Patent GB-684561-A (GB)
Title: Improvements in the manufacture of water-soluble cellulose ethers
Inventor: DOWNING JOHN
IPC: A23L29/262
Filed: 1949-09-22
Abstract: Water-soluble cellulose ethers are produced by subjecting alkali cellulose of "packing density" above 15 lb./cu. foot to the simultaneous action, at over 65 DEG  C., of the vapours of methyl chloride and another alkyl chloride containing up to 4 carbon atoms in the molecule, the total amount of alkyl chloride being 1.75-3 molecular proportions for each molecular proportion of cellulose (reckoned as one anhydroglucose unit) and the molecular ratio of methyl chloride to the other alkyl chloride being 20 : 1-3 : 1 or 1 : 2-1 : 20.  The method of determining the "packing density" of the alkali cellulose is described.  The alkali cellulose preferably has a packing density of 18-30.  It may be made by impregnating cellulose, e.g. wood pulp, in sheet form with caustic soda solution, preferably of 20-40 per cent concentration and squeezing it to give a molar ratio of alkali to cellulose after squeezing roughly equal to the molar ratio of the total amount of lower alkyl chlorides (with which the cellulose is to be treated) to cellulose.  The alkali cellulose is then broken down and milled.  The reaction with the alkyl chlorides may be carried out at about 70-120 DEG  C. and the temperature may be constant or may be raised, e.g. 1-2 hours at 70-90 DEG  C. and 1-3 hours at 100-115 DEG  C.  Preferably, at least during the earlier stages of the reaction, the pressure of the alkyl chlorides in the reaction vessel should be such that the higher boiling of the alkyl chlorides is nearly but not quite at its liquefaction pressure.  In an example, sulphite cellulose pulp sheet is passed through a bath of 30-33 per cent caustic soda at 60 DEG  C. and then squeezed between nip rolls to a caustic soda/cellulose molar ratio of about 2.75 : 1.  The sheet is broken down in a hammer mill and then milled for about 3 hours at room temperature to give an alkali cellulose having a packing density of about 22 lb./cu. foot. The alkali cellulose is heated in an autoclave with 2 molecular proportions of ethyl chloride and 0.6 molecular proportion of methyl chloride for 1 hour at 75 DEG  C. and 3 hours at 105 DEG  C.  The product is washed free from salts with alcohol.  In other examples, cellulose ethers are similarly produced, using other molecular proportions of methyl and ethyl chlorides.  In each example, the ethyl chloride can be replaced by an equimolecular amount of isopropyl chloride.  The cellulose ethers are said to be suitable and substituents for white of egg (see Group VI).  The Provisional Specification refers to Specification 672,975.ALSO:Water-soluble cellulose ethers for use in substitution for white of egg are produced by subjecting alkali cellulose of packing density above 15 lb./cu. ft. to the simultaneous action, at a temperature above 65 DEG C. of the vapours of methyl chloride and another alkyl chloride containing up to 4 carbon atoms, the total amount of alkyl chloride being between 1.75 and 3 molecular proportions for each molecular proportion of cellulose (reckoned as one anhydroglucose unit) and the molecular ratio of methyl chloride to the other alkyl chloride being between 20 : 1 and 3 : 1 or between 1 : 2 and 1 : 20 (see Group IV (a)).  The products, e.g. when used in 1-2 per cent aqueous solution, are suitable to replace the white of egg used in the production of meringues, particularly when the proportion of alkyl chloride such as ethyl chloride exceeds that of methyl chloride in the production of the cellulose ethers.  The viscosity at 20 DEG  C. of a 2 per cent aqueous solution of the products is preferably between 10 and 100 cp. The solutions have the property of forming a relatively stable foam with water, e.g. a column of foam prepared with a 2 per cent aqueous solution of the cellulose ether loses less than half its height in 3 hours.  The solution may also be heated up to 85-95 DEG  C. without any of the pronounced thickening which occurs with solutions of methyl cellulose at about 45-55 DEG  C.