JPH0940837A - Water-swelling rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-swelling rubber containing a liquid-absorbing agent comprising the alkaline earth metal salt of a copolymer comprising an anionic monomer, etc., reduced in eluted components, high in the swelling ratio, excellent in durability and safety, and suitable as a water-stopping material for civil engineering works, etc. SOLUTION: This water-swelling rubber contains a liquid-absorbing agent comprising the alkaline earth metal (e.g. magnesium) salt of a copolymer introduced from monomer components comprising (A) an anionic monomer such as (meth)acrylic acrid and (B) a nonionic monomer of the formula [R is H, methyl; (X)n are 2-4C oxyalkylene units containing oxyethylene units in a mole fraction of >=50mol.% based on the whole oxyalkylene units; Y is a 1-5C alkoxy, phenoxy, etc.; n is 3-100]. The liquid-absorbing ratio of the liquid-absorbing material for an artificial sea water is preferably >=5g/g.

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 formed by copolymerizing a (meth) acrylic acid ester-based monomer having a specific structure and a water-soluble unsaturated monomer containing a carboxyl group in the presence of a crosslinking agent. It consists of a cross-linked polymer. 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, the following problems occur.
That is, the water-swellable rubber containing the conventional water-absorbing agent swells significantly when contacted with water close to fresh water such as tap water, but contacts with water containing a large amount of polyvalent metal ions such as cement water. If you do, it swells only a little. In other words, there is a large difference in the swelling ratio depending on the type of water with which it comes into contact, which leaves a problem in waterproof performance and durability.

Further, the above-mentioned water-swellable rubber containing a conventional water-absorbing agent is used in a field of application where a high degree of safety is required because a relatively large amount of eluted components elute when contacted with an aqueous liquid. Still water still had problems.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to swell the salt and polyvalent metal ions in the case of absorbing fresh water such as tap water or water close to fresh water. Hard water or seawater containing, there is almost no difference with the swelling ratio when absorbing an aqueous liquid such as cement water, and moreover, the elution component eluted into water and the aqueous liquid is reduced as compared with the conventional one, the water stopping performance, It is to provide a water-swellable rubber having excellent durability and safety.

[0006]

Means for Solving the Problems As a result of intensive studies by the inventors of the present invention to achieve the above object, a copolymer derived from a monomer component containing an anionic monomer and a nonionic monomer. The water-swellable rubber containing a liquid absorbent composed of an alkaline earth metal salt, absorbs fresh water such as tap water or water close to fresh water, and the swelling ratio, and hard water or seawater containing salts or polyvalent metal ions. , There is almost no difference with the swelling ratio when absorbing an aqueous liquid such as cement water, and moreover, an elution component (soluble component) that elutes in water and an aqueous liquid
However, the present invention has been completed by finding out that it is reduced compared with the conventional one.

That is, in order to solve the above-mentioned problems, the water-swellable rubber of the invention according to claim 1 is a copolymer derived from a monomer component containing an anionic monomer and a nonionic monomer. It is characterized in that it contains a liquid absorbing agent composed of the alkaline earth metal salt of.

In order to solve the above-mentioned problems, the water-swellable rubber according to the second aspect of the present invention is the water-swellable rubber according to the first aspect, wherein the liquid absorbent has a liquid absorption capacity of 5 g with respect to artificial seawater.
It is characterized by being / g or more.

In order to solve the above-mentioned problems, the water-swellable rubber of the third aspect of the present invention is the water-swellable rubber of the first or second aspect, wherein the liquid absorbing agent is an alkali of an anionic monomer. It is characterized in that it is obtained by copolymerizing an earth metal salt and a nonionic monomer.

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, in which the nonionic monomer is General formula (1)

[0011]

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 oxyethylene groups is 50 mol% or more based on all 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.

In order to solve the above-mentioned 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 nonionic monomer is It is characterized by being methoxy polyethylene glycol methacrylate.

In order to solve the above-mentioned problems, the water-swellable rubber of the invention according to claim 6 is the water-swellable rubber according to any one of claims 1 to 5, wherein the alkaline earth metal is magnesium. It is characterized by being.

According to the above constitution, the liquid absorbing agent contained in the water-swellable rubber is an alkaline earth metal salt of a copolymer derived from a monomer component containing an anionic monomer and a nonionic monomer. Is. As a result, the swelling ratio is high, and the swelling ratio when absorbing fresh water such as tap water or water close to fresh water, and absorbing hard water or seawater containing salts or polyvalent metal ions, or an aqueous liquid such as cement water is absorbed. In this case, it is possible to provide a water-swellable rubber having almost no difference from the swelling ratio and having a reduced amount of elution component (soluble component) eluted in water and an aqueous liquid as compared with conventional rubbers.

Hereinafter, the present invention will be described in detail. The artificial seawater in the present invention means deionized water containing calcium sulfate (CaSO ₄ ), magnesium sulfate (MgSO ₄ ), magnesium chloride (MgCl ₂ ), potassium chloride (KC).
l) and sodium chloride (NaCl) in artificial seawater to be prepared have a concentration of CaSO ₄ : 1.38 g / kg, M
gSO ₄ : 2.10 g / kg, MgCl ₂ : 3.32 g / kg, KCl:
An aqueous solution prepared by dissolving so that the concentration becomes 0.72 g / kg and NaCl: 26.69 g / kg is shown.

The water-swellable rubber according to the present invention contains a liquid absorbent and an elastomer. The liquid absorbing agent is an alkaline earth metal salt of a copolymer derived from a monomer component containing an anionic monomer and a nonionic monomer. The above alkaline earth metal is more preferably magnesium and calcium, and particularly preferably magnesium. The above-mentioned monomer component may contain a monomer other than the anionic monomer and the nonionic monomer.

The above-mentioned anionic monomer may be a monomer capable of forming a salt with an alkaline earth metal as described below,
There is no particular limitation. Specific examples of the anionic monomer include unsaturated monocarboxylic acid type monomers such as (meth) acrylic acid and crotonic acid; maleic acid,
Unsaturated dicarboxylic acid type monomers such as fumaric acid, itaconic acid and citraconic acid; vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, sulfoethyl (meth ) Unsaturated sulfonic acid type monomers such as acrylate, sulfopropyl (meth) acrylate, 2-hydroxysulfopropyl (meth) acrylate; (meth) acrylamide methanephosphonic acid, 2- (meth) acrylamide
An unsaturated phosphonic acid-based monomer such as -2-methylpropanephosphonic acid can be used. These anionic monomers may be used alone, or two or more kinds may be appropriately mixed and used. Among the above-exemplified monomers, unsaturated monocarboxylic acid type monomers are more preferable, (meth) acrylic acid is further preferable, and methacrylic acid is particularly preferable.

The above-mentioned nonionic monomer is not particularly limited as long as it is a monomer copolymerizable with the anionic monomer. Specific examples of the nonionic monomer include (meth) acrylic acid ester monomers represented by the general formula (1); 2-hydroxyethyl (meth).
Unsaturated hydroxyl group-containing monomers such as acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, allyl alcohol, vinyl alcohol; (meth) acrylamide, N-
Amide-based unsaturated monomers such as vinylacetamide and t-butyl (meth) acrylamide; hydrophobic unsaturated monomers such as (meth) acrylic acid ester, styrene, 2-methylstyrene and vinyl acetate; (meth) acrylonitrile Nitrile unsaturated monomers such as ethylene, propylene, 1-butene,
Isobutylene, α-amylene, 2-methyl-1-butene, 3-
Methyl-1-butene (α-isoamylene), 1-hexene,
Α-Olefin-based monomers such as 1-heptene; alkoxypolyalkylene glycol mono (meth) acrylate and the like. Moreover, as the above-mentioned (meth) acrylic acid ester-based monomer, specifically, for example, methoxy polyethylene glycol mono (meth) acrylate, butoxy polyethylene glycol mono (meth) acrylate,
Methoxy polyethylene 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 / polybutylene glycol mono (meth) acrylate, etc. Is mentioned. These nonionic monomers may be used alone or as a mixture of two or more. Of the above-exemplified monomers, the (meth) acrylic acid ester-based monomer represented by the general formula (1) is 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.

The ratio of the anionic monomer to the nonionic monomer, that is, the ratio of the anionic monomer in the copolymer component is not particularly limited, but is 5% by weight to 95%. It is more preferably within the range of 10% by weight, and even more preferably within the range of 10% by weight to 70% by weight. When the proportion of the anionic monomer is less than 5% by weight, the amount of eluted components in the obtained copolymer tends to increase. Further, when the proportion of the anionic monomer is more than 95% by weight, the liquid absorption capacity of the liquid absorbent becomes low. Therefore, a water-swellable rubber having desired physical properties may not be obtained.

A method for producing an alkaline earth metal salt of a copolymer derived from a monomer component containing an anionic monomer and a nonionic monomer, that is, a method for producing a liquid absorbent is particularly limited. However, for example, an anionic monomer is reacted with a chloride such as calcium chloride or magnesium chloride to form an alkaline earth metal salt of the anionic monomer, and then a nonionic monomer is added. And a copolymerization method, in which an anionic monomer is reacted with a hydroxide such as calcium hydroxide or magnesium hydroxide to form an alkaline earth metal salt of the anionic monomer, and then the nonionic monomer is added. A method of adding a monomer and performing copolymerization, after reacting an anionic monomer with a carbonate such as calcium carbonate or magnesium carbonate to form an alkaline earth metal salt of an anionic monomer, and then adding a nonionic A method of copolymerizing by adding a monomer, a method of copolymerizing an anionic monomer and a nonionic monomer, and then adding the above chloride to form an alkaline earth metal salt, anionic After copolymerizing the monomer and the nonionic monomer, a method of adding the above hydroxide to form an alkaline earth metal salt, and copolymerizing the anionic monomer and the nonionic monomer. After the polymerization, various methods such as a method of adding the above-mentioned carbonate to form an alkaline earth metal salt can be adopted. Alternatively, the liquid absorbing agent can be produced by mixing the anionic monomer, the nonionic monomer, and the above-mentioned chloride, hydroxide or carbonate, and then copolymerizing them. Among these methods, the method and method are more preferable, and the method is particularly preferable. When the above method is adopted, magnesium hydroxide is particularly preferable as the hydroxide. The magnesium salt of an anionic monomer has a large solubility in water and is suitable for the polymerization reaction.

It is not clear why the alkaline earth metal salt of the copolymer of the present invention has less elution components than the alkali metal salts such as sodium salt and potassium salt, but it is presumed as follows. It

That is, the elution component is mainly composed of a soluble polymer, but the soluble polymer is two-dimensionally or three-dimensionally crosslinked by the alkaline earth metal, so that the solubility of the soluble polymer decreases. It is presumed that

As the polymerization method, various conventionally known methods such as a solution polymerization method, a suspension polymerization method and a reverse phase suspension polymerization method can be adopted. The stirring method for carrying out the polymerization reaction is not particularly limited, but a gel-like copolymer (described later) produced by using a double-arm kneader as a stirring device is used. It is more preferable to stir while subdividing by shearing force.

The reaction temperature is not particularly limited, but a relatively low temperature is preferable because the molecular weight of the copolymer becomes large, and a range of 20 ° C. to 100 ° C. is more preferable because the polymerization reaction is completed. . The reaction time may be appropriately set depending on the reaction temperature, the type (property) and combination of the monomer component, the polymerization initiator, and the solvent, the amount used, etc. so that the polymerization reaction is completed. Good.

When copolymerizing the monomer components, a polymerization initiator can be used. Specific examples of the polymerization initiator include peroxides such as hydrogen peroxide, benzoyl peroxide and cumene hydroperoxide;
2,2'-azobisisobutyronitrile, 2,2'-azobis (2
Azo compounds such as amidinopropane) hydrochloride; radical generators (radical polymerization initiators) such as persulfates such as ammonium persulfate, sodium persulfate and potassium persulfate. These polymerization initiators may be used alone, or two or more of them may be used as an appropriate mixture. Further, a redox-based initiator obtained by combining these radical generators with a reducing agent such as sodium bisulfite, L-ascorbic acid (salt), and ferrous salt may be used.
Incidentally, instead of using the polymerization initiator, radiation, electron beams, ultraviolet rays, or the like may be irradiated, and the polymerization initiator may be used in combination with these radiation, electron beams, ultraviolet rays, or the like.

The amount of the polymerization initiator used is not particularly limited, but is preferably within the range of 0.001% to 10% by weight, and more preferably within the range of 0.01% to 1% by weight with respect to the monomer component. 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.

When the monomer components are copolymerized,
You may use a crosslinking agent as needed. Specific examples of the cross-linking agent include divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol. Di (meta)
Acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, N, N-methylenebisacrylamide, triallyl isocyanurate, trimethylolpropane diallyl ether, etc. in one molecule A compound having two or more ethylenically unsaturated groups; ethylene glycol, diethylene glycol,
Polyethylene alcohol such as triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, polypropylene glycol, polyvinyl alcohol, pentaerythritol, diethanolamine, triethanolamine, sorbit, sorbitan, glucose, mannitol, mannitan, sucrose, glucose Ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane Diglycidyl ether, trimethylolpropane trig Examples thereof include polyepoxy compounds such as lysidyl 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.

The crosslinking density of the copolymer can be controlled by using the crosslinking agent. 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 0.0005 to 0.02, and further preferably within the range of 0.001 to 0.01, in terms of molar ratio to the monomer component. still,
When a polyhydric alcohol is used as the cross-linking agent, it is preferable to heat-treat the copolymer at 150 ° C to 250 ° C after the polymerization reaction. When a polyepoxy compound is used as the crosslinking agent, it is preferable to heat-treat the copolymer at 50 ° C to 250 ° C after the polymerization reaction.

Further, when copolymerizing the monomer components, a solvent may be used if necessary. Specific examples of the solvent include water; cyclohexane, toluene; aqueous solvents such as methanol, ethanol, acetone, dimethylformamide, and dimethylsulfoxide. These solvents may be used alone or as a mixture of two or more. Of the above-exemplified solvents, water and a mixture of water and an aqueous solvent are more preferable because the liquid absorbent can be produced with higher safety and at low 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 setting the concentration of the monomer component in the solution containing the monomer component, the polymerization initiator, the cross-linking agent, etc. within the above range, the polymerization reaction can be easily controlled and the yield of the copolymer can be controlled. The rate can be improved and the copolymer can be economically obtained.

Since the alkaline earth metal salt of the copolymer is obtained in a gel form after the polymerization reaction, the alkaline earth metal salt of the gel copolymer is used as it is, or if necessary, washed or thawed. After performing a predetermined operation such as crushing, it is dried. The drying temperature is not particularly limited, but may be 50 ° C to 180 ° C.
A temperature range of 100 ° C. is suitable, and a temperature range of 100 ° C. to 170 ° C. is optimum. Further, the dried product is pulverized by an operation such as pulverization, and then, if necessary, a classification operation such as sieving is performed. As a result, the absorption capacity for artificial seawater is 5 g / g
The above liquid absorbent can be obtained.

Further, in order to reduce the amount of unreacted monomer components remaining in the liquid-absorbent agent to reduce the elution component and further improve the safety of the liquid-absorbent agent, a gel-like copolymer is used. Alkaline earth metal salt or its dried product,
Treatment with a reducing agent is preferred. As the reducing agent, specifically, for example, sodium sulfite, potassium sulfite, ammonium sulfite, sodium hydrogen sulfite, potassium hydrogen sulfite, ammonium hydrogen sulfite, sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, L-ascorbic acid, Ammonia, monoethanolamine, glucose and the like can be mentioned. 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 used is not particularly limited, but specifically, the molar ratio to the used monomer component is more preferably within the range of about 0.0001 to 0.02, and further within the range of 0.001 to 0.01. preferable.

The shape and the like of the liquid absorbing agent are not particularly limited, but the shape is such that the water-swellable rubber can be uniformly mixed (dispersed) with the elastomer and the water-swellable rubber can be uniformly swollen. The average particle diameter is preferably about 5 μm to 70 μm, more preferably about 10 μm to 50 μm. The above average particle diameter is a volume average particle diameter.

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.

The ratio of the liquid absorbent to the elastomer in the water-swellable rubber, that is, the weight ratio of the liquid absorbent to the elastomer is preferably in the range of 5:95 to 50:50, and 15:85 to 40 :.
The range of 60 is more preferable. When the weight ratio of the liquid absorbing agent is less than the above range (less than 5), the water-swellable rubber cannot swell sufficiently, which is not preferable. Also,
The weight ratio of the liquid absorbent is higher than the above range (more than 50)
In this case, the water-swellable rubber becomes brittle and the strength is reduced, which is not preferable.

The method for producing the water-swellable rubber, that is, the method for mixing (kneading) the liquid absorbing agent 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 mix uniformly using a conventionally known mechanical method used for manufacturing a rubber product. 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 liquid absorbent and the elastomer, the water-swellable rubber may contain additives, if necessary. Examples of the additive include a vulcanizing agent, a vulcanization accelerator,
Vulcanization aids, inorganic fillers, reinforcing agents, softeners, plasticizers, colorants, ultraviolet absorbers, lubricants, antioxidants, etc. may be mentioned.
These additives may be used alone, or two or more of them may be used as an appropriate mixture. The amount of the additive used is, for example, 1 with respect to the total amount of the liquid absorbent and the elastomer.
The content may be 00% by weight or less, preferably 0.1% by weight to 60% by weight, but may be any amount as long as it does not impair the physical properties of the water-swellable rubber (for example, strength) and is not particularly limited. Absent. 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 used is, for example, 0.1% by weight to 10% by weight based on the total amount of the liquid absorbent and the elastomer.
However, it 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 is, for example, 0.1% by weight based on the total amount of the liquid absorbent and the elastomer.
It may be in the range of up to 10% by weight, but is not particularly limited.

Specific examples of the above-mentioned vulcanization aids include sodium hydroxide, calcium oxide, magnesium oxide (magnesia), zinc white, lead (II) oxide, etc., 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 is, for example, 0.1% by weight to the total amount of the liquid absorbent and the elastomer.
It may be in the range of 10% by weight, 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 carried out, for example, during or after the molding of the mixture of the liquid absorbent and the elastomer.

Specific examples of the above-mentioned inorganic filler 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 is, for example, 10% by weight based on the total amount of the liquid absorbent and the elastomer.
The amount may be in the range of up to 50% by weight, but is not particularly limited.

As described above, the water-swellable rubber according to the present invention is composed of an alkaline earth metal salt of a copolymer derived from a monomer component containing an anionic monomer and a nonionic monomer. It is a configuration including a liquid agent.

As described above, the water-swellable rubber has a liquid absorption capacity of the artificial seawater of 5 g / g or more. Furthermore, as described above, the water-swellable rubber has a constitution in which the liquid absorbing agent is obtained by copolymerizing the alkaline earth metal salt of the anionic monomer and the nonionic monomer.
As described above, the water-swellable rubber has a configuration in which the nonionic monomer is the (meth) acrylic acid ester-based monomer represented by the general formula (1). Further, the water-swellable rubber has a constitution in which the nonionic monomer is methoxy polyethylene glycol methacrylate as described above.
In addition, the water-swellable rubber has a configuration in which the alkaline earth metal is magnesium as described above.

As a result, the swelling ratio is high, and the swelling ratio when absorbing fresh water such as tap water or water close to fresh water and hard water or sea water containing salts, polyvalent metal ions, etc.
Provided is a water-swellable rubber in which there is almost no difference from the swelling ratio when absorbing an aqueous liquid such as cement water, and in which the elution component (soluble component) eluted in water and the aqueous liquid is reduced as compared with the conventional one. be able to. 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 molded into a predetermined shape such as a block shape.

[0046]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these. 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) Liquid Absorption Capacity of Liquid Absorbing Agent About 1 g of the liquid absorbing agent was uniformly put in a tea bag type bag and immersed in artificial seawater. After standing still for 24 hours, the tea bag type bag was pulled up and drained for a certain period of time, and then the weight W ₁ (g) of the tea bag type bag was measured. Further, the same operation was performed without using the liquid absorbent, and the weight W ₀ (g) of the tea bag type bag at that time was measured. And these weights W ₁ · W
_{From 0} , the liquid absorption capacity (g / g) was calculated according to the following equation: liquid absorption capacity (g / g) = (weight W ₁ (g) -weight W ₀ (g)) / weight of liquid absorbent (g). . The liquid absorption ratio is an equilibrium value.

(B) Swelling property of water-swelling rubber A water-swelling rubber was cut into a 2 cm × 2 cm square so as to have a thickness of 3 mm to prepare a test piece, and its weight (g) was measured. The pieces were immersed in tap water or artificial seawater. 30
After allowing to stand for a day, the test piece was pulled up, and the weight (g) was measured after lightly wiping off the water with a filter paper. Then, from these weights, the swelling ratio (times) was calculated according to the following formula: swelling ratio (times) = weight of test piece after immersion (g) / weight of test piece before immersion (g).

Further, the ratio of the swelling ratio when absorbing tap water and the swelling ratio when absorbing artificial seawater (the swelling ratio when absorbing artificial seawater / the swelling ratio when absorbing tap water) This value was determined as the swelling ratio.

(C) Dissolution property of water-swellable rubber The dissolution property of the water-swellable rubber was measured in accordance with the dissolution test judgment method of JIS K 6353 "rubber for water supply". First,
A water-swellable rubber was cut out to have a thickness of 3 mm and a surface area of 20 cm ² to prepare a test piece, and the test piece was deionized water 1 L.
Soaked in. Collect the deionized water after standing for 24 hours,
This was used as sample water. Moreover, the same operation was performed without immersing the test piece to prepare empty sample water. On the other hand, an N / 100 potassium permanganate aqueous solution and an N / 100 sodium oxalate aqueous solution were prepared, and the N / 100 potassium permanganate aqueous solution was titrated with the N / 100 sodium oxalate aqueous solution or the like, The factor of the / 100 potassium permanganate aqueous solution was calculated.

Next, the above sample water and empty sample water were titrated using this N / 100 potassium permanganate aqueous solution. Then, the consumption amount (mg / l) of potassium permanganate was calculated according to the following formula, and the elution of the water-swellable rubber was evaluated by this value.

A = (ab) f × (1000 / I) × B where A: consumption of potassium permanganate (mg / l) a: N / 100 potassium permanganate required for sample water Total volume of aqueous solution (ml) b: Total volume of N / 100 potassium permanganate aqueous solution required for empty sample water (ml) f: Factor of N / 100 potassium permanganate aqueous solution I: Volume of sample water (ml) B: 0.316 (mg / l).

Example 1 A plastic reactor having an internal volume of 600 ml equipped with a thermometer, a nitrogen gas introduction tube, and a stirrer was charged with 35 wt% methacrylic acid as an alkaline earth metal salt of an anionic monomer. 203 parts of aqueous magnesium solution, 169 parts of methoxypolyethylene glycol methacrylate as nonionic monomer, ion-exchanged water as solvent 2
3.2 parts and 0.41 part of polyethylene glycol diacrylate as a crosslinking agent were charged to prepare a reaction solution. The average number of moles of ethylene oxide added in the above methoxypolyethylene glycol methacrylate is 9 moles. The average number of moles of ethylene oxide added to polyethylene glycol diacrylate is 8 moles.

That is, the molar ratio of the methacrylic acid component in the aqueous solution of magnesium methacrylate and methoxypolyethylene glycol methacrylate is set to 67:33, and the methacrylic acid component and methoxypolyethylene glycol methacrylate in the reaction solution are mixed. Both were charged so that the total concentration, that is, the concentration of the monomer component was 60% by weight. In addition, the ratio of polyethylene glycol diacrylate to the above monomer component is 0.12
It was prepared so that it would be mol%.

Next, nitrogen gas was blown into the above reaction solution to expel dissolved oxygen, and the reaction system was replaced with nitrogen gas. Then, the temperature of the reaction solution was raised to 40 ° C. using a water bath, 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) 4.44 parts of aqueous solution was added. And
After stirring and mixing the reaction liquid, stirring was stopped. Then, the polymerization reaction was immediately started. 2,2'-azobis (2-
Amidinopropane) hydrochloride was added so that the ratio with respect to the monomer component would be 0.15 mol%.

In the above polymerization reaction, the temperature of the reaction solution reached 93 ° C. and reached a peak 38 minutes after the reaction was started. During this time, the temperature of the water bath 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 water bath was maintained at 80 ° C., and the reaction solution was aged for 30 minutes. After completion of the reaction, the obtained hydrogel polymer was taken out and crushed into fine particles.

The crushed hydrous gel-like polymer was dried at 150 ° C. for 1 hour in a nitrogen stream using a hot air circulation dryer, and the dried product was crushed using a table crusher, and then wire mesh or the like. The liquid absorbent having a size of 60 mesh to 100 mesh was obtained by classification with.

The liquid absorption capacity of the obtained liquid absorbent was measured by the above method. As a result, the liquid absorption capacity was 20.8 g / g. The average particle size of this liquid absorbent was measured using a jet mill.
Further, it was pulverized so as to have a particle size of 15 μm to obtain a liquid absorbent powder.

Next, 100 parts of chloroprene rubber as an elastomer, 50 parts of the above-mentioned liquid absorbent powder, 4 parts of magnesium oxide as a vulcanizing agent and a vulcanization aid, 5 parts of zinc oxide as a vulcanizing agent, and vulcanization. 1 part of an accelerator, 1 part of a lubricant, 2 parts of an anti-aging agent, 20 parts of calcium carbonate as an inorganic filler, and 15 parts of a softening agent were mixed. Then, after kneading the mixture for 20 minutes using a 10-inch test roll machine, a thickness of 3.5 mm
To obtain a compound. Then, the above compound was vulcanized at 170 ° C. for 10 minutes by using an electric heat press to obtain a sheet-shaped water-swellable rubber having a thickness of 3 mm.

The swelling property and elution property of the obtained water-swelling rubber were measured by the above-mentioned methods. As a result, the swelling ratio when absorbing tap water was 3.2 times, the swelling ratio when absorbing artificial seawater was 3.0 times, and the swelling ratio was 0.94.
Met. The consumption of potassium permanganate is 1.6.
It was mg / l. These results are shown in Table 1.

Example 2 In place of 169 parts of methoxypolyethylene glycol methacrylate in which the average addition mole number of ethylene oxide in Example 1 was 9 moles,
A liquid absorbing agent was obtained by performing the same reaction and operation as in Example 1 except that 169 parts of methoxypolyethylene glycol methacrylate (nonionic monomer) having an average addition mole number of ethylene oxide of 50 moles was used. The liquid absorption capacity of the obtained liquid absorbent was 23.3 g / g. This liquid absorbing agent was further pulverized in the same manner as in Example 1 to obtain a liquid absorbing agent powder having an average particle diameter of 32 μm.

Next, Example 1 was conducted using the above liquid absorbent powder.
The same operation as above was performed to obtain a water-swellable rubber. The swelling property and elution property of the obtained water-swelling rubber were measured. The results are shown in Table 1.

Example 3 Instead of 169 parts of methoxypolyethylene glycol methacrylate in Example 1,
The same reaction and operation as in Example 1 were carried out except that 169 parts of butoxy polyethylene glycol methacrylate (nonionic monomer) having an average added mole number of ethylene oxide of 80 moles was used to obtain a liquid absorbent. The liquid absorption capacity of the obtained liquid absorbent was 18.3 g / g. This liquid absorbing agent was further pulverized in the same manner as in Example 1 to obtain a liquid absorbing agent powder having an average particle diameter of 74 μm.

Next, using the above liquid absorbent powder, Example 1 was used.
The same operation as above was performed to obtain a water-swellable rubber. The swelling property and elution property of the obtained water-swelling rubber were measured. The results are shown in Table 1.

Example 4 The amount of polyethylene glycol diacrylate used in Example 1 was changed from 0.41 part to 4.1.
I changed to the department. That is, the same reaction and operation as in Example 1 were carried out except that polyethylene glycol diacrylate was charged so that the ratio to the monomer component was 1.5 mol%, to obtain a liquid absorbent. The liquid absorption capacity of the obtained liquid absorbent was 5.5 g / g. This liquid absorbing agent was further pulverized in the same manner as in Example 1 to obtain a liquid absorbing agent powder having an average particle diameter of 7 μm.

Next, using the above liquid absorbent powder, Example 1
The same operation as above was performed to obtain a water-swellable rubber. The swelling property and elution property of the obtained water-swelling rubber were measured. The results are shown in Table 1.

Example 5 In the same reactor as in Example 1,
A 10 wt% aqueous solution of calcium methacrylate as an alkaline earth metal salt of an anionic monomer 313 parts, methoxy polyethylene glycol methacrylate 68.7 parts, ion-exchanged water 16.9 parts, and polyethylene glycol diacrylate 0.17 parts were charged to prepare a reaction solution. did. The average number of moles of ethylene oxide added in the above methoxypolyethylene glycol methacrylate is 9 moles. The average number of moles of ethylene oxide added to polyethylene glycol diacrylate is 8 moles.

That is, the molar ratio of the methacrylic acid component to the methoxypolyethylene glycol methacrylate in the calcium methacrylate aqueous solution was 67:33, and the concentration of the monomer component in the reaction solution was 25% by weight. Both were prepared so that In addition, polyethylene glycol diacrylate was charged so that the ratio to the above-mentioned monomer component was 0.12 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 50 ° C. using a water bath, and then 10% by weight 2,2′-azobis (2-amidinopropane)
1.21 parts of aqueous hydrochloric acid 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%.

In the above polymerization reaction, the temperature of the reaction solution reached 58 ° C. and reached a peak 60 minutes after the reaction was started. During this time, the temperature of the water bath 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 water bath was maintained at 80 ° C., and the reaction solution was aged for 60 minutes. After completion of the reaction, the obtained hydrogel polymer was taken out and crushed into fine particles.

The hydrous gel polymer thus crushed was dried and crushed in the same manner as in Example 1 to give 60 mesh-
A liquid absorbent having a size of 100 mesh was obtained. The liquid absorption capacity of the obtained liquid absorbent was 51.3 g / g. This liquid absorbent was used in Example 1.
Further pulverization was performed in the same manner as in (1) to obtain a liquid absorbent powder having an average particle diameter of 23 μm.

Next, using the above liquid absorbent powder, Example 1 was prepared.
The same operation as above was performed to obtain a water-swellable rubber. The swelling property and elution property of the obtained water-swelling rubber were measured. The results are shown in Table 1.

Example 6 The amount of polyethylene glycol diacrylate used in Example 5 was changed from 0.17 part to 0.51.
I changed to the department. That is, the same reaction and operation as in Example 5 were carried out except that the polyethylene glycol diacrylate was charged so that the ratio with respect to the monomer component was 0.36 mol% to obtain a liquid absorbent. The liquid absorption capacity of the obtained liquid absorbent was 22.4 g / g. This liquid absorbing agent was further pulverized in the same manner as in Example 1 to obtain a liquid absorbing agent powder having an average particle diameter of 18 μm.

Next, using the above liquid absorbent powder, Example 1 was used.
The same operation as above was performed to obtain a water-swellable rubber. The swelling property and elution property of the obtained water-swelling rubber were measured. The results are shown in Table 1.

Example 7 In a reactor similar to that of Example 1,
400.2% by weight aqueous magnesium acrylate solution as an alkaline earth metal salt of anionic monomer 100.2 parts, 40% by weight aqueous acrylamide solution as a nonionic monomer 199.8
Parts, 73.8 parts of deionized water and 1.5 as a cross-linking agent
A reaction solution was prepared by charging 16.5 parts by weight of an aqueous solution of N, N-methylenebisacrylamide.

That is, the molar ratio of the acrylic acid component in the magnesium acrylate aqueous solution to acrylamide is
Both were prepared so that the ratio was 3: 7, and the concentration of the monomer component in the reaction solution was 30% by weight.
Further, N, N-methylenebisacrylamide was charged so that the ratio to the above-mentioned monomer component was 0.1 mol%.

Next, nitrogen gas was blown into the above reaction solution to expel dissolved oxygen, and the reaction system was replaced with nitrogen gas. Then, after raising the temperature of the reaction solution to 20 ° C. using a water bath, 4.88 parts of a 10 wt% sodium persulfate aqueous solution (radical generator) as a polymerization initiator and a 1 wt% L-ascorbate aqueous solution ( (Reducing agent) 4.81 parts was added. After stirring and mixing the reaction solution, the stirring was stopped. Then, the polymerization reaction was immediately started. Sodium persulfate was added so that the ratio to the monomer component was 0.15 mol%. Further, sodium L-ascorbate was added so that the ratio to the monomer component was 0.02 mol%.

In the above polymerization reaction, the temperature of the reaction solution reached 108 ° C. and reached a peak 3 minutes after the reaction was started. During this time, the temperature of the water bath was appropriately raised until the temperature reached 90 ° C. so that it was almost equal to the temperature of the reaction solution. After the temperature of the reaction solution reached the peak, the temperature of the water bath was maintained at 80 ° C., and the reaction solution was aged for 30 minutes. After completion of the reaction, the obtained hydrogel polymer was taken out and crushed into fine particles.

The crushed hydrogel polymer was dried and crushed in the same manner as in Example 1 to give 60 mesh-
A liquid absorbent having a size of 100 mesh was obtained. The liquid absorption capacity of the obtained liquid absorbent was 24.6 g / g. This liquid absorbent was used in Example 1.
Further, it was pulverized in the same manner as in (1) to obtain a liquid absorbent powder having an average particle diameter of 26 μm.

Next, Example 1 was conducted using the above liquid absorbent powder.
The same operation as above was performed to obtain a water-swellable rubber. The swelling property and elution property of the obtained water-swelling rubber were measured. The results are shown in Table 1.

Example 8 In a reactor similar to that of Example 1,
A reaction solution was prepared by charging 159 parts of a 40 wt% magnesium acrylate aqueous solution, 176.4 parts of methoxy polyethylene glycol methacrylate, 59.3 parts of ion-exchanged water, and 0.65 part of polyethylene glycol diacrylate. The average number of moles of ethylene oxide added in the above methoxypolyethylene glycol methacrylate is 9 moles.
The average number of moles of ethylene oxide added to polyethylene glycol diacrylate is 8 moles.

That is, the molar ratio of the acrylic acid component in the aqueous solution of magnesium acrylate and methoxypolyethylene glycol methacrylate was set to 67:33, and the concentration of the monomer component in the reaction solution was 60% by weight.
Both were prepared so that In addition, polyethylene glycol diacrylate was charged so that the ratio to the above-mentioned monomer component was 0.12 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 50 ° C. using a water bath, and then 10% by weight 2,2′-azobis (2-amidinopropane)
4.64 parts of aqueous hydrochloric acid 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%.

In the above polymerization reaction, the temperature of the reaction solution reached 104 ° C. and reached a peak 49 minutes after the reaction was started. During this time, the temperature of the water bath was appropriately raised until the temperature reached 90 ° C. so that it was almost equal to the temperature of the reaction solution. After the temperature of the reaction solution reached the peak, the temperature of the water bath was maintained at 80 ° C., and the reaction solution was aged for 30 minutes. After completion of the reaction, the obtained hydrogel polymer was taken out and crushed into fine particles.

The crushed hydrous gel polymer was dried and crushed in the same manner as in Example 1 to give 60 mesh-
A liquid absorbent having a size of 100 mesh was obtained. The liquid absorption capacity of the obtained liquid absorbent was 13.4 g / g. This liquid absorbent was used in Example 1.
Further, it was pulverized in the same manner as in to obtain a liquid absorbent powder having an average particle diameter of 25 μm.

Next, Example 1 was conducted using the above liquid absorbent powder.
The same operation as above was performed to obtain a water-swellable rubber. The swelling property and elution property of the obtained water-swelling rubber were measured. The results are shown in Table 1.

[Comparative Example 1] The amount of polyethylene glycol diacrylate used in Example 1 was changed from 0.41 part to 8.2.
I changed to the department. That is, the same reaction and operation as in Example 1 were carried out except that polyethylene glycol diacrylate was charged so that the ratio to the monomer component was 3.0 mol%, to obtain a liquid absorbent for comparison. The liquid absorption capacity of the obtained liquid absorbent for comparison was 3.8 g / g. The liquid absorbent for comparison was further pulverized in the same manner as in Example 1 to obtain a liquid absorbent powder for comparison having an average particle diameter of 20 μm.

Next, the same operation as in Example 1 was carried out using the above liquid absorbent powder for comparison to obtain a water swellable rubber for comparison. The swelling property and elution property of the obtained comparative water-swelling rubber were measured. The results are shown in Table 1.

[Comparative Example 2] In a reactor similar to that of Example 1,
43wt% sodium methacrylate aqueous solution 178.0 parts, methoxy polyethylene glycol methacrylate 163.4 parts,
53.9 parts of ion-exchanged water and 0.25 part of polyethylene glycol diacrylate were charged to prepare a reaction solution. The average number of moles of ethylene oxide added in the above methoxypolyethylene glycol methacrylate is 9 moles. The average number of moles of ethylene oxide added to polyethylene glycol diacrylate is 8 moles.

That is, both were charged so that the methacrylic acid component in the aqueous sodium methacrylate solution and the methoxypolyethylene glycol methacrylate had a molar ratio of 67:33. The ratio of polyethylene glycol diacrylate to the above monomer components is 0.05 mol%
I was prepared to become.

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 using a water bath, and then 10% by weight of 2,2'-azobis (2-amidinopropane)
4.3 parts of aqueous hydrochloric acid 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%.

In the above polymerization reaction, the temperature of the reaction solution reached 88 ° C. and reached a peak 107 minutes after the reaction was started. During this time, the temperature of the water bath was appropriately raised so as to be substantially equal to the temperature of the reaction solution. After the temperature of the reaction solution reached its peak, the temperature of the water bath was maintained at 80 ° C.
Aged for minutes. After completion of the reaction, the obtained hydrogel polymer was taken out and crushed into fine particles.

The crushed hydrous gel polymer was dried and crushed in the same manner as in Example 1 to give 60 mesh-
A comparative liquid absorbent having a size of 100 mesh was obtained. The liquid absorption capacity of the obtained liquid absorbent for comparison was 21.8 g / g. The liquid absorbent for comparison was further pulverized in the same manner as in Example 1 to obtain a liquid absorbent powder for comparison having an average particle diameter of 20 μm.

Next, the same operation as in Example 1 was performed using the above liquid absorbent powder for comparison to obtain a water swellable rubber for comparison. The swelling property and elution property of the obtained comparative water-swelling rubber were measured. The results are shown in Table 1.

[Comparative Example 3] In a reactor similar to that of Example 1,
37 wt% sodium acrylate aqueous solution 116.8 parts, 40 wt% acrylamide aqueous solution 192 parts, ion-exchanged water 64.5 parts,
Further, 15.8 parts of a 1.5% by weight N, N-methylenebisacrylamide aqueous solution was charged to prepare a reaction solution.

That is, the molar ratio of the acrylic acid component in the sodium acrylate aqueous solution to the acrylamide is 3:
Both were prepared so that the concentration of the monomer component in the reaction solution was 30% by weight. Further, N, N-methylenebisacrylamide was charged so that the ratio to the above-mentioned monomer component was 0.1 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 20 ° C. using a water bath, and then 5.5 parts by weight of a 10 wt% sodium persulfate aqueous solution and 1
5.42 parts by weight of an aqueous L-sodium ascorbate solution were added. After stirring and mixing the reaction solution, the stirring was stopped. Then, the polymerization reaction was immediately started. Sodium persulfate was added so that the ratio to the monomer component was 0.15 mol%. Further, sodium L-ascorbate was added so that the ratio to the monomer component was 0.02 mol%.

In the above polymerization reaction, the temperature of the reaction solution reached 108 ° C. and reached a peak 17 minutes after the reaction was started. During this time, the temperature of the water bath was appropriately raised until the temperature reached 90 ° C. so that it was almost equal to the temperature of the reaction solution. After the temperature of the reaction solution reached the peak, the temperature of the water bath was maintained at 80 ° C., and the reaction solution was aged for 30 minutes. After completion of the reaction, the obtained hydrogel polymer was taken out and crushed into fine particles.

The crushed hydrous gel polymer was dried and pulverized in the same manner as in Example 1 to give 60 mesh-
A comparative liquid absorbent having a size of 100 mesh was obtained. The liquid absorption capacity of the obtained liquid absorbent for comparison was 21.7 g / g. The liquid absorbent for comparison was further pulverized in the same manner as in Example 1 to obtain a liquid absorbent powder for comparison having an average particle diameter of 19 μm.

Next, the same operation as in Example 1 was performed using the above liquid absorbent powder for comparison to obtain a water swellable rubber for comparison. The swelling property and elution property of the obtained comparative water-swelling rubber were measured. The results are shown in Table 1.

Comparative Example 4 Liquid absorbent powder in Example 1
The same operation as in Example 1 was carried out except that 50 parts of a commercially available sodium polyacrylate-based water absorbent resin (manufactured by Nippon Shokubai Co., Ltd .; trade name: AQUALIC K-4) was used instead of 50 parts, A water-swellable rubber for comparison was obtained. The swelling property and elution property of the obtained comparative water-swelling rubber were measured. The results are shown in Table 1.

[0102]

[Table 1]

As is clear from Table 1, the water-swellable rubber according to this example has a swelling ratio when absorbing tap water,
Also, the swelling ratio when absorbing artificial seawater is 2
It is more than double and the swelling ratio is close to 1. In contrast, the comparative water-swellable rubber of Comparative Example 1 has a swelling ratio of less than 2 times because the liquid absorbing agent has a liquid absorption ratio of less than 5 g / g. In addition, the comparative water-swellable rubbers of Comparative Examples 2 to 4 have a swelling ratio that is extremely smaller than 1. further,
In the water-swellable rubber according to the present example, the consumption amount of potassium permanganate is less than 5 mg / l, whereas the water-swellable rubbers for comparison in Comparative Examples 2 to 4 have the consumed amount. It is 5 mg / l or more.

That is, as is clear from the results of Examples 1 to 8 and Comparative Examples 1 to 4, the water-swellable rubber according to this Example has a swelling ratio when tap water is absorbed. , And, while being excellent in swelling ratio when absorbing artificial seawater, there is almost no difference between both swelling ratios, and
It can be seen that the eluted component (soluble component) is reduced as compared with the comparative water-swellable rubber.

[0105]

As described above, the water-swellable rubber according to claim 1 of the present invention is an alkaline earth of a copolymer derived from a monomer component containing an anionic monomer and a nonionic monomer. This is a configuration including a liquid absorbing agent composed of a metal salt.

Further, the water-swellable rubber according to the second aspect of the present invention is configured such that the liquid absorption capacity of the liquid absorbent to artificial seawater is 5 g / g or more. Further, in the water-swellable rubber according to claim 3 of the present invention, as described above, the liquid absorbing agent is obtained by copolymerizing an alkaline earth metal salt of an anionic monomer and a nonionic monomer. It is a composition. In addition, the water-swellable rubber according to claim 4 of the present invention, as described above,
The nonionic monomer is represented by the general formula (1)

[0107]

Embedded image

(Wherein 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. Furthermore, the water-swellable rubber according to claim 5 of the present invention is
As described above, the nonionic monomer is methoxypolyethylene glycol methacrylate. Also,
As described above, the water-swellable rubber according to claim 6 of the present invention is configured such that the alkaline earth metal is magnesium.

As a result, the swelling ratio is high and the swelling ratio in the case of absorbing fresh water such as tap water or water close to fresh water, and hard water or seawater containing salts or polyvalent metal ions,
Provided is a water-swellable rubber in which there is almost no difference from the swelling ratio when absorbing an aqueous liquid such as cement water, and in which the elution component (soluble component) eluted in water and the aqueous liquid is reduced as compared with the conventional one. There is an effect that can be.

Claims (6)

[Claims] 1. A water-swellable rubber containing a liquid absorbing agent composed of an alkaline earth metal salt of a copolymer derived from a monomer component containing an anionic monomer and a nonionic monomer. 2. The absorption capacity of the absorbent for artificial seawater is 5 g.
The water-swellable rubber according to claim 1, wherein the water-swellable rubber is not less than / g. 3. The water-swellable rubber according to claim 1, wherein the liquid absorbing agent is obtained by copolymerizing an alkaline earth metal salt of an anionic monomer and a nonionic monomer. . 4. The nonionic monomer has 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 3, which is a (meth) acrylic acid ester-based monomer. 5. The water-swellable rubber according to any one of claims 1 to 4, wherein the nonionic monomer is methoxy polyethylene glycol methacrylate. 6. The water-swellable rubber according to any one of claims 1 to 5, wherein the alkaline earth metal is magnesium.