Surface sizing is a process in the process of paper or paperboard processing. it is usually located at the end of the drying stem of the paper machine. when the paper sheet is not completely dried but has a certain strength, it is sprayed with a layer of glue. after subsequent drying, it forms a layer of glue film on the surface of the paper and paperboard, thus achieving the purpose of changing the surface performance of the paper or paperboard.
From the perspective of the development of the paper industry, surface sizing is one of the indispensable processes in paper making. through surface sizing, surface additives can be added to improve the properties of paper sheets or increase the water resistance of paper or paperboard.
Previously, due to the limitation of technical level and paper type requirements, surface sizing agents could only be used on special paper types, such as banknote paper, securities paper, sea drawings, etc. With the improvement of the technical level of the paper industry, the surface sizing of paper has become a conventional paper processing procedure. especially in recent years, due to the popularization of printing, copying and faxing, higher requirements have been put forward for the surface properties, strength and water resistance of cultural paper, wrapping paper and corrugated paper. therefore, the paper industry is continuously searching for new surface sizing techniques.
1 ) improving the printing performance of paper and paperboard;
2 ) the surface strength or water resistance of the paper can be improved by selecting different surface sizing agents;
3 ) improving the physical strength of paper and paperboard;
4 ) surface sizing can reduce the difference between the two sides of the paper;
5 ) it is not affected by papermaking water quality and water temperature, and the sizing effect is relatively stable;
6 ) the sizing material has good retention effect and low sizing cost;
7 ) when used together with internal sizing, it can make up for some defects of internal sizing. According to the function of the surface sizing agent, we are divided into anti-water type and reinforcing type. Alkyl ketene dimer ( akd ) and styrene maleic anhydride copolymer can be used as surface sizing agents for improving water resistance. Starch, carboxymethyl cellulose ( CMC ), polyethylene ( PVA ) alcohol and the like can be used as reinforcing materials.
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