Method for forming halobutyl elastomers

Abstract

The present disclosure relates to a method for forming a halobutyl rubber. In at least one embodiment, the method for forming a halobutyl elastomer includes polymerizing a C4-C7 isomonoolefin and at least one comonomer in a first reactor to obtain a C4-C7 isomonoolefin-derived elastomer. The method includes transferring the C4-C7 isomonoolefin-derived elastomer via a line to a second reactor. The method includes introducing about 20 ppm to about 400 ppm of a Structure III stabilizer, relative to the amount of the C4-C7 isomonoolefin-derived elastomer and the Structure III stabilizer, to the C4-C7 isomonoolefin-derived elastomer. The method includes introducing a halogenating agent to the C4-C7 isomonoolefin-derived elastomer to form a halobutyl elastomer.

Description

[Technical Field]

[0001] Inventor :Simon N.Watson;Peter D.Ventress;Gavin Hunt;Rachel C.Hounslow;Christian Briard;Sunny Jacob;Stephen T.Dalpe CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and benefit of U.S. Provisional Patent Application No. 63 / 404,584, filed September 8, 2022, entitled "Method of Forming Halobutyl Elastomers," the disclosure of which is incorporated herein by reference in its entirety. The present disclosure relates to methods of forming halobutyl elastomers. [Background technology]

[0002] Butyl rubber (also called halobutyl rubber, e.g., halobutyl elastomer) is an important material in the manufacture of tubeless tires, inner tubes, and the like due to its low gas and vapor permeability. Butyl rubber is typically produced by the slurry polymerization of methylpropene (isobutylene) and 2-methyl-1,3-butadiene (isoprene) in a diluent in the presence of an initiator and co-initiator. Halobutyl rubbers, such as bromobutyl rubber, are typically formed in a two-step process, first by polymerization of isobutylene and isoprene to produce butyl rubber, followed by halogenation. Bromobutyl rubber can be described as having different types of monomer units known as Structure 1, Structure 2, and Structure 3. Structure 1 refers to unbrominated isobutylene or isoprene units. Structure 2 refers to isobutylene or isoprene units that are brominated at a carbon atom along the polymer backbone (e.g., not at a methyl substituent on the isobutylene or isoprene unit). Structure 3 refers to isobutylene or isoprene units that are brominated at a methyl substituent on the isobutylene or isoprene unit (e.g., not at a carbon atom along the polymer backbone).

[0003] During the bromination of butyl rubber, bromobutyl rubber can have a high amount of structure 2 units formed, but over time, the bromobutyl rubber formed will undesirably begin to have a high content of structure 3, at which point the bromination conditions must be analyzed and modified and / or the bromination must be stopped. Ultimately, bromobutyl rubber with a high content of structure 3 reduces the yield of bromobutyl rubber with a high content of structure 2. High Structure 3 content also leads to an increase in the Mooney viscosity of bromobutyl rubber (called "marching Mooney"), which can lead to poor processability in compound formulations such as innerliner formulations (e.g., for innertubes). Furthermore, bromobutyl rubber produced using an in-situ bromine regeneration process for bromination through the use of hydrogen peroxide is known to produce increased marching Mooney properties compared to bromination processes that do not utilize bromine regeneration. The increase in marching Mooney properties occurs during bromine regeneration because bromine regeneration promotes further attachment of bromine to the bromobutyl rubber polymer chain. There is a need for an improved process that provides halobutyl elastomers with a high content of structure 2, improved yields, and bromine regeneration options. Throughout this specification, "Structure 2" is used interchangeably with "Structure II," and "Structure 3" is used interchangeably with "Structure III."

[0004] References for citation in the Disclosure Statement (37 C.F.R. 1.97(h)): U.S. Patent No. 10,479,845; U.S. Patent No. 4,154,924; U.S. Patent No. 3,257,349; U.S. Patent No. 7,858,735; U.S. Patent No. 4,508,592; China Patent No. 111548436B Summary of the Invention

[0005] The present disclosure relates to methods of forming halobutyl elastomers. In at least one embodiment, a method for forming a halobutyl elastomer includes polymerizing a C4-C7 isomonoolefin and at least one comonomer in a first reactor to obtain a C4-C7 isomonoolefin-derived elastomer. The method includes transferring the C4-C7 isomonoolefin-derived elastomer via a line to a second reactor. The method includes introducing about 20 ppm to about 400 ppm of a Structure III stabilizer, based on the amount of the C4-C7 isomonoolefin-derived elastomer and the Structure III stabilizer, to the C4-C7 isomonoolefin-derived elastomer. The method includes introducing a halogenating agent to the C4-C7 isomonoolefin-derived elastomer to form a halobutyl elastomer. To assist those skilled in the art to which it pertains in making and using the subject matter of the present invention, reference is made to the accompanying drawings. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 illustrates the formation of butyl rubber, according to an embodiment. [Figure 2] FIG. 1 illustrates solvent displacement, according to an embodiment. [Figure 3] FIG. 1 illustrates steps for halogenating and neutralizing cement to form a halobutyl elastomer, according to an embodiment. [Figure 4] FIG. 10 illustrates finishing of a crumb, according to an embodiment. [Figure 5] FIG. 1 illustrates the recycling and recovery of diluents and monomers, according to an embodiment. [Figure 6] 1 is a graph showing BHT versus Structure 3 in an Irganox run, according to an embodiment. [Figure 7] 1 is a graph showing BHT versus Structure 3 in an Irganox run, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present disclosure relates to methods of forming halobutyl elastomers. In some embodiments, butyl rubber is produced by slurry polymerization of methylpropene (isobutylene) and 2-methyl-1,3-butadiene (isoprene) in a methyl chloride diluent in the presence of an initiator and a co-initiator. The initiator is HCl, and the co-initiator is aluminum chloride or an alkyl aluminum, such as EADC (ethylaluminum dichloride) or EASC (ethylaluminum sesquichloride). The butyl copolymer is then quenched using alcohol or water and sent to a processing unit known as a "solvent displacement process," where the polymer is dissolved in a hydrocarbon solvent to produce a polymer / solvent solution, hereafter known as cement. The cement, diluent, and monomers are then sent to a series of distillation columns, where the diluent and monomers are removed from the cement, the cement is concentrated, and the remaining hydrocarbon solvent is recovered for recycle. The cement is sent to storage for subsequent halogenation / neutralization, solvent removal, drying, and packaging. The diluent-monomer stream from the solvent recovery process is dried, compressed, and sent to a series of recycle columns, where the streams are separated. The high purity diluent stream is recycled for catalyst diluent. The diluent / isobutylene and isoprene streams are recovered for the reactor feed blend. Heavies from the process are purged from the unit. Inerts and lights from the process are purged from the unit.

[0008] It has been discovered that a Structure III stabilizer (such as butylated hydroxytoluene) can be introduced into the halogenation process upstream of the halogenation reactor, providing a halobutyl elastomer having a high Structure 2 content in higher yields than conventional processes, and providing the option of performing bromine regeneration without marching Mooneys. Such a Structure III stabilizer can be provided upstream of (or within) the halogenation reactor in amounts less than the conventional use of BHT in halobutyl processes.

[0009] While several different factors influence the ratio of Structure 2 to Structure 3 formation, one of the most important factors is the low amount of background Structure III stabilizer, such as butylated hydroxytoluene (BHT), in the cement. BHT is typically present in the hexane used to make halogenated cement. The source of BHT comes from BHT injected into the reslurry. Some of the BHT then accompanies the hexane removed in the flash drum and is recovered back in the main hexane storage tank. The remaining BHT accompanies the rubber and ends up in the finished product. However, for example, when producing halobutyl rubber using Irganox™ antioxidant, BHT is not typically injected into the reslurry. The BHT level is allowed to fall below a certain level in the hexane tank (typically 3-5 days), and then the Irganox™ production run is initiated. The problem with this approach is that the background BHT level continues to fall during the Irganox™ run, promoting the formation of Structure 3 as this continues. The inventors have discovered that by monitoring the BHT level (e.g., ppm) in the finished rubber, the amount of Structure III stabilizer can be monitored for process control and grading purposes. If the BHT level falls below the desired amount, Structure III stabilizer can be introduced upstream of the halogenation reactor to improve the yield of the desired halobutyl elastomer with a high Structure 2 content. In other words, by introducing a certain amount of Structure III stabilizer upstream of the halogenation reactor, the background level of BHT / other Structure III stabilizers can be maintained sufficiently high to prevent the formation of Structure 3 and provide a halogenated rubber product suitable for pharmaceutical grade specifications. The introduction of Structure III stabilizer can be carried out at any suitable flow rate.

[0010] Furthermore, with respect to halogen regeneration processes, the presence of Structure III stabilizers can provide the added benefit of reducing or preventing oxidation of the halobutyl elastomer product in the neutralization unit, flash drum, or stripper due to the presence of residual oxidizing agent from the emulsion fed to the upstream halogenation reactor. Such oxidation has been shown to adversely affect molecular weight (e.g., Z-average molecular weight) control of the halobutyl elastomer product in conventional halogen regeneration processes. Without being bound by theory, when the polymer is subjected to significant thermal changes, such as in a slurry process following neutralization, the oxidized structures decompose to generate polymer free radicals. Unhindered, the radicals form a sufficient amount of crosslinked networks in situ within the polymer to demonstrate increases in molecular weight, Mz, and Mooney viscosity.

[0011] As used herein, polymer may be used to refer to a homopolymer, copolymer, interpolymer, terpolymer, etc. Similarly, a copolymer may refer to a polymer comprising at least two monomers, and optionally other monomers. 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 polymerized form of a derivative from the monomer (i.e., a monomer unit). However, for ease of reference, the phrase "including each" monomer or the like is used as a shorthand. Similarly, when a catalyst component is described as comprising the neutral stable form of the component, those skilled in the art will appreciate that the ionic form of the component is the form that reacts with the monomer to produce the polymer.

[0012] Elastomer refers to a polymer or blend of polymers that conforms to the ASTM D1566 definition: "A material capable of recovering from large deformation and capable of being, or has been modified upon vulcanization, rendered essentially solvent-insoluble (although capable of swelling)." Elastomers are often also referred to as rubbers, and the term elastomer may be used interchangeably herein. Elastomers may have melting points that cannot be measured by differential scanning calorimetry (DSC), or, if measurable by DSC, may have melting points below 40°C, such as below 20°C, such as below 0°C. Elastomers may have a glass transition temperature (Tg) as measured by DSC of -50°C or less. Mooney viscosity or viscosity refers to a measurement of the viscosity of a polymer (e.g., rubber). It is defined as the shear torque that resists rotation of a cylindrical metal disk (or rotor) embedded in a polymer within a cylindrical cavity. Shear disk viscometer dimensions, testing temperatures, and procedures for determining Mooney viscosity are defined in ASTM D1646. Mooney viscosity is measured in Mooney units and reported herein as ML1+8 at 125°C.

[0013] Isoolefin refers to any olefin monomer having at least one carbon and two substitutions on that carbon. Multiolefin refers to any monomer having two or more double bonds. In a preferred embodiment, the multiolefin is any monomer containing two conjugated double bonds, such as a conjugated diene like isoprene. An isobutylene-based elastomer or polymer refers to an elastomer or polymer that contains at least 70 mol % isobutylene units.

[0014] Elastomer The elastomeric polymers (e.g., rubbers) of the present disclosure comprise elastomers derived from a mixture of monomers having at least: (1) a C4-C7 isoolefin monomer component; and (2) at least one multiolefin or other polymerizable monomer component. The isoolefin can be present in a range of 70 to 99.5 weight percent of the total monomers, such as 85 to 99.5 weight percent. The multiolefin-derived or other polymerizable monomer component is present in an amount of about 30 weight percent to about 0.5 weight percent, or about 15 weight percent to about 0.5 weight percent, or about 8 weight percent to about 0.5 weight percent.

[0015] Isoolefins can be C4-C7 compounds, non-limiting examples of which include compounds such as isobutylene, isobutene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 1-butene, 2-butene, methyl vinyl ether, indene, vinyltrimethylsilane, hexene, and 4-methyl-1-pentene. Multiolefins can be C4-C7 compounds such as isoprene, butadiene, 2,3-dimethyl-1,3 butadiene, myrcene, 6,6-dimethylfulvene, hexadiene, cyclopentadiene, and piperylene. 14 Other polymerizable monomers such as styrene and dichlorostyrene are also suitable for homopolymerization or copolymerization in butyl rubber. The elastomer may include an isobutylene-based copolymer. As discussed above, an isobutylene-based polymer refers to a polymer (e.g., an elastomer) having at least 70 mol % repeat units from isobutylene and at least one other polymerizable unit. These polymers are also commonly referred to as butyl rubber. In some embodiments, butyl rubber is obtained by reacting isobutylene with 0.5 to 8 wt % isoprene, or by reacting isobutylene with 0.5 to 5.0 wt % isoprene, with the remaining weight percent of the polymer being derived from isobutylene.

[0016] Other elastomeric polymers of the present disclosure can be derived from at least one random copolymer comprising a C4-C7 isoolefin and an alkylstyrene comonomer. The isoolefin can be selected from any of the C4-C7 isoolefin monomers listed above and can be an isomonoolefin or isobutylene. The alkylstyrene can be para-methylstyrene containing at least 80% para isomer by weight, such as at least 90%, such as at least 95%, and can also include functionalized terpolymers. The random copolymer has at least one or more alkyl substituents present on the styrene monomer units. In some embodiments, the elastomer comprises a random polymer of isobutylene and 0.5 to 20 mol% para-methylstyrene. In some embodiments, other useful elastomers include other unsaturated copolymers of isoolefins, non-limiting examples of which are poly(isobutylene-co-butadiene), star-branched isobutylene-isoprene, star-branched isobutylene-p-methylstyrene, isobutylene-isoprene-alkylstyrene block polymers, and random polymers of isobutylene-isoprene-alkylstyrene.

[0017] In some embodiments, the halobutyl elastomer (halobutyl rubber) of the present disclosure can have from about 0.1 mol% to about 3 mol% isoprene (brominated + non-brominated), such as from about 0.5 mol% to about 3 mol%, such as from about 1.5 mol% to about 1.8 mol%, such as from about 1.6 mol% to about 1.7 mol%, based on the total moles of monomer units (e.g., isoprene (brominated + non-brominated) + isobutylene). The halobutyl elastomer (halobutyl rubber) of the present disclosure may have from about 0.6 mol% to about 1.1 mol%, such as from about 0.6 mol% to about 0.9 mol%, such as from about 0.7 mol% to about 0.9 mol%, of Structure II units, based on the total moles of monomer units. The halobutyl elastomer (halobutyl rubber) of the present disclosure may have about 0.01 mol % to about 0.15 mol %, such as about 0.03 mol % to about 0.15 mol %, such as about 0.07 mol % to about 0.1 mol %, of Structural III units based on the total moles of monomer units. In some embodiments, the halobutyl elastomers (halobutyl rubbers) of the present disclosure may have a Structure III stabilizer content of about 20 ppm or less, such as about 15 ppm or less, such as about 10 ppm or less, such as about 7 ppm or less.

[0018] Butyl Rubber Process The above polymers can be produced by any suitable polymerization method. The polymers can be produced by either a slurry polymerization process or a solution polymerization process. When produced by a slurry polymerization process, the polymer is precipitated from the reaction medium, and then dissolved in a suitable solvent prior to halogenation, for example, to produce a polymer cement. For polymers produced via a solution process, the same polymer-containing solution or polymer cement can be used for halogenation after removal of unreacted monomers and removal or neutralization of unused catalyst. The polymer cement can contain from about 1% to about 70% by weight of polymer, such as from about 10% to about 60% by weight of polymer, such as from about 10% to about 50% by weight of polymer, such as from about 10% to about 40% by weight of polymer.

[0019] Preparation of monomers High-purity isobutylene (typically about 95% to about 100% by weight) and isoprene (such as about 95% to about 99.9% by weight) can be used in the production of butyl rubber. Impurities can affect isobutylene / isoprene conversion, polymer molecular weight distribution, and reactor performance. Monomer purity is controlled by strict quality control with purchasing specifications and additional purification completed at the production unit if desired. High-purity isobutylene can be derived from fossil fuels, advanced recycling processes, or bio-based sources.

[0020] Catalyst preparation High-purity diluent (typically about 98% to about 100% by weight) from the diluent recovery column, used as the catalyst diluent, is combined with the initiator and then with the catalyst. The initiator is typically HCl, and the catalyst is typically an alkylaluminum or aluminum chloride catalyst. Figure 1 shows a diagram 100 illustrating butyl rubber formation. When an alkylaluminum catalyst is used, the catalyst diluent and catalyst are combined at 102 and mixed in a static mixer to ensure good distribution. When an aluminum chloride catalyst is used, the catalyst diluent stream is split; one portion of the catalyst diluent is cooled at 102 and sent through a molten aluminum chloride bed, then recombined with the other portion of the catalyst diluent to achieve the desired catalyst concentration. The catalyst / diluent / initiator stream is injected into the reactor 106 at a high velocity, such as about 1.5 m / s to about 5 m / s, to ensure good distribution within the reactor. The catalyst to initiator ratio is about 1 mol / mol to about 5 mol / mol, such as about 1.5 to about 2.5 mol / mol. The reaction is sensitive to oxygenates, oxygen, and moisture. Moisture is removed from the fresh isoprene at 108 and from the isobutylene at 110 and sent to reactor 106. The diluent / monomer recycle stream is dried in a fixed-bed alumina and / or molecular sieve dryer at 112 to remove residual moisture and oxygenates. The recycle solvent stream is dried in a fixed-bed molecular sieve dryer or by fractional distillation at 114 and reused in the process. The recycle and feed streams are equipped with moisture, oxygen, and oxygenate analyzers to ensure control of moisture, oxygen, and oxygenate levels. The diluent recovery column distillate drum is purged of oxygen-containing lights.

[0021] Feed Blend and Reactor Isobutylene and isoprene in diluent are prepared to a predetermined composition in a feed blend drum 116, cooled to −90° C. to −100° C. using a series of heat exchangers, and fed to reactor 106. Catalyst and cocatalyst are prepared in a high-purity diluent and fed to reactor 106. A copolymer of isobutylene and isoprene is produced in reactor 106. An exemplary diluent used is methyl chloride. In some embodiments, the feed blend contains about 20% to about 40% by weight isobutylene and about 0.4% to about 1.4% by weight isoprene, depending on the grade, with the remainder primarily being diluent.

[0022] Butyl reactors become contaminated over time and are periodically shut down for cleaning. The butyl reaction process can thus be a semi-batch process, with several reactors in production and several in non-production mode. At the end of the production cycle, the production reactors are quenched by injecting alcohol or water into the reactor to stop the reaction, and then flushed with diluent at temperatures of approximately -40°C to -80°C, removing most of the rubber slurry and gradually warming the reactor. Solvent is introduced to further warm the reactor to 0°C to 50°C. The reactor 106 is then rinsed with solvent at temperatures of 0°C to 90°C to remove rubber foulants that have accumulated on the vessel surface. Once the reactor 106 is clean, the solvent is replaced with diluent at -40°C to -80°C to gradually cool the reactor, then cool it to -90°C to -100°C and prepare it for production. The flow rate, temperature, and duration of each non-production stage are controlled to ensure that the mechanical design of the reactor and reactor pumps is not compromised.

[0023] Once the reactor 106 is cooled for production, a mixture of diluent, isobutylene, and isoprene is primed into the reactor 106. The diluent, isobutylene, and isoprene concentrations are set to mimic normal background concentrations during reactor production to ensure the polymer is on-spec quickly. The initiator and coinitiator are then injected at a high rate to ensure the reaction starts quickly, and then set at normal rates to ensure the rubber is on-spec.

[0024] Solvent Replacement Process For example, as described in U.S. Pat. No. 4,154,924, incorporated herein by reference, an alcohol or water quench is injected into the reactor overflow outlet to quench the catalyst at 118. FIG. 2 illustrates the solvent displacement 118. As shown in FIG. 2, the quench 202 may be premixed with a polar diluent, then diluted with a solvent, with or without a static mixer, and added to the reactor outlet. The quench 202 is injected and mixed with the reactor slurry at 204, with or without a mechanical mixer. The resulting stream is then sent to a solution drum 206, where solvent vapor 208 is added to heat the process and dissolve the polymer, forming a polymer / solvent solution known as cement. A typical solvent is a mixture of normal hexane and hexane isomers. The solution drum liquid outlet 210 is then sent to a surge drum 212. The solution drum 206 and surge drum 212 may be combined into a single drum. The solution may be periodically sampled and analyzed to monitor polymer properties. Statistical process control techniques and fundamental or empirical models may be used to monitor product quality and guide optimization of polymerization conditions. Drum operating temperatures can range from about −20° C. to about +30° C., such as about −20° C. to about +10° C., and operating pressures can range from about 0 kPa to about 1000 kPa, such as about 0 kPa to about 500 kPa. The process is operated to generate a vapor stream of about 0% to about 30% of the total drum feed, as described, for example, in U.S. Pat. No. 3,257,349, incorporated herein by reference. Liquid streams from these drums containing cement, solvent, diluent, and unreacted monomer are sent via line 216 to cement stripping tower 214. Vapor streams containing solvent, diluent, and unreacted monomer from drums 206 and 212 are sent via line 216 to cement stripping tower 214 or via line 218 to the cement stripping tower overhead. The cement stripping tower 214 is a dual flow tray tower with 20 to 60 trays, such as 40 to 60 trays, suitable for fouling service, such as a TECHNIP RIPPLE TRAY™ tower, as described in U.S. Pat. No. 3,257,349.Solvent vapor is injected into the bottom of the tower via line 220 and flows countercurrently with the cement. The overhead of the cement stripping tower, which contains the diluent, unreacted monomer, and a portion of the solvent, is sent via line 222 to a solvent recovery tower 224, where high purity solvent is recovered in the bottoms stream for recycle and diluent (line 226) and unreacted monomer is recovered overhead (line 228) and sent to a diluent recycle stream dryer 230.

[0025] Cement stripping column 214 is operated to ensure a very low concentration of monomers in the cement stream, since any monomers would react in the subsequent halogenation process and exceed desired product specifications (e.g., industrial hygiene regulations). The monomer concentration in the cement stream (line 232) is <200 ppm by weight, with good industrial hygiene regulations typically requiring <50 ppm by weight.

[0026] The bottom cement stream (line 232) from the cement stripping tower 214 is flashed to one or two cement thickener drums 234. The cement is cooled and the cement concentration is increased. The cement thickener overhead vapor stream (line 234) has a temperature determined by the utility temperature, usually cooling water or air. The operating pressure of the thickener drums 234 is determined by the solvent vapor pressure curve; a typical solvent is a mixture of normal hexane and hexane isomers. The cement thickeners 234 are operated at pressures of about 40 kPaa to about 150 kPaa, such as about 50 kPaa to about 100 kPaa, as described, for example, in U.S. Pat. No. 3,257,349. The cement thickener drums 234 are fitted with transverse trays or baffle plates (shower decks) to separate the solvent vapor from the viscous cement and minimize vapor entrainment in the bottom cement stream (line 236). The overhead solvent from the cement thickener is recycled in the process. The bottoms cement stream (line 236) is sent to storage 238. The cement concentration sent to storage 238 is from about 18% to about 30% by weight, such as from about 22% to about 28% by weight. Heat integration is used extensively in the solvent recovery section of the plant and in the reslurry section of the unit to maximize energy efficiency.

[0027] Halogenation and Neutralization The halogenation and neutralization can be carried out using any suitable process. Figure 3 is a diagram 300 illustrating the halogenation and neutralization of cement to form halobutyl rubber. As shown in Figure 3, cement from storage 238 is pumped via pump 302 and line 304 to a well-mixed halogenation reactor 306, where a halogen (e.g., Br2, Cl2, NaBr, NaCl, or a combination thereof) is added via line 308 to form the halobutyl rubber. The halogen can be gaseous chlorine or liquid bromine, depending on the grade of halobutyl being produced. The halogenation reactor 306 can be a CSTR (continuous stirred tank reactor) or a high-speed mixing device such as a STRATCO™ CONTACTOR™. In some embodiments, the reactor vessel is a mixed-flow stirred tank, a conventional stirred tank, a packed column, or piping with sufficient flow and residence time to allow the desired reaction to occur. Additional piping and valves may be included downstream to control the reaction residence time. The Structure III stabilizer is introduced into any suitable location in the halogenation process, such as into the cement tank 238, into the pump 302, into the halogenation reactor 306, or into line 304 via line 336 (as shown in FIG. 3).

[0028] The halogenated cement and reaction by-products (line 310) are then mixed with a neutralizing agent (such as sodium hydroxide) (line 320) in a first neutralization unit 312 to neutralize the resulting HCl or HBr / bromine. The first neutralization stage can be one to four individual process units and can be a CSTR, CONTACTOR™, static mixer, or combinations thereof. The stream from the first neutralization unit 312 (line 314) is then mixed with an additive in a second neutralization unit 316 to complete the neutralization and form a stable emulsion. The additive is typically a calcium stearate dispersion with a surfactant (line 318). In some embodiments, the surfactant is a nonionic alcohol ethoxylate, such as ethoxytridecyl alcohol. The second stage neutralization process unit can be one to four individual process units and can be a CSTR, CONTACTOR™, static mixer, or combinations thereof.

[0029] The water / hydrocarbon emulsion (line 322) from the halogenation and neutralization section is sent to a flash drum 324 and a stripper 338 vessel for solvent removal and recovery (line 328). The water / hydrocarbon emulsion is flashed to an agitated flash drum 324, where steam is injected into the liquid to remove the solvent from the stream. A rubber crumb forms in the flash drum 324, and an additive (line 326) is added to the flash drum 324 to prevent polymer agglomeration and vessel plugging. The additive is typically a calcium stearate dispersion with a surfactant. The water / crumb mixture flows to an agitated stripper 338, where additional residence time and reduced pressure allow the solvent to diffuse from the crumb into the vapor stream (line 330). Additional steam may be injected into the stripper 338 to aid the solvent diffusion process. Water is sprayed into the vapor space of the flash drum 324 and the stripper 338 to reduce vessel fouling and provide cooling; the spray pattern is typically a hollow cone or solid cone. Slurry concentration to the flash drum 324 and stripper 338 process units is controlled to minimize the tendency for flocculation and clogging, for example by controlling the calcium and surfactant flow rates injected into the flash drum to manage crumb size within desired operating parameters: lower injection rates result in larger crumb size and vice versa.

[0030] The solvent / water in the vapor stream (line 328) from the flash drum is condensed, the solvent is separated in condenser / separator 332 and sent to storage for subsequent drying and recycle, and the water is recycled in the process.

[0031] To ensure a favorable reaction that matches the hardening properties of the final product, during the production of halobutyl, the cement temperature for halogenation is controlled below 65°C, such as 20°C to 65°C, or 40°C to 60°C.

[0032] Flash drum 324 operates at a pressure of about 140 kPaa to about 190 kPaa, with a liquid temperature of about 105°C to about 120°C. Stripper 338 can operate at a pressure of about 80 kPaa to about 130 kPaa, such as about 90 kPaa to about 120 kPaa, with a liquid temperature of about 90°C to about 110°C. The pressure in stripper 338 is controlled by a vacuum pump or vacuum jet. The stripper overhead stream (line 330) is recycled to flash drum 324 to conserve energy. In larger production facilities, multiple flash drums and strippers can be operated in parallel. In facilities where parallel flash drums and strippers are used, instrumentation can be used to ensure uniform flow distribution between the parallel units. The flash drum 324 may have an agitator, such as an eccentric flat blade agitator, to ensure good mixing between the cement and water and promote crumb formation. The agitator in the stripper 338 may include an up-and-down pumping pitched blade turbine or an up-and-down pumping hydrofoil to ensure good mixing of the buoyant rubber particles in the liquid. Crumb size can be controlled in the flash drum 324 and stripper 338 because too small crumbs can cause fouling of vessels and pipes and difficulty in dewatering / drying, while too large crumbs can make solvent removal difficult and cause pipe clogging. Crumb size is controlled by the addition of calcium stearate, the particle size and particle size distribution of the calcium stearate, and the surfactant added with the calcium stearate. Crumb size distribution is measured and monitored depending on downstream processing, such as extruder sizing.

[0033] In some embodiments of the halogenation process, isobutylene-based polymers having unsaturation within the polymer backbone, such as isobutylene-isoprene polymers, can be halogenated using an ionic mechanism during contact of the polymer with a halogen source, e.g., molecular bromine or chlorine, at temperatures between about 20° C. and 80° C. Isobutylene-based polymers without unsaturation within the polymer backbone, such as isobutylene-alkylstyrene polymers, can be halogenated under free-radical halogenation conditions, e.g., in the presence of white actinic light or by inclusion of an organic free-radical initiator in the reaction mixture, at temperatures between 20° C. and 90° C. In some embodiments, the halogenation process of the present disclosure is a regenerative halogenation process. A conventional regenerative halogenation process can occur by contacting a polymer solution with an emulsion containing a halogenating agent and an oxidizing agent. The oxidizing agent interacts with the hydrogen halide produced during halogenation and returns the halogen to a form useful for further halogenation of the polymer, thereby improving halogen utilization.

[0034] For regenerative halogenation, an emulsion is fed into the halogenation reactor 306 via feed stream E. The emulsion contains an oxidant, water, a solvent, and an emulsifier, such as a surfactant. The emulsion is prepared by preparing an approximately 10% to approximately 80% by weight oxidant solution, such as 20% to approximately 70% by weight or approximately 25% to approximately 45% by weight, in water and mixing it with a solvent and emulsifier under suitable mixing conditions to form a stable emulsion. The emulsion can be achieved by mixing an aqueous phase into an emulsifier containing a solvent, or by first mixing the oxidant with an emulsifier and then combining it with a solvent. The amount of oxidant can be about 0.1 to 3 moles, such as about 0.25 to about 3, such as about 0.5 to about 3 moles, of active oxidant per mole of halogenating agent. By using an oxidant during bromination, bromine utilization can increase to about 70 to 85%.

[0035] The oxidizing agent useful in the process of the present disclosure is an oxygen-containing material, such as a water-soluble oxygen-containing agent. Suitable agents include hydrogen peroxide, organic hydrogen peroxides, sodium chlorate, sodium bromate, sodium hypochlorite or bromate, oxygen, nitrogen oxides, ozone, peroxides and peroxide-forming substances such as urea peroxidate, and acids such as pertitanic, perzirconic, perchromic, permolybdic, pertungstic, pernanic, perboric, perphosphoric, perpyrophosphoric, persulfate, perchloric acid, perchlorates, and periodic acids. Of the foregoing, hydrogen peroxide and hydrogen peroxide-forming compounds, such as peracids and sodium peroxide, have been found to be highly suitable for performing halogen regeneration.

[0036] The solvent selected for the emulsion can be any solvent suitable or used to form the polymer cement. In one embodiment, the solvent is selected to be the same solvent used to form the polymer cement. Suitable solvents include hydrocarbons such as pentane, hexane, heptane, etc.; inert halogen-containing hydrocarbons such as mono-, di-, or tri-halogenated C1-C6 paraffin-based hydrocarbons; halogenated aromatic hydrocarbons such as methyl chloride, methylene chloride, ethyl chloride, ethyl bromide, dichloroethane, n-butyl chloride, and monochlorobenzene; or mixtures of hydrocarbons and inert halo-hydrocarbon solvents. Additionally, the solvent can be a combination of the solvents provided herein, including their isomers. The emulsion fed via feed stream E can be introduced into halogenation reactor 306 at the beginning of the halogenation cycle or after halogen consumption via polymer halogenation has begun. The halogenation and halogen regeneration reactions can occur at temperatures from about 20°C to about 90°C for a time sufficient to complete the halogenation of the polymer. When molecular bromine is the halogenating agent introduced via feed stream (line) 308, bromine consumption is indicated by a change in the color of the reaction mixture from reddish-brown to light tan or amber. After sufficient reaction time in halogenation reactor 306, the effluent exiting halogenation reactor 306 via line 310 can be neutralized, for example, as described above.

[0037] Structure III stabilizer Free radical stabilizers, free radical scavengers, or antioxidants, collectively referred to herein as "Structure III stabilizers," are provided at a location upstream of the halogenation reactor. The Structure III stabilizers can be organic-soluble or water-compatible compounds, such as oil-soluble or hexane-soluble compounds. Suitable Structure III stabilizers include sterically hindered nitroxyl ethers, sterically hindered nitroxyl radicals, butylated hydroxytoluene (BHT), hydroxyhydrocinnamite, thiodipropinoate, phosphites, and combinations thereof. The sterically hindered nitroxyl ether is represented by the formula (I) where n is a number from 1 to 10 and R 1 Each instance of is independently C1-C, such as methyl, ethyl, propyl, butyl, pentyl, etc. 10 The compound may have a structure represented by any one of the following formulas:

[0038] [ka] (I) The sterically hindered nitroxyl radical can have a structure represented by formula (II) (wherein n is a number from 1 to 10).

[0039] [ka]

[0040] Commercially available examples of Structure III stabilizers that can be added during the preparation of the halobutyl rubber of the present disclosure include, but are not limited to, TEMPO, Tinuvin™ NOR 371, Irganox PS800, Irganox 1035, Irganox 1010, Irganox 1076, and Irgafos 168. TEMPO is a term commonly used to refer to (2,2,6,6-tetramethylpiperidin-1-yl)oxy. The sterically hindered nitroxyl radical can be TEMPO. Tinuvin™ NOR 371 may also be used, which is a high molecular weight hindered amine NOR stabilizer and is commercially available as a plastic additive from BASF. Irganox PS800 may also be used, which is commercially available from CIBA and is the trade name for didodecyl-3,3'-thiodipropionate. Irganox 1035 may be used, which is commercially available from CIBA / BASF and is a trade name for thiodiethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate). Irganox 1010 may be used, which is commercially available from BASF and is a trade name for pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate). Irganox 1076 may be used, which is commercially available from CIBA and is a trade name for octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. The sterically hindered phenol may include BHT, Irganox PS800, Irganox 1035, or a combination thereof. Irgafos 168 may be used, which is commercially available from BASF and is a general purpose phosphite. In some embodiments, other Structure III stabilizers may be added to the bromobutyl rubber of the present disclosure, including, but not limited to, light stabilizers and ultraviolet light absorbers.

[0041] In one embodiment, the Structure III stabilizer may be added at more than one position in the halogenation process. In some embodiments, the total amount of Structure III stabilizer added during the process of preparing the halobutyl rubber is greater than about 20 ppm, such as greater than 50 ppm, such as greater than 75 ppm, such as greater than 100 ppm, and less than about 500 ppm, such as less than about 400 ppm, such as less than about 300 ppm, such as less than about 200 ppm, such as less than about 150 ppm, such as less than about 100 ppm. The ppm weight basis is by weight of the halobutyl rubber (whether in solution, slurry, or recovered form).

[0042] Finishing The bottoms stream 334 from the stripper containing rubber crumb and water is sent to an agitated slurry tank 402 shown in Figure 4. Figure 4 is a diagram 400 showing the finishing of the crumb. Typically, a pitched blade impeller or a combination of pitched and horizontal blade impellers is used in an up and down pumping mode.

[0043] The rubber crumb / water slurry is pumped through a dewatering screen 404 to remove bulk water. The rubber crumb is then fed to two or three extruders in series: a rubber crumb dewatering extruder 406 and a drying extruder 408. The dewatering / first stage drying extruders 406 and 408 can be one or more of the following: expanders, expellers, dewatering extruders, slurry dewatering units, and volatile content control units. The final stage drying extruder can be, for example, a dual-worm drying extruder, as described in U.S. Pat. No. 7,858,735, incorporated herein by reference. The temperature and pressure of the extruder are controlled by adjusting the restriction at the extruder outlet, typically using a fixed or variable die plate. Heat may be applied by equipping the extruder with a steam jacket. Inert gas may be injected to improve drying, as described in U.S. Patent No. 4,508,592, which is incorporated herein by reference. Polymer additives are injected at various stages of the extrusion process to meet product specifications and, depending on the grade, may or may not consist of one or more of the following polymer additives: epoxidized soybean oil, calcium stearate, butylated hydroxytoluene, Irganox, or antioxidants.

[0044] The crumb from the final drying extruder is then transported to a fluidized bed conveyor 412 (line 410) for drying to product specifications; the rubber crumb may be transported by a mechanical conveyor. In some embodiments, the fluidized bed conveyor 412 has two sections: a first hot section for drying the crumb and a second cooled section for cooling the crumb. The crumb from the fluidized bed conveyor 412 is then sent to a packaging unit 414, where the crumb is compressed into packets, packaged, and checked for quality. The final rubber polymer product at 416 is warehoused for delivery to customers. In large production facilities, multiple extrusion and fluidized bed drying lines are operated in parallel. Solvent vapors from the slurry tank, extruder, and fluidized bed conveyor can be captured in an air capture system for processing. The finished water recovered from the dewatering screen and extruder is stripped of rubber fines for recycling or disposal. The fines-free finished water is recycled to the reslurry and halogenation unit, purging excess water from the process. The excess water is further treated in facilities before final disposal. Additional antifouling and additives may be added to the recycled water to reduce fouling and control pH. Additives include, but are not limited to, one or more of calcium chloride, proprietary antifouling agents such as PETROFLO™, or borate-based buffers.

[0045] In some embodiments involving halogen regeneration, additives including epoxidized soybean oil (also known as ESBO) and calcium stearate may be added during the regeneration process. For example, ESBO may be added to the drying extruder 408 before or during drying in a range of about 1 to about 2 phr. Additionally or alternatively, as described above, calcium stearate may be added to the cement in the second neutralization unit 316 and / or to the flash drum 324 to prevent polymer buildup on equipment and to control rubber particle size in the water slurry, and / or to the drying extruder 408 during drying. In some embodiments, additives such as ESBO may be added to stripper 338 and / or line 334 .

[0046] Recycle Flow Dryer The diluent / monomer recycle stream from the solvent displacement process section (line 240 in Figure 2) is dried using a combination of a fixed-bed alumina dryer and a chloride-resistant molecular sieve dryer 242 to remove moisture. The alumina dryer also removes oxygenates. The alumina dryer and molecular sieve dryer may be operated in series or parallel, or a combination of both, for example, operating an alumina dryer in series with a molecular sieve dryer in parallel. The fixed-bed alumina dryer and chloride-resistant molecular sieve dryer 242 are taken out of service for regeneration once their water or oxygenate retention capacities are reached. Regeneration may involve one to three depressurizations to deep vacuum to recover hydrocarbons from the bed. Regeneration may involve one to three warm pressurizations and depressurizations to maximize hydrocarbon removal before full regeneration. Regeneration can be performed at 240°C to 300°C for the molecular sieve dryer and at 190°C to 250°C for the alumina dryer. The humidity of the regeneration gas can be controlled by cooling the stream before heating and removing the moisture in a cooled heat exchanger. To minimize oil make-up from the molecular sieve process, the regeneration includes a steaming step.

[0047] Recovery and recycling of monomers from isobutylene-based polymers using a distillation process The diluent / monomer stream (244 in Figure 2) is sent to a recycle column to separate and recover the diluent and monomer for reuse in the process. Figure 5 is a diagram 500 illustrating the diluent and monomer recycle and recovery. As shown in Figure 5, the first recycle column 502 can be a single column or two separate columns. The first recycle column 502 recovers the diluent and isobutylene in overhead stream 504. The overhead stream is separated, with a portion (line 506) sent to diluent recovery column 508, where high-purity diluent is recovered for use as catalyst diluent, and a portion sent for recycle. The bottoms 528 of the diluent recovery column 508 are combined with another portion of the recycle column overhead (line 510) and recycled to the feed blend. The bottoms 512 of the first recycle column are sent to the second recycle column 514. The overheads 516 of the second recycle column are sent to the diluent recovery column 508. The bottoms 518 of the second recycle column 514, containing isobutylene, isoprene, and some heavies, are sent to an isobutylene recovery column 520, with isobutylene recovered for recycle overhead (line 522). The bottoms 524 of the isobutylene recovery column 520 are sent to an isoprene recovery column 526, with isoprene recovered for recycle overhead (line 530). The bottoms 532 of the isoprene recovery column 526 are purged from the process. The isobutylene and isoprene recovery columns can be combined into a single distillation column. The distillate drum above the diluent recovery column 508 can have an inerts vent system. This inerts vent system recovers the diluent from the inerts stream and releases any remaining ethylene / ethane by-products from the alkylaluminum catalyst and inerts from the process. The inerts recovery system can include a distillation column or a series of refrigerated heat exchangers to recover the diluent.

[0048] Antifouling agents are injected into isobutylene recovery column 520 and isoprene recovery column 526 to minimize fouling. The antifouling agents may include a Structure III stabilizer of the present disclosure and / or one or more other suitable antioxidants or antifoulants, including but not limited to, BHT (butylated hydroxytoluene) and proprietary antifoulants such as PETROFLO™. Isoprene recovery column 526 trays and isobutylene recovery column 520 trays may be electropolished to minimize fouling. Oxygen analyzers are installed overhead in second recycle column 514 and diluent recovery column 508.

[0049] In some embodiments, the isobutylene concentration in the overhead of the diluent recovery column 508, used in the catalyst diluent, is <50 ppm isobutylene by mass, such as <20 ppm isobutylene by mass. The temperature of the recycle / diluent recovery column can be set by the utility temperature of the overhead condenser, typically cooling water or air. The column pressure is set by the stream composition based on the vapor pressure curve at the column operating temperature. The pressure of the second recycle column 514 can be from about 800 kPag to about 1200 kPag, such as from about 1000 kPag to about 1200 kPag. The operating pressure of the diluent recovery column 508 can be from about 800 kPag to about 1200 kPag, such as from about 1000 kPag to about 1200 kPag. The isobutylene recovery column 520 can use a coolant in the overhead condenser to set the column operating pressure at about 150 kPag to about 250 kPag. Isoprene recovery column 526 can use a coolant or cooling water in the overhead condenser and can be operated at a pressure of about 50 kPaa to about 150 kPaa to minimize fouling. Second recycle column 514 and isobutylene recovery column 520 can recover from about 95% to about 99.999%, such as from about 99.8% to about 99.9%, of the isobutylene in the feed. The isobutylene composition in the recycle stream is set by the reactor conversion.

[0050] Additional Aspects The present disclosure provides, inter alia, the following aspects, each of which may be considered to optionally include any alternative aspects.

[0051] Clause 1 1. A method of forming a halobutyl elastomer, comprising: polymerizing a C4-C7 isomonoolefin and at least one comonomer in a first reactor to obtain a C4-C7 isomonoolefin-derived elastomer; transferring the C4-C7 isomonoolefin-derived elastomer via a line to a second reactor; incorporating into the C4-C7 isomonoolefin derived elastomer about 20 ppm to about 400 ppm of a Structure III stabilizer, based on the amount of the C4-C7 isomonoolefin derived elastomer and the Structure III stabilizer; introducing a halogenating agent to the C4-C7 isomonoolefin-derived elastomer to form a halobutyl elastomer; A method comprising: Clause 2 10. The method of claim 1, wherein the step of introducing the Structure III stabilizer into the C4-C7 isomonoolefin derived elastomer is carried out at about 75 ppm to about 150 ppm of Structure III stabilizer relative to the amount of C4-C7 isomonoolefin derived elastomer and Structure III stabilizer. Clause 3 3. The method of claim 1 or 2, wherein the step of introducing the Structure III stabilizer to the C4-C7 isomonoolefin derived elastomer is carried out in the line that transfers the C4-C7 isomonoolefin derived elastomer to the second reactor. Clause 4 4. The method of any one of clauses 1-3, wherein the step of introducing the Structure III stabilizer to the C4-C7 isomonoolefin-derived elastomer is carried out in a second reactor.

[0052] Clause 5 5. The method of any one of clauses 1 to 4, wherein the step of introducing a halogenating agent to the C4-C7 isomonoolefin-derived elastomer is carried out in a second reactor. Clause 6 6. The method of any one of clauses 1 to 5, wherein the step of introducing a halogenating agent to the C4-C7 isomonoolefin-derived elastomer further comprises the step of introducing an emulsion comprising an oxidizing agent, water, a solvent, and a surfactant to the C4-C7 isomonoolefin-derived elastomer and the halogenating agent. Clause 7 7. The method of any one of clauses 1 to 6, wherein the halogenating agent is Br2. Article 8 8. The method of any one of clauses 1-7, wherein the Structure III stabilizer is selected from the group consisting of nitroxyl ethers, nitroxyl radicals, phenols, phosphites, and combinations thereof. Article 9 Halobutyl elastomer about 0.7 mol % to about 0.9 mol % of Structure II units; and Approximately 0.03 mol% to approximately 0.15 mol% of structural III units 9. The method according to any one of clauses 1 to 8, comprising:

[0053] Article 10 Halobutyl elastomer about 0.6 mol % to about 0.9 mol % of Structure II units; and Approximately 0.05 mol% to approximately 0.1 mol% of structural III units 10. The method according to any one of clauses 1 to 9, comprising: Article 11 11. The method of any one of clauses 1-10, further comprising providing the effluent of the second reactor to a first neutralization unit, and providing a neutralizing agent and water to the first neutralization unit. Article 12 12. The method of any one of clauses 1-11, further comprising providing the effluent of the first neutralization unit to a second neutralization unit; and providing a salt of stearic acid to the second neutralization unit. Article 13 13. The method of any one of clauses 1-12, further comprising providing the effluent of the second neutralization unit to a flash drum, and introducing calcium stearate and steam into the flash drum. Article 14 14. The method of any one of clauses 1-13, further comprising providing the flash drum effluent to a stripper vessel and introducing steam into the stripper vessel.

[0054] Article 15 15. The method of any one of clauses 1-14, further comprising spraying water into the vapor space of each of the flash drum and the stripper vessel. Article 16 16. The method of any one of clauses 1 to 15, wherein the step of introducing a halogenating agent to the C4-C7 isomonoolefin-derived elastomer is carried out at a temperature of about 40°C to about 60°C. Article 17 17. The method of any one of clauses 1-16, further comprising operating the flash drum at a pressure of about 140 kPaa to about 190 kPaa and a liquid temperature of about 105°C to about 120°C. Article 18 18. The method of any one of clauses 1-17, further comprising operating the stripper vessel at a pressure of from about 90 kPaa to about 120 kPaa and a liquid temperature of from about 90°C to about 110°C. Article 19 19. The method of any one of clauses 1 to 18, wherein the C4-C7 isomonoolefin is isobutylene.

[0055] Article 20 20. The method of any one of clauses 1 to 19, wherein at least one comonomer is isoprene. Article 21 introducing a Structure III stabilizer into the C4-C7 isomonoolefin-derived elastomer is carried out in the line that transfers the C4-C7 isomonoolefin-derived elastomer to the second reactor; Halobutyl elastomer about 0.7 mol % to about 0.9 mol % of Structure II units; and Approximately 0.03 mol% to approximately 0.15 mol% of structural III units 21. The method of any one of clauses 1 to 20, comprising:

[0056] Article 22 22. The method of any one of clauses 1-21, wherein the step of introducing the Structure III stabilizer to the C4-C7 isomonoolefin derived elastomer is carried out at about 75 ppm to about 150 ppm of Structure III stabilizer relative to the amount of C4-C7 isomonoolefin derived elastomer and Structure III stabilizer. Article 23 Halobutyl elastomer about 0.6 mol % to about 0.9 mol % of Structure II units; and Approximately 0.05 mol% to approximately 0.1 mol% of structural III units 23. The method of any one of clauses 1 to 22, comprising: Article 24 24. The method of any one of clauses 1-23, wherein the halobutyl elastomer has a Structure III stabilizer content of about 15 ppm or less, such as about 10 ppm or less, such as about 7 ppm or less. [Example]

[0057] The BHT injection point into the cement line is upstream of the halogenation reactor, just prior to the halogenation reactor. This allows for the injection of a small amount of BHT to maintain background levels above (below maximum specification). The injection has a control valve, which, when tested, can be controlled at the desired flow rate to maintain a stable, low level of BHT and promote the formation of Structure 2 of bromobutyl rubber. This maintains a uniform structure during the production of Irganox-grade rubber, thus maintaining desirable finished rubber properties. As used herein, "Irganox-grade rubber" refers to a grade of rubber in which Irganox is the primary antioxidant. It has been discovered that the disclosed process can provide pharmaceutical-grade operations with fewer off-grades and a more uniform product. Pharmaceutical-grade polymers are typically completed following extensive cleaning of the finished building and are produced within two weeks of cleaning. Irganox grades were studied and Structure 3 in the finished rubber was plotted against BHT using a laboratory test method.

[0058] The first step was to test the control of BHT at normal grade, understanding and verifying the response of the control valve, and verifying the required flow rate of BHT, then backing it up with testing once BHT was injected based on the mass balance of the next Irganox run. This process control with a laboratory feedback loop should allow for the production of more stable Irganox grade rubber, potentially with a longer pharmaceutical grade run, since the halobutyl rubber that is formed is not hindered by the formation of Structure 3. The amount of BHT added after the control valve was measured on the finished rubber using gas chromatography, and Structure 3 was measured using Fourier transform infrared spectroscopy (FTIR).

[0059] To calculate the amount of BHT in the rubber, a known amount of butyl rubber sample was dissolved in hexane. Once completely dissolved, acetone was added to precipitate the polymer, which was stirred until a clear solution was obtained. The solution was then filtered and loaded into a GC (gas chromatography) vial. A GC method was developed using an Agilent 9000GC with split injection and a repeatable temperature gradient. The GC sample was then detected with an FID detector. The peak area was compared to a known amount of BHT previously injected using the same conditions. The GC conditions were as follows: - Entrance (split / splitless) Carrier gas: Hydrogen Make-up gas: Nitrogen Makeup flow: 25ml / min ·Temperature: 300℃ Injection size: 2 μl (use a 5 μl syringe) Injection mode: Split - Furnace Program: ·Initial temperature: 120℃ Speed ​​(gradient 1): 30°C / min Time 1:1 minute ·Final temperature: 220℃ Total runtime: 5 minutes - Column Program ·Constant flow rate: 15ml / min Pressure: 14.43 psi - Detector temperature: 300℃ - The column is a 30m x 0.32mm i.d. x 1µm DB-FFAP capillary column. Table 1 shows the results of ppm BHT from rubber and the corresponding content of Structure 3, plotted in FIG.

[0060] [Table 1-1] [Table 1-2]

[0061] A second test was conducted with the control valve open while measuring grade and subsequent BHT and Structure 3. The result was a more controlled increase in Structure 3 formation, resulting in a stable Structure 3 at a lower limit than without BHT addition. The reduction in Structure 3 increases the validity of the functional bromine model. Typically, before adding BHT to the bromination reactor, high Structure 3 formation could reduce the accuracy of functional bromine predictions (based on the macrodevelopment described below). This test was completed using manufacturing specifications and applied safety factors, which resulted in a throttled FCV566. However, there were still promising results, including improved rubber finishability toward the end of the run, which would otherwise typically be unsatisfactory. Background BHT in the hexane system has a cumulative effect over time and may itself have a secondary effect on Structure 3, but this must be carefully balanced with the flow from FCV566.

[0062] Functional bromine models are generated using FTIR and NMR data, which are the rubber specifications. Macros are developed by PerkinElmer's Technology Department using software and sent to the relevant plants to test samples. This software is used to determine the mol% of each property.

[0063] [Table 2]

[0064] It has been discovered that bromination carried out in the presence of an antioxidant can reduce the amount of structure 3 formed, which is detrimental to the reactivity and marching Mooney properties of halobutyl rubber. It has been observed that injection of a certain amount of BHT (approximately 80-100 ppm) upstream of bromination, upstream of 35% peroxide injection, and upstream of caustic addition for neutralization results in less Structure III (see Table 3). The presence of high Structure III in bromobutyl products can be undesirable, resulting in high marching Mooney (Mooney change) upon storage, poor shelf stability, scorch behavior (see Table 4), and increased cure rate within the compound (see Table 5) due to its high reactivity.

[0065] Adding BHT prior to bromination reduces the free radical bromination that leads to the formation of Structure III. Reducing the level of Structure III, and adding additional amounts of BHT to the neutralized cement after bromination but before the thermal history associated with the finishing step, inhibits the polymer network that forms from thermo-oxidative crosslinking, resulting in reduced Warehouse Mooney growth and reduced scorch and hardening rate of the compound.

[0066] [Table 3]

[0067] [Table 4]

[0068] [Table 5]

[0069] [Table 6-1] [Table 6-2]

[0070] [Table 7]

[0071] [Table 8]

[0072] Overall, the present disclosure provides a method for forming halobutyl rubber using a Structure III stabilizer (such as butylated hydroxytoluene) that can be introduced into the halogenation process upstream of (or within) the halogenation reactor, which has been discovered to provide halobutyl rubber with a high Structure 2 content in higher yields than conventional processes and to provide the option of performing bromine regeneration without marching Mooneys. Such Structure III stabilizer can be provided upstream of (or within) the halogenation reactor in amounts lower than conventional BHT use in halobutyl processes. Unless otherwise specified, the terms "consists essentially of" and "consisting essentially of" do not exclude the presence of other steps, elements, or materials, whether specifically mentioned herein or not, so long as those steps, elements, or materials do not affect the basic and novel characteristics of the disclosure and further, so long as they do not exclude impurities and variations normally associated with the elements and materials used.

[0073] For brevity, only certain ranges are explicitly disclosed herein. However, a range from any lower limit may be combined with any upper limit to describe a range not expressly stated, and similarly, a range from any lower limit may be combined with any other lower limit to describe a range not expressly stated, and similarly, a range from any upper limit may be combined with any other upper limit to describe a range not expressly stated. Furthermore, even if not expressly stated, a range includes every point or individual value between its endpoints. Thus, every point or individual value may be combined with any other point or individual value, or any other lower or upper limit, to serve as its own lower or upper limit and describe a range not expressly stated.

[0074] All numerical values ​​within the detailed description herein are modified by "about" the stated value to account for experimental error and variations that would be expected by one of ordinary skill in the art. All documents described herein, including any priority documents and / or testing procedures, are incorporated herein by reference, unless inconsistent herewith. While aspects of the present disclosure have been illustrated and described, as is apparent from the foregoing general description and specific embodiments, various modifications can be made without departing from the spirit and scope of the present disclosure. Accordingly, the present disclosure is not intended to be limited thereby. Similarly, under U.S. law, the term "comprising" is considered synonymous with the term "including." Similarly, when a composition, element, or group of elements is preceded by the transitional phrase "comprising," it is understood that the composition, element, or description of elements is considered to be the same composition or group of elements as if the transitional phrase "consisting essentially of," "consisting of," "selected from the group of consisting of," or "is" preceded the composition, element, or description of elements, and vice versa.

[0075] While this disclosure has been described in terms of multiple embodiments and examples, those skilled in the art, having the benefit of this disclosure, will recognize that other embodiments may be devised that do not depart from the scope and spirit of the present disclosure.

Claims

1. 1. A method of forming a halobutyl elastomer, comprising: C 4 -C 7 An isomonoolefin and at least one comonomer are polymerized in a first reactor to produce C 4 -C 7 obtaining an isomonoolefin-derived elastomer; C 4 -C 7 transferring the isomonoolefin-derived elastomer via a line to a second reactor; C 4 -C 7 The isomonoolefin-derived elastomer includes C 4 -C 7 introducing about 20 ppm to about 400 ppm of a Structure III stabilizer relative to the amount of isomonoolefin-derived elastomer and Structure III stabilizer; C 4 -C 7 introducing a halogenating agent to the isomonoolefin-derived elastomer to form a halobutyl elastomer; A method comprising:

2. C 4 -C 7 The step of incorporating a Structure III stabilizer into the isomonoolefin-derived elastomer comprises: 4 -C 7 10. The method of claim 1 carried out at about 75 ppm to about 150 ppm of Structure III stabilizer, based on the amount of isomonoolefin-derived elastomer and Structure III stabilizer.

3. C 4 -C 7 The step of incorporating a Structure III stabilizer into the isomonoolefin-derived elastomer comprises: 4 -C 7 3. The process of claim 2 carried out in a line that transfers the isomonoolefin-derived elastomer to a second reactor.

4. C 4 -C 7 3. The method of claim 2, wherein the step of introducing the Structure III stabilizer into the isomonoolefin-derived elastomer is carried out in a second reactor.

5. C 4 -C 7 3. The method of claim 2, wherein the step of introducing the halogenating agent to the isomonoolefin-derived elastomer is carried out in a second reactor.

6. C 4 -C 7 The step of introducing a halogenating agent into the isomonoolefin-derived elastomer comprises: 4 -C 7 10. The method of claim 1, further comprising the step of introducing an emulsion comprising an oxidizing agent, water, a solvent, and a surfactant to the isomonoolefin-derived elastomer and the halogenated agent.

7. The halogenating agent is Br 2 The method of claim 1, wherein

8. 10. The method of claim 1, wherein the Structure III stabilizer is selected from the group consisting of nitroxyl ethers, nitroxyl radicals, phenols, phosphites, and combinations thereof.

9. Halobutyl elastomer about 0.7 mol % to about 0.9 mol % of Structure II units; and about 0.03 mol % to about 0.15 mol % of Structure III units 2. The method of claim 1, comprising:

10. Halobutyl elastomer about 0.6 mol % to about 0.9 mol % of Structure II units; and about 0.05 mol % to about 0.1 mol % of Structure III units 2. The method of claim 1, comprising:

11. 10. The method of claim 1, further comprising providing the effluent of the second reactor to a first neutralization unit, and providing a neutralizing agent and water to the first neutralization unit.

12. 12. The method of claim 11, further comprising providing the effluent of the first neutralization unit to a second neutralization unit, and providing the salt of stearic acid to the second neutralization unit.

13. 13. The method of claim 12, further comprising providing the effluent of the second neutralization unit to a flash drum, and introducing calcium stearate and steam into the flash drum.

14. 14. The method of claim 13, further comprising the steps of providing the flash drum effluent to a stripper vessel and introducing steam into the stripper vessel.

15. 15. The method of claim 14, further comprising spraying water into the vapor space of each of the flash drum and the stripper vessel.

16. C 4 -C 7 10. The method of claim 1, wherein the step of introducing the halogenating agent to the isomonoolefin-derived elastomer is carried out at a temperature of from about 40°C to about 60°C.

17. 16. The method of claim 15, further comprising operating the flash drum at a pressure of from about 140 kPaa to about 190 kPaa and a liquid temperature of from about 105°C to about 120°C.

18. 18. The method of claim 17, further comprising operating the stripper vessel at a pressure of from about 90 kPaa to about 120 kPaa and a liquid temperature of from about 90°C to about 110°C.

19. C 4 -C 7 2. The process of claim 1, wherein the isomonoolefin is isobutylene.

20. 20. The method of claim 19, wherein at least one comonomer is isoprene.

21. C 4 -C 7 The step of incorporating a Structure III stabilizer into the isomonoolefin-derived elastomer comprises: 4 -C 7 conducted in a line transferring the isomonoolefin-derived elastomer to a second reactor; Halobutyl elastomer about 0.7 mol % to about 0.9 mol % of Structure II units; and about 0.03 mol % to about 0.15 mol % of Structure III units 2. The method of claim 1, comprising:

22. C 4 -C 7 The step of incorporating a Structure III stabilizer into the isomonoolefin-derived elastomer comprises: 4 -C 7 22. The method of claim 21 practiced at about 75 ppm to about 150 ppm of Structure III stabilizer, based on the amount of isomonoolefin-derived elastomer and Structure III stabilizer.

23. Halobutyl elastomer about 0.6 mol % to about 0.9 mol % of Structure II units; and about 0.05 mol % to about 0.1 mol % of Structure III units 23. The method of claim 22, comprising:

24. 24. The method of claim 23, wherein the halobutyl elastomer has a Structure III stabilizer content of about 15 ppm or less.

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