Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-06-01
2002-11-12
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S322000, C528S323000, C528S324000, C528S332000, C528S335000
Reexamination Certificate
active
06479620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a process for the conversion of caprolactam to nylon-6.
2. Related Art
Nylon-6 is produced commercially using caprolactam as the starting material. A commercial process typically involves heating caprolactam in a VK tube at atmospheric pressure for 12 to 24 hours. This process produces a nylon-6 product that contains 7 to 10% caprolactam in the product. Excess caprolactam is extracted using an 8 to 12 hour aqueous extraction process. The extracted product is then dried for 8 to 12 hours producing a dry product containing 0.2 to 0.3% caprolactam. While this process has met with commercial success, it has a long reaction residence time and a slow extraction/drying step.
U.S. Pat. No. 6,201,096 discloses a process for the production of a polyamide by reaction of an omega-aminonitrile with water in a vertical multistage reactor that is swept by steam. For example, this process can convert 6-aminocapronitrile to nylon-6.
SUMMARY OF THE INVENTION
The present invention is a process for making nylon-6, comprising:
(a) establishing a reactive distillation column having a top and a bottom, the top having a temperature of 150 to 200 degrees C. and the bottom having a temperature of 240 to 260 degrees C., the column having a plurality of spaced apart plates disposed therein, thereby defining a plurality of stages, each stage being defined by the column volume between adjacent plates, each stage being separately heated to a predetermined temperature;
(b) introducing caprolactam and water into a reaction zone having a temperature of 200 to 250 degrees C. and a pressure of 100 to 300 psia (0.69 to 2.07 MPa) to make a reaction product comprising caprolactam, linear aminocaproic acid and water;
(c) introducing the reaction product into the reactive distillation column at or near the top of the column while introducing steam at or near the bottom of the column; and
(d) recovering nylon 6 from the bottom of the column.
The process is expected to involve relatively short holdup times for the conversion of caprolactam to nylon-6. It is also expected to produce nylon-6 with relatively low amounts of free caprolactam and/or other low molecular weight compounds.
REFERENCES:
patent: 4310659 (1982-01-01), Yates et al.
patent: 4327208 (1982-04-01), Hehr et al.
patent: 4354020 (1982-10-01), Rotzoll et al.
patent: 4816557 (1989-03-01), Pipper et al.
patent: 4978743 (1990-12-01), Selbeck et al.
patent: 5223183 (1993-06-01), Monkelbaan et al.
patent: 5283315 (1994-02-01), Kawakami et al.
patent: 6093488 (2000-04-01), Born et al.
patent: 6194572 (2001-02-01), Buijs et al.
patent: 6201096 (2001-03-01), Marchildon et al.
patent: 6320021 (2001-11-01), Hildenbrand et al.
Fergusson Stuart B.
Marchildon Ernest Keith
Mutel Ahmet Turgut
Deitch Gerald E.
E. I. du Pont de Nemours and Company
Hampton-Hightower P.
LandOfFree
Process for converting caprolactam to nylon 6 does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for converting caprolactam to nylon 6, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for converting caprolactam to nylon 6 will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2971301