METHOD FOR THE CONTINUOUS PREPARATION OF POLYAMIDE PREPOLYMERS

Abstract

The present invention relates to a method for continuously preparing a polyamide prepolymer, the viscosity in solution of which is comprised between 0.25 dL/g and 0.70 dL/g, as measured according to ISO 307:2007 in m-cresol at 20 C., the method being characterized in that it comprises a step of polycondensation on the basis of one or more polyamide precursor monomers, said polycondensation step being carried out in a extruder comprising at least two co-rotating conveying screws, the at least one monomer being previously added therein in solid or liquid form without being dissolved in a solvent or in water, and said polycondensation step being carried out without extracting the water formed during said polycondensation.

Claims

1. A method for the continuous preparation of a polyamide prepolymer, the viscosity in solution of which is comprised between 0.25 dL/g and 0.70 dL/g, as measured according to ISO 307:2007 in m-cresol at 20 C., said formulated polyamide prepolymer having a weight-average molecular weight (Mn) less than 10,000 g/mol, as determined by calculation from the level of terminal functions determined by potentiometric titration in solution and the functionality of said prepolymers or by NMR assay or by size exclusion chromatography, wherein it comprises a step of polycondensation from one or more polyamide precursor monomers, said polycondensation step being carried out in a single extruder comprising at least two co-rotating conveying screws, the said monomer(s) being previously added in solid or liquid form without dissolving in a solvent or in water, and said polycondensation step being carried out without extraction of the products formed, said extruder not having any degassing devices, or of a device for removing the polycondensation by-product(s) formed, consisting of an outlet on the outside at atmospheric pressure, or of an outlet connected to a device making it possible to create a low-pressure zone in the extruder.

2. The method according to claim 1, wherein the average degree of polymerization (DPn) of the resulting polyamide is less than 50, as determined from the number-average molecular weight (Mn) of the polyamides according to the following formula:
DPn=Mn/M0[Formula 1] with Mn, the number-average molecular weight of the polyamide, M0 the number-average molecular weight of the monomers.

3. The method according to claim 1, wherein the polyamide is an aliphatic polyamide.

4. The method according to claim 3, wherein the monomer(s) is (are) at least one C6 to C18 carboxylic amino acid.

5. The method according to claim 3, wherein the monomer(s) is (are) at least one C6 to C18 lactams.

6. The method according to claim 3, wherein the monomer(s) is (are) at least one C6 to C18 aliphatic diamine, and at least one C6 to C18 aliphatic dicarboxylic acid.

7. The method according to claim 1, wherein the extruder is a twin-screw extruder with two co-rotating conveying screws.

8. The method according to claim 7, wherein it is carried out at a temperature comprised between 220 and 340 C., preferentially comprised between 260 and 300 C.

9. The method according to claim 8, wherein the residence time of the material in the extruder at the temperature comprised between 220 and 340 C. allows executing the polycondensation reaction so as to arrive at the desired average degree of polymerization, said residence time being greater than or equal to 1 minute.

10. The method according to claim 1, wherein the extruder is an annular multi-screw extruder comprising at least 6 screws that are co-rotating.

11. The method according to claim 10, wherein the residence time of the material in the extruder at the temperature comprised between 220 and 340 C. allows executing the polycondensation reaction so as to arrive at the desired average degree of polymerization, said residence time being greater than or equal to 1 minute.

12. The method according to claim 7, wherein the residence time of the material in the extruder is greater than or equal to 1 minutes.

13. The method according to claim 1, wherein at least one additive is added during the polycondensation in the extruder.

Description

EXAMPLES

Example 1 (Comparative)

[0094] General procedure for the preparation of a prepolymer in a batch:

[0095] To a 14 liter autoclave reactor, 5 kg of the following raw materials are added: [0096] 500 g water, [0097] the diamine and the dicarboxylic acid and/or the amino acid, [0098] 0.1 g of a WACKER AK1000 antifoam agent (from Wacker Silicones).

[0099] The closed reactor is purged of its residual oxygen then heated to a material temperature of 230 C. After 30 minutes of stirring under these conditions, the pressurized vapor that formed in the reactor is relaxed progressively over 60 minutes, while progressively adjusting the material temperature of the material such that it stabilizes at Tf+10 C. at atmospheric pressure.

[0100] The oligomer (prepolymer) is then emptied through the bottom valve then cooled in a water bath then milled.

[0101] A PA11 prepolymer of Mn=3000 and viscosity 0.40 was prepared, without the use of diamine or dicarboxylic acid, from 11-aminoundecanoic acid (CAS 2432-99-7) in the solid state, according to this procedure with a residence time much longer (more than one hour) than that of the method described in examples 2 and 3 of the invention (between 1 and 5 minutes),

Example 2 (Invention)

[0102] PA11 prepolymers were prepared from 11-aminoundecanoic acid (CAS 2432-99-7) in the solid state on a ZSK18M1 twin-screw extruder (Coperion) of diameter D=18 mm (length=40 D or 60 D) or on a twin-screw Evolum32HT extruder (EV32 Clextral) with a diameter D=32 mm (length=40 D), without extraction of the by-products formed during the polycondensation, under several temperature and flow rate conditions (Table 1 to Table 6):

[0103] ZSK18 twin-screw extruder:

TABLE-US-00001 TABLE 1 Profile screw 40D Flow rate (kg/hr) 3 2 Temperature ( C.) 260 270 280 290 300 320 260 270 280 290 300 Screw speed (rpm) 300 300 Viscosity in solution 0.26 0.25 0.29 0.35 0.39 0.42 0.30 0.30 0.39 0.43 0.44 ISO 307: 2007 (m- cresol at 20 C.)

[0104] Temperature profile ( C.):

TABLE-US-00002 TABLE 2 T ( C.) Profiles 260 C.= AT 40 40 40 40 100 150 250 260 260 260 260 260 260 260 260 270 C.= AT 40 40 40 40 100 150 250 270 270 270 270 270 270 270 270 280 C.= AT 40 40 40 40 100 150 250 280 280 280 280 280 280 280 280 290 C.= AT 40 40 40 40 100 150 250 290 290 290 290 290 290 290 290 300 C.= AT 40 40 40 40 100 150 250 300 300 300 300 300 300 300 300 310 C.= AT 40 40 40 40 100 150 250 310 310 310 310 310 310 310 300 320 C.= AT 40 40 40 40 100 150 250 320 320 320 320 320 320 320 300 AT = ambient temperature

TABLE-US-00003 TABLE 3 Profile screw 60D Flow rate (kg/hr) 3 Temperature ( C.) 250 260 270 280 290 300 Screw speed (rpm) 300 Viscosity in solution ISO 0.26 0.28 0.32 0.36 0.42 0.44 307: 2007 (m-cresol at 20 C.)

[0105] Temperature profile ( C.):

TABLE-US-00004 TABLE 4 T (C.) Profiles 250 C.= AT 100 150 250 250 250 250 250 250 250 250 250 250 250 250 250 260 C.= AT 100 150 250 260 260 260 260 260 260 260 260 260 260 260 260 270 C.= AT 100 150 250 270 270 270 270 270 270 270 270 270 270 270 270 280 C.= AT 100 150 250 280 280 280 280 280 280 280 280 280 280 280 280 290 C.= AT 100 150 250 290 290 290 290 290 290 290 290 290 290 290 290 300 C.= AT 100 150 250 300 300 300 300 300 300 300 300 300 300 300 300 AT = ambient temperature

[0106] EV32 twin-screw extruder:

TABLE-US-00005 TABLE 5 Profile screw 40D Flow rate (kg/hr) 12 12 12 9 9 9 9 6 6 6 6 Temperature ( C.) 280 300 320 260 280 300 320 260 280 300 320 Screw speed (rpm) 300 225 150 Viscosity in solution 0.30 0.34 0.37 0.25 0.32 0.38 0.44 0.30 0.37 0.45 0.52 ISO 307: 2007 (m- cresol at 20 C.)

[0107] Temperature profile ( C.):

TABLE-US-00006 TABLE 6 T (C.) Profiles 260 C.= AT/100/200/260/260/260/260/260/260/260 260 280 C.= AT/100/200/280/280/280/280/280/280/280 260 300 C.= AT/100/200/300/300/300/300/300/300/300 260 320 C.= AT/100/200/320/320/320/320/320/320/320 260

Example 3 (Invention)

[0108] PA11 prepolymers were prepared from 11-aminoundecanoic acid (CAS 2432-99-7) in the solid state on an RE1 XPV (Extricom) extruder comprising 12 screws with diameter D=19 mm (length=36 D or 100 D) or on a RE3 XPV (Extricom) extruder comprising 12 screws with diameter D=31 mm (length=55 D), without extraction of the by-products formed during the polycondensation, under several temperature and flow rate conditions (Table 7 to Table 12):

[0109] Extruder comprising 12 screws RE1 XPV:

TABLE-US-00007 TABLE 7 Profile screw 36D Flow rate (kg/hr) 6 12 Temperature ( C.) 240 260 280 300 280 300 Screw speed (rpm) 25 55 Viscosity in solution ISO 307: 2007 0.42 0.48 0.57 0.63 0.32 0.38 (m-cresol at 20 C.)

[0110] Temperature profile ( C.):

TABLE-US-00008 TABLE 8 T ( C.) Profiles 240 C.= AT 240 240 240 240 240 240 240 240 260 C.= AT 260 260 260 260 260 260 260 260 280 C.= AT 280 280 280 280 280 280 280 280 300 C.= AT 300 300 300 300 300 300 300 300 AT = ambient temperature

TABLE-US-00009 TABLE 9 Profile screw 100D Flow rate (kg/hr) 24 36 Temperature ( C.) 240 260 280 300 280 300 Screw speed (rpm) 120 250 Viscosity in solution ISO 307: 2007 0.34 0.44 0.51 0.58 0.37 0.45 (m-cresol at 20 C.)

[0111] Temperature profile ( C.):

TABLE-US-00010 TABLE 10 T ( C.) Profiles 240 C.= AT 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 260 C.= AT 260 260 260 260 260 260 260 260 260 260 260 260 260 260 260 260 260 260 280 C.= AT 280 280 280 280 280 280 280 280 280 280 280 280 280 280 280 280 280 280 300 C.= AT 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 AT = ambient temperature

[0112] Extruder comprising 12 screws RE3 XPV:

TABLE-US-00011 TABLE 11 Profile screw 55D Flow rate (kg/hr) 27 41 Temperature ( C.) 260 280 260 280 Screw speed (rpm) 60 120 Viscosity in solution ISO 307: 0.38 0.26 0.44 0.33 2007 (m-cresol at 20 C.)

[0113] Temperature profile ( C.):

TABLE-US-00012 TABLE 12 T ( C.) Profiles 260 C.= AT/260/260/260/260/260/260/260/260/260/260/260 280 C.= AT/280/280/280/280/280/280/280/280/280/280/280

[0114] The continuous method of the invention makes it possible to prepare a PA11 prepolymer having the required solution viscosity with a residence time of a few minutes (between 1 and 5 minutes) very much lower than that necessary to obtain a PA11 prepolymer in a batch method (more than one hour).