JP4500134B2 - Particulate water-absorbing resin composition - Google Patents

Description

  The present invention relates to a particulate water-absorbing resin composition. More specifically, the present invention relates to an excellent particulate water-absorbent resin composition that can exhibit a high absorption capacity over a long period of time when used in sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads.

Currently, sanitary materials such as paper diapers, sanitary napkins, so-called incontinence pads, and the like, have a wide range of water-absorbing resins and compositions for absorbing body fluids and hydrophilic fibers such as pulp. in use. Examples of the water-absorbing resin include a crosslinked polyacrylic acid partially neutralized product, a hydrolyzate of starch-acrylic acid graft polymer, a saponified vinyl acetate-acrylic ester copolymer, an acrylonitrile copolymer, or an acrylamide. A hydrolyzate of a copolymer, a cross-linked product thereof, a cross-linked polymer of a cationic monomer or the like is used as a main raw material.
In recent years, sanitary materials such as disposable diapers and sanitary napkins have become highly functional and thin. There is a tendency that the mass ratio of the conductive resin increases. In other words, by reducing the number of hydrophilic fibers with a small bulk specific gravity and using many water absorbent resins with excellent water absorption and large bulk specific gravity, the content ratio of the water absorbent resin in the absorber is increased, thereby reducing the amount of water absorption. The sanitary material is made thinner without reducing it.

When evaluating the performance of a water-absorbent resin, evaluation based on an absorption capacity under no pressure, an absorption capacity under pressure, an absorption index under pressure, and the like has been generally performed (for example, see Patent Document 1).
In conventional methods for evaluating a water-absorbent resin, it has been common to measure the absorption rate in one hour from the start of absorption. The reason is that the conventional water-absorbent resin reaches almost the saturation magnification in one hour from the start of absorption.
However, when focusing on the actual use of a diaper, the diaper is worn for several hours, and urination is performed several times at intervals of about several tens of minutes to one hour during the wearing time.
Therefore, the water-absorbent resin suitable for applications such as diapers does not reach saturation in 1 hour, but maintains a certain level of absorption capacity in the initial short time, and the absorption capacity continues for a longer time. In addition, it is required to have a liquid permeability and diffusibility. In particular, in recent years when the thickness is reduced, a material capable of exhibiting a high absorption capacity under pressure for a long time is required.

  As described above, most of the conventional water-absorbent resins reach the saturation ratio in one hour, but some of them have an extremely low absorption capacity under pressure. Such a water-absorbent resin has a weak gel strength and cannot ensure liquid permeability and diffusibility, and therefore has a problem in use for diapers and the like. In fact, when used for diapers, it swells only in the vicinity of the urine and gel blocking occurs, making it impossible to diffuse urine throughout the absorber, resulting in poor absorption performance. ing. In particular, it becomes remarkable in a high-concentration absorber that appears due to a reduction in thickness and has a ratio of the water-absorbing resin in the absorber exceeding 40% or 50%.

In addition, it is generally known that a water-absorbent resin having a lower absorption capacity under no pressure has higher liquid permeability and diffusibility. There is a problem that the amount of absorbed diapers is reduced, although the liquid uptake (liquid permeability) is high.
In order to continuously increase the absorption capacity over a long period of time, there is a method of increasing the particle diameter of the water absorbent resin. However, when the particle size is increased, there is a problem that when used for a diaper, the touch of the diaper surface is deteriorated and the user feels a foreign object.
In order to continuously increase the absorption capacity over a long period of time, several techniques using a mixed bed type ion exchange resin have been reported.

A superabsorbent material including a combination of an anionic superabsorber in which 20 to 100% of functional groups are in a free acid form and an anion exchanger in which 20 to 100% of functional groups are in a salt form has been reported. (For example, refer to Patent Document 2).
A mixed bed ion-exchange water-absorbing resin obtained by mixing a water-swellable anion exchanger having a free functional group and a water-swellable cation exchanger having a free functional group, under pressure (0.7 psi (4 A composition having an absorption capacity PUP (Performance Under Pressure) at 2 hours of 30 g / g or more, or 8 hours of 40 g / g or more, or 16 hours of 42 g / g or more. Has been reported (for example, see Patent Document 3).

A water-absorbing resin in which a functional group showing basicity exists in a free state and a water-absorbing resin in which a functional group showing acidity exists in a free state form a microdomain in one particle have been reported. (For example, refer to Patent Document 4).
Both of these technologies apply mixed bed type ion-exchange resin technology to water-absorbent resins, and absorb salts by incorporating salts dissolved in urine into functional groups on the water-absorbent resin by ion exchange. The urinary salt concentration to be reduced is reduced, and osmotic pressure is generated by dissociation of the ions, resulting in higher absorption capacity. Therefore, in the above technique, the decrease in the absorption rate is achieved by adjusting the ion exchange rate.

However, in the above technique, when an aqueous liquid having a salt concentration exceeding the ion exchange capacity is exposed, although ion exchange occurs, it does not lead to a reduction in the large volume salt concentration. Has the disadvantage of a sharp drop. Further, many of the cationic superabsorbers (anion exchangers) are extremely expensive, and it has been difficult to provide an inexpensive water-absorbing resin.
In addition, a technique for controlling liquid permeability by adding polyacrylic acid fine particles (corresponding to 45 μm or less) to water-absorbent resin particles has been reported (for example, see Patent Document 5). Furthermore, as a technique for obtaining a water-absorbing agent by mixing water-absorbing resin particles having different neutralization rates, it has also been reported for the purpose of deodorizing ammonia or the like (see, for example, Patent Document 6). Is low, and the effect of increasing the absorption ratio over a long period of time is little or small.
US Pat. No. 5,601,542 International Publication No. 96/15180 Pamphlet International Publication No. 99/34843 Pamphlet International Publication No. 99/25393 Pamphlet JP 2001-98170 A International Publication No. 03/28778 Pamphlet

  Therefore, the problem to be solved by the present invention is to provide an excellent particulate water-absorbing resin composition for preventing urine leakage and the like over a long period of time when used in sanitary materials such as disposable diapers and sanitary napkins. There is to do.

The present inventor has intensively studied to solve the above problems. As a result, it is important to solve the problem that the absorption capacity in the initial short time is secured to a certain extent, the absorption capacity is continuously increased over a long time, and liquid permeability and diffusivity are also secured. More specifically, specific properties of the particulate water-absorbing resin composition include, as a specific range, a specific particle size absorption capacity under specific pressure and a specific particle size absorption index increase, and / or a specific range of mass average particle diameter, The present invention has been completed because it is considered important to satisfy the reduction ratio and the increase in absorption index.
Moreover, as an example for obtaining a water-absorbing resin composition satisfying the novel parameters according to the present invention, the present inventors first focused on the relationship between the neutralization rate of the carboxyl group-containing water-absorbing resin and the absorption capacity. In other words, the absorption capacity of the carboxyl group-containing water-absorbing resin increases as the neutralization rate increases, but the increase in the absorption capacity is not constant, and the absorption capacity increases rapidly until the neutralization ratio is about 50%. It was noted that a unique phenomenon was observed in which the increase in the absorption capacity was moderated when the neutralization rate was about 50% or more.

Next, the present inventor mixed a low neutralization rate carboxyl group-containing water absorbent resin with a large degree of increase in absorption capacity and a high neutralization rate carboxyl group-containing water absorbent resin with a small degree of increase in absorption capacity. We considered using it. As a result, when two or more kinds of carboxyl group-containing water absorbent resins having different neutralization rates are mixed as described above, it is surprising compared to the case of using only one type of carboxyl group-containing water absorbent resin having a certain neutralization rate. In particular, it has been found that the absorption capacity can be increased continuously over a long period of time while ensuring the absorption capability in the initial short time to some extent, and the liquid permeability and diffusibility can be secured.
Furthermore, it has been found that it is preferable to adjust to a specific particle size for the expression of such functions.

In other words, grain child-like water absorbent resin composition that written to the present invention is a particulate water-absorbent resin composition comprising a carboxyl group-containing water-absorbent resin 80 wt% or more, as the carboxyl group-containing water-absorbent resin, A carboxyl group-containing water absorbent resin (A) having a carboxyl group neutralization rate of 50% or more and a carboxyl group-containing water absorbent resin (B) having a carboxyl group neutralization rate of less than 50%, (A): (B) = 90: 10 to 10:90 in a mass ratio, the mass average particle diameter is in the range of 320 to 700 μm, and the absorption capacity under pressure (0.3 psi (2.06 kPa), 1 hour) is 20 g. / G or more, and the increase in absorption index in 20 hours is 3 g / g or more.
The particulate water-absorbent resin composition according to the present invention has an absorption capacity (0.29 psi (2.00 kPa), 1 hour) under a specific particle size pressure of 20 g / g or more and 20 hours or more in the above. The specific particle size absorption index increase may be 3 g / g or more.

  Furthermore, the water absorbent article according to the present invention uses the particulate water absorbent resin composition of the present invention.

  According to the present invention, an excellent particulate water absorption which can ensure the absorption capability in the initial short time to a certain extent, the absorption capacity is continuously increased over a long time, and furthermore, liquid permeability and diffusibility can be secured. Water absorbent resin composition can be provided, and when such a particulate water absorbent resin composition is used in a water absorbent article such as a paper diaper, the absorbent performance of the water absorbent article can be improved, leakage, etc. The problem can be avoided.

Hereinafter, the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and modifications other than the following examples can be made as appropriate without departing from the spirit of the present invention.
(Water absorbent resin)
In the present invention, the water-absorbing resin means, for example, deionized water that absorbs a large amount of water of 5 times or more, preferably 50 to 1000 times its own weight, and is anionic, nonionic, or cationic. It is a conventionally known crosslinked polymer that forms a water-insoluble hydrogel.

  In addition, the particulate water-absorbing resin composition referred to in the present invention includes a water-absorbing resin as a main component (essentially including a carboxy group-containing water-absorbing resin in a solid content of 80% by mass or more and 100% by mass or less). If it is a thing, content of components other than a water absorbent resin may be 0 mass%, and the water absorbent resin as a main component is a mixture of a plurality of different water absorbent resins (for example, a polymer composition). In addition, a single water-absorbing resin is also referred to as a particulate water-absorbing resin composition in the present invention. That is, the particulate water-absorbing resin composition referred to in the present invention is synonymous with a particulate water-absorbing agent having a water-absorbing resin as a main component, and the particulate water-absorbing resin composition has a water-absorbing resin as a main component. In other words, the particulate water-absorbing agent. Note that a single water-absorbing resin alone is referred to as a water-absorbing resin composition as described in US Pat. No. 5,061,259 and US-Reissued Patent No. 32649.

The water-absorbing resin used in the present invention must be water-swellable and water-insoluble, and the uncrosslinked water-soluble component (water-soluble polymer) in the water-absorbing resin is preferably 50% by mass or less, more preferably Is 25% by mass or less, more preferably 20% by mass or less, further preferably 15% by mass or less, and particularly preferably 10% by mass or less.
Examples of water-absorbing resins include polyacrylic acid partially neutralized polymers, hydrolysates of starch-acrylonitrile graft polymers, starch-acrylic acid graft polymers, saponified vinyl acetate-acrylic ester copolymers, and acrylonitrile copolymers. A hydrolyzate of a polymer or an acrylamide copolymer, a cross-linked product thereof, a carboxyl group-containing cross-linked polyvinyl alcohol modified product, a cross-linked isobutylene-maleic anhydride copolymer, and the like can be given.

Only 1 type may be used for a water absorbing resin, and 2 or more types may be used together.
In the present invention, it is preferable to use a carboxyl group-containing water absorbent resin.
The carboxyl group-containing water-absorbent resin referred to in the present invention is a hydrophilic polymer having a carboxyl group represented by the general formula -COOM (M = hydrogen, alkali metal, alkaline earth metal, amine, ammonium, etc.) as a side chain. It is a three-dimensional crosslinked body. Here, when M = H, the term “unneutralized product” or “acid type” may be used. In cases other than M = H, the term “neutralized product” or “salt” may be used.
Specific examples of the carboxyl group-containing water-absorbing resin include, for example, carboxyl group-containing monomers such as (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, cinnamic acid and / or the like. Examples thereof include water-absorbing resins mainly composed of a crosslinked polymer obtained by crosslinking polymerization of a monomer component mainly composed of a salt, and further, carboxyl group-containing polymers such as poly (meth) acrylic acid and carboxymethylcellulose. And / or a water-absorbing resin obtained by crosslinking the salt thereof. Among these, a water-absorbing resin mainly composed of a crosslinked polymer obtained by crosslinking polymerization of a monomer component mainly composed of acrylic acid and / or a salt thereof is preferable. The cross-linked polymer may contain a graft component as necessary.

Examples of the acrylate include alkali metal salts such as sodium, potassium and lithium of acrylic acid, ammonium salts and amine salts.
In addition, about acrylic acid to be used, a conventionally well-known thing can be used. For example, it is described in US Patent Application Publication No. 2001/0016668, US Patent Application Publication No. 5817865, US Patent No. 6,596,901, and the like.
In the carboxyl group-containing water-absorbent resin used in the present invention, the neutralization rate is the molar ratio of the total amount of carboxyl groups contained in the carboxyl group-containing water-absorbent resin and its salt (M = having a counter cation other than hydrogen). This is a parameter indicating the ratio of neutralization. Neutralization of the water-absorbent resin for forming the salt may be performed in a monomer state before polymerization, or may be performed in the state of a polymer during or after polymerization, or a combination thereof. May be.

As a monomer for obtaining the water absorbent resin used in the present invention, a monomer other than the carboxyl group-containing monomer and / or a salt thereof may be contained.
The monomer other than the carboxyl group-containing monomer and / or a salt thereof is not particularly limited, and specific examples include vinyl sulfonic acid, styrene sulfonic acid, 2- (meth) acrylamide- Anionic unsaturated monomers such as 2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid and their salts; 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, poly Nonionic hydrophilic group-containing unsaturated monomers such as tylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine, N-vinylacetamide; N, N-dimethylamino Cations such as ethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, and quaternary salts thereof Unsaturated unsaturated monomers; and the like. These monomers may be used alone or in combination of two or more as appropriate.

In the present invention, when a monomer other than a carboxyl group-containing monomer and / or salt thereof is used, the proportion of the monomer other than the carboxyl group-containing monomer and / or salt thereof is used as the main component. Preferably it is 30 mol% or less with respect to the total amount of the carboxyl group-containing monomer and / or its salt to be used, More preferably, it is 10 mol% or less. By using a monomer other than the carboxyl group-containing monomer and / or its salt in the above proportion, the absorption characteristics of the finally obtained water-absorbent resin or particulate water-absorbent resin composition are further improved. In addition, it is possible to obtain a water-absorbing resin or a particulate water-absorbing resin composition at a lower cost.
When polymerizing the above-mentioned monomers to obtain the water-absorbent resin used in the present invention, bulk polymerization or precipitation polymerization can be performed. However, performance and ease of polymerization control, swelling gel absorption From the viewpoint of characteristics, it is preferable to perform aqueous solution polymerization or reverse phase suspension polymerization by using the monomer as an aqueous solution.

Polymerization methods for aqueous solution polymerization and reverse phase suspension polymerization are conventionally known. For example, US Pat. No. 4,462,001, US Pat. No. 4,769,427, US Pat. No. 4,873,299, US Pat. No. 4,093,763, US Pat. U.S. Pat. No. 4,446,261, U.S. Pat. No. 4,683,274, U.S. Pat. No. 4,690,996, U.S. Pat. No. 4,721,647, U.S. Pat. No. 4,738,867, U.S. Pat.
When the monomer is an aqueous solution, the concentration of the monomer in the aqueous solution (hereinafter referred to as the monomer aqueous solution) depends on the temperature of the monomer aqueous solution and the monomer, and is not particularly limited. However, the inside of the range of 10-70 mass% is preferable, and the inside of the range of 20-60 mass% is further more preferable. In addition, when performing aqueous solution polymerization, a solvent other than water may be used in combination as necessary, and the type of the solvent used in combination is not particularly limited.

As a method for aqueous solution polymerization, a monomer aqueous solution is polymerized while crushing the resulting hydrogel in a double-arm kneader, or a monomer aqueous solution is supplied in a predetermined container or on a driving belt for polymerization. And a method of pulverizing the obtained gel with a meat chopper or the like.
When starting the polymerization, for example, radicals such as potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-amidinopropane) dihydrochloride, etc. Polymerization initiators; Photopolymerization initiators such as 2-hydroxy-2-methyl-1-phenyl-propan-1-one; and the like can be used.
Further, a reducing agent that promotes the decomposition of the polymerization initiator may be used in combination, and a redox initiator may be obtained by combining the two.

Examples of the reducing agent include (bi) sulfurous acid (salt) such as sodium sulfite and sodium hydrogensulfite; L-ascorbic acid (salt); reducing metal (salt) such as ferrous salt; amines; However, it is not particularly limited.
The amount of the polymerization initiator used is preferably in the range of 0.001 to 2 mol%, and more preferably in the range of 0.01 to 0.1 mol%. When the amount of the polymerization initiator used is less than 0.001 mol%, the amount of unreacted monomers increases, and the amount of residual monomers in the resulting water absorbent resin or particulate water absorbent resin composition increases. This is not preferable. When the usage-amount of a polymerization initiator exceeds 2 mol%, since the amount of water-soluble components in the obtained water-absorbent resin and particulate water-absorbent resin composition increases, it is not preferable.

The polymerization reaction may be initiated by irradiating the reaction system with active energy rays such as radiation, electron beam or ultraviolet ray, and the above polymerization initiator may be used in combination.
Although the reaction temperature in a polymerization reaction is not specifically limited, The range of 10-130 degreeC is preferable, The inside of the range of 15-120 degreeC is more preferable, The range of 20-100 degreeC is especially preferable.
The reaction time and polymerization pressure in the polymerization reaction are not particularly limited, and may be set as appropriate according to the type of monomer or polymerization initiator, reaction temperature, and the like.
The water-absorbing resin may be a self-crosslinking type that does not use a cross-linking agent, but a cross-linking agent having two or more polymerizable unsaturated groups and / or reactive groups in one molecule (water-absorbing resin). Or a cyclic compound which is copolymerized or reacted with a crosslinking agent in which two or more reactive groups appear in one molecule by a ring-opening reaction.

  Specific examples of the internal crosslinking agent include, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (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 Polyhydric alcohols such as recall, propylene glycol, 1,3-butanediol, 1,4-butanediol, glycerin, pentaerythritol; and the like; ethylenediamine, ethylene carbonate, propylene carbonate, polyethyleneimine, glycidyl (meth) acrylate, etc. Can do.

An internal crosslinking agent may be used independently and may use 2 or more types together suitably.
The internal cross-linking agent may be added to the reaction system all at once or in divided portions.
In the case of using an internal cross-linking agent, in consideration of the absorption characteristics of the finally obtained water-absorbent resin or particulate water-absorbent resin composition, a compound having two or more polymerizable unsaturated groups is polymerized. It is preferable to use it essentially.
The amount of the internal crosslinking agent used is preferably in the range of 0.001 to 2 mol%, more preferably in the range of 0.02 to 1.0 mol%, based on the monomer (excluding the crosslinking agent). More preferably, it is in the range of 0.06 to 0.30 mol%, and particularly preferably in the range of 0.08 to 0.15 mol%. When the amount of the internal cross-linking agent used is less than 0.001 mol% and more than 2 mol%, sufficient absorption characteristics may not be obtained.

When a cross-linked structure is introduced into the polymer using an internal cross-linking agent, the internal cross-linking agent should be added to the reaction system before or during polymerization of the monomer, after polymerization, or after neutralization. However, it is preferably added before polymerization.
In the polymerization, 0-50 mass% (hydrophilic polymers such as starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt), polyacrylic acid (salt) cross-linked product) are added to the reaction system. You may add within the range of a monomer. In addition, various foaming agents such as carbonic acid (hydrogen) salts, carbon dioxide, azo compounds, inert organic solvents; various surfactants; chelating agents; chain transfer agents such as hypophosphorous acid (salts); kaolin, talc, silicon dioxide Inorganic fine particles such as polyvalent aluminum salts such as polyaluminum chloride, aluminum sulfate, magnesium sulfate, etc. may be added within the range of 0 to 10% by mass (with respect to the monomer).

When the crosslinked polymer having a crosslinked structure introduced into the inside of the polymer using an internal crosslinking agent is obtained by aqueous solution polymerization and is in the form of a gel, that is, a hydrogel crosslinked polymer, the hydrogel The cross-linked polymer is finely divided as necessary, and then dried and ground. The pulverization may be performed before drying, at the same time, or after drying. Preferably, it is pulverized after drying.
In the present invention, the drying is preferably performed on the particulate hydrogel polymer (for example, the mass average particle diameter is 2 cm or less, preferably 1 cm or less, more preferably 5 mm or less). In the present invention, as a fragmentation method for making the hydrogel polymer into particles, the kneader may be used for fragmentation simultaneously with the polymerization, or after the polymerization, You may use together the fragmentation at the time of superposition | polymerization, and the subdivision after superposition | polymerization. In addition, when a hydrogel polymer is a particulate form and is not dried, for example, in a film form etc., a physical property and a particle size may be inferior.

The particle diameter of the hydrogel crosslinked polymer before drying is preferably a mass average particle diameter in the range of 45 to 4000 μm, more preferably in the range of 50 to 2000 μm, still more preferably in the range of 100 to 400 μm from the viewpoint of drying efficiency and physical properties. It is in the range of 1500 μm, particularly preferably in the range of 200 to 1000 μm.
Suitable devices for subdivision include, for example, a kneader, a vertical slitting slitter with a cutter blade, a horizontal slitting slitter with a cutter blade, a cutter-type crusher with a rotating blade, a meat chopper with a predetermined hole diameter, etc. Can be illustrated. In addition, when the mass average particle diameter of the hydrogel polymer is out of the above range, there is a risk of causing a decrease in the water absorption ratio or an increase in the water-soluble content of the resulting water-absorbent resin.

The hydrogel polymer thus obtained is preferably dried. Drying means that the solid content of the hydrogel polymer is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and particularly preferably 93% by mass or more. . In addition, the drying here does not necessarily need to be a dry polymer having a solid content of 100% by mass (water content is zero).
The drying method that can be used in the present invention is not particularly limited, and for example, one of drying methods such as hot air drying, thin film drying using a drum dryer, vacuum drying method, stirring drying, fluidized bed drying, and the like. Or 2 or more types can be used. The continuous or batch of drying is not particularly limited. In the present invention, hot air drying, particularly continuous hot air drying is preferably used from the viewpoint of physical properties and drying efficiency. For example, it may be dried by standing on a belt.

  In hot air drying, from the viewpoint of drying efficiency, for example, a particulate hydrogel polymer is laminated on a punching metal having a metal mesh / or holes or slits, and then the vertical or horizontal direction of the gel, preferably the vertical direction. In addition, hot air may be ventilated between the voids of the laminated particles. As the hole diameter of the wire mesh used, for example, in the case of a hole or wire mesh, it is preferable to have a ventilation hole of preferably 0.1 to 5 mm, more preferably about 0.2 to 2 mm. From the viewpoint of physical properties after drying, the lamination of the gel on the metal mesh or punching metal is preferably 1 to 20 cm, more preferably 1.5 to 10 cm, and even more preferably 2 to 8 cm in a particulate hydrous gel form. What is necessary is just to laminate | stack a polymer.

  The drying temperature at the time of drying the hydrogel polymer is preferably 100 ° C. or higher, more preferably in the range of 110 to 230 ° C., more preferably in the range of 130 to 200 ° C., from the viewpoint of physical properties and productivity. Especially preferably, it is the range of 150-190 degreeC. The drying temperature is defined by the material temperature or the temperature of the heat medium (hot air or the like), but is preferably defined by the heat medium temperature. The drying temperature during the drying period may be constant, or may be appropriately changed during the drying in the above temperature range. When performing hot air drying, the dew point of the hot air is preferably in the range of 40 to 100 ° C, more preferably in the range of 50 to 90 ° C, and still more preferably in the range of 60 to 85 ° C, from the viewpoint of physical properties and energy efficiency.

The particulate hydrogel polymer that has been laminated and dried tends to become a block-like dried product that loses fluidity due to aggregation between particles after drying. Since such a block-like dried product is an aggregate of dry polymer particles, it has continuous voids and air permeability to the inside of the block, but has no fluidity due to aggregation. For this reason, a crushing (crushing) process may be required.
The pulverization may be performed before drying, at the same time, or after drying, but is preferably performed after drying. More preferably, it is pulverized and further classified. Drying and pulverization, and if necessary, classification are preferably performed in a continuous process.
The pulverization method is not particularly limited as long as the dry polymer or the aggregate (block-like product) can be made into a flowable powder, preferably a powder having a mass average particle diameter of 2 mm or less. For example, a hammer type pulverizer One type or two or more types of pulverization methods using a roll type pulverizer, jet airflow type pulverizer, etc., and various conventionally known pulverization or pulverization methods can be used. In addition, when the aggregation at the time of drying is weak, the polymer may be pulverized by loosening the aggregation of the polymer by applying vibration to the dried polymer and classifying it without using a pulverizer.

After the pulverization, if necessary, it may be preferably classified to remove coarse particles and fine powder.
When obtaining the water-absorbent resin used in the present invention, classification may be performed in order to control to a specific particle size distribution.
The classifier used for classification is not particularly limited. For example, a vibration sieve (unbalanced weight drive type, resonance type, vibration motor type, electromagnetic type, circular vibration type, etc.), in-plane motion sieve (horizontal motion type, Horizontal circular-linear motion type, three-dimensional circular motion type, etc.), movable mesh screen, forced stirring screen, mesh surface vibration screen, wind screen, sonic screen, etc., preferably vibrating screen, in-plane motion screen Is used.

The water-absorbent resin particles obtained in this way are preferably adjusted to a specific particle size. The particle size is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 97% by mass or more, of particles less than 850 μm and 150 μm or more.
The mass average particle diameter of the water-absorbent resin particles obtained in this way is determined according to the purpose, but in order to sufficiently exhibit the effects of the present invention, the mass average particle diameter (D50) is preferably 300 to 300. In the range of 700 μm, more preferably in the range of 320 to 700 μm, further preferably in the range of 330 to 700 μm, further preferably in the range of 340 to 700 μm, further preferably in the range of 360 to 700 μm, still more preferably in the range of 380 to 700 μm, especially Preferably it is the range of 400-700 micrometers.

The proportion of water-absorbing resin particles having a particle diameter of less than 150 μm is preferably 0% by mass or more and less than 10% by mass, more preferably 0% by mass or more and less than 7% by mass, and further preferably 0% by mass or more and less than 5% by mass. Especially preferably, it is 0 mass% or more and less than 3 mass%.
Further, the logarithmic standard deviation σζ representing the narrowness of the particle size distribution is preferably 0.1 or more and 0.46 or less, more preferably 0.1 or more and 0.44 or less, and still more preferably 0.1 or more and 0.42 or less. Preferably they are 0.1 or more and 0.40 or less. If the logarithmic standard deviation σζ is less than 0.1, the productivity is drastically lowered, which is not realistic, and if it exceeds 0.46, problems such as segregation become prominent.

The bulk specific gravity of the water-absorbing resin particles thus obtained varies depending on the true specific gravity (g / cm ³ ) determined uniquely by the monomer composition. For example, the water-absorbing resin is sodium polyacrylate, and in particular, the neutralization rate. In the case of 50 to 90 mol% sodium polyacrylate, and further in the case of sodium polyacrylate having a neutralization rate of 60 to 80 mol%, the bulk specific gravity is usually preferably 0.63 g / ml or more, and 0.65 g / Ml or more is more preferable. The bulk specific gravity may be measured with an apparatus according to JIS K-3362.
After the pulverization, coarse particles (for example, 850 μm ON product) and fine powder (for example, 150 μm pass product) may be recycled as appropriate. Coarse particles are reground, and fine particles are removed or collected, so that the particle size distribution can be obtained. The method of recycling the water-absorbent resin fine powder includes US Pat. No. 4,950,692, US Pat. No. 5,064,582, US Pat. No. 5,264,495, US Pat. No. 5,478,879, European Patent No. 081873, European Patent No. 0885917, and European Patent No. No. 0844270 and the like. The amount of fine powder recycled is preferably 15% by mass or less, more preferably in the range of 1 to 10% by mass, and still more preferably in the range of 2 to 8% by mass.

In the water-absorbing resin particles obtained as described above, the absorption capacity without load (CRC) with respect to a 0.90 mass% sodium chloride aqueous solution (saline) is a neutralization rate as shown in Reference Example 1 described later. However, the neutralization rate is preferably 5 g / g or more, more preferably 10 g / g or more, and still more preferably. 15 g / g or more, particularly preferably 20 g / g or more.
The water-absorbent resin particles obtained as described above preferably have a soluble content of 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and particularly preferably 20% by mass or less. Most preferably, it is 15 mass% or less.

The water-absorbing resin used in the present invention may be the water-absorbing resin obtained as described above. Preferably, the surface of the water-absorbing resin particles obtained as described above is surfaced with a surface crosslinking agent. It was obtained by carrying out a crosslinking treatment.
In the surface-crosslinked water-absorbing resin particles, the absorption capacity without load (CRC) with respect to a 0.90 mass% sodium chloride aqueous solution (physiological saline) is about the neutralization rate as shown in Reference Example 1 described later. Depending on the conditions, the neutralization rate is preferably 50 g or more, more preferably 10 g / g or more, and even more preferably 15 g / g. As described above, it is particularly preferably 20 g / g or more.

The surface-crosslinked water-absorbing resin particles preferably have a soluble content of 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, particularly preferably 20% by mass or less, and most preferably. Is 15% by mass or less.
The surface-crosslinked water-absorbing resin particles are preferably adjusted to a specific particle size. The particle size is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 97% by mass or more, of particles less than 850 μm and 150 μm or more.
The mass average particle diameter of the surface-crosslinked water-absorbing resin particles obtained in this way is determined according to the purpose, but in order to sufficiently exert the effects of the present invention, the mass average particle diameter (D50) is: Preferably in the range of 300 to 700 μm, more preferably in the range of 310 to 700 μm, more preferably in the range of 320 to 700 μm, still more preferably in the range of 330 to 700 μm, still more preferably in the range of 340 to 700 μm, still more preferably in the range of 360 to 700 μm. More preferably, it is the range of 380-700 micrometers, Most preferably, it is the range of 400-700 micrometers.

Further, the ratio of the surface-crosslinked water-absorbing resin particles having a particle diameter of less than 150 μm is preferably 0% by mass or more and less than 10% by mass, more preferably 0% by mass or more and less than 7% by mass, and further preferably 0% by mass or more. It is less than 5% by mass, particularly preferably 0% by mass or more and less than 3% by mass.
Further, the logarithmic standard deviation σζ representing the narrowness of the particle size distribution is preferably 0.1 or more and 0.46 or less, more preferably 0.1 or more and 0.44 or less, and still more preferably 0.1 or more and 0.42 or less. Preferably they are 0.1 or more and 0.40 or less. If the logarithmic standard deviation σζ is less than 0.1, the productivity is drastically lowered, which is not realistic, and if it exceeds 0.46, problems such as segregation become prominent.

As the surface cross-linking agent that can be used in the present invention, a compound having at least two functional groups capable of reacting with functional groups in the water-absorbent resin (preferably functional groups capable of dehydration or transesterification with carboxyl groups). It can be illustrated. The functional group in the water absorbent resin is preferably an anionic dissociation group, more preferably a carboxyl group.
Examples of the surface cross-linking agent include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentane. Diol, polypropylene glycol, glycerin, polyglycerin, 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 Polyhydric alcohol compounds such as sorbitol, 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 And epoxy compounds such as glycidol; polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneimine; and their inorganic or organic salts (for example, azetidinium salts); 2 Polyisocyanates such as 1,4-tolylene diisocyanate and hexamethylene diisocyanate Aziridine compounds such as polyaziridine; polyvalent oxazoline compounds such as 1,2-ethylenebisoxazoline, bisoxazoline and polyoxazoline; carbonic acid derivatives such as urea, thiourea, guanidine, dicyandiamide and 2-oxazolidinone; Dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolane-2- ON, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxane Alkylene carbonates such as 2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxopan-2-one Haloepoxy compounds such as epichlorohydrin, epibromhydrin, α-methylepichlorohydrin, and adducts thereof with polyvalent amines (for example, Kaimen (registered trademark) manufactured by Hercules); oxetane compounds; γ- Silane coupling agents such as glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane; hydroxides, chlorides, sulfates, nitrates or carbonates such as zinc, calcium, magnesium, aluminum, iron, and zirconium And the like. Only 1 type of these may be used and 2 or more types may be used together.

The amount of the surface crosslinking agent used is preferably in the range of 0.001 to 10 parts by mass, more preferably in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the water absorbent resin particles. When the amount of the surface cross-linking agent used exceeds 10 parts by mass, it is not preferable because not only a suitable performance is not obtained, but also the amount of the remaining surface cross-linking agent increases. When the amount of the surface cross-linking agent used is less than 0.001 part by mass, sufficient absorption performance may not be exhibited.
In order to further accelerate the reaction with the surface crosslinking agent and further improve the absorption characteristics, an inorganic acid, an organic acid, or the like may be used. These inorganic acids and organic acids include sulfuric acid, phosphoric acid, hydrochloric acid, citric acid, glyoxylic acid, glycolic acid, glycerin phosphoric acid, glutaric acid, cinnamic acid, succinic acid, acetic acid, tartaric acid, lactic acid, pyruvic acid, fumaric acid. Acid, prohynoic acid, 3-hydroxypropionic acid, malonic acid, butyric acid, isobutyric acid, imidinoacetic acid, malic acid, isethionic acid, citraconic acid, adipic acid, itaconic acid, crotonic acid, oxalic acid, salicylic acid, gallic acid, sorbic acid , Gluconic acid, p-toluenesulfonic acid and the like. Further, inorganic acids, organic acids, polyamino acids and the like shown in European Patent No. 0668080 may be used. Although these usage-amounts change with pH etc. of a water absorbent resin, Preferably it is in the range of 0-10 mass parts with respect to 100 mass parts of water absorbent resin particles, More preferably, it is the range of 0.1-5 mass parts. Is within.

When mixing the water absorbent resin particles and the surface cross-linking agent, it is preferable to use water as a solvent. The amount of water used depends on the type and particle size of the water-absorbent resin particles, but is more than 0 and preferably 20 parts by mass or less with respect to 100 parts by mass of the solid content of the water-absorbent resin particles. The range of 10 parts by mass to 10 parts by mass is more preferable, and the range of 0.5 to 5 parts by mass is more preferable.
When mixing the water-absorbent resin particles and the surface cross-linking agent, a hydrophilic organic solvent may be used as a solvent, if necessary. Examples of the hydrophilic organic solvent include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol and other lower alcohols; acetone and other ketones; dioxane, tetrahydrofuran And ethers such as alkoxy polyethylene glycol; amides such as N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide; The amount of the hydrophilic organic solvent used is preferably 20 parts by mass or less, preferably 10 parts by mass or less, based on 100 parts by mass of the solid content of the water-absorbent resin particles, although it depends on the type and particle size of the water-absorbent resin particles. More preferred is 5 parts by mass or less.

In order to more uniformly mix the water-absorbent resin particles and the surface cross-linking agent, non-crosslinkable water-soluble inorganic bases (preferably alkali metal salts, ammonium salts, alkali metal hydroxides, and ammonia or hydroxylated thereof) Products) and non-reducing alkali metal salt pH buffering agents (preferably hydrogen carbonate, dihydrogen phosphate, hydrogen phosphate, etc.) when mixing water-absorbing resin particles and surface cross-linking agent. You may let them. The amount of these used depends on the type and particle size of the water-absorbent resin particles, but is preferably in the range of 0.005 to 10 parts by mass with respect to 100 parts by mass of the solid content of the water-absorbent resin particles. Within the range of ˜5 parts by mass is more preferable.
When mixing the surface cross-linking agent with the water-absorbing resin particles, for example, after dispersing the water-absorbing resin particles in the hydrophilic organic solvent, the surface cross-linking agent may be added. A method in which the surface cross-linking agent dissolved or dispersed in a hydrophilic organic solvent is added directly to the water-absorbent resin particles by spraying or dropping while stirring is preferable. Moreover, when mixing using water, you may coexist inorganic fine particle powder insoluble in water, water-soluble polyvalent metals, surfactant, etc.

The mixing device used when mixing the water-absorbent resin particles and the surface cross-linking agent preferably has a large mixing force in order to mix them both uniformly and reliably. Examples of the mixing apparatus include a cylindrical mixer, a double wall conical mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, a fluidized-type furnace rotary disk mixer, an airflow mixer, A double-arm kneader, an internal mixer, a pulverizing kneader, a rotary mixer, a Redige mixer, a screw extruder, and the like are suitable.
After mixing the water-absorbing resin particles and the surface cross-linking agent, the surface of the water-absorbing resin particles is cross-linked by performing a heat treatment and / or a light irradiation treatment. When performing the heat treatment, the treatment time is preferably within the range of 1 minute to 180 minutes, more preferably within the range of 3 minutes to 120 minutes, and even more preferably within the range of 5 minutes to 100 minutes. The treatment temperature is preferably within the range of 60 to 250 ° C, more preferably within the range of 100 to 210 ° C, and even more preferably within the range of 120 to 200 ° C. When the heat treatment temperature is less than 60 ° C., the heat treatment takes time, causing not only a reduction in productivity, but also a uniform cross-linking is not achieved, and the intended particulate water-absorbent resin composition may not be obtained. . On the other hand, if the heat treatment temperature exceeds 250 ° C., the water-absorbent resin particles may be damaged, and it may be difficult to obtain a product having excellent water absorption characteristics.

The heat treatment 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, an infrared dryer, and the like.
When performing light irradiation treatment, it is preferable to irradiate with ultraviolet rays, and a photopolymerization initiator can be used.
When the water absorbent resin particles are heated in the surface crosslinking treatment, it is preferable to cool the heated water absorbent resin particles. The cooling is preferably performed within a range of 100 to 20 ° C. Moreover, as a cooler used for cooling, what converted the heat medium of the dryer used for the said heat processing into the refrigerant | coolant body is used, for example.

The water absorbent resin used in the present invention may be granulated.
Granulation refers to the formation of particles larger than the original particles by agglomerating and fixing a plurality of particles. Typical granulated particles include NON WEBENS WORK October-November 2000 (Marketing Technology Service, Inc.). 1) on page 75 of publishing). Agglomerated Beads and Broccoli-like. However, in the present invention, the granulation means that the above granulated particles may be formed in a part of the water absorbent resin or the water absorbent resin composition, and all the particles form the shape of the granulated particles. There is no need to be. By subjecting the water-absorbent resin composition to granulation and forming granulated particles of the water-absorbent resin in part, it is possible to reduce fine particles and improve handling. That is, the particulate water-absorbing resin composition according to the present invention preferably includes a part of the granulated particles of the water-absorbing resin formed by granulation.

For granulation, conventionally known methods such as those disclosed in JP-A-61-97333, JP-A-6-313043, etc. may be appropriately employed. A method of granulating particles and water or an aqueous solution of an organic solvent miscible with water or an aqueous solution of a water-soluble polymer by dropwise mixing or spray mixing may be mentioned. Among these, it is preferable to granulate with water in order not to impair the water absorption properties of the water-absorbing resin obtained.
Examples of the organic solvent miscible with water include lower alcohol, lower glycol, monoether of ethylene glycol and lower alcohol, glycerin, acetone and the like.

Examples of the water-soluble polymer include polyacrylic acid, polyacrylic acid metal salt, carboxymethylcellulose, polyethylene glycol, polyvinyl alcohol and the like. In the case of using a water-soluble polymer, it is preferably adjusted to an aqueous solution concentration of 10% by mass or less from the viewpoint of preparation and transfer of the aqueous solution.
The amount of water or aqueous solution added to the water absorbent resin particles is preferably 1 to 30% by mass with respect to the water absorbent resin particles. If the amount used is less than 1% by mass, a sufficient granulation effect cannot be obtained.

As a mixing apparatus preferably used for granulation, it is preferable to have a large mixing force in order to perform uniform and reliable mixing, for example, a cylindrical mixer, a double wall conical mixer, V-shaped mixer, ribbon-type mixer, screw-type mixer, fluid-type furnace rotary disk-type mixer, airflow-type mixer, double-arm kneader, internal mixer, pulverizing-type kneader, rotary mixer, screw type An extruder or the like is suitable.
By performing such granulation, effects such as reduction of the amount of fine particles and prevention of dust generation can be exhibited.
[Particulate water-absorbing resin composition]
The particulate water-absorbing resin composition according to the present invention is a particulate water-absorbing resin composition containing a carboxyl group-containing water-absorbing resin as a main component.

The particulate water-absorbing resin composition according to the present invention contains a carboxyl group-containing water-absorbing resin as a main component. The main component referred to here is a carboxyl group in the solid content of the particulate water-absorbing resin composition. The content ratio of the contained water absorbent resin is preferably 80% by mass or more and 100% by mass or less, more preferably 85% by mass or more and 100% by mass or less, further preferably 90% by mass or more and 100% by mass or less, and particularly preferably 95% by mass. This is the case of 100% by mass or less.
The ratio of particles (specific particle size) of 300 μm or more and less than 600 μm contained in the particulate water-absorbing resin composition according to the present invention is preferably 40% by mass or more, more preferably 50% by mass or more, and Preferably it is 55 mass%. If the proportion of particles (specific particle size) of 300 μm or more and less than 600 μm contained in the particulate water-absorbing resin composition is within the above range, the mass average particle diameter is in the range of 300 μm or more and less than 600 μm, and is 300 μm or more and less than 600 μm. These particles can be judged to have a particle diameter representative of the particulate water-absorbing resin composition.

The particulate water-absorbing resin composition according to the present invention preferably has an absorption capacity under specific particle size pressure (0.01 psi (0.069 kPa), 1 hour) of 20 g / g or more, more preferably 25 g / g or more. More preferably, it is 30 g / g or more. Moreover, the upper limit is 60 g / g or less from the balance between ease of production and performance.
The particulate water-absorbing resin composition according to the present invention preferably has an absorption capacity (0.29 psi (2.00 kPa), 1 hour) under a specific particle size pressure of 20 g / g or more, more preferably 21 g / g or more. More preferably, it is 22 g / g or more, More preferably, it is 23 g / g or more, More preferably, it is 24 g / g or more, Most preferably, it is 25 g / g or more. Moreover, the upper limit is 60 g / g or less from the balance between ease of production and performance.

The particulate water-absorbent resin composition according to the present invention preferably has an absorption capacity under a specific particle size pressure (0.57 psi (3.93 kPa), 1 hour) of 16 g / g or more, more preferably 17 g / g or more. More preferably 18 g / g or more, more preferably 19 g / g or more, further preferably 20 g / g or more, more preferably 21 g / g or more, further preferably 22 g / g or more, more preferably 23 g / g or more, particularly Preferably it is 24 g / g or more. Moreover, the upper limit is 60 g / g or less from the balance between ease of production and performance.
Absorption capacity under specific particle pressure (0.01 psi (0.069 kPa), 1 hour), Absorption capacity under specific particle pressure (0.29 psi (2.00 kPa), 1 hour), Absorption capacity under specific particle pressure (0.57 psi) (3.93 kPa), 1 hour) is a specific pressure (0.01 psi (0)) that is measured by selecting and measuring a particulate water-absorbing resin composition having a specific particle size, as will be described in the Examples below. 069 kPa), 0.29 psi (2.00 kPa), 0.57 psi (3.93 kPa)).

The specific particle size absorption index is represented by the sum of the specific particle size absorption capacity under 0.01 psi (0.069 kPa) and the specific particle size absorption capacity under 0.29 psi (2.00 kPa). Is an index.
The particulate water-absorbing resin composition according to the present invention preferably has a specific particle size absorption index increase of 3 g / g or more at 20 hours and / or 4 hours, more preferably at least 3.5 g / g, Preferably 4 g / g or more, more preferably 4.5 g / g or more, more preferably 5 g / g or more, more preferably 5.5 g / g or more, more preferably 6 g / g or more, more preferably 7 g / g or more. Particularly preferably, it is 7.5 g / g or more, and most preferably 8 g / g or more. Moreover, the upper limit is 20 g / g or less from the balance between ease of production and performance.

The specific particle size absorption index increase is an increase over time in the absorption index after 1 hour, which is measured by selecting a particulate water-absorbing resin composition having a specific particle size, as will be described in the Examples below.
The particulate water-absorbent resin composition according to the present invention preferably has an absorption capacity under pressure (0.06 psi (0.41 kPa), 1 hour) of 20 g / g or more, more preferably 25 g / g or more, Preferably it is 30 g / g or more. Moreover, the upper limit is 60 g / g or less from the balance between ease of production and performance.
The particulate water-absorbing resin composition according to the present invention preferably has an absorption capacity under pressure (0.3 psi (2.06 kPa), 1 hour) of 20 g / g or more, more preferably 21 g / g or more, Preferably it is 22 g / g or more, More preferably, it is 23 g / g or more, More preferably, it is 24 g / g or more, Most preferably, it is 25 g / g or more. Moreover, the upper limit is 60 g / g or less from the balance between ease of production and performance.

The particulate water-absorbent resin composition according to the present invention preferably has an absorption capacity under pressure (0.7 psi (4.83 kPa), 1 hour) of 15 g / g or more, more preferably 16 g / g or more, Preferably it is 17 g / g or more, More preferably, it is 18 g / g or more, More preferably, it is 19 g / g or more, Most preferably, it is 20 g / g or more. Moreover, the upper limit is 60 g / g or less from the balance between ease of production and performance.
The particulate water-absorbing resin composition according to the present invention preferably has an absorption index increase of 3 g / g or more, more preferably 3.5 g / g or more, more preferably 20 hours and / or 4 hours. 4 g / g or more, more preferably 4.5 g / g or more, more preferably 5 g / g or more, more preferably 5.5 g / g or more, more preferably 6 g / g or more, more preferably 7 g / g or more, particularly Preferably it is 7.5 g / g or more, Most preferably, it is 8 g / g or more. Moreover, the upper limit is 20 g / g or less from the balance between ease of production and performance.

The absorption index is an index represented by the sum of the absorption capacity under pressure at 0.06 psi (0.41 kPa) and the absorption capacity under pressure at 0.3 psi (2.06 kPa).
The amount of increase in absorption index is the amount of increase in absorption index over time after 1 hour, as will be described in the examples below.
The particulate water-absorbing resin composition according to the present invention has a non-pressurized absorption ratio (1 hour) under no pressure and an absorption capacity under specific particle size pressurization (0.29 psi (2.00 kPa), 1 hour). Absorption rate (1 hour) + 3 ≧ absorption rate under specific particle size pressurization (0.29 psi (2.00 kPa), 1 hour) ≧ 20 g / g is preferable.

The particulate water-absorbing resin composition according to the present invention has an absorption capacity under no pressure between an absorption capacity without pressure (1 hour) and an absorption capacity under pressure (0.3 psi (2.06 kPa), 1 hour). It is preferable that (1 hour) + 3 ≧ absorption capacity under pressure (0.3 psi (2.06 kPa), 1 hour) ≧ 20 g / g.
The particulate water-absorbing resin composition according to the present invention has an absorption capacity without pressure (1 hour), preferably 15 g / g or more, more preferably 20 g / g or more, still more preferably 25 g / g or more, particularly preferably. 30 g / g or more, most preferably 35 g / g or more. Moreover, the upper limit is 60 g / g or less from the balance between ease of production and performance.

The particulate water-absorbent resin composition according to the present invention preferably has a mass average particle diameter in the range of 300 to 700 μm, more preferably in the range of 320 to 700 μm, still more preferably in the range of 340 to 700 μm, still more preferably. Is in the range of 360 to 700 μm, more preferably in the range of 380 to 700 μm, particularly preferably in the range of 400 to 700 μm.
In the particulate water-absorbing resin composition according to the present invention, the proportion of particles having a particle diameter of less than 150 μm is preferably 0% by mass or more and less than 10% by mass, more preferably 0% by mass or more and less than 7% by mass, and still more preferably. It is 0 mass% or more and less than 5 mass%, Most preferably, it is 0 mass% or more and less than 3 mass%. The particles having a particle diameter of less than 150 μm are preferably water absorbent resin particles.

Particulate water-absorbent resin composition according to the present invention are those having preferably the properties described above, as particularly preferred, grain child water-absorbent resin compositions such as are exemplified below.
In other words, grain child-like water absorbent resin composition that written to the present invention is a particulate water-absorbent resin composition comprising a carboxyl group-containing water-absorbent resin 80 wt% or more, as the carboxyl group-containing water-absorbent resin, A carboxyl group-containing water absorbent resin (A) having a carboxyl group neutralization rate of 50% or more and a carboxyl group-containing water absorbent resin (B) having a carboxyl group neutralization rate of less than 50%, (A): (B) = 90: 10 to 10:90 in a mass ratio, the mass average particle diameter is in the range of 320 to 700 μm, and the absorption capacity under pressure (0.3 psi (2.06 kPa), 1 hour) is 20 g. / G or more, and the increase in absorption index at 20 hours and / or 4 hours is 3 g / g or more, and further, the absorption capacity under specific particle pressure (0.29 psi (2.00 kPa), 1 hour) is 20g / g Above, and can be identified granularity absorption index increment in 20 hours and / or 4 hours is 3 g / g or more.

Also, the particulate water absorbent resin composition according to the present invention, absorption capacity without load (1 hour) + 3 ≧ specific particle size absorbency against pressure (0.29psi (2.00kPa), 1 hour) ≧ 20 g / g It is preferable that the specific particle size absorption index increase in 20 hours and / or 4 hours is 3 g / g or more.

Moreover, the particulate water-absorbing resin composition according to the present invention has a mass average particle diameter in the range of 320 to 700 μm, and absorbency under no pressure (1 hour) + 3 ≧ absorption under pressure (0.3 psi (2 0.06 kPa), 1 hour) ≧ 20 g / g, and the increase in absorption index at 20 hours and / or 4 hours is preferably 3 g / g or more.
By having such specific properties (absorption characteristics, mass average particle diameter, etc.), the particulate water-absorbing resin composition according to the present invention can sufficiently exhibit the effects of the present invention.
The production method of the particulate water-absorbent resin composition according to the present invention is not particularly limited, and examples thereof include the following production methods 1 to 3.

Production method 1: A method of mixing a plurality of water-absorbent resins having different neutralization rates in a specific range under conditions in a specific range (neutralization rate, absorption ratio, and mixing index described later).
Production method 2: A method in which a plurality of water-absorbing resins having different neutralization rates in a specific range are mixed under conditions in a specific range (the neutralization rate, particle diameter, absorption capacity, and mixing index described later).
Production method 3: A method in which a water-absorbent resin having a controlled neutralization rate is subjected to surface crosslinking, and then mixed with a substance capable of neutralizing carboxyl groups (for example, sodium hydrogen carbonate).
Of the production methods 1 to 3, the production methods 1 and 2 are preferred. Hereinafter, the particulate water-absorbent resin composition according to the present invention will be further described with the production methods 1 and 2 as preferred examples.

As an example for obtaining the particulate water-absorbent resin composition according to the present invention, the carboxyl group-containing water-absorbent resin (A) having a carboxyl group neutralization rate of 50% or more and the carboxyl group neutralization rate of less than 50% The carboxyl group-containing water absorbent resin (B) is a mass ratio of (A) :( B) = 90: 10 to 10:90, and the neutralization rate of the carboxyl group-containing water absorbent resin (A) And the difference between the neutralization rate of the carboxyl group-containing water absorbent resin (B) is preferably 30% or more.
Each of the carboxyl group-containing water absorbent resins (A) and (B) may be one kind of carboxyl group-containing water absorbent resin or a mixture of two or more kinds of carboxyl group-containing water absorbent resins. .

When the carboxyl group-containing water absorbent resin (A) is a mixture of two or more kinds of carboxyl group-containing water absorbent resins, the average calculated from the neutralization rate and mixing ratio of each of the carboxyl group-containing water absorbent resins contained The sum ratio may be 50% or more. When the carboxyl group-containing water absorbent resin (B) is a mixture of two or more kinds of carboxyl group-containing water absorbent resins, the average calculated from the neutralization rate and mixing ratio of each of the carboxyl group-containing water absorbent resins contained The sum ratio may be less than 50%. For example, a mixture of a carboxyl group-containing water absorbent resin having a carboxyl group neutralization ratio of X% and a carboxyl group-containing water absorbent resin having a carboxyl group neutralization ratio of Y% in a ratio of 1: 2. If the
Average neutralization rate (%) = X × 1/3 + Y × 2/3
It becomes.

When water-absorbing resins having different neutralization rates are already mixed, using an electron probe X-ray microanalyzer (EPMA) or an energy dispersive X-ray spectrometer (EDS), The ammonium ion content can be examined to determine the neutralization rate and mixing ratio.
The set neutralization rate of the carboxyl group-containing water absorbent resin (A) is preferably 50% or more and 100% or less, more preferably 60% or more and 100% or less, and further preferably 70% or more and 100% or less. .
The set neutralization rate of the carboxyl group-containing water-absorbent resin (B) is important in that it has a large influence on the specific particle size absorption index increase, and is preferably 0% or more and less than 50%, more preferably 0. % Or more and less than 30%, more preferably 0% or more and less than 25%, more preferably 0% or more and less than 20%, particularly preferably 0% or more and less than 15%, and most preferably 0% or more and less than 10%.

It is preferable that at least one of the carboxyl group-containing water-absorbing resins (A) and (B) is surface-treated, particularly surface-crosslinked, and both are surface-treated, particularly surface-crosslinked. More preferred. When the carboxyl group-containing water absorbent resin (A) or (B) is a mixture of two or more carboxyl group-containing water absorbent resins, at least one carboxyl group-containing water absorbent resin is surface-treated. It is preferable that all of the carboxyl group-containing water-absorbing resins are surface-treated.
The particle shape of the carboxyl group-containing water-absorbing resin (A) or (B) may be irregularly crushed or spherical, or may be a mixture of irregularly crushed particles and spherical particles.

The carboxyl group-containing water-absorbing resin (A) or (B) is preferably granulated. When the carboxyl group-containing water absorbent resin (A) or (B) is a mixture of two or more carboxyl group-containing water absorbent resins, at least one carboxyl group-containing water absorbent resin is granulated. It is preferable that all of the carboxyl group-containing water-absorbent resins are granulated. A preferred granulation method is a method as described in the granulation method above.
The mass ratio of the carboxyl group-containing water absorbent resin (A) and the carboxyl group containing water absorbent resin (B) is in the range of (A) :( B) = 90: 10 to 10:90. The mass ratio of the carboxyl group-containing water-absorbent resin (A) and the carboxyl group-containing water-absorbent resin (B) may be within this range, and the optimum range is the carboxyl group-containing water-absorbent resin (A) and the carboxyl group. Since it depends on what neutralization rate the group-containing water-absorbent resin (B) has, it cannot be defined unconditionally. However, as an approximate trend, preferably (A) :( B) = 85: 15-15: 85, more preferably (A) :( B) = 80: 20-20: 80, more preferably (A) : (B) = 80: 20 to 40:60, more preferably (A) :( B) = 80: 20 to 50:50.

In the particulate water absorbent resin composition according to the present invention, the difference between the neutralization rate of the carboxyl group-containing water absorbent resin (A) and the neutralization rate of the carboxyl group-containing water absorbent resin (B) is 30% or more. It is preferable. Thus, the difference between the neutralization rate of the carboxyl group-containing water absorbent resin (A) having a high carboxyl group neutralization rate and the neutralization rate of the carboxyl group-containing water absorbent resin (B) having a low carboxyl group neutralization rate By increasing the value, the absorption capacity in the initial short time is secured to some extent, the absorption capacity is continuously increased over a longer time, and liquid permeability and diffusibility can be secured.
The liquid permeability and diffusibility referred to in the present invention represent the mobility and permeability of the liquid between the water-absorbent resin gel particles, and also indicate the liquid uptake into a water-absorbent article such as a paper diaper. . More specifically, as an index indicating the mobility and permeability of the liquid between the water-absorbent resin gel particles, for example, the absorption capacity under pressure and the absorption capacity under specific particle size pressure described in detail in the following examples are given. Furthermore, the “saline flow inductivity test (SFC)” described in WO05 / 22356 pamphlet and the “saline solution” described in JP-A-6-57010 Liquid passage time "and the like. Examples of the index indicating the liquid uptake property to a water-absorbing article such as a paper diaper include the liquid uptake time into the paper diaper described in detail in the following examples.

In the present invention, when the difference between the neutralization rate of the carboxyl group-containing water absorbent resin (A) and the neutralization rate of the carboxyl group-containing water absorbent resin (B) is 30% or more, the absorption capacity in the initial short time The principle that the effect of the present invention that the absorption capacity is continuously increased over a long period of time and the liquid permeability and the diffusibility can be secured is expressed by the inventor's study, It is guessed as follows.
As shown in Reference Example 1 described later, the absorption ratio of the carboxyl group-containing water absorbent resin increases as the neutralization rate increases, but the degree of increase in the absorption ratio is not constant, and the neutralization rate is about 50%. Until then, the rate of increase in the absorption rate due to the increase in the neutralization rate is abrupt, and if the neutralization rate is about 50% or more, the rate of increase in the absorption rate due to the increase in the neutralization rate becomes moderate. The phenomenon is seen.

On the other hand, as in the particulate water absorbent resin composition according to the present invention, the carboxyl group-containing water absorbent resin (A) having a carboxyl group neutralization rate of 50% or more and the carboxyl group neutralization rate is less than 50%. When the carboxyl group-containing water-absorbing resin (B) coexists, in order to make the neutralization rate uniform with the difference in pH between the carboxyl group-containing water-absorbing resins (A) and (B) as the driving force, It is considered that “ion transfer” occurs in which counter counter cations (for example, Na ions) that have been summed move between the carboxyl group-containing water-absorbing resins (A) and (B).
Therefore, since the neutralization rate of the carboxyl group is 50% or more, the neutralization rate of the carboxyl group-containing water-absorbing resin (A) having an originally high absorption capacity gradually decreases, and the neutralization rate of the carboxyl group is 50%. When the neutralization rate of the carboxyl group-containing water-absorbent resin (B), which is less than the above, gradually increases, a gentle absorption rate is exhibited and an increase in absorption capacity with time is exhibited. As a result, it is considered that the effects of the present invention are exhibited.

  In the particulate water absorbent resin composition according to the present invention, the difference between the neutralization rate of the carboxyl group-containing water absorbent resin (A) and the neutralization rate of the carboxyl group-containing water absorbent resin (B) is 30% or more. However, it is important to secure a difference of at least 30%, and the effect of the present invention is not necessarily expressed as the difference in the neutralization rate increases from 30%. The optimum range of the difference in neutralization rate is the mass ratio of the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B), the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin. This is because the particle size, the particle size distribution, the amount of fine powder, and the absorption performance under neutralization are selected depending on how (B) is selected. However, as an approximate tendency, the difference between the neutralization rate of the carboxyl group-containing water absorbent resin (A) and the neutralization rate of the carboxyl group-containing water absorbent resin (B) is preferably 35% or more, more preferably 40%. More preferably, it is 50% or more, particularly preferably 60% or more, and most preferably 65% or more.

Further, the difference (ΔN) between the neutralization rate of the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) and the mixing ratio (the ratio of the carboxyl group-containing water absorbent resin (A): α) and It was found that an effective increase in specific particle size absorption index (specific particle size absorption index increase amount) appears when the relationship of the following formula 1 is satisfied during
ΔN × (0.5− | 0.5−α |) ≧ 11 (Formula 1)
The left side of Equation 1 is referred to as “neutralization rate / mixing index (NM Index)”.
The above (0.5− | 0.5−α |) is a term derived from the experimental fact that the amount of increase in the absorption index is maximized at the mixing ratio α = 0.5.

In the present invention, the neutralization ratio / mixing index is preferably 11 or more, more preferably 13 or more, still more preferably 15 or more, still more preferably 17 or more, still more preferably 19 or more, and still more preferably 20 or more. More preferably, it is 21 or more, more preferably 22 or more, more preferably 23 or more, still more preferably 24 or more, still more preferably 25 or more, and particularly preferably 27 or more. Moreover, the upper limit is 50 or less from the balance between ease of production and performance.
Under specific particle size conditions of less than 600 μm and 300 μm or more, the specific particle size absorption index increase is very closely related to the neutralization rate / mixing index.

Furthermore, when the relationship of the following formula | equation 2 which considered the absorption characteristic of the water absorbing resin composition is satisfy | filled, it turned out that the increase (specific amount particle size absorption index increase amount) of a more effective specific particle size absorption index expresses.
ΔN × (0.5− | 0.5−α |) × absorption capacity under specific particle size pressure (0.30 psi (2.06 kPa), 1 hour) / absorption capacity under no pressure (1 hour) ≧ 11 (Formula 2 )
The left side of Equation 2 is referred to as “neutralization rate / absorption capacity / mixing index (NCM Index)”.
The absorption capacity under pressure in the above formula 2 (0.30 psi (2.06 kPa), 1 hour) is obtained when the particle diameters of the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) are the same. Uses the value of absorption capacity under specific particle pressure (0.29 psi (2.00 kPa), 1 hour).

In the present invention, the neutralization rate / absorption ratio / mixing index is preferably 11 or more, more preferably 13 or more, still more preferably 15 or more, still more preferably 17 or more, still more preferably 19 or more, and still more preferably. Is at least 20, more preferably at least 21, more preferably at least 22, more preferably at least 23, even more preferably at least 24, even more preferably at least 25, particularly preferably at least 27. Moreover, the upper limit is 50 or less from the balance between ease of production and performance.
Under specific particle size conditions of less than 600 μm and 300 μm or more, the specific particle size absorption index increase is very closely related to the neutralization rate, the absorption ratio, and the mixing index.

Further, when considering the particle diameter of the water-absorbent resin composition, it was found that a more effective increase in absorption index (absorption index increase amount) appears when the relationship of Formula 3 is satisfied.
ΔN × (0.5− | 0.5−α |) × (d / d ′) ² × absorption capacity under pressure (0.30 psi (2.06 kPa), 1 hour) / absorption capacity without pressure (1 hour) ) ≧ 11 (Formula 3)
The left side of the above formula 3 is referred to as “neutralization rate / particle diameter / absorption capacity / mixing index (NPCM Index)”.
Here, d is the average particle size of the water-absorbent resin composition (the average when the particle sizes of (A) and (B) are different), and d ′ is the average particle size of particles of less than 600 μm and 300 μm or more. (450 μm). (D / d ′) ² has a meaning as a correction value from the particle surface area of the water-absorbent resin composition based on particles of less than 600 μm and 300 μm or more.

In the present invention, the neutralization rate, particle diameter, absorption ratio, and mixing index are preferably 11 or more, more preferably 13 or more, still more preferably 15 or more, still more preferably 17 or more, and still more preferably 19 or more. More preferably, it is 20 or more, more preferably 21 or more, more preferably 22 or more, still more preferably 23 or more, still more preferably 24 or more, still more preferably 25 or more, and particularly preferably 27 or more. Moreover, the upper limit is 50 or less from the balance between ease of production and performance.
The set neutralization rate of the carboxyl group-containing water absorbent resin (A) is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more.

The set neutralization rate of the carboxyl group-containing water-absorbent resin (B) is important in that it has a large effect on the absorption index increase, and is preferably less than 50%, more preferably less than 30%, and even more preferably. Is less than 25%, more preferably less than 20%, particularly preferably less than 15%, most preferably less than 10%.
In the particulate water-absorbing resin composition according to the present invention, a carboxyl group-containing water-absorbing resin (increase in specific particle size absorption index or absorption index increase) is achieved in order to achieve a continuous increase in absorption capacity over a long period of time (a specific particle size absorption index increase amount or absorption index increase amount). It is preferable to set the mass average particle diameters of A) and the carboxyl group-containing water absorbent resin (B) to specific conditions.

That is, the mass average particle diameter of at least one of the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) is preferably 300 μm or more, more preferably 320 μm or more, still more preferably 340 μm or more, More preferably, it is 360 μm or more, particularly preferably 380 μm or more, and most preferably 400 μm or more.
Further, the mass average particle diameter of both the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) is more preferably 300 to 700 μm, still more preferably 320 to 700 μm, still more preferably 340. ˜700 μm, more preferably 360 to 700 μm, particularly preferably 380 to 700 μm, and most preferably 400 μm to 700 μm.

Further, the logarithmic standard deviation σζ representing the narrowness of the particle size distribution is preferably 0.1 or more and 0.46 or less, more preferably 0.1 or more and 0.44 or less, and still more preferably 0.1 or more and 0.42 or less. Preferably they are 0.1 or more and 0.40 or less. If the logarithmic standard deviation σζ is less than 0.1, the productivity is drastically lowered, which is not realistic, and if it exceeds 0.46, problems such as segregation become prominent.
When the mass average particle diameter of both the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) used in the present invention is less than 300 μm, ion migration occurs but the surface area is large. Therefore, the speed of ion movement is high, and the effect of increasing the absorption capacity over a long period of time becomes small, and there is a possibility that there is no large difference from the case of one kind of water-absorbing resin as conventionally known.

When the mass average particle diameter of both the carboxyl group-containing water-absorbent resin (A) and the carboxyl group-containing water-absorbent resin (B) used in the present invention exceeds 700 μm, the touch is poor when used for diapers or the like. There is a risk of problems such as becoming.
The method for producing the particulate water-absorbing resin composition according to the present invention is not particularly limited. For example, dry blend, gel blend of carboxyl group-containing water absorbent resin (A) and carboxyl group-containing water absorbent resin (B), Examples thereof include mixing when the water-containing gel-like polymer for producing the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) is dried and pulverized, preferably dry blend, gel It is a blend.

Examples of the dry blending method include a method of mixing a dried product of the carboxyl group-containing water absorbent resin (A) and the carboxyl group containing water absorbent resin (B) at a predetermined mixing ratio. The mixing device preferably has a large mixing force in order to perform uniform and reliable mixing. For example, a cylindrical mixer, a double wall conical mixer, a V-shaped mixer, a Redige mixer , Ribbon type mixer, screw type mixer, fluidized-type furnace rotary disk type mixer, airflow type mixer, double arm type kneader, internal mixer, pulverizing type kneader, rotary mixer, screw type extruder, etc. are suitable It is.
As a method of gel blending, for example, a hydrated gel pulverized product of carboxyl group-containing water absorbent resin (A) obtained by aqueous solution polymerization and a hydrated gel pulverized product of carboxyl group-containing water absorbent resin (B) are mixed in a predetermined manner. A method of drying after mixing at a ratio is mentioned. As another method, the water-containing gel of the carboxyl group-containing water absorbent resin (A) and the water-containing gel of the carboxyl group-containing water absorbent resin (B) obtained individually by aqueous solution polymerization are simultaneously mixed so as to have a predetermined mixing ratio. A method of supplying to a pulverizer such as a meat chopper, mixing at the same time as the pulverization, and drying. Examples of the hydrogel mixing and pulverizer include a kneader, a meat chopper, and a twin screw extruder.

By the gel blending technique as described above, the carboxyl group-containing water-absorbing resin (A) and the carboxyl group-containing water-absorbing resin (B) can be produced with one dryer, and the production efficiency can be improved. .
In the particulate water-absorbent resin composition according to the present invention, as described above, at least one of the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) is a surface treatment (preferably a surface crosslinking treatment). It is preferable that both are surface-treated (preferably surface cross-linking treatment), and as a technique thereof, for example, a carboxyl group-containing water-absorbing resin (A) and a carboxyl group-containing A method in which the water-absorbent resin (B) is individually surface-treated and then dry blended, or a mixture in which the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) are mixed by the dry blend method. Alternatively, two types of surface-treated dry mixtures of water-absorbent resins obtained by gel blending are simultaneously treated in the same manner as the surface treatment described above. Method can be mentioned. In particular, the latter method has an advantage that the production efficiency can be increased because two types of surface treatment are simultaneously performed on one machine.

  In the particulate water-absorbing resin composition according to the present invention, as described above, the carboxyl group-containing water-absorbing resin (A) and the carboxyl group-containing water-absorbing resin (B) are preferably granulated. However, as the method, for example, the carboxyl group-containing water-absorbing resin (A) and the carboxyl group-containing water-absorbing resin (B) are granulated separately and then mixed by a dry blend method or obtained by a gel blend method. Examples thereof include a method of granulating the obtained dry mixture, and a method of granulating when the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) are dry blended or thereafter. By performing any one of these three methods, it is possible to reduce the amount of fine powder that causes dust generation, and there is an advantage that the working environment is remarkably improved. In particular, the carboxyl group-containing water-absorbing resin (A) and the carboxyl group-containing water-absorbing resin (A) and the carboxyl group-containing water-absorbing resin (B) are dry-blended or granulated thereafter. The resin (B) forms agglomerated particles, and in the particulate water-absorbent resin composition according to the present invention, a mixed state (distributed state) of the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) ) Is improved, and segregation is less likely to occur.

  When producing the water-absorbent resin used in the present invention and the particulate water-absorbent resin composition according to the present invention, further, if necessary, inorganic fine particles such as fumed silica, kaolin, bentonite, calcium carbonate, deodorant Agent, antibacterial agent, fragrance, foaming agent, pigment, dye, hydrophilic short fiber, plasticizer, adhesive, metal soap, surfactant, fertilizer, oxidizing agent, reducing agent, water, salt, chelating agent, disinfectant, Various functions for water-absorbent resin particles such as addition of hydrophilic polymers such as polyethylene glycol, paraffin, hydrophobic polymers, thermoplastic resins such as polyethylene and polypropylene, thermosetting resins such as polyester resins and urea resins, etc. The process of providing may be included. The amount of these additives used is preferably 0 to 10 parts by mass, more preferably 0 to 1 part by mass with respect to 100 parts by mass of the water absorbent resin particles.

The additive is added in the form of an aqueous solution, a suspension, or a powder. As for the method of adding the additive, for example, the additive is added to the carboxyl group-containing water-absorbing resin (A) and / or the carboxyl group-containing water-absorbing resin (B), and then mixed by a dry blend method to form particles. A method of forming a water absorbent resin composition, a method of adding the above additives to a dry mixture obtained by a gel blend method, and dry blending a carboxyl group-containing water absorbent resin (A) and a carboxyl group-containing water absorbent resin (B). The method of adding the said additive at the time or after that is mentioned.
It is obtained by the above-mentioned production method 3 in which the water-absorbent resin having a controlled neutralization rate is subjected to surface cross-linking and then mixed with a substance capable of further neutralizing carboxyl groups (for example, sodium hydrogen carbonate). The particulate water-absorbing resin composition is a particulate water-absorbing resin composition obtained by mixing a surface-crosslinked carboxyl group-containing water absorbent resin and a substance capable of neutralizing carboxyl groups. The content ratio of the carboxyl group-containing water absorbent resin in the particulate water absorbent resin composition is preferably 80 to 95% by mass, more preferably 80 to 90% by mass, and still more preferably 80 to 85% by mass. When the content ratio of the carboxyl group-containing water-absorbent resin in the particulate water-absorbent resin composition is less than 80% by mass, the absorption characteristics in a short time are deteriorated, and the particulate water-absorbent resin composition according to the present invention is satisfactory. There is a possibility that physical properties (parameters) to be satisfied cannot be satisfied. If it exceeds 95% by mass, the absorption ratio with time is not increased sufficiently, and the particulate water-absorbent resin composition according to the present invention may not be able to satisfy satisfactory physical properties (parameters).

  5-20 mass% is preferable, as for the content rate of the substance which can neutralize the carboxyl group in the said particulate water-absorbent resin composition, 10-20 mass% is more preferable, and 15-20 mass% is further preferable. When the content ratio of the substance capable of neutralizing the carboxyl group in the particulate water-absorbing resin composition is less than 5% by mass, the increase in absorption ratio with time is not sufficient, and the particulate water absorption according to the present invention There is a possibility that the functional resin composition cannot satisfy satisfactory physical properties (parameters). When it exceeds 20% by mass, the absorption characteristics in a short time are deteriorated, and the particulate water-absorbing resin composition according to the present invention may not be able to satisfy satisfactory physical properties (parameters).

The neutralization rate of the water-absorbent resin with a controlled neutralization rate is preferably 0% or more and less than 70%, more preferably 10% or more and less than 60%, further preferably 10% or more and less than 50%, and more preferably 20% or more and 40%. Less than is particularly preferred.
As the substance capable of neutralizing the carboxyl group, a substance that can be handled as a powder at room temperature is preferable, for example, sodium carbonate, sodium hydrogen carbonate, lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, Mention may be made of alkali metal carbonates.
The mass average particle diameter (D50) of the substance capable of neutralizing the carboxyl group is preferably in the range of 300 to 700 μm, more preferably in the range of 320 to 700 μm, still more preferably in the range of 340 to 700 μm. More preferably, it is in the range of 360 to 700 μm, particularly preferably in the range of 380 to 700 μm, and most preferably in the range of 400 to 700 μm.

The logarithmic standard deviation (σζ) of a substance capable of neutralizing a carboxyl group is preferably within the range of 0.1 to 0.46, more preferably within the range of 0.1 to 0.44, and even more preferably It is in the range of 0.1 to 0.42, particularly preferably in the range of 0.1 to 0.40. If the logarithmic standard deviation (σζ) is less than 0.1, the productivity is drastically lowered and is not realistic. If it exceeds 0.46, problems such as segregation become remarkable, which is not preferable.
The substance capable of neutralizing the carboxyl group has a proportion of particles having a particle diameter of less than 150 μm, preferably 0% by mass or more and less than 10% by mass, more preferably 0% by mass or more and less than 7% by mass, and still more preferably 0%. The content is not less than 5% by mass and particularly preferably not less than 0% by mass and less than 3% by mass.

The method of mixing the surface-crosslinked carboxyl group-containing water-absorbent resin and the substance capable of neutralizing the carboxyl group is preferably a dry blend method in a dry state. Such a method may be performed in accordance with the description regarding the dry blend method described above.
[Water absorbent body, water absorbent article]
By combining the particulate water-absorbing resin composition of the present invention with an appropriate material, for example, a water-absorbing body suitable as an absorbent layer for sanitary materials can be obtained.
A water-absorbing body is formed of a particulate water-absorbing resin composition and other materials used for sanitary materials such as disposable diapers, sanitary napkins, incontinence pads, and medical pads that absorb blood, body fluids, and urine. Composition.

  Examples of the material used in combination with the particulate water-absorbing resin composition include cellulose fibers. Specific examples of cellulose fibers include wood pulp fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp from wood, and artificial cellulose fibers such as rayon and acetate. A preferred cellulose fiber is wood pulp fiber. These cellulose fibers may partially contain synthetic fibers such as nylon and polyester. When the particulate water-absorbing resin composition of the present invention is used as a part of the water-absorbing body, the mass ratio of the particulate water-absorbing resin composition of the present invention contained in the water-absorbing body is preferably 20 to 100 mass. %, And more preferably in the range of 30 to 90% by mass. When the mass ratio of the particulate water-absorbing resin composition of the present invention contained in the water-absorbing body is less than 20% by mass, sufficient effects may not be obtained.

  In order to obtain a water-absorbing body from the particulate water-absorbing resin composition and cellulose fibers, for example, a method in which the particulate water-absorbing resin composition is sprayed on paper or mat made of cellulose fibers, and sandwiched between these, if necessary, cellulose fibers and Known means for obtaining a water-absorbing body such as a method of uniformly blending the particulate water-absorbing resin composition can be appropriately selected. Preferably, it is a method in which the particulate water-absorbent resin composition and the cellulose fiber are dry mixed and then compressed. By this method, dropping of the particulate water-absorbing resin composition from the cellulose fiber can be suppressed. The compression is preferably performed under heating, and the temperature range is preferably in the range of 50 to 200 ° C. In order to obtain a water-absorbing body, methods described in JP-A-9-509591 and JP-A-9-290000 can be preferably used.

When the particulate water-absorbing resin composition of the present invention is used in a water-absorbing body, it has a good balance between liquid permeability and capillary suction force, so that the liquid can be taken up quickly, and the remaining amount of liquid on the surface of the water-absorbing body is high. A very good water absorbing body with a small amount can be obtained.
Since the particulate water-absorbing resin composition of the present invention has excellent water-absorbing properties, it can be used as a water-absorbing article, that is, a water-absorbing water retaining agent for various uses. For example, water absorbent water absorbents for absorbent articles such as paper diapers, sanitary napkins, incontinence pads, medical pads; Anti-condensation agent for materials, water retention agent for construction such as cement additive; release control agent, cold insulation agent, disposable body warmer, sludge coagulant, food freshness preservation agent, ion exchange column material, sludge or oil dehydrating agent, desiccant Can be used as a humidity control material. The particulate water-absorbing resin composition of the present invention is particularly preferably used for sanitary materials for absorbing feces, urine or blood, such as disposable diapers and sanitary napkins.

The water absorbent obtained from the particulate water-absorbing resin composition of the present invention, when used for sanitary materials such as paper diapers, sanitary napkins, incontinence pads, medical pads, etc., (a) is disposed adjacent to the wearer's body. A liquid permeable topsheet, (b) a liquid impervious backsheet positioned far from the wearer's body and adjacent to the wearer's clothing, and (c) a topsheet It is preferably used in a configuration comprising a water absorbent disposed between the backsheets. Two or more water absorbent bodies may be used, or a water absorbent body may be used together with a pulp layer.
In a more preferred configuration, the particulate water-absorbing resin composition in the water-absorbent body has a basis weight of preferably 60 g / m ^{2 to} 1500 g / m ² , more preferably 100 g / m ^{2 to} 1000 g / m ² , and still more preferably. He is a ^{200g / m 2 ~800g / m 2} .

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Hereinafter, for convenience, “part by mass (part by weight)” may be simply referred to as “part”, and “liter” may be simply referred to as “L”. In addition, “mass% (weight%)” may be described as “wt%”.
Various performances of the water absorbent resin (sometimes referred to as water absorbent resin particles) or the particulate water absorbent resin composition were measured by the following methods. The following measurement was performed under conditions of room temperature (25 ° C.) and humidity of 50 RH%.
In the case of the particulate water-absorbing resin composition used as a final product such as sanitary material, the particulate water-absorbing resin composition absorbs moisture, so that the particulate water-absorbing resin composition is appropriately removed from the final product. What is necessary is just to measure after isolate | separating and drying under reduced pressure low temperature (for example, 1 mmHg or less, 60 degreeC for 12 hours).

The water content of the water-absorbent resin and particulate water-absorbent resin composition used in the following examples and comparative examples were all 6% by mass or less.
The absorbed solution used in the present invention is a 0.9% by mass sodium chloride aqueous solution, and may be abbreviated as physiological saline.
<Absorption capacity without pressure (CRC)>
0.20 g of the water-absorbent resin or the particulate water-absorbent resin composition was accurately weighed to a level of 0.0001 g, and uniformly put into a non-woven bag (85 mm × 60 mm) and sealed.
A 1 L container was charged with 1 L of a 0.9 mass% sodium chloride aqueous solution, and one evaluation sample was immersed in each container for 1 hour. Since the present invention focuses on the effect of ion migration, a plurality of samples must not be immersed in one container.

After 1 hour, the bag was pulled up and drained for 3 minutes with a centrifugal force (250 G) described in edana ABSORBENCY II 441.1-99 using a centrifuge (manufactured by Kokusan Co., Ltd., centrifuge: model H-122). After the measurement, the bag mass W1 (g) was measured. The same operation was performed without using the water absorbent resin or the particulate water absorbent resin composition, and the mass W0 (g) at that time was measured. And from these W1 and W0, the absorption capacity (g / g) under no pressure was calculated according to the following formula.
Absorption capacity without pressure (g / g) =
[(W1 (g) -W0 (g)) / mass (g) of water absorbent resin or particulate water absorbent resin composition] -1
<Absorption capacity under specific particle size pressurization (AUL)>
Absorption capacity under specific particle size pressurization is an absorption capacity under pressure, which is performed by selecting particles that pass through 600 μm of JIS standard sieve and do not pass through 300 μm in order to eliminate the influence of particle size on the water absorption rate.

  A stainless steel 100 mesh wire mesh (mesh size 150 μm) is fused to the bottom of a plastic support cylinder with an inner diameter of 25.4 mm, on the wire mesh under conditions of room temperature (20-25 ° C.) and humidity 50 RH%. The particulate water-absorbing resin composition 0.16 g is uniformly sprayed on it, and 0.01 psi (0.069 kPa), 0.29 psi (2.00 kPa) with respect to the particulate water-absorbing resin composition, Or the outer diameter is slightly smaller than 25.4 mm, adjusted so that a load of 0.57 psi (3.93 kPa) can be applied uniformly, and there is no gap between the support cylinder and the vertical movement is hindered. A non-piston and a load were placed in this order, and the mass Wa (g) of this measuring device set was measured.

A glass filter of 90 mm in diameter (manufactured by Mutual Riken Glass Co., Ltd., pore diameter: 100 to 120 μm) is placed inside a petri dish of 150 mm in diameter, and 0.90 mass% sodium chloride aqueous solution (20 to 25 ° C.) is glass. It added so that it might become the same level as the upper surface of a filter. On top of that, one sheet of 37 mm diameter filter paper (Whatman, type: GF / A, cat No. 1820 037) was placed so that the entire surface was wetted, and excess liquid was removed.
A set of measuring devices was placed on the wet filter paper, and the liquid was absorbed under load for a predetermined time. This absorption time was calculated from the start of measurement, and was 1 hour, 2 hours, 4 hours, 8 hours, and 20 hours later. Specifically, after 1 hour, the measuring device set was lifted and its mass Wb (g) was measured. This mass measurement must be performed as quickly as possible and without vibrations. Also, the load must not be removed during the measurement. Thereafter, the measuring device was again placed on the wet filter paper, and the liquid was absorbed in preparation for the next 2 hours, further 4 hours, 8 hours, and 20 hours.

Note that from the start of measurement to the end of measurement, the liquid level of the 0.90 mass% sodium chloride aqueous solution must be adjusted to the same level as the upper surface of the glass filter.
Absorption capacity under specific particle size pressurization at each time was calculated according to the following formula from Wa and Wb.
Absorption capacity under specific particle size pressure (g / g) = (Wb (g) −Wa (g)) / mass of particulate water-absorbent resin composition (0.16 (g))
In the present invention, for the sake of convenience, the absorption capacity under a specific particle size pressurization when the load is p is AUL (p), the absorption capacity under the specific particle size pressurization when the absorption time is q, AUL (q), and the load May be expressed as AUL (p, q) when the absorption time is q and the absorption time is q.

<Specific particle size absorption index>
The specific particle size absorption index when the absorption time was q was defined by the following formula.
Specific particle size absorption index (q) = AUL (0.01 psi (0.069 kPa), q) + AUL (0.29 psi (2.00 kPa), q)
<Increase in specific particle size absorption index>
The specific particle size absorption index at absorption times of 1, 2, 4, 8, and 20 hours was determined, and the difference between the 20 hour value or 4 hour value and 1 hour value was defined as the increase in absorption index.
For example, the specific particle size absorption index increase in 20 hours is calculated as follows.

Increase in specific particle size absorption index in 20 hours = specific particle size absorption index (20 hours) −specific particle size absorption index (1 hour)
<Mass average particle diameter (D50) and logarithmic standard deviation (σζ)>
The water-absorbing resin or the particulate water-absorbing resin composition is sieved with a JIS standard sieve having an aperture of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 45 μm, etc. Plotted. Thereby, the particle size corresponding to R = 50% by mass was read as the mass average particle size (D50). Further, the logarithmic standard deviation (σζ) is calculated by the following formula, 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%)
The classification method for measuring the mass average particle diameter (D50) and the logarithmic standard deviation (σζ) is as follows. Under a condition of 850 μm, 600 μm, 300 μm, 150 μm, and 45 μm, a JIS standard sieve (THE IIDA TESTING SIVE: diameter 8 cm) was charged and a vibration classifier (IIDA SIEVE SHAKER, TYPE: ES-65 type, SER. .0501), classification was performed for 5 minutes.

<Soluble content>
In a 250 ml capacity plastic container with a lid, weigh out 184.3 g of 0.9 mass% aqueous sodium chloride solution (saline), add 1.00 g of the water absorbent resin or particulate water absorbent resin composition to the aqueous solution, The soluble component in the resin was extracted by stirring for 16 hours. Filtration of this extract using one sheet of filter paper (ADVANTEC Toyo Co., Ltd., product name: (JIS P 3801, No. 2), thickness 0.26 mm, retained particle diameter 5 μm) gave 50. 0 g was measured and used as a measurement solution.
First, a 0.9% by mass sodium chloride aqueous solution (saline) is first titrated to pH 10 with a 0.1N NaOH aqueous solution, and then titrated to a pH 2.7 with a 0.1N HCl aqueous solution. Titration amounts ([bNaOH] ml, [bHCl] ml) were obtained.

By performing the same titration operation on the measurement solution, titration amounts ([NaOH] ml, [HCl] ml) were obtained.
For example, in the case of a water-absorbing resin or water-absorbing resin particles or a particulate water-absorbing resin composition comprising a known amount of acrylic acid and its sodium salt, based on the weight average molecular weight of the monomer and the titration obtained by the above operation. In addition, the soluble content in the water-absorbent resin was calculated by the following formula. In the case of an unknown amount, the weight average molecular weight of the monomer was calculated using the neutralization rate obtained by titration.
Soluble content (mass%) = 0.1 × (mass 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)>
A stainless steel 400 mesh wire mesh (mesh size 38 μm) is fused to the bottom of a plastic support cylinder with an inner diameter of 60 mm, and particles are formed on the wire mesh at room temperature (20 to 25 ° C.) and humidity 50 RH%. 0.90 g of the water-absorbent resin composition is uniformly sprayed, and 0.06 psi (0.41 kPa), 0.3 psi (2.06 kPa), or 0.8. A piston and a load that are adjusted so that a load of 7 psi (4.83 kPa) can be applied uniformly and whose outer diameter is slightly smaller than 60 mm, do not cause a gap with the support cylinder, and do not hinder vertical movement. It mounted in this order and mass Wa (g) of this measuring apparatus set was measured.

A glass filter of 90 mm in diameter (manufactured by Mutual Riken Glass Co., Ltd., pore diameter: 100 to 120 μm) is placed inside a petri dish of 150 mm in diameter, and 0.90 mass% sodium chloride aqueous solution (20 to 25 ° C.) is glass. It added so that it might become the same level as the upper surface of a filter. On top of that, a sheet of 90 mm diameter filter paper (ADVANTEC Toyo Co., Ltd., product name: (JIS P 3801, No. 2), thickness 0.26 mm, retained particle diameter 5 μm) was placed so that the entire surface was wetted, and Excess liquid was removed.
A set of measuring devices was placed on the wet filter paper, and the liquid was absorbed under load for a predetermined time. This absorption time was calculated from the start of measurement, and was 1 hour, 2 hours, 4 hours, 8 hours, and 20 hours later. Specifically, after 1 hour, the measuring device set was lifted and its mass Wb (g) was measured. This mass measurement must be performed as quickly as possible and without vibrations. Also, the load must not be removed during the measurement. Thereafter, the measuring device was again placed on the wet filter paper, and the solution was absorbed in preparation for the next 2 hours, further 4 hours, 8 hours, and 20 hours.

Note that from the start of measurement to the end of measurement, the liquid level of the 0.90 mass% sodium chloride aqueous solution must be adjusted to the same level as the upper surface of the glass filter.
The absorption capacity under pressure at each time was calculated from Wa and Wb according to the following formula.
Absorption capacity under pressure (g / g) = (Wb (g) -Wa (g)) / mass of particulate water-absorbing resin composition (0.9 (g))
In the present invention, for the sake of convenience, the absorption capacity under pressure when the load is p is AAP (p), the absorption capacity under pressure when the absorption time is q is AAP (q), the load is p, and absorption. The absorption capacity under pressure when the time is q may be expressed as AAP (p, q).

<Absorption index>
The absorption index at the absorption time q was defined by the following formula.
Absorption index (q) = AAP (0.06 psi (0.41 kPa), q) + AAP (0.3 psi (2.06 kPa), q)
<Absorption index increase>
The absorption index at the absorption time of 1, 2, 4, 8, and 20 hours was obtained, and the difference between the 20-hour value or the 4-hour value and the 1-hour value was defined as the increase amount of the absorption index.
For example, the amount of increase in absorption index at 20 hours is calculated as follows.

Absorption index increase in 20 hours = absorption index (20 hours) −absorption index (1 hour)
<Creation of water absorbent article>
A water absorbent article for performance evaluation was prepared by the following method.
First, 50 parts by mass of the water absorbent resin composition obtained in Examples and Comparative Examples described later and 50 parts by mass of pulverized wood pulp were dry-mixed using a mixer. Next, the resulting mixture is formed into a 120 mm × 400 mm web by air-making on a wire screen formed with 400 mesh (aperture size of 38 μm) using a batch type air-making machine. did. Further, the web was pressed at a pressure of 2 kg / cm ² (196.14 kPa) for 60 seconds to obtain an absorbent having a basis weight of about 500 g / m ² . Subsequently, a back sheet (liquid impermeable sheet) made of liquid impervious polypropylene and having a so-called leg gather, the above-described absorber, and a top sheet (liquid permeable sheet) made of liquid permeable polypropylene. In addition to sticking each other in this order using a double-sided tape, two so-called tape fasteners were attached to the sticking product to obtain a water absorbent article (paper diaper).

<Performance evaluation of water-absorbing articles>
The water-absorbent article was placed on a horizontal laboratory table so that the top sheet was on top, and the four corners of the water-absorbent article were fixed with an adhesive tape in a state where the water-absorbent article was well stretched without wrinkles. Subsequently, a 20 mesh (mesh size: 850 μm) wire mesh (140 mm × 400 mm) was placed thereon, and a cylinder having a diameter of 70 mm and a height of 50 mm was laid at the center so that liquid could be poured from the center. An acrylic plate (140 mm × 400 mm) was installed. In addition, the mass of the used acrylic board was 1.5 kg. Subsequently, 4.25 kg of weights were placed one by one (two in total) on the acrylic plate and on both sides of the cylinder. The total of the mass of the acrylic plate and the mass of the weight is 10 kg, and the load applied to the absorber is 2.06 kPa. In this state, 75 ml of 0.9 mass% sodium chloride aqueous solution (physiological saline) was poured at once from the cylinder, and the time until the liquid disappeared from the cylinder was measured. This time was defined as the liquid uptake time. After standing for 1 hour, the same operation was repeated, and the liquid was charged four times, and the liquid charging time from the first to the fourth time was measured. One hour after the fourth addition of the liquid, the weight, acrylic plate, and wire mesh are quickly removed, and then 30 sheets of paper towel, flat acrylic plate, and 10 kg weight 2 with a size of 140 mm x 400 mm with known mass. I put it on. After 1 minute, the weight was removed, the weight of the paper towel was measured, and the return amount was measured from the change in the weight of the paper towel.

It is determined that the absorption performance of the water-absorbent article is superior as the liquid charging time from the first time to the fourth time is shorter, and it is determined that the absorption performance is better as the return amount is smaller.
[Synthesis Example 1]: Synthesis of water-absorbent resin particles (L-1) In a 10 L polyethylene beaker, 2000 g of acrylic acid, 17.1 g of methylenebisacrylamide and 7724 g of water were uniformly dissolved, and this was used as a reaction solution. . Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 60.5 g of a 10% by mass V-50 (2,2′-azobis (2-amidinopropane) dihydrochloride) aqueous solution and 66.6 g of a 3% by mass aqueous hydrogen peroxide solution and 0.5% by mass were added to the reaction solution. 99.9 g of an L-ascorbic acid aqueous solution of mass% was added with stirring. Polymerization started after about 10 minutes. The reaction vessel was left at room temperature for 12 hours to complete the polymerization. Thereafter, the hydrogel crosslinked polymer was taken out and pulverized with a meat chopper (manufactured by Iizuka Kogyo Co., Ltd., type: VR-400K, die diameter 9.5 mm). The finely divided hydrogel crosslinked polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 1 hour. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water absorbent resin particles (L-1).

The resulting water-absorbent resin particles (L-1) had an absorption capacity without load (CRC) of 4.0 g / g and a soluble content of 2.9%.
The obtained water-absorbent resin particles (L-1) have a particle size distribution of 19.4% by mass of particles less than 850 μm and 600 μm or more, 61.7% by mass of particles less than 600 μm and 300 μm or more, and 150 μm or more less than 300 μm. The particles were 16.8% by mass, particles less than 150 μm and 45 μm or more were 1.9% by mass, and particles less than 45 μm were 0.2% by mass. In addition, mass average particle diameter (D50) = 426 μm, logarithmic standard deviation (σζ) = 0.382.
[Reference Example 1]
Reference Example 1 examines a change in absorption behavior due to neutralization of an unneutralized water absorbent resin. In addition, the measurement of the absorption capacity in Reference Example 1 was different from the above-described measurement method of absorption capacity under no pressure (CRC), and the following method was adopted.

A sample of 0.20 g of the water-absorbent resin particles (L-1) obtained in Synthesis Example 1 was accurately weighed to a level of 0.0001 g, and uniformly put in a non-woven bag (85 mm × 60 mm) and sealed. 10 were prepared.
1000 ml of 0.9 mass% sodium chloride aqueous solution was put into a container with a plastic lid having a capacity of 1000 ml, and 10 pieces thereof were prepared. Necessary to neutralize 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% of the carboxyl groups of the water-absorbing resin charged Sodium hydroxide was added to each container. After adding sodium hydroxide, the above-mentioned bag was immersed. After standing for 20 hours, the bag is pulled up and drained with a centrifugal force (250 G) described in edana ABSORBENCY II 441.1-99 using a centrifuge (manufactured by Kokusan Co., Ltd., centrifuge: model H-122) for 3 minutes. After carrying out, the mass W1 (g) of the bag was measured. Further, the same operation was performed without using the water absorbent resin, and the mass W0 (g) at that time was measured. And from these W1 and W0, the absorption capacity (g / g) under no pressure was calculated according to the following formula.

Absorption capacity without pressure (g / g) =
[(W1 (g) -W0 (g)) / {mass of water-absorbing resin (g) + amount of added NaOH (g) × 23/40}]-1
The results of Reference Example 1 are shown in FIG. From FIG. 1, it can be seen that the relationship between the neutralization rate and the absorption ratio is not a proportional relationship, but is an upward convex curve, and the inflection point is at the neutralization rate of 50%.
[Synthesis Example 2]: Synthesis of water-absorbing resin particles (H-1) In a reactor formed by attaching a cover to a jacketed stainless steel double-arm kneader having two sigma-shaped blades and having an internal volume of 10 liters, 71 Polyethylene glycol diacrylate (average number of moles of ethylene oxide added 8) 9.36 g (0.08 mol%) to 5438 g (monomer concentration 39 mass%) of an aqueous solution of sodium acrylate having a neutralization rate of 3 mol% The reaction solution was dissolved. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 29.34 g of a 10% by mass sodium persulfate aqueous solution and 24.45 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 1 minute. Then, polymerization was performed while pulverizing the generated gel. The polymerization initiation temperature was 20 ° C., and the maximum temperature reached was 95 ° C. The hydrogel crosslinked polymer was taken out 30 minutes after the start of the polymerization.

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 50 mesh (mesh opening 300 μm) wire net and dried in hot air at 180 ° C. for 50 minutes. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.
A surface treatment agent composed of a mixed solution of 0.4 g of 1,4-butanediol, 0.6 g of propylene glycol and 2.7 g of pure water was mixed with 100 g of the obtained water-absorbent resin particles, and then the mixture was heated at 212 ° C. at 40 ° C. Heat-treated for minutes. Further, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (H-1) whose surface was crosslinked.

The absorption capacity without load (CRC) of the water absorbent resin particles (H-1) was 27.7 g / g, and the soluble content was 9.8%.
The particle size distribution of the water-absorbent resin particles (H-1) is 18.8% by mass of particles of less than 850 μm and 600 μm or more, 62.2% by mass of particles of less than 600 μm and 300 μm or more, and particles of less than 300 μm and 150 μm or more. 17.9% by mass, particles less than 150 μm and 45 μm or more were 1.1% by mass, and particles less than 45 μm were 0% by mass. In addition, mass average particle diameter (D50) = 423 μm, logarithmic standard deviation (σζ) = 0.378.
[Synthesis Example 3]: Synthesis of water-absorbent resin particles (L-2) In a 10 L polyethylene beaker, 2000 g of acrylic acid, 4.275 g of methylenebisacrylamide, and 7724 g of water were uniformly dissolved, and this was used as a reaction solution. . Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 60.5 g of a 10% by mass V-50 (2,2′-azobis (2-amidinopropane) dihydrochloride) aqueous solution and 66.6 g of a 3% by mass aqueous hydrogen peroxide solution and 0.5% by mass were added to the reaction solution. 99.9 g of an L-ascorbic acid aqueous solution of mass% was added with stirring. Polymerization started after about 10 minutes. The reaction vessel was left at room temperature for 12 hours to complete the polymerization. Thereafter, the hydrogel crosslinked polymer was taken out and pulverized with a meat chopper (manufactured by Iizuka Kogyo Co., Ltd., type: VR-400K, die diameter 9.5 mm). The finely divided hydrogel crosslinked polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 1 hour. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.

A surface treatment agent composed of a mixed solution of 0.1 g of ethylene glycol diglycidyl ether, 0.5 g of propylene glycol, 2 g of pure water and 1 g of isopropanol was mixed with 100 g of the obtained water-absorbing resin particles, and then the mixture was stirred at 150 ° C. for 40 minutes. Heat-treated. Further, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (L-2) whose surface was crosslinked.
The absorption capacity without load (CRC) of the water absorbent resin particles (L-2) was 5.8 g / g, and the soluble content was 7.2%.
The particle size distribution of the water-absorbent resin particles (L-2) is 21.0% by mass of particles of less than 850 μm and 600 μm or more, 62.1% by mass of particles of less than 600 μm and 300 μm or more, and particles of less than 300 μm and 150 μm or more. 15.4% by mass, particles less than 150 μm and 45 μm or more were 1.5% by mass, and particles less than 45 μm were 0% by mass. In addition, mass average particle diameter (D50) = 437 μm, logarithmic standard deviation (σζ) = 0.359.

[Example 1]
The water-absorbing resin particles (H-1) obtained in Synthesis Example 2 and the water-absorbing resin particles (L-2) obtained in Synthesis Example 3 were mixed at a mixing ratio (mass ratio) of 8: 2, 7: 3, Dry blending was performed at 6: 4, 5: 5 to obtain particulate water-absorbing resin compositions (1-1), (1-2), (1-3), and (1-4).
The particle size distribution of the obtained particulate water-absorbing resin composition (1-1), (1-2), (1-3), (1-4) is the same as the water-absorbing resin particles (H-1) used. It is the same as the weighted average value of the particle size distribution of (L-2), the mass average particle diameter (D50) is in the range of 426 to 430 μm, and the logarithmic standard deviation (σζ) is in the range of 0.368 to 0.374. It was in.

The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.069 kPa)), AUL at each absorption time (0.29 psi ( 2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, and specific particle size absorption index increase at 20 hours are shown in Table 1.
[Comparative Example 1]
CRC, AUL (0.01 psi (0.069 kPa)) for each absorption time, each of which is adjusted to a particle size of the water-absorbent resin particles (H-1) obtained in Synthesis Example 2 less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Is shown in Table 1.

[Comparative Example 2]
CRC, AUL (0.01 psi (0.069 kPa)) for each absorption time alone, adjusted to a particle size of the water-absorbent resin particles (L-2) obtained in Synthesis Example 3 less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Is shown in Table 1.

[Synthesis Example 4]: Synthesis of water-absorbent resin particles (H-2) In a reactor formed by attaching a cover to a jacketed stainless steel double-arm kneader having two sigma-shaped blades and having an internal volume of 10 liters, 71 Polyethylene glycol diacrylate (average number of moles of ethylene oxide added 8) 7.02 g (0.06 mol%) to 5500 g of an aqueous solution of sodium acrylate having a neutralization rate of 3 mol% (monomer concentration 38 mass%) The reaction solution was dissolved. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 24.6 g of a 10% by mass sodium persulfate aqueous solution and 10 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 1 minute. Polymerization was performed while pulverizing the generated gel. The polymerization initiation temperature was 25 ° C., and the maximum temperature reached was 95 ° C. The hydrogel crosslinked polymer was taken out 40 minutes after the start of the polymerization.

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 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 90 minutes. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.
A surface treatment agent composed of a mixed solution of 0.4 g of 1,4-butanediol, 0.6 g of propylene glycol and 2.7 g of pure water was mixed with 100 g of the obtained water absorbent resin particles, and then the mixture was heated at 210 ° C. at 40 ° C. Heat-treated for minutes. Further, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (H-2) whose surface was crosslinked.

The absorption capacity without load (CRC) of the water-absorbent resin particles (H-2) was 31.5 g / g, and the soluble content was 12.5%.
The particle size distribution of the water-absorbent resin particles (H-2) is 19.4% by mass of particles of less than 850 μm and 600 μm or more, 61.7% by mass of particles of less than 600 μm and 300 μm or more, and 150 μm or more of particles less than 300 μm. 16.8% by mass, particles less than 150 μm and 45 μm or more were 1.9% by mass, and particles less than 45 μm were 0.2% by mass. In addition, mass average particle diameter (D50) = 426 μm, logarithmic standard deviation (σζ) = 0.382.
[Example 2]
The water absorbent resin particles (H-2) obtained in Synthesis Example 4 and the water absorbent resin particles (L-2) obtained in Synthesis Example 3 were mixed at a mixing ratio (mass ratio) of 8: 2 and 6: 4. Dry blending was performed to obtain particulate water-absorbing resin compositions (2-1) and (2-2).

The particle size distribution of the obtained particulate water-absorbing resin compositions (2-1) and (2-2) is the weighted average value of the particle size distributions of the water-absorbing resin particles (H-2) and (L-2) used. The mass average particle diameter (D50) was in the range of 428 to 430 μm, and the logarithmic standard deviation (σζ) was in the range of 0.373 to 0.377.
The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.069 kPa)), AUL at each absorption time (0.29 psi ( Table 2 shows the AUL (0.57 psi (3.93 kPa)) at each absorption time, the specific particle size absorption index at each absorption time, and the specific particle size absorption index increase at 20 hours.

[Comparative Example 3]
CRC, AUL (0.01 psi (0.069 kPa)) for each absorption time, each of which is adjusted to a particle size of the water-absorbent resin particles (H-2) obtained in Synthesis Example 4 less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Are shown in Table 2.

[Synthesis Example 5]: Synthesis of water-absorbent resin particles (H-3) In a reactor formed by attaching a lid to a jacketed stainless steel double-arm kneader having two sigma-shaped blades and having an internal volume of 10 liters, 75 3.4 g (0.03 mol%) of polyethylene glycol diacrylate (average added mole number of ethylene oxide 8) was dissolved in 5500 g of an aqueous solution of sodium acrylate having a neutralization rate of mol% (monomer concentration 38 mass%). To prepare a reaction solution. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 24.6 g of a 10% by mass sodium persulfate aqueous solution and 10 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 1 minute. Polymerization was performed while pulverizing the generated gel. The polymerization initiation temperature was 25 ° C., and the maximum temperature reached was 95 ° C. The hydrogel crosslinked polymer was taken out 40 minutes after the start of the polymerization.

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 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 90 minutes. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.
After mixing the surface treatment agent consisting of a mixed liquid of 0.03 g of ethylene glycol diglycidyl ether, 0.3 g of 1,4-butanediol, 0.5 g of propylene glycol and 3 g of pure water with 100 g of the obtained water absorbent resin particles, The mixture was heat treated at 210 ° C. for 55 minutes. Furthermore, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (H-3) whose surface was crosslinked.

The absorption capacity without load (CRC) of the water absorbent resin particles (H-3) was 36 g / g, and the soluble content was 17%.
The particle size distribution of the water-absorbent resin particles (H-3) is 20.5% by mass of particles less than 850 μm and 600 μm or more, 61.9% by mass of particles less than 600 μm and 300 μm or more, and particles of 150 μm or more less than 300 μm. 15.5% by mass, particles less than 150 μm and 45 μm or more were 1.8% by mass, and particles less than 45 μm were 0.3% by mass. In addition, mass-average particle diameter (D50) = 433 μm, logarithmic standard deviation (σζ) = 0.368.
Example 3
The water absorbent resin particles (H-3) obtained in Synthesis Example 5 and the water absorbent resin particles (L-2) obtained in Synthesis Example 3 were mixed at a mixing ratio (mass ratio) of 8: 2 and 6: 4. Dry blending was performed to obtain particulate water-absorbing resin compositions (3-1) and (3-2).

The particle size distribution of the obtained particulate water-absorbing resin compositions (3-1) and (3-2) is a weighted average value of the particle size distributions of the water-absorbing resin particles (H-3) and (L-2) used. The mass average particle diameter (D50) was in the range of 434 to 435 μm, and the logarithmic standard deviation (σζ) was in the range of 0.364 to 0.366.
The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.69 kPa)), AUL at each absorption time (0.29 psi ( 2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, and specific particle size absorption index increase at 20 hours are shown in Table 3.

[Comparative Example 4]
CRC, AUL (0.01 psi (0.69 kPa)) for each absorption time, each of which was adjusted to 300 μm or more with a particle size of the water absorbent resin particles (H-3) obtained in Synthesis Example 5 AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Are shown in Table 3.

[Synthesis Example 6]: Synthesis of water-absorbent resin particles (H-4) In a reactor formed by attaching a cover to a jacketed stainless steel double-arm kneader having two sigma-shaped blades and having an internal volume of 10 liters, 75 3.4 g (0.03 mol%) of polyethylene glycol diacrylate (average number of moles of ethylene oxide added 8) was dissolved in 5500 g of an aqueous solution of sodium acrylate having a neutralization rate of mol% (monomer concentration: 33% by mass). To prepare a reaction solution. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 24.6 g of a 10% by mass sodium persulfate aqueous solution and 10 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 1 minute. Polymerization was performed while pulverizing the generated gel. The polymerization initiation temperature was 20 ° C., and the maximum temperature reached was 95 ° C. The hydrogel crosslinked polymer was taken out 40 minutes after the start of the polymerization.

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 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 90 minutes. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.
After mixing the surface treatment agent consisting of a mixed liquid of 0.03 g of ethylene glycol diglycidyl ether, 0.3 g of 1,4-butanediol, 0.5 g of propylene glycol and 3 g of pure water with 100 g of the obtained water absorbent resin particles, The mixture was heat treated at 200 ° C. for 40 minutes. Further, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (H-4) whose surface was crosslinked.

The absorption capacity without load (CRC) of the water absorbent resin particles (H-4) was 45 g / g, and the soluble content was 30%.
The particle size distribution of the water-absorbent resin particles (H-4) is 20.3% by mass of particles less than 850 μm and 600 μm or more, 62.8% by mass of particles less than 600 μm and 300 μm or more, and particles of less than 300 μm and 150 μm or more. 15.8% by mass, particles less than 150 μm and 45 μm or more were 1.1% by mass, and particles less than 45 μm were 0% by mass. In addition, mass average particle diameter (D50) = 435 μm, logarithmic standard deviation (σζ) = 0.357.
Example 4
The water absorbent resin particles (H-4) obtained in Synthesis Example 6 and the water absorbent resin particles (L-2) obtained in Synthesis Example 3 were mixed at a mixing ratio (mass ratio) of 8: 2 and 6: 4. Dry blending was performed to obtain particulate water-absorbing resin compositions (4-1) and (4-2).

The particle size distribution of the obtained particulate water-absorbing resin compositions (4-1) and (4-2) is a weighted average value of the particle size distributions of the water-absorbing resin particles (H-4) and (L-2) used. The mass average particle diameter (D50) was in the range of 435 to 436 μm, and the logarithmic standard deviation (σζ) was 0.358.
The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.69 kPa)), AUL at each absorption time (0.29 psi ( 2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, and specific particle size absorption index increase at 20 hours are shown in Table 4.

[Comparative Example 5]
CRC, AUL (0.01 psi (0.69 kPa)) for each absorption time, each of which is adjusted to a particle size of the water-absorbent resin particles (H-4) obtained in Synthesis Example 6 to be less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Are shown in Table 4.

[Synthesis Example 7]: Synthesis of water-absorbing resin particles (L-3) 5200 g of an aqueous acrylic acid solution (monomer concentration 20% by mass) having a neutralization rate of 10 mol% in a 10 L polyethylene beaker, methylenebisacrylamide 2 .16 g was added and dissolved uniformly to obtain a reaction solution. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 20% by weight of V-50 (2,2′-azobis (2-amidinopropane) dihydrochloride) aqueous solution 15 g, 10% by weight hydrogen peroxide aqueous solution 10 g and 5% by weight L-ascorbine were added to the reaction solution. 5 g of an acid aqueous solution was added with stirring. Polymerization started after about 5 minutes. The reaction vessel was left to stand at room temperature for 12 hours to complete the polymerization. Thereafter, the hydrogel crosslinked polymer was taken out and pulverized with a meat chopper (manufactured by Iizuka Kogyo Co., Ltd., type: VR-400K, die diameter 9.5 mm). The finely divided hydrogel crosslinked polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 1 hour. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.

A surface treatment agent composed of a mixed solution of 0.1 g of ethylene glycol diglycidyl ether, 0.5 g of propylene glycol, 2 g of pure water and 1 g of isopropanol was mixed with 100 g of the obtained water absorbent resin particles, and then the mixture was stirred at 150 ° C. for 40 minutes. Heat-treated. Furthermore, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (L-3) whose surface was crosslinked.
The absorption capacity without load (CRC) of the water-absorbent resin particles (L-3) was 7.3 g / g, and the soluble content was 5.3%.
The particle size distribution of the water-absorbing resin particles (L-3) is 18.3% by mass of particles of less than 850 μm and 600 μm or more, 62.8% by mass of particles of less than 600 μm and 300 μm or more, and particles of less than 300 μm and 150 μm or more. 16.5% by mass, particles less than 150 μm and 45 μm or more were 2.2% by mass, and particles less than 45 μm were 0.2% by mass. In addition, mass-average particle diameter (D50) = 422 μm and logarithmic standard deviation (σζ) = 0.384.

[Synthesis Example 8]: Synthesis of water-absorbing resin particles (L-4) 5200 g of an aqueous acrylic acid solution (monomer concentration 20 mass%) having a neutralization rate of 20 mol% in a 10 L polyethylene beaker, methylene bisacrylamide 8 .6 g was added and dissolved uniformly to make a reaction solution. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 20% by weight of V-50 (2,2′-azobis (2-amidinopropane) dihydrochloride) aqueous solution 15 g, 10% by weight hydrogen peroxide aqueous solution 10 g and 5% by weight L-ascorbine were added to the reaction solution. 5 g of an acid aqueous solution was added with stirring. Polymerization started after about 5 minutes. The reaction vessel was left to stand at room temperature for 12 hours to complete the polymerization. Thereafter, the hydrogel crosslinked polymer was taken out and pulverized with a meat chopper (manufactured by Iizuka Kogyo Co., Ltd., type: VR-400K, die diameter 9.5 mm). The finely divided hydrogel crosslinked polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 1 hour. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.

A surface treatment agent composed of a mixed solution of 0.1 g of ethylene glycol diglycidyl ether, 0.5 g of propylene glycol, 2 g of pure water and 1 g of isopropanol was mixed with 100 g of the obtained water absorbent resin particles, and then the mixture was stirred at 150 ° C. for 40 minutes. Heat-treated. Further, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (L-4) whose surface was crosslinked.
The absorption capacity without load (CRC) of the water absorbent resin particles (L-4) was 18 g / g, and the soluble content was 3%.
The particle size distribution of the water-absorbent resin particles (L-4) is less than 850 μm and 20.0% by mass of particles of 600 μm or more, 60.7% by mass of particles of less than 600 μm and 300 μm or more, and 16 particles of less than 300 μm and 150 μm or more. .2% by mass, particles less than 150 μm and 45 μm or more were 2.9% by mass, and particles less than 45 μm were 0.2% by mass. In addition, mass-average particle diameter (D50) = 426 μm, logarithmic standard deviation (σζ) = 0.393.

Example 5
The water absorbent resin particles (L-3) obtained in Synthesis Example 7 or the water absorbent resin particles (L-) obtained in Synthesis Example 8 with respect to the water absorbent resin particles (H-1) obtained in Synthesis Example 2 4) was dry blended at a mixing ratio (mass ratio) of 6: 4 to obtain particulate water-absorbing resin compositions (5-1) and (5-2).
The particle size distribution of the obtained particulate water-absorbing resin compositions (5-1) and (5-2) is the same as that of the water-absorbing resin particles (H-1) and (L-3) or (L-4) used. It was the same as the weighted average value of the particle size distribution, the mass average particle diameter (D50) was in the range of 423 to 425 μm, and the logarithmic standard deviation (σζ) was in the range of 0.380 to 0.383.

The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.069 kPa)), AUL at each absorption time (0.29 psi ( Table 5 shows the AUL (0.57 psi (3.93 kPa)) at each absorption time, the specific particle size absorption index at each absorption time, and the specific particle size absorption index increase at 20 hours.
[Comparative Example 6]
CRC, AUL (0.01 psi (0.069 kPa)) for each absorption time, each of which is adjusted to a particle size of the water-absorbent resin particles (L-3) obtained in Synthesis Example 7 to be less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Are shown in Table 5.

[Comparative Example 7]
CRC, AUL (0.01 psi (0.069 kPa)) for each absorption time alone, adjusted to a particle size of the water-absorbent resin particles (L-4) obtained in Synthesis Example 8 less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Are shown in Table 5.

[Synthesis Example 9]: Synthesis of water-absorbing resin particles (H-5) In a reactor formed by attaching a cover to a jacketed stainless steel double-arm kneader having an inner volume of 10 liters having two sigma-type blades, 7.3 g (0.05 mol%) of polyethylene glycol diacrylate (average number of moles of ethylene oxide added 8) was dissolved in 6570 g of an aqueous solution of sodium acrylate having a neutralization rate of mol% (monomer concentration: 39% by mass). To prepare a reaction solution. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 24.6 g of a 10% by mass sodium persulfate aqueous solution and 10 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 1 minute. Polymerization was performed while pulverizing the generated gel. The polymerization initiation temperature was 20 ° C., and the maximum temperature reached was 95 ° C. The hydrogel crosslinked polymer was taken out 40 minutes after the start of the polymerization.

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 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 180 ° C. for 50 minutes. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.
A surface treatment agent composed of a mixed solution of 0.5 g of glycerin, 2 g of pure water and 0.5 g of isopropanol was mixed with 100 g of the obtained water absorbent resin particles, and then the mixture was heat-treated at 212 ° C. for 30 minutes. Further, the particles were pulverized until passing through a JIS standard sieve having an opening of 850 μm, thereby obtaining water-absorbing resin particles (H-5) having a crosslinked surface.

The absorption capacity without load (CRC) of the water absorbent resin particles (H-5) was 23 g / g, and the soluble content was 13%.
The particle size distribution of the water-absorbent resin particles (H-5) is 17.7% by mass of particles less than 850 μm and 600 μm or more, 63.4% by mass of particles less than 600 μm and 300 μm or more, and particles of 150 μm or more less than 300 μm. 15.5% by mass, particles less than 150 μm and 45 μm or more were 3.2% by mass, and particles less than 45 μm were 0.2% by mass. In addition, mass-average particle diameter (D50) = 421 μm and logarithmic standard deviation (σζ) = 0.390.
Example 6
The water absorbent resin particles (L-2) obtained in Synthesis Example 3 with respect to the water absorbent resin particles (H-5) obtained in Synthesis Example 9 and the water absorbent resin particles (L-) obtained in Synthesis Example 7 3) The water-absorbent resin particles (L-4) obtained in Synthesis Example 8 were dry blended at a mixing ratio (mass ratio) of 6: 4, respectively, and the particulate water-absorbent resin composition (6-1), (6-2) and (6-3) were obtained.

The particle size distributions of the obtained particulate water-absorbing resin compositions (6-1), (6-2), and (6-3) are the water-absorbing resin particles used (H-5) and (L-2), It is the same as the weighted average value of the particle size distribution of (L-3) or (L-4), the mass average particle diameter (D50) is in the range of 421 to 427 μm, and the logarithmic standard deviation (σζ) is 0.376. It was in the range of ~ 0.391.
The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.069 kPa)), AUL at each absorption time (0.29 psi ( 2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, and specific particle size absorption index increase at 20 hours are shown in Table 6.

[Comparative Example 8]
CRC, AUL (0.01 psi (0.069 kPa)) for each absorption time alone, adjusted to a particle size of the water-absorbent resin particles (H-5) obtained in Synthesis Example 9 less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Are shown in Table 6.

[Synthesis Example 10]: Synthesis of water-absorbent resin particles (H-6) In a reactor formed by attaching a lid to a jacketed stainless steel double-arm kneader having two sigma-shaped blades and having an internal volume of 10 liters, 50 Reaction was carried out by dissolving 15 g (0.1 mol%) of polyethylene glycol diacrylate (average number of moles of ethylene oxide added 8) in 6570 g of an aqueous solution of sodium acrylate having a neutralization rate of mol% (monomer concentration: 39% by mass). Liquid. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 29.34 g of a 10% by mass aqueous sodium persulfate solution and 24.45 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring, and polymerization started about 1 minute later. Polymerization was performed while pulverizing the generated gel. The polymerization initiation temperature was 20 ° C., and the maximum temperature reached was 95 ° C. The hydrogel crosslinked polymer was taken out 30 minutes after the start of the polymerization.

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 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 180 ° C. for 50 minutes. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.
A surface treatment agent composed of a mixed liquid of 0.32 g of 1,4-butanediol, 0.5 g of propylene glycol, 2.73 g of pure water, and 0.45 g of isopropanol was mixed with 100 g of the obtained water absorbent resin particles, and then the mixture was mixed. Heat treatment was performed at 205 ° C. for 10 minutes. Further, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (H-6) whose surface was crosslinked.

The absorption capacity without load (CRC) of the water absorbent resin particles (H-6) was 23.6 g / g, and the soluble content was 7%.
The particle size distribution of the water-absorbent resin particles (H-6) is 22.7% by mass of particles of less than 850 μm and 600 μm or more, 58.6% by mass of particles of less than 600 μm and 300 μm or more, and particles of less than 300 μm and 150 μm or more. 17.7% by mass, particles less than 150 μm and 45 μm or more were 1.0% by mass, and particles less than 45 μm were 0% by mass. In addition, mass-average particle diameter (D50) = 437 μm, logarithmic standard deviation (σζ) = 0.373.
Example 7
The water absorbent resin particles (L-2) obtained in Synthesis Example 3 and the water absorbent resin particles (L-) obtained in Synthesis Example 7 with respect to the water absorbent resin particles (H-6) obtained in Synthesis Example 10 3) The water-absorbent resin particles (L-4) obtained in Synthesis Example 8 were dry blended at a mixing ratio (mass ratio) of 6: 4, respectively, to form a particulate water-absorbent resin composition (7-1), (7-2) and (7-3) were obtained.

The particle size distributions of the obtained particulate water-absorbing resin compositions (7-1), (7-2), and (7-3) are the water-absorbing resin particles (H-6) and (L-2) used, It is the same as the weighted average value of the particle size distribution of (L-3) or (L-4), the mass average particle diameter (D50) is in the range of 431 to 437 μm, and the logarithmic standard deviation (σζ) is 0.368. It was in the range of ~ 0.381.
The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.069 kPa)), AUL at each absorption time (0.29 psi ( Table 7 shows the AUL (0.57 psi (3.93 kPa)) at each absorption time, the specific particle size absorption index at each absorption time, and the specific particle size absorption index increase at 20 hours.

[Comparative Example 9]
CRC, AUL (0.01 psi (0.069 kPa)) for each absorption time alone, with the particle size of the water absorbent resin particles (H-6) obtained in Synthesis Example 10 adjusted to less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Are shown in Table 7.

[Synthesis Example 11]: Synthesis of water-absorbing resin particles (H-7) 6400 g of an acrylic acid aqueous solution (monomer concentration 20% by mass) having a neutralization rate of 90 mol% in a 10 L polyethylene beaker, methylenebisacrylamide 8 .63 g was added and dissolved uniformly to prepare a reaction solution. Next, dissolved oxygen was removed from the reaction solution for 30 minutes under a nitrogen gas atmosphere. Subsequently, 15.3 g of an aqueous solution of 20% by mass of V-50 (2,2′-azobis (2-amidinopropane) dihydrochloride), 10 g of an aqueous solution of 10% by mass of hydrogen peroxide and 5% by mass of L were added to the reaction solution. -5 g of ascorbic acid aqueous solution was added with stirring, polymerization started after about 5 minutes, and the reaction vessel was left to stand at room temperature for 12 hours to complete the polymerization. Thereafter, the hydrogel crosslinked polymer was taken out and pulverized with a meat chopper (manufactured by Iizuka Kogyo Co., Ltd., type: VR-400K, die diameter 9.5 mm). The finely divided hydrogel crosslinked polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 1 hour. The obtained dried product was pulverized, classified and prepared using a roll mill to obtain amorphous crushed water-absorbent resin particles.

A surface treatment agent composed of a mixed solution of 0.1 g of ethylene glycol diglycidyl ether, 0.5 g of propylene glycol, 2 g of pure water and 1 g of isopropanol was mixed with 100 g of the obtained water-absorbent resin particles, and the mixture was mixed at 195 ° C. for 40 minutes. Heat-treated. Further, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (H-7) having a crosslinked surface.
The absorption capacity without load (CRC) of the water-absorbent resin particles (H-7) was 37 g / g, and the soluble content was 12.3%.
The particle size distribution of the water-absorbent resin particles (H-7) is 24.0% by mass of particles less than 850 μm and 600 μm or more, 57.6% by mass of particles less than 600 μm and 300 μm or more, and 150 μm or more of particles less than 300 μm. 16.8% by mass, particles less than 150 μm and 45 μm or more were 1.5% by mass, and particles less than 45 μm were 0.1% by mass. The mass average particle diameter (D50) was 442 μm, and the logarithmic standard deviation (σζ) was 0.374.

Example 8
The water absorbent resin particles (L-2) obtained in Synthesis Example 3 were dry blended at a mixing ratio (mass ratio) of 6: 4 with respect to the water absorbent resin particles (H-7) obtained in Synthesis Example 11. Thus, a particulate water-absorbing resin composition (8-1) was obtained.
The particle size distribution of the obtained particulate water absorbent resin composition (8-1) is the same as the weighted average value of the particle size distributions of the water absorbent resin particles (H-7) and (L-2) used, and the mass. The average particle diameter (D50) was 440 μm, and the logarithmic standard deviation (σζ) was 0.368.
The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.069 kPa)), AUL at each absorption time (0.29 psi ( 2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, and specific particle size absorption index increase at 20 hours are shown in Table 8.

[Comparative Example 10]
CRC, AUL at each absorption time (0.01 psi (0.069 kPa)), each adjusted to a particle size of the water-absorbent resin particles (H-7) obtained in Synthesis Example 11 less than 600 μm and 300 μm or more, each AUL at absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption index increase at 20 hours Is shown in Table 8.

[Synthesis Example 12]: Synthesis of Water Absorbent Resin Particles (L-5), (L-6), and (L-7) The unneutralized water absorbent resin particles obtained in Synthesis Example 3 have the following particle size distribution. The particles having different particle sizes (L-5), (L-6), and (L-7) were obtained.
(L-5): 5% by mass of particles of less than 850 μm and 600 μm or more, 64.9% by mass of particles of less than 600 μm and 300 μm or more, 27% by mass of particles of less than 300 μm and 150 μm or more, and 45 μm or more of less than 150 μm Particles were 2.5% by mass, particles less than 45 μm were 0.7% by mass, and mass average particle size (D50) = 354 μm.
(L-6): The particle size obtained in Synthesis Example 3 was used as it was. That is, 21.0% by mass of particles of less than 850 μm and 600 μm or more, 62.1% by mass of particles of less than 600 μm and 300 μm or more, 15.4% by mass of particles of less than 300 μm and 150 μm or more, 45 μm or more of less than 150 μm Particles were 1.5 mass%, particles less than 45 μm were 0 mass%, mass average particle diameter (D50) = 437 μm, logarithmic standard deviation (σζ) = 0.359.

(L-7): Particles of less than 600 μm and 500 μm or more were 50% by mass, particles of less than 500 μm and 300 μm or more were 50% by mass, and mass average particle diameter (D50) = 500 μm.
Example 9
In Example 9, in order to measure the change in absorption rate under a wide range of particle size conditions, the measurement of the absorption ratio under pressure and the absorption index (specific particle size absorption ratio and specific particle size absorption index) in the specific particle size range that has been shown so far. Instead, the absorption capacity under pressure (AAP) and the absorption index were measured.
The water absorbent resin particles (L-5), (L-6) and (L-7) obtained in Synthesis Example 12 were mixed with the water absorbent resin particles (H-1) obtained in Synthesis Example 2. Particles granulated by dry blending at a ratio (mass ratio) of 6: 4, adding 2% by weight of water under stirring, mixing, leaving to stand for 1 hour, and passing through a sieve with an opening of 850 μm. Water-absorbing resin compositions (9-1), (9-2), and (9-3) were obtained.

(9-1): Particles of less than 850 μm and 600 μm or more are 15.2% by mass, particles of less than 600 μm and 300 μm or more are 65.5% by mass, particles of less than 300 μm and 150 μm or more are 19.2% by mass, less than 150 μm The particle size of 45 μm or more was 0.1 mass%, and the particle size of less than 45 μm was 0 mass%. In addition, mass-average particle diameter (D50) = 412 μm and logarithmic standard deviation (σζ) = 0.362.
(9-2): 21% by mass of particles of less than 850 μm and 600 μm or more, 64.5% by mass of particles of less than 600 μm and 300 μm or more, 14.3% by mass of particles of less than 300 μm and 150 μm or more, 45 μm of less than 150 μm The above particles were 0.2% by mass, and particles less than 45 μm were 0% by mass. Further, the mass average particle diameter (D50) = 445 μm and the logarithmic standard deviation (σζ) = 0.336.

(9-3): 13% by mass of particles less than 850 μm and 600 μm or more, 79.5% by mass of particles less than 600 μm and 300 μm or more, 7.4% by weight of particles less than 300 μm and 150 μm or more, 45 μm less than 150 μm The above particles were 0.1% by mass, and the particles less than 45 μm were 0% by mass. In addition, mass average particle diameter (D50) = 443 μm and logarithmic standard deviation (σζ) = 0.27.
CRC of the obtained particulate water-absorbing resin composition, AAP at each absorption time (0.06 psi (0.41 kPa)), AAP at each absorption time (0.3 psi (2.06 kPa)), at each absorption time Table 9 shows AAP (0.7 psi (4.83 kPa)), absorption index at each absorption time, and increase in absorption index at 20 hours.

[Synthesis Example 13]: Synthesis of water-absorbent resin particles (H-8) The water-absorbent resin particles (H-1) obtained in Synthesis Example 2 were prepared so as to be particles of less than 300 μm and 150 μm or more in mass. Water-absorbing resin particles (H-8) having an average particle diameter (D50) = 225 μm were obtained.
[Comparative Example 11]
The water absorbent resin particles (H-8) obtained in Synthesis Example 13 and the water absorbent resin particles (L-7) obtained in Synthesis Example 12 were dry blended at a mixing ratio (mass ratio) of 6: 4. Then, 2% by mass of water was added and mixed under stirring, left for 1 hour, and passed through a sieve having an opening of 850 μm to obtain a granulated particulate water-absorbing resin composition (c11-1). It was.

(C11-1): 2% by mass of particles of less than 850 μm and 600 μm or more, 43.3% by mass of particles of less than 600 μm and 300 μm or more, 54.7% by mass of particles of less than 300 μm and 150 μm or more, 45 μm of less than 150 μm The above particles were 0% by mass, and the particles less than 45 μm were 0% by mass. The mass average particle diameter (D50) was 300 μm, and the logarithmic standard deviation (σζ) was 0.158.
CRC of the obtained particulate water-absorbing resin composition, AAP at each absorption time (0.06 psi (0.41 kPa)), AAP at each absorption time (0.3 psi (2.06 kPa)), at each absorption time Table 9 shows AAP (0.7 psi (4.83 kPa)), absorption index at each absorption time, and increase in absorption index at 20 hours.

[Comparative Example 12]
The water-absorbent resin particles (H-3) obtained in Synthesis Example 5 and the water-absorbent resin particles (L-3) obtained in Synthesis Example 7 were less than 850 μm and 2% by mass and 600 μm or more particles were 600 μm or more, respectively. 45.5% by mass of particles of less than 300 μm and 47.5% by mass of particles of less than 300 μm and of 150 μm or more, 4.5% by mass of particles of less than 150 μm and 45 μm or more, and 0.5% of particles of less than 45 μm %, And the water-absorbent resin particles (H-9) and the water-absorbent resin particles (L-8) were obtained.
The obtained water-absorbent resin particles (H-9) and water-absorbent resin particles (L-8) were dry blended at a mixing ratio (mass ratio) of 6: 4, and 2% by mass of water was added with stirring. The mixture was allowed to stand for 1 hour and passed through a sieve having an opening of 850 μm to obtain a granulated particulate water-absorbing resin composition (c12-1).

(C12-1): 2% by mass of particles of less than 850 μm and 600 μm or more, 46.7% by mass of particles of less than 600 μm and 300 μm or more, 48.7% by mass of particles of less than 300 μm and 150 μm or more, 45 μm of less than 150 μm The above particles were 2.6% by mass, and the particles less than 45 μm were 0% by mass. In addition, mass-average particle diameter (D50) = 297 μm and logarithmic standard deviation (σζ) = 0.347.
CRC of the obtained particulate water-absorbing resin composition, AAP at each absorption time (0.06 psi (0.41 kPa)), AAP at each absorption time (0.3 psi (2.06 kPa)), at each absorption time Table 9 shows AAP (0.7 psi (4.83 kPa)), absorption index at each absorption time, and increase in absorption index at 20 hours.

[Comparative Example 13]
The water absorbent resin particles (H-1) obtained in Synthesis Example 2 were sieved to a range of less than 850 μm and 600 μm or more to obtain water absorbent resin particles (H-10).
The obtained water-absorbent resin particles (H-10) alone, CRC, AAP at each absorption time (0.06 psi (0.41 kPa)), AAP at each absorption time (0.3 psi (2.06 kPa)), each Table 9 shows the AAP (0.7 psi (4.83 kPa)) at the absorption time, the absorption index at each absorption time, and the increase in absorption index at 20 hours.
[Comparative Example 14]
CRC, AAP (0.06 psi (0.41 kPa)) at each absorption time, and AAP (0.3 psi (2.06 kPa) at each absorption time of the water absorbent resin particles (L-7) obtained in Synthesis Example 12 alone )), AAP (0.7 psi (4.83 kPa)) at each absorption time, absorption index at each absorption time, and increase in absorption index at 20 hours are shown in Table 9.

[Comparative Example 15]
In order to show the water absorption behavior when water-absorbing resins having a high neutralization rate are mixed, a particulate water-absorbing resin composition having the following combination is prepared, and the particulate water-absorbing resin composition (c15-1), ( c15-2) was obtained.
(C15-1): The water-absorbent resin particles (H-1) obtained in Synthesis Example 2 and the water-absorbent resin particles (H-4) obtained in Synthesis Example 6 were mixed at a mixing ratio (mass ratio) of 6: Particulate water-absorbing resin composition obtained by mixing in No. 4 (mass average particle diameter (D50) = 428 μm, logarithmic standard deviation (σζ) = 0.369).

(C15-2): Mixing ratio (mass ratio) of the water absorbent resin particles (H-3) obtained in Synthesis Example 5 and the water absorbent resin particles (H-5) obtained in Synthesis Example 9: Particulate water-absorbing resin composition obtained by mixing in No. 4 (mass average particle diameter (D50) = 428 μm, logarithmic standard deviation (σζ) = 0.377).
For the obtained particulate water-absorbing resin compositions (c15-1) and (c15-2), the particle size was adjusted to less than 600 μm to 300 μm or more, CRC, AUL at each absorption time (0.01 psi (0.069 kPa)) ), AUL at each absorption time (0.29 psi (2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, specific particle size absorption at 20 hours Table 10 shows the index increase.

[Comparative Example 16]
A particulate water-absorbing resin composition (c16-1) to which polyacrylic acid fine particles were added was obtained in the same manner as in Example 4 of JP-A-2001-98170.
CRC of the obtained particulate water-absorbing resin composition (c16-1), AUL at each absorption time (0.01 psi (0.069 kPa)), AUL at each absorption time (0.29 psi (2.00 kPa)) Table 11 shows the AUL (0.57 psi (3.93 kPa)) at each absorption time, the specific particle size absorption index at each absorption time, and the specific particle size absorption index increase at 20 hours.

Example 10
Using the water-absorbent resin particles (H-1) obtained in Example 1 and the particulate water-absorbent resin compositions (1-1) and (1-3) obtained in Example 1, and according to the method described above, Then, water-absorbent articles were prepared and performance evaluation was performed. The results are shown in Table 12.

Example 11
Sodium carbonate powder (manufactured by Kanto Chemical Co., Inc.) was adjusted to the same particle size as the water absorbent resin particles (L-4) obtained in Synthesis Example 8, and the water absorbent resin particles (L-4) and the above sodium carbonate powder were mixed. By mixing at a ratio (mass ratio) of 8: 2, a particulate water-absorbing resin composition (11-1) was obtained.
The particle size distribution of the obtained particulate water-absorbent resin composition (11-1) is almost equal to the particle size distribution of the water-absorbent resin particles (L-4) used, and the mass average particle diameter (D50) is 425 μm. The logarithmic standard deviation (σζ) was 0.390.
The particle size of the obtained particulate water-absorbing resin composition was adjusted to 300 μm or more with less than 600 μm, CRC, AUL at each absorption time (0.01 psi (0.069 kPa)), AUL at each absorption time (0.29 psi ( 2.00 kPa)), AUL at each absorption time (0.57 psi (3.93 kPa)), specific particle size absorption index at each absorption time, and specific particle size absorption index increase at 20 hours are shown in Table 13.

  Since the particulate water-absorbing resin composition of the present invention has excellent water-absorbing properties, it can be used as a water-absorbing article, that is, a water-absorbing water retaining agent for various uses. For example, water absorbent water absorbent for absorbent articles such as paper diapers, sanitary napkins, incontinence pads, medical pads; Anti-condensation agent for materials, water retention agent for construction such as cement additive; release control agent, cold insulation agent, disposable body warmer, sludge coagulant, food freshness preservation agent, ion exchange column material, sludge or oil dehydrating agent, drying agent Can be used as a humidity control material. The particulate water-absorbing resin composition of the present invention is particularly preferably used for sanitary materials for absorbing feces, urine or blood, such as disposable diapers and sanitary napkins.

It is a relationship figure of the neutralization rate and absorption rate which shows the result of reference example 1.

Claims (10)

A particulate water-absorbing resin composition containing 80% by mass or more of a carboxyl group-containing water absorbent resin , wherein the carboxyl group-containing water absorbent resin has a carboxyl group neutralization rate of 50% or more as the carboxyl group-containing water absorbent resin. (A) and a carboxyl group-containing water-absorbing resin (B) having a carboxyl group neutralization rate of less than 50% in a mass ratio of (A) :( B) = 90: 10 to 10:90, The average particle size is in the range of 320 to 700 μm, the absorption capacity under pressure (0.3 psi (2.06 kPa), 1 hour) is 20 g / g or more, and the increase in absorption index in 3 hours is 3 g / g. The particulate water-absorbent resin composition, which is g or more. JP Teitsubudo absorption capacity under (0.29psi (2.00kPa), 1 hour) at the 20 g / g or more, and is a particular particle size absorption index increment in 20 hours 3 g / g or more, according to claim 1 The particulate water-absorbent resin composition described in 1 .   A carboxyl group-containing water absorbent resin (A) having a carboxyl group neutralization rate of 50% or more and a carboxyl group-containing water absorbent resin (B) having a carboxyl group neutralization rate of less than 50%, (A): (B) = 90: 10 to 10:90, and the difference between the neutralization rate of the carboxyl group-containing water absorbent resin (A) and the neutralization rate of the carboxyl group-containing water absorbent resin (B) is The particulate water-absorbent resin composition according to claim 1 or 2, which is 30% or more.   The particulate water-absorbent resin composition according to claim 3, wherein the mass average particle diameters of both the carboxyl group-containing water absorbent resin (A) and the carboxyl group-containing water absorbent resin (B) are 320 µm or more.   The particulate water-absorbing resin composition according to claim 3 or 4, wherein the carboxyl group-containing water-absorbing resin (A) and the carboxyl group-containing water-absorbing resin (B) are both surface-treated.   The particulate water-absorbing resin composition according to any one of claims 1 to 5, wherein the content of particles having a particle diameter of less than 150 µm is less than 5% by mass.   The particulate water-absorbent resin composition according to any one of claims 1 to 6, comprising a part of granulated particles of the water-absorbent resin formed by granulation treatment.   The particulate water-absorbent resin composition according to any one of claims 1 to 7, wherein the logarithmic standard deviation σζ of the particle size distribution is 0.46 or less.   The particulate water-absorbent resin composition according to any one of claims 3 to 8, wherein the neutralization rate, absorption ratio, and mixing index are 11 or more.   A water absorbent article comprising the particulate water absorbent resin composition according to any one of claims 1 to 9.

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