, polyglycerin fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene acyl ester, polyoxyethylene sorbitan fatty acid ester, oxyethylene-oxypropylene block copolymer is used. The starting surfactants are used.

In the reverse phase suspension polymerization, a water-soluble polymer may coexist with or in place of the surfactant as exemplified above. The purpose of coexistence with the water-soluble polymer is to provide a protective colloid, thickening or grafting, and it is expected that the effects such as improvement of suspension stability and regulation of particle size can be obtained.

[0006] When the reverse phase suspension polymerization of (meth) acrylic acid and the water-soluble salt of (meth) acrylic acid in a hydrocarbon solvent is carried out, coexistence of a water-soluble polymer is disclosed in the following applications. There is something like.

Japanese Unexamined Patent Publication No. 2-153907 discloses an HL
It is disclosed that a mixed surfactant of a sorbitan fatty acid ester having a B value in the range of 1 to 8 and a sucrose fatty acid ester having an HLB value in the range of 1 to 6 coexists. , Sorbitan monostearate and sucrose fatty acid ester are coexistent with hydroxyethyl cellulose.

In JP-A-2-196802, a sucrose fatty acid ester and / or a polyglycerin fatty acid ester is used as a dispersant, and in order to adjust the viscosity of a water-soluble ethylenically unsaturated monomer aqueous solution, a hydroxy compound is used. Ethyl cellulose, hydroxypropyl cellulose,
It is described that a thickener such as methylcellulose, carboxymethylcellulose, polyethylene glycol, polyacrylamide, polyethyleneimine, polyacrylic acid, polyacrylic acid (partial) neutralized product crosslinked product, dextrin, sodium alginate can be used,
In the example, an example in which hydroxyethyl cellulose or sodium polyacrylate is present in the aqueous monomer solution is given.

JP-A-3-195713 discloses that an acrylic acid-based monomer containing (meth) acrylic acid and its salt as a main component is used as a dispersant in the presence of a water-soluble radical polymerization initiator and hydroxyethyl cellulose. HLB3
It has been shown to polymerize by the water-in-oil type reverse phase suspension polymerization method using sorbitan fatty acid ester of ~ 6.

JP-A-56-76419 discloses that an aqueous solution of an alkali metal acrylate containing hydroxyethyl cellulose is dispersed in the presence of a sorbitan fatty acid ester of HLB 3 to 6 and polymerized in the absence of a crosslinking agent. A method of making a water-swellable polymer is shown.

In JP-A-60-36534, sorbitan fatty acid ester, cellulose ether (ethyl cellulose, benzyl cellulose, etc.), cellulose ester (cellulose acetate, cellulose butyrate) is used as a protective colloid for reverse phase suspension polymerization. , Cellulose acetate butyrate, etc.) and polymer dispersants (maleinated polybutadiene, maleated polyethylene, maleated α-olefin, etc.) can be used.

JP-A-63-118308 describes that graft polymerization may be carried out in the presence of a monomer component such as a partially neutralized salt of acrylic acid and starch, cellulose or a derivative thereof, polyvinyl alcohol or the like. There is.

In JP-A-60-186506, in suspension polymerization of an aqueous solution of poly (meth) acrylate in a hydrocarbon or a halogenated aromatic hydrocarbon, oil-soluble cellulose ester or a protective ester is used as a protective colloid. It has been shown to use cellulose ethers.

JP-A-4-120111 and JP-A-4-120112 disclose that a water-soluble monomer is polymerized with a polysaccharide (starch, cellulose) and / or a crosslinking agent. Examples using polysaccharides, including Example 11 (both publications) relating to reverse phase suspension polymerization, are not mentioned.

The highly water-absorbent resin is also required to have a high swelling gel strength, have mamako-preventing properties, and have improved water-absorbing ability and water-absorbing speed. From this point of view, Japanese Patent Application Laid-Open No. 3-126730 filed by the applicant of the present invention discloses that the surface of superabsorbent resin particles having a carboxyl group has two or more functional groups capable of reacting with the carboxyl group in the molecule. A method is shown in which a polyfunctional compound is attached and then superabsorbent resin particles to which the polyfunctional compound is attached are treated with a carboxyl group-containing water-soluble polymer.

[0016]

In the production of superabsorbent resin, if a large amount of fine particles are produced or the particle size distribution is wide, the yield of the target particle size is reduced, and the productivity is lowered. Especially when a large amount of fine particles are generated, it is difficult to smoothly perform various processes such as decantation, filtration, and drying.
Dust is also generated during handling, which is a significant disadvantage in terms of workability.

Also in terms of the performance of the super absorbent polymer, the dispersion of the powder performance becomes large when the particle size distribution is wide. In addition, when the particle size is small, the Mamako phenomenon occurs when it comes into contact with water or body fluid, and when it is used in combination with a material with coarse mesh such as non-woven fabric, the particles may leak from the eyes of the material. It will cause troubles during use.

Therefore, it is strongly desired that generation of fine particles is suppressed during reverse phase suspension polymerization, particles having an appropriate average particle size of about 200 to 350 μm are obtained, and that the particle size distribution at that time is sharp. .

However, although the method disclosed in JP-A-2-153907 has succeeded in increasing the average particle size, it has a relatively wide particle size distribution and a considerable amount of fine particles, so that the target particle size is obtained. However, there is a problem in that the acquisition rate of the product decreases, and processes such as filtration and drying cannot be performed smoothly. The particles obtained in Comparative Example 6 according to an example in which hydroxyethyl cellulose coexisted with sorbitan monostearate and sucrose fatty acid ester had an average particle size of 490 μm, which was too large, and had a tendency to aggregate. There are various problems such as low speed and low water retention capacity.

The method disclosed in JP-A-2-196802 is
Particles with a particle size of about 150 to 550 μm can be obtained, but the allowable range of manufacturing conditions is narrow, and there is a tendency for them to agglomerate due to slight differences in the conditions such as the shape of the stirring blade and reaction vessel, stirring conditions, and the amount dropped. There is a problem that it is difficult to adopt industrially. In addition, in the method of this publication, there is a disadvantage that scaling easily occurs on the wall of the polymerization reactor and the stirring blades, and one of the causes is considered to be the thickener added for viscosity adjustment. .

The method disclosed in Japanese Patent Laid-Open No. 3-195713 is
Although particles of 202 to 355 μm are obtained in the examples, since the particle size distribution is wide, fine particles are also generated in a considerable proportion, and the obtained particles are actually aggregates of small particles and are not classified as primary particles. The particle size itself is small, for example, when it is applied to a disposable diaper, it has a fine particle size of 1 when absorbing urine.
There is a problem that the particles return to the next particles and leak out from the eyes of materials such as nonwoven fabric.

Japanese Unexamined Patent Publication (Kokai) No. 60-36534 does not describe the particle size of the superabsorbent resin obtained, and it is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 4-1.
Although there is no description in JP-A No. 20111 and JP-A No. 4-120112 about the particle size of the super absorbent polymer obtained by reverse phase suspension polymerization, the particle size is appropriately large and the particle size distribution is sharp in each case. Things are hard to come by. In JP-A-56-76419, the particle size is 10 to 300.
A highly water-absorbent resin of about μm is obtained, and there is a problem that the proportion of fine particles is too large. In JP-A-60-186506, since an oil-soluble cellulose ester or cellulose ether is used and dissolved in the hydrocarbon side, there is a risk of agglomeration due to a slight difference in conditions. Although particles having a median particle diameter of about 100 to 350 μm are obtained, there is a problem that a large proportion of particles having a small particle diameter is large. In Japanese Patent Laid-Open No. 63-118308, a super absorbent polymer is obtained in small pieces, which are then cut and further pulverized.

Further, in order to improve the strength of the swollen gel, the mamako prevention property, the water absorption capacity and the water absorption speed, the surface of the superabsorbent resin particles having a carboxyl group has a functional group capable of reacting with the carboxyl group in the molecule. The method described in JP-A-3-126730, in which a polyfunctional compound having at least one polyfunctional compound is adhered, and then the superabsorbent resin particles to which the polyfunctional compound is adhered are treated with a carboxyl group-containing water-soluble polymer, is also the original high water absorption. In producing the resin particles, it is inevitable that fine particles are generated, the average particle size is small, or the particle size distribution is wide, so even if the above method is taken, only a certain degree of effect can be obtained. There was a limit.

The present invention has the following background.
During reverse phase suspension polymerization of an aqueous solution of a water-soluble unsaturated monomer containing (meth) acrylic acid and a water-soluble salt of (meth) acrylic acid as main components, a specific polysaccharide is allowed to coexist, together with a specific polysaccharide. By subjecting the resin after polymerization to a specific surface treatment, scaling does not occur in the reactor or stirring blade during polymerization, the generation of fine particles is suppressed, and it has a moderate average particle size and sharp particle size distribution that are easy to handle. Furthermore, it is an object of the present invention to provide a method for obtaining a highly water-absorbent resin having a high swelling gel strength, a mamako prevention property, and an improved water absorption capacity and water absorption rate.

[0025]

The method for producing a superabsorbent resin of the present invention comprises the steps of adding (meth) acrylic acid and a water-soluble salt of (meth) acrylic acid in the presence of β-1,3-glucans. To obtain super absorbent polymer particles by reverse phase suspension polymerization of an aqueous solution of a water-soluble unsaturated monomer as a main component in a hydrocarbon solvent using a radical polymerization initiator in the presence or absence of a cross-linking agent. , And a polyfunctional compound having two or more functional groups capable of reacting with a carboxyl group in the molecule attached to the surface of the superabsorbent resin particles obtained above, and then the superabsorbent polymer having the attached polyfunctional compound. The functional resin particles are treated with a carboxyl group-containing water-soluble polymer.

The present invention will be described in detail below.

In the present invention, a water-soluble unsaturated monomer containing (meth) acrylic acid and a water-soluble salt of (meth) acrylic acid as main components is used as the monomer. This monomer can be obtained by partially neutralizing (meth) acrylic acid with an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate, ammonium hydroxide or amines.

The mixing ratio of (meth) acrylic acid and the water-soluble salt of (meth) acrylic acid is 40:60 to 5: 9 by weight.
It is preferably 5, especially 30:70 to 10:90. That is, the degree of partial neutralization of (meth) acrylic acid is 60 to 95 mol% of the total (meth) acrylic acid, especially 70 to 9%.
It is preferably 0 mol%, in other words, the number n of free carboxyl groups contained in 100 structural units of the super absorbent polymer is preferably 5 to 40, particularly preferably 10 to 30. When the number n of free carboxyl groups is too small, the desired effect cannot be obtained because the reactivity with the polyfunctional compound is poor.
Further, it is difficult for the product particles to be alkaline. On the other hand, when the number n of free carboxyl groups is too large, the water-absorption capacity and water-absorption rate of the resulting superabsorbent resin decrease, and it is difficult for the product particles to exhibit acidity.

The cross-linking agent may or may not be present, but it is desirable to use a small amount of cross-linking agent. Examples of the crosslinking agent when the crosslinking agent is used include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth).
Acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, N, N'-methylenebis (meth) acrylamide,
Examples thereof include triallyl isocyanurate, (poly) ethylene glycol diglycidyl ether, glycerin polyglycidyl ether, sorbitol polyglycidyl ether and pentaerythritol polyglycidyl ether. The amount of the cross-linking agent used is 0.0001 to the monomer component.
It is often about 0.5% by weight.

Examples of the radical polymerization initiator include azobisisobutyronitrile, t-butyl peroxide, cumene hydroperoxide, di-t-butyl peroxide, acetyl peroxide, lauroyl peroxide, stearoyl peroxide and benzoyl peroxide. Examples include oxide, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxypivalate, methyl ethyl ketone peroxide, cyclohexanone peroxide, hydrogen peroxide, ammonium persulfate, potassium persulfate, and cerium salt. Those that are water-soluble are particularly preferable. The amount of the radical polymerization initiator used is often about 0.01 to 1% by weight with respect to the monomer component.

As the hydrocarbon solvent, cyclohexane,
Alicyclic hydrocarbons such as cyclopentane and methylcyclohexane, n-pentane, n-hexane, n-heptane, n
Examples thereof include aliphatic hydrocarbons such as oritan and ligroin, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, and halogenated hydrocarbons such as chlorobenzene and carbon tetrachloride. Among these, n-hexane and cyclohexane are particularly important in consideration of the boiling point, melting point, cost, and industrial availability of the solvent.

As described above, an aqueous solution of a water-soluble unsaturated monomer containing (meth) acrylic acid and a water-soluble salt of (meth) acrylic acid as a main component is added to a radical polymerization initiator in the presence or absence of a crosslinking agent. Is used for reverse phase suspension polymerization in a hydrocarbon solvent. At this time, it is suitable to set the polymerization temperature to 50 to 90 ° C. and the polymerization time to about 0.5 to 5 hours.

In the present invention, the reverse phase suspension polymerization is carried out in the presence of β-1,3-glucans. This is the first point of the present invention.

Β-1,3-glucans are β-1,3
-Refers to a polysaccharide having a backbone consisting of glucosidic bonds,
Particularly, a branched β-1,3-glucan having a glucose branch having β-1,6-bonded to such a main chain glucose is desirable, and further, one of the β-1,6-bonded glucose is preferable. Those having a sulfur-containing substituent in the part are particularly desirable. Here, as the sulfur-containing substituent, a sulfoacetic acid group is particularly important, and in addition, a sulfonic acid group, a polysulfonic acid group, a cysteine group, a methionine group and the like can be mentioned.

Such β-1,3-glucans are typically prepared from a microorganism belonging to the genus Aureobasidium,
Sucrose, glucose, fructose, etc. are used as a carbon source, sodium nitrate, ammonium nitrate, ammonium sulfate, yeast extract, peptone, etc. are used as a nitrogen source, and magnesium sulfate, an inorganic sulfur source such as iron sulfate is used as a trace factor, and further required. Depending on the use, a medium to which metal ions such as magnesium ions and iron ions and vitamins such as ascorbic acid and pantothenic acid are added is used at 1 to 60 ° C. (preferably 25 to 35 ° C.).
A culture solution is obtained by culturing under aeration conditions for about 10 days, cells are separated from the culture solution by means such as centrifugation and filtration, and a solvent and metal ions are added to the resulting clean solution to cause precipitation. It is then obtained by drying and crushing.

A typical β-1,3-glucan obtained by this method is a branched β-1,3-glucan having a sulfoacetic acid group as a substituent, as shown in the following chemical formula 1. In addition, there are 3 branches of β-1,6-bonded glucose per 4 glucose in the main chain, and 0.1 to 1 of the sulfoacetic acid group-containing substituents are present in the glucose branch.
% By weight.

[0037]

Embedded image

The coexisting amount of β-1,3-glucans in the reverse phase suspension polymerization is 0.001 to 5 with respect to the water-soluble unsaturated monomer.
% By weight, preferably 0.002 to 2% by weight, especially 0.0
It is set to 05-1% by weight. When the amount is too small, it is not possible to sufficiently achieve the intended purpose of suppressing the generation of fine particles, obtaining particles having an appropriate average particle diameter, and sharpening the particle size distribution, while the amount is too small. When the amount is large, β-1,3-glucans are not uniformly dispersed or dissolved in the solution, so that the particle size distribution may be broadened.

In addition to β-1,3-glucans, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, dextrin, sodium alginate, polyvinyl alcohol, polyacrylamide, polyethylene glycol and The use of other water-soluble polymers such as polyethyleneimine does not cause any problems.

In the reverse phase suspension polymerization, it is usual to coexist with an oil-soluble surfactant having an HLB of 10 or less (preferably 9 or less). Typical examples of such oil-soluble surfactants include sorbitan fatty acid ester (sorbitan monopalmitate, sorbitan monostearate, sorbitan sesquistearate, sorbitan tristearate, etc.), sucrose fatty acid ester (sucrose and stearin). Acid, palmitic acid, lauric acid, mono-, di- or triester with fatty acid such as oleic acid) and the like. This oil-soluble surfactant is dissolved on the hydrocarbon solvent side. The coexisting amount of the oil-soluble surfactant is 5% by weight or less with respect to the water-soluble unsaturated monomer, usually 0.05 to 3% by weight,
Especially, it is often set to 0.1 to 2% by weight. The use of oil-soluble surfactants is advantageous in preventing particle size reduction or agglomeration.

In the inverse layer suspension polymerization, a hydrocarbon solvent is charged with an aqueous solution of a water-soluble unsaturated monomer containing β-1,3-glucans and a radical polymerization initiator. And the ratio by weight is 1
It is often 0: 1 to 1: 1 and preferably 5: 1 to 2: 1.

The method of charging the aqueous solution at this time may be batch charging, intermittent charging, or continuous charging. However, intermittent charging or continuous charging is performed, and during such charging, a part of the water is hydrocarbon. Azeotropic removal with the solvent to the outside of the system is particularly preferable because the heat of polymerization is uniformly generated and the polymerization reaction can be kept stable.

After completion of the polymerization, decantation, filtration,
The produced particles are separated by centrifugation or the like, and then washed and dried. As a result, generation of fine particles is suppressed, and a highly water-absorbent resin particle having an appropriate particle size (about 200 to 350 μm) and a sharp particle size distribution and having a porous shape is obtained. Moreover, in the present invention in which β-1,3-glucans are allowed to coexist, scaling does not easily occur in the reactor and the stirring blade during polymerization.

In the present invention, the surface of the super absorbent polymer particles before or after drying obtained as described above is
A polyfunctional compound having two or more functional groups capable of reacting with a carboxyl group is attached to the molecule, and then the super absorbent polymer particles to which the polyfunctional compound is attached are treated with a carboxyl group-containing water-soluble polymer. This is the second point of the present invention.

Examples of the polyfunctional compound having two or more functional groups capable of reacting with a carboxyl group in the molecule include 3,4-
Epoxycyclohexanecarboxylic acid-3 ', 4'-epoxycyclohexyl ester, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol Diglycidyl ether, trimethylolpropane triglycidyl ether, etc. are used.

As the carboxyl group-containing water-soluble polymer, one or more polymers of ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, cholic acid, maleic acid, maleic anhydride, itaconic acid, etc. And a copolymer of the other ethylenically unsaturated carboxylic acid with another copolymerizable monomer. The number average polymerization degree of the carboxyl group-containing water-soluble polymer is 100 or more (especially 500).
To 60,000) is desirable.

Number N of free carboxyl groups contained in 100 constitutional units of carboxyl group-containing water-soluble polymer
Is usually 40 or more, preferably 50 or more, especially 7
It is desirable that the number is 0 or more, and n <N is satisfied in relation to the number n of free carboxyl groups contained in 100 constituent units of the super absorbent polymer particles described above.

To attach the polyfunctional compound to the surface of the super absorbent polymer particles, for example, the polyfunctional compound is dissolved in a hydrophobic solvent such as benzene, toluene, xylene, cyclohexane or hexane to form a solution. After mixing with the super absorbent polymer particles, a method of expelling the solvent at room temperature or under heating is adopted. It should be noted that the use of a hydrophilic solvent is preferably avoided if possible because the polyfunctional compound may enter the super absorbent polymer particles and react therewith to lower the water absorbing ability.

It is desirable that the amount of the polyfunctional compound attached to the superabsorbent resin particles be 10 ppm or more (particularly 20 to 500 ppm). When the amount of the attached polyfunctional compound is too small, the strength of the swollen gel is lowered. Tend to do.

To treat the super absorbent polymer particles (the former) to which the polyfunctional compound is attached with the carboxyl group-containing water-soluble polymer (the latter), both are mixed in a powder state and the latter is heated while spraying water. Method of dissolving and reacting,
A method of mixing the latter powder with the former to heat and dissolve it, a method of spraying the latter with an aqueous solution of the latter for heating, and the like are adopted. These heating reactions are usually carried out at a temperature of 40 to 10.
The final cross-linking reaction is achieved at 0 ° C. for about 0.1 to 2 hours.

The amount of the carboxyl group-containing water-soluble polymer attached to the highly water-absorbent resin particles to which the polyfunctional compound is attached is preferably 0.2 to 6% by weight, particularly 0.5 to 5% by weight.

The superabsorbent resin obtained by the method of the present invention described above is particularly useful as a body fluid absorbent for absorbing body fluids and excretions and preventing leakage in sanitary products and sanitary products. In addition, soil water retention agent, seed coating agent,
Waterstops, thickeners, anti-condensation agents, dehydrators, desiccants, humidity regulators, coagulants for sludge and liquid waste, heavy metal adsorbents, chemicals
It can also be used for applications such as sustained-release agents for fragrances and poultices.

[0053]

In the present invention, the reverse phase suspension polymerization of the water-soluble unsaturated monomer is devised so as to be carried out in the coexistence of β-1,3-glucans (or the oil-soluble surfactant) and the polymerization. Occasionally, the reactor and the stirring blade are less likely to be scaled, and the generation of fine particles is suppressed, and super absorbent polymer particles having an appropriate average particle size (about 200 to 350 μm) and a sharp particle size distribution that are easy to handle are obtained. This is because in the system of high viscosity (meth) acrylic acid partially neutralized salt, the thickening effect is diminished by the usual water-soluble polymer,
One reason is that high viscosity is maintained in the system in which β-1,3-glucans are present.

Further, after the superabsorbent resin particles were obtained as described above, a special measure was taken for the surface treatment, so that the swelling gel was combined with the preferable particle size and particle size distribution of the original superabsorbent resin particles. It is possible to obtain a highly water-absorbent resin having a high strength, an anti-muddy property, and an improved water absorbing ability and water absorbing speed.

[0055]

EXAMPLES The present invention will be further described with reference to examples. Hereinafter, "%" means% by weight.

Example 1 <Production of β-1,3-glucans> Aureobasidium sp. K-1 which is a microorganism belonging to the genus Aureobasidium
(FERM P-12989) was added to Czapek medium (sucrose 3
%, Sodium nitrate 0.2%, potassium phosphate 0.1%, potassium chloride 0.05%, magnesium sulfate heptahydrate 0.05
%, Ferrous sulfate heptahydrate (0.001%) at 27 ° C for 48 hours with shaking, as the inoculum, under the conditions of a temperature of 27 ° C with a jar fermenter, a stirring rate of 300 rpm, and an aeration rate of 50 liters / min. It was cultured for 96 hours.

Then, the cells were separated and removed from the culture broth by filtration, and 1.2 volumes of isopropanol was gradually added to the obtained filtrate with vigorous stirring. The precipitated polysaccharide fibers were collected, immersed in an acetone bath, washed, dehydrated, and dried at 70 ° C. Such fibers were pulverized with a feather shoe to be powdered to obtain a polysaccharide.

When this polysaccharide was analyzed by a conventional method (Science and Industry, 64 (3), 131-135 (1990), Agricultura
l & Biological Chemistry, 47 (6), 1167-1172 (1983)
This is a polysaccharide having the structure of the above-mentioned chemical formula 1, that is, a branched β having a sulfoacetic acid group as a substituent.
It was confirmed to be -1,3-glucan. The total number of glucose units in one molecule was about 1500, and the total sulfur content was 0.05%.

<Reverse Phase Suspension Polymerization> Next, polyacrylic acid partially neutralized salt-based highly water-absorbent resin particles were produced by the reverse phase suspension polymerization method described in detail below.

In a 2 liter separable flask A equipped with a stirrer, a reflux condenser and a nitrogen gas inlet tube, 800 g of cyclohexane and 0.8 g of sorbitan monostearate.
And 0.8 g of sucrose fatty acid ester ("DK Ester F-70" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was charged and nitrogen bubbling was performed for 30 minutes to expel the dissolved air and the air in the flask.

260 g of an 80% aqueous solution of acrylic acid was charged into another separable flask B, and 310 g of a 28% aqueous sodium hydroxide solution was gradually added dropwise under cooling to neutralize. This neutralized 75% of the acrylic acid. Next, 8 g of 0.5% N, N'-methylenebisacrylamide aqueous solution and 0.3 g of the branched β-1,3-glucan having the sulfoacetic acid group as a substituent obtained above (almost to the monomer).
0.1%) was added and dissolved. After the dissolution, 4 g of a 10% ammonium persulfate aqueous solution was added, and nitrogen bubbling was performed while stirring to expel the dissolved air.

After the temperature of Flask A was raised to 73 ° C., the solution in Flask B was added dropwise over 1.5 hours. The rotation speed during polymerization was set to 350 rpm. After that, keep warm water in the jacket at 75 ° C and azeotrope cyclohexane with water.
Expelled 30 ml. Then, after decanting, the produced particles are dried at a temperature of 105 ° C. for 3 hours to obtain a water content of 3
0% super absorbent polymer particles were obtained. Almost no scaling was observed on the flask wall and the stirring blade used for the polymerization.

The average particle size of this particle is 308 μm, 105
The proportion of fine particles below μm is 3.5%, and the water absorption capacity is 8 for pure water.
90 g / g, 0.9% saline was 72 g / g.

<Post-treatment> The highly water-absorbent resin particles obtained above (the number n of free carboxyl groups contained in 100 structural units n)
= 25) and a water content of 30%
0 g was charged in a kneader, and 3,4-epoxycyclohexanecarboxylic acid-3 ′, which was an example of a polyfunctional compound,
A solution of 0.025 g of 4'-epoxycyclohexyl ester dissolved in 30 g of cyclohexane was added and mixed, and then cyclohexane was expelled to deposit 250 ppm of the polyfunctional compound on the superabsorbent resin particles.

Then, the super absorbent polymer particles to which the polyfunctional compound was attached were added to a polyacrylic acid powder (number average molecular weight 300) as an example of a carboxyl group-containing water-soluble polymer.
00, particle size 100 mesh pass, and 1 g of free carboxyl groups contained in 100 constitutional units (N = 100) were added and mixed sufficiently to obtain a uniform composition. The mixture was heat-treated under kneading at a temperature of 90 ° C. for 0.5 hours, and further dried at 90 ° C. for 1.5 hours in a vacuum dryer to obtain the desired highly water-absorbent resin.

The average particle size of the obtained resin is 360 μm, 1
The ratio of fine particles of 05 μm or less is 1.5%, the water absorption capacity is 870 g / g of pure water, 70 g / g of 0.9% saline solution, the water absorption rate of 0.9% saline solution is 40 g / g, the strength of swelling gel is ◎, Mamako The preventive property was ○.

<Characteristic Evaluation Method of Super Water Absorbent Resin> In the above and below, the characteristic evaluation of the super water absorbent resin was performed as follows.

The average particle size was determined based on the mesh size at which 50% of the particles passed when the standard sieve was used for sieving.

The water absorption rate was measured according to the tea bag method using 0.9% saline. With respect to 1 g of the highly water-absorbent resin, the amount of water absorbed after 1 minute was measured and expressed in g.

Water absorption capacity of pure water and 0.9% saline solution 300 containing 200 g of pure water or 60 g of 0.9% saline solution
Weigh 0.1 g of super absorbent polymer into a beaker of ml capacity, put it into the beaker, leave it at room temperature for 1 hour, and then filter the swollen gel with a 200 mesh wire net for 20 minutes, and weigh the swollen gel after draining. Was measured and calculated.

Strength of swollen gel Superabsorbent resin 1 in a glass bottle having a diameter of 50 mm and a height of 90 mm
Grams were taken, 0.9% saline solution was added 0.7 times the 0.9% saline absorption amount per 1 g determined in the above water absorption rate measurement, and the mixture was left to stand for 1 hour for swelling to form a gel. After leaving it, lay the above glass bottle on a wooden table and tap it gently.
The swollen gel in the glass bottle was evaluated according to the following criteria. ⊚: The swollen gel does not move even when hitting the glass bottle. ○: When the glass bottle is hit, the swollen gel finally moves. ×: The swollen gel moves just by laying the glass bottle on its side.

Mammaco-preventing property 1 g of the highly water-absorbent resin was put into a beaker having a capacity of 100 ml at a time, and the occurrence of Mamako was evaluated based on the following criteria. ○: Mamako does not occur at all. △: A little Mamako occurred. ×: A large lump of Mamako occurred.

Example 2 Except that the amount of the branched β-1,3-glucan having a sulfoacetic acid group as a substituent was 1/10 of that in Example 1, 0.03 g (approximately 0.01% based on the monomer). Example 1 was repeated. Almost no scaling was observed on the flask wall and the stirring blade. The average particle size of the resulting super absorbent polymer particles is 225 μm, and the ratio of fine particles of 105 μm or less is
The water absorption capacity was 7.8%, pure water was 910 g / g, and 0.9% saline was 73 g / g.

Using the resin particles, surface treatment was carried out in the same manner as in Example 1. The average particle size of the obtained resin is 28.
The proportion of fine particles of 0 μm and 105 μm or less is 3.4%, and the water absorption capacity is 900 g / g for pure water and 71 g / g for 0.9% saline solution.
The water absorption rate of 0.9% saline was 37 g / g, the strength of the swollen gel was ⊚, and the anti-muddyness was ∘.

Comparative Example 1 Inverse layer suspension polymerization was carried out in the same manner as in Example 1 except that the addition amount of branched β-1,3-glucan having a sulfoacetic acid group as a substituent was omitted. The average particle size of the resulting super absorbent polymer was 173 μm, and the ratio of fine particles of 105 μm or less was 17.7%.
Water absorption capacity is 920g / g for pure water and 73g / g for 0.9% saline.
Met.

Using this resin particle, a surface treatment was carried out in the same manner as in Example 1. The average particle size of the obtained resin is 19
The proportion of fine particles of 0 μm and 105 μm or less is 15.6%, and the water absorption capacity is 865 g / g for pure water and 70 g / g for 0.9% saline solution.
The water absorption rate of 0.9% saline was 32 g / g, the strength of the swollen gel was ⊚, and the anti-muddyness was ∘.

Comparative Example 2 Example 1 was repeated except that 0.3 g of hydroxyethyl cellulose was added instead of the branched β-1,3-glucan having a sulfoacetic acid group as a substituent. At this time, some scaling was observed on the flask wall and the stirring blade. The average particle diameter of the superabsorbent resin particles obtained was 184 μm, 10
The proportion of fine particles of 5 μm or less was 16.3%, and the water absorption capacity was 920 g / g in pure water and 73 g / g in 0.9% saline.

Using this resin particle, a surface treatment was carried out in the same manner as in Example 1. The average particle size of the obtained resin is 20
The proportion of fine particles of 0 μm and 105 μm or less is 15.6%, and the water absorption capacity is 900 g / g for pure water and 69 g / g for 0.9% saline solution.
The water absorption rate of 0.9% saline was 32 g / g, the strength of the swollen gel was ⊚, and the anti-muddyness was ∘.

Comparative Example 3 By repeating the procedure of Comparative Example 2 except that the amount of hydroxyethyl cellulose added was changed to 1.5 g, superabsorbent resin particles having substantially the same properties as those of Comparative Example 2 were obtained. And the scaling to the stirring blade was significant.

[0080]

INDUSTRIAL APPLICABILITY In the present invention, reverse phase suspension polymerization of an aqueous solution of a water-soluble unsaturated monomer is carried out in the presence of β-1,3-glucans (or an oil-soluble surfactant thereof). As a result of the ingenuity, scaling did not occur in the reactor and stirring blade during polymerization, the generation of fine particles was suppressed, and a super absorbent polymer particle with a moderate average particle size (about 200 to 350 μm) and a sharp flow distribution that was easy to handle was used. Can be manufactured stably. Therefore, the yield of the target particle size is increased and the productivity is improved, various processes such as decantation, filtration, and drying can be smoothly performed, and the generation of dust during handling is small, and the workability is good. Becomes

Further, after the superabsorbent resin particles were obtained as described above, a special measure was taken for the surface treatment of the superabsorbent resin particles, so that the swelling gel was combined with the preferable particle size and particle size distribution of the original superabsorbent resin particles. It is possible to obtain a highly water-absorbent resin having a high strength, an anti-muddy property, and an improved water absorbing ability and water absorbing speed.

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Claims (6)

[Claims] 1. In the presence of β-1,3-glucans, an aqueous solution of a water-soluble unsaturated monomer containing (meth) acrylic acid and a water-soluble salt of (meth) acrylic acid as main components is used as a crosslinking agent. To obtain superabsorbent resin particles by reverse phase suspension polymerization in a hydrocarbon solvent using a radical polymerization initiator under or in the absence, and, on the surface of the superabsorbent resin particles obtained above, A polyfunctional compound having two or more functional groups capable of reacting with a carboxyl group is attached to the molecule, and then the super absorbent polymer particles to which the polyfunctional compound is attached are treated with a carboxyl group-containing water-soluble polymer. A method for producing a superabsorbent resin having a characteristic feature. 2. β-1,3-glucans are β-1,3-glucans.
Β-1,6 is added to the main chain glucose composed of glucoside bonds.
2. The method according to claim 1, which is a branched β-1,3-glucan having a branch of bound glucose, wherein the β-1,6-linked glucose has a sulfur-containing substituent in part thereof. 3. The method according to claim 2, wherein the sulfur-containing substituent is a sulfoacetic acid group. 4. The method according to claim 1, wherein the coexisting amount of β-1,3-glucans is 0.001 to 5% by weight based on the water-soluble unsaturated monomer. 5. The method according to claim 1, wherein the reverse phase suspension polymerization is carried out in the coexistence of 5% by weight or less of an oil-soluble surfactant having an HLB of 10 or less with respect to the water-soluble unsaturated monomer. . 6. The number of free carboxyl groups contained in 100 constituent units of the super absorbent polymer particles is n, and the number of free carboxyl groups contained in 100 constituent units of the carboxyl group-containing water-soluble polymer is N. The manufacturing method according to claim 1, wherein n <N at the time of performing.