Preparation Of Dry-strength Agent By Grafting Polyacrylamide On Starch And Its Application In Tube Roll Base Paper

At present there are more and more manufacturers of tube roll base paper. A few years ago the supply of tube roll base paper is not adequate to the demand. Howeve r, it is oversupply now. How to manufacture tube roll base paper products with excell ent quality by using relatively cheap paper pulps is the problem that an enterprise mu st consider.In this paper a preparation method of paper dry strengthening agent was put forw ard by grafting polyacrylamide onto starch. The application of the as-prepared strength ening agent in the manufacture of tube roll base paper was investigated in a laborator y scale. It was found that the optimum reaction conditions for the grafting of polyacr ylamide onto starch is as follows:the reaction temperature is 65℃; the monomer cone entration and initiator dosage are 15-20% and 0.0125%, respectively; the percentages o f cationic starch and cationic monomer are 5% and 25%, respectively; the charge leve Is of cross-linker and chain transfer agent are 0.5% and 0.3%, respectively.The starch-grafted polyacrylamide performs well as a paper dry strengthening age nt of tube roll base paper. It can significantly improves the drainage rate of paper fur nish and tensile strength. The improvements can be reached as high as 30% and 3 ti mes, respectively at the charge level of 2.0% based on the oven-dry paper stock. Furt hermore, paper furnish drainage rate and paper tensile strength can be enhanced under various pH conditions, especially significant at weak acidic pH value. The introductio ns of cationic dispersed rosin size, alum and cationic starch also favor the improveme nt of paper tensile strength. The as-prepared samples have synergistic effects with thos e commercial products. Compared to the commercial product of paper dry strengthenin g agent, the as-prepared starch-grafted polyacrylamide has similar strength improvement but shows higher improvement in drainage rate of paper furnish. By further applicati on in pilot scale, it was proved that the first pass retention of paper furnish is increas ed by 4.5%, while the physical quality is not changed at the same charge level with commercial product. At the same time, the dewatering rate is accelerated i.e., the dry line in the paper machine shifted toward headbox for 30 cm, and the machine speed i s improved by 10 m/min. The production rate is increased by 4.5%. The steam pressu re in the cylinder part can be averagely decreased by 110 kPa.