Wet end chemistry ch 12

WPS, CBNU

Reasons for sizing paper

• Strong natural tendency to interact with water

• Important properties to the development of strong interfiber hydrogen bonds during papermaking and to strength loss when saturated with water

• Liquid (water) penetration resistance by sizing

Two types of sizing processes

• Sizing: impart resistance to water penetration in paper

• Surface sizing and internal sizing

• Surface sizing: the paper web is formed and dried and a sizing agent is applied to the paper surface by a size press

• Internal sizing: sizing additives are added to the papermaking furnish and get incorporated into the web when it is formed.

Some sizing terminology

• Waterleaf papers: very absorbent papers which have no water

resistance

• Slack sized papers: papers that have intermediate levels of water resistance

• Hard sized papers: highly water resistant paper

• Fugitive sizing: the disappearance of liquid penetration resistance after it is manufactured

• Self sizing: the gradual development of water resistance in a paper that does not have after being manufactured

Basic surface science considerations

important to sizing

• Four ways that liquid penetrates paper

– 1)capillary flow in pores: the Washburn equation

– 2)diffusion through pores

– 3)diffusion through fiber solid fractions

– 4) evaporation, vapor phase diffusion, and condensation

Wet end chem chapter 13

WPS

CBNU

Wet end chem chapt 14

Wood and Paper Science

Chungbuk National University