WO2020136030A1

WO2020136030A1 - Multilayer composite and fluid line

Info

Publication number: WO2020136030A1
Application number: PCT/EP2019/085372
Authority: WO
Inventors: Dirk Kramer; Thomas May
Original assignee: Aft Automotive Gmbh
Priority date: 2018-12-28
Filing date: 2019-12-16
Publication date: 2020-07-02
Also published as: DE102018251759B4; DE102018251759A1

Abstract

The invention relates to a multilayer composite, in particular for a fluid line (1). Said multilayer composite is characterized by a first layer (5) made of a fluoropolymer, a second layer made of a polyamide and following directly to the first layer (5), and at least one third layer (7), wherein both the first layer (5) and the second layer (6) are modified so as to be electrostatically conductive. The invention also relates to a fluid line (1) made of a multilayer composite.

Description

DESCRIPTION

Multi-layer composite and fluid line

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

For example, the document EP 1 162 061 Al is known from the prior art. This relates to a thermoplastic multi-layer composite, in particular in the form of a multi-layer hose, a multi-layer tube or a multi-layer container, containing at least one intermediate layer made of a molding composition based on ethylene-vinyl alcohol copolymers between layers of molding compositions based on polyamide, the intermediate layer being over At least one adhesion-promoting layer made of a molding compound based on polyamide, selected from the group copolyamide 6/12, block copolyamide 6/12, polyamide 612, polyamide 610, mixture of polyamide 6 and polyamide 12 with a compatibility agent, mixture of polyamide 6 and polyamide 11 with compatibility mediator, with at least one secondary layer made of a molding compound based on polyamide 12, polyamide 11, polyamide 10/10, polyamide 10/12 or polyamide 12/12.

The publication WO 2006/040206 A1 also shows a multilayer composite which contains the following layers: an inner layer selected from a fluoropolymer molding compound and a polyolefin molding compound; an adhesion promoter layer which has 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 being the parts by weight of a), b) and c) is 100, and additionally in the sum of components a) and b) at least 20 parts by weight consist of monomer units which are composed of caprolactam and / or the combination of hexamethylene diamine / adipic acid, Derive hexamethylenediamine / suberic acid, hexamethylenediamine / 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 toughening rubber and / or customary auxiliaries or additives; a layer of an EVOH molding compound.

A hollow body is also known from the publication WO 2007/019921, 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 directly connected to each other.

Finally, the publication EP 3 069 876 A1 shows a multilayer composite which contains the following layers: a first layer made of a molding composition which contains at least 40% by weight of an aliphatic polyamide and a second layer made of a molding composition which comprises at least 60% contains the following components: 60 to 100 parts by weight of a partially aromatic copolymer which consists of monomer units which are derived from 30 to 90 mol% of a combination of hexamethylenediamine and terephthalic acid and 70 to 10 mol% of a combination of hexamethylenediamine and a linear aliphatic dicarboxylic acid with 8 to 19 carbon atoms and 40 to 0 parts by weight of an olefinic copolymer as an impact modifier, where the sum of the parts by weight of the partially aromatic copolyamide and the combination of hexamethylenediamine and terephthalic acid gives 100. Such a multi-layer composite should have high heat resistance, very good impact resistance, high elongation at break and good layer adhesion.

It is an object of the invention to propose a multi-layer composite which has advantages over known multi-layer composites, in particular can be produced inexpensively and is also extremely durable, and at the same time an excellent electrostatic conductivity is ensured.

This is achieved according to the invention with a multilayer composite with the features of claim 1. This is characterized by a first layer made of a fluoropolymer, a second layer made of a polyamide immediately following the first layer, and at least a third layer, both the first layer and the second layer being modified to be electrostatically conductive.

The multi-layer composite, which is particularly preferably used for producing or forming the fluid line, has so far at least three layers, in this respect has at least three layers, namely the first layer, the second layer and the third Layer. The layers mentioned follow each other directly, so that the second layer lies directly on the first layer and the third layer lies directly on the second layer. In other words, the second layer is arranged between the first layer and the third layer and bears 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 designed to be of the same material, so that the respective layer consists entirely and consistently of the material designated in each case.

The first layer consists at least partially, but preferably completely, of the fluoropolymer. The fluoropolymer is to be understood as 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 in principle be of any design. For example, it is in the form of ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE) or ethylene-tetrafluoroethylene-hexafluoropropylene (EFEP).

The second layer consists of the polyamide, i.e. a linear polymer. The polyamide can be present, for example, as an aliphatic polyamide, partially aromatic polyamide or as an aromatic polyamide. Additionally or alternatively, it can be semi-crystalline or amorphous. Examples of the polyamide are PA6, PA612, PA6 / 66 or PA616. The second layer can consist of a partially aromatic polyamide. This is preferably to be understood as a partially crystalline aromatic polyamide, which can also be referred to as polyphthalamide (PPA). The partially aromatic polyamide can be strengthened to improve its mechanical strength and have an additive or a fiber reinforcement for this purpose. For example, ground glass or ground silicon dioxide is used as an additive. The fiber reinforcement is, for example, in the form of a glass fiber reinforcement, a carbon fiber reinforcement or an aramid fiber reinforcement. However, the second layer or the polyamide can also be designed without reinforcement.

The variety of available polyamides is enormous. Numerous material modifications regarding stabilization, elasticity, adhesion modification and the like are available. The layer adhesion of the polyamide to the fluoropolymer and / or the material of the third layer can be improved by means of a suitable modification or additive. The polyamide of the second layer thus represents an electrically conductive adhesion promoter, which serves for an excellent connection of the first layer to the third layer. The polyamide is also inexpensive. Its mechanical properties can also be easily modified. The elasticity of the polyamide is preferably adjusted in order to limit, for example, the tendency of the first layer to creep when the connectors are hammered in. The polyamide is preferably made oligomer-free in order to avoid washing out through the fluoropolymer barrier. In addition, the polymer is further preferably heat-stabilized, for example by adding a copper-based heat stabilizer. In principle, it is readily thermally available. The layer thickness of the second layer results, for example, from the required radial elasticity of a composite of the first layer and the second layer, in particular for connectors that are turned in, and from the necessary conductivity of the multi-layer composite, which is realized with the aid of the first layer and the second layer .

The third layer preferably also has or consists of polyamide and / or an ethylene-vinyl alcohol copolymer. Examples of the polyamide of the third layer are PA6, PA612, PA6 / 66, PA616 or PPA. The polyamide can be an aliphatic polyamide, a partially aromatic polyamide or an aromatic polyamide. Additionally or alternatively, the polyamide of the third layer is partially crystalline or amorphous. The aliphatic polyamide can have a monomer which is derived from aliphatic bases, for example from a lactam, in particular an epsilon-caprolactam, or from hexamethylenediamine and adipic acid. In addition or as an alternative to the polyamide, the third layer has or consists of the ethylene-vinyl alcohol copolymer. The ethylene-vinyl alcohol copolymer (also abbreviated as EVAL or EVOH) is to be understood as a copolymer which is formally composed of the monomers ethylene and vinyl alcohol. The ethylene-vinyl alcohol copolymer is an inexpensive barrier material with a good barrier effect against volatile organic compounds.

It can be provided that the multilayer composite consists exclusively of the three layers mentioned, so that the first and third layers are each present as an outer layer or, in the case of the fluid line, the first layer is present as an inner layer and the third layer as an outer layer. In the latter case in particular, the first layer is used to guide a fluid in the fluid line, the excellent resistance of the fluoropolymer being used.

The multilayer composite described, consisting of the three layers, has excellent strength properties and high durability. However, it can be provided in addition to the three layers already mentioned, add at least one additional layer to the multilayer system. However, the first layer preferably 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, the second layer immediately following the first layer and the third layer adjacent to the second layer.

An exemplary multi-layer composite of the first layer, the second layer and the third layer, which preferably consists of or has at least ethylene-vinyl alcohol copolymer, can also be referred to as a three-layer barrier system which is resistant to permeation, oligomer leaching and water . Regardless of its design, the multilayer composite is preferably used to manufacture the fluid line. However, it can also be used to form any other hollow body, for example a fluid container or the like.

In particular when using the multilayer composite or the fluid line in the motor vehicle area, it is necessary to design the multilayer composite or the fluid line to be electrostatically conductive. For this purpose, for example, the fluoropolymer of the first layer can be modified accordingly to improve the electrostatic conductivity of the first layer. For example, the fluoropolymer is enriched with carbon for this purpose. The electrostatic conductivity is used to achieve equipotential bonding. 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, avoid sparking due to an excessive potential difference. This can be achieved by means of a corresponding configuration of the first layer. For this purpose, the fluoropolymer is enriched with carbon, for example, so that the fluoropolymer or the first layer has the desired conductivity. For example, the fluoropolymer should be enriched with carbon in such a way that there is a surface resistance of at most 10 ⁵ W / square, at most 5 x 10 ⁶ W / square or at most 10 ⁶ W / square. In the latter case, the regulations of the SAE J 2260 standard are met in particular.

However, the more the fluoropolymer is modified to be conductive, the more unfavorable its barrier properties develop. In addition, the electrostatically conductive modified fluid polymer is comparatively expensive, so that its material mass per unit area of the multilayer composite should be kept low. For example, the first layer has a layer thickness of at most 0.2 mm, at most 0.15 mm, at most 0.12 mm or at most 0.1 mm. This minor Layer thickness can lead to problems when connecting the multilayer composite or the fluid line, because the low layer thickness leads to a small contact area. In addition, the melting point of the fluoropolymer changes as a result of the electrostatically conductive modification, so that when the multilayer composite is welded, it does not participate in the weld, or does not participate intensively enough. It would be necessary to either modify the fluoropoly mer relatively electrostatically conductive, or to choose a very large layer thickness for the first layer. The former leads to a restricted barrier effect of the first layer, the latter to high costs of the multi-layer composite.

For this reason, it is envisaged to modify not only the first layer, but also the second layer in an electrostatically conductive manner. Because the second layer consists of a material which is significantly less expensive than the fluoropolymer of the first layer, the layer thickness of the second layer can easily be chosen to be comparatively large. Because the electrostatically conductive modified second layer thus has a comparatively high conductivity, the first layer has to be modified much less electrostatically conductive than in other configurations in which only the first layer is modified electrostatically conductive. To this extent, for example, the first layer or the fluoropolymer of the first layer is modified such that it has a surface resistance of at most 10 ⁶ W / square, at most 5 x 10 ⁶ W / square, at most 2.5 x 10 ⁶ W / square or at most 10 ⁵ W / square. Due to the electrostatically conductive modification of both the first layer and the second layer or the corresponding materials, cost-effective production can be ensured despite the high resistance and good conductivity.

A further embodiment of the invention provides that the second layer has a higher conductivity than the first layer. This means, for example, that the material of the first layer has a lower conductivity or a lower surface resistance than the material of the second layer. Additionally or alternatively, the higher conductivity of the second layer can also be achieved by a layer thickness that is greater than a layer thickness of the first layer. For example, the surface resistance of the polyamide of the second layer is at most 10 ⁵ W / square, at most 2.5 x 10 ⁶ W / square, at most 5 x 10 ⁶ W / square or at most 10 ⁶ W / square. For example, the conductivity of the second layer is greater than the conductivity of the first layer by a factor of at least 1.1, at least 1.25, at least 1.5, at least 1.75 or at least 2.0. As a result, a particularly inexpensive design of the multilayer composite is realized. Another embodiment of the invention provides that the second layer has a greater layer thickness than the first layer. If the material of the first layer and the material of the second layer have the same sheet resistance, the higher conductivity of the second layer compared to the first layer is ensured by the choice of the layer thickness. The layer thickness of the second layer is preferably greater than the layer thickness of the first layer by a factor of at least 1.5, at least 2, at least 2.5, at least 3, at least 4 or at least 5. For example, the layer thickness of the second layer is at least 0.15 mm, at least 0.2 mm, at least 0.25 mm, at least 0.3 mm, at least 0.4 mm or at least 0.5 mm. Because the polyamide of the second layer is extremely inexpensive, the mechanical and electrostatic properties of the multilayer composite can be achieved in a cost-effective manner using the second layer or the polyamide of the second layer.

A preferred embodiment of the invention provides that the fluoropolymer of the first layer is ETFE or EFEP. This has already been discussed above. Both materials can be easily processed and are also largely inert to media which are usually used in the motor vehicle sector. The permeation properties against volatile organic compound (VOC) and water are very good, especially in the case of the ETFE. Although the EFEP has slightly poorer permeation properties, it has even better adhesion and processing properties than ETFE. The use of ETFE or EFEP as the fluoropolymer of the first layer enables particularly good properties of the multilayer composite.

A further development of the invention provides that the polyamide of the second layer is PA6, PA612, PA6 / 66 or PA616. In principle, the advantages of the polyamide have already been discussed. It enables a particularly cost-effective formation of the multilayer composite with simultaneous realization of a high conductivity.

In a further embodiment of the invention it is provided that the third layer comprises polyamide, in particular PA6, PA612, PA616 or PPA, and / or ethylene-vinyl alcohol copolymer. With regard to the polyamide, reference is made to the further statements in the context of this description. The polyphthalamide (PPA) is characterized by good thermal resistance and low moisture absorption. The chemical resistance and the corrosion resistance are very good. Due to the low tendency of the polyphthalamide to swell, only slight forces occur at layer boundaries with other materials. The polyphthalamide has only slight oligomer washings. The cold impact resistance is usually better than that of other polyamides. It adheres to a variety of elastomers and thermoplastics without an adhesion promoter. Liability can be increased by a suitable modification or additive. Polyphthalamides have proven themselves in automotive applications, especially in the fuel sector, for years. The polyphthalamide used for the third layer has, for example, the base polymer PA10T / X.

The ethylene-vinyl alcohol copolymer is an inexpensive barrier material with a good barrier effect, especially against volatile organic compounds, especially hydrocarbons. It has been found that the layer adhesion between the ethylene-vinyl alcohol copolymer and the polyamide, in particular the polyphthalamide, which can be produced by good process control and skillful choice of materials, is good and also permanently resistant, so that adhesion promoters between the polyamide of the second layer and the Ethylene-vinyl alcohol copolymer of the third layer can be dispensed with or is dispensed with. The ethylene-vinyl alcohol copolymer is protected from the inside by the fluoropolymer and polyamide from harmful water absorption. For protection from the direction opposite to the first layer and the second layer, a further layer can be provided, which is present as an outer layer. This further layer consists, for example, of polyamide, for example PA612.

The third layer preferably has a layer thickness which at most corresponds to the layer thickness of the second layer, and is preferably smaller. For example, the layer thickness of the third layer is at most 0.4 mm, at most 0.3 mm, at most 0.25 mm, at most 0.2 mm, at most 0.15 mm or at most 0.1 mm. This results in a particularly inexpensive configuration of the multilayer composite with good properties.

Finally, a further embodiment of the invention can provide that the third layer has a plurality of partial layers and / or is designed as an outer layer. To this extent, the third layer can have the plurality of sublayers, which are directly adjacent to one another. For example, the third layer has a first partial layer and a second partial layer. In addition, a third sub-layer can optionally be present. To this extent, the outermost of the sub-layers forms the outer layer of the multilayer composite. All sub-layers of the third layer preferably consist of a polyamide, in particular of lower layers. different polyamides. At least one of the sub-layers can also be in the form of an adhesive middle layer.

For example, the first sub-layer consists of polyphthalamide and the second sub-layer of ethylene-vinyl alcohol copolymer or vice versa. However, it can also be provided that an adhesion promoter layer is present between the sub-layers, so that the first sub-layer consists of polyphthalamide, the second sub-layer consists of adhesion promoter and the third sub-layer consists of ethylene-vinyl alcohol copolymer. Here too, the reverse configuration is possible, so that the first partial layer consists of the ethylene-vinyl alcohol copolymer and the third partial layer consists of the polyphthalamide. It can also be provided that the first partial layer consists of PA6 and the second partial layer consists of PA612. Another structure provides that the first sub-layer is made of polyphthalamide, the second sub-layer is made of PA6 and the third sub-layer is made of PA612. Yet another embodiment provides that the first part layer is made of ethylene-vinyl alcohol copolymer, the second part layer is made of PA6 and the third part layer is made of PA612.

The invention further relates to a fluid line made of a multi-layer composite, in particular of a multi-layer composite as described in the context of this description. There are a first layer made of a fluoropolymer, a second layer immediately following the first layer made of a polyamide and at least a third layer, the first layer and the second layer being modified to be electrostatically conductive.

The advantages of such a configuration of the fluid line or of the multilayer composite have already been pointed out. Both the fluid line and the multilayer composite can be further developed in accordance with 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 numerous chemicals that are used, for example, in the automotive sector. For this reason, the first layer should directly 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 it can be provided that the fluid line is in the form of a corrugated fluid tube. A corrugated fluid pipe is a pipe made of a material with a certain strength, which has a greater flexibility with a certain configuration, namely a corrugation, than an embodiment with an undulating shape. The corrugation is formed by a diameter which changes in a wave shape in the direction of a longitudinal central 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 as the outer layer has at least one coating, in particular a flame and / or abrasion protection coating and / or an insulation coating. The coating is 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 means of a much smaller layer thickness. For example, the layer thickness of each of the layers is at least 0.1 mm, whereas the layer thickness of the coating is less than 0.1 mm, in particular at most 0.5 mm or at most 0.01 mm.

The coating can have any functionality. For example, it serves as a flame retardant coating, that is to say represents a thermal barrier to thermal influences. Additionally or alternatively, it can be designed as a fire protective coating which offers protection against mechanical influences. The coating can also be designed as an insulation coating which is electrically insulated, that is to say has at least a higher electrical resistance than the fluid line or the multilayer composite itself.

The invention is explained below on the basis of the exemplary embodiments illustrated in the drawing, without the invention being restricted. The only one shows

Figure is a schematic sectional view through a fluid line from a multilayer composite.

The figure shows a schematic representation of a fluid line 1, which consists of a multilayer composite 2. The multi-layer composite 2 surrounds to form a fluid flow space 3 of the fluid line 1 a longitudinal central axis 4 of the fluid line 1 in the circumferential direction fully. Seen in cross section, the multilayer composite 2 consists of a first layer 5, a second layer 6 and a third layer 7, which is radially outward successive. Each of the layers 5, 6 and 7 is formed continuously in the circumferential direction and preferably has a constant layer thickness in the circumferential direction.

The third layer 7 is composed of a first sub-layer 8, a second sub-layer 9 and a third sub-layer 10. For these, preferably the same designs apply as for the layers 5, 6 and 7. In any case, the sub-layers 8, 9 and 10 are formed continuously in the circumferential direction, ie encompass the longitudinal central axis 4 in the circumferential direction completely. The sub-layers 8, 9 and 10 also have a constant layer thickness in the circumferential direction. Individual layers 5, 6 and 7 and / or partial layers 8, 9 and 10 can be omitted. All of the layers or partial layers shown here need not necessarily be realized.

In the embodiment shown here, the first layer 5 consists of a fluoropoly mer, the second layer 6 of polyamide and the third layer 7 of different materials. Specifically, the fluoropolymer of the first layer 5 is an ethylene-tetrafluoroethylene copolymer (ETFE) or an ethylene-tetrafluoroethylene-hexafluoropropylene (EFEP). The polyamide of the second layer 6 is preferably PA6, PA612, PA6 / 66 or PA616. The first sub-layer 8 consists, for example, of polyphthalamide or ethylene-vinyl alcohol copolymer, the second sub-layer 9 of PA6 and the third sub-layer 10 of PA612.

In principle, the layer thicknesses of the layers 5, 6 and 7 shown here and of the sub-layers 8, 9 and 10 can be identical. The layer thickness of the layers 5, 6 and 7 and of the sub-layers 8, 9 and 10 preferably increases in the radial direction outwards from the first layer 5 for at least some of the successive layers. It can be provided that the third layer 7, that is to say the sub-layers 8, 9 and 10 in total, have the same or a smaller layer thickness than the first layer 5 and / or the second layer 6. The layer thickness of the third layer is preferred 7, however, in particular the layer thickness of at least one of the sub-layers 8, 9 and 10, in particular several or all of the sub-layers 8, 9 and 10 is greater than the layer thickness of the first layer 5 or the layer thickness of the second layer 6.

The fluid line 1 is preferably used in the motor vehicle sector, for example as a fuel-carrying fluid line 1, which can also be referred to as a fuel line. The requirements for such a fuel line have increased in recent years as a direct and direct consequence, above all, of increasing safety and environmental requirements. There are also increased expectations of product quality. At the same time, however, economic requirements in manufacturing have to be met to an ever increasing extent.

Fuel lines made of metallic materials have already been replaced almost without exception by fuel lines made of elastomers or plastic pipes, at least in the low-pressure circuit. The reasons for this include better behavior against internal and / or external corrosion, better resistance to vibrations, better pulsation damping properties, better processing properties, lower component weight and lower costs. For economic reasons, but also for reasons of a low-permeation connection technology, metallic fuel lines that are still found in engine compartment applications are increasingly being replaced by plastic lines. It should be noted that due to the fire behavior and the ability of ignitable mixtures of the pumped medium to form, components of the fuel circuit are safety-relevant components.

The variety of fuels that are used regionally worldwide continues to increase. The quality and composition of the refined fuels vary. Certain foreign substances, such as sulfur or water, are limited differently. Regionally, depending on availability, legal requirements or tax incentives, more and more biofuels are being blended, especially those used in petrol engines. This can 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 in development and testing.

It has to be assumed that different fuels are filled alternately. The components of the fuel system should be as uniform as possible worldwide, so that cost-effective production can be implemented. The diversity of liquid fuels, especially synthetic fuels, is expected to grow in the coming years. The use of gaseous fuels is also expected to increase. In practice, it has been found that elastomer or plastic pipes react to some of these fuels with swelling and / or the removal of substances from the fuel lines, for example plasticizers, stabilizers, and so on.

The engine's fuel injection systems are being developed for increasingly precise fuel metering. As a rule, their complexity and precision increases significantly. A fol- This means that the injection systems are becoming more sensitive to foreign substances that are not intended. Technically, this development is countered with improved filter systems in the fuel circuit, for example. For fuel lines, for example, there are stricter requirements for the permissible residual soiling of the components. Also to be emphasized is 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 spray patterns of injection nozzles and thus lead to changes in combustion that are relevant to performance or emissions over the course of the engine. The leaching of oligomers from the large-area walls of the fuel lines must therefore be minimized.

For reasons of environmental protection, the permeation of organic compounds or volatile hydrocarbons from vehicles is also increasingly limited. Due to the high concentration of volatile hydrocarbons in the fuel, the concentration and pressure drop to the outside and the large wall surface, the fuel lines are of great importance in preventing permeation. Many thermoplastic materials tend to emit themselves, for example from plasticizers, and to be permeable to hydrocarbons from the fuel through the line. Addition of short-chain alcohols to petrol can still promote this passage of hydrocarbons depending on the concentration.

Fuel systems on today's motor vehicles include not only the system of low-pressure fuel supply itself, but also, if necessary, fuel return lines, lines in the area of tank filling and in the area of tank ventilation and active carbon regeneration. The same requirements usually apply to these lines. However, the fuel lines also have a variety of other requirements, of which only an incomplete selection is to be mentioned in part. 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, kink resistance, flame resistance, electrostatic dissipation and so on must be realized.

Of course, the properties must be preserved over the entire life of the vehicle despite internal and external chemical and thermal stress (including hydrolysis and stress crack resistance). Secure cable connection technology, which is of course also the same, is of particular importance thermal and mechanical requirements, but also requirements for freedom from oligomers, cleanliness and permeation. The requirements mentioned also apply mutatis mutandis to other fluid circuits in motor vehicles, for example SCR lines, lines for air conditioning systems, lines for blow-by and coolant lines and hydraulic lines.

The requirements can no longer be met by single-layer pipes, so-called mono pipes. For this reason, so-called multi-layer pipes are usually used, in which several functional materials are arranged in certain layer arrangements with certain layer thicknesses. These tubes can be manufactured, for example, in coextrusion processes or in jacketing processes. Each layer in the network makes a defined contribution to fulfilling the requirements for the overall pipe and brings positive properties for an individual function. The layers in such multilayer structures can be, for example, inner layers, barrier layers, solution inhibitor layers, protective layers, adhesive layers, support layers, filler layers, outer layers, insulation layers, marking layers or wear protection layers. The layers are made from thermoplastically processable materials in the interest of ease of manufacture and further processing.

The fluid line 1 described above from the multilayer composite 2 fulfills the requirements to a particular extent. In particular, the permeation requirements in connection with high temperature requirements are met. The fluid line 1 has, for example, the dimensions 10x1.6 mm to 10x2 mm, preferably 10x1.8 mm, the first number describing the outside or inside diameter and the second number describing the wall thickness. However, other dimensions of the fluid line 1 can of course also be realized. An example of specific materials of the layers or sub-layers 5, 6, 7, 8, 9 and 10 has already been reproduced. The fluid line 1 described, just like the multilayer composite 2 from which the fluid line 1 is made, has the advantage of high durability while at the same time having very good availability of the materials. In addition, the structure of the multilayer composite 1 enables cost-effective production.

Claims

EXPECTATIONS

1. Multi-layer composite (2), in particular for a fluid line (1), characterized by a first layer (5) made of a fluoropolymer, a second layer (6) made of a polyamide immediately following the first layer (5) and at least a third layer (7), both the first layer (5) and the second layer (6) being modified to be electrostatically conductive.

2. Multi-layer composite according to claim 1, characterized in that the second layer (6) has a higher conductivity than the first layer (5).

3. Multi-layer composite according to one of the preceding claims, characterized in that the second layer (6) has a greater layer thickness than the first layer (5).

4. Multi-layer composite according to one of the preceding claims, characterized in that the fluoropolymer of the first layer (5) is ETFE or EFEP.

5. Multi-layer composite according to one of the preceding claims, characterized in that the polyamide of the second layer (6) is PA6, PA612, PA6 / 66 or PA616.

6. Multi-layer composite according to one of the preceding claims, characterized in that the third layer (7) has polyamide, in particular PA6, PA612, PA616 or PPA and / or ethylene-vinyl alcohol copolymer.

7. Multi-layer composite according to one of the preceding claims, characterized in that the third layer (7) has a plurality of partial layers (8, 9, 10) or is formed as an outer layer.

8. fluid line (1) from a multilayer composite (2), in particular from a multilayer composite (2) according to one or more of the preceding claims, characterized by a first layer (5) made of a fluoropolymer, one directly on the first layer (4) follow de second layer (6) made of a polyamide and at least a third layer (7), whereby the first layer (5) and the second layer (6) are probably modified electrostatically conductive.

9. Fluid line according to claim 8, characterized in that the first layer (5) is a fluid flow space (3) delimiting inner layer of the fluid line (1).

10. Fluid line according to one of the preceding claims, characterized in that the inner layer and / or one of the layers (5, 6, 7) present as an outer layer has at least one coating, in particular a flame and / or abrasion protection coating and / or an insulation coating.