US4091080A
Expired / Lapsed
US
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Method for the production of alpha type calcium sulfate hemihydrate
Assignee: Kureha Corp
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Filing: 1976-10-14
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Granted: 1978-05-23
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Expires: 1996-10-14
Abstract
Abstract Alpha type calcium sulfate hemihydrate gypsum is obtained by suspending gypsum in an aqueous solution containing a specific monocarboxylate in a specific concentration and heating the resultant suspension in a specific temperature range under atmospheric pressure. The production of this alpha type calcium sulfate hemihydrate is accomplished at an increased rate by adding a specific monocarboxylic acid to the aqueous solution, suspending gypsum in the resultant solution and heating the resultant suspension in a specific temperature range under atmospheric pressure.
Inventors
- 👤 Jyuniti Kosugi
- 👤 Yoshihiko Kudo
- 👤 Kiyoshi Tagaya
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 01:30
CPC Classifications
C; C01; C01F; C01F11/00; C01F11/46; C01F11/466; C04; C04B; C04B11/00; C04B11/02; C04B11/024
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
102 words
A method for the production of alpha type hemihydrated calcium sulfate, which method comprises: (a) suspending hydrated calcium sulfate containing 1/2 to 2 mols of water of crystallization in an aqueous solution containing at least 10% by weight of at least one member selected from the group consisting of magnesium salts of lower monocarboxylic acids having one to four carbon atoms and zinc salts of lower monocarboxylic acids having one to four carbon atoms; and (b) subsequently heating the resultant suspension under atmospheric pressure at a temperature in the range of from 80° C to the boiling point of said aqueous solution.
Claim 2
Independent Claim
102 words
A method for the production of alpha type hemihydrated calcium sulfate, which method comprises: (a) suspending hydrated calcium sulfate containing 1/2 to 2 mols of water of crystallization in an aqueous solution containing at least 10% by weight of at least one member selected from the group consisting of magnesium salts of lower monocarboxylic acids having one to four carbon atoms and zinc salts of lower monocarboxylic acids having one to four carbon atoms; and (b) subsequently heating the resultant suspension under atmospheric pressure at a temperature in the range of from 80° C to the boiling point of said aqueous solution.
Claim 3
Dependent Claim
67 words
The method according to claim 1, wherein said calcium sulfate containing 1/2 to 2 moles of water of crystallization is beta type calcium sulfate hemihydrate, gypsum, a mixture of alpha type calcium sulfate hemihydrate with beta type calcium sulfate hemihydrate, a mixture of alpha type calcium sulfate hemihydrate with gypsum or a mixture of alpha type calcium sulfate hemihydrate with beta type calcium sulfate hemihydrate and gypsum.
Claim 4
Independent Claim
119 words
A method for the production of alpha type calcium sulfate hemihydrate, which method comprises: (a) adding a lower monocarboxylic acid having one to four carbon atoms to an aqueous solution containing at least 10% by weight of at least one member selected from the group consisting of magnesium salts of lower monocarboxylic acids having one to four carbon atoms and zinc salts of lower monocarboxylic acids having one to four carbon atoms; (b) suspending a hydrated calcium sulfate containing 1/2 to 2 mols of water of crystallization in the resultant solution; and (c) subsequently heating the resultant suspension under atmospheric pressure at a temperature in the range of from 80° C to the boiling point of said resultant solution.
Claim 5
Independent Claim
119 words
A method for the production of alpha type calcium sulfate hemihydrate, which method comprises: (a) adding a lower monocarboxylic acid having one to four carbon atoms to an aqueous solution containing at least 10% by weight of at least one member selected from the group consisting of magnesium salts of lower monocarboxylic acids having one to four carbon atoms and zinc salts of lower monocarboxylic acids having one to four carbon atoms; (b) suspending a hydrated calcium sulfate containing 1/2 to 2 mols of water of crystallization in the resultant solution; and (c) subsequently heating the resultant suspension under atmospheric pressure at a temperature in the range of from 80° C to the boiling point of said resultant solution.
Claim 6
Dependent Claim
32 words
The method according to claim 3, wherein said lower monocarboxylic acid is added to said aqueous solution in an amount of from 1 to 20% by weight based on said aqueous solution.
Claim 7
Dependent Claim
67 words
The method according to claim 3, wherein said calcium sulfate containing 1/2 to 2 moles of water of crystallization is beta type calcium sulfate hemihydrate, gypsum, a mixture of alpha type calcium sulfate hemihydrate with beta type calcium sulfate hemihydrate, a mixture of alpha type calcium sulfate hemidrate with gypsum or a mixture of alpha type calcium sulfate hemihydrate with beta type calcium sulfate hemihydrate and gypsum.
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) | 1981-05-22 | 1981-11-21 | 1982-05-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-05-22 | 1985-11-21 | 1986-05-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-05-22 | 1989-11-21 | 1990-05-23 | $7700.00 | Window Closed / Lapsed |