Patent GB-1011284-A (GB)
Title: Electrically insulating resin
IPC: C08L63/00
Filed: 1961-12-18
Abstract: A heat-curable one-part liquid insulating resin composition comprises a blend of (1) a branched-chain, acid terminated polyester of at least one dicarboxylic acid, at least one dihydroxy alcohol and a polyhydric alcohol having at least three non-tertiary hydroxyl groups or a polybasic acid having at least three carboxyl groups, from 2 to 8% of the total of said acids and alcohols containing aromatic rings, which polyester contains an average of 2.1 to 3.0 carboxyl groups per molecule, has an acid number of 20 to 155, a hydroxyl number of less than 10, is free from ethylenic unsaturation in its skeletal chain and has a viscosity at 23 DEG  C. of less than 300,000 centipoises, (2) an epoxy resin containing at least 1.5 oxirane groups per average moecular weight, and (3), as catalyst, 0.01 to 0.5% of stannic chloride or 0.5 to 4% dicyandiamide, the per cents being based on the total of (1) plus (2), said blend containing about 1.8 to 2.1 epoxy groups percarboxyl group, and the epoxy resin being so selected that a simple mixture of ingredients (1), (2) and (3) does not exceed 300,000 centipoises in viscosity at 23 DEG  C.  Specified epoxy resins are the polyglycidyl ethers of polyhydric phenols, e.g. resorcinol, bis-phenol-A and phenol-formaldehyde novolaks; the compound <FORM:1011284/C3/1> limonene dioxide, dicyclopentadiene dioxide, vinyl cyclohexane dioxide and 3:4-epoxy-6-methyl cyclohexyl methyl-3:4-epoxy-6-methylcyclohexane carboxylate.  Monoepoxides, e.g. dodecene oxide, octylene oxide, dipentene monoxide, a -pinene oxide, styrene oxide, phenyl glycidyl ether, vinyl cyclohexane monoxide and epoxidized long chain olefins; liquid polycarboxylic acid anhydrides, e.g. alkenyl succinic anhydride and methyl-endomethylene-tetrahydrophthalic anhydride; fillers, e.g. ground mica, slate or calcium carbonate; diluents, e.g. chlorinated diphenyl and thixotropic agents, e.g. finely powdered silica, aluminium silicate and aluminium stearate, may also be present in the compositions.  The Specification describes the preparation of polyesters from:-(A), (C) and (D) adipic acid, isophthalic acid, propylene glycol and trimethylol propane and (B) a mixture of 2-ethyl suberic acid, 2:5-diethyl adipic acid and n-sebacic acid, isophthalic acid, propylene glycol and trimethylol propane; other polyester-forming reactants specified being o-phthalic acid, azelaic acid, chlorendic anhydride, 1:4-butane diol, ethylene glycol, 2:2 - bis - (4 - (2 - hydroxy - propoxy)-phenyl) propane, glycerol, pentaerythritol, trimesic acid, citric acid, trimellitic acid, benzene tetracarboxylic acid and tricarballylic acid. The examples describe curable compositions comprising:-(I) polyester A, a liquid epichlorhydrin-bis-phenol-A reaction product and hydrated stannic chloride; (II) as in (I) with the addition of ground mica and an ammonium organic complex in magnesium montmorillonite; (III) polyester B, a liquid epichlorhydrin - bis - phenol - A reaction product and stannic chloride hydrate and (IV) polyester A, an epoxy resin of Formula (I) and dicyandiamide. Specification 965,550 is referred to.