JPH0810615A - Water absorbing composition - Google Patents

Abstract

PURPOSE:To obtain a water absorbing compsn. excellent in water absorbing, water swelling property, water retention and mechanical strength by constituting a principal part of a specific epoxy-modified block polymer and a highly water- absorbing resin to specify the water absorption thereof. CONSTITUTION:A water absorbing compsn. is constituted of an epoxy-modified block polymer (a) obtained by epoxidizing the unsaturated carbon-carbon double bond of the conjugated diene compd. of a block copolymer consisting of a polymer block based on a vinyl aromatic compd. and a polymer block based on a conjugated diene compd. and a highly water-absorbing resin (b) and the water absorption thereof is set to 5-100wt.%. By this constitution, the water absorbing compsn. excellent in water absorbency, water swelling property, water retention and mechanical strength is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to water absorbability, water swellability,
The present invention relates to a water absorbing composition having excellent water retention and mechanical strength.

[0002]

2. Description of the Related Art A rubber composition prepared by blending natural rubber or synthetic rubber with polyvinyl alcohol, polyacrylic acid salt, carboxymethyl cellulose, hydroxyl ethyl cellulose or the like as a water absorbing material is disclosed in, for example, JP-A-54-143653.
JP-A-54-7461, JP-A-54-7463, JP-A-54-2
[0066] Known from Japanese Patent Publication No. 0066, they absorb water and swell,
It is useful as a water-swelling material such as a waterproof material in civil engineering, construction, and other fields. However, conventional water-swellable materials use natural rubber or ordinary synthetic rubber as rubber, and therefore the compound requires a vulcanization operation with sulfur, peroxide, etc., and the molding process is complicated. It was In order to improve such drawbacks, a thermoplastic elastomer having elasticity similar to vulcanized natural rubber or synthetic rubber at room temperature without vulcanization and having processability similar to that of thermoplastic resin at high temperature is obtained. Attempts have been made to incorporate water-absorbing substances. For example, JP-A-60-41092 discloses a composition in which a water-swellable solid lower olefin-maleic anhydride crosslinked product is blended with a thermoplastic elastomer composed of styrene-butadiene.

[0003]

However, the thermoplastic elastomer composed of styrene-butadiene also has an insufficient affinity with the water-absorbing substance, and in particular, when a large amount of the water-absorbing substance is blended, the strength of the compound decreases. There are problems such as easy damage and difficulty in achieving a desired degree of swelling by dropping off the water-absorbing substance in water.

The inventors of the present invention have made earnest studies to obtain an excellent water-absorbing composition which does not have such a problem. As a result, a block copolymer comprising a conjugated diene and a vinyl aromatic hydrocarbon has a water-absorbing resin. In the compounded composition, by using an epoxy-modified block polymer in which the unsaturated carbon double bond of the conjugated diene compound of the block copolymer is epoxidized, water absorption, water swelling property, water retention property and mechanical property can be obtained. The present invention has been completed by finding that a water absorbent composition having excellent strength can be obtained.

[0005]

That is, the present invention is
"(A) and (b) (a) of a block copolymer composed of a polymer block A mainly containing a vinyl aromatic compound and a polymer block B mainly containing a conjugated diene compound in the same molecule: Epoxy-modified block polymer in which double bond of unsaturated carbon of conjugated diene compound is epoxidized (b) Made of highly water-absorbent resin and having water absorption of 5 to 1000% by weight
And “(a) and (b) (a) a polymer block A containing a vinyl aromatic compound as a main component and a conjugated diene compound as a main component in the same molecule. Epoxy-modified block polymer obtained by epoxidizing the unsaturated carbon double bond of the conjugated diene compound of the partially hydrogenated block polymer obtained by partially hydrogenating the block polymer consisting of the polymer block B Made of water-soluble resin, water absorption rate is 5 ~ 1000wt%
And a water-absorbing composition ".

Examples of the vinyl aromatic compound constituting the block polymer of the component (a) used in the present invention include styrene, α-methylstyrene, vinyltoluene, p-tertiary butylstyrene, divinylbenzene, p- One or more of methylstyrene, 1,1-diphenylstyrene, vinylnaphthalene, vinylanthracene and the like can be selected, and styrene is preferably used from the viewpoint of cost.

Further, as the conjugated diene compound, for example,
Butadiene, isoprene, 1,3-pentadiene, 2,
3-dimethyl-1,3-butadiene, piperylene, 3-
Butyl-1,3-octadiene, phenyl-1,3-butadiene, etc. are selected from 1 type, or 2 or more types,
Of these, butadiene, isoprene and combinations thereof are preferably used in terms of cost.

The block copolymer referred to herein is a block copolymer composed of a polymer block A mainly containing a vinyl aromatic compound and a polymer block B mainly containing a conjugated diene compound. The copolymerization ratio of the group compound and the conjugated diene compound is 5/95 to 70/30, especially 10/90
A polymerization ratio of ~ 60/40 is preferred.

The block copolymer used in the present invention has a number average molecular weight of 5,000 to 600,000, preferably 10,000 to 5,000.
The range is 00, and the molecular weight distribution [weight average molecular weight (Mw)
And the number average molecular weight (Mn) (Mw / Mn)]) is 10
It is the following. The copolymerization ratio, the molecular weight and the molecular weight distribution limited here are generally within the range widely used as a styrene-based thermoplastic elastomer, and it is not necessary in the present invention to use a special one out of this range. It simply leads to difficulty in acquisition and cost increase. The molecular structure of the block polymer may be linear, branched, radial or any combination thereof.

For example, A-B-A, B-A-B-A,
(A-B-) ₄ is a vinyl aromatic compound-conjugated diene compound block polymer having a structure such as Si and A-B-A-B-A. Further, the unsaturated bond of the conjugated diene compound of the block polymer may be partially hydrogenated.

As the method for producing the block polymer used in the present invention, any method can be used as long as it has the above-mentioned structure. For example, Japanese Examined Japanese Patent Sho 40-23798
Issue, Japanese Examined Sho 43-17979, Examined Sho 46-32415, Examined Sho 56-2
According to the method described in 8925, a vinyl aromatic compound-conjugated diene compound block copolymer can be synthesized in an inert solvent using a lithium catalyst or the like. Further, according to the method described in JP-B-42-8704, JP-B-43-6636, or JP-A-59-133203,
Hydrogenating in the presence of a hydrogenation catalyst in an inert solvent,
The partially hydrogenated block copolymer used in the present invention can be synthesized.

The method of epoxy-modifying these block copolymers is not particularly limited in the present invention. For example, a vinyl aromatic compound-conjugated diene compound block copolymer may be hydroperoxides in an inert solvent,
It can be obtained by reacting with an epoxidizing agent such as peracids.

As the inert solvent, for example, hexane, cyclohexane, toluene, benzene, ethyl acetate, carbon tetrachloride, chloroform and the like can be used.

Hydroperoxides include hydrogen peroxide, tertiary butyl hydroperoxide, cumene peroxide and the like. Examples of peracids include formic acid, peracetic acid, perbenzoic acid, and trifluoroperacetic acid. Of these, peracetic acid is a preferred epoxidizing agent because it is industrially produced in large quantities, is inexpensively available, and has high stability. Further, a catalyst can be used if necessary in the epoxidation. For example, in the case of peracids, an alkali such as sodium carbonate or an acid such as sulfuric acid can be used as a catalyst. There is no strict regulation on the amount of epoxidizing agent and the optimum amount in each case depends on such variables as the particular epoxidizing agent used, the degree of epoxidation desired, the individual block copolymers used, etc. .

There are no strict restrictions on the epoxidation reaction conditions. The reaction temperature range that can be used depends on the reactivity of the epoxidizing agent used. For example, peracetic acid is 0
70 ° C. is preferable, and decomposition of peracetic acid occurs above 70 ° C. No special manipulation of the reaction mixture is necessary, for example the mixture may be stirred for 2-10 hours. Isolation of the obtained epoxy-modified copolymer can be carried out by a suitable method, for example, a method of precipitating with a poor solvent, a method of charging the polymer in hot water with stirring, and removing the solvent by distillation.

The degree of epoxidation of the epoxy modified block polymer in the present invention is calculated by the following formula after titration with hydrobromic acid.

[0017] The epoxy equivalent of the epoxy modified block polymer in the present invention is not strictly regulated. However, when the amount of the introduced epoxy group is too small, a sufficient effect cannot be expected, but the introduction of an extremely large amount of epoxy group not only makes the production of the epoxy-modified block copolymer difficult but also increases the cost. Therefore, there is a proper range naturally in balance with the expected effect, and the epoxy equivalent is 140 to 10000 g /
mol is preferable, and particularly preferably 200 to 6000 g / mol.

The superabsorbent resin of component (b) used in the present invention has a superabsorbent resin having a water absorption capacity of 20 to 1000 times, preferably 50 to 500 times. Here, the water absorption capacity of the high water-absorbent resin is a saturated water absorption amount (g) per 1 g of the high water-absorbent resin. When the water absorption capacity is small, the water absorbency and water swelling property of the composition are poor. On the other hand, when the water absorption capacity is excessively high, the strength of the super absorbent polymer swollen with water becomes too low, which is not preferable.

Examples of such highly water-absorbent resins include carboxyl groups such as carboxyl groups, carboxylates, carboxylic acid amides, carboxylic acid imides, and carboxylic acid anhydrides from the viewpoint of water absorbency and durability of the water-swellable rubber layer. A crosslinked polymer is preferred which contains as a monomer component an .alpha..beta.-unsaturated compound having in the molecule one or two carboxyl groups that can be derived into a group.

Examples of the α / β-unsaturated compound include acrylic acid, methacrylic acid, acrylic acid amide, methacrylic acid amide, maleic anhydride, maleic acid, maleic acid amide, maleic imide, itaconic acid, crotonic acid, and fumar. Acids, mesaconic acid, etc. may be used in combination with other copolymerizable monomer components as long as the performance required for the super absorbent polymer is satisfied. As the other copolymerizable monomer, ethylene, propylene, isobutylene,
Examples thereof include 1-butylene, diisobutylene, methyl vinyl ether, styrene, vinyl acetate, acrylic acid ester, methacrylic acid ester, α-olefins such as acrylonitrile, vinyl compounds, and vinylidene compounds.
When combined with other monomers, the amount of the .alpha..beta.-unsaturated compound containing a carboxyl group or a functional group capable of being converted into the carboxyl group is appropriately 40 mol% or more in all the monomer components.

The above-mentioned polymer containing as a monomer an .alpha..beta.-unsaturated compound having a carboxyl group or a functional group capable of being converted into a carboxyl group is a peroxide, an azo compound, or an oxidizing agent and a reducing agent. It is prepared by conventional radical polymerization using an initiator such as a combined binary system (redox).
The degree of polymerization is not particularly limited, and is in the range generally applied to these polymers, that is, 10 to 3000.
Good.

Among the above-prepared polymers prepared in this way, inexpensive and widely used polymers such as acrylic acid and methacrylic acid, and copolymers of α-olefin or vinyl compound and maleic anhydride are available. preferable. These polymers or copolymers are prepared by reacting compounds such as hydroxides, oxides or carbonates of alkali metals or alkaline earth metals such as sodium, potassium, magnesium, calcium and barium, ammonia, amines and the like. Due to
It is preferable to make it more hydrophilic.

This reaction is carried out by dissolving the polymer in a solvent, preferably water, and adding the alkali metal compound, alkaline earth metal compound, ammonia, amine and the like thereto with stirring. In this reaction, sodium hydroxide, potassium hydroxide and ammonia are preferably used from the viewpoints of reactivity and durability of the resulting super absorbent polymer. The polymer containing the α / β-unsaturated compound thus obtained as a monomer component is subjected to a crosslinking reaction, and as the crosslinking agent used, a polyvalent epoxy compound, a polyvalent amine, Examples thereof include polyhydric alcohols, amino alcohols, polyisocyanates, polyvalent halohydrins, and the like, and polyvalent epoxy compounds and polyvalent amines are particularly preferably used.

Examples of the polyepoxy compound include glycerin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, or trimethylolpropane triglyceride. Glycidyl ether may be used, and as the polyvalent amine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, or polyethyleneimine having a molecular weight of 5000 or less may be used.

The cross-linking reaction is carried out by adding the cross-linking agent to the polymer containing the α-β-unsaturated compound as a monomer component. At this time, heating may be performed or a solvent may be used. When a polyvalent epoxy compound or a polyvalent amine is used as the cross-linking agent, it is preferably carried out under heating and in the presence of water.

In such a case, drying or heat treatment is preferable. The degree of cross-linking is adjusted by appropriately selecting the amount of the cross-linking agent used so that the highly water-absorbent resin having the desired absorption capacity is obtained.

Preferred examples of the super absorbent resin according to the present invention are listed below.

(1) Maleic acid or a maleic acid derivative such as maleic anhydride, maleic acid amide or maleic acid imide, and a carbon number such as ethylene, propylene, butylene, isobutylene or diisobutylene having 2 to 12, preferably 2 to A crosslinked product of a reaction product of the copolymer of 8 with a linear or branched α-olefin and an alkali metal compound, an alkaline earth metal compound, ammonia, an amine or the like.

(2) A copolymer of maleic acid or a derivative thereof with a vinyl or vinylidene compound such as styrene, vinyl acetate, methyl vinyl ether, acrylic acid ester, methacrylic acid ester or acrylonitrile.
A crosslinked product of a reaction product with an alkali metal compound, an alkaline earth metal compound, ammonia, an amine and the like.

(3) A crosslinked product of a reaction product of a polymer of acrylic acid or methacrylic acid with an alkali metal compound, an alkaline earth metal compound, ammonia, amine and the like.

(4) A copolymer of acrylic acid or methacrylic acid and the vinyl or vinylidene compound of (2) above,
A crosslinked product of a reaction product with an alkali metal compound, an alkaline earth metal compound, ammonia, an amine and the like.

Among these, from the viewpoint of water absorption and durability, a cross-linked product of a reaction product of isobutylene-maleic anhydride copolymer and sodium hydroxide or ammonia, and a reaction product of polyacrylic acid and sodium hydroxide. Particularly preferred is a crosslinked product of (ie, sodium polyacrylate).

The super absorbent resin thus obtained is
It is desirable to use it by crushing it into particles that pass through a 20-mesh screen. If the particle size of the superabsorbent resin is too large, the superabsorbent resin other than the vicinity of the interface with the modified block copolymer is likely to be damaged or fallen off when swollen with water.

In the present invention, the modified block copolymer of the component (a) and the superabsorbent resin of the component (b) are blended so that the water absorption is 5 to 1000% by weight, preferably 50 to 500% by weight. It is selected as appropriate. That is, the appropriate mixing ratio is determined by the water absorption capacity of the super absorbent polymer used, and generally 5 to 300 parts by weight of the component (b), preferably 100 parts by weight of the component (a), Add 10 to 200 parts by weight.

If the water absorption rate is less than 5% by weight, there is no water absorption effect or water swelling effect. On the contrary, if the water absorption rate exceeds 1000% by weight, the strength of the composition swollen with water becomes low, which is not preferable. The water absorption rate is defined by the following equation.

[0036] The composition of the present invention may contain a softening agent and / or a component (a) if necessary.
Blended with different thermoplastic resin, elastomer, etc.
It is also possible to improve workability, hardness, water absorption speed, and the like.
As the softener, lubricating oil, paraffin-based process oil, naphthene-based process oil, aroma-based process oil, paraffin, vaseline, asphalt, vegetable oil (castor oil, cottonseed oil, rapeseed oil, soybean oil, etc.), sub, rosin, fatty acid, etc. Can be mentioned. As a thermoplastic resin,
Examples thereof include olefin resins, styrene resins, acrylate resins, vinyl chloride resins, polyamide resins, polyester resins, polycarbonate resins, polyphenylene ether resins, polyacetal resins, polyurethane resins and the like.

As the elastomer, natural rubber, synthetic polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, styrene-butadiene block copolymer, styrene-isoprene block copolymer, chloroprene rubber, ethylene-propylene rubber, acrylic rubber,
Examples thereof include polyisoprene isobutylene rubber and polypentenamer rubber.

Further, the composition of the present invention contains various pigments,
Additives such as dyes, flame retardants, antistatic agents, lubricants, plasticizers and inorganic / organic fillers can also be added.

The composition of the present invention can be produced by any conventionally known compounding method. For example, open roll,
Melt kneading method using a general kneader such as an intensive mixer, an internal mixer, a cokneader, a continuous kneader with a twin-screw rotor, or a single-screw or twin-screw extruder,
A method in which the solvent is removed by heating after the component (b) is dispersed and mixed in the solution in which the component (a) is dissolved is used.

[0040]

The water-absorbent composition of the present invention can be utilized in various applications by taking advantage of its excellent water absorbency, water swellability, water retention and mechanical strength such as tensile strength and impact resistance. Suitable for sealing materials, packing materials, water blocking materials, various waterproof materials, water retaining materials, oil / water separating materials, sludge solidifying materials, dew condensation preventing materials, sweat absorbing materials, sanitary goods such as diapers, and cold storage materials. Is.

<Examples> Examples will be shown below. However,
The block copolymer (A) used in Examples and Comparative Examples,
(B), (C), super absorbent polymer (I), (II) and additive (N) are as follows.

<Production of Block Copolymer> (A) A reactor equipped with a jacket equipped with a stirrer, a reflux condenser, and a thermometer, TR2000 manufactured by Nippon Synthetic Rubber Co., Ltd.
(Styrene content 40% by weight linear polystyrene-polybutadiene-polystyrene block copolymer) 300 g,
1500 g of ethyl acetate was charged and dissolved. Then 30 of peracetic acid
Continuously add 169 g of a wt% ethyl acetate solution and stir at 40 ° C.
The epoxidation reaction was carried out for 3 hours. The reaction solution was returned to room temperature and taken out from the reactor. A large amount of methanol was added to precipitate the polymer, which was filtered, washed with water and dried to obtain an epoxy-modified polymer having an epoxy equivalent of 470. This is designated as block copolymer A.

(B) TR2000 manufactured by Nippon Synthetic Rubber Co., Ltd. in a reactor with a jacket equipped with a stirrer and a thermometer
(Styrene content 40% by weight linear polystyrene-polybutadiene-polystyrene block copolymer) 300 g,
3000 g of cyclohexane was charged and dissolved, and the temperature was 60 ° C., and the hydrogenation catalyst was a di-P-tolylbis (1-cyclopentadienyl) titanium / cyclohexane solution (concentration 1 mmol / l).
A mixture of 40 ml and 8 ml of n-butyllithium solution (concentration 5 mmol / l) under 0 ° C. and a hydrogen pressure of 2.0 kg / cm ² was added, and the mixture was reacted at a hydrogen partial pressure of 2.5 kg / cm ^{2 for} 30 minutes. . The obtained partially hydrogenated polymer solution was dried under reduced pressure to remove the solvent (hydrogenation rate of the entire butadiene part was 30%).

300 g of this partially hydrogenated polymer, cyclohexane
1500 g was charged and dissolved in a jacketed reactor equipped with a stirrer, a reflux condenser and a thermometer. Then 30 of peracetic acid
Continuously add 300 g of a wt% ethyl acetate solution and stir at 40 ℃.
The epoxidation reaction was carried out for 3 hours. The reaction solution was returned to room temperature and taken out from the reactor, and a large amount of methanol was added to precipitate a polymer, which was filtered, washed with water and dried to obtain an epoxy-modified polymer having an epoxy equivalent of 275. This is designated as block copolymer B.

(C) TR2000 (straight chain polystyrene-polybutadiene-polystyrene block copolymer having a styrene content of 40% by weight) manufactured by Japan Synthetic Rubber Co., Ltd., which is a raw material for the block copolymers A and B.

<Highly water-absorbent resin> (I) Crosslinked product of isobutylene-maleic anhydride copolymer (the molar ratio of isobutylene and maleic anhydride is 1: 1 and sodium hydroxide and glyceryl glycidyl ether are used. A cross-linked product (water absorption capacity: 200 times) was crushed into a 400 mesh pass to obtain a super absorbent resin I.

(II) A fine powder of vinyl alcohol / acrylate copolymer having an average particle size of 20 μm.

<Additives> (N) naphthenic process oil [Examples 1 to 4 and Comparative Examples 1 to 2] According to the composition of Table 1, the block copolymer and the super absorbent resin were thoroughly kneaded with a mixing roll, It was molded into a sheet having a thickness of 2 mm, and the tensile strength of the molded product was measured. A 3 cm × 4 cm square test piece was cut out from the sheet and immersed in distilled water for 7 days to measure the water absorption. The results are shown in Table 1.

It can be seen that the composition containing the epoxy-modified block copolymer specified in the present invention is a composition having excellent tensile strength retention and good water absorption. Also, the composition of the present invention showed better water retention than that of the comparative example.

Examples 5 and 6 and Comparative Example 3 Example 1
In the same manner as in No. 4 to No. 4, mixing was performed according to the composition shown in Table 2 to prepare a water absorbing composition. When a sheet molded product of the composition was immersed in distilled water at 20 ° C. for 24 hours and the water absorption rate was measured, the composition of the present invention showed a good value. In addition, the water retention property was also good.

[Examples 7 to 8 and Comparative Example 4] According to the compositions shown in Table 2, the block copolymer and the superabsorbent polymer were kneaded with a twin-screw extruder and pelletized. The obtained pellet was injection-molded to form a flat plate having a thickness of 3 mm. The Izod impact strength of these compositions and the water absorption after immersion in distilled water for 7 days were measured. The composition of the present invention showed better values for both Izod impact strength and water absorption than those of Comparative Example.

Table 1 Examples Comparative Examples Composition (parts by weight) 1 2 3 4 1 2 A 100 100 Block copolymer B 100 100 C 100 100 Super absorbent resin I 30 30 30 II 50 50 50 Tensile strength retention rate ( %) 75 80 70 70 70 50 Water absorption (%) 210 205 45 200 205 40 Table 2 Examples Comparative Examples Composition (parts by weight) 5 6 7 8 3 4 4 A 100 100 block copolymer B 100 100 C 100 100 super absorbent resin I 40 40 20 20 40 20 additive N 50 50 − − 50 − Water absorption rate (%) 400 400 50 55 40 15 Izod impact strength (Kg · cm / cm) − − 32 33 − 19 (hereinafter, margin)

Claims (2)

[Claims] 1. A block composed of a polymer block A containing a vinyl aromatic compound as a main component and a polymer block B containing a conjugated diene compound as a main component in the same molecule (a) and (b) below. Epoxy-modified block polymer obtained by epoxidizing unsaturated carbon double bond of conjugated diene compound of copolymer (b) Superabsorbent resin, having water absorption rate of 5 to 1000% by weight Sex composition. 2. A block comprising a polymer block A containing a vinyl aromatic compound as a main component and a polymer block B containing a conjugated diene compound as a main component in the same molecule (a) and (b) below. Epoxy-modified block polymer obtained by epoxidizing the unsaturated carbon double bond of a conjugated diene compound of a partially hydrogenated block polymer obtained by partially hydrogenating a polymer. (B) Superabsorbent resin having a water absorption of 5 The water-absorbent composition is characterized in that the content is up to 1000% by weight.