APPLICATION OF POLYMERIC MULTIFUNCTIONAL CARBOXYLIC-ACIDS TO IMPROVE WET STRENGTH

BTCA (1,2,3,4-butanetetracaraboxylic acid) is an effective crosslinkin g agent for wood cellulose that can improve the wet strength of paper products. However, the high cost of BTCA has prevented its application on a commercial scale. Two polymeric multifunctional carboxylic acids -a homopolymer of maleic acid (PMA) and a terpolymer of maleic acid, a crylic acid, and vinyl alcohol (TPMA)-were studied for their potential to improve the wet performance of kraft paper. Sheets treated with PM A and TPMA were compared with BTCA-treated sheets. Wet-sheet propertie s-wet tensile strength, wet strength to dry strength (W/D) ratio, wet stiffness, and dimensional stability-were markedly improved by acid tr eatment, with high acid pickup levels producing W/D ratios over 70%. H owever, folding endurance of the acid-treated papers decreased substan tially at higher levels of acid pickup. Acid treatment hd little effec t on dry tensile strength. The effectiveness of PMA as a wet-strength agent was comparable with that of BTCA, while TPMA was slightly less e ffective. Because the cost of PMA and TPMA is only a fraction of that of BTCA, these two polymeric carboxylic acids have greater potential f or commercial application as wet-strength agents.