Pigment dispersant for aqueous paints
AssigneeRohm and Haas Company
InventorsPeter R. Sperry, Richard J. Wiersema
Life of this patent
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Abstract
Described herein is a pigment paste for use in an aqueous paint comprising a film-forming latex polymer, a pigment and a dispersant copolymer. Also described is the dispersant copolymer which serves the function of dispersing the pigment in the preparation of the paste and maintaining the dispersion in the paste and paint made therefrom. The dispersant copolymer is such that its complex salt formed with Zn++ and ammonia is water-soluble at a pH of 9.6. The dispersant is a copolymer of an .alpha.,.beta.-unsaturated monovinylidene carboxylic acid and at least one other ethylenically unsaturated monomer. The dispersant is particularly adapted to preparing paste for difficult-to-formulate paints such as paints with reactive pigments and paints requiring high levels of dispersant.
Claims14
A pigment paste, adapted for use in a wide variety of aqueous latex paints, comprising a water-compatible suspension of a finely divided pigment and, for dispersion thereof, an effective amount of a water soluble dispersant comprising (1) an addition copolymer of greater than about 30 % by weight of an .alpha.;
- .beta.-unsaturated monovinylidene carboxylic acid or a mixture of such acids and (2) at least one other ethylenically unsaturated monomer, the copolymer having an apparent pKa between 6.0 and 7.5 and a number average molecular weight between about 500 and about 15,000;
- the copolymer being characterized by forming a water soluble salt with a zinc ammonia complex ion at a pH of 9.6.
A process for preparing a pigment paste comprising adding to a vessel paste components comprising (A) water, (B) a pigment, (C) about 0.01% to about 10%, on the weight of the pigment, of a water soluble dispersant comprising (1) an addition copolymer of greater than about 30% by weight of an .alpha., .beta.-unsaturated monovinylidene carboxylic acid or a mixture of such acids and (2) at least one other ethylenically unsaturated monomer, the copolymer having an apparent pKa between 6.0 and 7.5 and a number average molecular weight between about 500 and about 15,000;
- the copolymer being characterized by forming a water soluble salt with a zinc ammonia complex ion at a pH 9.6;
- and, optionally, (D) a wetting agent, an antifoam agent, a solvent, a thickener or any combination thereof and grinding the components under high shear to form a paste.
A water-soluble dispersant copolymer, adapted for use in pigment paste, consisting of (1) at least about 30% by weight of an .alpha.,.beta.-unsaturated monovinylidene carboxylic acid or a mixture of such acids and (2) at least one other ethylenically unsaturated monomer, the copolymer having an apparent pKa between 6.0 and 7.5 and a number average molecular weight between about 500 and about 15,000;
- the copolymer being characterized by forming a water-soluble salt with a zinc ammonia complex ion at a pH of 9.6.
Dependencies are inferred from the claim text.