THE ROLE OF POLY (ETHYLENE OXIDE)-WATER SOLUTION-PHASE BEHAVIOR IN THE RETENTION OF FIBER FINES AND CLAY

The retention of fibre fines and clay particles in chemi-thermo-mechan ical pulp (CTMP) suspensions with poly (ethylene oxide) as a retention aid was investigated. The experiments were conducted at 303 and 343 K . These two temperatures correspond to points below and above the Lowe r Critical Solution Temperature (LCST) of a 0.005 mass% Poly (ethylene oxide) solution in the presence of 2 mol/L KCl. The KCl was added to lower the LCST to a temperature near papermaking conditions. Poly (eth ylene oxide) with molar masses of 1 x 10(6) and 5 x 10(6) Da was used. All the LCST measurements of the poly (ethylene oxide)-KCl system agr ee with those in the literature. The retention study revealed that con siderably more fibre fines as well as clay are retained at temperature s above the LCST. In particular, the average fibre fines retention was 5.9 percent at 303 K and 22.1 percent at 343 K when the poly (ethylen e oxide) with the molar mass of 1 x 10(6) Da was used. Clay retention was also measured and found to be 5.0 and 15.9% at 303 and 343 K, resp ectively. Higher retention values were obtained when the polymer with a molar mass of 5 x 10(6) Da was used. At 303 K the fibre fines retent ion was 55.0%, whereas at 343 K it was 82.2%. The corresponding clay r etentions were 31.7 and 71.9%.