Date of Award

4-1996

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

First Advisor

Dr. Raymond L. Janes

Abstract

The objective of this study was to determine the feasibility of thermal-chemical conversion of corn starch for use in pigmented paper coatings.

Thermal-chemical conversion of starch is capable of creating a wide range of starch solids and characteristics at one location with on-site conversion. It involves the use of high temperatures and pressures, along with a conversion agent (i.e. ammonium persulfate [A.P.], or a peroxide), to hydrolyze and oxidize the unmodified starches.

In this study corn starch was converted using a National Starch Company C-1 Laboratory Jet Cooker. The study was done in three phases. Preliminary work was done to become familiar with the jet cooker operation. Next, three runs were made to prepare starches of different viscosities. These starches were used to prepare coatings which were applied on the CLC coater. Finally, the coated sheets were tested for brightness, smoothness, gloss, and wax pick.

During the running of the jet cooker a number of difficulties were experienced. These included: poor retention, significant dilution due to flashing and quench water, plugging of the retention coil, poor back pressure control and unpredictable starch viscosities.

Runability during coating of starch as a binder was excellent. The low dewatering effect that starch added to the coating aided in blade coating operability.

The results of the testing of the coatings showed that brightness, smoothness and gloss were best at the medium addition level of A.P. (1.3%). The values of wax pick were indistinguishable from one another because they were within one standard deviation. These low molecular weights are most often caused by over conversion of the starch structure. The high-shear rheology of the three coating colors was thixotropic, of increasing hysteresis area as binder A.P. level increased. This suggests that as the A.P. level was increased greater reduction of starch molecular weight occurred.

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