The Controlling Of Stickies In Deinking Pulp Process By Enzyme

Waste paper recycling is one of important direction to achieve sustainable development of paper industry. However, with increase of recycled paper, adhesive contaminants (stickies) become one of the biggest technical challenges in papermaking. These adhesive materials not only affect the papermaking process but also the quality of the final product seriously. In this study, a rapid measurement method to predict the stickies content in recycled pulp was developed. A technical of controlling stickies by enzymes was systematically studied, and the depositional mechanism of stickies was also discussed.There were a good relationship between Near Infrared Spectroscopy and stickies content of pulps, which can become a feasible way to fulfill rapid analysis requirement. No matter which types of samples(Deinked Pulp or Liner Board)and analysis methods of stickies content (Screening method or HPLC-ELSD method), the vector normalization method was the best spectral pretreatment methods compared with other methods such as first derivative, straight line subtraction, vector normalization, and the spectral information in 4601.6- 4246.8cm-1 were implemented within calibration models.Compared with different analysis methods of stickies content, the calibration model developed using the data of total stickies content was more accurate to predict unknown samples. The calibration model for deinked pulp was more accurate than the model for Liner Board by using the same measurement method.Considered of various factors, such as the pulp quality and control performance of stickies, the optimal conditions for control stickies in process were: (a) pretreatment by xylanase: pulp consistency 10%, 60℃, 60min, pH 5.5, enzyme dosage 3 IU ? g-1; (b) after treatment by esterase: pulp consistency 10%, 50℃, 120min, pH 9, the enzyme dosage 4 IU·g-1. By this control process, the decrement of stickies content of recycled pulp can be reached about 68%, and the tensile index and tear index increased by 33.4% and 35.6%, respectively. Pulp storage time extended from 1 day to 32 days, the amount of THF extracts decreased by 33%; the stickies content in the THF extract reduced by about 63% in the 12-day period, then the decrease trend of stickies content slowed down after this time. The extractives from pulps were analyzed by GPC and FT-IR to show that a large number of esters bond of THF extracted polymers were degraded and the molecular weights of THF extractives decreased slightly.