Redispersible emulsion powder - VAc/BA copolymer emulsion
The invention relates to a synthesis method of VAc/BA polyemulsion for redispersible emulsion powder, belonging to the technical field of copolymer emulsion.The steps are divided into the following three steps: 1) add deionized water and polyvinyl alcohol to the reactor, heat 80℃ to completely dissolve polyvinyl alcohol, add polyvinyl acetal solution, cool it to 60-65℃, and add non-ionic emulsifier, ionic emulsifier and buffer.2) mix vac and butyl acrylate monomers, add 1/5 of the mass of the mixed monomer into the reactor, pre-emulsify for 1h, add some initiator to initiate monomer polymerization, and drop the remaining monomer and initiator into the reactor after 30min;3) heat up to 75-80℃, heat preservation reaction for 1h, and cool the discharging.The emulsion prepared by the invention can be used to modify cement mortar, the synthesis process is simple, the pollution is small, and the re-dispersible emulsion powder can be prepared by spray drying.
1. A synthesis method of VAc/BA copolymerized emulsion for redispersible emulsion powder, which is characterized by the preparation of VAc/BA copolymerized emulsion with non-ionic/ionic emulsifier using vinyl acetate and butyl acrylate as raw materials and polyvinyl alcohol and polyvinyl acetal solution as protective colloid.
It includes the following steps:
1) add deionized water and polyvinyl alcohol to the reactor equipped with stirring paddle, thermometer and refluxing condenser. Open the stirring paddle, heat up 80℃ and completely dissolve polyvinyl alcohol. Add polyvinyl acetal solution and cool it to 60-65℃.
2) mix vac and butyl acrylate monomers, take 1/5 of the mass of the mixed monomer and add it to the reactor of step 1), preemulsify for 1h, add some initiator to initiate monomer polymerization, after the reaction for 30min, add the remaining mixed monomer to the reactor, and add the remaining initiator for 4-6h;
3) the new VAc/BA copolymer emulsion with viscosity of 200-400cp and solid content of 40%-44% was obtained by heat preservation reaction at 75-80℃ for 1h and discharging by cooling.
2. According to the above methods, the characteristics of the polyvinyl alcohol are as follows: PVA1788 and 1.0%-5.0% of the mass of mixed monomer;The mass concentration of polyvinyl acetal solution was 10%, the degree of acetal was 9%, and the dosage was 0.5% to 2.0% of the total mass of mixed monomer.The non-ionic emulsifier was op-10, and the dosage was 0.5-1.5% of the mass of the mixed monomer.The ionic emulsifier is one or more of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate. The dosage is 0.5-1.5% of the mass of mixed monomer.Buffer for sodium bicarbonate, sodium acetate, sodium dihydrogen phosphate one or more, the dosage of mixed monomer mass of 0.5%-1.0%;, the ratio of vac to butyl acrylate in the mixed monomer was 7∶3-9∶1.The ratio of vac to butyl acrylate in the mixed monomer was 8∶2.The initiator was a 2% persulfuric acid solution with a mass concentration of 0.3-0.6% of the mass of the mixed monomer.
redispersible polymer powder
,redispersible latex powder,rdp,vae