Date of Award

12-1980

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

A literature review is presented that reviews the various considerations of retention in papermaking. The definition of retention and the three methods of retention,(sieving,entrapment, and coflocculation), are reviewed. Coagulation and flocculation are respectively discussed. Zeta potential and the various methods with which it is measured are reviewed, as well as various factors that influence zeta potential. The role of fines in the retention of wet end additives in the papermaking process is also discussed.

An experiment is designed to evaluate the effect of fiber length on titanium dioxide pigment retention. The experiment involves the determination of an optimum level of addition of a cationic retention aid in order to achieve maximum retention of titanium dioxide pigment in a papermaking furnish. A Laser-Zee microelectrophoresis meter was used to determine this point of optimum flocculation.

A 50% hardwood- 50% softwood furnish was prepared and beaten to a CS freeness of 500. This pulp was fractionated with a Clark Fiber Classifier into four different distributions. Each fiber fraction was placed in a Dynamic Drainage Jar at 0.5% consistency along with 20% by weight of fiber TiO2. Three different levels of retention aid addition and three different levels of shear were used with each fiber length. 100 ml samples were taken at each level of shear and each level of addition. These samples were filtered and ashed in order to determine retention of the TiO2 .

The results showed a significant improvement in retention at levels of retention aid 100 and 200 times the calculated optimum addition level of 0.001 lb./ton. Optimum retention was obtained at the lowest level of shear for each fiber length. Shorter fibers appeared to provide better retention than longer fibers, regardless of shear rate and retention aid level.

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