Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
1994-09-28
2001-09-11
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S115000, C502S119000, C502S120000, C502S125000
Reexamination Certificate
active
06288005
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a catalyst component for ethylene polymerization and copolymerization with other olefins.
2. Description of the Prior Art
The scientific literature (publication and patent literature) contains numerous examples of catalyst components for the homo- and copolymerization of ethylene. The following are exemplary as describing unsupported catalyst components:
1. European Patent Publication No. 140,536 describes a titanium halide-containing catalyst prepared by (1) reacting a magnesium hydrocarboyloxide with a silicon compound having at least one hydrogen-silicon bond; (2) contacting the resulting product with an electron donor; and (3) contacting the resulting product with a titanium halide;
2. PCT International Publication No. WO 88/05056 describes a catalyst component obtained by (1) treating an organomagnesium compound without chlorine with a solid silane compound containing one or two hydroxyl groups and (2) then with a titanium halide compound; and
3. European Patent Publication No. 261,808 describes formation of a catalyst component, useful in the polymerization of ethylene-propylene copolymer rubber, which is formed by contacting a metal oxide with a magnesium compound, such as a dialkylmagnesium, and subsequently contacting the resulting product with a titanium compound, such as titanium tetrachloride, or, optionally, first with an alcohol or a silicon compound. 4. U.S. Pat. No. 5,063,188 to D. B. Malpass describes a catalyst component formed by reaction of an organomagnesium compound and a tetraalkyl silicate, contact of the resulting product with a chlorinating reagent, and treatment of the product from that previous step with liquid titanium halide.
Examples of the synthesis of supported catalyst components are provided in the following:
1. U.S. Pat. Nos. 4,378,304 and 4,458,058 to R. A. Dombro describe reaction of a support with a Group IIA organometallic compound free of aluminum alkyls, reaction of the resulting product with water or a hydrocarbyl alcohol, then reaction of that product with, for example, titanium tetrachloride.
2. U.S. Pat. No. 4,396,533 to A. Johnstone heats a refractory oxide support having surface hydroxyl with, for example, an organic derivative of a metal, such as tetraethyl silicate, followed by reaction of the resulting product with one or more organometallic compounds, followed by impregnation of the resulting solid product with a halogen-containing transition metal compound, such as titanium tetrachloride.
3. U.S. Pat. No. 4,481,301 to T. E. Nowlin et al. treats a support with an organomagnesium composition and then suspends the supported magnesium composition thus formed in a liquid medium with a tetravalent titanium compound.
4. European Patent Publication No. 261,808 contacts a metal oxide with an organomagnesium compound, then contacts the resulting composition, optionally, first with an alcohol or silicon compound (which can either contain hydrocarbyloxy groups or halogen atoms) and then with a titanium compound and an organoaluminum compound.
High density ethylene homopolymers are widely used in injection molding operations. Advantageously such resins, when used in injection molding operations, should have a narrow molecular weight distribution (MWD) which is largely determined by the nature of the catalyst. The catalyst should also exhibit other desirable characteristics for commercial use. The catalyst productivity should be as high as possible so that the resin will have low catalyst residue. It is also very desirable that the catalyst result in a polymer having a large particle size and high bulk density. Another desirable characteristic of the catalyst is that it have a high hydrogen response. A high hydrogen response means that small increases in the amount of hydrogen used in the reactor will result in substantial decrease in molecular weight and a higher melt index polymer.
SUMMARY OF THE INVENTION
The catalyst component of the instant invention is formed by: (1) initially reacting a metal oxide support with an organomagnesium compound to form a supported organomagnesium composition; (2) reacting an organomagnesium compound with a tetraalkyl silicate; (3) contacting the resulting product with a chlorinated reagent; and (4) contacting the resulting product with a liquid titanium compound containing halogen.
In accordance with this invention a silica supported catalyst is treated with an organomagnesium compound, then with alkoxysilane and halogenate reagent, and finally with titanium tetrachloride. The catalyst is particularly suitable for preparing HDPE with narrow MWD and large particle size, good productivity and hydrogen response.
DETAILED DESCRIPTION OF THE INVENTION
The first step in the process for forming the catalyst component of the present invention involves the reaction of an appropriate metal oxide support material (e.g., silica, alumina, zirconia, titania, and the like) with an organomagnesium compound to form a supported organomagnesium compound. This support is porous and particulate in nature and is substantially inert to many of the other components of the catalyst composition desired, with the exception of the organomagnesium compound, as well as the active components of the reaction system used to form the catalyst component described herein. It is preferably in the form of a dry powder having an average particle size of from about 1 micron to about 250 microns, preferably from about 15 microns to about 100 microns. The specific surface area of the support is preferably at least about 3 m
2
/gm, and preferably at least about 50 m
2
/gm. The support should be dry, that is, free of absorbed water. Drying of the support material can be affected by heating at about 100° C. to about 800° C., preferably from about 150° C. to about 600° C. The silica of the most preferred embodiment is a high surface area, amorphous silica (surface area =300 m
2
/gm; pore volume of 1.65 cm
3
/gm). A material of this type is marketed under the trade names Davison 952 or Davison 955 by the Davison Chemical Division of W. R. Grace. The contacting of organomagnesium compound and support causes reaction of certain organo (e.g., alkyl) groups with hydroxy functionality in the support. The contacting preferably takes place in a suitable hydrocarbon solvent (e.g., heptane) at reflux, for example. The organomagnesium compound is preferably dialkylmagnesium where the alkyl groups are C
1
to C
8
such as butylethylmagnesium, dibutylmagnesium, diisobutylmagnesium and dihexylmagnesium.
It has been found that treatment of the support with a chlorinating reagent, such as silicon tetrahalide, prior to treatment with the organomagnesium compound, enables the production of a final catalyst in accordance with this invention which produces a polymer product having a higher bulk density.
The next step involves the reaction of the supported organomagnesium compound with an alkoxy silane which serves to replace remaining organo (e.g., alkyl) groups on the supported organomagnesium compound with alkoxy groups. This reaction is also preferably conducted in a suitable hydrocarbon solvent (e.g., heptane) at reflux, for example, using substantially equimolar amounts of magnesium and silicon compounds. The alkoxy silane is of the formula R
n
Si(OR′)
4−n
with n ranging, for example, from 0 to 3, where R and R′ are also alkyl (e.g., C
1
to C
6
alkyl). Representative compounds include tetraethyl silicate, tetramethyl silicate, tetrabutyl silicate, and dimethoxydiphenylsilane.
The foregoing reaction yields a supported product which comprises an admixture of magnesium alkoxide and silicon compounds which contain a typical magnesium content of about 2% to about 4%, by weight. This material is then contacted with a suitable chlorinating agent to yield a composition comprising a mixture of magnesium compound of the general formula Mg(OR)
2−n
Cl
n
, where R is as defined above and n can range from 0 to 2. Examples of suitable chlorinating agents incl
Band Elliot I.
Epstein Ronald A.
Wang Bor-Ping E.
Akzo N.V.
Fennelly Richard P.
Wood Elizabeth D.
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