Method of sizing paper

A method for sizing paper products comprising the steps of

• 1. providing a paper stock system;
• 2. forming, in the absence of high shearing forces and under normal pressures, a sizing emulsion consisting essentially of:
• a. from 80 to 97 parts of substituted cyclic dicarboxylic acid anhydride corresponding to the formula ##STR5## wherein R represents a dimethylene or trimethylene radical and wherein R' is a hydrophobic group containing more than 5 carbon atoms which may be selected from the class consisting of alkyl, alkenyl, aralkyl, or aralkenyl groups;
• ##STR6## wherein R.sub.x is an alkyl radical containing at least 4 carbon atoms and R.sub.y is an alkyl radical containing at least 4 carbon atoms, and R.sub.x and R.sub.y are interchangeable;
• ##STR7## wherein R.sub.x is an alkyl radical containing at least 5 carbon atoms and R.sub.y is an alkyl radical containing at least 5 carbon atoms and R.sub.x and R.sub.y are interchangeable;
• b. from 3 to 20 parts of a polyoxyalkylene alkyl or polyoxyalkylene alkyl-aryl ether or the corresponding mono- or diester selected from the group consisting of:
• ##STR8## wherein x and n are integers in the range of 8 to 20;
• R is an aryl radical;
• m is an integer in the range of 5 to 20;
• and i is 0 or 1;
• and
• 3. forming a web from the paper stock system;
• c. water;
• 4. intimately dispersing said emulsion within the paper stock either before or after formation of said web but prior to passing said web through the drying stage of the paper making operation in an amount sufficient to provide a concentration of the substituted cyclic dicarboxylic acid anhydride of from 0.1 to 2.0%, based on dry fiber weight.