Abstract
Dual-chemical retention systems based on 2 cationic polyacrylamides, a colloidal silica, and a globular anionic polymer microparticles were investigated and an exfoliated nanoparticle indigenous mica mineral, sericite, was examined for its efficacy in substituting commercial microparticle preparations. The results indicated that nanosericite generated FPR between 76.9 and 80.9% for fines and chemicals. Its ash retention values, however, were higher and tended to increase with doses of polymer, nanosericite, or Sc to between 16 and 24%. As for paper physical properties, nanosericite was not amenable to substitute the c-PAMb/polymer with only handsheet stiffness superior to the combination. Nanosericite, however, showed good substitution capacity than the c-PAMa-colloidal silica combination. Regardless of the c-PAMa doses, all examined handsheet physical properties incorporating nanosericite were superior to colloidal silica. The optimal performance was observed with c-PAMa dose of 200 ppm. Optical properties of the handsheets indicated that with nanosericite substitution, brightness values were comparable to the polymer group, while its substitution capacity for colloidal silica decreased with increasing c-PAMb dose. Only at c-PAMa dose of 300 ppm, it appeared to have good substitution for colloidal silica. Substituting nanosericite for colloidal silica appeared to reduce the c-PAMa charge and increased the overall cost effectiveness.
Highlights
Dual-chemical retention system has been used in papermaking wet end for decades
The most frequently deployed dual-chemical system comprises low molecular weight cationic polyacrylamides as the cationic polymers, together with anionic charged microparticles with size range from 1 nm to 1 μm which are insoluble in water and have large specific surface areas [6,7,8,9]
The actual procedure was as follows: (1) pulp was disintegrated at 0.3% consistency with a standard disintegrator; (2) sizing agent (AKD, 1%), cationic starch 1%, and filler 25% were added in sequence separately and maintained in stirring for 30 min; (3) polyacrylamide was added and stirred for 60 s; (4) microparticle was added and stirred for 60 s; (5) handsheets of 60 g/m2 were formed using a standard sheet mold, air-dry overnight; (6) handsheets were conditioned in the standard atmosphere for >24 h; and (7) handsheet physical and optical properties were measured
Summary
Dual-chemical retention system has been used in papermaking wet end for decades. The system uses short-chain branched cationic polymer to destabilize the well-dispersed state of pulp and which is conducive to the formation of small flocs with surface cationic charges. The most frequently deployed dual-chemical system comprises low molecular weight cationic polyacrylamides as the cationic polymers, together with anionic charged microparticles with size range from 1 nm to 1 μm which are insoluble in water and have large specific surface areas [6,7,8,9]. Major suppliers such as BASF, Eka, Nalco, and Ashland offer microparticle systems mostly of colloidal silica or globular high-molecular polymers. The information may provide reference for further developing NS as a viable paper-making chemical
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