| 摘要 |
<p>A polyester is made by reacting together (1) 25 to 56 equivalents per cent of terephthalic acid and/or isophthalic acid (or ester-forming derivatives thereof); (2) 15 to 46 equivalents per cent of ethylene glycol and (3) 13 to 44 equivalents per cent of a saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, e.g. glycerine, 1:1:1-trimethylol ethane, 1:1:1-trimethylol propane, pentaerythritol, sorbitol, mannitol, diglycerol or dipentaerythritol. The ester-forming derivatives may be the acid chlorides or half esters but are preferably the dialkyl esters. Polyesterification is effected by heating the reactants for 2-6 hours from room temperature to 200 DEG to 270 DEG C. and maintaining the reactants at the final temperature for 2-4 hours and is preferably effected in presence of xylene. When starting from the dialkyl esters, alcoholysis catalysts are preferably used, e.g. lead oxides, lead acetate, zinc oxide, cadmium acetate, cuprous acetate, zinc acetate, magnesium acetate, beryllium acetate, stannic acetate, ferric acetate or nickel acetate. The reaction is terminated by adding a solvent, e.g. cresols, xylenols, polyhydroxy benzenes, petroleum hydrocarbons, or xylenes and other polyalkyl benzenes, e.g. "Solvesso" (Registered Trade Mark) 100 or 150. The resulting solutions may be used for insulating conductors (see Specification 775,082, [Group XXXV]) in which case the resin is cured on the wire by adding curing catalysts, e.g. zinc octoate, cadmium octoate, aromatic diisocyanates or aliphatic diisocyanates. The resins may also be used as slot insulation in dynamo-electric machines, as the dielectric medium in capacitors, in paint or varnish formulations, as moulding powders in admixture with fillers, e.g. wood flour, diatomaceous earth, carbon or silica, or as impregnants or bonding materials for metallic and fibrous laminates. Minor amounts of other resins may be added, e.g. melamine-formaldehyde, aniline-formaldehyde, urea-formaldehyde, silicone, cellulose acetate, polyamide, vinyl, ethylene, styrene or butadiene/styrene resins.</p> |
