Stock material or miscellaneous articles – Composite – Of polyamide
Reexamination Certificate
2001-12-26
2004-09-21
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamide
C428S474900, C428S476900, C428S036910, C525S180000, C525S184000
Reexamination Certificate
active
06794048
ABSTRACT:
The invention relates to a multilayer composite in which a polyamide layer and a polyolefin layer are joined to one another by means of a specific bonding agent.
Multilayer composites comprising a polyamide layer and a polyolefin layer are known per se. Thus, DE-A 37 15 251 describes a two-layer tube consisting of a polyamide layer and a polyolefin layer for conveying an alcoholic medium. To achieve any adhesion at all between the layers, the polyolefin contains groups derived from maleic acid.
DE-C 40 00 434 describes a multilayer coolant line which, in one embodiment, comprises an outer polyamide layer, an inner polyolefin layer and an intermediate bonding layer of a polyolefin bearing functional groups.
Such composites have firm adhesion between the layers after their production. However, it has been found that adhesion between the layers of functionalized polyolefin and polyamide becomes lower and lower on prolonged contact with aqueous liquids or alcohol-containing fuel, particularly at elevated temperatures, and finally drops to values which are no longer acceptable in practice; the reasons for this are considered to be alcoholysis or hydrolysis reactions.
A different concept is presented in U.S. Pat. No. 3,561,493. There, a mixture of polyamide and polyethylene is recommended as bonding agent between a polyamide layer and a polyolefin layer. However, attempts to reproduce this disclosure show that, depending on which polymer forms the coherent phase in the mixture, only adhesion either to the polyamide layer or to the polyethylene layer is obtained, but never both at the same time.
Finally, EP Application No. 00 10 9633.8 (intended Publication Number 1 065 048), which is not a prior publication, describes a multilayer composite comprising a bonding agent which comprises a polyamine-polyamide copolymer. A polyolefin layer or the presence of a polyolefin in the bonding agent is not disclosed there.
It is an object of the present invention to produce a multilayer composite comprising a polyamide layer and a polyolefin layer joined by means of a bonding layer which does not consist of a functionalized polyolefin. A further object is to produce such a multilayer composite in which the adhesion between layers remains largely intact even on prolonged contact with alcohol-containing or aqueous media at elevated temperatures. A further object is to firmly join a polyamide layer and a layer which has the features of a polyolefin molding composition and therefore may make an additional polyolefin layer unnecessary.
These objects are achieved by a multilayer composite which comprises the following layers bound directly to one another:
I. a layer I of a polyamide molding composition;
II. a layer II of a bonding agent comprising at least 50% by weight, preferably at least 70% by weight and particularly preferably at least 85% by weight, of a mixture of
a) from 30 to 70 parts by volume of polyamide, preferably from 40 to 60 parts by volume, and
b) from 70 to 30 parts by volume of polyolefin, preferably from 60 to 40 parts by volume, where the sum of the parts by volume is 100 and in addition at least some of the polyamide is present either in the form of a polyamide-polyolefin graft copolymer or as a highly branched polyamine-polyamide copolymer;
III. if desired a layer III of a polyolefin molding composition.
Possible polyamides for the layer I or the bonding agent are first and foremost aliphatic homopolycondesates and copolycondensates, for example PA 46, PA 66, PA 68, PA 612, PA 88, PA 810, PA 1010, PA 1012, PA 1212, PA 6, PA 7, PA 8, PA 9, PA 10, PA 11 and PA 12. (The designation 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 of the dicarboxylic acid. If only one number is given, this means that the polyamide has been prepared from an &agr;, &ohgr;-aminocarboxylic acid or from the lactam derived therefrom; for further information, reference may be made to H. Domininghaus, Die Kunstatoffe und ihre Eigenschaften, pages 272 ff., VDI-Verlag, 1976.)
If copolyamides are used, they can comprise, for example, adipic acid, sebacic acid, suberic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, etc., as coacid and bis(4-aminocyclohexyl)methane, trimethylhexamethylenediamine, hexamethylenediamine or the like as codiamine. Lactams such as caprolactam or laurolactam or aminocarboxylic acids such as &ohgr;-aminoundecanoic acid can likewise be incorporated as cocomponents.
The preparation of these polyamides is known (e.g. D. B. Jacobs, J. Zimmermann, Polymerization Processes, pp. 424-467, Interscience Publishers, New York, 1977; DE-B 21 52 194) .
Further suitable 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 and 3,393,210 and also in Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd edition, Vol. 18, pages 328 ff. and 435 ff., Wiley & Sons, 1982. Other suitable polyamides are polyether ester amides) or poly(ether amides); such products are described, for example, in DE-A 25 23 991, 27 12 987 and 30 06 961.
The polyamide molding composition can comprise either one of these polyamides or a mixture of a plurality of them. Up to 40% by weight of other thermoplastics can also be present, as long as they do not interfere with the bonding capability. Particular examples of such further thermoplastics are impact-toughening rubbers such as ethylene-propylene or ethylene-propylene-diene copolymers (EP-A-0 295 076), polypentenylene, polyoctenylene, random or block copolymers of alkenylaromatic compounds with aliphatic olefins or dienes (EP-A-0 261 748) or core/shell rubbers having a tough elastic core of (meth)acrylate, butadiene or styrene-butadiene rubber having a glass transition temperature T
g
of <−10° C., where the core may be crosslinked and the shell may be made up of styrene and/or methyl methacrylate and/or further unsaturated monomers (DE-A 21 44 528, 37 28 685).
The polyolefin of layer III or of the bonding agent is, for example, polyethylene or polypropylene. It is in principle possible to use any commercial type. Thus, for example, possible polyolefins are: linear polyethylene of high, intermediate or low density, LDPE, isotactic or atactic homopolypropylene, random copolymers of propene with ethene and/or 1-butane, ethylene-propylene block copolymers and the like. The polyolefin can further comprise an impact-toughening component such as EPM or EPDM rubber or SEBS. Furthermore, the customary auxiliaries and additives may also be present. The polyolefin can be prepared by any known process, for example by the Ziegler-Natta process, by the Phillips process, by means of metallocenes or by a free-radical process.
The molding composition of layer III can be crosslinked as described in the prior art so as to achieve an improvement in the mechanical properties, e.g. the cold impact toughness, the heat distortion resistance or the creep behavior, or in the permeability. Crosslinking is carried out, for example, by radiation crosslinking or by means of moisture crosslinking of polyolefin molding compositions containing silane groups.
The bonding agent of layer II may further comprise, in addition to the mixture of polyamide and polyolefin, other polymers or the customary auxiliaries and additives, as long as these do not significantly impair the bonding action.
In the mixture of polyamide and polyolefin, at least part of the constituents is present in the form of a polyamide-polyolefin graft copolymer. The lower limit of this is determined by the effect according to the invention being still just achieved. It can easily be determined by simple experiments.
Polyamide-polyolefin graft copolymers can be formed by various methods, for example by
reaction of suitable functional groups of the polyamide, for instance the amino or carboxyl and groups of the polyamide, with f
Haeger Harald
Schmitz Guido
Bissett Melanie
Degussa - AG
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Seidleck James J.
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