MXPA97001862A - Composite of surface of rolling of lla - Google Patents

Abstract

The present invention discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition comprising (a) a diblock rubber of isoprene-butadiene, the diblock rubber of isoprene-butadiene consists of a butadiene block and an isoprene-butadiene block wherein the butadiene block has a number average molecular weight that falls within the range of about 25,000 to about 350,000, where the isoprene-butadiene block it has a number average molecular weight that is within the range of about 25,000 to about 350,000 where the isoprene-butadiene diblock rubber essentially has a glass transition temperature that falls within the range of about -100øC to about -70 ° C, where the diblock polymer of isoprene-butadiene has a Mooney viscosity ML-4 at 100 ° C which is within the range of about 50 to about 140, and wherein the repeating units derived from isoprene and 1,3-butadiene in the isoprene-butadiene block are in an essentially random order, and (b) a second rubber that is selected from the group consisting of high vinyl polybutadiene rubber, styrene-isoprene-butadiene rubber, styrene-butadiene rubber solution and emulsion styrene-butadiene rubber

Description

"COMPOSITE OF SURFACE OF RIMING OF RIM" BACKGROUND OF THE INVENTION The cost of replacing tires is one of the main expenses found by the transportation industry. The cost and frequency of tire replacement is of course also of concern to most car and light truck owners. In recent years many modifications have been implemented to improve the tread characteristics of the tires. However, improvements in the tread characteristics of the rim have sometimes been achieved by compromising the tire's traction and / or rolling resistance characteristics. In order to reduce the rolling resistance of a tire, rubbers can be used which have a considerable bounce when manufacturing the running surfaces of the rims. The rims manufactured with these rubbers experience less loss of energy during rolling and usually exhibit improved tread characteristics as well. The traditional problem associated with this approach is that the number traction of the rim and the characteristics of resistance to wet skid are compromised. This is because a good rolling resistance that favors low energy loss and good tensile characteristics that favor high energy loss are viscoelastically inconsistent properties. In order to balance these two viscoelastically inconsistent properties, blends of different types of synthetic and natural rubber are normally used on the tread surfaces of the rim. For example, various mixtures of styrene-butadiene rubber and polybutadiene rubber are commonly used as a rubbery material for automotive tire treads. However, these mixtures are not totally satisfactory for all purposes. U.S. Patent No. 4,843,120 discloses that tires having improved performance characteristics can be prepared using rubbery polymers having multiple vitreous state transition temperatures such as rubber for the tread surface. These rubbery polymers having multiple vitreous state transition temperatures exhibit a first glass transition temperature which falls within the range of about -110 ° C to -20 ° C and which exhibits a second glass transition temperature which It falls within the range of approximately -50 ° C to 0 ° C. According to U.S. Patent No. 4,843,120, these polymers are manufactured by polymerizing at least one conjugated diolefin monomer in a first reaction zone, at a temperature and under conditions sufficient to produce a first polymeric segment having a state transition temperature. vitreous which is at -110 ° C and -20 ° C, and subsequently continuing in the polymerization in a second reaction zone at a temperature and under conditions sufficient to produce a second polymeric segment having a glass transition temperature which is between -20 ° C and 20 ° C. These polymerizations are usually catalyzed with an organolithium catalyst and are usually carried out in an inert organic solvent. U.S. Patent No. 5,137,998 discloses a process for preparing a rubbery terpolymer of styrene, isoprene and butadiene, having multiple vitreous state transition temperatures and having an excellent combination of properties for use in manufacturing tire tread surfaces comprising terpolymerize styrene, isoprene and 1,3-butadiene, in an organic solvent at a temperature no greater than about 40 ° C, in the presence of (a) at least one member selected from the group consisting of tripiperidino phosphine oxide and alkali metal alkoxides and (b) an organolithium compound. The American Patent Number 5No. 047,483 discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur-cured rubber composition comprising, based on 100 parts by weight of rubber (phr), (A) of about 10 to about 90 parts by weight of a terpolymer rubber of styrene, isoprene, butadiene (SIBR), and (B) from about 70 percent to about 30 percent by weight of at least one rubber of cis-1, 4-polyisoprene and a cis-1,4-polybutadiene rubber, wherein the SIBR rubber comprises (1) from about 10 percent to about 35 percent by weight of combined styrene, (2) of about 30 percent by weight about 50 percent combined isoprene and (3) about 30 percent to about 40 percent by weight of butadiene combined and is characterized by having a single glass transition temperature (Tg) that stays within e the scale from about -10 ° C to about -40 ° C and, in addition, the combined butadiene structure contains from about 30 percent to about 40 weight percent of 1,2-vinyl units, the isoprene structure combined contains from about 10 percent to about 30 percent of 3,4-units and the sum of the percentage of 1,2-vinyl units of the combined butadiene and the percentage of the 3,4-units of the combined isoprene is within from the scale of about 40 percent to about 70 percent. US Pat. No. 5,272,220 discloses a styrene-isoprene-butadiene rubber which is particularly valuable for use in making truck rim running surfaces exhibiting improved rolling resistance and tread characteristics, the rubber being comprised of units repeating, which are derived from about 5 weight percent to about 20 weight percent styrene, from about 7 weight percent to about 35 weight percent isoprene, and from about 55 weight percent to about 88 weight percent weight percent 1,3-butadiene, wherein the repeating units derived from styrene, isoprene and 1,3-butadiene, are essentially in a random order, wherein from about 25 percent to about 40 percent of the repeating units derived from 1,3-butadiene and are from a cis-microstructure, wherein about 40 percent to about 6 0 percent of the repeating units derived from 1,3-butadiene are from a trans-microstructure, where from about 5 percent to about 25 percent of the repeating units derived from 1,3-butadiene are from a vinyl -microstructure, wherein from about 75 percent to about 90 percent of the repeating units derived from isoprene are of 1, 4-microstructure, wherein from about 10 percent to about 25 percent of the repeat units derived from the Isoprene are from the 3, 4-microstructure, wherein the rubber has a glass transition temperature that falls within the range from about -90 ° C to about -70 ° C, where the rubber has an average molecular weight in number that is within the range of about 150,000 to about 400,000 where the rubber has a weight average molecular weight of about 300,000 to about 800.00 0 and where the rubber has an inhomogeneity that is within the range of about 0.5 to about 1.5. U.S. Patent No. 5,239,009 discloses a process for preparing a rubbery polymer comprising: (a) polymerizing a conjugated diene monomer with a lithium initiator in the substantial absence of polar modifiers at a temperature that falls within the range of about 5 ° C at about 100 ° C in order to produce an active polybutadiene segment having a number average molecular weight that falls within the range of about 25, 000 to approximately 350,000; and (b) using the active polybutadiene segment to initiate the terpolymerization of 1,3-butadiene, isoprene and styrene, wherein the terpolymerization is carried out in the presence of at least one polar modifier at a temperature remaining within the scale from about 5 ° C to about 70 ° C, in order to produce a final segment comprising repeating units derived from 1,3-butadiene, isoprene and styrene, wherein the final segment has an average number-average molecular weight which is within the range of 25,000 to about 350,000. The rubbery polymer made by this process is disclosed as being useful for improving the wet skid resistance and tire traction characteristics without sacrificing the tread or rolling resistance. US Pat. No. 5,061,765 discloses isoprene-butadiene copolymers having high vinyl contents which can be reportedly used to make tires having improved traction, rolling resistance and abrasion resistance. These high vinyl isoprene-butadiene rubbers are synthesized by copolymerizing the 1,3-butadiene monomer and the isoprene monomer in an organic solvent at a temperature that falls within the range of about -10 ° C to about 100 °. C in the presence of a catalyst system consisting of (a) an iron organ compound, (b) an organoaluminum compound, (c) an aromatic chelating amine and (d) a proton compound; wherein the molar ratio of the chelation amine to the iron organ compound is within the range of about 0.1: 1 to about 1: 1, wherein the molar ratio of the organoaluminum compound to the iron organ compound is within the range of about 5. 1 to about 200: 1, and here the molar ratio of the protonic compound to the organoaluminum compound falls within the range of about 0.001: 1 to about 0.2: 1. U.S. Patent No. 5,405,927 discloses an isoprene-butadiene rubber that is particularly valuable for use in making truck tire treads, the rubber consists of repeat units that are derived from about 20 weight percent to about 50. percent isoprene, and from about 50 weight percent to about 80 weight percent 1,3-butadiene, wherein the repeating units derived from isoprene and 1,3-butadiene are essentially in a random order, wherein from about 3 percent to about 10 percent of the repeating units in the rubber are 1, 2-polybutadiene units, wherein from about 50 percent to about 70 percent of the repeating units in the rubber, are units of 1,4-polybutadiene, wherein from about 1 percent to about 4 percent of the repeat units in rubber are units of 3, 4-polyisoprene, wherein from about 25 percent to about 40 percent of the repeating units in the polymer are 1, 4-polyisoprene units, wherein the rubber has a glass transition temperature that remains within the scale from about -90 ° C to about -75 ° C, and wherein the rubber has a Mooney viscosity which falls within the range from about 55 to about 140. US Patent Application Serial No. 08 / 524,666 filed on 8 of September 1995, discloses an isoprene-butadiene diblock rubber having an excellent proprietary combination for use in making automobile rim surfaces, the isoprene-butadiene diblock rubber consists of a butadiene block and an isoprene-butadiene block wherein the butadiene block has a number average molecular weight that is within the range of approximately 25, 000 to about 350,000, wherein the isoprene-butadiene block has a number average molecular weight that falls within the range of about 25,000 to about 350,000, wherein the isoprene-butadiene diblock rubber has a transition temperature of glassy state which is within the range of about -100 ° C to about -70 ° C, wherein the isoprene-butadiene diblock rubber may optionally have a second glass transition temperature which falls within the scale of about -50 ° C to about 0 ° C, wherein the diblock polymer of isoprene-butadiene has a Moonesy viscosity ML-4 at 100 ° C which is within the range of about 50 to about 140 and wherein the repeating units derivatives of isoprene and 1,3-butadiene in the isoprene-butadiene block are essentially in a random order. US Patent Application Serial No. 08 / 524,666 further discloses tire tread compounds which are (1) mixtures of these isoprene-butadiene diblock rubbers with 3,4-polyisoprene rubbers, (2) mixture of these isoprene-butadiene diblock rubbers with rubbers of high content of cis-1,4-polybutadiene and (3) mixtures of these isoprene-butadiene diblock rubbers with natural rubber.

COMPENDIUM OF THE INVENTION By using the isoprene-butadiene diblock polymers of this invention in tire tread surface compounds, the tread characteristics can be improved without compromising attraction or rolling resistance. Since the isoprene-butadiene diblock polymers of this invention do not contain styrene, the cost of raw materials can also be reduced. This is because styrene and other vinyl aromatic monomers are costly relative to the cost of conjugated diene monomers, such as 1,3-butadiene and isoprene. 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 rubber, of (a) from about 30 to about 80 parts of an isoprene-butadiene diblock rubber, the isoprene-butadiene diblock cylinder comprises a butadiene block and an isoprene-butadiene block, wherein the butadiene block has a weight number-average molecular mass ranging from about 25,000 to about 350,000 where the isoprene-butadiene block has a number average molecular weight that falls within the range of about 25,000 to about 350,000 where the isoprene-butadiene diblock rubber has essentially a glass transition temperature that falls within the range of about -100 ° C to about -70 ° C, where the isoprene-butadiene diblock polymer has a Mooney viscosity ML -4 to 100 ° C which is within the range of about 50 to about 140, and wherein the repeating units derived from isoprene and 1,3-butadiene in the isoprene-butadiene block are essentially in a random order; and (b) from about 20 to about 70 parts of a second rubber that is selected from the group consisting of high content vinyl polybutadiene rubber and styrene-isoprene-butadiene rubber. The present invention further discloses 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 the rubber, (a) of about 30 a About 80 parts of an isoprene-butadiene diblock rubber, the isoprene-butadiene diblock rubber comprises a butadiene block and an isoprene-butadiene block, wherein the butadiene block has a number-average molecular weight that falls within from the scale of about 25,000 to about 350,000 where the isoprene-butadiene block has a number average molecular weight that falls within the range of about 25,000 to about 350,000 where the isoprene-butadiene diblock queue has a first temperature of transition of vitreous state that remains within the scale of approximately -100 ° C to approximately -70 C, wherein the isoprene-butadiene diblock rubber has a second glass transition temperature that falls within the range of about -50 ° C to about 0 ° C, where the isoprene-butadiene diblock polymer has a Mooney viscosity ML-4 at 100 ° C which is within the range of about 50 to about 140, and wherein the repeating units derived from isoprene and 1,3-butadiene in the isoprene-butadiene block are essentially in a random order; and (b) from about 20 to about 70 parts of a second rubber that is selected from the group consisting of high content vinyl polybutadiene rubber and styrene-isoprene-butadiene rubber. The present invention also provides an air tire having an outer circumferential running surface wherein the running surface is a sulfur cured rubber composition comprising on the basis of 100 parts by weight of rubber, (a) from about 50 to about 75 parts of an isoprene-butadiene diblock rubber, the isoprene-butadiene diblock rubber consists of a butadiene block and an isoprene-butadiene block, wherein the butadiene block has a number average molecular weight that falls within the range of about 25,000 to about 350,000 where the isoprene-butadiene block has a number average molecular weight that falls within the range of about 25,000 to about 350,000 where the rubber isoprene-butadiene diblock has essentially a glass transition temperature that falls within the range of about -100 ° C to about -70 ° C, where the isoprene-butadiene diblock polymer has a Mooney viscosity ML-4 at 100 ° C which is within the range of about 50 to about 140, and wherein the repeating units derived from isoprene and 1,3-butadiene in the isoprene-butadiene block are essentially in a random order; and (b) from about 25 to about 50 parts of a second rubber that is selected from the group consisting of styrene-butadiene emulsion rubber and styrene-butadiene solution rubber. The present invention further discloses an air tire having an outer circumferential running surface, wherein the running surface is a sulfur-cured rubber composition consisting of 100 parts by weight of the rubber, (a) of about 50 a about 75 parts of an isoprene-butadiene diblock rubber, the isoprene-butadiene diblock rubber being comprised of a butadiene block and an isoprene-butadiene block, wherein the butadiene block has a number average molecular weight which is within the range of about 25,000 to about 350,000 where the isoprene-butadiene block has a number average molecular weight that falls within the range of about 25,000 to about 350,000 where the isoprene-butadiene diblock rubber has a first transition temperature of vitreous state that is within the range of approximately -100 ° C to approximately at -70 ° C, wherein the diblock rubber of isoprene-butadiene has a second glass transition temperature which falls within the range from about -50 ° C to about 0 ° C, wherein the diblock polymer of isoprene-butadiene has a viscosity of Mooney ML-4 at 100 ° C which falls within the range of about 50 to about 140, and wherein the repeating units derived from isoprene and 1,3-butadiene in the isoprene-block butadiene are in an essentially random order; and (b) from about 25 to about 50 parts of a second rubber that is selected from the group consisting of styrene-butadiene emulsion rubber, styrene-butadiene rubber solution.

DETAILED DESCRIPTION OF THE INVENTION The isoprene-butadiene diblock rubber (IBR) used in the compounds of this invention is synthesized by solution polymerization. In the first step of the solution polymerization process, the 1,3-butadiene monomer is polymerized to a molecular weight that falls within the range of about 25,000 to about 350,000. The polymerization is carried out in an inert organic medium using a lithium catalyst. This polymerization step is carried out without using a polar modifier. It is important to carry out this polymerization step in the absence of significant amounts of polar modifiers, to achieve the desired microstructure and transition temperature of vitreous state. For example, repeating units derived from 1,3-butadiene made in the first polymerization step will have a low vinyl content microstructure (about 6 percent to about 10 percent vinyl). The polybutadiene block made in this step will also have a low vitreous state transition temperature that falls within the range of about -100 ° C to about -70 ° C. The inert organic medium that is used as the solvent will typically be a hydrocarbon which is liquid at ambient temperatures which may be one or more of the aromatic, paraffinic or cycloparaffinic compounds. These solvents will normally contain from 4 to 10 carbon atoms per molecule and will be liquid under the conditions of polymerization. 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 the organolithium compounds. Preferred organolithium compounds can be represented by the formula R-Li, wherein R represents a hydrocarbyl radical containing from about 20 carbomn atoms. Generally, these monofunctional organolithium compounds will contain from 1 to about 10 carbon atoms. Some representative examples of organolithium compounds that may be employed include methyl lithium, ethyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, n-octyl lithium, tert-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. Organomonolithium compounds such as alkyl lithium compounds and aryl lithium compounds are usually employed. Some representative examples of preferred organomono-lithium compounds that can be used include ethyl lithium, isopropyl lithium, n-butyllithium, sec-butyllithium, nor al-hexyl lithium, tert-octyllithium, phenyllithium. , 2-naphthyl-lithium, 4-phenyl-lithium, 4-phenylbutyl-lithium, cyclohexyl-lithium and the like. Normal-butyl lithium and sec-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 isoprene-butadiene diblock rubber being synthesized. As a general rule, in all anionic polymerizations, the molecular weight (Mooney viscosity) of the polymer produced is inversely proportional to the amount of the catalyst used. An amount of the organolithium initiator will be selected to result in the production of an isoprene-butadiene diblock rubber having a Mooney viscosity that falls within the range of about 50 to about 140. As a general rule, about 0.01 phm (parts per hundred parts by weight of monomer) will be used at 1 phm of the lithium catalyst. In most cases, 0.01 phm to 0.1 phm of the lithium catalyst will be used, being preferable to use 0.025 phm to 0.07 phm of the lithium catalyst. Typically, about 5 weight percent to about 35 weight percent of the conjugated diene monomer will be charged to the polymerization medium (based on the total weight of the polymerization medium including the organic solvent and the monomers). In most cases, it will be preferred that the polymerization medium contain from about 10 weight percent to about 30 weight percent monomers. It is typically particularly preferred that the polymerization medium contain from about 20 weight percent to about 25 weight percent monomers. The 1,3-butadiene will polymerize at a temperature that falls within the range of about 5 ° C to about 100 ° C. The polymerization temperature will preferably be within the range of about 40 ° C to about 90 ° C in order to achieve the desired microstructure for the block segment. Especially preferred are temperatures "within the range of about 60 ° C to about 80 ° C. The microstructure of the polybutadiene block segment being prepared depends to some degree on the polymerization temperature. The process is allowed to continue until essentially all of the 1,3-butadiene monomer has been exhausted In other words, the polymerization is allowed to proceed to completion, since a lithium catalyst is used to polymerize the monomer of 1,3-butadiene. -butadiene, a block segment of active polybutadiene is produced.The active polybutadiene segment synthesized will have a number average molecular weight that falls within the range of about 25,000 to about 350,000.The active polybutadiene segment will preferably have a weight molecular weight that falls within the range of approximately 50,000 to approximately 200,000 and higher will have a number average molecular weight that falls within the range of about 70,000 to about 150,000. The second step in the solution polymerization process involves using the active polybutadiene block segment to inhibit the copolymerization of the additional 1,3-butadiene monomer and isoprene monomer. This copolymerization is carried out in the presence of at least one polar modifier. 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-ethylmorpholine, 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 may 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-1,2,3-triethoxybenzene, 5-methyl-1,2,3-trimethoxybenzene and 5-propyl- 1,2,3-trimethoxybenzene. Some representative examples of the 1,2,4-trialkoxybenzenes that may 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, dipyrrolidinoethane, 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 of U.S. Patent Number 4,696,986 are hereby incorporated by reference in their entirety. The microstructure of the repeating units that are derived from conjugated diene monomers is a function of the polymerization temperature and the amount of the polar modifier present. For example, in the polymerization of 1,3-butadiene, it is known that higher temperatures result in lower vinyl contents (lower levels of 1/2-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 polymer segment being synthesized. In the second step of the solution polymerization process, the final polymer segment is synthesized. This is typically carried out by adding the additional polar modifier, 1,3-butadiene and isoprene to the medium containing the active polydiene segment made in the first step. This is achieved by first adding the modifier to the medium containing the active polybutadiene block and subsequently adding the isoprene and the additional 1,3-butadiene. The additional solvent may also be added if necessary to maintain the total amount of monomers and polymer within the polymerization medium within the range of about 5 percent to about 35 percent by weight (based on the total weight of the polymerization medium including monomers, polymer and solvent). It is desirable to add a sufficient amount of the solvent to keep the total amount of the polymer and the monomers within the range of about 10 percent to about 30 percent by weight and preferably within the range of about 20 to about 25 percent by weight. weight, based on the total weight of the reaction medium. The repeating units in the final segment are, of course, derived from 1,3-butadiene and isoprene. The isoprene-butadiene block will typically consist of about 10 weight percent to about 60 weight percent repeating units that are derived from isoprene, and from about 40 weight percent to about 90 weight percent units. repeat that are derived from 1,3-butadiene. It is usually preferred that the final segment contain from about 20 percent to about 50 percent by weight of repeating units that are derived from isoprene and from about 50 percent by weight to about 80 percent by weight of repeating units that are derive from 1,3-butadiene. It is especially preferred that the final segment contains from about 30 percent to about 45 percent repeating units that are derived from isoprene, and from about 55 percent by weight to about 70 percent by weight of units that are derived from 1. , 3-butadiene. In the second segment, the distribution of repeating units derived from isoprene and butadiene is essentially random. The term "essentially random" as used herein means that it lacks a defined pattern. However, it will be understood that the concentration of the repeating units derived from isoprene and butadiene can vary to some degree from one end of the block to the other. The repeating units that are derived from isoprene or 1,3-butadiene differ from the monomer from which they were derived since a double bond was comsumed by the polymerization reaction. The copolymerization of butadiene and isoprene which is carried out in the second step of this process can be carried out at the same temperature that is used in the synthesis of the first block (the polybutadiene block). In most cases, the second polymerization step will be carried out at the same temperature that is used in the first polymerization step. However, the copolymerization will be carried out at a lower temperature which is within the range of about 5 ° C to about 70 ° C if one wishes to achieve a higher glass transition temperature and higher vinyl content. for the isoprene-butadiene block. The second polymerization step is usually allowed to continue until the monomers are exhausted. In other words, the copolymerization of 1,3-butadiene and isoprene is allowed to continue until the polymerization reaction is complete. A sufficient amount of monomers will be used to achieve a number-average molecular weight for the final segment that falls within the range of about 25,000 to about 350,000. It is usually preferred that the second segment have a number average molecular weight that is within the range of 50,000 to 200,000 with the number average molecular weight within the range of 70,000 to 150.00 being especially preferred. The ratio of the number average molecular weight of the first segment to the number average molecular weight of the final segment will typically be within the range of about 25/75 to about 75/25. This relationship has an important role in determining the morphology of the polymer and will usually be within the range of about 35/65 to about 65/35. The Mooney viscosity ML-4 at 100 ° C of the segmented rubbery polymers will generally be greater than about 50 and less than about 140. It is usually preferred that the Mooney viscosity ML-4 at 100 ° C of the rubbery diblock polymer falls within the scale from 80 to 135, with Mooney viscosities ML-4 within the range of 100 ° to 130 °, being especially preferred for rubbers diluted with oil before dilution with oil. After the copolymerization is complete, the isoprene-butadiene diblock rubber can be recovered from the organic solvent. The diblock rubber can be recovered from the organic solvent and the residue by any means, such as decanting, filtration and centrifugation. It is often desirable to precipitate the isoprene-butadiene diblock rubber from the organic solvent by the addition of lower alcohols containing from about 1 to about 4 carbon atoms, to the polymer solution. The lower alcohols suitable for the precipitation of the diblock rubber from the polymer cement include methanol, ethanol, isopropyl alcohol, normal propyl alcohol and tertiary butyl alcohol. The use of the lower alcohols to precipitate the isoprene-butadiene diblock rubber from the polymer segment also "kills or inactivates" the active polymer, inactivating the lithium end groups. After the diblock rubber is recovered from the solution, steam scrubbing can be employed to reduce the level of volatile organic compounds in the diblock rubber. There are valuable benefits associated with using the isoprene-butadiene diblock rubbers of this invention to make the compounds of the tread surface of the rim. The rolling surface compounds of the rim can be made using these diblock rubbers without the need to mix in the same additional rubbers. However, in many cases, it will be desirable to mix the isoprene-butadiene diblock rubber with one or more additional rubbers to achieve the desired performance characteristics of the tire tread surface compound. The isoprene-butadiene diblock rubbers of this invention can be stirred using conventional ingredients and standard techniques. For example, isoprene-butadiene diblock rubbers will typically be mixed with carbon black and / or silica, sulfur, additional fillers or fillers, accelerators, oils, waxes, scorch inhibiting agents, coupling agents and processing aids. In most cases, the isoprene-butadiene diblock rubber will be stirred with the sulfur and / or a sulfur-containing compound, at least one filler or filler, at least one accelerator, at least one antidegradant , at least one processing oil, zinc oxide, optionally a tackifying resin, optionally a reinforcing resin, optionally one or more fatty acids, optionally a peptide and optionally one or more singe inhibiting agents. These mixtures will typically contain from about 0.5 to 5 phr (parts per hundred parts of rubber by weight) of sulfur and / or a sulfur-containing compound of from 1 phr to 2.5 phr being preferred. It may be desirable to use insoluble sulfur in cases where blooming is a problem. Typically, 10 to 150 phr of at least one filler or filler material with 30 to 80 phr will be used in the mixture being the preferred amount. In most cases, at least a certain amount of carbon black will be used in the filling or loading material. The filling or loading material can of course completely comprise 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 may be included in the filler or filler material to reduce the cost. The mixture will also typically include 0.1 to 2.5 phr of at least one accelerator, with an amount of 0.2 to 1.5 phr being preferred. Antidegradants, such as antioxidants and antiozonants, will generally 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, in general, be included in the mixture in amounts ranging from 2 to 100 phr, with amounts ranging from 5 to 50 phr being preferred. The IBR-containing mixtures of this invention will also typically contain from 0.5 to 10 phr of zinc oxide, with an amount of from 1 to 5 phr being preferred, these mixtures optionally containing from 0 to 10 phr of tackifying resins, from 0 to 10 phr of reinforcement resins, 1 to 10 phr of fatty acids, 2 to 2.5 phr of peptizizadores and 0 to 1 phr of singe inhibiting agents. To fully understand the total advantages of the blends of this invention, silica may be included in the tread surface rubber formulation. Processing of the rubber mixture is normally carried out in the presence of an organosilicon compound containing sulfur for maximum benefits. Examples of organosilicon compounds containing appropriate sulfur are those of the formula: Z-Alc-Sn-Alc-Z (I! wherein Z is selected from the group consisting of: RJ RJ Yes Rl Yes R2 Yes - R2 R2 R2 R2 wherein R 1 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 where Ale is a divalent hydrocarbon of 1 to 18 carbon atoms and n is an integer from 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 (trimethoxysilylpropyl) tetrasulfide, 3, 3'-bis (trimethoxysilylpropyl) octasulfide, 3,3'-bis (trimethoxysilylpropyl) tetrasulfide, 2,2'-bis (tritoxysilylethyl) tetrasulfide, 3,3'-bis (trimethoxysilylpropyl) trisulphide, 3,3'-bis (triethoxysilylpropyl) trisulfide, 3,3'-bis (tributoxysilylpropyl) disulfide, 3,3 * -bis (trimethoxysilylpropyl) 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 (ethoxy diethoxy silyl ethyl) tetrasulfide, 2,2' -bis (tripropoxysilylethyl) pentas ulfuro, 3,3 '-bis (triciclonexoxisililpropyl) tetrasulfide, 3,3' -bis (tricyclopentoxysilylpropyl) trisulfide, 2,2'-bis (tri-2"-methylcyclohexoxysilylethyl) tetrasulfide, bis (trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy 3-propoxysilyl -dietoxybutoxy-silylpropyltetrasulfide, 2,2'-bis (dimethylmethoxysilylethyl) disulphide, 2,2'-bis (dimethyl sec.butoxysilylethyl) trisulfide, 3, 3'-bis (methyl butylethoxysilylpropyl) tetrasulfide, 3,3'- bis (di-t-butylmethoxysilylpropyl) tetrasulfide, 2,2'-bis (phenylmethylmethoxysilylethyl) trisulfide, 3,3'-bis (diphenyl isopropoxysilylpropyl) tetrasulfide, 3,3'-bis (diphenylcyclohexoxysilylpropyl) 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 diethoxypropyl) disulfide, 3,3'-bis (butyl dimethoxy) xysilylpropyl) trisulfide, 3,3'-bis (phenyl-dimethoxysilylpropyl) tetrasulfide, 3-phenyl-ethoxybutoxysilyl-3'-trimethoxysilylpropyl tetrasulfide, 4,4'-bis (trimethoxysilylbutyl) tetrasulfide, 6,6'-bis (triethoxysilylhexyl) tetrasulfide, , 12'-bis (triisopropoxysilyl dodecyl) 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, and 3,3'-bis (dimethoxyphenylsilyl-2-methylpropyl) disulfide.

The preferred sulfur-containing organosilicon compounds are 3, 3 'bis (trimethoxy or triethoxy silylpropyl) sulfides. The especially preferred compound is 3, 3'-bis (triethoxysilylpropyl) tetrasulfide. Therefore, as for formula I, preferably Z is R2 - Yes - R2 R2 wherein R2 is an alkoxy of 2 to 4 carbon atoms, with 2 carbon atoms being particularly preferred; Ale 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-contemporaneous silicon-containing compound of the formula I in the rubber composition will vary depending on the level of silica used. Generally speaking, the amount of the compound of the formula I will vary from 0.01 to about 1.0 part by weight per part by weight of silica. Preferably, the amount will vary from about 0.02 to about 0.4 parts by weight per part by weight of the silica. Particularly preferably, 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 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 tear strength. The filler or filler or silica 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 50 phr to about 120 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 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 carbon black, namely, premixing with a carbon black prior to the addition of the rubber composition, and this carbon black must be included in the amount of carbon black. carbon previously mentioned 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 about 30 phr, but preferably is about 45 to about 130 phr. The silicon pigments commonly used in rubber blending applications can be used as the silica in this invention including the pyrogenic and precipitated silicon pigments (silica) even though the precipitated silicas are preferred. The preferred silicon pigments used in this invention are precipitated silicas such as, for example, those obtained by the acidification of the soluble silicate, eg, sodium silicate. These silicas could be characterized, for example, because they have a BET surface area, as measured using nitrogen gas, preferably within the range of 40 to about 600, and more usually within 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, Volume 60, Page 304 (1930). The silica can also be characterized typically having a dibutylphthalate absorption value (DBP) within the range of about 100 to about 400 and more usually about 150 to about 300. The silica could be expected to have an average final particle size, per example, within the range of 0.01 to 0.05 micron, as determined by an electron microscope even though the silica particles may be of an even smaller or possibly larger size. Various silicas commercially obtainable for use in this invention may be taken into account, such as only as an example herein and without limitation, the silicas commercially available from PPG Industries under the trademark Hi-Sil with designations 210, 243, etc .; silicas obtainable from Rhone-Poulenc with, for example, designations of Z1165MP and silicas obtainable from Degussa AG with, for example, designations VN2 and VN3. The tire tread surface formulations can include silica and an organosilicon compound can be blended using a thermomechanical mixing technique to achieve a better balance of the performance characteristics of the tread compound, for example traction, tread and rolling resistance characteristics. On the other hand, the mixing of the rubber formulation of the tire tread surface can be achieved by conventional methods known to those skilled in the art for mixing rubber. For example, the ingredients are typically mixed in at least two stages, namely, at least one non-productive stage followed by a productive mixing stage. 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 lower temperature or final temperature than the temperature (s) of mixed, than the previous non-productive mixing stage (s). The rubber, silica and organosilicon containing sulfur and 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 art of rubber mixing. In typical non-productive mixing procedures, mixing is carried out through a total mixing period of only one to three minutes with the rubber mixture being discharged from the mixing equipment at a temperature not higher than 160 ° C. When silica and a coupling agent are present, the maximum discharge temperature of the mixing step is normally no greater than about 145 ° C. For best results, the sulfur-vulcanizable rubber composition containing the sulfur-containing organosilicon compound, the vulcanizable rubber generally at least part of the silica, must undergo a thermomechanical mixing step. The thermomechanical mixing step usually comprises the mechanical treatment in a mixer, a mill or an 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 thermomechanical treatment or work varies as a function of the operating conditions and the volume and nature of the components. For example, the treatment or thermomechanical work can be through a duration of time that is within the range of about 1 minute to about 20 minutes. Normally it will be preferred that the rubber reaches a temperature that is within the range of about 145 ° C to about 180 ° C and that it is maintained at that temperature for a period of time remaining within the range of about 2 minutes to about 10 minutes. minutes It will normally be especially preferred that the rubber reaches a temperature that is within the range of about 155 ° C to about 170 ° C and that it is maintained at that temperature for a period of time remaining within the range of about four minutes to about eight minutes.

The isoprene-butadiene diblock rubber containing the tire tread surface compounds of this invention can be used on rim treads together with regular tire fabrication techniques. The tires are made using normal procedures with isoprene-butadiene diblock rubber simply by being replaced by the rubber compounds typically used as the rubber on the tread surface. After the tire has been made with the isoprene-butadiene diblock rubber containing the mixture, it can be vulcanized using a normal tire cure cycle. The rims manufactured in accordance with this invention can be cured through a wide temperature range. However, it is generally preferred that the tires of the invention be cured at a temperature ranging from about 132 ° C to about 175 ° C. It is more typical that the tires of this invention are cured at a temperature ranging from 143 ° C to about 165 ° C. Generally, it is preferred that the cure cycle used to vulcanize the tires of this invention have a duration of about 8 to about 20 minutes with a cure cycle of about 10 to about 18 minutes being especially preferred.

Using the isoprene-butadiene diblock polymers of this invention in the tire tread surface compounds, the characteristics of the tread can be improved without compromising traction or rolling resistance. Since the isoprene-butadiene diblock polymers of this invention do not contain styrene, the cost of raw materials can also be reduced. This is because the monomers of styrene and other vinyl aromatic monomers are costly relative to the cost of the conjugated diene monomers, such as 1,3-butadiene and isoprene. The isoprene-butadiene diblock rubbers of this invention can be advantageously used in both automotive and truck tire tread surfaces. As a general rule, isoprene-butadiene diblock rubber used for truck tire compounds will have a single glass transition temperature that falls within the range of about -100 ° C to about -70 ° C. On the other hand, the isoprene-butadiene diblock rubbers which are used to make the automotive tire tread surface compounds will usually have a first glass transition temperature which falls within the range of about -100 ° C to about -70 ° C, and a second glass transition temperature that falls within the range of about -50 ° C to about 0 ° C. Isoprene-butadiene diblock rubber having two glass transition temperatures can be blended with natural rubber to produce rolling surface compounds for passenger car tires exhibiting remarkable rolling resistance, traction and tread characteristics. The use of natural rubber in these blends leads to improved processability. These blends will typically contain from about 5 percent to about 30 percent by weight of natural rubber and about 70 percent to about 95 percent of a diblock rubber of isoprene-butadiene having two glass transition temperatures. These blends will preferably contain from about 20 weight percent to about 30 weight percent natural rubber, and from about 70 weight percent to about 80 weight percent of the isoprene-butadiene diblock rubber. High-performance tires that exhibit exceptional traction characteristics but comprised of a tread can be prepared by mixing the isoprene-butadiene diblock rubber that has at least two glass transition temperatures with a solution or emulsion of styrene-butadiene rubber (SBR). These mixtures will typically contain from about 50 weight percent to about 75 weight percent of the isoprene-butadiene diblock polymer and from about 25 weight percent to about 50 weight percent of the styrene-butadiene rubber solution or emulsion. It is typically preferred that these mixtures contain from about 55 weight percent to about 65 weight percent of the isoprene-butadiene diblock polymer and from about 35 weight percent to about 45 weight percent of the styrene-butadiene rubber by solution or emulsion. In cases where the tread is of greater importance than the traction, from about 5 percent to about 30 weight percent of a high content of cis-1,4-polybutadiene mixed with from about 70 percent to about 95 percent by weight of the isoprene-butadiene diblock rubber can be blended it has two vitreous state transition temperatures. These mixtures preferably will contain from about 20 weight percent to about 30 weight percent of the high cis-1,4-polybutadiene rubber and from about 70 weight percent to about 80 weight percent of the rubber of the rubber. isoprene-butadiene diblock. In another scenario, the isoprene-butadiene rubber of this invention having essentially a glass transition temperature can be used to improve the traction, the tread and the rolling resistance of automotive tires made therewith including in the 3,4-polyisoprene mixture. This mixture will typically contain from about 5 percent to about 30 weight percent of 3,4-polyisoprene and from about 70 percent to about 95 percent by weight of the isoprene-butadiene rubber having essentially a state transition temperature vitreous that remains within the scale of approximately -100 ° C to approximately -70 ° C. These mixtures will normally contain from about 20 weight percent to about 30 weight percent of the 3,4-polyisoprene and about 70 weight percent of about 80 weight percent of the isoprene-butadiene diblock rubber. The 3, 4-polyisoprene used in these mixtures can be synthesized by the technique disclosed in US Pat. No. 5,239,023. This technique for producing 3,4-polyisoprene involves: (1) adding 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 a state oxidation of +3, (b) a partially hydrolyzed organoaluminum compound, which was prepared by adding a protonic compound selected from the group consisting of water, alcohols and carboxylic acids to the organoaluminum compound, and (c) an aromatic amine of chelation, wherein the molar ratio of the chelation amine to the organoiron compound is within the range of about 0.1: 1 to about 1: 1, wherein the molar ratio of the organoaluminum compound to the organoiron compound is within the scale from about 5: 1 to about 200: 1, and wherein the molar ratio of the protonic compound to the organoaluminum compound falls within the approximate scale and 0.001: 1 to about 0.2: 1 to a polymerization medium containing an isprene monomer and an organic solvent, and (2) allowing the isoprene monomer to polymerize at a temperature that falls within the range of about -10. ° C at approximately 100 ° C. Another representative example of the 3,4-polyisoprene rubber that can be employed in the automotive tire tread surface compounds of this invention is sold by Huels AG under the trade name Vestogrip® A6001. Tire rim tread compounds are typically prepared by mixing from about 5 percent to about 30 percent by weight of natural rubber and / or rubber with high content of cis-1,4-polybutadiene with about 70 percent by weight to about 95 weight percent of the single glass transition temperature version of the isoprene-butadiene diblock rubber. The high cis-1,4-polybutadiene content rubber that is suitable for use in these mixtures can be made by the process described in Canadian Patent Number 1,236,648. The high content of 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 Budene® 1208 a polybutadiene rubber. The running surfaces for high performance tires can also be made by mixing from about 30 weight percent to about 80 weight percent of the isoprene-butadiene diblock rubber with about 20 weight percent to about 70 weight percent of the high vinyl polybutadiene content rubber having a vinyl content of 60 percent to about 90 percent. Better traction characteristics can usually be obtained by incorporating a higher level of the high vinyl polybutadiene rubber in the mixture. Accordingly, it is usually preferred to mix from about 50 weight percent to about 70 weight percent of the isoprene-butadiene diblock rubber with from about 30 weight percent to about 50 weight percent of high polybutadiene rubber of vinyl. It is generally especially preferred to mix from about 55 weight percent to about 65 weight percent of the isoprene-butadiene diblock rubber with about 35 weight percent to about 45 weight percent of the high rubber content. vinyl polybutadiene. The high vinyl polybutadiene rubber will typically have a vinyl content that is within the range of about 60 percent to about 80 percent. Rolling surfaces for high-performance tires can also be made by mixing medium-content polybutadiene rubber with isoprene-butadiene rubber in cases where better rolling resistance is demanded. The medium content polybutadiene vinyl rubber used in these cases, has a vinyl content that falls within the range of approximately 30 percent to 59 percent. The vinyl polybutadiene medium content rubber preferably has a vinyl content that is within the range of about 40 percent to about 50 percent. For example, running surfaces for high performance tires can be made by mixing from about 30 weight percent to about 80 weight percent of isoprene-butadiene diblock rubber with from about 20 percent to about 70 percent by weight. weight of medium content rubber of vinyl polybutadiene. It is usually preferred to mix from about 50 weight percent to about 70 weight percent of the isoprene-butadiene diblock rubber with from about 30 weight percent to about 50 weight percent of the medium content rubber of vinyl polybutadiene. . It is generally especially preferred to mix from about 55 weight percent to 65 weight percent of the isoprene-butadiene diblock rubber with from about 35 weight percent to about 45 weight percent of the medium content polybutadiene rubber of vinyl.

Rolling surfaces for high-performance automobile tires can also be made by mixing styrene-isoprene-butadiene rubber (SIBR) with isoprene-butadiene diblock rubber. These mixtures will typically contain from 30 weight percent to about 80 weight percent of the isoprene-butadiene diblock rubber and from about 20 percent to about 70 weight percent of SIBR. It is usually preferred to mix from about 50 weight percent to about 70 weight percent of the isoprene-butadiene diblock rubber with from about 30 weight percent to about 50 weight percent SIBR. It is generally especially preferred to mix about 55 weight percent to about 65 weight percent of the isoprene-butadiene diblock rubber with from about 35 weight percent to about 45 weight percent of the SIBR. The SIBR used in these tire tread compounds will typically have a glass transition temperature that falls within the range of about -40 ° C to about -20 ° C. For the purposes of this patent application, the microstructures of the polymer are determined by nuclear magnetic resonance (NMR) spectroscopy. The glass transition temperature (Tg) temperatures are determined by differential scanning calorimetry at a heating rate of 10 ° C per minute, and the molecular weights are determined by gel permeation chromatography (GPC). This invention is illustrated by the following examples which are for the purpose of illustration only and should not be construed as limiting the scope of the invention and the manner in which it may be carried out. Unless specifically indicated otherwise, all parts and percentages are given by weight.

Examples 1-3 In this series of experiments, rubberized isoprene-butadiene diblock elastomers were prepared with a low Tg / high Tg, using the techniques of this invention. The rubbers synthesized in this series of experiments were comprised of a first segment consisting of repeating units derived from 1,3-butadiene and a second segment consisting of repeating units derived from isoprene and 1,3-butadiene . The diblock polymers prepared in this series of experiments were synthesized in a 3.8 liter capacity reactor, a batch or intermittent polymerization reactor. In the process used, 509 grams of a premix solution containing 19.6 percent of a 1,3-butadiene monomer in hexane was charged into the polymerization reactor. Polymerization is initiated by the addition of 2.1 milliliters of a 1.02 M solution of n-butyllithium (0.15 milliliter of which 2.1 milliliters of n-butyl lithium were used to clean the impurities contained in the premix). The reactor was maintained at a temperature of about 65 ° C until an essentially complete conversion had been achieved. At this point, 7.4 milliliters of a 1.05 M solution of ethyl tetrahydrofurfuryl ether (TEE) in hexane were added to the reactor. Then, 1,500 grams of a wash pre-mix solution containing 19.95 percent isoprene and 1,3-butadiene in hexane were added. The premixed monomer solution contained an isoprene ratio in 1,3-butadiene of 50:50. The polymerization was continued at 65 ° C until an essentially complete conversion was achieved. 3 milliliters of a 1M ethanol solution (in hexane) was added to the reactor to stop the polymerization and the polymer was removed from the reactor and stabilized with a phm of an antioxidant. After evaporating the hexane, the resulting polymer was dried in a vacuum oven at 50 ° C. The ratio of the two segments in this polymer was 25:75. The diblock rubbers with other segment ratios were prepared in a similar manner and are shown in Table I. The three diblock rubbers synthesized in this series of experiments had two vitreous state transition temperatures that fall within the scale of approximately - 94 ° C to about -95 ° C, and about -23 ° C and -24 ° C. The microstructure of the diblock rubbers is also shown in Table I.

Table I Ex Ratio Tg ML-4 1,2- 1,4- 1,2- 3,4- 1,4- Seg- (° C) PBd PBd Pl Pl Pl :75 -94, -24 100 30 32 28 2 50:50 -95, -23 86 21 52 2 19 6 3 75:25 -94, -23 106 14 74 Examples 4-6 The procedure described in Examples 1 to 3 was used in these examples with the exception that the ratio of isoprene to 1,3-butadiene in the premix of the second monomer was changed from 50:50 to 30:70 and no TEE modifier was used to complete the polymerization of the monomers for the second segment of the diblock rubbers. The three diblock rubbers synthesized in this series of experiments presented only a glass transition temperature that remained within -89 ° C and -94 ° C. The Tg, Mooney viscosities ML-4 at 100 ° C, and microstructures of the resulting diblock rubbers are listed in Table II.

Table II Ex Ratio Tg ML-4 1,2- 1,4- 1,2- 3,4- 1,4- Seg- (° C) PBd PBd Pl Pl Pl :75 -89 54 69 23 50:50 -90 53 7 77 0 1 15 6 75:25 -94 51 8 83 Example 7 The 50/50 diblock of PBD- (30/70) IBR prepared in this experiment was synthesized in a continuous system of two reactors (20 liters for the first reactor and 40 liters for the second reactor) at 90 ° C. A premix containing 14 percent 1,3-butadiene in hexane in a first polymerization reactor was charged continuously at a rate of 150 grams per minute. Polymerization was started by adding a 0.207 M solution of n-butyllithium in the first reactor at a rate of 0.32 gram per minute. The polymerization medium was pushed continuously above the first reactor into the second reactor where the second premixed monomer mixture was added at a rate of 150 grams per minute. The second premixed monomer solution contained a ratio of isoprene to 1,3-butadiene of 30:70 and had a total monomer concentration of 14 percent in hexane. The temperature of the second reactor was also maintained at 90 ° C. The residence time for both reactors was graduated to 1.5 hours. The average monomer conversions were determined to be 94 percent for the first reactor and 97 percent for the second reactor.

The polymerization medium was then pushed continuously over a holding tank containing isopropanol (as a retainer) and an antioxidant. The resulting polymer cement was then steam stripped and the recovered diblock rubber was dried in a vacuum oven at a temperature of 50 ° C. The polymer was determined to have a glass transition temperature at 89 ° C and that it had a Mooney viscosity ML-4 at 100 ° C of 73. It was also determined that it had a microstructure containing 10 percent units of 1, 2-polybutadiene, 73 percent 1,4-polybutadiene units, 15 percent 1,4-polyisoprene units and 2 percent 1,2-polyisoprene units.

Examples 8-9 The procedure described in Example 7 was used in these experiments to sinter the low Tg / high Tg diblock of IBR-IBRs except that the first premix solution was changed from 1,3-butadiene to a mixture of isoprene and 1.3. -butadiene and also mixed modifiers, N, N, N ', N'-tetramethylethylene (TMEDA) / sodium-t-amylate (STA) was charged to the second reactor in TMEDA at STA and at a molar ratio of n-butyl-lithium 3: 0.5: 1. The two diblock rubbers prepared in this series of experiments exhibited two glass transition temperatures that were within the range of about -77 ° C to about -83 ° C and about -15 ° C to -23 ° C. The compositions of each segment in these diblock rubbers and their glass transition temperatures, Mooney viscosities ML-4 at 100 ° C and microstructures are shown in Table III: Table III Ej Ratio Composition Tg of sec- First Second (° C) mentioned Segment Isop / Bd Isop / Bd 50:50 30/70 30/70 -83, -23 50:50 50/50 50/50 -77, -15 Table III (continued) Ex Mooney 1,2-PBd 1,4-PBD 1,2-PI 3,4-PI 1,4-P- 70 30 44 0 8 18 51 21 30 4 17 28 Examples 10-14 The isoprene-butadiene diblock rubbers made in Examples 1 and 6 were then stirred using a normal rim rolling surface test formulation and compared with the rim rolling surface formulations made with styrene-butadiene rubber by solution, styrene-isoprene-butadiene rubber and a mixture of 50 percent / 50 percent natural rubber and styrene / butadiene rubber. The tire tread test formulations were made by mixing 100 parts of the rubber being tested with 45 parts of carbon black, 9 parts of the process oil, 3 parts of stearic acid, 3 parts of zinc oxide, 1 part of microcrystalline wax, 0.5 part of paraffin wax, 1 part of mixed antioxidant of aryl-p-phenylenediamine, 2 parts of N- (1,3-dimethyl-butyl) -N '-phenyl-p-phenylene diamine , 0.8 part of benzothiazole-2-sulfenamide of N-oxydiethylene, 0.4 part of diphenyl guanidine and 1.6 parts of sulfur. In Example 10, the isoprene-butadiene diblock rubber made in Example 1 was included in the formulation and, Example 11, the isoprene-butadiene diblock rubber made in Example 2 was included in the formulation. Examples 12 to 14 were carried out as comparison examples and included styrene-butadiene rubber, styrene-isoprene-butadiene rubber and a mixture of 50 percent / 50 percent natural rubber and styrene-butadiene rubber, respectively , like the rubber component. The physical properties of the mixed tire tread surface formulations are disclosed in Table IV.

Table IV Physical Properties of the Compound Example 10 11 12 13 14 Rubber Component IBR IBR SBR SIBR NR / SBR Rheometer, 150 ° C ML, dNm 4.4 3.2 4.0 2.7 2.6 MH, dNm 19.8 21.6 22.8 17.8 15.8 tsl, min. 5.7 5.7 9.1 7.7 5.9 T25, min. 8.4 8.6 12.5 10.4 7.7 T90, min. 16.9 13.6 20.3 18.8 14.7 Voltage-Deformation, 18 '/ 150 ° C Module at 100%, MPa 2.0 2.4 2.1 1.8 1.8 Module at 300%, MPa 9.4 9.3 8.2 8.8 9.0 Resistance to Break, MPa 16.4 11.7 17.0 16.1 19.9 Elongation at Break, 473% 380% 558% 515% 554% Rebound Bounce at 23 ° C 36% 64% 52% 31% 59% Bounce at 100 ° C 65% 711 63% 64% 66% Abrasion of DIN, cc1 126 28 71 179 123 Autovibron, 11 Hz tan delta at 0 ° C .392 .076 .117 .368 .163 tan delta at 60 ° C .065 .048 .096 .100 .084 1 Reported in cubic centimeters of volume loss Table IV shows that the isoprene-butadiene diblock rubbers of this invention exhibit low tan delta values at 60 ° C while exhibiting very high tan delta values at 0 ° C. . Low tan delta values at 60 ° C are indicative of good rolling resistance when incorporated into tire treads and high tan delta values at 0 ° C are indicative of good traction characteristics. Accordingly, the rim rolling surfaces can be made with the isoprene-butadiene diblock rubbers of this invention which have both improved traction characteristics and rolling resistance. Example 10 illustrates an excellent compound for tire tread surface for automobile rims that will provide remarkable traction, tread surface durability and rolling resistance. This is because it exhibits a tan delta at 0 ° C. greater than 0.35 while exhibiting a tan delta at 60 ° C of less than 0.070. These compounds would of course be highly desirable in high performance tires. These compounds that exhibit large differences between the tan delta value at 0 ° C and their tan delta value at 60 ° C offer a group of advantages in tire tread surface mixing applications. For example, it is generally considered good that the difference between tan delta at 0 ° C and tan delta at 60 ° C is 0.150 or greater. It is excellent for the difference between tan delta at 0 ° C and tan delta at 60 ° C that is 0.2 or higher and it is very exceptional that this difference in delta values is greater than 0.25. In the case of the compound made in Example 10, the difference between tan delta at 0 ° C and tan delta at 60 ° C is greater than 0.30. The tire tread surface compound illustrated in Example 11 could be used on a truck tire to provide exceptional rolling resistance and durability of rolling surfaces with somewhat compromised traction characteristics. In the case of truck tires, the traction characteristics are usually not of great concern due to very heavy vehicle weights. Therefore, the compound made in Example 11 has good characteristics for truck tires. In any case, the compound illustrated in Example 11 exhibits a tan delta at 60 ° C of less than 0.050 which is indicative of superb rolling resistance as well as tread characteristics. As can be seen, the tan delta obtained at 60 ° C in Example 11 is lower than that obtained in any of the control compounds. The abrasion resistance observed in Example 11 was remarkable with the abrasion of DIN being less than 30 cubic centimeters, a DIN abrasion of less than 50 cubic centimeters is considered to be excellent and a DIN abrasion of less than 40 cubic centimeters It is considered as being superb for the tread of the tire.

Examples 15-19 The isoprene-butadiene diblock rubbers made in Examples 8 and 9 were then stirred using a tire tread surface test formulation and compared with tire tread surface formulations made of a styrene-rubber mixture. butadiene by emulsion and rubber with a high content of cis-1,4-polybutadiene. The tire tread surface test formulations were made by mixing the ingredients shown in Example V. Example 15 was carried out as a comparison example and did not include any isoprene-butadiene diblock rubber of this invention, such as rubber component.

Table V Example 15 16 17 18 19 SBR1 Emulsion 96.3 - - - - Cis-1, 4-PBD2 37.5 - 37.5 - 37.5 IBR (Example 8) - 100 70 - - IBR (Example 9) - - - 100 70 carbon black 93 93 93 93 93 wax 4 4 4 4 4 zinc oxide 4 4 4 4 4 stearic acid 2 2 2 2 2 CBS 3.5 3.5 3.5 3.5 3.5 TMTD 0.25 0.25 0.25 0.25 0.25 sulfur 0.85 0.85 0.85 0.85 0.85 Processing Oil - 33.8 26.3 33.8 26.3 Antidegradant 1.5 1.5 1.5 1.5 1.5 1 The 96.3 parts of the emulsion styrene-butadiene rubber contained 70 parts of rubber and 26.3 parts of processing oil. The styrene-butadiene emulsion rubber contained 23.5 weight percent of the combined styrene. 2 The 37.5 parts of the high cis-1,4-polybutadiene rubber contained 30 parts of rubber and 7.5 parts of processing oil.

The physical properties of the mixed tire tread surface formulations are disclosed in Table VI.

Table VI Physical Properties of the Compound Example 15 16 17 18 19 Component of rubber SBR / IBR IBR / IBR IBR / PBD PBD PBD Rheometer, 150 '> C ML, dNm 9.1 8.9 9.2 6.3 8.0 MH, dNm 34.8 33.2 34.1 25.8 28.0 tsl, min. 7.5 6.2 6.2 7.0 6.5 T25, min. 10.0 9.0 7.8 8.0 7.5 T90, min. 14.0 10.7 10.0 11.0 9.6 Voltage-Deformation, 18 '' / 150 ° C Module at 100%, MPa 1.85 1.85 1.78 1.78 1.56 Module at 300%, MPa 7.47 7.01 6.65 6.57 5.57 Resistance to Break, MPa 15.8 12.1 12.3 9.3 9.6 Elongation at Breakage 596% 516% 534% 461% 478% Rebound bounce at 23 ° C 24% 24% 27% 19% 22% bounce at 100 ° C 39% 39% 41% 34% 35% Abrasion of DIN, ce 113 135 104 200 145 Autovibron, 11 Hz tan delta 0 ° C .103 .105 .098 .182 .122 tan delta at 60 ° C .145 .140 .139 .154 .143 Examples 20-22 The isoprene-butadiene diblock rubbers made in Example 7 were stirred using two different tire tread surface test formulations were compared to a rim rolling surface formulation made with an emulsion styrene-butadiene rubber mixture. and rubber with a high content of cis-1,4-polybutadiene. The tire tread surface test formulations were made by mixing the ingredients shown in Table VII. Example 20 was carried out as a comparison example and did not include any isoprene / butadiene diblock rubber of this invention, such as the rubber component.

Table VII Example 20 21 22 IBR (Example 7) 70 55 3, 4-polyisoprene 15 SBR1 of Emulsion 96.25 Rubber of High Content of cis-1, 4-polybutadiene2 37.5 37.5 37.5 Process Oil 10 36.25 36.25 Carbon Black 70 70 70 Zinc oxide Wax Stearic acid CBS TMTD 0.3 0.3 0.3 Sulfur 1.5 1.5 1.5 Antioxidant Wingstay® 100 1 The 96.25 parts emulsion styrene-butadiene rubber contained 70 parts of rubber and 26.25 parts of processing oil. The styrene-butadiene emulsion rubber contained 23.5 percent styrene combined. 2 Log 37.5 parts of the high cis-1,4-polybutadiene rubber contained 30 parts of rubber and 7.5 parts of processing oil. The high cis-1,4-polybutadiene rubber was Budene® 1254 polybutadiene rubber. The physical properties of the mixed tire tread surface formulations are disclosed in Table VIII. Table VIII Physical Properties of the Compound Example 15 16 17 Rubber Component SBR / PBD IBR IBR / 3,4-PI Rheometer, 150 ° C ML, dNm 2.9 3.2 3.1 MH, dNm 13.4 16.7 16.2 tsl, in 5.6 4.8 4.6 T25, min. 6.5 5.3 5.1 T90, min. 15.5 8.9 8.5 Voltage-Deformation, 18 '/ 150 ° C Module at 100%, MPa 1.2 1.3 1.4 Module at 300%, MPa 4.3 3.9 4.4 Elongation at Break 785% 639% 630% Rebound Rebound at 23 ° C 32% 41% 35% bounce at 100 ° C 46% 51% 51% Abrasion of DIN, CE 107 81 91 Autovibron, 11 Hz tan delta at 0 ° C .122 103 186 tan delta at 60 ° C 132 106 107 Example 19 In this experiment, a diblock polymer of isoprene-butadiene having a first block consisting of repeating units which were derived from isoprene and 1,3-butadiene and a second block which also consisted of repeating units which were isoprene derivatives and 1,3-butadiene was synthesized. The first isoprene-butadiene block in the processed polymer had a low vinyl content and the second block had a high vinyl content. In this experiment, ethyl tetrahydrofurfuryl ether (TEE) was used as the modifier. In the procedure used, 830 grams of a dried silica / molecular sieve / alumina premix containing isoprene and 1,3-butadiene in hexane was charged in a 3.8 liter capacity reactor. The premixed monomer solution contained an isoprene to 1,3-butadiene ratio of 50:50 and the total monomer concentration was 18.2 percent. The solution of the monomer premix had been previously washed for impurities with a solution of n-butyllithium. Polymerization is initiated by the addition of 1.6 milliliters of 1.04 M to the solution of n-butyllithium.

The reactor was maintained at a temperature of about 65 ° C until essentially a full monomer conversion had been achieved which required approximately 2.5 hours. Then, 4.2 milliliters of a 1.0 M TEE solution was added to the polymerization medium and was followed by an additional 1620 grams of the washed monomer premix (the premix had a ratio of 50:50 of isoprene to 1,3-butadiene and a concentration of 18.2 percent in hexane). The copolymerization was allowed to continue at 65 ° C until all the monomers had been consumed which received approximately two hours. The polymerization was stopped by the addition of ethanol to the polymerization medium and the synthesized isoprene-butadiene diblock rubber was stabilized with 1 phr (parts per hundred parts of rubber) of an antioxidant. After evaporating the hexane solvent, the resulting isoprene-butadiene diblock rubber was dried in a vacuum oven at a temperature of 50 ° C. The produced isoprene-butadiene diblock rubber was determined to have two glass transition temperatures at -80 ° C and -31 ° C. The processed rubber was also determined to have a microstructure containing 24 percent 1,2-polybutadiene units, 27 percent 1,4-polybutadiene units, 24 percent 3,4-polyisoprene units, 24 percent one hundred units of 1, 4-polyisoprene and 1 percent of 1,2-polyisoprene units. Variations in the present invention are possible in view of the description thereof which is provided herein. 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. Therefore, it should be understood that the changes may be made in the specific embodiments described that will fall within the proposed full scope of the invention as defined by the following appended claims.

Claims (10)

CLAIMS:

1. A pneumatic tire having an outer circumferential running surface wherein the running surface is a sulfur-cured rubber composition which is comprised of, based on 100 parts of rubber, (a) from 30 parts to 80 parts of an isoprene-butadiene diblock rubber, the isoprene-butadiene diblock rubber comprises a butadiene block and an isoprene-butadiene block, wherein the butadiene block has a number-average molecular weight that falls within the scale of 25,000 to 350,000, wherein the isoprene-butadiene block has a number-average molecular weight that falls within the range of 25,000 to 350,000, wherein isoprene-butadiene diblock rubber essentially has a glass transition temperature that is within the range of -100 ° C to -70 ° C, where the isoprene-butadiene block polymer has a Mooney viscosity ML-4 at 100 ° C which remains within the creek from 50 to 140, and wherein the repeating units derived from isoprene and 1,3-butadiene in the isoprene-butadiene block are essentially in a random order; and (b) from 20 to 70 parts of a second rubber that is selected from the group consisting of high vinyl polybutadiene rubber, medium content vinyl polybutadiene rubber, isoprene-styrene-butadiene rubber and styrene rubber -butadiene.

2. 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 consists of, based on 100 parts by weight of rubber, (a) of 30 a 80 parts of an isoprene-butadiene diblock rubber, the isoprene-butadiene diblock rubber comprises a butadiene block and an isoprene-butadiene block, wherein the butadiene block has a number average molecular weight that falls within the scope of the invention. the scale of 25,000 to 350,000, wherein the isoprene-butadiene block has a number average molecular weight that falls within the range of 25,000 to 350,000, wherein isoprene-butadiene diblock rubber has a first transition temperature of vitreous state that falls within the range of -100 ° C to -70 ° C, where the isoprene-butadiene diblock rubber has a second glass transition temperature that remains within the scale from -50 ° C to 0 ° C, where the diblock polymer of isoprene-butadiene has a Mooney viscosity ML-4 at 100 ° C which is within the range of 50 to 140, and where the repeating units derivatives of isoprene and 1,3-butadiene in the isoprene-butadiene block are essentially in a random order; and (b) from 20 to 70 parts of a second rubber that is selected from the group consisting of rubber and high content of vinyl polybutadiene, styrene-isoprene-butadiene rubber and styrene-butadiene rubber.

3. A pneumatic tire according to claim 1 or 2, wherein the second rubber is a styrene-butadiene rubber and wherein the styrene-butadiene rubber is present at a level of 25 to 50 parts.

4. A pneumatic tire according to claim 1 or 2, characterized in that the second rubber is a high vinyl polybutadiene content rubber having a vinyl content that is within the range of 60 percent to 80 percent. A pneumatic tire according to claim 1 or 2, characterized in that the second rubber is a styrene-isoprene-butadiene rubber having a glass transition temperature that falls within the range of -40 ° C to - 20 ° C. A rim according to claim 4, characterized in that the running surface comprises 50 weight percent to 70 weight percent of the isoprene-butadiene diblock rubber and 30 weight percent to 50 weight percent of rubber with a high content of polybutadiene vinyl; wherein the diblock rubber of isoprene-butadiene has a Mooney viscosity at 100 ° C which is within the range of 80 to 135: and wherein the butadiene block has a number average molecular weight that falls within the scale of 50,000 to 200,000; wherein the isoprene-butadiene block has a number average molecular weight that falls within the range of 50,000 to 200,000; wherein the isoprene-butadiene block in the isoprene-butadiene diblock polymer comprises from 10 weight percent to 60 weight percent repeating units which are derived from isoprene, and from 40 weight percent to 90 weight percent. 100 percent by weight of the repeating units that are derived from 1,3-butadiene; wherein the ratio of the number average molecular weight of the butadiene block to the number average molecular weight of the isoprene-butadiene block is within the range of 25/75 to 75/2

5. 7. A pneumatic tire according to claim 6, characterized in that the butadiene block in the isoprene-butadiene diblock polymer has a number average molecular weight that falls within the range of 70,000 to 150,000; wherein the isoprene-butadiene block in the isoprene-butadiene diblock polymer has a number average molecular weight that falls within the range of 70,000 to 150,000; wherein the isoprene-butadiene block in the isoprene-butadiene diblock polymer consists of from about 20 weight percent to 50 weight percent repeating units that are derived from isoprene, and from 50 weight percent to 80 percent by weight of repeating units that are derived from 1,3-butadiene; wherein the ratio of the number average molecular weight of the butadiene block to the number average molecular weight of the isoprene-butadiene block is within the range of 35/65 to 65/35; wherein isoprene-butadiene diblock rubber has a Mooney viscosity at 100 ° C which is within the range of 100 to 130; wherein the tread comprises 55 percent to 65 percent by weight of the isoprene-butadiene diblock rubber and from 35 percent to 45 percent by weight of the high-vinyl polybutadiene rubber. A pneumatic tire according to claim 7, characterized in that the running surface is a sulfur-cured rubber composition further comprising carbon black, at least one antidegradate, at least one processing oil, zinc oxide and silica. 9. A pneumatic tire according to claim 1 or 2, characterized in that the running surface is a sulfur cured rubber composition further comprising silica; wherein the silica is present in an amount that is within the range of 10 phr to 250 phr; and wherein the silica is added by a thermomechanical mixing step. 10. A pneumatic tire according to claim 9, characterized in that the silica is present in an amount that falls within the scale of 50 phr to 120 phr; and wherein the rubber composition further comprises a silica coupling agent. SUMMARY OF THE INVENTION The present invention discloses a pneumatic rim having an outer circumferential tread surface wherein the tread surface is a sulfur cured rubber composition comprising (a) a diblock rubber of isoprene-butadiene, the diblock rubber of isoprene-butadiene consists of a butadiene block and an isoprene-butadiene block wherein the butadiene block has a number average molecular weight that falls within the range of about 25,000 to about 350,000, where the isoprene-butadiene block it has a number average molecular weight that falls within the range of about 25,000 to about 350,000, wherein isoprene-butadiene diblock rubber essentially has a glass transition temperature that falls within the range of about -100 °. C at about -70 ° C, wherein the diblock polymer of isoprene-butadiene has a Mooney viscosity ML-4 at 100 ° C remaining within the range of about 50 to about 140, and wherein the repeating units derived from isoprene and 1,3-butadiene in the isoprene-butadiene block are in an essentially random order; and (b) a second rubber that is selected from the group consisting of high vinyl polybutadiene rubber, styrene-isoprene-butadiene rubber, styrene-butadiene rubber solution and emulsion styrene-butadiene rubber.