Dextrin-Poly(acrylic acid) Copolymer as an Additive for Surface Sizing with Oxidized Starch (II) : Effect on Strength and Drying Rate

Abstract

Drying energy demand in the after-dryer section for the surface sized paper is an important economic factor in papermaking. Using an efficient sizing solution with high solids content and decreasing the pickup weight can reduce the drying energy requirement in the after-dryer section. A dextrin-poly(acrylic acid) copolymer was used as an additive for surface sizing of linerboard, and its effect on the mechanical properties of linerboard, and drying energy consumption were investigated. Results showed that, addition of dextrin poly(acrylic acid) copolymer had beneficial effects on the holdout of surface sizing starch and provided higher compressive and bending strengths. It was possible to reduce pickup weight by 23% while keeping the compressive strength and bending resistance at a similar level. Consequently, the reduced pickup resulted in higher dryness after surface sizing. Even though, drying analysis of wet sized sheets at a laboratory gave a lower drying rate when the copolymer was used as an additive, the result from a mill trial revealed that steam usage decreased significantly when the copolymer was used as an additive for surface sizing, which was attributed to the reduction in the pickup weight and improvement in holdout of the surface sizing agents on linerboard surface that is more pronounced on a high speed paper machine.