Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Removing and recycling removed material from an ongoing...
Patent
1993-08-23
1995-07-11
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Removing and recycling removed material from an ongoing...
526 82, 526 83, 526 84, 526 85, C08F 240
Patent
active
054322421
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The invention relates to processes for polymerizing olefins using metallocenes and in particular to catalyst killing systems for use in such processes. The term catalyst killing refers to the deactivation of the catalyst. The deactivation may be a partial or complete suppression of polymerisation appropriate to enable the overall process to be performed in a stable manner.
BACKGROUND OF THE INVENTION
It is known to use low molecular weight gases or liquids in order to kill Ziegler-Natta catalyst systems to reduce the catalyst system activity to a level where the polymerisation stops. Ziegler-Natta catalyst systems usually employ a titanium chloride transition metal component and an aluminum alkyl co-catalyst component or activator.
EP 116917 (Ruhrchemie) for example describes a killer of CO.sub.2 and alcohols. These products are said to react with catalyst to form non-volatile compounds, not active in polymerization.
The use of water as a Ziegler-Natta catalyst killer is disclosed in U.S. Pat. No. 4,701,489 (El Paso). However whilst water is a known effective catalyst killer, acid may evolve and at high levels corrosion may be caused.
It is also known to use high molecular weight products (polyglycols; epoxides; ethylene copolymers; organic titanium compounds; alkoxysilanes; peroxides; zeolites as a water carrier; or surface-active agents) as Ziegler-Natta catalyst killers.
EP 162274 (Ruhrchemie) discloses a high pressure Ziegler-Natta catalyzed polymerization process involving deactivation with an oxygen-containing waxy ethylene copolymer. The purpose is to prevent polymerization of residual monomer in the separator and gas circulating system. EP 140131 (Ruhrchemie) uses polyglycols for similar purposes.
DE-3322329 (Mitsubishi Petrochemical) discloses killers of peroxides which break up into a complex mixture of volatile CO.sub.2 and other mainly volatile components.
It is further more known from JP-A-57158206 (Sumitomo) to use in a slurry polymerization process a mixture of water, sorbitan alkyl ester, and an aliphatic C.sub.3 -C.sub.8 hydrocarbon as catalyst killer to avoid use of a large amount of water, presumably by using the sorbitan alkyl ester to emulsify the water in the C.sub.3 -C.sub.8 solvent. EP-B-71252 (Sumitomo) discloses use of a suspension of water containing fatty acid salt in a hydrocarbon for a similar purpose. The fatty acid salt may act to neutralise acids formed by the water-catalyst reaction.
In recent years use of metallocene based polymerisation catalyst systems using metallocenes as the transition metal component has been suggested; generally using alumoxane as a cocatalyst. For the purpose of this text the term Ziegler-Natta catalyst systems is used to exclude metallocene/alumoxane systems. The metallocene based systems employ relatively small, molecules of generally unsupported (particularly in high pressure processes) metallocene transition metal components which can have a significant, although still low, vapor pressure at conditions for separation of polymer and unreacted monomer. The cocatalyst has generally a much higher molecular weight than conventional aluminumalkyl cocatalysts and may be an alumoxane as afore mentioned or other suitable cocatalyst complex. However these compounds may still have an appreciable vapor pressure at separation conditions. Often the cocatalyst is used in great excess over the metallocene but the overall catalyst system has a high activity so that catalyst concentrations can be low.
EP-35242 (BASF) uses methanol as a catalyst killer for such metallocene/alumoxane systems; DE 3127133 (Hoechst) uses n-butanol.
Metallocene/alumoxane based catalyst systems have been proposed in which water is introduced into the polymerization zone to create alumoxane in situ (See DE 2608933 Kaminsky; Exxon EP 308177). EP 308177 (Exxon) uses water in the monomer feed to activate, not deactivate, TMA separately introduced as part of the catalyst system.
EP 328348 (Mitsui Petrochemical) uses water in addition to alumoxane and optionally an or
REFERENCES:
patent: 4701489 (1987-10-01), Hughes et al.
patent: 4719270 (1988-01-01), Miwa et al.
patent: 5066736 (1991-11-01), Dumain et al.
Exxon Chemical Patents Inc.
Schofer Joseph L.
Warner Darrell E.
Weber Tom
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