Anionic dispersion polymerization process for producing random copolymer rubbers

Abstract

To provide an improved reactor anionic dispersion polymerization process which yields a higher molecular weight random SBR at higher solids content.SOLUTION: Embodiments are directed to anionic rubber polymerization processes conducted in a non-aqueous dispersion by utilizing conjugated diene and vinyl aromatic monomers, and a dispersing agent formed in-situ during the polymerization process.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Embodiments of the present disclosure generally relate to anionic rubber polymerization processes carried out in non-aqueous dispersions utilizing conjugated diene and vinyl aromatic monomers and dispersants formed in situ during the polymerization process. [Background technology]

[0002] Random rubber copolymers, such as random styrene-butadiene rubber (SBR) with a styrene content greater than 35%, are more typically polymerized via solution polymerization in aromatic or alicyclic solvents, as opposed to solvents in which SBR is insoluble, such as hexane or other aliphatic solvents. Thus, U.S. Pat. No. 5,891,947, incorporated herein by reference in its entirety, discloses polymerizing styrene and butadiene monomers in a non-aqueous dispersion to produce random SBR rubber having 35 to 70 weight percent styrene monomer. In this process, polymerization is carried out by a two-reactor anionic dispersion polymerization process, in which a soluble dispersant is formed in the first polymerization reactor and an insoluble dispersant is formed in the second polymerization reactor.

[0003] This process can produce a dispersion product with a solids content of at least 20%, which is desirable from the standpoint of industrial needs. In addition to a higher solids content, it is also desirable to increase the molecular weight and Mooney viscosity of the random SBR in the product of the second polymerization reactor, as this can increase the abrasion resistance of the random SBR and products incorporating the random SBR. However, gelation and reactor fouling can occur when increasing the molecular weight of the dispersion product. This gelation is exacerbated in a continuous process.

[0004] Therefore, there is a continuing need for improved reactor anionic dispersion polymerization processes that result in higher molecular weight random SBR at higher solids contents. Summary of the Invention

[0005] Embodiments of the present disclosure meet these dual needs of increased solids content and increased molecular weight in an anionic dispersion polymerization process. Specifically, the present embodiments relate to a process for producing random SBR using anionic dispersion polymerization in two reactors. Without being bound by theory, ensuring that at least 8 wt.% total monomers are added to the first polymerization reactor plays an important role in ensuring that the process obtains increased solids content and increased molecular weight without causing gelation and reactor fouling.

[0006] According to one embodiment, a process for producing a copolymer by anionic dispersion polymerization is provided. The process includes adding a first monomer charge, including a first conjugated diene monomer and optionally a first vinyl aromatic monomer, an organolithium polymerization initiator, and a non-aqueous dispersion medium to a first polymerization reactor. The first monomer charge is polymerized to form a first block of the dispersant, the first block being soluble in the non-aqueous dispersion medium, with at least 8% by weight of the total monomer provided by the first monomer charge, the total monomer being the sum of all monomer charges (e.g., the sum of the first monomer charge and the second monomer charge). The process further includes adding the first block, the non-aqueous dispersion medium, a second monomer charge, including a second vinyl aromatic monomer and a second conjugated diene monomer, and the organolithium polymerization initiator to a second polymerization reactor. The second monomer charge is polymerized to form a copolymer, the copolymer being the polymerization reaction product of at least 30% by weight of a second vinyl aromatic monomer and at least 10% by weight of a second conjugated diene monomer. The second polymerization reactor produces an outlet stream containing the copolymer product and a second block of a dispersant, the second block being insoluble in the non-aqueous dispersion medium and linking with the first block to form the dispersant. The dispersant disperses the copolymer in the non-aqueous dispersion medium. The process may further include adding a coupling agent to the outlet stream, the coupling agent bonding to the copolymer to increase the Mooney viscosity of the copolymer.

[0007] Additional features and advantages of the embodiments described herein are set forth in the Detailed Description below, and in part will be readily apparent to those skilled in the art from this description or will be recognized by practice of the embodiments described herein, including the Detailed Description, Claims, and accompanying drawings. [Brief explanation of the drawings]

[0008] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the drawings included herein.

[0009] [Figure 1] 1 is a schematic illustration of an anionic dispersion polymerization process according to one or more embodiments of the present disclosure.

[0010] The embodiments set forth in the drawings are illustrative in nature and are not intended to limit the embodiments defined by the claims. Moreover, individual features of the drawings will become more fully apparent and understood by consideration of the Detailed Description. DETAILED DESCRIPTION OF THE INVENTION

[0011] definition

[0012] As used herein, "copolymer" or "copolymer rubber" means a copolymer prepared by the sequential copolymerization of at least one conjugated diene monomer and at least one vinyl aromatic monomer. "Copolymer" may include the polymerization reaction product of two or more monomers.

[0013] As used herein, a "random copolymer" is a copolymer of a conjugated diene monomer and a vinyl aromatic monomer (VAM), wherein no more than 5% by weight of the copolymer consists of vinyl aromatic monomer (VAM) blocks of 10 or more VAM units. Similarly, a "random SBR" is a copolymer of butadiene and a styrene monomer, wherein no more than 5% by weight of the copolymer consists of styrene blocks of 10 or more styrene units.

[0014] As used herein, the terms "first block," "A block," "block A," and "A" may be used interchangeably as partial components of a dispersant. Similarly, as used herein, the terms "second block," "B block," "block B," and "B" may be used interchangeably as partial components of a dispersant.

[0015] As used herein, "charge," "manifold," and "feed" may be used interchangeably to refer to the reactant streams introduced into the first polymerization reactor and / or the second polymerization reactor.

[0016] As used herein, "percent (%) solids" is defined by the following formula:

[0017] % solids = ((weight of polymer) / total weight of solution) * 100%.

[0018] An embodiment of the present disclosure relates to a process for producing a copolymer by anionic dispersion polymerization. Referring to the embodiment of FIG. 1, the process 1 includes adding a first monomer charge 14 to a first polymerization reactor 10, the first monomer charge 14 including a first conjugated diene monomer and optionally a first vinyl aromatic monomer. While FIG. 1 shows the first conjugated diene monomer and the first vinyl aromatic monomer being fed in a single stream (first monomer charge 14), it is contemplated that the monomers may be delivered to the first polymerization reactor 10 in separate feed streams. As further shown in FIG. 1, a second feed stream 12 to the first polymerization reactor 10 includes an organolithium polymerization initiator and a non-aqueous dispersing medium. Again, while the embodiment of FIG. 1 shows the feed components, the organolithium polymerization initiator and the non-aqueous dispersing medium, being fed in a single stream (e.g., stream 12), it is contemplated that these feed components may be delivered to the first polymerization reactor 10 in separate feed streams.

[0019] 1 , additional components, such as a randomizer or modifier as further described below, may be fed to the first polymerization reactor 10. In one embodiment, the randomizer is delivered along with the first conjugated diene monomer and the first vinyl aromatic monomer in the first monomer charge 14 stream. In further embodiments, the randomizer may be added to the first polymerization reactor, to the second polymerization reactor described below, or to both.

[0020] During operation, the first monomer charge 14 in the first polymerization reactor 10 is polymerized to form a first block 16 of the dispersant, which is soluble in the non-aqueous dispersion medium. As described further below, at least 8 wt. % of the total monomers is provided by the first monomer charge 14, the total monomers being the sum of the first monomer charge 14 and the second monomer charge 22. In further embodiments, at least 10 wt. % of the total monomers is provided by the first monomer charge 14. In other words, the first monomer charge 14 may deliver 8 wt. % to 20 wt. % of the total monomers to the first polymerization reactor 10, or 10 wt. % to 20 wt. %, or 8 wt. % to 20 wt. %. In one or more embodiments, the first monomer charge comprises 75 to 98 wt. % of the first conjugated diene monomer and 2 to 25 wt. % of the first vinyl aromatic monomer. In one or more embodiments, the first monomer charge comprises 75 to 100 weight percent of a first conjugated diene monomer and 0 to 25 weight percent of a first vinyl aromatic monomer.

[0021] Maintaining at least 8 wt% total monomer in the first polymerization reactor 10 ensures that a sufficient amount of first block 16 is produced in the first polymerization reactor 10. Without being limited by theory, controlling the amount of first block 16 produced, which can be considered a seed polymer, helps control the composition and viscosity of the product in the second polymerization reactor 20, reducing concerns about gelation due to molecular weight growth in the second reactor and during any in-line addition of a coupling agent downstream of the second polymerization reactor 20.

[0022] 1 , the first block 16 is subsequently fed to a second polymerization reactor 20. In addition to the first block 16, a second monomer charge 22 comprising a second vinyl aromatic monomer and a second conjugated diene monomer is fed to the second polymerization reactor 20. In most embodiments, the first vinyl aromatic monomer and the second vinyl aromatic monomer are compositionally the same, and the first conjugated diene monomer and the second conjugated diene monomer are also compositionally the same. However, it is contemplated that the monomer composition may vary in alternative embodiments.

[0023] Referring again to FIG. 1 , an organolithium polymerization initiator 18 is also fed to the second polymerization reactor 20. In one embodiment, the organolithium polymerization initiator 18 is shown in FIG. 1 as being mixed with the first block 16 upstream of the second polymerization reactor 20 to produce a combined stream 19 comprising the first block 16 and the organolithium polymerization initiator 18. In an alternative embodiment, it is contemplated that the organolithium polymerization initiator 18 may be fed to the second polymerization reactor 20 separately from the first block 16. Similar to the feed to the first polymerization reactor 10, additional components, such as a randomizer or modifier as described further below, may be fed to the second polymerization reactor 20. In one embodiment, the modifier is delivered along with the second conjugated diene monomer and the second vinyl aromatic monomer in the second monomer charge 22 stream. In further embodiments, the modifier may be added to the first polymerization reactor, the second polymerization reactor, or both.

[0024] In the second polymerization reactor 20, a second monomer charge 22 of a second vinyl aromatic monomer and a second conjugated diene monomer is polymerized to form a copolymer that is the polymerization reaction product of at least 30% by weight of the second vinyl aromatic monomer and at least 10% by weight of the second conjugated diene monomer. In further embodiments, the copolymer may comprise at least 33%, at least 35%, or at least 38% by weight of the second vinyl aromatic monomer and at least 15%, at least 20%, at least 25%, at least 30%, or at least 35% by weight of the second conjugated diene monomer.

[0025] Referring again to FIG. 1 , in addition to the copolymer, outlet stream 24 of second polymerization reactor 20 also contains a second block of dispersant. The second block of the dispersant is insoluble in the non-aqueous dispersion medium and is linked with the first block to form the dispersant. The dispersant disperses the copolymer in the non-aqueous dispersion medium in outlet stream 24. Because the polymerization reactor is not terminated in outlet stream 24, the copolymer may be considered a living copolymer. In one or more embodiments, outlet stream 24 may contain 15-30 wt % solids, 15-25 wt % solids, or 20-25 wt % solids.

[0026] Dispersants useful in the present disclosure are selected from a variety of polymers containing at least two blocks linked by chemical valence, and are polyblock copolymers in that at least one of the blocks (the first block) is soluble in the non-aqueous dispersion medium and at least another of the blocks (the second block) is insoluble in the non-aqueous dispersion medium. The insoluble second block provides an anchor segment for binding to the copolymer through a physical adsorption process, for example, by van der Waals forces. Therefore, their primary criterion for success as anchors is their relative immiscibility in the dispersion medium. The soluble first block of the dispersant provides a sheath around the otherwise insoluble copolymer, maintaining the copolymer product as many small, individual particles rather than as an aggregated or highly coalesced mass. The insoluble second block may optionally contain multiple pendant groups.

[0027] The soluble first block of the dispersant constitutes at least 8 weight percent of the total dispersion copolymer, including the dispersant and copolymer, in the outlet stream 24. The insoluble second block of the dispersant is prepared in situ during the continuous polymerization of the SBR-type random copolymer, so that the second block has the same composition as the copolymer formed during the dispersion copolymerization process. The total dispersion copolymer composition contains 8 to 20 weight percent of the soluble first block and about 80 to about 92 weight percent of the insoluble second block and copolymer, or specifically 10 to 12 weight percent of the first block and 88 to about 90 weight percent of the second block and copolymer. The number average molecular weight Mn of the first block is 500 to 200,000 g / mol, or 1,000 to 100,000 g / mol. The number average molecular weight of the second block is the same as that of the copolymer, ie, 20,000 to 2,500,000 g / mol, or 75,000 to 500,000 g / mol.

[0028] The soluble first block is a polymer formed from 75 to 100 parts by weight, or 75 to 98 parts by weight, of a conjugated diene monomer and 0 to 25 parts by weight, or 2 to 25 parts by weight, of a vinyl aromatic monomer, with all polymer or copolymer blocks being soluble in the hydrocarbon dispersing medium. The insoluble second block can be prepared by copolymerizing 30 to 70 parts by weight of a conjugated diene monomer with 35 to 70 parts by weight of a vinyl aromatic monomer. The dispersant prepared in situ and used in the preparation of the SBR copolymer is recovered as a blend with the copolymer. The dispersant is prepared and present in an amount ranging from about 2 to 50 weight percent of the total weight of the dispersant copolymer, including the dispersant and copolymer, in outlet stream 24.

[0029] The sequential polymerization reactions in the first polymerization reactor 10 and the second polymerization reactor 20 can be carried out at a temperature ranging from 0°C to 155°C. In one embodiment, the reaction temperature is 90°C to 130°C, which may occur naturally due to the exothermic polymerization reaction. The reactor residence time in such sequential polymerizations can vary depending on the reaction temperature, monomer concentration, catalyst system, and catalyst level. Generally, the reactor residence time can vary from about 10 minutes up to 60 minutes, or from 15 minutes to 45 minutes. It is desirable to carry out the polymerizations in an oxygen- and moisture-free environment.

[0030] Referring again to FIG. 1 , a coupling agent 26 may be added to the outlet stream 24 after it exits the second polymerization reactor 20. In one embodiment, the coupling agent is added along with the non-aqueous dispersing medium. During operation, the coupling agent 26 bonds to the copolymer in the outlet stream 24, increasing the molecular weight and Mooney viscosity of the copolymer. As shown, the coupling agent 26 may be provided to the outlet stream 24 upstream of a downstream collection vessel 30, which recovers the dispersed copolymer and dispersing agent from the second polymerization reactor 20. Addition of the coupling agent 26 downstream of the second polymerization reactor 20 but upstream of the collection vessel 30 may be described as providing the coupling agent 26 “in-line.” Adding the coupling agent 26 to the outlet stream 24 causes the coupling agent 26 to react with the dispersion, thereby allowing the coupling agent to react and bond to the copolymer.

[0031] In addition to providing additional residence time for reaction of the coupling agent with the copolymer, collection vessel 30 may be used to terminate the copolymer. Accordingly, additional components may be added to collection vessel 30. For example, one or more polymerization terminators (e.g., isopropanol or water) may be added. Additional additives, such as extenders and antioxidants, may also be added.

[0032] The bound copolymer 32 exiting the recovery vessel 30 can be recovered from the non-aqueous dispersion medium (e.g., hydrocarbon solvent) by steam desolventization or drum drying techniques, thus providing energy savings due to higher solids levels. With proper control of particle size, the copolymer can be recovered by filtration or centrifugation techniques.

[0033] Conjugated Copolymer

[0034] The binder copolymer may comprise at least 30% by weight of the second vinyl aromatic monomer and at least 10% by weight of the second conjugated diene monomer. In further embodiments, the binder copolymer may comprise at least 33%, at least 35%, or at least 38% by weight of the second vinyl aromatic monomer and at least 15%, at least 20%, at least 25%, at least 30%, or at least 35% by weight of the second conjugated diene monomer. The number average molecular weight of the binder copolymer may be 75,000 to 500,000 g / mol. The binder copolymer may have a Mooney viscosity of 120 to 160.

[0035] reactor

[0036] The first polymerization reactor 10 and the second polymerization reactor 20 downstream of the first polymerization reactor 20 may comprise a variety of contemplated reaction vessels well known to those skilled in the art. During polymerization, it may be desirable to provide some form of stirring or agitation to the first polymerization reactor 10 and the second polymerization reactor 20. As a result, embodiments may include continuous stirred tank reactors such as those shown in FIG. 1 for the first polymerization reactor 10 and the second polymerization reactor 20.

[0037] monomer

[0038] The first conjugated diene monomer and the second conjugated diene monomer refer to a monomer composition having at least two double bonds separated by a single bond. The processes described herein may use at least one conjugated diene monomer containing fewer than 20 carbon atoms (i.e., 4 to 19 carbons), 4 to 12 carbons, or 4 to 8 carbons. Examples of conjugated diene monomers include 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, and 2,4-hexadiene. Mixtures of two or more conjugated dienes may also be utilized in the copolymerization. In one embodiment, the first conjugated diene monomer is a 1,3-butadiene monomer. In a further embodiment, the first conjugated diene monomer and the second conjugated diene monomer comprise 1,3-butadiene.

[0039] The first vinyl aromatic monomer and the second vinyl aromatic monomer may include any vinyl or α-methyl vinyl aromatic compound that can be polymerized by an anionic initiator. Particularly useful monomers for this purpose are vinyl aryl compounds and α-methyl vinyl aryl compounds, such as styrene, α-methyl styrene, vinyl toluene, vinyl naphthalene, α-methyl vinyl toluene, vinyl diphenyl, and corresponding compounds in which the aromatic nucleus can have other alkyl derivatives up to 8 carbon atoms. Certain vinyl aromatic monomers are not suitable for use in this dispersion polymerization process because their homopolymers are soluble in linear alkane solvents such as hexane, and their copolymers with dienes are also soluble. An example of an unsuitable monomer type is t-butylstyrene. In one or more embodiments, the first conjugated diene monomer and the second conjugated diene monomer comprise butadiene, and the first vinyl aromatic monomer and the second vinyl aromatic monomer comprise styrene.

[0040] non-aqueous dispersion medium

[0041] The non-aqueous dispersing medium used in the present polymerization process is an aliphatic hydrocarbon, preferably a straight chain aliphatic hydrocarbon including butane, pentane, hexane, heptane, octane, nonane, and a branched chain aliphatic hydrocarbon including isopentane, isohexane, isoheptane, isooctane, and isononane, and the like, and mixtures thereof.

[0042] A specific solvent for use as the dispersion medium in this process is isohexane. The solvent can be composed of up to 100% acyclic or linear aliphatic hydrocarbons, preferably up to 70% acyclic aliphatic hydrocarbons or linear aliphatic hydrocarbons, although up to 30% by weight of the total solvent can be provided by at least one alicyclic hydrocarbon such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and aromatic hydrocarbons such as benzene and toluene. A higher proportion of VAM units in SBR allows for a higher proportion of non-aliphatic linear hydrocarbons to be present in the solvent mixture.

[0043] The solvent has a Hansen solubility parameter of 7.6 (cal / mL). 1 / 2 , 7.5 (cal / mL) 1 / 2 , or 7.4 (cal / mL) 1 / 2 A method for calculating the Hansen solubility parameter is provided in Handbook of Solubility Parameters, Allan F.M. Barton, Ph.D., CRC Press, 1983.

[0044] Organolithium Polymerization Initiator

[0045] The organolithium polymerization initiator catalyst system is an anionic initiator for use in preparing SBR copolymers and dispersants, and can be any organolithium catalyst known in the art as being useful, for example, for the polymerization of vinyl aromatic hydrocarbons and conjugated dienes. Suitable organolithium polymerization initiators for initiating the polymerization of the monomer system and dispersant include organolithium catalysts having the formula R(Li), where R represents 1 to 20 hydrocarbyl radicals, preferably 2 to 8 carbon atoms per R group, and x is an integer from 1 to 4, preferably 1 or 2. Typical R groups include aliphatic and alicyclic radicals, such as alkyl, cycloalkyl, cycloalkylalkyl, alkylcycloalkyl, aryl, and alkylaryl radicals.

[0046] Illustrative examples of R groups for substitution in the above formula include primary, secondary, and tertiary groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-amyl, isoamyl, n-hexyl, n-octyl, n-decyl, cyclopentyl-methyl, cyclohexyl-ethyl, cyclopentyl-yl, methyl-cyclopentylethyl, cyclopentyl, cyclohexyl, 2,2,1-bicycloheptyl, methylcyclopentyl, dimethylcyclopentyl, ethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, isopropylcyclohexyl, and the like.

[0047] Other suitable lithium catalysts include phenyllithium, naphthyllithium, 4-butylphenyllithium, p-tolyllithium, 4-phenylbutyllithium, 4-butylcyclohexyllithium, 4-cyclohexylbutyllithium, 1,4-dilithiobutane, 1,10-dilithio-decane, 1,20-dilithioeicosane, 1,4-dilithiobenzene, 1,4-dilithionaphthalene, 1,10-dilithioanthracene, 1,2-dilithio-1,2-diphenylethane, 1,3,5-trillithiopentane, 1,5,15-trillithioeicosane, 1,3,5-trillithiocyclohexane, 1,3,5,8-tetralithiodecane, 1,5,10,20-tetralithioeicosane, 1,2,4,6-tetralithiocyclohexane, 4,4'-dilithiobiphenyl, and the like.

[0048] Preferably R(Li) x Mixtures of different organolithium polymerization initiators may also be used, containing one or more lithium compounds such as, In one embodiment, the organolithium polymerization initiator for use in the present disclosure is n-butyllithium.

[0049] Other organolithium polymerization initiators that can be used are lithium dialkylamines, lithium dialkylphosphines, lithium alkylarylphosphines, lithium diarylphosphines, and trialkyltinlithiums such as tributyl-tin-lithium.

[0050] The organolithium polymerization initiator is typically charged to the reaction vessel in an amount ranging from 0.2 millimoles to 20 millimoles of organolithium polymerization initiator per 100 grams of total monomer. All amounts of organolithium polymerization initiator are expressed in terms of 100 grams of monomer or ratio of components in the instant process and are considered to be catalytically effective amounts, i.e., an amount effective to initiate and effect polymerization of the dispersant block with the disclosed monomer system to produce the copolymers of the present disclosure.

[0051] For example, the first block of the dispersant may be prepared using 0.5 to 200 millimoles of organolithium polymerization initiator per 100 grams of monomer. A second stream of 0.2 to 20 millimoles of organolithium polymerization initiator is then added to a second polymerization reactor to simultaneously produce the second block of the dispersant and a copolymer of the vinyl aromatic monomer and the conjugated diene monomer. The copolymer may be considered a separate block. In one or more embodiments, 10 to 50 weight percent of the total amount of organolithium polymerization initiator added to the first and second polymerization reactors is added to the first polymerization reactor. In further embodiments, 20 to 40 weight percent, or 25 to 35 weight percent, of the organolithium polymerization initiator is used in the preparation of the first block. Conversely, the remaining 50 to 90 weight percent of the organolithium polymerization initiator is charged during the in-situ preparation of the second block and copolymer. In further embodiments, 60 to 80 weight percent, or 65 to 75 weight percent, of the organolithium polymerization initiator is used during the in situ preparation of the second block and copolymer.

[0052] Randomizer

[0053] Various randomizer compositions suitable for promoting the random copolymerization of vinyl aromatic monomers and conjugated diene monomers are contemplated. These may include oligomeric oxolanylpropane, tetrahydrofuran, tetramethylethylenediamine, diethyl ether, ditetrahydrofurylpropane, and the like. In one embodiment, the randomizer comprises 2,2-ditetrahydrofurylpropane. In another embodiment, the randomizer comprises the meso form of ditetrahydrofurylpropane, as described in U.S. Pat. No. 9,868,795, the entire contents of which are incorporated by reference. The randomizer may generally be used in the polymerization system in a molar ratio of randomizer to organolithium polymerization initiator ranging from 1:100 to 4:1.

[0054] Modifier

[0055] As used herein, modifiers encompass additives that affect the final properties of the copolymer by broadening the molecular weight distribution (MWD = Mw / Mw) or adjusting the vinyl content of the copolymer. In one embodiment, the modifier comprises 1,2-butadiene. 1,2-butadiene may be considered a gel suppressant and, as such, can be used to affect the molecular weight distribution. It is often used at low levels because it can react with the catalyst and adversely affect coupling.

[0056] Coupling Agent

[0057] In the case of coupling agents, various components suitable for coupling to the copolymer to increase the molecular weight and Mooney viscosity of the copolymer are contemplated. In one or more embodiments, the coupling agent may be a non-organometallic aromatic triester coupling agent. Suitable non-organometallic aromatic triester coupling agents may be defined by the following formula I: [ka]

[0058] wherein R, R', and R" are independently selected from hydrocarbyl groups containing 1 to 20 carbons. Non-limiting specific examples include trimethyl 1,2,4-benzenetricarboxylate, triethyl 1,2,4-benzenetricarboxylate, tripropyl 1,2,4-benzenetricarboxylate, tributyl 1,2,4-benzenetricarboxylate, tripentyl 1,2,4-benzenetricarboxylate, trihexyl 1,2,4-benzenetricarboxylate, triheptyl 1,2,4-benzenetricarboxylate, tricyclohexyl 1,2,4-benzenetricarboxylate, trioctyl 1,2,4-benzenetricarboxylate, tri(2-ethylhexyl) Representative examples of non-organometallic trimellitate coupling agents include tri-2-ethylhexyl trimellitate, also known as tri(2-ethylhexyl) 1,2,4-benzenetricarboxylate, or triisononyl trimellitate, also known as trinonyl 1,2,4-benzenetricarboxylate.

[0059] In another embodiment, the non-organometallic aromatic triester coupling agent is of Formula II: [ka]

[0060] wherein R, R', and R" are independently selected from hydrocarbyl groups containing 1 to 20 carbons. Non-limiting specific examples include trimethyl 1,2,3-benzenetricarboxylate, triethyl 1,2,3-benzenetricarboxylate, tripropyl 1,2,3-benzenetricarboxylate, tributyl 1,2,3-benzenetricarboxylate, tripentyl 1,2,3-benzenetricarboxylate, trihexyl 1,2,3-benzenetricarboxylate, triheptyl 1,2,3-benzenetricarboxylate, tricyclohexyl 1,2,3-benzenetricarboxylate, trioctyl 1,2,3-benzenetricarboxylate, tri(2-ethylhexyl) Representative examples of non-organometallic trimellitate coupling agents include tri-2-ethylhexyl hemimellitate, also known as tri(2-ethylhexyl) 1,2,3-benzenetricarboxylate, or triisononyl hemimellitate, also known as trinonyl 1,2,3-benzenetricarboxylate.

[0061] In another embodiment, the non-organometallic aromatic triester coupling agent is of Formula III: [ka]

[0062] wherein R, R', and R" are independently selected from hydrocarbyl groups containing 1 to 20 carbons. Non-limiting specific examples include trimethyl 1,3,5-benzenetricarboxylate, triethyl 1,3,5-benzenetricarboxylate, tripropyl 1,3,5-benzenetricarboxylate, tributyl 1,3,5-benzenetricarboxylate, tripentyl 1,3,5-benzenetricarboxylate, trihexyl 1,3,5-benzenetricarboxylate, triheptyl 1,3,5-benzenetricarboxylate, tricyclohexyl 1,3,5-benzenetricarboxylate, trioctyl 1,3,5-benzenetricarboxylate, tri(2-ethylhexyl) Representative examples of non-organometallic trimellitate coupling agents include tri-2-ethylhexyl trimesitate, also known as tri(2-ethylhexyl) 1,3,5-benzenetricarboxylate, or triisononyl trimesitate, also known as trinonyl 1,3,5-benzenetricarboxylate.

[0063] In an exemplary embodiment, the coupling agent comprises trioctyl trimellitate.

[0064] In another embodiment, the coupling agent comprises a metal halide, a metalloid halide, an alkoxysilane, and an alkoxystannane.

[0065] In one or more embodiments, useful metal halides or metalloid halides have the formula (1) R 1 n M 1 X 4-n , Equation (2)M 1 X4, and formula (3)M 2X3, wherein R 1 are the same or different and represent a monovalent organic group having 1 to about 20 carbon atoms, and M in formula (1) and formula (2) 1 represents a tin atom, a silicon atom, or a germanium atom; M 2 represents a phosphorus atom, X represents a halogen atom, and n represents an integer of 0 to 3.

[0066] Representative compounds represented by formula (1) include organometallic halogenated compounds, and compounds represented by formulas (2) and (3) include metal halide compounds.

[0067] M 1 When represents a tin atom, the compound represented by formula (1) may be, for example, triphenyltin chloride, tributyltin chloride, triisopropyltin chloride, trihexyltin chloride, trioctyltin chloride, diphenyltin dichloride, dibutyltin dichloride, dihexyltin dichloride, dioctyltin dichloride, phenyltin trichloride, butyltin trichloride, octyltin trichloride, etc. Furthermore, the compound represented by formula (2) may include tin tetrachloride, tin tetrabromide, etc.

[0068] M 1 When M represents a silicon atom, the compound represented by formula (1) may be, for example, triphenylchlorosilane, trihexylchlorosilane, trioctylchlorosilane, tributylchlorosilane, trimethylchlorosilane, diphenyldichlorosilane, dihexyldichlorosilane, dioctyldichlorosilane, dibutyldichlorosilane, dimethyldichlorosilane, methyltrichlorosilane, phenyltrichlorosilane, hexyltrichlorosilane, octyltrichlorosilane, butyltrichlorosilane, methyltrichlorosilane, etc. Furthermore, the compound represented by formula (2) may include silicon tetrachloride, silicon tetrabromide, etc. 1represents a germanium atom, compounds represented by formula (1) can be, for example, triphenylgermanium chloride, dibutylgermanium dichloride, diphenylgermanium dichloride, butylgermanium trichloride, etc. Additionally, compounds represented by formula (2) can include germanium tetrachloride, germanium tetrabromide, etc. Compounds represented by formula (3) can include phosphorus trichloride, phosphorus tribromide, etc. In one or more embodiments, mixtures of metal halides and / or metalloid halides can be used.

[0069] In one or more embodiments, useful alkoxysilanes or alkoxystannanes are represented by the formula (4) R 1 n M 1 (OR) 4-n wherein R 1 are the same or different and represent a monovalent organic group having 1 to about 20 carbon atoms; M 1 represents a tin atom, a silicon atom, or a germanium atom; OR represents an alkoxy group in which R represents a monovalent organic group; and n represents an integer of 0 to 3.

[0070] Representative compounds represented by formula (4) include tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate, tetraethoxytin, tetramethoxytin, and tetrapropoxytin.

[0071] rubber composition

[0072] The recovered bound copolymer products, depending on their molecular weight and composition, can be used in a variety of articles such as tires and various rubber molded articles. [Example]

[0073] Referring to Figure 1, polymerizations were conducted in a test setup containing two 20-gallon reactors connected in series. Feed components were metered into the bottom of a first polymerization reactor 10 via first monomer charge stream 14 and feed stream 12, as shown in Table 1 below. The resulting first block 16 was continuously fed to a second polymerization reactor 20, to which the following additional components were added via feed stream 18 and second monomer charge 22:

[0074] [Table 1]

[0075] The resulting dispersion 24 was continuously fed to a collection vessel 30. A coupling agent, TO™, was added to the transfer line at the outlet of the second polymerization reactor 20 upstream of the collection vessel 30.

[0076] The jacket temperature was adjusted to maintain an internal temperature at the end of the second polymerization reactor 20 to support 98-100% conversion of monomer to polymer.

[0077] The copolymer was terminated in a collection vessel 30 with isopropanol at a level of approximately 0.5% w / w relative to the polymer. An antioxidant (Santoflex 6PPD) was then added to the polymer at a level of 0.75% w / w, and BO125 Hyprene (Ergon Refining, Inc.) was added to the polymer at 37.5% w / w, and the dispersion was mixed for 2 hours. The cement was then steam desolventized and dried to a residual water level of 0.75% or less to obtain the final product. Properties for this example (Example 1) are provided in Table 2 below.

[0078] As shown in Table 2, the Mooney and GPC values ​​of Example 1 are compared to a conventional solution polymerized continuous SBR (Comparative Example 1).

[0079] [Table 2]

[0080] As shown, all values ​​obtained in Example 1 are comparable to the rubber of Comparative Example 1 produced by solution polymerization; however, the amount of solids produced in the solution polymerization process is lower than the solids produced in Example 1 utilizing the anionic dispersion polymerization process of the present invention.

[0081] The following examples in Table 3 were prepared as follows:

[0082] [Table 3]

[0083] Referring to Table 4 below, Examples 2 and 3 had bonding measurements taken after having a residence time of at least 2.5 minutes in collection vessel 30. Examples 4 and 5 had bonding measurements taken upstream of collection vessel 30, and therefore, these examples had less bonding residence time. Similar to Comparative Example 1, Comparative Example 2 (CE2) is an SBR produced by solution polymerization.

[0084] [Table 4]

[0085] As shown, Examples 2 and 3, which had increased residence time in the collection vessel, had higher combined Mooney viscosities than Examples 4 and 5, and slightly lower Mooney viscosities than the control. Regarding dispersion ratings, Examples 2-5 all achieved good to excellent dispersions according to the dispersion rating defined below. Compared to CE2, Examples 2-5 all achieved higher total solids than solution-polymerized CE2. Additionally, Examples 2-5 all had higher vinyl content than solution-polymerized CE2.

[0086] The following examples in Table 5 were prepared as follows:

[0087] [Table 5]

[0088] Referring to Table 6 below, Mooney and GPC values ​​are shown for Example 6. Referring to Table 7 below, Example 6 had binding measurements taken upstream of collection vessel 30, and therefore, this example had a relatively low binding residence time.

[0089] [Table 6]

[0090] [Table 7]

[0091] As shown, Example 6, which contained only butadiene in the first monomer charge, obtained the same amount of solids as Examples 1, 4, and 5, and achieved a higher amount of solids as Examples 2 and 3, all of which contained both butadiene and styrene in the first monomer charge.

[0092] Test Method

[0093] Mooney Viscosity: The Mooney viscosity of the polymers disclosed herein was measured at 100°C using an Alpha Technologies Mooney Viscometer with a large rotor, a 1-minute preheat time, and a 4-minute run time. More specifically, the Mooney viscosity was measured by preheating each polymer to 100°C for 1 minute before the rotor started. Four minutes after the rotor started, the Mooney viscosity of each sample was recorded as torque. After the 4-minute measurement was completed, the torque relaxation was recorded. t80 was the time required to decay 80% of the torque for each polymer. The method follows ASTM D-1646.

[0094] Gel Permeation Chromatography (GPC)

[0095] The molecular weight of the polymer (M n , Mw and M p - Peak, M of GPC curve n ) and molecular weight distribution (M w / M n ) was determined by GPC. The GPC measurements disclosed herein are calibrated with polystyrene standards and the Mark-Houwink constants of the produced polystyrene.

[0096] Fourier Transform Infrared Spectroscopy (FTIR)

[0097] The styrene and vinyl % of the polymers were determined by FTIR, specifically by dissolving the samples in carbon disulfide and running the FTIR on a Perkin Elmer Spectrum GX instrument.

[0098] Distributed Evaluation

[0099] The following rating system was used to evaluate the dispersed products in this process: The dispersed products were placed in clear glass bottles and evaluated with the naked eye, after which the following scores were provided: [Table 8]

[0100] It will be apparent that modifications and variations are possible without departing from the scope of the present disclosure, as defined in the appended claims. More specifically, while certain aspects of the present disclosure have been identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure should not necessarily be limited to these aspects.

[0101] Claims:

Claims

1. 1. A process for producing a copolymer by anionic dispersion polymerization, comprising: adding to a first polymerization reactor a first monomer charge comprising a first conjugated diene monomer and optionally a first vinyl aromatic monomer, an organolithium polymerization initiator, and a non-aqueous dispersing medium containing at least one of a linear aliphatic hydrocarbon and a branched aliphatic hydrocarbon; the straight chain aliphatic hydrocarbon comprises butane, pentane, hexane, heptane, octane, nonane, or a mixture thereof, and the branched aliphatic hydrocarbon comprises isopentane, isohexane, isoheptane, isooctane, isononane, or a mixture thereof; polymerizing said first monomer charge to form a first block of a dispersant, said first block being soluble in said non-aqueous dispersion medium; 8 to 20 weight percent of the total monomers is provided by the first monomer charge, the total monomers being the sum of all monomer charges; adding to a second polymerization reactor the first block, the non-aqueous dispersing medium, a second monomer charge comprising a second vinyl aromatic monomer and a second conjugated diene monomer, and an organolithium polymerization initiator; polymerizing said second monomer charge to form said copolymer, said copolymer being the polymerization reaction product of 30 to 90 weight percent of said second vinyl aromatic monomer and 10 to 70 weight percent of said second conjugated diene monomer; an outlet stream from the second polymerization reactor comprising the copolymer and a second block of the dispersant, the second block being insoluble in the non-aqueous dispersion medium and linking with the first block to form the dispersant; the dispersant disperses the copolymer in the non-aqueous dispersion medium; the first conjugated diene monomer and the second conjugated diene monomer have the same composition, and the first vinyl aromatic monomer and the second vinyl aromatic monomer have the same composition; the first conjugated diene monomer and the second conjugated diene monomer comprise 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2,4-hexadiene, or a mixture thereof; and the first vinyl aromatic monomer and the second vinyl aromatic monomer comprise styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, α-methyl-vinyltoluene, vinyldiphenyl, or a mixture thereof; adding a coupling agent to the outlet stream, the coupling agent bonding to the copolymer to increase the Mooney viscosity of the copolymer, the coupling agent comprising a non-organometallic aromatic triester coupling agent; process.

2. 10. The process of claim 1, wherein the total monomer comprises 10 to 20 weight percent of the first monomer charge.

3. 3. The process of claim 1 or claim 2, wherein the outlet stream comprises 15 to 30 wt% solids.

4. 4. The process of any one of claims 1 to 3, further comprising recovering the dispersed copolymer and the dispersing agent from the second polymerization reactor after addition of the coupling agent in a downstream recovery vessel.

5. 5. The process of any one of claims 1 to 4, wherein the first monomer charge comprises 75 to 98 wt% of a first conjugated diene monomer and 2 to 25 wt% of a first vinyl aromatic monomer.

6. The process of any one of claims 1 to 5, wherein the coupling agent comprises trioctyl trimellitate.

7. The process of any one of claims 1 to 6, wherein the coupling agent is added with a non-aqueous dispersion medium.

8. 8. The process of any one of claims 1 to 7, wherein the organolithium polymerization initiator is butyllithium.

9. 9. The process of any one of claims 1 to 8, wherein the first conjugated diene monomer and the second conjugated diene monomer comprise butadiene, and the first vinyl aromatic monomer and the second vinyl aromatic monomer comprise styrene.

10. 10. The process of any one of claims 1 to 9, wherein the organolithium polymerization initiator added to the first polymerization reactor provides 20 to 40 wt% of the total amount of organolithium polymerization initiator added to the first polymerization reactor and the second polymerization reactor.

11. The process of any one of claims 1 to 10, wherein a randomizer is added to the first polymerization reactor, the second polymerization reactor, or both.

12. 12. The process of claim 11, wherein the randomizer comprises an oligomeric oxolanyl propane.

13. The process of any one of claims 1 to 12, wherein a modifier is added to the first polymerization reactor, the second polymerization reactor, or both.

14. The process according to any one of claims 1 to 13, wherein the copolymer has a number average molecular weight of 75,000 to 500,000 g / mol.

15. The process of any one of claims 1 to 14, wherein the copolymer has a Mooney viscosity of 120 to 160.

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