Лако-красочные материалы — производство

In this example, a copolymer of vinyl acetate (VA) and methyl methacrylate (MMA) is formed. As in the last example, a single surfactant and initiator are used and added to these are a buffer and a protective colloid.

Nitrogen is not required as the vapour pressure of vinyl acetate monomer ensures that an oxygen free atmosphere exists above the reactants. The reactivity ratio’s for vinyl acetate and methyl methacrylate indicate that MMA is 20-40 times more reactive towards free radicals than is VA.

The initial period of 30 minutes refluxing produces some copolymer rich in MMA and the addition of the balance of the monomer mixture at a rate approximating to that of the polymerisation ensures a random copolymer approximating 73% by weight of VA is formed. The use of a protective colloid (hydroxy ethyl cellulose) is partially responsible for the larger particle size compared to the methyl methacrylate homopolymer in the previous example.