JPS6023122B2 - Manufacturing method of water absorbent resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the water absorption performance of a water absorbent resin in an ionic aqueous solution.

Water-absorbing resins that are cross-linked with an appropriate amount of electrolyte polymer generally have excellent performance, and polyacrylic acid is a typical example, but these have remarkable water-absorbing performance in ionic aqueous solutions. It has the disadvantage of decreasing.

Moreover, ions are present to varying degrees in the environments in which they are used. The present invention improves the performance as described above.
This is intended to be achieved by buffering the effects of ions present in aqueous solutions on water-absorbing resins, but many saturated carboxylates with monovalent intestinal ions exhibit a buffering effect;
Among them, those whose acidity is lower than that of polyacrylic acid and whose intestinal ions are the same have a low degree of influence on the water absorption performance of the water absorbent resin in an aqueous solution. In addition, if the cations are the same, it can be neutralized after addition in the acid state, which is convenient for production, and some aromatic compounds have a preservative effect, which is useful for the storage stability of the resin. . Furthermore, by adding hydrogen carbonate, the degree of neutralization is maintained at 100% and the buffering effect is also improved. Preferred embodiments of the present invention will be described below. Example 1 A 10% aqueous solution of polyacrylic acid polymerized using persulfate as a catalyst was diluted to make a 1% solution, and sodium hydroxide was added to neutralize it to about pH 6. Add sodium aluminate dissolved in water, mix well, and leave for 10 hours or more. Add a slightly excessive amount of sodium bicarbonate and 20% by weight of polyacrylic acid solids until the pH becomes constant. Dry the aqueous solution containing sodium citrate.

The water absorption amount of the thus obtained water absorbent resin in a 1% aqueous solution was 28 times or more of its own weight, and the performance was about 2.5 to 3 times that of conventional water absorbent resins.

This performance improvement effect is also influenced by the addition of sodium hydrogen carbonate, and it is thought that the degree of neutralization can be maintained at 100% at all times, and that the remaining sodium hydrogen carbonate also acts as a buffer. Example 2 The same mole of citric acid as that added in Example 1 was previously dissolved in an aqueous polyacrylic acid solution, and then neutralized and crosslinked as in Example 1. The water absorption performance was also the same as above.

The carboxylic acid that can be used in the present invention can be appropriately selected as long as it has weaker acidity than polyacrylic acid and is soluble in water, as described above, and the amount added can be adjusted depending on the ion concentration of the aqueous solution. .

As described above, the method for producing a water absorbent resin according to the present invention is suitable for industrial production and has excellent performance and economical efficiency.

Claims (1)

[Claims] 1. A method for producing a water absorbent resin in which polyacrylic acid is neutralized and crosslinked with monovalent cations and aluminum ions,
A method for producing a water-absorbing resin, characterized in that a saturated carboxylate salt and a hydrogen carbonate salt of the cation are present. 2. The manufacturing method according to claim 1, wherein a saturated carboxylic acid is dissolved in an aqueous polyacrylic acid solution in advance, and then neutralized and crosslinked.