Oxazoline polyester oligomers

DETAILED DESCRIPTION OF THE INVENTION The present oligomers are prepared from monocarboxlic acids, dicarboxylic acids or anhydrides, glycols and tris-hydroxyakyl amino methane.
The basic components of the polyester oligomer are the dicarboxylic acid or anhydride and the glycol.
Dicarboxylic acids which can be used in the preparation of the present oligomers include those having the general formula ##STR1## wherein R is a saturated aliphatic or an aromatic moiety of 2 to 30 carbon atoms.
When R is aliphatic, it preferably has from 2 to 12 carbon atoms.
When R is aromatic, it preferably has from 6 to 28 carbon atoms.
Of these, aromatic dibasic acids are preferred, of which phthalic, iso-phthalic, terephthalic, uritic and cumidimic acids have been found to be particularly satisfactory.
In addition, alicyclic dicarboxylic acids such as hexahydrophthalic anhydride and orthophthalic anhydride can be used.
The second basic component of the present polyesters is a branched-chain glycol.
Preferably, the glycol contains less than 8 carbon atoms.
Glycols that have been found to be particularly satisfactory include neopentyl glycol and pinacol.
A third component for the polyester oligomer, which is necessary for the formation of the oxazoline moiety, is tris-hydroxyalkyl amino methane, in which the alkyl groups have from 1 to 3 carbon atoms.
Of these, tris-hydroxymethyl amino methane is preferred.
The ratios of the components used in the reaction mixture, in general, will be adjusted to provide the molecular weight desired in the final oligomer.
The dicarboxylic acid should contain an aliphatic dibasic acid, but can also comprise an aromatic dibasic acid.
When both aromatic and aliphatic dibasic acids make up this reaction component, the ratio of aliphatic to aromatic acids should be about from 100:0 to 10:90.
The balance of dibasic acid to glycol should be adjusted so that the average molecular weight of the oligomer does not exceed 10,000.
The molecular weight of the polyester oligomer, for purposes of the present invention, is determined using gel permeation chromatography and a polystyrene sample, according to ASTM method D-3593-80