Paper Coating Using A Core / Shell Structure Of Benzene - C - Silicone Copolymer Emulsion

A series of the title core/shell styrene-acrylate-siloxane copolymer emulsions were synthesized by pre-emulsified, stepwise emulsion co-polymerization and stepwise controlling pH techniques starting from styrene (St), methyl methacrylate (MMA), butyl acrylate (BA) and carboxylic monomer as hard core monomers, MMA, BA, epoxy monomer as soft shell-I monomers, MMA, BA, epoxy monomer and siloxane monomer as soft shell-2 monomers in the presence of ammonium persulfate (A PS) as initiator, sodium dodecylbenzene sulfonate (SDBS) and octyl polyoxyethylene glycol (OP) as composite emulsifier. Many technical conditions, polymerization stability, calcium ion stability, storage stability and film-forming properties of emulsions were studied. The rheological properties, chemical structure, glass transition temperature (Tg), thermal-oxidation stability, water-resistance, stain-resistance and other properties of copolymers (including latex films) were characterized. From the experimental data, it was found that: The core and shell for copolymer emulsions were connected by chemical bond through the reaction of carboxylic and epoxy group. Almost half of siloxane monomer participated in co-polymerization. Latex particles had good stability and film-forming properties at lo~ver temperature (room temperature). The latex films had formed moderate cross-linkage by self-cross linking during dried at 60 or 1050C, which were transparent, bright and had excellent properties such as water-resistance, stain-resistance, solvent-resistance and thermal-oxidation stability etc. The materials had rich and facilitate source. And the emulsions prepared were ideal gloss paper coatings. A series of better technical conditions were selected as follows: core/shell ratio 50/50; carboxylic monomer concentration3-4%; epoxy monomer concentration 6-8%; siloxane monomer concentration ~ 10%; pH controller amount 0.2g; composite emulsifier ratio 70130; composite emulsifier concentration was 3% of the whole amount of water and monomers in emulsions; APS concentration 0.2%; 70% core monomers were firstly pre-emulsified and co-polymerized by batch feed mode, then 30% core monomers co-polymerized by semi-continuous feed mode without pre-emulsified ; Initiator for shell was added after shell pre-emulsified emulsion dropping; Core and shell-i monomers both co-polymerized at 80, and shell-2 monomers co-polymerized at 85+1 ; polymerization increased rate for core was 2 1mm, and for shell was lml/2min; pH controller solution was added before pre-emulsified emulsions for shell-2 dropping; p11 6-7; agitation rate 230rpm. Conversions were approximately 100%. In the studied range of shear stress (t) and shear rate (V), copolymer emulsions shown nearly Newton flow behavior. The thermal oxidation on-top temperature (To) were all above 220C, and glass transition temperature (Tg) were 14-40...