Patent GB-570857-A (GB)
Title: Improvements in or relating to the manufacture of oil- and grease-resistant sheets or films
IPC: C08K5/12
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, an oil-insoluble, thermosetting, artificial resin, and an oil-insoluble plasticizer comprising an oil-insoluble mono- or di-(ether-alcohol) ester of phthalic acid which contains in the ether-alcohol radical of its molecule not more than six carbon atoms. The base sheet or film may be of regenerated cellulose or a lowly substituted cellulose ester or ether precipitated from an aqueous solution.  It may be a glycol cellulose ether or glycollic acid cellulose ether.  The base sheet may contain a softening agent such as glycerine or glycol.  The cellulose derivative of the coating composition may be cellulose acetate, cellulose nitrate, cellulose aceto-butyrate, or other ester, or ethyl cellulose or other cellulose ether.  The oil-insoluble, thermosetting, artificial resin increases the strength of the heat-seal bond, and anchors the surface coating more securely to the base sheet.  The composition may contain a wax or waxy substance to increase the resistance of the coated film to the passage of water-vapour therethrough.  The plasticizer may be an ester of phthalic acid, e.g. mono- or di-(glycol mono-methyl, ethyl, propyl, or butyl ether) phthalate, or mono- or di-(diethylene glycol mono-methyl or ethyl ether) phthalate.  As thermosetting resin there may be used a partially condensed alkyl urea-formaldehyde resin.  The waxy substance may be paraffin wax, or a true wax, i.e. a monohydric alcohol ester of a higher fatty acid.  When a wax moisture-proofing agent is used, a gum or resin blending agent is preferably also included in the composition. The coating composition is preferably applied as a solution in a volatile solvent.  The composition may also contain a condensing agent for the synthetic resin such as toluene sulphonic acid which has been treated to remove traces of sulphuric acid.  Traces of sulphuric acid may be removed by dissolving the toluene sulphonic acid in isobutanol, heating to boiling, adding calcium hydroxide cautiously and with vigorous stirring to avoid excessive foaming, continuing the boiling treatment for several minutes, and filtering the solution while still hot to remove the precipitated calcium sulphate.  In an example, regenerated cellulose film softened with glycerine is coated with a solution containing di-(diethylene glycol ethyl ether) phthalate, dibutyl urea formaldehyde resin, maleic acid, maleate modified ester gum, paraffin wax, cellulose nitrate, and volatile solvents. Regenerated cellulose film softened with ethylene glycol is coated on one side with a composition comprising cellulose nitrate, partially polymerized isobutyl ether of dimethylol urea, p-toluene sulphonic acid, di-(diethylene glycol ethyl ether) phthalate, and volatile solvents, and the other side is coated with a composition comprising cellulose nitrate, dibutyl phthalate, dicyclohexyl phthalate, paraffin wax, dammar resin, and volatile solvents.  The film or sheet may be used for wrapping greasy material such as chocolate.  In another example, the coating composition comprises di-(diethylene glycol ethyl ether) phthalate, partially polymerized butyl ether of dimethylol urea, maleic acid, cellulose nitrate, modified rosin, paraffin wax, and volatile solvents.  The modified rosin is made by dissolving rosin in gasolene, adding slowly a fairly concentrated solution of sulphuric acid while agitating and cooling, separating the gasolene portion, and evaporating the gasolene.  The treated rosin is of improved colour, free from sulphur, and of higher molecular weight. Regenerated cellulose sheet is coated with a composition containing cellulose nitrate, butyl methacrylate polymer, maleate modified ester gum, butyl urea formaldehyde resin, maleic acid and glycol methyl ether phthalate.  Sheets of polyvinyl alcohol are similarly coated. The coated sheets or films may be used as such or two or more of them may be laminated, or paper sheet may be laminated on one or both surfaces to a coated sheet or film.  The sheets may be used as sheet wrapping materials which may be folded round objects and heat-sealed at the joints.  They may be fashioned into bags, envelopes, or other containers.  A container may be formed of a spirally wound tubular paper casing having an integrally-formed liner of spirally wound sheet or film, in which the spirals overlap, forming liquid-tight seals, and the liner may be sealed to the inner surface of the paper casing.  The coated sheets and containers made from them are resistant to hot and cold oils and greases and may be used for packaging butter, cheese, lard, cakes, chocolates, nuts, waxes, lubricating oils and petroleum greases.  Specification 283,109, [Class 2 (ii)], is referred to.