Process for beading and drying carbon nanotube-based compositions

Abstract

Process for beading and drying carbon nanotube-based compositions with minimal effect on end product performance.

Description

PROCESS FOR BEADING AND DRYING CARBON NANOTUBE-BASEDCOMPOSITIONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority' to U.S. Provisional Application No. 63 / 515,465, filed July 25, 2023, which is incorporated into this application by reference.BACKGROUND

[0002] Carbon nanotube compositions are often supplied in wet form due to their production methods, ty pically involving an acid purification process followed by' a wash with a liquid such as water. For end applications, such as those for electrical conductivity7, such compositions usually need to be dried before being applied to the article or substrate. A variety of methods exist to dry compositions but these methods often result in diminished performance, which is believed to result from carbon nanotubes or other composition components being agglomerated together in the final product. For example, freeze-diying can remove moisture with minimum agglomeration but freeze-dry ing can be four to eight times more costly than conventional air drying, which limits practical commercial applications. A need in the art exists for new methods for process carbon nanotube-based compositions without sacrificing end performance.SUMMARY

[0003] Described herein is a method comprising: (a) providing a composition comprising carbon nanotubes and at least 20% of a liquid beading agent by weight of the composition;(b) beading the composition to form a beaded composition; and (c) drying the beaded composition to form a dried composition comprising less than 1% of the liquid beading agent by weight of the dried composition. In some embodiments, the composition further comprises a carbonaceous material having a graphitic or amorphous form, which is not a carbon nanotube.

[0004] Also described is a carbon nanotube product or carbon nanotube hybrid product prepared by the disclosed beading and drying method.

[0005] A millbase formulation is also described. The millbase formulation comprises (a) a polyol; (b) a solvent capable of at least partially dissolving the polyol; and (c) the dried composition prepared by7the disclosed beading and drying method.

[0006] A general solvent-borne coating composition is also described which is prepared or letdown from the millbase formulation, The solvent-borne composition generally comprises (a) the millbase formulation; and (b) a letdown formulation comprising: a crosslinker and a catalyst capable of catalyzing the reaction between the crosslinker and the polyol. Also described are articles and substrates comprising a coating cured from the general solvent-home coating composition.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The foregoing summary, as well as the following description of the disclosure, is better understood when read in conjunction with the appended drawings. The following figures, which are incorporated into and constitute part of the specification, assist in explaining the principles of the disclosure.

[0008] Fig. 1. is a graph showing the percolation profile of certain vacuum dried powders in acrylic coatings compared to freeze-dried reference samples.

[0009] Fig. 2 is a graph showing the percolation profile of certain vacuum dried powder in HDPE compared to a hybrid carbon black / carbon nanotube material.

[0010] Fig. 3 is a graph showing the percolation profile of hybrid carbon black / carbon nanotube materials, including those incorporating beaded samples, in an acrylic coating.

[0011] Fig. 4 is a graph showing the percolation profile of certain hybrid carbon black / carbon nanotube materials in HDPE.DETAILED DESCRIPTIONI. Drying and Beading Method

[0012] The disclosed method generally comprises (a) providing a composition comprising carbon nanotubes and at least 20% of a liquid beading agent by weight of the composition; (b) beading the composition to form a beaded composition; and (c) drying the beaded composition to form a dried composition comprising less than 1% of the liquid beading agent by weight of the dried composition.

[0013] In some embodiments, the starting composition may already comprise a liquid beading agent, e.g., the starting composition may be purchased for instance with a liquid beading agent already introduced to the composition. In other embodiments, a suitable liquid beading agent can be added to a starting carbon nanotube composition. A variety of liquid beading agents are contemplated and include water, a variety of solvents such as ethanol.methanol, and like. Polar solvents such as these and others can be useful liquid beading agents. Other suitable liquid beading agents include oils, fats, sugars, and polysaccharides, e.g., lignin and lignin salts such as lignin sulfonate, and starch. Still other liquid beading agent examples include polyvinyl alcohol (PVA), poly vinylidene difluoride (PVDF), polyvinylpyrrolidone (PVP), and sodium carboxymethyl cellulose. In some embodiments, the beaded composition comprises 20-95% of the liquid beading agent by weight of the beaded composition, e.g., 30-90%, 40-90%. 50-90%, 60-90%, or 70-90% of the liquid beading agent by weight of the beaded composition.

[0014] The starting composition with the liquid beading agent can be beaded through a variety of methods, including mixing, other application of a shear force, or on a large scale, beaded in a beading apparatus. An example is a pin beader. One such pin method, known as the wet-beading process, involves vigorously agitating the starting composition which includes the liquid beading agent with a rotating shaft provided with projecting pins, whereby the composition is converted to a cohering, wet or pasty mass, and continuing the agitation until the mass and liquid beading agent have been converted to tiny, spheroidal beads. Individual aggregates of the starting composition become associated and distributed throughout the composition to form a beaded product.

[0015] Once beaded, the composition can then be dried by any conventional method. Generally, the beaded composition can be dried in a conventional drying apparatus at temperatures sufficiently low so as not to decompose the beaded composition. The residual amount of the liquid beading agent can be monitored throughout the drying process until an acceptable level is obtained. In some embodiments, the dried composition comprises less than 0.8%, e.g., 0.5% or less, of the liquid beading agent by weight of the dried composition.

[0016] Drying temperatures, times, and pressure can vary within wide margins depending on the process. In an exemplary embodiment, the beaded composition can be dried (e.g.. in a vacuum oven) at a temperature ranging from 60°C to 180°C, e.g., 80°C-120°C or 100°C- 120°C, for a sufficient time to reach the desired residual liquid beading agent level. In a further embodiment, drying can be performed under reduced pressure in a vacuum oven, e.g., 10-25 inches Hg (or 4.9-12.3 psi).

[0017] The described method can in some embodiments result in an increase in bulk density7of the dried composition relative to the starting composition (prior to mixing the starting composition with the liquid beading agent). For example, the dried composition can have a bulk density of at least 0. 1 g / cc. In some embodiments, the dried composition can have a bulk density- of 0.1-0.4 g / cc, such as 0.1-0.3 g / cc, 0. 1-0.2 g / cc. 0.15-0.4 g / cc, 0.15g / cc-0.3 g / cc, or 0.15-0.2 g / cc.

[0018] In some embodiments, the ratio of the bulk density of the dried composition to the bulk density of a starting composition compnsing the carbon nanotubes prior to being combined with the liquid beading agent ranges from 1.5: 1 to 4: 1, i.e., the beading and drying method results in a significant increase in bulk density relative to the starting material. In some embodiments, the ratio of the bulk density of the dried composition to the bulk density of a starting composition comprising the carbon nanotubes prior to being combined with the liquid beading agent ranges from 1.5: 1 to 4: 1, e.g., 1.5: 1 to 3.5: 1, 1.5:1 to 3.2: 1, 2: 1 to 4: 1, 2: 1 to 3.5: 1, 2: 1 to 3.2:1, or 2.2: 1 to 3.2:1. The reference “starting composition” in some embodiments can be a carbon nanotube composition, including for example a hybrid starting composition comprising carbon nanotubes and a carbonaceous material such as carbon black, prior to that composition being combined or mixed with a liquid beading agent (e.g.. Example 2 below). In additional embodiments, the “starting composition” can be freeze-dried prior to measuring bulk density (e.g., Example 3 below, which was prepared by freeze-diying Example 2). “Bulk density” in this context refers to the poured bulk density or loose bulk density, which is determined by measuring the mass of untapped powder per a known volume (e g., the volume of a graduated cylinder, volumeter, or other suitable vessel).A. Carbon Nanotubes (CNTs)

[0019] The disclosed method is suitable for beading and drying carbon nanotube compositions as well as carbon nanotubes blended or otherwise mixed with various carbonaceous materials such as carbon blacks. The carbon nanotubes can be single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs). Carbon nanotubes can be characterized by various physical and chemical properties, such as average diameter, length, carbon purity', metal oxide impurity, and surface area, among others. SWCNTs typically will have a diameter ranging from 0.3 to 3 nanometers, e.g., 0.5-2.5 nanometers, with lengths as large as 1 mm, and aspect ratios up to 10,000. MWCNTs ty pically have larger average diameters, generally ranging from 5 to 100 nm, with lengths up to 1 mm, and aspect ratios of 50-4,000.

[0020] In some embodiments, the carbon nanotube is a MWCNT having an average diameter of 5-50 nm. e.g., 5-40 nm, 5-30 nm, 5-20 nm, 5-15 nm, 8-12 nm, or about 10 nm. In a further embodiment, the carbon nanotube is a MWCNT having an average length of 0. 1- 100 pm, e g., 0.1-80 pm, 0.1-60 pm, 0.1-50 pm, 0.1-40 pm, 0.1-30 pm, 0.1-20 pm, or 0.1-10pm. Average diameter and length of carbon nanotubes can be determined by transmission electron microscopy (TEM).

[0021] In certain embodiments, the carbon nanotube is a MWCNT having a carbon purity of at least 80%, e.g., 80%, 85%, or 90%. In a further embodiment, the MWCNT can have a metal oxide impurity of 1-15%, e.g., 1-12%, 1-10%, or about 10%. Carbon purity' and metal oxide impurity can be determined by thermal gravimetric analysis (TGA). In additional embodiments, the MWCNT can have a surface area of 100-500 m2 / g. e.g., 100-400 m2 / g, 100-300 m2 / g, 200-300 m2 / g, or 250-300 m2 / g. Surface area can be determined by the Brunauer, Emmett, and Teller (BET) method.

[0022] Carbon nanotubes including MWCNTs can be made according to methods known in the art or obtained commercially. Suitable production methods can include for instance a variety of catalytic based methods, such as those described in U.S. Patent Nos. 11,826,732, 9,731,277, 8,470,709, 7,923,615, 7,754,181, and International Patent Publication WO 2006 / 135991, each of which is incorporated into this application by reference for its teaching of carbon nanotube production methods and catalysts systems for use with those methods.B. Carbonaceous Materials

[0023] For CNT materials blended together with other carbonaceous materials (hybrid materials), a variety of carbon products can be used. The term “carbonaceous material’7refers to elemental carbon that is in the form of graphite or an amorphous form of carbon, and combinations thereof. Specific examples of amorphous carbonaceous materials include activated carbon, carbon black, natural graphite, synthetic graphite, graphene, carbon fiber, or activated carbon.

[0024] In some embodiments, the carbonaceous material is carbon black. A “carbon black” refers not only to carbon blacks but also to hybrid carbon black materials (e.g., surface- modified carbon blacks, encapsulated carbon blacks, and the like). The method is not limited to any particular type of carbon black. Generally, morphological characteristics of carbon black include, for example, particle size / fineness, surface area, aggregate size / structure, aggregate size distribution, and aggregate shape. Particle size is a measurement of diameter of the primary particles of carbon black. Roughly spherical particles of carbon black have an average diameter in the nanometer range. Particle size can be measured directly via electron microscopy or indirectly by surface area measurement. Average particle size is a factor that can determine the dispersibility ', tensile strength, tearresistance, hysteresis, and abrasion resistance in liquids and plastics systems. Average particle size can influence the relative color strength, UV stability, and conductivity of a carbon black composite. At equal structure, smaller particle size imparts higher tensile strength, tear resistance, hysteresis and abrasion resistance, stronger color, UV resistance, and increased difficulty of dispersion.

[0025] Carbon black particles coalesce to form larger clusters or aggregates, which are the primary dispersible units of carbon black. Aggregate size and structure are controlled in the reactor. Measurement of aggregate structure can be obtained from electron microscopy or oil absorption. Structure was historically measured by N-dibutyl phthalate, or DBP, absorption, now replaced by oil absorption number, or OAN (ASTM D2414-18, ISO 4656 / 1). Another measure of structure is the compressed oil absorption number, or COAN (ASTM D3493-18), where a carbon black sample is mechanically compressed prior to performing the oil absorption measurement. The difference between OAN and COAN values can be an indicator of the stability of the carbon black structure. Grades with relatively large aggregates with a high number of primary particles can be high structure grades, with bulkier aggregates that have more void space and high oil absorption. High structure carbon black can increase electrical conductivity.

[0026] The basic method for the production of carbon black is well known.Generally, carbon black is produced by the partial oxidation or thermal decomposition of hydrocarbon gases or liquids, where a hydrocarbon raw material is injected into a flow of hot gas wherein the feedstock hydrocarbon is pyrolyzed and converted into a smoke before being quenched by a water spray. The hot gas is produced by burning fuel in a combustion section. The hot gas flows from the combustion section into a reaction section which is in open communication with the combustion section. The feedstock hydrocarbon is introduced into the hot gas as the hot gas flows through the reaction section, thereby forming a reaction mixture comprising particles of forming carbon black. The reaction mixture flows from the reactor into a cooling section which is in open communication with the reaction section. At some location in the cooling section, one or more quench sprays of, for example, water, are introduced into the flowing reaction mixture thereby lowering the temperature of the reaction mixture below the temperature necessary for carbon black production and halting the carbon formation reaction. The black particles are then separated from the flow of hot gas. A broad range of carbon black ty pes can be made by controlled manipulation of the reactor conditions.

[0027] Many carbon black reactors normally comprise a cylindrical combustion sectionaxially connected to one end of a cylindrical or frusto-conical reaction section. A reaction choke is often axially connected to the other end of the reaction section. The reaction choke has a diameter substantially less than the diameter of the reaction section and connects the reaction section to the cooling section. The cooling section is normally cylindrical and has a diameter which is substantially larger than the diameter of the reaction choke.

[0028] The carbon black material of the present invention can be made using techniques generally known in the carbon black art. Variations on these methods can be determined by one of skill in the art. In one aspect, the carbon blacks can be produced in a carbon black reactor, such as those described generally in United States Patents Nos. 4,927,607 and 5,256.388, the disclosure of which are incorporated by reference in their entireties. Other carbon black reactors can be used, and one of skill in the art can determine an appropriate reactor for a particular application. Feedstock, combustion feeds, and quenching materials are well known in the carbon black art. The choice of these feeds is not critical to the carbon blacks described here. One of skill in the art can determine appropriate feeds for a particular application. The amounts of feedstock, combustion feeds, and quenching materials can also be determined by one of skill in the art which are suitable for a particular application.

[0029] It is well known that carbon black exists as a collection of aciniform aggregates that cover a wide range of surface area and structure or absorptive capacity. More fundamentally and from a morphological standpoint, structure manifests itself through shape and / or the degree of aggregate complexity, with lower structure aggregates having a more compact, spherical, and ellipsoidal structure and higher structure aggregates having a more branched and open architecture. In certain aspects, the larger an aggregate size and / or the more branching that exists within an aggregate, the more electrically conductive a hybrid material will be that incorporates such carbon black.

[0030] Non-limiting examples of suitable carbon blacks include those having a nitrogen surface area (NSA) of 25-600 m2 / g, e.g., 25-500 m2 / g, 25-400 m2 / g, 25-300 m2 / g, 25-200 m2 / g, 25-100 m2 / g, 25-75 m2 / g, or about 50 m2 / g. NSA can be measured according to ASTM D6556 (2015). In some embodiments, the carbon black has an oil absorption number (OAN) of 45-260 cm3 / g, e.g., 45-200 cm3 / g, 75-200 cm3 / g, 100-200 cm3 / g, 150-200 cm3 / g, or about 170 cm3 / g. OAN can be measured according to ASTM D2414 (2019). Electrical conductivity of the carbon black will generally be within 101- 105S / m.C. CNT / Carbonaceous Hybrid Materials

[0031] When the drying and beading method is used with hybrid CNT and carbonaceous materials, any suitable ratio of each component can be used. For example, the hybrid material can comprise from 1% to 99% of a CNT material by weight of the hybrid material. In a further embodiment, the hybrid material can comprise 10-90% by weight of a CNT material, e.g., 20-90%. 30-90%. 30-80%, or 40-70% of a CNT material by weight of the hybrid material.II. Compositions Comprising the Beaded CNT / CNT Hybrid Materials

[0032] Coating formulations can be prepared by first forming a mill base. The mill base can be prepared by grinding a mixture of the dried composition, resin (such as a polyol), and solvent in a high speed disc disperser such as Byk-Gardner DISPERMAT® Model CV to form a concentrate. The mill base can also be prepared using a Lau disperser, which involves placing the compositions and milling beads into a container and shaken in a Lau disperser for a suitable amount of time. This mill base can then be let dow n (mixed) under mixing conditions with the remaining components of the formulation which include additional resin (e.g., polyol), solvent, crosslinking agent, and a catalyst.

[0033] In addition to the dried composition prepared by the beading and drying method, the millbase can include a suitable resin forming material such as a polyol. The polyol can be an acry lic polyols, natural oil polyols, polyester polyols, polyether polyols, polycarbonate polyols, and blends thereof. Suitable acrylic polyols include acrylic polymers that range in Tgfrom 0-45°C. e.g., 10-40°C, or 20-35°C. and have number average molecular weights (Mn) in the range of 2,000-25,000 g / mol, e.g., 3,000-15,000 g / mol, or 4,000-8,000 g / mol. The glass transition temperature (“Tg”) of the polyols can be measured using dynamic light scattering (DSC).

[0034] Any suitable solvent can be used in the millbase formulation. In some embodiments, the solvent is capable of at least partially dissolving the polyol. Suitable solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl isoamyl ketone, methyl heptyl ketone, isophorone, isopropanol, n-butanol, secbutanol, isobutanol, amyl alcohol, isoamyl alcohol, hexanols, and heptanols, among others.

[0035] The millbase formulation can be let down into a general solvent-bome coating composition. The coating composition generally comprises (a) the millbase formulation; and (b) a letdow n formulation comprising a crosslinker, a catalyst capable of catalyzing thereaction between the crosslinker and the polyol, and in some embodiments, additional solvent used for at least partially dissolving the polyol. The solvent-borne composition can be applied to a variety of articles and substrates and cured according to methods known in the art. The coating compositions may be applied to substrates and articles by any suitable conventional technique such as spraying, roller coating, dip coating., and the like. The composition can be applied in liquid form, e.g., dispersed in a the solvent. Also contemplated are a variety of articles comprising a coating cured from the general solvent-bome coating composition.III. Exemplary Embodiments

[0036] (1) A method comprising: providing a composition comprising carbon nanotubes and at least 20% of a liquid beading agent by weight of the composition; beading the composition to form a beaded composition; and dry ing the beaded composition to form a dried composition comprising less than 1% of the liquid beading agent by weight of the dried composition.

[0037] (2) Embodiment (1), wherein the carbon nanotubes are multi-walled carbon nanotubes having an average diameter of 5-50 nm.

[0038] (3) Embodiment (1) or (2), wherein the carbon nanotubes are multi -w alled carbon nanotubes having an average diameter of 5-40 nm.

[0039] (4) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average diameter of 5-30 nm.

[0040] (5) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average diameter of 5-20 nm.

[0041] (6) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average diameter of 5-15 nm.

[0042] (7) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average length of 0. 1-100 pm.

[0043] (8) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average length of 0. 1-80 pm.

[0044] (9) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average length of 0. 1-60 pm.

[0045] (10) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average length of 0. 1-50 pm.

[0046] (11) Any prior Embodiment, wherein the carbon nanotubes are multi-walledcarbon nanotubes having an average length of 0. 1-40 gm.

[0047] (12) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average length of 0. 1-30 pm.

[0048] (13) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average length of 0. 1-20 pm.

[0049] (14) Any prior Embodiment, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average length of 0. 1-10 pm.

[0050] (15) Any prior Embodiment, wherein the composition further comprises a carbonaceous material having a graphitic or amorphous form, which is not a carbon nanotube.

[0051] (16) Embodiment (15). wherein the carbonaceous material is carbon black.

[0052] (17) Embodiment (16), wherein the carbon black has a nitrogen surface area(NS A) of 25-600 m2 / g.

[0053] (18) Embodiment (16) or (17), wherein the carbon black as an oil absorption number (OAN) of 45-260 cm3 / g.

[0054] (19) Any Embodiment (16)-( 18). wherein the carbon black exhibits an electrical conductivity of lO'-lO5S / m.

[0055] (20) Any Embodiment (15)-(l 9), wherein the composition comprises 1-99% of the carbon nanotubes by weight of the composition.

[0056] (21) Any Embodiment (15)-(20). wherein the composition comprises 20-90% of the carbon nanotubes by weight of the composition.

[0057] (22) Any Embodiment (15)-(21 ), wherein the composition comprises 30-90% of the carbon nanotubes by weight of the composition.

[0058] (23) Any Embodiment (15)-(22). wherein the composition comprises 30-80% of the carbon nanotubes by weight of the composition.

[0059] (24) Any Embodiment (15)-(23), wherein the composition comprises 40-70% of the carbon nanotubes by weight of the composition.

[0060] (25) Any prior Embodiment, wherein the dried composition exhibits an electrical conductivity of 103- 106S / m.

[0061] (26) Any prior Embodiment, wherein the beaded composition comprises 20-95% of the liquid beading agent by weight of the beaded composition.

[0062] (27) Any prior Embodiment, wherein the beaded composition comprises 30-90% of the liquid beading agent by weight of the beaded composition.

[0063] (28) Any prior Embodiment, wherein the beaded composition comprises 40-90%of the liquid beading agent by weight of the beaded composition.

[0064] (29) Any prior Embodiment, wherein the beaded composition comprises 50-90% of the liquid beading agent by weight of the beaded composition.

[0065] (30) Any prior Embodiment, wherein the beaded composition comprises 60-90% of the liquid beading agent by weight of the beaded composition.

[0066] (31) Any prior Embodiment, wherein the beaded composition comprises 70-90% of the liquid beading agent by weight of the beaded composition.

[0067] (32) Any prior Embodiment, wherein the dried composition comprises less than0.8% of the liquid beading agent by weight of the dried composition.

[0068] (33) Any prior Embodiment, wherein the dried composition comprises 0.5% or less of the liquid beading agent by weight of the dried composition.

[0069] (34) Any prior Embodiment, wherein the dried composition has a bulk density of at least 0.1 g / cc.

[0070] (35) Any prior Embodiment, wherein the dried composition has a bulk density of0. 1-0.4 g / cc.

[0071] (36) Any prior Embodiment, wherein the ratio of the bulk density of the dried composition to the bulk density of a starting composition comprising the carbon nanotubes prior to being combined with the liquid beading agent ranges from 1.5: 1 to 4:1.

[0072] (37) A carbon nanotube product or carbon nanotube hybrid product prepared by the method of any prior Embodiment.

[0073] (38) A millbase formulation, comprising: a polyol; a solvent capable of at least partially dissolving the polyol; and the dried composition of any prior Embodiment.

[0074] (39) The millbase formulation of Embodiment (38), further comprising a dispersant.

[0075] (40) A general solvent-borne coating composition, comprising the millbase formulation of Embodiment (38) or (39); and a letdown formulation comprising: (i) a crosslinker; and (ii) a catalyst capable of catalyzing the reaction between the crosslinker and the polyol.

[0076] (41) An article comprising a coating cured from the general solvent-borne coating composition of Embodiment (40).EXAMPLES

[0077] The following examples further illustrate this disclosure. The scope of the disclosure and claims is not limited by the scope of the following examples.

[0078] The examples below evaluated CNT / carbon black (CB) hybrid materials comprising purified carbon black. Pristine CNT / CB hybrid material (Example 1) was synthesized via chemical vapor deposition(CVD) to grow CNT on the catalyst with alumina substate. Before the CNT growth, the catalyst on alumina substrate was blended with carbon black.

[0079] Hybrid materials with low iron content are useful for lithium-ion batten' applications. In general, chemically purified hybrid materials were prepared by acid purification followed by neutralization in aqueous solution. The aqueous solution was then compressed to remove water, resulting in a cake-type of material (Example 2). The wet cake material contained about 90% water by weight. Table 1 provides a description of the samples used in the Examples. Comparisons were made between powdered and beaded samples as further discussed below.Table 1.I. Beading

[0080] 500 g of Example 2 was loaded into the mixing bowl of a stand mixer. A whisk head was utilized for beading. Example 2 cake was beaded in the mixer for 2 minutes with the rotating speed set at 10. The Example 2 cake was turned into beads after the beading process.II. Dry ing MethodsA. Freeze drying

[0081] Example 2 wet cake was loaded into a fast-freeze flask connected with the freeze drier. The material was dried under the condition of 187 mT vacuum and -85°C for 24 hours. The resulting sample was Example 3.B. Sequential Drying in Vacuum Oven (Powder)

[0082] Example 2 wet cake was loaded in an aluminum pan and placed in the vacuum oven for 30 minutes at the temperature of about 110°C under vacuum (20 inches Hg). After every' 30 minutes of drying, the sample was taken out and ground using a mortar pestle, followed by another 30 minutes of drying under the same conditions. The process was repeated until the weight of the material in the aluminum pan was constant. The resulting sample was Example 4.C. Direct Drying Process in Vacuum Oven (Powder)

[0083] Example 2 cakes were loaded in an aluminum pan and placed in the vacuum oven (20 inches Hg) at three different temperature ranges: 80°C-96°C, 110°C-l 17°C, and 120°C- 140°C for 20, 7, and 6 hours, respectively. The dried hard clumps were ground into powderswith a mortar pestle, providing Examples 5, 6, and 7, respectively .D. Drying Process in Vacuum Oven (Beads)

[0084] Cake beads were loaded in an aluminum pan and the material was dried in the vacuum oven at a temperature of 110°C-l 17°C and under vacuum (20 inches Hg) for at least 5 hours. The resulting sample was Example 8.E. Drying Process in Rotary Tube Furnace (Beads)

[0085] Four inch quartz tube with an expansion in the middle section (MTI EQ-QZTube- R2) was connected in a rotary tube furnace. A long-handled scoop was used to load 356.3g of hybrid material cake bead into the expansion zone of the tube where the heating zone was located. The tube rotating speed was adjusted at 2 rpm and air flow rate was set at 2 slm. After making sure the tube rotation and air flow were properly set, the upper furnace heating zone was closed. The temperature controller was programed to dry cake beads at 200°C for 6 hours. As the temperature increased to 200°C, water vapor started coming out of the heating zone, and it was observed on both inlet and outlet sides of the tube. More water vapor came out of the outlet side of the tube as the air flowed out in that direction. Some vapor was condensed on the tube, forming water. As a result, the furnace was tilted towards the outlet direction to prevent the backflow of water into the heating zone. Some water was condensed in the metal collection vessel. After about 4 hours drying, the beads in the heat zone were nearly dried. After 6 hours drying at 200°C, beads in the heating zone were visually dry.

[0086] The drying process was continued the following day under the same conditions. After an additional 6 hours drying, condensed water on the inlet side of the tube had disappeared. After drying was complete, heat, tube rotation, and air flow were shut down. The dried beads were collected, and the process tube was cleaned. The resulting sample was Example 9.III. Millbase. Letdown, and HDPE CompoundingA. Millbase

[0087] JONCRYL® 500, and methyl isamyl ketone ("MIAK") were weighed first in a high-density polyethylene (“HDPE’') bottle (internal diameter 1.75'’, internal height 4.00”, and wall thickness —1 / 8”). About 385 grams of 3 / 32” stainless steel media was poured insideof the HDPE bottle. The bottles were then transferred to the glovebox. The sample was weighed in the glovebox and poured into the HDPE bottles. The bottles were sealed and hand shaken to incorporate the ingredients before being removed from the glovebox. The samples in the bottles were mixed for 1 hour on the Lau DAS 200 laboratory shaker. Millbase compositions are shown in Table 2.Table 2.B. Letdown and Coating Compositions

[0088] The letdown was prepared by mixing the ingredients in Table 3 in a lOOmL FlackTek cup. The letdown was mixed under high viscosity liquid (5 min 800 rpm, 2 min 2000 rpm). The letdown formulation was used for both powder and bead compositions.Table 3.

[0089] The millbases were diluted with letdown to the target filler loading in the final coatings according to the formulations in Table 4 (applicable to both powdered and beaded compositions). Each final coating solution was prepared with a 15 g batch in a small FlackTek cup. The solution was mixed on a benchtop FlackTek mixer at 2500 rpm for 3 minutes. The final coating as prepared on a 5 millimeter polyethylene terephthalate (“PET”) substrate with a 3 millimeter w et film drawdown applicator. The wet film w as allowed to dry at ambient temperature for 30 minutes in the chemical hood and then thermally cured at 135°C for 30 minutes.Table 4.C. HDPE Compounding

[0090] Prior to compounding, the dried powders or beads were encapsulated as an HDPE masterbatch using a micro compounder (Xplore MC 15HT). The dried beads were first premixed with virgin HDPE (DMDA 8920, granulated 4 mm mesh) at 15 wt.% loading. Premixing was done in a nanomaterial glovebox. After premixing, samples were transferred to a walk-in fume hood and fed into the micro-compounder using a vibration feeder. During encapsulation, the micro compounder was set to 210°C and 100 rpm.

[0091] Compounding and letdown of the masterbatches were done with the PRISM twin- screw extruder in HDPE. Granulated masterbatches were premixed with granulated virgin HDPE to achieve the target loadings shown in Table 5 and poured into the PRISM’s Feeder 1. The tape die head was used to facilitate surface resistivity measurements.Table 5.IV. Testing Methods

[0092] The moisture content of dried beads was measured by the Moisture Quik method.

[0093] The poured bulk density of powder and beads was measured by loading the hybrid materials into lOOcc graduated cylinder without tapping, and the mass of the material was measured. The pour density was calculated by dividing the mass with the volume (lOOcc) of the materials.

[0094] The surface resistivity' of all the cured films were measured f by the Hiresta UP MCP-HT450 (standard probe, 50 j.tm thickness, variable voltage) and Loresta GP MCP-T600(standard probe, 50 j.tm thickness, variable voltage) as applicable.

[0095] Tape Resistivity was measured using the Hiresta UP MCP-HT450 (standard probe, 1 mm thickness, variable voltage) and Loresta GP MCP-T600 (standard probe, 1 mm thickness, variable voltage) as applicable.V. Results

[0096] The physical form of Example 4 was evaluated over varying drying times (0.5h, Ih, 2.5h, 3.5h, 4.5h, and 6h). The gradual transition of large clumps into fine powder was observed. Examples 5, 6, and 7 transformed from cake into hard clumps then turned into fine powder with mortar pestle grinding. The moisture content was characterized. All samples (powder and beads) showed relatively low moisture content (Table 6). The freeze-dried powder (Example 3) was a fluffy powder, and its poured bulk densify was close to the pristine hybrid materials (Example 1). The rotary furnace and vacuum oven dried beads (Example 8 and 9) showed more than twice higher poured bulk density than the freeze-dried powder (Example 3). For material handling, materials in the bead form were safer and easier compared to freeze-dried powder due to higher poured bulk densify.Table 6.Table 7.

[0097] The surface resistivity of the dried powders in the acrylic coating is shown Fig. 1. Regardless of drying method (sequential drying or direct drying), the vacuum oven dried powders exhibited similar surface resistivity' behavior. The drying temperature of direct vacuum oven dry ing had no effect on the electrical conductivity performance of the acrylic coating. As shown in Fig. 2, an inventive composition (Example 6) relative to comparative material (Example 1) exhibited significantly higher surface resistivity7properties. As Fig. 2 shows, the surface resistivity7of the dried powder (without beading) is higher than the reference sample. The lower the surface resistivity7, the better performance. Thus, the powder form demonstrated a significant performance loss likely due to the formation of agglomerates, which beading was demonstrated to avoid.

[0098] The surface resistivity of the dried beads in the acrylic coating is shown in Fig. 3. The vacuum oven and rotary7tube furnace dried beads exhibited similar surface resistivity7performance in the coating as compared to freeze-dried powder (Example 3). Both samples achieved the percolation of surface resistivity at about 0.25 wt.% loading with the ultimate surface resistivity at the level of 104Q / sq. Tn contrast, when the wet cake (Example 2) was used in the acrylic coating directly, the surface resistivity7at 0.25% was slightly higher.

[0099] The surface resistivity7of hybrid materials, including those incorporating beaded samples, in HDPE. is shown in Fig. 4. The percolation threshold and ultimate conductivity for dried beads (Example 8 and 9) w ere comparable to the reference sample (Example 1) and freeze-dried powder (Example 3).

[0100] As compared to the powder (Example 6) prepared by the direct drying and grinding process, the beaded samples (Example 8 and 9) exhibited a lower percolation threshold and better conductivity7performance. Without being bound by theory, this is likely a result of the formation of hard clumps during the direct drying process in the vacuum oven. The shear stress of the extrusion process is likely too weak to break dow n hard agglomerates formed from the pow der (Example 6), leading to poor dispersion in HDPE. By contrast, the beading process appeared to avoid hard clump formation during the vacuum oven drying process. The soft beads were able to be broken down under the shear stress of the extrusion process. The dispersion of beads in HDPE was improved, w hich imparted better electrical conductivity. In addition, the rotating tube furnace provides a method for scaling the drying process. The beads are also safer and easier to handle due to less dust compared to the powder form.

[0101] Features and advantages of this disclosure are apparent from the detailed specification, and the claims cover all such features and advantages. Numerous variations will occur to those skilled in the art, and any variations equivalent to those described in this disclosure fall within the scope of this disclosure. Those skilled in the art will appreciate that the conception upon which this disclosure is based may be used as a basis for designing other compositions and methods for carrying out the several purposes of this disclosure. As a result, the claims should not be considered as limited by the description or examples.

Claims

CLAIMSWhat is claimed is:

1. A method comprising: a) providing a composition comprising carbon nanotubes and at least 20% of a liquid beading agent by weight of the composition; b) beading the composition to form a beaded composition; and c) drying the beaded composition to form a dried composition comprising less than1 % of the liquid beading agent by weight of the dried composition.

2. The method of claim 1, wherein the carbon nanotubes are multi -walled carbon nanotubes having an average diameter of 5-50 nm.

3. The method of claim 1 or 2, wherein the carbon nanotubes are multi-walled carbon nanotubes having an average length of 0. 1-100 pm.

4. The method of any preceding claim, wherein the composition further comprises a carbonaceous material having a graphitic or amorphous form, which is not a carbon nanotube.

5. The method of claim 4, wherein the carbonaceous material is carbon black.

6. The method of claim 5, wherein the carbon black has a nitrogen surface area (NSA) of 25-600 m2 / g.

7. The method of claim 5 or 6, wherein the carbon black as an oil absorption number (OAN) of 45-260 cm3 / g.

8. The method of any of claims 5-7, wherein the carbon black exhibits an electrical conductivity of lO'-lO5S / m.

9. The method of any of claims 4-8, wherein the composition comprises 1-99% of the carbon nanotubes by weight of the composition.

10. The method of any preceding claim, wherein the dried composition exhibits an electrical conductivity of 103-l 06S / m.

11. The method of any preceding claim, wherein the beaded composition comprises 20- 95% of the liquid beading agent by weight of the beaded composition.

12. The method of any preceding claim, wherein the dried composition comprises less than 0.8% of the liquid beading agent by weight of the dried composition.

13. The method of any preceding claim, wherein the dried composition has a bulk density of at least 0.1 g / cc.

14. The method of any preceding claim, wherein the dried composition has a bulk density of 0. 1-0.4 g / cc.

15. The method of any preceding claim, wherein the ratio of the bulk density of the dried composition to the bulk density of a starting composition comprising the carbon nanotubes prior to being combined with the liquid beading agent ranges from 1.5: 1 to 4:1.

16. A carbon nanotube product or carbon nanotube hybrid product prepared by the method of any preceding claim.

17. A millbase formulation, comprising: a) a polyol b) a solvent capable of at least partially dissolving the polyol; and c) the dried composition of any preceding claim.

18. The millbase formulation of claim 17, further comprising a dispersant.

19. A general solvent-bome coating composition, comprising a) the millbase formulation of claim 17 or 18; and b) a letdown formulation comprising: i) a crosslinker; and ii) a catalyst capable of catalyzing the reaction between the crosslinker and the polyol.

20. An article comprising a coating cured from the general solvent-borne coating composition of claim 19.