GB1010649A - Surface treatment of polyolefin film - Google Patents

Abstract

The surface of a polyolefin film is made adherent to polymeric materials by passing the film through a flame emanating from the discharge opening of a burner supplied with a gaseous mixture of a paraffinic or olefinic hydrocarbon fuel and oxygen-enriched air, the mixture having a fuel equivalence ratio of 0,85 to 1,15 and an oxygen ratio of 0,25 to 0,30, the path of the film as it traverses the flame being at a distance from the burner less than the length of the unimpeded primary envelope of the flame but not less than the distance below which the velocity of the burning gases escaping from the immediate vicinity of the discharge opening exceeds the burning velocity of the flame, the film as it traverses the flame being supported as a surface maintained at 50-80 DEG C., the exposure of the film to the action of the flame being from 0,0005 to 0,1 secs. whereby the contact angle of the film surface is reduced to a value below 65 degrees. Fuel equivalence ratio is defined as the ratio of the amount of hydrocarbon fuel present in the gaseous mixture supplied to the burner to the amount of hydrocarbon fuel necessary for complete stoichiometric combustion. Oxygen ratio is defined as the ratio of the total amount of oxygen present in the gaseous mixture supplied to the burner to the total amount of non-fuel components in the mixture, said components including chiefly oxygen and nitrogen. Preferably the fuel equivalence ratio of the gaseous mixture is from 0,95 to 1,05, the temperature of the film-supporting surface is from 55-75 DEG C., and the film is a biaxially oriented film. Linear polyethylene and polypropylene films are specified. Films so treated may be coated with vinylidene chloride copolymers, branched polyethylene, pressure-sensitive adhesive coatings, electromagnetic coatings, and printing inks. In examples: (2) polypropylene film is coated with an aqueous dispersion of a vinylidene chloride copolymer containing methyl acrylate and acrylic acid; (3) polyethylene film is coated likewise, or with a vinylidene chloride copolymer containing also methyl methacrylate, or methyl methacrylate and itaconic acid; (4)-(7) polyethylene film is coated with aqueous dispersions of vinylidene chloride copolymers containing, in place of acrylic acid, vinyl pinonate, vinyl carbazole, vinyl triethoxysilane or diethylamino ethyl acrylate; (8) polypropylene film is coated with a composition comprising urea-formaldehyde resin, "Superfloss" (a mineral filler), ethylene glycol, titanium dioxide, water, methyl cellulose and phosphoric acid, by means of an air knife coater; (9) polypropylene film is coated with a composition comprising urea formaldehyde resin, "Superfloss", ethylene glycol, titanium dioxide and water by means of a doctor roll coater; (10) polypropylene film is coated with a pressure-sensitive adhesive formulation comprising high-molecular weight grade, polyvinyl butyl ether and low molecular weight grade polyvinyl butyl ether dissolved in toluene; (11) polypropylene film is treated with an aqueous solution of "Quilon" (chromium complex) and the other side coated with an acrylate type adhesive, a polyvinyl ether adhesive, or a polyisobutylene modified GR-S rubber. Specification 1,010,650, and U.S.A. Specifications 2,570,478, 2,824,024, 2,824,025, 2,829,068 and 2,829,069 are referred to.