Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-11-12
2002-08-06
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036910, C428S213000, C428S421000, C428S422000, C428S474700, C428S475200, C428S476900, C428S483000, C428S516000, C428S518000
Reexamination Certificate
active
06428866
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multilayer plastic composition pipe having an inner layer that has been made lastingly antistatic by addition of graphite fibrils.
2. Discussion of the Background
Multilayer pipes based on polyamides are known (DE-A 41 12 662, 41 12 668, 41 37 430, 41 37 431, 41 37 434, 42 07 125, 42 14 383, 42 15 608, 42 15 609, 42 40 658, 43 02 628, 43 10 884, 43 26 130, 43 36 289, 43 36 290, 43 36 291, 44 10 148, W0-A93/21466, EP-A-0 198 728 and EP-A-0 558 373). Making the inner layer conductive by addition of carbon black or carbon fibers is also know (see DE-A 40 25 301).
However, the use of such conductive inner layers is associated with a series of disadvantages:
a) They are insufficiently resistant to peroxide-containing fuels (sour gas). This shows up, for example, in a serious deterioration of the cold impact toughness occurring after only relatively short storage time in contact with sour-gas-containing fuels (e.g. according to the Ford specification FLTM AZ 105-01, PN 180 or according to the GM specification GM213M, PN 50).
b) After bending, thermoforming or after prolonged contact with fuel, the layers have sharply reduced conductivity, which can lead to complete loss.
c) The surface roughness leads to leakages at connections using conventional Quick Connectors.
d) The high carbon black or fiber loading in the molding compositions results in a high pressure build-up during extrusion. This requires a lowering of the production rate to uneconomically low values.
e) The use of carbon fibers causes an undesired increase in the flexural stiffness.
f) Finally, the conventional amounts of added carbon black undesirably reduce the cold impact toughness.
SUMMARY OF THE PRESENT INVENTION
Accordingly, one object of the present invention is to provide a multilayer plastic composition having an electrically conductive inner layer, which avoids the above-noted disadvantages.
Another object of the present invention is to provide a plastic pipe prepared from the multilayer plastic composition which is useful for transport of (petro)chemical materials in either solid or liquid form.
Another object of the present invention is to provide a filling port for tanks in the motor vehicle industry prepared from the multilayer plastic composition.
These and other objects of the present invention have been satisfied by the discovery of a multilayer plastic composition containing the following layers:
I. An outer layer comprising a thermoplastic molding composition and
II. An inner layer comprising an electrically conductive thermoplastic molding composition,
wherein the electrically conductive molding composition contains graphite fibrils.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to a multilayer plastic composition comprising:
(I) an outer layer comprising a thermoplastic molding composition and
(II) an inner layer comprising an electrically conductive thermoplastic molding composition and graphite fibrils.
The multilayer plastic composition can take any desired form, with multilayer pipes, hollow bodies (such as fuel tanks), filling ports for tanks, etc. being preferred.
In addition, further layers may be present, such as a conventional barrier layer for fuel components, as an intermediate layer. The barrier layer can, if desired, be adhesively bonded to the adjacent layers by means of a bonding agent.
The outer layer of the present invention comprises a polyamide molding composition, a polyolefin molding composition, a polyacetal molding composition, a polyketone molding composition, or molding composition of thermoplastic polyesters or polyester elastomers. Molding compositions suitable as inner layers for the present multilayer pipe include those based on polyamides, polyolefins, polyacetals, polyketones, thermoplastic polyesters or fluoropolymers.
Polyamides useful in the present invention are primarily aliphatic homopolyamides and copolyamides. Suitable examples include the 4.6-, 6.6-, 6.12-, 8.10-, and 10.10-polyamides with 6-, 10.12-, 11-, 12- and 12.12-polyamides being preferred. (The naming of the polyamides corresponds to the international standard, where the first digit(s) indicates the number of carbon atoms in the starting diamine and the last digit(s) indicates the number of carbon atoms in the dicarboxylic acid. If only one number is given, this means that the starting material was an &agr;,•-aminocarboxylic acid or the lactam derived therefrom—H. Domininghaus, Die Knust stoffe und ihre Eigenschaften, page 272, VDI-Verlag (1976).)
If copolyamides are used, these can contain coacids, such as adipic acid, sebacic acid, suberic acid, isophthalic acid or terephthalic acid or codiamine, such as bis(4-aminocyclohexyl)methane, trimethylhexamethylenediamine, or hexamethylenediamine.
The preparation of these polyamides is known (for example: D. B. Jacobs, J. Zimmermann, Polymerization Processes, pp. 424-467; Interscience Publishers, New York (1977); DE-B 21 52 194).
Likewise suitable as polyamides are mixed aliphatic/aromatic polycondensates as are described, for example, in U.S. Pat. Nos. 2,071,250, 2,071,251, 2,130,523, 2,130,948, 2,241,322, 2,312,966, 2,512,606, 3,393,210 or in Kirk-Othmer; Encyclopedia of Chemical Technology, 3rd edition, Vol. 18, Wiley & Sons (1982), pp. 328 and 435. Further polycondensates which are suitable as polyamides are poly(ether esteramides) or poly(etheramides). Such products are described in DE-A 27 12 987, 25 23 991 and 30 06 961.
The number average molecular weight, Mn, of the polyamides is above 4000, preferably above 10,000. The relative viscosity (&eegr;
rel
) is preferably in the range from 1.65 to 2.4.
The polyamides can contain up to 40% by weight of other thermoplastics, as long as they do not interfere with the properties required in the multilayer composition of the present invention. Suitable other thermoplastics include polycarbonate (H. Schnell, Chemistry and Physics of Polycarbonates, Interscience Publishers, New York (1981)], acrylonitrile/styrene/butadiene copolymers [Houben-Weyl, Methoden der organischen Chemie, Vol. 14/1, Georg Thieme Verlag Stuttgart, pp. 393-406; Ullmanns Encyclopädie der technischen Chemie, 4th edition, Vol. 19, Verlag Chemie Weinheim (1981), pp. 279-284], acrylonitrile/styrene/acrylate copolymers [Ullmanns Encyclopädie der technischen Chemie, 4th edition, Vol. 19, Verlag Chemie Weinheim (1981), pp. 277-295], acrylonitrile/styrene copolymers [Ullmanns Encyclopädie der technischen Chemie], 4th edition, Vol. 19, Verlag Chemie Weinheim (1981), p. 273 ff.] or polyphenylene ethers (DE-A 32 24 691 and 32 24 692, U.S. Pat. No. 3,306,874, 3,306,875 and 4,028,341).
If required, the polyamides can be impact modified. Suitable modifiers include ethylene/propylene copolymers or ethylene/propylene/diene copolymers (EP-A-0295 076), polypentenylene, polyoctenylene or random or block copolymers of alkenylaromatic compounds with aliphatic olefins or dienes (EP-A-0 261 748). Furthermore, core/shell rubbers having a viscoelastic core of (meth)acrylate, butadiene or styrene/butadiene rubber having glass transition temperatures T
g
<−10° C. can be used as impact-modifying rubbers, with the core of the rubbers being crosslinkable. The shell can be made up of styrene and/or methyl methacrylate and/or further unsaturated monomers (DE-A 21 44 528, 37 28 685). The proportion of impact-modifying components is to be selected such that the desired properties are not impaired.
The polyamides can be used on their own or in mixtures.
Suitable polyolefins include homopolymers and copolymers of &agr;-olefins having from 2 to 12 carbon atoms, such as ethylene, propene, 1-butene, 1-hexene or 1-octene. Also suitable are copolymers and terpolymers containing further ethylenically unsaturated monomers, in particular dienes such as ethylideneorbornene, cyclopentadiene or butadiene.
Preferred polyolefins are polyethylene and polypropylene. In principle, any commercial grade of these can be
Jadamus Hans
Ries Hans
Roeber Stefan
Degussa-Huels Aktiengesellschaft
Dye Rena L.
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