US4180433A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Production of improved chrysotile asbestos fibres
Assignee: Ortech Corp
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Filing: 1977-08-15
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Granted: 1979-12-25
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Expires: 1997-08-15
Abstract
Abstract The filtration rate of asbestos-cement slurries formed from chrysotile asbestos fibres is improved by controlled heat treatment of the fibres at a temperature of about 400° to about 600° C. without loss of water of crystallization and fibre strength. The improved filtration rate allows an increased rate of production of asbestos-cement products.
Inventors
- 👤 Roger W. Glass
- 👤 Richard A. Kuntze
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 06:57
CPC Classifications
C; C04; C04B; C04B14/00; C04B14/38; C04B14/40
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
138 words
A method for the production of chrysotile asbestos fibres having improved filtration properties in asbestos-cement uses, which comprises heating chrysotile asbestos fibres selected from Group 4 and Group 5 chrysotile asbestos fibres having a filtration rate in asbestos cement uses of about 11 to about 12 ml/sec in an ambient atmosphere having a substantially uniform temperature of about 400° to about 600° C. for a time from about 1 to about 5 hours sufficient to increase the filtration rate of said fibres in asbestos cement uses to at least about 19 ml/sec and insufficient to result in a loss of water of crystallization of the fibres of greater than about 2% by weight of the total weight of water of crystallization in the fibres, whereby said improved filtration properties are obtained without any significant overall fibre strength loss.
Claim 2
Independent Claim
138 words
A method for the production of chrysotile asbestos fibres having improved filtration properties in asbestos-cement uses, which comprises heating chrysotile asbestos fibres selected from Group 4 and Group 5 chrysotile asbestos fibres having a filtration rate in asbestos cement uses of about 11 to about 12 ml/sec in an ambient atmosphere having a substantially uniform temperature of about 400° to about 600° C. for a time from about 1 to about 5 hours sufficient to increase the filtration rate of said fibres in asbestos cement uses to at least about 19 ml/sec and insufficient to result in a loss of water of crystallization of the fibres of greater than about 2% by weight of the total weight of water of crystallization in the fibres, whereby said improved filtration properties are obtained without any significant overall fibre strength loss.
Claim 3
Dependent Claim
30 words
The method of claim 1 wherein said heating is effected to effect substantially the maximum increase in said filtration properties without any loss of water of crystallization from the fibres.
Claim 4
Dependent Claim
31 words
The method of claim 1 wherein said heating is carried out in an ambient atmosphere at a temperature of about 500° to about 550° C. for about 2 to 3 hours.
Claim 5
Dependent Claim
18 words
The method of claim 1 wherein said fibres are in a pressure packed form during said heating step.
Claim 6
Dependent Claim
21 words
The method of claim 4 wherein said fibres are pressure packed to a density of about 25 to about 50 lb/cu.ft.
Claim 7
Dependent Claim
42 words
The method of claim 1 wherein said chrysotile asbestos fibres have an average surface area of about 3000 to about 5000 sq.cm/g and are opened to an average surface area of about 8000 to about 12000 sq.cm/g prior to said heating step.
Claim 8
Dependent Claim
30 words
The method of claim 6 including pressure packing said opened fibres after said opening step and prior to said heating step to density of about 25 to about 50 lb/cu.ft.
Claim 9
Dependent Claim
31 words
The method of claim 1 including classifying asbestos fibres into a coarse fraction and a fine fraction prior to said heating step and subjecting said fine fraction to said heating step.
Claim 10
Dependent Claim
15 words
The method of claim 1 wherein said ambient atmosphere is provided in a muffle furnace.
Claim 11
Dependent Claim
71 words
The method of claim 1 wherein, prior to said heating, said fibres are provided in a form having a surface area of about 8000 to about 12000 sq.cm/g and said latter fibres are pressure packed to a density of about 25 to about 50 lb/cu.ft, and said heating step is effected in an ambient atmosphere at a temperature of about 500° to about 550° C. for about 2 to 3 hours.
Claim 12
Dependent Claim
15 words
The method of claim 10 wherein said ambient atmosphere is provided in a muffle furnace.
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) | 1982-12-24 | 1983-06-25 | 1983-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-12-24 | 1987-06-25 | 1987-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-12-24 | 1991-06-25 | 1991-12-25 | $7700.00 | Window Closed / Lapsed |