Production method of water-absorbent resin, water-absorbent resin, and usage of water-absorbent resin

Abstract

The subject invention produces a water-absorbent resin by carrying out stationary polymerization of an ethylenically-unsaturated monomer containing acrylic acid and / or acrylate; cutting the resulting hydrous gelatinous polymer; and drying the hydrous gelatinous polymer which mainly contains angular particles having 6 smooth planes. The resulting water-absorbent resin particles are not aggregate, and can be efficiently dried. By coating at least a part of the surface of each of the particles with an adhesion block agent before, after, and / or at the time of cutting process, the adhesion preventing effect further increases.

Description

technical field [0001] The present invention relates to a method for producing a water-absorbent resin capable of preventing adhesion of a water-containing colloidal polymer and allowing smooth drying, the water-absorbent resin and its application. Background technique [0002] Conventionally, there are many methods for obtaining a water-containing gel-like polymer of a water-absorbing polymer by aqueous solution polymerization of a water-soluble ethylenically unsaturated monomer (for example, Patent Document 1). This hydrogel-like polymer is a semi-solid and highly elastic gel-like substance, so it is cut and dried and used as a water-absorbent resin, that is, a water-absorbing agent. [0003] When the hydrogel is cut, if it is only cut without any other treatment, the cut hydrogel-like polymers will adhere to each other, for example, it cannot be cut continuously during mechanical cutting, which reduces the processing efficiency. Therefore, in order to prevent the occurre...

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Problems solved by technology

[0006] However, in the above-mentioned conventional techniques, there is a problem that mutual adhesion of hydrogel-like polymers cannot be sufficiently prevented.

[0007] Moreover, in Patent Documents 6 and 7, there is also the problem of unpleasant odors. Although the detailed cause is not clear, it is presumed that it is caused by the heat treatment in the subsequent process, the added reducing substances and the impurities from the raw materials. cause

In the above-mentioned Patent Document 8, the amount of residual monomers can be reliably reduced, but there is a problem that the amount of residual monomers of the absorbent varies widely, the amount of residual monomers is not reduced to the desired level, or defective products occur.

[0008] On the other hand, when the techniques of the aforementioned Patent Documents 4 and 5 are used to reduce the amount of residual monomers, there is a problem that the obtained water-absorbent resin is colored and the commercial value is lowered.

In addition, when reducing the amount of residual monomers, various strict reaction conditions are necessary, so there is a problem that the material properties are lowered due to the deterioration of the monomers, and it is difficult to take into account the reduction of the residual monomers to the desired level and maintenance. , Improvement of absorption efficiency under no pressure, absorption efficiency under pressure, etc. coexistence of two aspects of absorption characteristics

[0009] That is, in Patent Document 4, polyethylene glycol, surfactants, etc. are listed as anti-adhesive agents, but there is no specific description of how to use them to treat the hydrogel polymer

In addition, in the technology described in Patent Document 5, in order to prevent the mutual adhesion of the hydrogel-like polymers, a surfactant or a high-molecular polyvalent alcohol or the like is used, but the particle size distribution of the hydrogel-like polymers is wide and The shape of the hydrogel-like polymer is not uniform, so it is easy to aggregate

[0010] As described in Patent Document 11, a method of spraying an aqueous solution of a polyvalent metal salt to dry powdery polymer particles has been disclosed, but the technology involved is not aimed at preventing the mutual adhesion of hydrogel-like polymers, and There is no technical knowledge about sufficient prevention of mutual adhesion of hydrogel-like polymers by covering with polyvalent metal salt solution, etc.

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