| 摘要 |
PROBLEM TO BE SOLVED: To obtain a paper-strengthening agent capable of fixing on paper in higher yield than those of slurry-addition type, using inexpensive raw materials and improving paper strength. SOLUTION: This paper-strengthening agent which is (1) a polymer-dispersing liquid consisting essentially of polymerized deposite from aqueous monomer solution including (meth)acrylic acid, has the following characteristics: (2) the concentration of the (meth)acrylic acid copolymer in the polymer-dispersing liquid is >=5 wt.%, (3) the (meth)acrylic acid copolymer powders in the polymer- dispersing liquid have 1-100μm mean particle diameter, (4) the viscosity of the polymer dispersing liquid is 30-1,000 cp just after deposition and one month after, (5) the polymer particles can be observed after diluted 10-fold with distilled water by magnification 400-fold with a microscope and (6) the polymer particles are dissolved into an aqueous solution by adding an alkali into the resultant suspension and adjusting the pH to be 7.0. The paper strength is improved by coating the aqueous solution of the paper-strengthening agent at the surface of dry paper.
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