Polyamide compositions prepared from recycled polyamide powder

Abstract

The present application relates to a method for preparing a polyamide composition, comprising the steps of: a) providing a mixture comprising virgin polyamide vPA and recycled polyamide rPA in the form of an untransformed powder obtained from additive manufacturing by sintering or from a coating process by powder spraying or by electrostatic spraying, or in the form of a powder obtained by grinding the polyamide base component of the object to be recycled, b) kneading the mixture in the molten state, resulting in a polyamide composition, and c) recovering the polyamide composition. The invention also relates to the polyamide composition obtained and its use for preparing an article by extrusion, injection or overmolding.

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a polyamide composition from untransformed powder obtained from additive manufacturing by sintering or from methods by powder spraying or by electrostatic spraying, or from powder obtained by grinding polyamide-based components of objects to be recycled, to a polyamide composition and its use for preparing an article. [Background technology]

[0002] In recent years, additive manufacturing (AM according to the generally accepted terminology) has experienced rapid growth, especially thanks to the possibility of designing objects with a great variety of forms and shapes, the short time between design and production, and the associated environmental and economic advantages.

[0003] The agglomeration or melt agglomeration of powders by melting (hereinafter "sintering") is caused by irradiation, for example by a laser beam ("laser sintering" or "selective laser sintering" SLS according to the generally accepted terminology), infrared radiation, UV radiation, or any source of electromagnetic radiation that allows powder to be melted layer by layer to produce a three-dimensional object. The SLS technique produces parts by applying powder layer by layer, each layer being in the form of a thin powder bed, generally on the order of 100 μm. A laser is used to melt portions of this powder in the desired locations, after which a new layer of powder is deposited. The process is repeated until a thermoplastic polymer object is formed layer by layer.

[0004] Other methods that may also be mentioned include selective sintering processes using absorbers, in particular the techniques known as "high speed sintering" (HSS) and "multi-jet fusion" (MJF), in which the production of 3D objects is also carried out layer by layer using polyamide-based powders that are melted in a controlled manner for each layer that makes up the 3D object, and on which the absorber is deposited (for example by means of a liquid ink in an "inkjet process") before the layer is exposed to electromagnetic radiation (for example infrared radiation) that causes melting of the areas containing said absorber.

[0005] Sintering produces a large amount of untransformed powder. For each layer, the powder not targeted by irradiation is not incorporated into the final object. This therefore results in a lot of powder remaining untransformed.

[0006] This untransformed powder is generally difficult to recover because it has deteriorated. In practice, the powder bed is preheated and maintained at a temperature close to the powder's melting point, typically 5–15°C below its melting point. This allows for proper fusion of the powder targeted by the laser and good definition of each layer of the laser-formed object. At this temperature, the untransformed powder undergoes aging degradation processes, such as solid-state polycondensation and oxidation reactions, which increase the polymer chain length and decrease the melt flow rate (MFR). As a result, these degraded powders usually cannot be directly reused in subsequent sintering-based additive manufacturing processes, especially if the viscosity of the degraded powder is too significantly different from that of the original powder. Any attempt to reuse these powders results in parts with poor surface finishes, such as an orange-peel appearance, and reduced mechanical properties, especially lower elongation at break due to defects that act as fracture initiation in tensile tests.

[0007] It is not easy to recycle this untransformed powder for other types of transformation processes (extrusion, injection), because the heating during the sintering technique affects the intrinsic viscosity of the powder. Generally speaking, when this degraded powder is extruded or molded, the resulting article is spongy and / or its mechanical properties, especially with regard to mechanical strength, and aesthetic properties (especially with regard to color, which tends to be brown), are inferior to those of articles formed from virgin polymer.

[0008] Sintering-based additive manufacturing therefore generates a large amount of waste in the form of degraded, untransformed powder, which is rarely recycled in practice.

[0009] Considering the example of polyamide 12 (PA12), the main type of synthetic resin used in SLS processes, the PA12 powder waste can represent up to 50%, or even up to 90%, of the total amount of powder used in the process, which represents a significant loss of PA12 powder due to the fact that this waste powder must be disposed of.

[0010] The literature reports several attempts to recycle this waste polyamide powder. US Patent Application No. 2022 / 0064405 describes a recycled polyamide composition comprising polyamide waste, preferably from additive manufacturing, a lubricant, and a crystallization agent. The subject of the present application is based on increasing the crystallization temperature and the enhanced flowability provided by these agents. The composition described in this application does not contain virgin polyamide, i.e., does not include virgin polyamide.

[0011] Therefore, there is a need to recycle polyamide powder waste resulting from additive manufacturing.

[0012] Furthermore, it is known to use polymer powders to produce coatings for substrates, particularly metal substrates, typically by powder or electrostatic spraying. The powdered polymer composition is applied in the form of a loose powder to a substrate, for example, by electrostatic spraying or by submerging the substrate to be coated in a fluidized bed of powder. The polymers used to produce the powder are usually thermosetting resins, although thermoplastic polymers may also be used. Polyamides are the polymers of choice for demanding applications, such as coating dishwasher baskets, due to their high chemical and thermal resistance.

[0013] However, these powders cannot be easily recycled: in fact, the small portion of powder that does not reach the substrate during the spraying process, known as "overspray" and which is preferably recovered for recycling, generally does not have the same composition and / or the same properties as the powder originally used in the process, such that the coating obtained therefrom does not compare with the original powder in terms of appearance and properties.

[0014] Therefore, there is a need to recycle the polyamide powder waste obtained from powder spray or electrostatic spray coating processes.

[0015] The poorer mechanical properties, in particular the reduced elongation at break, of polyamide powder waste obtained from additive manufacturing or from powder spray or electrostatic spray coating processes make it less attractive than virgin polyamide, in particular for the preparation of articles.

[0016] Finally, there is a need to recycle many polyamide-based components that belong to defective objects and / or are necessary to promote a circular economy and the reuse of materials, and due to the previous use to which these components have been subjected, the polyamide contained therein generally has properties inferior to those of virgin polyamide. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] U.S. Patent Application No. 2022 / 0064405 [Non-patent literature]

[0018] [Non-Patent Document 1] PhD thesis by E. Goncalves, chapter II.2.3, published in 2011 Summary of the Invention [Problem to be solved by the invention]

[0019] One of the aims of the present patent application is to provide the ability to recycle untransformed powders obtained from additive manufacturing or from coating processes by powder spraying or by electrostatic spraying, or powders obtained by grinding the polyamide base components of the objects to be recycled.

[0020] One of the objectives is to reduce the impact on the environment, - Additive manufacturing or powder spray or electrostatic spray coating processes, by recycling the untransformed powder, - a method for preparing new polyamide articles using as raw material said untransformed powder or a powder obtained by grinding the polyamide base component of the object to be recycled. The goal is to reduce the cost of

[0021] One of the objectives of the present patent application is to provide PA11 or PA12 polyamide compositions having certain mechanical and / or physicochemical properties that are better than those of polyamide compositions prepared solely from virgin polyamide.

[0022] One of the objectives of the present patent application is to provide polyamide compositions that offer enhanced processability (i.e., adaptability to work performance in transformation processes) by extrusion, injection molding, or overmolding. [Means for solving the problem]

[0023] To achieve this object, according to a first object, the present invention provides a method for preparing a composition for preparing a polyamide composition, comprising: a) from 5 to 90% by weight of virgin polyamide vPA, 10 to 95% recycled polyamide rPA by mass providing a mixture comprising: The recycled polyamide rPA is in the form of an untransformed powder obtained from additive manufacturing by sintering or from coating methods by powder spraying or electrostatic spraying, or in the form of a powder obtained by grinding the polyamide base component of the object to be recycled, b) kneading the mixture in a molten state (melt-kneading step), resulting in a polyamide composition; c) recovering the polyamide composition; The present invention relates to a method, including:

[0024] The method comprises step a) of providing a mixture comprising virgin polyamide vPA and recycled polyamide rPA, wherein the recycled polyamide rPA is in the form of a powder.

[0025] For the purposes of this patent application, the term "vPA" refers to virgin polyamide, the latter having not undergone any prior transformation and in particular not been used in a prior additive manufacturing process by sintering or in a coating process by powder or electrostatic spraying, nor has it been obtained from components of an existing article.

[0026] The term "prior" refers to a method or process carried out prior to step a) of the method according to the invention.

[0027] For the purposes of this patent application, the term "rPA" refers to recycled polyamide, also known as recycled polyamide. - in the form of untransformed powders obtained from additive manufacturing by sintering or from coating methods by powder spraying or electrostatic spraying, preferably in the form of untransformed powders obtained from additive manufacturing by sintering, also known as 3D printing by sintering; - or in the form of a powder obtained by grinding the polyamide-based component of the object to be recycled It exists in either

[0028] The term "untransformed powder obtained from additive manufacturing by sintering" refers to powder that was not targeted by irradiation during a prior additive manufacturing by sintering process and was not used to form an object formed during a prior additive manufacturing process. Typically, this powder was subjected to a temperature greater than 100°C for at least 1 minute in an additive manufacturing apparatus.

[0029] The term "untransformed powder obtained from a powder spray or electrostatic spray coating process" refers to powder that was not used to form a coating on a substrate in a previous powder spray or electrostatic spray coating process. Typically, this powder has been used in a process to coat a substrate by powder spray or electrostatic spray.

[0030] In both cases, the untransformed powder used as recycled polyamide in the process according to the invention corresponds to the polyamide powder waste obtained from a previous process carried out previously, and the recycled polyamide rPA has therefore undergone degradation, generally thermal degradation.

[0031] The term "polyamide-based component of an object to be recycled" refers to a component obtained by a prior transformation process such as injection molding, extrusion or overmolding. The object (or component) to be recycled may be used, destroyed, of poor quality and / or unsuitable for performing its function. Therefore, the polyamide in this component is also considered waste.

[0032] The untransformed powder, or the powder obtained by grinding the polyamide-based component of the object to be recycled, generally contains more than 10% by weight, typically more than 50% or even more than 75% by weight of polyamide (or a mixture of polyamides) relative to the weight of the powder. The proportion of polyamide is generally less than 99.9% by weight.

[0033] Powders are generally such that the volume median diameter (Dv50) of the particles they contain is in the range of 5 to 250 μm, in particular 5 to 200 μm, and preferably 10 to 150 μm. According to the present patent application, the "volume mean diameter" or "Dv" is the volume mean diameter of a powder material, measured according to the standard ISO 9276 Parts 1-6: "Representation of results of particle size analysis" in the 2022 edition. Various different diameters may be identified. More specifically, Dv50 refers to the volume median diameter, i.e., the diameter corresponding to the 50th percentile of the volume, while Dv10 and Dv90 refer to the mean diameter of the volume below which 10 and 90% of the particle volume lies, respectively. The volume mean diameter may be measured using a laser particle size analyzer, for example, a laser particle size analyzer from Malvern Systeme Insitec. The associated software (RT Sizer) then functions to obtain the volume distribution of the powder and derive the Dv10, Dv50, and Dv90 from it.

[0034] The polyamides rPA and vPA may independently be homopolyamides, copolyamides, copolymers having polyamide blocks and polyether blocks (polyether block amides or PEBAs), or mixtures thereof. The polyamides rPA and vPA may also independently be mixtures of a polyamide and at least one other polymer, where the polyamide forms the matrix and the other polymer(s) form the dispersed phase.

[0035] Preferably, the polyamides rPA and vPA are independently - one or more amino acids, one or more lactams, or one or more salts of diamines with diacids or mixtures thereof It is a condensation product of

[0036] As examples of amino acids, mention may be made of alpha-omega amino acids such as aminocaproic acid, amino-7-heptanoic acid, amino-11-undecanoic acid, n-heptyl-11-aminoundecanoic acid, and amino-12-dodecanoic acid.

[0037] The lactam monomer preferably contains between 3 and 12 carbon atoms in the main ring and may be substituted. As examples of lactams, mention may be made of β,β-dimethylpropriolactam, α,α-dimethylpropriolactam, amylolactam, caprolactam, capryllactam, oenantholactam, 2-pyrrolidone, and lauryllactam.

[0038] Preferably, the diamines used in the compositions of the rPA and / or vPA polyamides are aliphatic diamines, aryl diamines, and / or saturated cyclic diamines having from 6 to 12 carbon atoms. As examples of diamines, mention may be made of hexamethylenediamine, decanediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1,5-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophoronediamine (IPD), methylpentamethylenediamine (MPDM), bis(aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), metaxylyenediamine, bis-p-aminocyclohexylmethane, and trimethylhexamethylenediamine.

[0039] Preferably, the dicarboxylic acids used in the composition of the rPA and / or vPA polyamides have between 4 and 18 carbon atoms. As examples of dicarboxylic acids, mention may be made of adipic acid, sebacic acid, azelaic acid, suberic acid, isophthalic acid, butanedioic acid, 1,4-cyclohexyldicarboxylic acid, and terephthalic acid, the sodium or lithium salts of sulfoisophthalic acid, dimerized fatty acids (these dimerized fatty acids have a dimer content of at least 98% and are preferably hydrogenated), and dodecanedioic acid HOOC-(CH2)10-COOH.

[0040] Preferably, the copolyamide rPA and / or vPA is obtained by condensation of at least two different monomers, for example, at least two different alpha-omega aminocarboxylic acids, or two different lactams, or a lactam and an alpha-omega aminocarboxylic acid having different carbon numbers. Mention may also be made of copolyamides obtained by condensation of at least one alpha-omega aminocarboxylic acid (or lactam), at least one diamine, and at least one dicarboxylic acid. Mention may also be made of copolyamides obtained by condensation of an aliphatic diamine with an aliphatic dicarboxylic acid with at least one other monomer selected from among the aforementioned aliphatic diamines and the aforementioned aliphatic dicarboxylic acids.

[0041] Preferably, the polyamide rPA and / or vPA powder has a molecular weight of 4.6, 4T, 5.4, 5.9, 5.10, 5.12, 5.13, 5.14, 5.16, 5.18, 5.36, 6, 6.4, 6.9, 6.10, 6.12, 6.13, 6.14, 6.16, 6.18, 6.36, 6T, 9, 10.4, 10.9, 10.10, 10.11, 10.12, 10.13, 10.14, 10. 12.16, 12.18, 12.36, 10T, 11, 12, 12.4, 12.9, 12.10, 12.12, 12.13, 12.14, 12.16, 12.18, 12.36, 12T, MXD6, MXD10, MXD12, MXD14, and mixtures thereof.

[0042] Preferably, the polyamide rPA and / or vPA is selected from the group consisting of PA6, PA6.6, PA10.10, PA11, PA12, PA10.11, PA6.10, PA6.12, PA6.13, and mixtures thereof.

[0043] Examples of copolyamides include copolymers of caprolactam and lauryllactam (PA6.12); copolymers of caprolactam, adipic acid, and hexamethylenediamine (PA6.66); copolymers of caprolactam, lauryllactam, adipic acid, and hexamethylenediamine (PA6.12.66); copolymers of caprolactam, lauryllactam, 11-aminoundecanoic acid, azelaic acid, and hexamethylenediamine (PA6.12.66). Polymer (PA6.69.11.12); copolymer of caprolactam, lauryllactam, amino-11-undecanoic acid, adipic acid, and hexamethylenediamine (PA6.66.11.12); copolymer of lauryllactam, azelaic acid, and hexamethylenediamine (PA69.12); copolymer of amino-11-undecanoic acid, terephthalic acid, and decamethylenediamine (PA11.10T) may be mentioned.

[0044] Preferably, the average number of carbon atoms (C) to nitrogen atoms (N) of the polyamide rPA and / or vPA is at least 8, in particular at least 10, preferably at least 11. Particularly preferably, the average number of carbon atoms (C) to nitrogen atoms (N) of the polyamide rPA and / or vPA is 11 or 12.

[0045] Preferably, the polyamides rPA and vPA are independently selected from PA11, PA10.10, PA10.12, PA12, PA12.12, PA10.14, or PA12.14, and mixtures thereof, preferably from PA11 or PA12 or mixtures thereof.

[0046] The nomenclature used to define polyamides is explained in the standard ISO 1874-1:2010 "Plastics - Polyamide (PA) moulding and extrusion materials - Part 1: Designation system and basis for specification", in particular page 3 (Tables 1 and 2), and is well known to those skilled in the art.

[0047] Preferably, the polyamides of polyamide rPA and polyamide vPA are identical in nature. For example, the virgin polyamide is vPA11 and the recycled polyamide rPA is rPA11. In another example, the virgin polyamide is vPA12 and the recycled polyamide rPA is rPA12.

[0048] Virgin polyamide vPA generally has an intrinsic viscosity of 1.50 or less, in particular 1.40 or less, preferably 1.30 or less. For the purposes of this patent application, intrinsic viscosity is as measured using an Ubbelohde tube on a 0.5% by weight solution in m-cresol at 20°C according to standard ISO 307 of 2019.

[0049] Generally, the intrinsic viscosity of the virgin polyamide vPA is lower than that of the powder of the blend, typically at least 10%, in particular at least 20%, preferably at least 30% lower than that of the powder of the blend.

[0050] The powder of the mixture generally has an intrinsic viscosity greater than or equal to 1.50, preferably greater than or equal to 1.60, and more often of the order of 1.70 to 5.00.

[0051] Generally, the polydispersity index (molecular weight-polydispersity index) Ip of the molecular weight distribution of the virgin polyamide vPA is lower than the molecular weight-polydispersity index Ip of the recycled polyamide rPA. Typically, the polydispersity index Ip of the virgin polyamide vPA is at least 20%, in particular at least 35%, and preferably at least 50% lower than the polydispersity index Ip of the recycled polyamide rPA. The molecular weight-polydispersity index Ip is the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn.

[0052] Preferably, the molecular weight-polydispersity index Ip of the virgin polyamide vPA is from 1.6 to 2.2, in particular from 1.6 to 2.1, and / or the molecular weight-polydispersity index Ip of the recycled polyamide rPA is from 2.5 to 15.0, in particular from 2.8 to 10.0.

[0053] Generally, the z-average polydispersity index Iz of the virgin polyamide vPA is lower than the polydispersity index Iz of the recycled polyamide rPA. Typically, the polydispersity index Iz of the virgin polyamide vPA is at least 30%, in particular at least 50%, and preferably at least 70% lower than the polydispersity index Iz of the recycled polyamide rPA. The z-average polydispersity index Iz is the ratio of the z-average molecular weight Mz to the number-average molecular weight Mn.

[0054] Preferably, the z-average polydispersity index Iz of the virgin polyamide vPA is from 1.5 to 3.5, in particular from 2.0 to 3.0, and / or the z-average polydispersity index Iz of the recycled polyamide rPA is from 3.5 to 50.0, in particular from 4.0 to 30.0.

[0055] The number-average molecular weight Mn, weight-average molecular weight Mw, and z-average molecular weight Mz are measured by steric exclusion chromatography (or gel permeation chromatography) according to standard ISO 16014-1 of 2012. Typically, the polyamide is solubilized in hexafluoroisoproponol stabilized with 0.05 M potassium trifluoroacetate at a concentration of 1 g / L at room temperature (20° C.) for 24 hours. The resulting solution was then filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.2 μm and subsequently injected at a flow rate of 1 mL / min into a liquid chromatography system equipped with a set of PFG columns from Polymer Standards Service, Inc., consisting of a precolumn with dimensions of 50 × 8 mm; a 1000 Å column with dimensions of 300 × 8 mm and a particle size of 7 μm; and a 100 Å column with dimensions of 300 × 8 mm and a particle size of 7 μm. The molar mass was measured by refractive index, expressed in PMMA equivalents, and used as a calibration standard, followed by conversion to g / mol.

[0056] The recycled polyamide rPA exhibits some particularities, especially new species resulting from the oxidation mechanism.

[0057] For the purposes of the present invention, the term "new species resulting from the oxidation mechanism" is used in the context of the present invention to refer to primary amide functional groups, nitriles, terminal methyl groups, alkenes, formamides, imides, carboxylic acids, and alcohols that may appear in the recycled polyamide rPA.

[0058] The recycled polyamide rPA in the context of the present invention contains functional groups resulting from oxidation reactions selected from primary amide functional groups, nitriles, terminal methyl groups, alkenes, formamides, imides, carboxylic acids, and alcohols.

[0059] According to one preferred embodiment of the invention, the recycled polyamide rPA in the context of the present invention contains functional groups resulting from the oxidation reaction chosen from among nitriles and terminal methyl groups in a molar ratio to secondary amide functional groups greater than that of the same virgin polyamide, and primary amine functional groups in a molar ratio to secondary amide functional groups less than that of the same virgin polyamide.

[0060] These functional groups may be identified and quantified by infrared spectroscopy and / or proton or carbon NMR.

[0061] NMR measurements may be performed in a hexafluoroisopropanol (HFIP) / CD2Cl2 mixture. For example, 20 mg of polymer may be dissolved in 0.7 mL of a solvent with a 1 / 3 HFIP / CD2Cl2 ratio. A mixture of dichloromethane (CD2Cl2) / trifluoroacetic anhydride (TFAA) may also be used.

[0062] This method is described in the PhD thesis by E. Goncalves, chapter II.2.3, published in 2011, which is incorporated by reference. Analysis in these two solvents provides a means to identify the majority of functional groups formed over the lifetime of the polyamide.

[0063] Thus, for example, in infrared spectroscopy, -1 The absorption bands from 1680 to 1720 cm correspond to imides. -1 The bands from 3580 to 3670 cm correspond to the carbonyl of the carboxylic acid. -1 The bands up to correspond to the alcohol functional groups of the carboxylic acids.

[0064] 3580 to 3670 cm -1 The absorption bands up to correspond to the free alcohol functional groups.

[0065] The amide functional group, on the other hand, exhibits a peak at 3100 to 3500 cm corresponding to the NH group of the amide. -1 and 15560 to 1640 cm -1 On the other hand, a pair of absorption bands at 1650 to 1700 cm corresponding to the carbonyl group of the amide -1 It is characterized by absorption bands up to .

[0066] 1180 and 1723 cm -1 The absorption bands at 900 and 1660 cm correspond to formate. -1 The band at corresponds to an alkene.

[0067] In the context of proton NMR, NMR quantification is performed, for example, by comparing the intensities of functional group lines not present in the virgin polymer with lines corresponding to amide, ether functional groups α-CH2, or other CH2. In carbon NMR, the intensities of functional group lines formed over the lifetime of the polymer are compared with the intensities of amide or CH2 carbon lines.

[0068] Some of the functional groups mentioned above can be observed, for example, in C NMR in the solvent HFIP / CDCl. Thus, the line at 36 ppm corresponds to the α-CH of the primary amide, and the line at 34 ppm corresponds to the α-CH of the carboxylic acid. These species may be quantified by integrating the areas under the lines and comparing them with the area under the line at 37.1 ppm corresponding to the secondary amide. Similarly, lines corresponding to the carbonyl groups of the primary amide, carboxylic acid, and secondary amide functional groups are observed at 181.2 ppm, 179.6 ppm, and 177.4 ppm, respectively. The line at 16.7 ppm corresponds to the α-CH of the nitrile group. Formamide groups produce chemical shifts at 163.0 ppm and 166.3 ppm.

[0069] The other functional groups mentioned above can be observed by proton NMR (H NMR) in the above-mentioned HFIP / CDCl solvent. The lines of the formamide CHO group appear at 7.92 and 8.01 ppm. The line corresponding to the α-CH group of the primary amide can be observed at 2.30 ppm. The line at 0.9 ppm corresponds to CH-(CH). n The line at 2.40 ppm corresponds to the α-CH of the nitrile functional group. A line corresponding to the protons of the formic acid functional group is observed at 8.1 ppm. A line corresponding to the protons of the aldehyde functional group is observed at 9.7 ppm. Similar to that described for carbon NMR, the ratio of new functional groups to secondary amides may be determined by integrating the areas under the lines and comparing them to the area under the line corresponding to the α-CH of the secondary amide (2.20 ppm) or the area under the line corresponding to the protons of the CONH of the secondary amide (6.0-6.1 ppm).

[0070] According to any one of the embodiments of the present invention, in the polyamide rPA to be recycled in the context of the present invention, the molar ratio of functional groups resulting from the oxidation reaction to secondary amide functional groups is between 0.0005 and 0.3.

[0071] According to any one of the embodiments of the present invention, in the recycled polyamide rPA in the context of the present invention, the molar ratio of imide functional groups to secondary amide functional groups is between 0.0005 and 0.1, in particular between 0.001 and 0.08, in particular between 0.005 and 0.05.

[0072] According to any one of the embodiments of the present invention, in the recycled polyamide rPA in the context of the present invention, the molar ratio of carboxylic acid functional groups to secondary amide functional groups is between 0.0005 and 0.1, in particular between 0.001 and 0.08, in particular between 0.005 and 0.05.

[0073] According to any one of the embodiments of the present invention, in the recycled polyamide rPA in the context of the present invention, the molar ratio of alcohol functional groups to secondary amide functional groups is between 0.0005 and 0.1, in particular between 0.001 and 0.08, in particular between 0.005 and 0.05.

[0074] According to any one of the embodiments of the present invention, in the recycled polyamide rPA in the context of the present invention, the molar ratio of primary amide functional groups to secondary amide functional groups is between 0.0005 and 0.1, in particular between 0.001 and 0.08, in particular between 0.005 and 0.05.

[0075] According to any one of the embodiments of the present invention, in the recycled polyamide rPA in the context of the present invention, the molar ratio of nitrile functional groups to secondary amide functional groups is between 0.0005 and 0.1, in particular between 0.001 and 0.08, in particular between 0.005 and 0.05.

[0076] According to any one of the embodiments of the present invention, in the recycled polyamide rPA in the context of the present invention, the molar ratio of alkene functional groups to secondary amide functional groups is between 0.0005 and 0.1, in particular between 0.001 and 0.08, in particular between 0.005 and 0.05.

[0077] According to any one of the embodiments of the present invention, in the recycled polyamide rPA in the context of the present invention, the molar ratio of formamide functional groups to secondary amide functional groups is between 0.0005 and 0.1, in particular between 0.001 and 0.08, in particular between 0.005 and 0.05.

[0078] According to any one of the embodiments of the present invention, in the recycled polyamide rPA in the context of the present invention, the molar ratio of terminal methyl functions to secondary amide functions is between 0.0005 and 0.2, in particular between 0.001 and 0.08, in particular between 0.005 and 0.05.

[0079] It is clear that depending on the waste materials and the exposure they have undergone, there may be one or more functional groups resulting from the oxidation reaction.

[0080] The mixture in step a) relative to the total mass of the mixture, 5 to 90% by weight, generally 5 to 70% by weight, in particular 20 to 65% by weight, preferably 40 to 60% by weight, of virgin polyamide vPA, 10 to 95% by weight, generally 30 to 95% by weight, in particular 35 to 80% by weight, preferably 40 to 60% by weight, of recycled polyamide rPA Includes.

[0081] The mixture in step a) may contain compounds / components other than virgin polyamide vPA or recycled polyamide rPA.

[0082] The mixture in step a) may comprise a chain limiter containing at least one, preferably at least two, functional groups, each independently selected from carboxylic acids and amines. This embodiment is particularly preferred when the proportion of recycled polyamide rPA in the mixture is greater than 50% by weight.

[0083] This chain limiter may be a carboxylic diacid, a diamine, or an amino acid, which serves to allow reaction with the amide-, amine-, or carboxylic acid functional groups of the rPA and / or vPA during compounding of the mixture in the molten state (melt compounding) and to reduce the intrinsic viscosity of the polyamide composition obtained by the process.

[0084] The amino acids may be selected from among aminocaproic acid, 7-amino-heptanoic acid, 11-amino-undecanoic acid, 12-aminododecanoic acid, and / or mixtures thereof.

[0085] To ensure good properties (flexibility, burst strength / burst resistance, tear strength, rheology, alloy morphology, compatibilization, homogeneity, consistency, adhesion) and in particular impact / shock resistance and impact resistance after aging (especially thermo-oxidative aging at high temperatures), it is possible to add impact modifiers to the mixture, in particular those that are elastomeric and preferably polar in nature.

[0086] Thus, the mixture may contain up to 20% by weight, relative to the total weight of the mixture, of an impact modifier consisting of a non-rigid polymer having a flexural modulus of less than 100 MPa, measured according to standard ISO 178 of 2010.

[0087] The non-rigid polymer is preferably as flexible as possible and has as low a glass transition temperature, Tg, as possible, i.e., below 0° C. If necessary, the impact modifier is chemically functionalized so as to be capable of reacting with the polyamide and forming a compatible alloy therewith.

[0088] The impact modifier is preferably composed in part or in whole of one or more polyolefins having functional groups selected from among carboxylic acids, carboxylic anhydrides, epoxides, and any other functional groups capable of chemically reacting with polyamides, typically with their amine chain ends (in the case of carboxylic acids, maleic anhydride) or acid chain ends (in the case of epoxides, particularly glycidyl methacrylate). For example, the polyolefin may be selected from elastomeric ethylene-propylene copolymers (EPR), ethylene-butene copolymers, ethylene-octene copolymers, elastomeric ethylene-propylene-diene copolymers (EPDM), and ethylene / alkyl(meth)acrylate copolymers, such as anhydride-grafted EPRs such as Exxelor VA1803 from Exxon, or copolymers of polyethylene, ethyl acrylate, and maleic anhydride (coPE / EA / MAH) such as Lotader 4700 from SK.

[0089] The mixture may also include polyamide additives such as pigments, dyes, light (UV) and / or heat stabilizers, plasticizers, surfactants, optical brighteners, antioxidants, natural waxes, mold release agents, fillers, reinforcing fibers, or mixtures thereof.

[0090] Contemplated fillers include, but are not limited to, mineral fillers such as those selected from the group including talc, kaolin, magnesia, slag, silica, carbon black, carbon nanotubes, expanded or non-expanded graphite, titanium oxide.

[0091] The reinforcing fibers are chosen from fibers, in particular short fibers, which may be of synthetic origin, in particular glass or carbon fibers, or of natural origin, typically derived from plants, such as flax, reed, bamboo or hemp fibers.

[0092] Typical stabilizers used with polymers are phenols, phosphites, UV absorbers, HALS stabilizers (hindered amine light stabilizers), metal iodides or thioethers. Examples that may be mentioned are Irganox 1010, 245, 1098, Irgafos 168, 126, Tinuvin 312, 770, Iodide P201 from Ciba, Nylostab S-EED from Clariant, AO412S from Adeka Palmarole.

[0093] Preferably, the additive in the mixture may be present in an amount that is less than or equal to 10% by weight, more particularly less than 5% by weight, relative to the weight of the mixture.

[0094] The sum of virgin polyamide vPA and powder comprising recycled polyamide rPA generally represents at least 40% by weight of the mixture, in particular at least 60% by weight or even at least 80% by weight, possibly at least 95% by weight or even 100% by weight of the mixture.

[0095] Preferably, the mixture does not contain any crystallizing agents (such as inorganic salts of organic acids, e.g., sodium benzoate, potassium benzoate, or calcium benzoate) and / or lubricants (such as zinc stearate, calcium stearate, or magnesium stearate).

[0096] Preferably, the mixture is free of H3PO2 and / or H3PO3. For the purposes of this patent application, H3PO2 and H3PO3 are not considered additives. Recycled untransformed powders obtained from additive manufacturing by sintering offer the advantage that, unlike virgin polyamide powders, they contain little, if any, phosphine-forming precursor species. This advantage provides the ability to transform recycled 3D powders (particularly by extrusion and injection) more safely than virgin polyamide powders.

[0097] In one embodiment, the mixture comprises: relative to the total mass of the mixture, from 5 to 70% by weight, in particular from 20 to 65% by weight, preferably from 40 to 60% by weight, of virgin polyamide vPA, 30 to 95% by weight, in particular 35 to 80% by weight, preferably 40 to 60% by weight, of recycled polyamide rPA, from 0 to 4% by weight, in particular between 0.01 and 4% by weight, preferably from 0.1 to 1%, advantageously from 0.2 to 0.8% of a chain limiter, in particular as defined above, 0 to 20% by weight, in particular 0 to 10% by weight, of an impact modifier, in particular as defined above, and 0 to 10% by weight, in particular 0 to 5% by weight, of additives, in particular as defined above It consists of a mixture of

[0098] The method comprises step b) of kneading said mixture in the molten state (melt kneading), resulting in a polyamide composition.

[0099] The compositions according to the invention are particularly easy to prepare, since all that is required is kneading of the mixture of vPA and rPA in the molten state.

[0100] Typically, the temperature during compounding is at least 5° C. higher, preferably at least 10° C. higher, than the highest of the melting temperatures of the vPA and rPA. This temperature should generally remain below 330° C. to avoid thermal degradation of the polyamide.

[0101] Typically the temperature during compounding is above 200°C and below 330°C, preferably above 220°C and below 320°C, such as between 220°C and 310°C, or such as between 230°C and 300°C.

[0102] Generally, the residence time of the mixture during kneading is less than 10 minutes, in particular less than 5 minutes, or less than 3 minutes, or even less than that.

[0103] This method of kneading in the molten state is preferably carried out in a single-screw, co-rotating twin-screw system or co-kneader such as a BUSS kneader.

[0104] The method comprises a step c) of recovering the polyamide composition obtained after compounding in the molten state. The recovery step c) may be carried out using methods known to those skilled in the art.

[0105] This process generally involves compounding in the molten state followed by extrusion of the resulting polyamide composition.

[0106] Extrusion may be carried out in a high shear mixer such as a single or twin screw extruder.

[0107] The extrusion may be carried out through a pelletizing die to produce pellets. The pellets advantageously have a volume median diameter Dv50 in the range of 1 to 10 mm, in particular 2 to 4 mm. Alternatively, the extrusion may be carried out through a die to a cooled rolling mill where the mixture is solidified, or even by calendering. The solidified mixture may then be fed to a crusher to produce chips. These chips typically have an average diameter of 5 x 5 x 1 mm.

[0108] Typically, the recovery process comprises an extrusion step, a cooling step in which the composition in the molten state is cooled using a cooling liquid, generally containing water, a cutting step in which the composition in the form of pellets is cut, and a separation step in which the cooling liquid is separated from the cooled composition.

[0109] The cutting step may be carried out during or after the cooling step, and before or after the separating step.

[0110] The recovery step may be followed by a grinding step to obtain the composition in chip or powder form.

[0111] These forms are then suitably further formed or shaped by extrusion, injection, or overmolding.

[0112] The method may be a batch process.

[0113] The method may be a continuous process.

[0114] According to a second object, the present invention relates to a polyamide composition obtainable by the process described above.

[0115] The embodiments described above, in particular with regard to the mixture and its constituents and their proportions as well as the form of the resulting composition, are most certainly applicable as the polyamide composition is obtainable by the above-mentioned process.

[0116] Advantageously, the composition according to the invention has an elongation at break, measured according to the 2019 standard ISO 527 1A, that is more favorable compared to that of an identical composition except that the recycled polyamide rPA has been replaced by virgin polyamide vPA (i.e. compared to a composition that does not contain rPA).

[0117] Advantageously, the composition according to the invention has a high cold impact resistance compared to an identical composition except that recycled polyamide rPA is replaced by virgin polyamide vPA (i.e., compared to a composition without rPA). The cold impact resistance is advantageously increased by at least 10%, preferably at least 30%, in particular at least 50%. Impact resistance may be determined according to the 2010 standard ISO 179-1eA.

[0118] Advantageously, the compositions according to the invention have, in the molten state, better rheological properties at frequencies typical of extrusion, injection or overmolding applications (for example, at angular frequencies between 5 and 500 rad / s) than identical compositions in which recycled polyamide rPA has been replaced by virgin polyamide vPA (i.e., compared to compositions without rPA), which is an advantage for processes of forming the composition by extrusion or injection and for processes of molding.

[0119] Without intending to be bound by any particular theory, recycled polyamide rPA in powder form generally has a higher molecular weight and a higher polydispersity index Iz (Mz / Mn) and / or Ip (Mw / Mn) than virgin polyamide vPA of the same nature. For example, rPA11 generally has a higher molecular weight and a higher polydispersity index Iz (Mz / Mn) and / or Ip (Mw / Mn) than vPA11. Consequently, when the powder is added to a virgin polyamide grade, it is possible to increase both the low-temperature impact strength and the elongation at break of the article (compared to an article without rPA).

[0120] This also makes it possible to improve the processability / operational performance of the compositions according to the invention: in fact, the higher polydispersity index Iz(Mz / Mn) of the polyamide compositions according to the invention compared to that of virgin polyamide vPA makes it possible to increase the melt strength (the melt being the composition in the molten state) during extrusion, molding or overmolding to form articles or components.

[0121] In addition, rPA has more oxidation functional groups than vPA, and therefore more polar groups. The addition of rPA to vPA grades provides better adhesive properties, thus facilitating the application of the composition of the present invention by overmolding. The improvement in adhesive properties can be experimentally demonstrated, for example, by a peel test at the interface between two components combined by overmolding.

[0122] In fact, during additive manufacturing, new species obtained from oxidation mechanisms, especially primary amide functionalities, nitriles, and terminal methyl groups (CH3(CH2) n Functional groups resulting from the decomposition of the alpha methylene of primary amides and / or said amide functional groups, such as alkenes (CH=CH-), formamides, imides, carboxylic acids, and alcohols, appear in the polyamide structure. These functional groups are described above.

[0123] Infrared radiation can be used to detect the presence or absence of these new species resulting from oxidation mechanisms.

[0124] Therefore, from 1700 to 1740 cm -1 The absorption bands from 1680 to 1720 cm correspond to imides. -1 up to 3580-3670cm, corresponding to the carbonyl of the carboxylic acid -1 up to corresponds to the alcohol functional group of the carboxylic acid.

[0125] 3580 to 3670 cm -1 The absorption bands up to correspond to the free alcohol functional groups.

[0126] The amide functional group, on the other hand, exhibits a peak at 3100 to 3500 cm corresponding to the NH group of the amide. -1 and 1560 to 1640 cm -1 On the other hand, a pair of absorption bands at 1650 to 1700 cm corresponding to the carbonyl group of the amide -1 It is characterized by absorption bands up to

[0127] Quantification of the new species resulting from the oxidation mechanism was performed using dichloromethane-d HFIP (hexafluoroisopropanol) to solubilize the polyamide. 2 This is done by proton NMR in the

[0128] For example, 20 mg of polymer may be dissolved in 0.7 mL of a solvent with a 1 / 3 HFIP / CD2Cl2 ratio.

[0129] Some of the functional groups mentioned below can be observed, for example, in C NMR. Thus, the line at 36 ppm corresponds to the α-CH of the primary amide, and the line at 34 ppm corresponds to the α-CH of the carboxylic acid. These species may be quantified by integrating the areas under the lines and comparing them with the area under the line at 37.1 ppm, which corresponds to the secondary amide.

[0130] Similarly, lines corresponding to the carbonyl groups of the primary amide, carboxylic acid, and secondary amide functional groups are observed at 181.2 ppm, 179.6 ppm, and 177.4 ppm, respectively.

[0131] The line at 16.7 ppm corresponds to the α-CH2 of the nitrile group.

[0132] The formamide groups give rise to chemical shifts at 163.0 ppm and 166.3 ppm.

[0133] The other functional groups mentioned above can be observed by proton NMR (H NMR) in the above-mentioned HFIP / CDCl solvent. The lines of the formamide CHO group appear at 7.92 and 8.01 ppm. The line corresponding to the α-CH group of the primary amide can be observed at 2.30 ppm. The line at 0.9 ppm corresponds to CH-(CH). n The line at 2.40 ppm corresponds to the α-CH of the nitrile functional group. Similar to that described for carbon NMR, the ratio of new functional groups to secondary amide may be determined by integrating the areas under the lines and comparing them to the area under the line corresponding to the α-CH of the secondary amide (2.20 ppm).

[0134] Preferably, the intrinsic viscosity of the polyamide composition according to the invention is at least 10%, in particular at least 20%, preferably at least 30% lower compared to the intrinsic viscosity of the powder of the mixture used in step a).

[0135] Preferably, when the average number of carbon atoms (C) to nitrogen atoms (N) of the polyamide rPA and / or vPA is 8 or more, in particular 10 or more, preferably 11 or more, the intrinsic viscosity of the polyamide composition according to the invention is 1.50 or less, preferably 1.40, 1.30, 1.25, 1.20, 1.15 or even 1.10 or less, in particular when the virgin polyamide used as starting material in the mixture and the recycled polyamide are independently PA11 or PA12. For example, the intrinsic viscosity of the polyamide composition may be between 0.80 and 1.50, preferably between 0.90 and 1.40, between 0.90 and 1.30, between 0.90 and 1.20, inclusive.

[0136] Preferably, when the average number of carbon atoms (C) to nitrogen atoms (N) of the polyamide rPA and / or vPA is 8 or more, in particular 10 or more, preferably 11 or more, in particular when the virgin polyamide used as starting material in the mixture and the recycled polyamide are independently PA11 or PA12, the "melt flow index" MFI or "melt flow rate" MFR (according to generally accepted terminology) of the composition according to the invention, measured at 235 ° C under 2.16 kg, is between 0.1 and 60 cm 3 / 10 min, advantageously between 0.2 and 45 cm 3 Preferably, the flowability index of the composition according to the invention, measured at 250°C under a mass of 5 kg according to standard ISO 1133, is higher than 30, advantageously higher than 40, in particular higher than 50, preferably between 60 cm 3 / Higher than 10min.

[0137] In general, the z-average polydispersity index Iz of the polyamides of the composition according to the invention is higher than that of the virgin polyamides used as starting materials in the mixtures, and / or the molecular weight polydispersity index Ip of the polyamides of the composition is higher than that of the virgin polyamides used as starting materials in the mixtures.

[0138] Preferably, the z-average polydispersity index Iz (Mz / Mn) of the polyamides of the composition according to the invention is 3.0 or greater, typically 3.5 or greater, in particular 4.0 or greater, and preferably 5.0 or greater, and / or the molecular weight polydispersity index Ip (Mw / Mn) of the polyamides of the composition is 1.5 or greater, typically higher than 2.0, in particular 2.5 or greater, preferably higher than 3.0, even higher than 4.0. Generally, the z-average polydispersity index Iz is lower than 30.0, in particular lower than 25.0, preferably lower than 15.0, and / or the molecular weight polydispersity index Ip is lower than 20.0, in particular lower than 15.0, preferably lower than 8.0, and particularly preferably lower than 7.0.

[0139] According to a third object, the present invention relates to a method for preparing an article, comprising the step of extruding, molding or overmolding a composition according to the invention, resulting in an article.

[0140] According to a fourth object, the present invention provides a method for preparing an article, comprising: a) relative to the total mass of the mixture, 5 to 90% by weight of virgin polyamide vPA, 10 to 95% recycled polyamide rPA by mass providing a mixture comprising: The recycled polyamide rPA is in the form of an untransformed powder obtained from additive manufacturing by sintering or from coating methods by powder spraying or electrostatic spraying, b) kneading the mixture in a molten state (melt-kneading step), resulting in a polyamide composition; c) recovering the polyamide composition; d) extruding, molding, or overmolding the recovered composition to result in an article; The present invention relates to a method, comprising:

[0141] According to a fifth object, the invention relates to an article obtainable by the method described above.

[0142] The articles are preferably formed and shaped articles, such as fibers, fabrics, films, sheets, rods, tubes, extruded members, and injected members, comprising the composition as defined above. Thus, the compositions according to the present invention are advantageous for the manufacture of articles, particularly sports articles or components of sports articles, that must exhibit both good impact resistance and good durability, especially when subjected to mechanical, chemical, UV, and thermal stress damage. Among these sports articles, mention may be made of sports footwear, sports equipment, and components of equipment, such as ice skates or other winter sports, and mountaineering equipment, ski bindings, snowshoes, sports bats, boards, horseshoes, flippers, golf balls, and leisure / recreational vehicles, especially those designed for activities in cold climates. In general terms, mention may be made of leisure and DIY / home repair articles, road work tools and equipment that are subject to climatic and mechanical stress damage, and personal protection articles, such as helmet visors, eyewear, and eyewear temples. As non-limiting examples, mention may also be made of car components such as headlight guards, rearview mirrors, small parts for all-terrain / off-road vehicles, fuel tanks, especially for mopeds, bikes and scooters, screws and bolts, pressure gauges and aesthetic protection components for cosmetic articles, lipsticks, gas cylinders, etc., which are subject to damage from mechanical and chemical stresses. Mention should also be made of objects or parts of objects used in the electronics industry, where strict adherence to dimensional specifications is required, such as parts for mobile phones, computers, tablets, etc.

[0143] Advantageously, articles according to the invention generally exhibit less exudation compared to articles prepared from compositions in which recycled polyamide rPA is replaced by virgin polyamide vPA (and therefore compared to compositions that do not contain rPA11 or rPA12). Typically, exudation is determined on 1 mm plates placed at 70°C and 62% RH (relative humidity) for 7 days. Exudation manifests itself as the appearance of deposits on the surface and is estimated visually.

[0144] Without intending to be bound by any particular theory, the increased molar mass of the polyamide chains of the powder waste indicates a lower proportion of oligomers in the latter. However, these oligomers are generally responsible for exudation. Therefore, the articles according to the invention exhibit lower exudation than those obtained from virgin polyamide alone.

[0145] The invention is illustrated by means of the following figures and examples, which are provided on a non-limiting basis. [Brief explanation of the drawings]

[0146] [Figure 1] 1 shows the rheological curves of virgin PA11 (vPA11), virgin PA12 (vPA12), untransformed recycled PA11 powder obtained from additive manufacturing by sintering (rPA11), untransformed recycled PA12 powder obtained from additive manufacturing by sintering (rPA12), a composition obtained by hot kneading 50% by weight of vPA11 with 50% by weight of vPA11 powder, and a composition obtained by hot kneading 50% by weight of vPA12 with 50% by weight of vPA12 powder. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0147] Example 1: Rheology of the composition according to the present invention Rheology of the polyamides in the molten state (polyamide melts) used as starting materials in the mixtures (virgin PA and untransformed recycled PA powder obtained from additive manufacturing by sintering) for two types of homopolymeric PA (PA11 (with an intrinsic viscosity of 1.0, supplied by Arkema) and PA12 (with an intrinsic viscosity of 1.0, supplied by Arkema)). These polyamides, mixed in proportions of 50% by weight of vPA and 50% by weight of rPA relative to the weight of the mixture, were then kneaded in the molten state (melt-kneaded) according to the method according to the invention to form two compositions of polyamide.

[0148] The rheological curve is as illustrated in FIG.

[0149] Capillary rheological analysis shows that at frequencies representative of working by extrusion or injection, the two compositions according to the invention exhibit better melt strength than virgin polyamide vPA, which is an advantage for the process of forming and molding the compositions by extrusion or injection.

[0150] Example 2: Intrinsic viscosity, polydispersity index Ip and Iz of compositions based on vPA11 and rPA11 according to the present invention Virgin vPA11 and untransformed recycled rPA11 powder obtained from additive manufacturing by sintering were mixed in a proportion of 50% by weight of vPA11 and 50% by weight of rPA, relative to the weight of the mixture, and then melt-kneaded according to the method according to the invention to form a polyamide composition.

[0151] It proved impossible to process rPA11 powder by injection molding. Due to the excessively high intrinsic viscosity (wide range of Ip and Iz), the mixture was too viscous for use in injection molding and did not properly fill the mold, resulting in parts with defects and poor surface appearance. In contrast, the composition obtained by kneading could be injected without any problems.

[0152] Table 1 below provides the intrinsic viscosity and polydispersity indices Ip and Iz of the starting materials and compositions according to the invention.

[0153] [Table 1]

[0154] Example 3: Intrinsic viscosity, polydispersity index Ip and Iz of compositions based on vPA12 and rPA12 according to the present invention Virgin vPA12 and untransformed recycled rPA12 powder obtained from additive manufacturing by sintering were mixed in a proportion of 70% by weight vPA12 and 30% by weight rPA12 relative to the weight of the mixture and subsequently melt-kneaded according to the method according to the invention to form a polyamide composition.

[0155] It proved impossible to process rPA12 powder by injection molding. Due to the excessively high intrinsic viscosity (wide range of Ip and Iz), the mixtures were too viscous for use in injection molding and did not properly fill the mold, resulting in parts with defects and poor surface appearance. In contrast, the compositions obtained by kneading could be injected without any problems.

[0156] Table 2 below provides the intrinsic viscosity and polydispersity indices Ip and Iz of the starting materials and compositions according to the invention.

[0157] [Table 2]

[0158] Example 4: Effect of the content of chain limiter in compositions based on vPA11 and rPA11 according to the present invention Adipic acid was used as the chain limiter.

[0159] Virgin vPA11 and untransformed recycled rPA11 powder obtained from additive manufacturing by sintering were 70% by weight of vPA11 and 30% by weight of rPA11, based on the weight of the mixture; or 28.8% by weight of vPA11 and 70% by weight of rPA11 and 1.2% adipic acid, based on the weight of the mixture; or 29.4% by weight of vPA11 and 70% by weight of rPA11 and 0.6% adipic acid, based on the weight of the mixture; or 29.8% by weight of vPA11 and 70% by weight of rPA11 and 0.2% adipic acid, based on the weight of the mixture Mix in any ratio of It was then melt-kneaded according to the method of the present invention to form a polyamide composition.

[0160] The composition obtained by kneading could be injected without any problems.

[0161] Table 3 below provides the intrinsic viscosity and polydispersity indices Ip and Iz of the virgin PA11 used as starting material and of the compositions according to the invention. The properties of rPA11 and vPA11 used as starting materials are presented in Table 1 above.

[0162] [Table 3A] [Table 3B]

[0163] The results show a decrease in the mechanical strength of the polyamide composition for a chain limiter content of 1.2% by weight.

Claims

1. 1. A method for preparing a composition for preparing a polyamide composition, comprising: a) relative to the total mass of the mixture, 5 to 90% by weight of virgin polyamide vPA, 10 to 95% by weight recycled polyamide rPA providing a mixture comprising: the recycled polyamide rPA is in the form of an untransformed powder obtained from additive manufacturing by sintering or from coating methods by powder spraying or electrostatic spraying, or in the form of a powder obtained by grinding the polyamide base component of the object to be recycled, the molecular weight-polydispersity index Ip (Mw / Mn) of the virgin polyamide vPA is lower than the polydispersity index Ip of the recycled polyamide rPA, Mw and Mn being measured by steric exclusion chromatography according to the 2012 standard ISO 16014-1; b) kneading the mixture in a molten state (melt-kneading), resulting in a polyamide composition having a molecular weight-polydispersity index Ip of 1.5 or more; c) recovering the polyamide composition; A method comprising:

2. 2. The method of claim 1, wherein the recycled polyamide rPA and virgin polyamide vPA are homopolyamides.

3. 3. The method according to claim 1 or 2, wherein the average number of carbon atoms (C) to nitrogen atoms (N) of the recycled polyamide rPA and / or virgin polyamide vPA is 8 or more, in particular 10 or more, preferably 11 or more.

4. 4. The method according to claim 1, wherein the recycled polyamide rPA and the virgin polyamide vPA are independently selected from PA11 or PA12.

5. The recycled polyamide rPA and virgin polyamide vPA are identical in nature, preferably The virgin polyamide is vPA11 and the recycled polyamide rPA is rPA11, or 5. The method according to any one of claims 1 to 4, wherein the virgin polyamide is vPA12 and the recycled polyamide rPA is rPA12.

6. 6. The method according to claim 1, wherein the virgin polyamide vPA has an intrinsic viscosity of 1.50 or less, in particular 1.40 or less, preferably 1.30 or less, and / or the powder of the mixture has an intrinsic viscosity of 1.50 or more, in particular 1.60 or more, typically from 1.70 to 5.

00.

7. the molecular weight-polydispersity index Ip (Mw / Mn) of the virgin polyamide vPA is at least 20%, in particular at least 35%, preferably at least 50% lower than the polydispersity index Ip of the recycled polyamide rPA; or the polydispersity index Iz (Mz / Mn) of the virgin polyamide vPA is at least 30%, in particular at least 50%, preferably at least 70% lower than the polydispersity index Iz of the recycled polyamide rPA, Mn and Mz being determined by steric exclusion chromatography in accordance with standard ISO 16014-1 of 2012.

8. 8. The method according to claim 1, wherein the virgin polyamide vPA has a molecular weight-polydispersity index Ip of from 1.6 to 2.2, in particular from 1.6 to 2.1, and / or the recycled polyamide rPA has a molecular weight-polydispersity index Ip of from 2.5 to 15.0, in particular from 2.8 to 10.

0.

9. 9. The method according to claim 1, wherein the proportion by mass of chain limiter in the mixture is 1.0% or less.

10. 10. A polyamide composition obtainable by the method according to any one of claims 1 to 9, wherein the polyamide has a molecular weight-polydispersity index Ip (Mw / Mn) of 1.5 or more, typically higher than 2.0, Mw and Mn being measured by steric exclusion chromatography according to standard ISO 16014-1 of 2012.

11. 11. The polyamide composition according to claim 10, wherein the polyamides of the composition have a z-average polydispersity index Iz(Mz / Mn) higher than the z-average polydispersity index Iz(Mz / Mn) of the virgin polyamides used as starting material in the mixture, and / or the polyamides of the composition have a molecular weight polydispersity index Ip higher than the molecular weight polydispersity index Ip of the virgin polyamides used as starting material in the mixture, wherein Mn and Mz are measured by steric exclusion chromatography in accordance with standard ISO 16014-1 of 2012.

12. 12. Polyamide composition according to claim 10 or 11, wherein the z-average polydispersity index Iz(Mz / Mn) of the polyamides of the composition is 3.0 or more, typically 3.5 or more, in particular 4.0 or more, preferably 5.0 or more, and / or the molecular weight polydispersity index Ip(Mw / Mn) of the polyamides of the composition is higher than 2.0, in particular 2.5 or more, preferably higher than 3.0, even higher than 4.

0.

13. 13. The polyamide composition according to any one of claims 10 to 12, having an intrinsic viscosity of between 0.80 and 1.50, preferably between 0.90 and 1.40, between 0.90 and 1.30, between 0.90 and 1.20, measured using an Ubbelohde tube on a 0.5% by weight solution in m-cresol at 20°C according to standard ISO 307 of 2019.

14. 14. A method for preparing an article, comprising the step of extruding, molding, or overmolding a composition according to any one of claims 10 to 13, resulting in an article.

15. 15. An article obtainable by the method of claim 14.

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