Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-07-24
2003-11-11
Choi, Ling-Siu (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S901000, C526S903000, C526S158000, C526S124300, C526S125200, C526S352000, C526S348000, C502S128000, C502S103000
Reexamination Certificate
active
06646073
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a continuous gas phase polymerization process for producing polyethylene and interpolymers of ethylene and at least one other olefin comprising introducing into a polymerization medium ethylene or ethylene and other olefin(s), a Ziegler-Natta catalyst comprising a titanium component and a co-catalyst component, and at least one saturated halogenated hydrocarbon(s) wherein the at least one or more saturated halogenated hydrocarbon(s) is present in a molar ratio of saturated halogenated hydrocarbon(s) to the titanium component of the Ziegler-Natta catalyst from 0.4:1 to about 3.5:1.
BACKGROUND OF INVENTION
The use of halogenated hydrocarbons with titanium containing Ziegler-Natta catalysts for the production of polyethylene is disclosed in U.S. Pat. Nos. 5,863,995; 5,990,251; 4,657,998 and 3,354,139. In general it is disclosed that the halogenated hydrocarbons may reduce the rate of ethane formation, control the molecular weight of the polyethylene, produce polyethylenes with broad molecular weight distributions, or provide other effects.
In U.S. Pat. No. 5,990,251 it is disclosed that halogenated hydrocarbons are used, in a polymerization process for producing polyethylene utilizing a titanium based Ziegler-Natta catalyst, for increasing the catalyst activity in the polymerization. It is further stated that the amount of halogenated hydrocarbon must be present in a molar ratio of halogenated hydrocarbon to titanium of the Ziegler-Natta catalyst from 0.001 to 0.15. Furthermore it is disclosed that when the molar ratio of halogenated hydrocarbon to titanium is too high, the activity of the catalyst is not appreciably modified or is substantially reduced in a continuous polymerization process. It is also stated that when the molar ratio is too low, the catalyst activity is not substantially modified.
In U.S. Pat. No. 5,863,995 there is also reference to catalytic activity in a process for producing polyethylene using a titanium containing Ziegler-Natta catalyst and a halogenated hydrocarbon in a specified amount. The patent states that the halogenated hydrocarbon is present in a molar ratio of halogenated hydrocarbon to the titanium in the catalyst of 0.01 to 1.8. It is further stated that the specified quantity of halogenated hydrocarbon results in no substantial variation of the average activity of the catalyst.
In U.S. Pat. No. 3,354,139 there is disclosed the use of halogenated hydrocarbons with a Ziegler-Natta catalyst to control the molecular weight of polyethylene prepared in a solution or slurry polymerization process.
In U.S. Pat. No. 4,657,998 there is disclosed a catalyst system comprising titanium containing catalyst component, isoprenylaluminum and a halohydrocarbon for the production of polyethylene having a broad molecular weight distribution.
SUMMARY OF THE INVENTION
Applicants have unexpectedly found that in a continuous gas phase polymerization process for producing polyethylene and interpolymers of ethylene and at least one other olefin comprising introducing into a polymerization medium the ethylene or ethylene and at least one other olefin, a Ziegler-Natta catalyst comprising a titanium component and a co-catalyst component, and at least one saturated halogenated hydrocarbon(s) wherein the at least one or more saturated halogenated hydrocarbon(s) is present in a molar ratio of saturated halogenated hydrocarbon(s) to the titanium component of the Ziegler-Natta catalyst from 0.4:1 to about 3.5:1 the activity of the catalyst is increased as compared with a process carried out in the absence of a saturated halogenated hydrocarbon.
DETAILED DESCRIPTION OF THE INVENTION
Applicants have unexpectedly found that in a continuous gas phase polymerization process for producing polyethylene and interpolymers of ethylene and at least one other olefin comprising introducing into a polymerization medium the ethylene or ethylene and at least one other olefin, a Ziegler-Natta catalyst comprising a titanium component and a co-catalyst component, and at least one saturated halogenated hydrocarbon(s) wherein the at least one or more saturated halogenated hydrocarbon(s) is present in a molar ratio of saturated halogenated hydrocarbon(s) to the titanium component of the Ziegler-Natta catalyst from 0.4:1 to about 3.5:1 the activity of the catalyst is increased as compared with a process carried out in the absence of a saturated halogenated hydrocarbon.
The continuous gas phase polymerization process for producing ethylene and interpolymers of ethylene and at least one other olefin may be carried out using any suitable continuous gas phase polymerization process. These types of processes and means for operating the polymerization reactors are well known and completely described in U.S. Pat. Nos. 3,709,853; 4,003.712; 4,011,382; 4,012,573; 4,302,566; 4,543,399; 4,882,400; 5,352,749 and 5,541,270. These patents disclose gas phase polymerization processes wherein the polymerization zone is either mechanically agitated or fluidized by the continuous flow of the gaseous monomer and diluent. The entire contents of these patents are incorporated herein by reference.
The polymerization process of the present invention is effected as a continuous gas phase process such as, for example, a gas phase fluid bed process. A fluid bed reactor for use in the process of the present invention typically comprises a reaction zone and a so-called velocity reduction zone. The reaction zone comprises a bed of growing polymer particles, formed polymer particles and a minor amount of catalyst particles fluidized by the continuous flow of the gaseous monomer and diluent to remove heat of polymerization through the reaction zone. Optionally, some of the recirculated gases may be cooled and compressed to form liquids that increase the heat removal capacity of the circulating gas stream when readmitted to the reaction zone. A suitable rate of gas flow may be readily determined by simple experiment. Make up of gaseous monomer to the circulating gas stream is at a rate equal to the rate at which particulate polymer product and monomer associated therewith is withdrawn from the reactor and the composition of the gas passing through the reactor is adjusted to maintain an essentially steady state gaseous composition within the reaction zone. The gas leaving the reaction zone is passed to the velocity reduction zone where entrained particles are removed. Finer entrained particles and dust may be removed in a cyclone and/or fine filter. The said gas is compressed in a compressor, passed through a heat exchanger wherein the heat of polymerization and the heat of compression are removed, and then returned to the reaction zone.
In more detail, the reactor temperature of the fluid bed process ranges from about 30° C. to about 130° C. In general, the reactor temperature is operated at the highest temperature that is feasible taking into account the sintering temperatures of the polymer product within the reactor.
The process of the present invention is suitable for the polymerization of ethylene and interpolymers of ethylene with at least one or more other olefins. The other olefins, for example, may contain from 3 to 16 carbon atoms. Included herein are homopolymers of ethylene and interpolymers of ethylene and the other olefin(s). The interpolymers include interpolymers of ethylene and at least one olefin(s) wherein the ethylene content is at least about 50% by weight of the total monomers involved. Exemplary olefins that may be utilized herein are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, 1-decene, 1-dodecene, 1-hexadecene and the like. Also utilizable herein are non-conjugated dienes and olefins formed in situ in the polymerization medium. When olefins are formed in situ in the polymerization medium, the formation of interpolymers of ethylene containing long chain branching may occur.
The Ziegler-Natta catalysts utilized herein are well known in the industry. The Ziegler-Natta catalysts in the simplest form are comprised of a tit
Dooley Kenneth Alan
Farrer Don Kent
Moore Glenn Edward
Noble Larry Allen
Choi Ling-Siu
Eastman Chemical Company
Graves Bernie
Owen Steven A.
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