Date of Award
Bachelor of Science
Paper Science and Engineering
Dr. John Cameron
Within the paper industry today, there are advancements in technology every year, every month, most likely every day as well. These new technologies work to obtain the same major goals. These goals include faster machine speeds for improved output. They-include less, pollution, and in fact are working towards a pollutant free system. And finally, product quality for today's high demanding consumer market.
To realize these goals, paper makers must effectively utilize the most amount of fiber and filler possible in their sheet. That is, they must bind up fines and filler within the sheet rather than sending it to the sewer. To achieve this a mill's first pass retention-must be high. This is becoming more and more difficult with today's higher machine speeds.
One possible solution to this problem is to incorporate a microparticle system into the process. In the past retention aids such as Alum (Al2(S04)3) were used to bring negatively charged species such as fiber and fillers together to achieve higher retention levels. With today's higher machine speeds however, Alum suffers under the higher sheer conditions.
To combat this problem, positively charged polymers are used to help bind up the particles and fines within the sheet. There is a limit to the amount of polymer that be added due to the fact that the floes formed by this polymer are large and can affect formation within the sheet. This is where microparticle technology can be particularly effective.
The system to be tested on a fine paper grade furnish consisting of 80% bleached, virgin, kraft hardwood and 20% bleached, virgin, kraft softwood. The filler loading was precipitated calcium carbonate (PCC) at 15 % solids. There were no other additives to the system in order to provide for a system with as few variables as possible.
By adding microparticle to the system, it is hypothesized that one can use less polymer in order to gain a higher first pass retention, and still maintain the desirable levels of formation. Drainage tests were also run in order to confirm the activity of the microparticle in the system. Two microparticles that will be used in this study are BMA-0 (unstructured) and BMA-780 (structured). There effects were measured within a system based on a Britt Dynamic Drainage Jar study.
The microparticles were tested at constant polymer dosage· and were determined to very little, if any effect on retention within the system. They were also run at constant addition rates themselves, while varying the polymer dosage. It was found that the polymer dosage seemed to be the only variable which affected retention. This holds true with current industry trends.(5) Adding microparticle to the system did in fact, increase the drainage of the pulp sample. It should be noted that polymer also helped to increase drainage as well. When coupled together, the enhanced drainage of the microparticle was evident.
Vermullen, Scott, "Silica Gel: An Experiment in surface area" (1997). Paper Engineering Senior Theses. 556.