Patent GB-642204-A (GB)
Title: Manufacture of pigments
IPC: C09C1/56
Filed: 1948-03-12
Abstract: Synthetic resins, e.g. polyvinyl chloride, or viscose or cellulose acetate may be pigmented by the addition of chocolate brown pigments manufactured by coupling one molecular proportion of tetrazotized benzidine or substituted benzidine with two molecular proportions of an aryl methyl pyrazolone in the presence of carbon black dispersed in one or other of the aqueous solutions of which the mixing brings about the coupling.  Specified examples of substituted benzidines are dianisidine, dichlorobenzidine and tolidine and of aryl methyl pyrazolones are phenylmethylpyrazolone and tolylmethylpyrazolone. Mixtures of the diamines or of the coupling components may be used to produce the correct shade of red pigment to give with the carbon the desired shade of brown. The mixtures of diamines used with 1-p-tolyl-3-methyl-5-pyrazolone in Specifications 621,599 and 633,215 may particularly be used. The carbon black should be highly dispersed before use, e.g. by gravel milling in the presence of water, caustic soda and disodium dinaphthylmethane-di-b -sulphonate until there are no particles greater than 10 microns in diameter and the bulk not greater than 6 microns.  The products may be kept in the form of aqueous pastes, or dried.  By limiting the proportion of carbon black strong bright tan brown shades can be obtained.  In an example, the tetrazonium sulphate solution prepared from 3 : 31-dichlorobenzidine sulphate and aqueous sulphuric acid is mixed with that prepared from o-dianisidine and aqueous sulphuric acid, sodium acetate added and then a suspension of dispersed carbon black in a solution of 1-p-tolyl-3-methyl-5-pyrazolone and aqueous caustic soda.  The suspension is heated, filtered, washed, dried and ground to a fine powder which is then incorporated into polyvinyl chloride producing bright strong tan-brown shades. Specification 604,875 also is referred to.ALSO:Chocolate brown pigments are manufactured by coupling one molecular proportion of tetrazotized benzidine or substituted benzidine with two molecular proportions of an aryl methyl pyrazolone in the presence of carbon black dispersed in one or other of the aqueous solutions of which the mixing brings about the coupling.  Specified examples of substituted benzidines are dianisidine, dichlorobenzidine and tolidine and of aryl methyl pyrazolones are phenylmethylpyrazolone and tolylmethylpyrazolone. Mixtures of the diamines or of the coupling components may be used to produce the correct shade of red pigment to give with the carbon the desired shade of brown.  The mixtures of diamines used with 1-p-tolyl-3-methyl-5-pyrazolone in Specifications 621,599 and 633,215 may particularly be used.  The carbon black should be highly dispersed before use, e.g., by gravel milling in the presence of water, caustic soda and disodium dinaphthylmethane-di-b -sulphonate until there are no particles greater than 10 microns in diameter and the bulk not greater than 6 microns.  The products may be kept in the form of aqueous pastes, or dried.  By limiting the proportion of carbon black, strong bright tan-brown shades can be obtained.  The products may be used for colouring rubber synthetic resins, viscose and cellulose acetate.  In examples: (1) carbon black is dispersed in water, caustic soda and disodium dinaphthylmethane-di-b -sulphonate and the suspension added to the tetrazonium sulphate solution from o-dianisidine sulphate and aqueous sulphuric acid, to which is added an aqueous solution of the condensation product of cetyl alcohol and ethylene oxide. Then a solution of 1-p-tolyl-3-methyl-5-pyrazolone, caustic soda and sodium acetate is added and the solution stored to complete the coupling, filtered, washed, and then mixed with aqueous disodium dinaphthylmethane-di-b -sulphonate to produce a paste; (2) as in (1) in which the tetrazonium sulphate is prepared from a mixture of 3 : 31-dichlorobenzidine sulphate and o-dianisidine; (3) as in (1), in which the tetrazonium sulphate is prepared from a mixture of o-dianisidine and benzidine; (5) as in (1) in which the tetrazonium sulphate is prepared from 3 : 31-dichlorobenzidine sulphate; (4) as in (2) but using 1-phenyl-3-methyl-5-pyrazolone; (6) the solution prepared by heating a mixture of 3 : 31-dichlorobenzidine sulphate and o-tolidine in aqueous hydrochloric acid is cooled and aqueous sodium nitrite added and then after filtering an aqueous solution of disodium dinaphthylmethane-di-b -sulphonate, sodium acetate crystals and a dispersion of carbon black prepared as in (1). The suspension is stirred, and a solution of 1-p-tolyl-3-methyl-5-pyrazolone and sodium hydroxide in water gradually added.  The brown pigment so obtained is isolated as a paste.  Specification 604,875 also is referred to.ALSO:Chocolate brown pigments are manufactured by coupling one molecular proportion of tetrazotized benzidine or substituted benzidine with two molecular proportions of an aryl methyl pyrazolone in the presence of carbon black dispersed in one or other of the aqueous solutions of which the mixing brings about the coupling.  Specified examples of substituted benzidines are dianisidine, dichlorobenzidine and tolidine and of aryl methyl pyrazolones are phenylmethylpyrazolone and tolylmethylpyrazolone. Mixtures of the diamines or of the coupling components may be used to produce the correct shade of red pigment to give with the carbon the desired shade of brown.  The mixtures of diamines used with 1-p-tolyl-3-methyl-5-pyrazolone in Specifications 621,599 and 633,215, [both in Group IV (a)], may particularly be used.  The carbon black should be highly dispersed before use, e.g. by gravel milling in the presence of water, caustic soda and disodium dinaphthylmethane-di-b -sulphonate until there are no particles greater than 10 microns in diameter and the bulk not greater than 6 microns.  The products may be kept in the form of aqueous pastes, or dried.  By limiting the proportion of carbon black, strong bright tan-brown shades can be obtained.  The products may be used for colouring rubber.  Specification 604,875 also is referred to.