PPA/FLUOROPOLYMER PIPE

Abstract

A pipe for transporting fluid in motor vehicles, such as fuel or oil under high tempature and pressure, comprises one layer constituted for the most part of polyphthalamide (PPA) and one layer constituted for the most part of fluoropoloymer. The pipe has a thickness formed mainly by the thickness of the polyphthalamide layer, the thickness of the polyphthalamide layer being five to ten times greater than the thickness of the fluoropolymer layer. The polyphthalamide layer can be directly in contact with the fluoropolymer and a bonding layer of polyamide can also be present between these two main layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

In a first embodiment, the pipe comprises one layer of polyphthalamide as an outer layer and one layer of fluoropolymer as an inner layer.

Suitable fluoropolymers comprise, in particular: polyvinylidene fluoride (PVDF); ethylene tertrafluoroethylene (ETFE); ethylene fluoroethylene perfluoride (EFEP); polytetrafluoroethylene (PTFE); fluoroethylene propylene (FEP); perfluoroalkoxy (PFA); ethylene chlorotrifluoroethylene (ECTFE), . . . .

By way of example, the fluoropolymer may be a Teflon FEP from the supplier DuPont de Nemours, and the polyphthalamide may be that produced under the trademark Amodel by the supplier Solvay.

This pipe is particularly well adapted to transporting fuel and in particular alcohol-containing fuels since the overall performance of the materials used is very stable in a medium containing alcohol.

In a variant, when the adhesive properties of the pipe are not sufficient for its conditions of use, it is possible to add a bonding layer between the inner layer and the outer layer, or possibly between said layers and intermediate layers. The bonding layers may be based on polyamide, for example.

In another variant, the pipe may have an additional layer, e.g. of thermoplastic elastomer (TPE). The layer of thermoplastic elastomer is preferably disposed as an outer layer for protecting the pipe against impacts and fire.

The fluoroethylene propylene (or more generally the fluoropolymer) used may also be made adhesive to polyamide and the pipe may include an intermediate layer of polyamide between the fluoroethylene propylene layer and the polyphthalamide layer. Other intermediate layers may be added.

In a second embodiment, the pipe in accordance with the invention has an inner layer made of polyphthalamide (PPA) with thickness lying in the range 1 mm to 1.5 mm.

The pipe also includes an outer layer made of a fluoropolymer and preferably a terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV). Other fluoropolymers can be used, such as: polyvinylidene fluoride (PVDF); ethylene tertrafluoroethylene (ETFE); ethylene fluoroethylene perfluoride (EFEP); polytetrafluoroethylene (PTFE); fluoroethylene propylene (FEP); perfluoroalkoxy (PFA); ethylene chlorotrifluoroethylene (ECTFE), . . . . The outer layer has a thickness of about 0.2 mm.

This thickness ratio is the optimum solution for making a pipe in accordance with the second embodiment of the invention.

The pipe in accordance with the invention is made by extrusion, and the outer layer is in direct contact with the inner layer. This is made possible by the good properties of mutual adhesion between polyphthalamide and the fluorinated terpolymer.

In a variant, when these adhesive properties are not sufficient, given the conditions of use of the pipe, it is possible to add a bonding layer between the inner layer and the outer layer.

Naturally, the invention is not limited to the embodiments described and variant embodiments can be provided without going beyond the ambit of the invention as defined by the claims.

The pipe may have more than two layers.

The materials used may include fillers, or additives, e.g. for the purpose of making them compatible with each other (improving their adhesive properties) or making them conductive, reinforcing them mechanically, or coloring them . . . or they may be associated with other materials within a single layer.

The thicknesses are given purely by way of indication. Thicknesses other than those mentioned could be used.

Claims

1. A pipe comprising at least a layer constituted for the most part of polyphthalamide, and a layer constituted for the most part of a fluoropolymer.

2. A pipe according to claim 1, in which the layer of polyphthalamide is an inner layer and the layer of fluoropolymer is an outer layer.

3. A pipe according to claim 1, in which the fluoropolymer is selected from: polyvinylidene fluoride (PVDF); ethylene tertrafluoroethylene (ETFE); ethylene fluoroethylene perfluoride (EFEP); polytetrafluoroethylene (PTFE); fluoroethylene propylene (PEP); perfluoroalkoxy (PFA); and ethylene chlorotrifluoroethylene (ECTFE).

4. A pipe according to claim 1, in which the layer of polyphthalamide is the innermost layer of the tube.

5. A pipe according to claim 1, in which the pipe has thickness formed mainly by the thickness of the layer of polyphthalamide.

6. A pipe according to claim 5, in which the thickness of the layer of polyphthalamide is five to ten times greater than the thickness of the layer of fluoropolymer.

7. A pipe according to claim 6, in which the thickness of the layer of polyphthalamide is about 1 mm to 1.5 mm and the thickness of the layer of thermoplastic material is about 0.2 mm.

9. A pipe according to claim 4, in which the fluoropolymer is a terpolymer of tetrafluoroethylene, hexafluoropropylene, and fluorinated vinylidene.

9. A pipe according to claim 1, in which the layer of fluoropolymer is directly in contact with the layer of polyphthalamide.

10. A pipe according to claim 1, comprising a bonding layer between the layer of polyphthalamide and the layer of fluoropolymer.

11. A pipe according to claim 10, wherein the bonding layer is a layer of polyamide.