Detection Of Surface Viscosity Of Stickies And Controlling Of Stickies By Phospholipase

Recycling of waste paper has the advantages of saving plant fiber raw materials,reducing environmental pollution, reducing energy consumption and reducing production costs and other advantages. However, stickies can do a lot of harm to the recycling and this problem can not be avoided. During the process of papermaking stickies present in waste paper, such as natural extractives, coating adhesives, hot-melt adhesives and pressure-sensitive adhesives, will adhere and deposit onto the inside wall of the headbox,pipes, wire and blanket, thus influencing the operation of the paper machine. Stickies will also result in stains, holes and other paper diseases and finally impact the paper product if they are carried in the paper inside along with fibers. Therefore, how to effectively remove and control stickies has been a problem for the paper industry to be solved.In this paper, the method using peeling strength to test the the surface viscosity of stickies was improved at first. Surface viscosity of stickies in waste paper pulp under different metal ion content, temperature, pH and enzyme treatment conditions were measured, deposition area and deposition number of stickies were also measured, then the relationship between the surface viscosity of stickies and its deposition tendency was further clarified. Phospholipase was used to control stickies in the waste paper pulp. The reaction mechanism of the phospholipase on stickies was confirmed by FT-IR, GC/MS,UV spectrophotometer and acid value detection. Control effect of stickies by phospholipase was investigated and was compared with that of lipase. In the experiment the optimal reaction conditions of phospholipase were explored and then phospholipase was used together with surfactant to control stickies. Finally, the effects of complexes on the properties of paper were investigated.The study on the surface viscosity of the stickies showed that the change of the conditions of the pulp system, such as inorganic salt content, temperature, pH, and enzyme treatment all affect the surface viscosity and deposition tendency of stickies. To be specific ,the addition of inorganic salts into the pulp, the increase of temperature and pH will strengthen the surface viscosity of the stickies, then the increased surface viscosity will enhance the deposition tendency of stickies, finally making the deposition area and deposition number of stickies higher. It is suggested to select the raw material of waste paper with lower filler content and use the water with lower metal ions content. Besides, in order to reduce the deposition tendency of stickies and its harm to the production process and the quality of paper , high alkaline substance content and high temperature of the pulp system should be avoided and enzymes can be utilized to control stickies.The reaction mechanism of phospholipase onto stickies is that phospholipase can act on the ester bond in stickies and destroys it, finally hydrolyzing stickies into fatty acids and alcohols. The best conditions for phospholipase to control stickies are as follows:temperature 60 ℃, pH 5.5, dosage of phospholipase 0.1% and treatment time 2 hours. The content and surface viscosity were lower after the treatment of phospholipase alone, and its control effects was better than that of lipase.Surfactant TDA100 was selected as the most effective surfactant among several kinds.The optimum ratio of phospholipase to surfactant TDA100 was 4:1, the dosage of phospholipase and TDA100 were 0.1% and 0.025% (relative to absolute dry pulp),respectively. Complexes of phospholipase and TD A100 were used to control stickies under optimal conditions, and results showed that peeling strength of stickies dropped from 0.1632 N/mm to 0.0461 N/mm, the surface viscosity of stickies was greatly weakened,removal rate of macrostickies reached 83.4%, CD value, turbidity and particle size were all reduced when compared with that of blank samples, indicating that the control effect of stickies was good.Waste paper pulp was treated with complexes of phospholipase and TDA100 and then made into hand sheets, detection results showed that the complexes treatment has no adverse effect on the physical strength properties of the handsheets, but can improved the physical strength property of the paper, and the formation, whiteness and residual ink index of the handsheets were also improved.