Patent GB-790201-A (GB)
Title: Improvements in or relating to the production of moistureproof sheet wrapping material
Inventor: BERRY WILLIAM
IPC: C08J7/052
Filed: 1955-06-10
Abstract: 790,201. Moistureproof sheet materials. BRITISH CELLOPHANE, Ltd. June 7, 1956 [June 10, 1955], No. 16819/55. Class 140. Moistureproof sheet wrapping material comprises a regenerated cellulose base film, e.g. in gel form, coated on one or both sides with a non-moisture-proofing water-repellent coating and a coating on the uncoated side or one of the coated sides of a moisture-proof substance. A " moistureproof coating " is defined as a uniform coating on one side of a regenerated cellulose film 0.0009 inches thick resulting in a degree of impermeability of the film of less than 700 gm. per 100 square metres per hour over a 24-hour period at 39.5 0.5 C. at a humidity differential of at least 95 per cent. The term " non-moistureproof coating " is defined as one resulting in a degree of impermeability in excess of 700 gm. per hour under the same conditions. The term " water-repellent surface " is a surface which when at 45 degrees to the horizontal and a drop of water is placed thereon, the drop rolls off the surface leaving no continuous trail. The non-moistureproof water-repellent coating, which may be present in a proportion of less than 1 per cent by weight of the product, may be applied from solution in a volatile solvent or solvent mixture, or an aqueous colloidal dispersion, emulsion or solution which may be cationic or non-ionic, and which may contain a softening-agent, e.g. glycerine. Suitable waterrepellent coatings have bases selected from polymers or copolymers of vinyl halides and esters, vinylidene halides, acrylic and methacrylic acid and their derivatives, styrene and its derivatives, acrylonitrile and methacrylonitrile, butadiene, isobutylene, ethylene and its homologues, nitrocelluloses, artificial and synthetic rubber latices, polyamide resins, silicones, waxes, watersoluble complex compounds of the Werner type containing a trivalent nuclear chromium atom co-ordinated with a carboxylic acid group having at least 10 carbon atoms, chlorinated polyvinyl halides, chlorinated polyethylene. Prior to coating with the moistureproof substance the uncoated side or one of the coated sides of the film may be coated with an anchoring agent, e.g. polyethylene imine, partially condensed products of melamine or urea and form. aldehyde, the colloidal particles of which, in aqueous dispersion, may be treated according to Specification 675,477, [Group IV (a)], to carry a positive electric charge. The moistureproof coating which renders the film heat-sealable may comprise nitrocellulose (as in Specification 446,383), cellulose ethers or esters, e.g. ethyl cellulose, synthetic polymers such as vinyl chloride-vinyl acetate, vinylidene chlorideacrylonitrile copolymers, natural or modified gums or resins, e.g. rosin, rosin derivatives, polybasic acid-polyhydric alcohol resin such as rosin-modified glycerol maleate, ester gum, and the polymerization product of monomeric vinylidene chloride, monomeric methyl meth. acrylate, and itaconic acid. Specification 790,200 also is referred to.