Method for producing a granular formulation of plastic-soluble colorants
The present invention relates to a method of producing a granular formulation of colorants soluble in plastics, which method comprises suspending in water a filter cake obtained from preparation of the colorant, adding thereto from 0.1 to 5.0% by weight, calculated with respect to the weight of colorant, of a polyvinylpyrrolidone and, where appropriate, further adjuvants, and then drying the aqueous suspension to form granules, to the granular formulations obtainable according to that method, and to the use thereof in the production of colored plastics or colored polymeric particles.
1. A method of producing a granular formulation of a colorant that is soluble in plastics, which granular formulation comprises from 91.5 to 99.8% by weight of a colorant soluble in plastics, from 0.1 to 5.0% by weight, calculated with respect to the weight of colorant, of a polyvinylpyrrolidone and, from 0.1 to 3.5% by weight, calculated with respect to the weight of colo-rant, of a viscosity regulator which process comprises suspending in water a filter cake obtained from preparation of the colorant, said colorant being selected from the group of solvent dyes, adding thereto from 0.1 to 5.0% by weight, calculated with respect to the weight of colorant, of a polyvinylpyrrolidone and from 0.1 to 3.5% by weight, calculated with respect to the weight of colorant, of a viscosity regulator and, where appropriate, further adjuvants, and then drying the aqueous suspension to form granules with a particle size of from 5 to 1000 microns.
2. A method according to claim 1 , wherein the viscosity regulator is hydroxypropyl methylcellulose, hydroxypropylcellulose or methylcellulose.
3. A method according to claim 1 , wherein the granulation is carried out with spray drying.
4. A method according to claim 1 wherein the colorant has a solubility at room temperature in water of less than 5% by weight.
5. A method according to claim 1 wherein the colorant has a solubility at room temperature in water of less than 2% by weight.
6. A method according to claim 1 wherein the colorant has a solubility at room temperature in water of less than 1% by weight.
7. A granular formulation of a colorant soluble in plastics, which comprises
(A) from 91.5 to 99.8% by weight of a colorant soluble in plastics said colorant being selected from the group of solvent dyes,
(B) from 0.1 to 5.0% by weight, calculated with respect to the weight of colorant, of a polyvinylpyrrolidone and from 0.1 to 3.5% by weight, calculated with respect to the weight of colorant, of a viscosity regulator and,
(C) where appropriate, further adjuvants,
wherein the granules have a particle size of from 5 to 100 microns.
8. A granular formulation according to claim 7 wherein the colorant has a solubility at room temperature in water of less than 5% by weight.
9. A granular formulation according to claim 7 wherein the colorant has a solubility at room temperature in water of less than 2% by weight.
10. A granular formulation according to claim 7 wherein the colorant has a solubility at room temperature in water of less than 1% by weight.
11. A method of producing colored plastics or colored polymeric particles, which method comprises incorporating into the plastic a granular formulation comprising
(A) from 91.5 to 99.8% by weight of a colorant soluble in plastics said colorant being selected from the group of solvent dyes,
(B) from 0.1 to 5.0% by weight, calculated with respect to the weight of colorant, of a polyvinylpyrrolidone and from 0.1 to 3.5% by weight, calculated with respect to the weight of colorant, of a viscosity regulator and,
(C) where appropriate, further adjuvants.
12. A method according to claim 11 wherein the plastic is food packaging.