Process for improving qualities of paper
AssigneesOtsuka Chemical Co., Ltd., Sansho Co., Ltd.
InventorsHideo Yamaguchi, Masahiro Kobayashi, Atsunobu Mizote, Yoshiyuki Iwamuro
Life of this patent
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Abstract
A process for improving the qualities of paper which comprises making co-exist (a) a water-soluble polymer containing hydrazide group or its adduct with a water-soluble inorganic salt of an alkaline earth metal and (b) a heavy metal ion capable of chelating with the polymer or its adduct in a pulp slurry in paper making. The use of the water-soluble polymer or its adduct in combination with the heavy metal ion improves markedly the paper strength, the retention of sizing agents and the retention of fillers at a pH value around neutrality.
Claims8
A process for improving strength and retention of paper which comprises adding to a paper pulp slurry (a) a water-soluble polymer containing hydrazide group of the following general formula:
- ##STR2## wherein X is hydrogen atom or carboxyl group, Y is hydrogen atom or methyl group, A is acrylamide unit, methacrylamide unit, an acrylate unit, a methacrylate unit or maleic anhydride unit, B is a unit derived from a monomer copolymerizable with acrylamide, methacrylamide, an acrylate, a methacrylate or maleic anhydride, and there is the following relationship among p, q and r:
- 30% by mole.ltoreq.p.ltoreq.100% by mole
- 0% by mole.ltoreq.q+r.ltoreq.70% by mole
- p+q+r=100% by mole
- or its adduct with a water-soluble inorganic salt of an alkaline earth metal in an amount of at least 0.01% by weight based upon the weight of the pulp in the presence of (b) a heavy metal ion which is at least one ion of a heavy metal selected from the group consisting of copper, cobalt, lead, zinc, iron, tin, mercury, nickel, cadmium and manganese at a concentration of at least 0.1 ppm in the pulp slurry to chelate said polymer or its adduct.
Dependencies are inferred from the claim text.