Carbon black for waterborne coatings
AssigneeCabot Corporation
InventorsLang H. Nguyen, Qingling Zhang, Lynne K. LaRochelle Richard
Life of this patent
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Abstract
An aqueous carbon black millbase, an aqueous carbon black liquid coating, and a method of making the millbase and liquid coating are provided. The carbon blacks are modified carbon blacks that are engineered to be able to be stirred into an aqueous vehicle without high energy milling of the carbon black. The modified carbon blacks include low organic treatment levels and the millbase and liquid coating do not require large quantities of dispersant. The resulting coatings exhibit excellent viscosity, color, hiding power and stability.
Claims23
A carbon black millbase dispersion comprising:
- an aqueous solvent comprising greater than 90% water by weight;
- at least 30% by weight of a modified carbon black, the modified carbon black having an STSA between 20 and 300 m2/g as measured prior to treatment, the modified carbon black modified with a treating agent comprising an organic group and an ionic or ionizable group at a treating agent concentration of between 1.0 and 3.0 μmol/m2;
- a dispersant concentration of less than 2.4 mg per square meter of carbon black surface area as measured by STSA prior to treatment;
- and
- wherein less than 10% by volume of the modified carbon black dispersed in the millbase has a particle size of greater than 0.5 μm.
A carbon black millbase dispersion comprising:
- an aqueous solvent comprising at least 90% water by weight;
- greater than 30% modified carbon black by weight, the modified carbon black treated with an organic treatment compound at a treatment level of between 1 and 3.0 μmol/m2, the organic treatment compound comprising both an aryl group and an ionic or ionizable group, the modified carbon black made from an untreated carbon black having an STSA of greater than 20 m2/g and less than 300 m2/g;
- less than or equal to 2.4 mg of dispersant per square meter of carbon black surface area;
- and
- wherein the carbon black millbase dispersion remains stably dispersed after one week at 52° C.
A carbon black millbase dispersion comprising greater than or equal to 30% of a modified carbon black and less than 2.4 mg of dispersant per square meter of carbon black surface area, the modified carbon black treated with a treating agent at a level of less than or equal to 2.0 μmol/m2, the millbase comprising an aqueous solvent that includes at least 90% water, and wherein the sum of the treatment level in μmol/m2 and the dispersant level in mg/m2 is greater than or equal to 2.5.
A method of making a stable aqueous liquid coating, the method comprising:
- mixing undispersed modified carbon black powder into an aqueous coating letdown vehicle comprising an aqueous solvent comprising at least 90% water by weight at a carbon black loading of greater than 0.01% by weight and less than 5% by weight of the stable aqueous liquid coating, the modified carbon black treated at a level of between 1.0 and 3.0 μmol/m2, the stable aqueous liquid coating having a dispersant concentration of less than 2.4 mg per square meter of carbon black surface area;
- and
- wherein the aqueous liquid coating exhibits a hiding power of greater than or equal to 0.97 at a wet film thickness of 0.0762 mm and wherein the undispersed modified carbon black powder is capable of being dispersed by stirring the modified carbon black into the aqueous coating letdown vehicle while not exceeding a blade tip speed of 4 m/s.
A method of making an aqueous millbase dispersion, the method comprising:
- stirring an undispersed modified carbon black dry powder free from milling media into an aqueous vehicle at a concentration of at least 30% by weight, based on the final weight of the millbase, to form a carbon black millbase, the modified carbon black treated with a treating agent at a loading between 1.0 and 3.0 μmol/m2, the treating agent comprising an aryl group and an ionic or ionizable group, the aqueous vehicle comprising a solvent that includes greater than 90% water by weight and less than 2.4 mg of dispersant per square meter of carbon black surface area, and
- wherein less than 10% by volume of the modified carbon black dispersed in the millbase has a particle size of greater than 0.5 μm.
Dependencies are inferred from the claim text.