Patent Description:
Tires are sometimes desired with treads for promoting a combination of both traction on wet surfaces and beneficially reduced rolling resistance. Various rubber compositions may be proposed for such tire treads. It is also a desirable feature of such tires to have minimum or no loss of winter traction performance.

Document D1 discloses a tire tread compound comprising a high vinyl polybutadiene, natural rubber, a tin coupled isoprene-butadiene rubber, a silica carbon black blend with a high silica load, and a processing oil but in the absence of solution SBR.

Document D2 discloses a tire tread compound composed of a high vinyl polybutadiene rubber, one or more isoprene/butadiene copolymer rubbers and cis <NUM>,<NUM> polyisoprene rubber. In an example this composition comprises further a high load of silica, process oils, resins and waxes, in the absence of solution SBR.

To promote wet traction, namely traction of the tire tread running surface on wet road surfaces, a tire tread rubber composition may, for example, contain a relatively high Tg (high glass transition temperature) diene based synthetic elastomer. Its rubber reinforcing filler may primarily be precipitated silica together with a silica coupler to aid in coupling the precipitated silica to the diene-based elastomer(s). Such tire tread rubber may be considered as being precipitated silica rich.

In one aspect, predictive improvement of wet traction performance (increase in the tread's wet traction) for the tread rubber composition may be based on at least one of maximization of its tan delta physical property value at about <NUM> and minimization of its rebound physical property value at about <NUM>.

Reducing rolling resistance for a tire can relate to reducing energy based hysteresis (promoting a reduction in the rubber composition's hysteresis) for the tire's tread rubber composition which promotes a reduction in internal heat generation for the cured rubber composition with an attendant reduction in temperature increase during tire tread service and predictive improved (reduced) rolling resistance for the tire with a resultant beneficially better (improved) fuel economy for an associated vehicle. In one aspect, improved (lower) hysteresis for a cured rubber composition can be based on at least one of minimizing its tan delta physical property value at about <NUM> and maximizing its rebound physical property value at about <NUM>.

Promoting cold weather (winter) performance for a tire can relate to providing a rubber composition for its tread having a lower stiffness at lower ambient temperatures which may be indicated by a lower storage modulus (G') value at a cold temperature for the rubber composition. A predictive promotion of cold weather performance for the tread rubber composition may be based on a minimization of its stiffness physical property, for example minimizing its storage modulus (G') property, at a temperature of about -<NUM>. This may present a challenge for a tire tread rubber which is based upon promoting beneficially wet traction and reduction of hysteresis by providing its rubber composition with a relatively high Tg elastomer with reinforcing filler being primarily precipitated silica where it might be expected that it could become stiffer (having a higher G' property) at cold ambient temperatures and thereby a reduction in cold weather performance, which may include vehicular driving conditions through snow covered road conditions.

Therefore, it is desirable to evaluate providing such vehicular tire tread with a rubber composition containing a combination of both relatively high and lower Tg elastomers with.

It is considered that significant challenges are presented for providing such tire tread rubber compositions that promote a combination of both good wet traction and beneficially reduced hysteresis (and associated beneficial reduction in associated tire rolling resistance) while limiting loss of (substantially maintaining) winter traction at low ambient temperatures. To achieve the challenge of promoting such balance of tread rubber performances with tread rubber compositions, it is recognized that concessions and adjustments would be expected.

To meet such challenge, it is desired to evaluate providing a tread rubber composition utilizing (containing) a combination of :.

In the description of this invention, the terms "compounded" rubber compositions and "compounds" are used to refer to rubber compositions which have been compounded, or blended, with appropriate rubber compounding ingredients. The terms "rubber" and "elastomer" may be used interchangeably unless otherwise indicated. The amounts of materials are usually expressed in parts of material per <NUM> parts of rubber by weight (phr).

The glass transition temperature (Tg) of the elastomers is determined by DSC (differential scanning calorimetry) measurements at a temperature rising rate of <NUM> per minute according to ASTM D7426 or equivalent.

The measurement of Tg for resins is DSC according to ASTM D6604 or equivalent.

The softening point of a resin is determined in accordance with ASTM E28, which might sometimes be referred to as a ring and ball softening point.

The invention relates to a rubber composition in accordance with claim <NUM> and to a tire in accordance with claim <NUM>.

In accordance with a preferred aspect of this invention, a pneumatic tire is provided having a circumferential rubber tread adapted to be ground-contacting, where the tread is of or comprises a rubber composition comprising, based on parts by weight per <NUM> parts by weight elastomer (phr):.

In a preferred embodiment, the vegetable triglyceride oil is or comprises at least one of sunflower, soybean, canola and safflower oil, usually desirably primarily at least one of sunflower and soybean oil.

In one embodiment, the rubber processing oil is exclusively vegetable triglyceride oil.

In a preferred embodiment, the Tg's of said relatively high vinyl polybutadiene rubber and said cis <NUM>,<NUM>-polyisoprene rubber are spaced apart by at least <NUM>.

In additional accordance with this invention, the tread rubber composition is exclusive of styrene containing elastomers including styrene/butadiene elastomers.

In further accordance with this invention, the tire tread may be provided as a sulfur cured rubber composition.

In a preferred embodiment, the tread rubber composition further contains up to <NUM>, alternately <NUM> to <NUM>, phr of at least one additional diene based elastomer exclusive of styrene containing elastomers and desirably exclusive of synthetic copolymer based elastomers (elastomers as copolymers comprised of at least two diene monomers which are different diene monomers from each other). Such additional elastomer may comprise, for example, at least one of a relatively low vinyl polybutadiene rubber (vinyl <NUM>,<NUM>-content of less than <NUM> percent) having a Tg in a range of from -<NUM> to -<NUM> and <NUM>,<NUM>-polyisoprene.

In a preferred embodiment, the relatively high vinyl polybutadiene elastomer is a functionalized high vinyl polybutadiene elastomer comprising a relatively high vinyl polybutadiene elastomer end-chain functionalized with at least one functional group reactive with hydroxyl groups contained on the silica. Representative of such end-chain functional groups (terminal groups) may be, for example, at least one of amine (e.g. primary and/or secondary amine groups), thiol, siloxy (e.g. alkoxysilane) and silane-sulfide groups which are reactive with hydroxyl groups on the silica, and which may be found, for example, in <CIT> and <CIT>.

In one embodiment, the silica, preferably the precipitated silica, and the silica coupling agent may be pre-reacted to form a composite thereof prior to addition to the rubber composition.

In such embodiment, the silica and silica coupling agent are provided as a composite of silica pre-reacted with silica coupling agent.

In one embodiment, the silica, preferably the precipitated silica, and silica coupling agent may be added to the rubber composition and thereby reacted together in situ within the rubber composition.

The resin is one of styrene/alphamethylstyrene resin, coumarone-indene resin, petroleum hydrocarbon resin, terpene polymer, terpene phenol resin and rosin based resin, including rosin derivatives and copolymers thereof.

In a preferred embodiment, the resin is a styrene/alphamethylstyrene resin. Such styrene/alphamethylstyrene resin may be, for example, a relatively short chain copolymer of styrene and alphamethylstyrene. In one embodiment, such a resin may be suitably prepared, for example, by cationic copolymerization of styrene and alphamethylstyrene in a hydrocarbon solvent.

The styrene/alphamethylstyrene resin preferably has a styrene content within a range of from <NUM> to <NUM> percent.

The styrene/alphamethylstyrene resin preferably has a softening point in a range of from <NUM> to <NUM>, alternately from <NUM> to <NUM> (ASTM E28).

A suitable styrene/alphamethylstyrene resin is, for example, Resin <NUM>™ from Eastman or Sylvares SA85™ from Arizona Chemical.

In another embodiment, the resin is a coumarone-indene resin. Such coumarone-indene resin preferably have a softening point in a range of from <NUM> to <NUM> containing coumarone and indene as the monomer components making up the resin skeleton (main chain). Minor amounts of monomers other than coumarone and indene may be incorporated into the coumarone-indene skeleton such as, for example, methyl coumarone, styrene, alphamethylstyrene, methylindene, vinyltoluene, dicyclopentadiene, cycopentadiene, and diolefins such as isoprene and piperylene.

In another embodiment, the resin is a petroleum hydrocarbon resin. Such petroleum hydrocarbon resin may be, for example, an aromatic and/or non-aromatic (e.g. paraffinic) based resin. Various petroleum resins are available. Some petroleum hydrocarbon resins have a low degree of unsaturation and high aromatic content, whereas some are highly unsaturated and yet some contain no aromatic structure at all. Differences in the resins are largely due to the olefins contained in the petroleum based feedstock from which the resins are derived. Conventional olefins for such resins include any C5 olefins (olefins and di-olefins containing an average of five carbon atoms) such as, for example, cyclopentadiene, dicyclopentadiene, isoprene and piperylene, and any C9 olefins (olefins and diolefins containing an average of nine carbon atoms) such as, for example, vinyltoluene and alphamethylstyrene. Such resins may be made from mixtures of such C5 and C9 olefins.

In another embodiment, the resin is or comprises a terpene resin. Such resin may comprise polymers of at least one of limonene, alpha pinene, beta pinene or delta-<NUM>-carene and having a softening point in a range of from <NUM> to <NUM>. Such terpene resins are, for example, available as Sylvatraxx <NUM>™.

In another embodiment, the resin is a terpene-phenol resin. Such terpene-phenol resin preferably comprises a copolymer of phenolic monomer with a terpene such as, for example, limonene and pinene.

In another embodiment, the resin is a resin derived from rosin (rosin based resin) and derivatives thereof. Representative thereof are, for example, gum rosin and wood rosin which are well known rosins. Gum rosin and wood rosin have similar compositions, although the amount of components of the rosins may vary. Such resins may be in the form of esters of rosin acids and polyols such as pentaerythritol or glycol. In one embodiment, the rosin is at least partially hydrogenated.

The silica or precipitated silica reinforcement is preferably characterized by having a BET surface area, as measured using nitrogen gas, in the range of, for example, <NUM> to <NUM>, and more preferably in a range of <NUM> to <NUM> square meters per gram. The BET method of measuring surface area might be described, for example, in the <NPL>, as well as ASTM D3037.

Such silicas may, for example, also be characterized by having a dibutylphthalate (DBP) absorption value, for example, in a range of <NUM> to <NUM>, and more usually <NUM> to <NUM> cc/<NUM>.

Various commercially available precipitated silicas may be used, such as for example silicas from PPG Industries under the Hi-Sil trademark with designations <NUM>, <NUM> abd <NUM>; silicas from Solvay with, for example, designations of Zeosil 1165MP™ and Zeosil 165GR™; silicas from Evonik with, for example, designations VN2 and VN3; and chemically treated (pre-hydrophobated) precipitated silicas such as for example Agilon™ <NUM> from PPG.

Representative examples of rubber reinforcing carbon blacks are, for example, and not intended to be limiting, are referenced in <NPL> with their ASTM designations. As indicated, such rubber reinforcing carbon blacks may have iodine absorptions ranging from, for example, <NUM> to <NUM>/kg and DBP values ranging from <NUM> to <NUM> cc/<NUM>.

Representative of silica coupling agents for the silica are, for example,.

Representative of such bis(<NUM>-trialkoxysilylalkyl) polysulfide is bis(<NUM>-triethoxysilylpropyl) polysulfide.

It is readily understood by those having skill in the art that the vulcanizable rubber composition would be compounded by methods generally known in the rubber compounding art. In addition, said compositions could also contain fatty acid, zinc oxide, waxes, antioxidants, antiozonants and peptizing agents. 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. Representative examples of sulfur donors include elemental sulfur (free sulfur), an amine disulfide, polymeric polysulfide and sulfur olefin adducts. Usually it is desired that the sulfur-vulcanizing agent is elemental sulfur. The sulfur-vulcanizing agent may be used in an amount ranging, for example, from <NUM> to <NUM> phr, with a range of from <NUM> to <NUM> phr being often more desirable. Typical amounts of processing aids for the rubber composition, where used, may comprise, for example, from <NUM> to <NUM> phr. Typical processing aids may be, for example, at least one of various fatty acids (e.g. at least one of palmitic, stearic and oleic acids) or fatty acid salts.

Rubber processing oils may be used as indicated, which are vegetable triglyceride oil. Such oils may be provided as an extending oil present in the elastomers and/or provided as a freely added oil during the compounding of the rubber composition. Suitable vegetable triglyceride oils may include, for example, sunflower, soybean, canola and safflower oils.

Typical amounts of antioxidants may comprise, for example, <NUM> to <NUM> phr. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine and others, such as, for example, those disclosed in The <NPL>. Typical amounts of antiozonants may comprise, for example, <NUM> to <NUM> phr. Typical amounts of fatty acids, if used, which can include stearic acid comprise <NUM> to <NUM> phr. Typical amounts of zinc oxide may comprise, for example, <NUM> to <NUM> phr. Typical amounts of waxes comprise <NUM> to <NUM> phr. Often microcrystalline waxes are used. Typical amounts of peptizers, when used, may be used in amounts of, for example, <NUM> to <NUM> phr. Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.

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. The primary accelerator(s) may be used in total amounts ranging, for example, from <NUM> to <NUM>, sometimes desirably <NUM> to <NUM>, phr. In another embodiment, combinations of a primary and a secondary accelerator might be used with the secondary accelerator being used in smaller amounts, such as, for example, from <NUM> to <NUM> phr, in order to activate and to improve the properties of the vulcanizate. 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, sulfenamides, and xanthates. Often desirably the primary accelerator is a sulfenamide. If a second accelerator is used, the secondary accelerator is often desirably a guanidine such as for example a diphenylguanidine.

The mixing of the vulcanizable 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 curatives, including sulfur-vulcanizing agents, 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) of the preceding non-productive mix stage(s). The rubber composition may be subjected to a thermomechanical mixing step. The thermomechanical mixing step generally comprises a mechanical working in a mixer or extruder for a period of time suitable in order to produce a rubber temperature between <NUM> and <NUM>. The appropriate duration of the thermomechanical working varies as a function of the operating conditions and the volume and nature of the components. For example, the thermomechanical working may be from <NUM> to <NUM> minutes.

The pneumatic tire of the present invention may be, for example, a passenger tire, truck tire, a race tire, aircraft tire, agricultural tire, earthmover tire and off-the-road tire. Usually desirably the tire is a passenger or truck tire. The tire may also be a radial or bias ply tire, with a radial ply tire being usually desired.

Vulcanization of the pneumatic tire containing the tire tread of the present invention is generally carried out at conventional temperatures in a range of, for example, from <NUM> to <NUM>. Often it is desired that the vulcanization is conducted at temperatures ranging from <NUM> to <NUM>. Any of the usual vulcanization processes may be used such as heating in a press or mold, heating with superheated steam or hot air. Such tires 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.

The following examples are presented for the purpose of illustrating the present invention. The parts and percentages are parts by weight, usually parts by weight per <NUM> parts by weight rubber (phr) unless otherwise indicated.

Exemplary rubber compositions were prepared for their evaluation as potential tire treads to promote a combination of wet traction and reduced rubber hysteresis with associated predicted beneficial reduction in tire rolling resistance, while limiting any loss of winter traction at low ambient temperatures. The general formulation for the rubber compositions is illustrated in the following Table <NUM>.

The rubber Samples were prepared by blending the ingredients, other than the sulfur curatives, in at least one sequential non-productive mixing stage (NP) in an internal rubber mixer for <NUM> minutes to a temperature of <NUM>. The resulting mixtures were subsequently individually mixed in a final productive mixing stage (P) in an internal rubber mixer with the sulfur curatives comprised of the sulfur and sulfur cure accelerators for <NUM> minutes to a temperature of <NUM>. The rubber compositions were removed from the internal rubber mixer after each mixing step and cooled to below <NUM> between each individual non-productive mixing stage and before the final productive mixing stage.

In this Example, which is not in accordance with the present invention, exemplary rubber compositions were prepared for evaluation for use as a tire tread to promote a combination of improved wet traction and beneficially reduced rubber hysteresis (with associated predictive beneficially reduced associated tire rolling resistance) with a minimum effect on cold weather (winter) performance.

A Control rubber composition was prepared and identified as Control rubber Sample A as a precipitated silica reinforced rubber composition containing elastomers as a combination of natural cis <NUM>,<NUM>-polyisoprene rubber and synthetic cis <NUM>,<NUM>-polybutadiene rubber.

An Experimental rubber composition was prepared and identified as Experimental rubber Sample B (not in accordance with the present invention) containing the natural cis <NUM>,<NUM>-polyisoprene and high vinyl polybutadiene elastomers.

The Control rubber Sample A and Experimental rubber Sample B compositions are based on the formulation exhibited in Table <NUM> with variable ingredients shown in the following Table <NUM>.

The following Table <NUM> illustrates various physical properties of rubber compositions based upon the basic formulation of Table <NUM> for Control rubber Sample A and Experimental rubber Sample B. Where cured rubber samples are reported, such as for the stress-strain, rebound, tan delta and storage modulus G' values, the rubber samples were cured for <NUM> minutes at a temperature of <NUM>.

To establish the predictive wet traction, a tangent delta (tan delta) test and rebound test were run at <NUM>.

To establish the predictive rolling resistance performance, a tangent delta (tan delta) test and rebound test were run at <NUM>.

To establish the predictive low temperature (winter snow) performance, a stiffness test (storage modulus G') was run at -<NUM> to provide a stiffness value of the compounds (rubber compositions) at lower operating temperatures.

The storage modulus (G') and tan delta physical properties may be determined by a Dynamic Mechanical Analyzer provided by Metravib™ Instruments. For the purpose of characterization of storage modulus (G') property and tan delta property for the cured rubber compositions, a frequency of <NUM> Hertz, strain value of <NUM> percent was used by the Metravib™ instrument.

From Table <NUM> it is observed that the tan delta value at <NUM> of <NUM> for Experimental rubber Sample B containing the high vinyl polybutadiene rubber is significantly higher than the tan delta value of <NUM> for Control rubber Sample A containing the high cis <NUM>,<NUM>-polybutadiene.

It is also observed that the rebound value at <NUM> of <NUM> percent for Experimental rubber Sample B is significantly lower than the rebound value at <NUM> of <NUM> percent for Control rubber Sample A containing the high cis <NUM>,<NUM>-polybutadiene.

It is therefore concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore a low vinyl polybutadiene rubber) with the high vinyl polybutadiene rubber for the petroleum based rubber processing oil containing rubber composition resulted in a beneficially substantial improvement (increased) predictive wet traction for a tire with tread comprised of Experimental rubber Sample B.

From Table <NUM> it is observed that the tan delta value at <NUM> of <NUM> for Experimental rubber Sample B containing the high vinyl polybutadiene rubber is significantly lower than the tan delta value of <NUM> for Control rubber Sample A containing the high cis <NUM>,<NUM>-polybutadiene.

It is also observed that the rebound value at <NUM> of <NUM> percent for Experimental rubber Sample B containing the high vinyl polybutadiene rubber is significantly higher than the rebound value at <NUM> of <NUM> percent for Control rubber Sample A containing the high cis <NUM>,<NUM>-polybutadiene.

It is therefore concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore a low vinyl polybutadiene rubber) with the high vinyl polybutadiene rubber for the petroleum based rubber processing oil containing rubber composition resulted in a beneficially improved (decreased) hysteresis for the rubber composition B with an associated predictive improved (reduction) in tire rolling resistance for a tire with tread of rubber composition comprised of rubber composition B with a predictive improved fuel economy for an associated vehicle.

From Table <NUM> it is observed that the storage modulus (G') value of <NUM> MPa at -<NUM> for Experimental rubber Sample B containing the high vinyl polybutadiene rubber is somewhat higher than the storage modulus (G') of <NUM> MPa for Control rubber Sample A containing the high cis <NUM>,<NUM>-polybutadiene instead of the high vinyl polybutadiene rubber.

It is concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore a low vinyl polybutadiene rubber) of Control rubber Sample A with the high vinyl polybutadiene rubber in Experimental rubber Sample B resulted in a somewhat higher stiffness at -<NUM> and therefore a somewhat reduced predictive cold weather performance for a tire with tread of rubber composition of Sample B.

Experimental rubber Sample B, when compared to Control rubber Sample A, would be predictive of the following tire performance when used as the tread compound: improved wet traction and rolling resistance, with a slight reduction of (therefore substantially maintaining) cold weather performance.

In this Example, exemplary rubber compositions were prepared for evaluation for use as a tire tread to promote a combination of improved wet traction and rolling resistance with a minimum effect on cold weather (winter) performance.

A Control rubber composition was prepared and identified as Control rubber Sample C as a precipitated silica reinforced rubber composition containing elastomers as a combination of natural cis <NUM>,<NUM>-polyisoprene rubber together with cis <NUM>,<NUM>-polybutadiene rubber.

For this example, the rubber compositions contained petroleum rubber processing oil and traction promoting resin.

An Experimental rubber composition was prepared and identified as Experimental rubber Sample D (not in accordance with the present invention) which also contained the natural cis <NUM>,<NUM>-polyisoprene together with high vinyl, high Tg, polybutadiene rubber.

The Control rubber Sample C and Experimental rubber Sample D (not in accordance with the present invention) compositions are based on the formulation exhibited in Table <NUM> with selected ingredients shown in the following Table <NUM>.

The following Table <NUM> illustrates various physical properties of Control rubber Sample C and Experimental rubber Sample D. Where cured rubber samples are reported, such as for the stress-strain, hot rebound and hardness values, the rubber samples were cured for <NUM> minutes at a temperature of <NUM>.

To establish the predictive rolling resistance performance, a tan delta test and rebound test were run at <NUM>.

To establish the predictive low temperature (winter snow) performance, the rubber's stiffness test (storage modulus G') was run at -<NUM> to provide a stiffness value of the compounds (rubber compositions) at lower operating temperatures.

From Table <NUM> it is observed that the tan delta value at <NUM> of <NUM> for Experimental rubber Sample D containing the high vinyl polybutadiene rubber together with the traction promoting resin is significantly higher than the tan delta value of <NUM> for Control rubber Sample C containing the high cis <NUM>,<NUM>-polybutadiene rubber.

It is also observed that the rebound value at <NUM> of eight percent for Experimental rubber Sample D is significantly lower than the rebound value at <NUM> of <NUM> percent for Control rubber Sample C containing the high cis <NUM>,<NUM>-polybutadiene rubber.

It is therefore concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore a low vinyl polybutadiene rubber) with the high vinyl polybutadiene rubber for the traction promoting resin-containing rubber composition resulted in a beneficially substantially improved (increased) predictive wet traction for a tire with a tread comprised of Experimental rubber Sample D.

From Table <NUM> it is observed that the tan delta value at <NUM> of <NUM> for Experimental rubber Sample D containing the high vinyl polybutadiene rubber together with the traction promoting resin is significantly lower than the tan delta value of <NUM> for Control rubber Sample C containing the high cis <NUM>,<NUM>-polybutadiene.

It is also observed that the rebound value at <NUM> of <NUM> percent for Experimental rubber Sample D containing the high vinyl polybutadiene rubber is higher than the rebound value at <NUM> of <NUM> percent for Control rubber Sample C containing the high cis <NUM>,<NUM>-polybutadiene.

It is therefore concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore a low vinyl polybutadiene rubber) with the high vinyl polybutadiene rubber-containing rubber composition, also containing the traction promoting resin, resulted in a beneficially improved (decreased) hysteresis for the rubber composition D and an associated predictive improved (reduction) in tire rolling resistance for a tire with tread of rubber composition comprised of rubber composition D with a predictive improved fuel economy for an associated vehicle.

From Table <NUM> it is observed that the Storage modulus (G') at -<NUM> value of <NUM> MPa for Experimental rubber Sample D containing the high vinyl polybutadiene rubber is significantly higher than the Storage modulus (G') of <NUM> MPa for Control rubber Sample C containing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore a low vinyl polybutadiene rubber).

It is concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber (low vinyl polybutadiene rubber) of traction promotingcontaining Control rubber Sample C with the high vinyl polybutadiene rubber in Experimental rubber Sample D resulted in higher stiffness for the rubber composition and therefore a reduced predictive cold weather performance for a tire with tread of rubber composition of Sample D.

Experimental rubber Sample D, when compared to Control rubber Sample C, would be predictive of the following tire performance when used as the tread compound: improved (increased) wet traction and improved (reduced) rolling resistance, with a reduction of cold weather performance.

In this Example, which is not in accordance with the present invention, exemplary rubber compositions were prepared for evaluation for use as a tire tread to promote a combination of improved wet traction and rolling resistance with a minimum effect on cold weather (winter) performance.

A Control rubber composition was prepared and identified as Control rubber Sample E as a precipitated silica reinforced rubber composition containing elastomers as a combination of natural cis <NUM>,<NUM>-polyisoprene rubber and cis <NUM>,<NUM>-polybutadiene rubber.

An Experimental rubber composition was prepared and identified as Experimental rubber Sample F containing the natural cis <NUM>,<NUM>-polyisoprene rubber together with high vinyl, high Tg, polybutadiene elastomer.

For this Example, the rubber compositions contained sunflower oil instead of petroleum based oil.

The Control rubber Sample E and Experimental rubber Sample F compositions (both not in accordance with the present invention) are based on the formulation exhibited in Table <NUM> with selected ingredients shown in the following Table <NUM>.

The following Table <NUM> illustrates various physical properties of Control rubber Sample E and Experimental rubber Sample F. Where cured rubber samples are reported, such as for the stress-strain, hot rebound, tan delta and storage modulus G' values, the rubber samples were cured for <NUM> minutes at a temperature of <NUM>.

To establish the predictive wet traction, a tan delta (tan delta) test and rebound test were run at <NUM>.

To establish the predictive low temperature (winter snow) performance, the rubber's stiffness test (storage modulus G') was run at -<NUM> to provide a stiffness value of the compounds (rubber compositions) at lower operating (lower ambient) temperatures.

From Table <NUM> it is observed that the tan delta value at <NUM> of <NUM> for Experimental rubber Sample F containing the high vinyl polybutadiene rubber together with the sunflower oil in place of the petroleum based rubber processing oil is higher than the tan delta value of <NUM> for Control rubber Sample E containing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore a low vinyl polybutadiene rubber).

It is also observed that the rebound value at <NUM> of <NUM> percent for Experimental rubber Sample F is lower than the rebound value at <NUM> of <NUM> percent for Control rubber Sample E containing the high cis <NUM>,<NUM>-polybutadiene rubber.

It is therefore is concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore the low vinyl polybutadiene rubber) with the high vinyl polybutadiene rubber for the sunflower oil-containing rubber compositions (instead of petroleum based rubber processing oil) resulted in a beneficially improved (increased) predictive wet traction for a tire with tread comprised of Experimental rubber Sample F.

From Table <NUM> it is observed that the tan delta value at <NUM> of <NUM> for Experimental rubber Sample F containing the high vinyl polybutadiene rubber together with the sunflower oil is significantly lower than the tan delta value of <NUM> for Control rubber Sample E containing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore the low vinyl polybutadiene rubber).

It is also observed that the rebound value at <NUM> of <NUM> percent for Experimental rubber Sample F containing the high vinyl polybutadiene rubber is higher than the rebound value at <NUM> of <NUM> percent for Control rubber Sample E containing the high cis <NUM>,<NUM>-polybutadiene rubber.

It is therefore concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore the low vinyl polybutadiene rubber) with the high vinyl polybutadiene rubber-containing rubber composition, also containing the sunflower oil, resulted in a beneficially improved (reduced) hysteresis for the rubber composition B and an associated predictive improved (reduction) in tire rolling resistance for a tire with tread of rubber composition comprised of rubber composition F with a predictive improved fuel economy for an associated vehicle.

From Table <NUM> it is observed that the storage modulus (G') at -<NUM> value of <NUM> MPa for Experimental rubber Sample F containing the high vinyl polybutadiene rubber is somewhat lower than the storage modulus (G') of <NUM> MPa for Control rubber Sample E containing the high cis <NUM>,<NUM>-polybutadiene rubber (therefore a low vinyl polybutadiene rubber).

It is therefore concluded that it was discovered that replacing the cis <NUM>,<NUM>-polybutadiene rubber with the high vinyl polybutadiene rubber-containing rubber composition, also containing the sunflower oil for Experimental rubber Sample F resulted in a beneficial reduction in stiffness for the rubber composition and therefore a somewhat improved (substantially maintained) predictive cold weather performance for a tire with a tread of rubber composition of Sample F.

Experimental rubber Sample F, when compared to Control rubber Sample E, would be predictive of the following tire performance when used as the tread compound: improved wet traction and rolling resistance, with no loss or a slight improvement of (substantially maintained) cold weather performance.

A Control rubber composition was prepared and identified as Control rubber Sample G as a precipitated silica reinforced rubber composition containing elastomers as a combination of natural cis <NUM>,<NUM>-polyisoprene rubber and cis <NUM>,<NUM>-polybutadiene rubber.

An Experimental rubber composition was prepared and identified as Experimental rubber Sample H containing the natural cis <NUM>,<NUM>-polyisoprene rubber together with high vinyl polybutadiene rubber.

For this Example, the rubber compositions contained a combination of sunflower oil (instead of petroleum based oil) and traction promoting resin.

The Control rubber Sample G and Experimental rubber Sample H compositions are based on the formulation exhibited in Table <NUM> with selected ingredients shown in the following Table <NUM>.

The following Table <NUM> illustrates various physical properties of Control rubber Sample G and Experimental rubber Sample H. Where cured rubber samples are reported, such as for the stress-strain, hot rebound, tan delta and storage modulus G' values, the rubber samples were cured for <NUM> minutes at a temperature of <NUM>.

From Table <NUM> it is observed that the tan delta value at <NUM> of <NUM> for Experimental rubber Sample H containing the high vinyl polybutadiene rubber together with the traction promoting resin and sunflower oil is significantly higher than the tan delta value of <NUM> for Control rubber Sample G containing the high cis <NUM>,<NUM>-polybutadiene rubber.

It is also observed that the rebound value at <NUM> of <NUM> percent for Experimental rubber Sample H is significantly lower than the rebound value at <NUM> of <NUM> percent for Control rubber Sample G containing the high cis <NUM>,<NUM>-polybutadiene rubber.

It is therefore concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber with the high vinyl polybutadiene rubber for the traction promoting resin and sunflower oil-containing rubber composition resulted in an improved predictive wet traction for a tire with tread comprised of Experimental rubber Sample H.

From Table <NUM> it is observed that the tan delta value at <NUM> of <NUM> for Experimental rubber Sample H containing the high vinyl polybutadiene rubber together with the traction promoting resin is significantly lower than the tan delta value of <NUM> for Control rubber Sample G containing the high cis <NUM>,<NUM>-polybutadiene rubber.

It is also observed that the rebound value at <NUM> of <NUM> percent for Experimental rubber Sample H containing the high vinyl polybutadiene rubber is higher than the rebound value at <NUM> of <NUM> percent for Control rubber Sample G containing the high cis <NUM>,<NUM>-polybutadiene rubber.

It is therefore concluded that it was discovered that replacing the high cis <NUM>,<NUM>-polybutadiene rubber with the high vinyl polybutadiene rubber-containing rubber composition, also containing the traction promoting resin and sunflower oil, resulted in a beneficially improved (reduced) hysteresis for the rubber composition H and an associated predictive improved (reduction) in tire rolling resistance for a tire with tread of rubber composition comprised of rubber composition H with a predictive improved fuel economy for an associated vehicle.

From Table <NUM> it is observed that the storage modulus (G') value of <NUM> MPa at -<NUM> for Experimental rubber Sample H containing the high vinyl polybutadiene rubber is higher than the storage modulus (G') of <NUM> MPa for Control rubber Sample G containing the high cis <NUM>,<NUM>-polybutadiene rubber.

Claim 1:
A rubber composition comprising, based on parts by weight per <NUM> parts by weight elastomer (phr):
(A) <NUM> phr of conjugated diene-based elastomers but exclusive of elastomers containing styrene and exclusive of polybutadiene elastomers having a vinyl <NUM>,<NUM>-content in a range of from <NUM> to <NUM> percent, comprising:
(<NUM>) from <NUM> to <NUM> phr of a polybutadiene rubber having a Tg in a range of from -<NUM> to -<NUM>, determined by differential scanning calorimetry measurements at a temperature rising rate of <NUM> per minute according to ASTM D7426, and an isomeric vinyl <NUM>,<NUM>-content in a range of from more than <NUM> percent up to <NUM> percent, and
(<NUM>) from <NUM> to <NUM> phr of <NUM>,<NUM>-polyisoprene rubber having a Tg in a range of from -<NUM> to -<NUM>, determined by differential scanning calorimetry measurements at a temperature rising rate of <NUM> per minute according to ASTM D7426, and an isomeric cis <NUM>,<NUM>- content of at least <NUM> percent;
(B) from <NUM> to <NUM> phr of a filler comprising a combination of silica and carbon black in a ratio of silica to carbon black of at least <NUM>/<NUM>, together with a silica coupling agent having a moiety reactive with hydroxyl groups on the silica and another different moiety interactive with the diene-based elastomers; and
(C) from <NUM> to <NUM> phr of at least one additive comprising:
(<NUM>) a traction promoting resin comprising at least one of styrene/alphamethylstyrene resin, coumarone-indene resin, petroleum hydrocarbon resin, terpene polymer, terpene phenol resin, rosin derived resin and copolymers thereof, said resins having a softening point within a range of from <NUM> to <NUM>, determined in accordance with ASTM E28; and wherein the additive further comprises:
(<NUM>) a vegetable triglyceride rubber processing oil.