JPH09235417A - Water swelling rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water swelling rubber having a smaller difference than the conventional one between the volume change by the absorption of aq. liq. such as artificial seawater and the volume change by the absorption of pure water such as ion-exchanged water and having a lower content of soluble org. carbon than the conventional one. SOLUTION: This water swelling rubber is obtd. by mixing a hygroscopic resin having a mean particle diameter within the range of 1-100μm and obtd. by polymerizing a monomer component comprising a nonionic monomer 20-100wt.% and a polyvalent metal salt of an anionic monomer 80-0wt.%, and an elastomer. The ratio of the volume change by the absorption of ion- exchanged water to the volume change by the absorption of an artificial seawater of thus obtd. water swelling rubber is in the range of 1.0-2.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-swellable rubber suitable for use as, for example, a waterproofing material in civil engineering works and construction works.

[0002]

2. Description of the Related Art Hitherto, there has been known a water absorbing agent having excellent salt resistance against an aqueous liquid such as hard water or seawater containing a polyvalent metal ion or the like (JP-A-2-253845). This water absorbing agent (liquid absorbing agent) is composed of a crosslinked polymer obtained by copolymerizing a (meth) acrylic acid ester-based monomer having a specific structure and a water-soluble unsaturated monomer containing a carboxyl group. There is. The water absorbing agent is excellent in the liquid absorption capacity for absorbing the above-mentioned aqueous liquid, and has the property that the liquid absorption capacity does not decrease with time.

[0003]

However, when the above-mentioned conventional water-absorbing agent is mixed with, for example, an elastomer and used as a water-swellable rubber, various problems as described below occur. That is, the water-swellable rubber containing the conventional water-absorbing agent,
Swells significantly when it comes into contact with fresh water such as ion-exchanged water or tap water, or water close to fresh water, but swells only slightly when it comes into contact with water containing large amounts of polyvalent metal ions, such as seawater . That is, the rate of change in volume (swelling ratio) varies greatly depending on the type of water with which it comes into contact. Therefore, the water-swellable rubber containing the conventional water-absorbing agent has a problem in water-stopping performance when used in an environment in which the type of water with which it comes into contact changes.

Further, in the water-swellable rubber containing the conventional water-absorbing agent, when contacted with water, a relatively large amount of soluble organic carbon is eluted, so that it is used in a field of application where a high degree of safety is required. Still water still had problems.

The present invention has been made in view of the above conventional problems, and an object thereof is to obtain a difference between a volume change rate when artificial seawater is absorbed and a volume change rate when ion-exchanged water is absorbed. Another object of the present invention is to provide a water-swellable rubber which is smaller than the conventional one and has a reduced soluble organic carbon content as compared with the conventional one.

[0006]

Means for Solving the Problems The inventors of the present application have made earnest studies to achieve the above object, and as a result, a water-swellable rubber containing a specific water-absorbent resin and an elastomer has a volume change when absorbing seawater. It was found that the difference between the rate and the rate of change in volume when absorbing ion-exchanged water is smaller than in the past, and the soluble organic carbon content is smaller than in the past, and the present invention has been completed.

That is, in order to solve the above-mentioned problems, the water-swellable rubber of the invention according to claim 1 is a nonionic monomer 20.
The average particle size obtained by polymerizing a monomer component composed of 100% by weight to 100% by weight and 80% to 0% by weight of a polyvalent metal salt of anionic monomer is in the range of 1 μm to 100 μm. It is characterized in that it contains a water-absorbent resin and an elastomer, and that the ratio of the volume change rate due to the absorption of ion-exchanged water to the volume change rate due to the absorption of artificial seawater is within the range of 1.0 to 2.0.

In order to solve the above-mentioned problems, the water-swellable rubber according to the second aspect of the present invention contains 20% by weight of a nonionic monomer.
To 99% by weight, and an average particle size obtained by polymerizing a monomer component consisting of 80% by weight to 1% by weight of an acid type anionic monomer and / or a monovalent salt of anionic monomer is 1 μm to
It contains a water-absorbent resin in the range of 100 μm, an elastomer, and a water-soluble polyvalent metal salt, and has a ratio of the volume change rate due to absorption of ion-exchanged water to the volume change rate due to absorption of artificial seawater of 1.0 to 2.0. It is characterized by being within the range of.

In order to solve the above-mentioned problems, the water-swellable rubber according to the third aspect of the present invention is the water-swellable rubber according to the second aspect, wherein the water-soluble polyvalent metal salt is magnesium sulfate. It has a feature.

In order to solve the above-mentioned problems, the water-swellable rubber according to the fourth aspect of the present invention is the water-swellable rubber according to any one of the first to third aspects, wherein the ion-exchanged water absorbs water. The volume change rate due to is within the range of 200% by volume to 700% by volume.

In order to solve the above problems, the water-swellable rubber according to the fifth aspect of the present invention is the water-swellable rubber according to any one of the first to fourth aspects, wherein the soluble organic carbon content is 20 ppm. It is characterized by the following.

In order to solve the above-mentioned problems, the water-swellable rubber according to the sixth aspect of the present invention is the water-swellable rubber according to any one of the first to fifth aspects, wherein the nonionic monomer is used. Is the general formula (1)

[0013]

Embedded image

(In the formula, R represents a hydrogen atom or a methyl group, X represents an oxyalkylene group having 2 to 4 carbon atoms in which the mole fraction of the oxyethylene group is 50 mol% or more based on all the oxyalkylene groups, Y represents an alkoxy group having 1 to 5 carbon atoms, a phenoxy group, or an oxyalkylphenyl group having 1 to 3 alkyl groups having 1 to 9 carbon atoms as a substituent, and n represents an integer of 3 to 100 on average. ) Is a (meth) acrylic acid ester-based monomer.

According to the above construction, the difference between the volume change rate when artificial seawater is absorbed and the volume change rate when ion-exchanged water is absorbed is smaller than before, and the type of water that comes into contact suddenly changes. Even if it is possible to exert a high water-stopping effect, the soluble organic carbon content is reduced compared to the past,
It is possible to provide a water-swellable rubber that can be suitably used even in an application field where high safety is required.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail. The water-swellable rubber according to the present invention,
It contains a water-absorbent resin having an average particle diameter in the range of 1 μm to 100 μm and an elastomer. Ratio of the volume change rate of the water-swellable rubber due to absorption of artificial seawater (hereinafter referred to as artificial seawater volume change rate) to the volume change rate due to absorption of ion-exchanged water (hereinafter referred to as ion-exchanged water volume change rate). Is in the range of 1.0 to 2.0. The rate of change in the volume of ion-exchanged water is in the range of 200% by volume to 700% by volume. Further, the soluble organic carbon content in the water-swellable rubber is 20 ppm or less.

The artificial seawater is deionized water,
Calcium sulfate (CaSO ₄ ), magnesium sulfate (M
gSO ₄ ), magnesium chloride (MgCl ₂ ), potassium chloride (KCl), and sodium chloride (NaCl)
The concentration in artificial seawater to be prepared is CaSO ₄ :
_{1.38g / kg, MgSO 4: 2.10g} / kg, MgCl 2: 3.32g /
kg, KCl: 0.72 g / kg, NaCl: 26.69 g / kg.

The water absorbent resin used in the present invention can be easily obtained by polymerizing a monomer component containing at least a nonionic monomer in the presence of a crosslinking agent. Alternatively, it can be obtained by polymerizing a monomer component containing at least a nonionic monomer, and then adding a crosslinking agent to effect crosslinking.

The nonionic monomer is not particularly limited, but specifically, for example, a (meth) acrylic acid ester monomer represented by the general formula (1); 2 -Hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, allyl alcohol, vinyl alcohol-containing unsaturated monomers; (meth) acrylamide, N-vinylacetamide,
Amide unsaturated monomers such as t-butyl (meth) acrylamide; hydrophobic unsaturated monomers such as (meth) acrylate, styrene, 2-methylstyrene, and vinyl acetate; nitriles such as (meth) acrylonitrile Unsaturated monomer; ethylene, propylene, 1-butene, isobutylene, α-amylene, 2-methyl-1-butene, 3-methyl-1-butene (α
-Isoamylene), 1-hexene, 1-heptene, and other α-olefin-based monomers. Further, as the above (meth) acrylic acid ester-based monomer, specifically, for example, methoxypolyethylene glycol mono (meth) acrylate, butoxypolyethylene glycol mono (meth) acrylate, methoxypolyethylene glycol / polypropylene glycol mono ( (Meth) acrylate, methoxy polyethylene glycol / polybutylene glycol mono (meth) acrylate, ethoxy polyethylene glycol / polypropylene glycol mono (meth) acrylate, ethoxy polyethylene glycol
And polybutylene glycol mono (meth) acrylate. These nonionic monomers may be used alone or as a mixture of two or more. Among the above exemplified monomers, (meth) acrylate monomers and amide unsaturated monomers represented by the general formula (1) are more preferable, and methoxypolyethylene glycol methacrylate is particularly preferable. When methoxypolyethylene glycol methacrylate is used as the nonionic monomer, the average number of moles of ethylene oxide added is preferably in the range of 5 mol to 50 mol.
That is, when X in the general formula (1) is an oxyethylene group, R is a methyl group, and Y is a methoxy group, n is preferably in the range of 5 to 50.

Further, in the above-mentioned monomer component, the other monomer used as necessary, that is, the other monomer copolymerizable with the nonionic monomer is an anionic monomer. It is a polyvalent metal salt.

The polyvalent metal salt of the above-mentioned anionic monomer is not particularly limited, but specifically, unsaturated monocarboxylic acid type simple salts such as (meth) acrylic acid and crotonic acid are used. Monomers; unsaturated dicarboxylic acid type monomers such as maleic acid, fumaric acid, itaconic acid, citraconic acid; vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane Unsaturated sulfonic acid type monomers such as sulfonic acid, sulfoethyl (meth) acrylate, sulfopropyl (meth) acrylate, 2-hydroxysulfopropyl (meth) acrylate; (meth) acrylamide methanephosphonic acid, 2- (meth) acrylamide Examples thereof include polyvalent metal salts such as unsaturated phosphonic acid-based monomers such as 2-methylpropanephosphonic acid.

The polyvalent metal salt of the anionic monomer may be used alone, or two or more kinds may be appropriately mixed and used. Among the above polyvalent metal salts of anionic monomers, divalent metal salts of unsaturated monocarboxylic acid type monomers are preferable, and magnesium acrylate is particularly preferable. The magnesium salt of an anionic monomer, especially an unsaturated monocarboxylic acid type monomer, is suitable for the polymerization reaction because it has a high solubility in water.

The ratio of the nonionic monomer to the polyvalent metal salt of the anionic monomer, that is, the proportion of the nonionic monomer in the monomer component is 20% by weight to 100% by weight. The range is preferable, and the range of 30% by weight to 90% by weight is particularly preferable. If the proportion of the nonionic monomer is less than 20% by weight, the water-swellable rubber finally obtained tends to have a low liquid absorption capacity, that is, a volume change rate, which is not preferable. When the proportion of the nonionic monomer exceeds 90% by weight, the soluble organic carbon content tends to increase. Therefore,
In order to reduce the soluble organic carbon content, it is more preferable to control the proportion of the nonionic monomer to 90% by weight or less.

Further, since the above-mentioned monomer component contains a polyvalent metal salt of an anionic monomer in addition to the nonionic monomer, the soluble organic carbon content of the finally obtained water-swellable rubber is further improved. It can be further reduced. It is not clear why the monomer component contains a polyvalent metal salt of an anionic monomer other than the nonionic monomer, thereby reducing the soluble organic carbon content of the obtained water-swellable rubber. It is inferred as follows.

That is, the soluble organic carbon component contains a soluble polymer as a main component, but as a result of secondary or tertiary crosslinking of the soluble polymer with a polyvalent metal, the solubility of the soluble polymer is lowered. It is presumed that this is because

Further, as the cross-linking agent, specifically,
For example, divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate,
Ethylene in one molecule such as trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, N, N-methylenebisacrylamide, triallyl isocyanurate, trimethylolpropane diallyl ether, etc. Compounds having two or more unsaturated groups; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, polypropylene glycol, polyvinyl alcohol, pentaerythritol, diethanolamine, triethanolamine, sorbit, sorbitan, Polyhydric alcohols such as glucose, mannitol, mannitan, sucrose, and glucose; ethylene glycol diglycidide Ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, propylene glycol diglycidyl ether,
Polyepoxy compounds such as polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane triglycidyl ether, and glycerin triglycidyl ether. . These cross-linking agents may be used alone, or two or more of them may be appropriately mixed and used.

By using a crosslinking agent, the crosslinking density of the resulting polymer can be controlled. The amount of the cross-linking agent used is not particularly limited, and may be appropriately set depending on, for example, the type of the monomer component and the cross-linking agent to be used, the desired cross-linking density, and the like. Specifically, the amount of the cross-linking agent used is more preferably within the range of about 0.0001 to 0.02, and further preferably within the range of 0.001 to 0.01, in terms of molar ratio to the monomer component. When a polyhydric alcohol is used as the cross-linking agent, it is preferable to heat-treat the obtained polymer after the polymerization reaction at 150 ° C to 250 ° C. When a polyepoxy compound is used as a cross-linking agent, it is preferable to heat-treat the obtained polymer at 50 ° C. to 250 ° C. after the polymerization reaction.

The method of polymerizing the above-mentioned monomer component is not particularly limited, and various conventionally known methods can be adopted. For example, a solution polymerization method, a suspension polymerization method, a reversed phase suspension polymerization method, or the like can be employed. Incidentally, the polymerization vessel for performing the polymerization reaction is not particularly limited,
A double-arm kneader capable of performing polymerization and gel disintegration is more preferable.

The reaction temperature is not particularly limited, but a relatively low temperature is preferable because the molecular weight of the obtained polymer is large, and the range of 20 ° C to 100 ° C is preferable because the polymerization reaction is completed. preferable. The reaction time is determined by the reaction temperature, the type (property) and combination of the monomer component, the polymerization initiator, and the solvent, so that the polymerization reaction is completed.
What is necessary is just to set suitably according to the used amount etc.

When polymerizing the monomer component, a polymerization initiator can be used. Specific examples of the polymerization initiator include peroxides such as hydrogen peroxide, benzoyl peroxide and cumene hydroperoxide;
2'-azobisisobutyronitrile, 2,2'-azobis (2-
Azo compounds such as amidinopropane) hydrochloride; and radical generators (radical polymerization initiators) such as persulfates such as ammonium persulfate, sodium persulfate and potassium persulfate. These polymerization initiators may be used alone,
Further, two or more kinds may be appropriately mixed and used. Furthermore, these radical generators, sodium bisulfite and
A redox initiator obtained by combining a reducing agent such as L-ascorbic acid (salt) and a ferrous salt may be used. still,
Instead of using the polymerization initiator, irradiation with radiation, electron beam, ultraviolet ray, or the like may be performed, or the polymerization initiator may be used in combination with irradiation with such radiation, electron beam, ultraviolet ray, or the like.

The amount of the polymerization initiator used is not particularly limited, but is preferably in the range of 0.001% to 10% by weight, more preferably 0.01% to 1% by weight, based on the monomer components. Is more preferable. The amount of the reducing agent used in the case of using the redox initiator is not particularly limited, but is 0.01% by weight to the radical generator.
-5 is more preferable, and 0.05-2 is more preferable.

Further, when polymerizing the monomer components,
A solvent may be used if necessary. The solvent is not particularly limited, but specifically, for example,
Water; cyclohexane, toluene; methanol, ethanol, acetone, dimethylformamide, dimethylsulfoxide and the like. These solvents may be used alone or as a mixture of two or more.
Among the above-mentioned solvents, water alone or a mixed solvent of water and a water-soluble aqueous solvent is more preferable since the water-absorbing resin can be produced with higher safety and at a lower cost. The concentration of the monomer component when using a solvent is not particularly limited, but is preferably in the range of 20% by weight to 80% by weight, more preferably in the range of 30% by weight to 60% by weight. preferable. By controlling the concentration of the monomer component in the solution containing the monomer component, the polymerization initiator, the crosslinking agent and the like within the above range, the polymerization reaction can be easily controlled and the yield of the polymer can be improved. Can be improved, and the polymer can be obtained economically.

When the polymer obtained after the polymerization reaction is in a gel form, the gel polymer is dried as it is, or after performing a predetermined operation such as washing or crushing, if necessary. The drying temperature is not particularly limited, but is 50 ° C.
A temperature in the range of -180 ° C is preferred, and a temperature in the range of 100-170 ° C is optimal. Further, it is desirable that the dried product is pulverized by a hammer mill, a jet mill, or the like to obtain fine particles, and then, if necessary, subjected to a classification operation such as sieving.

In order to further reduce the unreacted monomer components remaining in the water absorbent resin and further improve the safety of the water absorbent resin, the gel polymer or its dried product is reduced. Treatment with an agent is preferred. Specific examples of the reducing agent include, for example, sodium sulfite, potassium sulfite, ammonium sulfite, sodium bisulfite, potassium bisulfite, ammonium bisulfite,
Examples include sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, L-ascorbic acid, ammonia, monoethanolamine, glucose and the like. These reducing agents may be used alone or as a mixture of two or more kinds. Among the reducing agents exemplified above, sodium sulfite, sodium hydrogen sulfite, and sodium thiosulfate are more preferable. The amount of the reducing agent is not particularly limited, but specifically, the molar ratio to the used monomer component is more preferably in the range of about 0.0001 to 0.02, and more preferably in the range of 0.001 to 0.01. preferable.

The shape and the like of the water-absorbent resin are not particularly limited, but in order to adjust the ratio of the volume change rate of ion-exchanged water to the volume change rate of artificial seawater within the range of 1.0 to 2.0, its average is adjusted. It is necessary to make the particle diameter uniform within the range of 1 μm to 100 μm. In order to make the average molecular weight within the range of 1 μm to 100 μm, as described above, for example, it is desirable to carry out fine graining by a jet mill or the like, or classification operation. The average particle diameter is a volume average particle diameter, and is not particularly limited as long as it is within the above range, but is preferably about 5 μm to 70 μm, more preferably about 10 μm to 50 μm. Particularly preferred. When the average particle size is in the range of 1 μm to 100 μm, the water-absorbent resin and the elastomer can be uniformly mixed (dispersed), and the water-swellable rubber uniformly swells. This increases the water stopping effect.

The above elastomer is not particularly limited, and various conventionally known compounds can be used. As the elastomer, specifically, for example,
Polybutadiene rubber, polyisoprene rubber, styrene
Butadiene copolymer rubber, chloroprene rubber, isoprene-isobutylene copolymer rubber, ethylene-α-olefin copolymer rubber, ethylene-propylene copolymer (E
PDM) synthetic rubber such as ethylene-α-olefin-non-conjugated diene copolymer rubber such as rubber; chlorinated polyethylene,
Synthetic resins having rubber elasticity such as chlorosulfonated polyethylene, ethylene-vinyl acetate copolymer, soft polyvinyl chloride, and polyurethane; and natural rubber. These elastomers may be used alone, or two or more of them may be used as an appropriate mixture. Of these elastomers, chloroprene rubber is particularly preferred.

The ratio of the water-absorbent resin and the elastomer in the water-swellable rubber, that is, the weight ratio of the water-absorbent resin and the elastomer is preferably in the range of 5:95 to 50:50, and 15:85.
It is more preferably within the range of to 45:55. If the weight ratio of the water-absorbent resin is less than the above range (less than 5), the water-swellable rubber cannot swell sufficiently, which is not preferable. On the other hand, if the weight ratio of the water-absorbent resin is higher than the above range (more than 50), the water-swellable rubber becomes brittle and the strength is lowered, which is not preferable.

The method for producing the water-swellable rubber, that is, the method for mixing (kneading) the water-absorbent resin and the elastomer is not particularly limited, but may be kneading using a kneader such as a roll mill or a Banbury mixer. It is preferable to uniformly mix them by using a conventionally known mechanical method used for the production of rubber products. Further, the mixture may be formed into a predetermined shape by using a molding method such as extrusion molding or press molding, if necessary. Thereby, a water-swellable rubber is obtained.

In addition to the water-absorbent resin and the elastomer, the water-swellable rubber may optionally contain additives. As the additive, for example, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, an inorganic filler, a reinforcing agent, a softener, a plasticizer,
Examples include a colorant, an ultraviolet absorber, a lubricant, and an antioxidant. These additives may be used alone, or two or more of them may be used as an appropriate mixture. The amount of additives used is based on the total amount of the water-absorbent resin and elastomer.
For example, the amount may be 100% by weight or less, preferably in the range of 0.1% by weight to 60% by weight, but is not particularly limited as long as it does not impair the physical properties (eg, strength) of the water-swellable rubber. Not something. The method for adding the additive is not particularly limited.

Specific examples of the above-mentioned vulcanizing agent include sulfur, sulfur white, deoxidized sulfur, precipitated sulfur, colloidal sulfur, sulfur chloride; zinc oxide, magnesium oxide, selenium,
Tellurium; peroxide; aromatic nitro compounds and the like, but are not particularly limited. These vulcanizing agents may be used alone, or two or more of them may be used as an appropriate mixture. The amount of the vulcanizing agent may be, for example, in the range of 0.1% by weight to 10% by weight based on the total amount of the water-absorbing resin and the elastomer, but is not particularly limited.

Specific examples of the above vulcanization accelerator include:
For example, guanidines, aldehyde ammonias, aldehyde amines, nitroso compounds, thiazoles, thiazolines, imidazolines, thioureas, thioacid salts,
Examples thereof include carbiothioates and isothiourea salts, but are not particularly limited. These vulcanization accelerators may be used alone, or two or more of them may be used as an appropriate mixture. The amount of the vulcanization accelerator used may be, for example, in the range of 0.1% by weight to 10% by weight based on the total amount of the water-absorbing resin and the elastomer, but is not particularly limited.

Specific examples of the above-mentioned vulcanization aids include sodium hydroxide, calcium oxide, magnesium oxide (magnesia), zinc white, and lead (II) oxide, but are not particularly limited. Not a thing. These vulcanization aids may be used alone, or two or more of them may be appropriately mixed and used. The amount of the vulcanization aid used may be, for example, in the range of 0.1% by weight to 10% by weight based on the total amount of the water-absorbing resin and the elastomer, but is not particularly limited.

When vulcanizing the elastomer, for example,
Heat treatment may be performed at 100 ° C. to 200 ° C. for 1 minute to 30 minutes, but the treatment conditions are not particularly limited. The heat treatment may be performed, for example, at the time of molding a mixture composed of a water-absorbing resin and an elastomer, or after molding.

Specific examples of the above-mentioned inorganic fillers include inorganic substances such as titanium dioxide, calcium carbonate, zinc white, clay, kaolin, bentonite, silica, talc, zeolite and white carbon. It is not particularly limited. These inorganic fillers may be used alone, or two or more kinds may be appropriately mixed and used. The amount of the inorganic filler used may be, for example, in the range of 10% by weight to 50% by weight based on the total amount of the water absorbent resin and the elastomer, but is not particularly limited.

The water-swellable rubber obtained by the above method has a ratio of the volume change rate of ion-exchanged water to the volume change rate of artificial seawater in the range of 1.0 to 2.0 and a volume change rate of ion-exchanged water of 200 volume. % To 700% by volume. Therefore, even if the type of contacting water changes suddenly, a high water-stopping effect can be exhibited, so that it can be suitably used even in an environment where the type of contacting water changes. Further, the soluble organic carbon content of the water-swellable rubber is 20 ppm or less, and the safety is very high. For this reason, it can be preferably used even in an application field where high safety is required.

As the monomer copolymerizable with the above nonionic monomer, an acid type anionic monomer and / or a monovalent salt of anionic monomer may be used. As the acid type anionic monomer, for example, the anionic monomers exemplified above can be used. Further, ammonium salts and amine salts of the above exemplified compounds can also be used. However, when a monovalent salt of the acid type anionic monomer and / or the anionic monomer is used as the monomer copolymerizable with the nonionic monomer, that is, the resulting water absorbent resin is When it contains an acid group such as a carboxylic acid group, a monovalent metal base such as sodium carboxylate, an ammonium group such as ammonium carboxylate, or an amine group such as a carboxylic acid organic amine group, together with the water-absorbent resin or elastomer,
It is necessary to add a water-soluble polyvalent metal salt. Since the water-swellable rubber further contains a water-soluble polyvalent metal salt, even if the water-absorbent resin contains an acid group, a monovalent metal base, an ammonium group, or an amine group as described above, The ratio of ion exchange water volume change rate to sea water volume change rate is 1.0 to 2.0.
The volume change rate of ion-exchanged water can be controlled within the range of 200% by volume to 700% by volume, and the soluble organic carbon content can be suppressed within 20 ppm.

That is, the average particle size obtained by polymerizing a monomer component consisting of a nonionic monomer and an acid type anionic monomer and / or a monovalent salt of anionic monomer is from 1 μm to By mixing the water-absorbent resin in the range of 100 μm, the elastomer, and the water-soluble polyvalent metal salt, the ratio of the volume change rate due to the absorption of ion-exchanged water to the artificial seawater volume change rate is 1.0 to 2.0. Within the range, the volume change rate due to absorption of ion-exchanged water is 200% by volume to 700
It is possible to obtain a water-swellable rubber having a soluble organic carbon content of 20 ppm or less in the range of volume%.

In this case, the mixing ratio of each monomer in the above-mentioned monomer components is 20% by weight to 99% by weight of nonionic monomer, acid type anionic monomer and / or anionic monomer. A ratio of 80% by weight to 1% by weight of the monovalent salt of is preferable. When the proportion of the nonionic monomer in the monomer component is less than 20% by weight, the finally obtained water-swellable rubber has a low liquid absorption capacity, that is, a volume change rate. Therefore, a water-swellable rubber having desired physical properties may not be obtained.

The method for polymerizing the above-mentioned monomer component, that is, the method for producing the water absorbent resin is not particularly limited, and the same method as the above-mentioned polymerization method can be used. That is, the water-absorbent resin can be obtained by polymerizing the monomer component in the presence of a crosslinking agent, or after the monomer component is polymerized, a crosslinking agent is added to crosslink. It can also be obtained by The cross-linking agent is not particularly limited, and the same cross-linking agents as those exemplified above can be used. Further, the conditions such as the addition amount are not particularly limited, and may be set in the same manner as the conditions described above. Further, other polymerization conditions are not particularly limited and may be set in the same manner as the above-mentioned polymerization conditions. Further, the compounding conditions of the water absorbent resin and the elastomer or other additives may be set in the same manner as described above.

As the monomer copolymerizable with the nonionic monomer, the water-soluble polyhydric acid used when the acid type anionic monomer and / or the monovalent salt of the anionic monomer is used. The valent metal salt is not particularly limited, but specifically, for example, magnesium, aluminum, calcium, titanium, manganese, iron, tin, cerium, lead, chromium, copper, molybdenum and the like nitrates, sulfuric acid salt,
Examples thereof include halides, phosphates, and organic acid salts such as formic acid and acetic acid. These water-soluble polyvalent metal salts may be used alone or as a mixture of two or more. Among these water-soluble polyvalent metal salts, nitrates, sulfates and halides of magnesium and calcium are preferable, and magnesium sulfate is particularly preferable.

The amount of the water-soluble polyvalent metal salt used is not particularly limited, but is preferably in the range of 1 part by weight to 1000 parts by weight, preferably 5 parts by weight, based on 100 parts by weight of the water absorbent resin. It is more preferably in the range of ˜100 parts by weight.

As a method of adding the water-soluble polyvalent metal salt,
It is not particularly limited, and may be added, for example, when the water-absorbent resin and the elastomer are mixed (kneaded). The kneading conditions and the like of the water absorbent resin and the elastomer are not particularly limited, and may be set to the same conditions as the kneading conditions and the like described above.

As described above, the water-swellable rubber according to the present invention comprises 20% by weight to 100% by weight of a nonionic monomer and 80% by weight to 0% by weight of a polyvalent metal salt of an anionic monomer. The average particle size obtained by polymerizing the following monomer component is from 1 μm to
It contains a water-absorbent resin in the range of 100 μm and an elastomer, and the ratio of the volume change rate due to absorption of ion-exchanged water to the volume change rate due to absorption of artificial seawater is 1.0 to
The configuration is within 2.0.

As described above, the water-swellable rubber according to the present invention contains the nonionic monomer of 20% by weight to 99% by weight, and the acid type anionic monomer and / or the anionic monomer. A water-absorbent resin having an average particle size of 1 μm to 100 μm, obtained by polymerizing a monomer component composed of 80% by weight to 1% by weight of a monovalent salt, an elastomer, and a water-soluble polyvalent metal salt. Included, and the ratio of the volume change rate due to absorption of ion-exchanged water to the volume change rate due to absorption of artificial seawater is 1.0.
The configuration is within the range of to 2.0. As the water-soluble polyvalent metal salt, magnesium sulfate is particularly preferable.

Furthermore, the water-swellable rubber according to the present invention has a volume change rate of 200% by volume or more due to absorption of the ion-exchanged water.
It is within the range of 700% by volume, and the soluble organic carbon content is 20 ppm.
It is as follows. Further, as the nonionic monomer, the (meth) acrylic acid ester-based monomer represented by the general formula (1) is particularly preferable.

According to the above constitution, the water-swellable rubber of the present invention can exhibit a high water-stopping effect even if the kind of the aqueous solution with which it comes into contact suddenly changes. Therefore, it can be suitably used even in an environment in which the type of water with which it comes into contact changes. Further, the water-swellable rubber of the present invention has a reduced soluble organic carbon content as compared with the conventional one, and is excellent in safety. For this reason, it can be preferably used even in an application field where high safety is required. The water-swellable rubber is preferably used as a waterproof material for civil engineering work such as tunnel excavation or construction work, a waterproof material for tap water, or a leakage prevention material for preventing leakage of industrial wastewater to the outside. It
The water-swellable rubber may be formed in a predetermined shape such as a block shape.

[0057]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto. The performances of the liquid absorbent and the water-swellable rubber were measured by the following methods. Moreover, "part" described in the examples and comparative examples indicates "part by weight".

(A) Volume change rate of ion-exchanged water: A plastic container having an internal volume of 1000 ml was charged with 1000
ml. Then, 10 mm × 10
A water-swellable rubber sheet cut to have a thickness of 2 mm on a square side was hung by a stainless wire and dipped, and then left standing in a thermostatic chamber adjusted to 23 ° C. After 30 days, the volume change rate of the water-swellable rubber sheet was measured by the method described in JIS K6301.

(B) Volume change rate of artificial seawater 1000 ml of artificial seawater was placed in a plastic container having an internal volume of 1000 ml. Then, in this artificial seawater, a water-swellable rubber sheet cut to have a thickness of 20 mm × 20 mm square and a thickness of 2 mm was hung by stainless wire and immersed in the artificial seawater, and then allowed to stand in a thermostatic chamber controlled at 23 ° C. did. After 30 days, the volume change rate of the water-swellable rubber sheet was measured by the method described in JIS K6301.

(C) Soluble organic carbon content 1000 ml of ion-exchanged water in a plastic container having an internal volume of 1000 ml.
ml. Then, in this artificial seawater, a water-swellable rubber sheet cut into a size of 35 mm × 25 mm square, a thickness of 2 mm and a surface area of 20 cm ² was hung by a stainless wire and dipped into the artificial seawater. It was left in the room. After 5 days, the soluble organic carbon content eluted was measured with a TOC meter (manufactured by Shimadzu Corporation; Model TOC-500).

Example 1 A kneader equipped with a jacket having a capacity of 10 L was charged with 4164 parts of a 35 wt% aqueous solution of magnesium methacrylate as a polyvalent metal salt of an anionic monomer, and methoxypolyethylene glycol methacrylate 1072 as a nonionic monomer. Part, 170 parts of ion-exchanged water as a solvent,
Then, 23.6 parts of polyethylene glycol diacrylate as a crosslinking agent was charged to prepare a reaction liquid. The average addition mole number of ethylene oxide in the above methoxy polyethylene glycol methacrylate is 9 moles, and the average addition mole number of ethylene oxide in the polyethylene glycol diacrylate is 8 moles. In addition, the mixing ratio of magnesium methacrylate and methoxy polyethylene glycol methacrylate in the magnesium methacrylate aqueous solution, that is, the content of each monomer in the monomer component, magnesium methacrylate 57.6 wt%, methoxy polyethylene glycol methacrylate It is 42.4% by weight. Also, of polyethylene glycol diacrylate,
The ratio to the above-mentioned monomer component is 0.29 mol%.

Next, nitrogen gas was blown into the above reaction solution to expel dissolved oxygen, and the reaction system was replaced with nitrogen gas. Subsequently, the temperature of the reaction solution was raised to 40 ° C by pouring hot water of 40 ° C into the jacket and stirring, and then 10% by weight of a polymerization initiator 2,2'-azobis (2-amidinopropane) Hydrochloride (manufactured by Wako Pure Chemical Industries, Ltd .; trade name V-
50) Add 70.3 parts of aqueous solution. After stirring and mixing the reaction solution, the stirring was stopped. Then, the polymerization reaction was immediately started. 2,2'-Azobis (2-amidinopropane) hydrochloride was added so that the ratio to the monomer component was 0.15 mol%. At this time, the concentration of the monomer component in the reaction solution was 46% by weight.

In the above polymerization reaction, the temperature of the reaction solution reached 83 ° C. and reached a peak 236 minutes after the reaction was started. During this time, the temperature of the jacket was appropriately raised so as to be substantially equal to the temperature of the reaction solution. After the temperature of the reaction solution reaches the peak, the temperature of the jacket is maintained at 80 ° C,
The reaction was aged for 30 minutes. After completion of the reaction, the rotation speed of the blade was adjusted to 40 rpm, and the obtained hydrogel polymer was crushed into fine particles.

Crushed fine hydrogel polymer (hereinafter referred to as
The hydrogel polymer (A) is dried with a hot air circulation dryer under a nitrogen stream at 150 ° C. for 3 hours, and the dried product is pulverized with a jet mill to give an average particle diameter of 14 μm.
To obtain a water absorbent resin (hereinafter, referred to as water absorbent resin (1)).

Next, 100 parts of chloroprene rubber (manufactured by Tosoh Corporation) as an elastomer, 70 parts of the above water-absorbent resin (1), magnesium oxide as a vulcanizing agent and a vulcanization aid (Kyowa Chemical Industry Co., Ltd.) Manufactured; trade name: Magnesium oxide # 150) 4 parts, zinc oxide as a vulcanizing agent (manufactured by Shiramizu Chemical Co., Ltd .; trade name: zinc oxide # 1) 5 parts
0.50 parts of a vulcanization accelerator (manufactured by Sanshin Chemical Industry Co., Ltd .; trade name: vulcanization accelerator # 22) and 0.5 part of stearic acid (manufactured by NOF Corporation) as a lubricant were mixed. Then, the mixture was kneaded for 20 minutes using a roll of 6 ″ Φ × 16 ″ size adjusted to 50 ° C. to obtain a compound. Next, the above compound was vulcanized at 160 ° C. for 10 minutes using an electric heating press to obtain a sheet-like water-swellable rubber having a thickness of 2 mm.

The volume change rate and the soluble organic carbon content of the obtained water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water is 250% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate is
1.1. The soluble organic carbon content was 6.2 ppm. These results are shown in Table 1. In addition, in the measurement of the rate of change in the volume of ion-exchanged water and the rate of change in the volume of artificial seawater, no swelling unevenness was observed after 30 days, and the swelling was almost uniform.

Example 2 In a kneader similar to that of Example 1, 3837 parts of a 43 wt% sodium methacrylate aqueous solution as a monovalent salt of an anionic monomer, 1100 parts of methoxypolyethylene glycol methacrylate, and 470 ion-exchanged water were added.
Parts, and polyethylene glycol diacrylate 20.9
A part was charged to prepare a reaction solution. The average addition mole number of ethylene oxide in the above methoxy polyethylene glycol methacrylate is 9 moles, and the average addition mole number of ethylene oxide in the polyethylene glycol diacrylate is 8 moles. Further, the mixing ratio of sodium methacrylate and methoxypolyethylene glycol methacrylate in the sodium methacrylate aqueous solution,
That is, the content of each monomer in the monomer component is 60% by weight of sodium methacrylate and 40% by weight of methoxy polyethylene glycol methacrylate. The ratio of polyethylene glycol diacrylate to the above monomer component is 0.26 mol%.

Next, nitrogen gas was blown into the above reaction solution to expel dissolved oxygen, and the reaction system was replaced with nitrogen gas. Subsequently, the temperature of the reaction solution was raised to 40 ° C by pouring hot water of 40 ° C into the jacket and stirring, and then 10% by weight of 2,2'-azobis (2-amidinopropane) hydrochloride (Wako Pure Yaku Kogyo KK; trade name V-50) 71.7 parts of an aqueous solution was added. After stirring and mixing the reaction solution, the stirring was stopped. Then, the polymerization reaction was immediately started.
2,2'-Azobis (2-amidinopropane) hydrochloride was added so that the ratio to the monomer component was 0.15 mol%. At this time, the concentration of the monomer component in the reaction solution was 50% by weight.

In the above polymerization reaction, the temperature of the reaction solution reached 91 ° C. and reached a peak 79 minutes after the reaction was started. During this time, the temperature of the jacket was appropriately raised so as to be substantially equal to the temperature of the reaction solution. After the temperature of the reaction solution reached the peak, the temperature of the jacket was maintained at 80 ° C., and the reaction solution was aged for 30 minutes. After completion of the reaction, the rotation speed of the blade was adjusted to 40 rpm, and the obtained hydrogel polymer was crushed into fine particles.

The crushed fine hydrogel polymer was dried at 150 ° C. for 3 hours in a nitrogen stream using a hot air circulation dryer, and the dried product was crushed using a jet mill to obtain an average particle diameter. To obtain a water-absorbent resin powder having a particle diameter of 15 μm (hereinafter referred to as water-absorbent resin powder (a)).

Next, 100 parts of the water-absorbent resin powder (a) was blended with 32.7 parts of anhydrous magnesium sulfate as a water-soluble polyvalent metal salt to give a water-absorbent resin composition (hereinafter referred to as water-absorbent resin composition). The product (2) is obtained.

Next, the water absorbent resin (1) in Example 1
Instead of the water-absorbent resin composition (2), the same operation as in Example 1 was performed to obtain a water-swellable rubber. The volume change rate and the soluble organic carbon content of the obtained water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 550% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate was 1.4. The soluble organic carbon content was 6.9 ppm. These results are shown in Table 1. In addition, in the measurement of the rate of change in the volume of ion-exchanged water and the rate of change in the volume of artificial seawater, no swelling unevenness was observed after 30 days, and the swelling was almost uniform.

Example 3 A water-absorbent resin composition was prepared by blending 100 parts of the water-absorbent resin fine powder (a) of Example 2 with 30.2 parts of anhydrous calcium chloride as a water-soluble polyvalent metal salt. (Hereinafter, water absorbent resin composition (3)
To be described).

Next, the water absorbent resin (1) in Example 1
Instead of the above water-absorbent resin composition (3), the same operation as in Example 1 was performed to obtain a water-swellable rubber. The volume change rate and the soluble organic carbon content of the obtained water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 670% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate was 1.9. The soluble organic carbon content was 8.7 ppm. These results are shown in Table 1. In addition, in the measurement of the rate of change in the volume of ion-exchanged water and the rate of change in the volume of artificial seawater, no swelling unevenness was observed after 30 days, and the swelling was almost uniform.

Example 4 A water-absorbent resin composition was prepared by blending 100 parts of the water-absorbent resin fine powder (a) in Example 2 with 31.0 parts of anhydrous aluminum sulfate as a water-soluble polyvalent metal salt. (Hereinafter, water-absorbent resin composition (4)
To be described).

Next, the water absorbent resin (1) in Example 1
Instead of the above water-absorbent resin composition (4), the same operation as in Example 1 was performed to obtain a water-swellable rubber. The volume change rate and the soluble organic carbon content of the obtained water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 620% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate was 1.8. The soluble organic carbon content was 16.7 ppm.
These results are shown in Table 1. In addition, in the measurement of the rate of change in the volume of ion-exchanged water and the rate of change in the volume of artificial seawater, no swelling unevenness was observed after 30 days, and the swelling was almost uniform.

Example 5 The same reaction and operation as in Example 1 were carried out to obtain a crushed fine hydrogel polymer (A). The hydrogel polymer (A) was dried at 150 ° C. for 3 hours in a nitrogen stream using a hot air circulation dryer, and the dried product was crushed with a hammer mill to absorb water having an average particle diameter of 96 μm. Resin (hereinafter referred to as water-absorbent resin composition (5)) was obtained.

Next, the water absorbent resin (1) in Example 1
Instead of the above water-absorbent resin composition (5), the same operation as in Example 1 was performed to obtain a water-swellable rubber. The volume change rate and the soluble organic carbon content of the obtained water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 210% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate was 1.2. The soluble organic carbon content was 7.3 ppm. These results are shown in Table 1. In addition, in the measurement of the rate of change in the volume of ion-exchanged water and the rate of change in the volume of artificial seawater, no swelling unevenness was observed after 30 days, and the swelling was almost uniform.

Example 6 A commercially available crosslinked polymer of N-vinylacetamide alone was pulverized using a jet mill, and a water absorbent resin having an average particle diameter of 41 μm (hereinafter referred to as water absorbent resin composition (6)). ) Got.

Next, the water absorbent resin (1) in Example 1
Instead of the above water-absorbent resin composition (6), the same operation as in Example 1 was performed to obtain a water-swellable rubber. The volume change rate and the soluble organic carbon content of the obtained water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 380% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate was 1.2. The soluble organic carbon content was 11.5 ppm.
These results are shown in Table 1. In addition, in the measurement of the rate of change in the volume of ion-exchanged water and the rate of change in the volume of artificial seawater, no swelling unevenness was observed after 30 days, and the swelling was almost uniform.

Comparative Example 1 Instead of the water absorbent resin (1) in Example 1, the water absorbent resin powder (a) obtained in the manufacturing process of the water absorbent resin composition (2) of Example 2 was used. The same operation as in Example 1 was carried out except that the water-swellable rubber for comparison was obtained. The volume change rate and the soluble organic carbon content of the obtained comparative water-swellable rubber were measured by the above methods. As a result, the ion exchanged water volume change rate was 2080% by volume, and the ratio of the ion exchanged water volume change rate to the artificial seawater volume change rate was 7.7. Also, the soluble organic carbon content is
It was 23.0 ppm. These results are shown in Table 1.

Comparative Example 2 1338 parts of a 40% by weight acrylamide aqueous solution as a nonionic monomer, 1432 parts of sulfoethyl methacrylate as an acid type anionic monomer and 50 parts of methacrylic acid were placed in the same kneader as in Example 1. Parts, 166 parts of sodium methacrylate as a monovalent metal salt of an anionic monomer, 3.3 parts of methylenebisacrylamide as a cross-linking agent, and ion-exchanged water to make a total amount of 5450 parts, and then dissolved by stirring. .

Next, nitrogen gas was blown into the above reaction solution to expel dissolved oxygen, and the reaction system was replaced with nitrogen gas. Subsequently, the temperature of the reaction solution was raised to 53 ° C by pouring hot water at 53 ° C into the jacket and stirring, and then 12.9 wt% 2,2'-azobis (2-amidinopropane) as a polymerization initiator was added. Hydrochloride (manufactured by Wako Pure Chemical Industries, Ltd .; trade name V-
50) Aqueous solution 25.6 parts and 9.6% by weight 2,2'-azobis
(N, N'-dimethyleneisobutylamidine) dihydrochloride aqueous solution
25.8 parts were added. After stirring and mixing the reaction solution, the stirring was stopped. Then, the polymerization reaction was immediately started. At this time, the concentration of the monomer component in the reaction solution was 40% by weight.

In the above polymerization reaction, the temperature of the reaction solution reached 103 ° C. and reached a peak 31 minutes after the reaction was started. During this time, the temperature of the jacket was appropriately raised so as to be substantially equal to the temperature of the reaction solution until reaching 80 ° C. After the temperature of the reaction solution reached the peak, the temperature of the jacket was maintained at 80 ° C., and the reaction solution was aged for 30 minutes. After completion of the reaction, the rotation speed of the blade was adjusted to 40 rpm, and the obtained hydrogel polymer was crushed into fine particles.

The crushed fine hydrogel polymer was dried at 160 ° C. for 1 hour in a nitrogen stream using a hot air circulation dryer, and the dried product was crushed using a jet mill to give an average particle diameter. To obtain a comparative water-absorbent resin fine powder having a particle diameter of 12 μm (hereinafter referred to as water-absorbent resin powder (b)).

Next, the water absorbent resin (1) in Example 1
Instead of using the water absorbent resin powder (b),
The same operation as in Example 1 was performed to obtain a water-swellable rubber for comparison. The volume change rate and the soluble organic carbon content of the obtained comparative water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 1090% by volume,
The ratio of the volume change rate of ion-exchanged water to the volume change rate of artificial seawater was 4.8. The soluble organic carbon content is 28.5 pp
m. These results are shown in Table 1.

Comparative Example 3 In a kneader similar to that of Example 1, 2911 parts of a 40% by weight aqueous acrylamide solution, 119 parts of a 43% by weight sulfoethyl methacrylate aqueous solution, 1786 parts of a 37% by weight aqueous sodium acrylate solution, and 2% by weight methylenebis were added. Acrylamide aqueous solution 361 parts, and ion-exchanged water 200
A part was charged to prepare a reaction solution.

Next, nitrogen gas was blown into the above reaction solution to expel dissolved oxygen, and the reaction system was replaced with nitrogen gas. Subsequently, warm water of 20 ° C. was flown through the jacket, the blade rotation speed was set to 40 rpm, and the mixture was stirred to raise the temperature of the reaction liquid to 20 ° C. After that, as a polymerization initiator
82 parts by weight of 10% by weight sodium persulfate aqueous solution and 2% by weight L
41 parts of aqueous sodium ascorbate solution were added. After stirring and mixing the reaction solution, the stirring was stopped.
Then, the polymerization reaction was immediately started. At this time, the concentration of the monomer component in the reaction solution was 33% by weight.

In the above polymerization reaction, the temperature of the reaction solution reached 99 ° C. and reached a peak 32 minutes after the reaction was started. During this time, the temperature of the jacket was appropriately raised so as to be substantially equal to the temperature of the reaction solution until reaching 80 ° C.
After the temperature of the reaction mixture reaches its peak, change the jacket temperature.
The temperature was maintained at 80 ° C., and the reaction solution was aged for 30 minutes. After completion of the reaction, the obtained fine hydrogel polymer was dried at 160 ° C. for 1 hour under a nitrogen stream using a hot air circulation dryer,
The dried product was crushed using a jet mill and the average particle size was 14
A water-absorbent resin fine powder (hereinafter referred to as water-absorbent resin powder (c)) for comparison having a size of μm was obtained.

Next, the water absorbent resin (1) in Example 1
Instead of using the water absorbent resin powder (c),
The same operation as in Example 1 was performed to obtain a water-swellable rubber for comparison. The volume change rate and the soluble organic carbon content of the obtained comparative water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 1320% by volume,
The ratio of the volume change rate of ion-exchanged water to the volume change rate of artificial seawater was 5.9. The soluble organic carbon content is 21.3 pp
m. These results are shown in Table 1.

Comparative Example 4 Instead of the water absorbent resin (1) in Example 1, a polyacrylic acid water absorbent resin obtained by polymerizing an anionic monomer (manufactured by Nippon Shokubai Co., Ltd .; trade name Aqua). Rick K-4) was pulverized with a jet mill and the same operation as in Example 1 was carried out except that a powder having an average particle diameter of 17 μm was used to obtain a water-swellable rubber for comparison. It was The volume change rate and the soluble organic carbon content of the obtained comparative water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 1600% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate was 13.2. Also, the soluble organic carbon content is
It was 22.6 ppm. These results are shown in Table 1.

[Comparative Example 5] Instead of the water absorbent resin (1) in Example 1, an isobutylene / maleic acid crosslinked polymer which is a crosslinked polymer of a nonionic monomer and an anionic monomer (K.K. Kuraray; trade name KI gel) was pulverized using a jet mill, and the average particle size was 21 μm.
The same operation as in Example 1 was carried out except that the above powder was used to obtain a water-swellable rubber for comparison. The volume change rate and the soluble organic carbon content of the obtained comparative water-swellable rubber were measured by the above methods. As a result, the volume change rate of ion-exchanged water was 1770% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate was 10.3. The soluble organic carbon content was 27.4 ppm. These results are shown in Table 1.

[Comparative Example 6] The same reaction and operation as in Example 1 were carried out to obtain a crushed fine hydrogel polymer (A). The hydrogel polymer (A) was dried at 150 ° C. for 3 hours in a nitrogen stream using a hot air circulation dryer, and the dried product was crushed with a hammer mill to give an average particle diameter of 110 μm.
A water absorbent resin for comparison (hereinafter referred to as water absorbent resin (d)) was obtained.

Next, the water absorbent resin (1) in Example 1
Instead of the above water-absorbent resin (d), the same operation as in Example 1 was performed to obtain a water-swellable rubber for comparison. As a result, in the measurement of the rate of change of ion-exchanged water volume and the rate of change of artificial seawater, uneven swelling was observed after 30 days, and uniform swelling property was not exhibited.

[Comparative Example 7] In place of the water absorbent resin (1) used in Example 1, a commercially available crosslinked polymer of N-vinylacetamide alone (average particle diameter: 400 μm) was used.
The same operation as in Example 1 was performed to obtain a water-swellable rubber for comparison. As a result, in the measurement of the rate of change of ion-exchanged water volume and the rate of change of artificial seawater, uneven swelling was observed after 30 days, and uniform swelling property was not exhibited.

[0096]

[Table 1]

As is clear from Table 1, the water-swellable rubbers obtained in this example have a volume change rate of ion-exchanged water of
Both are in the range of 200% by volume to 700% by volume, and the ratio of the volume change rate of ion-exchanged water to the artificial seawater volume change rate is 1.0.
Within the range of ~ 2.0. Therefore, the water-swellable rubber obtained in this example, compared with the water-swellable rubber obtained in Comparative Example, even in an environment in which the type of water to contact changes, sufficient water-stopping effect. Obtainable. Moreover, it can be seen that the water-swellable rubber obtained in this example has a lower soluble organic carbon content than the comparative water-swellable rubber. Further, when the water-absorbent resin contains an acid group or a monovalent base, the ratio of the volume change rate of ion-exchanged water to the volume change rate of artificial seawater is adjusted within the above range by adding a water-soluble polyvalent metal salt. It was found that the soluble organic carbon content can be suppressed to 20 ppm or less.

[0098]

As described above, the water-swellable rubber according to claim 1 of the present invention comprises 20% by weight to 100% by weight of a nonionic monomer and 80% by weight of a polyvalent metal salt of an anionic monomer. % ~
A water-absorbent resin having an average particle size of 1 μm to 100 μm, which is obtained by polymerizing 0% by weight of a monomer component,
An elastomer is included, and the ratio of the volume change rate due to the absorption of ion-exchanged water to the volume change rate due to the absorption of artificial seawater is within the range of 1.0 to 2.0.

As described above, the water-swellable rubber according to claim 2 of the present invention comprises 20% by weight to 99% by weight of a nonionic monomer, an acid type anionic monomer and / or an anionic monomer. The average particle size obtained by polymerizing a monomer component consisting of 80% by weight to 1% by weight of a monovalent salt of a monomer is 1 μm to 100 μm.
containing a water-absorbent resin within the range of m, an elastomer, and a water-soluble polyvalent metal salt, and having a ratio of the volume change rate due to the absorption of ion-exchanged water to the volume change rate due to the absorption of artificial seawater of 1.0 to 2.0. The configuration is within the range.

Furthermore, the water-swellable rubber according to claim 3 of the present invention is, as described above, the water-swellable rubber according to claim 2, wherein the water-soluble polyvalent metal salt is magnesium sulfate. .

The water-swellable rubber according to claim 4 of the present invention is, as described above, the water-swellable rubber according to any one of claims 1 to 3, which is obtained by absorbing the ion-exchanged water. The volume change rate is in the range of 200% by volume to 700% by volume.

Further, the water-swellable rubber according to claim 5 of the present invention is as described above, in which the soluble organic carbon content is 2 in the water-swellable rubber according to any one of claims 1 to 4.
The composition is 0 ppm or less.

Further, as described above, the water-swellable rubber according to claim 6 of the present invention is the water-swellable rubber according to any one of claims 1 to 5, wherein the nonionic monomer is General formula (1)

[0104]

Embedded image

(In the formula, R represents a hydrogen atom or a methyl group, X represents an oxyalkylene group having 2 to 4 carbon atoms in which the mole fraction of the oxyethylene group is 50 mol% or more based on all the oxyalkylene groups, Y represents an alkoxy group having 1 to 5 carbon atoms, a phenoxy group, or an oxyalkylphenyl group having 1 to 3 alkyl groups having 1 to 9 carbon atoms as a substituent, and n represents an integer of 3 to 100 on average. ) Is a (meth) acrylic acid ester-based monomer.

According to the above construction, the difference between the volume change rate when artificial seawater is absorbed and the volume change rate when ion-exchanged water is absorbed is smaller than before, and the type of water that comes into contact suddenly changes. Even if it is possible to exert a high water-stopping effect, the soluble organic carbon content is reduced compared to the past,
The water-swellable rubber can be provided which can be suitably used even in the field of use where safety is highly required.

Claims (6)

[Claims] 1. A nonionic monomer 20% by weight to 100% by weight,
And a water-absorbent resin having an average particle size in the range of 1 μm to 100 μm obtained by polymerizing a monomer component consisting of 80% by weight to 0% by weight of a polyvalent metal salt of an anionic monomer, and an elastomer. The ratio of the volume change rate due to absorption of ion-exchanged water to the volume change rate due to absorption of artificial seawater is
A water-swellable rubber characterized by being in the range of 1.0 to 2.0. 2. A monomer comprising 20% by weight to 99% by weight of a nonionic monomer and 80% by weight to 1% by weight of an acid type anionic monomer and / or a monovalent salt of anionic monomer. Ion exchange with respect to volume change rate due to absorption of artificial seawater, which contains water-absorbent resin having an average particle size obtained by polymerizing components in the range of 1 μm to 100 μm, elastomer, and water-soluble polyvalent metal salt The ratio of volume change rate due to water absorption is
A water-swellable rubber characterized by being in the range of 1.0 to 2.0. 3. The water-swellable rubber according to claim 2, wherein the water-soluble polyvalent metal salt is magnesium sulfate. 4. The water-swellable rubber according to any one of claims 1 to 3, wherein the volume change rate due to absorption of the ion-exchanged water is in the range of 200% by volume to 700% by volume. . 5. The water-swellable rubber according to any one of claims 1 to 4, wherein the soluble organic carbon content is 20 ppm or less. 6. The above nonionic monomer is represented by the general formula (1): (In the formula, R represents a hydrogen atom or a methyl group, X represents an oxyalkylene group having 2 to 4 carbon atoms in which the mole fraction of the oxyethylene group with respect to all the oxyalkylene groups is 50 mol% or more, and Y is a carbon atom. An alkoxy group having a number of 1 to 5, a phenoxy group, or an oxyalkylphenyl group having 1 to 3 alkyl groups having a carbon number of 1 to 9 as a substituent, and n represents an integer of 3 to 100 on average) The water-swellable rubber according to any one of claims 1 to 5, which is a (meth) acrylic acid ester-based monomer.