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US 6,476,181 B1Granted
Increased volatile removal during solid phase processing of nylon 6 by temperature programming
AssigneeE. I. Du Pont de Nemours and Company
InventorsAlbert W. Alsop, David N. Marks
Life of this patent
Estimating the term…
Abstract
Process for increasing the molecular weight of nylon 6 while reducing its content of caprolactam and other volatiles by a two-staged heating process.
Claims2
A process for making nylon 6 having a desired molecular weight and a desired caprolactam content, comprising
- (1) heating nylon 6 having an initial molecular weight less than the desired molecular weight and an initial caprolactam content greater than the desired caprolactam content to a first temperature in the range of 130 to 220 degrees centigrade in the presence of an inert gas;
- (2) maintaining said first temperature for a time sufficient to raise the molecular weight of the nylon 6 by 5% to 95% of the difference between said initial molecular weight and the desired molecular weight;
- (3) lowering the temperature of said nylon 6 to a second temperature at least 1 degree centigrade below said first temperature;
- and
- (4) maintaining said second temperature for a time sufficient to achieve the desired caprolactam content and the desired molecular weight.
2 more elements
A process for making nylon 6 having a desired molecular weight and a desired caprolactam content, comprising
- (1) heating nylon 6 having an initial molecular weight less than the desired molecular weight and an initial caprolactam content greater than the desired caprolactam content to a first temperature in the range of 130 to 220 degrees centigrade in the presence of an inert gas;
- (2) maintaining said first temperature for a time sufficient to raise the molecular weight of the nylon 6 by 5% to 95% of the difference between said initial molecular weight and the desired molecular weight;
- (3) allowing the nylon 6 to cool at least 1 degree centigrade below the first temperature of step (1);
- (4) re-heating the nylon 6 to a second temperature equal to or less than the first temperature of step (1);
- and
- (5) maintaining said second temperature for a time sufficient to achieve the desired caprolactam content and the desired molecular weight.
3 more elements
Dependencies are inferred from the claim text.