CA2291414C

CA2291414C - Product with antistatic properties

Info

Publication number: CA2291414C
Application number: CA002291414A
Authority: CA
Inventors: Franz-Erich Baumann; Reinhard Beuth; Josef Kubber; Michael Schlobohm
Original assignee: Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 1998-11-27
Filing date: 1999-11-25
Publication date: 2006-01-31
Anticipated expiration: 2019-11-25
Also published as: JP2004277753A; DE19854819A1; KR20000035718A; EP1004618A1; CN1128846C; US6656997B2; CZ296329B6; JP3589919B2; CN1255512A; ATE271091T1; US20020037955A1; CA2291414A1; BR9906157A; PL193271B1; CZ9904235A3; ES2224524T3; PL336748A1; US20040097636A1; DE59909949D1; EP1004618B1

Abstract

Disclosed is an article made of plastic and composed, at least in part, of a thermoplastic molding composition which comprises polyamide and from 3 to 30% by weight of conductive carbon black that has the following parameters:
a) a dibutyl phthalate (DBP) absorption of from 100 to 300 m1/100 g;
b) a specific surface area of from 30 to 180 m2/g;
c) an ash content of less than 0.1% by weight and d) a grit content of not more than 25 ppm.
The article has improved heat-ageing resistance, and also improved resistance to peroxide-containing motor fuels.

Description

Product with antistatic properties The present invention relates to articles having antistatic properties.
Appropriate thermoplastics are increasingly replacing metals as a material in piping systems which transport combustible fluids, e.g. motor fuel piping systems for vehicles or aircraft, or supply piping in gas stations. This results in savings in weight and in production costs, but in turn gives rise to the disadvantage that electrostatic charges can arise.
Under certain conditions the electrostatic charge created by the flow of motor fuel or solvent can discharge extremely rapidly and produce holes in the pipeline wall, through which the motor fuel or the solvent can escape. On contact with hot components in the vicinity, or if sparks are generated, motor fuel or solvent can ignite and cause a fire in the vehicle or installation. In partly filled,tanks where the motor fuel can move around freely, the electrical charge can also cause explosion of ignitable mixtures within the tanks.
It is known that this problem can be avoided by providing the components of the piping system with antistatic properties. For example, German Patent DE 40 25 301 C1 describes antistatic motor fuel piping for motor vehicles which is composed of at least two different layers of polymer. At least one of the layers has been modified with electrically conducting additives, such as conductivity black. Although the motor fuel piping is described in that text as peroxide-resistant, it has become apparent that this applies only to layers which do not comprise the carbon black. The test conditions used take no account of the damage to the relatively thin layer provided with antistatic properties.

It has now also been found that the conductivity blacks (i.e., electrically conductive carbon black) used hitherto have a disadvantageous catalytic action. Pipes provided with these conductivity blacks, and having two or more layers show serious deterioration in low-temperature impact strength even after a relatively short time on storage in peroxide-containing motor fuels (sour gas), e.g. to the Ford* specification FLTM AZ
105-O1, PN180 or the GM* specification GM213M, PN50. Another problem which has been found is that the ageing of pipes of this type having two or more layers is markedly more rapid on exposure to heat, e.g. in the engine compartment, with attendant embrittlement.
European Patent Publication EP-A-0 730 115 is based upon the recognition that the resistance to peroxide-containing motor fuels of pipes having two or more layers and provided with antistatic properties is improved by using non-conductive black, and using graphite fibrils in its place. However, in practice this improvement is insufficient in many cases. In addition, ageing on exposure to heat continues here to be at a level inappropriately high for practical purposes. A further factor is that graphite fibrils are very expensive.
EP-A-0 745 763 describes a motor fuel filter made of plastic.
It has a casing composed of at least three layers, and the inner and the outer layer are composed of a plastic provided with conductive properties. Electrically conducting additives mentioned are, inter alia, conductive black and graphite fibrils. This motor fuel filter suffers from the disadvantages discussed above.
A major object of the present invention is therefore to produce *Trade-mark articles having antistatic properties and having both high resistance to peroxide-containing motor fuels or solvents and low susceptibility.to heat-ageing.
Attempting to achieve this object, the present invention provides an article made of plastic and composed, at least in part, of a thermoplastic molding composition which comprises polyamide and from 3 to 30o by weight, preferably from 10 to 25o by weight and particularly preferably from 16 to 20o by weight, of a conductive black, wherein the conductive black has the following parameters:
a) a dibutyl phthalate (DBP) absorption according to ASTM D2414 of from 100 to 300 m1/100 g, preferably from 140 to 270 ml/100g;
b) a specific surface area, as measured by nitrogen absorption according to ASTM D3037, of from 30 to 180 m2/g, preferably from 40 to 140 m2/g;
c) an ash content according to ASTM D1506 of less than 0.1o by weight, preferably below 0.06% by weight, particularly preferably below 0.040 by weight, and d) a grit content of not more than 25 ppm, preferably not more than 15 ppm and particularly preferably not more than 10 ppm.
For the purposes of the present invention, a grit is understood to be a hard coke-like particle which arise as a result of cracking reactions in the preparation process;
and an article is understood to have a definite shape.
Two embodiments of this invention are possible:
1. The article made of plastic is entirely composed of this molding composition, i.e. it has a one-layer structure.

2. The article product made of plastic is composed of at least two layers, where at least one layer is composed of the molding composition used according to the invention and the other layer or layers are composed of another molding composition which has not been rendered antistatic. For example, the article may be composed of 2, 3, 4, 5, 6 or even more layers. When the article made of plastic is hollow, the antistatic layer may be an outer layer or have its location in the middle. However, it is preferably an innermost layer.
In the case of a hollow article made of plastic, e.g. a pipe, the antistatic layer may also preferably cover the entire extent of the hollow article. However, it may also cover just a relatively small part of this extent, and so may take a form of a straight or spiral band.
A function of the non-antistatic layers is to give the article the required functional properties, such as strength, impact strength, flexibility or barrier action with respect to motor fuel components. Except in specialized designs, the individual layers here should adhere firmly to one another, and this can be brought about using an adhesion promoter if the layers are not mutually compatible.
Suitable materials and configurations are layers for systems conveying motor fuels can be found, for example, in DE-A 40 25 301, 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, 44 18 006, 195 07 026, 196 41 946, and also WO-A-93/21466, WO-A-93/25835, WO-A-94/09302, WO-A-94/09303, WO-A-95/27866, WO-A-95/30105, EP-A-0 198 728, EP-A-0 558 373 and EP-A-0 730 115. In the case of the hollow profiles or hollow articles disclosed in these texts, one of the layers may have been provided according to the invention with antistatic properties, or an additional antistatic layer may be added.

5 The molding composition having antistatic properties may comprise at least 10% by weight, preferably at least 40% by weight and particularly preferably at least 70% by weight, but not more than about 95% by weight, of any desired polyamide.
The other layers may be composed, for example, of a polyamide molding composition, a polyolefin molding composition of a rubber. In the case of a barrier layer for motor fuel constituents or solvents as in the prior art, the other layers may be composed of a molding composition based on thermoplastic polyester, polyvinylidene fluoride (PVDF), ethylene-tetraflouroethylene copolymer, (ETFE) or tetrafluoroethylene-hexafluoropropene-vinylidene fluoride terpolymer (THV), or of polyolefins, or ethylenevinyl alcohol copolymer (EVOH). For suitable embodiments, reference should be made to the abovementioned patent applications.
Possible polyamides here are primarily aliphatic homo-and copolyamides. Examples which may be mentioned are nylon-4,6, -6,6, -6,12, -8,10 and -10,10 and the like. Preference is given to nylon-6, -10,12, -11, -12 and -12,12. [The polyamides are identified as in the international standard, where the first numbers) gives) the number of carbon atoms in the starting diamine and the final numbers) gives) the number of carbon atoms in the dicarboxylic acid. If only one number is given, this means that the starting material was an a, c~-aminocarboxylic acid or the lactam derived therefrom - H.
Domininghaus, Die Kunststoffe and ihre Eigenschaften [Plastics and their Properties], page 272, VDI-Verlag (1976)].

If copolyamides are used, they may contain, for example, adipic acid, sebacic acid, suberic acid, isophthalic acid or terephthalic acid as coacid and, respectively, bis(4-aminocyclohexyl)methane, trimethylhexamethylenediamine or hexamethylenediamine or the like as codiamine.
The preparation of these polyamides is generally well known (e. g.. D.8. Jacobs, J. Zimmermann, Polymerization Processes, pp. 424 - 467; Interscience Publishers, New York (1977); DE-B 21 52 194 ) .
Other suitable polyamides are mixed aliphatic/aromatic polycondensates, as described, for example, in U.S. Patent Nos.
2,071,250; 2,071,251; 2,130,523; 2,130,948; 2,241,322;
2,312,966; 2,512,606 or 3,393,210 or in Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ed., Vol. 18, Wiley &
Sons (1982), pp. 328 and 435. Other polycondensates suitable as polyamides are poly(etheresteramides) and, respectively, poly(etheramides). Products of this type are described, for example, in DE-A 27 12 987, 25 23 991 and 30 06 961.
The molecular weight (number-average) of the polyamides is usually above 4000, preferably above 10,000. The relative viscosity (rlrel) here is preferably in the range from 1.65 to 2.4 (measured to ISO 307/DIN 53 727).
If required, the polyamides may be rendered impact-resistant.
Examples of suitable modifiers are ethylene-propylene copolymers or ethylene-propylene-dime copolymers (EP-A-0 295 076), acrylate-nitrile rubber, polypentenylene, polyoctenylene, or copolymers of random or block structure made from alkenylaromatic compounds with aliphatic olefins or dimes (EP-A-0 261 748). Other impact-modifying rubbers which may be used are core-shell rubbers with an elastomeric core made from (meth)acrylate rubber, from butadiene rubber or from styrene-butadiene rubber with, in each case, a glass transition temperature Tg is usually less than -10°C. The core may have been crosslinked. The shell may be composed of styrene and/or methyl methacrylate and/or of other unsaturated monomers (DE-A
21 44 528 or 37 28 685). The proportion of impact-modifying component should be selected in such a way as not to impair the desired properties and is preferably up to about 50 parts by weight per 100 parts by weight of the polyamides, usually up to about 30% by weight of the thermoplastic molding composition.
The polyamides mentioned are used alone or in mixtures. The molding compositions may also - apart from the abovementioned impact-resistance components - comprise other blend components, e.g. polyolefins, polyesters and polyether block amides (PEBA).
The molding compositions may in addition comprise the usual additives, such as processing aids, mold-release agents, stabilizers, flame retardants, reinforcing agents, e.g. glass fibers or carbon fibers, or mineral fillers, e.g. mica or kaolin, and plasticizers. The total content of these other blend components is usually not more than 50%, preferably not more than 30% by weight of the thermoplastic molding composition.
In a preferred embodiment, the molding composition also comprises from 0.1 to 20% by weight of carbon fibers, based on the total weight. However, a content of not more than 16% by weight, in particular not more than 12% by weight, is generally sufficient. Since the carbon fibers themselves contribute to the electrical conductivity, the amount of carbon black used in this case is preferably from 5 to 18% by weight.
Carbon fibers are available commercially and are described, for example, in Rompp Chemie Lexikon (Rompp's Chemical Encyclopedia], 9th edition, pp. 2289 et seq., Thieme, Stuttgart, 1993, and also in the literature mentioned therein.
It must, however, be taken into account that carbon fibers markedly increase stiffness. In many cases, e.g. for quick connectors, this can be desirable, but in other cases, e.g. for motor fuel piping, it is acceptable only to a prescribed degree.
Possible polyolefins are homopolymers and copolymers of a-olefins having from 2 to 12 carbon atoms, for example those of ethylene, propene, 1-butene, 1-hexene or 1-octene. Copolymers and terpolymers which, in addition to these monomers, contain other monomers, in particular dienes such as ethylidene-norbornene, cyclopentadiene or butadiene, are also suitable.
Examples of preferred polyolefins include polyethylene and poly-propylene. In principle, any commercially available grade of these may be used, for example: high-, medium- or low-density linear polyethylene, LDPE, ethylene copolymers with relatively small amounts (up to not more than about 40% by weight) of comonomers, such as n-butyl acrylate, methyl methacrylate, malefic anhydride, styrene, vinyl alcohol, acrylic acid or glycidyl methacrylate or the like, isotactic or atactic homopolypropylene, random copolymers of propene with ethylene and/or 1-butene, ethylene-propylene block copolymers and others of this type. Polyolefins of this type may also comprise an impact-resistance component, e.g. EPM, or EPDM rubber or SEBS.
They may also, as in the prior art, contain functional monomers, such as malefic anhydride, acrylic acid or vinyltrimethoxysilane grafts.
The thermoplastic polyesters generally have the following fundamental structure:

O O

O- R- 0- ~~-' I I

R -where R is a bivalent, branched or unbranched, aliphatic and/or cycloaliphatic radical having from 2 to 12 carbon atoms, preferably from 2 to 8 carbon atoms, in the carbon chain, and R' is a bivalent aromatic radical having from 6 to 20 carbon atoms, preferably from 8 to 12 carbon atoms, in the carbon backbone.
Examples of the diols to be used in the preparation are ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, cyclohexanedimethanol and the like.
Up to 25 mol% of the diol mentioned may have been replaced by a diol of the following general formula;
HO R" 0 H
x where R" is a bivalent radical having from 2 to 4 carbon atoms and x may be from 2 to 50.
Preferred diols are ethylene glycol and tetramethylene glycol.
Examples of aromatic dicarboxylic acids to be used in the preparation are terephthalic acid, isophthalic acid, 1,4-, 1,5-, 2,6- and 2,7-naphthalenedicarboxylic acid, diphenic acid, diphenyl ether 4,4'-dicarboxylic acid and the polyester-forming derivatives of these, e.g. dimethyl esters.

Up to 20 moll of these dicarboxylic acids may have been replaced by aliphatic dicarboxylic acids, e.g. succinic acid, malefic acid, fumaric acid, sebacic acid or dodecanedioic acid, inter alia.

The preparation of the thermoplastic polyesters is prior art (DE-A 24 07 155, 24 07 156; Ullmanns Encyclopadie der technischen Chemie [Ullmann's Encyclopedia of Industrial Chemistry], 4th edition, Vol. 19, pp. 65 et seq., Verlag Chemie 10 GmbH, Weinham 1980).
The polyesters optionally used according to the invention generally have a viscosity number (J value) in the range from 80 to 240 cm3/g.
Preferred thermoplastic polyesters are polyethylene terephthalate, polybutylene terephthalate, polyethylene 2,6-naphthalate and polybutylene 2,6-naphthalate.
If required, the polyesters may be rendered impact-resistant.
Examples of suitable fluoropolymers are ethylene-tetrafluoroethylene copolymers (ETFE; e.g. Tefzel* 200 from DuPont or Hostaflon* ET 6235 from Hoechst), tetrafluoroethylene-hexafluoropropene-vinylidene fluoride terpolymers (THV; e.g.
Hostaflon* TFB from Hoechst), ethylene-chlorotrifluoroethylene copolymers (ECTFE; e.g. Halar* from Ausimont) or polyvinylidene fluoride (PVDF). These polymers may comprise plasticizers.
However, the use of plasticizer-free fluoropolymers is preferred.
ETFE, THV and ECTFE are described, for example, in *Trade-mark H. Domininghaus, Die Kunststoffe and ihre Eigenschaften [Plastics and their Properties], 4th edition, chapter 2.1.7 (Fluor-Kunststoffe [Fluoroplastics]).
The preparation and structure of polyvinylidene fluoride are also known (Hans R. Kricheldorf, Handbook of Polymer Synthesis, Part A, Marcel Dekker Inc. New York - Basel - Hong Kong, pp. 191 et seq.; Kunststoff-Handbuch [Plastics Handbook] 1st edition, Vol. XI, Carl Hanser Verlag Munich (1971), pp. 403 et seq.).
It is also possible for polymers to be present which are based on polyvinylidene fluoride and have up to 40% by weight of other monomers. Examples which may be mentioned of additional monomers of this type are: trifluoroethylene, ethylene, propene and hexafluoropropene.
The polyvinylidene fluoride used generally has a melt flow rate of < 17 g/10 min, preferably from 2 to 13 g/10 min (DIN 53 735), measured at 230°C with a load of 5 kg.
For the purposes of the present invention, EVOH is a hydrolyzed ethylene-vinyl acetate copolymer. The hydrolyzed form is then an ethylene-vinyl alcohol copolymer.
The conductive black used according to the invention is a specific grade which differs from conventional conductive blacks in the parameters given in this specification. A typical commercially available extra conductive carbon black (EC black) has, for example, a DBP absorption of 350 m1/100 g, a specific N2 surface area of 1000 m2/g and an ash content of 0.7% by weight. The reason for the different behavior in relation to resistance to peroxide-containing motor fuels, and also heat-ageing, is not known. However, it is likely that the difference in behavior is connected to the differences in surface structure and the resultant differences in catalytic activity, and moreover that the ash content of the carbon black also has a catalytic effect.
The carbon blacks used according to the invention may be obtained, for example, by the MMM process. The MMM process is based on the partial combustion of oil (N. Probst, H. Smet, Kautschuk Gummi Kunststoffe [Rubbers and Plastics], 7 - 8/95, pp. 509 - 511; N. Probst, H. Smet, GAK 11/96 (Year 49), pp. 900 - 905). Corresponding products are commercially available.
In one embodiment, the novel product has been shaped in such a way that a gaseous, liquid or disperse medium can be passed through the same or stored in the same. The product is preferably a component of a system conveying a combustible solvent or motor fuel, for example in the motor vehicle sector, in aircraft construction or in the petrochemical industry.
Examples which should be mentioned are gas station supply piping, filling nozzles, motor fuel tanks, piping for gas-removal systems, motor fuel piping, quick connectors, motor fuel filter casings, canisters for supplementary supplies, piping for brake fluids, for coolants or for hydraulic fluids, and piping for conveying combustible powders or dusts.
The novel product is produced by conventional plastics processing methods, for example, depending on its design, by injection molding (quick connectors), extrusion (single-layer pipe), coextrusion (pipe having two or more layers) or blow molding (motor fuel tank). A person skilled in the art is familiar with these methods, and there is therefore no need for a further description of them here.
If the mode of construction has two or more layers, the thickness of the layer rendered antistatic is selected in such a way that, on the one hand, any electrical potential generated can be reliably dissipated but, on the other hand, as little material as possible is needed, for reasons of cost. The thickness of the antistatic layer here may be very low, for example from 0.01 to 0.1 mm. However, thicknesses of from 0.2 to 0.3 mm can also be advantageous for particular applications.
The ratio of the thickness of the antistatic layer to the total of the thickness of the other layers is generally from 1:5 to 1:100.
The novel products have good heat-ageing resistance and also good sour-gas resistance and fulfill, for example, the requirement of the Ford* specification WSL-M98D28-A with respect to motor fuel in accordance with Ford* FLTM AZ 105-O1 or, respectively, PN180, and also the GM* specification GM213M with respect to PN50.
They moreover effectively prevent the build-up of high voltages and fulfill, for example, the GM* specification GM213M (April 1993 draft), point 4.19. Their surface resistivity is preferably less than 106 ~/sq. This continues to hold true after repeated buckling and after storage in the motor fuel.
A more detailed description of some exemplary embodiments is given below:
- Single-layer quick connector made from a molding composition which is composed of 63% by weight of nylon-12, 16% by weight of conductive carbon black having the parameters given according to the invention (e.g. Ensaco* 250 from MMM Carbon, Brussels), 23% by *Trade-mark weight of glass fibers and 5% by weight of impact modifier (such as EPDM rubber functionalized with malefic anhydride).
- Three-layer pipe composed of:
a) an outer layer made of a polyamide molding composition, b) attached thereto, a barrier layer as given in EP-A-0 673 762, made of a mixture of from 97.5 to 50%
by weight of a vinylidene fluoride polymer and from 2.5 to 50% by weight of polymethylacrylimide, and c) an antistatic inner layer made of the thermoplastic molding composition according to the present invention.
- Two-layer pipe composed of:
a) an outer layer made of a polyamide molding composition, where appropriate impact-modified, (for example from 70 to 99% by weight of nylon-11 and from 1 to 30% by weight of EPM rubber functionalized with malefic anhydride), and b) an antistatic inner layer made of the thermoplastic molding composition according to the present invention.
- Four-layer pipe composed of:
a) an outer layer made of a polyamide molding composition, b) a barrier layer as given in EP-A-0 569 681 (from 60 to 99% by weight of a semicrystalline thermoplastic polyester, such as polybutylene terephthalate, and from 1 to 40% by weight of a compound having at least two isocyanate groups), c) an intermediate layer made of a polyamide molding composition, and d) an antistatic inner layer made of the thermoplastic molding composition according to the 5 present invention.
The invention also provides molding compositions which comprise polyamide and from 3 to 30% by weight, preferably from 10 to 25%
by weight, and particularly preferably from 16 to 20% by weight, 10 of a conductive black having the parameters described above.
When compared with corresponding molding compositions which comprise a conventional conductive carbon black or graphite fibrils, molding compositions of this type have better ageing resistance when exposed to heat and/or oxidizing conditions.
The following examples compare the resistance of the novel molding compositions to peroxide-containing motor fuel with that of molding compositions prepared using a conventional conductivity black.
Components used:
VESTAMID* L 1801 nf, an uncolored nylon-12 from Degusssa-Huls AG
PRINTEX* L, a conductive black not having the parameters of the present invention ENSACO* 250, a conductive black having the parameters of the present invention NAUGARD* 445, a stabilizer IRGANOX* MD 1024, a stabilizer HOECHST* WACHS OP, a processing aid EXXELOR* VA 1801, a malefic-anhydride-modified ethylene-propylene rubber *Trade-mark EXXELOR* VA 1803, a malefic-anhydride-modified ethylene-propylene rubber.
The individual molding compositions were prepared in a usual manner by mixing the melts of the respective components, extruding and pelletizing. The amount given in the table are parts by weight.
Tensile specimens according to DIN EN ISO 527/1A were produced from the molding compositions by injection molding.
As a control test, these tensile specimens were subjected to a tensile test according to DIN ISO 527 without pretreatment.
The conditions for the treatment of the tensile specimens with peroxide-containing motor fuel were as follows:
Storage conditions: full contact Test motor fuel: FORD* (AZ 105-O1) PN 90 Peroxide content: 90 mmol of 02/1 Temperature : 60°C
Motor fuel changed: weekly The tensile test according to DIN ISO 527 followed, carried out on test specimens moist with motor fuel. The damage to the matrix of the plastic is illustrated in the table below by means of the elongation ES. and the elongation at break eR. The fall-off with time of both elongation values is significantly slower in the case of the novel molding compositions.
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Claims

1. An article made of plastic and composed of at least two layers, where at least one of the layers is made of an antistatic thermoplastic molding composition which comprises polyamide and from 3 to 30% by weight of conductive carbon black, wherein the conductive black has the following parameters:
a) a dibutyl phthalate (DBP) absorption of from 100 to 300 m1/100 g according to ASTM D2414;
b) a specific surface area of from 30 to 180 m2/g according to ASTM D3037;
c) an ash content of less than 0.1% by weight according to ASTM D1506; and d) a grit content of not more than 25 ppm, and at least one other layer is made of a molding composition selected from the group consisting of a polyolefin rubber molding composition, a polyethylene 2,6-naphthalate molding composition, a polybutylene 2,6-naphthalate molding composition, a polyvinylidene fluoride (PVDF) molding composition, an ethylene-tetrafluoroethylene copolymer (ETFE) molding composition, a tetrafluoroethylene-hexafluoropropene-vinylidene fluoride terpolymer (THV) molding composition, an ethylene-chlorofluoroethylene copolymer molding composition, a polyolefin molding composition and an ethylene-vinyl alcohol copolymer molding composition.

2. The article as claimed in claim 1, wherein the antistatic thermoplastic molding composition comprises from to 25% by weight of the conductive black.

3. The article as claimed in claim 1, wherein the antistatic thermoplastic molding composition comprises from 16 to 20% by weight of the conductive black.

4. The article as claimed in any one of claims 1 to 3, wherein the antistatic thermoplastic molding composition also comprises from 0.1 to 20% by weight of carbon fibers.

5. The article as claimed in any one of claims 1 to 4, which is shaped in such a way that a gaseous, liquid or disperse medium can be passed through or stored in the article.

6. The article as claimed in claim 5, which is a component of a system transporting solvents or motor fuels.

7. The article as claimed in claim 6, wherein the layer made of the antistatic thermoplastic molding composition is an innermost layer.

8. The article as claimed in claim 7, which further comprises an outer layer made of a polyamide molding composition.

9. A thermoplastic molding composition, which comprises:
polyamide, from 3 to 20% by weight of conductive carbon black, wherein the conductive black has the following parameters:
a) a dibutyl phthalate (DBP) absorption of from 100 to 300 m1/100 g according to ASTM D2414;
b) a specific surface area of from 30 to 180 m2/g according to ASTM D3037;

c) an ash content of less than 0.1% by weight according to ASTM D1506; and d) a grit content of not more than 25 ppm, and from 0.1 to 20% by weight of carbon fibers.

10. The thermoplastic molding composition as claimed in claim 9, which comprises from 10 to 20% by weight of the conductive carbon black.

11. The thermoplastic molding composition as claimed in claim 9 or 10, which comprises from 0.1 to 12% by weight of the carbon fibers.

12. The thermoplastic molding composition as claimed in any one of claims 9 to 11, wherein the polyamide is a nylon-4,6, -6,6, -6,12, -8,10, -10,10, -6, -10,12, -11, -12 or -12,12.

13. An article for transporting or storing a combustible solvent or motor fuel, which is made of plastic and is composed of either a single layer or at least two layers, wherein:
(A) when the article is composed of a single layer, the layer is made of an antistatic thermoplastic molding composition which comprises:
(i) at Least 40% by weight (based on the composition) of polyamide, (ii) from 3 to 30% by weight (based on the composition) of conductive carbon black, (iii) 0 to 30% by weight (based on the composition) of an impact resistance modifier for the polyamide, and (iv) 0 to 50% by weight (based on the composition) of at least one other component or additive selected from the group consisting of polyolefin, polyester, polyether block amide, a processing aid, a mold-release agent, stabilizer, a flame retardant, a reinforcing agent, a mineral filler and a plasticizer, where the conductive carbon black (ii) has the following parameters:
a) a dibutyl phthalate (DBP) absorption of from 100 to 300 m1/100 g according to ASTM D2414;
b) a specific surface area of from 30 to 180 m2/g according to ASTM D3037;
c) an ash content of less than 0.1% by weight according to ASTM D1506; and d) a grit content of not more than 25 ppm, and (B) when the article is made of at least two layers, an innermost layer is made of the antistatic thermoplastic molding composition as defined above and the other layer or layers are made of at least one other molding composition which has not been rendered antistatic and impart strength, impact strength, flexibility or barrier action to the article, wherein the innermost layer and the other layer and layers are firmly adhered to each other.

14. The article as claimed in claim 13, which is made of 2 to 6 layers.

15. The article as claimed in claim 14, wherein the other layer or layers are made of at least one non-antistatic polyamide, polyolefin or rubber molding composition.

16. The article as claimed in claim 14, wherein the other layer or layers comprises a barrier layer for motor fuel constituents or solvents that is made of a non-antistatic molding composition based on thermoplastic polyester, polyvinylidene fluoride (PVDF), ethylene-chlorotrifluoroethylene copolymer (ECTFE), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropene-vinylidene fluoride terpolymer (THV), polyolefin or ethylene-vinyl alcohol copolymer (EVOH).

17. The article as claimed in any one of claims 13 to 16, wherein the polyamide (i) of the antistatic thermoplastic molding composition is aliphatic polyamide.

18. The article as claimed in any one of claims 13 to 17, wherein the antistatic thermoplastic molding composition contains more than 0 but not more than 30% by weight (based on the antistatic thermoplastic molding composition) of the impact resistance modifier.

19. The article as claimed in any one of claims 13 to 18, wherein the antistatic thermoplastic molding composition contains more than 0 but not more than 30% by weight (based on the antistatic thermoplastic molding composition) of glass fibers as the reinforcing agent.