| 摘要 |
A polyester coating composition, suitable for use as a wire varnishes comprises (1) a linear hydroxyl polyester derived by reacting terephthalic acid or a mixture thereof with isophthalic acid (or functional derivatives thereof) in ethylene glycol and having a viscosity number of greater than 0.5 and (2) a branched hydroxyl polyester derived by reacting tere- and/or iso-phthalic acid (or functional derivatives thereof), ethylene glycol and a saturated aliphatic polyhydric alcohol containing at least three hydroxyl groups (e.g. glycerol, pentaerythritol, trimethylolpropane, trimethylolethane, sorbitol, mannitol, diglycerol or dipentaerythritol). Preferably polyester (1) contains 70-50% terephthalic acid and 30-50% isophthalic acid and polyester (2) is derived from terephthalic acid, ethylene glycol and glycerol. The mixture may be dissolved in organic solvents, e.g. phenol, cresols, xylenols, diacetone alcohol and methoxyethyl acetate which may be used alone or in admixture with a diluent (e.g. benzol). The composition may also contain a hardening agent, e.g. an organic salt of Zn, Ce, Zt, Sb, Mg, Na, Mn, Co or Pb (e.g. zinc or lead octoate), an alcohalate of Na, Mg or Al; or a compound of Ti, Al, Si or B (e.g. tetrabutyl titanate or a polymer thereof). |
