DE102017221467A1 - Multi-layer composite and fluid line - Google Patents

Abstract

The invention relates to a multi-layer composite (2), in particular for a fluid line (1), and a corresponding fluid line (1). The multilayer composite (2) has a first layer (5) made of a fluoropolymer, a second layer (6) made of a partially aromatic polyamide directly following the first layer (5) and a third layer (7) immediately following the second layer (6) ) of an ethylene-vinyl alcohol copolymer and / or an aliphatic polyamide.

Description

The invention relates to a multilayer composite, in particular for a fluid line, and further to a fluid line made of a multilayer composite.

From the prior art, for example, the publication EP 1 162 061 A1 known. This relates to a thermoplastic multilayer composite, in particular in the form of a multilayer tube, a multilayer tube or a multilayer container containing at least one intermediate layer of a molding composition based on ethylene-vinyl alcohol copolymers between layers of molding compositions based on polyamide, wherein the intermediate layer via at least one adhesion-promoting layer from a molding composition based on polyamide, selected from the group consisting of copolyamide 6/12, block copolyamide 6/12, polyamide 612, polyamide 610, mixture of polyamide 6 and polyamide 12 with compatibilizer, mixture of polyamide 6 and polyamide 11 with compatibilizer, is bonded to at least one secondary layer of a molding compound based on polyamide 12, polyamide 11, polyamide 10/10, polyamide 10/12 or polyamide 12/12.

Furthermore, the document shows WO 2006/040206 A1 a multi-layer composite comprising the following layers: an inner layer selected from a fluoropolymer molding composition and a polyolefin molding composition; a primer layer having the following composition: a) 0 to 80 parts by weight of a polyamine-polyamide graft copolymer, b) 0 to 100 parts by weight of polyamide, c) 0 to 85 parts by weight of a polymer selected from fluoropolymers and polyolefins, the sum of the parts by weight of a), b) and c) gives 100, and wherein additionally in the sum of components a) and b) at least 20 parts by weight consist of monomer units derived from caprolactam and / or the combination hexamethylenediamine / adipic acid, hexamethylenediamine / suberic acid, hexamethylenediamine / Derive sebacic acid, hexamethylenediamine / dodecanedioic acid, hexamethylenediamine / isophthalic acid or hexamethylenediamine / terephthalic acid; d) a maximum of 50 parts by weight of additives selected from impact-modifying rubber and / or customary auxiliaries or additives; a layer of an EVOH molding compound.

Furthermore, the document shows DE 10 2013 013 163 A1 a multilayer composite having volatile organic compound barrier properties comprising first and second surfaces and comprising at least a first layer and at least one further layer. It is provided that one of the two layers comprises at least one adsorption material for volatile organic compounds and at least one polymeric carrier material in admixture or in combination with the adsorption material, wherein for the case that the at least one adsorbent material and the at least one polymeric carrier material are present in the composite in that the composite material comprises at least three layers, wherein the polymeric carrier material is selected from the group consisting of elastomers, thermoplastics and thermoplastic elastomers and mixtures thereof.

Finally, the document describes WO 2007/019921 A1 a hollow body comprising an inner layer and an outer layer, each made of a thermoplastic material, and two barrier layers provided between the inner layer and the outer layer. The two barrier layers should be connected directly to each other.

It is an object of the invention to propose a multilayer composite, in particular for a fluid line, which has advantages over known multilayer composites, in particular is inexpensive to produce and also extremely resistant, so that high permeation requirements are met in connection with high temperature requirements.

This is achieved according to the invention with a multi-layer composite with the features of claim 1. It is provided that the multi-layer composite comprises: a first layer of a fluoropolymer, a second layer of a partially aromatic polyamide immediately following the first layer and a third layer of an ethylene-vinyl alcohol copolymer immediately following the second layer and / or an aliphatic polyamide.

The multi-layer composite, which is particularly preferably used for producing or forming the fluid line, has at least three layers, namely the first layer, the second layer and the third layer. The layers mentioned each follow one another directly, so that therefore the second layer directly adjoins the first layer and the third layer directly adjoins the second layer. In other words, the second layer is arranged between the first layer and the third layer and rests on the one hand on the first layer and on the other hand on the third layer. Preferably, the first layer and / or the second layer and / or the third layer are each of a material-uniform design, so that the respective layer consists completely and continuously of the respectively designated material.

The first layer consists at least partially, but preferably completely, of the Fluoropolymer. By the fluoropolymer is meant a fluorinated polymer. It is characterized by a high resistance to chemicals and high temperatures, in other words by a high chemical resistance and / or high temperature resistance. The fluoropolymer can basically be configured as desired. For example, it is in the form of ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) or polychlorotrifluoroethylene (PCTFE).

The second layer consists of the partly aromatic polyamide. By this is meant a partially crystalline aromatic polyamide, which may also be referred to as polyphthalamide (PPA). The partially aromatic polyamide may be reinforced to improve its mechanical strength and to this end have an additive or a fiber reinforcement. The additive used is, for example, ground glass or ground silicon dioxide. The fiber reinforcement is in the form of, for example, a glass fiber reinforcement, a carbon fiber reinforcement or an aramid fiber reinforcement. However, the second layer or the partly aromatic polyamide can also be designed without reinforcement.

The third layer, in turn, consists of either the ethylene-vinyl alcohol copolymer or the aliphatic polyamide. The ethylene-vinyl alcohol copolymer (also abbreviated EVAL or EVOH) is a copolymer which is formally composed of the monomers ethylene and vinyl alcohol. The ethylene-vinyl alcohol copolymer is a low-cost barrier material with good barrier to volatile organic compounds. The aliphatic polyamide has a monomer which is derived from aliphatic bases, for example from a lactam, in particular an epsilon-caprolactam, or from hexamethylenediamine and adipic acid. The aliphatic polyamide is, for example, in the form of PA6, PA66 or PA666.

It may be provided that the multi-layer composite consists exclusively of the three layers mentioned, so that the first layer and the third layer are each present as an outer layer or, in the case of the fluid line, the first layer is present as the inner layer and the third layer as the outer layer. Especially in the latter case, therefore, the first layer serves to guide a fluid in the fluid conduit, taking advantage of the excellent durability of the fluoropolymer.

The multi-layer composite described, consisting of the three layers, has excellent strength properties and high durability. However, it may be provided to add at least one further layer to the multi-layer composite in addition to the already mentioned three layers. Preferably, however, the first layer always represents the outer layer or, in the case of the fluid line, the inner layer. The first layer is always followed by the second layer and the third layer, wherein the second layer directly adjoins the first layer and the third layer directly adjacent to the second layer.

An exemplary multi-layer composite of the first layer, the second layer, and the third layer at least having the ethylene-vinyl alcohol copolymer in this case may also be referred to as a three-layer barrier system which is resistant to permeation, oligomer leaching, and water. Regardless of its configuration, the multilayer composite preferably serves to produce the fluid line. However, it can also be used to form any other hollow body, such as a fluid container or the like.

A further embodiment of the invention provides that the fluoropolymer of the first layer is enriched with carbon in order to improve the electrostatic conductivity of the first layer. The electrostatic conductivity serves to realize a potential equalization. This is particularly important in the case of the fluid line, if it is used for organic compounds, in particular carbon-containing compounds. In this case sparking due to too high potential difference should be avoided. This can be achieved in a particularly simple manner by means of a corresponding configuration of the first layer. For this purpose, the fluoropolymer is enriched with carbon, so that the fluoropolymer or the first layer has the desired conductivity. For example, the fluoropolymer is said to be carbon enriched to have a sheet resistance of at least 10 ⁵ ohms / square, at least 5 × 10 ⁶ ohms / square, or at least 10 ⁶ ohms / square. In the latter case, in particular, the rules of Standard SAE J 2260 Fulfills.

A further preferred embodiment of the invention provides that the partially aromatic polyamide of the second layer is a polyphthalamide with a polyamide as the base polymer. The polyphthalamide is a partially crystalline aromatic polyamide, so far a semiaromatic polyamide. The polyphthalamide is characterized by good thermal resistance and low moisture absorption. Also, the chemical resistance and corrosion resistance are very good. In addition, the polyphthalamide has only a small Swelling on so that only small forces can occur at the layer boundaries of the second layer to the materials of the first layer and the third layer.

The use of the polyphthalamide has advantages, in particular in the case of the fluid line, because in this case only slight oligomer leaching occurs. Also, the cold impact strength is better than that of other polyamides. The polyphthalamide adheres to a variety of elastomers and thermoplastics without adhesion promoter. This advantage can be further enhanced by suitable modification or addition of the polyphthalamide. For this purpose, the polyphthalamide is enriched with an additive or an additive. The polyphthalamide has a base polymer which is in the form of the polyamide. For example, the polyamide PA10T / X is used as the base polymer. In this case, the polyphthalamide has a particularly good resistance and is also available at low cost.

Within the scope of a further embodiment of the invention, provision can be made for the second layer and the third layer to be connected to one another with adhesion promoter. Under a primer substances are to be understood that produce a chemical bond between different materials. Such an adhesion promoter may in principle be provided between the first layer and the second layer and / or between the second layer and the third layer in order to better bond the corresponding materials together. The bonding agent is chosen such that it promotes a chemical bond between the two layers. Despite the use of the adhesion promoter, it is spoken so far that the respective layers follow one another directly or lie directly against one another. Thus, in no case is an additional layer of adhesion promoter arranged between the corresponding layers.

However, it is particularly advantageous if it is possible to dispense with the use of the adhesion promoter. This should be the case, at least for the second layer and the third layer, so that they are adhesively bonded together. This is in particular implemented by the use of the partly aromatic polyamide for the second layer. This already has an excellent binding effect against both the ethylene-vinyl alcohol copolymer and the aliphatic polyamide of the third layer.

In addition or as an alternative, it can of course be provided that the first layer and the second layer are adhesively bonded together. This may be the case in particular due to the use of the partially aromatic polyamide for the second layer. Of course, both the first layer and the second layer as well as the second layer and the third layer are particularly preferably connected to one another without adhesion. In this case, a particularly cost-effective production of the multi-layer composite is realized.

A development of the invention provides that immediately following the third layer, a fourth layer of a further polyamide, which intervenes between the first layer and the third layer, follows, which is different from the polyamide of the third layer. In addition to the layers already mentioned, the fourth layer is provided insofar as it consists of the further polyamide. The fourth layer follows directly on the third layer, so it is directly on this. The third layer is disposed between the first layer and the fourth layer such that the first layer and the fourth layer collectively sandwich the third layer.

The further polyamide is preferably different from the aliphatic polyamide from which the third layer consists or can at least exist. If the third layer consists of the ethylene-vinyl alcohol copolymer, then the further polyamide can in principle be chosen as desired, that is also in the form of an aliphatic polyamide. However, it may also be in the form of a partially aromatic polyamide or an aromatic polyamide. Particularly preferred PA6 / 12 or PA12 is used as another polyamide. These polyamides have good mechanical properties, high temperature stability, good mechanical wear resistance and good stress corrosion resistance to chemical thawing agents, in particular ZnCl. They also have a very good adhesion to the materials of the third layer, in particular the aliphatic polyamide. If the fourth layer is present, it preferably forms an outer layer of the multilayer composite or of the fluid line.

A preferred embodiment of the invention provides that the polyamide of the fourth layer is a polyamide of hexamethylenediamine or a polyamide of laurolactam. As an example of the polyamide of hexamethylenediamine, PA6 / 12 is given as an example of the polyamide of laurolactam PA12. On the one hand, these polyamides are extremely resistant and, on the other hand, are available inexpensively, so that an inexpensive production of the multi-layer composite and thus of the fluid line can be realized.

A further preferred embodiment of the invention provides that the third layer is a first sublayer of the ethylene-vinyl alcohol copolymer and a second sublayer of the aliphatic polyamide, wherein the first sublayer immediately follows the second layer and the second sublayer forms an outer layer or directly adjacent to the outer layer. The third layer has in this respect both of the aforementioned materials, namely both the ethylene-vinyl alcohol copolymer and the aliphatic polyamide. For this purpose, the third layer has the first partial layer and the second partial layer. The first sub-layer is arranged between the second layer and the second sub-layer.

The second sub-layer either forms the outer layer, namely on the side of the multi-layer composite facing away from the first layer, or adjoins directly the layer forming the outer layer, for example the fourth layer. Thus, if the fourth layer is present, then the second part-layer is arranged between the first part-layer and the fourth layer and lies directly against each of these. If the fourth layer is present, the multi-layer composite is five-layered, the first layer, the second layer, the third layer and the fourth layer being present and the third layer being divided into the first partial layer and the second partial layer.

The first sublayer consists of the ethylene-vinyl alcohol copolymer and the second sublayer of the aliphatic polyamide. The advantages of using these materials have already been pointed out. The aliphatic polyamide may be enriched with an additive or additive and / or a reinforcing agent. As a reinforcing agent, for example, a fiber reinforcement is used. The fiber reinforcement is in the form of, for example, a glass fiber reinforcement, a carbon fiber reinforcement or an aramid fiber reinforcement. The division of the third layer into the two partial layers has the advantage that the amount of the aliphatic polyamide or the layer thickness of the second partial layer can be chosen such that the multi-layer composite is overall inexpensive to produce.

A preferred embodiment of the invention provides that the fluoropolymer is ethylene-tetrafluoroethylene copolymer, and / or the aliphatic polyamide PA6 or PA666 and / or the further polyamide PA6 / 12 or PA12. The ethylene-tetrafluoroethylene copolymer has good properties with respect to oligomer leaching and is resistant to abrasion. The material is chemically largely inert to various fluids which can be used in the automotive sector, in particular to organic compounds. It is therefore predestined for the formation of the outer layer or the inner layer of the fluid line. Furthermore, the permeation properties for volatile organic compounds, especially for oxygen-containing volatile organic compounds (for example, alcohols) and water are very good. The material is easy to process and adhesion-optimized available. If necessary, it can be made electrostatically conductive without changing the properties relevant. This has already been pointed out above.

The use of PA6 or PA666 as the aliphatic polyamide has the advantage that these materials are available with a tremendous variety. Numerous modifications regarding stabilization, elasticity, adhesion modification and the like are available. In addition, the material is very inexpensive. In particular, PA6 tends to swell by volatile organic compounds, water and alcohols, or release oligomers. In addition, it does not have sufficient stress corrosion resistance to some thawing agents. For this reason, the aliphatic polyamide or the concretely designated materials are preferably not used for the outer layer or inner layer.

The polyamides PA6 / 12 or PA12 have good mechanical properties, high temperature stability, high mechanical wear resistance and good stress corrosion resistance to chemical thawing agents, in particular ZnCl. The resistance to fluids used in the automotive industry is very good. Many different materials based on the polyamides are available at a low cost. The polyamides PA6 / 12 and PA12 have very good adhesion to the aliphatic polyamide, in particular PA6.

A further, particularly preferred embodiment of the invention provides that the wall thickness of the first layer is less than or equal to the wall thickness of the second layer, and / or the wall thickness of the second layer is less than or equal to the wall thickness of the third layer or the first part layer, and / or the wall thickness of the third layer or the first sub-layer is less than or equal to the wall thickness of the fourth layer. Overall, it is preferably provided that the wall thicknesses of the individual layers starting from the first layer to the third layer, including - if provided - the first sub-layer and the second sub-layer, or the fourth layer steadily increase or at least remain constant, at least not lower ,

In this way, the multi-layer composite can be realized particularly cost-effectively, because roughly the material costs per weight unit and / or volume unit, starting from the first Layer rise to the third or fourth layer. The required properties of the multi-layer composite in terms of its strength or stiffness is achieved by the use of multiple layers even at low wall thicknesses or thicknesses readily.

Finally, in the context of a further embodiment of the invention, it may be provided that the wall thickness of the first layer is at least 0.1 mm and at most 0.2 mm, and / or the second layer is at least 0.1 mm and at most 0.3 mm, and / or the third layer or the first part-layer is at least 0.15 mm and at most 0.4 mm, and / or the fourth layer is at least 0.2 mm and at most 0.4 mm. It is particularly preferred that the wall thicknesses of the layers increase steadily from layer to layer starting from the first layer. With the wall thicknesses mentioned above, the advantageous properties already described can be achieved with simultaneously low costs of the multi-layer composite.

By way of example, the wall thickness of the first layer is at most 0.12 mm, the second layer at least 0.12 mm and at most 0.15 mm, the third layer or the first partial layer at least 0.15 mm and at most 0.2 mm and the fourth layer at least 0.25 mm and at most 0.3 mm. The second sub-layer of the third layer may have any wall thickness. For example, it is determined only from the desired total wall thickness of the multi-layer composite minus the wall thicknesses of the other layers. The second sub-layer represents insofar a filling layer.

The invention further relates to a fluid conduit made of a multilayer composite, in particular of a multilayer composite according to the statements in this description, having a first layer of a fluoropolymer, a second layer of a partially aromatic polyamide immediately following the first layer and directly onto the second layer the following third layer of an ethylene-vinyl alcohol copolymer and / or an aliphatic polyamide.

The advantages of such a configuration of the multilayer composite or the fluid line have already been pointed out. Both the fluid line and the multilayer composite can be further developed according to the statements in the context of this description, so that reference is made to this extent.

A further embodiment of the invention provides that the first layer is an inner layer of the fluid line delimiting a fluid flow space. The fluoropolymer is particularly resistant to many chemicals used in the automotive industry, for example. For this reason, the first layer should immediately limit the fluid flow space. For this purpose, it is present as the inner layer of the fluid line.

In a preferred embodiment of the invention can be provided that the fluid line is present as a fluid corrugated pipe. A fluid corrugated tube is a tube of a material with a certain strength, which with a certain configuration, namely a corrugation, has a higher flexibility than a configuration with an unconstrained shape. The corrugation is formed by a wave-shaped diameter changing in the direction of a longitudinal center axis of the fluid line. This has the advantage that a particularly good flexibility of the fluid line is realized.

A preferred further embodiment of the invention provides that the inner layer and / or one of the layers present as outer layer has at least one coating, in particular a flame and / or abrasion protection coating and / or an insulation coating. The coating constitutes a component of the respective layer. Alternatively, the coating can be applied to the respective layer. The coating can be delimited from the layers by a much smaller wall thickness. For example, the wall thickness of each of the layers is at least 0.1 mm, whereas the wall thickness of the coating is less than 0.1 mm, in particular at most 0.05 mm or at most 0.01 mm.

The coating can have any functionality. For example, it serves as a flame-retardant coating, thus providing a thermal barrier to thermal influences. In addition or as an alternative, it can be designed as a scuff-resistant coating which offers protection against mechanical influences. Also, the coating may be configured as an insulation coating which is electrically insulated, that is, has at least a higher electrical resistance than the fluid line or the multilayer composite itself.

Finally, a further embodiment of the invention can provide that the outer layer is formed by the third layer, the second partial layer of the third layer or the fourth layer. The outer layer bounds the fluid line on the outside, ie on its side facing away from the fluid flow space. The outer layer may be formed by any of the layers, for example, the third layer or the fourth layer. If the third layer consists of the several sublayers, then For example, the outer layer is usually formed by the second sublayer of the third layer.

• Figur eine schematische Schnittdarstellung durch eine Fluidleitung aus einem Mehrschichtverbund.

The invention will be explained in more detail with reference to the embodiments illustrated in the drawings, without any limitation of the invention. The only one shows

• FIG. 1 is a schematic sectional view through a fluid line made of a multi-layer composite.

The 1 shows a schematic representation of a fluid line 1 made of a multi-layer composite 2 consists. The multi-layer composite 2 encompasses the formation of a fluid flow space 3 the fluid line 1 a longitudinal central axis 4 the fluid line 1 completely in the circumferential direction. Seen in cross-section, there is the multi-layer composite 2 from a first layer 5 , a second layer 6 , a third layer 7 and a fourth layer 8th , which follow each other in the radial direction seen from the outside. Each of the layers 5 . 6 . 7 and 8th is formed continuously in the circumferential direction and preferably has a constant wall thickness in the circumferential direction.

The third layer 7 consists of a first sub-layer 9 and a second sub-layer 10 together. For these, preferably the same statements apply as for the layers 5 . 6 . 7 and 8th , In any case, the two sublayers 9 and 10 formed continuously in the circumferential direction, so embrace the longitudinal center axis 4 completely in the circumferential direction. Also have the sublayers 9 and 10 in the circumferential direction on a constant wall thickness. Single of the layers 5 . 6 . 7 and 8th and / or sublayers 9 and 10 can be omitted. Thus, not necessarily all of the layers shown here must be realized.

In the embodiment shown here, the first layer 5 from a fluoropolymer, the second layer 6 from a partly aromatic polyamide, the first part-layer 9 from an ethylene-vinyl alcohol copolymer, the second part layer 10 from an aliphatic polyamide and the fourth layer 8th from a further polyamide, which of the polyamide of the second sub-layer 10 preferably different. Concretely, the fluoropolymer of the first layer is an ethylene-tetrafluoroethylene copolymer, the partially aromatic polyamide of the second layer is a polyphthalamide, the aliphatic polyamide of the second part layer 10 PA6 or PA666 and the further polyamide of the fourth layer 8th PA612 or PA12.

In principle, the wall thicknesses of the layers shown here 5 . 6 . 7 and 8th as well as the partial layers 9 and 10 be identical. Preferably, the wall thickness of the layers decreases 5 . 6 . 7 and 8th as well as the partial layers 9 and 10 radially outward from the first layer 5 at least for some of the successive layers too.

The fluid line 1 is preferably used in the automotive sector, for example as a fuel-carrying fluid line 1 , which may also be referred to as a fuel line. The requirements for such a fuel line have steadily increased in recent years as a direct and indirect consequence, especially of growing safety and environmental requirements. Added to this are increased expectations of product quality. At the same time, however, economic requirements in manufacturing must be met to an ever greater extent.

Fuel lines made of metallic materials have already been displaced almost exclusively by fuel lines made of elastomers or plastic tubes, at least in the low-pressure circuit today. Reasons for this include a better behavior against internal and / or external corrosion, better resistance to vibrations, better Pulsationsdämpfungseigenschaften, better processing properties, lower component weight and lower costs. For economic reasons, but also for reasons of low-permeation connection technology, metallic fuel lines, which are still found in engine compartment applications, are increasingly being replaced by plastic pipes. It should be noted that components of the fuel circuit are safety-relevant components due to the fire behavior and the ability to form ignitable mixtures of the pumped medium.

The variety of fuels used worldwide for regional applications continues to increase. The quality and composition of refined fuels varies. Certain foreign substances, such as sulfur or water, are limited differently. Regionally, depending on availability, legal requirements or tax incentives, more and more biofuel components are added to fuels for Otto engine combustion. These may be, for example, methanol or ethanol in various proportions between 0% and 100%. Methanol or ethanol contents of 15 to 20% in classic gasoline have proven to be chemically critical. In addition, various synthetic fuels are under development and testing.

It must be assumed that various fuels are being changed over. The components of the fuel system should be as uniform as possible worldwide, in order to implement a cost-effective production. In the coming years, there is an increase in the diversity of liquid fuels, in particular the synthetic fuels, expected. Furthermore, the use of gaseous fuels is expected to increase. In practice, it has been found that elastomeric or plastic pipes react to some of these fuels with swelling and / or the release of substances from the fuel lines, for example plasticizers, stabilizers, and so forth.

The engine's fuel injection systems are evolving to provide more accurate fuel metering. As a rule, their complexity and precision increases greatly. One consequence of this is that the injection systems become more sensitive to unintended foreign matter. This development is technically countered for example with improved filter systems in the fuel cycle. For fuel lines, for example, stricter requirements apply to the permissible residual dirt of the components. However, it should also be emphasized a strong limitation of solid or liquid oligomers, which can be washed out of conventional elastomer or plastic pipes and can lead to harmful deposits in parts of the injection system. These deposits can, for example, change jet patterns of injection nozzles and thus lead to performance or emission-relevant changes in the combustion over the engine running time. Therefore, the leaching of oligomers from the large walls of the fuel lines must be minimized.

For reasons of environmental protection, the permeation of organic compounds or volatile hydrocarbons from vehicles is increasingly limited. Due to the high concentration of volatile hydrocarbons in the fuel, the concentration and pressure gradient to the outside and the large wall surface in this case the fuel lines is a high priority in the permeation avoidance. Many thermoplastic materials are prone to self-emission, for example plasticizers, as well as permeability of hydrocarbons from the fuel through the conduit. Concentration of short-chain alcohols to gasoline fuels can still promote the passage of hydrocarbons in a concentration-dependent manner.

Fuel systems on today's motor vehicles include not only the system of low-pressure fuel supply itself, but possibly also fuel return lines, lines in the tank filling and in the field of tank ventilation and activated carbon regeneration. For these lines usually the same requirements apply. However, the fuel lines also a variety of other requirements are made, of which only an incomplete selection should be mentioned in extracts. For example, a high internal pressure resistance, high cold flexibility and high temperature resistance, high impact strength, high vibration resistance, high elasticity, high dimensional stability, buckling strength, flame resistance, electrostatic dissipation capability and so on must be realized. Of course, the properties must be maintained over the entire vehicle life despite internal and external chemical stress and thermal stress (including hydrolysis and stress cracking resistance). Of particular importance is also a secure line connection technology, which must of course also meet the stated thermal and mechanical requirements, but also requirements for oligomer freedom, cleanliness and permeation. Incidentally, the aforementioned requirements apply mutatis mutandis to other fluid circuits in motor vehicles, for example, SCR lines, cables for air conditioning systems, lines for blow-by and coolant lines and hydraulic lines.

The requirements can no longer be met by single-layer tubes, so-called mono tubes. For this reason, so-called multilayer pipes are usually used in which a plurality of functional materials are arranged in specific layer arrangements with specific layer thicknesses. These tubes can be made, for example, by coextrusion or by jacketing techniques. Each layer in the composite makes a defined contribution to the fulfillment of the requirements of the overall pipe and thereby brings positive properties to a single function. Thus, the layers in such multi-layer constructions may be, for example, inner layers, barrier layers, dissolution inhibitor layers, protective layers, adhesion promoter layers, support layers, filler layers, outer layers, insulation layers, marking layers or wear protection layers. The layers are made in the interest of ease of manufacture and processability from thermoplastically processable materials.

The above-described fluid line 1 from the multi-layer composite 2 meets the requirements in particular. In particular, the permeation requirements associated with high temperature requirements are met. The fluid line 1 For example, has the dimensions 10x1.6 mm to 10x2 mm, preferably 10x1.8 mm, wherein the first number describes the outer or inner diameter and the second number describes the wall thickness. Also other dimensions of the fluid line 1 are of course feasible. An example of concrete materials of the layers 5 . 6 . 7 . 8th . 9 and 10 has already been played. Alternatively, it may be provided in this example as the aliphatic polyamide of the third layer instead of the PA6 PA666 to use. Also, the further polyamide could be the fourth layer PA612 or alternatively PA12.

It could also be provided on the first sub-layer 9 to dispense with the ethylene-vinyl alcohol copolymer, so that the third layer 7 completely composed of the aliphatic polyamide. In that regard, there would be a four-layer fluid line, which consists of the following materials from the inside to the outside: the fluoropolymer, the partly aromatic polyamide, the aliphatic polyamide and the other polyamide. The fourth layer could be dispensed with, so that the outer layer consists of the aliphatic polyamide and insofar as the third layer represents the outer layer. In this case, a three-layer fluid line is realized, which consists of the following materials from the inside to the outside: the fluoropolymer, the partly aromatic polyamide and the aliphatic polyamide.

The described fluid line 1 just like the multi-layer composite 2 from which the fluid line 1 There is the advantage of a high durability with a simultaneous very good availability of the materials. In addition, the structure of the multi-layer composite allows 1 a cost-effective production.

In addition, the fluid line 1 very easy to process, for example, by low-permeability and secure connection technologies such as welding, especially laser welding. The welding can preferably by a targeted and localized and matched in intensity and time to the materials and geometries penetrating a laser beam through the with the fluid line 1 to be welded device that is made completely or locally made of laser-transparent material done. The device is for example in the form of a fluid coupling. The material of the outer layer of the fluid conduit, for example the third layer, the second sub-layer or the fourth layer, must be laser-absorbent to the required extent in this case. Preferably, the material of the respective layer is already suitably selected or rendered sufficiently laser-absorbent by means of an additive.

Because the outer layer preferably also for marking and / or labeling of the fluid line 1 In this case, the Matieral should also have the property of a color change in common laser marking methods. If printing is to be used for labeling, suitable pigment-rich inks are to be preferred.

The materials and / or the wall thicknesses of the individual layers are chosen in particular such that the fluid line 1 can be thermoformed even in tight bending radii without the use of arranged inside the pipe bending auxiliary tools, such as springs. In addition to a rational production, this has further advantages, so connectors can be added to the tubes in a still rotationally symmetrical state before bending, which minimizes the number of devices. Furthermore, in bending variants on the basis of equal output tube lengths, the storage of the precursors can be simplified.

But above all, it is technically significant that no local deformations and stresses on the sensitive inner layer occur due to the elimination of internal compression springs. The risk of damage to the layer is reduced. Damage caused by local pressure points of the bending springs, which would locally reduce the wall thicknesses of the inner layer, are non-destructively difficult to detect from the outside. The damage can also be of great importance in particular when it comes to a minimum electrical conductivity of the inner layer. Local unwanted wall thickness reductions can result in the required conductivity of the inner layer not being complied with. As a result, the usually cost-intensive inner layer can be kept thin.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1162061 A1 [0002]
• WO 2006/040206 A1 [0003]
• DE 102013013163 A1 [0004]
• WO 2007/019921 A1 [0005]

Cited non-patent literature

• Standard SAE J 2260 [0015]

Claims (15)

Multilayer composite (2), in particular for a fluid line (1), comprising a first layer (5) of a fluoropolymer, a second layer (6) of a partially aromatic polyamide immediately following the first layer (5) and directly onto the second layer (6) The following third layer (7) of an ethylene-vinyl alcohol copolymer and / or an aliphatic polyamide. Multilayer composite after Claim 1 , characterized in that the fluoropolymer of the first layer (5) is enriched with carbon for improving an electrostatic conductivity of the first layer (5). Multi-layer composite according to one of the preceding claims, characterized in that the partially aromatic polyamide of the second layer (6) is a polyphthalamide with a polyamide as base polymer. Multi-layer composite according to one of the preceding claims, characterized in that the second layer (6) and the third layer (7) are connected to one another with adhesion promoter. Multilayer composite according to one of the preceding claims, characterized in that immediately following the third layer (7), a fourth layer (8) of another polyamide, which intervenes between the third layer (7) and the third layer (7), follows the polyamide of the third layer (7) is different. Multi-layer composite according to one of the preceding claims, characterized in that the polyamide of the fourth layer (8) is a polyamide of hexamethyldiamine or a polyamide of laurolactam. Multi-layer composite according to one of the preceding claims, characterized in that the third layer (7) comprises a first part-layer (9) of the ethylene-vinyl alcohol copolymer and a second part layer (10) of the aliphatic polyamide, wherein the first part-layer (9) immediately following the second layer (6) and the second sub-layer (6) forming an outer layer or immediately adjacent to the outer layer. Multi-layer composite according to one of the preceding claims, characterized in that a) the fluoropolymer is ethylene-tetrafluoroethylene copolymer, or b) the aliphatic polyamide PA6 or PA666, or c) the further polyamide PA612 or PA12. Multi-layer composite according to one of the preceding claims, characterized in that the wall thickness of the first layer (5) is less than or equal to the wall thickness of the second layer (6), and / or the wall thickness of the second layer (6) is less than or equal to the wall thickness of the third layer (7) or the first partial layer (9), and / or the wall thickness of the third layer (7) or the first partial layer (9) is less than or equal to the wall thickness of the fourth layer (8). Multi-layer composite according to one of the preceding claims, characterized in that the wall thickness a) of the first layer is at least 0.1 mm and at most 0.2 mm, and / or b) of the second layer (6) is at least 0.1 mm and at most 0, 3 mm, and / or c) the third layer (7) or the first part layer (9) at least 0.15 mm and at most 0.4 mm, and / or d) the fourth layer (8) at least 0.2 mm and at most 0.4 mm. Fluid line (1) comprising a multilayer composite (2), in particular a multilayer composite (2) according to one or more of the preceding claims, having a first layer (5) of a fluoropolymer, a second layer immediately following the first layer (5) ( 6) consists of a partly aromatic polyamide and a third layer (7) immediately following the second layer (6) of an ethylene-vinyl alcohol copolymer and / or an aliphatic polyamide. Fluid line after Claim 11 , characterized in that the first layer (5) is a fluid flow chamber (3) defining inner layer of the fluid line (1). Fluid line according to one of the preceding claims, characterized in that the fluid line (1) is present as a fluid corrugated pipe. Fluid line according to one of the preceding claims, characterized in that the inner layer and / or an outer layer of the layers (5,6,7,8) has at least one coating, in particular a flame and / or chafing coating and / or an insulation coating. Fluid line according to one of the preceding claims, characterized in that the outer layer of the third layer (7), the second sub-layer (10) of the third layer (7) or the fourth layer (8) is formed.

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