Preparation and characterization of organosilicon RAFT-modified anionic surface sizing agents

Abstract

Novel anionic surface sizing agents were innovatively prepared to improve the compatibility of macromolecular silicones with acrylates and to enhance the performance of paper. In this paper, a novel anionic surface sizing agent was synthesized for the first time by using a silicon-based RAFT reagent (RAFT-PDMS) with acrylic resin and diacetone acrylamide (DAAM). Specifically, DAAM and acrylate monomers are introduced by reversible addition-breakage chain transfer (RAFT) polymerization and cross-linked with adipic dihydrazide (ADH) to obtain sizing emulsions. The properties and characteristics of the emulsions and latexes were analyzed by laser particle size analyzer, transmission electron microscope, rheometer and differential scanning calorimeter. The results indicated that the increase of RAFT-PDMS content was able to reduce the particle size from 119.5 nm to 57.98 nm and the glass transition temperature (Tg) from 48.3 °C to 42.3 °C. Then, the silicone modified emulsions were mixed with starch to obtain surface sizing agents (PDMS-Y-PA) with excellent properties. The increase of RAFT-PDMS content was further verified by gloss meter, 3D profilometer and scanning electron microscope observation to improve the gloss of paper surface and reduce the surface roughness. In addition, we confirmed the excellent hydrophobic properties of PDMS-Y-PA sizing paper by contact angle and Cobb value measurements. The Cobb value of the paper was reduced by 33.28 % and the contact angle increased from 83.9° to 111.7°. Finally, we compared the mechanical strength of the base paper with that of the sizing paper. The folding resistance, bursting strength and ring compression index of the sized paper all showed great improvement, and the tensile strength increased by 197 %. This modified anionic surface sizing agent enhances the water resistance and mechanical properties of paper on the basis of safeguarding paper properties and has great application prospects.