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The invention relates to a process for preparing pigments, which comprisessubjecting a crude pigment or mixture of crude pigments and a crystalline inorganic salt or mixture of crystalline inorganic salts together, essentially in the absence of other constituents, to the action of a rotor having a t

The invention relates to a process for preparing pigments, which comprisessubjecting a crude pigment or mixture of crude pigments and a crystalline inorganic salt or mixture of crystalline inorganic salts together, essentially in the absence of other constituents, to the action of a rotor having a tangential speed of at least 10 m/s, so that a temperature of at least 80° C. is attained by means of friction effects; and subsequentlykneading the product of this treatment with an organic liquid, during which it is possible if desired to add additional substances selected from the group consisting of inorganic salts, inert additives and colorant.These pigments and their use in polymers, printing inks and colours filters are also claimed.The invention in particular relates to a novel pigment form of Pigment Violet 23 obtained by above-mentioned process and having higher colour strength and colour saturation as well as excellent other applications properties in particular in printing inks.The invention also relates to a highly crystalline novel form of Pigment Red 254 obtained by above-mentioned process, too, and having a steep slope on the bathochromic side of the absorption spectrum's maximum, and the use thereof in particular in colour filters.

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1. A process for preparing a pigment, which comprisesa subjecting a crude pigment or mixture of crude pigments and a crystalline inorganic salt or mixture of crystalline inorganic salts together, essentially in the absence of other constituents, to the action of a rotor having a tangential speed of

1. A process for preparing a pigment, which comprisesa subjecting a crude pigment or mixture of crude pigments and a crystalline inorganic salt or mixture of crystalline inorganic salts together, essentially in the absence of other constituents, to the action of a rotor having a tangential speed of at least 10 m/s, so that a temperature of at least 80° C. is attained by means of friction effects; and subsequently b kneading the product of step a with an organic liquid, optionally adding substances selected from the group consisting of inorganic salts, inert additives and colorants wherein the pigment is an organic pigment of the quinacridone, anthraquinone, perylene, indigo, quinophthalone, indanthrone, isoindolinone, isoindoline, dioxazine, azo, phthalocyanine or diketopyrrolopyrrole series or inorganic pigment;the crystalline inorganic salt is a salt soluble in water to the extent of at least 10 g/100 ml;the organic liquid is soluble in water to the extent of at least 10 g/100 ml, and said crystalline inorganic salt being further insoluble or soluble to an extent of ?100 mg/l in said organic liquid at 20° C.2. A process according to claim 1, wherein during kneading the proportion of organic liquid to inorganic salt is from 1 ml:6 g to 3 ml:7 g and the proportion of organic liquid to the overall weight of inorganic salt and pigment is from 1 ml:2.5 g to 1 ml:7.5 g.3. A process for converting a crude pigment into an substantially amorphous fine-particled form, which comprises subjecting a crude pigment and a crystalline inorganic salt or mixture of crystalline inorganic salts together, essentially in the absence of other components, to the action of a rotor having a tangential speed of at least 10 m/s, so that by means of frictional effects a temperature of at least 80° C. is reached wherein the pigment is an organic pigment of the quinacridone, anthraquinone, perylene, indigo, quinophthalone, indanthrone, isoindolinone, isoindoline, dioxazine, azo, phthalocyanine or diketopyrrolopyrrole series or inorganic pigment;the crystalline inorganic salt is a salt soluble in water to the extent of at least 10 g/100 ml.4. A process according to claim 3, wherein the tangential speed is from 15 to 40 m/s and the ratio of inorganic salt to crude pigment is from 1:1 to 1:12.5. A process for preparing a pigment according to claim 1 by kneading a composition wherein the pigment is a compound of the formula whereinat the beginning of kneading, the compound of the formula (I) is in substantially amorphous form; the composition consists essentially of the compound of the formula (I), a crystalline inorganic salt or mixture of crystalline inorganic salts and an organic liquid; the organic liquid contains molecules with at least one oxo group; and the proportion of organic liquid to inorganic salt is from 1 ml:6 g to 3 ml:7 g, and the proportion of organic liquid to the overall weight of inorganic salt and compound of the formula (I) is from 1 ml:2.5 g to 1 ml:7.5 g. 6. A process according to claim 5, wherein the resulting pigment has a specific surface area of from 60 to 150 m2/g.7. A process according to claim 5, wherein said organic liquid is a ketone, an ester, an amide, a sulfone, a sulfoxide, a nitro compound or a mono-, bis- or trishydroxy-C2-C12alkane compound which is substituted by 1 or 2 oxo groups and on one or more hydroxyl groups may be etherified with C1-C8alkyl or esterified with C1-C8alkylcarbonyl, or a mixture thereof.8. A process according to claim 7, wherein said organic is liquid dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, dimethylacetamide or, in particular, dimethylformamide.9. A process according to claim 5, wherein said inorganic salt is aluminium sulfate, sodium sulfate, calcium chloride, potassium chloride or sodium chloride.10. A process according to claim 5, wherein the resulting pigment has a specific surface area of from 90 to 120 m2/g.