EP0306224A1
Expired / Lapsed
EP
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Iron oxide pigment showing golden color and process for producing the same
Assignee: Toda Kogyo Corp
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Filing: 1988-08-25
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Granted: —
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Expires: 2008-08-25
Abstract
Abstract An iron oxide pigment suitable for use in paints, inks and cosmetics comprises plate-like hematite particles having an average diameter of from 0.5 to 5.0 um, a thickness of from 5 to 50 nm (50 to 500 Å), a plate ratio (the ratio of the average diameter to the thickness) of from 50:1 to 500:1, a lightness (L* value) of not less than 30, a hue (ϑ = tan⁻¹b*/a*) of not less than 50° and a chroma (C*ab =√a *2 + b *2 ) of not less than 17 (wherein L*, a* and b* are values represented by the (L*, a*, b*) uniform sensory color space of the CIE 1976).
Inventors
- 👤 Tokihiro Kurata
- 👤 Tsutomu Katamoto
- 👤 Nanao Horiishi
- 👤 Masao Kiyama
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 19:55
CPC Classifications
C; C09; C09D; C09D7/00; C09D7/40; C09D7/66; C09D7/69; B; B82; B82Y; B82Y30/00; C01; C01G; C01G49/00; C01G49/02; C01G49/06; C09C; C09C1/00; C09C1/22; C09C1/24; C09C1/245; C09D5/00; C09D5/36; C09D7/60; C09D7/61; C09D7/68; C09D7/70; C01P; C01P2002/00; C01P2002/70; C01P2002/72; C01P2002/80; C01P2002/84; C01P2004/00; C01P2004/01; C01P2004/03; C01P2004/20; C01P2004/50; C01P2004/51; C01P2004/52; C01P2004/54; C01P2004/60; C01P2004/61; C01P2004/62; C01P2004/64; C01P2006/00; C01P2006/12; C01P2006/42; C01P2006/60; C01P2006/62; C01P2006/63; C01P2006/64; C01P2006/65; C01P2006/66; C08; C08K; C08K3/00; C08K3/18; C08K3/20; C08K3/22
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
102 words
An iron oxide pigment comprising plate-like hematite particles having an average diameter of from 0.5 to 5.0 µm, a thickness of from 5 to 50 nm (50 to 500 Å), a plate ratio (the ratio of the average diameter to the thickness) of from 50:1 to 500:1, a lightness (L* value) of not less than 30, a hue (ϑ = tan⁻¹b*/a*) of not less than 50° and a chroma (C*ab =√a *2 + b *2 ) of not less than 17 (wherein L*, a* and b* are values represented by the (L*, a*, b*) uniform sensory color space of the CIE 1976).
Claim 2
Dependent Claim
102 words
An iron oxide pigment comprising plate-like hematite particles having an average diameter of from 0.5 to 5.0 µm, a thickness of from 5 to 50 nm (50 to 500 Å), a plate ratio (the ratio of the average diameter to the thickness) of from 50:1 to 500:1, a lightness (L* value) of not less than 30, a hue (ϑ = tan⁻¹b*/a*) of not less than 50° and a chroma (C*ab =√a *2 + b *2 ) of not less than 17 (wherein L*, a* and b* are values represented by the (L*, a*, b*) uniform sensory color space of the CIE 1976).
Claim 3
Dependent Claim
75 words
A pigment according to claim 1, wherein the said plate-like hematite particles have an average diameter of from 1.0 to 4.0 um, a thickness of from 10 to 40 nm (100 to 400 Å), a plate ratio of from 100:1 to 300:1, a lightness (L* value) of 35 to 50, a hue (ϑ = tan⁻¹b*/a*) of not less than 50° and a chroma (C*ab =√a *2 + b *2 ) of not less than 20.
Claim 4
Dependent Claim
98 words
A process for producing an iron oxide pigment composed of plate-like hematite particles according to claim 1, which process comprises autoclaving an alkaline suspension of iron (III) hydroxide oxide particles, FeO x .Fe₂O₃ (0 ≦ x ≦ 1) particles or a ferric salt, the said alkaline suspension having a pH of not less than 9 and containing from 0.1 to 15.0 mol of a water-soluble salt per mol of Fe and a Si-containing compound in an amount of from 1.5 to 20.0 mol% calculated on the basis of the Si therein with respect to total amount of Fe.
Claim 5
Dependent Claim
21 words
A process according to claim 3, wherein the autoclave method is carried out at a temperature of from 200 to 300°C.
Claim 6
Dependent Claim
23 words
A process according to claim 3 or 4, wherein the water-soluble salt is a sulfate, nitrate, chloride or acetate of an alkali metal.
Claim 7
Dependent Claim
14 words
A process according to claim 5, wherein the alkali metal is sodium or potassium.
Claim 8
Dependent Claim
24 words
A process according to any one of claims 3 to 6, wherein the pH of the said alkaline suspension is not less than 12.
Claim 9
Dependent Claim
26 words
A process according to any one of claims 3 to 7, wherein the Si-containing compound is the silicate of potassium or sodium or is colloidal silica.
Claim 10
Dependent Claim
42 words
A process according to any one of claims 3 to 8, wherein the Si-containing compound is added in an amount of from 5.0 to 15.0 mol% calculated on the basis of the Si therein with respect to the total amount of Fe.
Claim 11
Dependent Claim
35 words
A paint, ink or cosmetic incorporating an iron oxide pigment as claimed in claim 1 or 2 or which has been produced by a process as claimed in any one of claims 3 to 9.
References Cited (Backward Citations)
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