EP0204840A4 - Modification de la distribution des poids moleculaires dans un reacteur tubulaire. - Google Patents

Modification de la distribution des poids moleculaires dans un reacteur tubulaire.

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Publication number
EP0204840A4
EP0204840A4 EP19860900540 EP86900540A EP0204840A4 EP 0204840 A4 EP0204840 A4 EP 0204840A4 EP 19860900540 EP19860900540 EP 19860900540 EP 86900540 A EP86900540 A EP 86900540A EP 0204840 A4 EP0204840 A4 EP 0204840A4
Authority
EP
European Patent Office
Prior art keywords
copolymer
catalyst
ethylene
reactor
polymerization
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19860900540
Other languages
German (de)
English (en)
Other versions
EP0204840A1 (fr
Inventor
Charles Cozewith
Shiaw Ju
Gary William Verstrate
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ExxonMobil Technology and Engineering Co
Original Assignee
Exxon Research and Engineering Co
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Filing date
Publication date
Application filed by Exxon Research and Engineering Co filed Critical Exxon Research and Engineering Co
Publication of EP0204840A1 publication Critical patent/EP0204840A1/fr
Publication of EP0204840A4 publication Critical patent/EP0204840A4/fr
Withdrawn legal-status Critical Current

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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
    • C08F2/00—Processes of polymerisation
    • C08F2/04—Polymerisation in solution
    • C08F2/06—Organic solvent
    • 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
    • C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/24—Stationary reactors without moving elements inside
    • B01J19/2415—Tubular reactors
    • 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
    • C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00051—Controlling the temperature
    • B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
    • B01J2219/00087—Controlling the temperature by indirect heating or cooling employing heat exchange fluids with heat exchange elements outside the reactor
    • B01J2219/00099—Controlling the temperature by indirect heating or cooling employing heat exchange fluids with heat exchange elements outside the reactor the reactor being immersed in the heat exchange medium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00051—Controlling the temperature
    • B01J2219/00159—Controlling the temperature controlling multiple zones along the direction of flow, e.g. pre-heating and after-cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00186—Controlling or regulating processes controlling the composition of the reactive mixture
    • 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
    • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F110/02—Ethene

Definitions

  • the present invention relates to novel copolymers of alpha-olefins. More specifically, it relates to novel copolymers of ethylene with other alpha-olefins which have a polymodal molecular weight distribution wherein individual nodes comprising the polymer have narrow molecular weight distributions.
  • Inter-CD defines compositional variation, in terms of ethylene content, among polymer chains. It is expressed as the minimum deviation (analogous to a standard deviation) in terms of weight percent ethylene from the average ethylene composition for a given copolymer sample needed to include a given weight percent of the total copolymer sample which is obtained by excluding equal weight fractions from both ends of the distribution. The deviation need not be symmetrical. When expressed as a single number, for example, 15% Inter-CD, it shall mean the larger of the positive or negative deviations. For example, for a Gaussian compositional distribution, 95.5% of the polymer is within 20 wt% ethylene of the mean if the standard deviation is 10%. The Inter-CD for 95.5 wt% of the polymer is 20 wt% ethylene for such a sample.
  • Intra-CD is the compositional variation, in terms of ethylene, within a copolymer chain. It is expressed as the minimum difference in weight (wt) % ethylene that exists between two portions of a single copolymer chain, each portion comprising at least 5 wt% of the chain.
  • MWD Molecular weight distribution
  • Ni is the number of molecules of weight Mi.
  • Ethylene-propylene copolymers are important commercial products. Two basic types of ethylene-propylene copolymers are commercially available; ethylene propylene copolymers and ethylene propylene terpolymers. Ethylene-propylene copolymers (EPM) are saturated compounds requiring vulcanization with free radical generators such as organic peroxides. Ethylene-propylene terpolymers (EPDM) contain a small amount of non-conjugated diolefin, such as dicyclopentadiene; 1,4-hexadiene or ethylidene norbornene, which provides sufficient unsaturation to permit vulcanization with sulfur. Such ethylene-propylene polymers that include at least two monomers, i.e., EPM and EPDM, will be hereinafter collectively referred to as ethylene-propylene copolymers.
  • copolymers have outstanding resistance to weathering, good heat aging properties and the ability to be compounded with large quantities of fillers and plasticizers resulting in low cost compounds which are particularly useful in automotive and industrial mechanical goods applications.
  • Typical automotive uses are tire sidewalls, inner tubes, radiator and heater hose, vacuum tubing, weather stripping, sponge doorseals and Viscosity Index (V.I.) improvers for lubricating oil compositions.
  • Typical mechanical goods uses are for appliance, industrial and garden hoses, both molded and extruded sponge parts, gaskets and seals and conveyor belt covers. These copolymers also find use in adhesives, appliance parts as in hoses and gaskets, wire and cable and plastics blending.
  • EPM and EPDM find many, varied uses. It is known that the properties of such copolymers which make them useful in a particular application are, in turn, determined by their composition and structure. For example, the ultimate properties of an EPM and EPDM copolymer are determined by such factors as composition, compositional distribution, sequence distribution, molecular weight, and molecular weight distribution (MWD).
  • the efficiency of peroxide curing depends on composition. As the ethylene level increases, it can be shown that the "chemical" crosslinks per peroxide molecule increases. Ethylene content also influences the rheological and processing properties, because crystallinity, which acts as physical crosslinks, can be introduced. The crystallinity present at very high ethylene contents may hinder processability and may make the cured product too "hard” at temperatures below the crystalline melting point to be useful as a rubber.
  • the processability is often measured by the Mooney viscosity. The lower this quantity the easier the elastomer is to mix and fabricate. It is desirable to have low Mooney yet to maintain a high number average molecular weight, M n , so that the polymers form good rubber networks upon cross-linking.
  • M n number average molecular weight
  • narrowing the molecular weight distribution results in the production of polymer with higher number average molecular weight at a given Mooney than the broader distribution polymer. In certain cases, the poor milling, calendering or extrusion behavior that results from the narrow MWD must be ameliorated.
  • the present invention is drawn to a novel copolymer of ethylene and at least one other alpha-olefin monomer which copolymer is composed of several such MWD components each of which is very narrow. It is well known that the breadth of the MWD can be characterized by the ratios of various molecular weight averages . For example, an indication of the narrow MWD of each component in accordance with the present invention is that the ratio of weight to number average molecular weight
  • a ratio of the Z-average molecular weight to the weight average molecular weight (M z /M w ) of less than 1.8 typifies a narrow MWD in accordance with the present invention. It is known that the property advantages of copolymers in accordance with the present invention are related to these ratios. Small weight fractions of material can disproportionately influence these ratios while not significantly altering the property advantages which depend on them. For instance, the presence of a small weight fraction (e . g .
  • the component polymers in accordance with the present invention, are characterized by having at least one of two characteristics; M w . /M n less than 2 and M z /M w less than 1.8.
  • the copolymers in accordance with the present invention are preferably made in a tubular reactor. It has been discovered that to produce such copolymers requires the use of numerous heretofore undisclosed method steps conducted within heretofore undisclosed preferred ranges. Accordingly, the present invention is also drawn to a method for making the novel copolymers of the present invention.
  • ethylene is preferentially polymerized, and if no additional make-up of the monomer mixture is made during the polymerization the concentration of monomers changes in favor of propylene along the tube. It is. further disclosed that since these changes in concentration take place during chain propagation, copolymer chains are produced which contain more ethylene on one end than at the other end. It is also disclosed that copolymers made in a tube are chemically non-uniform, but fairly uniform with respect to molecular weight distribution. Using the data reported in their Figure 17 for copolymer prepared in the tube, it was estimated that the M w /M n ratio for this copolymer was 1.6.
  • U.S. 3,681,306 is drawn to a process for producing ethylene/higher alpha-olefin copolymers having good processability, by polymerization in at least two consecutive reactor stages.
  • this two-stage process provides a simple polymerization process that permits tailor-making ethylene/alpha-olefin copolymers having predetermined properties, particularly those contributing to processability in commercial applications such as cold-flow, high green strength and millability.
  • the disclosed process is particularly adapted for producing elastomeric copolymers, such as ethylene/ propylene/5-ethylidene-2-norbornene, using any of the coordination catalysts useful for making EPDM.
  • the preferred process uses one tubular reactor followed by one pot reactor.
  • tubular reactor could be used, but operated at different reaction conditions to simulate two stages.
  • the process makes polymers of broader MWD than those made in a single stage reactor.
  • intermediate polymer from the first (pipeline) reactor is disclosed as having a ratio of M w /M n of about
  • the final polymers produced by the process have an M w /M n of 2.4 to 5.
  • U.S. 3,625,658 co Closon discloses a closed circuit tubular reactor apparatus with high recirculation rates of the reactants which can be used to make elastomers of ethylene and propylene.
  • a hinged support 10 for vertical leg 1 of the reactor allows for horizontal expansion of the bottom leg thereof and prevents harmful deformations due to thermal expansions, particularly those experienced during reactor clean out.
  • U.S. 4,065,520 to Bailey et al. discloses the use of a batch reactor to make ethylene copolymers, including elastomers, having broad compositional distributions.
  • Several feed tanks for the reactor are arranged in series, with the feed to each being varied to make the polymer.
  • the products made have crystalline to semi-crystalline to amorphous regions and gradient changes in between.
  • the catalyst system can comprise vanadium compounds alone or in combination with titanium compounds and is exemplified by vanadium oxy-tri-chloride and diisobutyl aluminum chloride. In all of the examples, titanium compounds are used. In several examples, hydrogen and diethyl zinc, known transfer agents, are used.
  • the polymer chains produced have a compositionally disperse first length and uniform second length. Subsequent lengths have various other compositional distributions.
  • Molecular weight distribution is a very important characteristic of ethylene-propylene copolymers and terpolymers.
  • Favorable distributions result in polymers which can have both faster cures and better processing characteristics.
  • An optimum combination of these properties is achieved where the polymers have a polymodal molecular weight distribution and a polymodal compositional distribution.
  • British Patent No. 1,233,599 is illustrative of two stage polymerization processes. While copolymers of ethylene are incidently disclosed, the examples and disclosure are directed toward polyethylene homopolymers and crystalline copolymers, e.g., 95Z ethylene.
  • the preferred catalysts are vanadium compounds such as vanadyl halide, vanadium tetrachloride or vanadium tris-(acetyl-acetonate) in conjunction with an aluminum compound, e.g., Br 2 AlCH Br 2 .
  • the different MWDs are obtained by using differing amounts of hydrogen in the first and second stage polymerization.
  • 4,078,131 discloses an ethylene-propylene rubber composition having a bimodal distribution in molecular weights comprising two polymer fractions each having a wide distribution of molecular weights and a monomer composition different from that of the other principal fractions.
  • the polymers are further characterized in that they are formed of: (a) a first principal fraction comprising from about 30% to about 85Z (by weight referred to the total weight of elastomers) of molecular weight fractions having an intrinsic viscosity distribution of from about 0.2 to about 3, and average intrinsic viscosity between about 0.8 to about 1.5, an average propylene content between about 36 to about 52% by weight, and a termonomer content of between 0% and about 5%, and of (b) a second fraction comprising about 70% to about 15% by weight of molecular weight fractions having an intrinsic viscosity distribution from about 3 to about 15, an average intrinsic viscosity of about 3.5 to about 7, and average propylene content of between about 26% to about 32% by weight and
  • the polymers are prepared by carrying out polymerization in two separate reactors connected in series.
  • the catalyst systems utilized include organic and inorganic component of a transition metal of Group 4A to 8A of the Mendeleev periodic table of the elements, e.g., VOCl 3 , VCl 4 , vanadium esters and acetyl acetonates.
  • Co-catalysts include organoaluminum compounds or mixtures of compounds, e.g., aluminum alkyIs.
  • U.S. Patent 3,681,306 discloses a two stage polymerization process for the preparation of ethylene- propylene co-and terpolymers.
  • the first stage is a "pipe reactor" and the second stage is a back-mixed pot reactor.
  • the polymerization is carried out so that the average ethylene/alpha olefin ratio in one state is at least 1.3 tines the average ratio of the other stage.
  • Any of the coordination catalysts know to be useful in producing EPDM polymers is said to be effective for the process.
  • U.S. Patent No. 4,259,468 discloses a broad molecular weight ethylene-propylene-diene rubber prepared using as a catalyst (a) the alcohol reaction product of vanadium oxytrichloride and (b) a mixture of aluminum sesquichloride and ethylaluminum dichloride.
  • the polymer is characterized in that the higher molecular weight fraction contains a larger proportion of the diene than does the lower molecular weight fraction.
  • the polymer has an intrinsic viscosity of about 1.0 to about 6.0 dl/g and a weight average molecular weight/number ratio of about 3 to about 15.
  • U.S. Patent No. 4,306,401 discloses a method of manufacture of EPDM type terpolymers which utilizes a two stage polymerization process. Substantially all of the non-conjugated diene monomer is fed to the first stage thereby producing a polymer having a non-uniform diene content.
  • Fig. 1 is a schematic representation of a process for producing polymer in accordance with the present invention.
  • Fig. 2 schematically illustrates a polymodal MWD polymer comprising narrow MWD polymers for each mode
  • Fig. 3 is a graphical illustration of a technique for determining Intra-CD of a copolymer
  • Fig. 4 graphically illustrates various copolymer structures that can be attained using processes in accordance with the present invention. Detailed Description of the Invention
  • the instant invention relates to a novel copolymer of ethylene and at least one other alpha-olefin monomer, which copolymer is a superposition of two or more copolymers, each of which has a MWD characterized by having at least one of two characteristics; an M w /M n of less than 2 and M z /M w of less than 1.8.
  • copolymers in accordance with the present invention are comprised of ethylene and at least one other alpha-olefin.
  • alpha-olefins can include those containing 3 to 18 carbon atoms.
  • Alpha-olefins of 3 to 6 carbons are preferred becavse of economic considerations.
  • alpha olefins useful in the practice of this invention are propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, dodecene-1, etc.
  • the most preferred copolymers in accordance with the present invention are those comprised of ethylene and propylene or ethylene, propylene and non-conjugated diene.
  • copolymers of ethylene and higher alpha-olefins such as propylene often include other polymerizable monomers. Typical of these other monomers can be non-conj ugated dienes.
  • non-conjugated dienes are: a. straight chain acyclic dienes such as: 1,4-hexadiene; 1,6-octadiene; b. branched chain acyclic dienes such as: 5-methyl-1, 4-hexadiene; 3,7-dimethyl-1, 6- octadiene; 3,7-dimethyl-1,7-octadiene and the mixed isomers of dihydro-myrcene;
  • c. single ring alicyclic dienes such as: 1,4-cyclohexadiene; 1,5-cyclooctadiene; and 1,5-cyclododecadiene;
  • d. multi-ring alicyclic fused and bridged ring dienes such as: tetrahydroindene; methyltetrahydroindene; dicyclopentadiene; bi- cyclo-(2,2,1)-hepta-2,5-diene; alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbornenes such as 5-methylene-2-norbornene (MNB), 5-ethylidene-2-norbornene (ENB), 5-propylidene-2-norbornene, 5-isopropylidene-2-norbornene, 5-(4-cyclopentenyl)-2-norbornene; 5-cyclohexylidene-2-norbornene.
  • dienes containing at least one of the double bonds in a strained ring are preferred.
  • the most preferred diene is 5-ethylidene-2-norbornene (EMB) .
  • EMB 5-ethylidene-2-norbornene
  • the amount of diene (wt. basis) in the copolymer can be about 0% to 20% with 0% to 15% being preferred. The most preferred range is 0% to 10%.
  • the most preferred copolymer in accordance with the present invention is ethylene-propylene or ethylene-propylene non-conjugated diene.
  • the average ethylene content of each component of these copolymers can be as lew as about 10Z on a weight basis.
  • the preferred minimum ethylene content is about 25%.
  • a more preferred minimum is about 30%.
  • the maximum ethylene content can be about 90% on a weight basis.
  • the preferred maximum is about 85%, with the cost preferred being about 80%.
  • the molecular weight of the component copolymer made in accordance with the present invention can vary over a wide range.
  • the weight average molecular weight (M w ) can be as low as about 2,000.
  • the preferred minimum is about 10,000.
  • the most preferred minimum is about 20,000.
  • the maximum weight average molecular weight can be as high as about 12,000,000.
  • the preferred maximum is about 1,000,000.
  • the most preferred maximum is about 750,000.
  • Another feature of the copolymers made in accordance with the present invention is that the molecular weight distribution (MWD) of each component is very narrow, as characterized by having at least one of two characteristics; a ratio of Mw/Mn of less than 2 and a ratio of M z /M w of less than 1.8.
  • the M w /M n ratio for the whole copolymer can range from about 1 to about 50.
  • the M w and MWD of the copolymer is controlled by adjusting the M w and weight fraction of polymer that make up the individual narrow MWD components.
  • the M w of any two adjacent MWD modes should differ by at least 50% and any one mode chould comprise at least 10 wt% of the total copolymer.
  • EPM and EPDM a typical advantage of such copolymers composed of several modes having narrow MWD is that when compounded and vulcanized, faster cure and better physical properties result than when copolymers having lower M n for a given Mooney are used.
  • Processes in accordance with the present invention produce copolymer by polymerization of a reaction mixture comprised of catalyst, ethylene, at least one additional alpha-olefin monomer, and optionally, a non- conjugated diene. Solution polymerizations are preferred.
  • any known solvent for the reaction mixture that is effective for the purpose can be used in conducting solution polymerizations in accordance with the present invention.
  • suitable solvents are hydrocarbon solvents such as aliphatic, cycloaliphatic and aromatic hydrocarbon solvents, or halogenated analogs of such solvents.
  • the preferred solvents are C 4 to C 12 , straight chain or branched chain, saturated hydrocarbons, C 5 to C 9 saturated alicyclic or aromatic hydrocarbons or C 2 to C 6 halogenated hydrocarbons. Most preferred are C 6 to C 12 , straight chain or branched chain hydrocarbons, particularly hexane.
  • Nonlimiting illustrative examples of such solvents are butane, pentane, hexane, heptane, cyclopentane, cyclohexane, cycloheptane, methyl cyclopentane, methyl cyclohexane, isooctane, benzene, toluene, xylene, chloroform, chlorobenzenes, tetrachloroethylene, dichloroethane and trichloroethane.
  • a number of processes can be used to prepare the copolymer products of this invention. These processes are based on carrying out the copolymerization in a batch or tubular reactor. As described in our copending patent application, Serial Number 504,582, copolymers of narrow MWD with M w /M n less than 2. 0 or M z /M w less than 1.8 can be obtained by operating such reactors at certain specified conditions. Firstly, in the course of the polymerization, substantially no mixing must occur between polymer chains that have been initiated at different times. This condition is defined as "mix free.” Tubular reactors are well known and are designed to minimize mixing of the reactants in the direction of flow. As a result, reactant concentration will vary along the reactor length.
  • a batch reactor is a suitable reaction vessel in which to carry out the process of this invention, preferably equipped with adequate agitation.
  • the catalyst, solvent, and monomer are added to the reactor at the start of the polymerization.
  • the charge of reactants is then left to polymerize for a time long enough to produce the desired product.
  • a tubular reactor is preferred to a batch reactor for carrying out the processes of this invention.
  • the polymerization should be conducted in a manner such that for each component or mode in the MWD: a. the catalyst system produces essentially one active catalyst species, b. the reaction mixture is essentially free of chain transfer agents, and c. for each mode the polymer chains are essentially all initiated simultaneously, which is at the same time for a batch reactor or at the same point along the length of the tube for a tubular reactor.
  • the desired polymer can also be obtained if additional solvent and reactants (e.g., at least one of the ethylene, alpha-olefin and diene) are added either along the length of a tubular reactor or during the course of polymerization in a batch reactor. Operating in this fashion can be desirable in certain circumstances to control the polymerization rate or polymer composition. However, it is necessary to add the catalyst at the inlet or specific locations of the tube or at the onset of or at specific times in batch reactor operation to meet the requirement that for each mode essentially all polymer chains are initiated simultaneously.
  • additional solvent and reactants e.g., at least one of the ethylene, alpha-olefin and diene
  • narrow MWD component copolymers are produced by carrying out a polymerization reaction:
  • these polymerization conditions are used to generate each of the narrow MWD modes that comprise the final polymer product.
  • a number of techniques are available for achieving this:
  • portions of the polymer product can be withdrawn after varying times in a batch reactor or at varying distances along a tubular reactor representing different average molecular weights and these portions can be blended.
  • a catalyst system that generates multiple active catalyst species can be added at the start of the polymerization. Each catalyst species produced must give simultaneous chain initiation and minimize chain transfer.
  • Additional catalyst and monomer can be added at varying lengths along a tubular reactor or times in a batch reactor to initiate the formation of additional MWD modes.
  • the catalysts can be the same or different, as long as chains are initiated simultaneously and chain transfer is minimized.
  • catalyst reactivator can be added during the course of the polymerization to regenerate the dead catalyst and form a new mode of narrow MWD copolymer.
  • Catalyst reactivators are well known in the art for increasing the productivity of vanadium Ziegler catalysts. These materials rejuvenate catalyst sites that have become inert due to termination reactions and thereby cause reinitiation of polymer chain growth. When added to a reactor operating according to the process of this invention, catalyst reactivators have an effect similar to that of adding a second catalyst feed. Many reactivators are known, and examples of suitable materials can be found in U.S. Patents 3,622,548, 3,629,212, 3,723,348, 4,168,358, 4,181,790 and 4,361,686. Esters of chlorinated organic acids are preferred reactivators for use with the vanadium catalyst systems of this invention. Especially preferred is butyl perchlorocrotanate.
  • the mix free condition of the reactor refers to the polymer chains of each individual mode of the MWD and not to the polymer as a whole.
  • a preferred multiple catalyst system comprises VCl 4 combined with VOCl 3 and an alkyl aluminum sesquihalide as a cocatalyst.
  • the resultant polymer is a bimodal MWD polymer.
  • EPM ethylene-propylene
  • EPDM ethylene-propylene-diene
  • Copolymer in accordance with the present invention is preferably made in a tubular reactor.
  • ethylene due to its high reactivity, will be preferentially polymerized.
  • the concentration of monomers changes along the tube in favor of propylene as the ethylene is depleted.
  • the result is copolymer chains which are higher in ethylene concentration in the chain segments grown near the reactor inlet (as defined at the point at which the polymerization reaction commences), and higher in propylene concentration in the chain segments formed near the reactor outlet.
  • An illustrative copolymer chain of ethylene- propylene is schematically presented below the E representing ethylene constituents and P representing propylene constituents in the chain:
  • the far left-hand segment (1) thereof represents that portion of the chain formed at the reactor inlet where the reaction mixture is proportionately richer in the more reactive constituent ethylene.
  • This segment comprises four ethylene molecules and one propylene molecule.
  • subsequent segments are formed from left to right with the more reactive ethylene being depleted and the reaction mixture proportionately increasing in propylene concentration, the subsequent chain segments become more concentrated in propylene.
  • the resulting chain is intramolecularly heterogeneous.
  • composition can vary between chains as well as along the length of the chain.
  • the Inter-CD can be characterized by the difference in composition between some fraction of the copolymer and the average composition, as well as by the total difference in composition between the copolymer fractions containing the highest and lowest quantity of ethylene.
  • Techniques for measuring the breadth of the Inter-CD are known as illustrated by Junghanns, et al., wherein a p-xylene-dimethylformamide solvent/non-solvent was used to fractionate copolymer into fractions of differing intermolecular composition.
  • Other solvent/non- solvent systems can be used, such as hexane-2-propanol, as will be discussed in more detail below.
  • the Inter-CD of the individual component copolymers in accordance with the present invention is such that 95 wt% of the copolymer chains have an ethylene composition that differs from the average component weight percent ethylene composition by 15 wt% or less.
  • the preferred Inter-CD is about 13% or less, with the most preferred being about 10% or less.
  • Junghanns, et al. found that their tubular reactor copolymer had an Inter-CD of greater than 15 wt%.
  • the Intra-CD of copolymer in accordance with the present invention is such that at least two portions of an individual component intramolecularly heterogeneous chain, each portion comprising at least 5 wt% of the chain, differ in composition from one another by at least 5 wt% ethylene.
  • this property of Intra-CD as referred to herein is based upon at least two 5 wt% portions of copolymer chain.
  • the Intra-CD of copolymer in accordance with the present invention can be such that at least two portions of copolymer chain differ by at least 10 wt% ethylene. Differences of at least 20 wt%, as well as of at least 40 wt% ethylene are also considered to be in accordance with the present invention.
  • the experimental procedure for determining Intra-CD is as follows. First, the Inter-CD is established as described below, then the polymer chain is broken into fragments along its contour and the Inter-CD of the fragments is determined. The difference in the two results is due to Intra-CD as can be seen in the illustrative example below.
  • A is 36.8 wt% ethylene
  • B is 46.6%
  • C is 50% ethylene.
  • the average ethylene content for the mixture is 44.3%.
  • the Inter-CD is such that the highest ethylene polymer contains 5.7% more ethylene than the average while the lowest ethylene content polymer contains 7.5% less ethylene than the average. Or, in other words, 100 wt% of the polymer is within +5.7% and -7.5% ethylene about an average of 44.3%. Accordingly, the Inter-CD is 7.5% when the given wtZ of the polymer is 100%.
  • the distribution may be represented graphically as by curve 1 in Figure 3.
  • compositional differences shown by (b) and (d) in the figure between original and fragmented chains give minimum values for Intra-CD.
  • the Intra-CD must be at least that great, for chain sections have been isolated which are the given difference in composition (b) or (d) from the highest or lowest composition polymer isolated from the original.
  • the original polymer represented at (b) had sections of 72.7% ethylene and 0% ethylene in the same chain. It is highly likely that due to the inefficiency of the fractionation process any real polymer with Intra-CD examined will have sections of lower or higher ethylene connected along its contour than that shown by the end points of the fractionation of the original polymer. Thus, this procedure determines a lower bound for Intra-CD.
  • the original whole polymer can be fractionated (e.g., separate molecule A from molecule B from molecule C in the hypothetical example) with these fractions refractionated until they show no (or less) Inter-CD. Subsequent fragmentation of this intermolecularly homogeneous fraction now reveals the total Intra-CD.
  • the mixture In order to determine the fraction of a polymer which is intramolecularly heterogeneous in a mixture of polymers combined from several sources or as several modes in the case described here, the mixture must be separated into fractions which show no further heterogenity upon subsequent fractionation. These fractions are subsequently fractured and fractionated to reveal which are heterogeneous.
  • the fragments into which the original polymer is broken should be large enough to avoid end effects and to give a reasonable opportunity for the normal statistical distribution of segments to form over a given monomer conversion range in the polymerization. Intervals of ca 5 wt% of the polymer are convenient. For example, at an average polymer molecular weight of about 10 5 , fragments of ca 5000 molecular weight are appropriate.
  • a detailed mathematical analysis of plug flow or batch polymerization indicates that the rate of change of composition along the polymer chain contour will be most severe at high ethylene conversions near the end of the polymerization. The shortest fragments are needed here to show the low propylene content sections.
  • compositional dispersity for non-polar polymers
  • solvent/non-solvent fractionation which is based on the thermodynamics of phase separation. This technique is described in "Polymer Fractionation,” M. Cantow editor, Academic 1967, p. 341 ff and in H. Inagaki, T. Tanaku, Developments in Polymer Characterization, 3, 1. (1982). These are incorporated herein by reference.
  • molecular weight governs insolubility more than does composition in a solvent/non-solvent solution.
  • High molecular weight polymer is less soluble in a given solvent mix.
  • a fractionation procedure is as follows: Unfragmented polymer is dissolved in n-hexane at 23 °C to form ca a 1% solution (1 g polymer/100 cc hexane). Isopropyl alcohol is titrated into the solution until turbidity appears at which time the precipitate is allowed to settle. The supernatant liquid is removed and the precipitate is dried by pressing between Mylar (polyethylene terphthalate) film at 150°C. Ethylene content is determined by ASTM method D-3900. Titration is resumed and subsequent fractions are recovered an analyzed until 100% of the polymer is collected. The titrations are ideally controlled to produce fractions of 5-10% by weight of the original polymer especially at the extremes of composition.
  • the data are plotted as % ethylene versus the cumulative weight of polymer as defined by the sum of half the weight % of the fraction of that composition plus the total weight % of the previously collected fractions.
  • Another portion of the original polymer is broken into fragments.
  • a suitable method for doing this is by thermal degradation according to the following procedure: In a sealed container in a nitrogen-purged oven, a 2 mm thick layer of the polymer is heated for 60 minutes at 330°C. This should be adequate to reduce a 10 molecular weight polymer to fragments of ca 5000 molecular weight. Such degradation does not change the average ethylene content of the polymer.
  • This polymer is fractionated by the same procedure as the high molecular weight precursor. Ethylene content is measured, as well as molecular weight on selected fractions.
  • Ethylene content is measured by ASTM-D3900 for ethylene-propylene-copolymers between 35 and 85 wt% ethylene. Above 85% ASTM-D2238 can be used to obtain methyl group concentrations which are related to percent ethylene in an unambiguous manner for ethylene-propylene copolymers.
  • ASTM-D3900 ASTM-D3900
  • 85% ASTM-D2238 ASTM-D2238
  • proton and carbon 13 nuclear magnetic resonance can be employed to determine the composition of such polymers. These are absolute techniques requiring no calibration when operated such that all nucleii contribute equally to the spectra. For ranges not covered by the ASTM tests for ethylene-propylene copolymers, these nuclear magnetic resonance methods can also be used.
  • Mw/Mn is calculated from an elution time-molecular weight relationship whereas M z /M w is evaluated using the light scattering photometer.
  • the numerical analyses can be performed using the commercially available computer softwear GPC2 , MOLWT2 available form LDC/Milton Roy-Riviera Beach, Florida.
  • tubular reactor is the preferred reactor system for carrying out processes in accordance with the present invention
  • the following illustrative descriptions and examples are drawn to that system, but will apply to other reactor systems as will readily occur to those skilled in the art having the benefit of the present disclosure.
  • various structures can be prepared by adding additional monomer(s) during the course of the polymerization, as shown in Fig. 4, wherein composition is plotted versus position along the contour length of a polymer chain.
  • the structure shown in curve 1 is obtained by feeding all of the monomers to the tubular reactor inlet or at the start of a batch reaction.
  • the structure depicted in curve 2 can be made by adding additional ethylene at a point along the tube or at a time in a batch reactor, where the chains have reached about half their length.
  • Curve 3 requires multiple feed additions.
  • the structure depicted by curve 4 can be formed if additional comonomer rather than ethylene is added. This structure permits a whole ethylene composition range to be omitted from the chain. In each case, a third or more comonomers may be added.
  • composition of the catalyst used to produce alpha-olefin copolymers has a profound effect on copolymer product properties such as compositional dispersity and MWD.
  • the catalyst utilized in practicing processes in accordance with the present invention should be such as to yield a controlled number of active species, each of which must be capable of simultaneous initiation of chains and must minimize chain transfer.
  • Each active catalyst species generated either by multiple catalyst feeds or by a single catalyst feed that generates multiple active species must produce copolymer product in accordance with the present invention, e.g., a copolymer of narrow MWD.
  • the extent to which a catalyst species contributes to the polymerization can be readily determined using the below described techniques for characterizing catalyst according to the number of active catalyst species.
  • MWD gel permeation chromatography
  • Catalyst systems to be used in carrying out processes in accordance with the present invention may be Ziegler catalysts, which may typically include components selected from:
  • a compound of a transition metal i.e., a metal of Groups I-B, III-B, IVB, VB, VIB, VIIB and VIII of the Periodic Table
  • an organometal compound of a metal of Groups I-A, II-A, II-B and III-A of the Periodic Table i.e., a compound of a transition metal, i.e., a metal of Groups I-B, III-B, IVB, VB, VIB, VIIB and VIII of the Periodic Table.
  • the preferred catalyst system in practicing processes in accordance with the present invention comprises hydrocarbon-soluble vanadium compound in which the vanadium valence is 3 to 5 and organo-aluminum compound, with the provision that the catalyst system yields one active catalyst species which has the capability to produce narrow MWD copolymers as described above. At least one of the vanadium compound/organo- aluminum pair selected must also contain a valence- bonded halogen.
  • vanadium compounds useful in practicing processes in accordance with the present invention could be:
  • R preferably represents a C 1 to C 10 aliphatic, alicyclic or aromatic hydrocarbon radical such as ethyl (Et), phenyl, isopropyl, butyl, propyl, n-butyl, i-butyl, t-butyl, hexyl, cyclohexyl, octyl, naphthyl, etc.
  • the most preferred vanadium compounds are VCl 4 , VOCl 3 , and VOCl 2 (OR).
  • the co-catalyst is preferably organo-aluminum compound.
  • organo-aluminum compound in terms of chemical formulas, these compounds could be as follows: AlR 3 , Al(OR')R 2 , AlR 2 Cl, R 2 Al-O-AlR' 2 , AlR'RCl AlR 2 I; Al 2 R 3 Cl 3 AlRCl 2 , and mixtures thereof where R and R' represent hydrocarbon radicals, the same or different, as described above with respect to the vanadium compound formula.
  • the most preferred organo-aluminum compound is an aluminum alkyl sesquichloride such as Al 2 Et 3 Cl 3 or Al 2 (iBu) 3 - Cl 3 .
  • the aluminum compound can be described by the formula AlR n X 3-n where R is as previously defined, X is halogen, preferably chlorine and n can vary from 1 to 2.
  • catalysts When catalysts are desired that produce a single active species, catalysts comprised of VOCl 3 or VCl 4 with Al 2 R 2 Cl 3 , preferably where R is ethyl, have been shewn to be particularly effective.
  • the molar amounts of catalyst components added to the reaction mixture should provide a molar ratio of aluminum/vanadium (Al/V) of at least about 2.
  • Al/V aluminum/vanadium
  • the preferred minimum Al/V is about 4.
  • the maximum Al/V is based primarily on the considerations of catalyst expense and the desire to minimize the amount of chain transfer that may be caused by the organo-aluminum compound (as explained in detail below). Since, as is known certain organo-aluminum compounds act as chain transfer agents, if too much is present in the reaction mixture the Mw/Mn of the copolymer may rise above 2.
  • the maximum Al/V can be about 25, however, a maximum of about 17 is more preferred. The most preferred maximum is about 15.
  • Chain transfer agents for the Ziegler-catalyzed polymerization of alpha-olefins are well known and are illustrated, by way of example, by hydrogen or diethyl zinc for the production of EPM and EPDM. Such agents are very commonly used to control the molecular weight of EPM and EPDM produced in continuous flow stirred reactors.
  • addition of chain transfer agents to a CFSTR reduces the polymer molecular weight but does not affect the molecular weight distribution.
  • chain transfer reactions during tubular reactor polymerization in accordance with the present invention broaden polymer molecular weight distribution. Thus the presence of chain transfer agents in the reaction mixture should be minimized or omitted altogether.
  • the amount of chain transfer agent used should be limited to those amounts that provide copolymer product in accordance with the desired limits as regards MWD and compositional dispersity. It is believed that the maximum amount of chain transfer agent present in the reaction mixture could be as high as about 0.2 mol/mol of transition metal, e.g., vanadium, again provided that the resulting copolymer product is in accordance with the desired limits as regards MWD and compositional dispersity. Even in the absence of added chain transfer agent, chain transfer reactions can occur because propylene and organo-aluminum cocatalyst can also act as chain transfer agents.
  • the organo-aluminum compound that gives the highest copolymer molecular weight at acceptable catalyst activity should be chosen. Furthermore, if the Al/V ratio has an effect on the molecular weight of copolymer product, that A1/V should be used which gives the highest molecular weight also at acceptable catalyst activity. Chain transfer with propylene can best be limited by avoiding excessive temperature during the polymerization as described below.
  • the catalyst components are preferably premixed, that is, reacted to form active catalyst outside of the reactor, to ensure rapid chain initiation. Aging of the premixed catalyst system, that is, the time spent by the catalyst components (e.g., vanadium compound and erg ⁇ noaluminum) in contact with one another outside of the reactor, must be kept within certain limits.
  • the components will not have reacted with each other sufficiently to yield an adequate quantity of active catalyst species, with the result of continued catalyst species formation in the reactor, resulting in non-simultaneour chain initiation. Also, it is known that the activity of the catalyst species will decrease with time so that the aging must be kept below a maximum limit.
  • the minimum aging period depending on such factors as concentration of catalyst components, temperature and mixing equipment, can be as low as about 0.1 second.
  • the maximum aging period is that period of aging after which the catalyst species has been deactivated to the point where it cannot effectively be used in the polymerization process.
  • the aging time will ordinarily be about 0.1 seconds to about 200 seconds or even longer, usually about 0.5 seconds to 100 seconds, preferably about 1 second to 50 seconds.
  • the premixing performed at low temperature such as 40 oC or below. It is preferred that the mixing be performed at 25°C or below, with 15°C or below being most preferred.
  • each catalyst and cocatalyst can be premixed separately.
  • the several pre-mixed streams of catalysts species are then combined and fed to the reactor.
  • the several pre-mixed catalyst feed streams can be fed separately to different points along the reactor.
  • the temperature of the reaction mixture should also be kept with certain limits.
  • the temperature at the reactor inlet should be high enough to provide complete, rapid chain initiation at the start of the polymerization reaction.
  • the length of time the reaction mixture spends at high temperature must be short enought to minimize the amount of undesirable chain transfer and catalyst deactivation reactions.
  • Temperature control of the reaction mixture is complicated somewhat by the fact that the polymerization reaction generates large quantities of heat. This problem is, preferably, taken care of by using prechilled feed to the reactor to absorb the heat of polymerization. With this technique, the reactor is operated adiabatically and the temperature is allowed to increase during the course of polymerization.
  • heat can be removed from the reaction mixture, for example, by a heat exchanger surrounding at least a portion of the reactor or by well-known autorefrigeration techniques in the case of batch reactors or multiple stirred reactors in series.
  • the inlet temperature of the reactor feed can be about -80°C to about 50°C.
  • the outlet temperature of the reaction mixture can be as high as about 200°C.
  • the preferred maximum outlet temperature is about 70°C.
  • the most preferred maximum is about 50°C.
  • the temperature of the reaction mixture will increase from reactor inlet to outlet by an amount dependent upon the heat of polymerization, reaction mixture specific heat and the percent of copolymer in the reaction mixture (weight of copolymer per weight of solvent). For ethylene-propylene copolymerization in hexane the temperature rise is about 13°C per weight percent of copolymer.
  • the preferred maximum copolymer concentration at the reactor outlet when this is the only stream drawn from the reactor is 25 wt/100 wt diluent.
  • the most preferred maximum concentration is 15 wt/100 wt.
  • the blend so formed has a preferred maximum copolymer concentration of about 25 wt./100 wt. of diluent.
  • the most preferred maximum is 15 wt./100 wt. diluent. In the case of either single or multiple product stream withdrawal, there is no lower limit to concentration due to reactor operability, but for economic reasons it.
  • the rate of flow of the reaction mixture through the reactor should be high enough to provide good mixing of the reactants in the radial direction and minimize mixing in the axial direction. Good radial mixing is beneficial to minimize radial temperature gradients due to the heat generated by the polymerization reaction. Radial temperature gradients will tend to broaden the molecular weight distribution of the copolymer since the polymerization rate is faster in the high temperature regions resulting from poor heat dissipation. The artisan will recognize that achievement of these objectives is difficult in the case of highly viscous solutions. This problem can be overcome to some extent through the use of radial mixing devices such as static mixers (e.g., these produced by the Kenics Corporation).
  • Residence time of the reaction mixture in the mix-free reactor can vary over a wide range.
  • the minimum can be .as low as about 1 second.
  • a preferred minimum is about 10 seconds.
  • the most preferred minimum is about 15 seconds.
  • the maximum can be as high as about 3600 seconds.
  • a preferred maximum is about 1800 seconds.
  • the most preferred maximum is about 900 seconds.
  • reference numeral 1 refers to a premixing device for premixing the catalyst components.
  • EPM ethylene and propylene
  • the polymerization is an adiabatic, solution polymerization process using hexane solvent for both the catalyst system and the reaction mixture.
  • the premixing device 1 comprises a temperature control bath 2, a fluid flow conduit 3 and mixing device 4 (e.g., a mixing tee).
  • mixing device 4 e.g., a mixing tee
  • To mixing device 4 are fed hexane solvent, vanadium tetrachloride and ethyl aluminum sesqui chloride through feed conduits 5, 6 and 7, respectively.
  • the resulting catalyst mixture is caused to flow within conduit 3, optionally in the form of a coiled tube, for a time long enough to produce the active catalyst species at the temperature set by the temperature bath.
  • the temperature of the bath is set to give the desired catalyst solution temperature in conduit 3 at the outlet of the bath.
  • the catalyst solution flows through conduit 8 into mixing zone 9 to provide an intimate mixing with hexane solvent and reactants (ethylene and propylene) which are fed through conduit 10.
  • Any suitable mixing device can be used, such as a mechanical mixer, orifice mixer or mixing tee. For economic reasons, the mixing tee is preferred.
  • the residence time of the reaction mixture in mixing zone 9 is kept short enough to prevent significant polymer formation therein before being fed through conduit 11 to tubular reactor 12.
  • streams 8 and 10 can be fed directly to the inlet of reactor 12 if the flow rates are high enough to accomplish the desired level of intimate mixing.
  • the hexane with dissolved monomers may be cooled upstream of mixing zone 9 to provide the desired feed temperature at the reactor inlet.
  • the tubular reactor is shown with optional feed and take off points.
  • the catalyst comprises only a single polymer species one or more take off points, 13, are used to withdraw polymer fractions at different points along the polymerization path.
  • additional solvent may be added to make up the volume of material withdrawn.
  • Additional catalyst and monomer can be introduced through line, 14, or line, 15.
  • the polymer withdrawn through line, 13, is combined with all other fractions withdrawn and collected with the reactor effluent for deashing and finishing.
  • multiple premixing devices, 1, are used.
  • the mixed catalyst can be directed to mixing zone, 9, for mixing with additional catalyst species and monomer or the effluent from the premixing devices can be combined prior to the mixing zone.
  • the molar ratio of VCl 4 /VOCl 3 can be about 0.01 to about 100, more preferably about 0.1 to about 10, most preferably about 0.5 to about 5.
  • the amount of the total polymer and the molecular weight of each component will be determined by the ratio and the feed locations and take off points along the reactor.
  • the molar ratio of alkyl aluminum sesquihalide to vanadium components can be about 1 to about 40, preferably about 2 to about 40, more preferably about 4 to about 20, most preferably about 4 to about 10, e.g., about 5 to about 10.
  • the alkyl group of the sesquihalide is preferably a C 1 -C 6 alkyl group, preferably ethyl.
  • the halide can be bromine, chlorine or iodine, preferably chlorine.
  • the preferred aluminum co-catalyst is ethylaluminum sesquichloride (EASC). In this system the two independent, non-interacting, mutually compatible catalyst systems are VCl 4 /EASC and VOCI 3 /EASC.
  • a Lewis base moderator is incorporated into the catalyst system.
  • the molar ratio of base to vanadium can be about 0 to about 5/1, preferably about 0.5/1 to about 2/1, more preferably about 1/1 to about 1.5/1.
  • Illustrative, non- limiting examples of Lewis bases suitable for use in the practice of this invention are NH 3 , phenol, cyclohexanone, tetrahydrofuran, acetylacetone, ethyl silicate and tri-n-butyl-phosphate.
  • the Lewis base suppresses some long chain branching reactions when EPDM terpolymers are prepared.
  • the polymer derived from the process of this invention is deashed and finished using conventional methods.
  • the polymer streams are preferably blended and a single deashing and finishing process used.
  • the result is a thoroughly mixed, homogeneous polymer blend.
  • each process stream can be finished independently and combined by mechanical mixing.
  • ethylene-alpha-olefin copolymers having polymodal MWD with each molecular weight fraction having very narrow MWD can be made by direct polymerization.
  • narrow MWD copolymers can be made using other known techniques, such as by fractionation or mechanical degradation, these techniques are considered to be impractical to the extent of being unsuitable for commercial-scale operation.
  • EPDM made in accordance with the present invention the products have enhanced cure properties at a given Mooney Viscosity.
  • polymodal molecular weight distribution is achieved by withdrawing polymer fractions from the reactor, it will be evident from reference to this disclosure that it is critical when or where polymer is withdrawn from the reaction zone. This can be determined without undue experimentation.
  • a pilot plant scale tubular reactor can be equipped with a multiplicity of take off points. By running the reactor and withdrawing polymer samples from the system, molecular weight of the polymer at points along the reactor can be determined.
  • a plot By converting the distance along the tube to time of reaction after introduction of catalyst, a plot can be made of molecular weight as a function of reaction time for a given catalyst/monomer/solvent system.
  • the molecular weight/reaction time plot can be used to position take off points.
  • a multiplicity of take off points can be installed, not all of which will be used in preparing a particular product with predetermined specifications.
  • inlet ports can be located at different locations for the introduction of additional mcnomer or catalyst streams.
  • MWD of the polymer will be modified. So long as the polymerization is carried out in this manner the polymer will be a polymodal MWD polymer of narrow MWD modes . Similar results are achieved by introducing fresh premixed catalyst with the additional monomer feed.
  • the polymodal MWD polymers of this invention can be prepared by blending the product of runs prepared under different conditions or using different catalyst. For example, one polymerization can be conducted using VCl 4 /EASC as the catalyst and another conducted using VOCI 3 /EASC as the catalyst. The product of the two runs can then be blended to form a bimodal MWD polymer blend. Other variations can be used to generate polymer species of different M w to prepare polymodal MWD compositions.
  • This example illustrates the method of this invention for preparing an EPM wherein polymer product is removed from the reactor at a point intermediate between the reactor inlet and outlet.
  • the polymerization was conducted in a 3/8 in. diameter tube and the residence time in the reactor was 30 seconds.
  • a take off port was located downstream of the inlet at a distance equivalent to 1 second residence time.
  • Hexane was used as the solvent, VCl 4 as the catalyst, and Al 2 Et 3 Cl 3 as the cocatalyst. Hexane is purified prior to use by passing over 4A molecular sieves (Union Carbide, Linde Div. 4A 1/16" pellets) and silica gel (W.R. Grace Co. , Davidson Chemical Div. , PA-400 20-4 mesh) to remove polar impurities which act as catalyst poisons.
  • 4A molecular sieves Union Carbide, Linde Div. 4A 1/16" pellets
  • silica gel W.R. Grace Co. , Davidson Chemical Div. , PA-400 20-4 mesh
  • Gaseous, ethylene and propylene is passed over hot (270°C) CuO (Harshaw Chemical Co., C01900 1 ⁇ 4" spheres) to remove oxygen followed by molecular sieve treatment for water removal and then combined with hexane upstream of the reactor and passed through a chiller which provided a low enough temperature to completely dissolve the monomers in the hexane.
  • hot 270°C
  • CuO Hardshaw Chemical Co., C01900 1 ⁇ 4" spheres
  • a catalyst solution is prepared by dissolving 18.5 g of vanadium tetrachloride, VCl 4 , in 5.0 1. of purified n-hexane.
  • the cocatalyst consists of 142 g of ethylaluminum sesquichloride, Al 2 Et 3 Cl 3 , in 5.0 1. of purified hexane.
  • the two solutions are premixed at 10°C and aged for 8 seconds. Typical feed rates and reacting conditions are shown in Table I.
  • Example I is repeated except that no effluent is taken from the take off port and two reactors in parallel are used.
  • the feed rates listed in Table 1 are split so that 17 kg./hr are passed through the reactor with one second residence time, and the remaining feed goes to the other reactor.
  • the residence times in these two reactors are 1 and 30 seconds, respectively. Otherwise all conditions are the same as in Example I.
  • the effluents fr ⁇ n the reactor outlets are blended. After steady state is achieved, the blend is deashed, washed and stripped of solvent.
  • the resulting polymer is a bimodal MWD EPM with a theoretical MWD as in Example I.
  • Example III Example III
  • Example I is repeated except that no effluent is taken from the take off port and VOCI 3 /EASC is used as an additional catalyst.
  • the second catalyst solution is prepared by dissolving 18.5g of VOCI 3 in 5.0 1. of purified hexane.
  • the cocatalyst consists of 142g of Al 2 Et 3 Cl 3 in 5.0 1. of purified hexane.
  • the VCl 4 and VOCl 3 are blended with cocatalysts in separate premixing units and aged for ten seconds.
  • the two premixed catalyst streams are then mixed with the monomer/ hexane stream and fed into the reactor. Reactor residence time is 50 seconds. Otherwise all conditions are the same as in Example I. After steady state is achieved, the reactor effluent is deashed, washed and stripped of solvent.
  • the resulting polymer is a bimodal MWD EPM.
  • Example I is repeated except that no effluent is taken from the take off port.
  • the catalyst system used is vanadium oxytrichloride (VOCI 3 ) and diethylaluminum chloride (AlEt 2 Cl). Otherwise all conditions are the same as in Example I.
  • This catalyst system produces at least two independent catalyst species, each of which initiates a separate MWD mode. After steady state is achieved, the reactor effluent is deashed, washed and stripped of solvent. The resulting polymer is a polymodal MWD EPM.
  • Example V Example I is repeated except that no take off port effluent is collected and the catalyst and feed streams are split. About 2/3 of the monomer/hexane stream and 2/3 of the premixed catalyst are mixed and fed to the reactor inlet and the remaining 1/3 of the monomer/hexane feed is mixed with the remaining catalyst stream and fed into the reactor at a point midway between the reactor inlet and outlet.
  • the EPM product is a polymodal MWD polymer.
  • Example I is repeated except that no effluent is taken from the take off port and a catalyst reactivator is used.
  • the catalyst reactivator solution is prepared by dissolving 30.5g of butyl perchlorocrotonate in 3.0 1 of purified hexane. This solution is fed into the reactor, at 3.6 g/hr along with 50 g/hr of ethylene, at a point midway between the reactor inlet and outlet. Otherwise all conditions are the same as in Example I. After steady state is achieved, the effluent is deashed, washed and stripped of solvent. The resulting product is a polymodal MWD EPM.
  • blends being made by combining product or reaction mixtures withdrawn from the reactor at one or more times after the start of polymerization with product from the "reactor outlet” or “completion of polymerization” this language is intended to include the last product or reaction mixture withdrawn from the reactor for the purpose of forming the blend whether or not the last product or reaction mixture is obtained from the physical reactor outlet or at the actual completion of polymerization, notwithstanding the fact that product from the actual reactor outlet or actual completion of polymerization is used for some purpose other than blending with fractions of polymer withdrawn.

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Abstract

Des copolymères nouveaux d'alpha-oléfines comprennent des substances copolymères hétérogènes au niveau intramoléculaire et homogènes au niveau intermoléculaire préparées par un procédé schématiquement illustré dans la Fig. 1.
EP19860900540 1984-12-14 1985-12-16 Modification de la distribution des poids moleculaires dans un reacteur tubulaire. Withdrawn EP0204840A4 (fr)

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US6610408B1 (en) 1996-11-08 2003-08-26 Solvay Engineered Polymers TPO blends containing multimodal elastomers
US6403520B1 (en) 1999-09-17 2002-06-11 Saudi Basic Industries Corporation Catalyst compositions for polymerizing olefins to multimodal molecular weight distribution polymer, processes for production and use of the catalyst
EP3715385B1 (fr) 2019-03-26 2024-01-31 SABIC Global Technologies B.V. Catalyseur d'oxyde de chrome destiné à la polymérisation de l'éthylène

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See also references of WO8603756A1 *

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KR870700641A (ko) 1987-12-30
CA1272846A (fr) 1990-08-14
EP0204840A1 (fr) 1986-12-17
JPS62501155A (ja) 1987-05-07
AU5301086A (en) 1986-07-22
KR900008459B1 (ko) 1990-11-22
AU579446B2 (en) 1988-11-24
WO1986003756A1 (fr) 1986-07-03

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