[Additives for mortar] VAE Re-dispersible Polymer Powder

VAE Re-dispersible Polymer Powder is a white or light-colored polymer powder, which is the main additive for dry-mixed mortars such as cement-based or gypsum-based mortars. Mainstream products include vinyl acetate and ethylene copolymer rubber powder (VAC/E), ethylene, vinyl chloride and vinyl laurate ternary copolymer rubber powder (E/VC/VL), vinyl acetate and ethylene and higher fatty acid vinyl ester terpolymer rubber powder. Yuan copolymer rubber powder (VAC/E/VeoVa). Among them, VAC/E occupies a leading position in the global field and represents the technical characteristics of vae copolymer redispersible. Latex powder is required to be redispersible in water, with good adhesion and fluidity when used in dry mixed mortar. When used in dry powder coatings, new requirements are put forward for its performance, that is, film formation at low temperature, no cracking in thick coatings, good water resistance, etc. VAE (rdp)  series products have the advantages of good bonding strength and low cost. , used in dry mixed mortar to meet its requirements.

The preparation process of VAE Re-dispersible Polymer Powder is mainly divided into two steps, namely emulsion polymerization and spray drying. The monomer used for emulsion polymerization determines the type of VAE Re-dispersible Polymer Powder. When selecting the monomer, both the glass transition temperature (Tg) and the minimum film forming temperature (MFT) should be considered. Polymers with high Tg are beneficial to the drying of emulsions, which can prevent the softening and adhesion of the polymer during the drying process and ensure its powdering. However, generally polymer emulsions with high Tg also have high MFT. Therefore, appropriate MFT must also be considered to ensure that the redispersion can form a film at a lower temperature. It is ideal to synthesize a soft-core and hard-shell polymer emulsion.

Spray drying is a process that uses an atomizer to disperse the liquid material into fine droplets and rapidly evaporates the solvent in a hot drying medium to form a dry powder product. Generally, spray drying consists of three stages: ① atomization of the material liquid; ② contact, mixing and flow of the mist group with the hot drying medium, that is, evaporation and drying of the mist droplets; ③ separation of the dried product from the drying medium. Since the emulsion is heated by hot air during the drying process and dehydrates rapidly, the latex particles in the emulsion will adhere or even agglomerate, affecting the performance of the vae copolymer redispersible. Therefore, the emulsion needs to be processed before drying, and some high Tg is usually added. Water-soluble substances act as protective colloids. Polyvinyl alcohol (PVA) is generally used as a protective colloid.