Acrylic Polymer Medium: Methyl Methacrylate Emulsified by Persulfate Alone

Acrylic polymer medium is an emulsion of acrylic polymer in water, the binder of acrylic paint. ICI's Renfrew and Gates (US 2,296,403, 1942) found that a persulfate alone both keeps the monomer dispersed and starts it polymerising, so no soap is needed. Their Example 2 stirs 30 parts methyl methacrylate and 20 parts dibutyl phthalate (a plasticiser) hard in 100 parts water with 1 part persulfate at about 80 °C; the batch heats itself to 90-95 °C and gives a very stable emulsion. Using it as paint medium is our choice. The picture: our diagram.