Patent GB-734624-A (GB)
Title: Bactericidal and similar compositions comprising cellulose ether carrier material
IPC: A01N25/10
Filed: 1953-02-16
Abstract: A fungicidal or bactericidal substance which can be dissolved, emulsified or dispersed in water at above 50 DEG  C. is applied to a solid cellulose ether, of the type which is soluble in water or aqueous alkali at normal temperature but insoluble in water above 50 DEG  C., by treating the solid cellulose ether with a solution, emulsion or dispersion of the substance in water at a temperature at which the cellulose ether is insoluble, preferably 80-100 DEG  C. Particularly suitable cellulose ethers are methyl, ethyl, methyl ethyl, methyl hydroxyethyl, ethyl hydroxyethyl, methyl carboxymethyl and ethyl carboxymethyl cellulose.  The cellulose ether may be of fibrous structure, and this structure may be maintained during the process.  The substances applied to the cellulose ether may be antibiotic materials produced by micro-organisms and which prevent the growth of, or kill, certain other micro-organisms, or such fungicidal, fungistatic, bactericidal, bacteriostatic and virus-killing substances as are not regarded as antibiotics.  If the active substance is insoluble in water and difficult to disperse or emulsify therein, even in the presence of emulsifying agents, it may be dissolved in a water-soluble organic solvent, e.g. methanol, ethanol or acetone, and the solution added to a larger volume of water.  In certain cases it may be preferable to remove the solvent from the emulsion or dispersion before applying the latter to the cellulose ether. The emulsion or dispersion may be prepared at a temperature below that at which the cellulose ether is insoluble in water and heated, immediately before its application to the cellulose ether, to a temperature above that at which the cellulose ether is insoluble.  If the cellulose ether is dry, it may be preheated to about the same temperature as the solution &c., to avoid gel-formation on the surface of the ether due to local cooling of the first added water.  The cellulose ether may be a crude product containing salts and other by-products formed during its production, and the process of the invention may then be combined with the step of washing the ether with water near the boiling point without previous drying and possibly grinding of the ether. When the active substance is capable of being adsorbed in the cellulose ether, the washing step may be followed by removal of the waste liquor by filtration or centrifuging, the ether redispersed in hot water, and the aqueous solution &c. of the active material added.  When adsorption equilibrium has been established, the water is again removed and the residue dried. When the active substance has no adsorptive affinity for the carrier, the hot moist mass of cellulose ether left after the removal of the wash liquor is sprayed with a hot aqueous solution &c., of the active material and the moist product is dried.  The cellulose ether, whether moist or dry, may be sprayed with a solution &c., of the active material in a shredder or kneader simultaneously with mechanical treatment.  The solubility of the cellulose ether in water at the operating temperature may be lowered by the addition to the water of water-soluble salts such as sodium fluoride, sodium sulphate or another water-soluble sulphate.  In an example, 50 g. of ethylhydroxyethyl cellulose, in which the degrees of substitution with regard to ethyl and hydroxyethyl are about 1.3 and 0.7 respectively, is suspended in boiling water to give an 8 per cent suspension and vacuum filtered to give a mat containing about 50 per cent solids.  A solution of 10 g. of lactic acid and 25 g. of sodium lauryl sulphate in 500 ml. of water with pH adjusted to about 3.5 with disodium hydrogen phosphate is poured almost at boiling point over the mat with application of suction.  The product is dried and, by defibration, given a loose woollen-like structure.ALSO:A bactericidal or fungicidal substance which can be dissolved, emulsified or dispersed in water at above 50 DEG  C. is applied to a solid cellulose ether, of the type which is soluble in water or aqueous alkali at normal temperature but insoluble in water above 50 DEG  C., by treating the solid cellulose ether with a solution, emulsion or dispersion of the substance in water at a temperature at which the cellulose ether is insoluble, preferably 80-100 DEG  C. Particularly suitable cellulose ethers are methyl, ethyl, methyl ethyl, methyl hydroxyethyl, ethyl hydroxyethyl, methyl carboxymethyl and ethyl carboxymethyl cellulose.  The cellulose ether may be of fibrous structure and this structure may be maintained during the process.  The substances applied to the cellulose ether may be antibiotic materials produced by micro-organisms and which prevent the growth of, or kill, certain other micro-organisms, or such fungicidal, fungistatic, bactericidal, bacteriostatic and virus-killing substances as are not regarded as antibiotics.  If the active substance is insoluble in water and difficult to disperse or emulsify therein, even in the presence of emulsifying agents, it may be dissolved in a water-soluble organic solvent, e.g. methanol, ethanol or acetone, and the solution added to a larger volume of water.  In certain cases it may be preferable to remove the solvent from the emulsion or dispersion before applying the latter to the cellulose ether. The emulsion or dispersion may be prepared at a temperature below that at which the cellulose ether is insoluble in water and heated, immediately before its application to the cellulose ether, to a temperature above that at which the cellulose ether is insoluble.  If the cellulose ether is dry it may be preheated to about the same temperature as the solution &c. to avoid gel-formation on the surface of the ether due to local cooling of the first added water.  The cellulose ether may be a crude product containing salts and other by-products formed during its production, and the process of the invention may then be combined with the step of washing the ether with water near the boiling point without previous drying and possibly grinding of the ether. When the active substance is capable of being adsorbed on the cellulose ether, the washing step may be followed by removal of the wash liquor by filtration or centrifuging, the ether redispersed in hot water, and the aqueous solution &c. of the active material added.  When adsorption equilibrium has been established, the water is again removed and the residue dried. When the active substance has no adsorptive affinity for the carrier, the hot moist mass of cellulose ether left after the removal of the wash liquor is sprayed with a hot aqueous solution &c. of the active material and the moist product is dried.  The cellulose ether, whether moist or dry, may be sprayed with a solution, &c. of the active material in a shredder or kneader simultaneously with mechanical treatment.  The solubility of the cellulose ether in water at the operating temperature may be lowered by the addition to the water of water-soluble salts such as sodium fluoride, sodium sulphate or another water-soluble sulphate.  In an example, 50 g. of ethylhydroxyethyl cellulose, in which the degrees of substitution with regard to ethyl and hydroxyethyl are about 1.3 and 0.7 respectively, is suspended in boiling water to give an 8 per cent suspension and vacuum-filtered to give a mat containing about 50 per cent solids.  A solution of 10 g. of lactic acid and 25 g. of sodium lauryl sulphate in 500 ml. of water with pH adjusted to about 3.5 with disodium hydrogen phosphate, is poured almost at boiling point over the mat with application of suction.  The product is dried and, by defibration, given a loose woollen-like structure.