Patent GB-936997-A (GB)
Title: Improvements in and relating to methods of producing delustered plastic films
IPC: B29C48/08
Filed: 1959-12-30
Abstract: Self-supporting delustered films of organic linear polymeric materials are continuously produced by spreading a layer of a composition which contains the film-forming material and which is of a paste-like consistency over a travelling fabric web which is impregnated and coated with a varnish containing a finely divided solid delustering or matting agent as a filler, causing the impregnated web carrying the layer of paste to travel through a heating zone wherein the web and paste are raised to a temperature sufficiently high to cause gelatinization of the paste and evaporation of any volatile solvent present in the paste, then causing the web to travel through a cooling zone wherein the film is solidified, and finally stripping the solidified film from the web. The composition may be in the form of a plastisol or an organosol. The matting agent may be finely divided chalk, finely divided silica obtained by dehydration of colloidal silicic acid, fine sand, finely powdered metal, finely powdered emery, finely powdered carborundum, or mixtures of two or more of these substances.  The web carrying the layer of film-forming composition after travelling through the heating zone may be caused to pass through the nip of a pair of compressing rolls before travelling through the cooling zone in order that the film may be embossed with the pattern of the fabric web. The varnish with which the web is impregnated and coated is formed by impregnating the web with a thermosetting or a cold curing plastic which is thereafter cured in situ and thereby converted into a varnish or solid impregnant which is not softened or dissolved by any plasticizer or solvent present in the film-forming composition.  The paste of film-forming composition may be applied to and spread over the upper surface of the horizontal upper run of one endless travelling impregnated fabric web and before the impregnated web coated with the composition passes through the heating zone the lower horizontal run of a second varnish-impregnated endless fabric web may be caused to contact the first coated web so that both webs with the film-forming composition sandwiched between them travel successively through a heating zone, the nip of a pair of compression rolls and a cooling zone before the film is stripped from both webs and collected on a wind-up roll.  Alternatively the second web and the compression rolls may be omitted.  In either case an impregnated firnite travelling fabric web or webs may be used instead of an endless web or webs and the web or webs together with the film collected on a wind-up roll prior to the film being stripped from the web or webs. The lacquer or varnish used for impregnating and coating the webs and which functions as a film coating surface may consist of 45 parts (by weight) of a solution of a castor oil alkyd in xylol, 4 parts of a 60% solution in butanol of an alkoxylated melamine resin, 50 parts of trichloroethylene, 1 part of aluminium stearate, and 11 parts of finely divided silica.  The film-forming composition applied to the web which has been impregnated with the above varnish and cured at 200 DEG -210 DEG C. may consist of 100 parts of polyvinyl chloride powder, 30 parts of dioctylphthalate, 30 parts of dioctylazelate, 5 parts of epoxidized soya bean oil, 1,5 parts of a barium-cadmium-zinc stabilizer, and 0,3 part of an ultra-violet light absorber.