Superparticles composed of dry-coated graphene particles, methods for manufacturing them, and their uses

Abstract

The present invention relates to a method for producing superparticles composed of dry-coated graphene particles, comprising: dry-coating a graphene material; dispersing the resulting particles in a solvent; adding an additive to the dispersion; and at least partially removing the solvent from the thus obtained dispersion by spray drying to obtain superparticles composed of dry-coated graphene particles.

Description

[Technical Field]

[0001] The present invention relates to a method for producing superparticles composed of dry-coated graphene particles, the superparticles themselves made of dry-coated graphene particles, and the use thereof.

[0002] Technical literature, such as Roempp online (ROEMPP editorial team, Balgar T, Graphene, RD-07-02758 (2010) in Boeckler F., Dill B., Eisenbrand G., Faupel F., Fugmann B., Gamse T., Matissek R., Pohnert G., Ruehling A., Schmidt S., Sprenger G., ROEMPP [Online], Stuttgart, Georg Thieme Verlag, [September 2022] https: / / roempp.thieme.de / lexicon / RD-07-02758), discusses various aspects of graphene, including its manufacturing, properties, and uses.

[0003] Similar to graphite, each carbon atom in graphene is covalently bonded to three adjacent atoms by sigma bonds. The CC bond length is 142 pm. The atoms are sp 2 It is hybridized, and the sigma bonds lie within a single plane. Therefore, graphite has a planar structure. Partially filled p z Orbitals remain in each atom. These p z The orbitals are perpendicular to the bonding plane and form the most important delocalized pi electron system when determining the electronic properties of graphene.

[0004] Crystallographically, graphene is a unit cell vector

number

[0005] The methods described below can be carried out using all graphenes specified thereafter. The definitions outlined earlier are applicable to these graphenes.

[0006] In the context of this invention, "graphene material" means a material in accordance with ISO / TS 80004-13, namely graphene, graphene carbon material, single-layer, double-layer and triple-layer graphene, epitaxial graphene, exfoliated graphene, multi-layer graphene, multi-layer graphene, multi-layer nanoribbon, graphene nanoplate, graphene nanoplatelet, graphene nanosheet, graphene microsheet, graphene nanoflake, graphene nanoribbon, graphene oxide, graphene oxide nanosheet, multi-layer graphene oxide, graphene quantum dot, graphite, graphite nanoplate, graphite nanosheet, graphite nanoflake, graphite oxide, reduced graphene oxide, or mixtures thereof.

[0007] In the context of this invention, fillers are understood to mean boron nitride, nitrides in general, carbon-based materials (diamond), aluminum-based materials, metal particles and alloys, TiO2, ZnO, MgO, noble metals and their alloys, as well as metal salts, silica and silicates, SiC materials, layered materials (WS2, vanadium-based, silicon-based), composite components (fibers, etc.), flame retardants, impact modifiers, pigments, and UV stabilizers.

[0008] Graphene materials are used in many technical fields, as described, for example, in European Patent Application No. 21150690. Materials composed of graphene materials, such as so-called composite materials, also constitute part of the prior art.

[0009] International Publication No. 2016078664 discloses a composite material in which a structure-granting material is imparted to a given macroscopic surface by using appropriately selected graphene as a binder material.

[0010] The polynorbornene / graphene oxide composite material described in Korean Registered Patent No. 1190014 plays a role in adjusting the gas barrier properties and various mechanical parameters in the layered structure.

[0011] Korean Published Patent No. 20190048574 outlines, for example, the production of a composite material containing graphene oxide using a 10 g / l dispersion in distilled water. Thus, a graphene material with a weight percentage of only 1% is achieved. The graphene oxide particles partially aggregated to form particles having an approximately spherical shape and a diameter of less than 30 μm. Another portion was in the form of flakes of a different shape. In this case, a free-flowing composite material was not obtained.

[0012] In the paper "Supraparticles: Functionality from Uniform Structural Motifs" by S. Wintzheimer et al., ACS NANO, 12 (2018), 5093-5120, nanoparticles are found to be components of superparticles. Using the controlled aggregation of only such individual nanoparticles, superparticles with specific electronic, plasmon, magnetic, and / or photon properties can be obtained. To induce this aggregation, van der Waals or electrostatic forces present between nanoparticles are utilized by spray drying, or alternatively, nanoparticles are bonded in an environment where they are formed by the sol-gel method, or ultrasonic chemistry is employed. In particular, in the case of spray drying, the geometric specificity of the apparatus used for this purpose, and its relationship to the properties of the thus aggregated product, are not discussed.

[0013] Graphene material is commercially available as a powder and often has a very low bulk density, typically ranging from 2 to 400 g / l. In addition to its low bulk density, most graphene material also has low fluidity and / or generates a large amount of dust when transported by gravity-driven flow. This worsens handling, causes problems during weighing and measurement, and should be considered a serious issue in terms of environmental protection and worker safety.

[0014] The deterioration in handling properties is evident, for example, when powders are incorporated into elastomer systems, such as during rubber compounding. The production of a good filled rubber compound depends on incorporating powdered fillers at the appropriate time and for the appropriate duration. These are poured into a mixing chamber by a hopper and then pushed toward a rotating roller by a pneumatic piston. The shear forces acting during such a mixing process break down aggregates of the fillers and thus contribute to their dispersion. Therefore, the maximum filler level that can be achieved is substantially determined by the shear forces acting upon it.

[0015] For example, it is known to produce fine graphite or graphene aggregates in electrode manufacturing. However, due to the size of the aggregate particles, this conventional material is not free-flowing enough to allow its use in conventional compounders or extruders.

[0016] Similarly, the spray drying process is known to be useful for optimizing powder systems, for example, by obtaining round aggregates through the spray drying of graphene dispersions. However, powders composed of graphene materials with improved fluidity have not yet been found.

[0017] In the context of this invention, several test methods, namely the following measurements or determinations, are employed to characterize the fluidity of the material: - Angle of repose in accordance with ISO 4324, - Dynamic avalanche angle, and - Hausner coefficient compliant with ASTM 527.

[0018] A further measured value in the context of the present invention is the dust value compliant with DIN 55992.

[0019] The above parameters are well-known to those skilled in the art and are confirmed by the test methods outlined below. Here, the angle of repose and the angle of avalanche are expressed in degrees (°).

[0020] The better at least two of these values of the material are, and even better three of these values are, that is, - the angle of repose is low, - the dynamic angle of avalanche is low, - the Hausner coefficient is low the better the flowability of the material. Further, the smaller the dust value, the less dust is obtained in the processing of the material used in the context of the present invention, that is, the material presented and claimed here.

[0021] The terms "dust value" and "dust generation" are synonymous in the context of the present invention. Conventionally produced graphene powder is cohesive, which is synonymous with high measured values, and thus has only low flowability and high dust generation. Such powders are either difficult to process or can only be processed with elaborate technical safety measures, and when the dust value is high, only a low bulk density is achieved.

[0022] Therefore, a technical approach is needed to provide a powdery graphene material with improved flowability.

[0023] Similarly, there is a continuing need to reduce the amount of dust formed. This is because, first, dust causes contamination and makes it difficult to measure the amount of filler actually introduced into the matrix system. Second, for reasons related to occupational health and environmental protection, it is essential to remove dust by suction or other means.

[0024] Furthermore, the dustiness and generally low bulk density of graphene material increase the cost of introducing the material into the desired matrix system. For example, corresponding problems arise when manufacturing thermoplastic compound materials filled with graphene material in an extruder. For these reasons, it is difficult or impossible to ensure compliance with essential time-dependent requirements when introducing powdered graphene material during the manufacturing process of thermoplastic systems.

[0025] Furthermore, the conductivity of graphene, known to those skilled in the art, limits the use of graphene material in electrical insulating composite materials. For this purpose, additional electrical insulating materials are required. However, the use of such materials has the disadvantage that the thermal conductivity of graphene is further limited. Therefore, in order to achieve a complete electrical insulating effect with high thermal conductivity, it is necessary to efficiently connect the graphene material to the insulator.

[0026] Therefore, the object of the present invention was to improve a spray drying method for producing a powder containing a freely flowable graphene material so that the graphene material or its compound or masterbatch has improved fluidity and / or less dust is generated during processing than conventional methods. The resulting graphene material was further thermally conductive and simultaneously electrically insulating.

[0027] The objective is a method for producing superparticles composed of dry-coated graphene particles, (a) At least one graphene material selected from SiO2, aluminum oxide, TiO2, MgO, ZnO, SbO, organic fillers, or polymers. Dry coating with the material, after that, (b) Disperse the dry-coated graphene material obtained in step (a) in a solvent. Simultaneously or afterward, (c) Add to the dispersion obtained in step (b) 0.1 to 150% by weight, preferably 0.1 to 100% by weight, of a dispersion aid, emulsifier, wetting aid, and / or defoaming agent, based on the mass of the graphene material used. after that, (d) Remove the solvent from the dispersion obtained in step (c) by spray drying, To obtain superparticles composed of dry-coated graphene particles, This was achieved by providing a method.

[0028] Surprisingly, it has been found that improved fluidity can be achieved by spray-drying a dispersion of dry-coated graphene material, which is dry-coated with a material selected from SiO2, aluminum oxide, TiO2, MgO, ZnO, SbO, organic fillers, or polymers, preferably containing a dispersion aid, emulsifier, wetting agent, and / or defoaming agent, and thereby obtaining the desired properties of thermal conductivity and electrical insulation of the dry-coated graphene material, as well as the spray-dried material.

[0029] During the drying process, the surface of the dry-coated graphene material particles is wetted or otherwise wetted by the additive, thereby stabilizing them. Spray drying utilizes aggregation to obtain ultrafine particles of the dry-coated graphene material.

[0030] The aggregated dry-coated graphene particles obtained after step (d) are superparticles composed of dry-coated graphene particles. These are referred to in the context of the present invention as "superparticles composed of dry-coated graphene particles". These superparticles composed of dry-coated graphene particles are preferably spherical or nearly spherical in shape and have a particle diameter d of 1 μm to 500 μm, preferably 5 μm to 250 μm, more preferably 50 μm to 100 μm. 50 It holds.

[0031] In the context of this invention, particle diameter is measured using a Rentsch Technology Partica laser scattering particle size analyzer LA-950V2. All particles were analyzed in water. Here, the pump transport circulation speed was set to 6 and the agitator speed was set to 6. For the analysis of the starting material, ultrasound was set to level 6 for 1 minute. The ultrafine particles were measured in a 0.001 wt% soap solution to stabilize them.

[0032] The method according to the present invention has the advantage that the superparticles composed of the dry-coated graphene particles thus obtained have improved fluidity compared to conventional graphene particles. Here, the superparticles composed of dry-coated graphene particles have a particle diameter d of at least 40 μm 50 It was found that good fluidity was only achieved when the particle diameter d was at least 50 μm, preferably at least 70 μm. 50 Superparticles composed of dry-coated graphene particles possessing a particularly good fluidity.

[0033] In this context, the use of additives such as dispersants, emulsifiers, wetting agents, and / or defoamers facilitates the handling of the dispersion without affecting the inherent properties of the coated graphene material.

[0034] It was found that electrical insulation can be achieved by selecting appropriate materials for dry coating.

[0035] Similar to the improved fluidity, the bulk density of the resulting superparticles composed of dry-coated graphene particles also increases. Furthermore, the material obtained by this method can be easily measured and added to any conventional matrix material. Moreover, the processing of superparticles composed of dry-coated graphene particles obtained according to the present invention results in relatively low dust levels. Thus, operational safety is improved. Furthermore, the usability of the further processed material is maintained. For example, in a conventional compounder, superparticles composed of dry-coated graphene particles can be decomposed into dry-coated graphene material using active shear forces in a matrix material, preferably a polymer, monomer, or solvent, thereby maintaining the original physical properties.

[0036] Similarly, the present invention relates to a superparticle composed of dry-coated graphene particles, - An angle of repose in accordance with ISO 4324, which is 50° to 20°, preferably 40° to 25°, more preferably 37.5° to 30°, and particularly preferably 37° to 27.5°, and - Dynamic avalanche angles of 65°~30°, preferably 55°~35°, most preferably 45°~40°, and / or - Hausner coefficients in accordance with ASTM 527, of 1.5 to 1, preferably 1.4 to 1.1, more preferably 1.3 to 1.2, or - Dust values ​​conforming to DIN 55992 Type I, of 10 to 0.001, preferably 5 to 0.01, more preferably 3 to 0.1. The present invention provides superparticles composed of dry-coated graphene particles, characterized by having the following properties.

[0037] The superparticles, which consist of dry-coated graphene particles obtained according to the present invention or in accordance with the present invention, provide a powder that is free-flowing yet does not produce dust.

[0038] The superparticles composed of dry-coated graphene particles according to the present invention preferably have the features claimed simultaneously. Thus, the superparticles composed of dry-coated graphene particles have an angle of repose of 50° to 20° in accordance with ISO 4324, a dynamic avalanche angle of 65° to 30°, a Hausner coefficient of 1.5 to 1 in accordance with ASTM 527, and a dust value of 10 to 0.001 in accordance with DIN 55992 Type I. These superparticles preferably have a diameter d of 1 μm to 500 μm. 50 It holds.

[0039] The superparticles, which consist of dry-coated graphene particles obtained according to the present invention or in accordance with the present invention, are collected into three different containers for classification purposes and can therefore be divided into three sizes.

[0040] The so-called "crude material" can be collected vertically into a collection container downstream of the drying chamber after step (d) of the method according to the present invention. The powder containing ultrafine particles composed of dry-coated graphene particles obtained according to or in accordance with the present invention is subjected to a correspondingly low level of shear force during the method, which means that there is little debris obtained.

[0041] Downstream from the drying chamber, the powder can be introduced into a cyclone. Here, the so-called "particulate fraction" is separated from the so-called "cyclone product." The cyclone product is subjected to a large shear force by centrifugal force, and as a result, the ultrafine particles, especially those composed of dry-coated graphene particles, tended to disintegrate. The particulate fraction can be collected on a filter mat downstream of the cyclone.

[0042] The present invention also, - In particular, thermally conductive materials and thermally conductive adhesives in the fields of batteries, sensors, ICs, and LEDs, such as films, underflow materials, pourable electronic materials, materials with phase transitions, thermal pastes, sealing compounds, - Composite materials based on thermoplastic resins, thermosetting resins, and / or elastomers having increased electrical conductivity and / or thermal conductivity, or for EMI shielding, particularly in the field of housings for electrical components, motors, battery packs, and pipelines. - Coatings and varnishes that are thermally conductive and / or electrically conductive, or for use in EMI shielding sectors. - Thermally conductive and / or conductive oils, coolants, or inks The present invention provides for the use of superparticles composed of dry-coated graphene particles obtained according to or in accordance with the present invention in the application of [the present invention].

[0043] In particular, superparticles composed of dry-coated graphene particles obtained according to the present invention or in accordance with the present invention are A standard thermoplastic resin, preferably selected from PE, PP, PS, PVC, alpha-olefin, butadiene derivatives, and / or Vestenamer®. Industrial thermoplastic resins, preferably PET, PMMA, PC, POM, PA, PBT, PEBA, TPU, PU, ​​and / or TPE, High-performance thermoplastic resins, preferably PPS, PEEK, PES, PI, and / or PEI, A paste containing copolymers, elastomers, preferably silicones, more preferably room temperature crosslinked (RTV) silicones, high temperature crosslinked (HTV) silicones, liquid silicone rubber (LSR), heat crosslinked rubber (HCR), acrylates, and / or polysiloxanes and oligosiloxanes. Polyurethane, rubber, preferably styrene-butadiene rubber (SBR), butadiene rubber (BR), and / or natural rubber, thermosetting resin, preferably polyurethane, polyester resin, phenolic resin, epoxy resin, acrylate resin, and / or silicone resin, Solvents, preferably aprotic-nonpolar, aprotic-polar, and / or protic solvents. Oil, preferably mineral oil, silicone oil, and / or process oil Suitable for use in [location / area].

[0044] More preferably, superparticles consisting of dry-coated graphene particles obtained according to or in accordance with the present invention are used as additives in the plastics processing industry. These are preferably used in the compounding, extrusion, or injection molding of plastics.

[0045] The claimed benefit of the use is that the incorporation of graphene becomes practical in several cases. Furthermore, the use of the present invention enables the easy and reliable processing of graphene, including so-called "rapid injection molding (RIM)".

[0046] This method allows for the efficient use of high-performance fillers such as graphene without compromising the high-performance properties of the matrix, as is the case with PA12, for example.

[0047] Ultrafine particles composed of dry-coated graphene particles, when used as an additive, enable improvements in thermal, electrical, and / or mechanical properties, such as improved degree of extrusion, in high-performance polymers in high-performance applications where it is necessary to keep the filler content low in order to maintain the properties of the matrix.

[0048] The use of ultraparticles composed of dry-coated graphene particles according to the present invention also achieves a favorable lubrication effect for easy compounding and extrusion, which is difficult with fillers. Furthermore, conductivity is improved.

[0049] Further advantages arise when handling in masterbatch processing for thermoplastic resins, epoxy, and elastomers, and / or when handling concentrates commonly referred to as masterbatches.

[0050] When used in gas membranes or gas conduction systems, the tendency for leakage is similarly reduced.

[0051] Hereinafter, the present invention will be described in more detail.

[0052] The method according to the present invention is schematically shown in FIG. 2.

[0053] In step (a) of the method according to the present invention, the graphene material is dry-coated with a further material selected from SiO2, aluminum oxide, TiO2, MgO, ZnO, SbO, an organic filler, or a polymer. In the context of the present invention, any method known to those skilled in the art is suitable for dry coating, for example, coating by a high-energy mixer. The starting material used may be, for example, aluminum oxide in powder form.

[0054] The particle dispersion obtained after step (b) preferably has a particle diameter d of 0.1 μm to 100 μm, more preferably 0.5 μm to 60 μm, and even more preferably 2 μm to 40 μm. 50 to have.

[0055] The graphene material in step (a) has the same particle size diameter d as the graphene material obtained in step (b). 50 to have.

[0056] These graphene particles are at least one order of magnitude larger than aluminum oxide particles, SiO2 particles, TiO2 particles, MgO particles, ZnO particles, SbO particles, polymer particles, or organic fillers.

[0057] [[ID=...]] The diameter d of the aluminum oxide particles, SiO2 particles, TiO2 particles, MgO particles, ZnO particles, SbO particles, polymer particles, or organic filler used in step (a) of the method according to the present invention 50 is smaller than the diameter d of the initial graphene particles 50 and the diameter d of the aluminum oxide particles, SiO2 particles, TiO2 particles, MgO particles, ZnO particles, SbO particles, polymer particles, or organic filler used in step a of the method according to the present invention 50The diameter of the graphene particles used in dry coating is d 50 More preferably at least 1 / 10th smaller, even more preferably at least 1 / 20th smaller, and most preferably at least 1 / 50th smaller. The aluminum oxide particles, SiO2 particles, TiO2 particles, MgO particles, ZnO particles, SbO particles, polymer particles, or organic fillers used are advantageously d with a diameter of 500 nm or less. 50 It may have.

[0058] Preferably, according to the present invention, the aluminum oxide particles, SiO2 particles, TiO2 particles, MgO particles, ZnO particles, SbO particles, polymer particles, or organic fillers used are hydrophobic materials. Therefore, the aluminum oxide particles, SiO2 particles, TiO2 particles, MgO particles, ZnO particles, SbO particles, polymer particles, or organic fillers used according to the present invention preferably do not have (surface) modifications that increase their water solubility, in contrast to hydrophilic materials.

[0059] Due to the improved material properties, it is advantageous that the superparticles, which consist of the dry-coated graphene particles obtained in step (d), can be broken down into dry-coated graphene material in a compounder while maintaining their original physical properties, by using active shear forces in a matrix material, preferably a polymer, monomer, or solvent.

[0060] In step (b), the organic filler used may be a polymer selected from PE, PP, PS, PVC, alpha-olefins, butadiene derivatives, Vestenamer® (a rubber additive from Evonik GmbH in Essen, Germany), industrial thermoplastics, preferably PET, PMMA, PC, POM, PA, PBT, PEBA, TPU, PU, ​​TPE, and high-performance thermoplastics, preferably PPS, PEEK, PES, PI, and PEI.

[0061] In the context of the present invention, the inorganic filler is also considered to contain a salt that is insoluble in the solvent used in step (a).

[0062] Furthermore, it may be advantageous to select the solvent in step (b) from water, distilled water, alkanol, and preferably ethanol.

[0063] The solvent can be selected from hexane, chlorobenzene, toluene, tetrachloromethane, dichloromethane, water, distilled water, ethanol, or a mixture of these solvents.

[0064] Suitable solvents for graphene materials and additives, including these and others, are known to those skilled in the art.

[0065] In the method according to the present invention, it may be advantageous to produce the dispersion in batch or continuously. In the case of batch formulation in step (b), the graphene material can be weighed and gradually added to the solvent. Here, a suitable stirring unit, such as an ultrasonic finger or Ultraturrax, can be used. It is observed that the viscosity of the dispersion increases as the mass percentage of the graphene material increases.

[0066] More preferably, a homogeneous dispersion is obtained in step (b). The properties of the dispersion are very important in carrying out step (d) of the method. This is because the size of the superparticles composed of dry-coated graphene particles is influenced by the viscosity, surface tension, density and mass ratio of the dry-coated graphene material, as well as the shape of the drying chamber.

[0067] As previously described, step (d) of the method according to the present invention involves subjecting the dispersion obtained in step (c) to spray drying. The drying method in step (d) is preferably the following steps: Step (c) involves spraying the dispersion obtained in step (c) into an inert gas stream using a spray unit to at least partially evaporate the solvent in the droplets formed by the spray. Includes.

[0068] In the spray drying method, a dispersion consisting of graphene material and additives is atomized by applying a shear force. During this process, an initial film is formed, and then the film separates into numerous droplets. Here, the droplets are surrounded by a high-temperature gas stream, preferably an inert gas, more preferably nitrogen, and are preferably in the range of 80 to 400°C. This temperature can be adjusted depending on the solvent.

[0069] In the context of the present invention, dry-coated graphene material particles obtained according to or in accordance with the present invention are referred to as "superparticles composed of dry-coated graphene particles" when they are in an aggregated form.

[0070] In step (d), the solvent in the droplet evaporates and is absorbed by the gas flow. This cools the gas. Due to the evaporation of the solvent, the volume of the droplet continuously decreases. Therefore, as the droplet passes through the gas flow, the mass ratio of graphene material and additives in the droplet increases. The drying of the droplet and the resulting volume reduction are initially linear until a so-called "rocking point" is reached. At the rocking point, a hard outer shell is formed, while the core of the superparticle, composed of dry-coated graphene particles, remains moist, meaning that solvent residues are present in the core and additives of the superparticle composed of dry-coated graphene particles. Further drying is slower because moisture needs to transfer from the core to the surface. The drying rate can be adjusted by the temperature of the inert gas flow during step (d) of the method.

[0071] If the drying rate is very high, it is possible to obtain hollow superparticles composed of dry-coated graphene particles.

[0072] When the drying rate is low, solid superparticles composed of dry-coated graphene particles are usually obtained.

[0073] In this second case, attention must be paid to the required residence time in the drying chamber; otherwise, drying will be incomplete.

[0074] Furthermore, the particle diameter of the superparticles composed of dry-coated graphene particles can be adjusted by the drying rate. Further means of influencing the size of the superparticles composed of dry-coated graphene particles include selecting a spraying unit which is preferably a two-phase nozzle, and selecting the ratio of the mass flow rate of gas to the sprayed dispersion, known as the air-to-liquid ratio.

[0075] Although not bound by any particular theory, as schematically shown in Figure 3, there may be various paths 1 to 4 for forming superparticles composed of dry-coated graphene particles during the implementation of the method according to the present invention. These paths depend on factors including the temperature of the inert gas flow. According to the path that followed the implementation of step (c), the superparticles composed of dry-coated graphene particles have different shapes F, J, and P, each with different properties for each pair.

[0076] By carrying out steps (a) and (b) of the method according to the present invention, dry-coated graphene particles are produced in a dispersion. Consequently, the method according to the present invention, in step (c), surprisingly yields superparticles composed of dry-coated graphene particles that do not have a core-shell structure. This is in stark contrast to results obtained by the prior art, because known fabrication methods yield superparticles with a core-shell structure when the primary particles used have distinctly different diameters.

[0077] The dispersion can be atomized, for example, by a two-phase nozzle. In this case, the required shear energy is supplied by the gas flow, which is significantly accelerated in the constricted section. Depending on the gas volumetric flow rate and the resulting gas velocity at the nozzle outlet, a higher or lower shear force is applied. This changes the droplet size and droplet size distribution of the dispersion.

[0078] Depending on the solvent, it is possible to use graphene material in a mass percentage of 5% to 50% by weight. The mass percentage of the additive used in wt% is based on the mass of the graphene material used.

[0079] The additives can be dispersed using a suitable agitator unit. To prevent demixing, the dispersion is preferably stirred continuously.

[0080] In the case of continuous preparation in step (b), the graphene material can be added to the mixture of solvent and additive by a suitable machine, preferably by a conveyor screw. If two phases are obtained, they can be pumped through a dispersion chamber. A corresponding agitator unit is required for the necessary energy input. The selection of the dispersion chamber and the energy input to be set are known to those skilled in the art. The dispersion is then continuously supplied to the agitator unit.

[0081] In step (c) of the method according to the present invention, at least one additive can be selected from the group consisting of dispersants, emulsifiers, or wetting agents, and / or defoaming agents.

[0082] At least one additive can be used in a mass percentage of 0.1% to 150% by weight, preferably 0.1% to 100% by weight, and more preferably 0.1% to 10% by weight, based on the mass of the graphene material used.

[0083] At least one wetting or dispersing agent can preferably be selected from copolymers based on oxyalkylene glycol alkenyl ethers or polyalkylene oxide alkenyl ethers and unsaturated dicarboxylic acid derivatives. Such copolymers are disclosed in the patent specification, European Patent No. 114292, and ensure, for example, the production of binder-free, co-solvent-free, or VOC-free pigment concentrates based on transparent iron oxide.

[0084] In step (d) of the method according to the present invention, the spray unit may be a device having at least one two-phase nozzle and / or the inert gas used may be nitrogen, preferably dry nitrogen, the temperature of the inert gas stream may be set more preferably from above the cooling limit temperature of the solvent to 200°C to 400°C, more preferably in the range of 220°C to 300°C and / or the spray droplets may have a size of 30 to 1000 μm.

[0085] The size of the sprayed droplets is determined by the force of the sprayer, which is known to those skilled in the art, and can be adjusted by the nitrogen flow rate or by the shear effect of the sprayer gas flow rate.

[0086] The present invention will be described in detail by examples without limiting the subject matter of the present invention.

[0087] The SEM images shown below were evaluated using a JEOL NeoScope by scattering the powdered material to be examined onto an adhesive graphene film and carefully removing the excess material with a bellows set. The SEM images shown in the context of this invention were recorded at 10kV.

[0088] Hausner coefficients compliant with ASTM 527 The Hausner coefficient was determined in accordance with ASTM 527. This is also a measure of the compressibility of the powder.

[0089] To determine the Hausner coefficient, the ratio of bulk density to compaction density is calculated. This is done by introducing 100g of powder material into a cylinder. Depending on the bulk density, a 100ml or 250ml cylinder can be used. The powder is introduced gradually and carefully. The volume of the loose layer is read; this is the bulk volume. The quotient between the mass of the introduced powder and its bulk volume is the bulk density.

[0090] Afterward, the powder is compacted until no further volume change is observed. The volume remaining at that point is the compacted volume, and this is then read.

[0091] The quotient between the mass of the introduced powder and the compacted volume is the compaction density.

[0092] The Hausner coefficients, calculated from bulk density and compaction density, can be classified into various evaluation classes as shown in Table 1.

[0093] [Table 1]

[0094] Dynamic avalanche angle measured with Revolution Powder Analyzer Similarly, dynamic avalanche angle is a measure of powder fluidity and can be measured directly.

[0095] In the context of this invention, we used the Revolution Powder Analyzer model Rev2015 from PS Prozesstechnik GmbH. This involved loading a specific amount into a rotating drum and using a camera to determine the angle at which the material began to form an avalanche, as shown in Figure 4a. A smaller avalanche angle (ava,h) between surfaces formed by horizontal (h) particles at the avalanche joint indicates better material flowability. The avalanche angle was measured mathematically in the positive direction between (ava) and horizontal (h). The operating modes of this Powder Analyzer, as well as the variables measured therein, are known to those skilled in the art. Further details can be found, for example, in the following article by Amado: "Advances in SLS powder characterization", 22nd Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference, SFF, 2011, pp. 438-452.

[0096] 100 ml of powder material was weighed and introduced into a glass chamber. The chamber rotated at 0.5 rpm, thereby creating an angle. When the dynamic avalanche angle, the maximum value of this angle, was reached, the powder began to flow down the slope. A camera recorded the movement of the powder, thus continuously monitoring the dynamic avalanche angle. Furthermore, the avalanche energy of the downward-flowing powder was calculated.

[0097] The dynamic avalanche angle can vary from 70° for very low-flow powders to 30° for very efficiently flowing powders.

[0098] The measurement parameters of the fluidity program corresponded to the standard settings for dark-colored powders: 0.5rpm • 150 avalanche occurrences • Avalanche threshold 0.65% Camera: Shutter speed 6ms, gain 6dB (black powder), 10 frames / second

[0099] Homogeneity and flow characteristics can be directly calculated from the standard deviation of the dynamic avalanche angle and avalanche energy.

[0100] Tilt angle compliant with ISO 4324 Measuring the angle of inclination provides further explanation regarding the fluidity of the powder.

[0101] In the context of this invention, 100 ml of powder material was introduced into a funnel having a 10 mm outlet. The outlet was closed. The funnel was fixed at a distance of 7.5 cm from a plate having a diameter of 10 cm and a height of 25 cm. When the outlet of the funnel was opened, the powder flowed onto the plate. In this way, the powder formed a cone with an angle of inclination of the object.

[0102] The inclination angle can be classified into various evaluation classes as shown in Table 2.

[0103] [Table 2]

[0104] Scanning electron microscope (SEM) The SEM images disclosed herein were obtained using a FlexSEM 1000 II VP-SEM. For this purpose, the powder to be examined was sprinkled onto an adhesive graphene film. Excess material was carefully removed with a bellows set. Images were recorded at 10kV.

[0105] Electrical insulation Electrical insulation was measured in accordance with ISO 62631 using an FE50 ring electrode and a Mili-TO 3 ohmmeter (Fischer Elektronik).

[0106] Thermal conductivity Thermal conductivity was determined in equilibrium according to ASTM E1530-19 using a two-dimensional sample approximately 10 mm thick in contact with a 120 silicone type (Wakefield-Vette) thermal joint compound, using a guarded hot plate (Thermtest GHFM-02). The upper plate was set to 35°C, while the lower plate was set to 15°C. Measurements were started after a 60-minute equilibrium period.

[0107] Devices used in the examples: Somakon MP-GL laboratory mixer, Buechi B290 spray dryer, UltraTurrax IKA T50. The spray dryer used is schematically shown in Figure 4b.

[0108] Example 1. First Graphene pure graph 20 The graphene material used was First Graphene pure graph 20 (manufactured by First Graphene, Inc., located in Henderson, Australia).

[0109] Figure 5 shows an SEM image of graphene material. It is in the form of platelets, which are partially in the form of aggregates.

[0110] Figure 6 shows the corresponding particle size distribution.

[0111] Here, the following characteristic diameter is measured: d 10 13 μm, d 50 22 μm, d 90 40 μm.

[0112] Dry coating: First, Graphene pure graph 20 and hydrophobic nanoparticle aluminum oxide are introduced into a high-energy mixer (Somakon) in a mass ratio of 80 / 20, and dry-coated at 2000 rpm for 20 minutes.

[0113] Manufacturing of dispersions: A dispersion consisting of water, a graphene-based material, and nanoparticle aluminum oxide is prepared as follows.

[0114] Dissolve the appropriate additive, TEGO® Antifoam KS 53 (manufactured by Evonik GmbH, Essen, Germany), in water. Gradually disperse the dry-coated powder into the solution, taking care to ensure that no clumps form. Then, disperse the dispersion using an H7 ultrasonic finger. The device is set to 100% amplitude and 0.75 cycles. Disperse for 5 minutes first. Then, close the container and shake vigorously for 30 seconds. Repeat this procedure a total of three times.

[0115] Once a homogeneous dispersion is obtained, it is stirred to prevent separation. This is done using a stirrer plate and a football-shaped stirrer bar at 600 rpm.

[0116] During step (c), the dispersion was stirred to prevent separation. The process parameters during step (c) were: Inlet temperature: 200℃, Outlet temperature: 92℃, Nozzle gas flow rate: 244 l / min Approximately 20m 3 Suction device output of 50% corresponding to / h, Pump output of 25% corresponds to approximately 6.5 ml / min. Air-to-liquid ratio: approximately 0.78 That was indeed the case.

[0117] The resulting superparticles, composed of dry-coated graphene particles, formed in the form of loose aggregates held together solely by van der Waals forces; therefore, they could break under moderate shear forces. Such forces occurred, for example, in the cyclone of a spray dryer. Consequently, the superparticles composed of dry-coated graphene particles were withdrawn from directly below the spray chamber, discarding any particles downstream of the cyclone. These consisted only of fragments of the superparticles.

[0118] Figures 7 to 9 show SEM images of superparticles.

[0119] Figure 7 shows the surface structure of a superparticle composed of dry-coated graphene particles. Here, it is clear that the superparticle consists of many dry-coated graphene particles, which aggregate under controlled conditions during the spraying process to form round superparticles composed of dry-coated graphene particles. Figure 8 shows that there is a wide range of particle sizes that do not adversely affect the processability of the graphene material. Figure 9 shows the internal structure of a superparticle composed of dry-coated graphene particles. Here, it can be seen that there is no particle separation depending on the particle size during the spraying process.

[0120] The particle size distribution of the superparticles composed of dry-coated graphene particles manufactured according to the present invention is evident from Figures 7 and 8. The superparticles composed of dry-coated graphene particles have a diameter of more than 40 μm.

[0121] Example 2: Fluidity and dust content liquidity To quantitatively evaluate the fluidity of the ultraparticles composed of dry-coated graphene particles obtained in Example 1, the Hausner coefficient in accordance with ASTM 527, the dynamic avalanche angle, and the inclination angle in accordance with ISO 4324 were measured in each case.

[0122] The compaction density and bulk density related to the Hausner coefficient from Example 1 are shown in Table 3.

[0123] [Table 3]

[0124] When comparing the bulk density and compaction density of ultraparticles composed of dry-coated graphene particles manufactured according to the present invention with those of graphene-based materials, a clear increase was observed after spray drying.

[0125] In the case of superparticles composed of dry-coated graphene particles manufactured according to the present invention, it was found that the Hausner coefficient was lower and therefore the compatibility was lower.

[0126] Table 4 shows the inclination angle and dynamic avalanche angle of the graphene material used, in accordance with ISO 4324, compared with the values ​​of the superparticles composed of dry-coated graphene particles.

[0127] [Table 4]

[0128] Due to the poor flow properties and significant fouling observed within the chamber, optical evaluation of the dynamic avalanche angle was not possible with graphene-based materials.

[0129] Therefore, it has become clear that the method according to the present invention can yield superparticles composed of dry-coated graphene particles with better fluidity.

[0130] Determination of dust levels in accordance with DIN 55992-1 (June 2006 edition) In the context of this invention, the dust level is determined by a Heubach dust meter Type I dust generating device using a rotation method in accordance with DIN 55992 (June 2006 edition), as schematically shown in Figure 1. The details of the structure of this device are known to those skilled in the art.

[0131] For determination, 5 g of powder material was introduced into the dust meter chamber as a sample weight. The chamber was equipped with a paddle, which was used to continuously move the powder. The filter unit was weighed before and after the measurement. A constant gas flow rate of 20 l / min was applied to the entire powder. The chamber rotated at 30 revolutions per minute.

[0132] The dust value is calculated from the ratio of the mass of powder in the filter after the experiment to the mass of powder initially loaded into the chamber, i.e., the mass of dust released from the sample weight by a standard dust generating device.

[0133] The mass of dust released from the sample weight by a standard dust generating device is based on the sample weight and is reported as a weight percentage.

[0134] Table 5 shows the results of the measured dust levels.

[0135] [Table 5]

[0136] It has been found that the ultraparticles composed of dry-coated graphene particles according to the present invention have a lower dust value than untreated graphene-based materials. In the case of the particles according to the present invention, the stability of the ultraparticles composed of dry-coated graphene particles is improved, particularly on the surface, because the gaps between smaller particles of the graphene material used are filled.

[0137] Example 3: Effects of using aluminum oxide Except for using different commercially available aluminum oxides, superparticles consisting of dry-coated graphene particles were prepared according to Example 1. Measurements of compaction density, bulk density, Hausner coefficient, inclination angle, and dynamic avalanche angle of the superparticles consisting of dry-coated graphene particles according to Example 2, performed according to Example 1, did not show significant differences from the measurements of the superparticles consisting of dry-coated graphene particles according to Example 1.

[0138] Example 4: Thermal conductivity and electrical insulation The superparticles of the present invention, consisting of dry-coated graphene particles according to Example 1, and the First Graphene pure graph 20 and aluminum oxide particles used in Example 3, were each introduced separately into an epoxy resin matrix in an amount of 20% by weight. The resulting products were tested for thermal conductivity and electrical insulation using the previously described test methods. These results are shown in Figure 10. As can be seen from this figure, the superparticles consisting of dry-coated graphene particles according to the present invention had a sheet resistance several orders of magnitude higher than the uncoated First Graphene pure graph 20, while no significant decrease in thermal conductivity was observed. A clear improvement in thermal conductivity was achieved compared to pure aluminum oxide. Furthermore, surprisingly, an even greater improvement in electrical insulation was found compared to pure aluminum oxide.

[0139] Therefore, superparticles composed of dry-coated graphene particles manufactured by the method according to the present invention have improved electrical insulation without lowering thermal conductivity. [Brief explanation of the drawing]

[0140] [Figure 1] This figure shows a Heubach dust meter Type I dust generating device. [Figure 2] This is a schematic diagram of a preferred method according to the present invention. [Figure 3] This is a schematic diagram of the hypothetical formation of superparticles F, J, and P, which are composed of dry-coated graphene particles according to the present invention, after the implementation of step c. [Figure 4a] This is a schematic diagram illustrating the principle of the Revolution Powder Analyzer's functionality. [Figure 4b] This is a schematic diagram of a spray dryer that is preferred for use. [Figure 5] First Graphene pure graph 20 This is a diagram showing the starting materials. [Figure 6] This figure shows the particle size distribution of the starting material in First Graphene pure graph 20, measured in water with agitator speed 6, ultrasonic waves for 1 minute, and circulation speed 6. [Figure 7] This figure shows the surface structure of 5% by weight additive ultraparticles composed of spray-dried First Graphene Pure Graph 20 (80 wt%) + Aluminum Oxide (20 wt%) + dry-coated graphene particles. [Figure 8] This figure shows 5% by weight additive ultraparticles composed of spray-dried First Graphene Pure Graph 20 (80 wt%) + Aluminum Oxide (20 wt%) + dry-coated graphene particles. [Figure 9] This figure shows the internal structure of 5% by weight additive ultraparticles composed of spray-dried First Graphene Pure Graph 20 (80 wt%) + Aluminum Oxide (20 wt%) + dry-coated graphene particles. [Figure 10] This figure compares the sheet resistance to thermal conductivity of the ultraparticles (black squares) of the present invention, which are composed of dry-coated graphene particles, with that of primary particles of pure First Graphene pure graph 20 (black diamonds) and pure aluminum oxide (black triangles), in both cases representing 20% ​​by weight of particles in epoxy resin.

Claims

1. A method for producing superparticles composed of dry-coated graphene particles, (a) At least one graphene material, SiO ２ , aluminum oxide, TiO ２ Selected from MgO, ZnO, SbO, organic fillers, or polymers. Dry coating with the material, after that, (b) Disperse the dry-coated graphene material obtained in step (a) in a solvent. Simultaneously or afterward, (c) Add to the dispersion obtained in step (b) 0.1 to 150% by weight, preferably 0.1 to 100% by weight, of a dispersion aid, wetting aid, emulsifier and / or defoaming agent based on the mass of the graphene material used: after that, (d) Remove at least partially the solvent from the dispersion obtained in step (c) by spray drying, To obtain superparticles composed of dry-coated graphene particles, method.

2. The spray drying in step (d) The dispersion obtained in step (c) is sprayed into an inert gas stream by a spray unit, and the solvent in the droplets formed by the spray is at least partially evaporated. The method according to claim 1, including the method described in claim 1.

3. (e) De-aggregating the resulting superparticles, which are composed of dry-coated graphene particles, by the action of shear force in a matrix material, preferably a polymer, monomer, or solvent, thereby homogeneously dispersing the dry-coated graphene material in the matrix material. The method according to claim 1 or 2, further comprising step (e) including the following:

4. The method according to claim 1, wherein the solvent in step (b) is selected from water, distilled water, and alkanol, and is preferably ethanol.

5. A diameter d of 1 μm to 500 μm, preferably 5 μm to 250 μm, and especially preferably 50 μm to 100 μm. ５０ The method according to any one of claims 1 to 4, wherein superparticles are obtained, which are composed of dry-coated graphene particles having the property.

6. The method according to any one of claims 1 to 5, wherein the mass percentage of graphene in the dispersion used in step (b) is 5% by weight to 50% by weight.

7. The spraying unit in step (d) is a device having at least one two-phase nozzle, And / or the inert gas used is nitrogen, preferably dry nitrogen. The temperature of the inert gas flow is more preferably set to a range of 200°C to 400°C above the cooling limit temperature of the solvent, and even more preferably within the range of 220°C to 300°C. and / or the sprayed droplets have a size of 30 to 1000 μm, The method according to any one of claims 1 to 6.

8. In a superparticle composed of dry-coated graphene particles obtained according to at least one of claims 1 to 7, An angle of repose in accordance with ISO 4324, of 50° to 20°, preferably 40° to 25°. Dynamic avalanche angle compliant with ISO 4324, 65° to 30° 1. Hausner coefficients in accordance with ASTM 527, from 1.5 to 1. and / or Dust values ​​compliant with DIN 55992 Type I, ranging from 10 to 0.

001. A superparticle composed of dry-coated graphene particles, characterized by the following features.

9. - In particular, thermally conductive materials and thermally conductive adhesives in the fields of batteries, sensors, ICs, and LEDs, such as films, underflow materials, pourable electronic materials, materials with phase transitions, thermal pastes, sealing compounds, - Composite materials based on thermoplastic resins, thermosetting resins, and / or elastomers having increased electrical conductivity and / or thermal conductivity, or for EMI shielding, particularly in the field of housings for electrical components, motors, battery packs, and pipelines. - Coatings and varnishes having thermal conductivity and / or electrical conductivity, or for EMI shielding sector applications. - Thermally conductive and / or conductive oil, coolant, or ink The use of superparticles comprising dry-coated graphene particles obtained according to claim 8 or at least one of claims 1 to 7.

10. - A standard thermoplastic resin, preferably selected from PE, PP, PS, PVC, alpha-olefin, butadiene derivatives, and / or Vestenamer®. - Industrial thermoplastic resins, preferably PET, PMMA, PC, POM, PA, PBT, PEBA, TPU, PU, ​​and / or TPE, - High-performance thermoplastic resin, preferably PPS, PEEK, PES, PI, and / or PEI, - Pastes containing copolymers, elastomers, preferably silicones, more preferably room temperature crosslinked (RTV) silicones, high temperature crosslinked (HTV) silicones, liquid silicone rubber (LSR), heat crosslinked rubber (HCR), acrylates, and / or polysiloxanes and oligosiloxanes. - Polyurethane, rubber, preferably styrene-butadiene rubber (SVR), butadiene rubber (BR), and / or natural rubber, thermosetting resin, preferably polyurethane, polyester resin, phenolic resin, epoxy resin, acrylate resin, and / or silicone resin, - Solvents, preferably aprotic-nonpolar, aprotic-polar, and / or protic solvents. - Oil, preferably mineral oil, silicone oil, and / or process oil The use of superparticles comprising dry-coated graphene particles obtained according to claim 8 or at least one of claims 1 to 7.

11. Use of superparticles, preferably as additives in compounders, extrusions, and injection moldings, in the plastics processing industry, comprising dry-coated graphene particles obtained according to claim 8 or at least one of claims 1 to 7.

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