Pneumatic tires

Abstract

To provide tire tread rubber compositions for promoting wet, rolling-resistance, wear and low-temperature performance while maintaining wet traction of both of them.SOLUTION: The present invention is directed to a pneumatic tire having a tread comprising a vulcanizable rubber composition comprising, based on 100 pts.wt. of elastomer (phr): (A) about 20 to about 100 phr of a solution polymerized functionalized isoprene-butadiene rubber having a glass transition temperature (Tg) ranging from -100°C to -50°C; (B) 0 to about 40 phr of a polybutadiene; (C) 0 to 20 phr of a process oil; (D) 40 to 80 phr of a resin having Tg greater than 30°C; and (E) 100 to 180 phr of silica.SELECTED DRAWING: None

Description

[Technical field]

[0001] [Background technology]

[0002]

[0001] It is highly desirable for a tire to have good wet skid resistance, low rolling resistance and good wear characteristics. It has been very difficult to improve the wear characteristics of a tire without sacrificing the wet skid resistance and traction characteristics. These properties are highly dependent on the dynamic viscoelastic properties of the rubber used in manufacturing the tire.

[0003]

[0002] To reduce the rolling resistance and improve the treadwear characteristics of tires, high resilience rubbers have traditionally been used in making tire tread rubber compounds. On the other hand, to increase the wet skid resistance of tires, rubbers that suffer from high energy loss have generally been used in tire treads. To balance these two viscoelastically incompatible properties, various types of synthetic and natural rubber blends are commonly used in tire treads.

[0004]

[0003] It may be desirable to have a tire with a tread to enhance traction on snowy surfaces. Various rubber compositions can be proposed for the tire tread. The challenge here is to reduce the cured stiffness of the tread rubber composition, as indicated by having a lower modulus of elasticity E' at -30°C, when the tread is intended for low temperature winter conditions, especially for use in snow driving of vehicles.

[0005]

[0004] It is believed that providing such a tire tread rubber composition presents a significant challenge in terms of enhancing wet, rolling resistance, wear and low temperature (e.g., winter) performance while maintaining both wet traction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 5,652,310 [Patent Document 2] U.S. Patent No. 7,214,731 [Patent Document 3] U.S. Patent No. 4,704,414 [Patent Document 4] U.S. Patent No. 6,123,762 [Patent Document 5] U.S. Patent No. 6,573,324 [Patent Document 6] U.S. Patent No. 6,608,125 [Patent Document 7] US Patent Application Publication No. 2003 / 0130535 [Non-patent literature]

[0007] [Non-Patent Document 1] Standard Methods for Analysis&Testing of Petroleum and Related Products and British Standard 2000 Parts, 2003, 62nd edition, the Institute of Petroleum, United Kingdom [Non-Patent Document 2] Journal of the American Chemical Society, Volume 60, Page 304 (1930) [Non-Patent Document 3] The Vanderbilt Rubber Handbook (1978), pp. 344-346 Summary of the Invention [Means for solving the problem]

[0008]

[0005] The present invention relates to a composition comprising, based on 100 parts by weight (phr) of elastomer: (A) about 20 to about 100 phr of solution polymerized functionalized isoprene-butadiene rubber having a glass transition temperature (Tg) in the range of -100°C to -50°C; (B) Polybutadiene 0 to about 40 phr; (C) process oil 0-20 phr; (D) 40 to 80 phr of a resin having a Tg greater than 30° C.; and (E) Silica 100~180phr The present invention is directed to a pneumatic tire having a tread comprising a vulcanizable rubber composition comprising:

[0009] The present invention is further directed to a method of manufacturing a tire. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Based on 100 parts by weight (phr) of elastomer, (A) about 20 to about 100 phr of solution polymerized functionalized isoprene-butadiene rubber having a glass transition temperature (Tg) in the range of -100°C to -50°C; (B) Polybutadiene 0 to about 40 phr; (C) process oil 0-20 phr; (D) 40 to 80 phr of a resin having a Tg greater than 30° C.; and (E) Silica 100~180phr A pneumatic tire is disclosed having a tread comprising a vulcanizable rubber composition comprising:

[0011] Also disclosed is a method of manufacturing a tire. The rubber composition comprises 20-100 phr, alternatively 70-95 phr, of a functionalized isoprene-butadiene rubber (IBR) having a glass transition temperature (Tg) in the range of -100°C to -50°C. The isoprene-butadiene rubber may be functionalized with various functional groups. In one embodiment, the isoprene-butadiene rubber is functionalized with silyl groups. In one embodiment, the isoprene-butadiene rubber is obtained by copolymerization of isoprene and butadiene, the isoprene-butadiene rubber being characterized by having silyl groups attached to the polymer chain. In one embodiment, the silyl groups may be substituted with one or more alkoxy groups, such as methoxy and ethoxy, alkyl groups, such as methyl, ethyl and propyl, or alkylamino groups, such as diethylamino and dimethylamino, or vinyl groups.

[0012]

[0010] As long as the silyl group is bonded to the isoprene-butadiene rubber chain, it may be bonded to any of the polymerization initiation terminal, polymerization termination terminal, main chain, and side chain of the isoprene-butadiene rubber. However, since the silyl group suppresses the loss of energy at the polymer terminal and improves the hysteresis loss characteristics, it is preferably introduced to the polymerization initiation terminal or polymerization termination terminal.

[0013]

[0011] Furthermore, the content of silyl groups bonded to the polymer chain of the (co)polymer rubber is preferably 0.5 to 200 mmol / kg of isoprene-butadiene rubber, more preferably 1 to 100 mmol / kg of isoprene-butadiene rubber, and particularly preferably 2 to 50 mmol / kg of isoprene-butadiene rubber.

[0014]

[0012] The silyl group may be bonded to any of the polymerization initiation end, polymerization termination end, main chain and side chain of the (co)polymer, so long as it is bonded to the (co)polymer chain. However, the silyl group is preferably introduced to the polymerization initiation end or polymerization termination end, since the energy dissipation can be suppressed from the (co)polymer end, thereby improving the hysteresis loss characteristics.

[0015] The IBR used in the tire tread rubber blend of the present invention may be synthesized by solution polymerization. Such solution polymerization is typically carried out in a hydrocarbon solvent which may be one or more aromatic, paraffinic or cycloparaffinic compounds. These solvents typically contain from 4 to 10 carbon atoms per molecule and become liquid under the polymerization conditions. Some representative examples of suitable organic solvents include pentane, isooctane, cyclohexane, normal hexane, benzene, toluene, xylene, ethylbenzene, and the like, either alone or in admixture.

[0016] In the solution polymerizations used in the synthesis of IBR, there is typically about 5 to about 35 weight percent monomer in the polymerization medium. Such a polymerization medium, of course, is composed of an organic solvent, 1,3-butadiene monomer, and isoprene monomer. In most cases, it is preferred that the polymerization medium contain 10 to 30 weight percent monomer. It is generally more preferred that the polymerization medium contain 20 to 25 weight percent monomer.

[0017] The monomer charge composition used in the synthesis of the IBR used in the tire tread rubber compound of the present invention typically contains from about 20 weight percent to about 50 weight percent isoprene and from about 50 weight percent to about 80 weight percent 1,3-butadiene monomer. Typically, the monomer charge composition preferably contains from about 25 weight percent to about 35 weight percent isoprene and from about 65 weight percent to about 85 weight percent 1,3-butadiene.

[0018] IBR is typically synthesized in a continuous manner. In such a continuous process, the monomers and organolithium initiator are continuously fed to a reaction vessel or series of reaction vessels. The pressure in the reaction vessels is usually sufficient to maintain a substantially liquid phase under the conditions of the polymerization reaction. The reaction medium is generally maintained at a temperature within the range of about 70° C. to about 140° C. during the copolymerization. It is generally preferred to carry out the copolymerization in a series of reaction vessels, increasing the reaction temperature from one reaction vessel to the next as the polymerization proceeds. For example, it is desirable to use a two reactor system, with the temperature in the first reactor being maintained within the range of about 70° C. to 90° C. and the temperature in the second reactor being maintained within the range of about 90° C. to about 100° C.

[0019] IBR may be synthesized using conventional organolithium initiators or may be synthesized using catalyst systems containing neodymium. The organolithium compounds which can be used as initiators are usually organomonolithium compounds. Preferred organolithium compounds can be represented by the formula R--Li, where R represents a hydrocarbyl group containing from 1 to about 20 carbon atoms. Generally, such organolithium compounds contain from 1 to about 10 carbon atoms. Some representative examples of organolithium compounds which can be used include methyllithium, ethyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, n-octyllithium, tert-octyllithium, n-decyllithium, phenyllithium, 1-naphthyllithium, 4-butylphenyllithium, p-tolyllithium, 1-naphthyllithium, 4-butylphenyllithium, p-tolyllithium, 4-phenylbutyllithium, cyclohexyllithium, 4-butylcyclohexyllithium and 4-cyclohexylbutyllithium.

[0020] The amount of organolithium initiator used depends on the molecular weight desired for the IBR being synthesized. The amount of organolithium initiator is selected to result in the production of an IBR having a Mooney ML1+4 viscosity in the range of 55 to 140.

[0021] As a general rule for all anionic polymerizations, the molecular weight (Mooney viscosity) of the polymer produced is inversely proportional to the amount of catalyst used. As a general rule, about 0.01 to about 1 phm (parts by weight per 100 parts of monomer) of organolithium compound is used. In most cases, it is preferred to use about 0.015 to about 0.1 phm of organolithium compound, and most preferred to use about 0.025 phm to 0.07 phm of organolithium compound.

[0022] To prevent gelation, it is important to carry out such polymerizations in the presence of trace amounts of polar modifiers, such as N,N,N',N'-tetramethylethylenediamine (TMEDA). For this reason, it is highly desirable to continuously feed the polar modifier into the reaction vessel used. Ethers and tertiary amines that act as Lewis bases are representative examples of polar modifiers that can be used. Some specific examples of typical polar modifiers include diethyl ether, di-n-propyl ether, diisopropyl ether, di-n-butyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, trimethylamine, triethylamine, N,N,N',N'-tetramethylethylenediamine, N-methylmorpholine, N-ethylmorpholine, N-phenylmorpholine, and the like. Dipiperidinoethane, dipyrrolidinoethane, tetramethylethylenediamine, diethylene glycol, dimethyl ether, TMEDA and tetrahydrofuran represent highly preferred modifiers.

[0023] Optionally, 1,2-butadiene can also be fed continuously to the reaction zone. 1,2-butadiene is typically present in the polymerization medium at a concentration ranging from 10 to about 500 ppm (parts per million). It is generally preferred that 1,2-butadiene be present at a level ranging from about 50 ppm to about 300 ppm. It is generally more preferred that 1,2-butadiene be present at a level ranging from about 100 ppm to about 200 ppm.

[0024] The polar modifier is typically present in a molar ratio of polar modifier to organolithium compound that is within the range of about 0.01:1 to about 0.2:1. The molar ratio of polar modifier to organolithium initiator should not be exceeded by more than about 0.2:1 since the polar modifier acts to increase the glass transition temperature of the resulting IBR.

[0025] The IBR produced is then recovered from the organic solvent. The IBR can be recovered from the organic solvent by standard techniques such as decantation, filtration, centrifugation, etc. In many cases, it is desirable to precipitate the IBR from the organic solvent by adding a lower alcohol containing from 1 to about 4 carbon atoms to the polymer solution. Lower alcohols suitable for precipitating the IBR from the polymer cement include methanol, ethanol, isopropyl alcohol, n-propyl alcohol, and t-butyl alcohol. The use of a lower alcohol to precipitate the IBR from the polymer cement also deactivates the lithium end groups. After the IBR has been recovered from the organic solvent, steam stripping can be used to reduce the level of volatile organic compounds in the rubber.

[0026]

[0025] Solution polymerized IBR has a glass transition temperature in the range of -100°C to -50°C. References to the glass transition temperature or Tg of an elastomer or elastomeric composition, when referred to herein, refer to the glass transition temperature of the respective elastomer or elastomeric composition in the uncured state, or possibly in the case of an elastomeric composition, in the cured state. Tg may be suitably determined by differential scanning calorimetry (DSC), for example as the peak midpoint at a heating rate of 10°C per minute according to ASTM D7426 or equivalent.

[0027] Solution polymerized IBR containing silyl groups substituted with groups such as alkoxy, amino, alkylamino, thioether, hydroxyl, vinyl, etc., may also be used as functionalized IBR. Such functional groups are useful because they can chemically interact with silica and carbon black fillers and with the unsaturation of the polymer. Such functionalized IBR may be prepared using functional initiators, functional monomers, or functional terminators known in the art. Functionalized IBR may contain functional groups attached to one or both ends of the IBR and / or along the length of the polymer chain.

[0028] Suitable functionalized IBRs may be prepared, for example, according to the procedure of US Pat. No. 5,652,310.

[0028] Solution polymerized functionalized isoprene-butadiene rubber has a glass transition temperature in the range of -100°C to -50°C. References to the glass transition temperature or Tg of an elastomer or elastomeric composition, as referred to herein, refer to the glass transition temperature of the respective elastomer or elastomeric composition in the uncured state or possibly in the cured state in the case of the elastomeric composition. Tg may be suitably determined by differential scanning calorimetry (DSC), for example as the peak midpoint at a heating rate of 10°C per minute according to ASTM D7426 or equivalent.

[0029] The rubber composition may further comprise 0 to about 40 phr, alternatively 5 to 30 phr, of polybutadiene. In one embodiment, the polybutadiene has a cis 1,4 content of greater than 95 percent and a Tg in the range of -90 to -110°C. In another embodiment, the polybutadiene has a cis 1,4 content in the range of 20 to 50 weight percent, or a vinyl content in the range of 5 to 20 weight percent. Suitable butadiene rubbers may be prepared, for example, by organic solution polymerization of 1,3-butadiene. The BR may be conveniently characterized, for example, as having a cis 1,4 content of at least 90 percent, and a glass transition temperature Tg in the range of about -90°C to about -110°C. Suitable polybutadiene rubbers are commercially available, such as Budene® 1223 from Goodyear, which has a Tg of -108°C and a cis 1,4 content of 96%.

[0030] The rubber composition may contain 0 to 20 phr of processing oil, alternatively 4 to 15 phr. The processing oil may be included in the rubber composition as an extender oil, typically used to extend the elastomer. The processing oil may also be included in the rubber composition by direct addition of oil during rubber compounding. The processing oil used may be included in both the extender oil present in the elastomer and the processing oil added during compounding. Suitable processing oils include various oils known in the art, including aromatic, paraffinic, naphthenic, and low PCA oils, such as MES, TDAE, and heavy naphthenic oils, vegetable oils, such as sunflower, soybean, and safflower oils, and monoesters of fatty acids selected from the group consisting of alkyl oleates, alkyl stearates, alkyl linoleates, and alkyl palmitates.

[0031] Suitable low PCA oils include those having a polycyclic aromatic content of less than 3 weight percent as determined by IP 346. The procedure for the IP 346 method can be found in Standard Methods for Analysis & Testing of Petroleum and Related Products and British Standard 2000 Parts, 2003, 62nd Edition, published by the Institute of Petroleum, United Kingdom.

[0032] Suitable TDAE oils are available as Tudalen SX500 from Klaus Dahleke KG, VivaTec 400 and VivaTec 500 from H&R Group, Enerthene 1849 from BP, and Extensoil 1996 from Repsol. The oils may be available alone as oils or together with elastomers in the form of extended elastomers.

[0033] Suitable vegetable oils include, for example, soybean oil, sunflower oil and canola oil, which are in the form of esters containing a certain degree of unsaturation.

[0034] The rubber composition further comprises 40 to 80 phr, alternatively 50 to 70 phr, of a resin having a Tg greater than 30°C.

[0034]

[0035] In one embodiment, the resin may be a hydrocarbon resin selected from a C5 / C9 resin, a dicyclopentadiene (DCPD) / C9 resin, and a terpene resin.

[0036] In one embodiment, the resin is a C5 / C9 hydrocarbon resin, including C5 and C9 hydrocarbon fractions, having a glass transition temperature greater than 30° C. A suitable measurement of Tg for a resin is DSC by ASTM D6604 or equivalent. Hydrocarbon resins have a softening point greater than about 80° C., as determined by ASTM E28, sometimes referred to as the Ring and Ball softening point.

[0035]

[0037] Suitable C5 / C9 resins may contain both aromatic and non-aromatic components. The difference between C5 / C9 resins is mainly due to the olefins in the feedstock from which the hydrocarbon components are derived. C5 / C9 resins may contain "aliphatic" hydrocarbon components with the hydrocarbon chain formed from the C4-C6 fraction containing variable amounts of piperylene, isoprene, monoolefins, and non-polymerizable paraffinic compounds. Such C5 / C9 resins are based on pentene, butane, isoprene, piperylene, and contain small amounts of cyclopentadiene or dicyclopentadiene. C5 / C9 resins may also contain "aromatic" hydrocarbon structures with the polymer chain formed from aromatic units such as styrene, xylene, alpha methyl styrene, vinyl toluene, and indene.

[0036]

[0038] According to the present invention, the C5 / C9 resins used in the rubber compounding contain olefins such as piperylene, isoprene, amylene, and cyclic components. The C5 / C9 resins may also contain aromatic olefins such as styrenic and indene components.

[0037]

[0039] Piperylene is generally a distillate or synthetic mixture of C5 diolefins, including but not limited to cis-1,3-pentadiene, trans-1,3-pentadiene, and mixed 1,3-pentadienes. Generally, piperylene does not include branched C5 diolefins such as isoprene. In one embodiment, the C5 / C9 resin has 40-90% (by weight), or 50-90%, more preferably 60-90% piperylene. In a particularly preferred embodiment, the C5 / C9 resin has 70-90% piperylene.

[0038]

[0040] In one embodiment, the C5 / C9 resin is substantially free of isoprene. In another embodiment, the C5 / C9 resin contains up to 15% isoprene, or less than 10% isoprene. In yet another embodiment, the C5 / C9 resin contains less than 5% isoprene.

[0039]

[0041] In one embodiment, the C5 / C9 resin is substantially free of amylene. In another embodiment, the C5 / C9 resin contains up to 40% amylene, or less than 30% amylene, or less than 25% amylene. In yet another embodiment, the C5 / C9 resin contains up to 10% amylene.

[0040]

[0042] Cyclic moieties are generally distillates or synthetic mixtures of C5 and C6 cyclic olefins, diolefins, and dimers therefrom. Cyclic moieties include, but are not limited to, cyclopentene, cyclopentadiene, dicyclopentadiene, cyclohexene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene. A preferred cyclic moiety is cyclopentadiene. Dicyclopentadiene may be in either the endo or exo form. Cyclic moieties may be substituted or unsubstituted. Preferred substituted cyclic moieties include cyclopentadiene and dicyclopentadiene substituted with C1-C40 linear, branched, or cyclic alkyl groups, preferably one or more methyl groups. In one embodiment, the C5 / C9 resin may contain up to 60% cyclic moieties or up to 50% cyclic moieties. Typical minimum limits include at least about 0.1% or at least about 0.5% cyclic moieties, or about 1.0% cyclic moieties. In at least one embodiment, the C5 / C9 resin may contain up to 20% cyclics, or more preferably up to 30% cyclics. In particularly preferred embodiments, the C5 / C9 resin contains from about 1.0 to about 15% cyclics, or from about 5 to about 15% cyclics.

[0041]

[0043] Preferred aromatics that may be present in the C5 / C9 resin include one or more of styrene, indene, derivatives of styrene, and derivatives of indene. Particularly preferred aromatic olefins include styrene, alpha-methylstyrene, beta-methylstyrene, indene, and methylindene, and vinyltoluene. The aromatic olefins are generally present in the C5 / C9 resin at 5-45%, or more preferably 5-30%. In a particularly preferred embodiment, the C5 / C9 resin contains 10-20% aromatic olefins.

[0042]

[0044] Styrenic components include styrene, derivatives of styrene, and substituted styrenes. Generally, styrenic components do not contain fused rings, such as indenes. In one embodiment, the C5 / C9 resin contains up to 60% styrenic components or up to 50% styrenic components. In one embodiment, the C5 / C9 resin contains 5-30% styrenic components or 5-20% styrenic components. In a preferred embodiment, the C5 / C9 resin contains 10-15% styrenic components.

[0043]

[0045] The C5 / C9 resin may contain less than 15% indenic components, or less than 10% indenic components. The indenic components include indene and derivatives of indene. In one embodiment, the C5 / C9 resin contains less than 5% indenic components. In another embodiment, the C5 / C9 resin is substantially free of indenic components.

[0044]

[0046] Preferred C5 / C9 resins have a melt viscosity of 300-800 centipoise (cP) at 160° C., or more preferably, 350-650 cP at 160° C. In particularly preferred embodiments, the melt viscosity of the C5 / C9 resin is 375-615 cP at 160° C. or 475-600 cP at 160° C. Melt viscosity can be measured with a Brookfield viscometer using an ASTM D6267 “J” type spindle.

[0045]

[0047] Typically, the C5 / C9 resin has a weight average molecular weight (Mw) of greater than about 600 g / mol, or greater than about 1000 g / mol. In at least one embodiment, the C5 / C9 resin has a weight average molecular weight (Mw) of 1650-1950 g / mol, or 1700-1900 g / mol. Preferably, the C5 / C9 resin has a weight average molecular weight of 1725-1890 g / mol. The C5 / C9 resin may have a number average molecular weight (Mn) of 450-700 g / mol, or 500-675 g / mol, or more preferably 520-650 g / mol. The C5 / C9 resin may have a z-average molecular weight (Mz) of 5850-8150 g / mol, or more preferably 6000-8000 g / mol. Mw, Mn, and Mz can be measured by gel permeation chromatography (GPC).

[0046]

[0048] In one embodiment, the C5 / C9 resin has a polydispersity index ("PDI", PDI=Mw / Mn) of less than or equal to 4. In a particularly preferred embodiment, the C5 / C9 resin has a PDI of 2.6 to 3.1.

[0047]

[0049] Preferred C5 / C9 resins have a glass transition temperature (Tg) of about -30°C to about 100°C, or about 0°C to 80°C, or about 40-60°C, or 45-55°C, or more preferably 48-53 degrees Celsius. Differential scanning calorimetry (DSC) may be used to measure the Tg of the C5 / C9 resins.

[0048]

[0050] In another embodiment, the C5 / C9 resin may be hydrogenated.

[0051] In one embodiment, the C5 / C9 resin contains 50-90% (by weight) piperylene, 0-5% isoprene, 10-30% amylene, 0-5% cyclic, 0-10% styrenic, and 0-10% indenic.

[0049]

[0052] In one embodiment, the C5 / C9 resin contains 50-90% (by weight) piperylene, 0-5% isoprene, 10-30% amylene, 2-5% cyclic, 4-10% styrenic, and 4-10% indenic.

[0050]

[0053] In one embodiment, C5 / C9 contains about 60% piperylene (by weight), about 22% amylene, about 3% cyclics, about 6% styrene, and about 6% indene, and further has a melt viscosity of 436 cP at 160° C.; Mn of 855 g / mol; Mw of 1595 g / mol; Mz of 3713 g / mol; PDI of 1.9; and Tg of 47° C.

[0051]

[0054] The C5 / C9 or DCPD / C9 resin may be further characterized by its aromatic hydrogen content as measured by 1H NMR. In one embodiment, the C5 / C9 resin has an aromatic hydrogen content of less than 25 mole percent. In one embodiment, the C5 / C9 resin has an aromatic hydrogen content between 3 and 15 mole percent.

[0052]

[0055] Examples of useful hydrocarbon polymer additives are the Oppera series of polymer additives available from ExxonMobil Chemical Company, including, but not limited to, Oppera 373.

[0053]

[0056] In one embodiment, the resin is a DCPD / C9 resin. A suitable DCPD / C9 resin is a hydrogenated DCPD / C9 resin available as Oppera 383 having an aromatic hydrogen content of about 10 mole percent.

[0054]

[0057] In one embodiment, the resin is a terpene resin. In one embodiment, the resin may be a terpene resin composed of at least one polymer of limonene, alpha pinene, and beta pinene.

[0055]

[0058] The phrase "rubber or elastomer containing olefinic unsaturation" is intended to include both natural rubber and its various raw and reclaim forms as well as various synthetic rubbers. In describing this invention, the terms "rubber" and "elastomer" may be used interchangeably unless otherwise specified. The terms "rubber composition," "compounded rubber," and "rubber compound" are used interchangeably to refer to rubber that has been blended or mixed with various raw materials and ingredients, such terms being well known to those skilled in the rubber mixing or rubber compounding art.

[0056]

[0059] The vulcanizable rubber composition may contain from about 100 to about 180 phr of silica, alternatively from 120 to 150 phr.

[0060] Commonly used siliceous pigments which may be used in the rubber compounds include conventional pyrogenic and precipitated siliceous pigments (silica), with precipitated silicas being preferred. The conventional siliceous pigments preferably used in the present invention are precipitated silicas such as those obtained by the acidification of a soluble silicate, e.g., sodium silicate.

[0057]

[0061] Such conventional silicas may be characterized as having a BET surface area, as measured, for example, using nitrogen gas, preferably in the range of about 40 to about 600 square meters per gram, more usually in the range of about 50 to about 300 square meters per gram. The BET method for measuring surface area is described in Journal of the American Chemical Society, Vol. 60, p. 304 (1930).

[0058]

[0062] Conventional silicas may also be characterized as having a dibutyl phthalate (DBP) absorption value, typically in the range of about 100 to about 400, more usually about 150 to about 300.

[0063] Conventional silica can be expected to have an average ultimate particle size in the range of 0.01 to 0.05 microns as determined, for example, by electron microscopy, although the silica particles may be smaller or possibly larger in size.

[0059]

[0064] Various commercially available silicas may be used, such as, by way of example only and not limitation, those commercially available under the Hi-Sil trademark from PPG Industries having the designations 210, 243, 315, etc.; silicas available from Rhodia having the designations, e.g., Z1165MP and Z165GR, and silicas available from Degussa AG having the designations, e.g., VN2 and VN3.

[0060]

[0065] Prehydrophobized precipitated silica may be used. Prehydrophobized means that the silica is pretreated, i.e., prior to its addition to the rubber composition, the prehydrophobized precipitated silica is hydrophobized by treatment with at least one silane. Suitable silanes include, but are not limited to, alkylsilanes, alkoxysilanes, organoalkoxysilyl polysulfides, and organomercaptoalkoxysilanes. Alternatively, instead of reacting the precipitated silica in situ with the silica coupling agent within the rubber, the precipitated silica may be pretreated with a silica coupling agent, for example, composed of an alkoxyorganomercaptosilane or a combination of an alkoxysilane and an alkoxyorganomercaptosilane, before mixing the rubber with the pretreated silica. See, for example, U.S. Pat. No. 7,214,731. For various pretreated precipitated silicas, see, for example, U.S. Pat. Nos. 4,704,414, 6,123,762, and 6,573,324. Suitable pretreated or pre-hydrophobized silicas are commercially available, for example as Agilon 400 from PPG.

[0061]

[0066] The vulcanizable rubber composition may contain from about 1 to about 20 phr of carbon black.

[0067] Commonly used carbon blacks can be used as conventional fillers. Representative examples of such carbon blacks include N110, N121, N134, N220, N231, N234, N242, N293, N299, S315, N326, N330, M332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990 and N991. These carbon blacks have iodine absorptions ranging from 9 to 145 g / kg and iodine absorptions ranging from 34 to 150 cm. 3 / 100g range of DBP numbers.

[0062]

[0068] Preferably, the rubber composition used in the tire component may further comprise a conventional sulfur-containing organosilicon compound. Examples of suitable sulfur-containing organosilicon compounds include those represented by the formula: Z-Alk-S n -Alk-Z V [In the formula, Z is

[0063] [ka]

[0064] wherein R 6 is an alkyl group having 1 to 4 carbon atoms, cyclohexyl or phenyl; R 7 is an alkoxy of 1 to 8 carbon atoms or a cycloalkoxy of 5 to 8 carbon atoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms, and n is an integer from 2 to 8.

[0065]

[0069] Specific examples of sulfur-containing organosilicon compounds which may be used in accordance with the present invention include the following: 3,3'-bis(trimethoxysilylpropyl) disulfide, 3,3'-bis(triethoxysilylpropyl) disulfide, 3,3'-bis(triethoxysilylpropyl) tetrasulfide, 3,3'-bis(triethoxysilylpropyl) octasulfide, 3,3'-bis(trimethoxysilylpropyl) tetrasulfide, 2,2'-bis(triethoxysilylethyl) tetrasulfide. , 3,3'-bis(trimethoxysilylpropyl) trisulfide, 3,3'-bis(triethoxysilylpropyl) trisulfide, 3,3'-bis(tributoxysilylpropyl) disulfide, 3,3'-bis(trimethoxysilylpropyl) hexasulfide, 3,3'-bis(trimethoxysilylpropyl) octasulfide, 3,3'-bis(trioctaoxysilylpropyl) tetrasulfide, 3,3'-bis(trihexaoxysilylpropyl) disulfide, 3,3' -Bis(tri-2''-ethylhexoxysilylpropyl) trisulfide, 3,3'-bis(triisooctaoxysilylpropyl) tetrasulfide, 3,3'-bis(tri-t-butoxysilylpropyl) disulfide, 2,2'-bis(methoxydiethoxysilylethyl) tetrasulfide, 2,2'-bis(tripropoxysilylethyl) pentasulfide, 3,3'-bis(tricyclonexoxysilylpropyl) tetrasulfide xysilylpropyl)tetrasulfide), 3,3'-bis(tricyclopentoxysilylpropyl) trisulfide, 2,2'-bis(tri-2''-methylcyclohexoxysilylethyl) tetrasulfide, bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxyethoxypropoxysilyl 3'-diethoxybutoxy-silylpropyl tetrasulfide, 2,2'-bis(dimethylmethoxysilylethyl) disulfide, 2,2'-bis(dimethylsec.butoxysilylethyl) trisulfide, 3,3'-bis(methylbutylethoxysilylpropyl) tetrasulfide, 3,3'-bis(di-t-butylmethoxysilylpropyl) tetrasulfide, 2,2'-bis(phenylmethylmethoxysilylethyl) trisulfide, 3,3'-bis(diphenylisopropoxysilylpropyl) tetrasulfide, 3,3'-bis(diphenylcyclohexoxysilylpropyl) disulfide, 3,3'-bis(dimethylethyl mer captosilylpropyl) tetrasulfide, 2,2'-bis(methyldimethoxysilylethyl) trisulfide, 2,2'-bis(methylethoxypropoxysilylethyl) tetrasulfide, 3,3'-bis(diethylmethoxysilylpropyl) tetrasulfide, 3,3'-bis(ethyldi-sec.butoxysilylpropyl) disulfide, 3,3'-bis(propyldiethoxysilylpropyl) disulfide, 3,3'-bis(butyldimethoxysilylpropyl) trisulfide Sulfide, 3,3'-bis(phenyldimethoxysilylpropyl)tetrasulfide, 3-phenylethoxybutoxysilyl 3'-trimethoxysilylpropyl tetrasulfide, 4,4'-bis(trimethoxysilylbutyl)tetrasulfide, 6,6'-bis(triethoxysilylhexyl)tetrasulfide, 12,12'-bis(triisopropoxysilyldodecyl)disulfide, 18,18'-bis(trimethoxysilyloctadecyl)tetrasulfide, 18 ,18'-Bis(tripropoxysilyloctadecenyl)tetrasulfide, 4,4'-Bis(trimethoxysilyl-buten-2-yl)tetrasulfide, 4,4'-Bis(trimethoxysilylcyclohexylene)tetrasulfide, 5,5'-Bis(dimethoxymethylsilylpentyl)trisulfide, 3,3'-Bis(trimethoxysilyl-2-methylpropyl)tetrasulfide, 3,3'-Bis(dimethoxyphenylsilyl-2-methylpropyl)disulfide.

[0066]

[0070] The preferred sulfur-containing organosilicon compounds are 3,3'-bis(trimethoxy or triethoxysilylpropyl)sulfides. The most preferred compounds are 3,3'-bis(triethoxysilylpropyl)disulfide and 3,3'-bis(triethoxysilylpropyl)tetrasulfide. Thus, for formula V, preferably Z is:

[0067] [ka]

[0068] is [In the formula, R 7 is an alkoxy of 2 to 4 carbon atoms, with 2 carbon atoms being particularly preferred; alk is a divalent hydrocarbon of 2 to 4 carbon atoms, with 3 carbon atoms being particularly preferred; and n is an integer of 2 to 5, with 2 and 4 being particularly preferred.

[0069]

[0071] In another embodiment, suitable sulfur-containing organosilicon compounds include those disclosed in U.S. Patent No. 6,608,125. In one embodiment, the sulfur-containing organosilicon compound includes 3-(octanoylthio)-1-propyltriethoxysilane, CH3(CH2)6C(=O)-S-CH2CH2CH2Si(OCH2CH3)3, available commercially as NXT™ from Momentive Performance Materials.

[0070]

[0072] In one embodiment, the sulfur-containing organosilicon compound comprises the reaction product of a hydrocarbon diol (e.g., 2-methyl-1,3-propanediol) with S-[3-(triethoxysilyl)propyl]thiooctanoate. In one embodiment, the sulfur-containing organosilicon compound is NXT-Z™ from Momentive Performance Materials.

[0071]

[0073] In another embodiment, suitable sulfur-containing organosilicon compounds include those disclosed in U.S. Patent Application Publication No. 2003 / 0130535. In one embodiment, the sulfur-containing organosilicon compound is Si-363 from Degussa.

[0072]

[0074] The amount of sulfur-containing organosilicon compound in a rubber composition may vary depending on the level of other additives used. Generally speaking, the amount of the compound of formula I ranges from 0.5 to 20 phr. Preferably, the amount ranges from 1 to 10 phr.

[0073]

[0075] It will be readily understood by those skilled in the art that the rubber composition can be compounded by methods generally known in the rubber compounding art, such as, for example, mixing the various components of the sulfur vulcanizable rubber with various commonly used additive materials, such as sulfur donors, curing aids, e.g., activators and retarders, and processing additives, fillers, pigments, fatty acids, zinc oxide, waxes, antioxidants, antiozonants and peptizers. Depending on the intended use of the sulfur vulcanizable and sulfur vulcanized materials (rubbers), as known to those skilled in the art, the additives listed above are selected and generally used in conventional amounts. Representative examples of sulfur donors include elemental sulfur (free sulfur), amine disulfides, polymeric polysulfides and sulfur olefin adducts. Preferably, the sulfur vulcanizing agent is elemental sulfur. The sulfur vulcanizing agent ranges from 0.5 to 8 phr, with a range of 1 to 6 phr being preferred. Typical amounts of antioxidants include from about 1 to about 5 phr. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine and others such as those disclosed in, for example, The Vanderbilt Rubber Handbook (1978), pages 344-346. Typical amounts of antiozonants include about 1-5 phr. Typical amounts of fatty acids, which, if used, may include stearic acid, include about 0.5 to about 5 phr. Typical amounts of zinc oxide include about 2 to about 5 phr. Typical amounts of wax include 1-5 phr. Microcrystalline wax is often used. Typical amounts of peptizers include 0.1-1 phr. Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.

[0074]

[0076] 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., a primary accelerator. The primary accelerator(s) may be used in a total amount ranging from 0.5 phr to 4 phr, preferably from about 0.8 to about 2.0 phr. In another embodiment, a combination of primary and secondary accelerators may be used, with the secondary accelerator being used in a lower amount, such as from about 0.05 to about 3 phr, to activate and improve the properties of the vulcanizate. These accelerator combinations can be expected to produce a synergistic effect on the final properties, which are somewhat better than those produced by the use of either accelerator alone. In addition, delayed action accelerators may be used that are not affected by normal processing temperatures but produce a satisfactory cure at normal vulcanization temperatures. Vulcanization retarders may 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.

[0075]

[0077] Mixing of the rubber composition can be accomplished by methods known to those skilled in the rubber mixing art. For example, the raw materials are typically mixed in at least two stages, namely, at least one non-productive stage followed by a productive mix stage. The final curatives, including sulfur vulcanizing agents, are typically mixed in a final stage, conventionally referred to as the "productive" mix stage, where mixing is typically performed at a temperature or final temperature that is lower than the mixing temperature(s) of the preceding non-productive mix stage(s). The terms "non-productive" and "productive" mix stages are well known to those skilled in the rubber mixing art. The rubber composition may be subjected to a thermodynamic mixing step. The thermodynamic mixing step generally involves mechanical operation in a mixer or extruder for a period of time suitable to produce a rubber temperature between 140°C and 190°C. The suitable duration of the thermodynamic operation varies as a function of the operating conditions and the amounts and nature of the components. For example, the thermodynamic operation may be from 1 to 20 minutes.

[0076]

[0078] The rubber composition may be incorporated into the tread of a tire.

[0079] The pneumatic tire of the present invention may be a race tire, passenger tire, aircraft tire, farm tire, earthmover, off-road, truck tire, etc. Preferably, the tire is a passenger or truck tire. The tire may also be radial or bias, although radial is preferred.

[0077]

[0080] Vulcanization of the pneumatic tires of the present invention is generally carried out at conventional temperatures ranging from 100° C. to 200° C. Preferably, vulcanization is carried out at a temperature ranging from 110° C. to 180° C. Any of the usual vulcanization methods may be used, such as heating in a press or mold, heating with superheated steam or hot air, etc. Such tires can be built, shaped, molded and cured by a variety of methods known and readily apparent to those skilled in the art.

[0078]

[0081] The following examples are presented for the purpose of illustrating, but not limiting, the present invention. All parts are by weight unless otherwise specified. EXAMPLES

[0079]

[0082] This example illustrates the advantages of the rubber compositions according to the present invention. Rubber compounds were mixed according to the recipes shown in Table 1, with the amounts given in phr. The compounds were cured and tested for physical properties as shown in Table 2. The rubber compositions of the present invention comprised of functionalized IBR demonstrate simultaneous improvements in the expected wetting, RR and wear properties of the tread compounds.

[0080] [Table 1]

[0081] [Table 2]

[0082]

[0083] While certain representative embodiments and details have been shown for the purpose of explaining the subject invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the subject invention.

[0083] [Embodiment of the invention] 1. Based on 100 parts by weight (phr) of elastomer, (A) about 20 to about 100 phr of solution polymerized functionalized isoprene-butadiene rubber having a glass transition temperature (Tg) in the range of -100°C to -50°C; (B) Polybutadiene 0 to about 40 phr; (C) process oil 0-20 phr; (D) 40 to 80 phr of a resin having a Tg greater than 30° C.; and (E) Silica 100~180phr A pneumatic tire having a tread comprising a vulcanizable rubber composition comprising: 2. The pneumatic tire of 1, wherein the functionalized isoprene-butadiene rubber is functionalized with a silyl group. 3. The pneumatic tire of 1, wherein the functionalized isoprene-butadiene rubber is functionalized with a silyl group substituted with at least one member of the group consisting of an alkoxy group, an alkyl group, and an alkylamino group. 4. The pneumatic tire of claim 1, wherein the functionalized isoprene-butadiene rubber is functionalized with a silyl group substituted with an alkoxy group selected from the group consisting of methoxy and ethoxy. 5. The pneumatic tire of claim 1, wherein the functionalized isoprene-butadiene rubber is functionalized with a silyl group substituted with an alkyl group selected from the group consisting of methyl, ethyl, and propyl. 6. The pneumatic tire of claim 1, wherein the functionalized isoprene-butadiene rubber is functionalized with a silyl group substituted with an alkylamino group selected from the group consisting of diethylamino and dimethylamino. 7. The pneumatic tire of claim 1, wherein the resin is a C5 / C9 resin containing 50-90% (by weight) piperylene, 0-5% isoprene, 10-30% amylene, 0-5% cyclics, 0-10% styrenes, and 0-10% indenes. 8. The pneumatic tire of claim 1, wherein the resin is a C5 / C9 resin containing 50-90% (by weight) piperylene, 0-5% isoprene, 10-30% amylene, 2-5% cyclics, 4-10% styrenes, and 4-10% indenes. 9. The pneumatic tire of 1, wherein the resin is a C5 / C9 resin and has an aromatic hydrogen content of less than 25 mole percent. 10. The pneumatic tire of 1, wherein the resin is a C5 / C9 resin and has an aromatic hydrogen content between 3 and 15 mole percent. 11. The pneumatic tire of 1, wherein the solution polymerized isoprene-butadiene rubber is functionalized with alkoxysilane groups and optionally amino groups. 12. The pneumatic tire of claim 1, wherein the oil is selected from the group consisting of aromatic, paraffinic, naphthenic, MES, TDAE, heavy naphthenic oils and vegetable oils. 13. The pneumatic tire of 1, wherein the amount of functionalized isoprene-butadiene rubber is in the range of 70 to 95 phr. 14. The pneumatic tire according to 1, wherein the amount of polybutadiene is in the range of 5 to 30 phr. 15. A pneumatic tire as described in 1, wherein the amount of oil is in the range of 4 to 15 phr. 16. A pneumatic tire as described in 1, wherein the amount of resin is in the range of 50 to 70 phr. 17. The pneumatic tire of 1, wherein the polybutadiene has a cis 1,4 content of greater than 95 percent and a Tg in the range of -80 to -110°C.

Claims

1. (A) an elastomer consisting of 20 to 100 parts by weight of a solution polymerized functionalized isoprene-butadiene rubber having a glass transition temperature (Tg) in the range of -100°C to -50°C, and (B) 0 to 40 parts by weight of polybutadiene; and based on 100 parts by weight (phr) of said elastomer, (C) process oil 0 to 20 phr; (D) 40 to 80 phr of a hydrocarbon resin having a Tg greater than 30° C. and selected from C5 / C9 resins, dicyclopentadiene (DCPD) / C9 resins, and terpene resins; and (E) Silica 100 to 180 phr wherein said solution polymerization functionalized isoprene-butadiene rubber is functionalized with silyl groups or said solution polymerization functionalized isoprene-butadiene rubber is functionalized with alkoxylsilane groups and optionally amino groups. A pneumatic tire comprising a tread including:

2. 2. The pneumatic tire of claim 1, wherein the solution polymerized functionalized isoprene-butadiene rubber is functionalized with a silyl group substituted with an alkoxy group selected from the group consisting of methoxy and ethoxy.

3. 2. The pneumatic tire of claim 1, wherein the solution polymerized functionalized isoprene-butadiene rubber is functionalized with a silyl group substituted with an alkyl group selected from the group consisting of methyl, ethyl, and propyl.

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