JPS626562B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polymeric material with excellent water absorption. More specifically, when using an aliphatic cyclic acid anhydride for a polyvinyl alcohol polymer with a degree of polymerization greater than 500, the reaction temperature should be 70°C or higher and 110°C.
℃ or less, reaction time is 30 minutes or more and 10 hours or less, and if aromatic cyclic acid anhydride is used, the reaction temperature is
Cyclic acid anhydride is reacted at 100°C or higher and 200°C or higher for a reaction time of 30 minutes or more and 10 hours or less, and then monovalent metal hydroxides, alkoxides, various salts, ammonia, ammonium salts, amines, and amines. The present invention relates to a method for producing a water-insoluble polymer material with excellent water absorption, which is obtained by treatment with at least one compound selected from the group consisting of salts, and has a water absorption rate of 50 to 500 times. (Here, the water absorption rate is determined by adding water to 1 g of sample and determining with the naked eye the maximum amount of water added (g) in which no free water is present.) In recent years, hydrophilic polymer materials have been used in medical treatments. As its use in industry, food industry, and agricultural fields progresses,
In particular, water-insoluble and hydrophilic or water-absorbing polymeric materials are used for separation and purification materials such as various membranes and liquid chromatographic carriers, media for microorganisms and plants, and medical materials such as contact lenses and suture coverings.
In addition, it has come to be used for various purposes that utilize its water absorption and water retention properties. Among these uses,
In particular, polymeric materials used in application fields that utilize water absorption properties are desired to have the ability to absorb as much water as possible in a short period of time when they come into contact with water. So far, natural and synthetic polymer materials such as modified polyethylene oxide, crosslinked polypynylpyrrolidone and sulfonated polystyrene, and saponified starch-acrylonitrile graft copolymers have been used as polymeric materials. Several materials have been proposed. However, except for saponified starch-acrylonitrile copolymers, their water absorption capacity is low and they are not satisfactory as water-absorbing materials. In addition, even in the case of saponified starch-acrylonitrile graft copolymers, which have a water absorption capacity of 30 times or more than their own weight, although various improvements have been made to the manufacturing methods, the process is relatively complicated. However, if it is used in a hydrated state for a long period of time, there are several practical problems, such as the possibility that the starch component will rot and the gel structure will be destroyed. The purpose of the present invention is to have a large water absorption capacity,
The purpose of the present inventor is to provide a method for producing a polymeric material with a low possibility of spoilage, and as a result of various studies in order to develop a water-absorbing polymeric material that does not have the above-mentioned drawbacks, When using an aliphatic cyclic acid anhydride for a polyvinyl alcohol polymer, the reaction temperature should be 70°C or higher and 110°C or lower, the reaction time should be 30 minutes or more and 10 hours or less, and aromatic cyclic acid anhydride should be used. When used, the cyclic acid anhydride is reacted at a reaction temperature of 100°C or more and 200°C or less and a reaction time of 30 minutes or more and 10 hours or less, and then monovalent metal hydroxides, alkoxides, various salts, ammonia, and ammonium. A water-insoluble polymeric material with excellent water absorption and a water absorption rate of 50 to 500 times, obtained by treatment with at least one compound selected from the group consisting of salts, amines, and amine salts. The present inventors have discovered that the manufacturing method satisfies the object of the present invention, and have completed the present invention. The polyvinyl alcohol polymer used as a raw material in the present invention may only have a saponification degree of 50 to 100 mol% obtained by saponifying vinyl acetate, other various vinyl ester polymers, and copolymers thereof. 30 mol% or less of various unsaturated monomers based on vinyl acetate and other various vinyl esters, such as α-olefins, vinyl chloride,
Also included are copolymers of acrylonitrile, acrylamide, acrylic esters, and methacrylic esters with a degree of saponification of 50 to 100 mol%. The polyvinyl alcohol polymer to be subjected to the reaction is preferably in the form of a powder, and the degree of polymerization is preferably greater than 500. Examples of the aliphatic cyclic acid anhydride used in the reaction include maleic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Examples of the aromatic cyclic acid anhydride used in the reaction include phthalic anhydride and trimellitic anhydride. The reaction is carried out in the absence of water as much as possible, but compounds with active hydrogen that are reactive with cyclic acid anhydrides are unsuitable as solvents for the reaction, and compounds without active hydrogen, For example, benzene, toluene, hexane, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, etc. are used, and toluene, dioxane, etc. are particularly preferred. When maleic anhydride is used as the cyclic acid anhydride, since this compound has a low melting point, it can also function as a solvent. The reaction involves dissolving a predetermined amount of a cyclic acid anhydride in a predetermined amount of a solvent, adding a predetermined amount of a polyvinyl alcohol polymer with a degree of polymerization of more than 500, and stirring and dispersing it.
Reaction temperature when using aliphatic cyclic acid anhydride
70°C or higher and 110°C or lower, reaction time 30 minutes or more and 10 hours or less, and when using an aromatic cyclic acid anhydride, reaction temperature 100°C or higher and 200°C or lower, reaction time.
React for 30 minutes or more and 10 hours or less. Regarding the reaction time, 1 to 5 hours is more preferable in any case. Since the reaction proceeds in a heterogeneous system, it is carried out with sufficient stirring so that the polyvinyl alcohol polymer is uniformly esterified. The esterification reaction may proceed satisfactorily even without a catalyst, but in general, monovalent metal hydroxides, alkoxides, carbonates, bicarbonates, or tertiary amines are combined with polyvinyl alcohol as catalysts to promote the reaction. It can be used in an amount of several percent or less based on the polymer. The amount of cyclic acid anhydride used is greater than the theoretical amount necessary to achieve the desired degree of esterification. The degree of esterification can be from 1 to 100 mol%, but for the purpose of the present invention, a degree of 5 to 50 mol% is suitable;
The amount of solvent used is preferably 2 to 5 times the amount of the polyvinyl alcohol polymer powder. For the purpose of the present invention, it is important that the entire powder particle has a lightly crosslinked network structure, and for this purpose it is appropriate to introduce about one crosslinking bond per polymer. The reaction conditions are controlled so that a certain degree of crosslinking is introduced. More specifically, the formation of crosslinks is significantly influenced by the degree of polymerization of the polyvinyl alcohol polymer used as the base, molecular weight distribution, reaction temperature, reaction time, type of cyclic acid anhydride used, size of polymer particles, etc. Ru. As already mentioned, when aliphatic cyclic acid anhydrides such as maleic anhydride and succinic anhydride are used as the cyclic acid anhydride, diester crosslinks are relatively formed, which is thought to be due to the high acidity of the carboxyl group. 30 at temperatures above 70℃ and below 110℃
If the reaction is carried out for more than a minute and less than 10 hours, a modified polyvinyl alcohol-based polymer with an appropriate amount of crosslinking and excellent water absorption performance can be obtained. On the other hand, when aromatic cyclic acid anhydrides such as phthalic anhydride and trimellitic anhydride are used, diester crosslinking is relatively difficult to form, probably due to the low acidity of the carboxyl group and steric hindrance. By carrying out the reaction at a temperature of 100° C. or higher and 200° C. or lower for 30 minutes or more and 10 hours or less, a water-absorbing modified polyvinyl alcohol polymer having an appropriate amount of crosslinking introduced therein can be obtained. Furthermore, the degree of polymerization of the polyvinyl alcohol polymer used as the base has a large influence, and if the degree of polymerization is less than 500, it is quite difficult to introduce crosslinking. Generally speaking, the higher the degree of polymerization used as the base polyvinyl alcohol polymer, the lower the crosslinking density, which makes the entire polymer insolubilized, resulting in a modified polyvinyl alcohol polymer with better water absorption performance. be able to. When the polyvinyl alcohol polymer has a wide molecular weight distribution and contains many low molecular weight fractions, only the fractions with a high degree of polymerization participate in crosslinking, and the low molecular weight fractions remain uncrosslinked and are eluted from the particles when water is absorbed. Therefore, it is not desirable. Furthermore, if the particle size is too large, it is not only difficult for the cyclic acid anhydride to react uniformly to the inside, but also it is difficult to uniformly generate crosslinks throughout the particle and make the entire particle insoluble. Therefore, it is preferable to use particles with a particle size that can pass through a 20-mesh sieve. The solid portion of the reaction mixture is separated by a method such as filtration or centrifugation, and the liquid is collected and reused. The solid part is washed with methanol, acetone, etc., and then washed with monovalent metal hydroxides, alkoxides, salts, etc.
After treatment with ammonia, ammonium salts, amines, amine salts, etc., free carboxyl groups are converted to carboxyl base salts, followed by washing and drying to obtain a powdered modified polyvinyl alcohol polymer with high water absorption. . Alternatively, powders of sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, and the like may be mixed with the modified polyvinyl alcohol polymer after the reaction. The amount of these salts mixed is equal to or less than the amount of carboxyl groups in the modified polyvinyl alcohol polymer. When the mixture thus obtained comes into contact with water during use, the carboxyl groups in the polymer decompose the carbonate and bicarbonate to produce carboxyl group sodium salts, potassium salts, and ammonium salts. can achieve the purpose. As mentioned above, the monovalent metal hydroxides include sodium hydroxide, potassium hydroxide, etc.
Examples of alkoxides include sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, etc., and examples of monovalent metal salts include sodium carbonate, sodium bicarbonate, sodium acetate, etc. Ammonium salts include ammonium carbonate, ammonium bicarbonate,
Examples of amines include ammonium chloride, ethylamine, diethylamine, triethylamine, propylamine, butylamine,
Examples include aniline and pyridine.
In addition, as amine salts, carbonates of the above amines,
Examples include bicarbonate. These are used as they are or diluted with a solvent to treat the polyvinyl alcohol polymer after the cyclic acid anhydride reaction, but it is sufficient to use the amount equivalent to the reacted acid anhydride. The modified polyvinyl alcohol polymer thus obtained has the ability to absorb 50 to 500 times its own weight of water, and is so remarkable that it reaches the above-mentioned water absorption rate in an extremely short time of about 1 to 10 minutes. Since it has a fast water absorption rate, it has extremely wide applications in each of the above-mentioned fields. Hereinafter, the present invention will be explained in further detail with reference to Examples. Example 1 In a 500 c.c. separable flask, 50 g of polyvinyl alcohol (hereinafter abbreviated as PVA, degree of polymerization 1700, degree of saponification 88 mol%) powder, maleic anhydride, dioxane 100 c.c. as a solvent, and toluene 100 c.c. Add . and 80
The reaction was carried out at ℃ for 3 hours. The reaction mixture was filtered, and the solid part was washed with acetone and filtered repeatedly, then an equivalent amount of ammonia water to maleic anhydride was added, and the mixture was reacted with the carboxyl group produced by the esterification reaction at room temperature (in an acetone solvent). . After standing for 30 minutes, it was filtered, washed with acetone, and filtered repeatedly, dried, and weighed. The modification rate (weight increase rate) was determined from the weight increase. 1 g of the obtained powder was placed in a beaker, water was added, and the water absorption rate was determined. The water absorption rate was determined by adding water and determining with the naked eye the maximum amount of water added at which no free water was present. Regarding the water absorption rate, the time taken to reach the above-mentioned water absorption rate was defined as the water absorption rate. The results are summarized in Table 1.

[Table] From the results in Table 1, extremely excellent water absorption PVA
It can be seen that a system polymer can be obtained. Control Example 1 The reaction was carried out in the same manner as in Inventive Example 1, but the water absorption rate was 20 times higher than that of the case without treatment with 25% aqueous ammonia. Control Example 2 The reaction was carried out in the same manner as in Inventive Example 2, but the water absorption rate was 30 times higher than that of the case without treatment with 25% aqueous ammonia. Example 2 Using phthalic anhydride instead of maleic anhydride,
Toluene was used as the solvent and the reaction temperature was set at 120°C.
The reaction was carried out in the same manner as in Example 1 except that the temperature was changed to .degree. The results are summarized in Table 2. It can be seen from the results in Table 2 that an extremely excellent water-absorbing PVA polymer can be obtained.

[Table] Control Example 3 The reaction was carried out under the same conditions as in Inventive Example 3, but at a reaction temperature of 80°C. Carboxyl groups were neutralized with 9.2 cc of 25% aqueous ammonia in acetone solvent. Because the reaction temperature was low, the obtained modified PVA did not form crosslinks and was soluble in water. When aliphatic maleic anhydride is used, crosslinked PVA is produced at a reaction temperature of 80°C for 3 hours as seen in Inventive Examples 1 and 2, but when aromatic phthalic anhydride is used, crosslinked PVA is produced at 80°C and 3 hours. It can be seen that crosslinking does not occur with time. Example 3 PVA (polymerization degree 1700, saponification degree 99 mol% or more)
The reaction was carried out in the same manner as in Example 2, except that powder was used and triethylamine was used as the esterification reaction promoting catalyst. The results are summarized in Table 3.

[Table] From the results in Table 3, it can be seen that an extremely excellent water-absorbing PVA polymer can be obtained. Control Example 4 A modified PVA was produced under the same conditions as in Inventive Example 7, except that PVA with a degree of polymerization of 500 was used as the raw material PVA. The obtained modified PVA did not form crosslinks because the raw material PVA had a low degree of polymerization, and was soluble in water. Control Example 5 Modified PVA was produced under the same conditions as Inventive Example 10, using succinic anhydride instead of phthalic anhydride. The obtained modified PVA had a low water absorption rate of 40 times, probably due to the high crosslinking density due to the use of aliphatic succinic anhydride. In the case of aliphatic succinic anhydride, the reaction temperature is lowered to 80℃.
You can see that it is necessary to perform a reaction before and after.

Claims (1)

[Claims] 1 When using an aliphatic cyclic acid anhydride for a polyvinyl alcohol polymer with a degree of polymerization greater than 500, the reaction temperature should be 70°C or higher and 110°C or lower, and the reaction time should be 30°C.
If an aromatic cyclic acid anhydride is used, the cyclic acid anhydride is reacted at a reaction temperature of 100°C or more and 200°C or less and a reaction time of 30 minutes or more and 10 hours or less. monovalent metal hydroxides,
A water-insoluble product with a water absorption rate of 50 to 500 obtained by treatment with at least one compound selected from the group consisting of alkoxides, various salts, ammonia, ammonium salts, amines, and amine salts.
A method for producing polymeric materials with twice as much water absorption.