Dispersible Berlin blue pigment
AssigneeMerck Patent GmbH
InventorsAxel Rau, Klaus-Dieter Franz
Life of this patent
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Abstract
A dispersible Berlin blue pigment comprises Berlin blue deposited on to mica platelets. The pigment is additionally coated with a first coat of basic aluminum sulfate and a second coat of a mixture of a metal hydroxide with a polysiloxane or a fatty acid.
Claims17
A dispersible Berlin blue pigment comprising mica platelets having a coating of Berlin blue thereon, further comprising a first coating of basic aluminum sulfate, and on the coating of basic aluminum sulfate, a second coating of a mixture of a hydroxide of an alkaline earth metal, aluminum, tin, zinc, iron, cobalt or chromium, and a fatty acid of 4-30 carbon atoms or a polysiloxane of the formula:
- ##STR4## where R.sup.1 and R.sup.3 are independently each ##STR5## H, C.sub.1-4 -alkyl or poly-(C.sub.1-4 -alkylene)ether, and R.sup.2 and R.sup.4 are each ##STR6## C.sub.1-4 -alkyl or poly(C.sub.1-4 -alkylene)ether.
A process for preparing a dispersible Berlin blue pigment comprising suspending a mica pigment coated with Berlin blue, and adding to the suspension an aluminum salt, a sulfate and a base at a pH of 3-8, whereby there is precipitated on the pigment a layer of aluminum sulfate, and thereafter simultaneously adding to the suspension a solution of a metal salt forming a sparingly soluble hydroxide and a solution of a polysiloxane or a solution of an alkali metal salt of a fatty acid, and then separating the pigment.
Dependencies are inferred from the claim text.