Method for preparing unimodal polyisoprene using dilithium initiator

Abstract

1. A method for polymerizing isoprene, the method comprising: (i) providing a dilithium initiator; (ii) introducing the dilithium initiator to isoprene monomers to form a polymerization mixture; and (iii) polymerizing the isoprene monomers to form polyisoprene, wherein the polyisoprene is characterized by a monomodal molecular weight distribution.

Description

[Technical Field]

[0001] Embodiments of the present invention provide a method for preparing polyisoprene having a monomodal molecular weight distribution from a dilithium initiator, as well as telechelic polyisoprene prepared using the method of the present invention. [Background technology]

[0002] Polydienes, such as poly(butadiene), and diene copolymers, such as poly(styrene-co-butadiene), are often made using anionic polymerization techniques, whereby diene monomers, optionally together with copolymerizable monomers such as vinyl aromatics, are polymerized using anionic initiators. The use of anionic polymerization techniques offers several advantages, including the ability to control molecular weight, prepare relatively linear polymer chains, and functionalize polymer chains through chain termination. Useful anionic initiators include alkyllithium compounds, such as n-butyllithium. Multifunctional initiators can be formed, for example, by reacting alkyllithium compounds with dialkenyl compounds, such as diisopropenylbenzene. Polymers prepared using multifunctional initiators have multiple reactive chain ends, which provides the ability to functionalize both ends of the polymer chain to form telechelic polymers. Summary of the Invention

[0003] One or more embodiments of the present invention provide a method for polymerizing isoprene, the method including: (i) providing a dilithium initiator; (ii) introducing the dilithium initiator to isoprene monomers to form a polymerization mixture; and (iii) polymerizing the isoprene monomers to form polyisoprene, wherein the polyisoprene is characterized by a monomodal molecular weight distribution.

[0004] Another embodiment of the present invention provides a polyisoprene polymer prepared by providing a dilithium initiator, introducing the dilithium initiator to isoprene monomers to form a polymerization mixture, and polymerizing the isoprene monomers to form polyisoprene, wherein the polyisoprene is characterized by a monomodal molecular weight distribution.

[0005] Yet another embodiment of the present invention provides a vulcanizable composition comprising a unimodal polyisoprene polymer.

[0006] Yet another embodiment of the present invention provides a vulcanizate prepared by vulcanizing a vulcanizable composition comprising a unimodal polyisoprene polymer.

[0007] Another embodiment of the present invention provides a tire prepared from a vulcanizable composition comprising a unimodal polyisoprene polymer. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a GPC trace of Sample 1, a multimodal polyisoprene polymer prepared without using the techniques of the present invention. [Figure 2] FIG. 2 is a GPC trace of Sample 2, a unimodal polyisoprene polymer prepared by using an embodiment of the present invention. [Figure 3A] FIG. 3A is a GPC trace of the unimodal polyisoprene polymer of Sample 3, prepared without using the techniques of the present invention. [Figure 3B] FIG. 3B is a GPC trace of the unimodal polyisoprene polymer of Sample 4, prepared without using the techniques of the present invention. [Figure 3C] FIG. 3C is a GPC trace of a multimodal polyisoprene polymer of Sample 5, prepared without using the techniques of the present invention. [Figure 3D] FIG. 3D is a GPC trace of a unimodal polyisoprene polymer of Sample 6 prepared by using an embodiment of the present invention. [Figure 4] FIG. 4 is a GPC trace of a unimodal polyisoprene polymer of Sample 11 prepared by using an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiments of the present invention are based, at least in part, on the discovery of a method for preparing unimodal polyisoprene using a dilithium initiator. According to embodiments of the present invention, the dilithium initiator is prepared by reacting an alkyllithium compound with a dialkenyl compound and then aging the initiator. The aged initiator is then introduced to the isoprene monomer to be polymerized. While dilithium initiators have been used to prepare polydienes such as polybutadiene and poly(styrene-co-butadiene), it has been discovered that polymerization of isoprene with these dilithium initiators results in multimodal polymer compositions. Embodiments of the present invention solve this problem. In one or more embodiments, the unimodal polymer is obtained by polymerizing isoprene with a dilithium initiator in the presence of a threshold amount of a Lewis base. In other embodiments, the unimodal polymer is obtained by first polymerizing polybutadiene oligomers and then polymerizing isoprene monomer. While unimodal polyisoprene is prepared by anionic polymerization techniques, the use of dilithium initiators advantageously results in multiple polymer active ends (i.e., reactive ends), which allows for the preparation of telechelic diene copolymers, which are advantageously used in the manufacture of tire components.

[0010] Initiator Preparation and Aging As noted above, the dilithium initiator is prepared by combining a dialkenyl compound with an alkyllithium compound in a solvent to form a reaction mixture in which the reactants and products are at least partially soluble. The initiator is then aged in a suitable solvent in the presence of a Lewis base.

[0011] In one or more embodiments, the dialkenyl compound is a 1,3-dialkenylbenzene compound, such as 1,3-diisopropenylbenzene. In one or more embodiments, the alkyllithium compound is a butyllithium compound, such as n-butyllithium, t-butyllithium, and / or sec-butyllithium. In certain embodiments, sec-butyllithium is used.

[0012] The amount of alkyllithium compound reacted with the dialkenyl compound may be quantified based on the molar ratio of lithium to alkenyl groups, i.e., the number of equivalents of lithium (i.e., moles of Li) associated with the alkyllithium compound relative to the number of equivalents of alkenyl groups in the dialkenyl compound (e.g., the number of equivalents of isopropenyl groups in 1,3-diisopropenylbenzene). In one or more embodiments, the ratio of moles of Li associated with the alkyllithium to the number of equivalents of alkenyl groups associated with the dialkenyl compound may be from about 1.95:1 to about 2.05:1, from about 1.97:1 to about 2.03:1 in other embodiments, and from about 1.99:1 to about 2.01:1 in other embodiments. When sec-butyllithium is reacted with 1,3-diisopropenylbenzene, 2.00 moles of sec-butyllithium may be reacted per mole of 1,3-diisopropenylbenzene.

[0013] The Lewis base may include any Lewis base that does not contain an active hydrogen atom, where the presence of an active hydrogen atom is determined by the Zerewitinoff test. Exemplary Lewis bases include oxolanylpropanes such as 2,2-bis(2-oxolanyl)propane (also known as 2,2-ditetrahydrofurylpropane), meso-2,2-ditelahydrofurylpropane, DL-2,2-ditetrahydrofurylpropane, and mixtures thereof, and trialkylamines such as triethylamine or N,N,N',N'-tetramethylethylenediamine (TMEDA). In certain embodiments, triethylamine is used. In other embodiments, a mixture of two or more different Lewis bases is used.

[0014] The amount of Lewis base introduced into the reaction mixture may be quantified based on the moles of Lewis base (e.g., 2,2-ditetrahydrofurylpropane) to the moles of lithium associated with the alkyllithium compound (i.e., the ratio of moles of Lewis base to moles of lithium). In one or more embodiments, the molar ratio of moles of Lewis base introduced into the reaction medium to moles of lithium introduced with the alkyllithium compound is from about 0.05:1 to about 2:1, in other embodiments from about 0.1:1 to about 1.5:1, and in other embodiments from about 0.5:1 to about 1:1.

[0015] The synthesis of the initiator is carried out in a solvent in which the reactants and products are at least partially soluble. Useful solvents include, but are not limited to, hydrocarbons with low or relatively low boiling points, such as aromatic hydrocarbons, aliphatic hydrocarbons, and cycloaliphatic hydrocarbons. Non-limiting examples of aromatic hydrocarbons include benzene, toluene, xylene, ethylbenzene, diethylbenzene, and mesitylene. Non-limiting examples of aliphatic hydrocarbons include n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, isopentane, isohexane, isopentane, isooctane, 2,2-dimethylbutane, petroleum ether, kerosene, and mineral spirits. Non-limiting examples of cycloaliphatic hydrocarbons include cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane. Mixtures of the above hydrocarbons can also be used.

[0016] As described above, the dilithium initiator formed by the above reaction is aged in a suitable solvent (e.g., the reaction medium) in the presence of a Lewis base. In one or more embodiments, the Lewis base is present at the time of introduction of the reactants to the reaction mixture. In other embodiments, the Lewis base is introduced after synthesis of the dilithium initiator, and aging occurs after introduction of the Lewis base.

[0017] In one or more embodiments, aging of the initiator is carried out under an inert atmosphere at ambient conditions at a temperature of from about 0° C. to about 150° C., in other embodiments from about 25° C. to about 100° C., and in other embodiments from about 35° C. to about 60° C. In one or more embodiments, the initiator is aged for more than 15 minutes, in other embodiments from more than 20 minutes, in other embodiments from more than 25 minutes, and in other embodiments from more than 30 minutes, before introducing the initiator to the monomers to be polymerized. In one or more embodiments, the initiator is aged for from about 15 minutes to about 4 hours, in other embodiments from about 20 minutes to about 3 hours, and in other embodiments from about 30 minutes to about 2 hours, before introducing the initiator to the monomers to be polymerized.

[0018] polymerization reaction The dilithium initiator, prepared and aged as described above, is combined with the monomers to be polymerized in a suitable solvent to form a polymerization mixture in which the monomers and the resulting polymer are at least partially soluble. In one or more embodiments, the initiator is also at least partially soluble in the polymerization mixture.

[0019] Generally speaking, polymerization of isoprene monomers with an initiator proceeds via anionic polymerization techniques. The preparation of polymers using anionic polymerization techniques is generally known. The important mechanistic features of anionic polymerization are described in books (e.g., Hsieh, HL; Quirk, RP; Anionic Polymerization: Principles and Practical Applications; Marcel Dekker: New York, 1996) and review articles (e.g., Hadjichristidis, N.; Pitsikalis, M.; Pispas, S.; Iatrou, H.; Chem. Rev. 2001, 101(12), 3747-3792). Anionic initiators can advantageously produce polymers with reactive chain ends (e.g., living polymers) that can react with additional monomers for further chain growth or with certain functionalizing agents to give functionalized polymers before quenching. Polymers with reactive polymer chain ends are sometimes simply referred to as reactive polymers. As will be appreciated by those skilled in the art, these reactive polymers contain reactive chain ends, which are believed to be ionic, at which a reaction can occur between a functionalizing agent and the reactive chain end of the polymer, thereby imparting functionality or functional groups to the polymer chain end or allowing multiple polymers to be coupled together.

[0020] The polymerization mixture can be formed by introducing the various components in any order, for example, in one or more embodiments, the isoprene monomer and solvent can be combined first, and then the aged initiator can be introduced to the mixture.

[0021] The amount of initiator used may depend on the interplay of various factors (e.g., the type of initiator used, the purity of the components, the polymerization temperature, the desired polymerization rate and conversion, the desired molecular weight, and many other factors). In one or more embodiments, the amount of initiator used may be expressed as millimoles of initiator per weight of monomer. In one or more embodiments, the amount of initiator introduced into the polymerization mixture is from about 0.1 to about 100 mmol, or in other embodiments from about 0.2 to about 50 mmol, or in other embodiments from about 0.3 to about 15 mmol, of initiator per 100 grams of monomer in the polymerization mixture (i.e., the monomer to be polymerized).

[0022] Solvent for the polymerization mixture In one or more embodiments, suitable solvents include organic compounds that do not undergo polymerization or incorporation into growing polymer chains during polymerization of monomers in the presence of a catalyst. In one or more embodiments, these organic species are liquid at ambient temperature and pressure. In one or more embodiments, these organic solvents are inert to the catalyst. Exemplary organic solvents include hydrocarbons with low or relatively low boiling points, such as aromatic hydrocarbons, aliphatic hydrocarbons, and cycloaliphatic hydrocarbons. Non-limiting examples of aromatic hydrocarbons include benzene, toluene, xylene, ethylbenzene, diethylbenzene, and mesitylene. Non-limiting examples of aliphatic hydrocarbons include n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, isopentane, isohexane, isopentane, isooctane, 2,2-dimethylbutane, petroleum ether, kerosene, and mineral spirits. Non-limiting examples of cycloaliphatic hydrocarbons include cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane. Mixtures of the above hydrocarbons can also be used. The low-boiling hydrocarbon solvent is typically separated from the polymer when the polymerization is complete. Other examples of organic solvents include high-molecular-weight, high-boiling hydrocarbons, such as paraffinic oils, aromatic oils, or other hydrocarbon oils commonly used in oil-extended polymers. Because these hydrocarbons are non-volatile, they typically do not need to be separated and remain entrapped within the polymer.

[0023] Denaturant The polymerization reaction may be carried out in the presence of a modifier, sometimes referred to as a polar coordinator or vinyl modifier. As those skilled in the art will appreciate, these compounds can serve multiple purposes in the polymerization. For example, they can help randomize the comonomers throughout the polymer chain. They can also modify the vinyl content of diene-derived monomer units. Compounds useful as randomizers include those containing oxygen or nitrogen heteroatoms and non-bonding electron pairs (i.e., Lewis bases). Examples include linear and cyclic oligomeric oxolanyl alkanes; dialkyl ethers of mono- and oligoalkylene glycols (also known as glyme ethers); "crown" ethers; tertiary amines; linear THF oligomers; and the like. Linear and cyclic oligomeric oxolanyl alkanes are described in U.S. Pat. Nos. 4,429,091 and 9,868,795, which are incorporated herein by reference. Specific examples of compounds useful as randomizers include 2,2-bis(2-oxolanyl)propane (also known as 2,2-ditetrahydrofurylpropane), meso-2,2-ditelahydrofurylpropane, DL-2,2-ditelahydrofurylpropane, and mixtures thereof, 1,2-dimethoxyethane, N,N,N',N'-tetramethylethylenediamine (TMEDA), tetrahydrofuran (THF), 1,2-dipiperidylethane, dipiperidylmethane, hexamethylphosphoramide, N-N'-dimethylpiperazine, diazabicyclooctane, dimethyl ether, diethyl ether, tri-n-butylamine, and mixtures thereof. In other embodiments, potassium alkoxides may be used to randomize the styrene distribution. In one or more embodiments, randomizers other than potassium alkoxides are used. In other embodiments, potassium alkoxides are the only randomizers present in the polymerization mixture.

[0024] The amount of randomizer to be used may depend on various factors, such as the desired polymer microstructure, the ratio of monomer to comonomer, the polymerization temperature, and the nature of the particular randomizer used.

[0025] As noted above, embodiments of the present invention provide for producing unimodal polyisoprene by polymerizing isoprene monomers in the presence of a threshold amount of a Lewis base. In certain embodiments, the Lewis base is selected from 2,2-bis(2-oxolanyl)propane (also known as 2,2-ditetrahydrofurylpropane), meso-2,2-ditelahydrofurylpropane, DL-2,2-ditetrahydrofurylpropane, triethylamine, N,N,N',N'-tetramethylethylenediamine (TMEDA), and mixtures thereof.

[0026] In one or more embodiments, the threshold amount of Lewis base present in the polymerization mixture required to achieve unimodal polyisoprene can include a Lewis base introduced into the reaction mixture used to make the initiator (i.e., carried over from the initiator solution), or can be added separately to the polymerization mixture (e.g., before, after, or simultaneously with the initiator or monomer). It will also be understood that this threshold amount can be achieved by one particular type of Lewis base (e.g., TMEDA) or can be achieved from two or more Lewis bases. For example, the threshold amount can be achieved by adding a Lewis base (e.g., triethylamine) to the reaction medium when preparing the initiator, and then adding an additional Lewis base (e.g., 2,2-ditetrahydrofurylpropane) directly to the polymerization mixture, with the combined (i.e., total) amounts of the two Lewis bases achieving the threshold amount required to achieve unimodal polyisoprene.

[0027] Within these embodiments, the total amount of Lewis base required to achieve unimodal polyisoprene according to the present invention can be quantified relative to the amount of lithium introduced into the polymerization system as part of the initiator. In one or more embodiments, the total amount of Lewis base (e.g., 2,2-ditetrahydrofurylpropane) present during initiator aging and subsequent polymerization is quantified as the molar ratio of moles of Lewis base to moles of lithium associated with the initiator. In one or more embodiments, the molar ratio of Lewis base to lithium is greater than 0.01:1, in other embodiments greater than 0.05:1, in other embodiments greater than 0.1:1, in other embodiments greater than 0.2:1, in other embodiments greater than 0.4:1, and in other embodiments greater than 0.5:1. In these or other embodiments, the molar ratio of Lewis base to lithium in the polymerization system is from about 0.05:1 to about 3:1, from about 0.1:1 to about 3:1 in other embodiments, from about 0.2:1 to about 2:1 in other embodiments, from about 0.3:1 to about 1.5:1 in other embodiments, from about 0.4:1 to about 1.5:1 in other embodiments, and from about 0.5:1 to about 1.1:1 in other embodiments.

[0028] Polymerization conditions and techniques The anionic initiator and other components of the polymerization system can be introduced into the polymerization system by a variety of methods. In one or more embodiments, the anionic initiator and modifier can be added separately to the monomers to be polymerized, either stepwise or simultaneously.

[0029] As described above, the polymerization of isoprene monomers in the presence of an effective amount of an initiator produces a reactive polymer. The introduction of the initiator and monomers forms a polymerization mixture in which the reactive polymer is formed. Polymerization in a solvent produces a polymerization mixture in which the polymer product is dissolved or suspended in the solvent. This polymerization mixture is sometimes referred to as a polymer cement.

[0030] In one or more embodiments, the polymerization may be carried out in any conventional polymerization vessel known in the art. For example, the polymerization may be carried out in a conventional stirred tank reactor. In one or more embodiments, all of the ingredients used for the polymerization may be mixed in a single vessel (e.g., a conventional stirred tank reactor), and all steps of the polymerization process may be carried out in this vessel. In other embodiments, two or more ingredients may be precombined in one vessel and then transferred to another vessel where polymerization of the monomers (or at least the majority of it) occurs. Because various embodiments of the present invention involve the use of multiple reactors or reaction zones, the vessel in which the polymerization occurs (e.g., a tank reactor) may be referred to as the first vessel or first reaction zone.

[0031] The polymerization can be carried out as a batch, continuous, or semi-continuous process. In a semi-continuous process, monomer is intermittently introduced as needed to replace already polymerized monomer. In one or more embodiments, the heat of polymerization can be removed by external cooling through a thermally controlled reactor jacket, internal cooling by vaporizing and condensing the monomer using a reflux condenser connected to the reactor, or a combination of the two methods. Conditions can also be controlled to carry out the polymerization under pressures of about 0.1 atmospheres to about 50 atmospheres, in other embodiments, about 0.5 atmospheres to about 20 atmospheres, and in other embodiments, about 1 atmosphere to about 10 atmospheres. In one or more embodiments, pressures at which the polymerization can be carried out include those that ensure that the majority of the monomer is in the liquid phase. In these or other embodiments, the polymerization mixture can be maintained under anaerobic conditions.

[0032] In one or more embodiments, the conditions under which the polymerization proceeds may be controlled to maintain a peak polymerization temperature of the polymerization mixture above 30° C., in other embodiments above 50° C., and in other embodiments above 70° C. In these or other embodiments, the conditions under which the polymerization proceeds may be controlled to maintain a peak polymerization temperature of the polymerization mixture below 120° C., in other embodiments below 110° C., and in other embodiments below 100° C. In one or more embodiments, the conditions under which the polymerization proceeds may be controlled to maintain the temperature of the polymerization mixture in the range of from about −10° C. to about 200° C., in other embodiments from about 0° C. to about 150° C., and in other embodiments from about 20° C. to about 110° C.

[0033] butadiene polymerization As described above, embodiments of the present invention involve first polymerizing 1,3-butadiene monomer to form polybutadiene oligomers, and then polymerizing isoprene monomer to form unimodal polyisoprene. This process is sometimes referred to as butadiene seeding. As will be appreciated by those skilled in the art, this can be accomplished by first introducing 1,3-butadiene monomer (which may be referred to as butadiene monomer unless otherwise specified) and an initiator, resulting in the formation of a polymerization mixture in which butadiene is polymerized, thereby forming a reactive macromolecule having two reactive butadiene chains extending from the initiator residue. Isoprene monomer is then introduced to the polymerization mixture. Polymerization continues by adding isoprene monomer to the reactive end of the butadiene chain, thereby forming polyisoprene chains extending from the butadiene oligomer chains.

[0034] In one or more embodiments, the butadiene chains formed are relatively short chains (e.g., they may be referred to as butadiene oligomer chains) formed by introducing a limited amount of butadiene monomer. The amount of butadiene used in the synthesis (i.e., in the seeding step) of the present invention can be quantified based on the number of equivalents of lithium relative to the initiator. In one or more embodiments, less than 100 moles, in other embodiments less than 75 moles, in other embodiments less than 50 moles, in other embodiments less than 30 moles, in other embodiments less than 15 moles, and in other embodiments less than 10 moles of 1,3-butadiene monomer per equivalent of lithium relative to the initiator are polymerized in the seeding step. In one or more embodiments, the amount of 1,3-butadiene monomer polymerized in the seeding step is from about 3 to about 100 moles, in other embodiments from about 5 to about 50 moles, and in other embodiments from about 10 to about 50 moles of 1,3-butadiene per equivalent of lithium relative to the initiator. Stated another way, the molar ratio of butadiene to DiLi initiator is less than 200:1, in other embodiments less than 150:1, in other embodiments less than 50:1, in other embodiments less than 30:1, in other embodiments less than 15:1, and in other embodiments less than 10:1. In one or more embodiments, the molar ratio of butadiene to lithium atoms associated with the DiLi initiator is from about 3:1 to about 100:1, in other embodiments from about 5:1 to about 50:1, and in other embodiments from about 10:1 to about 50:1.

[0035] The butadiene seeding process is particularly advantageous when it is desired to produce unimodal polyisoprene. As will be appreciated by those skilled in the art, if unimodal polyisoprene is achieved by introducing a threshold amount of Lewis base into the polymerization mixture, increasing the loading of Lewis base will not only produce unimodal polyisoprene, but will also increase the vinyl content of the resulting polymer. Thus, in one or more embodiments, the butadiene seeding and subsequent isoprene polymerization are carried out in the presence of a limited amount of Lewis base. In one or more embodiments, the limited amount is less than the amount that would otherwise be required to produce unimodal polyisoprene in accordance with aspects of the present invention. As with other embodiments, the limited amount of Lewis base present during butadiene seeding and subsequent isoprene polymerization can be quantified as the molar ratio of moles of Lewis base to moles of lithium associated with the initiator. In one or more embodiments, the molar ratio of Lewis base to lithium (in the polymerization mixture) is less than 0.1:1, in other embodiments less than 0.08:1, in other embodiments less than 0.5:1, and in other embodiments less than 0.3:1. In these or other embodiments, the molar ratio of Lewis base to lithium in the polymerization system is from about 0.01:1 to about 0.1:1, in other embodiments from about 0.02:1 to about 0.08:1, and in other embodiments from about 0.03:1 to about 0.05:1.

[0036] Characterization of polymer before functionalization Prior to functionalization, as further described below, reactive polymers prepared by the practice of the present invention can be characterized by their molecular weights, which may include number average molecular weight (Mn), weight average molecular weight (Mw), and peak molecular weight (Mp). As will be understood by those skilled in the art, molecular weights can be determined, for example, by using gel permeation chromatography (GPC) in conjunction with UV absorption, differential refractometer (DRI), refractive index (RI), and infrared (IR) absorption detectors, and by using appropriate calibration standards and THF as the solvent. For purposes herein, GPC measurements use polystyrene standards and polystyrene Mark-Hwink constants unless otherwise specified. For purposes herein, prior to functionalization, the polymer may be referred to as the base polymer, and the pre-functionalization properties of the polymer may be referred to as the properties of the base polymer.

[0037] According to embodiments of the present invention, the polymer prior to functionalization has a single peak molecular weight (Mp). In one or more embodiments, the polymer prior to functionalization has an Mp greater than 160 kg / mol, in other embodiments greater than 170 kg / mol, and in other embodiments greater than 180 kg / mol, which may also be referred to as the base Mp. In these or other embodiments, the polymer prior to functionalization has a base Mp less than 280 kg / mol, in other embodiments less than 260 kg / mol, and in other embodiments less than 250 kg / mol. In one or more embodiments, the polymer prior to functionalization has a base Mp of from about 160 to about 280 kg / mol, in other embodiments from about 170 to about 260 kg / mol, and in other embodiments from about 180 to about 250 kg / mol.

[0038] In one or more embodiments, the polymer prior to functionalization has a Mn, sometimes referred to as the base Mn, greater than 130 kg / mol, in other embodiments greater than 140 kg / mol, and in other embodiments greater than 150 kg / mol. In these or other embodiments, the polymer prior to functionalization has a base Mn less than 300 kg / mol, in other embodiments less than 280 kg / mol, and in other embodiments less than 260 kg / mol. In one or more embodiments, the polymer prior to functionalization has a base Mn of from about 130 to about 300 kg / mol, in other embodiments from about 140 to about 280 kg / mol, and in other embodiments from about 150 to about 260 kg / mol.

[0039] In one or more embodiments, the polymer prior to functionalization has a Mw, sometimes referred to as the base Mw, greater than 180 kg / mol, in other embodiments greater than 190 kg / mol, and in other embodiments greater than 200 kg / mol. In these or other embodiments, the polymer prior to functionalization has a base Mw less than 500 kg / mol, in other embodiments less than 450 kg / mol, and in other embodiments less than 400 kg / mol. In one or more embodiments, the polymer prior to functionalization has a base Mw of from about 180 to about 500 kg / mol, in other embodiments from about 190 to about 450 kg / mol, and in other embodiments from about 200 to about 400 kg / mol.

[0040] In one or more embodiments, the base polymer may be characterized by a polydispersity, sometimes referred to as a molecular weight distribution (Mw / Mn), of less than 3, in other embodiments less than 2.5, in other embodiments less than 2.0, and in other embodiments less than 1.8.

[0041] Polymers produced according to aspects of the present invention prior to functionalization may be characterized by their vinyl content, which may be described as the ratio of unsaturation in the 3,4-microstructure to the total number of unsaturations in the polymer chain. As will be appreciated by those skilled in the art, vinyl content can be determined by NMR analysis at 400 MHz using CDCl3 as the solvent. In one or more embodiments, the polymer prior to functionalization contains greater than 5%, greater than 8%, greater than 10%, greater than 20%, and in other embodiments, 35% vinyl. In these or other embodiments, the polymer prior to functionalization contains less than 80% by weight, less than 60% by weight, and less than 46% by weight in other embodiments. In one or more embodiments, the polymer prior to functionalization contains from about 5 to about 80%, from about 8 to about 60% in other embodiments, and from about 20 to about 46% vinyl in other embodiments.

[0042] Polymer Functionalization The polymers produced by the polymerization of the present invention (i.e., proceeding by anionic polymerization techniques) contain reactive ends (i.e., growing ends) that can be modified (sometimes referred to as functionalized) to provide functionalized polymers (sometimes referred to as telechelic polymers) having functional groups at both ends of the linear polymer. That is, the reactive ends of the polymer are modified by introducing a functionalizing agent into the polymerization mixture, which is sometimes referred to as functionalization. It is believed that the polymer chain ends react with the functionalizing agent (sometimes referred to as a modifying agent) to provide residues of the functionalizing agent at the ends of the polymer chain. Thus, the reaction between the polymer and the functionalizing agent produces a polymer composition containing end groups derived from the functionalizing agent at both ends of the linear polymer. It should be understood that the reaction between a functionalizing agent and the reactive ends of the polymer can also result in polymer coupling of two or more polymer chains. In either case, both the polymer having chain end functional groups or the polymer coupled with residues of the functionalizing agent are referred to as modified polymers or functionalized polymers, unless otherwise specified.

[0043] Functionalizing Agents Useful functionalizing agents include those conventionally used in the art. In one or more embodiments, the functionalizing agent imparts terminal functionality that may be reactive or interactive with other polymer chains (propagating and / or non-propagating) or with other materials in the rubber compound, such as particulate reinforcing fillers (e.g., carbon black or silica). As discussed above, increased interaction between the polymer and the particulate filler in the rubber compound improves the mechanical and dynamic properties of the resulting vulcanizate. For example, certain functionalizing agents may impart terminal functional groups containing one or more heteroatoms. In one or more embodiments, the functionalizing agent may produce a functionalized polymer that can be used in a rubber composition to provide vulcanizates that may have a lower high-temperature (e.g., 50°C) hysteresis loss than vulcanizates prepared from similar rubber compounds without the functionalized polymer. The reduction in high-temperature hysteresis loss may be at least 5%, in some cases at least 10%, and even at least 15%.

[0044] Exemplary types of compounds that can be used to end-functionalize the reactive branched polymers of the present invention include imines, amines, hydrocarbyloxysilanes, amine-containing hydrocarbyloxysilanes, halogenated organics, trialkyltin compounds, carbon dioxide, benzophenones, benzaldehydes, imidazolidinones, pyrrolidinones, carbodiimides, ureas, isocyanates, and Schiff bases. It should also be understood that two or more different types of functionalizing agents can be used in the practice of the present invention.

[0045] Hydrocarbyloxysilane Functionalizing Agents In one or more embodiments, the hydrocarbyloxysilane functionalizing agent has the formula: (R 1 ) 4-z-y Si(R 2 )y(OR 2 ) z where R 1 is a halogen atom or a monovalent organic group, and each R 2is a monovalent organic group, z is an integer from 1 to 4, and y is an integer from 0 to 2. In one embodiment, the halogen atom is chlorine.

[0046] In one or more embodiments, monovalent organic groups include hydrocarbyl groups such as, but not limited to, alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, aryl, aralkyl, alkaryl, or alkynyl groups. Hydrocarbyl groups also include substituted hydrocarbyl groups, which refer to hydrocarbyl groups in which one or more hydrogen atoms have been replaced by a substituent (e.g., a hydrocarbyl group). In one or more embodiments, these groups may contain from 1 (or the minimum number of carbon atoms appropriate to form the group) to about 20 carbon atoms. These groups may or may not contain heteroatoms. Suitable heteroatoms include, but are not limited to, nitrogen, boron, oxygen, silicon, sulfur, tin, and phosphorus atoms. In one or more embodiments, the cycloalkyl, cycloalkenyl, and aryl groups are non-heterocyclic groups. In these or other embodiments, the substituents forming the substituted hydrocarbyl groups are non-heterocyclic groups.

[0047] Suitable examples of siloxane endstoppers include tetraalkoxysilanes, alkylalkoxysilanes, arylalkoxysilanes, alkenylalkoxysilanes, and haloalkoxysilanes.

[0048] Examples of tetraalkoxysilane compounds include tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, tetra(2-ethylhexyl) orthosilicate, tetraphenyl orthosilicate, and tetratoluyloxysilane.

[0049] Examples of alkylalkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltri-n-butoxysilane, methyltriphenoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltri-n-butoxysilane, ethyltriphenoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-propoxysilane, dimethyldi-n-butoxysilane, dimethyldiphenoxysilane, diethyldimethoxysilane, and diphenyldimethoxysilane.

[0050] Examples of arylalkoxysilane compounds include phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n-propoxysilane, phenyltri-n-butoxysilane, and phenyltriphenoxysilane.

[0051] Examples of alkenylalkoxysilane compounds include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-n-propoxysilane, vinyltri-n-butoxysilane, vinyltriphenoxysilane, allyltrimethoxysilane, octenyltrimethoxysilane, and divinyldimethoxysilane.

[0052] Examples of haloalkoxysilane compounds include trimethoxychlorosilane, triethoxychlorosilane, tri-n-propoxychlorosilane, tri-n-butoxychlorosilane, triphenoxychlorosilane, dimethoxydichlorosilane, diethoxydichlorosilane, di-n-propoxydichlorosilane, diphenoxydichlorosilane, methoxytrichlorosilane, ethoxytrichlorosilane, n-propoxytrichlorosilane, phenoxytrichlorosilane, trimethoxybromosilane, triethoxybromosilane, tri-n-propoxybromosilane, triphenoxybromosilane, dimethoxydibromosilane, Examples of the iodosilane include mosilane, diethoxydibromosilane, di-n-propoxydibromosilane, diphenoxydibromosilane, methoxytribromosilane, ethoxytribromosilane, n-propoxytribromosilane, phenoxytribromosilane, trimethoxyiodosilane, triethoxyiodosilane, tri-n-propoxyiodosilane, triphenoxyiodosilane, dimethoxydiiodosilane, di-n-propoxydiiodosilane, diphenoxydiiodosilane, methoxytriiodosilane, ethoxytriiodosilane, n-propoxytriiodosilane, and phenoxytriiodosilane.

[0053] Techniques for preparing functionalized polymers by using hydrocarbyloxysilane compounds are described in U.S. Pat. Nos. 3,244,664, 6,008,295, 6,228,908, and 4,185,042, which are incorporated herein by reference.

[0054] In one or more embodiments, the hydrocarbyloxysilane functionalizing agent has the formula:

[0055] [ka] wherein R is an imino-containing hydrocarbyloxysilane that can be defined by 2 , R 3 , and R 7 is a monovalent organic group, and R 4 is a divalent organic group, and R5 and R 6 are each independently a hydrocarbyloxy group or a hydrocarbyl group.

[0056] In one or more embodiments, the divalent organic group is a hydrocarbylene group, such as, but not limited to, an alkylene, cycloalkylene, alkenylene, cycloalkenylene, alkynylene, cycloalkenylene, or arylene group. Hydrocarbylene groups include substituted hydrocarbylene groups, which refer to hydrocarbylene groups in which one or more hydrogen atoms have been replaced with a substituent (e.g., a hydrocarbyl group). In one or more embodiments, these groups may contain from 1 (or the minimum number of carbon atoms appropriate to form the group) to about 20 carbon atoms. These groups may or may not contain heteroatoms. Suitable heteroatoms include, but are not limited to, nitrogen, boron, oxygen, silicon, sulfur, tin, and phosphorus atoms. In one or more embodiments, the cycloalkylene, cycloalkenylene, and arylene groups are non-heterocyclic groups. In these or other embodiments, the substituents forming the substituted hydrocarbylene group are non-heterocyclic groups.

[0057] Examples of these imino-containing hydrocarbyloxysilane compounds include, but are not limited to, triethoxy compounds such as N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-(triethoxysilyl)-1-propanamine, N-ethylidene-3-(triethoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine, N-(4-N,N-dimethylaminobenzylidene)-3-(triethoxysilyl)-1-propanamine, and N-(cyclohexylidene)-3-(triethoxysilyl)-1-propanamine. Other examples include, but are not limited to, trimethoxy compounds such as N-(1,3-dimethylbutylidene)-3-(trimethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-(trimethoxysilyl)-1-propanamine, N-ethylidene-3-(trimethoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(trimethoxysilyl)-1-propanamine, N-(4-N,N-dimethylaminobenzylidene)-3-(trimethoxysilyl)-1-propanamine, and N-(cyclohexylidene)-3-(trimethoxysilyl)-1-propanamine. Other examples include, but are not limited to, methyldiethoxy compounds such as N-(1,3-dimethylbutylidene)-3-(methyldiethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-(methyldiethoxysilyl)-1-propanamine, N-ethylidene-3-(methyldiethoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(methyldiethoxysilyl)-1-propanamine, N-(4-N,N-dimethylaminobenzylidene)-3-(methyldiethoxysilyl)-1-propanamine, and N-(cyclohexylidene)-3-(methyldiethoxysilyl)-1-propanamine.Other examples include, but are not limited to, ethyldimethoxy compounds such as N-(1,3-dimethylbutylidene)-3-(ethyldimethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-(ethyldimethoxysilyl)-1-propanamine, N-ethylidene-3-(ethyldimethoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(ethyldimethoxysilyl)-1-propanamine, N-(4-N,N-dimethylaminobenzylidene)-3-(ethyldimethoxysilyl)-1-propanamine, and N-(cyclohexylidene)-3-(ethyldimethoxysilyl)-1-propanamine.

[0058] Techniques for preparing functionalized polymers by using imine-containing hydrocarbyloxy compounds are disclosed in U.S. Patent Application Publication Nos. 2005 / 0009979, 2010 / 0113683, and 2011 / 0092633, which are incorporated herein by reference.

[0059] In one or more embodiments, the hydrocarbyloxysilane functionalizing agent has the formula:

[0060] [ka] wherein R 4 is a divalent organic group, and R 5 and R 6 are each independently a hydrocarbyloxy group or a hydrocarbyl group, and R 5 is a monovalent organic group, and A is selected from the group consisting of carboxylic acid ester, cyclic tertiary amine, acyclic tertiary amine, pyridine, silazane, epoxy, isocyanate, cyano, carboxylic acid anhydride, and sulfide groups.

[0061] Examples of hydrocarbyloxysilane compounds containing carboxylic acid ester groups include, but are not limited to, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, and 3-methacryloyloxypropyltriisopropoxysilane.

[0062] Examples of hydrocarbyloxysilane compounds containing a cyclic tertiary amine group include 3-(1-hexamethyleneimino)propyltriethoxysilane, 3-(1-hexamethyleneimino)propyltrimethoxysilane, (1-hexamethyleneimino)methyltriethoxysilane, (1-hexamethyleneimino)methyltrimethoxysilane, 2-(1-hexamethyleneimino)ethyltriethoxysilane, 3-(1-hexamethyleneimino)ethyltrimethoxysilane, and 2-(1-hexamethyleneimino)ethyltriethoxysilane. propyltriethoxysilane, 3-(1-pyrrolidinyl)propyltrimethoxysilane, 3-(1-pyrrolidinyl)propyltriethoxysilane, 3-(1-heptamethyleneimino)propyltriethoxysilane, 3-(1-dodecamethyleneimino)propyltriethoxysilane, 3-(1-hexamethyleneimino)propyldiethoxymethylsilane, and 3-[10-(triethoxysilyl)decyl]-4-oxazoline.

[0063] Examples of hydrocarbyloxysilane compounds containing acyclic tertiary amine groups include, but are not limited to, 3-dimethylaminopropyltriethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 3-diethylaminopropyltriethoxysilane, 2-dimethylaminoethyltriethoxysilane, 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyldiethoxymethylsilane, 3-diethylaminopropyldiethoxymethylsilane, 3-dimethylaminopropyldimethoxymethylsilane, 3-diethylaminopropyldimethoxymethylsilane, and 3-dibutylaminopropyltriethoxysilane.

[0064] Examples of hydrocarbyloxysilane compounds containing pyridine groups include, but are not limited to, 2-trimethoxysilylethylpyridine.

[0065] Examples of hydrocarbyloxysilane compounds containing silazane groups include, but are not limited to, N,N-bis(trimethylsilyl)-aminopropylmethyldimethoxysilane, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane, and N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane.

[0066] Examples of hydrocarbyloxysilane compounds containing an isocyanate group include, but are not limited to, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropylmethyldiethoxysilane, and 3-isocyanatopropyltriisopropoxysilane.

[0067] Examples of hydrocarbyloxysilane compounds containing a cyano group include, but are not limited to, 2-cyanoethyltriethoxysilane, 2-cyanoethyldiethoxymethylsilane, 3-cyanopropyltriethoxysilane, 2-cyanoethylpropyltriethoxysilane, and 3-cyanopropyldiethoxymethylsilane.

[0068] Examples of hydrocarbyloxysilane compounds containing a carboxylic acid anhydride group include, but are not limited to, 3-trimethoxysilylpropylsuccinic anhydride, 3-triethoxysilylpropylsuccinic anhydride, and 3-methyldiethoxysilylpropylsuccinic anhydride.

[0069] Examples of hydrocarbyloxysilane compounds containing epoxy groups include, but are not limited to, 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2-glycidoxyethyl)methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane.

[0070] Further examples of useful functionalizing agents include trialkyltin halides such as tributyltin chloride, as described in U.S. Patent Nos. 4,519,431, 4,540,744, 4,603,722, 5,248,722, 5,349,024, 5,502,129, and 5,877,336, which are incorporated herein by reference. Examples of useful halogenated organic compounds include cyclic amino compounds such as hexamethyleneimine alkyl chlorides, as described in U.S. Patent Nos. 5,786,441, 5,916,976, and 5,552,473, which are incorporated herein by reference. Further examples include cyclic sulfur- or oxygen-containing azaheterocycles as disclosed in International Patent Publication No. 2004 / 020475, U.S. Patent Application Publication No. 2006 / 0178467, and U.S. Patent No. 6,596,798. Other examples include boron-containing terminators as disclosed in U.S. Patent No. 7,598,322, which is incorporated herein by reference. Still other examples include cyclic siloxanes such as hexamethylcyclotrisiloxane, including those disclosed in U.S. Patent No. 9,920,149, which is incorporated herein by reference. Still other examples include polydimethylsiloxanes.

[0071] Amount of functionalizing agent used The amount of functionalizing agent used in the practice of the present invention can be described in terms of the lithium or metal cation associated with the initiator. In one or more embodiments, the amount of functionalizing agent introduced into the polymerization mixture is greater than 0.70, in other embodiments greater than 0.75, in other embodiments greater than 0.80, in other embodiments greater than 0.85, and in other embodiments greater than 0.90 moles of functionalizing agent per mole of lithium in the initiator. In these or other embodiments, less than 0.99 moles, in other embodiments less than 0.97 moles, and in other embodiments less than 0.95 moles of functionalizing agent per mole of lithium are introduced into the polymerization mixture. In one or more embodiments, from about 0.7 to about 1.0 moles, in other embodiments from about 0.75 to about 0.99 moles, and in other embodiments from about 0.80 to about 0.97 moles of functionalizing agent per mole of lithium are introduced into the polymerization mixture.

[0072] Functionalization Reactions The reaction of each type of functionalizing agent with the polymer can be carried out by introducing the functionalizing agents to the reactive polymer sequentially or simultaneously.

[0073] In one or more embodiments, the reaction between the functionalizing agent and the reactive polymer may occur at a temperature of from about 10° C. to about 150° C., and in other embodiments, from about 20° C. to about 100° C. The time required for the reaction between the functionalizing agent and the reactive polymer to be complete depends on various factors, including the type and amount of initiator used in preparing the reactive polymer, the type and amount of functionalizing agent, and the temperature at which the functionalization reaction is carried out. In one or more embodiments, the reaction between the functionalizing agent and the reactive polymer may be carried out for about 10 to 60 minutes.

[0074] In one or more embodiments, the functionalizing agent is introduced into the polymer cement (i.e., polymerization mixture) while the polymer is dissolved or suspended in the solvent. As will be understood by those skilled in the art, this solution may be referred to as a polymer cement, or more specifically, a reactive or living polymer cement. In one or more embodiments, the characteristics of the polymer cement, such as its concentration, are the same as or similar to the characteristics of the cement prior to functionalization. The composition comprising the functionalized polymer and solvent may be referred to as a polymerization mixture, or in other words, a polymerization mixture comprising a functionalized polymer.

[0075] In one or more embodiments, the polymer modification (i.e., the introduction of the functionalizing agent into the polymer cement) occurs in the same vessel in which the polymerization occurs. In other embodiments, the polymer modification occurs outside of the reaction vessel in which the polymerization occurs. For example, the first and second functionalizing agents can be introduced into the polymerization mixture (i.e., the polymer cement) in a downstream vessel or downstream transfer conduit.

[0076] According to one or more embodiments, as a result of the functionalization reaction, greater than 60 mol%, in other embodiments greater than 70 mol%, in other embodiments greater than 80 mol%, in other embodiments greater than 85 mol%, in other embodiments greater than 90 mol%, and in other embodiments greater than 95 mol% of the polymer chains in the polymer cement comprise a terminal functional group (i.e., residues of a functionalizing agent). In one or more embodiments, from about 60 mol% to about 100 mol%, in other embodiments from about 70 mol% to about 99 mol%, in other embodiments from about 80 mol% to about 98 mol%, and in other embodiments from about 90 mol% to about 97 mol% of the polymer chains in the polymer composition comprise a terminal functional group.

[0077] Polymer Stabilization In one or more embodiments, after modification, the modified polymer (i.e., telechelic polymer) can be optionally stabilized (i.e., stabilized after functionalization). That is, the modified polymer can be stabilized by introducing a stabilizer into the polymerization mixture containing the modified polymer. It is believed that the stabilizer reacts with certain terminal functional groups (e.g., hydrocarbyloxy substituents), and this reaction can occur either upon introduction of the two molecules or after aging of the composition.

[0078] In one or more embodiments, stabilizers known in the art may be used. For example, the stabilizer may include an alkylalkoxysilane as disclosed in U.S. Pat. No. 6,255,404, which is incorporated herein by reference. An exemplary alkylalkoxysilane is octyltriethoxysilane. In other embodiments, the stabilizer may include a long-chain alcohol as disclosed in U.S. Pat. No. 6,279,632, which is incorporated herein by reference. An exemplary long-chain alcohol is sorbitan stearate or sorbitan monooleate. In still other embodiments, the polymer may be stabilized by treating it with an alkylalkoxysilane, as disclosed in U.S. Pat. No. 9,546,237, which is incorporated herein by reference, followed by treatment with a silane containing a hydrolyzable group that forms an acidic species upon hydrolysis, such as methyltrichlorosilane.

[0079] In one or more embodiments of the present invention, arylsilanols (also known as hydroxyphenylsilanes) are advantageously used as stabilizers. Useful arylsilanols are disclosed in U.S. Patent No. 9,255,167, which is incorporated herein by reference. Exemplary arylsilanols include, but are not limited to, triphenylsilanol, also known as hydroxytriphenylsilane, diphenylsilanediol, also known as dihydroxydiphenylsilane, and phenylsilanetriol, also known as trihydroxy(phenyl)silane.

[0080] In one or more embodiments, the functionalized polymers of the present invention can be stabilized by treatment with a silane containing a hydrolyzable group that forms an acidic species upon hydrolysis, either simultaneously with or after treatment with an aryl silanol (e.g., an aryl silane diol or aryl silane triol). Silanes containing a hydrolyzable group that forms an acidic species upon hydrolysis are disclosed in U.S. Patent No. 9,546,237, which is incorporated herein by reference. In certain embodiments, the functionalized polymer is treated with diphenyl silane diol and trimethylsilyl chloride.

[0081] In one or more embodiments, the stabilizing agent is added to the polymer cement after sufficient time has been provided to complete the reaction between the reactive polymer and the functionalizing agent. In one or more embodiments, the stabilizing agent is added to the polymer cement 30 minutes, in other embodiments 15 minutes, and in other embodiments 10 minutes after the time the functionalizing agent is introduced to the polymer cement.

[0082] The amount of stabilizer (i.e., arylsilanol) used in the practice of the present invention can be described in terms of the number of moles of lithium relative to the initiator. In one or more embodiments, greater than 0.5 moles, in other embodiments greater than 1 mole, in other embodiments greater than 2 moles, and in other embodiments greater than 3 moles of stabilizer per mole of lithium in the initiator are introduced into the polymerization mixture. In these or other embodiments, less than 8 moles, in other embodiments less than 7 moles, in other embodiments less than 6 moles, in other embodiments less than 5 moles, and in other embodiments less than 4.5 moles of stabilizer per mole of lithium are introduced into the polymerization mixture. In one or more embodiments, from about 1 to about 7 moles, in other embodiments from about 2 to about 6 moles, and in other embodiments from about 3 to about 5 moles of stabilizer per mole of lithium are introduced into the polymerization mixture.

[0083] In other embodiments, the amount of stabilizer (i.e., aryl silanol) used in the practice of the present invention can be described as a molar ratio to the moles of functionalizing agent used. In one or more embodiments, the ratio of moles of stabilizer to moles of functionalizing agent used is from about 0.5:1 to about 8:1, from about 1:1 to about 7:1 in other embodiments, from about 2:1 to about 6:1 in other embodiments, and from about 3:1 to about 5:1 in other embodiments. In these or other embodiments, the ratio of moles of stabilizer to moles of functionalizing agent used is less than 7:1, less than 6:1 in other embodiments, less than 5.5:1 in other embodiments, less than 5:1 in other embodiments, and less than 4.5:1 in other embodiments.

[0084] When two reagents are used, for example, when treating a polymer with an aryl silanol (e.g., an aryl silanediol or aryl silanetriol) along with a silane containing hydrolyzable groups that form acidic species upon hydrolysis (e.g., a hydrocarbylsilyl chloride, such as trimethylsilyl chloride), the amounts of each reagent used can be the same or different. In one or more embodiments, the total amount of stabilizer (i.e., both compounds), when expressed as a molar ratio to the moles of functionalizing agent, is from about 3:1 to about 10:1, in other embodiments from about 4:1 to about 8:1, and in other embodiments from about 5:1 to about 7:1. In these or other embodiments, the molar ratio of aryl silanol to silane containing hydrolyzable groups that form acidic species upon hydrolysis is from about 0.5:1 to about 4:1, in other embodiments from about 1:1 to about 3:1, and in other embodiments from about 1.5:1 to about 2.5:1.

[0085] In one or more embodiments, stabilization of the polymer (i.e., introduction of the stabilizer) occurs in the same vessel in which polymerization occurred. In these embodiments, this includes the same vessel in which modification occurred. In other embodiments, stabilization of the polymer (i.e., introduction of the stabilizer) occurs outside the vessel in which polymerization occurred. Similarly, in one or more embodiments, stabilization of the polymer occurs outside the vessel in which polymer modification occurred. For example, in one or more embodiments, the stabilizer may be added to the polymerization mixture (i.e., polymer cement) in a vessel or transfer line downstream from the vessel in which polymerization occurred and downstream from the vessel in which polymer modification occurred. For purposes of this specification, the vessel or conduit into which the stabilizer is introduced relative to the polymerization vessel may also be referred to as a second vessel or second reaction zone. In other embodiments, the stabilizer may be introduced to the polymer while it is suspended or dissolved in the monomer.

[0086] Condensation accelerator In one or more embodiments, a condensation promoter may be added to the polymerization mixture after the functionalizing agent has been introduced into the reactive polymer, optionally after the addition of a quenching agent and / or antioxidant, optionally after or together with the stabilizer, and optionally after recovery or isolation of the functionalized polymer. Useful condensation promoters include tin and / or titanium carboxylates and tin and / or titanium alkoxides. One specific example is titanium 2-ethylhexyl oxide. Useful condensation catalysts and their uses are disclosed in U.S. Patent Application Publication No. 2005 / 0159554 (U.S. Patent No. 7,683,151), which is incorporated herein by reference. In other embodiments, organic acids can be used as condensation promoters. Useful types of organic acids include aliphatic, alicyclic, and aromatic monocarboxylic, dicarboxylic, tricarboxylic, and tetracarboxylic acids. Specific examples of useful organic acids include, but are not limited to, acetic acid, propionic acid, butyric acid, hexanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, cyclohexanoic acid, and benzoic acid.

[0087] The amount of condensation promoter used in the practice of the present invention can be described in terms of moles of lithium relative to the initiator. In one or more embodiments, the amount of condensation promoter per mole of lithium is greater than 1.0, in other embodiments greater than 1.5, and in other embodiments greater than 1.8 moles of condensation promoter per mole of lithium in the initiator. In these or other embodiments, less than 4.0, in other embodiments less than 3.3, and in other embodiments less than 3.0 moles of condensation promoter per mole of lithium are introduced into the polymerization mixture. In one or more embodiments, from about 1.0 to about 4.0, in other embodiments from about 1.5 to about 3.3, and in other embodiments from about 1.8 to about 3.0 moles of condensation promoter per mole of lithium are introduced into the polymerization mixture.

[0088] antioxidants In one or more embodiments, an antioxidant may be added to the polymerization mixture after the functionalizing agent has been introduced into the reactive polymer, optionally after the addition of a quenching agent and / or antioxidant, optionally after or together with the stabilizer, and optionally after recovery or isolation of the functionalized polymer. An exemplary antioxidant includes 2,6-di-tert-butyl-4-methylphenol.

[0089] In one or more embodiments, processing aids and other optional additives, such as oils, may be added to the polymer cement after the polymer is formed.

[0090] Optional Quenching In one or more embodiments, after the polymerization reaction or after the reaction between the reactive polymer and the functionalizing agent is achieved or completed, a quenching agent can be added to the polymerization mixture to deactivate any remaining reactive polymer chains and catalyst or catalyst components. The quenching agent can include protic compounds, including, but not limited to, alcohols, carboxylic acids, inorganic acids, water, or mixtures thereof. The amount of quenching agent used can range from 0.5 to 10 moles of quenching agent per mole of lithium used to initiate the polymerization.

[0091] Desolvation of polymers After polymerization and / or polymer modification, optional stabilization, optional introduction of a condensation promoter and / or introduction of an antioxidant, the polymer product can be separated from the solvent, which is sometimes referred to as desolventization. In other words, as described above, the polymer is synthesized in an organic solvent, and during the desolventization step, the organic solvent is separated from the resulting polymer.

[0092] In certain embodiments, desolventization involves hot water and / or steam coagulation. For example, a polymerization mixture containing a blend of modified polymers can be combined with steam or a hot water stream. The heat associated with the steam or hot water stream volatilizes the solvent and any unreacted monomers. The polymer product is then dispersed within the aqueous phase, for example, in the form of polymer crumbs. The nature and size of the polymer crumbs can generally be manipulated by the introduction of mechanical energy (e.g., in the form of a mixer).

[0093] In one or more embodiments, the polymer crumbs are temporarily stored in water as a crumb dispersion until the subsequent drying step described below. The crumb dispersion is generally a mixture of polymer particles or crumbs and water. The polymer particles, sometimes referred to as coagulated polymer, are generally macroscale and have dimensions of at least 1 mm or greater. This crumb dispersion can be contained in a vessel, such as a conventional reactor vessel, such as a continuous stirred tank reactor.

[0094] In one or more embodiments, the polymer crumbs may be further processed to remove residual solvent and dry the polymer (i.e., separate the polymer from the water). In the practice of the present invention, the polymer may be dried using conventional techniques, which may include one or more of filtration, squeezing, and heating. After desolventization and drying, the volatile content of the dried polymer may be less than 2.0% by weight of the polymer, less than 1.0% by weight in other embodiments, and less than 0.5% by weight in other embodiments.

[0095] In other embodiments, the polymer product may be stripped using a devolatilizer, which is an extruder-type device that may operate in conjunction with heat and / or vacuum. In yet other embodiments, the polymerization mixture may be directly drum dried.

[0096] Regardless of the method used to desolventize and dry the polymer, the finished polymer product may be referred to as a dried polymer. The dried polymer may be shaped or otherwise manipulated into bales using conventional techniques. [Industrial Applicability]

[0097] In one or more embodiments, the polymers of the present invention can be used in compounding vulcanizable rubber compositions, which can be useful, for example, in preparing tire components. Rubber compounding techniques and additives used therein are generally disclosed in *The Compounding and Vulcanization of Rubber*, in *Rubber Technology* (2nd Ed. 1973).

[0098] Generally speaking, these vulcanizable rubber compositions include a vulcanizable rubber component, a reinforcing filler, and a curative or curative system. These compositions may also optionally include metal activators, resins, and processing oils, as well as various ingredients that may conventionally be included in these vulcanizable rubber compositions.

[0099] In one or more embodiments, the polyisoprene polymers of the present invention, including telechelic polyisoprenes, may form all or part of the rubber component of a vulcanizable composition, i.e., the rubber component may include other vulcanizable rubbers, sometimes referred to as elastomeric polymers or simply elastomers.

[0100] Rubber compositions can be prepared by using the polyisoprene polymers of the present invention alone or together with other elastomers (i.e., polymers that can be vulcanized to form compositions with rubbery or elastomeric properties). Other elastomers that may be used include natural and synthetic rubbers. Synthetic rubbers are typically obtained from the polymerization of conjugated diene monomers, copolymerization of conjugated diene monomers with other monomers such as vinyl-substituted aromatic monomers, or copolymerization of ethylene with one or more α-olefins and, optionally, one or more diene monomers.

[0101] Exemplary synthetic rubbers include polybutadiene, polyisobutylene-co-isoprene, neoprene, poly(ethylene-co-propylene), poly(styrene-co-butadiene), poly(styrene-co-isoprene), poly(styrene-co-isoprene-co-butadiene), poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene), polysulfide rubber, acrylic rubber, urethane rubber, silicone rubber, epichlorohydrin rubber, and mixtures thereof. These elastomers can have a myriad of macromolecular structures, including linear, branched, and star structures. Natural rubber is synthesized by and obtained from plant life. For example, natural rubber can be obtained from Hevea rubber trees, guayule shrub, gopher plant, mariola, rabbitbrush, milkweed, goldenrods, pale Indian plantain, rubber vine, Russian dandelions, mountain mint, American germander, and tall bellflower.

[0102] Generally, the rubber compositions of the present invention comprise from about 30% to about 65% by weight, and in other embodiments from about 35% to about 60% by weight, and in other embodiments from about 40% to about 55% by weight of rubber (i.e., rubber component), based on the total weight of the tire components.

[0103] In one or more embodiments, the rubber component of the rubber composition of the present invention comprises from about 1% to about 100% by weight, in other embodiments from about 10% to about 90% by weight, and in other embodiments from about 20% to about 80% by weight of polyisoprene polymer produced by the present technology.

[0104] As mentioned above, the rubber composition may include fillers such as inorganic and organic fillers. Examples of organic fillers include carbon black and starch. Examples of inorganic fillers include silica, aluminum hydroxide, magnesium hydroxide, mica, talc (hydrated magnesium silicate), and clay (hydrated aluminum silicate). Carbon black and silica are the most common fillers used in tire manufacturing. In certain embodiments, a mixture of different fillers may be advantageously used.

[0105] The total filler amount used in the rubber composition may be up to about 150 parts by weight per 100 parts by weight of rubber (phr), with from about 5 to about 125 phr, or from about 30 to about 110 phr being typical. In certain embodiments, the total filler content is greater than about 100 phr. In other embodiments, the total filler content is from about 50 to about 100 phr, and in further embodiments, from about 55 to about 95 phr.

[0106] In one or more embodiments, carbon blacks include furnace blacks, channel blacks, and lamp blacks. More specific examples of carbon blacks include super abrasion furnace blacks, medium super abrasion furnace blacks, high abrasion furnace blacks, high speed extrusion furnace blacks, fine furnace blacks, semi-reinforced furnace blacks, medium processed channel blacks, hard processed channel blacks, conductive channel blacks, and acetylene blacks.

[0107] In certain embodiments, the carbon black has a surface area (EMSA) of at least 20 m 2 / g, in other embodiments, at least 35 m 2 The surface area may be expressed in terms of % by mass per gram, and the surface area value may be determined using the cetyltrimethylammonium bromide (CTAB) technique according to ASTM standard D-1765. The carbon black may be in pelletized or non-pelletized flocculent form. The preferred form of the carbon black may depend on the type of mixing equipment used to mix the rubber compound.

[0108] In one or more embodiments, the amount of carbon black used in the rubber composition may be up to about 75 parts by weight per 100 parts by weight of rubber (phr), with exemplary embodiments using from about 5 to about 6 parts by weight phr, or from about 10 to about 55 parts by weight phr.

[0109] In one or more embodiments, silica can be characterized by its surface area, which is a measure of its reinforcing properties. The Brunauer, Emmett, and Teller ("BET") method (described in J. Am. Chem. Soc., 1939, vol. 60, 2 pp. 309-319) is an accepted method for determining surface area. The BET surface area of ​​silica is generally 450 m 2 / g. A useful range of surface area is from about 32 to about 400 m2 / g, about 100~250m 2 / g, and about 150 to about 220 m 2 / g. In one or more embodiments, the silica can be characterized by a pH of about 5 to about 7, or slightly above 7, or in other embodiments, about 5.5 to about 6.8. In certain embodiments, the silica used in the rubber composition is derived solely from rice hull ash, while in other embodiments, the rubber composition does not contain silica from a non-rice hull ash derived process. Some commercially available silicas that can be used include Hi-Sil™ 215, Hi-Sil™ 233, and Hi-Sil™ 190 (PPG Industries, Inc.; Pittsburgh, Pa.). Other suppliers of commercially available silica include Grace Davison (Baltimore, Md.), Degussa Corp. (Parsippany, NJ), Rhodia Silica Systems (Cranbury, NJ), and JM Huber Corp. (Edison, NJ).

[0110] In one or more embodiments, the rubber composition may contain from about 1 to about 150 parts by weight of silica per 100 parts by weight of rubber, from about 5 to about 140 parts by weight in other embodiments, and from about 10 to about 130 parts by weight in other embodiments. In certain embodiments, the present invention includes rubber compositions having high silica loadings, for example, greater than 70 parts by weight per 100 parts by weight of rubber, greater than 90 parts by weight in other embodiments, and greater than 110 parts by weight in other embodiments, with the useful upper limit being limited by the high viscosity imparted by the silica. When silica is used in conjunction with carbon black, the amount of silica or carbon black can be as low as about 1 phr. In one or more embodiments, when carbon black and silica are used in combination as fillers, the weight ratio of silica to total filler may be from about 5% to about 99% by weight of total filler, from about 10% to about 90% by weight in other embodiments, or from about 50% to about 85% by weight in still other embodiments.

[0111] In one or more embodiments, when silica is used as a filler (alone or in combination with other fillers), a coupling agent may be added to the rubber composition during mixing to enhance the interaction between the silica and the elastomer. Useful coupling agents are disclosed in U.S. Patent Nos. 3,842,111, 3,873,489, 3,978,103, 3,997,581, 4,002,594, 5,580,919, 5,583,245, 5,663,396, 5,674,932, 5,684,171, and 5,684,172. Nos. 5,684,172, 5,696,197, 6,608,145, 6,667,362, 6,579,949, 6,590,017, 6,525,118, 6,342,552, and 6,683,135, which are incorporated herein by reference.

[0112] In one or more embodiments, the amount of coupling agent may be from about 2% to about 30% by weight, from about 4% to about 25% by weight in other embodiments, and from about 6% to about 20% by weight in other embodiments, based on the weight of silica in the composition.

[0113] In one or more embodiments, when silica is used as a filler (alone or in combination with other fillers), a silica dispersant, which may include a silica shielding agent, may be included in the rubber compound. The use of one or more silica dispersants has been found to be particularly useful in the practice of the present invention in view of multifunctional polymers and / or high silica loadings. In one or more embodiments, useful silica dispersants include alkylalkoxysilanes, fatty acid esters of hydrogenated or non-hydrogenated C5 or C6 sugars, polyoxyethylene derivatives of fatty acid esters of hydrogenated or non-hydrogenated C5 or C6 sugars, and esters of polyols, including glycols and polyhydroxy compounds, and mixtures thereof. In a particular embodiment, the silica dispersant is glycol monostearate. Useful silane dispersants are disclosed in U.S. Pat. Nos. 6,608,145, 7,799,870, 7,897,661, 8,962,746, 9,758,639, 9,951,208, and U.S. Patent Application Publication Nos. 2004 / 0152811 and 2005 / 0070672, which are incorporated herein by reference.

[0114] In other embodiments, useful silica dispersants include metal glycerolates, such as zinc glycerolate, calcium glycerolate, and magnesium glycerolate, which are described in more detail in U.S. Pat. Nos. 10,087,306 and 11,220,595, and U.S. Patent Application Publication No. 2021 / 0388188, which are incorporated herein by reference.

[0115] In one or more embodiments, the rubber composition of this invention may comprise from about 0.1% to about 30% by weight of silica dispersant, in other embodiments from about 1.0% to about 25% by weight of silica dispersant, in other embodiments from about 3.0% to about 20% by weight of silica dispersant, and in other embodiments from about 4.0% to about 10% by weight of silica dispersant, based on the weight of silica in the composition. In one or more embodiments, the rubber composition comprises greater than 3% by weight, in other embodiments greater than 5% by weight, and in other embodiments greater than 7% by weight of dispersant, based on the weight of silica. In these or other embodiments, the rubber composition may comprise greater than 3 parts by weight, in other embodiments greater than 4 parts by weight, in other embodiments greater than 5 parts by weight, and in other embodiments greater than 6 parts by weight of silica dispersant per 100 parts by weight of rubber.

[0116] A number of rubber curing agents (also called vulcanizing agents) may be used, including sulfur- or peroxide-based cure systems. Curing agents are described in Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 20, pp. 365-468, (3rd Ed. 1982), particularly "Vulcanization Agents and Auxiliary Materials," pp. 390-402, and A.Y. Coran, "Vulcanization," Encyclopedia of Polymer Science and Engineering, (2nd Ed. 1989), which are incorporated herein by reference. Vulcanizing agents may be used alone or in combination.

[0117] Other ingredients typically used in rubber compounding can also be added to the rubber composition. These include accelerators, accelerator activators, oils, plasticizers, waxes, antiscorch agents, processing aids, zinc oxide, tackifying resins, reinforcing resins, fatty acids such as stearic acid, peptizers, and antidegradants such as antioxidants and antiozonants. In certain embodiments, the oils used include those traditionally used as extender oils, as described above. Generally, the rubber compositions of the present invention can contain from about 1 to about 70 parts by weight, or in other embodiments from about 5 to about 50 parts by weight, of total oil per 100 parts by weight of rubber.

[0118] All components of the rubber composition can be mixed using standard mixing equipment, such as, but not limited to, Banbury mixers, Brabender mixers, intermesh mixers, including tandem intermesh mixers, extruders, kneaders, and two-roll mills. In one or more embodiments, the components are mixed in two or more stages. In the first stage (often referred to as the masterbatch mixing stage), a so-called masterbatch (typically containing the rubber component and filler) is prepared. To prevent premature vulcanization (also known as scorch), vulcanizing agents may be omitted from the masterbatch. The masterbatch may be mixed at an initiation temperature of about 25°C to about 125°C and an extrusion temperature of about 135°C to about 180°C. Once the masterbatch is prepared, vulcanizing agents may be introduced and mixed into the masterbatch in a final mixing stage, which is typically performed at a relatively low temperature to reduce the possibility of premature vulcanization. Optionally, an additional mixing stage, often referred to as a remill, may be used between the masterbatch mixing stage and the final mixing stage. When the rubber composition contains silica as a filler, one or more remill stages are often used, and the addition of various ingredients, including the polymer of the present invention, can occur during these remills.

[0119] Mixing procedures and conditions particularly applicable to silica-filled tire compounds are described in U.S. Patent Nos. 5,227,425, 5,719,207, and 5,717,022, and European Patent No. 890,606, all of which are incorporated herein by reference. In one embodiment, an initial masterbatch is prepared by including the polymer and silica in the substantial absence of coupling and shielding agents.

[0120] Rubber compositions prepared from the polymers of this invention are particularly useful in forming tire components such as treads, subtreads, sidewalls, body ply skims, bead fillers, etc. In one or more embodiments, these tread or sidewall compounds may include from about 10% to about 100% by weight, in other embodiments from about 35% to about 90% by weight, and in other embodiments from about 50% to about 80% by weight of the polymers of this invention (based on the total weight of rubber in the compound).

[0121] When rubber compositions are used in tire manufacturing, they can be processed into tire components using conventional tire manufacturing techniques, such as standard rubber molding, molding, and curing techniques. Typically, vulcanization is accomplished by heating the vulcanizable composition in a mold, which can be heated to, for example, about 140°C to about 180°C. The cured or crosslinked rubber composition may be referred to as a vulcanizate, which generally contains a thermoset three-dimensional polymer network. Other ingredients, such as fillers and processing aids, may be uniformly dispersed throughout the crosslinked network. Pneumatic tires can be made as described in U.S. Patent Nos. 5,866,171, 5,876,527, 5,931,211, and 5,971,046, which are incorporated herein by reference. [Example]

[0122] In order to demonstrate the practice of the present invention, the following examples have been prepared and tested. However, these examples should not be construed as limiting the scope of the invention. The claims shall define the invention.

[0123] Sample 1 Synthesis of Di-Li initiator To a small, N2-purged, sealed glass vessel charged with sec-BuLi (2.84 mL of a 1.49 M hexane solution, 4.23 mmol) was added 1,3-diisopropenylbenzene (DIPB) (0.36 mL, 2.1 mmol). To this mixture was added triethylamine (NEt) (0.30 mL, 2.1 mmol), resulting in a deep red solution. The mixture was stirred at 50 °C for 2 h and then used for the polymerization of isoprene.

[0124] Synthesis of multimodal polyisoprene A stainless steel reactor charged with hexane (3.8 kg) and isoprene (0.64 kg) was treated with 2,2-di(2-tetrahydrofuryl)propane (0.66 mL of a 0.16 M hexane solution, 0.11 mmol), followed by the preformed Di-Li catalyst described above. The reactor jacket was heated from 25°C to 50°C. The polymerization reached a peak temperature of 66.7°C after 62 minutes. Analysis of a sample from the reactor 10 minutes after the peak temperature indicated a 94% conversion. A portion of the reactor contents was terminated and coagulated by discharging into a solution (approximately 8 L) of isopropyl alcohol containing 2,5-di-tert-butyl-4-methylphenol (BHT) (approximately 1.8 g / L isopropyl alcohol).

[0125] The polymer obtained from this sample was analyzed for molecular weight moments. The number average (Mn), weight average (Mw), and peak (Mp) molecular weights, as well as the polydispersity (PDI), were determined by gel permeation chromatography (GPC) using a TOSOH Ecosec HLC-8320 GPC system and a TOSOH TSKgel GMHx1-BS column with THF as the solvent. The system was calibrated using polystyrene (PS) standards and referenced to PS and BR standards.

[0126] As mentioned above, Figure 1 shows the GPC trace of the polymer of Sample 1, which shows that the polymer is multimodal. Specifically, the polymer had three peaks (Mp1 = 421 kg / mol, Mp2 = 988 kg / mol, and Mp3 = 1.901 kg / mol), Mn was 473 kg / mol, mw was 878 kg / mol, and polydispersity was 1.86.

[0127] Sample 2 Synthesis of Di-Li initiator To a small, N2-purged, sealed glass vessel charged with sec-BuLi (14.42 mL of a 1.40 M solution in hexane, 20.2 mmol) was added 1,3-diisopropenylbenzene (DIPB) (1.63 mL, 9.53 mmol). To this mixture was added triethylamine (1.33 mL, 9.53 mmol), resulting in a deep red solution. The mixture was stirred at 50 °C for 2 h to form the DIPB Di-Li species.

[0128] Synthesis of Di-Li butadiene oligomers To a separate small, N2-purged, sealed glass vessel charged with hexane (23.0 mL) and a hexane solution of 1,3-butadiene (24.1 mL of a 21.2 wt% solution, 63.5 mmol), 2,2-di(2-tetrahydrofuryl)propane (1.32 mL of a 0.16 M hexane solution, 0.21 mmol) (0.05:1 Li) was added, followed by the above DIPB Di-Li solution (3.86 mL of a 0.548 M solution, 2.12 mmol). The mixture was stirred at 50 °C for 0.5 h to form the DIPB-BD Di-Li initiator, a golden-colored solution with a relatively low viscosity.

[0129] Synthesis of unimodal polyisoprene A stainless steel reactor charged with hexane (3.8 kg) and isoprene (0.64 kg) was treated with the above preformed DIPB-BD Di-Li initiator (51.7 mL of a 0.041 M hexane solution, 2.12 mmol). The reactor jacket was ramped from 25°C to 50°C. The polymerization reached a peak temperature of 83.2°C after 38 minutes. Analysis of a sample from the reactor 20 minutes after peak temperature indicated a 91% conversion. A portion of the reactor contents was terminated and coagulated by discharging into a solution (approximately 8 L) of isopropyl alcohol containing 2,5-di-tert-butyl-4-methylphenol (BHT) (approximately 1.8 g / L isopropyl alcohol) to obtain an unfunctionalized control sample that was found to be unimodal (see Table 2 and Figure 2 for characterization details).

[0130] The polymer obtained from this sample was analyzed for molecular weight moments using the same techniques provided for Sample 1. The polymer was also analyzed for vinyl content by 400 MHz NMR using CDCl3 as the solvent.

[0131] Figure 2, as described above, is a GPC trace of the polymer of Sample 2, showing that the polymer is unimodal. Specifically, the polymer was characterized by an Mn of 387 kg / mol, an Mw of 477 kg / mol, an Mw / Mn of 1.23, a 1,4-cis content of 72.9%, a 1,4-trans content of 19.7%, and a 3,4-vinyl content of 7.4%.

[0132] This example highlights that by first forming polybutadiene oligomers and then polymerizing isoprene, a polymer with a relatively narrow, unimodal polymer chain distribution can be obtained. In addition, this route allows for the use of relatively low levels of lithium coordination modifier, resulting in a unimodal distribution with a relatively low content (less than 10%) of 3,4-vinyl microstructure.

[0133] Sample 3 and Sample 9 Synthesis of Di-Li initiator source solution To a small, N2-purged, sealed glass vessel charged with sec-BuLi (13.74 mL of a 1.40 M solution in hexane, 19.2 mmol) was added 1,3-disisopropenylbenzene (DIPB) (1.63 mL, 9.53 mmol). To this mixture was added triethylamine (NEt) (1.33 mL, 9.53 mmol), resulting in a deep red solution. The mixture was stirred at 50 °C for 2 h, after which a portion of the Di-Li solution (1.75 mL) was diluted with hexane (8.25 mL) to form a 0.100 M Di-Li initiator stock solution.

[0134] Polymerization of isoprene A hexane solution (19.5 mL) of a 15 wt% isoprene blend was introduced into each of eight 25 mL reactors under a nitrogen atmosphere. Various amounts of 0.016 M 2,2-di(2-tetrahydrofuryl)propane (i.e., Lewis base) solution were then added to each reactor, as shown in Table I, followed by a fixed amount of 0.100 M Di-Li initiator stock solution (0.130 mL, 0.0130 mmol). Samples 3–6 were then heated at 50°C for 3 hours, and samples 7–10 were heated at 65°C for 3 hours, after which a quench containing 2,5-di-tert-butyl-4-methylphenol (BHT) was added to each reactor. Samples were collected for GPC analysis (see Table I).

[0135] As shown in Figures 3A-3D and Table I, the use of a sufficient amount of Lewis base during polymerization yields monomodal polymers with narrow molecular weight distributions typical of anionic polymerizations. Increasing the polymerization temperature from 50 to 65 °C did not significantly affect these results.

[0136] [Table 1]

[0137] Sample 11 Synthesis of Di-Li initiator To a small, N2-purged, sealed glass vessel charged with sec-Buli (14.42 mL of a 1.40 M hexane solution, 20.2 mmol) was added 1,3-diisopropenylbenzene (DIPB) (1.63 mL, 9.53 mmol). To this mixture was added N,N,N',N'-tetramethylethylenediamine (TMEDA) (1.43 mL, 9.53 mmol), resulting in a deep red solution. The mixture was stirred at 50 °C for 2 h, after which a portion was used for the polymerization of isoprene.

[0138] Synthesis of unimodal polyisoprene A stainless steel reactor charged with hexane (3.8 kg) and isoprene (0.64 kg) was treated with 2,2-di(2-tetrahydrofuryl)propane (1.32 mL of a 0.16 M solution in hexane, 0.21 mmol) (0.10:1 LiDO), followed by a portion of the preformed Di-Li catalyst described above (3.88 mL of a 0.545 M solution in hexane, 2.12 mmol). The reactor jacket was heated from 25°C to 50°C. The polymerization reached a peak temperature of 67.8°C after 81 minutes. Analysis of a sample from the reactor 20 minutes after peak temperature indicated 90% conversion. A portion of the reactor contents was terminated and coagulated by discharging into a solution (approximately 8 L) of isopropyl alcohol containing 2,5-di-tert-butyl-4-methylphenol (BHT) (approximately 1.8 g / L isopropyl alcohol).

[0139] The polymer obtained from this sample was analyzed for molecular weight moment and vinyl content using the same techniques provided for Sample 2. Figure 4, as described above, is a GPC trace of the polymer of Sample 11, showing that the polymer is unimodal. Specifically, the polymer was characterized by an Mn of 312 kg / mol, an Mw of 359 kg / mol, an Mw / Mn of 1.15, a 1,4-cis content of 60.9%, a 1,4-trans content of 21.4%, and a 3,4-vinyl content of 17.7%.

[0140] Various modifications and alterations that do not depart from the scope and spirit of the present invention will be apparent to those skilled in the art. This invention is not to be duly limited to the illustrative embodiments set forth herein.

Claims

1. 1. A method for polymerizing isoprene, said method comprising: (i) providing a dilithium initiator; (ii) introducing the dilithium initiator into isoprene monomer to form a polymerization mixture; (iii) polymerizing the isoprene monomers to form polyisoprene, wherein the polyisoprene is characterized by a monomodal molecular weight distribution.

2. 10. The method of claim 1, wherein the step of providing a dilithium initiator comprises aging the dilithium initiator for greater than 15 minutes.

3. 3. The method of claim 1 or 2, wherein the dilithium initiator is aged in the presence of a Lewis base.

4. 4. The method of any one of claims 1 to 3, wherein the dilithium initiator is aged in the presence of an alkylenediamine, and the molar ratio of the alkylenediamine to lithium atoms associated with the dilithium initiator is greater than 0.05:

1.

5. The method of any one of claims 1 to 4, wherein the alkylenediamine is N,N,N',N'-tetramethylethylenediamine.

6. 6. The method of any one of claims 1 to 5, wherein the polymerization mixture comprises a Lewis base and the molar ratio of the Lewis base to lithium atoms associated with the dilithium initiator is greater than 0.05:

1.

7. 7. The method of any one of claims 1 to 6, wherein the Lewis base in the polymerization mixture is selected from the group consisting of 2,2-bis(2-oxolanyl)propane (also known as 2,2-ditetrahydrofurylpropane), meso-2,2-ditelahydrofurylpropane, DL-2,2-ditetrahydrofurylpropane, triethylamine, TMEDA, and mixtures thereof.

8. 8. The method of any one of claims 1 to 7, further comprising the steps of: introducing the dilithium initiator to 1,3-butadiene before the step of introducing the dilithium initiator to isoprene monomer; and polymerizing the 1,3-butadiene to form a macromolecule comprising two reactive polybutadiene chains.

9. 9. The method of any one of claims 1 to 8, wherein the amount of 1,3-butadiene in which the dilithium initiator is introduced is represented by a molar ratio of 1,3-butadiene to lithium atoms associated with the dilithium initiator of from about 3:1 to about 100:

1.

10. 10. The method of any one of claims 1 to 9, wherein the dilithium initiator is formed by reacting an alkyllithium compound with a dialkenyl compound.

11. The method of any one of claims 1 to 10, wherein the dialkenyl compound is 1,3-diisopropenylbenzene.

12. The method of any one of claims 1 to 11, wherein the polymerization mixture comprises a solvent.

13. 13. The method of any one of claims 1 to 12, further comprising the step of introducing a functionalizing agent into the polymerization mixture to form telechelic polyisoprene.

14. The functionalizing agent has the formula: 【Chemistry 1】 wherein R ４ is a divalent organic group, and R ５ and R ６ are each independently a hydrocarbyloxy group or a hydrocarbyl group, and R ５ is a monovalent organic group and A is selected from the group consisting of carboxylic acid ester, cyclic tertiary amine, acyclic tertiary amine, pyridine, silazane, epoxy, isocyanate, cyano, carboxylic acid anhydride, and sulfide groups.

15. 15. The method of any one of claims 1 to 14, wherein a stabilizing agent is introduced into the polymerization mixture after the step of introducing a functionalizing agent into the polymerization mixture, thereby forming telechelic polyisoprene.

16. The method of any one of claims 1 to 15, wherein the stabilizing agent is an aryl silanol.

17. 17. The method of any one of claims 1 to 16, wherein the amount of aryl silanol introduced is from about 1 to about 7 moles of aryl silanol per mole of lithium introduced into the polymerization mixture.

18. 18. The method of any one of claims 1 to 17, wherein the aryl silanol is selected from the group consisting of triphenyl silanol, diphenyl silane diol, and phenyl silane triol.

19. 19. The method of any one of claims 1 to 18, wherein after the step of introducing a functionalizing agent to the polymerization mixture, thereby forming telechelic polyisoprene, an aryl silanol and a silane comprising a hydrolyzable group that forms an acidic species upon hydrolysis are introduced to the polymerization mixture.

20. 20. The method of any one of claims 1 to 19, wherein the molar ratio of the aryl silanol to the silane containing a hydrolyzable group that forms an acidic species upon hydrolysis is from about 0.5:1 to about 4:

1.

21. 21. The method of any one of claims 1 to 20, further comprising isolating the telechelic polyisoprene from the polymerization mixture.

22. A telechelic polyisoprene formed by the method of any one of claims 1 to 21.

23. 23. The branched polymer according to any one of claims 1 to 22, wherein the polyisoprene is characterized by a weight average molecular weight of more than 180 kg / mol.

24. A branched polymer according to any one of claims 1 to 23, wherein the polyisoprene is characterized by a vinyl content of more than 10%.

25. A vulcanizable composition comprising the telechelic polyisoprene of any one of claims 1 to 24.

26. A vulcanizate prepared by vulcanizing the vulcanizable composition of any one of claims 1 to 25.

27. A tire component prepared from the vulcanizable composition of any one of claims 1 to 26.

28. A tire tread prepared from the vulcanizable composition of any one of claims 1 to 27.

29. 1. A vulcanizable composition comprising: (i) a branched polymer, (a) providing a dilithium initiator; (b) introducing the dilithium initiator into isoprene monomer to form a polymerization mixture; (c) polymerizing the isoprene monomers to form a polyisoprene, the polyisoprene being characterized by a monomodal molecular weight distribution; and (ii) silica; and (iii) a curing agent.

30. 30. The vulcanizable composition of claim 29, further comprising a silica coupling agent.

31. 31. The vulcanizable composition of any one of claims 29 or 30, further comprising a silica dispersant.

32. The silica dispersant is an alkylalkoxysilane, hydrogenated or non-hydrogenated C ５ or C ６ Fatty acid esters of sugars, hydrogenated or non-hydrogenated C ５ or C ６ 32. The vulcanizable composition according to any one of claims 29 to 31, wherein the polyoxyethylene derivatives of fatty acid esters of sugars and esters of polyols are selected from the group consisting of polyoxyethylene derivatives of fatty acid esters of sugars and esters of polyols, and mixtures thereof.

33. 33. The vulcanizable composition of any one of claims 29 to 32, wherein said silica dispersant is glycol monostearate.

34. The vulcanizable composition of any one of claims 29 to 33, wherein the silica dispersant is a metal glycerolate.

35. The vulcanizable composition of any one of claims 29 to 34, wherein the metal glycerolate is zinc glycerolate.

36. 36. The vulcanizable composition of any one of claims 29 to 35, wherein the vulcanizable composition comprises greater than 70 parts by weight of silica per 100 parts by weight of rubber.

37. 37. The vulcanizable composition of any one of claims 29 to 36, wherein the vulcanizable composition comprises from about 2% to about 30% by weight of a silica coupling agent, based on the weight of the silica.

38. 38. The vulcanizable composition of any one of claims 29 to 37, wherein the vulcanizable composition comprises from about 0.1 wt% to about 30 wt% of a silica dispersant, based on the weight of the silica.

39. 39. The vulcanizable composition of any one of claims 29 to 38, wherein the polyisoprene is a telechelic polyisoprene formed by reacting the polymer with a functionalizing agent.

40. A vulcanizate prepared by vulcanizing the vulcanizable composition of any one of claims 1 to 39.

41. A tire component prepared from the vulcanizable composition of any one of claims 1 to 40.

42. A tire tread prepared from the vulcanizable composition of any one of claims 1 to 41.

43. 1. A method for forming a vulcanizable composition, said method comprising: (i) a polyisoprene polymer, the polyisoprene polymer comprising: (a) providing a dilithium initiator; (b) introducing the dilithium initiator into isoprene monomer to form a polymerization mixture; (c) polymerizing the isoprene monomers to form polyisoprene, wherein the polyisoprene is characterized by a monomodal molecular weight distribution; (ii) providing silica; (iii) providing a curing agent; (iv) mixing the branched polymer, the silica, and the curing agent to form the vulcanizable composition.

44. 44. The method of claim 43, wherein the polyisoprene is a telechelic polyisoprene formed by reacting the polyisoprene with a functionalizing agent.

45. 45. The method of claim 43 or 44, further comprising providing a silica coupling agent, and further comprising mixing the telechelic polyisoprene, the silica, and the silica coupling agent.

46. 46. ​​The method of any one of claims 43-45, further comprising providing a silica dispersant, and further comprising mixing the telechelic polyisoprene, the silica, and the silica dispersant.

47. 47. The method of any one of claims 43 to 46, further comprising providing a silica coupling agent and a silica dispersing agent, and further comprising mixing the telechelic polyisoprene, the silica, the silica dispersing agent, and the silica coupling agent.

48. The silica dispersant is an alkylalkoxysilane, hydrogenated or non-hydrogenated C ５ or C ６ Fatty acid esters of sugars, hydrogenated or non-hydrogenated C ５ or C ６ 48. The method of any one of claims 43 to 47, wherein the polyoxyethylene derivatives of fatty acid esters of sugars and esters of polyols are selected from the group consisting of polyoxyethylene derivatives of fatty acid esters of sugars and esters of polyols, and mixtures thereof.

49. 49. The method of any one of claims 43 to 48, wherein the silica dispersant is glycol monostearate.

50. 50. The method of any one of claims 43 to 49, wherein the silica dispersant is a metal glycerolate.

51. 51. The method of any one of claims 43 to 50, wherein the metal glycerolate is zinc glycerolate.

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