JP2005154758A - Particulate water-absorbing resin composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particulate water-absorbing resin composition and a method for producing the same, in which both “liquid permeability” and “liquid sucking property” of a water-absorbing resin, which have conventionally been contradictory properties, are improved.
The first particulate water-absorbing resin composition of the present invention is a particulate material mainly composed of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. A water-absorbent resin composition, wherein the particle size of the composition is less than 850 μm, and particles of 150 μm or more are 90% by weight or more of the whole, and contain at least a polyol (B) having a valence of 4 or more on the surface. Features.
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Description

  The present invention relates to a particulate water-absorbing resin composition and a method for producing the same. More specifically, the present invention relates to a particulate water-absorbent resin composition having a small amount of fine powder and excellent liquid permeability and liquid uptake characteristics, and a method for producing the same.

In recent years, water-absorbent resins have been widely used as main constituent materials in hygiene materials (absorbent articles) such as disposable diapers, sanitary napkins, incontinence pads, etc., for the purpose of absorbing bodily fluids (urine and blood). Yes.
Examples of the water-absorbing resin include a crosslinked polyacrylic acid partially neutralized product, a hydrolyzate of starch-acrylonitrile graft polymer, a neutralized product of starch-acrylic acid graft polymer, and a vinyl acetate-acrylate ester copolymer. Saponified product of polymer, crosslinked carboxymethyl cellulose, hydrolyzate of acrylonitrile copolymer or acrylamide copolymer or cross-linked product thereof, crosslinked product of cationic monomer, crosslinked isobutylene-maleic acid copolymer, 2-acrylamide-2 -A cross-linked product of methylpropanesulfonic acid and acrylic acid is known.

Conventionally, the water-absorbing properties desired for the above water-absorbing resin include a high water absorption ratio when in contact with an aqueous liquid such as a body fluid, an excellent absorption rate, liquid permeability, gel strength of a swollen gel, and a group containing an aqueous liquid. The amount of suction that sucks up water from the material is advocated.
In recent years, sanitary materials such as disposable diapers have become highly functional and thin, and by increasing the amount of water-absorbent resin used (g) and the proportion used (% by weight / ratio in the absorbent), the amount absorbed can be prevented and leakage can be prevented. The thickness is reduced while aiming at. The sanitary material with increased water-absorbing resin is a preferable direction from the standpoint of simply storing the liquid, but in actual use of the diaper, the water-absorbing resin swells by absorbing water and becomes a soft gel, so-called diapers. There was a problem that gel blocking occurred, causing a decrease in absorption and leakage.

Therefore, attention has recently been paid to the liquid permeability of water-absorbent resins, and for example, water-absorbent resins with improved liquid permeability have been reported (see, for example, Patent Documents 1 to 7). However, when trying to develop high liquid permeability with a conventional water-absorbent resin, it is necessary to increase the particle size and the gel gap in order to increase the liquid permeability. The resin generally has a problem that the liquid sucking property is lowered.
It is also known that the particle size distribution contributes greatly to liquid permeability, and a technique for controlling the particle size of the water-absorbent resin has also been known (see, for example, Patent Documents 8 to 11). There was a problem that the characteristics deteriorated. The liquid uptake characteristic is an important characteristic conventionally known (see, for example, Patent Documents 12 and 13), but the particulate water absorption in which both “liquid permeability” and “liquid uptake characteristic” of the water absorbent resin are improved. It was very difficult to obtain a functional resin composition because of their contradictory physical properties.

The “liquid permeability” in the present invention is the liquid permeability of the particulate water-absorbent resin composition after water absorption under pressure, that is, the liquid permeability under pressure between the swollen gel particles. It is a liquid-permeable model in diapers. In addition, the “liquid uptake characteristic” in the present invention is the liquid uptake or liquid diffusion performance when the particulate water-absorbent resin composition before water absorption absorbs water, that is, the speed at which the dry particles before water uptake up the liquid, or This is the rate at which the liquid diffuses into the particulate water-absorbent resin composition, and is a liquid diffusion model in a diaper during actual use that was first discovered in the present invention.
International Publication No. 95/26209 Pamphlet EP 0951913 European Patent No. 0640330 International Publication No. 2001/066066 Pamphlet International Publication No. 98/47454 Pamphlet US Pat. No. 6,414,214 US Publication No. 2002/128618 US Pat. No. 5,051,259 EP 0349240 European Patent No. 0579764 European Patent No. 0629411 European Patent No. 053002 US Pat. No. 6,399,668

  Accordingly, the problem to be solved by the present invention is to provide a particulate water-absorbing resin composition that has improved both the “liquid permeability” and “liquid uptake characteristics” of a water-absorbing resin, which has conventionally been a contradictory physical property. Thus, an object of the present invention is to provide a novel particulate water-absorbent resin composition used for paper diapers and sanitary napkins, and a method for producing the same. An object of the present invention is to provide a particulate water-absorbing resin composition suitable for a high-concentration absorber, that is, the concentration (weight ratio) of the particulate water-absorbing resin composition in an absorbent body (other name: core) of a paper diaper or sanitary napkin. An object of the present invention is to provide a particulate water-absorbing resin composition suitable for a high-absorber.

  The present inventor has intensively studied to solve the above problems. As a result, (1) a particulate water-absorbing resin composition controlled to a specific particle size, and when a tetravalent or higher polyol exists on the surface, (2) a particulate water-absorbing resin composition, When a polyol having a valence of 4 or more and a polycation having a valence of 3 or more are present on the surface, (3) a particulate water-absorbing resin composition controlled to a specific particle size, wherein the liquid diffusion rate (LDV) and water absorption without pressure When a specific relationship is established with the magnification (CRC), or (4) a particulate water-absorbent resin composition controlled to a specific particle size, which is obtained by measuring the surface OH / It has been found that when the C ratio is in a specific range, a particulate water-absorbing resin composition having excellent liquid permeability and liquid uptake characteristics is obtained. In addition, such a particulate water-absorbing resin composition having excellent liquid permeability and liquid uptake characteristics can be easily produced by mixing a water-absorbing resin controlled to a specific particle size with a tetravalent or higher polyol. I also found. The present invention has been completed as described above.

That is, the particulate water-absorbing resin composition of the present invention is a particulate water-absorbing resin composition mainly composed of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. And the particle size of the said composition is less than 850 micrometers, and the particle | grains of 150 micrometers or more are 90 weight% or more of the whole, and tetravalent or more polyol (B) is contained in the surface at least.
Another particulate water-absorbing resin composition of the present invention is a particulate water-absorbing resin composition mainly composed of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. It is characterized in that the polyol (B) having a valence of 4 or more and a polycation having a valence of 3 or more are contained at least on the surface.

Another particulate water-absorbing resin composition of the present invention is a particulate water-absorbing resin composition mainly composed of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. The particle size of the composition is 90% by weight or more of particles less than 850 μm and 150 μm or more, and the liquid diffusion rate (LDV) (mm / s)> − 0.186 × absorption capacity without pressure (CRC) (g / g) +5.75 (however, LDV> 0.10 (mm / s)) is satisfied.
Another particulate water-absorbing resin composition of the present invention is a particulate water-absorbing resin composition mainly composed of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. The particle size of the composition is 90% by weight or more of particles of less than 850 μm and 150 μm or more, and the OH / C ratio of the surface determined based on photoelectron spectroscopic analysis is 0.03 to 0.15. It is characterized by being.

  The method for producing the particulate water-absorbing resin composition of the present invention comprises a particulate water-absorbing resin composition comprising as a main component a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. The water-absorbent resin (A) is composed of 90% by weight or more of particles having a particle size of less than 850 μm and 150 μm or more. Furthermore, the water-absorbent resin (A) and a tetravalent or higher polyol ( B) is mixed.

  According to the present invention, a particulate water-absorbent resin composition having a small amount of fine powder and having improved both the “liquid permeability” and the “liquid suction property” of a water-absorbent resin, which has conventionally been a contradictory physical property, and a method for producing the same Can be provided.

Hereinafter, the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and modifications other than the following examples can be made as appropriate without departing from the spirit of the present invention.
In the present invention, “weight” is treated as a synonym for “mass”, and “weight%” is treated as a synonym for “mass%”.
(1) Water-absorbing resin The water-absorbing resin in the present invention is a water-swellable water-insoluble cross-linked polymer that can form a hydrogel. For example, water-swelling property is essential weight 5 in ion-exchanged water. More than double, preferably 50 to 1000 times, that absorbs a large amount of water. Water-insoluble means that the non-crosslinked water-soluble component (water-soluble polymer) in the water-absorbent resin is preferably 0 to 50% by weight More preferably, it is 25% by weight or less, more preferably 20% by weight or less, further preferably 15% by weight or less, particularly preferably 10% by weight or less. In addition, these measuring methods are prescribed | regulated in the Example mentioned later.

In the present invention, the water-absorbent resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer is preferably used as the water-absorbent resin from the viewpoint of liquid permeability and liquid uptake characteristics.
As the acid group-containing unsaturated monomer, a monomer that becomes an acid group after polymerization by hydrolysis after polymerization, such as acrylonitrile, is also an acid group-containing unsaturated monomer in the present invention. Sometimes acid group-containing unsaturated monomers containing acid groups are used.
As the water-absorbing resin in the present invention, polyacrylic acid partially neutralized polymer, hydrolyzate of starch-acrylonitrile graft polymer, starch-acrylic acid graft polymer, saponified product of vinyl acetate-acrylic ester copolymer , One or more of hydrolyzate of acrylonitrile copolymer or acrylamide copolymer, cross-linked product thereof, carboxyl group-containing cross-linked polyvinyl alcohol modified product, cross-linked isobutylene-maleic anhydride copolymer, etc. However, a partially neutralized polyacrylic acid polymer obtained by polymerizing and crosslinking a monomer mainly composed of acrylic acid and / or a salt thereof (neutralized product) is preferably used.

  When acrylic acid and / or a salt thereof are the main components, other monomers may be used in combination. Examples of other monomers used in combination include methacrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, vinyl sulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acryloxyalkanesulfonic acid and its alkali metal salts, ammonium salts, N-vinyl-2-pyrrolidone, N-vinylacetamide, (meth) acrylamide, N -Isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, isobutylene, lauryl (meth) acrylate, etc. Water soluble or hydrophobic Unsaturated monomers, and the like.

When a monomer other than acrylic acid (salt) is used in the present invention, the monomer other than acrylic acid (salt) is based on the total amount of acrylic acid and / or its salt used as the main component. , Preferably 0 to 30 mol%, more preferably 0 to 10 mol%, and the absorption characteristics of the finally obtained water absorbent resin (composition) are further improved, and the water absorbent resin (composition) ) Can be obtained even more inexpensively.
The water-absorbent resin must have a crosslinked structure, but may be of a self-crosslinking type that does not use a crosslinking agent, but two or more polymerizable unsaturated groups or two or more reactions in one molecule. Those obtained by copolymerizing or reacting a crosslinking agent having a functional group (an internal crosslinking agent for a water-absorbent resin) are more preferred.

  Specific examples of these internal crosslinking agents include, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri ( (Meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, tri Allylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene Glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, ethylene carbonate, propylene carbonate, polyethylenimine, and glycidyl (meth) acrylate.

These internal cross-linking agents may be used alone or in combination of two or more. These internal cross-linking agents may be added to the reaction system all at once or in divided portions. In the case of using at least one kind or two or more kinds of internal crosslinking agents, two or more polymerizable unsaturated groups are taken into consideration in consideration of the absorption characteristics of the finally obtained water absorbent resin or water absorbent resin composition. It is preferable to use a compound having an essential component during polymerization.
The amount of these internal crosslinking agents to be used is preferably 0.001 to 2 mol%, more preferably 0.005 to 1 mol%, and still more preferably 0.005 to 0.005 mol% with respect to the monomer (excluding the crosslinking agent). 0.5 mol%, more preferably 0.01 to 0.5 mol%, more preferably 0.01 to 0.2 mol%, particularly preferably 0.03 to 0.2 mol%, most preferably 0.00. It is set within the range of 03 to 0.15 mol%. When the amount of the internal cross-linking agent used is less than 0.001 mol% and more than 2 mol%, it is sufficient that the water-soluble component is increased or the water absorption ratio is decreased. May not be obtained.

When a crosslinked structure is introduced into the polymer using the internal cross-linking agent, the internal cross-linking agent is added to the reaction system before, during or after the polymerization of the monomer, or after the polymerization or neutralization. What should I do?
When polymerizing the above-mentioned monomer to obtain the water-absorbent resin used in the present invention, bulk polymerization or precipitation polymerization can be performed. However, performance and ease of control of polymerization, and swelling gel From the viewpoint of the absorption characteristics, it is preferable to perform aqueous solution polymerization or reverse phase suspension polymerization by using the monomer as an aqueous solution.
When the monomer is an aqueous solution, the concentration of the monomer in the aqueous solution (hereinafter referred to as the monomer aqueous solution) is determined by the temperature of the aqueous solution and the monomer, and is not particularly limited. It is preferably within the range of -70% by weight, and more preferably within the range of 20-60% by weight. Moreover, when performing the said aqueous solution polymerization, you may use together solvents other than water as needed, and the kind of solvent used together is not specifically limited.

  Reverse phase suspension polymerization is a polymerization method in which an aqueous monomer solution is suspended in a hydrophobic organic solvent. For example, U.S. Pat. Nos. 4,093,764, 4,367,323, 4,446,261, U.S. Pat. Nos. 4,683,274 and 5,244,735. The aqueous solution polymerization is a method of polymerizing an aqueous monomer solution without using a dispersion solvent. For example, U.S. Pat. Nos. 4,462,001, 4,873,299, 4,286,082, 4,973,632, and 4,985,518. Specification, US Pat. No. 5,124,416, US Pat. No. 5,250,640, US Pat. No. 5,264,495, US Pat. No. 5,145,906, US Pat. No. 5,380,808, US Pat. No. 0922717, and other European patents. Monomers and initiators exemplified in these polymerization methods can also be applied in the present invention.

When starting the polymerization, for example, potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-amidinopropane) dihydrochloride, etc. A radical polymerization initiator or a photopolymerization initiator such as 2-hydroxy-2-methyl-1-phenyl-propan-1-one can be used. The amount of these polymerization initiators used is usually from 0.001 to 2 mol%, preferably from 0.01 to 0.1 mol% (based on the total monomers) in view of physical properties.
After the polymerization, it is usually a water-containing gel-like cross-linked polymer, which is dried as necessary, and is usually pulverized before and / or after drying to obtain a water-absorbing resin. Moreover, drying is normally performed in the temperature range of 60 to 250 degreeC, Preferably it is 100 to 220 degreeC, More preferably, it is 120 to 200 degreeC. The drying time depends on the surface area of the polymer, the moisture content, and the type of dryer, and is selected to achieve the desired moisture content.

  The water content of the water-absorbent resin (composition) that can be used in the present invention (specified by the amount of water contained in the water-absorbent resin or water-absorbent resin composition / measured by loss on drying at 105 ° C. for 3 hours) is particularly limited. However, it is a powder that exhibits fluidity even at room temperature in view of the physical properties of the resulting water-absorbent resin composition, and the water content is preferably 0.1 to 40% by weight, more preferably 0.2 to 30% by weight, even more preferably. Is in a powder state of 0.3 to 15% by weight, particularly preferably 0.5 to 10% by weight, and a preferable particle diameter of the water absorbent resin (composition) will be described later. When the water content of the water-absorbent resin is more than 40% by weight, the water absorption ratio is lowered, and when the water content is less than 0.1% by weight, the liquid suction property may be lowered.

The water-absorbent resin obtained by the above method has an absorption capacity under non-pressurization (CRC) with respect to physiological saline under no pressure (measurement method is defined in Examples described later), preferably 8 to 50 g / g, More preferably, it is 10-50 g / g, More preferably, it is 20-40 g / g, Most preferably, it is the range of 25-35 g / g. The physical properties such as the absorption capacity without load (CRC) are appropriately adjusted according to the purpose. However, when it is less than 8 g / g or more than 50 g / g, the water absorbent resin composition of the present invention is obtained. There is a risk of disappearing.
(2) Shape and particle diameter of water-absorbent resin and particulate water-absorbent resin composition The water-absorbent resin in the present invention and the particulate water-absorbent resin composition obtained in the present invention have a specific particle size for achieving the present invention. Preferably, particles of less than 850 μm and 150 μm or more (specified by sieve classification: JIS Z8801-1: 2000) are 90% by weight or more of the whole, more preferably particles of less than 850 μm and 150 μm or more of the whole The amount is 95% by weight or more, and more preferably less than 850 μm and 150 μm or more is 98% by weight or more of the whole. Moreover, it is preferable that the particle | grains of 300 micrometers or more are 60 weight% or more of the whole.

In addition, the whole here means the whole particulate water-absorbing resin composition.
Further, the particle size of 250 μm or more is preferably 70% by weight or more (upper limit 100% by weight), more preferably 75% by weight or more. The weight average particle diameter (D50) of the water absorbent resin or particulate water absorbent resin composition is preferably 200 to 600 μm, more preferably 300 to 600 μm, still more preferably 300 to 500 μm, and particularly preferably 350 to 450 μm. Is done. The particle diameter of the water-absorbent resin or particulate water-absorbent resin composition may be adjusted by granulation if necessary. (Hereinafter, the water absorbent resin in the present invention and the particulate water absorbent resin composition obtained in the present invention may be collectively referred to as a water absorbent resin (composition) ^).

The particle shape of the water-absorbent resin or particulate water-absorbent resin composition thus obtained is not particularly limited, such as spherical shape, crushed shape, irregular shape, etc., but the irregular crushed shape obtained through the pulverization step The shape can be preferably used. Further, the bulk specific gravity (specified in JIS K-3362: 1998) is preferably 0.40 to 0.80 g / ml, more preferably 0.50 to 0.75 g, from the balance between liquid permeability and liquid uptake characteristics. / Ml, more preferably in the range of 0.60 to 0.73 g / ml.
In the water absorbent resin and particulate water absorbent resin composition of the present invention, the logarithmic standard deviation (σζ) of the particle size distribution is preferably 0.25 to 0.45, more preferably 0.30 to 0.40. is there. The smaller the logarithmic standard deviation (σζ) of the particle size distribution is, the smaller the particle size distribution is. However, in the water absorbent resin and the particulate water absorbent resin composition in the present invention, the particle size distribution is not simply narrow but has a certain extent. It becomes important. When the logarithmic standard deviation (σζ) is less than 0.25, not only the target performance may not be obtained, but also the productivity is significantly reduced. If it exceeds 0.45, the particle size distribution is too wide, and the target performance may not be obtained.

The “particles of 300 μm or more” referred to in the present invention refers to particles remaining on a JIS standard sieve having a 300 μm opening measured after classification by the sieve classification method described later. Similarly, “particles of less than 300 μm” refer to particles that have been classified by a classification method described later and passed through a mesh having a mesh opening of 300 μm. The same applies to the sizes of the other openings. Further, when 50% by weight of the particles are classified with a mesh having an opening of 300 μm, the weight average particle diameter (D50) is 300 μm.
The particle size may be adjusted as appropriate by polymerization, gel pulverization (other name: gel fragmentation), drying, pulverization, classification, granulation, mixing of a plurality of water-absorbing resin particles, and the like.

(3) Surface cross-linking of water-absorbing resin The water-absorbing resin used in the particulate water-absorbing resin composition of the present invention may be obtained by the above cross-linking polymerization and drying. ) Is preferred.
There are various crosslinking agents for performing the surface crosslinking, but from the viewpoint of physical properties, generally, a polyhydric alcohol compound, an epoxy compound, a polyvalent amine compound or a condensate thereof with a haloepoxy compound, Oxazoline compounds, mono-, di-, or polyoxazolidinone compounds, polyvalent metal salts, alkylene carbonate compounds, and the like are used.
Specific examples of the surface cross-linking agent used in the present invention include US Pat. No. 6,228,930, US Pat. No. 6,071,976, US Pat. No. 6,254,990, and the like. For example, mono, di, tri, tetra or polyethylene glycol, 1,2-propylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin Polyglycerin, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, etc. Polyhydric alcohol compounds, epoxy compounds such as ethylene glycol diglycidyl ether and glycidol, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, polyamide polyamine Polyhalogen amine compounds; haloepoxy compounds such as epichlorohydrin, epibromohydrin, α-methylepichlorohydrin; condensates of the polyvalent amine compounds with the haloepoxy compounds; oxazolidinone compounds such as 2-oxazolidinone ( US65559239); Oxetane compounds; Cyclic urea compounds; Alkylene carbonate compounds such as ethylene carbonate (US5409771) and the like, but are not particularly limited. In order to maximize the effect of the present invention, it is preferable to use at least one selected from oxetane compounds (US2002 / 72471), cyclic urea compounds, and polyhydric alcohols among these crosslinking agents, more preferably carbon. At least one selected from oxetane compounds having 2 to 10 carbon atoms or polyhydric alcohols, more preferably polyhydric alcohols having 3 to 8 carbon atoms are used.

The amount of the surface cross-linking agent used depends on the compounds used and combinations thereof, but is preferably in the range of 0.001 to 10 parts by weight with respect to 100 parts by weight of the water-absorbent resin, 0.01 parts by weight More preferably within the range of ˜5 parts by weight.
In the present invention, water is preferably used for surface crosslinking. At this time, the amount of water used depends on the water content of the water-absorbing resin used, but is usually preferably 0.5 to 20 parts by weight, more preferably 0.5 to 100 parts by weight of the water-absorbing resin. It is the range of -10 weight part. Moreover, in this invention, you may use a hydrophilic organic solvent other than water, Preferably it is 0-10 weight part with respect to 100 weight part of water absorbing resin, More preferably, it is 0-5 weight part, More preferably, it is 0-0. The range is 3 parts by weight.

Furthermore, in the present invention, among various mixing methods, a method in which water and / or a hydrophilic organic solvent is mixed in advance, if necessary, and then the aqueous solution is sprayed or mixed dropwise onto the water-absorbent resin is preferable. Is more preferable. The size of the droplets to be sprayed is preferably 1 to 300 μm and more preferably 10 to 200 μm in terms of average particle diameter. In mixing, a water-insoluble fine particle powder and a surfactant may be allowed to coexist within a range not impeding the effects of the present invention.
The water-absorbent resin after mixing with the crosslinking agent is preferably heat-treated. As conditions for performing the above heat treatment, the heating temperature (specified by the heating medium temperature) is preferably 100 to 250 ° C., more preferably 150 to 250 ° C., and the heating time is preferably 1 minute to 2 hours. Range. Preferable examples of the combination of temperature and time are 0.1 to 1.5 hours at 180 ° C. and 0.1 to 1 hour at 200 ° C.

In carrying out the surface crosslinking of the present invention, the following tetravalent or higher polyol (B) is preferably used or used in combination.
(4) Polyhydric or higher polyol In the particulate water-absorbing resin composition according to the present invention, it is preferable that a tetravalent or higher polyol (B) is an essential component. As the polyol (B) having 4 or more valences, 4 to 30 valences, 4 to 20 valences, and further 4 to 10 valence polyols are preferably used, and the carbon number thereof is 0.5 to 2 times the valence of the polyol. Is more preferable, and it is more preferably controlled within a range of 1.0 to 1.5 times. When the polyol (B) has a valence of less than 4, the liquid wicking property is poorly improved, and when the valence exceeds 30, when used for surface cross-linking, the absorption capacity under pressure (AAP described later), etc. The improvement effect is low. Furthermore, when the number of carbon atoms in the polyol is out of the above range, the improvement of the liquid suction property of the present invention may be poor.

  Examples of the polyol (B) having a valence of 4 or more preferably used in the present invention include polyglycerin, polyhydric alcohols such as pentaerythritol, monosaccharide alcohols such as meso-erythritol, xylitol, D (+)-xylose, D-sorbitol. Or optical isomers of monosaccharide alcohols, mixtures of optical isomers of monosaccharide alcohols, disaccharide alcohols such as maltitol and lactitol, optical isomers of disaccharide alcohols, or Examples thereof include a mixture of optical isomers of disaccharide alcohols, gluconic acid or a salt thereof such as sodium. These tetravalent or higher polyols (B) may be partially modified within a range in which four or more free hydroxyl groups remain. From the viewpoints of hydrophilicity, physical properties, safety, and coloring after heat treatment, the polyol (B) preferably has an unmodified hydroxyl group, more preferably an unmodified sugar alcohol, a sugar having a disaccharide or less. Alcohols are used, particularly preferably monosaccharide alcohols, most preferably D-sorbitol.

The amount of the tetravalent or higher polyol (B) used is preferably 0.01 to 20% by weight, more preferably 0.1 to 10% by weight, and still more preferably 0.1% with respect to the water absorbent resin (A). It is ˜5% by weight, particularly preferably in the range of 0.1 to 1% by weight. These polyols (B) can be extracted from the particulate water-absorbing resin composition and quantified by liquid chromatography, gas chromatography, or the like.
In addition, when all the hydroxyl groups in the polyol (B) react with the acid groups of the water-absorbent resin and disappear, it is difficult to obtain the effect of improving the liquid suction property of the present invention. It is preferable that the hydroxyl group of exists in the surface of a water absorbing resin. Examples of such free hydroxy groups include unreacted polyol (B) and polyol-water absorbent resin in which only a part of the hydroxyl group of polyol (B) reacts with and binds to the water absorbent resin.

  The method for adding the tetravalent or higher polyol (B) may be performed in accordance with the method for adding the surface cross-linking agent in the surface cross-linking of the water-absorbent resin (2). Specifically, the tetravalent or higher valent polyol (B) may be added dropwise or sprayed to the water absorbent resin (A) as a solution, particularly as an aqueous solution, if necessary. At that time, it is preferable to use the above-described surface cross-linking agent (C) other than the polyol (B) having a valence of 4 or more, if necessary, more preferably a polyhydric alcohol, and a trivalent or less of 3 to 8 carbon atoms. More preferably, a polyol is used in combination. The amount of the surface cross-linking agent (C) other than the polyol (B) is preferably 0 to 8 parts by weight, more preferably 0.01 to 5 parts by weight, still more preferably 0. It is the range of 1-3 weight part.

  In the particulate water-absorbing resin composition of the present invention comprising a water-absorbing resin (A) having a specific particle size and a polyol (B) having a specific particle size and having a valence of 4, the polyol (B) having a valence of 4 or more is a water content after polymerization. It may be simply added to the gel-like crosslinked polymer, the crosslinked polymer after drying, or the particulate water-absorbing resin after surface crosslinking, or may be used or used in combination with the surface-crosslinking agent of the water-absorbing resin. Preferably, a polyol (B) having a valence of 4 or more is used or used in combination with the surface cross-linking agent of the water-absorbent resin, and is partially reacted with the water-absorbent resin. Among the polyols having a valence of 4 or more, sugar alcohols, particularly D-sorbitol, is very safe and is preferably used or used in combination with the surface cross-linking agent of the water-absorbent resin.

That is, the method for producing the particulate water-absorbing resin composition of the present invention comprises a particulate water-absorbing resin mainly comprising a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. It is a manufacturing method of a resin composition, Comprising: The said water absorbing resin (A) is less than 850 micrometers, and the particle | grains of 150 micrometers or more are 90 weight% or more of the whole, Furthermore, the said water absorbing resin (A) and tetravalent or more The polyol (B) is mixed.
In order to partially react the polyol (B), the reaction temperature and time are appropriately adjusted, and if necessary, the reaction between the polyol (B) and the water absorbent resin (A) is controlled by forced cooling after the reaction. That's fine. The particulate water-absorbent resin composition of the present invention is preferably obtained by reacting only a part of the polyol (B) having a valence of 4 or more with the water-absorbent resin under such control by surface crosslinking (stopping the reaction in the middle). It is done. Forcibly cooling after the reaction, the temperature (material temperature) of the water-absorbent resin after the reaction is preferably 100 ° C. or less (lower limit is preferably 5 ° C. or more) within 40 minutes, more preferably 100 ° C. or less within 30 minutes. More preferably, it is cooled to 100 ° C. or less within 10 minutes, particularly preferably to 100 ° C. or less within 5 minutes. That is, in achieving the present invention, the added tetravalent or higher polyol (B) or its hydroxy group is preferably 10 to 90%, more preferably 20 to 80%, and still more preferably 30 to 70%. It is preferable to heat-treat so that it may remain in a water-absorbent resin composition.

  The residual amount (total amount) and the residual rate (%) can be easily obtained by extracting from the particulate water-absorbent resin composition and quantifying it. In the present invention, since the hydroxyl group derived from the polyol (B) present on the surface of the particulate water-absorbent resin is important, only a part of the hydroxyl group of the unreacted polyol (B) or polyol (B) absorbs water. The hydroxy group in the particulate water-absorbing resin composition part that reacts and binds with the reactive resin may be determined by titration, or the hydroxy group that reacts and binds using XPS (X-ray Photoelectron Spectroscopy) or unreacted hydroxy group You may check. Moreover, you may measure the amount of unreacted polyol (B) by the liquid chromatography mentioned later.

(5) Particulate water-absorbing resin composition The particulate water-absorbing resin composition of the present invention is mainly composed of a water-absorbing resin (A) having a cross-linked structure obtained by polymerizing an acid group-containing unsaturated monomer. In the particulate water-absorbing resin composition, the particle size of the composition is 90% by weight or more (upper limit is 100% by weight) of particles of less than 850 μm and 150 μm or more.
The water absorbent resin (A) in the composition is preferably 80% by weight or more (the upper limit is 100% by weight or less), more preferably 90% by weight or more, still more preferably 95% by weight or more, and particularly preferably 98% by weight. That's it.

The particle size of the composition is preferably 70% by weight or more (upper limit 100% by weight) of particles having a size of 250 μm or more.
The particulate water-absorbing resin composition of the present invention preferably contains at least the surface of a tetravalent or higher polyol (B). By containing at least the surface of the polyol (B) having a valence of 4 or more, OH groups that have not changed in form due to a crosslinking reaction or the like remain, so that hydrophilicity is exhibited and the wettability of the particulate water-absorbent resin composition. Is more effective. The tetravalent or higher polyol (B) is as described above.
That is, the first particulate water-absorbing resin composition of the present invention is a particulate water-absorbing resin composed mainly of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. It is a resin composition, Comprising: The particle size of the said composition is less than 850 micrometers, and the particle | grains 150 micrometers or more are 90 weight% or more of the whole, and contains the polyol (B) more than tetravalence at least on the surface.

The particulate water-absorbing resin composition of the present invention preferably contains at least the surface of the polyol (B) having a valence of 4 or more and a polycation having a valence of 3 or more. By containing at least the surface of the polyol (B) having a valence of 4 or more and a polycation having a valence of 3 or more, the wettability of the particulate water-absorbing resin composition is exhibited and the liquid permeability is also exhibited. In this case as well, the particle size of the composition is preferably less than 850 μm and 90% by weight or more of particles of 150 μm or more.
The trivalent or higher polycation is a trivalent or higher polycation selected from a polymeric polyamine or a polyvalent metal. The high molecular polyamine is an amine compound having 3 or more cationic groups in the molecule. The trivalent or higher polycation is preferably water-soluble. Water-soluble means that it is preferably 0.5 g or more, more preferably 1 g or more, with respect to 100 g of water at 25 ° C.

Examples of the trivalent or higher polycation include polyethyleneimine, polyallylamine, polyvinylamine cationic polymer, and polyvalent metal salt. The weight average molecular weight of the cationic polymer is preferably 1000 to 1,000,000, more preferably. Is 10,000 to 500,000. The amount used depends on the combination with the water-absorbent resin and / or the particulate water-absorbent resin composition, but is preferably 0 to 10 parts by weight, for example, with respect to 100 parts by weight of the particulate water-absorbent resin composition. Preferably it is 0.001-8 weight part, More preferably, it is the range of 0.01-5 weight part.
Although it does not specifically limit as a polyvalent metal more than trivalence, For example, at least 1 sort (s) of metal atom chosen from the group which consists of Al, Fe, Ti, Hf, Zr, and another transition metal is illustrated preferably. . Among these, at least one metal atom selected from the group consisting of Al, Fe, Ti, Hf, and Zr, which has a strong bond with a carboxyl group, is more preferable, and Al and Zr are more preferable.

That is, the second particulate water-absorbing resin composition of the present invention is a particulate water-absorbing resin composed mainly of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. It is a resin composition, Comprising: The polyol (B) more than tetravalence and the polycation more than trivalence contain at least on the surface.
In the second particulate water-absorbing resin composition of the present invention, the content of the trivalent or higher polyvalent metal is 0.01 to 10% by weight with respect to the particulate water-absorbing resin composition. Preferably, it is 0.1 to 5.0% by weight, more preferably 0.2 to 2.0% by weight.

The trivalent or higher polyvalent metal is not particularly limited as long as it is a range that can be used as a water-soluble compound, but as a counter anion, for example, inorganic compounds having OH ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , acetic acid or propion It is preferably used as at least one compound selected from the group consisting of organic acids such as acids and halogens. Examples of such compounds include aluminum sulfate (including hydrates), potassium aluminum sulfate, sodium aluminum sulfate, aluminum hydroxide, acetylacetone zirconium complex, zirconium acetate, zirconium propionate, zirconium sulfate, zirconium hexafluoride. Preferred examples include potassium, sodium hexafluorozirconium, ammonium zirconium carbonate, potassium zirconium carbonate, and sodium zirconium carbonate, and among these, water-soluble compounds are more preferred.

The trivalent or higher polyvalent metal may be added before the surface cross-linking of the water-absorbent resin (A), may be added simultaneously with the surface cross-linking, or may be added to the particulate water-absorbing resin composition after the surface cross-linking. It may be added. Among these, it is preferable to add to the particulate water-absorbing resin composition simultaneously with surface crosslinking or after surface crosslinking, and it is particularly preferable to add to the particulate water-absorbing resin composition after surface crosslinking.
The trivalent or higher polyvalent metal may be added in the form of powder (powdered particles) or in the form of a slurry dispersed in water, an organic solvent, or the like, but may be added to an aqueous solution or a mixed solvent of water / organic solvent. It is preferable to add in a state of a solution of a polyvalent metal such as a dissolved solution. The organic solvent that can be used here is not particularly limited. For example, monovalent alcohols such as isopropyl alcohol; polyhydric alcohols such as propylene glycol and glycerin; acids such as acetic acid and lactic acid; water such as acetone and tetrahydrofuran. An organic solvent having good miscibility with the organic solvent can be preferably exemplified. Further, the polyvalent metal solution may contain a metal compound having less than three valences such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, sodium acetate, sodium lactate, potassium hydroxide, lithium hydroxide and the like.

  The particulate water-absorbing resin composition of the present invention has a liquid diffusion velocity (LDV) (mm / s)> − 0.186 × water absorption capacity without pressure (CRC) (g / g) +5.75 ( However, it is preferable to satisfy the relationship LDV> 0.10 (mm / s). More preferably, liquid diffusion rate (LDV) (mm / s)> − 0.186 × water absorption capacity without pressure (CRC) (g / g) +5.85 (however, LDV> 0.10 (mm / s) More preferably, the liquid diffusion rate (LDV) (mm / s)> − 0.186 × water absorption capacity without pressure (CRC) (g / g) +5.95 (however, LDV > 0.10 (mm / s)), more preferably liquid diffusion rate (LDV) (mm / s)> − 0.186 × water absorption capacity without pressure (CRC) (g / g) +6.05 (where LDV> 0.10 (mm / s)), more preferably liquid diffusion rate (LDV) (mm / s)> − 0.186 × no addition Reduction water absorption ratio (CRC) (g / g) +6.15 (LDV> .10 (mm / s)), particularly preferably liquid diffusion rate (LDV) (mm / s)> − 0.195 × absorption capacity without load (CRC) (g / g) +6.45 (LDV> 0.10 (mm / s)).

  The liquid diffusion rate (LDV) is a parameter indicating “liquid uptake characteristics” measured by a measurement method described in the examples described later. In order to improve the performance of absorbent articles such as disposable diapers and sanitary napkins, or absorbent bodies, the absorption capacity under no pressure (CRC) is mainly the amount that the absorbent articles or absorbent bodies absorb the liquid. On the other hand, the liquid diffusion speed (LDV) is mainly related to the speed at which the liquid diffuses in the absorbent article or the absorbent body, and more particularly to the speed at which the initial liquid is absorbed. Liquid diffusion rate (LDV) (mm / s)> − 0.186 × absorption capacity without pressure (CRC) (g / g) +5.75 (where LDV> 0.10 (mm / s)) By satisfying the above, it becomes a particulate water-absorbing resin composition in which both the “liquid permeability” and the “liquid suction property” of the water-absorbing resin, which have been contradictory properties, have been improved. More wettability. In addition, an absorbent article or an absorbent body that is superior in the amount of liquid absorption and the speed of absorbing the initial liquid than before can be obtained.

That is, the third particulate water-absorbing resin composition of the present invention is a particulate water-absorbing resin composed mainly of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. A resin composition having a particle size of less than 850 μm and a particle size of 150 μm or more is 90% by weight or more, and a liquid diffusion rate (LDV) (mm / s)> − 0.186 × no addition The reduced water absorption ratio (CRC) (g / g) +5.75 (LDV> 0.10 (mm / s)) is satisfied.
The particulate water-absorbing resin composition of the present invention preferably has a surface OH / C ratio of 0.03 to 0.15 determined based on photoelectron spectroscopic analysis. More preferably, the OH / C ratio of the surface determined based on photoelectron spectroscopic measurement is 0.035 to 0.12, more preferably 0.04 to 0.1, and particularly preferably 0.045 to 0. .1.

  The OH / C ratio of the surface determined based on the photoelectron spectroscopic analysis measurement is the OH / C ratio of the surface measured by the measurement method described in the examples below, and the surface of the particulate water-absorbing resin composition is not The surface OH / C ratio was determined based on photoelectron spectroscopic analysis after washing with a water-soluble solvent, a water-soluble solvent, and water (saline). That is, the OH group and C (carbon element) present in the compound immobilized on the surface of the particulate water-absorbent resin composition, preferably by a covalent bond or an ionic bond, more preferably a covalent bond (a compound that is not washed away by washing). In general, the OH groups immobilized by surface crosslinking or surface reaction are quantified. The wettability of the particulate water-absorbing resin composition when the range of the surface OH / C ratio found on the surface of the particulate water-absorbing resin composition based on photoelectron spectroscopy is 0.03 to 0.15. Is preferably exhibited. Further, the OH / C ratio determined based on the photoelectron spectroscopic analysis inside the particles of the particulate water-absorbent resin composition is preferably 0.000 to 0.025, more preferably 0.000 to 0.023. More preferably, it is 0.000-0.020. When the OH / C ratio determined based on the photoelectron spectroscopy inside the particles of the particulate water-absorbing resin composition is larger than 0.025, the liquid permeability may be lowered. The OH / C ratio inside the particulate water-absorbing resin composition can be easily determined by pulverizing the particulate water-absorbing resin composition with a hammer and analyzing the inside of the particulate water-absorbing resin composition by photoelectron spectroscopy. Can be requested.

That is, the fourth particulate water-absorbing resin composition of the present invention is a particulate water-absorbing resin composed mainly of a water-absorbing resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer. The particle size of the composition is less than 850 μm and the particle size of 150 μm or more is 90% by weight or more, and the surface OH / C ratio determined based on photoelectron spectroscopic analysis is 0.03 to 0.03. 0.15.
The third and fourth particulate water-absorbing resin compositions of the present invention can be achieved by, for example, the first and second particulate water-absorbing resin compositions of the present invention, but other methods, for example, other hydrophilic properties. The novel parameter (relational expression) may be controlled so as to satisfy the third and fourth particulate water-absorbing resin compositions of the present invention by using an agent. The third and fourth particulate water-absorbing resin compositions of the present invention are not limited to the first and second particulate water-absorbing resin compositions of the present invention, but the parameters (relationships) of the present invention. It was found that the structure satisfying the formula (2) gives excellent diapers and excellent effects, and the third and fourth particulate water-absorbing resin compositions of the present invention were completed here.

Preferably, the particulate water-absorbing resin composition of the present invention has a water absorption capacity (CRC) of 0.90% by weight with respect to 0.90% by weight physiological saline, 0.90% by weight physiological saline. The water absorption capacity under pressure at 4.9 kPa for 60 minutes (AAP: Absorbency Against Pressure), saline flow conductivity (SFC: Saline Flow Conductivity), and liquid uptake rate (WR: Wicking Rate) satisfy the following conditions: Fulfill. In the present invention, the term “water absorption rate” is synonymous with the term “absorption rate”.
That is, the particulate water-absorbing resin composition of the present invention preferably has a non-pressurized water absorption capacity (CRC) of preferably 8 to 20 g / g or more, and a pressurized water absorption capacity (AAP) of preferably 8 to 20 g / g or more. The water flow conductivity (SFC) is preferably 10 (unit: 10 ⁻⁷ × cm ³ × s × g ⁻¹ ) or more, and the liquid suction speed (WR) is preferably 180 s or less.

CRC is more preferably 25 to 50 g / g, further preferably 27 to 40 g / g, and particularly preferably 28 to 35 g / g.
AAP is more preferably 23 to 40 g / g, further preferably 24 to 40 g / g, particularly preferably 25 to 40 g / g, and most preferably 25 to 30 g / g.
The SFC is more preferably 20 or more, further preferably 30 or more, particularly preferably 40 or more, and most preferably 50 or more.
WR is more preferably 2 to 120 s, further preferably 5 to 90 s, particularly preferably 5 to 80 s, and most preferably 5 to 70 s.

The above CRC, AAP, SFC and WR are parameters of a suitable water-absorbent resin when used in a diaper, and it is preferable from the viewpoint of high absorption and low leakage in actual use to control such parameters within the above ranges. . These physical properties can be obtained by appropriately adjusting the manufacturing conditions (for example, adjusting the cross-linking density by polymerization or surface cross-linking) by the above-described manufacturing method.
When the water absorption capacity (CRC) under no pressure is 8 to less than 20 g / g, when used in an absorber and / or an absorbent article (for example, a paper diaper, etc.) to be described later, Causes problems such as rash.
When the water absorption capacity under pressure (AAP) is less than 8 to 20 g / g and the saline flow conductivity (SFC) is less than 10 (unit: 10 ⁻⁷ × cm ³ × s × g ⁻¹ ), the particulate water absorbent resin When a load such as body weight is applied to the composition, the liquid diffusion and absorption ability of the liquid is poor, so that the liquid does not diffuse in the absorbent body and / or absorbent article, causing the liquid to block, and actual use in a disposable diaper And there are problems such as leakage and skin irritation.

When the liquid sucking speed (WR) exceeds 180 s, in actual use, the liquid is not sucked up on the entire diaper or the upper surface of the diaper mounted along the buttocks, which is not suitable for actual use of the diaper.
Further, conventionally, liquid permeability and liquid uptake properties were contradictory physical properties, whereas in the particulate water absorbent resin composition of the present invention, a particulate water absorbent resin composition with both well-balanced is obtained, Compared to AAP and SFC, the liquid suction speed (WR) is very fast.
That is, the balance between the liquid permeability and the liquid suction property of the particulate water-absorbent resin composition is the liquid permeability / liquid suction speed, that is, SFC (unit: 10 ⁻⁷ × cm ³ × s × g ⁻¹ ) / WR. It is expressed by the liquid suction efficiency defined by (s). The particulate water-absorbing resin composition of the present invention preferably has a liquid passing-up efficiency (SFC / WR) of 0.50 (unit: 10 ⁻⁷ × cm ³ × g ⁻¹ ) or more and 100 (unit: 10 ^−7). × cm ³ × g ⁻¹ ) or less, more preferably 0.70 (unit: 10 ⁻⁷ × cm ³ × g ⁻¹ ) or more and 100 (unit: 10 ⁻⁷ × cm ³ × g ⁻¹ ) or less, particularly preferably. Is 1.00 (unit: 10 ⁻⁷ × cm ³ × g ⁻¹ ) or more and 100 (unit: 10 ⁻⁷ × cm ³ × g ⁻¹ ) or less, and conventional (0.4 (unit: 10 ⁻⁷ × cm). ³ × g ⁻¹ )), which is much higher than that of the present invention, is excellent in the balance between liquid permeability and liquid uptake characteristics, and is suitable as a sanitary material.

  Further, the particulate water-absorbing resin composition of the present invention has an excellent balance between the water absorption capacity without pressure and the liquid suction property, and the balance is the water absorption capacity without pressure / liquid suction speed, that is, CRC (g / g ) / WR (s). The particulate water-absorbing resin composition of the present invention has a non-pressurization magnification suction efficiency (CRC / WR), preferably 0.15 (g / g / s) to 2 (g / g / s), more preferably. It is 0.20 (g / g / s) or more and 2 (g / g / s) or less, and particularly preferably 0.25 (g / g / s) or more and 2 (g / g / s) or less. 1 (g / g / s), which is much higher than that of 1 (g / g / s).

  The particulate water-absorbent resin composition of the present invention also has an excellent balance between the water absorption capacity under pressure and the liquid uptake characteristic, and the balance is the water absorption capacity under pressure / liquid uptake speed, that is, AAP (g / g) / It is expressed by the suction magnification suction efficiency defined by WR (s). The particulate water-absorbent resin composition of the present invention has a pressure magnification suction efficiency (AAP / WR) of preferably 0.15 (g / g / s) to 2 (g / g / s), more preferably 0. 20 (g / g / s) or more and 2 (g / g / s) or less, particularly preferably 0.25 (g / g / s) or more and 2 (g / g / s) or less (0.1 (Approx. (G / g / s) before and after) and is excellent in the balance between water absorption capacity under pressure and liquid uptake characteristics, and is suitable as a sanitary material.

The shape of the particulate water-absorbent resin composition of the present invention, the amount of water-soluble component, and the like are also in the above-mentioned range, and the water-soluble component is preferably 25% by weight or less (lower limit 0% by weight), more preferably 20% by weight. Hereinafter, it is more preferably 15% by weight or less. Further, the water content of the particulate water-absorbing resin composition of the present invention is preferably 0.1 to 5% by weight, more preferably 0.1 to 3% by weight, further based on the particulate water-absorbing resin composition. Preferably it is 0.2 to 2 weight%. When the water content is higher than 5% by weight, the water absorption ratio may be decreased. When the water content is lower than 0.1% by weight, the liquid diffusion rate may be decreased. ^Further, the colored state of the particulate water-absorbing resin composition of the present invention is preferably in the YI values (see Yellow Index / European Patent 942,014 Pat and the 1,108,745 Pat) 0-15, more preferably 0-13 More preferably, it is 0-10, Especially preferably, it is 0-5, Furthermore, a residual monomer also preferably shows 0-400 ppm, More preferably, it shows 0-300 ppm.

(6) Third component of particulate water-absorbing resin composition As the third component, various inorganic powders (D) may be further added to the water-absorbing resin and / or particulate water-absorbing resin composition. It is preferable to add in the range which does not impair the liquid suction speed (liquid diffusion speed).
Specific examples of the inorganic powder (D) used include metal oxides such as silicon dioxide and titanium oxide, silicic acid (salts) such as natural zeolite and synthetic zeolite, kaolin, talc, clay, bentonite and the like. Silicon dioxide and silicic acid (salt) having an average particle size of 200 μm or less measured by a Coulter counter method are preferred.

  In the mixing method of the inorganic powder (D) and the particulate water-absorbent resin composition, when the inorganic powder (D) is a solid particle, a dry blend method, a wet mix, or the like that mixes the powders can be employed. However, when powders are mixed, the inorganic powder (D) is not uniformly mixed with the particulate water-absorbing resin composition, or the inorganic powder (D) and the particulate water-absorbing resin composition are bonded or bonded. May not be enough. When such a particulate water-absorbing resin composition is used for absorbent articles such as diapers, the particulate water-absorbing resin composition and the inorganic powder (D) are separated and segregated in the production process, etc. It is difficult to obtain an absorbent article such as a diaper having a good performance, which may not be preferable. Such a phenomenon is caused by, for example, a difference between a value obtained by measuring the liquid diffusion rate (LDV) using the particle size of the particulate water-absorbent resin composition as it is (Bulk) and a value obtained by classification into a range of 500 to 300 μm. It can be seen from the big thing.

When the inorganic powder (D) is solid particles, the amount used depends on the combination of the water-absorbent resin and / or the particulate water-absorbent resin composition, for example, 100 parts by weight of the particulate water-absorbent resin composition. On the other hand, it is preferably 0 to 0.5 parts by weight, more preferably 0 to 0.3 parts by weight, still more preferably 0 to 0.1 parts by weight, and particularly preferably 0 to 0.05 parts by weight. When the added amount of the solid particulate inorganic powder (D) is more than 0.5 parts by weight, it may be difficult to obtain a water-absorbing article such as a diaper having the uniform performance described above, which is not preferable.
Further, in the particulate water-absorbing resin composition and the method for producing the same according to the present invention, a deodorant, an antibacterial agent, a fragrance, a foaming agent, a pigment, a dye, a plasticizer, an adhesive, an interface, if necessary. Activators, fertilizers, oxidizing agents, reducing agents, water, salts, chelating agents, bactericides, hydrophilic polymers such as polyethylene glycol, paraffin, hydrophobic polymers, thermoplastic resins such as polyethylene and polypropylene, polyester resins and urea The range in which the liquid absorption rate (liquid diffusion rate) of the thermosetting resin such as a resin is not lowered in the water absorbent resin and / or the particulate water absorbent resin composition, for example, the water absorbent resin and / or the particulate water absorbent resin composition You may add about 0-10 weight part with respect to 100 weight part of things.

(7) Applications, Absorbers and / or Absorbent Articles The particulate water-absorbing resin composition of the present invention is excellent in moisture absorption properties, and has been used for conventional water absorption such as agriculture, horticulture, cable waterproofing agents, civil engineering / architecture, and foods. Can be widely used for the application of adhesive resin, but it is suitable for use as a solidifying agent (absorbing gelling agent) for urine, feces, or blood because it has both liquid permeability and liquid absorption properties, which are necessary physical properties of absorbent articles such as diapers. Is done.
Since the particulate water-absorbing resin composition of the present invention is particulate, it is usually molded and used as an absorber containing the particulate water-absorbing resin composition. In the present invention, the absorber preferably has a content (core concentration) of the particulate water-absorbing resin composition with respect to the total weight of the particulate water-absorbing resin composition and the hydrophilic fiber of 20 to 100% by weight, More preferably, it is 30-100 weight%, More preferably, it is 30-90 weight%, Most preferably, it is the range of 40-80 weight%. When the core concentration is less than 20% by weight, it is difficult to make use of the characteristics of the particulate water-absorbing resin composition.

An example of a preferred use of the particulate water-absorbing resin composition of the present invention in an absorbent body is a water-absorbing composite having expansion anisotropy (expandability in the thickness direction) exemplified in US Pat. No. 5,853,867. By using the particulate water-absorbing resin composition having excellent diffusibility according to the present invention, the liquid diffusion in the lateral direction (planar direction) is remarkably improved by using the particulate water-absorbing resin composition of the present invention. Absorbers are obtained and preferred.
Such an absorbent body is preferably compression-molded to a density of 0.06 to 0.50 g / cc and a basis weight of 0.01 to 0.20 g / cm ² . Examples of the fiber base used include hydrophilic fibers such as pulverized wood pulp, cotton linters and cross-linked cellulose fibers, rayon, cotton, wool, acetate, and vinylon. Preferably, they are airlaid.

  Furthermore, the absorbent article in this invention is an absorbent article provided with the above-mentioned absorber of this invention, the surface sheet which has liquid permeability, and the back sheet | seat which has liquid impermeability, for example. Specific examples of the absorbent article include adult paper diapers that have been growing rapidly in recent years, hygiene materials such as diapers for children, sanitary napkins, and so-called incontinence pads.

Hereinafter, although an example and a comparative example explain the present invention still in detail, the present invention is not limited to these examples.
In addition, when applying the measuring method described in the present specification to a water-absorbent resin or particulate water-absorbent resin composition taken out from an absorbent article such as a diaper, it is dried for 16 hours or more in a vacuum dryer adjusted to 60 ° C. It is preferable to measure after the water content of the water-absorbent resin or the particulate water-absorbent resin composition is 5% by weight or less.
Unless otherwise specified, the following tests were measured under an atmosphere of 1 atm, 25 ± 2 ° C., and a relative humidity of 30-50% RH, and the liquid temperature used was also in the range of 25 ± 2 ° C.

<Measurement of water content>
1 g of the particulate water-absorbing resin composition was uniformly spread on the bottom surface of the aluminum cup in an aluminum cup having a bottom diameter of 4 cm and a height of 2 cm. This was left for 3 hours in a hot air dryer adjusted to 105 ° C., and the water content (%) of the particulate water-absorbent resin composition was calculated from the weight loss before and after.
<Water absorption capacity without pressure (CRC)>
0.200 g of water-absorbent resin (or particulate water-absorbent resin composition) is uniformly placed in a non-woven bag (manufactured by Nankoku Pulp Industries Co., Ltd., trade name: Heaton paper, model: GSP-22) (60 mm × 60 mm) And immersed in 0.9 wt% physiological saline (sodium chloride aqueous solution) adjusted to 25 ° C. After 30 minutes, the bag was pulled up and drained for 3 minutes at a centrifugal force of 250 cm / sec ² (250 G) using a centrifuge (manufactured by Kokusan Co., Ltd., centrifuge, model: H-122). The weight W1 (g) was measured. The same operation was performed without using the water absorbent resin (or particulate water absorbent resin composition), and the weight W0 (g) at that time was measured. And from these W1 and W0, the water absorption capacity | capacitance (g / g) under no pressure was computed according to following Formula.
Water absorption capacity without pressure (g / g) = [(W1 (g) −W0 (g)) / weight of water absorbent resin (or particulate water absorbent resin composition) (g)] − 1
<Water absorption capacity under pressure (AAP)>
A stainless steel 400 mesh wire mesh (aperture 38 μm) is fused to the bottom of a plastic support cylinder having an inner diameter of 60 mm, and 0.900 g of water absorbent resin (or particulate water absorbent resin composition) is uniformly applied on the mesh. The outer diameter was adjusted so that a load of 4.83 kPa (0.7 psi) was uniformly applied to the water absorbent resin (or particulate water absorbent resin composition). A piston and a load, which are slightly smaller and do not cause a gap with the support cylinder and do not hinder vertical movement, were placed in this order, and the weight Wa (g) of this measuring device set was measured.

A glass filter of 90 mm in diameter (manufactured by Mutual Riken Glass Co., Ltd., pore diameter: 100 to 120 μm) is placed inside a 150 mm diameter Petri dish, and 0.90 wt% physiological saline is at the same level as the upper surface of the glass filter. Added as follows. On top of that, a filter paper having a diameter of 90 mm (ADVANTEC; No. 2 manufactured by Toyo Filter Paper Co., Ltd.) was placed so that the entire surface was wetted, and excess liquid was removed.
The set of measuring devices was placed on the wet filter paper, and the liquid was absorbed under load. After 1 hour, the measuring device set was lifted and its weight Wb (g) was measured. And the water absorption capacity | capacitance under pressure (g / g) was computed from Wa and Wb according to following Formula.

Water absorption capacity under pressure (g / g)
= (Wb (g) -Wa (g)) / weight of water absorbent resin (or particulate water absorbent resin composition) ((0.9) g)
<Saline flow conductivity (SFC)>
The test was conducted in accordance with the saline flow conductivity (SFC) test of JP-T 9-509591.
Using the apparatus shown in FIG. 1, the particulate water-absorbing resin composition (0.900 g) uniformly placed in the container 40 is swollen in artificial urine (1) for 60 minutes under a pressure of 0.3 psi (2.07 kPa). (120 minutes when measuring saline flow conductivity (SFC) retention) and recording the gel layer height of gel 44, then 0.69 under pressure of 0.3 psi (2.07 kPa) A gel layer swollen from the tank 31 was passed through a weight% sodium chloride aqueous solution 33 at a constant hydrostatic pressure.

Using a computer and a balance, the amount of liquid passing through the gel layer at 20 second intervals as a function of time was recorded for 10 minutes. The flow rate F _S (t) through the swollen gel 44 (mainly between the particles) was determined in units of g / s by dividing the increased weight (g) by the increased time (s). _Let t _S be the time at which a constant hydrostatic pressure and a stable flow rate were obtained, and use only the data obtained between t _S and 10 minutes for the flow rate calculation, and calculate the flow rate obtained between t _S and 10 minutes. Used to calculate the value of F _S (t = 0), ie the initial flow rate through the gel layer. F _S (t = 0) was calculated by extrapolating the result of the least square method of F _S (t) versus time to t = 0.
Saline flow conductivity = (F _S (t = 0) × L ₀ ) / (ρ × A × ΔP)
= (F _S (t = 0) × L ₀ ) / 139506
here,
F _S (t = 0) flow rate L ₀ expressed in g / s L ₀ : initial gel layer thickness ρ expressed in cm: density of NaCl solution (1.003 g / cm ³ )
A: Area above the gel layer in the cell 41 (28.27 cm ² )
ΔP: hydrostatic pressure applied to the gel layer (4920 dyne / cm ² )
The unit of saline flow conductivity (SFC) is (10 ⁻⁷ × cm ³ × s × g ⁻¹ ).

  In the apparatus shown in FIG. 1, a glass tube 32 is inserted into a tank 31, and the lower end of the glass tube 32 is 5 cm above the bottom of the swollen gel 44 in the cell 41 with a 0.69 wt% sodium chloride aqueous solution 33. It arrange | positioned so that it could maintain at the height of. The 0.69 wt% sodium chloride aqueous solution 33 in the tank 31 was supplied to the cell 41 through the L-shaped tube 34 with a cock. Under the cell 41, a container 48 for collecting the passed liquid is disposed, and the collection container 48 is installed on an upper pan balance 49. The inner diameter of the cell 41 is 6 cm. A 400 stainless steel wire mesh (aperture 38 μm) 42 was installed. There is a hole 47 sufficient for the liquid to pass through the lower part of the piston 46, and a glass filter 45 with good permeability is attached to the bottom so that the water absorbent resin composition or its swelling gel does not enter the hole 47. there were. The cell 41 was placed on a table on which the cell was placed, and the surface of the table in contact with the cell was placed on a stainless steel wire mesh 43 that did not prevent liquid permeation.

Artificial urine (1) is calcium chloride dihydrate 0.25 g, potassium chloride 2.0 g, magnesium chloride hexahydrate 0.50 g, sodium sulfate 2.0 g, ammonium dihydrogen phosphate 0.85 g, A mixture of 0.15 g of diammonium hydrogen phosphate and 994.25 g of pure water was used.
<Soluble content>
In a 250 ml lidded plastic container (diameter 6 cm × height 9 cm), weigh out 184.3 g of 0.900 wt% sodium chloride aqueous solution and put (particulate) water absorbent resin (composition) in the aqueous solution. 00 g was added, and the soluble component in the resin was extracted by stirring at 500 rpm with a magnetic stirrer having a diameter of 8 mm and a length of 25 mm for 16 hours. 50.0 g of the filtrate obtained by filtering this extract using one filter paper (ADVANTEC Toyo Co., Ltd., product name: JIS P 3801 No. 2, thickness: 0.26 mm, reserved particle diameter 5 μm) A measurement solution was obtained.

First, only 0.900 wt% sodium chloride aqueous solution was titrated to pH 10 with 0.1N NaOH aqueous solution, and then titrated to pH 2.7 with 0.1N HCl aqueous solution ([bNaOH]). ml, [bHCl] ml).
The titration ([NaOH] ml, [HCl] ml) was determined by performing the same titration operation on the measurement solution.
For example, in the case of a water-absorbing resin composed of a known amount of acrylic acid and its sodium salt, based on the average molecular weight of the monomer and the titration amount obtained by the above operation, the soluble content in the water-absorbing resin is expressed by the following equation: Can be calculated. In the case of an unknown amount, the average molecular weight of the monomer was calculated using the neutralization rate obtained by titration.

Soluble content (% by weight) = 0.1 × (average molecular weight) × 184.3 × 100 × ([HCl] − [bHCl]) / 1000 / 1.0 / 50.0
Neutralization rate (mol%) = [1-([NaOH]-[bNaOH]) / ([HCl]-[bHCl])] × 100
<Liquid uptake speed (WR) and liquid diffusion speed (LDV)>
The liquid suction speed (WR) was measured using a suction index measuring device (FIGS. 2 and 3) described in JP-A-5-200068 (EP532002). The trough sheet was made of SUS304 stainless steel grade 2B finish.

1.00 g ± 0.005 g of the particulate water-absorbing resin composition classified into 300 to 500 microns was evenly distributed between 0 to 20 cm in the trough groove of the trough sheet installed at an angle of 20 °. Furthermore, the particulate water-absorbing resin composition was more evenly dispersed using a spatula.
In this measurement, it is preferable to use a particulate water-absorbing resin composition classified into a particle size range of 300 to 500 μm. However, when it is difficult to obtain a particulate water-absorbing resin composition in the particle size range, the obtained particulate water-absorbing resin composition is used. You may measure as it is in the state (Bulk), without classifying the property resin composition in particular.
The liquid used for sucking up liquid is 1% of 0.9% by weight of physiological saline (sodium chloride aqueous solution), edible blue No. 1 (Tokyo Kasei Kogyo Co., Ltd.) at a ratio of 0.01 g of physiological saline. Using.

The liquid uptake speed (WR) was adjusted so that the liquid level of the liquid storage tank was 0.5 cm above the lowest position of the trough, and then the measurement was started simultaneously with the contact of the stainless steel screen mesh with the liquid. . The liquid suction speed (WR) represents the time (sec) during which the liquid is sucked up to the scale position at 10 cm. In addition, the speed at which the liquid in the liquid storage tank and the stainless steel screen mesh are immersed from the lowest position of the trough to 0.5 cm above is 1.35 to 1.40 mm / s in the vertical direction from the liquid surface. It was done.
The liquid diffusion rate (LDV) is calculated by the following equation.
LDV (mm / s) = 100 (mm) / WR (s)
<Weight average particle diameter>
The pulverized water-absorbent resin (or particulate water-absorbent resin composition) is JIS standard sieves (JIS Z8801-1: 2000) such as 850 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, and 75 μm. Sieving and residual percentage R was plotted on log probability paper. Thereby, the weight average particle diameter (D50) was read.

<Logarithmic standard deviation of particle size distribution (σζ)>
The water-absorbing resin (or particulate water-absorbing resin composition) is sieved with JIS standard sieves having openings of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, and 45 μm, and the residual percentage R is logarithmic probability paper. Plotted. Therefore, when X1 is R = 84.1% by weight and X2 is each particle size when 15.9% by weight, the logarithmic standard deviation (σζ) is expressed by the following formula, and the smaller the value of σζ, the smaller the particle size. Means a narrow distribution.
σζ = 0.5 × ln (X2 / X1)
The classification method for measuring the logarithmic standard deviation (σζ) in the particle size distribution is as follows: 10.0 g of a water-absorbent resin (or particulate water-absorbent resin composition) with an opening of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, Charged into 212 μm, 150 μm and 45 μm JIS standard sieves (THE IIDA TESTING SIVE: diameter 8 cm), and classified for 5 minutes using a vibration classifier (IIDA SIEVE SHAKER, TYPE: ES-65 type, SER No. 0501). It was.

<Polyol content>
1 g of the particulate water-absorbing resin composition was stirred into 100 g of a 0.9 wt% sodium chloride aqueous solution placed in a beaker having a bottom diameter of 6 cm (using a magnetic stirrer having a diameter of 8 mm and a length of 25 mm with a magnetic stirrer at 500 rpm). Stirring at the rotational speed) and adding for 1 hour to extract the polyol that has not reacted with the particulate water-absorbent resin composition, and analyzing it by liquid chromatography. Asked. The amount of unreacted polyol was determined as the amount (unit: ppm) relative to the particulate water-absorbing resin composition per unit amount.
<Photoelectron Spectroscopic Analysis (XPS: X-ray Photoelectron Spectroscopy)>
(Experimental operation h1: Organic solvent cleaning treatment)
About 200 mg of the particulate water-absorbing resin composition was placed in a 10 ml sample tube (inner diameter 18 mm × height 44 mm), and 5 ml of cyclohexane was added. After adding a magnetic stirrer having a diameter of 4 mm and a length of 10 mm, the sample tube was sealed and stirred at room temperature for 1 hour using a magnetic stirrer with the particles dispersed in the whole liquid. Thereafter, decantation was performed, and further, cyclohexane was removed using a filter paper cut into a strip shape to the extent that no liquid remained between the particles. After performing this operation twice, the obtained particulate water-absorbing resin composition was dried at 100 ° C. under a reduced pressure of 100 mmHg for 2 hours using a vacuum drier to obtain particulates subjected to organic solvent washing treatment. A water absorbent resin composition was obtained.

(Experimental operation h2: physiological saline washing treatment)
About 100 mg of the particulate water-absorbing resin composition washed with the organic solvent obtained in the experimental operation h1 is placed in the 10 ml sample tube (inner diameter 18 mm × height 44 mm), and 10 ml of 0.9 wt% sodium chloride aqueous solution is added, The sample tube was sealed and stirred with a magnetic stirrer for 1 hour in the same manner as in experimental operation h1. Next, after adding 4 drops (0.1-0.2 g) of concentrated hydrochloric acid with stirring using a pipette, stirring was stopped, decanted, and then visually cut between the particles with a filter paper cut into strips. The liquid was removed to such an extent that no liquid remained. The obtained particulate water-absorbing resin composition was dried at 60 ° C. and about 100 mmHg for 4.5 hours, then at 100 ° C. and about 100 mmHg for 17 hours, and further dried at 100 ° C. and about 1 mmHg for 3 hours using a vacuum dryer. As a result, a particulate water-absorbing resin composition subjected to the physiological saline washing treatment was obtained.

(Experimental operation h3: methanol / water washing treatment)
Approximately 50 mg of the particulate water-absorbing resin composition washed with physiological saline obtained by the experimental operation h2 is placed in a sample tube (inner diameter 18 mm × height 44 mm), and 0.5% of 36 wt% hydrochloric acid is mixed with 100 ml of methanol. 2 ml of the prepared solution was added. The sample tube was sealed, and the particulate water-absorbing resin composition and solution therein were stirred for 5 minutes using an ultrasonic cleaner equipped with a 35 kHz vibrator, then decanted and then cut into strips. With filter paper, the liquid was removed to such an extent that no liquid remained clearly between the particles. This operation was performed twice. Next, 5 ml of methanol was added to the same sample tube containing the obtained particulate water-absorbent resin composition, stirred for 5 minutes using an ultrasonic cleaner, and then decanted from methanol, and then cut into strips. Then, the operation of removing the liquid was performed twice to the extent that the liquid remained clearly between the particles. Furthermore, the obtained particulate water-absorbent resin composition was dried at 90 ° C. and about 100 mmHg for 15 hours, then at 90 ° C. and about 1 mmHg for 2 hours, and then washed with methanol and water. A particulate water-absorbing resin composition was obtained.

(Experimental operation h4: surface trifluoroacetation)
The particulate water-absorbing resin composition (about 50 mg) subjected to the methanol / water washing treatment obtained in the experimental operation h3 is 10 mm in diameter and 20 mm in height with 40 to 50 holes having a diameter of 100 to 300 μm on the side surface. Taken in a polypropylene cup (1). The polypropylene cup (1) was placed on a stage of a 50 ml sample tube (inner diameter 31 mm × height 75 mm) provided with a stage having a diameter of 10 mm and a height of 5 mm in the center of the bottom surface. Around the stage in the sample tube, 500 μl of trifluoroacetic anhydride (TFAA) was added. Thereafter, the sample tube was sealed, left at room temperature for 1 to 3 hours, and reacted with OH groups on the surface of the particulate water-absorbent resin composition that passed through TFAA and experimental operations h1 to h3 (the surface was washed) (this) The operation is such that the liquid TFAA does not directly touch the particulate water-absorbing resin composition in the cup, and the vapor of TFAA contacts and reacts with the particulate water-absorbing resin composition). Next, in the presence of KOH solid, it was dried at 60 ° C. and about 100 mmHg for 2 hours or more using a vacuum dryer, and further dried at 60 ° C. and about 1 mmHg for 2 hours or more. The obtained particulate water-absorbing resin composition was sealed in a sample tube and stored in a desiccator in the presence of silica gel. The stored sample was subjected to the measurement shown in experimental operation h5 within one week.

(Experimental operation h5: Measurement of OH / C ratio)
The particulate water-absorbing resin composition obtained in the experimental operation h4 was evenly spread on a rectangular sample table of about 6 cm × 1 cm with a conductive adhesive tape cut into about 1 cm square, and used as a measurement sample. Each elemental spectrum of carbon and fluorine was evacuated for 3 hours or more in the preliminary exhaust chamber using an XPS analyzer (JEOL JPS-9000MX), then moved to the sample chamber for measurement, and MgK _α rays were used as an excitation X-ray source. The photoelectron spectrum was obtained by repeating the scan 10 times and integrating the acceleration voltage 10 kV, the emission current 10 mA, the detector pass energy 10 eV, and the energy sweep interval 0.1 eV. Relative sensitivity provided in the analysis software (Spec XPS Version 1.2.3, manufactured by Jeol System) attached to the device for the area value (eV × cps) obtained from the spectrum subjected to background correction (implemented by the Shirley method) Quantitative correction calculation was performed using factors (C = 4.079042, F = 15.619373), and element percentage values of each element were calculated. From these values, the OH / C ratio was determined by calculating using the following calculation formula.

OH / C ratio = [element percentage value of elemental fluorine] / [element percentage value of carbon element] / 3
[Reference Example 1]
5438 g of an aqueous solution of sodium acrylate having a neutralization rate of 71.3 mol% in a reactor formed by attaching a cover to a stainless steel double-armed kneader with a volume of 10 liters having two sigma type blades and a jacket ( 11.7 g (0.10 mol%) of polyethylene glycol diacrylate (ethylene glycol repeating unit number: 9) was dissolved in a monomer concentration of 39% by weight to prepare a reaction solution. Next, dissolved oxygen was removed from the reaction solution for 30 minutes in a nitrogen gas atmosphere. Subsequently, 29.34 g of a 10 wt% sodium persulfate aqueous solution and 24.45 g of a 0.1 wt% L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 1 minute. Then, polymerization was performed at 20 to 95 ° C. while pulverizing the generated gel, and a hydrogel crosslinked polymer (1) subdivided into about 1 to 3 mm was taken out 30 minutes after the start of the polymerization. This hydrogel crosslinked polymer (1) was spread on a 50 mesh (mesh opening 300 μm) wire mesh and dried with hot air at 175 ° C. for 50 minutes. In this way, an absorptive, water-absorbent resin mass composed of a dry particulate aggregate that was easily pulverized was obtained.

The obtained water absorbent resin block was pulverized using a roll mill, and further classified with a JIS standard sieve having an opening of 600 μm. Next, the water-absorbing resin particles that have passed through the JIS standard sieve having an opening of 150 μm are removed by classifying the particles that have passed 600 μm in the above-described operation with a JIS standard sieve having an opening of 150 μm, and the obtained water-absorbing resin The particles were water absorbent resin particles (a). The soluble content of the water absorbent resin particles (a) was 7% by weight.
[Reference Example 2]
A water-absorbent resin mass was obtained in the same manner as in Reference Example 1 except that the amount of polyethylene glycol diacrylate (number of ethylene glycol repeating units: 9) in Reference Example 1 was changed to 6.39 g (0.05 mol%).

The obtained water absorbent resin block was pulverized using a roll mill, and further classified with a JIS standard sieve having an opening of 850 μm. Next, the particles having passed 850 μm in the above operation are classified with a JIS standard sieve having an opening of 150 μm to remove the water absorbent resin particles having passed the JIS standard sieve having an opening of 150 μm, and the resulting water absorbent resin is obtained. The particles were water absorbent resin particles (b). The soluble content of the water-absorbent resin particles (b) was 10.5% by weight.
[Example 1]
A surface treatment agent composed of a mixture of 10 g of D-sorbitol and 10 g of pure water was uniformly mixed with 500 g of the water-absorbent resin particles (a) obtained in Reference Example 1, and the resulting mixture (1) was equipped with a stirrer. The mixture was put in a mortar mixer, immersed in an oil bath adjusted to 210 ° C., and heated and crosslinked under stirring under heating and crosslinking conditions for 20 minutes. Furthermore, the particulate water-absorbent resin composition (1) was obtained by crushing the particles until they passed through a JIS standard sieve having an opening of 600 μm. Various physical properties were measured and the results are shown in Table 1.

[Example 2]
A surface treatment agent composed of a mixture of 2.5 g of D-sorbitol, 1.6 g of 1,4-butanediol and 15 g of pure water was uniformly mixed with 500 g of the water-absorbent resin particles (a) obtained in Reference Example 1. The obtained mixture (2) was heated and crosslinked at 210 ° C. for 20 minutes in the same manner as in Example 1. Furthermore, the particulate water-absorbent resin composition (2) was obtained by similarly pulverizing until passing through a JIS standard sieve having an aperture of 600 μm. Various physical properties were measured, and the results are shown in Table 1.
Example 3
A mixture of 1.25 g of D-sorbitol, 1.6 g of 1,4-butanediol, 1.25 g of 1,2-propanediol, and 15 g of pure water to 500 g of the water-absorbent resin particles (a) obtained in Reference Example 1. The surface treatment agent consisting of was uniformly mixed, and the resulting mixture (3) was heated and crosslinked at 210 ° C. for 20 minutes in the same manner as in Example 1. Furthermore, the particulate water-absorbent resin composition (3) was obtained by similarly pulverizing until it passed through a JIS standard sieve having an aperture of 600 μm. Various physical properties were measured, and the results are shown in Table 1.

[Comparative Example 1]
A surface treatment agent comprising a mixture of 1.6 g of 1,4-butanediol, 2.5 g of 1,2-propanediol and 15 g of pure water is uniformly applied to 500 g of the water absorbent resin particles (a) obtained in Reference Example 1. To obtain a comparative mixture (1). The obtained comparative mixture (1) was heat-crosslinked at 210 ° C. for 20 minutes in the same manner as in Examples 1 to 3. Furthermore, the comparative particulate water-absorbent resin composition (1) was obtained by similarly pulverizing until passing through a JIS standard sieve having an aperture of 600 μm. Various physical properties were measured, and the results are shown in Table 1. The weight average particle diameter (D50) of the comparative water absorbent resin composition (1) was 322 microns, and the logarithmic standard deviation (σζ) of the particle size distribution was 0.36.

[Comparative Example 2]
Table 1 shows the results of measuring various physical properties of the water-absorbent resin particles (a) obtained in Reference Example 1 as they are as the comparative particulate water-absorbent resin composition (2).

As shown in Table 1 above, the particulate water-absorbing resin composition of the present invention has an extremely excellent liquid uptake rate (WR), and also has a balance between liquid permeability and liquid uptake characteristics (SFC / WR), In addition, it is excellent in the balance (AAP / WR) between the water absorption magnification under pressure and the liquid suction property.
The particulate water-absorbing resin composition of the present invention has a high CRC, AAP, and SFC, and has a liquid suction speed (WR) as fast as 120 seconds or less. In addition, the liquid suction efficiency (SFC / WR) is 0.15 or higher, which is significantly higher than the conventional value (around 0.1), and the pressure magnification suction efficiency (AAP / WR) is 0.50 or higher, which is the conventional value (0). (About 4).

[Examples 4 to 9, Comparative Examples 3 to 9]
By changing the water-absorbent resin particles obtained in the reference example described in Example 1 above, the surface treatment agent, the heat-crosslinking conditions, and the standard sieve used to the conditions shown in Table 2, particulate water-absorbent resin Compositions (4) to (9) and comparative particulate water-absorbing resin compositions (3) to (8) were obtained. Moreover, the water absorbent resin particle IM-1000 (manufactured by Sanyo Chemical Co., Ltd.) as a commercial product was used as a comparative particulate water absorbent resin composition (9). The performances of the obtained particulate water-absorbing resin compositions (4) to (9) and comparative particulate water-absorbing resin compositions (3) to (9) are shown in Tables 2, 3 and 4. The water content of the particulate water-absorbing resin composition (4) obtained in Example 4 was 0.2% by weight.

Example 10
To 100 parts by weight of the particulate water-absorbing resin composition (4) obtained in Example 4, 100 parts by weight of a 50% by weight aqueous solution of aluminum sulfate 14-18 hydrate (manufactured by Kanto Chemical Co., Ltd.) and 50 parts of sodium lactate 2.4 parts by weight of a mixed solution obtained by mixing 20 parts by weight of a weight% aqueous solution was added and mixed with stirring. The obtained water-absorbent resin was spread evenly on a glass petri dish, covered with a glass lid, and then left in a hot air drier adjusted to 60 ° C. for 60 minutes. Thereafter, the particulate water-absorbing resin composition taken out was passed through an opening of 600 μm using a JIS 600 μm standard sieve to obtain a particulate water-absorbing resin composition (10). The performance of the obtained particulate water-absorbing resin composition (10) is shown in Tables 5 and 6. Moreover, the water content of the obtained particulate water-absorbent resin composition (10) was 1.5% by weight.

Example 11
To 100 parts by weight of the particulate water-absorbing resin composition (5) obtained in Example 5, 2.0 parts by weight of a 50% by weight aqueous solution of aluminum sulfate 14-18 hydrate (manufactured by Kanto Chemical Co., Inc.) was added. And mixed with stirring. The obtained water-absorbent resin was spread evenly on a glass petri dish, covered with a glass lid, and then left in a hot air drier adjusted to 60 ° C. for 60 minutes. Thereafter, the particulate water-absorbing resin composition taken out was passed through an opening of 600 μm using a JIS 600 μm standard sieve to obtain a particulate water-absorbing resin composition (11). The performance of the obtained particulate water-absorbing resin composition (11) is shown in Tables 5 and 6.

[Comparative Example 10]
In the method described in Example 10, the same procedure as in Example 10 is performed except that the particulate water-absorbent resin composition (4) used in the practice is changed to a comparative particulate water-absorbent resin composition (3). Thus, a comparative particulate water-absorbing resin composition (10) was obtained. The performance of the comparative particulate water-absorbing resin composition (10) obtained is shown in Tables 5 and 6.
[Comparative Example 11]
To 100 parts by weight of the comparative particulate water-absorbing resin composition (3) obtained in Comparative Example 3, 0.1 part by weight of Leolosil QS-20 (manufactured by Tokuyama Corporation) was added and mixed. The particulate water-absorbing resin composition after mixing was passed through an opening of 600 μm using a JIS 600 μm standard sieve to obtain a comparative particulate water-absorbing resin composition (11). Tables 5 and 6 show the performance of the obtained comparative particulate water-absorbing resin composition (11).

[Examples 12 and 13, Comparative Examples 12 and 13]
The OH / C ratio of the particulate water absorbent resin composition was measured. Table 7 shows the particulate water-absorbing resin composition used for the measurement and the measurement results.

[Reference Example 3]
The particulate water-absorbing resin composition (4) obtained in Example 4 was hit with a hammer and pulverized. The pulverized particulate water-absorbing resin composition had a weight average particle diameter (D50) of 143 μm. The OH / C ratio of the pulverized particulate water-absorbing resin composition was measured and found to be 0.012.
Example 14
<Preparation of absorbent injection test>
80 parts by weight of the particulate water-absorbing resin composition (4) obtained in Example 4 and 20 parts by weight of wood pulverized pulp were dry-mixed with a mixer. The resulting mixture was formed into a web having a size of 440 mm × 120 mm. The web was pressed at a pressure of 2 kg / cm ² for 5 seconds to obtain an absorber having a basis weight of 280 g / m ² . A liquid-impermeable polypropylene backsheet, the absorbent body, and a liquid-permeable polyethylene topsheet were attached to each other in this order with a double-sided tape to obtain an absorbent article. On the absorbent article, a transparent acrylic resin flat plate of 500 mm × 150 mm provided with a cylinder having a diameter of 70 mm and a height of 90 mm in the center and having a bottom penetrated was installed. A weight was placed on the flat plate so that a 0.3 psi load was uniformly applied.

<Liquid injection test>
Pour 75 ml of 0.9 wt% physiological saline adjusted to 35-37 ° C into the cylinder at once, measure the time from the time of pouring, and wait until the liquid in the cylinder is absorbed by the absorber and cannot be seen visually Was measured (first time). Five minutes after the first liquid injection, as in the first time, 75 ml of 0.9% by weight physiological saline adjusted to 35 to 37 ° C. was poured into the cylinder at once, and the time was measured from the time of pouring. The time until the liquid inside was absorbed by the absorber and disappeared visually was measured (second time). Five minutes after the second liquid injection, as in the first time, 75 ml of 0.9 wt% physiological saline adjusted to 35 to 37 ° C. was poured into the cylinder at once, and the time was measured from the time of the injection. The time until the liquid inside was absorbed by the absorber and disappeared visually was measured (third time). Five minutes after the third liquid injection, similarly to the first time, 75 ml of 0.9 wt% physiological saline adjusted to 35 to 37 ° C. was poured into the cylinder at once, and the time was measured from the time of the injection. The time until the liquid inside was absorbed by the absorber and disappeared visually was measured (fourth time).

<Measurement of return amount>
Ten minutes after the fourth injection, the weight and acrylic resin flat plate were removed, and 30 paper towels (kitchen towel WRG22 (50C) made by Oji Napier Co., Ltd.) were placed on the absorbent article. Then, an acrylic resin flat plate was installed, and the plate was further left for 1 minute under a load of 20 g / cm ² . By measuring the change in weight of the paper towel, the amount of liquid absorbed by the paper towel was determined, and this was defined as the return amount (g).
The obtained results are shown in Table 8.
[Comparative Examples 14-15]
The particulate water-absorbing resin composition (4) obtained in Example 4 was compared with the comparative particulate water-absorbing resin composition (3) obtained in Comparative Example 3, and the comparative particulate water-absorbing resin obtained in Comparative Example 5 The test was conducted in the same manner as in Example 14 except that the composition (5) was changed.

  The obtained results are shown in Table 8.

  ADVANTAGE OF THE INVENTION According to this invention, the particulate water-absorbing resin composition which made compatible the "liquid permeability" and the "liquid uptake | capture characteristic" which were the physical properties which conflicted conventionally is provided safely and easily. Such a particulate water-absorbent resin composition has an absorption characteristic that has not existed in the past, so it can be suitably used for an absorbent body (molded absorbent layer) such as a disposable diaper, and can greatly improve the absorption power of the diaper, Reduce leakage.

It is a schematic sectional drawing of the measuring apparatus used for the measurement of the saline flow conductivity (SFC) of a water absorbing resin composition. It is a perspective view of the apparatus used in order to determine the liquid suction speed. FIG. 3 is a side view of FIG. 2.

Explanation of symbols

31 Tank 32 Glass tube 33 0.69 wt% sodium chloride aqueous solution 34 L-shaped tube with cock 35 Cock 40 Container 41 Cell 42 Stainless steel wire mesh 43 Stainless steel wire mesh 44 Swelling gel 45 Glass filter 46 Piston 47 Hole 48 in piston Collection Container 49 Upper pan balance 51 Trough sheet 52 Trough groove 53 Screen 54 Yokogi 55 Experimental stand 56 Liquid reservoir tank 57 Liquid 58 Experimental jack 59 Particulate water-absorbing resin composition (weight 1 g, spraying distance 20 cm)

Claims (18)

A particulate water-absorbent resin composition mainly comprising a water-absorbent resin (A) having a cross-linked structure obtained by polymerizing an acid group-containing unsaturated monomer,
The particle size of the composition is less than 850 μm, and particles of 150 μm or more are 90% by weight or more of the whole,
Containing at least the surface of the polyol (B) having a valence of 4 or more,
A particulate water-absorbing resin composition. A particulate water-absorbent resin composition mainly comprising a water-absorbent resin (A) having a cross-linked structure obtained by polymerizing an acid group-containing unsaturated monomer,
Containing at least the surface of the tetravalent or higher polyol (B) and the trivalent or higher polycation.
A particulate water-absorbing resin composition.   The particulate water-absorbent resin composition according to claim 2, wherein the particle-sized water-absorbent resin composition has a particle size of less than 850 μm and 150 μm or more is 90% by weight or more of the whole. A particulate water-absorbent resin composition mainly comprising a water-absorbent resin (A) having a cross-linked structure obtained by polymerizing an acid group-containing unsaturated monomer,
The particle size of the composition is less than 850 μm, and particles of 150 μm or more are 90% by weight or more of the whole,
Liquid diffusion rate (LDV) (mm / s)> − 0.186 × absorption capacity without pressure (CRC) (g / g) +5.75
(However, LDV> 0.10 (mm / s))
Satisfy the relationship
A particulate water-absorbing resin composition. A particulate water-absorbent resin composition mainly comprising a water-absorbent resin (A) having a cross-linked structure obtained by polymerizing an acid group-containing unsaturated monomer,
The particle size of the composition is less than 850 μm, and particles of 150 μm or more are 90% by weight or more of the whole,
The OH / C ratio of the surface determined based on photoelectron spectroscopic analysis is 0.03 to 0.15.
A particulate water-absorbing resin composition.   The particulate water-absorbing resin composition according to claim 4 or 5, which contains at least the surface of a tetravalent or higher polyol (B).   The water absorbent resin (A) has a weight average particle diameter (D50) of 300 to 600 µm and a logarithmic standard deviation (σζ) of a particle size distribution of 0.25 to 0.45. The particulate water-absorbing resin composition according to claim 1.   The particle according to any one of claims 1 to 3, or the particle according to any one of claims 1 to 3, wherein the tetravalent or higher polyol (B) is contained in an amount of 0.01 to 20 wt% with respect to the water absorbent resin (A). Water-absorbent resin composition.   The particulate water-absorbent resin composition according to any one of claims 1 to 3 or claim 6 to 8, wherein the tetravalent or higher polyol (B) is a sugar alcohol.   The particulate water-absorbent resin composition according to any one of claims 1 to 9, wherein the composition has a water absorption capacity (CRC) of 20 g / g or more under no pressure.   The particulate water-absorbent resin composition according to any one of claims 1 to 10, wherein the water absorption capacity under pressure (AAP) of the composition is 20 g / g or more. Saline flow conductivity (SFC) is 10 ^{(Unit: 10 -7 × cm 3 × s} × g -1) of the composition is at least, the particulate water absorbent according to any one of claims 1 to 11 Resin composition.   Any one of Claims 1 to 12, wherein the water absorption capacity (CRC) (g / g) / liquid suction speed (WR) (s) of the composition is 0.15 (g / g / s) or more. The particulate water-absorbing resin composition according to claim 1.   The water absorption capacity under pressure (AAP) (g / g) / liquid uptake speed (WR) (s) of the composition is any one of claims 1 to 13, which is 0.15 (g / g / s) or more. The particulate water-absorbent resin composition described in 1. Saline flow conductivity (SFC) (unit: 10 ⁻⁷ × cm ³ × s × g ⁻¹ ) / liquid suction speed (WR) (s) of the composition is 0.50 (unit: 10 ⁻⁷ × cm) ^The particulate water-absorbent resin composition according to any one of claims 1 to 14, which is ³ xg- ¹ ) or more.   The particles according to any one of claims 1 to 15, wherein the composition has a weight average particle diameter (D50) of 300 to 600 µm and a logarithmic standard deviation (σζ) of a particle size distribution of 0.25 to 0.45. Water-absorbent resin composition.   The particulate water-absorbent resin composition according to any one of claims 1 to 16, wherein the water-absorbent resin (A) having a crosslinked structure is further surface-crosslinked. A method for producing a particulate water-absorbent resin composition comprising as a main component a water-absorbent resin (A) having a crosslinked structure obtained by polymerizing an acid group-containing unsaturated monomer,
The water-absorbent resin (A) is less than 850 μm and particles of 150 μm or more are 90% by weight or more of the total, and further, the water-absorbent resin (A) and a tetravalent or higher polyol (B) are mixed.
A method for producing a particulate water-absorbing resin composition.

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