Patent GB-1066781-A (GB)
Title: Phthalate polyesters
IPC: H01B3/42
Filed: 1964-07-03
Abstract: A phthalate polyester of a bis-(hydroxyphenyl) alkane in which the phenyl nucleus contains 0-2 C1- 8 alkyl substituents, and the alkane group contains 1-5 carbon atoms, the phthalate radicals being 50-100% isophthalate and 50-0% terephthalate, which is coesterified with 1-15 mol. per cent (based on the total mols. of bisphenol and diphenolic acid) of a diphenolic acid of formula <FORM:1066781/C3/1> wherein n is 0, 1 or 2, R1 is C1- 8 alkyl group, R2 is an alkyl group, and R3 is an alkylene group of at least 2 carbon atoms, the hydroxy group being para-substituted when n is 0, is prepared by the reaction of a lower alkyl monocarboxylic acid ester of the bis-(hydroxyphenyl) alkane with a lower alkyl monocarboxylic acid ester of the diphenolic acid and the phthalic acid mixture.  The reaction is conducted in a solvent boiling at 210-280 DEG  C. at a temperature between 210 DEG C. and the reflux temperature. Suitable solvents are biphenyl, diphenyl ether or cresol.  The product may be obtained as a solid mixture of polyester and biphenyl or diphenyl ether, which may be used as such or be extracted with e.g. benzene, toluene or acetone to remove the biphenyl or diphenyl ether, or it may be diluted before cooling with e.g. cresol or dimethylacetamide, benzonitrile, or N-methyl pyrrolidone, with or without hydrocarbon diluents, to give a homogeneous solution at room temperature. A molar ratio of total hydroxy groups to total carboxylic acid groups in the ester of 1-1.05: 1 is preferred. In examples polyesters are prepared from the diacetate of 2,2-bis-(4-hydroxyphenyl) propane and 1, 3 or 5 mol. per cent of the diacetate of 4,4 - bis - (4 - hydroxyphenyl) pentanoic acid and a phthalic acid mixture containing 0, 5, 10, 20 or 50% of terephthalic acid in biphenyl or diphenyl ether solvent amounting to 40 or 50 wt. per cent of the mixture. To these mixtures cresol is added to give solutions of 10, 15 or 20 wt. per cent polymer solids content.  The use of 2,2 - bis - (3 - methyl - 4 - hydroxyphenyl) propane and 4,4 - bis - (2 - methyl - 4 - hydroxyphenyl) pentanoic acid is also described.  Uses.-Insulating varnishes and tapes for electrical conductors.ALSO:A bisphenol/isophthalic acid polyester, prepared in biphenyl solution, may be dissolved in cresol to give a solution which may be used to impregnate asbestos cloth.  The cloth is then heated to drive off cresol and biphenyl and may be used as electrically insulating tape or sheet.  The bisphenol is a diphenylolalkane containing 1-15 mole % of a diphenolic and the isophthalic acid may contain up to 50 mole % terephthalic acid.  In Example 6 the polyester derives from bisphenol A, 4:4-diphenylol-pentanoic acid and isophthalic acid.ALSO:A bisphenol/isophthalic acid polyester prepared in biphenyl solution, may be dissolved in, an organic solvent giving a solution which may be used to impregnate glass and asbestos cloth. The cloth is then heated to drive off the solvent and used as electrically insulating tape or sheet.  The bisphenol is a diphenlolalkane containing 1-15 mol % of a diphenolic acid, and the isophthalic acid may contain up to 50 mole % terephthalic acid.  Suitable solvents are cresols, dimethylacetamide, benzonitrile and N-methyl pyrrolidone.  The esters may also be used to coat electrical conductors such as copper wire. The esters may be mixed with ether resins such as melamine-formaldehyde resins, epoxide resins, phenol-formaldehyde resins, aniline-formaldehyde resins, urea-formaldehyde resins, silicone resins, cellulose acetal resins, polyamide resins, vinyl resins, ethylene resins, styrene resins, butadiene-styrene resins, polylarbonate resins and polyimide resins.  Coatings of another synthetic plastic may be applied before or after the polyester coating.