WO2003059961A1 - Method of preventing coloration of water-absorbing resin - Google Patents

Method of preventing coloration of water-absorbing resin Download PDF

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Publication number
WO2003059961A1
WO2003059961A1 PCT/JP2002/013768 JP0213768W WO03059961A1 WO 2003059961 A1 WO2003059961 A1 WO 2003059961A1 JP 0213768 W JP0213768 W JP 0213768W WO 03059961 A1 WO03059961 A1 WO 03059961A1
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Prior art keywords
water
acid
absorbent resin
added
chelating agent
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PCT/JP2002/013768
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French (fr)
Japanese (ja)
Inventor
Masayoshi Handa
Naoyuki Hashimoto
Yasuhiro Nawata
Masato Fujikake
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Sumitomo Seika Chemicals Co., Ltd.
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Publication of WO2003059961A1 publication Critical patent/WO2003059961A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/17—Amines; Quaternary ammonium compounds
    • C08K5/175—Amines; Quaternary ammonium compounds containing COOH-groups; Esters or salts thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F6/00—Post-polymerisation treatments

Definitions

  • the present invention relates to a method for preventing coloring of a water-absorbent resin. More specifically, the present invention relates to a method for preventing discoloration of a water-absorbing resin which can be suitably used as a water-absorbing agent for absorbent articles of sanitary materials such as disposable diapers and sanitary napkins. Background art
  • Water-absorbent resins take advantage of the fact that they absorb water-based liquids, for example, body fluids such as human urine, blood, and sweat quickly and in large quantities, and do not release the liquid once absorbed under load. It is widely used as a water-absorbing agent for absorbent articles made of sanitary materials such as disposable diapers and sanitary napkins.
  • the conventional water-absorbent resin has a problem that, if left unattended, it tends to be colored yellow or brown due to external factors such as heat and humidity.
  • the water-absorbent resin in the absorbent article such as a disposable diaper or a sanitary napkin is colored, the commercial value as the absorbent article is significantly reduced. Therefore, it is required that the water-absorbent resin used in the absorbent article does not discolor even when left in a harsh environment of high temperature and high humidity such as in a warehouse in summer.
  • Examples of the water-absorbing resin having an anti-coloring effect include a super-water-absorbing polymer composition obtained by adding an organic phosphoric acid compound or a salt thereof to a super-water-absorbing polymer (JP-A-5-82651), acidic water A water-absorbing agent composition comprising a swellable cross-linked polymer, a basic water-swellable cross-linked polymer, a coloring inhibitor, a di- or anti-oxidant, and a di- or boron compound No. 0-230201), a water-absorbing agent composition comprising a water-absorbing resin and an organic carboxylic acid and Z or a salt thereof (Japanese Patent Application Laid-Open No. 2000-329792) Publication).
  • these compositions have not been able to exert a sufficiently satisfactory effect when left for a long time in a harsh environment of high temperature and high humidity.
  • An object of the present invention is to provide a method for preventing coloring of a water-absorbing resin, which can prevent coloring even when left under high temperature and high humidity for a long period of time.
  • An amino carboxylic acid-based metal chelating agent is added to at least one of the steps in the process for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer, or in the water-absorbent resin after the production.
  • An amino carboxylic acid-based metal chelating agent is used in at least one of the steps in the process for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer, or in the water-absorbent resin after the production.
  • a method of using an aminocarboxylic acid-based metal chelating agent for preventing coloring of the obtained water-absorbent resin characterized by adding
  • the method for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer is included in at least one of the processes or after the production of the water-absorbent resin.
  • the addition of an aminocarboxylic acid-based metal chelating agent has a feature in that coloring of the water-absorbing resin can be suppressed even under high temperature and high humidity.
  • aminocarboxylic acid-based metal chelating agent used in the present invention examples include: Mino diacetic acid, hydroxyethylimino diacetic acid, tri-tri-acetic acid, tri-tri-propionic acid, ethylenediamine tetra-acetic acid, dimethylene triamine penta-acetic acid, triethylene tetramine hexa-acetic acid, trans-l, 2-diaminocyclohexane Tetraacetic acid, N, N-bis (2-hydroxyethyl) glycine, diaminopropanol tetraacetic acid, ethylenediamine dipropionic acid, hydroxyethylenediamine triacetic acid, glyco-leterdiamine tetraacetic acid, diaminopropane tetraacetic acid, N , N, -bis (2-hydroxybenzyl) ethylenediamine mono-N, N-diacetic acid, 1,6-hexamethylenediamine-N,
  • diethylenetriamine pentaacetic acid triethylenetetramine hexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid and salts thereof are preferably used from the viewpoint of having a more effective coloring prevention effect.
  • the aminocarboxylic acid-based metal chelating agent may be added by A) a method of adding to an aqueous monomer solution containing an unsaturated carboxylic acid before polymerization, (mouth) a method of adding to an aqueous gel after polymerization, (c) a method of adding to a water-absorbing resin during drying (2) a method in which powder is mixed with the dried water-absorbent resin; and (e) a method in which the powder is added to the water-absorbent resin dispersed in an organic solvent and heated and desolvated, and the like.
  • the aminocarboxylic acid-based metal chelating agent in the water-absorbent resin or on the surface of the water-absorbent resin as simply as possible by a simple method.
  • a water-absorbing resin in which an aminocarboxylic acid-based metal chelating agent is uniformly dispersed in particular, (mouth) a method of adding to a hydrogel after polymerization, (c) a method of adding to a water-absorbing resin during drying, (2) A method of mixing the powder with the dried water-absorbent resin is preferable.
  • the form in which the aminocarboxylic acid-based metal chelating agent is added is not particularly limited, but in order to uniformly disperse the aminocarboxylic acid-based metal chelating agent in the water-absorbing resin, A form in which a liquid or powdery amino carboxylic acid-based metal chelating agent is dissolved in a hydrophilic solvent such as water is added, or a form in which a fine powdered amino carboxylic acid-based metal chelating agent is added in a powder state is preferable. .
  • the particle size of the finely powdered aminocarboxylic acid-based metal chelating agent is not particularly limited. The particle diameter is preferably 100 m or less.
  • the amount of the aminocarboxylic acid-based metal chelating agent used is such that a sufficient anti-coloring effect can be obtained, and an effect commensurate with the amount used can be obtained. 0.001 to 6 parts by weight, preferably 0.006 to 3 parts by weight, more preferably 0.01 to 2 parts by weight, based on 100 parts by weight of the unsaturated carboxylic acid as a body. preferable.
  • the aminocarboxylic acid-based metal chelate is added to at least one of the steps of the process for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer or to the water-absorbent resin after the production.
  • a method for using an aminocarboxylic acid-based metal chelating agent for preventing coloring of a resulting water-absorbent resin which is characterized by adding a single agent.
  • the water-absorbing resin containing the unsaturated monomeric ruponic acid as an essential monomer produced in the present invention includes a crosslinked product of an acrylate polymer and a crosslinked product of hydrolysis and decomposition of a starch monoacrylate graft copolymer.
  • the acid ester copolymer include a gent product. Among them, a crosslinked product of an acrylate polymer capable of absorbing a large amount of water and capable of retaining the absorbed water in the molecule even when a slight load is applied is preferable.
  • unsaturated ruponic acids examples include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid and the like. These may be used alone, 2 02 13768
  • the unsaturated carboxylic acid may be partially neutralized with an alkali metal or the like, and among them, acrylic acid, methacrylic acid and salts of these metals such as sodium and potassium are preferably used.
  • the unsaturated carboxylic acid may be copolymerized with another monomer.
  • Other monomers include, for example, (meth) acrylamide [r (meth) acryl J means “acryl J and“ methacryl ”. The same applies hereinafter), N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, etc.
  • Amino group-containing unsaturated monomers such as vinylsulfonic acid, styrenesulfonic acid, 2- (meth) acrylamide 2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, and salts thereof. Sulfonic acid monomers and the like can be mentioned.
  • the method for polymerizing the water-absorbent resin is not particularly limited, and typical production methods such as a reversed-phase suspension polymerization method and an aqueous solution polymerization method are used.
  • the reverse phase suspension polymerization method is illustrated below.
  • a monomer initiator is dispersed in an organic solvent in the presence of at least one of a surfactant and a polymer protective colloid. By using, polymerization is performed.
  • the concentration of the monomer in the aqueous monomer solution is preferably from 25% by weight to a saturated concentration.
  • the monomer aqueous solution may be added all at once, or may be added separately.
  • organic solvent examples include aliphatic hydrocarbon solvents such as n-pentane, n-hexane, n-heptane, and lignin; cyclopentane, methylcyclopentane, and cyclohexane.
  • Alicyclic hydrocarbon solvents such as hexane and methylcyclohexane; benzene, toluene
  • aromatic hydrocarbon solvents such as chidylene.
  • aromatic hydrocarbon solvents such as chidylene.
  • n-heptane and cyclohexane are preferably used.
  • the amount of the organic solvent to be used is preferably from 50 to 600 parts by weight, more preferably 100 to 600 parts by weight, based on the total amount of the monomers of 100 parts by weight, from the viewpoint of removing the heat of polymerization and easily controlling the polymerization temperature. ⁇ 550 parts by weight is more preferred.
  • surfactant examples include sorbitan fatty acid ester, mono-fatty acid glycerin ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene hydrogenated castor oil, lauric acid polyoxyethylene hydrogenated castor oil, and (tri) polyisoxtearate
  • nonionic surfactants such as tylene-hardened castor oil, polyoxetylene alkylphenyl ether, polyoxyethylene lauryl ether, and polyoxyethylene hexyldecyl ether.
  • polymer protective colloid examples include ethyl cellulose, hydroxyethyl cellulose, oxidized polyethylene, anhydrous maleated polyethylene, anhydrous maleated polybutadiene, anhydrous maleinated polyethylene propylene diene terpolymer, and the like.
  • the polymer protective colloid may be used as a mixture of two or more kinds.
  • the nonionic surfactant and the polymer or polymer protective colloid can be used in combination with an anionic surfactant.
  • anionic surfactant include a fatty acid salt, an alkyl benzene sulfonate, an alkyl methyl taurate, a polyoxyethylene alkyl phenyl ether sulfate, a polyoxyethylene alkyl ether sulfonate, and the like.
  • the amount of the surfactant and / or polymer protective colloid used is such that the aqueous monomer solution is sufficiently dispersed, an effect commensurate with the amount used is obtained, and the total amount of the monomer is 10 from the viewpoint of economy. 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight per 0 parts by weight 2/13768
  • the water-absorbent resin can be synthesized by a self-crosslinking type reaction without using a crosslinking agent.However, the water-absorbing resin is crosslinked by using an internal crosslinking agent having two or more polymerizable unsaturated groups or two or more reactive groups. You may.
  • Internal crosslinking agents include N, N'-methylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane (Meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropanedi (meth) aryl ether, triarylamine, etc., compounds having two or more ethylenic unsaturated groups in one molecule; (poly) ethyleneglycoldiglycidyl And polyglycidyl ethers such as ether and glycerin triglycidyl ether; and halogenated oxy compounds such as epichlorohydrin and moebhydrin. One or more of these can be used in consideration of the reactivity and water solubility in the polymerization system.However, a compound having two or more glycidyl groups in one molecule
  • the amount of the internal cross-linking agent used is determined based on the total amount of the above-mentioned monomers of 100 parts by weight, from the viewpoint that the obtained water-absorbent resin has appropriate cross-linking to suppress the water-soluble property and exhibit sufficient water absorption. 0.001 to 3 parts by weight, more preferably 0.003 to 1 part by weight, and even more preferably 0.05 to 0.5 part by weight.
  • polymerization initiator examples include persulfuric acid sodium, sodium persulfate, ammonium persulfate, benzoyl peroxide, hydrogen peroxide, 1,2-diazobis (cyclohexane-one-potency nitrile), 2, 2, —Azobis (2-methyl-butyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2-cyano-2-propylazoformamide And a radical polymerization initiator such as dimethyl 2,2′-azobis (2-methylpropionic acid).
  • radical polymerization initiators are used in combination with sulfites, etc. 02 13768
  • the amount of the polymerization initiator used is 0 with respect to 100 mol of the total amount of the above monomers.
  • the amount be 0.05 to 1.0 mol.
  • the surfactant and / or polymer protective colloid is dissolved in an organic solvent, the monomer aqueous solution and a polymerization initiator are added, and the mixture is heated under stirring to perform reverse phase suspension polymerization in a water-in-oil system.
  • the reaction temperature of the polymerization reaction varies depending on the type of polymerization initiator and monomer used, or the concentration of the aqueous monomer solution, but the polymerization proceeds rapidly, the polymerization time is shortened, and it is economically preferable. From the viewpoint of easy removal of heat and smooth reaction, the temperature is preferably from 20 to 110 ° C, more preferably from 40 to 80 ° C.
  • the reaction time is usually 0.5 to 4 hours.
  • a surface cross-linking may be performed by acting a cross-linking agent containing two or more functional groups reactive with a carboxyl group.
  • a cross-linking agent one that can react with a carboxyl group in the water-absorbing resin is used.
  • epoxy compounds such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerol polyglycidyl ether, and glycidyl; epichlorohydrin, epibromohydrin Haxen-modified compounds such as ⁇ , methyl-epichlorohydrin, etc .; (poly) ethylene glycol, (poly) propylene glycol, (poly) glycerin, diols, pentanediols, hexanediols, Examples include polyhydric alcohol compounds such as methylolpropane, diethanolamine, and triethanolamine. Among them, epoxy compounds are preferably used. These surface crosslinking agents may be used alone or in combination of two or more.
  • the amount of the surface cross-linking agent used is 0.01 to 5 parts by weight with respect to 100 parts by weight of the total amount of the above monomers, from the viewpoint of sufficiently maintaining the gel strength and water absorption of the water-absorbent resin at the time of water absorption. Parts by weight, preferably from 0.02 to 4 parts by weight, more preferably from 0.33 to 3 parts by weight. Good.
  • the method of adding the surface cross-linking agent is not particularly limited, and examples thereof include a method of adding the water-absorbing resin to a water-absorbing resin dispersed in an organic solvent, and a method of spraying the water-absorbing resin with a spray while stirring. Can be mentioned.
  • Examples of the timing of adding the surface cross-linking agent include a stage of a hydrogel after polymerization, a stage of hydrous particles during drying, and a stage after drying.
  • a method of adding to a water-absorbent resin dispersed in an organic solvent at the stage of a hydrogel after polymerization and a method of spraying the water-absorbent resin at the stage of water-containing particles during drying by spraying or the like are preferable.
  • the form of addition of the surface cross-linking agent is not particularly limited, but in order to uniformly add the surface cross-linking agent to the water-absorbing resin, the surface cross-linking agent must be dissolved and added to a hydrophilic solvent such as water. Is preferred.
  • a hydrophilic solvent such as water.
  • n-heptane 50-OmL of n-heptane was added to a 100-Om one-volume five-necked cylindrical round-bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen gas inlet tube.
  • decaglycerin pentastearate surfactant: Sunsoft Q-185S, manufactured by Taiyo Kagaku Co., Ltd.
  • the whole amount of the aqueous monomer solution for polymerization was added to the above-mentioned five-necked cylindrical round-bottom flask with stirring and dispersed, and the system was sufficiently purged with nitrogen, and then heated to a bath temperature of 70 °. C, and the polymerization reaction was carried out for 1 hour.
  • 0.66 g of a 14% by weight aqueous solution of trans-1,2-diaminocyclohexanetetraacetic acid tetrasodium as an aminocarboxylate metal chelating agent was added with stirring. Thereafter, water was removed from the hydrogel by azeotropic dehydration out of the system.
  • n-heptane 500 ml of n-heptane was added to a 1000 ml five-necked cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas inlet tube. 0.92 g of a sucrose fatty acid ester having an HLB of 3.0 (surfactant: S-370 manufactured by Mitsubishi Chemical Corporation) was added and dispersed, and the temperature was raised to dissolve the surfactant. Cooled to 55 ° C.
  • surfactant S-370 manufactured by Mitsubishi Chemical Corporation
  • the monomer aqueous solution for the first-stage polymerization was added and dispersed in the above-described five-necked cylindrical round bottom flask under stirring with stirring, and the system was sufficiently purged with nitrogen, and then heated. After the polymerization reaction was carried out for 1 hour while maintaining the temperature at 70 ° C, the polymerization slurry was cooled to room temperature. Was.
  • n-heptane 500 ml of n-heptane was added to a 100 ml 5-neck cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas inlet tube. 0.92 g of a sucrose fatty acid ester having an HLB of 3.0 (surfactant: S-370 manufactured by Mitsubishi Chemical Corporation) was added and dispersed, and the temperature was raised to dissolve the surfactant. Cooled down to 55.
  • surfactant S-370 manufactured by Mitsubishi Chemical Corporation
  • the whole amount of the aqueous monomer solution for polymerization was added to the above-mentioned five-necked cylindrical round-bottom flask with stirring and dispersed, and the system was sufficiently purged with nitrogen, and then heated to a bath temperature of 70 °. C, and the polymerization reaction was carried out for 1 hour. After completion of the polymerization, water was removed from the hydrogel by azeotropic dehydration. To the obtained gel, 4.14 g of a 2% by weight aqueous solution of ethylene glycol diglycidyl ether was added, and water was removed again by distillation together with n-heptane. Then, powder was used as an aminocarboxylic acid-based metal chelating agent.
  • Example 5 The same operation as in Example 3 was carried out except that triethylenetetramine-6-acetic acid was not added, to obtain 92.0 g of a water-absorbent resin. 0.46 g of the above water-absorbent resin and powdered disodium diethylenetriamine pentaacetate (85 wt% of the total particle size is 100 am or less) are added and thoroughly mixed in a polyethylene bag. 92.5 g of resin were obtained.
  • Example 5 Example 5
  • N-heptane 50 Oml was added to a 100 ml 5-volume cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas inlet tube.
  • 0.92 g of sorbitan monostearate with an HLB of 4.7 surfactant: Nonionic SP-6 OR manufactured by NOF Corporation was added and dispersed, and the temperature was raised to increase the surfactant. After dissolving, the mixture was cooled to 50 ° C.
  • n-heptane n-heptane was added to a 1500 ml five-necked cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas inlet tube.
  • 0.84 g of sorbitan monolaurate with an HLB of 8.6 surfactant: Nonionic LP-2OR manufactured by NOF Corporation was added and dispersed, and the temperature was raised to increase the surfactant. After dissolving, the mixture was cooled to 40 ° C.
  • the whole amount of the aqueous monomer solution for polymerization was added to the above-mentioned five-necked cylindrical round-bottomed flask under stirring and dispersed, and the system was sufficiently purged with nitrogen, and then heated to a bath temperature of 70 °. C While maintaining the temperature, the polymerization reaction was performed for 3 hours. After the polymerization was completed, 0.175 g of a 40% by weight aqueous solution of diethylenetriamine pentaacetic acid and 5% sodium acetate was added to the hydrogel product under stirring as an aminocarboxylate-based metal chelating agent. Thereafter, water was removed from the hydrogel by azeotropic dehydration.
  • a water-absorbent resin was obtained in the same manner as in Example 5, except that 1.2 g of a 38% by weight aqueous solution of tetrasodium ethylenediamine tetraacetate was added in place of pentasodium diethylenetriamine pentaacetate. g was obtained. Comparative Example 1
  • Example 1 was repeated, except that no aminocarboxylic acid-based metal chelating agent was added, to obtain 92.1 g of a water-absorbent resin. Comparative Example 2
  • Example 2 The same operation as in Example 2 was carried out except that the aminocarboxylic acid-based metal chelating agent was not added in Example 2, to obtain 22.5 g of a water absorbent resin. Comparative Example 3
  • Example 4 The same operation as in Example 3 was carried out except that the aminocarboxylic acid-based metal chelating agent was not added, to obtain 92.1 g of a water-absorbing resin. Comparative Example 4
  • Example 1 trans- 1,2-diaminocyclohexanetetraacetic acid 92.8 g of a water-absorbent resin was obtained in the same manner as in Example 1, except that an aqueous solution in which 0.92 g of cunic acid was dissolved in 9.2 g of water was added instead of thorium. Comparative Example 5
  • Example 3 The same procedure as in Example 3 except that 0.46 g of sodium tripolyphosphate (90% by weight of the whole particles was 100 zm or less) was used instead of triethylenetetramine hexaacetic acid in Example 3 was carried out to obtain 92.6 g of a water-absorbing resin.
  • the coloring test of the water absorbent resin obtained in the above Examples and Comparative Examples was performed by the following method.
  • the measurement was performed using a double beam illuminating photometric colorimeter ⁇ —1001 DP (Nippon Denshoku Industries Co., Ltd.). From the X, Y, Z (tristimulus values) of the obtained water-absorbent resin, the yellowness was calculated by the following equation. Similarly, the yellowness of the water-absorbent resin before the test, which was left in a table-top constant temperature and humidity chamber for 20 days, was determined. The above measurement was performed three times, and the average of the values was defined as yellowness.
  • Table 1 shows the results of the coloring tests of the aminocarboxylic acid-based metal chelating agents used in the above Examples and the water-absorbing resins obtained in the above Examples and Comparative Examples.
  • the amounts in parentheses in Table 1 are based on 100 parts by weight of acrylic acid.
  • Table 1 shows that the water-absorbent resin to which the aminocarboxylic acid-based metal chelating agent obtained in the examples was added had a small change in yellowness before and after the test, and the coloring was suppressed.
  • the aminocarboxylic acid-based metal chelate obtained in Comparative Example It can be seen that the water-absorbent resin to which no agent was added had a large change in yellowness and was considerably colored.

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Abstract

A method of preventing the coloration of a water-absorbing resin obtained using an unsaturated carboxylic acid as an essential monomer, characterized by adding an aminocarboxylic acid type metal-chelating agent either to the system in at least one of the steps for producing the water-absorbing resin or to the water-absorbing resin after production; and a method of using an aminocarboxylic acid type metal-chelating agent for preventing the coloration of a water-absorbing resin obtained using an unsaturated carboxylic acid as an essential monomer, characterized by adding the aminocarboxylic acid type metal-chelating agent either to the system in at least one of the steps for producing the water-absorbing resin or to the water-absorbing resin after production.

Description

明 細 書 吸水性樹脂の着色防止方法 技術分野  Description Method for preventing coloring of water-absorbent resin
本発明は、 吸水性樹脂の着色防止方法に関する。 さらに詳しくは、 紙おむつ、 生理用ナプキン等の衛生材料の吸収性物品の吸水剤として好適に使用しうる吸水 性樹脂の着色防止方法に関する。 背景技術  The present invention relates to a method for preventing coloring of a water-absorbent resin. More specifically, the present invention relates to a method for preventing discoloration of a water-absorbing resin which can be suitably used as a water-absorbing agent for absorbent articles of sanitary materials such as disposable diapers and sanitary napkins. Background art
吸水性樹脂は、 水系の液体、 例えば、 人尿、 血液、 汗等の体液等を速やかに、 かつ大量に吸収し、 荷重下においても、 一旦吸収した液体は放出しないという特 徵を活かして、 紙おむつ、 生理用ナプキン等の衛生材料の吸収性物品の吸水剤と して広く使用されている。  Water-absorbent resins take advantage of the fact that they absorb water-based liquids, for example, body fluids such as human urine, blood, and sweat quickly and in large quantities, and do not release the liquid once absorbed under load. It is widely used as a water-absorbing agent for absorbent articles made of sanitary materials such as disposable diapers and sanitary napkins.
従来の吸水性樹脂は、 放置しておくと熱や湿度等の外的要因によって黄色や茶 色に着色しやすいといった問題がある。 特に、 上記衛生材料の分野において、 紙 おむつ、 生理用ナプキン等の吸収性物品中の吸水性樹脂が着色している場合、 吸 収性物品としての商品価値は著しく低下する。 そのため、 吸収性物品に使用され る吸水性樹脂は、 夏場の倉庫内のような高温高湿下の厳しい環境下に放置されて も、 吸水性樹脂が着色しないことが求められている。  The conventional water-absorbent resin has a problem that, if left unattended, it tends to be colored yellow or brown due to external factors such as heat and humidity. In particular, in the field of the above-mentioned sanitary materials, when the water-absorbent resin in the absorbent article such as a disposable diaper or a sanitary napkin is colored, the commercial value as the absorbent article is significantly reduced. Therefore, it is required that the water-absorbent resin used in the absorbent article does not discolor even when left in a harsh environment of high temperature and high humidity such as in a warehouse in summer.
着色防止効果を有する吸水性樹脂としては、 例えば、 高吸水性ポリマーに有機 リン酸化合物またはその塩を添加した高吸水性ポリマー組成物 （特開平 5— 8 6 2 5 1号公報） 、 酸性水膨潤性架橋重合体と塩基性水膨澗性架橋重合体と、 着色 防止剤およびノまたは酸化防止剤およひンまたはホゥ素化合物とを含んでなる吸 水剤組成物 （特開 2 0 0 0— 2 3 0 1 2 9号公報） 、 吸水性樹脂と有機カルボン 酸類および Zまたはその塩からなる吸水剤組成物 （特開 2 0 0 0 - 3 2 7 9 2 6 号公報） 等が知られている。 しかしながら、 これらの組成物は、 高温高湿下の厳 しい環境下に長期間放置した場合、 十分満足のいく効果を発揮できるものではな かった。 Examples of the water-absorbing resin having an anti-coloring effect include a super-water-absorbing polymer composition obtained by adding an organic phosphoric acid compound or a salt thereof to a super-water-absorbing polymer (JP-A-5-82651), acidic water A water-absorbing agent composition comprising a swellable cross-linked polymer, a basic water-swellable cross-linked polymer, a coloring inhibitor, a di- or anti-oxidant, and a di- or boron compound No. 0-230201), a water-absorbing agent composition comprising a water-absorbing resin and an organic carboxylic acid and Z or a salt thereof (Japanese Patent Application Laid-Open No. 2000-329792) Publication). However, these compositions have not been able to exert a sufficiently satisfactory effect when left for a long time in a harsh environment of high temperature and high humidity.
本発明の目的は、 高温高湿下に長期間放置した場合でも着色を防止することが できる吸水性樹脂の着色防止方法を提供することにある。  An object of the present invention is to provide a method for preventing coloring of a water-absorbing resin, which can prevent coloring even when left under high temperature and high humidity for a long period of time.
これらの本発明の目的及び他の目的は、 以下の記載から明らかにされるであろ Ό ο 発明の開示  These and other objects of the invention will be apparent from the description below.
すなわち、 本発明は、  That is, the present invention
〔1〕 不飽和カルボン酸を必須単量体とする吸水性樹脂の製造工程の、 少なくと もいずれかの工程の系内にまたは製造後の吸水性樹脂に、 ァミノカルボン酸系金 属キレート剤を添加することを特徵とする、 吸水性樹脂の着色防止方法、 ならび に、  [1] An amino carboxylic acid-based metal chelating agent is added to at least one of the steps in the process for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer, or in the water-absorbent resin after the production. A method for preventing coloring of a water-absorbent resin, and
〔2〕 不飽和カルボン酸を必須単量体とする吸水性樹脂の製造工程の、 少なくと もいずれかの工程の系内にまたは製造後の吸水性樹脂に、 ァミノカルボン酸系金 属キレート剤を添加することを特徴とする、 得られる吸水性樹脂の着色を防止す るための、 ァミノカルボン酸系金属キレート剤の使用方法、  (2) An amino carboxylic acid-based metal chelating agent is used in at least one of the steps in the process for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer, or in the water-absorbent resin after the production. A method of using an aminocarboxylic acid-based metal chelating agent for preventing coloring of the obtained water-absorbent resin, characterized by adding
に関する。 発明を実施するための最良の形態 About. BEST MODE FOR CARRYING OUT THE INVENTION
本発明の吸水性樹脂の着色防止方法においては、 不飽和カルボン酸を必須単量 体とする吸水性樹脂の製造工程の、 少なくともいずれかの工程の系内にまたは製 造後の吸水性樹脂に、 ァミノカルボン酸系金属キレート剤を添加することで、 高 温高湿下においても吸水性樹脂の着色が抑制できる点に特徵を有する。  In the method for preventing coloring of a water-absorbent resin according to the present invention, the method for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer is included in at least one of the processes or after the production of the water-absorbent resin. The addition of an aminocarboxylic acid-based metal chelating agent has a feature in that coloring of the water-absorbing resin can be suppressed even under high temperature and high humidity.
本発明で用いられるアミノカルボン酸系金属キレート剤としては、 例えば、 ィ ミノ 2酢酸、 ヒドロキシェチルイミノ 2酢酸、 二トリ口 3酢酸、 二トリ口 3プロ ピオン酸、 エチレンジァミン 4酢酸、 ジェチレントリアミン 5酢酸、 トリエチレ ンテトラミン 6酢酸、 t r a n s— l , 2—ジアミノシクロへキサン 4酢酸、 N , N—ビス （2—ヒドロキシェチル） グリシン、 ジァミノプロパノール 4酢酸、 エチレンジァミン 2プロピオン酸、 ヒドロキシエチレンジァミン 3酢酸、 グリコ —ルェ一テルジァミン 4酢酸、 ジァミノプロパン 4酢酸、 N, N， —ビス （2— ヒドロキシベンジル） エチレンジァミン一 N, N— 2酢酸、 1 , 6—へキサメチ レンジァミン— N, N, N， , N' —4酢酸およびその塩等が挙げられる。 中で も、 より着色防止効果を有する観点から、 ジエチレントリアミン 5酢酸、 トリエ チレンテトラミン 6酢酸、 t r a n s— l , 2—ジアミノシクロへキサン 4酢酸 およびその塩が好ましく用いられる。 Examples of the aminocarboxylic acid-based metal chelating agent used in the present invention include: Mino diacetic acid, hydroxyethylimino diacetic acid, tri-tri-acetic acid, tri-tri-propionic acid, ethylenediamine tetra-acetic acid, dimethylene triamine penta-acetic acid, triethylene tetramine hexa-acetic acid, trans-l, 2-diaminocyclohexane Tetraacetic acid, N, N-bis (2-hydroxyethyl) glycine, diaminopropanol tetraacetic acid, ethylenediamine dipropionic acid, hydroxyethylenediamine triacetic acid, glyco-leterdiamine tetraacetic acid, diaminopropane tetraacetic acid, N , N, -bis (2-hydroxybenzyl) ethylenediamine mono-N, N-diacetic acid, 1,6-hexamethylenediamine-N, N, N ,, N'-4acetic acid and salts thereof. Among them, diethylenetriamine pentaacetic acid, triethylenetetramine hexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid and salts thereof are preferably used from the viewpoint of having a more effective coloring prevention effect.
吸水性樹脂を製造するいずれかの工程の系内にまたは製造後の吸水性樹脂に、 アミノカルボン酸系金属キレ一ト剤を添加するには、 前記アミノカルボン酸系金 属キレート剤を、 （ィ） 重合前の不飽和カルボン酸を含む単量体水溶液に添加す る方法、 （口） 重合後の含水ゲル状物に添加する方法、 （ハ） 乾燥中の吸水性樹 脂に添加する方法、 （二） 乾燥後の吸水性樹脂に粉体混合する方法、 （ホ） 有機 溶媒中に分散した吸水性樹脂に添加して、 加熱 ·脱溶媒する方法等が挙げられる 本発明においては、 生産性を維持し、 高い着色防止効果をもたらす観点から、 簡便な方法で吸水性樹脂中、 あるいは吸水性樹脂表面にできるだけ均一に、 アミ ノカルボン酸系金属キレ一ト剤を分散させることが好ましい。 ァミノカルボン酸 系金属キレート剤が均一に分散された吸水性樹脂を得るには、 特に （口） 重合後 の含水ゲル状物に添加する方法、 （ハ） 乾燥中の吸水性樹脂に添加する方法、 （ 二） 乾燥後の吸水性樹脂に粉体混合する方法が好ましい。  To add the aminocarboxylic acid-based metal chelating agent into the system of any of the processes for producing the water-absorbing resin or to the manufactured water-absorbing resin, the aminocarboxylic acid-based metal chelating agent may be added by A) a method of adding to an aqueous monomer solution containing an unsaturated carboxylic acid before polymerization, (mouth) a method of adding to an aqueous gel after polymerization, (c) a method of adding to a water-absorbing resin during drying (2) a method in which powder is mixed with the dried water-absorbent resin; and (e) a method in which the powder is added to the water-absorbent resin dispersed in an organic solvent and heated and desolvated, and the like. From the viewpoint of maintaining the property and providing a high anti-coloring effect, it is preferable to disperse the aminocarboxylic acid-based metal chelating agent in the water-absorbent resin or on the surface of the water-absorbent resin as simply as possible by a simple method. In order to obtain a water-absorbing resin in which an aminocarboxylic acid-based metal chelating agent is uniformly dispersed, in particular, (mouth) a method of adding to a hydrogel after polymerization, (c) a method of adding to a water-absorbing resin during drying, (2) A method of mixing the powder with the dried water-absorbent resin is preferable.
アミノカルボン酸系金属キレート剤を添加する形態は、 特に限定されないが、 ァミノカルボン酸系金属キレート剤を吸水性樹脂に均一に分散させるためには、 液状又は粉体のァミノカルボン酸系金属キレ一ト剤を水等の親水性溶媒に溶解し た溶液を添加する形態、 あるいは微粉末状のァミノカルボン酸系金属キレート剤 を粉末状態で添加する形態が好ましい。 なお、 微粉末状のァミノカルボン酸系金 属キレート剤の粒子径は特に限定されないが、 粗粒部分が少ないほうが、 十分な 着色防止効果が得られる観点から、 全体の 8 0重量％以上の粒子が 1 0 0 m以 下の粒子径であることが好ましい。 The form in which the aminocarboxylic acid-based metal chelating agent is added is not particularly limited, but in order to uniformly disperse the aminocarboxylic acid-based metal chelating agent in the water-absorbing resin, A form in which a liquid or powdery amino carboxylic acid-based metal chelating agent is dissolved in a hydrophilic solvent such as water is added, or a form in which a fine powdered amino carboxylic acid-based metal chelating agent is added in a powder state is preferable. . The particle size of the finely powdered aminocarboxylic acid-based metal chelating agent is not particularly limited. The particle diameter is preferably 100 m or less.
前記ァミノカルボン酸系金属キレート剤の使用量は、 十分な着色防止効果が得 られ、 また、 使用量に見合う効果が得られ、 経済的である観点から、 吸水性樹脂 を製造するための必須単量体である不飽和カルボン酸 1 0 0重量部に対して 0 . 0 0 1〜6重量部が好ましく、 0 . 0 0 6〜3重量部がより好ましく、 0 . 0 1 〜 2重量部が最も好ましい。  The amount of the aminocarboxylic acid-based metal chelating agent used is such that a sufficient anti-coloring effect can be obtained, and an effect commensurate with the amount used can be obtained. 0.001 to 6 parts by weight, preferably 0.006 to 3 parts by weight, more preferably 0.01 to 2 parts by weight, based on 100 parts by weight of the unsaturated carboxylic acid as a body. preferable.
従って、 本発明により、 不飽和カルボン酸を必須単量体とする吸水性樹脂の製 造工程の、 少なくともいずれかの工程の系内にまたは製造後の吸水性樹脂に、 ァ ミノカルボン酸系金属キレ一ト剤を添加することを特徵とする、 得られる吸水性 樹脂の着色を防止するための、 ァミノカルボン酸系金属キレート剤の使用方法が 提供される。  Therefore, according to the present invention, the aminocarboxylic acid-based metal chelate is added to at least one of the steps of the process for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer or to the water-absorbent resin after the production. Provided is a method for using an aminocarboxylic acid-based metal chelating agent for preventing coloring of a resulting water-absorbent resin, which is characterized by adding a single agent.
本発明で製造される不飽和力ルポン酸を必須単量体とする吸水性樹脂としては 、 アクリル酸塩重合体の架橋物、 でんぷん一アクリル酸塩グラフト共重合体の加 水分解生成物の架橋物、 ビニルアルコール-アクリル酸塩共重合体の架橋物、 無 水マレイン酸グラフトポリビニルアルコール架橋物、 架橋イソプチレン—無水マ レイン酸共重合体、 ポリアクリル酸部分中和物架橋体、 酢酸ビニルーアクリル酸 エステル共重合体のゲン化物等を挙げることができる。 中でも、 大量の水を吸収 することができ、 多少の荷重をかけても吸収した水を分子内に保持することので きるァクリル酸塩重合体の架橋物が好ましい。  The water-absorbing resin containing the unsaturated monomeric ruponic acid as an essential monomer produced in the present invention includes a crosslinked product of an acrylate polymer and a crosslinked product of hydrolysis and decomposition of a starch monoacrylate graft copolymer. Product, cross-linked product of vinyl alcohol-acrylate copolymer, water-free maleic acid-grafted polyvinyl alcohol cross-linked product, cross-linked isobutylene-maleic anhydride copolymer, cross-linked polyacrylic acid partially neutralized product, vinyl acetate-acrylic Examples of the acid ester copolymer include a gent product. Among them, a crosslinked product of an acrylate polymer capable of absorbing a large amount of water and capable of retaining the absorbed water in the molecule even when a slight load is applied is preferable.
不飽和力ルポン酸としては、 例えば、 ァクリル酸、 メタクリル酸、 マレイン酸 、 無水マレイン酸、 フマル酸等が挙げられる。 これらは単独で用いてもよく、 2 02 13768 Examples of unsaturated ruponic acids include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid and the like. These may be used alone, 2 02 13768
種以上混合して用いてもよい。 不飽和カルボン酸は、 アルカリ金属等により部分 的に中和されていてもよく、 中でも、 アクリル酸、 メタクリル酸およびこれらの ナトリウム、 力リウム等のアル力リ金属塩が好ましく用いられる。 You may mix and use more than one kind. The unsaturated carboxylic acid may be partially neutralized with an alkali metal or the like, and among them, acrylic acid, methacrylic acid and salts of these metals such as sodium and potassium are preferably used.
前記不飽和カルボン酸は、 必要により他の単量体を共重合させてもよい。 他の 単量体としては、 例えば、 （メタ） アクリルアミ ド 〔 r (メタ） ァクリ J とは 「 ァクリ J および 「メタクリ」 を意味する。 以下同じ〕 、 N—置換 （メタ） ァクリ ルアミ ド、 2—ヒドロキシェチル （メタ） アタリレート、 2—ヒドロキジプロピ ル （メタ） ァクリレート、 メトキシポリエチレングリコール （メタ） ァクリレー ト、 ポリエチレングリコール （メタ） ァクリレート等のノニオン性親水性基含有 単量体； N, N—ジメチルアミノエチル （メタ） ァクリレート、 N, N—ジメチ ルァミノプロピル （メタ） ァクリレート、 N, N—ジメチルァミノプロピル （メ 夕） アクリルアミ ド等の含ァミノ基不飽和単量体； ビニルスルホン酸、 スチレン スルホン酸、 2— (メタ） アクリルアミ ドー 2—メチルプロパンスルホン酸、 2 - (メタ） ァクリロイルエタンスルホン酸およびそれらの塩等のスルホン酸系単 量体等を挙げることができる。  If necessary, the unsaturated carboxylic acid may be copolymerized with another monomer. Other monomers include, for example, (meth) acrylamide [r (meth) acryl J means “acryl J and“ methacryl ”. The same applies hereinafter), N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, etc. N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (methyl) acrylamide, etc. Amino group-containing unsaturated monomers such as vinylsulfonic acid, styrenesulfonic acid, 2- (meth) acrylamide 2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, and salts thereof. Sulfonic acid monomers and the like can be mentioned.
前記吸水性樹脂の重合方法としては、 特に限定されず、 代表的な製造法である 、 逆相懸濁重合法、 水溶液重合法等が用いられる。 以下に逆相懸濁重合法につい て例示する。  The method for polymerizing the water-absorbent resin is not particularly limited, and typical production methods such as a reversed-phase suspension polymerization method and an aqueous solution polymerization method are used. The reverse phase suspension polymerization method is illustrated below.
逆相懸濁重合法では、 界面活性剤および高分子保護コロイドのうち、 少なくと も一方の存在下で、 有機溶媒中に単量体水溶液を分散させた状態で、 例えば、 重 合開始剤を用いることにより、 重合が行われる。  In the reversed-phase suspension polymerization method, a monomer initiator is dispersed in an organic solvent in the presence of at least one of a surfactant and a polymer protective colloid. By using, polymerization is performed.
前記単量体水溶液における単量体の濃度は、 2 5重量％〜飽和濃度であること が好ましい。 また、 前記単量体水溶液は、 重合反応において、 一括して添加して もよく、 分割して添加してもよい。  The concentration of the monomer in the aqueous monomer solution is preferably from 25% by weight to a saturated concentration. In the polymerization reaction, the monomer aqueous solution may be added all at once, or may be added separately.
前記有機溶媒としては、 n—ペンタン、 n—へキサン、 n—ヘプタン、 リグ口 イン等の脂肪族炭化水素溶媒；シクロペンタン、 メチルシクロペンタン、 シクロ へキサン、 メチルシクロへキサン等の脂環族炭化水素溶媒；ベンゼン、 トルエンExamples of the organic solvent include aliphatic hydrocarbon solvents such as n-pentane, n-hexane, n-heptane, and lignin; cyclopentane, methylcyclopentane, and cyclohexane. Alicyclic hydrocarbon solvents such as hexane and methylcyclohexane; benzene, toluene
、 キジレン等の芳香族炭化水素溶媒等を挙げることができる。 中でも、 n—ヘプ タン、 シクロへキサンが好ましく用いられる。 And aromatic hydrocarbon solvents such as chidylene. Among them, n-heptane and cyclohexane are preferably used.
有機溶媒の使用量は、 重合熱を除去し、 重合温度を制御しやすい観点から、 単 量体の合計量 1 0 0重量部に対して 5 0〜 6 0 0重量部が好ましく、 1 0 0〜 5 5 0重量部がより好ましい。  The amount of the organic solvent to be used is preferably from 50 to 600 parts by weight, more preferably 100 to 600 parts by weight, based on the total amount of the monomers of 100 parts by weight, from the viewpoint of removing the heat of polymerization and easily controlling the polymerization temperature. ~ 550 parts by weight is more preferred.
前記界面活性剤としては、 ソルビタン脂肪酸エステル、 モノ脂肪酸グリセリン エステル、 ポリグリセリン脂肪酸エステル、 ショ糖脂肪酸エステル、 ポリオキシ エチレン硬化ヒマシ油、 ラウリン酸ポリオキシエチレン硬化ヒマシ油、 （トリ） イソステアリン酸ポリォキシェチレン硬化ヒマシ油、 ポリォキシェチレンアルキ ルフエニルエーテル、 ポリオキシエチレンラウリルエーテル、 ポリオキシェチレ ンへキシルデシルエーテル等の非イオン界面活性剤が挙げられる。  Examples of the surfactant include sorbitan fatty acid ester, mono-fatty acid glycerin ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene hydrogenated castor oil, lauric acid polyoxyethylene hydrogenated castor oil, and (tri) polyisoxtearate Examples include nonionic surfactants such as tylene-hardened castor oil, polyoxetylene alkylphenyl ether, polyoxyethylene lauryl ether, and polyoxyethylene hexyldecyl ether.
前記高分子保護コロイドとしては、 ェチルセルロース、 ヒドロキシェチルセル ロース、 酸化ポリエチレン、 無水マレイン化ポリエチレン、 無水マレイン化ポリ ブタジェン、 無水マレィン化工チレンプロピレンジエンターポリマー等が挙げら これら非イオン界面活性剤および高分子保護コロイドは、 2種類以上を混合し て用いてもよい。  Examples of the polymer protective colloid include ethyl cellulose, hydroxyethyl cellulose, oxidized polyethylene, anhydrous maleated polyethylene, anhydrous maleated polybutadiene, anhydrous maleinated polyethylene propylene diene terpolymer, and the like. The polymer protective colloid may be used as a mixture of two or more kinds.
前記非イオン界面活性剤および Ζまたは高分子保護コロイドは、 ァニオン界面 活性剤と併用することもできる。 ァニオン界面活性剤としては、 脂肪酸塩、 アル キルベンゼンスルホン酸塩、 アルキルメチルタウリン酸塩、 ポリオキシエチレン アルキルフヱニルェ一テル硫酸ェステル塩、 ポリオキジエチレンアルキルエーテ ルスルホン酸塩等が挙げられる。  The nonionic surfactant and the polymer or polymer protective colloid can be used in combination with an anionic surfactant. Examples of the anionic surfactant include a fatty acid salt, an alkyl benzene sulfonate, an alkyl methyl taurate, a polyoxyethylene alkyl phenyl ether sulfate, a polyoxyethylene alkyl ether sulfonate, and the like.
界面活性剤および/または高分子保護コロイドの使用量は、 単量体水溶液の分 散が十分となり、 使用量に見合う効果が得られ、 経済的である観点から、 単量体 の合計量 1 0 0重量部に対して 0 . 1〜5重量部が好ましく、 0 . 2〜3重量部 2/13768 The amount of the surfactant and / or polymer protective colloid used is such that the aqueous monomer solution is sufficiently dispersed, an effect commensurate with the amount used is obtained, and the total amount of the monomer is 10 from the viewpoint of economy. 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight per 0 parts by weight 2/13768
がより好ましい。 Is more preferred.
前記吸水性樹脂は、 架橋剤を用いない自己架橋型の反応でも合成できるが、 2 個以上の重合性不飽和基や 2個以上の反応性基を有する内部架橋剤を用いて、 架 橋させてもよい。 内部架橋剤としては、 N, N' —メチレンビス （メタ） ァクリ ルアミ ド、 エチレングリコールジ （メタ） ァクリレート、 ジエチレングリコール ジ （メタ） ァクリレート、 トリエチレングリコ一ルジ （メタ） ァクリレート、 ト リメチロールプロパンジ （メタ） ァクリレート、 トリメチロールプロパントリ （ メタ） ァクリレート、 トリメチロールプロパンジ （メタ） ァリルエーテル、 トリ ァリルァミン等の 1分子中にェチレン性不飽和基を 2個以上有する化合物； （ポ リ） ェチレングリコ一ルジグリシジルエーテル、 グリセリントリグリシジルェ一 テル等のポリグリシジルエーテル；ェピクロロヒドリン、 ェビブ口モヒドリン等 のハロゲン化工ポキシ化合物等が挙げられる。 これらの 1種または 2種以上を、 重合系中での反応性および水溶性を考慮した上で用いることができるが、 1分子 中にグリシジル基を 2個以上有する化合物を内部架橋剤として用いることが好ま しい。  The water-absorbent resin can be synthesized by a self-crosslinking type reaction without using a crosslinking agent.However, the water-absorbing resin is crosslinked by using an internal crosslinking agent having two or more polymerizable unsaturated groups or two or more reactive groups. You may. Internal crosslinking agents include N, N'-methylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane (Meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropanedi (meth) aryl ether, triarylamine, etc., compounds having two or more ethylenic unsaturated groups in one molecule; (poly) ethyleneglycoldiglycidyl And polyglycidyl ethers such as ether and glycerin triglycidyl ether; and halogenated oxy compounds such as epichlorohydrin and moebhydrin. One or more of these can be used in consideration of the reactivity and water solubility in the polymerization system.However, a compound having two or more glycidyl groups in one molecule should be used as the internal crosslinking agent. Is preferred.
内部架橋剤の使用量は、 得られる吸水性樹脂が適度な架橋により水溶性の性質 が抑制され、 十分な吸水性を示す観点から、 上記単量体の合計量 1 0 0重量部に 対して、 0 . 0 0 1〜3重量部が好ましく、 0 . 0 0 3〜1重量部がより好まし く、 0 . 0 0 5〜0 . 5重量部がさらに好ましい。  The amount of the internal cross-linking agent used is determined based on the total amount of the above-mentioned monomers of 100 parts by weight, from the viewpoint that the obtained water-absorbent resin has appropriate cross-linking to suppress the water-soluble property and exhibit sufficient water absorption. 0.001 to 3 parts by weight, more preferably 0.003 to 1 part by weight, and even more preferably 0.05 to 0.5 part by weight.
重合開始剤としては、 過硫酸力リゥム、 過硫酸ナトリゥム、 過硫酸ァンモニゥ ム、 過酸化ベンゾィル、 過酸化水素、 1 , Γ —ァゾビス （シクロへキサン一 1 一力ルポ二トリル） 、 2 , 2， —ァゾビス （2—メチル—ブチロニトリル） 、 2 , 2 ' —ァゾビスイソブチロニトリル、 2 , 2 ' ーァゾビス （2—アミジノプロ パン） 2塩酸塩、 2—シァノ— 2—プロピルァゾホルムアミ ド、 ジメチル 2 , 2 ' ーァゾビス （2—メチルプロピオン酸） 等のラジカル重合開始剤を挙げること ができる。 このようなラジカル重合開始剤は、 亜硫酸塩等と併用して、 レドック 02 13768 Examples of the polymerization initiator include persulfuric acid sodium, sodium persulfate, ammonium persulfate, benzoyl peroxide, hydrogen peroxide, 1,2-diazobis (cyclohexane-one-potency nitrile), 2, 2, —Azobis (2-methyl-butyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2-cyano-2-propylazoformamide And a radical polymerization initiator such as dimethyl 2,2′-azobis (2-methylpropionic acid). Such radical polymerization initiators are used in combination with sulfites, etc. 02 13768
ス系重合開始剤として用いてもよい。 You may use as a polymerization initiator.
重合開始剤の使用量は、 重合反応の時間を短縮し、 急激な重合反応を防ぎ重合 反応の制御を容易にする観点から、 上記単量体の合計量 1 0 0モルに対して、 0 From the viewpoint of shortening the polymerization reaction time, preventing the rapid polymerization reaction and facilitating the control of the polymerization reaction, the amount of the polymerization initiator used is 0 with respect to 100 mol of the total amount of the above monomers.
. 0 0 5〜1 . 0モルであることが望ましい。 It is desirable that the amount be 0.05 to 1.0 mol.
前記界面活性剤および/または高分子保護コロイドを有機溶媒に溶解し、 前記 単量体水溶液と重合開始剤等を添加し、 攪拌下、 加熱して、 油中水系において、 逆相懸濁重合を行う。 前記重合反応の反応温度は、 使用する重合開始剤および単 量体の種類、 あるいは単量体水溶液の濃度によって異なるが、 重合が迅速に進行 し、 重合時間が短くなり、 経済的に好ましく、 重合熱を除去することが簡単で、 円滑に反応を行う観点から、 2 0〜1 1 0 °Cが好ましく、 4 0〜8 0 °Cが更に好 ましい。 反応時間は、 通常、 0 . 5〜4時間である。  The surfactant and / or polymer protective colloid is dissolved in an organic solvent, the monomer aqueous solution and a polymerization initiator are added, and the mixture is heated under stirring to perform reverse phase suspension polymerization in a water-in-oil system. Do. The reaction temperature of the polymerization reaction varies depending on the type of polymerization initiator and monomer used, or the concentration of the aqueous monomer solution, but the polymerization proceeds rapidly, the polymerization time is shortened, and it is economically preferable. From the viewpoint of easy removal of heat and smooth reaction, the temperature is preferably from 20 to 110 ° C, more preferably from 40 to 80 ° C. The reaction time is usually 0.5 to 4 hours.
得られた吸水性樹脂においては、 カルボキシル基と反応性を有する官能基を 2 個以上含有する架橋剤を作用させ、 表面架橋してもよい。 表面架橋剤としては、 吸水性樹脂中のカルボキシル基と反応しうるものが用いられる。 例えば、 （ポリ ) エチレングリコールジグリシジルエーテル、 (ポリ） プロピレングリコールジ グリシジルエーテル、 (ポリ） グリセ口一ルポリグリシジルエーテル、 グリシド —ル等のェポキシ化合物；ェピクロロヒドリン、 ェピブロムヒドリン、 α—メチ ルェピクロロヒドリン等のハ口ゲン化工ポキシ化合物； （ポリ） エチレングリコ —ル、 （ポリ） プロピレングリコール、 （ポリ） グリセリン、 ジオール類、 ペン タンジオール類、 へキサンジオール類、 トリメチロールプロバン、 ジエタノール ァミン、 トリエタノールァミン等の多価アルコール化合物等が挙げられる。 中で も、 エポキシ化合物が好ましく用いられる。 これら表面架橋剤は、 単独で用いて もよく、 2種類以上を併用してもよい。  In the obtained water-absorbent resin, a surface cross-linking may be performed by acting a cross-linking agent containing two or more functional groups reactive with a carboxyl group. As the surface cross-linking agent, one that can react with a carboxyl group in the water-absorbing resin is used. For example, epoxy compounds such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerol polyglycidyl ether, and glycidyl; epichlorohydrin, epibromohydrin Haxen-modified compounds such as α, methyl-epichlorohydrin, etc .; (poly) ethylene glycol, (poly) propylene glycol, (poly) glycerin, diols, pentanediols, hexanediols, Examples include polyhydric alcohol compounds such as methylolpropane, diethanolamine, and triethanolamine. Among them, epoxy compounds are preferably used. These surface crosslinking agents may be used alone or in combination of two or more.
表面架橋剤の使用量は、 吸水性樹脂の吸水時のゲル強度および吸水量を十分保 つ観点から、 上記単量体の合計量 1 0 0重量部に対して、 0 . 0 1〜5重量部が 好ましく、 0 . 0 2〜4重量部がより好ましく、 0 . 0 3〜3重量部がさらに好 ましい。 The amount of the surface cross-linking agent used is 0.01 to 5 parts by weight with respect to 100 parts by weight of the total amount of the above monomers, from the viewpoint of sufficiently maintaining the gel strength and water absorption of the water-absorbent resin at the time of water absorption. Parts by weight, preferably from 0.02 to 4 parts by weight, more preferably from 0.33 to 3 parts by weight. Good.
前記表面架橋剤の添加方法は、 特に限定されるものではなく、 例えば、 有機溶 媒中に分散した吸水性樹脂に添加する方法；吸水性樹脂を撹拌しつつ、 スプレー 等により噴霧する方法等を挙げることができる。 表面架橋剤の添加時期は、 重合 後の含水ゲル状物の段階、 乾燥中の含水粒子の段階、 乾燥後の段階等を挙げるこ とができる。 中でも、 重合後の含水ゲル状物の段階で、 有機溶媒中に分散した吸 水性樹脂に添加する方法、 乾燥中の含水粒子の段階で吸水性樹脂にスプレー等に より噴霧する方法が好ましい。  The method of adding the surface cross-linking agent is not particularly limited, and examples thereof include a method of adding the water-absorbing resin to a water-absorbing resin dispersed in an organic solvent, and a method of spraying the water-absorbing resin with a spray while stirring. Can be mentioned. Examples of the timing of adding the surface cross-linking agent include a stage of a hydrogel after polymerization, a stage of hydrous particles during drying, and a stage after drying. Above all, a method of adding to a water-absorbent resin dispersed in an organic solvent at the stage of a hydrogel after polymerization and a method of spraying the water-absorbent resin at the stage of water-containing particles during drying by spraying or the like are preferable.
表面架橋剤の添加形態は、 特に限定されないが、 表面架橋剤を吸水性樹脂に対 して均一に添加するためには、 表面架橋剤を水等の親水性溶媒に溶解して添加す ることが好ましい。 以下、 実施例により本発明を詳細に説明するが、 本発明は、 これら実施例のみ に限定されるものではない。 実施例 1  The form of addition of the surface cross-linking agent is not particularly limited, but in order to uniformly add the surface cross-linking agent to the water-absorbing resin, the surface cross-linking agent must be dissolved and added to a hydrophilic solvent such as water. Is preferred. Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to only these Examples. Example 1
撹拌機、 還流冷却器、 滴下ロート、 温度計および窒素ガス導入管を備えた 1 0 0 O m 1容の五つ口円筒型丸底フラスコに n—ヘプタンを 5 0 O m l加えた。 こ れに H L Bが 5 . 0のペンタステアリン酸デカグリセリン （界面活性剤：太陽化 学株式会社製のサンソフト Q— 1 8 5 S ) を 1 . 3 8 g添加して分散させ、 昇温 して界面活性剤を溶解後、 5 5 °Cまで冷却した。  50-OmL of n-heptane was added to a 100-Om one-volume five-necked cylindrical round-bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen gas inlet tube. To this, 1.38 g of decaglycerin pentastearate (surfactant: Sunsoft Q-185S, manufactured by Taiyo Kagaku Co., Ltd.) with an HLB of 5.0 was added, dispersed, and heated. After dissolving the surfactant by cooling, the mixture was cooled to 55 ° C.
上記とは別に、 5 0 O m l容の三角フラスコに、 8 0重量 アクリル酸水溶液 9 2 gを加えた。 これに、 外部から冷却しつつ、 3 0重量％水酸化ナトリウム水 溶液 1 0 2 . 2 gを滴下して、 アクリル酸の 7 5モル％を中和し、 アクリル酸の 部分中和物水溶液を調製した。 さらに、 水 5 0 . 2 gと、 重合開始剤の過硫酸力 リウム 0 . 1 1 gと、 架橋剤のエチレングリコールジグリシジルエーテル 1 8 . 2/13768 Separately from the above, to a 50 O ml Erlenmeyer flask was added 92 g of an aqueous solution of 80 weight acrylic acid. While cooling from the outside, 102.2 g of a 30% by weight aqueous sodium hydroxide solution was added dropwise to neutralize 75 mol% of acrylic acid, and an aqueous solution of partially neutralized acrylic acid was added. Prepared. Furthermore, 50.2 g of water, 0.11 g of potassium persulfate as a polymerization initiator, and 180.1 g of ethylene glycol diglycidyl ether as a crosslinking agent. 2/13768
4mgを添加し、 重合用の単量体水溶液を調製した。 4 mg was added to prepare a monomer aqueous solution for polymerization.
この重合用の単量体水溶液を、 上記の五つ口円筒型丸底フラスコに、 撹拌下で 全量加えて分散させ、 系内を窒素で十分に置換した後に昇温し、 浴温を 70°Cに 保持して、 重合反応を 1時間行った。 重合終了後の含水ゲル状物に、 ァミノカル ボン酸系金属キレ一ト剤として 14重量 t r an s— 1, 2—ジアミノシクロ へキサン 4酢酸 4ナトリウム水溶液 0. 66 gを撹拌下で添加した。 その後、 含 水ゲル状物から、 共沸脱水により水分を系外に除去した。 得られたゲル状物に 2 重量％エチレングリコールジグリシジルエーテル水溶液 4. 14 gを添加し、 さ らに水分および n—ヘプタンを蒸留により除去して乾燥し、 吸水性樹脂 93. 0 gを得た。 実施例 2  The whole amount of the aqueous monomer solution for polymerization was added to the above-mentioned five-necked cylindrical round-bottom flask with stirring and dispersed, and the system was sufficiently purged with nitrogen, and then heated to a bath temperature of 70 °. C, and the polymerization reaction was carried out for 1 hour. To the hydrogel obtained after the completion of the polymerization, 0.66 g of a 14% by weight aqueous solution of trans-1,2-diaminocyclohexanetetraacetic acid tetrasodium as an aminocarboxylate metal chelating agent was added with stirring. Thereafter, water was removed from the hydrogel by azeotropic dehydration out of the system. 4.14 g of a 2% by weight aqueous solution of ethylene glycol diglycidyl ether was added to the obtained gel, and water and n-heptane were removed by distillation and dried to obtain 93.0 g of a water-absorbent resin. Was. Example 2
撹拌機、 還流冷却器、 滴下ロート、 温度計および窒素ガス導入管を備えた 10 00ml容の五つ口円筒型丸底フラスコに n—ヘプタンを 500 ml加えた。 こ れに H L Bが 3. 0のショ糖脂肪酸エステル （界面活性剤：三菱化学株式会社製 の S— 370) を 0. 92 g添加して分散させ、 昇温して界面活性剤を溶解後、 55 °Cまで冷却した。  500 ml of n-heptane was added to a 1000 ml five-necked cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas inlet tube. 0.92 g of a sucrose fatty acid ester having an HLB of 3.0 (surfactant: S-370 manufactured by Mitsubishi Chemical Corporation) was added and dispersed, and the temperature was raised to dissolve the surfactant. Cooled to 55 ° C.
上記とは別に、 500 ml容の三角フラスコに、 80重量％アクリル酸水溶液 92 gを加えた。 これに、 外部から冷却しつつ、 30重量％水酸化ナトリウム水 溶液 1 02. 2 gを滴下して、 アクリル酸の 75モル％を中和し、 アクリル酸の 部分中和物水溶液を調製した。 さらに、 水 50. 2gと、 重合開始剤の過硫酸力 リウム 0. 1 1 gと、 架橋剤のエチレングリコールジグリシジルェ一テル 9. 2 mgを添加し、 1段目重合用の単量体水溶液を調製した。  Separately from the above, 92 g of an 80% by weight aqueous solution of acrylic acid was added to a 500 ml Erlenmeyer flask. While cooling from the outside, 100. 2 g of a 30% by weight aqueous sodium hydroxide solution was added dropwise to neutralize 75 mol% of acrylic acid, thereby preparing an aqueous solution of partially neutralized acrylic acid. Further, 50.2 g of water, 0.11 g of potassium persulfate as a polymerization initiator, and 9.2 mg of ethylene glycol diglycidyl ether as a cross-linking agent were added, and a monomer for the first-stage polymerization was added. An aqueous solution was prepared.
この 1段目重合用の単量体水溶液を、 上記の五つ口円筒型丸底フラスコに、 撹 拌下で全量加えて分散させ、 系内を窒素で十分に置換した後に昇温し、 浴温を 7 0°Cに保持して、 重合反応を 1時間行った後、 重合スラリー液を室温まで冷却し た。 The monomer aqueous solution for the first-stage polymerization was added and dispersed in the above-described five-necked cylindrical round bottom flask under stirring with stirring, and the system was sufficiently purged with nitrogen, and then heated. After the polymerization reaction was carried out for 1 hour while maintaining the temperature at 70 ° C, the polymerization slurry was cooled to room temperature. Was.
さらに別の 50 Om 1容の三角フラスコに、 8 0重量％アクリル酸水溶液 1 1 9. 1 gを加え、 冷却しつつ 30重量％水酸化ナトリウム水溶液 1 32. 2 gを 滴下して、 アクリル酸の 75モル％を中和し、 さらに水 27. 4 g、 過硫酸カリ ゥム 0. 1 4 g、 エチレングリコールジグリシジルエーテル 35. 7mgを添加 し、 2段目重合用の単量体水溶液を調製し、 氷水浴内で冷却した。  To another 50-Om 1-volume Erlenmeyer flask, add 19.1 g of an 80% by weight aqueous solution of acrylic acid, add 132.2 g of a 30% by weight aqueous solution of sodium hydroxide dropwise with cooling, and add acrylic acid. And 27.4 g of water, 0.14 g of potassium persulfate, and 35.7 mg of ethylene glycol diglycidyl ether were added, and the aqueous monomer solution for the second-stage polymerization was added. Prepared and cooled in an ice-water bath.
この 2段目重合用の単量体水溶液を、 上記重合スラリー液に全量添加後、 再び 系内を窒素で十分に置換した後に昇温し、 浴温を 70°Cに保持して、 2段目の重 合反応を 2時間行った。 重合終了後、 n—ヘプタンに分散した含水ゲル状物に、 ァミノカルボン酸系金属キレート剤として 40重量％ジエチレントリアミン 5酢 酸 5ナトリウム水溶液 0. 53 gを撹拌下で添加した。 その後、 含水ゲル状物か ら、 共沸脱水により水分を系外に除去した。 得られたゲル状物に 2重量％ェチレ ングリコールジグリシジルエーテル水溶液 8. 44 gを添加し、 さらに水分およ ぴ n—ヘプタンを蒸留により除去して乾燥し、 吸水性樹脂 2 1 4. 8 gを得た。 実施例 3  After the entire amount of the monomer aqueous solution for the second stage polymerization was added to the above polymerization slurry solution, the inside of the system was sufficiently replaced with nitrogen again, and then the temperature was raised, and the bath temperature was maintained at 70 ° C. An eye polymerization reaction was performed for 2 hours. After completion of the polymerization, 0.53 g of a 40% by weight aqueous solution of pentasodium diethylenetriamine-5-acetate as an aminocarboxylate-based metal chelating agent was added to the hydrogel dispersed in n-heptane under stirring. Thereafter, water was removed from the hydrogel by azeotropic dehydration. To the obtained gel, 8.44 g of a 2% by weight aqueous solution of ethylene glycol diglycidyl ether was added, water and n-heptane were removed by distillation, and the mixture was dried. g was obtained. Example 3
撹拌機、 還流冷却器、 滴下ロート、 温度計および窒素ガス導入管を備えた 1 0 00m l容の五つ口円筒型丸底フラスコに n—ヘプタンを 500 m l加えた。 こ れに HLBが 3. 0のショ糖脂肪酸エステル （界面活性剤：三菱化学株式会社製 の S— 370) を 0. 92 g添加して分散させ、 昇温して界面活性剤を溶解後、 55 まで冷却した。  500 ml of n-heptane was added to a 100 ml 5-neck cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas inlet tube. 0.92 g of a sucrose fatty acid ester having an HLB of 3.0 (surfactant: S-370 manufactured by Mitsubishi Chemical Corporation) was added and dispersed, and the temperature was raised to dissolve the surfactant. Cooled down to 55.
上記とは別に、 50 Oml容の三角フラスコに、 80重量％アクリル酸水溶液 92 gを加えた。 これに、 外部から冷却しつつ、 30重量％水酸化ナトリゥム水 溶液 1 02. 2 gを滴下して、 アクリル酸の 75モル％を中和し、 アクリル酸の 部分中和物水溶液を調製した。 さらに、 水 50. 2 gと、 重合開始剤の過硫酸力 リウム 0. 1 1 gと、 架橋剤のエチレングリコ一ルジグリシジルエーテル 9. 2 mgを添加し、 重合用の単量体水溶液を調製した。 Separately from the above, 92 g of an 80% by weight aqueous solution of acrylic acid was added to a 50 Oml Erlenmeyer flask. To this, while cooling from the outside, 102. 2 g of a 30% by weight aqueous sodium hydroxide solution was added dropwise to neutralize 75 mol% of acrylic acid to prepare a partially neutralized aqueous solution of acrylic acid. Further, 50.2 g of water, 0.1 g of potassium persulfate as a polymerization initiator, and ethylene glycol diglycidyl ether as a crosslinking agent 9.2 mg was added to prepare a monomer aqueous solution for polymerization.
この重合用の単量体水溶液を、 上記の五つ口円筒型丸底フラスコに、 撹拌下で 全量加えて分散させ、 系内を窒素で十分に置換した後に昇温し、 浴温を 70°Cに 保持して、 重合反応を 1時間行った。 重合終了後、 含水ゲル状物から、 共沸脱水 により水分を系外に除去した。 得られたゲル状物に、 2重量％エチレングリコ一 ルジグリシジルエーテル水溶液 4. 1 4 gを添加し、 再び水分を n—ヘプタンと ともに蒸留により除去した後、 ァミノカルボン酸系金属キレート剤として、 粉体 のトリエチレンテトラミン 6酢酸 （粒子全体の 87重量％が1 0 O m以下） 0 . 4 6 gを撹拌下で添加した。 さらに乾燥し、 水分を n—ヘプタンとともに除去 して、 吸水性樹脂 92. 8 gを得た。 実施例 4  The whole amount of the aqueous monomer solution for polymerization was added to the above-mentioned five-necked cylindrical round-bottom flask with stirring and dispersed, and the system was sufficiently purged with nitrogen, and then heated to a bath temperature of 70 °. C, and the polymerization reaction was carried out for 1 hour. After completion of the polymerization, water was removed from the hydrogel by azeotropic dehydration. To the obtained gel, 4.14 g of a 2% by weight aqueous solution of ethylene glycol diglycidyl ether was added, and water was removed again by distillation together with n-heptane. Then, powder was used as an aminocarboxylic acid-based metal chelating agent. 0.46 g of triethylenetetramine hexaacetic acid (87% by weight of the whole particles was 10 Om or less) was added with stirring. Further drying was carried out, and water was removed together with n-heptane to obtain 92.8 g of a water absorbent resin. Example 4
実施例 3において、 トリエチレンテトラミン 6酢酸を添加しない以外は、 実施 例 3と同様の操作を行い、 吸水性樹脂 92. 0 gを得た。 ポリェチレン袋内に上 記吸水性樹脂全量と粉体のジエチレントリアミン 5酢酸 2ナトリウム （粒子全体 の 85重量 の粒子径が 1 00 am以下） 0. 4 6 gを添加して十分に混合し、 吸水性樹脂 92. 5 gを得た。 実施例 5  The same operation as in Example 3 was carried out except that triethylenetetramine-6-acetic acid was not added, to obtain 92.0 g of a water-absorbent resin. 0.46 g of the above water-absorbent resin and powdered disodium diethylenetriamine pentaacetate (85 wt% of the total particle size is 100 am or less) are added and thoroughly mixed in a polyethylene bag. 92.5 g of resin were obtained. Example 5
撹拌機、 還流冷却器、 滴下ロート、 温度計および窒素ガス導入管を備えた 1 0 0 0m 1容の五つ口円筒型丸底フラスコに n—ヘプタンを 50 Oml加えた。 こ れに HLBが 4. 7のソルビ夕ンモノステアレート （界面活性剤： 日本油脂株式 会社製のノニオン SP— 6 OR) を 0. 92 g添加して分散させ、 昇温して界面 活性剤を溶解後、 5 0 °Cまで冷却した。  N-heptane (50 Oml) was added to a 100 ml 5-volume cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas inlet tube. 0.92 g of sorbitan monostearate with an HLB of 4.7 (surfactant: Nonionic SP-6 OR manufactured by NOF Corporation) was added and dispersed, and the temperature was raised to increase the surfactant. After dissolving, the mixture was cooled to 50 ° C.
上記とは別に、 5 0 Om 1容の三角フラスコに、 80重量％アクリル酸水溶液 92 gを加えた。 これに、 外部から冷却しつつ、 30重量％水酸化ナトリゥム水 溶液 1 02. 2 gを滴下して、 ァクリル酸の 75モル％を中和し、 ァクリル酸の 部分中和物水溶液を調製した。 さらに、 水 20. 8 gと、 重合開始剤の過硫酸力 リウム 0. 1 1 gと、 架橋剤の N, N' —メチレンビスアクリルアミ ド 23. 0 mgを添加した。 これに、 アミノカルボン酸系金属キレート剤として 4 0重量％ ジエチレントリアミン 5酢酸 5ナトリウム水溶液 0. 23 gを添加し、 重合用の 単量体水溶液を調製した。 Separately from the above, 92 g of an 80% by weight aqueous solution of acrylic acid was added to a 50 Om 1 Erlenmeyer flask. While cooling from outside, 30% by weight sodium hydroxide water 1002.2 g of the solution was added dropwise to neutralize 75 mol% of acrylic acid to prepare an aqueous solution of a partially neutralized acrylic acid. Further, 20.8 g of water, 0.11 g of potassium persulfate as a polymerization initiator, and 23.0 mg of N, N'-methylenebisacrylamide as a crosslinking agent were added. To this was added 0.23 g of a 40% by weight aqueous solution of pentasodium diethylenetriamine pentaacetate as an aminocarboxylic acid-based metal chelating agent to prepare an aqueous monomer solution for polymerization.
この重合用の単量体水溶液を、 上記の五つ口円筒型丸底フラスコに、 撹拌下で 全量加えて分散させ、 系内を窒素で十分に置換した後に昇温し、 浴温を 70°Cに 保持して、 重合反応を 2時間行った。 重合終了後の含水ゲル状物から、 共沸脱水 により水分を系外に除去した。 得られたゲル状物に 2重量％ェチレングリコール ジグリシジルエーテル水溶液 4. 60 gを添加し、 さらに水分および n—ヘプ夕 ンを蒸留により除去して乾燥し、 吸水性樹脂 93. 8 gを得た。 実施例 6  The whole amount of the aqueous monomer solution for polymerization was added to the above-mentioned five-necked cylindrical round-bottom flask with stirring and dispersed, and the system was sufficiently purged with nitrogen, and then heated to a bath temperature of 70 °. C, and the polymerization reaction was carried out for 2 hours. After the polymerization, water was removed from the hydrogel by azeotropic dehydration. To the obtained gel, 4.60 g of a 2% by weight aqueous solution of ethylene glycol diglycidyl ether was added, and water and n-heptane were removed by distillation and dried to obtain 93.8 g of a water absorbent resin. Obtained. Example 6
撹拌機、 還流冷却器、 滴下ロート、 温度計および窒素ガス導入管を備えた 1 5 00m l容の五つ口円筒型丸底フラスコに n—ヘプタンを 550 ml加えた。 こ れに HLBが 8. 6のソルビタンモノラウレート (界面活性剤： 日本油脂株式会 社製のノニオン LP— 2 OR) を 0. 84 g添加して分散させ、 昇温して界面活 性剤を溶解後、 40 °Cまで冷却した。  550 ml of n-heptane was added to a 1500 ml five-necked cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas inlet tube. 0.84 g of sorbitan monolaurate with an HLB of 8.6 (surfactant: Nonionic LP-2OR manufactured by NOF Corporation) was added and dispersed, and the temperature was raised to increase the surfactant. After dissolving, the mixture was cooled to 40 ° C.
上記とは別に、 500m l容の三角フラスコに、 80重量％アクリル酸水溶液 70 gを加えた。 これに、 外部から冷却しつつ、 30重量％水酸化ナトリゥム水 溶液 77. 8 gを滴下して、 アクリル酸の 75モル％を中和し、 アクリル酸の部 分中和物水溶液を調製した。 さらに、 水 33. 3 gと、 重合開始剤の過硫酸カリ ゥム 0. 084 gを添加し、 重合用の単量体水溶液を調製した。  Separately from the above, 70 g of an 80% by weight aqueous solution of acrylic acid was added to a 500 ml Erlenmeyer flask. While cooling from the outside, 77.8 g of a 30% by weight aqueous sodium hydroxide solution was added dropwise to neutralize 75 mol% of acrylic acid, thereby preparing a partially neutralized aqueous solution of acrylic acid. Further, 33.3 g of water and 0.084 g of potassium persulfate as a polymerization initiator were added to prepare a monomer aqueous solution for polymerization.
この重合用の単量体水溶液を、 上記の五つ口円筒型丸底フラスコに、 撹拌下で 全量加えて分散させ、 系内を窒素で十分に置換した後に昇温し、 浴温を 70°Cに 保持して、 重合反応を 3時間行った。 重合終了後の含水ゲル状物に、 ァミノカル ボン酸系金属キレ一ト剤として 40重量％ジエチレントリアミン 5酢酸 5ナトリ ゥム水溶液 0. 1 75 gを撹拌下で添加した。 その後、 含水ゲル状物から、 共沸 脱水により水分を系外に除去した。 得られたゲル状物に 2重量％ェチレングリコ ールジグリシジルエーテル水溶液 3. 1 5 gを添加し、 さらに水分および n—へ ブタンを蒸留により除去して乾燥し、 吸水性樹脂 74. O gを得た。 実施例 7 The whole amount of the aqueous monomer solution for polymerization was added to the above-mentioned five-necked cylindrical round-bottomed flask under stirring and dispersed, and the system was sufficiently purged with nitrogen, and then heated to a bath temperature of 70 °. C While maintaining the temperature, the polymerization reaction was performed for 3 hours. After the polymerization was completed, 0.175 g of a 40% by weight aqueous solution of diethylenetriamine pentaacetic acid and 5% sodium acetate was added to the hydrogel product under stirring as an aminocarboxylate-based metal chelating agent. Thereafter, water was removed from the hydrogel by azeotropic dehydration. 3.15 g of a 2% by weight aqueous solution of ethylene glycol diglycidyl ether was added to the obtained gel, and water and n-butane were removed by distillation and dried to obtain 74. O g of a water-absorbent resin. Was. Example 7
実施例 5において、 ジエチレントリアミン 5酢酸 5ナトリウムに代えて、 38 重量％エチレンジァミン 4酢酸 4ナトリウム水溶液 1. 2 1 gを添加した以外は 、 実施例 5と同様の操作を行い、 吸水性樹脂 93. 6 gを得た。 比較例 1  A water-absorbent resin was obtained in the same manner as in Example 5, except that 1.2 g of a 38% by weight aqueous solution of tetrasodium ethylenediamine tetraacetate was added in place of pentasodium diethylenetriamine pentaacetate. g was obtained. Comparative Example 1
実施例 1において、 ァミノカルボン酸系金属キレート剤を添加しない以外は、 実施例 1と同様の操作を行い、 吸水性樹脂 92. 1 gを得た。 比較例 2  Example 1 was repeated, except that no aminocarboxylic acid-based metal chelating agent was added, to obtain 92.1 g of a water-absorbent resin. Comparative Example 2
実施例 2において、 アミノカルボン酸系金属キレート剤を添加しない以外は、 実施例 2と同様の操作を行い、 吸水性樹脂 2 1 2. 5 gを得た。 比較例 3  The same operation as in Example 2 was carried out except that the aminocarboxylic acid-based metal chelating agent was not added in Example 2, to obtain 22.5 g of a water absorbent resin. Comparative Example 3
実施例 3において、 ァミノカルボン酸系金属キレ一ト剤を添加しない以外は、 実施例 3と同様の操作を行い、 吸水性樹脂 92. 1 gを得た。 比較例 4  The same operation as in Example 3 was carried out except that the aminocarboxylic acid-based metal chelating agent was not added, to obtain 92.1 g of a water-absorbing resin. Comparative Example 4
実施例 1において、 t r an s— 1, 2—ジアミノシクロへキサン 4酢酸 4ナ トリウムに代えて、 クェン酸 0. 92 gを水 9. 2 gに溶解した水溶液を添加し た以外は、 実施例 1と同様の操作を行い、 吸水性樹脂を 92. 8 gを得た。 比較例 5 In Example 1, trans- 1,2-diaminocyclohexanetetraacetic acid 92.8 g of a water-absorbent resin was obtained in the same manner as in Example 1, except that an aqueous solution in which 0.92 g of cunic acid was dissolved in 9.2 g of water was added instead of thorium. Comparative Example 5
実施例 3において、 トリエチレンテトラミン 6酢酸に代えて、 トリポリリン酸 ナトリウム （粒子全体の 90重量％が 1 0 0 zm以下） 0. 4 6 gを添加した以 外は、 実施例 3と同様の操作を行い、 吸水性樹脂を 92. 6 gを得た。 上記実施例および比較例で得られた吸水性樹脂の着色試験を以下の方法により 订つた。  The same procedure as in Example 3 except that 0.46 g of sodium tripolyphosphate (90% by weight of the whole particles was 100 zm or less) was used instead of triethylenetetramine hexaacetic acid in Example 3 Was carried out to obtain 92.6 g of a water-absorbing resin. The coloring test of the water absorbent resin obtained in the above Examples and Comparative Examples was performed by the following method.
〔吸水性樹脂の着色試験〕 (Coloring test of water absorbent resin)
吸水性樹脂 2. 0 gを、 内径 3 cm、 深さ 1 cmのポリプロピレン製容器中に 均一に入れた。 この容器を、 温度 50±2°C、 相対湿度 9 0±2%RHに設定さ れた卓上型恒温恒湿槽内に 20日間放置した。 放置後、 恒温恒湿槽内から容器を 取り出し、 しばらく放置して室温まで冷却した。 内径 3 cmのガラス製測定容器 に、 容器内の吸水性樹脂全量を入れ、 吸水性樹脂の黄色度を、 標準用白板で測色 色差計の三刺激値である、 X、 Υ、 Ζを補正したダブルビーム交照測光方式測色 色差計 Ζ— 1 00 1 DP (日本電色工業株式会社製） で測定した。 得られた吸水 性樹脂の X, Y, Z (三刺激値） から、 次式により黄色度を算出した。 同様に、 卓上型恒温恒湿槽内に 20日間放置する試験前の吸水性樹脂の黄色度を求めた。 なお、 上記測定は 3回行い、 値を平均したものを黄色度とした。  2.0 g of the water-absorbent resin was uniformly placed in a polypropylene container having an inner diameter of 3 cm and a depth of 1 cm. The container was left for 20 days in a table-top constant temperature / humidity chamber set at a temperature of 50 ± 2 ° C and a relative humidity of 90 ± 2% RH. After standing, the container was taken out of the thermo-hygrostat and left for a while to cool down to room temperature. Put the entire amount of water-absorbent resin in a glass measuring container with an inner diameter of 3 cm, and correct the yellowness of the water-absorbent resin with a white plate for standard colorimetry. The measurement was performed using a double beam illuminating photometric colorimeter 色 —1001 DP (Nippon Denshoku Industries Co., Ltd.). From the X, Y, Z (tristimulus values) of the obtained water-absorbent resin, the yellowness was calculated by the following equation. Similarly, the yellowness of the water-absorbent resin before the test, which was left in a table-top constant temperature and humidity chamber for 20 days, was determined. The above measurement was performed three times, and the average of the values was defined as yellowness.
黄色度 = 1 0 0 ( 1. 28 X- 1. 0 6 Z) Ύ 上記実施例で使用したアミノカルボン酸系金属キレート剤、 および上記実施例 および比較例で得られた吸水性樹脂の着色試験の結果を表 1に示す。 なお、 表 1 中の括弧内の量は、 アクリル酸 1 0 0重量部に対する量である。 Yellowness = 1 0 0 (1.28 X-1.06 Z) Ύ Table 1 shows the results of the coloring tests of the aminocarboxylic acid-based metal chelating agents used in the above Examples and the water-absorbing resins obtained in the above Examples and Comparative Examples. The amounts in parentheses in Table 1 are based on 100 parts by weight of acrylic acid.
表 1 table 1
Figure imgf000018_0001
Figure imgf000018_0001
表 1から、 実施例で得られたアミノカルボン酸系金属キレート剤を添加した吸 水性樹脂は、 試験前と試験後の黄色度の変化が少なく、 着色が抑制されているこ とがわかる。 それに対して、 比較例で得られたアミノカルボン酸系金属キレート 剤を添加していない吸水性樹脂は、 黄色度の変化が大きく、 かなり着色している ことがわかる。 産業上の利用可能性 Table 1 shows that the water-absorbent resin to which the aminocarboxylic acid-based metal chelating agent obtained in the examples was added had a small change in yellowness before and after the test, and the coloring was suppressed. In contrast, the aminocarboxylic acid-based metal chelate obtained in Comparative Example It can be seen that the water-absorbent resin to which no agent was added had a large change in yellowness and was considerably colored. Industrial applicability
本発明によれば、 ァミノカルボン酸系金属キレート剤の存在下に吸水性樹脂を 製造することにより、 高温高湿下のような厳しい環境条件下においても、 吸水性 樹脂の着色を抑制することができる。 以上に述べた本発明は、 明らかに同一性の範囲のものが多種存在する。 そのよ うな多様性は発明の意図及び範囲から離脱したものとはみなされず、 当業者に自 明であるそのようなすべての変更は、 以下の請求の範囲の技術範囲内に含まれる。  According to the present invention, by producing a water-absorbing resin in the presence of an aminocarboxylic acid-based metal chelating agent, coloring of the water-absorbing resin can be suppressed even under severe environmental conditions such as high temperature and high humidity. . In the present invention described above, there are various types in the range of obvious identity. Such variations are not considered to be a departure from the spirit and scope of the invention, and all such changes that are obvious to those skilled in the art are included within the scope of the following claims.

Claims

請求の範囲 The scope of the claims
1 . 不飽和カルボン酸を必須単量体とする吸水性樹脂の製造工程の、 少なくと もいずれかの工程の系内にまたは製造後の吸水性樹脂に、 ァミノカルボン酸系金 属キレ一ト剤を添加することを特徵とする、 吸水性樹脂の着色防止方法。 1. Aminocarboxylic acid-based metal chelating agent in at least one of the processes for producing a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer, or in the water-absorbent resin after the production. A method for preventing coloring of a water-absorbent resin.
2 . アミノカルボン酸系金属キレート剤の使用量が、 不飽和カルボン酸 1 0 0 重量部に対して 0 . 0 0 1〜 6重量部である請求項 1記載の着色防止方法。 2. The method according to claim 1, wherein the amount of the aminocarboxylic acid-based metal chelating agent is 0.001 to 6 parts by weight based on 100 parts by weight of the unsaturated carboxylic acid.
3 . アミノカルボン酸系金属キレート剤が、 ジエチレントリアミン 5酢酸、 ト リエチレンテトラミン 6酢酸、 t r a n s— 1， 2 —ジァミノシクロへキサン 4 酢酸およびそれらの塩からなる群より選ばれた少なくとも 1種である、 請求項 1 または 2記載の着色防止方法。 3. The aminocarboxylic acid-based metal chelating agent is at least one selected from the group consisting of diethylenetriamine pentaacetic acid, triethylenetetramine hexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid, and salts thereof. Item 1. The coloring prevention method according to item 1 or 2.
4 . 不飽和カルボン酸を必須単量体とする吸水性樹脂の製造工程の、 少なくと もいずれかの工程の系内にまたは製造後の吸水性樹脂に、 ァミノカルボン酸系金 属キレ一ト剤を添加することを特徴とする、 得られる吸水性樹脂の着色を防止す るための、 アミノカルボン酸系金属キレート剤の使用方法。 4. Aminocarboxylic acid-based metal chelating agent, in at least one of the processes in the production process of a water-absorbent resin containing an unsaturated carboxylic acid as an essential monomer, or in the water-absorbent resin after the production. A method for using an aminocarboxylic acid-based metal chelating agent for preventing coloring of the obtained water-absorbent resin, characterized by adding
5 . ァミノカルボン酸系金属キレート剤の使用量が、 不飽和カルボン酸 1 0 0 重量部に対して 0 . 0 0 1〜6重量部である請求項 4記載の使用方法。 5. The use according to claim 4, wherein the amount of the aminocarboxylic acid-based metal chelating agent is 0.001 to 6 parts by weight based on 100 parts by weight of the unsaturated carboxylic acid.
6 . ァミノカルボン酸系金属キレート剤が、 ジエチレントリアミン 5酢酸、 ト リエチレンテトラミン 6酢酸、 t r a n s — l , 2 —ジアミノシクロへキサン 4 酢酸およびそれらの塩からなる群より選ばれた少なくとも 1種である、 請求項 4 または 5記載の使用方法。 6. The aminocarboxylic acid-based metal chelating agent is at least one selected from the group consisting of diethylenetriamine pentaacetic acid, triethylenetetramine hexaacetic acid, trans-l, 2-diaminocyclohexanetetraacetic acid, and salts thereof. Use as described in Section 4 or 5.
PCT/JP2002/013768 2002-01-15 2002-12-27 Method of preventing coloration of water-absorbing resin WO2003059961A1 (en)

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