Patent Application
20160082774
This invention relates to a tire containing a directional heat conductive conduit comprised of at least one tire component for conducting internally generated heat to an external surface of the tire for dissipation of the conducted heat.
Pneumatic rubber tires generate internal heat, such as for example, by flexing, as the tire is being worked during service. Further, heat is not generated internally equally throughout the tire due, for example, to some components of the tire flexing more than others during the tire service as well as some components being volumetrically larger than others to thereby generate or store heat disproportionally. Therefore, some components of the tire may tend to run hotter than others. Accordingly, internal conduction combined with external dissipation of internally generated heat is desired.
Historically, a longitudinal element comprised of a rubber composition containing an appreciable content of carbon nanotubes aligned in a parallel, end-to-end, or overlapping relationship with each other has been suggested to extend through a tire component for conduction of heat from an interior of a tire to the tire's outer surface. For example see U.S. Patent Publication No. 2006/0061011. However, for this invention, it is desired to provide a directional heat conductive conduit comprised of one or more of an entire tire rubber component which contains a particulate heat conductive dispersion throughout the tire component. Representative of such tire components are for example, external (atmospherically exposed) tire components comprised of at least one of a tire rubber sidewall, peripheral tread shoulder rubber component and groove(s) contained in an outer tread cap rubber layer individually and combined with at least one of each other or with a tread base rubber layer to form said heat conductive conduit, as well as a heat conductive conduit comprised of a tire chafer component.
Also, historically, rubber containing dispersions of acetylene carbon black have been proposed to provide a heat conduction in a tire. For example, see U.S. Pat. No. 7,337,815.
As indicated, for this invention, it is desired to provide a directional heat conductive a conduit as a heat conductive path to enable dissipation of heat from an outer surface of a tire which has been directed by a heat conductive conduit composed of at least one tire component (which may include a combination of tire components) from an internal portion of a tire to an outer surface of the tire instead of by a heat conductive element which extends through a tire component without including the entire tread component.
In the description of this invention, the term “phr” is used to designate parts by weight of a material per 100 parts by weight of elastomer. The terms “rubber” and “elastomer” may be used interchangeably unless otherwise indicated. The terms “vulcanized” and “cured” may be used interchangeably, as well as “unvulcanized” or “uncured”, unless otherwise indicated.
In accordance with this invention, a pneumatic rubber tire is provided which contains a directional heat conductive rubber conduit comprised of at least one heat conductive tire component where said heat conductive tire conduit extends from an internal portion of the tire to an external surface of the tire (to thereby direct internally generated heat from an internal portion of the tire to a tire external surface for atmospheric dissipation of the conducted heat), and where at least one of said heat conductive tire components contains an outer atmospherically exposed surface of the tire.
In one embodiment, the said heat conductive tire conduit is comprised of at least two interconnecting (thereby joined, or linked together) heat conductive tire components (to facilitate heat to be conducted through both of the tire components). In such embodiment, the heat conductive tire components may be interconnected in series to facilitate conduction of the heat sequentially through each of the tire components or may interconnected in a parallel configuration to facilitate the transfer of heat simultaneously through the interconnected tire components.
In practice, the rubber composition of said heat conductive tire component has a heat conductivity of at least 0.6, alternately at least about 0.1, W/m/K (Watts/meter/Kelvin degrees temperature) and at least 0.3 W/m/K greater than tire rubber components which are joined to said heat conductive tire component(s).
In one embodiment, rubber composition of said heat conductive tire component(s) contains a dispersion of heat conductive particles sufficient to provide such heat conductivity comprised of at least one of: exfoliated graphite platelets, carbon nanotubes, acetylene carbon black, boron nitride powder, carbonyl nickel powder, Al2O3, SiC, LiClO4, zinc oxide and metal particles (e.g. at least one of nickel, copper, aluminum and iron powders).
Representative examples of such heat conductive tire components are at least one of tread base rubber layer component, tread peripheral shoulder component, tire sidewall component and tire chafer component, exclusive of a running surface of the tire tread.
The pneumatic rubber tire is conventionally comprised of a circumferential rubber tread of a cap/base construction comprised of an outer tread cap rubber component configured with lugs and intervening grooves where an outer surface of the tread lugs contains the running surface of the tire, an underlying tread base rubber layer component (underlying the outer tread cap rubber layer) where said tread may optionally contain a lateral peripheral tread shoulder component; two spaced apart beads, a pair of tire rubber sidewall components and a tire rubber chafer component (to fit against a rigid wheel rim).
Representative examples of such heat conduit is comprised of heat conductive tire components comprised of at least one of tread base rubber layer component, tread peripheral shoulder component, tire sidewall component and tire chafer component, and combinations thereof comprised of:
(A) a tire sidewall outer rubber layer (with atmospherically exposed outer surface to enable dissipation of heat conducted from an internal portion of the tire) and tread base rubber layer component (to enable conduction of internally generated from within the tire to the outer sidewall layer), and
(B) a tread peripheral shoulder component (with atmospherically exposed surface to enable dissipation of heat conducted from an internal portion of the tire) and tread base rubber layer component (to enable conduction of internally generated from within the tire to the tread peripheral shoulder component),
In one embodiment, said rubber composition of said heat conductive rubber component is a product of blending a pre-formed masterbatch comprised of at least one conjugated diene-based elastomer and exfoliated graphite platelets with the same or at least one additional conjugated diene-based elastomer.
In one embodiment, said conduit of heat conductive tire component is comprised of one or more of:
(A) the tread base rubber layer tire component which extends axially outward from an internal portion of the tire axially outward to and including an external surface of the tire sidewall,
(B) a combination of the tread base rubber layer tire component which extends axially outward from an internal portion of the tire to and including an outer tire sidewall rubber layer tire component containing an external surface of the tire,
(C) a combination of the tread base rubber layer tire component which extends axially outward from an internal portion of the tire to and including a peripheral tread rubber shoulder tire component of the tire containing an external surface of the tire,
(D) a tread rubber shoulder tire component containing an external tire surface,
(E) a tread base rubber layer tire component having a portion which extends radially outward to include an external tread groove surface in the outer tread cap rubber layer exclusive of a running surface of the tire, and
(F) a tire chafer rubber layer tire component containing an outer tire rubber surface.
A significant aspect of the invention is the providing and placement of heat conductive conduit in a manner to provide a path of directional heat conductivity to conduct heat from within the tire to an external surface of the tire for dissipation of the internally generated heat.
In one embodiment, the heat conducting rubber component is comprised of at least one diene-based elastomer and containing a dispersion therein of from about 0.5 to about 60, alternately from about 3 to about 30, parts by weight per 100 parts by weight of said elastomer (phr) so long as said heat conducting rubber has a heat has a heat conductivity of at least about 0.6, alternately at least about 1, W/m/K.
In one embodiment the rubber composition of said heat conductive tire component is comprised of
(A) 100 phr of at least one diene-based elastomer,
(B) from about 20 to about 120, alternately about 30 to about 120 phr of particulate reinforcing filler comprised of:
(e.g. containing at least about 10 phr of precipitated silica);
(C) silica coupling agent for said precipitated silica (when precipitated silica is used) containing a moiety reactive with hydroxyl groups (e.g. silanol groups) on said precipitated silica and another, different, moiety interactive with said diene based elastomer(s), and
(D) from about 0.5 to about 60, alternately about 3 to about 30 phr of heat conductive particles sufficient to provide a heat conductivity for the heat conductive tire component in a range of at least about 0.6, alternately at least about 1, W/m/K, comprised of at least one of exfoliated graphite platelets, carbon nanotubes, acetylene carbon black, boron nitride powder, carbonyl nickel powder, Al2O3, SiC, LiClO4, zinc oxide and metal particles (e.g. at least one of nickel, copper, aluminum and iron powders).
Exfoliated graphite platelets may be provided as a product of exfoliated, intercalated graphite in a form of irregular shaped platelets. Such platelets may have an average lateral dimension, for example, in a range of from about 0.1 to 1 micrometers. Carbon nanotubes may be nano sized cylindrically shaped particles having as average diameter in a range of, for example, from about 1 to about 100 nanometers and an average L/D (length to diameter), for example, in a range of from about 10/1 to about 10,000/1. For example, see U.S. Pat. Nos. 7,479,516, 6,476,154 and US Patent Application Nos. 2011/0146859, 2010/0078194, 2006/0229404 and 2006/0061011.
Acetylene carbon black is reportedly made by exothermic decomposition of acetylene (The Vanderbilt Rubber Handbook, (1978) Page 411).
As indicated, representative of metal particles (e.g. powder) is, for example, at least one of nickel, copper, aluminum and iron powders.
Drawings are provided for a further understanding of the invention to illustrate positional heat conductive rubber conduits in a form of tire components, which contain a dispersion of heat conductive particles (as hereinbefore described) sufficient to provide a heat conductivity of at least about 0.6 and alternately at least about 1, W/m/K, which conduct internally generated heat from an internal portion of the tire to the tire's outer atmospherically exposed surface for dissipation of the heat into the atmosphere. At least one of the components of the directional heat conductive conduit contains an outer surface of the tire (to enable dissipation of the conducted heat from the tire).
The invention will be described by way of example and with reference to the accompanying drawings in which:
In practice, various diene-based elastomers may be used for the rubber composition said tire tread base rubber layer and said tire rubber skirt component such as, for example, polymers and copolymers comprised of at least one monomer comprised of at least one of isoprene and 1,3-butadiene and from styrene copolymerized with at least one of isoprene and 1,3-butadiene.
Representative of such conjugated diene-based elastomers are, for example, comprised of at least one of cis 1,4-polyisoprene (natural and synthetic), cis 1,4-polybutadiene, styrene/butadiene copolymers (aqueous emulsion polymerization prepared and organic solvent solution polymerization prepared), medium vinyl polybutadiene having a vinyl 1,2-content in a range of about 15 to about 90 percent, isoprene/butadiene copolymers, styrene/isoprene/butadiene terpolymers and butadiene/acrylonitrile copolymers.
In one aspect, the conjugated diene-based elastomer may be an elastomer such as, for example, styrene/butadiene copolymer, containing at least one functional group reactive with hydroxyl groups on a precipitated silica such as, for example, comprised of at least one of amine, siloxy, thiol, imine and hydroxyl groups.
Representative of functionalized elastomers are, for example, styrene/butadiene elastomers containing one or more functional groups comprised of
(A) amine functional group reactive with hydroxyl groups on said precipitated silica,
(B) siloxy functional group, including end chain siloxy groups, reactive with hydroxyl groups on said precipitated silica,
(C) combination of amine and siloxy functional groups reactive with hydroxyl groups on said precipitated silica,
(D) combination of thiol and siloxy (e.g. ethoxysilane) functional groups reactive with hydroxyl groups on said precipitated silica,
(E) combination of imine and siloxy functional groups reactive with hydroxyl groups on said precipitated silica, and
(F) hydroxyl functional groups reactive with said precipitated silica.
For the functionalized elastomers, representative of amine functionalized SBR elastomers are, for example, in-chain functionalized SBR elastomers mentioned in U.S. Pat. No. 6,936,669.
Representative of a combination of amino-siloxy functionalized SBR elastomers with one or more amino-siloxy groups connected to the elastomer is, for example, HPR355™ from JSR and amino-siloxy functionalized SBR elastomers mentioned in U.S. Patent Application Publication No. 2007/0185267.
Representative styrene/butadiene elastomers end functionalized with a silane-sulfide group are, for example, mentioned in WO 2007/047943 patent publication.
Tin coupled elastomers may also be used, such as, for example, tin coupled organic solution polymerization prepared styrene/butadiene co-polymers, isoprene/butadiene copolymers, styrene/isoprene copolymers, polybutadiene and styrene/isoprene/butadiene terpolymers as well as said functionalized styrene/butadiene elastomers.
Commonly employed synthetic amorphous silica, or siliceous pigments, used in rubber compounding applications can be used as the precipitated silica for this invention.
The precipitated silica aggregates employed in this invention are typically obtained by the acidification of a soluble silicate, e.g., sodium silicate and may include co-precipitated silica and a minor amount of aluminum. Such synthetic, amorphous silicas are generally referred to as “precipitated silicas”.
Such precipitated silicas might usually be characterized, for example, by having a BET surface area, as measured using nitrogen gas, preferably in the range of about 40 to about 600, and more usually in a range of about 50 to about 300 square meters per gram. The BET method of measuring surface area is described in the Journal of the American Chemical Society, Volume 60 (1938), as well as ASTM D5604 for precipitated silica.
The silica may also be typically characterized, for example, by having a dibutylphthalate (DBP) absorption value in a range of about 50 to about 400 cc/100 g, and more usually about 100 to about 300 cc/100 g (ASTM D2414).
Various commercially available precipitated silicas may be considered for use in this invention such as, only for example herein, and without limitation, silicas from PPG Industries under the Hi-Sil trademark with designations Hi-Sil 210, Hi-Sil 243, etc., silicas from Solvay as, for example, Zeosil 1165MP and Zeosil 165GR, silicas from Evonic with, for example, designations VN2 and VN3, as well as other grades of silica, particularly precipitated silicas, which can be used for elastomer reinforcement.
Various coupling agents, as previously described, may be used if desired to aid in coupling the silica (e.g. precipitated silica with hydroxyl groups on its surface), as well as interacting with said functionalized exfoliated graphene platelets.
In practice, the coupling agent for the precipitated silica reinforcement of the respective zones of the tread may be, for example, an alkoxysilyl polysulfide such as for example, a bis(3-trialkoxysilylalkyl)polysulfide wherein alkyl radicals for said alkoxy groups are selected from one or more of methyl and ethyl radicals, preferably an ethyl radical and the alkyl radical for said silylalkyl component is selected from butyl, propyl and amyl radicals, preferably a propyl radical and wherein said polysulfide component contains from 2 to 8, with an average of from 2 to 2.6 or an average of from 3.5 to 4, connecting sulfur atoms in its polysulfidic bridge, preferably an average of from 2 to 2.6 connecting sulfur atoms.
Representative of such coupling agents are, for example, bis(3-triethoxysilylpropyl)polysulfide having an average of from 2 to 2.6 or an average of from 3.5 to 4, connecting sulfur atoms in its polysulfidic bridge, sometimes preferably an average of from 2 to 2.6 connecting sulfur atoms.
Such coupling agent may, for example, be added directly to the elastomer mixture or may be added as a composite of precipitated silica and such coupling agent formed by treating a precipitated silica therewith or by treating a colloidal silica therewith and precipitating the resulting composite.
Representative examples of other silica couplers may be alkoxyorganomercaptosilanes such as, for example, triethoxy mercaptopropyl silane, trimethoxy mercaptopropyl silane, methyl dimethoxy mercaptopropyl silane, methyl diethoxy mercaptopropyl silane, dimethyl methoxy mercaptopropyl silane, triethoxy mercaptoethyl silane, and tripropoxy mercaptopropyl silane.
In one embodiment, the precipitated silica may be a pre-treated (treated prior to adding to the rubber composition) precipitated silica with at least one of bis(3-triethoxysilylpropyl)polysulfide containing an average f of from about 2 to about 4 sulfur atoms in its polysulfidic bridge and of a alkoxyorganomercaptosilane.
It is readily understood by those having skill in the art that the rubber composition would be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable constituent rubbers with various commonly used additive materials such as, for example, curing aids, such as sulfur, activators, retarders and accelerators, processing additives, such as oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, peptizing agents and reinforcing fillers materials such as, for example, the aforementioned rubber reinforcing carbon black and precipitated silica. As known to those skilled in the art, depending on the intended use of the sulfur vulcanizable and sulfur vulcanized material (rubbers), the additives mentioned above are selected and commonly used in conventional amounts.
Typical amounts of tackifier resins, if used, may, for example, comprise about 0.5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts of processing aids, if used, may comprise, for example from about 1 to about 50 phr. Such processing aids can include, for example and where appropriate, aromatic, naphthenic, and/or paraffinic processing oils. Typical amounts of antioxidants where used may comprise, for example, about 1 to about 5 phr. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine and others, such as, for example, those disclosed in The Vanderbilt Rubber Handbook (1978), Pages 344 through 346. Typical amounts of antiozonants, where used, may comprise for example about 1 to 5 phr. Typical amounts of fatty acids, if used, which can include stearic acid and combinations of stearic acid with one or more of palmitic acid oleic acid and may comprise, for example, from about 0.5 to about 3 phr. Typical amounts of zinc oxide may comprise, for example, from about 1 to about 10 phr. Typical amounts of waxes, such as for example microcrystalline waxes, where used, may comprise, for example, from about 1 to about 5 phr. Typical amounts of peptizers, where used, may comprise, for example, from about 0.1 to about 1 phr.
The vulcanization 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 may be used, for example, in an amount ranging from about 0.5 to about 4 phr, or even, in some circumstances, up to about 8 phr.
Sulfur vulcanization 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, for example, from about 0.5 to about 4, alternately 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, where used, being usually used in smaller amounts (for example 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, for example, which are not affected by normal processing temperatures but produce a satisfactory cure at ordinary vulcanization temperatures. Vulcanization retarders might also be used, where desired or appropriate. Suitable types of accelerators that may be used in the present invention may be, for example, 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 may be, for example, a guanidine, dithiocarbamate or thiuram compound.
The presence and relative amounts of the above additives are not considered to be an aspect of the present invention, unless otherwise indicated herein, which is more primarily directed to a tire containing directionally positioned heat conductive elements.
The mixing of the rubber composition can be accomplished by methods known to those having skill in the rubber 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) than the preceding non-productive mix stage(s). The rubber, and reinforcing fillers, including the exfoliated graphene platelets and alternative additional reinforcing fillers such as, for example precipitated silica and rubber reinforcing carbon black 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 following Example is presented to illustrate one aspect of the invention and is not intended to be limiting. The parts and percentages are by weight unless otherwise designated.
An exemplary control rubber Sample A and exemplary experimental rubber Sample B are provided to illustrate preparation of a heat conductive graphite platelet-containing rubber composition suitable as an example of a heat conductive tire component for a heat conductive conduit of this invention.
Control rubber Sample A used reinforcing filler as rubber reinforcing carbon black.
Experimental rubber Sample B was prepared by blending a masterbatch of diene-based elastomers and graphite platelets followed by blending the masterbatch with diene-based elastomers.
The basic formulation for the rubber Sample A and rubber Sample B are illustrated in the following Table 1 where the ingredients are expressed in terms of parts by weight per 100 parts of rubber (phr) unless otherwise indicated.
The rubber compositions may be prepared, for example, by mixing the elastomers(s), which may include a masterbatch, without sulfur and sulfur cure accelerators in a first non-productive mixing stage (NP-1) in an internal rubber mixer for about 4 minutes, for example, to an elevated temperature. If desired, the rubber mixture may then mixed in a second non-productive mixing stage (NP-2) in an internal rubber mixer for about 4 minutes, for example, to an elevated temperature, sometimes without adding additional ingredients. The resulting rubber mixture may then mixed in a productive mixing stage (PR) in an internal rubber mixer with sulfur and sulfur cure accelerator(s) for about 2 minutes, for example, to a lower temperature of, for example, about 110° C. The rubber composition may then sheeted out and cooled to below 50° C. between each of the non-productive mixing steps and prior to the productive mixing step. Such rubber mixing procedure is well known to those having skill in such art.
1Synthetic cis 1,4-polyisoprene rubber as Natsyn 2200 ™ from The Goodyear Tire & Rubber Company
2Pre-blends of graphite platelets (stacked platelets) and synthetic cis 1,4-polyisoprene as Natsyn 2200 ™ from The Goodyear Tire & Rubber Company containing 15 phr of graphite platelets
3Rubber reinforcing carbon black as N205, an ASTM designation
4Mixture of fatty acids comprised of stearic, palmitic and oleic acids
5Sulfenamide and diphenyl guanidine sulfur cure accelerators
The following Table 2 represents the uncured and cured behavior and various physical properties of the rubber compositions based upon the basic formulation of Table 1, and reported for Control rubber Sample A and Experimental rubber Samples B.
1Thermal conductivity was measured by a Hot Disk Thermal Conductivity Analyzer, Hot Disk TPS 2500, with Probe Type 5501. The test was conducted at ambient (23° C.) temperature. The thermal conductivity unit is expressed as Watts/meter/Kelvin degrees temperature.
It can be seen from Table 2 that a satisfactory heat conductivity was reported for experimental rubber Sample B of at least about 0.6 W/m/K which contained the graphite platelets as made therein without departing from the spirit or scope of the invention. compared to control rubber Sample A of about 0.2 W/m/K which contained the rubber reinforcing carbon black instead of graphite platelets.
While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made within the scope of the invention.
