WO2006068067A1

WO2006068067A1 - Process for producing water-absorbing resin particle

Info

Publication number: WO2006068067A1
Application number: PCT/JP2005/023224
Authority: WO
Inventors: Kenya Matsuda; Yasuhiro Nawata
Original assignee: Sumitomo Seika Chemicals Co., Ltd.
Priority date: 2004-12-24
Filing date: 2005-12-19
Publication date: 2006-06-29
Also published as: JPWO2006068067A1

Abstract

A process for producing water-absorbing resin particles which comprises: mixing a precursor (A) for water-absorbing resin particles with a compound (B) having two or more polymerizable unsaturated groups, the precursor (A) being one obtained by polymerizing a water-soluble ethylenic monomer and the amount of the compound (B) being 0.01-10 parts by weight per 100 parts by weight of the water-soluble ethylenic monomer; and reacting the resultant mixture. The water-absorbing resin particles are usable in, e.g., sanitary materials such as a disposable diaper and sanitary napkin, agricultural or horticultural materials such as a water-holding material and soil-improving material, and industrial materials such as a waterstop material for cables and material for dew condensation prevention.

Description

Specification

Method for producing water absorbent resin particles

Technical field

[0001] The present invention relates to a method for producing water-absorbent resin particles. More specifically, the present invention relates to a method for producing water-absorbent rosin particles having a high water absorption capacity even under a load.

Background art

[0002] Water-absorbent coagulants are widely used in various fields such as sanitary materials such as disposable diapers and sanitary items, agricultural and horticultural materials such as water retention materials and soil improvement materials, water-proofing materials for cables, and anti-condensation materials. Has been.

[0003] Examples of such a water-absorbing resin include a hydrolyzate of starch-acrylonitrile graft copolymer, a neutralized product of starch-acrylic acid graft copolymer, and a keny of butyl acetate acrylate copolymer. And polyacrylic acid partially neutralized products are known. In particular, polyacrylic acid partially neutralized products are excellent in productivity and economy, and thus are suitably used for sanitary materials and the like.

[0004] In recent years, water-absorbing articles such as disposable diapers tend to be thinned by reducing the content of hydrophilic fibers that are bulky and having a small amount of water absorption, increasing the proportion of water-absorbing resin having a large amount of water absorption. . In addition to a high water absorption ratio, the water-absorbent resin used in the absorbent containing a high concentration of water-absorbent resin has excellent water absorption rate, gel strength during swelling, and water absorption performance under load. It is required to be.

[0005] However, when the water absorption capacity is increased, the water absorption capacity generally tends to decrease the water absorption speed, gel strength, and water absorption capacity under load. In particular, when water-absorbing resin is used for the absorber, the body fluid is not sufficiently absorbed by the water-absorbing resin when the absorbent is heavily loaded. The performance of the liquid is not fully demonstrated, and the amount of return of the liquid increases.

[0006] Therefore, as a conventional method for increasing the water absorption capacity under load, water-absorbent resin particles using a crosslinking agent having at least two reactive groups capable of reacting with carboxylic acid and Z or carboxylic acid group. For cross-linking the surface layer of, for example, a polyvalent glycidyl compound, The cross-linking density of the surface layer is increased under a load by a method using a polyamine compound, a polyvalent isocyanate compound, etc. (for example, see Patent Document 1), a method using a polyhydric alcohol (for example, see Patent Document 2), etc. A method for increasing the amount of water absorption has been proposed.

[0007] However, the method using a crosslinking agent has a problem in the safety and reactivity of the crosslinking agent used. For example, crosslinkers with high reactivity such as isocyanate groups have skin irritation, so control of unreacted crosslinkers for use in hygiene materials that may come into direct contact with the skin. Need to be strict. On the other hand, since polyhydric alcohol has low reactivity, it requires a high reaction temperature and a long reaction time, so that not only the productivity is low, but also the water-absorbent resin particles after surface crosslinking are colored or deteriorated. Sometimes.

[0008] Therefore, in recent years, there has been a demand for development of a method for improving the water absorption capacity under load by a new method replacing the method using a crosslinking agent.

Patent Document 1: Japanese Patent Laid-Open No. 59-189103

Patent Document 2: JP-A-58-180233

Disclosure of the invention

Problems to be solved by the invention

[0009] An object of the present invention is to provide a method for producing water-absorbent resin particles having a high water absorption capacity under no load and also having a high water absorption capacity under a load.

Means for solving the problem

That is, the present invention relates to a precursor (A) of water-absorbent resin particles obtained by polymerizing a water-soluble ethylenically unsaturated monomer, and 100 parts by weight of the water-soluble ethylenically unsaturated monomer. The present invention relates to a method for producing water-absorbent resin particles in which 0.01 to 10 parts by weight of a compound (B) having two or more polymerizable unsaturated groups is mixed and the resulting mixture is reacted.

The invention's effect

[0011] According to the present invention, it is possible to produce water-absorbent resin particles that not only have a high water absorption capacity under no load but also have a high water absorption capacity under a load.

Brief Description of Drawings

FIG. 1 is a schematic explanatory diagram of an apparatus for measuring water absorption under pressure. Explanation of symbols

[0013] X measuring device

1 Bullet

10 Burette

11 Intake pipe

12 = f

13 = 3

14 Rubber bowl

2 conduit

3 Measuring table

4 Measurement unit

40 cylinder

41 nylon mesh

42 Weight

5 Water absorbent oil particles

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] The precursor of the water-absorbent resin particles is obtained by polymerizing a water-soluble ethylenically unsaturated monomer.

[0015] Examples of the water-soluble ethylenically unsaturated monomer include (meth) acrylic acid ["(meth) atari" means "atari" or "metatali". The same shall apply hereinafter), 2- (meth) acrylamide, 2-methylpropanesulfonic acid or alkali metal salts thereof; (meth) acrylamide, N, N-dimethylacrylamide, 2-hydroxyethyl (meth) acrylate, N— Nonionic monomers such as methylol (meth) acrylamide; amino group-containing unsaturated monomers such as jetylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, or quaternized products thereof They may be used alone or in combination of two or more. Examples of the alkali metal in the alkali metal salt include lithium, sodium and potassium.

[0016] The water-soluble ethylenically unsaturated monomer is preferable because it is easily available industrially. Is at least one selected from the group consisting of (meth) acrylic acid and its alkali metal salts, (meth) acrylamide and N, N-dimethylacrylamide, more preferably (meth) acrylic acid and (meth) At least one selected from the group consisting of sodium acrylate

[0017] The water-soluble ethylenically unsaturated monomer can usually be used as an aqueous solution. It is preferable that the concentration of the water-soluble ethylenically unsaturated monomer in the aqueous solution of the water-soluble ethylenically unsaturated monomer is 25% by weight to the saturated concentration.

[0018] When the water-soluble ethylenically unsaturated monomer contains an acid group, the acid group may be neutralized with an alkali metal and used as an alkali metal salt. The degree of neutralization of water-soluble ethylenically unsaturated monomers with alkali metals is problematic in terms of safety, etc. due to the presence of surplus alkali metals with high osmotic pressure and high water absorption speed of the resulting water-absorbent resin particles. From the viewpoint of preventing the occurrence, it is preferably within the range of 10 to LOO mol% of the acid groups of the water-soluble ethylenically unsaturated monomer before neutralization. Examples of the alkali metal include lithium, sodium, and potassium. Of these, sodium and potassium are preferred.

[0019] The polymerization method of the water-soluble ethylenically unsaturated monomer is not particularly limited, and examples thereof include a reverse phase suspension polymerization method and an aqueous solution polymerization method.

[0020] In the aqueous solution polymerization method, polymerization is performed by heating a water-soluble ethylenically unsaturated monomer aqueous solution, a water-soluble radical polymerization initiator, and, if necessary, a crosslinking agent while stirring as necessary. Done.

[0021] In reversed-phase suspension polymerization, a water-soluble ethylenically unsaturated monomer aqueous solution, a surfactant and Z or a polymer protective colloid, a water-soluble radical polymerization initiator, and, if necessary, a crosslinking agent as a hydrocarbon. Polymerization is carried out by heating under stirring in a system solvent.

[0022] Hereinafter, the reverse phase suspension polymerization method will be described in more detail as an example of the polymerization method of the water-soluble ethylenically unsaturated monomer.

[0023] As the surfactant, for example, sorbitan fatty acid ester, (poly) glycerin fatty acid ester ["(poly)" means both the case with and the prefix of "poly". The same shall apply hereinafter), non-ionic surfactants such as sucrose fatty acid ester, sorbitol fatty acid ester, polyoxyethylene alkylphenol ether, hexaglyceryl monobelate Agents: Fatty acid salts, alkylbenzene sulfonates, alkylmethyl taurates, polyoxyethylene alkylphenol ether sulfates, and cation surfactants such as polyoxyethylene alkyl ether sulfonates. May be used alone or in combination of two or more. Among them, sorbitan fatty acid ester, polyglycerol fatty acid ester and sucrose fatty acid ester are preferable.

[0024] Examples of the polymer protective colloid include ethyl cellulose, ethyl hydroxyethyl cellulose, polyethylene oxide, anhydrous maleated polyethylene, anhydrous maleated polybutadiene, and anhydrous maleated EPDM (ethylene Z propylene Z gen Z ter Polymers)), etc., which may be used alone or in combination of two or more.

[0025] The amount of the surfactant and Z or the polymer protective colloid is determined depending on the water-soluble ethylenic unsaturated from the viewpoint of the control of the particle size of the water-absorbent resin particles and the suspension stability during polymerization. Preferably it is 0.05-5 weight part with respect to 100 weight part of monomer aqueous solution, More preferably, it is 0.1-3 weight part. If the amount of surfactant and Z or polymer protective colloid is less than 0.05 parts by weight, the suspension stability during polymerization tends to be low, and if it is more than 5 parts by weight, the amount is only commensurate with the amount. However, there is a tendency to be economically disadvantageous.

[0026] Examples of the water-soluble radical polymerization initiator include persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate; hydrogen peroxide perhydrogen; 2, 2'-azobis (2-amidinopropan ) Azo compounds such as dihydrochloride and azobis (cyananovaleric acid) can be used, and these can be used alone or in combination of two or more. Among them, potassium persulfate, ammonium persulfate and sodium persulfate are preferred because they are readily available and have good storage stability.

[0027] The water-soluble radical polymerization initiator can be used as a redox polymerization initiator when used in combination with a sulfite or the like.

[0028] The amount of the water-soluble radical polymerization initiator is usually preferably 0.00 per mole of the water-soluble ethylenically unsaturated monomer from the viewpoint of shortening the polymerization reaction time and preventing a rapid polymerization reaction. 001 to 0.02 mol, more preferably 0.0001 to 0.01 mol.

[0029] Examples of the hydrocarbon solvent include aliphatic hydrocarbon compounds such as n-hexane, n-heptane, and lignin; fats such as cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane. Cyclic hydrocarbon compounds; aromatic hydrocarbon compounds such as benzene, toluene, xylene, and the like can be mentioned. These may be used alone or in combination of two or more. Among them, n-hexane, n-heptane and cyclohexane are preferable because they are easily available industrially, have stable quality, and are inexpensive.

[0030] The amount of the hydrocarbon-based solvent is usually preferably 50 to 600 with respect to 100 parts by weight of the water-soluble ethylenically unsaturated monomer, from the viewpoint of removing the heat of polymerization and easily controlling the polymerization temperature. Part by weight, more preferably 100 to 550 parts by weight.

As the crosslinking agent, for example, (poly) ethylene glycol [“(poly)” means with or without the prefix “poly”. The same shall apply hereinafter), (poly) propylene glycol, 1,4 butanediol, trimethylolpropane, diols such as (poly) glycerin, triols and polyols, and unsaturated acids such as (meth) acrylic acid, maleic acid and fumaric acid. Polyesters obtained by reacting polyepoxides with (meth) acrylic acid; unsaturated polyesters obtained by reacting bisacrylamides; bisacrylamides such as N, N'-methylenebisacrylamide; Di (meth) acrylic acid rubamyl esters obtained by reacting polyisocyanates such as tolylene diisocyanate and hexamethylene diisocyanate with hydroxyethyl (meth) acrylate; Polymerizable unsaturated compounds such as rylphthalate, N,, ', ,, triallyl isocyanurate, Compounds having two or more groups; diglycidyl ether compounds such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether; epichlorohydrin, epibromhydride Haloepoxy compounds such as phosphorus and oc-methylepoxyhydrin; 2, 4 compounds having two or more reactive functional groups such as isocyanate compounds such as tolylene diisocyanate and hexamethylene diisocyanate; Methyl-3-oxetane methanol, 3-Ethyl-3-oxetanemethanol, 3-Butyl-3-Oxetanemethanol, 3-Methyl-3-oxetaneethanol, 3-Ethyl-3-oxetaneethanol, 3-Butyl-3 —Oxetane compounds such as oxetane ethanol, etc. Et al. May be used alone or in combination of two or more. Among them, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, glycerin diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polyglycerin diglycidyl ether and N, N, -methylenebisacrylamide are It is preferable because of its excellent reactivity at low temperatures.

[0032] The amount of the crosslinking agent is 100% by weight of a water-soluble ethylenically unsaturated monomer from the viewpoint of suppressing the water-soluble property of the obtained polymer by appropriate crosslinking and exhibiting sufficient water absorption. The amount is preferably 3 parts by weight or less, more preferably 0.001 to 1 part by weight based on the part.

[0033] The reaction temperature during the polymerization varies depending on the type of the water-soluble radical polymerization initiator to be used, and thus cannot be determined unconditionally. Usually, the reaction temperature is preferably 20 to 110 ° C., more preferably 40 to 90, from the viewpoint of allowing the polymerization to proceed rapidly to shorten the polymerization time and easily removing the heat of polymerization to perform the reaction smoothly. ° C. The reaction time is usually from 0.1 to 4 hours.

[0034] A precursor of water-absorbent resin particles can be obtained by polymerizing a water-soluble ethylenically unsaturated monomer by force.

[0035] The obtained water-absorbing resin particles precursor is appropriately adjusted in water content, then mixed with a compound having two or more polymerizable unsaturated groups, and subjected to the reaction.

[0036] A feature of the present invention is that after obtaining a water-absorbent resin particle precursor by polymerizing a water-soluble ethylenically unsaturated monomer, the resulting water-absorbent resin particle precursor and polymerizability are obtained. The point is that a compound having two or more unsaturated groups is mixed and the resulting mixture is reacted.

[0037] The timing for carrying out the reaction is not particularly limited, and may be immediately after the polymerization of the precursor of the water-absorbent resin particles, during the drying step, or after the drying.

[0038] Examples of the compound having two or more polymerizable unsaturated groups include diols such as (poly) ethylene glycol, (poly) propylene glycol, 1,4 butanediol, trimethylolpropane, and (poly) glycerin. , Triols and polyols and unsaturated polyesters obtained by reacting (meth) acrylic acid, maleic acid, fumaric acid and other unsaturated acids; bisacrylamides such as N, N'-methylenebisacrylamide; Rilphthalate, N, Ν ', Ν, ... Examples thereof include compounds having two or more polymerizable unsaturated groups such as triallyl isocyanurate and divinylbenzene. Among them, at least one selected from the group consisting of N, N, monomethylene bisacrylamide and (poly) ethylene glycol diatalate is preferable from the viewpoint of easy mixing with a water-soluble ethylenically unsaturated monomer. .

[0039] The amount of the compound having two or more polymerizable unsaturated groups is 0. 100 parts by weight of the water-soluble ethylenically unsaturated monomer used in the polymerization of the precursor of the water-absorbent resin particles. 01 to 10 parts by weight, preferably 0.02 to 5 parts by weight, more preferably 0.05 to 3 parts by weight. Quantity of compound having 2 or more polymerizable unsaturated groups Water-soluble ethylenically unsaturated monomer 100 parts by weight If less than 0.01 part by weight, the reaction of the surface layer becomes insufficient and the load There is a tendency that the amount of water absorption below does not increase, and when the amount is more than 10 parts by weight, the reaction becomes excessive, so that the water-absorbent resin particles do not exhibit sufficient water absorption. .

[0040] When mixing the precursor of the water-absorbent resin particles with the compound having two or more polymerizable unsaturated groups, in order to increase the reactivity of the compound having two or more polymerizable unsaturated groups, Water-soluble ethylenically unsaturated monomers and Z or radical polymerization initiators may be added.

[0041] The water-soluble ethylenically unsaturated monomer and the radical polymerization initiator used in mixing the precursor of the water-absorbent resin particles and the compound having two or more polymerizable unsaturated groups are a water-absorbent resin. It may be the same as or different from the one used during the polymerization of the particle precursor.

[0042] Examples of the water-soluble ethylenically unsaturated monomer include (meth) acrylic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid or alkali metal salts thereof; Nonionic monomers such as rilamide, N, N-dimethylacrylamide, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide; jetylaminoethyl (meth) acrylate, jetylaminopropyl ( Examples thereof include amino group-containing unsaturated monomers such as (meth) acrylate and quaternized compounds thereof, and these may be used alone or in combination of two or more. Examples of the alkali metal in the alkali metal salt include lithium, sodium, and potassium.

[0043] Since water-soluble ethylenically unsaturated monomers are easily available industrially, (meth) acrylic acid and its alkali metal salts, (meth) acrylamide and N, N-dimethyl are preferred. At least one selected from the group consisting of tilacrylamide, more preferably at least one selected from the group consisting of (meth) acrylic acid and sodium (meth) acrylate.

[0044] The water-soluble ethylenically unsaturated monomer can usually be used as an aqueous solution. It is preferable that the concentration of the water-soluble ethylenically unsaturated monomer in the aqueous solution of the water-soluble ethylenically unsaturated monomer is 25% by weight to the saturated concentration.

[0045] When the water-soluble ethylenically unsaturated monomer used in mixing the precursor of the water-absorbent resin particles and the compound having two or more polymerizable unsaturated groups has an acid group, the acid group May be neutralized with alkali metal. The degree of neutralization of water-soluble ethylenically unsaturated monomers with alkali metals increases the osmotic pressure of the resulting water-absorbent resin particles, increases the water absorption rate, and there are problems with safety due to the presence of excess alkali metals. From the standpoint of preventing the occurrence of water, it is preferably within the range of 10 to LOO mol% of the acid groups of the water-soluble ethylenically unsaturated monomer before neutralization. Examples of the alkali metal include lithium, sodium, and potassium. Of these, sodium and potassium are preferred.

[0046] The amount of the water-soluble ethylenically unsaturated monomer used in mixing the precursor of the water-absorbent resin particles and the compound having two or more polymerizable unsaturated groups is determined by the amount of the water-absorbent resin particles. The amount is preferably 0.05 to 10 parts by weight, more preferably 0.05 to 3 parts by weight with respect to 100 parts by weight of the water-soluble ethylenically unsaturated monomer used for the polymerization of the precursor. When the amount of the water-soluble ethylenically unsaturated monomer used is more than 10 parts by weight, the effect corresponding to the amount cannot be obtained, and it tends to be economically disadvantageous.

[0047] Examples of the radical polymerization initiator include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; 2,2'-azobis (2-amidinopropane) dihydrochloride, azobis Azoi compounds such as (Cyananovalerate); hydrogen peroxide, etc. may be mentioned, and these may be used alone or in combination of two or more. Among them, potassium persulfate, ammonium persulfate and sodium persulfate are preferable from the viewpoint of easy availability and good storage stability.

[0048] The radical polymerization initiator can be used as a redox polymerization initiator when used in combination with a sulfite or the like. [0049] The amount of the radical polymerization initiator is preferably from 0.0001 to 0.02 moles per mole of the compound having two or more polymerizable unsaturated groups and Z or water-soluble ethylenically unsaturated monomer. More preferably from 0.0001 to 0.01 mol.

[0050] When mixing the precursor of the water-absorbent resin particles and the compound having two or more polymerizable unsaturated groups, a hydrophilic organic solvent may be used as a solvent, if necessary.

[0051] Examples of the hydrophilic organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, _n- propyl alcohol and isopropyl alcohol, ketones such as acetone and methyl ethyl ketone, jetyl ether, dioxane and tetrahydrofuran. Ethers, amides such as N, N-dimethylformamide, sulfoxides such as dimethyl sulfoxide, and the like. These hydrophilic organic solvents may be used alone or in combination of two or more. Good.

[0052] Further, the mixing of the precursor of the water-absorbent rosin particles and the compound having two or more polymerizable unsaturated groups can be performed in the presence of water. The amount of water when mixing the precursor of the water-absorbent resin particles and the compound having two or more polymerizable unsaturated groups varies depending on the type, particle size and water content of the water-absorbent resin particles. The amount is preferably 1 to 150 parts by weight per 100 parts by weight of the water-soluble ethylenically unsaturated monomer subjected to the polymerization. The amount of water in this case is as necessary when mixing the water contained in the polymerization reaction, the precursor of the water-absorbent resin particles and the compound having two or more polymerizable unsaturated groups. Means the total amount of water used.

[0053] By controlling the amount of water during mixing of the precursor of the water-absorbent resin particles and the compound having two or more polymerizable unsaturated groups as described above, the surface layer of the water-absorbent resin particles can be polymerized. A compound having two or more unsaturated groups can be reacted more suitably.

[0054] The reaction temperature at the time of reacting the mixture of the precursor of the water-absorbent resin particles with the compound having two or more polymerizable unsaturated groups is preferably 20 to 190 ° C, more preferably 40 to 150 °. C. When the reaction temperature is less than 20 ° C, the reaction is difficult to proceed and the reaction tends to take an excessive amount of time. When the reaction temperature exceeds 190 ° C, the resulting water-absorbent resin particles tend to be decomposed. is there.

[0055] The reaction time refers to the reaction temperature, the type of compound having two or more polymerizable unsaturated groups, and the type thereof. However, it is preferably 1 to 300 minutes, more preferably 5 to 200 minutes.

[0056] The average particle diameter of the water-absorbent slag particles obtained by force is usually the point of preventing gel blocking due to fine powder in the absorbent article, and prevents the soft feeling due to coarse particles. From the viewpoint of improving the property, it is desired to be 100 to 600 111, preferably 200 to 500 m. The average particle diameter is a value when measured by the method described in Test Example 1-1 (1) described later.

[0057] The amount of water absorption of the water-absorbent resin particles under no load can be measured by the method described in Test Example 1 (2). In general, the water absorption amount of the water-absorbent resin particles is preferably 40 g Zg or more under no load from the viewpoint of sufficient liquid absorption performance and reduced liquid return in an absorbent article. .

[0058] Further, the amount of water absorption under load of the water-absorbent resin particles can be measured by the method described in Test Example 1- (3). The load at the time of measurement is set to 2.07 kPa from the viewpoint of reproducing the state where the load is applied to the absorbent body when an infant uses a water absorbent article. It is preferable that the water-absorbent resin particles have a water absorption amount of 20 mLZg or more under a pressure of 07 kPa from the viewpoint of reducing the amount of liquid returned from the absorber under load.

[0059] After a water-soluble ethylenically unsaturated monomer is polymerized by force to obtain a precursor of water-absorbent resin particles, a compound having two or more polymerizable unsaturated groups and the water-absorbent resin Mixing particle precursors and reacting with water-soluble ethylenically unsaturated monomers and Z or radical polymerization initiators as necessary, water-absorbent resin with high water absorption capacity under load Particles are obtained. As described above, the reason why the water-absorbent resin particles having a high water absorption capacity under load is obtained is not clear, but is presumed to be based on the following reasons.

[0060] That is, a mixture obtained by mixing a precursor of water-absorbent resin particles, a compound having two or more polymerizable unsaturated groups, and, if necessary, a water-soluble ethylenically unsaturated monomer. By reacting, the crosslink density in the surface layer of the water-absorbent resin particles is increased. Increased crosslink density in the surface layer increases the gel strength of the water-absorbent resin particles during water absorption On the other hand, since the cross-linking reaction does not easily reach the inside of the water-absorbent resin particles, the water absorption ratio itself does not decrease. Since such water-absorbent rosin particles maintain a sufficient gel strength even under load, it is presumed that the water absorption magnification becomes high even under load.

[0061] It should be noted that additives such as a lubricant, deodorant and antibacterial agent may be further added to the water-absorbent resin particles of the present invention depending on the purpose.

Example

[0062] Next, the present invention will be described in more detail based on examples. However, the present invention is not limited to only the examples that work.

[0063] Production Example 1

In an Erlenmeyer flask with an internal volume of 1 liter, 92 g of an 80% by weight aqueous solution of acrylic acid was added and 153 g of 20.1% by weight aqueous sodium hydroxide solution was added dropwise with ice cooling to neutralize 75 mol% of acrylic acid. A 37% by weight aqueous solution of partially neutralized acrylic acid salt was prepared, and 4.6 mg of N, N'-methylenebisacrylamide and 92 mg of potassium persulfate were added to the resulting aqueous solution of partially neutralized salt of talic acid as an internal crosslinking agent. This was used as a monomer aqueous solution for polymerization.

[0064] On the other hand, in a 2-liter five-necked cylindrical round bottom flask equipped with a stirrer, a two-stage paddle blade, a reflux condenser, a dropping funnel and a nitrogen gas introduction tube, 340 g of n-heptane and sucrose Fatty acid ester [Mitsubishi Chemical Products Co., Ltd., trade name: S-370] 0.92 g was added and dissolved in n-hebutane, and then the monomer aqueous solution for polymerization was added and stirred. Suspended. Thereafter, the inside of the system was replaced with nitrogen gas, and the temperature was raised to 70 ° C. to carry out reverse phase suspension polymerization.

[0065] After the reverse phase suspension polymerization is completed, by heating again, water is extracted from the azeotrope of n-heptane and water, and then the n-heptane in the system is distilled off to obtain a water-absorbing solution. A precursor of fat particles (A1) was obtained.

[0066] Production Example 2

Place 184 g of 80 wt% acrylic acid aqueous solution in a 1 liter Erlenmeyer flask and add 305 g of 20.1 wt% sodium hydroxide aqueous solution dropwise with ice cooling to neutralize 75 mol% acrylic acid. Prepare a weight% aqueous solution of partially neutralized acrylic acid, and add 9.2 mg of N, N'-methylenebisacrylamide and 184 mg of potassium persulfate as an internal crosslinking agent to the resulting aqueous solution of partially neutralized talic acid. did. Next, this prepared monomer aqueous solution Were divided into two parts, which were an aqueous monomer solution for the first stage polymerization and an aqueous monomer solution for the second stage polymerization, respectively.

[0067] On the other hand, in a 2-liter five-necked cylindrical round bottom flask equipped with a stirrer, a two-stage paddle blade, a reflux condenser, a dropping funnel and a nitrogen gas introduction tube, 340 g of n-heptane and sucrose Fatty acid ester [Mitsubishi Chemical Products Co., Ltd., trade name: S-370] 0.92g was added and dissolved in n-butane, and then the monomer aqueous solution for the first stage polymerization was added. And suspended under stirring. Thereafter, the inside of the system was replaced with nitrogen gas, the temperature was raised to 70 ° C., and the first-stage reversed-phase suspension polymerization was performed.

[0068] After completion of the first-stage reversed-phase suspension polymerization, the reaction solution was cooled to room temperature, and a monomer aqueous solution for the second-stage polymerization was added dropwise thereto, followed by stirring for 30 minutes. Thereafter, the inside of the system was replaced with nitrogen gas, the temperature was raised to 70 ° C., and the second-stage reversed-phase suspension polymerization was performed.

[0069] After the reverse phase suspension polymerization is completed, by heating again, water is extracted from the azeotropic mixture of n-heptane and water, and then the n-heptane in the system is distilled off to absorb water. A precursor (A2) of the resin particles was obtained.

[0070] Production Example 3

Into a 2-liter five-necked cylindrical round bottom flask equipped with a stirrer, two-stage paddle blade, reflux condenser, dropping funnel and nitrogen gas inlet tube, put 184 g of 80% by weight acrylic acid aqueous solution while cooling. The mixture was stirred and 540 g of 11.4 wt% sodium hydroxide aqueous solution was added dropwise to neutralize 75 mol% of acrylic acid, and a 25 wt% partially neutralized aqueous solution of acrylic acid was prepared. To this partially neutralized acrylic acid aqueous solution, 9.2 mg of N, N′-methylenebisacrylamide, 184 mg of potassium persulfate, and 18.4 mg of sodium sulfite were added, and the system was replaced with nitrogen gas. The polymerization reaction was carried out by holding in a C water bath.

[0071] The resulting polymerization reaction product was coarsely pulverized with a SUS meat chopper, and then dried with a hot air dryer at 105 ° C for 60 minutes. Next, the coarsely pulverized product was pulverized with a desktop mixer and classified with a JIS standard sieve having an opening of 1 000 μm to obtain a precursor (A3) of water-absorbent grease particles.

[0072] Example 1

All the precursor (A1) of the water-absorbent resin particles obtained in Production Example 1 was placed in a flask having an internal volume of 2 liters equipped with a stirrer, an anchor blade, a cooler, and a gas introduction tube. [0073] On the other hand, 4 weight ⁰ / oN, N, the over methylenebisacrylamide solution 11. 5 g, 80 weight ^_0/0 Atari Le acid solution 1. aqueous solution mixed with 84g and 2 wt% aqueous solution of potassium persulfate 92mg prepared Then, the aqueous solution was sprayed with the aqueous solution while stirring the precursor of the water-absorbent resin particles at 200 rpm!

[0074] After the addition, the system was replaced with 200 mL of nitrogen gas while stirring the precursor of the water-absorbent resin particles at lOOrpm, and the reaction was carried out for 30 minutes by heating in a 130 ° C oil bath. After the reaction, 94 g of water-absorbing resin particles having a water content of 4.0% by weight and an average particle size of 202 m was obtained.

[0075] Example 2

The total amount of the precursor (A2) of the water-absorbing resin particles obtained in Production Example 2 was placed in a flask having an internal volume of 2 liters equipped with a stirrer, an anchor blade, a cooler, and a gas introduction tube.

[0076] On the other hand, 4 weight ⁰ / oN, N, the over methylenebisacrylamide solution 23. 0 g, 80 weight ^_0/0 Atari Le acid solution 3. aqueous solution mixed with 68g and 2 wt% aqueous solution of potassium persulfate 184mg prepared The aqueous solution was added by spraying while stirring the water-absorbent resin particles at 200 rpm.

[0077] After the addition, the system was replaced with 200 mLZ min of nitrogen gas while stirring the precursor of the water-absorbent resin particles at lOOrpm, and the reaction was carried out for 30 minutes by heating in a 130 ° C oil bath. . After the reaction, 189 g of water-absorbent resin particles having a water content of 4.5% by weight and an average particle size of 351 / zm were obtained.

[0078] Example 3

All the precursors (A3) of the water-absorbent resin particles obtained in Production Example 3 were placed in a flask having an internal volume of 2 liters equipped with a stirrer, an anchor blade, a cooler, and a gas introduction tube.

[0079] On the other hand, 4 weight ⁰ / oN, N, over methylenebisacrylamide solution 23. 0 g, 80 weight ^_0/0 Atari Le aqueous acid 3. 68 g, and mixed with aqueous solution of 2 wt% aqueous solution of potassium persulfate 184mg The aqueous solution was added by spraying while stirring the precursor of the water-absorbent resin particles at 200 rpm.

[0080] After the addition, while the precursor of the water-absorbent resin particles was stirred at lOOrpm, the inside of the system was replaced with 200 mLZ min of nitrogen gas, and the reaction was performed for 30 minutes by heating in a 130 ° C oil bath. . After the reaction, 168 g of water-absorbing resin particles having a water content of 3.0% by weight and an average particle size of 295 m were obtained.

[0081] Example 4 The whole amount of the precursor (A2) of the water-absorbent resin particles obtained in the same manner as in Production Example 2 was placed in a flask having an internal volume of 2 liters equipped with a stirrer, an end blade, a cooler and a gas introduction tube.

[0082] On the other hand, 4 weight ⁰ / oN, N, the over methylenebisacrylamide solution 46. 0 g, 80 weight ^_0/0 Atari Le acid solution 3. aqueous solution mixed with 68g and 2 wt% aqueous solution of potassium persulfate 184mg prepared The aqueous solution was added by spraying while stirring the water-absorbent resin particles at 200 rpm.

[0083] After the addition, the system was replaced with 200 mLZ min nitrogen gas while stirring the precursor of the water-absorbent resin particles at lOOrpm, and the reaction was carried out for 30 minutes by heating in a 130 ° C oil bath. . After the reaction, 194 g of water-absorbent resin particles having a water content of 7.3% by weight and an average particle size of 343 m were obtained.

[0084] Example 5

The whole amount of the precursor (A2) of the water-absorbent resin particles obtained in the same manner as in Production Example 2 was placed in a flask having an internal volume of 2 liters equipped with a stirrer, an end blade, a cooler and a gas introduction tube.

[0085] On the other hand, 4 weight ⁰ / oN, N, over methylenebisacrylamide solution 46. Og and 2 wt ^_0/0 to prepare an aqueous solution of a mixture of aqueous solution of potassium persulfate 92 mg, 200 rpm precursor of the water-absorbing榭脂particles The aqueous solution was added by spraying with stirring.

[0086] After the addition, while the precursor of the water-absorbent resin particles was stirred at lOOrpm, the inside of the system was replaced with 200 mLZ min of nitrogen gas, and the reaction was performed for 30 minutes by heating in a 130 ° C oil bath. . After the reaction, 197 g of water-absorbing resin particles having a water content of 8.7% by weight and an average particle size of 360 m were obtained.

[0087] Example 6

[0088] On the other hand, 16 wt% polyethylene glycol Atari rate [Kyoeisha I匕学Co., Ltd., trade name: Light Atari rate 14EG- A] solution 23. 0 g, 80 weight ^_0/0 aqueous solution of acrylic acid 3. 68 g Contact An aqueous solution was prepared by mixing 184 mg of a 2% by weight aqueous potassium persulfate solution, and the aqueous solution was added by spraying while stirring the precursor of the water-absorbent coagulate particles at 200 rpm.

[0089] After the addition, the system was replaced with 200 mLZ min of nitrogen gas while stirring the precursor of the water-absorbent resin particles at lOOrpm, and the reaction was performed for 30 minutes by heating in a 130 ° C oil bath. . After the reaction, 189 g of water-absorbing resin particles having a water content of 4.4% by weight and an average particle size of 340 / zm were obtained. [0090] Comparative Example 1

The water-absorbing resin particle precursor (A2) having a water content of 3.5% by weight and an average particle diameter of 352 m obtained in the same manner as in Production Example 2 was subjected to measurement of water absorption performance as it was.

[0091] Comparative Example 2

[0092] On the other hand, 2 weight ⁰ / oN, N, over methylenebisacrylamide solution 0. 46 g and 2 weight ^_0/0 to prepare an aqueous solution of a mixture of aqueous solution of potassium persulfate 92 mg, 200 rpm precursor of the water-absorbing榭脂particles The aqueous solution was added by spraying with stirring.

[0093] After the addition, the system was replaced with 200 mLZ min nitrogen gas while stirring the precursor of water-absorbent resin particles at lOOrpm, and the reaction was carried out for 30 minutes by heating in a 130 ° C oil bath. . After the reaction, 187 g of water-absorbent resin particles having a water content of 3.4% by weight and an average particle size of 333 m were obtained.

[0094] Comparative Example 3

All the precursor (A2) of the water-absorbing resin particles obtained in the same manner as in Production Example 2 was placed in a flask having an internal volume of 2 liters equipped with a stirrer, an end blade, a cooler and a gas introduction tube.

[0095] On the other hand, an aqueous solution in which 1.84 g of 80 wt% aqueous acrylic acid solution and 92 mg of 2 wt% potassium persulfate aqueous solution were mixed was prepared, and the precursor of the water-absorbent resin particles was stirred at 200 rpm. The aqueous solution was added by spraying.

[0096] After the addition, the system was replaced with 200 mLZ min nitrogen gas while stirring the precursor of the water-absorbent resin particles at lOOrpm, and the reaction was carried out for 30 minutes by heating in a 130 ° C oil bath. . After the reaction, 186 g of water-absorbent resin particles having a water content of 2.9% by weight and an average particle size of 361 / zm were obtained.

[0097] Comparative Example 4

On the other hand, a 4% by weight 1,4-butanediol aqueous solution 23.Og was prepared, and the aqueous solution was added by spraying while stirring the water-absorbent resin particles at 200 rpm.

[0099] After the addition, while stirring the precursor of the water-absorbent resin particles at lOOrpm, the inside of the system was replaced with 200 mLZmin of nitrogen gas, and the reaction was performed in a 130 ° C oil bath for 30 minutes. . After reaction As a result, 190 g of water-absorbing resin particles having a water content weight of 4.9% and an average particle diameter of 359 m was obtained.

[0100] Test example 1

The average particle diameter, water absorption, and water absorption under pressure of the water-absorbent resin particles obtained in each Example and each Comparative Example were measured by the following methods. Table 1 shows the performance results of the water-absorbent resin particles.

[0101] (1) Average particle size

JIS standard sieve from above, sieve with 850 / zm, sieve with 600 / zm, sieve with 425 m, sieve with 300 m, sieve with 150 m, sieve with 75 m Then, about 10 OOg of the water-absorbent waving particles were placed in the uppermost sieve and shaken for 20 minutes using a low-tap shaker.

[0102] Next, the weight of the water-absorbent resin particles remaining on each sieve is calculated as a percentage by weight with respect to the total amount, and is accumulated in the order of decreasing particle diameter, thereby remaining on the sieve openings and sieves. The relationship between the weight percentage and the integrated value was plotted on a logarithmic probability paper. By connecting the plots on the probability paper with a straight line, the particle diameter corresponding to 50% by weight of the cumulative weight percentage was taken as the average particle diameter.

[0103] (2) Water absorption

In a 500 mL beaker, 2 g of the water-absorbent resin particles were dispersed in 500 g of 0.9 wt% physiological saline, and the mixture was sufficiently swollen by stirring for 60 minutes. With a standard sieve with a mesh size of 75 μm and a weight Wa (g) measured beforehand, 0.9% by weight physiological saline containing swollen gel was filtered, and the sieve was about 30 degrees to the horizontal. The gel was left to stand for 30 minutes in a tilted state to remove the excess water. Thereafter, the weight Wb (g) of the sieve containing the swollen gel was measured, and the formula:

(Water absorption (gZg)) = (Wb-Wa) ÷ 2

The amount of water absorption was determined.

[0104] (3) Water absorption under pressure

The water absorption starting force of the water-absorbing resin particles under a pressure of 2.07 kPa was also measured using a measuring device X whose schematic configuration is shown in FIG.

[0105] The measuring device X shown in FIG. 1 includes a burette part 1, a conduit 2, a measuring table 3, and a measuring part 4. In the bullet part 1, a cock 12 is provided at the bottom of the bullet 10, and The intake pipe 11 is connected to the side. A cock 13 is connected to the upper part of the intake pipe 11. A rubber stopper 14 is attached to the top of the bullet 10. A conduit 2 having a diameter of 6 mm is attached to the lower end of the burette 1, and is connected to a hole having a diameter of 2 mm formed in the center of the measuring table 3. The measurement unit 4 is placed on the measurement table 3 and includes a cylinder 40, a nylon mesh 41 and a weight 42 attached to the bottom of the cylinder 40. The inner diameter of the cylinder 40 is 2. Ocm. Nylon mesh 41 is formed to 200 mesh (aperture 75 μm). A predetermined amount of the water-absorbent resin particles 5 is uniformly distributed on the nylon mesh 41. The mass of the weight 42 is 59.8 g and its bottom diameter is 1.9 cm. The bottom of the weight 42 is fitted into the cylinder 40 so as to move up and down while in contact with the water-absorbing resin particles 5. With this weight 42, a load of 2.0 07 kPa is applied to the water-absorbing resin particles 5.

[0106] A method for measuring the physiological saline water-absorbing capacity of the water-absorbent resin particles under a load using the measuring device X will be described below. First, close the cock 12 and the cock 13, the 25 ° regulated 0.9 mass ^_0/0 saline C from above was placed in burette 10, after stoppered burette top with a rubber stopper 14, cock 12 and Open cock 13. Next, the measurement table 3 is so positioned that the upper surface of the measurement table 3 and the top of 0.9 mass% physiological saline sprayed from the conduit port (not shown) at the center of the measurement table 3 are at the same height. Adjust the height.

[0107] On the other hand, 0.1 lg of water-absorbing resin particles 5 are uniformly distributed on the nylon mesh 41 of the cylinder 40, and the weight 42 is fitted into the cylinder 40, and the bottom thereof is evenly placed on the water-absorbing resin particles. Make contact. Thereafter, the measuring unit 4 is placed on the measuring table 3 so that the center part coincides with the conduit port of the central part of the measuring table 3. When the measuring unit 4 is placed on the measuring table 3, the water-absorbent resin particles 5 begin to absorb the physiological saline coming out from the conduit port (not shown) through the nylon mesh 41.

[0108] Decreasing amount of physiological saline in the burette 10 from the time when the water-absorbing fat particles 5 start to absorb water until the elapse of 60 minutes (the amount of saline absorbed by the water-absorbing fat particles 5) Wc (mL) Is read. After 60 minutes from the start of water absorption, the amount of water absorption under pressure of the water-absorbent resin particles 5 is expressed by the formula:

[Water absorption under pressure (! 111 ^ 73)] = ¹ \ ^ ÷ 0. 10 Determined by

[0109] [Table 1]

[0110] As is clear from the results shown in Table 1, it can be seen that the water-absorbent resin particles obtained in each Example are both high in water absorption and water absorption under pressure. On the other hand, it can be seen that the water-absorbent resin particles obtained in each Comparative Example have a low water absorption under pressure.

Industrial applicability

[0111] The water-absorbent resin particles obtained by the production method of the present invention have a high water absorption amount under no load and under load, and therefore can be suitably used for sanitary materials such as sanitary products and disposable diapers. You can.

Claims

The scope of the claims

[1] Precursor of water-absorbent resin particles obtained by polymerizing water-soluble ethylenically unsaturated monomers (

A) is mixed with 0.01 to 10 parts by weight of a compound (B) having two or more polymerizable unsaturated groups per 100 parts by weight of the water-soluble ethylenically unsaturated monomer, and the resulting mixture is mixed. A method for producing water-absorbent rosin particles to be reacted.

[2] per 100 parts by weight of the water-absorbent resin particles precursor (A), the compound (B) having two or more polymerizable unsaturated groups, and the water-soluble ethylenically unsaturated monomer The production method according to claim 1, wherein 0.05 to 10 parts by weight of the water-soluble ethylenically unsaturated monomer (C) is mixed and the resulting mixture is reacted.

[3] The production method according to claim 2, wherein the water-soluble ethylenically unsaturated monomer (C) force (meth) acrylic acid and (meth) acrylic acid sodium force are at least one selected.

[4] Compound having two or more polymerizable unsaturated groups (B) At least one selected from the group consisting of N, N′-methylenebisacrylamide and (poly) ethylene glycol ditalylate Item 1-3, the manufacturing method according to any of the above.

[5] The production method according to any one of claims 1 to 4, wherein the water absorption amount of the water-absorbent resin particles under a pressure of 07 kPa is 20 mLZg or more.