JPS58154709A - Production of cationic, highly water-absorptive resin - Google Patents

Abstract

PURPOSE:To produce the titled resin which is water-insoluble and can absorb water in an amount several hundred times its own weight, by copolymerizing a specified vinyl monomer with acrylamide in the presence of a water-miscible or water-soluble divinyl compound. CONSTITUTION:A low-moisture, porous, cationic highly waterabsorptive resin is prepared by dissolving (A) 25-100mol% vinyl monomer containing a tert. or quat. amino group, (e.g., dimethylaminoethyl (meth)acrylate), (B) 75-0% acrylamide and (C) 0.005-0.1pt.wt. (per 100pts.wt. total monomer) water-miscible or water-soluble divinyl compound (e.g., N,N-methylenebis(meth)acrylamide), adjusting the solution to a pH of 3-7, subjecting the solution to a copolymerization reaction in the presence of an initiator such as a redox type or an azo type, and evaporating the moisture by the heat of polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a water-insoluble superabsorbent resin that absorbs several hundred times its own weight of water by copolymerizing a water-soluble monomer with a divinyl compound.

In Japan, pulp products have been used to absorb and retain water. However, the amount of water absorbed by pulp is about 10 times its own weight, and if you try to absorb and retain a large amount of water, you will need a large amount of pulp, resulting in a very bulky product. It had the disadvantage of easily separating water when added.

Therefore, various efforts have been made to develop super absorbent resins that absorb and retain large amounts of water with a small weight. This super-absorbent resin absorbs and retains several hundred times its own weight in water, and has the characteristic that it forms a stable gel when it absorbs water, and does not separate water even when a small amount of pressure is applied. Such superabsorbent resins have a wide range of uses, including disposable diapers, napkins, microbial culture media, and water retention agents for gardening. As a super absorbent resin that has already been developed, starch graft polymer
46199) Cellulose modified product (JP-A-5O-8037
6) If starch graft time coalescence is used as a water-containing gel for a long period of time, the starch may rot.
Furthermore, modified cellulose has the disadvantage that it absorbs less water than cellulose.

The present inventors conducted intensive research to overcome this drawback, and as a result, they arrived at the present invention.

That is, in the present invention, when copolymerizing a vinyl monomer having a tertiary amino group or a quaternary amino group and acrylamide at a molar ratio in the range of 25 to 100:0,
The present invention relates to a method for producing a cationic superabsorbent resin, characterized in that 0.005 to 0.01 parts by weight of a water-miscible or water-soluble dihinyl compound is allowed to coexist with 100 parts by weight of the total monomers.

Examples of vinyl monomers having a tertiary amino group or a quaternary amino group used in the present invention include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, and diethylaminopropyl (meth)acrylate. ) acrylamide, dimethylaminomethyl (meth)acrylamide, and monomers obtained by quaternizing these with methyl chloride, diethyl sulfate, dimethyl sulfate, etc. However, in the present invention, the types of monomers are limited. However, two or more of these types may be used.

Regarding the molar ratio of the vinyl monomer having an amino group to acrylamide, if the molar ratio of acrylamide is increased by reducing the monomer having an amino group to less than 25 mol%, the strength of the hydrogel increases (although the water absorption capacity decreases). will decrease.

In addition, examples of water-miscible or water-soluble divinyl compounds include N%N-methylenebis(meth)acrylamide,
Tetraethylene glycol di(meth)acrylate, di(meth)acrylate
Examples include decaethylene glycol meth)acrylate, but N,N-methylenehisacrylamide is industrially preferred. The strength of the divinyl compound is preferably 0.005 to 0.1 part by weight when the sum of the weights of the monomer having an amino group and acrylamide is 100 parts by weight, and if it is less than this range, the hydrogel will be in a semi-dissolved state. In addition, if the amount is too large, the degree of crosslinking will increase, and in both cases, the water absorption capacity will decrease.

The polymerization of the product of the present invention is usually carried out in an aqueous solution, and the pH of the aqueous solution is preferably adjusted to 3 to 7 using an acid, but the type of acid is not particularly selected.

The polymerization initiator is a commonly used redox type,
Any material may be used, such as A-I type. Further, the polymerization concentration is not particularly limited and can be selected within any concentration range, or considering the drying process, it is advantageous to carry out the polymerization at a concentration as high as possible.

For example, a method can be selected in which polymerization is carried out using a highly concentrated aqueous solution of about 70%, water is evaporated by the generated heat of polymerization, and the solution is directly taken to a pulverization step after a drying step. Furthermore, the starting temperature is not particularly limited, as the temperature at which polymerization starts varies depending on the type of initiator, and it is sufficient to start the polymerization once the initiator is used.

Next, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 41.3 g of dimethylaminoethyl methacrylate and 1 g and 7 g of acrylamide were dissolved in distilled water 140S,
The pH was adjusted to 4 with 5% hydrochloric acid at 27.49. Furthermore, N,
N-methylenebisacrylamide o, oaf! added. 2,2'-Anobis(2-amidinopropane) hydrochloride o, oay was added as an initiator, and polymerization was initiated at 50°C.

Example 2 53.8 g of dimethylamine ethyl methacrylate and 16.211 g of acrylamide were dissolved in 20 g of distilled water.
1 Qcc of an acetone solution containing 0.7 g of isobutyronitrile dissolved in 17.5% sulfuric acid was added. 80% of this solution
It was heated by placing it in a box-shaped container (Teflon-treated glass fiber material) heated in a constant temperature water bath at ℃. As the temperature of the solution rose, the polymerization reaction started, and water was evaporated by the generated heat of polymerization, yielding a super absorbent resin as a porous solid with a very low water content.

Example 3 0.06f1 of N,N-methylene/bisacrylamide was added to 100 g of an 80% aqueous solution of methacryloxyethyltrimethylammonium chloride, and 2,2'-azohis(2-amidinopropane) hydrochloric acid was added as an initiator. Add O, S Ii and mix. This solution was placed in the aforementioned box-shaped container heated in a constant temperature water bath at 85°C and heated.

As the polymerization started, water evaporated due to the heat of polymerization, and a super absorbent resin was obtained as a porous solid with a low water content.

Example 4 The polymer obtained in Example 1 was dehydrated with acetone, dried, and then ground. Further, the polymer obtained in Example 2.3 was directly pulverized without passing through drying + QT and Pj to obtain a powdery super absorbent resin.

The powdered superabsorbent resins of Examples 1 to 3 were compared with commercially available products, and a water absorption test was conducted. The test method was to add superabsorbent resin powder 111 to distilled water 11 with stirring, leave it for 1 hour, pass through a 100 mesh sieve, and measure the amount of water absorbed from the amount of liquid.

Also, 1% saline solution and 80% methanol aqueous solution 11 times, powder 5 times! In addition, water absorption was measured in the same manner.

The results are shown in Table 1 in terms of water absorption capacity (water absorption amount ÷ weight of added super absorbent resin 11).

Table 1 Water absorption performance (water absorption capacity)

Claims (1)

[Claims] If q is a tertiary amino group, a vinyl monomer having a quaternary amino group and acrylamide are combined in a molar ratio of 25 to 5 to too:
0.005 to 0.1 part by weight of a water-miscible or water-soluble divinyl compound is present in the copolymerization in the range of 0.0 to 100 parts by weight of the total monomer. Resin manufacturing method