WO2019133324A1

WO2019133324A1 - Temperature control for a polymerization vessel

Info

Publication number: WO2019133324A1
Application number: PCT/US2018/065983
Authority: WO
Inventors: Timothy L. Tartamella; Joseph P. Padolewski
Original assignee: Bridgestone Corporation
Priority date: 2017-12-26
Filing date: 2018-12-17
Publication date: 2019-07-04

Abstract

Processes for controlling temperature in polymerization reactions are described as including a monomer recovery system. Monomer vapor is removed from pressurized head space of a horizontally disposed reaction vessel, condensed to a liquid and recycled back to the polymerization reaction in multiple streams that are fed to the reactor at multiple introduction points. The introduction feed points of recycle monomer can be spaced along the horizontal reactor to inject cool liquid monomer to allow for control of the temperature, pressure and viscosity of the mixture in the reaction chamber of the reactor.

Description

Temperature Control for a Polymerization Vessel

TECHNICAL FIELD

[001] The present disclosure relates to a method for the bulk polymerization of conjugated diene monomer, and more particularly, to selective monomer recycle in a horizontal, high-solids polymerization vessel.

BACKGROUND

[002] Polymerization of monomers can be produced by bulk or mass polymerization. Bulk polymerization is often carried out in the absence or substantial absence of any solvent, which has an effect of the monomer itself acting as a diluent and heat sink for the reaction. The lack of solvent results in the bulk polymerization involving primarily monomer and catalyst, which provides the benefit of less contaminants and reactants to remove and separate from the polymerization product downstream in the process. This benefit saves both production time and costs, and potentially a reduction in emissions from lower solvent usage.

[003] Bulk polymerization processes require careful temperature control and effective mixing since the polymerization mixture becomes very viscous. The thick mixture and cement, and lack of solvent, make temperature control difficult. As a result, a polymerization reaction can have hot spots that promote degradation, gelation or discoloration of a polymer product. Further, lack of adequate temperature control can result in run-away reactions which can be dangerous and cost prohibitive.

[004] The many advantages provided by bulk polymerization systems make them a continued source for improvements. There is a need to enhance the temperature control of bulk polymerization reactions to improve yield, quality of product and to prevent run-away reactions. The various configurations of polymerization vessels, for example, horizontal reactors, make arriving at a solution for temperature control not trivial. SUMMARY

[005] In a first aspect, there is a method for controlling temperature of a bulk

polymerization process. The process includes feeding fresh monomer and catalyst to an agitated reaction chamber of a horizontally disposed polymerization reactor, the polymerization reactor having a central pressurized vapor head space and the reaction chamber containing a reacted polymer mixture having an average increased viscosity along the horizontal length of the reaction chamber from the inlet of the reaction chamber to the outlet of the reaction chamber; removing a portion of monomer vapor produced from a polymerization reaction in the reaction chamber from the central pressurized head space of the horizontally disposed polymerization reactor; condensing the removed monomer vapor to form a recycle monomer; pumping the recycle monomer back into the reaction chamber of the horizontally disposed polymerization reactor, portions of the recycle monomer are introduced into the reaction chamber in at least two separate introduction points; and collecting a reacted polymer cement from the horizontally disposed polymerization reactor.

[006] In an example of aspect 1, the fresh monomer and catalyst are fed to the horizontally disposed polymerization reactor and the reacted polymer cement is collected from the horizontally disposed polymerization reactor in a continuous mode.

[007] In another example of aspect 1, the fresh monomer is a conjugated diene monomer.

[008] In another example of aspect 1, the portions of the recycle monomer are fed into the reacted polymer mixture along the bottom half of the horizontally disposed polymerization reactor.

[009] In another example of aspect 1 , the process further includes controlling the temperature of the reacted polymer mixture to a range of 50 to 150 degrees Celsius in in the reaction chamber by introducing the portions of the recycle monomer to the reaction chamber.

[0010] In another example of aspect 1 , the recycle monomer is continuously introduced into the at least two introduction points.

[0011] In another example of aspect 1, the recycle monomer being substantially free of solvent.

[0012] In another example of aspect 1, the monomer vapor removed from the central pressurized head space can further be substantially free of solvent. [0013] In another example of aspect 1, the recycle monomer is continuously fed into the central pressurized vapor head space to control the temperature of the reacted polymer mixture in the reaction chamber.

[0014] In another example of aspect 1 , the reaction chamber includes at least three introduction points, each of the three introduction points having a recycle monomer feed that introduces condensed monomer.

[0015] In another example of aspect 1, the two or more introduction points are spaced equally from one another along the axial length of the reaction chamber, for example, along the outer perimeter of the reactor or reaction chamber.

[0016] In another example of aspect 1, the recycle monomer is fed into the two or more equally spaced introduction points at the same flow rate.

[0017] In another example of aspect 1, the recycle monomer is fed into the reaction chamber of the horizontally disposed polymerization reactor at a temperature in the range of 20 to 50 degrees Celsius.

[0018] In another example of aspect 1 , the introduction point of each portion of the recycle monomer feed is not more than 50 percent of the axial length of the horizontally disposed polymerization reactor apart. In other words, the spacing between the introduction points is at least 50 percent of the axial length of the reaction chamber.

[0019] In another example of aspect 1, the introduction point of each portion of the recycle monomer feed is not more than 30 percent of the axial length of the horizontally disposed polymerization reactor apart.

[0020] In another example of aspect 1, the residence time of the fresh monomer in the reaction chamber is in the range of 30 to 90 minutes.

[0021] In another example of aspect 1, the flow rate of the monomer vapor removed from the reaction chamber is controlled by a pressure control valve that maintains a constant pressure range in the central pressurized head space of the horizontally disposed polymerization reactor.

[0022] The first aspect may be provided alone or in combination with any one or more of the examples of the first aspect discussed above.

[0023] In a second aspect, there is a method for regulating the average reaction temperature in a continuous bulk polymerization process. The method includes continuously feeding a conjugated diene monomer and catalyst to an agitated cylindrical reaction chamber of a horizontal polymerization reactor, the reaction chamber is substantially free of a solvent;

removing monomer vapor from a gas collection area connected to the reaction chamber and condensing the removed monomer vapor to form a recycle monomer; feeding the recycle monomer into the reaction chamber through two or more introduction points along the axially length of the horizontal polymerization reactor, at least one introduction point is positioned in the first half of the axial length of the horizontal polymerization reactor and at least one introduction point is positioned in the second half of the axial length of the horizontal polymerization reactor; and extracting a reacted polymer cement from the horizontal polymerization reactor in a continuous mode.

[0024] In an example of aspect 2, the recycle monomer includes a mixture of two or more monomers.

[0025] In another example of aspect 2, the recycle monomer is fed at the same flow rate to each of the two or more introduction points.

[0026] In another example of aspect 2, the two or more introduction points are equally spaced along the length of the horizontal polymerization reactor.

[0027] The second aspect may be provided alone or in combination with any one or more of the examples of the second aspect discussed above, or in the first aspect.

[0028] The accompanying drawings are included to provide a further understanding of principles of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain, by way of example, principles and operation of the invention. It is to be understood that various features disclosed in this specification and in the drawings can be used in any and all combinations. By way of non-limiting example the various features may be combined with one another as set forth in the specification as aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above description and other features, aspects and advantages are better understood when the following detailed description is read with reference to the accompanying drawings, in which: [0030] FIG. 1 shows a process flow diagram of a continuous bulk polymerization system using a monomer recovery and recycle set up for controlling temperature in ta horizontal, high- solids polymerization vessel as described herein.

DETAILED DESCRIPTION

[0031] The terminology as set forth herein is for description of the embodiments only and should not be construed as limiting the invention as a whole.

[0032] Herein, when a range such as 5-25 (or 5 to 25) is given, this means preferably at least or more than 5 and, separately and independently, preferably not more than or less than 25. In an example, such a range defines independently at least 5, and separately and independently, not more than 25.

[0033] The present disclosure relates to methods for controlling the temperature of a reaction mixture in an agitated horizontal, high-solids polymerization vessel of a bulk polymerization process. Monomer vapor generated in the polymerization vessel during a polymerization reaction is removed and condensed to form a recycle monomer stream. The recycle monomer stream, or one or more portions thereof, can be fed back into the horizontal polymerization vessel at multiple introduction points to selectively control the temperature of the reaction mixture. The recycle monomer fed into the horizontal polymerization vessel, as well as the operation of the vessel and reaction therein, can be in continuous mode.

[0034] Polymerization as described herein is conducted within a bulk system where monomer acts as a solvent, and which generally refers to the fact that the system includes, for example, less than 50%, in other examples less than 20%, 10%, 5%, or 2% by weight organic solvent based on the total weight of the monomer, polymer, and solvent within the bulk system. In one embodiment, the bulk polymerization is carried out in the substantial absence of an organic solvent or diluent. That is, in the absence of an amount of solvent that would otherwise ’ have an impact on the bulk polymerization conditions. In another embodiment, the bulk polymerization may be carried out in the absence of an organic solvent or diluent other than those organic solvents or diluents that are inherent to the raw materials employed. To the extent solvent is not present in any materials charged to the polymerization vessel, the polymerization system can be entirely devoid of organic solvent. In such a case, it is preferred that all recovered monomer vapor that is fed back into the reactor as recycle monomer be free of or substantially free of solvent.

[0035] The term organic solvent or diluent is used herein conventionally, for instance, to refer to organic compounds that do not polymerize or become introduced into the produced polymer product or cement. The organic solvents are generally non-reactive or inert to the catalyst composition employed in the bulk polymerization reaction. Example organic solvents can include aromatic hydrocarbons, aliphatic hydrocarbons, and cycloaliphatic hydrocarbons. Some examples of aromatic hydrocarbons include benzene, toluene, xylenes, ethylbenzene, diethylbenzene, and mesitylene; examples of aliphatic hydrocarbons include n-pentane, n- hexane, n-heptane, n-octane, n-nonane, n-decane, isopentane, isohexanes, isopentanes, isooctanes, 2,2-dimethylbutane, petroleum ether, kerosene, and petroleum spirits; and examples of cycloaliphatic hydrocarbons include cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane. Any combination or mixtures of these organic solvents is also considered.

[0036] To begin the polymerization process, monomer and catalyst, or a catalyst system, are charged to the agitated, horizontal polymerization vessel. The bulk polymerization is preferably a continuous process or semi-continuous process such that the monomer and catalyst are continually fed to the vessel. However, the manner in which the monomer and catalyst system are charged may vary based upon the catalyst system employed.

[0037] In one or more embodiments, the bulk polymerization process includes a continuous polymerization process whereby catalyst and monomer are continuously fed to the horizontal polymerization vessel or reactor and a portion of the polymerization medium or reacted polymer mixture is continuously removed from the vessel. The reacted polymer mixture removed from the horizontal vessel can include unreacted monomer, polymer, and residual catalyst.

[0038] The monomers that can be polymerized according to the bulk process of this disclosure can vary, for example, they can be volatile monomers and optionally non-volatile monomers. Volatile monomers can include those that are sufficiently volatile to allow heat removal by vaporization of unreacted monomer at a rate equal to the rate at which heat is generated by the polymerization reaction and at a temperature that will allow the formation of the desired polymer product. In one example, the monomers can include those that have a boiling point of at least 10 C, at least 20 C, or at least 30 C lower than the set polymerization temperature or temperature range. In one embodiment, the monomers can devoid of halogens, e.g., vinyl chloride monomers can be excluded.

[0039] Examples of monomers included in the present disclosure include conjugated diene monomers such as 1,3 -butadiene, isoprene, l,3-pentadiene, l,3-hexadiene, 2, 3 -dimethyl- 1,3- butadiene, 2-ethyl- 1,3 -butadiene, 2-methyl- 1, 3 -penta-diene, 3-methyl-l,3-pentadiene, 4-methyl- l,3-pentadiene, 2,4-hexadiene and combinations thereof. In another example, useful olefins include ethylene, propylene, 1 -butene, and l-pentene.

[0040] The catalyst employed in practicing the process of this disclosure preferably includes a coordination catalyst system. One type of coordination catalyst system includes lanthanide- based systems and another type includes cobalt-based systems as known in the art. For example, lanthanide catalyst systems are well known in the art as described in U.S. Pat. Nos. 3,297,667, 3,541,063, 3,794,604, 4,461,883, 4,444,903, 4,525,594, 4,699,960, 5,017,539, 5,428,119, 5,064,910, and 5,844,050, which are incorporated herein by reference.

[0041] The bulk production of polymer by using catalyst systems generally employs a catalytically effective amount of a catalyst composition, for example, as mentioned above. The total catalyst concentration included in the polymerization mass depends on the interaction of variables such as material purity, polymerization temperature, polymerization rate or set conversion, desired molecular weight, etc. A specific total catalyst concentration is not disclosed but may be adjusted as known in the art, for example, the catalytically effective amounts of catalyst ingredients should be used. In one example, the amount of the catalyst used can be varied from 0.01 to 2 mmol, 0.02 to 1 mmol, or 0.05 to 0.5 mmol per 100 g of monomer, e.g., conjugated diene monomer.

[0042] Catalyst ingredients, for example those of a lanthanide system, can be charged to the horizontal polymerization vessel in a variety of techniques and order of addition. For instance, a small quantity of an organic solvent may be employed as a carrier to either dissolve or suspend the catalyst ingredients to promote catalyst delivery. In another example, monomer, such as conjugated diene monomer, can be used as a catalyst carrier.

[0043] The polymerization reaction within the reaction chamber of the horizontal polymerization vessel can be carried out under anaerobic conditions at low temperatures and at or below the vapor pressure of the monomer at the polymerization temperature. In the presence of an organic solvent, the solvent can impact the vapor pressure at which the process is conducted. Irrespective of the bulk polymerization or copolymerization process carried out, polymerization or copolymerization should be carried out at temperatures sufficiently high to ensure reasonable polymerization or copolymerization rates and avoid unduly long reactor residence times, but not so high as to result in the production of unreasonably high levels of strings and lumps due to excessively rapid polymerization or copolymerization rates. Generally, polymerization temperatures range from 0 to 120° C, 20° C to 95° C being more preferred from the standpoint of attaining good catalyst performance and high production rates. More preferably, polymerization in the reaction chamber can be carried out at temperatures ranging from 50° C to 80° C.

[0044] The polymerization or copolymerization time will generally range from about 30 minutes to 60 minutes to several hours. Thus, the fresh monomer being fed to the horizontal polymerization vessel can have an average residence time in the range of 30 minutes to 2 hours, and more preferably 30 minutes to 90 minutes before being reacted and/or exiting the vessel in a reacted polymer product.

[0045] The polymerization temperature can be controlled by externally cooling the horizontal vessel and thereby the reaction chamber contained within the vessel, internally cooling the polymerization reaction by removal of monomer vapor, optionally recycling the monomer vapor in a condensed form at selective introduction points, or by using a combination of the three methods. In one embodiment, monomer vapor can be removed from the reaction chamber and condensed for future polymerization within the process or direct feed back into reaction chamber. For example, an auto-refrigeration loop can be employed whereby monomer vapor can be removed from the vessel, condensed, and re-circulated back into the vessel. In other embodiments, the vessel can be equipped with an evaporation column that can be controlled by water flow and/or water temperature. Alternatively, the vapor can be removed, condensed, and the monomer condensate can be fed to a recovery tank and selectively fed back to the vessel in a recycle distribution having one to ten introduction points along the axially length of the vessel.

[0046] The liquid polymerization or reaction mixture may contain unreacted monomer, reacted polymer, catalyst or a mixture of catalysts, residual solvent, and residual contaminates or impurities. The reaction chamber of the vessel contains an appropriate head space that is maintained within the vessel to achieve a desired cooling effect from the vaporization of monomer and removal thereof. This head space can be a centralized head space that collects vapor from the entire reaction chamber and during operation the head space is considered pressurized. The degree of pressurization can be controlled by selective removal of monomer vapor from the head space. The head space includes the volume of the vessel that is not filled with the liquid polymerization medium and can contain monomer vapor. In an example, the centralized head space of the horizontal polymerization reactor can be 20 to 60, 30 to 50, or 35, 40 or 45 percent by volume of the total volume of the polymerization vessel during operation.

An advantage of using the head space is to remove monomer vapor and heat from the reaction chamber to control pressure and temperature within the reactor. In vertical reactors, for example a continuous stirred tank reactor, head space is generally advantageous to collapse foam, which minimizes fouling. Horizontal reactors of the present disclosure typically do not require precise foam control and thus the volume fraction dedicated to reactor head space can optionally be reduced as compared to vertical vessels.

[0047] The polymerization reaction mixture, preferably in the liquid phase, can be mixed by employing mixing techniques that are known in the art for horizontally disposed reactors. The mixing technique and equipment used to carry out mixing preferably is designed to handle high viscosities. In one embodiment, the horizontally disposed polymerization reactor or vessel can include a screw apparatus, such as a twin screw extruder, for agitating and mixing the reaction mixture in the reaction chamber.

[0048] An extruder-like reactor or mixing means can include a shaft having paddles attached thereto, for example, a single shaft or multiple shafts. The shaft can be axial to the length of the reactor and the flow of polymer or polymerization reaction mixture. In a twin-screw set up, the paddles on each shaft may be aligned so as to mesh with one another as they rotate. The rotation of the shafts can occur in the same direction or in opposite directions.

[0049] The polymer or polymerization reaction mixture can be forced through the reactor by using a pump, and the mixing system in the reactor can further assist in the polymerization of unreacted monomer present in the reaction chamber. The paddles can be angled so as to promote movement of the polymerization reaction mixture axially through the reactor and at the same time can function to pull and carry or drag the mixture as it increases in viscosity through the reactor to its outlet or discharge section.

[0050] In another embodiment, the horizontally disposed reactor can further include a backmixing agitator. In general, these backmixing vessels can include a single shaft that includes a blade that can be arranged to vigorously mix and masticate the polymerization reaction mixture.

[0051] Horizontal reactors can offer advanced shaft geometry that provides gentle kneading for minimal shear and maximum heat transfer within the polymerization reaction mixture. It also enables operators to process high- viscosity and other hard-to-handle materials like a polymer cement. The results are improved product quality, lower operating cost, increased safety, and more efficient overall processing. Horizontal reactors are suitable for solvent-free living and free-radical polymerization produced in a bulk polymerization process. Horizontal reactor equipment is known in the art and commercially available. For example, horizontal reactor equipment can be obtained from LIST (Switzerland); Coperion Werner & Phleiderer.

[0052] In one or more embodiments, the horizontal reactors having a head space are attached to a monomer recovery system. As monomer is separated from the reacted polymer product through the head space, the monomer can be directed to a cooling or condensing system. The monomer that is recovered from the reactor, for example as a condensed monomer (i.e. liquid monomer), can optionally be returned as a raw material (unreacted recycle monomer) to the reaction chamber for polymerization.

[0053] In an example of the present disclosure, FIG. 1 shows an example of a continuous bulk polymerization system using a monomer recovery and recycle set up for controlling temperature in the horizontal, high-solids bulk polymerization vessel. Monomer and catalyst 1 are fed to the horizontal polymerization reactor 10 through an inlet to the reactor. As shown, monomer and catalyst 1 are fed in combination to the reactor 10 as a single stream. Optionally, monomer and catalyst 1 can be fed to reactor 10 in one or more separate streams that utilize separate reactor inlets, for example, a catalyst system can be fed to reactor 10 through one or more inlets with the monomer being fed alone. Preferably, as noted above, the feed to reactor 10 is substantially free of solvent. Together the inlet feeds to reactor 10 form a polymerization reaction mixture in agitated reaction chamber 3 to produce reacted polymer mixture being polymerized that ultimately exits reactor 10 through one or more outlets, shown as single stream 6. Transfer of the reacted polymer mixture or product from the outlet of reactor 10 may be accomplished by employing a pump. The pump speed can control the discharge rate of the product out of reactor 10. [0054] Within reactor 10, or in a subsequent processing of discharge 6 from reactor 10, the polymerization reaction can be terminated as known in the art. For example, the polymerization reaction can be terminated by adding an appropriate terminating agent to reactor 10 or a discharge feed line or pump between reactor 10 and another vessel, or in the other vessel itself, preferably under agitation conditions. The polymerization reaction can be terminated by using many of the techniques known in the art. For example, useful techniques include the addition of a protonating or quenching agent, the addition of a coupling agent, the addition of a

functionalized terminator, or a combination thereof, which react or interact with living polymer chains and prevent further growth or polymerization. The amount of a terminating agent can be added as conventional in the art.

[0055] In one embodiment, the polymer mixture or product 6 exiting reactor 10 can be further processed, for example, further desolventization or removal of monomer from the polymerization reaction mixture or further polymerization of the mixture itself. Desolventization or removal of unreacted monomer can be achieved by employing a variety of techniques which are known in the art, for instance, by processing the exiting stream 6 through yet another extruder such as a single or twin screw extmder. The polymer product can then be baled, and in certain embodiments diced or pelletized prior to baling.

[0056] Reactor 10 can have any suitable shape and cross section, for example, reactor 10 can have a horizontal cylindrical shape with a circular cross section, and can have a uniform or substantially uniform cross section dimensions or diameter along its axial length, which is in the direction of fluid flow through reactor 10 or in the horizontal direction. As horizontally disposed, reactor 10 has a top half and a bottom half, wherein in the bottom half contains the majority or all of the polymerization reaction mixture.

[0057] Reactor 10 is equipped with a mixing or agitating means 2 such as a kneader or extruder. The mixing means 2 can be a rotating shaft centrally disposed along a portion of the axial length of reaction chamber 3. The rotating shaft can have one or more blades, paddles, anchor hooks or other variations of mixing accessories extending from the rotating shaft for agitating, pulling and generally dispersing the components of the polymerization reaction mixture. For example, the shaft can be equipped with one or more paddles at multiple positions along its length to provide uniform mixing of the polymerization reaction mixture as it travels through length of the reaction chamber to the discharge section. At each position along the shaft, 2, 3 or 4 mixing paddles or the like can be equally spaced around the outer circumference of the shaft and extend outward therefrom towards the walls of reaction chamber 3. These mixing sections can be equally spaced apart from one another along the mixing shaft. The rotating shaft provides gentle mixing of the contents in reaction chamber 3 and promotes shear and heat transfer during the polymerization and in high viscosity mixtures as the polymerization progresses along the length of reaction chamber 3.

[0058] The flow of reagents into reactor 10, polymerization reaction mixture through reactor 10, together with the flow of polymerization product out of reactor 10, can be controlled so as to not completely fill the volume of reactor 10 and thereby create headspace 4, for example a central head space that can be under pressure. During operation and polymerization, reactor 10 will have a pressure above atmospheric conditions and be considered pressurized. The head space 4 can include a portion of reaction chamber 3 (e.g., the non-filled portion or non-liquid portion) and an overhead collection hood or dome that is not in contact with the liquid polymerization reaction mixture. During polymerization, head space 4 can contain unreacted monomer vapor and other materials, for example, organic solvents, volatiles and impurities. For bulk polymerization processes, it is preferable that the head space contain primarily unreacted monomer vapor, for example, head space 4 contains at least 50, 60, 70, 80, 90 or 95 weight percent unreacted monomer vapor or substantially no solvent vapor. Head space 4 contains at least one outlet connected to a monomer vapor recovery system for removing monomer vapor form reaction chamber 3.

[0059] As shown, outlet stream 5 provides a discharge path for monomer vapor to be condensed. Outlet stream 5 can optionally contain control valve 7 that monitors the pressure in reaction chamber 3 and head space 4 and selectively permits monomer vapor and other gas to exit reactor 10 to maintain a set or pre-determined pressure in chamber 3. Outlet stream 5 is fed to a condenser, for example, heat exchanger 8 or a compressor (not shown), to convert the monomer vapor into a condensed liquid monomer stream 12. Condensed monomer can be collected in a storage vessel 14. Storage vessel 14 can be equipped with a cooling jacket or coils to control the temperature of the condensed monomer, for example, the condensed monomer can have a temperature in the range of 10 to 60, 20 to 50, or 30 or 40° C. Condensed, recycle monomer 16 exiting vessel 14 can be fed to reactor 10 by pump 18. Alternatively, condensed recycle monomer can be directly fed to reaction chamber 3 without storage or further processing of the monomer.

[0060] Recycle monomer 20 is pumped back into reaction chamber 3 of horizontal reactor 10 at one or more introduction points, for example, 22, 24, 26 as shown. Introduction points can be inlets, for example, an injection port, that is open to the reaction area of reaction chamber 3. Recycle monomer 20 can be split into one or more streams (e.g., 2, 3, 4, 5, 6 or more) for selectively feeding recycle monomer to the reacted polymer mixture in reaction chamber 3. For example, recycle monomer recycle monomer 20 is split into three streams, 20a, 20b, 20c and fed into reaction chamber 3 at three separate introduction points, 22, 24, 26, respectively.

[0061] Reactor 10 can have two or more introduction points, for instance, in the form of an inlet port in fluid connection with reaction chamber 3. The introduction points can be spaced along the axial length of reactor 10 at any suitable distance from one another or be equally spaced from one another. In one embodiment, there is at least one introduction point along the first half of reactor 10 (i.e. on the inlet side) and at least one introduction point along the second half of the reactor 10 (i.e. on the outlet side).

[0062] Spacing multiple introduction points along the axial length of reactor 10 allows an operator to control the temperature of the polymerization reaction. As the polymerization reaction mixture or reacted polymer mixture travels through reaction chamber 3 of horizontal reactor 10, the viscosity increases as higher conversion rates are achieved such that on average the reacted polymer mixture has an average increase in viscosity along the axial length of reactor 10. Selective introduction of recycle monomer along the length of reactor 10 can address hot spots, viscosity rises or peaks, and pressure in reaction chamber 3, which can lead to better mixing and prevent exposure of the reacted polymer mixture to high temperatures than can negatively affect polymer product properties. Multi-point recycle monomer feeds provides additional temperature control ability separate from using head space 4 to remove hot monomer vapor from reaction chamber 3 through a vapor recovery system.

[0063] The position of the introduction points (e.g., 22, 24, 26) can be at any suitable location. Preferably, the introduction points are located along the bottom half of reaction chamber 3 of reactor 10. Positioned along the bottom half of reactor 10 allows the recycle monomer 20 to be introduced directly into the liquid reacted polymer mixture of reaction chamber 3 rather than in head space 4 or above the liquid level in reaction chamber 3. The introduction points can equally spaces apart from one another and the reaction chamber 3 can be exposed to recycle monomer feeds in select areas. For example, traveling from the inlet area to the outlet area of reactor 10 along its axial length, recycle monomer can be fed to reaction chamber 3 through an induction point in the first 10, 20, 30, 40, 50, 60, 70, 80 or 90 percent of the axial length, along with any combination of those axial positions or all of the positions. In one embodiment, reactor 10 can be equipped with introduction points at 10% intervals of its axial length and recycle monomer feed can be introduced to reaction chamber 3 through any combination of introduction points at a particular time depending on the desirability to control the temperature of the reacted polymer mixture in each axial length interval.

[0064] Each introduction point to reaction chamber 3 preferably feeds recycle monomer into the polymerization mixture. The flow rate of recycle monomer in each introduction stream can vary depending on temperature control desired in a particular zone of reaction chamber 3, e.g., upstream sections versus downstream sections. The flow rates of the recycle monomer streams can be the same to equally introduce recycle monomer to reaction chamber 3 at each introduction point.

[0065] Spacing distance between introduction points can depend on the number of introduction points used to charge recycle monomer. For example, two introduction points can be spaced apart at a distance at least 20, 30, 40 or 50 percent of the axial length of reactor 10. In another example, three introduction points can each be spaced apart at a distance at least 10, 20, of 30 percent of the axial length of reactor 10. In yet another example, four introduction points can each be spaced apart at a distance at least 5, 10, 15 or 20 percent of the axial length of reactor 10.

[0066] The introduction points can be equipped with a valve, for example, a flow control valve as shown, upstream of the entry point into reaction chamber 3. In the case a select recycle monomer stream being fed to a specific introduction point comes from a branch flow or pipe from a main recycle monomer stream, the flow control valve is positioned in the branch flow portion or pipe feeding the individual introduction point. The flow control valve can regulate and monitor the flow rate of the recycle monomer to reaction chamber 3, for example, in response to reaction conditions in reaction chamber 3. Reaction conditions can include temperature, pressure, and viscosity. In one example, the flow control valve can increase or decrease the flow rate of recycle monomer to reaction chamber 3 to adjust the local or bulk temperature of the reacted polymer mixture being agitated in reactor 10.

[0067] In one or more embodiments, the process of this disclosure may allow for the production of polymers having targeted properties that are affected by the temperature of the polymerization reaction. In certain embodiments, the process can advantageously be employed to impart a temperature control aspect to a polymerization reaction, for example, a butadiene mnonomer reaction, that allows the polybutadiene to be employed for specialized uses.

[0068] All references, including but not limited to patents, patent applications, and non-patent literature are hereby incorporated by reference herein in their entirety.

[0069] While various aspects and embodiments of the compositions and methods have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the claims.

Claims

CLAIMS:

1. A method for controlling temperature of a bulk polymerization process comprising:

feeding fresh monomer and catalyst to an agitated reaction chamber of a horizontally disposed polymerization reactor, the polymerization reactor having a central pressurized vapor head space and the reaction chamber containing a reacted polymer mixture having an average increased viscosity along the length of the reaction chamber from the inlet of the reaction chamber to the outlet of the reaction chamber;

removing a portion of monomer vapor produced from a polymerization reaction in the reaction chamber from the central pressurized vapor head space of the horizontally disposed polymerization reactor;

condensing the removed monomer vapor to form a recycle monomer;

pumping the recycle monomer back into the reaction chamber of the horizontally disposed polymerization reactor, portions of the recycle monomer being introduced into the reaction chamber in at least two separate introduction points; and

collecting a reacted polymer cement from the horizontally disposed polymerization reactor.

2. The method of claim 1 , the portions of the recycle monomer being fed into the reacted polymer mixture being along the bottom half of the horizontally disposed polymerization reactor.

3. The method of claim 1 or claim 2, further comprising controlling the temperature to a range of 50 to 150 degrees Celsius in the reaction chamber by introducing the portions of the recycle monomer to the reaction chamber.

4. The method of any one of claims 1-3, the recycle monomer being continuously

introduced into the at least two introduction points.

5. The method of any one of claims 1-4, the recycle monomer being substantially free of solvent.

6. The method of any one of claims 1-5, the recycle monomer being continuously fed into the central pressurized vapor head space to control the temperature of the reaction chamber.

7. The method of any one of claims 1-6, the reaction chamber comprising at least three introduction points, each of the three introduction points having a recycle monomer feed that introduces condensed recycle monomer.

8. The method of any one of claims 1-7, the at least two introduction points being spaced equally from one another along the axial length of the reaction chamber.

9. The method of any one of claims 1-8, the recycle monomer being fed into the reaction chamber of the horizontally disposed polymerization reactor at a temperature in the range of 20 to 50 degrees Celsius.

10. The method of any one of claims 1-9, the introduction point of each portion of the recycle monomer feed being not more than 30 percent of the axial length of the horizontally disposed polymerization reactor apart.

11. The method of any one of claims 1-10, the flow rate of the monomer vapor removed from the reaction chamber being controlled by a pressure control valve that maintains a constant pressure range in the central pressurized vapor head space of the horizontally disposed polymerization reactor.

12. A method for regulating the reaction temperature in a continuous bulk polymerization process comprising:

continuously feeding a conjugated diene monomer and catalyst to an agitated cylindrical reaction chamber of a horizontal polymerization reactor, the reaction chamber being substantially free of a solvent; removing monomer vapor from a gas collection area connected to the reaction chamber and condensing the removed monomer vapor to form a recycle monomer;

feeding the recycle monomer into the reaction chamber through two or more introduction points along the axially length of the horizontal polymerization reactor, at least one introduction point being positioned in the first half of the axial length of the horizontal polymerization reactor and at least one introduction point being positioned in the second half of the axial length of the horizontal polymerization reactor; and

extracting a reacted polymer cement from the horizontal polymerization reactor in a continuous mode.

13. The method of claim 12, the recycle monomer comprising a mixture of two or more monomers.

14. The method of claim 12 or claim 13, the recycle monomer being fed at the same flow rate to each of the two or more introduction points.

15. The method of any one of claims 12-14, the two or more introduction points being

equally spaced along the length of the horizontal polymerization reactor.