SOLID AGGLOMERATED WITH CARBON NANOTUBES

DISAGGREGATES

FIELD OF INVENTION

The invention relates to an agglomerated solid material comprising disaggregated carbon nanotubes free from organic compounds, as well as its method of preparation, and its uses.

TECHNICAL BACKGROUND

Carbon nanotubes are recognized today as materials with great advantages, due to their mechanical properties, their very high aspect ratios (length / diameter) as well as their electrical properties.

It is recalled, in fact, that carbon nanotubes (hereinafter, CNTs) have particular crystalline structures, tubular, hollow, and closed, which may however have open ends, composed of atoms arranged regularly in pentagons, hexagons and / or heptagons, obtained from carbon. CNTs generally consist of one or more coiled graphite sheets. A distinction is thus made between single-wall nanotubes (SWNT) and multi-wall nanotubes (Multi Wall Nanotubes or MWNT).

It is also recalled that the carbon nanotubes usually have an average diameter ranging from 0.1 to 200 nm, preferably from 0.1 to 100 nm, and advantageously a length of more than 0.1 mhi and advantageously of 0 , 1 to 20 mhi. Thus, their length / diameter ratio is advantageously greater than 10 and most often greater than 100.

The production of CNTs can be implemented by different processes, however the synthesis by chemical vapor deposition (CVD) makes it possible to ensure the manufacture of a large quantity of CNTs.

In general, the CNT synthesis methods according to the CVD technique consist in bringing a carbon source into contact, at a temperature between 500 and 1500 ° C., with a catalyst, generally in the form of grains of coated substrate. of metal, placed in a fluidized bed.

The synthesized CNTs bind to the grains of catalytic substrate in the form of an entangled three-dimensional network, forming powder comprising agglomerates of CNTs, the average dimensions of which are of the order of a few hundred microns. Typically, the agglomerates, which are also referred to as primary aggregates, have an average size d50 of the order of 300 to 600 microns, the d50 representing the apparent diameter of 50% of the population of the agglomerates. The CNTs thus obtained can be used as they are, but it is also possible to subject them to a subsequent additional purification step, intended to remove the grains from the catalytic substrate.

By observation by electron microscopy, at the micron scale, the surface of CNTs in a primary aggregate exhibits a granular structure, characterizing a disorderly entanglement of CNTs.

The naturally entangled structure of CNTs limits their use in certain applications, due to the difficulty in homogeneously integrating aggregates of size greater than a few hundred microns in certain matrices.

It has thus been proposed to reduce the size of the CNT agglomerates during their production, for example according to the method described in document WO 2007/074312. This process includes a grinding step, inside or outside the synthesis reactor, making it possible to limit the size of the entangled three-dimensional network of CNTs on the catalyst, and to make active catalytic sites of said catalyst accessible.

This process makes it possible to limit the formation of CNT agglomerates larger than 200 μm and / or to reduce their number, and produces CNTs of greater purity while significantly improving the productivity of the catalyst used.

However, the grinding, carried out according to known techniques in devices such as ball, hammer, grindstone, knife or gas jet mills, makes it possible to divide the primary aggregates into aggregates of reduced size, in particular having an average size. d50 between 10 and 200 μm, but does not modify the entanglement of CNTs. Consequently, the nature of the aggregates is not modified and the processability of the CNTs thus obtained is not improved.

In addition, this process does not make it possible to overcome the problems of handling CNTs, due to their powdery nature.

In order to solve these problems, it is proposed in document WO 17/126775 to prepare CNT granules from a mixture of CNT in powder form with a dispersion solvent, in a mass ratio ranging from 5: 1 to 1: 2, and extrusion of the paste obtained in the form of granules which are then dried. This process has the characteristic of using only a small amount of solvent. The granules thus obtained have an apparent density greater than the density of the CNT powder, in particular a density greater than 90 kg / m 3 and generally less than 250 kg / m 3.. The solvent used can be chosen from a wide list of compounds, such as water, alcohols (methanol, ethanol, propanol), ketones (acetone), amides (dimethylformamide, dimethylacetamide), esters or ethers , aromatic hydrocarbons (benzene, toluene) or aliphatic hydrocarbons. This process makes it possible to compact the CNT powder and to reduce the average size d50 of the agglomerates constituting the CNT granules by more than 60% relative to the size of the agglomerates constituting the CNT powder. The granules thus obtained generally have a particle size d50 of less than 200 mhi, preferably less than 150 mhi, and even less than 20 mih, or even less than 15 mih. However, the morphology of the aggregates, that is to say the entanglement of the CNTs, does not appear to be modified according to this process.

Document WO 2008/000163 describes a method for preparing carbon nanotube aerogels comprising aggregates of well dispersed carbon nanotubes having a diameter of about 1 nm to about 100 microns and a density ranging from 0.1 to about 100 g / l. These aerogels are solvent free and are used to prepare carbon nanotube membranes and nanocomposite materials.

Document WO 2012/080626 describes a process for introducing nanofillers of carbon origin into a metal or a metal alloy. This results in a metallic composite comprising well dispersed nanofillers, with a density close to that of the metal, which can be used for producing metallic structures.

Other approaches have been proposed to solve the problems of handling CNTs in the powder state. It has been proposed in particular to disperse the CNTs in different reception matrices in order to form CNT masterbatches and thus to use CNTs in agglomerated solid form of macroscopic size. These masterbatches are ready to use and can be safely introduced into a matrix to form composites with improved properties. Preferably, the host matrix of the CNT masterbatch is chosen so as to correspond to, or be compatible with, the matrix of the composite material.

Generally, according to these methods, the primary aggregates are broken up by the mechanical shearing used to homogeneously disperse the CNTs in a liquid or viscoelastic host matrix.

Different preparations of such masterbatches are described in the prior art, for example in documents WO 09/047466; WO 10/109118; WO 10/109119; WO 2011/031411; WO 2011/117530: WO 2014/080144; WO 2016/066944; WO 2016/139434 in the name of the Applicant.

These methods are for the most part based on the principle of compatibility between the CNTs and the host matrix leading to a homogeneous dispersion of the CNTs, and consequently aim at modifying the NTC-host matrix interfaces.

For this purpose, organic compounds can be introduced to modify the NTC - host matrix interfaces, generally these are surfactants, dispersants, plasticizers, or other compound of an essentially organic nature.

The presence of an organic compound on the surface of CNTs is acceptable for many application sectors. However, certain fields of application require the use of pure CNTs, in particular CNTs free of organic compounds liable to contaminate the matrix into which they are introduced to form a composite material with improved properties.

There therefore remains a need to have carbon nanotubes free of any trace of organic contaminant on their surface and in an agglomerated solid form suitable for the preparation of homogeneous dispersions.

Thus, the present invention meets this need by providing an agglomerated solid material comprising carbon nanotubes free of organic compounds which are no longer in the form of primary aggregates such as obtained during the synthesis of these carbon nanotubes.

SUMMARY OF G INVENTION

The invention relates firstly to an agglomerated solid material comprising disaggregated carbon nanotubes (CNTs) free from organic compounds, consisting of a continuous network of carbon nanotubes comprising aggregates of carbon nanotubes of average size d50 less than 5. mhi, in a proportion of less than 60% by surface determined by image analysis by electron microscopy.

The agglomerated solid material according to the invention has an apparent density of between 0.01 g / cm 3 and 2 g / cm 3 .

The agglomerated solid material can be in any coarse form, or for example in spherical, cylindrical form, in the form of scales, granules, bricks or other massive bodies etc., the smallest dimension of which is greater than one millimeter, of preferably greater than 3 mm, without there being any limitation in size.

According to a preferred embodiment, the agglomerated solid material is in the form of granules.

The term “free from organic compounds” means that the loss in mass between 150 ° C. and 350 ° C. is less than 1% according to the ATG method in air carried out with a temperature rise of 5 ° C./min.

By “disaggregated”, it should be understood that in mass, the CNTs no longer exhibit the primary aggregates obtained during their synthesis. The morphology of the agglomerated solid material according to the invention does not correspond to a material retaining the shape memory of the primary aggregates resulting from the synthesis of CNTs, but the size (diameter, number of walls) of the CNTs constituting this agglomerated solid material n is not changed. The present invention therefore excludes the agglomerated solid material consisting of carbon nanotubes in the form of compressed primary aggregates. The morphology of the agglomerated solid material of the invention is characterized by image analysis by electron microscopy leading to the determination of the average proportion of aggregates of size d50 less than 5 μm present on a sample surface of 20 x 20. mhi2 using the following method:

Ten electron microscopy images are taken on a 20 µm x 20 µm area, including 5 in areas rich in aggregates and 5 in areas where aggregates are less visible. All images are taken on a fresh fracture of the solid material.

The images are analyzed so as to select the identifiable shapes of size between 0.5 and 5mhi. Identifiable forms are either aggregates (light areas) or voids (dark areas).

The gray areas allocated to the continuous network of CNTs are considered as the surface of the image background which is not covered by the identifiable shapes.

The% of the image area filled with identifiable shapes is calculated as follows: S (identifiable shapes, in mhi 2 ) * 100 / 400mhi 2 .

By “continuous network” is meant the background image by electron microscopy of the agglomerated solid material, which is not covered by aggregates of size d50 less than 5 μm. According to the invention, the continuous CNT network does not have a clearly defined shape or form and is unclassifiable at the scale of 0.5 - 5 microns.

According to the invention, the continuous network represents more than 40% in area according to image analysis.

According to one embodiment of the invention, the surface of the carbon nanotubes constituting the agglomerated solid material may exhibit a certain level of oxidation.

According to one embodiment of the invention, the agglomerated solid material may contain at least one chemical compound of inorganic nature intimately included in the continuous network of carbon nanotubes. Inorganic materials include entities of a metallic, carbon, silicon, sulfur, phosphorus, boron, and other solid nature; oxides, sulphides, nitrides of metals; hydroxides and salts; ceramics of complex structure or mixtures of all these inorganic materials.

According to one embodiment, the agglomerated solid material contains carbon in the form of other carbon nanofillers such as graphene, graphite or carbon black at a content suitable for the envisaged application.

These chemical compounds of inorganic nature can have a different form factor, isotropic or anisotropic and a maximum dimension of 1 mm.

According to one embodiment, the bulk density of the agglomerated solid material is between 0.1 g / cm 3 and 2 g / cm 3 , preferably between 0.1 and 1.0 g / cm 3 .

The invention also relates to a process for preparing said agglomerated solid material.

The preparation process according to the invention is characterized in that it comprises at least one step of compressing a CNT powder in the presence of at least one sacrificial substance, and optionally of at least one inorganic compound, followed by high shear mixing of the powder in the compressed state, then shaping to obtain an agglomerated solid material and final removal of the sacrificial substance.

The CNT powder may be a CNT powder directly coming from the synthesis reactor, or a CNT powder having undergone a preliminary grinding and / or a purification treatment or any chemical treatment, or mixture with a compound of inorganic nature.

The step of compressing the CNT powder leads to denser compacted CNTs, with an apparent density markedly greater than the apparent density of the CNTs in the powder state.

The high-shear mixing of the powder in the compressed state makes it possible to shear the CNT aggregates present in the powder, in order to reduce their size, and simultaneously to change the nature of the entanglement of the CNTs in the aggregates, or even completely eliminate the aggregates, so as to obtain a continuous network of CNTs.

The compression step and the high shear mixing step are advantageously carried out in a compounding device.

The term “sacrificial substance” is understood to mean a substance which does not modify the surface of the CNTs after its final elimination. It can be a liquid, solid or supercritical compound. The sacrificial substance can be water, a solvent, an organic molecule or a polymer, or mixtures thereof in any proportion. The sacrificial substance can be hydrophilic or hydrophobic in nature.

The sacrificial substance can be removed by any means suitable to its nature, for example by drying, calcination, thermal cracking, pyrolysis, degassing, etc. The sacrificial substance is chosen so that its elimination can be carried out completely without leaving any trace or residue in the final product.

The mass ratio between the CNTs and the sacrificial matrix is ​​chosen as a function of the density of the desired agglomerated solid material.

Advantageously, the percentage of porosity of the agglomerated solid material corresponds to the volume fraction of the sacrificial substance used in the process.

According to one embodiment, the process for preparing the agglomerated solid material according to the invention is characterized in that it comprises at least the following steps:

a) The introduction into a compounding device of CNTs in powder form and of at least one sacrificial substance in a mass proportion ranging from 10/90 to 40/60, preferably from 10/90 to 32/68 , and optionally at least one inorganic compound;

b) mixing the CNTs and the sacrificial substance within said device to form a mixture in agglomerated physical form;

c) recovering the mixture as an agglomerated solid;

d) elimination of the sacrificial matrix.

Steps b) and c) can be repeated in order to achieve a greater level of disaggregation.

The term “compounding device” is understood to mean, according to the invention, an apparatus conventionally used in the plastics industry for the mixture in the molten state of thermoplastic polymers and additives with a view to producing composites.

Compounding devices are well known to those skilled in the art and generally comprise supply means, in particular at least one hopper for pulverulent materials and / or at least one injection pump for liquid materials; high shear mixing means, for example a co-rotating or counter-rotating twin-screw extruder or a co-kneader, a conical mixer, or any type of screw mixer, usually comprising an endless screw disposed in a barrel heated (tube) or multi-chamber internal mixer; an exit head which shapes the exiting material; and means for cooling, in air or using a water circuit, the material. This is usually found in the form of a rush

leaving the device continuously and which can be cut or formed into granules. Other shapes can however be obtained by fitting a die of the desired shape to the outlet die.

Another subject of the invention is the agglomerated solid material obtainable according to the process of the invention.

The use in a certain proportion of a sacrificial substance in the process according to the invention makes it possible to adapt the density and / or the porosity desired for the agglomerated solid material.

The disaggregated CNTs constituting the agglomerated solid material obtained according to the process of the invention have a better ability to be dispersed in a wide variety of media, liquid, solid, or in the molten state, compared to the CNTs in the state of. powder. They are therefore advantageously used to confer improved properties, in particular of conductivity or of mechanical resistance, in numerous fields of application.

The invention also relates to the use of the solid material agglomerated according to the invention or obtained according to the process of the invention for integrating carbon nanotubes in liquid formulations with an aqueous or organic base.

The invention also relates to the use of the solid material agglomerated according to the invention or obtained according to the process of the invention for the manufacture of composite materials, of thermoplastic or thermosetting type.

The invention also relates to the use of the solid material agglomerated according to the invention or obtained according to the process of the invention for the preparation of elastomeric compositions.

The invention also relates to the use of the solid material agglomerated according to the invention or obtained according to the process of the invention for the manufacture of battery and supercapacitor components.

The invention also relates to the use of the solid material agglomerated according to the invention or obtained according to the process of the invention for the preparation of electrode formulations for lithium-ion batteries, lithium-sulfur batteries, sodium batteries. -Sulfur, or lead acid batteries or other types of energy storage system.

The invention also relates to the use of the solid material agglomerated according to the invention or obtained according to the process of the invention for preparing catalytic supports constituting electrodes.

The present invention makes it possible to overcome the drawbacks of the state of the art while respecting the constraints related to health and industrial hygiene.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates on SEM the morphology of the agglomerated solid material according to the invention.

FIG. 2 illustrates with SEM the morphology of a CNT powder (comparative) DETAILED DESCRIPTION OF THE INVENTION

The invention is now described in more detail and in a nonlimiting manner in the description which follows.

The disaggregated carbon nanotubes constituting the agglomerated solid material according to the invention can be of the single-walled (SWNT), double-walled (DWNT) or multi-walled (MWNT) type.

The carbon nanotubes usually have an average diameter ranging from 0.1 to 200 nm, preferably from 0.1 to 100 nm, more preferably from 0.4 to 50 nm and, better, from 1 to 30 nm, or even 10 at 15 nm, and advantageously a length of more than 0.1 μm and advantageously from 0.1 to 20 mhi, preferably from 0.1 to 10 mhi, for example about 6 mhi. Their length / diameter ratio is advantageously greater than 10 and most often greater than 100.

They can be with closed and / or open ends. These nanotubes are generally obtained by chemical vapor deposition. Their specific surface is for example between 100 and 300 m 2 / g, advantageously between 200 and 300 m 2 / g, and their apparent density can in particular be between 0.01 and 0.5 g / cm3 and more preferably between 0 , 07 and 0.2 g / cm3. Multi-walled carbon nanotubes

can for example comprise from 5 to 15 sheets and more preferably from 7 to 10 sheets.

An example of NTC crude in the form of powder used to prepare the NTC disaggregated according to the invention is in particular the tradename Graphistrength ® Cl 00 from Arkema.

According to one embodiment of the invention, the disaggregated CNTs comprise metallic or mineral impurities, in particular the metallic and mineral impurities originating from the synthesis of crude CNTs in the powder state. The amount of non-carbonaceous impurities can be between 2 and 20% by weight.

According to one embodiment of the invention, the disaggregated CNTs are free from metallic impurities, and result from crude CNTs in the powder state which have been purified in order to remove the impurities inherent in their synthesis.

The purification of the crude or ground nanotubes can be carried out by washing with a sulfuric acid solution, so as to rid them of any residual mineral and metallic impurities, such as for example iron from their preparation process. . The weight ratio of the nanotubes to sulfuric acid can in particular be between 1: 2 and 1: 3. The purification operation can moreover be carried out at a temperature ranging from 90 to 120 ° C., for example for a period of 5 to 10 hours. This operation can advantageously be followed by steps of rinsing with water and of drying the purified nanotubes. The nanotubes can alternatively be purified by heat treatment at high temperature, typically greater than 1000 ° C.

According to one embodiment of the invention, the disaggregated CNTs are oxidized CNTs.

The oxidation of the nanotubes is advantageously carried out by bringing them into contact with a sodium hypochlorite solution containing from 0.5 to 15% by weight of NaOCl and preferably from 1 to 10% by weight of NaOCl, for example in a weight ratio of nanotubes to sodium hypochlorite ranging from 1: 0.1 to 1: 1. The oxidation is advantageously carried out at a temperature below 60 ° C. and preferably at room temperature, for a period ranging from a few minutes to 24 hours. This

oxidation operation can advantageously be followed by stages of filtration and / or centrifugation, washing and drying of the oxidized nanotubes.

The disaggregated CNTs form a continuous network comprising aggregates of CNTs of average size d50 less than 5 mhi, in a proportion of less than 60% by area determined by image analysis by electron microscopy.

The proportion of aggregates of average size d50 less than 5 mhi is preferably less than 40% by area, more preferably less than 20% by area, or even less than 10% by area.

The continuous network of CNTs preferably represents more than 60% by surface, more preferably more than 80% by surface, or even more than 90% by surface, according to image analysis by electron microscopy.

Disaggregated CNTs are free from organic compounds on their surface.

A process for preparing the disaggregated CNTs constituting the agglomerated solid material of the invention uses a compounding device to compress a CNT powder and shear the CNT aggregates so as to reduce their size and the entanglement of the CNTs.

Examples of co-mixers which can be used according to the invention are the BUSS® MDK 46 co-mixers and those of the BUSS® MKS or MX series, sold by the company BUSS AG, which all consist of a screw shaft provided with 'fins, arranged in a heating sleeve optionally made up of several parts and the inner wall of which is provided with mixing teeth adapted to cooperate with the fins to produce shear of the mixed material. The shaft is rotated, and provided with an oscillating movement in the axial direction, by a motor. These co-mixers can be equipped with a granule production system, adapted for example to their outlet orifice, which can consist of an extrusion screw or of a pump.

The co-kneaders which can be used according to the invention preferably have an L / D screw ratio ranging from 7 to 22, for example from 10 to 20, while the co-rotating extruders advantageously have an L / D ratio ranging from 15 to 56, for example from 20 to 50.

To achieve optimal shear of CNT aggregates as well as minimal entanglement of CNTs in aggregates, it is generally necessary

to apply, in the compounding device, a significant mechanical energy, which is preferably greater than 0.05 kWh / kg of material.

According to the process of the invention, the compounding of the powder is carried out in the presence of a sacrificial substance in a mass ratio ranging from 10:90 to 40:60, preferably from 10:90 to 32:68, or even from 20 : 80 to 30: 70, so as to obtain agglomerated particles comprising disaggregated CNTs and the sacrificial substance, the sacrificial substance then being removed to form the disaggregated CNTs free of organic compounds. It has indeed been shown that in this report, compounding can be done optimally for a wide range of sacrificial substances.

As sacrificial substances, it is possible to use, without this list being limiting, a solvent which leaves no residue after its removal by drying from the agglomerated solid material, or an organic substance which leaves no residue after pyrolysis of the agglomerated solid material. , or a substance in the supercritical state which leaves no residue after degassing, for example supercritical C0 2

Preferably, water, an alcohol or other hydrophilic solvents are used as solvent, as well as their mixtures, preferably water.

Preferably, a polymer such as polypropylene PP, polyethylene terephthalate PET, polycarbonate PC, polyamide PA, preferably polypropylene PP, is used as organic substance.

According to one embodiment, it is possible to add, to the compounding device, inorganic compounds such as oxides, metal salts in order to obtain an agglomerated solid material of disaggregated CNTs comprising inorganic compounds beneficial for the application. considered. Mention may be made, for example, of sodium hydroxide, zinc oxide or titanium oxide, a carbonate, a hydroxide, a metal oxide or sulphide, for example of lithium, manganese, nickel or cobalt.

It is also possible to add other carbon nanofillers such as graphene, graphite or carbon black at a content suitable for the envisaged application.

The invention will now be illustrated by the following examples, which are not intended to limit the scope of the invention, defined by the appended claims.

EXAMPLES

Example 1: Preparation of an agglomerated solid material of disaggregated CNTs with a polypropylene (PP) as sacrificial substance

A PP homopolymer, grade PPH 155 (produced by BRASKEM) was used as the sacrificial substance. The carbon nanotubes (Graphistrength ® Cl 00 from ARKEMA) and PPH 155 were introduced in a 25/75 mass proportion using two gravimetric feeders in the hopper of a BUSS ® MDK 45 co-mixer equipped with a take-up extrusion screw and a granulation device.

The temperature of the two heating zones of the co-mixer is 290 ° C and 240 ° C. The profile of each mixer zone has the restriction ring ensuring the compression of the material undergoing the mechanical shear applied by the screw of the co-mixer. The take-up extruder was set at 250 ° C. The final composition was then formed into cylindrical shaped granules 3.5mm in diameter and 3-4mm in length.

500 g of granules were passed through a vertical cylindrical 3-liter oven, gradually heated at 10 ° C / min up to 400 ° C under a stream of nitrogen, and maintained at 400 ° C for 1 hour, then cooling in the oven. ambient temperature. Granules of the same size as the starting formulation were discharged.

The TGA measurement carried out on this agglomerated solid material of disaggregated CNTs demonstrates the absence of loss of mass between 150 and 250 ° C., which signifies the absence of organic substance likely to be present after thermal decomposition.

The density of the agglomerated solid material obtained is estimated at 0.24 g / cm 3 .

Ligure 1 illustrates by SEM electron microscopy the morphology of this agglomerated solid material. According to this image, the proportion of CNT aggregates of average size d50 less than 5 mhi represents 3% on the surface.

By way of comparison, FIG. 2 illustrates the morphology of a crude CNT powder, exhibiting a granular structure on the scale of 2 mhi, characterized by the presence of CNT aggregates in a proportion greater than 90% on the surface.

Example 2: Preparation of an agglomerated solid material of disaggregated CNTs with water

In this example, the sacrificial matrix used is demineralized water.

The equipment used is identical to that of example 1.

The CNTs ( ARKEMA Graphistrength ® Cl 00) were introduced into the hopper of the co-mixer by the gravimetric doser, and the water, preheated to 60 ° C, was injected by the piston pump into the 1st zone of the co-mixer. The dosage of CNTs was set at 25% by mass relative to water. The temperature of the mixture was kept below 100 ° C.

The mixture was formed into granules 4 mm in diameter and length.

4-5 mm. Then, the granules were passed through a ventilated oven heated to 130 ° C. After 3 h of drying, the agglomerated solid material of CNT in the form of granules has the same appearance as the material obtained in Example 1.

The density is estimated at 0.22 g / cm 3

Example 3 Production of polymer-based formulations with an agglomerated solid material of disaggregated CNTs according to the invention

EPDM gum, VISTALON 2504N grade, was used as polymer base.

The reference formulation without carbon additive is as follows:

2 phr stearic acid

ZnO 5 phr

ZDTP (Mixland + 50GA F500) 3.1 phr

TBBS (Mixland + 75GA F500) 2.67 phr

S80 (Mixland S80 GAF500) 1.5 phr

CNTs were added at 3 phr and at 7 phr in 4 different forms:

Formulation 1: Agglomerated solid material according to the invention of Example 1 Formulation 2: Agglomerated solid material according to the invention of Example 2 - Formulation 3: CNTs in powder form, commercial grade of ARKEMA Graphistrength ® C 100

- Formulation 4: ARKEMA Commercial Master Mix: Graphistrength C

EPDM 20, containing 20 phr of CNT Graphistrength ® Cl 00

Preparation of formulations

the ere mixing step

The mixer used has a mixing capacity of approximately 260cm3 (Figure 1). The mixer chamber has two Banbury tangential type rotors. The rotors are driven by a motor fitted with a speed variator.

Mixing protocol:

T tank = 90 ° C

Table 1

2nd step: formulation with vulcanization additives on the external mixer

The roller mixer consists of two cylinders rotating in opposite directions of rotation at identical or different speeds. The ratio between the 2 speeds is called the coefficient of friction.

The external mixer is used here to achieve a dispersive state in the mixture and to introduce the vulcanization system (sulfur and accelerators).

Table 2

The densities were measured on the raw materials after introduction of the vulcanization system, on a helium pycnometer. The mixtures more loaded with CNT are logically more dense than the more weakly loaded mixtures.

Table 3

Formulations 1 and 2 prepared with the agglomerated solid material comprising disaggregated CNTs have values ​​of comparable density.

Formulation 3 prepared with the CNTs in the form of the primary aggregates (Graphistrength Cl 00) is characterized by a lower density due to the defects of the possible dispersion.

A Mooney MV One apparatus (TA instruments) is then used for the characterization of the viscosity. This test consists in measuring the torque to be applied to rotate a flat rotor at constant speed (2 rpm 1 ) in a sealed cylindrical chamber filled with rubber, with a volume equal to 25 cm 3 , and heated at constant temperature.

The resistance offered by the rubber to this rotation corresponds to the Mooney consistency of the elastomer. It is expressed in an arbitrary unit proportional to the measured torque and called the Mooney Unit (MU).

It is established that 1 Mooney unit equals 0.083 Nm

The introduction of a higher level of CNT leads to an increase in the Mooney ML (1 + 4) 100 ° C for each formulation. The more the viscosity increases, the better the distribution of CNTs in the volume.

Table 4

Formulations 1 and 2 are superior to formulation 3 comprising crude CNTs introduced in powder form.

Formulations 1 and 2 are superior to formulation 4 which comprises CNTs already pre-dispersed in a masterbatch.

These results confirm that the disaggregated CNTs present in the agglomerated solid material according to the invention show a higher dispersability compared to the crude CNT powder, and also greater compared to crude CNTs already pre-dispersed in the same polymer matrix.

Example 4: Vulcanized materials containing the agglomerated solid material according to the invention

The shaping of the elastomeric base formulations obtained in Example 3 was carried out by thermocompression on a 30T plate press. The raw mixture is positioned in a 2mm thick frame between two Teflon papers themselves sandwiched in two steel plates. The forming temperature is fixed at 165 ° C., and the vulcanization time is determined by a kinetics measurement carried out on the RP A measuring apparatus.

The kinetic monitoring of the vulcanization of the mixtures was carried out in a rheometer with a moving chamber. An RPA Elite rheometer from TA Instruments was used.

The sample, with a volume of 4 cm3, is placed in a thermally regulated chamber. We measure the change in the resistive torque opposed by the rubber to a low amplitude oscillation (0.2; 0.5; 1; 3 ° of arc) of a biconical rotor. The oscillation frequency is fixed at 1.67 Hz.

The measurements were carried out at a temperature of 180 ° C for 20 minutes with an angle of 0.5 ° of arc.

The values ​​of t95 measured by RPA are in Table 5 below:

Table 5

The plates were molded at 180 ° C at t95 on the 30T platen press. The mechanical tests were carried out according to standard IS037 on an INSTRON Universal traction machine at room temperature. The standardized specimens were cut beforehand:

As shown by the results of Table 6, formulations 1, 2 and 4 are all superior in tensile strength compared to formulation 3 made with powdered CNTs.

The disaggregated CNTs present in the agglomerated solid material prepared in Example 2 in the hydrophilic medium exhibit slightly lower performance than those obtained with the disaggregated CNTs present in the agglomerated solid material prepared in Example 1 in the hydrophobic medium.

Table 6

The mechanical behavior at 60 ° C was evaluated for the 4 formulations.

The strain scanning tests (Table 7) were carried out at 10Hz and 60 ° C on samples crosslinked for 10 minutes at 180 ° C, vulcanization done in RPA.

Table 7

As expected, the PAYNE or non-linearity effect, represented by delta G *, is greater for charged mixtures. This parameter is linked to the state of dispersion. According to this criterion, the disaggregated CNTs according to Example 2 give a very good result for dispersability, superior to the masterbatch of the state of the art (formulation 4). The lower tensile results of formulation 2 can be explained more by the more favorable CNT / EPDM interfaces in hydrophobic systems.

Example 5: Electrical performance of the formulations.

Measurements of electrical resistance R are carried out on plates 2mm thick and 100x100mm in size. In this case, it is possible to measure the surface or volume conductivity. From the resistance measurement and depending on the geometry of the test piece and the probe, the resistivity p (W.ah) or the electrical conductivity s = 1 / r (S. cm 1 ) is calculated . Or using strips of crosslinked mixtures on which an electrode is painted with silver lacquer, a volume measurement is obtained.

The results obtained for the 4 formulations are collated in Table 8 below.

Table 8

The agglomerated solid material of the invention makes it possible to approach the antistatic domain, even at the low rate of 3 phr, by marking the start of percolation.

At 7 phr, it is formulation 2 which demonstrates a performance at the same level as formulation 4 of the state of the art, prepared from a masterbatch comprising a pre-dispersion of crude CNTs, which is at to date the best technological approach, transposable to industrial scale.

The agglomerated solid material of the invention makes it possible to obtain results that are similar or superior to this reference of the state of the art, in terms of mechanical or electrical properties.

The agglomerated solid material of the invention can be used for a wide choice of polymer matrices, and thus becomes a universal solution for efficiently introducing CNTs, unlike the “masterbatch” approach which requires a similar nature of the matrix of the invention. NTC concentrate and polymer matrix application.

CLAIMS

1. Agglomerated solid matter in any coarse form, the smallest dimension of which is greater than one millimeter, preferably greater than 3 millimeters, comprising disaggregated carbon nanotubes (CNTs) free of organic compounds, consisting of a continuous network of nanotubes of carbon comprising aggregates of carbon nanotubes of average size d50 less than 5 mhi, in a proportion of less than 60% by area, preferably less than 40% by area, determined by image analysis by electron microscopy, characterized in that that it has an apparent density of between 0.01 g / cm 3 and 2 g / cm 3 .

2. Material according to claim 1, characterized in that it comprises at least one chemical compound of inorganic nature intimately included in the continuous network of carbon nanotubes.

3. Material according to claim 1 or 2 characterized in that it has an apparent density between 0.1 g / cm 3 and 2 g / cm 3 , preferably between 0.1 and 1.0 g / cm 3. .

4. Process for preparing an agglomerated solid material as defined in any one of claims 1 to 3, characterized in that it comprises at least one step of compressing a powder of carbon nanotubes in the presence of at least one sacrificial substance, and optionally at least one inorganic compound, followed by mixing the powder at high shear in the compressed state, then shaping to obtain an agglomerated solid material and final elimination of the sacrificial substance.

5. Method according to claim 4, characterized in that it comprises at least the following steps:

a) the introduction into a compounding device of carbon nanotubes in the powder state and of at least one sacrificial substance in a mass proportion ranging from 10/90 to 40/60, preferably from 10/90 to 32 / 68, and optionally at least one inorganic compound;

b) kneading the carbon nanotubes and the sacrificial substance within said device to form a mixture in agglomerated physical form;

c) recovering the mixture as an agglomerated solid;

d) elimination of the sacrificial matrix.

6. Method according to claim 4 or 5, characterized in that the sacrificial substance is a solvent which leaves no residue after its removal by drying the agglomerated solid material, an organic substance which leaves no residue after pyrolysis of the agglomerated solid matter, or a substance in the supercritical state.

7. Method according to any one of claims 4 to 6, characterized in that the carbon nanotubes in the powder state are crude, purified and / or oxidized.

8. Method according to any one of claims 4 to 7 characterized in that the inorganic compound comprises entities of metallic nature, carbon, silicon, sulfur, phosphorus, boron, and other solid elements; oxides, sulphides, nitrides of metals; hydroxides and salts; ceramics of complex structure or mixtures of all these inorganic materials.

9. Agglomerated solid material capable of being obtained according to the process as defined according to any one of claims 4 to 8, characterized in that its percentage of porosity corresponds to the volume fraction of the sacrificial substance used in said process. .

10. Use of the agglomerated solid material according to any one of claims 1 to 3 or according to claim 9 for integrating carbon nanotubes in liquid formulations with an aqueous or organic base.

11. Use of the agglomerated solid material according to any one of claims 1 to 3 or according to claim 9 for the manufacture of composite materials, of thermoplastic or thermosetting type.

12. Use of the agglomerated solid material according to any one of claims 1 to 3 or according to claim 9 for the preparation of elastomeric compositions.

13. Use of the agglomerated solid material according to any one of claims 1 to 3 or according to claim 9 for the manufacture of battery components and supercapacitors.

14. Use of the agglomerated solid material according to any one of claims 1 to 3 or according to claim 9 for the preparation of electrode formulations for lithium-ion batteries, lithium-sulfur batteries, sodium-sulfur batteries, or lead acid batteries or other types of energy storage system.

15. Use of the agglomerated solid material according to any one of claims 1 to 3 or according to claim 9 for preparing catalytic supports constituting electrodes.