FUEL LINE, METHOD FOR PRODUCING SAME, AND USES THEREOF

Abstract

A multi-layer composite in the form of a hollow body enclosing an interior space (2) is proposed, consisting of three or four layers: an inner layer (3) adjoining the interior space (2), a middle layer (4) adjoining the latter and an outer layer (5) adjoining the middle layer (4) and closing the multi-layer composite (1) to the outside. If necessary, there is a further innermost layer (8) which directly adjoins the said inner layer (3) and is equipped with a conductive finish. The inner layer (3) is based on polyamide 6, the middle layer (4) is based on EVOH, and the outer layer (5) is based on a mixture of (A) polyamide 6 and (B) at least one other polyamide selected from the following group: polyamide 612, polyamide 614, polyamide 616 and polyamide 618.

Claims

1. A multilayer composite in the form of a hollow body enclosing an inner space, consisting of three layers, an inner layer adjoining the inner space, a middle layer adjoining the inner layer and an outer layer adjoining the middle layer and bordering the multilayer composite to the outside, wherein the inner layer is based on polyamide 6, the middle layer is formed on the basis of EVOH, and the outer layer is based on a mixture of (A) polyamide 6 and (B) at least one other polyamide selected from the following group: polyamide 612, polyamide 614, polyamide 616 and polyamide 618, is trained or consisting of four layers, the said three layers and a further innermost layer directly adjacent to the said innermost layer, and being conductive.

2. The multilayer composite according to claim 1, wherein the outer layer contains at least the following further constituents: (C1) a plasticizer, (C2) at least one impact modifier, and (C3) at least one adhesion promoter.

3. The multilayer composite according to claim 2, wherein the impact modifier (C2) is an ethylene/-olefin copolymer, grafted with an anhydride, and/or in that the adhesion promoter (C3) is a polyethylene grafted with an anhydride.

4. The multilayer composite according to claim 1 wherein the outer layer consists of: (A) 5-35% by weight of polyamide 6; (B) 30-60% by weight of at least one of said other polyamides selected from the following group: polyamide 612, polyamide 614, polyamide 616 and polyamide 618; (C) 20 to 40% by weight of other components different from (A) and (B); wherein the sum of components (A)-(C) is 100% by weight of the material used to produce the outer layer.

5. The multilayer composite according to claim 1, wherein at least one of the said other polyamides (B) of the outer layer, selected from the following group: polyamide 612, polyamide 614, polyamide 616 and polyamide 618, has a relative solution viscosity, measured in m-cresol according to ISO 307 at a temperature of 20 C., in the range 2.0-2.5, and/or in that at least one of the said other polyamides (B) of the outer layer, selected from the following group: polyamide 612, polyamide 614, polyamide 616 and polyamide 618, has a melting point in the range 180-240 C., and/or in that the polyamide 6 of the outer layer has a relative solution viscosity measured in sulphuric acid according to ISO 307 at a temperature of 20 C. in the range of 3.0-3.8, and/or in that the polyamide 6 of component (A) of the outer layer has a melting point in the range from 200-240 C.

6. The multilayer composite according to claim 1, wherein the inner layer has a copper stabilization, in a proportion in the range of 0.01-0.10 weight percent, wherein the weight percentages are based on 100 weight percent of the material for producing the inner layer, and/or in that the inner layer contains an impact modified.

7. The multilayer composite according to claim 1, wherein the inner layer consists of: (A_I) Polyamide 6; (B_I) 10-30 weight percent impact modifier (C_I) 0.01-0.1 weight percent heat stabilizer, (D_I) 0-15% by weight, where the sum of the components (A_I)-(D_I) add up to 100% by weight of the material used to produce the inner layer.

8. The multilayer composite according to claim 1, wherein the middle layer consists of an EVOH, with an ethylene content in the range of 20-25 percent by weight.

9. The multilayer composite according to claim 1, wherein the inner layer has a thickness in the range 0.3-0.6 mm, and/or that the middle layer has a thickness in the range of 0.05-0.2 mm, and/or that the outer layer has a thickness in the range of 0.3-0.6 mm, and/or that, if present, the innermost layer has a thickness in the range of 0.08-1 mm.

10. The multilayer composite according to claim 1, wherein it is produced in a co-extrusion process.

11. The multilayer composite according to claim 1, wherein the at least one polyamide (A) of the outer layer is selected from polyamide 612, polyamide 616 or a mixture thereof.

12. The multilayer composite according to claim 1, wherein the at least one other polyamide (A) is exclusively polyamide 612.

13. The multilayer composite according to claim 1 in the form of a pipe which can be structured at least in sections as a corrugated pipe.

14. The multilayer composite according to claim 1, wherein the pipe consists exclusively of the inner layer, the middle layer and the outer layer.

15. The multilayer composite according to claim 1, wherein the innermost layer is based on polyamide or on a thermoplastic fluoropolymer, and/or wherein the innermost layer consists of the following components: (a) 75-100% by weight, of a polyamide base or fluoropolymer based on at least ethylene and tetrafluoroethylene, with or without hexafluoropropylene blocks and/or perfluorohexane blocks; (b) 0-25% by weight of additives other than (c); (c) 0.1-20 weight percent conductivity additive; wherein the components (a) and (c) to 100 weight percent of the material of the innermost layer.

16. The multilayer composite according to claim 15, wherein component (b) is selected from at least one additive from the following group: antioxidants, processing aids, UV stabilizers, heat stabilizers, pigments, masterbatch carriers, lubricants or mixtures thereof, and/or that component (c) contains at least one additive for increasing electrical conductivity.

17. The multilayer composite according to claim 15, wherein component (b) contains at least one conductivity additive, in a proportion in the range of 1-15% by weight, based on the total mass of the innermost layer.

18. A method for producing a multilayer composite according to claim 1, wherein at least 2, or all 3 or 4 layers, are formed into a hollow body, in a continuous or discontinuous process.

19. A method of using a multilayer composite according to claim 1 as a tube for combustion engines.

20. The multilayer composite according to claim 1, wherein the outer layer contains at least the following further constituents: (C1) a plasticizer, selected as a hydroxybenzoic acid ester- or sulfonamide-based plasticizer or a mixture thereof (C2) at least one impact modifier, and (C3) at least one adhesion promoter, the proportion of plasticiser (C1) being in the range of 3-12% by weight, and/or wherein the proportion of impact modifier (C2) is in the range of 10-30% by weight, and/or wherein the proportion of adhesion promoter (C3) is in the range of 3-12% by weight, in each case based on the total mass of the material used to produce the outer layer as 100 percent by weight.

21. The multilayer composite according to claim 1, wherein the outer layer contains at least the following further constituents: (C1) a plasticizer, selected as BBSA, HDPB or a mixture thereof (C2) at least one impact modifier, and (C3) at least one adhesion promoter, the proportion of plasticiser (C1) being in the range of 5-8% by weight, and/or wherein the proportion of impact modifier (C2) is in the range of 10-20% by weight, and/or wherein the proportion of adhesion promoter (C3) is in the range of 5-10% by weight, in each case based on the total mass of the material used to produce the outer layer as 100 percent by weight.

22. The multilayer composite according to claim 1, wherein the outer layer contains at least the following further constituents: (C1) a plasticizer, (C2) at least one impact modifier, and (C3) at least one adhesion promoter, wherein the outer layer consists exclusively of the components (A), (B), (C1), (C2) and (C3) and optionally additives, including additives of a copper stabilizer and a colour masterbatch.

23. The multilayer composite according to claim 2, wherein the impact modifier (C2) is an ethylene/butylene or ethylene/propylene copolymer, or mixtures thereof, grafted with an anhydride, and/or in that the adhesion promoter (C3) is a polyethylene grafted with maleic anhydride.

24. The multilayer composite according to claim 2, wherein the impact modifier (C2) is an ethylene/butylene or ethylene/propylene copolymer, or mixtures thereof, grafted with maleic anhydride, and/or in that the adhesion promoter (C3) an LLDPE grafted with maleic anhydride.

25. The multilayer composite according to claim 1 that the outer layer consists of: (A) 5-35% by weight of polyamide 6; (B) 30-60% by weight of at least one of said other polyamides selected from the following group: polyamide 612, polyamide 614, polyamide 616 and polyamide 618; (C) 20 to 40% by weight of other components different from (A) and (B); wherein the sum of components (A)-(C) is 100% by weight of the material used to produce the outer layer, the other components (C) being composed as follows: (C1) 3-8 weight percent plasticizer; (C2) 9-30 weight percent impact modifier; (C3) 3-10 weight percent adhesion promoter; (C4) 0-3% by weight of additives, including processing aids, UV stabilizers, heat stabilizers, pigments, masterbatch carriers or mixtures thereof, where the proportions of (C1)-(C4) are based on the 100 weight percent of the material for producing the outer layer formed by the sum of (A)-(C).

26. The multilayer composite according to claim 1, wherein at least one of the said other polyamides (B) of the outer layer, selected from the following group: polyamide 612, polyamide 614, polyamide 616 and polyamide 618, has a relative solution viscosity, measured in m-cresol according to ISO 307 at a temperature of 20 C., in the range 2.15-2.4, and/or in that at least one of the said other polyamides (B) of the outer layer, selected from the following group: polyamide 612, polyamide 614, polyamide 616 and polyamide 618, has a melting point in the range 185-225 C., and/or in that the polyamide 6 (A) of the outer layer has a relative solution viscosity measured in sulphuric acid according to ISO 307 at a temperature of 20 C. in the range of 3.30-3.7, and/or in that the polyamide 6 (A) of the outer layer has a melting point in the range from 210-230 C.

27. The multilayer composite according to claim 1, wherein the inner layer has a copper stabilization, based on CuI, in a proportion in the range of 0.01-0.10 weight percent, or in a proportion of 0.03-0.07 weight percent, and/or in that the inner layer contains an impact modifier, in a proportion in the range of 10-25% by weight or in a range of 10-20% by weight, the impact modifier being an ethylene/-olefin copolymer grafted with an anhydride, and wherein the weight percentages are each based on 100 weight percent of the material for producing the inner layer.

28. The multilayer composite according to claim 1, wherein the inner layer consists of: (A_I) Polyamide 6, having a relative solution viscosity measured in sulphuric acid according to ISO 307 at a temperature of 20 C. in the range 3.5-3.8, or 3.6-3.75; (B_I) 10-30 weight percent impact modifier (C_I) 0.01-0.1 weight percent heat stabilizer, based on copper(I) (D_I) 5-10 or 0-1 weight percent additives, selected from the group: conductivity additives, crystallization accelerators, processing aids, lubricants, and mixtures thereof where the sum of the components (A_I)-(D_I) add up to 100% by weight of the material used to produce the inner layer.

29. The multilayer composite according to claim 1, wherein the middle layer consists of an EVOH with an ethylene content in the range of 25-30 percent by weight.

30. The multilayer composite according to claim 1, wherein the inner layer has a thickness in the range 0.4-0.5 mm, and/or that the middle layer has a thickness in the range of 0.075-0.125 mm, and/or that the outer layer has a thickness in the range of 0.4-0.5 mm, and/or that, if present, the innermost layer has a thickness in the range of 0.1-0.9 mm.

31. The multilayer composite according to claim 1, wherein the total wall thickness of the multilayer composite is in the range of 0.5-2.5 mm, or in the range of 0.75-1.5 mm.

32. The multilayer composite according to claim 1 in the form of a pipe which can be structured at least in sections as a corrugated pipe, as a fuel pipe for combustion engines, in the automotive sector.

33. The multilayer composite according to claim 1, wherein the innermost layer is based on polyamide or on a thermoplastic fluoropolymer, wherein the polyamide base is selected from the group consisting of PA 6, PA 12, PA 612, PA 10T/6T, PA 1212, PA 66, PA 11, PA 106, PA 1012, PA 10T/612, PA 10T/610, PA 9T, and/or the thermoplastic fluoropolymer is based at least on ethylene and tetrafluoroethylene, with or without further blocks selected from the group: propylene blocks, including hexafluoropropylene blocks, hexene blocks, including perfluorohexene blocks, and/or that the innermost layer consists of the following components: (a) 85-98% by weight of said polyamide base or fluoropolymer based on at least ethylene and tetrafluoroethylene, with or without hexafluoropropylene blocks and/or perfluorohexene blocks; (b) 0-25% by weight of additives other than (c); (c) 0.1-20 weight percent conductivity additive; wherein the components (a) and (c) to 100 weight percent of the material of the innermost layer.

34. The multilayer composite according to claim 1, wherein the innermost layer is based on polyamide or on a thermoplastic fluoropolymer, wherein the thermoplastic fluoropolymer is a fluorine-containing ethylenic polymer with a carbonyl group, which does not contain any amide, imide, urethane or urea group, and/or that the innermost layer consists of the following components: (a) 85-98% by weight of said polyamide base or fluoropolymer based on at least ethylene and tetrafluoroethylene, with or without hexafluoropropylene blocks and/or perfluorohexene blocks, with carbonyl groups; (b) 0-25% by weight of additives other than (c); (c) 0.1-20 weight percent conductivity additive; wherein the components (a) and (c) to 100 weight percent of the material of the innermost layer.

35. The multilayer composite according to claim 15, wherein component (c) contains at least one additive for increasing electrical conductivity, in the form of particles of metal fibres, metal powder, metal oxide powder, conductive carbon black, conductive carbon fibre, conductive carbon nanotubes, conductive graphite powder, conductive graphite fibre, graphene, bronze powder, bronze fibre, steel powder, steel fibre, iron powder, iron fibre, copper powder, copper fibre, silver powder, silver fibre, aluminium powder, aluminium fibre, nickel powder, nickel fibre, tungsten powder, tungsten fibre, gold powder, gold fibre, copper-manganese alloy powder, copper-manganese fibre and combinations.

36. The multilayer composite according to claim 15, wherein component (b) contains at least one conductivity additive, in a proportion in the range of 3-8% by weight, based on the total mass of the innermost layer.

37. The method according to claim 18, wherein at least 2, or all 3 or 4 layers, are formed into a pipe or a tube or a container, in a continuous and/or discontinuous process, in an extrusion blow moulding, tandem extrusion, sheathing or coextrusion process.

38. The method of use according to claim 19 as a tube for internal combustion engines, in the automotive sector, for fuel, urea or coolant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Preferred embodiments of the invention are described in the following on the basis of the drawings, which are for explanatory purposes only and are not to be interpreted restrictively. In the drawings shows:

[0081] FIG. 1 a fuel tube with three layers in a sectional view perpendicular to the direction of flow;

[0082] FIG. 2 a fuel tube with four layers in a sectional view perpendicular to the direction of flow.

DESCRIPTION OF PREFERRED FORMS OF EXECUTION

[0083] FIG. 1 shows an exemplary fuel tube 1 according to the invention in a section transverse to the main direction.

[0084] The cross-sectional area can be constant over the main direction, i.e. the pipe can be essentially hollow cylindrical in shape.

[0085] However, the cross-sectional area can also vary over the main direction, for example in the form of a corrugated pipe.

[0086] An interior 2 is enclosed by the pipe wall. The inner chamber 2 is followed radially outwards by an inner layer 3, which borders on and delimits the inner chamber 2 with its inner surface 7. This inner layer is based on polyamide 6 without other polyamide components.

[0087] Directly adjacent to the inner layer 3 without an intermediate adhesion promoter layer is a middle layer 4 in the sense of a barrier layer, which is based on EVOH.

[0088] Directly adjacent to the outside of this middle layer 4 and again without an intermediate bonding agent layer is the outer layer 5, which is based on polyamide 616 in a blend with PA 6. The outer surface 6 of the outer layer 5 limits the tube to the outside.

[0089] An alternative exemplary fuel tube after the invention is shown in FIG. 2. Here, in addition to the three layers already described above, there is another innermost layer 7, which closes the fuel tube to the inside and in this case borders directly on the interior 2. This innermost layer has a conductive finish, i.e. it contains, for example, additives of conductive particles, such as conductive soot.

[0090] Starting Materials Used:

[0091] Polyamide 6 (I) (Outer Layer): [0092] .sub.rel=3.4 (sulfuric acid); [0093] Tm measured with DSC according to ISO 11357 (2011)=222 C.

[0094] Polyamide 612 (Outer Layer): [0095] .sub.rel=2.3 (m-cresol); [0096] Tm measured with DSC according to ISO 11357 (2011)=218 C.

[0097] Polyamide 616 (Outer Layer): [0098] .sub.rel=2.2 (m-cresol); [0099] Tm measured with DSC according to ISO 11357 (2011)=196 C.

[0100] Polyamide 12 (Outer Layer, VB):

[0101] Grilamid L25, high viscosity polyamide 12, trading product of EMS-CHEMIE AG, [0102] Domat/Ems, Switzerland [0103] Melt volume rate (MVR): 275 C./5 kg, ISO 1133; [0104] Tm measured with DSC according to ISO 11357 (2011)=178 C.

[0105] Polyamide 610 (Outer Layer, VB): [0106] Grilamid 2S 20 Natural, Polyamide 610 with relative viscosity 1.9-2.0, product of EMS-CHEMIE AG, Domat/Ems, Switzerland; [0107] Tm measured with DSC according to ISO 11357 (2011)=213 C.

[0108] Polyamide 6 (II) (Inner Layer): [0109] .sub.rel=3.7 (sulfuric acid); [0110] Tm measured with DSC according to ISO 11357 (2011)=222 C.

[0111] Ethylene Vinyl Alcohol (Barrier Layer): [0112] An ethylene/vinyl alcohol copolymer (EVOH) was used as material for the barrier layer. Specifically, the examples involved a product of the KURARAY company, which is available under the name EVAL under the product designation F170B and has an ethylene content of 27 mol %. It is available in Europe from EVAL Europe N.V. in Zwijindrecht, Belgium.

[0113] Plasticizer (Outer Layer):

[0114] BBSA (N-butylbenzenesulphonamide) was used as the plasticiser (WM). This is available under the brand name Uniplex 214, from Lanxess.

[0115] Impact modifier (for inner and outer layer):

[0116] Acid-modified ethylene/-olefin copolymers were used as impact modifiers (SZM), namely maleic anhydride-grafted ethylene-butylene and ethylene-propylene copolymers and mixtures thereof.

[0117] Impact Modifier of the Inner Layer: [0118] MVR value (measured at 230 C./2.16 kg) of 1.2 g/10 min (ASTM D1238), [0119] DSC glass transition temperature, according to ISO standard 11357-2 (2013) of 65 C., [0120] available under the name Tafmer MH5020C from Mitsui Chemicals.

[0121] Impact Modifier of the Outer Layer or the Inner Layer of the Comparative Example: [0122] MVR value (measured at 230 C./2.16 kg) of 1.3 g/10 min (ASTM D1238), [0123] DSC glass transition temperature, according to ISO standard 11357-2 (2013) of 60 C., [0124] available under the name Tafmer MC201 from Mitsui Chemicals.

[0125] Copper Stabilizer (Inner Layer):

[0126] CuI/KI (weight ratio 1:6) was used as copper stabiliser in a proportion of 0.05 weight percent in relation to the total mass of the inner layer. The copper (I) iodide is commercially available from Merck KGaA and the potassium iodide from Liquichem Handelsgesellschaft mbH.

[0127] Adhesion Promoter (Outer Layer):

[0128] The adhesion promoter (HVM) is a maleic anhydride grafted LLDPE, available from Mitsui Chemicals under the name Admer NF358E, with an MFR (190 C., 2.16 kg) of 1.6 g/10 min (ASTM D1238), a density of 0.91 g/cm.sup.3 (ASTM D1505), and a Vicat Softening Point of 82 C. (ASTM D1525). Tm, measured in DSC according to ISO 11357-3 (2011) is 120 C.

[0129] Masterbatch (Outer Layer):

[0130] Euthylen Black, soot-based (40%) colour masterbatch based on PE, available from BASF (Ludwigshafen, Del.)

[0131] Production of the Test Specimens:

[0132] Pipes were co-extruded at mass temperatures between 210 and 260 C. under vacuum of 56 mbar and an extrusion speed of 32.8 m/min. Pipes with an outside diameter of 8 mm and a wall thickness of 1 mm were used as test specimens. The length of the pipe was adjusted according to the test requirements. The thickness of the inner layer was 0.45 mm, the middle layer 0.10 mm and the outer layer 0.45 mm.

[0133] Tests Carried Out on the Pipe Assemblies:

[0134] Washing out: Test according to SAE J2260 with test fuel FAM-B (according to SAE J1681 (2000))test 96 hours, 60 C. sealed tube of 200 cm; maximum extract according to VW TL 52712 6 g/m2.

[0135] Cold behaviour: is tested in accordance with TL 52712 in line with VW standard PV 3905. The drop height of the ball is 65 cm. At least 10 test specimens are measured and the number of fractures is given as a percentage.

[0136] Pipe tensile test: Pipe tensile tests were carried out according to ISO 527-2 (2012). For tests, test specimens with a length of 150 mm (tensile tests in the direction of extrusion) or 10 mm (for tensile tests transverse to the direction of extrusion) were used. The test temperature was 23 C. and the test speed 100 mm/min (for tests in the direction of extrusion) or 25 mm/min (for tests transverse to the direction of extrusion).

[0137] Specifically, the following measurements were carried out according to ISO 527: elongation at break in the direction of extrusion, elongation at break transverse to the direction of extrusion, yield stress in the direction of extrusion, yield stress transverse to the direction of extrusion.

[0138] Layer adhesion: has been tested according to SAE J2260.

[0139] Relative viscosity: DIN EN ISO 307 (2007), in 0.5% by weight m-cresol solution or 1% by weight sulphuric acid solution (PA6) at a temperature of 20 C.

[0140] Thermal behavior (melting point Tm, melting enthalpy and glass transition temperature (Tg): ISO standard 11357-1 (2016), -2 (2013) and -3 (2011), granules, the differential scanning calorimetry (DSC) was carried out at a heating rate of 20 C./min.

TABLE-US-00001 TABLE 1 Compositions and structure B1 B2 VB1 outer inner outer inner outer inner Unit layer layer layer layer layer layer polyamide weight 44.25 72 612 % polyamide weight 44.25 616 % polyamide weight 25.0 25.0 6 (I) % polyamide weight 78.55 78.55 70.1 6 (II) % SZM weight 20.0 20 18 19.5 (Tafmer % MC201) SZM weight 20.00 20 (Tafmer % MH5020C) HVM weight 5.0 5.0 % WM weight 5.0 5.0 10 5.0 % Cul/KI weight 0.05 0.05 % Black weight 0.75 1.4 0.75 1.4 5.4 master % batch

TABLE-US-00002 TABLE 2 Mechanical and chemical test results B1 B2 VB1 Yield stress in N/mm2 35 38 30 extrusion direction Yield stress N/mm2 37 42 32 transverse to the extrusion direction Elongation at % 344 366 300 break in extrusion direction Elongation at % 320 330 280 break transverse to the extrusion direction Cold impact, % No No 20 25 C., ball breakage breakage mass 880 g Cold impact, % No No 40 0 C., ball breakage breakage mass 500 g Wash-out g/m2 5.6 4.4 33.7 resistance, according to TL 52712 Layer Layers not Layers not outer layer adhesion separable separable separable

[0141] While all the examples show acceptable mechanical suitability for automotive applications, the cold behaviour of the tubes with a structure according of the invention is an unexpected and significant improvement over the comparative example. The comparative example clearly cannot meet the industrial requirements. Also with regard to elongation at break, the structures according to the invention are unexpectedly advantageous. The molding compounds of all examples can be co-extruded, but only the examples according to the invention show good adhesion between the outer layer and the intermediate layer of EVOH.

[0142] The unexpectedly good suitability of the pipes with a structure according to the invention for the application is also shown by the very good wash-out resistance. The industrial requirement according to TL 52712 is a washout of less than 6 g/m2 pipe surface. This requirement is fulfilled here only with the examples according to the invention. In order to allow further comparison with state of the art, in particular for comparison with the examples of EP-A-1 884 356, the structures shown in Table 3 were manufactured using the same process and tested for properties as shown in Table 4.

TABLE-US-00003 TABLE 3 Compositions and structure of further comparative examples VB2 and VB3 VB2 VB3 outer inner outer inner Unit layer layer layer layer polyamide 6 (I) weight % 42.5 42.5 polyamide 6 (II) weight % 83 polyamide 12 weight % 42.5 polyamide 610 weight % 83 Grilon XE 3871 weight % 42.5 SZM (Tafmer weight % 15 10 15 MC201) SZM (Tafmer weight % 10 MH15020C) WM weight % 7 7

TABLE-US-00004 TABLE 4 Mechanical and chemical test results VB2 and VB3 VB2 VB3 Yield stress in extrusion N/mm2 30 28 direction Yield stress transverse N/mm2 32 30 to the extrusion direction Elongation at break in % 298 276 extrusion direction Elongation at break % 280 249 transverse to the direction of extrusion Cold impact, % 30 30 25 C., ball mass 880 g Cold impact, % 40 40 40 C., ball mass 500 g Wash-out resistance, g/m2 42 48 according to TL 52712 Layer adhesion outer outer layer layer separable separable

[0143] A reworking of the structures from D1 shows poor mechanical properties, especially with regard to impact strength and washout. The poor composition/combination of the layers also leads to layer separation.

[0144] The order of the additives (plasticizers) is reversed in the D1, thus the composition and structure of the D1 teaches away from the inventive structure, i.e. the compositions and sequences of the layers as claimed.

[0145] In connection with D1, it should be that the inner layers of D1 are mostly provided with plasticizer, which makes the washout unacceptable.

LIST OF REFERENCE SIGNS

[0146]

TABLE-US-00005 1 Fuel tube 5 Outer layer 2 Interior of 2 6 Outside surface of 1 3 Inner layer 7 Inner surface of 1 4 Middle layer 8 innermost layer of 1