Heat-curable polyester compositions

摘要

A heat-curable polyester composition comprises (1) a polyester resin composed of the residues of terephthalic and/or isophthalic acid, ethylene glycol and a saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, (2) an organic polycarboxylic anhydride and (3) a certain tertiary amine. The latter is quinoline, an amine of formula R3N where R is a monovalent hydrocarbon radical (e.g. alkyl, aryl, aralkyl, alkenyl, cycloalkyl or cycloalkenyl), or a compound capable of generating such an amine on heating (e.g. a hydrochloride or acetate thereof or a quaternary ammonium hydroxide or methoxide derived from the amine). The polyester is preferably derived from the dialkyl ester of terephthalic and/or isophthalic acid and the polyhydric alcohol may be glycerine, 1:1:1-trimethylol ethane, 1:1:1-trimethylol propane, pentaerythritol, sorbitol, mannitol, diglycerol or dipentaerylthritol. The polycarboxylic anhydride is preferably one of formula where R1 is a tetravalent radical containing at least two carbon atoms. Many examples of suitable anhydrides are given. The polyesters may be mixed with fillers (e.g. wood flour, diatomaceous earth, carbon or silica) or other resins (e.g. epoxides, urea-, melamine- or aniline - formaldehyde, silicones, polyamides, polyethylene, polystyrene, cellulose acetate or butadiene-styrene resins) or dissolved in solvents (e.g. methylnaphthalene, cresol, N-methyl-2-pyroolidone, dimethyl acetamide or a mixture of diphenyl and diphenyl oxide). Uses.-Coating by wet and dry techniques, moulding, casting into films.ALSO:Electrical components (e.g. stators or motors, copper or aluminium wire), are insulated by heating the component to 150 DEG to 250 DEG C., dipping the component into a fluidised bed of a certain heat-curable polyester powder and thereafter heating it to 150 DEG C. to 350 DEG C. to cause the discrete particles of the powder to coalesce. The polyester powder comprises (a) a branched polyester based on terephthalic and/or isophthalic acid (b) a polycarboxylic anhydride and (c) a tertiary amine. Powder spraying techniques, e.g. flame or electrostatic, or solutions of the powder may be used. Woven or random glass cloth may also be treated. The polyester resins may be mixed and cured with minor amounts of other resins such as melamine-, aniline-, shenolurea formaldehyde resins, epoxide, silicone, polyamide, vinyl, ethylene, styrene, butadiene-styrene resins, cellulose acetate.