Abstract

In papermaking, chemical additives can be characterized either as process additives or as functional additives. Process additives are materials that improve the operation of the paper machine and include retention, formation, and drainage aids; defoamers; wet-web strength additives; pitch control agents; effluent treatment aids; slimicides and biocides; and creping aids. Functional additives are materials that enhance or alter specific properties of the paper product, and include sizing agents; dry-strength and wet-strength additives; fillers; pigments; and synthetic fibers. Process additives are primarily added internally, ie, at the wet end of the paper machine, while the sheet is being formed. Functional additives may be added either internally or onto the surface of the sheet, ie, at the dry end of the paper machine. The chemistry, mechanisms, and interactions of these various additives with other additives and with the papermaking fibers are discussed. Methods that test the effectiveness of the chemical additives are mentioned. Attention is also given to the effect that recycled fibers have on the use of papermaking additives, and to other environmental concerns.