Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-04-29
2002-10-22
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C138S137000, C524S496000, C524S601000, C524S606000
Reexamination Certificate
active
06469092
ABSTRACT:
DESCRIPTION
The invention concerns molding compounds based on polyamides and/or polyesters that are simultaneously anti-static and stabilized against peroxides. These anti-static molding compounds can be used for the production of injection-molded or extruded parts, for the production of sheets or multi-layer hoses or tubes.
Making polymers anti-static with conductive additives such as carbon black, carbon fibers and metal powder has been known in the art for a long time (see Gaechter, Muller in “Plastics Additives” p. 762, 1993). With metal powder, large quantities of fill material are necessary, whereby the mechanical properties are strongly influenced. Moreover, these metal powders are, for the most part, very expensive. The addition of carbon fibers leads to stiffening and to a reduction of impact strength and elongation at break, which is particularly disadvantageous if tubes are to be made anti-static.
Fuel lines made of plastics such as polyamides have been installed in vehicles for a long time. Through high fuel circulation, such as is typical with fuel-injected motors, these tubes can become highly charged. In the extreme case, this static charging can lead to an explosion-like destruction of the lines and to leaking of fuel from the lines. There is an increased safety risk because of the acute danger of fire. Therefore, developments were implemented for producing polymers with low conductivity and, especially in polyamide 11 or polyamide 12, to blend in electrically conductive additives such as the above-mentioned carbon black, carbon fibers and metal powder.
In DE-A-40 25 301, anti-static and peroxide-stable fuel lines are described in which carbon black-filled polyamides and polyethylenes are used in multi-layer tubes. However, it cannot be determined from this document how the problem of peroxide resistance is effectively to be resolved.
If polyamide or polyester molding compounds are filled with conductive carbon black, even though they show an anti-static effect, the thermal and chemical resistance is reduced. In particular, the resistance against peroxides is of foremost significance for applications in automobile construction, in which polyamides and polyesters are in constant contact with fuel. An additional possibility for making polyamides and polyesters anti-static is the incorporation of graphite fibers, which were described in applications U.S. Pat. No. 5171560 and WO 94/23433 and in Plastics World (September 1996). With these graphite fibers, making polyamides and polyesters anti-static is accomplished without losing the peroxide stability. However, these graphite fibers are very expensive and their incorporation into polyamides and polyesters is difficult because of the high viscosities of the resulting compounds.
It is therefore the objective of the invention to make molding compounds based on polyamides and/or polyesters anti-static without losing their resistance to peroxides.
This objective is fulfilled via the anti-static, peroxide-stable molding compounds according to claim
1
, whereby the molding compounds are modified with very pure conductive carbon black with low specific surface area.
These molding compounds can be used for the production of injection molded or extruded parts, for the production of sheets or multi-layer hoses or tubes (claim
7
).
The above-mentioned objective is also accomplished by means of thermoplastic multi-layer composites according to claim
8
, whereby at least one layer consists of a molding compound based on a polyester or polyamide that is specified with very pure conductive carbon black with a low specific surface area. The multi-layer composite contains at least one second layer at least partially adjacent to the previously mentioned layer on the basis of a polyamide molding compound and, in some cases, a coupling layer lying between them which binds the polyester or polyamide layer to the previously mentioned polyamide or polyester layer by adhesion.
Beneficial embodiments of the invention are included in the remaining subclaims.
Surprisingly, it was determined that if these very pure conductive carbon blacks are incorporated into polyamide and/or polyester molding compounds, the molding compounds are peroxide-resistant. In this case, “pure” means that the carbon black has only very small quantities of metallic impurities, such as copper or iron. Furthermore, it is important that the oxygen and sulfur content of these carbon blacks is as small as possible.
In a preferred embodiment of the invention, the molding compound with the polyamide basis possesses a continuous polyamide phase and the molding compound with the polyester basis possesses a continuous polyester phase.
The possible polyamides according to the invention are:
Homo- and copolymers derived from dicarboxylic acids, diamines, aminocarboxylic acids and/or lactams. Lactams with 6 to 12 C atoms, &agr;,&ohgr;-aminocarboxylic acids with 6 to 12 C atoms, dicarboxylic acids with 2 to 44 C atoms and aliphatic and/or cycloaliphatic diamines with 2 to 12 C atoms are preferred. According to the invention, the polyamides selected from homo- and/or copolyamides based on PA 6, PA 46, PA 66, PA 612, PA 1010, PA 1012, PA 69, PA 11, PA 12, PA 1212, PA 6T, PA 61, PA 12T, PA121, PA 12/6T, PA 12/61 and/or mixtures of them are preferred, whereby PA 12 in particular is preferred.
The nomenclature of the polyamides corresponds to international standards, whereby the first number(s) specify the number of C atoms in the starting amine and the last number(s) specify the number of C atoms in the dicarboxylic acid. If only one number is specified, then this means that one is starting with an aminocarboxylic acid or its lactam. The number average of the molecular weight of the polyamides should be above 5,000, preferably above 10,000.
Insofar as copolymers are used, they can contain, for example, adipic acid, sebacic acid, suberic acid, isophthalic acid, terephthalic acid, di-lauric acid as a co-acid, or 4,4′-diaminodicyclohexylmethane, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane trimethyl hexamethylene diamine, hexamethylene diamine or similar compounds as co-diamines.
The production of these copolyamides is known, for example, from DE-AS 21 52 194.
Mixed aliphatic/aromatic polycondensates, as described for example in U.S. Pat. No. 2,071,250, 2,071,251 et al. are also suitable as polyamides. Polyether ester amides or polyether amides are likewise appropriate as polyamide-suitable polycondensates. Products of this type are described, for example, in DE OS 27 12 987. Furthermore, polyesteramides, which are known from DE-A 19 64 313, are a possibility within the context of the invention.
To the extent that it is required, the polyamides can be impact modified. Suitable impact resistance modifiers are, for example, ethylene/propylene copolymers or ethylenelpropylene/diene copolymers or even other impact resistance-enhancing rubbers.
In addition, a flame retardant as well as other additive materials such as pigments, oligomers and polymers, stabilizers and processing aids, as well as reinforcing agents can be included. The portion of reinforcing agents can amount to up to 50% of the entire molding compound, that of the flame retardant up to 15%, and that of all remaining additive materials together can be up to 5%, relative to the total molding mass in each case.
Especially preferred for the applications in the fuel line area, or in the automotive area, are polyamide 12 and semi-aromatic polyamides.
Those polymers in which the monomer units are predominately (i.e., through ester linkages) linked with one another are understood to be polyesters. Possibilities here are homopolymers and copolymers derived from dicarboxylic acids, diols, bisphenols, hydroxy carboxylic acids and/or lactones. Ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, 1,4-cyclohexane dimethanol and neopentyl gycol, for example, can be considered for diol components, and isophthalic acid, terephthalic acid, 2,6-, 2,7-, 1,5-, 1,4-naphthaline d
Hewel Manfred
Stöppelmann Georg
ENS-Inventa AG
Niland Patrick D.
Standley & Gilcrest LLP
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