FR2766548A1 - Fluid transfer pipe, especially motor vehicle fuel pipe - Google Patents

Abstract

Fluid transfer pipe, used in cars, comprises at least one inner layer (10) of a plastic, especially a polyphthalamide based plastic or one reinforced by the addition of a polyphthalamide elastomer, and an outer layer (12) of rubber, elastomer or thermoplastic material. Preferably the rubber or elastomer is a peroxide vulcanised CSM (chlorosulphonated polyethylene) or EPDM (ethylene propylene diene monomer terpolymer), and the two layers are stuck directly together. In a variant of the design the inner plastic layer has a thin inner covering of a rubber or elastomer material, and the inner and outer layers can have a thin layer of a plastic adhesive material between them, e.g. a rubber solution, an EVA (ethylene vinyl acetate copolymer) adhesive or PVA (polyvinyl alcohol) combined with vinyl acetate. The pipe can be made by extrusion or coextrusion.

Description

FLUID TRANSFER PIPE, PARTICULARLY FUEL
FOR MOTOR VEHICLE.

 The invention relates to a fluid transfer pipe, in particular fuel for a motor vehicle, which can also be used in other fields such as the chemical industry and the petroleum industry, for example.

 Fluid, especially fuel, transfer hoses, which were traditionally made of rubber, have been replaced by plastic hoses which are lighter, less bulky and less expensive, but which have poor fire resistance, or by pipes with a complex structure comprising at least one internal layer of plastic material and an external protective layer of rubber or vulcanized elastomer, the plastic material possibly being a fluorinated material (generally very expensive) or a polyamide (including the impermeability to fuels alcoholic is poor).

 We are therefore currently seeking to produce a fuel hose which is inexpensive and easy to manufacture and which has a simple structure, excellent impermeability to fuels (including alcoholic fuels), good fire resistance, good impact resistance and good mechanical characteristics.

 The invention provides, for this purpose, a pipe comprising at least one internal layer of plastic and an external layer of rubber, elastomer or thermoplastic material, characterized in that the above-mentioned internal layer is based on polyphthalamide.

 Such a hose meets the needs mentioned above, because it has excellent mechanical and thermal resistance and very good impermeability, in particular to alcoholic fuels.

 Preferably, the outer layer of this pipe is a rubber or an elastomer vulcanized with peroxides, of the CSM or EPDM type for example, which allows direct adhesion to the internal layer of polyphthalamide.

 Alternatively, the outer layer may be made of a thermoplastic such as PA12 or PAll, or a polypropylene.

 The internal layer of polyphthalamide can be covered internally with a thin layer of rubber or elastomer, to improve the tightness of the mounting of this pipe on a connector or a rigid connection tube.

 The hose according to the invention is intended in particular for transporting fuel for a motor vehicle, but can be used for the transfer of any fluid (water, oil, air, etc.) in industry in general.

The invention will be better understood and other characteristics, details and advantages thereof will appear more clearly on reading the description which follows, made with reference to the accompanying drawings in which
- Figure 1 is a schematic sectional view of a pipe according to the invention
- Figure 2 is a schematic sectional view of an alternative embodiment.

 The pipe shown in FIG. 1 is typically a fuel transfer pipe for a motor vehicle and comprises an internal layer 10 of plastic material impermeable to the transported fluid and an external protective layer 12 made of rubber or vulcanized elastomer, which adheres directly to the layer internal 10.

According to the invention, this internal layer 10 is made of polyphthalamide, such as that which is marketed under the name AMODEL by the company AMOCO OIL
COMPANY, this polyphthalamide being in principle intended for injection molding, but being used according to the invention in extrusion or coextrusion processes. Advantageously, the impact resistance of this material can be improved by adding an elastomer to the polyphthalamide.

 The elastomer layer 12 which covers the internal layer 10 of polyphthalamide is preferably made of an elastomer or a rubber vulcanized with peroxides, such as in particular a CSM (chlorosulfonated polyethylene) or an EPDM (terpolymer of ethylene, propylene and of a monomer diene), these materials having the property of adhering directly to the abovementioned polyphthalamide.

 Of course, it is also possible to provide a thin layer of an appropriate adhesive [adhesives, binders, dissolution of rubber in a solvent, graft polymers, ethylene-vinyl acetate (poly (EVA)) copolymers, poly (vinyl alcohol), in combination with vinyl acetate (PVAL or EVOH)] between the inner layer 10 of polyphthalamide and the outer layer 12 of rubber or vulcanized elastomer.

 Typically, and in the case of a fuel transfer pipe, the total thickness of the wall of the pipe can be of the order of 3 mm or less, for example around 1 mm, the thickness of the layer inner 10 being about 0.5 mm or less and that of the outer layer 12 about 0.5 to 2.5 mm. When the total thickness is approximately 1 mm, the thickness of the internal layer 10 is approximately 0.3 to 0.5 mm and that of the external layer 12 approximately 0.5 to 0.7 mm .

 In the variant embodiment shown diagrammatically in FIG. 2, the hose according to the invention comprises a protective layer 12 of vulcanized rubber or elastomer, an intermediate layer 10 of polyphthalamide, and an internal layer 14 of rubber or elastomer which covers internally the layer 10 of polyphthalamide and which has a small, but sufficient thickness (typically a few tenths of a mm) to ensure satisfactory sealing on a tube or a rigid connection end-piece, the materials of the layers 12 and 14 may be identical or different.

 As in the embodiment of FIG. 1, a thin layer of a suitable adhesive can be provided between layers 10 and 12 on the one hand and between layers 10 and 14 on the other hand, if necessary.

 In general, the pipe according to the invention has mechanical and thermal characteristics and impermeability to fuels, in particular alcoholic fuels, which are notably superior to those of pipes of the prior art with a complex structure comprising an internal layer of polyamide or the like and a protective outer layer of rubber or vulcanized elastomer.

In particular, the pipes according to the invention can withstand temperatures of continuous use of the order of 180-1900C, while those of polyamides are of the order of 110 to 1500C and those of
PBT (polybutylene terephthalate) of the order of 120 to 160 OC. The permeability of a polyphthalamide to a lead-free fuel containing 5% methanol is approximately 30 g / m2 / 24h, while that of a polyamide 6 is 150 g / m2 / 24h. The permeability of a polyphthalamide to an ether-containing fluid is 15 g / m2 / 24h, that of a polyamide 6 of 35 g / m2 / 24h and that of a PBT of 120 g / m2 / 24h.

 Finally, the pipe according to the invention can be produced conventionally by extrusion or coextrusion, with a competitive cost price.

Claims (8)

 1) Fluid transfer hose, in particular fuel for a motor vehicle, comprising at least one internal layer (10) of plastic material and an external layer (12) of rubber, elastomer or thermoplastic material, characterized in that the inner layer (10) mentioned above is based on polyphthalamide.  2) Pipe according to claim 2, characterized in that the impact resistance of the internal layer (10) is reinforced by the addition of an elastomer to the polyphthalamide.  3) Pipe according to claim 1 or 2, characterized in that the outer layer (12) is made of a rubber or an elastomer vulcanized with peroxides.  4) Pipe according to claim 3, characterized in that the rubber or the elastomer is a CSM or a EPDM.  5) Pipe according to one of the preceding claims, characterized in that the internal layer (10) of plastic material adheres directly to the external layer (12).  6) Pipe according to one of the preceding claims, characterized in that its thickness is approximately 1 mm in the case of a fuel transport pipe, the thickness of the internal layer (10) of plastic being 'about 0.3 to 0.5 mm and that of the outer layer (12) of rubber or elastomer being about 0.5 to 0.7 mm.  7) Pipe according to one of the preceding claims, characterized in that the layer (10) of plastic material is covered internally with a thin layer (14) of rubber or elastomer.  8) Pipe according to one of the preceding claims, characterized in that it comprises a thin layer of adhesive material between the layer (10) of plastic material and the layer or layers (12, 14) of rubber or elastomer.