WO2008148499A1

WO2008148499A1 - Imine catalyst

Info

Publication number: WO2008148499A1
Application number: PCT/EP2008/004278
Authority: WO
Inventors: Edwin Gerard Ijpeij; Philip Mountford
Original assignee: Dsm Ip Assets B.V.
Priority date: 2007-06-06
Filing date: 2008-05-29
Publication date: 2008-12-11

Abstract

The invention relates to a one component imine catalyst system for polyolefin polymerization, according to the following formula (I), wherein Cp is a cyclopentadienyl comprising ligand, N=Y is an anionic imine ligand chosen from the group of phosphinimine, amidine, iminoimidazolidine, or ketimide, M is Ti, Zr, or Hf, and X is a hydride or a hydrocarbyl group and Z' is a borate anion. The invention further relates to a process for the preparation of the one component catalyst according to the invention and to an olefin polymerization process in the presence of the one component catalyst of the invention.

Description

IMINE CATALYST

The invention relates to a single site catalyst and in particular a single site catalyst for an olefinic polymerization process A single site catalyst is typically used in olefin polymerization in combination with a co-catalyst like methylaluminoxane, (MAO) or a borate salt like e g A⁺BF20^~ wherein A⁺ is the cation in the BF20^" (tetrakιs(pentafluorophenyl)borate) salt, e g H⁺, Li⁺, NH₄ ⁺, dialkylanilinium or the tπtyl (T) cation

In an olefin polymerization an active catalyst, with a general formula L₁L₂MX⁺BF20^' is formed by equimolar reaction of L₁L₂MX₂ with e g TBF20 as shown below

L₁L₂MX₂ + Ph₃C⁺ BF2θ^" L₁ L₂MX⁺ BF20- + Ph₃CX

(equation 1 )

In equation 1 L₁ is a monoanionic hgand, L₂ is a monoanionic or neutral ligand, M is Ti, Zr or Hf, and X is a hydride or an hydrocarbyl group that is able to react with the cation of the borate salt Often, in olefin polymerisation a slight excess (1 5-2 equivalents) of the costly borate salt is needed

An excess of catalyst above the 1 1 molar metal to boron ratio is harmful for the catalyst productivity due to the fact that (ι) for this excess no ABF20 is present, and (n) occasionally the catalyst acts also as catalyst poison or modifies the catalyst generating an undesirable second active site This is caused by the dimeπzation reaction of neutral catalyst with the cationic catalyst as described by M Bochmann in the Journal of Organometallic Chemistry 689 (2004) 3982-3998, Scheme 3 on page 3984 A dimeπzed catalyst molecule may inhibit the catalytic activity in olefinic polymerizations

A too high amount of ABF20 is inactive without the required equimolar amount of catalyst As the catalyst is generally more expensive than the co- catalyst, in a polyolefin polymerization plant usually the co-catalyst is dosed slightly in excess to compromise catalyst productivity to optimize catalyst costs

A disadvantage of the present catalyst is that catalyst and ABF20 have to be dosed in two different feed streams with either an excess of ABF20 or a risk of an amount unused catalyst, and in any case additional dosing and control equipment An object of the present invention is to provide a single component catalyst system that can be dosed via just one feedstream to a polymerization reactor.

Surprisingly we have found that a compound according to formula 1 is an active one component catalyst system for olefin polymerization,

Formula (1)

wherein Cp is a cyclopentadienyl comprising ligand, N=Y is an anionic imine ligand chosen from the group of phosphinimine, amidine, iminoimidazolidine, or ketimide, M is

Ti, Zr, or Hf, and X is an hydride or a hydrocarbyl group, and Z^' is a borate anion. Formula (1) comprises both the trans and the cis isomers of the catalyst according to the invention.

With the catalyst system of the present invention just one component need to be fed to a reactor for polyolefin polymerization without the risk of deviating from a 1 :1 ration between catalyst and co-catalyst. The single site catalyst of the invention comprised a borate anion.

Examples of borate anions are: tetrakisphenylborate, tetrakis(p-tolyl)borate, tetrakis(m-tolyl)borate, tetrakis(o-tolyl)borate, tetrakis(o,p-dimethylphenyl)borate, tetrakis(m,m-dimethylphenyl)borate, tetrakis(p-trifluoromethylphenyl)borate, tetrakis(3,5-bistrifluoromethylphenyl)borate tetrakis(n-butylphenyl)borate, tetrakispentafluorophenyl borate, phenyltrispentafluorophenyl borate, phenyltrispentafluorophenyl borate, tetrakis (2,3,5,6-tetrafluorophenyl) borate, tetrakis (3,4,5-tπfluorophenyl) borate, tetrakis (1 ,2,2-tnfluoroethenyl) borate, and tetrakis (2,3,4,5-tetrafluorophenyl) borate

The borate anion is preferably a tetrakιs(perfluorophenyl)borate anion (BF20 ) The activity of the compound of the present invention is surprising since the vacant site of the Ti atoms is obviously blocked It may be speculated that the dimer is opened to a monomer by the monomers when entering the reactor

In one embodiment of the invention hydrocarbyl groups X are monoanionically charged hydrocarbyl groups The hydrocarbyl groups optionally contain heteroatoms of groups 13-17 Preferred hydrocarbyl groups include hydride, alkyl, aryl, aralkyl, alkaryl, substituted vinyl and substituted allyl groups More preferred hydrocarbyl groups include hydride, alkyl, aryl, aralkyl and alkaryl groups Most preferred hydrocarbyl groups include alkyl, aryl, aralkyl and alkaryl groups Examples of such most preferred hydrocarbyl groups are methyl, benzyl, methyltπmethylsilyl, phenyl, methoxyphenyl, dimethoxyphenyl, N,N-dιmethylamιnophenyl, bis (N₁N- dιmethylamιno)phenyl, fluorophenyl, difluorophenyl, trifluorophenyl, tetrafluorophenyl, perfluorophenyl, trialkylsilylphenyl, bιs(trιalkylsιlyl)phenyl, trιs(trιalkylsιlyl)phenyl and the like

The hydrocarbyl group is preferably chosen from methyl, benzyl, diphenylmethyl, neopentyl or methyltrimethylsilyl X is most preferably methyl or benzyl

Cp preferably is a substituted Cp or a substituted indenyl Substituents on Cp or indenyl can be hydrocarbyl groups The metal M is preferably Ti

Sita, J Am Chem Soc 2000, 122, 12909-12910, describes a dimeric Zr compound of an amidinate with BF20 as counterion for polyolefin polymerization However the compound described by Sita is based ion η³-amιdιnate and decomposes above -10⁰C, whereas olefin polymerization temperatures are typically above 7O⁰C Obviously, the productivity of Sita's compound is economically not viable An advantage of the catalyst of the present invention is its surprisingly high stability It has been shown that the catalyst of the present invention is stable well above room temperature and even above 9O⁰C

The invention further relates to a process for the preparation of a one component catalyst system for polyolefin polymerization by stirring a mixture of CpM(N=Y)X₂ and A⁺Z^' , in an inert solvent, wherein A⁺ is a cation and Z^" is a borate anion Examples of solvents include chlorobenzene, fluorobenzene, iodobenzene, dichlorobenzene, dibromobenzene and dijodobenzene The preparation usually proceeds at room temperature within 30 minutes Often, the reaction is instantaneously and quantitative in yield Typical cations A⁺ are Li⁺, NH₄ ⁺, triphenylmethylium ⁺(trιtylι⁺)

The choice of the solvent is essential since halogenated aliphatic solvents may give decomposition reactions of the cationic catalyst by e g solvent activation Therefore, solvents generally used for the preparation of cationic catalysts such as chloroform and dichloromethane are less useful for the preparation of the cationic catalyst according to the invention

The invention further relates to a process for the preparation of a polyolefin wherein said process is being undertaken in the presence of a catalyst which comprises an unbridged catalyst having a single cyclopentadienyl hgand and a monosubstituted monoanionic nitrogen hgand Such a process is known from EP1162214 In the process described in EP1162214 the polymerization is carried out in the presence of a catalyst having a single cyclopentadienyl hgand and a monosubstituted monoanionic nitrogen hgand and a boron activator, which are dosed to the reactor as two separate feed streams The present invention now provides a process for the preparation of a polyolefin wherein said process is being undertaken in the presence of a one component imine catalyst system according to the invention and optionally a scavenger Examples of polyolefins that can be made by the process of the invention are polymers prepared from monomers like ethylene, propylene, butylenes, hexene, octene, decene, diolefins or mixtures thereof

The process of the invention can be carried out in solution, the gasphase or in a slurry Solution processes for the polymerization of polyolefins are well known in the art These processes are conducted in the presence of an inert hydrocarbon solvent such as a C5-12 hydrocarbon which may be unsubstituted or substituted by a C1-4 alkyl group such as pentane, methyl pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane and hydrogenated naphtha

The process of the invention is particularly suitable to produce polyolefins and in particular EPDM and polyethylene with an average molecular weight of more than 10 kg/mol, preferably more than 100 kg/mol and most preferably more than 1000 kg/mol Polyolefins with a molecular weight of more than 1000 kg/mol are typically made according to the process of the invention in a slurry

To prepare elastomer co- and terpolymers of ethylene, propylene and optionally one or more diene monomers, the process of this invention is generally undertaken at a temperature of from 20⁰C to 15O⁰C A higher polymerization temperature will generally reduce solution viscosity (which is desirable) but also reduce molecular weight (which may be undesirable) The preferred polymerization temperature is less than 100⁰C, where a surprising combination of excellent polymerization activity and excellent molecular weight may be obtained

The present invention is a process which is also used to prepare elastomer co- and ter- polymers of ethylene, propylene and optionally one or more diene monomers Generally such polymers will contain about 50 to about 80 weight % ethylene (preferably about 50 to 60 weight % ethylene) and correspondingly from 50 to 20 weight % of propylene The elastomers of this invention may also be prepared with a small amount of diene monomer so as to facilitate crosslinking or vulcanization of the elastomer-as is well known to those skilled in the art The diene is preferably present in amounts up to 10 weight % of the polymer and most preferably is present in amounts from about 3 to 7 weight % The resulting polymer may have a composition comprising from 40 to 75 weight % of ethylene, from 50 to 15 weight % of propylene and up to 10 weight % of a diene monomer to provide 100 weight % of the polymer More than one type of diene monomer may be included Preferred but not limiting examples of the dienes are dicyclopentadiene, 1 ,4-hexadιene, 5-methylene-2-norbomene, 5-ethylιdene- 2-norbornene and 5-vιnyl-2-norbornene, especially 5-ethylιdene-2-norbomene and 1 ,4- hexadiene

The monomers are dissolved/dispersed in a solvent either prior to being fed to the reactor (or for gaseous monomers the monomer may be fed to the reactor so that it will dissolve in the reaction mixture) Prior to mixing, the solvent and monomers are generally purified to remove potential catalyst poisons such as water, oxygen or metal impurities The feedstock purification follows standard practices in the art, e g molecular sieves, alumina beds and oxygen removal catalysts are used for the purification of monomers The solvent itself as well (e g methyl pentane, cyclohexane, hexane or toluene) is preferably treated in a similar manner

The monomers and/or solvents may be heated or cooled prior to feeding to the polymerization reactor Additional monomers and solvent may be added to a second reactor (if employed) and it may also be heated or cooled The residence time in the polymerization reactor will depend on the design and the capacity of the reactor Generally the reactors should be operated under conditions to achieve a thorough mixing of the reactants If a dual reactor polymerization process is employed, it is preferred that from 20 to 60 weight % of the final polymer is polymerized in the first reactor, with the balance being polymerized in the second reactor. On leaving the reactor the solvent is removed and the resulting polymer is finished in a conventional manner.

Synthesis of the components

Example 1. Preparation of [pentamethylcyclopentadienyl-N, N-diisopropyl-2, 6- difluorobenzamidinato titanium(IV) methyl]₂.[tetrakis(pentafluorophenyl)borate]₂

(catalyst 1).

To a mixture of pentamethylcyclopentadienyl-N, N-diisopropyl-2, 6- difluorobenzamidinato titanium(IV) dimethyl (catalyst A) (0.5Og, 1.1 mmol) and trityl tetrakis(pentafluorophenyl)borate (TBF20) (1.02g, 1.1 mmol) was added fluorobenzene

(20 ml_) at room temperature. The mixture was stirred for 30 minutes and the magnetic stirring bar was removed. Dark red single crystals (0.63 g, 53%) were obtained by cooling the mixture to -20^°C for 3 days.

The crystal structure of pentamethylcyclopentadienyl-N, N-diisopropyl- 2,6-difluorobenzamidinato titanium(IV) methyl tetrakis(pentafluorophenyl)borate

(catalyst 1) is shown in Fig. 1. Figure 1 clearly shows a dimeric complex of

[pentamethylcyclopentadienyl-N, N-diisopropyl-2, 6-difluorobenzamidinato titanium(IV) methyl]₂.[tetrakis(pentafluorophenyl)borate]₂, (catalyst 1) wherein for clarity reasons the

.[tetrakis(pentafluorophenyl)borate]₂ anion has been omitted. Hydrogen atoms (except those for the bridging methyl groups) and borate ions are omitted for clarity reasons.

Anal. Results for C₉₆H₇₀B₂F₄₄N₄Ti₂: calc. C 51.64; H, 3.16; N, 2.51 found C 51.57, H 3.07, N 2.41

Comparative experiment A. NMR scale activation of catalyst A. An NMR tube was charged with compound A (10 mg, 22 μmol and trityl tetrakis(perfluorophenyl borate (TBF20, 22 mg, 24 μmol). Chlorobenzene-d5 (0.5 ml_) was added to the mixture and the ¹H-NMR spectrum was measured on a Bruker 300 MH₂ NMR spectrometer. ¹H-NMR δ (ppm, C₆D₅CI): 7.40 (m, 15H, Ar(Ph₃CMe), 7.30 (t, 1 H, ArH (amidine ligand)), 7.0 (t, 2H, ArH (amidine ligand)), 4.1 (bs, 1H, i-Pr), 3.8 (m, 1 H, i-Pr), 2.30 (s, 3H, Me(Ph₃CMe), 2.00 (s, 15H, Me-Cp^*), 1.51 (d, 6H₁ /-Pr) 1.23 (d, 6H₁ /-Pr)), 1.20 (s, 3H, Ti-Me).

The ¹H-NMR spectrum shows a 1,1 ,1-triphenylethane singlet at 2.3 ppm as the product of the reaction between pentamethylcyclopentadienyl-N, N- diisopropyl-2, 6-difluorobenzamidinato titanium(IV) dimethyl and tritylium- tetrakis(pentafluorophenyl)borate. However, the dimeric nature of the present compound of the present invention in solution cannot be confirmed from the present NMR spectrum due to its symmetric nature.

In order to investigate whether a dimeric structure in the solution is present or not, ¹H-NMR experiments were further carried out on Cp(C₆F₅)((tert- Bu)₃PN)TiMe₂ (compound B) and on a mixture of A and B, all of which were activated with TBF20.

An NMR tube was charged with Cp(C_BF5)((tert-Bu)₃PN)TiMe₂ (10 mg, 19 μmol) and trityl tetrakis(perfluorophenyl borate (TBF20, 18 mg, 19 μmol) and C₆D₅CI (0.5 ml.) was added.

¹H-NMR δ (ppm, C₆D₅CI): 7.40 (m, 15H, Ar(Ph₃CMe), 6.75 (m, 2H, CpH), 6.50 (m, 2H, CpH), 2.30 (s, 3H, Me(Ph₃CMe), 1.6 (s, 3H, Me-Ti), 1.5 (d, 27H, tert-Bu) 3¹P-NMR δ (ppm, C₆D₅CI): 75 (1 P)

The ¹H-NMR spectrum shows again the 1 ,1 ,1-triphenylethane singlet at 2.3 ppm as a reaction product.

In case of dimerization in the solution a statistical mixture of two symmetrical dimeric comounds and one asymmetric dimeric compound as depicted in the scheme below would have been expected:

asymmetric

In compound A the Tι-CH3 resonance is at +1 2 ppm, in compound B the Tι-CH3 resonance is found at 1 6 ppm,

In a third experiment an NMR tube was charged with compound A (10 mg, 22 μmol), Compound B (12 mg, 22 μmol) and trityl tetrakιs(perfluorophenyl borate (TBF20, 44 mg, 48 μmol) Chlorobenzene-d5 (0 5 mL) was added to the mixture and the ¹H-NMR spectrum is measured ¹H-NMR ¹H-NMR δ (ppm, C₆D₅CI) 7 40 (m, 3OH, Ar(Ph₃CMe), 7 30 (t, 1 H, ArH (amidine ligand)), 7 00 (t, 2H, ArH (amidine ligand)), 6 75 (m, 2H, CpH), 6 50 (m, 2H, CpH), 4 1 (bs, 1H, i-Pr), 3 8 (m, 1 H, i-Pr), 2 30 (s, 6H, Me(Ph₃CMe), 2 00 (s, 15H, Me-Cp^*), 1 6 (s, 3H, Me-Ti), 1 5 (d, 27H, tert-Bu), 1 51 (d, 6H, /-Pr) 1 23 (d, 6H, /-Pr)) 1 20 (s, 3H, Ti-Me)

In an asymmetric dimeric compound a chemical shift of both Tι-CH3 protons in the ¹H-NMR spectrum is expected due to their new chemical environment

However the spectrum of the mixture is a mere superposition of the spectra from the activated compounds A and B As no new NMR signals are present in the spectrum of the asymmetric mixed compound, it is concluded that a dimeπc structure is not present in solution and a dimer is formed at least in the crystalline phase as concluded from figure 1 and possibly also in the oil phase

Comparative experiment B

Attempted preparation of tert-butylamidodimethylsilyl- 1 (2, 3, 4, 5- tetramethylcyclopentadienyl) tιtanιum(IV) methyl tetrakιs(pentafluorophenyl)borate Tert-butylamidodimethylsilyl-1(2,3,4,5-tetramethylcyclopentadienyl) titanium(IV) dimethyl was mixed with TBF20 in deuterochlorobenzene (0.5 ml_) in a 5 mm NMR tube.

In the ¹H-NMR spectrum, the 1 ,1,1-triphenylethane triplet is absent as well as the fingerprint of the phenyl ring protons from the same molecule at 7.4 ppm. A set of 3 aromatic signals is visible. This spectrum clearly indicates the absence of triphenylethane, which is the expected reaction product of the methyl of the catalyst with the tritylium ion of TBF20. Additionally , it can be concluded from the ¹H-NMR spectrum, that the formation of tert-butylamidodimethylsilyl-1 (2,3,4,5- tetramethylcyclopentadienyl) titanium(IV) methyl tetrakis(pentafluorophenyl)borate is accompanied with the formation of either lots of by-product or the instability of the product.

Polymerization experiments Example 2 Batch EP copolvmerisation

The batch copolymerizations were carried out in a 2-liter batch autoclave equipped with a double intermig and baffles. The reaction temperature was set on 90⁰C and controlled by a Lauda Thermostat. The feed streams (solvents and monomers) were purified by contacting with various absorption media to remove catalyst killing impurities such as water, oxygen and polar compounds as is known to those skilled in the art. During polymerisation the ethylene and propylene monomers were continuously fed to the gas cap of the reactor. The pressure of the reactor was kept constant by a back- pressure valve.

In an inert atmosphere of nitrogen, the reactor was filled with 950 ml solvent, triisobutylaluminium (TIBA, Crompton) (4.5 mL 0.1 M = 0.45 mmol) , 4-methyl- 2,6-di-terf-butylphenol (BHT) (0.45mmol). The reactor was heated to 90⁰C, while stirring at 1350 rpm. The reactor was pressurized to 7 barg and conditioned under a determined ratio of ethylene and propylene for 15 minutes. Next, the catalyst 1 was added to the reactor in a single component feedstreem and the catalyst vessel was rinsed with 50 mL pentamethylheptane (PMH) subsequently. After 10 minutes of polymerisation, the monomer flow was stopped, and the solution was carefully dumped in a 2 L Erlenmeyer flask, containing a solution of lrganox-1076 in iso-propanol and dried over night at 100 ⁰C under reduced pressure. Results are found in Table 1. The polymers were analysed for molecular weight distribution (SEC- DV) and composition (FT-IR).

Comparative Experiment C Batch EP copolvmerisation. The batch copolymerizations were carried out in a 2-liter batch autoclave equipped with a double iπtermig and baffles. The reaction temperature was set on 90⁰C and controlled by a Lauda Thermostat. The feed streams (solvents and monomers) were purified by contacting with various absorption media to remove catalyst killing impurities such as water, oxygen and polar compounds as is known to those skilled in the art. During polymerisation the ethylene and propylene monomers were continuously fed to the gas cap of the reactor. The pressure of the reactor was kept constant by a back- pressure valve.

In an inert atmosphere of nitrogen, the reactor was filled with 950 ml solvent, TIBA (4.5 ml. 0.1 M = 0.45 mmol), and 4-methyl-2,6-di-terf-butylphenol (BHT) (0.45mmol). The reactor was heated to 90 ⁰C, while stirring at 1350 rpm. The reactor was pressurized to 7 barg and conditioned under a determined ratio of ethylene and propylene for 15 minutes. Next, the catalyst A was added to the reactor and the catalyst vessel was rinsed with 50 ml. pentamethylheptane (PMH) subsequently. The [Ph₃C][B(C₆Fs)₄] (TBF20) was added directly after the catalyst was added. After 10 minutes of polymerisation, the monomer flow was stopped, and the solution was carefully dumped in a 2 L Erlenmeyer flask, containing a solution of lrganox-1076 in iso-propanol and dried over night at 100 ⁰C under reduced pressure. Results are found in Table 1.

The polymers were analysed for molecular weight distribution (SEC- DV) and composition (FT-IR).

Table 1. Co-polymeπzation results obtained using 1 and A using ethylene (C2), propylene (C3), TB A = 2. All experiments include TIBA, 4-methyl-2,6-dι-tert- butylphenol (BHT), BHT:AI=1 (mol/mol) 7 barg of monomer feed consisting of C2

200NL/h and C3 400NL/h, 90⁰C, determined by FT-IR; ^bDetermined by Size Exclusion Chromatography using a Differential Viscosimeter.

The results clearly show that the productivity of the compound of the present invention is higher than that of the ιn-situ prepared catalyst. The obtained polymer is similar to that produced by the ιn-situ prepared catalyst

Claims

One component imine catalyst system for polyolefin polymerization, according to the following formula,

.wherein Cp is a cyclopentadienyl comprising ligand, N=Y is an anionic imine hgand chosen from the group of phosphinimine, amidine, iminoimidazohdine, or ketimide, M is Ti, Zr, or Hf, and X is a hydride or hydrocarbyl group and Z is a borate anion 2 Imine catalyst according to claim 1 , wherein Cp is a substituted cyclopentadieneyl or indenyl

3 Imine catalyst according to claim 1 , wherein M is Ti

4 Process for the preparation of a one component imine catalyst system according to claim 1 , by stirring a mixture of CpMYX₂ and A⁺Z in fluorobenzene at room temperature for about 30 minutes and keeping the stirred mixture for at least 2 days at a temperature of less than 10 ⁰C, wherein A⁺ is a cation

Olefin polymerization process, characterized in that the process is carried out in the presence of a one component imine catalyst system according to claim 1