JPH0519563B2 - - Google Patents

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, but it is insoluble in water and the swollen polymer has high gel strength. It can be advantageously used in the production of water-absorbing materials or various materials that are used in a swollen state after absorbing water. [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, 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 bulky. There were drawbacks such as the fact that when pressurized a material that had absorbed water, the water easily separated. In order to improve the above-mentioned drawbacks of this type of water-absorbing material, various highly water-absorbing polymeric materials have 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 water-soluble polymers (Japanese Patent Publication No. 43-23462, etc.) , Self-crosslinking type acrylic acid alkali metal salt polymer (Special Publication No. 54-30710
Publications, etc.), etc. were proposed. However, these superabsorbent polymer materials either have low water absorption capacity, or even if they have high water absorption capacity, the water absorption rate is slow, and when they come into contact with a body to be absorbed, so-called "mamako" is generated and the absorption is not efficient. It takes a long time to absorb the desired amount of water. Therefore, it is particularly unsuitable for uses such as sanitary napkins, paper diapers, etc., which absorb a large amount of absorbent material at once and require instant water absorption ability, and have 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 sorbitan monostearate, a nonvolatile hydrocarbon, calcium stearate, etc. into a powdered aqueous polymer, the dispersibility in water was improved. However, even if this method is applied to superabsorbent polymers, although the dispersibility in water is improved in the very early stages, the water absorption rate is slow, and if this is not improved, so-called "mamako" will be formed during the water absorption process. However, sufficient effects are not achieved. 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 implemented, the water absorption rate will be slightly improved, but
This method does not have a very significant effect, and in this case, the water absorption capacity is significantly lowered and the inherent performance of the super absorbent polymer is impaired, so it is difficult to say that it is a preferable method. [Problems to be Solved by the Invention] The present invention solves the above-mentioned problems with super absorbent materials, that is, provides a method for producing a super absorbent polymer that has significantly improved water absorption rate and gel strength, especially water absorption rate. This is what I am trying to do. [Means for Solving the 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 carboxyl group and/or a carboxylate group can be converted into a polymer or a copolymer. In the presence of water, the superabsorbent polymer contained as a component of the polymer is prepared using the general formula RR′SiY ₂ (wherein, R represents an olefinic unsaturated hydrocarbon group or a hydrocarbonoxy group, and Y represents a hydrolyzable represents an organic group, and R' represents a group R or Y.However, at least one of R and R' is an olefinic unsaturated hydrocarbon group. They discovered that a highly absorbent polymer with a particularly high water absorption rate can be obtained by a simple processing method by grafting, leading to the completion of the present invention. (Specific 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 superabsorbent polymers include acrylic acid (salt) polymers, methacrylic acid (salt) polymers,
Polymer, acrylic acid (salt)/methacrylic acid (salt)
Copolymers, starch/acrylic acid (salt) graft copolymers, saponified starch/ethyl acrylate graft copolymers, saponified starch/methyl methacrylate graft copolymers, methyl methacrylate/vinyl acetate copolymers Saponified products of methyl acrylate/vinyl acetate copolymer, saponified products of starch/acrylonitrile graft copolymer, saponified products of starch/acrylamide graft copolymer, starch/
Saponified products of acrylonitrile-2-acrylamido-2-methylpropanesulfonic acid graft copolymer, crosslinked products of saponified starch/acrylonitrile/vinylsulfonic acid graft copolymers, polyethylene oxide crosslinked with acrylic acid, sodium carboxylic acid Examples include crosslinked methylcellulose. In addition, acrylic acid (salt) or methacrylic acid (salt), maleic acid (salt), itaconic acid (salt), acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, 2-(meth)
Copolymers in which comonomers such as acryloylethanesulfonic acid and 2-hydroxyethyl (meth)acrylate are copolymerized within a range that does not reduce the performance of the water-absorbing polymer produced can 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 to produce these superabsorbent 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, haloepoxy compounds such as epichlorohydrin, polyaldehydes such as glutaraldehyde and glyoxal, polyols such as ethylene glycol and glycerin, and ethylene diamine, etc. A method of crosslinking by reacting polyamines with a polyfunctional compound that can react with a functional group in a superabsorbent polymer, such as a carboxyl group or a carboxylate group, and other methods that involve pseudo-crosslinking or high degree of entanglement of molecular chains during the polymerization process. Examples include self-crosslinking. The silane coupling agent used in the production method of the present invention is represented by the general formula _RR'SiY2 , where R is an olefinic unsaturated hydrocarbon group or a hydrocarbon group having an acyloxy group, an acyl group, or an alkoxy group. Indicates a hydrocarbonoxy group that refers to
Examples of such groups include vinyl, allyl, putenyl, cyclohexenyl, cyclopentadienyl, 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, -ON=C
Oxime groups such _as ( _CH3 ) ₂ , -ON=C( _{C6H5 ) 2} or _-NHCH3 , _-NHC2H5 , and _-NH ( _C6H5 )
There are alkylamino groups such as and arylamino groups. Further, B' is a group R or a group Y.
However, at least one of R and R' is an olefinic unsaturated hydrocarbon group. Among the above-mentioned silane coupling agents, 3
It is preferable to use a hydrolyzable organic group, and specifically, vinyltrimethoxysilane, vinyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane are preferable. The amount of these silane coupling agents used varies slightly depending on the type of superabsorbent polymer used, the degree of grafting, the amount of water present, and the type and amount of inert solvent, but in general, superabsorbent The amount is 0.001 to 50 parts by weight, preferably 0.2 to 10 parts by weight, per 100 parts by weight of the polymer. If the amount used is less than 0.001 part by weight, the effect of its addition will not be expressed, and if it is more than 50 parts by weight, no more significant effect will be produced, resulting in high costs, and the water absorption capacity of the polymer after treatment will be reduced. This is not preferable because it lowers the temperature. 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, organic peroxides such as benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, t-butyl peroxide, azoisobutyronitrile Any method may be used as long as it generates free radicals in the super absorbent polymer, such as a method using an azo compound such as dimethyl azodiisobutyrate. 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. , preferably 0.02 to 2 parts by weight. usage is 0.005
If it is less than 5 parts by weight, effective grafting is difficult to occur, and if it is more than 5 parts by weight, no significant 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. slurry in an inert solvent such as hydrocarbons such as n-pentane, n-hexane, n-heptane, cyclohexane, benzene, toluene, xylene, halogenated hydrocarbons such as methylene chloride, chloroform, ethylene dichloride, etc. and a mixture of a silane coupling agent, a free radical generator and water is added, and the slurry liquid is heated, preferably under reflux, or after the addition of a silane coupling agent, water and a free radical generator. An example is a method of heating and evaporating. 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. By heating and evaporating the slurry liquid after adding the agent and the free radical generator,
Can be processed by reaction. In this case, dibutyltin dilaurylate, dibutyltin diacetate, dibutyltin dioctoate, etc., which are generally known as silanol condensation catalysts, are added together with a silane coupling agent and a free radical generator, or after the grafting treatment. By carrying out the reaction treatment, it is possible to more effectively obtain a super absorbent polymer having an excellent water absorption rate, which is the object of the present invention. In the reaction treatment of the present invention, the amount of water present is 0.5 parts by weight per 100 parts by weight of the superabsorbent polymer.
~300 parts by weight is suitable. If the amount of water is less than 0.5 parts by weight, the superabsorbent polymer will be in an almost unswollen state, making it difficult for grafting with the silane coupling agent and silanol condensation reaction to proceed, requiring a long reaction time. is disadvantageous. 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 it is not very effective in increasing the water absorption rate, and a large amount of silane coupling agent is required to increase the water absorption rate. This is not preferable because the water absorption capacity is significantly reduced as a result. When using the above-mentioned inert solvents shown in the specific examples in the reaction treatment of the present invention, it is of course a solvent that does not have any influence on the superabsorbent polymer, and may be used alone or in combination. It can be used even if more than one species is mixed. The amount used varies depending on the type of superabsorbent polymer and inert solvent used, but generally it is 10 to 5,000 parts by weight, preferably 50 to 500 parts by weight, per 100 parts by weight of superabsorbent polymer. Use it with good results. The smaller the amount of inert solvent, the better the volumetric efficiency, but the dispersibility of the superabsorbent polymer deteriorates, making it difficult to proceed with the reaction process. On the other hand, if the amount of the 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 very good 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, by adding the silanol condensation catalyst as described above together with the silane coupling agent, a polymer having a higher water absorption rate can be obtained.In this case, the amount of the 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 agent. If the amount is less than 0.1 weight, the effect of adding it will be small.
Moreover, if it is more than 500 parts by weight, there is no advantage to further increase the effect, and the cost becomes industrially high, so it is not very meaningful. The temperature conditions for smoothly performing the reaction treatment in the present invention include the type of silane coupling agent used, the type and amount of the inert solvent, the amount of water present,
Although it is difficult to make a general statement because it varies depending on the type of superabsorbent polymer, it is generally recommended to carry out the reaction at a temperature of 20 to 180°C, preferably 50 to 150°C. [Effects of the Invention] The features of the present invention are that the processing method is simple, that the water absorption rate is significantly increased by preventing "stickiness" that tends to occur during water absorption while retaining the water absorption ability, and that the gel strength is high. There are things you can get. Therefore, the polymer obtained by the production method of the present invention is
Due to its excellent water absorption performance and water absorption rate, it can be advantageously used in the production of sanitary napkins, paper diapers, and other sanitary materials. In addition, soil conditioners that have recently been attracting attention due to their excellent water absorption performance and gel strength.
It can also be used in the production of various materials for horticulture or agriculture, including water retention agents. [Examples of the Invention] The present invention will be described in further detail below with reference to 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 values measured by the following test method. A. Pure water absorption capacity: Weigh about 0.5 g of polymer and about 1 g of pure water into a beaker, mix, and then add about 60 g of pure water.
The polymer was allowed to swell sufficiently with water by standing for a minute.
Next, drain the water using a 100 mesh filter, weigh the amount of the filtrate, and calculate the pure water absorption capacity according to the formula below. Pure water absorption capacity (g/g tree) = Charged water absorption capacity (g) - Filtrate volume (g) / Charged polymer quantity (g) B Salt water absorption capacity Approximately 0.5g of polymer and concentration in a 300ml beaker
Approximately 200 g of 0.9% by weight saline solution was weighed and mixed, and the mixture was allowed to stand for approximately 60 minutes to allow the polymer to sufficiently swell with the saline solution. then 100
After draining with a mesh filter, weigh the amount of filtered saline and calculate the water absorption capacity of the saline according to the following formula. Water absorption capacity of saline water (g/g) = Amount of saline solution (g) - Amount of filtrate (g) / Amount of polymer (g) C Water absorption rate Add saline solution with a concentration of 0.9% by weight to a 300ml beaker.
Weigh out 200 g, add and disperse about 0.5 g of polymer, and leave to swell for a predetermined period of time (1 minute, 3 minutes, 5 minutes). After a predetermined 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. That is, a capacity 1 equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet pipe.
Cyclohexane 375 in a four-necked round-bottomed flask.
After adding 4.5 g of sorbitan monostearate and dissolving it, nitrogen gas was blown into it.
Dissolved oxygen was expelled. Separately, 75 g of acrylic acid in a 500 ml flask.
31.2g of caustic soda dissolved in 201g of water was added to the mixture while cooling it with ice externally to remove the carboxyl group.
Neutralized 74.9%. In this case, the monomer concentration relative to water corresponds to 30% by weight. Next, 0.25 g 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 four-necked flask, stirred and dispersed, and the temperature inside the flask was raised in an oil bath while bubbling nitrogen gas, resulting in a temperature of 60°C. After reaching the vicinity, the internal temperature rose rapidly, reaching 75 degrees Celsius several tens of minutes later. Next, the internal temperature was maintained at 60 to 65° C., and the reaction was allowed to proceed for 4 hours while stirring. The stirring speed is 250rpm.
I went there. When stirring was stopped after 4 hours of reaction, the wet polymer particles settled to the bottom of the flask and could be easily separated from the cyclohexane phase by decantation. Transfer the separated wet polymer to a vacuum dryer and dry at 80°C.
Heating to ˜90° C. to remove adhering cyclohexane and water resulted in a powdered polymer containing free-flowing, easily grindable lumps. Comparative Example 2 A superabsorbent polymer was produced based on Example 1 of Japanese Patent Publication No. 54-30710. i.e. 500ml with stirrer, reflux condenser, dropping funnel and nitrogen gas inlet tube.
228 ml of n-hexane was placed in a four-necked round bottom flask, and 1.8 g of sorbitan monostearate was added and dissolved therein. Nitrogen gas was blown in to drive out dissolved oxygen. Separately, in an Erlenmeyer flask, 13.1 g of acrylic acid was dissolved in 39 g of water while cooling with ice from the outside.
% caustic soda neutralized 75% of the carboxyl groups. The monomer concentration in the aqueous phase was 45% by weight.
Next, 0.1 g of potassium persulfate was added and dissolved, and nitrogen gas was blown into the solution to remove oxygen present in the solution. The contents of the Erlenmeyer flask were added to the four-necked flask and dispersed, 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. The reaction system became a suspension system in which the swollen polymer particles easily sedimented and separated when stirring was stopped. The n-hexane was distilled off under reduced pressure, and the remaining swollen polymer portion 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 based on Example 1 of JP-A-56-131608. i.e. 30g of acrylic acid
Transfer to a 100ml flask and stir while cooling.
Drop 58.7 g of a 22.6% by weight aqueous solution of caustic soda.
After neutralization of 80 mol%, potassium persulfate 0.1
g and continued stirring to dissolve at room temperature. 500ml with a reflux condenser with the system replaced with nitrogen in advance
A flask was charged with 163.4 g of cyclohexane and 1.9 g of sorbitan monolaurylate with an HLB of 8.6, and after the surfactant was dissolved at room temperature with stirring, the above-mentioned partially neutralized acrylic acid salt aqueous solution was added dropwise and suspended. After the inside of the system was sufficiently purged with nitrogen again, the temperature was raised, and the temperature of the oil bath was maintained at 55 to 60°C to carry out a polymerization reaction for 3 hours. The produced 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 produced based on Example 9 of JP-A-52-25886. That is, 15 g of corn starch and 115 g of water were placed in a reaction vessel equipped with a stirring rod, a nitrogen blowing tube, and a thermometer, stirred for 1 hour at 80°C under a nitrogen stream, and then cooled to 30°C. Acrylic acid, 15g acrylamide,
0.15 g of calcium oxide, 0.15 g of ammonium persulfate, and 0.015 g of sodium bisulfite were added as polymerization catalysts, and the mixture was stirred at 40° C. for 3 hours to polymerize. 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. To this powder was added 146.5 g of a mixed solution of 5% sodium hydroxide in water/methanol (weight ratio of water to methanol 1:5), left at room temperature for 1 hour, dried under reduced pressure at 80 to 90°C, and pulverized. Obtained as a brown powder. Comparative Example 5 A superabsorbent polymer was produced based on Example 3 of JP-A-52-27455. i.e. 60g of vinyl acetate
0.5 g of benzoyl peroxide was added as a polymerization initiator to 40 g of methyl acrylate, and this was dispersed in 300 ml of water containing 3 g of partially saponified polyvinyl alcohol as a dispersion stabilizer. After polymerization at 65°C for 6 hours, The copolymer was filtered and dried. Next, 25 g of the copolymer was dissolved in 800 ml of methanol while heating, and 58.1 ml of 40% aqueous caustic soda solution was added.
The mixture was added and saponified at 60°C for 5 hours. After the reaction, the saponified product is washed with methanol and dried under reduced pressure.
Obtained as a powder. Comparative Example 6 A superabsorbent polymer was produced based on Example 11 of JP-A-58-71907. i.e. 30g of acrylic acid
was added to 9.24 g of deionized water, and to this was added 20.6 g of potassium hydroxide with a purity of 85% as a neutralizing agent, N,
0.00832 g of N'-methylenebisacrylamide was sequentially added to prepare a potassium acrylate aqueous solution (neutralization degree 75%) with a mixed monomer concentration of 70% by weight. The aqueous solution prepared above was kept at 70°C, and a mixture of 0.208 g of 2,2'-azobis(2-amidinopropane) dihydrochloride dissolved in 1.0 g of water was added to it, and immediately the solution had an inner diameter of about 10 cm. Flow and spread in a cylindrical reactor. (The reactor is kept at 70℃ in advance)
Polymerization started after a few seconds and was completed within about 1 minute, resulting in a dry polymer foamed by the heat of polymerization, which was pulverized into powder. Example 1 20 g of a dry polymer obtained using the same recipe as in Comparative Example 1 was added to a 100 ml four-necked round-bottomed flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen gas inlet tube. Next, a mixture of 0.1 g of vinyltrimethoxylane dissolved in 20 g of cyclohexane was added to form a slurry, and while stirring, a mixture of 0.05 g of 30% hydrogen peroxide dissolved in 4.5 g of water and dilaurin in 5 g of cyclohexane were added. Di-n-butyltin acid 0.05g
The dissolved mixtures were each added and treated at room temperature for 30 minutes. After that, the temperature was raised to 70℃ in an oil bath.
It was 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,
A dry polymer was obtained using the same recipe as in Example 1, except that 0.2 g of vinyltrimethoxysilane was added and di-n-butyltin dilaurate was not added. Example 8 Using a dry polymer obtained with the same formulation as Comparative Example 2,
A dry polymer was obtained using the same recipe as in Example 1, except that 0.2 g of vinyltrimethoxysilane was added and di-n-butyltin dilaurate was not added. Example 9 185g of water was obtained from the polymerization solution obtained using the same recipe as in Comparative Example 1.
After distillation, vinyltrimethoxysilane is added to it.
0.5 g of 30% hydrogen peroxide, 0.2 g of n-dibutyltin dilaurate, and 0.5 g of n-dibutyltin dilaurate were added and mixed thoroughly, followed by reaction treatment 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 10 After distilling 32g of water from a polymerization solution obtained using the same recipe as in Comparative Example 2, vinyltrimethoxysilane was added to the solution.
0.25g, 30% hydrogen peroxide 0.05g, dilauric acid n
-0.3g of dibutyltin was added to each, and after thorough mixing, 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 Using a dry polymer obtained with the same formulation as Comparative Example 1,
A dry polymer was obtained using the same recipe as in Example 1, except that r-methacryloxypropyltrimethoxysilane was used as the silane coupling agent.

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Claims (1)

[Scope of Claims] 1. A highly water-absorbent polymer containing a carboxyl group or/and a carboxylate group as a constituent component of a polymer or copolymer having the general formula RR′SiY ₂ (wherein, R represents an olefinic unsaturated hydrocarbon group or a hydrocarbonoxy group, Y represents a hydrolyzable organic group, and R' represents a group R or Y. However, at least one of R and R' is an olefinic unsaturated group. 1. A method for producing a superabsorbent polymer, which comprises grafting the polymer with an olefinic unsaturated silane coupling agent represented by a saturated hydrocarbon group. 2. The manufacturing method according to claim 1, wherein the super absorbent 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.