Pearlescent pigment for water-borne surface-coating systems
AssigneeMerck Patent GmbH
InventorsJoachim Duschek, Ralf Glausch
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Abstract
A pearlescent pigment based on a metal oxide-coated, platelet-shaped substrate and a top layer on the metal oxide layer, where the top layer comprises silicon dioxide, at least one further metal hydroxide or metal oxide hydrate and at least one organic coupling reagent. The further metal hydroxides or metal oxide hydrates are hydroxides or oxide hydrates of cerium, aluminum or zirconium, or mixtures thereof. The coupling reagents employed are organofunctional silanes, zirconium aluminates or metal acid esters.
Claims13
A pearlescent pigment comprising a metal oxide-coated, platelet-shaped substrate and a top layer on the metal oxide coating, wherein the top layer comprises silicon dioxide, at least one metal hydroxide or metal oxide hydrate and at least one organic coupling reagent.
A process for the preparation of a pearlescent pigment comprising a metal oxide-coated, platelet-shaped substrate and a top layer on the metal oxide coating, comprising suspending the metal oxide-coated substrate in water, depositing silicic acid by adding a water-soluble silicate at a pH from 6 to 9, then, after adding one or more water-soluble metal salts at a pH from 3 to 7 and heating to from 30.degree. to 100.degree. C., partly depositing the metal hydroxides or metal oxide hydrates, adding at east one coupling reagent and hydrolyzing at a pH from 3 to 4, and depositing the part of the metals remaining in solution as hydroxides or oxide hydrates together with the coupling reagent at a pH of from 4 to 8.5, and subsequently drying the pigment from 80.degree. to 160.degree. C.
Dependencies are inferred from the claim text.