Process for the continuous preparation of formulated polyamide prepolymer

Abstract

The invention relates to a process for the continuous preparation of a formulated polyamide prepolymer, the solution viscosity of which is between 0.25 dL / g and 0.70 dL / g, measured in m-cresol at 20°C according to ISO 307:2007, the process being characterized in that it comprises a polycondensation step based on one or more polyamide precursor monomers, said polycondensation step being carried out in an extruder comprising at least two co-rotating conveying screws, at least one monomer being added to the extruder in solid or liquid form without being previously dissolved in a solvent or in water, and said polycondensation step being carried out without extraction of the water formed during said polycondensation, and comprising the addition of at least one additive during said polycondensation step in the extruder.

Description

Technical Field

[0001] This patent application relates to a method for the continuous preparation of formulated polyamide prepolymers by polycondensation, and an extruder suitable for carrying out this method. Background Technology

[0002] Polyamides (PAs) are typically prepared via a batch process in a reactor by the polycondensation of a diamine with a dicarboxylic acid, an amino acid, or a lactam. In this process, monomers are added in batches and heated under pressure until a mixture of sufficient viscosity is obtained. The monomers are often added in aqueous solution, and water present and / or formed during polycondensation must be removed by placing the reactor under reduced pressure.

[0003] However, the molar mass of polyamides is difficult to control / manage due to their "reactive" nature, as the product cannot have the same molar mass (same viscosity) at the beginning and end of reactor evacuation.

[0004] If the target molar mass is exceeded, it is impossible to return to the original state, and the product is "déclassé" for the entire batch produced.

[0005] Furthermore, batch production is a more capital-intensive method (for a fixed amount of product produced each year) and less ecological (more energy and water consumption, more gaseous effluents and waste generation, etc.).

[0006] In addition, water removal often leads to the loss of added monomers, especially in the case of polycondensation of diamines and dicarboxylic acids, which requires the use of excessive monomers, thus increasing the cost of the method.

[0007] Recently, methods for continuous synthesis have been developed.

[0008] Therefore, patent EP 2,877,516 describes a method for the continuous synthesis of polyamides with a weight-average molecular weight (Mw) greater than or equal to 14,000 g / mol. This method requires at least two drainage operations and produces a polymer instead of a prepolymer.

[0009] U.S. Patent 8,765,902 describes a method for the continuous preparation of 6T / 6I copolyamides. This method requires the evaporation of water and produces a polymer instead of a prepolymer.

[0010] Patent EP 0,410,650 describes a method for the continuous preparation of prepolymers via the polycondensation of diamines and dicarboxylic acids. This method requires the evaporation of water.

[0011] In addition, the preparation of the resulting batch requires an additional step, which involves batch-by-batch mixing of the resulting product with one or more additives.

[0012] Therefore, it is necessary to overcome the above-mentioned problems, and one of the objectives of this invention is to provide a method for preparing formulated polyamide prepolymers that is simpler, faster, more reliable, and cheaper than existing methods, and is completed in a single step.

[0013] Therefore, the present invention relates to a method for the continuous preparation of a formulated polyamide prepolymer having a viscosity in solution between 0.25 dL / g and 0.70 dL / g, which is measured in m-cresol at 20°C according to ISO 307:2007.

[0014] The method is characterized by comprising a step of polycondensation of one or more polyamide precursor monomers, said polycondensation step being carried out in a single extruder comprising at least two co-rotating conveyor screws, said monomers being added in advance in solid or liquid form without being dissolved in a solvent or water, and said polycondensation step being carried out without extracting the byproducts formed, particularly the water formed during said polycondensation, and including the addition of at least one additive during said polycondensation step in the extruder.

[0015] Therefore, the inventors have discovered that a trade-off between the residence time of the material in the extruder and the reaction temperature in the extruder can be found without removing water (especially by placing the extruder under vacuum) to prepare a prepolymer of the desired viscosity. At the same time, the prepolymer can also be formulated during the polycondensation step in the extruder to obtain a formulated prepolymer.

[0016] In fact, placing prepolymers under vacuum in an extruder to remove water is a technical challenge because the medium, due to its low viscosity, tends to foam and rises very easily in the vacuum line. This can lead to blockages and loss of vacuum effectiveness.

[0017] Since the residence time in the extruder is always the same, the resulting product always has the same number-average molar mass (Mn) or the same viscosity.

[0018] The resulting products can also be characterized online, which allows for the modification of method parameters through feedback to ensure proper control over the final product.

[0019] Throughout this specification, the term prepolymer has the same meaning as the term oligomer.

[0020] The term prepolymer refers to polyamides with a number-average molecular weight Mn of less than 10,000 g / mol, particularly 1,000 to 9,000, particularly 1,500 to 7,000, and even more particularly 2,000 to 5,000 g / mol.

[0021] Mn is specifically determined by the following methods: by potentiometric titration in solution to determine the level of terminal functional groups and the calculation of the functionality of the prepolymer, or by NMR testing (Postma et al. Polymer, 47, 1899–1911 (2006)).

[0022] Mn can also be determined by size exclusion chromatography.

[0023] In polymerizations carried out by condensation, especially the condensation of diamines and dicarboxylic acids or the condensation of a single monomer that includes both carboxylic acid functional groups and amine functional groups, each step is a condensation reaction that takes place with the elimination of small molecules (called reaction byproducts, such as H2O), depending on the monomers involved.

[0024] In the method of the present invention, the formed byproducts, especially the formed water, are not eliminated, which means that the extruder does not have any means for discharging the reaction byproducts (which are water in most cases) formed by the polycondensation reaction.

[0025] The extruder, in particular, does not have any degassing device, especially by adding an inert gas therein, or any device for removing the condensation byproducts formed, especially the water formed, which consists of an external outlet at atmospheric pressure, or an outlet connected to a device, such as a vacuum pump, that utilizes it to create a low-pressure zone in the extruder during the reaction.

[0026] However, the extruder is equipped with a device for returning to atmospheric pressure after the reaction is complete and therefore after the screw.

[0027] The extruder used includes two feed screws.

[0028] The method for preparing polyamide according to the present invention comprises the following sequential steps, all of which are performed in an extruder:

[0029] The step of mixing the selected monomers,

[0030] And the polycondensation step performed by shearing the material conveyed by the conveying screw.

[0031] In a preferred embodiment, the following step is also performed: between the mixing and polycondensation steps, a continuously renewed cap or seal is formed by conveying material on a conveying screw. Advantageously, the cap or seal, made of the material in progress, fills all the volume available for material passage and constitutes an area that is hermetically sealed to vapors, especially to any monomer vapors that may be generated.

[0032] In an extruder, each feed screw consists of different elements that follow each other in the conveying direction. These different elements are placed adjacent to each other on the axis of rotation. In a co-rotating extruder, all feed screws rotate in the same direction, which typically corresponds to a counterclockwise direction. In the case of a linear extruder, the elements are located adjacent to each other in a single straight line, or in the case of a toroidal extruder, in a circle. The different feed screws constituting the extruder all have the same diameter, which remains constant along the feed screw. Most commonly, this diameter ranges from 18 to 134 mm.

[0033] Such an extruder is specifically described in patent EP 2,877,516, which excludes elements for depressurization or for extracting the resulting byproducts, elements that are absent in the method of the present invention.

[0034] The monomers used as precursors to polyamides are added in advance in solid or liquid form according to their natural appearance, but are insoluble in any solvent or water under any circumstances.

[0035] The term "pre-" means that the monomer is added before the polymerization reaction begins.

[0036] In the context of this invention, the monomer is added without prior reaction and without prior preparation of the corresponding salt.

[0037] Regarding polyamide

[0038] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics--Polyamide(PA) Moulding And Extrusion Materials--Part 1:Designation" and is well known to those skilled in the art.

[0039] Polyamide can be any polyamide, whether it is aliphatic, alicyclic, aromatic or semi-aromatic polyamide.

[0040] It can be a homopolymer or a copolymer.

[0041] Advantageously, the polyamide is a homopolymer.

[0042] The aromatic polyamide is obtained, in particular, by polycondensation of an aromatic amine, selected from m-phenylenediamine (MXD, CAS No.: 1477-55-0) or p-phenylenediamine (PXD, CAS No.: 539-48-0), with an aromatic dicarboxylic acid, particularly selected from terephthalic acid, isophthalic acid, and naphthalic acid.

[0043] The semi-aromatic polyamide optionally modified with a urea unit may be, in particular, a semi-aromatic polyamide of formula X / YAr as described in EP1,505,099, especially a semi-aromatic polyamide of formula A / XT, wherein A is selected from a unit obtained from an amino acid monomer, a unit obtained from a lactam monomer, and a unit corresponding to the formula (Ca diamine)·(Cb diacid), both of which represent monomers, wherein a represents the number of carbon atoms of the diamine, b represents the number of carbon atoms of the diacid, and a and b are each between 4 and 36, advantageously between 9 and 18, the unit (Ca diamine) is selected from linear or branched aliphatic diamines, alicyclic diamines, and alkyl aromatic diamines, and the unit (Cb diacid) is selected from linear or branched aliphatic diacids, alicyclic diacids, and aromatic diacids;

[0044] XT represents a unit obtained by the polycondensation of Cx diamine and terephthalic acid, where x represents the number of carbon atoms in the Cx diamine, x being between 6 and 36, advantageously between 9 and 18, especially polyamides having the formula A / 6T, A / 9T, A / 10T or A / 11T, where A is as defined above, particularly polyamides PA 6 / 6T, PA 66 / 6T, PA 6I / 6T, PA MPMDT / 6T, PA MXDT / 6T, PAPA11 / 10T, PA 5T / 10T, PA 11 / 5T / 10T, PA 11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PABACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA 11 / BACT / 10T, PA 11 / BACT / 6T, PA 11 / MPMDT / 10T and PA 11 / MXDT / 10T, and block copolymers, especially polyamide / polyether (PEBA).

[0045] T corresponds to terephthalic acid, MXD corresponds to m-phenylenediamine, MPMD corresponds to methylpentamethylenediamine, and BAC corresponds to bis(aminomethyl)cyclohexane.

[0046] The alicyclic polyamide is obtained, in particular, by polycondensation of the following monomers: alicyclic diamine with alicyclic dicarboxylic acid, or alicyclic diamine with alicyclic dicarboxylic acid, or alicyclic diamine with alicyclic dicarboxylic acid.

[0047] Alicyclic diamines may be selected from, for example: 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-aminocyclohexyl)butane, bis(3-methyl-4-aminocyclohexyl)methane or 3′-dimethyl-4,4′-diamino-dicyclohexylmethane commonly referred to as “BMACM” or “MACM” (and hereinafter referred to as B), p-bis(aminocyclohexyl)methane commonly referred to as “PACM” (and hereinafter referred to as P), isopropylidene di(cyclohexylamine) commonly referred to as “PACP”, isophorone diamine (hereinafter referred to as IPD) and 2,6-bis(aminomethyl)norbornene commonly referred to as “BAMN”.

[0048] A non-exhaustive list of these alicyclic diamines can be found in the publication "Cycloaliphatic Amines" (Encyclopaedia of Chemical Technology, Kirk-Othmer, 4th Edition (1992), pp. 386–405).

[0049] Alicyclic dicarboxylic acids may contain the following carbon skeletons: norbornylmethane, cyclohexane, cyclohexylmethane, dicyclohexylmethane, dicyclohexylpropane, di(methylcyclohexyl) or di(methylcyclohexyl)propane.

[0050] Aliphatic diamines and aliphatic dicarboxylic acids are as described below for aliphatic polyamides.

[0051] The aliphatic polyamide may be produced by the polycondensation of one or more monomers, wherein the monomer is at least one C6 to C18, particularly C6 to C12, more particularly C10 to C12 carboxylic acid, especially 11-aminoundecanoic acid.

[0052] The aliphatic polyamide can be obtained from the polycondensation of one or more monomers, wherein the monomer is at least one C6 to C18, particularly C6 to C12, more particularly C10 to C12 lactam, especially laurolactam.

[0053] The aliphatic polyamide may be derived from the polycondensation of one or more monomers, wherein the monomer is at least one C6 to C18, particularly C6 to C12, more particularly C10 to C12 aliphatic diamine, and at least one C6 to C18, particularly C6 to C12, more particularly C10 to C12 aliphatic dicarboxylic acid.

[0054] The aliphatic diamine used is an aliphatic diamine having a linear backbone containing at least 6 carbon atoms.

[0055] If necessary, the linear backbone may include one or more methyl and / or ethyl substituents; in the latter configuration, this is referred to as a “branched aliphatic diamine.” When the backbone does not contain any substituents, the aliphatic diamine is referred to as a “linear aliphatic diamine.”

[0056] When the diamine is a linear aliphatic diamine, it specifically corresponds to the formula H2N-(CH2)x-NH2, and can be selected from, for example, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanedanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, hexadecanediamine, and octadecenediamine. All the linear aliphatic diamines mentioned above can be of biological origin in the sense of standard ASTM D6866.

[0057] When the diamine is a branched aliphatic diamine, it can be 2-methylpentanediamine, 2-methyl-1,8-octanediamine or trimethylene(2,2,4- or 2,4,4)-hexanediamine.

[0058] Dicarboxylic acids can be selected from linear or branched aliphatic dicarboxylic acids.

[0059] Advantageously, the diamine is a linear aliphatic diamine.

[0060] When the dicarboxylic acid is aliphatic and linear, it can be selected from succinic acid (6), heptanic acid (7), octanoic acid (8), azelaic acid (9), sebacic acid (10), undecanoic acid (11), dodecanoic acid (12), tridecanoic acid (13), tetradecanoic acid (14), hexadecanoic acid (16), octadecanoic acid (18), and octadecenoic acid (18).

[0061] Advantageously, the polyamide is a semi-aromatic, alicyclic, or semi-aromatic polyamide.

[0062] More advantageously, the polyamide is semi-aromatic or aliphatic, particularly aliphatic.

[0063] More advantageously, the polyamide is aliphatic and is obtained from a single aminocarboxylic acid or a single lactam, particularly from 11-aminoundecanoic acid or laurolactam, particularly from 11-aminoundecanoic acid.

[0064] About additives

[0065] The at least one additive is selected from catalysts, fillers, dyes, stabilizers (especially light stabilizers, particularly UV and / or heat stabilizers), plasticizers, surfactants, nucleating agents, pigments, whitening agents, antioxidants, lubricants, flame retardants, natural waxes, and mixtures thereof.

[0066] Examples of one or more pigments or dyes as additives may be given.

[0067] Pigments can, in principle, be freely selected from pigments used in a conventional manner. They can be particularly selected from mineral pigments such as titanium dioxide, carbon black, cobalt oxide, nickel titanate, molybdenum disulfide, aluminum flakes, iron oxide, zinc oxide, and zinc phosphate, as well as organic pigments such as phthalocyanine and anthraquinone derivatives.

[0068] The dye may also be of any type known to those skilled in the art. In particular, azo dyes, anthraquinone dyes, indigo dyes, triarylmethane dyes, chlorinated dyes, and polymethyl dyes may be mentioned.

[0069] It may also mention one or more additives selected from the following: catalysts, anti-cratering agents or spreading agents, reducing agents, antioxidants, reinforcing fillers, UV stabilizers, fluidizing agents, corrosion inhibitors or mixtures thereof.

[0070] The anti-cratering agent and / or spreading agent may be of any type known to those skilled in the art. Preferably, the anti-cratering agent and / or spreading agent is selected from polyacrylate derivatives.

[0071] The UV stabilizer can be any type known to those skilled in the art. Preferably, the UV stabilizer is selected from resorcinol derivatives, benzotriazole, phenyltriazine, and salicylates / salicylates.

[0072] The antioxidant can be of any type known to those skilled in the art. Preferably, the antioxidant is selected from copper iodide in combination with potassium iodide, phenol derivatives, and hindered amines.

[0073] The fluidizing agent can be any type known to those skilled in the art. Preferably, the fluidizing agent is selected from alumina and silica.

[0074] The corrosion inhibitor can be of any type known to those skilled in the art. Preferably, the corrosion inhibitor is selected from phosphosilicates and borosilicates.

[0075] The term "catalyst" refers to a polycondensation catalyst, such as a mineral acid or an organic acid.

[0076] Advantageously, the catalyst is selected from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2), or a salt thereof, such as sodium hypophosphorous acid sold in its monohydrate form, or another salt thereof, such as calcium salt, lithium salt, magnesium salt, potassium salt, vanadium salt, zinc salt, manganese salt, tin salt, titanium salt, zirconium salt, antimony salt, germanium salt, aluminum salt, and ammonium salt.

[0077] Or a mixture thereof.

[0078] At least one additive is added to the extruder, and the proportion of addition is based on the type of additive.

[0079] The additives are preferably present in an amount of 1 to 30%, more preferably 2 to 10%, even more preferably 3 to 5%, for example 0 to 5%, or 5 to 10%, or 10 to 15%, or 15 to 20%, or 20 to 25%, or 25 to 30% by mass relative to the total weight of the added monomers and additives.

[0080] If the additive is a catalyst, then the weight percentage of the catalyst relative to the total weight of the added monomer and the additive, including about 50 ppm to about 20,000 ppm, particularly about 100 to about 10,000 ppm, and more particularly 1,000 to 10,000 ppm.

[0081] In the implementation

[0082] Regarding the method

[0083] Preferably, the polyamide obtained by the method according to the invention has an average degree of polymerization (DPn) of less than 50, particularly less than or equal to 45, and particularly between 5 and 45.

[0084] Advantageously, the polyamides obtained by the method according to the invention have an average degree of polymerization (DPn) of 8 to 40, particularly 12 to 30.

[0085] The term "average degree of polymerization (DPn)" refers to the average number of structural units present in a polymer chain. The average degree of polymerization (DPn) is typically assessed using the number-average molecular weight (Mn) of the polyamide according to the following formula:

[0086] [Formula 1]

[0087] DPn=Mn / M0

[0088] in

[0089] Mn is the number-average molecular weight of polyamide.

[0090] M0 is the number average molecular weight of the monomer.

[0091] Advantageously, the polyamides obtained by the method according to the invention have a weight-average molecular weight (Mn) of less than 10,000 g / mol, particularly between 1,000 and 9,000 g / mol, particularly between 1,500 and 7,000 g / mol, and more particularly between 2,000 and 5,000 g / mol.

[0092] Weight-average molecular weight can be determined by size exclusion chromatography.

[0093] In one embodiment, the extruder includes two to twelve co-rotating feed screws.

[0094] In a first variant of this embodiment, the extruder is a twin-screw extruder comprising two co-rotating feed screws.

[0095] Advantageously, in this first variant, the method is carried out at a temperature between 220 and 340°C, preferably between 260 and 300°C.

[0096] In one embodiment of this first variant, the residence time of the material in the extruder at a temperature between 220°C and 340°C allows for polycondensation to achieve the desired average degree of polymerization.

[0097] Advantageously, the required degree of polymerization is 8 to 40, especially 12 to 30.

[0098] In one embodiment of this first variant, the residence time of the material in the extruder at a temperature of 220°C to 340°C allows for polycondensation to achieve a desired viscosity between 0.25 and 0.7 dL / g.

[0099] In a second variant of this embodiment, the extruder is an annular multi-screw extruder comprising at least six feed screws, particularly twelve, rotating in the same direction.

[0100] In one embodiment of this second variant, the residence time of the material in the extruder at a temperature of 220°C to 340°C allows for polycondensation to achieve the desired average degree of polymerization.

[0101] Advantageously, the required degree of polymerization is 8 to 40, especially 12 to 30.

[0102] In one embodiment of this second variant, the residence time of the material in the extruder at a temperature of 220°C to 340°C allows for polycondensation to achieve a desired viscosity between 0.25 and 0.7 dL / g.

[0103] 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 especially 1 to 10 minutes, particularly 2 to 6 minutes.

[0104] In another embodiment of one or the other of the two variants, the extruder flow rate is greater than or equal to 10 kg / h, especially greater than or equal to 15 kg / h, particularly greater than or equal to 30 kg / h, and even more particularly greater than or equal to 50 kg / h.

[0105] Advantageously, the extruder used has a flow rate of 10 kg / h or more, especially 15 kg / h or more, especially 30 kg / h or more, and even more especially 50 kg / h or more, and is an extruder comprising 6 to 12 co-rotating feed screws, especially 12 co-rotating feed screws.

[0106] In one embodiment, the extruder having the above-mentioned flow rate has a length greater than or equal to 30 L / D, particularly 30 to 100 L / D, and the extruder includes 6 to 12 co-rotating feed screws, particularly 12 co-rotating feed screws.

[0107] In the method of the present invention, at least one additive is added during polycondensation in the extruder. The at least one additive may be added in the monomer addition zone, or in a subsequent working zone, or even in both zones, for example, added in the monomer addition zone and then in the subsequent working zone.

[0108] When adding several additives, each additive can be added according to the method defined above.

[0109] In one embodiment of the method according to the invention, online analysis is performed during the method.

[0110] In a first variant of this latter implementation, if online analysis characterizes the resulting product as having the desired properties, particularly the desired degree of polymerization, the operating parameters of the method, particularly the residence time and temperature of the extruder, are not modified.

[0111] In a second variant of this latter embodiment, if online analysis characterizes that the resulting product does not have the desired properties, especially the desired degree of polymerization, the operating parameters of the method, especially the residence time and temperature of the extruder, are modified to obtain a product with the desired properties, especially the desired degree of polymerization.

[0112] In one embodiment, the at least one additive is added to the single extruder in the main hopper.

[0113] Advantageously, the at least one additive is selected from catalysts, fillers, dyes and stabilizers.

[0114] In another embodiment, the at least one additive is added to the single extruder following the main hopper.

[0115] Advantageously, the at least one additive is selected from phosphoric acid and phosphorous acid.

[0116] In yet another embodiment, at least one additive is added to the single extruder in the main hopper, and at least one additive is added to the single extruder after the main hopper.

[0117] Advantageously, the at least one additive added in the main hopper is selected from catalysts, fillers, dyes, and stabilizers, and the additive added after the main hopper is selected from phosphoric acid and phosphorous acid.

[0118] According to another aspect, the present invention relates to formulations that can be obtained by methods as defined above.

[0119] Therefore, this formulation corresponds to the polyamide prepolymer prepared by the method defined above.

[0120] According to another aspect, the present invention relates to an extruder suitable for carrying out the methods as defined above. Example:

[0121] Example 1 (Comparative):

[0122] Representative examples of the preparation of formulated aliphatic polyamides

[0123] PA11 prepolymer prepared with H3PO2 in two steps:

[0124] The first step in each batch process for preparing the prepolymer:

[0125] Add 5 kg of the following raw materials to a 14-liter high-pressure reactor:

[0126] -500g water,

[0127] -Diamines and dicarboxylic acids and / or amino acids,

[0128] -0.1g of WACKER AK1000 defoamer (from Wacker Silicones).

[0129] The residual oxygen in the sealed reactor was removed, and the material was then heated to a temperature of 230°C. After stirring under these conditions for 30 minutes, the pressurized vapor formed in the reactor was gradually released over 60 minutes, while the material temperature was gradually adjusted to stabilize at Tf+10°C under atmospheric pressure.

[0130] The oligomer (prepolymer) is then vented through a bottom valve, cooled in a water bath, and then ground.

[0131] According to this procedure, a PA11 prepolymer with Mn = 3000 and viscosity of 0.40 is prepared from 11-aminoundecanoic acid (CAS 2432-99-7) without the use of diamines or dicarboxylic acids, wherein the residence time (more than 1 hour) is much longer than the residence time (between 1 and 5 minutes) described in Examples 2 and 3 of the present invention.

[0132] Then comes the second mixing step, which involves mixing the H3PO2 additive (8000 ppm H3PO2) in solution in an Evolum 32HT twin-screw extruder (EV32 Clextral) with a diameter of D = 32 mm (length = 40 D).

[0133] Example 2 (Invention):

[0134] PA11 prepolymer was formulated from solid 11-aminoundecanoic acid (CAS 2432-99-7) on an EV32 twin-screw extruder (Clextral) with a diameter D = 32 mm (length = 40 D) without extracting byproducts formed during polycondensation, and H3PO2 (8,000 ppm H3PO2) was added in or after the main hopper as an aqueous solution (Tables 1 and 2).

[0135] [Table 1]

[0136]

[0137] [Table 2]

[0138] Example 3 (Invention):

[0139] PA11 prepolymer was formulated from solid 11-aminoundecanoic acid (CAS 2432-99-7) on an EV32 twin-screw extruder (Clextral) with a diameter of D = 32 mm (length = 40 D) without extracting byproducts formed during polycondensation, and H3PO4 (5,300 ppm H3PO4) was added in or after the main hopper as an aqueous solution (Tables 3 and 4).

[0140] [Table 3]

[0141]

[0142] [Table 4]

[0143]

[0144] Examples 2 and 3 demonstrate that a formulated PA11 with the desired viscosity characteristics can be obtained in a single step using the continuous method of the present invention.

[0145] Furthermore, the formulations obtained by the method of the present invention are comparable to those obtained by batch methods in several respects, such as solution viscosity, grinding ability, shaping and mechanical properties of the resulting products.

Claims

1. A method for continuously preparing a polyamide prepolymer having a viscosity in solution of 0.25 dL / g to 0.70 dL / g, measured in m-cresol at 20°C according to ISO 307:2007, wherein the number-average molecular weight (Mn) of the prepared polyamide prepolymer is less than 10,000 g / mol, determined by: the level of terminal functional groups determined by potentiometric titration in solution and calculation of the functionality of the prepolymer, or by NMR testing, or by size exclusion chromatography. Its features are, The method includes a step of polycondensation of one or more polyamide precursor monomers, said polycondensation step being carried out in a single extruder comprising at least two co-rotating conveyor screws, said monomers being added in advance in solid or liquid form without being dissolved in a solvent or water, and said polycondensation step being carried out without extracting the resulting byproducts, and includes the addition of at least one additive during said polycondensation step in the extruder. The extruder does not have any degassing device or any device for removing the formed condensation byproducts. The device consists of an external outlet at atmospheric pressure or an outlet connected to a device that allows a low-pressure zone to be created in the extruder during the reaction. The method is carried out at a temperature between 220 and 340°C and the residence time of the material in the extruder is 1 to 10 minutes.

2. The method according to claim 1, characterized in that, The number-average molecular weight (Mn) of the prepared polyamide prepolymer is between 1,000 and 9,000 g / mol, determined by the following methods: potentiometric titration in solution to determine the level of terminal functional groups and the calculation of the functionality of the prepolymer, or NMR test, or size exclusion chromatography.

3. The method according to claim 2, characterized in that, The number-average molecular weight (Mn) of the prepared polyamide prepolymer is 1,500 to 7,000 g / mol, determined by the following methods: by potentiometric titration in solution to determine the level of terminal functional groups and the calculation of the functionality of the prepolymer, or by NMR test, or by size exclusion chromatography.

4. The method according to claim 3, characterized in that, The number-average molecular weight (Mn) of the prepared polyamide prepolymer is 2,000 to 5,000 g / mol, determined by the following methods: calculation of the terminal functional group level by potentiometric titration in solution and the functionality of the prepolymer, or by NMR test, or by size exclusion chromatography.

5. The method according to claim 1, characterized in that, The polycondensation step is carried out without extracting the water formed during the polycondensation.

6. The method according to claim 1, characterized in that, The extruder does not have any degassing device for adding inert gas therein.

7. The method according to claim 1, characterized in that, The polycondensation byproduct is water.

8. The method according to claim 1, characterized in that, The device that enables the creation of a low-pressure zone in the extruder during the reaction is a vacuum pump.

9. The method according to claim 1, characterized in that, The average degree of polymerization (DPn) of the obtained polyamide is less than 50, which is determined by the number-average molecular weight (Mn) of the polyamide according to the following formula: [Formula 1] in Mn, the number-average molecular weight of the polyamide as defined in claim 1. M0 is the number-average molecular weight of the monomer.

10. The method according to claim 9, characterized in that, The average degree of polymerization (DPn) of the resulting polyamide is less than or equal to 45.

11. The method according to claim 10, characterized in that, The average degree of polymerization (DPn) of the resulting polyamides ranged from 5 to 45.

12. The method according to any one of claims 1 to 11, characterized in that, The polyamide is an aliphatic polyamide.

13. The method according to claim 12, characterized in that, The monomer is at least one C6 to C18 carboxylic amino acid.

14. The method according to claim 13, characterized in that, The monomer is at least one C6 to C12 carboxylic amino acid.

15. The method according to claim 14, characterized in that, The monomer is at least one C10 to C12 carboxylic amino acid.

16. The method according to claim 15, characterized in that, The monomer is 11-aminoundecanoic acid.

17. The method according to claim 12, characterized in that, The monomer is at least one C6 to C18 lactam.

18. The method according to claim 17, characterized in that, The monomer is at least one C6 to C12 lactam.

19. The method according to claim 18, characterized in that, The monomer is at least one C10 to C12 lactam.

20. The method according to claim 19, characterized in that, The monomer is laurolactam.

21. The method according to claim 12, characterized in that, The monomer is at least one C6 to C18 aliphatic diamine and at least one C6 to C18 aliphatic dicarboxylic acid.

22. The method according to claim 21, characterized in that, The aliphatic diamine is a C6 to C12 aliphatic diamine.

23. The method according to claim 22, characterized in that, The aliphatic diamine is a C10 to C12 aliphatic diamine.

24. The method according to claim 21, characterized in that, The aliphatic dicarboxylic acid is a C6 to C12 aliphatic dicarboxylic acid.

25. The method according to claim 24, characterized in that, The aliphatic dicarboxylic acid is a C10 to C12 aliphatic dicarboxylic acid.

26. The method according to any one of claims 1 to 11, characterized in that, The extruder is a twin-screw extruder with two co-rotating feed screws.

27. The method according to claim 1, characterized in that, The method is carried out at a temperature of 260 to 300°C.

28. The method according to any one of claims 1 to 11, characterized in that, The extruder is an annular multi-screw extruder comprising at least six screws.

29. The method according to claim 28, characterized in that... The extruder is an annular multi-screw extruder comprising at least 12 screws rotating in the same direction.

30. The method according to claim 1, characterized in that, The residence time of the material in the extruder is 2 to 6 minutes.

31. The method according to any one of claims 1 to 11, characterized in that, The at least one additive is selected from catalysts; fillers; dyes; stabilizers; plasticizers; surfactants; nucleating agents; pigments; whitening agents; antioxidants; lubricants; flame retardants; and mixtures thereof.

32. The method according to any one of claims 1 to 11, characterized in that, The at least one additive is selected from natural waxes.

33. The method according to claim 31, characterized in that, The stabilizer is a light stabilizer.

34. The method according to claim 31, characterized in that, The stabilizer is a UV and / or heat stabilizer.

35. The method according to any one of claims 1 to 11, characterized in that, The at least one additive is added to the single extruder in the main hopper.

36. The method according to any one of claims 1 to 11, characterized in that, The at least one additive is added to the single extruder after the main hopper.

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