WO2014143140A1

WO2014143140A1 - Rubber products including carbon nanotubes and method of making same

Info

Publication number: WO2014143140A1
Application number: PCT/US2013/053971
Authority: WO
Inventors: Edward G. APSEGA
Original assignee: Apv Nano Fusing, Llc
Priority date: 2013-03-15
Filing date: 2013-08-07
Publication date: 2014-09-18

Abstract

A fabricated elastomeric product includes at least one curable, elastomer material, at least one vulcanizing agent, at least one vulcanization accelerator, and a processing aid, wherein the processing aid includes an effective amount of a non-aggregated nanomatenal containing an effective amount of an organic solvent. The invention generally relates to elastomeric compositions which include a nanomaterial and method of making same.

Description

RUBBER PRODUCTS INCLUDING CARBON NANOTUBES AND METHOD OF

MAKING SAME

TECHNICAL FIELD

[0001 ] The invention generally relates to elastomeric compositions which include a nanomaterial and method of making same. More particularly, the invention relates to a rubber composition, including tires, hoses, gaskets, belts and other molded rubber products which includes a nanomaterial that provides an improvement in wear resistance, tear resistance, rolling resistance, and scuff resistance to the tire.

BACKGROUND OF THE INVENTION

[0002] Pneumatic rubber tires are conventionally prepared in a multi-step process. This process includes the mixing of a rubber compound, the preparation of a fabric cord, a steel cord, and a bead wire, calendering of an innerliner, steel belt and ply cord, extruding the sidewall and tread of the tire, and then building and curing the various components.

[0003] Conventionally, there are four rubbers typically used in the rubber compound of a tire. These rubbers are natural rubber, styrene-butadiene rubber, polybutadiene rubber, and butyl rubber including halogenated butyl rubber. The first three are primarily used as tread and sidewall compounds, while butyl rubber and halogenated butyl rubber are primarily used for the innerliner, or the inside portion that holds the compressed air inside the tire. Polyurethane elastomers have also been developed for use in the construction of tires.

[0004] The rubber compound also includes various fillers. The most typical fillers are carbon black and silica. The selection of the types of carbon black and silica depends upon the desired performance requirements of the various parts of the tire including the tread, sidewall, and bead filler. Other ingredients also used in the processing of the tire include antioxidants, antiozonants, and anti-aging agents. Additionally, a cure package, which includes a combination of curatives and accelerators, is used to form the tire and give it its elasticity.

[0005] The rubber compound is then subjected to a mixing operation in order to effectively mix all of the components. An industrial size mixer, which includes a series of rotors housed within a mixing chamber, is used mix all of the components of the rubber compound. The mixing operation is usually a batch process.

[0006] A process oil is typically added to the rubber compound during the mixing operation. The process oil assists in reducing the amount of time required for mixing, maximizing the dispersion of the components of the rubber compound, extending the product volume, and maintaining the physical properties of the rubber compound. [0007] In order to be effective, the process oil should have a degree of miscibility for the rubber. The degree of miscibility of the process oil for the rubber depends upon the nature of the rubber, the components with which it is blended or compounded, and its final use. For a rubber containing largely saturated groups, such as butyl rubber, paraffinic process oils are

conventionally used. Similarly, for a rubber containing a significant proportion of aromatic groups, such as styrene-butadiene rubber, a highly aromatic process oil is typically employed.

[0008] Once the mixing is completed, the batch is dumped out of the mixer and sent through a series of machines to form it into a continuous sheet called a "slap." The slap is then transferred to other areas for bead wire assembly preparation, innerliner calendering, steel and/or fabric belt/ply cord calendering, tire sidewall extrusion, and tire tread extrusion.

[0009] The development of nanomaterials has seen tremendous growth in recent years. For example, full-length (unshortened) carbon nanotubes, due to their high aspect ratio, small diameter, light weight, high strength, high electrical- and thermal-conductivity, are recognized as the desired carbon fibers for nanostructured materials. For instance, nanomaterials are now used in the manufacturing of baseball bats, golf clubs, bicycles, and car parts.

[001 0] The nanomaterials, which include carbon fibers, carbon fibrils, and carbon nanotubes, have been identified as a filler for use in various rubber molded products, including tires, to yield benefits such as increased wear resistance, tear resistance, scuff resistance, and roll resistance. However, given their extremely small size, their light weight, and their large surface area, these nanomaterials constitute a potential health risk if not properly handled and are problematic when used in the rubber compounding process.

[001 1 ] Recent studies have shown that nanomaterials, such as carbon nanotubes, can be inhaled and ultimately make their way into the lungs which can result in health complications. It is for this reason, in particular, that various controls must be put in place when handling

nanomaterials. In particular, it is suggested that any operation which involves the potential release of free nanomaterials into the air should be conducted in a contained installation, i.e. a safe room , where personnel are otherwise isolated from the process. Engineering controls, including pneumatic conveying and an exhaust ventilation system having a high-efficiency particulate air filter, are commonly implemented. Finally, personal protective equipment, including respiratory protection devices, dermal protection and eye protection, are commonly provided for personnel who directly work with nanomaterials.

[0012] Besides having to implement the use of various safety controls, as described above, for handling the nanomaterials, the direct addition of the nanomaterials into the rubber compound during the rubber compounding has proved difficult. In particular, sufficient dispersion of the nanomaterials within the rubber compound is poor given the high viscosity of the rubber.

Furthermore, upon introduction into the rubber compound, the high surface area of the nanomaterial increases the viscosity of the rubber compound and limits adequate dispersion of the nanomaterial throughout the rubber compound.

[0013] Notwithstanding the state of the art as described herein, there is a need for safely and effectively incorporating a nanomaterial to be used in conjunction with, or as an alternative to, carbon black for elastomeric and rubber compositions that impart improved properties including wear resistance, tear resistance, rolling resistance, and scuff resistance.

SUMMARY OF THE INVENTION

[0014] In general, one aspect of the invention is to provide a composition for forming a tire. The composition includes at least one curable elastomer, at least one vulcanizing agent, at least one vulcanization accelerator, and a processing aid, wherein the processing aid includes a nanomaterial dispersed within an organic solvent.

[001 5] In another aspect of the invention, a fabricated rubber product is provided. The rubber product includes at least one curable, elastomer material, at least one vulcanizing agent, at least one vulcanization accelerator, and a processing aid, wherein the processing aid includes a nanomaterial dispersed within an organic solvent.

[001 6] In still yet another aspect of the invention, a method of forming a fabricated rubber product is provided. The method includes the steps of compounding ingredients of the rubber product to form a compounded mixture, wherein the ingredients of the rubber product include at least one curable, elastomer material, at least one vulcanizing agent, at least one vulcanization accelerator, and a processing aid, wherein the processing aid includes a nanomaterial dispersed within an organic solvent, mechanically mixing the compounded mixture to form a mixed batch, subjecting the mixed batch to a process selected from the group consisting of calendaring, extrusion, and bead building to form components of the rubber product, vulcanizing the components, assembling the components to form the rubber product, and curing the rubber product through the application of heat and pressure.

[001 7] In another aspect of the invention, a processing aid for the preparation of molded elastomeric materials is provided. The processing aid includes a nanomaterial and a process oil, wherein the process oil is selected from the group consisting of paraffinic oil, aromatic oil, castor oil, naphthenic oil, mineral oil, tall oil, and combinations thereof, and wherein the nanomaterial is dispersed with the process oil. The processing aid can subsequently be used as a vehicle in which to safely introduce nanoparticles, such as nanotubes into elastomeric products.

BRIEF DESCRIPTION OF THE DRAWINGS

[001 8] FIGS. 1 A-1 C show examples of polymer wrapping of carbon nanotubes; [001 9] FIGS 2A-2B show an example molecular model of a functionalized polymer that associates with a carbon nanotube in a non-wrapping fashion;

[0020] FIG. 3 is a graph showing Trouser Tear, the Shore A, and the Tension Set % measurements for compounded samples including 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black;

[0021 ] FIG. 4 is a graph showing 100% Modulus and 300% Modulus measurements for compounded samples including 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black;

[0022] FIG. 5 is a graph showing Ultimate Elongation measurements for compounded samples including 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black;

[0023] FIG. 6 is a graph showing Tensile Strength measurements for compounded samples including 1 5 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black;

[0024] FIG. 7 is a graph showing Demattia Flex measurements for compounded samples including 1 5 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black; and

[0025] FIG. 8 is a graph showing Thermal Conductivity measurements for compounded samples including 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black.

DETAILED DESCRIPTION OF THE INVENTION

[0026] As used herein, a non-limiting definition for the term, "effective amount" means a quantity sufficient to improve at least one performance result when compared to a control without the added functionalized or non-functionalized carbon nanotube.

[0027] As used herein, a non-limiting definition for the term, "effectively dispersed" means a degree of dispersion (or wetting) so that a majority of the carbon nanotubes (functionalized or non-functionalized) are non-agglomerated so that -60% of the nanotubes have particle sizes which are less than -10 μΐη and -95% of all nanotube particles have sizes which are less than -47 μΐτι . Preferably, the mean carbon nanotube particle size is -10 μΐη or less.

[0028] As used herein, a non-limiting definition for the term "approximately" means a deviation from the stated end points of a range within normal experimental error in the analytics of the rubber compounding industry for the measurement being discussed or employed. [0029] In one embodiment of the invention, the composition includes at least one curable, elastomer. In another embodiment, the elastomer is a sulfur curable, i.e., vulcanizable elastomer. The at least one curable elastomer is selected from the group consisting of natural rubber, a homopolymer of conjugated dienes, a copolymer of conjugated dienes, and mixtures thereof.

[0030] Based on the high aspect ratio, strength and remarkable physical properties of carbon nanotubes, they were considered to be ideal fillers in high performance polymers, elastomers and rubbers. Adding small amounts of carbon nanotubes can turn electrically insulating polymers into a conductive composite, which is not possible with the same amount of conventional (lower aspect ratio or spherical) conductive fillers, e.g., carbon black. However, most composites which incorporate carbon nanotubes do not result in a random distribution in the matrix, but rather form agglomerates non-homogeneously dispersed within. This is attributable at least in part, to physical entanglements of the carbon nanotubes due to structural defects during growth and van der Waals interactions between them. Such initial agglomerates can possess very high cohesive strength and are difficult to disperse. At least one aspect of this invention involves the ability to wet these agglomerates with a processing oil, and reduce the particle size to an average of 10 μΐη or less.

[0031 ] The elastomer, which includes rubber, may be selected, for example, from at least one of cis 1 ,4-polyisoprene rubber (natural and/or synthetic, and preferably natural rubber), 3,4- polyisoprene rubber, styrenetbutadiene copolymer rubbers, butadiene/acrylonitrile copolymer rubbers, styrene/isoprene/butadiene terpolymer rubbers, and cis 1 ,4-polybutadiene rubber. Also included are neoprene and butyl and halobutyl rubbers, including chlorobutyl and bromobutyl rubbers, silicone rubbers (polysiloxanes), and the like.

[0032] In another embodiment of the invention, the elastomer includes at least two diene based rubbers. For example, a combination of two or more rubbers may include combination such as cis 1 ,4-polyisoprene (natural or synthetic, although natural is preferred), 3,4-polyisoprene rubber, styrene/isoprene/butadiene rubber, emulsion and solution polymerization derived styrene/butadiene rubbers, cis-1 ,4-polybutadiene rubbers and emulsion polymerization prepared butadiene/acrylonitrile copolymers.

[0033] Other copolymers include, but are not limited to, isoprene/butadiene copolymer rubbers, isobutylene/isoprene copolymer rubbers, styrene/butadiene copolymer rubbers, styrene/isoprene copolymer rubbers, butadiene/acrylonitrile copolymer rubbers,

isoprene/acrylonitrile copolymer rubbers, styrene/isoprene/butadiene terpolymer rubbers, alpha- methylstyreneibutadiene copolymer rubbers, alpha-methylstyrenelisoprene copolymer rubbers, butadienetacrylonitrile copolymer rubbers, isoprene/acrylonitrile copolymer rubbers, alpha- methylstyrene/isoprene/butadiene terpolymer rubbers, neoprene, butyl rubbers, halobutyl rubbers, chlorobutyl rubber, bromobutyl rubbers, fluoroelastomers, and mixtures thereof. [0034] In addition to the elastomer, the composition of the invention may contain fillers such as carbon black, silica, and calcium carbonate, and additives such as plasticizers, zinc oxide, vulcanization assistants, foaming agents, antioxidants, and waxes all of which are well known to those skilled in the art.

[0035] In order to impart improvements in wear resistance, tear resistance, rolling resistance, and scuff resistance in a final fabricated product, the composition also contains a nanomaterial. In some embodiments of the invention, the nanomaterial includes, but is not limited to, carbon fibers, carbon nanofibrils, carbon nanotubes, nanographene platelets, and

combinations thereof.

[0036] The carbon nanotubes include, but are not limited to, single-wall carbon nanotubes (SWNTs), multi-wall carbon nanotubes (MWNTs), buckytubes, fullerene tubes, vapor-grown carbon fibers, and combination thereof.

[0037] The carbon nanotubes may comprise a variety of lengths, diameters, and they may be either open or capped at their ends. In particular, the carbon nanotubes have elongated tubular bodies which are typically only a few atoms in circumference. The carbon nanotubes are hollow and may have a linear fullerene structure. The length of the carbon nanotubes potentially may be millions of times greater than their molecular-sized diameter. In one embodiment of the invention, the surface of the carbon nanotubes are functionalized in a non-wrapping fashion by functional conjugated polymers.

[0038] These nanomaterials, however, are extremely small size, are light weight, and have a large surface area, and therefore, constitutes a potential health risk, create handling issues, and are difficult to use in a compounding process.

[0039] Given their unique physical properties, the nanomaterials can become airborne when exposed to an open environment. Inhalation of these nanomaterials can result in possible accumulation of these materials in the lungs. Therefore, personal protective equipment, including respiratory protection devices, dermal protection and eye protection, should be used when handling nanomaterials.

[0040] The unique physical properties of the nanomaterials also suggest the use of sophisticated engineering controls for handling purposes. These engineering controls can include, for example, pneumatic conveying and an exhaust ventilation system having a high- efficiency particulate air filter.

[0041 ] Furthermore, when using the appropriate safety and engineering controls described above, the direct addition of the nanomaterial into an elastomeric composition during the compounding process is difficult. It is known that sufficient dispersion of the nanomaterials within the elastomer compound is hindered given the high viscosity of the elastomer. Additionally, upon introduction into the elastomer compound, the high surface area of the nanomaterial increases the viscosity of the elastomer compound and reduces adequate dispersion of the nanomaterial throughout the elastomer compound.

[0042] In an embodiment of the invention, which overcomes the problems described herein, the nanomaterial is dispersed within an organic solvent therein forming a processing aid. Any means of safely transferring the nanomaterial into the organic solvent known to those skilled in the art can be used. Suitable mixing through the use of an industrial grade mixer known to those skilled in the art can be used to adequately coat and disperse the nanomaterial within the organic solvent.

[0043] The benefit of the processing aid is that the risk of inhalation of the nanomaterial is essentially removed and the mixture can be safely transported while complying with applicable transportation regulations. Furthermore, the organic solvent, in which the nanomaterial is dispersed, can have a degree of miscibility for the elastomer compound which can result in maximizing the dispersion of the nanomaterial in the elastomer compound, reducing the amount of time required for mixing, extending the product volume, and maintaining the physical properties of the elastomer compound during the compounding process.

[0044] In one embodiment, the organic solvent of the processing aid is a process oil. The process oil includes, but is not limited to, paraffinic oil, aromatic oil, castor oil, naphthenic oil, mineral oil, tall oil, and combinations thereof. In certain formulations, the processing aid includes a loading in the range from about 50.0-99.0% by weight of the organic solvent or oil

(synonymously processing aid) and from about 1 .0-50.0% by weight of the nanomaterial. In other formulations, the processing aid includes a loading in the range from about 20.0-50.0% by weight of the nanomaterial and from about 50.0-80.0% by weight of the organic solvent. It is recognized that for shipping purposes based upon current U.S. regulations, all carbon nanotubes must be saturated solids.

[0045] Preferably, the nanomaterial and process oil of the processing aid are mixed together prior to incorporation into the elastomer composition in the compounding process. Typically, between about 0.5 part and about 30 parts by weight of processing aid per 100 parts by weight of the elastomer are employed. Preferably, between about 1 and about 20, more preferably between about 2 and about 10, parts of processing aid per 100 parts by weight of the elastomer are employed. During the wetting or mixing process, it is one aspect of the invention that agglomerated nanomaterial wetted with the processing aid, is sufficiently mixed, imparting work energy into the nanomaterial / processing aid combination so that the mean particle size of the nanomaterial is reduced to about 10 microns as measured using an appropriate particle size analyzer analytical equipment adapted for measurement in the appropriate size range. By reducing the average nanomaterial particle size into this range, a thixotropic-like material (exhibiting characteristics of non-Newtonian behavior) is produced which more uniform ly distributes itself within a polymer and/or rubber matrix.

[0046] After the addition of the processing aid, the nanomaterial / processing aid combination is subjected to sufficient shear stresses so that a particle size distribution sim ilar to that illustrated in summary form in the following table is obtained.

What is illustrated above is that more than -60% of the nanotubes have particle sizes which are less than -1 0 μΐη and -95% of all particles have sizes which are less than -47 μΐη , actual data illustrated below.

[0047] A comparison of the efficacy of the application of shearing stresses to the agglomerated nanomaterial was conducted by the following simple test in which the same natural rubber and additives were compared with a compounded sample having essentially non- agglomerated nanomaterial with the above characteristics compared to nanomaterial which was agglomerated (i.e., before the application of the shearing forces described above).

[0048] Molecular engineering (e.g., cutting, solubilization, chemical functionalization, chromatographic purification, manipulation and assembly) of single-walled and multi-walled carbon nanotubes may play a vital role in exploring and developing the applications of carbon nanotubes. Non-covalent functionalization of carbon nanotubes has received attention, because it offers the potential to add a significant degree of functionalization to carbon nanotube surfaces (sidewalls) while still preserving nearly all of the nanotubes' intrinsic properties.

[0049] An example of the non-covalent functionalization of carbon nanotubes is provided by a chemistry platform that uses rigid conjugated polymers called Kentera™ which is developed by Zyvex Technologies. In the Kentera™ technology platform, the predominant interaction between the polymer backbone and nanotube surface occurs through %-% interaction. Although %-% interaction is a weaker bond than covalent bonding, the sum of π-ρ interactions creates a large net-stabilizing energy that results in superior and stable systems. As used in this application, the functionalized carbon nanotubes used were Kentera™ KHA2, Kentera™ K3, Kentera™ K1 and Kentera™ KHA2CH .

[0050] In supramolecular chemistry, %-% interactions are the result of intermolecular overlapping of p-orbitals in p-conjugated systems. This non-covalent interaction becomes stronger as the number of p-electrons increases. The %-% interactions act strongly on flat polycyclic aromatic hydrocarbons, such as anthracene, triphenylene and coronene because of the many delocalized p-electrons.

[0051 ] The Kentera™ technology platform provides a non-covalent functionalization method for carbon nanotubes through the use of %-% interactions in extended p-conjugated systems. By molecular design and by applying the rules and the structural requirement of %-% interactions in host-guest systems, a polymer can be developed with strong affinity to carbon nanotube sidewalls. The Kentera™ technology platform can also provide a conjugated polymer that has an irreversible association with nanotubes through %-% interactions. [0052] The non-covalent functionalization of carbon nanotubes can be accomplished through polymer wrapping. FIGS. 1 A-1 C show examples of such polymer wrapping of a carbon nanotube. In polymer wrapping, a polymer "wraps" around the diameter of a carbon nanotube. For instance, FIG. 1 shows an example of polymers 102A and 102B wrapping around single-walled carbon nanotube (SWNT) 101. FIG. 1 B shows an example of polymer 103A and 103B wrapping around SWNT 101. FIG. 1 C shows an example of polymers 104A and 104B wrapping around SWNT 101. It should be noted that the polymers in each of the examples of FIGS. 1 A 1 C are the same, and the FIGURES illustrate that the type of polymer-wrapping that occurs is random (e.g., the same polymers wrap about the carbon nanotube in different ways in each of FIGS. 1 A-1 C).

[0053] In an embodiment of the invention, for instance, an example molecular model of a polymer that associates (e.g., noncovalently bonds) with a carbon nanotube in a non-wrapping fashion is shown in FIGS. 2A and 2B. FIG. 2B is a cross-sectional view of FIG. 2A taken as indicated in FIG. 2A. As shown in this example, a carbon nanotube (and more specifically a single-walled carbon nanotube in this example) 201 has polymer 202 associated with it in a non- wrapping fashion therewith.

[0054] Polymer 202 comprises a relatively rigid backbone 203 that associates with carbon nanotube 201 substantially along the length, as opposed to about the diameter, of such carbon nanotube 201. Thus, polymer 202 associates with carbon nanotube 201 in a non-wrapping fashion, which is advantageous for various reasons, some of which are described more fully herein. The specific rigidity of various backbones 203 that may be implemented in accordance with embodiments of the present invention may vary (e.g., certain implementations may enable a portion of backbone 203 to bend beyond half-diameter 205 while another portion of such backbone is arranged at location 206 of nanotube 201 ), but such backbones 203 are preferably sufficiently rigid such that they do not wrap (i.e., fully envelop the diameter of) nanotube 201. Of course, as shown in the example of FIGS. 2A 2B, portions of polymer 202 (e.g., functional extensions 204A and 204B) may extend about all or a portion of the diameter of nanotube 201 , but backbone 203 of polymer 202 is preferably sufficiently rigid such that it does not wrap about the diameter of nanotube 201.

[0055] Polymer 202 may further comprise various functional extensions from backbone 203, such as functional extensions 204A and 204B, which may comprise any of various desired functional groups for functionalizing carbon nanotube 201. As described further herein, embodiments of the present invention include functional groups in polymer 202 that are suitable for functionalizing carbon nanotube 201 in any of various desired ways, including without limitation solubilizing carbon nanotube 201 or implementing "chemical handles" on carbon nanotube 201. [0056] The non-wrapping approach of embodiments of the present invention allows better control over the distance between functional groups on the carbon nanotube surface by precisely varying the length and constitution of the primary backbone (or other selected backbone) and side chain. This strategy opens the door to the (semi-)site-controlled non-covalent functionalization of carbon nanotube surfaces. Such functionalization may introduce numerous neutral and ionic functional groups onto the carbon nanotube surfaces. It may provide "chemical handles" for manipulation and assembly of carbon nanotubes, enabling applications in a variety chemical applications including rubber compounding.

[0057] Thus, one advantage of polymer 202 associating with carbon nanotube 201 (e.g., via π -stacking interaction) in a non-wrapping fashion is that it enables functional groups, such as functional extensions 204A and 204B, to be arranged along backbone 203 in a desired manner to accurately control the spacing of such functional groups. In polymers that associate with a carbon nanotube in a wrapping fashion, it becomes much more difficult to control the relative spacing of the functional groups arranged on the polymer because their spacing is dependent on the wrapping of the polymer. By controlling the spacing of such functional groups along backbone 202, more control may be provided over if/how the functional groups interact with each other, carbon nanotube 201 , and/or other elements to which the functional groups may be exposed.

[0058] Another advantage of such non-covalent functionalization of carbon nanotubes is that it allows for a significant degree of functionalization to be added to carbon nanotube surfaces (sidewalls) while still preserving nearly all of the nanotubes' intrinsic properties. That is, as described above, carbon nanotubes possess a very desirable and unique combination of physical properties relating to, for example, strength, weight, electrical conductivity, etc. Having the ability to functionalize carbon nanotubes while preserving nearly all of the nanotubes' properties thus offers many advantages. For instance, in certain applications, carbon nanotubes may be solubilized and thus used in forming a desired composition of matter (or "material") that has desired properties supplied at least in part by the nanotubes. That is, suitable functional groups for solubilizing the nanotube may be included in the polymer in certain embodiments of the present invention.

[0059] The advantages of using functionalized carbon nanotubes in rubber formulations are shown in FIGS. 3-8. Rubber compounds containing functionalized carbon nanotubes, raw carbon nanotubes, or carbon black were evaluated by various physical tests. In most cases, the rubber formulations containing the functionalized carbon nanotubes performed better than or equal to the formulations containing raw carbon nanotubes or carbon black. One aspect of the invention is to be able to allow the rubber industry (e.g., tire manufacturers) to use their existing manufacturing lines but still obtain the benefits of using carbon nanotubes. One effective approach is to employ the carbon nanotubes in a processing aid as described above. By substituting at least a portion of the carbon black with carbon nanotubes, a weight reduction is achieved and superior properties result. However, this beneficial substitution is only achieved by an appropriate level of dispersion of the carbon nanotubes within the processing oil. There are several approaches which can be used to ascertain whether the dispersion is sufficient, one approach employing a particle size metric, and wherein the majority of carbon nanotubes are less than 10 μΐτι. This insures that the particles are not agglomerated, but rather are segregated to a high degree. When in this state, up to 50% of the carbon black may be substituted with carbon nanotubes. However, for reasons primarily related to cost, typically between 10-20% of the carbon black is replaced with carbon nanotubes (preferably about 15%). Without being held to any one theory, it is believed that approximately 0.5% replacement is required to achieve a measurable improvement in physical properties.

[0060] FIG. 3 shows a comparison of the results of samples containing 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black, after Trouser Tear, Shore A Durometer, and Tension Set tests. For the Trouser Tear test, a high tear strength measurement is desirable. For the Shore A Durometer test, a lower measurement is desired since this represents that the test compound is more like rubber and not hard like a plastic material. For the Tension Set test, the test compound is stretched to 300% its normal length for a period of time and then released. The measurement shows how close the compound returns to its normal length. In each of the tests, the samples formulated with the functionalized carbon nanotubes performed better than or were equal to the samples formulated with the raw carbon nanotubes and/or the carbon black.

[0061 ] FIG. 4 shows a comparison of the results of samples containing 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black, after 100% and 300% Modulus tests. A high modulus measurement can be interpreted as the test compound being harder/stiffer when compared to a low modulus measurement which is interpreted as the test compound being softer/pliable. In each of the Modulus tests, the samples formulated with the functionalized carbon nanotubes performed better than or were equal to the samples formulated with the raw carbon nanotubes and/or the carbon black.

[0062] FIG. 5 shows a comparison of the results of samples containing 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black, after Elongation testing. Typically, a higher elongation % measurement is desired because this is interpreted as the test compound being able to stretch more before the test compound breaks. In Elongation tests, the sample formulated with the functionalized carbon nanotubes performed better than the sample formulated with the carbon black. However, the sample formulated with the raw carbon nanotubes performed better than the sample formulated with the functionalized carbon nanotubes. [0063] FIG. 6 shows a comparison of the results of samples containing 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black, after Tensile Strength testing. Typically, a higher tensile strength measurement is desired because this is interpreted as the test compound being stronger. In the Tensile Strength tests, the samples formulated with the functionalized carbon nanotubes performed better than the samples formulated with the raw carbon nanotubes and the carbon black.

[0064] FIG. 7 shows a comparison of the results of samples containing 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black, after Demattia Flex testing. Typically, a higher flex measurement is desired because this is interpreted as the test compound having enhanced cut growth resistance. In the Demattia Flex tests, the samples formulated with the functionalized carbon nanotubes were markedly better than the samples formulated with the raw carbon nanotubes and the carbon black.

[0065] FIG. 8 shows a comparison of the results of samples containing 15 phr functionalized carbon nanotubes / 45 phr carbon black; 15 phr raw carbon nanotubes / 45 phr carbon black; and 60 phr carbon black, after Thermal Conductivity testing. Typically, a higher thermal conductivity measurement is desired because this is interpreted as the test compound having enhanced heat transfer properties which can result in a shorter cure time. In the Thermal Conductivity tests, the sample formulated with the functionalized carbon nanotubes performed better than the sample formulated with the carbon black. However, the sample formulated with the raw carbon nanotubes performed better than the sample formulated with the functionalized carbon nanotubes.

[0066] Vulcanization of the elastomer compound is conducted in the presence of a sulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agents include elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. Preferably, the sulfur vulcanizing agent is elemental sulfur. As known to those skilled in the art, sulfur vulcanizing agents are used in an amount ranging from about 0.5 to about 4 phr, or even, in some circumstances, up to about 8 phr, with a range of from about 1 .5 to about 2.5 phr, sometimes from 2 to 2.5 phr, being preferred. Other vulcanizing agents include, and are not limited to, peroxides, metallic oxides, urethane crosslinkers, acetoxysilane, and others known to those skilled in the art.

[0067] Accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. In one embodiment, a single accelerator system may be used, i.e., primary accelerator. Conventionally and preferably, a primary accelerator(s) is used in total amounts ranging from about 0.5 to about 4, preferably about 0.8 to about 1 .5, phr. In another embodiment, combinations of a primary and a secondary accelerator might be used with the secondary accelerator being used in smaller amounts (of about 0.05 to about 3 phr) in order to activate and to improve the properties of the vulcanizate. Combinations of these accelerators might be expected to produce a synergistic effect on the final properties and are somewhat better than those produced by use of either accelerator alone. In addition, delayed action accelerators may be used which are not affected by normal processing temperatures but produce a satisfactory cure at ordinary vulcanization temperatures.

Vulcanization retarders might also be used. Suitable types of accelerators that may be used in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. Preferably, the primary accelerator is a sulfenamide. If a second accelerator is used, the secondary accelerator is preferably a guanidine, dithiocarbamate or thiuram compound.

[0068] The mixing of the elastomer composition can be accomplished by methods known to those having skill in the elastomer mixing art. For example, the ingredients are typically mixed in at least two stages, namely, at least one non-productive stage followed by a productive mix stage. The final curatives are typically mixed in the final stage which is conventionally called the

"productive" mix stage in which the mixing typically occurs at a temperature, or ultimate temperature, lower than the mix temperature(s) in the preceding non-productive mix stage(s). The rubber and functionalized carbon nanotubes, and other granular carbon black, if used, are mixed in one or more non-productive mix stages. The terms "non-productive" and "productive" mix stages are well known to those having skill in the rubber mixing art. The tires and other fabricated rubber products can be built, shaped, molded and cured by various methods which are known and will be readily apparent to those having skill in such art.

[0069] By way of example only, other applications for the processing aid composition include additional tire components, including the bead, sidewall, and shoulder, belts, hoses, molded rubber goods and the like. Various diene-based elastomers are also considered within the scope of the invention. Preferably, such elastomers are sulfur curable elastomers. For example, such elastomers are selected from homopolymers and copolymers of conjugated dienes such as 1 ,3- butadiene and isoprene, and from copolymers of conjugated dienes such as, for example, 1 ,3- butadiene and/or isoprene with a vinyl aromatic compound such as styrene or alpha- methylstyrene. Additional polymers such as neoprene, butyl rubber and halobutyl rubber, including chlorobutyl and bromobutyl polymers, are considered to be within the scope of the invention. Representative of homopolymers of conjugated dienes are, for example, cis-1 ,4- polybutadiene, a polymer of 1 ,3-butadiene and cis 1 ,4-polyisoprene. Representative of copolymers of conjugated dienes are, for example, isoprenelbutadiene copolymers.

Representative of copolymers of conjugated diene(s) and vinyl aromatic compounds are, for example, styrene butadiene copolymers and styrene/isoprene/butadiene terpolymers.

Fluoroelastomers are also considered to be within the scope of the invention. A fluoroelastomer is a fluorocarbon-based synthetic rubber. This class of elastomers includes copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF), terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) as well as

perfluoromethylvinylether (PMVE) containing specialties. Generally, the utilization of a processing aid or processing oil as a vehicle in which to introduce nanoparticles, such as nanotubes, into elastomeric products is taught by this invention. Through this method, safe handling and thorough mixing into the elastomeric material can be achieved.

EXAMPLES

[0070] The following Examples illustrate the components, as well as amounts, of various representative elastomeric compositions that utilize a standard process oil in each of the formulations and a composition that includes the processing aid according to an embodiment of the invention. These Examples are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

[0071 ] Example 1 . Representative Tire Formulation

[0072] Physical properties of the tire formulation of Example #1 after curing for 25 minutes at 307°F (153°C) :

[0073] Example 2. Representative Tire Formulation Including Processing Aid

[0074]

[0075] Physical properties of Example #3 after curing for 15 minutes at 316°F (158°C) :

[0076] Example 4. Representative Tire Tread Formulation Including Processing Aid

[0077]

[0078] Physical properties of Example #5 after curing for 20 minutes at 307°F (153°C) :

[0079] Example 6. Representative White Sidewall Formulation Including Processing Aid

[0080]

[0081 ] Physical properties of Example #7 after curing for 20 minutes at 307°F (153°C) :

[0082] Example 8. Representative Conveyor Belt Formulation Including Processing Aid

[0083]

[0084] Physical properties of Example #9 after curing for 10 minutes at 290°F (143°C) :

[0085] Example 10. Representative Hose Formulation Including Processing Aid

[0086] Example 1 1 . Representative Gasket Formulation

[0087] Physical properties of Example #1 1 after curing for 15 minutes at 307°F (153°C) :

[0088] Example 12. Representative Gasket Formulation Including Processing Aid

[0089]

[0090] Physical properties of Example #13 after curing for 10 minutes at 287°F (142°) :

[0091 ] Example 14. Representative Shoe Sole Formulation Including Processing Aid

[0092]

[0093] Composition of Processing Aid for Bladder of Example #15:

[0094] Based upon the foregoing disclosure, it should now be apparent that rubber and elastomeric compositions including a processing aid by which to introduce nanoparticles as described herein will carry out the objects set forth hereinabove. It is, therefore, to be understood that any variations evident fall within the scope of the claimed invention and thus, the selection of specific component elements can be determined without departing from the spirit of the invention herein disclosed and described.

Claims

1 . A composition for forming a tire, the composition comprising:

at least one curable elastomer;

at least one vulcanizing agent;

at least one vulcanization accelerator; and

an effective amount of a processing aid, wherein the processing aid includes a nanomaterial effectively wetted with a processing oil.

2. The composition of claim 1 , wherein the at least one elastomer is selected from the group consisting of natural rubber, a homopolymer of conjugated dienes, and a copolymer of conjugated dienes.

3. The composition of claim 2, wherein the homopolymer is selected from the group

consisting of natural cis-1 ,4-polyisoprene rubber, synthetic cis-1 ,4-polyisoprene rubber, 3,4-polyisoprene rubber, cis-1 ,4-polybutadiene rubber and mixtures thereof.

4. The composition of claim 2, wherein the copolymer is selected from the group consisting of isoprene/butadiene copolymer rubbers, styrenetbutadiene copolymer rubbers, styrene/isoprene copolymer rubbers, butadiene/acrylonitrile copolymer rubbers, isoprene/acrylonitrile copolymer rubbers, styrene/isoprene/butadiene terpolymer rubbers, alpha-methylstyreneibutadiene copolymer rubbers, alpha-methylstyrenelisoprene copolymer rubbers, butadienetacrylonitrile copolymer rubbers, isoprene/acrylonitrile copolymer rubbers, alpha-methylstyrene/isoprene/butadiene terpolymer rubbers, neoprene, butyl rubbers, halobutyl rubbers, chlorobutyl rubber, bromobutyl rubbers, fluoroelastomers, silicone rubbers, polysiloxanes, and mixtures thereof.

5. The composition of claim 1 , wherein the nanomaterial is selected from the group

consisting of carbon fibers, carbon nanofibrils, carbon nanotubes, nanographene platelets, and combinations thereof.

6. The composition of claim 5, wherein the carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, buckytubes, fullerene tubes, vapor-grown carbon fibers, and combination thereof.

7. The composition of claim 6, wherein the carbon nanotubes are functionalized.

8. The composition of claim 7, wherein the functionalized nanotubes include a polymer that is non-covalently bonded to the nanotubes in a non-wrapping fashion.

9. The composition of claim 8, wherein the polymer includes at least one functional group.

10. The composition of claim 1 , wherein the organic solvent is a process oil.

1 1 . The composition of claim 10, wherein the process oil is selected from the group consisting of paraffinic oil, aromatic oil, castor oil, naphthenic oil, mineral oil, tall oil, and combinations thereof.

12. The composition of claim 1 wherein -95% of all nanomaterial has a particle size which is less than -47 μΐη.

13. The composition of claim 12 wherein more than -60% of the nanomaterial has a particle size which is less than -10 μΐη .

14. A fabricated rubber product comprising:

at least one curable elastomer;

at least one vulcanizing agent;

at least one vulcanization accelerator; and

an effective amount of a processing aid, wherein the processing aid includes an effectively wetted nanomaterial by an organic oil.

15. The product of claim 14, wherein the at least one elastomer is selected from the group consisting of natural rubber, a homopolymer of conjugated dienes and a copolymer of conjugated dienes.

16. The product of claim 15, wherein the homopolymer is selected from the group consisting of natural cis-1 ,4-polyisoprene rubber, synthetic cis-1 ,4-polyisoprene rubber, 3,4- polyisoprene rubber, cis-1 ,4-polybutadiene rubber and mixtures thereof.

17. The product of claim 15, wherein the copolymer is selected from the group consisting of isoprene/butadiene copolymer rubbers, styrenetbutadiene copolymer rubbers, styrene/isoprene copolymer rubbers, butadiene/acrylonitrile copolymer rubbers, isoprene/acrylonitrile copolymer rubbers, styrene/isoprene/butadiene terpolymer rubbers, alpha-methylstyreneibutadiene copolymer rubbers, alpha-methylstyrenelisoprene copolymer rubbers, butadienetacrylonitrile copolymer rubbers, isoprene/acrylonitrile copolymer rubbers, alpha-methylstyrene/isoprene/butadiene terpolymer rubbers, neoprene, butyl rubbers, halobutyl rubbers, chlorobutyl rubber, bromobutyl rubbers, silicone rubbers, polysiloxanes, and mixtures thereof.

18. The product of claim 14, wherein the nanomaterial is selected from the group consisting of carbon fibers, carbon nanofibrils, carbon nanotubes, nanographene platelets, and combinations thereof.

19. The product of claim 18, wherein the carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, buckytubes, fullerene tubes, vapor-grown carbon fibers, and combination thereof.

20. The product of claim 19, wherein the carbon nanotubes are functionalized.

21 . The product of claim 20, wherein the functionalized nanotubes comprise a polymer that is non-covalently bonded to the nanotubes in a non-wrapping fashion.

22. The product of claim 21 , wherein the polymer includes at least one functional group.

23. The product of claim 14, wherein said fabricated product is selected from the group

consisting of tires, hoses, transmission belts, conveyor belts, and molded rubber goods.

24. The product of claim 14, wherein said fabricated product is selected from the group

consisting of a tire tread, a bladder, a gasket, a shoe sole.

25. The product of claim 14 wherein -95% of all nanomaterial has a particle size which is less than -47 μΐτι.

26. The product of claim 25 wherein more than -60% of the nanomaterial has a particle size which is less than -10 μΐτι.

27. A method of forming a fabricated rubber product, the method comprising the steps of: wetting an agglomerated nanomaterial with an organic solvent and subjecting said nanomaterial to shearing forces so as to reduce said agglomerated nanomaterial to essentially non-agglomerated nanomaterial having a particle size wherein -95% of all nanomaterial has a particle size which is less than -47 μΐη ;

compounding ingredients of the rubber product to form a compounded mixture, wherein

the ingredients of the rubber product include at least one curable, elastomer material, at least one vulcanizing agent, at least one vulcanization accelerator, and an effective amount of a processing aid, wherein the processing aid includes said essentially non-agglomerated nanomaterial effectively dispersed within an organic solvent;

mechanically mixing the compounded mixture to form a mixed batch;

subjecting the mixed batch to a process selected from the group consisting of

calendaring, extrusion, and bead building to form components of the rubber product;

vulcanizing the components;

assembling the components to form the rubber product; and

curing the rubber product through an application of heat and pressure.

28. The method of claim 23, wherein the nanomaterial is selected from the group consisting of carbon fibers, carbon nanofibrils, carbon nanotubes, nanographene platelets, and combinations thereof.

29. The method of claim 24, wherein the carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, buckytubes, fullerene tubes, vapor-grown carbon fibers, and combination thereof.

30. The method of claim 25, wherein the carbon nanotubes are functionalized.

31 . The method of claim 26, wherein the functionalized nanotube comprises a polymer that is non-covalently bonded to the nanotube in a non-wrapping fashion.

32. The method of claim 27, wherein the polymer includes at least one functional group.

33. The method of claim 23, wherein the fabricated product is selected from the group

consisting of tires, hoses, bladders, transmission belts, gaskets, shoe soles, conveyor belts, and molded rubber goods.

34. The method of claim 23, wherein said fabricated product is a tire.

35. The product of claim 27 wherein more than -60% of the nanomaterial has a particle size which is less than -10 μΐτι.

36. A processing aid for the preparation of molded elastomeric materials, the processing aid comprising:

an effective amount of a non-agglomerated nanomaterial having a particle size wherein -95% of all nanomaterial has a particle size which is less than -47 μΐη ; and

an organic process oil, wherein the process oil is selected from the group

consisting of paraffinic oil, aromatic oil, castor oil, naphthenic oil, mineral oil, tall oil, and combinations thereof, and wherein the nanomaterial wetted with an effective amount of the organic processing oil.