JP2015066164A - Water absorbent for sustained release agent and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sustained release agent that, for the sustained release agent application, enables an absorbed agent to be released stably for the long term, and a water absorbent used for the sustained release agent.SOLUTION: The present invention provides a sustained release agent using a water absorbent with an exposure surface area evaluation of 10% or more, and a water absorbent used for the sustained release agent.

Description

  The present invention relates to a water-absorbing agent for sustained release agent and a method for producing the same. More specifically, the present invention relates to a particulate water-absorbing agent having a polyacrylic acid (salt) -based water-absorbing resin as a main component, a particulate water-absorbing agent having a specific water-absorbing performance used for a sustained-release agent, and production thereof. Regarding the method.

  Polyacrylic acid (salt) -based water-absorbing resin is used as a material (hygiene material) that absorbs moisture, such as diapers, and in addition, it absorbs predetermined chemicals such as fragrances and deodorants. It is also used as a sustained release agent that gradually dissipates.

  Patent Document 1 discloses that a light yellow gel-like composition is obtained by adding a cross-linked polyacrylate-based superabsorbent resin to a chlorite aqueous solution containing a pH adjusting agent. Patent Document 2 discloses the use of a cross-linked product in which a part of the acid group is substituted with an onium cation in order to absorb a large amount of drug and stabilize the volatilization amount.

  According to Non-Patent Document 1, it is described that a sustained-release agent that has been preliminarily absorbed in a gel form has insufficient release of the drug compared to a sustained-release agent that has been gelled immediately before use. Yes.

JP-A-11-278808 JP 2004-000581 A

Products that were sterilized with chlorine dioxide (November 11, 2010 press release), National Life Center, Incorporated Administrative Agency

  An object of the present invention is to provide a sustained-release agent and a water-absorbing agent used in the sustained-release agent, which can stably disperse the absorbed drug over a long period of time in the sustained-release agent application.

  As a result of intensive studies on the above problems, the present inventors have found that the cause of a decrease in the radiation performance when stored for a long time under sealed conditions is that during storage, even if it has sufficient radiation performance immediately after gelation. The present invention has been completed by discovering that the radiation performance is lowered because the substantial radiation area is reduced due to the deformation of the gel particles and the reduction in the gap between the gel particles due to vibration such as transportation, etc.

  Therefore, by using a water-absorbing agent that makes drug absorption uneven, even after long-term storage, water-absorbing agent particles with insufficient drug absorption improve the diffusion area, and further, the amount of drug absorbed after the start of use It was found that long-term stable emission performance can be maintained by liquid transfer between different particles.

  The water-absorbing agent of the present invention can be suitably used particularly in a sustained-release agent type in which a drug solution and a water-absorbing agent are mixed in advance because the release performance does not deteriorate even when stored for a long period of time.

[1] Definition of terms (1-1) “Water absorbing agent”
The “water-absorbing agent” in the present invention is an aqueous liquid gelling agent containing 80% by mass, preferably 90% by mass or more of the following water-absorbing resin. In addition to the water-absorbent resin, 0 to 20% by mass of water, inorganic particles and the like are included.

(1-2) “Water Absorbent Resin”
The “water-absorbing resin” in the present invention means a water-swellable, water-insoluble polymer gelling agent and has the following physical properties. That is, as an indicator of “water swellability”, the CRC (water absorption capacity under no pressure) defined by ERT441.2-02 (2002) is 5 (g / g) or more, and as an indicator of “water insolubility”, It means a polymer gelling agent having a physical property of Ext (water-soluble content) defined by ERT470.2-02 (2002) of 50% by weight or less.

  The water-absorbent resin can be appropriately designed according to its use, and is not particularly limited, but is preferably a hydrophilic cross-linked polymer obtained by cross-linking an unsaturated monomer having a carboxyl group. Moreover, the whole amount (100 weight%) is not limited to the form which is a polymer, The water absorbing resin composition containing the additive etc. may be sufficient in the range which satisfies the said physical property (CRC, Ext).

  Furthermore, the water-absorbent resin in the present invention is not limited to the final product, but is an intermediate in the water-absorbent resin production process (for example, water-containing gel after polymerization, dried polymer after drying, water-absorbent resin powder before surface crosslinking, etc.) ), Which are collectively referred to as “water absorbent resin”.

  The shape of the water-absorbing resin includes a sheet shape, a fiber shape, a film shape, a particle shape, a gel shape, and the like. In the present invention, a particulate water-absorbing resin is preferable.

(1-3) "Polyacrylic acid (salt)"
The “polyacrylic acid (salt)” in the present invention optionally contains a graft component, and contains acrylic acid and / or a salt thereof (hereinafter referred to as “acrylic acid (salt)”) as a main component as a repeating unit. It means a polymer.

  The “main component” means that the content (amount of use) of acrylic acid (salt) is usually 50 to 100 mol%, preferably 50 to 100 mol%, based on the entire monomer (excluding the internal crosslinking agent) used for polymerization. Means 70 to 100 mol%, more preferably 90 to 100 mol%, still more preferably substantially 100 mol%. Moreover, the polyacrylic acid salt as a polymer essentially contains a water-soluble salt, preferably a monovalent salt, more preferably an alkali metal salt or an ammonium salt.

(1-4) “EDANA” and “ERT”
“EDANA” is an abbreviation for European Disposables and Nonwovens Associations, and “ERT” is an abbreviation for European standard water-absorbing resin measurement methods (EDANA Recommended Test Methods). In the present invention, unless otherwise specified, the physical properties of the water-absorbent resin are measured based on the original ERT (revised in 2002).

(A) "CRC" (ERT441.2-02)
“CRC” is an abbreviation for Centrifugation Retention Capacity (centrifuge retention capacity) and means water absorption capacity without pressure (sometimes referred to as “water absorption capacity”). Specifically, 0.2 g of the water-absorbent resin in the nonwoven fabric was freely swollen for 30 minutes with respect to a large excess of 0.9 wt% sodium chloride aqueous solution, and then drained with a centrifuge (250 G). It is a water absorption magnification (unit; g / g).

(B) "Ext" (ERT470.2-02)
“Ext” is an abbreviation for Extractables and means a water-soluble component. Specifically, for 1.0 g of water-absorbing resin, a value obtained by measuring the amount of dissolved polymer after stirring for 16 hours at 500 rpm with respect to 200 ml of 0.9 wt% aqueous sodium chloride solution (unit: wt%) ).

(C) “AAP” (ERT442.2-02)
“AAP” is an abbreviation for Absorption Against Pressure, which means water absorption capacity under pressure. Specifically, with respect to 0.9 g of the water-absorbing resin, the water absorption capacity after swelling under a load of 2.06 kPa (0.3 psi) for 1 hour against a large excess of 0.9 wt% sodium chloride aqueous solution ( Unit; g / g). In this specification, the load condition was changed to 4.83 kPa (0.7 psi).

(D) “Residual Monomers” (ERT410.2-02)
“Residual Monomers” means the amount of monomer (monomer) remaining in the water-absorbent resin (hereinafter referred to as “residual monomer”). Specifically, with respect to 1.0 g of the water-absorbing resin, the amount of residual monomer dissolved after stirring for 1 hour at 500 rpm with respect to 200 ml of 0.9 wt% sodium chloride aqueous solution was measured by high performance liquid chromatography (HPLC). Value (unit: ppm).

(E) "Moisture Content" (ERT430.2-02)
“Moisture Content” means the water content of the water-absorbent resin. Specifically, it is a value (unit:% by weight) calculated from a loss on drying when 4.0 g of the water absorbent resin is dried at 105 ° C. for 3 hours. In this specification, the measurement was performed by changing the water-absorbing resin to 1.0 g and the drying temperature to 180 ° C.

(F) "PSD" (ERT420.2-02)
“PSD” is an abbreviation for Particle Size Distribution, and means a particle size distribution measured by sieve classification. The mass average particle size (D50) and the particle size distribution width are the same as those described in “(1) Average Particle Diameter and Distillation of Particle Diameter” described in European Patent No. 0349240, page 7, lines 25-43. Measure with

(1-5) “Liquid permeability”
“Liquid permeability” of the water-absorbent resin refers to the fluidity of the liquid passing between the particles of the swollen gel under load or no load. As a typical measurement method, SFC (Saline Flow Conductivity / Saline flow conductivity) and GBP (Gel Bed Permeability / gel bed permeability).

  “SFC (Saline Flow Inducibility)” refers to the liquid permeability of a 0.69 wt% sodium chloride aqueous solution to a water absorbent resin under a load of 2.07 kPa, and the SFC test disclosed in US Pat. No. 5,669,894. Measured according to the method.

  “GBP (gel bed permeability)” refers to the liquid permeability of a 0.9 wt% sodium chloride aqueous solution to a water-absorbent resin under load or free swelling, and is disclosed in International Publication No. 2005/016393. Measured according to the test method.

(1-6) Others In this specification, “X to Y” indicating a range means “X or more and Y or less”. Further, unless otherwise noted, “t (ton)” as a unit of weight means “Metric ton”, and “ppm” means “weight ppm” or “mass ppm”. Further, “weight” and “mass”, “parts by weight” and “parts by mass”, “% by weight” and “% by mass” are treated as synonyms. Further, “˜acid (salt)” means “˜acid and / or salt thereof”, and “(meth) acryl” means “acryl and / or methacryl”.

  For convenience, “liter” may be described as “l” or “L”, and “wt%” may be described as “wt%”. Further, in the case of measuring a trace component, N.sub. Described as D (Non Detected).

[2] Manufacturing method of water-absorbing agent Hereinafter, manufacturing steps (2-1) to (2-9) of the water-absorbing agent according to the present invention will be described.

(2-1) Preparation step of monomer aqueous solution This step is a step of preparing an aqueous solution (monomer aqueous solution) containing acrylic acid (salt) as a main component. In place of the monomer aqueous solution, a monomer slurry may be used to such an extent that the water absorption properties are not lowered.

(Acrylic acid)
In the present invention, known acrylic acid can be used, and such acrylic acid usually contains a trace component such as a polymerization inhibitor and impurities. As the polymerization inhibitor, phenols are preferable, and methoxyphenols are more preferable. Moreover, the density | concentration is 1-200 ppm from the color tone of polymerizability or a water absorbing resin, and 10-160 ppm is more preferable. For example, US Patent Publication No. 2008/0161512 is referred to as impurities.

(Monomer used together)
In the present invention, other monomers can be used in combination with acrylic acid (salt). Examples of the other monomers include water-soluble or hydrophobic unsaturated monomers, and more specifically, monomers described in paragraph [0035] of US Patent Application Publication No. 2005/215734. However, acrylic acid is excluded). In addition, what uses the said water-soluble or hydrophobic unsaturated monomer as a copolymerization component is contained in the water absorbing resin which concerns on this invention.

  Examples of the monomer component to be polymerized to be a water-absorbent resin used in the present invention include (meth) acrylic acid, (anhydrous) maleic acid, itaconic acid, cinnamic acid, vinyl sulfonic acid, allyl toluene sulfonic acid, Vinyltoluenesulfonic acid, styrenesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2-hydroxyethyl (meth) Anionic unsaturated monomers such as acryloyl phosphate and salts thereof; mercaptan group-containing unsaturated monomers; phenolic hydroxyl group-containing unsaturated monomers; (meth) acrylamide, N-ethyl (meth) acrylamide, N Amide group-containing unsaturated monomer such as N, N-dimethyl (meth) acrylamide; N, N-dimethyl Minoechiru (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) amino group-containing unsaturated monomer acrylamide. These monomers may be used singly or may be used in combination of two or more, but acrylic acid and / or a salt thereof (for example, sodium) from the viewpoint of performance and cost of the water-absorbing resin obtained. It is necessary to use a salt of lithium, potassium, ammonium, amines, etc., among which a sodium salt is preferable from the viewpoint of cost) as a main component. Preferably, acrylic acid and / or a salt thereof is 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, particularly preferably 95 mol%, based on all monomer components excluding the crosslinking agent. The upper limit is 100 mol%.

(Basic composition)
The water-absorbent resin obtained in the present invention is polyacrylic acid (salt) obtained by crosslinking and polymerizing acrylic acid (salt). In order to obtain the polyacrylic acid (salt), acrylic acid is contained in a basic composition. It is preferable to have a step of neutralization (neutralization step). In the present invention, the “basic composition” means a composition containing a basic compound.

  Examples of the basic compound include an alkali metal carbonate (hydrogen) salt, an alkali metal hydroxide, ammonia, an organic amine, and the like. In order to obtain a water-absorbing resin having higher physical properties, strong alkaline Substances, ie, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide are preferred, and sodium hydroxide is particularly preferred.

(Neutralization process)
The neutralization step of the present invention includes neutralization of acrylic acid as a monomer or neutralization (post-neutralization step) of a hydrogel crosslinked polymer obtained by crosslinking polymerization of acrylic acid. In either case, the neutralization step can be applied either continuously or batchwise, but is preferably continuous. As for the neutralization conditions such as preferable apparatus, basic composition, temperature condition, residence time, the contents disclosed in International Publication No. 2009/123197 and US Patent Application Publication No. 2008/0194863 are preferably applied.

  In addition, as a neutralization rate in this invention, 10-90 mol% is preferable with respect to the acid group in monomer aqueous solution, 40-85 mol% is more preferable, 50-80 mol% is still more preferable, 60 -75 mol% is particularly preferred. When the neutralization rate is less than 10 mol%, the water absorption capacity under no pressure (CRC) may be remarkably lowered. On the other hand, when the neutralization ratio exceeds 90 mol%, the water absorption capacity under pressure (AAP) is high. A water absorbent resin may not be obtained, which is not preferable. When neutralization is performed after polymerization, the same applies to the neutralization rate of the water-absorbent resin of the final product. In the present invention, the acrylate is a substantially monovalent salt, but may be neutralized as a polyvalent metal salt in a very small amount (for example, about 0 to 5 mol%).

(Internal crosslinking agent)
The internal cross-linking agent used in the present invention is a compound having two or more substituents capable of reacting with acrylic acid, and examples thereof include the cross-linking agent described in the 14th column of US Pat. No. 6,241,928. Of these, one or more are used. In consideration of the water-absorbing properties of the resulting water-absorbing resin, the compound having two or more polymerizable unsaturated groups, further a compound having thermal decomposability at the drying temperature described below, particularly (poly) alkylene glycol It is preferable to use di (meth) acrylate during the polymerization.

  Examples of the crosslinking agent include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and trimethylolpropane di. (Meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, N, N'-methylenebis (meth) acrylamide, isocyanuric Acid triallyl, trimethylolpropane di (meth) allyl ether, triallylamine, tetraallyloxyethane, glycerol propoxytria Compounds having two or more ethylenically unsaturated groups in one molecule such as relate; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, 1,4-butanediol, 1,5- Polyhydric alcohols such as pentanediol, 1,6-hexanediol, neopentyl alcohol, diethanolamine, tridiethanolamine, polypropylene glycol, polyvinyl alcohol, pentaerythritol, sorbit, sorbitan, glucose, mannitol, mannitan, sucrose, glucose; ethylene Polyglycidyl ethers such as glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether; Haloepoxy compounds such as lolohydrin and α-methylchlorohydrin; polyaldehydes such as glutaraldehyde and glyoxal; polyamines such as ethylenediamine; calcium hydroxide, calcium chloride, calcium carbonate, calcium oxide, magnesium borax chloride, magnesium oxide, and chloride Periodic table such as aluminum, zinc chloride and nickel chloride Group 2A, Group 3B, Group 8 metal hydroxides, halides, carbonates, oxides, borates such as borax, polyvalent metals such as aluminum isopropylate Compounds can be used, and one or more of these can be used in consideration of reactivity, but a compound having two or more ethylenically unsaturated groups in one molecule is used as a crosslinking agent. Is most preferred.

  The amount of the internal crosslinking agent used is preferably 0.005 to 2 mol%, more preferably 0.01 to 1 mol%, still more preferably 0.05 to 0.5 mol%, based on the monomer. By setting the amount of the internal cross-linking agent used within the above range, desired water absorption characteristics can be obtained.

  In the present invention, in addition to the method of crosslinking by adding an internal crosslinking agent before polymerization, a method of adding an internal crosslinking agent after polymerization or post-crosslinking after polymerization, a method of radical crosslinking with a radical polymerization initiator, an electron Although a method of radiation cross-linking with a wire or the like can be adopted, a method in which a predetermined amount of an internal cross-linking agent is previously added to the monomer for polymerization and a cross-linking reaction at the same time as the polymerization is more preferable.

(Other substances added to monomers)
In the present invention, the following substances may be added in addition to the substances described above when preparing the monomer aqueous solution. Specifically, for the purpose of improving various properties of the water-absorbent resin, the water-soluble resin or the water-absorbent resin is preferably added in an amount of 0 to 50% by weight, more preferably 0 to 20% by weight. A foaming agent (for example, carbonate, azo compound, bubbles, etc.), surfactant, chelating agent, chain transfer agent, etc. is preferably added in an amount of 0 to 5% by weight, more preferably 0 to 1% by weight. it can. These substances may be added not only in the form of adding to the monomer aqueous solution, but also during the polymerization.

  The use of the water-soluble resin or water-absorbent resin gives a graft polymer or a water-absorbent resin composition (for example, starch-acrylic acid polymer, PVA-acrylic acid polymer, etc.). The water absorbent resin composition is also collectively referred to as a water absorbent resin in the present invention.

(Concentration of monomer component)
In this step, a monomer aqueous solution is prepared by mixing the above-described substances. At that time, the concentration of the monomer component in the aqueous monomer solution is not particularly limited, but is preferably 10 to 80% by mass from the viewpoint of the physical properties of the water-absorbent resin, more preferably 20 to 75% by mass, 30-70 mass% is still more preferable.

  In addition, when adopting aqueous solution polymerization or reverse phase suspension polymerization as a polymerization form, a solvent other than water can be used together as necessary, and in that case, the type of solvent used is particularly limited. is not.

  The “concentration of the monomer component” is a value obtained by the following formula, and the aqueous monomer solution does not include the graft component, the water-absorbing resin, and the hydrophobic solvent in the reverse phase suspension polymerization.

(Concentration of monomer component (mass%)) = (mass of monomer component) / (mass of monomer aqueous solution) × 100
(2-2) Polymerization step In this step, the acrylic acid (salt) monomer aqueous solution obtained in the monomer preparation step is polymerized to form a hydrogel crosslinked polymer (hereinafter referred to as "hydrogel"). ).

(Polymerization initiator)
The polymerization initiator used in the present invention is not particularly limited because it is appropriately selected depending on the polymerization form and the like. For example, the thermal decomposition type polymerization initiator, the photodecomposition type polymerization initiator or the decomposition of these polymerization initiators is used. Examples thereof include a redox polymerization initiator combined with a promoting reducing agent. Specifically, one or more of the polymerization initiators exemplified in the fifth column of US Pat. No. 7,265,190 are used. From the viewpoint of ease of handling and physical properties of the water-absorbent resin, it is preferable to use a peroxide or an azo compound, further a peroxide, particularly a persulfate.

  Usually, the polymerization is carried out under normal pressure for ease of apparatus and operation, but it is also a preferred embodiment to carry out under reduced pressure to lower the boiling temperature of the polymerization system.

  There is no restriction | limiting in particular as a polymerization initiator used by this invention, According to the kind of polymerization monomer, superposition | polymerization conditions, etc., it selects from 1 type, or 2 or more types from what is utilized in normal water-absorbing-resin manufacture. Can be used. For example, a pyrolytic initiator (for example, persulfate: sodium persulfate, potassium persulfate, ammonium persulfate; peroxide: hydrogen peroxide, t-butyl peroxide, methyl ethyl ketone peroxide; azo compound: azonitrile compound, Azoamidine compounds, cyclic azoamidine compounds, azoamide compounds, alkylazo compounds, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride And photodegradable initiators (for example, benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, azo compounds) and the like. Persulfate is preferred because of its cost and ability to reduce residual monomer. In addition, 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 bisulfite, L-ascorbic acid (salt), reducing metal (salt) such as ferrous salt, amines, and the like. Although it is mentioned, it is not particularly limited. When an oxidative polymerization initiator and a reducing agent are used like a redox initiator, each may be merged with the monomer solution by the method of the present invention, or the reducing agent may be mixed with the monomer solution in advance. . More preferably, a photodegradable initiator and a thermal decomposable initiator are used in combination.

  0.001-1 mol% is preferable with respect to a monomer, and, as for the usage-amount of the said polymerization initiator, 0.001-0.5 mol% is more preferable. Moreover, the usage-amount of the said reducing agent has preferable 0.0001-0.02 mol% with respect to a monomer.

  Further, instead of the polymerization initiator, active energy rays such as radiation, electron beam, and ultraviolet rays may be irradiated to carry out the polymerization reaction, and these active energy rays and the polymerization initiator may be used in combination.

(Polymerization method)
The polymerization method applied in the present invention is not particularly limited, but from the viewpoint of water absorption characteristics and ease of polymerization control, spray droplet polymerization, aqueous solution polymerization, and reverse phase suspension polymerization are preferred, and aqueous solution polymerization and reverse phase suspension are preferred. Polymerization is more preferable, and aqueous solution polymerization is still more preferable. Among them, continuous aqueous solution polymerization is particularly preferable, and either continuous belt polymerization or continuous kneader polymerization may be used.

  As specific polymerization forms, continuous belt polymerization is disclosed in U.S. Pat. Nos. 4,893,999 and 6,241,928 and U.S. Patent Application Publication No. 2005/215734, and continuous kneader polymerization is disclosed in U.S. Pat. Nos. 6,987,151 and 6,710,141. , Respectively. By adopting such continuous aqueous solution polymerization, the production efficiency of the water-absorbent resin is improved.

  Moreover, high temperature initiation polymerization and high concentration polymerization are mentioned as a preferable example of the said continuous aqueous solution polymerization. “High temperature initiation polymerization” means that the temperature of the aqueous monomer solution is preferably 30 ° C. or higher, more preferably 35 ° C. or higher, still more preferably 40 ° C. or higher, particularly preferably 50 ° C. or higher (the upper limit is the boiling point). “High concentration polymerization” means that the monomer concentration is preferably 30% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, and particularly preferably 45% by mass. This refers to a polymerization method in which polymerization is carried out at the above (upper limit is a saturated concentration). These polymerization methods can also be used in combination.

  In addition, you may raise solid content concentration during superposition | polymerization by said polymerization method. As an indicator of such an increase in the solid content concentration, the solid content increase degree is defined by the following equation.

(Solid content rise (mass%)) = (Solid content concentration of polymer gel after polymerization (mass%))-(Solid content concentration of monomer aqueous solution (mass%))
However, the solid content concentration of the monomer aqueous solution is a value obtained by the following formula, and the components in the polymerization system include the monomer aqueous solution, the graft component, the water-absorbing resin, and other solids (for example, water-insoluble fine particles, etc. And does not include the hydrophobic solvent in reverse phase suspension polymerization.

(Solid content of monomer aqueous solution (mass%)) = (mass of (monomer component + graft component + water absorbent resin + other solids)) / (mass of components in polymerization system) × 100
A preferable solid content increase degree is 1 mass% or more, More preferably, it is 2 mass% or more.

  Furthermore, although these polymerization methods can be carried out in an air atmosphere, it is preferred to carry out in an inert gas atmosphere such as nitrogen or argon from the viewpoint of color tone. In this case, for example, the oxygen concentration is preferably controlled to 1% by volume or less. Moreover, it can also be set as foaming polymerization which superpose | polymerizes by disperse | distributing a bubble (especially said inert gas etc.) to monomer aqueous solution. In addition, it is preferable that the dissolved oxygen in the monomer or the monomer aqueous solution is sufficiently substituted with an inert gas (for example, less than 1 dissolved oxygen (mg / l)).

(2-3) Gel crushing step (gel crushing step)
In this step, the water-containing gel obtained in the above polymerization step is subjected to gel pulverization with a gel pulverizer such as a kneader, meat chopper, cutter mill, etc. to form a particulate water-containing gel (hereinafter referred to as “particulate water-containing gel”). It is the process of obtaining. In addition, when the said superposition | polymerization process is kneader polymerization, the superposition | polymerization process and the gel grinding | pulverization process are implemented simultaneously.

  Although it does not specifically limit in the gel grinding | pulverization process of this invention, The gel grinding | pulverization method disclosed by the international publication 2011/126079 pamphlet is applied preferably.

(2-4) Drying step This step is a step of obtaining a dry polymer by drying the particulate hydrogel obtained in the polymerization step and / or the gel grinding step to a desired resin solid content. In addition, the said resin solid content is calculated | required from drying loss (mass change at the time of heating the water-absorbing resin 1.0g for 3 hours at 180 degreeC), 80 mass% or more is preferable, 85-99 mass% is more preferable, 90-98 mass% is still more preferable, and 92-97 mass% is especially preferable.

  In the drying step of the present invention, although not particularly limited, for example, heat drying, hot air drying, vacuum drying, fluidized bed drying, infrared drying, microwave drying, drum dryer drying, drying by azeotropic dehydration with a hydrophobic organic solvent, Various drying methods such as high-humidity drying using high-temperature steam are applied.

  Among the above drying methods, hot air drying is preferable because of high efficiency, and band drying in which hot air drying is performed on a belt is particularly preferable. The hot air temperature is preferably from 100 to 250 ° C, more preferably from 120 to 220 ° C, from the viewpoint of color tone and efficiency. In addition, when performing band drying, as other conditions, for example, International Publication No. 2006/100300 Pamphlet, International Publication No. 2011/025012 Pamphlet, International Publication No. 2011/025013 Pamphlet, International Publication No. 2011-111657 Pamphlet, etc. Reference is made to the conditions described in.

  By setting the above-described drying temperature and drying time within the above ranges, the water absorption capacity (CRC), water-soluble component (Ext), and color tone of the resulting water-absorbent resin are set within a desired range (see [3] below). be able to.

(2-5) Grinding step, classification step In this step, the dried polymer obtained in the drying step is pulverized (pulverization step), adjusted to a predetermined particle size (classification step), and water-absorbing resin powder ( This is a step of obtaining a powdery water-absorbing resin before surface cross-linking for the sake of convenience as “water-absorbing resin powder”.

  As a device used in the pulverization process of the present invention, a roll mill is essential, but other devices that can be used in combination include, for example, a high-speed rotary pulverizer such as a hammer mill, a screw mill, and a pin mill, a vibration mill, and a knuckle type pulverizer. Machine, cylindrical mixer and the like.

  In addition, the particle size adjustment method in the classification step of the present invention is not particularly limited, and examples thereof include sieve classification using JIS standard sieve (JIS Z8801-1 (2000)), airflow classification, and the like. The particle size adjustment of the water-absorbent resin is not limited to the above pulverization step and classification step, but a polymerization step (especially reverse phase suspension polymerization or spray droplet polymerization) or other steps (for example, granulation step, fine powder recovery step). Therefore, it can be implemented as appropriate.

  As for the particle size of the water absorbent resin powder in the present invention, the mass average particle diameter (D50) is preferably 200 to 700 μm, more preferably 250 to 600 μm, further preferably 250 to 500 μm, and particularly preferably 300 to 450 μm. The proportion of particles having a particle size of less than 300 μm is preferably more than 20% by mass, more preferably more than 30% by mass, still more preferably more than 40% by mass, and the proportion of particles having a particle size of 850 μm or more is 0. -20 mass% is preferable, 0-15 mass% is more preferable, and 0-10 mass% is still more preferable.

  Furthermore, the logarithmic standard deviation (σζ) of the particle size distribution is preferably 0.20 to 0.50, more preferably 0.25 to 0.40, and still more preferably 0.27 to 0.35. In addition, these particle sizes are measured using a standard sieve according to the measurement methods disclosed in International Publication No. 2004/69915 and EDANA ERT420.2-02.

  The particle size described above applies not only to the water-absorbing resin after surface cross-linking (hereinafter sometimes referred to as “water-absorbing resin particles” for convenience) but also to the water-absorbing agent as the final product. Therefore, it is preferable that the water-absorbent resin particles are subjected to surface cross-linking treatment so as to maintain the particle size in the above range.

(2-6) Surface cross-linking step This step is a step of providing a portion having a higher cross-linking density in the surface layer of the water-absorbent resin powder obtained through the above-described steps (portion of several tens of micrometers from the surface of the water-absorbent resin powder). It comprises a mixing step of mixing the water-absorbent resin powder and the surface cross-linking agent solution to obtain a mixture, a heat treatment step for heat-treating the mixture, and a cooling step for cooling if necessary.

  In the surface cross-linking step, a water-absorbing resin (water-absorbing agent) surface-crosslinked by radical cross-linking or surface polymerization on the surface of the water-absorbing resin powder, a cross-linking reaction with a surface cross-linking agent, or the like is obtained.

(Surface cross-linking agent)
Although it does not specifically limit as a surface crosslinking agent which can be used by this invention, For example, various organic or inorganic surface crosslinking agents are mentioned, Among these, from a viewpoint of the physical property of a water absorbing resin, and the handleability of a surface crosslinking agent. An organic surface crosslinking agent that reacts with a carboxyl group to form a covalent bond is preferred. More specifically, one or more surface cross-linking agents described in the ninth and tenth columns of US Pat. No. 7,183,456, and optionally a hydrophilic organic solvent can be applied to the present invention. 0.01-10 mass parts is preferable with respect to 100 mass parts of water absorbent resin powder, and, as for the usage-amount of a total surface crosslinking agent, 0.01-5 mass parts is more preferable. Moreover, it is preferable to use water when adding the surface cross-linking agent, and the surface cross-linking agent is preferably added as an aqueous solution. 0.1-20 mass parts is preferable with respect to 100 mass parts of water absorbent resin powder, and, as for the usage-amount of water, 0.5-10 mass parts is more preferable. If necessary, the amount used when a hydrophilic organic solvent is used is preferably within 10 parts by mass, more preferably within 5 parts by mass with respect to 100 parts by mass of the water-absorbent resin powder. In addition to the above surface cross-linking agent (aqueous solution), the additives used in the “rehumidification step” described later are each mixed with the surface cross-linking agent (aqueous solution) within 5 parts by mass, or added separately during this step. May be.

  The surface cross-linking agent constituting the liquid (B) has a plurality of functional groups capable of reacting with two or more carboxyl groups in the water-absorbent resin (A) in one molecule, and a covalent bond is formed by a cross-linking reaction. The compound is not particularly limited as long as it is a compound. Specific examples of the surface crosslinking agent include ethylene glycol, propylene glycol, glycerin, pentaerythritol, sorbitol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,3- Butanediol, 1,4-butanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 1,6-hexanediol, 2,5-hexane Polyhydric alcohols such as diol and trimethylolpropane, polyamines such as diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine and triethylenetetramine, ethylene glycol diglycidyl ether Polyglycol compounds such as polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 2,4-tolylene diisocyanate, Ethylene carbonate (1,3-dioxolan-2-one), propylene carbonate (4-methyl-1,3-dioxolan-2-one), 4,5-dimethyl-1,3-dioxolan-2-one, (poly , Di- or mono) 2-oxazolidinone, epichlorohydrin, epibromohydrin, diglycol silicate, 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) Ropioneto] polyvalent aziridine compounds such like, but not limited to these compounds.

  Moreover, these surface crosslinking agents may use only 1 type, and may use 2 or more types together. Among them, at least one kind is a surface cross-linking agent selected from polyhydric alcohol, polyvalent glycidyl compound, 1,3-dioxolan-2-one, poly-2-oxazolidinone, bis-2-oxazolidinone, and mono-2-oxazolidinone. And at least one kind is more preferably a surface cross-linking agent containing a polyhydric alcohol.

  When mixing the water absorbent resin (A) and the surface cross-linking agent, it is preferable to use water as a solvent, and the liquid (B) is preferably a surface cross-linking agent aqueous solution. The amount of water used depends on the type and particle size of the water-absorbent resin (A), but is more than 0 and preferably 20 parts by mass or less with respect to 100 parts by mass of the water-absorbent resin (A) solid content. A range of 0.5 to 10 parts by mass is more preferable. Moreover, when mixing a water absorbing resin (A) and a surface crosslinking agent, you may use a hydrophilic organic solvent as a solvent as needed. Specific examples of the hydrophilic organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol; acetone and the like Ketones; ethers such as dioxane, tetrahydrofuran and alkoxy polyethylene glycol; amides such as N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide, and the like. The amount of the hydrophilic organic solvent used is preferably 20 parts by mass or less, more preferably 100 parts by mass based on the solid content of the water absorbent resin (A), although it depends on the type and particle size of the water absorbent resin (A). Is 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, and particularly preferably 0 to 1 part by mass. However, in the present invention, since the mixing property is excellent, uniform mixing can be achieved without using a hydrophilic solvent.

(Mixing process)
The method for adding and mixing the surface cross-linking agent solution in the surface cross-linking step of the present invention is not particularly limited, but after preparing the surface cross-linking agent and water as a solvent, a hydrophilic organic solvent or a mixture thereof in advance, the water-absorbing resin The powder is preferably added by spraying or dropping and mixed, more preferably added by spraying and mixing.

  The mixing device used for mixing the surface cross-linking agent solution and the water-absorbent resin powder is not particularly limited, but preferably a high-speed stirring type mixer, more preferably a high-speed stirring type continuous mixer.

(Heat treatment process)
The water-absorbent resin powder to which the above-described surface cross-linking agent solution has been added and mixed is subjected to heat treatment, and then subjected to cooling treatment as necessary. A known dryer can be used for heating, but a paddle dryer is preferable. The heating temperature is preferably 80 to 250 ° C, more preferably 100 to 220 ° C.

(2-7) Rehumidification step This step is performed by adding the following polyvalent metal salt compound, polycationic polymer, chelating agent, inorganic reducing agent, hydroxycarboxylic acid compound to the water absorbent resin particles obtained in the surface cross-linking step. A step of adding at least one additive selected from the group consisting of:

  The above-mentioned additive is preferably added as an aqueous solution or slurry, and therefore the water-absorbent resin is again swollen with water, so this step is referred to as a “rehumidification step”. In addition, you may add and mix the said additive simultaneously with the surface crosslinking agent solution mentioned above. Preferably, the moisture content described later is controlled, particularly the moisture content is 2 to 9% by mass.

(Polyvalent metal salt and / or cationic polymer)
In the present invention, a polyvalent metal salt and / or a cationic polymer may be added from the viewpoint of improving the water absorption rate (Vortex), liquid permeability (SFC), fluidity at the time of moisture absorption, etc. preferable.

  Specifically, the polyvalent metal salt and / or cationic polymer described in “[6] Polyvalent metal salt and / or cationic polymer” of International Patent Publication No. 2011/040530 pamphlet, and the amount used thereof are Applies to the invention.

(Chelating agent)
In the present invention, a chelating agent can be further added from the viewpoint of preventing coloring and deterioration of the resulting water-absorbent resin.

  As said chelating agent, the chelating agent described in "[2] chelating agent" of the international patent publication 2011/040530 pamphlet, for example, and its usage-amount are applicable to this invention.

(Inorganic reducing agent)
In the present invention, an inorganic reducing agent can be further added from the viewpoint of preventing coloring and deterioration of the resulting water-absorbent resin and reducing the residual monomer.

  As the inorganic reducing agent, for example, the inorganic reducing agent described in “[3] Inorganic reducing agent” in International Patent Publication No. 2011/040530, and the amount used thereof can be applied to the present invention.

(Α-hydroxycarboxylic acid compound)
In the present invention, an α-hydroxycarboxylic acid compound can be further added from the viewpoint of preventing coloring of the resulting water-absorbent resin. The “α-hydroxycarboxylic acid compound” is a carboxylic acid having a hydroxyl group in the molecule or a salt thereof, and is a hydroxycarboxylic acid having a hydroxyl group at the α-position.

  Examples of the α-hydroxycarboxylic acid compound include the α-hydroxycarboxylic acid compound described in “[6] α-hydroxycarboxylic acid compound” of International Patent Publication No. 2011/040530 pamphlet, and the use amount thereof. Applicable to.

(2-8) Addition process of other additives Additives other than the additives described above can be added to impart various functions to the water-absorbing agent. For example, a surfactant, a compound having a phosphorus atom, an oxidizing agent, an organic reducing agent, water-insoluble inorganic fine particles described in “(5) Water-insoluble inorganic fine particles” of International Patent Publication No. 2011/040530, metal soap, etc. Organic powder, deodorant, antibacterial agent, pulp, thermoplastic fiber and the like. In addition, the surfactant disclosed in International Publication No. 2005/077500 is preferably applied as the surfactant.

  The amount of these additives used is appropriately determined according to the application and is not particularly limited, but is preferably 0 to 3% by mass, more preferably 0 to 1% by mass based on the water-absorbing agent. .

(2-9) Other steps In addition to the steps described above, a granulation step, a sizing step, a fine powder removal step, a fine powder reuse step, and the like can be provided as necessary. Moreover, you may further include 1 type, or 2 or more types of processes, such as a transport process, a storage process, a packing process, and a storage process. Here, the sizing process includes a fine powder removing process after the surface cross-linking process and a process of classifying and crushing when the water-absorbing resin aggregates and exceeds a desired size. Further, the fine powder recycling step includes a step of adding the fine powder as it is or making it into a large hydrogel in the fine powder granulation step and adding it in any step of the production process of the water absorbent resin.

[3] Physical properties of the water-absorbing agent The water-absorbing agent of the present invention is preferably used in a fragrance, a deodorant, a disinfectant, etc., which functions by gradually releasing the agent into the air, and volatilizes chlorine dioxide. The use of a disinfectant is more preferable, and the use of a drug solution and a water absorbing agent immediately before use is particularly preferable.

  Hereinafter, the physical properties of the water absorbent resin will be described. In addition, the following physical property is prescribed | regulated based on the method as described in an Example unless there is particular notice.

(3-1) Absorption amount of drug solution A suitable absorption amount of drug solution can be determined by a balance between the amount of drug solution used as a sustained release agent and the amount of water-absorbing resin. However, if the drug solution absorption is low, (a) use a large amount of water-absorbing resin for a certain amount of drug solution, or use a high-concentration drug solution to reduce the amount of water-absorbing resin used There is a need to. In the case of (a), the water-absorbent resin that has absorbed the drug solution becomes a gel while swelling, causing a so-called gel blocking phenomenon that inhibits the movement of the unabsorbed drug solution and takes a long time to absorb the drug solution. There is a thing. In the case of (b), as a result of an increase in the drug concentration, the volatilization amount of the drug increases, and the drug concentration in the atmosphere may increase more than necessary.

  Usually, the drug solution absorption amount may be 25 (g / g) or more, preferably 30 (g / g) or more, and more preferably 35 (g / g) or more. Although an upper limit is not specifically limited, 90 (g / g) or less is preferable, 75 (g / g) or less is more preferable, 65 (g / g) or less is still more preferable. A water-absorbing resin having a drug solution water absorption amount exceeding 90 (g / g) is not preferable because the gel that has absorbed the drug solution tends to be soft and causes the gel blocking phenomenon described above.

(3-2) Drug solution absorption rate The drug solution absorption rate of the water absorbent resin of the present invention is preferably 0.18 (g / g / s) or more, more preferably 0.20 (g / g / s) or more. 0.22 (g / g / s) or more is more preferable, and 0.25 (g / g / s) or more is particularly preferable. Although an upper limit is not specifically limited, 5.0 (g / g / s) or less is preferable and 3.0 (g / g / s) or less is more preferable.

  If the drug solution absorption rate is less than 0.18 (g / g / s), the amount of radiation immediately after the start of use may be more than necessary, and there is a high risk of drug solution leakage due to overturning of the container, It is not preferable.

(3-3) Particle size The water-absorbent resin obtained by the production method according to the present invention is preferably in the form of particles, and if it is indefinite, the above-mentioned chemical solution absorption rate is more preferred. As for the particle size of the water-absorbent resin of the present invention, the mass average particle size (D50) is preferably 200 to 700 μm, more preferably 250 to 600 μm, still more preferably 250 to 500 μm, and particularly preferably 300 to 450 μm. The proportion of particles having a particle size of less than 300 μm is preferably more than 20% by mass, more preferably more than 30% by mass, still more preferably more than 40% by mass, and the proportion of particles having a particle size of 850 μm or more is 0. -20 mass% is preferable, 0-15 mass% is more preferable, and 0-10 mass% is still more preferable.

(3-4) Exposed Area Evaluation Method The exposed area evaluation of the water absorbent resin of the present invention is preferably 10% or more, more preferably 15% or more, and further preferably 20% or more. If the evaluation is too high, there is a high possibility that a water-absorbing agent that is not functioning effectively is contained. Therefore, it is preferably 50% or less, and more preferably 40% or less.

(3-5) Whitening index The whitening index of the water absorbent resin of the present invention is preferably 1 or more, more preferably 2 or more, and still more preferably 3 or more. When the whitening index is 0, the amount of emission after storage may be small, and it is not suitable for use for performing the intended function.

[4] Sustained release agent The sustained release agent of the present invention is preferably a type in which a drug solution and a water-absorbent resin are mixed in advance, and is preferably used as a disinfectant using a drug solution that volatilizes chlorine dioxide as a main drug.

  As the chemical solution, an aqueous solution containing chlorine dioxide and / or chlorite is preferable, and an aqueous solution containing chlorine dioxide and chlorite is preferable. Further, when citric acid or the like is contained, a buffering action with chlorite occurs, which is particularly preferable. Specific examples thereof include a pure chlorine dioxide solution disclosed in JP-A-11-278808. Moreover, sodium dihydrogen phosphate and / or disodium hydrogen phosphate may be included as a pH adjuster, and specific examples thereof include pure water chlorine dioxide solution described in JP2013-075820A.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail according to an Example and a comparative example, this invention is limited to these Examples and is not interpreted. Unless otherwise specified, the water-absorbing resin powder, water-absorbing resin particles, water-absorbing agent composition and absorbent article obtained in the present invention are measured under conditions of an air temperature of 25 ° C. ± 2 ° C. and a relative humidity of 50% RH. did.

(Evaluation method of water-absorbing agent)
[Adjustment of test solution (drug solution)]
The test solution was obtained by adding 2.42 parts by mass of sodium chlorite (manufactured by Kanto Chemical Co., Ltd.) and 0.325 parts by mass of anhydrous sodium dihydrogen phosphate (Wako Pure Chemical Industries, Ltd.) to 97.255 parts by mass of ion-exchanged water. It was created by dissolving.

[Granularity]
The particle size of the water-absorbent resin according to the present invention was measured according to the measurement method disclosed in European Patent 0349240.

  That is, using a JIS standard sieve (JIS Z8801-1 (2000)) having an opening of 850 μm, 500 μm, 300 μm, 212 μm, and 150 μm or a corresponding sieve, 10 g of the particulate water-absorbing agent was classified and remained on each sieve. The masses of the water absorbent resin and the water absorbent resin that passed through the entire sieve were measured.

[Drug absorption]
After 0.20 g of the water-absorbent resin was uniformly put in a non-woven bag (120 × 180 mm) and heat-sealed, the temperature was adjusted to 25 ± 3 ° C. and immersed in 2 L of the test liquid. After 30 minutes, the bag was pulled up and suspended for 10 minutes for draining. Thereafter, the bag mass W9 [g] was measured. The same operation was performed without putting the absorber, and the mass W10 [g] of the bag at that time was measured. The absolute absorption amount (g) of the absorber was calculated according to the following equation 1. (Equation 1) Absorption amount = W9−W10
[Drug absorption rate]
1.00 g of water-absorbing resin was put in a 25 ml glass beaker (diameter 32 to 34 mm, height 50 mm). At this time, the upper surface of the water-absorbent resin placed in the beaker was made to be horizontal (if necessary, the surface of the water-absorbent resin may be made horizontal by carefully striking the beaker or the like).

  Next, 24 g of the test liquid adjusted to 23 ° C. ± 0.2 ° C. was weighed into a 50 ml glass beaker, and the total weight (mass W4 [g]) of the test liquid and the glass beaker was measured. The test solution weighed out was carefully and quickly poured into a 25 ml beaker containing a water absorbent resin. The time measurement was started at the same time as the poured test liquid contacted the water-absorbent resin. When the upper surface of the test liquid in the beaker into which the test liquid is poured is visually observed at an angle of about 20 °, the upper surface that was the surface of the test liquid first absorbs the test liquid by the water absorbent resin absorbing the test liquid. When the surface of the water-absorbent resin was replaced, the time measurement was completed (time ts [seconds]).

  Next, the weight (mass W5 [g]) of the 50 ml glass beaker after pouring the test liquid was measured. The weight (mass W6 [g]) of the poured test solution was determined from the following formula 2, and the absorption rate was calculated from the following formula 3.

(Formula 2) W6 [g] = W4-W5
(Formula 3) Water absorption rate [g / g / s] = W6 / (ts × mass of water absorbent resin [g])
[Whitening index]
After 10 minutes have passed since the start of the measurement of the water absorption rate, the water-absorbent resin was visually observed from directly above the 25 ml beaker after absorbing the test liquid, and the total area of the water-absorbent resin after absorption (area of 32 to 34 mm in diameter) On the other hand, the area ratio of the portion where the water-absorbent resin after absorbing the liquid appears white was determined in four steps as follows.

Whitening index 1: No area ratio of the portion that appears white Whitening index 2: Area ratio of the portion that appears white is greater than 0% and less than 33% (one third of the total) Whitening index 3 : The area ratio of the part that appears white is 33% (1/3 of the whole) or more and less than 66% (2/3 of the whole). Whitening index 4: Area ratio of the part that appears white Is more than 66% (1/3 of the total) of the total area [Exposure area evaluation method]
Water-absorbing resin 0.500 g was put in a test tube (inner diameter 14 mm, height 125 mm, thickness 1 mm). Next, the test liquid (25 ° C. ± 2 ° C.) was quickly poured into the 8.50 g test tube. 10 minutes after the test solution is poured, the height (height H1 (unit: mm)) from the bottom surface of the test tube to the upper surface replaced with the absorbed water absorbent resin surface, and the water absorbent resin after absorbing the liquid are The height of the portion that looks white (height H2 (unit: mm)) was measured. The inter-gel particle interstitial liquid retention ability was determined by the following formula 4.

(Formula 4) Interstitial fluid retention capacity between gel particles [%] = H2 / H1 × 100
[Production Example 1]
7.5 g of polyethylene glycol diacrylate (average added mole number of ethylene oxide 9) was dissolved in 5500 g of an aqueous solution of sodium acrylate having a neutralization rate of 75 mol% (monomer concentration: 38 mass%) to obtain a reaction solution [a001]. It was. Next, this reaction solution [a001] was degassed under a nitrogen gas atmosphere for 30 minutes, and then a reaction was formed by attaching a lid to a double-arm jacketed stainless steel kneader having two sigma type blades with an internal volume of 10 L. The reactor was supplied with the above reaction solution, and nitrogen gas was blown into the reactor while maintaining the reaction solution temperature at 30 ° C., and nitrogen substitution was performed so that the dissolved oxygen in the system was 1 ppm or less.

  Subsequently, 29.8 g of a 10% by weight aqueous solution of sodium persulfate and 21.8 g of a 0.2% by weight aqueous solution of L-ascorbic acid were added while stirring the reaction solution, and polymerization started about 1 minute later. A polymerization peak temperature of 86 ° C. was exhibited 17 minutes after the start of polymerization, and a hydrogel polymer [b001] was taken out 60 minutes after the start of polymerization.

  The obtained hydrogel polymer [b001] was subdivided into particles of about 1 to 5 mm. The finely divided hydrogel polymer [b001] was spread on a 50 mesh (mesh size 300 μm) wire net and dried in hot air at 180 ° C. for 45 minutes to obtain a dried product [b011].

  Next, the dried product [b011] was pulverized with a roll mill, and further classified continuously with a wire mesh having openings of 450 μm and 106 μm. Particles of 450 μm or more were pulverized again with a roll mill. The particles that passed through the 106 μm wire mesh accounted for 13% by mass with respect to the total amount of pulverization. The water-absorbent resin fine particles that passed through the 106 μm wire mesh were mixed with the same amount of water heated to 90 ° C., dried again under the same conditions, and pulverized to obtain irregularly crushed water-absorbent resin particles [A010]. . The CRC (water absorption capacity under no pressure) of the water absorbent resin powder [A010] was 47.6 [g / g].

  Next, 100 parts by mass of the obtained water-absorbent resin particles [A010], 0.03 part by mass of ethylene glycol diglycidyl ether, 0.3 part by mass of 1,4-butanediol, 0.5 part by mass of propylene glycol, and water A surface crosslinking agent aqueous solution [c001] consisting of 2.5 parts by mass was mixed with 3.33 parts by mass. The above mixture was heat-treated in a mortar mixer heated to 175 ° C. for 40 minutes to obtain a water absorbent resin [A110].

  Particulate water-absorbing agent [A111] was obtained by adding 0.3 part by weight of fumed silica AEROSIL200 manufactured by Nippon Aerosil Co. to 100 parts by weight of water-absorbing resin powder [A110] and mixing them uniformly.

[Production Example 2]
The amount of polyethylene glycol diacrylate (average added mole number 9 of ethylene oxide) described in Production Example 1 was changed to 7.5 g to 2.8 g to obtain a reaction solution [a002], and the dried product was obtained in the same manner as in Production Example 1. [B012] was obtained.

  Next, the dried product [b012] was pulverized with a roll mill, and further classified continuously with a metal mesh having openings of 600 μm and 106 μm. Particles of 600 μm or more were pulverized again with a roll mill to obtain amorphous crushed water-absorbent resin particles [A020]. The CRC (water absorption capacity under no pressure) of the water absorbent resin powder [A020] was 51.6 [g / g].

  Next, 100 parts by mass of the obtained water-absorbent resin particles [A020], 0.03 parts by mass of ethylene glycol diglycidyl ether, 0.3 parts by mass of 1,4-butanediol, 0.5 parts by mass of propylene glycol, and water A surface crosslinking agent aqueous solution [c002] consisting of 2.5 parts by mass was mixed with 3.33 parts by mass. The above mixture was heat-treated in a mortar mixer heated to 165 ° C. for 60 minutes to obtain a water absorbent resin [A220].

  Particulate water-absorbing agent [A221] was obtained by adding 0.3 part by weight of fumed silica AEROSIL200 manufactured by Nippon Aerosil Co., Ltd. to 100 parts by weight of water-absorbing resin powder [A220] and mixing them uniformly.

[Production Example 3]
7.5 g of polyethylene glycol diacrylate described in Production Example 1 (average number of moles of added ethylene oxide 9) was changed to 3.5 g of trimethylolpropane triacrylate (molecular weight 296) to obtain a reaction solution [a003]. In the same manner as in the method, a dried product [b013] was obtained.

  Next, the dried product [b013] was pulverized with a roll mill, and further continuously classified with a wire mesh having openings of 1400 μm and 75 μm. The particles of 1400 μm or more were pulverized again with a roll mill to obtain irregularly crushed water-absorbing resin particles [A030]. The CRC of the water absorbent resin powder [A030] was 47.0 [g / g].

  Next, an aqueous surface cross-linking agent solution [c003] consisting of 0.5 parts by mass of glycerin, 0.5 parts by mass of isopropyl alcohol, and 2.5 parts by mass of water is added to 100 parts by mass of the obtained water absorbent resin particles [A030]. 5 parts by mass were mixed. The above mixture was heat-treated in a mortar mixer heated to 170 ° C. for 40 minutes to obtain a water absorbent resin [A330].

  Particulate water-absorbing agent [A331] was obtained by adding 0.2 part by weight of fumed silica AEROSIL200 manufactured by Nippon Aerosil Co., Ltd. to 100 parts by weight of water-absorbent resin powder [A330] and mixing the mixture uniformly.

[Production Example 4]
The amount of trimethylolpropane triacrylate (molecular weight 296) described in Production Example 3 is changed to 3.5 g to 3.2 g to obtain a reaction solution [a004], and the dried product [b014] is treated in the same manner as in Production Example 3. Obtained.

  Next, the dried product [b014] was pulverized with a roll mill, and further continuously classified with a wire mesh having openings of 710 μm and 106 μm. The particles having a particle size of 710 μm or more were pulverized again with a roll mill to obtain irregularly crushed water-absorbent resin particles [A040]. The CRC of the water absorbent resin powder [A040] was 48.3 [g / g].

  Next, an aqueous surface cross-linking agent solution [c004] consisting of 0.5 parts by mass of glycerin, 0.5 parts by mass of isopropyl alcohol and 2.5 parts by mass of water is added to 100 parts by mass of the obtained water-absorbing resin particles [A040]. 5 parts by mass were mixed. The above mixture was heat-treated for 40 minutes in a mortar mixer heated to 170 ° C. to obtain a water absorbent resin [A440].

  Particulate water-absorbing agent [A441] was obtained by adding 0.3 part by weight of fumed silica AEROSIL200 manufactured by Nippon Aerosil Co., Ltd. to 100 parts by weight of water-absorbing resin powder [A440] and mixing the mixture uniformly.

[Production Example 5]
The amount of polyethylene glycol diacrylate (average added mole number 9 of ethylene oxide) described in Production Example 1 was changed to 7.5 g to 4.4 g to obtain a reaction solution [a005], and a dry product was obtained in the same manner as in Production Example 1. [B015] was obtained.

  Next, the dried product [b015] was pulverized with a roll mill, and further continuously classified with a wire mesh having openings of 710 μm and 106 μm. The particles of 710 μm or more were pulverized again with a roll mill to obtain irregularly crushed water-absorbent resin particles [A050]. The CRC of the water absorbent resin powder [A050] was 41.7 [g / g].

  Next, 100 parts by mass of the obtained water-absorbent resin particles [A050], 0.03 parts by mass of ethylene glycol diglycidyl ether, 0.4 parts by mass of 1,4-butanediol, 0.4 parts by mass of propylene glycol, and water 2.83 parts by mass of a surface crosslinking agent aqueous solution [c005] consisting of 2.0 parts by mass was mixed. The above mixture was heat-treated in a mortar mixer heated to 200 ° C. for 40 minutes to obtain a water absorbent resin [A550].

  Particulate water-absorbing agent [A551] was obtained by adding 0.3 part by weight of fumed silica AEROSIL200 manufactured by Nippon Aerosil Co. to 100 parts by weight of water-absorbing resin powder [A550] and mixing them uniformly.

[Production Example 6]
A water absorbent resin [A660] was obtained in the same manner as in Production Example 2 except that the mixture heat treatment temperature described in Production Example 2 was changed from 180 ° C to 195 ° C.

  Particulate water-absorbing agent [A661] was obtained by adding 0.3 part by weight of fumed silica AEROSIL200 manufactured by Nippon Aerosil Co., Ltd. to 100 parts by weight of water-absorbing resin powder [A660] and mixing them uniformly.

[Production Example 7]
The amount of polyethylene glycol diacrylate (average added mole number 9 of ethylene oxide) described in Production Example 1 was changed to 7.5 g to 2.2 g to obtain a reaction solution [a007], and the dried product was obtained in the same manner as in Production Example 1. [B017] was obtained.

  Next, the dried product [b017] was pulverized with a roll mill, and further continuously classified with a metal mesh having openings of 850 μm and 106 μm. The particles having a particle size of 850 μm or more were pulverized again with a roll mill to obtain irregularly crushed water-absorbent resin particles [A070]. The CRC of the water absorbent resin powder [A070] was 54.5 [g / g].

  Next, 100 parts by mass of the obtained water-absorbent resin particles [A070], 0.03 part by mass of ethylene glycol diglycidyl ether, 0.3 part by mass of 1,4-butanediol, 0.5 part by mass of propylene glycol, and water The surface crosslinking agent aqueous solution [c002] consisting of 2.8 parts by mass was mixed with 3.63 parts by mass. The above mixture was heat-treated in a mortar mixer heated to 195 ° C. for 40 minutes to obtain a water absorbent resin [A770].

  Particulate water-absorbing agent [A771] was obtained by adding 0.3 part by weight of fumed silica AEROSIL200 manufactured by Nippon Aerosil Co., Ltd. to 100 parts by weight of water-absorbing resin powder [A770] and mixing the mixture uniformly.

[Comparative Example 1]
Table 1 shows the physical properties of the particulate water-absorbing agent [A111] obtained in Production Example 1 as the water-absorbing agent 1.

[Comparative Example 2]
Table 1 shows the physical properties of the particulate water-absorbing agent [A221] obtained in Production Example 2 as the water-absorbing agent 2.

[Comparative Example 3]
Table 1 shows the physical properties of the particulate water-absorbing agent [A331] obtained in Production Example 3 as the water-absorbing agent 3.

[Comparative Example 4]
Table 1 shows the physical properties of the particulate water-absorbing agent [A441] obtained in Production Example 4 as the water-absorbing agent 4.

[Example 1]
Table 1 shows the physical properties of the particulate water-absorbing agent [A551] obtained in Production Example 5 as the comparative water-absorbing agent 1.

[Example 2]
Table 1 shows the physical properties of the particulate water-absorbing agent [A661] obtained in Production Example 6 as the water-absorbing agent 5.

[Comparative Example 5]
Table 1 shows the physical properties of the particulate water-absorbing agent [A771] obtained in Production Example 7 as the comparative water-absorbing agent 2.

  When Example 1 and Comparative Example 5 in Table 1 are compared, although Comparative Example 5 has a large amount of drug solution absorption, the exposed area evaluation is low. That is, it can be seen that the exposure area evaluation does not simply depend on the amount of absorption.

Claims (2)

  A sustained-release agent using a water-absorbing agent having an exposed surface area evaluation of 10% or more.   The water absorbing agent used for the sustained release agent according to claim 1.