Acrylic oligomers as melt flow modifiers of thermoplastic coatings and

Abstract

The application discloses a mixture of high molecular weight hard resins such as polymethyl methacrylate, cellulose acetate butyrate, and cellulose nitrate containing a minor proportion of a very viscous or solid oligomer of one or more vinyl monomers such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tertiary butyl methacrylate, isobutyl methacrylate, or tertiary butyl acrylate, which monomers when polymerized give a polymer which has a glass transition temperature calculated by the formula used for high molecular weight polymers to be at least 30.degree. C., and preferably at least 50.degree. C. The oligomers have a number averaging chain length of 4 to 25 mers. They have a narrow molecular weight distribution such that the ratio of the weight average molecular weight to the number average molecular weight is 2 or less, preferably less than 1.5. This ratio is referred to as the heterogeneity index. The oligomers are used to lower the melting point and improve the flow of the high molecular weight polymers and yet do this without excessively plasticizing the hard polymers to a point where they are noticeably softened at the use temperatures as contrasted with fluid oligomers and oligomers of 'soft' monomers such as butyl acrylate, ethylhexyl acrylate, ethyl acrylate, octyl acrylate, and lauryl methacrylate. The mixture is useful for coatings applied in the form of a powder, solution, or dispersion. Molded and cast articles can also be made. As used herein, 'thermoplastic' includes thermosetting resins which go through a thermoplastic flowable stage before becoming thermoset.