JPS617316A - Water absorption high polymer material - Google Patents

Abstract

PURPOSE:The titled material useful as an agent for preventing moisture condensation or as a drug without requiring after-treatment such as hydrolysis, etc., by using an inexpensively obtainable raw material consisting of a graft copolymer of a specific acrylamide mixed monomer and an acrylamidomethylated starch. CONSTITUTION:Preferably, (B) a mixed monomer of 2-acrylamido-2-methylpropanesulfonic acid:acrylic acid = 3:1 (weight ratio) or (C) a mixed monomer of 2- acrylamido-2-methylpropanesulfonic acid:acrylamide = 1:1 (weight ratio) is grafted onto (A) acrylamideomethylated starch having about 0.02 degree of substitution by polymerization, to give the aimed material.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a water-absorbing polymeric material comprising a graft copolymer obtained by graft polymerizing a hydrophilic monomer to a starch derivative. The water-absorbing polymer material of the present invention can be effectively used as, for example, a dew-preventing agent or a medical product.

<Prior art> In general, when attempting to produce graft copolymerization or polymerization by introducing various monomers into a backbone polymer by graft polymerization, it is necessary that an active group exists in the backbone polymer as an initiation point for graft polymerization. It is. When starch is used as the backbone polymer, the graft polymerization reaction hardly progresses because such active groups are not present in the glucose units that constitute the starch.

Therefore, when modifying starch through kraft polymerization to produce a water-absorbing polymer substance, it is necessary to provide the starch with a starting point for graft polymerization, and the methods for this can be roughly divided into the following two types. This method has been used for a long time.

■ As in the case of using a cerium salt as a polymerization initiator, the hydroxyl groups of the 2- and 3-position carbon atoms of glucose are oxidized and converted into carbonyl groups to open the glucose ring and initiate graft polymerization. (1) A method in which the ether bond between glucose units is broken and graft polymerization is initiated from there, as in the case of introducing acrylonitrile into starch using a Ce catalyst.

<Problems to be solved by the invention> However, both of the above methods (■) and (■) chemically change the starch itself, which is the backbone polymer, resulting in undesirable problems such as a decrease in the molecular weight and durability of the starch. A phenomenon that does not exist occurs. Furthermore, since the starch-acrylonitrile graft copolymer obtained in step ① above contains toxic nitrile groups, it is necessary to perform post-treatment to hydrolyze this copolymer with an alkali to remove the nitrile groups. There is.

Therefore, the present invention aims to provide a water-absorbing polymer material using a starch derivative having an active group as a polymerization initiation point in the starch without chemically changing the starch itself used as a backbone polymer, and This was done for the purpose of providing a water-absorbing graft copolymer that does not require hydrolysis as a post-treatment.

<Means for solving the problems> The water-absorbing polymeric material according to the present invention is a graft copolymer of a mixed monomer of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid or acrylamide, and acrylamide methylated starch. It consists of a combination.

In this invention, by using a starch derivative in which the hydroxyl group present on the 6-position carbon atom of glucose is acrylamide methylated as the backbone polymer, a hydrophilic monomer can be directly introduced into the starch chain.

This starch derivative, ie, acrylamide methylated starch, has a chemical structure as shown in formula (1) below, and because it has an unsaturated group, it is active against heat or light, and an appropriate polymerization initiator must be used. This unsaturated group becomes the starting point for graft polymerization.It is also important that the affinity (copolymerization ratio) with the hydrophilic polymer to be introduced is good, and that the starch itself is chemically modified. Among the many starch derivatives, starch derivatives are particularly preferred for use in the present invention because they do not cause a decrease in the molecular weight or durability of the starch.

Acrylamidomethylation of starch can be easily carried out using a known dehydration condensation method, but acrylamide methylated starches having various degrees of acrylamide methyl substitution can also be obtained as commercial products. In this case, the acrylamide methyl substituent greatly influences the water absorption of the resulting graft copolymer. As a result of experiments, a graft with high water absorption was found when using acrylamide methylated starch (2 glucoses per 100 glucose molecules are acrylamide methylated) with a degree of substitution of 0.02. It has been found that copolymers can be obtained.

By graft copolymerizing the above-mentioned acrylamide methylated starch with a hydrophilic monomer, a water-absorbing polymer substance can be obtained. In this invention, as such a hydrophilic monomer, 2-acrylamide-2
- A mixed monomer system of methylpropanesulfonic acid (formula '2I below) and acrylic acid (formula (3) below) or acrylamide (formula (4) below) is used.

Cal.

CH,=CHC0NH,...(3) OH, -CHCooI-(...(4) 2-acrylamido-2-methylpropanesulfonic acid monomer having a hydrophilic sulfone group is grafted alone onto acrylamide methylated starch Polymerized copolymers cannot be obtained in the form of Iζ water-absorbing polymeric materials that exhibit high water solubility, but by using mixed monomer systems such as those described above, water solubility can be reduced and highly A graft copolymer with water absorption properties can be obtained.

In addition, as a result of experiments, it was found that a mixture of 2-acrylamide-2-methylpropanesulfonic acid niacrylamide-3:1 (weight ratio), or a mixture of 2-acrylamide-2-methylpropanesulfonic acid niacrylamide=1:1 (weight ratio) was used. It has been found that graft copolymers with the highest water absorption properties are obtained when a mixed monomer system with a weight ratio of

The thus prepared graft copolymer does not contain any toxic groups unlike the starch-acrylonitrile graph 1 copolymer, and thus does not require post-treatment such as hydrolysis.

<Examples> This invention will be further explained below by giving examples and usage examples.

Example 1 A commercially available product (degree of substitution: 0.05) was used as acrylamide methylated starch.

89 parts of the above acrylamide methylated starch and 22 parts of water (]
2-acrylamido-2-methylpropanesulfonic acid and acrylamide are mixed in various ratios to the base 1 flaky starch that has been cooled and heated at 100℃ for 10 minutes to gelatinize the starch and bind it into a paste. Mixed monomer 80 and 1% Fenton's reagent (H,02/Fe 2 ) 4,2o as a polymerization initiator were added and stirred well. After the whole was transferred to a polymerization tube and nitrogen substitution was repeated several times, the pressure inside the system was reduced and a polymerization reaction was carried out at 70° C. for 10 hours. After the reaction was completed, the reaction product was purified by immersing it in ion-exchanged water for 18 hours, and dried under reduced pressure to obtain a graft copolymer of the following formula as a dry product.

Crystallization bar S-AAIIIM niacrylamide methylated starch x: 1-30 y: 1-10 The results of measuring the water absorption rate (gH, 0/9 copolymer) of the obtained graft copolymer are shown in Figure 1. Shown in the graph. As can be seen from this graph, the highest water absorption was obtained when a mixed monomer containing 2.5% by weight of acrylic acid (2-acrylamide-2-methylpropanesulfonic acid-niacrylic acid-3:1) was used.

Example 2゜Mixture of 2-acrylamide-2-methylpropanesulfonic acid and acrylamide in various proportions [Zuma-
A dried product of the graft copolymer of the following formula was obtained in the same manner as in Example 1 except that 8 g was used.

However, as a result of measuring the water absorption rate of the obtained graft copolymer, S-ΔΔIIIM Niacrylamide Methylated Demetine The highest water absorption was shown when the mixed monomer containing (2-acrylamide-2-methylpropanesulfonic acid niacrylamide = 1:1) was used.

Example 3 A commercially available product (degree of substitution: 0.02) was used as acrylamide methylated starch.

A graft copolymer was obtained in the same manner as in Example 1 using 8 g of the above acrylamide methylated starch and 8 g of a mixed monomer obtained by mixing 2-acrylamido-2-methylpropanesulfonic acid and acrylamide in various proportions. The results of measuring the water absorption rate of the obtained graft copolymer are shown in the graph of FIG. In addition, the comparison 1 = the degree of substitution is 0
．． The water absorption rate of the graft copolymer (Example 1) obtained using the acrylamide methylated starch No. 05 is also shown in FIG.

As is clear from the graph in Figure 3, acrylamide methylated starch with a degree of substitution of 0.02 is used as a polymer, and a mixed polymer (2-acrylamido-2-methylpropanesulfonic acid) containing 25% by weight of acrylic acid is added to this polymer. A graft copolymer obtained by graft polymerizing Niacrylic acid (3=1) can absorb 500 times more water than the weight of this copolymer.

Usage Example A dry fine powder of a water-absorbing polymer substance that showed the highest water absorption rate among the graft copolymers obtained in Example 3 above is dispersed in a lower alcohol such as methanol or ethanol.
Furthermore, 1% by weight of vinyl acetate was added as an adhesive to prepare a paint.

The above coating material was applied to a portion where dew condensation is likely to occur, for example, the surface of an air blowing blade of an air conditioner, and then dried at 60 to 70° C. for about 30 minutes to form a dew condensation prevention coating.

This coating absorbed and dispersed water droplets that condensed on the blades during operation of the air conditioner, and also released the absorbed moisture into the air, effectively functioning as a dew condensation prevention coating.

<Effects of the Invention> As explained above, the water-absorbing polymer phase separation according to the present invention is achieved by using acrylamide methylated starch, which is relatively inexpensive and easily available, as a backbone polymer and graft polymerizing a hydrophilic monomer onto this. It is easy to manufacture. In addition, this acrylamide methylated starch has good affinity with the mixed hydrophilic monomer used in the present invention, and can be used as a safe graft copolymer with high water absorption that does not require post-treatment such as hydrolysis. Obtainable.

[Brief explanation of drawings]

Figure 1 shows the proportion of acrylic acid in the mixed monomer and the resulting copolymer in the water-absorbing graft copolymer of the present invention obtained using a mixed monomer of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid. It is a graph showing the relationship with the water absorption rate of a polymer. Figure 2 shows the proportion of acrylamide in the mixed monomer and the resulting copolymer in the water-absorbing graft copolymer of the present invention obtained using a mixed monomer of 2-acrylamide-2-methylpropanesulfonic acid and acrylamide. It is a graph showing the relationship with the water absorption rate of a polymer. Figure 3 is a graph showing changes in water absorption of the copolymer due to differences in the degree of substitution of the acrylamide methylated starch used, where the solid line is for a degree of substitution of 0.02 and the broken line is for a degree of substitution of 0.
．． This is the case of 05.

Claims (1)

[Scope of Claims] A water-absorbing polymer material comprising a graft copolymer of a mixed monomer of 1,2-acrylamido-2-methylpropanesulfonic acid and acrylic acid or acrylamide, and acrylamide methylated starch. 2. The water-absorbing polymeric material according to claim 1, wherein the mixed monomer is a 3:1 (weight ratio) mixture of 2-acrylamide-2-methylpropanesulfonic acid and acrylamide. 3. The water-absorbing polymeric material according to claim 1, wherein the mixed monomer is a 1:1 (weight ratio) mixture of 2-acrylamide--methylpropanesulfonic acid and acrylamide. 4. The water-absorbing polymeric material according to claim 1, wherein the acrylamide methylated starch has a degree of acrylamide methyl substitution of about 0.02.