Multilayer tube

Details Multilayer tube Multilayer tube

1999-11-29

2001-05-15

Hook, James (Department: 3752)

Pipes and tubular conduits

Flexible

Distinct layers

C138S141000, C138S146000

Reexamination Certificate

active

06230749

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a multilayer tube for use in motor vehicles, which does not require an intermediate bonding or primer layer to join thermoplastic layers.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,678,611 discloses a multilayer tube for use as a fuel line or vapor return or recovery line. The tube is composed of a thermoplastic outer tubing, a bonding layer, and an inner hydrocarbon barrier layer. When a multilayer tube with a bonding layer, such as that in U.S. Pat. No. 5,678,611, is used in a motor vehicle, the individual layers frequently delaminate (or separate from one another) after prolonged contact with fuel, oil, or antifreeze (which typically can be a mixture of water and alcohol); heating; or cooling.
There is a continuing need for multilayer tubes for use in motor vehicles which do not delaminate after prolonged contact with fuel, oil or antifreeze; heating; or cooling.
SUMMARY OF THE INVENTION
The present invention provides a multilayer tube comprising (a) a first outer thermoplastic layer and (b) a second inner thermoplastic diffusion barrier layer which is bonded or fused to the first layer by a material-to-material bond. The second layer has a thickness of from about 0.1 to about 0.6 mm. At least one layer of the multilayer tube has an elongation value at break of at least about 130%. Also, at least one layer of the multilayer tube includes a heat stabilizer. The multilayer tube of the present invention is able to withstand 1,000 hours or more of contact with fuels without the layers delaminating. Furthermore, the multilayer tube is able to withstand 1,000 hours or more in an antifreeze mixture of 5 to 50 percent by volume of methanol in water at from about −20 to about 80° C. without the layers delaminating.
The multilayer tube of the present invention does not require an intermediate bonding or primer layer to join the thermoplastic layers. Additionally, the multilayer tube does not delaminate after prolonged contact with fuel, oil, and antifreeze or heating and cooling. The multilayer tube may be used in motor vehicles as a fuel line or a vapor return or recovery line.


REFERENCES:
patent: 4196464 (1980-04-01), Russell
patent: 4407888 (1983-10-01), Crofts
patent: 4508870 (1985-04-01), Dufour et al.
patent: 5038833 (1991-08-01), Brunnhofer
patent: 5076329 (1991-12-01), Brunnhofer
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patent: 5996642 (1999-12-01), Noone et al.
patent: 2204376A (1988-11-01), None
SAE-XJ2260,Non-Metallic Fuel System Tubing With One Or More Layers, Draft for Ballot, May 1, 1996.
Test Specification General Motors, Engineering Standards Europe, GME 08 100; Jan. 1991.

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