Patent GB-573067-A (GB)
Title: Improvements relating to the production of hollow articles from cellulose derivativecompositions
IPC: B29C41/14
Filed: 1943-10-26
Abstract: Hollow articles are made by coating a former with a hot composition comprising fibrous material dispersed throughout a solution of a thermoplastic derivative of cellulose in a liquid which is not a solvent for the derivative at ordinary temperatures, converting the solution into a gel by cooling, stiffening the gel by evaporation of the liquid or of a substantial proportion of a constituent or constituents thereof, and removing the stiffened gel from the former. The liquid may be (a) a mixture of a liquid which alone, even when boiling, is not a solvent for the derivative, with a solvent plasticizer for the derivative: e.g. a solution of dimethyl phthalate in ethanol; other examples are given; or (b) a mixture of two liquids, neither of which, even when hot, dissolves the derivative: e.g. a mixture of an "associated" liquid with a non-associated liquid which is miscible with the associated liquid; e.g. a mixture of normal propanol, or isopropanol, with chlorinated aliphatic hydrocarbons such as ethylene dichloride, trichlorethylene or ethylenetetrachloride; to a solution of the derivative in this p mixture may be added solvent or non-solvent plasticizers, e.g. triphenyl phosphate; or (c) a single liquid such as (1) ethyl acetate or methyl ethyl ketone (for dissolving cellulose acetate); (2) diacetone alcohol or butyl acetate (for dissolving cellulose acetatestearate): solvent or non-solvent plasticizers may be added; or (3) toluene (for dissolving ethyl cellulose); or (d) a true solvent for the derivative, diluted with one or more non-solvents, e.g. (1) acetone plus benzene or plus benzene and ethanol (for dissolving cellulose acetate); and (2) ethylene dichloride plus benzene (for dissolving cellulose acetate-stearate).  The fibrous material may be wood pulp, chopped paper, cotton or linen yarn, stretched regenerated cellulose, disintegrated rags, asbestos fibres or macerated asbestos fabric. The composition may contain (a) substances which afford protection against ultra-violet radiation, e.g. salol, Michler's ketone, fluoranthrene or benzal-acetophone; and (b) pigments, metallic powders and carbon black.  The temperature at which the composition is applied to the former may range from 50 DEG to 160 DEG  C.  The former may be (a) coated by dipping; (b) coated initially with a layer of material which facilitates removal of the article from the former, e.g. polyvinyl alcohol, chlorinated rubber, soaps, waxes and esters of soap-forming acids; (c) cooled so that the composition gels immediately on contact therewith; (d) rotated to ensure evenness of coating; and (e) inflatable, flexible, resilient, disintegratable, frangible or collapsable.  The former may be hollow, the composition being placed therein and the former being spun about its axis, whereby the composition is caused by centrifugal force to coat the inside of the former. After the coating has been set by cooling, the volatile liquid may be evaporated at ordinary or elevated temperatures.  To facilitate the removal of a cellulose acetate-containing coating, it may be swollen in an aqueous bath.ALSO:Hollow articles are made by coating a former with a hot composition comprising fibrous material dispersed throughout a solution of a thermoplastic derivative of cellulose in a liquid which is not a solvent for the derivative at ordinary temperatures, converting the solution into a gel by cooling, stiffening the gel by evaporation of the liquid or of a substantial proportion of a constituent or constituents thereof, and removing the stiffened gel from the former.  The liquid may be (a) a mixture of a liquid which alone, even when boiling, is not a solvent for the derivative, with a solvent plasticiser for the derivative: e.g. a solution of dimethyl phthalate in ethanol: other examples are given; or (b) a mixture of two liquids neither of which, even when hot, dissolves the derivative : e.g. a mixture of an "associated" liquid with a non-associated liquid which is miscible with the associated liquid; e.g. a mixture of normal propanol, or isopropanol, with chlorinated aliphatic hydrocarbons such as ethylene dichloride, trichlorethylene or ethylenetetrachloride: to a solution of the derivative in this mixture may be added solvent or non-solvent plasticisers, e.g. triphenyl phosphate; or (c) a single liquid such as (1) ethyl acetate or methyl ethyl ketone (for dissolving cellulose acetate), (2) diacetone alcohol or butyl acetate (for dissolving cellulose acetate-stearate): solvent or non-solvent plasticisers may be added; or (3) toluene (for dissolving ethyl cellulose); or (d) a true solvent for the derivative, diluted with one or more non-solvents, e.g. (1) acetone plus benzene or plus benzene and ethanol (for dissolving cellulose acetate), and (2) ethylene dichloride plus benzene (for dissolving cellulose acetate-stearate).  The fibrous material may be wood pulp, chopped paper, cotton or linen yarn, stretched regenerated cellulose, disintegrated rags, asbestos fibres or macerated asbestos fabric. The composition may contain (a) substances which afford protection against ultra-violet radiation, e.g. salol, Michler's ketone, fluoranthrene or benzal-acetophone, and (b) pigments, metallic powders and carbon black.  The temperature at which the composition is applied to the former may range from 50 DEG to 160 DEG  C. The former may be (a) coated by dipping, (b) coated initially with a layer of material which facilitates removal of the article from the former, e.g. polyvinyl alcohol, chlorinated rubber, soaps, waxes and esters of soap-forming acids, (c) cooled so that the composition gells immediately on contact therewith, (d) rotated to ensure evenness of coating, and (e) inflatable, flexible, resilient, disintegratable, frangible or collapsable.  The former may be hollow, the composition being placed therein and the former being spun about its axis, whereby the composition is caused by centrifugal force to coat the inside of the former.  After the coating has been set by cooling, the volatile liquid may be evaporated at ordinary or elevated temperatures.  To facilitate the removal of a cellulose acetate-containing coating, it may be swollen in an aqueous bath.