Effect of polyvinyl alcohol with a thiol end group on the properties of polyacrylic dispersions and spray-dried powder

Abstract

The emulsion polymerization of highly shear-stable copolymer dispersions of methyl methacrylate and butyl acrylate were carried out using poly (vinyl alcohol) with a thiol end group (PVA-SH) as protective colloid. The dispersions can be transformed into corresponding redispersible powder via a spray drying-cooling process. On-line FT-IR monitoring shows that grafting polymer of PVA-g-PMMA was formed mainly at the stage-1 of the emulsion polymerization. TEM images show, the PVA-SH shell was fragmentary when adding SDS at initial stage and integrated when adding at particle growing or final stage. The particle size turns to be smaller when delayed adding SDS surfactant. Triethanolamine, a co-regulator of PVA-SH, controlled the M _n to 50 000–70 000 and reduced the PDI to 1.5–1.7. The acrylic dispersions with 0.8wt%–1.5wt% PVA-SH₁ can be spray-dried into super dispersible polymer powder (SDPP), which can easily disperse in water and form reconstituted dispersions with an average particle size smaller than 1 micron.

Keywords

thiol poly (vinyl alcohol) / polymeric emulsifier / emulsion polymerization / redispersible powder

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