| 摘要 |
Cold-swelling starch ethers and/or esters are obtained by reacting starch or a high polymeric non-gelatinized starch derivative in any desired sequence with both a bi- or polyfunctional agent (i.e. a substance capable of reacting with two or more hydroxyl groups of the starch) and with a monofunctional etherifying and/or esterifying agent under such conditions that during the reaction with the bi- or polyfunctional agent the starch granules are substantially nongelatinized, and subjecting the reaction mixture to the cold swelling starch process, if desired before the reaction with the mono-functional agent is completed, the proportion of bi- or polyfunctional agent being so selected that all or substantially all of the starch granules of the final product obtained have lost their morphological form. The "cold-swelling starch process" is defined as a treatment wherein a mixture of starch and water is heated for a very short time to a temperature above the gelatinizing point, the mass being pressed out into thin layers under mechanical pressure and simultaneously or immediately thereafter dried. This treatment is preferably carried out on a rotating drying drum heated to 100-180 DEG C., the starch being gelatinized thereby. It is preferred to react the starch first in nongelatinized condition with the polyfunctional agent and subsequently in gelatinized condition with the monofunction agent, followed by the cold-swelling starch process. The reaction with monofunctional agent may likewise be applied to non-gelatinized starch, prior to, simultaneous with, or after, the reaction with the polyfunctional agent. The reacted starch subjected to the cold-swelling process may be in unpurified condition or may first be purified, e.g. by water washing. The reacted starch may also be gelatinized in water, precipitated by means of organic solvents or inorganic salts, e.g. alum, and further purified before the coldswelling process. The treatment with monofunctional agent may take place before or during the cold-swelling starch process and it is preferred that the reaction has proceeded to three quarters or more of completion before the heating and drying on drums. The ratio of monoand polyfunctional reagents may vary within wide limits but it is preferred that the proportion of polyfunctional agent is so chosen that an aqueous dispersion of the final product consists of only partly disintegrated starch granules. The starting material may be raw starch, e.g. potato, maize, cassave, wheat, sago or waxy starch or amylopectin, degraded starches, such as thin-boiling starch or dextrin, or natural or artificial mixtures of starch or starch derivatives with protein and cellulose, e.g. wheat, rye or buckwheat flour, ground cassave or manioc roots. Suitable polyfunctional etherifying or esterifying agents are: glycerol dichlorohydrin, epichlorohydrin, butadiene dioxide, b ,b 1-dichlorodiethyl ether, phosphorus oxychloride, hexamethylene di-isocyanate and toluene diisocyanate, synthetic resin precondensates, e.g. dimethylol-urea, dimethylol acetone and trimethylol melamine, and aldehydes, such as formaldehyde and glyoxal. Suitable monofunctional agents include halogenated fatty acids, halogen hydrins, epoxyalkanes, dialkyl sulphates, alkyl halides, sulphonic acids, polybasic anhydrides, glycidic acid, ethylene imine, acrylonitrile, acetic acid anhydride, benzyl and benzoyl chlorides, and isocyanates. Many examples are specified. The reaction of the starch with the poly- and the monofunctional agent may be effected in known manner both by the wet or by the dry method, in the presence of substances of alkaline, neutral or acid nature, and if desired in the presence of solvents. One, two or more polyfunctional agents of the same or different nature may be used. This applies also to the monofunctional agent. The poly- and monofunctional agents may be applied simultaneously, successively or in any order. The products may be used as sizing agents, printing paste thickening agents and laundry starches, as protective colloids in drilling muds, as adhesives, and in foodstuffs, e.g. ice cream, puddings, salad dressings, chocolate milk and fruit squashes. In examples: (1) potato starch is reacted with glycerol dichlorohydrin in caustic soda solution, and then with monochloracetic acid sodium salt; (2) potato starch is reacted with glycerol dichlorohydrin in caustic soda solution and the product after filtering and water washing is formed into an alkaline starch paste and reacted with epoxyethane; (3) thin-boiling potato starch is reacted with diepoxybutane in caustic soda solution and then with b -propiolactone; (4) cassave starch is reacted with phosphorus oxychloride in caustic soda solution and then with 1,2-epoxypropanol; (5) potato starch is dispersed in water containing dimethylol urea and, after acidification with dilute phosphoric acid, is stirred at 45-50 DEG C., and the product is formed into an alkaline paste with caustic soda and reacted with epoxyethane; (6) maize starch in caustic soda solution is reacted with epichlorohydrin and then with the sodium salt of monochloracetic acid; (7) potato starch is reacted with phosphorus oxychloride in caustic soda solution and then with 1,2-epoxypropanol. In each of the examples the final product is pressed out into a thin layer on a heated rotating drum and dried. Specifications 601,374 and 685,959 are referred to. |
