Nippon Shokubai Co., Ltd.

Ryoko Tahara

Kazushi Torii

Katsuyuki Wada

Hiroyuki Ikeuchi

Hirotama Fujimaru

Kazuhiko Sakamoto

Shigeru Sakamoto

Yoshifumi Adachi

Makoto Nagasawa

Masatoshi Nakamura

Eri Nagasawa

An object of the present invention is to provide a particle-shaped water absorbing agent having a remarkably improved surface color and excellent water-absorbing properties (better water absorption capacity, and lower water soluble content and residual monomer content) at the same time. In order to attain the object, a particle-shaped water absorbing agent according to the present invention is a particle-shaped water absorbing agent whose main component is a polyacrylic acid and/or a salt thereof, the particle-shaped water absorbing agent having a surface color of Hunter b value in a range of &#x2212;5 to 10, and having a cross-linking absorption property index (CPI) in a range of 1 to 100, the CPI defined by the following two equations:=(+17)/Ln (water soluble content);&#x2003;&#x2003;Equation 1:=(/residual monomer content)&#xd7;100&#x2003;&#x2003;Equation 3:

Particle-shaped water absorbing agent and method for producing the same

A particulate water absorbing agent includes a polyacrylic acid and/or a salt thereof water absorbent resin as a main component, wherein the water absorbent resin includes &#x3b1;-hydroxycarboxylic acid and/or a salt thereof, and the absorbing agent satisfies a specific particle size distribution and a specific water absorbing performance, thereby solving the conventional problems. Further, a production method of the water absorbing agent is characterized in that &#x3b1;-hydroxycarboxylic acid and/or a salt thereof is added to (a) a monomer aqueous solution whose main component is acrylic acid and/or a salt thereof and which is being cross-linked and polymerized or (b) a hydrogel polymer after the polymerization. As a result, in the particulate water absorbing agent containing the water absorbent resin as a main component, it is possible to realize both excellent water absorbing performance and excellent coloring prevention effect. Further, it is possible to provide an absorbing article particulate water absorbing agent which is suitable for practical use.

Particulate water absorbing agent and production method thereof

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Ibaraki, Japan

Ryoko Tahara