Patent GB-760116-A (GB)
Title: Pigments and processes of producing same
IPC: C09B67/00
Filed: 1953-07-09
Abstract: Pigments of improved dispersability and tinctorial value prepared by mixing finely-divided organic colours in a liquid medium with activated silica gel and thereafter removing the liquid (see Group IV (c)) are used to colour cellulose acetate and nitrate, phenol-formaldehyde, urea-formaldehyde and polyamide resins and polyethylene and polyvinyl resins, e.g. vinyl and vinylidene chloride polymers.  A series of green pigments prepared by mixing 5, 10 and 20 parts of activated silica gel with 1 part of dimethoxy-dibenzanthrone and water to a paste followed by grinding and drying are (a) mixed with polystyrene and injection-moulded at 320 DEG  F.; and (b) mixed with cellulose acetate and injection-moulded at 350 DEG  to 380 DEG F.ALSO:The invention comprises pigments of improved dispersibility and tinctorial value, which are produced by a process wherein an activated silica gel which has a surface area of at least 100 square meters, and preferably 180 to 900 square meters per gram, an oil absorption value of at least 100, and preferably from 150 to 180, and an average particle size of from 0.01 to 50 microns, and preferably from 0.02 to 20 microns, is mixed with a finely divided organic colour in a liquid medium, and thereafter the liquid is removed from the mixture.  From 1/20 to 20 parts and preferably from 1/5 to 5 parts by weight of activated silica gel are used per part by weight of organic colour. Specified organic colours are vat, azo, phthalocyanine or triphenylmethane dyes and lakes.  Any organic colour which forms a dispersion of finely divided particles in a liquid medium or which may be precipitated in finely divided form from a liquid medium may be used, the silica gel being added prior to the drying thereof.  When the organic colour is precipitated from an aqueous medium the silica gel may be added before, during, or after the precipitation.  The organic colour may also be separated from the liquid medium, e.g. by filtration and admixed with the silica gel prior to drying.  The silica gel and organic colour may also be mixed in a volatile organic solvent, in which the organic colour may be soluble, and the mixture evaporated to dryness.  The pigments are suitable for colouring printing inks, enamels, paints, lacquers, and plastics such as cellulose acetate and nitrate and polyethylene or polyvinyl resins (see Group IV(a)), phenol - formaldehyde resins, urea - formaldehyde resins, polyamide resins and rubber.  In examples: (1) dimethoxy - dibenzanthrone is mixed to a paste with silica gel and water, ground and dried to give a soft and readily dispersible pigment, 5 : 51 - dichloro - 6 : 61 - dimethyl - 2 : 21 - bis - thionaphthen - indigo and monochloro - N - dihydro - 1 : 2 : 11 : 21 - anthraquinone azine being treated similarly; (2) silica gel is added to the solution of the leuco compound of monochloro - N - dihydro - 1 : 2 : 11 : 21 - anthraquinone azine, the dyestuff is precipitated by oxidation with hydrogen peroxide and the mixture filtered and dried; (3) a filter cake of the monazo dyestuff from diazotized xylidine coupled with b  - napthol is treated as in (1); (4) a filter cake of the monoazo-dyestuff from diazotized 2 - chloro - 4 - nitro - aniline coupled with b  - napthol is treated as in (1); (5) copper phthalocyanine is treated as in (1); (6) the hydrochloride of pentamethyl triamino triphenylcarbinol anhydride is formed into a lake with alumina, the lake filtered and the resultant press cake mixed with silica gel and dried; (7) the alumina lake of 1 : 2 - dihydroxyanthraquinone is treated as in (6).ALSO:Pigments of improved dispersibility and tinctorial value, are produced by mixing wherein an activated silica gel which has a surface area of at least 100 square meters, and preferably 180 to 900 square meters per gram, an oil absorption value of at least 100, and preferably from 150 to 180, and an average particle size of from 0.01 to 50 microns, and preferably from 0.02 to 20 microns, with a finely divided organic colour in a liquid medium, and thereafter the liquid is removed from the mixture.  From 1/20 to 20 parts and preferably from 1/5 to 5 parts by weight of activated silica gel are used per part by weight of organic colour.  Specified organic colours are vat, azo, phthalocyanine or triphenylmethane dyes and lakes.  Any organic colour which forms a dispersion of finely divided particles in a liquid medium or which may be precipitated in finely divided form from a liquid medium may be used, the silica gel being added prior to the drying thereof.  When the organic colour is precipitated from an aqueous medium the silica gel may be added before, during, or after the precipitation.  The organic colour may also be separated from the liquid medium, e.g. by filtration and admixed with the silica gel prior to drying.  The silica gel and organic colour may also be mixed in a volatile organic solvent, in which the organic colour may be soluble, and the mixture evaporated to dryness.  The pigments are suitable for colouring enamels, paints and lacquers. In examples: (1) dimethoxy-dibenzanthrone is mixed to a paste with silica gel and water, ground and dried to give a soft and readily dispersable pigment, 5:51-dichloro-6:61-dimethyl-2:21-bisthionaphthen -indigo and monochloro-N-dihydro-1:2:11:21-anthraquinone azine being treated similarly; (2) silica gel is added to the solution of the leuco compound of monochloro - N - dihydro - 1:2:11:21 - anthraquinone azine, the dyestuff is precipitated by oxidation with hydrogen peroxide and the mixture filtered and dried; (3) a filter cake of the monoazo dyestuff from diazotized xylidine coupled with b -napthol is treated as in (1); (4) a filter cake of the monoazodyestuff from diazotized 2-chloro4-nitro-aniline coupled with b -naphthol is treated as in (1); (5) copper phthalocyanine is treated as in (1); (6) the hydrochloride of pentamethyl triamino triphenylcarbinol anhydride is formed into a lake with alumina, the lake filtered and the resultant press cake mixed with silica gel and dried, (7) the alumina lake of 1:2-dihydroxyanthraquinone is treated as in (6).