The acrylate copolymer emulsion modified with organosilicon is called silicone acrylate emulsion. Polysiloxane has excellent low temperature resistance and high temperature resistance. It can overcome the fatal shortcoming of acrylate polymer emulsion "thermal viscosity, cold crisp" by modifying acrylate polymer emulsion. It can give emulsion polymers excellent weather resistance, water resistance, anti fouling, breathability, light retention, color retention, gloss and powdery resistance. The copolymer emulsion can have good film forming, adhesion and construction properties. The service life of the emulsion polymer can be greatly extended. Therefore, the organosilicon modified acrylate polymer emulsion can be used to prepare the high-grade exterior wall coatings. It can also be used for the use of adhesives manufacturing, fabric finishing, leather finishing, metal material bottom coating, machine equipment coating and so on.
There are two methods of physical modification and chemical modification with organosilicon modified acrylate polymer emulsion. The physical modification method is to blend the silicone resin emulsion with the acrylate copolymer emulsion in a certain proportion to achieve the purpose of modification. Because the stability of the blend emulsion is poor, and the modification effect has some limitations, more chemical modification methods are adopted at present. The chemical modification method is a random copolymer emulsion through the emulsion polymerization of organosilicon monomers and acrylate monomers. Or a copolymer emulsion with block or graft polymer molecules.
The production process of silicone modified acrylate copolymer emulsion can be divided into seven steps: batch method (one batch feeding method), seed emulsion polymerization, pre emulsifying semicontinuous method, pre emulsifying full continuous process, non pre emulsifying full continuous method, monomer drop method and initiator drop method. The properties of polymer emulsions and emulsion polymers obtained by different production processes are different.
The temperature of the conventional emulsion polymerization is usually above 80 degrees centigrade. However, at this temperature, siloxane is liable to hydrolyze and crosslink in aqueous phase, which will seriously affect the copolymerization of acrylate monomers and organosiloxane. Therefore, it is best to use the redox initiator to reduce the polymerization temperature as much as possible. The test shows that it is reasonable to control the reaction temperature at 60-62 degrees centigrade. In addition, both acid and alkali can catalyze the hydrolysis and polycondensation of organosiloxane, so the polymerization should be carried out under the neutral condition of pH value of 6-7.