EP4244289A1

EP4244289A1 - Method for the continuous preparation of formulated polyamide prepolymers

Info

Publication number: EP4244289A1
Application number: EP21820662.1A
Authority: EP
Inventors: Sébastien QUINEBECHE; Gérald ROMAZINI; Pierrick ROGER-DALBERT; Thierry Briffaud
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2020-11-12
Filing date: 2021-11-10
Publication date: 2023-09-20
Also published as: WO2022101580A1; KR20230104924A; CN116547126A; US20230407006A1; FR3116058B1; FR3116058A1; JP2023548885A

Abstract

The present invention relates to a method for continuously preparing a formulated polyamide prepolymer of which the solution viscosity is from 0.25 dl/g to 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 an extruder comprising at least two co-rotating conveying screws, the at least one monomer being previously fed therein in solid or liquid form without being dissolved in a solvent or in water, and said polycondensation step being carried out without extraction of the water formed during said polycondensation step and including the introduction of at least one additive during said polycondensation step in the extruder.

Description

DESCRIPTION :

TITLE OF THE INVENTION: CONTINUOUS PREPARATION PROCESS FOR PREPOLYMERS OF

FORMULATED POLYAMIDES

[Technical area]

This patent application relates to a process for the continuous preparation of formulated polyamide prepolymers, by polycondensation, as well as the extruders suitable for implementing such a process.

[prior technique]

Polyamides (PA) are conventionally prepared by polycondensation of a diamine with a dicarboxylic acid, or of an amino acid, or even of a lactam, in a reactor by a batch process (discontinuous) in which the monomer or monomers are introduced and heated under pressure until a mixture of sufficient viscosity is obtained. The monomers are frequently introduced in aqueous solution and the water present and/or formed during the polycondensation must be eliminated by placing the reactor under reduced pressure.

However, the molar mass of polyamide is difficult to control/master due to its “living” character because when emptying the reactor, the product may not have the same molar mass (the same viscosity) at the beginning and at the end. draining the reactor.

If the target molar mass is exceeded, there is no going back, the product is “downgraded” for the entire batch produced.

Furthermore, the batch process is a more capital-intensive process (for a quantity of product produced annually) and less ecological (more energy and water consumption, more production of gaseous effluent and waste, etc.).

In addition, the evacuation of the water frequently also leads to a loss of the monomers introduced, in particular in the case of the polycondensation of diamines with dicarboxylic acids, which requires working with an excess of monomers and therefore causes an additional cost of the process.

More recently, continuous synthesis methods have been developed.

Thus, patent EP2877516 describes a process for the continuous synthesis of polyamide with a weight-average molecular mass (Mw) greater than or equal to 14,000 g/mol. This process requires at least two water evacuation operations and leads not to prepolymers but to polymers.

Patent US8765902 describes a process for the continuous preparation of 6T/6L copolyamide. This process requires the evaporation of water and leads not to prepolymers but to polymers. Patent EP 0410650 describes a process for the continuous preparation of prepolymers by polycondensation of diamines and dicarboxylic acids. This process requires the evaporation of water.

Moreover, the formulation of the batch obtained requires an additional step which consists in compounding the product obtained by batch with one or more additives.

There is therefore a need to overcome the problems described above and one of the objectives of the present invention is to provide a process for preparing formulated polyamide prepolymers which is simpler, faster, reliable and less expensive than the processes of the prior art and in a single step.

The present invention therefore relates to a process for the continuous preparation of a formulated polyamide prepolymer whose solution viscosity is between 0.25 dl/g and 0.70 dl/g, as measured according to ISO 307:2007 in the m-cresol at 20°C, characterized in that it comprises a step of polycondensation starting from one or more polyamide precursor monomers, the said polycondensation step being carried out in a single extruder comprising at least two conveying screws rotating in a co-rotating manner, said monomer(s) being introduced beforehand in solid or liquid form without dissolving in a solvent or in water, and said polycondensation stage being carried out without extraction of the by-products formed, in particular of the water formed during said polycondensation, and comprising introducing at least one additive during said polycondensation step into the extruder.

The inventors have therefore found that a compromise between the residence time of the material in the extruder with the reaction temperature in the extruder could be found without requiring the evacuation of the water, in particular by placing under vacuum. of the extruder, to prepare a prepolymer of the required viscosity and that at the same time, this prepolymer could also be formulated during the polycondensation step in the extruder to lead to the formulated prepolymer.

Indeed, vacuuming a prepolymer in an extruder to remove the water is a technical difficulty because due to the low viscosity, the medium tends to foam and rise very easily in the vacuum line. This therefore leads to blockages and a loss of vacuum efficiency. Since the residence time is always the same in the extruder, the product formed therefore always has the same number-average molar mass (Mn) or the same viscosity.

The formed product can also be characterized online, which allows feedback to modify the process parameters to guarantee good control of the finished product.

Throughout the description, the term prepolymer has the same meaning as the term oligomer. The term prepolymer denotes a polyamide having a number-average molecular mass Mn of less than 10,000 g/mol, in particular comprised from 1,000 to 9,000, in particular from 1,500 to 7,000, more particularly from 2,000 to 5,000 g/mol.

The Mn is determined in particular by calculation from the rate of the terminal functions determined by potentiometric titration in solution and the functionality of said prepolymers or by NMR assay (Postma et al. (Polymer, 47, 1899-1911 (2006)).

It can also be determined by steric exclusion chromatography.

In the polymerization by polycondensation, and in particular the polycondensation of diamine and dicarboxylic acid or even of a single monomer comprising both a carboxylic acid function and an amine function, each step is a condensation reaction which is carried out with elimination of small molecules, called reaction by-products, such as H2O, depending on the monomers involved.

In the process of the invention, there is no elimination of the by-products formed and in particular of the water formed, which means that the extruder has no devices for discharging the by-product(s). reaction products formed by the polycondensation reaction (which is water in most cases).

In particular, the extruder does not have any degassing devices, in particular by introducing an inert gas therein, or any device for removing the polycondensation by-product(s) formed, and in particular the water formed, consisting of an outlet on the outside at atmospheric pressure, or an outlet connected to a device making it possible to create a depression zone in the extruder, such as a vacuum pump during the reaction.

The extruder is nevertheless equipped with a device for restoring atmospheric pressure after completion of the reaction and therefore after the screws.

The extruder used includes two feed screws

The method for preparing a polyamide according to the invention comprises the following successive steps, all carried out within the extruder: a step of mixing the selected monomer(s), and a step of polycondensation carried out by carrying out shearing operations on the material conveyed by the conveying screws.

Preferably, a step is also carried out for forming a plug or seal of material that is renewed continuously by conveying the material on the conveying screws, between the mixing and polycondensation stages. Advantageously, the stopper or gasket consisting of the advancing material fills the entire volume available for the passage of the material and constitutes a zone which is hermetic to vapours, and in particular to monomer vapors which may be generated. In an extruder, each conveying screw is made up of different elements which follow one another according to the conveying direction. These different elements are placed next to each other on a rotating shaft. In a co-rotating extruder all the conveying screws turn in the same direction, which most often corresponds to the anti-clockwise direction, The elements are located next to each other on the same line in the case of an extruder linear, or on a circle in the case of an annular extruder. The different conveying screws constituting an extruder all have the same diameter which remains constant all along the conveying screw. Most often, this diameter belongs to the range from 18 to 134 mm.

Such an extruder is described in particular in patent EP2877516, excluding the elements for depressions or for extracting the by-products formed which are not present in the method of the invention.

The polyamide precursor monomers are introduced beforehand in solid or liquid form depending on their natural appearance but are in no case dissolved in any solvent or in water.

The expression “previously” means that the monomers are introduced before any start of the polycondensation reaction.

In the context of the invention, the monomers are introduced, without prior reaction and without prior preparation of the corresponding salt.

With regard to polyamide

The nomenclature used to define polyamides is described in standard ISO 1874-1:2011 "Plastics -- Polyamide (PA) materials for molding and extrusion -- Part 1: Designation" and is well known to those skilled in the art.

The polyamide can be any polyamide, whether it is an aliphatic, cyclo-aliphatic, aromatic or semi-aromatic polyamide.

It can be homopolyamide or copolyamide.

Advantageously, said polyamide is a homopolyamide.

Said aromatic polyamide is in particular obtained from the polycondensation of an arylamine which can be chosen from meta-xylylene diamine (MXD, CAS No.: 1477-55-0) or para-xylylene diamine (PXD, CAS No. : 539-48-0), with an aromatic dicarboxylic acid, in particular chosen from a terephthalic acid, an isophthalic acid and a naphthalenic acid.

Said semi-aromatic polyamide, optionally modified with urea units, may in particular be a semi-aromatic polyamide of formula X/YAr, as described in EP1505099, in particular a semi-aromatic polyamide of formula A/XT in which A is chosen from a unit obtained from a monomeric amino acid), a unit obtained from a lactam (monomer) and a unit corresponding to the formula (Ca diamine). (Cb diacid), all deus representing the monomers, with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b each being between 4 and 36, advantageously between 9 and 18, the unit (diamine in Ca) being chosen from aliphatic diamines, linear or branched, cycloaliphatic diamines and alkylaromatic diamines and the unit (diacid in Cb) being chosen from aliphatic diacids, linear or branched, the cycloaliphatic diacids and aromatic diacids; XT denotes a unit obtained from the polycondensation of a Cx diamine and terephthalic acid, with x representing the number of carbon atoms of the Cx diamine, x being between 6 and 36, advantageously between 9 and 18, in particular a polyamide of formula A/6T, A/9T, A/10T or A/11T, A being as defined above, in particular a polyamide PA 6/6T, a PA 66/6T, a PA 6I/6T, a MPMDT/6T PA, an MXDT/6T PA, a PA11/10T PA, a 5T/10T PA, a 11/5T/10T PA, a 11/6T/10T PA, an MXDT/10T PA, a PA MPMDT/10T, a PA BACT/10T, a PA BACT/6T, PA BACT/10T/6T, a PA 11/BACT/10T, a PA 11/BACT/6T, a PA 11/MPMDT/10T and a PA 11/MXDT/10T, and block copolymers, in particular polyamide/polyether (PEBA).

T stands for terephthalic acid, MXD stands for m-xylylene diamine, MPMD stands for methylpentamethylene diamine and BAC stands for bis(aminomethyl)cyclohexane.

Said cycloaliphatic polyamide is in particular obtained by polycondensation of the following monomers: a cycloaliphatic diamine with an aliphatic dicarboxylic acid or an aliphatic diamine with a cycloaliphatic dicarboxylic acid or a cycloaliphatic diamine with a cycloaliphatic dicarboxylic acid.

The cycloaliphatic diamine can be chosen, for example, from bis(3,5-dialkyl-4-aminocyclohexyl)-methane, bis(3,5-dialkyl-4-aminocyclohexyl)ethane, bis(3,5-dialkyl-4 -aminocyclohexyl)-propane, bis(3,5-dialkyl-4-aminocyclo-hexyl)-butane, bis-(3-methyl-4-aminocyclohexyl)-methane or 3'-dimethyl-4,4'-diamino -dicyclohexyl-methane commonly referred to as "BMACM" or "MACM" (and denoted B below), p-bis(aminocyclohexyl)-methane commonly referred to as "PACM" (and denoted P below), isopropylidenedi(cyclohexylamine ) commonly called "PACP", isophorone-diamine (denoted IPD below) and 2,6-bis (amino methyl) norbornane commonly called "BAMN".

A non-exhaustive list of these cycloaliphatic diamines is given in the publication "Cycloaliphatic Amines" (Encyclopaedia of Chemical Technology, Kirk-Othmer, 4th Edition (1992), pp. 386-405).

The cycloaliphatic dicarboxylic acid may comprise the following carbon skeletons: norbornyl methane, cyclohexane, cyclohexylmethane, dicyclohexylmethane, dicyclohexylpropane, di(methylcyclohexyl) or di(methylcyclo-hexyl)propane.

The aliphatic diamine and the aliphatic dicarboxylic acid are as for the aliphatic polyamide described below. Said aliphatic polyamide may be derived from the polycondensation of one or more monomer(s) which is (are) at least one C6 to C18 amino carboxylic acid, in particular C6 to C12, more particularly CIO to C12, in particular 11-aminoundecanoic acid.

Said aliphatic polyamide may result from the polycondensation of one or more monomer(s) which is (are) at least one C6 to C18 lactam, in particular C6 to C12, more particularly C10 to C12, in particular laurylactam.

Said aliphatic polyamide may result from the polycondensation of one or more monomer(s) which is (are) at least one C6 to C18 aliphatic diamine, in particular C6 to C12, more particularly CIO to C12, and at least an aliphatic dicarboxylic acid C6 to C18, in particular C6 to C12, more particularly C10 to C12.

The aliphatic diamine used is an aliphatic diamine which has a linear main chain comprising at least 6 carbon atoms.

This linear main chain may, where appropriate, comprise one or more methyl and/or ethyl substituents; in this last configuration, one speaks of "branched aliphatic diamine". In the case where the main chain has no substituent, the aliphatic diamine is called "linear aliphatic diamine".

When this diamine is a linear aliphatic diamine, it then corresponds to the formula H2N- (CH2)x-NH2 and can be chosen for example from hexanediamine, heptanediamine, octanediamine, nonane-diamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, hexadecanediamine and octadecanediamine. The linear aliphatic diamines which have just been mentioned can all be bioresourced within the meaning of standard ASTM D6866.

When this diamine is a branched aliphatic diamine, it may in particular be 2-methylpentanediamine, 2-methyl-1,8-octanediamine or trimethylene (2,2,4 or 2,4,4) hexanediamine. The dicarboxylic acid can be chosen from aliphatic, linear or branched dicarboxylic acids.

Advantageously, the diamine is a linear aliphatic diamine,

When the dicarboxylic acid is aliphatic and linear, it can be chosen from adipic acid (6), heptanedioic acid (7), octanedioic acid (8), azelaic acid (9), sebacic acid (10), undecanedioic acid (11), dodecanedioic acid (12), brassylic acid (13), tetradecanedioic acid (14), hexadecanedioic acid (16), octadecanedioic acid ( 18), octadecenedioic acid (18).

Advantageously, the polyamide is a semi-aromatic, cyclo-aliphatic or semi-aromatic polyamide. More advantageously, said polyamide is semi-aromatic or aliphatic, in particular said polyamide is aliphatic.

More advantageously, the polyamide is aliphatic and obtained from a single aminocarboxylic acid or a single lactam, in particular it is obtained from 11-aminoundecanoic acid or lauryllactam, in particular it is obtained from the acid 11-aminoundecanoic.

Regarding additives

Said at least one additive is chosen from catalysts, fillers, colorants, stabilizers, in particular light stabilizers, in particular UV and/or heat stabilizers, plasticizers, surfactants, nucleating agents, pigments, brighteners, antioxidants, lubricants, flame retardants, natural waxes and mixtures thereof.

Mention may be made, as examples of additives, of one or more pigments or dyes.

The pigment can in principle be freely chosen from the pigments used in the conventional manner. It can in particular be chosen from mineral pigments such as titanium dioxide, carbon black, cobalt oxide, nickel titanate, molybdenum disulphide, aluminum flakes, iron oxides, zinc, zinc phosphate, and organic pigments, such as phthalocyanine and anthraquinone derivatives.

The dye can also be of any type known to those skilled in the art. Mention may be made in particular of azo dyes, anthraquinone dyes, dyes derived from indigo, triarylmethane dyes, chlorine dyes and polymethine dyes.

Mention may also be made of one or more additives which are chosen from the group consisting of catalysts, anti-crater agents or spreading agents, reducing agents, antioxidants, reinforcing fillers, UV stabilizers, fluidizing agents, corrosion inhibitors, or mixtures thereof.

The anti-crater and/or spreading agent can be of any type known to those skilled in the art. Preferably, the anticrater and/or spreading agent is selected from the group consisting of polyacrylate derivatives.

The UV stabilizer may be of any type known to those skilled in the art. Preferably, the UV stabilizer is selected from the group consisting of resorcinol derivatives, benzotriazoles, phenyltriazines and salicylates.

The antioxidants can be of any type known to those skilled in the art. Preferably, the antioxidants are selected from the group consisting of copper iodide combined with potassium iodide, phenol derivatives and hindered amines.

The fluidizing agent may be of any type known to those skilled in the art. Preferably, the fluidizing agent is selected from the group consisting of aluminas and silicas. The corrosion inhibitors can be of any type known to those skilled in the art. Preferably, the corrosion inhibitors are selected from the group consisting of phosphosilicates and borosilicates.

The term “catalyst” denotes a polycondensation catalyst such as an inorganic or organic acid.

Advantageously, the catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2), or one of its salts such as sodium hypophosphite, which is marketed under its monohydrate form or another of its salts such as the calcium, lithium, magnesium, potassium, vanadium, zinc, manganese, tin, titanium, zirconium, antimony, germanium, aluminum and ammonium salts, or a mixture thereof.

At least one additive is introduced into the extruder and its proportion introduced depends on the type of additives.

The additives are preferably present in a mass quantity, relative to the total sum of the weights of the monomers and the additives introduced, of 1 to 30%, more preferably of 2 to 10%, even more preferably of 3 to 5%, per example from 0 to 5%, or from 5 to 10%, or from 10 to 15%, or from 15 to 20%, or from 20 to 25%, or from 25 to 30%.

If the additive is a catalyst, the proportion by weight of catalyst is between about 50 ppm to about 20,000 ppm, in particular from about 100 to about 10,000 ppm, more particularly from 1,000 to 10,000 ppm with respect to the total sum the weights of the monomers and of the additives introduced. In one embodiment

Regarding the process

Preferably, the average degree of polymerization (DPn) of the polyamide obtained according to the process of the invention is less than 50, in particular less than or equal to 45, in particular comprised from 5 to 45.

Advantageously, the average degree of polymerization (DPn) of the polyamide obtained according to the process of the invention is comprised from 8 to 40, in particular from 12 to 30.

By average degree of polymerization (DPn), is meant the average number of structural units present in a polymer chain. The average degree of polymerization (DPn) is typically evaluated from the number-average molar mass (Mn) of the polyamide according to the following formula:

[Math 1]

D n = hfc With

Mn the number molar mass of the polyamide

Mo the molar mass in number of the monomers

Advantageously, the weight-average molecular mass (Mn) of the polyamide obtained according to the process of the invention is less than 10000 g/mol, in particular comprised from 1000 to 9000, in particular from 1500 to 7000, more particularly from 2000 to 5000 g /mol.

The weight average molecular weight can be determined by size exclusion chromatography.

In one embodiment, said extruder includes two to twelve co-rotating feed screws.

In a first variant of this embodiment, said extruder is a twin-screw extruder comprising two conveying screws rotating in a co-rotating manner.

Advantageously, in this first variant, said process is carried out at a temperature of 220 to 340°C, preferably of 260 to 300°C.

In one embodiment of this first variant, the residence time of the material in the extruder at the temperature between 220 and 340° C. makes it possible to carry out the polycondensation reaction to achieve the desired average degree of polymerization.

Advantageously, the desired degree of polymerization is comprised from 8 to 40, in particular from 12 to 30. In an embodiment of this first variant, the residence time of the material in the extruder at the temperature comprised from 220 to 340 ° C allows the polycondensation reaction to be carried out to achieve the desired viscosity between 0.25 and 0.7 dl/g.

In a second variant of this embodiment, said extruder is an extruder comprising annular multi-screw comprising at least 6 conveying screws, in particular 12 conveying screws, rotating in a co-rotating manner.

In one embodiment of this second variant, the residence time of the material in the extruder at the temperature between 220 and 340° C. makes it possible to carry out the polycondensation reaction to achieve the desired average degree of polymerization.

Advantageously, the desired degree of polymerization is comprised from 8 to 40, in particular from 12 to 30. In one embodiment of this second variant, the residence time of the material in the extruder at the temperature comprised from 220 to 340 ° C allows the polycondensation reaction to be carried out to achieve the desired viscosity between 0.25 and 0.7 dl/g.

Advantageously, the residence time of the material in the extruder of the first or second variant is greater than or equal to 1 minute, and in particular comprised from 1 to 10 minutes, in particular comprised from 2 to 6 minutes. In another embodiment of one or other of the two variants, the throughput of the extruder is greater than or equal to 10 kg/h, in particular greater than or equal to 15 kg/h, in particular greater than or equal to 30 kg/h. h, more particularly greater than or equal to 50 kg/h.

Advantageously, the extruder used with a flow rate greater than or equal to 10 kg/h, in particular greater than or equal to 15 kg/h, in particular greater than or equal to 30 kg/h, more particularly greater than or equal to 50 kg/h is an extruder comprising six twelve co-rotating conveying screws, in particular twelve co-rotating conveying screws.

In one embodiment, the length of the extruder comprising six to twelve co-rotating conveying screws, in particular twelve co-rotating conveying screws with the flow rate described above is greater than or equal to 30L/ D, in particular from 30 to 100L/D.

In the process of the invention, at least one additive is added during the polycondensation in the extruder. The introduction of said at least one additive can be done in the zone for introducing the monomer(s), or in a subsequent working zone, or even in two places, for example, in the zone for introducing the monomer(s), then in a later work area.

When several additives are introduced, each additive introduced can be introduced according to the methods defined above.

In one embodiment of the method according to the invention, an online analysis is carried out during said method.

In a first variant of this last embodiment, if the online analysis characterizes a product obtained having the required characteristics and in particular the desired degree of polymerization, then the operating parameters of the process, in particular the pair of residence time and temperature of the extruder, are not modified.

In a second variant of this last embodiment, if the online analysis characterizes a product obtained that does not have the required characteristics and in particular the desired degree of polymerization, then the operating parameters of the process, in particular the pair of residence time and temperature of the extruder, are modified to make it possible to obtain a product having the required characteristics and in particular the desired degree of polymerization.

In one embodiment, said at least one additive is added to said single extruder in the main hopper.

Advantageously, said at least one additive is chosen from catalysts, fillers, colorants, stabilizers.

In another embodiment, said at least one additive is added in said single extruder after the main hopper. Advantageously, said at least one additive is chosen from phosphoric acid and phosphorous acid.

In yet another embodiment, at least one additive is added to said single extruder in the main hopper and at least one additive is added to said single extruder after the main hopper.

Advantageously, said at least one additive added in the main hopper is chosen from catalysts, fillers, dyes, stabilizers and said additive added after the main hopper is chosen from phosphoric acid and phosphorous acid.

According to another aspect, the present invention relates to the formulated product capable of being obtained by the process as defined above.

The formulated product therefore corresponds to the formulated polyamide prepolymer obtained by the process defined above.

According to another aspect, the present invention relates to an extruder suitable for implementing the method as defined above.

Examples

Example 1 (comparative):

Representative example of the preparation of an aliphatic polyamide formulated

A PAU prepolymer formulated with H3PO2 was prepared in two stages: a first stage by batch process for the preparation of the prepolymer: In a 14-litre autoclave reactor, 5 kg of the following raw materials are introduced: 500 g of water, the diamine and the dicarboxylic acid and/or the amino acid, 0.1 g of a WACKER AK1000 defoamer (from Wacker Silicones).

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 steam under pressure which has formed in the reactor is gradually expanded over 60 minutes, while gradually adjusting the material temperature so that it settles at Tf + 10 °C at atmospheric pressure. The oligomer (prepolymer) is then drained through the bottom valve then cooled in a tank of water then ground.

A PAU prepolymer with Mn=3000 and viscosity 0.40 was prepared, without using diamine or dicarboxylic acid, from 11-aminoundecanoic acid (CAS 2432-99-7), according to this procedure with a residence time much greater (more than one hour) than that of the process described in Examples 2 and 3 of the invention (between 1 and 5 minutes), then a second step of compounding with the H3PO2 additive in aqueous solution (8000 ppm in H3PO2) in a twin-screw extruder Evolum32HT (EV32 Clextral) with a diameter D = 32 mm (length = 40D)

Example 2 (invention):

A formulated PAU prepolymer was prepared from solid-state 11-aminoundecanoic acid (CAS 2432-99-7) on a twin-screw extruder EV32 (Clextral) with diameter D = 32 mm (length = 40D) without extraction of the by-products formed during the polycondensation, and addition of H3PO2 in aqueous solution (8000 ppm in H3PO2) in the main hopper or after the main hopper (tables 1 and 2).

[Table 1]

[Table 2]

Example 3 (invention):

A formulated PAU prepolymer was prepared from solid-state 11-aminoundecanoic acid (CAS 2432-99-7) on an EV32 twin-screw extruder (Clextral) with diameter D = 32 mm (length = 40D) without extraction of the by-products formed during the polycondensation, and addition of H3PO4 in aqueous solution (5300 ppm in H3PO4) in the main hopper or after the main hopper (tables 3 and 4). [Table 3]

[Table 4]

Examples 2 and 3 show that a formulated PAU can be obtained in a single step by the process of the invention continuously with the required viscosity characteristics.

Furthermore, the formulated products obtained by the process of the invention are comparable to those obtained by the batch process as regards several points such as the viscosity in solution, the grindability, the shaping and the mechanical properties of the product. obtained.

Claims

CLAIMS Process for the continuous preparation of a formulated polyamide prepolymer whose viscosity in solution is 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 mass (Mn) is less than 10000 g/mol, in particular between 1000 and 9000, in particular from 1500 to 7000, more particularly from 2000 to 5000 g/mol, as determined by calculation from the rate of the terminal functions determined by potentiometric titration in solution and the functionality of the said prepolymers or by assay by NMR or by steric exclusion chromatography, characterized in that 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 conveying screws rotating in a co-rotating manner, the said monomer or monomers being introduced beforehand in solid or liquid form without dissolving in a solvent or in water, and the said polycondensation step being carried out without extracting the by-products formed, in particular the water formed during the said polycondensation and comprising the introduction of at least one additive during said polycondensation step into the extruder, said extruder being devoid of degassing devices, in particular by introducing an inert gas therein, or of a device for eliminating the or polycondensation by-products formed, and in particular the water formed, consisting of an outlet on the outside at atmospheric pressure, or an outlet connected to a device making it possible to create a depression zone in the extruder , such as a vacuum pump during the reaction. Process according to Claim 1, characterized in that the average degree of polymerization (DPn) of the polyamide obtained is less than 50, in particular less than or equal to 45, in particular comprised from 5 to 45, as determined from the mass number-average molar (Mn) of the polyamide according to the following formula:

[Math 1]

DPn = Mn

With Mn the number molar mass of the given polyamide as defined in claim 1,

Mo the molar mass in number of the monomers

3. Method according to one of claims 1 or 2, characterized in that the polyamide is an aliphatic polyamide.

4. Method according to claim 3, characterized in that the monomer or monomers is (are) at least one C6 to C18 amino carboxylic acid, in particular C6 to C12, more particularly CIO to C12, in particular the amino acid 11 undecanoic.

5. Method according to claim 3, characterized in that the monomer or monomers is (are) at least one C6 to C18 lactam, in particular C6 to C12, more particularly CIO to C12, in particular laurylactam.

6. Method according to claim 3, characterized in that the monomer or monomers is (are) at least one aliphatic diamine C6 to C18, in particular C6 to C12, more particularly CIO to C12, and at least one dicarboxylic acid aliphatic C6 to C18, in particular C6 to C12, more particularly C10 to C12.

7. Method according to one of claims 1 to 6, characterized in that the extruder is a twin-screw extruder with two conveying screws rotating co-rotatingly.

8. Process according to claim 7, characterized in that it is carried out at a temperature comprised from 220 to 340°C, preferably comprised from 260 to 300°C.

9. Method according to claim 8, characterized in that the residence time of the material in the extruder at the temperature between 220 and 340° C. makes it possible to carry out the polycondensation reaction to achieve the desired average degree of polymerization, said residence time being greater than or equal to 1 minute.

10. Method according to one of claims 1 to 6, characterized in that the extruder is an annular multi-screw extruder comprising at least 6 screws, in particular 12 screws, rotating in a co-rotating manner. 16 Process according to claim 10, characterized in that the residence time of the material in the extruder at the temperature of 220 to 340° C. makes it possible to carry out the polycondensation reaction to achieve the desired average degree of polymerization, said time dwell being greater than or equal to 1 minute. Process according to one of Claims 7 to 11, characterized in that the residence time of the material in the extruder is greater than or equal to 1 minute, and in particular comprised from 1 to 10 minutes, in particular comprised from 2 to 6 minutes. Process according to one of Claims 1 to 12, characterized in that the said at least one additive is chosen from catalysts, fillers, dyes, stabilizers, in particular light, in particular UV and/or heat stabilizers , plasticizers, surfactants, nucleating agents, pigments, brighteners, antioxidants, lubricants, flame retardants, natural waxes and mixtures thereof. Process according to one of Claims 1 to 13, characterized in that the said at least one additive is added to the said single extruder in the main hopper. Process according to one of Claims 1 to 14, characterized in that the said at least one additive is added in the said single extruder after the main hopper.