Polyamide composition containing recycled carbon fibers and use of said polyamide composition

Abstract

The present invention relates to a molding composition comprising, by weight: a) 50% to 99% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 1 to 50% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0%-5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

Description

[Technical field]

[0001] The present invention relates to polyamide compositions containing recycled carbon fibers and uses thereof. [Background technology]

[0002] For sports-related applications, carbon fiber reinforced polyamides, especially polyamide 11 (PA11), are well known for their stiffness, lightness and high mechanical performance qualities.

[0003] Carbon fiber has been around for many years, and the reason this type of fiber has become so essential is simple: the material produced is extremely strong, durable and very light, properties that are highly valued by sporting goods manufacturers who want lightness, stiffness and long life.

[0004] Today, product durability is essential to consumers and has become a key requirement for major sports brands.

[0005] Carbon fibre reinforced compositions have a large impact on CO2 emissions, especially since carbon fibre production is energy intensive and carbon fibre consists of almost 100% carbon (C).

[0006] There is therefore a need to have available compositions reinforced with carbon fibres, whilst retaining high mechanical properties in terms of modulus, stress, elongation and impact strength, but with a much smaller impact on CO2 emissions.

[0007] One solution is to use recycled carbon fiber.

[0008] Therefore, International Publication No. 2015 / 074945 (WO 2015 / 074945) describes a molding material having the following composition, which is (a) at least one plastic substrate (A) forming a base material, 49% to 97%; (b) 3% to 40% of at least one carbon fiber covered with at least one plastic substrate (B); (c) at least one other additive (C) in an amount of 0% to 48% The total of the components (a) to (c) is 100% by weight, The surface resistance of the plastic molding material is 1×10 7 ~1×10 22 Ω and volume resistivity is 1×10 5 ~1×10 20 Ω·m (both determined in accordance with IEC 60093).

[0009] The carbon fibres may be recycled or cellulosic, the plastic (B) is selected from the group consisting of polyamides, in particular copolyamides, polyesters, in particular copolyesters, polyurethanes, epoxy resins, polyhydroxyethers, acrylic copolymers and blends or superimposed layers of two or more of these plastics, the plastic (A) of component (a) being selected from the group consisting of acetal resins, liquid crystal polymers, polyacrylates, polymethacrylates, olefin-based and cycloolefin-based polymers, polyamides, polyamide elastomers, in particular polyesteramides, polyetheramides and polyetheresteramides, polyamide-imides, polyethers, polyarylethers (polyethers), ... thermoplastics selected from the group consisting of polyvinyl ethers (including polyphenyl ethers), polyhydroxy ethers, polycarbonates, polysulfones, polyetherimides, polyimides, polyesters, polyester polycarbonates, polyoxyethylene, polystyrene, copolymers of styrene, polysulfones, vinyl polymers such as polyvinyl chloride and polyvinyl acetate, and blends of two or more of the thermoplastics mentioned, or thermosetting resins selected from the group consisting of melamine resins, phenoplasts, polyester resins, aminoplasts, epoxy resins, polyurethanes, crosslinked polyacrylates, and blends of two of the thermosetting resins mentioned.

[0010] However, these compositions suffer from the drawback of having an elongation at break of less than 3% and being brittle.

[0011] Some of the recycled materials may have been adversely affected by their history and experience, and therefore their performance qualities, especially the mechanical qualities, may be lower compared to virgin materials and do not meet the requirements of compositions based on high performance quality polymers (e.g. PA11).

[0012] There is therefore a need to have available compositions reinforced with recycled carbon fibres that do not have the above mentioned drawbacks in terms of their impact on CO2 emissions and loss of mechanical properties.

[0013] The present invention thus relates to a molding composition comprising, by weight: a) 50% to 99% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 1 to 50% recycled carbon fibers having an average length of 6 mm or less before compounding, which are surface-coated with polyamide, particularly aliphatic polyamide; c) 0% to 5% additives; wherein the sum of components a), b) and c) is 100%.

[0014] The inventors have thus surprisingly found that by selecting a polyamide exhibiting an appropriate intrinsic viscosity and by selecting recycled carbon fibers sized with the polyamide, it is possible to improve the mechanical properties of the polyamide preparation and also the CO2 emissions compared to polyamide preparations reinforced with virgin carbon fibers.

[0015] The molding compositions are produced in principle by melt blending the various components in an extruder, in particular a twin-screw extruder. The compounded material leaves the extruder in the form of a rod, which is then cooled and chopped into granules.

[0016] The term "pre-compounding" therefore means that the recycled carbon fibres (those introduced into the extruder during processing) exhibit an average length of 6 mm or less.

[0017] Semicrystalline aliphatic polyamide (a) The nomenclature used to define polyamides is described in ISO standard 1874-1:2011 "Plastics - Polyamide (PA) molding and extrusion materials - Part 1: Designation", in particular page 3 (tables 1 and 2) thereof, and is well known to the skilled person. Semicrystalline polyamides in the sense of the present invention are polyamides that exhibit a glass transition temperature (Tg) and a melting point (Tm), determined according to ISO standards 11357-2 and 3:2013, respectively, and a crystallization enthalpy of more than 30 J / g, preferably more than 35 J / g, measured by DSC during a cooling step at a rate of 20 K / min, according to ISO standard 11357-3 (2013).

[0018] The polyamide may be a homopolyamide, or a copolyamide, or a blend thereof.

[0019] The semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, particularly 1.00 or less, particularly 0.95 or less, and especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20° C. and a concentration of 0.5% by weight), is present in the composition in an amount of 50% to 99%, preferably 60.0% to 90.0%, more preferably 60.0% to 80.0%, and even more preferably 65.0% to 80.0%, each based on the total of the components of the composition.

[0020] The average number of carbon atoms to nitrogen atoms is 6 or more.

[0021] Advantageously, the semi-crystalline aliphatic polyamide is other than PA6 and PA66.

[0022] Advantageously, the average number of carbon atoms to nitrogen atoms is 8 or more, in particular 9 or more, especially 10 or more.

[0023] Advantageously, the average number of carbon atoms to nitrogen atoms is greater than or equal to 8 and the semicrystalline aliphatic polyamide is other than PA612.

[0024] In the case of homopolyamides of the PA-XY type, the number of carbon atoms per nitrogen atom is the average of the X and Y units.

[0025] In the case of copolyamides, the number of carbon atoms per nitrogen atom is calculated according to the same principle, the calculation being carried out on a molar pro rata basis from the various amide units.

[0026] First embodiment: In a first alternative form of this first embodiment, the semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one amino carboxylic acid having from 6 to 18 carbon atoms, preferably from 9 to 18 carbon atoms, more preferably from 10 to 18 carbon atoms, even more preferably from 10 to 12 carbon atoms, said amino carboxylic acid may thus be selected from 6-aminohexanoic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, 13-aminotridecanoic acid, 14-aminotetradecanoic acid, 15-aminopentadecanoic acid, 16-aminohexadecanoic acid, 17-aminoheptadecanoic acid, 18-aminooctadecanoic acid.

[0027] Preferably, the semi-crystalline aliphatic polyamide results from the polycondensation of one amino carboxylic acid.

[0028] In a second alternative form of this first embodiment, the semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one lactam having from 6 to 18 carbon atoms, preferably from 9 to 18 carbon atoms, more preferably from 10 to 18 carbon atoms, more preferably from 10 to 12 carbon atoms.

[0029] Preferably, the semi-crystalline aliphatic polyamide results from the polycondensation of one lactam.

[0030] In a third alternative form of this first embodiment, the semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one aliphatic diamine having from 4 to 36 carbon atoms, advantageously from 6 to 18 carbon atoms, advantageously from 6 to 12 carbon atoms, advantageously from 10 to 12 carbon atoms, with at least one aliphatic dicarboxylic acid having from 4 to 36 carbon atoms, advantageously from 6 to 18 carbon atoms, advantageously from 6 to 18 carbon atoms, advantageously from 6 to 12 carbon atoms, advantageously from 10 to 12 carbon atoms.

[0031] The aliphatic diamine used to obtain the repeat unit XY is an aliphatic diamine exhibiting a linear backbone having at least 4 carbon atoms.

[0032] The linear backbone may, where appropriate, carry one or more methyl and / or ethyl substituents, in which case the term "branched aliphatic diamine" is used. If the backbone does not carry any substituents, the aliphatic diamine is called a "linear aliphatic diamine".

[0033] The aliphatic diamine used to obtain this repeat unit XY, whether or not it has methyl and / or ethyl substituents in the main chain, has from 4 to 36 carbon atoms, advantageously from 4 to 18 carbon atoms, advantageously from 6 to 18 carbon atoms, advantageously from 6 to 14 carbon atoms.

[0034] When the diamine is a linear aliphatic diamine, it has the formula H2N-(CH2) xIt corresponds to -NH2 and may be selected, for example, from butanediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, hexadecanediamine, octadecanediamine, and octadecenediamine. All the linear aliphatic diamines just mentioned may be biobased within the meaning of ASTM standard D6866.

[0035] When the diamine is a branched aliphatic diamine, it may in particular be 2-methylpentanediamine, 2-methyl-1,8-octanediamine, or (2,2,4- or 2,4,4-)trimethylhexanediamine.

[0036] The dicarboxylic acid may be selected from linear or branched aliphatic dicarboxylic acids. When the dicarboxylic acid is aliphatic and linear, it may be selected from succinic acid (4), pentanedioic acid (5), adipic acid (6), heptanedioic acid (7), octanedioic acid (8), azelaic acid (9), sebacic acid (10), undecanedioic acid (11), dodecanedioic acid (12), brassylic acid (13), tetradecanedioic acid (14), hexadecanedioic acid (16), octadecanedioic acid (18), octadecenedioic acid (18), eicosanedioic acid (20), docosanedioic acid (22) and fatty acid dimers with 36 carbon atoms.

[0037] The fatty acid dimers are dimerized fatty acids obtained by oligomerization or polymerization of unsaturated monobasic fatty acids with long hydrocarbon chains, such as linoleic acid and oleic acid, as described in particular in EP 0 471 566.

[0038] In a fourth alternative form of this first embodiment, the semi-crystalline aliphatic polyamide is obtained from a mixture of these three alternative forms.

[0039] Second embodiment: In a first alternative form of this second embodiment, the semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one amino carboxylic acid having from 6 to 18 carbon atoms, preferably from 8 to 12 carbon atoms, more preferably from 10 to 12 carbon atoms.

[0040] Preferably, the semi-crystalline aliphatic polyamide results from the polycondensation of one amino carboxylic acid.

[0041] In a second alternative form of this second embodiment, the semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one lactam having from 6 to 18 carbon atoms, preferably from 8 to 12 carbon atoms, more preferably from 10 to 12 carbon atoms.

[0042] Preferably, the semi-crystalline aliphatic polyamide results from the polycondensation of one lactam.

[0043] In a third embodiment, the semicrystalline polyamide is selected from PA610, PA612, PA1010, PA1012, PA1212, PA11 and PA12, in particular from PA1010, PA1012, PA1212, PA11, PA12.

[0044] Advantageously, the semicrystalline polyamide is chosen from PA11 and PA12, in particular PA11.

[0045] In one embodiment, the semicrystalline polyamide of the composition consists of at least 30% by weight, in particular at least 50% by weight, of recycled semicrystalline polyamide.

[0046] About Carbon Fiber The recycled carbon fibers in the semi-crystalline aliphatic polyamide molding composition according to the invention are preferably present in an amount of 1.0% to 50.0% by weight, preferably 10.0% to 40.0% by weight, more preferably 20.0% to 40.0% by weight, more preferably 25.0% to 40.0% by weight, each based on the sum of the components of the composition.

[0047] The recycled carbon fibers used in the semi-crystalline aliphatic polyamide molding compositions can be provided in the form of chopped (or short) fibers, or in the form of bundles of chopped (or short) fibers, or in the form of crushed carbon fibers.

[0048] Before compounding, the carbon fibres are preferably chopped (or short) fibres with an average length of 0.1 to 6 mm, in particular 2 to 6 mm.

[0049] Before being compounded, the pulverized carbon fibers have an average length of 50 μm to 400 μm.

[0050] After compounding, in the composition to be molded, the comminuted carbon fibers have an average length of less than 400 μm.

[0051] After compounding, in the composition to be molded, the carbon fibers have an average length of 100 to 600 μm, particularly 150 to 500 μm.

[0052] The recycled carbon fibres used are surface coated (sized) which must be compatible with the plastic matrix to ensure good coating, good adhesion and the best possible reinforcing effect.

[0053] The polyamide size of the recycled carbon fibers can be a semi-aromatic polyamide, or an aliphatic polyamide, or a blend thereof.

[0054] Advantageously, the polyamide is an aliphatic polyamide.

[0055] Advantageously, the aliphatic polyamide is a semicrystalline polyamide, in particular one having an average number of carbon atoms per nitrogen atom (C / N) of 10 or less, in particular 9 or less, more particularly 8 or less, and especially 6 or less.

[0056] In one embodiment, the semi-crystalline aliphatic polyamide is selected from PA6, PA66, and blends thereof.

[0057] Examples of aliphatic polyamides, particularly semi-crystalline aliphatic polyamides, are given above.

[0058] Advantageously, the recycled carbon fibres are sized with said polyamide, in particular said aliphatic polyamide, in a range of 0.5% to 6%, in particular 1% to 5%, in particular 1.5% to 4% by weight, based on the sum of the carbon fibres and the sizing agent.

[0059] In one embodiment, the carbon footprint of the recycled carbon fibers is at least half that of virgin carbon fibers, particularly as determined according to Life Cycle Assessment (LCA) methods for determining environmental impact according to international standards ISO 14040:2006, ISO 14044:2006 and / or ISO 14067:2018.

[0060] Additive (c) Additives are optional and are present in an amount of 0% to 5.0%, particularly 0.1% to 5.0%, by weight.

[0061] The additives are selected from fillers, glass beads, dyes, stabilizers, plasticizers, surfactants, nucleating agents, pigments, gloss agents, antioxidants, lubricants, flame retardants, natural waxes, and mixtures thereof.

[0062] Fillers quite explicitly exclude carbon fibers, recycled or non-recycled.

[0063] Advantageously, the additives are selected from fillers, dyes, stabilizers, plasticizers, surfactants, nucleating agents, pigments, gloss agents, antioxidants, flame retardants, natural waxes, and mixtures thereof.

[0064] Advantageously, the additives are selected from dyes, stabilizers, nucleating agents, pigments, gloss agents, antioxidants, natural waxes, and mixtures thereof.

[0065] For example, the stabilizer may be a UV stabilizer, an organic stabilizer, or more generally a combination of organic stabilizers, such as phenolic antioxidants (e.g., of the type Irganox 245 or 1098 or 1010 from Ciba-BASF), phosphite antioxidants (e.g., Irgafos® 126 from Ciba-BASF), and, optionally, other stabilizers, such as HALS (hindered amine light stabilizers (e.g., Tinuvin 770 from Ciba-BASF), UV absorbers (e.g., Tinuvin 312 from Ciba), phosphorus stabilizers. Amine antioxidants, such as Naugard 445 from Crompton, or multifunctional stabilizers, such as Nylostab S-EED from Clariant, may also be used.

[0066] The stabilizer may also be an inorganic stabilizer, such as a copper-based stabilizer. Examples of such inorganic stabilizers include copper halides and copper acetate. Other metals, such as silver, may also be optionally considered, but are known to be less effective. These copper-based compounds are usually combined with halides of alkali metals, especially potassium.

[0067] For example, the plasticizer is selected from benzenesulfonamide derivatives, such as n-butylbenzenesulfonamide (BBSA); ethyltoluenesulfonamide, or N-cyclohexyltoluenesulfonamide; esters of hydroxybenzoic acid, such as 2-ethylhexylparahydroxybenzoic acid and 2-decylhexylparahydroxybenzoic acid; esters or ethers of tetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfuryl alcohol; and esters of citric acid or hydroxymalonic acid, such as oligoethyleneoxymalonate.

[0068] It would not depart from the scope of the invention to use a mixture of plasticizers.

[0069] For example, the fillers may be chosen from silica, graphite, expanded graphite, carbon black, kaolin, magnesia, slag, talc, wollastonite, nanofillers (carbon nanotubes), pigments, metal oxides (titanium oxide), metals, advantageously wollastonite and talc, preferably talc.

[0070] About the composition The molding composition is as defined above and in a first embodiment comprises, by weight: a) 50% to 99% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 1 to 50% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0%-5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

[0071] Advantageously, the molding composition comprises, by weight: a) 50% to 98.9% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, particularly 1.00 or less, particularly 0.95 or less, and especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 1 to 50% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0.1% to 5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

[0072] According to a first alternative form, the molding composition comprises, by weight: a) 60% to 90% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 10 to 40% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0%-5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

[0073] Advantageously, the molding composition comprises, by weight: a) 60% to 89.9% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 10 to 40% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0.1% to 5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

[0074] According to a second alternative form, the molding composition comprises, by weight: a) 60% to 80% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 20 to 40% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0%-5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

[0075] Advantageously, the molding composition comprises, by weight: a) 60% to 79.9% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 20 to 40% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0.1% to 5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

[0076] According to a third alternative form, the molding composition comprises, by weight: a) 60% to 75% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, in particular 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 25 to 40% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0%-5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

[0077] Advantageously, the molding composition comprises, by weight: a) 60% to 74.9% of a semi-crystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, especially 0.9 or less, determined according to ISO standard 307:2007 (but using m-cresol instead of sulfuric acid, at a temperature of 20°C and a concentration of 0.5% by weight), b) 25 to 40% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0.1% to 5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

[0078] In a second embodiment, the composition according to the invention consists of the various elements a, b and c, the sum of which is 100% by weight, as defined in the first embodiment and in three alternative forms, the specific embodiments of which are as defined above.

[0079] In any embodiment of the above compositions, the composition is characterized in that its mechanical properties are at least equivalent to those of the same composition, except that, prior to the compounding step, instead of the recycled carbon fibers, the virgin carbon fibers have an average length of 6 mm or less, and the virgin carbon fibers are surface coated (sized) with the same polyamide or a polymer other than a polyamide.

[0080] In particular, when measured at 23°C with a Charpy impact of 1 eU on an unnotched bar, the resilience of the composition according to the invention is more than 10% greater than the resilience obtained with virgin carbon fibres sized with polyamide or with recycled carbon fibres (but sized with a polymer other than polyamide).

[0081] Advantageously, the elongation at break of the composition according to the invention is more than 10% greater than the elongation at break obtained with virgin carbon fibres sized with polyamide or with recycled carbon fibres, but sized with a polymer other than polyamide.

[0082] In one embodiment, the resilience of the composition according to the invention, measured with a Charpy impact of 1 eU on an unnotched bar at 23° C., is more than 10% greater than the elongation at break obtained with virgin carbon fibers sized with polyamide or with recycled carbon fibers (but sized with a polymer other than polyamide).

[0083] In another embodiment, the resilience and elongation at break of the compositions according to the invention, when measured with a Charpy impact of 1 eU on an unnotched bar at 23° C., are more than 10% greater than the elongation at break obtained with virgin carbon fibers sized with polyamide or with recycled carbon fibers (but sized with a polymer other than polyamide).

[0084] According to another aspect, the invention relates to the use of a composition as defined above for manufacturing an article obtainable by injection moulding, said article being selected from sports equipment, in particular sports shoes, in particular ski boots or parts of ski boots, or hard boots with spikes, such as football, rugby or American football boots, hockey boots or parts of hockey boots, or running shoes, golf balls or parts of golf balls, or lacrosse sticks, hockey equipment, such as helmets, as well as sports equipment for protecting the head, shoulders, elbows, hands, knees, back or shins, such as helmets, gloves, shoulder pads, elbow pads, knee pads or shin pads.

[0085] According to yet another aspect, the present invention relates to the use of a composition as defined above for manufacturing articles for the electronics industry, for the automotive industry, for communication applications or for data exchange, such as for autonomous vehicles or for interconnected applications.

[0086] According to another aspect, the invention relates to an article obtained by injection molding of the composition defined above. EXAMPLES

[0087] The present invention will now be illustrated by the following examples, without however being limited thereto.

[0088] Preparation and mechanical properties of the compositions according to the invention: The compositions in Table I were prepared by melt blending the polymer granules with the carbon fibers and additives. The blending was carried out by compounding in a co-rotating twin screw extruder with a diameter of 26 mm, with a flat temperature profile (T°) of 240° C. The screw speed was 200 rpm and the throughput was 16 kg / h.

[0089] The carbon fibers are introduced by side feeding.

[0090] The polyamide(s) and additives are added via the main hopper during the compounding process.

[0091] These compositions were then molded into dumbbell or bar shapes in an injection molding machine at a material temperature of 260° C. and a molding temperature of 50° C., and the mechanical properties were investigated according to the following criteria. TIFF2024540488000001.tif255170CE: Comparison example E: Examples of the present invention The percentages here are given as percentages by weight (%).

[0092] PAN-based virgin carbon fibers and PAN-based recycled carbon fibers sized with polyurethane or polyamide sizes are commercially available from, for example, Mitsubishi, SGL, ACECA, Teijin, Zoltek, or Hexcel.

[0093] PA11: Synthesized by the applicant's company.

[0094] Tensile modulus, elongation at break, and stress at break were measured on dry samples at 23° C. according to ISO standard 527-1: 2012.

[0095] The machine used is of the type Instron 5966. The crosshead speed is 1 mm / min for the measurements of the elastic modulus and 5 mm / min for the breaking stress and the elongation at break. The test conditions are 23° C.±2° C. on dry samples.

[0096] The impact strength was determined according to ISO 179-1: 2010 (Charpy impact) on notched and unnotched bars with dimensions 80 mm x 10 mm x 4 mm at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 10% or at a temperature of -30°C ± 2°C and a relative humidity of 50% ± 10% on dry samples.

[0097] The above examples and comparative examples show that the mechanical properties of compositions based on recycled carbon fibers sized with polyamide are better than those of compositions based on virgin carbon fibers sized with polyamide or based on virgin carbon fibers sized with other polymers.

Claims

1. 1. A molding composition comprising, by weight: a) 50% to 99% of a semicrystalline aliphatic polyamide having an intrinsic viscosity of 1.10 or less, in particular 1.00 or less, in particular 0.95 or less, and especially 0.9 or less, determined according to ISO standard 307:2007 (wherein m-cresol is used instead of sulfuric acid, at a temperature of 20° C. and a concentration of 0.5% by weight), b) 1 to 50% recycled carbon fibers having an average length of 6 mm or less before compounding, the recycled carbon fibers having a surface coated (sized) with polyamide, particularly aliphatic polyamide; c) 0% to 5% of at least one additive; wherein the sum of components a), b) and c) is 100%.

2. The semi-crystalline aliphatic polyamide (a) is At least one C ６ ~C １８ , preferably C ９ ~C １８ , more preferably C １０ ~C １８ , especially C １０ ~C １２ or At least one C ６ ~C １８ , preferably C ９ ~C １８ , more preferably C １０ ~C １８ , especially C １０ ~C １２ lactam, or At least one C ４ ~C ３６ , preferably C ６ ~C １８ , preferably C ６ ~C １２ , more preferably C １０ ~C １２ Diamine Ca and At least one C ４ ~C ３６ , preferably C ６ ~C １８ , preferably C ６ ~C １２ , more preferably C １０ ~C １２ Dicarboxylic acid Cb 2. The molding composition according to claim 1, characterized in that it is obtained by polycondensation of:

3. 2. The molding composition according to claim 1, wherein the polyamide (a) has an average number of carbon atoms per nitrogen atom of at least 8, in particular at least 9, and especially at least 10.

4. 4. The molding composition according to claim 3, characterized in that the polyamide (a) is selected from PA610, PA612, PA1010, PA1012, PA1212, PA11 and PA12, in particular from PA1010, PA1012, PA1212, PA11, PA12, more particularly from PA11 and PA12, in particular from PA11.

5. 2. A molding composition according to claim 1, characterized in that the resilience of the composition is more than 10% greater than the resilience obtained with virgin carbon fibres sized with polyamide or with recycled carbon fibres (but sized with a polymer other than polyamide) when measured with a 1 eU Charpy impact on an unnotched bar at 23°C.

6. 2. A molding composition according to claim 1, characterized in that the resilience and elongation at break of said composition, measured by Charpy impact of 1 eU on an unnotched bar at 23°C, are more than 10% greater than the resilience and elongation at break obtained with virgin carbon fibres sized with polyamide or with recycled carbon fibres, provided that they are sized with a polymer other than polyamide.

7. 10. Use of a composition according to claim 1 for the manufacture of an article obtainable by injection molding, said article being selected from sports equipment, in particular sports shoes, in particular ski boots or parts of ski boots, or hard boots with spikes, such as football, rugby or American football boots, hockey boots or parts of hockey boots, or running shoes, golf balls or parts of golf balls, or lacrosse sticks, hockey equipment, such as helmets, and sports equipment for protecting the head, shoulders, elbows, hands, knees, back or shins, such as helmets, gloves, shoulder pads, elbow pads, knee pads or shin pads.

8. 10. Use of the molding composition according to claim 1 for producing articles for the electronics industry, the automotive industry, for communication applications or for data exchange, such as for autonomous vehicles or for interconnected applications.

9. 10. An article obtained by injection molding the composition of claim 1.