Patent GB-765513-A (GB)
Title: Improvements in and relating to thin polymeric films
IPC: C08J7/043
Filed: 1955-01-27
Abstract: Films of organic polymers have their surfaces rendered ink-receptive by bringing the surface of the film into brief contact with silicon monoxide vapour.  The treatment is preferably effected in a high vacuum, e.g. by exposing the film for 1/4 -\ba1/2 second at a distance of 5-10 inches from a graphite crucible containing silicon monoxide electrically heated to 1300-1400 DEG  C., under a pressure of a few microns of mercury.  The crucible is most conveniently heated by induction. In a continuous process, film is drawn over a polished metal surface, which may be fixed or in the form of a rotatable drum and is cooled, past a crucible of silicon monoxide heated to 1300-1400 DEG  C., at a distance of 5-10 inches therefrom, at a rate controlled to give an exposure to the vapour lasting 1/40 -\ba1/2 sec. and preferably 1/4 -\ba1/2 sec., at a pressure of not more than 1 micron of mercury. Instead of silicon monoxide, the crucible may contain equimolecular portions of elementary silicon and silicon dioxide as ground quartz, which evolves silicon monoxide vapour at the temperatures specified.  In an example for the production of an adhesive decorative film, a thin transparent film made from a condensation product of terephthalic acid and ethylene glycol is coated on one side with a reflective coating of aluminium, applied by vapour deposition in a high vacuum in sufficient quantity just to provide an opaque coating, which resembles chromium plating. The reverse side of the film is then treated with silicon monoxide vapour under high vacuum.  An adhesive is then applied over the aluminium coating, comprising a rubber-like butadiene-acrylonitrile polymer, a heat-hardening phenol-formaldehyde resin compatible therewith, additional tackifier resins, pigments and plasticisers, the whole being despersed or dissolved in methylethyl ketone solvent. The adhesive may be applied directly to the aluminium coating, or it may be applied to a temporary carrier web, dried, and reactivated with the solvent and transferred to the aluminium coating.  The film so prepared is adherent to metal, wood, glass, fabric or other surfaces, and its exposed surface is receptive to printing inks.  In another example, for the production of a reflective sheeting, e.g. suitable for use in road signs, a thin transparent film as above is treated with silicon monoxide vapour in a high vacuum on one or both surfaces and is then coated on one side with small glass beads in a resinous binder comprising plasticised polyvinyl butyral resin and urea-formaldehyde resin in solution in a volatile solvent.  A coating of aluminium is then applied over the beads from aluminium vapour, to increase their reflective power.  A suitable adhesive is then applied to the aluminium coating to provide a self-adhesive highly reflective sheeting. The treatment of the film with silicon monoxide vapour promotes the adhesion of the resinous binder to the film. Specification 598,330, [Group VIII], is referred to.ALSO:Aluminium is deposited from the vapour form in high vacuum on to a thin, transparent polyester film whose surface has first been treated with the vapour of silicon monoxide in high vacuum to render coatings more adherent.  Alternatively, the aluminium may be deposited on to glass beads previously applied to the treated film with the aid of resinous binder.  Specification 598,330 [Group VIII] is referred to.