Polymerization initiating system and method to produce highly reactive olefin functional polymers

Abstract

A method for producing highly reactive olefin polymers wherein at least 50 mol % of the polymer chains have terminal double bonds, and a novel polymerization initiating system for accomplishing the same includes contacting isobutene or an isobutene-containing monomer mixture, wherein a Lewis acid catalyst is complexed with an oxygen and/or sulfur-containing Lewis base, in an apolar solvent, and wherein an initiator is employed to initiate polymerization of the isobutene or isobutene-containing monomer mixture.

Claims

1. A process for the preparation of polybutene having an exo-olefin content of at least 50 mol %, which process comprises contacting isobutene or an isobutene-containing monomer mixture, with a Lewis acid catalyst complexed with a Lewis base, in an apolar polymerization medium, and initiating polymerization of said isobutene or an isobutene-containing monomer mixture with an initiator, wherein said Lewis acid catalyst is a Lewis acid of the formula MR″.sub.mY.sub.n, wherein M is a metal selected from Al, Fe, Ga, Hf, Zr or W; R″ is a hydrocarbyl group; Y is halogen; m is 0 or an integer of 1 to 5; and n is an integer of 1 to 6, with the proviso that m+n is equal to the valency of metal M; said Lewis base is dihydrocarbyl ether, wherein each ether hydrocarbyl group is independently selected from C.sub.1 to C.sub.8 hydrocarbyl, wherein one or each of said ether hydrocarbyl groups are substituted with an electron-withdrawing group; the initiator is HCl, H.sub.2O or a compound of the formula ROH, wherein R is a hydrocarbyl group capable of forming a stable carbocation and wherein the carbon linking group R to the hydroxyl group is tertiary or benzylic.

2. The process of claim 1, wherein M is Al or Fe, and R″ is a C.sub.1 to C.sub.8 alkyl group.

3. The process of claim 1, wherein m is 0 or 1.

4. The process of claim 1, wherein Y is Cl or Br.

5. The process of claim 1, wherein one or each of said ether hydrocarbyl groups are substituted with said electron-withdrawing group on a carbon atom other than the carbon atom adjacent to the oxygen atom of the ether group.

6. The process of claim 1, wherein said ether hydrocarbyl groups are alkyl groups.

7. The process of claim 5, wherein said ether hydrocarbyl groups are C.sub.1 to C.sub.4 alkyl groups.

8. The process of claim 1, wherein said electron-withdrawing group is a halogen atom.

9. The process of claim 7, wherein said electron-withdrawing group is a chlorine atom.

10. The process of claim 6, wherein said electron-withdrawing group is a halogen atom.

11. The process of claim 10, wherein said electron-withdrawing group is a chlorine atom.

12. The process of claim 1, wherein said apolar polymerization medium is selected from saturated C.sub.4 hydrocarbons, unsaturated C.sub.4 hydrocarbons, and mixtures thereof.

13. The process of claim 1, wherein said isobutene or an isobutene-containing monomer mixture is selected from pure isobutene; a C.sub.4 refinery cut containing between about 5% and about 50% butene-1, between about 2% and about 40% butene-2, between about 2% and about 60% iso-butane, between about 2% and about 20% n-butane, and up to about 0.5% butadiene, wherein all percentages are by mass, based on the total mass of the C.sub.4 refinery cut; or mixtures of pure isobutene and said C.sub.4 refinery cut.

14. The process of claim 1, wherein said complex is contacted with said isobutene or an isobutene-containing monomer at a concentration of millimoles of Lewis acid-Lewis base complex per liter of medium of from about 1 mM to about 200 mM.

15. The process of claim 1, wherein said Lewis acid and said Lewis base are complexed by dissolving the Lewis acid in solvent to form a solution, and then adding said Lewis base to said solution.

16. The process of claim 1, wherein the polymerization process is conducted continuously.

17. The process of claim 1, wherein said polybutene product has an exo-olefin content of at least 70 mol %.

18. The process of claim 1, wherein said initiator is introduced into the reaction mixture separate from the catalyst complex.

19. A catalyst-initiator system for catalyzing the polymerization of isobutene or an isobutene-containing monomer mixture in a substantially or completely apolar solvent to provide a polybutene product having an exo-olefin content of at least 50 mol. %, wherein said catalyst comprises a Lewis acid catalyst complexed with a Lewis base, wherein said Lewis acid catalyst is a Lewis acid of the formula M″.sub.mY.sub.n, wherein M is a metal selected from Al, Fe, Ga, Hf, Zr or W; R″ is a hydrocarbyl group; Y is halogen; m is 0 or an integer of 1 to 5; and n is an integer of 1 to 6, with the proviso that m+n is equal to the valency of metal M; said Lewis base is dihydrocarbyl ether, wherein each ether hydrocarbyl group is independently selected from C.sub.1 to C.sub.8 hydrocarbyl, wherein one or each of said ether hydrocarbyl groups are substituted with an electron-withdrawing group; and the polymerization is initiated via an initiator, wherein the initiator is HCl, H.sub.2O or a compound of the formula ROH, wherein R is a hydrocarbyl group capable of forming a stable carbocation and wherein the carbon linking group R to the hydroxyl group is tertiary or benzylic, and wherein said initiator is introduced into the reaction mixture separate from, and subsequent to the introduction of, the catalyst complex.

20. The catalyst-initiator system of claim 19, wherein M is Al or Fe, and R″ is a C.sub.1 to C.sub.8 alkyl group.

21. The catalyst-initiator system of claim 19, wherein m is 0 or 1.

22. The catalyst-initiator system of claim 19, wherein Y is Cl or Br.

23. The catalyst-initiator system of claim 19, wherein one or each of said ether hydrocarbyl groups are substituted with said electron-withdrawing group on a carbon atom other than the carbon atom adjacent to the oxygen atom of the ether group.

24. The catalyst-initiator system of claim 19, wherein said ether hydrocarbyl groups are alkyl groups.

25. The catalyst-initiator system of claim 23, wherein said ether hydrocarbyl groups are C.sub.1 to C.sub.4 alkyl groups.

26. The catalyst-initiator system of claim 19, wherein said electron-withdrawing group is a halogen atom.

27. The catalyst-initiator system of claim 25, wherein said electron-withdrawing group is a chlorine atom.

28. The catalyst-initiator system of claim 23, wherein said electron-withdrawing group is a halogen atom.

29. The catalyst-initiator system of claim 27, wherein said electron-withdrawing group is a chlorine atom.

30. The catalyst-initiator system of claim 19, wherein said Lewis acid and said Lewis base are complexed by dissolving the Lewis acid in solvent to form a solution, and then adding said Lewis base to said solution.

31. The catalyst-initiator system of claim 19, wherein said initiator is introduced into the reaction mixture separate from the catalyst complex.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) A description of example embodiments of the invention follows.

(2) Lewis acid catalysts useful in the practice of the present invention can be represented by the general formula (MR″.sub.mY.sub.n), wherein M is selected from Al, Fe, Ga, Hf, Zr and W; preferably Al, Ga or Fe, more preferably Al or Fe; R″ is a hydrocarbyl group, preferably a C.sub.1 to C.sub.8 hydrocarbyl group, more preferably a C.sub.1 to C.sub.8 alkyl group; m is 0 or an integer of 1 to 5, preferably 0 or 1, more preferably 0; Y is halogen (F, Cl, Br), preferably either Cl or Br, more preferably Cl, and n is an integer of 1 to 6, preferably 3 to 5; with the proviso that m+n is equal to the valency of M. As used herein, the term “hydrocarbyl” means a chemical group of a compound that contains hydrogen and carbon atoms and that is bonded to the remainder of the compound directly via a carbon atom. The group may contain one or more atoms other than carbon and hydrogen (“hetero atoms”), provided they do not affect the essentially hydrocarbyl nature of the group.

(3) The Lewis base (B) is dihydrocarbyl ether, wherein each hydrocarbyl group is independently selected from C.sub.1 to C.sub.8 hydrocarbyl. The hydrocarbyl groups of the above Lewis bases are preferably alkyl groups. The hydrocarbyl groups of the ether may be branched, straight chained or cyclic. Where the hydrocarbyl groups of the ether are branched or straight chained, the hydrocarbyl groups are preferably alkyl groups, more preferably C.sub.1 to C.sub.4 alkyl. One or each of the hydrocarbyl groups of the dihydrocarbyl ether Lewis base is substituted with an electron-withdrawing group, particularly a halogen atom, preferably chlorine. Preferably, the ether hydrocarbyl groups are substituted with the electron-withdrawing group on a carbon atom other than the carbon atom adjacent to the oxygen atom of the ether group. Preferred chlorinated dialkyl ethers include 2-chloroethyl ethyl ether, bis-(2-chloroethyl) ether and bis-(2-chloro methyl ethyl) ether.

(4) An “initiator” is defined as a compound that can initiate polymerization, in the presence or absence of adventitious water and in the presence of a proton trap. The initiator of the present invention is HCl, H.sub.2O or a compound of the formula ROH, wherein R is a hydrocarbyl group capable of forming a stable carbocation and wherein the carbon linking group R to the hydroxyl group is tertiary or benzylic. In one preferred embodiment of the invention, the initiator is HCl. In another preferred embodiment of the invention, the initiator is a compound of formula ROH. In yet another preferred embodiment of the invention, the initiator is H.sub.2O.

(5) The polymerization medium must be a substantially or completely apolar medium, such as a mixture of hexanes or saturated and unsaturated C.sub.4 hydrocarbons.

(6) In the polymerization process of the present invention, the feedstock may be pure isobutylene or a mixed C.sub.4 hydrocarbyl feedstock containing isobutylene, such as a C.sub.4 cut resulting from the thermal or catalytic cracking operation of, for example, naphtha. Thus, suitable feedstocks will typically contain at least 10%, and up to 100% isobutylene, by mass, based on the total mass of the feed. In addition to isobutylene, conventional C.sub.4 cuts suitable for use as feedstocks that are of industrial importance typically will contain between about 5% and about 50% butene-1, between about 2% and about 40% butene-2, between about 2% and about 60% iso-butane, between about 2% and about 20% n-butane, and up to about 0.5% butadiene, all percentages being by mass, based on the total feed mass. Feedstocks containing isobutylene may also contain other non-C.sub.4 polymerizable olefin monomers in minor amounts, e.g., typically less than 25%, preferably less than about 10%, and most preferably less than 5%, such as propadiene, propylene and C.sub.5 olefins. The C.sub.4 cut may be purified by conventional means to remove water, polar impurities and dienes.

(7) The term “polybutene”, as employed herein is intended to include not only homopolymers of isobutylene, but also copolymers of isobutylene and one or more other C.sub.4 polymerizable monomers of conventional C.sub.4 cuts as well as non-C.sub.4 ethylenically unsaturated olefin monomers containing 5 carbon atoms, provided such copolymers contain typically at least 50 mass %, preferably at least 65 mass %, and most preferably at least 80 mass % isobutylene units, based on the polymer number average molecular weight (Me).

(8) The Lewis acid and Lewis base can be complexed by, for example, dissolving the Lewis acid in a solvent (e.g., dichloromethane or 1, 2-dichloroethane) to form a solution and then adding the Lewis base to the solution, while the solution is stirred. The complex may be added to the polymerization medium with the solvent; alternatively, the solvent may be removed prior to the addition of the complex to the polymerization medium.

(9) The molar ratio of Lewis acid to Lewis base in the complex will typically be maintained within a range of from about 1:0.5 to about 1:2, preferably from about 1:0.7 to about 1:1.5, more preferably from about 1:0.9 to about 1:1.4, such as from about 1:1 to about 1:1.3.

(10) The amount of the Lewis acid-Lewis base complex employed in the process of the present invention can be controlled, in conjunction with the concentration of initiator and monomer, reaction time and temperature, to achieve the target M.sub.n of the polybutene polymer product, the conversion of butene and yield of polybutene. In view of the above, the Lewis acid-Lewis base complex is typically employed in an amount sufficient to contact the butene monomer in a liquid phase reaction mixture at a concentration of millimoles of Lewis acid-Lewis base complex per liter of reaction mixture of from about 1 mM to about 200 mM, preferably from about 5 mM to about 100 mM, and more preferably from about 10 mM to about 50 mM, such as from about 10 mM to about 30 mM.

(11) The initiator will typically be employed in an amount sufficient to contact the butene monomer in a liquid phase reaction mixture at a concentration of millimoles of initiator per liter of medium, and independent from the amount of Lewis acid-Lewis base complex, of from about 1 mM to about 200 mM, preferably from about 5 mM to about 100 mM, and more preferably from about 10 mM to about 50 mM, such as from about 10 mM to about 30 mM.

(12) The polymerization reaction can be conducted batch-wise, semi-continuously, or continuously. On an industrial scale, the polymerization reaction is preferably conducted continuously. Conventional reactors, such as tubular reactors, tube-bundle reactors or loop reactors, or tube or tube-bundle reactors with continuous circulation of the reaction material, may be used.

(13) The polymerization reaction is conducted in the liquid phase to induce linear or chain-type polymerization, as opposed to ring or branch formation. Thus, if a feed is used that is gaseous under ambient temperature, it is preferred to control the reaction pressure and/or dissolve the feed in an inert solvent or liquid diluent, in order to maintain the feed in the liquid phase. Typical C.sub.4 cuts comprising the feed are liquid under pressure and do not require a solvent or diluent. Typical diluents suitable for use with the process include C.sub.3 to C.sub.6 alkanes, such as propane, butane, pentane or isobutane like.

(14) The Lewis acid-Lewis base complex is typically introduced into the reactor as a liquid partially or completely dissolved in a solvent, or as a solid. Polymerization is preferably conducted at a pressure sufficient to maintain the C.sub.4 feed in a liquid state at the reaction temperature, or at higher pressures. The initiator may be introduced to the monomer feed or the reaction mixture in liquid form by a line separate from the Lewis acid-Lewis base complex addition line. In the process of the present invention, the initiator is preferably introduced into the reaction mixture (feedstock) separate from the catalyst complex.

(15) The liquid phase reaction mixture temperature is controlled by conventional means to be typically from about −30° C. to about +50° C., preferably from about −10° C. to about +30° C., more preferably from 0° C. to about +20° C., or from 0° C. to about +10° C.

(16) The residence time of the butene to be polymerized may be from about 5 seconds to several hours, but will typically be from about 1 to about 300 minutes, such as 2 to about 120 minutes, preferably from about 5 to about 60 minutes.

(17) In order to insure even distribution of the catalyst within the reactor, turbulent flow of the reactor contents can be generated by mixing, or with suitable baffles, such as baffle plates or oscillating baffles, or by dimensioning the reactor tube cross sections so that a suitable flow velocity is established. Preferably, the reactor will be constructed such that no surface that contacts the Lewis acid-Lewis base complex is constructed of a material other than stainless steel, as it is believed that contact with stainless steel may cause the partial deactivation of the catalyst.

(18) The process of the present invention is typically conducted in a manner achieving an isobutylene conversion in the range of from about 20% up to about 100%, preferably from about 50% to about 100%, and more preferably from about 70% to about 100%. The combined use of temperature control and catalyst feed rate permits formation of polybutenes having a M.sub.n of from about 400 Daltons to about 4000 Daltons, preferably from about 700 Daltons to about 3000 Daltons, more preferably from about 1000 Daltons to about 2500 Daltons; a molecular weight distribution (MWD) of typically from about 1.1 to about 4.0, preferably from about 1.5 to about 3.0, an exo-olefin content of greater than 50 mol. %, preferably greater than 60 mol. %, more preferably greater than 70 mol. %, such as from about 80 mol. % to about 95 mol. %; a tetrasubstituted olefin content of less than about 20 mol. %, such as less than about 15 mol. %, preferably less than about 10 mol. %, more preferably less than about 5 mol. %; and a chlorine content of less than about 10 mol. %, such as less than about 5 mol. %, preferably less than about 2 mol. %, more preferably less than about 1 mol. %, based on the total moles of polymer.

(19) Once the target molecular weight of the polymer is achieved, the polymer product can be discharged from the reactor and passed into a medium that deactivates the polymerization catalyst and terminates the polymerization. Suitable deactivation media include water, amines, alcohols and caustics. The polyisobutylene product can then be separated by distilling off the remaining C.sub.4 hydrocarbons and low molecular weight oligomers. Preferably residual amounts of catalyst are removed, usually by washing with water or caustic.

(20) This invention will be further understood by reference to the following examples, which are not intended, and should not be construed as listing all possible embodiments within the scope of the invention.

EXAMPLES

(21) Polymerization

(22) Polymerizations were carried out under a dry nitrogen atmosphere in an MBraun 150-M glove box (Innovative Technology Inc., Newburyport, Mass.) Isobutene (IB) was condensed and distributed to the polymerization reactors, screw top culture tubes (75 ml) at −30° C. Polymerizations were conducted in hexanes initiated with H.sub.2O or HCl and co-initiated with the appropriate ethyl aluminum dichloride (EtAlCl.sub.2 or “EADC”) concentration with a monomer concentration of 1 M, at 0° C. The initiator was added to the reaction mixture subsequent to the addition of the catalyst complex. After a predetermined time, polymerization was terminated by addition of 0.2 mL methanol. The polymer was recovered and purified by re-precipitation from NH.sub.4OH solution. Conversions were determined by gravimetric analysis.

(23) Preparation of Lewis Acid (La/Ether Complexes)

(24) EADC*bis-(2-chloroethyl) ether (CEE) complexes were prepared at room temperature just before the polymerization of IB. In a glovebox, the required amount of CEE was added to EADC solution in toluene and stirred to form a 1.0 M Lewis acid/CEE complex, followed by dilution with hexanes to make a 0.5 M solution.

(25) Characterization

(26) Number average molecular weights (M.sub.n) of the polymers were obtained from size exclusion chromatography with universal calibration using a Waters 717 Plus autosampler, a 515 HPLC pump, a 2410 differential refractometer, a 2487 UV-VIS detector, a MiniDawn multi angle laser light scattering (MALLS) detector (measurement angles of 44.7°, 90.0°, and 135.4°) from Wyatt Technology Inc, ViscoStar viscosity detector from Wyatt Technology Inc., and five Ultrastyragel GPC columns connected in the following order: 500, 10.sup.3, 10.sup.4, 10.sup.5 and 100 Å. Refractive index (RI) was the concentration detector. Tetrahydrofuran was used as the eluent at a flow rate of 1.0 ml/min at room temperature. The results were processed by Astra 5.4 software from Wyatt Technology Inc.

(27) Nuclear Magnetic Resonance

(28) Proton nuclear magnetic resonance (.sup.1H NMR) spectra were recorded on a Bruker 500 MHz spectrometer using CDCl.sup.3 as solvent (Cambridge Isotope Laboratory, Inc.). The polyisobutene (PIB) end group content was determined by .sup.1H NMR as previously reported (see Kumar, R.; Dimitrov, P.; Bartelson, K. J.; Faust, R., Macromolecules 2012, 45, 8598-8603).

(29) Results

(30) TABLE-US-00001 TABLE 1 Polymerization of IB in hexanes at 0° C. initiated by H.sub.2O and coinitiated by EADC•CEE. (IB) = 1.0M, (H.sub.2O) = 0.01M and (EADC) = 0.01M. Quenched with MeOH. Entry EADC:CEE Time Conv..sup.a M.sub.n NMR Exo.sup.b Endo + Tri.sup.b Tetra.sup.b # ratio (min.) (%) g/mol (%) (%) (%) 1 1:1.sup.  10 34 1800 77 12 11 2 1:1.sup.  20 56 1540 76 12 12 3 1:1.sup.  40 69 1400 74 13 13 4 1:1.sup.  60 86 1460 74 13 13 5 1:1.5 10 27 1800 80 7 13 6 1:1.5 20 47 1400 83 8 9 7 1:1.5 40 71 1000 81 8 11 8 1:1.5 60 78 1000 83 9 8 .sup.aGravimetric conversion. .sup.bDetermined by .sup.1H NMR spectroscopy.

(31) TABLE-US-00002 TABLE 2 Polymerization of IB in hexanes at 0° C. initiated by HCl and coinitiated by EADC•CEE. (IB) = 1.0M, (HCl) = 0.01M (EADC) = 0.01M and (CEE) = 0.01M. Quenched with MeOH. Entry EADC:CEE Time Conv..sup.a M.sub.n NMR Exo.sup.b Endo + Tri.sup.b Tetra.sup.b # ratio (min.) (%) g/mol (%) (%) (%) 9 1:1 2 22 2500 64 15 21 10 1:1 5 25 2100 63 17 20 11 1:1 10 49 1800 67 18 15 12 1:1 20 83 1300 73 15 12 13 1:1 30 85 1400 72 17 11 .sup.aGravimetric conversion. .sup.bDetermined by .sup.1H NMR spectroscopy.

(32) While certain representative embodiments and details have been provided to illustrate the invention, it will be apparent to the skilled artisan that various product and process changes from those disclosed herein may be made without departing from the scope of the present invention. The appended claims define the scope of the invention

(33) All cited patents, test procedures, priority documents, and other cited documents are fully incorporated by reference to the extent that such material is consistent with this specification and for all jurisdictions in which such incorporation by reference is permitted.

(34) Certain features of the present invention are described in terms of a set of numerical upper limits and a set of numerical lower limits. This specification discloses all ranges formed by any combination of these limits. It is to be understood that the upper limits and lower limits, as well as range and ratio limits set forth herein may be independently combined, and that all combinations of these limits are within the scope of the invention unless otherwise indicated.

(35) The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.

(36) While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.