GB891469A - Improvements in polymers - Google Patents

Abstract

<PICT:0891469/IV (a)/1> The surface of a polymer containing the group <FORM:0891469/IV (a)/1> is subjected to a low pressure electrical discharge emitting ultra-violet light of wavelength at least as short as 1800 or to the emissions from said discharge, in the presence of oxygen, to render said surface receptive to adhesives, printing inks, coatings, potting resins and other materials. Polymers specified are polyesters (polyethylene terephthalate, poly-p-hexahydroxylylene terephthalate), polyamides (polyhexamethylene adipamide, polycaprolactam), polyurethanes (from butanediol and hexamethylene diisocyanate), polyvinyl acetate, cellulose acetate (these materials being irradiated in the examples in the form of thin tapes) and an alkyd resin composition (82,5% medium soya type alkyd oil and 17,5% melamine-formaldehyde, dried with 1% cobalt naphthenate) which is irradiated as a coating on a polyethylene terephthalate film substrate. As illustrated in Fig. 5, a thin tape 82 of the polymeric material is passed from reel 78 to reel 80, supported in a chamber 66, which can be evacuated through outlet 68 and which contains cooled electrodes 70, 72 above and below said tape. Plates 84, 86 protect the reels from the discharge between the electrodes. In a typical example, 1,750 volts are applied across the electrodes whereby a current of 250 m.a. flows at a vacuum of 0,5 to 0,6 mm. of mercury and the tape is passed between the electrodes to provide an exposure, in the area defined by the visible glow around the electrodes, of about 10 seconds. The polymers may be subjected to the emission in a chamber separated from the discharge chamber by a synthetic sapphire window and maintained at about the same vacuum as the discharge apparatus. There are also disclosed as coating compositions which can be applied to various films which have been activated according to the invention:-(a) a composition comprising 15% solids solution of the terpolymer of 87% vinyl chloride, 12% vinyl acetate and 1% maleic anhydride, (b) a curable epoxy resin comprising the reaction product of bisphenol A and epichlorhydrin modified with an acid anhydride and an amine catalyst and (c) an epoxy resin composition comprising the reaction product of bisphenol A and diglycidyl ether containing 10% diethylene triamine as a curing agent.