JPS61252212A - Production of highly water-absorptive polymer - Google Patents

Abstract

PURPOSE:To obtain the titled polymer of a high absorption rate of water and a high wet gel strength, by grafting a specified olefinically unsaturated silane coupling agent onto a highly water-absorptive polymer having carboxyl and/or carboxylate groups. CONSTITUTION:To 100pts.wt. highly water-absorptive polymer having carboxyl and/or carboxylate groups as a constituent of the (co)polymer [e.g., starch- acrylic acid (salt) graft copolymer], 0.001-50pts.wt. olefinically unsaturated silane coupling agent of the formula (wherein R is an olefinically unsaturated hydrocarbon or a hydrocarboxy, Y is a hydrolyzable organic group and R' is R or Y), 0.5-300pts.wt. water, 0.005-5pts.wt. organic peroxide (e.g., benzoyl peroxide) and, optionally, 10-5,000pts.wt. inet solvent (e.g., methanol) are added and the mixture is refluxed by heating to effect a graft reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a superabsorbent polymer that has a high water absorption rate and high water absorption gel strength.

[Industrial application field]

The polymer obtained by the production method of the present invention absorbs a large amount of water in a short period of time and swells. However, since it is insoluble in water and has a high gel strength, the swollen polymer has high gel strength. It can be advantageously used in the production of various materials that are used in a swollen state.

[Prior art]

Conventionally, paper, pulp, nonwoven fabrics, sponge-like urethane resins, and the like have been used as water-retaining agents in various sanitary materials such as sanitary napkins and paper diapers, and in various agricultural materials. However, these materials absorb only 10 to 50 times their own weight of water, so in order to absorb or retain a large amount of water, a large amount of material is required, which not only makes them extremely bulky, but also makes them extremely bulky. There were drawbacks, such as the fact that if a material that had absorbed water was pressurized, the water would easily separate.

In order to improve the above-mentioned drawbacks of this type of water-absorbing material, a highly water-absorbing single-molecule material has been proposed in recent years. For example, starch graft polymers (Japanese Patent Publication No. 53-46199, etc.), modified cellulose (Japanese Patent Publication No. 50-80376, etc.), crosslinked products of water-soluble polymers (Japanese Patent Publication No. 43-234, etc.),
No. 62, etc.), self-crosslinking type acrylic acid alkali metal salt polymers (Japanese Patent Publication No. 54-30710, etc.), and the like have been proposed.

However, these superabsorbent polymer materials also have low water absorption capacity, and even if they have high water absorption capacity, the water absorption rate is slow.
When it comes into contact with an absorbent material, a so-called @mamako is generated and water is not absorbed efficiently, and it takes a long time to absorb the desired amount of water. Therefore, it is unsuitable for applications that require instantaneous water absorption ability and absorbs a large amount of material at once, and has many problems.

Generally, in order to improve the dispersibility and solubility in water or the water absorption rate of a hydrophilic polymer, a method of making the surface of the polymer hydrophobic is known. That is, by mixing a surfactant such as nrubitan monostearate, a non-volatile hydrocarbon, calcium stearate, etc. into a powdered hydrophilic polymer, it has been possible to improve the dispersibility in papermaking and water. however,
Even if this method is applied to superabsorbent polymers, the dispersibility in water is improved in the very early stage, but the water absorption rate is slow, so if this is not improved, so-called "!ma" will be generated during the water absorption process. , the sufficient effect is not exerted.

Another method for increasing the water absorption rate of superabsorbent polymers is to increase the crosslinking density to reduce the hydrophilicity of the polymer. However, if this method is carried out, the water absorption rate is slightly improved, but it does not have a very significant effect, and in this case, the water absorption capacity is significantly reduced, and the performance of a single super absorbent polymer is impaired, so it is not a preferred method. It's hard to say.

[Problem that the invention seeks to solve]

The present invention aims to address the above-mentioned problems with superabsorbent materials, ie, to provide a method for producing a superabsorbent polymer that has significantly improved water absorption rate and gel strength, particularly water absorption rate.

[Means for solving problems]

(Structure of the Invention) As a result of various studies aimed at solving the above-mentioned problems, the present inventors have discovered that a superabsorbent polymer containing a carboxyl group or/and a carboxylate group as a component of a polymer or copolymer has been developed. % (wherein R represents an olefinically unsaturated hydrocarbon group or a hydrocarbonoxy group, Y represents a hydrolyzable organic group, and R' represents a group R or We have discovered that by grafting with an olefinically unsaturated silane coupling agent represented by
This led to the completion of the present invention.

(Detailed Description of the Invention) The superabsorbent polymer used in the production method of the present invention may be any polymer or copolymer containing a carboxyl group or/and a carboxylate group as a constituent component. Any type of polymer or polymerization method may be used. Examples of these super absorbent polymers include acrylic acid (salt) polymer, methacrylic acid (salt) polymer, acrylic acid (salt)/methacrylic acid (salt) polymer, etc.
Copolymer, starch/acrylic acid (salt) graft copolymer,
saponified product of starch/ethyl acrylate graft copolymer,
saponified product of starch/methyl methacrylate graft copolymer, saponified product of methyl methacrylate/vinyl acetate copolymer,
Saponified products of methyl acrylate/vinyl acetate copolymer, saponified products of starch/acrylonitrile graft copolymer, saponified products of starch/acrylamide graft copolymer, starch/acrylonitrile-2-acrylamide-2-methylpropanesulfonic acid graft Examples include saponified copolymers, crosslinked saponified starch/acrylonitrile/vinyl sulfonic acid graft copolymers, polyethylene oxide crosslinked with acrylic acid, and crosslinked sodium carboxymethyl cellulose. In addition, acrylic acid (salt) or methacrylic acid (salt), maleic acid (salt), itaconic acid (salt), acrylamide, 2-acrylamide-
2-methylpropanesulfonic acid, 2-(meth)acryloylethanesulfonic acid, 2-hydroxyethyl (meth)
Copolymers in which comonomers such as acrylates are copolymerized to the extent that they do not reduce the performance of the resulting water-absorbing polymer may also be used in the method of the present invention.

Examples of the salts of the carboxylate groups of these superabsorbent polymers include alkali metal salts, alkaline earth metal salts, ammonium salts, and amine salts, among which alkali metal salts are preferred.

Further, specific examples of crosslinking methods used in producing these super absorbent polymers include divinyl compounds such as N,N'-methylenebisacrylamide and (poly)ethylene glycol di(meth)acrylate. Polyglycidyl ethers such as (poly)ethylene glycol diglycidyl ether, herroeboxy compounds such as epichlorohydrin, polyaldehydes such as geltaraldehyde and glyoxal, polyols such as ethylene glycol and glycerin, and ethylene diamine, etc. A method of crosslinking by reacting polyamines etc. with a polyfunctional compound that can react with functional groups in super absorbent polymers, such as carboxyl groups or carboxylate groups, and other methods that cause pseudo-crosslinking or high degree of entanglement of molecular chains during the polymerization process. Self-crosslinking by

The silane coupling agent used in the production method of the present invention is represented by the general formula RR'sty, where R
is an olefinically unsaturated hydrocarbon group or an acyloxy group,
A hydrocarbonoxy group refers to a hydrocarbon group having an acyl group or an alkoxy group. Examples of such groups include vinyl, allyl, butenyl, cyclohexenyl, cyclo-C dipentazinonyl, acryloxypropyl, methacryloxypropyl, and the like. Among these, vinyl groups and methacryloxypropyl groups are particularly preferred.

Y represents a hydrolyzable organic group, such as an alkoxy group such as a methoxy group, an ethoxy group, a butoxy group, an acyloxy group such as a formyloxy group, an acetoxy group, or a propionoxy group, -0N=C(CHJ)2, - 0N=C(
Oxime groups such as C, f(5)2(7) or -NHCH
3, -NHC2H5, and alkylamino groups such as -NH(C,H5), and -ruamino groups. Further, R' is a group R or a group Y.

Among the above-mentioned silane coupling agents, those containing three hydrolyzable organic groups are preferable, and specifically, for example, vinyltrimethoxysilane, vinyltriethoxysilane, and γ-methacryloxypropyl Trimethoxysilane is preferred.

The amount of these silane coupling agents used varies depending on the type and degree of grafting of the superabsorbent polymer used, the amount of water present, and the type and amount of inert solvent, but in general, superabsorbent o per 100 parts by weight of polymer
, o o t to 50 parts by weight, preferably 0.2 to 10 parts by weight. o, o o i parts by weight If the amount used is too small, the effect of the addition will not be expressed, and if it is more than 50 parts by weight, even more significant effects will be produced, resulting in high costs and the polymer quality after treatment. This is not preferable because the water absorption capacity decreases.

The method of grafting the superabsorbent polymer used in the present invention with the silane coupling agent may be any conventionally known method, such as a method of irradiating with radiation, an electron beam, an ultraviolet ray, etc. Diserium salts, persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide,
Methods that generate free radicals in superabsorbent polymers, such as methods using organic peroxides such as cumene hydroperoxide and t-butyl peroxide, and azo compounds such as azoisobutyronitrile and dimethyl azodiisobutyrate. Any method is fine.

Among these, organic peroxides such as hydrogen peroxide and benzoyl peroxide are particularly preferably used.

The amount of these free radical generators used varies slightly depending on the type of superabsorbent polymer used, the reaction temperature level, etc., but generally it is 0.005 to 5 parts by weight per 100 parts by weight of superabsorbent polymer. Part by weight, preferably 0.02~
2 parts by weight. When the amount used is less than 0.005 parts by weight, effective grafting is difficult to occur, and when it is used more than 5 parts by weight, no remarkable effect is observed and it is not advantageous in terms of cost.

To describe a specific embodiment of grafting the above-mentioned silane coupling agent onto a superabsorbent polymer, for example, a silane coupling agent and the above-mentioned free radicals are grafted into a dry superabsorbent polymer. A mixture of a generator and water is added and heated, or the dried superabsorbent polymer is mixed with alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, ethers such as diethyl ether, dibutyl ether, dioxane, and tetrahydrofuran. Inert solvents such as hydrocarbons such as n-pentane, n-hexane, n-hebutane, cyclohexane, benzene, toluene, and xylene, halogenated hydrocarbons such as methylene chloride, chloroform, and ethylene dichloride, etc. to form a slurry, add a mixture of a silane coupling agent, a free radical generator and water, and heat-treat, preferably under reflux, or after adding the silane coupling agent, water and a free radical generator. A method of heating and evaporating the slurry liquid can be mentioned. In addition, a silane coupling agent and a free radical generator are added to the above-mentioned inert solvent and water or a reaction solution obtained from the polymerization reaction step containing water, and the mixture is preferably heated under reflux or silane coupling is carried out. After adding the agent and the free radical generator, the slurry liquid is heated and evaporated, and after the reactive digrafting treatment, diptyltin diclaurylate, diptyltin diacetate, which are generally known as silanol condensation catalysts, are added. By adding diptyltin dioctoate or the like and carrying out the reaction treatment, the superabsorbent polymer having an excellent water absorption rate, which is the object of the present invention, can be obtained more effectively.

In the reaction treatment in the present invention, the amount of water present is 0.5 to 30 parts by weight per 100 parts by weight of the superabsorbent polymer.
0 parts by weight is suitable. If the amount of water is less than 0.5 parts by weight, the superabsorbent polymer will not be swollen, and the grafting with the silane coupling agent and silanol condensation reaction will be difficult to proceed, requiring a long reaction time. Therefore, it is disadvantageous industrially.

On the other hand, if the amount of water is 300 parts by weight or more, the gel strength of the superabsorbent polymer obtained is improved, but the main point is that
As a result, the water absorption capacity is significantly reduced, which is not preferable.

When using the above-mentioned inert solvent shown in this specific example for the reaction treatment in the present invention, it is known in the literature that it is a solvent that does not have any influence on the superabsorbent polymer. They can be used alone or in combination of two or more. The amount used varies depending on the type of superabsorbent polymer and inert solvent used, but is generally 10 to 5ooo parts by weight, preferably 50 to 50ooo parts by weight, based on the superabsorbent polymer and ioo parts by weight.
Good results are obtained when used in amounts of 50 ON parts. The smaller the amount of inert solvent, the better the volumetric efficiency, but the dispersibility of the superabsorbent polymer is poor, making it difficult for the reaction treatment to proceed. On the other hand, if the amount of inert solvent is large, it will be easier to disperse and the reaction will proceed more easily, but the volumetric efficiency will be poor and the cost will be high, which is not a good idea from an industrial perspective. Therefore, in carrying out the reaction treatment in the present invention, it is preferable that the inert solvent is present within the above concentration range and the reaction treatment is carried out.

Furthermore, in the present invention, if a silanol condensation catalyst as described above is added together with a silane coupling agent, a polymer with a much higher water absorption rate can be obtained, but in this case, the amount of silanol condensation catalyst added is generally The amount is 0.1 to 500 parts by weight, preferably 1 to 200 parts by weight, per 100 parts by weight of the silane coupling agent. If it is less than 0.1 part by weight, the effect of adding it will be small, and if it is more than 500 parts by weight, it will not be advantageous enough to further increase the effect, and the cost will be high industrially, so there is no point in adding it.

The temperature conditions for smooth reaction treatment in the present invention vary depending on the type of silane coupling agent used, the type and amount of inert solvent, the amount of water present, the type of superabsorbent polymer, etc. ＼It's different so I can't give you a general idea, but it's usually 20
It is preferable to carry out the reaction at a temperature of 180°C to 180°C, preferably 50 to 150°C.

〔Effect of the invention〕

The features of the present invention are that the processing method is simple, and that the water absorption rate is significantly increased by preventing the "scattering" that occurs during water absorption while retaining the water absorption ability, and that the gel strength is thick. There are many things that can be done.

Therefore, the polymer obtained by the production method of the present invention can be advantageously used in the production of sanitary napkins, paper diapers, and other sanitary materials by utilizing its excellent water absorption performance and water absorption rate.

In addition, by taking advantage of its excellent water absorption performance and gel strength, it can be used to manufacture various materials for horticulture and agriculture, including soil conditioners and water retention agents, which have recently been attracting attention. I can do it.

[Embodiments of the invention]

The present invention will be explained in more detail below by giving Examples and Comparative Examples.

Note that the pure water absorption capacity, saline water absorption capacity, and water absorption rate described in these examples refer to the values measured by the following test method. After weighing and mixing 1 piece of each, the polymer was left to stand for about 60 minutes to sufficiently swell the polymer with water.

Next, after draining with a 100-mesh filter, the amount of filtrate is weighed, and the pure water absorption capacity is calculated according to the following formula.

B. Polymer approximately 0.5 f and concentration 0 in a beaker with a saline water absorption capacity of 300
．． After weighing and mixing 9% by weight of salt Honsuri 2001, let it stand for about 60 minutes, and draining it with a 0 and 100 mesh fluid to fully swell the polymer with salt water, and then add the filtered salt. Weigh the water 'Jli and calculate the saline water absorption capacity according to the following formula.

C Water absorption rate: 300 sd Beaker 1c Weigh out about 2002 saline solution with a concentration of 0.9% by weight, add and disperse about 0.52 weight percent of polymer therein, and let it stand still for a predetermined period of time (1 minute, 3 minutes, 5 minutes). Leave to swell. After the specified time, drain with a 100 mesh sieve,
Weigh the amount of filtrate and calculate the amount of water absorbed using the formula shown in B.

The results of Examples and Comparative Examples are summarized in Table 1 below.

Comparative Example-1 A super absorbent polymer was produced based on Example 1 of Japanese Patent Application No. 59-236685. i.e. stirrer, reflux condenser,
Cyclohexane 375? After adding and dissolving 4.51 g of sorbitan monostearate, nitrogen gas was blown in to drive out dissolved oxygen.

Separately, acrylic acid 751 was dissolved in water 2011 (3x) in a 7 flask with a volume of 500 - while externally cooling on ice;
74.99 of carboxyl group by adding caustic powder of zr
6 was neutralized. In this case, the monomer concentration relative to water corresponds to 30% by weight. Next, 0.25 F of potassium persulfate was added and dissolved, and then nitrogen gas was blown in to drive out dissolved oxygen. The contents of this 500-ml flask were added to the contents of the 4-ml flask, stirred to disperse, and while nitrogen gas was being bubbled, the temperature inside the 500-ml flask was raised in an oil bath. After dropping to around 60°C, the internal temperature rose rapidly and reached 75°C several tens of minutes later. Then, the internal temperature was maintained at 60 to 65°C (I) and reacted for 4 hours with stirring.
I did it at rpm.

When stirring was stopped after 4 hours of reaction, the wet polymer particles settled to the bottom of the 72 SCO and could be easily separated from the cyclohexane phase by decantation.

The separated wet polymer was transferred to a vacuum dryer and dried at 80-90%
The adhering cyclohexane and water were removed by heating to 0.degree. C., resulting in a powdered polymer containing free-flowing, easily grindable lumps.

Comparative Example 2 A super absorbent polymer was produced based on Example 1 of Japanese Patent Publication No. 54-30710. i.e. stirrer, reflux condenser,
After adding and dissolving 2213 dt of n-hexane and 1.81 ml of sorbitan monostearate into a 500 mm four-necked round bottom flask equipped with a dropping funnel and a nitrogen gas inlet tube, nitrogen gas was blown into the flask to remove dissolved oxygen. kicked out. Separately, in an Erlenmeyer flask, cool 309 gold acrylic acid with ice from the outside and water 39 gold.
75 of the carboxyl groups were neutralized with 95% caustic soda dissolved in 1 3.1 f. The monomer concentration in the aqueous phase was 45% by weight. Then potassium persulfate 0.12
was added to dissolve the solution, and then nitrogen gas was blown into the solution to remove oxygen present in the solution. The contents of the Erlenmeyer flask were added to and dispersed in the four-hole flask, and the reaction was continued for 6 hours while introducing a slight amount of nitrogen gas and maintaining the internal temperature of the flask at 60 to 65° C. using an oil bath. When stirring was stopped, the reaction system became a suspension system in which the swollen polymer particles easily sedimented and separated. The n-hexane was distilled off under reduced pressure, and a portion of the remaining swollen polymer was dried under reduced pressure at 80 to 90°C. The polymer was obtained as a powder containing free-flowing, easily powderable masses.

Comparative Example 3 A super absorbent polymer was produced according to Japanese Patent Application Laid-Open No. 58-13160831608. That is, 1 acrylic acid 30F
00- flask, and while cooling and stirring, add 58.72% of a 22.6% by weight aqueous solution of caustic soda dropwise to neutralize 80 mol, then add 0.1 t of potassium persulfate, and stir. was continuously dissolved at room temperature.

Add 163.4 t of cyclohexane to a 500 flask equipped with a reflux condenser and purify the system with nitrogen in advance.
The surfactant was dissolved at room temperature under stirring, and then the above-mentioned partially neutralized aqueous syneresis solution of acrylic acid was added dropwise and suspended. After sufficiently purging the system with gold nitrogen again, the temperature was raised and the polymerization reaction was carried out for 3 hours while maintaining the temperature of the oil bath at 55 to 60°C.

The resulting polymer solution was evaporated to dryness under reduced pressure to obtain a dry polymer in the form of fine granules.

Comparative Example 4 A super absorbent polymer was developed based on Example 9 of JP-A-52-25886. That is, 15 tons of corn starch and 115 tons of water were placed in a reaction vessel equipped with a stirring rod and a nitrogen blowing tube thermometer, and heated at 80°C under a nitrogen stream for 1 hour.
After stirring for an hour and then cooling to 30° C., 151 F acrylic acid, 152 F acrylamide, 0.15 F calcium oxide, and 0.15 F ammonium persulfate, 0.015 F sodium bisulfite as polymerization catalysts were added. , and polymerization was carried out by stirring at 40° C. for 3 hours.

The reaction solution became an elastic white solid. The obtained white solid was dried under reduced pressure at 80 to 90°C and ground into powder. Add 5% sodium hydroxide to this powder in a water/methanol mixed solution (water to methanol weight ratio 1:5) 14
After adding 6.5 f and leaving it at room temperature for 1 hour, it was heated to 80-90°C.
The mixture was dried under reduced pressure and pulverized to obtain a slightly brown powder.

Comparative Example-5 A super absorbent polymer was created based on Example 3 of JP-A No. 52-27455, and 90% of vinyl acetate, 40% of methyl acrylate, and 0.5% of benzoyl peroxide as a PI/C polymerization initiator were used. In addition, this was dispersed in 300 d of water containing 3 f of partially saponified polyvinyl alcohol as a dispersion stabilizer, and after polymerization at 65° C. for 6 hours, the resulting copolymer was filtered and dried.

Next, the copolymer 25y was dissolved in 800 methanol under heating, and 4 (58.1 l) of an aqueous solution of caustic soda was added thereto and saponified at 60°C for 5 hours. After the reaction, the saponified product was washed with methanol. After that, it was dried under reduced pressure to obtain a powder.

Comparative Example-6 A super absorbent polymer was produced based on Example 11 of JP-A-58-71907. That is, 30 f of acrylic acid was added to 9.24 f/C of deionized water, and to this was added 20°61 of potassium hydroxide having a degree of IiB of 85 as a neutralizing agent, and N,N.
'-Methylenebisacrylamide 0.00832 S'
are added sequentially to prepare an aqueous potassium acrylate solution (degree of neutralization: 75%) with a mixed monomer concentration of 70% by weight.

The aqueous solution subjected to ms above was kept at a temperature of 70 cK, and 1 part of water was added to it.
．． 02 to 2,2'-azobis(2-amidinopropane)
A mixed solution containing 0.208 f of dihydrochloride is added and immediately spread in a cylindrical reactor having an inner diameter of 10 cm. (The reactor was kept at 70°C in advance, and this was ground into powder.

Example 1 Dry polymer 202 obtained from the same formulation as in Comparative Example was added to a four-neck round bottom flask with a capacity of Lot) d equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube. Then, 0.1 f of vinyltrimethoxylane was added to 20 g of cyclohexane.
9 was added to form a slurry, and while stirring, a mixture of 30% hydrogen peroxide and di-n-butyl disyurate in cyclohexane was added to the slurry. A mixed solution containing tin o and o s r dissolved therein was added and treated at room temperature for 30 minutes. Thereafter, the temperature was raised to 70°C in an oil bath and treated at the same temperature for 3 hours. After the treatment, the mixture was evaporated to dryness using a rotary evaporator and further dried under reduced pressure to obtain a dry polymer.

Example-2 A dry polymer was obtained using the same recipe as in Example-1, except that a dry polymer obtained using the same recipe as in Comparative Example-2 was used.

Example-3 A dry polymer was obtained using the same recipe as in Example-1, except that a dry polymer obtained using the same recipe as in Comparative Example-3 was used.

Example-4 A dry polymer was obtained using the same recipe as in Example-1, except that a dry polymer obtained using the same recipe as in Comparative Example-4 was used.

Example-5 A dry polymer was obtained using the same recipe as in Example-1, except that a dry polymer obtained using the same recipe as in Comparative Example-5 was used.

Example-6 A dry polymer was obtained using the same recipe as in Example-1, except that a dry polymer obtained using the same recipe as in Comparative Example-6 was used.

Example 7 Using a dry polymer obtained with the same formulation as Comparative Example 1, vinyltrimethoxysilane was adjusted to 0.22, and dilauric acid di-n
A dry polymer was obtained using the same recipe as in Example 1, except that -butyltin was not added.

Example-8 Using a dry polymer obtained with the same formulation as in Comparative Example-2, vinyltrimethoxysilane was adjusted to 0.22, and dilauric acid di-n
A dry polymer was obtained using the same recipe as in Example 1, except that -butyltin was not added.

Example-9 After distilling 1852 liters of polymer solution obtained using the same recipe as Comparative Example-1, 0.5F vinyltrimethoxysilane,
After adding 0.2 f of hydrogen peroxide and 0.51 f of n-dibutyltin dilaurate and mixing thoroughly,
The reaction was carried out at ℃ for 4 hours with stirring. After the treatment, the pressure was reduced and the mixture was evaporated to dryness to obtain a dry polymer.

Example-10 After distilling 321 liters of water from the polymerization solution obtained using the same recipe as in Comparative Example-2, vinyl trimethoxy 7 run 0.25F,
After adding 0.05 r of 30 t hydrogen peroxide and 0.3 t of n-dibutyltin dilaurate and mixing thoroughly, reaction treatment was carried out at 70°C for 4 hours with stirring. After the treatment, the pressure was reduced and the mixture was evaporated to dryness to obtain a dry polymer.

Example 11 Dry polymer obtained using the same formulation as Comparative Example 1 and drying using the same formulation as Example 1 except that r-methacryloxyprobyltrimethoxycin was used as the silane coupling agent. A polymer was obtained.

Claims (2)

[Claims] (1) A superabsorbent polymer containing a carboxyl group or/and a carboxylate group as a component of the polymer or copolymer is prepared with the general formula RR'SiY_2 (wherein, R is olefinically unsaturated) in the presence of water. Grafting treatment with an olefinically unsaturated silane coupling agent represented by a hydrocarbon group or a hydrocarbonoxy group, Y represents a hydrolyzable organic group, and R' represents a group R or Y. A method for producing a superabsorbent polymer characterized by: (2) The production according to claim 1, wherein the superabsorbent polymer is a polymer containing (meth)acrylic acid or/and an alkali metal salt of (meth)acrylic acid as a constituent component of the polymer or copolymer. Method.