GB676618A - Alkylene glycol esters of alginic acid - Google Patents

Abstract

Alkylene glycol esters of alginic acid are prepared for the purpose of modifying the alginic acid to render it water-soluble, by reacting the acid with a 1 : 2 or 1 : 3-alkylene monoxide in the presence of an aqueous medium in which the alkylene monoxide is soluble. This medium may be water or a mixture of water and an inert water-miscible solvent for the alkylene monoxide such as lower monohydric and polyhydric alcohols and ketones. The esterification is normally effected in a closed vessel at temperatures of 35-70 DEG C. Lower 1 : 2- and 1 : 3-alkylene monoxides having less than 6 carbon atoms may be reacted at temperatures of the order of 35 DEG to 50 DEG C. using water alone as reaction medium; the higher monoxides are generally reacted in the presence of the aqueous medium containing the inert water-miscible solvent though the inert solvent may be omitted in the case of the intermediate alkylene monoxides when higher temperatures, e.g. 70 DEG C. are used. If desired, the alginic acid may be reacted with a higher 1 : 2- or 1 : 3- alkylene monoxide, the resulting product freed of by-product glycol and then again reacted with a further quantity of the same or different higher 1 : 2- or 1 : 3-alkylene monoxide. Alternatively, following the first reaction with the higher alkyelene oxide, the product is reacted with a lower 1 : 2- or 1 : 3-alkylene monoxide, removal of by-product glycol at the intermediate stage then being optional. In all the esterifications, the alginic acid may be employed in a partially neutralized but still water-insoluble form, the neutralizing base being one capable of producing a water-soluble alginate; normally, about 5 to 50 per cent of the carboxylic groups are neutralized. Suitable bases are ammonia, lower amines and basic compounds of the alkali metals and magnesium. The alginic acid starting material may be prepared as described in U.S. Specification 1,814,981. The esters are emulsifying agents of animal, vegetable and mineral oils and may be used in foodstuffs (see Group VI), adhesives (see Group V) and in acidic cleaning compounds. In examples: (1) shredded alginic acid containing 55 per cent solids and the remainder water and isopropanol is heated with ethylene oxide under pressure at 48-57 DEG C. to form ethylene glycol alginate; (2) moist alginic acid (50 per cent solid) is partially neutralized with anhydrous ammonia and heated with propylene oxide in a pressure reaction vessel at 35-50 DEG C. yielding propylene glycol alginate; (3) alginic acid is partially neutralized by means of an alcoholic slurry of sodium phosphate, the water content adjusted to 50 per cent and the material then heated in an autoclave at 40 DEG C. with 1 : 2-epoxyhexane, by-product hexylene glycol removed by washing with isopropanol and the product again reacted with 1 : 2-epoxyhexane to yield hexylene glycol alginate; (4) octylene glycol alginate is formed by heating a mixture of partially neutralized alginic acid, water acetone and 1 : 2-epoxyoctane in an autoclave at 50 DEG C., the product being extracted with acetone to remove by-product glycol; (5) decylene glycol alginate is formed by heating partially neutralized alginic acid with water and 1 : 2-epoxydecane in an autoclave at 50 DEG C. and then at 60 DEG C.; (6) dodecylene glycol alginate is prepared by heating partially neutralized alginic acid with water, glycerol and 1 : 2-epoxydodecane in an autoclave at 50 DEG C.; (7) octadecylene glycol alginate is prepared from 1 : 2-epoxyoctadecane by the method of (6); (8) a mixed glycol alginate is prepared by treating the product of (4) with aqueous alcoholic hydrochloric acid to liberate the neutralized carboxylic groups, adjusting the water content of the ester to 50 per cent, particularly neutralizing the free carboxyl groups with gaseous ammonia and then reacting the product with propylene oxide to form a propylene glycol-octylene glycol alginate; ethylene oxide may be used similarly; (9) trimethylene glycol alginate is prepared by partially neutralizing with ammonia alginic acid containing 50 per cent moisture and then reacting with trimethylene oxide in an autoclave at 35-50 DEG C.ALSO:Alkylene glycol alginates, prepared by reacting a 1:2- or 1:3- alkylene monoxide with alginic acid which may be partially neutralized (see Group IV(b)), may be used as emulsifying agents in the production of animal, vegetable and mineral oil-in-water emulsions. Esters mentioned are the ethylene glycol, propylene glycol, hexylene glycol, octylene glycol, decylene glycol, dodecylene glycol, octadecylene glycol, octylene glycol-propylene glycol and trimethylene glycol alginates.