Patent GB-782014-A (GB)
Title: Improvements in or relating to water-soluble gums, or water-soluble cellulose ethershaving improved properties
IPC: C08B11/12
Filed: 1953-12-15
Abstract: A water-soluble cellulose ether, such as a carboxyalkyl- or carboxyalkyl-hydroxyalkylcellulose ether, having the form of porous granules, a bulk density of at least 0.35 gram per millilitre and a particle size range of 20-150 U.S. mesh contains at least 5 per cent by weight of at least one water-soluble alkali or alkaline-earth metal salt of an inorganic or organic acid, the water solution of the salt having a pH value of not less than 4.5 and the salt, together with water to form an aqueous solution, having been included in the cellulose ether prior to its conversion into granular form.  The salt may be present in the original cellulose ether as a by-product of its manufacture, water then being added to the non-purified cellulose ether prior to converting it into granular form.  The cellulose ether may be carboxymethyl, carboxyethyl, carboxypropyl, carboxymethyl hydroxyethyl or carboxyethyl hydroxyethyl cellulose.  The salts may be halides, sulphates, nitrates, phosphates, chlorates, perchlorates, nitrites, phosphites, sulphites, formates, acetates, glycolates, carbonates, oxalates, citrates, phthalates, benzoates or naphthenates.  In an example, a sodium carboxymethyl cellulose containing 0.57 carboxymethyl radical per glucose anhydride unit and having a viscosity of 135 cp. in a 2 per cent aqueous solution, which had not been purified by the removal of reaction salts such as sodium chloride and sodium glycolate, and which consequently contains 15 per cent by weight of these impurites, is converted into porous granular form by mixing the fibrous CMC with 1.5 parts of water per part of CMC, drying the mixture in an oven at 100 DEG C., comminuting and screening the dried product to obtain a fraction passing a 40-mesh and retained on an 80-mesh screen.  In another example, portions of a sodium carboxymethyl-cellulose containing substantially no salt impurities are each wetted with 15 per cent aqueous solutions of various salts of sodium, potassium and calcium in sufficient proportion in each case to introduce 25 per cent by weight of salt, based on the dry CMC weight, as additive.  The treated portions of CMC are then converted into porous granules by drying and grinding and screened to obtain fractions passing the 40 mesh and retained on the 100-mesh U.S. screens.  The process increases the rate of solution of the cellulose ether in water.ALSO:A water-soluble gum, such as gum arabic or gum tragacanth, having the form of porous granules, a bulk density of at least 0,35 gram per millilitre and a particle size range of 20-150 U.S. mesh contains at least 5 per cent by weight of at least one water-soluble alkali or alkaline-earth metal salt of an inorganic or organic acid, the water solution of the salt having a pH value of not less than 4,5 and the salt, together with water to form an aqueous solution, having been included in the gum prior to its conversion into granular form.  The salts may be halides, sulphates, nitrates, phosphates, chlorates, perchlorates, nitrites, phosphites, sulphites, formates, acetates, glycolates, carbonates, oxalates, citrates, phthalates, benzoates or naphthenates.  In an example gum tragacanth is wetted with a 15 per cent aqueous solution of sodium chloride in sufficient proportion to introduce 25 per cent by weight of the salt, based on the dry weight of the gum.  The process improves the rate of solution in water of the gum.