DE10110964A1 - Thermoplastic multilayer composites - Google Patents

Abstract

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 compound based on ethylene / vinyl alcohol copolymers between layers of molding compounds based on polyamide, the intermediate layer comprising 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 a compatibility agent, with at least one Side layer of a molding compound based on polyamide 12, polyamide 11, polyamide 1010, polyamide 1012 or polyamide 1212 is connected.

Description

The present invention relates to thermoplastic multilayer composites, in particular in the form of a multi-layer hose, a multi-layer tube, which in particular a Fuel line can be, or a multi-layer container containing at least one Layer of a molding compound based on ethylene / vinyl alcohol copolymers and Layers of molding compounds based on polyamide, as well as manufacturing processes the same.

The invention particularly relates to hose or piping for gaseous or liquid media that consist of several polymer layers and an improved Show barrier effect especially against fuels. These fuels can too have alcoholic components. Therefore relates to the invention Multi-layer automotive pipeline also the management of alcoholic media. This Pipelines should be alcohol-resistant, which means that the plastic pipe when guiding a fuel that contains alcohol does not experience a disruptive elongation. Such The line is intended for the practically elongation-free management of premium gasoline with one Alcohol content of 5% and possibly more. The term alcohol in common usage means especially methyl alcohol and ethyl alcohol and Mixtures of these with water, but also higher quality alcohols. The term alcoholic medium does not only refer to fuel in this context Alcohol additive, but also e.g. B. liquids of a windscreen washer or Print 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.  

If alcohol is present in the medium to be conveyed, there will be disruptive effects triggered. The polyamide that comes into direct contact with the alcohol becomes swollen, with size increases of 5-10%. The polyamide is through but also extracted the alcohol, d. H. Monomers, oligomers, plasticizers, Stabilizers etc. are released and pass into the medium of alcohol. Thereby the properties of the pipe change. Furthermore, at lower temperatures the extracted monomers and oligomers fail and in the gasoline system (e.g. in Filters and nozzles) lead to blockages. This phenomenon occurs particularly Polyamide 11 and polyamide 12.

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

Therefore one could also think of replacing the material polyamide for the Motor vehicle piping to use other, namely alcohol-resistant plastics. This however do not meet the requirements placed on media-carrying systems in vehicle construction special requirements that range from the lowest permeability values of the media demanding 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. You specified for customized Polyamide types dimensions, burst pressure depending on 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. It should be noted that this very old DIN 73378 for under the body Installed pipes only allow modified polyamide 12 and polyamide 11 materials become.

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 Brake lines and coils approved.  

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 Highest barrier properties against volatile organic health reasons Have connections. According to the current state of the art, there is one Plastic fuel line for passenger cars made of several layers of material. there properties of several polymers are combined in a targeted manner. This happens in the Paths of coextrusion. It is necessary that the individual layers in the are in direct contact with one another, are compatible, thus ensuring good adhesion to achieve throughout the life of the component. Between incompatible It is therefore necessary for polymers to use an adhesion promoter.

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 on their own mechanical properties, in particular good toughness, suffice No blocking effect against alcoholic fuels. In particular polar substances Zen can easily migrate through polyamides. This is the case with fuel, for example Lines in which alcohol-containing fuel is carried, extremely disadvantageous. This is in With regard to environmental protection and safety issues that have emerged in recent years considerations 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. Even when using very thin layers of this material material costs for the entire pipe are 40-60% higher than for one Single-layer pipe made of PA 11 or PA 12. In addition, when using fluoropolymers in processing as well as in 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 polar 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. Therefore it is preferred as an intermediate layer and not in direct contact used with the fluid. It is also known that EVOH in pure form only in small layer thicknesses can be used. Ethylene / vinyl alcohol copolymers with The required barrier properties are known to be extremely fragile Polymers with low 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 own Materials have a significant moisture absorption capacity. It is described that these EVAL types lose the barrier effect with a water content of 3 to 8%. Saechtling therefore recommends EVAL as a multilayer film between PE, PP and PA or Use PET.

It would therefore be desirable if suitable polymers could be at the same time as EVOH, as well as polyamides such as PA 11 and PA 12 Multilayer composite result in good and permanent adhesion. The EVOH The intermediate layer has, as already described in EP 0 428 833 B1, next to it Main function as a barrier layer against the medium (e.g. fuel) is the second Function that from this layer and the layers arranged outwards Monomers, oligomers and other substances not in solution in the transport medium go (hence the additional name "solution inhibitor layer").

EP 0 428 833 B1 (Technoflow), which corresponds to DE 40 01 125 C1, describes five layers term automotive piping for alcoholic media, consisting of an outside layer of the polymers PA 11 or PA 12, an intermediate layer of PA 6, one  Solution inhibitor intermediate layer made of EVAL and an inner layer made of PA 6. PA 6 and EVAL adhere to each other without a bonding agent. As the fifth shift between PA 6 and PA 12, the line described contains an adhesion promoter Polyethylene or polypropylene base with active side chains. According to EP 0 428 833 B1 the preferred EVAL types have an ethylene content of 30 to 45%. According to EP 0 428 833 B 1 are therefore two adhesion promoter layers consisting of polyamide 6 or Polyolefin necessary to connect the EVAL to the polyamide 12.

EP 0 428 834 A2 (Technoflow), which corresponds to DE 40 O1 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-OS 35 10 395 (Technoflow) describes three-layer fuel lines Ethylene / vinyl alcohol copolymer (EVAL) as an alcohol barrier. DE-OS 35 10 395 sees already the need to protect EVAL from moisture absorption. As a solution for these purposes polyamide and in particular PA 11 and PA 12 are used Water barrier layer proposed. Between EVAL and PA 11 or PA 12 is according to DE-OS 35 10 395 no adhesion promoter provided. In practice, however, this does not mean that sufficient adhesion between the layers is achieved. As a result, the Layers of the pipe and it 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 promoter is allegedly possible, but an adhesion promoter for polyolefins is necessary. Both Technoflow in DE-OS 35 10 395 and Kuraray go there do not address the special liability problems between EVOH and PA 12.

JP 07-308996 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 can be overcome by adding a certain amount of copolyamide to the EVOH 6/12 mixes. With less than 10 wt .-% copolyamide 6/12 in the mixture, however  the stress cracking resistance is insufficient, while at more than 50% by weight Copolyamid 6/12 the barrier properties become worse. According to JP 07-308996 multilayer composites with two to seven layers are also described. To the Further thermoplastic layers are explained that these also include Polyamide or polyester but also from mixtures of polyamide 6 with polyolefins can exist. Furthermore, JP 07-308996 states that in copolyamide 6/12 a copolymerization ratio of caprolactam to laurolactam in a range of 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 The outer layer of the pipeline consists of polyamide 12; an EVOH layer is between the inner and outer layer and another adhesive layer.

EP 0 617 219 A2 (Technoflow) describes multi-layer coextrusion Motor vehicle pipelines that are used as barrier layer plastics EVOH, polyamide and / or PBT included. According to EP 0 617 219, however, at least two thin ones must be used Barrier / laminate films are worked, the same in terms of material or can be different, and these junction films are made by Bonding agent films brought together. Through this multilayer structure of the laminate it is possible that even with brittle barrier plastics, considerable bending deformations of such a tube are possible, especially if the adhesion promoter films are set up to compensate for shear stress.

US 5,469,892 (ITT) describes fuel lines with at least three layers and 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 is called polyamide 12; Polyamide 6 is the preferred material for the inner layer listed, which can also be electrically conductive. The Multi-layer pipe according to US 5,469,892 can also contain intermediate layers, which are 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 (ITT), which corresponds to EP 0 743 894 B1 or DE 69 51 4645 T2 a process for the production of corrugated tubes from three or more layers of corrugated tubes for fuel transportation. As a material for the inner layer are next to Fluoropolymers also listed various polyamides (PA 6, PA 11, PA 12) the outer layer can consist of polyamide 12 or polyamide 11. alternative to Fluoropolymer barrier layers can consist of intermediate barrier layers EVOH exist. The problem of the lack of liability between EVOH and PA 12 or PA 11, however, no suggestions are made.

In the automotive industry, pre-formed assemblies are used to achieve efficient assembly processes Fuel lines used. For this purpose, the plastic pipes thermoformed, d. H. permanently deformed under the influence of heat. This is preferred Process carried out with hot air, oil, infrared or steam. A high Profitability is achieved with steam at temperatures in the range of 140 ° C to 160 ° C reached. However, this high thermal load requires optimal adhesion and temperature resistance of the pipe materials used.

It is therefore an object of the present invention to provide an inexpensive thermoplastic Multi-layer composite, that means in particular a multi-layer fuel line Barrier effect for the automotive industry without the use of fluoropolymers To provide, allowing easy manufacturing and processing. In particular, even with a high thermal load, as z. B. at Thermoforming is the case, optimal adhesive strength and temperature resistance of the used pipe materials.

The above task is accomplished by the thermoplastic multilayer composite according to the Features of claim 1 and solved by the method according to claim 11.

Advantageous embodiments of the invention are contained in the subclaims.  

The inventors have surprisingly found that polyamides are selected from the group Copolyamide 6/12, in particular with 40 to 83% by weight of caprolactam (hereinafter referred to as polyamide 6), block copolyamide 6/12, homopolyamide 612 (= Polyamide 612), polyamide 610, a mixture of polyamide 6 and polyamide 12 with Compatibility agent, a mixture of polyamide 6 and polyamide 11 with Compatibility agent, at the same time a good, constant and permanent liability ensure both for EVOH and for polyamide 12 or polyamide 11. At the Copolyamide 6/12, a polyamide 6 content of 55 to 80 wt .-% is particularly preferred.

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 Homopolyamides, copolyamides and mixtures of homopolyamides and / or Copolyamides are understood), with the intermediate layer on at least one side via an adhesion-promoting layer made of a molding compound based on the previous paragraph listed 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 can also polyamide 1010, polyamide 1012 in the latter layer or polyamide 1212 can be used, which is also insufficient compared to EVOH Have liability.

The multilayer composites according to the invention can take the form of a multilayer hose, a multi-layer tube 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 promoter Molding compound, the proportion of polyamide 6 is preferably between 25 and 80 Parts by weight, based on 100 parts by weight of both polyamides together.  

In a particular embodiment of the invention has been used in thermoforming To avoid restrictions, be careful that the melting point of the adhesion-promoting 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, whereby in the case of copolyamide 6/12 the polyamide 6 content is 55 to 80% by weight, and an outer layer (d) a molding compound based on polyamide 12 or polyamide 11 (see claim 8).

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. equipped so that the inner layer becomes electrically conductive. For this purpose but also an additional fifth, thin one, made electrically conductive by antistatic agents Inner layer based on the polyamides of layer (a) can be provided. Such additional 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 does not apply to the polyamides previously mentioned under (a) is limited to antistatic equipment. So, for example, is one symmetrical construction possible with 5 layers, with EVOH as middle layer and PA 12 as the outer and inner layer, each with an adhesion promoter layer according to the invention between. The polyamide 12 inner layer can be electrically conductive, in particular with carbon fibers or conductive carbon black.

The polyamide molding compositions of the thermoplastic multilayer according to the invention Composites can also have one or more impact strengthening agents Rubbers included.  

Such rubbers, also called impact modifiers, are among others described in EP 0 654 505 A1, from page 4, line 38, to page 5, line 58, and on the basis of this detailed list is well known to the person 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 Copolymerize the starting polymers with suitable reactive compounds such as Maleic anhydride, (meth) acrylic acid or glycidyl (meth) acrylate. You can often therefore describe impact modifiers as grafted copolyolefins. It can mixtures of different impact modifiers can also be 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 Compatibility agent can take over. Are preferred Acid-modified ethylene / α-olefin copolymers used according to the invention. Other suitable compatibilizers for the adhesion-promoting layer according to the invention are z. 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 one innermost layer, the polyamide molding compounds can also contain a flame retardant other additives such as pigments, oligomers and polymers, stabilizers and Contain processing aids and reinforcing agents (e.g. glass fibers). The amount reinforcing agents can contain up to 50% by weight of the flame retardants 15% by weight and all the other additives in total up to 5% by weight, in each case 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. The resulting layers are next to one improved permeation behavior also the strength, heat resistance and Improves rigidity without sacrificing toughness and elongation like this is the case with conventional fillers such as glass fibers or minerals. According to the invention can therefore at least one of the layers of the multilayer composite, but preferably also the molding compound for the intermediate layer based on ethylene / vinyl alcohol Copolymers containing layered silicates in the polymer matrix. Because layered silicates look good can swell and exchange the cations present in the layer levels let, it is possible to incorporate the mineral into the polyamide and / or Ethylene / vinyl alcohol copolymer in nano-fine distribution during polycondensation or polymerization, or during the 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 minerals of the montmorillonite series, such as montmorillonite, hectorite, nontronite, saponite, Vermiculite, in question, since these clays have a large base exchange capacity. The Polyamide layered silicate nanocomposites has been manufactured 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, e.g. B. by (co-) extrusion, (multi-component) injection molding or extrusion blow molding. In the one-step extrusion process, for example, the different Melt co-extruded. In the case of a multi-stage procedure, at least a component is brought into the desired shape by thermoplastic processing and then acted on with the remaining components, which by pressing, injection molding (e.g. back injection), extrusion or extrusion blow molding (e.g. sequential Extrusion blow molding) can happen.  

Multilayer pipelines according to the invention can thus be used in the coex process (Simultaneously) 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. Find in particular the multilayer composites according to the invention, use as multilayer pipes, preferably as fuel lines, such as. B. diesel or gasoline lines, or as Tank filler neck. They are in compliance with the regulations for food contact Applications in the food sector are also conceivable, for example hoses or pipes for the transport of alcoholic beverages. The multilayer according to the invention Composite can also have the shape of a hollow body or container to hold liquid in it Store media from the application areas mentioned, 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, according to the Invention fuel line made of plastic made by coextrusion in cross section. The reference symbols mean:
a: inner layer
b: barrier and solution inhibitor layer
c: Intermediate layer of adhesion promoter
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:
a: inner layer of a molding compound based on polyamide 6; 0.2 to 0.7 mm thick,
b: barrier and solution inhibitor layer made of a molding compound based on an ethylene / vinyl alcohol copolymer; 0.1 to 0.3 mm thick,
c: Adhesion promoter intermediate layer based on a molding compound made of polyamide, selected from the group consisting of copolyamide 6/12 with 55 to 80% by weight of polyamide 6, block copolyamide 6/12, polyamide 612, mixture of polyamide 6 and polyamide 12 with compatibility agent and polyamide 610; 0.05 to 0.2 mm thick,
d: outer layer made 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 101 A: 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® A 6059M: a copolyamide 6/12 with a 10% by weight polyamide 6 content, a product from EMS-CHEMIE AG, Domat / Ems, Switzerland;
  • - Grilon® A 6060M: a copolyamide 6/12 with 20% by weight polyamide 6 content, a product from EMS-CHEMIE AG, Domat / Ems, Switzerland;
  • - Grilon® A 6061 M: a copolyamide 6/12 with 30% by weight polyamide 6 content, a product from EMS-CHEMIE AG, Domat / Ems, Switzerland;
  • - Grilon® CF 65: a copolyamide 6/12 with a polyamide 6 content of 40% by weight, a product of EMS-CHEMIE AG, Domat / Ems, Switzerland;
  • - Grilon® CF 7: a copolyamide 6/12 with a polyamide 6 content of 55% by weight, a product from EMS-CHEMIE AG, Domat / Ems, Switzerland;
  • - Grilon® CR 8: a copolyamide 6/12 with a polyamide 6 content of 73% by weight, a product of EMS-CHEMIE AG, Domat / Ems, Switzerland;
  • - Grilon® CR 10 CA: a copolyamide 6/12 similar to type CR 8 but modified, a product of EMS-CHEMIE AG, Domat / Ems, Switzerland;
  • - Grilon® CR 9: a copolyamide 6/12 with 83% by weight polyamide 6 content, a product from EMS-CHEMIE AG, Domat / Ems, Switzerland;
  • - Zytel® 350 PHS2-NC010: a polyamide 612 from DU PONT;
  • - Grilon® XS 1261: a polyamide 610, a product of EMS-CHEMIE AG, Domat / Ems, Switzerland.
  • - 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 following diagram with the heading: "CoPA 6/12 with a different composition ratio as an adhesion promoter between PA 12 and EVOH" shows the suitability of the copolyamide 6/12 used according to the invention as an adhesion promoter for polyamide 12 and EVOH. The scale of the abscissa is not strictly linear, because the difference in the composition ratio for the CoPA 6/12 types that were available was not always equidistant. Therefore the curve with the effective melting points looks somewhat distorted. The specified composition ratio (PA 6 / PA 12 content) corresponds to the ratio of caprolactam to laurolactam in the production of these statistical copolyamides. In addition to the types used in the adhesion tests, a diagram is entered in the diagram as a further gradation in the composition and melting point range, which has a PA 6 content of 80% by weight.

Table 2 below shows the permeation rate of tubes of the prior art in the so-called mini-SHED test (Sealed Housing for Evaporative Determination) in Comparison to a 4-layer pipe according to the invention shown, according to the test of EG & G AUTOMOTIVE RESEARCH, where a cyclical Temperature profile according to regulation CARB 95 (regarding California law Hydrocarbon emissions in automotive engineering) was applied.

Table 2

(Permeation values with test conditions according to CARB 95)

In summary, it can be stated that the multilayer tube according to the invention also the construction from the inside out: PA6 / EVOH / CoPA6 / 12 / PA12 a very good, d. H. has very low permeation rate.

The multilayer pipe according to the invention meets the SAE J 2260 requirements, as in Attempts by the inventors could be shown. It shows good extrudability, and Production as a corrugated pipe is also possible (so that at least partial areas have a have corrugated wall). High impact and temperature resistance can also be certified for the multilayer pipe according to the invention, since none Adhesion promoters based on polyethylene or polypropylene can be used. Farther standardized and proven materials can be used.

Of particular note is the advantage of excellent adhesion according to the invention, which is not lost even with steam thermoforming. In this regard, they are  Embodiments with the described polyamide mixtures as adhesion promoters Molding compounds particularly resistant.

Steam thermoforming also has another advantage: The Multi-layer pipes are becoming more flexible, which makes them easier to assemble. This The effect is already from the similarly constructed multilayer films from DE 198 06 468 A1 is known, but in which no multilayer composite with layer sequence according to the present Invention is disclosed.

What is surprising, however, is the fact that steam-thermoformed Multi-layer pipes according to the invention have no deterioration in the barrier properties (Permeation) is measured when the steam thermoforming under normal Practical conditions, d. H. not more than 5 minutes at not more than 150 ° C, is carried out. This was due to the statement regarding the blocking effect of EVAL Influence of water in the plastic paperback (Saechtling) cited at the beginning does not admit expect.

Finally, it should also be pointed out that when assessing the Prior art problems of EVOH, namely its Break sensitivity and susceptibility to stress cracking in the present invention did not appear. This is apparently due to the very good embedding in the multilayer composite according to the invention, d. H. in excellent liability to both neighboring polyamide layers, which optimally support the EVOH layer.

Claims (11)

1. Thermoplastic multilayer composite, 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 copolyamide 6/12, block copolyamide 6/12, polyamide 612, polyamide 610, a mixture made of polyamide 6, polyamide 12 and a compatibilizer, a mixture of polyamide 6, polyamide 11 and a compatibilizer. 2. Thermoplastic multilayer composite according to claim 1, characterized in that that the intermediate layer of ethylene vinyl alcohol copolymers on both sides is bound to secondary layers via adhesion-promoting layers. 3. Thermoplastic multilayer composite according to claim 1 or 2, characterized characterized that he gave a multi-layer hose, a multi-layer pipe at least in some areas has a corrugated wall, or more layer container is. 4. Thermoplastic multilayer composite according to claims 1 to 3, characterized shows that as a molding compound for the adhesion-promoting layer copolyamide 6/12 with 40 up to 83 wt .-% polyamide 6 content is used, with copolyamide 6/12 with 55 to 80 wt .-% polyamide 6 content is preferred. 5. Thermoplastic multilayer composite according to claims 1 to 3, characterized is characterized by the fact that as a molding compound for the adhesion-promoting layer, a polyamide Mixture of polyamide 6, polyamide 12 and a compatibility agent with  a polyamide 6 content between 25 and 80 parts by weight, based on 100 parts by weight Parts of the two polyamide components in the mixture, or a polyamide mixture made of polyamide 6, polyamide 11 and a compatibilizer with a poly Amide 6 content of between 25 and 80 parts by weight, based on 100 parts by weight of the two polyamide components in the mixture. 6. Thermoplastic multilayer composite according to claims 1 to 3 or 5, characterized characterized that the compatibility agent in the polyamide mixtures impact modifier used to improve the toughness of polyamides decorative polymer, in particular an impact modifier, elastomer or rubber is, acid-modified ethylene / α-olefin copolymers are preferred, and the Compatibility mediators, in particular in amounts of up to 30% by weight in the Polyamide blends are present. 7. Thermoplastic multilayer composite according to one of the preceding claims 1 to 6, characterized in that the polymer molding compositions for the individual Layers, especially the molding compound for the ethylene / vinyl alcohol copolymer layer, with layered silicates in an amount of 0.5 to 50 parts by weight per 100 parts by weight of the polymer matrix are filled. 8. Thermoplastic multilayer composite according to one of the preceding claims 1 to 7, 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) an adhesion-promoting layer of a molding compound based on polyamide, which is arranged between the intermediate layer (b) and the outer layer (d) and adjoins this, selected from the group consisting of copolyamide 6/12 with 55 to 80% by weight of polyamide 6- Proportion, block copolyamide 6/12, polyamide 612, polyamide 610, a mixture of polyamide 6 and polyamide 12 with a compatibilizer, in particular with a polyamide 6 proportion of 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 polyamide 6 component of 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 of a molding compound based on polyamide 12 or polyamide 11.

9. Thermoplastic multilayer composite according to claim 8, 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, whereby Carbon fibers and / or conductive carbon black are preferred. 10. Thermoplastic multilayer composite according to one of claims 3 to 9, characterized characterized in that the multilayer pipe is a fuel line. 11. Method for producing a thermoplastic multilayer composite in one or several stages according to claims 1 to 10 by injection molding, coex trusion, extrusion blow molding, pressing, or in the coating process.