JP2018127508A - Absorptive resin particle and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorptive resin particle which has a slow absorption rate pattern with an absorption rate of a middle stage to a latter stage, has high water retentivity, and has less deviation in an absorption rate and an absorption amount depending on a portion of an absorber even when a user repeatedly urinates, exhibits excellent absorption performance and hardly causes rash, when applied to an absorption article.SOLUTION: There is provided an absorptive resin particle that contains 0.01-0.5% of a crosslinked polymer (A) of a monomer composition containing a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2) and a crosslinking agent (b) and a surface active agent (B) having an HLB value of 10 or less based on the weight of the crosslinked polymer (A), where (i) an absorption amount after 5 minutes based on DW method is 10-35 g/g; (ii) a water retaining amount is 36-50 g/g; (iii) a gel modulus is 1.8-3.0 kN/m; and (iv) an initial wet time based on Drop test method is 5-20 seconds.SELECTED DRAWING: None

Description

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

  Sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads are made of absorbent fibers (super absorbent polymer is abbreviated as “SAP” for short) of hydrophilic fibers such as pulp and acrylic acid (salt). Combinations are widely used. In recent years, with the rapid increase in demand in emerging countries, there is a growing need for long-use diapers, i.e., diapers that do not cause moles or rashes even after repeated urination. Therefore, further enhancement of functionality of the absorbent resin is demanded.

  One of the functions required of the absorbent resin is water retention. As means for improving the water retention amount, a method of reducing the crosslinking density of the resin by devising an internal crosslinking agent or a surface crosslinking agent is generally known. However, in this method, the gel strength is reduced, the gels are blocked, and the diffusion of the liquid in the diaper is inhibited. For this reason, there was a problem that the leakage and liquid return were worsened.

  In order to solve the above problems, as absorbent resin particles having both high water retention and diffusibility, absorbent resin particles containing a hydrophobic substance inside the crosslinked polymer (Patent Document 1), water retention ability and gel strength Absorbent resin particles (Patent Document 2) that have been enhanced, and Absorbent resin particles (Patent Document 3) in which a hydrophobic substance adheres to the surface of a crosslinked polymer are known. However, these conventional absorbent resin particles are not suitable for the absorption rate change (hereinafter referred to as absorption rate pattern) over time after contact with the liquid to be absorbed. That is, these conventional absorbent resin particles have an absorption rate pattern that is (i) fast in the initial stage, normal in the middle period and normal in the latter period (absorbent resin particles in Patent Documents 1 and 2), or (Ii) Late in the early stage, normal in the middle period and normal in the latter period (absorbent resin particles of Patent Document 3). In the absorbent body using these absorbent resin particles, the absorption speed and the amount of absorption of the absorbent resin particles are uneven depending on the site of the absorbent body, and it is easy to generate a site where the liquid to be absorbed is not absorbed, or The problem that the time during which the liquid that has not been absorbed in the entire absorbent body remains is likely to be increased. In response to this problem, there has been proposed an absorbent resin particle having an absorption rate pattern of (iii) late in the early period, normal in the middle period, and fast in the latter period (Patent Document 4).

  However, although the absorbent resin particles described in Patent Document 4 are suitable for thin diapers on the premise that they are changed a plurality of times a day, they are assumed when applied to long-time use type diapers with a small number of replacements. Not only is the amount of water retained insufficient with respect to the amount of urine discharged, but also the intermediate-to-late absorption rate is too fast, so that the liquid diffusibility after repeated urination may be poor. As a result, the liquid that has not been absorbed stays in the diaper for a long time, causing problems such as leakage and fogging.

JP 2005-097569 A WO2012 / 144564 Japanese Patent Laid-Open No. 2004-261796 JP 2011-252088 A

  The object of the present invention is to have an absorption rate pattern in which the absorption rate is slow from middle to late and has high water retention, and when applied to an absorbent article, the absorption rate by the site of the absorber even when urinating repeatedly for a long time The present invention provides an absorbent resin particle and a method for producing the same that exhibit little absorption unevenness, exhibit excellent absorption performance (absorption amount and absorption rate), and are less susceptible to fog.

The present invention includes a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) (hereinafter also referred to as a hydrolyzable vinyl monomer (a2)) that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a crosslinking agent ( 0.01 to 0 based on the weight of the crosslinked polymer (A), the crosslinked polymer (A) of the monomer composition containing b) and at least one surfactant (B) having an HLB value of 10 or less. Absorbent resin particles containing 5%,
(I) Absorption after 5 minutes based on Demand Wettability test method is 10 to 35 g / g,
(Ii) 0.9% by weight physiological saline has a water retention amount of 36 to 50 g / g per unit weight,
(Iii) Gel elastic modulus is 1.8 to 3.0 kN / m ² ,
(Iv) an initial wetting time based on the Drop test method of 5 to 20 seconds,
It is an absorptive resin particle characterized by being.
The present invention also provides a crosslinked polymer (A) of a monomer composition containing a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a crosslinking agent (b) and an HLB value of 10 or less. Containing 0.01 to 0.5% of at least one surfactant (B) based on the weight of the crosslinked polymer (A),
(I) Absorption after 5 minutes based on Demand Wettability test method is 10 to 35 g / g,
(Ii) 0.9% by weight physiological saline has a water retention amount of 36 to 50 g / g per unit weight,
(Iii) Gel elastic modulus is 1.8 to 3.0 kN / m ² ,
(Iv) an initial wetting time based on the Drop test method of 5 to 20 seconds,
A method for producing absorbent resin particles,
Including a polymerization step of the monomer composition and a drying step of the hydrogel of the crosslinked polymer (A), after the polymerization step is started and before the polymerization step is completed, or after the polymerization step is completed. A step of mixing 0.01 to 0.5% of the surfactant (B) with the hydrogel of the crosslinked polymer (A) based on the weight of the crosslinked polymer (A) before the completion of the drying step; It is a manufacturing method of the absorbent resin particle containing this.

The absorbent resin particle of the present invention has a specific range of absorption rate pattern in which the absorption rate after 5 minutes based on the demand wettability test method and the initial wetting time based on the drop test method are slow, and the absorption rate is slow from middle to late. At the same time, the water retention amount of 0.9% by weight physiological saline is in a specific range and has high water retention.
Therefore, when the absorbent resin particles of the present invention are applied to an absorbent article, even if the urination is repeated for a long time, the absorption rate and the amount of absorption of the absorbent resin particles due to the site of the absorber are small, and excellent absorption performance ( Absorption amount and absorption speed), and it is difficult for fog to occur.

FIG. 1 is a schematic diagram of a measuring apparatus used in the Demand Wettability test method.

  The absorbent resin particles of the present invention include a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2), and a crosslinked polymer (A1) and an HLB of a monomer composition containing a crosslinking agent (b). At least one surfactant (B) having a value of 10 or less is contained in an amount of 0.01 to 0.5% based on the weight of the crosslinked polymer (A1).

  The water-soluble vinyl monomer (a1) in the present invention is not particularly limited, and is a known monomer, for example, at least one water-soluble substituent group disclosed in Japanese Patent No. 3648553, paragraphs 0007 to 0023 and an ethylenic group. Vinyl monomers having a saturated group (for example, anionic vinyl monomers, nonionic vinyl monomers, and cationic vinyl monomers), anionic vinyl monomers disclosed in paragraphs 0009 to 0024 of JP-A No. 2003-165883, nonionic Selected from the group consisting of a carboxylic group, a sulfo group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group and an ammonio group disclosed in paragraphs 0041 to 0051 of JP-A-2005-75982 At least one kind Vinyl monomers can be used.

  The hydrolyzable vinyl monomer (a2) is not particularly limited, and known {for example, at least one hydrolyzable substituent that becomes a water-soluble substituent by hydrolysis disclosed in paragraphs 0024 to 0025 of Japanese Patent No. 3648553. A vinyl monomer having at least one hydrolyzable substituent [1,3-oxo-2-oxapropylene (—CO—O—CO—) disclosed in paragraphs 0052 to 0055 of JP-A-2005-75982. ), A vinyl monomer having a group such as an acyl group and a cyano group]. The water-soluble vinyl monomer is a concept well known to those skilled in the art, but when expressed in terms of quantity, for example, it means a vinyl monomer that dissolves in 100 g of water at 25 ° C. The hydrolyzability in the hydrolyzable vinyl monomer (a2) is a concept well known to those skilled in the art. More specifically, for example, it can be expressed by the action of water and, if necessary, a catalyst (acid or base). It means the property of being hydrolyzed to become water-soluble. Hydrolysis of the hydrolyzable vinyl monomer (a2) may be performed either during polymerization, after polymerization, or both of them, but from the viewpoint of the absorption performance of the resulting absorbent resin particles, it is preferably after polymerization.

  Among these, the water-soluble vinyl monomer (a1) is preferable from the viewpoint of absorption performance and the like, more preferably the above-mentioned anionic vinyl monomer, carboxy (salt) group, sulfo (salt) group, amino group, carbamoyl group, Vinyl monomers having an ammonio group or a mono-, di- or tri-alkylammonio group, more preferred are vinyl monomers having a carboxy (salt) group or a carbamoyl group, particularly preferred are (meth) acrylic acid (salt) and (Meth) acrylamide, particularly preferred is (meth) acrylic acid (salt), and most preferred is 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 alkali metal (such as lithium, sodium and potassium) salts, alkaline earth metal (such as magnesium and calcium) salts and ammonium (NH ₄ ) salt. Among these salts, alkali metal salts and ammonium salts are preferable from the viewpoint of absorption performance and the like, more preferable are alkali metal salts, and particularly preferable are sodium salts.

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

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

Other vinyl monomers (a3) that can be copolymerized are not particularly limited, and are known (for example, hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553, Japanese Patent Laid-Open No. 2003-165883). 0025 paragraph and vinyl monomer disclosed in JP-A-2005-75982, paragraph 0058) can be used. Specifically, for example, 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 ethylenic monomer Alkenes (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); and alkadienes (butadiene, isoprene, etc.) and the like.
(Iii) C5-C15 alicyclic ethylenic monomer Monoethylenically unsaturated monomer (such as pinene, limonene and indene); and polyethylene vinyl monomer [such as cyclopentadiene, bicyclopentadiene and ethylidene norbornene].

  The content (mol%) of the other vinyl monomer (a3) unit in the crosslinked polymer (A) is such that the water-soluble vinyl monomer (a1) unit and hydrolyzable vinyl monomer (a2) unit are from the viewpoint of absorption performance and the like. Based on the total number of moles, 0 to 5 is preferable, more preferably 0 to 3, particularly preferably 0 to 2, and particularly preferably 0 to 1.5. From the viewpoint of absorption performance and the like, other vinyl monomers ( a3) The unit content is most preferably 0 mol%.

  The cross-linking agent (b) is not particularly limited and is known (for example, it reacts with a cross-linking agent having two or more ethylenically unsaturated groups and water-soluble substituents disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553. Crosslinking agent having at least one functional group and at least one ethylenically unsaturated group, and crosslinking agent having at least two functional groups capable of reacting with a water-soluble substituent, Japanese Patent Application Laid-Open No. 2003-165883 The crosslinking agent having two or more ethylenically unsaturated groups, the crosslinking agent having an ethylenically unsaturated group and a reactive functional group, and the crosslinking agent having two or more reactive substituents disclosed in paragraphs 0028 to 0031 of , A crosslinkable vinyl monomer disclosed in paragraph 0059 of JP-A-2005-75982, and paragraphs 0015 to 0016 of JP-A-2005-95759. Crosslinking agents such as disclosed crosslinkable vinyl monomer) can be used. Among these, from the viewpoint of absorption performance and the like, a crosslinking agent having two or more ethylenically unsaturated groups is preferable, and more preferable are bis (meth) acrylamides such as N, N′-methylenebisacrylamide; ) Poly (meth) acrylates of polyhydric alcohols such as alkylene glycol, trimethylol propane, glycerin, pentaerythritol and sorbitol; (poly) poly (alcohols of polyhydric alcohols such as alkylene glycol, trimethylol propane, glycerin, pentaerythritol and sorbitol ( Multivalent (meth) allyl compounds such as (meth) allyl ether, tetraallyloxyethane and triallyl isocyanurate, and most preferred are polyvalent (meth) allyl compounds. A crosslinking agent (b) may be used individually by 1 type, or may use 2 or more types together.

  The content (mol%) of the crosslinking agent (b) unit is (a1) when other vinyl monomers (a3) of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit are also used. Based on the total number of moles of (a3), 0.001 to 5 is preferable, 0.005 to 3 is more preferable, and 0.01 to 1 is particularly preferable. Within this range, the absorption performance is further improved.

  As a polymerization method of the crosslinked polymer (A), known solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; Japanese Patent Laid-Open No. 55-133413, etc.), and known reverse phase suspension polymerization (Japanese Patent Publication) 54-30710, JP-A-56-26909, and JP-A-1-5808).

  The crosslinked polymer (A) is obtained by polymerizing a monomer composition containing water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and crosslinking agent (b) as essential components. However, a solution polymerization method is preferable as the polymerization method, and it is advantageous in terms of production cost because it is not necessary to use an organic solvent or the like. Therefore, an aqueous solution polymerization method is particularly preferable, and a water retention amount is large. The aqueous solution adiabatic polymerization method is most preferable because a water-absorbing resin composition having a small amount of water-soluble component is obtained and temperature control during polymerization is unnecessary.

When aqueous solution polymerization is performed, a mixed solvent containing water and an organic solvent can be used. Examples of the organic solvent include methanol, ethanol, acetone, methyl ethyl ketone, N, N-dimethylformamide, dimethyl sulfoxide, and two or more of these. A mixture of
When aqueous solution polymerization is performed, the amount (% by weight) of the organic solvent used is preferably 40 or less, more preferably 30 or less, based on the weight of water.

In the case of using an initiator for polymerization, conventionally known initiators for radical polymerization can be used. For example, azo compounds [azobisisobutyronitrile, azobiscyanovaleric acid and 2,2′-azobis (2-amidinopropane) Hydrochloride, etc.], inorganic peroxides (hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, etc.), organic peroxides [benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, succinate Acid peroxide and di (2-ethoxyethyl) peroxydicarbonate, etc.] and redox catalyst (alkali metal sulfite or bisulfite, ammonium sulfite, ammonium bisulfite, ascorbic acid and the like, and alkali metal persulfate) Such as salt, ammonium persulfate, hydrogen peroxide and organic peroxide And those comprising a combination with an oxidizing agent). These catalysts may be used alone or in combination of two or more thereof.
The use amount (% by weight) of the radical polymerization initiator is preferably 0.0005 to 5, more preferably 0.001 based on the total weight of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2). ~ 2.

At the time of polymerization, a polymerization control agent typified by a chain transfer agent may be used as necessary. Specific examples thereof include sodium hypophosphite, sodium phosphite, alkyl mercaptans, alkyl halides. And thiocarbonyl compounds. These polymerization control agents may be used alone or in combination of two or more thereof.
The amount (% by weight) of the polymerization control agent used is preferably from 0.0005 to 5, more preferably from 0.001 to 5, based on the total weight of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2). 2.

  When a suspension polymerization method or a reverse phase suspension polymerization method is used as the polymerization method, the polymerization may be carried out in the presence of a dispersant or a surfactant as necessary. In the case of the reverse phase suspension polymerization method, polymerization can be carried out using a hydrocarbon solvent such as xylene, normal hexane and normal heptane.

  The polymerization start temperature can be appropriately adjusted depending on the type of catalyst used, but is preferably 0 to 100 ° C, more preferably 2 to 80 ° C.

  When using a solvent (such as an organic solvent and water) for the polymerization, the solvent is preferably distilled off after the polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably based on the weight of the crosslinked polymer (A). Is 0-3, most preferably 0-1. Within this range, the absorbent performance of the absorbent resin particles is further improved.

  When water is contained in the solvent, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, based on the weight of the crosslinked polymer (A). Most preferably, it is 3-8. Within this range, the absorption performance is further improved.

By the above polymerization method, the crosslinked polymer (A) can obtain a water-containing gel-like product containing water (hereinafter abbreviated as a water-containing gel), and the water-containing gel is further dried to obtain the crosslinked polymer (A). Can be obtained.
When an acid group-containing monomer such as acrylic acid or methacrylic acid is used as the water-soluble vinyl monomer (a1), the hydrogel may be neutralized with a base. The neutralization degree of the acid group is preferably 50 to 80 mol%. When the degree of neutralization is less than 50 mol%, the resulting water-containing gel polymer has high tackiness, and the workability during production and use may deteriorate. Furthermore, the water retention amount of the resulting absorbent resin particles may be reduced. On the other hand, when the degree of neutralization exceeds 80%, the pH of the obtained resin becomes high, and there is a concern that the safety of human skin may be concerned.
The neutralization may be performed at any stage after the polymerization of the crosslinked polymer (A) in the production of the absorbent resin particles. For example, a method such as neutralization in the state of a hydrogel is preferable. Illustrated.
As the base to be neutralized, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate, sodium hydrogen carbonate and potassium carbonate can be usually used.

  The water-containing gel obtained by polymerization can be shredded as necessary before drying. 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 performed using a shredding device (for example, a bex mill, rubber chopper, pharma mill, mincing machine, impact pulverizer, and roll pulverizer).

  In addition, the content and water content of the organic solvent were measured using an infrared moisture meter [JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specifications 100V, 40W ] Is obtained from the weight loss of the measurement sample when heated.

  As a method of distilling off the solvent (including water) of the hydrogel and drying it, a method of distilling (drying) with hot air at a temperature of 80 to 230 ° C., a drum dryer heated to 100 to 230 ° C., etc. A thin film drying method, a (heating) vacuum drying method, a freeze drying method, a drying method using infrared rays, decantation, filtration, and the like can be applied.

  After the hydrogel is dried to obtain the crosslinked polymer (A), it can be further pulverized. The pulverization method is not particularly limited, and a pulverizer (for example, a hammer pulverizer, an impact pulverizer, a roll pulverizer, and a shet airflow 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 size (μm) of the crosslinked polymer (A) when screened 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 (McGlow Hill Book Company, 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 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 [horizontal axis is sieve aperture (particle size ), The vertical axis is plotted in the weight fraction], and then a line connecting the points is drawn to obtain the particle diameter corresponding to the weight fraction of 50% by weight, which is defined as the weight average particle diameter.

  Further, when pulverized, the smaller the content of the fine particles contained in the crosslinked polymer (A) after pulverization, the better the absorption performance. Therefore, 106 μm or less (preferably 150 μm) of the total weight of the crosslinked polymer (A). The content (% by weight) of the following fine particles is preferably 3 or less, more preferably 1 or less. The content of the fine particles can be determined using a graph created when determining the above-mentioned weight average particle diameter.

  When pulverized, the shape of the crosslinked polymer (A) after pulverization 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 crosslinked polymer (A) may contain some other components such as a residual solvent and a residual crosslinking component as long as the performance is not impaired.

  The absorbent resin particles of the present invention preferably have a structure in which the surface of the crosslinked polymer (A) is crosslinked by the surface crosslinking agent (d). By cross-linking the surface of the cross-linked polymer (A), the gel strength of the absorbent resin particles can be improved, and the desired water retention amount and absorption amount under load of the absorbent resin particles can be satisfied. Examples of the surface cross-linking agent (d) include known polyvalent glycidyl compounds, polyvalent amines, polyvalent aziridine compounds and polyvalent isocyanate compounds described in JP 59-189103 A, JP 58-180233 A. And polyhydric alcohols described in JP-A-61-16903, silane coupling agents described in JP-A-61-211305 and JP-A-61-252212, and JP-A-5-508425. Use is made of a surface crosslinking agent or the like of an alkylene carbonate, a polyvalent oxazoline compound described in JP-A-11-240959, and a polyvalent metal described in JP-A-51-136588 and JP-A-61-257235) it can. Of these surface cross-linking agents, from the viewpoint of economy and absorption properties, polyvalent glycidyl compounds, polyhydric alcohols and polyhydric amines are preferred, polyvalent glycidyl compounds and polyhydric alcohols are more preferred, and many are particularly preferred. Valent glycidyl compounds, most preferred are ethylene glycol diglycidyl ethers. A surface crosslinking agent may be used individually by 1 type, and may use 2 or more types together.

  In the case of surface crosslinking, the amount (% by weight) of the surface crosslinking agent (d) is not particularly limited because it can be variously changed depending on the type of the surface crosslinking agent, the conditions for crosslinking, the target performance, etc. From the viewpoint of absorption characteristics and the like, 0.001 to 3 is preferable with respect to 100 parts by weight of the crosslinked polymer (A), more preferably 0.005 to 2, and particularly preferably 0.01 to 1.5.

  Surface crosslinking of the crosslinked polymer (A) can be performed by mixing the crosslinked polymer (A) and the surface crosslinking agent (d) and heating as necessary. As a mixing method of the crosslinked polymer (A) and the surface crosslinking agent (d), a cylindrical mixer, a screw mixer, a screw extruder, a turbulator, a nauter mixer, a double arm kneader, a flow Cross-linked polymer using a mixing device such as a mixing mixer, a V-type mixer, a minced mixer, a ribbon-type mixer, a fluid-type mixer, an airflow-type mixer, a rotating disk-type mixer, a conical blender, and a roll mixer. A method of uniformly mixing A) and the surface cross-linking agent (d) can be mentioned. At this time, the surface crosslinking agent (d) may be used after diluted with water and / or an arbitrary solvent.

  Although the temperature at the time of mixing a crosslinked polymer (A) and a surface crosslinking agent (d) is not specifically limited, 10-150 degreeC is preferable, More preferably, it is 20-100 degreeC, Most preferably, it is 25-80 degreeC. .

  After mixing the cross-linked polymer (A) and the surface cross-linking agent (d), heat treatment is usually performed. The heating temperature is preferably 100 to 180 ° C., more preferably 110 to 175 ° C., and particularly preferably 120 to 170 ° C. from the viewpoint of breakage resistance of the resin particles. Heating at 180 ° C. or lower is advantageous in terms of equipment because indirect heating using steam is possible, and absorption performance may deteriorate at heating temperatures below 100 ° C. Moreover, although heating time can be suitably set with heating temperature, from a viewpoint of absorption performance, Preferably it is 5 to 60 minutes, More preferably, it is 10 to 40 minutes. The water-absorbing resin obtained by surface cross-linking can be further surface cross-linked using the same or different type of surface cross-linking agent as the first used surface cross-linking agent.

  After the surface of the crosslinked polymer (A) is crosslinked with the surface crosslinking agent (d), the particle size is adjusted by sieving as necessary. The average particle size of the obtained particles is preferably 100 to 600 μm, more preferably 200 to 500 μm. The content of fine particles is preferably small, the content of particles of 100 μm or less is preferably 3% by weight or less, and the content of particles of 150 μm or less is more preferably 3% by weight or less.

  The absorbent resin particles of the present invention contain at least one surfactant (B) having an HLB value of 10 or less from the viewpoint of the specific and appropriate absorption rate pattern and the absorption performance upon repeated use.

  As the surfactant (B), a surfactant (B1) containing a hydrocarbon group, a surfactant (B2) containing a hydrocarbon group having a fluorine atom, and a surfactant (B3) having a polysiloxane structure. Etc. are included.

  As the surfactant (B1) containing a hydrocarbon group, polyolefin resin, polyolefin resin derivative, polystyrene resin, polystyrene resin derivative, wax, long chain fatty acid ester, long chain fatty acid and salt thereof, long chain aliphatic alcohol, long A chain aliphatic amide and a mixture of two or more of these are included, and those having a hydrocarbon group having 8 to 30 carbon atoms are preferable.

  As the polyolefin resin, an olefin having 2 to 4 carbon atoms {ethylene, propylene, isobutylene, isoprene, etc.} as an essential constituent monomer (the olefin content is at least 50% by weight based on the weight of the polyolefin resin) And polymers having an average molecular weight of 1,000 to 1,000,000 {for example, polyethylene, polypropylene, polyisobutylene, poly (ethylene-isobutylene), isoprene, etc.}.

  Examples of the polyolefin resin derivative include polymers having a weight average molecular weight of 1,000 to 1,000,000 introduced by introducing a carboxyl group (—COOH), 1,3-oxo-2-oxapropylene (—COOCO—) or the like into a polyolefin resin {for example, polyethylene heat Degradation, polypropylene thermal degradation, maleic acid modified polyethylene, chlorinated polyethylene, maleic acid modified polypropylene, ethylene-acrylic acid copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, maleation Polybutadiene, ethylene-vinyl acetate copolymer, and maleated product of ethylene-vinyl acetate copolymer}.

  As the polystyrene resin, a polymer having a weight average molecular weight of 1,000 to 1,000,000 can be used.

  As the polystyrene resin derivative, a polymer having a weight average molecular weight of 1,000 to 1,000,000 (for example, styrene-containing styrene as an essential constituent monomer (the content of styrene is at least 50% by weight based on the weight of the polystyrene derivative)). Maleic anhydride copolymer, styrene-butadiene copolymer, styrene-isobutylene copolymer, etc.}.

  Examples of the wax include waxes having a melting point of 50 to 200 ° C. (for example, paraffin wax, beeswax, carbana wax, beef tallow, etc.).

  As long-chain fatty acid esters, esters of fatty acids having 8 to 30 carbon atoms and alcohols having 1 to 12 carbon atoms {for example, methyl laurate, ethyl laurate, methyl stearate, ethyl stearate, methyl oleate, oleic acid Ethyl, glycerin lauric acid monoester, glycerin stearic acid monoester, glycerin oleic acid monoester, pentaerythritol lauric acid monoester, pentaerythritol stearate monoester, pentaerythritol oleic acid monoester, sorbit lauric acid monoester, Sorbit stearic acid monoester, sorbit oleic acid monoester, sucrose palmitic acid monoester, sucrose palmitic acid diester, sucrose palmitic acid triester, sucrose stearic acid monoester Ester, sucrose stearic acid diester, sucrose stearic acid triester, and beef tallow} and the like.

  Examples of long chain fatty acids and salts thereof include fatty acids having 8 to 30 carbon atoms (for example, lauric acid, palmitic acid, stearic acid, oleic acid, dimer acid, behenic acid, etc.), and salts thereof include zinc, calcium, Examples thereof include salts with magnesium or aluminum (hereinafter abbreviated as Zn, Ca, Mg, Al) {for example, palmitic acid Ca, palmitic acid Al, stearic acid Ca, stearic acid Mg, stearic acid Al, etc.}.

  Examples of the long-chain aliphatic alcohol include aliphatic alcohols having 8 to 30 carbon atoms (for example, lauryl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol, etc.). From the viewpoint of the moisture resistance of the absorbent article, palmityl alcohol, stearyl alcohol, and oleyl alcohol are preferable, and stearyl alcohol is more preferable.

As long-chain aliphatic amide, an amidation product of a long-chain aliphatic primary amine having 8 to 30 carbon atoms and a carboxylic acid having a hydrocarbon group having 1 to 30 carbon atoms, ammonia or a primary amine having 1 to 7 carbon atoms And amidated product of a long chain fatty acid having 8 to 30 carbon atoms, a long chain aliphatic secondary amine having at least one aliphatic chain having 8 to 30 carbon atoms and a carboxylic acid having 1 to 30 carbon atoms, and Examples include amidated products of secondary amines having two aliphatic hydrocarbon groups having 1 to 7 carbon atoms and long chain fatty acids having 8 to 30 carbon atoms.
As an amidation product of a long-chain aliphatic primary amine having 8 to 30 carbon atoms and a carboxylic acid having a hydrocarbon group having 1 to 30 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 30 carbon atoms, ammonia or a primary amine and a carboxylic acid reacted in 1: 1 and 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 ones reacted in 1: 2 were dinonanoic acid amide, dinonanoic acid N-methylamide, dinonanoic acid N-heptylamide, dioctadecanoic acid amide, dioctadecanoic acid N-ethylamide, dioctadecanoic acid N-heptylamide, diheptacosanoic acid amide. And diheptacosanoic acid N-methylamide, diheptacosanoic acid N-heptylamide, and diheptacosanoic acid N-hexacosylamide. In addition, as a thing which ammonia or primary amine and carboxylic acid reacted by 1: 2, the carboxylic acid to be used may be the same or different.

  Examples of the amidated product of a long-chain aliphatic secondary amine having at least one aliphatic chain having 8 to 30 carbon atoms and a carboxylic acid having 1 to 30 carbon atoms include N-methyloctylamide acetate, N-methylhexacoxy acetate 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 30 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 (B2) containing a hydrocarbon group having a fluorine atom include perfluoroalkane, perfluoroalkene, perfluoroaryl, perfluoroalkyl ether, perfluoroalkyl carboxylic acid, perfluoroalkyl alcohol, and those 2 A mixture of seeds or more is included.

  As perfluoroalkanes, alkanes having 4 to 42 fluorine atoms and 1 to 20 carbon atoms {for example, trifluoromethane, pentafluoroethane, pentafluoropropane, heptafluoropropane, heptafluorobutane, nonafluorofluorohexane, tridecafluoro Octane and heptadecafluorododecane, etc.}.

  The perfluoroalkene includes alkenes having 4 to 42 fluorine atoms and 2 to 20 carbon atoms (for example, trifluoroethylene, pentafluoropropene, trifluoropropene, heptafluorobutene, nonafluorofluorohexene, tridecafluorooctene and hepta Decafluorododecene etc.}.

  Perfluoroaryl includes aryl having 4 to 42 fluorine atoms and 6 to 20 carbon atoms (for example, trifluorobenzene, pentafluorotoluene, trifluoronaphthalene, heptafluorobenzene, nonafluorofluoroxylene, tridecafluorooctylbenzene and Heptadecafluorododecylbenzene, etc.}.

  Examples of perfluoroalkyl ether include ethers having 2 to 82 fluorine atoms and 2 to 40 carbon atoms (for example, ditrifluoromethyl ether, dipentafluoroethyl ether, dipentafluoropropyl ether, diheptafluoropropyl ether, diheptafluoro). Butyl ether, dinonafluorofluorohexyl ether, ditridecafluorooctyl ether, diheptadecafluorododecyl ether, etc.}.

  Examples of perfluoroalkylcarboxylic acids include carboxylic acids having 3 to 41 fluorine atoms and 1 to 21 carbon atoms (for example, pentafluoroethanoic acid, pentafluoropropanoic acid, heptafluoropropanoic acid, heptafluorobutanoic acid, nonafluorofluorohexane). Acid, tridecafluorooctanoic acid, heptadecafluorododecanoic acid, and salts of these metals (alkali metal and alkaline earth metal etc.), etc.}.

  Perfluoroalkyl alcohols include alcohols having 3 to 41 fluorine atoms and 1 to 20 carbon atoms (for example, pentafluoroethanol, pentafluoropropanol, heptafluoropropanol, heptafluorobutanol, nonaflufluorohexanol, tridecafluorooctanol and Heptadecafluorododecanol and the like} and ethylene oxide (1 to 20 mol per 1 mol of alcohol) adduct of this alcohol.

  Examples of the mixture of two or more of these include a mixture of perfluoroalkylcarboxylic acid and perfluoroalkyl alcohol {for example, a mixture of pentafluoroethanoic acid and pentafluoroethanol, etc.}.

  As the surfactant (B3) having a polysiloxane structure, polydimethylsiloxane, polyether-modified polysiloxane {polyoxyethylene-modified polysiloxane and poly (oxyethylene / oxypropylene) -modified polysiloxane, etc.}, carboxy-modified polysiloxane, Epoxy-modified polysiloxane, amino-modified polysiloxane, alkoxy-modified polysiloxane and the like, and mixtures thereof are included.

  The position of the organic group (modified group) of the modified silicone {polyether-modified polysiloxane, carboxy-modified polysiloxane, epoxy-modified polysiloxane, amino-modified polysiloxane, etc.} is not particularly limited, but the side chain of polysiloxane, polysiloxane Both ends of the polysiloxane, one end of the polysiloxane, and both the side chain and both ends of the polysiloxane may be used. Among these, from the viewpoint of absorption characteristics and the like, both the side chain of polysiloxane and the side chain and both ends of polysiloxane are preferred, and both the side chain and both ends of polysiloxane are more preferred.

  Examples of the organic group (modified group) of the polyether-modified polysiloxane include a group containing a polyoxyethylene group or a poly (oxyethylene / oxypropylene) group. The content (pieces) of oxyethylene groups and / or oxypropylene groups contained in the polyether-modified polysiloxane is preferably 2 to 40, more preferably 5 to 30, particularly preferably per molecule of the polyether-modified polysiloxane. 7-20, most preferably 10-15. Within this range, the absorption characteristics are further improved. Moreover, when it contains an oxyethylene group and an oxypropylene group, the content (% by weight) of the oxyethylene group is preferably 1 to 30, more preferably 3 to 25, and particularly preferably 5 based on the weight of the polysiloxane. ~ 20. Within this range, the absorption characteristics are further improved.

The polyether-modified polysiloxane can be easily obtained from the market. For example, the following products {modified position, type of oxyalkylene} can be preferably exemplified.
* Shin-Etsu Chemical Co., Ltd. KF-945 {side chain, oxyethylene and oxypropylene}, KF-6020 {side chain, oxyethylene and oxypropylene}, X-22-6191 {side chain, oxyethylene and oxypropylene} X-22-4922 {side chain, oxyethylene and oxypropylene}, X-22-4272 {side chain, oxyethylene and oxypropylene}, X-22-6266 {side chain, oxyethylene and oxypropylene}

FZ-2110 {both ends, oxyethylene and oxypropylene}, FZ-2122 {both ends, oxyethylene and oxypropylene}, FZ-7006 {both ends, oxyethylene and oxypropylene}, manufactured by Toray Dow Corning Co., Ltd. FZ-2166 {both ends, oxyethylene and oxypropylene}, FZ-2164 {both ends, oxyethylene and oxypropylene}, FZ-2154 {both ends, oxyethylene and oxypropylene}, FZ-2203 {both ends, oxy Ethylene and oxypropylene} and FZ-2207 {both ends, oxyethylene and oxypropylene}

  The organic group (modified group) of the carboxy-modified polysiloxane includes a group containing a carboxy group, and the organic group (modified group) of the epoxy-modified polysiloxane includes a group containing an epoxy group. Examples of the organic group (modified group) of polysiloxane include groups containing amino groups (1, 2, and tertiary amino groups). The organic group (modified group) content (g / mol) of these modified silicones is preferably 200 to 11000, more preferably 600 to 8000, and particularly preferably 1000 to 4000 as carboxy equivalent, epoxy equivalent or amino equivalent. It is. Within this range, the absorption characteristics are further improved. The carboxy equivalent is measured according to “16. Total acid value test” of JIS C2101: 1999. Moreover, an epoxy equivalent is calculated | required based on JISK7236: 2001. The amino equivalent is measured according to “8. Potentiometric titration method (base number / hydrochloric acid method)” of JIS K2501: 2003.

The carboxy-modified polysiloxane can be easily obtained from the market. For example, the following products {modified position, carboxy equivalent (g / mol)} can be preferably exemplified.
* Shin-Etsu Chemical Co., Ltd. X-22-3701E {side chain, 4000}, X-22-162C {both ends, 2300}, X-22-3710 {single end, 1450}

-Toray Dow Corning Co., Ltd. BY16-880 {side chain, 3500}, BY16-750 {both ends, 750}, BY16-840 {side chain, 3500}, SF8418 {side chain, 3500}

The epoxy-modified polysiloxane can be easily obtained from the market. For example, the following products {modified position, epoxy equivalent} can be preferably exemplified.
・ X-22-343 {side chain, 525}, KF-101 {side chain, 350}, KF-1001 {side chain, 3500}, X-22-2000 {side chain, 620} manufactured by Shin-Etsu Chemical Co., Ltd. X-22-2046 {side chain, 600}, KF-102 {side chain, 3600}, X-22-4741 {side chain, 2500}, KF-1002 {side chain, 4300}, X-22-3000T {Side chain, 250}, X-22-163 {both ends, 200}, KF-105 {both ends, 490}, X-22-163A {both ends, 1000}, X-22-163B {both ends, 1750}, X-22-163C {both ends, 2700}, X-22-169AS {both ends, 500}, X-22-169B {both ends, 1700}, X-22-173DX {single end, 4500} , X-22-9002 { Side chain, both ends, 5000}

・ FZ-3720 {Side Chain, 1200}, BY16-839 {Side Chain, 3700}, SF8411 {Side Chain, 3200}, SF8413 {Side Chain, 3800}, SF8421 {Side Chain, 11000, manufactured by Toray Dow Corning Co., Ltd. }, BY16-876 {side chain, 2800}, FZ-3736 {side chain, 5000}, BY16-855D {side chain, 180}, BY16-8 {side chain, 3700}

The amino-modified silicone can be easily obtained from the market. For example, the following products {modified position, amino equivalent} can be preferably exemplified.
-Shin-Etsu Chemical Co., Ltd. KF-865 {side chain, 5000}, KF-864 {side chain, 3800}, KF-859 {side chain, 6000}, KF-393 {side chain, 350}, KF-860 {Side Chain, 7600}, KF-880 {Side Chain, 1800}, KF-8004 {Side Chain, 1500}, KF-8002 {Side Chain, 1700}, KF-8005 {Side Chain, 11000}, KF-867 {Side Chain, 1700}, X-22-3820W {Side Chain, 55000}, KF-869 {Side Chain, 8800}, KF-861 {Side Chain, 2000}, X-22-3939A {Side Chain, 1500} , KF-877 {side chain, 5200}, PAM-E {both ends, 130}, KF-8010 {both ends, 430}, X-22-161A {both ends, 800}, X-22-161B {both Terminal 1500 }, KF-8012 {both ends, 2200}, KF-8008 {both ends, 5700}, X-22-1660B-3 {both ends, 2200}, KF-857 {side chain, 2200}, KF-8001 { Side chain, 1900}, KF-862 {side chain, 1900}, X-22-9192 {side chain, 6500}

-FZ-3707 {side chain, 1500}, FZ-3504 {side chain, 1000}, BY16-205 {side chain, 4000}, FZ-3760 {side chain, 1500}, FZ- manufactured by Toray Dow Corning Co., Ltd. 3705 {side chain, 4000}, BY16-209 {side chain, 1800}, FZ-3710 {side chain, 1800}, SF8417 {side chain, 1800}, BY16-849 {side chain, 600}, BY16-850 { Side chain, 3300}, BY16-879B {side chain, 8000}, BY16-892 {side chain, 2000}, FZ-3501 {side chain, 3000}, FZ-3785 {side chain, 6000}, BY16-872 { Side chain, 1800}, BY16-213 {side chain, 2700}, BY16-203 {side chain, 1900}, BY16-898 {side chain, 2900}, BY 16-890 {side chain, 1900}, BY16-893 {side chain, 4000}, FZ-3789 {side chain, 1900}, BY16-871 {both ends, 130}, BY16-853C {both ends, 360}, BY16-853U {both ends, 450}

  Examples of these mixtures include a mixture of polydimethylsiloxane and carboxyl-modified polysiloxane, a mixture of polyether-modified polysiloxane and amino-modified polysiloxane, and the like.

The viscosity (mPa · s, 25 ° C.) of the hydrophobic substance having a polysiloxane structure is preferably 10 to 5000, more preferably 15 to 3000, and particularly preferably 20 to 1500. Within this range, the absorption characteristics are further improved. The viscosity is JIS Z8803-1991 “Viscosity of liquid”. Cone and cone-measured according to the viscosity measurement method using a flat plate rotational viscometer {for example, E-type viscometer with temperature adjusted to 25.0 ± 0.5 ° C. (RE80L, Toki Sangyo Co., Ltd., radius 7 mm) , Angle 5.24 × 10 ⁻² rad cone). }

  1-10 are preferable, as for the HLB value of surfactant (B), More preferably, it is 2-8, Most preferably, it is 3-7. Within this range, the absorption rate pattern is further improved. The HLB value means a hydrophilic-hydrophobic balance (HLB) value, and is determined by the Oda method (new introduction to surfactants, page 197, Takehiko Fujimoto, Sanyo Chemical Industries, Ltd., published in 1981). .

  Of the surfactants (B), surfactants (B1) containing a hydrocarbon group having 8 to 30 carbon atoms are preferable, and long chain fatty acids are more preferable, from the viewpoint of easy availability and development of a specific absorption pattern. Esters, long-chain fatty acids and salts thereof, long-chain fatty alcohols and long-chain aliphatic amides, more preferably sorbite stearate, sucrose stearate, stearic acid, Mg stearate, Ca stearate, stearic acid Zn and Al stearate, particularly preferably sucrose stearate and Mg stearate, most preferably sucrose stearate.

  The surfactant (B) may be present in any part of the absorbent resin particles, but is preferably present in the vicinity of the surface from the viewpoint of developing a specific absorption pattern. The content (% by weight) of the surfactant (B) is preferably 0.01 to 0.5% by weight based on the weight of the crosslinked polymer (A) from the viewpoint of the initial absorption rate and the absorption amount, and preferably Is 0.015 to 0.45% by weight, more preferably 0.02 to 0.4% by weight, and particularly preferably 0.03 to 0.3% by weight.

  The mixing time of the cross-linked polymer (A) and the surfactant (B) should not be before the polymerization step, so after the start of the polymerization step and before the completion of the polymerization step, It is preferable to mix with the water-containing gel of the crosslinked polymer (A) at any time after completion of the above-described polymerization step and before completion of the above-mentioned water-containing gel drying step. It is preferable that the surfactant (B) is not a dried product of the crosslinked polymer (A), but is mixed with the hydrogel of (A) or the polymerization liquid of (A), more preferably with the hydrogel of (A) To be mixed. In addition, it is preferable to mix uniformly so that mixing may be carried out.

  When the cross-linked polymer (A) is obtained by the aqueous solution polymerization method, the timing of mixing the surfactant (B) and (A) is not particularly limited, but during the polymerization process {in the presence of the surfactant (B) And (A) is manufactured}, immediately after the polymerization step, during crushing (minching) of the hydrogel and during drying of the hydrogel. Among these, from the viewpoint of allowing the surfactant (B) to be uniformly present in the vicinity of the surface of the absorbent resin particles, it is preferable immediately after the polymerization step and during the crushing (mincing) step of the hydrous gel, more preferably the hydrous gel. Is in the process of mincing.

When the crosslinked polymer (A) is obtained by the reverse phase suspension polymerization method or emulsion polymerization, the timing of mixing the surfactants (B) and (A) is not particularly limited, but during the polymerization process {surfactant (B) is mixed with the polymerization solution to produce (A)}, 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, and the organic used in the polymerization Examples include the step of separating and distilling off the solvent and the drying of the hydrogel. Among these, from the viewpoint of allowing the surfactant (B) to be uniformly present in the vicinity of the surface of the absorbent resin particles, during the polymerization step, immediately after the polymerization step, during the dehydration step, immediately after the dehydration step, the organic used for the polymerization During the step of separating and distilling off the solvent is preferable, and more preferably during the polymerization step and immediately after the polymerization step.

  When mixing during the crushing or 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.

  Mixing temperature (degreeC) can be suitably adjusted with the process of adding surfactant (B). For example, 20-100 are preferable, as for the mixing temperature (degreeC) in the case of adding and mixing immediately after a superposition | polymerization process and the crushing (mincing) process of a hydrogel, More preferably, it is 40-90, Most preferably, it is 50-80. . Within this range, it becomes easier to mix evenly and the absorption characteristics are further improved.

  In the method for producing the crosslinked polymer (A) in the presence of the surfactant (B), the surfactant (B) is uniformly dissolved or emulsified (dispersed) in the polymer solution of the crosslinked polymer (A). It is preferable to keep it. In the case where it is difficult to make the surfactant (B) uniform, it can be made uniform during the crushing step of the hydrogel. It can be carried out while precipitating the surfactant (B) as the polymerization of (A) proceeds.

  The surfactant (B) 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 using water and / or a volatile solvent, these usage-amount (weight%) is preferable 1-900 based on the weight of surfactant (B), More preferably, it is 5-700, Most preferably 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 surfactant (B) can be shredded 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 (A) 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 and 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 (A).

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 (A).

The smaller the content of fine particles, the better the absorption performance. The content of fine particles of 106 μm or less in the total particles is preferably 3% by weight or less, and 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 (A) can be employed.

  The apparent density (g / ml) of the absorbent resin particles of the present invention is preferably 0.50 to 0.80, more preferably 0.52 to 0.75, and particularly preferably 0.54 to 0.70. . 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 (A).

  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 of the present invention may further contain a polyvalent metal salt (e). For this reason, the production method of the present invention may further include a step of mixing with the polyvalent metal salt (e). good. By containing the polyvalent metal salt (e), the blocking resistance and liquid permeability of the absorbent resin particles are improved. Examples of the polyvalent metal salt (e) include salts of at least one metal selected from the group consisting of magnesium, calcium, zirconium, aluminum, and titanium with the above inorganic acid or organic acid.

  As the polyvalent metal salt (e), an inorganic acid salt of aluminum and an inorganic acid salt of titanium are preferable from the viewpoint of availability and solubility, and aluminum sulfate, aluminum chloride, potassium aluminum sulfate and sulfuric acid are more preferable. Sodium aluminum, particularly preferred are aluminum sulfate and sodium aluminum sulfate, and most preferred is sodium aluminum sulfate. These may be used alone or in combination of two or more.

  The use amount (% by weight) of the polyvalent metal salt (e) is preferably from 0.01 to 5, more preferably from 0,5 based on the weight of the crosslinked polymer (A) from the viewpoint of absorption performance and blocking resistance. 05-4, particularly preferably 0.1-3.

  When the production method of the present invention includes a step of mixing with the polyvalent metal salt (e), the timing of mixing with the polyvalent metal salt (e) is not particularly limited, but may be mixed after the drying step. It is preferable from the viewpoint of absorption performance and blocking resistance.

The mixing method of the polyvalent metal salt (e) includes a cylindrical mixer, a screw mixer, a screw extruder, a turbulator, a nauter mixer, a double-arm kneader, a fluid mixer, and a V mixer. And a uniform mixing method using a known mixing device such as a machine, a minced mixer, a ribbon mixer, a fluid mixer, an airflow mixer, a rotating disk mixer, a conical blender and a roll mixer.
Although the temperature at the time of mixing is not specifically limited, 10-150 degreeC is preferable, More preferably, it is 20-100 degreeC, Most preferably, it is 25-80 degreeC.
In the production method of the present invention, the particle size may be further adjusted after the step of mixing with the polyvalent metal salt (e).

The surface of the absorbent resin particle of the present invention can be further coated with an inorganic powder (D). Examples of the inorganic powder (D) include 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, a fiber shape, etc., but an 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 (A). 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.

The absorbent resin particles of the present invention have an absorption amount of 10 to 35 g / g after 5 minutes under no load measured by a demand wettability test method (hereinafter also referred to as a DW test), and a water retention amount of 36 to 50 g / g, gel elastic modulus is 1.8 to 3.0 kN / m ² , initial wetting time based on Drop test method is 5 to 20 seconds.

  The amount of absorption after 5 minutes under no load measured by Demand Wettability test method (hereinafter also referred to as DW test) can be measured by the method described later, and is preferably from the viewpoint of suppressing leakage of absorbent articles. It is 12-34 g / g, 14-33 g / g is still more preferable, and 16-32 g / g is especially preferable. If it is less than 10 g / g, the middle to late absorption rate is too slow, and leakage is likely to occur due to insufficient absorption rate, such being undesirable. On the other hand, if it exceeds 35 g / g, the absorption rate in the middle to late period is too high, and the liquid diffusibility after repeated use is inferior, so that leakage tends to occur, which is not preferable. The amount absorbed after 5 minutes can be appropriately adjusted depending on the type and addition amount of the surfactant (B). Therefore, for example, when it is necessary to increase the amount of absorption after 5 minutes, it can be easily realized by optimizing the amount of surfactant used or increasing the surface area by decreasing the particle size.

  The water retention amount can be measured by the method described later, and is preferably 37 to 49 g / g, more preferably 38 to 48 g / g, and particularly preferably 39 to 47 g / g from the viewpoint of suppressing leakage of the water absorbent article. preferable. If it is less than 36 g / g, leakage is likely to occur during repeated use. Moreover, since it will become easy to block when it exceeds 50 g / g, it is not preferable. The water retention amount can be appropriately adjusted by the type and amount of the crosslinking agent (b) and the surface crosslinking agent (d). Therefore, for example, when it is necessary to increase the water retention amount, it can be easily realized by reducing the amount of the crosslinking agent (b) and the surface crosslinking agent (d) used.

The gel elastic modulus can be measured by the method described later, and is preferably 1.9 to 2.9 kN / m ² from the viewpoint of the shape retention of the absorber, and is 2.0 to 2.8 kN / m ^2. Further preferred is 2.1 to 2.7 kN / m ² . If it is less than 1.8 kN / m ² , the strength of the absorber is insufficient during repeated use, which is not preferable. On the other hand, if it exceeds 3.0 kN / m ² , the absorber is liable to collapse or shift during repeated use. The gel elastic modulus can be appropriately adjusted by the kind and amount of the crosslinking agent (b) and the surface crosslinking agent (d). Therefore, for example, when it is necessary to increase the gel elastic modulus, it can be easily realized by increasing the amounts of the crosslinking agent (b) and the surface crosslinking agent (d) used.

  The initial wetting time based on the Drop test method can be measured by the method described later, and is preferably 7 to 19 seconds, more preferably 8 to 18 seconds, and more preferably 9 to 16 seconds from the viewpoint of suppressing leakage of the absorbent article. Is particularly preferred. If it is less than 5 seconds, the initial absorption rate is too high, and the liquid diffusibility of the absorbent article is insufficient, such being undesirable. Further, if it exceeds 20 seconds, the initial absorption rate is too slow, and leakage is likely to occur due to insufficient absorption rate, which is not preferable. The initial wetting time based on the Drop test method can be adjusted as appropriate depending on the type and addition amount of the surfactant (B). Therefore, for example, when it is necessary to increase the initial wetting time based on the Drop test method, it can be easily realized by increasing the amount of the surfactant used.

The absorber of the present invention contains the absorbent resin particles of the present invention. As the absorber, absorbent resin particles may be used alone, or may be used together with other materials as the absorber.
Examples of other materials include fibrous materials. The structure and production method of the absorber when used together with the fibrous material are the same as those known (JP 2003-225565 A, JP 2006-131767 A, JP 2005-097569 A, etc.). is there.

  Preferred as the fibrous material are cellulosic fibers, organic synthetic fibers, and mixtures of cellulosic fibers and organic synthetic fibers.

  Examples of the cellulosic fibers include natural fibers such as fluff pulp, and cellulosic chemical fibers such as viscose rayon, acetate, and cupra. There are no particular restrictions on the raw materials (conifers, hardwoods, etc.), production methods (chemical pulp, semi-chemical pulp, mechanical pulp, CTMP, etc.), bleaching methods, etc. of this cellulose-based natural fiber.

  Examples of organic synthetic fibers include polypropylene fibers, polyethylene fibers, polyamide fibers, polyacrylonitrile fibers, polyester fibers, polyvinyl alcohol fibers, polyurethane fibers, and heat-fusible composite fibers (the above fibers having different melting points). And a fiber obtained by compounding at least two of the above into a sheath core type, an eccentric type, a parallel type, and the like, a fiber obtained by blending at least two kinds of the above fibers, and a fiber obtained by modifying the surface layer of the above fibers).

  Among these fibrous materials, preferred are cellulose-based natural fibers, polypropylene-based fibers, polyethylene-based fibers, polyester-based fibers, heat-fusible conjugate fibers, and mixed fibers thereof, and more preferable are obtained. The fluff pulp, the heat-fusible conjugate fiber, and the mixed fiber thereof are preferable in that the water-absorbing agent has excellent shape retention after water absorption.

  The length and thickness of the fibrous material are not particularly limited, and can be suitably used as long as the length is 1 to 200 mm and the thickness is in the range of 0.1 to 100 denier. The shape is not particularly limited as long as it is fibrous, and examples thereof include a thin cylindrical shape, a split yarn shape, a staple shape, a filament shape, and a web shape.

  When the absorbent resin particle is used as an absorbent body together with the fibrous material, the weight ratio of the absorbent resin particle to the fiber (weight of the aqueous liquid absorbent resin particle / weight of the fiber) is preferably 40/60 to 90/10, More preferably, it is 70 / 30-80 / 20.

  The absorbent article of the present invention uses the above absorbent body. The absorbent article is applicable not only to sanitary articles such as paper diapers and sanitary napkins, but also to various uses such as absorption of various aqueous liquids described below, use as a retention agent, and use as a gelling agent. The manufacturing method etc. of an absorbent article are the same as that of what is well-known (The thing of Unexamined-Japanese-Patent No. 2003-225565, Unexamined-Japanese-Patent No. 2006-131767, Unexamined-Japanese-Patent No. 2005-097569, etc.).

Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Hereinafter, unless otherwise specified, parts indicate parts by weight and% indicates% by weight.
Absorption after 5 minutes under no load measured by Demand Wettability test method (hereinafter also referred to as DW test), water retention amount, gel elastic modulus, initial wetting time based on Drop test method is 25 ± 2 ° C., It is measured by the following method in a room with a humidity of 50 ± 10%. The temperature of the physiological saline used is adjusted to 25 ° C. ± 2 ° C. in advance.

<Demand Wetability (DW) Test Method> The DW (Demand Wettability) method is a measurement method performed using the apparatus shown in FIG. 1 in a room at 25 ° C. and a humidity of 50%. The measuring apparatus shown in FIG. 1 includes a burette part (2) {scale capacity 50 ml, length 86 cm, inner diameter 1.05 cm,}, conduit {inner diameter 7 mm}, and measuring table (6). The burette part (2) is connected to the rubber stopper (1) at the upper part, the intake introduction pipe (9) {tip inner diameter 3 mm} and the cock (7) at the lower part, and the upper part of the intake introduction pipe (9) is There is a cock (8). A conduit is attached from the burette part (2) to the measurement table (6). At the center of the measurement table (6), there is a hole with a diameter of 3 mm as a physiological saline supply unit, and a conduit is connected. Using the measuring device of this configuration, first, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are closed, and a predetermined amount of physiological saline (salt) adjusted to 25 ° C. (Concentration 0.9 wt%) from the top of the burette part (2), and after plugging the top of the buret with the rubber plug (1), the cock (7) of the burette part (2) and the cock of the air introduction pipe (9) Open (8). Next, after wiping off the physiological saline overflowing the measurement table (6), the upper surface of the measurement table (6) and the surface of the saline solution coming out from the conduit port at the center of the measurement table (6) The height of the measurement table (6) is adjusted so that it is the same height. While wiping the physiological saline from the physiological saline supply part, the surface of the physiological saline in the burette part (2) is adjusted to the top (0 ml line) of the burette part (2) scale.

Subsequently, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are closed, and the plain weave nylon mesh (on the measurement table (6) is placed so that the physiological saline supply part is at the center. 5) (Opening 63 μm, 5 cm × 5 cm) is placed on the plain woven nylon mesh (5), and 1.0 g in a range of 2.7 cm in diameter with a physiological saline supply part of the measuring table (6) as the center. The absorbent resin particles (4) are uniformly dispersed. Thereafter, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are opened. When the absorbent resin particles (4) begin to absorb water and the first bubble introduced from the air introduction tube (9) reaches the surface of the physiological saline in the burette portion (2) (burette portion (2) The measurement start time is defined as the time when the physiological saline water in the inside drops, and the amount of physiological saline (3) in the burette portion (2) is continuously reduced (the physiological state in which the absorbent resin particles (4) have absorbed water). Saline amount) M (ml) is read. The absorption amount of the absorbent resin particles (4) after the elapse of a predetermined time from the start of water absorption is determined by the following equation. In this application, the 5-minute value is used as an index of the absorption rate. Absorption by DW method (ml / g) = M ÷ 1.0

<Measurement method of water retention amount> 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 physiological saline (saline concentration: 0.2%). (9 wt%) After being immersed in 1,000 ml for 1 hour without stirring, it was suspended for 15 minutes to drain water. 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)

<Method for Measuring Gel Elastic Modulus> 60.0 g of physiological saline was weighed into a 100 ml beaker (inner diameter: 5 cm), 2.0 g of a measurement sample was precisely weighed in the same manner as described in JIS K7224-1996, and the above Put in a beaker to make a 30-fold swollen gel. Wrap in a beaker containing a 30-fold swollen gel so that the swollen gel does not dry, leave it in an atmosphere of 25 ± 2 ° C. for 0.5 hours, remove the wrap, and obtain a gel elastic modulus of the 30-fold swollen gel. Is measured using a card meter (for example, Card Meter Max ME-500 manufactured by ITEC Techno Engineering Co., Ltd.). The card meter conditions are as follows.・ Pressure sensitive axis: 8 mm ・ Spring: 100 g ・ Load: 100 g ・ Raising speed: 1 inch / 7 seconds ・ Test properties: rupture ・ Measurement time: 6 seconds ・ Measurement ambient temperature: 25 ± 2 ° C.

<Apparent Density> The apparent density of the absorbent resin particles of the present invention is measured at 25 ° C. in accordance with JIS K7365: 1999.

<Measurement method of initial wetting time (Drop method) of absorbent resin particles>
In the present invention, the initial wetting time (second) by the Drop method is measured by the following measuring method.
The Drop method is measured in a room at 25 ° C. and a humidity of 50%. About 10 g of the absorbent resin particles are classified into 300 to 500 μm using a JIS standard sieve (JIS Z8801-1: 2006). A polyethylene film having a thickness of 100 μm or more is cut into 3 × 4 cm, and a double-sided tape {Nice Duck NM-40 (manufactured by Nichiban Co., Ltd.)} is attached to one side. Thereafter, the classified absorbent resin particles are sprayed on the upper part of the adhesive surface of the film until the adhesive surface of the film is completely hidden. After spraying, the film is turned over to remove the absorbent resin particles that did not stick. Subsequently, an appropriate amount of Blue No. 1 is added to physiological saline (saline concentration: 0.9% by weight) to obtain a stained physiological saline. Using a 200 μl micropipette {PIPETMAN Model P-200 (manufactured by Gilson)} and a 200 μl microchip, 40 μl of dyed physiological saline is sucked out and dropped onto a film to which absorbent resin particles are adhered. The time is measured with the time of dropping as 0 seconds, and the time (seconds) obtained with the time when the liquid on the absorbent resin particles disappears as the end point is recorded. This measurement is repeated 5 times and the average value (seconds) is defined as the initial wetting time.

<Example 1> Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts (2.15 mol parts), cross-linking agent (b1) {pentaerythritol triallyl ether, Manufactured by Daiso Co., Ltd.} 0.6225 parts (0.0024 mol part), 309.27 parts deionized water, and polyoxyethylene alkylene ether {manufactured by Sanyo Chemical Industries, Ltd., NAROACTY CL-40, carbon number 12-15 , HLB: 9} 31 parts of a 1% aqueous dispersion was 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 0.62 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 an aqueous solution of 2-methyl-N- (2-hydroxyethyl) -propionamide] 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 (1-1). Next, while adding 502.27 parts of this hydrous gel (1-1) with a mincing machine (12VR-400K manufactured by ROYAL), add 118.54 parts of 48.5% aqueous sodium hydroxide solution, mix and mix. A cut gel (1-2) was obtained. Further, the chopped gel (1-2) was dried at 140 ° C. for 65 minutes 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). 4 parts of amino acid and 20 parts of 1% methanol dispersion of amino-modified silicone {Shin-Etsu Chemical Co., Ltd., KF-393} are added by spraying and mixed, and after standing for 30 minutes at 130 ° C., surface crosslinking is performed. Then, 4.00 parts of a 30% potassium alum aqueous solution was spray-added to obtain the absorbent resin particles (D-1) of the present invention. The weight average particle diameter of the absorbent resin particles (D-1) was 390 μm, the water retention amount was 39 g / g, the DW5 minute value was 21 ml / g, and the apparent density was 0.62 g / ml.

<Example 2> "Polyoxyethylene alkylene ether {Sanyo Kasei Kogyo Co., Ltd., NAROACTY CL-40, carbon number 12-15, HLB: 9} 1% aqueous dispersion 31 parts" A hydrogel (2-1) was obtained in the same manner as in Example 1 except that it was changed to “parts”. Next, the hydrated gel (2-1) 502.27 parts was shredded with a minced machine (12 VR-400K manufactured by ROYAL) and 118.54 parts of a 48.5% aqueous sodium hydroxide solution and sucrose stearate {Mitsubishi Chemical Foods Co., Ltd. make, Ryoto sugar ester S-770, HLB: 7} 0.62 part was added and mixed, and the chopped gel (2-2) was obtained. Further, the chopped gel (2-2) was dried at 140 ° C. for 65 minutes 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). 4 parts and 40% aluminum sulfate aqueous solution 4.00 parts were added while being sprayed and mixed, and the mixture was allowed to stand at 130 ° C. for 30 minutes to cross-link the surface to obtain the absorbent resin particles (D-2) of the present invention. Obtained. The weight average particle diameter of the absorbent resin particles (D-2) was 390 μm, the water retention amount was 39 g / g, the DW5 minute value was 27 ml / g, and the apparent density was 0.63 g / ml.

<Example 3> "Polyoxyethylene alkylene ether {31 parts of 1% aqueous dispersion of NAROACTY CL-40, carbon number 12-15, HLB: 8.7} manufactured by Sanyo Chemical Industries, Ltd." Modified silicone {Shin-Etsu Chemical Co., Ltd., KF-352A, HLB: 7} 2% dispersion 31 parts "and" 30% potassium alum aqueous solution 2.00 parts "" 40% aluminum sulfate aqueous solution 4. Absorbent resin particles (D-3) of the present invention were obtained in the same manner as in Example 1 except that it was changed to "00 parts". The weight average particle diameter of the absorbent resin particles (D-3) was 390 μm, the water retention amount was 39 g / g, the DW5 minute value was 28 ml / g, and the apparent density was 0.63 g / ml.

<Example 4> While shredding 502.27 parts of the hydrogel (2-1) obtained in Example 2 with a mincing machine (12VR-400K manufactured by ROYAL), 48.5% aqueous sodium hydroxide solution 118.54. Part and sucrose stearate {Mitsubishi Chemical Foods, Ryoto Sugar Ester S-770, HLB: 7} 0.21 part was added and mixed to obtain a chopped gel (4-2). Further, the chopped gel (4-2) was dried at 140 ° C. for 65 minutes 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). 4 parts and 4.00 parts of a 40% aqueous solution of aluminum sulfate are added while being sprayed and mixed. The mixture is allowed to stand at 130 ° C. for 30 minutes for surface crosslinking, and the absorbent resin particles (D-4) of the present invention are obtained. Obtained. The weight average particle diameter of the absorbent resin particles (D-4) was 390 μm, the water retention amount was 39 g / g, the DW5 minute value was 35 ml / g, and the apparent density was 0.63 g / ml.

<Example 5> While shredding 502.27 parts of the hydrogel (2-1) obtained in Example 2 with a mincing machine (12VR-400K manufactured by ROYAL), 48.5% aqueous sodium hydroxide solution 118.54. Parts and sucrose stearate ester {Mitsubishi Chemical Foods, Ryoto Sugar Ester S-270, HLB: 2} 0.93 parts were added and mixed to obtain a chopped gel (5-2). Further, the chopped gel (5-2) was dried at 140 ° C. for 65 minutes 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). 4 parts and 40% aluminum sulfate aqueous solution 4.00 parts were added while being sprayed and mixed, and the mixture was allowed to stand at 130 ° C. for 30 minutes for surface crosslinking to obtain the absorbent resin particles (D-5) of the present invention. Obtained. The weight average particle diameter of the absorbent resin particles (D-5) was 390 μm, the water retention amount was 39 g / g, the DW5 minute value was 10 ml / g, and the apparent density was 0.63 g / ml.

<Example 6> 48.5% aqueous sodium hydroxide solution 118.54 while chopping 502.27 parts of the hydrogel (2-1) obtained in Example 2 with a mincing machine (12VR-400K manufactured by ROYAL). Parts and sucrose stearate {Mitsubishi Chemical Foods, Ryoto Sugar Ester S-270, HLB: 2} 0.21 part was added and mixed to obtain a chopped gel (6-2). Further, the chopped gel (6-2) was dried at 140 ° C. for 65 minutes 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). 1.5 parts of the above and 2.00 parts of a 40% aqueous solution of aluminum sulfate were added while being sprayed and mixed. ) The weight average particle diameter of the absorbent resin particles (D-6) was 390 μm, the water retention amount was 44 g / g, the DW5 minute value was 22 ml / g, and the apparent density was 0.63 g / ml.

<Example 7> 48.5% aqueous sodium hydroxide solution 118.54 while chopping 502.27 parts of the hydrogel (2-1) obtained in Example 2 with a mincing machine (12VR-400K manufactured by ROYAL). Parts and sucrose stearate {Mitsubishi Chemical Foods, Ryoto Sugar Ester S-270, HLB: 2} 0.21 part was added and mixed to obtain a chopped gel (7-2). Further, the chopped gel (7-2) was dried at 140 ° C. for 65 minutes 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 and 40% aluminum sulfate aqueous solution 4.00 parts were added while being sprayed and mixed, and the mixture was allowed to stand at 130 ° C. for 30 minutes to cross-link the surface to obtain the absorbent resin particles (D-7) of the present invention. Obtained. The weight average particle diameter of the absorbent resin particles (D-7) was 390 μm, the water retention amount was 36 g / g, the DW5 minute value was 20 ml / g, and the apparent density was 0.63 g / ml.

<Comparative Example 1> Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts (2.15 mol parts), cross-linking agent (b1) {pentaerythritol triallyl ether, Made by Daiso Corporation} 0.6225 parts (0.0024 mol parts) 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 performed at 90 ± 2 ° C. for about 5 hours to obtain a hydrogel (3-1). Next, while adding 502.27 parts of this hydrous gel (3-1) with a mincing machine (12VR-400K manufactured by ROYAL), add 48.5% sodium hydroxide aqueous solution 118.54 parts, and mix. A sheared gel (3-2) was obtained. Further, the chopped gel (3-2) was dried at 140 ° C. for 75 minutes 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 (H1). The weight average particle diameter of the absorbent resin particles (H1) was 400 μm, the water retention amount was 36 g / g, the DW5 minute value was 24 ml / g, and the apparent density was 0.62 g / ml.

Comparative Example 2 Comparative absorbent resin particles (H2) were obtained according to Example 1 of JP-A-2007-291351. The weight average particle diameter of the absorbent resin particles (H2) was 400 μm, the water retention amount was 51 g / g, the DW5 minute value was 8 ml / g, and the apparent density was 0.70 g / ml.

<Comparative example 3> "Sucrose stearate {Mitsubishi Chemical Foods Co., Ltd., Ryoto Sugar Ester S-770, HLB: 7} 0.62 parts" was replaced with "Polyether-modified silicone {Shin-Etsu Chemical Co., Ltd., KF-352A, HLB: 7} 2% dispersion 31 parts ”, except that“ 30% potassium alum aqueous solution 4.00 parts ”was not added, and the absorbency for comparison was the same as in Example 2. Resin particles (H3) were obtained. The weight average particle diameter of the absorbent resin particles (H3) was 400 μm, the water retention amount was 39 g / g, the DW5 minute value was 26 ml / g, and the apparent density was 0.63 g / ml.

<Comparative example 4> "Sucrose stearate {Mitsubishi Chemical Foods Co., Ltd., Ryoto Sugar Ester S-770, HLB: 7} 0.62 parts" was replaced with "Polyether-modified silicone {Shin-Etsu Chemical Co., Ltd., Absorbent resin particles for comparison (H4) were obtained in the same manner as in Example 2 except that the composition was changed to 31 parts of a 2% dispersion of KF-354L, HLB: 16}. The weight average particle diameter of the absorbent resin particles (H4) was 390 μm, the water retention amount was 39 g / g, the DW5 minute value was 45 ml / g, and the apparent density was 0.57 g / ml.

  As can be seen from Table 1, the absorbent resin particles (Examples 1 to 7) of the present invention have an appropriate absorption rate pattern as compared with the absorbent resin particles of Comparative Examples 1 to 4. That is, since the absorbent resin particles of the examples have an absorption amount after 5 minutes based on the demand wettability test method and an initial wetting time based on the drop test method, the absorption rate is within a specific range in the present invention. It has an absorption rate pattern that is slow from middle to late. At the same time, the water retention amount of 0.9% by weight physiological saline is in a specific range and has high water retention.

  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 7 and Comparative Examples 1 to 4, absorbent articles (paper diapers) were prepared as follows, and the surface dryness value by the SDME method was evaluated. Are shown in Table 2.

<Preparation 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. Thereafter, this mixture was uniformly laminated on an acrylic plate (thickness 4 mm) so as to have a basis weight of about 700 g / m ² and pressed at a pressure of 5 kg / cm ² for 30 seconds to obtain an 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) in which the detector of the SDME (Surface Dryness Measurement Equipment) tester (manufactured by WK system) was sufficiently moistened. %, Sodium chloride 0.8% by weight, and deionized water 99.09% by weight). }, 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 set to 1-1 {center}, 1-2 {left}, and 1-3 {right}, respectively. Subsequently, 5 minutes after the end of the measurement, a metal ring was set in the center of the paper diaper again, and 80 ml of artificial urine was injected. When the artificial urine was absorbed, the metal ring was immediately removed. Thereafter, every 10 minutes after the start of artificial urine injection, the above injection operation was repeated, and artificial urine was injected five times in total including the first injection. Thereafter, when the artificial urine has been absorbed, the metal ring is immediately removed, and the surface dryness value is measured for 5 minutes using the SDME detector as in the first time. 5-1 {center}, 5-2 {left} 5-3 {right}. The artificial urine, measurement atmosphere, and standing atmosphere were 25 ± 5 ° C. and 65 ± 10% RH.

As apparent from Table 2, it can be seen that the surface dryness value after repeatedly injecting artificial urine in the examples shows a sufficiently high value. Moreover, the deviation of the surface dryness value due to the position of the paper diaper is small. On the other hand, in the comparative example, the first surface dryness value was not much different from the example, but the fifth surface dryness value was greatly reduced. Moreover, the deviation of the surface dryness value depending on the position of the paper diaper is large. From these, it was clear that in Examples, even if urination was repeated for a long time, there was little bias in absorption rate and absorption amount due to the site of the absorber, and excellent absorption performance (absorption amount and absorption rate) could be exhibited. .

  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.

DESCRIPTION OF SYMBOLS 1 Rubber stopper 2 Bullet part 3 Saline 4 Absorbent resin particle 5 Plain weave nylon mesh 6 Measuring stand 7 Cock 8 Cock 9 Intake pipe

Claims (12)

Cross-linked polymer (A) and HLB of monomer composition comprising water-soluble vinyl monomer (a1) and / or vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis, and cross-linking agent (b) Absorbent resin particles containing 0.01 to 0.5% of at least one surfactant (B) having a value of 10 or less based on the weight of the crosslinked polymer (A),
(I) Absorption after 5 minutes based on Demand Wettability test method is 10 to 35 g / g,
(Ii) 0.9% by weight physiological saline has a water retention amount of 36 to 50 g / g per unit weight,
(Iii) Gel elastic modulus is 1.8 to 3.0 kN / m ² ,
(Iv) an initial wetting time based on the Drop test method of 5 to 20 seconds,
Absorbent resin particles characterized by being.   The absorptive resin particle of Claim 1 in which the said surfactant (B) has a C8-C30 hydrocarbon group.   The absorbent resin particle according to claim 1 or 2, wherein the surfactant (B) is a long-chain fatty acid ester.   The absorbent resin particle according to any one of claims 1 to 3, wherein the surfactant (B) has a polysiloxane structure. Cross-linked polymer (A) and HLB of monomer composition comprising water-soluble vinyl monomer (a1) and / or vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis, and cross-linking agent (b) Containing 0.01 to 0.5% of at least one surfactant (B) having a value of 10 or less based on the weight of the crosslinked polymer (A),
(I) Absorption after 5 minutes based on Demand Wettability test method is 10 to 35 g / g,
(Ii) 0.9% by weight physiological saline has a water retention amount of 36 to 50 g / g per unit weight,
(Iii) Gel elastic modulus is 1.8 to 3.0 kN / m ² ,
(Iv) an initial wetting time based on the Drop test method of 5 to 20 seconds,
A method for producing absorbent resin particles,
Including a polymerization step of the monomer composition and a drying step of the hydrogel of the crosslinked polymer (A), after the polymerization step is started and before the polymerization step is completed, or after the polymerization step is completed. A step of mixing 0.01 to 0.5% of the surfactant (B) with the hydrogel of the crosslinked polymer (A) based on the weight of the crosslinked polymer (A) before the completion of the drying step; The manufacturing method of the absorbent resin particle containing this.   The production method according to claim 5, wherein the surfactant (B) has a hydrocarbon group having 8 to 30 carbon atoms.   The production method according to claim 5 or 6, wherein the surfactant (B) has a polysiloxane structure.   The production method according to claim 5, wherein the step of mixing the surfactant (B) is performed after completion of the polymerization step and before completion of the drying step.   The production according to any one of claims 5 to 8, comprising a step of mixing 0.01 to 5.0% of the polyvalent metal salt (e) based on the weight of the crosslinked polymer (A) after the drying step. Method.   The production method according to claim 9, wherein the polyvalent metal salt is an aluminum salt.   The absorber containing the absorptive resin particle of Claims 1-4.   An absorbent article comprising the absorbent body according to claim 11.

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