EP1954752A1

EP1954752A1 - Pulverulent composition based on carbon nanotubes, methods of obtaining them and its uses, especially in polymeric materials.

Info

Publication number: EP1954752A1
Application number: EP06842069A
Authority: EP
Inventors: Serge Bordere; Sylvain Bourrigaud; Sylvie Cazaumayou; Laurence Couvreur; Nour-Eddine El Bounia; Nicolas Passade-Boupat; Patrick Piccione
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2005-11-30
Filing date: 2006-11-29
Publication date: 2008-08-13
Also published as: FR2893947A1; WO2007063253A1; KR20080065688A; US20090176924A1; JP2009517517A; BRPI0619221A2

Abstract

The present invention relates to pulverulent compositions based on carbon nanotubes, which exhibit excellent dispersibility in polymeric materials and advantageously can be used as reinforcements and/or modifiers of conducting and/or thermal properties. They can easily be incorporated into polymeric matrices in masterbatch form.

Description

Carbon nanotube-based pulverulent composition, methods for obtaining same and uses thereof, especially in polymeric materials

The present invention relates to materials based on carbon nanotubes (CNTs) and more particularly to powder compositions based on CNTs.

The carbon nanotubes are composed of coiled graphite sheets terminated by hemispheres consisting of pentagons and hexagons of structure close to fullerenes and have a tubular structure with a diameter of between 0.4 and 50 nm, preferably less than

100 nm and very long length / diameter ratio, typically greater than 10 and most often greater than 100.

We distinguish the nanotubes composed of a single sheet and we then speak of

SWNT (for Single Wall Nanotubes) nanotubes composed of several concentric layers called MWNT (for Multi Wall Nanotubes) then the

SWNTs are generally considered to be more difficult to manufacture than

MWNT.

The processes for synthesizing CNTs are well known: mention may be made of

WO 86/03345 A1 of Hyperion Catalysis International Inc. corresponding to EP 225,556 B1 which can be considered as one of the basic patents on the synthesis of MWNT type CNTs. Other documents claim process improvements, such as the use of a continuous fluidized bed which makes it possible to control the state of aggregation of the catalyst and the carbonaceous materials formed (see, for example, WO 02 / 94713A1 in the name of Tsinghua University), product improvements such as, for example, WO 02/095097 A1 on behalf of Trustées Of Boston Collège, which offers nanotubes of varied and non-aligned morphology, by varying the nature of the catalyst and the reaction conditions.

At the end of the synthesis, CNTs are obtained in the form of a powder (the CNTs are attached to the catalyst grains in the form of an entangled network), with a particle size most often greater than or equal to 300 μm.

CNTs are used for their excellent properties of electrical and thermal conductivity as well as their mechanical properties (reinforcing agents, etc.). They are thus increasingly used as additives to provide materials including macromolecular type electrical, thermal and / or mechanical properties but a brake to their development, in addition to their high cost compared to other additives bringing the one and / or the other of these properties, is that they are difficult to disperse and handle because of their small size and their powderiness.

With regard to HSE aspects, NTCs are still poorly understood. In the expectation of in-depth studies, it is preferred, as a precaution, to avoid handling "naked" CNTs, for example directly derived from the synthesis.

There is an unmet demand to implement more manipulable CNTs, particularly at the industrial level, than those resulting from the actual synthesis while presenting less or no fines.

There is also an unmet demand for improving the dispersibility of CNTs in materials, especially polymers, in which they are incorporated in order to obtain more homogeneous materials.

In order to try to solve the problem of the dispersibility of CNTs, one or more of the many solvent mixing techniques have been used to position on the surface of the nanotubes agents (polymers, surfactants or others). used to aid in dispersion such as in

EP1.495.171.

Another route consists in producing a dispersion of CNTs in a solvent and a monomer, which monomer is then polymerized in situ, and in certain cases, such a route makes it possible to functionalize the CNTs as described in EP 1 359 121 and EP 1.359. 169.

However, these different techniques have the following disadvantages: the mixtures or polymerizations are carried out in the presence of solvent (s) and / or in a very diluted NTC medium (generally less than 20 parts by weight), which leads to limiting the applications of these NTC solutions, especially to cases compatible with the large amount of solvent (s) used, high content which must then be eliminated. This also leads to having to incorporate a large amount of dispersing agent to introduce a large amount of CNT. In the literature are described bulk polymerizations in the presence of CNTs as in the article Macromol. Rapid Common. 2003, 24, vol. 18, 1070-1073 of Park et al. These different techniques also have the disadvantage of being limited to very low NTC levels, very much less than 20%.

To solve the problems of dispersibility of CNTs, it has also been proposed in EP 692.136 masterbatches based on polymeric materials and may contain up to 60% of molten CNT in high shear tools of the extruder type; however, in the examples of EP 692.136, the NTC concentration of the masterbatches never exceeds 20%.

The present invention relates to compositions based on CNT, which are in the form of a powder but do not have the HSE disadvantages of the crude CNTs, for example directly derived from the synthesis, as previously stated.

Compared to the crude synthetic CNTs, the pulverulent compositions of the invention have the advantage of having a higher density and a higher density, to offer better dispersibility in polymer matrices than those of the prior art, while avoiding the manipulation of crude NTC powders.

Unlike the masterbatches of the prior art containing CNTs, the compositions according to the invention may contain a very high level of CNTs, while retaining excellent dispersion properties when they are incorporated into materials, in particular polymers. Unless otherwise indicated, percentages in this text are mass percentages.

The pulverulent compositions according to the invention comprise from 20% to 95% of CNTs, in particular from 35% to 90% of CNTs, and for example from 40% to 90% of CNTs. The average particle size of the powder compositions according to the invention is generally less than or equal to 1 mm, preferably less than or equal to 800 μm. Preferably, at most 10%, and advantageously at most 5%, of the particles of the compositions according to the invention have a size less than 40 microns measured in particular by dry sieving on vibrating screen.

The composition according to the invention as defined above may, in addition, comprise one or more other pulverulent fillers, different from the CNTs. By way of example of these fillers, mention may be made of carbon blacks, activated carbons, silicas, glass fibers, pigments, clays, calcium carbonate, boron and / or nitrogen nanotubes and / or or transition metals.

The present invention also relates to a process for obtaining these powdery compositions.

The process according to the invention for preparing the pulverulent compositions defined above comprises: a) a step of contacting / dispersing the CNTs with at least one compound A, b) optionally a step consisting of a heat treatment, c) optionally a step purification and / or separation of the composition from the reactants for recovery, the mixture obtained at the end of each of steps a, b, c remaining in powder form. Step a) consists in dispersing the CNTs with at least one compound A which acts as a dispersing agent. In what follows, for simplification, the expression "compound A" can correspond to one or more compounds A.

According to the invention, the content of compound A in the pulverulent composition is such that the sum of the contents of CNT and optionally other pulverulent fillers represents the complement to 100%. In particular, the compound A or the mixture of compounds A represents from 5 to 80%, in particular from 5 to 65%.

The compound A may be a monomer, a monomer mixture, a molten polymer or melted polymer mixture, a solution of monomer (s) and / or polymer (s) in a solvent, one or more polymers in solution in one or more several monomers, a non-reactive species of oil type or plasticizer type, an emulsifier or surfactant, a coupling agent (in particular for promoting charge dispersion in an elastomeric composition), and / or a carboxylic acid.

The document FR 2870251 describes the use as a compatibilizer of a block copolymer obtained by controlled radical polymerization and having at least one block bearing acid and / or anhydride functions for obtaining stable dispersions of carbon nanotubes in organic solvents or aqueous or in polymer matrices. The method described in this document differs from that of the present invention, inter alia, in that the mixture is not in powder form at the end of each of the steps but in the form of a solution. On the other hand, this document only discloses the ratio of NTC / copolymer and not the content of CNT in the final composition, which corresponds to a very wide range of CNT content. In other words, this document neither discloses nor suggests to a person skilled in the art powder compositions with a high CNT content, the production steps of which are carried out solely in the form of a powder.

The term polymer according to the invention also covers oligomers; the term "solution" covers not only mixtures where the compounds are miscible and form a single phase but also immiscible mixtures such as emulsions, suspensions or others. The monomer that can be used as compound A according to the invention also refers to the monomers that can be (co) polymerized radically, ionically, anionically or cationically, polycondensation or polyaddition, it being understood that certain monomers can be polymerized independently of one another according to one or more of these polymerization techniques. Among the monomers capable of free-radical polymerization which can be used as compound A, mention may be made of monomers having a carbon-carbon double bond, such as vinyl monomers, preferably vinyl chloride, vinylidene, diene and olefinic, allyl, acrylic, methacrylic, etc. Mention may in particular be made of vinylaromatic monomers such as styrene or substituted styrenes, especially α-methylstyrene and sodium styrene sulfonate, dienes such as butadiene or isoprene, 1,4-hexadiene, acrylic monomers such as acrylic acid or its salts, alkyl, cycloalkyl or aryl acrylates such as methyl, ethyl, butyl, ethylhexyl or phenyl acrylate, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, ether alkyl acrylates such as acrylate methoxyethyl, alkoxy- or aryloxy-polyalkylene glycol acrylates such as methoxypolyethylene glycol acrylates, ethoxypolyethylene glycol acrylates, methoxypolypropylene glycol acrylates, methoxy-polyethylene glycol-polypropylene glycol acrylates or mixtures thereof, aminoalkyl acrylates such as 2- (dimethylamino) ethyl acrylate (ADAME), amine salt acrylates such as [2- (acryloyloxy) ethyl] trimethylammonium chloride or sulfate or [2- (acryloyloxy) chloride or sulfate ethyl] dimethylbenzylammonium, fluorinated acrylates, silylated acrylates, phosphorus acrylates such as alkylene glycol phosphate acrylates, methacrylic monomers such as methacrylic acid or its salts, alkyl, cycloalkyl, alkenyl or aryl methacrylates such as methyl, lauryl, cyclohexyl, allyl or phenyl methacrylate, hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate, ether alkyl methacrylates such as 2-ethoxyethyl methacrylate, alkoxy- or aryloxy-polyalkylene glycol methacrylates such as methoxypolyethylene glycol methacrylates, ethoxypolyethylene glycol methacrylates, methoxypolypropylene glycol methacrylates, methacrylates methoxy-polyethyleneglycol-polypropylene glycol or mixtures thereof, aminoalkyl methacrylates such as 2- (dimethylamino) ethyl methacrylate (MADAME), amine salt methacrylates such as [2- (methacryloyloxy) chloride or sulfate ) ethyl] trimethylammonium or [2- (methacryloyloxy) ethyl] dimethylbenzylammonium chloride or sulphate, fluo methacrylates such as 2,2,2-trifluoroethyl methacrylate, silylated methacrylates such as 3-methacryloylpropyltrimethylsilane, phosphorus methacrylates such as alkylene glycol phosphate methacrylates, hydroxyethylimidazolidone methacrylate, hydroxyethylimidazolidinone methacrylate, 2- (2-oxo-1-imidazolidinyl) ethyl methacrylate, acrylonitrile, acrylamide or substituted acrylamides, 4-acryloylmorpholine, N-methylolacrylamide, acrylamidopropyltrimethylammonium chloride (APTAC), acrylamidomethylpropane acid sulphonic acid (AMPS) or its salts, methacrylamide or substituted methacrylamides, N-methylolmethacrylamide, methacrylamidopropyltrimethylammonium chloride (MAPTAC), itaconic acid, maleic acid or its salts, maleic anhydride, alkyl or alkoxy- or aryloxy maleates or hemimeatates polyalkylene glycol, vinylpyridine, vinylpyrrolidinone, (alkoxy) poly (alkylene glycol) vinyl ether or divinyl ether, such as methoxy poly (ethylene glycol) vinyl ether, poly (ethylene glycol) divinyl ether, olefinic monomers, among which include ethylene, propylene, butene, hexene and 1-octene as well as fluorinated olefinic monomers, and vinylidene monomers, among which mention may be made of vinylidene fluoride, preferably vinylidene chloride , alone or as a mixture of at least two monomers mentioned above.

The radical polymerization may be carried out in the presence or absence of at least one polymerization initiator chosen for example from organic or inorganic peroxides, azo compounds, redox couples and / or alkoxyamines.

By way of example of monomers according to the invention which can be used as compound A, mention may be made of carboxylic monomers, their salts and anhydrides, vinyl esters of saturated or unsaturated carboxylic acids, such as, for example, acetate or propionate of vinyl; amino acids, such as aminocaproic, amino-7-heptanoic, amino-11-undecanoic and amino-12-dodecanoic acids, lactams such as caprolactam, oenantholactam and lauryllactam; salts or mixtures of diamines such as hexamethylenediamine, dodecamethylenediamine, metaxylylenediamine, bis-p amiocyclohexyl methane and trimethylhexamethylenediamine with diacids such as isophthalic, terephthalic, adipic, azelaic, suberic, sebacic and dodecanedicarboxylic acids.

By monomer usable as compound A according to the invention is also meant ring-opening polymerizable epoxy resin monomers, such as aliphatic glycidyl esters and ethers such as allyl glycidyl ether, vinyl glycidyl ether, maleate, and the like. glycidyl itaconate, glycidyl (meth) acrylate, alicyclic glycidyl esters and ethers such as 2-cyclohexene-1-glycidyl ether, cyclohexene-4,5-diglycidyl dicarboxylate, cyclohexene-4-glycidyl carboxylate, 5-norbomene-2-methyl-2-glycidyl carboxylate and endo cis-bicyclo (2,2,1) -5-heptene-2,3-diglycidyl dicarboxylate.

According to the invention, the compound A can also be a polymer melted a mixture of molten polymer, one or more polymers in solution in a solvent and / or in one or more monomers.

By polymer (s) usable as compound (s) A is meant in all that follows any composition based on polymer (s) of any kind: thermoplastic or thermosetting, rigid or elastomeric, amorphous, crystalline and / or semicrystalline, homopolymer, copolymer, gradient, block, random or block, these compositions may be mixtures of one or more polymers with one or more additives, additives and / or fillers conventionally added to the polymers, such as stabilizers, plasticizers, polymerization catalysts, dyes, pigments, lubricants, flame retardants, reinforcements and / or fillers, polymerization solvents, etc. The polymers may be obtained in a nonlimiting manner from one or more monomers listed above and / or or from one or more other monomeric entities known to those skilled in the art.

By polymer usable as compound A is also meant any random, gradual or block copolymers made from the homopolymers corresponding to the description above. This covers, in particular, anionic block copolymers of the SBS, SIS, SEBS, SB type and the SBM (polystyrene-co-polybutadiene-co-polymethylmethacrylate) type copolymers. This also covers copolymers produced by controlled radical polymerization, such as by Examples are copolymers of SABuS type (polystyrene-butyl co-polyacrylate-co-polystyrene), MABuM (polymethyl methacrylate-butyl co-polyacrylate co-polymethyl methacrylate) and all of their functionalized derivatives.

By epoxy resin is meant in the present description, any organic compound, alone or in admixture, having at least two functions of oxirane type, polymerizable by ring opening and designating all usual epoxy resins liquid at room temperature (20-25 ^{° C).} C) or at a higher temperature. These epoxy resins can be monomeric or polymeric, on the one hand, aliphatic, cycloaliphatic, heterocyclic or aromatic on the other hand. By way of examples of such epoxy resins, mention may be made of diglycidyl ether of resorcinol, diglycidyl ether of bisphenol A, triglycidyl p-amino phenol, diglycidyl ether of bromo-bisphenol F, triglycidyl ether of m-amino phenol, tetraglycidyl methylene dianiline, (trihydroxyphenyl) methane triglycidyl ether, novolac phenol-formaldehyde polyglycidyl ethers, orthocresol novolac polyglycidyl ethers and / or tetraphenyl ethane tetraglycidyl ethers.

To the epoxy resin can be added at least a second chemical species called hardener, intended to ensure the subsequent crosslinking of the epoxy resin by reacting with it. With regard to the hardener, there may be mentioned:

acid anhydrides, among which mention may be made of succinic anhydride;

aromatic or aliphatic polyamines, among which mention may be made of diamino diphenyl sulphone (DDS), methylene dianiline, 4,4'-methylenebis (3-chloro-2,6-diethylaniline) (MCDEA), 4,4'-methylenebis (2,6-diethylaniline) (MDEA);

dicyandiamide and its derivatives;

imidazoles;

polycarboxylic acids; polyphenols.

In the case where the resin and the hardener are simultaneously brought into contact with the CNTs, it may be preferable to use the composition according to the invention before the epoxy resin and the hardener have reacted with each other.

Other monomers of thermosetting resins may also be used as compound A, such as the monomers from which phenolic resins are derived, for example methylphenolformaldehyde resins and bromomethylphosphoformaldehyde reactive alkyls, polyester or vinyl ester resins, polyurethane resins. Examples of unsaturated polyester or vinyl ester resins are described in the article by M. MaNk et al in JMS - Rev. Macromol. Chem. Phys., C40 (2 & 3), p.139-165 (2000), which describes a classification of such resins on the basis of their structure into five groups: (1) ortho resins such as 1,2-propylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propylene glycol, dipropylene glycol, tripropylene hydrogen, neopentyl glycol or bisphenol-A hydrogen, (2) iso-resins, (3) bisphenol-A-fumarates, (4) chlorinated resins and (5) vinyl ester resins such as bisphenol A vinyl ester resins, novolak type vinylester resins, "mixed" vinylester resins having both types of motifs and halogenated vinylester resins.

Among the polymers that can be used as compound A according to the invention, polystyrene (PS) is particularly suitable; polyolefins and more particularly polyethylene (PE), polypropylene (PP); polyamides (for example PA-6, PA-6,6, PA-11, PA-12); polymethyl methacrylate (PMMA); polyether terephthalate (PET); polyethersulfones (PES); polyphenylene ether (PPE); polyvinylidene fluoride (PVDF); acrylonitrile polystyrene (SAN); polyethylether ketones (PEEK); polyvinyl chloride (PVC); polyurethanes, consisting of flexible polyether blocks which are residues of polyetherdiols and rigid blocks (polyurethanes) which result from the reaction of at least one diisocyanate with at least one short diol; the short chain extending diol which may be chosen from the glycols mentioned above in the description; the polyurethane blocks and the polyether blocks being connected by bonds resulting from the reaction of the isocyanate functional groups with the OH functions of the polyetherdiol; polyesterurethanes, for example those comprising diisocyanate units, units derived from amorphous polyester diols and units derived from a chain-extending short diol chosen for example from the glycols listed above; polyamide block and polyether block copolymers (PEBA) resulting from the copolycondensation of polyamide sequences with reactive ends with polyether sequences with reactive ends, such as, inter alia, 1) polyamide sequences with diamine chain ends with polyoxyalkylene blocks with dicarboxylic chains, 2) polyamide sequences with dicarboxylic chain ends with polyoxyalkylene sequences with diamine chain ends obtained by cyanoethylation and hydrogenation of aliphatic alpha-omega dihydroxylated polyoxyalkylene sequences known as polyetherdiols, 3) polyamide sequences with dicarboxylic chain ends with polyetherdiols, the products obtained being, in this particular case, polyetheresteramides; polyetheresters. The polymers that can be used as compound A can be polymers containing epoxide and / or glycidyl ether functions, of mono-, di- or polycarboxylic acid type, unsaturated or unsaturated, aromatic or non-aromatic, or functional derivative of acid such as anhydride, ester, amide and / or imide, of the vinyl, aromatic vinyl type, etc., it being understood that the definitions of the polymers given below may be redundant insofar as certain polymers contain several of the functions listed above.

According to the invention, the compound A is in particular a polymer in solution in a solvent resulting from the polymerization or copolymerization of a (meth) acrylic acid monomer, more particularly resulting from the copolymerization of (meth) acrylic acid and an oxyalkylenated monomer, in particular oxyethylene.

According to another embodiment of the invention, compound A is a polymer in solution in a solvent resulting from the polymerization of alkyl (meth) acrylate (methyl, ethyl, propyl, butyl especially with styrene and / or or butadiene.

By non-reactive species usable as compound A according to the invention is any type of oil or liquid plasticizer used in the polymer industry. For example: hydrocarbon oils of animal origin, such as perhydrosqualene (or squalane);

hydrocarbon-based oils of plant origin, such as liquid triglycerides of fatty acids whose fatty acids contain from 4 to 22 carbon atoms and in particular from 4 to 10 carbon atoms, such as the triglycerides of heptanoic or octanoic acids, or the oils of vegetable origin, for example sunflower, corn, soya, squash, grape seed, sesame, hazelnut, apricot, macadamia, arara, coriander, castor oil, avocado, jojoba oil, shea butter oil or triglycerides of caprylic / capric acids such as those sold by the company Stearineries Dubois or those sold under the trade names Miglyol 810, 812 and 818 by the company Dynamit Nobel;

esters and synthetic ethers, in particular of fatty acids, such as the oils of formulas R1COOR2 and R1OR2 in which R1 represents the remainder a fatty acid having from 8 to 29 carbon atoms, and R2 represents a hydrocarbon chain, branched or unbranched, containing from 3 to 30 carbon atoms, for example Purcellin oil, isononyl isononanoate, isopropyl myristate, 2-ethylhexyl palmitate, octyl-2-dodecyl stearate, octyl-2-dodecyl erucate, isostearyl isostearate;

hydroxylated esters such as isostearyl lactate, octylhydroxystearate, octyldodecyl hydroxystearate, diisostearyl malate, triisocetyl citrate, heptanoates, octanoates and decanoates of fatty alcohols; polyol esters, such as propylene glycol dioctanoate, neopentyl glycol diheptanoate and diethylene glycol diisononanoate;

pentaerythritol esters such as pentaerythritol tetraisostearate; lipophilic derivatives of amino acids, such as isopropyl lauroyl sarcosinate (INCI name: Isopropyl Lauroyl sarcosinate) sold under the name Eldew SL 205 by the company Ajinomoto; linear or branched hydrocarbons of mineral or synthetic origin, such as mineral oils (mixture of hydrocarbon oils derived from petroleum, INCI name: Ore), paraffin oils, volatile or not, and derivatives thereof, petroleum jelly, polydecenes, isohexadecane, isododecane, hydrogenated isoparaffin such as Parléam® oil marketed by NOF Corporation (INCI name: Hydrogenated Polyisobutene);

silicone oils such as volatile or non-volatile polymethylsiloxanes (PDMSs) with a linear or cyclic silicone chain, which are liquid or pasty at room temperature, in particular cyclopolydimethylsiloxanes (cyclomethicones) such as cyclopentasiloxane and cyclohexadimethylsiloxane;

polydimethylsiloxanes comprising alkyl, alkoxy or phenyl groups, during or at the end of the silicone chain, groups having from 2 to 24 carbon atoms; phenyl silicones such as phenyltrimethicones, phenyldimethicones, phenyltrimethylsiloxydiphenylsiloxanes, diphenyl-dimethicones, diphenylmethyldiphenyltrisiloxanes, 2-phenylethyltrimethylsiloxysilicates, and polymethylphenylsiloxanes;

fluorinated oils such as those partially hydrocarbon-based and / or silicone-type, such as those described in document JP-A-2-295912; ethers such as dicaprylic ether (CTFA name: Dicaprylyl ether); and 35 fatty alcohol benzoates C12-C1 ₅ (Finsolv® TN from Finetex);

- their mixtures.

Mention may also be made of trimellitate-type oils, such as tri-octyl trimellitate, or else predominantly naphthenic oils such as Shell's Catenex N956 oil, paraffinic type oils (typically Primol 352, from Exoon-Mobil), liquid polybutene type (typically Napvis 10) and resorcinol bis (diphenyl phosphate) (RDP) products which act as a plasticizer while providing additional properties, such as improved fire resistance.

External plasticizers commonly used in the processing of plastics can also be used as compound A according to the invention. By way of example, non-limiting mention may be made of: octadecanol, fatty acids such as stearic acid and palmitic acid. By emulsifier used as compound according to the invention is meant any anionic, cationic or nonionic surfactant. The emulsifying agent may also be an amphoteric or quaternary or fluorinated surfactant. It may for example be chosen from alkyl or aryl sulphates, alkyl or aryl sulphonates, fatty acid salts, polyvinyl alcohols and polyethoxylated fatty alcohols.

By way of example, the emulsifying agent can be chosen from the following list:

sodium lauryl sulphate,

sodium dodecylbenzenesulphonate,

- sodium stearate, - nonylphenolpolyethoxylated,

sodium dihexylsulfosuccinate,

sodium dioctylsulfosuccinate,

- lauryl dimethyl ammonium bromide,

lauryl amido betaine, perfluoro octyl potassium acetate.

The emulsifying agent may also be an amphiphilic block or random or graft copolymer, such as copolymers of sodium styrene sulphonate and in particular sodium polystyrene-b-poly (sodium styrene sulfonate) or any amphiphilic copolymer prepared by any other polymerization technique.

The compound A according to the invention may also be chosen from coupling agents intended to promote the dispersion of filler in an elastomeric composition and in particular the poly (alkyl phenol) polysulfides described in WO 05/007738, the content of which is incorporated by reference. ; as coupling agents, mention may also be made of the polysulfide organosilanes described in EP 501.227, in WO 97/42256 and in WO 02/083719.

Compound A according to the invention may also be a carboxylic acid. By carboxylic acid is meant a compound containing at least one carboxylic acid function. By way of example, mention may be made of acetic acid, acrylic acid or methacrylic acid, alone or as a mixture.

According to the invention, the compound A can be one or more monomers and / or one or more polymers in solution in a solvent. This solvent may be chosen from water, cyclic or linear ethers, alcohols, ketones such as methyl ethyl ketone, aliphatic esters, acids such as, for example, acetic acid, propionic acid, and the like. butyric acid, aromatic solvents such as benzene, toluene, xylenes, ethylbenzene, halogenated solvents such as dichloromethane, chloroform, dichloroethane, alkanes such as pentane, n-hexane, cyclohexane , heptane, octane, nonane, dodecane or isododecane, amides such as dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), alone or in admixture.

According to the invention the compounds A can be in gaseous, liquid and / or solid form. The contacting of the CNTs (step a) with the compound A can be carried out in different ways and in particular by dispersion, adsorption or mixing:

In the case where the compound A is in liquid form, the contacting of the CNT powder with A corresponds for example to a dispersion either by direct introduction by pouring the compound A into the powder (or the opposite), or by dropwise introduction of compound A into the CNT powder, or by nebulization of compound A with a sprayer on the CNT powder. The dispersion method can also be done by pouring the CNT powder into the solution of compound A which may or may not be in the form of a fluid film or fine droplets (dew) deposited on a solid surface. In the case where the compound A is in gaseous form, bringing the CNT powder into contact with A corresponds to adsorption of vapors of A transported or not by a gas, preferably inert.

In the case where the compound A is in solid form, bringing the CNT powder into contact with A corresponds to a dry mixture of powders or dry-blend and must be followed by step b) (heat treatment) where the passage of A in liquid or gaseous form takes place in order to ensure the intimate and homogeneous mixture of the compound A with the CNTs.

The dispersion between the CNTs and the compound A can also be carried out using a preliminary stage of dissolving the compound A in the presence of the CNTs in a solvent.

In this case, this preliminary step will be followed by a solvent evaporation phase carried out preferably with stirring so as to recover the composition in powder form. It is advantageous to use a filtration process so as to accelerate the cycle time to obtain the powder composition of CNT and of compound A in dry form.

In the case where compounds A of different physical form are introduced, the bringing into contact of the compounds of different physical form with the CNTs will preferably be made successively; for example, adsorption of compound (s) A in gaseous form on the CNTs and then dry mixing with a second compound A in solid form or in liquid form.

This step a) can be carried out in conventional synthesis reactors, fluidized bed reactors or in mixers mixing type Z arm, Brabender, extruder, or any other mixing device of the same type known to man of art. At the end of this first step a), the mixture between the CNTs and the compound A remains in solid powder form and retains good properties. of flowability (it does not take in mass). If necessary, it can be stirred mechanically or not.

The amount of compound A introduced is such that, at the end of this step a), it is below the threshold for which one obtains either a liquid suspension of CNT or a paste in which the CNT grains are totally or partially pasted. . This threshold depends in particular on the ability of the compound A to impregnate the CNT powder, and in the case where A is a liquid or a solution, on its viscosity of the introduced liquid.

In the case where compound A is acrylic acid, the content of compound A is in general between 30 and 90%.

The process for obtaining the compositions according to the invention comprises a possible step b) which consists of a heat treatment of the powder resulting from step a).

This heat treatment consists of putting (raising) the temperature of the powder obtained after step a) so that the physicochemical properties of the powder are modified by this heat treatment.

In the case where a liquid containing monomers has been introduced in step a) (monomer (s) in the liquid state, monomer solution (s), etc.), this heat treatment step may for example consist of in a heating which allows the polymerization of the monomers and / or a strong physical adsorption and / or a chemical adsorption with creation of bonds between the CNTs and a fraction of the monomers or polymer (s) formed.

The bond between the NTC and the polymer synthesized in-situ via the monomers introduced in the first step or with the polymer added during the first step is characterized in that part of this polymer created in situ or added to the CNTs before the treatment the heat of step b) is no longer extractable from the CNT by different washings with selective solvents of the polymer, whereas the same washes on the mixture (CNT / compound A) resulting from step a) make it possible to extract all the compound A of CNTs. In the case where a solution of (co) polymer (s) was used in step a), the heat treatment step b) makes it possible to obtain a strong physical adsorption and / or a chemical adsorption with creation of bonds. covalent between the CNTs and the polymer and / or the continuation of the polymerization, with, for example, increasing the molar mass of the polymer.

In the case where compound A is in liquid form or in solution in a solvent, step b) may also make it possible to improve the distribution between the liquid and the CNTs.

When it is desired that a polymerization takes place during step b), the pressure and temperature conditions of this heat treatment step will be in accordance with the usual polymerization conditions known to those skilled in the art. The atmosphere during the polymerization may or may not be inert depending on the nature of the monomers and polymers concerned.

When the compound A is (meth) acrylic acid, its during step b) is carried out at a pressure generally between 0 and 3 bars and at a temperature between 40 and 150 ^° C. The time heating is then between 5 and 1000 min and more precisely between 300 and 600 min. Advantageously, the heat treatment (step b) is carried out according to the following thermal cycle: first a plateau at 64 ^° C. for 150 to 500 min followed by a second plateau at 120 ^° C. for 100 to 200 min before cooling at ambient temperature, the pressure remains substantially equal to the atmospheric pressure. At the end of step b), the product (mixture) obtained remains in the form of solid powder and retains good flowability properties (it does not take in bulk). At the end of this step, the product obtained, like that resulting from step a) is below the threshold for which one obtains either a liquid suspension of CNT, or a paste in which the CNT grains are totally or partially pasted.

The process for obtaining the compositions according to the invention comprises a possible step c) which consists in the possible separation of the compounds present in the powder composition based on CNT and not bound to the composition resulting from step a) or b ) by physical and / or chemical adsorption. This step may for example consist of washing with a solution comprising a solvent of the compounds to be removed and / or drying in order to devolatilize the volatile products. To carry out the washing, it is possible for example to use a mixture of solvents. Washing can be done in several steps, preferably between 1 and 5 steps, to improve the separation of unbound compounds. It is also possible to combine several separation techniques, such as washing and drying.

The drying consists in putting the volatile compounds under conditions of temperature and pressure such that their desorption is facilitated. Thus it will be preferable to use partial evacuation at a temperature lower than the chemical decomposition temperature of the compounds, more particularly less than 200 ^° C. and a pressure of between 100 Pa and 200 kPa. To accelerate this extraction of volatile compounds, it is also possible to start with a first phase of filtration. In this step c), it is possible to carry out the final drying phase, for example, with stirring in order to recover a non-agglomerated CNT powder that would fall outside the scope of the invention. In the case of a process without step b) where the compound A is the acid

(Meth) acrylic, step c) may consist of a washing with an aqueous solution of alcohol and more particularly a 50% aqueous solution of ethanol.

The compositions according to the invention can be used in many fields, in particular in electronics (depending on the temperature and their structure, they can be conductive, semiconducting or insulating), in mechanics, for example for the reinforcement of composite materials (the NTC are one hundred times stronger and six times lighter than steel), and electromechanical (CNTs can expand or contract by charge injection).

For example, materials intended for example for the packaging of electronic components, for example electromagnetic shielding and / or antistatic dissipation, such as mobile phone housings, computers, on-board electronic devices on motor vehicles may be mentioned. , rail and air, to parts of structures for motor vehicles, rail and air, medical instruments, fuel lines (petrol or diesel) (or fuel line), materials adhesives, antistatic coatings (or coatings), thermistors, electrodes, especially for supercapacitors, etc.

Given their excellent ability to disperse in the polymers, the compositions according to the invention can advantageously be used as a masterbatch which is diluted in the final material, for example based on polymer (s).

The dilution of the composition according to the invention can be carried out in conventional synthesis reactors, fluidized bed reactors or in Z-arm mixer mixing apparatus, Brabender, extruder, in melters when the polymer material is thermosetting or any other mixing apparatus of the same type known to those skilled in the art.

EXAMPLES

In all the examples, multi-walled nanotubes (hereinafter referred to as "CNTs" obtained by CVD method) were used on a catalytic support and a statistical study by transmission electron microscopy showed that almost 100% of The tubes are multi-walled with a diameter varying between 10 and 50 nm and their electrical conductivity when pressed in the form of a pellet is greater than 20 S / cm The ash content evaluated by calcination at 65 ^° C. under air is about 7%.

EXAMPLE 1 Composition According to the Invention Based on NTC and Acrylic Acid (Spray Impregnation with Acrylic Acid)

10 g of acrylic acid are incorporated in 10 g of CNT powder by spraying the acrylic acid solution with a cosmetic perfume spray type spray. The powder is agitated during spraying using a mechanical stir bar type stirrer to facilitate the proper distribution of the acrylic acid (step a).

The resulting powder is then heated in an airtight container. The temperature follows the temperature cycle which consists of a first temperature step at 64 ^° C. for about 250 minutes followed by a second temperature step at 120 ^° C. for about 100 minutes before cooling to room temperature (step b). The properties of the powder thus obtained (denoted NTCIa) are combined in Table 1.

The powder thus obtained is then washed and dried (stage c). The washing is done with a solution of ethyl alcohol diluted to 50% in water. Two successive washes are performed on the powder, which is each time dewatered using a beaker filter with a porosity of 11 microns. The powder thus obtained is then dried at 120 ^° C. under a partial vacuum of 1000 Pa for 1 h.

The properties of the powder thus obtained (denoted NTC1 b) are combined in Table 1. The average particle size of the NTCI powder b is 200 μm and the level of fines (<100 μm) is less than 2% (measured by dry sieving on vibrating screen).

EXAMPLE 2 Composition According to the Invention Based on NTC and Acrylic Acid (Step a): Impregnation by Pouring Dropwise an Acrylic Acid + Radical Primer Mixture

A solution containing 40 g of acrylic acid and 0.04 g of AIBN are incorporated in 10 g of CNT powder by pouring the solution dropwise using a "pasteur" pipette. The powder is agitated during the impregnation with the aid of a mechanical bar stirrer type stirrer for 1 hour to facilitate the good distribution of the acrylic acid.

The resulting powder is then heated in an airtight container. The temperature follows the temperature cycle of step b) of Example 1 (step b).

The properties of the powder thus obtained (denoted NTC 2a) are combined in Table 1.

The powder is then dried at 120 ^° C. under a partial vacuum of 1 kPa for 1 h (step c), a powder (denoted NTC 2b) is obtained, the properties of which are shown in Table 1. Alternatively, it is It is possible to wash and dry the powder (denoted NTC 2a) in order to extract the unreacted monomers and the polymer chains which are not grafted or irreversibly adsorbed on the CNTs. The washing is done with a solution of ethyl alcohol diluted to 50% in water. Two successive washes are carried out on the powder, which is each time dewatered using a filter buchner with a porosity of 11 μm. The powder thus obtained is then dried at 120 ^° C. under a partial vacuum of 1 kPa for 1 h and has the same properties as the powder noted NTC 2b.

Example 3 Adsorption Impregnation of Acrylic Acid Fumes (Step a) and Heat Treatment (Step b)

In a container containing a solution of acrylic acid, a stream of nitrogen gas is bubbled at room temperature. The vapors are then introduced into a scrubber bottle containing CNTs through a sintered glass, which makes it possible to suspend the CNTs and promote exchanges between the CNT powder and the gaseous vapors. The vapors are then trapped in a vessel refrigerated with liquid nitrogen. This vapor phase impregnation (step a) lasts 4 hours. The properties of the powder thus obtained (denoted NTC3a) are combined in Table 1. The NTC3a powder is then heated in an airtight container. The temperature follows the temperature cycle of step b) of Example 1 (step b). The properties of the powder thus obtained (denoted NTC3b) are combined in Table 1.

The powder thus obtained is then washed and dried (stage c). The washing is done with a solution of ethyl alcohol diluted to 50% in water. Two successive washes are performed on the powder, which is each time dewatered using a buchner filter with a porosity of 11 microns. The powder thus obtained is then dried at 120 ^° C. under a partial vacuum of 1 kPa for 1 h. The properties of the powder thus obtained (denoted NTC3c) are combined in Table 1.

In Table 1, the percentage of NTC of the powder, the uncompacted density of the powder and the conductivity of a 2% PVDF or 1% NTC sample obtained by dilution are indicated for each composition. the amount of composition necessary to obtain this concentration in the final mixture.

The uncompacted density of the powder is determined by measuring the volume occupied by 1 g of powder put in a test tube after three successive slow reversals of the tube. Three measurements are made and the average volume obtained is used to determine the density.

The dispersion in PVDF is prepared in the following manner: PVDF (Kynar® 720 from Arkema) mixtures with CNTs or powder compositions based on CNTs as defined above are made using a micro -Heocord Haake Mixer 90. The mixing conditions are as follows:

- temperature of the mixture: 23O ⁰ C

- rotor speed: 50 rpm

- mixing time: 15 min

The samples are then compression molded at 230 ^° C. Pellets are taken by a punch to measure conductivity. Conductivity tests are performed on a 4-wire cell device.

Table 1

The table shows that the compositions according to the invention disperse well in a polymer matrix; the distribution of the CNTs is homogeneous, which confers a lower electrical resistivity than that of compositions of the prior art. EXAMPLE 4 Composition According to the Invention Based on NTC and Acetic Acid (AAc) of methacrylic acid (AMA). mixture of acrylic acid (AA) and styrene (S) (impregnation by vaporization of acetic acid, methacrylic acid and a mixture of acrylic acid and styrene)

Samples of CNT powder are impregnated with various types of products according to the conditions described in Example 2. The powder is stirred during the impregnation with the aid of a mechanical bar stirrer type stirrer for 1 hour for facilitate the proper distribution of components. The details of the mixtures are summarized in Table 2. (step a)

Table 2

The powders thus obtained are then heated in an airtight container at 80 ^° C. for 4 hours and then at 125 ^° C. for 70 minutes (step b1). It is verified by mass conservation that all of the compounds A introduced are in the CNTs after step 1. For some samples, a second check is made by pyrolysis, making sure that the percentage of catalyst in the sample is in good agreement with the advertised NTC rate. The properties of the powders thus obtained are determined and grouped together in Table 3. The powders thus obtained are then dried at 120 ^° C. under a partial vacuum of 1 kPa for 1 h. The properties of the powders thus obtained are combined in Table 3. (Step b2)

The powders thus obtained are then washed and dried (step c). The washing is done with a solution of ethyl alcohol diluted to 50% in water. Two successive washes are carried out on the powder which is each time dewatered using a buchner filter with a porosity of 11 μm. The powders thus obtained are then dried at 120 ^° C. under a partial vacuum of 1 kPa for 1 h. The properties of the powders thus obtained are combined in Table 3.

Table 3

The resistivities on the powder samples from step b2 mixed in the PVDF are determined according to the methods described in Example 3 and are present in Table 4 below: Table 4

The table shows that the compositions according to the invention disperse well in a polymer matrix; the distribution of the CNTs is homogeneous, which confers a lower electrical resistivity than that of compositions of the prior art.

EXAMPLE 5 Composition according to the invention based on NTC and a copolymer of (meth) acrylic acid and an oxyethylenated monomer step a): NTC mixture with the polymer in solution with possibly step b) posterior grafting)

In a Z-arm mixer, a mixture is prepared containing 80 parts by weight of solution of DV1256 (solution of (meth) acrylic acid and an oxyethylenated monomer) of the company Coatex described in patent FR 2766106, 100 parts by weight. weight of NTC and 40 parts by weight of water. DV 1256 is a 25% by weight aqueous solution of copolymer.

Part of the product obtained is dried under vacuum at room temperature to remove the water. When the powder resulting from this drying is washed according to the protocol described in Example 2, all the polymer is extracted from the CNT. Another part of the powder is dried at 100 ^° C. for 5 h 30 min.

When the powder resulting from this drying is washed according to the protocol described in Example 2, only 21% of the polymer is extracted from the CNT: 79% of the polymer introduced by the addition of DV1256 to the NTC appears to have grafted or to be irreversibly adsorbed on the CNT.

Example 6 NTC mixtures with various compounds A with mechanical stirring

For each mixture made with a Rhéocord micromalaxeur

(step a) the operating conditions are detailed in table 5

(temperature, speed and mixing time) for each mixture. A total mass of 20 g is fixed in the mixer whose mixing chamber has a volume of 66 cm ³ .

For all mixtures, the procedure is as follows:

1. Two thirds of the CNTs that occupy the entire available volume are introduced into the mixing chamber.

2. The polymer is added in small successive amounts, which has the effect of reducing the overall volume of CNTs.

3. It is then possible to add to the mixture the remaining third of NTC.

Table 5:

HT 121 is a PMMA grade of Arkema having a melt flow index (MeIt index Flow or MFI), equal to 2 measured at 23O ⁰ C under 3.8 kg and Vicat temperature 121 ⁰ C under 5ON according to the ISO306 standard.

35BA320 is a functionalized Polyolefin Lotryl® ethylene-butyl acrylate from Arkema having a MFI, measured for 10 min, between 260 and 350. MAM M22 and M22N are polymethylmetacrylate-polybutylacrylate-polymethylmethacrylate (MAM) copolymers from Arkema whose viscosity in solution at 10% in toluene is of the order of 8 cP for M22 and respectively of the order of 15 cP. for the M22N. SBM E40 is a polystyrene-polybutadiene-polymethylmethacrylate (SBM) copolymer from Arkema whose viscosity in solution at 10% in toluene is of the order of 4cP.

D320 is a core-shell type acrylic shock modifier from Arkema. DER 332 is a bisphenol A diglycidyl ether monomer (DGEBA) from Dow of high purity (equivalent epoxide weight of 171 to 175 g / eq) and viscosity of about 5 Pa.s at room temperature.

PAA GE1903 in water is a PAA in aqueous solution from Coatex. Vultac TB7 is a coupling agent according to WO 05/007738 of the company

Arkema.

Evatane 2803 is a copolymer of ethylene and vinyl acetate (EVA) Arkema containing about 28% vinyl acetate and having an MFI of the order of 3 g / 10 min. Evazole is a low molecular weight EVA copolymer of the company

Arkema.

Primol 352 is a mineral oil whose kinematic viscosity at 40 ^° C. is 70 mm ² / sec.

Noram M2C is a surfactant of CECA of the methyl-cocoamino type.

After the mixing step, in all cases powder compositions are obtained whose flowability is very good and whose density (or density) has been increased relative to the density (or the density) of the powder. initial NTC (resulting from the synthesis but also obtained after mixing).

The particle size of these powders is indicated in Table 6. The particle size measurements were made in a dry process with a Malvern Mastersizer particle size analyzer taking as reference indexes for the CNTs of (1, 45, 0.100). It should be noted that in the dry process, the compressed air supply of the powder tends to reduce the particle size and increase the amount of fines for each powder. The average particle size D ₅₀ of the particles of the powder NTC + DER 332 is 200 μm and the level of fines (<40 μm) is less than 4% (measured by dry sieving on a vibrating screen) while its Di ₀ is 42 μm. .

Table 6

D _x the apparent mean diameter of x% of the particle population.

4% of NTC / DER332 (50/50) mixture prepared above is redispersed in 96% of DER 332 epoxy resin with mechanical stirring and then via an ultrasonic probe for 30 minutes. DER 332 is then added so as to bring the level of CNT to 0.16% in the final composition.

A comparative mixture containing 98% of DER 332 and 2% of NTC is carried out with mechanical stirring and then stirred with an ultrasound probe for 30 minutes. DER 332 is then added so as to reduce the level of CNT to 0.16% in the final composition.

Samples of each of the mixtures are then observed under a microscope to evaluate the dispersion as shown below. At the same magnification, it is found that the dispersion of the powder of the composition in the epoxy resin according to the invention is improved with respect to the dispersion of NTC powder alone in epoxy resin.

For the dispersion of CNT directly in the epoxy resin, we see a poor dispersion / distribution of CNTs in the polymer matrix which results in the presence of numerous clusters whose size can go up to about 45 microns.

For the dispersion of the powdery composition according to the invention in the epoxy resin, we do not see any cluster of this size, but only very rare clusters whose size rarely exceeds 10 μm.

EXAMPLE 7 Powder Composition Obtained by Solvent Mixing of CNT and Block Copolymer (Step a)

A mixture of CNT and block copolymer is made in a solvent described in Table 7. This mixture is stirred under an ultrasonic probe for 30 minutes and then separated into two parts.

Part is filtered on a sintered glass No. 2 or No. 3 until a paste whose solid content is of the order of 20%. It should be noted that a part of the copolymer put into the starting solution is extracted in the amount of filtered solvent. In order to carry out the extraction of the solvent remaining in the dough thus obtained, the mixture is stirred in a Z-arm kneader or in a Brabender-type kneader under temperature conditions allowing a sufficiently rapid evaporation of the solvent (ie a temperature of about 40 ⁰ C on acetone and about 80 ⁰ C on toluene).

Table 7

Part of the solution is put directly into the Brabender mixer or Z-arm so as to evaporate the solvent under the temperature conditions described above. The time required for evaporation of the solvent is longer according to this protocol than according to the previous protocol.

At the end of the two experimental protocols described above, NTC powders loaded with polymers similar to the powders described in Example 5, the bulk density of which is not compacted, are of the order of 6 to 9 cm ³ / g. .

The dispersion of these powder compositions used as a masterbatch in DER 332 epoxy resin according to the procedure described in Example 6 is similar to that of the NTC powders obtained in Example 6; it is significantly improved compared to the direct mixture of CNT and resin DER 332 for the same level of CNT.

In Table 8 below, it is shown that the dispersion in the PVDF (according to the procedure of Example 3) of this composition is improved relative to the dispersion of CNT directly in the PVDF.

Table 8

Example 8 (comparative) dispersion with a composition based on NTC which is not in powder form The solution obtained in Example 7 containing 50% of CNT and 50% of

MAM M22 in toluene is evaporated in an oven without stirring.

When all the solvent is evaporated without stirring, a powder is not obtained but macroscopic blocks of NTC and copolymers of very irregular shape and size of the order of one to ten millimeters.

When an attempt is made to disperse these aggregates in PVDF so as to obtain 2% of CNT in the final mixture, a non-conductive and very poorly dispersed product is obtained: macroscopically, the presence of numerous aggregates whose size is close to that of blocks of CNT introduced initially (1 to 10 mm).

Example 9: NTC mixtures with various compounds A with mechanical stirring

A useful 16-liter powder mixer of the Hosokawa Nauta Minimix 020-FFC-50 type is used in which one of the compounds A will be injected.

(or a solution comprising compound A) with peristaltic pumps of power adapted for the viscosity of the product to be injected according to the scheme

1 below to perform step a.

Diagram 1

We operate according to the protocol described below - Loading the NTC powder into the mixer via the cover;

- Start agitation at maximum speed;

- Mixing powders for 5 minutes; Injection of compound A or of the solution comprising compound A via 2 peristaltic pumps. The introduction is done by 2 taps on the top of the mixer.

- The pumps are set for an insertion time of about 30 minutes;

- At the end of the injection, the mixture is continued for 5 minutes; - Draining by the bottom valve with agitation in PE drums.

At the end of this step a, the powder can be dried in the mixer or an oven or external oven so as to evaporate the residual solvent if step a consisted of the injection of a polymer solution. In the case where the step a) consisted in the injection of monomer or a species having functionalities, such as acetic acid, it may be possible to perform a step b aimed at the reaction of the species on the NTC powder. Following this step, it will be possible to dry the powder to eliminate the species that would not react. This step may be done in the mixer, in an oven or in an oven.

Table 9 summarizes the data on the various mixtures that have been made.

Kynar® 2801 and Kynar®721 are two grades of PVDF from ARKEMA. Abbreviations AA, AAc and MEK correspond respectively to acrylic acid, acetic acid and methyl vinyl ketone. The masses are expressed in grams (g).

The speeds of the arms and screws (respectively V arms and V screws are expressed in rpm). The times of mixing and introduction are expressed in minutes (min).

Table 9 (b)

The CNT 10 is dried for 4 hours at 80 ^° C. in an oven. A particle size is achieved by dry-sieving in comparison with the CNT of departure. The flow at 50 .mu.m is 0.2% for the crude NTC and 0.37% for the coated product. Graph 1 shows the particle size distribution of the product.

Graph 1

1

1 s ε

<50 50 100 160 200 400 800 1000 2000 diameter (micron)

Displacement of the average diameter of 400 μm to 200 μm

NTC 10 is used as a mixture in polycarbonate in comparison with the reference CNT before modification according to the invention.

The polycarbonate used is Makrolon 2207, from Bayer, MFI (g / 10min) equal to 38 to 300 ⁰ C under a load of 1.2 kg. The polycarbonate is mixed with the equivalent of 2% of CNTs from the reference CNT or the CNT 10. The mixture is produced on a twin-screw micro-extruder of DSM at 24 ^° C. with a screw speed of 100 revolutions per minute and a mixing time of 8 min to arrive at the homogeneity of the mixture and the stabilization of the mixing torque. The samples are then compressed in the form of plates 2 mm thick at a temperature of 24O ⁰ C using a cycle of 5 minutes of creep and 2 minutes at 240 bars before cooling in press for 30 min by cutting the heating then a cooling off press under a mass of 12 kg. The electrical conductivity of the samples is measured according to Example 3. The results are given in Table 10.

Table 10

The table shows that the composition according to the invention disperses well in a polymer matrix; the distribution of CNTs is homogeneous, which confers a lower electrical resistivity than that of the composition of the prior art.

CNT 12 is dried for 2 hours at 80 ^° C. under vacuum. Particle size is achieved by dry sieving in comparison with the starting CNT. The flux at 50 .mu.m is 0.2% for the crude NTC and 0.07% for the coated product. Graph 2 shows the particle size distribution of the product.

Graph 2

<50 50 100 160 200 400 800 1000 2000 diameter (micron) There is a displacement of the average diameter of 400 microns to 200 microns.

On the starting CNT 12, drying is carried out for 4 hours at 100 ^° C. After this step, the amount of polymer extractable from the mixture is determined by washing. 10 g of dried product are weighed and introduced into 250 ml of water. 'Demineralized Water.

The mixture is left stirring and the suspension is filtered on paper. The extraction is carried out 4 times, ie 1 liter of water for 5 g of polymer to extract. The results are summarized in Table 11.

Table 11

A dry extract at 100 ^° C. is carried out on the filtrate to evaluate the amount of polymer extracted.

Extraction eliminated only 60% of the polymer and reached an asymptote.

It can be estimated that 20 to 30% of the polymer remained bound to the CNT (ie approximately 50% of the initially introduced polymer) as illustrated in graph 2. Graph 2

0 200 400 600 800 1000 volume of water (ml)

At the end of stage A, the CNTs 17 and 18 are tested either as they are, or after drying for 2 hours at 80 ^° C. under vacuum, or after a step B carried out for 4 hours at 64 ^° C. followed by 70 ^° C. minutes at 125 ^° C. and then followed by drying for 2 hours at 80 ^° C. under vacuum. The characteristics of the powders and the electrical properties after dispersion of the products in the PVDF according to the data of Example 3 are collated in Tables No. 12 and 13.

Table n ° 12

Table n ° 13

Claims

1. Process for obtaining pulverulent compositions comprising from 20% to 95% of CNT, characterized in that it comprises one or more of the following steps: a) a step of bringing the CNTs into contact with at least one compound A, b) optionally a step consisting of a heat treatment, c) optionally a step of purification and / or separation of the composition from the reactants with a view to its recovery, mixing at the end of each of the steps a, b and c remaining as a solid powder. and in that the compound (s) A is (are) a monomer, a mixture of monomers, a molten polymer or a mixture of molten polymers, a solution of monomer (s) and / or polymer (s) in a solvent, a mixture of polymers in solution in one or more monomers, a non-reactive species of oil type or plasticizer type, an emulsifier or surfactant, a coupling agent and / or a carboxylic acid.

2. Method according to claim 1, characterized in that the pulverulent compositions comprise from 35 to 90% of CNT.

3. Method according to claim 1 or 2, characterized in that the pulverulent compositions comprise from 45 to 90% of CNT.

4. Process according to any one of the preceding claims, characterized in that the compound (s) A is (are) in liquid form.

5. Process according to any one of the preceding claims, characterized in that the compound (s) A is (are) in solid form.

6. Process according to any one of the preceding claims, characterized in that (s) compound (s) A is (are) in gaseous form.

7. Method according to any one of the preceding claims, characterized in that implements several compounds A of different physical form.

8. Process according to any one of the preceding claims, characterized in that the compound (s) A is (are) chosen from (meth) acrylic monomers, preferably acrylic acid, olefins, preferably ethylene, propylene, butene, hexene and / or 1-octene, dienes, preferably butadiene, vinylic, preferably vinyl chloride, vinylidene, preferably vinylidene chloride, vinylaromatic, and especially styrenic monomers, amino acids, lactams, carboxylic monomers, their salts and their anhydrides, vinyl esters Saturated or unsaturated carboxylic acids, preferably vinyl acetate, ring-opening polymerizable epoxy resin monomers, preferably bisphenol A diglycidyl ether.

9. Method according to any one of the preceding claims, characterized in that it comprises a step b) with (co) polymerization of (s) lo compound (s) A.

10. Process according to any one of the preceding claims, characterized in that the compound (s) A is (are) chosen from PS, polyolefins, polyamides, PMMA, PET, PES, PEP, PEEK, PVC, PVDF, polyester urethanes, PEBA, polyetheresteramides, π polyetheresters, SBS block copolymers, SIS, SEBS, SB, SBM, SABuS (polystyrene-co butylpolyacrylate-co-polystyrene), MABuM, the polymers containing epoxide and / or glycidyl ether functional groups.

11. Method according to one of the preceding claims, characterized in that the compound A is a polymer in solution in a solvent resulting from Ia.

Polymerization or copolymerization of a (meth) acrylic acid monomer.

The process according to claim 11, wherein the polymer is a copolymer of (meth) acrylic acid and an oxyalkylenated monomer.

13. Method according to one of the preceding claims, characterized in that the compound A is a polymer in solution in a resulting solvent

From the polymerization of alkyl (meth) acrylate with styrene and / or butadiene.

14. Process according to any one of the preceding claims, characterized in that the compound (s) A is (are) chosen from surfactants, non-reactive species of oil type or plasticizer type. , the

Coupling agents, and / or a carboxylic acid.

15. Process according to any one of the preceding claims, characterized in that the compound (s) A is (are) acetic acid, acrylic acid and / or methacrylic acid.

16. A pulverulent composition obtainable by the process as defined in any one of the preceding claims.

17. A composition according to claim 16, wherein the average particle size is less than or equal to 1 mm, preferably less than or equal to 800 μm, and preferably at most 10%, and advantageously at most 5%, of the particles of the particles. compositions according to the invention have a size less than 40 microns.

The composition of claim 16 or 17, wherein up to 50 parts by weight of the CNTs is replaced by one or more other powdery fillers, such as carbon blacks, activated carbons, silicas, glass fibers. .

19. Use of a composition according to claims 16 to 18, in materials, in particular polymeric materials, as a reinforcing agent and / or as modifying conductive and thermal properties.

20. Use of a composition according to claim 19 for carrying out:

- packaging of electronic components, such as mobile phone cases, computers, for on-board electronic devices on motor vehicles, rail vehicles and air vehicles, - structural parts for motor vehicles, rail and air vehicles,

- medical instruments,

- fuel lines,

antistatic coatings, adhesive materials,

thermistors,

- Electrodes, especially for supercapacities.