Patent GB-720392-A (GB)
Title: Improvements in or relating to lettering-film units
IPC: B44C1/17
Filed: 1951-04-09
Abstract: 720,392. Transfers. MINNESOTA MINING & MANUFACTURING CO. April 9, 1951 [April 10, 1950; April 10, 1950], No. 8165/51. Class 100 (2). In a transfer, a thin flexible and conformable weather - resistant film 12 (see (1) below) at least 0.001 inch thick in the form of a letter or other design adapted to be applied to bare metal or the beaded surface of a reflex-reflective road sign, and having a heat- or solvent-activatable waterproof adhesive layer 11 permanently bonded to one surface, is dry-strippably mounted on a flexible carrier sheet 13 each surface 14, 15 of which comprises a continuous polymer film ; the adhesive (see (2) below) and polymers (see (3) and (4) below) are so chosen that when a number of transfers are temporarily bonded in a stack the adhesion at normal temperatures of the decorative films 12 to the adjacent carrier sheet surfaces 14 is greater than the adhesion of the adhesive layers 11 to the opposite carrier sheet surfaces 15. A stack of sheets of transfer film and carrier may be punched, stamped, sawn, &c. to provide a large number of letters &c. of the same shape in pad form. Transfers for strip marking may be wound up in roll form in which case the adhesion between the layer 11 and surface 15 may be higher than in the case of a stack. In use the adhesive layer 11 may be activated by cyclohexanone. (1) The film 12 may be formed of a weatherresistant film-forming polymer not suitable for application to a surface to be decorated by normal brushing, spraying or screen-processing methods: in examples, solutions of the following in xylol are applied to the carrier sheet 13 by a spreader bar and dried at moderate heat: (a) n-butyl methacrylate polymer, pigmented with carbon black ; an underlayer of the polymer in unpigmented solution may be first applied; (b) polyethyl methacrylate, pigmented with titanium dioxide, cadmium selenide, or toluidine red; one-fifth of the polyethyl methacrylate may be replaced by n-butyl methacrylate polymer, or equal parts of normal butyl methacrylate and isobutyl methacrylate polymers, or a co-polymer of n-butyl and isobutyl methacrylates or of methyl methacrylate and 2-ethyl-butyl acrylate, may be used. Other transfer film materials referred to are (c) an alkyd resin enamel such as a solution in a mixture of xylol and n-butyl alcohol, pigmented and with driers, of the condensation product of glycerine, phthalic anhydride, and linseed-oilfree fatty acids; this may be applied to the carrier sheet 13 by brushing, roll coating, screen processing (e.g. in multicolour-the final colour being a continous layer) etc.; in an example containing bronze pigment, onefifth of the above condensation product (the fatty acids being obtained from castor oil) is replaced by the condensation product of melamine, formaldehyde, and butyl alcohol; (d) pigmented drying oil varnish; (e) pigmented nitrocellulose lacquer; (f) a solution in cyclohexanone of a co-polymer of vinyl chloride and diethyl fumarate, with bronze pigment. (2) The adhesive layer may be based either on rubbery butadiene-acrylonitrile polymers or on polychloroprene rubber in combination with compatible reactive phenol-aldehyde resin; alternatively either on butadiene-styrene rubbery polymers or on crude rubber in combination with oil-soluble heat-advancing phenolaldehyde resins. Examples (the figures being parts by weight) are : (a) a solution of rubbery butadiene-acrylonitrile co-polymer 100, zinc oxide 10, glycerol ester of a gasoline-insoluble resinous extract of pine wood 50, heat-advancing 100 per cent phenol-formaldehyde resin compatible with the co-polymer 50, and dibutyl phthalate 7.8, in methyl ethyl ketone 400; this adhesive is activated at 180‹ F. in use; (b) polychloroprene 100, heat-advancing 100 per cent phenol-formaldehyde resin 75, hard coumarone-indene resin 25, toluol 350. In order to apply adhesive (a) to film (1) (c) it may be coated on to the back of the carrier sheet 13 (on which it will spread evenly) and then transferred to the alkyd resin film by winding the sheet up in roll form; or it may be transferred from a removable carrier web. (3) The carrier sheet base may be (a) heavy paper (e.g. 70 Ibs. per ream); (b) polyethylene film; (c) regenerated cellulose; (a) is facesized at 14 as indicated at (4) below, and backsized at 15 with a solution of polyethylene in xylol; (b) requires no additional surfacing; (c) requires only a back-size of any suitable low-adhesion size. (4) Examples of sizes to provide the continuous polymer face film 14 on a paper carrier sheet are: (a) urea-formaldehydebutyl alcohol resin in a mixture of butanol and xylol, plasticized with castor oil (or oil-modified alkyd resins), to which a solution in butyl alcohol of an acid alkyl ester of phosphoric acid is added as catalyst shortly before sizing; (b) an amino-aldehyde-alcohol solution plasticized with a drying-oil-modified glycerol phthalate alkyd resin in a volatile aliphatic hydrocarbon solvent, to which an organic acid phosphate is added as catalyst; (c) the ureaformaldehyde resin solution of (a), plasticized with a slower curing oil-modified alkyd resin, with an organic acid phosphate as catalyst; (d) polyethylene; (e) polyethyl methacrylate; (f) a co-polymer of equal parts of n-butyl and isobutyl methacrylates.