JP2016204632A - Manufacturing method of water absorptive resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a water absorptive resin composition excellent in dry efficiency and having no degeneration of a water absorptive resin.SOLUTION: There is provided a manufacturing method of a water absorptive resin composition containing a crosslinked polymer (A) having a water soluble vinyl monomer (a1) and/or a vinyl monomer (a2) which becomes the water soluble vinyl monomer (a1) by hydrolysis and a crosslinking agent (b) as constitutional monomers, and an inorganic particle (B), the method including a process of volume expanding a mixture (X) containing the water soluble vinyl monomer (a1) and/or the vinyl monomer (a2) which becomes the water soluble vinyl monomer (a1) by hydrolysis, the crosslinking agent (b) and a compressive fluid.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a water absorbent resin composition.

As a method for producing the water-absorbent resin, for example, (1) a method of chopping a neutralized acrylic acid with a double-arm kneader while polymerizing an aqueous solution and drying with hot air, and (2) an aqueous solution polymerization of the neutralized acrylic acid , Chopping the polymer with a shredder and drying it with hot air or drum dryer, (3) polymerizing acrylic acid in aqueous solution, and then neutralizing and chopping the polymer with shredder , A method of drying a thin film with hot air drying or a drum dryer, (4) a method of polymerizing a high-concentration acrylate aqueous solution while removing a certain amount of water by heat during polymerization, and then heating and drying the polymer. Are known.
However, since the water-absorbing resin containing water after polymerization (hereinafter referred to as a water-containing gel) has adhesiveness, the hydrated gels that are chopped by these methods adhere to each other, leading to a decrease in drying efficiency. Have a problem to say

As a production method with improved drying efficiency, production of a water-absorbent resin that is dried by mixing inorganic particles and a surfactant before chopping, during or after chopping the polymer of the water-absorbent resin after polymerization and before drying A method has been proposed (see Patent Document 1).
However, the method described in Patent Document 1 has a problem that the water-absorbent resin is denatured by shearing stress at the time of mixing the inorganic particles and causes poor appearance and reduced water absorption performance.

Japanese Patent No. 4717979

  An object of this invention is to provide the manufacturing method of the water absorbing resin composition which is excellent in drying efficiency and does not have quality change of a water absorbing resin.

  As a result of intensive studies to achieve the above object, the present inventor has found the following. That is, the present invention relates to a water-soluble vinyl monomer (a1) and / or a crosslinked polymer comprising a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis and a crosslinking agent (b) as essential constituent monomers ( A) a method for producing a water-absorbent resin composition containing inorganic particles (B), wherein the water-soluble vinyl monomer (a1) and / or the vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis, A method for producing a water-absorbent resin composition comprising a step of volume-expanding a mixture (X) containing inorganic particles (B) and a compressive fluid.

  The production method of the present invention is excellent in drying efficiency and has no alteration of the water absorbent resin.

FIG. 1 is a flowchart of a production apparatus used when the production of the mixture (X) and the volume expansion step in the production method of the present invention are carried out by line blending using a continuous mixing and dispersing apparatus.

The present invention is described in detail below.
Water-soluble vinyl monomer (a1) and / or vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis, cross-linked polymer (A) and inorganic particles containing cross-linking agent (b) as essential constituent monomers A method for producing a water-absorbent resin composition comprising (B), wherein a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis, inorganic particles (B) And a step of expanding the volume of the mixture (X) containing the compressive fluid.

  The water-soluble vinyl monomer (a1) is not particularly limited as long as it is a monomer having a polymerizable unsaturated double bond and having a solubility of 10 g or more with respect to 100 g of water at 80 ° C. Includes the following anionic water-soluble vinyl monomers (a1-1), cationic water-soluble vinyl monomers (a1-2) and nonionic water-soluble vinyl monomers (a1-3).

  Examples of the anionic water-soluble vinyl monomer (a1-1) include a water-soluble vinyl monomer having a carboxyl group (a1-11), a water-soluble vinyl monomer having a sulfo group (a1-12), and a water-soluble vinyl monomer having a phospho group. (A1-13) and salts thereof [for example, alkali metal salts (such as sodium salt and potassium salt), alkaline earth metal salts (such as calcium salt and magnesium salt), amine salt and ammonium salt] and the like.

  Examples of the water-soluble vinyl monomer having a carboxyl group (a1-11) include unsaturated mono- or poly (divalent to hexavalent) carboxylic acids having 3 to 10 carbon atoms [(meth) acrylic acid, maleic acid, crotonic acid, sorbine. Acid, fumaric acid, itaconic acid, cinnamic acid, citraconic acid and the like] and acid anhydrides thereof.

  Examples of the water-soluble vinyl monomer (a1-12) having a sulfo group include aliphatic vinyl sulfonic acids having 2 to 20 carbon atoms (such as vinyl sulfonic acid and allyl sulfonic acid), and aromatic vinyl sulfonic acids having 8 to 20 carbon atoms (vinyl). Toluenesulfonic acid and styrenesulfonic acid), (meth) acrylic alkylsulfonic acid having 2 to 20 carbon atoms [2-hydroxy-3- (meth) acryloyloxypropanesulfonic acid, 2- (meth) acryloyloxyethanesulfonic acid, 2- (meth) acryloyloxypropanesulfonic acid, 3- (meth) acryloyloxypropanesulfonic acid, 2- (meth) acryloyloxybutanesulfonic acid, 4- (meth) acryloyloxybutanesulfonic acid, 2- (meth) acryloyl Oxy-2,2-dimethylethanesulfonic acid, p- ( T) acryloyloxymethylbenzenesulfonic acid and the like] and (meth) acrylamide alkylsulfonic acid having 4 to 10 carbon atoms (2- (meth) acryloylaminoethanesulfonic acid, 2- or 3- (meth) acryloylaminopropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2- or 4- (meth) acryloylaminobutanesulfonic acid, 2- (meth) acryloylamino-2,2-dimethylethanesulfonic acid and p- (meth) acryloylaminomethyl Benzenesulfonic acid etc.] and alkyl (C1-20) (meth) allyl sulfosuccinic acid ester [methyl (meth) allyl sulfosuccinic acid ester etc.] and the like.

  Examples of the water-soluble vinyl monomer (a1-13) having a phospho group include (meth) acrylic acid hydroxyalkyl phosphate monoester [2-hydroxyethyl (meth) acryloyl phosphate and phenyl-2- (meth) having 4 to 24 carbon atoms. ) Acrylyloxyethyl phosphate, etc.].

  Examples of the cationic water-soluble vinyl monomer (a1-2) include an amino group-containing water-soluble monomer (a21) and salts thereof [for example, inorganic acid (hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, etc.) salts, organic acids ( Formic acid, lactic acid, acetic acid and the like) salts, methyl chloride salts, dimethyl sulfate salts and benzyl chloride salts].

  Examples of the water-soluble vinyl monomer (a1-21) having an amino group include vinylamines having 2 to 8 carbon atoms [vinylamine, vinylaniline, (meth) allylamine, p-aminostyrene, etc.], aminoalkyls (2 to 3 carbon atoms). (Meth) acrylate [aminomethyl (meth) acrylate and aminopropyl (meth) acrylate, etc.], N, N-dialkyl (C1-2) aminoalkyl (C2-3) (meth) acrylate [N, N-dimethylaminoethyl (Meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, etc.], heterocyclic-containing (meth) acrylate [N -Morpholinoethyl (meth) acrylate, etc.], N, N- Alkyl (C1-2) aminoalkyl (C2-3) (meth) acrylamide [N, N-dimethylaminoethyl (meth) acrylamide etc.], 1,1,1-trimethylamine (meth) acrylimide, 1,1-dimethyl Examples include -1-ethylamine (meth) acrylimide and 1,1-dimethyl-1- (2′-phenyl-2′-hydroxyethyl) amine (meth) acrylimide.

The nonionic water-soluble vinyl monomer (a1-3) includes a water-soluble vinyl monomer having a hydroxyl group (a1-31), a water-soluble vinyl monomer having a poly (oxyalkylene) group (a1-32), and 1 or 2 carbon atoms. And esters (a1-33) (such as methyl acrylate and ethyl acrylate) of the above alcohol and the anionic water-soluble vinyl monomer (a1-11).
Examples of the water-soluble vinyl monomer (a1-31) having a hydroxyl group include di- or poly (2-8 valent) alcohols (ethylene glycol, glycerin, pentaerythritol, etc.) and the water-soluble vinyl monomer having the carboxyl group (a1-11). ) And monoesters. The nonionic water-soluble vinyl monomer (a1-32) having a poly (oxyalkylene) group is a polyoxyalkylene obtained by adding a C2-C3 alkylene oxide to a di- or poly (2- to 8-valent) alcohol. Examples include esters of alcohol (degree of polymerization 2 to 50) and the above water-soluble vinyl monomer (a1-11) having a carboxyl group.

  The vinyl monomer (a2) that becomes a water-soluble vinyl monomer by hydrolysis [hereinafter also referred to as hydrolyzable vinyl monomer (a2). ] Is not particularly limited and is known (for example, a vinyl monomer having at least one hydrolyzable substituent which becomes a water-soluble substituent by hydrolysis as disclosed in paragraphs 0024 to 0025 of Japanese Patent No. 3648553; At least one hydrolyzable substituent [1,3-oxo-2-oxapropylene (—CO—O—CO—) group, acyl group and cyano group disclosed in paragraphs 0052 to 0055 of JP-A-775982 The vinyl monomer, etc.] can be used, and the term “hydrolyzable” means the property of being hydrolyzed by the action of water at 50 ° C. and, if necessary, the catalyst (acid or base) to become water-soluble. Hydrolysis of the hydrolyzable vinyl monomer may be either during polymerization, after polymerization, or both, but the molecular weight of the resulting water-absorbent resin particles After the polymerization in view or the like are preferable.

  Of these, the water-soluble vinyl monomer (a1) is preferred. Examples of the water-soluble vinyl monomer (a1) include a water-soluble vinyl monomer having a carboxyl group (a1-11), a water-soluble vinyl monomer having a sulfo group (a1-12), and a water-soluble vinyl monomer having an amino group (a1-21). ), A water-soluble vinyl monomer having a hydroxyl group (a1-31) and at least one water-soluble vinyl monomer selected from the group consisting of these salts, and more preferably an anionic water-soluble vinyl having a carboxyl group It is a monomer (a1-11) and its salt.

  When either the water-soluble vinyl monomer (a1) or the hydrolyzable vinyl monomer (a2) is used as a structural unit, each may be used alone as a structural unit, or two or more kinds may be used as a structural unit if necessary. The same applies when the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as constituent units. Further, when the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as structural units, the content molar ratio (a1 / a2) is preferably 75/25 to 99/1, more preferably. 85/15 to 95/5, particularly preferably 90/10 to 93/7, and most preferably 91/9 to 92/8. Within this range, the absorption performance is further improved.

  As a structural unit of the crosslinked polymer (A), in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), other vinyl monomers (a3) copolymerizable therewith are used as the structural unit. Can do.

Other vinyl monomers (a3) that can be copolymerized are not particularly limited and are known (for example, hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553, JP-A No. 2003-165883, The hydrophobic vinyl monomers (vinyl monomers disclosed in paragraph 0058 of JP-A-2005-75982) can be used, and the following vinyl monomers (i) to (iii) can be used.
(I) C8-C30 aromatic ethylenic monomer Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, and halogen substituted products of styrene such as vinylnaphthalene and dichlorostyrene.
(Ii) C2-C20 aliphatic ethylene monomer Alkene [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.]; and alkadiene [butadiene, isoprene, etc.], etc.
(Iii) C5-C15 alicyclic ethylene monomer Monoethylenically unsaturated monomer [pinene, limonene, indene and the like]; and polyethylene vinyl polymerizable monomer [cyclopentadiene, bicyclopentadiene, ethylidene norbornene and the like] and the like.

  When the other vinyl monomer (a3) is used as a structural unit, the content (mol%) of the other vinyl monomer (a3) unit in the crosslinked polymer (A) is determined depending on the water-soluble vinyl monomer (a1) unit and hydrolyzability. Based on the number of moles of the vinyl monomer (a2) unit, 0.01 to 5 is preferable, more preferably 0.05 to 3, then preferably 0.08 to 2, particularly preferably 0.1 to 1.5. It is. In spite of the above, it is most preferable that the content of other vinyl monomer (a3) units is 0 mol% from the viewpoint of absorption characteristics and the like.

The crosslinking agent (b) is not particularly limited and is known (for example, a crosslinking agent having two or more ethylenically unsaturated groups, disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553, a water-soluble substituent (carboxy group). A crosslinking agent having at least one functional group capable of reacting with a sulfo group and a hydroxyl group) and having at least one ethylenically unsaturated group, and at least two functional groups capable of reacting with a water-soluble substituent. Cross-linking agent, cross-linking agent having two or more ethylenically unsaturated groups disclosed in JP-A-2003-165883, paragraphs 0028 to 0031, cross-linking agent having ethylenically unsaturated groups and reactive functional groups, reaction Cross-linking agent having two or more polymerizable substituents, cross-linkable vinyl monomer disclosed in paragraph 0059 of JP-A-2005-75982, JP-A-2005-9575 No. crosslinking agent of which it is crosslinkable vinyl monomer) which is disclosed in the 0015-0016 paragraph publications can be used.
Among these, from the viewpoint of absorption characteristics, the cross-linking agent having two or more ethylenically unsaturated groups is preferably a poly (meth) allyl ether of a polyol having 2 to 10 carbon atoms and N, N-alkylenebisacrylamide. And particularly preferably a triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, and the crosslinking agent having at least two functional groups capable of reacting with a water-soluble substituent is an aqueous solution substituent. When is a hydroxyl group, a blocked isocyanate and glycylaldehyde are preferred. When the water-soluble substituent is a carboxylic acid, glycol diamine and glycol polyglycidyl are preferred, and when the water-soluble monomer is an amino group. Is blocked isocyanate and glycol polyg Glycidyl is preferable.

  The content (mol%) of the crosslinking agent (b) unit contained in the crosslinked polymer (A) is 0 based on the number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. 0.001 to 5 is preferable, 0.005 to 3 is more preferable, and 0.01 to 1 is particularly preferable. Within this range, the absorption characteristics are further improved.

Examples of the inorganic particles (B) include natural inorganic particles and synthetic inorganic particles excluding metal particles. Natural inorganic particles and synthetic inorganic particles include particles made of metal oxides (silicon oxide, magnesium oxide, calcium carbonate, aluminum oxide, titanium oxide, zirconium oxide, etc.), clay minerals (montmorillonite, hydrotalcite, talc, zeolite, And particles composed of bentonite and attapulgite). In the present invention, the clay mineral is an inorganic substance mainly composed of a layered silicate mineral.
Among these, from the viewpoint of dispersibility of the inorganic particles (B), clay minerals are preferable, and montmorillonite and hydrotalcite are particularly preferable. When the inorganic particles (B) are clay minerals, the compressive fluid penetrates between layers of the layered structure of the inorganic particles (B), and the inorganic particles (by the expansion of the compressive fluid generated in the step of volumetric expansion of the mixture (X) ( B) can be efficiently dispersed in the crosslinked polymer (A).

The inorganic particles (B) preferably have a primary particle thickness of 1 to 100 nm and an aspect ratio of 100 to 100,000 (more preferably 1,000 to 100,000).
Examples of the inorganic particles (B) in which the thickness and aspect ratio of the primary particles are within this range include clay minerals, and montmorillonite and hydrotalcite are preferable.

  The weight of the inorganic particles (B) can be adjusted depending on the properties of the crosslinked polymer (A), but the total weight of the water-soluble vinyl monomer (a1), hydrolyzable vinyl monomer (a2) and crosslinking agent (b). Is preferably 0.01 to 10% by weight (more preferably 0.1 to 5% by weight). Within this range, the effect of improving the drying property is further improved, and the resulting water-absorbent resin composition does not generate much dust and does not cause deterioration in powder handling properties, which is preferable.

The production method of the present invention has a step of volume-expanding the mixture (X) containing the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2), the inorganic particles (B) and the compressive fluid. As a characteristic, the mixture (X) preferably further comprises a nonionic surfactant (C).
Nonionic surfactants (C) include aliphatic alcohols (8 to 24 carbon atoms) alkylene oxide (2 to 8 carbon atoms) adducts (polymerization degree = 1 to 100) [lauryl alcohol ethylene oxide addition (polymerization degree). = 20) product, oleyl alcohol ethylene oxide addition (polymerization degree = 10) product and McCoal alcohol ethylene oxide addition (polymerization degree = 35) product, etc.], polyoxyalkylene (carbon number 2-8, polymerization degree = 1-100) Higher fatty acid (carbon number 8-24) ester [polyethylene glycol monostearate (polymerization degree = 20), polyethylene glycol distearate (polymerization degree = 30), etc.], polyvalent (divalent to 10-valent or higher) alcohol fatty acid (C8-C24) ester [glyceryl monostearate, ethylene glycol monostearate Cole, sorbitan lauric acid (mono / di) ester, sorbitan palmitic acid (mono / di) ester, sorbitan stearic acid (mono / di) ester, sorbitan oleic acid (mono / di) ester and sorbitan coconut oil (mono / di) Ester, etc.], polyoxyalkylene (carbon number 2-8, polymerization degree = 1-100) polyvalent (divalent to 10-valent or higher) alcohol higher fatty acid (carbon number 8-24) ester [polyoxyethylene (polymerization) Degree = 10) sorbitan lauric acid (mono / di) ester, polyoxyethylene (degree of polymerization = 20) sorbitan palmitic acid (mono / di) ester, polyoxyethylene (degree of polymerization = 15) sorbitan stearic acid (mono / di) Esters, polyoxyethylene (degree of polymerization = 10) sorbitan oleic acid (mono / di) , Polyoxyethylene (degree of polymerization = 25) lauric acid (mono / di) ester, polyoxyethylene (degree of polymerization = 50) stearic acid (mono / di) ester, polyoxyethylene (degree of polymerization = 18) oleic acid ( Mono / di) esters and polyoxyethylene (degree of polymerization = 50) dioleic acid methyl glucoside, etc.], fatty acid alkanolamides [1: 1 type coconut oil fatty acid diethanolamide, 1: 1 type lauric acid diethanolamide, etc.], polyoxyalkylene (C2-C8, polymerization degree = 1-100) alkyl (C1-C22) phenyl ether (polyoxyethylene (polymerization degree = 20) nonylphenyl ether etc.), polyoxyalkylene (C2-C8, Degree of polymerization = 1-100) alkyl (8-24 carbon atoms) amino ether and alkyl (8 carbon atoms) -24) Dialkyl (C1-6) amine oxide [lauryl dimethylamine oxide and the like], polydimethylsiloxane polyoxyethylene adduct, polyoxyethylene / polyoxypropylene block polymer (weight average molecular weight = 150 to 10,000), etc. Can be mentioned.

  As the nonionic surfactant (C), polyoxyalkylene (2 to 8 carbon atoms, degree of polymerization = 1 to 100) higher fatty acid (8 to 24 carbon atoms) ester is preferable from the viewpoint of water absorption, and more preferably monoionic surfactant (C). Polyethylene glycol stearate (polymerization degree = 20) and polyethylene glycol distearate (polymerization degree = 30).

The amount of the nonionic surfactant (C) used is adjusted according to the properties of the crosslinked polymer (A) and the amount of inorganic particles (B) used, but from the viewpoint of water absorption, the water-soluble vinyl monomer (a1). Based on the total weight of the hydrolyzable vinyl monomer (a2) and the crosslinking agent (b), it is preferably 0.005 to 1% by weight (more preferably 0.01 to 0.7% by weight). Within this range, the drying effect is further improved.
The weight ratio between the nonionic surfactant (C) and the inorganic particles (B) is not particularly limited, but is preferably 0.1: 99.9 to 10:90 from the viewpoint of water absorption.
The reason why the drying property is improved by using the inorganic particles (B) and the nonionic surfactant (C) in combination is that the nonionic surfactant (C) helps the uniform dispersion of the inorganic particles (B). At the same time, since the hydrophilic group of the surfactant has an affinity for the crosslinked polymer (A), the hydrophobic group of the nonionic surfactant (C) is oriented outward and the gel is fused. It is presumed that the effect of preventing is improved.

  The production method of the present invention comprises a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2), inorganic particles (B), a compressive fluid, and a nonionic surfactant (C) used as necessary. It has the process of carrying out volume expansion of the mixture (X) containing.

  As the compressive fluid in the production method of the present invention, carbon dioxide, nitrogen, methane, ethylene, and alternative chlorofluorocarbons can be used, but from the viewpoint of safety and ease of handling, preferably carbon dioxide, More preferred is carbon dioxide or nitrogen in the liquid state, subcritical state or supercritical state, and particularly preferred is carbon dioxide in the subcritical state or supercritical state.

  In the production method of the present invention, when carbon dioxide is used as the compressive fluid, the carbon dioxide in the liquid state is the triple point of carbon dioxide (temperature = −) on the phase diagram represented by the temperature axis and the pressure axis of carbon dioxide. 57 ° C, pressure 0.5 MPa) and the gas-liquid boundary line passing through the critical point of carbon dioxide (temperature = 31 ° C, pressure = 7.4 MPa), the isotherm of the critical temperature, and the part surrounded by the solid-liquid boundary line Carbon dioxide under temperature / pressure conditions. Supercritical carbon dioxide means carbon dioxide under temperature / pressure conditions above the critical temperature. Subcritical carbon dioxide is slightly lower than the critical temperature. It refers to carbon dioxide, which is a condition. The pressure means the total pressure in the case of a mixed gas of two or more components.

  In the production method of the present invention, when nitrogen is used as the compressive fluid, the nitrogen in the liquid state is the triple point of nitrogen (temperature = −210 ° C., pressure on the phase diagram represented by the temperature axis and the pressure axis of nitrogen). 0.01 MPa) and the critical point of nitrogen (temperature = -147 ° C., pressure = 3.4 MPa), gas-liquid boundary line, critical temperature isotherm, and temperature / pressure conditions of the part surrounded by the solid-liquid boundary line The nitrogen in the supercritical state refers to nitrogen that is at a temperature and pressure condition higher than the critical temperature, and the nitrogen in the subcritical state refers to nitrogen that is slightly lower in temperature than the critical temperature. The pressure means the total pressure in the case of a mixed gas of two or more components. The pressure means the total pressure in the case of a mixed gas of two or more components.

  Carbon dioxide or nitrogen in the liquid state, subcritical state or supercritical state compresses and heats the gas using known pressurizing equipment (such as a blanker pump) and heating equipment (such as an oil temperature controller). Can be obtained.

  The carbon dioxide used in the production method of the present invention is not particularly limited as long as it can be obtained with a known recovery facility or the like, and preferred examples include carbon dioxide having a purity of 90% or more. Examples of a method for obtaining carbon dioxide having a purity of 90% include a chemical adsorption method, a PAS method, and a gas cooling recovery method.

In the production method of the present invention, the mixture (X) may further contain water and / or an organic solvent.
Water and organic solvents are not limited except that they are compatible with the cross-linked polymer (A) and dissolve carbon dioxide in a liquid state, subcritical state or supercritical state, but ketone solvents (acetone, methyl ethyl ketone, etc.) , Ether solvents (tetrahydrofuran, diethyl ether, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, cyclic ether, etc.), ester solvents (acetic ester, pyruvate, 2-hydroxyisobutyrate, lactate, etc.), amide solvent (Dimethylformamide, etc.), alcohol solvents (methanol, ethanol, isopropanol, fluorine-containing alcohols, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.), aliphatic hydrocarbon solvents (octane, cyclohexane, decane, etc.) and mixtures thereof And the like.
In particular, when the crosslinked polymer (A) is produced by aqueous solution polymerization or reverse phase suspension polymerization using an organic solvent, it preferably contains the same water and / or organic solvent used in the polymerization, and is preferably used water. And / or organic solvents include water, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents and mixtures thereof.
When the mixture (X) contains water and / or an organic solvent, the content of water and the organic solvent is 0.1 to 80 weight based on the total weight of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2). % Is preferred.

In the production method of the present invention, the mixture (X) may further contain a crosslinking agent (b). As the crosslinking agent (b) contained in the mixture (X), those exemplified above can be used, and preferable ones are also the same.
When the mixture (X) contains a crosslinking agent (b), the content (mol%) of the crosslinking agent (b) contained in the mixture (X) is the unit of water-soluble vinyl monomer (a1) contained in the mixture (X). And 0.001-5 is preferable with respect to the total mole number of a hydrolyzable vinyl monomer (a2) unit, More preferably, it is 0.005-3, Most preferably, it is 0.01-1.

The mixture (X) comprises a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2), inorganic particles (B), a compressible fluid, and a crosslinking agent (b) used as necessary, a nonionic surfactant (C ), Can be obtained by mixing water and a solvent, and can be prepared by a batch-type mixing method and a continuous-type mixing method.
Examples of the batch type mixing method include a method of mixing in a pressure vessel, and examples of the continuous type mixing method include a method of mixing using a line blend (in-line mixing) apparatus.
Among these, continuous mixing by a line blending apparatus that is a continuous mixing method is preferable from the viewpoint of improving productivity, stabilizing quality, and reducing manufacturing space.

Specific examples of the apparatus used for the batch type mixing method include a mixer such as a pressure vessel with a stirrer, and it is preferable to include a nozzle for taking out the mixture for performing volume expansion of the mixture (X). .
As a preparation procedure of the mixture (X) by the batch type mixing method, the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2), the inorganic particles (B), and the crosslinking agent (b) used as necessary, nonion After introducing the surfactant (C), water and solvent into the pressure vessel, heat as necessary, and introduce the compressive fluid into the vessel until the desired pressure is reached by a pressurizing means such as a pump provided in the pressure vessel. To do. Then, the method etc. which mix by stirring etc. for predetermined time are mentioned. When water and an organic solvent are used, the water and the organic solvent are put into a pressure vessel in a state of being mixed with a water-soluble vinyl monomer (a1), a hydrolyzable vinyl monomer (a2), or a necessary crosslinking agent (b). It may be sufficient or may be supplied alone.

Specific examples of the apparatus used in the continuous mixing method include a line blending apparatus (static type line mixer (static mixer, in-line mixer, lamond super mixer, sulzer mixer, etc.)) having a stirring section in a liquid flow path, and A stirring type line mixer (vibration mixer, turbo mixer, etc.)], and a nozzle for taking out the mixture for volumetric expansion of the mixture (X) is preferably provided at the outlet thereof. Further, the length of the mixer portion of the apparatus, the pipe diameter, and the number of mixing apparatuses (elements) are not limited at all, but must be able to withstand the target pressure.
As a preparation procedure of the mixture (X) using a line blending apparatus, a monomer composition (M) and inorganic particles (B) and a nonionic surfactant (C) to be used if necessary using a liquid feed pump, Water (Solvent) and solvent are introduced into the line blending apparatus, and then fed into the line blending apparatus adjusted to a desired pressure, whereby the mixture (X) can be obtained. The residence time in the apparatus is not particularly limited as long as mixing is sufficiently performed, but is preferably 0.1 to 1800 seconds.

  The content of the compressive fluid in the liquid state, subcritical state, or supercritical state contained in the mixture (X) is the same as that of the compressive fluid in the liquid state, subcritical state, or supercritical state from the viewpoint of production efficiency. It is preferable that the ratio (volume percentage) of the volume to the total volume of the mixture (X) is 5 to 20% by volume.

The volume expansion of the mixture (X) is a phenomenon that occurs as the volume of the compressive fluid contained in the mixture (X) expands, and is performed by reducing the pressure of the environment in which the mixture (X) is placed. be able to.
As a method of expanding the volume of the mixture (X), the mixture is moved from a device (such as a pressure vessel and a line blending device) where the mixture (X) is manufactured to a place adjusted to a pressure lower than the pressure in the manufacturing device or an atmospheric pressure. It can be carried out by a method of transferring (X) and a method of reducing the pressure in the production apparatus to a lower pressure after producing the mixture (X).
Especially, it is preferable that the pressure at the time of carrying out volume expansion is a pressure from which the carbon dioxide contained in mixture (X) turns into gas. The rate of change when the pressure is changed is preferably reduced to a target pressure all at once from the viewpoint of the dispersibility of the inorganic particles (B). Therefore, it is preferable that the apparatus which manufactures mixture (X) is equipped with the exhaust pressure valve which can be pressure-reduced to the target pressure at a stretch.
In addition, when the mixture (X) is transferred from the pressure vessel or the line blending device to another receiving vessel adjusted to the target pressure, the nozzle having a diameter capable of transferring the mixture (X) and the receiving vessel are set to the same pressure. It is necessary to have a regulator to keep. However, if the pressure in the receiving container is atmospheric pressure, a regulator is not necessary.

In the production method of the present invention, it is preferable to further perform a step of removing carbon dioxide after performing the step of expanding the volume of the mixture (X). In addition, since carbon dioxide becomes gas as a result of volume expansion of the mixture (X), the removal of carbon dioxide can be performed by exhausting the carbon dioxide that has become gas.
The vaporized carbon dioxide may be discharged from the production apparatus alone, or may be discharged simultaneously with the mixture (X) when taking out the mixture (X) from the production apparatus, and the mixture (X It is preferable to simultaneously perform the operation of discharging the liquid from the production container and the operation of expanding the volume, and the discharge operation is preferably performed at a discharge speed such that the amount of change in pressure within a unit time is small. The discharge speed is more preferably a speed at which the pressure change in the production apparatus is 3 MPa or less, and particularly preferably a speed at which the pressure is 1 MPa or less.

A case where the production method of the present invention is produced by line blending using a continuous mixing and dispersing apparatus will be described with reference to the drawings.
A water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) inorganic particles (B) and, if necessary, a crosslinking agent (b), a nonionic surfactant (C), water and an organic solvent are dissolved in a dissolution tank ( The monomer composition is prepared by mixing in T1). Inside the static mixer using the valve (V1) while introducing carbon dioxide from the carbon dioxide cylinder (B1) filled with carbon dioxide into the apparatus [static mixer (M1)] that performs line blending through the carbon dioxide pump (P2) The static mixer (M1) is filled with carbon dioxide in a liquid state, a subcritical state or a supercritical state by adjusting the pressure and temperature. Next, the monomer composition is introduced into carbon dioxide in the static mixer (M1) through the solution pump (P1) from the dissolution tank (T1), and live blend is performed to prepare the mixture (X) in the static mixer (M1). . The temperature at the time of line blending is not particularly limited, but is preferably 100 to 120 ° C. Moreover, the residence time in the static mixer (M1) when performing line blending is not particularly limited, but is preferably 0.1 to 1800 seconds. Next, the liquid line-blended by the static mixer (M1) is discharged to the pressure receiving tank (T2) through the valve (V1). The step of expanding the volume of the mixture (X) can be performed by keeping the pressure of the pressure receiving tank (T2) as a discharge destination lower than that of the tatic mixer (M1). Furthermore, the process of exhausting the vaporized carbon dioxide can also be performed.

In the production method of the present invention, the water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) obtained after performing the volume expansion of the mixture (X) and further volume expansion, inorganic It is preferable to include a polymerization step in which the particles (B) and an inorganic particle dispersion liquid containing a crosslinking agent (b) and a nonionic surfactant (C) used as necessary are further polymerized.
The polymerization step may be a known aqueous solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; Japanese Patent Laid-Open No. 55-133413, etc.) or a known reverse phase suspension polymerization using an organic solvent (Japanese Patent Publication No. 54-30710). In the case of manufacturing by reverse phase suspension polymerization, a compressive fluid is used as a polymerization solvent. You can also.

In the production method of the present invention, when the polymerization step is performed using water and an organic solvent, it is preferable to perform a drying step in order to further remove water and the organic solvent.
A drying process can be performed by heating the reaction material after superposition | polymerization of a superposition | polymerization process preferably 60-230 degreeC (more preferably 100-200 degreeC). When the heating temperature is 60 ° C. or higher, the time required to remove water and organic solvent is shortened and economical in terms of energy consumption. On the other hand, when the heating temperature is 230 ° C. or lower, side reactions, resin decomposition, etc. Does not occur, and the absorption performance of the water absorbent resin composition does not decrease.
As a device used for the drying process, a known device used for drying a normal water absorbent resin can be used. A parallel flow band dryer (tunnel dryer), an aeration band dryer, and a jet flow (nozzle jet) dryer. And a heat source for these devices are not particularly limited. These devices can be used in combination.

The production method of the present invention includes a step of volumetric expansion of the mixture (X), a polymerization step, and a drying step of removing water and an organic solvent, and then a step of pulverizing and adjusting the particle size as required by a known method. But you can.
The particle size distribution of the water-absorbent resin composition after the pulverization and, if necessary, the step of adjusting the particle size is such that the content in the range of 1000 μm to 150 μm is 90% by mass or more, preferably 95% by mass or more. When the amount of coarse particles exceeding 1000 μm is 10% by mass or less, the absorption rate tends to increase. When the amount of fine particles less than 150 μm is 10% by mass or less, the generation of dust does not increase, blocking is not likely to occur under high humidity conditions, and there is no problem of deterioration in powder handling properties and work environment. preferable. The average particle size is 200 to 800 μm, preferably 300 to 600 μm.

  The production method of the present invention is a particulate water-absorbent resin obtained by subjecting a mixture (X) to volume expansion and a polymerization step, then pulverizing after removing water and organic solvent, and adjusting the particle size as necessary. A step of surface cross-linking the surface vicinity of the composition by a known method using a cross-linking agent having at least two functional groups capable of reacting with the water-soluble substituent may be included.

  The water absorbent resin composition obtained by the production method of the present invention is particularly suitable for disposable paper diapers (children's and adult paper diapers). In addition, other sanitary materials (eg sanitary napkins, incontinence pads, breast milk pads, surgical underpads, postpartum mats, wound protection dressings, pet sheets, etc.) and various absorbent sheets (eg freshness) Holding sheet, drip absorption sheet, anti-condensation sheet, paddy rice seedling sheet, concrete curing sheet, water running prevention sheet for cables, oil / water separation sheet, fire extinguishing sheet, etc.). Furthermore, applications (eg, soil water retention agent, sludge solidifying agent, solidifying agent such as waste blood and aqueous waste liquid, portable urine gelling agent, battery electrolyte gelling agent, etc.) and water absorption It can also be used for applications in which gel is applied (for example, chemical warmers, poultices, gel beds, artificial snow, gel-like fragrances, etc.).

  EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. In the following description, “parts” indicates parts by weight.

<Production Example 1>
A mixture of 16.7 liters of sodium acrylate (manufactured by Nippon Shokubai Co., Ltd.) and 23 g of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), a crosslinking agent (b- 1) N, N′-methylenebisacrylamide (Mitsubishi Rayon Co., Ltd.) 0.3 g and deionized water 295 g were added, and the temperature of the contents of the glass reaction vessel was kept at 5 ° C. while stirring and mixing. After flowing nitrogen into the contents to make the dissolved oxygen amount 1 ppm, 1 g of 1% aqueous solution of hydrogen peroxide, 1.2 g of 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidinopropane dihydrochloride 2.8 g of a 2% aqueous solution of was added and mixed to initiate polymerization. After polymerizing and aging for 6 hours, the crosslinked polymer (A-1) was obtained by drying.

<Example 1>
Line blending apparatus having the configuration shown in FIG. 1 [in a static mixer, 76.7 g of sodium acrylate (manufactured by Nippon Shokubai Co., Ltd.) which is a water-soluble vinyl monomer (a1-1) and 23 g of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) 0.3 g of N, N′-methylenebisacrylamide (Mitsubishi Rayon Co., Ltd.) which is the mixture and the crosslinking agent (b-1), 200 parts of water, 1 part of talc (Matsumura Sangyo Co., Ltd .; Crown Talc P), polyethylene distearate 0.05 parts of glycol (manufactured by Sanyo Chemical Industries; Emalmine 862) was charged into a dissolution tank (T1) and stirred to prepare a monomer composition.
Next, a static mixer (M1) in which carbon dioxide in a liquid state is adjusted to 60 ° C. at a flow rate of 0.2 L / h using a carbon dioxide pump (P2) from a carbon dioxide cylinder (B1) (manufactured by Noritake Company Limited; inner diameter) 0.5 m, 27 elements, 2 m in length), and the valve (V1) was adjusted to a pressure of 15 MPa in the static mixer to create supercritical carbon dioxide.
While maintaining the flow rate, temperature and pressure, carbon dioxide was continuously introduced, and at the same time, the monomer composition was removed from the dissolution tank (T1) using a solution pump (P1) at a flow rate of 1 L / h. ) And line blended with a static mixer (M1) to prepare a mixture (X-1). The mixture (X-1) after the line blending is opened from a nozzle provided at the static mixer outlet into a pressure-resistant receiving tank (T2) adjusted to 0.1 MPa, and the mixture (X) is expanded in volume while simultaneously producing carbon dioxide. The inorganic particle dispersion was obtained by evaporating and removing.
The inorganic particle dispersion was put into a glass reaction vessel having a capacity of 1 liter, and the temperature of the contents was kept at 5 ° C. while stirring and mixing. After flowing nitrogen into the contents to make the dissolved oxygen amount 1 ppm, 1 g of 1% aqueous solution of hydrogen peroxide, 1.2 g of 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidinopropane dihydrochloride 2.8 g of a 2% aqueous solution was added and mixed to initiate polymerization (polymerization concentration 25%). A gel polymer (1) was obtained by polymerizing and aging for about 6 hours. The gel polymer (1) is chopped into 3-7 mm size with a screw type extruder, then laminated to a thickness of 5 cm, and dried with aeration band under conditions of 140 ° C. and wind speed of 2.0 m / sec. It dried with the machine (made by Inoue Metal). The obtained dried product was pulverized and adjusted to a particle size of 20 to 100 mesh to prepare a water absorbent resin composition (Z-1).

<Example 2>
A water-absorbent resin composition (Z) was prepared in the same manner as in Example 1 except that 1 part of talc (manufactured by Matsumura Sangyo Co., Ltd .; Crown Talc P) was changed to 1 part of montmorillonite (Kunimine Kogyo Co., Ltd .; Kunipia F). -2).

<Example 3>
The water-absorbent resin composition was the same as in Example 1 except that polyethylene glycol distearate (manufactured by Sanyo Chemical Industries; Emalmine 862) was changed to polyoxyalkylene alkyl ether (manufactured by Sanyo Chemical Industries; NAROACTY ID50) in Example 1. Z-3 was created.

<Example 4>
A water absorbent resin composition (Z-4) was prepared in the same manner as in Example 1 except that 1 part of talc (manufactured by Matsumura Sangyo Co., Ltd .; Crown Talc P) was changed to 0.5 part in Example 1.

<Comparative Example 1>
100 parts of the crosslinked polymer (A-1) obtained in Production Example 1 and 200 parts of water were shredded to a size of 3 to 7 mm with a screw extruder, and subsequently talc (manufactured by Matsumura Sangyo Co., Ltd .; crown talc) P) 1 part and 0.05 part of polyethylene glycol distearate (manufactured by Sanyo Chemical Industries; Emalmine 862) were added and mixed by passing through an internal mixer, and then the mixture was laminated to a thickness of 5 cm, 140 ° C, It dried with the ventilation type | mold band dryer (made by Inoue Metal) on the conditions of the wind speed of 2.0 m / sec. The obtained dried product was pulverized and adjusted to a particle size of 20 to 100 mesh to prepare a water absorbent resin composition (Z′-1).

<Drying speed and drying property>
In Examples 1 to 4 and Comparative Example 1, the time until the water content became 5% after being placed in the aeration type band dryer was measured and listed in Table 1 as the drying time. The moisture content was calculated by measuring the mass of the dried product and calculating the difference from the mass of the hydrogel polymer before drying (the moisture content is known).
Furthermore, the dried product obtained by placing in a ventilated band dryer for 1 hour and drying was pulverized, and the weight of an undried product of 20 mesh or more that could not be pulverized due to insufficient drying was measured. The mass% of the undried product with respect to the total weight of the dried product was calculated, and the drying property was evaluated according to the following criteria. In addition, it means that it is excellent in drying property, so that the weight of an undried material is small.
◎: No undried product of 20 mesh or more ○: Less than 2% of undried product of 20 mesh or more △: Less than 2-5% of undried product of 20 mesh or more ×: 5% of undried product of 20 mesh or more that's all

<Coloring>
In the above drying rate and drying test, the colored state of the water-absorbent resin composition that passed through 20 meshes was visually confirmed, and the results are shown in Table 1. When the water absorbent resin composition is colored, it means that the water absorbent resin has been altered.

<Pressure absorption amount>
In the above drying speed and drying test, the water-absorbing resin composition that passed through 20 mesh was placed in a plastic cylinder (inner diameter 25 mm, height 30 mm) with a 250-mesh nylon net attached to the bottom. 0.160 g of the product was placed, and a weight of 200 g that smoothly moved up and down the cylinder with a uniform outer surface diameter of 25 mm was placed thereon (the load applied to the surface of the water absorbent resin composition was 40 g / cm ² ). In a petri dish (diameter 12 cm) containing physiological saline 60 ml, the nylon cylinder side of a plastic cylinder containing a water-absorbing resin and a weight was immersed on the bottom surface, left for 60 minutes, and then pulled up from the petri dish. Then, the mass which increased by subtracting the dry weight of the water-absorbent resin composition from the weight of the water-absorbent resin composition after the pulling to absorb physiological saline was calculated. The value was converted to a value per 1 g of water-absorbing agent, and the pressure absorption amount at 40 g / cm ² was obtained.

  As shown in Table 1, it is clear that the particles of the present invention described in the examples are superior in drying property and not colored as compared with the particles of the comparative example. In addition, a water-absorbent resin composition which is not colored and has no alteration in the water-absorbent resin has a large amount of pressure absorption and is excellent in absorption performance.

The water-absorbent resin composition prepared by the production method of the present invention is particularly suitable for disposable paper diapers (children's and adult paper diapers).
In addition, other sanitary materials (eg sanitary napkins, incontinence pads, breast milk pads, surgical underpads, postpartum mats, wound protection dressings, pet sheets, etc.) and various absorbent sheets (eg freshness) Holding sheet, drip absorption sheet, anti-condensation sheet, paddy rice seedling sheet, concrete curing sheet, water running prevention sheet for cables, oil / water separation sheet, fire extinguishing sheet, etc.). Furthermore, applications (eg, soil water retention agent, sludge solidifying agent, solidifying agent such as waste blood and aqueous waste liquid, portable urine gelling agent, battery electrolyte gelling agent, etc.) and water absorption It can also be used for applications in which gel is applied (for example, chemical warmers, poultices, gel beds, artificial snow, gel-like fragrances, etc.).

T1: Dissolution tank (maximum operating pressure 20 MPa, maximum operating temperature 200 ° C., with stirrer)
T2: pressure tank B1: carbon dioxide cylinder P1: solution pump P2: carbon dioxide pump M1: static mixer (pressure vessel for reaction)
V1: Valve

Claims (5)

  Water-soluble vinyl monomer (a1) and / or vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis, cross-linked polymer (A) containing inorganic monomer (A) and cross-linking agent (b) B) a water-absorbent resin composition comprising a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis, inorganic particles (B), and A method for producing a water-absorbent resin composition, comprising a step of expanding a volume of a mixture (X) containing a compressive fluid.   The method for producing a water-absorbent resin composition according to claim 1, wherein the mixture (X) further contains a nonionic surfactant (C).   The method for producing a water absorbent resin composition according to claim 1 or 2, wherein the inorganic particles (B) are clay minerals.   The method for producing a water-absorbent resin composition according to any one of claims 1 to 3, wherein the inorganic particles (B) have a thickness of 1 to 100 nm and an aspect ratio of 100 to 100,000.   The weight of the inorganic particles (B) is 0.1 to 10% by weight based on the total weight of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis. The manufacturing method of the water absorbing resin composition in any one of 1-4.