CA1054154A - Tetra(neophyl) zirconium and its use in process for the polymerization of olefins - Google Patents
Tetra(neophyl) zirconium and its use in process for the polymerization of olefinsInfo
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- CA1054154A CA1054154A CA306,718A CA306718A CA1054154A CA 1054154 A CA1054154 A CA 1054154A CA 306718 A CA306718 A CA 306718A CA 1054154 A CA1054154 A CA 1054154A
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Abstract
Abstract of the Disclosure There are disclosed olefin polymerization catalysts based on tetra(neophyl) zirconium and its reac-tion products with surrace-hydroxylated oxides of metals of Groups II(a), III(a), IV(a) and IV(b) of the Periodic Table of the Elements, processes for their preparation, and processes for the polymerization of olefinic monomers em-ploying such catalysts. Neophyl zirconium aluminate supported on alumina is disclosed as the preferred, most active catalyst.
Description
1~)54~LS4 t I. BACKGROUND 0~ ~HE INVENTI~N
1. Field of the Invention This invention relates to an improved process for the polymerization of olefins to provide linear polymers and copolymers, said process employing an improved catalyst comprising tetra(neophyl) zirconium, or its reaction pro-ducts with metal oxides, for use therein. More specifically, the metal oxide can be an oxide selected from a metal o~
Groups II(a), III(a), IV(a), or IV(b) of the Bohr Periodic Table of the Elements. -~
1. Field of the Invention This invention relates to an improved process for the polymerization of olefins to provide linear polymers and copolymers, said process employing an improved catalyst comprising tetra(neophyl) zirconium, or its reaction pro-ducts with metal oxides, for use therein. More specifically, the metal oxide can be an oxide selected from a metal o~
Groups II(a), III(a), IV(a), or IV(b) of the Bohr Periodic Table of the Elements. -~
2. Prior Art In 1954 and 19~5 pioneering advances in olefin polymerization catalysts were disclosed by Karl Ziegler and associates at the r~ax-Planck Institute for Coal Research in MUlheim, Germany, and by Arthur Anderson and associates in the laboratories of E. I. du Pont de Nemours and Company in Wilmington, Delaware. These new catalyst systems, now frequently termed coordirlation catalysts, were based on transition metal salts (e.g. titanium, zirconium or vanadium halides) which had been converted into reduced valence states by reaction with a variety of alkylating or arylating substances, usually simple organo-metallic compounds of a metal of Groups I, II or III of the Periodic Table of Elements (the Bohr long form).
More recently some more stable organometallic transition metal complexes, usually including a halide ~ -anionic ligand or a neutral Lewis Base ligand, have been disclosed in a number of patents. Illustrative are U.S. -Patents 3,681,317, 3,740,384, 3,738,944 and British Patent 1,314,828 which involve tetra(benzyl)-transition metal lOS~lS4 ':
compounds (e.g. tetra(benzyl) zirconium) complexed with anionic ligands (e.g. halide) and/or neutral ligands (e.g.
pyridine) as ethylene polymerization catalysts. In certain cases the reaction products of tetra(benzyl)-zirconium compounds with inorganic oxides free of absorbed water but containing surface HO- groups are disclosed as catalysts for the polymerization of olefinic hydrocarbons. Reason-able thermal stability is achieved with these substances.
They apparently yield high molecular weight polyethylene but the polymerization rate and efficiency and polymer yield obtained with those catalysts in processes for the polymerization of ethylene are generally not as good as with classical coordination catalysts.
II. SUM~ARY OF THE INVENTION
There has been discovered a catalyst system for the polymerization of olefins in hyd~ocarbon medium which comprises a solution in inert hydrocarbon solvent of tetra(neophyl) zirconium or, preferably, a suspension of a metal oxide of a metal of Groups II(a), III(a), IV(a) or IV(b), preferably alumina, having chemically bonded onto its surfaces neophyl zirconium metallate prepared, prior to contacting with an olefin monomer, by reacting a hydro-carbon solution of a tetra(neophyl) zirconium with a sus-pension in hydrocarbon medium of a surface hydrated metal ~-oxide free from any merely absorbed H2O. Representative examples of suitable oxides are A12O3, ~iO2, SiO2, MgO, coprecipitated A12O3.ZrO2 and coprecipitated SiO2.A12O3, in each case having a surface area in the range of 10-500 m2/g, as measured by N2 adsorption. Preferred and especially active metal oxide supports have been prepared
More recently some more stable organometallic transition metal complexes, usually including a halide ~ -anionic ligand or a neutral Lewis Base ligand, have been disclosed in a number of patents. Illustrative are U.S. -Patents 3,681,317, 3,740,384, 3,738,944 and British Patent 1,314,828 which involve tetra(benzyl)-transition metal lOS~lS4 ':
compounds (e.g. tetra(benzyl) zirconium) complexed with anionic ligands (e.g. halide) and/or neutral ligands (e.g.
pyridine) as ethylene polymerization catalysts. In certain cases the reaction products of tetra(benzyl)-zirconium compounds with inorganic oxides free of absorbed water but containing surface HO- groups are disclosed as catalysts for the polymerization of olefinic hydrocarbons. Reason-able thermal stability is achieved with these substances.
They apparently yield high molecular weight polyethylene but the polymerization rate and efficiency and polymer yield obtained with those catalysts in processes for the polymerization of ethylene are generally not as good as with classical coordination catalysts.
II. SUM~ARY OF THE INVENTION
There has been discovered a catalyst system for the polymerization of olefins in hyd~ocarbon medium which comprises a solution in inert hydrocarbon solvent of tetra(neophyl) zirconium or, preferably, a suspension of a metal oxide of a metal of Groups II(a), III(a), IV(a) or IV(b), preferably alumina, having chemically bonded onto its surfaces neophyl zirconium metallate prepared, prior to contacting with an olefin monomer, by reacting a hydro-carbon solution of a tetra(neophyl) zirconium with a sus-pension in hydrocarbon medium of a surface hydrated metal ~-oxide free from any merely absorbed H2O. Representative examples of suitable oxides are A12O3, ~iO2, SiO2, MgO, coprecipitated A12O3.ZrO2 and coprecipitated SiO2.A12O3, in each case having a surface area in the range of 10-500 m2/g, as measured by N2 adsorption. Preferred and especially active metal oxide supports have been prepared
3 --t lOS4154 from fumed aluminas, such as those sold by ~egussa ("Alumina C") and Cabot Corporation ("Alon~ G").
III. DESCRIPTION OF THE DRAWINGS
Figure I is a schematic drawing of the continuous i olefin polymerization process of this invention which ln- -: cludes the preparation of the catalyst, injection of the .. catalyst into the polymerizer and continuous recovery of polyolefin therefrom.
Figure II-A shows the nuclear magnetic resonance spectrum (60MC) of tetra(neophyl) zirconium. On Figure II-A, the absorption peak due to the methylene protons is indicated at (1), that due to the methyl protons at (2)~
and that due to protons on the aromatic ring at (3); these protons can be identified by reference to the chemical formula:
2) (3) (3) -Zr ~ Cl (3) (3) ~~ 4 (2) -In Figure II-B there is shown for comparison the NMR spectrum obtained in the same manner, of tetra. ~-(benzyl) zirconium.
(2) (3) ~:
Zr ~ C112~ H (3) (1)' H H
- (2) (3) - 4 .
` lOS~154 On Figure II-B the absorPtion due to the methylene protons is again shown at (l); there are, of course, no methyl pro- -tons, but two bands for the protons on the aromatic ring are seen at (2) and (3) corresponding to protons at posi-tions indicated by (2) and (3) on the above formula.
IV. DESCRIPTION OF PREFERRE~ EMBODIMENTS
It has been discovered that in order to obtain the most active catalyst of this invention, it is preferred to modify the crystalline form of the alumina and control the extent of hydration on its surfaces prior to reaction with tetra(neophyl) zirconium by activating the alumina by heat treatment under a flow of an inert anhydrous gas (e.g.
N2) at a temperature in the range of 900 to 1100C. for 1 to 10 hours followed by hydration to the extent of 3% to 5% by contact with an atmosphere containing water vapor followed by dehydration by heating at 300 to 500C. for 1 to 10 hours to provide an alumina containing 0.5% to 1.5%
water as HO- groups on the surfaces of the alumina. The preferred catalyst, neophyl zirconium aluminate, bonded onto the surfaces of the alumina, is then prepared by contacting a suspension of the hydrated alumina in anhydrous inert hydrocarbon medium with from 0.05 to 0.6, preferably 0.15 to 0.35, millimoles of tetra(neophyl) zirconium, dissolved in any anhydrous inert hydrocarbon solvent, per gram of suspended A12O3 at 0 to 100C. until the reaction is complete~ ` ' It has been found that the reaction product of ; tetra(neophyl) zirconium with a hydrated metal oxide tends to undergo spontaneous transformation, particularly at temperatures of 50 to 100C. and above, to thermally ~O5~lS~
` stable, lower valence states in which the zirconium is present at least in part at a valence of three. However, such prior transformation is not necessRry if the catalyst is to be employed in polymerization processes conducted at temperatures above 100C.
The polymerization of olefins with the catalysts of this invention can be conducted at temperatures in the range of 10 to 300C. at pressures varying, with tempera-ture, from atmospheric to 1000 atmospheres or above, the pressure being selected high enough to keep the monomers in solution. For ethylene polymerization of a slurry type, temperatures in the range of 10 to 110C. are suitable.
For the solution polymerization of ethyleneJ which is pre-ferred, temperatures can range from 125C to 300C, but pre-ferred temperatures are in the range of 130 to 270C. Any inert hydrocarbon can be employed as a polymerization medium. -Suitable classes include n-alkanes, cycloalkanes and aromatic hydrocarbons, representative example being propane, n-hexane, cyclohexane, n~heptane, and toluene. Hydrogen can be added to the polymerization zone to control and limit the molecular weight of the polyolefin produced.
Tetra(neophyl) zirconium, otherwise identified as tetra kis(2-methyl, 2-phenylpropyl) zirconium, can be pre-pared by the reaction of a zirconium tetrahalide, preferably ZrC14, with an organometallic compound of a metal ~f Groups I, II or III of the Periodic Table of the Elements accord- -ing to Bohr (see T. Moeller, "Inorganic Chemistry", p. 122) in which the organic radicals attached to the metal are neophyl radicals. A convenient method of preparation is the reaction of an ethereal solution of the neophyl . .
lOS4154 Grignard reagent ~ith ZrC14 according to the following reaction:
CH3 r CH3
III. DESCRIPTION OF THE DRAWINGS
Figure I is a schematic drawing of the continuous i olefin polymerization process of this invention which ln- -: cludes the preparation of the catalyst, injection of the .. catalyst into the polymerizer and continuous recovery of polyolefin therefrom.
Figure II-A shows the nuclear magnetic resonance spectrum (60MC) of tetra(neophyl) zirconium. On Figure II-A, the absorption peak due to the methylene protons is indicated at (1), that due to the methyl protons at (2)~
and that due to protons on the aromatic ring at (3); these protons can be identified by reference to the chemical formula:
2) (3) (3) -Zr ~ Cl (3) (3) ~~ 4 (2) -In Figure II-B there is shown for comparison the NMR spectrum obtained in the same manner, of tetra. ~-(benzyl) zirconium.
(2) (3) ~:
Zr ~ C112~ H (3) (1)' H H
- (2) (3) - 4 .
` lOS~154 On Figure II-B the absorPtion due to the methylene protons is again shown at (l); there are, of course, no methyl pro- -tons, but two bands for the protons on the aromatic ring are seen at (2) and (3) corresponding to protons at posi-tions indicated by (2) and (3) on the above formula.
IV. DESCRIPTION OF PREFERRE~ EMBODIMENTS
It has been discovered that in order to obtain the most active catalyst of this invention, it is preferred to modify the crystalline form of the alumina and control the extent of hydration on its surfaces prior to reaction with tetra(neophyl) zirconium by activating the alumina by heat treatment under a flow of an inert anhydrous gas (e.g.
N2) at a temperature in the range of 900 to 1100C. for 1 to 10 hours followed by hydration to the extent of 3% to 5% by contact with an atmosphere containing water vapor followed by dehydration by heating at 300 to 500C. for 1 to 10 hours to provide an alumina containing 0.5% to 1.5%
water as HO- groups on the surfaces of the alumina. The preferred catalyst, neophyl zirconium aluminate, bonded onto the surfaces of the alumina, is then prepared by contacting a suspension of the hydrated alumina in anhydrous inert hydrocarbon medium with from 0.05 to 0.6, preferably 0.15 to 0.35, millimoles of tetra(neophyl) zirconium, dissolved in any anhydrous inert hydrocarbon solvent, per gram of suspended A12O3 at 0 to 100C. until the reaction is complete~ ` ' It has been found that the reaction product of ; tetra(neophyl) zirconium with a hydrated metal oxide tends to undergo spontaneous transformation, particularly at temperatures of 50 to 100C. and above, to thermally ~O5~lS~
` stable, lower valence states in which the zirconium is present at least in part at a valence of three. However, such prior transformation is not necessRry if the catalyst is to be employed in polymerization processes conducted at temperatures above 100C.
The polymerization of olefins with the catalysts of this invention can be conducted at temperatures in the range of 10 to 300C. at pressures varying, with tempera-ture, from atmospheric to 1000 atmospheres or above, the pressure being selected high enough to keep the monomers in solution. For ethylene polymerization of a slurry type, temperatures in the range of 10 to 110C. are suitable.
For the solution polymerization of ethyleneJ which is pre-ferred, temperatures can range from 125C to 300C, but pre-ferred temperatures are in the range of 130 to 270C. Any inert hydrocarbon can be employed as a polymerization medium. -Suitable classes include n-alkanes, cycloalkanes and aromatic hydrocarbons, representative example being propane, n-hexane, cyclohexane, n~heptane, and toluene. Hydrogen can be added to the polymerization zone to control and limit the molecular weight of the polyolefin produced.
Tetra(neophyl) zirconium, otherwise identified as tetra kis(2-methyl, 2-phenylpropyl) zirconium, can be pre-pared by the reaction of a zirconium tetrahalide, preferably ZrC14, with an organometallic compound of a metal ~f Groups I, II or III of the Periodic Table of the Elements accord- -ing to Bohr (see T. Moeller, "Inorganic Chemistry", p. 122) in which the organic radicals attached to the metal are neophyl radicals. A convenient method of preparation is the reaction of an ethereal solution of the neophyl . .
lOS4154 Grignard reagent ~ith ZrC14 according to the following reaction:
CH3 r CH3
4 ~C-C~MoCl + ZrCl~ C-c~12--~r + ~ Cl CII3 ~_ C~13 _ The reaction of the Grignard reagent with the ZrC14 is most conveniently carried out in an anhydrous liquid medium by adding powdered ZrC14 as a solid or slurry - in an inert anhydrous liquid to a solution of the neophyl Grignard reagent. The temperature in the reaction vessel should be maintained in the range of 0 to 70C. Mainte- -nance of dry, oxygen-free conditions during the addition and reaction is essential. An ethyl ether-toluene mixed solvent is suitable as the medium. The resultant tetra-(neophyl) zirconium is soluble in hydrocarbon solvents or ether-hydrocarbon mixed solvents, and the solution is readily separated from the precipitated MgC12 by decanta-tion or f'iltration. Pure crystalline tetra(neophyl) zirconium can be recovered by evaporation of the solvent followed by recrystallization from a hydrocarbon solvent such as toluene by warming, cooling and filtration. The resultant purified crystals are cream to light tan in color and melt at 67-68C. (hot stage) or 69C. (DSC
method). The crystalline tetra(neophyl) zirconium is thermally stable and can be stored without decomposition at 25C. for many hours or at -35C. ~or many weeks.
Thermolysis studies showed that very little decomposition, as measured by weight loss, occurred when tetra(neophyl) zirconium was heated at 10C./min. until a~ter temperatures above 100C. were reached. This thermal stability was .
unexpected in view of the known instability of many other tetrathydrocarbyl) zirconium compounds such as tetra(alkyl) zirconiums. Thermal decomposition of tetra(neophyl) ; zirconium at temperatures above 100C. yields primarily t-butyl benzene and a dark residue readily oxidized to a white zirconium oxide by air.
The unique structure of tetra(neophyl) zirconium is also revealed by its nuclear magnetic resonance spectrum (NMR) Figure II-A, which shows methylene protons at 8.93~ , methyl protons at 8.76 ~ and phenyl protons at 2.7r Since the NMR spectrum of tetra(neophyl) zirconium shows no broadening of the peak due to the phenyl protons, it appears that no interaction between the -electrons of the benzene ring and the d-orbitals of zirconium occurs in this compound distinguishing it from the -allyl and benzyl zirconium compounds of the prior art which show such inter-action (see Figure II-B). The absence of such interaction changes the chemical reactivity of the zirconium-hydrocarbon bond. Also, the greater stability of tetra(neophyl) zir-conium, compared to many other tetra(hydrocarbyl) zirconiumcompounds (e.g. tetra(alkyl) zirconium) must be associated with the absence of a hydrogen atom on the carbon beta to the metal; this reduces the tendency for decomposition via ~-hydride transfer and olefin elimination.
Rather surprisingly, tetra(neophyl) zirconium alone has been found to be an effective~-catalyst for the polymerization of ethylene and other a-olefins to yield high molecular weight, solid, linear polyolefins. While not wishing to be bound by any particular theory of the mechanism, it is believed probable that, upon contact of .
:
~054154 the tetra(neophyl) zirconium with a polymerizable olefin under polymerization conditions, a metathesis occurs where-by one or more neophyl radicals are replaced by the alipha-tic radicals corresponding to the olefin to be polymerized, and, thereupon~ there occurs a partial decomposition due to the known instability of Zr-aliphatic bonds so that the zirconium is then reduced in valence to the lower-valence forms (ZrII and ZrIII) known to be active as coordination catalysts in the polymerization of olefins.
Even more active catalysts for the polymerization of olefins are obtained by reacting tetra(neophyl) zircon-ium with a hydrated metal oxide of the classes previously defined. In the course of this reaction, particularly as - the temperature of the reactants is raised, the zirconium-metal oxide reaction product undergoes partial decomposi-tion to provide neophyl zirconium in the active, lower ~
valence states, chemically bonded to the surfaces of the ~ metal oxide which can then be dispersed in an inert hydro-; carbon and passed to a polymerization zone where the catalyst contacts the olefin monomer and converts it to a high molecular weight, solid, linear polyolefin. If desired, these supported zirconium neophyl metal oxide catalysts can also be used as fluldized beds to polymerize gaseous olefins to high molecular weight polyolefins.
The preferred catalyst, because of its stability and the high rates of olefin polymerization obtained with this catalyst, in a process for the polymerization of ethylene and/or other l-olefins~ is neophyl zirconium aluminate supported on and bonded to fumed alumina having a surface area in the range of 10 to 500 m2/g, as measured _ g _ "
by N2 adsorption. Prior to injection of the catalyst sus-pended in an inert hydrocarbon solvent, into the polymeri-zation zone, the zirconium may,due to spontaneous rearrange-ments, have a reduced valency and be at least in part in the Zr(III) valence state although some Zr(II) and Zr(IV) may also be present.
The polymerization process is carried out in an -inert, substantially anhydrous hydrocarbon medium. The temperature employed may range from about 20C. to 300C., depending on the monomer or monomers to be polymerized and upon whether a slurry or a solution polymerization process is to be used. In the case of the polymerization of ethyl-ene, either homopolymerization or copolymerization with other olefins, the preferred temperature is in the range of 130-270C. where a single phase, solution polymerization process occurs at maximum rates and high efficiency (yield of polymer per unit of zirconium catalyst). Propylene is preferably polymerized at lower temperatures in the range of 50 to 150C.when cr~stalline polypropylene is ~he d~ed product, although higher temperatures can be employed.
The pressure employed is not critical so long as it is sufficient, at the temperature chosen, to prevent --boiling of the hydrocarbon solvent and maintain the MOnO-mers employed in solution in the solvent. Thus the pres-sure may range from atmospheric to 1,000 atm. and above at the highest temperatures of operation of the process.
In order to achieve optimum catalytic activity it is preferred that there be employed an alumina ha~ing a surface area of 10 to 500 m2/g, free from absorbed water but containing hydroxyl groups generally randomly ~, . , -~054154 distributed on its surfaces. Preferably this alumina sup-port is most readily produced by activation of fwned alumina (a product obtained by burning aluminum chloride in the presence of water vapor) by heating in a stream of dry N2 at temperatures in the range of 900-1100C. for a period in the range of 1 to 10 h~urs. This treatment not only removes water and residual chloridc from the fumed alumina but alters the morphology of the crystalline alumina from predominantly gamma-alumina to a particular mixture of the gamma-, delta-, theta-, and alpha-forms. The re-sultant mixture of crystalline forms is essential for ob-taining, in the subsequent reactions with tetra(neophyl) zirconium, the unique chemical composition of the zirconium neophyl aluminate necessary to produce the optimum catalyst which exhibits the unexpected and surprising activity and efficiency characteristic of the preferred polymerization process of this invention.
The fumed alumina, activated as described above, is then subjected to partial hydration by contact with an atmosphere comprising some water vapor until a minor pro-portion of water has reacted with the alumina surface, conveniently about 3% to 5% by weight water of hydration.
This rehydrated alumina may then be partially dehydrated by heating at a temperature in the range of 300 to 500C.
for from 1 to 10 hours, the time required being in the lower portion of the range at the higher; temperatures in the range of temperatures. The final product contains from 0.5% to 1.5% by weight water as H0-groups distributed on the surfaces of the alumina. This second heat treatment not only assures that no merely absorbed molecular H20 remains on the surraces Or the alumina but also elîminates any large clusters of H0-groups on the surfaces lea~ing randomly distributed on the A12O3 surfaces pairs and rela-tively isolated H0-groups as reaction sites.
The high temperature activation removes essen-tially all H20 and HO-groups from the alumina, decreases the amount of residual chloride from an initial 0.7% to 0.2% by weight and, very importantly, converts a portion of the original crystalline ~amm~,A1203 to the more active delta-and theta-forms. Partial rehydration with water vapor in a moist atmosphere replaces hydroxyl groups on the A1203 surfaces.
The final drying at about 400C. reduces the con- -~
; centration of H0-groups on the surfaces of the A1203 to an optimum value in the range of 0.5 to 1.5% by weight water, thus providing isolated single and pairs of HO-groups on the alumina surfaces, making these surfaces most suitable for reaction with tetra(neophyl) zirconium in solution.
The preferred catalyst is next prepared by mixing together a suspension of the activated, hydroxylated alumina ; in anhydrous mineral oil with a solution in hydrocarbon solvent of tetra(neophyl) zirconium. In general, the pro- ~ -portion of tetra(neophyl) zirconium employed is at least 0.05 millimoles per gram of A1203, preferably 0.15 to 0.35 ~ -millimoles per gram A1203, or other metal oxide. Larger proportions are operable but provide no advantage since they provide no enhancement of catalyst activity.
The reaction between tetra(neophyl) zirconium and hydroxylated alumina can be conducted at temperatures in the range of 0 to lOO~C., depending on the time allowed.
~ ~ ( ~054154 Upon mixing the suspension of alumina with the solution of tetra(neophyl) zirconium, a reaction occurs between the HO-groups on the surfaces whereby Zr-O-Al chemical bonds are formed with the elimination of approximately 2.5 of the 4 hydrocarbyl radicals originally bonded to the zirconium.
The reaction may be approximately described by the equations , ~
__.. .- - - . .. _ _ . :
___ ' .
.
, . _ ... _ .__ - 13 _ , .
~054~5~
(A) and (B):
A l-OH CH3 (A) (~ + <~ C--CH2- -Zr- >
Al-OH CH3 4 -. O\ ' zr~CH2-C ~> + 2 CH3-C ~3 ~1-0 3 2 (B) + 2[~>C-CH2~Zr~
Al-OH CH
~.......... \ : .
Al-O-Zr~cH2-c ~3]
¦ I H3 +2 CH3-- C
Al-O-Zr{CH2-C ~>]
O\ CH3 3 There then follows, upon aging, particularly at 50C. and . . :
-: 10541S4 above, a parti~l decomposition to form the active catalyst in which zirconium is at least in part in lower valence states. This is shown approximately by (C):
''' / ' , O O
\ O
r l~13 1 Al-0\
l1-I3 (C ) ~ / r t C~2~ \ Zr-CH2-C ~>
o L C1~3 . 2 Al-0 C~I3 -~
O\
I ~3~ -- '~C~I2-C~
. C~3 The neophyl radicals eliminated may either be converted to t-butyl benzene by picking up a proton from the solvent, or may couple. Some zirconium may similarly be reduced to Zr(II) at active polymerization sites, particularly in the presence of olefin monomers.
In the ethylene polymerization process of this in-vention when conducted in continuous manner in a stirred autoclave, the yields obtained have been in excess of lO,000 parts of polyethylene per part of zirconium when using the preferred neophyl zirconium aluminate bonded onto alumina catalyst. Inherently, batch processes are less efficient but yields in the range of 700-lO00 g. ?
polyethylene per millimole of zirconiu~ p~er hour are readily obtainable as compared with only 50 to lO0 g.
polyethylene per millimole Zr obtained in a process of the prior art where there is used as catalyst the reaction . - 15 -:
~054154 product of tetra(benzyl) zirconium with hydrated A1203.
In the preferred continuous process, the catalyst suspension and the ethylene dissolved in an aliphatic or cycloaliphatic hydrocarbon are each fed continuously to the ~ stirred polymerization zone, the molar ratio of ethylene - fed to zirconium being maintained at a value in the range of 35,000-400,000 to one.
The polyolefins obtained by the process of this invention are linear, head-to-tail polymers of high 1~ molecular weight. In the case of ethylene homopolymeriza-tions, the resultant linear polyethylene has a crystalline melting point in the range of 133-138C., an annealed -density in the range of 0.96 to 0.97 g./cm3. If desired, ethylene polymers of lower density (o.90-0.96 g./cm3) can be obtained by copolymerization of ethylene with minor proportions (0.1 to 15 mole%) of higher ~olefins (preferably C4 to C10) to provide copolymers containing 0.1 to 12 weight % copolymerized higher oleIin using the process and catalyst of this invention. Such copolymers contain randomly-distributed side chains of controlled length which impede somewhat the development of crystallinity in the solid polymers which are, as a result, polymers of increased toughness and stress-crack resistance. As is well known, all of the ethylene polymers find ~commercial use as self-supporting films, wire coatings, pipe, and molded articles~of commerce. If desired, they can be filled with glass or other stiff fibers, clays and the like to produce hard, sti~f moldings.
The homopolymerization of propylene using the catalysts of thls invention in the process Or this , ~054154 invention can be directed, by control of process conditions, to yield highly stereoregular, head-to-tail crystalline polypropylene of high molecular weight insoluble in hydro-carbons at ambient temperatures and sparingly soluble even at temperatures above 100C. and having a crystalline melting point in the range of 162-170C., as determined by either differential thermal analysis or hot-stage microscope using polarized light, as well as high molecular weight, linear, head-to-tail polypropylene which is amorphous, due to atactic steric structure, and soluble in hydrocarbons even at room temperature. The crystalline polypropylene has come to be termed, following the suggestion of Giulio Natta, polypropylene exhibiting "isotactic" structure due to the presence of long segments in the macromolecules in which the groups attached to suc-cessive asymmetric carbon atoms along the chains have the same configuration. As is well known, crystalline polypro-pylene finds many commercial uses, particularly as textile fibers, in both woven and non-woven textiles and as films, strappings, coatings and molded articles of commerce.
Amorphous polypropylene is useful in blends with crystal-line polyolefins to provide toughness, and in adhesive compositions and rubbers.
The catalysts and processes of this invention can be used to produce amorphous ethylene/propylene rubbers where from about 30% to about 72~ by weight (preferably about 50% by weight) of ethylene and, I correspondingly, 70% to 28% of propylene are combined in the macromolecules by copolymerization, under constant environment conditions, of ethylene and propylene. Due , . .
.
1054~54 to the higher reactivity of ethylene in the polymerization reaction, a higher proportion of propylene should be used -~
in the monomer feed fed to the polymerization zone than it is desired to incorporate in the copolymer macromolecules.
If desired to provide ready sites for subsequent - traditional chemical vulcanizations (cross-linking), minor proportions of unconjugated dienes (e.g. 1,4-hexadiene, 2-methyl-1,5-hexadiene, etc.) may be included in the co-polymers by including minor proportions of these diene mono- -mers in the mixture of monomers fed to the polymerization zone in the process. Rubbers can also be obtained by the homopolymerization of conjugated diolefins such as butadiene or isoprene using the catalysts and process of this inven-tion. The properties and utilities of these synthetic rubbers are well known in the rubber industry.
Because the process of this invention uses such an active and efficient catalyst system, the very low level of catalyst residues in the polyolefin products produce no adverse effects on the properties of these polymers.
Therefore, the polymers are used as formed without the necessity of the expensive and complex catalyst removal procedures customarily employed in connection with prior art commercial practice.
The following examples are provided to illustrate the invention and to provide comparative examples closer to the more relevant prior art. However, t~e invention is not to be considered as limited to the particular examples pro-vided but rather is of the scope hereinabove described.
Example 1. Preparation of Tetra(neophyl) Zirconium.
Magnesium turnings (48.6 g., 2.0 moles) were ' charged into a 2-liter, 3-necked glass flask fitted with a stirrer, N2 inlet, N2 exit connected to a Mineral oil bubbler, and 500 cc. dropping funnel. The flask was swept with N2 overnight to remove air and moisture. Then 160 cc. of dry, deoxygenated diethyl ether was added. A
crystal of iodine was added to activate the Mg surface, and then 11~ g. (0.7 moles) of neophyl chloride dissolved in 160 cc. of dry toluene was added dropwise. The reaction mixture was continuously stirred and maintained at 30-35C. until all of the neophyl chloride had been added. The reaction mixture turned brown during this period. After one hour a 5 cc. aliquot of the supernatent solution was removed from the reaction mixture, neutralized with 20 cc. of 0.1 M aqueous ~Cl and back-titrated to a pink phenolphthalein end point with 5 cc. of 0.2 M aqueous NaOH. The concentration of the Grignard reagent was therefore found to be 2 molar.
The Grignard reagent was transferred to a 2-liter flask swept with a stream of dry N2. The unreacted Mg was washed with 400 cc. of dry toluene and the washing added to the Grignard solution. The Grignard solution (neophyl magnesium chloride) was cooled to -10C. and then 40 g. of 97% ZrC14 (0.166 moles) was added through a solids addition tube. The slurry was stirred for 1 hour and warmed to 50C., then transferred to an inert atmosphere box and filtered through a l-inch bed of"dried "Celite"
(diatomaceous earth). The filtrate was concentrated by evaporation. Crystals of solid tetra(neophyl) zirconium formed upon cooling. The yield of this product was about 70 g. The crystals were purified by recrystallization -- 19 -- ., '' ~ ~ ' , . :
: ``
` - 1054i54 from n-hexane. The purified tetra(neophyl) æirconium product was found to melt at 67-68C. by observation on a ~isher-Johns hot-stage and 69C. by DSC melting point deterrrlination in N2. Elemental analysis of this product ; gave C = 75.85%, H = 8.20%; theory for tetra(neophyl) zirconium, C = 76.99%, H = 8.40%.
Example 2. Preparation of a Neophyl Zirconium Aluminate on Alumina Catalyst.
; a) Activation of Alumina 111.2 g. of a commercial grade of fumed alumina having a surface area of 100 m2/g was charged to a vertical quartz reactor and dried at 1000C. in a stream of flowing N2 for 6 hours. The dry A1203 was partially rehydrated by contact with a 50% relative humidity atmosphere at 73F.(23C.) for 16 hours and then redried to optimum H0-group content by heating at 4003C. for 4 hours in a stream of flowing N2.
The resultant activated alumina was suspended under a N2 atmosphere in 1900 cc. of mineral oil containing 100 cc. of petroleum jelly and stored under N2 until used.
A sample of the slurry was ashed and found to contain 0.048 g. alumina per cubic centimeter.
`b) Catalyst Preparation Ten cubic centimeters of a solution containing 0.074 g. of the tetra(neophyl) zirconium of ~xample 1 dissolved in decahydronaphthalene was added to 10 cc. of the suspension of alumina in mineral oil with continuous stirring and this rnixture was allowed to react at 25C. for 21 hours to provide a suspension of neophyl zirconium aluminate bonded onto alumina in mineral oil which was subsequently used to polymerize ethylene. The zirconium in this Product was in a reduced state.
Example 3. Polymerization of Ethylene at 150C. Using Neophyl Zirconium Aluminate on Alumina as - Catalyst.
A 350 cc. crown-capped bottle was charged with 340 cc. of dry, deoxygenated decahydronaphthalene solvent, heated to 150C. and the solvent saturated with ethylene charged at 40 psi. 3.0 cc. of the suspension of neophyl zir~onium aluminate bonded onto alumina in mineral oil prepared in Example 2 was then charged into the solution of ethylene. After 3 minutes, the polymerization was terminated by the addition of 2 cc. of isopropanol which reacts to destroy the activity of the catalyst. The reaction mixture was cooled which caused the polyethylene to precipitate. The solid polyethylene was isolated by filtration, washed with cyclohexane and methanol and dried in a vacuum oven at 80C. for 16 hours. The yield of solid, dry polyethylene was 0.7 g. Based on this yield, the rate of polymerization was calculated to have been 780 g/millimole Zr/hr. The solid, linear polyethylene was white and had a crystalline melting point of 133C., as determined by DSC technique, and was of high molecular weight.
Example 4. Polymerization of Ethylene at 80C. Using Neophyl Zirconium Aluminate on Alumina as Catalyst.
A 350 cc. crown-capped Pyrex~ bottle containing 200 cc. of dry, deoxygenated toluene maintained at 80C.
was saturated with ethylene at 40 psi. There was then charged into this solution of ethylene 3.0 cc. of the suspension in mineral oil of neophyl zirconium aluminate on alumina, prepared in Example 2. Polymerization .
~;` ~ 'i 4~54 commenced at once as shown by precipitation of polymer.
Additional ethylene was charged into the reactor to maintain the pressure at 40 psi. After 1 hour at 80C., the polymerization was terminated by the addition of 2 cc.
of isopropanol, and the granular polyethylene ~as recovered by filtration and dried in a vacuum oven at 80C. for 16 hours. The weight of dry, solid linear polyethylene recovered was 1.3 g. The polyethylene had a crystalline melting point of 135C. as determined by DSC techniques and was of high molecular weight.
Example 5. Polymerization of Ethylene at 80C. Using Tetra(neophyl? Zirconium as Catalyst. _ A 350 cc. crown-capped bottle was charged with 200 cc. of dry, deoxygenated toluene and saturated at 80C.
with ethylene. A 0.1 M solution in benzene of the tetra-(neophyl) zirconium of Example 1 was prepared, and 1 cc.
of this solution was charged into the toluene solution of ethylene. Polymerization comrnenced immediately as shown by the precipitation of polymer. Additional ethylene was charged to maintain the pressure at 40 psi. After 1 hour at 80C., polymerization was terminated by addition of 2 cc. of isopropanol. The solid polyethylene was isolated by filtration and dried in a vacuum oven for 16 hours at 80C. The weight of the recovered~ dry, solid white polyethylene was 0.934 g. The polyethylene had a - crystalline melting point of 135.8C., as determined by DSC measurement. Based on the yield of polymer, the rate of polymerization was calculated to have been 9.34 g/milli-mole Zr/hr. The polyethylene was of high molecular weight.
Example 6. Comparative Activity of Neophyl Zirconium Aluminate and Benzyl Zirconium Aluminate on Alumina as Catalysts for the Polymerization of Ethylene in a_Continuous Process.
: -~054~54 a) Polymerization of ethylene using neophyl zirconiumaluminate on alumina as catalyst .
A 0.000625 M solution in n-hexane of the tetra-(neophyl) zirconium of Example 1 was pr~pared. Using the process and apparatus diagrammed in Figure I, a suspension of an active supported catalyst comprising neophyl zirconium aluminate on alumina is continuously prepared by feeding the 0.000625 M solution of tetra(neophyl) zirconium from feed tank, 6, through mixing valve, 15, to premix vessel, 1, at a rate of 200 cc./hr. and a suspension of activated alumina, prepared as in Example 2(&), also is fed from feed tank, 7, through mixing valve, 15, at a rate of 0.5 g. A1203/hr. into premix vessel, 1, a stainless steel, stirred autoclave of 975 cc. capacity where it is diluted with 1400 cc. per hour of hexane and maintained at 50~.
Not shown in Figure 1 is a feed tank and line through which the hexane is fed to premix vessel, 1. After a hold-up time of approximately 40 minutes, to allow for the reactions between tetra(neophyl) zirconium and the activated alumina to produce neophyl zirconium aluminate, the catalyst suspension is continuously fed to a 265 cc.
second stainless steel autoclave, 2, at the same rate, and there diluted with 800 cc./hr. of n-hexane while stirring with mixer, 13. Not shown is a li~e from a hexane feed tank to autoclave, 2, through which the n-hexane is fed. -After a hold-up of 6 minutes in the autoclave the diluted catalyst suspension then is continuously fed through valve, 16, to a 253 cc. stainless stee~ agitated polymeri-zation vessel, 3, stirred by mixer, 14, and maintained at 2250 psi and 250C. where it is contacted with ethylene fed, from reservoir, 9, through valve, 17, as a 7~ weight solution in n-hexane, at 200 g. ethylene/hr.
The concentration of the catalyst in the reactor - with respect to zirconium was 2.0 x 10-5 molar. In order to control and limit molecular weight o~ the polyethylene, ~2 was also fed to the polymerization vessel at a rate of 100 millimoles/hr. as a 0.0825 M solution in n-hexane.
The H2 tank and feed line are not shown in Figure I; if desired, this stream can also be fed through mixing valve, The hold-up time in the polymerization vessel is maintained at approximately 2.56 minutes by continuously withdrawing the polymerization mixture through mixing valve, 19, to a deactivation chamber, a tubu~ar, turbulent mixer, 4, where the catalyst is deactivated to terminate the polymerization by addition from reservoir, 12, through mixing valve, 19, o~ a 0.0033 M solution of isopropanol in n-hexane at a rate of 600 cc./hr to the reaction mixture containing dissolved polyethylene.
Instead of isopropanol, other alkanols, stearn or CO2, can be used as the deactivator.
The solution of polyethylene is continuously dis-charged through an automatic, controlled pressure-reducing valve, 20, into a product receiver, 5, maintained at 50C.
where the solid polyethylene phase is separated from solvent; the polymer stream is passed to polymer recovery system, 11, and recovered from the polyme~ization medium by filtration, and the polyethylene, wet with n-hexane, is chopped in a blender, washed with n-hexane and dried in a vacuum oven at 80C. for 16 hours. Monomers and solvent recovered from the top of separator, 5, are passed - 24 _ 1054~4 through a refining train, not shown, and then recycled through mixing valve, 17, to polymerizer, 3.
The rate of polyethylene production during steady-state operation over a period of several hours was 177 g./hr. (88.5~ cGnversion of the ethylene fed to the polymeri~er). The yield of polyethylene was 1415 kg./mole of zirconium. The dried polyethylene had a melt flow, as determined by ASTM Method 1238-65T, Condition E, of 2.8 decigrams/min. The density of the polyethylene produced, as determined by ASTM D792-64T (method corrected to 23C.) was found to be o.960 g./cc. Thus the polyethylene produced was a highly linear, crystalline polyethylene of high molecular weight suitable for use in production of films and ~njection-molded articles, ~;
b) Polymerization of ethylene using benzyl zirconium aluminate as a catalyst .
The foregoing experiment (Example 6-a) was repeated using, however, as a catalyst the reaction product of the activated alumina and tetra(benzyl) zirconium except that the concentration of zirconium catalyst was increased ; 20 slightly over that in Example 6(a) to 2.14 x 10 5 molar in the polymerization autoclave. In this instance the rate of polyethylene formation was L67 g./hr. (83.8~ con-version of the ethylene fed).
An analysis of the reactions based on the change in activity (a) as shown by where r = hold-up ti~e in the polymerizer Q = ethylene conversion ~ lOS~lS~
reveals a's of 3.029 min 1 for the neophyl zirconium alumi-nate catalyst vs. only 2.017 min 1 for the benzyl zirconium aluminate catalyst. Thus even though the concentration of neophyl zirconium aluminate catalyst in the polymerizer was less (2.0 x 10 5 molar) than benzyl zirconium aluminate ~; catalyst (2.14 x 10 5 molar~ the activity of the neophyl zirconium aluminate was 1.5 times that of benzyl zirconium - aluminate.
Example 7. Polymerization of Propylene Using Neophyl Zirconium Aluminate on Alumina as Catalyst . 10 Into a l-literJ stirred, nitrogen-filled autoclave -was charged 600 ml of cyclohexane purified by purging with nitrogen followed by passing it through a bed of acid alumina under nitrogen. As the autoclave was kept blanketed with nitrogen 0.2 millimoles of neophyl zirconium aluminate supported on one gram of fumed alumina, prepared ~ -as in Example 2, was in~ected by syringe as a slurry in 20 ml of cyclohexane. Propylene was pressured into 20 psi as the system was stirred at ~00 rpm. The tempera~
ture and propylene pressure were raised to 50~60 psi and maintained at this for 4 hrs. The ten grams of poly-propylene obtained was in the form of a gel, which was evaporated to give a tough, flexible sheet. The inherent viscosity of this polymer was 12.5 dl/100 as measured at 0.1% concentration in decalin at 130C. Thirty-five percent of the polymer was insoluble in boiling heptane.
The insoluble polypropylene was highly crystalline and exhibited the isotactic structure. A very tough, rubbery film 5 mils thick was obtained by compression molding 0.5 g. of the total polymer at 230C., 3000 lbs ram pressure.
~OS4154 Exa~ple 8. Polymerizatiorl of Ethylene with a Neophyl Zirconium Silicate on Si~ica Catalyst . . _ 20 g. of a commercially available fumed silica having a surface area of 225 m2/g.was char~ed to a vertical glass reactor and dried at 200C. in a stream of flowing nitrogen for 4 hours. One gram of the dried silica was suspended in 38.5 cubic centimeters of decahydronaphthalene and 1.5 cc. of 0.2M tetra(neophyl) zirconium in benzene was added. After 40 minutes the supernatent liquid above the catalyst was analyzed by gas chromatography. A
material balance showed approximately 2.1 neophyl groups were displaced from each mole of tetra(neophyl) zirconium ; during formation of the neophyl zirconium silicate on silica catalyst.
The polymerization of ethylene was brought about by charging a crown capped bottle containing 340 cc.
of decahydronaphthalene saturated with ethylene at 150C.
and 40 psi with 4 cubic centimeters of the neophyl zirconium silicate on silica catalyst (0.1 g. silica, 0.03 millimole Zr). After 3 minutes the polymerization was stopped by addition of 2 cubic centimeters of` isopropanol.
The solution was cooled and the precipitated polymer separated by filtration, washed with cyclohexane and methanol, and dried in a vacuum ov~en for 16 hrs. at 80C.
The product recovered, including catalyst residue, weighed 0.345 g. which is equivalent to 0.245 g. of polyethylene.
Based on this yield the rate of polymerization was calculated to have been 163 g./millimole Zr/hr as contrasted with the 780 g./millimole Zr/hr achieved in Example 3 by use of the preferred catalyst of this invention.
... .
..
,: Example 9. Copolymerization Or Ethylene and Propylene , with a Neophyl Zirconium Aluminate on ` Alumina Catalyst to for~ a Crystalline Copolymer.
80 cubic centimeters of deoxygenated hexane in an agitated vessel was saturated at 25C. with propylene at 20 psi. The pressure was raised to 40 psi with ethylene and ;~ the copolymerization brought about by the addition of 10 cubic centimeters of a neophyl zirconium aluminate catalyst slurry prepared by reaction of 10 g. of alumina activated - as in Example 1 and 2.0 millimoles of tetra(neophyl) -~ zirconium in 210 cubic centimeters of deoxygenated hexane.
After 20 minutes at 25C. the polymerization was stopped by venting the unreacted olefins. The polymer was separated by filtration washed with methanol and dried at 80C. for 16 hrs. The product recovered weighed 6.44 g.
This copolyrner had a crystalline melting point of 122.5C.
by DSC techniques and was found to contain 10.1 weight %
copolymerized propylene by infrared analysis.
Example 10. Copolymerization of Ethylene and Propylene With a Neophyl Zirconium Aluminate on Alumina Catalyst to Produce an Amorphous ~ 20 Copolymer.
;'''` ' -2 grams of alumina activated as in Example 1 was suspended in 40 cubic centimeters of hexane and 2 cubic centimeters of a 0.2 molar solution of tetra(neophyl) zir-conium in benzene added. After l hr. a portion of the slurry was transferred to a vial and the hexane evaporated under vacuum leaving 1. o6 g. of catalystl The vial was sealed and placed in a stainless steel-reactor with two ,~ stainless steel balls. The reactor was sealed and charged .
with 50 g. of propylene, warmed to 25C. and ethylene added until the pressure in the reactor reached 500 p,i.
':
'' .
r ~ 28 -.
:
The catalyst ampoule was broken and the polymerization allowed to proceed for 1 hr. The amorphous copolymer, isolated as a rubbery ball, was separated from the glass and dried to yield 29 g. of copolymer having a copolymer-ized propylene content of 28.3 weight per cent, as determined by infrared analysis.
Example 11. Polymerization of 1,3-Butadiene with a Neophyl Zirconium Aluminate on Alumina Catalvst ~- A 1 liter agitated flask swept with nitrogen was charged with 500 cubic centimeters of deoxygenated toluene, heated to 50C. and saturated with 1,3-butadiene at 2 psi.
Neophyl zirconium alu~inate on alumina catalyst in hexane, equivalent to 0.38 g. of catalyst (o.076 milli-moles Zr), was added and the polymerization continued for 1 hr. The product which formed was separated by filtra-tion, chopped in a blender and dried in a vacuum oven at 80C. for 16 hrs. The drled product weighed 1.13 g.
which is equivalent to 0.75 g. of polybutadiene. Based on this yield the rate of polymerization was calculated to be 9.9 g./millimole Zr/hr. Infrared analysis showed the structure of the polymer to be of the 1,4-trans-type.
Example 12. Polymerization of Propylene With a Neophyl "
Zirconium Aluminate on Alumina Catalyst 1 gram of alumina activated as in Example 1 was ; suspended in 40 cubic centimeters of dry hexane in a , . . .
stirred flask under nitrogen. 5 cubic centimeters of ; 0.1 molar tetra(neophyl) zirconium was charged to the flask. After 16 hrs. the neophyl zirconium aluminate catalyst was transferred to an ampoule and the hexane evaporated under high vacuum. The ampoule was sealed lOS4~5~
and placed in a stainless steel reactor with two stainless steel balls. The reactor was swept with nitrogen to exclude all air, sealed, evacuated, cooled and 75 g.
of propylene charged. The reactor was warmed to 50C. -and the ampoule broken by shaking the reactor. A~ter 1 hour the polymer was isolated, separated from the glass and dried to yield 26 g. of polypropylene having a melting point of 158C. and a crystallization point of 110C. by DSC. The polypropylene had an inherent viscosity in decahydronaphthalene at 130C. (0.1% solution) of 9.64. Extraction of the polypropylene with boiling hexane for 4 hrs. removed 3% of the polymer indicating the remainder to be substantially high molecular weight polypropylene of isotactic structure. The hexane insoluble fraction was further extracted with boiling toluene. The swollen toluene-insoluble residue, after drying, had a melting point of 162.5C. by D.S.C., and amounted to 90% of the or~ginal crude product. The ; insolubility in toluene at the boiling point indicates that this crystalline polypropylene comprises macromolecules having substantially completely the isotactic structure.
Example 13. Terpolymerization of Ethylene, Propylene and 1,4-Hexadiene with Neophyl Zirconium ; Aluminate on Alumina Catalyst _ _ 4 grams of alumina activated as in Example 1 was suspended in 80 cubic centimeters of hexane and reacted with 12 cubic centimeters of a 0.1 molar solution of tetra(neophyl) zirconium in benzene. A portion of the slurry was transferred to a glass ampoule and the liquid evaporated and the catalyst dried under high vacuum. The iO54154 dry catalyst in the ampoule weighed 1.277 g. The ampoule was placed in a stainless steel reactor with 2 stainless steel balls. The reactor was closed and charged with 50 cubic centimeters of l,4-hexadiene and 50 cubic centimeters of n-hexane. The reactor was cooled, charged wi~h 50 grams of propylene, warmed to 100C. and pressured to 800 psi with ethylene. The catalyst ampoule was broken and the terpolymerization allowed to proceed for 1 hour. The polymer isolated as a crumb was separated from glass and 10 dried to yield 9 g. of terpolymer. A melt pressed film -of the terpolymer was analyzed by infrared analysis and -found to contain 5.5 methyl groups/100 carbons and 8.3 trans-olefin groups/2000 carbons which is equivalent to 15.6% propylene and 2.1~3% hexadiene by weight.
Example 14. Terpolymerization of Ethylene, Propylene and
method). The crystalline tetra(neophyl) zirconium is thermally stable and can be stored without decomposition at 25C. for many hours or at -35C. ~or many weeks.
Thermolysis studies showed that very little decomposition, as measured by weight loss, occurred when tetra(neophyl) zirconium was heated at 10C./min. until a~ter temperatures above 100C. were reached. This thermal stability was .
unexpected in view of the known instability of many other tetrathydrocarbyl) zirconium compounds such as tetra(alkyl) zirconiums. Thermal decomposition of tetra(neophyl) ; zirconium at temperatures above 100C. yields primarily t-butyl benzene and a dark residue readily oxidized to a white zirconium oxide by air.
The unique structure of tetra(neophyl) zirconium is also revealed by its nuclear magnetic resonance spectrum (NMR) Figure II-A, which shows methylene protons at 8.93~ , methyl protons at 8.76 ~ and phenyl protons at 2.7r Since the NMR spectrum of tetra(neophyl) zirconium shows no broadening of the peak due to the phenyl protons, it appears that no interaction between the -electrons of the benzene ring and the d-orbitals of zirconium occurs in this compound distinguishing it from the -allyl and benzyl zirconium compounds of the prior art which show such inter-action (see Figure II-B). The absence of such interaction changes the chemical reactivity of the zirconium-hydrocarbon bond. Also, the greater stability of tetra(neophyl) zir-conium, compared to many other tetra(hydrocarbyl) zirconiumcompounds (e.g. tetra(alkyl) zirconium) must be associated with the absence of a hydrogen atom on the carbon beta to the metal; this reduces the tendency for decomposition via ~-hydride transfer and olefin elimination.
Rather surprisingly, tetra(neophyl) zirconium alone has been found to be an effective~-catalyst for the polymerization of ethylene and other a-olefins to yield high molecular weight, solid, linear polyolefins. While not wishing to be bound by any particular theory of the mechanism, it is believed probable that, upon contact of .
:
~054154 the tetra(neophyl) zirconium with a polymerizable olefin under polymerization conditions, a metathesis occurs where-by one or more neophyl radicals are replaced by the alipha-tic radicals corresponding to the olefin to be polymerized, and, thereupon~ there occurs a partial decomposition due to the known instability of Zr-aliphatic bonds so that the zirconium is then reduced in valence to the lower-valence forms (ZrII and ZrIII) known to be active as coordination catalysts in the polymerization of olefins.
Even more active catalysts for the polymerization of olefins are obtained by reacting tetra(neophyl) zircon-ium with a hydrated metal oxide of the classes previously defined. In the course of this reaction, particularly as - the temperature of the reactants is raised, the zirconium-metal oxide reaction product undergoes partial decomposi-tion to provide neophyl zirconium in the active, lower ~
valence states, chemically bonded to the surfaces of the ~ metal oxide which can then be dispersed in an inert hydro-; carbon and passed to a polymerization zone where the catalyst contacts the olefin monomer and converts it to a high molecular weight, solid, linear polyolefin. If desired, these supported zirconium neophyl metal oxide catalysts can also be used as fluldized beds to polymerize gaseous olefins to high molecular weight polyolefins.
The preferred catalyst, because of its stability and the high rates of olefin polymerization obtained with this catalyst, in a process for the polymerization of ethylene and/or other l-olefins~ is neophyl zirconium aluminate supported on and bonded to fumed alumina having a surface area in the range of 10 to 500 m2/g, as measured _ g _ "
by N2 adsorption. Prior to injection of the catalyst sus-pended in an inert hydrocarbon solvent, into the polymeri-zation zone, the zirconium may,due to spontaneous rearrange-ments, have a reduced valency and be at least in part in the Zr(III) valence state although some Zr(II) and Zr(IV) may also be present.
The polymerization process is carried out in an -inert, substantially anhydrous hydrocarbon medium. The temperature employed may range from about 20C. to 300C., depending on the monomer or monomers to be polymerized and upon whether a slurry or a solution polymerization process is to be used. In the case of the polymerization of ethyl-ene, either homopolymerization or copolymerization with other olefins, the preferred temperature is in the range of 130-270C. where a single phase, solution polymerization process occurs at maximum rates and high efficiency (yield of polymer per unit of zirconium catalyst). Propylene is preferably polymerized at lower temperatures in the range of 50 to 150C.when cr~stalline polypropylene is ~he d~ed product, although higher temperatures can be employed.
The pressure employed is not critical so long as it is sufficient, at the temperature chosen, to prevent --boiling of the hydrocarbon solvent and maintain the MOnO-mers employed in solution in the solvent. Thus the pres-sure may range from atmospheric to 1,000 atm. and above at the highest temperatures of operation of the process.
In order to achieve optimum catalytic activity it is preferred that there be employed an alumina ha~ing a surface area of 10 to 500 m2/g, free from absorbed water but containing hydroxyl groups generally randomly ~, . , -~054154 distributed on its surfaces. Preferably this alumina sup-port is most readily produced by activation of fwned alumina (a product obtained by burning aluminum chloride in the presence of water vapor) by heating in a stream of dry N2 at temperatures in the range of 900-1100C. for a period in the range of 1 to 10 h~urs. This treatment not only removes water and residual chloridc from the fumed alumina but alters the morphology of the crystalline alumina from predominantly gamma-alumina to a particular mixture of the gamma-, delta-, theta-, and alpha-forms. The re-sultant mixture of crystalline forms is essential for ob-taining, in the subsequent reactions with tetra(neophyl) zirconium, the unique chemical composition of the zirconium neophyl aluminate necessary to produce the optimum catalyst which exhibits the unexpected and surprising activity and efficiency characteristic of the preferred polymerization process of this invention.
The fumed alumina, activated as described above, is then subjected to partial hydration by contact with an atmosphere comprising some water vapor until a minor pro-portion of water has reacted with the alumina surface, conveniently about 3% to 5% by weight water of hydration.
This rehydrated alumina may then be partially dehydrated by heating at a temperature in the range of 300 to 500C.
for from 1 to 10 hours, the time required being in the lower portion of the range at the higher; temperatures in the range of temperatures. The final product contains from 0.5% to 1.5% by weight water as H0-groups distributed on the surfaces of the alumina. This second heat treatment not only assures that no merely absorbed molecular H20 remains on the surraces Or the alumina but also elîminates any large clusters of H0-groups on the surfaces lea~ing randomly distributed on the A12O3 surfaces pairs and rela-tively isolated H0-groups as reaction sites.
The high temperature activation removes essen-tially all H20 and HO-groups from the alumina, decreases the amount of residual chloride from an initial 0.7% to 0.2% by weight and, very importantly, converts a portion of the original crystalline ~amm~,A1203 to the more active delta-and theta-forms. Partial rehydration with water vapor in a moist atmosphere replaces hydroxyl groups on the A1203 surfaces.
The final drying at about 400C. reduces the con- -~
; centration of H0-groups on the surfaces of the A1203 to an optimum value in the range of 0.5 to 1.5% by weight water, thus providing isolated single and pairs of HO-groups on the alumina surfaces, making these surfaces most suitable for reaction with tetra(neophyl) zirconium in solution.
The preferred catalyst is next prepared by mixing together a suspension of the activated, hydroxylated alumina ; in anhydrous mineral oil with a solution in hydrocarbon solvent of tetra(neophyl) zirconium. In general, the pro- ~ -portion of tetra(neophyl) zirconium employed is at least 0.05 millimoles per gram of A1203, preferably 0.15 to 0.35 ~ -millimoles per gram A1203, or other metal oxide. Larger proportions are operable but provide no advantage since they provide no enhancement of catalyst activity.
The reaction between tetra(neophyl) zirconium and hydroxylated alumina can be conducted at temperatures in the range of 0 to lOO~C., depending on the time allowed.
~ ~ ( ~054154 Upon mixing the suspension of alumina with the solution of tetra(neophyl) zirconium, a reaction occurs between the HO-groups on the surfaces whereby Zr-O-Al chemical bonds are formed with the elimination of approximately 2.5 of the 4 hydrocarbyl radicals originally bonded to the zirconium.
The reaction may be approximately described by the equations , ~
__.. .- - - . .. _ _ . :
___ ' .
.
, . _ ... _ .__ - 13 _ , .
~054~5~
(A) and (B):
A l-OH CH3 (A) (~ + <~ C--CH2- -Zr- >
Al-OH CH3 4 -. O\ ' zr~CH2-C ~> + 2 CH3-C ~3 ~1-0 3 2 (B) + 2[~>C-CH2~Zr~
Al-OH CH
~.......... \ : .
Al-O-Zr~cH2-c ~3]
¦ I H3 +2 CH3-- C
Al-O-Zr{CH2-C ~>]
O\ CH3 3 There then follows, upon aging, particularly at 50C. and . . :
-: 10541S4 above, a parti~l decomposition to form the active catalyst in which zirconium is at least in part in lower valence states. This is shown approximately by (C):
''' / ' , O O
\ O
r l~13 1 Al-0\
l1-I3 (C ) ~ / r t C~2~ \ Zr-CH2-C ~>
o L C1~3 . 2 Al-0 C~I3 -~
O\
I ~3~ -- '~C~I2-C~
. C~3 The neophyl radicals eliminated may either be converted to t-butyl benzene by picking up a proton from the solvent, or may couple. Some zirconium may similarly be reduced to Zr(II) at active polymerization sites, particularly in the presence of olefin monomers.
In the ethylene polymerization process of this in-vention when conducted in continuous manner in a stirred autoclave, the yields obtained have been in excess of lO,000 parts of polyethylene per part of zirconium when using the preferred neophyl zirconium aluminate bonded onto alumina catalyst. Inherently, batch processes are less efficient but yields in the range of 700-lO00 g. ?
polyethylene per millimole of zirconiu~ p~er hour are readily obtainable as compared with only 50 to lO0 g.
polyethylene per millimole Zr obtained in a process of the prior art where there is used as catalyst the reaction . - 15 -:
~054154 product of tetra(benzyl) zirconium with hydrated A1203.
In the preferred continuous process, the catalyst suspension and the ethylene dissolved in an aliphatic or cycloaliphatic hydrocarbon are each fed continuously to the ~ stirred polymerization zone, the molar ratio of ethylene - fed to zirconium being maintained at a value in the range of 35,000-400,000 to one.
The polyolefins obtained by the process of this invention are linear, head-to-tail polymers of high 1~ molecular weight. In the case of ethylene homopolymeriza-tions, the resultant linear polyethylene has a crystalline melting point in the range of 133-138C., an annealed -density in the range of 0.96 to 0.97 g./cm3. If desired, ethylene polymers of lower density (o.90-0.96 g./cm3) can be obtained by copolymerization of ethylene with minor proportions (0.1 to 15 mole%) of higher ~olefins (preferably C4 to C10) to provide copolymers containing 0.1 to 12 weight % copolymerized higher oleIin using the process and catalyst of this invention. Such copolymers contain randomly-distributed side chains of controlled length which impede somewhat the development of crystallinity in the solid polymers which are, as a result, polymers of increased toughness and stress-crack resistance. As is well known, all of the ethylene polymers find ~commercial use as self-supporting films, wire coatings, pipe, and molded articles~of commerce. If desired, they can be filled with glass or other stiff fibers, clays and the like to produce hard, sti~f moldings.
The homopolymerization of propylene using the catalysts of thls invention in the process Or this , ~054154 invention can be directed, by control of process conditions, to yield highly stereoregular, head-to-tail crystalline polypropylene of high molecular weight insoluble in hydro-carbons at ambient temperatures and sparingly soluble even at temperatures above 100C. and having a crystalline melting point in the range of 162-170C., as determined by either differential thermal analysis or hot-stage microscope using polarized light, as well as high molecular weight, linear, head-to-tail polypropylene which is amorphous, due to atactic steric structure, and soluble in hydrocarbons even at room temperature. The crystalline polypropylene has come to be termed, following the suggestion of Giulio Natta, polypropylene exhibiting "isotactic" structure due to the presence of long segments in the macromolecules in which the groups attached to suc-cessive asymmetric carbon atoms along the chains have the same configuration. As is well known, crystalline polypro-pylene finds many commercial uses, particularly as textile fibers, in both woven and non-woven textiles and as films, strappings, coatings and molded articles of commerce.
Amorphous polypropylene is useful in blends with crystal-line polyolefins to provide toughness, and in adhesive compositions and rubbers.
The catalysts and processes of this invention can be used to produce amorphous ethylene/propylene rubbers where from about 30% to about 72~ by weight (preferably about 50% by weight) of ethylene and, I correspondingly, 70% to 28% of propylene are combined in the macromolecules by copolymerization, under constant environment conditions, of ethylene and propylene. Due , . .
.
1054~54 to the higher reactivity of ethylene in the polymerization reaction, a higher proportion of propylene should be used -~
in the monomer feed fed to the polymerization zone than it is desired to incorporate in the copolymer macromolecules.
If desired to provide ready sites for subsequent - traditional chemical vulcanizations (cross-linking), minor proportions of unconjugated dienes (e.g. 1,4-hexadiene, 2-methyl-1,5-hexadiene, etc.) may be included in the co-polymers by including minor proportions of these diene mono- -mers in the mixture of monomers fed to the polymerization zone in the process. Rubbers can also be obtained by the homopolymerization of conjugated diolefins such as butadiene or isoprene using the catalysts and process of this inven-tion. The properties and utilities of these synthetic rubbers are well known in the rubber industry.
Because the process of this invention uses such an active and efficient catalyst system, the very low level of catalyst residues in the polyolefin products produce no adverse effects on the properties of these polymers.
Therefore, the polymers are used as formed without the necessity of the expensive and complex catalyst removal procedures customarily employed in connection with prior art commercial practice.
The following examples are provided to illustrate the invention and to provide comparative examples closer to the more relevant prior art. However, t~e invention is not to be considered as limited to the particular examples pro-vided but rather is of the scope hereinabove described.
Example 1. Preparation of Tetra(neophyl) Zirconium.
Magnesium turnings (48.6 g., 2.0 moles) were ' charged into a 2-liter, 3-necked glass flask fitted with a stirrer, N2 inlet, N2 exit connected to a Mineral oil bubbler, and 500 cc. dropping funnel. The flask was swept with N2 overnight to remove air and moisture. Then 160 cc. of dry, deoxygenated diethyl ether was added. A
crystal of iodine was added to activate the Mg surface, and then 11~ g. (0.7 moles) of neophyl chloride dissolved in 160 cc. of dry toluene was added dropwise. The reaction mixture was continuously stirred and maintained at 30-35C. until all of the neophyl chloride had been added. The reaction mixture turned brown during this period. After one hour a 5 cc. aliquot of the supernatent solution was removed from the reaction mixture, neutralized with 20 cc. of 0.1 M aqueous ~Cl and back-titrated to a pink phenolphthalein end point with 5 cc. of 0.2 M aqueous NaOH. The concentration of the Grignard reagent was therefore found to be 2 molar.
The Grignard reagent was transferred to a 2-liter flask swept with a stream of dry N2. The unreacted Mg was washed with 400 cc. of dry toluene and the washing added to the Grignard solution. The Grignard solution (neophyl magnesium chloride) was cooled to -10C. and then 40 g. of 97% ZrC14 (0.166 moles) was added through a solids addition tube. The slurry was stirred for 1 hour and warmed to 50C., then transferred to an inert atmosphere box and filtered through a l-inch bed of"dried "Celite"
(diatomaceous earth). The filtrate was concentrated by evaporation. Crystals of solid tetra(neophyl) zirconium formed upon cooling. The yield of this product was about 70 g. The crystals were purified by recrystallization -- 19 -- ., '' ~ ~ ' , . :
: ``
` - 1054i54 from n-hexane. The purified tetra(neophyl) æirconium product was found to melt at 67-68C. by observation on a ~isher-Johns hot-stage and 69C. by DSC melting point deterrrlination in N2. Elemental analysis of this product ; gave C = 75.85%, H = 8.20%; theory for tetra(neophyl) zirconium, C = 76.99%, H = 8.40%.
Example 2. Preparation of a Neophyl Zirconium Aluminate on Alumina Catalyst.
; a) Activation of Alumina 111.2 g. of a commercial grade of fumed alumina having a surface area of 100 m2/g was charged to a vertical quartz reactor and dried at 1000C. in a stream of flowing N2 for 6 hours. The dry A1203 was partially rehydrated by contact with a 50% relative humidity atmosphere at 73F.(23C.) for 16 hours and then redried to optimum H0-group content by heating at 4003C. for 4 hours in a stream of flowing N2.
The resultant activated alumina was suspended under a N2 atmosphere in 1900 cc. of mineral oil containing 100 cc. of petroleum jelly and stored under N2 until used.
A sample of the slurry was ashed and found to contain 0.048 g. alumina per cubic centimeter.
`b) Catalyst Preparation Ten cubic centimeters of a solution containing 0.074 g. of the tetra(neophyl) zirconium of ~xample 1 dissolved in decahydronaphthalene was added to 10 cc. of the suspension of alumina in mineral oil with continuous stirring and this rnixture was allowed to react at 25C. for 21 hours to provide a suspension of neophyl zirconium aluminate bonded onto alumina in mineral oil which was subsequently used to polymerize ethylene. The zirconium in this Product was in a reduced state.
Example 3. Polymerization of Ethylene at 150C. Using Neophyl Zirconium Aluminate on Alumina as - Catalyst.
A 350 cc. crown-capped bottle was charged with 340 cc. of dry, deoxygenated decahydronaphthalene solvent, heated to 150C. and the solvent saturated with ethylene charged at 40 psi. 3.0 cc. of the suspension of neophyl zir~onium aluminate bonded onto alumina in mineral oil prepared in Example 2 was then charged into the solution of ethylene. After 3 minutes, the polymerization was terminated by the addition of 2 cc. of isopropanol which reacts to destroy the activity of the catalyst. The reaction mixture was cooled which caused the polyethylene to precipitate. The solid polyethylene was isolated by filtration, washed with cyclohexane and methanol and dried in a vacuum oven at 80C. for 16 hours. The yield of solid, dry polyethylene was 0.7 g. Based on this yield, the rate of polymerization was calculated to have been 780 g/millimole Zr/hr. The solid, linear polyethylene was white and had a crystalline melting point of 133C., as determined by DSC technique, and was of high molecular weight.
Example 4. Polymerization of Ethylene at 80C. Using Neophyl Zirconium Aluminate on Alumina as Catalyst.
A 350 cc. crown-capped Pyrex~ bottle containing 200 cc. of dry, deoxygenated toluene maintained at 80C.
was saturated with ethylene at 40 psi. There was then charged into this solution of ethylene 3.0 cc. of the suspension in mineral oil of neophyl zirconium aluminate on alumina, prepared in Example 2. Polymerization .
~;` ~ 'i 4~54 commenced at once as shown by precipitation of polymer.
Additional ethylene was charged into the reactor to maintain the pressure at 40 psi. After 1 hour at 80C., the polymerization was terminated by the addition of 2 cc.
of isopropanol, and the granular polyethylene ~as recovered by filtration and dried in a vacuum oven at 80C. for 16 hours. The weight of dry, solid linear polyethylene recovered was 1.3 g. The polyethylene had a crystalline melting point of 135C. as determined by DSC techniques and was of high molecular weight.
Example 5. Polymerization of Ethylene at 80C. Using Tetra(neophyl? Zirconium as Catalyst. _ A 350 cc. crown-capped bottle was charged with 200 cc. of dry, deoxygenated toluene and saturated at 80C.
with ethylene. A 0.1 M solution in benzene of the tetra-(neophyl) zirconium of Example 1 was prepared, and 1 cc.
of this solution was charged into the toluene solution of ethylene. Polymerization comrnenced immediately as shown by the precipitation of polymer. Additional ethylene was charged to maintain the pressure at 40 psi. After 1 hour at 80C., polymerization was terminated by addition of 2 cc. of isopropanol. The solid polyethylene was isolated by filtration and dried in a vacuum oven for 16 hours at 80C. The weight of the recovered~ dry, solid white polyethylene was 0.934 g. The polyethylene had a - crystalline melting point of 135.8C., as determined by DSC measurement. Based on the yield of polymer, the rate of polymerization was calculated to have been 9.34 g/milli-mole Zr/hr. The polyethylene was of high molecular weight.
Example 6. Comparative Activity of Neophyl Zirconium Aluminate and Benzyl Zirconium Aluminate on Alumina as Catalysts for the Polymerization of Ethylene in a_Continuous Process.
: -~054~54 a) Polymerization of ethylene using neophyl zirconiumaluminate on alumina as catalyst .
A 0.000625 M solution in n-hexane of the tetra-(neophyl) zirconium of Example 1 was pr~pared. Using the process and apparatus diagrammed in Figure I, a suspension of an active supported catalyst comprising neophyl zirconium aluminate on alumina is continuously prepared by feeding the 0.000625 M solution of tetra(neophyl) zirconium from feed tank, 6, through mixing valve, 15, to premix vessel, 1, at a rate of 200 cc./hr. and a suspension of activated alumina, prepared as in Example 2(&), also is fed from feed tank, 7, through mixing valve, 15, at a rate of 0.5 g. A1203/hr. into premix vessel, 1, a stainless steel, stirred autoclave of 975 cc. capacity where it is diluted with 1400 cc. per hour of hexane and maintained at 50~.
Not shown in Figure 1 is a feed tank and line through which the hexane is fed to premix vessel, 1. After a hold-up time of approximately 40 minutes, to allow for the reactions between tetra(neophyl) zirconium and the activated alumina to produce neophyl zirconium aluminate, the catalyst suspension is continuously fed to a 265 cc.
second stainless steel autoclave, 2, at the same rate, and there diluted with 800 cc./hr. of n-hexane while stirring with mixer, 13. Not shown is a li~e from a hexane feed tank to autoclave, 2, through which the n-hexane is fed. -After a hold-up of 6 minutes in the autoclave the diluted catalyst suspension then is continuously fed through valve, 16, to a 253 cc. stainless stee~ agitated polymeri-zation vessel, 3, stirred by mixer, 14, and maintained at 2250 psi and 250C. where it is contacted with ethylene fed, from reservoir, 9, through valve, 17, as a 7~ weight solution in n-hexane, at 200 g. ethylene/hr.
The concentration of the catalyst in the reactor - with respect to zirconium was 2.0 x 10-5 molar. In order to control and limit molecular weight o~ the polyethylene, ~2 was also fed to the polymerization vessel at a rate of 100 millimoles/hr. as a 0.0825 M solution in n-hexane.
The H2 tank and feed line are not shown in Figure I; if desired, this stream can also be fed through mixing valve, The hold-up time in the polymerization vessel is maintained at approximately 2.56 minutes by continuously withdrawing the polymerization mixture through mixing valve, 19, to a deactivation chamber, a tubu~ar, turbulent mixer, 4, where the catalyst is deactivated to terminate the polymerization by addition from reservoir, 12, through mixing valve, 19, o~ a 0.0033 M solution of isopropanol in n-hexane at a rate of 600 cc./hr to the reaction mixture containing dissolved polyethylene.
Instead of isopropanol, other alkanols, stearn or CO2, can be used as the deactivator.
The solution of polyethylene is continuously dis-charged through an automatic, controlled pressure-reducing valve, 20, into a product receiver, 5, maintained at 50C.
where the solid polyethylene phase is separated from solvent; the polymer stream is passed to polymer recovery system, 11, and recovered from the polyme~ization medium by filtration, and the polyethylene, wet with n-hexane, is chopped in a blender, washed with n-hexane and dried in a vacuum oven at 80C. for 16 hours. Monomers and solvent recovered from the top of separator, 5, are passed - 24 _ 1054~4 through a refining train, not shown, and then recycled through mixing valve, 17, to polymerizer, 3.
The rate of polyethylene production during steady-state operation over a period of several hours was 177 g./hr. (88.5~ cGnversion of the ethylene fed to the polymeri~er). The yield of polyethylene was 1415 kg./mole of zirconium. The dried polyethylene had a melt flow, as determined by ASTM Method 1238-65T, Condition E, of 2.8 decigrams/min. The density of the polyethylene produced, as determined by ASTM D792-64T (method corrected to 23C.) was found to be o.960 g./cc. Thus the polyethylene produced was a highly linear, crystalline polyethylene of high molecular weight suitable for use in production of films and ~njection-molded articles, ~;
b) Polymerization of ethylene using benzyl zirconium aluminate as a catalyst .
The foregoing experiment (Example 6-a) was repeated using, however, as a catalyst the reaction product of the activated alumina and tetra(benzyl) zirconium except that the concentration of zirconium catalyst was increased ; 20 slightly over that in Example 6(a) to 2.14 x 10 5 molar in the polymerization autoclave. In this instance the rate of polyethylene formation was L67 g./hr. (83.8~ con-version of the ethylene fed).
An analysis of the reactions based on the change in activity (a) as shown by where r = hold-up ti~e in the polymerizer Q = ethylene conversion ~ lOS~lS~
reveals a's of 3.029 min 1 for the neophyl zirconium alumi-nate catalyst vs. only 2.017 min 1 for the benzyl zirconium aluminate catalyst. Thus even though the concentration of neophyl zirconium aluminate catalyst in the polymerizer was less (2.0 x 10 5 molar) than benzyl zirconium aluminate ~; catalyst (2.14 x 10 5 molar~ the activity of the neophyl zirconium aluminate was 1.5 times that of benzyl zirconium - aluminate.
Example 7. Polymerization of Propylene Using Neophyl Zirconium Aluminate on Alumina as Catalyst . 10 Into a l-literJ stirred, nitrogen-filled autoclave -was charged 600 ml of cyclohexane purified by purging with nitrogen followed by passing it through a bed of acid alumina under nitrogen. As the autoclave was kept blanketed with nitrogen 0.2 millimoles of neophyl zirconium aluminate supported on one gram of fumed alumina, prepared ~ -as in Example 2, was in~ected by syringe as a slurry in 20 ml of cyclohexane. Propylene was pressured into 20 psi as the system was stirred at ~00 rpm. The tempera~
ture and propylene pressure were raised to 50~60 psi and maintained at this for 4 hrs. The ten grams of poly-propylene obtained was in the form of a gel, which was evaporated to give a tough, flexible sheet. The inherent viscosity of this polymer was 12.5 dl/100 as measured at 0.1% concentration in decalin at 130C. Thirty-five percent of the polymer was insoluble in boiling heptane.
The insoluble polypropylene was highly crystalline and exhibited the isotactic structure. A very tough, rubbery film 5 mils thick was obtained by compression molding 0.5 g. of the total polymer at 230C., 3000 lbs ram pressure.
~OS4154 Exa~ple 8. Polymerizatiorl of Ethylene with a Neophyl Zirconium Silicate on Si~ica Catalyst . . _ 20 g. of a commercially available fumed silica having a surface area of 225 m2/g.was char~ed to a vertical glass reactor and dried at 200C. in a stream of flowing nitrogen for 4 hours. One gram of the dried silica was suspended in 38.5 cubic centimeters of decahydronaphthalene and 1.5 cc. of 0.2M tetra(neophyl) zirconium in benzene was added. After 40 minutes the supernatent liquid above the catalyst was analyzed by gas chromatography. A
material balance showed approximately 2.1 neophyl groups were displaced from each mole of tetra(neophyl) zirconium ; during formation of the neophyl zirconium silicate on silica catalyst.
The polymerization of ethylene was brought about by charging a crown capped bottle containing 340 cc.
of decahydronaphthalene saturated with ethylene at 150C.
and 40 psi with 4 cubic centimeters of the neophyl zirconium silicate on silica catalyst (0.1 g. silica, 0.03 millimole Zr). After 3 minutes the polymerization was stopped by addition of 2 cubic centimeters of` isopropanol.
The solution was cooled and the precipitated polymer separated by filtration, washed with cyclohexane and methanol, and dried in a vacuum ov~en for 16 hrs. at 80C.
The product recovered, including catalyst residue, weighed 0.345 g. which is equivalent to 0.245 g. of polyethylene.
Based on this yield the rate of polymerization was calculated to have been 163 g./millimole Zr/hr as contrasted with the 780 g./millimole Zr/hr achieved in Example 3 by use of the preferred catalyst of this invention.
... .
..
,: Example 9. Copolymerization Or Ethylene and Propylene , with a Neophyl Zirconium Aluminate on ` Alumina Catalyst to for~ a Crystalline Copolymer.
80 cubic centimeters of deoxygenated hexane in an agitated vessel was saturated at 25C. with propylene at 20 psi. The pressure was raised to 40 psi with ethylene and ;~ the copolymerization brought about by the addition of 10 cubic centimeters of a neophyl zirconium aluminate catalyst slurry prepared by reaction of 10 g. of alumina activated - as in Example 1 and 2.0 millimoles of tetra(neophyl) -~ zirconium in 210 cubic centimeters of deoxygenated hexane.
After 20 minutes at 25C. the polymerization was stopped by venting the unreacted olefins. The polymer was separated by filtration washed with methanol and dried at 80C. for 16 hrs. The product recovered weighed 6.44 g.
This copolyrner had a crystalline melting point of 122.5C.
by DSC techniques and was found to contain 10.1 weight %
copolymerized propylene by infrared analysis.
Example 10. Copolymerization of Ethylene and Propylene With a Neophyl Zirconium Aluminate on Alumina Catalyst to Produce an Amorphous ~ 20 Copolymer.
;'''` ' -2 grams of alumina activated as in Example 1 was suspended in 40 cubic centimeters of hexane and 2 cubic centimeters of a 0.2 molar solution of tetra(neophyl) zir-conium in benzene added. After l hr. a portion of the slurry was transferred to a vial and the hexane evaporated under vacuum leaving 1. o6 g. of catalystl The vial was sealed and placed in a stainless steel-reactor with two ,~ stainless steel balls. The reactor was sealed and charged .
with 50 g. of propylene, warmed to 25C. and ethylene added until the pressure in the reactor reached 500 p,i.
':
'' .
r ~ 28 -.
:
The catalyst ampoule was broken and the polymerization allowed to proceed for 1 hr. The amorphous copolymer, isolated as a rubbery ball, was separated from the glass and dried to yield 29 g. of copolymer having a copolymer-ized propylene content of 28.3 weight per cent, as determined by infrared analysis.
Example 11. Polymerization of 1,3-Butadiene with a Neophyl Zirconium Aluminate on Alumina Catalvst ~- A 1 liter agitated flask swept with nitrogen was charged with 500 cubic centimeters of deoxygenated toluene, heated to 50C. and saturated with 1,3-butadiene at 2 psi.
Neophyl zirconium alu~inate on alumina catalyst in hexane, equivalent to 0.38 g. of catalyst (o.076 milli-moles Zr), was added and the polymerization continued for 1 hr. The product which formed was separated by filtra-tion, chopped in a blender and dried in a vacuum oven at 80C. for 16 hrs. The drled product weighed 1.13 g.
which is equivalent to 0.75 g. of polybutadiene. Based on this yield the rate of polymerization was calculated to be 9.9 g./millimole Zr/hr. Infrared analysis showed the structure of the polymer to be of the 1,4-trans-type.
Example 12. Polymerization of Propylene With a Neophyl "
Zirconium Aluminate on Alumina Catalyst 1 gram of alumina activated as in Example 1 was ; suspended in 40 cubic centimeters of dry hexane in a , . . .
stirred flask under nitrogen. 5 cubic centimeters of ; 0.1 molar tetra(neophyl) zirconium was charged to the flask. After 16 hrs. the neophyl zirconium aluminate catalyst was transferred to an ampoule and the hexane evaporated under high vacuum. The ampoule was sealed lOS4~5~
and placed in a stainless steel reactor with two stainless steel balls. The reactor was swept with nitrogen to exclude all air, sealed, evacuated, cooled and 75 g.
of propylene charged. The reactor was warmed to 50C. -and the ampoule broken by shaking the reactor. A~ter 1 hour the polymer was isolated, separated from the glass and dried to yield 26 g. of polypropylene having a melting point of 158C. and a crystallization point of 110C. by DSC. The polypropylene had an inherent viscosity in decahydronaphthalene at 130C. (0.1% solution) of 9.64. Extraction of the polypropylene with boiling hexane for 4 hrs. removed 3% of the polymer indicating the remainder to be substantially high molecular weight polypropylene of isotactic structure. The hexane insoluble fraction was further extracted with boiling toluene. The swollen toluene-insoluble residue, after drying, had a melting point of 162.5C. by D.S.C., and amounted to 90% of the or~ginal crude product. The ; insolubility in toluene at the boiling point indicates that this crystalline polypropylene comprises macromolecules having substantially completely the isotactic structure.
Example 13. Terpolymerization of Ethylene, Propylene and 1,4-Hexadiene with Neophyl Zirconium ; Aluminate on Alumina Catalyst _ _ 4 grams of alumina activated as in Example 1 was suspended in 80 cubic centimeters of hexane and reacted with 12 cubic centimeters of a 0.1 molar solution of tetra(neophyl) zirconium in benzene. A portion of the slurry was transferred to a glass ampoule and the liquid evaporated and the catalyst dried under high vacuum. The iO54154 dry catalyst in the ampoule weighed 1.277 g. The ampoule was placed in a stainless steel reactor with 2 stainless steel balls. The reactor was closed and charged with 50 cubic centimeters of l,4-hexadiene and 50 cubic centimeters of n-hexane. The reactor was cooled, charged wi~h 50 grams of propylene, warmed to 100C. and pressured to 800 psi with ethylene. The catalyst ampoule was broken and the terpolymerization allowed to proceed for 1 hour. The polymer isolated as a crumb was separated from glass and 10 dried to yield 9 g. of terpolymer. A melt pressed film -of the terpolymer was analyzed by infrared analysis and -found to contain 5.5 methyl groups/100 carbons and 8.3 trans-olefin groups/2000 carbons which is equivalent to 15.6% propylene and 2.1~3% hexadiene by weight.
Example 14. Terpolymerization of Ethylene, Propylene and
5-Ethylidene Norbornene with Neophyl Zircon-_ ium Aluminate on Alumina_Catalyst 0.7353 gram of dry neophyl zirconium aluminate on alumina catalyst prepared as in Example 13 was sealed in a glass ampoule. The catalyst ampoule was placed in a stainless steel reactor with 2 stainless steel balls. The reactor was closed, charged with 20 cubic centimeters of 5-ethylidene norbornene, cooled, and charged with 75 g. of propylene. After warming to 100C. the reactor was charged with 700 psi ethylene and the cataiyst ampoule broken.
After 1 hour the polymer was isolated, separated from glass iand dried in a vacuum oven at 80C. for 16 hours. A melt-pressed film of the terpolymer was analyzed by infrared analysis and found to contain 12 methyl groups/100 carbons and 4.6 trans-olefinic groups/100 carbons, which is equiva-lent to a composition of 32 weight % propylene and 1.97 weight % ethylidene norbornene in the terpolymer.
, : `-~054~54 Example 15. Copolymerization of Ethylene and l-Octene ~sing Neophyl Zirconium Aluminate on ~lum na Catalyst. _ _ 1.12 gram of dry neophyl zirconium aluminate catalyst prepared as in Example 13 except having a zireonium content of 0.2 millimoles per gram of alu~ina was sealed in an ampoule and charged to a stainless steel reaetor eontaining 2 stainless steel balls. The reaetor was freed of air and eharged with 10 cubie eentimeters of l-oetene, warmed to 100C., and pressured with 700 psi of ethylene. The eatalyst vial was broken and the eopolymerization allowed to proceed for 1 hour.
The product was isolated, separated from glass and dried. The dry copolymer weighed 3.3 g. and had a melting point of 120C. as determined on a differential scanning calorimeter (Du Pont Model 900).
Since the catalysts of this invention are subject to deactivation by 2~ H20, C02 or other reactive substances, in all of the examples precautions were taken to maintain the equipment clean and dry and free from atmospheric contact, and the solvents, H2 and . .
monomer were freed from traces of moisture or oxygen by the use of conventional desiccating agents and alkali metals.
As shown by the examples, the preferred eatalyst of this invention has a remarkably high aetivity as an olefin polymerization catalyst compared to coordination eatalysts previously known. It has the further very signifieant advantage that, due to its high activity, the low coneentration and the innocuous character of the catalyst residues, which are white, free from : 105415as corrosive halogens and non-toxic, it is not necessary to remove the low level of catalyst residues from the polyolefins produced. This eliminates the expensive, time-consuming catalyst-removal process steps characteristic of previously ~nown commercial processes -. for the preparation of polyolefins using coordination catalysts.
The olefin polymers produced by the process of this invention are regular, linear head-to-tail polymers of high molecular weight useful for subsequent fabrication by conventional equipment into tough colorless films, fibers, molded articles, pipe and wire coatings.
~` V. ANALYTICAL METHODS
(a) The melting points of the polyolefins prepared ---- were accurately determined by differential thermal analysis ; according to the general method described in khe chapter "Application of Differential Thermal Analysis to High Polymers'l, Organic Analysis Volume IV, page 361, Inter-science Publishers, Inc. (1960). Using a differential thermal analyzer, e.g., a Du Pont Model 900 DTA, fitted with a differential scanning calorimeter (DSC) cell ! adjusted to a heating rate of 5C. per minute using an empty alumlnum pan as a reference, a sample of the polymer was heated in an aluminum pan to 20C. above its melting point. The sample was cooled approximately 15 minutes until it reached a temperature of about 50C. and then reheated, again at 5C. per minute, and the melting point observed. This procedure gives comparable melting points fo~ polyolefins to those obtained by visual ; 30 observation using a hot-stage microscope equipped with 1C~5~5a~
crossed polarizers in accord with the ASTM procedure Designation D2117-64 for the determination of the melting point of semicrystalline polymers.
(b) One method for molecular weight determination is the measurement of inherent viscosity of the polymer ;`- in solution. The measurement of inherent viscosity bears a direct relationship to the number average molecular weight for each class of polyolefin and it was used in the above examples to characterize the polypropylene products of the examples. The inherent viscosity (~I~
of the polypropylene was measured by dissolving 0.05 g.
of the polyolefin in 50 milliliters of decahydronaphthalene ~' at 170C. The solution was filtered and transferred to an ^ Ostwald viscometer and the viscosity of the polymer solution and of the decahydronaphthalene solvent measured at 130C. by noting the time required to pass the same volume of each material through the viscometer.
The inherent viscosity (~I) was then calculated by using the following formula:
2.303 log /~low time for soln'n/flow time ~I for solvent7 gm.-of polymer~~n 10~ mL. of s-oIvent.
The inherent viscosity may be correlated with the number average molecular weight of the linear polyolefin, e.g., an inherent viscosity o~ 1.0 corresponds to a number average molecular weight of 180,000, an ~I of 5 corresponds - to 750,000 and an ~I of 10 corresponds to 1,800,000 for the polypropylene polymers disclosed herein.
(c) The weight average molecular weight of the poly-olefin products herein may be measured by the classical methods of light scattering. However, in the case of the , linear polyethylene products of the examples, the welght average molecular weights of the products herein were determined from a previously-established correlation be-tween melt flow (ASTM 1238-65T Conditlon E) and weight average molecula.r weight as determined by light ~catterlng, e.g., a melt ~low of 1 corresponds to a weight average molecular weight (~ ) of 140,000 and a melt ~low o~ 3.5 to ~W = 100,000.
(d3 The characterization of tetra(neophyl) zirconium -10 b~ nuclear magnetic resonance spectroscopy was carried out according to the general procedure described ~n "Interpre-;tatlon o~ NMR Spectra" by R. H. Bible, Plenum Press, 1965;
Appendix, page 119. me tetra(neophyl) zirconlum (0.02 g) was dissolved in 0.2 cc. of deutrobenzene (99.8~) in a 5 mm. O.D. x 5 inch .glass NMR tube, The Rpectrum was determlned at 42C.
The application is a division of copending appli-cation Serial No. 227,242, filed May 16, 1975.
After 1 hour the polymer was isolated, separated from glass iand dried in a vacuum oven at 80C. for 16 hours. A melt-pressed film of the terpolymer was analyzed by infrared analysis and found to contain 12 methyl groups/100 carbons and 4.6 trans-olefinic groups/100 carbons, which is equiva-lent to a composition of 32 weight % propylene and 1.97 weight % ethylidene norbornene in the terpolymer.
, : `-~054~54 Example 15. Copolymerization of Ethylene and l-Octene ~sing Neophyl Zirconium Aluminate on ~lum na Catalyst. _ _ 1.12 gram of dry neophyl zirconium aluminate catalyst prepared as in Example 13 except having a zireonium content of 0.2 millimoles per gram of alu~ina was sealed in an ampoule and charged to a stainless steel reaetor eontaining 2 stainless steel balls. The reaetor was freed of air and eharged with 10 cubie eentimeters of l-oetene, warmed to 100C., and pressured with 700 psi of ethylene. The eatalyst vial was broken and the eopolymerization allowed to proceed for 1 hour.
The product was isolated, separated from glass and dried. The dry copolymer weighed 3.3 g. and had a melting point of 120C. as determined on a differential scanning calorimeter (Du Pont Model 900).
Since the catalysts of this invention are subject to deactivation by 2~ H20, C02 or other reactive substances, in all of the examples precautions were taken to maintain the equipment clean and dry and free from atmospheric contact, and the solvents, H2 and . .
monomer were freed from traces of moisture or oxygen by the use of conventional desiccating agents and alkali metals.
As shown by the examples, the preferred eatalyst of this invention has a remarkably high aetivity as an olefin polymerization catalyst compared to coordination eatalysts previously known. It has the further very signifieant advantage that, due to its high activity, the low coneentration and the innocuous character of the catalyst residues, which are white, free from : 105415as corrosive halogens and non-toxic, it is not necessary to remove the low level of catalyst residues from the polyolefins produced. This eliminates the expensive, time-consuming catalyst-removal process steps characteristic of previously ~nown commercial processes -. for the preparation of polyolefins using coordination catalysts.
The olefin polymers produced by the process of this invention are regular, linear head-to-tail polymers of high molecular weight useful for subsequent fabrication by conventional equipment into tough colorless films, fibers, molded articles, pipe and wire coatings.
~` V. ANALYTICAL METHODS
(a) The melting points of the polyolefins prepared ---- were accurately determined by differential thermal analysis ; according to the general method described in khe chapter "Application of Differential Thermal Analysis to High Polymers'l, Organic Analysis Volume IV, page 361, Inter-science Publishers, Inc. (1960). Using a differential thermal analyzer, e.g., a Du Pont Model 900 DTA, fitted with a differential scanning calorimeter (DSC) cell ! adjusted to a heating rate of 5C. per minute using an empty alumlnum pan as a reference, a sample of the polymer was heated in an aluminum pan to 20C. above its melting point. The sample was cooled approximately 15 minutes until it reached a temperature of about 50C. and then reheated, again at 5C. per minute, and the melting point observed. This procedure gives comparable melting points fo~ polyolefins to those obtained by visual ; 30 observation using a hot-stage microscope equipped with 1C~5~5a~
crossed polarizers in accord with the ASTM procedure Designation D2117-64 for the determination of the melting point of semicrystalline polymers.
(b) One method for molecular weight determination is the measurement of inherent viscosity of the polymer ;`- in solution. The measurement of inherent viscosity bears a direct relationship to the number average molecular weight for each class of polyolefin and it was used in the above examples to characterize the polypropylene products of the examples. The inherent viscosity (~I~
of the polypropylene was measured by dissolving 0.05 g.
of the polyolefin in 50 milliliters of decahydronaphthalene ~' at 170C. The solution was filtered and transferred to an ^ Ostwald viscometer and the viscosity of the polymer solution and of the decahydronaphthalene solvent measured at 130C. by noting the time required to pass the same volume of each material through the viscometer.
The inherent viscosity (~I) was then calculated by using the following formula:
2.303 log /~low time for soln'n/flow time ~I for solvent7 gm.-of polymer~~n 10~ mL. of s-oIvent.
The inherent viscosity may be correlated with the number average molecular weight of the linear polyolefin, e.g., an inherent viscosity o~ 1.0 corresponds to a number average molecular weight of 180,000, an ~I of 5 corresponds - to 750,000 and an ~I of 10 corresponds to 1,800,000 for the polypropylene polymers disclosed herein.
(c) The weight average molecular weight of the poly-olefin products herein may be measured by the classical methods of light scattering. However, in the case of the , linear polyethylene products of the examples, the welght average molecular weights of the products herein were determined from a previously-established correlation be-tween melt flow (ASTM 1238-65T Conditlon E) and weight average molecula.r weight as determined by light ~catterlng, e.g., a melt ~low of 1 corresponds to a weight average molecular weight (~ ) of 140,000 and a melt ~low o~ 3.5 to ~W = 100,000.
(d3 The characterization of tetra(neophyl) zirconium -10 b~ nuclear magnetic resonance spectroscopy was carried out according to the general procedure described ~n "Interpre-;tatlon o~ NMR Spectra" by R. H. Bible, Plenum Press, 1965;
Appendix, page 119. me tetra(neophyl) zirconlum (0.02 g) was dissolved in 0.2 cc. of deutrobenzene (99.8~) in a 5 mm. O.D. x 5 inch .glass NMR tube, The Rpectrum was determlned at 42C.
The application is a division of copending appli-cation Serial No. 227,242, filed May 16, 1975.
Claims (3)
1. Tetra(neophyl) zirconium having the composition represented by the formula 4.
2. In a process for the polymerlzation of olefins in hydrocarbon media to produce solid, linear, high molecular weight polyolefins, the improvement which comprises using tetra(neophyl) zirconium as the polymerization catalyst.
3. A process according to Claim 2 in which ethylene is the sole olefin employed and solid, linear polyethylene is the polgolefin produced.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/471,813 US3932307A (en) | 1974-05-20 | 1974-05-20 | Tetra(neophyl) zirconium and its use in process for the polymerization of olefins |
| CA227,242A CA1052763A (en) | 1974-05-20 | 1975-05-16 | Tetra(neophyl) zirconium and its use in process for the polymerization of olefins |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1054154A true CA1054154A (en) | 1979-05-08 |
Family
ID=25667952
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA306,718A Expired CA1054154A (en) | 1974-05-20 | 1978-07-04 | Tetra(neophyl) zirconium and its use in process for the polymerization of olefins |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1054154A (en) |
-
1978
- 1978-07-04 CA CA306,718A patent/CA1054154A/en not_active Expired
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