IP Library › Granted Patent US 7,138,528
Granted Patent B2
US 7,138,528 · App. 11/047,843 · Granted Nov 21, 2006

Method for crystallizing N-vinyl-2-pyrrolidone

View Patent ↗
Loading inventors, assignments & file history…
Monitor This Case
Get email alerts when status or documents change.
Order Certified Copies
Most orders are placed with the USPTO same day — all within 24 business hours.
Order via The Patent Place →
Pre-filled with this patent's details
Quick Facts
Patent No.
US 7,138,528
App. No.
11/047,843
Granted
Nov 21, 2006
Kind
B2
Abstract

A method for purifying N-vinyl-2-pyrrolidone (NVP) is disclosed. The method comprises crystallizing NVP in the presence of added water to produce purified NVP crystals and a mother liquor, and then isolating the purified crystals. In a preferred method, 0.5 to 4 wt. % of water based on the amount of NVP to be purified is added, and the NVP crystals are washed with additional pure NVP, preferably NVP crystal melt, to give crystals having a purity greater than 99.99%. The method provides a fast, effective way to generate and isolate pure NVP in a single-stage crystallization.

Claims (11)

1. A method which comprises: (a) crystallizing liquid N-vinyl-2-pyrrolidone (NVP) in the presence of added water to produce purified NVP crystals and a mother liquor; and (b) separating the purified NVP crystals from the mother liquor.

2. The method of claim 1 wherein the water is added in an amount within the range of 0.5 to 4 weight percent based on the amount of NVP to be purified.

3. The method of claim 1 wherein the water is added in an amount within the range of 1 to 2 weight percent based on the amount of NVP to be purified.

4. The method of claim 1 wherein the crystallization is performed at a temperature within the range of −5° C. to 15° C.

5. The method of claim 1 wherein the crystallization is performed at a temperature within the range of 4° C. to 10° C.

6. The method of claim 1 wherein the purified NVP crystals are washed with additional pure NVP to a purity greater than 99.99%.

7. The method of claim 6 wherein the washing is repeated to provide NVP having a purity greater than 99.999%.

8. The method of claim 1 wherein separation step (b) is performed by filtration, centrifugation, or both.

9. A method which comprises: (a) crystallizing liquid N-vinyl-2-pyrrolidone (NVP) in the presence of 0.5 to 4 wt. % of added water at a temperature within the range of −5° C. to 15° C. to produce purified NVP crystals and a mother liquor; (b) separating the purified NVP crystals from the mother liquor; and (c) washing the purified NVP crystals with additional pure NVP to a purity greater than 99.99%.

10. The method of claim 9 wherein separation step (b) is performed by filtration, centrifugation, or both.

11. The method of claim 9 wherein step (c) is repeated to provide NVP having a purity greater than 99.999%.