GB396071A - Improvements in and relating to resinous compositions and methods of making the same - Google Patents

Abstract

A phenol such as phenol, cresols or xylenols and an aldehyde, preferably non-aqueous are condensed in the presence of a substance which maintains in the reacting mass a pH value of between 6,5 and 8,5 and a secondary catalyst in order to obtain a liquid resinous mass which can be converted by heat into a hard infusible resin. Suitable substances to maintain the pH value are triethanolamine, sodium carbonate, trisodium phosphate, sodium phthalate or mixtures of trisodium phosphate and sodium hydroxide, phthalic anhydride and sodium hydroxide, or borax and sodium hydroxide. Suitable secondary catalysts which accelerate the conversion of the resin to the infusible state include magnesium, sodium, potassium, calcium and barium salts of sulphuric, nitric, hydrochloric, hydrobromic, hydroiodic and thiocyanic acids. Water acting as a solvent for the substance to maintain the pH value may be replaced by a substance having a lower vapour pressure, such as glycerol. In example (1) cresol and paraformaldehyde are rapidly heated in the presence of a mixture of a potassium bromide solution, a sodium carbonate solution and glycerol and then rapidly chilled to give a clear liquid resin which may be hardened by heating. In further examples cresol and paraformaldehyde are similarly condensed in the presence of mixtures of (2) triethanolamine, calcium bromide solution and lime water; (3) potassium bromide solution, trisodium phosphate solution and glycerol; (4) potassium bromide solution, glycerol and trisodium phosphate-sodium hydroxide solution; (5) potassium bromide solution, glycerol and phthalic anhydride - sodium hydroxide solution; (6) potassium bromide solution, glycerol and borax-sodium hydroxide solution; (7) a solution of sodium hydroxide, phthalic anhydride and potassium bromide in glycerol. The liquid resinous product may be dissolved in a mixture of toluol, butanol and alcohol for use as a varnish. The liquid resin may be used for impregnating various electrical parts such for example as coils by placing the coil in a chamber, evacuating the chamber, introducing the resin and applying pressure. After the pressure is released the coil is drained and cured. Plasticizers, such as camphor and acetanilide, pigments and dyes may be added. Specification 364,304 is referred to.ALSO:The liquid condensation product of a phenol and an aldehyde made in the presence of a substance which maintains in the reacting mass a pH value of between 6,5 and 8,5, and a secondary catalyst which accelerates the conversion of the liquid product into a solid product by heat may be used with a solvent such as a mixture of toluol, butanol and alcohol for use as a varnish.ALSO:The liquid condensation product of a phenol and an aldehyde made in the presence of a substance which maintains in the reacting mass a pH value of between 6,5 and 8,5 and a secondary catalyst which accelerates the conversion of the liquid product into a solid product in the presence of heat may be used for impregnating electric parts. In impregnating coils the coil may be placed in a chamber, the chamber evacuated, the resin introduced and pressure applied. After the pressure is released the coil is drained and cured.