| 摘要 |
PROBLEM TO BE SOLVED: To provide a paper strengthening agent responsive to an increase in compounding ratio of used paper pulp which is deteriorated pulp fiber according to cost reduction, closed systematization of a papermaking system and a change from acidic papermaking to neutral or further alkaline papermaking etc., in production of paper or paperboard and capable of improving the paper strength while improving the freeness or retention and further improving paper product performances or productivity and to provide a papermaking method. SOLUTION: The paper strengthening agent is obtained by mixing an aqueous slurry of undissolved particles of raw starch or a modified starch prepared by subjecting the raw starch to a nonionic treatment with an aqueous solution of a high-molecular weight cationic polyacrylamide derivative having an advanced structural type molecular structure. By using the paper strengthening agent, the papermaking method comprises a step of adding the paper strengthening agent to a stock slurry and carrying out papermaking of the resultant pulp slurry. Thereby, the undissolved starch particles can be fixed on the pulp fibers with the cationic polymer and the starch particles can be dissolved in the subsequent drying step thereof to improve the paper strength. COPYRIGHT: (C)2008,JPO&INPIT
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