JP2011252088A - Absorbing resin particle, absorbing material containing the same, and absorbing article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide absorbing resin particles having a specific absorbing speed pattern, and to provide an absorbing article in which the absorbing resin particles are used, and thereby, which does not cause conventional problems of rash or the like.SOLUTION: The absorbing resin particles contain: a crosslinked polymer (A1) containing, as essential constituent units, a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2), and a crosslinking agent (b); and a hydrophobic substance (C). The (C) is a compound having at least one monovalent 8-26C aliphatic hydrocarbon group and at least one functional group capable of forming hydrogen bond with carboxylic group. The (C) exists inside the absorbing resin particle in an amount of 0.01-10.0 wt.%, and exists in the surface of the absorbing resin particle in an amount of 0.001-1.0 wt.%, each on the basis of the weight of the (A1).

Description

  The present invention relates to absorbent resin particles, an absorbent body containing the same, and an absorbent article.

As an absorbent resin particle having an excellent absorption rate, an absorbent resin particle having a structure containing a part or all of a hydrophobic substance inside a crosslinked polymer is known (Patent Document 1).
Further, there is known an absorbent resin particle having improved powder flowability by adhering a hydrophobic substance to the surface of a crosslinked polymer (Patent Document 2).

However, with conventional absorbent resin particles and water-absorbing agents, the absorption rate over time after contact with the liquid to be absorbed (hereinafter referred to as an absorption rate pattern) is not appropriate. Specifically, the conventional absorbent resin particles have an absorption rate pattern of (i) early early, medium normal, late normal, (ii) early late, medium normal, late normal (the above-mentioned water absorption of Patent Document 2). Resin particles).
When these absorbent resin particles are applied to an absorbent article (such as a paper diaper), the absorbent article used in the absorbent article is biased in the absorption rate of the absorbent resin depending on the site of the absorbent article. It cannot be used effectively, and a problem such as blurring is likely to occur at the portion where the liquid to be absorbed remains, or the time during which the liquid that has not been absorbed in the entire absorber remains is increased.
Specifically, when the absorbent resin particle (i) is used, the liquid is rapidly absorbed after contact with the absorbent resin particle at the site where the liquid to be absorbed comes into contact. The resin particles swell and become gelled, preventing the liquid that is not absorbed from diffusing and absorbing in the absorber, and as a result, the area where the absorbed liquid is in contact has a high absorption rate of the absorbent resin particles, and the other areas are Absorption rate deviation that the absorption rate of the absorbent resin particles is low occurs. And the time for which the liquid which was not absorbed stays in the site | part which the absorbed liquid contacted becomes long.
On the other hand, when the absorbent resin particles of (ii) are used, the liquid is only gradually absorbed after contact with the absorbent resin particles at the site where the liquid to be absorbed comes into contact, and the liquid that is not absorbed in the absorbent article. As a result, the absorptivity of the absorbent resin particles tends to be equal at the site where the absorbed liquid is in contact with the other site. However, the absorption speed is generally slow, and the time during which the liquid that has not been absorbed in the entire absorber stays is increased.
And in the site | part where the liquid which was not absorbed stays long, there exists a problem that the wearer's skin which contacts the site | part tends to produce problems, such as a blur.

JP 2005-097569 A Japanese Patent Laid-Open No. 2004-261796

Absorbent articles using conventional water-absorbent resin particles (paper diapers, etc.) could not absorb the liquid completely, and the liquid that could not be absorbed would touch the wearer's skin and cause problems such as fogging. . And the absorbent article which does not have such problems, such as a fog, and the absorbent resin particle which can be used for this were strongly desired.
An object of the present invention is to provide an absorbent resin particle having a specific absorption rate pattern, that is, it is possible to provide an absorbent resin particle having an initial absorption rate pattern that is slow in the initial stage, normal in the middle period, and early in the latter period. An object of the present invention is to provide an absorbent article that does not cause problems such as fogging as described above.

The inventors of the present invention have reached the present invention as a result of intensive studies to achieve the above object.
That is, the absorbent resin particle of the present invention is hydrophobic with the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the crosslinked polymer (A1) having the crosslinking agent (b) as essential constituent units. Absorbent resin particles comprising a substance (C), wherein (C) has at least one monovalent aliphatic hydrocarbon group having 8 to 26 carbon atoms, and has a carboxyl group and a hydrogen bond. It is a compound having at least one functional group that can be formed, and (C) is present in the interior of the absorbent resin particles in an amount of 0.01 to 10.0% by weight based on the weight of (A1). The gist is that it is present at 0.001 to 1.0% by weight on the surface.

  The gist of the absorbent body of the present invention is that it comprises the above-described absorbent resin particles and a fibrous material.

  The gist of the absorbent article of the present invention is that the absorbent article is provided.

Absorbent resin particles of the present invention. The absorption rate pattern has a specific absorption rate pattern such that the initial phase is slow, the middle period is normal, and the late period is early.
Therefore, when the absorbent resin particles of the present invention are applied to absorbent articles (paper diapers, sanitary napkins, etc.), there is no bias in the absorption rate, and excellent absorption performance (absorption amount and absorption rate) is exhibited, causing fogging. Hateful.

The measurement result by the swelling volume measuring method of the absorbent resin particle obtained in Example 1 and Comparative Examples 1 and 3. FIG. (Up to 150 seconds) The measurement result by the swelling volume measuring method of the absorbent resin particle obtained in Example 1 and Comparative Examples 1 and 3. FIG. (Up to 1800 seconds) Front sectional drawing which showed typically the whole apparatus for measuring the amount of absorption by the swelling volume measuring method. The side projection figure which showed typically the bottomed cylinder 1 and the disk 2 for measuring the amount of absorption by the swelling volume measuring method. The top view which showed typically the disk 2 for measuring the amount of absorption 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.

  As a structural unit of the absorbent resin particles, in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), other vinyl monomers (a3) copolymerizable therewith can be used as the structural unit. .

Other vinyl monomers (a3) that can be copolymerized are not particularly limited and are known {for example, 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, 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 constituent unit, the content (mol%) of the other vinyl monomer (a3) unit is that of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. Based on the number of moles, 0.01 to 5 is preferable, more preferably 0.05 to 3, then preferably 0.08 to 2, and particularly preferably 0.1 to 1.5. From the viewpoint of absorption characteristics and the like, the content of other vinyl monomer (a3) units is most preferably 0 mol%.

There are no particular limitations on the crosslinking agent (b), and known crosslinking agents such as those disclosed in known {eg, 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}, and the like. 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 (b) 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.

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

  The cross-linked polymer (A1) can be prepared by known aqueous solution polymerization {adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.} or known reverse-phase suspension polymerization {Japanese Examined Patent Publication No. 54-30710. Gazette, JP-A-56-26909 and JP-A-1-5808, etc.}. Among the polymerization methods, the solution polymerization method is preferable, and an aqueous solution polymerization method is particularly preferable because it is not necessary to use an organic solvent and is advantageous in terms of production cost.

  Water-containing gel obtained by polymerization {consists of a crosslinked polymer and water. } Can be shredded as necessary. 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. Within this range, the drying property in the drying process is further improved.

  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}. .

  When using a solvent (organic solvent, water, etc.) for the polymerization, it is preferable to distill off the solvent after the polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after the distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably 0, based on the weight of the absorbent resin particles. ~ 3, most preferably 0-1. It is. Within this range, the absorption performance (particularly the water retention amount) of the absorbent resin particles is further improved.

  When water is contained in the solvent, the water content (% by weight) after the distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, most preferably based on the weight of the crosslinked polymer. 3-8. Within this range, the absorption performance and the breakability of the absorbent resin particles after drying are further improved.

  In addition, the content and moisture of the organic solvent are an infrared moisture meter {JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specification 100V, 40W } Is obtained from the weight loss of the measurement sample before and after heating.

  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, decantation, filtration, etc. can be applied.

  The crosslinked polymer can be pulverized after drying. The pulverization method is not particularly limited, and a normal pulverizer (for example, a hammer-type pulverizer, an impact-type pulverizer, a roll-type pulverizer, and a shet airflow-type pulverizer) can be used. The pulverized crosslinked polymer can be adjusted in particle size by sieving or the like, if necessary.

  The weight average particle diameter (μm) of the crosslinked polymer (A1) when sieved as necessary is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, Most preferably, it is 350-450. Within this range, the absorption performance is further improved.

  In addition, the weight average particle diameter was measured using a low-tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006), Perry's Chemical Engineers Handbook, 6th edition (Mac Glow Hill Book, 1984). , Page 21). That is, JIS standard sieves are combined in the order of 1000 μm, 850 μm, 710 μm, 500 μm, 425 μm, 355 μm, 250 μm, 150 μm, 125 μm, 75 μm and 45 μm, and a tray from the top. About 50 g of the measured particles are put in the uppermost screen and shaken for 5 minutes with a low-tap test sieve shaker. Weigh the measured particles on each sieve and the pan, and calculate the weight fraction of the particles on each sieve with the total as 100% by weight. This value is the logarithmic probability paper {the horizontal axis is the sieve aperture (particle size ), The vertical axis is plotted in the weight fraction}, a line connecting the points is drawn, and the particle diameter corresponding to the weight fraction of 50% by weight is obtained, and this is defined as the weight average particle diameter.

  Further, since the absorption performance is better when the content of fine particles is smaller, the content of fine particles of 106 μm or less (preferably 150 μm or less) in the total particles is preferably 3% by weight or less, more preferably 1% by weight or less. It is. The content of the fine particles can be determined using a plot created when determining the above weight average particle diameter.

  The apparent density (g / ml) of the crosslinked polymer (A1) is preferably 0.54 to 0.70, more preferably 0.56 to 0.65, and particularly preferably 0.58 to 0.60. Within this range, the absorption performance is further improved. The apparent density is measured at 25 ° C. according to JIS K7365: 1999.

  The shape of the crosslinked polymer (A1) 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, from the viewpoint of good entanglement with the fibrous material in the use of paper diapers and the like and no fear of dropping off from the fibrous material, an irregular crushed shape is preferable.

  The crosslinked polymer (A1) can be subjected to a surface crosslinking treatment with a surface crosslinking agent, if necessary. As the surface cross-linking agent, known {Japanese Patent Laid-Open Nos. 59-189103, 58-180233, 61-16903, 61-21305, 61-252212 are known. , JP-A-51-136588, JP-A-61-257235, etc.} surface crosslinking agent {polyvalent glycidyl, polyhydric alcohol, polyvalent amine, polyvalent aziridine, polyvalent isocyanate, silane coupling Agents and polyvalent metals, etc.} can be used. Of these surface cross-linking agents, from the viewpoint of economy and absorption properties, polyvalent glycidyl, polyhydric alcohol and polyvalent amine are preferable, more preferably polyvalent glycidyl and polyhydric alcohol, particularly preferably polyvalent glycidyl, most preferably Preferred is ethylene glycol diglycidyl ether.

  In the case of surface cross-linking treatment, the amount (% by weight) of the surface cross-linking agent is not particularly limited because it can be variously changed depending on the type of surface cross-linking agent, the conditions for cross-linking, the target performance, etc. From the viewpoint of the above, based on the weight of the water-soluble vinyl monomer (a1), the hydrolyzable vinyl monomer (a2) and the crosslinking agent (b), 0.001 to 3 is preferable, more preferably 0.005 to 2, Most preferably, it is 0.01-1.

  In the case of performing the surface cross-linking treatment, the method of the surface cross-linking treatment is known {for example, the method of Japanese Patent No. 3648553, JP-A No. 2003-165883, JP-A No. 2005-75982, JP-A No. 2005-95759}. Is applicable.

  The absorbent resin particle of the present invention is a hydrophobic substance which is a compound having at least one 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 (C) is present in a specific amount inside the absorbent resin particles and present in a specific amount on the surface of the absorbent resin particles.

The content (% by weight) of the hydrophobic substance (C) inside the absorbent resin particles is 0.01 to 10.0% by weight, preferably 0.01%, based on the weight of the crosslinked polymer (A1). It is -5.0, More preferably, it is 0.05-2.0, Most preferably, it is 0.1-1.0. If the content of (C) in the absorbent resin particles is less than 0.01% by weight, the anti-fogging property of the absorbent article is deteriorated, and the content of (C) in the absorbent resin particles is 10.0% by weight. If it exceeds, the anti-moisture resistance of the absorbent article will deteriorate.
The content (% by weight) of the hydrophobic substance (C) present on the surface of the absorbent resin particles is 0.001 to 1.0 based on the weight of the crosslinked polymer (A1), preferably 0.8. 005 to 0.5, more preferably 0.01 to 0.3, and particularly preferably 0.01 to 0.1. If the content of (C) on the surface of the absorbent resin particles is less than 0.001% by weight, the anti-fogging property of the absorbent article is deteriorated, and the content of (C) on the surface of the absorbent resin particles is 1.0% by weight. If it exceeds, the anti-moisture resistance of the absorbent article will deteriorate.

In addition, content of the hydrophobic substance which exists on the surface is measured by the following method. The content of the hydrophobic substance present in the interior is obtained by subtracting the content of the hydrophobic substance on the surface from the total content of the hydrophobic substance.
<Method for measuring content of hydrophobic substance>
In a glass beaker, 1 part by weight of absorbent resin particles and an organic solvent (an organic solvent capable of dissolving at least 0.01 part by weight of a hydrophobic substance in 100 parts by weight of an organic solvent at 25 ° C. to 110 ° C.) The temperature that can be obtained is taken as the dissolution temperature.) 1000 parts by weight is added and the mixture is allowed to stand at the dissolution temperature for 24 hours to obtain an extract of a hydrophobic substance. The extract is filtered using filter paper, 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 was repeated twice, and the total amount of the evaporated and dried product obtained by the extraction three times was determined as the content of hydrophobic substances present on the surface (wt% ).

  Examples of the monovalent aliphatic hydrocarbon group having 8 to 26 carbon atoms that the hydrophobic substance (C) has 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 octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, icosyl group, docosyl group, tetracosyl group and hexacosyl group. Is mentioned.

  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. .

The hydrophobic substance (C) has 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.
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 hydrophobic substance (C) having a carboxyl group include nonanoic acid, dodecanoic 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, octadecyl 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 octyl sulfonic acid, octadecyl sulfonic acid, and hexacosyl sulfonic 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, octadecylamine 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, octyl octadecanoate, Glycerol nonanoic acid monoester, glycerin octadecanoic acid monoester, glycerin heptacosanoic acid monoester, pentaerythrit nonanoic acid monoester, pentaerythlitoctadecanoic acid monoester, pentaerythrit heptacosanoic acid monoester, sorbit nonanoic acid monoester, Sorbit slit octadecanoic acid monoester, sorbit heptacosanoic acid monoester, sucrose nonanoic acid monoester, sucrose nonanoic acid diester, sucrose nonanoic acid triester, sucrose ester Tadekan acid monoester, sucrose octadecanoic acid diester, sucrose octadecanoic acid triester, sucrose heptacosanoic acid monoester, sucrose heptacosanoic acid diester, 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 methyl nonanoate, octyl acetate, octyl octylate, hexacosyl acetate and octylic acid Examples include hexacosyl.

  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, octadecyl 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. For example, octyl sulfate, octadecyl sulfate, hexacosyl sulfate and the like can be mentioned, 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 at least one aliphatic chain having 8 to 26 carbon atoms and a carboxylic acid having 1 to 26 carbon atoms And amidated products of secondary amines having two aliphatic hydrocarbon groups having 1 to 7 carbon atoms 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 amidated products of a long-chain aliphatic secondary amine having at least one aliphatic chain having 8 to 26 carbon atoms and a carboxylic acid having 1 to 26 carbon atoms include acetic acid N-methyloctylamide, acetic acid N-methylhexacosi Luamide, acetic acid N-octylhexacosylamide, acetic acid N-dihexacosylamide, heptacosanoic acid N-methyloctylamide, heptacosanoic acid N-methylhexacosylamide, heptacosanoic acid N-octylhexacosylamide and heptacosane Examples include acid N-dihexacosylamide.

  Examples of amidated products of secondary amines having two aliphatic hydrocarbon groups 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, heptacosanoic acid N-dimethylamide, heptacosanoic acid N-methylheptylamide, heptacosanoic acid N-diheptylamide and the like can be mentioned.

  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 long-chain aliphatic alcohols include octyl alcohol, octadecyl alcohol, and hexacosyl alcohol. Examples of compounds having at least one isocyanate group include methyl isocyanate, dodecyl isocyanate, hexacosyl isocyanate, methylene diisocyanate, and hexamethylene. Diisocyanate etc. are mentioned.

  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, octadecylamine 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, dodecyl 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 have a structure comprising a hydrophobic substance (C) inside and on the surface thereof. The absorbent resin particles are divided into (1) a hydrophobic substance (C) and a crosslinked polymer ( It can be produced by a method of mixing and kneading with the water-containing gel of A1), or (2) a method of polymerizing the structural units in the presence of the hydrophobic substance (C) to obtain a water-containing gel of the crosslinked polymer (A1).

The mixing method of the crosslinked polymer (A1) and the hydrophobic substance (C) is not limited as long as the hydrophobic substance (C) is mixed so as to exist inside and on the surface of the crosslinked polymer (A1). .
However, the hydrophobic substance (C) is preferably not mixed with the dried polymer of the crosslinked polymer (A1) but with the hydrogel (A1) or the polymerization solution (A1), and more preferably (A1). To be mixed with hydrous gel. In addition, it is preferable to mix uniformly so that mixing may be carried out.
When the crosslinked polymer (A1) is obtained by the aqueous solution polymerization method, the timing for mixing and kneading the hydrophobic substances (C) and (A1) is not particularly limited, but during the polymerization process, immediately after the polymerization process, Examples thereof include crushing (minching) and drying of the hydrogel. Among these, from the viewpoint of the anti-moisture resistance of the absorbent article, it is preferable to be immediately after the polymerization step and during the water-containing gel crushing (mincing) step, and more preferably during the water-containing gel crushing (mincing) step.

  When the crosslinked polymer (A1) is obtained by the reverse phase suspension polymerization method or emulsion polymerization, the timing of mixing the hydrophobic substance (C) and (A1) is not particularly limited, but during the polymerization process {(C) In the presence of (A1)}, immediately after the polymerization step, during the dehydration step (during the step of dehydrating to about 10% by weight of water), immediately after the dehydration step, during the step of separating and distilling off the organic solvent used in the polymerization And during the drying of the hydrogel. Among these, from the viewpoint of the anti-moisture resistance of the absorbent article, it is preferable during the polymerization step, immediately after the polymerization step, during the dehydration step, immediately after the dehydration step, and during the step of separating and distilling off the organic solvent used for the polymerization. Is immediately after the polymerization step during the polymerization step.

  In the case of mixing during the drying of the hydrogel, a normal apparatus such as a bex mill, rubber chopper, pharma mill, mincing machine, impact pulverizer, and roll pulverizer can be used. When mixing in the polymerization solution, a device having a relatively high stirring force such as a homomixer or a biomixer can be used. Moreover, when mixing in drying of a hydrogel, kneading apparatuses, such as SV mixer, can also be used.

  The mixing temperature (° C.) is preferably 20 to 100, more preferably 40 to 90, and particularly preferably 50 to 80. Within this range, it becomes easier to mix evenly and the absorption characteristics are further improved.

  In the method (2) for producing the crosslinked polymer (A1) in the presence of the hydrophobic substance (C), the hydrophobic substance (C) is dissolved or emulsified (dispersed) in the polymer solution of the crosslinked polymer (A1). In addition, it can be carried out while precipitating (C) as the polymerization of (A1) proceeds. The polymerization method is the same as in the case of the crosslinked polymer (A1) except that the polymerization is performed in the presence of the hydrophobic substance (C).

The hydrophobic substance (C) can also be used in a form dissolved and / or emulsified in water and / or a volatile solvent (however, no emulsifier is used). The volatile solvent preferably has a vapor pressure (Pa) at 20 ° C. of 0.13 to 5.3, more preferably 0.15 to 4.5, particularly preferably, from the viewpoint of easy removal. Is from 0.23 to 3.8.
Examples of the volatile solvent include alcohols having 1 to 3 carbon atoms (such as methanol, ethanol and isopropyl alcohol), hydrocarbons having 5 to 8 carbon atoms (such as pentane, hexane, cyclohexane and toluene), and ethers having 2 to 4 carbon atoms ( Dimethyl ether, diethyl ether, tetrahydrofuran, etc.), C3-C4 ketones (acetone, methyl ethyl ketone, etc.), C3-C5 esters (ethyl formate, ethyl acetate, isopropyl acetate, diethyl carbonate, etc.) and the like. When water and / or a volatile solvent is used, the amount (% by weight) of these used is preferably 1 to 900, more preferably 5 to 700, particularly preferably based on the weight of the hydrophobic substance (C). 10-400. When water and a volatile solvent are used, the amount (% by weight) of water used is preferably from 50 to 98, more preferably from 60 to 95, particularly preferably from 70 to 90, based on the weight of water and the volatile solvent. It is.

The water-containing gel containing the hydrophobic substance (C) can be chopped as necessary. The size (longest diameter) of the hydrogel particles after chopping 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, the drying property in the drying process is further improved.
As the shredding method, the same method as in the case of the crosslinked polymer (A1) can be adopted.

When a solvent (including an organic solvent and / or water) is used for production of the absorbent resin particles, the solvent can be distilled off after polymerization.
When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after the distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably 0, based on the weight of the absorbent resin particles. ~ 3, most preferably 0-1. It is. Within this range, the absorption performance (particularly the water retention amount) of the absorbent resin particles is further improved.

Moreover, when water is contained in the solvent, the water content (% by weight) after the distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, based on the weight of the absorbent resin particles. Most preferably, it is 3-8. Within this range, the absorption performance (particularly the water retention amount) and the breakability of the absorbent resin particles after drying are further improved.
In addition, the content of the organic solvent, the method for measuring the water content, and the method for distilling off the solvent are the same as in the case of the crosslinked polymer (A1).

The absorbent resin particles can be pulverized. When the absorbent resin particles contain a solvent, the solvent is preferably pulverized after being distilled off (dried).
When pulverizing, the weight average particle size (μm) after pulverization is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, and most preferably 350 to 450. It is. Within this range, handling properties after pulverization (powder fluidity of absorbent resin particles and the like) and anti-fogging properties of the absorbent article are further improved. In addition, a weight average particle diameter can be measured like the case of a crosslinked polymer (A1).

The smaller the content of fine particles, the better the absorption performance, and the content of fine particles of 106 μm or less in the total particles is preferably 3% by weight or less, more preferably the content of fine particles of 150 μm or less in the total particles is 3% by weight It is as follows. The content of the fine particles can be determined using a plot created when determining the above weight average particle diameter.
For pulverization and particle size adjustment, the same method as in the case of the crosslinked polymer (A1) can be employed.

  The apparent density (g / ml) of the absorbent resin particles of the present invention is preferably 0.54 to 0.70, more preferably 0.56 to 0.65, and particularly preferably 0.58 to 0.60. . Within this range, the anti-fogging property of the absorbent article is further improved. The apparent density can be measured in the same manner as in the case of the crosslinked polymer (A1).

  The shape of the absorbent resin particles is not particularly limited, and examples thereof include an irregularly crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, from the viewpoint of good entanglement with the fibrous material in the use of paper diapers and the like and no fear of dropping off from the fibrous material, an irregular crushed shape is preferable.

  The absorbent resin particles can be subjected to surface crosslinking as necessary. As the crosslinking agent (surface crosslinking agent) for performing the surface crosslinking, the same as the internal crosslinking agent (b) can be used. As the surface cross-linking agent, from the viewpoint of the absorption performance of the absorbent resin particles, the water-soluble substituent of the water-soluble vinyl monomer (a1) and / or the water-soluble substituent generated by hydrolysis of the vinyl monomer (a2) is reacted. The cross-linking agent (b3) having at least two functional groups that can be used is preferable, more preferably polyvalent glycidyl, particularly preferably ethylene glycol diglycidyl ether and glycerin diglycidyl ether, and most preferably ethylene glycol diglycidyl ether.

  In the case of surface cross-linking, the content (% by weight) of the surface cross-linking agent is the total weight of the vinyl monomers (a1) and / or (a2), the internal cross-linking agent (b) and other vinyl monomers (a3) used as necessary. Is preferably 0.001 to 7, more preferably 0.002 to 5, particularly preferably 0.003 to 4. That is, in this case, the upper limit of the content (% by weight) of the surface cross-linking agent is preferably 7 based on the total weight of (a1) and / or (a2), (b) and (a3), more preferably 5, particularly preferably 4. Similarly, the lower limit is preferably 0.001, more preferably 0.002, and particularly preferably 0.003. In this range, the absorption performance is further improved. Surface cross-linking can be achieved by a method of spraying or impregnating absorbent particles with an aqueous solution containing a surface cross-linking agent, followed by heat treatment (100 to 200 ° C.).

The absorbent resin particles of the present invention can further contain an inorganic powder (D) on the surface. 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) is preferably 0.01 to 3.0, more preferably 0.05 to 1.0, and then preferably based on the weight of the crosslinked polymer (A1). Is 0.1 to 0.8, particularly preferably 0.2 to 0.7, and 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.

In the method for measuring the swelling volume with respect to physiological saline per gram of the absorbent resin particles of the present invention, the ratio of the time until the swelling volume reaches 5 ml (t1) and the time until the swelling volume reaches 40 ml (t2) (t2 / t1) is preferably from 5 to 20, more preferably from 5 to 15, and most preferably from 5 to 10. Further, t1 is preferably 20 seconds to 60 seconds, more preferably 20 seconds to 50 seconds, and most preferably 30 seconds to 40 seconds.
Within this range, the anti-fogging property of the absorbent article is further improved. By adjusting the content of the hydrophobic substance (C), the apparent density of the absorbent resin particles, the weight average particle diameter of the absorbent resin particles, etc. to the above preferred ranges, the amount of absorption by the swelling volume measurement method is adjusted to the preferred range. it can.

The swelling volume measurement method is a measurement method performed using the apparatus shown in FIG. 3 in a room with a temperature of 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. 3 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.
Further, the disk 2 is made up of 64 holes having a diameter of 2 mm radially (see FIG. 5). 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 size of 150 to 850 μm is weighed in a vertically standing cylinder 1 with a bottom plate, and a uniform thickness is obtained at the bottom of the cylinder 1 with a bottom plate. 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, the pressure applied to the absorbent resin particles is 3.9 ± 0.3 g / cm ² due to the weight (140 g ± 10 g) of the measuring rod of the digimatic indicator and the weight of the disc 2 with handle. 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 at which the disk is started is set to 0, and the distance H (cm) at which the disk 2 has risen as time elapses from the start of charging is recorded as continuous data. By calculating the swelling volume (ml) per 1 g of the absorbent resin particles according to the following formula, data of the swelling volume change with time is obtained. From this data, the time (t1) until the swelling volume reaches 5 ml and the time (t2) until the swelling volume reaches 40 ml are determined. The same measurement is performed 5 times, and the average value is taken as the measured value.

  The water retention amount (g / g) of the absorbent resin particles of the present invention is preferably from 28 to 45, more preferably from 32 to 40, particularly preferably from 34 to 38, from the viewpoint of anti-fogging properties of the absorbent article. The water retention amount of the absorbent resin particles is measured by the following method.

<Measurement method of water retention amount of absorbent resin particles>
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 being immersed in the inside for 1 hour without stirring, it was suspended for 15 minutes and drained. 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 used physiological saline and measurement atmosphere shall be 25 degreeC +/- 2 degreeC.
The weight of the tea bag after centrifugal dehydration is measured (h2) in the same manner as above except that no measurement sample is used.

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

The gel elastic modulus (N / m ² ) of the 30-fold swollen gel obtained by absorbing 1 part by weight of the absorbent resin particles of the present invention by 30 parts by weight of artificial urine is preferably 2,000 to 3,000, more preferably. Is 2,025 to 2950, particularly preferably 2,050 to 2,900, most preferably 2,075 to 2,850. Within this range, when the water-absorbing agent of the present invention is applied to an absorbent article, more excellent resistance to leakage is exhibited. The gel elastic modulus (N / m ² ) is a value obtained by the following measurement method.

<Measurement method of gel modulus>
Artificial urine [200 parts by weight of urea, 80 parts by weight of sodium chloride, 8 parts by weight of magnesium sulfate (7-hydrate), 3 parts by weight of calcium chloride (dihydrate), 2 parts by weight of ferric sulfate (7-hydrate), ions 9704 parts by weight of exchanged water] 60.0 g was weighed into a 100 ml beaker (inner diameter 5 cm), and in the same manner as described in JIS K7224-1996, 2.0 g of a measurement sample was precisely weighed and put into the beaker. Create a 30-fold swollen gel.
The beaker containing the 30-fold swollen gel was allowed to stand in an atmosphere of 40 ± 2 ° C. for 3 hours, and further in an atmosphere of 25 ± 2 ° C. for 0.5 hour. (For example, it measures using the card meter MAX ME-500 by ITEC Techno Engineering Co., Ltd.). The card meter conditions are as follows.
・ Pressure sensitive axis: 8mm
・ Spring: 100g ・ Load: 100g
・ Rising speed: 1 inch / 7 seconds ・ Test properties: rupture ・ Measurement time: 6 seconds ・ Measurement ambient temperature: 25 ± 2 ° C.

  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”. In addition, the absorption amount by the swelling volume measuring method of an absorbent resin particle, the water retention amount, and content of the hydrophobic substance (C) were measured by the method mentioned above. In the measurement of the content of the hydrophobic substance (C) present on the surface, the extraction of the hydrophobic substance (C) was performed at 25 ° C. using methanol or 110 ° C. using xylene.

<Example 1>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts (2.15 mole parts), crosslinking agent (b1) {pentaerythritol triallyl ether, manufactured by Daiso Corporation } 0.6225 parts (0.0024 mole part) and 340.27 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 0.62 part of 1% aqueous hydrogen peroxide solution, 1.1625 part of 2% aqueous ascorbic acid solution and 2% 2,2′-azobis [ 2.325 parts of 2-methyl-N- (2-hydroxyethyl) -propionamide] aqueous solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 90 ° C., polymerization was carried out at 90 ± 2 ° C. for about 5 hours to obtain a hydrogel (1).
Next, hydrated this hydrogel (1) 502.27 parts with a mincing machine (12VR-400K manufactured by ROYAL), added and mixed 128.42 parts of 48.5% sodium hydroxide aqueous solution, followed by hydrophobicity 0.95 part of the substance (C-1) {octadecanoic acid} was added and mixed to obtain a chopped gel (2). Further, the chopped gel (2) was dried with a ventilation band dryer {150 ° 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 Co., Ltd.), and then adjusted to a particle size of 150 to 710 μm using a 150 and 710 μm sieve to obtain dried particles. While stirring 100 parts of the dry particles (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), a 2% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 70/30). 5 parts were added while being sprayed and mixed, and the mixture was allowed to stand at 150 ° C. for 30 minutes to crosslink the surface to obtain the absorbent resin particles (1) of the present invention. The weight average particle diameter of the absorbent resin particles (1) was 395 μm, and the apparent density was 0.58 g / ml. Further, the hydrophobic substance (C-1) was present at 0.490% inside the absorbent resin particles and was present at 0.010% on the surface.

<Examples 2 to 60>
In Example 1, except that 0.95 part of the hydrophobic substance (C-1) was changed to the number of parts of the hydrophobic substance (C) and the charged amount shown in Tables 1 and 2, Absorbent resin particles (2) to (60) of the invention were obtained. Tables 3 and 4 show the weight-average particle diameter, apparent density, and the absorptive resin particle internal abundance and surface abundance of the hydrophobic substance (C) of the absorptive resin particles (2) to (60). In addition, in content of (C) of Table 3 and 4,% shows content (weight%) based on the weight of a crosslinked polymer (A1).

<Example 61>
The absorbent resin particles (61 of the present invention) were used in the same manner as in Example 1 except that 0.6 part of hydrophilic inorganic particles (d-1) {Aerogel 200PE (product of Nippon Aerogel Co., Ltd.)} was added after surface crosslinking. ) The weight average particle diameter of the absorbent resin particles (61) was 390 μm, and the apparent density was 0.57 g / ml. Further, the hydrophobic substance (C-1) was present at 0.490% inside the absorbent resin particles and was present at 0.010% on the surface.

<Example 62>
Preparatory Step 145.4 parts of acrylic acid was diluted with 9.4 parts of water and neutralized by adding 242.3 parts of 25% aqueous sodium hydroxide while cooling to 20-30 ° C. After 0.09 part of ethylene glycol diglycidyl ether (manufactured by Nagase Kasei Kogyo Co., Ltd., Denacol EX-810), 0.0146 part of sodium hypophosphite monohydrate, and potassium persulfate are uniformly dissolved in this solution. A monomer aqueous solution (1) was obtained by adding 1.45 parts of a hydrophobic substance (C-1).
Next, in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas introduction tube, 624 parts of cyclohexane is added and 1.56 parts of sorbitan monostearate is added and dissolved therein, followed by stirring. While replacing with nitrogen.

・ Process (1)
Subsequently, after the temperature in the reaction vessel was raised to 70 ° C., 397 parts of the monomer aqueous solution (1) was added dropwise at 6.6 parts / min over 60 minutes while maintaining the temperature at 70 ° C. Thereafter, aging was performed at 75 ° C. for 30 minutes to obtain an aqueous solution containing the absorbent resin precursor (1).

・ Process (2)
Thereafter, the water content of the aqueous solution containing the absorbent resin precursor (1) is about 20% by azeotropic distillation of water and cyclohexane (infrared moisture meter (FD-100 type, manufactured by Kett, 180 ° C., 20 minutes). When the stirring was stopped after cooling to 30 ° C., the resin particles settled, and the resin particles and cyclohexane were separated by decantation. The resin particles were dried until the water content was 20% or less, and 0.013 part of a 1% aqueous solution of ethylene glycol diglycidyl ether (manufactured by Nagase Kasei Kogyo Co., Ltd., Denacol EX-810) was sprayed on the resin particles at 80 parts. The surface cross-linking reaction was carried out for 1 hour, and then further dried at 110 ° C. to obtain the absorbent resin particles (62) of the present invention. ) Was 400 μm, the apparent density was 0.60 g / ml, and the hydrophobic substance (C-1) was present in the inside of the absorbent resin particles in an amount of 0.98%. 0.02% was present.

<Example 63>
Absorbent resin particles of the present invention in the same manner as in Example 62 except that 1.45 parts of “hydrophobic substance (C-1)” was changed to “2.9 parts of hydrophobic substance (C-1)” (63) was obtained. The weight average particle diameter of the absorbent resin particles (63) was 400 μm, and the apparent density was 0.60 g / ml. Further, the hydrophobic substance (C-1) was present at 1.95% inside the absorbent resin particles and was present at 0.05% on the surface.

<Comparative Example 1>
A solution prepared by dissolving 0.004 part of amino-modified silicone (Shin-Etsu Chemical Co., Ltd. product: KF354) in 80 parts of methanol was added to 40 parts of clay (ROCKWOOD ADDIIVES LIMITEDED: LAPONIPE XLG) and stirred at 25 ° C. for 2 minutes. Then, it dried at 60 degreeC * 1 hour, and obtained the material particle (F). The volume average particle diameter of the material particles (F) was 80 μm.

Next, in a glass reaction vessel, 77 parts of sodium acrylate, 22.85 parts of acrylic acid, 0.15 part of N, N′-methylenebisacrylamide and 293 parts of deionized water, dichlorotris (triphenylphosphine) ruthenium 0 0.001 part was charged, and the temperature of the contents was kept at 3 ° C. while stirring and mixing. After flowing nitrogen into the contents to make the dissolved oxygen amount 1 ppm or less, 0.3 part of 1% aqueous solution of hydrogen peroxide, 0.8 part of 0.2% aqueous solution of ascorbic acid and 2,2′-azobis Polymerization is started by adding and mixing 0.8 parts of a 2% aqueous solution of amidinopropane dihydrochloride, and after the reaction solution reaches 80 ° C., it is polymerized at a polymerization temperature of 80 ± 2 ° C. for about 5 hours. Gel (1) was obtained.
30 parts of the material particles (F) and 0.3 part of the surfactant (1) (Sanyo Kasei Kogyo Co., Ltd .: Sanmorin OT70) are added to 300 parts of the hydrous gel (1), and the mincing machine (hole diameter of the eye plate: 6 mm, After kneading for 5 minutes at 25 ° C. with 12VR-400K manufactured by Iizuka Kogyo Co., Ltd., it was dried with an air-flowing band dryer under conditions of 135 ° C. and a wind speed of 2.0 m / sec to obtain a dried polymer product.
The polymer dried product was pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster) and adjusted to a particle size of 150 to 710 μm using 150 and 710 μm sieves. 2 parts of a 10% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 70/30) was added while being sprayed and mixed while the high-speed stirring turbulizer was rotated at 2000 rpm. Absorbent resin particles (H1) for comparison were obtained by allowing to stand at 140 ° C. for 30 minutes and crosslinking by heating. The weight average particle diameter of the absorbent resin particles (H1) was 395 μm, and the apparent density was 0.55 g / ml. Further, the hydrophobic substance (C) was present at 0.001% inside the absorbent resin particles and was not present on the surface.

<Comparative example 2>
“Material part (E) 30 parts” was changed to “silicone beads (Toshiba Silicone Corp .: Tospearl average particle size 2 μm) 30 parts” and “Surfactant (1) (Sanyo Chemical Industries, Ltd .: Sanmorin OT70) ) 0.3 parts "was changed to" Surfactant (2) (Sanyo Kasei Kogyo Co., Ltd .: NAROACTY ID50) 0.3 parts "in the same manner as Comparative Example 1 except that the absorbent resin particles for comparison were used. (H2) was obtained. The weight average particle diameter of the absorbent resin particles (H2) was 400 μm, and the apparent density was 0.55 g / ml. Further, the hydrophobic substance (C) was present at 0.01% inside the absorbent resin particles and was not present on the surface.

<Comparative Example 3>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts (2.15 mole parts), crosslinking agent (b1) {pentaerythritol triallyl ether, manufactured by Daiso Corporation } 0.6225 parts (0.0024 mole part) and 340.27 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 0.62 part of 1% aqueous hydrogen peroxide solution, 1.1625 part of 2% aqueous ascorbic acid solution and 2% 2,2′-azobis [ 2.325 parts of 2-methyl-N- (2-hydroxyethyl) -propionamide] aqueous solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 90 ° C., polymerization was carried out at 90 ± 2 ° C. for about 5 hours to obtain a hydrogel (1). Next, while adding 502.27 parts of this hydrous gel (1) with a mincing machine (12VR-400K, manufactured by ROYAL), 128.42 parts of 48.5% sodium hydroxide aqueous solution was added and mixed to obtain a chopped gel. (2) was obtained. Further, the chopped gel (2) was dried with a ventilation band dryer {150 ° 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 Co., Ltd.), and then adjusted to a particle size of 150 to 710 μm using a 150 and 710 μm sieve to obtain dried particles. While stirring 100 parts of the dry particles (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), a 2% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 70/30). 5 parts of was added while being sprayed and mixed, and the mixture was allowed to stand at 150 ° C. for 30 minutes for surface crosslinking to obtain comparative absorbent resin particles (H3). The weight average particle diameter of the absorbent resin particles (H3) was 405 μm, and the apparent density was 0.61 g / ml. Further, the hydrophobic substance (C) was not present inside or on the surface of the absorbent resin particles.

<Comparative example 4>
Absorbent resin particles (H4) for comparison were obtained in the same manner as in Comparative Example 1 except that 1.9 parts of the hydrophobic substance (C-1) was mixed after the surface crosslinking. The weight average particle diameter of the absorbent resin particles (H4) was 400 μm, and the apparent density was 0.61 g / ml. Further, the hydrophobic substance (C-1) was not present inside the absorbent resin particles, and 1.0% was present on the surface.

<Comparative Example 5>
Absorbent resin particles (H5) for comparison were obtained according to Example 1 of JP2007-291351. The weight average particle diameter of the absorbent resin particles (H5) was 400 μm, and the apparent density was 0.70 g / ml. Further, the hydrophobic substance (C) was not present inside or on the surface of the absorbent resin particles.

  The measurement result by the swelling volume measurement method of the absorbent resin particles obtained in Example 1 and Comparative Examples 1 and 3 is shown in FIGS. In addition, the distance which the disk rose was measured using a Digimatic indicator ID-F150 manufactured by Mitutoyo.

  As can be seen from FIG. 1 and FIG. 2, the absorption rate pattern of the absorbent resin particles of Example 1 draws an S-shaped absorption rate curve that is initially slow, medium-term normal, and late.

  Tables 3 and 4 show performance evaluation results {swelling volume measurement method, water retention amount, gel elastic modulus} for the absorbent resin particles obtained in Examples 1 to 63 and Comparative Examples 1 to 5. In addition, in content of (C) of Table 3 and 4,% shows content (weight%) based on the weight of a crosslinked polymer (A1).

As can be seen from Tables 3 and 4, the absorbent resin particles (Examples 1 to 63) of the present invention have an appropriate absorption rate pattern as compared with the absorbent resin particles of Comparative Examples 1 to 5.
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 63 and Comparative Examples 1 to 5, absorbent articles (paper diapers) were prepared as follows, and the surface dryness value by the SDME method was evaluated. Are shown in Tables 5 and 6.

<Preparation 1 of absorbent article (paper diaper)>
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.

<Preparation 2 of absorbent article (paper diaper)>
Preparation of absorbent article (paper diaper) 1 except that “100 parts fluff pulp and 100 parts evaluation sample {absorbent resin particles}” were changed to “80 parts fluff pulp and 120 parts evaluation sample {absorbent resin particles}” The paper diaper (2) was adjusted in the same manner as described above. The weight ratio of absorbent resin particles to fibers (weight of absorbent resin particles / weight of fiber) was 60/40.

<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 Tables 5 and 6, the absorbent article using the absorbent resin particles of the present invention has a surface dryness value (1-1), (compared to an absorbent article using comparative absorbent resin particles). 1-2) and (1-3) were excellent with no bias. That is, the absorbent resin particles of the present invention have excellent absorption characteristics because they have a specific absorption rate pattern when applied to absorbent articles. Therefore, even if an absorbent article to which the absorbent resin particles of the present invention are applied is used, it is easily predicted that there is no concern about blurring or the like.

  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 (6)

Absorbency comprising a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a crosslinked polymer (A1) having a crosslinking agent (b) as essential constituent units and a hydrophobic substance (C) A resin particle, wherein (C) has 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 And (C) is present in the interior of the absorbent resin particles in an amount of 0.01 to 10.0% by weight based on the weight of (A1), and 0.001 to 1.0% by weight on the surface of the absorbent resin particles. Absorbent resin particles present. Functional groups capable of forming hydrogen bonds with carboxyl groups are carboxyl groups, phosphate groups, sulfonate groups, primary amino groups, secondary amino groups, tertiary amino groups, hydroxyl groups, ester bonds, phosphate ester bonds, sulfonic acids The absorbent resin particle according to claim 1, wherein the absorbent resin particle is at least one functional group selected from the group consisting of an ester bond, an amide bond, a urethane bond, and a urea bond. 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 The absorbent resin particle according to claim 1 or 2, which is 5 to 20. The absorbent resin particle according to any one of claims 1 to 3, further comprising 0.01 to 3.0% by weight of the inorganic powder (D) based on the weight of the crosslinked polymer (A1). An absorbent comprising the absorbent resin particles according to any one of claims 1 to 4 and a fibrous material. An absorbent article using the absorber according to claim 5.

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