JPS6336321B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a highly water-absorbing polymeric material (hereinafter referred to as hydrogel) that has the ability to absorb a large amount of water, and its purpose is to:
The object of the present invention is to provide a hydrogel that can be suitably used as various water-absorbing materials or as a gel material used in a swollen state after absorbing water. Another object of the present invention is to provide an economical and simple method for producing a hydrogel having sufficient gel strength, excellent water absorption, and large particle size. In recent years, as the use of hydrophilic polymer materials has progressed in the medical industry, food industry, and agricultural fields, hydrogels that are insoluble in water and have hydrophilic or water-absorbing properties have been used as separation and purification materials such as various membranes and liquid chromatography carriers. It has come to be used as an enzyme-immobilized carrier, a culture medium for microorganisms and plants, a medical material such as contact lenses and suture coverings, and a variety of other uses that utilize its water absorption and water retention properties. Among these applications, hydrogels used particularly in application fields that utilize water absorption or water retention are desired to have the ability to absorb as much water as possible in a short period of time upon contact with water. Methods for producing hydrogels for such uses include crosslinking water-soluble polymeric substances using a crosslinking agent, replacing some of the hydrophilic groups with lipophilic groups, and modifying them to make them water-insoluble. Methods such as crosslinking of polyethylene oxide, polyacrylic acid, polyvinylhyrrolidone, sulfonated polystyrene, sodium polyacrylate, etc., cellulose derivatives, polyacrylonitrile, or starch-acrylonitrile graft combinations have been used. Several materials using natural or synthetic polymeric substances, such as saponified polymers, have been proposed. In JP-A No. 53-46389, as a method for producing a self-crosslinking type alkali metal acrylate polymer, HLB3~ was disclosed using an aqueous alkali metal acrylate solution as a dispersant.
A method for producing a hydrogel with high water absorption capacity by polymerization in the presence of sorbitan fatty acid ester No. 6 has been proposed, but the average particle size of the hydrogel obtained by this method is 50 μm, as is clear from the examples.
These are as follows. When the average particle size is small, when water is absorbed, water enters the gaps between the particles and becomes sticky, which limits its use. For example, when mixing hydrogel with soil and using it as a soil water retention agent,
If the particle size of the hydrogel becomes too small, the solid-liquid-vapor phase structure of the soil will collapse, resulting in stickiness and excessive humidity, making the soil undesirable for growing plants. In addition, in applications that come into contact with the human body, such as disposable diapers, tampons, sanitary cotton, and napkins, fine particles have disadvantages such as undesirable sticky texture. In view of the above-mentioned circumstances, the present inventors have conducted intensive studies on a method for producing a hydrogel that has high water absorption, an average particle size of 50μ or more, and sufficient gel strength, and as a result, they have discovered the present invention. Ivy.
That is, the present invention provides a method for producing a polymeric material in which α,β-unsaturated carboxylic acid monomer or/and its alkali metal salt is subjected to water-in-oil reverse phase suspension polymerization in the presence of a crosslinking agent. The present invention provides a method for producing a polymeric material having a large particle size and excellent water absorption, which is characterized by using a carboxyl group-containing polymer having an affinity for organic solvents. According to the present invention, hydrogels with a particle size of 100 to 3000 microns can be produced. Hydrogels with such large particle sizes can be obtained because of the dispersion stabilizer used in the water-in-oil type reverse-phase suspension polymerization method. It is known that the particle size of suspended particles in a two-phase dispersion of water and oil is primarily influenced by the following three factors. The first is the stirring power during stirring, the second is the interfacial tension of the two phases, and the third is the viscosity of the system. If the two-phase dispersibility is too good, the particles will be dispersed in fine particles; if the two-phase dispersibility is too poor, the particles will not be suspended or dispersed in the form of particles. The carboxyl group-containing polymer used as a dispersion stabilizer in the present invention contains 0.01 mol% or more of carboxyl groups, an α,β-unsaturated carboxylic acid monomer or/and its alkali metal salt monomer, and a water-insoluble organic polymer. Those that are soluble in the solvent can be used. carboxyl group
If it is less than 0.01 mol%, it will not contribute to the formation of large particle size hydrogels. Examples include ethylene-(meth)acrylic acid copolymer, ethylene-alkyl(meth)acrylate-(meth)acrylic acid copolymer, ethylene-vinyl acetate-(meth)acrylic acid copolymer, and ethylene-acetic acid copolymer. Acrylic acid grafted vinyl copolymer,
Maleic anhydride modified product of ethylene-vinyl acetate copolymer, alkyl (meth)acrylate-(meth)
Acrylic acid copolymer, vinyl acetate-(meth)acrylic acid copolymer, half-ester compound of maleic anhydride-modified polybutadiene and lower alcohol (C ₁ to C ₆ ), polybutadiene grafted with butyl methacrylate and methacrylic acid, Ethylene-propylene made by graft polymerization of α,β-unsaturated carboxylic acid and alkyl ester or hydroxyalkyl ester of α,β-unsaturated carboxylic acid.
Examples include diene monomer copolymers (hereinafter abbreviated as EPDM). Among these, those that can be used particularly preferably include ethylene-acrylic acid copolymer and ethylene-acrylic acid copolymer.
Maleic anhydride modified product of vinyl acetate copolymer, methyl methacrylate - methacrylic acid - acrylic acid -
2-ethylhexyl copolymer, reaction product of maleic anhydride-modified polybutadiene with 2-hydroxyethyl methacrylate, polybutadiene-butyl methacrylate-methacrylic acid graft copolymer,
EPDM-α,β-Unsaturated carboxylic acid-α,β-
Examples include carboxylic acid alkyl esters or hydroxyalkyl ester graft copolymers. More preferably used is a methyl methacrylate-methacrylic acid-2-ethylhexyl acrylate copolymer with a composition ratio of 0 to 16:
2-10: A reaction product of 98-74 copolymer and maleic anhydride-modified polybutadiene with 2-hydroxyethyl methacrylate, where the molecular weight of the polybutadiene is 500-5000 and the maleic anhydride content of the maleic anhydride-modified polybutadiene is compounds ranging from 0.1 to 20% by weight, and EPDM-α,β-unsaturated carboxylic acids-α,β-unsaturated carboxylic acid alkyl esters or hydroxyalkyl ester graft copolymers as α,β-unsaturated carboxylic acids. are preferably acrylic acid and methacrylic acid, and the α,β-unsaturated carboxylic acid alkyl ester or hydroxyalkyl ester is preferably ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, Hydroxypropyl acrylate and hydroxypropyl methacrylate. The content of α,β-unsaturated carboxylic acid is preferably 2 to 50% by weight, the content of α,β-unsaturated carboxylic acid alkyl ester or hydroxyalkyl ester is preferably 2 to 50% by weight, and the content of EPDM is preferably 2 to 50% by weight. may range from 12 to 95% by weight. It has affinity for organic solvents. The affinity here means that the dispersion stabilizer dissolves or partially dissolves in the organic solvent. The amount used is 0.01 per organic solvent
~20% by weight. More preferably, it is 0.05 to 10% by weight. If it is less than 0.01% by weight, the dispersion stability during production of the hydrogel will be poor and it will not be dispersed in the form of beads, which is not preferable. On the other hand, if it exceeds 20% by weight, the viscosity of the system becomes high and the particle size of the hydrogel becomes fine. Moreover, it requires time and effort to wash, which is not preferable. The α,β-unsaturated carboxylic acid monomers and/or their alkali metal salt monomers used in the present invention include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, and their alkali metal salt monomers. I can give it to you. Among these, acrylic acid, methacrylic acid, and alkali metal salt monomers thereof can be mentioned as those which can be particularly preferably used. Examples of alkali metals include sodium, potassium, calcium, and barium. n-
Hexane, n-heptane, cyclohexane as an alicyclic hydrocarbon, benzene, toluene, xylene, etc. as an aromatic hydrocarbon. The crosslinking agents used in the present invention include α, β
- Polyols such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, etc. may be used as long as they are copolymerizable with unsaturated carboxylic acid monomers and/or their alkali metal salt monomers. di- or tri(meth)acrylic acid esters, unsaturated polyesters obtained by reacting the above polyols with unsaturated acids such as maleic acid and fumaric acid, and bisacrylamides such as N,N-methylenebisacrylamide. di- or tri(meth)acrylic acid esters obtained by reacting polyepoxide and (meth)acrylic acid, reacting polyisocyanates such as tolylene diisocyanate and hexamethylene diisocyanate with hydroxyethyl (meth)acrylate. Examples include di(meth)acrylic acid carbamyl esters, allylated starch, allylated cellulose, diallyl phthalate, N,N',N''-triallylisocyanurate, divinylbenzene, etc. Particularly preferred are ethylene glycol. Diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, diallyl phthalate, N, N′, N″-triallyl isocyanate Nurate, N,N'-methylenebisacrylamide, etc. are used. In the superabsorbent hydrogel of the present invention, the crosslinking agent is generally 0.001 to 1% by weight, preferably 0.01 to 1% by weight.
It is used at a proportion of 0.5% by weight, but if the proportion of the crosslinking agent is less than 0.001% by weight, the strength of the resulting hydrogel will decrease, while if it exceeds 1% by weight, the water absorption of the hydrogel will decrease to less than 50%. This is not desirable because it causes The hydrogel of the present invention obtained by the method described above has sufficient gel strength and large particle size. Additionally, they usually have the ability to absorb more than 100 times their own weight in water, but in general, if the water to be absorbed contains other substances, this ability changes depending on the type and amount of those substances. For example, when it comes to absorption ability for water with different pH values, it has the highest absorption ability for water with a pH of around 8 to 10, and in this case, it can absorb more than 500 times its own weight in water. Moreover, in a pH range of 5 or less, the absorption capacity decreases significantly. However, when the material that has been immersed in an acidic solution is immersed in an alkaline solution again, its absorption capacity is completely restored. In addition, highly water-absorbing gels, such as
It has properties such as releasing a large amount of water when salts such as NaCl are added. In other words, it exhibits reversible changes in water absorption and water release depending on changes in water pH and salt concentration. The superabsorbent hydrogel of the present invention as described above has the following advantages. In other words, it is transparent, has little coloring, and, as can be easily deduced from its molecular structure, has almost no toxicity. Therefore, it is used in various sanitary materials, such as disposable diapers,
It is expected that it can be used without any problems in applications that come into contact with the human body, such as tampons, sanitary cotton, hot towels, and napkins.It also has excellent gel strength in a hydrated state, and the gel strength will not break down even after long-term use. Therefore, it can be used in various industrial applications, such as as a water-in-oil separation agent, other dehydration or desiccation agents, or as a water-retention agent such as plants and soil, liquid chromatography carrier, and other water-absorbing and water-retaining properties. The superabsorbent hydrogel of the present invention has the advantage that it can be suitably used for various applications, and that it can be manufactured industrially very easily and can be molded into various shapes depending on the application. There is. Coloring agents, fragrances, other additives, and various inorganic and organic fillers can be added to the hydrogel of the present invention as long as they do not adversely affect its properties. Furthermore, the hydrogel of the present invention has
It can also be used in combination with paper, fibers, cloth, and other different materials. The method of the present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. In the examples, the water absorption rate of the hydrogel was expressed as water absorption rate (g/g) = (weight of water-absorbing hydrogel)/weight of dry hydrogel). Also, the number of copies is in units of weight. The average particle size was determined by the sieving method. Example 1 Put 100 g of water into a polymerization tank and dissolve 0.1 g of polyvinyl alcohol (degree of polymerization: 1700, degree of saponification: 88%). Add 4g of sodium chloride and dissolve. To the polymerization tank were added 19.8 g of 2-ethylhexyl acrylate, 0.5 g of methacrylic acid, 1.25 g of methyl methacrylate, 0.005 g of dodecyl mercaptan, and 0.1 g of lauroyl peroxide, and suspension polymerization was carried out at 60° C. for 6 hours. After polymerization, it is filtered, washed with water, and dried. The yield was 20.5g. Using a 300ml flask, add 1.5g of this copolymer to 150ml of n-hexane.
It was dissolved in Next, 20ml of water and 15g of acrylic acid.
and 6.7 g of sodium hydroxide, and further add 15 mg of potassium persulfate and 3 mg of N,N'-methylene-bis-(acrylamide) to prepare an aqueous sodium acrylate solution. The aqueous solution is added dropwise to the n-hexane solution while stirring at 250 rpm. Polymerize at 60°C for 3 hours with stirring. After polymerization, it is filtered and dried under reduced pressure at 80°C for 10 hours. The water absorption rate of the obtained hydrogel was 550 g/g. The average particle size is
It was 300μ. Examples 2 to 6 Hydrogels were prepared in the same manner as in Example 1 by changing the type and amount of the carboxyl group-containing copolymer, the α,β-unsaturated carboxylic acid monomer or/and its alkali salt monomer, and the organic solvent. Synthesized. The results are shown in Table 1, and the obtained polymeric material had an average particle size of 260 to 320μ and exhibited excellent water absorption.

[Table] Example 8 Using a 300 ml flask, dissolve 0.5 g of ethylene-acrylic acid copolymer (acrylic acid content 20% by weight) in 150 ml of toluene, then add 20 ml of water, 15 g of acrylic acid, and 6.7 g of sodium hydroxide. Mix and further add 15 mg of potassium persulfate and 10 mg of polyethylene glycol diacrylate (molecular weight of polyethylene glycol 400) to prepare an aqueous sodium acrylate solution. Turn the aqueous solution into toluene solution
Polymerize at 70° C. for 3 hours while stirring at 250 rpm.
After polymerization, it is filtered and dried under reduced pressure at 80°C for 10 hours. The water absorption rate of the obtained hydrogel was 580 g/g.
The average particle size was 290μ. Example 9 13.5 g of liquid polybutadiene (high cis 1,4 type polybutadiene, molecular weight 1700) in a 200 ml flask
and 0.027g of iron naphthenate. Furthermore, add 1.5 g of maleic anhydride and heat to 190°C while flowing nitrogen gas.
By raising the temperature to 100% and reacting for 4 hours with stirring, maleic anhydride-modified liquid polybutadiene is obtained. Add 2-hydroxyethyl methacrylate to 10 g of the maleic anhydride-modified liquid polybutadiene obtained here.
Add 1.99g of hydroquinone monomethyl ether, further add 0.012g of hydroquinone monomethyl ether, 5.64g of toluene, and 0.154g of triethylamine and react at 75°C to 80°C for 3 hours to form 2 of maleic anhydride-modified liquid polybutadiene.
-A half-ester compound with hydroxyethyl methacrylate is obtained. Using a 300 ml flask, 0.5 g of this half-ester compound was dissolved in 150 ml of toluene. Next, 20 ml of water, 15 g of acrylic acid, and 6.7 g of sodium hydroxide are mixed, and 15 mg of potassium persulfate and 3 mg of N,N'-methylene-bis-(acrylamide) are added to prepare an aqueous sodium acrylate solution. Turn the aqueous solution into toluene solution
Add dropwise while stirring at 250 rpm. while stirring
Polymerize at 70°C for 3 hours. After polymerization, filter at 80℃
Dry under reduced pressure for 10 hours. The water absorption rate of the obtained hydrogel was 460 g/g. The average particle size was 170μ. Example 10 Ethylene-vinyl acetate copolymer (vinyl acetate content 40% by weight, MI60) using a 300 ml flask
maleic anhydride modified product (maleic anhydride content
Dissolve 1 g of 2.5% by weight in 120 ml of toluene, then add 20 ml of water, 15 g of acrylic acid, and sodium hydroxide.
Mix 6.7g of the solution, and further add 15mg of potassium persulfate and 6mg of propylene glycol diacrylate to prepare an aqueous sodium acrylate solution. The aqueous solution is polymerized in toluene solution at 60° C. for 3 hours while stirring at 300 rpm. After polymerization, it is filtered and dried at 80°C under reduced pressure for 10 hours. The water absorption rate of the obtained hydrogel was 410 g/g. The average particle size was 240μ. Comparative Example 1 Using a 300 ml flask, 0.9 g of sorbitan monostearate is dissolved in 100 ml of n-hexane.
Next, mix 20 ml of water, 15 g of acrylic acid, and 6.7 g of sodium hydroxide, and then add 15 mg of potassium persulfate and N,N'-methylene-bis-(acrylamide).
Add 3 mg to prepare an aqueous sodium acrylate solution. The aqueous solution is added dropwise to the hexane solution while stirring at 250 rpm. Polymerize at 60°C for 3 hours with stirring. After polymerization, it is filtered and dried under reduced pressure at 80°C for 10 hours. Water absorption rate of the obtained hydrogel: 420g/g
However, the average particle size was 45μ, which was small. Example 11 Hydrogel obtained in Example 1 on 500 g of Masago soil
Eggplant seedlings were planted in soil well mixed with 1 g of hydrogel obtained in Comparative Example 1 or in soil without the addition of hydrogel, and watered with 200 c.c. once every 3 days. Seedlings were raised for a week. In the soil without the addition of hydrogel, the plants wither and die, and in the soil to which the hydrogel obtained in Comparative Example 1 is added, they become root-bound.
It grew smoothly in the soil to which the hydrogel obtained in Example 1 was added. Example 12 22 g of EPDM (Espren, 501A manufactured by Sumitomo Chemical Co., Ltd.) and 270 g of hexane in a 300 ml flask.
After heating and dissolving, add 4g of methacrylic acid,
Add 4g of butyl methacrylate and 0.3g of azobisisobutyronitrile, replace with nitrogen, and stir for 60 minutes.
The reaction was carried out at ℃ for 7 hours. In a 500 ml flask, 14 g of this graft polymer hexane solution was dissolved in 200 ml of n-hexane. Next, 27 ml of water, 20 g of acrylic acid, and 9 g of sodium hydroxide are mixed, and 20 mg of potassium persulfate and 4 mg of N,N'-methylenebisacrylamide are added to prepare an aqueous sodium acrylate solution. The aqueous solution was added to the n-hexane solution while stirring at 450 rpm, and polymerization was carried out at 60° C. for 3 hours while stirring. After polymerization, it is filtered and dried under reduced pressure at 80°C for 10 hours. The water absorption rate of the obtained hydrogel was 520 g/g. The average particle size was 700μ. Example 13 In the same manner as in Example 12, 15 g of EPDM (manufactured by Sumitomo Chemical Co., Ltd., Espren 501A) was dissolved in 270 g of hexane, and 6 g of methacrylic acid, 9 g of hydroxyethyl methacrylate, and 0.03 g of dicumyl peroxide were dissolved.
was added, and the mixture was reacted at 60°C for 7 hours with stirring. In a 500 ml flask, 8 g of this graft polymer hexane solution was dissolved in 200 ml of n-hexane. Next, the same sodium acrylate aqueous solution as in Example 12 was added, stirred at 500 rpm, and polymerized at 60°C for 3 hours. After polymerization, it is filtered and dried under reduced pressure at 80°C for 10 hours. The water absorption rate of the obtained hydrogel is 550g/
It was hot at g. The average particle size was 320μ. Example 14 Similar to Example 12, 20 g of EPDM (manufactured by Sumitomo Chemical Co., Ltd., Espren 505) was dissolved in 270 g of hexane, and 4 g of methacrylic acid and ethyl methacrylate were added.
Add 6g and 0.10g of t-butyloxylaurate,
The reaction was carried out at 60°C for 7 hours while stirring. Add 20g of this graft polymer hexane solution to a 500ml flask.
It was dissolved in 200ml. Next, the same aqueous sodium acrylate solution as in Example 12 was added, stirred at 500 rpm, and polymerized at 60°C for 3 hours. The water absorption rate of the hydrogel obtained by filtration and drying was 490 g/g. The average particle size was 280μ. Example 15 200ml with cooling tube, thermometer and stirrer connected
A three-necked flask was charged with 40 g of liquid polybutadiene (Sumika Oil #150 manufactured by Sumitomo Chemical Co., Ltd.), 5 g of butyl methacrylate, 5 g of methacrylic acid, 0.5 g of benzoyl peroxide, and 50 g of n-hexane, and heated under nitrogen while stirring. , react at 68°C for 4 hours. The resulting translucent liquid has a solid content concentration
It was 51%. 500ml with cooling tube, thermometer and stirrer connected
A three-necked flask is charged with 170 g of n-hexane and 1 g of the above graft polymer hexane solution. Additionally, 28 g of acrylic acid, 49 g of 25.3% by weight aqueous sodium hydroxide solution, 0.018 g of potassium persulfate, and N,
Prepared with 0.004g of N-methylenebisacrylamide.
The mixture was heated under nitrogen while stirring at 500 rpm, and reacted at 62° C. for 4 hours. After passing through a 350 mesh wire mesh, it was dried under reduced pressure at 60°C. The obtained hydrogel had an average particle size of 180μ and a water absorption amount of 550g/g. Example 16 In a 500 ml flask, 22 g of EPDM (Esplen 501A manufactured by Sumitomo Chemical Co., Ltd.) was dissolved in 270 g of cyclohexane, and 4 g of methacrylic acid, 6 g of ethyl methacrylate, and 1.0 g of azobisisobutylnitrile were added.
was added, and after purging with nitrogen, the mixture was reacted at 75°C for 7 hours with stirring. 27 g of the cyclohexane solution of the above graft polymer and cyclohexane 2 were added to the flask No. 5 and stirred to completely dissolve. Meanwhile, after mixing 270ml of water, 200g of acrylic acid and 90g of sodium hydroxide, 150mg of potassium persulfate
and 30 mg of N,N'-methylenebisacrylamide were added to prepare an aqueous sodium acrylate solution.
This sodium acrylate aqueous solution was added dropwise into the flask in step 5 above while stirring at 200 rpm, and heated to 70°C.
Polymerization was carried out for 3 hours. After polymerization, the polymerization reaction product was centrifuged at room temperature to separate the hydrogel. The average particle size of the obtained hydrogel was 210μ, and the water absorption rate was 600g/g.

Claims (1)

[Claims] 1 α,β monounsaturated carboxylic acid monomer or/
A carboxyl group-containing polymer having an affinity for organic solvents is used as a dispersant in a method for producing a polymer material in which alkali metal salts thereof are subjected to water-in-oil reverse phase suspension polymerization in the presence of a crosslinking agent. A method for producing a granular polymeric material with excellent water absorption, characterized by using. 2. The manufacturing method according to claim 1, wherein the organic solvent is n-hexane, n-heptane, cyclohexane, benzene, xylene, or toluene. 3 The carboxyl group-containing polymer is methacrylic acid-
Methyl methacrylate-2-ethylhexyl acrylate copolymer; reaction product of maleic anhydride-modified liquid polybutadiene and 2-hydroxyethyl methacrylate; polybutadiene-butyl methacrylate-methacrylic acid graft copolymer; and α,
A patent for a carboxyl group-containing polymer selected from the group consisting of ethylene-propylene-diene monomer copolymers obtained by graft polymerization of alkyl esters or hydroxyalkyl esters of β-unsaturated carboxylic acids and α,β-unsaturated carboxylic acids. The manufacturing method according to claim 1. 4. The manufacturing method according to claim 1, wherein the α,β-unsaturated carboxylic acid monomer is acrylic acid or methacrylic acid. 5. The manufacturing method according to claim 1, wherein the average particle size is from 100μ to 3000μ.