The invention relates to a process for preparing pigments, which comprises
- 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
- kneading 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
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##STR1##
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
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##STR2##
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.
