FR3012813A1 - POLYMERIC COMPOSITION OF BLACK COLOR ADAPTED TO LASER WELDING - Google Patents

Abstract

The invention relates to a part comprising a portion adapted to be welded to a portion of another part by application of laser radiation, said portion of the part being transparent to the laser radiation and said portion of the other part being absorbent for the laser radiation, and said portion of the piece being black in color and having at least one layer of a composition comprising a thermoplastic polymer and carbon nanofillers.

Description

FIELD OF THE INVENTION The present invention relates to a polymeric composition of black color suitable for laser welding, and more particularly having properties of transparency to laser radiation. The invention also relates to parts made from this composition, such as fluid transport circuit parts (especially in the automotive field). BACKGROUND ART There are various methods for welding thermoplastic elements. Thus, it is known to use heated blades with or without contact, to apply ultrasound, to apply vibrations or to proceed by rotating one element to be welded against the other. All these methods give rise to practical problems, for example the appearance of burrs (in the case of rotational welding) or the generation of an abrasion powder. The laser welding technique is a particularly advantageous alternative assembly method. In particular, it provides good axial resistance and good sealing, is resistant to chemical attack and offers great flexibility in terms of welded parts shapes. Laser welding requires that the two elements to be welded have different properties vis-à-vis the laser radiation: one of the elements must be transparent to the laser radiation, and the other must absorb the laser radiation. The laser radiation thus passes through the transparent element 35 and then reaches the absorbent element, where it is converted into heat. This melts the contact area between the two elements and thus to achieve the weld. Thermoplastic polymers are generally transparent for the purposes of laser welding. In order to make them absorbent, it is known to add various additives, including for example carbon black, which gives the polymer a black color.

In some applications, it is desirable that the two parts to be welded be black, including the piece transparent to laser radiation. This is particularly the case in the field of vehicles and more particularly automobiles: for commercial reasons, the manufacturers want the fluid transport circuits (for example the fuel distribution circuit) to be entirely black in color - in particular because that other colors undergo aging with use. The use of the technique of laser welding in this context therefore requires having plastic materials of black color and transparent to laser radiation.

US 2003/0125429 discloses dark-colored, laser-transparent thermoplastic compositions in which the dark color is provided by a combination of non-black dyes, for example yellow, red and green organic pigments. The corresponding formulations are complex and do not easily make it possible to obtain a sufficiently pure black color. In addition, the organic pigments can be degraded if the parts thus manufactured are put in contact with certain solvents (for example the alcohols present in certain fuels). US 2004/0140668 discloses the realization of a laser welding connection between two absorbent parts to laser radiation, by means of a transparent adapter. US 2005/0137325 and EP 1533105 disclose the use of anthraquinone black dyes to impart a black appearance to thermoplastic compositions transparent to laser radiation. The same remarks as for the document US 2003/0125429 apply, with regard to these two documents. US 2005/0217790 discloses thermoplastic compositions of natural color or pigmented and absorbent for laser radiation.

EP 1552916 describes various connection methods between tubes by laser welding based on the use of various absorbent or transparent parts vis-à-vis the laser radiation. WO 2008/047022 discloses a conductive composite material based on thermoplastic polymer and carbon nanotubes in an amount of less than 6% and especially 0.2 to 2%. IN 1037K02008 discloses a laser welding process in which the strength of the welded joint is improved by the presence of reliefs. US 2011/0288220 discloses polyester-based thermoplastic compositions having improved transparency to laser radiation through the use of salts and other additives. It is specified that the charge content having a high absorbance for the laser radiation is advantageously less than 1% and more particularly less than 0.05%. US 2012/0183778 discloses compositions comprising a mixture of crystalline or semi-crystalline polymer and amorphous polymer to obtain improved transparency to laser radiation. US 2013/0062271 discloses a filter element having a laser-transparent portion and an absorbent portion for the laser radiation to permit laser welding of these portions. Additives can be used to obtain a property of electrical conductivity, among which carbon nanotubes. In view of the foregoing, there is a need for the development of thermoplastic compositions for the production of laser-transparent parts having a satisfactory black visual appearance and resistant to degradation. SUMMARY OF THE INVENTION The invention relates first of all to a part comprising a portion adapted to be welded to a portion of another part by application of laser radiation, said portion of the part being transparent to the laser radiation and said the portion of the other piece being absorbent for laser radiation, and said portion of the piece being black in color and having at least one layer of a composition comprising a thermoplastic polymer and carbon nanofillers. According to one embodiment, the amount of carbon nanofillers in the composition is from 100 ppm to 500 ppm, and preferably from 100 ppm to 250 ppm. According to one embodiment, the carbon nanofillers are chosen from carbon nanotubes, carbon nanofibers, graphene, nanometric carbon black and their mixtures. According to one embodiment, the laser radiation is infrared laser radiation, and preferably has a wavelength between 700 and 1200 nm, and preferably between 800 nm and 1100 nm. According to one embodiment, the thermoplastic polymer is chosen from polyamides, polyacetals, polyketones, polyacrylics, polyolefins, polycarbonates, polystyrenes, polyesters, polyethers, polysulfones, fluorinated polymers, polyurethanes, polyamideimides, polyarylates, polyarylsulfones, polyethersulfones, polyarylene sulfides, polyvinyl chlorides, polyetherimides, polyetherketones, copolymers thereof and miscible mixtures thereof; and preferably is a polyamide. According to one embodiment, the layer has a thickness of 0.1 to 4 mm, preferably 0.5 to 3 mm and more particularly 1 to 2 mm. According to one embodiment, the part is chosen from tubings, connectors for tubings and filtration elements. According to one embodiment, the part is a part of a fluid transport circuit, and preferably is a fluid transport circuit piece for a vehicle and in particular for an automobile; and / or is a part of a transport circuit for fuel, oil, air, refrigerant or aqueous solution such as engine coolant or urea-water mixture. The invention also relates to the use of carbon nanofillers to impart a black color to a layer of a composition comprising a thermoplastic polymer, while maintaining the transparency of the laser radiation of said layer. According to one embodiment, the laser radiation is an infrared laser radiation, and preferably has a wavelength between 700 nm and 1200 nm and preferably between 800 nm and 1100 nm. According to one embodiment, the carbon nanofillers are incorporated in the composition in an amount of from 100 ppm to 500 ppm, and preferably from 100 ppm to 250 ppm. According to one embodiment, the carbon nanofillers are chosen from carbon nanotubes, carbon nanofibers, graphene, nanometric carbon black and their mixtures. According to one embodiment, the thermoplastic polymer is chosen from polyamides, polyacetals, polyketones, polyacrylics, polyolefins, polycarbonates, polystyrenes, polyesters, polyethers, polysulfones, fluoropolymers, polyurethanes, polyamideimides, polyarylates, polyarylsulfones, polyethersulfones, polyarylene sulfides, polyvinyl chlorides, polyetherimides, polyetherketones, copolymers thereof and miscible mixtures thereof; and preferably is a polyamide. The invention also relates to a method of manufacturing a workpiece 10 as described above, comprising providing the composition and forming the workpiece, preferably by extrusion or injection. According to one embodiment, the method comprises a preliminary step of incorporating the carbon nanofillers into the composition, preferably in the form of a masterbatch comprising said carbon nanofillers. The invention also relates to a method of assembling a first piece with a second piece, comprising welding with laser radiation a portion of the first piece with a portion of the second piece, said portion of the first piece being transparent to the laser radiation and said portion of the second piece being absorbent for laser radiation, and said portion of the first piece being black in color and having at least one layer of a composition comprising a thermoplastic polymer and carbon nanofillers. According to one embodiment, the first piece is a piece as described above. According to one embodiment, the first piece is a flexible hose and the second piece is a rigid connector; or the first piece is a rigid connector and the second piece is a flexible hose. The invention also relates to a composition comprising a thermoplastic polymer and carbon nanofillers in an amount of 100 to 500 ppm. According to one embodiment, the carbon nanofillers are present in an amount of 100 to 250 ppm, preferably 100 to 200 ppm. In one embodiment, the carbon nanofillers are selected from carbon nanotubes, carbon nanofibers, graphene, nanoscale carbon black, and mixtures thereof.

According to one embodiment, the thermoplastic polymer is chosen from polyamides, polyacetals, polyketones, polyacrylics, polyolefins, polycarbonates, polystyrenes, polyesters, polyethers, polysulfones, fluorinated polymers, polyurethanes, polyamideimides, polyarylates, polyarylsulfones, polyethersulfones, polyarylene sulfides, polyvinyl chlorides, polyetherimides, polyetherketones, copolymers thereof and miscible mixtures thereof; and preferably is a polyamide. The present invention overcomes the disadvantages of the state of the art. It provides more particularly thermoplastic compositions allowing the production of parts transparent to laser radiation and having a satisfactory black visual appearance and resistant to degradation. This is accomplished through the use of carbon nanofillers in thermoplastic compositions. It has been discovered that when the carbon nanofillers are present in a suitable amount (sufficiently low), black thermoplastic compositions are obtained, but nevertheless transparent to the laser radiation.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 schematically represents an embodiment of a seal formed between two parts of a fluid transport circuit. Figure 2 schematically shows another embodiment of a seal formed between two parts of a fluid transport circuit.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION The invention is now described in more detail and in a nonlimiting manner in the description which follows. All proportions are mass proportions unless otherwise stated. General Definitions As stated in the introduction, the laser weld rests on the connection of a portion of a first part with a portion of a second part, said portion of the first part being transparent for the laser radiation and said portion of the second part piece being absorbent for laser radiation. In addition, according to the present invention, the portion of the first piece is black in color. By "transparent portion for laser radiation" is meant throughout the present application that the portion in question transmits (through its thickness) at least 15% of a laser radiation, preferably at least 20%, or at least 25%, or at least 30%, or at least 35%, or at least 40%, or at least 45%, or at least 50%, or at least 55%, or at least 60%, or at least minus 65%, or at least 70%, or at least 75% of incident laser radiation. The incident laser radiation is preferably infrared laser radiation. It preferably has a wavelength (that is to say wavelength at which the intensity emitted is maximum) is between 700 and 1200 nm, and especially between 800 and 1100 nm. By way of example, it may have a wavelength of 1064 nm (wavelength of the Nd: YAG laser) or 940 nm (laser diode). The measurement of the transmission of the laser radiation through the portion considered is performed by means of a transmission measuring device comprising a spectrophotometer and an integrating sphere photometer, in order to detect both the directly transmitted light flux and the diffused light flux. By "absorbent portion for laser radiation" is meant that the portion in question transmits (through its thickness) less than 1%, preferably less than 0.5%, and more particularly less than 0.1% of a laser radiation - the remarks and embodiments mentioned above for laser radiation applying mutatis mutandis. By "black" portion, it is meant that the portion has a black visual appearance for an informed observer. Alternatively, the color may be considered black if the portion in question transmits less than 10%, preferably less than 8%, or less than 6%, or less than 5%, or less than 4%, or less than 3%, or less than 2% or less than 1% of incident radiation for the entire visible spectrum, i.e. for wavelengths of 400 to 700 nm. Thus, according to particular embodiments, the term "portion transparent to laser radiation and black color" means a portion 35 as defined in one of the lines of one of the following two tables: No. Transmission at 1064 nm Transmission in the whole spectrum 400-700 nm 1> 20% <10% 2> 20% <5% 3> 20% <2% 4> 20% <1%> 30% <10% 6> 30% < 5% 7> 30% <2% 8> 30% <1% 9> 40% <10%> 40% <5% 11> 40% <2% 12> 50% <1% 13> 60% <10% 14> 60% <5%> 60% <2% 16> 60% <1% 17> 70% <10% 18> 70% <5% 19> 70% <2%> 70% <1% N ° Transmission at 940 nm Transmission in the whole spectrum 400-700 nm 21> 20% <10% 22> 20% <5% 23> 20% <2% 24> 20% <1%> 30% <10% 26> 30% <5% 27> 30% <2% 28> 30% <1% 29> 40% <10%> 40% <5% 31> 40% <2% 3012 813 9 No. Transmission at 940 nm Transmission in the whole spectrum 400-700 nm 32> 50% <1% 33> 60% <10% 34> 60% <5%> 60% <2% 36> 60% <1% 37> 70% <10% 38> 70% <5% 39> 70% <2%> 70% <1% Transparent thermoplastic composition According to the invention, the portion transparent to the radiation A laser for soldering comprises at least one layer of a thermoplastic composition comprising carbon nanofillers. It is the carbon nanofillers that provide the black color while preserving the transparency to the laser radiation of the composition. This composition can be qualified as a "transparent" thermoplastic composition for convenience. By "thermoplastic composition" is meant a composition containing predominantly one or more thermoplastic polymers, that is to say, whose glass transition temperature Tg is greater than a temperature of 20 ° C., in the dry state. (ie with a quantity of water in the material less than 0.05%). Tg is conventionally measured by DSC (Differential Scanning Calorimetry). It is determined here by the temperature of the point of inflection of the heat flux as a function of the temperature during a temperature ramp of 20 ° C / min. The thermoplastic polymers that can be used are preferably chosen from polyamides, polyacetals, polyketones, polyacrylics, polyolefins, polycarbonates, polystyrenes, polyesters, polyethers, polysulfones, fluorinated polymers, polyurethanes, polyamideimides, polyarylates, polyarylsulfones, polyethersulfones, polyarylene sulfides, polyvinyl chlorides, polyetherimides, polyetherketones and copolymers thereof. The polyamides are preferred polymers, in particular PA 6.10 (polyhexamethylene sebacam ide), PA 6.12 (polyhexamethylene dodecanediamide), PA 10.10 (polydecamethylene sebacamide), PA 10.12 (polydecamethylene dodecanediamide), PA 11 (polyundecanamide) and the PA 12 (polylauroamide). Other preferred polymers are polyarylethersketone (PAEK), and in particular polyether ether ketone (PEEK) and polyether ketoneketone (PEKK). Other preferred polymers are vinylidene fluoride-based polymers, namely homopolymers (PVDF) and copolymers. These polymers have in fact an advantageous temperature resistance. Polyolefins that may be used include polypropylene or polyethylene, or a functionalized polyolefin. As polyacrylamide, it is possible to use homopolymers and copolymers based on methyl methacrylate, such as PMMA (poly methyl methacrylate) and P (MMA-ABU), a copolymer formed with butyl acrylate.

Polyether amide block (PEBA) can also be used. According to a preferred embodiment, the composition contains a single polymer. Indeed, the presence of several polymers in the composition can lead to the formation of particles or aggregates which disturb the transmission of the laser radiation.

Alternatively, it is possible to provide several polymers in the composition, if they are miscible, that is to say form a homogeneous mixture. By way of example, it is possible to use a mixture of PVDF and PMMA with a majority of PVDF. The composition also comprises carbon nanofillers.

By "carbon nanofillers" is meant mainly carbon-containing fillers having at least one dimension (minimum dimension) less than or equal to 100 nm, preferably less than or equal to 50 nm, and more particularly preferably less than or equal to 20 nm. nm. Preferably, the minimum dimension of the carbon nanofillers is greater than or equal to 0.4 nm, preferably greater than or equal to 1 nm. The carbon nanofillers may in particular be carbon nanotubes, carbon nanofibers, nanometric carbon black, graphene, or mixtures thereof. Preferably, it is carbon nanotubes.

Carbon nanotubes are hollow tubular structures having a graphitic plane disposed about a longitudinal axis or several graphitic planes (or leaflets) arranged concentrically about a longitudinal axis. The carbon nanotubes may be of the single-walled, double-walled or multi-walled type. The double-walled nanotubes may in particular be prepared as described by Flahaut et al in Chem. Com. (2003), p.1442. The multi-walled nanotubes may be prepared as described in WO 03/02456. The carbon nanotubes generally have a mean diameter (perpendicular to the longitudinal axis, the mean value being a linear average along the longitudinal and statistical axis over a set of nanotubes) ranging from 0.4 to 100 nm, from preferably 1 to 50 nm and more preferably 2 to 30 nm, or even 10 to 15 nm, and preferably 0.1 to 10 μm in length. The length / diameter ratio is preferably greater than 10 and most often greater than 100. Their specific surface area is, for example, from 100 to 300 m2 / g, advantageously from 200 to 300 m2 / g, and their apparent density may especially be worth from 0.05 to 0.5 g / cm3 and more preferably from 0.1 to 0.2 g / cm3. The multiwall nanotubes may for example comprise from 5 to 15 sheets (or walls) and more preferably from 7 to 10 sheets. These nanotubes can be treated or not. The dimensions and in particular the average diameter of the carbon nanotubes can be determined by transmission electron microscopy. An example of crude carbon nanotubes is in particular marketed by Arkema under the trade name Graphistrength® C100. These carbon nanotubes may be purified and / or treated (for example oxidized) and / or milled and / or functionalized before being used within the scope of the invention. The grinding of the carbon nanotubes may in particular be carried out cold or hot and be carried out according to the known techniques used in devices such as ball mills, hammers, grinders, knives, jet gasses or any another grinding system capable of reducing the size of the entangled network of nanotubes. It is preferred that this grinding step is performed according to a gas jet grinding technique and in particular in an air jet mill. The purification of the raw or milled carbon nanotubes can be carried out by washing with a sulfuric acid solution, so as to rid them of any residual mineral and metal impurities, such as iron, originating from their preparation process. The weight ratio of nanotubes to sulfuric acid may in particular be from 1: 2 to 1: 3. The purification operation may also be carried out at a temperature ranging from 90 to 120 ° C, for example for a period of 5 to 10 hours. This operation can advantageously be followed by steps of rinsing with water and drying of the purified carbon nanotubes. Carbon nanotubes may alternatively be purified by high temperature heat treatment, typically above 1000 ° C. The oxidation of the carbon nanotubes is advantageously carried out by putting them in contact with a solution of sodium hypochlorite containing from 0.5 to 15% by weight of NaOCI and preferably from 1 to 10% by weight of NaOCI, for example in a weight ratio of carbon nanotubes to sodium hypochlorite ranging from 1: 0.1 to 1: 1. The oxidation is advantageously carried out at a temperature below 60 ° C. and preferably at room temperature, for a duration ranging from a few minutes to 24 hours. This oxidation operation may advantageously be followed by filtration and / or centrifugation, washing and drying steps of the oxidized nanotubes. Functionalization of carbon nanotubes can be carried out by grafting reactive units such as vinyl monomers on their surface. The material constituting the carbon nanotubes is used as a radical polymerization initiator after having been subjected to a heat treatment at more than 900 ° C., in an anhydrous and oxygen-free medium, which is intended to eliminate the oxygenated groups from its surface. It is thus possible to polymerize methyl methacrylate or hydroxyethyl methacrylate on the surface of carbon nanotubes in order to facilitate in particular their dispersion in the polyamides. In the present invention, it is preferable to use optionally milled raw carbon nanotubes, ie carbon nanotubes which are neither oxidized nor purified nor functionalized and have undergone no other chemical and / or thermal treatment. The term "graphene" is used to designate a sheet of graphite plane, isolated and individualized, but also, by extension, an assembly comprising between one and a few tens of sheets and having a flat structure or more or less wavy. This definition includes FLGs (Few Layer Graphene or Graphene NanoRegons), Nanosized Graphene Plates (NGPs), CNS (Carbon NanoSheets or nano-graphene sheets), and Graphene NanoRibbons (Graphene NanoRibbons). nano-ribbons of graphene). It is furthermore preferred that the graphene used according to the invention is not subjected to an additional step of chemical oxidation or functionalization. As indicated above, the graphene used according to the invention is obtained by chemical vapor deposition or CVD. It is typically in the form of particles having a thickness of less than 50 nm, preferably less than 15 nm, and more preferably less than 5 nm, and less than one micron side dimensions, preferably from 10 nm to less than 1000 nm, preferably from 50 to 600 nm, and more preferably from 100 to 400 nm. Each of these particles generally contains from 1 to 50 sheets, preferably from 1 to 20 sheets, more preferably from 1 to 10 sheets, or even from 1 to 5 sheets, which are capable of being disconnected from each other in the form of independent leaflets, for example during an ultrasound treatment. The process for the manufacture of graphene by CVD generally comprises the decomposition of a gaseous source of carbon, in particular a hydrocarbon, such as ethylene, methane or acetylene, under a flow of inert gas such as argon or nitrogen, the dilution ratio of the hydrocarbon in the inert gas being for example about 1: 5. This decomposition is carried out at a temperature of 900 to 1000 ° C., preferably from 960 to 1000 ° C., generally at atmospheric pressure, over a catalyst in the form of a powder. The catalyst may especially be a metal catalyst supported or not on an inert substrate. It may be for example cobalt optionally mixed with iron and supported on magnesia, in a molar ratio of cobalt to magnesia generally less than 10%. The catalyst is usually prepared by impregnating the support with alcoholic or glycol solutions of cobalt salts and optionally iron, followed by evaporation of the solvent and a calcination step. Another CVD method for obtaining graphene according to this invention comprises the following steps: a) the introduction into a synthesis reactor, and optionally the fluidized bed in said reactor, of an active catalyst for the synthesis of graphene, comprising a mixed oxide of formula AFe 2 O 4 in which A is at least one mixed valence metal element having at least two valencies, one of which is equal to +2, in particular chosen from cobalt, copper or nickel, the catalyst being of spinel structure, b) heating said catalyst in the reactor at a temperature between 500 and 1500 ° C, preferably between 500 and 800 ° C, or even between 610 and 800 ° C, c) bringing into contact a gaseous source of carbon, with the catalyst of step b), possibly in a fluidized bed, and its catalytic decomposition at a temperature of 500 to 800 ° C, preferably from 610 to 800 ° C, the gaseous source being chosen among the alco C 1 -C 12 hydrocarbons and C 1 -C 12 hydrocarbons, such as alkanes or alkenes, preferably ethylene, which may be mixed with a stream of a reducing agent such as hydrogen and optionally with an inert gas, d) the recovery of graphene produced in c) at the outlet of the reactor.

Carbon nanofibers are filament-shaped objects. Unlike carbon nanotubes, these are not hollow objects. By way of example, the carbon nanofibers may have a so-called "herringbone" structure (stack of graphene layers oriented symmetrically on either side of the longitudinal axis); or a platelet or lamellar structure (graphene sheets piled perpendicular to the axis); or a conical structure, still called "stacked cup" (continuous sheet of graphene wound on itself); or a so-called bamboo structure (fiber having periodic variations in diameter, formed of compartments separated by a graphitic sheet); or a ribbon structure (graphene sheets oriented parallel to the longitudinal axis without being wound); or a tubular structure (similar to the structure of multiwall carbon nanotubes). The carbon nanofibers may have a mean diameter (perpendicular to the longitudinal axis, the mean value being a linear average along the longitudinal and statistical axis over a set of nanofibers) ranging from 0.4 to 100 nm, preferably from 1 to 50 nm and more preferably from 2 to 30 nm, even from 10 to 15 nm, and advantageously from 0.1 to 10 μm in length. The length / diameter ratio is preferably greater than 10 and most often greater than 100.

The dimensions and in particular the average diameter of the carbon nanofibers can be determined by scanning electron microscopy.

It is necessary to adjust both the carbon nanofillers mass content in the composition and the thickness of the layer formed with the composition, in order to obtain both a black color and a transparency to the laser radiation.

Generally, the content of carbon nanofillers ranges from 100 ppm to 500 ppm, especially in order to produce layers of 500 μm to 3 mm thick, and more particularly from 1 mm to 2 mm thick. Lower levels of this range are possible in certain embodiments for producing thicker layers, and levels higher than this range are conceivable in some embodiments for producing thinner layers. According to some embodiments, the content of carbon nanofillers in the composition ranges from 100 ppm to 120 ppm; or from 120 ppm to 140 ppm; or from 140 ppm to 160 ppm; or from 160 to 180 ppm; or from 180 to 200 ppm; or from 200 to 220 ppm; or from 220 to 240 ppm; or from 240 to 260 ppm; or from 260 to 280 ppm; or from 280 to 300 ppm; or from 300 ppm to 320 ppm; or from 320 ppm to 340 ppm; or from 340 ppm to 360 ppm; or from 360 to 380 ppm; or from 380 to 400 ppm; or from 400 to 420 ppm; or from 420 to 440 ppm; or from 440 to 460 ppm; or from 460 to 480 ppm; or from 480 to 500 ppm.

A range of 100 to 250 ppm is particularly preferred, in particular for the formation of layers of 500 μm to 3 mm thick, and more particularly of 1 mm to 2 mm thick. A range of 120 to 200 ppm is also particularly preferred, especially for the formation of layers of 500 μm to 3 mm thick, and more particularly 1 mm to 2 mm thick. The transparent thermoplastic composition may also include other additives. As additives may be provided reinforcements, to improve some of the mechanical properties, including the tensile modulus of the material obtained from this composition. By reinforcements is meant in particular balls, fibers (such as glass fibers, natural or polymeric fibers), ground materials, flours. According to one embodiment, the reinforcing additives (such as glass fibers) are present in the composition in an amount of about 30%. It should be noted that the amount of reinforcements acceptable in the composition depends on the thickness of the layer formed with this composition. The thinner the layer, the higher the reinforcing content can be without degrading the transparency to the laser radiation excessively. The transparent thermoplastic composition may also comprise one or more additives chosen from fillers (which are not carbon nanofillers or reinforcements), dyes, stabilizers, in particular UV stabilizers, plasticizers, impact modifiers, surfactants. , pigments, brighteners, antioxidants, lubricants, flame retardants, natural waxes and mixtures thereof. As flame retardants, it is possible, for example, to use Mg (OH) 2, melamine pyrophosphates, melamine cyanurates, ammonium polyphosphates, metal salts of phosphinic acid or diphosphinic acid, or else polymers containing at least one metal salt of phosphinic acid or diphosphinic acid. The salt may for example be chosen from aluminum methylethylphosphinate and aluminum diethylphosphinate. Mixtures containing such metal salts are marketed by Clariant under the trade names Exolit OP1311, OP1312, OP1230 and OP1314. The total amount of additives in the composition is preferably less than or equal to 40%.

The total amount of fillers in the composition (which are not carbon nanofillers or reinforcements) is preferably less than or equal to 10%, and more particularly less than or equal to 5%, or 4%, or 3% , or 2%, or 1%, or 0.5%, or 0.1%. According to a particular embodiment, the composition is devoid of (or substantially free from) any filler (which are not carbon nanofillers or reinforcements), dye, pigment and brightening agent outside the carbon nanofillers. The carbon nanofillers are incorporated in the composition either by direct mixing of the thermoplastic polymer in the molten state with the carbon nanofillers in powder form; either by mixing the thermoplastic polymer in the molten state with a masterbatch comprising carbon nanofillers dispersed in said thermoplastic polymer (at a concentration greater than the final concentration, for example at a concentration of 0.5 to 15%, especially of 1 to 10% and for example 2 to 4%). Any other additives may be added during mixing between the thermoplastic base polymer and the masterbatch, or may be pre-incorporated in one or other of these two components.

Parts According to the Invention The invention provides parts made from the above transparent thermoplastic composition, which can be described for convenience as transparent parts. These parts each comprise a portion adapted to the laser weld (so-called solder portion), the above transparent thermoplastic composition being present in the form of at least one layer in this portion. According to one embodiment, the solder portion comprises a single layer consisting of the transparent thermoplastic composition. According to an alternative embodiment, the solder portion comprises two or more layers, at least one of which consists of the transparent thermoplastic composition. In this case, the other layers have laser radiation transparency properties such that the entire solder portion is well regarded as transparent to the laser radiation. Preferably, in these multilayer structures, the transparent thermoplastic composition layer described above is the outer layer, in order to benefit from the black visual aspect offered by this layer.

According to one embodiment, the entire transparent piece is made from the single layer of transparent thermoplastic composition or, if appropriate, from the plurality of layers (including at least one layer of transparent thermoplastic composition) present in the solder portion. This offers a greater simplicity of manufacture.

Alternatively, it is possible to provide that the remainder of the transparent piece is made from one or more other layers. For example, it is possible in some cases to impart the black color to the rest of the part (that is to say with the exception of the solder portion) by means of a material other than the carbon nanofillers, for example with traditional carbon black (micrometric). The transparent parts may be shaped for example by extrusion or co-extrusion (possibly directly after the incorporation of the carbon nanofillers in the transparent thermoplastic composition with a masterbatch) or by injection molding. The parts according to the invention are intended to be assembled by laser welding with other parts, which have a portion (called solder portion) which is absorbent for the laser radiation. These parts can be qualified as absorbent parts, for convenience. Absorbent parts may be manufactured in part (in particular the solder portion thereof), or preferably in full, from at least one thermoplastic polymer-based composition. Absorbent parts can be monolayers or multilayers. In this case, preferably at least one layer, or all the layers, are made from a composition based on thermoplastic polymer. The thermoplastic polymer may be chosen from polyamides, polyacetals, polyketones, polyacrylics, polyolefins, polycarbonates, polystyrenes, polyesters, polyethers, polysulfones, fluoropolymers, polyurethanes, polyamide-imides, polyarylates, polyarylsulfones, polyethersulfones, polyarylene sulfides, polyvinyl chlorides, polyetherimides, polyetherketones, polyester thermoplastic elastomers (TPEs), copolymers thereof, and mixtures thereof. Preferably it is a polyamide. This thermoplastic polymer may especially be chosen from: homo- and copolymers of olefins such as polyethylene, polypropylene, polybutadiene, polybutylene and acrylonitrile-butadiene-styrene copolymers; acrylic homo- and copolymers and alkyl poly (meth) acrylates such as poly (methyl methacrylate); homo- and copolyamides; polycarbonates; polyesters including poly (ethylene terephthalate) and poly (butylene terephthalate); polyethers such as poly (phenylene ether), poly (oxymethylene) and poly (oxyethylene) or poly (ethylene glycol); polystyrene; copolymers of styrene and maleic anhydride; polyvinyl chloride; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene and polychlorotrifluoroethylene; natural or synthetic rubbers; thermoplastic polyurethanes; polyaryl ether ketones (PAEK) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK); polyetherimide; polysulfone; poly (phenylene sulfide); cellulose acetate; poly (vinyl acetate); and their mixtures. According to one embodiment, the polymer is chosen from olefin homo- and copolymers, in particular ethylene or propylene homo- and copolymers, and amide homopolymers and copolymers such as polyamides 6, 6.6. , 6.10, 6.12, 11, 12, 10.10, 10.12, 12.12, 4.6, or copolymers with olefins or esters, ethers or phenolic compounds. This thermoplastic polymer may especially be chosen from: homo- and copolymers of olefins such as polyethylene, polypropylene, polybutadiene, polybutylene and acrylonitrile-butadiene-styrene copolymers; acrylic homo- and copolymers and alkyl poly (meth) acrylates such as poly (methyl methacrylate); homo- and copolyamides; polycarbonates; polyesters including poly (ethylene terephthalate) and poly (butylene terephthalate); polyethers such as poly (phenylene ether), poly (oxymethylene) and poly (oxyethylene) or poly (ethylene glycol); polystyrene; copolymers of styrene and maleic anhydride; polyvinyl chloride; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene and polychlorotrifluoroethylene; natural or synthetic rubbers; thermoplastic polyurethanes; polyaryl ether ketones (PAEK) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK); polyetherimide; polysulfone; poly (phenylene sulfide); cellulose acetate; poly (vinyl acetate); and their mixtures. According to one embodiment, the polymer is chosen from olefin homo- and copolymers, in particular ethylene or propylene homo- and copolymers, and amide homopolymers and copolymers such as polyamides 6, 6.6. , 6.10, 6.12, 11, 12, 10.10, 10.12, 12.12, 4.6, or copolymers with olefins or esters, ethers or phenolic compounds. According to one embodiment, the weld portion of the absorbent parts is black, or preferably the absorbent parts are completely black. According to another embodiment, the absorbent parts may be non-black in whole or in part, for example white or of another color, for example using appropriate mineral fillers.

The black color of the absorbent parts is advantageously obtained from a traditional black pigment, such as conventional (micrometric) carbon black. The invention is particularly applicable in the field of fluid transport, and more particularly in vehicles, including automobiles, trucks or others. Absorbent parts and transparent parts mentioned above are then elements of a fluid transport circuit, for example a fuel transport circuit, cooling liquid, urea-water mixture, refrigerant (for the air conditioning), oil, air or vacuum. These parts may in particular be pipes or tubings (preferably flexible), but also connectors (preferably rigid) or functional parts such as filters. For example, the transparent part may be a tubing, and the absorbent part a connector. Conversely, the transparent part can be a connector, and the absorbent part a tubing. In order to allow laser welding, the solder portion of the transparent part is mounted externally with respect to the solder portion of the absorbent part. By way of example, and with reference to FIG. 1, a pipe 3 (or tubing) has an end which constitutes its solder portion 4. This is introduced into the end of the light of a connector 1 which constitutes the solder portion 2 thereof. The connector 1 is a transparent piece as described above, and the pipe 3 is an absorbent piece as described above. Laser radiation 5 is applied to the seal formed by the two solder portions 2, 4 in order to weld the parts. Still as an example, and with reference to FIG. 2, a pipe 6 (or pipe) has an end which constitutes its weld portion 8. The end of a connector 7, which constitutes the weld portion 10 of the latter, is introduced into the tube of the pipe 6. In the illustrated example, the solder portion 10 of the connector comprises reliefs (for example fir tail) creating pressurized contact zones with the solder portion The connector 7 is an absorbent piece as described above, and the pipe 6 is a transparent piece as described above. Laser radiation 9 is applied to the seal formed by the two solder portions 8, 10 in order to proceed to the welding of the parts. The parts can be assembled using laser welding alone or by other means (for example a self-locking connection or a press fitting as can be seen in FIG. 2), the complementary laser welding, reinforcing or security. Two or a plurality of parallel welds may also be provided to reinforce the assembly if necessary.

Alternatively the parts according to the invention can be for example parts of medical equipment, glasses, or other.

Laser radiation for soldering can be produced by any type of conventional laser, including a crystalline laser, a gas laser or a semiconductor laser. The laser radiation is preferably infrared laser radiation, especially near infrared. Its wavelength may especially be from 700 to 1200 nm, and especially from 800 to 1100 nm. By way of example, the wavelength can be 1064 nm or 940 nm. The power of the laser radiation and the scanning speed of the radiation on the gasket are adapted to provide an effective weld. By way of example, it is possible to use a laser beam with a power of 10 to 1000 W, in particular from 20 to 300 W, for example from 50 to 200 W, with a scanning speed of 1 to 2000 mm / s, in particular from 10 to 1000 mm / s, and more particularly from 50 to 300 mm / s. The laser weld can be continuous, over the entire circumference of the seal, or can be a spot weld, especially in the case where the laser welding is not the only means of assembling parts. In some cases, especially when the solder portion of the transparent piece has a relatively low transparency (while still being sufficient to allow the transmission of a substantial fraction of the radiation to the solder portion of the absorbent part), the solder portion of the transparent part tends to partially melt during irradiation so that the points or weld lines are visible by observing the seal from the outside. This makes it possible to visually verify that the weld has been correctly performed.

EXAMPLES The following examples illustrate the invention without limiting it. Example 1 - Solvent Sensitivity Tests Solvent sensitivity tests are carried out on masterbatches usable for making thermoplastic compositions of black appearance and transparent to laser radiation, namely: a PA 11 masterbatch containing 0.2% of carbon nanotubes, supplied by Arkema; this 5% composition is extracted into ethanol; A masterbatch of PA 11 supplied by Treffert France comprising an organic pigment; this 4% composition is extracted into ethanol; A masterbatch of PA 6 supplied by Colloïds comprising an organic pigment; this 1.5% composition is extracted into ethanol. In all cases, the extraction is carried out in ethanol at 60 ° C. under 40 bar for 50 minutes, so as to obtain an extract of about 20 ml. It is found that the extract of the sample of PA 11 + carbon nanotubes is not colored. On the other hand, the extract from the Treffert France sample has a gray coloring and the extract of the Colloids sample has a pink coloration.

EXAMPLE 2 - WELDING TESTS Laser welding tests are carried out on assemblies of parts according to the invention with a laser diode at 940 nm. The two parts to be welded are held under pressure under a glass tile so that their surfaces, where the welding will be done, are in perfect contact. The laser beam passes through the glass plate and then through the transparent piece. The laser, with a power of 160 W, is used between 50 and 100% of its power. The scanning speed of the beam on the parts to be assembled is 50 to 300 mm / s. The absorbent part used is a polyamide made black with carbon black. The force required to break the weld by pulling it by shear is measured with a tensile tester. The breaking stress (in MPa) which is equal to the breaking force (in N) divided by the area of the weld bead (mm 2), which is itself the width of the bead (1.6 mm), is calculated. x its length (which is usually the width of the wafer). In a first test, the transparent part is a black-colored plate 1 mm thick made from a PA 11 composition containing 120 ppm of carbon nanotubes. The wafer is obtained by injecting the polymer in the molten state in a mold whose cavity to a thickness of 1 mm and a section of 100 x 100 mm. The laser beam is driven by optical fiber to the place of welding, and controlled by computer. It is found that the weld is properly performed. In a second test, the transparent part has a double thickness (it consists of two black plates 1 mm thick each made from a composition of PA 11 containing 120 ppm of carbon nanotubes. , and arranged one on the other). The test conditions are similar to those of the first test, except that. It is found that the weld is properly performed (with the transparent wafer in contact with the absorbent part). In a third test, the transparent part is a black-colored plate 1 mm thick made from a composition of PA 11 containing 180 ppm of carbon nanotubes. The wafer is obtained by injecting the polymer in the molten state into a mold having a cavity at a thickness of 1 mm and a section of 100 x 100 mm. The test conditions are similar to those of the first test, except that. It is found that the weld is properly performed. In a fourth test, the transparent piece is a 2 mm thick black color plate manufactured from an AP 11 composition containing 180 ppm of carbon nanotubes. The wafer is obtained by injecting the polymer in the molten state in a mold whose cavity to a thickness of 2 mm and a section of 100 x 100 mm. It is found that the weld is properly performed.

Claims (6)

REVENDICATIONS1. Part comprising a portion adapted to be welded to a portion of another part by application of laser radiation, said portion of the part being transparent to the laser radiation and said portion of the other part being absorbent for the laser radiation, and said portion of the part being black in color and having at least one layer of a composition comprising a thermoplastic polymer and carbon nanofillers. 2. Part according to claim 1, wherein the amount of carbon nanofillers in the composition is from 100 ppm to 500 ppm, and preferably from 100 ppm to 250 ppm. 3. Part according to claim 1 or 2, wherein the carbon nanofillers are selected from carbon nanotubes, carbon nanofibres, graphene, nanoscale carbon black and mixtures thereof. 4. Part according to one of claims 1 to 3, wherein the laser radiation is infrared laser radiation, and preferably has a wavelength of between 700 and 1200 nm, and preferably between 800 nm and 1100 nm. 5. Part according to one of claims 1 to 4, wherein the thermoplastic polymer is selected from polyamides, polyacetals, polyketones, polyacrylics, polyolefins, polycarbonates, polystyrenes, polyesters, polyethers, polysulfones , fluorinated polymers, polyurethanes, polyamideimides, polyarylates, polyarylsulfones, polyethersulfones, polyarylene sulfides, polyvinyl chlorides, polyetherimides, polyetherketones, copolymers thereof and miscible mixtures thereof. this ; and preferably is a polyamide. 3012 813 25 6. The article according to one of claims 1 to 5, wherein the layer has a thickness of 0.1 to 4 mm, preferably from 0.5 to 3 mm and more particularly from 1 to 2 mm. Part according to one of claims 1 to 6, which is selected from tubing, connectors for tubing and filter elements. Part according to one of claims 1 to 7, which is a part of a fluid transport circuit, and which is preferably a fluid transport circuit part for vehicle and in particular for automobile; and / or which is a part of a transport circuit for fuel, oil, air, refrigerant or aqueous solution such as engine coolant or a urea-water mixture. Use of carbon nanofillers to impart a black color to a layer of a composition comprising a thermoplastic polymer, while maintaining the transparency of the laser radiation of said layer. Use according to claim 9, wherein the laser radiation is infrared laser radiation, and preferably has a wavelength of between 700 nm and 1200 nm and preferably between 800 nm and 1100 nm. Use according to claim 9 or 10, wherein the carbon nanofillers are incorporated in the composition in an amount of from 100 ppm to 500 ppm, and preferably from 100 ppm to 250 ppm. Use according to one of Claims 9 to 11, in which the carbon nanofillers are chosen from carbon nanotubes, carbon nanofibers, graphene, nanometric carbon black and their mixtures. Use according to one of claims 9 to 12, wherein the thermoplastic polymer is selected from polyamides, polyacetals, polyketones, polyacrylics, polyolefins, polycarbonates, polystyrenes, polyesters, polyethers, polysulfones, fluorinated polymers, polyurethanes, polyamideimides, polyarylates, polyarylsulfones, polyethersulfones, polyarylene sulphides, polyvinyl chlorides, polyetherimides, polyetherketones, copolymers thereof and miscible mixtures thereof; and preferably is a polyamide. A method of manufacturing a part according to one of claims 1 to 8, comprising providing the composition and forming the workpiece, preferably by extrusion or injection. The method of claim 14 comprising a preliminary step of incorporating the carbonaceous nanofillers into the composition, preferably in the form of a masterbatch comprising said carbonaceous nanofillers. A method of assembling a first piece with a second piece, comprising welding with laser radiation a portion of the first piece with a portion of the second piece, said portion of the first piece being transparent to the laser radiation and said portion of the second piece being absorbent for laser radiation, and said portion of the first piece being black in color and having at least one layer of a composition comprising a thermoplastic polymer and carbon nanofillers. The method of claim 16, wherein the first part is a part according to one of claims 1 to 8. The method of claim 16 or 17, wherein the first part is a flexible pipe and the second part is a rigid connector; or wherein the first piece is a rigid connector and the second piece is a flexible hose. A composition comprising a thermoplastic polymer and carbon nanofillers in an amount of 100 to 500 ppm. 20. The composition of claim 19, wherein the carbon nanofillers are present in an amount of 100 to 250 ppm, preferably 100 to 200 ppm. 21. The composition of claim 19 or 20, wherein the carbon nanofillers are selected from carbon nanotubes, carbon nanofibers, graphene, nanoscale carbon black and mixtures thereof. 22. Composition according to one of Claims 19 to 21, in which the thermoplastic polymer is chosen from polyamides, polyacetals, polyketones, polyacrylics, polyolefins, polycarbonates, polystyrenes, polyesters and polyethers. polysulfones, fluorinated polymers, polyurethanes, polyamideimides, polyarylates, polyarylsulfones, polyethersulfones, polyarylene sulfides, polyvinyl chlorides, polyetherimides, polyetherketones, copolymers thereof and miscible mixtures of these ; and preferably is a polyamide.