Polyesterimide resins and synthesis thereof

A process for preparing a polyesterimide resin having increased stability against gelation and wherein during the process, sublimation of the lower dialkyl ester of a phthalic acid component is substantially reduced, which process comprises reacting under ester imide resin forming conditions a reaction mixture composition consisting essentially of:

• (I) an imide-group-contributing component selected from the group consisting of
• (A) both (1) a diamine component and (2) an anhydride component including at least one (a) aromatic carboxylic acid anhydride containing at least one additional carboxylic group, said additional group being esterifiable and substantially non-imidizable, or (b) the corresponding acid thereof containing two-imide-forming vicinal carboxylic groups in lieu of the anhydride group.
• (B) the carboxy functional polyimide reaction product of said diamine component and said anhydride component, and
• (C) mixtures of (A) above and (B) above;
• (II) an ester-group-contributing component comprising
• (D) at least one dihydric alcohol containing two esterifiable hydroxy groups,
• (E) at least one polyhydric alcohol containing at least three esterifiable hydroxyl groups,
• (F) at least one lower dialkyl ester of a phthalic acid component selected from the group consisting of terephthalic acid, isophthalic acid, and mixtures of said acids;
• and
• (G) a saturated aliphatic monohydric alcohol selected from the class consisting of n-hexanol, 2-ethylhexanol, n-nonanol n-decanol, n-dodecanol, 2-butyloctanol, tetradecanol, 2,6,8-trimethylnonane-4-ol, and mixtures thereof, wherein said reaction mixture comprises (a) from about 0.035 to 0.25 mole of the dihydric alcohol, (b) from about 0.025 to 0.15 mole of the polyhydric alcohol, (c) from about 0.03 to 0.18 mole of the lower dialkyl ester, (d) from about 0.1 to 0.2 mole of the aromatic carboxylic acid anhydride containing at least one additional carboxylic group, (e) from 0.05 to 0.10 mole of the diamine component, and from about 1.0 to 20.0 parts of the monohydric alcohol, said amounts being per 100 parts, by weight, of the total weight of the five components (a) through (e) recited herein.