Patent ID: 6146495
Filing Date: 2000-11-14
Classification: C02F,D21C

Abstract:
In a kraft process for the production of wood pulp which comprises the steps of digesting wood chips in a digesting zone, bleaching the resulting wood pulp in a bleaching zone, and concentrating the separated liquor from the digesting zone in an evaporation zone, the improvement which comprises adding to at least one of said digesting zone, bleaching zone and evaporation zone a polymeric antiscalant in an amount sufficient to inhibit the scale formation therein, said polymeric antiscalant comprising:(A) at least one monomer unit consisting of 1,2-dihydroxy-3-butene; and(B) at least one monomer unit selected from the group consisting of maleic acid and a combination of maleic acid and acrylic acid;wherein said polymeric antiscalant is added in an amount in the range of from about 1 ppm to about 200 ppm, wherein said polymeric antiscalant has a weight average molecular weight in the range of from about 1,000 to about 100,000 and wherein said 1,2-dihydroxy-3-butene monomer units are present in an amount in the range of from about 1 mole percent to about 50 mole percent.