Use of a polymer product for deposit formation control in manufacture of paper or board

A method to control deposit formation caused by hydrophobic substances in a process for manufacture of paper or board, the method comprising:

• providing an aqueous fibre suspension;
• fixing in the aqueous fiber suspension microstickies having a particle size of 3-150 μm, and pitch or colloidal stickies having a particle size of 0.2-3 μm onto the fiber by adding into the aqueous fibre suspension before a mixing chest a water-soluble polymer product comprising amphoteric polyacrylamide having a neutral or cationic net charge at pH 7, a weight-average molecular weight of 2,500,000-18,000,000 g/mol and a total ionicity of 4-28 mol-%, the amphoteric polyacrylamide comprising 3-25 mol-% of structural units derived from cationic monomers, and 0.5-5 mol-% of structural units derived from anionic monomers;
• optionally diluting the aqueous fibre suspension;
• delivering the aqueous fibre suspension to a headbox, and draining the aqueous fibre suspension on a wire screen to form a wet web of the paper or the paperboard;
• and
• pressing and drying the wet web to obtain a web of the paper or the board.