US4978516A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for treating talc
Assignee: ASADA MILL Co Ltd 46-25 HONCHO 2-CHOME NAKANO-KU TOKYO JAPAN A CORP OF JAPAN
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Filing: 1989-07-25
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Granted: 1990-12-18
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Expires: 2009-07-25
Abstract
Abstract A process for improving a purity and/or whiteness degree of a talc powder is disclosed. A talc powder with a particle size of about 0.8 mm or less containing impurities such as asbestos, etc. is treated with a phosphoric acid agent under heating at from 70° to 250° C. to remove impurities such as asbestos, etc. by utilizing the difference in the rate of dissolution as between the talc and the impurities. The phosphoric acid agent is one selected from the group consisting of phosphoric acid, pyrophosphoric acid, sodium phosphate, ammonium phosphate, calcium phosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate and mixtures thereof. Thus, asbestos, which is considered to be carcinogenic, can be effectively removed from talc.
Inventors
- 👤 Osamu Yamada
- 👤 Kozo Shinohara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 07:22
CPC Classifications
C; C09; C09C; C09C1/00; C09C1/28; C01; C01B; C01B33/00; C01B33/20; C01B33/22; C01P; C01P2002/00; C01P2002/70; C01P2002/72; C01P2002/80; C01P2002/82; C01P2004/00; C01P2004/51; C01P2004/60; C01P2004/61; C01P2006/00; C01P2006/10; C01P2006/19; C01P2006/60; C01P2006/80; C01P2006/82; C01P2006/90
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
105 words
A process for improving both the degree of purity and whiteness of a talc powder comprising heating a talc powder having a particle size of about 0.8 millimeters or less containing at least one impurity selected from the group consisting of asbestos, dolomite, magnesite, chlorite and calcium carbonate, with a phosphoric acid agent in a concentration of about 85%, by weight, as H 3 PO 4 at a temperature between 70° and 250° C. under atmospheric pressure to remove at least one of the aforementioned impurities therefrom by utilizing the difference in the rate of dissolution between the talc and said one or more impurities
Claim 2
Dependent Claim
105 words
A process for improving both the degree of purity and whiteness of a talc powder comprising heating a talc powder having a particle size of about 0.8 millimeters or less containing at least one impurity selected from the group consisting of asbestos, dolomite, magnesite, chlorite and calcium carbonate, with a phosphoric acid agent in a concentration of about 85%, by weight, as H 3 PO 4 at a temperature between 70° and 250° C. under atmospheric pressure to remove at least one of the aforementioned impurities therefrom by utilizing the difference in the rate of dissolution between the talc and said one or more impurities
Claim 3
Dependent Claim
59 words
The process according to claim 1, wherein said phosphoric acid agent in a concentration of about 85%, by weight as H 3 PO 4 is produced by heating a phosphoric acid agent having a concentration of less than about 85% by weight, as H 3 PO 4 and the talc powder at a temperature of at least 100° C.
Claim 4
Dependent Claim
20 words
The process according to claim 1, wherein said talc powder has a particle size of about 0.15 millimeters or less.
Claim 5
Dependent Claim
37 words
The process according to claim 1, wherein said phosphoric acid agent is selected from the group consisting of phosphoric acid, pyrophosphoric acid, sodium phosphate, ammonium phosphate, calcium phosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate and mixtures thereof.
Claim 6
Dependent Claim
20 words
The process according to claim 2, wherein said talc powder has a particle size of about 0.15 millimeters or less.
Claim 7
Dependent Claim
37 words
The process according to claim 2, wherein said phosphoric acid agent is selected from the group consisting of phosphoric acid, pyrophosphoric acid, sodium phosphate, ammonium phosphate, calcium phosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate and mixtures thereof.
Claim 8
Dependent Claim
17 words
The process according to claim 1 wherein said talc contains asbestos as an impurity which is removed.
Claim 9
Dependent Claim
17 words
The process according to claim 2 wherein said talc contains asbestos as an impurity which is removed.
Claim 10
Dependent Claim
20 words
The process according to claim 7, wherein said talc powder has a particle size of about 0.15 millimeters or less.
Claim 11
Dependent Claim
37 words
The process according to claim 9, wherein said phosphoric acid agent is selected from the group consisting of phosphoric acid, pyrophosphoric acid, sodium phosphate, ammonium phosphate, calcium phosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate and mixtures thereof.
Claim 12
Dependent Claim
20 words
The process according to claim 8, wherein said talc powder has a particle size of about 0.15 millimeters or less.
Claim 13
Dependent Claim
37 words
The process according to claim 11, wherein said phosphoric acid agent is selected from the group consisting of phosphoric acid, pyrophosphoric acid, sodium phosphate, ammonium phosphate, calcium phosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate and mixtures thereof.
Claim 14
Dependent Claim
14 words
The process according to claim 7, wherein said phosphoric acid agent is phosphoric acid.
Claim 15
Dependent Claim
14 words
The process according to claim 8, wherein said phosphoric acid agent is phosphoric acid.
Claim 16
Dependent Claim
14 words
The process according to claim 9, wherein said phosphoric acid agent is phosphoric acid.
Claim 17
Dependent Claim
14 words
The process according to claim 11, wherein said phosphoric acid agent is phosphoric acid.
Claim 18
Dependent Claim
14 words
The process according to claim 1, wherein said phosphoric acid agent is phosphoric acid.
Claim 19
Dependent Claim
14 words
The process according to claim 2, wherein said phosphoric acid agent is phosphoric acid.
Claim 20
Dependent Claim
14 words
The process according to claim 3, wherein said phosphoric acid agent is phosphoric acid.
Claim 21
Dependent Claim
14 words
The process according to claim 5, wherein said phosphoric acid agent is phosphoric acid.
Claim 22
Dependent Claim
14 words
The process according to claim 1, wherein said phosphoric acid agent is pyrophosphoric acid.
Claim 23
Dependent Claim
14 words
The process according to claim 2, wherein said phosphoric acid agent is pyrophosphoric acid.
Claim 24
Dependent Claim
14 words
The process according to claim 9, wherein said phosphoric acid agent is pyrophosphoric acid.
Claim 25
Dependent Claim
14 words
The process according to claim 11, wherein said phosphoric acid agent is pyrophosphoric acid.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-12-17 | 1994-06-18 | 1994-12-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-17 | 1998-06-18 | 1998-12-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-17 | 2002-06-18 | 2002-12-18 | $7700.00 | Window Closed / Lapsed |