PURPOSE: To obtain the subject preventing agent effective for continuously preventing the deposition of silica scale, stabilizing the operation and quality and prolonging the continuous operation period by using an acrylic acid-itaconic acid copolymer, etc., as an active component.
CONSTITUTION: The objective preventing agent contains at least one kind of compound selected from acrylic acid-itaconic acid copolymer, acrylic acid-maleic acid copolymer, EDTA and their salts as an active component. Preferably, the copolymer has a molecular weight of 500-20,000 and a molar ratio of the constituent monomers of 1:19 to 19:1. The preventing agent is preferably added to the process water of a waste-paper deinking process or to a pulp slurry in an amount of 0.1-1,000ppm based on water.
YASUDA KOJI
ITO KENICHI
