US4840688A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for the production of fibrous plaster boards
Assignee: PFLEIDERER INDUSTRIE & Co KG INGOLSTADTER STRASSE 51 8430 NEUMARKT FED REP OF GERMANY A CORP OF FED REP OF GERMANY GmbH
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Filing: 1988-09-01
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Granted: 1989-06-20
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Expires: 2008-09-01
Abstract
Abstract A method for the production of fibrous plaster boards for which a suspension is prepared from wet-digested fiber material and calcium sulfate dihydrate, the suspension is formed into a board with removal of water, and the dihydrate is recrystallized with heating at atmospheric pressure to a hemihydrate which is subsequently converted back into the dihydrate by the addition of water. For this purpose, the suspension is dewatered from a water content of about 300 to 600% to one of about 30 to 40% in dewatering equipment, the dihydrate is recrystallized in air and without pressure to the beta form of the hemihydrate and the water, required for setting, is aspirated through the board by suction.
Inventors
- 👤 Winold Vogt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 15:30
CPC Classifications
C; C04; C04B; C04B28/00; C04B28/14; C04B28/141; Y; Y02; Y02W; Y02W30/00; Y02W30/50; Y02W30/91
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
75 words
A method for the production of fibrous plaster boards comprising preparing a suspension from wet-digested fiber material and calcium sulfate dihydrate, dewatering the suspension to a residual moisture content of 30 to 40% while simultaneously forming the suspension into boards, recrystallizing the dihydrate by heating the boards in air and without pressure to convert the dihydrate to a beta form of a hemihydrate, and setting the boards by aspirating water through the boards by suction.
Claim 2
Independent Claim
75 words
A method for the production of fibrous plaster boards comprising preparing a suspension from wet-digested fiber material and calcium sulfate dihydrate, dewatering the suspension to a residual moisture content of 30 to 40% while simultaneously forming the suspension into boards, recrystallizing the dihydrate by heating the boards in air and without pressure to convert the dihydrate to a beta form of a hemihydrate, and setting the boards by aspirating water through the boards by suction.
Claim 3
Dependent Claim
21 words
A method as in claim 1, wherein said heating comprises dry calcination at a board temperature of 100° to 170° C.
Claim 4
Dependent Claim
15 words
A method as in claim 2, wherein said board temperature is 115° to 140° C.
Claim 5
Dependent Claim
19 words
A method as in claim 1, wherein said aspirating comprises flooding the boards with a stoichiometric excess of water.
Claim 6
Dependent Claim
24 words
A method as in claim 4, wherein said stoichiometric excess is at least 2.5 times the stoichiometric amount of water required for the boards.
Claim 7
Dependent Claim
16 words
A method as in claim 1 further comprising calibrating the boards in a press after aspiration.
Claim 8
Dependent Claim
13 words
A method as in claim 6 further comprising dewatering the boards during calibration.
Claim 9
Dependent Claim
20 words
A method as in claim 7 further comprising consolidating the calibrated boards for final conversion of the hemihydrate to dihydrate.
References Cited (Backward Citations)
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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) | 1992-06-19 | 1992-12-19 | 1993-06-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-06-19 | 1996-12-19 | 1997-06-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-06-19 | 2000-12-19 | 2001-06-20 | $7700.00 | Window Closed / Lapsed |