| 摘要 |
Polyester resins having good electrical insulating properties are prepared by reacting at least one vegetable oil with a polyhydric alcohol, mixing the product obtained with at least one a ,b -unsaturated polycarboxylic acid and/or saturated polycarboxylic acid and subjecting the mixture to a polycondensation reaction to form an unsaturated alkyd resin, adding dicyclopentadiene prior to, during, or subsequently to the formation of the unsaturated alkyd resin, heating the mixture to form a cyclopentadiene unsaturated alkyd resin, mixing the latter with a compound containing a CH2=C< radical, adding a silicone resin and if desired a hardening catalyst and a hardening accelerator. Examples of vegetable oils, mixture of which may be used, are drying oils and semi-drying oils e.g. safflower, soyabean, tung, perilla, linseed, sesame, cotton seed and rape seed oils. The usual accelerators, catalysts and inhibitors may be added. An electrical conductor may be insulated by coating the conductor with the polyester of the invention. In the examples: (1) safflower oil and glycerine are heated together, in the presence of calcium acetate and then maleic anhydride, phthalic anhydride, ethylene glycol, dicyclopentadiene and hydroquinone are added and the mixture is allowed to react in a CO2 atmosphere for one hour at 160 DEG C., three hours at 180 DEG C. and then the temperature is raised to 200 DEG C. The liquid resin is then polymerized with styrene in the presence of a silicone resin. In other examples the unsaturated polyester is prepared from (a) safflower oil, glycerine, maleic anhydride, isophthalic acid, ethylene glycol and dicyclopentadiene; (b) soyabean oil, linseed oil, glycerine, dicyclopentadiene, maleic anhydride and phthalic anhydride; (c) cotton seed oil, soyabean oil, trimethylolpropane, propylene glycol, maleic anhydride, phthalic anhydride and dicyclopentadiene and (d) cotton seed oil, pentaerythritol, ethylene glycol, fumaric acid, phthalic anhydride and dicyclopentadiene. |
