CONDUCTIVE MOLDING COMPOUNDS

Description

[0001] The invention is directed to semi-crystalline polyamide components as a component of molding compositions, wherein the polyamide component does not have a crystallite melting point (T m ) below 50°C.

[0002] Flexible pipes used to convey liquid or gaseous media in motor vehicles are well known. Previously, this task was satisfactorily solved using monopipes made of polyamide or other thermoplastic molding compounds. These monopipes have proven that the mechanical properties present after installation, such as high elongation at break and high impact strength, are not altered so drastically by exposure to cold or heat or by contact with the media, even over the service life of the vehicle, to the point of causing line failure.

[0003] Stricter environmental regulations have led to a move away from the further development and use of monotubes for use as fuel lines, as well as single-layer fuel tanks. For both, the automotive industry demands not only sufficient fuel resistance but also an improved barrier effect against the fuel components in order to reduce their emissions. This has led to the development of multilayer hollow bodies that utilize a barrier layer material. Such multilayer composites, which contain additional layers based on aliphatic polyamides in addition to a barrier layer, are known, for example, from EP 1216826 A2.

[0004] Polyamides are suitable materials for both the inner and outer layers due to their good mechanical properties, low water absorption capacity, and resistance to environmental influences. Adhesion between adjacent layers is desirable and can be ensured by interposing an adhesion promoter layer. In the automotive industry, there has also been a recent trend toward higher temperatures in the engine compartment, and thus the demand for the hollow bodies used to be resistant to these temperatures. Solutions that include an adhesion promoter layer based on polyolefins, for example, are unsuitable due to their low heat resistance.In EP1216826A2, this problem is solved by using an adhesion-promoting layer containing a polyamide selected from PA6, PA66 and PA6 / 66, optionally a polyamine-polyamide copolymer and a polyamide selected from PA11, PA12, PA612, PA1012 and PA1212.

[0005] The ongoing trend toward "downsizing," i.e., the reduction of technical sizes while maintaining the same performance with the goal of reducing energy consumption, for example, in vehicle engines, is leading not only to an increase in the prevailing temperatures in the engine compartment but also to a reduction in the size of fuel injectors. These valves are nozzles that inject fuel into the intake tract or combustion chamber of an internal combustion engine. Polar components contained in fuels require the multilayer pipe used to be resistant to the extraction of components from the materials used. US 6467508 describes the precipitation of such extracts in the fuel and the potential clogging of fuel injectors as a problem. This problem is solved by using a low-precipitate polyamide in the inner layer.Low precipitate polyamide is washed polyamide obtained through a complex and costly pre-extraction with methanol. This removes interfering components such as oligomers.

[0006] With the progressive miniaturization of injection nozzles, the automotive industry is demanding not only a reduction in the extracts precipitating in the fuel, but also a reduction in the extracts soluble in the fuel. This demand has intensified with the introduction of hybrid vehicles, as these vehicles do not use the combustion engine for extended periods. Soluble extracts in the fuel can therefore also dry out and clog injection nozzles. Extracts include, in addition to the oligomers described in US Pat. No. 6,467,508, additives such as plasticizers and stabilizers in the molding compounds used.

[0007] Both DE 3 724 997 C2 and DE 2 716 004 C3, as well as EP 0 566 755 B1, use polyether block amides with laurolactam as the monomer for the polyamide block. Corresponding modified blends with polyamide 12 are also mentioned in the Polyamide Plastics Handbook, 3 / 4, 1998, Carl Hanser Verlag, on page 872, paragraph 8.3.3. These blends exhibit partial compatibility, which is based on the co-crystallization of the polyamide 12 blocks with the homopolyamide.

[0008] EP1884356 discloses blends of polyamide / polyamide elastomers (TPEA), and the addition of conductive additives is also mentioned in a list of possible additives. The disclosed blends contain both large amounts of polyetheramides and large amounts of polyolefin-based impact modifiers.

[0009] The preparation of polyetheramides is described, for example, in EP0459862B1 and CH642982. The polyetheramides are prepared starting from polyamide sequences containing carboxyl groups at both chain ends with polyoxyalkylene sequences containing amino groups at both chain ends.

[0010] WO 2017 / 121961 A1 and WO 2017 / 121962 A1 claim multilayer pipes whose inner layers comprise at least three different polyamides with different chain lengths. These layers can also comprise polyether block amides and can also be conductive. EP1893689A1 discloses conductive polymeric materials containing carbon nanotubes and a method for their production.

[0011] DE102005061530A1 discloses thermoplastic multilayer composites in the form of hollow bodies, which are used, among other things, in fuel lines.

[0012] Typical thermoplastics have specific surface resistances in the range of 10 16< to 10 14< ohms (Ω) and can therefore build up voltages of up to 15,000 volts. Effective antistatic agents can reduce the specific surface resistance of plastics to 10 10< to 10 9< ohms. However, a significantly higher level of electrical charge dissipation must be achieved if plastics are to be used in electronic components of large devices, such as in the transformer or electrical cabinet manufacturing sector, or in a variety of applications in automotive and aircraft construction. Here, electrically conductive molding compounds must be used, which must have a specific surface resistance of less than 10 9< ohms.

[0013] It is also crucial that in such plastic applications, not only the surface resistance but also the volume resistance through plastic parts with a thickness of up to several millimeters must be in the same range, and that anisotropy effects often develop in parts manufactured by injection molding, which are generally difficult to prevent.

[0014] For the production of conductive plastic molded parts, there is therefore only the possibility of either using already conductive plastics such as polyanilines etc. or of making the previously mentioned plastics, which are characterized as electrical insulators, conductive by using carbon blacks, in particular conductive carbon blacks, carbon fibers, graphite, graphene and / or carbon nanotubes (CNTs).

[0015] Carbon nanotubes are, alongside graphite, diamond, amorphous carbon, and fullerenes, another modification of the element carbon. The carbon atoms are arranged in hexagons. The structure corresponds to a rolled-up monoatomic or polyatomic layer of graphite, creating a hollow cylinder typically a few nanometers in diameter and up to a few millimeters in length. A fundamental distinction is made between multi-walled and single-walled carbon nanotubes, commonly referred to in the literature as MWNTs and SWNTs (multi-walled nanotubes and single-walled nanotubes). Due to van der Waals forces, carbon nanotubes exhibit a strong tendency to bundle together, which is why uncoiling / dispersion without significant shortening due to strong shear forces is essential during the extrusion process.Typical commercial products are available from various manufacturers, including Bayer, Cyclics (formerly Electrovac), Nanocyl, and Arkema with their grades Baytubes ®< C150P (trademark Bayer AG, Germany), Baytubes C 150 HP, Baytubes C 70P, Electrovac HTF 110 FF, Nanocyl ®< NC 7000 (trademark Nanocyl SA, Belgium), and Graphistrength C100. Other manufacturers offer CNTs in the form of masterbatches, for example, Hyperion and C-Polymers.

[0016] Accordingly, the object of the invention is to provide conductive molding compounds which do not require low molecular weight plasticizers or other extractable substances to improve the mechanical properties and the aging resistance.

[0017] This object is achieved by semi-crystalline polyamide components as a component of molding compounds, wherein the polyamide component does not have a crystallite melting point (T m ) below 50°C as described in more detail below and in the claims.

[0018] The invention relates to a molding compound which contains at least 50% by weight, preferably 60% by weight, more preferably 70% by weight, particularly preferably 80% by weight and especially preferably at least 90% by weight of a semi-crystalline polyamide component and the molding compound contains a filler which imparts conductivity to the molding compound, characterized in that the molding compound does not have a crystallite melting point below 50°C, wherein the polyamide component contains components A and B, A PA homopolymer of the type PA XY or PA Z , where X is a diamine residue (DA), Y is a dicarboxyl residue (DC), and Z is an alpha-omega-amino acid residue; B PA copolymer of the type PA X'.Y' where X' is a diamine residue (DA') and Y' is a dicarboxyl residue (DC'); where some of the diamine residues (DA') are replaced by a polyether which has at least two amino termini or at least two hydroxy termini; where the PA copolymer has a polyether content of 8 to 30 wt.%, based on the total mass of the PA copolymer; where the proportion of polyether in the sum of components A and B is between 0.5 to 15 wt.% and where the proportion of filler is 2.5 to 6 wt.-%, based on the total mass of polyamide component and filler, wherein the PA homopolymer can be formed from up to 10 mol% of other amide-forming building blocks, wherein up to 10 mol% of the diamine residues (DA') can be replaced by a polyether which has only one amino terminus or only one hydroxy terminus.

[0019] A further object of the invention is the use of the molding compound according to the invention for the production of hollow profiles.

[0020] The invention further relates to single- or multi-layer hollow profiles which have at least one layer consisting of the molding compound according to the invention.

[0021] The molding compositions and molded articles (such as hollow profiles) containing the molding compositions according to the invention, and also the use according to the invention, are described below by way of example, without the invention being restricted to these exemplary embodiments. Where percentages are given below, these are by weight unless otherwise stated. For compositions, the percentages refer to the total composition unless otherwise stated. Where mean values ​​are given below, these are by mass unless otherwise stated. Where measured values ​​are given below, these were determined at a pressure of 101,325 Pa and a temperature of 25°C unless otherwise stated.

[0022] The scope of protection includes the customary commercial packaging and packaging of the products according to the invention, both as such and in any comminution forms, unless these are defined in the claims.

[0023] The various units of the polyether are statistically distributed. Statistical distributions are structured in blocks with any number of blocks and any sequence, or they are subject to a random distribution. They can also be structured alternately or form a gradient across the polymer chain. In particular, they can also form all mixed forms, in which groups of different distributions can follow one another. Special designs can result in the statistical distributions being restricted by the design. For all areas not affected by the restriction, the statistical distribution remains unchanged.

[0024] One advantage of the molding compositions according to the invention is that a single- or multi-layer hollow body, the inner layer of which is formed from the molding composition according to the invention, exhibits high washout resistance. A test using a test fuel according to ASTM D471-15, "Reference Fuel I," on a pipe as described in the examples demonstrates this. The test fuel is characterized by containing 15 vol.% methanol. Other methods for determining washout resistance may be known in the art; the method preferred according to the invention is detailed in the examples. Both soluble and insoluble components can be extracted. Preferably, less than 6 g of soluble components per square meter of internal surface of the test body are extracted from the test body, more preferably less than 5.5 g / m².

[0025] A further advantage of the molding compositions according to the invention is that the degree of crystallinity of the polyamide component consisting of components A, B and C is lower than the degree of crystallinity of a mixture comprising the same components A and C in equal amounts.

[0026] One advantage of the multilayer hollow bodies according to the invention, whose inner layer is formed from the molding compound according to the invention and which have a barrier layer, is their low fuel permeability. A test with a test fuel according to ASTM D471-15, "Reference Fuel I," on a pipe as described in the examples demonstrates this. The test fuel is characterized by containing 15 vol.% methanol. Other methods for determining washout resistance may be known in the prior art; the preferred method according to the invention is detailed in the examples.

[0027] Preferably, a maximum of 6 g / m 2< diffuses out of the test body during the test period of one day when stored at 60°C, preferably less than 5.5 g / m 2< , more preferably less than 5.0 g / m 2< and particularly preferably less than 4.5 g / m 2< .

[0028] Amide-forming building blocks are alpha-omega-amino acid residues or the combination of diamine residues with dicarboxyl residues. Preferred alpha-omega-amino acid residues are free amino acids or their lactams, more preferably epsilon-caprolatam, 11-aminoundecanoic acid, 12-aminolauric acid, or the corresponding lauryllactam.

[0029] Diamine residues are residues that have a hydrocarbon which carries an amino group at the terminal end, whereby the amino group can form the terminus of the polymer, but usually contributes to the chain formation with a valence.

[0030] Preferred hydrocarbons are aliphatic, more preferably having 2 to 18 carbon atoms, particularly preferably 3 to 14 carbon atoms, and especially preferably 4 to 12 carbon atoms. If the hydrocarbons have more than 3 carbon atoms, they are linear, branched, or cyclic, preferably linear, more preferably linear up to a number of 6 carbon atoms.

[0031] Particularly preferred diamine residues are ethylenediamine, 1,4-diaminobutane, 1,6-diaminohexane, 1,10-diaminodecane, and 1,12-diaminododecane; especially preferred is 1,6-diaminohexane. Dicarboxyl residues (DC) are residues that contain a hydrocarbon that carries a terminal carboxyl group. The carboxyl group can form the terminus of the polymer, but usually contributes to chain formation as a carbonyl group with a valence.

[0032] Preferred hydrocarbons are aliphatic, more preferably having 3 to 18 carbon atoms, particularly preferably having 6 to 14 carbon atoms, and especially preferably having 8 to 12 carbon atoms. Further preferably, the hydrocarbons are linear, branched, or cyclic, more preferably linear.

[0033] Preferred dicarboxyl radicals are radicals of succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, dodecanedioic acid, particularly preferably dodecanedioic acid.

[0034] The PA homopolymer comprises polyamides (PA) for component A, preferred polyamides are PA 6, PA 11, PA 12, PA 4.6, PA 6.6, PA 6.9, PA 6.10, PA 6.12, PA 9.10, PA 9.12, PA 10.10, PA 10.12, PA 12.12; more preferably PA 6.6, PA 6.10, PA 6.12, PA 10.10; particularly preferably PA 6.10, PA 6.12, PA 10.10 and especially preferably PA 6.12.

[0035] The PA copolymer of component B has a polyether content of 8 to 30 wt.%, more preferably 9 to 25 wt.%, particularly preferably 10 to 20 wt.%, especially preferably 12 to 18 wt.%, based on the total mass of the PA copolymer.

[0036] The polyether preferably has at least 3 up to 50 repeating units, more preferably 4 to 40, particularly preferably 5 to 30, especially preferably 6 to 20, wherein the repeating units are linked to one another by oxygen atoms.

[0037] Preferably, the polyether is free of nitrogen atoms which do not contain hydrogen atoms, and further preferably is free of amino groups of the formula -NH-, =NH in the polymer chain.

[0038] More preferably, the polyether comprises exclusively alkyleneoxy building blocks, preferably if alkyleneoxy building blocks with 3 to 18 carbon atoms are present, the polyether has a tacticity, e.g. isotactic, syndiotactic, heterotactic, hemiisotactic, atactic.

[0039] Particularly preferred polyethers consist of ethyleneoxy, propyleneoxy, and butyleneoxy units, or mixtures thereof, where the mixtures are random. Particularly preferred polyethers consist of ethyleneoxy and propyleneoxy units, or consist of n-butyleneoxy units, or consist of propyleneoxy units.

[0040] The polyether preferably has a number-average molecular weight M n of at most 5000 g / mol, particularly preferably of at most 2000 g / mol and especially preferably of at most 1000 g / mol, the lower limit being at least 200 g / mol, preferably 300 g / mol, more preferably 400 g / mol.

[0041] The polyether preferably has no more than two amino termini or two hydroxy termini, more preferably exactly two amino termini or two hydroxy termini.

[0042] The polyamide component of the molding compositions according to the invention preferably has a polyether content of 1 to 12 wt.%, preferably 1.5 to 9 wt.%, particularly preferably 2.0 to 8 wt.%, especially preferably 2.5 to 7 wt.%, based on the total mass of components A and B.

[0043] The chain lengths of the PA copolymer and the PA homopolymer of the polyamide component preferably differ from each other by no more than 10% on average with respect to the number of carbon atoms in the amide-forming building blocks, with the deviation being based on the higher value of the chain length. When using a PA copolymer (PA 10.12) and the PA homopolymer (e.g., PA 10.10), the average of PA 10.12 is 11, and the deviation is thus 9.1%.

[0044] The molding compounds according to the invention contain a proportion of filler to increase conductivity (component C) of 2.5 to 6 wt.%, based on the total mass of the polyamide component and the filler to increase conductivity, i.e., the sum of components A, B, and C. The lower limit of 2.5 wt.% has the advantage that the conductivities are sufficiently high and the resistances sufficiently low to enable use in electronic components of large devices and in automotive and aircraft construction. Filler concentrations greater than 6 wt.% continue to result in insufficiently low notched impact strengths, which indicate material embrittlement at excessively high filler concentrations.

[0045] Preferred fillers for increasing conductivity do not form aggregates, so they are dispersible under the application of shear forces.

[0046] Furthermore, the molding compositions according to the invention preferably have a degree of crystallinity which is lower than the degree of crystallinity of a mixture which has the same components A and C (filler to increase the conductivity) in equal amounts, wherein any further constituents of the molding composition are also identical in identity and amount.

[0047] The degree of crystallinity is determined according to state-of-the-art methods, preferably the degree of crystallinity is calculated using equation (1) X C = Δ H m Δ H m 0

[0048] The quantities T m , T g and ΔH m are determined within the scope of the present invention by means of DSC, preferably determined according to EN ISO 11354-1:2016D, more preferably as described in the examples.

[0049] The values ​​ΔH m 0< for calculating the degree of crystallinity Xc are taken from tables, e.g. van Krevelen "Properties of Polymers", 4th edition, 2009. The following values ​​are preferably used: polyamide ΔH m 0< T g T m PA6 230 40 260 PA11 226 46 220 PA12 210 37 179 PA6.6 300 50 280 PA 6.10 260 50 233 PA 6.12 215 54 215 PA 10.9 250 214 PA 10.10 200 60 216

[0050] The molding compositions of the invention preferably do not contain any ionic liquids to increase conductivity, as described, for example, in EP2635638A1 (US20130299750A1). Furthermore, the molding compositions of the invention preferably do not contain any metals in elemental form.

[0051] The molding compositions of the invention are preferably free of plasticizers, preferably low-molecular-weight plasticizers. Plasticizers in this sense are listed in DIN EN ISO 1043-3:2017 and also include, for example, esters of p-hydroxybenzoic acid with 2 to 20 carbon atoms in the alcohol component or amides of arylsulfonic acids with 2 to 12 carbon atoms in the amine component, preferably amides of benzenesulfonic acid; ethyl p-hydroxybenzoate, octyl p-hydroxybenzoate, i-hexadecyl p-hydroxybenzoate, n-octyl toluenesulfonamide, n-butyl benzenesulfonamide, or 2-ethylhexyl benzenesulfonamide.

[0052] The molding composition according to the invention is preferably produced from the individual components by melt mixing in a kneading unit, i.e. by applying shear forces.

[0053] The present invention therefore also relates to a process for producing the molding composition according to the invention, in which the individual components are mixed by melt mixing.

[0054] The individual components of the composition according to the invention can be added simultaneously or sequentially. Although, in preferred embodiments, the filler can first be dispersed in component A or B (particularly in component B) as part of masterbatch production, with the masterbatch produced then being subsequently diluted with the respective component B or A not present in the masterbatch, a process for producing the molding composition according to the invention in which the individual components A, B, and filler are mixed simultaneously by melt mixing is very particularly preferred. Any further components of the molding composition according to the invention can be added at the same time as components A, B, and filler, or thereafter.

[0055] Preferred carbon nanotubes typically have the shape of tubes formed from graphite layers. The graphite layers are arranged concentrically around the cylinder axis. Carbon nanotubes are also referred to as carbon nanofibrils. They have a length-to-diameter ratio of at least 5, preferably at least 100, particularly preferably at least 1,000. The diameter of the nanofibrils is typically in the range of 0.003 to 0.5 µm, preferably in the range of 0.005 to 0.08 µm, particularly preferably in the range of 0.006 to 0.05 µm. The length of the carbon nanofibrils is typically 0.5 to 1,000 µm, preferably 0.8 to 100 µm, particularly preferably 1 to 10 µm. The carbon nanofibrils have a hollow, cylindrical core. This cavity typically has a diameter of 0.001 to 0.1 µm, preferably a diameter of 0.008 to 0.015 µm.In a typical embodiment of carbon nanotubes, the fibril wall surrounding the cavity consists of, for example, eight graphite layers. The carbon nanofibrils can be present as agglomerates of up to 1,000 µm in diameter, composed of multiple nanofibrils. The agglomerates can have the shape of bird's nests, combed yarn, or open network structures. The synthesis of carbon nanotubes takes place, for example, in a reactor containing a carbon-containing gas and a metal catalyst, as described, for example, in US5643502A.

[0056] In addition to multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs) can also be used according to the invention. SWCNTs typically have a diameter in the range of a few nanometers, but reach considerable lengths relative to their cross-section, typically in the range of several micrometers. The structural design of SWCNTs is derived from monoatomic graphite layers (graphene), which can be imagined rolled up into a seamless cylinder. SWCNTs can be excellent electrical conductors. The achievable current densities of 10 9 < A / cm 2 < are about 1000 times higher than those of metal wires made of copper or silver. The production of SWCNTs is described, for example, in US5424054.

[0057] Furthermore, a molding compound is preferred which contains at least 70% by weight, particularly preferably 80% by weight and especially preferably at least 90% by weight of a semi-crystalline polyamide component and the molding compound contains a filler which imparts conductivity to the molding compound, characterized in that the molding compound does not have a crystallite melting point below 50°C, wherein the polyamide component contains components A and B, A PA homopolymer of the type PA XY or PA Z , where X is a diamine residue (DA), Y is a dicarboxyl residue (DC), and Z is an alpha-omega-amino acid residue; B PA copolymer of the type PA X'.Y' where X' is a diamine residue (DA') and Y' is a dicarboxyl residue (DC'); where some of the diamine residues (DA') are replaced by a polyether which has two amino termini or two hydroxy termini; where the proportion of polyether in the sum of components A and B is between 0.5 and 15 wt.% and where the proportion of filler is 2.5 to 6 wt.%, based on the total mass of polyamide component and filler; where the PA homopolymer can be formed from up to 10 mol% of other amide-forming building blocks; wherein the PA copolymer of component B has a polyether content of 8 to 30 wt.%, based on the total mass of the PA copolymer.

[0058] Furthermore, a molding compound is preferred which contains at least 70% by weight, particularly preferably 80% by weight and especially preferably at least 90% by weight of a semi-crystalline polyamide component and the molding compound contains a filler which imparts conductivity to the molding compound, characterized in that the molding compound does not have a crystallite melting point below 50°C, wherein the polyamide component contains components A and B, A PA homopolymer of the type PA XY or PA Z , where X is a diamine residue (DA), Y is a dicarboxyl residue (DC), and Z is an alpha-omega-amino acid residue; B PA copolymer of the type PA X'.Y' where X' is a diamine residue (DA') and Y' is a dicarboxyl residue (DC'); where some of the diamine residues (DA') are replaced by a polyether which has two amino termini or two hydroxy termini; where the proportion of polyether in the sum of components A and B is between 0.5 and 15 wt.% and where the proportion of filler is 2.5 to 6 wt.-%, based on the total mass of polyamide component and filler; wherein the PA homopolymer can be formed from up to 10 mol% of other amide-forming building blocks; wherein the polyether has a number-average molecular weight M n of at most 5000 g / mol; wherein the chain lengths of the PA copolymer and the PA homopolymer of the polyamide component differ on average by no more than 10% with respect to the number of carbon atoms of the amide-forming building blocks, wherein the deviation is related to the higher value of the chain lengths.

[0059] Furthermore, a molding compound is preferred which contains at least 70% by weight, particularly preferably 80% by weight and especially preferably at least 90% by weight of a semi-crystalline polyamide component and the molding compound contains a filler which imparts conductivity to the molding compound, characterized in that the molding compound does not have a crystallite melting point below 50°C, wherein the polyamide component contains components A and B, A PA homopolymer is selected from PA 6, PA 11, PA 12, PA 4.6, PA 6.6, PA 6.9, PA 6.10, PA 6.12, PA 9.10, PA 9.12, PA 10.10, PA 10.12, PA 12.12; B PA copolymer, of the type PA X'.Y' where X' stands for a diamine radical (DA') and Y' stands for a dicarboxyl radical (DC'); wherein some of the diamine radicals (DA') are replaced by a polyether which has two amino termini or two hydroxy termini; wherein the proportion of polyether in the sum of components A and B is between 0.5 and 15 wt.% and wherein the proportion of filler is 2.5 to 6 wt.-%, based on the total mass of polyamide component and filler; where the PA homopolymer can be formed from up to 10 mol% of other amide-forming building blocks; where the molding compound has a degree of crystallinity which is lower than the degree of crystallinity of a mixture which has the same components A and filler for increasing the conductivity in the same amounts, where any further constituents of the molding compound are also identical in identity and amount.

[0060] The molding compositions according to the invention preferably contain further additives.

[0061] Preferred additives are oxidation stabilizers, UV stabilizers, hydrolysis stabilizers, impact modifiers, pigments, dyes and / or processing aids.

[0062] In a preferred embodiment, the molding compositions contain an effective amount of an oxidation stabilizer, and more preferably, an effective amount of an oxidation stabilizer in combination with the effective amount of a copper-containing stabilizer. Suitable oxidation stabilizers include, for example, aromatic amines, sterically hindered phenols, phosphites, phosphonites, thiosynergists, hydroxylamines, benzofuranone derivatives, acryloyl-modified phenols, etc. Such oxidation stabilizers are commercially available in a variety of types, for example under the trade names Naugard 445, Irganox 1010, Irganox 1098, Irgafos 168, P-EPQ, or Lowinox DSTDP. Generally, the molding compositions contain about 0.01 to about 2 wt.%, and preferably about 0.1 to about 1.5 wt.%, of an oxidation stabilizer.

[0063] In addition, the molding compounds can also contain a UV stabilizer or a HALS-type light stabilizer. Suitable UV stabilizers are primarily organic UV absorbers, such as benzophenone derivatives, benzotriazole derivatives, oxalanilides, or phenyltriazines. HALS-type light stabilizers are tetramethylpiperidine derivatives; these are inhibitors that act as free radical scavengers. UV stabilizers and light stabilizers can be used advantageously in combination. Both are commercially available in a variety of types; the manufacturer's instructions can be followed regarding dosage.

[0064] The molding compositions may additionally contain a hydrolysis stabilizer such as a monomeric, oligomeric or polymeric carbodiimide or a bisoxazoline.

[0065] The molding compounds can also contain impact modifiers. Impact-modifying rubbers for polyamide molding compounds are state of the art. They contain functional groups derived from unsaturated functional compounds that are either polymerized into the main chain or grafted onto the main chain. The most common are EPM or EPDM rubbers radically grafted with maleic anhydride. Such rubbers can also be used together with an unfunctionalized polyolefin such as isotactic polypropylene, as described in EP0683210A2 (US5874176A).

[0066] Suitable pigments and / or dyes are, for example, iron oxide, zinc sulfide, ultramarine, nigrosine, pearlescent pigments.

[0067] Suitable processing aids include paraffins, fatty alcohols, fatty acid amides, stearates such as calcium stearate, paraffin waxes, montanates or polysiloxanes.

[0068] Multilayer hollow profiles according to the invention have at least one layer made from the molding compounds according to the invention that is in direct contact with a liquid. This is preferably the innermost layer of the hollow body.

[0069] The liquid is preferably a mixture of chemical substances containing hydrocarbons and at least one alcohol, more preferably the liquid is a fuel that is suitable as a propellant for internal combustion engines, particularly preferably the fuel is a motor vehicle fuel such as diesel or gasoline.

[0070] The fuel preferably contains alcohols with 1 to 8 carbon atoms, more preferably methanol, ethanol, propanol, butanol, or pentanol. The alcohols with at least three carbon atoms can be present in their n-form, i.e., linear and with a terminal hydroxy group, or in their various iso-forms. The hydroxy group can be primary, secondary, or tertiary, preferably primary. More preferably, at least 80 vol.% of the alcohols are linear hydrocarbons with a terminal hydroxy group.

[0071] The fuels preferably contain at least 7 vol.%, more preferably at least 10 vol.%, particularly preferably at least 13 vol.%, especially preferably at least 16 vol.% alcohol.

[0072] The single- or multi-layer hollow body according to the invention is preferably a pipe or container, preferably a component of a fuel-carrying system, preferably a fuel line or a fuel tank.

[0073] The layer produced from the molding compounds of the invention, which is preferably in contact with the liquid, is electrically conductive. The hollow body has a specific surface resistance of a maximum of 10 9 < Ω / square and preferably a maximum of 10 6 < Ω / square. Suitable measurement methods are known in the art; the specific surface resistance is preferably determined as explained in SAE J 2260 of November 2004.

[0074] A preferred multilayer hollow body according to the invention has a so-called barrier layer. This barrier layer has a very low diffusion coefficient for the fuel components. Suitable materials for the barrier layer are fluorocarbons and vinyl alcohol polymers. The preferred multilayer hollow body preferably has a so-called EVOH barrier layer. EVOH is a copolymer of ethylene and vinyl alcohol. The ethylene content in the copolymer is preferably 20 to 45 mol% and in particular 25 to 35 mol%. Numerous types are commercially available. For example, reference is made to the company publication "Introduction to Kuraray EVAL™ Resins," Version 1.2 / 9810 from Kuraray EVAL Europe. In addition to EVOH, the barrier layer can contain other additives, as is customary for barrier layer applications, according to the state of the art. Such additives are generally the expertise of the EVOH supplier.

[0075] The preferred multilayer hollow body according to the invention has a barrier layer (SpS) and, as the innermost layer (Si), a layer made from the molding compositions according to the invention, wherein the hollow body has a specific surface resistance of at most 10 6< Ω / square according to SAE J 2260 of November 2004.

[0076] Additional layers can be arranged between the barrier layer (SpS) and the innermost layer (Si) of the preferred multilayer hollow body, preferably at least one layer (HVi), which ensures adhesion between Si and SpS. Preferably, only one adhesion-promoting layer is arranged between SpS and Si. If the adhesion between SpS and Si is sufficiently strong, the adhesion-promoting layer (HVi) can, of course, be omitted.

[0077] Adhesion promoters between the barrier layer and the layer of the molding composition according to the invention are known to the person skilled in the art; preferred adhesion promoters are based on polyamides, preferably mixtures of PA 6.12 and PA 6, particularly preferably impact-modified polyamides and especially preferably containing 60 to 80% by weight of PA 6.12, 10 to 25% by weight of PA 6 and 5 to 15% by weight of impact modifier, the mass fractions being selected such that their sum amounts to 100% by weight.

[0078] Layers arranged on the inside of the barrier layer in the preferred hollow body according to the invention are preferably free of plasticizers as defined above. Furthermore, these layers preferably contain only the absolutely necessary amount of additives, such as stabilizers and processing aids.

[0079] The preferred hollow body according to the invention preferably has at least one further layer extending from the barrier layer outwards. These outer layers are preferably also layers containing at least 50 wt.%, more preferably at least 60 wt.%, even more preferably at least 70 wt.%, particularly preferably at least 80 wt.%, and especially preferably at least 90 wt.% polyamides.

[0080] These polyamides are preferably PA homopolymers of the type PA XY or PA Z, as already described above. Preferably, the PA homopolymer of the outer layer (Sa) of the preferred hollow body is not identical to that of the innermost layer (Si). Preferably, the PA homopolymer of the outer layer (Sa) is a PA of the type PA Z, particularly preferably a PA11 or PA12, especially preferably a PA12.

[0081] Additional layers can be arranged between the outer layer (Sa) and the barrier layer (SpS) of the preferred hollow body according to the invention, preferably at least one layer (HVa), which ensures adhesion between Sa and SpS. Preferably, only one adhesion-promoting layer is arranged between Sa and SpS. If the adhesion between Sa and SpS is sufficiently high, the adhesion-promoting layer (HVa) can, of course, be omitted.

[0082] The adhesion-promoting layer (HVa) is preferably free of plasticizers as defined above. Furthermore, this layer preferably contains only the necessary amount of additives, such as stabilizers and processing aids.

[0083] Preferably, the adhesion promoter layers HVi and HVa are identical in their chemical composition.

[0084] Also preferred are multilayer hollow profiles which have at least one layer consisting of the molding compound according to the invention, said layer being in direct contact with a liquid; and which further have at least one barrier layer.

[0085] Also preferred are multilayer hollow profiles which have at least one layer consisting of the molding compound according to the invention, which further have at least one barrier layer made of fluorocarbons or vinyl alcohol polymers; wherein layers arranged in the hollow body on the inside of the barrier layer are free of plasticizers.

[0086] The hollow profile according to the invention can also be coated with an additional elastomer layer. Both cross-linked rubber compounds and thermoplastic elastomers are suitable for the coating. The coating can be applied to the multilayer composite with or without the use of an additional adhesion promoter, for example, by coextrusion, extrusion via a crosshead, or by sliding a prefabricated elastomer tube over the fully extruded multilayer pipe. The coating typically has a thickness of 0.1 to 4 mm, and preferably 0.2 to 3 mm.

[0087] Suitable elastomers include chloroprene rubber, ethylene / propylene rubber (EPM), ethylene / propylene / diene rubber (EPDM), epichlorohydrin rubber (ECO), chlorinated polyethylene, acrylate rubber, chlorosulfonated polyethylene, silicone rubber, plasticized PVC, polyetheresteramides or polyetheramides.

[0088] The multi-layer composite can be manufactured in one or more stages, for example by means of single-stage processes using multi-component injection molding, coextrusion, coextrusion blow molding (e.g. also 3D blow molding, tube extrusion into an open mold half, 3D tube manipulation, suction blow molding, 3D suction blow molding, sequential blow molding) or by means of multi-stage processes, as described, for example, in US5554425.

[0089] The invention will be explained by way of example in the following experimental part.

[0090] The following components or molding compounds were used in the examples: PA Homopolymer 1 An extrusion molding compound based on PA 6.12 from EVONIK Resource Efficiency GmbH (VESTAMID D22) PA Homopolymer 2 An extrusion molding compound based on PA 10.10 from EVONIK Resource Efficiency GmbH (VESTAMID DS22) PA Homopolymer 3 An extrusion molding compound based on PA 12 from EVONIK Resource Efficiency GmbH (VESTAMID L1901) PEBA 1 An extrusion molding compound based on PA 6.12 from EVONIK Resource Efficiency GmbH, containing 25 wt. % of a bisamino-terminated polyether with a molecular weight of 400 g / mol (Elastamin RP-405, Huntsman) PEBA 2 An extrusion molding compound based on PA 10.10 from EVONIK Resource Efficiency GmbH, containing 35.4 wt.% of a bishydroxy-terminated polyether (polytetrahydrofuran) with a molecular weight of 650 g / mol PEBA 3 An extrusion molding compound based on PA 12 from EVONIK Resource Efficiency GmbH, containing 29 wt.% of a bishydroxy-terminated polyether (polytetrahydrofuran) with a molecular weight of 1000 g / mol is EVAL An EVOH from Kuraray with 27 mol% ethylene (EVAL LA170B) IN THE Impact modifier: Exxelor VA1803 (9%) + 1% Lotader AX8900 stabilizer Mixture of Irgafos and Irganox. Adhesion promoter An extrusion molding compound based on PA 6.12 from EVONIK Resource Efficiency GmbH (VESTAMID SX8002 or VESTAMID SX8080; SX8080 has the same characteristics as SX8002, but without plasticizer) Example 1, molding compounds:

[0091] The following molding compounds were compounded by melt mixing the components in a Haake kneader (HAAKE Rheomix 600 OS). Table 1: Composition of the molding compounds of Example 1. PEBA means PA copolymer, PE means polyether, CNT means carbon nanotubes; the PE content means the weight fraction of the polyether in the molding compound, without taking into account the mass of the CNT; the CNT content is the mass fraction based on the total molding compound molding compound PA homopolymer PEBA PE content [wt.%] CNT content [wt.%] 1 1 0 0 0 11 1 0 0 3 12 1 1 4,25 0 13 1 1 4,25 3 14 0 1 25 0 15 1 1 21 0 2 2 0 0 0 21 2 0 0 3 22 2 2 4,25 0 23 2 2 4,25 3 24 0 2 35,4 0 3 3 0 0 0 31 3 0 0 3 32 3 3 4,25 0 33 3 3 4,25 3 34 3 3 2,15 0 35 3 29 0

[0092] The molding compounds 13 and 33 are according to the invention. Example 2, Determination of thermal properties:

[0093] Using DSC in accordance with ISO 11357 (Perkin Elmer) at a rate of 20K / min, the glass transition temperature T g and the crystallite melting points T m were determined during the first heating, and the degree of crystallinity Xc was calculated from the determination of the enthalpy of fusion during the second heating. Table 2: Determination of thermal properties according to Example 2; nb means the value was not determined molding compound Tg [°C] T m [°C] Xc [%] 1 41 215 38 11 39 216 45 12 37 216 37 13 39 216 44 14 43 0 / 163 / 197 32 15 38 0 / 184 / 195 / 206 31 2 41 200 41 21 37 198 45 22 37 200 43 23 42 198 43 24 42 -23 / 186 32 3 38 178 32 31 40 179 37 32 37 179 36 33 40 179 36 34 40 177 32 35 35 -22 / 167 24

[0094] In all cases, it can be observed that the degree of crystallinity Xc increases upon addition of the carbon nanotubes to the base polymer. Furthermore, it can be observed in all cases that the crystallinity Xc can be reduced if a small portion of the base polymer is replaced with a PEBA. The molding compounds according to the invention do not have a crystallite melting point below 50°C; this also applies to molding compound 34, which has a lower polyether content. Example 3, production of hollow profiles:

[0095] Five-layer pipes with an outer diameter of 8 mm and a total wall thickness of 1 mm were produced by coextrusion on a multi-layer pipe line from Bellaform.

[0096] The comparison example differs only in the composition of the inner layer (layer I) Table 3: Layer configuration of the hollow profiles according to Example 3 according to the invention Layer V VESTAMID LX9002 outer layer 0.45 mm Layer IV Adhesion promoter, exterior Adhesive layer 0.1 mm Layer III EVAL barrier layer 0.15 mm Layer II Adhesion promoter, inside Adhesive layer 0.1 mm Layer I Extrusion molding compound based on PEBA 1 inner layer 0.2 mm Composition: Molding compound 13 89.5% by weight IN THE 10 wt.% stabilizer 0.5 wt.% Comparison Layer I Extrusion molding compound based on PA homopolymer 1 Composition: inner layer 0.2 mm Molding compound 11 89.5% by weight IN THE 10 wt.% stabilizer 0.5 wt.% Example 4: Examinations:

[0097] Pipes of Example 3 were subjected to the following tests. a) Tensile test (with MLT): The mono- and multi-layer pipes were tested in accordance with DIN EN ISO 527-1 at a pull-off speed of 100 mm / min. The test specimens were approximately 200 mm long, the clamping length was 100 mm, and the spacing between the strain gauges was 50 mm. b) Impact tests: The impact strength of the mono- and multi-layer pipes was measured at 23 °C according to DIN 73378. The impact strength of the mono- and multi-layer pipes was measured at -25 °C according to VWTL52435 using a drop hammer with a mass of 880 g. The impact strength of the mono- and multi-layer pipes was measured at -40 °C according to SAE J2260 using a drop hammer with a mass of 500 g. For all tests, 10 test pieces of approximately 100 mm in length were measured. After exposure, a visual inspection for damage was carried out. c) Separation test: The separation test was carried out using a tensile testing machine of type BZ 2.5 / TN1S from Zwick, to which a tensile device and a rotating metal pulley are attached in order to separate the individual layers of the test specimens. The separation test, based on DIN EN ISO 2411, assessed the adhesion between two layers by measuring the force required to separate the two layers. For this purpose, 20 cm long sections of the multi-layer pipes were cut lengthwise into thirds using a cutting device. Before starting the measurement, the specimen width was measured several times at different points using a caliper, and the average value was used for evaluation. The cut end of one layer was then clamped in a clamp, which continuously pulled it away from the second layer at an angle of 90°.The layers were peeled away from each other at a test speed of 50 mm / min and, at the same time, a graph was recorded showing the required force in Newtons versus distance in millimeters. From this, the separation resistance in N / mm, which relates to the width of the adhesive contact surface, was determined in the plateau region. d) Fuel permeability: The permeation measurement was used to determine how much fuel permeates through a fuel line per day and meter of pipe or square meter of internal pipe surface during static storage at 60°C. For this purpose, 300 mm long pipe sections were screwed to a pressure-resistant storage vessel at one end, weighed, then filled with 300 ml of CM 15 and the other end closed. These test specimens were stored in an explosion-proof heating cabinet with forced ventilation at 60°C.The filled tubes were weighed again to determine the mass loss and thus the permeated fuel mass at specific intervals. The effective permeation length was 285 mm. e) Leachate resistance: The leachate determination was used to determine how many g / m² of soluble and insoluble components were extracted from the multilayer composite after fuel storage. For this purpose, a 2 m long section of tube was completely filled with the test fuel CM15 and stored at 60 °C for 96 h. After cooling, the tube was emptied into a beaker and rinsed with 20 ml of CM 15. The resulting liquid was stored at 23 °C for 24 h. The test liquid was then filtered under vacuum at 23 °C and rinsed with 20 ml of CM 15. The filtered medium was allowed to evaporate in a fume hood at room temperature. The soluble extracts were then determined by weighing.The filter was dried for 24 hours at 40°C and weighed. The insoluble extracts were determined using the difference to the original weight of the filter. The test is considered passed if less than 6 g / m² of soluble and less than 0.5 g / m² of insoluble components were washed out. f) Describe the heat aging procedure for the MLTs (circulating air oven, 200 hours at 150°C and 1 hour at 170°C). Approximately 100 or 200 mm long pipe sections of the corresponding mono- or multi-layer pipes were stored at elevated temperatures for defined times in a circulating air oven. Care must be taken to ensure that the pipe sections hang freely in the circulating air oven without touching each other or the metal surfaces. The length of the pipe sections depends on the subsequent mechanical test. As described under b), test specimens approximately 100 mm long were used for pipe impact tests.After storage at 150°C for 200 hours followed by conditioning in a standard atmosphere of 23°C / 50% relative humidity for > 24 hours, a pipe impact test is performed as described under b). The pipe impact test is performed analogously on pipe sections that were previously stored at 170°C for 1 hour. g) Determination of insulation resistance and its change due to fuel storage with CM15, CE10, and FAM B at 60°C. The electrical resistance was determined on at least three 42 cm long pipe sections according to SAE J2260-1996. For this purpose, the inner surfaces of the pipes were contacted at the pipe ends with plugs of defined length and diameter. Using test voltages between 10 V and 500 V, the electrical resistance was measured in the range from 10 2 < to 10 14 < Ω and converted to the required surface resistance using the unit "ohm per square" based on the pipe's inner surface between the plugs.The pipe sections were then screwed to a storage container at one end and weighed, then filled with 300 ml of test fuel (CM15) and the other end closed. The pipe is located below the storage container so that the inner surface of the pipe was completely filled with fuel during storage and the electrical measurements. The inner layer was contacted via the metal pipe fittings with support sleeves at the pipe ends and the resistance was determined immediately after filling. The test specimens were stored in an explosion-proof heating cabinet with forced ventilation at 60 °C and cooled to 23 °C at regular intervals. The change in electrical resistance was determined for a test period of approximately 1000 hours. In parallel with the electrical resistance, the absolute length of the free pipe section was determined using a tape measure between the pipe fittings and the change in length was determined using a dial indicator in the range 0 to 5 %.

[0098] The test is passed if the resistance is determined to be less than 10 6< Ohm / area. The composition of the test fuels CE10 and CM 15 and FAM B are in the references of SAE J2260-1996; CM 15 corresponds to ASTM D471-15, "Reference Fuel I" (isooctane / toluene, methanol); FAM B corresponds to the test liquid according to DIN 51604-2 (1984); CE10 corresponds to a mixture of "Fuel C" according to ASTM D471-15 plus 10 ± 1 vol.% ethanol.

[0099] The results are presented in Table 4. Table 4: Test results of the pipes according to Example 3 Test according to the invention Comparison Ageing resistance at 150°C for 200 h (DIN 53497) followed by pendulum impact according to ISO 179-1 at RT no break 10 out of 10 broken Cold impact at -25°C / 880 g no break 1 out of 10 broken Cold impact at -40°C / 500 g no break 2 out of 10 broken Washout resistance according to point e) passed not determined Insulation resistance according to point g) passed failed Fuel permeability according to point d) 4.3 g / (m 2< *d) n. determined Example 5 - Molding compounds with different filler contents

[0100] First, a filler-containing masterbatch is produced using a Nanocyl twin-screw extruder based on a polyether-modified polyamide (PA612.6T, ground powder) with a concentration of 10% CNT.

[0101] The masterbatch is then diluted on the twin-screw extruder with the addition of polyamide, impact modifier, stabilizer, and colorant. This produces molding compounds with the components and filler contents shown in Table 5. Table 5 - Recipes composition 1 2 3 Wt.% CNT (based on total mass of polyamide component and filler) 3,68 4,91 7,36 Plasticyl Masterbatch (10 wt.% CNT) 30 40 60 Vestamid Htplus 51,5 41,5 21,5 Impact modifiers 15 15 15 stabilizer 1,5 1,5 1,5 Vestamid FG black 2 2 2

[0102] Test specimens are made from the molding compounds. For the impact test, these are injection-molded / multipurpose bars measuring 170x10x4 mm 3< . For the electrical test, 1 mm thick tapes are extruded.

[0103] The following Table 6 shows the results of the impact tests and the electrical tests including the measuring conditions. Table 6 - Examinations composition 1 2 3 Wt.% CNT (based on total mass of polyamide component and filler) 3,68 4,91 7,36 Notched impact strength according to ISO179 1-eA at 23°C (in kJ / m 2< ) 105,4 (P) 102,31 (P) 82,45 (P) Specific resistance based on SAE J2260, measured on the extruded ribbon (in ohm / square) 1,51E+13 3,45E+10 1,73E+05

[0104] The decrease in impact strength above 6% is clearly visible. Furthermore, the resistivity is too high below 2.5%.

Claims

1. Moulding compound comprising at least 50% by weight of a semicrystalline polyamide component and comprising a filler that imparts conductivity to the moulding compound, characterized in that the moulding compound does not have a crystallite melting point (T)m below 50°C, where the polyamide component comprises components A and B A PA homopolymer of the PA X.Y or PA Z type, where X represents a diamine residue (DA), Y represents a dicarboxyl residue (DC), and Z represents an alpha,omega-amino acid residue; B PA copolymer of the PA X'.Y' type where X' represents a diamine residue (DA') and Y' represents a dicarboxyl residue (DC'); where some of the diamine residues (DA') are replaced by a polyether having at least two amino termini or at least two hydroxy termini, where the PA copolymer has a polyether content of 8% to 30% by weight, based on the total mass of the PA copolymer; where the proportion of polyether in the sum total of components A and B is between 0.5% and 15% by weight, and where the proportion of filler is 2.5% to 6% by weight, based on the total mass of polyamide component and filler, and the filler is CNT; where up to 10 mol% of the PA homopolymer may be formed from other amide-forming units; where up to 10 mol% of the diamine residues (DA') may be replaced by a polyether having just one amino terminus or just one hydroxy terminus; wherein conductivity is determined according to Example 4 section g), and melting points by means of DSC according to Example 2.

2. Moulding compound according to Claim 1, wherein the polyether has a number-average molecular weight Mn of not more than 5000 g / mol.

3. Moulding compound according to either of Claims 1 and 2, wherein the chain lengths of the PA copolymer and of the PA homopolymer of the polyamide component differ from one another by an average of not more than 10% in relation to the number of carbon atoms in the amide-forming units, where the difference is based on the higher value of the chain lengths.

4. Moulding compound according to any of Claims 1 to 3, characterized in that it has a degree of crystallinity lower than the degree of crystallinity of a mixture including the same components A and filler for increasing conductivity in equal amounts, where any further constituents of the moulding compound are likewise identical in identity and amount; where the degree of crystallinity is calculated by equation (1) X C = Δ H m Δ H m 0 wherein the enthalpy of fusion of the numerator is determined according to Example 2, and the enthalpy of the denominator is taken from tabular works as cited in the description on page 8.

5. Moulding compound according to any of Claims 1 to 4, characterized in that it is free of plasticizers.

6. Use of a moulding compound according to any of Claims 1 to 5 for production of hollow profiles.

7. Single-layer or multilayer hollow profiles having at least one layer consisting of a moulding compound according to any of Claims 1 to 5.

8. Single-layer or multilayer hollow profiles according to Claim 7, having at least one barrier layer.

9. Single-layer or multilayer hollow profiles according to either of Claims 7 and 8, wherein layers arranged on the inside of the barrier layer in the hollow body are free of plasticizers.

10. Process for producing a moulding compound according to any of Claims 1 to 5, characterized in that the individual constituents are mixed by melt mixing.

11. Process according to Claim 10, characterized in that constituents A and B and the filler are mixed simultaneously with one another.