Benzoic acid terminated oligoesters as melt flow modifiers of

Abstract

The application discloses a mixture of high molecular weight hard resins, such as polymethyl methacrylate, cellulose acetate butyrate and cellulose nitrate with low molecular weight benzoic acid terminated polyesters having a glass transition temperature in the range of -30.degree. C. to 40.degree. C. and a molecular weight in the range of 500 to 1500. The hard polyesters of this invention are obtained by the use of small diols and hard dibasic acids in addition to termination of the chain by the hardening component benzoic acid. Saturated linear dicarboxylic acids are used for less than half of the acid monomer content, on a molar basis, since these are softening components. The polyesters are used to lower the melting point and improve the flow of the high molecular weight polymers without excessively plasticizing these high molecular weight polymers to the point where they are noticeably softened at use temperatures. In contrast, the usual polyesters contain high amounts of saturated dicarboxylic acids and are terminated with saturated fatty acids. The mixture is useful for coatings applied in the form of a powder, a solution or a dispersion. Molded and cast articles can also be made from this mixture. As used herein, 'thermoplastic' includes thermosetting resins which go through a thermoplastic flowable stage before becoming thermoset.