A process for preparing a conductive composition using a masterbatch.

ES 2 628 331 T3

DESCRIPTION

A method of preparing a conductive composition using a masterbatch

The present invention relates to a process for the preparation of a polymer composition comprising carbon nanotubes. In particular, the present invention relates to a process for the preparation of conductive polymer compositions comprising carbon nanotubes.

As electronic devices get smaller and faster, their sensitivity to electrostatic charges increases and electronic packaging has been provided to improve electrostatic dissipative properties. Electronic product packaging is designed to prevent the build-up of static electrical charges and consecutive electrostatic discharge (ESD) that can be responsible for serious damage to electronic products and lead to product defects and high disposal rates.

In order to ensure ESD protection, inherently and electrically insulating polymers can be made conductive or dissipative by incorporating conductive charges (such as carbon black, CB) allowing effective dissipation of static electrical charges.

Currently conductive or dissipative plastic products are dominated by CB, mainly because CB is relatively cheap compared to other conductive fillers, such as carbon fiber, carbon nanotubes (CNT), metal fiber, metal-coated carbon fiber , and metal powder. The level of addition of CB must be sufficient so that the particles create a conductive path through the materials. Consequently, high levels of CB (15-30%) are required to meet the requirements, which alter the critical physical properties of the basic polymer such as impact resistance, elongation and viscosity of the compound.

These properties need to be preserved when other fillers are used instead of CB as conductive fillers. However, a minimum concentration is required to obtain the desired conductivity. Since other fillers are more expensive than CB, there remains a need to provide improved conductive compositions that are electrically insulating.

Therefore, an object of the present invention is to provide a process for preparing a conductive composition, said process comprising the steps of (a) providing a masterbatch comprising at least 5% by weight of carbon nanotubes based on weight total of the masterbatch, and a polyolefin and / or styrenic copolymer; (b) mixing the masterbatch of step (a) with polystyrene or modified polystyrene or a mixture thereof, and with a polyolefin, in amounts so as to obtain the conductive composition comprising a maximum of 1.90% by weight of carbon nanotubes based on the total weight of the composition.

The independent and dependent claims set out the particular and preferred features of the invention. The features of the dependent claims may be combined with the features of the independent or other dependent claims, as appropriate.

In the following steps, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly stated otherwise. In particular, any characteristic indicated as preferred or advantageous can be combined with any other characteristic or characteristics indicated as preferred or advantageous.

As used herein, the singular forms "a", "an", "the" and "the" include both singular and plural referents unless the content clearly dictates otherwise. By way of example, "a polystyrene" means one polystyrene or more than one polystyrene.

The terms "comprising", "comprises" and "composed of", as used herein, are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional and unlisted members, items, or procedural steps. It will be appreciated that the terms "comprising", "comprises" and "composed of", as used herein, comprise the terms "consisting of", "consists" and "consists of".

Enumeration of number ranges using endpoints includes all whole numbers and, where appropriate, fractions subsumed within that range (for example, 1 through 5 may include 1, 2, 3, 4 when referring to, for example, a number of items, and can also include 1.5, 2, 2.75, and 3.80, when referring to, for example, measurements). The endpoint enumeration also includes the endpoint values ​​themselves (for example, 1.0 to 5.0 includes both 1.0 and 5.0).

Any numerical range listed in this document is intended to include all subranges subsumed therein.

The present invention provides a conductive composition comprising a polystyrene or modified polystyrene or mixture thereof, wherein the composition further comprises a polyolefin; and in which the

The composition further comprises at most 1.90% by weight of carbon nanotubes, based on the total weight of the composition.

In one embodiment, the composition comprises the melt-blended product of said polystyrene or modified polystyrene or mixture thereof, said polyolefin or said carbon nanotubes.

As used herein, the term "fusion mixing" implies the use of shear force, extensional force, compression force, ultrasonic energy, electromagnetic energy, thermal energy, or combinations that comprise at least one of the forces or energy forms above and is carried out in the processing equipment in which the above-mentioned forces are exerted by single screw, multiple screws, co-rotating or counter-rotating screws meshed with each other, co-rotating or counter-rotating screws not meshing with each other, reciprocating screws, bolted screws, bolted cylinders, rollers, pistons, helical rotors, or combinations comprising at least one of the foregoing. Melt mixing can be carried out in machines such as single or multi-screw extruders, Buss kneader, Eirich, Henschel, Helicone-type mixers, Ross, Banbury mixers, roller mills, molding machines such as machines. injection molding machines, vacuum forming machines, blow molding machines, or the like, or combinations comprising at least one of the above machines. It is generally desirable during melting or mixing of the composition solution to confer a specific energy of from about 0.01 to about 10 kilowatt-hours / kilogram (kWh / kg) of the composition. In a preferred embodiment, melt mixing is performed in a twin screw extruder, such as a Brabender corotation twin screw extruder.

Preferably, the composition comprises at least two immiscible phases: a polystyrene phase and a polyolefin phase.

In some embodiments, the composition may comprise at least 30% by weight of the polystyrene or modified polystyrene or mixture thereof, based on the total weight of the composition. Preferably the composition comprises at least 35% by weight, eg at least 40% by weight, eg at least 45% by weight, more preferably at least 50% by weight of the polystyrene or modified polystyrene or mixture thereof, even more preferably at least 54% by weight of the polystyrene or modified polystyrene or mixture thereof, based on the total weight of the composition.

Non-limiting examples of suitable polystyrenes that can be used in the composition include polystyrene, modified polystyrene, or blends of polystyrene and modified polystyrene.

In modified polystyrene, part of the styrene may be replaced by unsaturated monomers copolymerizable with styrene, for example alphamethylstyrene or (meth) acrylates, Other examples that may be mentioned are chloropolystyrene, polyalpha-methylstyrene, styrene-chlorostyrene copolymers, styrene-copolymers of styrene propylene, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-vinyl chloride copolymers, styrene-vinyl acetate copolymers, styrene-alkyl acrylate copolymers (methyl, ethyl, butyl, octyl, phenyl acrylate), styrene-alkyl methacrylate copolymers (methyl, ethyl, butyl, phenyl methacrylate), styrene-methyl chloroacrylate copolymers, and styrene-methyl-chloroacrylate copolymers -alkyl acrylate.

Polystyrenes for use in the present invention can be copolymers or homopolymers of styrene, alpha methyl styrene, and para methyl styrene. Preferably, the polystyrene is homopolystyrene.

Polystyrenes can be prepared by a number of procedures. This procedure is well known to those skilled in the art and is described, for example, in the reference mentioned above.

The polystyrene modified for use in the composition can be rubber modified.

Rubber can be prepared by a number of procedures, preferably by emulsion or solution polymerization. These procedures are well known to those of skill in the art.

If present, the rubber is preferably present in an amount of about 3 to 15% by weight. Polybutadiene is a particularly useful rubber.

Preferably, the modified polystyrene is rubber modified polystyrene.

In one embodiment, the rubber modified polystyrene is a high impact polystyrene (HIPS). The process for making HIPS is well known to those of skill in the art. For example, the process may comprise polymerizing the styrene monomer in the presence of dissolved rubber. The polymerization of styrene, and optionally a comonomer, can be initiated by heating and / or by an initiator, for example a radical initiator. The rubber can be "dissolved" in the styrene monomer. Common types of rubber used in the manufacture of HIPS include polybutadiene (PB), styrene-butadiene rubber (SBR), and styrene-butadiene-styrene rubber (SBS). Polystyrene can be formed initially from styrene monomer within the homogeneous rubber solution in styrene. In HIPS, a part of the styrene can be replaced by unsaturated monomers copolymerizable with styrene such as other monomers

ES 2 628 331 T3 monovinylaromatics, alkyl esters of acrylic or methacrylic acid and acrylonitrile. Non-limiting examples of suitable procedures for preparing HIPS are described in NS2010 / 240832.

Advantageously, the modified polystyrene is a HIPS or a mixture of polystyrene and HIPS. In one embodiment, the composition comprises at least 30% by weight of HIPS or a mixture of polystyrene and HIPS, based on the total weight of the composition. For example, the composition comprises at least 35%, at least 40%, at least 45%, at least 50% by weight of HIPS or a mixture of HIPS and polystyrene, based on the total weight of the composition. The composition also comprises at least one polyolefin. As used herein, the terms "olefin polymer" and "polyolefin" are used interchangeably.

In one embodiment, the composition comprises at most 70%, eg at most 60%, by weight of polyolefin based on the total weight of the composition. For example, the composition comprises at least 15% by weight, eg at least 20%, eg at least 25%, eg at least 30% polyolefin based on the total weight of the composition preferably at least 35% polyolefin based on the total weight of the composition, preferably at least 40% polyolefin based on the total weight of the composition.

Suitable polyolefins used in the present invention can be any olefin homopolymer or any copolymer of an olefin or one or more comonomers. As used herein, the term "homopolymer" refers to a polymer that is made by linking monomers (preferably olefin, preferably ethylene), in the absence of comonomers. As used herein, the term "copolymer" refers to a polymer, which is made by joining two different types of monomers in the same polymer chain. Polyolefins can be atactic, syndiotactic, or isotactic. The olefin can be monoolefin, or di-olefin. The monoolefin can be, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene or 1-octene, but also cycloolefins such as, for example, cyclopentene, cyclohexene, cyclooctene or norbornene. Preferably, the olefin is alpha-olefin. The di-olefin can also be, for example, butadiene (such as 1,3-butadiene), 1,2-propadiene, 2-methyl-1,3-butadiene, 1,5-cyclooctadiene, norbornadiene, dicylopentadiene, 1, 3-heptadiene, 2,3-dimethylbutadiene, 2-ethyl-1,3-pentadiene, 1,3-hexadiene, or 2,4-hexadiene.

The comonomer, if present, is different from the olefin and is chosen in such a way as to be suitable for copolymerization with the olefin. The comonomer can also be an olefin, as defined above. The comonomers may comprise, but are not limited to, aliphatic C2-C20 alpha olefins. Examples of aliphatic C2-C20 alpha olefins include ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1 -octadecene and 1-eicosne. Additional examples of suitable comonomers are vinyl acetate (H3C-C (= O) O-CH = CH2) or vinyl alcohol ("HO-CH = CH2", which as such is not stable and tends to polymerize). Examples of suitable olefin copolymers for use in the present composition are random copolymers of propylene and ethylene, random copolymers of propylene and 1-butene, heterophasic copolymers of propylene and ethylene, ethylene-butene copolymers, copolymers of ethylenehexene, copolymers of ethylene- octene, ethylene vinyl acetate copolymers (EVA), ethylene vinyl alcohol copolymers (EVOH).

The amount of comonomer can be 0 to 12% by weight, based on the weight of the polyolefin, more preferably it can be 0 to 9% by weight and most preferably it can be 0 to 7% by weight. A copolymer can be a random or block (heterophasic) copolymer. Preferably the copolymer is a random copolymer.

Preferred polyolefins for use in the present composition are olefin homopolymers and copolymers of an olefin and optionally one or more comonomers. In a preferred embodiment, the polyolefin is a homopolymer or a copolymer of ethylene, or propylene. In one embodiment, the polyolefin is selected from the group consisting of polyethylene, polypropylene, or a combination thereof. Preferably, the polyolefin is selected from homopolymers and copolymers of polyethylene and polypropylene. Preferably, the polyolefin is polyethylene or polypropylene, or a copolymer thereof.

In a preferred embodiment, the polyolefin is selected from the group comprising linear low-density polyolefin, low-density polyolefin, and high-density polyolefin.

In one embodiment, the polyolefin has a density of 0.890 to 0.975 g / cm³, preferably 0.890 to 0.960 g / cm³, preferably 0.890 to 0.930 g / cm³, preferably 0.890 to 0.925 g / cm³, preferably 0.890 to 0.920 g / cm³ with the density being determined with the standardized test of ASTM D-1505 at a temperature of 23 ° C.

Preferably, the polyolefin is a linear low density polyolefin. Preferably, the polyolefin is selected from the group comprising linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), and high-density polyethylene (HDPE). Suitable linear low-density polyethylene (LLDPE) and low-density polyethylene have a density of below 0.930 g / cm³ with the density being determined with the standardized test of ASTM D-1505 at a temperature of 23 ° C. Suitable high-density polyethylene (HDPE) has a density ranging from 0.940 to 0.975 g / cm³, with the density being determined with the standardized test of ASTM D-1505 at a temperature of 23 ° C. Preferably, the

ES 2 628 331 T3 polyolefin is linear low density polyethylene (LLDPE).

Linear low-density polyethylenes are commercially available, for example, through Total Petrochemicals, through Exxon under the trade name Escorene, or through Dow Chemicals under the trade name DOWLEX. Alternatively, they can be readily prepared by state-of-the-art polymerization procedures such as those described in US 4,354,009, US 4,076,698, European Patent Application 4645 (published 10-17-79), and US 4,128,607. Suitable linear low-density polyethylene polymers may be copolymers of ethylene and a minor amount, for example less than 20 mol%, preferably less than 15 mol%, of an alpha olefin of 3 to 18 carbon atoms, preferably 3 to 10 carbon atoms, most preferably 4 to 8 carbon atoms.

Preferred linear low density copolymers can be prepared from ethylene and one or more alpha olefins selected from the group consisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene, most preferably 1-butene. Polymers of desired density can be obtained by controlling the alpha olefin copolymerization rate and the rate of polymer formation during copolymerization. The addition of increasing amounts of the comonomers to the copolymers results in a reduction in the density of the copolymer.

Polyolefin, such as polyethylene, can be prepared, as is known in the art, in the presence of any catalyst known in the art. As used herein, the term "catalyst" refers to a substance that causes a change in the rate of a polymerization reaction without itself consuming itself in the reaction. In the present invention, it is especially applicable to catalysts suitable for the polymerization of ethylene to polyethylene. These catalysts will be referred to as ethylene polymerization catalysts or polymerization catalysts. In one embodiment of the invention, the polymer composition comprises a polyolefin prepared in the presence of a catalyst selected from a Ziegler-Natta catalyst, a metallocene catalyst, or a chromium catalyst. In a preferred embodiment of the invention, the polymer composition comprises a polyolefin prepared in the presence of a catalyst selected from a Ziegler-Natta catalyst, a metallocene catalyst, or both; preferably prepared in the presence of a metallocene catalyst.

The term "chromium catalysts" refers to catalysts obtained by the deposition of chromium oxide on a support, for example a silica or aluminum support. Illustrative examples of chromium catalysts include, but are not limited to, CrSiO2 or CrAl2O3.

The term "Ziegler-Natta catalyst" or "ZN catalyst" refers to catalysts having a general formula M¹Xv, in which M¹ is a transition metal compound selected from the group IV to VII of the periodic table of elements, where X is a halogen, and where v is the valence of the metal. Preferably, M¹ it is a group IV, group V or group VI metal, more preferably titanium, chromium or vanadium and most preferably titanium. Preferably X is chlorine or bromine, and most preferably chlorine. Illustrative examples of transition metal compounds include, but are not limited to, TiCl3 and TiCl4. Suitable ZN catalysts for use in the invention are described in US6930071 and US6864207.

The term "metallocene catalyst" is used herein to describe any transition metal complex consisting of metal atoms bonded to one or more ligands. Metallocene catalysts are compounds of the Group 4 transition metals of the periodic table such as titanium, zirconium, hafnium, etc., and have a coordinated structure with a metal compound and ligands composed of one or more cyclo-pentadienyl groups. , indenyl, fluorenyl or their derivatives. The structure and geometry of the metallocene can be varied to suit the specific need of the producer depending on the desired polymer. Metallocenes comprise a single metal site, which allows greater control of branching and molecular weight distribution of the polymer. The monomers are inserted between the metal and the polymer growth chain.

In one embodiment, the metallocene catalyst has a general formula (I) or (II):

(Ar) 2MQ2 (I);

or

R¹(Ar) 2MQ2 (II) in which the metallocenes according to formula (I) are unbranched metallocenes and the metallocenes according to formula (II) are bridged metallocenes;

wherein said metallocene according to formula (I) or (II) has two Ar linked to M that can be the same or different from each other;

wherein Ar is an aromatic ring, group or moiety and wherein Ar is independently selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, or fluorenyl, wherein each of said groups may be optionally substituted with one or more independently selected substituents

ES 2 628 331 T3 each from the group consisting of halogen, a hydrocarbon, an SR group²3 in which R² is a hydrocarbon having 1 to 20 carbon atoms, and a hydrocarbon having 1 to 20 carbon atoms, in which the hydrocarbon optionally contains one or more atoms selected from the group comprising B, Sl, S, O , F, Cl and P;

where M is a transition metal selected from the group consisting of tltanlo, zlrconlo, hafnlo, and vanadlo; y preferably is zlrconlo;

wherein each Q is independently selected from the group consisting of halogen; a hydrocarbon having 1 to 20 carbon atoms; and a hydrocarbon having 1 to 20 carbon atoms and wherein the hydrocarbon optionally contains one or more atoms selected from the group comprising B, Sl, S, O, F, Cl and P; and in which R¹ is a dlvalent group or moiety that bridges the two Ar groups and is selected from the group consisting of a C1-C20 alkyl, a germanol, a silicon, a slloxane, an alkylphosphine and an amine, and in which R¹is optionally substituted with one or more independently selected substituents each from the group consisting of halogen, a hydrochloride, a SIR group³3 in which R³ is a hydrocarbon having 1 to 20 carbon atoms, and a hydrocarbon having 1 to 20 carbon atoms, in which the hydrocarbon optionally contains one or more atoms selected from the group comprising B, Sl, S, O , F, Cl and P.

The term "hydrocarbon having 1 to 20 carbon atoms" as used herein is intended to refer to a moiety selected from the group comprising a linear or branched C1-C20 alkyl; C3-C20 cycloalkyl; arllo C6-C20; C7-C20 rental and C7-C20 rental, or a combination of the same. Exemplary hydrocarbon groups are metal, ethyl, propyl, butyl, amyl, isoamyl, hexyl, lsobutyl, heptyl, octyl, nonllo, decllo, cello, 2-ethylhexyl, and phenol. Exemplary halogen atoms include chlorine, bromine, fluorine, or iodine, and of these halogen atoms, fluorine and chlorine are preferred.

As used herein, the term "alkyl" by itself or as part of another substituent, refers to a group of linear or branched saturated hydrocarbon radicals with single carbon-carbon bonds having 1 or more atoms. of carbon, for example 1 to 20 carbon atoms, for example 1 to 12 carbon atoms, for example 1 to 6 carbon atoms, for example 1 to 4 carbon atoms, for example 2 to 3 carbon atoms. When a subscript is used herein after a carbon atom, the subscript is reflected to the number of carbon atoms that the named group can contain. Thus, for example, C1-12 alkyl contains an alkyl of 1 to 12 carbon atoms. Examples of C1-12 alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, lsobutyl, sec-butyl, ferc-butyl, pentyl and its chain lsomers, hexyl and its chain lsomers, heptyl and its chain lsomers, octllo and its chain lassomers, nonllo and its chain lasers, decllo and its chain lasers, undecllo and its chain lasers, dodecllo and its chain lasers.

As used herein, the term "C3-20 alkyl", by itself or as part of another substituent, will reflect a radical or partially saturated cyclical alkyl containing 3 to 20 carbon atoms. Examples of C3-20 cycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

As used herein, the term "C6-20 aryl", by itself or as part of another substituent, reflects an aromatic and polyunsaturated hydrocarbon group having a single ring (ie, phenol) or multiples. aromatic rings fused together (eg, naphthalene), or covalently linked, typically containing 6 to 20 carbon atoms; in which at least one ring is aromatic. Examples of C6-20 aryl include phenyl, naphthyl, lndanllo, blfenl, or 1,2,3,4-tetrahydro-naphthyl.

The term "cell", as a group or part of a group, refers to a cell, as defined herein, in which one or more hydrogen atoms are replaced by a ring, as described above. defined in this document. Examples of arllalqullo radicals include bencllo, fenetllo, dlbencllmetllo, metllfenllmetllo, 3- (2-naftll) -butllo, and sylmllars.

As used herein, the term "rent", by itself or as part of another substituent, refers to an aryl group, as defined herein, in which one or more atoms of Hydrogen are replaced by an alkyl, as defined herein.

The expression "hydrocarbon having 1 to 20 carbon atoms" is reflected to a radical having the formula -ORa where Ra is hydrocarbon having 1 to 20 carbon atoms. Preferred hydrocarboxy groups are alkoxy groups. The term "alkoxl" or "alkylxl" as used herein refers to a radical having the formula -O-Rb where Rb is alkyl. Non-limiting examples of suitable alkoxy groups include methoxl, ethoxl, propoxl, isopropoxl, butoxl, lsobutoxl, sec-butoxl, tert-butoxl, pentlloxl, amlloxl, hexlloxl, heptlloxl, and octlloxl. Preferred hydrocarboxy groups are methoxy, ethoxy, propoxy, butoxyl, and amylloxy.

Illustrative examples of metallocene catalysts include, but are not limited to, bls dlchloride (cyclopentadlenll) zlrconlo (Cp2ZrCL), bls dlchloride (cyclopentadlenll) tltanlo (Cp2TlCL), dlchloride

ES 2,628,331 T3 bis (cyclopentadienyl) hafnium (Cp2HfCj); b¡s (tetrahydro¡nden¡l) zlrconlo dichloride, bis (indenyl) zlrconlo dichloride, and bls (n-butll-clclopentadlenll) zlrconlo dichloride, ethylenebis (4,5,6,7-tetrahydro dichloride -1-indenyl) zlrconlo, etllenbls (l-lndenll) dichloride zlrconlo, dimethylsilen bls (2-metll-4-fenll-lnden-1-ll) dichloride zlrconlo, diphenylmethylene (clclopentadlenll) dichloride (fluoren-9-ll ) zlrconlo, and dimethylmethylene [1- (4-tert-butll-2-methylclclopentadlenll)] (fluoren-9-ll) zlrconlo dichloride.

Metallocene catalysts can be provided on a solid support. The support can be an inert organic or inorganic solid, which is chemically unreactive with any of the components of the conventional metallocene catalyst. Suitable support materials for the supported catalyst of the present invention include solid organic oxides, such as silica, alumina, magnesium oxide, titanium oxide, thorium oxide, as well as mixed oxides of silica and one or more metal oxides of Group 2 or 13, such as mixed oxides of silica-magnesia and silica-alumina. Silica, alumina, and mixed oxides of silica and one or more Group 2 or 13 metal oxides are preferred support materials. Preferred examples of such mixed oxides are those of silica-alumina. Silica is the most preferred. Silica can be in granular, agglomerated, pyrogenic, or other forms. The support is preferably a silica compound. In a preferred embodiment, the metallocene catalyst is provided on a solid support, preferably a silica support.

Preferably, the metallocene catalyst is activated with a cocatalyst. The cocatalyst, which activates the metallocene catalyst component, can be any known cocatalyst for this purpose such as an aluminum-containing cocatalyst, a boron-containing cocatalyst or a fluorinated catalyst. The aluminum-containing cocatalyst may comprise an alumoxane, an alkyl aluminum, a Lewis acid, and / or a fluorinated catalyst support.

In one embodiment, the alumoxane is used as an activating agent for the metallocene catalyst. Alumoxane can be used in conjunction with a catalyst in order to improve the activity of the catalyst during the polymerization reaction.

As used herein, the term "alumoxane" and "aluminoxane" are used interchangeably, and refer to a substance, which is capable of activating the metallocene catalyst. In one embodiment, the alumoxanes comprise oligomeric linear and / or cyclic alkyl alumoxanes. In a further embodiment, the alumoxane has the formula (III) or (IV)

R^to- (Al (R^to) -O) x-AlR^totwo (III) for oligomeric and linear alumoxanes; or (-Al (R^to) -O-) and (IV) for oligomeric and cyclic alumoxanes where x is 1-40, and preferably 10-20; where y is 3-40, and preferably 3-20; and in which each R^to is independently selected from Ci-Ca alkyl, and is preferably methyl.

In a preferred embodiment, the alumoxane is methylalumoxane (MAO).

In one embodiment, the catalyst used to prepare the polyolefin is a supported metallocene-alumoxane catalyst comprising a metallocene and an alumoxane that are attached on a porous silica support.

The composition comprises a maximum of 1.90% by weight of carbon nanotubes (CNT), based on the total weight of the composition.

Suitable carbon nanotubes used in the present invention may generally be characterized as having a size of 1 nm to 500 nm, this definition of size may be limited to only two dimensions, that is, the third dimension may be outside these limits.

Suitable carbon nanotubes, also referred to as "nanotubes" herein, can be cylindrical in shape and structurally related to fullerenes, one example of which is Buckminster fullerene (C60). Suitable carbon nanotubes can be open or end capped. The end encapsulation may be, for example, a Buckminster-type fullerene hemisphere. Suitable carbon nanotubes used in the present invention may comprise more than 90%, more preferably more than 95%, even more preferably more than 99% and more preferably more than 99.9% of their total weight in carbon. However, minor amounts of other atoms may also be present.

Suitable carbon nanotubes to be used in the present invention can be prepared by any method known in the art. They can be prepared by catalyst decomposition of hydrocarbons, a technique called catalytic carbon vapor deposition (CCVD). Other processes for preparing carbon nanotubes include the arc discharge process, the plasma decomposition of hydrocarbons, or the pyrolysis of the selected polyolefin under the oxidative conditions.

ES 2 628 331 T3 selected. The starting hydrocarbons can be acetylene, ethylene, butane, propane, ethane, methane or any other compound that contains volatile or gaseous carbon. The catalyst, if present, is used in pure or supported form. The presence of a support greatly improves the selectivity of the catalysts, but it contaminates the carbon nanotubes with support particles, in addition to the soot and amorphous carbon prepared during pyrolysis. Purification can remove these by-products and impurities. This can be done according to the following two stages:

1) dissolution of the support particles, typically carried out with an appropriate agent depending on the nature of the support and

2) removal of the pyrolytic carbon component, typically based on oxidation or reduction procedures.

Nanotubes can exist as monolayer nanotubes (SWNT) and multilayer nanotubes (MWNT), that is, nanotubes that have a single layer and nanotubes that have more than one layer, respectively. In monolayer nanotubes, a one-atom-thick sheet of atoms, for example a one-atom-thick sheet of graphite (also called graphene), is perfectly rolled to form a cylinder. Multilayer nanotubes consist of a series of said cylinders arranged concentrically. The arrangement in a multilayer nanotube can be described by the so-called Russian doll model, in which a larger doll is opened to reveal a smaller doll.

In one embodiment, the nanotubes are multilayer carbon nanotubes, more preferably multilayer carbon nanotubes having an average of 5 to 15 layers.

Nanotubes, regardless of whether they are monolayer or multilayer, can be characterized by their external diameter or their length or both.

Monolayer nanotubes are preferably characterized by an outer diameter of at least 0.5 nm, more preferably at least 1 nm, and more preferably at least 2 nm. Preferably, its external diameter is at most 50 nm, more preferably at most 30 nm, and more preferably at most 10 nm. Preferably, the length of the monolayer nanotubes is at least 0.1 µm, more preferably at least 1 µm, even more preferably at least 10 µm. Preferably, its length is at most 50mm, more preferably at most 25mm.

Multilayer nanotubes are preferably characterized by an external diameter of at least 1 nm, more preferably at least 2 nm, 4 nm, 6 nm or 8 nm, and most preferably at least 10 nm. The preferred outer diameter is at most 100 nm, most preferably at most 80 nm, 60 nm or 40 nm, and most preferably at most 20 nm. Most preferably, the outer diameter is in the range of 10 nm to 20 nm. The preferred length of the multilayer nanotubes is at least 50 nm, more preferably at least 75 nm, and most preferably at least 100 nm. Its preferred length is at most 20 mm, more preferably at most 10 mm, 500 pm, 250 pm, 100 pm, 75 pm, 50 pm, 40 pm, 30 pm or 20 pm, and most preferably at most 10 p.m. The most preferred length is in the range of 100 nm to 10 pm. In one embodiment, the multilayer carbon nanotubes have an average outer diameter in the range of 10 nm to 20 nm or an average length in the range of 100 nm to 10 pm or both.

Preferred carbon nanotubes are carbon nanotubes having a surface area of ​​200-400 µm²/ g (measured by the BET procedure).

Preferred carbon nanotubes are carbon nanotubes having an average number of 5-15 layers.

Non-limiting examples of commercially available multilayer carbon nanotubes are Graphistrength ™ 100, available through Arkema, Nanocyl ™ NC 7000 available through Nanocyl, FloTube ™ 9000 available through CNano Technology, Baytubes® C 150 B available through from Bayer Material Science.

In preferred embodiments, said carbon nanotubes are provided as a polyolefin masterbatch or styrenic copolymer. As used herein, the term "masterbatch" refers to concentrates of active material (such as carbon nanotubes) in one polymer, which are intended to be subsequently incorporated into another polymer (compatible or not compatible with the polymer already contained in these masterbatches). The use of carbon nanotubes containing masterbatches makes the processes more easily adaptable on an industrial scale, compared to the direct incorporation of carbon nanotube powder.

In one embodiment, the composition comprises at least 0.10% by weight of carbon nanotubes, relative to the total weight of the composition. For example, the composition of the present invention may comprise at least 0.30% by weight of carbon nanotubes, for example, at least 0.40% by weight, for example at least 0.45% by weight of carbon nanotubes, relative to the total weight of the composition, preferably at least 0.50% by weight, preferably at least 0.55% by weight, more preferably at least 0.60% by weight, more preferably at least 0.55% by weight less 0.65% by weight, most preferably at least 0.68% by weight, relative to

ES 2 628 331 T3 total weight of the composition.

In one embodiment, the composition comprises at most 1.75% by weight, eg at most 1.50% by weight, eg at most 1.25% by weight, eg at most 1 .00% by weight, for example, at most 0.95%, for example, at most 0.90% by weight of carbon nanotubes, based on the total weight of the composition.

In one embodiment, the composition comprises:

at least 40% by weight of polystyrene or modified polystyrene, or a mixture thereof, based on the total weight of the composition, preferably at least 45%, more preferably at least 50% by weight of polystyrene or modified polystyrene , or a mixture thereof; preferably high impact polystyrene or a mixture of high impact polystyrene and polystyrene; at least 15% by weight of polyolefin, based on the total weight of the composition, preferably at least 20% by weight of polyolefin, preferably at least 25% by weight of polyolefin, preferably at least 30% by weight of polyolefin, preferably at least 40% by weight polyolefin, preferably polyethylene or polypropylene; and at most 1.90% by weight of carbon nanotubes, preferably at most 1.75% by weight of carbon nanotubes, preferably at most 1.50% by weight of carbon nanotubes, preferably at most 1 , 25% by weight of carbon nanotubes, preferably at most 1.00%, eg at most 0.95%, eg at most 0.90%, by weight of carbon nanotubes based on the total weight of the composition.

In one embodiment, the composition comprises:

at least 40% by weight of polystyrene or modified polystyrene, or a mixture thereof, based on the total weight of the composition, preferably at least 45% by weight of polystyrene or modified polystyrene, or a mixture thereof; preferably high impact polystyrene or a mixture of high impact polystyrene and polystyrene;

at most 60% by weight of polyolefin, preferably at most 55% by weight of polyolefin, and at least 15% by weight of polyolefin, preferably at least 20% by weight of polyolefin, preferably at least 25% by weight of polyolefin, preferably at least 30% by weight of polyolefin, preferably at least 40% by weight of polyolefin, based on the total weight of the composition; preferably polyethylene or polypropylene; and at least 0.10% by weight of carbon nanotubes, preferably at least 0.30% by weight of carbon nanotubes, preferably at least 0.40% by weight of carbon nanotubes, preferably at least 0 , 50% by weight, preferably at least 0.55% by weight, more preferably at least 0.60% by weight, more preferably at least 0.65% by weight, most preferably at least 0.68 % by weight, and a maximum of 1.90% by weight of carbon nanotubes, preferably at most 1.75% by weight of carbon nanotubes, preferably at most 1.50% by weight of carbon nanotubes, preferably at most 1.25% by weight of carbon nanotubes, preferably at most 1 0.00% by weight, eg, at most 0.95% by weight, eg, at most 0.90% by weight, of carbon nanotubes based on the total weight of the composition.

The composition may further comprise a styrenic copolymer, preferably wherein the styrenic copolymer is selected from styrene-butadiene-styrene block copolymer (SBS) or styrene-ethylene-butadiene-styrene block copolymer (SEBS).

Preferably, the styrenic copolymer is a styrenic block copolymer. Suitable styrenic block copolymers include at least two monoalkenyl arene blocks, preferably two polystyrene blocks, separated by a block of a saturated conjugated diene, such as a saturated polybutadiene block. Suitable unsaturated block copolymers include, but are not limited to, those represented by the following formulas: ABR (-BA) not Ax- (BA-) and -BA in which each A is a polymer block comprising an aromatic monomer of vinyl, such as styrene, and each B is a polymer block comprising a conjugated diene, such as isoprene or butadiene, and optionally a vinyl aromatic monomer, such as styrene; R is the remnant of a multifunctional coupling agent (if R is present, the block copolymer can be a star or branched block copolymer); n is an integer from 1 to 5; x is zero or 1; and y is a real number from zero to 4.

In one embodiment of the invention, the composition comprises one or more additives selected from the group comprising an antioxidant, an antacid, a UV absorber, an antistatic agent, a light stabilizing agent, an acid neutralizer, a lubricant, a clarifying / nucleating agent, a colorant or a peroxide. An overview of suitable additives can be found in Plastics Additives Handbook, ed. H. Zweifel, 5^toedition, 2001, Hanser Publishers.

In one embodiment, the composition is free of any compatibilizer.

The composition comprises from 0% to 10% by weight of at least one additive such as antioxidant, based on the

ES 2 628 331 T3 total weight of the composition. In a preferred embodiment, said composition comprises less than 5% by weight of additive, based on the total weight of the composition, for example 0.1 to 3% by weight of additive, based on the total weight of the composition.

In one embodiment, the composition comprises an antioxidant. Suitable antioxidants include, for example, phenolic antioxidants such as pentaerythritol fefragu / 's [3- (3', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate] (referred to herein as Irganox 1010 ), tris (2,4-di-tert-buylphenyl) phosphite (herein referred to as Irgafos 168), 3DL-alpha-tocopherol, 2,6-di-tert-butyl-4-methylphenol, dibutylhydroxyphenylpropionic acid stearyl ester , 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, 2,2'-methylenebis (6-tert-butyl-4-methyl-phenol), hexamethylene bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], benzenepropanamide, N, N ' -1,6-hexanediyl bis [3,5bis (1,1-dimethylethyl) -4-hydroxy] (Antioxidant 1098), diethyl 3,5-di-tert-butyl-4-hydroxybenzyl phosphonate, bis [monoethyl (3 Calcium, 5-di-tert-butyl-4-hydroxylbenzyl) phosphonate], triethylene glycol bis (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate (Antioxidant 245), 6,6'-di-tert butyl-4,4'-butylidenedi-m-cresol, 3,9-bis (2- (3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 1,3 , 5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane , tris [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] of (2,4,6-trioxo-1,3,5-triazine-1,3,5 (2H, 4H, 6H) -triyl) triethylene, tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, ethylene bis [3,3-bis (3-tert-butyl-4-hydroxyphenyl) butyrate], and 2,6-bis [[3- (1,1-dimethylethyl) -2-hydroxy-5-methylphenyl] octahydro-4 , 7-methane-1H-indenyl] -4-methyl-phenol. Suitable antioxidants also include, for example, dual functional phenolic antioxidants such as 4,4'-thio-bis (6-tert-butyl-m-methyl phenol) (Antioxidant 300), 2,2'-sulfanodiylbis (6- tert-butyl-4-methylphenol) (Antioxidant 2246-S), 2-methyl-4,6-bis (octylsulfanylmethyl) phenol, bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] thiodyethylene, 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1.3.5-triazin-2-ylamino) phenol, N- (4-hydroxyphenyl) stearamide, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butylmalonate, 3,5-di-tert-butyl 2,4-di-tert-butylphenyl -4-hydroxybenzoate, 3,5-di-tert-butyl-4-hydroxy-hexadecyl benzoate, 2- (1,1-dimethylethyl) -6 - [[3- (1, 1-dimethylethyl) -2-hydroxy-5-methylphenyl] methyl] -4-methylphenyl, and Cas No. 128961-68-2 (Sumilizer GS). Suitable antioxidants also include, for example, amino antioxidants such as N-phenyl-2-naphthylamine, poly (1,2-dihydro-2,2,4-trimethyl-quinoline), N-isopropyl-N'-phenyl-p -phenylenediamine, N-phenyl-1-naphthylamine, CAS # 6841146-1 (Antioxidant 5057), and 4,4-bis (alpha, alpha-dimethylbenzyl) diphenylamine (Antioxidant KY 405). Preferably, the antioxidant is selected from pentaerythritol fefragu / s [3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate] (referred to herein as Irganox 1010), tris phosphite ( 2,4-ditert-buylphenyl) (herein referred to as Irgafos 168), or a mixture thereof.

The composition can have improved conductive-dissipative conductivity. Target resistivity may depend on the particular application (ANSI-ESD F 541-2008). Preferably, the surface resistivity is at most 10¹¹Ω, preferably a maximum of 10⁸ Ω, preferably a maximum of 10⁶ Ω, for example, maximum 10⁵ Ω, for example, maximum 10⁴ Ω, for example, maximum 10³ Ω. Resistivity can be measured using the procedure described in ASTM-D257, or described herein later in the examples section.

In one embodiment, the composition comprises at most 1.90% by weight of carbon nanotubes, preferably at most 1.75% by weight of carbon nanotubes, preferably at most 1.50% by weight of carbon nanotubes. , preferably at most 1.25% by weight of carbon nanotubes, preferably at most 1.00%, for example, at most 0.95%, for example, at most 0.90%, by weight of carbon nanotubes based on the total weight of the composition; and a surface resistivity of maximum 10¹¹ ohms, preferably maximum 10⁸ ohms, preferably maximum 10⁶ ohms, for example max 10⁵ ohms, for example max 10⁴ ohms, for example max 10³ ohms.

The present invention encompasses a process for preparing a conductive composition made from the present composition, said process comprising the steps of:

(a) providing a masterbatch comprising at least 5% by weight of carbon nanotubes based on the total weight of the masterbatch, and a polyolefin and / or a styrenic copolymer;

(b) mixing the masterbatch of step (a) with polystyrene or modified polystyrene or a mixture thereof, and with a polyolefin, in amounts so as to obtain the conductive composition comprising a maximum of 1.90% by weight of carbon nanotubes, based on the total weight of the composition.

Suitable polystyrene or polystyrene, styrenic copolymer, polyolefin and nanotubes may be as defined above.

As used herein, the term "masterbatch" refers to concentrates of active material (such as carbon nanotubes (CNTs)) in a polymer, which are intended to be subsequently incorporated into another polymer (compatible or non-compatible with the polymer already contained in these masterbatches). The use of masterbatches makes the procedures more easily adaptable on an industrial scale, compared to direct incorporation of CNT powder. In one embodiment, the masterbatch comprises at least 5% by weight of

ES 2 628 331 T3 carbon nanotubes based on total weight of masterbatch. Preferably, the masterbatch comprises at least 8% by weight of carbon nanotubes based on the total weight of the masterbatch. Preferably, the masterbatch comprises at least 10% by weight of carbon nanotubes based on the total weight of the masterbatch. Preferably, the content of carbon nanotubes in the masterbatch is between 5 and 30% by weight, preferably between 8 and 20% by weight based on the total weight of the masterbatch.

To form a masterbatch, the CNT and polymer powders can be mixed in a mixer that is integrated into, or positioned upstream of, the processing equipment.

In some embodiments, step (b) of the present process is performed by simultaneously adding polystyrene or modified polystyrene or a mixture thereof, the polyolefin, and the carbon nanotube masterbatch.

In one embodiment, the polyolefin of step (b), or if present in step (a), is selected from the group consisting of polyethylene, polypropylene, or a combination thereof. Preferably, the polyolefin is polyethylene.

In a preferred embodiment, the polyolefins of step (a) and (b) are the same.

In one embodiment, in step (a) of the present process, when a masterbatch comprising styrenic copolymer is used, the content of the styrenic copolymer in the conductive composition is between 1 and 25% by weight, preferably between 2 and 20% based on the total weight of said composition.

This mixing of powders, mixtures and masterbatch can be carried out in conventional synthesis reactors, blade mixers, fluidized bed reactors or in the mixing equipment of the Brabender Z-type blade mixer or extruder. According to a variant of the invention, it is thus possible to use a paddle or blade mixer.

In some embodiments, the method may comprise the steps of:

- mixing a masterbatch comprising a polyolefin or styrenic copolymer and carbon nanotubes (CNT), with a polyolefin to prepare a first mixture; Y

- mixing a polystyrene and / or modified polystyrene with said first mixture.

In some embodiments, the method may comprise the steps of:

- mixing a masterbatch comprising a polyolefin or styrenic copolymer and carbon nanotubes (CNT), with a polystyrene and / or modified polystyrene to prepare a first mixture; Y

- mixing a polyolefin with said first mixture.

Preferably, the polyolefin forms an immiscible phase in the polystyrene or modified polystyrene.

In one embodiment, the polystyrene, modified polystyrene, or mixture thereof is the major constituent or at least the major continuous or co-continuous polymer phase. In one embodiment, the polyolefin is the minor constituent in at most one co-continuous or dispersed polymer phase.

In a preferred embodiment, the composition comprises a modified polystyrene (PS) such as HIPS and a polyethylene (PE), for example LLDPE. All polymer-polymer or polymer-CNT blends can be manufactured by a classical twin screw extrusion process.

For example, the composition can be prepared by first making a conductive PS by mixing the PE-CNT masterbatch with PS or the SEBS-CNT masterbatch with PS. The conductive composition can then be obtained by mixing the conductive PS with PE in which the PE phase forms an immiscible phase in the PS. In another example, the composition can be prepared by first making a conductive PE by mixing the PE-CNT masterbatch with PE or the SEBS-CNT masterbatch with PE. The conductive composition can then be obtained by mixing the conductive PE with PS. In another example, the conductive composition can be prepared directly by mixing the PS, PE and PE-CNT masterbatch or the SEBS-CNT masterbatch in which the conductive PS will be prepared in situ and the PE phase forms an immiscible phase in the PS. The same procedure can be used to prepare a conductive composition comprising polystyrene, a polyolefin, and CNT, wherein the polyolefin is polypropylene, low-density or high-density polyethylene, and the like.

The description also refers to shaped articles comprising the composition according to the first aspect of the invention.

The composition may be suitable for typical injection, extrusion and stretch blow molding applications, but also thermoforming, foaming and rotational molding. Articles made according to these processes can be monolayer or multilayer, in which at least one of the layers comprises the compositions of the invention.

Articles made from the composition can be commonly used in electronic and material handling devices such as packaging films, foils, and thermoformed objects.

ES 2 628 331 T3 themselves, chip carriers, computers, printers and photocopier components where electrostatic dissipation or electromagnetic shielding are important requirements. Preferably, the formed article comprises the packaging. Preferably, the formed article comprises electronic product packaging.

The invention provides new conductive-dissipative compositions and materials thereof which comprise low amounts of CNT, below 1.9% by weight. Preferably, the composition is a mixture of at least two immiscible polymers: polystyrene and polyolefin.

Such compositions are economically viable in comparison to the usual conductive-dissipative compounds loaded with carbon black. The advantage of the present conductive-dissipative composition comprising carbon nanotubes over that comprising carbon black is less alteration of the mechanical properties, higher processability, smoother part surface, cleanliness, deformation of the lower part, less degassing of volatiles and stretching of the material.

The description also refers to a composition comprising at least two immiscible phases: a polystyrene phase comprising polystyrene or modified polystyrene, or a mixture thereof, and a polyolefin phase comprising a polyolefin, wherein said composition comprises in addition, carbon nanotubes, in a concentration of a maximum of 1.90% by weight, based on the total weight of the composition.

The present invention may be further illustrated by the following examples, although it will be understood that these examples are included for purposes of illustration only and are not intended to limit the scope of the invention unless specifically stated otherwise.

Examples

Mixtures according to embodiments of the invention were prepared using a two-step procedure. The blends comprised polystyrene, linear low-density polyethylene, and carbon nanotubes.

For the carbon nanotubes (CNTs), Nanocyl ™ NC 7000 multilayer carbon nanotubes, commercially available from Nanocyl, were used. These nanotubes have a surface area of ​​250-300 μm²/ g (measured by the BET procedure), a carbon purity of about 90% by weight (measured by thermogravimetric analysis), an average diameter of 9.5 nm and an average length of 1.5 pm (measured by microscopy transmission electronics).

For the polystyrene polymer, Polyestyrene Impact 8350 high impact polystyrene (HIPS), available from Total Petrochemicals, was used. Polystyrene Impact 8350 has a melt flow index of 4.5 g / 10 min measured according to ISO 1133 H (200 ° C-5 kg), a Rockwell hardness of R 54 (ISO 2039-2), a density of 1.04 g / cm³(ISO 1183), a surface resistivity> 10¹³ ohms measured according to ISO IEC 93.

For the polyethylene polymer, Total 1810 linear low-density polyethylene (LLDPE) was used, available from Total Petrochemicals. LL 1810 is an ethylene-butene copolymer produced in a gas phase reactor. LL1810 has a density of 0.919 g / cm³ measured according to ISO 1183, and a melt flow rate of 1.0 g / 10 min measured according to ISO 1133 (190 ° C / 2.16 kg).

Commercially available polyethylene / carbon nanotube masterbatch (MB-PE-CNT), PLASTICYL ™ LDPE2001, and PLASTICYL ™ SEBS / carbon nanotubes (MB-SEBS-CNT), SEBS1001 were used to exemplify the present procedure. A mixture of high impact polystyrene (HIPS) -LLDPE conductive-dissipative was prepared by mixing, using the classical twin screw extrusion process, the high impact polystyrene (HIPS) Total 8350 with the linear low density polyethylene (LLDPE) and the carbon nanotube masterbatch, either MB-PE-CNT or MB-SEBS-CNT in the Brabender corotation twin screw extruder using the same extrusion parameters as in step 1. Comparative examples consist of Total 8350 High Impact Polystyrene (HIPS) mixed with High Impact Polystyrene Carbon Nanotube Masterbatch (MB-PS-CNT).

The content of the mixtures in% by weight are shown in Table 1 (HIPS-PE-CNT compounds, examples 1-2) and Table 2 (HIPS-CNT compounds, comparative examples 9-12). Comparative Examples (9-12) consist of Total 8350 high impact polystyrene (HIPS) mixed with the high impact polystyrene carbon nanotube masterbatch (MB-PS-CNT).

The content of carbon nanotubes in% by weight in the mixtures (% CNT) was determined by thermogravimetric analysis (TGA) according to ISO 11358 and ASTM E1131, using a STAR TGA / DSC 1 apparatus from Mettler Toledo. Before the determination of the content of carbon nanotubes in% by weight in the mixtures (% of CNT), the carbon content of the carbon nanotubes in% by weight (% of C-CNT) was determined: 2 to 3 milligrams of carbon nanotubes in a TGA. The material was heated at a rate of 20 ° C / min from 30 ° C to 600 ° C under nitrogen (100 ml / min). At 600 ° C, the gas was changed to air (100 ml / min), and the carbon oxidized, yielding the carbon content of the carbon nanotubes in% by weight (% C-CNT). The% C-CNT value was the average of 3 measurements. For the content of carbon nanotubes in% by weight in the mixtures (% CNT), 10 to 20 milligrams of sample were placed in a TGA. The material was heated to a

ES 2 628 331 T3 speed of 20 ° C / min from 30 ° C to 600 ° C in nitrogen (100 ml / min). At 600 ° C, the gas was changed to air (100 ml / min), and the carbon oxidized, producing the carbon content of the carbon nanotubes in the sample (% of Sample). The% C-sample value was the average of 3 measurements. The content of carbon nanotubes in% by weight in the sample (% CNT) was then determined by dividing the carbon content of the carbon nanotubes in% by weight in the samples (% C-sample) by the carbon content of carbon nanotubes in% by weight (% C-CNT) and multiplying by 100.

% of CNT =% of C-sample /% of C-CNT * 100

The surface resistivity (SR) of the mix was measured using a 2410 SourceMeter® apparatus. The conditions that were used were similar to those described in the IEC 60167 and NF C26-215 test procedures. Surface relativity (SR) was measured on a 2mm thick compression molded plate at 200 ° C for 12 minutes. The resistance measurement was performed using an electrode system made of two conductive paint lines using silver ink and an adhesive mask that features 2 parallel grooves 25mm long, 1mm wide and 2mm apart. The samples were conditioned at 23 ° C / 50% RH for a minimum of 4 hours before carrying out the test. The resistance measurement in ohms was indicated for a square measurement area and it was expressed in ohm / square using the following equation: SR = (R x L) / d, where: SR is the average resistance indicated for an area square measurement, conventionally called surface resistivity (expressed in ohms / square), R is the average of the resistance measurements (ohms), L is the length of the paint line (cm), d is the distance between the electrodes ( cm). L = 2.5 cm and d = 0.2 cm and SR = R x 12.5. The surface resistivity (SR) value was the average of 3 measurements.

The measurement results are shown in Table 1 and Table 2.

Table 1 - examples

<td>Mixtures</td><td> 1</td><td> 2</td>

<td>% HIPS</td><td> 49,5</td><td> 59,4</td>

<td>% PE</td><td> 49,5</td><td> 39,6</td>

<td>% of CNT</td><td> 0,97</td><td> 0,98</td>

<td>MR (ohms / square do)</td><td> 9 10³</td><td> 1 10⁴</td>

Table 2 - comparative examples

<td>Mixtures</td><td> 9</td><td> 10</td><td> 11</td><td> 12</td>

<td>% HIPS</td><td> 98,59</td><td> 98,45</td><td> 98,18</td><td> 97,94</td>

<td>% of CNT</td><td> 1,41</td><td> 1,55</td><td> 1,82</td><td> 2,06</td>

<td>MR (ohms / square do)</td><td> 1 10⁶</td><td> 4 10⁴</td><td> 3 10⁴</td><td> 8 10³</td>

The mixtures prepared by the process according to the invention, in particular, when the carbon nanotubes were provided in a polyolefin masterbatch, had good surface resistivity at low CNT concentration, as demonstrated above.

Excellent results were also obtained for compositions prepared according to the present procedure in which the carbon nanotubes were provided in a SEBS master mix. Good surface resistivity was also measured in these latter compositions comprising SEBS even at low concentration of CNT in the sample (1% by weight of CNT).