Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-07-13
2001-04-17
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S160000, C526S943000, C526S352000, C502S117000, C502S152000, C502S158000
Reexamination Certificate
active
06218487
ABSTRACT:
The invention relates to a process for polymerizing olefins by bringing olefins into contact with a transition metal catalyst and a cocatalyst.
The polymerization of olefins usually requires the use of not only a transition metal catalyst, but also the use of a cocatalyst to obtain an active catalyst system.
Since the 1950s, Ziegler-Natta catalysts have been used for the polymerization of olefins. If olefin polymerizations are to proceed satisfactory with these Ziegler-Natta catalysts, it is necessary to add cocatalysts. Aluminium-containing cocatalysts such as, for example, diethylaluminium chloride, are often used in combination with Ziegler-Natta catalysts.
Recently, other types of transition metal catalysts such as, for example, metallocene catalysts have also been used for the polymerization of olefins. If olefin polymerizations using metallocene catalysts are to proceed satisfactory it is likewise necessary to use a cocatalyst. Among cocatalysts often used in combination with metallocene catalysts are aluminoxanes. An example of an aluminoxane is methylaluminoxane (MAO).
The use of aluminoxanes as a cocatalyst in the polymerization of olefins with the aid of a metallocene catalyst has the drawback that a very large excess of the aluminoxane with respect to the metallocene catalyst has to be used in order to obtain an active catalyst system. Consequently, the polyolefin produced contains a high aluminium concentration, and as a result it is often necessary for the aluminium to be washed out from the polyolefin.
It is an object of the invention to provide cocatalysts which can be used in conjunction with a transition metal catalyst for the polymerization of olefins, which do not have this drawback.
The invention relates to a cocatalyst in accordance with formula
XR
4
,
wherein
X is Si, Ge, Sn or Pb,
R is hydrogen or an alkyl, aryl, arylalkyl or alkylaryl group and wherein at least one R group is not hydrogen and contains one or more halogen atoms, or to a cocatalyst in accordance with the formula [XR
5
]
−
[Y]
+
,
wherein
X is Si, Ge, Sn or Pb,
R is hydrogen or an alkyl, aryl, arylalkyl or alkylaryl group and wherein at least one R group is not hydrogen and contains one or more halogen atoms, and
Y is a cation.
In this way an active catalyst system consisting of a transition-metal catalyst with one of the compounds according to the invention as co-catalyst is obtained which is suitable for the polymerization of olefins. If the compounds according to the invention are used as a cocatalyst for the polymerization of olefins, the amount of cocatalyst which has to be used with respect to the transition metal catalyst is much lower than when an aluminoxane is used as a cocatalyst.
Lewis acids or ion complexes are also used as cocatalysts in combination with metallocene catalysts. Examples of Lewis acids are boranes such as, for example, tris(pentafluorophenyl)borane, and examples of ion complexes are borates such as, for example, dimethylanilinium tetrakis(pentafluorophenyl)borate, triphenylcarbenium tetrakis(pentafluorophenyl)borate and trityl tetrakis(3,5-trifluoromethylphenyl)borate.
Such boron-containing cocatalysts are described, for example, in EP-A-426,637, EP-A-277,003 and EP-A-277,004.
A further advantage of the use of the compounds according to the invention as a cocatalyst in the polymerization of olefins is that using these compounds is cheaper, as a rule, than using aluminoxanes, boranes or borates.
Compounds suitable as a cocatalyst are compounds in accordance with the formula XR
4
and compounds in accordance with the formula [XR
5
]
−
[Y]
+
. X is an atom from group 14 of the Periodic Table of the Elements and can be selected from Si, Ge, Sn and Pb. Preferably, X is Si, because Si is not toxic. Here and hereinafter, the Periodic Table of the Elements is to be understood as the periodic table shown on the inside of the cover of the Handbook of Chemistry and Physics, 70th edition, 1989/1990 (New IUPAC notation).
The R groups may be identical or different and can be selected from hydrogen and alkyl, aryl, arylalkyl or alkylaryl groups. At least one R group is not hydrogen and contains one or more halogen atoms. This implies that in a compound in accordance with the formula XR
4
or in accordance with the formula [XR
5
]
−[Y]
+
at least one halogen atom is present which does not form part of the cation Y. Preferably, the R group is a hydrocarbon group containing 1-20 carbon atoms. Examples of suitable R groups are methyl, ethyl, propyl, isopropyl, hexyl, decyl and phenyl. Two R groups may together form a bridged R
2
group such as, for example, a biphenyl-2,2′-diyl group and a diphenyl-2,2′-diylmethane group. These R groups may contain one or more halogen atoms.
Halogen atoms are F, Cl, Br and I. Combinations of different halogen atoms may be present in one R group or distributed over various R groups. Examples of R groups containing a halogen atom are chloromethyl, 1,2-dibromoethyl, pentafluorophenyl and octafluorobiphenyl-2,2′-diyl. Preferably, at least 2 R groups together form a bridged aryl group. More preferably, the compound in accordance with the formula XR
4
or [XR
5
]
−
[Y]
+
contains octafluorobiphenyl-2,2′-diyl groups.
The cation Y is, for example, a Brönsted acid which is able to donate a proton, a cation of an alkali metal or a carbene. Examples of cations are Li
+
, K
+
, Na
+
, H
+
, triphenylcarbenium, anilinium, guanidinium, glycinium, ammonium or a substituted ammonium cation in which at most 3 hydrogen atoms have been replaced by a hydrocarbyl radical having 1-20 carbon atoms, or a substituted hydrocarbyl radical having 1-20 carbon atoms, in which 1 or more of the hydrogen atoms have been replaced by a halogen atom, phosphonium radicals, substituted phosphonium radicals, in which at most 3 hydrogen atoms have been replaced by a hydrocarbyl radical having 1-20 carbon atoms or a substituted hydrocarbyl radical having 1-20 carbon atoms, in which or more of the hydrogen atoms have been replaced by a halogen atom.
Preferably, the cation is dimethylanilinium, triphenylcarbenium or Li
+
.
Compounds in accordance with the formula XR
4
which contain at least one halogen atom are disclosed, for example, by ‘Cohen and Massey, J. Organometal. Chem. 10(1967) 471-481’, ‘Tamborski et al., J. Organometal. Chem., 4(1965) 446-454’ and ‘Fearon and Gilman, J. Organometal. Chem., 10 (1967) 409-419’. Compounds in accordance with the formula [XR
5
]
−[Y]
+
are disclosed in Angew. Chem. Int. Ed. Engl. 1996, 35, No. 10. This publication mentions lithium (2,2′-biphenyldiyltrimethylsilicate).4THF, lithium (2,2′-biphenyldiyldimethylphenylsilicate).4THF, lithium (2,2′-biphenyldiyldimethyl-t-butylsilicate).4THF and lithium pentaphenylsilicate.4HMPA. (THF is tetrahydrofuran and HMPA is hexamethylphosphortriamide.) These compounds however, do not contain any halogen atoms and nothing is suggested regarding the possible use of these compounds as a cocatalyst in the polymerization of olefins.
The abovementioned compounds can be synthesized in accordance with synthesis methods known to the man skilled in the art.
It is also possible to use the compounds according to the invention supported on a carrier material as a cocatalyst for the polymerization of olefins. Suitable carrier materials to be mentioned are SiO
2
, Al
2
O
3
, MgCl
2
and polymer particles such as polystyrene beads. These carrier materials may also be modified with, for example, silanes and/or aluminoxanes and/or aluminiumalkyls. The supported cocatalysts can be synthesized prior to the polymerization but can also be formed in situ.
Various types of transition metal catalysts can be used as a catalyst for the polymerization of olefins. Examples of such catalysts are described, for example, in U.S. Pat. No. 5,096,867, WO-A-92/00333, EP-A347,129, EP-A-344,887, EP-A-129,368, EP-A-476,671, EP-A-46
DSM N.V.
Harlan R.
Pillsbury & Winthrop LLP
Wu David W.
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