Method for manufacturing poly(hexamethylene adipamide) from monomethyladipate and hexamethylenediamine

• US 6,011,134 A
• Filed: 01/30/1998
• Issued: 01/04/2000
• Est. Priority Date: 01/30/1998
• Status: Expired due to Term

• Current Assignee: Invista North America Sarl (Invista)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Marks, David Neil, Lane, Samuel Livingston
• Primary Examiner(s): HAMPTON HIGHTOWER, PATRICIA
• Application Number:
  US09/016,385
• Time in Patent Office: 704 Days
• Field of Search: 528/310, 528/322, 528/332, 528/335, 528/336, 528/339, 528/338, 528/347
• US Class Current: 528/310
• CPC Class Codes: C08G 69/04 Preparatory processes
• CPC Class Codes: C08G 69/28 Preparatory processes

Abstract

An improved method for manufacturing poly(hexamethylene adipamide), i.e. nylon 6,6, by reacting monomethyl adipate with hexamethylenediamine in an approximately equimolar ratio in the presence of water at a temperature of 100 to 165° C. while simultaneous distilling off of a stoichiometric amount of methanol. The resulting aqueous intermediate product is then heated to 200 to 260° C. while distilling off substantially all water at a pressure of 150 to 250 psig (1.03 ×10⁶ to 1.72 ×10⁶ Pa) followed by reducing the pressure to atmospheric pressure and increasing the temperature to 270 to 280° C. to polycondense the distillate residue. Such a process is useful in producing high purity commercial grade poly(hexamethylene adipamide) that advantageously avoids problems caused by N-methylation of the polyamide.

Claims

1. A method for preparing poly(hexamethylene adipamide) comprising the steps of:

(a) reacting monomethyl adipate and hexamethylenediamine in an approximately equimolar ratio in the presence of water at a temperature of 100 to 165°

C. while simultaneous distilling off methanol and water for a time sufficient to remove at least 90 mole % of the theoretical stoichiometric amount of methanol;

(b) heating the aqueous reaction product of step (a) to 200 to 260°

C. while distilling off substantially all water at a pressure of 100 to 250 psig (6.89 ×

10⁵ to 1.72 ×

10⁶ Pa) followed by reducing the pressure to atmospheric pressure and increasing the temperature to 270 to 280°

C. to polycondense the distillate residue; and

(c) recovering poly(hexamethylene adipamide) having a relative viscosity of 20 to 100, measured at 8.4 wt % polyamide in 90/10 wt % formic acid/water @ 25°

C., and a concentration of N-methylated groups in the polyamide, analyzed as N-methylhexamethylenediamine, of less than 50 moles per million grams of polyamide.

2. The method of claim 1 wherein said reacting monomethyl adipate and hexamethylenediamine in an approximately equimolar ratio in the presence of water is at a temperature of 120 to 150°

C.

3. The method of claim 1 wherein said poly(hexamethylene adipamide) being recovered has a relative viscosity of 20 to 100.