Patent GB-571701-A (GB)
Title: Improvements in or relating to the manufacture of oil- and grease-resistant sheets and films
IPC: C08J7/052
Filed: 1943-08-24
Abstract: An oil- and grease-resistant, heat-sealable sheet or film comprises a non-fibrous, water-sensitive, organic base sheet or film coated on at least one side with a surface coating comprising a cellulose derivative and an oil-insoluble plasticizer comprising an oil-insoluble amide which is a N-cyclohexyl amide of an aliphatic acid, an aryl amide, an amide of a methylene dicarboxylic acid, or a N-substituted mono-phenyl amide of an aliphatic acid.  The base sheet may be of regenerated cellulose or of a lowly substituted cellulose ester or ether precipitated from an aqueous solution or dispersion, e.g. glycol cellulose, or cellulose glycollic acid.  The base sheet may contain a softening agent such as glycerine or glycol.  The cellulose derivative of the coating composition may be an acetate, nitrate, acetopropionate, or other ester or ether.  The amide plasticizer may be cyclohexyl glycolamide, crotonamide, or myristamide, or cyclohexyl 2-ethyl butyramide; benzamide, dimethyl-, diethyl-, or monobutyl-benzamide; N-N1-diamyl sebacamide, N-N1-dibutyl adipamide, N - N1 - diethyl succinamide, N - N1 - dibutyl oxamide, N - N1 - dibutyl malonamide, N - N1-dibutyl azelamide, N - N - N1 - N1 - tetra - ethyl adipamide; phenyl butyramide, phenyl caproamide, or phenyl caprylamide.  The coating composition may contain an oil-insoluble thermosetting artificial resin to increase the strength of the heat-seal bond and to anchor the surface coating more tenaciously to the base sheet.  As such resin there may be used a partially condensed alkyl urea-formaldehyde resin.  A condensing agent for the thermosetting resin may be present, e.g. toluene sulphonic acid which has been treated to remove the last traces of sulphuric acid.  The crude acid is dissolved in isobutanol and heated to boiling and then the calculated amount of calcium hydroxide to neutralize the sulphuric acid impurity is added cautiously and with stirring.  The solution is filtered hot.  The coating composition may contain a wax moisture-proofing agent, e.g. a true wax, that is a monohydric alcohol ester of a higher fatty acid, or a waxy substance such as paraffin wax.  A gum or resin may be included as blending agent for the wax.  The coating composition may be applied as a solution in volatile solvents.  In an example, a sheet of regenerated cellulose, softened with glycerine, is coated on both sides with a composition comprising partially condensed isobutyl ether of dimethylol urea, maleic acid, benzamide, cellulose nitrate, paraffin wax, dewaxed gum dammar, ethyl acetate, toluene, and isobutanol.  The coated films or sheets may be used as such, or two or more of them may be laminated by heat and pressure.  One or more of the sheets may be laminated with a paper sheet.  The sheets may be used as wrapping material which may be folded around objects and heat-sealed at the joints.  They may be fashioned into bags, envelopes and other containers, and the seams may be heat-sealed.  A spirally-wound tubular paper container may have an integrally formed liner of spirally wound non-fibrous sheet or film coated as described, the spirals overlapping and thereby forming liquid-tight seals, and the liner may be sealed to the inner surface of the paper container.  The container may have a liquid-tight crimped end-section of metal.  It may be used for holding lubricating oil or other liquid.  The sheets, films, or containers made from them, may be used for wrapping or storing butter, cheese, lard, chocolates, cakes, greases, or waxes.  Specification 283,109, [Class 2 (ii)], is referred to.