Patent GB-788539-A (GB)
Title: Method for the production of werner type chromium-iii-compounds containing inorganic acid radicals and organic carboxylic acid radicals, and the compounds so produced
IPC: D21H17/12
Filed: 1954-06-24
Abstract: A Werner-type chromium-III compound containing inorganic acid radicals and organic carboxylic acid radicals, wherein the stoichiometrical ratio of chromium to organic acid radicals is 1 : 1 or 2 : 1, is produced by heating together an organic carboxylic acid, a neutral salt of trivalent chromium with a strong mono-basic mineral acid (i.e. a salt having 3 mineral acid ions per chromium-III ion) and a salt of a strong inorganic base with a relatively weak acid in substantial absence of water in an organic solvent, soluble in or miscible with water, and in such proportions that a Werner-type compound is formed, the inorganic salts precipitated being separated and the Werner-type compound being isolated or used directly in the form of the solution obtained.  The term "a relatively weak acid" means any acid, inorganic or organic, which is weaker than a strong mono-basic mineral acid, and the term "strong inorganic base" means alkali metal and alkaline earth metal bases.  Suitable solvents are the alcohols containing one to four carbon atoms, polyhydric alcohols, lower ketones, dioxane and tetrahydrofuranes.  Thus a solution of chromium-III chloride and stearic or oleic acid may be treated with sodium bicarbonate or sulphite.  In a modification, the salt of the relatively weak acid and strong base is an alkali or alkaline earth salt of the organic acid which is to be incorporated in the complex, and the organic acid is liberated in situ by the acidic reaction of the chromium-III salt used.  Thus a solution or suspension of chromium-III chloride in alcohol or acetone may be reacted with a sodium or potassium soap of a carboxylic acid such as a fatty acid or resinic acid, or with an alkali or alkaline earth metal salt of methacrylic or maleic acid. In another modification, a chromate or bichromate is used as the salt of the relatively weak acid with the strong base.  In this method, part of the chromium-III ions forming the complex may be produced in situ by reduction of the chromate or bichromate by heating with an alcohol which is oxidized during the reaction, e.g. isopropyl alcohol.  Also, the whole of the chromium-III salt may be formed in situ by reducing the chromate or bichromate with an alcohol and simultaneously adding hydrogen chloride.  For example, gaseous hydrogen chloride may be passed into an agitated mixture of sodium bichromate, stearic acid and an excess of isopropyl alcohol and as the temperature rises the bichromate is reduced to a chromium-III salt and the desired complex is formed immediately if the introduction of hydrogen chloride is stopped when 6 mols. have reacted per mol. of bichromate.  Aqueous solutions of the complexes may be used for water-proofing paper, textiles and leather, and for pretreating glass fibres used for reinforcing articles of unsaturated polyester resins.  In examples: (1) to a solution of potassium hydroxide in ethanol, sodium stearate and technical chromium-III chloride are added and the mixture is boiled for 30 minutes, filtered, and the ethanol evaporated to give a dark green paste of the chromium complex; (2) potassium hydroxide, ethanol, potassium methacrylate and chromium-III chloride are boiled for 30 minutes, the mixture is filtered and the solution is used for impregnating glass fibre; (3) to a solution of stearic acid in methanol magnesium carbonate and chromium-III chloride are added and the mixture is boiled for 10 minutes to give a green solution having the same properties as that in (1); (4) to an ethanol solution of chromium-III chloride, bi-potassium maleinate is added and the mixture is boiled for 10 minutes and then filtered; (5) to an ethanol solution of chromium-III chloride, mono-potassium phthalate is added and the mixture is boiled for 30 minutes and then filtered; (6) to a methanol solution of chromium-III nitrate, sodium stearate is added and the mixture boiled for 15 minutes and then filtered; (7) a mixture of isopropanol, sodium stearate, chromium-III chloride and sodium bichromate is boiled for 40 minutes and then treated as in (1); (8) to a solution of stearic acid in isopropanol, chromium-III chloride and sodium bicarbonate are added and the mixture is boiled for 20 minutes and the solution is filtered; (9) to a solution of stearic acid in isopropanol, chromium-III chloride and magnesium bicarbonate are added, and the mixture is boiled for 10 minutes and then filtered; (10) to a solution of stearic acid in ethanol, chromium-III chloride and sodium sulphite are added and the mixture is boiled for 15 minutes; (11) to a solution of stearic acid in isopropanol, sodium bichromate is added and dry hydrogen chloride is bubbled in at room temperature, whereby the temperature rises, external heating being applied to complete the reaction.