Harima Chemicals, Incorporated

Sadayuki Uchida

Yoshihide Ishikawa

Masao Hamada

Tomohiko Nakata

Satoru Iwasa

Shinichi Kimura

The invention provides a sizing agent with good stability, particularly which is rapid in getting started in the neutral zone and a method of producing the same. A sizing agent for papermaking in neutral zone is characterized by a main component of said sizing agent being selected from the group consisting of a diester of rosin-based substances having a dicarboxylic acid or acid anhydride group expressed by the following formula (I), ##STR1## (in which R.sub.1 represents a rosin acid residue or maleopimaric acid, R.sub.2 represents a dihydric alcohol residue and R.sub.3 represents a maleopimaric acid residue); and 2) a polyester reaction product expressed by the following formula (I'), ##STR2## (in which R'.sub.1 and R'.sub.5 represent a rosin acid residue or an .alpha.,.beta.-unsaturated polybasic carboxylic acid added rosin residue, at least one of them represents .alpha.,.beta.-unsaturated polybasic carboxylic acid added rosin residue, R'.sub.2 and R'.sub.4 represent polyhydric alcohol residues, R'.sub.3 represents a polybasic carboxylic acid residue being at least tribasic, x and z are integers of 1 to 3, y is 0, 1 or 2 and m and n are 1 or 2); and 3) a mixture comprising a rosin, a rosin modified by .alpha.,.beta.-unsaturated carboxylic acid and/or or an anhydride thereof and a polyhydric alcohol ester of rosin.

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Kasai, Japan

Sadayuki Uchida