Concentrates for improving polyester compositions and method of making same

A polyester foam composition comprising a mixture of Components (A) and (B),

• wherein Component (A) is prepared prior to mixing with Component (B) by the melt blending of:
• 1) about 50 to about 99 weight % of a polyolefin selected from (1) ethylene homopolymers and copolymers of ethylene with .alpha.-olefins having 2 to 10 carbon atoms having a melt index of about 0 to about 100 at 190.degree. C. and (2) propylene homopolymers, 1-butene homopolymers and copolymers consisting of propylene and/or 1-butene having a melt flow rate of about 0 to about 100 at 230.degree. C.;
• and
• 2) about 1 to about 50 weight % of one or more polyfunctional carboxylic acid, anhydride or polyol branching agents selected from the group consisting of trimesic acid, pyromellitic acid, pyromellitic dianhydride, trimellitic anhydride, 1,2,3,4-benzenetetracarboxylic acid, glycerins, trimethlolpropane and pentaerythritol;
• wherein Component (B) comprises one or more polyesters comprising repeat units from an aromatic, aliphatic or cycloaliphatic dicarboxylic acid having 6-40 carbon atoms, and an aliphatic or cycloaliphatic glycol having 2-10 carbon atoms, and
• wherein said polyester composition comprises from 1000:1 to 4:1 ratio by weight of Component (B) to Component (A).