Polyamide used in the manufacture of foam

Abstract

The present invention relates to a particular branched polyamide (also called "branched polyamide") that can be used to manufacture an article, in particular a foamed article. The invention also relates to a foam made from said branched polyamide and methods for its preparation.

Description

Title of the invention: Branched polyamide for the manufacture of a foam Scope of the invention

[0001] The present invention relates to a particular branched polyamide (also called "branched polyamide"), which can be used for the manufacture of an article, in particular a foamed article.

[0002] The invention also relates to a foam made from said branched polyamide and its preparation processes. Technical background

[0003] Polymer foams are used in sports articles such as sports shoe soles, surfboards, in particular with the aim of reducing the weight of the articles to provide comfort to users.

[0004] To obtain a low-density foam with good mechanical properties, it is preferable to have a maximum number of closed cells in the foam's cellular structure. During a foaming process, in the cell enlargement stage, the polymer to be foamed is subjected to significant elongation between cells. Melt strength (strain hardening) is necessary to prevent rupture of the cell walls and thus the formation of open cells. By preventing rupture of the cell walls, the gas used for foam expansion can be retained within the cells, thereby enabling the achievement of low foam densities.

[0005] It is known that one way of obtaining strength in the melt state is by introducing branches into the polymer chains.

[0006] However, the solution proposed today involves branching via a compounding process in which a chain extender is used to react with the amine or carboxylic acid chain ends of polyamides. Reference can be made to EP 3688079. However, when a chain extender is used to branch polyamides, the molten viscosity becomes very high, making it difficult to process. In such cases, the reaction medium must be heated further, which carries a risk of degradation.

[0007] There is a continuing need to offer foams of increasingly lower densities while maintaining satisfactory mechanical properties such as high compressive strength, in order to meet the increasingly high demands of users.

[0008] The present invention therefore aims to provide a particular branched polyamide, enabling the preparation of low density foams and providing a preparation process that is easier to implement, in particular by avoiding the creation of excessively high molar masses during preparation, and thus avoiding difficulties in transforming the molten polymer. Summary of the invention

[0009] According to a first aspect, the invention relates to a branched polyamide, suitable for the preparation of a foam, in which the polyamide comprises branching points provided by a motif from a monomer T comprising x function(s) A and y function(s) B, - A being a carboxylic acid function, - B being an amine function, - x representing the number of functions A, - y representing the number of functions B, - x and y being integers greater than or equal to 0 and x+y >=3,

[0010] the branched polyamide having a weight average molar mass (Mw) greater than or equal to 60,000 g / mol, and the ratio of the weight average molar mass (Mz) to the weight average molar mass (Mw) is greater than 1.80.

[0011] According to one embodiment, the average weight molar mass (Mw) of the branched polyamide is from 60,000 to 300,000 g / mol, preferably from 60,000 to 250,000 g / mol.

[0012] According to one embodiment, the ratio of the average molar mass in z (Mz) to the average molar mass by weight (Mw) of the branched polyamide (“Iz”) is greater than or equal to 1.80, for example greater than or equal to 1.90, preferably greater than or equal to 2.00, for example greater than or equal to 2.10.

[0013] According to one embodiment, the ratio of the average molar mass by weight (Mw) of the polyamide to the average molar mass by number (Mn) of the polyamide (“Ip”) is greater than 2.20, for example greater than or equal to 2.30, preferably greater than or equal to 2.40, for example greater than or equal to 2.50, even more preferably greater than or equal to 2.60, for example greater than or equal to 2.80.

[0014] It has been observed in the context of the present invention that branched polyamide, as defined above, makes it possible to increase the closed cell ratio of a foam prepared from branched polyamide, while ensuring a low density of the foam.

[0015] The polyamide that may be used in the context of the invention may in particular be chosen from a homopolyamide PA 11, PA12, PA 610, PA 612, PA 614, PA 618, PA 910, PA 912, PA 106, PA 1010, PA 1011, PA 1012, PA 1014, PA 1018, and / or PA1036 or a copolyamide of these.

[0016] According to one embodiment, x the number of function A or y the number of function B of monomer T is an integer greater than or equal to 0, preferably x or y is an integer equal to 0.

[0017] For example, the monomer T may comprise 3 A functions and 0 B functions, or 0 A functions and 3 B functions, or 1 A function and 2 B functions, or 2 A functions and 1 B function.

[0018] According to one embodiment, the monomer T is chosen from a polyacid, a polyamine and a compound containing at least one amine function and at least one carboxylic acid function.

[0019] According to one embodiment, the branched polyamide as defined above comprising motifs from a bifunctional co-monomer selected from a diamine or a diacid, which may be selected from a dicarboxylic acid, in particular those having 4 to 36 carbon atoms, or a diamine, preferably an aliphatic, cycloaliphatic or aromatic diamine, in particular those having 2 to 20 carbon atoms.

[0020] According to one embodiment, the branched polyamide has a melt strength coefficient (resistant to "strain hardening") greater than 1.0, preferably greater than 1.3.

[0021] According to one embodiment, the branched polyamide has a melt strength coefficient (resistant to "strain hardening") greater than 2.0, preferably greater than 3.0.

[0022] The present invention also relates to a method for preparing a branched polyamide as defined above, comprising at least one step of mixing the monomer T with monomers of a polyamide and a step of synthesizing the branched polyamide by polycondensation, preferably, the monomer T being mixed in an amount of 0.05 to 3% by mole, preferably 0.2 to 1% by mole, relative to the total number of moles of monomer T and the monomers of the polyamide.

[0023] According to one embodiment, a bifunctional co-monomer, preferably a diamine or a diacid, is mixed together with the monomer T, with the polyamide monomers, preferably, in an amount enabling the polyamide to have a difference in absolute value between its total acidity and its total basicity of less than 0.070 mEq / g.

[0024] According to one aspect, the invention relates to a composition comprising branched polyamide as described above and one or more additive polymers, one or more additives, fillers and / or reinforcing fibers.

[0025] The present invention provides a branched polyamide and a composition containing said branched polyamide having improved foamability and enabling the formation of a foam having a high closed cell ratio, and exhibiting a very low density.

[0026] According to another aspect, the invention relates to an article made of branched polyamide as defined above or made of a composition comprising branched polyamide as defined above.

[0027] The article may advantageously be a foam.

[0028] Thus, the present invention also relates to a foam made of a branched polyamide as defined above or made of a composition comprising a branched polyamide as described above.

[0029] According to one embodiment, the foam has a density less than or equal to 800 kg / m3, preferably less than or equal to 600 kg / m3, more preferably less than or equal to 400 kg / m3, even more preferably less than or equal to 300 kg / m3.

[0030] The article, preferably foam, as described above may be chosen from sports shoe soles, balls or balloons, gloves, surfboards, personal protective equipment, rail soles, automotive parts, construction parts and electrical and electronic equipment parts.

[0031] According to another aspect, the present invention relates to a method for manufacturing a foam as defined above, comprising the following steps: • the mixture of branched polyamide, possibly with one or more additives, and with a blowing agent; and • the foaming of the mixture of branched polyamide, possibly with one or more additives and expanding agent.

[0032] The invention is now described in detail and in a non-limiting manner in the following description. Description of the invention Definition

[0033] In the present description, it is specified that when reference is made to intervals, expressions of the type "between... and..." or "from... to..." include the bounds of the interval.

[0034] Unless otherwise stated, the percentages expressed are mass percentages. Unless otherwise stated, the parameters referred to are measured at atmospheric pressure and ambient temperature (23°C).

[0035] The "average molar mass by weight (Mw)", the "average molar mass by number (Mn)" and the "average molar mass in Z (Mz)" in the present inventions are expressed in PMMA equivalents (used as calibration standard) and are measured by size exclusion chromatography (SEC) according to ISO 16014-1:2012, the copolymer being solubilized in hexafluoroisopropanol stabilized with 0.05 M potassium trifluoroacetate for 24 h at room temperature at a concentration of 1 g / L before being passed on the columns, for example at a flow rate of 1 mL / min, the molar mass being measured by the refractive index.

[0036] Size exclusion chromatography can be carried out using modified silica columns, for example on a set of two columns and a pre-column of modified silica (such as the PGF columns and pre-columns from Polymer Standards Service) comprising a 1000 Å column, with dimensions of 300 x 8 mm and particle size of 7 pm, a 100 Å column, with dimensions of 300 x 8 mm and particle size of 7 pm and a pre-column with dimensions of 50 x 8 mm, for example at a temperature of 40°C.

[0037]

[0038]

[0039]

[0040]

[0041] The "total acidity" of the polyamide in the present invention is measured according to the following method: 1 g of polyamide is dissolved in 80 mL of hot 2-tert-butylphenol. The sample is then cooled. It is then titrated potentiometrically using a Metrohm titrator (888 or 716) with a combined pH electrode, with a 0.02 N tetrabutylammonium hydroxide solution. The potential-volume curve shows a jump at an equivalent volume from which the total acidity is calculated using the following formula: [Math.1] Total acidity (mEq J g) - in which Veq denotes the equivalent volume obtained by potentiometric titration, [TBAOH] denotes the concentration of the tetrabutylammonium hydroxide solution, i.e. 0.02 N, m denotes the mass of the sample, i.e. 1g. The "total basicity" of the polyamide in the present invention is measured according to the following method. 1 g of polyamide is dissolved in 80 mL of hot metacresol. The sample is then cooled. It is then titrated potentiometrically using a Metrohm titrator (888 or 716) with a combined pH electrode, with a 0.02 N perchloric acid solution in acetic acid. The potential-volume curve shows a jump at an equivalent volume from which the total basicity is calculated using the following formula: [Math.2] „ . . , , II \ Veqx[HClO4] Total basicity \tnEq g} =----m----

[0042] in which Veq designates the equivalent volume obtained by potentiometric titration, [HC1O4] designates the concentration of the perchloric acid solution, i.e. 0.02 N, m designates the mass of the sample, i.e. 1g.

[0043] The "melting temperature (Tf)" in the present invention is measured by Differential scanning calorimetry (DSC) according to ISO 11357-3:2018. The melting temperature corresponds to the maximum intensity of the signal of the melting peak in the first heating with a temperature ramp of 20°C / min.

[0044] The "melting end temperature" corresponds to the temperature after the melting peak, where the melting curve measured by DSC and the baseline overlap. The baseline designates the portion of the recorded thermogram without any transitions, specifically here without any first-order transitions such as melting or crystallization. At a transition zone, a virtual baseline can be determined: this is an imaginary line drawn through the transition zone, assuming that the heat due to the transition is zero.

[0045] The "molten strength coefficient", also called the "strain hardening coefficient", is calculated from rheological measurements:

[0046] A first measurement of the viscosity in oscillation as a function of time is carried out at the end-melting temperature on an ARES G2 equipped with parallel plane geometry of 25mm diameter, rotation speed 0.01 s-1, under nitrogen scanning.

[0047] A second measurement of extensional viscosity as a function of time is carried out at the melting end temperature on ARES G2 equipped with the EVF (Extensional Viscosity Fixture) module, rotation speed 1 s 1 under nitrogen scanning on samples of 750pm thickness and 10mm length.

[0048] The coefficient of resistance in the molten state is calculated using the following formula:

[0049] [Math.3] max) Molten strength coefficient = “ose

[0050] where max (p is the maximum value of the elongational viscosity curve as a function of time and f^sc is the value of the oscillating viscosity measured at the same time as the value»w / x . Monomer T

[0051] The monomer T used to create the branch points in the polyamide comprises x function(s) A and y function(s) B, - A being a carboxylic acid function, - B being an amine function, - x representing the number of functions A, - y representing the number of functions B, - x and y being integers greater than or equal to 0 and x+y >=3,

[0052] According to one embodiment, the monomer T is chosen from a compound containing at least one amine function and at least one carboxylic acid function, polyacids, polyamines, for example triacids, triamines.

[0053] For example, the monomer T may be a compound containing an amine function and two carboxylic acid groups, or a compound containing two amine groups and a carboxylic acid function.

[0054] Among the polyacids, we can cite trimesic acids, [2,2':6',2"-Terpyridine]-4,4',4"-tricarboxylic acid, 1,2-Diaminopropane-N,N,N',N'-tetraacetic acid, Biphenyl-3,3',5,5'-tetracarboxylic acid, fatty acid trimers; Among polyamines, melamines, tri(aminoalkyl)amines, tris(2-aminoethyl)amine, polyalkylenetriamine, dialkylenetriamine, diethylenetriamine, polyethertriamine (e.g., marketed as Jeffamine® T403); among compounds containing at least one amine group and at least one carboxylic acid group, α,co-amino acids (e.g., aspartic acid, lysine, glutamic acid) and / or aniline dicarboxylates (e.g., 2-aminoterephthalic acid, 5-aminoisophthalic acid, etc.); branched polyamide

[0055] Typically, the branched polyamide has a weight average molar mass (Mw) greater than or equal to 60,000 g / mol, preferably greater than or equal to 65,000 g / mol, even more preferably greater than or equal to 70,000 g / mol.

[0056] According to one embodiment, the average molar mass by weight (Mw) of the branched polyamide is from 60,000 to 300,000 g / mol.

[0057] The polyamide on which the branching is obtained can be a homopolyamide or a copolyamide or a mixture of these.

[0058] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", in particular on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0059] Homopolyamide in the sense of the invention means the polymerization products of aminocarboxylic acid monomers, lactams or diacids with diamines.

[0060] According to a first type, the polyamides are derived from the condensation of a dicarboxylic acid, in particular those having 4 to 36 carbon atoms, preferably those having 4 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, and an aliphatic, cycloaliphatic or aromatic diamine, in particular those having 2 to 20 carbon atoms, preferably those having 6 to 14 carbon atoms, possibly in the presence of a chain limiter.

[0061] Examples of dicarboxylic acids include 1,4-cyclohexyldicarboxyl acid, butanedioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic, octadecanedicarboxylic acids and terephthalic and isophthalic acids, as well as dimerized fatty acids.

[0062] Examples of diamines include tetramethylenediamine, rhexamethylenediamine, 1,10-decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, isomers of bis-(4-aminocyclohexyl)-methane (BACM), bis-(3-methyl-4-aminocyclohexyl)methane (BMACM), and 2-2-bis-(3-methyl-4-aminocyclohexyl)-propane (BMACP), para-amino-di-cyclo-hexyl-methane (PACM), isophoronediamine (IPDA), 2,6-bis-(aminomethyl)-norbomane (BAMN) and piperazine (Pip).

[0063] Advantageously, polyamides PA 412, PA 414, PA 418, PA 610, PA 612, PA 614, PA 618, PA 910, PA 912, PA 106, PA 1010, PA 1011, PA 1012, PA 1014, PA 1018, and / or PA1036 are used.

[0064] In the notation "PA XY", X represents the number of carbon atoms from diamine, and Y represents the number of carbon atoms from diacid, in a conventional manner.

[0065] According to a second type, polyamides result from the condensation of one or more α,co-aminocarboxylic acids and / or one or more lactams having 6 to 12 carbon atoms, possibly in the presence of a chain limiter.

[0066] Examples of lactams include caprolactam, oenantholactam and lauryllactam.

[0067] Examples of α,co-amino carboxylic acids include aminocaproic, amino-7-heptanoic, amino-10-decanoic, amino-11-undecanoic and amino-12-dodecanoic acids.

[0068] Advantageously, the polyamides of the second type are PA 10 (polydecanamide), PA 11 (polyundecanamide), PA 12 (polydodecanamide) or PA 6 (polycaprolactam).

[0069] In the notation “PA Z”, Z represents the number of carbon atoms derived from amino acid or lactam.

[0070] According to a third type, polyamides result from the condensation of at least one α,co-aminocarboxylic acid (or a lactam), at least one diamine and at least one dicarboxylic acid

[0071] In this case, the polyamide PAs are prepared by polycondensation: • of the linear or cycloaliphatic or aromatic aliphatic diamine(s) having X carbon atoms, X being between 2 and 20; • of the dicarboxylic acid(s) having Y carbon atoms, Y being between 4 and 36; and • of the comonomer(s) {Z}, chosen from lactams and α,co-aminocarboxylic acids having Z carbon atoms, Z being between 6 and 12 and equimolar mixtures of at least one diamine having XI carbon atoms and at least one dicarboxylic acid having Y1 carbon atoms, XI being between 2 and 20, Y1 being between 4 and 36 and (XI, Y1) being different from (X, Y),

[0072] in the possible presence of a chain limiter.

[0073] According to a variant of this third type, the polyamides result from the condensation of at least two α,co-aminocarboxylic acids or at least two lactams having from 6 to 12 carbon atoms or of a lactam and an aminocarboxylic acid not having the same number of carbon atoms in the possible presence of a chain limiter.

[0074] Examples of third-type polyamide blocks include: PA 11 / 12, PA 10 / 11 / 12.

[0075] The notations "PA X / Y, PA HJY / 'L", etc. refer to copolyamides in which X, Y, Z, etc. represent homopolyamide units as described above.

[0076] Typically, a chain limiter comprises at least one, preferably at least two, functional groups, each independently selected from carboxylic acids and amines. The chain limiter may be a monocarboxylic acid, a dicarboxylic acid, a monoamine, or a diamine. It allows reaction with the amine or carboxylic acid functional groups of the polyamide.

[0077] Preferably, the polyamide is an aliphatic polyamide. Composition

[0078] • Additional polymers

[0079] The composition according to one aspect of the invention may include one or more additional polymers, for example, unbranched polyamides, thermoplastic elastomers (for example, TPU, PEBA, COPE), functional polyolefins, ethylene and vinyl acetate copolymers (for example, the products marketed under the Evatane brand by SK functional polymer), or ethylene and acrylate copolymers, or ethylene and alkyl(meth)acrylate copolymers (for example, the products marketed under the Lotryl brand by SK functional polymer).

[0080] These additional polymers can be used to adjust the hardness of the branched polyamide. They can be present in a content of 0 to 30% by weight, preferably 5 to 30% by weight, relative to the total weight of the branched polyamide present in the composition. • Additives, Fillers and Fibers

[0081] The composition according to one aspect of the invention may also include one or more additives, such as one or more flame retardants, one or more flame retardant synergists, one or more metal oxides, a catalyst, one or more antioxidants, one or more thermal stabilizers, one or more UV stabilizers, one or more light stabilizers, one or more lubricants, one or more fillers, one or more plasticizers, one or more nucleating agents, one or more colorants, one or more electrically conductive agents, one or more thermally conductive agents, or a mixture thereof.

[0082] The fillers that may be used include mineral fillers, such as those selected from the group, given by way of non-limiting, including for example calcium carbonate, barium sulfate and / or silicon dioxide, talc, kaolin, boron nitride, magnesia, slags, silica, carbon black, carbon nanotubes, expanded or non-expanded graphite, titanium oxide which may be used as a nucleating agent (in pure form or in concentrated form, (for example, CaCO3, ZnO, SiO2) or combinations thereof).

[0083] The reinforcing fibers are selected from among the fibers, particularly short fibers. The fibers may be of synthetic origin, notably glass or carbon fibers, or natural, typically of plant origin such as flax, reed, bamboo, or hemp fibers. Preferably, the reinforcing fibers are glass fibers.

[0084] The composition may include from 0.05 to 10% by weight of one or more additives relative to the total weight of the composition.

[0085] The composition may comprise from 0.5 to 50% by weight of fillers relative to the total weight of the composition.

[0086] The composition may include from 5 to 75% by weight of reinforcing fibers relative to the total weight of the composition.

[0087] The composition may comprise from 0.1 to 80% by weight of fillers, reinforcing fibers, and additives, cumulatively relative to the total weight of the composition. Process for preparing branched polyamide

[0088] According to one aspect of the invention, the branched polyamide as defined above is prepared according to a process comprising at least one step of mixing the monomer T with the monomers of a polyamide and a step of synthesizing the branched polyamide by polycondensation, preferably, the monomer T being mixed in an amount of 0.05 to 3% by mole, preferably 0.2 to 1% by mole, relative to the total number of moles of polyamide monomer.

[0089] This process can, for example, be carried out in an autoclave reactor.

[0090] According to one embodiment, a bifunctional co-monomer is mixed together with monomer T, preferably with the polyamide monomers, allowing to obtain a polyamide exhibiting an absolute difference between its total acidity and its total basicity of less than 0.070 mEq / g.

[0091] The bifunctional co-monomer can typically be selected from a diamine or a diacid, for example, selected from a dicarboxylic acid, in particular those having 4 to 36 carbon atoms, preferably those having 4 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, or an aliphatic, cycloaliphatic or aromatic diamine, preferably an aliphatic or cycloaliphatic diamine, in particular those having 2 to 20 carbon atoms, preferably those having 6 to 14 carbon atoms.

[0092] Examples of dicarboxylic acids include 1,4-cyclohexyldicarboxyl acid, butanedioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic, octadecanedicarboxylic acids and terephthalic and isophthalic acids, as well as dimerized fatty acids.

[0093] Examples of diamines include tetramethylenediamine, rhexamethylenediamine, 1,10-decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, isomers of bis-(4-aminocyclohexyl)-methane (BACM), bis-(3-methyl-4-aminocyclohexyl)methane (BMACM), and 2-2-bis-(3-methyl-4-aminocyclohexyl)-propane (BMACP), para-amino-di-cyclo-hexyl-methane (PACM), isophoronediamine (IPDA), 2,6-bis-(aminomethyl)-norbomane (BAMN) and piperazine (Pip).

[0094] According to another aspect, a branched polyamide according to the invention can be prepared according to a preparation process comprising a step of mixing a polyamide, a monomer T, and optionally a co-monomer, in the molten state and a step of extruding the mixture in the molten state.

[0095] The conditions applied to the mixing step are to be chosen to allow intimate mixing of the compounds in the molten state.

[0096] According to one embodiment, the process can be carried out by reactive extrusion, typically in an extruder.

[0097] To prepare a composition as described above, one or more additional polymers and / or one or more additives may be added during the aforementioned processes.

[0098] Any device for mixing, kneading or extruding plastics in the molten state known to those skilled in the art may be used. Foaming process and foam

[0099] The foam of the present invention can be prepared by a manufacturing process comprising: • the supply of a mixture comprising branched polyamide as defined above, possibly with one or more additives, and with a blowing agent; and • foaming of the mixture, possibly with one or more additives and expanding agent.

[0100] The blowing agent may be a chemical or physical agent, or a mixture of both. Preferably, it is a physical agent, such as, for example, nitrogen or carbon dioxide, or water, or a hydrocarbon, chlorofluorocarbon, hydrochlorocarbon, hydrofluorocarbon, or hydrochlorofluorocarbon (saturated or unsaturated). For example, butane or pentane may be used.

[0101] The foam thus formed consists essentially, or even consists, of the composition described above and optionally one or more additives dispersed in the matrix.

[0102] One or more of the additives may be the compounds described above.

[0103] In the case where a chemical blowing agent is used, the foam may including, in addition to the composition described above, the decomposition products of the chemical expanding agent, these being dispersed in the matrix.

[0104] Foaming technologies may be those known to the person skilled in the art, for example, batch foaming, injection foaming, extrusion foaming, autoclave foaming and microwave foaming.

[0105] The step of supplying the mixture occurs either in the solid state or in the molten state.

[0106] Advantageously, the process according to the invention comprises an injection step The mixture is placed in a mold, and a foaming step is performed on the mixture. Foaming is produced either during the injection of a volume of polymer smaller than the mold's capacity into the mold, or by opening the mold. These two techniques, individually or in combination, allow for the direct production of three-dimensional foamed objects with complex geometries.

[0107] Other injection foaming techniques that can be used within the framework of the present invention include injection foaming with a breathing mold, with application of a counter pressure of gas, under dosing, or with a mold equipped with a Variotherm® system.

[0108] According to one embodiment, the foaming process according to the invention comprises a step of supplying the mixture in a molten state, and a step of extruding said mixture, inducing the foaming of said mixture directly at the outlet of the extrusion die.

[0109] According to yet another embodiment, the foaming process comprises a step of impregnating an object of a composition as described above with a gas, typically an inert gas, at a pressure above the pressure Atmospheric pressure is used to force the introduction of gas into the object, followed by a pressure reduction step that allows the gas to dissipate and produce foam. In this case, the object can typically be a particle, a part injected, or extruded from the composition.

[0110] According to yet another embodiment, the foaming process comprises a step of impregnating an object made from a composition such as described above with a gas, typically an inert gas, at a pressure above atmospheric pressure to force the gas into the object, and a step of reducing the pressure to recover the unfoamed object. The object is then heated to produce the foam. In this case, the object can typically be a particle, a part injected, or extruded from the composition.

[0111] The foam according to the invention preferably has a density less than or equal to 800 kg / m3, more preferably less than or equal to 600 kg / m3.

[0112] The foam according to the invention can be used to manufacture sports equipment, such as surfboards, such as soles of sports shoes, ski boots, midsoles, insoles, or functional components of soles, in the form of inserts in different parts of the sole (heel or arch for example), or components of shoe uppers in the form of reinforcements or inserts in the structure of the shoe upper, in the form of protections.

[0113] It can also be used to manufacture balls, sports gloves (for example football gloves), golf ball components, rackets, protective elements (vests, internal elements of helmets, shells...).

[0114] The foam according to the invention exhibits interesting shock-absorbing, vibration-damping, and noise-dampening properties, combined with haptic properties suitable for capital goods. It can therefore also be used for the manufacture of railway track pads, insulation materials, or various parts in the automotive, transportation, electrical and electronic equipment, construction, or manufacturing industries.

[0115] According to one embodiment, the foams according to the invention can be recycled, for example by melting them in an extruder equipped with a degassing outlet (optionally after cutting them into pieces). Examples

[0116] The examples below illustrate the present invention without limiting its scope. In the examples, unless otherwise indicated, all percentages and parts are expressed by weight.

[0117] Example 1: Preparation of polyamides

[0118] The polyamide, denoted Cl, is PA 11. This polyamide is prepared according to the following process. After loading 40 g of 11-aminoundecanoic acid and 2 g of water, the autoclave reactor is placed under an inert atmosphere. The reaction medium is then heated to 270°C while maintaining stirring. The reaction medium is maintained at 270°C under autogenous pressure for 1hOO. Then, the pressure is reduced to atmospheric pressure while maintaining the temperature at 250°C. The reactor is then subjected to nitrogen purging until the measured stirring torque reaches a predefined value. Indeed, the viscosity of the medium is monitored by measuring the stirring torque. The material is then extruded in the form of granules.

[0119] The polyamide designated C2 is a PA 11 / TMA. This polyamide is prepared according to the following process. After loading 40 g of 11-aminoundecanoic acid, 0.251 g of trimesic acid (TMA), and 2 g of water, the autoclave reactor is placed under an inert atmosphere. The reaction medium is then heated to 270°C while maintaining stirring. The reaction medium is maintained at 270°C under autogenous pressure for 1hOO. Then, the pressure is reduced to atmospheric pressure while maintaining the temperature at 250°C. The reactor is then subjected to nitrogen purging until the measured stirring torque reaches a predefined value. Indeed, the viscosity of the medium is monitored by measuring the stirring torque. The material is then extruded into granules.

[0120] The polyamide designated C3 is a PA 11 / 10TMA. This polyamide is prepared according to the following process. After loading 40 g of 11-aminoundecanoic acid, 0.026 g of 1,10-decanediamine, 0.021 g of trimesic acid (TMA), and 2 g of water, the autoclave reactor is placed under an inert atmosphere. The reaction medium is then heated to 270°C while maintaining stirring. The reaction medium is maintained at 270°C under autogenous pressure for 1hOO. Then, the pressure is reduced to atmospheric pressure while maintaining the temperature at 250°C. The reactor is then subjected to nitrogen purging until the measured stirring torque reaches a predefined value. Indeed, the viscosity of the medium is monitored by measuring the stirring torque. The material is then extruded into granules.

[0121] The polyamide denoted Al is a PA 11 / 10TMA. This polyamide is prepared according to the following process. After loading 40 g of 11-aminooundecanoic acid, 0.103 g of 1,10-decanediamine, 0.084 g of trimesic acid (TMA), and 2 g of water, the autoclave reactor is placed under an inert atmosphere. The reaction medium is then heated to 270°C while maintaining stirring. The reaction medium is maintained at 270°C under autogenous pressure for 1hOO. Then, the pressure is reduced to atmospheric pressure while maintaining the temperature at 250°C. The The reactor is then subjected to nitrogen purging until the measured stirring torque reaches a predefined value. The viscosity of the medium is monitored by measuring the stirring torque. The material is then extruded into granules.

[0122] The polyamide designated A2 is a PA 11 / 10TMA. This polyamide is prepared according to the following process. After loading 40 g of 11-aminoundecanoic acid, 0.308 g of 1,10-decanediamine, 0.251 g of trimesic acid (TMA), and 2 g of water, the autoclave reactor is placed under an inert atmosphere. The reaction medium is then heated to 270°C while maintaining stirring. The reaction medium is maintained at 270°C under autogenous pressure for 1hOO. Then, the pressure is reduced to atmospheric pressure while maintaining the temperature at 250°C. The reactor is then subjected to nitrogen purging until the measured stirring torque reaches a predefined value. Indeed, the viscosity of the medium is monitored by measuring the stirring torque. The material is then extruded into granules.

[0123] The polyamide designated A3 is PA 11 / T40310. This polyamide is prepared according to the following process. After loading 40 g of 11-aminoundecanoic acid, 0.121 g of sebacic acid, 0.175 g of Jeffamine T403 (T403), and 2 g of water, the autoclave reactor is placed under an inert atmosphere. The reaction medium is then heated to 250°C while maintaining stirring. The reaction medium is maintained at 250°C under autogenous pressure for 1hOO. Then, the pressure is reduced to atmospheric pressure while maintaining the temperature at 250°C. The reactor is then subjected to nitrogen purging until the measured stirring torque reaches a predefined value. Indeed, the viscosity of the medium is monitored by measuring the stirring torque. The material is then extruded into granules.

[0124] The polyamide designated A4 is PA 11 / T40310. This polyamide is prepared according to the following process. After loading 40 g of 11-aminoundecanoic acid, 0.482 g of sebacic acid, 0.699 g of Jeffamine T403 (T403), and 2 g of water, the autoclave reactor is placed under an inert atmosphere. The reaction medium is then heated to 250°C while maintaining stirring. The reaction medium is maintained at 250°C under autogenous pressure for 1hOO. Then, the pressure is reduced to atmospheric pressure while maintaining the temperature at 250°C. The reactor is then subjected to nitrogen purging until the measured stirring torque reaches a predefined value. Indeed, the viscosity of the medium is monitored by measuring the stirring torque. The material is then extruded into granules.

[0125] [Table 1]: Natures and proportions of monomers for the preparation of polyamides Polyamide Nature Molar % of A 11 Molar % Monomer T Molar % Co-monomer Cl 11 100 0 0 C2 11 / TMA 99.40 0.60 0 C3 11 / 10TMA 99.88 0.05 0.07 Al 11 / 10TMA 99.50 0.20 0.30 A2 11 / 10TMA 98.50 0.60 0.90 A3 11 / T40310 99.50 0.20 0.30 A4 11 / T40310 98.00 0.80 1.20

[0126] [Table 2]: Total basicity and acidity values Polyamide Total Basicity (mEq / g) Total Acidity (mEq / g) Difference in absolute value u (mEq / g) Cl 0.043 0.054 0.011 C2 0.019 0.094 0.075 C3 0.06 0.061 0.001 Al 0.055 0.058 0.003 A2 0.064 0.069 0.005 A3 0.046 0.054 0.008 A4 0.063 0.069 0.006

[0127] [Table 3]: SEC values ​​and molten strength coefficient (strain hardening coefficient). The molten strength coefficients (strain hardening coefficients) were measured at 215°C, corresponding to the final melting temperature of polyamides (Tf = 190°C). Polyamide Mn (g / mol) Mw (g / mol) Mz (g / mol) Mw / Mn (Ip) Mz / Mw (Iz) Molten strength coefficient (strain hardening coefficient) Cl 33200 74200 126500 2.23 1.70 1.0 C2 38900 74000 113800 1.90 1.54 1.0 C3 27000 61300 105000 2.27 1.71 1.0 Al 33700 84200 158400 2.50 1.88 1.7 A2 31000 91900 197100 2.96 2.14 3.6 A3 35300 86900 161300 2.46 1.86 1.4 A4 31100 100400 240300 3.23 2.39 4.6

[0128] Examples A1 to A4 illustrate branched polyamides according to the invention.

[0129] For examples A1 and A2, the trimesic acid is a triacid, for examples A3 and A4, the Jeffamine T403 used is a polyethertriamine.

[0130] Al to A4 branched polyamides exhibiting improved rheological properties with melt strength coefficients (strain hardening coefficients) greater than 1.0 compared to Cl, C2 and C3 polyamides. Al to A4 polyamides will allow the production of foams with lower density and containing more closed cells.

Claims

Demands

1. Branched polyamide, suitable for the preparation of a foam, in which the polyamide comprises branching points made by a motif from a monomer T comprising x function(s) A and y function(s) B, - A being a carboxylic acid function, - B being an amine function, - x representing the number of functions A, - y representing the number of functions B, - x and y being integers greater than or equal to 0 and x +y >=3, the branched polyamide having a weight average molar mass (Mw) greater than or equal to 60,000 g / mol, and the ratio of the z-average molar mass (Mz) to the weight average molar mass (Mw) is greater than 1.

80.

2. Branched polyamide according to claim 1, wherein the weight average molar mass (Mw) of the branched polyamide is from 60,000 to 300,000 g / mol, preferably from 60,000 to 250,000 g / mol.

3. Branched polyamide according to claim 1 or 2, wherein the ratio of the average molar mass in z (Mz) to the average molar mass by weight (Mw) of the branched polyamide (“Iz”) is greater than or equal to 1.80, for example greater than or equal to 1.90, preferably greater than or equal to 2.00, for example greater than or equal to 2.

10.

4. Branched polyamide according to any one of claims 1 to 3, wherein the ratio of the weight average molar mass (Mw) of the polyamide to the number average molar mass (Mn) of the polyamide (“Ip”) is greater than 2.20, for example greater than or equal to 2.30, preferably greater than or equal to 2.40, for example greater than or equal to 2.50, even more preferably greater than or equal to 2.60, for example greater than or equal to 2.

80.

5. Branched polyamide according to any one of claims 1 to 4, wherein the polyamide is selected from a homopolyamide PA 11, 12, PA 610, PA 612, PA 614, PA 618, PA 910, PA 912, PA 106, PA 1010, PA 1011 PA 1012, PA 1014, PA 1018, and / or PA1036 or a copolyamide of these.

6. Branched polyamide according to any one of claims 1 to 5, wherein x the number of function A or y the number of function B of monomer T is an integer equal to 0.

7. Branched polyamide according to any one of claims 1 to 6, wherein monomer T is selected from a polyacid, a polyamine and a compound containing at least one amine function and at least one carboxylic acid function, preferably selected from trimesic acid, [2,2':6',2"-Terpyridine]-4,4',4"-tricar boxyl acid, 1,2-Diaminopropane-N,N,N',N'-tetraacetic acid, Biphenyl-3,3',5,5'-tetracarboxylic acid, from polyamines, melamines, tri(aminoalkyl)amines, tris(2-aminoethyl)amine, polyalkylenetriamine, dialkylenetriamine, diethylenetriamine, polyethertriamine, α,co-amino acids and / or aniline dicarboxylate.

8. Branched polyamide according to any one of claims 1 to 7, comprising motifs from a bifunctional co-monomer selected from a diamine or a diacid, which may be selected from a dicarboxylic acid, in particular those having from 4 to 36 carbon atoms, or an aliphatic or cycloaliphatic diamine, in particular those having from 2 to 20 carbon atoms.

9. Branched polyamide according to any one of claims 1 to 8, having a difference in absolute value between its total acidity and its total basicity of less than 0.070 mEq / g.

10. Branched polyamide according to any one of claims 1 to 9, having a melt strength coefficient (strain hardening coefficient) greater than 1.0, preferably greater than 1.

3.

11. A process for preparing a branched polyamide according to any one of claims 1 to 10, comprising at least one step of mixing monomer T with monomers of a polyamide and a step of synthesizing the branched polyamide by polycondensation, preferably monomer T being mixed in an amount of 0.05 to 3 mol%, preferably 0.2 to 1 mol%, relative to the total number of moles of monomer T and polyamide monomers.

12. A method according to claim 11, wherein a bifunctional co-monomer is mixed together with monomer T, to the polyamide monomers.

13. A method according to claim 12, wherein the bifunctional co-monomer is selected from a diamine or a diacid, which be chosen from a dicarboxylic acid, in particular those having 4 to 36 carbon atoms, or an aliphatic, cycloaliphatic or aromatic diamine, in particular those having 2 to 20 carbon atoms.

14. Composition comprising a branched polyamide according to any one of claims 1 to 10, and one or more additive polymers, one or more additives, fillers, and / or reinforcing fibers.

15. Article consisting of a branched polyamide according to any one of claims 1 to 10 or of a composition according to claim 1 A

16. 1H-. Article according to claim 15 being a foam, preferably having a density less than or equal to 800 kg / m3, preferably less than or equal to 600 kg / m3.

17. Article according to any one of claims 15 or 16, being selected from sports shoe soles, balls or balloons, gloves, personal protective equipment, rail soles, automotive parts, construction parts and electrical and electronic equipment parts.

18. A method for manufacturing a foam according to claim 16, comprising the following steps: • supplying a mixture comprising branched polyamide, optionally with one or more additives, and with a blowing agent; and • foaming the mixture, optionally with one or more additives and blowing agent.