Process for preparation of a novel pigmented composition for use in gravure inks
The invention pertains to a novel, simpler dry-milling method for comminuting crude pigments (especially crude phthalocyanines) for use in publication gravure and packaging inks, wherein the crude pigment is dry-milled at relatively low temperature in combination with a resin and a pigment derivative, preferably further together with an extender and optionally an antioxidant. The invention also pertains to the thus obtained, new compositions, which are extraordinarily easily dispersible in aromatic solvents, and their use for the preparation of publication gravure or packaging inks or ink concentrates. Pigment dispersions obtained from the preferred compositions are also claimed.
1. A process for producing a pigment composition, comprising the step of milling together at 0 to 70° C. a composition comprising
(a) a crude pigment;
(b) from 8 to 15% by weight, based on the amount of crude pigment (a), of a chromophore substituted by sulfo; SO 3 R 1 ; alkali, earth alkali or N + R 1 R 2 R 3 R 4 sulfonato; SO 2 NR 1 R 2 ; CH 2 NR 1 R 2 , phthalimidomethyl, N-pyrazolylmethyl or N-saccharinylmethyl, wherein R 1 , R 2 , R 3 and R 4 are independently from each other hydrogen or C 1 -C 24 alkyl, C 3 -C 24 cycloalkyl, C 2 -C 24 alkenyl, C 7 -C 24 aralkyl or C 6 -C 24 aryl each unsubstituted or substituted by hydroxy and/or halogen, whereby alkyl may be uninterrupted or optionally interrupted from one to ten times by O, N(C 1 -C 8 alkyl) or NH, and phthalimido is unsubstituted or substituted by halogen or nitro;
(c) from 20 to 55% by weight, based on the amount of crude pigment (a), of a resin selected from the group consisting of rosin, phenol-modified rosins, metal salts of rosin, metal salts of chemically modified rosins and mixtures thereof;
(d) from 2 to 18% by weight, based on the total weight of (a) and (b), of an extender; and
(e) optionally from 1 to 10% by weight, based on the amount of crude pigment (a), of an antioxidant and further optional components,
wherein the composition remains pulverulent or granular during milling.
2. The process according to claim 1 , wherein the pigment is a phthalocyanine, dioxazine or carbon black.
3. The process according to claim 2 , wherein the pigment is Colour Index Pigment Blue 15:1, 15:3, 15:6 or 16, Pigment Green 7, 36 or 37, Pigment Violet 23 or 37 or Pigment Black 6, 7 or 8.