Preparation And Mechanism Of Retention And Drainage Aids Obtained By Modified Organobentonite Microbeads

Choosing a reasonable and efficient drainage and retention aids can effectively reduce the amount of white water and the subsequent dehydration pressure to obtain high-speed of papermaking machine’s and height cycle mode of white water. China is rich in resources, but the bentonite s montmorillonite content is low so that the utilization of local bentonite is ineffective and limited.This paper synthesized anionic polyacrylamide (APAM) by inverse micro-emulsion polymerization, cooperating with sodiμm carbonate to modify calciμm bentonite with the low content of montmorillonite and detected the retention and drainage properties of aids composed by CPAM and organobentonite and research its mechanism.In the inverse micro-emulsion polymerization reaction, we learned that as the monomer molar ratio of acrylic acid:acrylamide varied from 1:1 to 1:3, the conversion of acrylamide rate increased, the intrinsic viscosity, the negative charge density and the viscosity-average molecular weight of APAM declined. With the monomer molar ratio of acrylamide increased, the boundaries of APAM particles were unobvious and sticked together, leading to the particle surface smooth and no obvious edges and corners.In the semi-dry process of APAM and sodiμm carbonate co-modified calciμm bentonite, we found that with the increase of the amount of APAM, the modified bentonite s expansion, charge density and Zeta potential were increasing, although the particle size firstly decreased and increased lately. The performence of the retention and drainage aids composed with CPAM and organobentonite(OR-BEN) on the pulp fines retention and the drainage property increased firstly and declined after, as the amount of 1%, the retention and drainage property was best, separately of 90.26% and 74.7s. With the increase of milling time, the expansion OR-BEN was increasing, and the particle size was decreasing, and the charge density was increasing firstly and was still lately, and the Zeta potential was decreasing firstly until still. In the same time, the retention and drainage performance of aids were increasing firstly and still after. When the concentration in the process of ball milling was less than 50%, the properties of OR-BEN was constant, but when more than 50%,these were poor. The add of APAM had no effect on the layer spacing of the OR-BEN.When the amount of CPAM was at 0.08% and OR-BEN at 0.2%, the retention and drainage system could achieve the best performance, and fines retention rate was 90.26%. But the add of sodiμm chloride, alμminμm sulfate seriously affected the retention and drainage performance of the aid until becoming invalid. Added the aids to paper, we obtained a good effect on paper tensile index and tear index, increasing with 70.76% and 64.67% respectively, compared with the paper added with commercial bentonite, the retenton and drainage increased as the same. The scanning electron microscope images showed that after modified with organic compound in the semi-dry way, the plates of OR-BEN were destroyed and appeared as small fragments, and the surface of fragments was smoother than calciμm bentonite, having a poor flatness.