DE10110964C2 - Thermoplastic multilayer composites - Google Patents

Description

The present invention relates to thermoplastic multilayer composites in the form of a Multi-layer pipe, which can in particular be a fuel line, or a multi-layer container containing at least one layer of a molding material based on Ethy len / vinyl alcohol copolymers and layers of molding compositions based on polyamide, see above like methods of making the same.

The invention particularly relates to hose or piping for gaseous or liquid media consisting of several polymer layers and an improved bar Show riereffekt especially against fuels. These fuels can also be alko have holic components. The multilayer according to the invention therefore relates to motor vehicle pipeline also the management of alcoholic media. This pipeline conditions should be alcohol-resistant, which means that the plastic tube when carrying a force substance that contains alcohol does not experience a disruptive elongation. Such a line is intended for the practically elongation-free management of premium gasoline with an alcohol content of 5% and possibly more. The term alcohol usually means Use of language in particular methyl alcohol and ethyl alcohol and mixtures thereof with water, but also higher quality alcohols. The term alcoholic medium be draws not only fuel with added alcohol in this context, but also z. B. liquids of a windshield washer or pressure media of a brake system.

The well-known multi-layer automotive pipelines have been around since the 1990s an increased need for security and stricter environmental regulations worn as the previously used polyamide monotubes. This was also in the German standards DIN 73378 and DIN 74342 are reflected.

In the presence of alcohol in the medium to be conveyed, disruptive effects are triggered.  The polyamide that comes into direct contact with the alcohol is swollen, where magnifications of 5-10% occur. The polyamide is made by the alcohol but also extracted, d. H. Monomers, oligomers, plasticizers, stabilizers etc. who the detached and go into the medium of alcohol. This changes the egg properties of the pipe. In addition, the detached at lower temperatures Monomers and oligomers fail and in the gasoline system (e.g. in filters and nozzles) lead to constipation. This phenomenon occurs particularly with polyamide 11 and polyamide 12 on.

The well-known multi-layer automotive piping had proven itself as long as that Medium that they carried, alcohol does not contain.

So you could think of it instead of the material polyamide for the power vehicle piping to use other, namely alcohol-resistant plastics. This fulfills However, the special requirements placed on media-carrying systems in vehicle construction are not Requirements from the lowest permeability values of the media to demanding full mechanical resistance with cold impact resistance from -40 ° C to 100 ° C up to high chemical resistance under the influence of road salt.

The German DIN 73378 mentioned above is the most important standard for in Europe Polyamide pipes for motor vehicles. It specifies for customized polya mid-type dimensions, burst pressure depending on the temperature up to 130 ° C, Impact resistance at 23 ° C and -40 ° C, stabilization, plasticizer content, flexibility (Tensile modulus of elasticity) and polyamide characteristics with defined short names. Festzu is that already in this very old DIN 73378 for laid under the body Pipes only modified polyamide 12 and polyamide 11 materials are permitted.

Also in the USA (SAE J 844d and J 1394), Great Britain (BS 5409) and Japan (JASO M 301) are only modified polyamide 12 and polyamide 11 types, e.g. B. for Bremslei cations and coils.

The standard requirements for today's fuel lines (SAE J 2260) are how  was mentioned above, varied. In addition to the typical mechanical and chemical Today's fuel lines must have polyamide characteristics from environmental protection and health highest barrier properties against volatile organic compounds gene. According to the current state of the art, there is a plastic fuel line device for passenger cars made of several layers of material. In doing so, they become targeted combined of several polymers. This is done by coextrusion. It is necessary that the individual layers that are in direct contact with each other stand, are compatible, in order to ensure good adhesion throughout the life of the Component. The use of egg is therefore between incompatible polymers nes adhesion promoter necessary.

Polyamides, especially polyamide 11 (PA 11) or polyamide 12 (PA 12), are because of good mechanical and chemical properties preferred for these applications Material for outer tube layers in use. Although polyamides are good mecha by themselves niche properties, especially good toughness, the blocking effect is sufficient compared to alcoholic fuels. Polar substances in particular can easily migrate through polyamides. This is, for example, the case with fuel lines in which alcohol containing fuel is extremely disadvantageous. This is with regard to the past Environmental and safety considerations that have arisen for years are undesirable.

Developments have therefore been carried out to improve multilayer pipes with To produce barrier layers. Nowadays, barrier layers are usually used Fluoropolymers such as PVDF and ETFE are used as a barrier. These materials are however expensive. This also occurs when using very thin layers of this material hen material costs for the entire pipe, which are 40-60% higher than with a one laminated tube made of PA 11 or PA 12. When using fluoropolymers, processing as well as disposal after using the product for Additional safety precautions must be taken for humans and the environment.

Ethylene / vinyl alcohol copolymers, also abbreviated EVAL, in English Language area also known as EVOH are barrier material against non-polar and po lare solvents are known and are used as barrier layers for multilayer Motor vehicle lines provided (cf. DE 35 10 395 A1, DE 38 27 092 C1 and  EP 0 428 834 A2). However, multilayer fuel lines with ethylene / Vinyl alcohol copolymers are hardly used as barrier layers in practice since the Availability of EVOH was very limited just a few years ago. So that EVOH Maintaining its excellent barrier properties, it needs to be protected from moisture become. It is therefore preferred as an intermediate layer and not in direct contact with the fluid used. It is also known that EVOH in pure form only in small amounts Layer thicknesses can be used. Ethylene / vinyl alcohol copolymers with the gefor Other barrier properties are known as extraordinarily brittle polymers with only little elongation at break.

According to the plastic paperback, Saechtling, 26th edition, contain typical EVAL Barrier types have a VAL content of 53 to 68 wt .-%. As a result, they have Ma materials has a significant moisture absorption capacity. It is described that this EVAL types with a water content of 3 to 8% lose the barrier effect. Saecht ling therefore recommends EVAL as a multilayer film between PE, PP and PA or PET use.

It would therefore be desirable if it were possible to find suitable polymers which at the same time as EVOH, as well as polyamides such as PA 11 and PA 12 of a multilayer result in good and permanent liability. The EVOH intermediate layer has there in, as already described in EP 0 428 833 B1, in addition to its main function as a barrier layer relative to the medium (e.g. fuel) the second function, that of this Layer and the layers arranged outwards monomers, oligomers and their substances do not dissolve in the transport medium (hence the additional designation "Solution inhibitor layer").

DE 41 30 486 A1 describes a multilayer tubular film for wrapping abge packed goods, especially food, during or after filling undergo a heat treatment. The film is made of at least three layers of polyamide built between the two EVOH layers for improved barrier effect are arranged between two polyamide layers. In a preferred embodiment Formation is also a layer based on ethylene and / or propylene between  two polyamide layers arranged, which has a water vapor barrier effect. The polyamide layers can optionally contain up to 30% by weight of (partially) aromatic polya contain mid and / or olefinic (co) polymer and / or (co) polyester.

DE 195 29 603 A1 (Wolff Walsrode) describes a four-layer tubular film, i.e. H. a sausage casing that has an inner and an outer layer on polyamide, an EVOH Layer as an oxygen barrier layer and a layer based on propylene as water includes vapor barrier layer.

DE 198 06 468 A1 (Wolff Walsrode) describes the as a variant of this arrangement Arrangement of a sealing layer as an outer layer. This is done on a carrier film Polyamide / EVOH / polyamide on one polyamide layer and an adhesion promoter layer then a layer based on polyethylene, ethylene copolymers or Polypropylene arranged.

EP 0 428 833 B1 (Technoflow), which corresponds to DE 40 01 125 C1, describes five layers Motor vehicle pipelines for media containing alcohol, consisting of an outer layer from the polymers PA 11 or PA 12, an intermediate layer made of PA 6, a solution intermediate layer of EVAL and an inner layer of PA 6. PA 6 and EVAL stick in direct contact with one another without an adhesion promoter. As the fifth shift between PA 6 and PA 12 contains the line described an adhesion promoter on polyethylene or Polypropylene base with active side chains. According to EP 0 428 833 B1, the be preferred EVAL types an ethylene content of 30 to 45%. According to EP 0 428 833 B1 are therefore two adhesion promoter layers, consisting of polyamide 6 or polyolefin not manoeuvrable to connect the EVAL with the polyamide 12.

EP 0 428 834 A2 (Technoflow), which corresponds to DE 40 01 126 C1, describes three-layered Fuel lines with ethylene / vinyl alcohol copolymer (EVAL) as interior, PA 11 or PA 12 as outer layer. As an adhesion promoter between EVAL and polyamide 11 or 12 polyethylene or polypropylene with active side chains is proposed.

DE 35 10 395 A1 (Technoflow) describes three-layer fuel lines with ethylene / vinyl alcohol copolymer  (EVAL) as an alcohol barrier. DE 35 10 395 A1 provides already the need to protect EVAL from moisture absorption. As a solution for this purpose is polyamide and in particular PA 11 and PA 12 as a water barrier proposed. According to DE-OS 35 10 395 there is no between EVAL and PA 11 or PA 12 Adhesion promoter provided. In practice, however, this does not result in sufficient liability between between layers. As a result, the layers of the pipe and it delaminate this loses its mechanical properties.

Kuraray Co., Ltd. describes in the product brochure: "KURARAY EVAL RESIN ", Oct. 92, that good adhesion between EVAL and" nylon "without adhesion allegedly possible, whereas an adhesion promoter is necessary for polyolefins. Likewise, US 5,491,009 A (Grace) describes a multilayer tubular film which is under including the layer sequence polyolefin / adhesion promoter / polyamide / EVOH / polya mid / adhesion promoter / polyolefin includes. Technoflow in DE 35 10 395 A1 as well Kuraray and US 5,491,009 A go between the special liability problems EVOH and PA 12 not one.

EP 0 692 374 A1 (Grace) describes a multilayer composite, i. H. a film according to US 5,491,009 A, with the exception that the EVOH layer on the polyamide layer up to 20 wt .-% copolyamide is added to the processability and the film structure to improve this layer.

JP 07-308996 A describes multilayer composites with EVOH barrier layers, however with the indication that these have the disadvantage that stress cracks in the EVOH the barrier effect decreases. This disadvantage can, according to JP 07-308996 A be overcome by adding a certain amount of copolyamide 6/12 to the EVOH mixed. With less than 10 wt .-% copolyamide 6/12 in the mixture, however, the Stress cracking resistance is insufficient, while more than 50 wt .-% copolyamide 6/12 the barrier properties deteriorate. According to JP 07-308996 A, too Multi-layer composites with two to seven layers are described. To the other ther It is explained that plastic layers also include polyamide or Polyester can also consist of mixtures of polyamide 6 with polyolefins.  

Furthermore, JP 07-308996 states that in copolyamide 6/12 a copolymer Ratio of caprolactam to laurolactam in a range from 85:15 to 55:45 is preferred.

EP 0 731 308 B1 (ELF ATOCHEM) describes multi-layer automotive pipelines described with an inner layer of a modified polyamide, in which a Polyolefin is dispersed as an impact modifier. The polyamide matrix made of polyamide 6 makes up the main component (65 parts). Inside is a copolymer of ethylene / butene and a copolymer of ethylene / ethyl acrylate / maleic anhydride dispersed. The Au The layer of the pipeline consists of polyamide 12; an EVOH layer is between the inner and outer layer and another adhesive layer arranged.

EP 1 036 968 A1 (Atofina), a document according to § 3 (2) 1 No. 2 PatG, describes more Layer polymer lines based on polyamides and in a preferred embodiment a layer sequence (from the inside out) with a first layer from one Mixture of polyamide and a polyolefin or a layer of polyamide, egg ner EVOH layer as a barrier layer, a layer of a copolyamide as an adhesive ler and a layer of a polyamide, in particular polyamide 11 or polyamide 12th can be. The adhesion promoters described in EP 1 036 968 A1 are copolyamide 6/12 with 20 up to 80% by weight of polyamide 6 as well as polyamide 612 and polyamide 610.

EP 0 617 219 A2 (Technoflow) describes multi-layer coextrusion Motor vehicle piping used as barrier layer plastics EVOH, polyamide and / or PBT contain. According to EP 0 617 219 A2, however, at least two thin barrier layers / Laminate films are worked, which can be the same or different in terms of material NEN, and these barrier films are bonded together by adhesion promoter films. Due to this multilayer structure of the laminate, it is possible that even with brittle barriers plastics significant bending deformations of such a tube are possible, in particular especially if the adhesion promoter films are set up to compensate for shear stress.

US 5,469,892 A (ITT) describes fuel lines with at least three layers and egg a corrugated area, d. H. corrugated walls. The fuel lines can be up to have a maximum of five layers. As the preferred material for the outer layer  Called polyamide 12; Polyamide 6 is the preferred material for the inner layer listed, which can also be electrically conductive. The more Layer tube according to US 5,469,892 A can also contain intermediate layers that do not are made of polyamide and have barrier properties against hydrocarbons the fuel. A PBT and / or EVOH layer is used as the barrier layer mentioned.

No. 5,460,771 A (ITT), which corresponds to EP 0 743 894 B1 and DE 695 14 645 T2 a process for the production of corrugated tubes from three or more layers of corrugated tubes for fuel transportation. In addition to fluoropoly, the material for the inner layer Ren also listed various polyamides (PA 6, PA 11, PA 12), while the exterior Layer can be made of polyamide 12 or polyamide 11. Alternative to fluoropolymer Barrier layers may consist of EVOH intervening barrier layers. Become a problem of the lack of liability between EVOH and PA 12 or PA 11 but made no suggestions.

DE 195 37 003 A1 (EMS Inventa AG) describes thermoplastic multilayer composites from at least one inner layer made of thermoplastically processable fluoropolymers, at least one adhesion promoter layer based on polyamide, which has an amino end group Excess pen and at least one added to the polymerized polyamide tes diamine and at least one polyamide outer layer, these layers by force are conclusively connected. The multilayer composites according to DE 195 37 003 A1 can also be in the form of multilayer pipes or multilayer containers. The Adhesion promoter described in DE 195 37 003 A1 is based on polyamide and works in in practice only with an added diamine. Furthermore, DE 195 37 003 A1 no multilayer composites with EVOH described as barrier layers.

In the automotive industry, pre-formed assemblies are used to achieve efficient assembly processes Fuel lines used. For this purpose, the plastic pipes are thermoge forms, d. H. permanently deformed under the influence of heat. This process is preferred with Hot air, oil, infrared or water vapor are carried out. A high level of profitability achieved with steam at temperatures in the range of 140 ° C to 160 ° C. This high  thermal stress, however, requires optimal adhesive strength and temperature durability of the pipe materials used.

It is therefore an object of the present invention to provide an inexpensive thermoplastic Multilayer composite in the form of a multilayer pipe or a multilayer container, in particular a multi-layer fuel line with a barrier effect for the automobile industry without providing the use of fluoropolymers, a simple manufacture position and further processing is made possible. In particular, even at high thermal stress, as z. B. is the case with thermoforming, optimal adhesion strength and temperature resistance of the pipe materials used.

The above object is achieved by the thermoplastic multilayer composite according to the Features of claim 1 and solved by the method according to claim 10.

Advantageous embodiments of the invention are contained in the subclaims.

The inventors have surprisingly found that polyamides are selected from the group a mixture of polyamide 6 and polyamide 12 with a compatibilizer, one Mixture of polyamide 6 and polyamide 11 with compatibility agent, at the same time good, permanent and permanent adhesion to both EVOH and polyamide 12 or ensure polyamide 11.

Multi-layer composites according to the invention contain at least one intermediate layer a molding compound based on ethylene / vinyl alcohol copolymers between layers from molding compounds based on polyamide (with the term polyamide homopo lyamides, copolyamides and mixtures of homopolyamides and / or copolyamides be understood), wherein the intermediate layer adheres to at least one side mediating layer of a molding compound based on that in the previous paragraph guided polyamides with at least one layer of a molding compound based on Polyamide 12 or polyamide 11 is connected. In addition to polyamide 12 or polyamide 11 In the latter layer, polyamide 1010, polyamide 1012 or polyamide 1212 are also used det, which also have insufficient liability to EVOH.  

The multilayer composites according to the invention are in the form of a multilayer pipe or a multi-layer container.

With regard to the EVOH intermediate layer, the layer structure on both sides be different or the same.

When using one of the polyamide mixtures mentioned as an adhesion-promoting form mass, the proportion of polyamide 6 is preferably between 25 and 80 parts by weight, be contracted to 100 parts by weight of both polyamides.

In a particular embodiment of the invention, in order to thermoform a To avoid restrictions, ensure that the melting point of the adhesive the polyamides is above 150 ° C.

In a preferred embodiment of the invention, the thermoplastic material consists Layer composite of an inner layer (a) made of a molding compound based on polyamide 6, polyamide 46, polyamide 66, polyamide 69, polyamide 610 or polyamide 612, which adhere directly to EVOH, followed by a layer (b) of a molding compound based on Ethylene / vinyl alcohol copolymers, an adhesion promoter layer (c) from a molding compound based on the aforementioned adhesion-promoting polyamides and an outer layer (d) made of egg ner molding compound based on polyamide 12 or polyamide 11 (see claim 7).

In a particularly preferred embodiment of the invention, the inner layer (a) with antistatic agents such as carbon black, carbon fibers, graphite fibers, metal powder or fibers, etc. permitted so that the inner layer becomes electrically conductive. For this purpose, however also an additional fifth, thin interior made electrically conductive by antistatic agents layer based on the polyamides of layer (a) are provided. Such an additional che innermost layer is cheaper than the thicker layer (a) to be antistatic.

Also within the scope of claim 1, it is of course possible, the inner layer of the Multi-layer composite, which is not limited to the polyamides previously mentioned under (a)  is to provide antistatic equipment. For example, a so-to-speak is symmetrical 5 layers possible, with EVOH as middle layer and PA 12 as outer and Inner layer, each with an adhesion promoter layer according to the invention in between. The polyamide 12 inner layer can be electrically conductive, especially with carbon serum or soot.

The polyamide molding compositions of the thermoplastic multilayer according to the invention composites can furthermore one or more chewing agents which improve the impact resistance Tschuke included.

Such rubbers, also called impact modifiers, have been described, among others ben in EP 0 654 505 A1, from page 4, line 38, to page 5, line 58, and because of this detailed listing well known to those skilled in the art. Common is such Impact modifiers that they contain an elastomeric component and at least one Have functional group that can react with the polyamide, for example one Carboxylic acid or carboxylic anhydride group.

Impact modifiers are produced by grafting or copoly merize the starting polymers with suitable reactive compounds such as malein acid anhydride, (meth) acrylic acid or glycidyl (meth) acrylate. Often you can Rewrite impact modifiers as grafted copolyolefins. Wed. different impact modifiers are used.

From the affinity of the impact modifiers with polyamides due to the functional Groups follows that in the adhesion promoting layer according to the invention in the case of Polyamide blends just impact modifiers at the same time the role of the contract can act as an intermediary. According to the invention, preference is given to acid remodified ethylene / α-olefin copolymers used. Other suitable contracts keitsvermittler for the adhesion-promoting layer according to the invention are, for. B. Block Copolyamides such as block copolyamide 6/12.

The proportion of compatibilizer in the mixtures is preferably up to  30% by weight, particularly preferably 5 to 15% by weight.

In addition to the already mentioned antistatic agents for the inner layer or an additional inner one top layer, the polyamide molding compounds can also contain a flame retardant and white tere additives such as pigments, oligo- and polymers, stabilizers and processing contain tools and reinforcing agents (e.g. glass fibers). The proportion of ampl Kungsmittel can up to 50 wt .-%, that of the flame retardant up to 15 wt .-% and of all other additives up to 5% by weight, based on the total Molding compound.

The polyamide molding compounds can be used as a variant to increase the barrier properties for the layers of the thermoplastic multilayer composites according to the invention Layered silicates can be filled. In the resulting layers, a ver improved permeation behavior also the strength, heat resistance and rigidity improved without the toughness and elongation at break deteriorating, as with usual fillers such as glass fibers or minerals is the case. According to the invention therefore at least one of the layers of the multilayer composite, but preferably also that Molding compound for the intermediate layer based on ethylene / vinyl alcohol copolymers, in the polymer matrix contain layered silicates. Because layered silicates are easy to swell and it is possible to exchange the cations present in the layer planes Lich, the incorporation of the mineral in the polyamide and / or ethylene / vinyl alcohol copolymer in nano-fine distribution during the polycondensation or polymerization, or wah rend saponification (hydrolysis) of ethylene / vinyl acetate copolymer.

The proportion of layered silicates in the polymer matrix can be 0.5 to 50 parts by weight per 100 parts by weight of the polymer matrix. As layered silicates such. B. Clay mine rale of the montmorillonite series, such as montmorillonite, hectorite, nontronite, saponite, vermi culit, in question because these clays have a large base exchange capacity. The Her Polyamide layered silicate nanocomposites have been available since the 1970s known. For example, reference is made to DE 36 32 865 C2.

The multilayer composites according to the invention can be produced in one or more stages  respectively. In one-step processes, the components are processed simultaneously, z. B. by (co-) extrusion, (multi-component) injection molding or extrusion blow molding. In the one-step extrusion process, for example, the different smelts Zen co-extruded. In a multi-stage process, at least one com component into the desired shape by thermoplastic processing and then with the other components, which are caused by pressing, injection molding (e.g. Hin injection molding), extrusion or extrusion blow molding (e.g. sequential extrusion blow molding shape) can happen.

Multi-layer pipelines according to the invention can thus be used in the coex process (simul tan) or in the coating process (two-stage). In umman At least one layer is applied to a precalibrated inner tube Layers applied.

The multilayer composites according to the invention are used as construction parts, above all in Mechanical and automotive industries use. In particular, the Multi-layer composites according to the invention Use as multi-layer pipes, preferred as fuel lines, such as B. diesel or gasoline lines, or as a tank filler Zen. In compliance with the regulations for food contact, there are also applications conceivable in the food sector, for example hoses or pipes for trans port of alcoholic beverages. The multilayer composite according to the invention can also have the shape of a hollow body or container to contain liquid media from the to store mentioned application areas, e.g. B. in the form of a bottle, a canister or as a tank, summarized under the term multi-layer container.

The multilayer composites according to the invention, in particular those according to the invention Motor vehicle pipelines preferably consist of four layers or five Layers with an additional antistatic inner layer.

Fig. 1 shows schematically a four-layer plastic fuel line according to the invention made by coextrusion made of plastic in cross section. The reference symbols mean:

• 1. a: inner layer
• 2. b: barrier and solution inhibitor layer
• 3. c: Intermediate layer of adhesion promoter
• 4. d: outer layer

Fuel lines for automobiles often have a dimension of 8 × 1 mm, ie 8 mm outside diameter and a wall thickness of 1 mm. A preferred fuel line according to the invention is now constructed, for example, as follows, without restricting the invention thereto:

• 1. a: inner layer of a molding compound based on polyamide 6; 0.2 to 0.7 mm thick,
• 2. b: barrier and solution inhibitor layer made of a molding compound based on an ethyl len / vinyl alcohol copolymer; 0.1 to 0.3 mm thick,
• 3. c: Intermediate adhesive layer based on a molding compound made of polyamide, selected from the group: Mixture of polyamide 6 and polyamide 12 with compatibility ver medium; 0.05 to 0.2 mm thick,
• 4. d: outer layer of a molding compound based on polyamide 12; 0.2 to 0.7 mm thick.

In the following, the tests carried out are explained in detail and first the described materials used.

used material

• a) for the inner layer:
  • - Grilon® BRZ 247 WCA: an impact-resistant and plasticized polyamide 6 from EMS-CHEMIE AG, Domat / Ems, Switzerland (the low-viscosity Grilon® BRZ 234 WCA is also suitable);
• b) for the barrier and inhibitor layer:
  • - EVAL® EP-F 101A: ethylene / vinyl alcohol copolymer, a product of KURARAY;
• c) for the outer layer:
  • - Grilamid® L 25 W 40 CA: an impact-resistant and plasticized polyamide 12 from EMS-CHEMIE AG, Domat / Ems, Switzerland (the Grilamid® L 25 W 20 CA type, which contains less plasticizer, is also suitable);
• d) for the intermediate adhesive layer:
  • - Admer® QB 510 E: a polypropylene grafted with maleic anhydride, a product from MITSUI;
  • - Grilon® C XE 3813: a mixture of 45% by weight of polyamide 6 and 45% by weight of polyamide 12 and 10% by weight of an acid-modified ethylene / α-olefin copolymer as a compatibilizer, a product from EMS- CHEMIE AG, Domat / Ems, Switzerland.

The various layers were brought together by coextrusion. Pipes measuring 8 × 1 mm were produced on a commercially available multilayer coextrusion plant, the material for the adhesion promoter layer (c) being varied. The following layer thicknesses were set:

• - Inner layer (a): 0.35 mm
• - Layer (b): 0.25 mm
• - Layer (c): 0.10 mm
• - Outer layer (d): 0.30 mm

Table 1 below shows the suitability of the investigated polyamide derivatives as Adhesion promoter between polyamide 12 (Grilamid® L 25 W 40 CA black 9992) and EVOH (EVAL® EP-F 101A) and the qualitative adhesive strength both in the original condition as well as after steam treatment.

The liability was checked according to SAE-XJ2260 (visual assessment according to mechanical Deformation).

Table 1

The multilayer pipe according to the invention meets the SAE J 2260 requirements, as described in Ver looking for the inventor could be shown. It shows good extrudability, and that too Production as a corrugated pipe is possible (so that at least partial areas have a corrugated wall exhibit). High impact resistance and temperature resistance can continue to invent multi-layer pipe according to the invention, since there are no adhesion promoters on polyethylene or Polypropylene base can be used. Furthermore, standardized and tried and tested Materials are used.

Of particular note is the advantage of excellent adhesion according to the invention is also not lost when thermoforming with steam. In this regard, the embodiments are  with the described polyamide mixtures as adhesion-promoting molding compositions particularly stable.

Steam thermoforming also has another advantage: the more layer pipes are becoming more flexible, which makes them easier to assemble. This effect is already known from the similarly constructed multilayer films from DE 198 06 468 A1, in which, however, does not disclose a multilayer composite with a sequence of layers according to the present invention is.

What is surprising, however, is the fact that steam-formed, inventive Multi-layer pipes measured no deterioration in the barrier properties (permeation) when steam thermoforming under normal practical conditions, i.e. H. no longer than 5 Minutes at not more than 150 ° C. This was due to the statement on Barrier effect of EVAL under the influence of water in the plastic paperback quoted at the beginning (Saechling) not to be expected.

Finally, it should also be pointed out that the assessment of the stand Problems of EVOH mentioned in the art, namely its sensitivity to breakage and chip susceptibility to cracking, did not appear in the present invention. This is often the case Can be seen in the very good embedding in the multilayer composite according to the invention, d. H. at the excellent adhesion to both adjacent polyamide layers, which is the EVOH layer optimal support.

Claims (10)

1. Thermoplastic multi-layer composite in the form of a multi-layer tube or a multi-layer container, containing
at least one intermediate layer made of a molding compound based on ethylene / vinyl alcohol copolymers between layers of molding compounds based on polyamide,
and at least on one side of the intermediate layer, a secondary layer made of a molding compound based on polyamide 12, polyamide 11, polyamide 1010, polyamide 1012 or polyamide 1212,
characterized in that between the at least one secondary layer and the intermediate layer, an adhesion-promoting layer made of a molding compound based on polyamide, selected from the group consisting of a mixture of polyamide 6, polyamide 12 and a compatibility agent, a mixture of polyamide 6, polyamide 11 and a compatibility agent is arranged. 2. Thermoplastic multilayer composite according to claim 1, characterized in that the intermediate layer of ethylene / vinyl alcohol copolymers on both sides via adhesion middle layers is bound to secondary layers. 3. Thermoplastic multilayer composite according to claim 1 or 2, characterized in that the multilayer pipe has a corrugated wall at least in some areas. 4. Thermoplastic multilayer composite according to claims 1 to 3, characterized in that as a molding compound for the adhesion-promoting layer, a polyamide mixture made of polyamide 6, Polyamide 12 and a compatibility agent with a proportion of polyamide 6 between 25 and 80 parts by weight, based on 100 parts by weight of the two polyamide components in the Mixture, or a polyamide blend of polyamide 6, polyamide 11 and a contract lichkeitsvermittler with a polyamide 6 content of between 25 and 80 parts by weight, be pulled to 100 parts by weight of the two polyamide components in the mixture, is used.   5. Thermoplastic multilayer composite according to claims 1 to 4, characterized in that the compatibility mediator in the polyamide blends is one to improve the Impact toughness-modifying polymer used by polyamides, in particular a Impact modifier, elastomer or rubber, with acid-modified ethylene / α- Olefin copolymers are preferred, and the compatibilizer particularly in men up to 30% by weight is present in the polyamide blends. 6. Thermoplastic multilayer composite according to one of the preceding claims 1 to 5, characterized in that the polymer molding compositions for the individual layers, esp especially the molding compound for the ethylene / vinyl alcohol copolymer layer, with layered silicates filled in an amount of 0.5 to 50 parts by weight per 100 parts by weight of the polymer matrix are. 7. Thermoplastic multilayer composite according to one of the preceding claims 1 to 6, characterized by

• a) an inner layer made of a molding compound based on polyamide 6, polyamide 46, polyamide 66, polyamide 69, polyamide 610 or polyamide 612,
• b) an intermediate layer made of a molding compound based on ethylene / vinyl alcohol copolymers,
• c) a between the intermediate layer (b) and the outer layer (d) and adjoining the se-promoting adhesion-promoting layer made of a molding compound based on polyamide, selected from the group consisting of a mixture of polyamide 6 and polyamide 12 with a compatibilizer, in particular with a Proportion of polyamide 6 from 25 to 80 parts by weight, based on 100 parts by weight of the two polyamide components in the mixture, a mixture of polyamide 6 and polyamide 11 with a compatibilizer, in particular with a proportion of polyamide 6 from 25 to 80 Parts by weight, based on 100 parts by weight of the two polyamide components in the mixture, and
• d) an outer layer made of a molding compound based on polyamide 12 or polyamide 11.

8. Thermoplastic multilayer composite according to claim 7, characterized in that the inner layer (a) or an additional innermost layer based on the polyamides of  Layer (a) contains additives that make them electrically conductive, carbon fibers and / or Lead black is preferred. 9. Thermoplastic multilayer composite according to one of claims 1 to 8, characterized ge indicates that the multilayer pipe is a fuel line. 10. Process for producing a thermoplastic multilayer composite in one or more reren stages according to claims 1 to 9 by injection molding, coextrusion, extrusion blow molding molding, pressing or in the coating process.