Patent GB-408952-A (GB)
Title: Improved manufacture of organic cellulose ester moulding powders
IPC: C08B3/22
Filed: 1932-07-18
Abstract: A granular finely divided powder suitable for moulding purposes is prepared by dissolving an organic ester of cellulose in an inert solvent in the proportion of at least three parts by weight of solvent to one part of ester, and precipitating it by adding an organic precipitant.  Any plasticizer may be added to the ester solution before precipitation.  The mixture of solvent and precipitant may be removed from the precipitated ester by filtration or by evaporation.  Organic esters specified are the acetate, acetate - propionate, propionate, butyrate, acetate - butyrate, and acetate - stearate.  Examples of precipitants for cellulose acetate are benzene, toluene, xylene, carbon tetrachloride, methyl and ethyl alcohols, gasoline, kerosene, butane, propane, pentane, hexane, n-butyl alcohol, amyl acetate, trichlorethylene, butoxy-ethyl alcohol, and propylene chloride; for cellulose acetate - propionate there are mentioned carbon tetrachloride, toluene, trichlorethylene, butyl alcohol, iso-propyl ether, and butoxy-ethyl alcohol. Iso-propyl ether precipitates all organic esters of cellulose from solution.  The drawings (not shown) show a curve which indicates that for a cellulose acetate-acetone (1 : 4) solution, using toluene as precipitant, the lower the temperature of precipitation, the smaller the particle size obtained.  This result is said to be general for cellulose organic esters.  The following examples are given: (1) Cellulose acetate is dissolved in six parts of acetone and one part of water is added; this does not produce precipitation.  Toluene is then added with thorough agitation to precipitate the ester.  (2) Toluene is added to a solution of cellulose acetate obtained as in (1) to produce a jelling of the acetate.  A small quantity of water is then added, followed by further additions of toluene, with or without water.  (3) Cellulose is dissolved in acetone (4 parts) together with dimethyl or diethyl phthalate as plasticizers.  Toluene is then added to precipitate the acetate.  (4) Cellulose acetate-stearate is dissolved in six parts of acetone, and precipitated by means of methyl alcohol.  (5) Cellulose acetatepropionate is dissolved in 8 parts of acetone, and 36 parts of carbon tetrachloride are added.  To the jelled material is then added more carbon tetrachloride to complete the precipitation.  (6) The solution of example (5) is treated with butyl alcohol, and the precipitate filtered and washed.  (7) The solution of example (5) is precipitated by means of iso-propyl ether.  (8) To the solution of example (5) there is first added trichlorethylene to produce a gel, followed by further quantities of trichorethylene to precipitate the cellulose acetate-propionate.  Specifications 275,558 and 285,829, [both in Class 70], are referred to.  The Specification as open to inspection under Sect. 91 refers in general to a process for dissolving an organic ester of cellulose in a solvent therefor and precipitating it from solution by the addition of an organic precipitant.  This subject-matter does not appear in the Specification as accepted.ALSO:A granular finely divided powder suitable for moulding purposes is prepared by dissolving an organic ester of cellulose in an inert solvent in the proportion of at least three parts by weight of solvent to one part of ester, and precipitating it by adding an organic precipitant.  Any plasticizer may be added to the ester solution before precipitation.  The mixture of solvent and precipitant may be removed from the precipitated ester by filtration or by evaporation.  Organic esters specified are the acetate, acetate-propionate, propionate, butyrate, acetate - butyrate, and acetate - stearate.  Examples of precipitants for cellulose acetate are benzene, toluene, xylene, carbon tetrachloride, methyl and ethyl alcohols, gasoline, kerosene, butane, propane, pentane, hexane, n-butyl alcohol, amyl acetate, trichlorethylene, butoxy-ethyl alcohol, and propylene chloride; for cellulose acetate-propionate there are mentioned carbon tetrachloride, toluene, trichlorethylene, butyl alcohol, isopropyl ether, and butoxy-ethyl alcohol.  Iso-propyl ether precipitates all organic esters of cellulose from solution.  The drawings (not shown) show a curve which indicates that for a cellulose acetate-acetone (1 : 4) solution, using toluene as precipitant, the lower the temperature of precipitation, the smaller the particle size obtained.  This result is said to be general for cellulose organic esters.  The following examples are given:-(1) Cellulose acetate is dissolved in six parts of acetone and one part of water is added; this does not produce precipitation.  Toluene is then added with thorough agitation to precipitate the ester.  (2) Toluene is first added to a solution of cellulose acetate obtained as in (1) to produce a jelling of the acetate.  A small quantity of water is then added, followed by further additions of toluene, with or without water.  (3) Cellulose is dissolved in acetone (4 parts) together with dimethyl or diethyl phthalate as plasticizer.  Toluene is then added to precipitate the acetate.  (4) Cellulose acetate-stearate is dissolved in six parts of acetone, and precipitated by means of methyl alcohol.  (5) Cellulose acetate-propionate is dissolved in 8 parts of acetone, and 36 parts of carbon tetrachloride are added.  To the jelled material is then added more carbon tetrachloride to complete the precipitation.  (6) The solution of example (5) is treated with butyl alcohol, and the precipitate filtered and washed.  (7) The solution of example (5) is precipitated by means of iso-propyl ether.  (8) To the solution of example 5 there is first added trichlorethylene to produce a gel, followed by further quantities of trichorethylene to precipitate the cellulose acetate-propionate.  Specifications 275,558 and 285,829, [both in Class 70], are referred to.  The Specification as open to inspection under Sect. 91 refers in general to a process for dissolving an organic ester of cellulose in a solvent therefor and precipitating it from solution by the addition of an organic precipitant.  This subject-matter does not appear in the Specification as accepted.