CA2048715A1

CA2048715A1 - Polyamide fuel lines having a glass fiber reinforced middle layer

Info

Publication number: CA2048715A1
Application number: CA002048715A
Authority: CA
Inventors: Franz Kerschbaumer
Original assignee: Franz Kerschbaumer; Ems-Inventa Ag
Current assignee: Uhde Inventa Fischer AG
Priority date: 1990-08-09
Filing date: 1991-08-08
Publication date: 1992-02-10
Also published as: EP0470605A1; DE4025300C1; JPH04248088A

Abstract

Abstract of the Disclosure A cold impact resistant polyamide fuel line for motor vehicles which is stable in length, which can be briefly thermally overloaded, and which consists of at least three layers of mutually compatible polyamides. The polyamide fuel line according to the invention preferably also has an internal layer and an external layer of impact strength-modified polyamide with or without a plasticizer, and a glass fiber-reinforced layer in the middle of the pipe wall of impact modifier-free or impact-modified homopolyamide, copolyamide or blends thereof.

Description

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Po]yamide Fuel Lines Having a Glass Fiber Reinforced Middle Laye_ This Application claims the benefit of the priority of German 40 25 300.7, filed August 9, 1990.

This invention rela~es to a cold impact resistant polyamide fuel line which is stable in length and can be briefly thermally loaded.

BACKGROUND OF T~IE IN~ENTION

Fuel lines, so-called mono-pipes consisting of a single homogeneous layer of polyamide 11 or 12, have been installed in motor vehicles for a long time. An essential disadvantage of such fuel lines resides in the considerable absorption capacity of the polymers for individual components of the fuels which leads to swelling and to changes of length in the walls and wall layers.
Differing swelling in various wall parts is a particular problem.

A further disadvantage is that there is considerable permeation of conventional fuels through the walls of such mono-pipes which is unreasonably high in view of the environmental and safety considerations which have arisen in recent years and have to be taken into consideration.

~ ~5 ,3 Developments have therefore been made in order to improve such mono-pipes. One possibility consists in replacement by multi-layered pipes fabricated of polymers of the same or different types~

A fuel line is known from DE 35 10 395 Al in which ethylene /vinyl alcohol copolymers are laminated to polyamide 11 or 12 layers. However, the adhesion between these layers is so low that they delaminate easily. Also, corrosive chemicals such as scattered salt can penetrate between the layers at the delaminated pipe ends.
Furthermore, the adhesion to fittings with mandrel profiles is markedly reduced. Moreover, the cold impact resistance of such pipes is so low that they cannot withstand cold impact tests according to ISO 7628, DIN 73 378, and SAE J 4844d, because of the extremely brittle polyethylene vinyl alcohol layer used as the inner wall. The three-layer-tube as claimed in DE 38 21 723 is made from polyamide with a polyolefin middle layer and shows, besides low-stability in length, a limited stability under elevated temperatures due to its polyolefin component.

In addition, DE 38 27 092 describes a fuel line in which thermoplastic polyester elastomers are laminated to polyamide 6 and to a polyethylene vinyl alcohol internal layer. As in the previously discussed case, only slight adhesion exists between the layers so that the above-described disadvantages arise here as well.

~ 3 Sl]MMARY OF TH~ INVENTION
_ It is therefore an object of the invention to provide a polyamide fuel line, which is stable in length, which exhibits sufficicnt resistance to permeation by all conventional fuels for current environmental and safety regulations without having the above-mentioned disadvantages.

To achieve this object, there is provided a cold impact resistant polyamide pipeline, which is not only s-table in length, but also can be briefly thermally overloaded. It consists of at least three layers of mutually compatible polyamide polymers, wherein at least one layer is reinforced with glass fibers.

The invention will be described in connection with a fuel line for a motor vehicle, but its application is by no means so limited. The fuel line according to the invention has a permeation barrier which is adequate for current environmental and safety regulations, is delamination-free, and can be briefly overloaded at the temperatures usually occurring in the engine chamber of motor vehicles. ~oreover, it is inexpensive to produce.

Known mono-pipes cannot withstand the bursting pressure test at 170C. On the other hand, the multi-layered fuel lines according to the invention withstand a bursting pressure of 7 bar even at 18~C for a 3 7 ~ ~
short time~ i.e. 1 to Z hours. This is of eonsider~le importance for the safe~y of fuel lines in cascs wllere the engine ov~rheats briefly, or example ;f the cooling system begins to malfunçtion.
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Surprisin~ly, it has been found that the stabilit~
in length of a ~ulti-layered p~lyamide pipeline is very high i~ at least one of the polymer laycrs is reinforced, for example with ~lass fibers. The high stabj]ity in ]en~th is also achieved if only one layer ig rcinforced.
It has been found that this can be achieved preferably by reinfor~lng the ~elatively thin middle layer with g]ass f ibers and can be improved by introducing impa~t strength modifiers into th~ Iniddle layer. This combination also cnsures good elongation at break behaYior.
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~5 It IIAS similarly been found ~hat the fo]]owing modified or un~odified polya~ide types, whieh mfly contain plasticiz~rs, are suit~ble as pipe layer materials:
polyamide ll; lZ; 12,]2; ~; ~,6; polyami~e elastomers based on polyamide 1~; and parti~lly aromatic polyamides.
~`he three last-m~ntioned polyalnides surpass the first~
entioned in their barrier e~fect against the arom~tic, usually toxic constituents o ~uels and are, thcrefoIe~parti~ularly preferred for use as barri~r layers in fuel lines.

~5 A glass fiber-reinforcedg impact-modi~ied or impac.t modi~er-~ree polyamide is co~patible Wit}l the sam~
~., ,-, ~....

, .
.., type of impact-modified but unreinforced polyamide. The same applies to other layer material cornbinations such as polyamide 6,6 with polyamide 6 on the one hand and polyamide 11 or 12 on the other hand, as well as polyamide 6,6 with blends of copolyamides and polyamide elastomers.
It is preferred to use polyether esteramides based on the monomers of polyamide 11 or 12; the copolyamides of the monomers with 6, 11 or 12 carbon atoms are particularly suitable for the above-mentioned blends. No delamination could be observed on the pipelines from such polyamide layers.

According to the invention, therefore, multi-layered polyamide pipelines are provided,the external layer of which consists of impact-modified polyamides which may contain plasticizers and of which the glass fiber-reinforced middle layer consists of impact-modifier-free or impact-modified polyamide, preferably of polyamide 6, polyamide 12, or polyamide 6,6. The glass fiber-reinforced middle layer of such pipelines preferably consists of polyamide 6 or 12 which can also contain impact-modifiers.

~unctionalized homopolyolefins or copolyolefins are used as impact-modifiers. These modifiers are present in amounts of 5% to 30% by weight and the glass fibers constitute 15% to 50% by weight. The ratio of the two additives is not critical and can be varied according to the requirements of the specific applications.

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Combinations which consist internally and externally of impact-modified polyamide 6 or impact-modified polyamide 12 are preferred. A further preferred embodiment has roughly the same layer thickness in the internal and external layers, which is between 0.2 and 1.0 mm in practice. Thicknesses of 5~ to 25% of the total wall thickness are sufficient for the glass fiber-reinforced middle layers. Thicknesses of 0.1 to 0.5 mm are, therefore, particularly preferred for the glass fiber-reinforced middle layer.

The polyamide pipelines according to the invention can obviously be made up from more than three layers if the principle of an impact-modified external layer and at least one reinforced layer, preferably between the internal and external layers is respected and the compatibility of the layer materials is ensured.

The multi-layered polyamide pipelines accordin to the invention are preferably produced by combining streams of melt in a coextrusion device. Such coextruded polyamide pipelines according to the invention have been tested with respect to their cold impact strength according to SAE J 844d, DIN 73 378, and IS0 7628, with respect to fuel permeation, and with respect to their stability in length.

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¦ Tlle reslllts of ~h~ ~old impa~t tes~s are repro~uced in 'I'a~le l. They have been carried out on pip~s l~aving an external diameter of B mm a wa~ thickness ~ o~ 1 mm, and the layer str~tures al~e ~l~o indicated in ¦ 5 ~he sa~e Table, The polyamides mentioned are:
, .....
GRILO~ XF31~s an impact-~odified PA 6 ...
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GRII,AMl~ X}s3]48 an impact-modified PA l~ with plasticizer 1. '.
GRtLON PYZ ~H an impact-modified PA 6 ~ith 30%
glass fiber .,', , 1.. .
GRI~AMID ~.Y~ ~ an impact modifier~frcc ~A 12 with 50~ ~lass fiber ~, .
" .
.. .
The ~bove-mentioned polyamides are produced by ~` ~MS-~H~MI~ AG, Zurich, Swit~crland. The sa~e applies to . .
~
~ 15 GRILON T300 GM ~n impac~modifier-free PA 66 ~., ~ GRILAMID ~LY20NZ an impact-modified po)y~ide .
~ elastomer }
GRIJ,ON CA6E an amorphous eopolyamidc based on ~ caprolactam/laurolact~m i~

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GRILON R47HW a high-viscosity, impact-modified PA 6 with a defined plasticizer content GRILAMID L25W20 a polyamide 12 with a defined plasticizer content GRILAMI`D L25W40 a polyamidc 12 with a defined (higher) plasticizer content which have additionally been used for comparison tests according to Table 1 and Figures 2 to 5.

In the accompanying drawings, constituting a part hereof and in which like reference characters indicate like parts, Figure 1 is a diagrammatic view of a permeability testing device;

Figures are bar graphs indicating the 2-4 permeability of various polyamide resins to various fuels; and Figure 5 is a graph similar to Figures 2-4 showing permeability at different temperatures.

~ 3 The apparatus used for the permeation tests is shown in Figure 1. The fuel flows in fuel circuit 1 which contains an air chamber 3 and passes through heater 4 and a portion of pipe 5 of a pipeline to be tested. Pressure tank 2 communicates with the air chamber 3 and serves to maintain a pressure of 4 bar in fuel circuit l. The fuel flows in the fuel circuit 1 at about 10 liters/h and is heated to 70C by heater ~.

The apparatus also includes carrier circuit 6 which is connected to both ends of pipe 5. Carrier circuit 6 also has array 7 of activated carbon filters.
The fuel which has permeated through the wall of pipe 5 is conveyed in carrier circuit 6 with 100 ml/min of nitrogen over activated carbon filter array 7, and its weight after 300 hours is determined. Like the impact measurements, these permeation tests were carried out on pipes having an external diameter of 8 mm and a wall thickness of 1 mm.

The length stability of the pipes according to the invention was determined by measuring the change in length of pipeline portions having an external diameter of 8 mm and a wall thickness of 1 mm while fuel flowed therethrough for 300 hours in an apparatus similar to the permeation apparatus of Figure 1.

The results of the length stability tests are to be found in Table 1. The results of the permeation tests are reproduced in Figures 2 to 4, while Figure 5 relates to the analysis of aromatic substances.

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Claims

1. A cold impact resistant pipeline comprising at least three component layers of mutually compatible polyamides, at least one of said component layers being reinforced by glass fibers, whereby said pipeline is stable in length, can be briefly thermally loaded, and is cold impact resistant.

2. The pipeline of Claim 1 wherein said glass fibers are in an intermediate layer located between at least two other layers.

3. The pipeline of Claim 1 wherein there are an internal layer, an external layer, and an intermediate layer between said internal layer and said external layer, said internal layer and said external layer being of impact-modified polyamides said intermediate layer of homopolyamide, copolyamide or blends thereof and containing said glass fibers.

4. The pipeline of Claim 3 wherein said intermediate layer is selected from the group consisting of polyamide 6,6; polyamide 6; polyamide 11; polyamide 12; polyamide 12,12; and partially aromatic polyamide.

5. The pipeline of Claim 3 wherein said intermediate layer is of a blend of polyamide elastomers.

6. The pipeline of Claim 5 wherein said elastomers are a polyether esteramide or a copolyamide.

7. The pipeline of Claim 6 wherein said elastomers are derived from monomers having 6 to 12 carbon atoms.

8. The pipeline of Claim 1 wherein at least one of said component layers contains an impact-modifier.

9. The pipeline of Claim 8 wherein said at least one of said component layers contains 5% to 30% by weight of said impact modifier.

10. The pipeline of Claim 8 wherein said impact-modifier is a functionalized homopolyolefin or a functionalized copolyolefin.

11. The pipeline of Claim 1 wherein said component layer containing said glass fiber has 15% to 50% by weight of said glass fibers.

12. The pipeline of Claim 1 comprising an internal layer and an external layer, said internal layer and said external layer having about the same thickness.

13. The pipeline of Claim 12 wherein said thickness is 0.2 to 1.0 mm.

14. The pipeline of Claim 1 wherein said component layer containing said glass fibers has a wall thickness of about 5% to about 25% of the total thickness of said component layers.

15. The pipeline of Claim 14 wherein said wall thickness is 0.1 to 0.5 mm.

16. The pipeline of Claim 3 wherein said internal layer and said external layer are of impact-modified polyamide 12, and said intermediate layer is of polyamide 12 having no impact-modifier.

17. The pipeline of Claim 3 wherein said intermediate layer contains an impact-modifier.

18. The pipeline of Claim 17 wherein said internal layer, said intermediate layer, and said external layer comprise polyamide 6, and said intermediate layer is impact modified.

19. The pipeline of Claim 1, wherein at least one of said component layers contains plasticizer.