WO2016097544A1

WO2016097544A1 - Mixing device for the manufacture of a composite material from a powder comprising carbon-based nanofillers and an elastomer resin

Info

Publication number: WO2016097544A1
Application number: PCT/FR2015/053415
Authority: WO
Inventors: Alexander Korzhenko; Serge Bordere; Amélie Merceron
Original assignee: Arkema France
Priority date: 2014-12-16
Filing date: 2015-12-10
Publication date: 2016-06-23
Also published as: FR3029926B1; FR3029926A1

Abstract

Mixing device (1) and process for the manufacture of a composite material from at least one powder comprising carbon-based nanofillers such as CNTs, and at least one elastomer resin, comprising a mixer (2) that makes it possible to mix the powder with the elastomer resin, a feed system (10) that makes it possible to introduce the powder into the mixer, said feed system comprising a charging device (14) that cooperates with a feed screw (11) that opens into the mixer, a piston (30) capable of being displaced from the chimney (5) in the mixer, and contributing with said mixer to the mixing of the powder with the elastomer resin.

Description

MIXING DEVICE FOR MANUFACTURING COMPOSITE MATERIAL FROM A POWDER COMPRISING NANOCHARGES

CARBONES AND ELASTOMERIC RESIN

The invention relates to the field of composite materials based on polymeric resins, and more particularly that of composite materials obtained from polymer resin and carbon nanofillers.

In the following description is meant by carbon nanofillers, carbon nanotubes (CNTs), carbon nanofibers, graphene, carbon black, or a mixture of said carbon nanofillers, or carbon nanotubes in association with another nanoburden.

[0003] The ^invention applies particularly but not exclusively to the realization of composite materials obtained from polymeric resin and carbon nanotubes (CNTs) alone or in combination with the above nanofillers.

More particularly, the invention relates to a device for the manufacture of a composite material from at least one powder comprising carbon nanofillers and preferably carbon nanotubes (CNTs), and at least one resin polymer consisting of a thermosetting elastomeric resin. The invention also relates to a method of manufacturing such a composite material, as well as a composite material part obtained by the implementation of this method.

[Prior art] [0005] Elastomers are polymers with rubber-elastic properties which find application in various fields, including the manufacture of automotive parts such as tires, seals or tubes, pharmacy, electrical industry , transport or building, for example. In some of these applications, it may be advantageous to give them electrical conduction properties and / or to improve their mechanical properties. To do this, it is possible to incorporate conductive fillers such as carbon nanotubes (or CNTs).

[0006] The ^{incorporation} of nanofillers as CNTs in elastomer compositions is, in ^industry, conditioned by mixing techniques and equipment used. Under customary conditions, a polymer resin, particularly an elastomeric resin, is introduced into a mixer, and then other components are added to the elastomeric resin, in the mixer, and in predetermined amounts. However, this technique is difficult to apply in the case of adding nanofillers such as CNTs to an elastomeric resin. Indeed, CNTs tend to form aggregates. Thus, a portion of the CNTs introduced into the mixer remain in the form of aggregates which are then encapsulated in the resin instead of being dispersed homogeneously within said resin. Another part of the CNTs is positioned in the mixer without mixing with the resin, and is often lost in the drain press or carried away by the ^air flow circulating in the ^{installation.}

[0007] WO 2007/035442 describes a process for incorporating from 0.1 to 30% by weight, and preferably from 0.1 to 1% by weight, of CNT into a liquid or solid silicone resin base, consisting of to disperse these in the resin base using conventional mixing devices, roll mills or ultrasound. Example 7 of this document more specifically discloses a 25 weight percent masterbatch of CNTs. prepared by dispersion of the CNTs in a silicone resin base using a mixer 2 Waring (knife mixer). The masterbatch obtained is in the form of a wet free powder.

The technique proposed in this document does not disperse amounts greater than 25% by weight of charges as low apparent density as the CNTs. In particular, it is not possible to incorporate in the resins these levels of CNT without substantially forming aggregates of more than 10 pm from them, given their naturally very entangled structure. This poor dispersion of CNTs leads to embrittlement of the composites formed therefrom, which is reflected in particular by the appearance of nanofissures.

Furthermore, knowing that the apparent density of the CNTs is about ten times lower than that of the elastomeric resin, the loading of the CNTs in the mixer is not easy. It is often performed via large volume bags containing a predetermined amount of CNT powder, which is poured directly into the mixer. The disadvantage of this method is that it leads to a heterogeneous mixture of CNTs within the elastomeric resin, which generally results in resins or composite materials having poor mechanical properties.

[0010] WO 2010/109118 discloses a method for preparing a composite material containing more than 5% by weight and ^up to 70% by weight of carbon nanotubes, and comprising introducing a resin elastomer and CNT in a co-kneader, kneading these two components, then recovering the formed composite material. The CNT powder is introduced into the co-kneader through the feed hopper of said co-kneader. However, this document does not disclose a method ^of introducing the special CNT powder in the co-kneader to prevent the CNT aggregates forming in said mixer and obtaining ^of a homogeneous mixture of CNTs in the elastomeric resin.

[001 1] We can also refer to the state of the art consisting of US 4,022,440. This document describes a device for manufacturing a plastic material. The device comprises a cylinder fed by an inlet by means of a hopper containing a thermoplastic or thermosetting polymer resin mixture and additives via a screw conveyor and a piston. In this document, the resin and additive I are both introduced into the hopper, then fed to ^the input of the mixer by the screw conveyor under the effect of the piston which then allows to close said inlet. The piston is movable in the inlet and allows to bring the resin-additive mixture of the screw conveyor to the cylinder.

Reference may also be made to the state of the art consisting of the document US Pat. No. 5,297,865. This document describes a machine for mixing a thermoplastic material with fillers. The mixing machine comprises a packaging machine / heating screw thermoplastic material, and an injection die opening on a mixing chamber and for injecting the conditioned thermoplastic material in said mixing chamber. According to this document, the charges are introduced into the mixing chamber via a handle and the thermoplastic material is introduced via the screw conditioning / heating machine provided with the injection die. The punch described serves to facilitate the entry of the charges into the mixing chamber and to close the latter. This document describes a machine in which the introduction of the thermoplastic material and the introduction of the charges into the mixer are performed by separate introduction means which are respectively the screw machine and the supply shaft.

None of the documents of the state of the art can solve the problem of control and regulation of the introduction of the nanofillers powder when it is mixed with an elastomeric resin.

The invention therefore aims to overcome the disadvantages of the prior art by providing a device for the manufacture of a composite material from at least one powder comprising carbon nanotubes (CNTs), and at least one elastomeric resin base for controlling and regulating the introduction of the powder comprising CNTs when mixing the elastomeric resin with said powder. The device thus makes it possible to obtain a homogeneous mixture of the powder with the elastomeric resin, and thus to obtain a composite material having good mechanical properties. The device also makes it possible to manufacture a composite material optimally ensuring the safety of the operator. [Brief description of the invention]

For this purpose, the subject of the invention is a mixing device for the manufacture of a composite material from at least one powder comprising carbon nanofillers, and at least one elastomeric resin, mainly characterized by it comprises: - a mixer for mixing the powder with the elastomer resin, said mixer comprising a chimney, a feed system for introducing the powder into the mixer, said feed system comprising a loading device cooperating with a feed screw opening into the mixer, a piston able to move in the chimney of the mixer and to contribute with said mixer to the mixture of the powder with the elastomeric resin.

According to other optional characteristics of the mixing device:

- The loading device comprises a container connected to a double valve coupling device ensuring the passage of the powder in the feed screw in a secure manner;

- The coupling device comprises an active valve connected to the container and a passive valve connected to the inlet for introducing the powder into the feed screw, the active valve and the passive valve being intended to be connected to enable the transfer powder from the container into the feed screw;

- The feed screw of the feed system has a length / diameter ratio, said L / D ratio, ranging from 10 to 70, preferably from 20 to 70 and preferably from 40 to 60. - The mixer comprises a lock of loading constituting the inlet of said mixer, the loading lock being connected to the feed screw, so that the powder enters directly into said lock after the output of the feed screw, said mixer further comprising a mixing chamber located under the loading chamber and capable of communicating with said airlock;

- The loading chamber is provided with a sealed secure closure separating said loading chamber from the mixing chamber;

Advantageously, the secure closure is achieved by its piston head and / or by a door. - The loading chamber further comprises a door for the introduction of the polymer resin in said lock;

- Advantageously, the resin introduction door is fixed to the airlock so as to tilt back outside the airlock, said door further comprises flanks on the sides facilitating the introduction of the resin. The mixer comprises extraction means comprising prefilters and filters;

The powder comprising carbon nanofillers comprises carbon nanotubes (CNTs) or carbon nanofibers or graphene. or carbon black, or a mixture of said carbon nanofillers, or preferably carbon nanotubes alone or in combination with another nanofiller.

- The powder comprising carbon nanofillers introduced into the mixer further comprises at least one vulcanizing agent;

- The powder comprising carbon nanofillers introduced into the mixer further comprises at least one additive.

Advantageously, the powder comprising carbon nanofillers comprises carbon nanotubes (CNTs).

The invention also relates to a method for manufacturing a composite material comprising at least one powder comprising carbon nanofillers, and at least one elastomeric resin, said method being implemented by the mixing device described above. mainly characterized in that it comprises the following steps: a) introduction of the elastomeric resin into the mixer, b) introduction of the powder in the mixer via the feeding ^system and control the feed rate by adjusting the speed of rotation of the feed screw, c) Mixing of the elastomer resin and the powder in the mixer in order to obtain a composite material, d) shaping of the composite material obtained in step c). [0018] According to ^other optional features of the manufacturing process:

the powder comprising carbon nanofillers comprises carbon nanotubes (CNTs) or carbon nanofibers or graphene, or carbon black; carbon, or a mixture of said carbon nanofillers, or preferably carbon nanotubes alone or in combination with another nanofiller, the powder comprising carbon nanofillers introduced into the mixer further comprises at least one vulcanizing agent,

The powder comprising carbon nanofillers comprises carbon nanotubes (CNTs) or nanofibers of carbon or graphene, or carbon black, or a mixture of said carbon nanofillers, or preferably carbon nanotubes alone or in combination with a carbon nanotube. other nanoburden.

The quantities of elastomer resin and of powder introduced during steps a) and b) are such that they make it possible to obtain a composite material in step c), the mass percentage of which is in the range of 1% to 60%, preferably greater than 10% in this range: preferably greater than 20%, and more preferably greater than 30%.

The mass percentage of CNTs in the composite material is less than 60%, preferably less than 50%, and more preferably less than 40%

The mass percentage of CNTs in the composite material is preferably between 30% and 40%.

During ^step b), the powder comprising CNTs is introduced into the mixer in a sequenced manner according to one or several input sequences of a volume of powder corresponding to a fraction of the total volume of powder to be introduced, each sequence comprising one or more powder introductions;

The powder is introduced into the mixer via the feed system according to an integer number n of sequences, each sequence comprising an integer number i of powder introductions, preferably n is between 1 and 5, and advantageously between 2 and 3 and preferably, i is between 1 and 10, and advantageously between 4 and 8:

The method of manufacturing a composite material comprises, prior to step b), a step of mixing the elastomer resin, then only in the mixer for a period of between 1 minute and 15 minutes, of preferably between 1 minute and 10 minutes, more preferably the mixing time of the elastomeric resin is 5 minutes and the mixing temperature of the elastomeric resin is in a range of 100 ° C to 160 ° C, the resin having a temperature in a range of 40 to 60 ° C before the introduction of carbon nanofillers.

[0019] Other advantages and features of the ^invention will appear on reading the following description given by way ^of illustrative and non-limiting example with reference to the appended figures which represent:

• Figure 1, a diagram of the mixing device, · Figure 2, a diagram of the mixer and the piston, said piston being in the up position,

• Figure 3, a diagram of the mixer and the piston, said piston being in the low position,

• Figure 4 is a light microscope image of a composite plate material obtained by the implementation of the mixing device according to Example 1 according to ^the invention,

FIG. 5, an optical microscope image of a plate made of composite material obtained by the implementation of the mixing device according to example 2, according to the invention. [Detailed description of the invention]

The elastomeric resin comprises or is constituted by. one or more polymers chosen from: fluorocarbon or fluorosilicone polymers; nitrile resins; homo- and copolymers of butadiene, optionally functionalized with unsaturated monomers such as maleic anhydride, (meth) acrylic acid, and / or styrene (SBR); neoprene (or polychloroprene); polyisoprene; copolymers of isoprene with styrene, butadiene, acrylonitrile and / or methyl methacrylate; copolymers based on propylene and / or ethylene and especially terpolymers based on ethylene, propylene and dienes (EPDM), and copolymers of these olefins with an alkyl (meth) acrylate or vinyl acetate; halogenated butyl rubbers; the resins of silicone; polyurethanes; polyesters; acrylic polymers such as poly (butyl acrylate) bearing carboxylic acid or epoxy functions; as well as their modified or functionalized derivatives and their mixtures.

Preferably, the elastomeric resin comprises, or consists of, one or more polymers chosen from: nitrile resins, in particular copolymers of acrylonitrile and butadiene (NBR); silicone resins, in particular poly (dimethylsiloxanes) bearing vinyl groups; fluorocarbon polymers, especially copolymers of hexafluoropropylene (HFP) and vinylidene difluoride (VF2) and terpolymers ^of hexafluoropropylene (HFP), vinylidene difluoride (VF2) and tetrafluoroethylene (TFE), each monomer may be greater than 0% and up to 80% of the terpolymer; and their mixtures.

The following description is made with, as an example embodiment, a powder comprising carbon nanofillers comprising carbon nanotubes (CNTs). The powder described below comprises carbon nanotubes, but in addition to carbon nanotubes, other compounds. It comprises for example at least one vulcanizing agent such as sulfur derivatives or organic peroxides, and optionally a vulcanization accelerator, as well as various additives such as antioxidants, lubricants, pigments (zinc oxide, lithopone for example). ), stabilizers, fillers or reinforcements, antistatic agents, fungicides, flame retardants, texturizing agents, electrical conductivity improvers (structured carbon black, for example). The compounds present in the powder, in addition to the CNTs, are necessarily in powder form so as to form a mixture of powders. Preferably, the particle size of the powder or mixture of powders is less than or equal to 1000 μm. In the following, the term "powder" denotes a powder comprising CNTs or a mixture of powders comprising CNTs may comprise other compounds.

The mixing device 1 for the manufacture of a composite material according to the invention is shown in the Figurel. It comprises a supply system 10 connected to a mixer 2, and for ^introducing a powder comprising CNTs in the mixer. The feed system comprises a feed screw 1 1 connected to a loading device 14 cooperating with said screw for the introduction of the powder into the mixer 2. The feeding screw 1 1 allows the transfer of the powder comprising CNTs from the loading device 14 to the mixer 2. It is located in a sleeve 12 and comprises a helical groove so as to constitute a worm. In addition, it has a Length / Diameter ratio, said L / D ratio, ranging from 10 to 70, preferably from 20 to 70 and preferably from 40 to 60. The sleeve 12 containing the feed screw 11 may be heated. to allow the ^introduction of the powder into the mixer at a higher than ambient temperature. Preferably, the sheath is not heated and the introduction of the powder into the mixer is then carried out at room temperature.

[0026] The ^screw supply 1 1 also includes a rotatable shaft about its longitudinal axis, and the rotation of which is generated by a motor 13. Rotation of ^the shaft causes rotation of the screw, and thus the displacement of the powder located in the cavities of the screw delimited by the shaft, the helical groove, and the sleeve to the mixer.

[0027] The adjustment of the speed of rotation of the ^screw supply 1 1 is used to adjust the feed rate of the powder comprising the CNTs in the mixer 2, and thus to regulate and control the amount of powder introduced into the mixer, so as to obtain an optimal mixture of said powder and the elastomeric resin in said mixer.

A first end of the feed screw 1 1 opens on the loading chamber 3 of the mixer 2, and a second end of said screw is connected to the loading device 14 of the feed system 10. Said loading device powder comprising CNTs comprises a receptacle 18 adapted to be connected to a double valve coupling device 19, of the butterfly valve or Buck® valve type sold by the company GEA Pharma Systems and described in the document WO 2009/098424. In particular, the container 18 consists of a metal drum containing a predetermined quantity of powder comprising NTCs

[0029] As a predetermined amount, is meant an amount of powder such that the final weight percentage of CNT in the composite material, ^that is to say the ratio between the mass of CNT introduced and the mass of composite material obtained, corresponds to the desired value. Preferably, the mass percentage of CNTs in the composite material is NTC is in the range of 1% to 60% and preferably greater than 10% and up to 60%; preferably greater than 10% in this range; preferably greater than 20%, and more preferably greater than 30%. This percentage is preferably less than 60%, preferably less than 50%, and more preferably less than 40%. In a preferred example, the mass percentage of CNTs in the composite material is between 30% and 40%. At this predetermined amount corresponds a volume and a mass of NTC powder.

The double valve coupling device 19 comprises a first valve 15, called the active valve, and a second valve 16, called passive valve. The active valve 15 is connected to the container 18 and the passive valve 16 is connected to the inlet 1 10 ^for introducing the powder of the feed screw January 1. The double valve coupling device 19 comprises an opening control 17 located at the periphery of the active valve 15 and allowing the opening and closing of the valves of the coupling device. Opening is only possible when the two valves are coupled to each other. The control ^opening 17 is locked in the ^absence of coupling. Such a device makes it possible to transfer the powder comprising CNTs to the feed screw safely, without leakage of said CNTs to the external medium, and without contact between the powder comprising CNTs and the external medium. Thus, the volume of powder entering the feed screw corresponds precisely to the volume of powder that it is desired to use for the manufacture of the composite material, initially present in the container 18. It is also possible to control the opening, and in particular the degree of opening of the active and passive valves of the coupling device 19 to vary the rate of introduction of the powder comprising CNTs into the mixer, so as to obtain an optimal mixture of said powder and of the elastomeric resin in the mixer. [0032] The power ^supply system 10 forms a perfectly isolated circuit from the outside environment, so that the transfer of the powder from the container 18 to the mixer 2 is effected without contact between said powder and said external environment. The The volume of powder entering the mixer 2 corresponds precisely to the volume of powder that it is desired to use for the manufacture of the composite material, transferred from the feed screw 1 1. The feed system 10 thus makes it possible to increase substantially the accuracy of the volume of powder introduced into the mixer 2.

Furthermore, the control of the rate of introduction of the powder into the mixer 2 through the feed system 10 allows a better incorporation of the powder comprising CNTs in the elastomeric resin, and thus contributes to obtaining a homogeneous composite material, without aggregates, in particular without CNT aggregates, and having good mechanical and / or electrical properties, being known that CNTs are excellent electrical conductors,

The mixer 2 advantageously comprises a loading chamber 3 constituting the inlet of said mixer, and opening onto the mixing chamber 6. The loading chamber 3 is connected to the feed screw 1 1, so that the powder penetrates directly into said lock after the exit of the feed screw. The loading chamber 3 is surmounted by a chimney 5 and comprises a door 50 allowing the introduction of the polymer resin into said airlock. Advantageously, the door 50 is a door fixed to the lock so as to be able to swing backward outside the airlock, said door also has flanks on the sides facilitating the introduction of the resin. Advantageously, its door 5 is provided with hinges on its lower base to allow tilting back outwards and the flanks close the gap between the airlock and the edges of the door preventing the resin from falling outside the airlock.

The loading chamber 3 is provided with a tight sealed closure 4 separating said loading chamber from the mixing chamber 6. The closure 4 is formed by the piston head 30 and / or by a door provided for this purpose. .

By mixer is meant in the present description, an apparatus conventionally used in the plastics industry for the melt blending of thermoplastic polymers and additives to produce composites. In this apparatus, which usually comprises a rotor provided with vanes adapted to cooperate with teeth mounted on a stator, the polymeric composition and the additives are mixed under high shear. The material melted generally comes out of the apparatus in solid physical form agglomerated, for example in the form of granules, or in the form of rods, tape or film.

Examples of mixers that can be used according to the invention are the BUSS ® MDK 46 mixers and those of the BUSS ® MKS or MX series sold by the company BUSS AG, all of which consist of a screw shaft provided with fins, disposed in a heating sleeve optionally consisting of several parts and whose inner wall is provided with kneading teeth adapted to cooperate with the fins to produce a shear of the kneaded material. The shaft is rotated and provided with oscillation movement in the axial direction by a motor. These mixers may be equipped with a pellet manufacturing system, adapted for example to their outlet orifice, which may consist of an extrusion screw or a pump.

Advantageously, the mixer is an internal mixer with two screws (not shown in the diagrams), allowing optimal mixing of the components.

The mixer 2 is also provided, at its lower end, with a drain hatch 7 located at the base of a receiving hopper 21. Thus, when the step of mixing the elastomer resin and the powder comprising CNTs is complete, the emptying hatch 7 is opened and the newly formed composite material falls into the receiving hopper 21. The emptying flap and the receiving hopper are separated by a safety slide valve 20 preventing in particular the contents of the mixing chamber 6 from falling into the receiving hopper 21 when the emptying hatch has been opened by mistake. When the composite material is formed and the mixing step is complete, the safety slide 20 and the drain hatch 21 open, allowing the transfer of the composite material from the mixing chamber 6 to the receiving hopper 21. The safety slide 20 can be opened before or simultaneously with the opening of the emptying hatch 21.

The mixing device 1 for the manufacture of the composite material further comprises a piston 30 having a body 31 and a base 32. The body 31 of the piston passes through the upper end of the mixing chamber 6, so that part of the piston body is in the chamber and another part is located in the chimney 5 of said chamber. Thus, the piston 30 is able to move in the chimney 5 of the mixer 2 to the mixing chamber 6 between at least a first position, said high position illustrated in Figure 2, and at least a second position, said position. 3. In the up position, the piston 30 is not in contact with the elastomer resin-powder mixture comprising CNTs.

When the piston 30 is in the up position, as shown in FIG.

2, the elastomer-powder resin mixture comprising NTCs occupies a volume VMi, or volume of resin-powder mixture at the i-th powder introduction, defined by its length L, its width I, and its height h. This volume is likely to vary, during the implementation of the manufacturing method according to the invention, between a VM0 volume corresponding to the volume of initial resin-powder mixture when only the polymer resin has been introduced into the mixing chamber, and a VMf volume corresponding to the final mixing volume when all of the powder comprising CNTs was introduced into said mixing chamber.

When the piston 30 is in the lower position, as shown in FIG.

3, a lower portion of the piston, including the base 32, is immersed in the polymer resin - powder mixture. At the volume VMi occupied by the polymer-powder resin mixture at the i-th powder introduction is added the volume of the part of the piston immersed in said mixture denoted VP, so that the total volume at the i-th introduction of powder noted VT is such that VTi = VMi + VP. This volume VTi is defined by its length L, its width I, and its height H, with H greater than h.

The elastomer resin is preferably introduced at one time into the loading chamber 3 by the door 50 and then into the mixing chamber 6 following the opening of the secured door 4 of the loading chamber 3 and / or piston in high position. It is also possible to introduce the elastomeric resin in several times. In any case, all of the elastomeric resin is introduced into the mixing chamber 6 of the mixer 2 prior ^to introduction of the powder comprising the CNTs in said mixer. The elastomer resin is introduced in the solid form, for example in the form of particles ground in the mixer 2 and liquefied in the mixer by heating and shearing before introduction of the CNTs, the temperature of the resin heating up to 40 ° C to 60 ° C.

The powder comprising CNTs is introduced into the mixer 2 sequentially, that is to say according to one or more sequences for introducing a volume of powder corresponding to a fraction of the total volume of powder to be introduced. . Each sequence may include one or more powder introductions. The volume of powder added at each introduction may be the same or different from one introduction to another. Preferably, the volume of powder added at each introduction is identical from one introduction to another. Similarly, the volume of powder introduced at each sequence may be the same or different from one sequence to another. Preferably, the volume of powder introduced at each sequence is different from one sequence to another.

Between each introduction of powder into the mixing chamber 6, the piston 30 is lowered in the lower position and is then in contact with the resin-powder mixture. The descent of the piston, in contact with the volume mixture VMi, causes a rise in the level of said mixture, the total volume occupied by the mixture and the piston being VTi = VMi + VP, and the height passing from h to H, with H greater than or equal to h. The displacement of the piston 30 and the rise of the level of the mixture makes it possible on the one hand to mix, with the elastomeric resin, the CNTs which may have been deposited on the walls of the chamber 6 of the mixer. This makes it possible to limit the losses of CNT not incorporated in the resin after mixing, and contributes to obtaining a volume of powder effectively mixed with the resin substantially equal to the total volume of powder introduced into the mixing device.

On the other hand, the resin-powder mixture is mainly mixed near the mixer screws. The portion of said mixture which is remote from said screws is much less mixed. This results in a heterogeneous mixture. The displacement of the piston 30 induces the compression mixture and the change in height of said mixture, mixes optimally ^the whole volume of said mixture and thus obtain a homogeneous composite material, with a very good dispersion the powder, and in particular CNT, in the elastomeric resin.

The control and regulation of the rate of introduction of the powder comprising CNTs in the mixer 2 by the feed system 10, and the displacement of the piston 30 in said mixer which compresses the elastomer-powder resin mixture, make it possible to obtain a homogeneous composite material, with a reduced number of defects compared to the techniques known to those skilled in the art, and with good properties, especially mechanical and electric. The mixing device 1 according to the invention may further comprise extraction means comprising in particular prefilters and filters, to minimize the pressure losses at the air flow, and thus reduce the risks. for an operator when using such a mixing device. The extraction means are provided at the loading chamber, the mixing chamber, the safety slide, and the receiving hopper, and are respectively numbered 23, 24, 25, 26 in FIG. extraction are generally provided at each stage of the process for manufacturing the composite material until transfer of said composite material in the receiving hopper 21, except at the level of the powder supply system 10 where they are not necessary because the presence of the double valve coupling device 19.

During the introduction of the elastomer resin in the loading chamber 3, then in the mixing chamber 6 after opening by opening the secured door 4 and / or piston in the up position, the extraction means 23 of said Loading locks are turned on, with a high extraction rate, to avoid contact of the resin particles that may be present in the air with the operator. Then, the extraction flow rate is reduced during the introduction of the powder into the loading chamber 3, then into the mixing chamber 6, in order to avoid forming a cloud of powder particles suspended in said loading chamber. .

The extraction means 24 of the mixing chamber 6 are turned on during the introduction of the powder and / or the elastomer resin into said chamber, and preferably operate for the duration of the step mixture.

The extraction means 25 of the safety slide 20 and the receiving hopper 21 are turned on during the emptying of the mixing chamber 6 of the mixer, and preferably operate until the hopper reception no longer contains composite material.

When the mixing step is complete, and the composite material, has been obtained and transferred from the mixing chamber 6 to the hopper of reception 21, said composite material is likely to undergo several processing steps including calendering, passing through calenders 22, to be made in a form suitable for future use. Preferably, the composite material undergoes one or more calendering steps to form plates. More preferably, these plates have a length equal to 1 meter, a width equal to 1 meter, and a small thickness so that said plates are able to be cut by a user without the use of industrial cutting means, for example with a cutter.

It is also possible to shape the composite material to obtain ribbons, packaging, or any other structured or semi-structured piece that can be obtained by shaping such a composite material.

The composite material obtained can be shaped by any suitable technique, including injection, extrusion, compression or molding, followed by a vulcanization treatment. A vulcanizing agent may be added to the composite material. The addition of the vulcanizing agent can be carried out during the mixing step (in the case where its activation temperature is higher than the mixing temperature). However, it is preferred that it be added to the composite material immediately before or during its shaping, so as to have more latitude to adjust the properties of the composite. Alternatively, the composite material according to the invention can be used as a masterbatch and thus diluted in a polymer matrix to form a composite product after shaping. Again, the vulcanizing agent can be introduced either during the mixing step, or preferably in the polymer matrix, that is to say during the formulation of the latter or during its shaping. In this embodiment of the invention, the final composite product may for example contain from 0.01% to 35% by weight of CNT, preferably from 1.5 to 20% by weight of CNT.

The polymer matrix generally contains at least one polymer chosen from homo- or copolymers with gradients, blocks, statistics or sequenced, thermosetting. At least one polymer chosen from those listed above is preferably used according to the invention. Advantageously, the polymer included in the polymer matrix belongs to the same chemical class (nitrile resin, resin silicone or fluorocarbon polymer. for example) that at least one of the polymers of the elastomeric resin obtained by the manufacturing method according to the invention.

The polymer matrix may further contain at least one vulcanizing agent such as sulfur derivatives or organic peroxides, and optionally a vulcanization accelerator, as well as various adjuvants and additives such as antioxidants, lubricants, pigments (Zinc oxide, lithopone for example), stabilizers, fillers or reinforcements, antistatic agents, fungicides, flame retardants, texturizing agents, electrical conductivity improvers (structured carbon black for example) and solvents.

The composite product thus obtained can in particular be used for the manufacture of body seals or sealing, tires, noise-reducing plates, static dissipators, internal conductive layer for cables with high and medium voltage, or anti-vibration systems such as automobile shock absorbers, or in the manufacture of structural elements bulletproof vests.

According to the present invention, the method for manufacturing a composite material comprising at least one carbon nanocharging powder, and at least one elastomeric resin, is implemented by the mixing device 1 previously described and comprises the following steps: ) introducing the elastomer resin in the mixer 2, b) introduction of the powder in the mixer 2 via the supply system 10 and controlling introduction flow by adjusting the speed of rotation of the ^feed screw. c) Mixing of the elastomer resin and the powder in the mixer to ^obtain a composite material, d) the composite material Formatting obtained in step c).

The powder comprises carbon nanotubes (CNTs).

The amounts of elastomer resin and powder introduced during steps a) and b) are such that they make it possible to obtain a composite material during the step c) whose mass percentage of CNT is in the range of 1% to 60% and preferably greater than 10% in this range. The mass percentage of CNT is preferably greater than 20%, and more preferably greater than 30%. Advantageously, the mass percentage of CNT is less than 60%, preferably less than 50%, and more preferably less than 40%. In a preferred example, the mass percentage of CNTs in the composite material is between 30% and 40%.

The method according to the invention may comprise, prior to step b), a step of mixing the elastomeric resin, then only in the mixer. The mixing time of the elastomeric resin is 1 minute and 15 minutes, preferably between 1 minute and 10 minutes. More preferably, the mixing time of the elastomeric resin is 5 minutes and the mixing temperature of the elastomeric resin is in a range of 100 ° C to 160 ° C, the resin having a temperature in a range of 40 to 60 ° C prior to the introduction of the NTC (carbon nanocarcia).

[0063] In step b), the powder is introduced into the mixer via the feeding ^system according to an integer number n of sequences, each sequence comprising an integer i powder introductions. Preferably, n is between 1 and 5, and advantageously between 2 and 3. Preferably, i is between 1 and 10, and advantageously between 4 and 8.

Each sequence is characterized by its number of introductions i, and its time necessary to perform all the introductions it includes. For example, and as illustrated in Example 1 below, step b) ^of introducing the powder may comprise a first sequence of 15 minutes with 5 powder introductions, and a second sequence having 2 20 minutes introductions of powder. Thus, it will take 15 minutes to complete the 5 introductions of the first sequence, then 20 minutes to complete the 2 introductions of the second sequence.

The time of a sequence is generally between 5 minutes and 30 minutes, preferably between 5 minutes and 15 minutes.

Moreover, the amount of powder introduced at each introduction, in a given sequence, is identical or different from one introduction to another. Of even, the amount of powder introduced to each sequence is the same or different from one sequence to another.

The time of a sequence is identical or different from one sequence to another. Preferably, the time of a sequence is different from one sequence to another. Similarly, the time of an introduction, for a given sequence, is identical or different from one introduction to another. Preferably, the time of an introduction, for a given sequence, is identical from one introduction to another.

The rate of introduction of the powder into the mixer during step b). depending in particular on the rotational speed of the feed screw, the degree of opening and the ^opening time of the double-valve device is thus adapted accordingly.

Between each introduction of a given sequence, and after the last introduction of a given sequence, the piston 30 is lowered to compress the mixture and allow a better incorporation of the powder in the elastomeric resin. The piston 30 and the motor 13 for driving the feed screw 11 are controlled by means of a PLC programmed for this purpose.

[0070] When mixing the elastomer resin and powder in ^step c), the mixer speed is 10 revolutions / minute and 40 revolutions / minute, preferably 20 revolutions / minute and 30 revolutions /minute. In addition, the mixing step is generally carried out at a temperature which is higher than the glass transition temperature (Tg) for the amorphous polymers and at the melting point for the semi-crystalline polymers. This temperature is a function of the polymer specifically used and generally mentioned by the supplier of the polymer. By way of example, the mixing temperature can range from room temperature to 260 ° C., for example from 80 to 260 ° C., preferably from 100 to 220 ° C., and more preferably from 100 to 150 ° C.

Preferably, the mixer chamber is not heated and the mixture is made at room temperature, or at a temperature above room temperature following heating caused by shearing components during mixing. When all of the powder has been introduced into the mixer according to step c), the speed of rotation of the mixer is increased so that the temperature of the mixture is greater than or equal to 150 ° C. The safety slide 20 and the emptying hatch 7 are then opened so as to empty the mixing chamber 6 and to transfer the composite material into the receiving hopper 21.

Examples of implementation of the process for manufacturing the composite material with the device according to the invention

The following examples relate to a non-optimized protocol (Example 1) and an optimized protocol (Example 2) for manufacturing a composite material, and show the impact of the powder introduction sequencing comprising CNTs in the mixer. .

Example 1: Non-optimized protocol for the introduction of the powder comprising CNTs

12 kg of a fluorinated elastomer resin are introduced into the mixing chamber of the mixer via the loading chamber. The entire fluorinated elastomer resin is introduced at one time. The resin is mixed for 30 minutes at a temperature between 30 ° C and 40 ° C. Is then introduced in several times, ^that is to say in a plurality of opening sequences, 3.2 kg of a powder of carbon nanotubes (CNTs) 100 C of Graphistrength ® brand manufactured by Arkema, and packaged in metal drums of 60 liters. The sequences for introducing the CNT powder into the mixer are as follows:

- 5 introductions. 15 minutes of mixing after each introduction

- 2 introductions, 20 minutes of mixing after each introduction [0075] The piston goes down and then goes up in the upper position between each powder introduction. The speed of rotation of the mixer is between 20 rpm and 30 rpm. The temperature of the mixture is about 120 ° C. After the last introduction of powder, the piston is lowered and then reassembled three times in order to ^optimize the mixing of the powder and the elastomer resin. The speed of rotation of the mixer is increased until the temperature of the mixture is approximately equal to 150 ° C., and the mixer is then drained. The composite material obtained undergoes several calendering steps to obtain a homogeneous plate, easily handled, and simple and fast to cut. The plate is analyzed by optical microscope, and ^the image shown in Figure 4 is obtained. At the macroscopic level, the plate is regular which implies a relatively homogeneous mixture of the powder and the elastomeric resin. However, optical microscopy reveals a plate dotted with spots 40 corresponding to the NTCs encapsulated in the elastomeric resin. The dispersion is satisfactory because the plate obtained has good properties, including mechanical and electrical, but ^is not optimal,

Example 2 Optimized Protocol for the Introduction of the Powder Including NTCs

[0077] are introduced 12 kg ^of a fluorinated elastomer resin in the mixer of the mixing chamber via the load lock. The entire fluorinated elastomer resin is introduced at one time. The resin is mixed for 30 minutes at a temperature between 20 ° C and 30 ° C. 3.2 kg of a carbonitrous carbon nanotube (CTC) powder C100 of the trademark Graphistrength® manufactured by the company ARKEMA, and packaged in several packings, are then introduced several times, that is to say into several introduction sequences. 60 liter metal drums. The sequences for introducing the CNT powder into the mixer are as follows:

- 8 introductions, 6 minutes of mixing after each introduction

- 5 introductions, 15 minutes of mixing after each introduction

The piston goes down and then goes up in the upper position between each powder introduction. The speed of rotation of the mixer is between 20 rpm and 30 rpm. The temperature of the mixture is about 100 ° C. After the last powder introduction, the piston is lowered and reassembled three times in order to optimize the mixing of the powder and the elastomer resin. The speed of rotation of the mixer is increased until the temperature of the mixture is approximately equal to 150 ° C., and the mixer is then drained. The composite material obtained undergoes several calendering steps until a homogeneous plate is obtained which is easy to handle and is simple and quick to cut. The plate is analyzed under an optical microscope, and the image shown in Figure 5 is obtained.

At the macroscopic level, the plate is regular which implies a relatively homogeneous mixture of the powder and the elastomeric resin, and a satisfactory dispersion of said powder in said elastomeric resin. Optical microscopy confirms this impression by the absence of NTC tasks. So we have a very good dispersion of the NTC powder in the elastomeric resin, and the resulting plate has good properties, including mechanical and electrical. These examples show the influence of the regulation of the introduction of the powder comprising CNTs, in particular the influence of the number of sequences of introduction of said powder into the mixer.

Claims

Mixing device (1) for the manufacture of a composite material from at least one powder comprising carbon nanofillers, and at least one elastomeric resin, characterized in that it comprises;

a mixer (2) for mixing the powder with the elastomer resin, said mixer comprising a chimney (5) and a mixing chamber (6),

- A feed system (10) for introducing the powder into the mixer (2), said feed system comprising a device (14) for loading the powder cooperating with a feed screw (1 1) opening in the mixer (2),

- a piston (30) adapted to move in the chimney (5) and in the mixing chamber (6) of the mixer (2) and contributing with said mixer to the mixture of the powder with the elastomer resin in the mixing chamber ( 6).

Mixing device for the manufacture of a composite material according to claim 1, characterized in that the loading device (14) comprises a container (18) connected to a double valve coupling device (19) ensuring the passage powder in the feed screw (1 1) in a secure manner.

Mixing device for the manufacture of a composite material according to claim 2, characterized in that the coupling device (19) comprises an active valve (15) connected to the container (18) and a passive valve (16) connected. an inlet (1 10) for introducing the powder into the feed screw (1 1), the active valve and the passive valve being intended to be connected to allow the transfer of the powder from the container (18) into the supply screw (1 1).

4. Mixing device for the manufacture of a composite material according to claim 1, characterized in that the feed screw (1 1) of the feed system (10) has a ratio Length / Diameter, said ratio L / D, ranging from 10 to 70, preferably from 20 to 70 and preferably from 40 to 60.

Mixing device for the manufacture of a composite material according to any one of the preceding claims, characterized in that the mixer (2) comprises a loading chamber (3) constituting the inlet of said mixer, the loading lock being connected to the feed screw (1 1), so that the powder penetrates directly into said lock (3) after the exit of the ^feed screw, the mixing chamber (6) being located under the load lock chamber (3) and capable of communicating with said lock, said load lock chamber (3) being surmounted by the stack (5).

6. Mixing device for the manufacture of a composite material according to claim 5, characterized in that the loading chamber (3) is provided with a sealed tight closure (4) separating said loading chamber from the mixing chamber. (6).

7. Mixing device for the manufacture of a composite material according to claim 5 or 6, characterized in that the loading chamber (3) comprises a door (50) allowing the introduction of the polymer resin into said airlock (3). ).

Mixing device for the manufacture of a composite material according to any one of the preceding claims, characterized in that the mixer (2) comprises extraction means (23, 24, 25, 26) comprising prefilters and filters.

9. A method of manufacturing a composite material comprising at least one powder comprising carbonaceous nanofillers, and at least one elastomeric resin, said method being implemented by the mixing device (1) according to ^one of the preceding claims, characterized in that it comprises the following steps: a) Introduction of the elastomeric resin into the mixer (2), b) introduction of the powder into the mixer (2) via the feed system (10) and flow control introduction by adjusting the rotational speed of the feed screw (1 1), c) mixing the elastomeric resin and the powder in the mixer (2) to obtain a composite material, d) Setting in the form of the composite material obtained in step c).

10. A method of manufacturing a composite material according to claim 9, characterized in that the powder comprising carbon nanofillers comprises carbon nanotubes (CNTs) or nanofibers carbon or graphene, or carbon black, or a mixing said carbon nanofillers, or preferably carbon nanotubes alone or in combination with another nanofiller.

11. A method of manufacturing a composite material according to claim 9 or 10, characterized in that the powder comprising carbon nanofillers, introduced into the mixer (2), further comprises at least one vulcanizing agent.

12. A method of manufacturing ^a composite material according to any one of claims 9-1 1 .. characterized in that the powder comprises carbonaceous nanofillers introduced into the mixer (2) further comprises at least one additive.

13. A method of manufacturing a composite material according to claims 9 to 12 characterized in that the amounts of elastomeric resin and powder introduced during steps a) and b) are such that they make it possible to obtain a composite material when of step c) whose weight percentage of CNT is in the range of 1% to 60%, preferably greater than 10% in this range; preferably greater than 20%, and more preferably greater than 30%.

14. A method of manufacturing a composite material according to claim 13, characterized in that the mass percentage of CNT in the composite material is less than 60%, preferably less than 50%, and more preferably less than 40%. .

15. A method of manufacturing a composite material according to claim 3 or 14, characterized in that the mass percentage of CNT in the composite material is between 30% and 40%.

16. A method of manufacturing a composite material according to claim 9, characterized in that during ^step b), the powder is introduced into the mixer (2) so as sequenced. according to one or more powder volume introduction sequences corresponding to a fraction of the total volume of powder to be introduced, each sequence comprising one or more powder introductions.

17. A method of manufacturing a composite material according to claim 9, characterized in that the powder is introduced into the mixer (2) via the system. feed (10) according to an integer number n of sequences, each sequence comprising an integer number i of powder introductions, preferably n is between 1 and 5, and advantageously between 2 and 3 and preferably, i is between 1 and 10, and advantageously between 4 and 8.

18. A method of manufacturing a composite material according to claim 9, characterized in that it comprises, prior to step b), a step of mixing the elastomeric resin, then only in the mixer (2) during a between 1 minute and 15 minutes, preferably between 1 minute and 10 minutes, more preferably the mixing time of the elastomeric resin is 5 minutes and the mixing temperature of the elastomeric resin is in a range of 40 ° C to 60 ° C,

19. A method of manufacturing a composite material according to claim 9, characterized in that during steps b) and c) the temperature of the resin mixture and carbon nanofillers powder is 40 ° C to 160 ° C, and so preferred from 100 ° C to 150 ° C.