US4040860A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Chromium oxide pigment from sodium chromate dihydrate plus ammonium salt
Assignee: Bayer AG
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Filing: 1976-02-06
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Granted: 1977-08-09
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Expires: 1996-02-06
Abstract
Abstract In the production of chromium oxide green pigment by heating a substantially stoichiometrically equivalent mixture of sodium dichromate dihydrate and an ammonium salt selected from the group consisting of the sulfate and chloride, the improvement which comprises dry mixing sodium dichromate dihydrate having a particle size less than 2 mm with the ammonium salt having a particle size less than about 0.5 mm, heating the resulting mixture over a period of about 15 minutes to a pigment-forming temperature of about 800° to 1100° C, calcining the mixture at a temperature in that range, and separating the formed pigment from the salts. To the mixture prior to heating there may be added sodium hydroxide solution, boron compounds such as borax and/or organic modifiers such as sawdust which improve the color and tinting strength of the resulting pigment. The pigments are brighter, and of higher tinting strength than heretofore produced.
Inventors
- 👤 Manfred Mansmann
- 👤 Wolfgang Rambold
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 08:18
CPC Classifications
C; C01; C01G; C01G37/00; C01G37/02; C01P; C01P2006/00; C01P2006/60
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
123 words
In the production of chromium oxide green pigment by heating a substantially stoichiometrically equivalent mixture of sodium dichromate dihydrate and an ammonium salt selected from the group consisting of the sulfate and chloride, the improvement which comprises thoroughly dry mixing sodium dichromate dihydrate having a particle size less than about 2 mm with the ammonium salt having a particle size less than about 0.5 mm, adding water to the mixture in about 1 to 10% by weight of the sodium dichromate dihydrate plus ammonium salt, heating the resulting mixture over a period of about 15 minutes to a pigment-forming temperature of about 800° to 1100° C., calcining the mixture at a temperature in that range, and separating the formed pigment from the salts.
Claim 2
Dependent Claim
123 words
In the production of chromium oxide green pigment by heating a substantially stoichiometrically equivalent mixture of sodium dichromate dihydrate and an ammonium salt selected from the group consisting of the sulfate and chloride, the improvement which comprises thoroughly dry mixing sodium dichromate dihydrate having a particle size less than about 2 mm with the ammonium salt having a particle size less than about 0.5 mm, adding water to the mixture in about 1 to 10% by weight of the sodium dichromate dihydrate plus ammonium salt, heating the resulting mixture over a period of about 15 minutes to a pigment-forming temperature of about 800° to 1100° C., calcining the mixture at a temperature in that range, and separating the formed pigment from the salts.
Claim 3
Dependent Claim
35 words
A process as claimed in claim 1, wherein to the mixture prior to heating there is added about 0,1 to 10% of a modifier based on the weight of sodium dichromate dihydrate plus ammonium salt.
Claim 4
Dependent Claim
22 words
A process as claimed in claim 2, wherein the modifier is inorganic and is added in about 2 to 5% by weight.
Claim 5
Dependent Claim
14 words
A process as claimed in claim 3, wherein the modifier is a boron compound.
Claim 6
Dependent Claim
55 words
A process as claimed in claim 2, wherein the modifier is added in about 1 to 4% by weight and is selected from the group consisting of a lignin derivative, cellulose derivative, molasses, starch, urea, medium-viscosity mineral oil, polyethylene powder, polyethylene oxide, sawdust, wood powder, colophony, rice straw powder, unsaturated polyester resins and active carbon.
Claim 7
Dependent Claim
28 words
A process as claimed in claim 1, wherein the water is added in the form of a sodium hydroxide solution of about 5 to 15% concentration by weight.
Claim 8
Dependent Claim
41 words
A process as claimed in claim 1, wherein the mixture is directly introduced into the hot zone of a rotary tubular kiln, disc-type kiln or rotary annular kiln, which hot zone is at a temperature of about 800° to 1100° C.
Claim 9
Dependent Claim
104 words
A process as claimed in claim 1, wherein the water added to the mixture before it is heated is in the form of a 5 to 15% sodium hydroxide solution and there is also added at least one modifier selected from the group consisting of (A) about 1 to 4% by weight of wood powder, starch or lignin, and (B) about 2 to 5% by weight of borax, and the mixture is directly introduced into the hot zone of a rotary tubular kiln, a disc-type kiln or a rotary annular kiln, which hot zone is at a temperature of about 800° to 1100° C.
Claim 10
Dependent Claim
83 words
A process as claimed in claim 1, wherein there is also added to the mixture before heating at least one modifier selected from the group consisting of (A) about 1 to 4% of wood powder, starch or lignin, and (B) about 2 to 5% of borax, and wherein the mixture is directly introduced into the hot zone of a rotary tubular kiln, a disc-type kiln or a rotary annular kiln, which hot zone is at a temperature of about 800° to 1100° C.
Claim 11
Dependent Claim
10 words
Chromium oxide green produced by the process of claim 1.
Claim 12
Dependent Claim
10 words
Chromium oxide green produced by the process of claim 8.
Claim 13
Dependent Claim
10 words
Chromium oxide green produced by the process of claim 9.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-08-08 | 1981-02-07 | 1981-08-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-08-08 | 1985-02-07 | 1985-08-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-08-08 | 1989-02-07 | 1989-08-09 | $7700.00 | Window Closed / Lapsed |