Date of Award

6-1995

Degree Name

Master of Science

Department

Chemical and Paper Engineering

Department

Paper Engineering, Chemical Engineering and Imaging

First Advisor

Dr. Raymond L. Janes

Second Advisor

Dr. John Crowell

Third Advisor

Dr. Ellsworth Shriver

Fourth Advisor

Dr. Raja Aravamuthan

Access Setting

Masters Thesis-Open Access

Abstract

The effects of repulping variables (pH, surfactant concentration, time, and temperature) on deinking paper printed with flexographic ink were studied. A series of alcohol ethoxylate surfactants was evaluated. The one with HLB= 11.8 was selected for the majority of the study.

pH was the variable that presented the greatest effect on repulping and deinking. The brightness after repulping and the final brightness after deinking was significantly higher at pH 5 than at pH 9.

Paper was repulped for 15, 25, and 40 minutes respectively. Highest brightness after repulping and highest gain in brightness by flotation was observed after 15 minutes of repulping. No significant differences in deinking efficiency were found between 25 and 40 minutes repulping. A separate study found that most of the ink was rapidly redeposited on or within the fiber structure, with over 80% of the brightness loss occurring during the first 15 minutes of repulping. No significant differences in the units of brightness loss were found between the repulping times of 15 and 30 minutes.

Paper which was aged for eight months deinked more easily than three months-aged paper. The improvement was especially significant when no surfactant was added or when a hydrophilic surfactant was used.

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