GB500357A - Improvements in or relating to the production of resinous compositions - Google Patents

Abstract

500,357. Synthetic resin compositions. BAKELITE, Ltd. Aug. 7, 1937, No. 21792. Convention date, Aug. 18, 1936. [Class 2 (iii)] A resinous composition comprises a mixture of a heat-hardenable urea-aldehyde resin with finely-divided C-stage alkyd resin, the latter constituting 3 to 50 per cent by weight of the mixture. The alkyd resin is preferably prepared by repeated heating and grinding. 10-30 per cent by weight (calculated on the mixture) of alkyd resin may be added to a urea-aldehyde syrup or varnish and used for impregnating absorbent cellulosic material, e.g. paper or textiles, which may be formed into laminated panels by hot-pressing. The alkyd resin may be prepared by condensing a polyhydric alcohol, e.g. glycerol, sorbitol, or pentaerythritol, with a polybasic acid or anhydride, e.g. phthalic anhydride, succinic, malic, or maleic acid, to incipient gelation, then cooling in thin layers and repeatedly grinding and heating at 140‹ C. to a total of 100 to 120 hours' treatment. The resin may then be refluxed with an organic solvent, e.g. acetone, ethyl acetate, or ethyleneglycel mono- or di-ethyl ether; soaked in warm acetone; or boiled in water at atmospheric or higher pressure. The alkyd resin may be added to the urea-aldehyde resin by grinding them together or by stirring the alkyd resin into the liquid-stage, molten, or dissolved urea-aldehyde resin. In examples : (1) urea and formaldehyde are condensed in the presence of ammonium hydroxide to the viscous stage, and ethyl alcohol, ethyl lactate, alkyd resin prepared as above, lithopone, and carnauba wax added, the composition being used to coat sheets of alpha-cellulose paper, which are then dried, superimposed, and hot-pressed; (2) urea and formalin are condensed in the presence of ethylenediamine to a syrup, and ethyl alcohol and alkyd resin prepared as above are added, the composition being used as in example 1. The Specification as open to inspection under Sect. 91 refers also to mixtures of finely-divided C-stage alkyd resins in any proportions, with urea-aldehyde or phenol-aldehyde resins. In an example, a fusible resin is prepared by condensing phenol and formalin in the presence of barium hydroxide, and is incorporated with an alkyd resin prepared as above and treated with water under pressure at 140‹ C., either by adding the latter in alcoholic suspension during condensation or by grinding the resins together. The products may be moulded or cast and may be used for the preparation of dentures. This subject-matter does not appear in the Specification as accepted.