Nippon Shokubai Kagaku Kogyo Co., Ltd.

Nippon Shokubai Co., Ltd.

Yasuhiro Mori

Hiroshi Ito

Hideyuki Tahara

Makoto Mizushima

Yoshinori Sano

Tsuyoshi Hirata

Tsuneo Tsubakimoto

A cement additive is added to increase flowability of a cement composition and to prevent a slump loss, but those characters are insufficient, or the cement additive becomes ununiform in the cement composition and causes a trouble of the hardening inferiority. Thus, to solve the subjects, the present invention provides a cement additive composed of a crosslinked polymer in which, between main chains having a water-soluble polymer structure of a molecular weight from 500 to 100,000, a bond having as a structural unit at least one group selected from divalent groups as shown in the following formula (I) is formed. ##STR1## �In the formula (I), R.sup.1 and R.sup.2 independently denote any one of the following. ##STR2## However, R.sup.1 may not be required in a case of that R.sup.2 is the following. ##STR3## Moreover, R and R' independently denote an alkyl group of carbon number of 1 to 5.!

Cement additive, method for producing the same, and cement composition

A cement dispersant containing a water-soluble polymer containing at least 10 mol % of structural units represented by the general formula I: ##STR1## wherein X is H or CH.sub.2 R.sup.1, R.sup.1 is H or COO--[--A).sub.m B).sub.n ]H, R is H, CH.sub.3, or COO--[--A).sub.m B).sub.n ]H (providing that R is H where X is CH.sub.2 R.sup.1), A is iminoalkylene having 2 to 4 carbon atoms, B is oxyalkylene having 2 to 4 carbon atoms, m is an average number in the range of 0.1 to 10, n is O or an average positive number not more than 100, --A).sub.m may be in a linear or branched configuration, wherein the sequence of A and B in the segment in parenthesis may be regular or random.

Cement dispersant

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Suita, Japan

Yasuhiro Mori