Pipes and tubular conduits – Flexible – Distinct layers
Patent
1995-04-04
2000-03-28
Brinson, Patrick
Pipes and tubular conduits
Flexible
Distinct layers
138140, 138DIG7, 428 367, F16L 1104, F16L 914
Patent
active
060418265
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a pipe for conveying or feeding petrol, in particular in engines, particularly motor vehicle engines. The pipe which is the subject of the invention is a polyamide-based petrol supply tube.
For safety reasons and to protect the environment, motor vehicle manufacturers impose mechanical characteristics on petrol pipes: strength and flexibility, and characteristics of increased resistance to permeability. The pipes must be as impervious as possible to petroleum products and to their additives, in particular methanol.
PRIOR ART
At present, polyamide pipes are commonly employed in the motor vehicle industry. Polyamides represent an ideal material for this pipe application, their mechanical strength being excellent and their flexibility being sufficient for a pipe to withstand, without breaking, the accumulation of flexural motions practically throughout the life of a vehicle. These polyamide pipes no longer meet the new requirements of the motor vehicle manufacturers where permeability is concerned. With the ever increasing presence of methanol in petrol, the sensitivity of polyamide pipes is reflected in a swelling of the pipe resulting in a decrease in the mechanical properties and dimensional changes.
DESCRIPTION OF THE INVENTION
The objective of the present invention is therefore to overcome these disadvantages while preserving the mechanical properties of the polyamides.
Thus, the present invention provides a polyamide-based petrol supply tube comprising an outer layer of polyamide, a middle layer of fluoropolymer, preferably of PVDF, and an inner layer of polyamide, these layers being respectively bonded to each other by layers of adhesive bonding agent.
The subject of the invention is therefore a pipe consisting of five layers made up respectively of PA/bonding agent/fluoropolymer/bonding agent/PA (PA meaning polyamide).
These pipes are particularly suitable for feeding petrol to engines.
The polyamide employed is usually a thermoplastic aliphatic polyamide and especially a polyamide 11 (PA-11), polyamide 12 (PA-12) or polyamide 12,12 (PA-12,12), plasticized or otherwise, or else a polyamide 6 (PA-6) or polyamide 6,6 (PA-6,6). The polyamide may optionally be a product modified to withstand impacts, or a copolymer. The polyamides of the outer and inner layers may be identical or different. Each polyamide layer may consist of one or a number of sublayers, each of these sublayers consisting of a different polyamide.
This polyamide may also contain conventional fillers for polyamides. The quantity of filler which is incorporated is itself also conventional and is a function of the specification of the motor vehicle manufacturers. One or both polyamide layers may contain such fillers.
According to an embodiment, this filler consists of a regrind. This term "regrind" refers to the ground product of a pipe misshapen during the manufacturing process, and therefore unsuitable for the application for which it is intended, which is thus recycled. It is therefore possible to grind up these misshapen pipes and to incorporate them into the inner and/or outer layer.
Among the fluoropolymers according to the invention there may be mentioned: chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE), hexafluoropropene (HFP) and/or ethylene units and optionally VF2 and/or VF3 units. By way of example there may be mentioned polytetrafluoroethylene (PTFE) and poly(ethylene-tetrafluoroethylene) (ETFE).
A fluoropolymer is also intended to mean mixtures of at least 70% by weight of the above with other polymers.
Among the fluoropolymers those advantageously employed are the vinylidene fluoride homo- and copolymers containing at least 70% by weight of VF2 residues, referred to as PVDF throughout the text. PVDF is also intended to mean mixtures of the above with at least one other thermoplastic polymer, provided that at least 50% by weight of VF2 units is present in the mixture.
Each layer of fluoropolymer may be made up of one or a number of sublayers, each of these subla
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Denizart Olivier
Lorek Serge
Siour Daniel
Brinson Patrick
Elf Atochem S.A.
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