Pipes and tubular conduits – Distinct layers – Bonded to each other
Patent
1996-09-23
1998-11-24
Stryjewski, William
Pipes and tubular conduits
Distinct layers
Bonded to each other
138137, 138140, 138153, F16L 914
Patent
active
058394788
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a cold-formable composite pipe capable of constituting a pipework for conveying any fluid, such as water, gasoline, air or lubricant, especially under pressure.
In accordance with document EP-A-0,270,347 such a pipe has been described including, from the inside outward: material, namely a technical polyamide, tube with overlapping of its edges, defining between them a connecting joint and thus forming a tubular metal sheath; said metal tape being bonded to the inner tube by a first adhesive, material which has a chemical nature which is different from that of the first thermoplastic material, in this case a polyethylene; this outer sheath is bonded to the reinforcement by a second adhesive which is compatible with the second thermoplastic material, in this case a copolymer of ethylene and of a monomer which has a reactive carboxylic group, first adhesive and a second inner strip of the second adhesive.
According to this document, in the configuration defined above, it is envisaged to use a first adhesive which is compatible with the first thermoplastic material (polyamide) while immediately noting that there already exist in the trade, under the name "Zetabon" (Dow Chemical Company's registered trademark), metal tapes coated on both sides with the adhesive chemically defined above, which is compatible with the second thermoplastic material (polyethylene) but not with the first thermoplastic material (polyamide). Nevertheless, when the "Zetabon" tape is used, this results either in abandoning an effective bond between the inner tube and the reinforcement, or in adopting for the inner tube a thermoplastic material of the same kind or identical with the second thermoplastic material, namely a polyethylene.
Whichever the case envisaged, the outcome according to the document EP-A-0,270,347 is a composite pipe with limited performance, especially in leakproofing or mechanical terms.
SUMMARY OF THE INVENTION
The subject of the present invention is therefore a composite pipe as defined above, of high performance, which can be employed especially for conveying all kinds of fluids, including volatile fluids, especially under pressure, and optionally at relatively high temperatures, for example above 100.degree. C., this being done in very good conditions of, on the one hand, leakproofing and, on the other hand, mechanical strength or elasticity.
In accordance with the present invention, in a reinforcement joint placing opposite one another a first inner strip of a first adhesive and a second strip of a second adhesive, and in which the first adhesive is compatible with the first thermoplastic material and optionally identical with the second adhesive, the first and second inner strips of the joint which are bonded to each other are crosslinked or co-crosslinked chemically and thus form a coherent joint.
By virtue of the invention it becomes possible to employ two different thermoplastic materials, for the inner tube and the outer sheath respectively, including a "technical" one, for example, for the inner tube, while effectively bonding these two materials to the reinforcement, and this being done without compromising, or even by reinforcing, the leakproofing of the joint.
"Coherent" or "coherence" is intended to mean a junction which integrally unites the two inner strips of adhesive opposite the connecting joint of the reinforcement without discontinuity liable to result in a breakdown in the leaktightness of said joint.
A means of coherent bonding can be illustrated by the joining, for example by melting, of two identical materials.
By virtue of the present invention it becomes possible to choose an inner tube which is, on the one hand, relatively inert toward the conveyed fluids and, on the other hand, relatively resistant to pressure and to temperature, which is obtained, for example, using a technical thermoplastic material, for example a polyamide, and, on the other hand, an outer sheath differing from the outer tube, contributing only to the pr
REFERENCES:
patent: 4421827 (1983-12-01), Phillips
patent: 4593853 (1986-06-01), Schad et al.
Colcombet Thierry
Grandouiller Alain
M.R. Industries
Stryjewski William
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