USE OF A POLYAMIDE CHAIN ​​EXTENDER COMPOUND

Abstract

 

Description

[0001] The invention relates to a polyamide that is stabilized against heat, light and atmospheric effects using a polyamide chain extender compound as an agent to stabilize the polyamide against heat, light and atmospheric effects. The present invention also relates to a polyamide composition comprising at least one polyamide chain extender compound and optionally reinforcing agents and optionally impact modifiers.

[0002] Polyamide is a synthetic polymer widely used for the manufacture of various articles, such as injection-molded and / or formed parts. Polyamide can undergo degradation when subjected to external elements or conditions such as UV rays, heat, and / or atmospheric effects. Degradation can also be induced by the heat used during its production and / or formation. This instability is reflected by degradation, loss of mechanical properties, and changes in color. These problems can become critical for a number of applications, such as, in particular, parts in the motor vehicle industry that are subjected to considerable heat.

[0003] In order to improve the heat stability of polyamides, it is known to combine them with particular stabilizers. Many additives are sold for this purpose. The use of copper iodide, in particular, in combination with potassium iodide, which is used in most cases and provides good stabilizing properties, is, for example, known. It is also known in practice to use more complex additives, such as hindered phenolic antioxidant compounds, stabilizers having at least one hindered amine unit of a HALS type, or stabilizers containing phosphorus.

[0004] However, there is a need to obtain polyamide compositions that are even more efficient in terms of heat stabilization, and that are less expensive.

[0005] The Applicant has developed a new polyamide composition that makes it possible to obtain excellent maintenance of mechanical properties after long exposure to heat, light and / or atmospheric effects, using an extender compound. 2 / 18 polyamide chain as an agent to stabilize the polyamide against heat, light and / or atmospheric effects. The resulting composition has particularly good compromise of mechanical and rheological properties.

[0006] The present invention relates to the use of a polyamide chain extender compound as an agent to stabilize polyamide against heat, light and / or atmospheric effects. The invention also relates to a composition comprising at least polyamide and the polyamide chain extender compound.

[0007] The expression “agent for stabilizing polyamide against heat, light and atmospheric effects” means a compound that is especially capable of maintaining a good level of mechanical properties for a polyamide composition subjected to heat, light and / or atmospheric effects for an extended period.

[0008] The composition according to the invention preferably has a tensile rupture strength retention of more than or equal to 50% measured according to ISO 527 / 1A standard on 4 mm thick specimens after an air aging test at 210°C for 1000 hours, compared with the same composition before the aging test.

[0009] The composition according to the invention most preferably has a tensile rupture stress retention of more than or equal to 50%, measured according to the ISO 527 / 1A standard on 4 mm thick specimens after an air aging test at 220°C for 1000 hours, compared with the same composition before the aging test.

[0010] Even more preferably, the composition according to the invention has a tensile rupture strength retention of more than or equal to 50%, measured according to ISO 527 / 1A standard on 4 mm thick specimens after an air aging test at 230°C for 1000 hours, compared with the same composition before the aging test.

[0011] The composition according to the invention may also have a tensile rupture stress retention of more than or equal to 50%, measured according to ISO 527 / 1A standard on 4 mm thick specimens after a test of 3 / 18 aging in air at 240°C for 1000 hours, compared to the same composition before the aging test.

[0012] Polyamide chain extender compounds (chain extenders) for the polyamide chain are usually capable of reacting with the amine or acid termination groups of the polyamide. The chain extenders contain at least two functional groups that are capable of reacting with the termination groups of the polyamide so as to connect two or more polyamide chains as a function of the functionality of the chain extender and the number of reactive termination groups of the polyamide and thus increase the molar mass and viscosity of the modified polyamide. The use of bis-lactams in particular is mentioned in US patent 2682526.

[0013] Chain extenders according to the invention that may be specifically mentioned include compounds selected from the group consisting of diols, such as ethylene glycol, propanediol, butanediol, hexanediol or hydroquinone bis(hydroxyethyl) ether, bis-epoxides, such as bisphenol A diglycidyl ether, polymers having epoxide functions, polymers having anhydride functions, bis-N-acyl bis-caprolactams, such as isophthaloyl bis-caprolactam (IBC), adipoyl biscaprolactam (ABC) or terphthaloyl bis-caprolactam (TBC), diphenyl carbonates, bisoxazolines, oxazolinones, diisocyanates, organic phosphites, such as triphenyl phosphite or caprolactam phosphite, bis-ketenimines and dianhydrides.

[0014] According to a first variant, the composition comprises a chain extender. According to a second variant, the composition comprises at least two chain extenders, and in particular comprises two. The composition may, according to the first and second variants, comprise at least one, and in particular one, additive that participates in the heat stabilization of the composition, as defined further in the description.

[0015] More specifically, the composition comprises a pair of chain extenders chosen from the following pairs,

[0016] - bis-epoxides, such as bisphenol A diglycidyl ether, and organic phosphites, such as triphenyl phosphite or caprolactam phosphite, and 4 / 18

[0017] - polymers having epoxide and organic phosphite functions, such as triphenyl phosphite or caprolactam phosphite

[0018] The composition preferably comprises from 0.01% to 5% by weight of polyamide chain extenders, relative to the total weight of the composition. More preferably, the composition comprises from 0.1% to 3% by weight of polyamide chain extenders, relative to the total weight of the composition. In particular, use may be made of 0.01% to 10% by weight of polyamide chain extenders, relative to the weight of the polyamide.

[0019] In the case where the composition:

[0020] - comprises at least one reinforcing agent, an impact modifier and / or other additive that participates in thermal stabilization and / or

[0021] - comprises at least two chain extenders,

[0022] the composition comprises a content of polyamide chain extender(s) of more than 1% by weight or up to 2% by weight relative to the weight of the polyamide. In addition, this content may vary from 1.1% to 8% by weight, especially from 1.3% to 6% by weight or even from 1.5% to 4% by weight relative to the weight of the polyamide.

[0023] In the case where the composition:

[0024] - is free of reinforcing agents, impact modifiers and / or other additives that participate in thermal stabilization and

[0025] - includes only one chain extender,

[0026] the composition comprises a content of polyamide chain extender(s) of more than 2% by weight relative to the weight of the polyamide. Furthermore, this content varies from 2.05% to 8% by weight, especially from 2.1% to 6% by weight or even from 2.1% to 4% by weight relative to the weight of the polyamide.

[0027] Preferred chain extender compounds are insensitive to the moisture content of the polyamide under polyamidation reaction conditions and do not generate secondary products.

[0028] The resulting composition may comprise in particular polyamide chains comprising covalently linked residues of extender compound. 5 / 18 chain, unlinked polyamide chains with a chain extender compound residue and free chain extender compounds diluted in the polyamide matrix.

[0029] The polyamide of the invention is specially selected from the group comprising polyamides obtained by polycondensation of at least one aliphatic dicarboxylic acid with an arylaliphatic or cycloaliphatic or cyclic diamine, for example, PA 6.6, PA 6.10, PA 6.12, PA 10.10, PA 10.6, PA 12.12, PA 4.6, MXD6, PA92, PA102, or between at least one aromatic dicarboxylic acid and an aromatic or aliphatic diamine, for example polyephthalamides of the type such as PA 9T, PA 10T, PA 11T, PA 12T, PA 13T or PA 6T / MT, PA 6T / 6I, PA 6T / 66, PA 66 / 6T, polyisophthalamide of the type such as PA 6I, PA 6I / 6T, Polynaphthalamides of the type such as PA 10N, PA 11N, PA 12N, polyaramids such as Kevlar, or a mixture thereof and (co)polyamides thereof.The polyamide of the invention can also be chosen from polyamides obtained by the polycondensation of at least one amino acid or lactam with itself, making it possible for the amino acid to generate, by hydrolytic opening of a lactam ring, such as, for example, PA6, PA7, PA11, PA12 or PA13, or a mixture thereof and (co)polyamides thereof. Types of copolyamide that may be especially mentioned include polyamide 6 / 66, polyamide 6 / 11, polyamide 6 / 12 and polyamide 11 / 12.

[0030] Diamines and diacids can generate heteroatoms. Mention may be made of 5-hydroxyisophthalic acid, 5-sulfoisophthalic acid or salts thereof, for example lithium, sodium or zinc salts.

[0031] Aliphatic or semi-aromatic semicrystalline polyamides are especially preferred.

[0032] Polyamide is preferably chosen from the group comprising: polyamide 6, polyamide 610, polyamide 66 and polyamide 66 / 6T.

[0033] In general, polyamide is a semicrystalline polyamide with an apparent melt viscosity of between 0.5 and 1500 Pa.s, measured according to ISO 11443 standard at a shear rate of 1000 s-1 at a temperature equal to 20°C above the melting point of polyamide, and preferably between 0.5 and 1000 Pa.s. 6 / 18

[0034] Use can especially be made of polyamides of varying molecular weights by adding, before or during the polymerization of the polyamide monomers, or even in the melt extrusion, monomers that modify the chain length such as, in particular, difunctional and / or monofunctional compounds having amine or carboxylic acid functions that are capable of reacting with the polyamide monomers or the polyamide.

[0035] The term “carboxylic acid” means carboxylic acids and derivatives thereof, for example, acid anhydrides, acid chlorides and esters. The term “amine” means amines and derivatives thereof capable of forming an amide bond.

[0036] It is possible to use, at the beginning, during or at the end of polymerization, any type of aliphatic or aromatic monocarboxylic or dicarboxylic acid or any type of aliphatic or aromatic monoamine or diamine amine.

[0037] Use may be made very particularly of a polyamide obtained from at least adipic acid and hexamethylenediamine or their salts, such as hexamethylenediamine adipate, which may optionally comprise various proportions of other polyamide monomers.

[0038] Polyamides according to the invention can also be obtained by mixing, in particular by melt mixing. It is possible, for example, to mix one polyamide with another polyamide, or a polyamide with a polyamide oligomer, or even a polyamide with monomers that modify the chain length, such as, in particular, diamines, dicarboxylic acids, monoamines and / or monocarboxylic acids. It is possible, in particular, to add isophthalic acid, terephthalic acid or benzoic acid to the polyamide, for example, at levels of approximately 0.2% to 2% by weight.

[0039] The composition of the invention may also comprise copolyamide derivatives, in particular of the above polyamides, or mixtures of these polyamides or (co)polyamides.

[0040] Use may also be made of branched polyamides with high melt flow, in particular obtained by mixing, during polymerization, in the presence of polyamide monomers, at least one multifunctional compound comprising 7 / 18 at least 3 identical reactive functions of the amine function or carboxylic acid function type.

[0041] Use may also be made, as a high melt flow polyamide, of a main polyamide comprising major macromolecular chains and, if appropriate, linear macromolecular chains. Polymers comprising such major macromolecular chains are described, for example, in documents WO 97 / 24388 and WO 99 / 64496.

[0042] These main polyamides are in particular obtained by mixing, during polymerization, in the presence of polyamide monomers, an amino acid or lactam, such as caprolactam, at least one multifunctional compound comprising at least 3 identical reactive functions of the amine or carboxylic acid type. The term “carboxylic acid” means carboxylic acids and derivatives thereof, for example, acid anhydrides, acid chlorides and esters. The term “amine” means amines and derivatives thereof capable of forming an amide bond.

[0043] The present invention relates to a process for manufacturing a composition in which at least one polyamide and a polyamide chain extender compound are mixed together. Said compound can be added to already formed or partially formed polyamide, especially by contacting polyamide oligomers. The polyamide chain extender compound can especially be added during the polymerization of the polyamide or as a mixture with the molten polyamide, for example, by extrusion. The chain extender compound can also be added without heating with the polyamide, followed by melting of the polyamide.

[0044] Polyamide compositions are generally obtained by mixing the various compounds, agents and / or additives, especially the chain extender compound included in the composition, without heating or melting. The process is carried out at a more or less high temperature and with a more or less high shear force, according to the nature of the various compounds. The compounds can be introduced simultaneously or successively. Use is generally made 8 / 18 of an extrusion device in which the material is heated, then melted and subjected to a shear force, and transported. According to particular embodiments, a premix, in the melt or non-melt form, of the chain extender compound can be prepared before preparing the final composition. It is possible, for example, to prepare a premix of the chain extender compound in a resin, for example, polyamide, in order to make a master batch.

[0045] The composition according to the invention may comprise one or more other polymers, preferably polyamides or copolyamides.

[0046] The composition according to the invention may comprise more than 20% by weight, preferably more than 40% by weight and most preferably more than 50% by weight of polyamide according to the invention, relative to the total weight of the composition.

[0047] The composition may also comprise at least one reinforcing or growth agent. Reinforcing or growth agents are agents conventionally used for the production of polyamide compositions. Mention may in particular be made of fibrous reinforcing agents, such as glass fibers, carbon fibers or organic fibers, non-fibrous agents, such as particulate or lamellar and / or exfoliating agents or non-exfoliating nanoagents, for example alumina, carbon black, clays, zirconium phosphate, kaolin, calcium carbonate, copper, diatomaceous earth, graphite, mica, silica, titanium dioxide, zeolites, talc, wollastonite, polymeric agents such as, for example, dimethacrylate particles, glass beads or glass powder.

[0048] Preferably, reinforcing agents, such as glass fibers, are used in particular. Preferably, the most widely used fiber is glass fiber, of the “chopped” type, having a diameter between 7 and 14 µm and a length of less than 5 mm. These agents may have a surface size that ensures mechanical adhesion between the fibers and the polyamide matrix.

[0049] The composition according to the invention may comprise between 1% and 60% by weight of reinforcing or growth agents and preferably between 10% and 40% by weight, with respect to the total weight of the composition. 9 / 18

[0050] The composition according to the invention comprising the polyamide as defined above may comprise at least one impact modifier, that is to say a compound capable of modifying the impact strength of a polyamide composition. These impact modifiers preferably comprise functional groups that react with the polyamide.

[0051] According to the invention, the term “functional groups that react with polyamide” means groups capable of reacting or chemically interacting with the acid or amine functions of the polyamide, in particular by covalent, ionic or hydrogen bonding or by Van der Waals bonding. Such reactive groups make it possible to ensure good dispersion of the impact modifiers in the polymer matrix. Good dispersion is generally obtained with impact modifier particles having an average size of between 0.1 and 2 µm in the matrix.

[0052] Use is preferably made of impact modifiers comprising functional groups that react with the polyamide as an acidic or amine function of the equation AEG=CEG-AEG (concentration of the acidic terminal groups CEG minus the concentration of the amine terminal groups AEG) of the polyamide. Thus, for example, if AEG is “acidic” (CEG>AEG), use will preferably be made of reactive functional groups capable of reacting or chemically interacting with the acidic functions of the polyamide, in particular by covalent, ionic or hydrogen bonding interaction or by Van der Waals bonding. If, for example, AEG is “amine” (AEG>CEG), use will preferably be made of reactive functional groups capable of reacting or chemically interacting with the amine functions of the polyamide, in particular by covalent, ionic or hydrogen bonding interaction or by Van der Waals bonding.The preferred method of use is impact modifiers with functional groups that react with the polyamide, exhibiting an AEG (anti-aging effect) of an "amine" nature.

[0053] Impact modifiers may very well comprise within themselves functional groups that react with polyamide, for example, as consider ethylene / acrylic acid (EAA) products.

[0054] Use can be made, according to the invention, of the modifiers of 10 / 18 impact compounds are oligomeric or polymeric compounds comprising at least one of the following monomers or a mixture thereof: ethylene, propylene, butene, isoprene, diene, acrylate, butadiene, styrene, octene, acrylonitrile, acrylic acid, methacrylic acid, vinyl acetate, vinyl esters, such as acrylic and methacrylic esters, and glycidyl methacrylate. These compounds according to the invention may also comprise, in addition, monomers other than those mentioned above.

[0055] The impact modifier base, optionally known as the elastomer base, may be selected from the group consisting of: polyethylenes, polypropylenes, polybutenes, polyisoprenes, ethylene / polypropylene rubbers (EPR), ethylene / polypropylene / diene rubbers (EPDM), ethylene butene rubbers, ethylene acrylate rubbers, butadiene styrene rubbers, butadiene acrylate rubbers, ethylene octene rubbers, acrylonitrile butadiene rubbers, ethylene / acrylic acid products (EAA), ethylene / vinyl acetate products (EVA), ethylene / acrylic ester products (EAE), acrylonitrile / butadiene / styrene copolymers (ABS), styrene / ethylene / butadiene / styrene block copolymers (SEBS), styrene / butadiene / styrene copolymers (SBS), core / shell elastomers of the methacrylate / butadiene / styrene (MBS) type, or mixtures of at least two elastomers listed above.

[0056] In addition to the groups listed above, these impact modifiers may also comprise, generally grafted or copolymerized, functional groups that react with the polyamide, such as, in particular, the following functional groups: acids, such as carboxylic acids, salified acids, esters in particular, acrylates and methacrylates, ionomers, glycidyl groups, in particular epoxy groups, glycidyl esters, anhydrides, in particular maleic anhydrides, oxazolines, maleimides or mixtures thereof.

[0057] Such functional groups in the elastomer are, for example, obtained by using a comonomer during the preparation of the elastomer.

[0058] Mention should be made in particular, as impact modifiers 11 / 18 comprising functional groups that react with polyamide, of ethylene, acrylic ester and glycidyl methacrylate terpolymers, ethylene and butyl acrylate ester copolymers, ethylene, n-butyl acrylate and glycidyl methacrylate copolymers, ethylene and maleic anhydride copolymers, ethylene / propylene / diene copolymers grafted with maleic anhydride, styrene / maleimide copolymers grafted with maleic anhydride, styrene / ethylene / butylene / styrene copolymers modified with maleic anhydride, styrene / acetronitrile copolymers grafted with maleic anhydrides, acrylonitrile / butadiene / styrene copolymers grafted with maleic anhydrides, and hydrogenated versions thereof.

[0059] The weight proportion of impact modifiers in the total composition is especially between 1% and 25% and preferably between 5% and 20% in relation to the total weight of the composition.

[0060] The composition according to the invention may also comprise other additives participating in the thermal stabilization of the composition, such as those selected from the group comprising: the Cu and Kl pair, the CuO / KBr pair, the Cu2O / KBr pair, hindered phenolic compounds, stabilizers comprising at least one hindered amine unit of the HALS type, stabilizers based on mineral or organic phosphorus, such as sodium or magnesium hypophosphite, or alternative compounds comprising at least one polyhydric alcohol comprising from 2 to 8 aliphatic hydroxyl groups, in particular the composition also comprises at least one polyhydric alcohol comprising from 2 to 8 aliphatic hydroxyl groups.

[0061] Polyhydric alcohols that may be mentioned in this way include those mentioned in the group comprising: diols, such as 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, triethylene glycol, poly(glycol ether)s, triols, for example glycerol, trimethylolpropane, 2,3-bis(2'-hydroxyethyl)cyclohexan-1-ol, hexane-1,2,6-triol, 1,1,1-tris(hydroxymethyl)ethane, 3-(2'-hydroxyethoxy)propane-1,2-diol, 3-(2'-hydroxypropoxy)propane-1,2-diol, 2-(2'-hydroxyethoxy)hexane-1,2-diol, 6-(2'-hydroxypropoxy)hexane-1,2-diol, 1,1,1-tris[(2'-hydroxyethoxy)methyl]ethane, 1,1,1 -tris[(2'hydroxypropoxy)methyl]propane, 1,1,1 -tris(4'-hydroxyphenyl)ethane, 1,1,1 12 / 18 tris(hydroxyphenyl)propane, 1,1,3-tris(dihydroxy-3-methylphenyl)propane, 1,1,4-tris(dihydroxyphenyl)butane, 1,1,5-tris(hydroxyphenyl)-3-methylpentane, di(trimethylolpropane), trimethylolpropane ethoxylate, or trimethylolpropane propoxylate; polyols, such as pentaerythritol, dipentaerythritol, and tripentaerythritol; and saccharides such as clodextrin, D-mannose, glucose, galactose, sucrose, fructose, xylose, arabinose, D-mannitol, D-sorbitol, D- or L-arabitol, xylitol, iditol, talitol, allitol, altritol, gulitol, erythritol, threitol, and D-gulonic-Y-lactone; and similar compounds, and in particular the polyhydric alcohol is chosen from polyols such as pentaerythritol, dipentaerythritol and tripentaerythritol.

[0062] The content of other additives participating in the thermal stabilization of the composition may vary from 0.01% to 5% by weight in relation to the total weight of the composition.

[0063] The composition according to the invention may also comprise additives normally used in the production of polyamide compositions. Thus, mention may be made of lubricants, flame retardants, plasticizers, nucleating agents, anti-UV agents, catalysts, antioxidants, antistatic agents, colorants, mattifying agents, mold aids or other conventional additives.

[0064] These agents and additives can be added to the modified polyamide by the usual means suitable for each agent or additive, for example during polymerization or by melt mixing.

[0065] Polyamide compositions are generally obtained by mixing the various compounds participating in the composition without heating or melting. The process is carried out at more or less the same temperature and shear force, depending on the nature of the various compounds. The compounds can be introduced simultaneously or successively. An extrusion device is generally used in which the material is heated, then melted and subjected to shear force, and transported.

[0066] It is possible to mix all compounds in the melting phase during a single operation, for example, during an extrusion operation. It is possible, for example, to mix grains of polymer materials, to introduce them into the extrusion device in order to melt them and subject them to shearing more or 13 / 18 less high. According to specific modalities, it is possible to premix some of the compounds, in the melt or not in the melt, before the preparation of the final composition.

[0067] Polyamide compositions comprising at least one polyamide chain extender compound and 1% to 60% by weight of reinforcing or growth agents, and 1% to 25% by weight of impact modifier, relative to the total weight of the composition, are especially preferred.

[0068] More specifically, the polyamide composition may comprise from 0.01% to 5% by weight of polyamide chain extender compound, from 5% to 20% by weight of reinforcing or growth agents, and from 5% to 20% by weight of impact modifier, relative to the total weight of the composition.

[0069] According to one modality, the composition comprises, or even consists of:

[0070] - polyamide, in particular PA6, PA66, PA610 and / or PA66 / 6T, especially in a content ranging from 30% to 80% by weight relative to the total weight of the composition;

[0071] - chain extender, in particular comprising a bis-epoxide, optionally in combination with an organic phosphite, in particular the content of the chain extender is greater than 1% by weight relative to the weight of polyamide;

[0072] - optionally reinforcing agents, in particular glass fibers, especially in a content ranging from 10% to 40% by weight relative to the total weight of the composition,

[0073] - optionally an impact modifier, in particular comprising functional groups that are reactive with polyamide, especially in a content ranging from 5% to 20% by weight relative to the total weight of the composition,

[0074] - optionally another additive participating in the thermal stabilization of the composition, in particular a polyhydric alcohol or a Cu / KI, CuO / KBr or Cu2O / KBr pair, especially in a content ranging from 0.01% to 5% by weight relative to the total weight of the composition, and 14 / 18

[0075] - optionally at least one additive chosen from lubricants, flame retardants, plasticizers, nucleating agents, anti-UV agents, catalysts, colorants, matting agents and mold release agents, especially in a content ranging from 0.01% to 8% by weight relative to the total weight of the composition.

[0076] The composition according to the invention, when prepared using an extrusion device, is preferably conditioned in the form of granules. The granules are intended to be formed using processes involving fusion in order to obtain articles. The articles are then constituted of the composition. According to a typical embodiment, the modified polyamide is extruded in the form of rods, for example, in a twin-screw extrusion device, which are then cut into granules. The molded parts are subsequently prepared by melting the granules produced above and feeding the molten composition into the forming devices, particularly injection molding devices.

[0077] The composition according to the invention can be used by any process to form plastics, for example, the molding process, in particular injection molding, extrusion, extrusion blow molding or rotary molding. The extrusion process can especially be a rotary process or a process for manufacturing films.

[0078] The present invention also relates to the manufacture of impregnated woven articles or composite articles containing continuous fibers. These articles can especially be manufactured by contacting a fabric and the polyamide composition according to the invention in the solid or molten state. Fabrics are textile surfaces obtained by assembling yarns or fibers that are made integral by any process, especially those such as adhesive bonding, felting, braiding, weaving or knitting. These fabrics are also referred to as fibrous or filamentous networks, for example, based on fiberglass, carbon fiber or the like. Their structure can be random, unidirectional (1D), or multidirectional (2D, 2.5D, 3D or others).

[0079] The present invention also relates to articles obtained by forming the 15 / 18 composition according to the invention, for example, by extrusion, molding or injection molding. Mention should be made, as articles, of those used in the motor vehicle industry or in the electronics and electrical industry, for example.

[0080] The present invention also relates to articles made of applications exposed to high temperatures, especially temperatures greater than or equal to 80°C, more particularly temperatures greater than or equal to 150°C and more specifically temperatures greater than or equal to 210°C, obtained by forming a composition according to the invention.

[0081] The expression “articles made for applications exposed to high temperatures, especially temperatures of more than or equal to 80°C” generally means articles manufactured to contain or transport fluids, e.g. liquids or gases, brought to high temperatures, for example, articles of the cooling circuit of a motor vehicle that are intended to maintain the engine at an optimum and virtually constant temperature of about 100°C. These articles according to the present invention are thus defined by their applications that expose them to high temperatures; this involving their design, manufacture and intended uses based on their technical constraint in a usual mode of operation.

[0082] Examples of items subject to high temperatures include items in the water / glycol cooling circuit, such as the radiator tank, transfer pipe, thermostatic tank, degassing tank, radiator; items in the air circuit, such as the turbo pipe, air / air exchanger (intercooler), turbo cooler air inlet or outlet box, exhaust gas recirculation circuit, air intake manifold and associated piping, catalytic converter, engine ventilation group parts, intercoolers; and items in the oil circuit, such as the cylinder head cover, oil pan, oil filtration unit, distribution sump, and oil transport assembly piping. These items are well known in the field of motor-driven vehicles, such as motor vehicles. 16 / 18

[0083] Specific terms are used in the description to facilitate understanding of the principles of the invention. However, it should be understood that no limitation of the scope of the invention is foreseen by the use of specific terms. The term “and / or” includes the meanings and, or and all other possible combinations of the elements connected to this term.

[0084] Other details or advantages of the invention will become more clearly apparent in light of the examples below, given only by indication. EXPERIMENTAL PART

[0085] Before extrusion, 66-grain polyamide with a VI of 153 ml / g (viscosity index in solution of polyamide in formic acid (VI in mL / g) according to ISO 307 standard) is dried to a water content of less than 1000 ppm. Formulations are prepared by melt mixing various components and additives in a Werner & Pfleiderer ZSK 40 twin-helix co-rotating extruder operating at 40 kg / h and a speed of 230-250 rpm. The temperature settings in the 8 zones are respectively: 245, 245, 245, 250, 255, 260, 260, 265QC. All components in the formulation are added at the start of the extruder. The rod exiting the extruder is cooled in a water tank and cut into granules using a granulator. The granules are then packaged in a heat-sealed bag. Before injection molding, the granules are dried to achieve a moisture content of less than 1000 ppm.

[0086] The additives used are as follows:

[0087] - 1.5% by weight of chain extender compound: Araldite® GT7071 (Huntsman)

[0088] - 15% by weight of impact modifier: Exxelor VA1801 (ethylene copolymer grafted with maleic anhydride)

[0089] - 0.2% by weight of Cui and Kl from Ajay Europe

[0090] - 15% by weight of Owens Corning Vetrotex OCV 983 fiberglass

[0091] Percentages by weight are expressed as a weight relative to the total weight of the composition.

[0092] The prepared formulations are injected into a Demag 50T press. 17 / 18 280-300QC with a mold temperature of 80QC, in the form of a 4mm thick multifunctional specimen, to characterize the tensile and mechanical properties (average obtained from the five samples (according to ISO 527 / 1A standard) before and after thermal aging in air.

[0093] Air-ventilated thermal aging is performed by placing specimens in a Heraeus TK62120 furnace set to the chosen temperature. At different aging times, specimens are removed from the furnace, cooled to room temperature, and placed in heat-sealed bags to prevent them from receiving moisture before their mechanical properties are evaluated.

[0094] The retention of tensile strength or impact strength at a given aging time is then defined with respect to those same properties before aging. Retention is then defined as a percentage.

[0095] The properties of the polyamide composition are compared in tables 1 and 2 below: Table 1 Properties Before aging After aging 1000h 150QC After aging 700h 210QC After aging 1000h 210QC Flexural Modulus (MPa) 4820 4910 5230 5300 Maximum bending stress (MPa) 157.5 153.9 116.2 105.5 Bending deformation (%) 4.6 3.81 2.4 2.19 18 / 18 Table 2 Tensile Properties: Modulus (MPa) Tensile Strength: Rupture Stress (MPa) Tensile Strength: Strain (%) Before aging 4773 92.5 (100%) 3.56 After aging 2000h 150QC 5110 82.5 (89%) 1.9 After aging 1000h 190QC 4708 67.5 (73%) 1.55 After aging 1000h 210QC 5998 67 (72%) 1.44 After aging 2000h 220QC 5360 59.3 (64%) 1.21 After aging 1000h 230QC 4707 61 (65%) 1.39 After aging 1000h 240QC 4784 63.6 (68%) 1.45

[0096] It was then observed that the addition of the compound according to the invention to polyamide notably allows retention of mechanical properties in both tension and tensile conditions, where standard compositions would have shown a dramatic loss in these properties.

[0097] The composition according to the invention then shows tensile breaking strength retention of more than or equal to 50% measured according to ISO 527 / 1A standard in 4mm thick specimens after an air aging test at 210QC for 1000 hours, compared with the same composition before the aging test.

Claims

1. Use of a polyamide chain extender compound as an agent to stabilize polyamide against heat, light and / or inclement weather, characterized in that the composition comprising at least polyamide and the polyamide chain extender compound has a tensile breaking strength retention greater than or equal to 50%, measured according to ISO 527 / 1A standard on 4 mm thick specimens after an aging test in air at 210°C for 1000 hours, compared with the same composition before the aging test, wherein the articles made from the composition comprising at least polyamide and the polyamide chain extender compound are articles made for applications exposed to high temperatures, especially temperatures greater than or equal to 80°C, wherein the polyamide is polyamide 66, wherein the polyamide chain extender compound is bisphenol A diglycidyl ether.

2. Use, according to claim 1, characterized in that the composition comprising at least polyamide and the polyamide chain extender compound comprises from 0.01% to 5% by weight of the polyamide chain extender compound relative to the total weight of the composition.

3. Use, according to any one of claims 1 to 2, characterized in that the composition comprising at least polyamide and the polyamide extender compound comprises at least one reinforcing or growth agent.

4. Use, according to any one of claims 1 to 3, characterized in that the composition comprising at least polyamide and the polyamide chain extender compound comprising at least one impact modifier.

5. Use, according to any of claims 1 to 4, characterized in that the composition comprising at least the polyamide and the polyamide chain extender compound comprises at least one other additive participating in the thermal stabilization of the composition.

6. Use according to claim 5, characterized in that the articles are those manufactured to contain or transport fluids.