JPS5937003B2 - Manufacturing method of water absorbent resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to starch-based water absorbent resin compositions.

Conventionally, non-woven fabrics, paper, pulp, sponge-like urethane resin, sponge, etc. have been used as water-absorbing materials in sanitary products, diapers, disposable kitchen towels, etc. However, these materials have low water-absorbing ability and are not suitable for the above applications. It wasn't completely satisfying.

In recent years, cross-linked polyethylene oxide, cross-linked poval, starch-polyacrylonitrile graft polymer hydrolysates, etc. have begun to appear as alternatives to these materials.
Although these have a relatively high water absorption capacity, they are not completely satisfactory; they are expensive due to difficult manufacturing methods; and some of them are not biodegradable, so there are problems with disposal. It has drawbacks such as: The object of the present invention is to improve these drawbacks, that is, to provide a method for producing a water-absorbing resin that is relatively easy to produce and has a high water-absorbing capacity.

From this point of view, the present inventors have conducted extensive research and have found that by adding a small amount of crosslinking agent when polymerizing starch and a certain type of monomer, a resin that is made water insoluble and has a high water absorption capacity can be created. It was discovered that the obtained resin is biodegradable, and the present invention was achieved. That is, the present invention provides starch, at least one monomer that is water-soluble or becomes water-soluble by hydrolysis and has an addition-polymerizable double bond, and a crosslinking agent (with O as an essential component, water, methanol, ethanol, etc.). , acetone, N3N-dimethylformamide, dimethyl sulfoxide and mixtures thereof, and hydrolysis is carried out if necessary.

The starch used in the present invention may be of any type, such as raw starch such as sweet potato starch, potato starch, wheat starch, corn starch, rice starch, tabioca starch, oxidized starch, dialdehyde starch, alkyl etherified starch, Examples include modified starches such as oxyalkylated starch, aminoethyl etherified starch, and cyanoethyl etherified starch.

The water-soluble monomers having an addition-polymerizable double bond used in the present invention include monomers having a carboxyl group such as (meth)acrylic acid and maleic anhydride: (meth)
Monomers with carboxyl groups in the form of salts such as sodium acrylate, trimethylamine (meth)acrylate, triethanolamine (meth)acrylate, sodium maleate, methylamine maleate: vinylsulfonic acid Monomers with sulfonic acid groups such as vinyltoluenesulfone, sulfopropyl (meth)acrylate, nivinylsulfonic acid sodium salt, vinylsulfonic acid methylamine salt, sulfopropyl sodium (meth)acrylate, (meth)acrylate Monomers having sulfonate salts such as acrylic acid sulfopropyl diethanolamine salt;
Monomers with hydroxyl groups such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate:
Monomers with ether groups such as (meth)acrylic acid ethylene glycol monomethyl ether and (meth)acrylic acid trioxyethylene glycol: (meth)acrylic acid dimethylaminoethyl and (meth)acrylic acid diethylaminoethyl etc. Monomer having:N-N-
Monomers having an amide group such as di-n-propylacrylamide, N-hexylacrylamide, (meth)acrylamide, N-vinylpyrrolidone, N-methylolated acrylamide, N-methylacrylamide, N-N-dimethylacrylamide: N-N -N-trimethyl-N-
Examples include monomers having a quaternary ammonium base such as (meth)acryloyloxyethylammonium chloride and N-N-N-triethyl-N-(meth)acryloyloxyethylammonium chloride.

In addition, examples of monomers that become water-soluble upon hydrolysis in the present invention include monomers having an ester bond such as methyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)atalylate, and vinyl acetate. body:(
Monomers having a nitrile group such as meth)acrylonitrile; and monomers having an amide group as described above. Among these water-soluble monomers having an addition-polymerizable double bond or monomers that become water-soluble by hydrolysis in the present invention, an easy method for producing a water-absorbing resin, which is one of the objects of the present invention, is preferred. From the viewpoint of providing the desired properties, water-soluble monomers having addition-polymerizable double bonds that do not require hydrolysis after polymerization are preferred.

Furthermore, from the viewpoint of providing a method for producing a water-absorbing resin having a high water-absorbing capacity, which is another object of the present invention, preferably a monomer having a carboxyl group such as (meth)acrylic acid or maleic anhydride; ) sodium acrylate,
Monomers having carboxylic acid groups such as (meth)acrylic acid trimethylamine salt and (meth)acrylic acid tritanolamine salt; N-N-N-trimethyl-N-(meth)acryloyloxyethylammonium chloride, N- N
It is a monomer having a quaternary ammonium base such as -N-triethyl-N-(meth)acryloyloxyethylammonium chloride. More preferably, a method of using a monomer having a carboxyl group and neutralizing it with an alkali after polymerization is convenient for obtaining a water-absorbing resin having a high water-absorbing ability. The crosslinking agent used in the present invention may be any agent as long as it can crosslink the reaction product between the prisoner and F3), such as ethylene glycol, trimethylolpropane, glycerin,
Di- or tri-(meth)acrylic acid esters of polyols such as polyoxyethylene glycol and polyoxypropylene glycol: Unsaturated polyesters obtained by reacting the above polyols with unsaturated acids such as maleic acid: Bisacrylamides such as N-N-methylene-bisacrylamide: Di- or tri-(meth)acrylic acid esters obtained by reacting polyepoxide with (meth)acrylic acid: Tolylene diisocyanate, hexamethylene diisocyanate, etc. Di-(meth)acrylic acid carbamyl esters obtained by reacting polyisocyanate with hydroxyethyl (meth)acrylate: Examples include allylated starch and allylated cellulose, but in some cases methylolated ( Difunctional compounds such as meth)acrylamide, glyoxal, phthalic acid, adipic acid, ethylene glycol, etc., which are formed by crosslinking the reaction product with meth)acrylamide, glyoxal, phthalic acid, adipic acid, and ethylene glycol, can also be used.

In the present invention, compounds other than those mentioned above that can react with CA), (B, (0), such as monomers such as styrene, ethylene, propylene, and butene, can also be used.

The polymerization method of CA), (B), and (0 in the present invention may be any method using a conventionally known polymerization solvent, such as a method of irradiating with radiation, an electron beam, an ultraviolet ray, etc., or a method of irradiating with ceric salt. Examples include methods of polymerization using radical polymerization catalysts such as hydrogen peroxide, benzoyl peroxide, azobisisobutyronic acid, ammonium persulfate, and the like.

Among these, methods using radiation or electron beam irradiation, polymerization methods using ceric salt catalysts or hydrogen peroxide catalysts are used to improve the graft polymerization rate between (4) and (B). However, it is more preferable from the viewpoint of providing a method for producing a water-absorbing resin having a high water-absorbing capacity, which is one of the objects of the present invention. CA used in the present invention)
, (B) and (0) are not particularly limited, but the polymerization ratio of (B) to (0 is CA) 100 to (T3 is 10 to 1000, (C) is 0. 0001~
A range of 10 is preferred.

In the polymerization in the present invention, as a polymerization solvent, dihydrate,
Methanol, ethanol, acetone, N,N-dimethylformamide, dimethylsulfoxide and mixtures thereof are used. Further, in the present invention, the temperature when polymerizing using a catalyst varies depending on the type of catalyst used, but is usually 10 to >150°C, preferably 20 to 100°C.
It is ℃. The hydrolysis carried out if necessary in the present invention may be carried out by any conventionally known method, but it is usually carried out in an aqueous solvent or in a mixed solvent of water and alcohol, such as sodium hydroxide, potassium hydroxide, etc. How to use 1
It is carried out at a temperature of 0 to 150°C. If free carboxyl groups, sulfonic acid groups, etc. are present in the resulting resin, they can be neutralized and converted into salts by conventionally known methods. (Alkali metal salts, ammonium salts, amine salts, etc.)
3 In the present invention, the reaction product can then be dried and pulverized to form a product, but if necessary, it may be washed with a mixed solvent of water and alcohol, then dried and pulverized to form a product. Alternatively, the reaction product may be diluted with water, or dried and pulverized and then dispersed in water 4 to form a product. The water-absorbing resin obtained by the present invention may be used in any manner, such as by mixing it as a powder with pulp, soil, plastic, etc., or by dispersing it in water and making it into bulbs, cloth, paper, wood, stone, etc. A method of spraying on a substrate such as concrete, or a method in which the substrate such as pulp, cloth, paper, wood, stone, concrete, etc. is immersed in an aqueous dispersion or solution of the powder, and then the substrate is dried, or the substrate is immersed and kneaded. There are methods for post-drying.

In some cases, bulbs, cotton, agricultural chemicals, fragrances, soil, etc. are mixed with the above CA), (B) and (0) and then polymerized, or if necessary, hydrolyzed and dried to be used as a product. The water-absorbing resin obtained by the present invention has a wide variety of uses.For example, when used in disposable diapers, sanitary products, gauze, paper towels, etc., products with excellent liquid absorption ability can be obtained, and when mixed with soil, it can be used to absorb soil. In addition, when used in interior construction materials, a product with a dew condensation prevention effect can be obtained, and by impregnating pesticides, fertilizers, fragrances, etc. into this water-absorbing resin composition, these effects can be further enhanced. It can last for a long time.

The water absorbent resin composition obtained by the production method of the present invention has various characteristics.

For example, it shows excellent absorption ability not only for water but also salt solutions, urine, blood, etc., and even though it shows excellent water absorption, its ability to absorb moisture in the air is extremely low when dry. It can be stored in the atmosphere for a long time, it is relatively inexpensive because the manufacturing method is easy, it has excellent biodegradability because it uses starch as an essential ingredient, and it is easy to dispose of. Even when starch is used as a part of the resin, the water-absorbing resin obtained by the production method of the present invention has resistance to enzymes such as amylase. In particular, the properties of biodegradability and resistance to enzymes make it ideal for use in disposable diapers, sanitary products, and the like. The water-absorbing resin obtained by the production method of the present invention may contain fillers, pigments, ultraviolet absorbers, antioxidants, fungicides, fungicides, insecticides, herbicides, fertilizers, fragrances, deodorants, etc. May be mixed.

The present invention will be explained below with reference to Examples.

In addition, the number of parts in the examples is parts by weight. Example 1 70 parts corn starch, 200 parts water and 120 parts
0 parts of methanol was placed in a reaction vessel equipped with a stirring bar, a nitrogen blowing tube, and a thermometer, and stirred at 55°C for 1 hour under a nitrogen stream, then cooled to 30°C, and 120 parts of acrylamide,
50 parts of ceric ammonium nitrate solution (1/10 mole cerium ion in 1N nitric acid), and 0.1
3 parts of methylene bisacrylamide was added and the solution was heated at 35°C.
When the mixture was stirred for a period of time and polymerized, the reaction solution turned into a somewhat viscous white sapon suspension.

Thereafter, this reaction solution was filtered, and the resulting powder was washed with a mixed solution of water and methanol (weight ratio of water to methanol: 2:10), dried under reduced pressure at 60°C for 3 hours, and then ground to obtain 176 parts of a powdered product. I got it. Example 2 30 parts of wheat starch, 200 parts of water, and 600 parts of ethanol were placed in a reaction vessel equipped with a stirring bar, nitrogen blowing tube, and thermometer, and stirred at 60°C under a nitrogen stream for 15 hours, then heated to 30°C. 100 parts of hydroxylethyl methacrylate, 50 parts of ceric ammonium nitrate solution (1/10 mole cerium ion in 1N nitric acid) and 0.1 part of methylene bisacrylamide were added,
When the mixture was stirred at 5° C. for 3 hours to polymerize, it became a suspension of pale yellow fine particles.

Thereafter, this reaction solution was filtered, and the resulting pale yellow fine particles were added to a water-methanol mixed solution (water to methanol weight ratio 2:10).
), dried under reduced pressure at 600C for 5 hours, and crushed to obtain 78 parts of a powdered product.

Example 3 50 parts corn starch, 200 parts water and 100 parts
0 parts of methanol was placed in a reaction vessel equipped with a stirring bar, nitrogen blowing tube, and thermometer, stirred for 5 hours under a nitrogen stream, cooled to 30°C, and mixed with 20 parts of acrylic acid and 80 parts of sodium acrylate. , 1 part of N-N-methylenebisacrylamide, and 0.5 part of azobisvaleric acid as a polymerization catalyst were added and polymerized by stirring at 60°C for 6 hours to obtain a white sapon suspension [1]. It was done.

Thereafter, this white sapon suspension [1] was filtered and the resulting powder was added to a water-methanol mixed solution (water to methanol weight ratio 2:1).
After washing with 0) and drying under reduced pressure for 3 hours at 6'C, the product was crushed to obtain 49 parts of a powdered product. Example 4 50 parts corn starch, 200 parts water and 100 parts
0 parts of methanol was placed in a reaction vessel equipped with a stirring bar, nitrogen blowing tube, and thermometer, stirred at 55°C for 1 hour under a nitrogen stream, cooled to 30°C, and mixed with 20 parts of acrylic acid and 80 parts of acrylic acid. 40 parts of sodium ceric ammonium nitrate solution (1/10 mol cerium ion in 1N nitric acid) and 1 part of N,N-methylenebisacrylamide were added and stirred at 40°C for 3 hours to polymerize, resulting in a white scum. It turned into liquid.

After that, the powder obtained by filtering this sap suspension was washed with a water-methanol mixed solution (water to methanol ratio 2:10),
After drying under reduced pressure for 3 hours, the product was crushed to obtain 138 parts of a powdered product.

Example 5 (Reference product outside the scope of the present invention) 50 parts of a fluff valve (cellulose), 300 parts of water, and 900 parts of methanol were mixed with a stirring bar, a nitrogen blowing pipe,
Pour into a reaction vessel equipped with a thermometer and heat for 55 minutes under a nitrogen stream.
After stirring at ℃ for 1 hour, cool to 30℃ and add 30 parts of acrylic acid,
Add 70 parts of sodium acrylate, 40 parts of ceric ammonium nitrate solution (1/10 mole cerium ion in 1N nitric acid) and 0.5 part of N,N-methylenebisacrylamide and stir for 45.C3 hours. When the mixture was polymerized, it became a white sapon suspension.

Thereafter, the powder obtained by filtering this reaction solution was washed with a water-methanol mixed solution (water to methanol weight ratio 2:10), dried under reduced pressure at 60°C for 3 hours, and then ground to obtain 135 parts of a powdered product. I got it. Example 6 (Reference product outside the scope of the present invention) 70 parts of fluff pulp, 300 parts of water, and 900 parts of methanol were placed in a reaction vessel equipped with a stirring bar, a nitrogen blowing tube, and a thermometer, and heated under a nitrogen stream. After stirring for 1 hour at 50℃ 3
Cooled to 0°C, added 86 parts of methyl methacrylate, asobisvaleryl acid as a polymerization catalyst, and 0.5 parts of trioxyethyl glycol dimethacrylic acid, and heated to 65°C.
When the mixture was stirred for a period of time and polymerized, it became a white sapon suspension.

Thereafter, 40 parts of sodium hydroxide dissolved in 100 parts of water was charged and hydrolyzed at 90°C for 3 hours.

Thereafter, this reaction solution was filtered, and the resulting powder was dried under reduced pressure at 60° C. for 3 hours and then ground to obtain 170 parts of a powdered product.

Example 7 70 parts of potato starch, 200 parts of water and 1200 parts
of methanol and 60 parts of acrylamide were charged into a reaction vessel equipped with a stirring bar, a nitrogen blowing tube, and a thermometer, and stirred at 55°C for 1 hour under a nitrogen stream, cooled to 30°C, and mixed with 60 parts of acrylamide and
parts of ethyl acrylate, 1.2 parts of ammonium persulfate, 0.1 part of sodium bisulfite, and 0.2 parts of N-
N-methylenebisacrylamide was added and polymerized by stirring at 30°C for 5 hours, resulting in a white sapon suspension.

After cooling, 105 parts of 30% aqueous sodium hydroxide solution was added to the reaction solution, and the mixture was stirred at room temperature for 2 hours. Thereafter, the reaction solution was filtered, and the resulting powder was washed with a mixed solution of water and methanol (weight ratio of water to methanol 2:10), dried under reduced pressure at 60°C for 3 hours, and then ground to obtain 195 parts of a powdered product. Ta. Example 8 50 parts corn starch and 300 parts water and 100 parts
0 parts of methanol was placed in a reaction vessel equipped with a stirring rod, nitrogen blowing tube, and thermometer, stirred at 50°C for 1 hour under a nitrogen stream, cooled to 30°C, and 60 parts of N,N,N-trimethyl-N-acrylate was added. royloxyethylammonium chloride, 0.2 parts of N,N-methylenebisacrylamide, and 0.2 parts of 30% hydrogen peroxide as a polymerization catalyst, 0.2 parts of 30% aqueous hydrogen peroxide,
When 1 part of L-niascorbic acid was added and polymerized at 45°C for 3 hours, a white sulfur suspension was obtained.

Thereafter, the powder obtained by filtering this reaction solution was washed with a mixed solution of water and methanol (weight ratio of water to methanol 2:10), dried under reduced pressure at 60°C for 3 hours, and then ground. Got the product.

Example 9 137 parts of corn starch and 600 parts of water were placed in a reaction vessel equipped with a stirring rod, a nitrogen blowing tube, and a thermometer, and stirred for 30 minutes at 55°C under a nitrogen stream.
℃, 140 parts of acrylic acid, 60 parts of acrylamide, 1 part of ethylene glycol dimethacrylate, and 0.2 parts of 30% hydrogen peroxide solution and 0.1 part of L-ascorbic as polymerization catalysts. Add acid, 354
When polymerized by stirring at ℃ for 3 hours, the reaction solution became an elastic white solid.

The obtained white solid was dried under reduced pressure at 60° C. for 5 hours and then ground to obtain 312 parts of white powder. This white powder 100
1 part was placed in a beaker, and 400 parts of a mixed solution of 5% NaOH in water and methanol (weight ratio of water to methanol 2:8) was added, and after being left at about 20°C for 1 hour, it was dried under reduced pressure at 60°C for 3 hours. , to obtain 118 parts of white powder. Example 10 137 parts of rice starch and 600 parts of water were mixed with a stirring bar,
The mixture was charged into a reaction vessel equipped with a nitrogen blowing tube and a thermometer, stirred at 55°C for 3 hours, cooled to 30°C, and mixed with 200 parts of acrylic acid, 1 part of triacrylic acid glyceride, and 0.2 parts as a polymerization catalyst. 30% hydrogen peroxide solution, 0.1
After adding 50% of L-ascorbic acid, the mixture was stirred at 35° C. for 3 hours to polymerize, and the reaction solution turned into an elastic white solid.

To this white solid was added 200 parts of a 30% NaOH aqueous solution, left overnight at 25°C, dried under reduced pressure at 60°C for 5 hours, and then crushed to obtain 361 parts of white powder. Example 11 30 parts of flat pulp was immersed in 100 parts of the white sapon suspension [A] obtained in Example 3 for 5 minutes, taken out, and dried under reduced pressure at 60°C for 3 hours to obtain 40 parts of a product. .

Example 12 Water of each product obtained in Examples 1 to 11,
The absorption capacity of liquids such as saline and urine was measured, and the results are shown in the table.

To measure the liquid absorption capacity, put 19 of each of the products obtained in Examples 1 to 11 into a beaker, add 500 ml of each of the liquids to be measured, and prepare a dispersion of each product.
The dispersion was applied onto 100 meshes of blue, the amount of liquid flowing out was measured, and the difference from 500 ml was calculated to determine the amount of liquid absorbed. As a comparative example, the liquid absorption capacity of flat pulp is also shown.

Claims (1)

[Claims] 1 Starch (A), at least one type of monomer that is water-soluble or becomes water-soluble by hydrolysis (B) having an addition-polymerizable double bond, and a crosslinking agent (C) as essential components, water, methanol, A method for producing a water-absorbing resin, which comprises polymerizing in the presence of a solvent selected from ethanol, acetone, N,N-dimethylformamide, dimethyl sulfoxide, and mixtures thereof, and carrying out hydrolysis if necessary.