HK1201285B - Rubber formulations including graphenic carbon particles - Google Patents

Abstract

Rubber formulations comprising a base rubber composition, graphenic carbon particles, and non-conductive filler particles such as silica are disclosed. The formulations possess favorable properties such as relatively low surface resistivities, and are useful for many applications such as tire treads.

Description

Rubber formulations containing graphenic carbon particles

Technical Field

The present invention relates to rubber formulations comprising graphenic carbon particles.

Background

Various fillers have been added to rubber compositions. For example, carbon black has been used for various portions of a tire including a tread (tread) to reduce generation of electric charges. Further, silica has been used for a tire tread (tire) to reduce rolling resistance. However, in order to improve the performance characteristics of tire tread formulations, it is necessary to add significant amounts of silica, the maximum amount which can be added being limited by the relatively large amount of carbon black (added to sufficiently reduce the generation of charge).

Disclosure of Invention

One aspect of the present invention provides a rubber formulation comprising a base rubber composition, 0.1 to 20 weight percent of grapheme carbon particles (graphene particles), and 1 to 50 weight percent of filler particles, wherein the tire tread formulation has less than 10¹⁰Surface resistivity (surface resistivity) of Ω/sq.

In another aspect of the invention, there is providedA method of preparing a rubber formulation comprising: mixing grapheme carbon particles and filler particles with a base rubber composition; and curing the resulting mixture, wherein the cured mixture has a viscosity of less than 10¹⁰Surface resistivity of Ω/sq.

Detailed Description

Rubber formulations according to embodiments of the present invention may be used in a variety of applications, including tire components such as vehicle tire treads, sub-treads (subtreads), tire casings, tire sidewalls, tire wedges, tire beads and tire cords, wire and cable jacketing, hoses, gaskets and seals, industrial and automotive drive belts, engine mounts, V-belts, conveyor belts, roll-coating coatings, shoe sole materials, seal rings, damping elements, and the like. While tire tread formulations are described herein as particular embodiments of the present invention, it should be understood that the rubber formulations of the present invention are not limited to these applications, but may also be used in a variety of other applications.

The rubber formulation of the present invention comprises a base rubber composition to which are added grapheme carbon particles. As used herein, the term "graphenic carbon particle" refers to a carbon particle having a structure comprising one or more layers of sp that are monoatomic in thickness²-planar sheets of bonded carbon atoms densely packed into a honeycomb lattice. The average number of stacked layers may be less than 100, for example less than 50. In certain embodiments, the average number of stacked layers is 30 or less, such as 20 or less, 10 or less, or in some cases 5 or less. The grapheme carbon particles may be substantially flat, but at least a portion of the planar sheets may be substantially pleated, curled, creased, or wrinkled. The particles typically do not have a spherical or equiaxed shape.

In certain embodiments, the grapheme carbon particles present in the compositions of the present invention have a thickness, measured along a direction perpendicular to the carbon atom layers, of no greater than 10 nanometers, no greater than 5 nanometers, or (in certain embodiments) no greater than 4 nanometers or 3 nanometers or 2 nanometers or 1 nanometer, such as no greater than 3.6 nanometers. In certain embodiments, the grapheme carbon particles may be from 1 atomic layer to 3, 6, 9, 12, 20, or 30 atomic layer thick, or thicker. In certain embodiments, the grapheme carbon particles present in the compositions of the present invention have a width and length, measured in a direction parallel to the carbon atom layers, of at least 50 nanometers, such as greater than 100 nanometers, in some cases greater than 100 nanometers to 500 nanometers, or greater than 100 nanometers to 200 nanometers. The grapheme carbon particles may take the form of ultra-flakes, platelets, or platelets, which have a relatively high aspect ratio (aspect ratio is defined as the ratio of the longest dimension of the particle to the shortest dimension of the particle) of greater than 3:1, such as greater than 10: 1.

In certain embodiments, the graphenic carbon particles used in the compositions of the invention have a relatively low oxygen content. For example, the grapheme carbon particles used in certain embodiments of the compositions of the present invention may have an oxygen content of no greater than 2 atomic weight percent, such as no greater than 1.5 or 1 atomic weight percent, or no greater than 0.6 atomic weight percent, such as about 0.5 atomic weight percent, even with a thickness of no greater than 5 nanometers or no greater than 2 nanometers. The oxygen content of the grapheme carbon particles can be determined using X-ray photoelectron spectroscopy, such as is described in chem.soc.rev.39,228-240(2010) of d.r.dreyer et al.

In certain embodiments, the grapheme carbon particles used in the compositions of the present invention have a B.E.T. specific surface area of at least 50 square meters per gram, such as from 70 to 1000 square meters per gram, or in some cases 200-1000 square meters per gram or 200-400 square meters per gram. As used herein, The term "b.e.t. specific surface area" refers to a specific surface area determined by nitrogen adsorption according to astm d 3663-78 standard based on The Brunauer-Emmett-Teller method described in The Journal "The Journal oft he American Chemical Society", 60,309 (1938).

In certain embodiments, the grapheme carbon particles used in the compositions of the present inventionHas a 2D/G peak ratio of at least 1.1, such as at least 1.2 or 1.3. As used herein, the term "2D/G peak ratio" refers to 2692cm^-1Intensity of 2D peak at position 1580cm^-1The ratio of the G peak intensities at (a).

In certain embodiments, the graphenic carbon particles used in the compositions of the invention have a relatively low bulk density. For example, the grapheme carbon particles useful in certain embodiments of the present invention are characterized as having less than 0.2g/cm³(e.g., not greater than 0.1 g/cm)³) Bulk density (tap density). To achieve the object of the present invention, the bulk density of the grapheme carbon particles is determined by: 0.4g of grapheme carbon particles are placed into a glass measuring cylinder with a readable scale, the cylinder is raised approximately 1 inch and tamped 100 times by hitting the bottom of the cylinder on a hard surface, thereby causing the grapheme carbon particles to sink inside the cylinder. The volume of the particles was then measured and the bulk density was calculated by dividing the measured volume by 0.4g, where bulk density is in g/cm³And (4) showing.

In certain embodiments, the grapheme carbon particles used in the compositions of the present invention have a compressed density and percent compaction (percent compaction) that is less than the compressed density and percent compaction of graphite powder and certain types of substantially flat grapheme carbon particles. At present, both lower compressed densities and lower percent compactions are believed to contribute to superior dispersion and/or rheological properties than grapheme carbon particles exhibiting higher compressed densities and higher percent compactions. In certain embodiments, the compressed density of the grapheme carbon particles is 0.9 or less, such as less than 0.8, less than 0.7, such as from 0.6 to 0.7. In certain embodiments, the percent compaction of the grapheme carbon particles is less than 40 percent, such as less than 30 percent, for example, from 25 to 30 percent.

To achieve the objects of the present invention, the compressed density of the grapheme carbon particles is calculated from the measured thickness of a given mass of compressed particles. Specifically, the measured thickness is determined by: 0.1 grams of grapheme carbon particles are cold pressed in a 1.3 centimeter (cm) die for 45 minutes (min) at a force of 15,000 pounds, with a contact pressure of 500 MPa. The compressed density of the grapheme carbon particles is then calculated from the measured thickness according to the following equation:

the percent compaction of the grapheme carbon particles is then determined as the ratio of the calculated compressed density of the grapheme carbon particles, as determined as having a compressed density of 2.2g/cm as determined above³Which is the density of graphite.

In certain embodiments, the grapheme carbon particles have a measured liquid volume conductivity of at least 100 micro siemens (microSiemens), such as at least 120 micro siemens, such as at least 140 micro siemens, at a later point in time after mixing, such as at 10min or 20min or 30min or 40 min. To achieve the object of the present invention, the liquid volume conductivity of the grapheme carbon particles is determined as follows. First, a sample of a butyl cellosolve solution containing 0.5% grapheme carbon particles is sonicated in a water bath sonicator for 30 minutes. Immediately after sonication, the samples were placed in a standard calibrated electrolytic conductivity cell (K ═ 1). A Fisher Scientific AB 30 conductivity meter was introduced into the sample to measure the conductivity of the sample. The conductivity curve was plotted over a period of about 40 minutes.

According to certain embodiments, percolation (percolation), defined as long range connectivity, occurs between conductive grapheme carbon particles. This percolation can reduce the resistivity of the formulation. The conductive graphene particles may occupy a minimum volume in the composite matrix such that the particles form a continuous or near continuous network. In this case, the aspect ratio of the grapheme carbon particles may affect the minimum volume required for percolation. Further, the surface energy of the grapheme carbon particles may be the same or similar to the surface energy of the elastomeric rubber. In addition, the particles may be prone to flocculation or delamination as they are treated.

The grapheme carbon particles used in the compositions of the present invention may be prepared, for example, by heat treatment. According to an embodiment of the present invention, grapheme carbon particles are prepared by heating a carbonaceous precursor material to an elevated temperature in a heating zone. For example, grapheme carbon particles may be prepared by the systems and methods disclosed in U.S. patent application serial nos. 13/249,315 and 13/309,894.

In certain embodiments, grapheme carbon particles may be produced using the apparatus and methods described in U.S. patent application serial No. 13/249,315 [0022] - [0048], the cited sections of which are incorporated herein by reference, wherein (i) one or more hydrocarbon precursor materials capable of forming two carbon fragment species (e.g., n-propanol, ethane, ethylene, acetylene, vinyl chloride, 1, 2-dichloroethane, allyl alcohol, propionaldehyde, and/or vinyl bromide) are introduced into a heating zone (e.g., a plasma zone); and (ii) heating the hydrocarbon in the heating zone to a temperature of at least 1,000 ℃ to form grapheme carbon particles. In further embodiments, grapheme carbon particles may be produced utilizing the apparatus and methods described in U.S. patent application serial No. 13/309,894 [0015] - [0042], the cited sections of which are incorporated herein by reference, wherein (i) a methane precursor material (e.g., a material comprising at least 50% methane, or in some cases, a material comprising gaseous or liquid methane having a purity of at least 95% or 99% or greater) is introduced into a heating zone (e.g., a plasma zone); and (ii) heating the methane precursor in the heating zone to form grapheme carbon particles. These methods are capable of producing grapheme carbon particles having at least some, and in some cases all, of the features described above.

In the preparation of grapheme carbon particles by the above-described process, the carbonaceous precursor is provided as a feed, which may be contacted with an inert carrier gas. The carbonaceous precursor material can be heated in a heating zone (e.g., by a plasma system). In certain embodiments, the precursor material is heated to a temperature in the range of 1,000 ℃ to 20,000 ℃, e.g., 1,200 ℃ to 10,000 ℃. For example, the temperature of the heating zone may be in the range of 1,500 ℃ to 8,000 ℃, e.g., 2,000 ℃ to 5,000 ℃. Although the heating zone may be created by a plasma system, it should be understood that any other suitable heating system may be used to create the heating zone, such as various forms of furnaces, including electrically heated tube furnaces and the like.

The gas stream may be contacted with one or more quench streams injected into the plasma chamber through at least one quench stream injection port. The quench stream may cool the gas stream to facilitate forming or controlling the particle size and shape of the grapheme carbon particles. In certain embodiments of the invention, after contacting the gaseous product stream with the quench stream, the ultrafine particles may be passed through a converging means. After the grapheme carbon particles exit the plasma system, they may be collected. The grapheme carbon particles may be separated from the gas stream onto a substrate using any suitable device, such as a bag filter, cyclone, or settler.

Without being bound by any theory, it is presently believed that the above-described method of producing grapheme carbon particles is particularly well suited to producing grapheme carbon particles having relatively low thicknesses and relatively high aspect ratios, as well as relatively low oxygen content (as described above). Further, it is also presently believed that such a process enables the production of a large number of grapheme carbon particles having a substantially wrinkled, curled, creased or wrinkled shape (referred to herein as a "3D" shape), as opposed to producing particles that are predominantly in a substantially two-dimensional (or flat) shape. Such characteristics are believed to be reflected in the aforementioned compressive density characteristics, and are believed to be advantageous for the present invention, since it is presently believed that "edge-to-edge" and "edge-to-face" contact between the grapheme carbon particles in the composition may be facilitated when a substantial portion of the grapheme carbon particles have a 3D shape. The reason for this is believed to be that particles having a 3D shape are less prone to aggregation in the composition (because of lower van der waals forces) than particles having a two-dimensional shape. Furthermore, it is presently believed that even in the case of "face-to-face" contact between particles having a 3D shape, since a particle may have more than one face plane, the entire particle surface does not form a separate "face-to-face" interaction with another single particle, but is capable of interacting with other particles in other planes, including other "face-to-face" interactions. Thus, grapheme carbon particles having a 3D shape are presently believed to be capable of providing the best conductive pathway in the present compositions and are presently believed to be useful in achieving the desired conductivity characteristics of the present invention, particularly when the grapheme carbon particles are present in relatively small amounts in the compositions, as described hereinbelow.

In certain embodiments, the grapheme carbon particles are present in the rubber formulation in an amount of at least 0.1 weight percent, such as at least 0.5 weight percent, or in some cases at least 1 weight percent. In certain embodiments, the grapheme carbon particles are present in the composition in an amount of no greater than 15 weight percent, such as no greater than 10 weight percent, or in some cases no greater than 5 weight percent, based on the weight of all non-volatile components in the composition.

In certain embodiments, the base rubber composition of a tire tread or other formulation includes synthetic rubber, natural rubber, mixtures thereof, and the like. In certain embodiments, the base rubber composition comprises a styrene butadiene copolymer, polybutadiene, a halobutyl, and/or natural rubber (polyisoprene). For tire tread applications, the base rubber composition typically comprises 30 to 70 weight percent of the total tire tread formulation, such as 34 to 54 weight percent.

In certain embodiments, the rubber formulation comprises a curable rubber. As used herein, the term "curable rubber" refers to both natural rubber and its various original and modified forms, as well as various synthetic rubbers. For example, the curable rubber may include styrene/butadiene rubber (SBR), Butadiene Rubber (BR), natural rubber, any other known form of organic rubber, and combinations thereof. As used herein, the terms "rubber," "elastomer," and "rubber elastomer" may be used interchangeably, unless otherwise indicated. The terms "rubber composition", "compounded rubber" and "rubber compound" are used interchangeably to refer to rubber that has been blended or mixed with various ingredients and substances. These terms are well known to those skilled in the art of rubber compounding or rubber compounding.

In addition to the amount of grapheme carbon particles described above, the tire tread in certain embodiments may also include filler particles. Suitable fillers for use in the rubber formulations of the present invention may include a variety of materials known to those of ordinary skill in the art. Non-limiting examples may include Inorganic oxides such as, but not limited to, Inorganic particles having (chemisorbed or covalently bonded) oxygen or (bonded or free) hydroxyl groups on exposed surfaces or amorphous solid materials such as, but not limited to, oxides of metals of groups Ib, IIb, IIIa, IIIb, IVa, IVb (except carbon), Va, VIa, VIIa and VIIa of the periodic Table of the elements in Advanced organic Chemistry: A Comprehensive Text, F.Albert Cotton et al, fourth edition, John Wiley and Sons, 1980. Non-limiting examples of inorganic oxides for use in the present invention may include precipitated silica, colloidal silica, silica gel, aluminum silicate, alumina, and mixtures thereof. Suitable metal silicates may include a variety of materials known in the art. Non-limiting examples may include, but are not limited to, alumina, lithium, sodium, potassium silicate, and mixtures thereof.

In certain embodiments, the filler particles comprise silica, typically in an amount of from 1 to 50 weight percent, such as from 28 to 44 weight percent. In certain embodiments, it is desirable to have a maximum amount of silica present in the formulation to improve traction and fuel efficiency performance. For example, it is advantageous to add silica in an amount of greater than 30 wt.%, for example greater than 40 wt.%.

In certain embodiments, the silica may be precipitated silica, colloidal silica, or mixtures thereof. The average final particle size of the silica may be less than 0.1 microns, or from 0.01 to 0.05 microns, or from 0.015 to 0.02 microns as measured by electron microscopy. In further alternative non-limiting embodiments, the surface area of the silica can be from 25 to 1000 square meters per gram or from 75 to 250 square meters per gram or 100 and 200 square meters per gram. Surface area can be measured using techniques conventionally known in the art.As used herein, surface area is measured by Brunauer, Emmett and Teller (BET) methods according to ASTM D1993-91. The BET surface area can be determined by fitting five relative pressure points from nitrogen adsorption isotherm measurements with a Micromeritics TriStar 3000.TM. instrument. FlowPrep-060^TMstation provides heat and a continuous stream of gas to prepare the sample for analysis. The silica samples were dried by heating them to a temperature of 160 ℃ for at least 1 hour in flowing nitrogen (grade P5) prior to nitrogen adsorption.

The silica fillers used in the present invention can be prepared using a variety of methods known to those of ordinary skill in the art. For example, silica may be prepared by the method disclosed in U.S. patent application serial No. 11/103,123, which is incorporated herein by reference. In a non-limiting embodiment, the silica used as the untreated filler may be prepared by: an aqueous solution of a soluble metal silicate is combined with an acid to form a silica slurry. The silica slurry may optionally be aged, and an acid or a base may be added to the optionally aged silica slurry. The silica slurry is filtered, optionally washed and dried using conventional techniques known in the art.

According to certain embodiments of the present invention, controlling the relative amounts of grapheme carbon particles and silica maximizes the amount of silica, thereby improving performance characteristics while minimizing the amount of grapheme carbon particles to an amount capable of providing sufficient static dissipation. For example, the amount of silica may be greater than 30 wt% or greater than 40 wt%, while the amount of grapheme carbon particles may be less than 10 wt% or 5 wt%, or less than 2 wt% or 1 wt%. In certain embodiments, the weight ratio of silica particles to grapheme carbon particles is greater than 2:1 or 3:1, such as greater than 4:1, 5:1, or 6: 1. In particular embodiments, the weight ratio may be greater than 8:1 or 10: 1.

In the composite systems of the present invention, in which both silica particles and grapheme carbon particles are present in the elastomeric rubber matrix, the conductive grapheme carbon particles may form a continuous, or nearly continuous, network, even when relatively large amounts of insulative silica particles, as described above, are present.

According to certain embodiments, the rubber formulation has less than 10¹⁰Omega/sq, e.g. less than 10⁹Omega/sq or less than 10⁷Surface resistivity of Ω/sq.

The formulations of the present invention may be prepared by: the grapheme carbon particles and/or filler particles are combined with an emulsion and/or solution polymer, such as an organic rubber comprising solution styrene/butadiene (SBR), polybutadiene rubber, or mixtures thereof, to form a masterbatch. Curable rubbers for masterbatches vary over a wide range and are well known to those skilled in the art and may include vulcanizable rubbers and sulfur curable rubbers. In non-limiting embodiments, the curable rubbers may include those used in rubber industry articles and tires. Non-limiting examples of masterbatches may include the following combinations of materials: an organic rubber, a water-immiscible solvent, a treated filler, and optionally a processing oil. Such products may be provided from rubber manufacturers to tire manufacturers. A benefit to tire manufacturers using masterbatches may be that the grapheme carbon particles and/or the silica particles are substantially uniformly dispersed in the rubber, which can substantially reduce or minimize the mixing time used to prepare the compounded rubber. In a non-limiting embodiment, the masterbatch may include 10 to 150 parts of grapheme carbon particles and/or silica particles per 100 parts of rubber (PHR).

The grapheme carbon particles and/or the silica particles may be mixed with the uncured rubber elastomer by conventional methods, such as in a Banbury mixer or rubber mill at temperatures from 100 DEG F to 392 DEG F (38 ℃ -200 ℃), for preparing the vulcanizable rubber composition. Non-limiting examples of other conventional rubber additives present in the rubber composition may include conventional sulfur or peroxide cure systems. In an alternative non-limiting embodiment, the sulfur curing system may comprise 0.5 to 5 parts of sulfur, 2 to 5 parts of zinc oxide, and 0.5 to 5 parts of an accelerator. In a further alternative non-limiting embodiment, the peroxide cure system may comprise 1-4 parts of a peroxide, such as dicumyl peroxide.

Non-limiting examples of conventional rubber additives may include: clay, talc, carbon black, etc.; oils, plasticizers, accelerators, antioxidants, heat stabilizers, light stabilizers, zone stabilizers; organic acids such as stearic acid, benzoic acid or salicylic acid; other activators, extenders, and color pigments. The formulation selected may vary depending on the particular vulcanizate being prepared. Such formulations are known to those skilled in the art of rubber formulation. In a non-limiting embodiment, the use of the silica particles of the present invention is beneficial in that when the coupling substance is a mercapto-containing organometallic compound, the rubber compound containing such silica particles is stable at elevated temperatures and when mixed for at least half a minute up to 60 minutes, curing of the compounded rubber at temperatures up to at least 200 ℃ does not substantially occur.

In alternative non-limiting embodiments, the compounding process can be conducted intermittently or continuously. In further non-limiting embodiments, the rubber composition and at least a portion of the grapheme carbon particles and/or silica particles may be continuously fed to an initial portion of a mixing channel to produce a blend, and the blend may be continuously fed to a second portion of the mixing channel.

The following examples are intended to illustrate certain aspects of the invention and are not intended to limit the scope of the invention.

Examples

A series of tire tread compounds containing varying amounts of conductive additives were prepared and evaluated for their surface resistivity. The reinforcing network of highly dispersed silica is present in an amount of 47 to 70 parts per 100 parts of rubber (PHR). The conductive particle additives include grapheme carbon particles prepared according to embodiments of the present invention, graphene available from XG Sciences, graphite, flake graphite, antimony tin oxide, nickel-coated graphite, and polypyrrole-coated silica. Grapheme carbon particles are prepared by the process disclosed in U.S. patent application serial No. 13/309,894. The components listed in table 1 were blended and cured using equipment and techniques known in the art of tire tread formulation. In a first blend, styrene butadiene rubber and polybutadiene rubber are mixed with conductive additives, fillers, processing aids, antioxidants, and a portion of the cure package to form a masterbatch. The components were mixed for 7 minutes or until the complex reached 160 ℃. In a second blend, the masterbatch was then fed into the mixer and treated for an additional 10 minutes at 160 ℃. In the third and final mixing, the remaining curatives and accelerators were added to the masterbatch and mixed for 2.5 minutes at 108 ℃.

TABLE 1

Tire tread composition

Composition/ingredient (PHR)	A	B	C	D	E	F	Control
								1 st time
Budene 12071	30.01	30.01	30.01	30.01	30.01	30.01	30.01
								VSL-5025-2HM 2	96.28	96.26	96.28	96.28	96.28	96.28	96.28
Si-2663	7.53	11.00	11.00	11.00	11.00	7.53	11.00
								Precipitated silica	47.09	49.02	49.02	--	70.00	47.09	70.00
Conductive particles	22.92	21.01	24.89	70.00	23.64	22.92	0.00
								Microsere 5816A	2.00	2.00	2.00	2.00	2.00	2.00	2.00
Nocheck 4757A	1.00	1.00	1.00	1.00	1.00	1.00	1.00
								TMQ	1.00	1.00	1.00	1.00	1.00	1.00	1.00
Santoflex 13	2.00	2.00	2.00	2.00	2.00	2.00	2.00
								Stearic acid	2.00	2.00	2.00	2.00	2.00	2.00	2.00
Tufflo 100	5.00	5.00	5.00	5.00	5.00	5.00	5.00

Zinc oxide (720C)	3.50	3.50	3.50	3.50	3.50	3.50	3.50
								2 nd time
Master batch
								3 rd time
Master batch
								RM Sulfur 4	1.70	1.70	1.70	1.70	1.70	1.70	1.70
Santocure CBS 5	2.00	2.00	2.00	2.00	2.00	2.00	2.00
								Diphenylguanidine (DPG)	2.00	2.00	2.00	2.00	2.00	2.00	2.00

A-graphene carbon particles

B-nickel coated graphite

C-antimony tin oxide

D-polypyrrole coated silica

E-Ashry carbon graphite (3725, M850,4014,3775,4821,230U)

F-XG Sciences graphene (C-750, C-300, M-25, M-5)

¹Polybutadiene Rubber available from Goodyear Tire and Rubber Co

²Styrene butadiene rubber from Lanxess

³Bis (triethoxysilylpropyl) polysulfide from Evonik

⁴Sulfur from rubber manufacturers

⁵N-Cyclohexylbenzo-thiazole-2-sulfenamide from Flexsys

The surface resistivity of the final cured rubber material was measured according to the following procedure: the dr. thiedig Milli-To ohmmeter was turned on and allowed To equilibrate for 0.5 hours before experimental sampling was performed; placing a rubber sample on an insulating plastic plate; place the 5lb concentric ring ground electrode on the rubber sample, press gently to ensure uniform contact; applying an electrode voltage, measuring surface resistivity using the lowest possible set voltage of 10,100 volts or 500 volts; and the surface resistivity was determined by 10 × screen reading (in Ω or Ω/sq).

The results of the surface resistivity are shown in table 2. Surface resistivity of 10⁶-10⁹Or 10⁶-10¹⁰The materials in the range of (a) are said to be electrostatically dissipative. For silica filled tread compositions, it may be advantageous for the percolation threshold of the conductive filler to be minimal in terms of both weight and volume percent. Among the materials tested, the grapheme carbon particles of the present invention are the only particles that exhibit static dissipative properties in the presence of silica and at low loadings (5% by volume). In addition to the electrical properties of the final rubber product, the grapheme carbon particles uniquely exhibit improved mixing properties.

TABLE 2

Surface resistivity of rubber formulations

In certain embodiments, it is advantageous to improve the dispersion of silica in the rubber mixture by breaking up large silica aggregates that may be present into smaller or submicron particles. The quality of the silica dispersion can be determined using a set of equipment known as a dispersator (disperser). When the rubber sample is tested using this device, the amount of white area should be minimal. The dispersion of the silica is important for uniform performance, abrasion resistance, good reinforcement and failure (e.g., crack propagation) restriction. Therefore, fillers that significantly reduce the dispersibility of silica at low addition levels are unacceptable. Standardized silica dispersions for tread composites were prepared using highly dispersible silica, with various types of conductive particles and silica shown in table 3.

TABLE 3

Dispersion of conductive particles (normalized to HDS)

In certain embodiments, grapheme carbon particles may provide improved reinforcement properties because they have a high specific surface area relative to the volume they occupy. Tread composites made with grapheme carbon particles and silica particles may exhibit increased tensile strength and may be improved in traction (defined by tan at 0 ℃). Although the wear and tear can be kept constant, the rolling resistance is improved. These properties are shown in table 4.

TABLE 4

Tread Properties

The combination of low percolation threshold, increased tensile strength, and excellent silica dispersion achieved by using the grapheme carbon particles according to the present invention makes the formulation very advantageous in tire tread applications.

In certain embodiments, by pre-dispersing the grapheme carbon particles in a compatible resin, the electrical resistivity of the tread compound can be reduced at lower grapheme carbon particle loadings, as shown in table 5. In this example, the grapheme carbon particles are pre-dispersed in a sulfur-containing resin known under the trade name Thioplast.

TABLE 5

Surface resistivity of treads prepared with pre-dispersed graphene

The criteria for evaluating the performance of the conductive filler particles in a system that does not contain a non-conductive filler can be to evaluate the resistivity of the rubber sample at different ratios of insulating filler to conductive filler, such as the volume or weight ratio of silica to grapheme carbon particles. Percolation is observed at lower loading of conductive filler as the ratio of non-conductive to conductive filler is decreased. Table 6 shows that the sample containing graphenic carbon particles of the invention have increased surface resistivity at a relatively high volume ratio of silica to graphenic carbon particles compared to another sample having the same volume ratio but different conductive particles.

TABLE 6

For purposes of this detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, unless otherwise indicated, all numbers expressing quantities used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated otherwise, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

Moreover, it should be understood that any numerical value mentioned herein is intended to include all smaller ranges subsumed therein. For example, a range of "1 to 10" is intended to include all small atmospheres between a minimum value of 1 and a maximum value of 10 (and includes a minimum value of 1 and a maximum value of 10), that is, a minimum value of equal to or greater than 1 and a maximum value of equal to or less than 10.

In this application, the use of the singular includes the plural, and the plural includes the singular, unless specifically stated otherwise. Further, in this application, the use of "or" means "and/or" unless explicitly stated otherwise, even if "and/or" is explicitly used in some instances.

It will be readily appreciated by those skilled in the art that changes could be made to the invention without departing from the concepts disclosed in the foregoing description. Such modifications are to be considered as included in the following claims, unless the description of the claims itself explicitly indicates otherwise. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims (19)

1. A vulcanizable rubber formulation, comprising:

a base rubber composition;

0.1-20 wt% grapheme carbon particles having a 3D shape; and

1-50 wt% of filler particles comprising silica,

the grapheme carbon particles are formed by introducing (i) a hydrocarbon precursor material capable of forming two carbon fragment species into a heating zone and heating the hydrocarbon precursor material to a temperature of at least 1000 ℃ in the heating zone, or (ii) prior to methaneA bulk material introduced into a heating zone and heating the methane precursor material in the heating zone, thereby forming grapheme carbon particles having an oxygen content of no greater than 2 atomic weight percent, and subsequently quenching and collecting the formed grapheme carbon particles, wherein the rubber formulation after curing has an oxygen content of less than 10¹⁰Surface resistivity of Ω/sq.

2. The rubber formulation of claim 1, wherein the rubber formulation comprises a tire tread formulation.

3. The rubber formulation of claim 1, wherein the grapheme carbon particles comprise less than 15 weight percent of the formulation.

4. The rubber formulation of claim 1, wherein the graphenic carbon particles have a liquid volume conductivity of at least 100 microsiemens.

5. The rubber formulation of claim 1, wherein the graphenic carbon particles have less than 0.2g/cm³The bulk density of (c).

6. The rubber formulation of claim 1, wherein the grapheme carbon particles have a compressed density of less than 0.9.

7. The rubber formulation of claim 1 wherein said silica comprises 28-44% by weight of said formulation.

8. The rubber formulation of claim 1, wherein the grapheme carbon particles comprise less than 15 weight percent of the formulation and the silica comprises greater than 28 weight percent of the formulation.

9. The rubber formulation of claim 8, wherein said silica and said grapheme carbon particles are present in said formulation in a weight ratio greater than 4: 1.

10. The rubber formulation of claim 9, wherein the silica comprises precipitated silica.

11. The rubber formulation of claim 1, wherein the base rubber composition comprises styrene/butadiene rubber, natural rubber, and/or functionalized derivatives thereof.

12. The rubber formulation of claim 11, wherein the base rubber composition comprises at least one additive selected from the group consisting of processing oils, antioxidants, curatives, and metal oxides.

13. The rubber formulation of claim 1, wherein the formulation is substantially free of carbon black.

14. A method of preparing a rubber composition comprising:

(a) mixing (i)0.1-20 wt% of grapheme carbon particles having a 3D shape and having an oxygen content of no greater than 2 atomic weight percent, (ii)1-50 wt% of filler particles comprising silica with a base rubber composition comprising (iii) at least one additive selected from the group consisting of processing oils, antioxidants, curatives, and metal oxides; and

(b) curing the resulting mixture, wherein the rubber composition cured has less than 10¹⁰The surface resistivity of omega/sq,

the grapheme carbon particles are prepared by introducing (i) a hydrocarbon precursor material capable of forming two carbon fragment species into a heating zone and heating the hydrocarbon precursor material to a temperature of at least 1000 ℃ in the heating zone, or (ii) a methane precursor material into a heating zone and heating the methane precursor material in the heating zone, thereby forming grapheme carbon particles, and subsequently quenching and collecting the formed grapheme carbon particles.

15. The method of claim 14, wherein the grapheme carbon particles are present in the rubber composition in an amount of no greater than 15 weight percent and the silica comprises greater than 28 weight percent of the rubber composition based on the weight of all non-volatile components in the rubber composition.

16. The method of claim 15, wherein the silica filler and the grapheme carbon particles are present in the composition in a weight ratio greater than 4: 1.

17. The method of claim 16, wherein the base rubber composition comprises a rubber selected from the group consisting of styrene/butadiene rubber, natural rubber, functionalized derivatives thereof, and mixtures of the foregoing.

18. A vulcanizable rubber formulation, comprising:

a base rubber composition comprising a rubber selected from the group consisting of styrene/butadiene rubber, natural rubber, functionalized derivatives thereof, and mixtures of the foregoing;

1-15 wt% grapheme carbon particles having a 3D shape and having an oxygen content of no greater than 2 atomic weight percent; and

1-50 wt% of filler particles comprising silica,

the grapheme carbon particles are prepared by introducing (i) a hydrocarbon precursor material capable of forming two carbon fragment species into a heating zone and heating the hydrocarbon precursor material to a temperature of at least 1000 ℃ in the heating zone, or (ii) a methane precursor material into a heating zone and heating the methane precursor material in the heating zone, thereby forming grapheme carbon particles, and subsequently quenching and collecting the formed grapheme carbon particles,

wherein the rubber formulation has less than 10 after curing¹⁰Ω/surface resistivity of sq.

19. The vulcanizable rubber formulation of claim 18, wherein the silica filler comprises precipitated silica, the silica filler and grapheme carbon particles are present in the formulation in a weight ratio greater than 8:1, and the cured rubber formulation has less than 10⁹Surface resistivity of Ω/sq.