Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1995-05-26
1998-02-10
Robinson, Ellis
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
428 357, 428215, 428421, 4284744, 4284758, 528178, 138137, 138141, 138DIG3, B32B 2734, B32B 2708, F16L 914
Patent
active
057166846
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention concerns polymer laminates and multi-layer polymer tubes made therefrom.
BACKGROUND
The invention particularly concerns a multilayer polymer tube produced by coextrusion. The term "tube" in the context of the invention encompasses both hard pipe and soft tubing. Tubes according to the invention can be fashioned smooth or corrugated and serve to transport chemical agents, such as freon in refrigeration lines. The preferred field of application, however, is the automotive sector, especially as fuel lines or coolant liquid lines.
Tubes made of polyamide are familiar and have diverse uses. Single-layer tubes do not meet the necessary requirements such as inertness with respect to the agent flowing through them, resistance to high and low temperature and resistance against mechanical stresses. During transport of, for example, aliphatic or aromatic solvents, when subjected to external force etc., considerable disadvantages are evident such as an inadequate barrier effect against the materials to be transported, undesirable changes, or inadequate mechanical loading capability.
Attempts have already been made to eliminate these drawbacks by using multilayer tubes, but this merely avoided specific disadvantages and failed to attain the desired overall pattern of properties. For example, in multilayer tubes it is difficult to promote adhesion between the individual tube layers.
In the patent applications of ATOCHEM EP 0 558 373, EP 0 198 723 and U.S. Pat. No. 5,112,692 it is described that polymers containing carbonyl groups can function as an adhesion promoter between PVDF and polymers that are not miscible with PVDF. On the other hand it has long been known that specific interactions occur between PVDF and the carbonyl group (E. Roerdink, G. Challa, Polymer 21 (1980), 509 and M. M. Coleman et al., J. Polym. Science, Polymer Lett. Ed. 15 (1977), 745). It is therefore not surprising that polymers containing carbonyl groups are partially compatible with PVDF. This partial miscibility alone is, however, not sufficient to allow for example polyamide/PVDF blends to act as an adhesion promoter between polyamide and PVDF. Nor does restriction to specific concentration ranges necessarily provide good adhesion between the adhesion promoter on the one hand and the inner and outer layer on the other. The dwell times during mixing of the individual layers in the coextrusion head are very short, so that the distribution of the molten polymers and the morphologies that occur strongly influence the adhesion of the individual layers.
SUMMARY OF THE INVENTION
Therefore, the present invention has the object to provide a novel polyamide/polyvinylidine fluoride blend which can be used in the production of a tube that offers good barrier properties with respect to the materials to be transported, dimensional stability, and good mechanical loading characteristics. In particular, the tube must resist mechanical stresses without experiencing separation of the tube layers.
This problem is solved by a polyamide/polyvinylidine fluoride blend (PA/PVDF blend) with spherical morhpology, having a PA matrix with dispersed PVDF phases, where the polyamide of the polyamide/PVDF blend has a shear viscosity 1.5 to 7 times greater than the PVDF of the blend.
Also the above problem is solved by a multilayer polymer tube with an outer layer based on polyamide and an inner layer of polyvinylidene fluoride (PVDF) or its copolymers, where the inner layer and outer layer are tightly bonded with each other by at least one adhesion promoting intermediate layer of a polyamide/PVDF and with the aforementioned special morphology.
It has been found that polyvinylidene fluoride surprisingly exhibits excellent high temperature and hydrolysis resistance as well as barrier properties with respect to chemical agents, particularly against pure hydrocarbons as well as against alcohol or their mixtures. To assure that the inner and outer layers are tensionally bonded to each other, an intermediate, adhesion-promoting layer is requir
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patent: 5320888 (1994-06-01), Stevens
patent: 5419374 (1995-05-01), Nawrot et al.
patent: 5441782 (1995-08-01), Kawahima et al.
Computerized Infra-red Study Of The Interaction Of Poly(vinylidene fluoride) With Stereoregular Poly(methyl methacrylate), Polymer, vol. 21, May, pp. 509-513 (1980), E. Roerdink and G. Challa, Dept. of Polymer Chemistry, State University of Groningen, The Netherlands (revised 11 Oct. 1979).
A Fourier Transform Infrared Study Of Polymer Blends. I. Poly(vinylidene fluoride)--Poly(methyl methacrylate) System, Polymer Letters Edition, vol. 15, pp. 745-750 (1977), M. M. Coleman et al.
Pfleger Wolfgang
Stoeppelmann Georg
Ems-Inventa AG
Robinson Ellis
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