US4720328A
Expired / Lapsed
US
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Method for removing impurities from caprolactam
Assignee: Akzona Inc
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Filing: 1983-09-02
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Granted: 1988-01-19
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Expires: 2003-09-02
Abstract
Abstract A method for removing impurities from caprolactam is disclosed. The method comprises the sequential steps of treating the impure caprolactam with phosphorus pentoxide so that the impurities react therewith to form high boiling species and then distilling the so treated impure lactam to recover substantially pure caprolactam as overhead, with the impurities remaining as bottoms.
Inventors
- 👤 Tom F. Corbin
- 👤 Jack A. Dellinger
- 👤 Kenneth B. Wagener
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 07:40
CPC Classifications
C; C07; C07D; C07D201/00; C07D201/16
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
71 words
A method for removing impurities from ε-caprolactam containing less than about 0.2% (wt.) of water which comprises the sequential steps of: (a) treating said impure caprolactam with phosphorus pentoxide so that said impurities react with said phosphorus pentoxide to form species which are substantially non-volatile with respect to caprolactam; and (b) distilling the so treated impure caprolactam to recover substantially pure caprolactam as overhead, with said reacted impurities remaining as bottoms.
Claim 2
Independent Claim
71 words
A method for removing impurities from ε-caprolactam containing less than about 0.2% (wt.) of water which comprises the sequential steps of: (a) treating said impure caprolactam with phosphorus pentoxide so that said impurities react with said phosphorus pentoxide to form species which are substantially non-volatile with respect to caprolactam; and (b) distilling the so treated impure caprolactam to recover substantially pure caprolactam as overhead, with said reacted impurities remaining as bottoms.
Claim 3
Dependent Claim
22 words
The method of claim 1 wherein said impurities are selected from the class of compounds comprising hydroxy, amino or carboxyl functional groups.
Claim 4
Dependent Claim
11 words
The method of claim 1 wherein said impurity is ethylene glycol.
Claim 5
Dependent Claim
25 words
The method of claim 1 wherein at least a stoichiometric equivalent of phosphorus pentoxide is used, based upon the concentration of impurity in said lactam.
Claim 6
Dependent Claim
45 words
The method of claim 1 comprising the additional steps of: (a) after said distillation step, treating said recovered lactam with a sufficient amount of an alkaline substance to neutralize any free acid present therein; and (b) further distilling said lactam to remove said alkaline substance.
Claim 7
Dependent Claim
18 words
The method of claim 2, where the substantially non-volatile species comprise, respectively, phosphate esters, amides or mixed anhydrides.
References Cited (Backward Citations)
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US2944944A
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US3145198A
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US3016375A
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Cited
US4264501A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-01-18 | 1991-07-20 | 1992-01-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-18 | 1995-07-20 | 1996-01-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-18 | 1999-07-20 | 2000-01-19 | $7700.00 | Window Closed / Lapsed |