Patent GB-1022621-A (GB)
Title: Producing pigments
Inventor: LEDERER GERALD
IPC: C09C1/36
Filed: 1963-02-15
Abstract: A process for producing pigmentary titanium dioxide comprises subjecting titanium dioxide to fluid energy milling in at least two milling stages wherein at least part of the milling fluid introduced into one milling stage is removed before the titanium dioxide is subjected to the next milling stage and wherein (a) the milling fluid is introduced into each milling stage at a pressure of at least 50 p.s.i.g., e.g. 150 to 250 p.s.i.g., or up to 500 p.s.i.g.; (b) the ratio of the weight of milling fluid introduced in each milling stage to the weight of titanium dioxide milled in that stage is between 0.5:1 and 5.0:1; and (c) the ratio of the total weight of milling fluid introduced in all milling stages to the total weight of titanium dioxide milled is at least 1.5: 1, e.g. at least 2.5: 1. The milling fluid is preferably a gas, e.g. air or steam, which does not react with the titanium dioxide. When the milling fluid is steam, the ratio of the weight of milling fluid introduced in each milling stage to the weight of titanium dioxide milled in that stage is from 1.0:1 to 2.0:1; alternatively, where there are at least three milling stages, the ratio of the weight of milling fluid introduced in each stage to the weight of titanium dioxide milled in that stage is from 0.8:1 to 1.2:1.  An organic modifying material may be added to the titanium dioxide during one or more of the milling stages.  This material may be a polyol, e.g. glycerol, pentaerythritol or trimethylolpropane, a fatty acid, e.g. oleic acid or stearic acid, an amine e.g. triethanolamine or a metal organic compound. The total amount of organic material added is 0.05-5%, e.g. 0.1-2.5%, by weight of the pigment.  The titanium dioxide particles before being subjected to the fluid energy milling may be coated with (a) a metal oxide or metal oxides, the metal or metals being aluminium, titanium, zirconium, cerium, tin and/or silicon, the amount of each metal oxide being 0.5-5%, e.g. 0.5 to 3.5% or 0.5-2.6% by weight of the titanium dioxide; (b) silica the amount of which is 0.2-2%, e.g. 0.5-1% or 0.5-0.7%, by weight of the titanium dioxide or (c) a phosphate, with or without other coating materials, the amount of which is 0.05-5%, e.g. 0.5-2.5%, by weight of the titanium dioxide. Examples are described.ALSO:A process for producing pigmentary titanium dioxide comprises subjecting titanium dioxide to fluid energy milling in at least two milling stages wherein at least part of the milling fluid introduced into one milling stage is removed before the titanium dioxide is subjected to the next milling stage and wherein (a) the milling fluid is introduced into each milling stage at a pressure of at least 50 p.s.i.g., e.g. 150-250 p.s.i.g. or up to 500 p.s.i.g., (b) the ratio of the weight of milling fluid introduced in each milling stage to the weight of titanium dioxide milled in that stage is between 0,5 : 1 and 5,0 : 1, and (c) the ratio of the total weight of milling fluid introduced in all milling stages to the total weight of titanium dioxide milled is at least 1,5 : 1, e.g. at least 2,5 : 1.  The milling fluid is preferably a gas, e.g. air or steam, which does not react with the titanium dioxide.  When the milling fluid is steam, the ratio of the weight of milling fluid introduced in each milling stage to the weight of titanium dioxide milled in that stage is from 1,0 : 1 to 2,0 : 1; alternatively, where there are at least three milling stages, the ratio of the weight of milling fluid introduced in each stage to the weight of titanium dioxide milled in that stage is from 0,8 : 1 to 1,2 : 1.  An organic modifying material may be added to the titanium dioxide during one or more of the milling stages.  This material may be a polyol e.g. glycerol, pentaerythritol or trimethylolpropane, a fatty acid e.g. oleic acid or stearic acid, an amine e.g. triethanolamine or a metal organic compound.  The total amount of organic material added is 0,05-5% e.g. 0,1-2,5% by weight of the pigment. The titanium dioxide particles before being subjected to the fluid energy milling may be coated with (a) a metal oxide or metal oxides, the metal or metals being aluminium, titanium, zirconium, cerium, tin and/or silicon, the amount of each metal oxide being 0,5-5% e.g. 0,5-3,5% or 0,5-2,6%, by weight of the titanium dioxide, (b) silica the amount of which is 0,2-2% e.g. 0,5-1% or 0,5-0,7%, by weight of the titanium dioxide, or (c) a phosphate, with or without other coating materials, the amount of which is 0,05-5% e.g. 0,5-2,5%, by weight of the titanium dioxide. Examples are described.