Patent GB-744276-A (GB)
Title: Improvements in or relating to hydroxyalkylation of polysaccharides
IPC: C08B11/08
Filed: 1953-09-07
Abstract: Cellulose is dispersed in a mixture of organic liquids comprising a major portion of one or more organic liquids boiling above 65 DEG C., selected from benzenoid hydrocarbons, alkanes, monoether derivatives of alkanes, and monoketone derivatives of alkanes, and a minor portion of one or a mixture of alkoxyalkanols having 1-4 carbon atoms in the alkoxy group, and to the dispersion there is added water and a caustic alkali.  The resulting dispersion is agitated with an alkylene oxide having 2-4 carbon atoms in the molecule at a temperature not above 50 DEG  C. and when the reaction has taken place the resulting hydroxyalkyl ether of cellulose is separated from the reaction mixture.  The cellulose may be in the form of cotton linters or purified wood-pulp.  The organic liquid forming the major part of the mixture of liquids may be present in an amount of 70-95 per cent.  The alkoxyalkanol may be methoxy or butoxy isopropanol, or a butoxyethanol or ethoxy propanol.  The alkylene oxide may be added to the slurry of cellulose, organic liquids, water, and caustic alkali, in a proportion of 10-105 per cent or more, based on the dry weight of the cellulose.  Water-soluble hydroxyethyl ethers of cellulose are obtained if the proportion of ethylene oxide used is 75 per cent or more.  The reaction may be carried out at 10 DEG -50 DEG C. for a period of 6-10 hours or more.  The mixture is then cooled to room temperature or below and may be filtered, centrifuged, or otherwise treated to isolate the liquid portion.  The solid product is extracted with solvents to remove caustic alkali.  Preferably, the air in the reaction vessel is expelled and replaced by nitrogen, before the addition of the caustic alkali solution and the alkylene oxide to the slurry of cellulose and organic liquids.  Water-soluble products of high molecular weights with viscosities at 20 DEG  C. for 5 per cent aqueous solutions of 1,500 to 100,000 centipoises are obtained. For removal of caustic alkali from the crude product a mixture of methanol with acetone or isopropanol may be used.  The final traces of caustic alkali may be removed by neutralization with a mineral or organic acid.  Toluene, heptane, n-propyl ether, n-butyl ether, methyl isopropyl ketone, methyl propyl ketone, methyl isobutyl ketone, or di-isopropyl ketone may be used as the liquid forming the major portion of the organic slurrying liquid. Caustic soda or caustic potash may be used as caustic alkali.  In examples, flocked chemical wood pulp is dispersed in a mixture of n-butyl ether with methoxyisopropanol, butoxyethanol, or a mixture of 3-ethoxyisopropanol and 3-ethoxypropanol-1, or in a mixture of toluene and methoxyisopropanol, or in a mixture of methyl isobutyl ketone and methoxyisopropanol.  Ethylene oxide, propylene oxide or butylene oxide is used as the etherifying agent.ALSO:Starch is dispersed in a mixture of organic liquids comprising a major portion of one or more organic liquids boiling above 65 DEG  C., selected from benzenoid hydrocarbons, alkanes, monoether derivatives of alkanes, and monoketone derivatives of alkanes, and a minor portion of one or a mixture of alkoxyalkanols having 1-4 carbon atoms in the alkoxy group, and to the dispersion there is added water and a caustic alkali.  The resulting dispersion is agitated with an alkylene oxide having 2-4 carbon atoms in the molecule at a temperature not above 50 DEG  C., and when the reaction has taken place the resulting hydroxyalkyl ether of starch is separated from the reaction mixture.  The organic liquid forming the major part of the mixture of liquids may be present in an amount of 70-95 per cent by weight of the mixture.  The alkoxyalkanol may be methoxy or butoxy isopropanol, or a butoxyethanol, or ethoxy propanol.  The alkylene oxide may be added to the slurry of starch, organic liquids, water, and caustic alkali, in a proportion of 10-105 per cent or more, based on the weight of the starch.  Ethylene oxide, propylene oxide, or butylene oxide may be used as the etherifying agent.  The reaction may be carried out at 10-50 DEG  C. for 6-10 hours or more. Preferably air in the reaction vessel is expelled and replaced by nitrogen before the addition of the caustic alkali solution and the alkylene oxide to the slurry of starch and organic liquids. Toluene, heptane, n-propyl ether, n-butyl ether, methyl isopropyl (or isobutyl) ketone, or di-isopropyl ketone may be used as the liquid forming the major portion of the organic slurrying liquid. Caustic soda or potash may be used as the caustic alkali.  In an example, corn starch is dispersed in a mixture of n-butyl ether and 3-methoxy-isopropanol, and after the addition of aqueous caustic soda the starch is etherified with ethylene oxide to form a hydroxyethyl starch which is partially soluble in cold water and almost completely soluble in hot water.  By varying the conditions of etherification, water-soluble or water-insoluble but dilute-alkali-soluble products may be obtained.