The paper summarizes the methods of upgrading the recycled fiber : the mechanical beating and refining,the use of chemical additives,the enzymatic treatment,physical fractionation and blending,each method has its own advantages and disadvantages,so in practice we combine some of them in order to get a high-grdae recycled fiber.

This article introduces the chemical additives effect the strength of sack paper ,The result shows that some type of chemical additives was suitable for improving sack paper strength.

At present, the chemical assistant has played a very important rol e in the development of the oil field, and the product quality is very important, too.

This paper described a method of improving the ?u idity of the liquid by adding chemical agents so as to enhance the web dryness on press section.

In order to improve the neatness, chemical agents are used in combination with direct steaming process, resulting in remarkable effects, with raw silk neatness scoring 92.

This paper summarizes the research development of the combined use of chemical filter aids during the past three decades, points out the existing problem and the future trend.