WO2005073295A1

WO2005073295A1 - Flexible fluid transfer tube

Info

Publication number: WO2005073295A1
Application number: PCT/FR2005/000037
Authority: WO
Inventors: Philippe Miranda; Philippe Sonntag; Victor Zarife
Original assignee: Hutchinson
Priority date: 2004-01-09
Filing date: 2005-01-07
Publication date: 2005-08-11
Also published as: FR2865015A1; EP1706446A1

Abstract

The invention relates to a flexible fluid transfer tube comprising at least one layer (3, 3') of thermoplastic or elastomer material which is coated with a deposit (10) forming a sealing barrier to the fluid transported by the tube. The invention is characterised in that the deposit (10) is a flexible layer of hydrogenated carbon resulting from the decomposition of a CnHm-type precursor gas.

Description

FLEXIBLE FLUID TRANSFER HOSE

The invention relates to a flexible fluid transfer hose, in particular but not exclusively for an air conditioning system, a fuel intake system or an air intake system of a motor vehicle. In general, a flexible fluid transfer hose must be tight and have mechanical properties which depend on the applications for which the hose is intended. The new standards and legislation are increasingly demanding in terms of impermeability and resistance to fuels and gases, in particular the new standard "UL761" which requires that the hoses resist alcoholic fuels. To satisfy the aforementioned conditions, the pipe generally has a multilayer structure, with at least one internal layer forming a fluid tightness barrier and resistant to chemical attack, an intermediate reinforcement structure in the form of a textile or metallic braid or web. and an external protective envelope. Its manufacturing cost depends in particular on the different materials used. Concretely, there are on the market, pipes with low manufacturing cost but whose performance, in particular in terms of sealing and adhesion between the layers, are just satisfactory, and very efficient pipes but having a high manufacturing cost. For these high-performance pipes, a thermoplastic polymer, for example a polyamide, is most often used as the barrier property layer. However, the presence of this layer causes a certain number of drawbacks due to the cost of this material and the difficulties of implementation and adhesion with the other layers. In particular, if it is desired to increase the barrier properties of the pipe, increasing the thickness of this layer of thermoplastic material has the drawback of reducing the flexibility of the pipe. The invention aims to design a fluid transfer pipe having excellent waterproofing characteristics while retaining good flexibility and a reasonable manufacturing cost. To this end, the invention provides a flexible fluid transfer pipe, this pipe comprising at least one layer of a thermoplastic or elastomer material which is coated with a deposit forming a barrier to the fluid transported by the pipe, characterized in that the deposition is a flexible layer of hydrogenated carbon resulting from the decomposition of a precursor gas of the C _n H _{m type} . In general, the deposition of hydrogenated carbon has a thickness of between 10 nm and 1 micron, and is obtained by a deposition technique of the PECVD type for example. The layer of hydrogenated carbon can be deposited both internally and externally on a pipe made of an elastomeric material, for example butyl, or a thermoplastic material, for example polyamide. According to a particular embodiment of the invention, the pipe can consist of at least one internal layer of a thermoplastic material, for example a polyamide, coated with a deposit of hydrogenated carbon forming a barrier to the transported fluid, an intermediate layer made of an elastomeric material such as EPDM, a reinforcing layer, for example a textile braid, and an outer layer made of an elastomeric material such as EPDM. Such a pipe with its layer of hydrogenated carbon not only forms an excellent barrier to the fluid transported, but is of low manufacturing cost taking into account the materials used. A hose according to the invention can be used in numerous applications, in particular in air conditioning systems of motor vehicles with a refrigerant such as R- ₃₄ or CO ₂ , as well as in transport systems of fuel for example. Other advantages, characteristics and details of the invention will emerge from the additional description which follows with reference to the appended drawings, given solely by way of example and in which: - Figure 1 is a perspective view with partial cutaway d 'a fragment of pipe according to an embodiment of the invention; and - Figures 2, 3 and 4 are also perspective views with partial cutaway of a pipe fragment according to alternative embodiments of the invention. The pipe 1 according to an exemplary embodiment of the invention as illustrated in FIG. 1, is a monolayer pipe comprising a layer 3 made of a thermoplastic material, for example polyamide. The layer 3 of the pipe is advantageously coated internally with a deposit 10, for example hydrogenated carbon, intended to form a barrier to the transported fluid. The deposit 10 can be produced using a technique known per se under the abbreviation PECVD ("Plasma Enhanced Chemical Vapor Deposition" in English), and the thickness of this deposit 10 can be between 10 nm and 1 micron, advantageously from around 100nm. The so-called "PECVD" technique is a deposition technique which consists in vapor deposition of a precursor gas of the C _n H _{m type} capable of decomposing in the presence of a radio frequency or microwave plasma, this precursor being able to be ethylene (C ₂ H ₂ ) in the case of the deposition of amorphous carbon. Furthermore, for the deposition of amorphous carbon, it is possible to add hydrogen to play on the hardness of the deposition and obtain a more flexible layer depending on the applications for which the pipe is intended. Instead of ethylene, the precursor gas could be methane, propane, butane or benzene for example, that is to say a precursor gas containing in its structure hydrogen atoms, these atoms conferring flexibility to the deposited layer. Such flexibility would not be obtained with a precursor gas without hydrogen atoms. According to the variant embodiment illustrated in FIG. 2, the deposition 10 of hydrogenated carbon is carried out on a layer 3 ′ of an elastomeric material, for example butyl or silicone. According to the variant embodiment illustrated in FIG. 3, the pipe is a multilayer pipe comprising at least one internal layer 3 made of a thermoplastic material, for example polyamide, a reinforcing layer

7 in the form of a textile braid for example, and an outer layer 9 of an elastomeric material such as EPDM for example. According to the variant embodiment illustrated in FIG. 4, the pipe 1 is a multilayer pipe comprising at least one internal layer 3 ′ of an elastomeric material, for example EPDM, the other layers 7 and 9 being respectively formed with the same materials as those used in the embodiment of FIG. 3. In general, the internal layer 3 or 3 ′ of the pipe 1 has a thickness which can vary between a few tenths of a millimeter to a few millimeters, and the internal diameter of the pipe 1 can range from a few millimeters for high pressure applications (air conditioning circuit for example) up to around 20cm for low pressure applications (air intake circuit for example). In general, the deposition 10 of hydrogenated carbon can be carried out on the inner wall of the layer 3 or 3 ', as illustrated in the drawings, or on the outer wall of the layer 3 or 3'. Comparative tests were carried out on a single-layer pipe of polyamide whose permeability was measured at 12g / m ² / 72h, whereas the same pipe coated with a hydrogenated carbon layer has a permeability which was measured within 5g / m ^2/72 h, which shows the importance of the invention. A pipe according to the invention has a very good seal against the fluid transported via the deposition of hydrogenated carbon on the one hand, and good mechanical properties in flexibility for example on the other hand, which make it a pipe of cost of low manufacturing that can be used both in air conditioning systems and fuel transport systems for example.

Claims

1. Flexible fluid transfer hose comprising at least one layer (3, 3 ') of a thermoplastic or elastomer material which is coated with a deposit (10) forming a sealing barrier against the fluid transported by the hose, characterized in that that the deposit (10) is a flexible layer of hydrogenated carbon resulting from the decomposition of a precursor gas of the nH _m type.

2. Pipe according to claim 1, in which the deposit (10) has a thickness of the order of 10 nm to 1 micron and is obtained by a deposition technique of the PECVD type for example.

3. Pipe according to claim 2, wherein the PECVD type technique uses a precursor gas such as ethylene to form a deposit (10) of amorphous carbon for example.

4. Pipe according to one of the preceding claims, wherein the deposit (10) is formed inside or outside the layer (3, 3).

5. Pipe according to one of the preceding claims, in which the internal layer (3) of the pipe is a thermoplastic material such as a polyamide for example.

6. Pipe according to one of claims 1 to 4, wherein the layer (3 ') of the pipe is an elastomeric material such as butyl or silicone for example.

7. Pipe according to claim 5 or 6, wherein the structure of the pipe is completed by at least one reinforcing layer (7) in the form of a textile braid, and an outer layer (9) made of an elastomeric material such as the 'EPDM for example.