Patent GB-600911-A (GB)
Title: Solvent stable phthalocyanine pigments
IPC: C09B67/12
Filed: 1944-03-28
Abstract: The invention consists in a finely divided, tinctorially strong, halogen free, sulphuric acid stable, crystalline phthalocyanine pigment, the particles of which are uncoated and on contact with a "crystallizing solvent" (i.e. one which induces crystal growth in ordinary forms of phthalocyanine pigments and selected from aromatic hydrocarbons, esters, ethers and alcohols which are liquid at air temperature) will show an average pigment particle size of less than 2 microns.  Such pigments are obtainable by transforming an acid pasted phthalocyanine pigment into a coarsely crystalline form, subjecting the latter to grinding in the presence of a grinding aid (i.e. an inert material of which the particles are harder than those of the pigment and which may subsequently be removed by leaching with water, as in the case of salt or soluble carbohydrates, or by acid leaching, as in the case of calcium carbonate, or which is capable of acting as a pigment extender and therefore need not be removed as in the case of inert fillers such as diatomaceous earth, blanc fixe or powdered silica) and treating the ground crystalline material with a "crystallizing solvent."  The initial transformation into a coarsely crystalline form may be effected by heating the pigment dry or in an autoclave with water, preferably to about 230 DEG  C., but preferably by heating with a "crystallizing solvent," in which case the three steps may be combined by mechanically working together the pigment, grinding aid and "crystallizing solvent." In examples: (1) crude copper phthalocyanine is acid pasted in the presence of xylenesulphonic acid, dried, crystallized by boiling with toluene or heating in air or in water under pressure, ground in a ball or pebble mill with the water-soluble carbohydrate sold under the Registered Trade Mark "Cerelose," leached with water and flushed with toluene; (2) crude copper phthalocyanine is acid pasted, dried, refluxed with ethyl acetate, ground with common salt, leached with water and suspended in xylene; (3) crude copper phthalocyanine is acid pasted, dried, refluxed with ethylene glycol, ground in a rod mill with calcium carbonate, leached with dilute hydrochloric or other acid and warmed with toluene; alternatively, the calcium carbonate is allowed to remain as an extender of the pigment, or silica may be used for this purpose; (4) copper phthalocyanine as pasted as in (1), dried, ground and then kneaded with sodium bicarbonate and xylene, dried, slurried in water, filtered, washed and dried; (5) acid pasted zinc phthalocyanine is boiled with toluene, ground with sodium chloride, with the addition of water in the later stages, leached with water and boiled with toluene; (6) nickel phthalocyanine is acid pasted as in (1), refluxed with toluene, ground as in (5), leached with water and boiled with toluene; (7) acid pasted copper phthalocyanine is boiled with xylene, filtered, dried, and ground with the diatomaceous earth sold under the Registered Trade Mark "Cellite," with the addition of xylene in the later stages; (8) acid pasted copper phthalocyanine is worked in a dough mixer or chaser mill with "Cellite" and xylene.  Reference is also made to the treatment of cobalt and iron phthalocyanines. Specification 503,666 is referred to.  The Specification as open to inspection under Sect. 91 comprises also the treatment of coarse phthalocyanine crystals originally obtained before acid pasting, and includes an example of this alternative.  This subject-matter does not appear in the Specification as accepted.ALSO:Phthalocyanine pigments in coarsely crystalline form are subjected to grinding in the presence of a grinding aid (i.e. an inert material of which the particles are harder than those of the pigment and which may subsequently be removed by leaching with water, as in the case of common salt, sodium bicarbonate or soluble carbohydrates such as that sold under the Registered Trade Mark "Cerelose," or by acid leaching, as in the case of calcium carbonate, or which is capable of acting as a pigment extender and therefore need not be removed, as in the case of inert fillers such as diatomaceous earth, blanc fixe or powdered silica), in some cases with the addition of water or xylene in the later stages.  Alternatively an acid - pasted phthalocyanine and the grinding aid are mechanically worked with a liquid ester, ether, alcohol or aromatic hydrocarbon (e.g. xylene) which causes the growth of coarse crystals which are immediately broken down. Specification 503,666, [Group IV], is referred to.