Patent GB-991524-A (GB)
Title: Improvements in or relating to finely divided nitrocellulose particles, and manufacture and use thereof
IPC: C09D101/18
Filed: 1963-08-23
Abstract: Finely-divided nitrocellulose particles, a substantial majority of which, preferably at least 95%, have a distribution of particle sizes up to 1-2 microns in all three dimensions, and the remainder of which are less than 3 microns in two dimensions, but exceed 3 microns in length, said particles being irregularly shaped fragments of fibrous nitrocellulose, which is made by nitrating natural cellulose fibres, are disclosed. The particles are made by subjecting fibrous nitrocellulose suspended in a non-solvent medium selected from water, straight and branched chain alkanols having 1-4 carbon atoms, especially n-butanol or mixtures thereof, to repeated crushing impacts until substantially all of the nitrocellulose fibres have been fractured and comminuted into fragments having particle sizes of less than 3 microns in at least one dimension.  Fibrous nitrocellulose is obtained by nitrating natural cellulose fibres, e.g. cotton, purified cotton linters or purified wood pulp.  The repeated crushing impacts may be effected by ball-milling. Compositions may be made comprising a smooth, fluid homogeneous dispersion of such nitrocellulose particles in a non-solvent dispersion medium selected from water, straight and branched chain alkanols having from 1 to 4 carbon atoms, or mixtures thereof in any proportion. A hydrophilic protective colloid may also be present suitably in a proportion of 0.5-2% by weight, based on the nitrocellulose. Specified protective colloids include methyl cellulose, ethyl, hydroxyethyl, hydroxypropyl, hydroxyisopropyl, methyl hydroxyethyl, methyl hydroxypropyl, ethyl hydroxyethyl, and ethyl hydroxypropyl celluloses; methyl starch, ethyl, hydroxyethyl, hydroxypropyl, hydroxyisopropyl, methyl hydroxyethyl, methyl hydroxypropyl, ethyl hydroxyethyl, and ethyl hydroxypropyl starch; ammonium sodium, potassium, lithium, rubidium and caesium caseinates; alkali metal and ammonium salts of lignosulphonic acid, or of naphthalene sulphonic acid, or of glucoronic, galacturonic, and mannaronic acids; polyoxyethylene and polyoxypropylene glycols, and adducts of ethylene oxide and vinyl phenol.  Nitrocellulose hydrosol and organosol dispersions so made may be utilized to produce disperse type coating compositions of high solids content without the use of any volatile nitrocellulose solvent. Examples illustrate formulations suitable for coating paper, wood and steel.  Examples 1-3 describe the coating of paper with nitrocellulose hydrosol compositions containing also a resin emulsion, a wax emulsion, a plasticizer emulsion and optionally a pigment dispersion.  The resin emulsion contains a balsamic alkyd resin of terpinene maleic anhydride, a surface-active agent consisting of the polyoxyethylene esters of mixed tall oil fatty and resin acids, and oleic acid, emulsified in aqueous ammonia.  The wax emulsion contains paraffin wax, a surface-active agent consisting of the polyoxyethylene esters of mixed tall oil fatty and resin acids, and stearic acid, emulsified in aqueous caustic potash.  The plasticizer emulsion contains dibutyl phthalate and a surface-active agent consisting of the polyoxyethylene esters of mixed tall oil fatty and resin acids, emulsified in water containing sodium dioctyl sulphosuccinate. The pigment dispersion contains carbon black dispersed in water containing methyl cellulose. The compositions are coated on the paper with an air knife coater, dried, fused under heater lamps and then hot calendered at 190-210 DEG F. to give smooth glossy coatings which are grease-resistant, waterproof, have low moisture vapour transmission rates, and good heat sealing characteristics. Examples 4-10 are similar, using different protective colloids. Examples 11 and 12 utilize rust-inhibitors in the ball-milling of the nitrocellulose, and the hydrosol dispersions so made are combined with the plasticizer emulsion of Example 3 and an emulsion containing a blend of a hard, high-melting alkyd resin with additional plasticizer and protective colloids to form paper coating compositions which may be applied, dried and fused at 105 DEG C. Modified compositions may be made containing additional paraffin wax and these may be used as second-coat compositions, which are dried and fused as above, and then supercalendered at 170 DEG  F.  Various protective colloids are used.  In Example 13 a nitrocellulose dispersion in n-butanol is mixed with a modified pentaerythritol ester of rosin and the composition used to coat steel and maplewood panels, which are dried in air, sprayed with butyl acetate; or with a solution of dibutyl phthalate in butyl acetate, and dried.  In Example 14, a nitrocellulose hydrosol dispersion is mixed with starch to form a paper coating composition. Papers so coated are further coated either with dibutyl phthalate, followed by supercalendering at 190-210 DEG  F., or with a solution of an alkyd resin in dibutyl phthalate, followed by spraying with butyl acetate and drying.  The nitrocellulose-starch hydrosol dispersion is also coated on two wood surfaces, and on two paper surfaces, and air dried.  The coated wood and paper surfaces are then sprayed with acetone, dried until just tacky, and pressed together.  A printing ink may be made by mixing the nitrocellulose-starch hydrosol dispersion with carbon black. After application and air drying the ink is sprayed with butyl acetate and again dried. Example 15 is similar to Example 11 but utilizes various protective colloids.ALSO:Finely-divided nitrocellulose particles, a substantial majority of which (preferably at least 95%) have a distribution of particle sizes up to 1-2 microns in all three dimensions, and the remainder of which are less than 3 microns in two dimensions but exceed 3 microns in length, have particle sizes less than 3 microns in at least one dimension, said particles being irregularly shaped fragments of fibrous nitrocellulose which is made by nitrating natural cellulose fibres, are disclosed.  The particles are made by subjecting fibrous nitrocellulose suspended in a non-solvent medium selected from water, straight and branched chain alkanols having 1-4 carbon atoms, especially n-butanol or mixtures thereof, to repeated crushing impacts until substantially all of the nitrocellulose fibres have been fractured and comminuted into fragments having particle sizes of less than 3 microns in at least one dimension.  Fibrous nitrocellulose is obtained by nitrating natural cellulose fibres, e.g. cotton, purified cotton linters or purified wood pulp.  The repeated crushing impacts may be effected by ball-milling. Compositions may be made comprising a smooth, fluid homogeneous dispersion of such nitrocellulose particles in a non-solvent dispersion medium selected from water, straight and branched chain alkanols having from 1-4 carbon atoms, or mixtures thereof in any proportion.  A hydrophilic protective colloid may also be present suitably in a proportion of 0,5-2% by weight, based on the nitrocellulose. Specified protective colloids include methyl cellulose, ethyl, hydroxyethyl, hydroxypropyl, hydroxyisopropyl, methyl hydroxyethyl, methyl hydroxypropyl, ethylhydroxyethyl, and ethylhydroxypropyl celluloses; methyl starch, ethyl, hydroxyethyl, hydroxypropyl, hydroxyisopropyl, methylhydroxyethyl, methylhydroxypropyl, ethylhydroxyethyl, and ethyl hydroxypropyl starch; ammonium, sodium, potassium, lithium, rubidium and caesium caseinates; alkali metal and ammonium salts of lignosulphonic acid, or of naphthalene sulphonic acid, or of glucoronic, galacturonic, and mannaronic acids; polyoxyethylene and polyoxypropylene glycols, and adducts of ethylene oxide and vinyl phenol.  Nitrocellulose hydrosol and organosol dispersions so made may be utilized to produce disperse type coating compositions of high solids content without the use of any volatile nitrocellulose solvent.  Examples illustrate formulations suitable for coating paper, wood and steel.  Examples 1-3 describe the coating of paper with nitrocellulose hydrosol compositions containing also a resin emulsion, a wax emulsion, a plasticizer emulsion and optionally a pigment dispersion.  The resin emulsion contains a balsamic alkyd resin of terpinene maleic anhydride, a surface active agent consisting of the polyoxyethylene esters of mixed tall oil fatty and resin acids, and oleic acid, emulsified in aqueous ammonia.  The wax emulsion contains paraffin wax, a surface active agent consisting of the polyoxyethylene esters of mixed tall oil fatty and resin acids, and oleic acid, emulsified in aqueous ammonia.  The wax emulsion contains paraffin wax, a surface active agent consisting of the polyoxyethylene esters of mixed tall oil fatty and resin acids, and stearic acid, emulsified in aqueous caustic potash.  The plasticizer emulsion contains dibutyl phthalate and a surface active agent consisting of the polyoxyethylene esters of mixed tall oil fatty and resin acids, emulsified in water containing sodium dioctyl sulphosuccinate.  The pigment dispersion contains carbon black dispersed in water containing methyl cellulose.  The compositions are coated on the paper with an air knife coater, dried, fused under heater lamps and then hot calendered at 190-210  DEG F. to give smooth glossy coatings which are grease resistant, waterproof, have low moisture vapour transmission rates, and good heat sealing characteristics.  Examples 4-10 are similar, using different protective colloids.  Examples 11 and 12 utilize rust-inhibitors in the ball-milling of the nitrocellulose, and the hydrosol dispersions so made are combined with the plasticizer emulsion of Example 3 and an emulsion containing a blend of a hard, high melting alkyd resin with additional plasticizer and protective colloids to form paper coating compositions which may be applied, dried and fused at 105  DEG C. Modified compositions may be made containing additional paraffin wax and these ma