Controlled molecular weight distribution isobutylene-based elastomer compositions and related processes

Abstract

A method for controlling the molecular weight distribution of an elastomeric composition, particularly an isobutylene-based elastomeric composition, particularly an elastomeric composition for use in tire compositions, such as innerliners. A polymerization medium containing monomers, a diluent, and a catalyst system is polymerized in a reactor. The molecular weight distribution is controlled using post-polymerization processing to achieve a Mooney stress relaxation index of greater than about 2.5.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and benefit of U.S. Provisional Patent Application No. 63 / 405,925, filed September 13, 2022, entitled CONTROLLED MOLECULAR WEIGHT DISTRIBUTION ISOBUTYLENE-BASED ELASTOMER COMPOSITIONS AND METHODS RELATED THERETO, the disclosure of which is incorporated herein by reference in its entirety. FIELD OF THE INVENTION This application relates to a method for controlling the molecular weight distribution of elastomeric compositions, particularly isobutylene-based elastomeric compositions, especially elastomeric compositions for use in tire compositions, such as innerliners. [Background technology]

[0002] Tires, for example, contain numerous rubber compounds and other materials that must function safely under a wide range of demanding conditions for passenger cars, trucks, buses, and airplanes. They are expected to function for thousands of miles while retaining essential performance and safety characteristics. Tire performance depends, at least in part, on their ability to retain air or inflation pressure. Butyl rubber, e.g., isobutylene-based elastomers, are particularly well-suited for air retention and may be formulated for certain tire applications, such as tire tubes or innerliners, i.e., the innermost layer of a tire. Specific butyl rubber compositions, including additional additives, are selected for use as innerliners to achieve favorable characteristics related to processability and uncured or cured physical properties, including mechanical strength, surface appearance, and bond integrity, among others. Several factors can affect these properties.

[0003] The molecular weight distribution (MWD = Mw / Mn), also known as the polydispersity index, has a significant effect on the mechanical and physical bulk properties of the polymer and the resulting compounded product, including processability and uncured and cured physical properties—properties essential for producing commercially viable tire innerliners. For innerliner applications, the Mooney viscosity and Mooney stress relaxation of the bulk rubber compound are important for producing a rubber with innerliner bonding characteristics that will provide suitable bond strength integrity after curing. A balance of the MWD (high or low molecular weight butyl rubber) of the butyl rubber is necessary to achieve these properties while maintaining processability. The high molecular weight fraction contributes to mechanical properties such as tensile break, elongation, and impact strength, while the low molecular weight fraction contributes to processability factors such as low melt viscosity and plasticity. Therefore, a wide MWD of butyl rubber is important for producing commercially viable tire innerliners and, ultimately, the final tire product. Butyl rubber polymerization is conventionally carried out using suitable monomers and Lewis acid catalysts (and initiators). However, wide discrepancies in the MWD of butyl rubber throughout the tire industry have been documented. It has further been observed that currently produced innerliner tire products typically exhibit narrow MWDs, for example, MWDs of less than about 2.5. As noted above, narrow MWDs can make processing difficult and / or result in undesirable physical and mechanical properties. Summary of the Invention

[0004] The present disclosure provides methods and systems for producing isobutylene-based elastomeric compositions with controlled MWD, particularly for use as tire innerliners. In a non-limiting aspect of the present disclosure, a method comprises the steps of polymerizing a polymerization medium in a reactor, the polymerization medium comprising monomer, diluent, and a catalyst system, the catalyst system comprising a Lewis acid and an initiator, thereby producing a reactor overflow; contacting the reactor overflow with a quenching agent; and controlling the quenching of the reactor overflow to obtain a Mooney Stress Relaxation Index (MRI) of greater than about 2.5, thereby producing a quenched reactor overflow. These and other features and attributes of the disclosed controlled MWD process and system for producing the isobutylene-based elastomeric compositions of the present disclosure, as well as their advantageous applications and / or uses, will become apparent from the detailed description that follows. To assist those skilled in the relevant art in making and using the subject matter herein, reference is made to the accompanying drawings. The following figures are included to illustrate certain aspects of the present disclosure and should not be viewed as exclusive. The disclosed subject matter is capable of considerable modification, alteration, combination and equivalents in form and function that will occur to those skilled in the art and having the benefit of this disclosure. [Brief explanation of the drawings]

[0005] [Figure 1] 1 is a schematic flow diagram of a simplified polymerization system 100 according to one or more embodiments of the present disclosure. [Figure 2] 1 is a chart showing MRI values ​​for experimental phase conditions, according to one or more embodiments of the present disclosure. [Figure 3] 1 is a gel permeation chromatography chart showing MWD values ​​for experimental phase conditions, according to one or more embodiments of the present disclosure. [Figure 4] 1 is a chart showing isobutylene conversion values ​​for experimental phase conditions according to one or more embodiments of the present disclosure. [Figure 5] 1 is a chart displaying isobutylene conversion values ​​for experimental phase conditions according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006] FIELD OF THE INVENTION This application relates to a method for controlling the molecular weight distribution of elastomeric compositions, particularly isobutylene-based elastomeric compositions, especially elastomeric compositions for use in tire compositions, such as innerliners. The present disclosure provides a methodology for controlling the MWD of isobutylene-based elastomer compositions by modifying certain polymerization characteristics. In particular, the present disclosure provides controlled MWD expansion during butyl polymer production by modifying post-polymerization reactor conditions to change the concentration of low molecular weight fractions, and the modification is achieved by controlling quenching of the reaction to promote post-reactor polymerization. According to the present disclosure, quenching can be controlled by one or more of: varying the amount of quenching agent; controlling mixing efficiency via one or more of reactor blender speed and / or reactor overflow viscosity; and / or increasing the temperature at the reactor discharge. The methodology presented herein enables isobutylene-based elastomer compositions with controlled MWD, including controlled expansion of MWD, for use in producing tire innerliners. In various aspects of the present disclosure, the Mooney stress relaxation index (MRI) is used as a measure to evaluate the MWD of an isobutylene-based elastomer composition. Mooney Viscometer Readings (MRI) are commonly used to measure downstream polymerization products and are correlated to MWD, as described later in this specification. The methodology of the present disclosure provides isobutylene-based elastomer compositions having an MRI greater than about 2.5. In fact, typical isobutylene-based elastomer compositions have MRI values ​​less than about 2.5.

[0007] definition As used herein, the term "catalyst system" and grammatical variations thereof refer to and include any Lewis acid or other metal complex, and optionally at least one initiator, used to catalyze the polymerization of hydrocarbon monomers. Other additives, such as catalyst modifiers, may also be included. The catalyst system, combined with a diluent for the polymerization, is collectively referred to as the "polymerization medium." As used herein, the term "polymerization system" and grammatical variations thereof refer to the use of a polymerization medium to produce a polymer. As used herein, the term "diluent" and grammatical variations thereof refer to a diluent or dissolving agent, including mixtures thereof (e.g., two or more individual diluents). Diluents may be used to act as diluents and also to affect mixing in the reactor (using an overhead blender). As used herein, the term "solvent" and grammatical variations thereof refer to a chemical agent capable of dissolving the resulting polymer.

[0008] As used herein, the term "reactor" and its grammatical variations refer to any container in which a chemical reaction, such as polymerization, occurs. Examples of butyl polymerization reactors include continuous-flow stirred-tank reactors, which utilize continuous vessel agitation, and draft-tube reactors. Various cooling jackets, piping, and the like can be used in conjunction with (and integrated into) the reactor to control or otherwise maintain the reactor temperature during polymerization. Commercial reactors can typically be well-mixed vessels with volumes greater than 1,000 to 10,000 liters (excluding jacket), with high circulation rates provided by axial pumps. Both polymerization and pumping can generate heat, and the reaction system can include a heat exchanger to keep the slurry cool. In some reactors, the slurry can be circulated through the heat exchanger tubes. Cooling can be provided, for example, by boiling ethylene on the shell side. The slurry temperature can be set by the boiling ethylene temperature, the required heat flux, and the overall heat transfer resistance. As used herein, the term "slurry" and grammatical variations thereof refer to a quantity of diluent containing a catalyst system and polymer that has precipitated from the diluent. The slurry concentration is the weight percent of partially or completely precipitated polymer based on the total slurry. As used herein, the term "quench" and grammatical variations thereof refer to the process of rapidly heating and stirring the reactor discharge stream with a quench medium to stop further polymerization.

[0009] As used herein, the term "polymer" and its grammatical variations refer to homopolymers, copolymers, interpolymers, terpolymers, etc. The term "copolymer" and its grammatical variations are meant to include polymers having two or more types of monomers. "Interpolymer" and its grammatical variations refer to any polymer or oligomer having a number average molecular weight of 500 or greater that is prepared by the polymerization or oligomerization of at least two different monomers. As used herein, when a polymer is referred to as "comprising" a monomer, the monomer is present in the polymer in the polymerized form of the monomer or in the derivative form of the monomer. Similarly, when a catalyst component is described as comprising the neutral stable form of the component, it is well understood by those skilled in the art that the ionic form of the component is the form that reacts with the monomer to produce the polymer.

[0010] As used herein, the term "olefin" and its grammatical variations refer to a hydrocarbon containing a carbon-carbon double bond. The term "isoolefin" and its grammatical variations refer to any olefin monomer having two substitutions on the same carbon. The term "diolefin" and its grammatical variations refer to any olefin monomer having two double bonds. As used herein, "elastomer" or "elastomeric composition," and grammatical variations thereof, refer to any polymer or composition of polymers that conforms to the definition in ASTM D1566-21A (November 2021). Elastomer may be used interchangeably with the term "rubber" herein.

[0011] As used herein, "Mooney viscosity" and grammatical variations thereof refer to the Mooney viscosity of a polymer or polymer composition. Polymer compositions analyzed to determine Mooney viscosity should be substantially devoid of diluents and solvents. For example, samples may be placed on a boiling water steam table in a hood to evaporate a large fraction of the diluent and unreacted monomers, then dried overnight in a vacuum oven (12 hours, 90°C) before testing according to laboratory analytical techniques; samples for testing may also be obtained from devolatilized polymers (i.e., post-devolatilization polymers in industrial-scale processes). Unless otherwise indicated, Mooney viscosity is measured using a Mooney viscometer according to ASTM D1646-19A (November 2019), with the following modifications / clarifications to the procedure: First, prior to testing, the polymer is pressed between two hot plates in a compression press. The plate temperature is 125°C ± 10°C, rather than the 50°C ± 5°C recommended in ASTM D1646-17, because sufficient massing cannot be achieved at 50°C. Furthermore, although ASTM D1646-17 allows for several options for die guard, if any two options provide competing results, PET 36 μm is used as the die guard. Furthermore, ASTM D1646-17 does not indicate sample mass in Section 8; therefore, where results may vary depending on sample mass, Mooney viscosity determined according to the procedure in D1646-17 Section 8 using a sample mass of 21.5±2.7 grams (g) applies. Finally, while the pre-test rest procedure specified in D1646-17 Section 8 is 30 minutes in air at 23±3°C, the Mooney values ​​reported herein were determined after a 30-minute rest in air at 24±3°C. Samples are placed on both sides of the rotor according to the ASTM D1646-17 test method, and the torque required to rotate the viscometer motor at 2 rpm is measured by the transducer for determining Mooney viscosity.Results are reported as Mooney Units (ML,1+4@125°C or ML,1+8@125°C), where MU is the Mooney viscosity number, L indicates the large rotor (defined as ML in ASTM D1646-17), 1 is the preheat time (minutes), 4 or 8 is the sample run time (minutes) after motor start, and 125°C is the test temperature. Thus, a Mooney viscosity of 90 determined by the aforementioned method would be reported as 90MU(ML,1+8@125°C) or 90MU(ML,1+4@125°C). Alternatively, Mooney viscosity may be reported as 90MU, and in such instances, unless otherwise noted, it should be assumed that such viscosity was determined using the (ML,1+4@125°C) method described above. In some instances, a lower test temperature may be used (e.g., 100°C), in which case the Mooney is reported as Mooney viscosity (ML,1+8 @ 100°C) or @ T°C (T is the test temperature).

[0012] As used herein, the terms "Mooney Stress Relaxation Index" or "MRI," and grammatical variations thereof, refer to a value that correlates to the MWD of an isobutylene-based elastomer. MRI is determined based on Mooney Stress Relaxation and may be determined by the following Equation 1: MRI=[(k / a+1)][60 (a+1) -4 (a+1) ] where a is the slope of the regression and k is the intercept of the regression for Mooney stress relaxation in seconds. Numerical ranges used herein include the values ​​recited within the range. For example, the numerical range "1% to 10% by weight" includes 1% and 10% by weight within the recited range.

[0013] Polymerization System The present disclosure provides methods for controlling MWD (and MRI) using post-polymerization control and modification of the polymerization system. In one or more embodiments described herein, the present disclosure provides methodologies for varying the low molecular weight fraction of an isobutylene-based elastomer, thereby controlling the ratio of the low molecular weight fraction relative to the high molecular weight fraction of the isobutylene-based elastomer as part of a polymerization system. Before describing the methodology of the present disclosure in further detail, a brief overview of an exemplary polymerization system for producing isobutylene-based elastomers is provided so that the various aspects of the present disclosure may be better understood. Polymerization systems for producing isobutylene-based elastomers are typically carried out using continuous slurry polymerization systems with polymerization reactor temperatures below 0° C., for example, in the range of about −105° C. to about 0° C. However, it should be recognized that batch polymerization systems may be used in accordance with one or more embodiments described herein without departing from the scope of the present disclosure.

[0014] 1, a schematic flow diagram of a polymerization system 100 is illustrated in accordance with one or more embodiments of the present disclosure. A catalyst system 102 and monomers 104 are fed to a polymerization reactor 108. In some examples, the catalyst system 102 and monomers 104 may be blended in a blending unit (not shown) before being fed to the polymerization reactor 108. Additionally, in some examples, the monomers 104 may be treated to remove impurities, if necessary, before being introduced into the polymerization reactor 108 (or blending unit). The catalyst system 102 and the monomer 104 may be fed simultaneously or separately to the polymerization reactor 108. The monomer 104, alone or in combination with the catalyst system 102, is fed to the polymerization reactor 108 at a temperature below 0°C, for example, in the range of about -105°C to about 0°C. The catalyst system 102 and the monomer 104 are mixed in the polymerization reactor 108 and may initially exist as a single phase dissolved in the diluent 106. The diluent 106 serves to dissolve the catalyst system 102 and the monomer 104 but not the polymerization product (polymer), thus precipitating the polymerization product and forming a slurry. When one or more of the inputs are fed simultaneously to the polymerization reactor 108, a single pump impeller may be used. The reactor pump impeller is typically capable of either or both upward and downward pumping and often includes an electric motor with a measurable current. The pump impeller serves to maintain a constant flow of monomer, catalyst system, and diluent, including reacted and unreacted species (e.g., monomer), within the reactor, providing high shear mixing to prevent plugging of the reactor.

[0015] The polymerization reactor 108 can be any suitable reactor for polymerization to produce isobutylene-based elastomers. In one or more embodiments, the polymerization reactor 108 is a continuous draft tube reactor or a draft tube with a circulation pump 108a for efficient agitation. Typically, the polymerization reactor 108 is equipped with an external cooling jacket 108c and associated internal cooling (or heat exchange) tubing to remove heat generated during the polymerization and maintain the desired reaction temperature. In one or more embodiments, the cooling tubing can contain liquid ethylene to extract heat from the polymerization reaction. The polymerization system further includes a steam jacket 122 to assist in controlling the molecular weight distribution as described herein. The steam jacket 122 can be piping that receives and provides heat to the reactor discharge stream; i.e., the reactor discharge stream flows through the steam jacket 122.

[0016] In one or more embodiments, the polymerization reactor, including the jacket and associated internal cooling tubing, can have a volume ranging from about 1,000 liters (L) to about 10,000 L, including all values ​​and subsets therebetween. Such volumes are conducive to large-scale volumetric polymerization reactions according to various embodiments described herein. Thus, reactors having larger volumes (and less preferably, smaller volumes) can be utilized to facilitate scale-up without departing from the scope of the present disclosure. Generally, the polymerization temperature in polymerization reactor 108 to produce the isobutylene-based elastomers of the present disclosure is within the range of about −105° C. to about 0° C. (including all values ​​and subsets therebetween, e.g., −100° C. to −50° C., or −98° C. to −92° C., etc.), preferably 0° C. to the freezing point of the polymerization medium, e.g., the mixture of diluent and monomer, and then the reaction is quenched by adding a quenching agent to the polymerization medium.

[0017] During polymerization, the catalyst system 102 and the monomer 104 react, and the resulting polymer precipitates from the diluent 106. A reactor vent stream 110, comprising the polymer (produced during polymerization), the diluent 106, the unreacted monomer 104, and the unreacted catalyst system 102, exits the reactor through the reactor outlet, sometimes collectively referred to herein as the "reactor overflow." In the case of an isobutylene-based elastomer polymerization system 100, the reactor vent stream 110 may be warmed to room temperature (RT) or otherwise heated, for example, from a temperature below 0° C. (in the polymerization reactor 108) to, for example, a temperature within the range of about −50° C. to about 20° C. (including all values ​​and subsets therebetween). A steam jacket 122 may be used to provide such heating.

[0018] Unreacted catalyst system 102 in the reactor effluent stream 110 can form undesirable species that interfere with downstream processing, such as functionalization, of the polymer produced during polymerization. During warming or heating, but before heating to above about −50° C. to about 20° C., the reactor effluent stream 110 may be quenched 118 with a quenching agent. The quenching serves to stop the reaction capacity of any unreacted catalyst system 102 (i.e., the catalyst within the catalyst system 102) prior to any significant warming or heating of the reactor effluent stream 110 to prevent subsequent polymerization and crosslinking reactions that could interfere with downstream processing as the reactor effluent stream 110 is heated. Conventional quenching agents include steam and / or hot water introduced into the reactor effluent stream 110. Other conventional quenching agents include linear or branched alcohols, such as ethanol, tert-butanol, methanol, triethylene glycol (TEG), and any combination thereof. During the quench, the reactor bleed stream 110 may be combined with solvent 116 using a mechanical agitator located inside the overflow pipe of 110 to dissolve the polymer stream 118 desired for downstream processing 120 (e.g., halogenation or other functionalization, etc.) and separate it from the diluent 106, solvent 116, and any unreacted monomer 104, or diluent or solvent towards a vessel or other storage container (not shown). The contents within the vessel may be recycled to one or more embodiments of the present disclosure.

[0019] Polymerization Systems for Controlling the MWD (and MRI) of Isobutylene-Based Elastomers The methodology of the present disclosure for producing isobutylene-based elastomers with controlled MWD (and MRI) generally utilizes existing polymerization systems, such as those described with reference to FIG. 1, but employs unconventional post-polymerization (post-reactor) processes. These post-polymerization processes can advantageously be used to extend the MWD of the resulting isobutylene-based elastomer product by generating lower molecular weight polymers while preventing polymer degradation. While the present disclosure is described with reference to tire innerliners in which the isobutylene-based elastomers have a desired wide MWD, it should be recognized that the present disclosure may be applicable to other types of air retention products, or other products having a desired wide MWD. ​​That is, various aspects of the present disclosure can be used to control the MWD (and MRI) for isobutylene-based elastomers generally without departing from the scope of the present disclosure.

[0020] In one or more embodiments, the present disclosure provides a polymerization system for polymerizing a polymerization medium, the polymerization medium comprising one or more monomers, a diluent, and a catalyst system. The one or more monomers for use in the present disclosure may include any hydrocarbon monomer. Examples of suitable hydrocarbon monomers include, but are not limited to, one or more of olefins, alpha-olefins, disubstituted olefins, isoolefins, conjugated dienes, non-conjugated dienes, styrenes, substituted styrenes, vinyl ethers, and any combination thereof. In one or more embodiments of the present disclosure, an exemplary monomer combination includes isobutylene and paramethylstyrene. In one or more embodiments of the present disclosure, an exemplary monomer combination includes isobutylene and isoprene, thus forming, for example, polyisobutylene-co-isoprene (or, if halogenated, halogenated polyisobutylene-co-isoprene). Each exemplary combination, and any monomer combination used in the polymerization system of the present disclosure, may additionally include a homopolymer of isobutylene.

[0021] In various embodiments of the present disclosure, when two monomers (with or without a homopolymer of isobutylene) are used, they may be present in equal or unequal amounts without departing from the scope of the present disclosure. For example, in various examples described later herein, the selected monomers are isobutylene and isoprene, with isobutylene being the most important monomer present in terms of concentration, thus forming, for example, polyisobutylene-co-isoprene (or, if halogenated, halogenated polyisobutylene-co-isoprene). In one or more embodiments, the monomer may be present in the polymerization medium in an amount ranging from about 30% to about 40% by weight, e.g., from about 30% to about 35% by weight, or from about 35% to about 40% by weight, including all values ​​and subsets therebetween.

[0022] The diluent is selected to dissolve the catalyst and monomers in the catalyst system and allow precipitation of the polymerization product (polymer). This results in an acceptable polymerization medium with a relatively low viscosity, allowing for more effective removal of the heat of polymerization by surface heat exchange. Suitable diluents include those that have an affinity for organic compounds, particularly hydrocarbon fluids. Examples of diluents suitable for use in the present disclosure include, but are not limited to, hydrocarbons such as hexane and heptane, halogenated hydrocarbons such as chlorinated hydrocarbons, e.g., ethyl chloride, methyl chloride, CHCl3, CCl4, n-butyl chloride, chlorobenzene, and the like, and any combination thereof. For example, methyl chloride is a commercially acceptable diluent due to its favorable freezing and boiling points, and tends to produce relatively high molecular weight butyl rubber polymers.

[0023] According to one or more embodiments of the present disclosure, diluents, such as methyl chloride or hexane, for use in the polymerization systems described herein to control MWD (and MRI) can be selected to advantageously achieve an isobutylene-based elastomer polymerization product concentration within the range of about 25% to about 40% by volume, e.g., about 26% to about 37% by volume, including all values ​​and subsets therebetween, e.g., about 30% to about 35% by volume. In some examples, the isobutylene-based elastomer polymerization product concentration is about 30% by volume. The amount of diluent may be adjusted to adjust the viscosity of the reactor overflow, as defined herein, to control the MWD (and MRI), according to one or more embodiments of the present disclosure.

[0024] The catalyst system of the present disclosure includes a Lewis acid or metal complex and an initiator. The Lewis acid or metal complex is intended to catalyze cationic polymerization to produce an isobutylene-based elastomer. Aluminum-based Lewis acids can be used in various embodiments of the present disclosure. Examples of suitable aluminum-based Lewis acids include, but are not limited to, aluminum trichloride, aluminum tribromide, ethylaluminum dichloride (EADC), ethylaluminum sesquichloride, diethylaluminum chloride, methylaluminum dichloride, methylaluminum sesquichloride, dimethylaluminum chloride, and the like, alone or in any combination with other suitable Lewis acids. Other suitable examples include boron-based Lewis acids, such as boron trifluoride, and titanium-based Lewis acids, such as titanium tetrachloride, alone or in any combination with other suitable Lewis acids. In an exemplary embodiment of the present disclosure, the Lewis acid selected includes ethylaluminum dichloride and ethylaluminum sesquichloride, optionally in combination. According to one or more embodiments of the present disclosure, ethylaluminum dichloride (EADC) is selected for use in the polymerization systems described herein to control MWD (and MRI). In one or more embodiments, the EADC Lewis acid and initiator is present in the polymerization systems described herein in a range of about 2.5 to about 3, based on 3 on a molar basis, including all values ​​and subsets therebetween. Such ratios apply equally to any Lewis acid or metal complex to initiator ratio described herein without departing from the scope of the present disclosure.

[0025] A variety of initiators may be used in the polymerization system of the present disclosure to control the MWD (and MRI) of isobutylene-based elastomers, so long as they are compatible with the other components of the polymerization medium. The initiators used in the present disclosure are selected so that they can be complexed with a selected Lewis acid or other metal complex in a suitable diluent to yield a complex that reacts rapidly with hydrocarbon monomers to form growing polymer chains (polymerization). Examples of initiators suitable for use in the present disclosure include, but are not limited to, Bronsted acids, such as HO, HCl, RCOOH (where R is an alkyl group), alkyl halides, such as (CH)CCl, CHC(CH)Cl, 2-chloro-2,4,4-trimethylpentane and 2-chloro-2-methylpropane, hydrogen halides, and any combination thereof. Other suitable initiators known to those skilled in the art may also be used.

[0026] According to one or more embodiments of the present disclosure, hydrogen chloride (HCl) is selected as the initiator for use in the polymerization systems described herein to control MWD (and MRI). According to one or more embodiments, the HCl initiator is diluted in a diluent (e.g., hexane, methyl chloride) to a concentration of about 70 parts per million (ppm) to about 300 ppm (including all values ​​and subsets therebetween), such as about 100 ppm to about 250 ppm, or about 150 ppm to about 200 ppm, or about 125 ppm, etc. The diluted initiator may be present in a ratio relative to the monomer (e.g., isobutylene), by weight, of about 30 ppm to about 60 ppm (including all values ​​and subsets therebetween), such as about 40 ppm to about 50 ppm, such as about 40 ppm. Such concentrations in the diluent and ratio relative to the monomer apply equally to any initiator described herein without departing from the scope of the present disclosure.

[0027] Methodology for controlling the MWD (and MRI) of isobutylene-based elastomers In one or more embodiments herein, methods are provided for using post-polymerization control and modification of polymerization systems by controlling certain characteristics of the reaction quench to facilitate post-polymerization. These post-polymerization controls and modifications may include one or more (including all) of varying the amount and / or quench efficiency of quenching agents, particularly TEG, to broaden the molecular weight distribution of the resulting polymer, and / or increasing the temperature at the polymerization reactor outlet (e.g., FIG. 1 , at the location of reactor vent stream 110 exiting polymerization reactor 108). Manipulation of quench efficiency may be achieved using one or more (including all) of adjusting the blending rate of an overhead blender, the amount of processing aid to change the viscosity of the reactor overflow, and / or changing reactor conditions to affect the viscosity of the reactor overflow, for example, by increasing the temperature at the reactor outlet.

[0028] Such post-polymerization control generates low molecular weight polymers, preventing both degradation of said polymers and downstream processing problems. In one or more embodiments of the present disclosure, the amount of quenching agent can be adjusted based on the concentration of the catalyst. In one or more embodiments, the molar ratio of quenching agent to catalyst is reduced compared to conventional polymerization methods and can be within a range of about 0.4 to about 0.8, such as about 0.4 to about 0.6, or about 0.6 to about 0.8, including all values ​​and subsets therebetween. In one or more embodiments of the present disclosure, the overhead blender (see FIG. 1, 108a) may be curtailed at one or more stages during the polymerization or quench to facilitate post-polymerization by reducing its speed or shutting it off completely by turning it off.

[0029] In one or more embodiments of the present disclosure, the steam jacket of the overhead piping can be controlled to increase the temperature and expand its MWD, particularly at the reactor discharge. For example, the steam jacket can be adjusted to provide a temperature greater than about −40° C., such as from about −40° C. to about 0° C., or from about −20° C. to about 0° C., or from about −40° C. to about −20° C., or from about −30° C. to about −10° C. (including all values ​​and subsets therebetween). Methodologies for controlling the MWD (and MRI) of isobutylene-based elastomers are further described herein below with reference to the Examples.

[0030] Exemplary Embodiments Non-limiting example embodiments of the present disclosure include the following: Embodiment A: A method comprising the steps of polymerizing a polymerization medium in a reactor, the polymerization medium comprising monomer, diluent, and a catalyst system, the catalyst system comprising a Lewis acid and an initiator, thereby producing a reactor overflow; contacting the reactor overflow with a quenching agent; and controlling the quenching of the reactor overflow to obtain a Mooney Stress Relaxation Index (MRI) of greater than about 2.5, thereby producing a quenched reactor overflow.

[0031] A non-limiting example embodiment A may include one or more of the following elements. Element 1: MRI is in the range of about 2.5 to about 4.5. Element 2: The controlling step includes adjusting the amount of quenching agent so that the molar ratio of the quenching agent to the Lewis acid is within the range of about 0.4 to about 0.8. Element 3: The controlling step includes adjusting the amount of quenching agent so that the molar ratio of the quenching agent to the Lewis acid is within the range of about 0.4 to about 0.6. Element 4: The reactor includes an overhead blender, and the controlling step includes slowing down or shutting off the overhead blender during one or both of the polymerization and the quench. Element 5: The reactor outlet includes a steam jacket, and the controlling step includes heating the steam jacket such that the temperature at the reactor outlet is within the range of about -40°C to about 0°C. Element 6: The reactor outlet includes a steam jacket, and the controlling step includes heating the steam jacket so that the temperature at the reactor outlet is within the range of about -30°C to about -10°C.

[0032] Element 7: The reactor includes an overhead blender, and the controlling step includes (1) slowing down or shutting off the overhead blender during one or both of the polymerization and the quench, and (2) adjusting the amount of quenching agent so that the molar ratio of quenching agent to Lewis acid is within the range of about 0.4 to about 0.8. Element 8: The reactor includes an overhead blender, and the controlling step includes: (1) slowing down or shutting off the overhead blender during one or both of the polymerization and the quench; and (2) adjusting the amount of quenching agent such that the molar ratio of quenching agent to Lewis acid is within the range of about 0.4 to about 0.8; and the reactor outlet includes a steam jacket, and the controlling step further includes: (3) heating the steam jacket such that the temperature at the reactor outlet is within the range of about −40° C. to about 0° C. Element 9: The reactor includes a steam jacket, and the controlling step includes (1) heating the steam jacket so that the temperature at the reactor outlet is within the range of about −40° C. to about 0° C., and (2) adjusting the amount of quenching agent so that the molar ratio of quenching agent to Lewis acid is within the range of about 0.4 to about 0.8.

[0033] Item 10: The reactor includes an overhead blender and the reactor outlet includes a steam jacket, and the controlling step includes (1) shutting off the overhead blender during one or both of the polymerization and the quench, and (2) heating the steam jacket so that the temperature at the reactor outlet is within the range of about −40° C. to about 0° C. Element 11: The monomer is one or more of an olefin, an alpha-olefin, a disubstituted olefin, an isoolefin, a conjugated diene, a non-conjugated diene, a styrene, a substituted styrene, and a vinyl ether. Element 12: The monomer is isobutylene, isoprene, or a combination thereof. Element 13: The monomer is present in the polymerization medium in an amount within the range of about 30% to about 40% by weight. Element 14: The diluent is one or more of a hydrocarbon, a halogenated hydrocarbon, and a chlorinated hydrocarbon. Element 15: The diluent is present in the polymerization medium in an amount ranging from about 60% to about 70% by volume.

[0034] Element 16: The Lewis acid is one or more of aluminum trichloride, aluminum tribromide, ethylaluminum dichloride, ethylaluminum sesquichloride, diethylaluminum chloride, methylaluminum dichloride, methylaluminum sesquichloride, and dimethylaluminum chloride. Element 17: The Lewis acid is ethylaluminum dichloride. Element 18: The initiator is one or both of a Bronsted acid, an alkyl halide, and a hydrogen halide. Element 19: The quenching agent is at least one alcohol. Element 20: The quenching agent is triethylene glycol.

[0035] Element 21: The reactor is a continuous reactor. Element 22: Further comprising separating a polymer fraction from the quenched reactor overflow. Element 23: The monomers are isobutylene and isoprene, and the polymerizing step forms polyisobutylene-co-isoprene. Element 24: The monomers are isobutylene and isoprene, and the polymerizing step further includes forming polyisobutylene-co-isoprene and halogenating the polyisobutylene-co-isoprene, thereby forming halogenated polyisobutylene-co-isoprene. Each of elements 1-24 can be combined in any combination without limitation. To facilitate a better understanding of embodiments of the present invention, the following examples of preferred or representative embodiments are provided. The following examples should in no way be read as limiting or defining the scope of the invention. [Example]

[0036] In the following non-limiting examples, a phase-by-phase approach (Phases 1-5) was taken to adjust post-polymerization reactor conditions using one or more of the factors described above in this specification. In certain instances, the previous phase conditions were maintained to perform subsequent phases, as shown later in this specification. Data from samples was used to adjust between phases and to determine MRI (a measure of MWD trend), as defined herein below. Gel permeation chromatography (GPC) was used to determine MWD. All examples were carried out under standard conditions and involved a polymerization system containing isobutylene and isoprene monomers, the Lewis acid catalyst EADC, and a hexane diluent. The quenching agent used was TEG.

[0037] (Example 1) Phase 1 In this example, Phase 1 conditions were used in which the quenching agent to catalyst ratio was reduced compared to the conventional ratio. The molar ratio of quenching agent to catalyst (TEG / EADC) in Phase 1 was greater than 0.6 and less than or equal to about 1.2 (see, for example, Samples P1-4, -7, -8, -11, and -16). The reactor conditions, MRI, and Mooney viscosity results are provided in Table 1 (samples separated by approximately 1 hour).

[0038] [Table 1] [Table 2]

[0039] The distribution of MRI values ​​for Phase 1 samples (with TEG / EADC of approximately 1.2) has a median of 2.70 and a mean of 2.70 (Phase 1 MRI samples are plotted in Figure 2).

[0040] (Example 2) Phase 2 In this example, Phase 2 conditions were used in which the quenching agent to catalyst ratio was further reduced compared to Phase 1 conditions. The molar ratio of quenching agent to catalyst (TEG / EADC) in Phase 2 was equal to about 0.6 (see, e.g., Samples P2-2, -7, -10, and -12). The reactor conditions, MRI, and Mooney viscosity results are provided in Table 2 (samples separated by 2 hours).

[0041] [Table 3] [Table 4]

[0042] The distribution of MRI values ​​for Phase 2 samples (with TEG / EADC of approximately 0.6) has a median of 2.74 and a mean of 2.77 (MRI samples for Phase 2 are plotted in Figure 2). Thus, using the post-processing methodology of reducing the quenching agent to catalyst ratio resulted in a broader MWD (represented by a higher MRI)—representing an increased amount of low molecular weight polymer fraction compared to Phase 1.

[0043] (Example 3) Phase 3 In this example, Phase 3 conditions were used in which a reduced quench to catalyst ratio in Phase 2 (TEG / EADC = approximately 0.6) was combined with turning off the reactor overhead blender, thereby affecting the mixing of the catalyst and quench agent. The reactor conditions, MRI, and Mooney viscosity results are provided in Table 3 (samples were approximately 2 hours apart).

[0044] [Table 5] [Table 6]

[0045] The distribution of MRI values ​​for Phase 3 samples (with a TEG / EADC of approximately 0.6 and the overhead blender turned off) has a median of 2.93 and a mean of 2.97 (MRI samples from Phase 3 are plotted in Figure 2). Thus, using the post-processing methodology of reducing the quench to catalyst ratio and additionally turning off the reactor overhead blender resulted in a broader MWD (represented by a higher MRI)—representing an increased amount of low molecular weight polymer fraction compared to both Phase 1 and Phase 2 conditions.

[0046] (Example 4) Phase 4 In this example, Phase 4 conditions were used in which a further reduction in the quenching agent to catalyst ratio compared to Phase 3 was combined with turning off the reactor overhead blender, thereby affecting the mixing of the catalyst and quenching agent. The quenching agent to catalyst molar ratio (TEG / EADC) in Phase 4 was approximately 0.5 (see, e.g., Samples P4-1, -7, -9, -10, and -11). The reactor conditions, MRI, and Mooney viscosity results are provided in Table 4 (samples separated by approximately 2 hours).

[0047] [Table 7] [Table 8]

[0048] The distribution of MRI values ​​for Phase 4 samples (with a TEG / EADC of approximately 0.5 and the overhead blender turned off) has a median of 3.17 and a mean of 3.20 (MRI samples from Phase 4 are plotted in Figure 2). Thus, using the post-processing methodology of reducing the quench to catalyst ratio to approximately 0.5 and additionally turning off the reactor overhead blender resulted in a broader MWD (represented by a higher MRI)—representing an increased amount of low molecular weight polymer fraction compared to each of the Phase 1 through Phase 3 conditions.

[0049] (Example 5) Phase 5 In this example, Phase 5 conditions were used, in which all of the Phase 4 conditions were combined with increasing the temperature of the reactor overhead stream (e.g., with steam) to promote post-polymerization reactions. Note that the minimum temperature in Phase 5 was approximately -30°C, as shown below. Reactor conditions, MRI, and Mooney viscosity results are provided in Table 5 (samples were approximately 2 hours apart).

[0050] [Table 9] [Table 10]

[0051] The distribution of MRI values ​​for Phase 5 samples (with a TEG / EADC of about 0.5, with the overhead blender turned off and the temperature of the overhead stream increased) has a median of 3.24 and a mean of 3.24 (MRI samples for Phase 5 are plotted in Figure 2). Thus, using the post-processing methodology of reducing the quench to catalyst ratio to about 0.5, plus turning off the reactor overhead blender and increasing the temperature at the reactor outlet, a broader MWD was obtained (represented by a higher MRI)—representing an increased amount of low molecular weight polymer fraction compared to each of the Phase 1 through Phase 4 conditions.

[0052] Referring to Examples 1-5, FIG. 2 is a chart showing the MRI values ​​for each of the above Phases 1-5. The average MRI across the phase conditions ranged from 2.7 to 3.24. Note again that while MRI is an indicator of MWD, the absolute values ​​between MRI and MWD are not equal, and an increasing trend in MRI indicates an increasing trend in MWD. ​​Indeed, referring now to FIG. 3, this is a gel permeation chromatography chart showing the MWD for the results of Example 1 (Phase 1) herein and Example 4 (Phase 4) herein. As shown, the MWD for Phase 1 is 3.1, and for Phase 4, the MWD is significantly shifted to 3.8. Therefore, it is believed (without being bound by theory) that the resulting butyl rubber exhibits a significant increase in both MRI and MWD, representing an increase in low molecular weight polymer, by using one or more of the post-polymerization methodologies of the present disclosure.

[0053] Furthermore, Examples 1-5 demonstrate an overall increase in feedstock conversion for similar reactant residence times. Figure 4 is a chart displaying isobutylene conversion values ​​for experimental phase conditions according to one or more embodiments of the present disclosure. Figure 5 is a chart displaying isobutylene conversion values ​​for experimental phase conditions according to one or more embodiments of the present disclosure.

[0054] Example 6 In this example, commercially available butyl rubber, a copolymer of isobutylene and isoprene, was prepared according to proprietary specifications (control samples C1-C12) and then prepared according to Phase 5 conditions (all other conditions kept unchanged) (experimental samples E1-E12). MRI and Mooney viscosity results are shown in Table 6 below.

[0055] [Table 11]

[0056] The distribution of MRI values ​​for the control sample has a median of 3.22 and a mean of 3.23, while the distribution of MRI values ​​for the experimental sample (processed according to Phase 5 described herein) has a median of 4.00 and a mean of 4.02. This example again demonstrates that using the post-processing methodology of the present disclosure results in a broader MWD (represented by a higher MRI) - representing an increased amount of low molecular weight polymer fraction.

[0057] Example 7 In this example, commercially available halogenated (functionalized) butyl rubber, a copolymer of isobutylene and isoprene, was prepared according to proprietary specifications (control samples C13-C24) and then prepared according to Phase 5 conditions (keeping all other conditions unchanged) (experimental samples E13-E24). MRI and Mooney viscosity results are shown in Table 7 below.

[0058] [Table 12]

[0059] The distribution of MRI values ​​for the control sample has a median of 3.3 and a mean of 3.4, while the distribution of MRI values ​​for the experimental sample (processed according to Phase 5 described herein) has a median of 4.1 and a mean of 4.1. This example again demonstrates that using the post-processing methodology of the present disclosure results in a broader MWD (represented by a higher MRI) - representing an increased amount of low molecular weight polymer fraction, including when processing halogenated butyl rubber. Thus, this disclosure demonstrates that post-polymerization control and modification of the polymerization system by one or more methodologies of this disclosure can be used to broaden the molecular weight distribution of the resulting polymer.

[0060] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and the like used in the specification and the related claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties sought to be obtained by embodiments of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should, at the very least, be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0061] One or more illustrative embodiments incorporating elements of one or more inventions are presented herein. For clarity, not all features of an actual implementation are described or shown in this application. It is understood that in developing an actual embodiment incorporating one or more elements of the present invention, various implementation-specific decisions must be made to achieve the developer's objectives, e.g., conformance with system-related, business-related, governmental, and other constraints, which may vary from implementation to implementation. While the developer's efforts may be time-consuming, such efforts are nonetheless routine for those of ordinary skill in the art and have the benefit of this disclosure.

[0062] Although compositions and methods have been described herein in terms of "comprising" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. The present invention is, therefore, well adapted to obtain the ends and advantages mentioned and inherent therein. The specific embodiments and configurations disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the specific illustrative embodiments disclosed above may be changed, combined, and modified, and all such variations are considered within the scope and spirit of the present invention. The invention illustratively disclosed herein may suitably be practiced without any element not specifically disclosed herein and / or any and all elements disclosed herein. Although compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps, compositions and methods may also "consist essentially of" or "consist of" the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower and upper limit is disclosed, every number and every included range falling within that range is specifically disclosed. In particular, all value ranges disclosed herein (in the form "about a to about b," or in other words, "from approximately a to b," or in other words, "from approximately a to b") should be understood to describe all numbers and ranges encompassed within that broad range of values. Again, terms in the claims have their ordinary and ordinary meanings unless expressly and clearly defined otherwise by the patentee.Moreover, the indefinite articles "a" or "an," when used in the claims, are defined herein to mean one or more than one of the element that it introduces.

Claims

1. polymerizing a polymerization medium in a reactor, the polymerization medium comprising monomer, diluent, and a catalyst system, the catalyst system comprising a Lewis acid and an initiator, thereby producing a reactor overflow; contacting the reactor overflow with a quenching agent; and controlling the quenching of the reactor overflow to obtain a Mooney Stress Relaxation Index (MRI) of greater than about 2.5, thereby producing a quenched reactor overflow. A method comprising:

2. 10. The method of claim 1, wherein the MRI is in the range of about 2.5 to about 4.

5.

3. 10. The method of claim 1, wherein the controlling step comprises adjusting the amount of quenching agent such that the molar ratio of quenching agent to Lewis acid is within the range of about 0.4 to about 0.

8.

4. 4. The method of claim 3, wherein the molar ratio of the quenching agent to the Lewis acid is in the range of about 0.4 to about 0.

6.

5. 10. The method of claim 1, wherein the reactor comprises an overhead blender, and the controlling step comprises slowing down or shutting off the overhead blender during one or both of the polymerization and the quench.

6. 10. The method of claim 1, wherein the reactor outlet comprises a steam jacket, and the controlling step comprises heating the steam jacket so that the temperature at the reactor outlet is within the range of about −40° C. to about 0° C.

7. 6. The method of claim 5, wherein the temperature at the reactor outlet is within the range of about -30°C to about -10°C.

8. 10. The method of claim 1, wherein the reactor comprises an overhead blender, and the controlling step comprises: (1) slowing down or shutting off the overhead blender during one or both of the polymerization and the quench; and (2) adjusting the amount of quench agent so that the molar ratio of quench agent to Lewis acid is within the range of about 0.4 to about 0.

8.

9. 9. The method of claim 8, wherein the reactor outlet includes a steam jacket, and the controlling step further comprises: (3) heating the steam jacket so that the temperature at the reactor outlet is within the range of about −40° C. to about 0° C.

10. 10. The method of claim 1, wherein the reactor outlet includes a steam jacket, and the controlling step includes: (1) heating the steam jacket so that the temperature at the reactor outlet is within the range of about −40° C. to about 0° C., and (2) adjusting the amount of quenching agent so that the molar ratio of quenching agent to Lewis acid is within the range of about 0.4 to about 0.

8.

11. 10. The method of claim 1, wherein the reactor comprises an overhead blender and the reactor outlet comprises a steam jacket, and the controlling step comprises: (1) slowing down or shutting off the overhead blender during one or both of the polymerization and the quench; and (2) heating the steam jacket so that the temperature at the reactor outlet is within the range of about −40° C. to about 0° C.

12. 10. The method of claim 1, wherein the monomer is one or more of an olefin, an alpha-olefin, a disubstituted olefin, an isoolefin, a conjugated diene, a non-conjugated diene, a styrene, a substituted styrene, and a vinyl ether.

13. The method of claim 1 , wherein the monomer is isobutylene, isoprene, or a combination thereof.

14. The process of claim 1, wherein the monomer is present in the polymerization medium in an amount within the range of from about 30% to about 40% by weight.

15. 10. The method of claim 1, wherein the diluent is one or more of a hydrocarbon, a halogenated hydrocarbon, and a chlorinated hydrocarbon.

16. The process of claim 1, wherein the diluent is present in the polymerization medium in an amount within the range of from about 60% to about 70% by volume.

17. 10. The method of claim 1, wherein the Lewis acid is one or more of aluminum trichloride, aluminum tribromide, ethylaluminum dichloride, ethylaluminum sesquichloride, diethylaluminum chloride, methylaluminum dichloride, methylaluminum sesquichloride, and dimethylaluminum chloride.

18. 2. The method of claim 1, wherein the Lewis acid is ethylaluminum dichloride.

19. 10. The method of claim 1, wherein the initiator is one or both of a Bronsted acid, an alkyl halide, and a hydrogen halide.

20. 10. The method of claim 1, wherein the quenching agent is at least one alcohol.

21. 10. The method of claim 1, wherein the quenching agent is triethylene glycol.

22. 10. The process of claim 1, wherein the reactor is a continuous reactor.

23. 10. The process of claim 1 further comprising separating a polymer fraction from the quenched reactor overflow.

24. 10. The method of claim 1, wherein the monomers are isobutylene and isoprene, and the polymerizing step forms polyisobutylene-co-isoprene.

25. 25. The method of claim 24, further comprising halogenating the polyisobutylene-co-isoprene, thereby forming a halogenated polyisobutylene-co-isoprene.

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