Date of Award

12-1996

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

The coated paper industry is rapidly changing and improving. Because of increasing demands by consumers, high quality paper at the lowest possible price is at a premium. Because of this paper makers and coaters are continually looking for ways to improve their sheet without increasing cost.

This experiment was designed to test the role which pigment and latex has in influencing the final sheet quality. This was tested in two stages. The first stage examined pigment variations and the second latex variations. In the pigment variation trial, a number 1 high brightness clay was replaced by a structured clay pigment. This structured pigment showed superior print quality characteristics, as well as superior surface properties. This led to further research involving reduction of titanium dioxide content. At 35% titanium reduction, print quality was still superior to control. Testing was also done to compare the structured pigment with precipitated calcium carbonate. Using a trial containing a lower clay to carbonate ratio, it was concluded that the structured pigment offered better print characteristics than the calcium carbonate. The excellent properties shown by the structured pigment can be explained by its ability to produce a bulkier, more open sheet which allows for increased ink absorbency and optical properties than that obtained with number 1 clay or precipitated calcium carbonate.

The second part of this experiment involved substitution of a control latex sample with other latex samples chosen with similar physical properties. In this work it was concluded that the latex which is chosen does definitely play a role in final sheet properties. The latex must be chosen with consideration of the pigment system which is used. It is important that the latex interacts well with the pigment so that a uniform coating can be applied, free of inconsistencies and variation. This is important when considering ink absorption because an inconsistent surface will lead to inconsistent absorption. Also, latex-pigment interactions influence the optical properties of the sheet. Ideally, a latex will be uniformly distributed throughout the coating layer, with no migration laterally or vertically.

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