| 摘要 |
The paper furnish contains: (a) a soluble aluminium compound selected from the group consisting of aluminium sulfate, aluminates, aluminium nitrate, polyaluminium chloride and polyaluminium sulfate, present in the amount of approximately 0.005 to 2.5 kilograms of Al2O3 per metric ton of dry paper, and (b) a modified starch prepared by cooking an aqueous solution of at least one amphoteric or cationic starch having a degree of substitution between about 0.01 to 0.2 with at least one nonionic or amphoteric polyacrylamide, or cationic or anionic polyacrylamide having a degree of substitution between 1% and 80% by weight, having a molecular weight of at least 500,000, with the provisos that: (i) cooking is conducted at a pH above 7.0 in the case that a cationic or non-ionic polyacrylamide is selected; (ii) cooking produces no more than 75% neutralization of the cationic starch if the anionic polyacrylamide molecular weight is [1,000,000 and no more than 50% neutralization of the cationic starch if the anionic polyacrylamide molecular weight is ³8,000,000; and (iii) the weight ratio of starch to polyacrylamide is greater than 2 to 1.
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