Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F210/02—Ethene

Definitions

• the present invention relates generally to the field of polymer synthesis. More particularly, it concerns the solution polymerization of a monomer and a comonomer, followed by sequential devolatilization to remove unreacted monomer, comonomer, or other reactants from the product.
• the polymerization of a monomer and a comonomer can be performed by combining the monomer and the comonomer under appropriate reaction conditions in any one of a number of phases.
• Commercially relevant polymerization is often performed in solution or in the gas phase.
• Solution polymerization involves dissolving the monomer and the comonomer in a mutual solvent.
• the solvent must later be removed from the polymer, and, if the solvent is an organic compound, such as toluene, extensive solvent removal is required. This is especially true if the polymer is intended for a food packaging use, such as an oxygen scavenging polymer in an oxygen scavenging packaging article.
• solution polymerization examples include emulsion polymerization (in wliich the monomer and the comonomer are present in an oil phase emulsified in an aqueous external phase) and suspension polymerization (in which the monomer and the comonomer are suspended in an aqueous solution by a suspending agent, such as poly vinyl alcohol).
• a suspending agent such as poly vinyl alcohol
• these latter forms of solution polymerization require more components, such as an oil and an emulsifier, or a suspending agent, which also must be removed from the polymer.
• Welborn et al. discloses a method for the synthesis of copolymers of ethylene and 4-vinyl-l-cyclohexene by solution polymerization.
• the solution polymerization process disclosed by Welborn et al. involves the use of hexane or toluene as the solvent (i.e. at least about 50 vol% of the reactor contents).
• Vidal, U.S. Patent No. 5,504,167 discloses a method for the free radical synthesis of copolymers of ethylene with a carboxylic acid, an ester, an anhydride, or a nitrilo derivative, by a continuous process involving 2-25 wt% of solvent comprising methanol.
• Hatch et al. U.S. Patent No. 5,028,674, discloses a method for the free radical synthesis of copolymers of ethylene with a carboxylic acid, an ester, or an anhydride, by a continuous process involving 2-25 wt%, preferably 5-20 wt%, of solvent comprising methanol.
• Kawata et al. U.S. Patent No. 5,272,235, discloses a method for the synthesis of copolymers of ethylene and a cycloolefin, involving copolymerizing the ethylene and the cycloolefin in a hydrocarbon solvent or a liquid phase comprising the cycloolefin. The method also generates solid polyethylene as an impurity.
• JP 51140983 discloses a method for the polymerization of propylene, or the copolymerization of propylene with ethylene, in the liquid phase of propylene.
• the present invention relates to a method of synthesizing a copolymer, comprising: providing a monomer, a comonomer, and a catalyst; reacting the monomer and the comonomer in the presence of the catalyst in a reactor, under conditions wherein the monomer is a liquid in which the comonomer is soluble, to yield a polymer comprising the monomer and comonomer; and separating unreacted monomer and unreacted comonomer from the polymer, to yield the purified polymer.
• the separating step can comprise heating the polymer to a temperature appropriate for degassing; subjecting the polymer to vacuum flashing; passing the polymer through a thin film evaporator; stripping the polymer with N 2 or steam; or any combination thereof. Further, the separated monomer and comonomer can be recycled to the providing step.
• the method has the advantage of not requiring the addition of a solvent. The monomer functions as a solvent for the other reactants. This provides cost savings, in that no further solvent is required and a solvent recovery step need not be performed. Environmental benefits may also be seen by not requiring a further solvent.
• the present invention relates to a method of synthesizing a copolymer, comprising: providing a monomer, a comonomer, and a catalyst; reacting the monomer and the comonomer in the presence of the catalyst in a reactor, under conditions wherein the monomer is a liquid in which the comonomer is soluble, to yield a polymer comprising the monomer and comonomer; and separating unreacted monomer and unreacted comonomer from the polymer, to yield the purified polymer.
• the monomer and comonomer can be any molecules from which it is desired to synthesize a polymer.
• the monomer and comonomer each comprises an ethylenic group (defined as two carbon atoms covalently linked by a double bond) which, under the conditions described below, undergoes polymerization with the ethylenic group of another monomer molecule or comonomer molecule, to yield a polymer with a polyethylenic backbone.
• the monomer or comonomer comprises a pendant group comprising a benzylic or a cyclic olefinic group
• pendant group is defined as a group that does not substantially participate in polymerization of the monomer or comonomer under the conditions described below).
• Such a group can be substituted or unsubstituted, and can be polycyclic.
• the monomer or comonomer comprises a cyclic olefinic pendant group having the structure I:
• q 1? q 2 , q 3 , q 4 , and r are independently selected from hydrogen, methyl, or ethyl; m is -(CH ) n -, wherein n is an integer from 0 to 4, inclusive.
• n is 1 and qi, q 2 , q , q 4 , and r are each hydrogen; i.e. the cyclic olefinic group is a cyclohexenyl group.
• the monomer is a compound that is liquid under conditions in which the reaction will take place. The monomer is chosen such that the comonomer is soluble in the monomer under reaction conditions. In other words, the reaction is a solution polymerization in which the monomer also functions as the solvent. This will be described in more detail below.
• an additional compound is present wliich is liquid under the reaction conditions and in which the comonomer is soluble, such as possibly toluene or benzene, among others, the additional compound can be present at any concentration.
• Such an additional compound can be a solvent for the catalyst or some other additive. However, such additional compound is not required in the present invention.
• Preferred monomers include vinyl cycloolefins, such as vinyl cyclopentene, 4-vinyl-l- cyclohexene, vinyl cycloheptene, or vinyl cyclooctene. More preferably, the monomer is 4- vinyl-1-cyclohexene.
• the comonomer is a vinyl compound, such as ethylene or styrene. More preferably, the comonomer is ethylene.
• the catalyst can be any compound useful in catalyzing the polymerization of the monomer and the comonomer, and will vary depending on the monomer and comonomer, the mechanism of polymerization, and other parameters known to one of skill in the art.
• the catalyst can also comprise a cocatalyst.
• Catalyst systems that can be used include metallocenes, such as those disclosed by U.S. Patent Nos. 6,043,180; 5,863,853; 5,770,663; and Ziegler-Natta catalysts, such as those disclosed by U.S. Patent Nos. 5,488,022 and 5,994,256. The listed patents are hereby incorporated by reference.
• Exemplary Ziegler-Natta catalysts include TiCb and A1(C 2 H5) Q; TiCk and A1(C 2 H5)3; Ti salt/organomagnesium compound/silane systems supported on silica, alumina, or both;
• Examplary metallocenes include cyclopentadienylide catalyst systems using a metallocene complex, e.g. titanocene or zirconocene, and an alumoxane, such as methyl alumoxane (MAO) or modified methaluminoxane (MMAO).
• MAO methyl alumoxane
• MMAO modified methaluminoxane
• Metallocene catalyst systems such as r ⁇ c-en(Ind) 2 ZrCl /MMAO (Ethylenebis(l-indenyl)zirconium dichloride/MMAO, CAS Registry No. 112243-78-4), r c-en(THInd) 2 ZrCl 2 /MMAO (Ethylenebis(tetrahydroindenyl)zircom ' um dichloride/MMAO, CAS Registry No.
• catalysts known in the art may also prove effective and can be used.
• the catalyst may be made up with a solvent, if desired, which could be either the monomer or a separate solvent.
• free radical initiators such as benzoyl peroxide, can be used, and are within the scope of "catalyst" as that term is used in the claims.
• the monomer, the comonomer, and the process gases can be purified before the reacting step.
• Typical impurities that may be present in the monomer, comonomer, or process gas include water, oxygen, alcohols, ketones, polymerization inhibitors, oxidation inhibitors, CO, CO 2 , acetylene, and H 2 S, among others. Removal of impurities can be brought about by passing the monomer, the comonomer, or the process gas through or over a molecular sieve, alumina, a deoxo column, or a combination of the above, among other purification apparatus.
• the deoxo column can comprise a CuO or CuO/ZnO system (such as are commercially available as R 3-11 (BASF) or G-66B (Girdler)) for removal of O 2 and CO from ethylene or nitrogen.
• Oxygen and CO can be removed from hydrogen by a deoxo column comprising a noble metal catalyst.
• catalyst, unreacted monomer, or unreacted comonomer derived from the effluent of the reactor as will be described below can be returned to the providing step, if desired, and can be subjected to purification as described above, if desired.
• the monomer, the comonomer, and the catalyst, as well as any further additives are fed to a reactor.
• the catalyst and any further additives are also fed to the reactor.
• the feeds into the reactor can be added through separate lines or a single line. If one of the compounds is added in a gas phase, it is preferably sparged through the liquid phase.
• the order and rate of addition, and the concentration, of the various compounds are generally routine parameters, although variations in the order or rate may have an impact on the rate of the polymerization reaction or the yield thereof.
• the reactor used can be any known in the art.
• reactor is meant any vessel or vessels into which reactants can be introduced, from which products and unreacted reactants can be withdrawn, and in which the temperature, pressure, and composition (reactants and inerts) can be controlled. Any such vessel or vessels known in the art can be used. Multiple vessels can be arranged in series, in parallel, or a combination thereof.
• the layout of the reactor is a manner of routine experimentation to the skilled artisan.
• the reactor is capable of continuous operation, although batch operation can also be undertaken.
• the contents of the reactor can be agitated, such as by the use of a paddle rotor, sonication, or other techniques known in the art.
• the reactor have temperature control capabilities, such as a jacket through which is circulated cold water or refrigerant, in order to remove heat generated by exothermic polymerization reactions.
• the polymerization can occur by any technique known in the art, such as Ziegler-Natta polymerization or metallocene polymerization, among others.
• the copolymer formed from the reaction of the monomer and the comonomer will typically be a random copolymer, although a block copolymer may also be generated by the method of the present invention.
• the proportions of monomer and comonomer units in the copolymer will roughly depend on the proportions of the monomer and the comonomer added to the reactor, and the relative reactivity of the monomer and the comonomer in polymerization.
• the reaction conditions can be selected to generate a polymer having a desired molecular weight range, a desired proportion of linearity or branched status, or other parameters known to one of ordinary skill in the art.
• the temperature can be any temperature at which the monomer is liquid and the monomer, comonomer, or polymer produced by the reaction do not degrade.
• the temperature is between about 38°C (100°F) and about 93 °C (200°F), more preferably between about 60°C (140°F) and about 83°C (180°F).
• the temperature can be about 60°C (140°F).
• the pressure is ambient pressure or higher, up to about 300 psi.
• the partial pressure of the ethylene can be about 18 psig, and the hydrogen partial pressure can be about 5 psig.
• the catalyst is Ti-based, the partial pressure of the ethylene can be about 100 psig, and the partial pressure of the hydrogen can be about 18 psig.
• the present invention can also be used to produce a terpolymer of the monomer, the comonomer, and a second comonomer.
• the second comonomer can be within the definitions of "monomer” or “comonomer” given above. If a terpolymer is to be made according to the present invention, all references herein to "monomer” or “comonomer” should be construed to also refer to the second comonomer, as appropriate.
• the separating step comprises heating the polymer to a temperature below the boiling point or thermal decomposition point of the polymer but above the boiling point of the monomer or the comonomer. This will cause at least some of the monomer or comonomer present in the effluent to flash off into the overhead gas stream.
• the boiling point is dependent on the pressure of the gas stream overhead, and that lowering the overhead pressure will reduce the temperature required to flash off the monomer or the comonomer.
• 4-vinyl-l-cyclohexene and ethylene are the monomer and the comonomer
• maintaining an overhead pressure at or below 2 psia, while heating the mixture to at least about 50°C is adequate.
• monomer or comonomer can be separated from the polymer by subjecting the polymer to vacuum flashing.
• vacuum flashing One of ordinary skill in the art will recognize that volatile molecules will more readily leave the liquid phase under vacuum flashing than will less volatile molecules, such as the polymer. Vacuum flashing can be performed using an appropriate apparatus, including one or more vacuum flash separators.
• the polymer can be passed through an evaporator, such as a wiped film evaporator, in order to remove monomer or comonomer.
• an evaporator such as a wiped film evaporator
• a wiped film evaporator is preferred over other forms of evaporators because it provides better temperature control and also the turning action of the wiped blades refreshes the polymer surface to maximize removal of monomer or comonomer. Any appropriate apparatus can be used.
• the polymer can be stripped with N 2 or steam, preferably under vacuum. Gas stripping can be performed using any appropriate apparatus.
• passing the polymer through an evaporator and gas stripping the polymer are performed together. Even more preferably, all four techniques of heating the polymer, vacuum flashing, passing through an evaporator, and gas stripping are performed. In all cases, the order of steps and the structure of the apparatus used can be varied as a matter of routine experimentation.
• the separating step can comprise solvent extraction, such as by the use of methanol, or supercritical fluid extraction, such as by the use of CO 2 or isobutane, following techniques known in the art.
• solvent extraction such as by the use of methanol
• supercritical fluid extraction such as by the use of CO 2 or isobutane, following techniques known in the art.
• the monomer, the comonomer, or both can be recycled to the reactor.
• recycled to the reactor is meant that unreacted monomer or unreacted comonomer is fed from the separating apparatus to the reactor, either directly or through intermediate processing apparatus (e.g. to purify the monomer or comonomer, to add process gas, or for other reasons). Further purification can be performed during the recycling process, if desired.
• the polymer can be used in the formation of a finished article, such as a packaging article, or can be stored in a form such as a film or pellets for eventual use.
• VCH 4-vinyl-l-cyclohexene
• the process gases undergo a similar two-stage pretreatment process for oxygen and moisture removal.
• oxygen is removed in a deoxo reactor.
• a catalyst such as CuO/ZnO (Girdler G-66B) or CuO (BASF R 3-11) catalyst is used in the deoxo reactor for oxygen and carbon monoxide removal.
• the catalyst used in the hydrogen reactor is a noble metal catalyst for oxygen removal.
• the second step in the pretreatment involves drying the individual streams by passing over beds of molecular sieves and alumina before entering the polymerization reactor or other process areas.
• the catalyst preparation system consists of two vessels, one containing the catalyst and the second for the optional co-catalyst.
• Two chemical metering pumps regulate the flow of catalyst and, if applicable, co-catalyst from their respective vessels to a static mixer, where the two streams mix and form the active catalyst species immediately before entering the reactor.
• the co-polymerization of ethylene and VCH takes place in the solution phase using a continuous stirred tank reactor equipped with jacketed cooling.
• the polymerization reaction is very exothermic; heat removal is essential to control the reaction.
• Feeds to the reactor are a combination of both fresh and recycle ethylene, hydrogen, and VCH.
• a large excess of VCH is utilized in order to encourage higher levels of VCH incorporation into the polymer.
• a mixture of ethylene and hydrogen feed in the mole ratio of approximately 4 to 1 is sparged through the liquid phase in the presence of the cocatalyst and catalyst, in this case MMAO and r ⁇ c-en(THInd) 2 ZrCl 2 , respectively, in a 2000:1 molar ratio
• Polymerization with this catalyst is achieved at the fairly mild conditions of 131°F (55°C) with an ethylene partial pressure of 18 psig, and 5 psig hydrogen. Concentration of the polymer in VCH effluent from the reactor is assumed not to exceed 10%, which is the approximate solubility limit of EVCH in VCH under these conditions.
• the effluent is heated to 93 °C (200°F) before entering a vacuum flash separator.
• Pressure in this vessel operated under vacuum is approximately 2 psia, causing ethylene and a large portion of the VCH to flash from the polymer and leave with the overhead gas stream.
• This overhead gas stream is then sent to the reactant recovery area for recovery of unreacted ethylene and VCH.
• the polymer bottom fraction leaves the flash vessel and is sent to the polymer purification and compounding area for further clean-up before pelletizing the EVCH.
• the polymer leaving the flash separator is fed to a two-stage thin film wiped film evaporator (TFE) where VCH incorporated in the polymer is reduced to low residual levels.
• TFE thin film wiped film evaporator
• a thin film evaporator was chosen for this application for several reasons.
• the TFE provides good temperature control because heat is added to the device through the cylindrical walls to the thin polymer film. Tight control of the heat history of the polymer is crucial to minimize thermal degradation.
• the turning action by the wiped blades in the TFE continuously renews or refreshes the polymer surface to maximize removal of the VCH.
• the TFE operates under vacuum using N 2 as the stripping gas to further enhance removal of unreacted VCH and result in low VCH residuals in the final product. (Steam may also be used as the stripping gas).
• the polymer After leaving the TFE, the polymer passes through a gear pump to an extruder.
• This extruder may be operated under vacuum to improve devolatilization of any remaining monomer or comonomer.
• the extruder is equipped with an underwater pelletizer. The pellets are then dried and sent to storage silos for later boxing or loading onto railcars or trucks.
• VCH and other volatile compounds present in the overhead stream from the TFE are condensed for separation from the N 2 stripping gas. With the exception of a small purge, the N 2 is recycled. VCH recovered from this stream, along with any condensable volatile compounds are sent to the distillation tower for separation.
• the overhead stream from the flash separator is rich in VCH as well as ethylene.
• This stream passes through several condensers to separate the VCH and other condensable byproducts from the ethylene before entering the vacuum pump. Removal of the condensable materials from this stream is necessary to reduce the size of the vacuum pump required.
• The. gas stream leaving the vacuum pump still contains a significant quantity of ethylene and hydrogen. These gases, together with the VCH vapors and VCH liquid from the condenser, are sent to the distillation column for further separation.
• VCH is recovered from the process streams and recycled back to the polymerization reactor.
• This area can consist of only one distillation column. Reactant gases are recovered from the top of the column and VCH from the bottom. However, depending on the purity level required of the recycle VCH, a second column may be necessary for separation of the heavier reaction byproducts from the recovered VCH.
• the overhead gas stream from the column is sent to a series of deoxo vessels and driers to remove trace quantities of oxygen incorporated into the system by vacuum leaks, before recycling to the reactor.

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• 2001
  • 2001-07-24 AU AU2001277149A patent/AU2001277149A1/en not_active Abandoned
  • 2001-07-24 WO PCT/US2001/023338 patent/WO2002018459A1/en active Application Filing

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