Process for preparing polyamides
AssigneeE. I. Du Pont de Nemours and Company
InventorsAlbert Walter Alsop, Elwood Neal Blanchard, Jeffrey D. Cohen, John Maurice Iwasyk, Clara Young Lin, David Neil Marks, Jan M. Stouffer
Life of this patent
Estimating the term…
Abstract
Disclosed is a process for the preparation of polyamide polymers via prepolymer formation in a reactor system comprising a reactor, flasher and separator, crystallization of the prepolymer under controlled temperature conditions and the subsequent conversion of these crystallized prepolymers to high molecular weight polymer.
Claims29
A process for the preparation of polyamide prepolymers, possessing less than about 6% of extractable impurities, comprising the step of:
- (a) prepolymerizing a polyamidation precursor selected from the group consisting of a polyamidation monomer, a mixture of polyamidation monomers, and a mixture of polyamidation monomers and comonomers in a polyamidation reactor, in the presence of a flowing vapor phase for between 10-600 minutes at pressures between 10 bar (145 psig, 130.3 psig, 1000 kPa) and the system vapor pressure so that boiling occurs resulting in operation in a two phase (vapor phase/liquid phase) region to form a polyamide prepolymer;
- (b) flashing excess dissolved liquid water and reaction product volatiles into the vapor phase by passing the liquid prepolymer solution/vapor stream through a flasher stage that follows the reactor to let down the pressure to approximately 1 atmosphere (101 kPa) and to strip off the extractable impurities;
- and
- (c) passing the flasher effluent through a very low holdup time separator at about 1 atm. (101 kPa) that follows the flasher.
A process for the preparation of polyamide prepolymers, possessing less than about 6% of extractable impurities, comprising the steps of:
- (a) prepolymerizing a caprolactam polyamidation precursor in a polyamidation reactor, in the presence of a flowing vapor phase for between 10-600 minutes at pressures between 10 bar (145 psig, 130.3 psig, 1000 kPa) and the system vapor pressure so that boiling occurs resulting in operation in a two phase (vapor phase/liquid phase) region to form a polyamide prepolymer;
- (b) flashing excess dissolved liquid water and reaction product volatiles into the vapor phase by passing the liquid prepolymer solution/vapor stream through a flasher stage that follows the reactor to let down the pressure to approximately 1 atmosphere (101 kPa) and to strip off the extractable impurities;
- and
- (c) passing the flasher effluent through a very low holdup time separator at about 1 atm. (101 kPa) that follows the flasher.
A process for the preparation of polyamide prepolymers, possessing less than about 6% of extractable impurities, comprising the steps of:
- (a) prepolymerizing an amino nitrile monomer, polyamidation precursor in the presence of a flowing vapor phase for between 10-600 minutes at pressures between 10 bar (145 psig, 130.3 psig, 1000 kPa) and the system vapor pressure so that boiling occurs resulting in operation in a two phase (vapor phase/liquid phase) region to form a polyamide prepolymer,
- (b) flashing excess dissolved liquid water and reaction product volatiles into the vapor phase by passing the liquid prepolymer solution/vapor stream through a flasher stage that follows the reactor to let down the pressure to approximately 1 atmosphere (101 kPa) and to strip off the extractable impurities;
- and
- (c) passing the flasher effluent through a very low holdup time separator at about 1 atm. (101 kPa) that follows the flasher.
A process for the preparation of crystalline polyamide prepolymers, comprising crystallizing a polyamide prepolymer having a molecular weight between 3,000 and 10,000 essentially isothermally at a temperature (Tc) within plus or minus 20.degree. C. of the temperature of maximum crystallization rate, provided that Tc is 30 or more degrees below the melting point of the polyamide prepolymer.
A process for the preparation of crystalline polyamide prepolymers, comprising crystallizing a polyamide prepolymer having a molecular weight between 3,000 and 10,000 essentially isothermally at a temperature (Tc) within plus or minus 20.degree. C. of the temperature of maximum crystallization rate, provided that Tc is 30 or more degrees below the melting point of the polyamide prepolymer wherein the polyamide prepolymer is a nylon 6 polyamide prepolymer, essentially isothermally, at a temperature of about 130.degree. C. to 170.degree. C.
A process for rapid solid phase processing and vapor phase extraction of impurities of nylon 6 polyamide polymers or their copolymers comprising:
- (i) supplying low extractable content crystalline nylon-6 polyamide prepolymers or copolymers to a solid state polymerizer;
- and
- (ii) solid state polymerizing in the presence of an inert gas having a superficial gas velocity of about 0.1 to 2 ft/sec. and at temperatures of at least about 1.degree. C. below the softening point as indicated by DSC curves, wherein polyamide precursor is removed and molecular weight of the resulting polymer is increased.
Dependencies are inferred from the claim text.