JP2011190426A - Absorbing resin particle and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of poor productivity and remarkably poor absorbing performance of the conventional absorbing resin particles using a plant-based material compared with the conventional polyacrylic acid-based absorbing resin particles. <P>SOLUTION: The absorbing resin particle includes (A) a cross-linked polymer (A1) having as the essential constituent units (a1) a water-soluble vinyl monomer and/or (a2) a hydrolyzable vinyl monomer and (a3) a cross-linking agent, and (B) a polylactic acid. The weight average molecular weight of (B) is 5,000 to 200,000. (B) is included by 5 to 30 wt.% based on the weight of (A1). (B) is included by 0.1 to 25 wt.% based on the weight of (A1) in the absorbing resin particle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to absorbent resin particles and a method for producing the same.

  Absorbent resin particles are resins that can absorb water several tens to several thousand times their own weight. For example, polyacrylic acid-based absorbent resins are known. These absorptive resins are often used in disposable sanitary goods because of their high water absorption. However, it has been pointed out that the treatment method of sanitary goods containing these absorbent resins has a problem from the viewpoint of environmental load, and that the treatment method in an incinerator causes global warming. Under such circumstances, absorbent resin particles using plant-derived materials are desired from the viewpoint of carbon neutral.

  Examples of absorbent resins using plant-derived raw materials include crosslinked carboxymethyl polylactic acid (Patent Documents 1 and 11), crosslinked alginic acid, crosslinked starch (Patent Document 2), and crosslinked polyamino acid (Patent Documents 3 to 7). Further, galactomannan-metal cross-linked bodies (Patent Documents 8 to 10) and the like are known.

JP 2004-010634 A Japanese Patent Laid-Open No. 55-15634 JP 7-224163 A JP 7-309943 A JP-A-8-59820 JP-A-8-504219 JP-A-9-169840 JP-A-8-59891 Japanese Patent Publication No. 3-66321 JP 56-97450 A U.S. Pat. No. 4,650,716

  However, the absorbent resin particles using these plant-derived raw materials have a problem that the productivity is worse than the conventional polyacrylic acid-based absorbent resin particles and the absorption performance is remarkably inferior, leading to practical use. Not in.

  An object of the present invention is to provide absorbent resin particles containing a plant-derived raw material and having excellent absorption performance, and a method for producing the same.

  The feature of the absorbent resin particles of the present invention is that the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2), and the crosslinked polymer (A1) having a crosslinking agent (a3) as essential constituent units and poly Absorbent resin particles comprising lactic acid (B), wherein (B) has a weight average molecular weight of 5,000 to 200,000, and (B) is contained in an amount of 5 to 30% by weight based on the weight of (A1); The gist is to contain 0.1 to 25% by weight of B) in the absorbent resin particles based on the weight of (A1).

A feature of the method for producing absorbent resin particles of the present invention is that the water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and crosslinking agent (a3) are essential components in the method for producing absorbent resin particles. After the monomer (a) is copolymerized to obtain a crosslinked polymer (A1), (A1) and polylactic acid (B) are mixed to form a crosslinked polymer (A1) / polylactic acid. A step of obtaining a composite gel (1); or a monomer having the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the crosslinking agent (a3) as an essential constituent monomer (a); And (2) comprising mixing the polylactic acid (B) and then copolymerizing the monomers to obtain a crosslinked polymer (A1) / polylactic acid composite gel.
(B) has a weight average molecular weight of 5,000 to 200,000,
The amount of (B) used is 5 to 30% by weight based on the weight of the crosslinked polymer (A1),
It is summarized that 0.1 to 25% by weight of (B) is contained in the absorbent resin particles based on the weight of the crosslinked polymer (A1).

  The absorbent resin particles of the present invention exhibit high absorption performance despite using plant-derived raw materials (polylactic acid). Moreover, according to the manufacturing method of the absorbent resin particle of this invention, although the plant-derived raw material (polylactic acid) is used, the absorbent resin particle which exhibits high absorption performance can be manufactured easily.

Front sectional drawing which showed typically the whole apparatus for measuring the swelling volume by a swelling volume measuring method. The side projection figure which showed typically the cylinder 1 with a baseplate and the disk 2 with a handle for measuring the swelling volume by a swelling volume measuring method. The top view which showed typically the disk 2 with a handle for measuring the swelling volume by a swelling volume measuring method.

  The water-soluble vinyl monomer (a1) is not particularly limited and is known {for example, a vinyl monomer disclosed in Japanese Patent No. 3648553, Japanese Patent Laid-Open No. 2003-165883, Japanese Patent Laid-Open No. 2005-75982, Japanese Patent Laid-Open No. 2005-95759}. Etc. can be used.

  The hydrolyzable vinyl monomer (a2) means a vinyl monomer that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and is not particularly limited (for example, Japanese Patent No. 3648553, JP-A No. 2003-165883, The vinyl monomer etc. of Unexamined-Japanese-Patent No. 2005-75982, Unexamined-Japanese-Patent No. 2005-95759} etc. can be used. The water-soluble vinyl monomer means a vinyl monomer having a property of dissolving at least 100 g in 100 g of water at 25 ° C. The term “hydrolyzable” refers to the property of being hydrolyzed by the action of 50 ° C. water and, if necessary, the catalyst (acid or base) to make it water-soluble. Hydrolysis of the hydrolyzable vinyl monomer may be performed either during polymerization, after polymerization, or both of them, but from the viewpoint of the molecular weight of the resulting absorbent resin particles, etc., is preferable.

  Of these, water-soluble vinyl monomers (a1) are preferred from the viewpoint of absorption characteristics, etc., more preferably anionic vinyl monomers, and more preferably carboxy (salt) groups, sulfo (salt) groups, amino groups, carbamoyl groups. Vinyl monomers having an ammonio group or a mono-, di- or tri-alkyl ammonio group, then preferably vinyl monomers having a carboxy (salt) group or a carbamoyl group, particularly preferably (meth) acrylic acid (salt) and (Meth) acrylamide, next particularly preferably (meth) acrylic acid (salt), most preferably acrylic acid (salt).

The “carboxy (salt) group” means “carboxy group” or “carboxylate group”, and the “sulfo (salt) group” means “sulfo group” or “sulfonate group”. Moreover, (meth) acrylic acid (salt) means acrylic acid, acrylate, methacrylic acid or methacrylate, and (meth) acrylamide means acrylamide or methacrylamide.
Examples of the salt include an alkali metal (such as lithium, sodium and potassium) salt, an alkaline earth metal (such as magnesium and calcium) salt or an ammonium (NH ₄ ) salt. Among these salts, alkali metal salts and ammonium salts are preferable from the viewpoint of absorption characteristics and the like, more preferably alkali metal salts, and particularly preferably sodium salts.

  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.

The cross-linking agent (a3) is not particularly limited, and known cross-linking agents such as those disclosed in known {eg, Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982, Japanese Patent Application Laid-Open No. 2005-95759}, Can be used.
Among these, from the viewpoint of absorption characteristics, etc., a crosslinking agent having two or more ethylenically unsaturated groups is preferable, more preferably a poly (meth) allyl ether of a polyol having 2 to 10 carbon atoms, particularly preferably triallylsia. Nurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether.

  The content (mol%) of the crosslinking agent (a3) unit is preferably 0.001 to 5, more preferably, based on the number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. Is 0.005 to 3, particularly preferably 0.01 to 1. Within this range, the absorption characteristics are further improved.

  In addition to these, monomers having water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and crosslinking agent (a3) as essential constituent monomers are copolymerizable with these. Of vinyl monomer (a4)

  Other vinyl monomers (a4) that can be copolymerized are not particularly limited and are known {eg, hydrophobicity of Japanese Patent No. 3648553, Japanese Patent Laid-Open No. 2003-165883, Japanese Patent Laid-Open No. 2005-75982, Japanese Patent Laid-Open No. 2005-95759}. Vinyl monomers can be used.

  When the other vinyl monomer (a4) is included, the usage amount (mol%) of the other vinyl monomer (a4) is based on the number of moles of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2). 0.01-5 is preferable, More preferably, it is 0.05-3, Next, Preferably it is 0.08-2, Most preferably, it is 0.1-1.5. In view of absorption performance and the like, it is most preferable not to use any other vinyl monomer (a4).

  As a method of obtaining a crosslinked polymer (A1) by copolymerizing a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a monomer having a crosslinking agent (a3) as an essential constituent monomer. Are known aqueous solution polymerization {adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.] and known reverse phase suspension polymerization {JP-B-54-30710, JP-A-56-26909. No. 1 and Japanese Patent Laid-Open No. 1-5808 etc.}.

  Water-containing gel obtained by polymerization {consists of a crosslinked polymer (A1) and water. } Can be shredded as necessary. When chopping, the size (longest diameter) of the gel after chopping is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and particularly preferably 1 mm to 1 cm.

  Shredding can be performed by a known method, and can be shredded using a normal shredding device {for example, a bex mill, rubber chopper, pharma mill, mincing machine, impact crusher and roll crusher}. .

  The cross-linked polymer (A1) may be one type or a mixture of two or more types.

In the present invention, the polylactic acid (B) has a weight average molecular weight of 5,000 to 200,000. From a viewpoint of absorption performance, More preferably, it is 10,000-200000, More preferably, it is 15000-200000.
The weight average molecular weight of the polylactic acid (B) used is measured by the following method.
A polylactic acid to be measured is dissolved in dimethylformamide to obtain a measurement sample. The measurement is performed at a column temperature of 40 ° C. using a Tosoh GPC measurement device (column: TSKgel α-M). For the analysis, polyethylene glycol is used as a standard substance, and the weight average molecular weight of polylactic acid is calculated in terms of polyethylene glycol molecular weight.

  The volume average particle diameter of the polylactic acid (B) is not particularly limited, but is preferably 0.5 to 100 μm, more preferably 0.5 to 80 μm, still more preferably 0.5 to 50 μm from the viewpoint of absorption performance. It is.

  The shape of the polylactic acid (B) used for this invention does not have limitation in particular, A fibrous form and a powder form can be used. Further, the property of (B) is not particularly limited, and an emulsion state or the like can be used. From the viewpoint of absorption performance, those in powder form and emulsion state are preferable, and those in emulsion state are more preferable.

Content (weight%) of polylactic acid (B) is 5-30 based on the weight of a crosslinked polymer (A1), Preferably it is 7-27, More preferably, it is 10-25. Within this range, the absorption performance is further improved.
When the content of (B) is less than 5, the anti-fogging property is deteriorated when used in an absorbent article, and when it exceeds 30, the anti-moisture resistance is deteriorated when used in an absorbent article.

Polylactic acid (B) is contained inside the absorbent resin particles. The content (% by weight) inside the absorbent resin particles of (B) is 0.1 to 25 based on the weight of the crosslinked polymer (A1), and from the viewpoint of absorption characteristics, preferably 0.5 to 25, more preferably 1-20.
When the content of the absorbent resin particles in (B) is less than 0.1, the anti-fogging property is deteriorated when used for an absorbent article, and when it is more than 25, the anti-moisture resistance is deteriorated when used for an absorbent article. To do.

In the present invention, the polylactic acid (B) is preferably present on the surface of the absorbent resin particles from the viewpoint of absorption characteristics.
The amount (% by weight) of (B) present on the surface of the absorbent resin particles is preferably 0.1 to 10, more preferably 0.8 based on the weight of the crosslinked polymer (A1) from the viewpoint of absorption performance. 3-5.

In addition, each content of the polylactic acid (B) mentioned above is measured by the following method.
<Measurement method of content of polylactic acid (B) present on absorbent resin particle surface>
Add 1 part by weight of absorbent resin particles to a glass beaker and add 100 parts by weight of acetone, stir for 1 hour at 25 ° C., and separate the residue on the filter paper and the filtrate by filtration using filter paper. A polylactic acid extract is used. The extract is collected in a pre-weighed glass beaker, and the solvent is evaporated at around 30 ° C. using an evaporator, and then weighed. The weight after evaporating the solvent minus the weight of the beaker weighed in advance is calculated and used as the weight of the evaporated dry product. Using the residue on the filter paper, the same operation of adding 100 parts by weight of acetone and extracting was repeated twice, and the total weight of the evaporated and dried product obtained by the three extractions was multiplied by 100 to obtain poly on the surface. Let the content (% by weight) of lactic acid.

<Measurement method of content of polylactic acid (B) present in absorbent resin particles>
After fully absorbing the absorbent resin particles after extraction used in the above measurement method in a glass beaker, 1 part by weight is swelled with 50 parts by weight of ion-exchanged water, 100 parts by weight of acetone is added, and the mixture is heated to 25 ° C. The mixture is left to stir for 24 hours, and is separated into a residue on the filter paper and a filtrate by filtration using a filter paper, and the filtrate is used as an extract of polylactic acid. The extract is collected in a pre-weighed glass beaker, and the solvent is evaporated at around 30 ° C. using an evaporator, and then weighed. The weight obtained by subtracting the weight of the beaker weighed in advance from the weight after evaporation of the solvent is calculated and used as the weight of the evaporated and dried product. Using the residue on the filter paper, the same operation of extraction by adding 50 parts by weight of ion exchange water and 100 parts by weight of acetone was repeated twice, and the total weight of the evaporated and dried product obtained by the three extractions was multiplied by 100. The content is the content (% by weight) of polylactic acid present in the interior.

  The absorbent resin particles of the present invention can further contain a hydrophobic substance (C).

  The content (% by weight) of the hydrophobic substance (C) with respect to the absorbent resin particles is based on the weight of the crosslinked polymer (A1) from the viewpoint of the anti-fogging resistance of the absorbent article and the anti-moisture resistance of the absorbent article. , 0.01 to 10, preferably 0.01 to 5, more preferably 0.05 to 2, particularly preferably 0.1 to 1.

The content (% by weight) of the hydrophobic substance (C) inside the absorbent resin particles is based on the weight of the crosslinked polymer (A1) from the viewpoint of the anti-fogging resistance of the absorbent article and the anti-moisture resistance of the absorbent article. 0.01 to 10 is preferable, more preferably 0.01 to 5, then more preferably 0.05 to 2, and particularly preferably 0.1 to 1.
The content (% by weight) of the hydrophobic substance (C) present on the surface of the absorbent resin particles is determined from the cross-linked polymer (A1) from the viewpoint of the anti-fogging property of the absorbent article and the anti-moisture resistance of the absorbent article. Based on weight, it is preferably 0.001-1, more preferably 0.005-0.5, still more preferably 0.01-0.3, and particularly preferably 0.01-0.1.

In addition, content of the hydrophobic substance (C) which exists on the surface of an absorbent resin particle is measured by the following method.
<Measurement method of content of hydrophobic substance present on surface of absorbent resin particles>
In a glass beaker, 1 part by weight of the absorbent resin particles and an organic solvent (an organic solvent in which at least 0.01 part by weight of a hydrophobic substance is dissolved in 100 parts by weight of the organic solvent at 25 ° C. to 110 ° C.). The temperature at which the solution can be dissolved is taken as the dissolution temperature.) 1000 parts by weight are added, and the mixture is stirred for 24 hours at the dissolution temperature and left to stand. Use an extract of a hydrophobic substance. The extract is collected in a pre-weighed glass beaker, the solvent is evaporated, and then weighed. Multiply by 100 times the weight of the beaker weighed in advance from the weight after evaporation of the filtrate. Using the sample after extraction remaining on the filter paper, the same operation is repeated twice, and the content of the hydrophobic substance contained in the absorbent resin particles is the total amount of the evaporated and dried product obtained by the extraction three times. (% By weight).

The hydrophobic substance (C) includes a compound having at least one monovalent aliphatic hydrocarbon group having 8 to 26 carbon atoms and at least one functional group capable of forming a hydrogen bond with a carboxyl group. It is.
The number of monovalent aliphatic hydrocarbon groups having 8 to 26 carbon atoms that (C) has is preferably from 1 to 5, more preferably from 1 to 4, and still more preferably from the viewpoint of anti-fogging properties of the absorbent article. Preferably it is 1-3.
The number of functional groups capable of forming hydrogen bonds with the carboxyl group (C) is preferably from 1 to 5, more preferably from 1 to 4, and even more preferably 1 from the viewpoint of the ability to absorb the absorbent article. ~ 3.

  Examples of the monovalent aliphatic hydrocarbon group having 8 to 26 carbon atoms include linear and branched hydrocarbon groups. From the viewpoint of the anti-fogging property of the absorbent article, a straight chain is preferable.

  Specific examples of the monovalent aliphatic hydrocarbon group having 8 to 26 carbon atoms include an octyl group and a hexacosyl group.

  The functional group capable of forming a hydrogen bond with the carboxyl group includes a carboxyl group (including this salt), a phosphate group (including this salt), a sulfo group (including this salt), and a primary amino group (including this salt). ), Secondary amino groups (including this salt), tertiary amino groups (including this salt), hydroxyl groups, ester bonds, phosphate ester bonds, sulfonate ester bonds, amide bonds, urethane bonds and urea bonds. .

  Examples of the hydrophobic substance (C) having a carboxyl group include nonanoic acid, octadecanoic acid, and heptacosanoic acid. Examples of the salt include salts with sodium, potassium, zinc, calcium, magnesium, aluminum (hereinafter abbreviated as Na, K, Zn, Ca, Mg, Al) and the like, and basic salts are also included.

  Examples of the hydrophobic substance (C) having a phosphoric acid group include octyl phosphoric acid and hexacosyl phosphoric acid. Examples of the salt include salts with Na, K, Zn, Ca, Mg, Al, and the like, and basic salts and acidic salts are also included.

  Examples of the hydrophobic substance (C) having a sulfonic acid group include octylsulfonic acid and hexacosylsulfonic acid. Examples of the salt include salts with Na, K, Zn, Ca, Mg, Al, and the like, and basic salts are also included.

  Examples of the hydrophobic substance (C) having a primary amino group include octylamine and hexacosylamine. Examples of the salt include salts with hydrochloric acid, carboxylic acid, sulfuric acid, nitric acid and the like, and acidic salts are also included.

  Examples of the hydrophobic substance (C) having a secondary amino group include methyloctylamine, methylhexacosylamine, octylhexacosylamine, dihexacosylamine, and methyloctadecylamine. Examples of the salt include salts with hydrochloric acid, carboxylic acid, sulfuric acid, nitric acid and the like, and acidic salts are also included.

  Examples of the hydrophobic substance (C) having a tertiary amino group include dimethyloctylamine, dimethylhexacosylamine, methyloctylhexacosylamine, and methyldihexacosylamine. Examples of the salt include salts with hydrochloric acid, carboxylic acid, sulfuric acid, nitric acid and the like, and acidic salts are also included.

  Examples of the hydrophobic substance (C) having a hydroxyl group include octyl alcohol, octadecyl alcohol, and hexacosyl alcohol.

  Examples of the hydrophobic substance (C) having an ester bond include an esterified product of a long chain fatty acid having 8 to 26 carbon atoms and an alcohol having 1 to 26 carbon atoms and an alcohol having 1 to 26 carbon atoms and a long chain fat having 8 to 26 carbon atoms. And an esterified product of a carboxylic acid having a hydrocarbon group having 1 to 7 carbon atoms and at least one carboxylic group.

  Examples of esterified products of long chain fatty acids having 8 to 26 carbon atoms and alcohols having 1 to 26 carbon atoms having at least one hydroxyl group include methyl nonanoate, methyl heptacosanoate, hexacosyl nonanoate, hexacosyl heptacosanoate, monoglyceryl nonanoate Esters, glycerin octadecanoic acid monoester, glycerin heptacosanoic acid monoester, pentaerythrit nonanoic acid monoester, pentaerythrit heptacosanoic acid monoester, sorbit nonanoic acid monoester, sorbit heptacosanoic acid monoester, sucrose nonanoic acid monoester Esters, sucrose nonanoic acid triester, sucrose dodecanoic acid monoester, sucrose octadecanoic acid monoester, sucrose octadecanoic acid diester, sucrose octadecanoic acid triester, sucrose docosanoic acid monoester Ester, sucrose heptacosanoic acid monoester, sucrose heptacosanoic acid triester and beef tallow, and the like.

  Examples of the esterified product of a long-chain aliphatic alcohol having 8 to 26 carbon atoms and a carboxylic acid having 2 to 8 carbon atoms having at least one carboxyl group include octyl acetate, octyl octylate, hexacosyl acetate and hexacosyl octylate. It is done.

  Examples of the hydrophobic substance (C) having a phosphate ester bond include a dehydration condensate of a long chain aliphatic alcohol having 8 to 26 carbon atoms and phosphoric acid, and a salt thereof. For example, octyl phosphate ester, hexacosyl phosphate ester and the like can be mentioned, and examples of the salt include salts with Na and K. The phosphate ester includes a diester and a triester in addition to the monoester.

  Examples of the hydrophobic substance (C) having a sulfate ester bond include a dehydration condensate of a long chain aliphatic alcohol having 8 to 26 carbon atoms and sulfuric acid, and a salt thereof. Examples thereof include octyl sulfate and hexacosyl sulfate, and examples of the salt include salts with Na and K. In addition to monoesters, sulfates include diesters.

  Examples of the hydrophobic substance (C) having an amide bond include an amidated product of a long-chain aliphatic primary amine having 8 to 26 carbon atoms and a carboxylic acid having a hydrocarbon group having 1 to 26 carbon atoms, ammonia, or 1 to 1 carbon atoms. An amidated product of a primary amine of 7 and a long chain fatty acid having 8 to 26 carbon atoms, a long chain aliphatic secondary amine having 8 to 26 carbon atoms of at least one linear aliphatic hydrocarbon group and 1 to 1 carbon atoms Examples thereof include amidated products of 26 carboxylic acids and amidated products of secondary amines having 1 to 7 carbon atoms of at least one hydrocarbon group and long-chain fatty acids having 8 to 26 carbon atoms.

  As an amidation product of a long-chain aliphatic primary amine having 8 to 26 carbon atoms and a carboxylic acid having a hydrocarbon group having 1 to 26 carbon atoms, a product obtained by reacting a primary amine and a carboxylic acid 1: 1 is used. : Divided into those reacted in 2. Examples of the product reacted at 1: 1 include acetic acid N-octylamide, acetic acid N-hexacosylamide, heptacosanoic acid N-octylamide, heptacosanoic acid N-hexacosylamide, and the like. Examples of those reacted at 1: 2 include diacetate N-octylamide, diacetate N-hexacosylamide, diheptacosanoic acid N-octylamide, and diheptacosanoic acid N-hexacosylamide. In the case where the primary amine and the carboxylic acid are reacted at 1: 2, the carboxylic acid used may be the same or different.

  As an amidation product of ammonia or a primary amine having 1 to 7 carbon atoms and a long-chain fatty acid having 8 to 26 carbon atoms, ammonia or a reaction product of primary amine and carboxylic acid 1: 1 may be used at 1: 2. Divided into reacted products. The products reacted at 1: 1 include nonanoic acid amide, nonanoic acid methylamide, nonanoic acid N-heptylamide, heptacosanoic acid amide, heptacosanoic acid N-methylamide, heptacosanoic acid N-heptylamide and heptacosanoic acid N-hexacosylamide Etc. The reaction in 1: 2 was as follows: dinonanoic acid amide, dinonanoic acid N-methylamide, dinonanoic acid N-heptylamide, diheptacosanoic acid amide, diheptacosanoic acid N-methylamide, diheptacosanoic acid N-heptylamide and diheptacosanoic acid N-hexacosoxy And luamide. In the case where ammonia or a primary amine and a carboxylic acid are reacted at a ratio of 1: 2, the carboxylic acid used may be the same or different.

  Examples of the amidated product of a long-chain aliphatic secondary amine having 8 to 26 carbon atoms and a carboxylic acid having 1 to 26 carbon atoms include N-methyloctylamide acetate, N-methylhexacosylamide acetate, and N-octylhexate acetate. Cosylamide, acetic acid N-dihexacosylamide, heptacosanoic acid N-methyloctylamide, heptacosanoic acid N-methylhexacosylamide, heptacosanoic acid N-octylhexacosylamide and heptacosanoic acid N-dihexacosylamide Etc.

  Examples of amidated products of secondary amines having 1 to 7 carbon atoms and long chain fatty acids having 8 to 26 carbon atoms include nonanoic acid N-dimethylamide, nonanoic acid N-methylheptylamide, nonanoic acid N-diheptylamide, heptacosane Examples include acid N-dimethylamide, heptacosanoic acid N-methylheptylamide, and heptacosanoic acid N-diheptylamide.

  Examples of the hydrophobic substance (C) having a urethane bond include a reaction product of a long-chain aliphatic alcohol having 8 to 26 carbon atoms and a compound having at least one isocyanate group. Examples of the long chain aliphatic alcohol include octyl alcohol and hexacosyl alcohol, and examples of the compound having at least one isocyanate group include methyl isocyanate, hexacosyl isocyanate, methylene diisocyanate, and hexamethylene diisocyanate.

  Examples of the hydrophobic substance (C) having a urea bond include a reaction product of a primary or secondary amine having a hydrocarbon group having 8 to 26 carbon atoms and a compound having at least one isocyanate group. Examples of the primary amine include octylamine and hexacosylamine. Examples of secondary amines include methyl octyl amine, methyl hexacosyl amine, octyl hexacosyl amine, and dihexacosyl amine. Examples of the compound having at least one isocyanate group include methyl isocyanate, hexacosyl isocyanate, methylene diisocyanate and hexamethylene diisocyanate.

  Among these hydrophobic substances (C), from the viewpoint of the moisture resistance of the absorbent article, as a functional group capable of forming a hydrogen bond with a carboxyl group, a carboxyl group (including this salt), a phosphate group (this Salt), sulfo group (including this salt), primary amino group (including this salt), secondary amino group (including this salt), tertiary amino group (including this salt), hydroxyl group, ester bond , A compound having at least one selected from the group consisting of a phosphate ester bond, a sulfonate ester bond and an amide bond, more preferably a carboxyl group (including this salt), a primary amino group (including this salt) A compound having at least one selected from the group consisting of a secondary amino group (including this salt), a tertiary amino group (including this salt), a hydroxyl group, an ester bond and an amide bond.

The absorbent resin particles of the present invention can further contain an inorganic powder (D) on the surface of the absorbent resin particles. The inorganic powder (D) includes hydrophilic inorganic particles (d1) and hydrophobic inorganic particles (d2).
Examples of the hydrophilic inorganic particles (d1) include particles such as glass, silica gel, silica, and clay.
Examples of the hydrophobic inorganic particles (d2) include particles of carbon fiber, kaolin, talc, mica, bentonite, sericite, asbestos, shirasu, and the like.
Of these, hydrophilic inorganic particles (d1) are preferred, and silica is most preferred.

  The shape of the hydrophilic inorganic particles (d1) and the hydrophobic inorganic particles (d2) may be any of an irregular shape (crushed shape), a true spherical shape, a film shape, a rod shape, and a fibrous shape, but the irregular shape (crushed shape). Alternatively, a true spherical shape is preferable, and a true spherical shape is more preferable.

  The content (% by weight) of the inorganic powder (D) present on the surface of the absorbent resin particles is preferably 0.01 to 3.0, more preferably 0.8, based on the weight of the crosslinked polymer (A1). 05 to 1, then preferably 0.1 to 0.8, particularly preferably 0.2 to 0.7, most preferably 0.3 to 0.6. Within this range, the anti-fogging property of the absorbent article is further improved.

  The absorbent resin particles of the present invention may contain other additives (for example, known preservatives, fungicides, antibacterial agents, antioxidants, ultraviolet rays (for example, JP 2003-225565 A, JP 2006-131767 A). An absorbent, a colorant, a fragrance, a deodorant, an organic fibrous material, etc.}. When these additives are contained, the content (% by weight) of the additives is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably based on the weight of the crosslinked polymer (A1). Preferably it is 0.05 to 1, most preferably 0.1 to 0.5.

The absorbent resin particles of the present invention have a time (t1) until the swollen volume reaches 5 ml and a time (t2) until the swollen volume reaches 40 ml in the method for measuring the swollen volume with respect to physiological saline per 1 g of the absorbent resin particles. ) (T2 / t1) is preferably 5 to 20, more preferably 5 to 15, and most preferably 5 to 10. Further, (t1) is preferably 20 seconds to 50 seconds, more preferably 20 seconds to 45 seconds, and most preferably 30 seconds to 40 seconds. Further, (t2) is preferably 230 to 820 seconds.
Within this range, the anti-fogging property of the absorbent article is further improved. The content of polylactic acid (B), the volume average particle diameter of (B), the content of hydrophobic substance (C), the apparent density of absorbent resin particles, the weight average particle diameter of absorbent resin particles, etc. are described above and below. By adjusting to the preferable range, (t2 / t1) and (t1) in the swelling volume measuring method can be adjusted to the preferable range.
For example, in order to increase (t1), a method of increasing the volume average particle diameter of polylactic acid (B) can be mentioned. Further, for example, in order to increase (t2 / t1), a method of decreasing the volume average particle diameter of polylactic acid (B) or increasing the content of polylactic acid (B) can be mentioned.

The swelling volume measurement method is a measurement method performed using the apparatus shown in FIG. 1 in a room at 25 ± 2 ° C. and a humidity of 50 ± 10%. The temperature of the physiological saline used is 25 ° C. ± 2 ° C. The apparatus shown in FIG. 1 comprises an acrylic bottomed cylinder 1 and an acrylic disk 2. The bottomed cylinder 1 is a bottomed cylinder having a bottom at one opening of a cylinder having an inner diameter of 81 mm and a length of 35 mm, and the other one being open.
The acrylic disk 2 is a disk having an outer diameter of 80.5 mm and a thickness of 12 mm. The disk 2 has a circular recess having a diameter of 70.5 mm and a depth of 4 mm at a position where the center of the disk coincides with the center of the circle. In the disk 2, a circular cylinder having a length of 13 mm and an outer diameter of 15 mm as a handle is located at a position where the center of the disk 2 coincides with the center of the bottom surface of the cylinder.
Furthermore, the disk 2 is made up of 64 holes having a diameter of 2 mm that are radially formed (see FIG. 3). The hole of the disk 2 will be described. There are five holes each having a diameter of 2 mm at equal intervals of 5 mm between the position of 10 mm from the center of the disk and the position of 30 mm on the bisector of the disk (total of 40 holes). In addition, three holes with a diameter of 2 mm are present at equal intervals of 5 mm on a bisector inclined at 22.5 ° from the above-mentioned bisector, between 20 mm and 30 mm from the center of the disk. 24 in total).
The weight of the disk 2 is 60 g ± 5 g.

<Measurement method of swelling volume>
2.50 g of a measurement sample (moisture content of 8.0% or less) sieved to a particle diameter of 150 to 850 μm is weighed in a vertically standing cylinder (1), and the bottom of the bottomed cylinder 1 has a substantially uniform thickness. The disc 2 is placed so that the column handle is facing upward, and the distance from the bottom surface of the cylinder to the top surface of the disc handle is measured using a thickness meter (for example, Digimatic Indicator ID-F150 manufactured by Mitutoyo). taking measurement. At this time, it is the weight (140 g ± 10 g) of the measuring rod of the digimatic indicator, and the pressure applied to the absorbent resin particles is 3.9 ± 0.3 g / cm ² because two weights of the measuring rod and the disk are applied. Next, the display of the thickness of the Digimatch indicator is set to zero. Subsequently, 120 ml of physiological saline is introduced into the bottomed cylinder 1 within 2 seconds. The time for starting the charging is set to 0, and the distance H (cm) at which the disk 2 is intermittently raised is recorded. The absorption amount of the absorbent resin particles after the elapse of a predetermined time from the start of water absorption is determined by the following formula.

The same measurement is performed 5 times, and the average value is taken as the measured value. There is no particular limitation as long as the pressure applied to the absorbent resin particles when measuring the distance the disk 2 has moved up is 3.9 ± 0.3 g / cm ² .

  The absorbent resin particles obtained by the production method of the present invention are excellent in absorption performance. The water retention amount of the absorbent resin particles is preferably 20 to 50 g / g, more preferably 20 to 45 g / g, and still more preferably 20 to 40 g / g. 10-25 g / g is preferable, as for the absorbed amount under load which an absorptive resin particle shows, More preferably, it is 12-20 g / g, More preferably, it is 15-20 g / g.

The water retention amount and the absorption amount under load of the absorbent resin particles are measured as follows.
<Measurement method of water retention>
1.00 g of a measurement sample is put into a tea bag (20 cm long, 10 cm wide) made of a nylon net having a mesh size of 63 μm (JIS Z8801-1: 2006), and 1,000 ml of physiological saline (saline concentration 0.9% by weight). After soaking for 1 hour without stirring, hang for 15 minutes and drain. Thereafter, each tea bag is placed in a centrifuge, centrifuged at 150 G for 90 seconds to remove excess physiological saline, and the weight (h1) including the tea bag is measured to obtain the water retention amount from the following equation. In addition, the temperature of the physiological saline used and measurement atmosphere is 25 degreeC +/- 2 degreeC.

Water retention amount (g / g) = (h1)-(h2)

  (H2) is the weight of the tea bag measured by the same operation as described above when there is no measurement sample.

Further, the amount of absorption under load is measured as follows.
<Absorption under load>
0.16 g of a measurement sample sieved to a particle diameter of 250 to 500 μm in a cylindrical plastic tube (inner diameter: 25 mm, height: 34 mm) having a nylon mesh of 63 μm (JIS Z8801-1: 2006) pasted on the bottom. Were weighed and the cylindrical plastic tube was placed vertically so that the measurement sample had a substantially uniform thickness on the nylon mesh, and then a weight (weight: 310.6 g, outer diameter: 24. 5mm,). After measuring the weight (M1) of the entire cylindrical plastic tube, a cylindrical type containing a measurement sample and a weight in a petri dish (diameter: 12 cm) containing 60 ml of physiological saline (salt concentration: 0.9% by weight). Stand the plastic tube vertically and immerse it with the nylon mesh side down, and let stand for 60 minutes. After 60 minutes, pull up the cylindrical plastic tube from the petri dish, tilt it diagonally, remove the dripping water drops, weigh the entire cylindrical plastic tube containing the measurement sample and weight (M2), and Obtain the amount absorbed under load. In addition, the temperature of the physiological saline used and measurement atmosphere is 25 degreeC +/- 2 degreeC.

Absorption under load (g / g) = {(M2)-(M1)} / 0.16

  100-800 are preferable, as for the weight average particle diameter (micrometer) of the absorptive resin particle | grains of this invention, More preferably, it is 200-500, Most preferably, it is 300-400. Within this range, the absorption performance is further improved.

  The smaller the content of fine particles, the better the absorption performance. Therefore, the content of fine particles of 106 μm or less (preferably 150 μm or less) in all particles is preferably 3% by weight or less, more preferably 1% by weight or less. .

In addition, the weight average particle size is obtained by measuring the particle size distribution of the measurement sample, and the logarithmic probability paper {horizontal axis: particle size, vertical axis: cumulative content (% by weight)} has a relationship between the cumulative content and the particle size. It is obtained by plotting and determining the particle size corresponding to a cumulative content of 50% by weight. The particle size distribution is measured in accordance with JIS Z8815-1994. For example, sieves having an inner diameter of 150 mm and a depth of 45 mm {openings: 710 μm, 500 μm, 300 μm, 150 μm, and 106 μm} are used with a narrow opening sieve. Overlay, put 50 g of measurement sample on top of 710 μm sieve with widest opening, sieve for 10 minutes with sieve shaker, measure weight of measurement sample remaining on each sieve, It is measured by determining the weight percent of the measurement sample remaining on each sieve based on the weight of the measurement sample.
The content of the fine particles can be determined using a plot created when determining the weight average particle diameter.

  The apparent density (g / ml) of the absorbent resin particles of the present invention is preferably from 0.54 to 0.70, more preferably from 0.56 to 0.65, particularly preferably from the viewpoint of anti-fogging properties of the absorbent article. Is 0.58 to 0.60.

  The shape of the absorbent resin particle of the present invention is not particularly limited, and examples thereof include an irregular crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, when applied to a paper diaper or the like, from the viewpoint of good entanglement with the fibrous material, no fear of dropping off from the fibrous material, and from the viewpoint of absorption performance, an irregularly crushed shape and a pearl shape are preferable.

The absorbent resin particles of the present invention can be preferably produced by the following production method of the present invention.
Copolymerization of water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and monomer having cross-linking agent (a3) as essential constituent monomer (a) in the method for producing absorbent resin particles To obtain a crosslinked polymer (A1), and then (A1) and polylactic acid (B) are mixed to obtain a crosslinked polymer (A1) / polylactic acid composite gel (1); or water-soluble vinyl After mixing the monomer (a1) and / or the monomer having the hydrolyzable vinyl monomer (a2) and the crosslinking agent (a3) as the essential constituent monomer (a) with the polylactic acid (B), a single amount Polymerizing the body to obtain a crosslinked polymer (A1) / polylactic acid composite gel (2),
(B) has a weight average molecular weight of 5,000 to 200,000,
The amount of (B) used is 5 to 30% by weight based on the weight of the crosslinked polymer (A1),
The manufacturing method of the absorbent resin particle which contains 0.1 to 15.0 weight% of (B) in the inside of an absorbent resin particle based on the weight of a crosslinked polymer (A1).

<About step (1)>
As a method of mixing the crosslinked polymer (A1) and the polylactic acid (B), (1) a method of mixing the crosslinked polymer (A1), a water-containing gel composed of water, and the polylactic acid (B); (2 ) A method of mixing the crosslinked polymer (A1) (dry particles), water, and polylactic acid (B) is included. Among these, the method (1) is preferable from the viewpoint of absorption performance and the like.

  The mixing temperature (° C.) of the crosslinked polymer (A1) and the polylactic acid (B) is preferably 30 to 150, more preferably 40 to 120, and particularly preferably 50 to 100. Within this range, it becomes easier to mix evenly, and the absorption performance is further improved.

  As a mixing device of the crosslinked polymer (A1) and the polylactic acid (B), a known device {double-arm kneader, internal mixer (Banbury mixer), self-cleaning mixer, gear compounder, screw-type extruder, Screw type kneader, minced machine, turbulizer, cylindrical mixer, V-shaped mixer, ribbon type mixer, screw type mixer, double arm type mixer, pulverizing type kneader, groove type mixer, vertical type mixer Can be used. These can be used in combination.

<About step (2)>
Mixing the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the monomer having the crosslinking agent (a3) as an essential constituent monomer (a) with polylactic acid (B) The method is not limited as long as it can be uniformly mixed, and can be carried out by a known method.

  As a mixing device of monomer and polylactic acid (B), known devices {double-arm kneader, internal mixer (Banbury mixer), self-cleaning mixer, gear compounder, screw extruder, screw kneader , Mincing machines, turbulizers, cylindrical mixers, V-shaped mixers, ribbon-type mixers, screw-type mixers, double-armed mixers, pulverizing kneaders, groove-type mixers, vertical mixers, etc.} Etc. can be used. A plurality of these may be combined.

  As a method for copolymerizing a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a monomer having a crosslinking agent (a3) as an essential constituent monomer (a), a known aqueous solution is used. Polymerization {adiabatic polymerization, thin film polymerization, spray polymerization, etc .; JP-A-55-133413, etc.} and known reverse phase suspension polymerization (JP-B-54-30710, JP-A-56-26909, and JP-A-1) −5808 etc.}.

  In the step (1) or (2), the volume average particle diameter of the polylactic acid (B) before mixing is preferably in the same range as the volume average particle diameter described above, and the polylactic acid (B before mixing) Similarly, the above-mentioned property is preferable.

The crosslinked polymer (A1) / polylactic acid composite gel obtained in the step (1) or (2) can be led to the absorbent resin particles by post-treatment.
Post-processing includes shredding, solvent evaporation (drying), pulverization, particle size adjustment, surface crosslinking, and mixing of additives. These post-processing may be performed in combination, or only one of them may be performed. Moreover, there is no restriction | limiting in the order of post-processing, Although it determines suitably, said order is preferable. Of these post-treatments, it is preferable to include drying. Moreover, when employ | adopting aqueous solution polymerization, it is preferable that a grinding | pulverization is included further.

<Shred>
Shredding can be performed by a known method, and can be shredded using a known shredding device {for example, a bex mill, rubber chopper, pharma mill, mincing machine, impact crusher and roll crusher}. .

  When shredding, the size (longest diameter) of the composite gel after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and particularly preferably 1 mm to 1 cm. Within this range, in addition to being easier to handle, when the solvent is subsequently distilled off, the solvent is further easily distilled off, and when pulverizing thereafter, the pulverization is further facilitated.

<Solvent evaporation (drying)>
In the copolymerization in the step (1) or (2), when a solvent (such as an organic solvent and water) is used, the solvent is preferably distilled off.
When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after distillation is preferably 10 to 0.01, more preferably 5 to 0.05, based on the weight of the absorbent resin particles. Particularly preferred is 3 to 0.1, and most preferred is 1 to 0.5. Within this range, the absorption performance is further improved.

  When water is contained in the solvent, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 0 to 10, particularly preferably 0 to 7, most preferably based on the weight of the absorbent resin particles. Is 0-3. Within this range, the absorption performance and handling properties after drying (powder fluidity of the absorbent resin particles, etc.) are further improved.

  In addition, the content and moisture of the organic solvent are an infrared moisture measuring device {JE400 manufactured by Kett Science Laboratory Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specification 100V, It is calculated | required from the weight loss of the measurement sample before and behind heating when heated by 40W}.

As a method of distilling off the solvent (including water), a method of distilling (drying) with hot air at a temperature of 80 to 230 ° C., a thin film drying method using a drum dryer heated to 100 to 230 ° C., (heating ) Vacuum drying, freeze drying, infrared drying, etc. can be applied.
Prior to distilling off the solvent, the solvent can be removed by decantation, filtration or the like.

<Crushing>
The pulverization is preferably performed after the solvent is distilled off.
The pulverization method is not particularly limited, and can be pulverized by a known pulverizer (for example, a hammer-type pulverizer, an impact-type pulverizer, a roll-type pulverizer, and a shet airflow-type pulverizer).

<Granularity control>
The size of the pulverized particles is adjusted by sieving or the like as necessary.

<Surface cross-linking>
The cut chopped gel or the pulverized particles can be subjected to surface cross-linking treatment with a surface cross-linking agent, if necessary.
As the surface crosslinking agent, known {for example, JP 59-189103, JP 58-180233, JP 61-16903, JP 61-2111305, JP 61-252212, Surface cross-linking agents {polyvalent glycidyl, polyhydric alcohol, polyvalent amine, polyvalent aziridine, polyvalent isocyanate, silane coupling agent and polyvalent metal of JP-A-51-136588 and JP-A-61-257235} Etc.} can be used. Of these surface cross-linking agents, from the viewpoint of economy and absorption performance, polyvalent glycidyl, polyhydric alcohol and polyvalent amine are preferable, more preferably polyvalent glycidyl and polyhydric alcohol, particularly preferably polyvalent glycidyl, Preferred is ethylene glycol diglycidyl ether.

  In the case of surface cross-linking, the amount (% by weight) of the surface cross-linking agent is not particularly limited because it can be changed variously depending on the type of surface cross-linking agent, cross-linking conditions, target performance, etc. From a viewpoint etc., based on the weight of an essential constituent monomer (a), 0.001-3 are preferable, More preferably, it is 0.005-2, Most preferably, it is 0.01-1.

  In the case of surface crosslinking, a known method {for example, Japanese Patent No. 3648553, Japanese Patent Laid-Open No. 2003-165883, Japanese Patent Laid-Open No. 2005-75982, Japanese Patent Laid-Open No. 2005-95759} can be applied.

<Mixing of additives>
The above-mentioned other additives can be mixed with the chopped gel, dry particles, pulverized particles, surface cross-linked particles, and the like.
When other additives are mixed, the mixing method is not limited as long as uniform mixing is possible, and a known mixing method can be applied.

  The absorbent resin particles of the present invention can be used as an absorbent body together with a fibrous material. The structure and manufacturing method of the absorber are the same as those known in the art (Japanese Patent Laid-Open Nos. 2003-225565, 2006-131767, and 2005-097569, etc.). Moreover, it is preferable that this absorber comprises absorbent articles {paper diapers, sanitary napkins, etc.}. The manufacturing method and the like of the absorbent article are the same as known ones (Japanese Unexamined Patent Publication Nos. 2003-225565, 2006-131767, and 2005-097569, etc.).

  When the absorbent resin particle of the present invention is used as an absorbent body together with a fibrous material, the weight ratio of the absorbent resin particle to the fiber (weight of absorbent resin particle / weight of fiber) is preferably 40/60 to 70/30, More preferably, it is 50 / 50-60 / 40.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Unless otherwise specified, “part” means “part by weight” and “%” means “% by weight”. The water retention amount and the absorption amount under load were measured by the methods described above.

<Production Example 1>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 108.5 parts (1.51 mol parts), cross-linking agent (a3-1) {pentaerythritol triallyl ether, diiso -Made by Co., Ltd.} 0.35 parts (0.0014 mol parts) and 389.9 parts deionized water were kept at 3 ° C. with stirring and mixing. Nitrogen was introduced into the mixture to bring the dissolved oxygen amount to 1 ppm or less, and then 0.43 part of 1% aqueous hydrogen peroxide solution and 0.81 part of 2% ascorbic acid aqueous solution were added and mixed to initiate polymerization. . After the temperature of the mixture reached 60 ° C., polymerization was performed at 60 ± 2 ° C. for about 8 hours to obtain a crosslinked polymer hydrogel (A1-1).

<Production Example 2>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 131.5 parts (1.83 mol parts), crosslinking agent (a3-1) {pentaerythritol triallyl ether, diiso -Made by Co., Ltd.} 0.43 parts (0.0017 mole part) and 366.5 parts deionized water were kept at 3 ° C. with stirring and mixing. Nitrogen was introduced into the mixture to bring the dissolved oxygen amount to 1 ppm or less, and then 0.53 parts of 1% aqueous hydrogen peroxide solution and 0.99 parts of 2% aqueous ascorbic acid solution were added and mixed to initiate polymerization. . After the temperature of the mixture reached 70 ° C., polymerization was performed at 70 ± 2 ° C. for about 8 hours to obtain a crosslinked polymer hydrogel (A1-2).

<Production Example 3>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 62.00 parts (0.86 mole parts), cross-linking agent (a3-1) {pentaerythritol triallyl ether, diiso -Made by Co., Ltd.} 0.20 part (0.0008 mol part) and 437.0 parts deionized water were kept at 3 ° C. with stirring and mixing. Nitrogen was introduced into the mixture to bring the dissolved oxygen amount to 1 ppm or less, and then 0.25 part of a 1% aqueous hydrogen peroxide solution and 0.47 part of a 2% aqueous ascorbic acid solution were added and mixed to initiate polymerization. . After the temperature of the mixture reached 35 ° C., polymerization was performed at 35 ± 2 ° C. for about 8 hours to obtain a crosslinked polymer hydrogel (A1-3).

<Production Example 4>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 77.45 parts (1.08 mol part), cross-linking agent (a3-1) {pentaerythritol triallyl ether, diiso -KK made} 0.25 part (0.0010 mol part) and 421.3 parts deionized water were kept at 3 ° C. with stirring and mixing. Nitrogen was introduced into the mixture to reduce the dissolved oxygen amount to 1 ppm or less, and then 0.31 part of 1% aqueous hydrogen peroxide solution and 0.58 part of 2% ascorbic acid aqueous solution were added and mixed to initiate polymerization. . After the temperature of the mixture reached 40 ° C., polymerization was performed at 40 ± 2 ° C. for about 8 hours to obtain a crosslinked polymer hydrogel (A1-4).

<Example 1>
While chopping 400 parts of the crosslinked polymer hydrogel (A1-1) obtained in Production Example 1 with a mincing machine (12VR-400K manufactured by ROYAL), add 99.2 parts of 35% aqueous sodium hydroxide and mix. Neutralization followed by polylactic acid (B1) {polylactic acid emulsion obtained by high-pressure emulsification using an activator (weight average molecular weight 50,000, volume average particle diameter 1.0 μm, effective content 40%)} 39. 7 parts were added and mixed to obtain a chopped gel. Further, the chopped gel was dried with a ventilation band dryer {90 ° C., wind speed 2 m / sec} to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster), and then sieved to adjust the particle size to a particle size range of 710 to 150 μm to obtain pulverized particles. Subsequently, 100 parts of the pulverized particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm), and a surface cross-linking agent {water / methanol mixture containing ethylene glycol diglycidyl ether at a concentration of 9% was added thereto. Solution (water / methanol = 70/30; weight ratio)} 5.5 parts was added, mixed uniformly, and then allowed to stand at 90 ° C. for 45 minutes to obtain absorbent resin particles (1) of the present invention. .

<Example 2>
“Polylactic acid (B1) 39.8 parts” is replaced with “polylactic acid (B2) {polylactic acid emulsion obtained by high-pressure emulsification using an activator (weight average molecular weight 5,000, volume average particle size 0.5 μm, effective Min. 35%)} 45.4 parts ”, except that the absorbent resin particles (2) of the present invention were obtained in the same manner as in Example 1.

<Example 3>
“Polylactic acid (B1) 39.7 parts” is replaced with “polylactic acid (B3) {polylactic acid emulsion obtained by high-pressure emulsification using an activator (weight average molecular weight 200,000, volume average particle diameter 100 μm, effective fraction 20). %)} 79.4 parts ”In the same manner as in Example 1, the absorbent resin particles (3) of the present invention were obtained.

<Example 4>
“400 parts of the crosslinked polymer hydrogel (A1-1) obtained in Production Example 1” was changed to “400 parts of the crosslinked polymer hydrogel (A1-2) obtained in Production Example 2”, “35% water “99.2 parts of aqueous sodium oxide solution” was changed to “120.2 parts of 35% aqueous sodium hydroxide solution”, and “39.7 parts of polylactic acid (B1)” was changed to “16.0 parts of polylactic acid (B1)”. Except having changed, it carried out similarly to Example 1, and obtained the absorbent resin particle (4) of this invention.

<Example 5>
“400 parts of the crosslinked polymer hydrogel (A1-1) obtained in Production Example 1” was changed to “400 parts of the crosslinked polymer hydrogel (A1-3) obtained in Production Example 3”, “35% water “99.2 parts of sodium oxide aqueous solution” was changed to “56.7 parts of 35% aqueous sodium hydroxide solution” and “39.7 parts of polylactic acid (B1)” was changed to “45.4 parts of polylactic acid (B1)”. Except having changed, it carried out similarly to Example 1, and obtained the absorbent resin particle (5) of this invention.

<Example 6>
“400 parts of the crosslinked polymer hydrogel (A1-1) obtained in Production Example 1” was changed to “400 parts of the crosslinked polymer hydrogel (A1-4) obtained in Production Example 4”, “35% water “99.2 parts of sodium oxide aqueous solution” was changed to “70.9 parts of 35% aqueous sodium hydroxide solution”, “39.7 parts of“ polylactic acid (B1) ”was changed to“ polylactic acid (B4) {using activator The polylactic acid emulsion obtained by high-pressure emulsification (weight average molecular weight 6,000, volume average particle diameter 50 μm, effective content 38%)} 10.0 parts ” Absorbent resin particles (6) were obtained.

<Example 7>
“400 parts of the crosslinked polymer hydrogel (A1-1) obtained in Production Example 1” was changed to “400 parts of the crosslinked polymer hydrogel (A1-4) obtained in Production Example 4”, “35% water “99.2 parts of sodium oxide aqueous solution” was changed to “70.9 parts of 35% aqueous sodium hydroxide solution”, and “39.7 parts of polylactic acid (B1)” was changed to “37.8 parts of polylactic acid (B1)”. Except having changed, it carried out similarly to Example 1, and obtained the absorbent resin particle (7) of this invention.

<Example 8>
“400 parts of the crosslinked polymer hydrogel (A1-1) obtained in Production Example 1” was changed to “400 parts of the crosslinked polymer hydrogel (A1-2) obtained in Production Example 2”, “35% water “99.2 parts of sodium oxide aqueous solution” was changed to “120.2 parts of 35% aqueous sodium hydroxide solution”, “39.7 parts of“ polylactic acid (B1) ”was changed to“ 32.1 parts of polylactic acid (B3) ” Except having changed, it carried out similarly to Example 1, and obtained the absorbent resin particle (8) of this invention.

<Example 9>
"39.7 parts of polylactic acid (B1)" is replaced with "polylactic acid (B5) {polylactic acid powder obtained by wet pulverization using a plasticizer (weight average molecular weight 50,000, volume average particle diameter 240 µm)} 10. Absorbent resin particles (9) of the present invention were obtained in the same manner as in Example 1 except that the amount was changed to “6 parts”.

<Example 10>
While chopping 400 parts of the crosslinked polymer hydrogel (A1-1) obtained in Production Example 1 with a mincing machine (12VR-400K manufactured by ROYAL), add 99.2 parts of 35% aqueous sodium hydroxide and mix. -Neutralized and subsequently 39.7 parts of polylactic acid (B1) and 1.06 part of hydrophobic substance (C-1) {sucrose stearate monoester} were added and mixed to obtain a chopped gel. Further, the chopped gel was dried with a ventilation band dryer {90 ° C., wind speed 2 m / sec} to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster), and then sieved to adjust the particle size to a particle size range of 710 to 150 μm to obtain pulverized particles. Subsequently, 100 parts of the pulverized particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm), and a surface cross-linking agent {water / methanol mixture containing ethylene glycol diglycidyl ether at a concentration of 9% was added thereto. Solution (water / methanol = 70/30; weight ratio)} 5.5 parts was added, mixed uniformly, and then allowed to stand at 90 ° C. for 45 minutes to obtain absorbent resin particles (10) of the present invention. .

<Examples 11 to 37>
Absorbent resin particles (11) to (37) of the present invention were obtained in the same manner as in Example 10 except that the hydrophobic substance (C) and the charged amount described in Table 1 were used.

<Example 38>
Water-soluble vinyl monomer (a1-1) {acrylic acid} 21.7 parts (0.30 mol part), water-soluble vinyl monomer (a1-2) {sodium acrylate} 72.9 parts (0.78 mol part) While stirring and mixing 0.17 part (0.00097 mol part) of the crosslinking agent (a3-2) {ethylene glycol diglycidyl ether}, 35.6 parts of polylactic acid (B1) and 492.2 parts of deionized water. Maintained at 3 ° C. Nitrogen gas is allowed to flow into this mixture so that the amount of dissolved oxygen in the mixture is 1 ppm or less, and then 0.31 part of 1% aqueous hydrogen peroxide solution and 0.58 part of 2% aqueous ascorbic acid solution are added and mixed. Polymerization was started. After the temperature of the mixture reached 40 ° C., polymerization was performed at 40 ± 2 ° C. for about 8 hours to obtain a crosslinked polymer hydrogel (A1-5).

  400 parts of the obtained crosslinked polymer hydrogel (A1-5) was chopped with a mincing machine (12VR-400K manufactured by ROYAL) to obtain a chopped gel. Further, the chopped gel was dried with a ventilation band dryer {90 ° C., wind speed 2 m / sec} to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster), and then sieved to adjust the particle size to a particle size range of 710 to 150 μm to obtain pulverized particles. Subsequently, 100 parts of the pulverized particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd .: rotation speed: 2000 rpm). 3.0 parts of a solution (water / methanol = 70/30; weight ratio)} was added, mixed uniformly, and then allowed to stand at 90 ° C. for 45 minutes to obtain absorbent resin particles (38) of the present invention. .

  Table 2 shows the internal content and surface content of the polylactic acid (B) and the internal content and surface content of the hydrophobic substance (C) in the absorbent resin particles (1 to 38) obtained in Examples 1 to 38. Shown in In Table 2,% indicates the content (% by weight) based on the weight of the crosslinked polymer (A1).

<Comparative Example 1>
4000 parts of a 5% aqueous solution of carboxymethyl cellulose (Aldrich, substitution degree 0.7) and 1000 parts of a 5% aqueous solution of polyvinyl alcohol (Wako Pure Chemical Industries, Ltd., weight average molecular weight 44000, saponification degree 88 mol%) Was stirred and mixed at 80 ° C. for 5 hours to obtain a mixed aqueous solution. Next, 50 parts of 40% glyoxal aqueous solution and 2.5 parts of concentrated sulfuric acid were added to this mixed aqueous solution, stirred uniformly, and then allowed to stand in a hot air dryer at 100 ° C. for 7 hours to dry the crosslinking reaction. As a result, a dried product was obtained. The dried product was pulverized with a juicer mixer (Osterizer BLENDER, manufactured by Oster Co., Ltd.) and then sieved with a sieve having openings of 710 μm and 150 μm to obtain comparative absorbent resin particles (H1).

<Comparative example 2>
While 100 parts of the absorbent resin particles (H1) obtained in Comparative Example 1 were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd .: rotation speed: 2000 rpm), the surface crosslinking agent {ethylene glycol diglycidyl ether was added at a concentration. Water / methanol mixed solution containing 9% (water / methanol = 70/30; weight ratio)} 5.0 parts was added, mixed uniformly, and then allowed to stand at 90 ° C. for 45 minutes for absorption for comparison. Resin particles (H2) were obtained.

<Comparative Example 3>
Absorbent resin particles (H3) for comparison were obtained in the same manner as in Comparative Example 1 except that the standing time in the hot air dryer was changed from “7 hours” to “10 hours”.

  About the absorptive resin particles obtained in Examples 1 to 38 and Comparative Examples 1 to 3, the apparent density, the weight average particle diameter, the water retention amount, the absorption amount under load, and the swelling volume measurement method are evaluated, and the results are shown. It was shown in 3.

  As can be seen from Table 3, the absorbent resin particles (Examples 1 to 38) of the present invention are significantly superior in water retention and absorption under load compared to the absorbent resin particles of Comparative Examples 1 to 3, and an absorption rate pattern. Is appropriate.

  Subsequently, when the absorption rate pattern was appropriate, it was evaluated what absorption characteristics were exhibited when applied to an absorbent article. Using the absorbent resin particles obtained in Examples 1 to 21 and Comparative Examples 1 to 3, absorbent articles (paper diapers 1 to 38) were prepared as follows, and the surface dryness value by the SDME method was evaluated. The results are shown in Table 4.

<Preparation of absorbent articles (paper diapers)>
100 parts of fluff pulp and 100 parts of an evaluation sample {absorbent resin particles} were mixed with an airflow type mixing apparatus {Pad former manufactured by Autech Co., Ltd.} to obtain a mixture. laminated on m ² and so as to uniformly acrylic plate (thickness 4 mm), and pressed for 30 seconds at a pressure of 5 kg / cm ^2, to obtain absorbent body (1). This absorbent body (1) is cut into a 10 cm × 40 cm rectangle, and water absorbent paper (basis weight 15.5 g / m ² , manufactured by Advantech, filter paper No. 2) having the same size as the absorbent body is arranged above and below each. Further, a paper diaper (1) was prepared by disposing a polyethylene sheet (polyethylene film UB-1 manufactured by Tamapoly Co., Ltd.) on the back surface and a non-woven fabric (basis weight 20 g / m ² , Eltas Guard manufactured by Asahi Kasei Co., Ltd.) on the surface. The weight ratio of the absorbent resin particles to the fibers (weight of the absorbent resin particles / weight of the fibers) was 50/50.

<Surface dryness value by SDME method>
A disposable diaper {artificial urine (0.03% by weight of potassium chloride, 0.08% by weight of magnesium sulfate, 0.88% by weight of sodium sulfate, 0.8% by weight of sodium chloride) in which the detector of the SDME (Surface Dryness Measurement Equipment) tester (manufactured by WK system) % And deionized water 99.09% by weight) and a paper diaper was soaked for 60 minutes. }, A 0% dryness value was set, and then the detector of the SDME tester was prepared by drying a paper diaper {paper diaper at 80 ° C. for 2 hours by heating. } Was set to 100% dryness, and the SDME tester was calibrated. Next, set a metal ring (inner diameter 70 mm, length 50 mm) in the center of the paper diaper to be measured, inject 80 ml of artificial urine, and absorb the artificial urine {until no gloss can be confirmed by artificial urine}, immediately Remove the metal ring, place three SDME detectors on the center of the paper diaper and its left and right sides (three locations at equal intervals of 10 cm from the end of the 40 cm paper diaper), and start measuring the surface dryness value, 5 minutes after the start of the measurement Were the surface dryness value (1-1) {center}, the surface dryness value (1-2) {left}, and the surface dryness value (1-3) {right}, respectively.
The artificial urine, measurement atmosphere, and standing atmosphere were 25 ± 5 ° C. and 65 ± 10% RH.

  As can be seen from Table 4, the absorbent article using the absorbent resin particles of the present invention has a surface dryness value (1-1), (1- 2) and (1-3) were excellent with no bias. That is, the absorbent resin particles of the present invention have excellent absorption characteristics when applied to absorbent articles. Therefore, it is easily predicted that the absorbent article to which the absorbent resin particles of the present invention are applied has little environmental load and there is no fear of leakage or fog.

  The absorbent resin particles of the present invention can be applied to an absorbent body containing absorbent resin particles and a fibrous material, and absorbent articles {paper diapers, sanitary napkins, and medical blood retaining bodies comprising the absorbent body. It is useful for the agent}. In addition, pet urine absorbent, urine gelling agent for portable toilets, freshness preservation agent for fruits and vegetables, drip absorbent for meat and seafood, cooler, disposable warmer, battery gelling agent, water retention agent for plants and soil, dew condensation It can also be used in various applications such as inhibitors, water-stopping agents, packing agents and artificial snow.

1 Cylinder with bottom plate 2 Disc with handle 3 Absorbent resin particle 4 Digimatic indicator thickness display 5 Digimatic indicator thickness measurement bar 6 Digimatic indicator base

Claims (11)

Absorbent resin comprising a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2), and a crosslinked polymer (A1) having a crosslinking agent (a3) as essential constituent units and polylactic acid (B) Particles having a weight average molecular weight of 5000 to 200000, containing 5 to 30% by weight of (B) based on the weight of (A1), and containing (B) in the absorbent resin particles (A1 Absorbent resin particles containing 0.1 to 25% by weight based on the weight of The absorbent resin particle according to claim 1, wherein polylactic acid (B) is present on the surface of the absorbent resin particle. The absorbent resin particles according to claim 1 or 2, further comprising a hydrophobic substance (C). The absorbent resin particle according to claim 3, wherein the content of the hydrophobic substance (C) present inside the absorbent resin particle is 0.01 to 10% by weight based on the weight of the crosslinked polymer (A1). . The absorptivity according to claim 3 or 4, wherein the content of the hydrophobic substance (C) present on the surface of the absorbent resin particles is 0.001 to 1% by weight based on the weight of the crosslinked polymer (A1). Resin particles. The absorbent resin particle according to any one of claims 1 to 5, wherein the inorganic powder (D) is present on the surface of the absorbent resin particle in an amount of 0.01 to 3% by weight based on the weight of the crosslinked polymer (A1). In the swelling volume measurement method for physiological saline per gram of absorbent resin particles, the ratio (t2 / t1) between the time (t1) until the swelling volume reaches 5 ml and the time (t2) until the swelling volume reaches 40 ml is It is 5-20, The absorptive resin particle in any one of Claims 1-6. In the swelling volume measurement method for physiological saline per 1 g of absorbent resin particles, the time (t1) until the swelling volume reaches 5 ml is 20 to 50 seconds, and the time (t2) until the swelling volume reaches 40 ml is 230 to 820. The absorbent resin particle according to claim 1, which is a second. Copolymerization of water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and monomer having cross-linking agent (a3) as essential constituent monomer (a) in the method for producing absorbent resin particles To obtain a crosslinked polymer (A1), and then (A1) and polylactic acid (B) are mixed to obtain a crosslinked polymer (A1) / polylactic acid composite gel (1); or water-soluble vinyl After mixing the monomer (a1) and / or the monomer having the hydrolyzable vinyl monomer (a2) and the crosslinking agent (a3) as the essential constituent monomer (a) with the polylactic acid (B), a single amount Polymerizing the body to obtain a crosslinked polymer (A1) / polylactic acid composite gel (2),
(B) has a weight average molecular weight of 5,000 to 200,000,
The amount of (B) used is 5 to 30% by weight based on the weight of the crosslinked polymer (A1),
The manufacturing method of the absorbent resin particle which contains 0.1 to 25weight% of (B) in the inside of an absorbent resin particle based on the weight of a crosslinked polymer (A1). The production method according to claim 9, wherein the volume average particle diameter of the polylactic acid (B) before mixing is 0.5 to 100 µm. The production method according to claim 9 or 10, wherein the polylactic acid (B) before mixing is in an emulsion state.

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