MXPA97002890A - Rim surface containing rubber of 3,4-poliisopr - Google Patents

Abstract

The present invention relates: This invention discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition comprising on the basis of 100 parts by weight rubber (1) of about 5 parts to about 50 parts of 3,4-polyisoprene rubber, wherein the 3,4-polyisoprene rubber has (a) a 3,4-isomer content of 75 percent to 95 percent, (b) a content of 1,2-isomer from 5 percent to 25 percent, (c) a glass transition temperature from 0øC to 25øC and (d) a number-average molecular weight that falls within the range of 3,000 to 180,000 y ( 2) from about 50 parts to about 95 parts of a rubbery polymer which is co-curable with the 3,4-polyisoprene rubber. The present invention further discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition consisting of 100 parts by weight rubber, (1) of about 20 parts. to about 60 parts of natural rubber, (2) from about 5 parts to about 30 parts of high cis-1,4-polybutadiene rubber, (3) from about 10 parts to about 50 parts of styrene-butadiene rubber and (4) from about 5 parts to about 30 parts of 3,4-polyisoprene rubber, wherein the 3,4-polyisoprene rubber has (a) a 3,4-isomer content of 75 percent to 95 percent. percent, (b) a 1,2-isomer content of 5 percent to 25 percent, (c) a glass transition temperature of 0øa to 25øC, and (d) a number-average molecular weight that falls within the scale from 30,000 to 180,0

Description

"RIM SURFACE CONTAINING RUBBER OF 3,4-POLYISOPRENE" BACKGROUND OF THE INVENTION It is highly desirable that the tires exhibit good traction characteristics on both dry and wet surfaces. However, it has traditionally been very difficult to improve the traction characteristics of the rim, without compromising its rolling resistance and tread surface wear. Low rolling resistance is important because good fuel economy is virtually always an important consideration. Good wear of the tread surface is also an important consideration because it is usually the most important factor that determines the duration of the rim. The traction, wear of the tread surface and rolling resistance of a rim depend to a considerable degree on the dynamic viscoelastic properties of the elastomers used to produce the tread surface of the rim. In order to reduce the rolling resistance of a rim, rubbers having a high rebound have traditionally been used to manufacture the tread surface of the rim. On the other hand, in order to increase the resistance to wet skidding of a tire, rubbers that experience a great loss of energy have generally been used on the running surfaces of the rim. In order to balance these two viscoelastically consistent properties, mixtures of different types of synthetic and natural rubber are usually used on the running surfaces of the rim. For example, various mixtures of styrene-butadiene rubber and polybutadiene rubber are commonly used as a rubber material for automobile rim running surfaces. However, these mixtures are not totally satisfactory for all purposes. In some cases, 3-polyisoprene can be used in the tire tread surface compounds to improve the performance characteristics of the rim, such as traction. For example, U.S. Patent No. 5,104,941 discloses a method for improving the wet skid resistance of a rubber mixture for a tire tread surface, which comprises adding from 5 to 35 parts by weight of a 3.4. polyisoprene a of 95 to 65 parts by weight of a sulfur vulcanizable elastomer containing filler or filler materials, auxiliary oils, and conventional vulcanizing agents, wherein 3,4-polyisoprene is at least partially incompatible with the vulcanizable elastomer with sulfur and has (a) a 3,4-polyisoprene content of 55 percent to 75 percent, as determined by nuclear magnetic resonance spectroscopy, (b) a vitreous state transition temperature of 0 ° C at -25 ° C, which is determined by differential scanning calorimetry at a heating rate of 10 ° C per minute, (c) a number-average molecular weight Mn that is determined by gel permeation of 220,000 or higher, and (d) an inhomogeneity U of less than 1.8, the inhomogeneity being defined by the equation U = Mw / Mn-1, where Mw and Mn is determined by gel permeation chromatography. U.S. Patent No. 5,104,941 further discloses a method for improving wet skid resistance of a rubber blend, comprising adding from 5 to 35 parts by weight of 3,4-polyisoprene to 95 to 65 parts by weight of a vulcanizable sulfur elastomer, which further contains fillers or fillers, auxiliary oils or conventional vulcanizing agents, wherein the 3,4-polyisoprene is at least partially incompatible with the elastomer vulcanizable with sulfur and has (a) a content of 3, 4-polyisoprene from 55 percent to 75 percent, which is determined by nuclear magnetic resonance spectroscopy, (b) a glass transition temperature of 0 ° to -25 ° C, which is determined by differential scanning colorimetry (calorimetry) at a heating rate of 10 ° C per minute, (c) a number-average molecular weight that is determined by gel permeation chromatography of 200,000 to 218,000, and (d) ) an inhomogeneity U of 1.4 or less. U.S. Patent No. 5,087,668, and U.S. Patent No. 5,300,577, disclose a pneumatic tire having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition composed of, based on 100 parts by weight of rubber, (a) from 5 to about 35 parts, preferably from about 10 to about 25 parts by weight of 3,4-polyisoprene rubber, (b) from about 20 to about 60 parts, preferably from about 30 to about 55 parts by weight of cis-1,4-polyisoprene rubber, and (c) about 10 to about 50 parts by weight of at least one rubber that is selected from at least one styrene / butadiene copolymer rubber formed by polymerization of solution having a styrene / butadiene ratio within the range of about 5/95 to about 30/70, preferably about 8 / 92 to about 25/75, a styrene / butadiene copolymer rubber formed by emulsion polymerization having a styrene / butadiene ratio in the range of about 10/90 to about 60/40, preferably about 15/85 at about 35/65, cis-1,4-polybutadiene rubber, rubber of an isoprene / butadiene copolymer having an isoprene / butadiene ratio within the range of about 30/70 to about 70/30, styrene rubber / isoprene having a styrene / isoprene ratio within the range of about 10/90 to about 35/65 and a styrene / isoprene / butadiene rubber; wherein the 3, 4-polyisoprene rubber in its uncured state, is characterized in that it has a glass transition temperature (Tg) within the range of about -15 ° C to about -20 ° C, a Mooney value (ML1 + 4) within the range of about 70 to about 90, preferably about 75 to about 85, and , in addition, a polymer structure containing from about 40 percent to about 70 percent, preferably from about 50 percent to about 60 percent of 3,4-polyisoprene units, from about 30 to about 50 percent of units of 1,4-cis and trans and approximately 2 percent to approximately 10 percent of 1,2-polyisoprene units with the total of their units of 3.4 and 1.2 remaining within the scale of approximately 56 per one hundred to about 63 percent. U.S. Patent Number 5,239,023 and the U.S. Patent No. 5,151,398 discloses a process for the synthesis of 3,4-polyisoprene which comprises polymerizing an isoprene monomer in an organic solvent at a temperature that falls within the range of about -10 ° C to about 100 ° C in US Pat. presence of a catalyst system consisting of (a) an organoiron compound that is soluble in the organic solvent, wherein the iron in the organoiron compound is in an oxidation state +3, (b) a partially hydrolyzed organoaluminium compound which was prepared by adding a proton compound which is selected from the group consisting of water, alcohols and carboxylic acids to the organoaluminum compound, and (c) an aromatic chelating amine; wherein the molar ratio of chelating amine to organoiron compound is within the range of from about 0.1: 1 to about 1: 1, wherein the molar ratio of the organoaluminum compound to the organoiron compound is within the range of about 5. : 1 to about 200: 1, and wherein the molar ratio of the protonic compound to the compound of - 1 - organoaluminum is within the range of about 0.001: 1 to about 0.2: 1. U.S. Patent Number 5,231,153, U.S. Patent Number 5,336,739 and U.S. Patent Number 5,448,003 disclose a process for the synthesis of 3,4-polyisoprene which comprises polymerizing the isoprene monomer in an organic solvent in the presence of a catalyst system consisting of of (a) a lithium initiator and (b) an alkyltetrahydrofurfuryl ether modifier, wherein the alkyl group in the alkyltetrahydrofurfuryl ether modifier contains from 6 to about 10 carbon atoms. U.S. Patent Application Serial No. 08-531,841, filed September 22, 1995, discloses an initiator system consisting of (a) a lithium initiator, (b) a sodium alkoxide, and (c) a modifier polar; wherein the molar ratio of the sodium alkoxide to the polar modifier is within the range of about 0.1: 1 to about 10: 1; wherein the molar ratio of sodium alkoxide to the lithium initiator is within the range of 0.01: 1 to about 20: 1.

SUMMARY OF THE INVENTION It has been determined that certain 3,4-polyisoprene rubbers having a high vitreous state transition temperature (Tg) can be used in rubber compositions for tire tread surface in order to significantly improve the characteristics of traction without compromising the wear of the running surface or the rolling resistance. These 3,4-polyisoprene rubbers have a Tg that falls within the range of about 0 ° C to about 25 ° C and preferably have a Tg that falls within the range of about 5 ° C to about 20 ° C. Particularly good traction characteristics can be achieved by using a combination of both 3,4-polyisoprene with high Tg and conventional low-Tg 3,4-polyisoprene in the tire tread surface compounds. The present invention discloses more specifically a pneumatic rim having an outer circumferential running surface wherein the running surface is a sulfur-cured rubber composition comprising, based on 100 parts by weight of rubber, (1) from about 20 parts to about 60 parts of natural rubber, (2) of about 5 parts to about 30 parts of the high content of cis-1,4-polybutadiene rubber, ( 3) from about 10 parts to about 50 parts of styrene-butadiene rubber and (4) from about 5 parts to about 30 parts of 3,4-polyisoprene rubber, wherein the 3,4-polyisoprene rubber has (a) ) a 3,4-isomer content of 75 percent to 95 percent, (b) a 1,2-isomer content of 5 percent to 25 percent, (c) a vitreous state transition temperature of 0 ° C at 25 ° C and (d) a number average molecular weight that falls within the range of 30,000 to 180,000. The present invention discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition consisting of, based on 100 parts by weight of the rubber, (1) of about 20. parts to approximately 60 parts of natural rubber, (2) from about 5 parts to about 30 parts of high cis-1-polybutadiene rubber, (3) from about 10 parts to about 50 parts of the styrene-butadiene rubber , (4) from about 2.5 parts to about 15 parts of a 3, 4-polyisoprene rubber of high Tg, wherein the 3, 4-polyisoprene rubber of high Tg has (a) a 3,4-isomer content from 75 percent to 95 percent, (b) a 1,2-isomer content of 5 percent to 25 percent, (c) a vitreous state transition temperature of 0 ° to 25 ° C, and (d) ) a number-average molecular weight that remains within the scale from 30,000 to 180,000, and (5) from about 2.5 parts to about 15 parts of the low Tg 3, 4-polyisoprene rubber, wherein the low Tg 3, 4-polyisoprene rubber has a glass transition temperature. less than about -5? C. The present invention further discloses a method for improving the wet skid resistance of a rubber mixture for a rim tread, which comprises adding from about 5 parts to about 50 parts by weight of a 3,4-polyisoprene rubber. , from 50 parts to 95 parts by weight of a vulcanizable elastomer with sulfur containing filler or filler materials, auxiliary oils and conventional vulcanizing agents, wherein the 3,4-polyisoprene rubber has (a) a content of 3, 4-isomer from 75 percent to 95 percent, (b) a 1,2-isomer content from 5 percent to 25 percent, (c) a vitreous state transition temperature from 0 ° to 25 ° C and (d) a number average molecular weight that falls within the range of 30,000 to 180,000. The present invention also discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition consisting of, based on 100 parts by weight rubber, (1) of about 5 parts to about 50 parts of 3,4-polyisoprene rubber, wherein the 3,4-polyisoprene rubber has (a) a 3,4-isomer content of 75 percent to 95 percent, (b) a content of the 1,2-isomer from 5 percent to 25 percent, (c) a vitreous state transition temperature from 0 ° C to 25 ° C and (d) a number average molecular weight that falls within the range of 30,000 to 180,000; and (2) of approximately 50 parts to about 95 parts of a rubbery polymer that is co-curable with the 3,4-polyisoprene rubber.

DETAILED DESCRIPTION OF THE INVENTION The 3,4-polyisoprene rubbers that can be employed in the blends of this invention are typically synthesized by anionic polymerization in an organic medium. The polymerization is usually carried out in an inert organic medium using a lithium catalyst. The content of the 3,4-isomer of the produced polyisoprene rubber is controlled by the amount of the modifier system present during the polymerization step.

The inert organic medium which is used as the solvent will typically be a hydrocarbon which is liquid at ambient temperatures which may be one or more of the paraffinic or cycloparaffinic aromatic compounds. These solvents will normally contain from 4 to 10 carbon atoms per molecule and will be liquid under the polymerization conditions. Of course, it is important that the selected solvent is inert. The term "inert" as used herein means that the solvent does not interfere with the polymerization reaction and reacts with the polymers made therefrom. Some representative examples of suitable organic solvents include pentane, isooctane, cyclohexane, normal hexane, benzene, toluene, xylene, ethylbenzene and the like alone or in admixture. Saturated aliphatic solvents such as cyclohexane and normal hexane are especially preferred. The lithium catalysts that can be used are typically organolithium compounds. The organo-lithium compounds that are preferred can be represented by the formula R-Li, wherein R represents a hydrocarbyl radical containing from 1 to about 20 carbon atoms. Generally, these monofunctional organolithium compounds will contain from 1 to about 10 carbon atoms. Some representative examples of organo-lithium compounds that may be employed include methyl lithium, ethyl lithium, isopropyl lithium, n-butyl lithium, secondary butyl lithium, n-octyl lithium, tertiary octyl lithium, n -decyl-lithium, phenyl-lithium, 1-naphthyl-lithium, 4-butylphenyl-lithium, p-tolyl-lithium, 1-naphthyl-lithium, 4-butylphenyl-lithium, p-tolyl-lithium, 4-phenylbutyl-lithium , cyclohexyl lithium, 4-butylcyclohexyl lithium and 4-cyclohexylbutyl lithium. Monolithium organ compounds, such as alkyl lithium compounds and aryl lithium compounds, are usually employed. Some representative examples of the preferred organo-monolithium compounds that can be used include ethyl aluminum, isopropyl aluminum, n-butyl lithium, secondary butyl lithium, normal hexyl lithium, tertiary octyl lithium, phenyl lithium, 2-naphthyl. -lithium, 4-butylphenyl-lithium, 4-phenylbutyl-lithium, cyclohexyl-lithium and the like. Normal butyl lithium and secondary butyl lithium are highly preferred lithium initiators. The amount of the lithium catalyst used will vary from one organolithium compound to another and with the molecular weight that is desired for the 3,4-polyisoprene rubber being synthesized. As a general rule, in all anionic polymerizations, molecular weight (Mooney viscosity) of the polymer produced is inversely proportional to the amount of the catalyst used. Since the 3, 4-polyisoprene of this invention is of relatively low molecular weight, the amount of the lithium initiator employed will be about three times more than that which is used to synthesize the conventional 3,4-polyisoprene rubber. As a general rule, about 0.02 phm (parts per hundred parts by weight of the monomer) will be used at about 1 phm of the lithium catalyst. In most cases, approximately 0.03 phm to about 0.3 phm of the lithium catalyst will be used. . It is typically preferred to use 0.06 phm to 0.2 phm of the liquid catalyst. Typically, about 5 weight percent to about 35 weight percent of the isoprene monomer in the polymerization medium will be charged. (based on the total weight of the polymerization medium, including the organic solvent and the monomer). In most cases, it will be preferred that the polymerization medium contain from about 10 weight percent to about 30 weight percent of the monomer. It is typically especially preferred that the polymerization medium contain from about 20 weight percent to about 25 weight percent of the monomer. Isoprene will polymerize at a temperature that is within the range of about 30 ° C to about 100 ° C. The polymerization temperature will preferably be within the range of about 40 ° C to about 70 ° C for practical reasons to achieve the desired microstructure. Temperatures within the range of about 50 ° C to about 60 ° C. they are especially preferred. The microstructure of the 3-polyisoprene rubber being prepared depends to some degree on the polymerization temperature. The polymerization is allowed to continue until essentially all of the isoprene monomer has been exhausted. In other words, the polymerization is allowed to run until complete. Since it employs a lithium catalyst to polymerize the isoprene monomer, an active 3,4-polyisoprene rubber is produced. The synthesized active polyisoprene rubber will have a number average molecular weight that ranges from about 30,000 to about 180,000, and a weight average molecular weight that falls within the range of about 40,000 to about 300,000. The synthesized polyisoprene rubber will most typically have a number average molecular weight that is within the range of about 50,000 to about 150,000 and preferably will have a number average molecular weight that falls within the range of about 70,000 to about 120,000. .

The 3,4-polyisoprene rubber will typically have a high glass transition temperature that falls within the range of about 0 ° C to about 25 ° C. More typically, it will have a glass transition temperature that falls within the range of about 5 ° C to about 20 ° C. The 3,4-polyisoprene rubber will usually have a 3,4-isomer content that is within the range of about 75 percent to about 95 percent, and a 1,2-isomer content that stays within the scale from about 5 percent to about 25 percent. A combination of a sodium alkoxide and polar modifier will normally be employed as the modifier system to achieve the very high 3,4-isomer content and to greatly improve (increase) the polymerization rate. It has been unexpectedly found that a combination of sodium alkoxide and a polar modifier acts synergistically to increase the content of the 3,4-isomer of the polyisoprene rubber synthesized in its presence. The molar ratio of the sodium alkoxide to the lithium initiator will normally be within the range of about 0.05: 1 to about 3: 1, and the molar ratio of the polar modifier to the lithium initiator will normally be within the range of about 0.25: 1 at about 5: 1. It is generally preferred that the molar ratio of the sodium alkoxide to the lithium initiator is within the range of about 0.15: 1 to about 1: 1, and that the molar ratio of the polar modifier to the lithium initiator is within the scale from about 0.4: 1 to about 3: 1. It is generally preferred that the molar ratio of the sodium alkoxide to the lithium initiator is within the range of about 0.3: 1 to about 0.5: 1, and that the molar ratio of the polar modifier to the lithium initiator is within the scale of approximately 0.5: 1 to approximately 2: 1. The sodium alkoxides that can be used in the modifier system will normally be of the NaOR formula, wherein R is an alkyl group containing from about 2 to about 12 carbon atoms. The sodium metal alkoxide will typically contain from about 2 to about 12 carbon atoms. It is generally preferred that the sodium alkoxide contains from about 3 to about 8 carbon atoms. In general, it is especially preferred that the sodium alkoxide contains from about 4 to about 6 carbon atoms. The sodium t-amyloxide (sodium t-pentoxide) is a representative example of a preferred sodium alkoxide which can be used in the modifier systems of this invention. The ethers and tertiary amines that act as Lewis bases are representative examples of the 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, dimethyl diethylene glycol, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, trimethylamine, triethylamine, N, N, N'-N'-tetramethylethylenediamine, N-methylmorpholine, N-ethyl-morpholine, N-phenylmorpholine and the like. The modifier can also be a 1,2,3-trialkoxybenzene or a 1,2,4-trialkoxybenzene. Some representative examples of the 1,2,3-trialkoxybenzenes that can be used include 1,2,3-trimethoxybenzene, 1,2,3-triethoxybenzene, 1,2,3-tributoxybenzene, 1,2,3-trihexoxybenzene, 4 , 5, 6-trimethyl-1,2,3-trimethoxybenzene, 4,5,6-tri-n-pentyl-l, 2,3-triethoxybenzene, 5-methyl-1,2,3-trimethoxybenzene and 5-propyl -l, 2, 3-trimethoxybenzene. Some representative examples of the 1,2-trialkoxybenzenes that can be used include 1, 2, 4-trimethoxybenzene, 1,2,4-triethoxybenzene, 1,2,4-tributoxybenzene, 1,2,4-tripentoxybenzene, 3, 5,6-trimethyl-1,2,4-trimethoxybenzene, 5-propyl-1,2,4-trimethoxybenzene and 3,5-dimethyl-1,2,4-trimethoxybenzene. Dipiperidinoethane, dipyrrolidinoetane, tetramethylethylene diamine, diethylene glycol, dimethyl ether and tetrahydrofuran are representative of the highly preferred modifiers. US Patent Number 4,022,959 describes the use of ethers and tertiary amines as polar modifiers, in greater detail. The use of 1, 2, 3-trialcoxybenzenes and 1, 2, 4-trialkoxybenzenes as modifiers is described in greater detail in U.S. Patent Number 4,696,986. The teachings of U.S. Patent Number 4,022,959 and U.S. Patent Number 4,696,986 are hereby incorporated by reference in their entirety. The microstructures of the repeating units that are derived from the isoprene monomer is a function of the polymerization temperature and the amount of the modifier present. For example, it is known that higher temperatures result in lower 3,4-isomer contents (lower levels of the 3,4-microstructure). Accordingly, the polymerization temperature, the amount of the modifier and the specific modifier selected will be determined taking into account the final desired microstructure of the polyisoprene rubber being synthesized. The coupling agents may optionally be used in order to improve the cold flow characteristics of the rubber and the rolling resistance of the tires made thereof. Coupling can lead to better processability and other beneficial properties. A wide variety of compounds suitable for use as coupling agents can be employed. Some representative examples of the appropriate coupling agents include multivinylaromatic compounds, multiepoxides, multiisocytes, multiimines, multialdehydes, multicetones, multihalides, multianhydrides, multi esters which are esters of polyalcohols with monocarboxylic acids, and diesters which are esters of monohydric alcohols with dicarboxylic acids.and similar Examples of suitable multivinylaromatic compounds include divinylbenzene, 1,2-trivinylbenzene, 1,3-divinylnaphthalene, 1 8-divinylnaphthalene, 1,3,5-trivinylnaphthalene, 2,4-divinylbiphenyl and the like. Divinyl aromatic hydrocarbons, particularly divinyl benzene, are preferred in either its isomer, ortho, meta or para. Commercial divinylbenzene, which is a mixture of three isomers and other compounds, is quite satisfactory. Although any multi-epoxide can be used, it is preferred to use those which are liquids that are handled more easily and form a relatively smaller core for the radial polymer. Especially preferred among the multi-epoxies are epoxidized hydrocarbon polymers such as epoxidized liquid polybutadienes and epoxidized vegetable oils such as epoxidized soy bean oil and epoxidized linseed oil. Other epoxy compounds such as 1,2,5,6,9,10-triepoxydecane and the like can also be used. Examples of suitable multiisocyanates include benzene-1,2,4-triisocyanate, naphthalene-1, 2, 5, 7-tetraisocyanate and the like. Especially suitable is a commercially obtainable product known as PAPI-1, a polyaryl polyisocyanate having an average of three isocyanate groups per molecule and an average molecular weight of about 380. This compound can be visualized as a series of linked isocyanate-substituted benzene rings. through methylene bonds. The multiimines, which are also known as multiaziridinyl compounds, which can be used preferably are those containing three or more aziridine rings per molecule. Examples of these compounds include triaziridinyl phosphine oxides or sulfides such as tri (l-arylidinyl) phosphine oxide, tri (2-methyl-1-aryidinyl) phosphine oxide, tri (2-ethyl-3-) sulfide. decyl-l-arididinyl) phosphine and the like. The multialdehydes that can be used are represented by the compounds such as 1,4-naphthalene tricarboxyaldehyde, 1, 7, 9-anthracene tricarboxyaldehyde, 1, 1, 5-pentane tricarboxyaldehyde and the like multialdehyde containing aliphatic compounds and aromatics. The multicetones are represented by compounds such as 1, 4, 9, 10-anthracenoterone, 2,3, diacetoneylcyclohexanone and the like. Examples of the multianhydrides include pyromellitic dianhydride, styrene-maleic anhydride copolymers and the like. Examples of the multi-esters include diethyladipate, triethyl citrate, 1,3,5-tricarbethoxybenzene and the like.

Preferred multihalides are silicon tetrahalides, such as silicon tetrachloride, silicon tetrabromide and silicon tetraiodide, and trihalosilanes such as trifluorosilane, trichlorosilane, trichloroethylsilane, tribromobenzylsilane and the like. Multihalogen-substituted hydrocarbons such as 1, 3, 5-tri (bromomethyl) benzene, 2, 4, 6, 9-tetrachloro-3,7-decadiene and the like are also preferred, wherein the halogen is attached to a carbon that is alpha with respect to an activation group such as an ether bond, a carbonyl group or a carbon-carbon double bond. Substituents inert with respect to the lithium atoms in the terminally reactive polymer may also be present in the active halogen-containing compounds. Alternatively, other appropriate reactive groups other than halogen may also be present as described above. Examples of compounds containing more than one type of functional group include: 1,3-dichloro-2-propanone, 2,2-dibromo-3-decanone, 3,5,5-trifluoro-4-octanone, 2, 4 -dibromo-3-pentanone, 1,2,4, 5-diepoxy-3-pentanone, 1,2,4,5-diepoxy-3-hexanone, 1,2,11, 12-diepoxy-8-pentadecanone, 1 , 3, 18, 19-diepoxy-7, 14-eicosandione and the like. In addition to the silicon multihalides as described above, other multihalides, particularly those of tin, lead or germanium, such as coupling and branching agents, can be easily employed. The difunctional duplicates of these agents can also be employed whereby a linear polymer results instead of a branched polymer. Broadly, and in exemplary manner, a scale of about 0.01 to 4.5 milliequivalents of the coupling agent can be employed per 100 grams of the polymer. It is usually preferred to use from about 0.01 to 1.5 milliequivalents of the coupling agent per 100 grams of the polymer. Larger amounts tend to result in the production of polymers containing terminally reactive or insufficient coupling groups. An equivalent of the treatment agent per equivalent of lithium is considered an optimum amount for maximum branching. If this result is desired, in the production line. The coupling agent may be added in a hydrocarbon solution, e.g., in cyclohexane, to the polymerization mixture in the final reactor, with mixing appropriate for distribution and reaction. The polymerization can be terminated with a conventional type of non-coupling terminator, such as water, an acid, a lower alcohol and the like or with a coupling agent. After the copolymerization has been completed, the 3,4-polyisoprene rubber can be recovered from the organic solvent. The 3,4-polyisoprene rubber can be recovered from the organic solvent and the residue by any means such as decanting, filtration, centrifugation and the like. It is often desirable to precipitate the polybutadiene rubber from the organic solvent by the addition of lower alcohols containing from about 1 to about 4 carbon atoms to the polymer solution. Lower alcohols suitable for precipitation of the 3,4-polyisoprene rubber from the polymer cement include methanol, ethanol, isopropyl alcohol, normal propyl alcohol and tertiary butyl alcohol. The use of lower alcohols to precipitate the 3,4-polyisoprene rubber from the polymer cement also "kills" the living polymer by inactivating the lithium end groups. After this 3,4-polyisoprene rubber is recovered from the solution, steam scrubbing can be employed to reduce the level of volatile organic compounds in the polymer. In the alternative, it may be desirable to remove the residual organic solvent from the polymer by evaporation which can be facilitated by the application of vacuum and elevated temperatures.

There are valuable benefits associated with using the 3, 4-polyisoprene rubber of a high Tg of this invention to produce compounds for tire tread surfaces. For example, the traction characteristics can be significantly improved without compromising the wear of the tread surface or the rolling resistance. As a general rule, the tire tread surface compounds, from about 5 phr (parts per 100 parts of rubber) to about 50 phr of the high 3, 4-polyisoprene, will be included. Typically, these tire tread compounds will contain from about 10 phr to 25 phr of high Tg 3, 4-polyisoprene. It is typically more preferred that the tire tread compounds contain from about 12 phr to about 20 phr of the high Tg 3,4-polyisoprene rubber. These tire tread compounds will of course also contain at least one other rubber that is co-curable with 3-polyisoprene. Some representative examples of other rubbers that are co-curable with 3,4-polyisoprene rubber include natural rubber, high cis-1,4-polybutadiene rubber, high vinyl polybutadiene rubber, polybutadiene rubber medium vinyl content, high trans-1, 4-polybutadiene rubber, styrene-butadiene rubber solution, emulsion styrene-butadiene rubber, styrene-isoprene-butadiene rubber, styrene-isoprene rubber, rubber isoprene-butadiene and other types of 3,4-polyisoprene rubber. A preferred mixture for high performance automobile tires consists of, based on 100 parts by weight of the rubber, (1) from about 20 parts to about 60 parts of natural rubber, (2) from about 5 parts to about 30 parts of rubber. high content of cis-1,4-polybutadiene, (3) from about 10 parts to about 50 parts of the styrene-butadiene rubber and (4) from about 5 parts to about 30 parts of the 3,4-polyisoprene rubber of high Tg of this invention. It is preferred that this mixture contain (1) from about 30 parts to about 50 parts of natural rubber, (2) from about 10 parts to about 20 parts of high cis-1, polybutadiene rubber, (3) of about 20 parts to about 40 parts of the styrene-butadiene rubber and (4) from about 10 parts to about 20 parts of the high Tg 3,4-polyisoprene rubber. It is especially preferred that this tire tread rubber formulation contain (1) from about 35 parts to about 45 parts of natural rubber, (2) from about 10 parts to about 20 parts of high cis-1 rubber content. , 4-polybutadiene, (3) from about 25 parts to about 35 parts of styrene-butadiene rubber and (4) from about 10 parts to about 20 parts of the high Tg 3,4-polyisoprene rubber. In these compounds it is usually preferred that the styrene-butadiene rubber be a styrene-butadiene rubber solution (a styrene-butadiene rubber which was synthesized by solution polymerization). The high cis-1,4-polybutadiene content rubber that is suitable for use in these mixtures typically has a cis-isomer content greater than 90 percent and can be produced by the process described in Canadian Patent Number 1,236,648. The high cis-1,4-polybutadiene rubber that is suitable for use in these mixtures is also sold by The Goodyear Tire & Rubber Company as Budene® 1207, a polybutadiene rubber and Bedene® 1208, a polybutadiene rubber. In order to maximize the performance characteristics of the rim, a combination of 3, 4-polyisoprene of high Tg and a 3,4-polyisoprene of low Tg can be used in the tire tread surface compound. Number 3, 4-polyisoprene of low Tg will have a Tg of less than about -5 ° C. Low Tg 3,4-polyisoprene will typically have a Tg that falls within the range of about -55 ° C to about -5 ° C. Preferably they will have a Tg that falls within the range of -30 ° C to about -10 ° C. and especially preferably it will have a Tg that falls within the range of about -20 ° C to about -10 ° C. The low Tg 3, 4-polyisoprene will also typically have a number average molecular weight greater than about 200,000. The low Tg 3,4-polyisoprene will generally have a number average molecular weight that falls within the range of 200,000 to about 500,000 and preferably will have a number average molecular weight that falls within the range of about 250, 000 to approximately 400,000. The weight ratio of high Tg to 3, 4-polyisoprene to 3,4-polyisoprene of low Tg will typically be within the range of about 0.1: 1 to about 10: 1. It is usually preferred that the weight ratio of 3,4-polyisoprene from high Tg to 3,4-polyisoprene of low Tg be within the range from about 0.5: 1 to about 2: 1. In general, it is especially preferred that the weight ratio of high Tg 3,4-polyisoprene to 3,4-polyisoprene of low Tg is within the range of about 0.8: 1 to about 1.2: 1. High Tg 3,4-polyisoprene and low Tg 3,4-polyisoprene will normally be used essentially in equal amounts to achieve optimal results. A highly preferred mixture for high performance automobile tires consists of, based on 100 parts by weight of rubber, (1) from about 20 to about 60 parts of natural rubber, (2) from about 5 parts to about 30 parts of rubber. high content of cis-1,4-polybutadiene, (3) from about 10 to about 50 parts of the styrene-butadiene rubber, (4) from about 2.5 to about 15 parts of the high Tg 3,4-polyisoprene rubber and (5) from about 2.5 to about 15 parts of the high Tg 3,4-polyisoprene rubber. It is preferred that this mixture contain (1) from about 30 parts to about 50 parts of natural rubber, (2) from about 10 parts to about 20 parts of high cis-1,4-polybutadiene rubber, (3) of about 20 parts to about 40 parts of styrene-butadiene rubber, (4) from about 5 parts to about 10 parts of high Tg 3,4-polyisoprene rubber and (5) from about 5 parts to about 10 parts of rubber of 3, 4-polyisoprene of low Tg. It is especially preferred that this rubber formulation for tire tread surfaces contain (1) from about 35 parts to about 45 parts of natural rubber, (2) from approximately 10 parts to about 20 parts of the high-cis-1 rubber content. , 4-polybutadiene, (3) from about 25 parts to about 35 parts of styrene-butadiene rubber, (4) from about 5 parts to about 10 parts of the high-T, 4-polyisoprene rubber, and (5) from about 5 parts to about 10 parts of a 3, 4-polyisoprene rubber of low Tg. In cases where it is desirable to maximize the tire's traction characteristics, the high cis-1,4-polybutadiene rubber can be removed from the mixture. However, it should be appreciated that in these cases the wear characteristics of the running surface can be compromised to a certain degree. In any case, the remarkable tire tread surface compounds for high performance tires can be produced by mixing, based on 100 parts by weight rubber, (1) of approximately 20 parts to approximately 60 parts of natural rubber, (2) about 10 to about 50 parts of ethylene-butadiene rubber and (3) from about 10 parts to about 30 parts of the rubber of, High Tg 4-polyisoprene of this invention. In another scenario, the mixture could comprise, based on 100 parts by weight of the rubber, (1) from about 20 parts to about 60 parts of natural rubber, (2) from about 10 parts to about 50 parts of styrene rubber. butadiene, (3) from about 5 parts to about 15 parts of the high Tg 3,4-polyisoprene rubber and (4) from about 5 parts to about 15 parts of the low Tg 3,4-polyisoprene. In cases where tread wear and rolling resistance are of greater importance, styrene-butadiene can be removed from the mixture. However, it should be noted that in these cases, traction characteristics can be compromised to a certain degree. Tire tread compounds of this type can be produced by mixing, based on 100 parts by weight of rubber, (1) from about 20 parts to about 60 parts of natural rubber, (2) from about 10 parts to about 30 parts. of high cis-1,4-polybutadiene rubber content and (3) from about 10 parts to about 30 parts of the high Tg 3,4-polyisoprene rubber of this invention. In another scenario, the blend could comprise of, based on 100 parts by weight of the rubber, (1) from about 20 parts to about 60 parts of natural rubber, (2) from about 10 parts to about 50 parts of the high content rubber of cis-1, -polybutadiene, (3) from about 5 parts to about 15 parts of the high-Tg 3,4-polyisoprene rubber, and (4) from about 5 parts to about 15 parts of the 3,4-polyisoprene of low Tg. The 3,4-polyisoprene rubber containing mixtures of this invention can be mixed using conventional ingredients and standard techniques. For example, polyisoprene rubber blends will typically be mixed with carbon black and / or silica, sulfur, fillers or fillers, accelerators, oils, waxes, singe inhibitors and processing aids. In most cases, the 3,4-polyisoprene rubber blends will be mixed with sulfur and / or a sulfur-containing compound, at least one filler or filler, at least one accelerator, at least one antidegradant, and at least one processing oil, zinc oxide, optionally a tackifying resin, optionally a reinforcing resin, optionally one or more fatty acids, optionally a peptizer and optionally one or more singe inhibiting agents. Other mixtures will normally contain from about 0.5 to 5 phr (parts per 100 parts rubber by weight) of sulfur and / or a sulfur-containing compound with an amount of 1 phr to 2.5 phr being preferred. It may be desirable to use insoluble sulfur in cases where fluorescence is a problem. Typically, 10 to 150 phr of at least one filler or filler in a mixture will be used with an amount of 30 to 80 phr being preferred. In most cases, at least some carbon black will be used in the filling or loading material. The filling or loading material, of course, can consist entirely of carbon black. Silica can be included in the filler or filler material to improve the resistance to breakage and heat buildup. The clays and / or talc can be included in the filling or loading material to reduce the cost. The mixture will also normally include from 0.1 to 2.5 phr of at least one accelerator with 0.2 to 1.5 phr being preferred. Antidegradants, such as antioxidants and antiozonants, will usually be included in the mixture of the tread compound, in amounts ranging from 0.25 to 10 phr with amounts within the range of 1 to 5 phr being preferred. The processing oils will generally be included in the mixture in amounts ranging from 2 to 100 phr, with amounts ranging from 5 to 50 phr being preferred. The polybutadiene blends of this invention will also typically contain from 0.5 to 10 phr of zinc oxide with an amount of 1 to 5 phr being preferred. These blends can optionally contain from 0 to 10 phr of the tackifying resin, from 0 to 10 phr of reinforcement resins, from 1 to 10 phr of fatty acids, from 0 to 2.5 phr of peptizers and from 0 to 1 phr of singe inhibiting agents. In order to fully understand the overall advantages of the blends of this invention, silica will normally be included in the rubber formulation for running surface. The processing of the 3,4-polyisoprene rubber mixture is normally carried out in the presence of an organosilicon compound containing sulfur to obtain the maximum benefits. Examples of suitable sulfur-containing organosilicon compounds are of the formula: Z-Alq-Sn-Alq-Z (1) where Z is selected from the group consisting of RJ Rl R2 -Yes - R? , - Si - R2 and -Si - R2 I I I R2 R2 R2 where R ^ is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl; wherein R2 is alkoxy of 1 to 8 carbon atoms or cycloalkoxy of 5 to 8 carbon atoms; and wherein Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is an integer of 2 to 8. Specific examples of sulfur-containing organosilicon compounds that can be used in accordance with the present invention include: 3,3 '- bis (trimethoxysilylpropyl) disulfide, 3,3'-bis (triethoxysilylpropyl) tetrasulfide, 3,3'-bis (triethoxysilylpropyl) octasulfuro, 3,3'-bis (trimethoxysilylpropyl) tetrasulfide, 2,2'-bis (triethoxysilylethyl) tetrasulfide, 3, 3'-bis (trimethoxysilylpropyl) trisufluro, 3, 3'-bis (triethoxysilylpropyl) trisulfide 3,3'-bis (tributoxysilylpropyl) disulfide, 3,3'-bis (trimethoxysilyl) hexasulfide, 3,3'- bis (trimethoxysilylpropyl) octasulfide, 3,3'-bis (trioctoxysilylpropyl) tetrasulfide, 3,3'-bis (trihexoxysilylpropyl) disulfide, 3,3'-bis (tri-2"-ethylhexoxysilylpropyl) trisulfide, 3,3'-bis (triisooctoxysilylpropyl) tetrasulfide, 3,3'-bis (tri-t-butoxysilylpropyl) disulfide, 2,2'-bis (methoxy diethoxysilylethyl) tetrasulfur or 2,2'-bis (tripropoxysilylethyl) pentasulfide, 3, 3 '-bis (triciclonexoxisililpropil) tetrasulfide, 3,3'-bis (triciclopentoxisililpropil) trisulfide, 2, 2' -bis (tri-2"-metilciclohexoxisililetil) tetrasulfide , bis (trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy-propoxysilyl-3'-diethoxybutoxy-silylpropyltetrasulfide, 2,2'-bis (dimethylmethoxysilylethyl) disulphide, 2,2'-bis (dimethyl sec.butoxysilylethyl) trisulfide, 3, 3 '-bis (butiletoxisililpropil methyl) tetrasulfide, 3, 3' -bis (di t-butilmetoxisililpropil) tetrasulfide, 2, 2 '-bis (phenyl methyl metoxisililetil) trisulfide, 3,3'-bis (diphenyl-isopropoxisililpropil) tetrasulfide, 3 , 3'-bis (diphenyl cyclohexoxysilylpropyl) disulfide, 3,3'-bis (dimethyl ethylmercaptosilylpropyl) tetrasulfide, 2,2'-bis (methyl dimethoxysilylethyl) trisulfide, 2,2'-bis (methyl ethoxypropoxysilylethyl) tetrasulfide, 3,3 '-bis (diethylmethoxysilylpropyl) tetrasulfide, 3, 3'-bis (ethyl di-sec. butoxysilylpropyl) disulfide, 3, 3 '-bis (propyl diethoxysilylpropyl) disulfide, 3, 3' -bis (butyl dimethoxysilylpropyl) trisulfide, 3, 3 '-bis (phenyl dimethoxysilylpropyl) tetrasulfide, 3-phenyl ethoxybutoxysilyl 3' -trimetoxisililpropil tetrasulfide, 4,4'-bis (trimethoxysilylbutyl) tetrasulfide, 6, 6'-bis (triethoxysilylhexyl) tetrasulfide, 12, 12 '-bis (triisopropoxysilyl dodecyl) disulfide, 18, 18' -bis (trimeoxisililoctadecil) tetrasulfide, 18, 18 '- bis (tripropoxysilyloctadecenyl) tetrasulfide, 4,4'-bis (trimethoxysilyl-buten-2-yl) tetrasulfide, 4, 4 '-bis (trimetoxisililciclohexilen) tetrasulfide, 5, 5' -bis (dimethoxymethylsilylpentyl) trisulfide, 3,3' - bis (trimethoxysilyl-2-methylpropyl) tetrasulfide and 3,3'- (bis (dimethoxyphenylsilyl-2-methylpropyl) disulfide Preferred sulfur-containing organosilicon compounds are the 3,3'-bis (trimethoxy or triethoxy silylpropyl) sulfides. The especially preferred compound is 3, 3'-bis (triethoxysilylpropyl) tetrasulfide. Therefore, in terms of Formula I, Z is preferably R2 I - Yes - R2 I R2 wherein R2 is an alkoxy of 2 to 4 carbon atoms, with 2 carbon atoms being particularly preferred, Alq is a divalent hydrocarbon of 2 to 4 carbon atoms with 3 carbon atoms being particularly preferred; and n is an integer from 3 to 5 with 4 being particularly preferred. The amount of the sulfur-containing organosilicon compound of the formula I in a rubber composition will vary depending on the level of silica used. Generally speaking, the amount of compound of the formula I will vary from about 0.01 to about 1.0 parts by weight per part by weight of the silica. Preferably, the amount will vary from about 0.02 to about 0.4 part by weight per part by weight of the silica. Most preferred, the amount of the compound of the formula I will vary from about 0.05 to about 0.25 part by weight per part by weight of the silica. In addition to the sulfur-containing organosilicon, the rubber composition must contain a sufficient amount of silica and carbon black, if used to contribute to a reasonably high modulus and high breaking strength. The silica filler or filler material can be added in amounts ranging from about 10 phr to about 250 phr. Preferably the silica is present in an amount ranging from about 15 phr to about 80 phr. If carbon black is also present, the amount of carbon black if used may vary. Generally speaking, the amount of carbon black will vary from about 5 phr to about 80 phr. Preferably, the amount of carbon black will vary from about 10 phr to about 40 phr. It will also be appreciated that the silica coupler can be used in conjunction with a carbon black, namely, pre-mixed with a carbon black prior to addition to the rubber composition, and this carbon black must be included in the amount above. cited carbon black for the formulation of the rubber composition. In any case, the total amount of silica and carbon black will be at least about 30 phr. The combined weight of silica and carbon black, as mentioned above, may be as low as 30 phr, but preferably is from about 45 to about 130 phr. The siliceous pigments commonly used in rubber blending applications can be used as the silica in this invention, including pyrogenic siliceous pigments and precipitates (silica), even though precipitated silicas are preferred. Preferred siliceous pigments used in this invention are precipitated silicas such as, for example, those obtained by the acidification of a soluble silicate, e.g., sodium silicate.

These silicas could be characterized, for example, by having a surface area of BET, as measured using nitrogen gas, preferably within the range of about 40 to about 600, and more usually within the range of about 50 to about 300 square meters per gram. The method for measuring the surface area of BET is described in Journal of the American Chemical Society, Volume 60, page 304 (1930). The silica can also be characterized typically because it has a dibutylphthalate absorption value (DBP) within the range of about 100 to about 400, and more usually of about 150 to about 300. The silica could be expected to have a final particle size average for example, within the range of 0.01 to 0.05 micron as determined by electron microscope, even though the silica particles may still be smaller or possibly larger in size. The various commercially available silicas can be considered for use in this invention such as only for one example herein and without limitation, the silicas commercially available from PPG Industries, under the trademark Hi-Sil with designations 210, 243, etc; the silicas obtainable from Rhone-Poulenc with, for example, the designations of Z1165MP; and the silicas obtainable from Degussa AG with, for example, designations VN2 and VN3. The formulations for tire tread surface including silica and an organosilicon compound will typically be mixed using a mechanical-mechanical mixing technique. The mixing of the rubber formulation for tire tread surface can be achieved by methods known to those skilled in the field of rubber mixing. For example, the ingredients are typically mixed in at least two stages, namely, at least one non-productive step followed by a productive mixing step. The final curing agents including sulfur vulcanization agents are typically mixed in the final stage which is conventionally called the "productive" mixing step, where mixing typically occurs at a temperature, or final temperature, less than the temperature ( s) of the mixture that in the previous nonproductive mixing stage (s). The organosilicon rubber containing silica and sulfur and the carbon black, if used, are mixed in one or more non-productive mixing stages. The terms "non-productive" and "productive" mixing stages are well known to those skilled in the field of rubber mixing. The sulfur vulcanizable rubber composition containing the sulfur-containing organosilicon compound, the vulcanizable rubber and generally at least part of the silica must be subjected to a thermomechanical mixing step. The thermomechanical mixing step usually comprises mechanical work in a mixer or extrusion apparatus for an appropriate period of time in order to produce a rubber temperature of between 140 ° C and 190 ° C. The appropriate duration of the thermomechanical treatment varies as a function of the operating conditions of the volume and nature of the components. For example, the thermomechanical treatment can be through a length of time that is within the range of about 2 minutes to about 20 minutes. It is usually preferred that the rubber reaches a temperature that is within the range of about 145 ° C to about 180 ° C and that temperature is maintained for a period of time remaining within the range of about 4 minutes to about 12 minutes. . It will normally be especially preferred that the rubber reaches a temperature which is within the range of about 155 ° C to about 170 ° C and is maintained at that temperature for a period of time which is within the range of about 5 minutes to about 10 minutes. minutes The rubber mixture of 34-polyisoprene containing the tire tread surface compounds of this invention can be used on rim treads together with regular rim manufacturing techniques. After the tire has been made with the mixture containing the 3,4-polyisoprene rubber it can be vulcanized using a normal tire curing cycle. The rims produced in accordance with this invention can be cured through a wide temperature range. However, it is generally preferred that the tires of this invention be cured at a temperature ranging from about 132 ° C to about 166 ° C. It is more typical that the tires of this invention are cured at a temperature ranging from about 143 ° C to about 154 ° C. It is generally preferred that the cure cycle used to vulcanize the tires of this invention have a duration of about 10 to about 20 minutes with a cure cycle of about 12 to about 18 minutes being especially preferred. The 3,4-isomer content of the 3,4-polyisoprene referenced herein can be determined by nuclear magnetic resonance (NMR) spectroscopy. Vitreous state transition temperatures can be determined by scanning calorimetry at a heating rate of 10 ° C per minute and a number average molecular weight (Mn) which is determined by gel permeation chromatography. This invention is illustrated by the following examples which are for the purpose of illustration only and are not to be construed as limiting the scope of the invention and the manner in which it may be carried out. Unless specifically indicated otherwise, the parts and percentages are given by weight.

Example 1 In this example, an isoprene rubber having a high Tg (vitreous state transition temperature) and a low molecular weight was synthesized by the technique of this invention using a tertiary amine and a sodium-t-amylate (STA) as the modifier system. In the method used, 2,000 grams of a dried silica / molecular sieve / aluminum premix containing 17.8 weight percent isoprene in hexane was charged in a 3.8 liter capacity reactor. After the impurity was removed from the premix by a solution of n-butyllithium (n-BuLi), 3.56 milliliters of a solution of 12.0 M TMEDA (N, N, N ', N'-) was added to the reactor. tetramethylethylenediamine in hexane), 3.56 milliliters of a 2.0 M solution of STA (in hexane) and 3.60 milliliters of a 0.96 M solution of n-BuLi (in hexane). The molar ratio of STA to TMEDA and n-BuLi was 2: 2: 1. The Mn of white (number average molecular weight) was 100,000. The polymerization was allowed to proceed at 40 ° C for one hour. An analysis of the residual monomer indicated that all the isoprene was consumed. Then, 2.0 milliliters of a 2M solution of ethanol (in hexane) was added to the reactor to stop the polymerization and the polymer was removed from the reactor and stabilized with 1 phr (parts per 100 parts by weight of rubber) of an antioxidant. After the hexane solvent had evaporated, the resulting isoprene rubber was dried in a vacuum oven at 50 ° C. The isoprene rubber was determined to have a Tg at + 14 ° C. It was also determined that it had a microstructure containing 15 percent 1,2-polyisoprene units, 82 percent 3,4-polyisoprene units and 3 percent 1,4-polyisoprene units. The Mooney viscosity (ML 1 + 4) at 100 ° C of the isoprene rubber produced was determined as being 13. The molecular weight of this isoprene rubber was sent using GPC (gel permeation chromatography) to have an Mn ( number average molecular weight) of 78,000 and one mw (weight average molecular weight) of 99,000 and a molecular weight distribution (MWD) of 1.30.

Example 2 The procedure described in Example 1 was used in this example with the exception that the number average molecular weight (Mn) of the isoprene rubber was increased from 100,000 to 200,000. To achieve this, the number of modifiers and n-BuLi was halved; that is, 1.78 milliliters of a 2 M solution of STA, 1.78 milliliters of a 2 M solution of TMEDA and 1.8 milliliters of a 0.96 M solution of n-BuLi were used in this experiment. The formed isoprene rubber was determined to have a glass transition temperature at + 18 ° C. It was also determined that it had a microstructure containing 15 percent 1,2-polyisoprene units, 79 percent 3,4-polyisoprene units and 6 percent 1,4-polyisoprene units. The Mooney viscosity (ML 1 + 4) at 100 ° C of the isoprene rubber produced was determined to be 37. The molecular weight of this isoprene rubber was measured using GPC to have an Mn of 121,000 and an Mw (average molecular weight) by weight) of 182,000, and a molecular weight distribution (MWD) of 1.50.

Example 3 The procedure described in Example 1 in this example was used except that the ratio of STA to TMEDA to n-BuLi was changed from 2: 2: 1 to 0.5: 0.5: 1. The formed isoprene rubber was determined to have a glassy state temperature at more than + 10 ° C. It was also determined that it had a microstructure containing 12 percent 1,2-polyisoprene units, 73 percent units. 3, 4-polyisoprene and 12 percent 1,4-polyisoprene units. The Mooney viscosity (ML 1 + 4) at 100 ° C of the isoprene rubber produced was determined to be 9. The molecular weight of this isoprene rubber was measured using GPC (gel permeation chromatography) to have an Mn (weight number average molecular) of 72,000 and one Mw (weight average molecular weight) of 80,000 and a molecular weight distribution (MWD) of 1.12.

Example 4 The procedure described in Example 1 was used in this example with the exception that the ratio of STA to TMEDA to n-BuLi was changed from 2: 2: 1 to 0.25: 3: 1 and the polymerization temperature was increased by 40. ° C to 65 ° C. GC analysis (gas chromatography) of the residual monomer indicated that 95 percent of the isoprene monomer was consumed in 5 minutes. A complete monomer conversion was achieved after 20 minutes. The produced isoprene rubber was determined to have a glass transition temperature at + 17 ° C. It was also determined that it had a microstructure containing 15 percent 1,2-polyisoprene units, 79 percent 3,4-polyisoprene units and 6 percent 1,4-polyisoprene units. The Mooney viscosity (ML 1 + 4) at 100 ° C and the polyisoprene rubber produced was determined to be 19. This polyisoprene rubber was measured to have an Mn of 72,400 and an Mw of 86,000 and a molecular weight distribution ( MWD) of 1.20.

Example 5 The procedure described in Example 1 was used in this example with the exception that the polymerization was changed from 40 ° C to 30 ° C and the ratio of STA to TMEDA to n-BuLi was changed from 2: 2: 1 to 0.25: 3: 1. It took 20 minutes to convert 95 percent of isoprene monomer into polyisoprene rubber. The glass transition state of the microstructure and the Mooney viscosity of the prepared polyisoprene rubber are shown in Table 1.

Comparison Example 6 The procedure described in Example 1 was used in this example with the exception that the polymerization was changed from 40 ° C to 30 ° C. and the modifier was changed from TMEDA / STA mixed to TMEDA alone. It took 280 minutes to convert 95 percent of the isoprene monomer into polyisoprene rubber. The transition temperature of vitreous state, microstructure and Mooney viscosity of the elaborated polyisoprene rubber is shown in Table 1.

Comparison Example 7 The procedure described in Example 1 was used in this example with the exception that the polymerization temperature decreased from 40 ° C to 30 ° C and with the exception that the modifier was changed from a TMEDA / mixed STA to diglyme (ether) of 2-methoxyethyl). It took 180 minutes or to convert 95 percent of the isoprene monomer into the polyisoprene rubber. The glass transition temperature and the microstructure of the produced polyisoprene rubber are shown in Table 1.

Comparison Example 8 The procedure described in Example 1 was used in this example with the exception that the polymerization temperature used was changed from 40 ° C to ° C and the modifier was changed from TMEDA / STA mixed to ETE (ethyltetrahydrofurfuryl ether). It took 140 minutes to convert 95 percent of the isoprene monomer into the polyisoprene rubber. The transition temperature of vitreous state, microstructure and viscosity ML-4 Mooney of the polyisoprene rubber produced are shown in Table 1. TABLE 1 No. Modifier T Tiieemmppoo T Tgg ML Microstructures of the reqreened 11 ++ 4411 1,2- 1,4- 3,4- Ex. ppaarraa Pl Pl Pl 95% conversion 4 STA / TMEDA 5 minutes + 17 ° C 19 15% 6% 79% STA / TMEDA 20 minutes + 19 ° C 22 15% 2% 84% 6 TMEDA 280 minutes + 8 ° C 12 15% 17% 68% 7 Diglima 180 minutes + 12 ° C 15 12% 9% 79% 8 ETE 140 minutes + 13 ° C 18 14% 6% 80% (1) The Mooney viscosity (ML 1 + 4) was measured at 100 ° C.

Example 9 In this example, an isoprene rubber having an Mn of 300,000 was prepared by the technique of this invention using tertiary amine and sodium-t-amylate (STA) mixed as the modifier. In the process used, 2,250 grams of a silica / molecular sieve / aluminum premix containing 20 weight percent isoprene in hexanes was charged in a 3.8 liter capacity reactor. After the impurity was removed from the premix by a solution of n-butyllithium (n-BuLi), 2.25 milliliters of a 2.0 M solution of DPE (N, N '-1,2-diperidinoethane) was added to the reactor.; in hexane), 1.5 milliliters of a 0.5 M solution of STA (in hexane) and 1.56 milliliters of a 0.96 M solution of n-BuLi (in hexane). The molar ratio of STA to DPE and n-BuLi was 0.5"3: 1. The polymerization was allowed to continue at 50 ° C. An analysis of the residual monomer indicated that the polymerization had essentially been completed (more than 95 percent isoprene was consumed) after 30 minutes Polymerization was continued for another 30 minutes to complete monomer consumption, then 1.0 milliliter of a 2M solution of ethanol (in hexane) was added to the reactor to stop polymerization and the polymer it was removed from the reactor and stabilized with 1 phr (parts per 100 parts by weight of rubber) of an antioxidant After the hexane solvent had evaporated, the resulting isoprene rubber was dried in a vacuum oven at 50 ° C. The formed isoprene rubber was determined to have a glass transition temperature of + 30 ° C. It was also determined that it had a microstructure containing 89 percent 3,4-polyisoprene units, 9 percent d e units of 1,2-polyisoprene and 2 percent of 1,4-polyisoprene units.

Example 10 The procedure described in Example 9 was used in this example with the exception that 1,3-butadiene was used as the monomer instead of isoprene. It took 15 minutes to convert 95 percent of the 1,3-butadiene monomer into butadiene rubber. The polybutadiene formed was determined to have a glass transition temperature at -9 ° C. It was also determined that it had a microstructure containing 93 percent of 1,2-polybutadiene units and 7 percent of 1,4-polybutadiene units.

Comparison Example 11 The procedure described in Example 9 was used in this example with the exception that the polymerization temperature was changed from 50 ° C to 70 ° C and the modifier was changed from STA / DPE to TMEDA alone. The glass transition temperature of the polyisoprene formed and the time required to consume more than 90 percent of the charged monomer are listed in Table 2.

Comparison Example 12 The procedure described in Example 9 was used in this example with the exception that the polymerization temperature was changed from 50 ° C to 70 ° C and the modifier was changed from STA / DPE to ETE alone. The glass transition temperature of polyisoprene formed and the time needed to consume more than 90 percent of the charged monomer are listed in Table 2.

Example 13 The procedure described in Example 9 was used in this example with the exception that the polymerization temperature was changed from 50 ° C to 70 ° C and the modifiers were changed from STA / DPE to STA / TMEDA. The glass transition temperature of the polyisoprene formed and the time required to consume more than 90 percent of the charged monomer are listed in Table 2.

Example 14 The procedure described in Example 9 was used in this example with the exception that the polymerization temperature was changed from 50 ° C to 70 ° C and the modifiers were changed from STA / DPE to STA / ETE. The glass transition temperature of the polyisoprene formed and the time required to consume more than 90 percent of the charged monomer are listed in Table 2.

TABLE 2 Ex. TemperaTg System Time needed to No. Modifier to reach a converPZN of 90% + 11 TMEDA 70 ° C -16 ° C 240 minutes 12 ETE 70 ° C -15 ° C 30 minutes 13 STA / ETE 70 ° C -3 ° C 20 minutes 14 STA / TMEDA 70 ° C 0 ° C 15 minutes Comparison Example 15 The procedure described in Example 9 was used in this example with the exception that 1,3-butadiene was used as the monomer instead of isoprene and the modifier was changed from STA / DPE to TMEDA alone. The glass transition temperature of the polybutadiene formed and the time needed to consume more than 90 percent of the charged monomer are listed in Table 3.

Comparison Example 16 The procedure described in Example 9 was used in this example with the exception that 1,3-butadiene was used as the monomer instead of isoprene and the modifier was changed from STA / DPE to ETE alone. The glass transition temperature of the polybutadiene formed and the time needed to consume more than 90 percent of the charged monomer are listed in Table 3.

Example 17 The procedure described in Example 9 was used in this example with the exception that 1,3-butadiene was used as the monomer instead of isoprene and the modifiers were changed from STA / DPE to STA / TMEDA. The transition temperature of the vitreous state of the polybutadiene formed and the time needed to consume more than 90 percent of the charged monomer are listed in Table 3.

TABLE 3 N Noo .. S Siisstteemmaa MMooddiiffiiccaaddoorr T Teemmppeerraa-Tg Necessary time of the quarter to stay Eg PZN a conversion of 90% + TMEDA 50 ° C -40 ° C 60 minutes 16 ETE 50 ° C -36 ° C 45 minutes 17 STA / TMEDA 50 ° C -22 ° C 15 minutes Comparison Example 18 The procedure described in Example 9 was used in this example with the exception that a premix containing a 50:50 mixture of 1,3-butadiene and isoprene in hexanes was used instead of isoprene and the modifier was changed from STA-DPE to TMEDA only. The glass transition temperature of 50/50 IBR (isoprene-butadiene rubber) formed and the time required to consume more than 90 percent of the charged monomers are listed in Table 4.

Comparison Example 19 The procedure described in Example 9 was used in this example with the exception that a mixture containing a 50:50 mixture of 1,3-butadiene and isoprene in hexanes was used instead of isoprene and the modifier was changed from STA / DPE to ETE only. The glass transition temperature of 50/50 IBR that formed and the time needed to consume more than 90 percent of the charged monomers are listed in Table 4.

Example 20 The procedure described in Example 9 was used in this example with the exception that a mixture containing a 50:50 mixture of 1,3-butadiene and isoprene in hexanes was used instead of isoprene and the modifier was changed from STA / DPE to STA / ETC. The glass transition temperature of 50/50 IBR formed and the time required to consume more than 90 percent of the charged monomers are listed in Table 4.

Example 21 The procedure described in Example 9 was used in this example with the exception that a mixture containing a 50:50 mixture of 1,3-butadiene and isoprene in hexanes was used instead of isoprene and the modifier was changed from STA / DPE to STA / TMEDA. The glass transition temperature of 50/50 IBR formed and the time needed to consume more than 90 percent of the charged monomers are listed in Table 4.

TABLE 4 Eg System Tempera Tg Time needed to No. Modifier to reach a converPZN of 90% + 18 TMEDA 65 ° C -26 ° C 210 minutes 19 TEE 65 ° C -27 ° C 60 minutes STA / ETE 65 ° C -25 ° C 20 minutes 21 STA / TMEDA 65 ° C -16 ° C 20 minutes Example 22 Comparison The procedure described in Example 9 was used in this example with the exception that the polymerization temperature was changed from 50 ° C to 70 ° C and the modifier was changed from STA / DPE to DMAMP (2-dimethylaminomethyl-1 piperidine) -methyl) alone. The glass transition temperature, the microstructure, the Mooney viscosity (ML 1 + 4) of the polyisoprene formed and the time required to consume more than 90 percent of the charged monomer are listed in Table 5.

Comparison Example 23 The procedure described in Example 9 was used in this example with the exception that the polymerization temperature was changed from 50 ° C to 70 ° C and the modifier was changed from STA / DPE to Esparteine alone. The glass transition temperature, microstructure, Mooney viscosity (ML 1 + 4) of the polyisoprene formed and the time required to consume more than 90 percent of the charged monomer are listed in Table 5.

Example 24 The procedure described in Example 9 was used in this example except that the polymerization temperature was changed from 50 ° C to 70 ° C and the modifier was changed from STA / DPE to STA / DMAMP. The glass transition temperature, microstructure, Mooney viscosity (ML 1 + 4) of the polyisoprene formed and the time necessary to consume more than 90 percent of the charged monomer are listed in TABLE 5.

Example 25 The procedure described in Example 9 was used in this example with the exception that the polymerization temperature was changed from 50 ° C to 30 ° C and the modifier was changed from STA / DPE to STA / Esparteine. The glass transition temperature, microstructure, Mooney viscosity (ML 1 + 4) of the polyisoprene formed and the time required to consume more than 90 percent of the charged monomer are listed in TABLE 5.

TABLE 5 System Number Temperature Tg ML Example Modifier of PZN 1 + 41 22 DMAMP 70 ° C -32 ° C 43 23 Esparteina 70 ° C -60 ° C 45 24 STA / DMAMP 70 ° C -2 ° C 56 STA / Esparteina 70 ° C -12 ° C 43 TABLE 5 (CONTINUED) Number of Microstructures Time required for Example 1,2-PI 1,4-PI 3,4-PI 90% conversion + 22 2 54 44 120 minutes 23 0 87 13 180 minutes 24 9 24 67 30 minutes 5 36 59 45 minutes (1) The Mooney viscosity (ML 1 + 4) was measured at 100 ° C. Example 26 The procedure described in Example 6 was used in this example with the exception that a mixture containing a mixture of 10:90 was used. styrene and 1, 3-butadiene in hexanes instead of isoprene and the modifier was changed from STA / DPE to STA / TMEDA. It took 10 minutes to consume more than 90 percent of the charged monomers. The 10/90 SBR (styrene / butadiene rubber) produced is determined to have a glass transition temperature at -20 ° C. It was also determined that it has a Mooney viscosity (ML 1 + 4) at 100 ° C of 69.

Examples 27 to 31 The procedure described in Example 9 was used in this example with the exception that the isoprene monomer was replaced with 25:75, 30:70, 35:65, 40:60 and 45:55 mixtures of styrene and 1, 3 -butadiene in hexanes and the modifier was changed from STA / DPE to STA / TMEDA. The ratio of STA to TMEDA and n-BuLi was also changed to 0.5: 0.3: 1. It took approximately 15 minutes to consume more than 90 percent of the monomers charged at the polymerization temperature of 70 ° C for all these experiments. Based on the proton NMR measurements (nuclear magnetic resonance), the polystyrenes contained in these SBR are randomly distributed in the polymer chains. The transition temperatures of the vitreous state and microstructures of these produced SBRs are listed in TABLE 6.

TABLE 6 System Number Temperature Ratio Example PZN Styrene-Butadiene Modifier 27 STA / TMEDA 25:75 70 ° C 28 STA / TMEDA 30:70 70 ° C 29 STA / TMEDA 35:65 70 ° C STA / TMEDA 40:60 70 ° C 31 STA / TMEDA 45:55 70 ° C TABLE 6 (CONTINUED) Tg number Microstructure Example 1,2-PBd 1,4-PBd Styrene (random) 27 -. 27 -35 ° C 39 36 25 28 -. 28 -30 ° C 38 33 29 29 -. 29 -27 ° C 32 34 34 -. 30 -21 ° C 30 30 40 31 -. 31 -13 ° C 28 28 44 Example 32-32 The procedure described in Example 9 was used in this example with the exception that the isoprene monomer was replaced with 40:60 and 45:55 mixtures of styrene and 1,3-butadiene in hexanes and the modifier was changed from STA / DPE to STA / TMEDA. The ratio of STA to TMEDA and N-BuLi was also changed to 0.5: 0.5: 1. It took approximately 15 minutes to consume more than 90 percent of the monomers charged at the polymerization temperature of 70 ° C for all these experiments. Based on the proton NMR measurements (nuclear magnetic resonance), the polystyrenes contained in these SBR are randomly distributed in the polymer chains. The transition temperatures of the vitreous state and microstructures of these produced SBRs are listed in TABLE 7. TABLE 7 System Number Temperature Ratio Example Styrene Modifier: PZN Butadiene 32 STA / TMEDA 40:60 70 ° C 33 STA / TMEDA 45:55 70 ° C TABLE 7 (CONTINUED) Tg number Microstructure Example 1,2-PBd 1,4-PBd Styrene (random) 32 -. 32 -12 ° C 35 26 39 33 -. 33 -8 ° C 30 25 45 Comparison Example 34 The procedure described in Example 9 was used in this example with the exception that a premix containing a mixture of 25:75 styrene and 1,3-isoprene in hexanes was used instead of isoprene and the modifier was changed from STA / DPE to ETE only. The molar ratio of TEE to n-BuLi was 0.5: 1. The glass transition temperature, microstructure of 25/75 SIR (styrene-isoprene rubber) formed and the time necessary to consume more than 90 percent of the charged monomers, is listed in TABLE 8.

Example 35 The procedure described in Example 9 was used in this example with the exception that it used a premix containing a mixture of 25:75 styrene and 1,3-isoprene in hexanes instead of isoprene, and the modifier was changed from STA / DPE to STA / ETE. The molar ratio of STA to ETE and n-BuLi was 0.5: 0.5: 1. The vitreous state transition temperature, 25/75 SIR microstructure formed and the time required to consume more than 90 percent of the charged monomers, are listed in TABLE 8.

TABLE 8 System Number Temperature Tg Example Modifier of PZN 34 ETE 70 ° C -30 ° C STA / ETE 70 ° C -10 ° C TABLE 8 (CONTINUED) Number of the Styrene Microstructure Time required Example 1,2-PI 1,4-PI 3,4-PI for 90% conversion + 34 2 52 21 25 30 minutes 5 27 52 25 20 minutes Examples 36-37 The procedure described in Example 9 was used in this example with the exception that the isoprene monomer was replaced by a mixture of 10:90 styrene and isoprene in hexanes and the modifier was changed from STA / DPE to STA / TMEDA or STA / ETE. It took approximately 10 minutes to consume more than 90 percent of the monomers charged at the polymerization temperature of 70 ° C for all these experiments. Based on proton nuclear magnetic resonance measurements, the polystyrenes contained in these SIRs are distributed randomly in the polymer chains. The transition temperatures of the vitreous state and microstructure of these produced SIRs are listed in TABLE 9.

TABLE 9 System Number Temperature Ratio Example Modifier Styrene PZN Butadiene 36 STA / TMEDA 10:90 70 ° C 37 STA / ETE 10:90 70 ° C TABLE 9 (CONTINUED) Tg number Microstructure Example 1,2-PI 1,4-PI 3,4-PI Styrene (random) 36 + 14 ° C 12 10 68 10 37 + 3 ° C 11 18 61 10 Example 38 The procedure described in Example 9 was used in this example with the exception that the isoprene monomer was replaced by a mixture of 25:50:25 styrene, isoprene and 1,3-butadiene in hexanes and the modifier was changed from STA / DPE to STA / ETE. It took approximately 12 minutes to consume more than 90 percent of the monomers charged at a polymerization temperature of 70 ° C. Based on proton nuclear magnetic resonance measurements, the polystyrenes contained in SIBR (styrene-isoprene-butadiene rubber) were randomly distributed in the polymer chains. The SIBR produced was determined to have a glass transition temperature at + 1 ° C. It was also determined that it had a microstructure containing 24 percent of polystyrene units, 13 percent of 1,2-polybutadiene units, 9 percent of 1,4-polybutadiene units, 7 percent of 1,2 units. -polysisoprene, 11 percent 1,4-polyisoprene units and 36 percent 3,4-polyisoprene units. The SIBR was also measured to have a Mooney viscosity (ML 1 + 4) at 100 ° C of 75.

Comparison Example 39 In this experiment, a mixture was made by mixing 40 parts of natural rubber, 15 parts of rubber with a high content of cis-1,4-polybutadiene, 30 parts of styrene-butadiene rubber solution, 15 parts of a rubber of 3, 4-polystyrene of conventional low Tg, 38 parts of carbon black, 10 parts of Hi-Sil ™ 210 silica, 2 parts of the coupling agent of Degussa X50S, 10 parts of a paraffinic process oil, 3.5 parts of anti-degradants, 3.5 parts of zinc oxide, 2 parts of stearic acid, 1 part of N-cyclohexylbenzthiazole-2-sulfenamide, 0.1 part of tetramethylthiouramyl disulfide and 1.5 parts of sulfur. The low Tg 3, 4-polyisoprene rubber used in this mixture had a vitreous state transition temperature of -16 ° C and a number average molecular weight of about 350,000. This rubber mixture was subsequently cured and evaluated to determine the physical properties disclosed in TABLE 10. The low values of tan delta at 70 ° C are indicative of low hysteresis and consequently the tread surfaces made with rubber. these rubbers exhibit lower rolling resistance than tires produced with rubbers having higher delta values at 70 ° C. On the other hand, rubbers having high tan delta values between -25 ° C and + 25 ° C can be used to produce rim treads that exhibit better traction characteristics than rims produced with rubber tread surface compositions. which have lower tan delta values through the temperature scale of -25 ° C to + 25 ° C. It is preferred that a rubber composition for the running surface has the highest possible delta value at each temperature within the range of -25 ° C to + 25 ° C to obtain the best traction characteristics possible through all the driving conditions and all driving speeds. The rubber mixture that is produced in this experiment had a high tan delta value of more than about 0.25 at temperatures of less than about -15 ° C. However, the delta values of this mixture decreased rapidly with temperatures increasing above -10 ° C. At 0 ° C this mixture exhibited a delta value of approximately 0.18. This experiment shows that the conventional low glass transition temperature 3,4-polyisoprene rubber can be used to produce formulations for tire tread surface having high tan delta values at temperatures of less than about 0 ° C. The low tan delta value at 70 ° C of less than 0.1 further shows that this rubber formulation can be used to produce rim rolling surface exhibiting good rolling resistance. Nevertheless, it would be highly desirable that the delta value of this rubber mixture be higher at temperatures within the range of about 0 ° C to about 25 ° C to exhibit noticeable traction characteristics throughout all driving conditions and all driving needs.

Example 40 In this experiment, a rubber formulation for tire tread surface was made using the same procedure as that used in Example 39 with the exception of the fact that the high-temperature transition state 3,4-polyisoprene rubber was replaced. vitreous by the low-temperature transition glass transition temperature 3, 4-polyisoprene rubber used in Example 39. The high Tg 3.4 polyisoprene rubber employed in this experiment had Mn of 121,000 and one Mw of 182,000 and one Mz of 245,000. It was synthesized by the procedure described in Example 2. The rubber formulation made in this experiment had the physical properties disclosed in TABLE 10. As can be seen, the tan delta values of the mixture increased through the temperature scale from about -2 ° C to about + 23 ° C. This mixture had a delta value at 70 ° C of about 0.07. This low delta value at 70 ° C of less than 0.1 shows that this rubber formulation can be used to produce rim rolling surfaces exhibiting good rolling resistance. This circular combination of high delta values at low temperatures and low tan delta values at high temperatures is indicative of a formulation for the rim running surface with good traction characteristics and good rolling resistance. In general, as the vitreous state transition temperature of a rubber tire tread surface formulation increases, the abrasion resistance is sacrificed. However, it has unexpectedly been found that this is not the case with the rubber formulations for rim rolling surface of this invention. In fact, it has been determined that the tire tread rubber formulations of this invention have DIN abrasion characteristics that are as good or better than the lower glassy state transition temperature control compounds. This means that a better duration of rolling surface can be expected while improving traction characteristics are also achieved.

Example 41 In this experiment, a rubber formulation for tire tread surface was made using the same procedure as used in Example 39 with the exception of the fact that a high Tg 3,4-polyisoprene rubber was replaced by rubber of 3, 4-polyisoprene of low Tg used in Example 39. The high Tg 3,4-polyisoprene rubber employed in this experiment had an Mn of 72,000 and an Mw of 86,000.

The rubber formulation made in this experiment had physical properties disclosed in TABLE 10. As can be seen, tan delta values of the mixture increased through the temperature scale from about -5 ° C to about + 17 °. C. This mixture had a tan delta value at 70 ° C of about 0.08. This low delta value at 70 ° C of less than 0.1 shows that this rubber formulation can be used to produce rim treads exhibiting good rolling resistance. This unique combination of high tan delta values at low temperatures and low tan delta values at high temperatures is indicative of a formulation for its tire tread surface with both good traction characteristics and good rolling resistance. In general, as the glass transition temperature of a rubber tire tread formulation increases, the abrasion resistance is sacrificed. However, it has unexpectedly been found that this is not the case with the rubber tire surface rolling formulations of this invention. In fact, it has been determined that the tire tread rubber formulations of this invention have DIN abrasion characteristics that are as good or better than those of the lowest Tg control compounds. This means that better rolling surface durability can be expected while improving traction characteristics are also achieved.

TABLE 10 Example 39 40 41 Module 100% 1.9 MPa 2.0 MPa 2.0 MPa Module at 300% 5 MPa 9.0 MPa 8.7 MPa Resistance to Breakage 16.2 MPa 14.6 MPa 14.3 MPa Elongation1 515% 469% 469% Hardness (20 ° C) 58 60 60 Hardness (100 ° C) 52 52 51 Rebound (20 ° C) 49 40 39 Rebound (100 ° C) 67 66 65 Abrasion of DIN2 116 105 111 tan delta @ -25 ° C 0.28 0.20 0.21 tan delta @ -20 ° C 0.26 0.17 0.18 tan delta @ -15 ° C 0.25 0.15 0.16 tan delta @ -10 ° C 0.24 0.14 0.15 * tan delta @ -5 ° C 0.22 0.14 0.15 tan delta @ 0 ° C 0.18 0.14 0.15 tan delta @ 5 ° C 0.16 0.14 0.17 tan delta @ 10 ° C 0.13 0.16 0.21 tan delta @ 15 ° C 0.12 0.19 0.23 tan delta @ 20 ° C 0.11 0.23 0.23 tan delta @ 25 ° C 0.10 0.23 0.19 tan delta @ 70 ° C 0.07 0.07 0.08 The elongation was measured until rupture. 2 DIN abrasion was measured at the volume lost in cubic centimeters (less is better).

Although certain embodiments and representative details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the present invention.

Claims (10)

R E I V I N D I C A C I O N E S:

1. A pneumatic tire having an outer circumferential running surface wherein the running surface is a sulfur cured rubber composition which is characterized in that it is based on 100 parts by weight of rubber, (1) of about 5 parts to about 50 parts of high Tg 3, 4-polyisoprene rubber, wherein the high Tg 3,4-polyisoprene rubber has (a) a 3,4-isomer content of 75 percent to 95 percent, (b) ) a 1,2-isomer content of 5 percent to 25 percent, (c) a vitreous state transition temperature of 0 ° C to 25 ° C, and (d) a number-average molecular weight that remains within the scale of 30,000 to 180,000; and (2) from about 50 parts to about 95 parts of at least one rubbery polymer that is co-curable with the 3,4-polyisoprene rubber.

2. An air tire according to claim 1, characterized in that the sulfur cured rubber composition comprises, based on 100 parts by weight of rubber, (1) from about 20 parts to about 60 parts of natural rubber, (2) ) from about 5 parts to about 30 parts of a high content of cis-1,4-polybutadiene rubber, (3) of 1 - about 10 parts to about 50 parts of a styrene-butadiene rubber, (4) from about 2.5 parts to about 15 parts of the high Tg 3,4-polyisoprene rubber and (5) from about 2.5 to about 15 parts of a 3, 4-polyisoprene rubber of low Tg, wherein the 3, 4-polyisoprene rubber of low Tg has a glass transition temperature of less than about -5 ° C.

3. A pneumatic tire according to claim 1, characterized in that the sulfur-cured rubber composition consists of 100 parts by weight of rubber (1) from about 20 parts to about 60 parts of natural rubber, (2) of about 5 parts to about 30 parts of high cis-1,4-polybutadiene rubber, (3) about 10 parts to about 50 parts of styrene-butadiene rubber, and (4) about 5 parts to parts to about 30 parts. of 3, 4-polyisoprene rubber of high Tg.

4. A pneumatic tire according to claim 1, characterized in that the high Tg-polyisoprene has a weight average molecular weight that ranges from about 40,000 to about 300,000; and a number average molecular weight that falls within the range of about 50,000 to about 150,000. A pneumatic tire according to claim 3, characterized in that the rubber composition contains from about 35 parts about 45 parts of natural rubber, from about 10 parts to about 20 parts of rubber with a high content of cis-1, 4- polybutadiene, from about 25 parts to about 35 parts of styrene-butadiene rubber and from about 10 parts to about 20 parts of the high Tg 3,4-polyisoprene rubber; wherein the high Tg 3,4-polyisoprene rubber has a glass transition temperature that falls within the range of about 5 ° C to about 20 ° C; and wherein the 3,4-polyisoprene has a number average molecular weight that falls within the range of about 70,000 to about 120,000. 6. A number rim according to claim 2, characterized in that the 3, 4-polyisoprene of low Tg has a number average molecular weight greater than 200,000; and wherein the 3, 4-polyisoprene of low Tg has a glass transition temperature that falls within the range of about -55 ° C to about -5 ° C; wherein the mixture contains (1) from about 30 parts to about 50 parts of natural rubber; (2) from about 10 parts to about 20 parts of the high cis-1 rubber, 4-polybutadiene, (3) from about 20 parts to about 40 parts of the styrene-butadiene rubber, (4) from about 5 parts to about 10 parts of high-T-4, 4-polybutadiene and (5) of about

5. parts to about 10 parts of the low Tg 3,4-polyisoprene rubber, wherein the 3,4-polyisoprene has a weight average molecular weight that falls within the range of about 40,000 to 300,000; wherein the 3, 4-polyisoprene of high Tg has a number average molecular weight that is within the range of about 50,000 to about 150,000; and wherein the high Tg 3, 4-polyisoprene rubber has a glass transition temperature that falls within the range of about 5 ° C to about 20 ° C. 7. A pneumatic tire according to claim 1, characterized in that the rubbery polymer which is co-curable with high Tg-4-polyisoprene is a mixture of natural rubber and styrene-butadiene rubber; wherein the rubber composition consists of (1) from about 20 parts to about 60 parts of natural rubber, (2) from about 10 parts to about 40 parts of the styrene-butadiene rubber and (3) from about 10 parts to about 30 parts of high Tg 3,4-polyisoprene rubber. A pneumatic tire according to claim 1, characterized in that the cauchotsso polymer which is co-curable with the high Tg 3,4-polyisoprene is a mixture of natural rubber, low Tg 3,4-polyisoprene rubber and styrene-butadiene rubber; wherein the rubber composition consists of (1) from about 20 parts to about 60 parts of natural rubber, (2) from about 10 parts to about 50 parts of styrene-butadiene rubber, (3) from about 5 parts to about 15 parts of high Tg 3, 4-polyisoprene rubber and (4) of about 5 parts to about 15 parts of a low Tg 3,4-polyisoprene rubber, where the low 3,4-polyisoprene rubber Tg has a glass transition temperature that falls within the range of about -55 ° C to about -5 ° C. 9. A pneumatic tire according to claim 1, characterized in that the rubbery polymer which is co-curable with the high Tg 3,4-polyisoprene is a mixture of natural rubber and high cis-1, 4- rubber. polybutadiene; and wherein the rubber composition comprises (1) from about 20 parts to about 60 parts of natural rubber, (2) from about 10 parts to about 30 parts of high cis-1,4-polybutadiene rubber and ( 3) from about 10 parts to about 30 parts of 3,4-polyisoprene rubber. 10. A pneumatic tire according to claim 1, characterized in that the rubbery polymer which is co-curable with high Tg 3,4-polyisoprene is a mixture of natural rubber, low Tg 3,4-polyisoprene rubber and rubber with a high content of cis-1,4-polybutadiene; wherein the rubber composition comprises (1) from about 20 parts to about 60 parts of natural rubber, (2) from about 10 parts to about 50 parts of high content of cis-1,4-polybutadiene rubber, (3) from about 5 parts to about 15 parts of high Tg 3,4-polyisoprene rubber and (4) from about 5 parts to about 15 parts of low Tg 3,4-polyisoprene rubber; wherein the 3, 4-polyisoprene rubber of low Tg has a glass transition temperature which falls within the range of about -55 ° C to about -5 ° C; wherein the 3, 4-polyisoprene of high Tg has a number average molecular weight that is within the range of about 50,000 to about 150,000; and wherein the high Tg 3, 4-polyisoprene rubber has a glass transition temperature that falls within the range of about 5 ° C to about 20 ° C. SUMMARY OF THE INVENTION This invention discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition comprising from 100 parts by weight rubber (1) of from about 5 parts to about 50 parts of 3, 4-polyisoprene rubber, wherein the 3,4-polyisoprene rubber has (a) a 3,4-isomer content of 75 percent to 95 percent, (b) a 1,2-isomer content from 5 percent to 25 percent, (c) a vitreous state transition temperature from 0 ° C to 25 ° C and (d) a number average molecular weight that falls within the range of 3,000 to 180,000 y (2) ) from about 50 parts to about 95 parts of a rubbery polymer that is co-curable with the 3,4-polyisoprene rubber. The present invention further discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition consisting of 100 parts by weight rubber, (1) of about 20 parts. to about 60 parts of natural rubber, (2) from about 5 parts to about 30 parts of high cis-1,4-polybutadiene rubber, (3) from about 10 parts to about 50 parts of styrene-butadiene rubber and (4) from about 5 parts to about 30 parts of rubber dfr 3,4-polyisoprene, wherein the 3,4-polyisoprene rubber has (a) a 3,4-isomer content of 75 percent at 95 percent. percent, (b) a 1,2-isomer content of 5 percent to 25 percent, (c) a vitreous state transition temperature of 0 ° to 25 ° C, and (d) a number-average molecular weight that it falls within the range of 30,000 to 180,000.