US4094693A
Expired / Lapsed
US
⏱️ 0.0 years remaining
D,L Tartaric acid as retardant for gypsum plaster
Assignee: Evonik Operations GmbH
•
Filing: 1976-09-14
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Granted: 1978-06-13
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Expires: 1996-09-14
Abstract
Abstract Industrial gypsum plaster (plaster of Paris) having a delayed setting time is prepared by including D,L-tartaric acid and sufficient calcium hydroxide that a 5 weight % aqueous suspension of the plaster has a pH of at least 11.5.
Inventors
- 👤 Helmut Knorre
- 👤 Manfred Langer
- 👤 Peter Leidl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 00:46
CPC Classifications
C; C04; C04B; C04B28/00; C04B28/14; C04B24/00; C04B24/04; C04B24/06; C04B2103/00; C04B2103/20
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
49 words
Gypsum plaster having sufficient D,L-tartaric acid therein to delay the setting time of the plaster and having sufficient calcium hydroxide that a 5% by weight aqueous paste of the plaster has a pH of at least 11.5, the content of D,L-tartaric acid being between 0.01 and 0.5 weight %.
Claim 2
Dependent Claim
49 words
Gypsum plaster having sufficient D,L-tartaric acid therein to delay the setting time of the plaster and having sufficient calcium hydroxide that a 5% by weight aqueous paste of the plaster has a pH of at least 11.5, the content of D,L-tartaric acid being between 0.01 and 0.5 weight %.
Claim 3
Dependent Claim
18 words
Gypsum plaster according to claim 1 wherein the content of D,L-tartaric acid is 0.02 to 0.2 weight %.
Claim 4
Dependent Claim
18 words
Gypsum plaster according to claim 2 wherein the content of calcium hydroxide is 1.5 to 6.0 weight %.
Claim 5
Dependent Claim
50 words
Gypsum plaster according to claim 2 wherein the calcium hydroxide is present in an amount ranging from the amount to provide a 5% by weight aqueous paste of the plaster having a pH of 12.00 up to the pH of a 5% by weight aqueous paste saturated with calcium hydroxide.
Claim 6
Dependent Claim
18 words
Gypsum plaster according to claim 1 wherein the content of calcium hydroxide is 1.5 to 6.0 weight %.
Claim 7
Dependent Claim
50 words
Gypsum plaster according to claim 1 wherein the calcium hydroxide is present in an amount ranging from the amount to provide a 5% by weight aqueous paste of the plaster having a pH of 12.00 up to the pH of a 5% by weight aqueous paste saturated with calcium hydroxide.
Claim 8
Dependent Claim
16 words
Gypsum plaster according to claim 1 wherein the D,L-tartaric acid is the sole tartaric acid present.
Claim 9
Dependent Claim
24 words
A gypsum plaster composition according to claim 1 wherein the composition consists essentially of the gypsum plaster, the D,L-tartaric acid and the calcium hydroxide.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-06-12 | 1981-12-12 | 1982-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-06-12 | 1985-12-12 | 1986-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-06-12 | 1989-12-12 | 1990-06-13 | $7700.00 | Window Closed / Lapsed |