JP5064032B2 - Method for producing water-absorbent resin granulated product and water-absorbent resin granulated product - Google Patents

Description

  The present invention relates to a method for producing a water absorbent resin granulated product and a water absorbent resin granulated product.

  Specifically, the present invention relates to a method for producing a water-absorbent resin granulated product containing a water-absorbent resin as a main component. More specifically, it is a water-absorbent resin granulated material suitably used for sanitary materials such as paper diapers (disposable diapers), sanitary napkins, so-called incontinence pads, waste liquid solidifying agents, water-stopping agents, etc. The present invention relates to a method for producing a water-absorbent resin granulated product having high granulation strength.

  In particular, the present invention relates to a method for efficiently producing a water-absorbent resin granulated product by mixing water-absorbent resin particles and an aqueous liquid and further mixing fine particles.

  In recent years, water-absorbing resins are widely used as hygroscopic materials for the purpose of absorbing body fluids in sanitary materials such as paper diapers and sanitary napkins, so-called incontinence pads (diapers). Water-absorbing resins are also widely used in various products such as agricultural and horticultural supplies such as water retention agents and soil conditioners.

  Properties that such water-absorbent resins should have include excellent absorption amount and absorption rate when in contact with aqueous liquids such as body fluids, liquid permeability, gel strength of swollen gel, and water suction from a substrate containing aqueous liquid Examples include suction force. However, the relationship between these characteristics does not necessarily show a positive correlation. For example, the higher the absorption ratio, the lower the physical properties such as liquid permeability, gel strength, and absorption rate.

  As a method for improving the water absorption characteristics of the water absorbent resin in a well-balanced manner, a technique for cross-linking the vicinity of the surface of the water absorbent resin (surface crosslinking treatment) is known, and various methods (for example, the following) Patent Documents 1 to 8) are disclosed.

  On the other hand, in general, the water-absorbent resin is more preferable as the content of the powder (fine powder) having a particle diameter of less than 150 μm is small. Such fine powder becomes a factor that lowers liquid permeability due to clogging even in absorbent articles such as diapers. In addition, there is a problem of dust during handling and loss during manufacturing of the diaper. For this reason, a water-absorbing resin with less fine powder is desired.

  Conventionally, as a method for producing a water-absorbent resin with a small amount of fine powder, (1) a method of adjusting the particle size by optimizing the degree of polymerization and pulverization, and (2) the generated fine powder is classified by a sieve or an air flow. The method of removing is known. However, even in the method (1), a large amount of fine powder such as several percent to several tens of percent is generated during the production process. Discarding the fine powder generated by the method (2) greatly reduces the yield and is disadvantageous in terms of disposal cost.

  Therefore, various proposals have been made to solve the above problem by granulating or regenerating fine powder that is inevitably generated in the production process of the water absorbent resin. For example, as methods other than granulation, for example, Patent Documents 9 to 11 propose a method in which fine powder is mixed with a polymer gel (or a substance having a high viscosity) and used. However, these methods cannot sufficiently reduce the amount of fine powder.

  Patent Documents 12 to 13 propose a granulation method by mixing fine powder and water. In these methods, although the granulation ratio of the fine powder is high, the amount of fine powder in the obtained granulated product is not sufficiently reduced.

  In Patent Documents 14 to 17, a method of mixing and granulating a water-absorbent resin and an aqueous liquid in the presence of an inorganic salt compound, a water-insoluble inorganic fine powder, a polymer compound, a metal ion-containing compound, or the like, which is a mixing aid. Proposed. Since these methods use mixing aids, in general, the problem of increased production costs, generation of dust due to water-insoluble inorganic fine powder, and the absorption characteristics of the resulting water-absorbent resin are said to be reduced. Have a problem.

  Further, in Patent Document 12, even if the fine powder is reduced by granulating the water-absorbent resin powder, the granulated particles are destroyed (granulated) in the process of transporting the water-absorbent resin and processing the final product (for example, a paper diaper). When the powder is regenerated and the fine powder is regenerated, the absorption rate decreases, the water-soluble content of impurities increases, or the physical properties such as the absorption capacity under pressure decrease. It is suggested that there is a need for high granulation strength in the granulated product.

  In addition, one of the factors affecting the physical properties of the water-absorbent resin is the particle size, and in order to satisfy various properties required for these products, adjusting the particle size of the water-absorbent resin by granulation is not possible. Very important.

  Granulation means agglomeration of a plurality of particles to form an aggregate having a constant particle diameter. Many techniques for granulating a water-absorbing resin have been studied so far, but in most cases, an aqueous liquid ( This is achieved by adding an additive such as water or an aqueous metal salt solution to the water-absorbent resin and stirring and mixing. On the other hand, generally, the smaller the content of the water-absorbent resin particles (hereinafter referred to as fine powder) whose main component is particles having a particle diameter of less than 200 μm, in particular, the water-absorbent resin particles whose main component is a particle diameter of less than 150 μm is preferable. .

  Such fine powder becomes a factor that decreases liquid permeability due to clogging even in an absorbent article such as a diaper. In addition, there is a problem of dust during handling and loss during manufacturing of the diaper. For this reason, a water-absorbent resin with less fine powder is desired.

  Therefore, various proposals have been made to solve the above-mentioned problems by granulating or regenerating fine powder that is inevitably generated in the production process of the water absorbent resin. As means other than granulation, for example, in Patent Documents 9, 10, and 14, the above fine powder is gelled by mixing the fine powder with water or a water-containing gel, and then the obtained gelled product is pulverized and dried. A method for regenerating large particles has been proposed. However, in these methods, the fine powder is once made into a gelled product, and after drying, a process such as pulverization is performed, and the obtained water-absorbent resin particles are not particularly reduced in fine powder.

  As for the amount of aqueous liquid added, most of the cases are adding a small amount of aqueous liquid (5% to 10% by weight or less) or a large amount of aqueous liquid (100% or more) to the water-absorbent resin. The reason for this is that when the water content of the water-absorbing resin hydrate is 60 to 80% (the amount of the aqueous liquid is 20 to 40%), the water-absorbing resin hydrate has the highest adhesiveness and is a lump. It has the property to become. Although it has nothing to do with the scope of rights of this patent, it is speculated that this adhesive force is derived from hydrogen bonding of polyacrylic acid (salt), which is also the raw material of the water-absorbent resin, and granulated particles are formed by this adhesive force. However, it becomes a lump by excessive adhesive force.

  On the other hand, a water-absorbent resin (water-absorbent resin hydrate) to which an aqueous liquid is added usually has poor fluidity, and the entire water-absorbent resin hydrate tends to aggregate and tend to be agglomerated. Therefore, in order to obtain fluidity, by drying the water-absorbing resin water-containing material, moisture existing near the surface of the water-absorbing resin water-containing material (the presence of this water softens the water-absorbing resin water-containing material, It is necessary to scatter (evaporate and dry) the water-absorbent resin hydrated product from the water-absorbing resin hydrated product, or to diffuse the surface moisture into the water-absorbent resin hydrated product (cured).

Also disclosed is a technique for producing a water-absorbent resin by adding not only an aqueous liquid but also inorganic particles. For example, in order to impart moderate strength to the water-absorbent resin and improve the water absorption speed of the granulated product, after adding an ethylene-acrylic acid copolymer and inorganic particles, water is added to produce the water-absorbent resin. Disclosed are methods (for example, Patent Document 19) and methods for producing a water-absorbent resin by adding an aqueous liquid and a dispersion of an inorganic powder in order to improve blocking properties under moisture absorption (for example, Patent Document 20). ing.
US Pat. No. 4,666,983 US Pat. No. 4,734,478 US Pat. No. 5,422,405 US Pat. No. 5140076 US Patent No. 6071976 US Pat. No. 6,720,389 US Pat. No. 5,164,459 US Pat. No. 6,254,990 European Patent No. 463388A European Patent No. 417761A European Patent 495594A US Pat. No. 6,228,930 US Pat. No. 6,458,921 US Pat. No. 4,970,267 European Patent 644224 US Pat. No. 5,200,286 European Patent No. 318989B European Patent No. 495594 JP-A-8-113653 (published May 7, 1996) JP 2000-93792 A (released on April 4, 2000)

  Many attempts have been made to reduce the fine powder of the water-absorbent resin as described above. However, there is no simple granulation method that is simple and significantly reduces the amount of fine powder.

  In addition, in the conventional method of adding an aqueous liquid and stirring and mixing, formation of a lump with strong adhesive force, non-uniform mixing of the added aqueous liquid, and the like, gradually becoming difficult to stir and mix. For example, a diameter of several centimeters to several tens of centimeters or more) is formed. To produce granulated particles with a uniform particle size using these highly adhesive water-absorbent resin hydrates, stronger agitation and crushing power and longer agitation time (granulation time) are required. It is speculated that this leads to an increase in the production cost of the granulated particles (for example, 1 mm to 0.15 mm) and a decrease in physical properties accompanying the necessity of crushing the lump.

  Moreover, since the water-absorbing resin hydrate obtained by the conventional method of adding an aqueous liquid and stirring and mixing is likely to become a lump as described above, it is very difficult to dry. When a lump is formed, not only the heat conduction efficiency to the water-absorbing resin hydrated product is deteriorated in a process such as drying, but also there is a tendency to prevent the movement of moisture. In addition, drying and the like are not uniform. As a result, efficient granulation such as physical property degradation cannot be performed.

  That is, since the conventional technology cannot prevent the formation of a mass of the water-absorbent resin hydrate, the water-absorbent resin hydrate cannot be efficiently dried or cured. There is a problem that it is not possible to efficiently produce granulated particles having slag.

  Patent Document 19 discloses that water mixing is performed by adding water after mixing inorganic powder, an ethylene-acrylic acid copolymer, and water in a water-absorbing resin, and then drying to obtain high particle strength and an appropriate particle size. However, it is described that a granulated product having a narrow particle size distribution can be obtained with a high yield, but this technology prevents the formation of a mass of the water-absorbing resin water-containing material and enables efficient drying or curing. It is not intended to do.

  Furthermore, Patent Document 20 describes a technique for obtaining a water-absorbing agent having excellent blocking properties under moisture absorption by mixing a water-absorbing resin, an aqueous liquid, and a dispersion of inorganic powder. No. 20 is not intended to prevent the formation of a mass of the water-absorbing resin hydrate, and to enable efficient drying or curing. Moreover, since the technique described in Patent Document 20 does not perform drying or the like after mixing the water-absorbent resin, the aqueous liquid, and the dispersion of the inorganic powder, it is not possible to sufficiently obtain granulated particles having fluidity. Can not.

  The present invention has been made in view of the above-described conventional problems, and its object is to solve various problems caused by the fine powder of the water-absorbent resin described above, and to have a high granulation strength and granulation. Water-absorbent resin granulated product that does not deteriorate in physical properties due to the production of the water-absorbent resin granulated product with a small amount of fine powder, or that prevents the formation of a mass of the water-absorbent resin water-containing product and enables efficient drying or curing It is providing the manufacturing method of a thing, and a water absorbent resin granulated material.

The method for producing a particulate water-absorbing agent of the present invention comprises a step (a) of mixing a first water-absorbing resin particle having a weight average particle diameter of less than 200 μm and an aqueous liquid to obtain a water-absorbing resin hydrate, and the water-absorbing agent. sexual resin hydrate is characterized by a weight average particle diameter and the step (b) mixing the second water-absorbing resin particles child is 200～800Myuemu.

A method of manufacturing a water absorbing resin granulation product of the present invention, it is preferable moisture content of the upper Symbol absorbent resin hydrate of 20 wt% to 99 wt% or less.

  In the method for producing a water-absorbent resin granulated product of the present invention, it is preferable that the first water-absorbent resin particle containing the aqueous liquid is a hydrogel.

  In the method for producing a water-absorbent resin granulated product of the present invention, the first water-absorbent resin particles are preferably subjected to surface cross-linking treatment.

  Moreover, the manufacturing method of the water absorbent resin granulated product of the present invention includes a step (c) of heating and drying a mixture of the first water absorbent resin particles and the second water absorbent resin particles containing the aqueous liquid. preferable.

  Moreover, it is preferable that the weight ratio of the 1st water absorbing resin particle and the 2nd water absorbing resin particle is the range of the manufacturing method of the water absorbing resin granulated material of this invention in the range of 1 / 99-50 / 50.

  According to the above configuration, since the aqueous liquid can be sufficiently distributed to the water absorbent resin particles, it is possible to provide a sufficient adhesive force to the water absorbent resin particles, and to obtain a granulated product having an optimum strength. Obtainable. Therefore, granulation of the water-absorbing resin particles can proceed smoothly in the aqueous liquid mixing step.

  The method for producing a water-absorbent resin granulated product of the present invention includes a step (d) of classifying a mixture of the first water-absorbent resin particles and the second water-absorbent resin particles containing the aqueous liquid or a dried product thereof. It is preferable to contain.

  In the method for producing a water-absorbent resin granulated product of the present invention, the obtained water-absorbent resin granulated product is preferably a granulated product of first water-absorbent resin particles and second water-absorbent resin particles. .

  In the method for producing a water-absorbent resin granulated product of the present invention, the first and second water-absorbent resin particles are preferably polyacrylic acid-based water-absorbent resins.

  The water-absorbent resin granulated product of the present invention is obtained through a specific mixing step, thereby solving various problems caused by the fine powder of the water-absorbent resin, having high granulation strength, and lowering physical properties due to granulation. Also, the amount of fine powder is greatly reduced.

The water-absorbent resin granulated product according to the present invention is a water-absorbent resin granulated product obtained by the method for producing a water-absorbent resin granulated product according to the present invention. 20 parts by weight or less in 5 parts by weight or more with respect to parts, seen including, (at 1) absorption capacity without load for 0.90 wt% sodium chloride aqueous solution 27 g / g or more, (2) 0.90 wt The absorption capacity under pressure at 1.9 kPa with respect to a 10% sodium chloride aqueous solution is 20 g / g or more, and (3) the absorption capacity under pressure at 4.8 kPa with respect to a 0.90% by weight sodium chloride aqueous solution is 10 g / g or more. (4) Absorption rate with respect to 0.90% by weight sodium chloride aqueous solution is 20 seconds or more and 50 seconds or less, and (5) JIS standard sieve having an opening of 150 μm with respect to 100 parts by weight of the water-absorbent resin granulated product. Zero particles passing through It is characterized in that part or 5 or less parts by weight.

  According to said structure, when a water absorbent resin granulated material is used for products, such as a diaper, a leak and return amount hardly arise in a product. Therefore, a product with high physical properties can be obtained.

(Embodiment 1)
[Water absorbent resin powder]
First, a method for producing a water absorbent resin powder used in the present invention will be described. In addition, the water absorbent resin granulated product according to the present invention is, in other words, a particulate water absorbing agent. The water absorbent resin particles according to the present invention are water absorbent resin powders in other words. In the present specification, the above terms are used as appropriate. As the water-absorbing resin powder used in the production of the particulate water-absorbing agent, known water-absorbing resins are widely used. Among them, those having a carboxyl group are preferably used, and typically acrylic acid and / or a salt thereof. Conventionally known water-absorbing resin resin powder that is obtained by polymerizing and crosslinking a hydrophilic unsaturated monomer containing as a main component, absorbing a large amount of water from 50 to 3000 times in water to form a hydrogel (Abbreviation: acrylate-based water-absorbing resin). In addition, the water-absorbent resin contains 40% by weight or less (lower limit of 0% by weight), preferably 30% of a water-soluble component in the water-absorbent resin (specified by the parallel extractable polymer of US Reissue Patent Re32649). A weight percent or less, more preferably 20 weight percent or less, and even more preferably 15 weight percent or less is used. In the present invention, the powder means a powder having a water content (specified in the examples) of 0 to 30% by weight, preferably 0 to 20% by weight, particularly 0 to 10% by weight.

  Examples of the acrylate include alkali metal salts, ammonium salts and amine salts of acrylic acid. The water-absorbing resin preferably has 10 to 40 mol% acrylic acid and 60 to 90 mol% acrylate as the constituent units (however, the total amount of both is 100 mol%). Neutralization of acrylic acid or its polymer may be performed with an unsaturated monomer, or may be performed during or after polymerization.

  When obtaining a water-absorbent resin, it may contain unsaturated monomers other than acrylic acid in combination with these acrylic acids or salts thereof, if necessary. The unsaturated monomer other than acrylic acid is not particularly limited. Specifically, for example, methacrylic acid, maleic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, 2- Anionic unsaturated monomers such as (meth) acryloylethanesulfonic acid and salts thereof; nonionic hydrophilic groups such as (meth) acrylamide, 2-hydroxypropyl (meth) acrylate and (methoxy) polyethylene glycol (meth) acrylate Containing unsaturated monomer; Cationic unsaturated monomer such as quaternary salt such as N, N-dimethylaminoethyl (meth) acrylate. These unsaturated monomers may be used independently and may mix 2 or more types suitably. These unsaturated monomers other than acrylic acid are usually used in an amount of 0 to 30 mol%, preferably 0 to 10 mol%, based on the total amount of acrylic acid and its salt used as the main component.

  In order to obtain the water-absorbent resin used in the present invention, it is possible to carry out bulk polymerization or precipitation polymerization when polymerizing the hydrophilic unsaturated monomer mainly composed of the above-mentioned acrylic acid or a salt thereof. However, from the viewpoint of performance and ease of polymerization control, it is preferable to perform aqueous solution polymerization or reverse phase suspension polymerization by using the hydrophilic unsaturated monomer as an aqueous solution.

  The 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, 4,683,274, and 5,244,735. Are described in US patents. Aqueous solution polymerization is a method of polymerizing an aqueous monomer solution without using a dispersion solvent. For example, US Pat. Nos. 4,462,001, 4,873,299, 4,286,082, 4,973,632, 4,985,518, 5,124,416, 5,250,640 are used. No. 5,264,495, US Pat. No. 5,145,906 and US Pat. No. 5,380,808, and European patents such as European Patents 081636, 09555086, and 0922717. The unsaturated monomers, crosslinking agents, initiators and the like exemplified in these polymerization methods can also be applied in the present invention.

  The concentration of the unsaturated monomer in the aqueous solution (hereinafter referred to as the monomer aqueous solution) when the hydrophilic unsaturated monomer is an aqueous solution is not particularly limited, but is preferably Is 10 to 70% by weight, more preferably 20 to 40% by weight. Moreover, when performing the said aqueous solution polymerization or reverse phase suspension polymerization, you may use together solvents other than water as needed, and the kind of solvent used together is not specifically limited.

  When starting the above polymerization, for example, potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-aminodipropane) dihydrochloride A radical polymerization initiator such as can be used. Further, a reducing agent that promotes the decomposition of the polymerization initiator can be used in combination, and a redox initiator can be obtained by combining the two. Examples of the reducing agent include (bi) sulfurous acid (salt) such as sodium sulfite and sodium bisulfite, L-ascorbic acid (salt), reducing metal (salt) such as ferrous salt, amines, and the like. Although it is mentioned, it is not particularly limited. The amount of these polymerization initiators used is usually from 0.001 to 2 mol%, preferably from 0.01 to 0.05 mol%, based on the physical properties, based on the unsaturated monomer.

  Further, the polymerization reaction may be carried out by irradiating the reaction system with active energy rays such as radiation, electron beam and ultraviolet ray. The reaction temperature in the polymerization reaction is not particularly limited, but is usually 10 to 130 ° C, preferably 20 to 120 ° C. Further, the reaction time is not particularly limited, and may be appropriately determined according to the kind of the hydrophilic unsaturated monomer or the polymerization initiator, the reaction temperature, and the like.

  The water-absorbing resin used in the present invention may be of a self-crosslinking type that does not use a crosslinking agent, but in one molecule, two or more polymerizable unsaturated groups or two or more reactive groups. Those obtained by copolymerizing or reacting an internal crosslinking agent having Specific examples of these internal crosslinking agents include, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meta) ) 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, triallylamine , 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.

  Moreover, these internal crosslinking agents may be used independently and may mix and use 2 or more types suitably. These internal cross-linking agents may be added all at once to the reaction system, or may be added in divided portions. In consideration of the absorption characteristics of the resulting water-absorbent resin, it is preferable to use a compound having two or more polymerizable unsaturated groups, and the amount used is relative to the unsaturated monomer component. It is preferably 0.005 to 2 mol%, more preferably 0.01 to 1 mol%.

  In the polymerization, various foaming agents such as carbonate (hydrogen) salt, carbon dioxide, azo compound, inert organic solvent; starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt) ), Hydrophilic polymers such as crosslinked polyacrylic acid (salt), various surfactants, chain transfer agents such as hypophosphorous acid (salt), chelating agents, etc., in the amount of 0 to 30% by weight, preferably You may add at 0 to 10 weight%.

  When the polymer obtained by the polymerization reaction is in a gel form, the gel polymer is dried, and is usually pulverized before and / or after drying to obtain a water absorbent resin powder.

  Moreover, the drying method of this gel-like polymer is not specifically limited, A normal dryer or a heating furnace is widely used, and drying is usually 80-250 degreeC, Preferably it is 100-220 degreeC, More preferably, it is 120-200 degreeC. In the temperature range. The drying time depends on the surface area of the gel polymer, the moisture content, and the type of the dryer or heating furnace, and is selected so as to achieve the desired moisture content.

  As the water-absorbent resin powder used in the present invention, those having a particle size obtained by pulverization may be used as they are, or those having an intentionally adjusted particle size according to the purpose may be used. The shape of the water-absorbent resin powder is preferably an indeterminate shape obtained by aqueous solution polymerization rather than a spherical shape obtained by reverse phase suspension polymerization in terms of granulation strength. The water-absorbing resin powder used for granulation of the present invention may or may not be subjected to surface cross-linking treatment, but preferably water-absorbing resin powder subjected to surface cross-linking treatment. It is. The weight average particle diameter of the water-absorbent resin powder before or after the surface cross-linking treatment is usually 50 to 1000 μm, depending on the particle size distribution of two types of water-absorbing resin powders (first and second) described later. Adjust it.

(2) Surface cross-linking treatment Hereinafter, the surface cross-linking treatment will be further described. As the surface cross-linking treatment used in the present invention, a known surface cross-linking treatment (for example, Patent Documents 1 to 8 described above) used for this purpose in the art is suitably used.

  For example, as the surface crosslinking agent used, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1, 3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedi Methanol 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbite Polyhydric alcohol compounds such as ruthenium; Epoxy compounds such as (poly) ethylene glycol diglycidyl ether, (poly or di to mono) glycerol polyglycidyl ether, (poly) propylene glycol diglycidyl ether, glycidol; ethylenediamine, diethylenetriamine, triethylene Polyamines such as tetramine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneimine, and their inorganic or organic salts (eg, aziridinium salts); polyvalent isocyanate compounds such as 2,4-tolylene diisocyanate; -Polyvalent oxazoline compounds such as ethylene bisoxazoline; carbonate compounds such as 1,3-dioxolan-2-one; epichlorohydrin, epibromohydrin, α-methyl epichloro Examples include haloepoxy compounds such as rhohydrin; hydroxides such as zinc, calcium, magnesium, aluminum, iron and zirconium, or polyvalent metal compounds such as chloride. These surface crosslinking agents may be used alone or in combination of two or more in consideration of reactivity. Among these surface crosslinking agents, polyhydric alcohol compounds, epoxy compounds, polyhydric amine compounds and salts thereof, at least one compound selected from the group consisting of alkylene carbonate compounds, and polyhydric alcohol compounds are preferred. .

In the surface cross-linking treatment, as proposed in US Pat. No. 5,422,405, the first surface cross-linking agent and the second surface cross-linking agent having different solubility parameters (SP values) as surface cross-linking agents capable of reacting with carboxyl groups. In the case of combining agents, an absorbent having an even better absorption capacity under pressure can be obtained. The first surface crosslinking agent is preferably a compound capable of reacting with a carboxyl group and having a solubility parameter of 12.5 (cal / cm ³ ) ^1/2 or more, and 13.0 (cal / cm ³ ) ^1/2 or more. The compound of is more preferable. The second surface crosslinking agent is preferably a compound capable of reacting with a carboxyl group and having a solubility parameter of less than 12.5 (cal / cm ³ ) ^1/2 , and 9.5 (cal / cm ³ ) ^1/2 to A compound within the range of 12.0 (cal / cm ³ ) ^1/2 is more preferred.

  The amount of the surface cross-linking agent used is preferably 0.001 to 10 parts by weight, preferably 0.01 parts by weight with respect to 100 parts by weight of the solid content of the water-absorbent resin powder, although it depends on the compounds used and combinations thereof. Part to 5 parts by weight is more preferred.

  In the present invention, when mixing the water absorbent resin powder and the surface cross-linking agent, it is preferable to use water as a solvent for the surface cross-linking agent. The amount of water used is preferably more than 0 and 20 parts by weight or less, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the water-absorbent resin powder.

  When mixing the water-absorbent resin powder and the surface cross-linking agent, a hydrophilic organic solvent (aqueous liquid) may be used in combination as necessary. Examples of the hydrophilic organic solvent include monohydric alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, and isopropyl alcohol; ketones such as acetone; ethers such as dioxane and tetrahydrofuran; The amount of the hydrophilic organic solvent to be used is preferably 20 parts by weight or less, more preferably 0 to 10 parts by weight with respect to 100 parts by weight of the water absorbent resin powder.

  Furthermore, in order to improve the mixing property and the reaction life, 0 to 5 weights of a basic compound such as a surfactant, an inert inorganic powder, an organic acid (salt), an inorganic acid (salt), and caustic soda in 100 parts by weight of the water-absorbing resin. You may use together.

  After mixing the water absorbent resin powder and the surface cross-linking agent, heat treatment is further performed to crosslink the vicinity of the surface of the water absorbent resin powder. That is, in order to react the cross-linking agent in the vicinity of the surface of the water-absorbent resin powder, it is preferable to perform heat treatment in consideration of the reactivity of the cross-linking agent, the simplicity of the production apparatus, and the productivity. Although the processing temperature of heat processing is based also on the surface crosslinking agent to be used, the range (heating medium temperature) of 80-250 degreeC and also 100-200 degreeC is preferable. Said heat processing can be performed using a normal dryer or a heating furnace. Examples of the dryer include a groove-type mixing dryer, a rotary dryer, a disk dryer, a fluidized bed dryer, an airflow dryer, and an infrared dryer.

(3) Addition of aqueous liquid The method for producing the particulate water-absorbing agent of the present invention comprises the step (a) of mixing the first water-absorbent resin powder and the aqueous liquid, the first water-absorbent resin powder containing the aqueous liquid, and A step (b) of mixing a second water-absorbent resin powder, and a method for producing a particulate water-absorbing agent.

  The first water-absorbing resin powder and the second water-absorbing resin powder used in the present invention may be water-absorbing resin powders having the same component or water-absorbing resin powders having different components. Further, the two types of water-absorbent resin powders (first and second) used in the present invention may have the same particle size distribution or different particle size distributions. A combination of acrylate-based water-absorbent resins, in which the weight-average particle diameter of the first water-absorbent resin powder is smaller than the weight-average particle diameter of the second water-absorbent resin powder is used. In addition to the two types of water-absorbing resin powders (first and second), there may be a third or more water-absorbing resin powder. In addition, the first water-absorbent resin powder is surface-crosslinked, and more preferably the second water-absorbent resin powder is also surface-crosslinked, due to the miscibility of the aqueous liquid.

  The first water-absorbent resin powder preferably has a weight average particle diameter of less than 200 μm. Further, the proportion of the water-absorbent resin powder having a particle diameter of 150 μm or less in the first water-absorbent resin powder is preferably 30% by weight or more (upper limit 100% by weight), more preferably 50% by weight or more, and further preferably 70% by weight. As mentioned above, it is still more preferably 90% by weight or more.

  The weight average particle diameter of the second water absorbent resin powder is preferably 200 to 800 μm, more preferably 230 to 600 μm, and still more preferably 260 to 500 μm.

  The second water absorbent resin powder is preferably in a dry state. In the present invention, the dry state does not necessarily mean that the water content of the water-absorbent resin powder is 0% by weight, and is usually within the range of 0 to 15% by weight, preferably 0 to 10% by weight.

  The ratio of the first water-absorbent resin powder and the second water-absorbent resin powder is not particularly limited, but is usually the ratio of the first water-absorbent resin powder and the second water-absorbent resin powder. The weight ratio of resin powder / second water-absorbent resin powder is in the range of 1/99 to 50/50, preferably 2/98 to 40/60, more preferably 3/97 to 30/70.

  The production method of the first water-absorbent resin powder and the second water-absorbent resin powder is not limited as long as it is the above-mentioned production method, and each of them is individually polymerized, dried, pulverized, and the particle size is adjusted as necessary. May be produced by subjecting to a surface cross-linking treatment, polymerization, drying, pulverization, particle size adjustment as necessary, and water-absorbing resin powder obtained by subjecting the surface cross-linking treatment to a first water absorption by classification. You may divide and manufacture in the resin resin powder and the 2nd water absorbing resin powder. In view of the miscibility of the aqueous liquid, preferably, the water-absorbing resin powder subjected to surface crosslinking treatment is used as the first water-absorbing resin powder, and further the second water-absorbing resin powder.

  In order to achieve the object of the present invention, the temperature of the two types of water-absorbent resin powder is not particularly limited, but is usually 5 ° C. or higher, preferably 20 ° C. or higher, and there is no significant change even when it exceeds 100 ° C. Usually, it is performed at 100 ° C. or lower.

  In the present invention, the aqueous liquid to be mixed with the first water-absorbent resin powder is not particularly limited, and examples thereof include water, an aqueous liquid containing a water-soluble salt, or a hydrophilic organic solvent. From the viewpoint of physical properties and granulation strength, the proportion of water in the aqueous liquid is in the range of 90 to 100% by weight, preferably 95 to 100% by weight, more preferably 99 to 100% by weight. For example, the surface cross-linking agent) or a surfactant may be included. By using a crosslinking agent in combination with the aqueous liquid, it may be possible to reduce the water-soluble component and further improve the granulation strength.

  In order to achieve the object of the present invention, the temperature of the aqueous liquid is not particularly limited, but is usually 5 ° C. or higher and the boiling point or lower, preferably 20 ° C. or higher, and since it does not change greatly even when it exceeds 100 ° C., At 100 ° C. or lower.

  The amount of the aqueous liquid used is usually 1 to 50 parts by weight, preferably 5 to 30 parts by weight, more preferably 100 parts by weight of the total weight of the first water absorbent resin powder and the second water absorbent resin powder. 10 to 20 parts by weight. When the amount of the aqueous liquid used exceeds 50 parts by weight, it is difficult to handle as a granulated product, and it is disadvantageous in terms of drying cost. On the other hand, when the amount of the aqueous liquid used is less than 1 part by weight, the granulation strength becomes insufficient, and there is a possibility that the granulation characteristics cannot be exhibited in the final product. Moreover, mixing may become non-uniform | heterogenous and a granulated material may not be obtained.

  The first water-absorbing resin powder containing the aqueous liquid according to the present invention is preferably a water-containing gel. That is, the water content (specified in the examples) of the water-containing gel is usually 20% by weight or more, preferably 30 to 95% by weight, more preferably 40 to 90% by weight. A strong granulated product is obtained.

  In the present invention, the step (a) of mixing the first water-absorbent resin powder and the aqueous liquid is not particularly limited, and after mixing the first water-absorbent resin powder and the aqueous liquid, there is no huge aggregate and is uniform. It only needs to be mixed. Usually, an aqueous liquid is added to the first water absorbent resin powder, but the first water absorbent resin powder may be added to the aqueous liquid.

  When the aqueous liquid is mixed with the first water absorbent resin powder, the mixing method is not particularly limited. The aqueous liquid may be poured into the first water-absorbing resin powder being stirred at once, or the aqueous liquid may be gradually added by a method such as spraying. However, if it takes a long time from the start of addition of the aqueous liquid to the first water absorbent resin powder until the end of the addition, the first water absorbent resin powder becomes a large agglomerate or kneaded during the process. As a result, the water absorbent resin is deteriorated. The charging time of the aqueous liquid is preferably 60 seconds or less, more preferably 30 seconds or less, and most preferably 10 seconds or less.

  Contrary to the above, when the first water-absorbing resin powder is mixed with the aqueous liquid, the mixing method is not particularly limited. For example, the first water-absorbing resin powder containing an aqueous liquid for achieving the object of the present invention can be obtained by a method in which the first water-absorbing resin powder is introduced into the aqueous liquid being stirred. In this case, the charging time of the water-absorbent resin powder is preferably 60 seconds or less, more preferably 30 seconds or less, and most preferably 10 seconds or less. In addition, the first water-absorbing resin powder containing the aqueous liquid for achieving the object of the present invention can also be obtained by a method in which the first water-absorbing resin powder and the aqueous liquid are simultaneously charged and mixed. In this case, the charging time of both raw materials is preferably 60 seconds or shorter, more preferably 30 seconds or shorter, and most preferably 10 seconds or shorter. Moreover, both raw materials may be continuously added and mixed simultaneously to produce a first water-absorbent resin powder containing an aqueous liquid for continuously achieving the object of the present invention.

  The time from the addition of the aqueous liquid to the first water-absorbent resin powder or the addition of the first water-absorbent resin powder to the aqueous liquid until the start of mixing increases with time. Since uniform mixing with the powder becomes difficult and large agglomerates are formed, it is better to start mixing as soon as possible, usually within 1 minute, preferably within 30 seconds. Further, the aqueous liquid may be added and mixed while stirring the first water absorbent resin powder, or the first water absorbent resin powder may be added to the aqueous liquid being stirred, Alternatively, the first water-absorbent resin powder and the aqueous liquid may be continuously added and mixed to produce the first water-absorbent resin powder containing the aqueous liquid used in the present invention continuously.

  In the present invention, the mixing of the first water absorbent resin powder containing the aqueous liquid and the second water absorbent resin powder in step (b) is not particularly limited, and the first water absorbent resin powder containing the aqueous liquid and It is only necessary that after the second water-absorbing resin powder is mixed, there is no huge aggregate and it can be mixed uniformly. Usually, the second water absorbent resin powder is added to the first water absorbent resin powder containing the aqueous liquid, but the first water absorbent resin powder containing the aqueous liquid is added to the second water absorbent resin powder. You may add. Add the second water absorbent resin powder to the first water absorbent resin powder containing the aqueous liquid, or add the first water absorbent resin powder containing the aqueous liquid to the second water absorbent resin powder and start mixing. The time until the time becomes longer, it becomes difficult to uniformly mix the first water-absorbent resin powder containing the aqueous liquid and the second water-absorbent resin powder, and a huge aggregate is formed. Since it is not possible to obtain a mixture that is a water-absorbent resin granulated product, the mixing is usually started within 1 minute, preferably within 30 seconds. Further, the second water-absorbing resin powder may be added and mixed while stirring the first water-absorbing resin powder containing the aqueous liquid, and further, the first water-absorbing resin powder containing the aqueous liquid and In some cases, the second water absorbent resin powder is continuously charged and mixed to continuously produce the water absorbent resin granulated product of the present invention.

  In the present invention, the step (a) of mixing the aqueous liquid and the step (b) of mixing the second water absorbent resin powder are preferably within 60 minutes.

  The mixing time in the step (a) or the step (b) is not particularly limited. However, if the mixing time is long, the first water-absorbing resin powder and / or the second water-absorbing resin powder is deteriorated. Within 10 minutes, preferably within 5 minutes, more preferably within 1 minute. If mixing is continued for a long time, the water-absorbent resin may be deteriorated, such as a decrease in water absorption capacity under pressure.

  The mixer to be used is not particularly limited as long as the mixing in the step (a) or the step (b) can be achieved, but a container-fixed mixer, among them, a mechanical stirring mixer is preferable. Examples of the mixer include a turbulizer (manufactured by Hosokawa Micron Co., Ltd.), a Redige mixer (manufactured by Redige Corporation), and a mortar mixer (manufactured by West Japan Tester Co., Ltd.). Either a batch type mixer or a continuous type mixer may be used. In some cases, a batch mixer is preferable in that stable performance can be achieved.

  The water-absorbent resin granulated product of the present invention can be further dried to improve the granulation strength. After the step (b), it is preferable to further include a step (c) of heating and drying a mixture of the first water absorbent resin powder and the second water absorbent resin powder containing the aqueous liquid.

  By heating and drying the mixture, the fine powder is more firmly integrated and regenerated to the same strength as the primary particles. The dried water-absorbent-resin granulated product obtained as described above is an excellent particulate water-absorbing agent having excellent impact resistance and a small amount of fine powder. The dried water-absorbent resin granulated product of the present invention is a water-absorbent resin granulated product obtained by heat-drying the water-absorbent resin granulated product by a method described later, and is specified in the range of moisture content and the like. is not. The drying method of the water-absorbent resin granulated product of the present invention is not particularly limited, and an ordinary dryer or a heating furnace is widely used, but preferably dried within a range of 40 to 150 ° C, more preferably 60 to 100 ° C. Then, since deterioration of a water absorbent resin granulated material decreases, it is preferable. As the drying time, it is necessary to carry out for a certain time or more from the viewpoint of physical properties, and it is usually 1 minute to 10 hours, preferably 3 minutes to 3 hours.

  Furthermore, in the present invention, following the steps (b) to (c), the mixture of the first water-absorbent resin powder and the second water-absorbent resin powder containing the aqueous liquid or the dried product thereof are crushed. And classification (d) is preferably included. The crushing is an operation for breaking granulation that is too large (for example, particles having a size of 850 μm or more), and may be performed entirely or only with coarse particles.

  The water-absorbent resin granulated product obtained as described above or the ground and classified product of the dried water-absorbent resin granulated product may be cross-linked in the vicinity of the surface as necessary. That is, the water-absorbent resin powder is made into a water-absorbent resin granulated product by the granulation method of the present invention described above, and further dried by heating to obtain a dried water-absorbent resin granulated product. A water-absorbing agent may be obtained, and the water-absorbing resin granulated product or the dried water-absorbing resin granulated product may be further subjected to the surface crosslinking treatment to produce a particulate water-absorbing agent.

  As mentioned above, the particulate water-absorbing agent according to the present invention is the water-absorbent resin granulated product and / or dried water-absorbent resin granulated product, and further, the water-absorbent resin granulated product and / or the water-absorbent resin granulated product. The dried granular material may have been subjected to the above surface cross-linking treatment.

  Unlike the method of the present invention, when two types of water-absorbent resin powders (first and second) are mixed in advance and mixed with an aqueous liquid (collective granulation), strong granulation is a feature of the present invention. It becomes difficult to obtain a strong water-absorbent resin granulated product and / or dried water-absorbent resin granulated product, and a particulate water-absorbing agent with a small amount of water-absorbent resin fine powder cannot be obtained.

  On the other hand, by mixing the first water-absorbing resin powder and the aqueous liquid and then mixing the first water-absorbing resin powder containing the aqueous liquid and the second water-absorbing resin powder, a special mixer There is no need to obtain a particulate water-absorbing agent with a small amount of fine powder, which is a granulated product of the first water-absorbent resin powder and the second water-absorbent resin powder. In the present invention, the particulate water-absorbing agent does not need to be an aggregate (granulated product) of a plurality of water-absorbent resin powders, but is composed of an aggregate of a plurality of water-absorbent resin powders (granulated). Or a mixture of the water-absorbent resin powder alone (primary particles). The fact that it is an aggregate (granulated product) of a plurality of water-absorbent resin powders means that a plurality of individual particles are aggregated and aggregated while maintaining the shape by an optical microscope, and swells as a plurality of discontinuous particles during liquid absorption. It can be confirmed by fact.

  The granulated product of the first water-absorbent resin powder and the second water-absorbent resin powder, which is the particulate water-absorbing agent of the present invention, has an increased weight average particle diameter of the water-absorbent resin powder used as a raw material, and It can be confirmed that the granulated product is generated by reducing the fine powder.

(4) The particulate water-absorbing agent of the present invention That is, the absorption capacity without load (CRC) with respect to physiological saline of the particulate water-absorbing agent of the present invention is 27 g / g or more, preferably 30 g / g or more, 33 g / g or more, It is set to 36 g / g or more. When the absorption capacity under no pressure is less than 20 g / g, there is a possibility that high physical properties are not exhibited when used for diapers. Moreover, although an upper limit is not ask | required in particular, about 60 g / g is enough from the cost increase by the difficulty on manufacture.

  The absorption capacity under load (AAP) under a 1.9 kPa load of the present invention is 20 g / g or more, more preferably 22 g / g or more, still more preferably 24 g / g or more, and particularly preferably 26 g / g or more. If the absorption capacity under pressure is less than 20 g / g, high physical properties may not be exhibited when used for diapers. Moreover, although an upper limit is not ask | required in particular, about 40 g / g is enough from the cost increase by the difficulty on manufacture.

  That is, the weight average particle diameter (D50) of the particulate water-absorbing agent of the present invention is 200 to 800 μm, more preferably 250 to 600 μm, still more preferably 300 to 500 μm, and the amount of fine powder less than 150 μm is explained in the examples. Before the impact resistance test, 0 to 5% by weight or less, further 3% by weight or less, particularly 1% by weight or less, and even after the impact resistance test, 0 to 5% by weight or less, and further 3% by weight or less. The logarithmic standard deviation (σζ) is controlled to 0.25 to 0.50, preferably 0.30 to 0.45.

  Disinfectant, antibacterial agent, fragrance, various inorganic powders, foaming agent, pigment, dye, hydrophilic short fiber, fertilizer, oxidizing agent, reducing agent, water, salt, etc. in the above particulate water-absorbing agent 0-30 weight %, Preferably in the range of 0 to 5% by weight, whereby various functions can be imparted. The particulate water-absorbing agent of the present invention can be applied to the use of various conventionally known water-absorbing resins, but it has few fine powders and is excellent in absorption characteristics and absorption speed under pressure. It can be suitably used for hygienic materials including absorbent materials such as diapers, sanitary napkins, and incontinence pads, and water-absorbing articles such as waste liquid solidifying agents and water-stopping agents.

(Embodiment 2)
As another embodiment, a method for producing a water-absorbent resin granulated product according to the present invention includes an aqueous liquid mixing step of obtaining a water-absorbent resin hydrate by mixing water-absorbent resin particles and an aqueous liquid, and Fine particle mixing step for obtaining a water-absorbing resin water-containing composition by mixing a resin water-containing material and fine particles, a curing step for curing the water-absorbing resin water-containing composition and / or a drying step for drying the water-absorbing resin water-containing composition And comprising. In addition, the manufacturing method according to the embodiment is referred to as “batch granulation method” for convenience. Hereafter, each said process is demonstrated.

<Aqueous liquid mixing process>
The aqueous liquid mixing step is a step of obtaining a water-absorbing resin hydrate by mixing the water-absorbing resin particles and the aqueous liquid. By this step, the water-absorbent resin particles can be obtained by granulating the water-absorbent resin particles by the action of the aqueous liquid.

  The water-absorbent resin particles of the present invention are conventionally known water-absorbent resins. For example, the water-absorbent resin particles absorb 50 to 1000 times as much water as ion-exchanged water, and are anionic, nonionic, or cationic. It is a conventionally known crosslinked polymer that forms a water-insoluble hydrogel.

  The water-absorbing resin particles must be water-swellable and water-insoluble, and the water-absorbing resin particles contain an uncrosslinked water-soluble component (water-soluble polymer), preferably 0% by weight or more. 30% by weight or less, more preferably 1% by weight or more and 25% by weight or less, further preferably 5% by weight or more and 20% by weight or less, and particularly preferably 5% by weight or more and 15% by weight or less.

  These are generally obtained by polymerizing in the form of a monomer solution, drying the polymer as necessary, and usually pulverizing it before and / or after drying. In the present invention, the water absorbent resin particles may be simply referred to as a water absorbent resin.

  Specific examples of the crosslinked polymer include partially neutralized crosslinked polyacrylic acid polymers (US Pat. No. 4,462,001, US Pat. No. 4,654,039, US Pat. No. 5,250,640, US Pat. No. 5,275,773). , European Patent No. 456136, etc.), cross-linked and partially neutralized starch-acrylic acid graft polymer (US Pat. No. 4,076,663), isobutylene-maleic acid copolymer (US Pat. No. 4,389,513) Saponification of vinyl acetate-acrylic acid copolymer (US Pat. No. 4,124,748), hydrolyzate of acrylamide (co) polymer (US Pat. No. 3,959,569), acrylonitrile polymer Examples thereof include hydrolysates (US Pat. No. 3,935,099).

  The water-absorbent resin particles used in the present invention are polyacrylic acid (salt) containing acrylic acid and / or acrylate as a structural unit obtained by polymerizing a water-soluble unsaturated monomer containing acrylic acid and / or a salt thereof. The particles are preferably water-absorbent resin particles made of a crosslinked polymer. Use of the monomer is preferable because the water absorption performance and safety of the resulting water absorbent resin particles are further improved.

  The above-mentioned polyacrylic acid (salt) -based crosslinked polymer means that acrylic acid and / or a salt thereof (excluding the crosslinking agent) is 50 mol% or more and 100 mol% or less, preferably 70 mol% or more and 100 mol in all constituent units. %, More preferably 90 mol% or more and a cross-linked polymer obtained by polymerizing a monomer containing 100 mol% or less. Moreover, it is preferable that 50 mol% or more and 90 mol% or less of the acid group in a polymer are neutralized, and it is more preferable that 60 mol% or more and 80 mol% or less are neutralized. Examples of the salt include alkali metal salts such as sodium, potassium and lithium, ammonium salts and amine salts. Neutralization for forming a salt may be performed in a monomer state before polymerization, or may be performed in a polymer state during polymerization or after polymerization, or may be used in combination.

  The polyacrylic acid (salt) -based crosslinked polymer is used in combination with a monomer (acrylic acid and / or a salt thereof) used as a main component and, if necessary, copolymerized with another monomer. There may be.

  Specific examples of other monomers include methacrylic acid, maleic acid, vinyl sulfonic acid, styrene sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, 2- (meth) acryloyloxyethane sulfonic acid Anionic unsaturated monomers such as 2- (meth) acryloyloxypropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (Meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, Nonionic hydrophilic group-containing unsaturated monomers such as nylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine and N-vinylacetamide; N, N-dimethylaminoethyl (meth) acrylate, N, N -Cationically unsaturated monomers such as diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and quaternary salts thereof Can do.

  The amount of the monomer other than acrylic acid and / or its salt is preferably 0 mol% or more and 30 mol% or less, more preferably 0 mol% or more and 10 mol% or less in the total monomers.

  Further, the monomer composition may contain another hydrophobic unsaturated monomer copolymerizable with the unsaturated monomer to the extent that the hydrophilicity of the resulting crosslinked polymer is not inhibited. . Specific examples of the copolymerizable monomer include (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate; vinyl acetate, vinyl propionate, and the like. And a hydrophobic monomer containing no acid group, hydroxyl group or amino group. These copolymerizable monomers may be used alone or in combination of two or more.

  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. However, it is preferably within the range of 10% by weight to 70% by weight, and more preferably within the range of 20% by weight to 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, 4,683,274, and 5,244,735, etc. In U.S. Patents. 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, 4,985,518, 5,124,416, No. 5,250,640, US Pat. No. 5,264,495, US Pat. No. 5,145,906 and US Pat. No. 5,380,808, and European patents such as European Patents 081636, 09555086, and 0922717. Monomer components and initiators exemplified in these polymerization methods can also be applied to the present invention.

  As a water-soluble polymerization method, a monomer aqueous solution is polymerized while crushing the resulting hydrogel in a double-arm kneader, or a monomer aqueous solution is supplied onto a belt driven in a predetermined container to polymerize. And a method of pulverizing the obtained gel with a meat chopper or the like.

  When starting the above 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.

  Further, a reducing agent that promotes the decomposition of the polymerization initiator can be used in combination, and a redox initiator can be obtained by combining the two. Examples of the initiator include (bi) sulfurous acid (salt) such as sodium sulfite and sodium bisulfite, L-ascorbic acid (salt), reducing metal (salt) such as ferrous salt, amines, and the like. Although it is mentioned, it is not particularly limited.

  The amount of these polymerization initiators used is usually from 0.001 mol% to 2 mol%, preferably from 0.01 mol% to 0.1 mol%, based on all monomers. When the amount of these polymerization initiators used is less than 0.001 mol%, the amount of unreacted monomers increases, and therefore, the residual monomer in the resulting water-absorbent resin and water-absorbing agent increases, which is preferable. Absent. On the other hand, when the usage-amount of these polymerization initiators exceeds 2 mol%, since the amount of water-soluble components in the obtained water-absorbing resin or water-absorbing agent increases, it may not be preferable.

  Further, the polymerization reaction may be initiated by irradiating the reaction system with active energy rays such as radiation, electron beam, and ultraviolet rays, and the above polymerization initiator may be used in combination. The reaction temperature in the polymerization reaction is not particularly limited, but the upper and lower limits of the reaction system are preferably in the range of 15 ° C. or higher and 130 ° C. or lower, and more preferably in the range of 20 ° C. or higher and 120 ° C. or lower. Further, the reaction time and the polymerization pressure are not particularly limited, and may be appropriately set according to the type of monomer or polymerization initiator, the reaction temperature, and the like.

  The crosslinked polymer may be of a self-crosslinking type that does not use a crosslinking agent, but a crosslinking agent having two or more polymerizable unsaturated groups or two or more reactive groups in one molecule. Those copolymerized or reacted are preferred.

  Specific examples of the crosslinking agent (also referred to as internal crosslinking agent) include, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, and (poly) propylene glycol di (meth) acrylate. , (Ethylene oxide modified) trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, (ethylene oxide modified) glycerin acrylate methacrylate, pentaerythritol tetra (meth) acrylate, dipenta Erythritol hexa (meth) acrylate, N, N-diallylacrylamide, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, diallyloxyacetic acid Bis (N-vinylcarboxylic acid amide), (ethylene oxide modified) tetraallyloxyethane, poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol Glycerin, pentaerythritol, ethylenediamine, polyethyleneimine, glycidyl (meth) acrylate, and the like.

  These internal crosslinking agents may be used alone or in combination of two or more. Among them, it is preferable to use a compound having two or more polymerizable unsaturated groups as an internal crosslinking agent from the viewpoint of water absorption properties of the water-absorbent resin particles obtained, and the amount used is based on the total amount of monomers. It is preferably within the range of 0.001 mol% to 2 mol%, more preferably within the range of 0.005 mol% to 0.5 mol%, and more preferably 0.01 mol% to 0.2 mol%. More preferably, it is within the range of mol% or less. When the amount of the internal cross-linking agent used is less than 0.001 mol% and more than 2 mol%, sufficient absorption characteristics 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?

  In the polymerization, the reaction system includes starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt), polyacrylic acid (salt) cross-linked hydrophilic polymer 0 wt% or more and 50% or more. Various foaming agents such as carbonic acid (hydrogen) salts, carbon dioxide, azo compounds, inert organic solvents, etc. in weight percent or less (based on monomer) or other weights ranging from 0% to 10% by weight; starch; various surfactants Chelating agent; chain transfer agent such as hypophosphorous acid (salt) may be added.

  In the case of aqueous solution polymerization, the crosslinked polymer obtained by the above polymerization is usually in the form of a lump, and is pulverized to form particles during or after the polymerization. The pulverization can be performed using various cutting means such as a roller cutter, a guillotine cutter, a slicer, a roll cutter, a shredder, a scissor, or a combination thereof, and is not particularly limited. In the case of reverse phase suspension polymerization, since it is polymerized in the form of particles, pulverization is usually unnecessary.

  When the water-absorbent resin particles are in the form of gel obtained by the aqueous solution polymerization, the crosslinked polymer is dried as necessary, if it is a hydrogel crosslinked polymer, It is usually pulverized before and / or after drying to obtain a water absorbent resin. Moreover, drying is normally performed in the temperature range of 80 to 250 ° C., preferably 100 to 220 ° C., more preferably 120 to 200 ° C. The drying time depends on the surface area of the polymer, the water content, and the type of the dryer, and is selected from 1 minute to 10 hours, for example, so as to achieve the desired water content.

  The water-absorbent resin particles may be particles obtained by pulverizing the water-containing gel-like crosslinked polymer in this way, and the water-containing gel-like crosslinked polymer is dried and further pulverized, classified, etc. It may be a shape. The particle diameter of the water-absorbent resin particles is not particularly limited, but is defined by standard sieve classification (JIS Z8801-1 (2000) or equivalent. The particle diameter is defined in the same manner below). The particle diameter is preferably less than 850 μm. When the particle size defined by the standard sieve classification is 850 μm or more, it is not preferable because it tends to be a lump during granulation and the physical properties such as the water absorption property of the water absorbent resin granulation are deteriorated.

  The particle size of the water-absorbent resin is 0% by weight or more and less than 20% by weight, particles having a particle size of 600 μm or more and 850 μm or less, 60% by weight or more and 60% by weight or less, and 20% by weight less than 200 μm. It is preferable that it is less than%. When the particle size is 600 μm or more and 850 μm or less is 20% by weight or more, or when the particle size is 300 μm or more and 600 μm or less is less than 60% by weight, and the particle size less than 200 μm is 20% by weight or more, body fluid (urine or blood Etc.) is not suitable because the absorption rate may be significantly reduced.

  The logarithmic standard deviation (σζ) of the particle size distribution is preferably in the range of 0.25 to 0.400, more preferably in the range of 0.270 to 0.380. When the logarithmic standard deviation (σζ) of the particle size distribution is smaller than 0.250, the manufacturing cost is remarkably increased, which is not appropriate. In addition, when the logarithmic standard deviation (σζ) of the particle size distribution exceeds 0.400, the particle size distribution at the time of granulation tends to be non-uniform and the granulation strength is not stable, which is not suitable for the present invention.

  The water-absorbent resin particles that can be used in the present invention preferably have an absorption capacity without load with respect to a 0.90% by weight sodium chloride aqueous solution of 10 g / g or more and 50 g / g or less, more preferably 20 g / g or more and 45 g. / G or less, more preferably 25 g / g or more and 45 g / g or less. When the pressureless absorption capacity with respect to the 0.90% by weight sodium chloride aqueous solution is smaller than 10 g / g, it is necessary to have many cross-linking agents when producing water-absorbing resin particles, and thus the above-mentioned water-soluble components are contained. Not only is it extremely reduced and the granulation strength is lowered, but also due to insufficient absorption of the water-absorbent resin, in the absorbent body such as diapers, the amount of liquid returned increases, resulting in a sticky feeling. It is not preferable.

  In addition, when the non-pressurized water absorption ratio with respect to the 0.90% by weight sodium chloride aqueous solution is larger than 50 g / g, the above-mentioned water-soluble components increase, and not only the water-soluble resin particles tend to become agglomerated during granulation. Since the gel strength of the gel particles swollen by the liquid absorption is reduced, the gel particles may be deformed under pressure such as body pressure, the gel layer volume of the water absorbent resin may be reduced, and leakage from the absorber may occur. is there.

  The water-absorbent resin particles that can be used in the present invention preferably have an absorption capacity under pressure at 1.9 kPa with respect to a 0.90% by weight sodium chloride aqueous solution of 10 g / g or more and less than 40 g / g, more preferably 20 g. / G or more and less than 35 g / g. The use environment of the absorbent body such as a diaper is that the pressure such as body pressure is always applied, and when the absorption capacity under pressure at 1.9 kPa with respect to the 0.90 wt% sodium chloride aqueous solution is smaller than 10 g / g, the water absorbent resin The amount of absorption under pressure is insufficient, which may cause leakage of body fluid (such as urine and blood) and / or a sticky feeling from the absorber.

  Further, in order to increase the absorption capacity under pressure at 1.9 kPa with respect to 0.90% by weight sodium chloride aqueous solution to 40 g / g or more, it is necessary to improve the absorbent resin, which causes an increase in production cost. Since the strength and the effect corresponding to the use of the diaper cannot be obtained, it is not necessary to make the absorption capacity under a load of 1.9 kPa with respect to the 0.90 wt% sodium chloride aqueous solution 40 g / g or more.

  The water-absorbent resin particles are not particularly limited, but are preferably surface-crosslinked. “Surface cross-linking” refers to reacting a functional group (particularly a carboxyl group) on the surface of water-absorbent resin particles with a compound capable of reacting with them (preferably an organic cross-linking agent or the like). By performing surface cross-linking, various properties required for a water-absorbing resin such as liquid permeability can be made more preferable.

  Examples of the surface cross-linking agent include organic cross-linking agents and polyvalent metal compounds that can form a cross-linked structure by reacting with functional groups of water-absorbent resin particles, in particular, carboxyl groups. Particularly preferably, the following organic crosslinking agents are used. For example, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, Glycerin, polyglycerol, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol Polyhydric alcohols of: ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycidol etc. Compound; polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and their inorganic or organic salts (for example, aziridinium salts); 2,4-tolylene Polyisocyanate compounds such as isocyanate and hexamethylene diisocyanate; 1,2-ethylene bi Polyvalent oxazoline compounds such as oxazoline; carbonic acid derivatives such as urea, thiourea, guanidine, dicyandiamide and 2-oxazolidinone; 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4 , 5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl- 1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, Alkylene carbonate compounds such as 1,3-dioxopan-2-one; haloepoxidation of epichlorohydrin, epibromohydrin, α-methylepichlorohydrin, etc. , And polyvalent amine adducts thereof (for example, Hercules Kaimen: registered trademark); silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane; 3-methyl-3- Oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, 3-butyl-3-oxetaneethanol, 3- Oxetane compounds such as chloromethyl-3-methyloxetane, 3-chloromethyl-3-ethyloxetane, and polyvalent oxetane compounds; These surface cross-linking agents may be used alone or in combination of two or more. Of these, polyhydric alcohols are preferred because they are highly safe and can improve the hydrophilicity of the surface of the water-absorbent resin particles.

In the surface cross-linking treatment, as proposed in US Pat. No. 5,422,405, the first surface cross-linking agent and the second surface cross-linking agent having different solubility parameters (SP values) as surface cross-linking agents capable of reacting with carboxyl groups. In the case of combining agents, an absorbent having an even better absorption capacity under pressure can be obtained. The first surface crosslinking agent is preferably a compound capable of reacting with a carboxyl group and having a solubility parameter of 12.5 (cal / cm ³ ) ^1/2 or more, and 13.0 (cal / cm ³ ) ^1/2 or more. A compound having an upper limit of 23.4 (cal / cm ³ ) ^1/2 is more preferable. The second surface crosslinking agent is preferably a compound capable of reacting with a carboxyl group and having a solubility parameter of less than 12.5 (cal / cm ³ ) ^1/2 , and 9.5 (cal / cm ³ ) ^1/2 or more A compound within a range of 12.0 (cal / cm ³ ) ^1/2 or less is more preferable.

  The amount of the surface cross-linking agent used is preferably 0.001 to 5 parts by weight with respect to 100 parts by weight of the solid content of the water-absorbent resin particles.

  When mixing the water-absorbent resin particles and the surface cross-linking agent, it is preferable to use water as a solvent for the surface cross-linking agent. The amount of water used is preferably more than 0 and 20 parts by weight or more, more preferably 0.5 parts by weight or more and 10 parts by weight or less, with respect to 100 parts by weight of the water-absorbent resin particles.

  When mixing the water-absorbent resin particles and the surface cross-linking agent, a hydrophilic organic solvent (aqueous liquid) may be used in combination as necessary. Examples of the hydrophilic organic solvent include monohydric alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, and isopropyl alcohol; ketones such as acetone; ethers such as dioxane and tetrahydrofuran; The amount of the hydrophilic organic solvent to be used is preferably 20 parts by weight or less, more preferably 0 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the water-absorbent resin particles.

  Furthermore, in order to improve mixing properties and reactivity, a basic compound such as a surfactant, an inert inorganic powder, an organic acid (salt), an inorganic acid (salt), or caustic soda is added in an amount of 0 part by weight or more to 100 parts by weight of the water absorbent resin. You may use together in 5 weight part or less.

  After mixing the water absorbent resin particles and the surface cross-linking agent in advance, the method of spraying or dropping and mixing the aqueous solution onto the water absorbent resin is preferable, and the method of spraying is more preferable. The size of the droplets to be sprayed is preferably in the range of 0.1 μm or more and 300 μm or less, more preferably in the range of 0.1 μm or more and 200 μm or less in terms of average particle size. When mixing the water-absorbent resin particles and the surface cross-linking agent, a water-insoluble fine particle powder or an active surfactant may be allowed to coexist within a range not impeding the effects of the present invention.

  After mixing the water-absorbent resin particles and the surface cross-linking agent, heat treatment is further performed to cross-link the vicinity of the surface of the water-absorbent resin particles. That is, in order to cause the crosslinking agent to react in the vicinity of the surface of the water-absorbent resin particles, it is preferable to perform heat treatment in consideration of the reactivity of the crosslinking agent, the simplicity of the production apparatus, and the productivity. The treatment temperature of the heat treatment depends on the surface crosslinking agent used, but is preferably in the range of 80 ° C. to 250 ° C., more preferably 100 ° C. to 200 ° C. Said heat processing can be performed using a normal dryer or a heating furnace. Examples of the dryer include a groove-type mixing dryer, a rotary dryer, a disk dryer, a fluidized bed dryer, an airflow dryer, and an infrared dryer.

  The “aqueous liquid” refers to an aqueous solution or slurry containing water, a water-soluble metal salt or a hydrophilic organic solvent, a water-soluble polymer, a surfactant, and water-insoluble inorganic particles.

  Although it does not specifically limit as said aqueous liquid, From the surface of a physical property or granulation strength, the ratio of the water in an aqueous liquid is 70 to 100 weight%, Preferably it is 80 to 100 weight% More preferably, it is in the range of 90 wt% or more and 100 wt% or less, and may contain a small amount of a crosslinking agent (for example, the surface crosslinking agent) or a surfactant. In order to achieve the object of the present invention, the temperature of the aqueous liquid is not particularly limited, but is usually 5 ° C. or higher and the boiling point or lower, preferably 20 ° C. or higher. At 100 ° C. or lower.

  The amount of the aqueous liquid used is usually 1 part by weight or more and 150 parts by weight or less, preferably 5 parts by weight or more and 100 parts by weight or less, more preferably 5 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the water absorbent resin particles. More preferably, it is 5 parts by weight or more and 30 parts by weight or less, and most preferably 5 parts by weight or more and 20 parts by weight or less. When the amount of the aqueous liquid used exceeds 150 parts by weight, a lump is easily formed and it is difficult to handle as a granulated product, and it is disadvantageous in terms of drying cost and physical property reduction. On the other hand, when the amount of the aqueous liquid used is less than 1 part by weight, the granulation strength becomes insufficient, and there is a possibility that the granulation characteristics cannot be exhibited in the final product. Moreover, mixing may become non-uniform | heterogenous and a granulated material may not be obtained.

  Mixing of the water-absorbent resin particles and the aqueous liquid can be performed using a conventionally known mixer. The mixer to be used is not particularly limited, but a container-fixed mixer, among them, a mechanical stirring mixer is preferable. For example, cylindrical mixer, screw mixer, screw extruder, turbulizer, nauter mixer, V mixer, ribbon mixer, double arm kneader, fluid mixer, airflow mixer Rotating disk type mixers, roll mixers, rolling mixers, paddle type mixers, Ladige mixers and the like. The mixer may be either a batch mixer or a continuous mixer. In some cases, a batch mixer is preferable in that stable performance can be achieved.

  Further, the method of adding the aqueous liquid to the water-absorbent resin particles is not particularly limited, but in order to perform granulation efficiently, a method that can uniformly distribute the aqueous liquid to the water-absorbent resin particles, for example, A method of charging an aqueous liquid into the mixer by spraying is preferably used.

  In the present specification, the “water-absorbing resin hydrate” refers to a product in which at least a water-absorbing resin particle and an aqueous liquid are mixed and at least a part of the aqueous liquid is absorbed inside the water-absorbing resin particles. The temperature of the water-absorbent resin hydrous material is 30 ° C. or higher and 100 ° C. or lower, preferably 40 ° C. or higher and 100 ° C. or lower, more preferably 50 ° C. or higher and 100 ° C. or lower. Other components that can be mixed are not particularly limited as long as they do not interfere with the granulation of the water-absorbent resin by the aqueous liquid. For example, a water-soluble polyvalent metal salt having an effect of enhancing the liquid permeability of the water-absorbent resin, the cross-linking agent, the anti-coloring agent, and the like can be mixed.

  Examples of the water-soluble polyvalent metal salt include aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium aluminum sulfate, sodium aluminum bissulfate, potassium alum, ammonium alum, sodium alum, sodium aluminate, calcium chloride, Calcium nitrate, magnesium chloride, magnesium sulfate, magnesium nitrate, zinc chloride, zinc sulfate, zinc nitrate, zirconium chloride, zirconium sulfate, zirconium nitrate and the like can be used.

  Examples of the anti-coloring agent include a sulfur-containing reducing agent, an amino polyvalent carboxylic acid or a salt thereof, a chelating agent such as an organic phosphoric acid compound or a salt thereof, hydrogen peroxide, and the like.

  The water-absorbing resin water-containing product may be obtained by further mixing the second water-absorbing resin particles in a system in which the first water-absorbing resin particles and the aqueous liquid are mixed. The terms “first water-absorbent resin particles” and “second water-absorbent resin particles” are used to mean mixing the water-absorbent resin particles and the aqueous liquid in two stages. In addition, as the first water-absorbing resin particles and the second water-absorbing resin particles, the same water-absorbing resin particles as already described can be used. The kind of 1st water absorbing resin particle and the kind of 2nd water absorbing resin may be the same, and may differ.

  Moreover, the particle diameter of the 1st water absorbing resin particle and the 2nd water absorbing resin particle may be the same, and may differ. For example, the first water absorbent resin particles may be the fine powder, and the second water absorbent resin particles may be coarse particles. As described above, a method of mixing the water absorbent resin particles and the aqueous liquid in two stages will be described later.

  According to the aqueous liquid mixing step described above, by mixing the water absorbent resin particles and the aqueous liquid, an adhesive force is generated, granulation is performed, and the water absorbent resin hydrate can be obtained.

<Particle mixing process>
The fine particle mixing step is a step of obtaining a water-absorbing resin water-containing composition by mixing at least a water-absorbing resin water-containing material and fine particles. By this process, the water-absorbing resin hydrated material is agglomerated and changed to granulated particles having a relatively uniform particle size (water-absorbing resin hydrated composition). Can be given. Moreover, since the water-absorbent resin hydrous material is unaggregated, the surface area per particle volume increases and the voids between the granulated particles increase, so that curing can be performed at a lower temperature and in a shorter time.

  Preferred fine particles used in the present invention include, for example, silicon dioxide, aluminum oxide, titanium dioxide, calcium phosphate, calcium carbonate, diatomaceous earth, bentonite, zeolite, and other metal oxides. The fine particles mixed with the water-absorbing resin hydrate in the fine particle mixing step do not include fine particles of the water-absorbing resin. Further, organic fine particles such as chitin, chitosan, cellulose, pulp, soluble starch and the like can be mentioned, and it is preferable that both inorganic fine particles and organic fine particles are water-insoluble or poorly water-soluble. Among these, water-insoluble inorganic fine particles that can be effective with a small addition amount are preferably used. The poor water solubility means a substance having a solubility in water at 23 ° C. of less than 5% by weight or 1% by weight or more.

  The particle diameter of these fine particles is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 10 μm or less, and the lower limit is about 1 nm. When the particle diameter exceeds 100 μm, it is not preferable because sufficient granulation strength cannot be obtained and aggregation of the water-absorbent resin-containing product cannot be sufficiently solved. The particle diameter can be measured with a Coulter counter or the like.

  The fine particles need to be added to the water-absorbing resin hydrate. That is, the fine particles need to be added to the reaction system after mixing the water absorbent resin particles and the aqueous liquid. It is not preferable to add an aqueous liquid after first mixing the water-absorbent resin particles and the fine particles because a mass of about several mm may be formed.

  The method of adding the fine particles to the water-absorbent resin hydrate is not particularly limited. For example, a method in which the fine particles are directly added to the water-absorbing resin hydrate, a method in which the fine particles are dispersed in an aqueous liquid, various organic solvents, or the like are sprayed or dropped onto the water-absorbing resin. Further, as described above, the water-absorbing resin hydrate may be obtained by further mixing the water-absorbing resin particles in a system in which the water-absorbing resin particles and the aqueous liquid are mixed. In this case, the fine particles may be mixed in advance with water absorbent resin particles to be added later.

  The water-absorbing resin hydrate and the fine particles can be mixed using, for example, a conventionally known mixer described in the section of the aqueous liquid mixing step.

  In the present specification, the “water-absorbing resin water-containing composition” refers to a mixture of at least a water-absorbing resin water-containing material and the fine particles. The water-absorbing resin hydrate and the fine particles may be bonded. Other components that can be mixed include an aqueous liquid for dispersing the fine particles and various organic solvents.

  The water-absorbing resin water-containing composition itself has fluidity. This is because, in the present invention, after mixing the water-absorbent resin particles and the aqueous liquid, the fine particles are further mixed, whereby aggregation of the water-absorbent resin water-containing material is released and block formation is prevented. Therefore, the hardening process and / or drying process which are mentioned later can be performed smoothly. Although it does not specifically limit as fluidity | liquidity, it is preferable that the flow-down speed | rate (it applies to the measuring method as described in the Example mentioned later) measured within 10 minutes within 30 second after completion | finish of a microparticle mixing process. .

  The amount of the fine particles is not particularly limited, but is preferably 0.01 parts by weight or more and 10 parts by weight or less, and 0.05 parts by weight or more with respect to 100 parts by weight of the total amount of the water-absorbent resin hydrate. It is more preferably 10 parts by weight or less, and particularly preferably 0.1 parts by weight or more and 10 parts by weight or less.

  If the amount of the fine particles is less than 0.01 parts by weight, the amount of fine particles is too small, so that the water-absorbent resin particles cannot sufficiently intervene on the surface where the water-absorbent resin particles are bonded to each other, and the water-absorbent resin grows excessively. It is not preferable because aggregation of the hydrated product cannot be sufficiently solved. On the other hand, if it exceeds 10 parts by weight, the performance as a water-absorbent resin (such as the water absorption capacity under pressure described later) may be lowered, which is not preferable.

  According to the fine particle mixing process described above, the excessively grown water-absorbent resin hydrates are agglomerated by the action of fine particles such as silicon dioxide, and granulated particles having a relatively uniform particle size (water-absorbent resin water-containing composition). Therefore, fluidity can be imparted to the water-absorbing resin hydrated material in a short time. Moreover, since the surface area per particle volume increases and the voids between the granulated particles increase due to the agglomeration of the water-absorbent resin hydrated material, the curing step described later can be smoothly advanced.

  FIG. 1 is a schematic diagram showing the flow of an aqueous liquid mixing step and a fine particle mixing step. As shown in FIG. 1, by mixing water absorbent resin particles and an aqueous liquid, granulation proceeds and a water absorbent resin hydrate is obtained. Next, the water-absorbing resin water-containing composition and / or the aggregates thereof and the fine particles are mixed to release aggregation and form a water-absorbing resin water-containing composition without forming a lump.

<Curing process>
The curing step is a step of curing by keeping or heating the water-absorbing resin water-containing composition. The term “curing” refers to a phenomenon in which water (aqueous liquid) contained in the water-absorbing resin water-containing composition is absorbed into the water-absorbing resin, and the surface of the water-absorbing resin is apparently dried. In addition, it can be judged by the improvement of the hardness and fluidity | liquidity of the granulated particle surface whether hardening was complete | finished.

<Drying process>
A drying process is a process of drying by heat-retaining or heating the water-absorbing resin water-containing composition. In the present specification, “drying” means that water (aqueous liquid) contained in the water-absorbing resin water-containing composition is scattered from the water-absorbing resin water-containing composition to the outside, and includes evaporation.

  Since both the curing step and the drying step are steps for heating or keeping the water-absorbing resin water-containing composition, the curing step and the drying step can be performed simultaneously. On the other hand, only the curing process or only the drying process may be performed.

  The method for keeping or heating the water-absorbent resin water-containing composition is not particularly limited, and examples thereof include one or more of airless dryers, band dryers, stirring dryers, fluidized bed dryers and the like. A conventional method using a heating device can be preferably used. The heat retention or heating may be performed while stirring the water-absorbing resin water-containing composition, or may be performed by standing as described later. The water content of the water-absorbent resin granulated product obtained through the curing step and / or the drying step is preferably 0.5% by weight to 50% by weight, more preferably 2% by weight to 30% by weight, particularly Preferably they are 5 weight% or more and 20 weight% or less.

  The temperature for heating or keeping the temperature is preferably 30 ° C. or higher and 250 ° C. or lower, more preferably 40 ° C. or higher and 200 ° C. or lower, and further preferably 50 ° C. or higher and 150 ° C. or lower. The time for heating or keeping warm is not less than 1 minute and not more than 2 hours, preferably not less than 1 minute and not more than 1 hour. Here, the above-mentioned “temperature for heating or keeping warm” refers to the temperature of the heat medium. If the temperature of the heating medium cannot be specified, such as when drying using microwaves, the temperature of the material is specified.

  In the production method according to the present invention, the water-absorbing resin water-containing composition obtained by mixing the water-absorbing resin water-containing material and the fine particles has not only fluidity but also sufficiently cured and / or cured at a low temperature and in a short time. Or newly found that it can be dried. This is because the fine particles mixed with the water-absorbing resin water-containing material breaks up the water-absorbing resin water-containing material, thereby increasing the surface area per particle volume and increasing the space between the granulated particles. This is considered to be due to the fact that the heat energy easily spreads between the granulated particles.

  On the other hand, in the technique described in Patent Document 19, a mixture of a superabsorbent resin powder and an oil-in-water emulsion of an ethylene-acrylic acid copolymer was mixed with fine powdered silica, resulting in a large number of lumps. It is disclosed. That is, after obtaining a water-absorbing resin water-containing product by mixing water-absorbing resin particles and an aqueous liquid, the water-absorbing water that has fluidity and can be efficiently heated by further adding and mixing the fine particles. It can be said that the water-soluble resin water-containing composition is obtained for the first time by the present invention.

  In addition, the invention disclosed in Patent Document 19 aims to improve the granulation strength (adhesion between particles) by adding an ethylene-acrylic acid copolymer. If it is considered that the purpose of addition of finely divided silica is the same as that of the present invention (reduction of adhesive force due to the presence of inorganic substances between granulated particles), Patent Document 19 adds an ethylene-acrylic acid copolymer. Due to strong granulation strength (granulation strength more than necessary), the fine powdered silica added after mixing the superabsorbent resin powder and the oil-in-water emulsion of ethylene-acrylic acid copolymer is granulated particles It is considered that it was difficult to intervene, resulting in a large number of lumps.

  That is, the technique described in Patent Document 19 and the present invention are completely different from each other in technical idea. After obtaining the water-absorbing resin water-containing material by mixing the water-absorbing resin particles and the aqueous liquid, further mixing the fine particles. It can be said that the water-absorbing resin water-containing composition having fluidity and capable of being efficiently cured and / or dried is obtained by the present invention for the first time.

<Standing, ventilation>
In the present invention, the curing step and / or the drying step may involve at least one of standing and aeration. That is, the curing step and / or the drying step may be performed under conditions involving at least one of standing and aeration. Here, the term “standing still” refers to placing the water-absorbing resin water-containing composition in a state where it is not stirred or in a non-flowing state.

  Since the curing step and / or drying step is accompanied by the above-mentioned standing, the curing step and / or drying step is performed in a non-stirring and non-flowing state, thereby preventing excessive particle destruction of the water-absorbent resin granulated product. It is possible to suppress deterioration of physical properties of the resulting water-absorbent resin granulated product. Moreover, since a special apparatus is not required for stationary, the hardening process and / or drying process which have the said effect can be performed with low energy.

  In the present invention, the curing step and / or the drying step may be accompanied by ventilation. By accompanying aeration, water evaporated from the water-absorbent resin composition moves out of the system. Therefore, the curing process and / or the drying process can be performed with high efficiency. The method for venting is not particularly limited. The air flow rate of the ventilation is from 0.01 m / second to 10 m / second, more preferably from 0.5 m / second to 3 m / second.

Since the curing step and / or the drying step may involve at least one of standing and aeration, the standing and aeration may be performed at the same time, or only one of them may be performed. Also good.

  Furthermore, these standing and ventilation may be accompanied by heating. “With heating” means that the heating device described above is heated in the curing step and / or the drying step. By accompanying heating, the curing step and / or the drying step are performed under heating conditions, and the efficiency of the above steps can be further improved.

  According to the present invention, curing and / or drying can be made much more efficient than before, and therefore, curing and / or drying can be performed in a short time even with a small dryer having a small amount of heat. Therefore, it is very useful from the viewpoint of shortening the manufacturing time, reducing the manufacturing cost, and saving energy. For example, in the technique described in Patent Document 19, it is disclosed that drying is preferably performed at a drying temperature in the range of 100 ° C. to 150 ° C. In the examples of the present invention described later, a water-absorbing resin water-containing composition is disclosed. Has been successfully cured by allowing it to stand in an airtight container at 60 ° C. for 1 hour (no stirring, non-flowing state).

  By the curing step and / or the drying step, a water-absorbent resin granulated product having a relatively uniform particle diameter and further improving the fluidity of the water-absorbing resin water-containing composition can be obtained. In the present specification, the “water absorbent resin granulated product” refers to a product obtained by curing and / or drying a water absorbent resin water-containing composition. The water-absorbent resin granulated product may be further pulverized and classified as necessary. The particle diameter after granulation of the water-absorbent resin granulated product is not particularly limited, but the difference in weight average particle diameter before and after granulation is preferably 10 μm or more and 1000 μm or less, more preferably 20 μm or more. It is 500 μm or less, more preferably 30 μm or more and 300 μm or less.

  The method of pulverization is not particularly limited, and a conventionally known method can be used. For example, the method of grind | pulverizing using grinders, such as a roller mill, a knife mill, a hammer mill, a pin mill, a jet mill, can be mentioned. The pulverizer preferably includes means for heating the inner wall surface of the pulverizer itself.

  Although the classification method is not particularly limited, it is preferable to use a sieve classification (metal sieve, made of stainless steel). Preferably, for the purpose of physical properties and particle size, it is preferable to use a plurality of sieves for classification.

<Split granulation method>
In another embodiment, the aqueous liquid mixing step further includes mixing the second water-absorbent resin particles in a system in which the first water-absorbent resin particles and the aqueous liquid are mixed, thereby adding water-absorbing resin water content. You may obtain things. Hereinafter, the manufacturing method according to the embodiment is referred to as “divided granulation method” for convenience. In the split granulation method, the aqueous liquid can be intentionally and non-uniformly added to the water-absorbent resin particles that require the aqueous liquid by adding the water-absorbing resin fine particles separately.

  In the split granulation method, the first water-absorbing resin particles are water-absorbing resin particles (hereinafter referred to as fine powder) mainly composed of particles having a particle diameter of less than 200 μm, and the fine powder and the aqueous liquid are mixed. The water-absorbent resin water-containing product is further mixed with the fine water-containing product obtained by mixing the second water-absorbent resin particles (hereinafter referred to as coarse particles) mainly composed of particles having a particle size of 200 μm or more and less than 850 μm. It is preferable to obtain. The “fine powder hydrated product” means a mixture of at least the fine powder and the aqueous liquid.

  The “water-absorbing resin particles having a particle diameter of less than 200 μm” refers to water-absorbing resin particles having a particle diameter defined by standard sieve classification of less than 200 μm. In other words, it refers to water-absorbent resin particles that pass through a JIS standard sieve having an opening of 200 μm.

  As described above, the water-absorbing resin particles (fine powder) are difficult to distribute the aqueous liquid, and therefore, in the water-absorbing resin particles containing fine powder, the proportion of fine powder remaining without granulation becomes high. It becomes difficult to obtain granulated particles having a uniform particle size. Moreover, when there are many fine powders remaining, it may become the cause of the working environment deterioration by generation | occurrence | production of dust etc., and the water absorption characteristic fall of a water absorbent resin granulated material.

  The present inventor separated the water-absorbing resin particles into fine powder and other particles in advance, first granulated the fine powder, then mixed the other particles, and further mixed the fine particles to efficiently remove the fine powder. It has been found that granulated particles having a uniform particle diameter that can be granulated and have a small amount of fine powder can be efficiently produced. As a result, fine powder can be effectively used as a raw material for the water-absorbent resin granulated product, so that the yield of the water-absorbent resin granulated product can be improved and the generation of dust can be reduced. Efficiency can also be improved. Moreover, since the obtained water-absorbent resin granulated product has a low residual ratio of fine powder, physical properties such as water absorption properties are good.

  As a method for separating fine powder from the water-absorbent resin particles, a conventionally known method can be used. For example, a method of classifying water-absorbent resin particles containing fine powder using a JIS standard sieve having an opening of 200 μm to 150 μm in consideration of the classification efficiency.

  The weight average particle diameter of the fine powder is preferably less than 200 μm. The fine powder is a water-absorbent resin particle mainly composed of particles having a particle diameter of less than 200 μm, and the proportion of the water-absorbent resin powder having a particle diameter of 150 μm or less is preferably 50% by weight or more (upper limit 100% by weight), more preferably It is 70% by weight or more, more preferably 90% by weight or more.

  The weight average particle diameter of the coarse particles is preferably 200 μm or more and 800 μm or less, more preferably 230 μm or more and 600 μm or less, and further preferably 260 μm or more and 500 μm or less. The coarse particles are preferably in a dry state. In the present invention, the dry state does not necessarily mean that the water content of the water-absorbent resin powder is 0%, and it may be in the range of usually 0% to less than 15%, preferably 0% to 10%. The coarse particles refer to water-absorbing resin particles mainly composed of particles having a particle size of 200 μm or more and less than 850 μm, and 80 particles of water-absorbing resin particles having a particle size defined by standard sieve classification of 200 μm or more and less than 850 μm. % Or more (upper limit 100%), preferably 90% or more of water-absorbent resin particles.

  The ratio of fine powder to coarse particles is not particularly limited, but the weight ratio of fine powder / coarse particles, which is usually the ratio of fine powder to coarse particles, is 1/99 or more and 50/50 or less, preferably 2/98 or more and 40/60 or less. More preferably, it is in the range of 3/97 or more and 30/70 or less.

  In the aqueous liquid mixing step, as a method of mixing the fine powder and the aqueous liquid, a method similar to the method of mixing the water absorbent resin particles and the aqueous liquid described above can be used. As other components that can be mixed in the present specification, the same components as those described in the description of the “water-absorbing resin water-containing product” can be used.

  The above-mentioned “coarse particle mixing step” is performed by mixing the above-mentioned fine powder hydrate with water-absorbent resin particles (hereinafter, also referred to as “coarse particles”) mainly composed of particles having a particle size of 200 μm or more and less than 850 μm. This is a process for obtaining a product. The coarse particles preferably contain 80% or more (upper limit of 100%) of water-absorbing resin particles having a particle size defined by standard sieve classification of 200 μm or more and less than 850 μm, and more preferably 90% or more. .

  The method for mixing the fine hydrated product and the coarse particles is not particularly limited, and can be carried out using a conventionally known mixer already described. In the water-absorbing resin hydrate containing the fine powder hydrate and the coarse particles, the fine powder hydrate and the coarse particles may be combined. Other components that can be mixed include, for example, an aqueous liquid for dispersing fine particles added in the fine particle mixing step, various organic solvents, and the like.

  The method of adding the fine particles to the water-absorbing resin hydrate, the mixing method, the kind of fine particles, the particle diameter, and the amount are the same as those described in the section of <Fine particle mixing step>. In addition, the amount of fine particles is preferably 0.05 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the water-absorbing resin particles also in the split granulation method. The term “100 parts by weight of resin particles” means “100 parts by weight of a combination of fine powder and coarse particles”.

  The curing step and / or the drying step are the same as those already described.

  In the split granulation method, the amount of the aqueous liquid is usually 1 part by weight or more and 150 parts by weight or less, preferably 5 parts by weight or more and 100 parts by weight or less, more preferably 5 parts by weight, with respect to 100 parts by weight of the water absorbent resin particles. It is preferable that they are 5 parts by weight or more and 50 parts by weight or less, more preferably 5 parts by weight or more and 30 parts by weight or less, and most preferably 5 parts by weight or more and 15 parts by weight or less.

  The moisture content (specified by the measurement method described in the examples described later) of the finely divided water-containing material (also referred to as a water-containing gel-like material) is usually 20% to 99% by weight, and 30% to 95% by weight. It is preferable that it is 40 wt% or more and 90 wt% or less.

  FIG. 2 is a schematic diagram showing the flow of the aqueous liquid mixing step and the fine particle mixing step in the split granulation method described above. As shown in FIG. 2, granulation progresses by mixing the fine powder and the aqueous liquid in the aqueous liquid mixing step, and a fine powder hydrate is obtained. Next, the water-absorbent resin hydrate is obtained by mixing the fine powder hydrate and / or the aggregate thereof and the coarse particles. Furthermore, by mixing the water-absorbing resin water-containing material and the fine particles, aggregation is released and a water-absorbing resin water-containing composition is generated without forming a lump.

<Physical properties of the water-absorbent resin granulated product obtained by the production method according to the present invention>
The absorption capacity (CRC) of the water-absorbent resin granulated product obtained by the production method according to the present invention under non-pressurized saline is 27 g / g or more, preferably 30 g / g or more, 33 g / g or more, 36 g / g. It is said above. When the absorption capacity under no pressure is less than 20 g / g, there is a possibility that high physical properties are not exhibited when used for diapers. Moreover, although an upper limit is not ask | required in particular, about 50 g / g is enough from the cost increase by the difficulty on manufacture.

  The absorption capacity under load (AAP 1.9 kPa) under a load of 1.9 kPa of the water absorbent resin granulated product obtained by the production method according to the present invention is 20 g / g or more, more preferably 22 g / g or more, and still more preferably. It is 24 g / g or more, particularly preferably 26 g / g or more. If the absorption capacity under pressure is less than 20 g / g, high physical properties may not be exhibited when used for diapers. Moreover, although an upper limit is not ask | required in particular, about 40 g / g is enough from the cost increase by the difficulty on manufacture.

  The absorption capacity under pressure (AAP 4.8 kPa) under a load of 4.8 kPa of the water absorbent resin granulated product obtained by the production method according to the present invention is 10 g / g or more, more preferably 15 g / g or more, and still more preferably. 20 g / g or more. When the absorption capacity under pressure is less than 10 g / g, high physical properties may not be exhibited when used for diapers. Moreover, although an upper limit is not ask | required in particular, about 30 g / g is enough from the cost increase by the difficulty on manufacture.

  The weight average particle diameter (D50) of the water-absorbent resin granulated product obtained by the production method according to the present invention is 200 or more and 800 μm or less, more preferably 250 or more and 600 μm or less, further preferably 300 or more and 500 μm or less, and less than 150 μm. It is preferable that the amount of the fine powder is very small. Specifically, it is preferably 0 or more and 5% or less, more preferably 3% or less, particularly 1% or less before the process damage, and preferably 0 or more and 5% or less, and further 3% or less even after the process damage. . The logarithmic standard deviation (σζ) is controlled to be 0.25 to 0.50, preferably 0.30 to 0.45.

  The water absorption rate (Vortex) of the water-absorbent resin granulated product obtained by the production method according to the present invention is 20 seconds to 50 seconds, more preferably 20 seconds to 40 seconds, and further preferably 20 seconds to 30 seconds. It is.

  When the water absorption speed exceeds 50 seconds, there is a possibility that leakage or an increase in the amount of return will occur when used for diapers. Moreover, when a water absorption speed is faster than 20 seconds, when it uses for a diaper, a gel block may arise in the absorber of a diaper by a high water absorption speed, and there exists a possibility of causing a leak.

  The water content (water content) of the water-absorbent resin granulated product obtained by the production method according to the present invention is 1% by weight or more and 150% by weight or less, preferably 5% by weight or more and 100% by weight with respect to the water-absorbent resin particles. Or less, more preferably 5% by weight or more and 50% by weight or less, further preferably 5% by weight or more and 30% by weight or less, still more preferably 5% by weight or more and 20% by weight or less, and particularly preferably 5% by weight or more and 15% by weight or less. % By weight or less. If the water content (moisture content) is less than 1% by weight, granulation is inadequate, which makes it easier to regenerate fine powder. When the final product such as diapers is used, clogging is likely to occur and causes leakage, etc. This is not preferable.

  On the other hand, when the water content (water content) is more than 150% by weight, it becomes easy to agglomerate due to excessive granulation strength, and when this is sized (pulverized), the water absorbent resin particles are damaged, Various physical properties such as absorptivity are reduced, and if it is a final product such as a diaper, it may cause a leakage or the like, which is not preferable.

  The fine particle content (inorganic fine particle content) of the water-absorbent resin granulated product obtained by the production method according to the present invention is 0.01% by weight or more and 20% by weight or less with respect to the water-absorbent resin particles, preferably 0.8%. The content is from 01% by weight to 15% by weight, and more preferably from 0.1% by weight to 10% by weight. When the fine particle content is less than 0.01% by weight, there is a possibility that sufficient fluidity cannot be obtained. When the content of the fine particles is 0.01% by weight or more and 10% by weight or less, sufficient fluidity can be obtained. If it exceeds 20% by weight, the performance as a water-absorbent resin (such as absorption capacity under pressure described later) may be lowered, which is not preferable.

  The water-absorbent resin granulated product obtained by the production method according to the present invention has 0 to 5 parts by weight of particles passing through a JIS standard sieve having an aperture of 150 μm with respect to 100 parts by weight of the water-absorbent resin granulated product. It is preferable that Thereby, when the water-absorbent resin granulated product is used for a diaper or the like, clogging due to fine powder is less likely to occur. Therefore, the fall of the liquid permeability in products, such as a diaper, can be suppressed.

  Thus, in the water-absorbent resin granulated product obtained by the production method according to the present invention, the particle passing through the JIS standard sieve having an opening of 150 μm is preferably lower in weight part, so the content is 0 wt. It doesn't matter if it's part.

  The water-absorbent resin granulated product according to the present invention has a water content of 5 to 15 parts by weight with respect to 100 parts by weight of the total amount of the water-absorbent resin granulated product, and inorganic fine particles of 100% by weight of the water-absorbent resin granulated product. 0.01 part by weight or more and 10 parts by weight or less with respect to part, (1) Absorption capacity under no pressure with respect to 0.90% by weight sodium chloride aqueous solution is 27g / g or more, (2) 0.90% by weight The absorption capacity under pressure at 1.9 kPa with respect to an aqueous sodium chloride solution is 20 g / g or more, and (3) the absorption capacity under pressure at 4.8 kPa with respect to a 0.90 wt% aqueous sodium chloride solution is 10 g / g or more. (4) Absorption rate with respect to 0.90% by weight sodium chloride aqueous solution is 20 seconds or more and 50 seconds or less, and (5) JIS standard sieve having an opening of 150 μm with respect to 100 parts by weight of the water-absorbent resin granulated product. Pass Having physical properties that the particles are less than 5 parts by weight or more 0 parts by weight.

  Such a water-absorbent resin granulated product can be produced by the method for producing a water-absorbent resin granulated product according to the present invention described above. That is, the production method may be a batch granulation method or a split granulation method. The physical properties described in the above (1) to (5) are as described above.

  When the water-absorbent resin granulated product according to the present invention is produced by the split granulation method, the aqueous liquid is added to 100 parts by weight of the total of the first water-absorbent resin particles and the second water-absorbent resin particles. More than 20 parts by weight is used. When the water absorbent resin granulated product according to the present invention is produced, the amount of water and inorganic fine particles contained in the water absorbent resin granulated product are the amount of water contained in the water absorbent resin particles and the amount of inorganic fine particles. It is preferable to appropriately adjust the addition amount of the aqueous liquid and the addition amount of the inorganic fine particles so as to obtain the fine particle content.

<Use of water-absorbent resin granulated product produced by the production method according to the present invention>
The water absorbent resin granulated product produced by the production method according to the present invention includes disinfectant, antibacterial agent, fragrance, foaming agent, pigment, dye, hydrophilic short fiber, fertilizer, oxidizing agent, reducing agent, water, and salts. Etc. may be added in the range of 0 wt% to 30 wt%, preferably 0 wt% to 5 wt%, thereby imparting various functions. The water-absorbent resin granulated product produced by the production method according to the present invention can be applied to the use of various conventionally known water-absorbent resins, but it has few fine powders and is excellent in absorption characteristics and absorption speed under pressure. It can be suitably used for hygienic materials including absorbent materials such as disposable diapers, sanitary napkins, and incontinence pads, and water-absorbing articles such as waste liquid solidifying agents and water-stopping agents.

Note that the present invention is not limited to the configurations described above, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments are appropriately combined. Embodiments obtained in this manner are also included in the technical scope of the present invention.
The present invention includes the following forms. In the method for producing a water absorbent resin granulated product of the present invention, it is preferable that the weight average particle diameter of the first water absorbent resin particles is smaller than the weight average particle diameter of the second water absorbent resin particles.
Further, in the method for producing a water absorbent resin granulated product according to the present invention, the step (b) is a fine particle mixing step of obtaining a water absorbent resin hydrous composition by mixing the water absorbent resin hydrous material and the fine particles. It is preferable to include a curing step for curing the water-absorbing resin water-containing composition and / or a drying step for drying the water-absorbing resin water-containing composition.
According to said structure, by mixing a water absorbing resin particle and an aqueous liquid, adhesive force arises and granulation is performed and a water absorbing resin hydrate is obtained. Further, by mixing the fine particles, the fine particles intervene on the surface where the water-absorbing resin hydrates are bonded to each other, so that the adhesion between the water-absorbing resin hydrates is peeled off, and it is considered that the point bonding through the fine particles results. .
As a result, the excessively grown water-absorbing resin hydrous material is deagglomerated and changed to granulated particles having a relatively uniform particle size (water-absorbing resin water-containing composition). It can give fluidity. In addition, since the water-absorbent resin hydrous material is deagglomerated, the surface area per particle volume increases and the gaps between the granulated particles increase, so that curing and / or drying can be performed at a lower temperature and in a shorter time. . Therefore, the water-absorbent resin granulated product can be produced very efficiently.
The method for producing a water-absorbent resin granulated product according to the present invention includes a second water-absorbent resin particle in a system in which the aqueous liquid mixing step is performed by mixing the first water-absorbent resin particles and the aqueous liquid. It is preferable that a water-absorbing resin hydrate is obtained by mixing.
According to the above configuration, by adding the water-absorbing resin fine particles separately, the aqueous liquid can be intentionally added non-uniformly to the water-absorbing resin particles that require the aqueous liquid.
In the method for producing a water absorbent resin granule according to the present invention, in the step (a), the amount of the aqueous solution is 1 part by weight or more and 150 parts by weight or less with respect to 100 parts by weight of the first water absorbent resin particles. It is preferable.
According to the said structure, the addition amount of aqueous liquid turns into an quantity which can provide strong adhesive force with respect to 1st water absorbing resin particle. Therefore, granulation can be smoothly advanced in the aqueous liquid mixing step.
In the method for producing a water-absorbent resin granulated product according to the present invention, the first water-absorbent resin particles are water-absorbent resin particles (hereinafter referred to as fine powder) mainly composed of particles having a particle diameter of less than 200 μm, Second water-absorbent resin particles (hereinafter referred to as coarse particles) mainly composed of particles having a particle diameter of 200 μm or more and less than 850 μm are further mixed with the finely powdered hydrate obtained by mixing the fine powder and the aqueous liquid. Thus, it is preferable to obtain a water-absorbing resin hydrate.
The water-absorbent resin particles are aggregates of water-absorbent resin particles having various particle diameters, and it is known that the ease of distribution of the aqueous liquid to each particle depends to some extent on the particle diameter. Therefore, when the water-absorbing resin particles and the aqueous liquid are mixed, the surface-crosslinked fine powder has a large particle size so that sufficient granulation strength can be obtained for the fine powder to be granulated. The aqueous liquid may not be distributed. Therefore, the proportion of fine powder remaining without granulation becomes high, and it becomes difficult to obtain granulated particles having a uniform particle size. Moreover, when there are many fine powders remaining, it may become the cause of the working environment deterioration by generation | occurrence | production of dust etc., and the water absorption characteristic fall of a water absorbent resin granulated material.
According to the above configuration, the water-absorbent resin particles are separated in advance into fine powder having a particle diameter of less than 200 μm and other particles, the fine powder is first granulated, and then the other particles are mixed, and further the fine particles are mixed. Fine powder can be efficiently granulated. Therefore, it is possible to efficiently produce granulated particles having a small particle size and a uniform particle size.
In the method for producing a water-absorbent granulated product according to the present invention, the water-absorbent resin particles are preferably subjected to surface cross-linking treatment.
By performing the surface cross-linking treatment, various characteristics of the water-absorbent resin particles such as liquid permeability can be made more preferable. Therefore, a water-absorbent resin granulated product having excellent characteristics can be obtained.
In the method for producing a water absorbent resin granulated product according to the present invention, the amount of the fine particles is preferably 0.01 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the water absorbent resin particles. According to the above configuration, since the amount of fine particles is a suitable amount for changing the adhesion of the particle surface of the water-absorbent resin water-containing material to the point adhesion involving the fine particles, the water-absorbent resin water-containing material is prevented from being agglomerated. be able to. Therefore, it is possible to efficiently obtain a water absorbent resin granulated product having a relatively uniform particle size.
In the method for producing a water-absorbent resin granulated product according to the present invention, the fine particles are preferably water-insoluble inorganic fine particles.
According to the said structure, aggregation of a water-absorbing-resin water content can be solved with a small addition amount. Therefore, it becomes easy to obtain granulated particles having a relatively uniform particle size.
In the method for producing a water-absorbent resin granulated product according to the present invention, the temperature range for retaining or heating the water-absorbent resin water-containing composition in the curing step and / or drying step may be 30 ° C. or more and 250 ° C. or less. preferable.
When the above temperature range is 30 ° C. or more and 250 ° C. or less, curing and / or drying can be made more efficient than conventional methods, so that even a small dryer with a small amount of heat can be heated in a short time. . Therefore, it is very useful from the viewpoint of shortening the manufacturing time, reducing the manufacturing cost, and saving energy.
In the method for producing a water absorbent resin granulated product according to the present invention, it is preferable that the curing step and / or the drying step include a step involving at least one of standing and aeration.
In the case where the curing step and / or the drying step is a step accompanied by standing (no stirring, non-flowing state), the curing step and / or the drying step are performed without stirring and non-flowing state. Or destruction of a granulated material hardly occurs in a drying process. Therefore, the physical property fall of the water absorbent resin granulation obtained can be suppressed. Furthermore, it is possible to perform a process that involves standing at a low energy cost.
Moreover, since the said hardening process and / or a drying process are equipped with the process accompanied by ventilation | gas_flowing, the evaporated water | moisture content moves outside the system by ventilation | gas_flowing, Therefore A hardening process and / or a drying process can be performed with high efficiency.
In the water-absorbent resin granulated product according to the present invention, the inorganic fine particles are preferably water-insoluble inorganic fine particles.
According to the above configuration, the water-absorbent resin hydrated product can be flocculated with a small addition amount, so that a water-absorbent resin granulated product having a relatively uniform particle diameter can be produced.

〔Example〕
Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples. In the present specification, “mass” and “mass%” are treated as synonymous with “weight” and “weight%” or “part by weight”, respectively. In addition, for convenience, “mass part” may be simply referred to as “part”, and “liter” may be simply referred to as “L”. In addition, “mass%” may be described as “wt%”.

  Various performances of the water-absorbent resin particles, the water-absorbent resin-containing composition, the water-absorbent resin granulated product and the like (hereinafter referred to as “sample” as appropriate) were measured by the following methods. Unless otherwise specified, the following measurements are performed under conditions of 25 ° C. ± 2 ° C. and humidity of 50 RH%.

〔Test method〕
(1) Weight average particle diameter (D50) and fine powder ratio (150 μm passage ratio)
The water-absorbing resin or particulate water-absorbing agent was sieved with a JIS standard sieve such as 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 45 μm, and the residual percentage was plotted on logarithmic probability paper. . Thereby, the weight average particle diameter (D50) and fine powder ratio (150 μm passage ratio) were read.

  In the sieving, 10.00 g of a water-absorbing resin or a particulate water-absorbing agent is charged into the JIS standard sieve (The IIDA TESTING SIEVE: inner diameter 80 mm), and a low-tap type sieve shaker (manufactured by Iida Seisakusho, ES-65 type). Classification for 5 minutes using a sieve shaker). The weight average particle diameter (D50) is a particle diameter of a standard sieve corresponding to 50% by weight of the whole particle with a standard sieve having a constant mesh as described in US Pat. No. 5,051,259.

  Further, the fine powder ratio (% by weight) was calculated from the total weight of the water-absorbing resin or particulate water-absorbing agent that passed through a JIS standard sieve having an opening of 150 μm, according to the following formula.

Fine powder ratio (% by weight) = (total weight (g) of water-absorbing resin (or particulate water-absorbing agent) passed through JIS standard sieve having 150 μm openings / total weight of water-absorbing resin (or particulate water-absorbing agent) ( g)) x 100
(2) Absorption capacity without pressure (CRC / Centrifuge Retention Capacity) with respect to 0.90% by weight sodium chloride aqueous solution (saline)
In a 0.90 wt% aqueous sodium chloride solution (physiological saline), 0.20 g of a water-absorbing resin (or particulate water-absorbing agent) is uniformly placed in a non-woven bag (60 mm x 85 mm) and the temperature is adjusted to 25 ± 2 ° C. Soaked in. After 30 minutes, the bag was pulled up, drained at 250 G for 3 minutes using a centrifuge, and the weight W ₁ (g) of the bag was measured. The same operation was performed without using the water-absorbent resin (or particulate water-absorbing agent), and the weight W ₀ (g) at that time was measured. From W ₁ and W ₀ , the absorption capacity without pressure (g / g) was calculated according to the following formula.

Absorption capacity without load (g / g) with respect to 0.90 wt% sodium chloride aqueous solution (physiological saline) = {(weight W ₁ (g) −weight W ₀ (g)) / water absorbent resin (or particulate water absorption) Weight) (g)}-1
(3) Moisture content In the water-absorbent resin (or particulate water-absorbing agent or hydrated gel-like product), it represents the proportion of moisture. The relationship with the solid content is as follows.

Moisture content (% by weight) = 100-solid content (% by weight)
The method for measuring the moisture content was as follows.

Weigh 1 g of water-absorbing resin (or particulate water-absorbing agent or water-containing gel) or water-containing material (weight W ₁ ) into an aluminum cup (weight W ₀ ) having a bottom diameter of about 5 cm. Allow to stand for 3 hours in a non-air dryer (16 hours when measuring a hydrogel) and dry. The weight (W ₂ ) of the dried aluminum cup + water-absorbent resin (or particulate water-absorbing material or water-containing gel-like material) was measured, and the water content was determined from the following equation.

Water content (% by weight) = {1− (W ₂ −W ₀ ) / W ₁ } × 100
(4) Absorption capacity under no pressure corrected for water content Absorption capacity under no pressure applied after water content correction is the absorption capacity under no pressure when the water content of the water absorbent resin (or particulate water absorbent) is assumed to be 0% by weight. And calculated according to the following equation.

Absorption capacity without pressure (g / g) after correction of water content = (absorption capacity without pressure (g / g) + water content (% by weight) / 100) / (1−water content (% by weight) / 100)
(5) Absorption capacity under load (AAP) at 1.9 kPa with respect to 0.90 wt% sodium chloride aqueous solution (saline)
0.90 g of water-absorbing resin (or particulate water-absorbing agent) is evenly sprayed on the metal mesh at the bottom of a plastic support cylinder with an inner diameter of 60 mm in which a stainless steel mesh with a mesh opening of 38 μm is welded to one side (bottom) of the cylinder cross section. Further, a piston (cover plate) whose outer diameter is slightly smaller than 60 mm and no gap is formed on the wall surface with the support cylinder and the vertical movement is not hindered is placed on the support cylinder and the water absorbent resin (or particles). And the weight W ₃ (g) of the piston were measured. On this piston, a load adjusted so that a 1.9 kPa load including the piston can be uniformly applied to the water-absorbing resin (or particulate water-absorbing agent) is placed, and a complete measuring device is completed. I let you. Place a glass filter with a diameter of 90 mm and a thickness of 5 mm inside a Petri dish with a diameter of 150 mm, and 0.90 wt% sodium chloride aqueous solution (saline) adjusted to 25 ± 2 ° C at the same level as the upper surface of the glass filter It was added to become. On top of that, a sheet of 9 cm diameter filter paper (Toyo Filter Paper Co., Ltd., No. 2) 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. When the liquid level dropped from the top of the glass filter, the liquid was added to keep the liquid level constant. After 60 minutes, the set of measuring devices was lifted, and the weight W ₄ (g) (the weight of the support cylinder, the swollen water-absorbing resin (or particulate water-absorbing agent) and the piston) after removing the load was measured again. Then, from these weights W ₃ and W ₄ , the absorption capacity (g / g) under pressure at 1.9 kPa with respect to a 0.90 wt% sodium chloride aqueous solution (physiological saline) was calculated according to the following formula.

Absorption capacity under load at 1.9 kPa (g / g) with respect to 0.90 wt% sodium chloride aqueous solution (saline) = (weight W ₄ (g) −weight W ₃ (g)) / water absorbent resin (or Weight of particulate water-absorbing agent (g)
(6) Absorption capacity under pressure corrected for water content (g / g)
The absorption capacity under pressure corrected for water content is the absorption capacity under pressure when the water content of the water-absorbent resin (or particulate water-absorbing agent) is assumed to be 0% by weight, and was calculated according to the following formula.

Absorption capacity under pressure corrected (g / g) = (Absorption capacity under pressure (g / g) + Moisture content (% by weight) / 100) / (1−Moisture content (% by weight) / 100)
(7) Impact resistance test The impact resistance test of the water-absorbent resin (or particulate water-absorbing agent) was performed as follows. That is, weigh each 30 g of water-absorbing resin (or particulate water-absorbing agent) and put it in each 250 ml mayonnaise bottle (55 mmφ × 110 mm) containing 10 g of glass beads (6-7 mmφ) prepared in advance. , Closed the lid. Four mayonnaise bottles were set in a paint shaker (manufactured by Toyo Seiki Co., Ltd.), the paint shaker was operated for 10 minutes, and then the water absorbent resin (or particulate water absorbing agent) was taken out from the mayonnaise bottle.

<Amount of soluble component (water-soluble component)>
A plastic container with a lid with a capacity of 250 ml was weighed 184.3 g of 0.90% by weight aqueous sodium chloride solution (saline), 1.00 g of a sample was added to the aqueous solution, and the diameter was 7 mm (coated with fluororesin). The soluble part in the sample was extracted by stirring at 300 rpm ± 30 rpm for 16 hours using a cylindrical stirrer chip having a diameter of 8 mm at the center and a length of 30 mm. The extract was filtered using filter paper, and 50.0 g of the filtrate was weighed to obtain a measurement solution.

  First, physiological saline alone was titrated to pH 10 with a 0.1N aqueous sodium hydroxide solution, and then titrated to pH 2.7 with 0.1N hydrochloric acid, followed by empty titration ([bNaOH] ml, [bHCl] Ml) was obtained. By performing the same titration operation on the measurement solution, titration amounts ([NaOH] ml, [HCl] ml) were obtained.

  For example, if the sample is a water-absorbing resin composed of a known amount of acrylic acid and its sodium salt, the soluble content in the water-absorbing resin is determined as follows based on the average molecular weight of the monomer and the titration amount obtained by the above operation. It can be calculated by the following formula. In the case of an unknown amount, the average molecular weight of the monomer is 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
<Absorption capacity under pressure (AAP 1.9 kPa) at 1.9 kPa with respect to 0.90 wt% sodium chloride aqueous solution (saline)>
0.90 g of a sample is uniformly dispersed on a metal mesh at the bottom of a plastic support cylinder having an inner diameter of 60 mm, in which a stainless steel mesh having a mesh opening of 38 μm is welded to one side (bottom) of the cylindrical cross section, and an outer diameter of 60 mm is applied thereon. A piston (cover plate) that is slightly smaller and has no gap on the wall surface with the support cylinder and that does not prevent vertical movement was placed, and the weight W ₃ (g) of the support cylinder, sample, and piston was measured.

  On this piston, a load adjusted so that a load of 1.9 kPa including the piston can be uniformly applied to the sample was placed, and a complete measuring apparatus was completed. Place a glass filter with a diameter of 90 mm and a thickness of 5 mm inside a Petri dish with a diameter of 150 mm, and 0.90 wt% sodium chloride aqueous solution (saline) adjusted to 25 ± 2 ° C at the same level as the upper surface of the glass filter It was added to become. On top of that, a sheet of 9 cm diameter filter paper (Toyo Filter Paper Co., Ltd., No. 2) 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. When the liquid level dropped from the top of the glass filter, the liquid was added to keep the liquid level constant. After 60 minutes, the set of measuring devices was lifted and the weight W ₄ (g) (weight of the supporting cylinder, swollen sample, and piston) after removing the load was measured again. Then, from these weights W ₃ and W ₄ , the absorption capacity (g / g) under pressure at 1.9 kPa with respect to a 0.90 wt% sodium chloride aqueous solution (physiological saline) was calculated according to the following formula.

AAP 1.9 kPa (g / g) = (weight W ₄ (g) −weight W ₃ (g)) / weight of sample (g)
<Absorption capacity under pressure (AAP 4.8 kPa) at 4.8 kPa with respect to 0.90 wt% sodium chloride aqueous solution (saline)>
In the measurement of the absorption capacity under pressure at 1.9 kPa against a 0.90% by weight sodium chloride aqueous solution (physiological saline), the measurement was performed by performing the same operation except that the piston load was changed to 4.8 kPa.

  The absorption capacity (g / g) under pressure at 4.8 kPa with respect to a 0.90% by weight sodium chloride aqueous solution (saline) is obtained by the following equation.

AAP 4.8 kPa (g / g) = (weight W ₄ (g) −weight W ₃ (g)) / weight of sample (g)
<Bulk specific gravity, flow velocity>
It measured according to JISK3362 using the bulk specific gravity measuring device (made by Kuramochi Scientific Instruments Seisakusho). In order to eliminate unevenness due to particle size, 100 g of a sufficiently mixed sample (water-absorbing resin particles) was placed in a funnel with a damper closed, and then the damper was quickly opened and the sample was dropped into a receiver. The time (seconds) from when the sample starts to drop to when it is dropped is taken as the flow velocity. The sample swelled from the receiver was scraped off with a glass rod, and the weight of the receiver containing the sample was accurately weighed to 0.1 g, and the bulk specific gravity was calculated by the following equation.

Bulk specific gravity (g / ml) = (Weight of receiver containing sample (g) −Weight of receiver (g)) / Receiver internal volume (100 ml)
The temperature at the time of measurement was 25 ± 2 ° C., and the relative humidity was 30 RH% or more and 50 RH% or less.

<Paint shaker test (process damage)>
The paint shaker test (PS) is a glass container having a diameter of 6 cm and a height of 11 cm, and 10 g of glass beads having a diameter of 6 mm and a sample of 30 g are placed on a paint shaker (Toyo Seisakusho Co., Ltd. product No. 488), and 800 cycles / The apparatus is shaken with min (CPM), and details of the apparatus are disclosed in Japanese Patent Laid-Open No. 9-235378. In this example and comparative example, the shaking time was 10 minutes.

  After shaking, the glass beads are removed with a JIS standard sieve having an opening of 2 mm to obtain a sample with process damage.

<Quantification of the amount of lumps>
The water-absorbent resin granulated product after the curing step or the water-absorbent resin granulated product further damaged by the process is charged into a sieve having a mesh opening of 850 μm (The IIDA TESTING SIVE: inner diameter 80 mm), and a low tap type sieve. Classification was carried out for 5 minutes using a shaker (manufactured by Iida Seisakusho, ES-65 type sieve shaker).

  After 5 minutes, the ratio of the amount of the water-absorbent resin granule remaining on the 850 μm sieve in the total amount of the water-absorbent resin granule (10.00 g) charged in the sieve was calculated and used as the amount of waste. That is, the amount of lumps is obtained by the following formula.

Dama amount (% by weight) = (Amount of water absorbent resin granule remaining on 850 μm sieve) / Total amount of water absorbent resin granule charged in sieve) × 100
<Weight average particle diameter (D50) and logarithmic standard deviation (σζ)>
The sample was sieved with JIS standard sieves of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 45 μm, and the residual percentage was plotted on log probability paper. Depending on the particle size of the sample, a sieve is added as necessary and measured. Thereby, the particle diameter corresponding to R = 50% by weight was read as the weight average particle diameter (D50). Further, the logarithmic standard deviation (σζ) of the particle size distribution is expressed by the following equation, and the smaller the value of σζ, the narrower the particle size distribution.

σζ = 0.5 × ln (X2 / X1)
(X1 is R = 84.1%, X2 is each particle size when R = 15.9%)
For sieving, a sample of 10.00 g is charged into a JIS standard sieve (The IIDA TESTING SIEVE: inner diameter 80 mm) such as an opening of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 45 μm. Classification was carried out for 5 minutes using a type sieve shaker (manufactured by Iida Seisakusho, ES-65 type sieve shaker).

  The weight average particle diameter (D50) is a particle diameter of a standard sieve corresponding to 50% by weight of the whole particle with a standard sieve having a constant mesh as described in US Pat. No. 5,051,259.

<Vortex>
According to JIS K7224-1996, the temperature of the test solution (0.9 wt% sodium chloride aqueous solution) was 30 ° C. ± 1 ° C., and the length of the stirrer chip was measured using a 40 mm one.

<Pass 150 μm>
Based on the following formula, the ratio (%) of Pass 150 μm was calculated from a sample that passed through a JIS standard sieve having a mesh size of 150 μm and whose weight average particle diameter (D50) was measured.

Pass 150 μm ratio (%) = (weight of the sample passed through a JIS standard sieve having an opening of 150 μm (g) / weight of the entire sample charged in the sieve (g)) × 100
<Inorganic fine particle content>
The content of inorganic fine particles indicates the proportion of inorganic fine particles contained in 100 parts by weight of the water absorbent resin granulated product.

  When quantifying the inorganic fine particles contained in the water-absorbent resin granulated product, the elements of the inorganic fine particles contained in the water-absorbent resin granulated product are changed to EPMA (Electron Probe Micro-Analysis) or SEM-EDS (Scanning Electron Microscopy / Energy). After conducting qualitative analysis by Dispersion X-ray Spectrometry), inorganic inorganic elements contained in the water-absorbent resin granulated product are quantified by fluorescent X-ray analysis by quantifying the inorganic fine particle elements contained in the water-absorbent resin granulated product. The fine particle content was determined.

(Production Example 1)
Production of water-absorbing resin formulation (C) and water-absorbing resin classification (D) In a reactor formed by attaching a lid to a 10-liter jacketed stainless steel double-arm kneader having two sigma type blades , 5.30 g of polyethylene glycol diacrylate (n = 9) was dissolved in 6600 g of an aqueous solution of sodium acrylate having a neutralization rate of 75 mol% (unsaturated monomer concentration: 37.7 wt%) to obtain a reaction solution. . Next, the reaction solution was purged with nitrogen for 20 minutes in a nitrogen gas atmosphere. Subsequently, 39.6 g of a 10 wt% aqueous sodium persulfate solution and 1.39 g of a 1 wt% aqueous L-ascorbic acid solution were added to the reaction solution with stirring. Polymerization started after about 30 seconds. Then, polymerization was performed at 20 to 95 ° C. while pulverizing the generated gel, and a hydrogel crosslinked polymer was taken out 45 minutes after the polymerization started. The obtained hydrogel crosslinked polymer was subdivided to have a diameter of about 5 mm or less. This finely divided hydrogel crosslinked polymer was spread on a wire mesh of a JIS standard sieve having an opening of 850 μm and dried with hot air at 180 ° C. for 35 minutes to obtain a water absorbent resin (A). Next, the mixture was pulverized using a roll pulverizer (WML type, Inoguchi Giken Co., Ltd.), and further classified and mixed with a JIS standard sieve having an opening of 850 μm to obtain a water-absorbing resin that passed 850 μm.

  To 100 parts by weight of the water-absorbent resin, 3.93 parts by weight of a crosslinking agent solution composed of 0.03 parts by weight of ethylene glycol diglycidyl ether / 0.9 parts by weight of propylene glycol / 3 parts by weight of water is mixed to form a mortar type. The mixture was added to the mixer and heat-treated at 190 ° C. for 45 minutes. The heat-treated product thus obtained was classified with a JIS standard sieve having an opening of 850 μm to obtain a water-absorbing resin (B) passing through 850 μm. The water-absorbent resin (B) has a weight average particle size of 275 μm and a fine powder ratio of 9.5% by weight passing through 150 μm. The absorption capacity under no pressure is 32.2 g / g, and the absorption capacity under pressure is 30.7 g. / G, and the water content was 4.0% by weight. Further, the water absorbent resin (B) was classified with a cylindrical screen having openings of 500 μm, 425 μm, 300 μm, 212 μm, and 150 μm using a turbo screener (manufactured by Turbo Industry Co., Ltd.). 500 μm passing part 425 μm not passing part, 425 μm passing part 300 μm not passing part, 300 μm passing part 212 μm not passing part, 212 μm passing part 150 μm not passing part, 500 μm passing part 150 μm passing part Water-absorbent resin formulation (C) and 150 μm-passage water-absorbent resin classified product (D) were obtained. The weight average particle size of the water absorbent resin formulation (C) was 288 μm, and the average particle size of the water absorbent resin classified product (D) was 125 μm.

(Production Example 2)
Manufacture of water-absorbent resin classification products (F) and (G) The water-absorbent resin (A) obtained in Reference Example 1 was pulverized using a roll pulverizer (WML type, Inoguchi Giken Co., Ltd.), and further an opening of 850 μm. It consists of 0.03 part by weight of ethylene glycol diglycidyl ether / 1.0 part by weight of propylene glycol / 3 parts by weight of water with respect to 100 parts by weight of the water-absorbing resin passing through 850 μm obtained by classifying and preparing with a JIS standard sieve. 4.03 parts by weight of the crosslinking agent solution was mixed, the mixture was added to a mortar type mixer, and heat treatment was performed at 190 ° C. for 40 minutes. The heat-treated product thus obtained was classified with a JIS standard sieve having an opening of 850 μm to obtain a water-absorbing resin (E) that passed through 850 μm. The water-absorbent resin (E) has a weight average particle size of 297 μm, the proportion of fine powder passing through 150 μm is 9.4% by weight, the absorption capacity under no pressure is 32.4 g / g, and the absorption capacity under pressure is 30.9 g. / G, and the water content was 3.9% by weight. Further, the water-absorbent resin (E) is classified with a sanitary minox shifter (manufactured by Nishimura Machinery Co., Ltd.) with a sieve having a mesh opening of 150 μm, and the water-absorbent resin classification product (F) of the 850 μm passage 150 μm non-passage portion and 150 μm A water-absorbent resin classification product (G) at the passing portion was obtained. The weight average particle diameter of the water absorbent resin classified product (F) was 293 μm, and the weight average particle diameter of the water absorbent resin classified product (G) was 120 μm.

(Production Example 3)
Manufacture of water-absorbent resin classification products (I) and (J) The water-absorbent resin (A) obtained in Reference Example 1 was pulverized using a roll pulverizer (WML type, Inoguchi Giken Co., Ltd.), and further an opening of 850 μm. It consists of 0.029 parts by weight of ethylene glycol diglycidyl ether / 1.0 part by weight of propylene glycol / 3 parts by weight of water with respect to 100 parts by weight of the water-absorbing resin passing through 850 μm obtained by classifying and preparing with a JIS standard sieve. 4.03 parts by weight of the crosslinking agent solution was mixed, the mixture was added to a mortar type mixer, and heat treatment was performed at 190 ° C. for 40 minutes. The heat-treated product thus obtained was classified with a JIS standard sieve having an aperture of 850 μm to obtain a water absorbent resin (H) that passed through 850 μm. The weight average particle diameter of this water absorbent resin (H) is 263 μm, the proportion of fine powder passing through 150 μm is 8.7 wt%, the proportion passing through 45 μm is 0.0 wt%, and the absorption capacity under no pressure is The absorption capacity under pressure was 32.7 g / g, the water content was 4.2% by weight. Further, the water-absorbing resin (H) is classified with a JIS standard sieve having an opening of 850 μm, and using 850 μm, the water-absorbing resin classification product (I) of the portion where 850 μm passes and 150 μm does not pass and the water-absorbing resin classification product (J ) And got. The weight average particle diameter of the water absorbent resin classified product (I) was 293 μm, and the weight average particle diameter of the water absorbent resin classified product (J) was 118 μm.

(Production Example 4)
Production of water-absorbing resin particles (K) by neutralization polymerization In a reactor formed by attaching a cover to a stainless steel double-armed kneader with two sigma-shaped blades and having a volume of 10 liters, the inner volume of 75 mol% A reaction solution was prepared by dissolving 5.45 g of polyethylene glycol diacrylate (n = 9) in 6600 g (monomer concentration: 40.0% by weight) of an aqueous solution of sodium acrylate having a sum ratio. Next, this reaction solution was degassed for 20 minutes in a nitrogen gas atmosphere. Subsequently, 35.8 g of a 10 wt% aqueous sodium persulfate solution and 1.49 g of a 1 wt% aqueous L-ascorbic acid solution were added to the reaction solution with stirring, and polymerization started after about 20 seconds.

  Then, polymerization was performed at 20 (start) ° C. or higher and 95 ° C. (peak) or lower while pulverizing the generated gel, and a hydrogel crosslinked polymer was taken out 42 minutes after the polymerization started. The obtained hydrogel crosslinked polymer was subdivided to have a diameter of about 5 mm or less. This finely divided hydrogel crosslinked polymer was spread on a 20 mesh (mesh 850 μm) wire mesh and dried with hot air at 180 ° C. for 40 minutes.

  Next, the mixture is pulverized using a roll mill and further classified and prepared with a JIS standard sieve having an opening of 850 μm, so that the ratio of the resin having a weight average particle size of 366 μm and a particle size of 600 μm or more and less than 850 μm is 3.2% by weight, Amorphous crushed water-absorbent resin particles (K) having a proportion of resin having a particle diameter of less than 150 μm of 3.3% by weight, a logarithmic standard deviation (σζ) of 0.377, and a moisture content of 6% by weight were obtained. .

  When the physical properties of the water-absorbing resin particles (K) obtained were measured, CRC (absorption capacity under no pressure with respect to 0.90 wt% sodium chloride aqueous solution (saline)) = 47.0 (g / g), acceptable The dissolved amount was 15.0% by weight.

  500 g of the obtained water-absorbent resin particles (K) were put into a 5 L Ladige mixer (manufactured by M5R type Ladige), and while the main shaft (squilled blade) of the Ladige mixer was rotated at 330 rpm, Denacol / 1 , 4-butanediol / propylene glycol / water = 0.03 / 0.32 / 0.5 / 2.73 wt% mixed solution 17.9 g was added while spraying and mixed for 1 minute. Stirring was then stopped and the resulting mixture was quickly removed.

  Next, the obtained mixture was put into a 5 L mortar mixer (manufactured by West Japan Testing Machine Co., Ltd.) whose container was heated to 210 ° C. by an oil bath, and stirred and mixed so that heat was uniformly applied to the mixture. After about 30 minutes, the mixture was taken out from the mortar mixer, and the entire amount was passed through a 850 μm JIS standard sieve to obtain surface-treated water-absorbent resin particles (K). Table 3 shows the physical properties of the surface-treated water-absorbent resin particles (K).

(Production Example 5)
Production of water-absorbing resin particles (L) by neutralization polymerization In a reactor formed by attaching a lid to a stainless steel double-armed kneader with a volume of 10 liters and having two sigma-type blades, A reaction solution was prepared by dissolving 5.45 g of polyethylene glycol diacrylate (n = 9) in 6600 g (monomer concentration: 40.0% by weight) of an aqueous solution of sodium acrylate having a sum ratio. Next, this reaction solution was degassed for 20 minutes in a nitrogen gas atmosphere. Subsequently, 35.8 g of a 10 wt% aqueous sodium persulfate solution and 1.49 g of a 1 wt% L-ascorbic acid aqueous solution were added while stirring the reaction solution, and polymerization was started after about 20 seconds.

  Then, polymerization was performed at 20 (start) ° C. or higher and 95 ° C. (peak) or lower while pulverizing the generated gel, and a hydrogel crosslinked polymer was taken out 42 minutes after the polymerization started. The obtained hydrogel crosslinked polymer was subdivided to have a diameter of about 5 mm or less. This finely divided hydrogel crosslinked polymer was spread on a 20 mesh (mesh 850 μm) wire mesh and dried with hot air at 180 ° C. for 40 minutes. Next, the mixture is pulverized using a roll mill and further classified and prepared with a JIS standard sieve having an opening of 600 μm, so that the ratio of the resin having a weight average particle size of 270 μm and a particle size of 500 μm or more and less than 600 μm is 0.2% by weight, The ratio of the resin having a particle diameter of less than 150 μm was 9.0% by weight, the logarithmic standard deviation (σζ) was 0.365, and the water content was 6% by weight. .

  When the physical properties of the water-absorbent resin particles (L) obtained were measured, CRC = 45.0 (g / g) and the soluble content was 13.0% by weight.

  500 g of the obtained water-absorbing resin particles (L) were put into a 5 L Ladige mixer (manufactured by M5R type Ladige), and while the main shaft (squilled blade) of the Ladige mixer was rotated at 330 rpm, Denacol / 1 , 4-butanediol / propylene glycol / water = 0.03 / 0.32 / 0.5 / 2.73 wt% mixed solution 17.9 g was added while spraying and mixed for 1 minute. Stirring was then stopped and the resulting mixture was quickly removed.

  Next, the obtained mixture was put into a 5 L mortar mixer (manufactured by West Japan Testing Machine Co., Ltd.) whose container was heated to 210 ° C. by an oil bath, and stirred and mixed so that heat was uniformly applied to the mixture. After about 30 minutes, the mixture was taken out from the mortar mixer, and the whole amount was passed through a 850 μm JIS standard sieve to obtain surface-treated water-absorbent resin particles (L).

  Table 3 shows the physical properties of the surface-treated water-absorbent resin particles (L). The surface-treated water-absorbing resin particles (L) are classified with a 150 μm JIS standard sieve to form particles having a particle size of 150 μm or more (coarse particles (α)) and particles having a particle size of less than 150 μm (fine powder (β)). Divided.

Example 1
The water-absorbent resin classification product (D) (4.8 g) passing through 150 μm was placed in a 600 ml plastic container (85 mmφ × 119 mm), deionized water (7.5 g) was added, and the mixture was mixed with a spatula for 30 seconds. The water absorbent resin preparation (C) (45.2 g) which did not pass 150 μm through 850 μm was added to the water absorbent resin classified product (D) which passed 150 μm mixed with deionized water, and further mixed with a spatula for 30 seconds. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ), dried in an airless dryer at 80 ° C. for 60 minutes, and classified to obtain a particulate water-absorbing agent (1) passing through 850 μm.

(Example 2)
The water-absorbing resin classification product (D) (4.8 g) passing through 150 μm was placed in a 600 ml plastic container (85 mmφ × 119 mm), deionized water (15 g) was added, and mixed with a spatula for 30 seconds. The water absorbent resin preparation (C) (45.2 g) which did not pass 150 μm through 850 μm was added to the water absorbent resin classified product (D) which passed 150 μm mixed with deionized water, and further mixed with a spatula for 30 seconds. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ), dried in an airless dryer at 80 ° C. for 90 minutes, and classified to obtain a particulate water-absorbing agent (2) passing through 850 μm.

(Example 3)
The water-absorbing resin classification product (D) (4.8 g) passing through 150 μm was placed in a 600 ml plastic container (85 mmφ × 119 mm), deionized water (2.5 g) was added, and mixed with a spatula for 30 seconds. The water absorbent resin preparation (C) (45.2 g) which did not pass 150 μm through 850 μm was added to the water absorbent resin classified product (D) which passed 150 μm mixed with deionized water, and further mixed with a spatula for 30 seconds. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ), dried in an airless dryer at 80 ° C. for 30 minutes, and classified to obtain a particulate water-absorbing agent (3) passing through 850 μm.

Example 4
The water absorbent resin classified product (D) (15.0 g) passing through 150 μm was placed in a 600 ml plastic container (85 mmφ × 119 mm), deionized water (22.5 g) was added, and the mixture was mixed with a spatula for 30 seconds. The water absorbent resin preparation (C) (35.0 g) which passed through 850 μm and did not pass 150 μm was added to the water absorbent resin classified product (D) which passed through 150 μm mixed with deionized water, and further mixed with a spatula for 30 seconds. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ), dried in an airless dryer at 80 ° C. for 150 minutes, and classified to obtain a particulate water-absorbing agent (4) passing through 850 μm.

(Example 5)
The water absorbent resin classified product (G) (28.5 g) passing through 150 μm was placed in a 600 ml plastic container (85 mmφ × 119 mm), and deionized water (45 g) was added and mixed for 60 seconds. Deionized water was mixed in a 5 L Leedige mixer (M-5R type, manufactured by Leedige) where 850 μm passed water absorbent resin classification (F) (271.5 g) that had not passed 150 μm was added. The 150 μm-passing water-absorbing resin classification product (G) was charged all at once, and the stirring blade was stirred at a rotation speed of 330 rpm and mixed for 10 minutes. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ), dried in an airless dryer at 80 ° C. for 60 minutes, and classified to obtain a particulate water-absorbing agent (5) passing through 850 μm.

(Example 6)
150 μm passing water absorbent resin classification (J) (27.0 g) is put into a 5 L pro-shear mixer (WB-5 type, manufactured by Taiheiyo Kiko Co., Ltd.), deionized water (135 g) is added, and the stirring blade is rotated at a rotational speed. Stir at 330 rpm and mix for 1 minute. While the mixture was being stirred, the water-absorbent resin classification product (I) (273.0 g) that passed through 850 μm but did not pass through 150 μm was charged all at once, and the stirring blade was further stirred at a rotation speed of 330 rpm and mixed for 1 minute. Immediately after mixing, the mixture was spread on a wire mesh with an opening of 38 μm, dried in a hot air dryer at 80 ° C. for 25 minutes, and classified to obtain a particulate water-absorbing agent (6) passing through 850 μm.

(Example 7)
A 150 μm-passage water-absorbent resin classification product (I) (27.0 g) is placed in a 5 L pro-shear mixer (WB-5 type, manufactured by Taiheiyo Kiko Co., Ltd.), deionized water (45 g) is added, and the stirring blade is rotated at a rotational speed. Stir at 330 rpm and mix for 10 minutes. While this mixture was being stirred, the water-absorbent resin classification product (I) (273.0 g) that passed 850 μm but not 150 μm was charged all at once, and the stirring blade was further stirred at a rotation speed of 330 rpm and mixed for 5 minutes. Immediately after mixing, the mixture was spread on a wire mesh with an opening of 38 μm, dried for 10 minutes with a hot air dryer at 80 ° C., and classified to obtain a particulate water-absorbing agent (7) that passed through 850 μm.

(Example 8)
A 150 μm-passage water-absorbent resin classification product (J) (27.0 g) is placed in a 5 L pro-shear mixer (WB-5 type, manufactured by Taiheiyo Kiko Co., Ltd.), deionized water (30 g) is added, and the stirring blade is rotated at a rotational speed. Stir at 330 rpm and mix for 10 minutes. While this mixture was being stirred, the water-absorbent resin classification product (I) (273.0 g) that passed 850 μm but not 150 μm was added all at once, and the stirring blade was further stirred at a rotation speed of 330 rpm and mixed for 10 minutes. Immediately after mixing, the mixture was spread on a wire mesh having a mesh opening of 38 μm, dried with a hot air dryer at 80 ° C. for 10 minutes, and classified to obtain a particulate water-absorbing agent (8) passing through 850 μm.

Example 9
500 g of the surface-treated water-absorbent resin particles (K) obtained in Production Example 4 were placed in a 5 L Ladige mixer (manufactured by M5R type Ladige), and the main shaft (squid-shaped blade) of the Ladige mixer was set at 330 rpm. While rotating at 50 ° C., 50 g of water was added by spraying and mixed for 1 minute to obtain a water-absorbing resin hydrated product (step of adding an aqueous liquid).

  Immediately after mixing, 1.5 g of water-insoluble inorganic fine particles (Aerosil 200: manufactured by Aerosil) are added under stirring with a Laedige mixer, and further mixed for 30 seconds (until the aggregates are dispersed) (fine particle mixing step) To obtain a water-absorbing resin water-containing composition (9).

  The water-absorbing resin water-containing composition (9) thus obtained had fluidity, and its flow rate (measured using a measuring device of JIS K3362) was measured and found to be 21 seconds / 100 g. The obtained water-absorbing resin water-containing composition (9) is transferred to a sealed container and left to stand in a windless dryer at 60 ° C. for 1 hour to cure (absorb water added to the water-absorbing resin). It was. After heating for 1 hour, the cured water absorbent resin granulated product (IX) was taken out from the dryer. The cured water-absorbent resin granulated product (IX) also has fluidity, and the flow rate was 18 seconds / 100 g.

  Process damage (Paint shaker (P / S): SAP / glass beads / shaking time = 30 g / 10 g / 10 min) was given to the water absorbent resin granulated product (IX), particle size distribution, CRC, AAP 1.9 kPa, AAP 4. Physical properties such as 8 kPa, Vortex, flow velocity, bulk specific gravity, moisture content, inorganic fine particle content were measured. The results are shown in Table 3.

(Example 10)
All operations were performed in the same manner as in Example 9, except that the amount of water added in Example 9 was changed to 250 g. The obtained water absorbent resin granulated product (X) was evaluated in the same manner as in Example 9, and the results are summarized in Table 3.

(Example 11)
45 g of the surface-treated fine powder (β) obtained in Production Example 5 was placed in a 5 L Ladige mixer (manufactured by M5R type Ladige), and the main shaft of the Ladige mixer (squilled blade) was rotated at 330 rpm. However, by adding 25 g of water all at once and mixing for 1 minute, a finely hydrated gel was obtained (aqueous liquid mixing step).

  Immediately after mixing, 455 g of the surface-treated coarse particles (α) was further added to the obtained finely powdered water-containing gel under stirring with a Roedige mixer and further mixed for 1 minute (aqueous liquid mixing step). Further, immediately after mixing the coarse particles, 1.5 g of water-insoluble inorganic fine particles (Aerosil 200: manufactured by Aerosil) are added under stirring with a Roedige mixer, and further mixed for 30 seconds (until the aggregates are dispersed). The water-absorbing resin water-containing composition (11) was obtained by performing (fine particle mixing step).

  The obtained water-absorbing resin water-containing composition (11) had fluidity, and its flow rate (using a measuring device of JIS K3362) was measured and found to be 20 seconds / 100 g. The obtained water-absorbing resin water-containing composition (11) is transferred to a hermetically sealed container and left to stand in an airless dryer having a temperature of 60 ° C. for 1 hour to cure (absorb water added to the water-absorbing resin). went. After 1 hour, the cured water absorbent resin granulated product (XI) was taken out from the dryer. The cured water absorbent resin granulated product (XI) also has fluidity, and the flow-down speed was 12 seconds / 100 g. Process damage (Paint shaker (P / S): SAP / glass beads / shaking time = 30 g / 10 g / 10 min) was given to the water absorbent resin granulated product (XI), particle size distribution, CRC, AAP 1.9 kPa, AAP 4. Physical properties such as 8 kPa, Vortex, flow velocity, bulk specific gravity, moisture content, inorganic fine particle content were measured. The results are shown in Table 3.

(Example 12)
All of the procedures were performed in the same manner as in Example 11 except that the amount of added water in Example 11 was changed to 50 g. The obtained water absorbent resin granulated product (XII) was evaluated in the same manner as in Example 11, and the results are summarized in Table 3.

(Example 13)
The procedure of Example 11 was repeated except that the amount of water added in Example 11 was changed to 75 g and the amount of Aerosil 200 added was changed to 5 g. The obtained water absorbent resin granulated product (XIII) was evaluated in the same manner as in Example 11, and the results are summarized in Table 4.

(Example 14)
The curing step and / or the drying step in Example 13 were carried out in an airless dryer having a temperature of 80 ° C. using an open container (SUS container (outer dimensions: 296 mm × 231 mm × 49 mm, bottom dimension: 250 mm × 185 mm)). All were performed in the same manner as in Example 13 except for changing to stationary for 60 minutes. The obtained water absorbent resin granulated product (XIV) was evaluated in the same manner as in Example 3, and the results are summarized in Table 4.

(Example 15)
The curing step and / or the drying step in Example 13 were carried out in an airless dryer having a temperature of 150 ° C. using an open container (SUS container (outer dimensions: 296 mm × 231 mm × 49 mm, bottom dimension: 250 mm × 185 mm)). All were performed in the same manner as in Example 13 except for changing to stationary for 60 minutes. The obtained water absorbent resin granulated product (XV) was evaluated in the same manner as in Example 11, and the results are summarized in Table 4.

(Example 16)
The amount of water added in Example 11 was changed to 50 g, and everything was the same as Example 11 except that 2.5 g of bamboo skin powder having a particle size of less than 45 μm was added with Aerosil 200 at the same time as Aerosil 200. The obtained water absorbent resin granulated product (XVI) was evaluated in the same manner as in Example 11, and the results are summarized in Table 4.

(Example 17)
The procedure was the same as in Example 11 except that the amount of water added in Example 11 was changed to 50 g and that 5 g of soluble starch was added instead of Aerosil 200. The obtained water absorbent resin granulated product (XVII) was evaluated in the same manner as in Example 11, and the results are summarized in Table 4.

(Example 18)
The same procedure as in Example 11 was performed except that the amount of water added in Example 11 was changed to 50 g and 1.5 g of CARPLEX 22S (Carplex) (manufactured by Shionogi Pharmaceutical Co., Ltd.) was added instead of Aerosil 200. The obtained water absorbent resin granulated product (XVIII) was evaluated in the same manner as in Example 11, and the results are summarized in Table 5.

(Example 19)
The same procedure as in Example 9 was carried out except that the water-absorbent resin particles (K) in Example 9 were changed to 200 g, the amount of added water was changed to 400 g, and the amount of Aerosil 200 added was changed to 20 g. However, since the obtained water-absorbing resin water-containing composition is not sufficiently cured, it must be dried. The water-absorbent resin water-containing composition was allowed to stand and dry at 150 ° C. for 30 minutes to obtain a water-absorbent resin granulated product (XIX). The water absorbent resin granulated product (XIX) was evaluated in the same manner as in Example 9, and the results are shown in Table 5. Under these conditions, a water-absorbent resin granulated product having fluidity can be obtained. However, since a drying step is required, it is advantageous in terms of energy cost to reduce the amount of added water.

(Example 20)
Instead of water in Example 11, 3% by weight aqueous colloidal silica (HS-30 (manufactured by Aldrich) was changed to pure and diluted 10-fold), Aerosil 200 was not added, and water-absorbent resin granulated product (XX) Got. The obtained water absorbent resin granulated product (XX) was evaluated in the same manner as in Example 11, and the results are shown in Table 5.

(Example 21)
In Example 11, Aerosil addition was not performed, and a water-absorbent resin granulated product (XXI) was evaluated in the same manner as in Example 10. The results are shown in Table 5.

(Example 22)
In Example 12, Aerosil addition was not performed, and a water-absorbent resin granulated product (XXII) was evaluated in the same manner as in Example 10. The results are shown in Table 6.

(Example 23)
In Example 13, Aerosil addition was not performed, and a water-absorbent resin granulated product (XXIII) was prepared. However, since it was not cured, drying was necessary. Therefore, the water-absorbent resin water-containing composition was allowed to stand at 150 ° C. for 30 minutes and dried to obtain a water-absorbent resin granulated product (XXIII). The obtained water absorbent resin granulated product (XXIII) was evaluated in the same manner as in Example 10, and the results are shown in Table 6.

(Example 24)
In Example 12, the addition of Aerosil 200 (1.5 g) was added to the finely divided water-containing gel, and then the coarse particles were added and mixed to obtain a water absorbent resin granulated product (XXIV). The obtained water absorbent resin granulated product (XXIV) was evaluated in the same manner as in Example 2, and the results are shown in Table 6.

(Comparative Example 1)
The water absorbent resin formulation (C) (45.2 g) that passed 850 μm and not passed 150 μm and the water absorbent resin classification (D) (4.8 g) that passed 150 μm were placed in a 600 ml plastic container (85 mmφ × 119 mm) and mixed. Then, deionized water (7.5 g) was added thereto and mixed with a spatula for 30 seconds. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ), dried in an airless dryer at 80 ° C. for 60 minutes, and classified to obtain a comparative particulate water-absorbing agent (1) that passed through 850 μm.

(Comparative Example 2)
The water absorbent resin formulation (C) (45.2 g) that passed 850 μm and not passed 150 μm and the water absorbent resin classification (D) (4.8 g) that passed 150 μm were placed in a 600 ml plastic container (85 mmφ × 119 mm) and mixed. Then, deionized water (2.5 g) was added thereto and mixed with a spatula for 30 seconds. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ), dried in an airless dryer at 80 ° C. for 30 minutes, and classified to obtain a comparative particulate water-absorbing agent (2) that passed through 850 μm.

(Comparative Example 3)
Water absorbent resin classification (G) (28.5 g) passing through 150 μm and water absorbent resin classification (F) (271.5 g) passing through 850 μm but not 150 μm were mixed with a 5 L-Radige mixer (M-5R type, Redige) In addition, deionized water (45 g) was simultaneously added and mixed for 10 minutes. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ), dried with an airless dryer at 80 ° C. for 60 minutes, and classified to obtain a comparative particulate water-absorbing agent (3) passing through 850 μm.

(Comparative Example 4)
Water absorbent resin classification (G) (28.5 g) passing through 150 μm and water absorbent resin classification (F) (271.5 g) passing through 850 μm but not 150 μm were mixed with a 5 L-Radige mixer (M-5R type, Redige) The mixture was stirred at a stirring blade speed of 330 rpm, and deionized water (90 g) was added and mixed for 10 minutes. The mixture had many lumps having a diameter of 1 cm or more. Immediately after mixing, the mixture was spread on a petri dish (145 mmφ) and dried in an airless dryer at 80 ° C. for 60 minutes. There were many hard lumps having a diameter of 1 cm or more in the dried product, and the comparative particulate water-absorbing agent (4) passing through 850 μm was hardly obtained, and good granulation could not be performed.

(Comparative Example 5)
In Example 9, Aerosil addition was not performed, and a comparative water absorbent resin granulated product (5) was obtained and evaluated in the same manner as in Example 9.

(Test example)
Measurement of the weight average particle diameter, fine powder ratio, absorption ratio under no pressure, absorption capacity under pressure, moisture content of the particulate water absorbing agent (1) to (8) and the comparative particulate water absorbing agent (1) to (4) An impact resistance test was performed. The results are shown in Tables 1-7.

  The first water-absorbent resin powder (water-absorbent resin classification (D)) and the second water-absorbent resin powder (water-absorbent resin formulation (C)) were mixed in advance by comparison with the same amount of aqueous liquid added. However, compared with the comparative particulate water-absorbing agent (1) (fine powder amount 6.0 wt%) mixed with an aqueous liquid (collective granulation), the particulate water-absorbing agent (1) of the present invention (fine powder amount 3. 6% by weight), the amount of fine powder was greatly improved. In addition, the particulate water-absorbing agent (3) of the present invention (fine powder amount 7.3 wt%) is finer than the batch-granulated comparative particulate water-absorbing agent (2) (fine powder amount 9.6 wt%). The amount of powder is greatly improved. Moreover, the amount of fine powder is improved, so that there is much addition amount of an aqueous liquid in particulate water absorbing agent (1)-(3). In the particulate absorbent (4), the amount of water added is as large as 45 parts by weight, and the weight ratio of the first water-absorbent resin powder to the second water-absorbent resin powder is 30/70, and the proportion of fine powder is as follows. Even when the amount was large, the amount of fine powder could be greatly reduced.

  Compared with the same amount of aqueous liquid added (15 parts by weight), the granulated comparative particulate water-absorbing agent (3) (the amount of fine powder before impact 1.9% by weight, after impact 4.9% by weight) Compared with the particulate water-absorbing agent (5) of the present invention (the amount of fine powder before impact is 0.5% by weight, the amount after impact is 1.5% by weight), the amount of fine powder is greatly improved. In the comparative particulate water-absorbing agent (4) which was granulated at once by adding a large amount of aqueous liquid of 30 parts by weight, a lump with a diameter of 1 cm or more was formed and granulation was impossible. However, the particulate water-absorbing agent (6 ), A large amount of an aqueous liquid of 45 parts by weight could be uniformly mixed, and the granulation strength could be further increased.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  As described above, in the present invention, at least the water-absorbent resin particles and the aqueous liquid are mixed, and further, the water-absorbent resin water-containing product is mixed with the water-absorbent resin or fine particles other than the water-absorbent resin. In addition, it is possible to obtain a particulate water-absorbing agent in which the amount of fine powder is greatly reduced, and the physical property deterioration due to granulation is small.

  In addition, the water-absorbing resin water-containing composition can be prevented from being agglomerated and the water-absorbing resin water-containing composition can be cured at a low temperature and in a short time. As a result, the water-absorbent resin granulated product can be produced very efficiently with a high water content (5 wt% or more and 20 wt% or less) and strong process damage.

  Therefore, the present invention can be applied in the field relating to products using the water-absorbent resin granulated product, specifically in the field relating to the manufacture of sanitary products, diapers, soil improvers and the like.

It is a schematic diagram which shows the flow of the aqueous liquid mixing process and fine particle mixing process of this invention. It is a schematic diagram which shows the flow of the aqueous liquid mixing process and fine particle mixing process in the division | segmentation granulation method of this invention.

Claims (10)

A step (a) of obtaining a water-absorbent resin hydrate by mixing the first water-absorbent resin particles having a weight average particle diameter of less than 200 μm and an aqueous liquid;
Method for producing a water-absorbent resin hydrate, weight average particle diameter of the water-absorbent resin granulation product and a step (b) mixing the second water-absorbing resin particles child is 200～800Myuemu. Method for producing a water-absorbent resin granule according to claim 1, wherein the moisture content of the upper Symbol absorbent resin hydrate of is not more than 99 wt% 20 wt% or more.   The method for producing a water-absorbent resin granulated product according to claim 1 or 2, wherein the first water-absorbent resin particles containing the aqueous liquid are water-containing gel-like materials. The method for producing a water-absorbent resin granulated product according to any one of claims 1 to 3 , wherein the first water-absorbent resin particles are subjected to surface crosslinking treatment. The water absorbent resin structure according to any one of claims 1 to 4 , comprising a step (c) of heating and drying a mixture of the first water absorbent resin particles and the second water absorbent resin particles containing the aqueous liquid. A method for producing granules. The water absorbent resin granulated product according to any one of claims 1 to 5 , wherein the weight ratio of the first water absorbent resin particles and the second water absorbent resin particles is in the range of 1/99 to 50/50. Manufacturing method. 7. The method according to claim 1 , comprising a step (d) of classifying a mixture of the first water-absorbent resin particles and the second water-absorbent resin particles containing the aqueous liquid or a dried product thereof. A method for producing a water-absorbent resin granulated product. The water absorbent resin granulated product according to any one of claims 1 to 7 , wherein the obtained water absorbent resin granulated product is a granulated product of first water absorbent resin particles and second water absorbent resin particles. Manufacturing method. The method for producing a water-absorbent resin granulated product according to any one of claims 1 to 8 , wherein the first and second water-absorbent resin particles are polyacrylic acid-based water-absorbent resins. A water absorbent resin granulated product obtained by the method for producing a water absorbent resin granulated product according to any one of claims 1 to 9,
20 parts by weight or less in 5 parts by weight or more relative to the total amount 100 parts by weight of the water-absorbent resin granulation product moisture, seen including,
(1) Absorption capacity under no pressure with respect to 0.90% by weight sodium chloride aqueous solution is 27 g / g or more,
(2) Absorption capacity under pressure at 1.9 kPa with respect to 0.90 wt% sodium chloride aqueous solution is 20 g / g or more,
(3) Absorption capacity under pressure at 4.8 kPa with respect to 0.90% by weight sodium chloride aqueous solution is 10 g / g or more,
(4) The absorption rate for a 0.90% by weight sodium chloride aqueous solution is 20 seconds to 50 seconds,
(5) A water-absorbent resin granulated product, wherein particles passing through a JIS standard sieve having an opening of 150 μm are 0 to 5 parts by weight with respect to 100 parts by weight of the water-absorbent resin granulated product.

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