| 摘要 |
Aqueous solutions of water-soluble macromolecular carbohydrates which have been treated with aldehydes and dried are made by introducing said water-soluble carbohydrates into water and thereafter, or after moistening said carbohydrates with water, the pH value of the solvent water is shifted into the alkaline region by the addition of an alkali. This may be effected by addition of alkaline-reacting substances, which are admixed dry with the macromolecular carbohydrates before the said carbohydrates are introduced into water. Specified water-soluble macromolecular carbohydrates include methyl cellulose, ethoxycellulose, methyl ethoxy cellulose, ethyl ethoxy cellulose, carboxy methyl cellulose, carboxy ethyl cellulose, methyl carboxy methyl cellulose, ethyl carboxy methyl cellulose, hydroxyethyl carboxymethyl cellulose, sulphomethyl cellulose, swelling starch, dextrin, methyl starch, carboxy methyl starch, pectin, carrageenin, tragacanth, carob meal, and guar meal. Reaction with aldehydes may be effected in the presence of weak acids, usually formic acid. Specified alkalis include caustic soda, caustic potash, calcium hydroxide, baryta, sodium and potassium carbonates, borax, alkali metal phosphates, alkali metal salts of carboxylic acids, e.g. sodium formate, potassium acetate, sodium benzoate, ammonia and amines. Alkaline substances suitable for pre-mixing with the macro-molecular carbohydrate include calcium carbonate, barium carbonate, and satin white (CaSO4 2H2O). Swelling starch may also be used. Examples describe the treatment of methyl cellulose, carboxy methylcellulose, swelling starch and guar meal first with glyoxal and then with ammonia, sodium carbonate, calcium carbonate, swelling statch, or trisodium phosphate.
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