Catalyst formulation and polymerization processes

Details Catalyst formulation and polymerization processes Catalyst formulation and polymerization processes

2000-08-30

2002-12-03

Teskin, Fred (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S122000, C526S124900, C526S125300, C526S128000

Reexamination Certificate

active

06489411

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the polymerization of unsaturated hydrocarbons over Ziegler-type catalyst systems and more particularly to polymerization processes carried out using transition metal catalyst components of such systems having varying internal electron donor-transition metal ratios.
BACKGROUND OF THE INVENTION
The polymerization of unsaturated hydrocarbons over Ziegler-type catalysts is well known in the art. Such hydrocarbons normally take the form of short chain alpha olefins such as ethylene, propylene and butylene, including substituted alpha olefins such as substituted vinyl compounds, for example, vinyl chloride or vinyl toluene. However, such unsaturated hydrocarbons can also include di-olefins such as 1-3-butadiene or 1-4-hexadiene or acetylenically unsaturated compounds such as methylacetylene or 2-butyne.
Ziegler-type catalysts incorporate a transition metal, usually titanium, zirconium or hafnium, although other transition metals found in Groups 4, 5 and 6 of the Periodic Table of Elements may be employed, which function to provide sites for the insertion of monomer units into growing polymer chains. One type of such polymerization catalysts are the so-called homogeneous catalyst systems in which the transition metal compound is a metallocene comprising one or more substituted or unsubstituted cyclopentadienyl groups coordinated with the transition metal atom forming the situs for polymer growth. Such metallocene-based catalyst systems are the subject of European Patent Application EP 129,368 and U.S. Pat. No. 4,794,096 to Ewen and U.S. Pat. No. 4,892,851 to Ewen et al., the latter two patents disclosing catalysts useful in the polymerization of propylene to form isotactic and syndiotactic polypropylene, respectively.
The more widely used transition metal catalysts are the so-called heterogeneous catalyst systems in which a transition metal halide, usually zirconium, hafnium or titanium, di-, tri-, or tetra-halides, are incorporated with a support structure, principally based upon magnesium or zinc halides, ethoxides or the like. For example, U.S. Pat. No. 4,476,289 to Mayr et al. discloses so called “activated” titanium tetrahalides, more specifically, titanium tetrachloride, supported on anhydrous magnesium or zinc halides, principally magnesium chloride or magnesium bromide. The transition metal component is used in conjunction with a second component, commonly referred to as a co-catalyst, which as described in the Mayr et al. patent, is a hydride or organometallic compound based primarily upon aluminum, although lithium or magnesium based compounds are also disclosed. A supported catalyst containing yet another component is disclosed in U.S. Pat. No. 4,636,486 to Mayr et al. Here, the titanium compound, which may be a halide, an oxyhalide or an alcoholate in either the di-, tri-, or tetravalent form, is composited with the magnesium support, together with an electron donor compound. Such electron donors, commonly referred to as internal electron donors because they are incorporated as part of the transition metal catalyst component, can be selected from a broad class of compounds including amines, amides, phosphines, ethers, thioethers, alcohol esters, aldehydes, and ketones. As in the case of the aforementioned U.S. Pat. No. 4,476,289 to Mayr, the catalyst system here also includes an organoaluminum co-catalyst such as triethylaluminum, commonly referred to as TEAL. Both of the Mayr et al. patents teach that the molar ratio of the organoaluminum compound and the titanium catalyst component is not critical. In the polymerization of ethylene, such ratio is said to preferably be between 50 and 1,000.
Yet a third component often employed in Ziegler-type catalyst systems is a so-called external electron donor. The external electron donors function similarly as the internal electron donors and in a complimentary or supplementary manner to regulate monomer insertion into the polymer chain growing on the transition metal active sites. Thus, the electron donors can have an impact upon catalyst activity, polymer molecular weight, and polymer morphology as reflected in stereospecificity and physical parameters such as melting point. For example, in the polymerization of propylene, the addition of electron donors under controlled conditions can result in dramatic increases in activity (the amount of polymer produced per unit of catalyst) and in stereoregularity, e.g., an increase in isotactic polymer with a corresponding decrease in atactic. The most widely used external electron donors are organosilicon compounds such as organosilanes and organosiloxanes, including silyl ethers and esters such as alkyl or arylalkyl alkoxysilanes.
The complimentary nature of the internal and external electron donors is addressed in Soga, K. et al., “Effect of Diesters and Organosilicon Compounds on the Stability and Stereospecificity of Ziegler-Natta Catalysts”,
Transition Metal Catalyzed Polymerizations: Ziegler-Natta and Metathesis Polymerizations,
Quirk, R. P., Ed., Cambridge University Press, New York, 1988, pp. 266-279. As discussed in Soga, the concentrations of the internal and external donors in the catalyst system can be adjusted in order to optimize the activity and the stereospecifity of the catalyst. In the experimental work reported there, the transition metal catalyst component comprising titanium tetrachloride supported on magnesium dichloride with an internal donor, e.g., di-N butylphthalate, was slurried in hexane followed by the addition of an external electron donor and triethylaluminum (TEAL) co-catalyst. Soga et al. report on polymerization rates over periods of several hours and isotactic indices measured over periods of several hours for various internal donor, external donor catalyst systems using several kinds of organosilicon compounds at varying concentrations expressed in terms of silicon/titanium mole ratios and TEAL/titanium mole ratios. Corresponding tests in the absence of electron donors were also carried out. Among the various external electron donors used in the Soga et al. experimental work, diphenyldimethoxysilane appeared to have the most efficiency in terms of improving activity and/or stereospecificity of the catalyst system, followed by phenyltriethoxysilane, followed in turn by phenyltrimethoxysilane and then by various tetraalkoxysilanes which were generally less efficient, although still effective. In various tests carried out with and without an external donor, phenyltriethoxysilane, the effect on rate time profiles for the polymerization of propylene varied depending upon the presence and nature of an internal donor. In absence of the external donor, the most active system was one employing ethyl benzoate as the internal donor followed by systems having no internal donor or di-n-butylphthalate or diphthalate grouped fairly closely together with the least active system employing dimethylphenol as the internal donor. Where the external donor was present, di-n-butylphthalate and then ethyl benzoate were the most effective internal donors followed in turn by the supported catalyst which was free of an internal donor and then systems employing diethylphthalate and dimethylphenol as internal donors. The aluminum/titanium mole ratios employed in Soga ranged from about 50 to 200; the silicon/titanium mole ratios range from about 10 to 50. Soga et al. proposed a mechanism to explain the experimental work involving several types of active sites available for production of isotactic polypropylene. The internal donor is hypothesized to coordinate with some of the active sites and to inhibit the formation of specific active sites which are not deactivated by the external donor.
U.S. Pat. No. 4,287,328 to Kikuta et al., is directed to the polymerization of alpha olefins in the presence of multi-component catalyst systems involving a “solid product” combined with an organoaluminum compound including, for example, C
1
-C
10
trialkylaluminum, triethylaluminum, alkyl alkyoxyaluminums, and alkylaluminum halides, and an electro

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