Patent GB-367817-A (GB)
Title: Improvements in the manufacture and production of firmly adherent coatings
IPC: B05D3/10
Filed: 1930-09-15
Abstract: Relates to the production of firmly adherent coatings of cellulose derivatives on solid articles, and the coatings may consist of alternate layers of cellulose derivatives and of paper, silk, cotton, asbestos board or fabric, or of metal wires which may be covered with fabric.  The process is particularly applicable for coating wires, rods or tubes, and in the manufacture of electric cables, condensers, and insulating layers for the groovings of dynamos and motors.  The process consists in the use of certain mixed cellulose derivatives, and in subsequently treating the coated article with a difficulty volatile swelling agent, i.e. one which is non-volatile at ordinary temperatures and boils at 100 DEG  C. or over under a pressure of 10mm. of mercury.  The mixed cellulose derivatives capable of swelling with such agents are those containing at least one group which increases their solubility in water, and at least one group which increases their solubility in hydrocarbons.  The group increasing the solubility in water may be a fatty acid radicle with less than 5 carbon atoms, the nitric acid radicle, a methyl group, or an hydroxy-alkyl group; the group which increases the solubility in hydrocarbons may be a fatty acid radicle with more than 10 carbon atoms or an alkyl group with two or more carbon atoms; the mixed cellulose derivatives may therefore be mixed esters, ether esters, hydroxy-ether esters, or mixed ethers, provided the groups present comply with these requirements.  Mixed fatty acid esters, and hydroxy-ether esters should contain 5-30 per cent by weight of the higher fatty acid.  Swelling agents specified are transformer oils, and soft or hard paraffin wax, montan wax, bitumen or asphalt, solutions of colophony in transformer oils, polymerization products of propylene or of other olefines, linseed or castor or other vegetable oils either raw or blown, and propyl-naphthalene.  The wax, bitumen, or asphalt may be used alone or with mineral oils.  The coating of cellulose derivative may be formed in any thickness from the dissolved, thermo-plastic, or fused coating material, or it may be applied in the form of ribbon.  The swelling treatment may be effected at 120 DEG  C. under increased or reduced pressure, or in a vacuum, e.g. at a pressure of 2-50 mm. of mercury, or the pressure may be alternately increased and reduced.  The coated wire may be wound into finished coils, e.g. for transformers, and afterwards subjected to the swelling treatment.  In order to produce layers having different dielectric constants several layers of different cellulose derivative may be employed having different capacities for swelling, and different swelling agents may be used one after another.  For example, a conductor may be coated with successive layers of a cellulose butyrate laurate containing 4 lauric to 1 butyric radicle and of paper, and then with successive layers of a similar ester containing 1 lauric to 1 butyric radicle and of paper, and treated at 80-120 DEG  C. under reduced pressure with transformer oil or with polymerized propylene, or with rosin oil. The inner layers are capable of swelling more strongly than the outer layers. In a modification of this process, the inner layers are treated with ordinary or blown castor oil as swelling agent, and the outher layers with transformer oil with or without rosin, this swelling agent having a lower dielectric constant than the castor oil.  In making condensers, paper may be combined with films of the mixed cellulose derivative, or coated with it, or the cellulose derivative may be incorporated with the paper during manufacture by the use of a suspension or emulsion; the prepared paper is dried and built up into a condenser, and the finished windings or layers then submitted to the swelling process.  In further examples, (1) a cable is coated by repeated lacquering with cellulose butyrate laurate, or cellulose acetate butyrate laurate and immersed for 48 hours in transformer oil at 100 DEG  C. under a pressure of 10 mm. mercury or less; (2) a cable is wound with a strip of film made from the same esters, or from an ether-ester such as ethyl cellulose nitrate, or from a mixed ether containing one or more methyl or hydroxy-alkyl groups and one or more ethyl or higher alkyl group, and treated for 1 or 2 days with transformer oil or propylnaphthalene at about 100 DEG  C. under raised and reduced pressure alternately; (3) a copper wire is wound with a film of cellulose butyrate laurate containing 2 lauric to 1 butyric radicle, then with paper, and again with cellulose ester and with paper, and the coiled wire is treated with transformer oil first under a pressure of 2-25 mm. of mercury to remove air and moisture, and then at 100 DEG  C. for 24 hours under atmospheric pressure or in vacuo; (4) condenser paper is coated with a solution of a similar cellulose butyrate laurate in benzene, butanol, and acetone, with or without polymerized indene, and is built up with tinfoil into a coiled condenser which is then immersed in castor oil at 80 DEG  C. for 12 hours at a pressure of 2-10 mm. of mercury.  Specifications 21293/00, [Class 36, Electricity, Conducting &c.], 259,131, [Class 38 (ii), Electric currents, Converting &c.], 288,221, and 319,371, [both in Class 95, Paints &c.], are referred to.ALSO:A coating process consists in the use of certain mixed cellulose derivatives, and in subsequently treating the coated article with a difficultly volatile swelling agent, i.e. one which is non-volatile at ordinary temperatures and boils at 100 DEG  C. or over under a pressure of 10 mm. of mercury.  The mixed cellulose derivatives capable of swelling with such agents are those containing at least one group which increases their solubility in water, and at least one group which increases their solubility in hydrocarbons.  The group increasing the solubility in water may be a fatty acid radicle with less than 5 carbon atoms, the nitric acid radicle, a methyl group, or an hydroxy-alkyl group; the group which increases the solubility in hydrocarbons may be a fatty acid radicle with more than 10 carbon atoms or an alkyl group with two or more carbon atoms; the mixed cellulose derivatives may therefore be mixed esters, ether esters, hydroxy-ether esters, or mixed ethers, provided the groups present comply with these requirements.  Mixed fatty acid esters, and hydroxy-ether esters should contain 5 to 30 per cent by weight of the higher fatty acid.  Swelling agents specified are transformer oils, and soft or hard paraffin wax, montan wax, bitumen or asphalt, solutions of colophony in transformer oils, polymerization products of propylene or of other olefines, linseed or castor or other vegetable oils either raw or blown, and propyl-naphthalene.  The wax, bitumen, or asphalt may be used alone or with mineral oils. The coating of cellulose derivatives may be formed in any thickness from the dissolved, thermoplastic, or fused coating material, or it may be applied in the form of ribbon.  In one example, a conductor is coated with successive layers of a cellulose butyrate laurate containing 4 lauric to 1 butyric radicle and of paper, and then with successive layers of a similar ester containing 1 lauric to 1 butyric radicle and of paper, and treated at 80-120 DEG  C. under reduced pressure with transformer oil or with polymerized propylene, or with rosin oil.  The inner layers are capable of swelling more strongly than the outer layers.  In a modification of this process, the inner layers are treated with ordinary or blown castor oil as swelling agent, and the outer layers with transformer oil with or without rosin.  In further examples, (1) a cable is coated by repeated lacquering with cellulose butyrate laurate, or cellulose acetate butyrate laurate and immersed for 48 hours in transformer oil; (2) a cable is wound with a strip of film made from the same esters, or from an ether-ester such as ethyl cellulose nitrate, or from a mixed ether containing one or more methyl or hydroxy-alkyl groups and one or more ethyl or higher alkyl group, and treated for 1 or 2 days with transformer oil or propylnaphthalene; (3) a copper wire is wound with a film of cellulose butyrate laurate containing 2 lauric to 1 butyric radicle, then with paper, and again with cellulose ester and with paper, and the coiled wire is treated with transformer oil; (4) condenser paper is coated with a solution of a similar cellulose butyrate laurate in benzene, butanol, and acetone, with or without polymerized indene, and is built up with tinfoil into a coiled condenser.  Specifications 21293/00, [Class 36, Electricity, Conducting &c.], 259,131, [Class 38 (ii), Electric currents, Converting &c.], 288,221, [Class 95, Paints &c.], and 319,371, [Class 2 (ii), Cellulose &c.], are referred to.