Patent GB-320362-A (GB)
Title: Improvements in the manufacture and production of artificial rubber
IPC: C08F136/08
Filed: 1928-03-30
Abstract: 320,362. Johnson, J. Y., (I. G. Farbenindustrie Akt.-Ges.). March 80, 1928. Isoprene is obtained from natural carbonaceous materials, including coal, brown coal, distillation products thereof, e.g. tars, also mineral oils and similar bituminous products, and natural gas by the following series of reactions : The initial materials are converted into acetylene, either directly or by previous conversion to methane, which is then treated to give acetylene. This is treated to obtain acetaldehyde, which is polymerized to aldol. On reduction of this compound, 1 : 3-butyleneglycol is obtained, which is subjected to partial dehydration, giving methylethylketone. On condensation with formaldehyde, this body gives methyl-2-ketone-3-butenol, which is reduced to 2-methyl-1 : 3-butyleneglycol, which, by dehydration, is converted into isoprene. On polymerization, a plastic product is obtained, which may be vulcanized to furnish a product resembling those from crude rubber. Acetaldehyde : aldol.-Conversion of acetylene to acetaldehyde is obtained by treatment with aqueous solutions of mercury, preferably mercuric, salts. Cold or warm dilute sulphuric acid solutions, or solutions in other mineral acids are employed. An aqueous solution of a mercury salt, with an addition of a salt of a base heavy metal, such as copper or iron sulphate, and of an acid alkali metal sulphate, e.g. acid potassium sulphate may be employed also, at room temperature or between 60-125‹ C. Acetylene or gases containing it may be passed with water vapour at temperatures between 200‹-400‹ C. over catalysts comprising phosphoric or boric acids, or their salts, or catalysts having both oxidizing and hydrating properties e.g. compounds of tin, silver or vanadium, at temperatures between 40‹-300‹ C. Gases containing hydrogen and oxygen may be employed instead of water vapour. The acetaldehyde may be recovered by cooling, or by passage over solid absorbents e.g. silica, active carbon, or by means of solvents. Pressure may be used. The polymerization to alcohol is effected at 8‹-10‹ C. or at room temperature by means of an alkaline agent e.g. aqueous solutions of alkali metal carbonates or dilute caustic alkalis, barium hydroxide, potassium cyanide or sodium sulphite. 1 : 3-Butyleneglycol.-The resulting aldol is then subjected to a reducing treatment e.g. electrolytically, or by means of nascent hydrogen, catalytic reduction with hydrogen, sodium or aluminium amalgam. The catalytic reduction is usually carried out in the liquid phase; catalysts containing nickel, cobalt or copper, or mixed catalysts in which nickel is replaced by cobalt, copper, iron or several of these elements may be used at temperatures between 50‹-110‹ C. Activating additions e.g. aluminium oxide, may be made. Methylethylketone and its condensation product with formaldehyde; 2-methyl 1 : 3-butyleneglycol. -The 1 : 3-butyleneglycol thus obtained is partially dehydrated by passing vapour at temperatures between 150‹-300‹ C., preferably between 180‹-250‹ C., over a catalyst comprising a heavy metal, or mixtures or compounds thereof. Activating additions such as oxides, hydroxides, carbonates, formates, acetates, oxalates, phosphates or silicates of the alkaline-earth metals may be made. Small amounts of a second class of activators, namely difficulty reducible metal oxides, e.g. oxides of thorium, aluminium, tungsten, chromium, cerium, titantium, manganese and magnesium may also be added. A copper catalyst containng alkali, and prepared by depositing basic copper carbonate on pumice, by means of water-glass, followed by reduction with hydrogen, may be used at 220‹ C. The methylethylketone is then condensed with formaldehyde, using potassium carbonate, potassium hydroxide or sodium alcoholate as a condensing agent, an inert solvent being used if desired. The condensation product thus obtained, methyl- (2) (ketone) (3) butanol, is reduced, in a manner similar to that described previously for 1 : 3- butyleneglycol, to obtain 2-methyl-1-1:3-butyleneglycol. Isoprene; caoutchouc, synthetic.-The 2-methyl- 1: 3-butyleneglycol is then dehydrated to give isoprene. The reaction may be carried out by passing the vapours, with the addition of water vapour if desired, over a dehydration catalyst at temperatures between 150‹-500‹ C. preferably between 220‹-250‹ C., at reduced, elevated or ordinary pressure. Suitable catalysts comprise the neutral or acid salts of the acids of phosphorus, preferably such as have an acid reaction under the conditions of working e.g. neutral alkaline-earth metal phosphates as tricalcium phosphate, phosphates of magnesium and the rare earths. Mixtures of different salts e.g. mono- and di-sodium phosphate &c. may be used. An addition of small amounts of free acid which are not volatile under the condition of working may be made. The isoprene may be separated in any suitable manner and then polymerized. This process may be carried out by subjecting isoprene to the action of ultra-violet light, preferably under increased pressure, and with the addition of catalysts. The hydrogen may also be polymerized by heating with water or caustic alkali under pressure to a temperature such as 100‹ C. Acid substances e.g. sulphuric or acetic acids, organo-metallic compounds, particularly of alkali-metals may be used. Alkali-metals, e.g. metallic sodium, or an alkalineearth metal, if desired with the addition of caustic alkali or of another metal e.g. zinc, may be used, and the isoprene may be diluted or dissolved by means of an inert solvent or liquid. ammonia; carbon dioxide may also be present. Substances possessing an oxidizing action, e.g. hydrogen peroxide, or an organic compound readily yielding it e.g. the double compound thereof with urea, betaine, pinacone, sodium acetate or benzoyl peroxide, inorganic peroxides e.g. sodium or barium peroxides, or double compounds e.g. with borax or potassium fluoride, or ozonides of butadiene hydrocarbons can also be used as polymerizing agents, the isoprene being dispersed, dissolved, or emulsified in an aqueous medium, and the reaction being carried out under pressure in an autoclave. Suitable emulsifying agents include alkylated aromatic, particularly polynuclear, sulphonic acids or salts thereof e.g. isobutyl naphthalene sodium sulphonate, sulphonated oils e.g. Turkey red oil, saponines, oxidized paraffins or soaps. Ammonia dissolved in water may be mixed with a solution of a fatty acid e.g. oleic acid in isoprene to form an emulsion. Albuminous substances e.g. casein facilitate both the emulsification and the polymerization. During polymerization a buffer system may be used e.g. acetic acid and sodium acetate, or secondary and tertiary sodium phosphates, a pH value of 4-8.5 being maintained. An acid fixing agent may be employed simultaneously with the oxidizing agent. Further, the isoprene may be emulsified in water with the aid of enzymes or natural juices, preferably having a proteolytic action e.g. papain from succus caricae papayae, or the sap from fica or musa species, e.g. banana juice. Activators such as hydrocyanic acid, and buffer spstems may advantageously be used. The above polymerization process may be carried out with the addition of crude rubber latex. Polymerization with halogenides which are easily decomposable by water e.g. tin tetrachloride, chlorides of phosphorus, aluminium chloride &c. may be used. The resulting plastic product may be worked up in any convenient way, by methods well-known for the treatment of crude rubber. A detailed example of the whole process is given. Specification 17193/13 is referred to.