Abstract A pearlescent pigment consisting of hexagonal platelets of basic lead carbonate is produced by bubbling carbon dioxide gas into an aqueous solution of a basic lead salt which is derived from the reaction of lead monoxide with an acid. The acid that is reacted with the lead monoxide can be nitric acid, but more preferably will have the general formula: WHEREIN X is a member from the group consisting of hydrogen, methyl and halogen. Reaction of the carbon dioxide with the basic lead salt is carried out in the presence of dimethylsulfoxide (DMSO) which is dissolved in the aqueous reaction medium, thus facilitating control over the rate and extent of crystal initiation and growth. The resulting basic lead carbonate pigment can be incorporated into plastics, lacquers, and the like to provide articles having the appearance of natural pearl.
The process of claim 1 in which the concentration of dimethylsulfoxide in the aqueous reaction medium is within the range of about 0.10 to about 60 weight percent.
Claim 2
Dependent Claim
28 words
The process of claim 1 in which the concentration of dimethylsulfoxide in the aqueous reaction medium is within the range of about 0.10 to about 10 weight percent.
Claim 3
Dependent Claim
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The process of claim 1 in which the carbon dioxide is introduced into said aqueous reaction medium as a gaseous stream which is diluted with a gas that is substantially nonreactive with said basic lead salt.
Claim 4
Dependent Claim
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The process of claim 1 in which said basic lead salt is produced by reacting lead monoxide with an aqueous solution of an organic acid having the general formula: wherein X is a member from the group consisting of hydrogen, methyl and halogen.
Claim 5
Dependent Claim
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The process of claim 5 in which said acid is acetic acid.
Claim 6
Dependent Claim
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The process of claim 5 in which said acid is propionic acid.
Claim 7
Dependent Claim
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The process of claim 5 in which said acid is betachloropropionic acid.
Claim 8
Dependent Claim
12 words
The process of claim 5 in which said acid is isobutyric acid.
Claim 9
Dependent Claim
12 words
The process of claim 5 in which said acid is n-butyric acid.
Claim 10
Dependent Claim
24 words
The process of claim 1 in which said basic lead salt is produced by reacting lead monoxide with an aqueous solution of nitric acid.
Claim 11
Dependent Claim
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The process of claim 1 in which the content of lead in said aqueous solution of basic lead salt is within the range of about 0.5 to about 7.0 weight percent.
Claim 12
Dependent Claim
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The process of claim 1 in which the temperature of said aqueous reaction medium is maintained within the range of about 0* C to about 100* C during reaction of the carbon dioxide with the basic lead salt.
Claim 13
Dependent Claim
40 words
The process of claim 1 in which said streams of basic lead salt solution and carbon dioxide are coextensively introduced into said solution of dimethylsulfoxide for a period of time within the range of about 6 to about 8 hours.