METHOD FOR ON-SITE GLYOXYLATION OF POLYACRYLAMIDE

The invention relates to a method for on-site glyoxylation of polyacrylamide in a paper mill, board mill or the like, where a discontinuous batch glyoxylation reaction of an aqueous reaction mixture is performed in a reactor vessel provided with a driven agitator to form an aqueous polymer composition comprising glyoxylated polyacrylamide for use in a manufacturing process of paper, board or the like. The method comprises forming or obtaining the aqueous reaction mixture comprising polyacrylamide base polymer and glyoxal, determining alkali consumption of the reaction mixture, and adding to the reaction mixture, on the basis of the determined alkali consumption, a pre-determined amount of alkali which is needed for adjusting the reaction mixture's pH value within a range of 8 ? 10, preferably 8.5 ? 9.5. The reaction mixture's temperature is optionally adjusted to a temperature range of 15 ? 40 °C, more preferably 20 ? 30 °C and the on-site glyoxylation reaction of polyacrylamide base polymer in the reaction mixture is allowed to proceed. Viscosity of the reaction mixture and/or a process variable that is related to the viscosity of the reaction mixture is measured, acid is added to the reaction mixture for lowering the pH value of the reaction mixture