Patent GB-748780-A (GB)
Title: Process for coating finely divided solid materials
IPC: C11D17/00
Filed: 1953-05-28
Abstract: Finely divided solid particles are coated with a liquid by spraying the liquid into a fluidized bed of the finely divided solid material so as to be distributed substantially uniformly over the solid particles.  The liquid is defined as a metal-free organic substance which, although solid or temperature, or as a fused metal-free organic substance which although solid or semi-solid at room temperature, is fusible without decomposition at temperatures below 200 DEG C. or as a solution of a normally solid, metal-free organic substance in a (preferably volatile) solvent.  Finely divided solid substances are defined as solid substances whose individual particles, of either regular or irregular shape, have dimensions, or average dimensions, of not more than 10 millimeters.  The atomization of the liquid to be injected, and also the fluidization of the finely divided solid substance, can be effected by means of air, nitrogen or carbon dioxide.  The sprayed liquid may be injected at a single point or at points which lie at the same level, for example, half way up, or at varying levels in the fluidized bed.  The point or points of injection preferably lie mainly in the downward-flowing stream of the fluidized solid, the atomizer or atomizers for the liquid being disposed close to the side wall of the apparatus in which the solid is fluidized.  The direction in which the liquid is sprayed into the fluidized bed usually runs counter to the gas stream used for fluidization, but may also be in parallel flow. The liquid may be sprayed into the fluidization gas before this is fed into the material to be fluidized.  The process can be operated batchwise, but is particularly suitable for continuous operation, the fluidized bed being maintained by the continuous introduction of fresh solid substance while an equivalent part of the bed is continuously discharged.  The process may be used for the addition to particulate synthetic detergents of liquids which improve their foaming and detergent action.  Examples of such solid detergents are sulphuric acid ester salts of primary or secondary alcohols containing at least 7 carbon atoms and alkyl and alkyl-aryl sulphonates.  Examples of liquids are the higher primary and secondary alcohols, the higher 1, 2-alkane diols, and the higher fatty acid amides.  In an example a powdered detergent obtained by spray-drying, which contains 25 per cent of secondary sodium alkyl sulphates containing 8-18 carbon atoms per molecule and 75 per cent of sodium sulphate, is introduced into a vertical tube, at the bottom of which is a constriction holding a sieve plate.  The powder, consisting of particles of average diameter about 0.1 mm., is fluidized by blowing air upwards through the sieve plate, and fuzed technical lauryl alcohol at about 80 DEG C. is sprayed in a downward direction, the spraying nozzle being located about half way up the bed of fluidized powder and at a distance of about 2 cm. from the inner wall of the tube.  The process may be used for the coating of other particulate solid substances, such as calcium chloride, with a thin layer of oil or wax, in order to protect them against the action of water.  Artificial fertilizers and seeds may also be coated (see Group I).  The process may also be used for supporting biocidal substances on solid carriers and for incorporatinb perfumes into cosmetic powders (see Group VI).ALSO:Finely divided solid particles are coated with a liquid by spraying the liquid into a fluidized bed of the finely divided solid material so as to be distributed substantially uniformly over the solid particles.  The liquid is defined as a metal-free organic substance which is liquid at room temperature, or as a fused metal-free organic substance which, although solid or semi-solid at room temperature, is fusible without decomposition at temperatures below 200 DEG  C., or as a solution of a normally solid, metal-free organic substance in a (preferably volatile) solvent.  Finely divided solid substances are defined as solid substances whose individual particles, of either regular or irregular shape, have dimensions, or average dimensions, of not more than 10 millimetres.  The atomization of the liquid to be injected, and also the fluidization of the finely divided solid substance, can be effected by means of air, nitrogen or carbon dioxide.  The sprayed liquid may be injected at a single point or at points which lie at the same level, for example, half-way up, or at varying levels in the fluidized bed.  The point or points of injection preferably lie mainly in the downward-flowing stream of the fluidized solid, the atomizer or atomizers for the liquid being disposed close to the side wall of the apparatus in which the solid is fluidized.  The direction in which the liquid is sprayed into the fluidized bed usually runs counter to the gas stream used for fluidization, but may also be in parallel flow. The liquid may be sprayed into the fluidization gas before this is fed into the material to be fluidized.  The process can be operated batchwise, but is particularly suitable for continuous operation, the fluidized bed being maintained by the continuous introduction of fresh solid substance while an equivalent part of the bed is being continuously discharged.  The process may be used for the coating of hygroscopic finely-divided solid substances, such as calcium chloride and certain artificial fertilizers, with a thin layer of oil or wax, in order to protect them against the action of water; for supporting insecticidal, fungicidal or other biocidal substances such as D.D.T. on solid carriers, the D.D.T. being suitably applied as a solution in benzene; and for covering seeds with biocidal or growth-promoting substances.  In an example rape seed is introduced into a vertical tube fitted with a sieve plate in a constricted part at the bottom, and is fluidized by blowing air upwards through the sieve plate.  A solution of about 1 per cent of chloranil in benzene is injected in spray form into the fluidized bed of rape seed by means of a downwardly directed spraying nozzle fitted close to the inner wall of the tube and about half-way up the bed.  The process may also be used for coating powdered synthetic detergents with liquids (see Group III) and for incorporating perfumes with cosmetic powders (see Group VI).ALSO:Finely divided solid particles are coated with a liquid by spraying the liquid into a fluidized bed of the finely divided solid material so as to be distributed substantially uniformly over the solid particles.  The liquid is defined as a metal-free organic substance which is liquid at room temperature, or as a fused metal-free organic substance which, although solid or semi-solid at room temperature, is fusible without decomposition at temperatures below 200 DEG C., or as a solution of a normally solid, metal-free organic substance in a (preferably volatile) solvent.  Finely divided solid substances are defined as solid substances whose individual particles, of either regular or irregular shape, have dimensions, or average dimensions, of not more than 10 millimetres.  The atomization of the liquid to be injected, and also the fluidization of the finely divided solid substance, can be effected by means of air, nitrogen or carbon-dioxide.  The sprayed liquid may be injected at a single point or at points which lie at the same level, for example, halfway up, or at varying levels in the fluidized bed.  The point or points of injection preferably lie mainly in the down-ward-flowing stream of the fluidized solid, the atomiser or atomisers for the liquid being disposed close to the side wall of the apparatus in which the solid is fluidized.  The direction in which the liquid is sprayed into the fluidized bed usually runs counter to the gas stream used for fluidization, but may also be in parallel flow.  The liquid may be sprayed into the fluidization gas before this is fed into the material to be fluidized.  The process can be operated batch-wise, but is particularly suitable for continuous operation, the fluidized bed being maintained by the continuous introduction of fresh solid substance while an equivalent part of the bed is continuously discharged.  The process may be used for the coating of hygroscopic finely-divided solid substances with a thin layer of oil or wax, in order to protect them against the action of water; for supporting insecticidal, fungicidal or other biocidal substances such as D.D.T. on solid carriers, the D.D.T. being suitably applied as a solution in benzene, and for the incorporation of perfumes into cosmetic powders.