NEW BIS-PHOSPHINIMIDE CATALYSTS FOR OLEFIN POLYMERIZATION

Abstract

A phosphinimide catalyst system comprises: i) a phosphinimide pre-polymerization catalyst having two phosphinimide ligands, at least one of which is substituted by a phosphinimide moiety; and ii) a catalyst activator. The catalyst system polymerizes ethylene with an alpha-olefin to give high molecular weight ethylene copolymer.

Claims

1. A phosphinimide pre-polymerization catalyst having the following structure: ##STR00021## wherein P is phosphorus; N is nitrogen; each X is independently an activatable ligand; R.sup.1 is independently selected from a hydrogen atom, a hydrocarbyl group which is unsubstituted or substituted with one or more halogen atom, an alkoxy group, an aryl group, an aryloxy group, an amido group, a silyl group, and a germanyl group; R.sup.2 is independently a hydrocarbyl group which is unsubstituted or substituted with one or more halogen atom; a is 1, 2 or 3; b is 2, 1, or 0; a+b=3; c is 0, 1, 2 or 3; d is 3, 2, 1 or 0; and c+d=3.

2. The phosphinimide pre-polymerization catalyst of claim 1, wherein R.sup.1 is independently a hydrocarbyl group which is unsubstituted or substituted with one or more halogen atom.

3. The phosphinimide pre-polymerization catalyst of claim 2, wherein R.sup.1 is a tert-butyl group.

4. The phosphinimide pre-polymerization catalyst of claim 1, wherein R.sup.2 is a tert-butyl group.

5. The phosphinimide pre-polymerization catalyst of claim 1, wherein each X is methide.

6. A polymerization catalyst system comprising: i) a phosphinimide pre-polymerization catalyst having the following structure: ##STR00022## wherein P is phosphorus; N is nitrogen; each X is independently an activatable ligand; R.sup.1 is independently selected from a hydrogen atom, a hydrocarbyl group which is unsubstituted or substituted with one or more halogen atom, an alkoxy group, an aryl group, an aryloxy group, an amido group, a silyl group, and a germanyl group; R.sup.2 is independently a hydrocarbyl group which is unsubstituted or substituted with one or more halogen atom; a is 1, 2 or 3; b is 2, 1, or 0; a+b=3; c is 0, 1, 2 or 3; d is 3, 2, 1 or 0; and c+d=3; and ii) a catalyst activator.

7. A polymerization process comprising polymerizing ethylene optionally with one or more C.sub.3-12 alpha olefins in the presence of a polymerization catalyst system comprising: i) a phosphinimide pre-polymerization catalyst having the following structure: ##STR00023## wherein P is phosphorus; N is nitrogen; each X is independently an activatable ligand; R.sup.1 is independently selected from a hydrogen atom, a hydrocarbyl group which is unsubstituted or substituted with one or more halogen atom, an alkoxy group, an aryl group, an aryloxy group, an amido group, a silyl group, and a germanyl group; R.sup.2 is independently a hydrocarbyl group which is unsubstituted or substituted with one or more halogen atom; a is 1, 2 or 3; b is 2, 1, or 0; a+b=3; c is 0, 1, 2 or 3; d is 3, 2, 1 or 0; and c+d=3; and ii) a catalyst activator.

8. The polymerization process of claim 7, wherein the polymerization process is a solution phase polymerization process carried out in a solvent.

9. The polymerization process of claim 8, wherein the process comprises polymerizing ethylene with one or more C.sub.3-12 alpha olefins.

10. The polymerization process of claim 9, wherein the process comprises polymerizing ethylene with 1-octene.

Description

EXAMPLES

General Experimental Methods

[0090] All reactions were conducted under nitrogen using standard Schlenk techniques or in an inert atmosphere glovebox. Reaction solvents were purified using the system described by Grubbs et al. (see: Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen R. K.; Timmers, F. J. Organometallics 1996, 15, 1518-1520) and then stored over activated molecular sieves in an inert atmosphere glovebox. Methylmagnesium bromide solution, di-tert-butylchlorophosphine, isopropyldichlorophosphine, copper(I) bromide dimethyl sulfide complex, trimethylsilyl azide, tetrabenzylhafnium(IV), tetrabenzylzirconium(IV), CpTiCl.sub.3, Cul and KOH were purchased from Aldrich and used as it is. 13× molecular sieves were purchased from Grace and activated at 260° C. overnight. LiBr was dried at 150° C. overnight under vacuum. 2,6-di-tert-butyl-4-ethylphenol (BHEB), and azidotrimethylsilane were purchased from Aldrich and used as received. MMAO-7 (7 wt % solution in Isopar-E) was purchase from Akzo Nobel and used as received. Triphenylcarbenium tetrakis(pentafluorophenyl)borate was purchased from Albemarle Corp. and used as received. Deuterated NMR solvents, toluene-d.sub.8 and dichloromethane-d.sub.2, were purchased from Aldrich and stored over 13× molecular sieves prior to use. NMR spectra were recorded on a Bruker 400 MHz spectrometer (.sup.1H: 400.1 MHz, .sup.31P: 162 MHz).

[0091] Molecular weight information (M.sub.w, M.sub.n and M.sub.z in g/mol) and molecular weight distribution (M.sub.w/M.sub.n), and z-average molecular weight distribution (M.sub.z/M.sub.w) were analyzed by gel permeation chromatography (GPC), using an instrument sold under the trade name “Waters 150c”, with 1,2,4-trichlorobenzene as the mobile phase at 140° C. The samples were prepared by dissolving the polymer in this solvent and were run without filtration. Molecular weights are expressed as polyethylene equivalents with a relative standard deviation of 2.9% for the number average molecular weight (“Mn”) and 5.0% for the weight average molecular weight (“Mw”). Polymer sample solutions (1 to 2 mg/mL) were prepared by heating the polymer in 1,2,4-trichlorobenzene (TCB) and rotating on a wheel for 4 hours at 150° C. in an oven. The antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT) was added to the mixture in order to stabilize the polymer against oxidative degradation. The BHT concentration was 250 ppm. Sample solutions were chromatographed at 140° C. on a PL 220 high-temperature chromatography unit equipped with four Shodex columns (HT803, HT804, HT805 and HT806) using TCB as the mobile phase with a flow rate of 1.0 mL/minute, with a differential refractive index (DRI) as the concentration detector. BHT was added to the mobile phase at a concentration of 250 ppm to protect the columns from oxidative degradation. The sample injection volume was 200 mL. The raw data were processed with CIRRUS®GPC software. The columns were calibrated with narrow distribution polystyrene standards. The polystyrene molecular weights were converted to polyethylene molecular weights using the Mark-Houwink equation, as described in the ASTM standard test method D6474.

[0092] The branch frequency of copolymer samples (i.e. the short chain branching, SCB per 1000 backbone carbon atoms) and the C.sub.8 comonomer content (in wt %) was determined by Fourier Transform Infrared Spectroscopy (FTIR) as per the ASTM D6645-01 method. A Thermo-Nicolet 750 Magna-IR Spectrophotometer equipped with OMNIC® version 7.2a software was used for the measurements.

[0093] The determination of branch frequency as a function of molecular weight (and hence the comonomer distribution) was carried out using high temperature Gel Permeation Chromatography (GPC) and FT-IR of the eluent. Polyethylene standards with a known branch content, polystyrene and hydrocarbons with a known molecular weight were used for calibration.

Example 1

[0094] The general synthetic steps and methods employed to make the phosphinimide pre-catalyst of Example 1, dimethyl bis[(di-tert-butyl(phosphinimide)phosphinimide]titanium are provided below.

Synthesis of Lithium tri-tert-butylphosphinimide

[0095] ##STR00012##

[0096] Tri-tert-butylphosphinimine (40.5 g, 186.34 mmol) was dissolved in a minimum amount of heptane at room temperature, and then nBuLi (120 mL, 192 mmol) was added dropwise. The mixture was stirred overnight, and the precipitate was filtered and washed with heptane (3×20 mL). After being dried in vacuo, the white solid was collected and stored in a −35° C. freezer. Yield: 32.3 g, 78%. .sup.31P{H} (THF-ds): δ31.0. .sup.1H NMR (THF-ds): δ1.31 (d).

[0097] Synthesis of (tri-tert-butylphosphiniminol(di-tert-butyl)phosohine

##STR00013##

[0098] A mixture of CuBr.SMe.sub.2 (0.5 g, 2.43 mmol), LiBr (1 g, 11.51 mmol), and lithium tri-tert-butylphosphinimide (10.5 g, 40.74 mmol) was suspended in THF (100 mL) and cooled to −72° C. with a dry ice/ethanol bath. A solution of CIP.sup.tBu.sub.2 (8.5 g, 47.05 mmol) in heptane (10 mL) was added dropwise. The reaction was stirred overnight, slowly warmed up to room temperature and then heated at 60° C. for ten days. All the volatiles were removed under vacuum, and the solid was extracted with hot toluene (90° C.) (3×100 mL). After being filtered through Celite, all toluene was removed, and the product was recrystallized out from a minimum amount of hot heptane (100° C.) solution overnight. Yield: 9 g, 53%. .sup.31P{.sup.1H} (toluene-d.sub.8): δ90.6 (d), 39.3 (d). .sup.1H NMR (toluene-d.sub.8): δ1.36 (d, 18H), 1.32 (d, 27H).

Synthesis of Trimethylsilyl-(Tri-Tert-Butylphosphinimino)(Di-Tert-Butyl)Phosphinimine

[0099] ##STR00014##

[0100] (Tri-tert-butylphosphinimino)(di-tert-butyl)phosphine (2 g, 5.53 mmol) and trimethylsilyl azide (0.87 g, 1 mL, 8.29 mmol) was mixed in toluene (30 mL) and heated up to 60° C. The second portion of trimethylsilyl azide (0.87 g, 1 mL, 8.29 mmol) was added after one hour at 60° C. The reaction was then heated at 100° C. overnight, all volatiles were removed in vacuo to give a white solid. Yield: 2.48 g, 100%. .sup.31P{.sup.1H} (CD.sub.2Cl.sub.2): δ40.4 (d), 18.9 (d). .sup.1H NMR (CD.sub.2Cl.sub.2): δ1.37 (d, 18H), 1.27 (d, 27H), 0.38 (s, 9H).

Synthesis of (tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimine

[0101] ##STR00015##

[0102] Sodium metal (ca. 0.2 g) was dissolved in degassed methanol (200 mL). This solution was then added into a flask containing trimethylsilyl-(tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimine (8.5 g, 18.94 mmol). The mixture was heated at 55° C. overnight. All volatiles were removed in vacuo. The product was extracted with toluene (3×50 mL) and filtered through a pad of Celite. A white solid was obtained after all solvent was removed. Yield: 6.85 g, 96%. .sup.31P{1H} (CD.sub.2Cl.sub.2): δ45.6(d), 42.4(d). .sup.1H NMR (CD.sub.2Cl.sub.2): δ1.50 (d, 27H), 1.29 (d, 18H).

Synthesis of trimethyl[(tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimide]titanium

[0103] ##STR00016##

[0104] (Tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimine (2.35 g, 6.24 mmol), and tetrakis(dimethylamido)titanium (1.40 g, 6.24 mmol) were mixed in toluene (50 mL) and heated to reflux overnight. After all volatiles were removed under vacuum, the product was re-dissolved in toluene (50 mL). TMSCI (2.10 g, 19.33 mmol) was added. The mixture was stirred overnight, and then dried in vacuo. The white solid was then re-dissolved in toluene (50 mL) again. CH.sub.3MgBr (15 mL, 45 mmol, 3M in diethyl ether) was added. After the mixture was stirred overnight again, all volatiles were removed. The product was extracted with toluene (3×30 mL) and filtered through a pad of Celite. After being recrystallized from toluene/heptane mixture, a white solid was obtained. Yield: 1.50 g, 51%. .sup.31P{.sup.1H} (CD.sub.2Cl.sub.2): δ45.2 (d), 12.4 (d). .sup.1H NMR (CD.sub.2Cl.sub.2): δ1.47 (d, 18H), 1.26 (d, 27H), 1.02 (s, 9H).

Synthesis of dimethyl bisRtri-tert-butylphosphinimino)(di-tert-butyl)phosphinimideltitanium

[0105] ##STR00017##

[0106] To a solution of trimethyl[(tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimide]titanium (1.50 g, 3.20 mmol) in toluene (25mL), (tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimine (1.20 g, 3.19 mmol) in toluene (15 mL) was added dropwise over half hour. The mixture was then stirred overnight at room temperature. All volatiles were then removed in vacuo. The product was crystallized from a mixture of toluene/pentane solution at −35° C. Yield: 1.40 g, 53%. .sup.31P{.sup.1H} (CD.sub.2Cl.sub.2): δ40.4 (d), 8.4(d). .sup.1H NMR (CD.sub.2Cl.sub.2): δ2.09 (d, 36H), 1.40 (d, 54H), 0.67 (s, 6H).

Example 2

Synthesis of dimethyl {(tri-tert-butylphosphinimide)[(tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimide]}titanium

[0107] ##STR00018##

[0108] To a solution of trimethyl(tri-tert-butylphosphinimide)titanium (2.93 mmol) in toluene (50 mL), (tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimine (1.10 g, 2.92 mmol) in toluene (15 mL) was added dropwise over half hour. The mixture was then stirred for 1 hour at room temperature. All volatiles were then removed in vacuo. The yellow tar was dissolved in pentane (50 mL) and evaporated to yield the product as an off-white powder. Yield: 1.65 g, 83%. .sup.31P{.sup.1H} (toluene-d.sub.8): δ42.2 (d), 24.1(d), 9.6(s). .sup.1H NMR (toluene-d.sub.8): δ1.54 (d, 18H), 1.40 (d, 54H), 0.66 (s, 6H).

Example 3

Synthesis of dibenzyl bis[(tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimide]zirconium

[0109] ##STR00019##

[0110] To a solution of tetrabenzylzirconium(IV) (0.91 g, 2 mmol) in toluene (25 mL), (tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimine (1.51 g, 4 mmol) in toluene (25 mL) was added dropwise over half hour. The mixture was then stirred overnight at room temperature. All volatiles were then removed in vacuo. The product was crystallized from a mixture of toluene/pentane solution at −35° C. Yield: 0.873 g, 43%. .sup.31P{.sup.1H} (toluene-d.sub.8): δ39.98 (d), 16.0 (d). .sup.1H NMR (toluene-d.sub.8): δ7.19 (m, 8H), 6.85 (m, 2H), 2.46 (s, 4H), 1.45 (d, 36H), 1.32 (d, 54H).

Example 4

Synthesis of dibenzyl bis[(tri-tert-butylphosphinimino)(di-tert-butyl)phosphinimide]hafnium

[0111] ##STR00020##

[0112] To a solution of tetrabenzylhafnium(IV) (1.09 g, 2 mmol) in toluene (25 mL), di-tert-butyl(phosphinimino)phosphinimine (1.51 g, 4 mmol) in toluene (25 mL) was added dropwise over half an hour. The mixture was then stirred overnight at room temperature. All volatiles were then removed in vacuo. The product was crystallized from a mixture of toluene/pentane solution at −35° C. Yield: 0.87 g, 39%. .sup.31P{.sup.1H} (toluene-d.sub.8): δ39.5 (d), 25.3 (d). .sup.1H NMR (toluene-d.sub.8): δ7.20 (m, 8H), 6.84 (m, 2H), 2.25 (s, 4H), 1.45 (d, 37H), 1.32 (d, 54H)

Solution Polymerization

[0113] Continuous solution polymerizations were conducted on a continuous polymerization unit (CPU) using cyclohexane as the solvent. The CPU contained a 71.5 mL stirred reactor and was operated at a temperature of 140° C., or 160° C. for the polymerization experiments. An upstream mixing reactor having a 20 mL volume was operated at 5° C. lower than the polymerization reactor. The mixing reactor was used to pre-heat the ethylene, 1-octene and some of the solvent streams. Catalyst feeds (xylene or cyclohexane solutions of phosphinimide pre-polymerization catalyst and (Ph.sub.3C)[B(C.sub.6F.sub.5).sub.4] as a catalyst activator) and additional solvent were added directly to the polymerization reactor in a continuous process. A total continuous flow of 27 mL/min into the polymerization reactor was maintained.

[0114] Copolymers were made at a 1-octene/ethylene weight ratio of 0.5, 0.3, or 0.15. The ethylene was fed at a 10 wt % ethylene concentration in the polymerization reactor. The CPU system operated at a pressure of 10.5 MPa. The solvent, monomer, and comonomer streams were all purified by the CPU systems before entering the reactor. The polymerization activity, k.sub.p (expressed in mM.sup.−1.Math.min.sup.−1), is defined as:

[00002]$k_p=\left(\frac{Q}{100-Q}\right)\left(\frac{1}{\left[M\right]}\right)\left(\frac{1}{\mathrm{HUT}}\right)$

where Q is ethylene conversion (%) (measured using an online gas chromatograph (GC)), [M] is catalyst concentration in the reactor (mM), and HUT is hold-up time in the reactor (2.6 min).

[0115] Copolymer samples were collected at 90±1% ethylene conversion (Q), dried in a vacuum oven, ground, and then analyzed using FTIR (for short-chain branch frequency) and GPC-RI (for molecular weight and distribution). Polymerization conditions are listed in Tables 1 and 3 and copolymer properties are listed in Tables 2 and 4.

[0116] An inventive ethylene homopolymerization with the catalyst of Example 1 was carried out in polymerization Run No. 4, while inventive copolymerzations of ethylene with 1-octene with the catalyst of Example 1 were carried out in polymerization Run Nos. 1, 2 and 3 under decreasing ratios of comonomer.

[0117] Inventive copolymerizations of ethylene with 1-octene (and homopolymerization with ethylene) with the catalyst of Example 2 were carried out in polymerization Run Nos. 5, 6, 7 and 8 under decreasing ratios of comonomer.

[0118] Comparative copolymerizations of ethylene with 1-octene using the catalyst ((t-Bu).sub.3PN).sub.2TiMe.sub.2, which was first disclosed in U.S. Pat. No. 6,649,558, were carried out in polymerization Run Nos. 9, 10 and 11 under decreasing ratios of comonomer.

TABLE-US-00001 TABLE 1 Polymerization Conditions Catalyst B (from Reactor C2 C2 k.sub.p Polymerization Example [Metal] Borate)/ Temp. Flow conversion, (mM.sup.−.sup.1 .Math. Run. No. No. (μM) Ti (° C.) (g/min) C8/C2 Q (%) min.sup.−.sup.1) 1 1 18.52 22.22 140 2.1 0.50 89.65 180 2 1 18.52 22.22 140 2.1 0.30 89.76 182 3 1 22.22 26.67 140 2.1 0.15 90.27 161 4 1 27.41 32.89 140 2.1 0 90.44 133 5 2 5.19 6.22 140 2.1 0.50 89.99 667 6 2 5.19 6.22 140 2.1 0.30 90.1 675 7 2 5.19 6.22 140 2.1 0.15 90.1 779 8 2 5.19 6.22 160 2.7 0 90.53 709 9 Comp. 0.63 0.75 140 2.1 0.50 89.26 5077 10 Comp. 0.63 0.75 140 2.1 0.30 89.40 5190 11 Comp. 0.63 0.75 140 2.1 0.15 90.72 6016 Note: C2 = ethylene; C8 = 1-octene

TABLE-US-00002 TABLE 2 Copolymer Properties FTIR Short Chain Catalyst FTIR 1-octene Branching per 1000 Polymerization Example content (weight carbon atoms Run. No. No. percent, wt %) (SCB/1000 C) Mw Mn Mw/Mn 1 1 6.7 8.8 160848 86953 1.85 2 1 5.6 7.4 181136 92965 1.95 3 1 2.8 3.5 216885 98584 2.30 4 1 — — 252868 119524 2.12 5 2 13.2  18.3 92413 39921 2.31 6 2 8.7 11.6 118880 56811 2.09 7 2 4.9 6.3 152397 77726 1.96 8 2 — — 130292 65030 2 9 Comp. 17.3  24.9 41408 23233 1.78 10 Comp. 11.7  16 56408 30890 1.83 11 Comp. 6.9 9.1 81849 42992 1.9

[0119] A person skilled in the art will see from the data provided in Tables 1 and 2, that under similar copolymerization conditions, the catalysts of Inventive Examples 1 and 2, provide higher molecular weight ethylene copolymers than does the comparative catalyst system. Compare for example polymer Run Nos. 2, 6 and 10 in which similar polymerization conditions were employed. The catalyst of Inventive Example 1 gave a weight average molecular weight (Mw) of 181,136, the catalyst of Inventive Example 2 gave a weight average molecular weight (Mw) of 118,880, while the catalyst of the Comparative Example produced a copolymer with a weight average molecular weight (Mw) of only 56,408. A similar outcome is found when comparing Inventive Polymer Run Nos. 3 and 7 with Comparative polymer Run No. 11: the weight average molecular weights achieved are 216,885, 152,397 and 81,849 respectively. It is evident then, that by altering the steric and electronic parameters of the supporting phosphinimide ligands, by adding a sterically encumbered and strongly electron donating phosphinimide substituent to a phosphinimide ligand, a person skilled in the art can change the molecular weight performance of these catalysts with respect to ethylene copolymerization.

[0120] Further polymerization experiments were attempted using Zr and Hf analogous of the catalyst of Example 1 with more limited results (see Table 3 and 4). The Zr based catalyst of Example 3 gave copolymers of ethylene and 1-octene with poor (e.g. very low) molecular weights (e.g. the M.sub.w values were below about 10,000 g/mol; see Polymerization Run Nos. 12-14), while the Hf based catalyst of Example 4 gave results which may be consistent with catalyst disproportionation or decomposition pathways (e.g. low catalyst activity and very large molecular weights distributions: Mw/Mn of more than about 40, indicated that a single catalytic species was not present under polymerization conditions; see Polymerization Run No. 16). These results suggest that titanium may be the ideal group 4 metal for the presently disclosed ligand set.

TABLE-US-00003 TABLE 3 Polymerization Conditions Catalyst B (from Reactor C2 C2 k.sub.p Polymerization Example [Metal] Borate)/ Temp. Flow conversion, (mM.sup.−.sup.1 .Math. Run. No. No. (μM) Zr or Hf (° C.) (g/min) C8/C2 Q (%) min.sup.−.sup.1) 12 3 20.00 24.00 140 2.1 0.5 89.56 165 13 3 19.63 23.56 140 2.1 0.30 89.77 172 14 3 19.26 23.11 140 2.1 0.15 89.97 179 15 3 20.74 24.89 140 2.1 0 90.07 168 16 4 51.85 62.22 140 2.1 0.15 82.60 35

TABLE-US-00004 TABLE 4 Copolymer Properties FTIR Short Chain Catalyst FTIR 1-octene Branching per 1000 Polymerization Example content (weight carbon atoms Run. No. No. percent, wt %) (SCB/1000 C) Mw Mn Mw/Mn 12 3 8.3 11.1  6055 1682 3.60 13 3 4.6 5.9 8104 3873 2.09 14 3 3.3 4.2 8194 2415 3.39 15 3 — — 9867 3512 2.81 16 4 7.2 9.4 55055 1166 47.22

INDUSTRIAL APPLICABILITY

[0121] Group 4 transition metal catalysts may be used to facilitate the polymerization of ethylene and alpha olefins into commercially useful thermoplastic materials. The present disclosure provides a new group 4 transition metal polymerization catalyst which polymerizes ethylene with an alpha-olefin to produce ethylene copolymers having high molecular weight.