Back to results
US 6,660,800 B1Granted
Process for making crosslinked polyvinylpyrrolidone
AssigneeArco Chemical Technology, L.P.
InventorsBeth M. Steinmetz, Manish K. Nandi
Life of this patent
Estimating the term…
Abstract
A process for making crosslinked polyvinylpyrrolidone (PVP-P) is disclosed. Crosslinker generation, followed by polymerization of NVP, gives a polymer containing up to 4 wt. % of residual NVP. An aqueous mixture of the polymer is then heated in the presence of a protic acid at pH<4 to eliminate NVP. Finally, the PVP-P is neutralized with aqueous alkali metal hydroxide. The process generates a reduced volume of low-toxicity aqueous waste (<20 L/kg PVP-P) and gives PVP-P that meets important product specifications.
Claims14
A process which comprises:
- (a) heating an aqueous mixture that contains from about 70 to about 90 wt. % of N-vinylpyrrolidone and an alkali metal hydroxide in a sealed reactor under added pressure to a temperature within the range of about 130° C. to about 150° C. to generate a crosslinker;
- (b) reducing the reactor temperature to a value within the range of about 95° C. to about 105° C. to initiate polymerization and produce a mixture containing crosslinked polyvinylpyrrolidone (PVP-P) and up to about 4 wt. % of residual N-vinylpyrrolidone;
- (c) adding water and heating the resulting aqueous PVP-P mixture in the presence of a protic acid at a mixture pH less than about 4 and at a temperature within the range of about 80° C. to about 100° C.;
- and
- (d) neutralizing the PVP-P with aqueous alkali metal hydroxide;
- wherein the volume of aqueous waste generated from the process is less than or equal to about 20 L/kg of PVP-P produced, wherein the resulting purified PVP-P has residual N-vinylpyrrolidone less than 5 ppm and residual alkali metal content less than 250 ppm;
- and wherein none of the aqueous waste generated from the process has a residual NVP concentration greater than about 10 ppm.
4 more elements
Dependencies are inferred from the claim text.