Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-05-19
2001-04-10
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...
C526S153000, C526S160000, C526S336000, C526S901000, C524S855000, C524S856000, C523S215000
Reexamination Certificate
active
06214946
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to gas phase EPDM production employing an inert particulate material and a single-site (e.g., metallocene) catalyst. More particularly, the invention provides a method for passivating an inert particulate material (e.g., carbon black) such that it can employed with a metallocene catalyst in the production of ethylene-propylene rubber such as an ethylene-propylene-diene rubber (EPDM).
BACKGROUND OF THE INVENTION
Ethylene propylene rubbers (including diene rubbers) are commercially produced in a gas phase process above the softening or sticking temperature of the polymer product by using an inert particulate material such as carbon black, silica, clay or talc, as disclosed in U.S. Pat. No. 4,994,534. The inert particulate material serves to make the forming bed of polymer fluidizable. Hence, it is required to prevent agglomeration of the bed in the gas phase reactor. The preferred inert particulate material is carbon black. Carbon black is preferred because it is most often included in molded or extruded article by an end user.
Presently, the catalyst of choice in gas phase polymerization is a vanadium catalyst (e.g., vanadium acetylacetonate supported on silica), though a titanium catalyst can be employed. However, the use of a vanadium catalyst does not afford latitude for producing a wide variety of EPR differing in amounts of individual monomers comprising them and various molecular weights and/or molecular weight distribution. Solution, slurry, and bulk EPR processes, which do not employ inert particulate material in the polymerization, employ a metallocene catalyst for these purposes.
However, in gas phase production requiring an inert particulate material, such as carbon black, attempts to use a metallocene catalyst, it has been discovered that the carbon black has a strong poisoning effect on the metallocene catalyst. That is, the poisoning effect of carbon black (CB) consumes cocatalyst such as MAO or modified MAO (MMAO) and decreases catalyst activity. Hence, more aluminoxane is needed in order to obtain sufficient metallocene activity and the catalyst cost is substantial.
Therefore, there exists, a need for a passivation process which alleviates the poisoning effects of inert particulate materials such as carbon black on metallocene catalysts so that catalyst activity increases and provides a reduction in the high cost of using aluminoxane such as methylaluminoxane (MAO) cocatalyst in the production of EPR.
SUMMARY OF THE INVENTION
Surprisingly, it has been discovered that the above-enumerated problems can be solved by contacting the carbon black with a trialkyl aluminum (e.g., tri-isobutylaluminum) prior polymerizing the monomers comprising EPR. There is provided a process for the gas phase production of an ethylene-propylene or ethylene-propylene-diene rubber in the presence of a single-site catalyst and an inert particulate material comprising pre-treating the inert particulate material before commencing polymerization with a trialkylaluminum having the formula AlR
3
, wherein each R is independently an alkyl having 1 to 14 carbon atoms.
DETAILED DESCRIPTION OF THE INVENTION
Pretreatment/Passivation. By passivation is meant that the inert particulate material (e.g., carbon black) is contacted with a trialkylaluminum, such as tri-isobutylaluminum (TIBA), such that the trialkylaluminum reacts with or “passivates” surface active or functional groups commonly associated with the inert particulate material. Surface active groups are contaminants resulting from the process for producing the inert particulate materials. These surface functional groups can include, for example, —OH, —COOH, —SH, —CO, —C(O)H, C(O)R, —OR, —COOR, —COOC, and mixtures thereof.
Passivation of the inert particulate material can be accomplished in at least three ways. One way, is to pretreat the inert particulate material with trialkylaluminum compound in a slurry using a diluent such as by using an aliphatic hydrocarbon having 5 to 20 carbon atoms, for example, hexane. The diluent can also be an aromatic hydrocarbon having 6 to 20 carbon atoms. Of course, if desired mixtures of these two kinds of diluents can be employed. This is followed by evacuation or purging at ambient or room temperature of the diluent to obtain dry inert particulate material. The dried passivated or pretreated inert particulate material is then introduced into the polymerization process. Preferably, it is introduced continuously via a feeding line into a fluid bed reactor, while simultaneously introducing catalyst and cocatalyst separately or together through one or more feeding lines.
The ratio of trialkylaluminum compound to the inert particulate material in diluent ranges from 0.001 mmol trialkylaluminum compound per gram inert particulate material to 100 mmol trialkylaluminum compound per gram inert particulate material; preferably 0.01 mmol trialkylaluminum compound per gram inert particulate material to 10 mmol trialkylaluminum compound per gram inert particulate material; most preferably about 0.03 mmol trialkylaluminum compound per gram inert particulate material to 0.60 mmol trialkylaluminum compound per gram inert particulate material.
A second procedure for passivating inert particulate material is to introduce dry untreated inert particulate material into a reactor and there contacting it with a trialkylaluminum slurry followed by removal of the diluent (e.g. hexane). The catalyst system and monomers are then introduced or fed to the reactor in any manner known to those skilled in the art to commence polymerization.
A third procedure for passivating the inert particulate material comprises first connecting three separate feeding lines to a reactor such that the untreated inert particulate material (e.g., CB), the passivating reagent or trialkylaluminum (e.g., TIBA) feeding line, and the cocatalyst/catalyst feeding line coexist. This is followed by simultaneously and continuously feeding the catalyst/cocatalyst, untreated inert particulate material, and TIBA into a reactor, along with or followed by the addition of one or more of the monomers to commence polymerization.
Single-Site Catalyst. The single site catalyst may be a metallocene, i.e., an organometallic coordination complex of one or more &pgr;-bonded moieties (i.e., cycloalkadienyl groups) in association with a metal atom from Groups IIIB to VIII or the Lanthanide series of the Periodic Table of Elements. Bridged and unbridged mono-, di-, and tri-cycloalkadienyl/metal compounds are the most common metallocenes, and generally are of the formula:
(L)
y
R
1
z
(L′)MX
(x-y-1)
(I)
wherein M is a metal from groups IIIB to VIII or a rare earth metal of the Periodic Table; L and L′ are the same or different and are &pgr;-bonded ligands coordinated to M, preferably cycloalkadienyl groups such as cyclopentadienyl, indenyl, or fluorenyl groups optionally substituted with one or more hydrocarbyl groups containing 1 to 20 carbon atoms; R
1
is selected from the group consisting of C
1
-C
4
substituted or unsubstituted alkylene radicals, dialkyl or diaryl germanium or silicon groups, and alkyl or aryl phosphine or amine radicals bridging L and L′; each X is independently hydrogen, an aryl, alkyl, alkenyl, alkylaryl, or arylalkyl radical having 1-20 carbon atoms, or a hydrocarboxy radical having 1-20 carbon atoms; y is 0, 1, or 2; x is 1, 2, 3, or 4 depending upon the valence state of M; z is 0 or 1 and is 0 when y is 0; and x-y≧1.
Illustrative but non-limiting examples of metallocenes represented by formula I are dialkyl metallocenes such as bis(cyclopentadienyl)titanium dimethyl, bis(cyclopentadienyl)titanium diphenyl, bis(cyclopentadienyl)zirconium dimethyl, bis(cyclopentadienyl)zirconium diphenyl, bis(cyclopentadienyl)hafnium methyl and diphenyl, bis(cyclopentadienyl)titanium di-neopentyl, bis(cyclopentadienyl)zirconium di-neopentyl, bis(cyclopentadienyl)titanium dibenzyl, bis(cyclopentadienyl)zirconium dibenzyl, bis(cyclopentadienyl)vanadium dimethyl; the mono alkyl metallocenes
Brown Robert C.
Teskin Fred
Union Carbide Chemicals & Plastics Technology Corporation
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