Sizing agent composite for papermaking

A method of producing a sizing agent for papermaking in a neutral range, comprising:

• reacting a) rosins, b) dihydric alcohols and c) .alpha.,.beta.-unsaturated carbonyl compounds, singularly or at the same time in a manner such that the ratio of the hydroxyl group equivalent of b) to the carboxyl group equivalent of a) is 0.2 to 1.5,
• obtaining at least one reaction product containing a diester of a rosin-based substance having a carboxylic acid or acid anhydride group, and which is expressed by formula (I),
• R.sub.1 --C(O)O--R.sub.2 --OC(O)--R.sub.3 (I)
• 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
• dispersing said reaction product into water.

A method of producing a sizing agent for papermaking in a neutral range characterized in that it comprises:

• reacting a rosin with a polyhydric alcohol, and then
• reacting therewith a polybasic carboxylic acid being at least tribasic, an anhydride thereof, or a mixture thereof, to provide complete esterification;
• adding an .alpha.,.beta.-unsaturated polybasic acid to the rosin, thereby resulting in a reaction product expressed by the following formula (I'), ##STR7## 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, provided that at least one of R'.sub.1 and R'.sub.5 represents an .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 dispersing the Formula (I') compound reaction product into a water.