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In the papermaking process, pulp paper fibers and fillers such as hydrophobic, there is a tendency of flocculation into a group, are often difficult to obtain uniform performance, strength paper that meets the requirements. Need to add an additive to increase the viscosity of the pulp, in order to facilitate uniform dispersion of fibers and fillers, so ferreted out the paper without holes uniformly smooth and flexible, so that stable performance papermaking, paper and paper-making is not easy to break from the powder, and can improve the tensile strength and wet and dry paper and pulp savings. Such additives added to the papermaking called dispersant..
There are many paper dispersant. There are LBD-1-carboxylic acid salts such as dispersants, starch modification. And it should have a thermal hydrolysis, with increasing temperature the viscosity decreased rapidly characteristics, thus ensuring not affect the performance of the original dry paper fibers.
Ultra high molecular weight anionic polyacrylamide polymer is a water-soluble organic polymer, soluble in water and forms a highly viscous liquid, at low addition amount can promote good dispersion of papermaking fibers and excellent sheet formation, improve pulp evenness and the softness of the paper, but also increased the strength properties of paper. Use in paper coating, paper dispersant has high dispersion efficiency, coating viscosity stability, less foam, non-toxic, non-corrosive, can paint solids content increased, and the mobility and scrub resistance, gloss paper can be maintained degree, easy to change mold. Paper dispersants can also increase the speed papermaking, beating save time, reduce energy consumption, with significant economic benefits.
Used as a dispersant is generally the sodium, because of a molecular chain containing a carboxyl group on the cellulose fibers are negatively charged dispersion effect, and when a relative molecular weight of about 3,000,000, to improve the slurry viscosity, is conducive to the fiber suspension, so is a long fiber efficient dispersant
Since the dispersion mechanism of PAM, molecular chain containing a carboxyl group, having the effect of reducing the surface tension, helps water wet solid, which is particularly advantageous for the dispersion of fibers in water, fillers and the like, when the PAM added to the slurry, can fiber, filler surface bilayer structure, the outer terminal of the dispersant has a strong affinity for water, increasing the level of fiber, filler and other solid particles are wetted water. Due to the electrostatic repulsion between the fibers, fillers and other solid particles away, to achieve good dispersion. Polyacrylamide as retention and drainage aids, rational use can obtain the following results: ①increase fines and filler retention, and in a paper dust content of increased quantitative increase; ②lower concentrations Whitewater net acceleration whitewater fines the sedimentation rate; ③improve drainage properties of paper materials; ④reduce forming networks of wear, keep clean blankets; ⑤undermine the evenness of a paper, which is one of the negative effects of the use of PAM
Generally used in papermaking dispersant ionic polyacrylamide having a molecular weight 17 million APAM appropriate, dissolution time about 60 minutes. Generally used napkins, newsprint, fine paper and toilet paper.
Note APAM papermaking dispersant used: dissolving an anionic polyacrylamide when the stirring speed is not too fast, to prevent the occurrence of mechanical shear degradation of the molecular chains. APAM dosing rate cannot be too fast to even prevent clumping form insoluble.