Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/005—Reinforced macromolecular compounds with nanosized materials, e.g. nanoparticles, nanofibres, nanotubes, nanowires, nanorods or nanolayered materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
  • B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/022—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the choice of material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/285—Feeding the extrusion material to the extruder
  • B29C48/288—Feeding the extrusion material to the extruder in solid form, e.g. powder or granules
  • B29C48/2886—Feeding the extrusion material to the extruder in solid form, e.g. powder or granules of fibrous, filamentary or filling materials, e.g. thin fibrous reinforcements or fillers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/285—Feeding the extrusion material to the extruder
  • B29C48/29—Feeding the extrusion material to the extruder in liquid form
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/375—Plasticisers, homogenisers or feeders comprising two or more stages
  • B29C48/39—Plasticisers, homogenisers or feeders comprising two or more stages a first extruder feeding the melt into an intermediate location of a second extruder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
  • B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/285—Feeding the extrusion material to the extruder
  • B29C48/297—Feeding the extrusion material to the extruder at several locations, e.g. using several hoppers or using a separate additive feeding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/50—Details of extruders
  • B29C48/76—Venting, drying means; Degassing means
  • B29C48/765—Venting, drying means; Degassing means in the extruder apparatus
  • B29C48/766—Venting, drying means; Degassing means in the extruder apparatus in screw extruders
  • B29C48/767—Venting, drying means; Degassing means in the extruder apparatus in screw extruders through a degassing opening of a barrel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/0005—Condition, form or state of moulded material or of the material to be shaped containing compounding ingredients
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
  • B29K2105/16—Fillers
  • B29K2105/162—Nanoparticles

Definitions

• the invention relates to a method for producing a composite material with reduced surface resistance comprising carbon nanotubes.
• Carbon nanotubes are referred to below as “CNT” (carbon nanotubes)
• CNT are microscopic tubular structures (molecular nanotubes) made of carbon
• the diameter of the tubes is usually in the range of 1-200 nm.
• the electric Conductivity inside the tube is metallic or semiconducting:
• the mechanical properties of carbon nanotubes are outstanding: CNTs have a density of 1.3 - 2 g / cm 3 and a tensile strength of 45 GPa the current carrying capacity and the thermal conductivity are interesting: the former is estimated to be 1000 times higher than copper wires, the latter at room temperature with 6000 W / (m * K) is almost twice as high as that of Diamant (3320 W / (m * K)).
• CNT may be added to materials to enhance the electrical and / or mechanical and / or thermal properties of the materials.
• Such composites comprising CNT are known in the art.
• WO-A 2003/079375 claims polymeric material which exhibits mechanically and electrically improved properties by the addition of CNT.
• WO-A 2005/015574 discloses compositions containing organic polymer and CNT which form rope-like agglomerates and contain at least 0.1% impurities.
• the compositions are characterized by a reduced electrical resistance and a minimum of notched impact strength.
• nanoparticles form agglomerates which must be comminuted in order to obtain the most homogeneous possible distribution of the nanoparticles in the composite material (A. Kwade, C.
• the medium is considered to penetrate into the interior of the CNT agglomerates (infiltration) (G. Kasaliwal, A. Göldel, P. Pötschke, Influence of Processing Conditions in Small scale melt mixing and compressing molding on the resistivity of polycarbonate-MWNT composites, Proceedings of the Polymer Processing Society, 24th Annual Meeting, PPS24, June 15-19, 2008 Sachto, Italy; WO-A 94/23433).
• Kasaliwal et al. Citing the infiltration process considered necessary, is described in the aforementioned publication.
• the object is to provide a method for producing composite materials comprising reduced carbon nanoparticles (CNT) which disperses CNT agglomerates in a fluid material and distributes them homogeneously in the material such that the CNT forms a three-dimensional network in the CNT Form material.
• CNT reduced carbon nanoparticles
• the number of CNT agglomerates having a sphere equivalent diameter greater than 20 ⁇ m in the composite per square millimeter should be less than 20 multiplied by the percent CNT concentration (ie, less than 100 for 5% CNT). More preferably, the number of CNT agglomerates having a sphere-equivalent diameter greater than 20 ⁇ m in the composite per square millimeter should be less than 2 multiplied by the concentration in percent.
• the process should be readily modifiable (applicable) for throughputs on an industrial scale, ie scalable to large throughputs on a ton scale. Furthermore, the process should not cause any appreciable reduction in CNT.
• the object can be achieved by subjecting the CNT agglomerates for dispersion in a fluid material to a minimum stress, which leads to comminution of the CNT agglomerates, without the CNTs being appreciably shortened, the minimum stress being dependent of the required size distribution of the CNT in the composite but independent of the selected fluid material.
• the present invention therefore provides a process for producing a composite material with reduced electrical resistance comprising carbon nanotubes (CNT) with a predeterminable size distribution, characterized in that a mixture comprising at least CNT and a fluid material in a dispersing machine an empirically determined depending on the predetermined size distribution Under stress is subjected to stress preferably occurring in the dispersing machine highest shear stress is to be understood.
• CNT carbon nanotubes
• carbon nanotube is understood to mean substantially cylindrical compounds consisting mainly of carbon
• the substantially cylindrical compounds may be single-walled carbon nanotubes (SWNTs) or multi-walled (multiwalled carbon nanotubes, MWNTs) a diameter d between 1 and 200 nm and a length / which is a multiple of the diameter, Preferably the ratio Ud (aspect ratio) is at least 10, more preferably at least 30.
• carbon nanotubes is understood here to mean compounds which consist entirely or mainly of carbon. Accordingly, carbon nanotubes containing "foreign atoms” (e.g., H, O, N) are also to be understood as carbon nanotubes, and such carbon nanotubes of the present invention are herein abbreviated to CNT.
• the CNTs to be used preferably have an average diameter of 3 to 100 nm, preferably 5 to 80 nm, particularly preferably 6 to 60 nm.
• CNT Common processes for the production of CNT include arc discharge, laser ablation, chemical vapor deposition (CVD) and vapor deposition (CCVD). Preference is given to using CNTs obtainable from catalytic processes, since they generally have a smaller proportion of, for example, graphite- or carbon black-like impurities.
• CVD chemical vapor deposition
• CCVD vapor deposition
• a particularly preferred method for the production of CNT is known from WO-A 2006/050903.
• the CNTs usually accumulate in the form of agglomerates, the agglomerates having a sphere-equivalent diameter in the range of 0.05 to 2 mm.
• the electrical resistance of the material is reduced, ie, the conductivity is increased.
• reduced electrical resistance is meant a surface resistance of less than 10 7 ohms / sq ( ⁇ / sq) (for measurement of surface resistance, see Figure XX).
• fluid material is meant a viscous material or a viscoelastic material or a viscoplastic material or a plastic material or yield point material.
• Fluid material in particular, means suspensions, pastes, liquids and melts.
• materials which are in a "fluid” state, can be converted into a "fluid” state or have a “fluid” precursor
• Materials which can be used are, for example, suspensions, pastes , Glass, ceramic masses, metals in the form of a melt, plastics, plastic melts, polymer solutions and rubber compounds, plastics and polymer solutions are preferably used, particularly preferably thermoplastic polymers, preferably at least one of the series polycarbonate, polyamide, polyester, in particular polybutylene terephthalate and polyethylene terephthalate, polyethers, thermoplastic polyurethane, polyacetal, fluoropolymer, in particular polyvinylidene fluoride, polyethersulfones, polyolefin, in particular polyethylene and polypropylene, polyimide, polyacrylate, in particular poly (methyl) methacrylate, polyphenylene oxide, polyphe nylon sulfide, polyether ketone, poly
• Other preferred feedstocks are rubbers.
• the rubber at least one of styrene-butadiene rubber, natural rubber, butadiene rubber, isoprene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, butadiene-acrylonitrile rubber, hydrogenated nitrile rubber, etc. is preferably used.
• a combination of two or more of the listed rubbers, or a combination of one or more rubber with one or more plastics is of course also possible.
• CNT is mixed in the form of agglomerates with at least one further material.
• the material is optionally heated before, during or after the addition of CNT to bring the material into a "fluid” state, and it is also conceivable to achieve the "fluid” state by introducing mechanical energy.
• the CNT agglomerates are comminuted by a minimum stress of the mixture comprising at least CNT and a fluid material.
• the minimum stress is made by introducing energy into the mixture.
• a dispersing machine is used whose task is the dispersion of CNT in a material.
• twin-screw or twin-screw extruders in particular co-rotating twin-screw extruders such as the ZSK 26 from Coperion Werner & Pfleiderer, planetary roller extruder, internal mixer, ring extruder, kneader, calender, co-kneader or a combination of at least two the mentioned machines.
• Dispersing machines introduce energy into the mixture comprising at least CNT and a fluid material which results in comminution of the CNT agglomerates and dispersion of the CNT in the fluid material.
• shear stresses that lead to this desired effect.
• shear stress is generally understood to mean a stress that has an analogous effect, such as a shear stress, i. which leads to a comminution of the CNT agglomerates and a distribution of CNT in the material (see also Equations 1 and 2).
• the minimum stress is expressed by the maximum shear stress occurring in the dispersing machine used.
• the minimum stress is preferably determined empirically.
• microscopically or macroscopically measurable characteristic target values can be defined.
• the conductivity of a CNT composite material increases as the CNT agglomerates shrink, thereby increasing the amount of deagglomerated CNT dispersed in the material. Accordingly, it makes sense to require a minimum conductivity, which occurs at a minimum stress.
• Empirically it can be determined which minimum stress is required to achieve the required minimum conductivity.
• the conductivity or its reciprocal of the resistance is understood as macroscopically measurable size.
• the characteristic size distribution of the CNT agglomerates may be e.g. with a microscope, which is why the characteristic size is understood as a microscopically measurable size.
• One possible characteristic target would be e.g. a number of CNT agglomerates with a sphere equivalent diameter greater than 20 microns in the composite per square millimeter less than 20 multiplied by the CNT concentration in percent (for 5% CNT content thus less than 100).
• a particularly preferred target size is a number of CNT agglomerates having a sphere equivalent diameter greater than 20 ⁇ m in the composite per square millimeter less than 2 multiplied by the concentration in percent. It has been empirically found that such a size distribution of CNT in the composite material leads to a reduced electrical resistance. To determine the number of CNT agglomerates above or below certain sizes, CLSM (Confocal Laser Scanning Microscopy) wells are very well suited.
• the value v indicates the volume fraction of the CNTs in percent. This can be easily calculated from the mass fraction of CNTs, according to Kasaliwal et al. For example, the density of CNTs is about 1.75 g / cm 3 .
• a value of the dispersing quality of 100% means that there are no agglomerates in the compound that exceed the selected limit. This indicates the state of very good dispersion. Kasaliwal et al.
• the dispersing quality DG can also be used as a characteristic, microscopically measurable variable and a corresponding target size can be defined.
• a minimum stress e.g. in the form of a minimum shear stress is necessary to achieve maximum conductivity at a given CNT content.
• Increasing the stress (shear stress) to a value above the minimum stress (minimum shear stress) does not lead to increased conductivity.
• the stress within the mixture comprising CNT and fluid material is the decisive factor for achieving maximum conductivity.
• the found relationship between minimum stress and maximum conductivity is independent of the material used.
• the CNT agglomerates are comminuted by energy input in the dispersing machine.
• the mixture of CNT and at least one further material is subjected to a minimum stress.
• the stress state in a fluid may be described by a stress tensor that determines the shape
• sp is the trace operator, that is, the sum of the elements of the tensor diagonal.
• the viscosity of various materials and the various methods for measuring the viscosity of the skilled worker for example, in Gl alonele (M.Pahl, W. Gl sandwichle, H. -M. Laun, Practical rheology of plastics and elastomers, 1st ed., VDI -Verlag 1991).
• the viscosity can be determined, for example, via capillary rheometer.
• the actual viscosity of the mixture occurring during dispersion is at least CNT and a fluid Use material at processing temperature and actual shear rate in the dispersing machine.
• each pass increases the proportion of CNT composite material that has experienced more than a certain shear stress.
• this could be demonstrated for CNT agglomerates (see Example 2).
• the minimum stress in the dispersing machine is expressed by the maximum shear stress, as these are easily calculated as shown above and can be easily varied in a dispersing machine. It is clear to the person skilled in the art that comminution does not necessarily require the maximum shear stress occurring in a dispersing machine. The shear stress actually required for comminuting a CNT agglomerate will be somewhat smaller than the maximum shear stress occurring in the dispersing machine; but it is not so easy to determine / specify. For this reason, the minimum stress is preferably expressed by the maximum shear stress occurring in the dispersing machine.
• the process according to the invention is characterized in that a mixture comprising at least CNT and a fluid material is subjected to a minimum stress of 75,000 Pa, stress being understood to mean preferably the maximum shear stress occurring in the dispersing machine.
• the minimum stress is greater than 90,000 Pa, more preferably greater than 100,000 Pa.
• the load is limited, otherwise irreversible damage to the CNT polymer composite material is to be expected. The upper limit of 2,000,000 Pa seems reasonable.
• Equation 11 For apparatus in which the maximum shear stress that occurs can not readily be calculated (for example, when dispersed in a nozzle in which the flow is turbulent), the approach of Equation 11 is used; It will be held in place of the maximum
• Shear stress indicates the mean shear stress required to achieve the desired sizes.
• the specific mechanical energy input in the dispersing machine to a value in the range of 0.1 kWh / kg to 1 kWh / kg, preferably from 0.2 kWh / kg to 0.6 kWh / kg and the minimum residence time on set a value in the range of 6 seconds to 90 seconds, preferably 8 seconds to 30 seconds.
• the minimum residence time of the mixture comprising at least CNT and a fluid material in the dispersing machine is Range from 6 s to 90 s, preferably 8 s to 30 s.
• the inventive method is characterized in that the minimum stress is achieved by a correspondingly high shear rate and / or a correspondingly high viscosity.
• the minimum stress in terms of the highest shear stress occurring in the dispersing machine may be a product of shear rate (highest shear rate occurring in the dispersing machine) of the mixture (at least comprising CNT and a fluid material) and viscosity (actual viscosity of the mixture during dispersion at processing temperature and actual shear rate in the dispersing machine).
• the viscosity of the mixture is selected so that the product of viscosity and shear rate is greater than or equal to the minimum stress, the minimum stress preferably greater than or equal to 75,000 Pa, more preferably greater than 90,000 Pa, most preferably greater than 100,000 Pa.
• the shear rate of the dispersing machine is selected such that the product of the highest shear rate occurring in the dispersing machine and the viscosity is greater than or equal to the minimum stress, the minimum stress being preferred greater than or equal to 75,000 Pa, more preferably greater than 90,000 Pa, most preferably greater than 100,000 Pa.
• the average residence time on a co-rotating ZSK 26 Mc twin-screw extruder from Coperion Werner & Pfleiderer with an L / D ratio of 36 at a throughput of 20 kg / hr is approximately 30 seconds.
• Common industrial compounding extruders have an L / D ratio of 20 to 40.
• a high viscosity of the dispersion can be achieved, for example, by selecting the material.
• the material is a polymer
• a higher viscosity can be achieved by selecting a type with a higher content of longer chain molecules.
• the viscosity is increased by a low processing temperature.
• the highest viscosities occur in the melting zone of the dispersing machine for thermoplastic polymers.
• a preferred embodiment of the method according to the invention consists in setting the temperature of the dispersing machine (for example twin-screw extruder) low, in particular in the region of the melting zone. In general, the Temperature of the thermoplastic polymers in dispersing machines at the beginning lowest, so that there the viscosities are higher due to the low temperature.
• a preferred embodiment of the process according to the invention consists in dispersing the CNT agglomerates in one pass on a dispersing machine, since this is particularly economical.
• a higher concentration of CNT is incorporated into the material than is provided for the later composite material and in a second step added a further amount of material for "dilution" of the CNT concentration of the dispersion
• the second step can be carried out downstream on the same dispersing machine, but it can also be carried out on the same or another dispersing machine as an extra process step
• the addition of the higher concentration of CNT in the first step has the same effect as the addition of fillers: The viscosity of the dispersion increases, and if shearing forces are introduced into the dispersion to break down the CNT agglomerates, the shear stress is higher than if a smaller amount of CNT had been added to the dispersion Wind speed reached, or is the shear stress in the case of higher concentrated CNT dispersion higher.
• the CNT agglomerates are effectively crushed without causing a significant reduction of CNT.
• the amount of a same and / or further material is added, which is necessary in order to obtain the composite material with the desired CNT concentration.
• the material added in the second step may have a different viscosity.
• a material having the same or lower viscosity is added in the second step, since low viscosities are advantageous for the further processing of the CNT compound.
• the shear rate can be increased to the necessary
• a dispersing machine for example single-screw extruder, identical or counterrotating twin or multi-screw extruder - in particular co-rotating twin-screw extruder such as, for example, the ZSK 26 Mc from Coperion Werner & Pfleiderer, planetary roller extruder, internal mixer, ring extruder, kneader,
• Calender, co-kneader consists e.g. through the use of higher speeds.
• Machines can be made small as another way to increase the shear rate. Particularly narrow gaps in which very high shear rates occur, e.g. Calender on.
• CNT are together with a thermoplastic polymer in solid phase the main entry of a single-screw extruder or an equal or opposite twin- or multi-screw extruder (as an example here is a co-rotating twin-screw extruder ZSK 26 Mc Coperion Werner & Pfleiderer called) or a planetary roller extruder or an internal mixer or a ring extruder or a kneader or a calender or a co-kneader.
• the CNTs are predispersed in the feed zone by solids friction to form a solids mixture.
• the polymer is melted, and the CNT in this melting zone is further dispersed predominantly by hydrodynamic forces and distributed homogeneously in further zones in the polymer melt.
• the CNTs are e.g. processed according to the invention by means of one or a combination of several of the following apparatuses to a composite material: jet disperser, high pressure homogenizers, rotor-stator systems (sprocket dispersing machines, colloid mills, ...), stirrers, nozzle systems, ultrasound.
• low-viscosity media containing CNT
• high stress can be achieved, for example, by ultrasound.
• the resulting cavitation generates pressure surges of over 1000 bar, which causes an effective crushing of CNT agglomerates.
• Low-viscosity media (containing CNT) can, for example, even under high pressure (eg 10 bar - 1000 bar) through narrow gaps (eg 0.05 - 2 mm) or correspondingly small holes or correspondingly small slots (fixed components or with moving components) be promoted, creating high Stresses occur. It is clear to the person skilled in the art that for such flows, even if they are turbulent, for example, a shear stress according to Eq. 7 or Eq. 10 can be calculated.
• the process according to the invention offers the advantage that CNT composite materials with homogeneously distributed CNTs and reduced electrical resistance, high thermal conductivity and very good mechanical properties can be produced on an industrial scale in an economically efficient manner.
• the process of the invention can be operated both continuously and discontinuously; it is preferably operated continuously.
• the invention also provides a CNT composite material obtained from the process according to the invention.
• the invention furthermore relates to the use of the CNT composite material obtained by the process according to the invention as an electrically conductive, electrically shielding or electrostatically dissipative material.
• Fig. 1 is a process diagram of a system for carrying out the method
• Fig. 2 is a schematic longitudinal sectional view of the system used in the Fig. 1
• Twin-screw extruder Fig. 3 shows a measuring arrangement for determining the surface electrical resistance of the CNT composite materials
• FIG. 4 Microscopic image of CNT from Example 1 (untreated, Experiment No. 1)
• FIG. 5 micrograph of CNT from example 1 (acid-treated (HCl), experiment no.
• FIG. 6 Light micrographs of CNT agglomerates
• Fig. 7 Viscosities of the PE types used in Example 3
• Fig. 8 Microscopic image of a mLLDPE-CNT compound from Example 3, experiment
• FIG. 10 Microscopic image of a HDPE-CNT compound from Example 3, Experiment No. 6
• FIG. 1 Micrograph of an LDPE-CNT compound from Example 3, Experiment No. 7
• Fig. 1 consists in the core of a twin-screw extruder 1 with a
• the constituents of the CNT composite e.g., polymer 1, additives (e.g.
• Antioxidants, UV stabilizers, mold release agents), CNT, optionally polymer 2) are required via metering screws 8-11 in the feed hopper 2 of the extruder 1. The from the
• Nozzle plate 3 emerging melt strands are cooled in a water bath 6 and solidified and then crushed with a granulator 7.
• the twin-screw extruder 1 (see FIG. 2) has, inter alia, a housing consisting of ten parts, in which two worm shafts (not shown) rotating in the same direction and meshing with one another are arranged.
• the components to be compounded including the CNT agglomerates are fed to the extruder 1 via the feed hopper 2 arranged on the housing part 12.
• a feed zone which preferably consists of threaded elements with a pitch of 2 times the screw shaft diameter (short: 2 DM) to 0.9 DM.
• the CNT agglomerates are promoted together with the other components of the CNT composite material to the melting zone 14, 15 and the CNT agglomerates by frictional forces between the solid-state polymer granules and also in the solid phase CNT powder intense mixed and predispersed.
• the melting zone which preferably consists of Knetblöcken; Alternatively, depending on the polymer, it is also possible to use a combination of kneading blocks and tooth mixing elements.
• the melting zone 14, 15 the polymeric constituents are melted and the predispersed CNT and additives are further dispersed and mixed intensively with the remaining composite components.
• the heating temperature of the extruder housing in the region of the melting zone 14, 15 is set to a value which is greater than the melting temperature of the polymer (in the case of semicrystalline thermoplastics) or the glass transition temperature (in the case of amorphous thermoplastics).
• a post-dispersion zone is provided downstream of the melting zone 14, 15 between the conveying elements of the screw shafts. She shows kneading and mixing elements, which cause a frequent rearrangement of the melt streams and a broad residence time distribution. In this way, a particularly homogeneous distribution of CNT is achieved in the polymer melt. Very good results were achieved with tooth mixing elements. Furthermore, for mixing the CNT and screw mixing elements, eccentric discs, return elements, etc. can be used. Alternatively, several Nachdispergierzonen can be connected in series to intensify the fine dispersion.
• the combination of predispersion in the solid phase, the main dispersion during the melting of the polymer (s) and the downstream fine dispersion, which takes place in the liquid phase, is important for achieving the most uniform possible CNT distribution in the polymer.
• the removal of volatile substances takes place in a degassing zone in the housing part 20 via a degassing opening 4, which is connected to a suction device (not shown).
• the degassing zone consists of threaded elements with a pitch of at least 1 DM.
• the last housing part 21 contains a pressure build-up zone, at the end of which the compounded and degassed product exits the extruder.
• the pressure build-up zone 21 has threaded elements with a pitch between 0.5 DM and 1, 5 DM.
• the (in the form of granules) obtained CNT composite materials can then be further processed by all known thermoplastic processing methods.
• moldings can be produced by injection molding.
• two LeitsilberstMail 23, 24 are applied, whose length B coincides with their distance L, so that a square area sq (Square) is defined.
• the electrodes of a resistance measuring device 25 are pressed onto the Leitsilberstsammlung 23, 24 and read the resistance value at the meter 25.
• the measuring voltage used was 9 volts for resistors up to 3x10 7 ohms / sq and from 3x10 7 ohms / sq
• CNT multi-walled carbon nanotubes
• the process parameters are shown in Table 1 below.
• the worm stock used was 23.6% kneading elements.
• the melt temperature was measured with a commercially available temperature sensor directly in the emerging at the nozzle plate 3 melt strand.
• the number and diameter of incompletely dispersed CNT agglomerates contained in the carbon nanotube polymer composite are measured by a light microscope on a 5 cm long strand of the CNT polymer composite.
• the further dispersion was carried out at 100 bar with a piston pump from Böllhoff (type 060.020.-DP, maximum pressure: 420 bar).
• a jet disperser with a 0.6 mm diameter bore was used. The throughput was about 72 kg / h. After passing through the jet disperser, the suspension was collected and the dispersing step was repeated. Overall, the dispersion was carried out in 10 passes at 100 bar. Thereafter, under the light microscope, a maximum particle size of about 20 microns was recognizable (Fig. 6, no. 1).
• the further dispersion was carried out at 200 bar again with the same piston pump from Böllhoff (type 060.020.-DP, maximum pressure: 420 bar).
• the dispersion was carried out in 10 passes with a jet disperser with a bore with a diameter of 0.35 mm. The throughput was about 47 kg / h. Thereafter, a maximum particle size of about 10 ⁇ m was recognizable under the light microscope (FIG. 6, no. 2). Subsequently, the dispersion was further dispersed at 200 bar with a jet disperser having a bore with a diameter of 0.35 mm. This dispersion took place in the circulation. That is, the dispersion was not collected after passing through the jet disperser, but fed directly to the pump. This dispersion was continued until the dispersion had a temperature of about 45 ° C. The duration was about 5 passes. Subsequently, another 15 passes were carried out at 200 bar. Again, these were "real" runs in which the dispersion was collected and then fed to the pump.
• a representative (mean) shear stress for the turbulent wake zone of a jet disperser can be calculated.
• the wake zone can be described as a truncated cone with a diameter of D at the nozzle and a diameter of 3D at the end and a length of 9D.
• a throughput of 20 kg / h a pressure drop of 1000 bar (inlet and outlet pressure losses are neglected here) and a viscosity of le-3 Pas (the true viscosity is significantly increased by the CNT agglomerates ), the representative shear stress according to Eq. 10 l, 76e4 Pa.
• the representative (mean) shear stress is 5.57e5 Pa.
• CNT multi-walled carbon nanotubes
• Baytubes® C 150P manufacturer Bayer Material Science AG, available
• mLLDPE polyethylene
• LLDPE LLDPE
• HDPE high density polyethylene
• LDPE low density polyethylene
• LF18P FAX mLLDPE
• LXl 8 K FA-TE LLDPE
• HDPE high density polyethylene
• LDPE low density polyethylene
• Basell ZSK 26 Mc co-rotating twin-screw extruder (Coperion Werner & Co.). Pfleiderer).
• both the polymer granules and the CNT were metered into the extruder via the main intake or hopper 2.
• the worm stock used consisted of 28.3% kneading elements.
• the melt temperature was measured with a commercially available temperature sensor directly in the emerging at the nozzle plate 3 melt strand.
• Example 3 explicitly shows that a certain voltage is required for good conductivity to be achieved and for the CNT agglomerates to be below a certain size. The higher this shear stress, the smaller are the remaining CNT agglomerates. With improved CNT fragmentation, a smaller amount of CNT is needed to make the CNT-PE compounds conductive, the percolation threshold shifts to lower CNT levels.
• This machine size has a particularly high surface to volume ratio, which is why the melt is strongly cooled.
• the measured melt temperature at the extruder outlet says nothing about the actual melt temperatures in the machine for this machine size, so that therefore no calculation of the shear stress is dispensed with.

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