JP4459209B2 - Method for producing a superabsorbent resin that is powdery, insoluble in water, absorbs water, human waste or blood, and has a low content of soluble matter - Google Patents

Description

  The present invention relates to a method for producing a water-absorbent resin, and more specifically, is a powder having a remarkably high water absorption rate and insoluble in water, absorbs water, human waste or blood, and has a low soluble matter content ( This relates to a method for producing a small amount of highly water-absorbent resin.

  Water-absorbing resins are used in sanitary products such as sanitary products, diapers, and disposable cloths, as well as in agriculture and horticulture as water retention agents. It has been.

  As this type of water-absorbent resin, a starch-acrylonitrile graft copolymer hydrolyzate (see, for example, Patent Document 1) and a starch-acrylic acid graft copolymer partially neutralized product (see, for example, Patent Document 2). ), Saponified vinyl acetate-acrylic acid ester copolymer (for example, see Patent Document 3), hydrolyzate of acrylonitrile copolymer or acrylamide copolymer (for example, see Patent Document 4), and polyacrylic acid. (For example, refer to Patent Document 5). Among them, it is most economical to obtain a highly water-absorbent resin by crosslinking polymerization reaction of acrylic acid and acrylate. Because these acrylic acids are quickly available from the market, and the water-absorbing resins produced thereby have the highest water absorption and are most popular because the manufactured products are cheap and economical. Because.

  The water-absorbing resin is an insoluble hydrophilic polymer, and the inside of the resin has a uniform cross-linked structure. For quality improvement, for example, water absorption rate, gel strength, anti-caking property, liquid permeability, etc. This surface cross-linking treatment, in which the surface of the resin is re-cross-linked after selection, may be any cross-linking agent having two or more functional groups capable of reacting with acid groups. Patents are presented. For example, a method in which a water-absorbing resin is suspended in an organic solvent and polymerized with a cross-linking agent (see, for example, Patent Documents 6 to 9), a water-absorbing resin and an inert multi-functional powder are stirred with a cross-linking agent. A method of adding water to cause a crosslinking reaction (for example, see Patent Documents 10 and 11) A method of adding a crosslinking agent having two or more functional groups and then treating with steam (for example, see Patent Document 12), organic A surface treatment method with a solvent, water and a polyhydric alcohol (for example, see Patent Documents 13 to 15), a method of treating with a crosslinking agent having two or more functional groups in the presence of water and an ether compound ( For example, see Patent Document 16.). These surface treatment methods increase the water absorption rate of the resin or the water absorption capacity under a high pressure, but the holding power decreases on the contrary, but the practicality is impaired.

  A method for obtaining a superabsorbent resin by copolymerizing acrylic acid and acrylate has been developed in many fields, and many of them are industrially produced. As the polymerization method, a polymerization apparatus of Nippon Shokubai (for example, refer to Patent Document 17), a method for performing a polymerization reaction on a belt conveyor (for example, refer to Patent Document 18), and a shearing force generated by shaft rotation of a kneader stirrer is used. While conducting a radical aqueous solution polymerization reaction (for example, see Patent Document 19), a reverse phase suspension polymerization method (for example, see Patent Document 20), or spraying or applying a monomer as a polymerization initiator to a fibrous substrate. There is a polymerization reaction method.

  However, in many of the above known polymerization methods, a radical free radical reaction is carried out together with a reaction material such as a monomer initiator and a crosslinking agent to form a gel-like solid of a superabsorbent resin. Control was not easy and the soluble content was relatively high.

49-43395 JP-A 51-125468 JP 52-14689 Shokoku 53-15959 JP 55-84304 JP 56-131608 JP-A-57-44627 JP-A-58-42602 JP 58-117222 JP 60-163956 JP-A-60-255814 Japanese Unexamined Patent Publication No. 1-113406 JP 63-270741 JP-A-64-50707 JP-A-1-292004 JP-A-2-153903 48-42466 JP 58-49714 A JP-A-57-34101 JP 59-37003

  In view of the above, the present invention provides a method for producing a superabsorbent resin that is powdery, insoluble in water, absorbs water, human waste or blood, and has a low content of soluble matter. In view of the process of the polymerization reaction, it is relatively stable and the reaction heat is not high. In addition to improving the operating environment, it aims to further improve the quality of the product.

The method for producing a superabsorbent resin in the form of powder according to the present invention which is insoluble in water, absorbs water, human waste or blood, and has a low content of soluble matter has at least a neutralization rate of 50 mol (mol)% or more. The acrylic acid monomer aqueous solution is polymerized with a polymerization initiator to form a sticky water-containing gel-like copolymer, and a hydrophilic polyvalent epoxy compound and a polymerization initiator are added to the water-containing gel-like copolymer. After that, it is irradiated with light to cause a repolymerization reaction to form a gel-like solid, and this gel-like solid is dried with hot air at a temperature of 100 ° C. to 250 ° C., crushed and selected, and a surface cross-linking agent is applied. After heating at 80 ° C. to 230 ° C., finally, an inorganic mineral salt powder is added and surface-treated to obtain a powder product. Acrylic acid monomers of the acrylic acid monomer aqueous solution is one selected from acrylic acid, or methacrylic acid, 2-acrylamide-2-methyl-flop Ropansuruhon acid or mixtures thereof.

  The above-mentioned acrylic acid monomer of the present invention can provide a polymer having further excellent water absorption by allowing a copolymerizable monomer other than acrylic acid to coexist. These monomers may be one or more of methacrylic acid, maleic acid, fumaric acid or 2-acrylamide-2-methylpropane sulfonic acid, or other unsaturated double bond hydrophilic monomers. May be added. For example, the properties of highly water-absorbent resins such as acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroethyl methacrylate, methyl acrylate, ethyl acrylate, 2-methylaminopropenyl acrylamide, propenyl acrylamide trimethyl ammonium chloride, etc. It is sufficient that the added amount is such that it does not break.

  The viscosity of the viscous gel-like copolymer obtained by the production method of the present invention is 10 to 10,000 cp, and a thermal decomposition type and a redox type are used as polymerization initiators. The reaction can be carried out in an upright reaction vessel or a horizontal cylindrical vessel equipped with a stirring blade, the polymerization temperature is 5 to 80 ° C., and the reaction time is 0.5 to 16 hours. Further, the time for causing the polymerization reaction by irradiation with light is within 10 seconds to 300 seconds, preferably 30 to 60 seconds. The light irradiation here refers to ultraviolet irradiation.

  The polymerization reaction vessel may be an upright or horizontal cylindrical vessel with a stirrer that can smoothly mix the raw materials used in the polymerization reaction and perform the polymerization reaction. The viscous water-containing gel-like copolymer produced by the polymerization reaction is continuously sent to the belt conveyor, and the belt-conveyor has a strong ultraviolet irradiation rod to irradiate the water-containing gel-like copolymer with light. Into a gel-like solid.

Polyepoxy compounds hydrophilic used in this invention include sorbitol polyglycidyl ether, polypropylene Punt triol ether, ethylene glycidyl copolymers over glycidyl ether, poly ethylene glycol diglycidyl ether, there is Bisupuro pan preparative Rio chromatography ether, etc., the surface The crosslinking agent is a polyhydric alcohol, polyethylene diglycidyl ether, ethylene carbonate or a mixture thereof, and the amount used is 0.005 to 5.0% by weight.

In addition, the fertile inorganic salt powder used as the surface treatment cross-linking agent of the present invention is aluminum sulfate, aluminum oxide, magnesium oxide, calcium oxide, kaolin, silicon dioxide, calcium carbonate, magnesium carbonate, etc., and a mixture thereof. The amount is 0.01-4.0% by weight.
The particle diameter of the water absorbent resin produced in the present invention is approximately 0.05 to 1 mm.

  Prior to the radical polymerization reaction of the present invention, the concentration control of the monomer aqueous solution is 20 to 50% by weight, preferably 30 to 45% by weight. When the concentration% by weight is 20 or less, the polymer is soft and sticky, which is disadvantageous for machining.On the other hand, when the concentration is 55% by weight or more, it becomes saturated and the preparation is not easy, and the reaction is difficult. Controlling the reaction heat is not easy.

  The carboxyl group of the acrylic acid monomer is partially neutralized, and the PH value of the product is neutral or slightly acidic, and the neutralizing agent is lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, Potassium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate and ammonia. The partially neutralized acrylic acid monomer becomes a lithium salt, a sodium salt, an amino salt or a mixed salt of two or more, and the concentration mol% is 45 to 85, and the preferred concentration is 50 mol% to 75 mol%, When the mol% of the neutralization concentration is 45 or less, the PH value of the product is low, and when it is 85 or more, the PH value is high, that is, when the PH value of the product is neutral or slightly acidic, It is not preferable because it lacks safety.

In the prepolymerization reaction, radical polymerization is initiated by decomposition of the polymerization initiator. A thermal decomposition type initiator is used as the polymerization initiator. Hydrogen peroxide in the thermally decomposable initiator are peroxide, di t- butyl peroxide, peroxide-amine, the persulfate (amino salts, alkali metal salts), etc., or azo compounds, 2, 2 '- Jiazobisu (2-formamidinium Npuropan) di chloride hydride, 2, 2'Jiazobisu (N, N-dimethyl-azobis di emissions) di chloride hydride; or without a redox initiator using a reducing agent , for example, acid sulfite, Ji Oh sulfate, ascorbic acid, ferrite salt, or the like used in conjunction mix redox initiator and a thermal decomposition initiator, first react with a redox initiator before, radicals When the radical is transferred onto the monomer and the polymerization reaction takes place at the same time, a large amount of heat is released to raise the temperature, and when that temperature reaches the decomposition temperature of the thermal decomposition initiator, The decomposition of the thermal decomposition initiator Is intended to perfect all of the polymerization reaction caused come. A reasonable use amount of a general radical polymerization initiator is 0.001 to 10% by weight (neutralizing dose of acrylate), and a better use amount is 0.1 to 5% by weight. When the amount used is 0.001% by weight or less, the reaction is slow and uneconomical, and when the amount used is 10% by weight or more, the reaction is too fast to easily control the heat, and because of excessive polymerization, a gel solid is formed. There is.

The crosslinking agent to which the crosslinking agent is added to the viscous pre-copolymer before the polymerization reaction by irradiation with light is selected from unsaturated compounds having two or more double bonds. For example, N, N-di (2-acryl) amino, N, N′-methylenebisacrylamide, N, N′-methylenebismethacrylamide, acrylic acrylate, ethylene glycol diacrylate, polyethylene glycol, diacrylate, ethylene glycol dimethyl Acrylate, polyethylene glycol, dimethacrylate, glycerol triacrylate, glycerol trimethacrylate, triacrylate of glycerol ethylene oxide, or triacrylate or trimethacrylate of trimethacrylate, trimethylolpropane ethylene oxide, trimethylolpropane trimethacrylate , trimethylolpropane triacrylate, N, N, N-tri (2-acrylic) amine, ethylene glycidyl copolymers over diacrylate, Polyglycolic, diacrylate, or two or more than two Okishikiru group compounds, sorbitol poly grayed ethers, Poripuropa down triol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, Bisupuropa emissions tri O Le, policy Jill ether is used.

  The water-absorbent resin after the radical reaction has an appropriate degree of crosslinking, and the gel product has an appropriate processability. The radical polymerization reaction crosslinking agent may be used alone or in combination of two or more. An appropriate amount added is 0.001 to 5% by weight (total solid content of the reaction product), preferably 0.01 to 3% by weight. If the addition amount is 0.001% by weight or less, the water-containing monomer after polymerization is soft and sticky, so that the device processability is not easy.

  The pre-copolymer with stickiness is subjected to a re-polymerization reaction by irradiating with ultraviolet rays for 10 to 300 seconds, preferably 30 to 60 seconds, in a belt conveyor type reactor or a horizontal reactor with a stirring blade. The water-absorbing resin is dried with a squeezing and cutting machine after making it into a gel-like material having a particle size of 20 mm or less, and preferably 10 mm or less. The drying temperature is 100 ° C. to 250 ° C. or less, preferably 120 ° C. to 180 ° C. If the temperature is 120 ° C or lower, the drying time is long and uneconomical. If the temperature is 180 ° C or higher, the polymerization reaction of the crosslinking agent proceeds too quickly, and the degree of crosslinking is too high in the drying process, so solubles cannot be removed. As a result, a low-soluble resin product cannot be obtained.

  After drying, it is pulverized and screened to a uniform particle size (screen), and then a surface cross-linking agent is applied, and the selected particle size with a constant particle size is preferably 0.06mm to 1.00mm, 0.10mm From 0.850mm is even better. If the particle size is 0.06mm or less, there is a lot of dust, and if it is 1.00mm or more, the water absorption rate of the resin is slow.

When a surface treatment is performed on a resin having a selected particle size, a crosslinking agent that simultaneously performs a polymerization reaction is a polyhydric alcohol, such as propanenitrile, ethylene glycol, diethylene glycol, triethine glycol, polyethylene glycol, Propylene glycol, 1, butylene glycol, trimethylpropane, sorbitol, etc .; or polyamines such as ethylenediamine, diethylenediamine, triethylenediamine, polyethylenediamine; or two or more epoxy group compounds such as sorbitol, polyglycidyl ethers, Poripuropa down triol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene Les glycol diglycidyl ether, polyethylene glycol diglycidyl et Ether, Bisupuropa down triol polyglycidyl ether, or hydro-oxyalkylene Cabo sulfonates, such as ethylene glycol carbonate, 4-methyl-1,3 dioxinyl -2-1-on or the like is used. You may use the crosslinking agent used for surface treatment individually or in mixture of 2 or more types. Better usage is 0.001 to 10% by weight (total reactants), even better usage is 0.005 to 5% by weight. When the addition amount of these surface treatment crosslinking agents is 0.001% by weight or less, there is no effect, and when it is 10% by weight or more, the water absorption efficiency is low and the resin performance is poor.

The surface cross-linking agent coating treatment may be added directly, added as an aqueous solution, or added as a surface cross-linking agent hydrophilic organic solvent aqueous solution.
For example, methanol, ethanol, propanol, isobutanol, acetone, methyl ether, ethyl ether and the like are used as the hydrophilic organic solvent, but it is most convenient and preferred to use methanol industrially.

  The resin coated with the surface cross-linking agent is heated again at a temperature of 80 ° C to 230 ° C to further copolymerize the inside of the cross-linking agent, and if the heating temperature is 80 ° C or lower, the cross-linking polymerization reaction time becomes longer, which is uneconomical. When the heat treatment temperature is 230 ° C. or higher, the resin itself is liable to deteriorate and adversely affect the quality.Therefore, the present invention shortens the time when the temperature is high, and extends the time when the temperature is low. Adjust within 150 minutes.

  Since the superabsorbent resin has a phenomenon of agglomeration after moisture absorption, the superabsorbent resin used in areas with high humidity usually avoids the agglomeration after moisture absorption. An activator was applied to make the surface oleophilic so that it did not clump easily after moisture absorption. These mineral inorganic salt powders are selected from aluminum sulfate, silicon dioxide, aluminum oxide, magnesium oxide, calcium oxide, kaolin, calcium carbonate, magnesium carbonate or mixtures thereof, with aluminum sulfate and silicon dioxide being more commonly used. The addition amount of the ferrous inorganic salt powder is related to the size of the inorganic salt powder granule. The relatively small granule has a large surface area and can reduce the amount of powder used.

  The addition amount is 0.005 to 10.0% by weight, preferably 0.01 to 4.0% by weight, the particle size is 0.001 to 100 μm, and powders smaller than 0.001 μm are fine in product and are not suitable for industrial production. If the particle size is larger than 100 μm, the amount of addition is too large and the resin water absorption is greatly affected.

The fertile inorganic salt may be added alone or mixed with a surfactant or a sticky organic compound. Surfactants or sticky organic compounds are nonionic surfactants with a hydrophilic-lipophilic balance (HLB) value of 12 or more, water-soluble anionic surfactants, cationic surfactants, anionic amphoteric surfactants Selected from an agent or a mixture thereof, and usually glycerin, ethylene glycol, hexamethylene glycol, polyethylene oxide, polyethylene glycol, stearyl acid polyethylene glycol ester, stearyl acid polyethylene glycol hexamethylene glycol stearate, polyoxyethylene noryl phenyl ether, Polyoxyethylene octylphenyl ether, polyoxyethylene dodecanyl phenyl ether, polyoxyethylene alkali ether, and polyoxyethylene lauryl ether are used. It is.
These surfactants or sticky organic compounds may be added in the form of an aqueous solution or may be added alone. A reasonable addition is 0.001 to 5% by weight, and a better addition is 0.01 to 3% by weight.

  The overall polymerization reaction of the present invention is one in which the prepolymerization reaction is performed first, and then the polymerization reaction is further advanced. The viscosity of the prepolymerization reaction product is clearly higher than the viscosity of the liquid reactant, and the flow rate It is easy to carry out highly stable polymerization reaction on a belt conveyor type reactor, and the reaction heat is not high, so it greatly improves the operating environment, and the production quality and quantity are greatly increased. It has a particularly good effect on lowering the low soluble content.

The superabsorbent resin that is powdery insoluble in water, absorbs water, human waste or blood, and has a low soluble content, obtained by the production method of the present invention, has a relatively high hydrogel polymer viscosity. It has the effects that it is higher than the viscosity of the material obtained by other liquid reactions, has low fluidity, can be easily operated in a belt conveyor reactor, has good overall polymerization reaction stability, and does not have high reaction heat.
The manufacturing method of the present invention not only improves the operating environment as described above, but also greatly increases the quality of the manufactured product, and particularly has a low soluble content.

  Hereinafter, a test example by the production method of the present invention and a production example by the conventional production method (conventional example) will be shown and will be described in more detail by comparing the content of soluble matter, etc., but the present invention is limited by these. It is not a thing.

A performance test in which the superabsorbent resin produced in the present invention is a resin having a low soluble content was performed by the following method.
Weigh 0.5 g of superabsorbent resin and 185 g of 0.9% salt solution in a 200 ml beaker and stir for 1 hour with a stirrer at 500 rpm. Collect the filtrate of superabsorbent resin with filter paper. To do. 20 g of the filtrate is first titrated with 0.1N NaOH and then back-titration neutralized again with 0.1N Hcl to calculate the soluble matter content of the superabsorbent resin.

Test example 1
1) Take 1760 g of acrylic acid and 2263.7 g of water into a 6000 ml flask purged with nitrogen in advance, and neutralize by adding dropwise 1476.3 g of 45% by weight aqueous soda with cooling while stirring, with a concentration of 38.6 wt% 68 mol% of acrylic acid obtained from the acrylic acid monomer aqueous solution becomes sodium acrylate after neutralization.
2) The partially neutralized acrylic acid monomer aqueous solution is mixed with 0.1 g of potassium persulfate and sodium sulfite (weight ratio is 1: 1) and charged into a jacketed horizontal tube type prepolymerization reactor. A prepolymerization reaction is performed by mixing, and a precopolymer having a viscosity of 100 cp is obtained in a reaction temperature of 20 ° C. and a reaction time of 60 minutes.
3) This sticky pre-copolymer, 1g of azodiisobutyronitrile, 0.768g of ethylene glycol triglycidyl ether (n = 7) are lifted onto a belt conveyor, and then irradiated with an ultraviolet irradiation pad provided on the belt conveyor. The mixture is irradiated for 40 seconds (irradiation degree is 7.1 J / cm ² ) to cause a crosslinking polymerization reaction to form a gel body.
4) Use a squeezing cutter to make a gel with a particle size of 2mm or less.
5) Dry at 130 ° C. for about 2 hours and sieve to obtain a powdery superabsorbent resin having a fixed particle size of 0.1 mm to 0.85 mm.
6) Take 10g of this superabsorbent resin, add 0.1g aluminum sulfate powder and mix well, then add 0.4g ethylene glycol carbonate / water / methanol = 1: 1: 1 aqueous solution and add 215 ℃ Heat at temperature for 10 minutes.
7) Results of measurement of the superabsorbent resin after cooling, holding force 29.2 g / g, 20g / cm absorption capacity under a ^second pressure is 29.5 g / g, 49g / cm 2 water absorption capacity under pressure 22.5 g / g. Soluble content was 5.1%.

Test examples 2 to 4:
1) Same as the operation method of Test Example 1, except that the prepolymerization reaction time is 180 minutes, the viscosity of the prepolymer obtained at 420 minutes and 720 minutes is 370 cp, 1350 cp and 5000 cp, respectively.
2) retention of the product 32.3 g / g on each other, 34.5 g / g, 37.1 g / g, absorbency under 20 g / cm ² pressure 32.7g / g, 31.5 g / g , 28.7 g / g, 49g The water absorption capacity under ² cm / pressure is 24.1 g / g, 22.9 g / g, 19.8 g / g, and the soluble content is 5.3%, 6.1%, 7.6%.

Test Examples 5-8:
1) The operating method was the same as in Test Example 1, except that the prepolymerization reaction temperatures were 5 ° C, 15 ° C, 25 ° C and 35 ° C, and the viscosities of the prepolymers were 15 cp, 80 cp, 270 cp and 1.50 cp, respectively. ,
2) retention of the product 27.1 g / g on each other, 28.6g / g, 31.7g / g , 33.4g / g, 20g / cm 2 water absorption capacity under pressure 27.3g / g, 28.7g / g, 30.9 g / g, 31.5g / g, 49g / cm 2 water absorption capacity under pressure 18.28g / g, 19.8g / g, 22.8g / g, 23.6g / g, solubles content of 2.5%, 3.4% 5.2% and 6.1%.

Test Examples 9-12:
1) instructions for same as in Test Example 1, except that the preliminary polymerization initiator is a mixture of ammonium persulfate and sodium sulfite (weight ratio 1: 1), hydrogen peroxide, di-i an isopropyl peroxide carbonate, 2,2 ' - Jiazobisu (2 Horumuami di Npuropan) a di chloride hydride;
2) The product holding power is 30.1g / g, 20.7g / g, 30.5g / g, 31.0g / g, 20g / cm respectively, and the water absorption capacity under ² pressure is 29.6g / g, 30.3g / g, 28.9g / g, 31.6g / g, 49g / cm2 Water absorption capacity under ² pressure is 23.0g / g, 22.5g / g, 29.2g / g, 23.6g / g, soluble content is 5.1%, 6.2%, 5.4% and 5.7%.

Test Examples 13-15:
1) instructions for same as in Test Example 1, except that the crosslinking agent (ethylene glycol triglycidyl ether) are each propane preparative Rio polyethylene glycol triglycidyl ether, triethylene propanyl amine, and ethylene glycol diacrylate;
2) The product holding power is 33.2g / g, 26.5g / g, 27.8g / g, 20g / cm respectively.The water absorption capacity under ² pressure is 31.3g / g, 27.9g / g, 28.7g / g, 49g / cm Water absorption capacity under cm ² pressure is 24.9g / g, 22.5g / g, 23.6g / g, soluble content is 5.7%, 3.5%, 3.9%

Test Examples 16-19:
1) The operation method is the same as in Test Example 1, except that the ultraviolet irradiation time is 60 seconds, 30 seconds, 20 seconds, 10 seconds, and the illuminance is 10.2 J / cm ² , 5.1 J / cm ² , 3.5 J / cm ² , Done at 1.7 J / cm ² ;
2) The product holding power is 27.6g / g, 29.6g / g, 30.2g / g, 36.1g / g, 20g // cm ² The water absorption capacity under pressure is 31.3g / g, 32.5g / g, 30.4 g / g, 32.9 g / g, 49 / cm2 Water absorption capacity under ² pressure is 24.9 g / g, 26.3 g / g, 24.3 g / g, 19.7 g / g, soluble content is 4.2%, 6.3% 7.1% and 8.1%.

Conventional example:
1) Take 1760 g of acrylic acid and 2263.7 g of water in a nitrogen-substituted 6000 ml flask and neutralize by adding dropwise 1476.3 g of 45% by weight of soda with cooling while stirring, with a concentration of 36.6 wt% 68 mol% of acrylic acid obtained from the above acrylic acid monomer aqueous solution became sodium acrylate after neutralization.
2) Add 0.768 g of ethylene glycol triglycidyl ether (n = 7) while maintaining the partially neutralized acrylic acid monomer aqueous solution at a temperature of 20 ° C. to the left and right.
3) addition of 1.9g hydrogen peroxide, 2,2 sodium persulfate and 1.0g of 3 g '- azobis (2-E Le Muami di Npuropan) was added di-chloride hydride crosslinking initiator copolymerization reaction allowed 1 hour Leave to form naturally in the form of a gel.
4) It is in a gel body with a particle size of 2mm or less with a drawing cutter.
5) Dry at 130 ° C. for about 2 hours and sieve to obtain a powdery superabsorbent resin having a fixed particle size of 0.1 mm to 0.85 mm.
6) Take 10g of this superabsorbent resin, add 0.1g of aluminum sulfate powder and mix well, then add 0.4g of ethylene glycol carbonate / water / methanol = 1: 1: 1 mixed aqueous solution and 215 ℃ Heat for 10 minutes.
7) As a result of measuring the highly water-absorbent resin after cooling, the holding power is 33.1 g / g, the water absorption capacity under the pressure of 20 g / cm2 is 32.0 g / g, the water absorption capacity under the pressure of 49 g / cm2 is 22.1 g / g, The soluble content was 12.1%.

  From the above results, it can be seen that according to the production method of the present invention, a high-quality water-absorbent resin having a soluble content lower than that of conventional products can be provided.

Claims (7)

Acrylic acid monomer aqueous solution having a neutralization rate of 50 mol% or more is prepolymerized with a thermal decomposition type or redox type prepolymerization initiator to obtain a sticky water-containing gel-like copolymer,
Sorbitol polyglycidyl ether, polypropylene punt triol polyglycidyl ether, ethylene glycol diglycidyl ether, after the addition of polyethylene glycol diglycidyl ether, or a bis-propanetriol polyglycidyl ether hydrophilic polyepoxy compound and re-polymerization initiator, A process for producing a superabsorbent resin, which is in a powder form, insoluble in water, absorbs water, human waste or blood, and has a low content of soluble matter, characterized by subjecting to a repolymerization reaction by irradiation with ultraviolet rays. The acrylic acid monomer in the acrylic acid monomer aqueous solution is one or a mixture of two or more of acrylic acid, methacrylic acid, or 2-acrylamido-2-methylpropanesulfonic acid. A process for producing a highly water-absorbent resin that is insoluble in water, absorbs water, human waste or blood, and has a low soluble matter content. The thermal decomposition type prepolymerization initiator is peroxide, hydrogen peroxide, di-t-butyl peroxide, amine peroxide, or persulfate (amino salt, alkali metal salt). 2, 2 '- Jiazobisu (2-formamidinium Npuropa down) di chloride hydride,
The powdery insoluble in water according to claim 1, wherein the oxidation- reduction type prepolymerization reaction initiator is acidic sulfite, thiosulfate , ascorbic acid , or ferrite salt. A method for producing a superabsorbent resin that absorbs blood and has a low soluble matter content. 2. The powdery water-insoluble, water, human waste or blood according to claim 1, wherein the polymerization reactor for the prepolymerization reaction is an upright reaction tank or a horizontal cylindrical vessel equipped with a stirring blade. And a method for producing a superabsorbent resin with a low content of soluble matter. 2. The prepolymerization reaction is conducted at a temperature of 5 to 80 [deg.] C. and a reaction time of 0.5 to 16 hours. The powder is insoluble in water and absorbs water, human waste or blood. And a method for producing a superabsorbent resin having a low soluble matter content. 2. The irradiation time for the re-polymerization reaction by irradiating with ultraviolet rays is performed within 30 to 60 seconds, and is insoluble in water and absorbs water, human waste or blood. And a method for producing a superabsorbent resin having a low content of soluble matter. In the method for producing a superabsorbent resin as claimed in claim 1, which is insoluble in water, absorbs water, human waste or blood, and has a low content of soluble matter,
Furthermore, a polyhydric alcohol, polyhydric amine, or two or more epoxy group compounds are finally applied as a surface cross-linking agent.