Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2003-07-14
2004-07-27
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...
C526S170000, C526S172000, C526S348000
Reexamination Certificate
active
06767975
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to olefin polymerization with pyridine moiety-containing single-site catalysts. More particularly, the invention relates to olefin polymerization with pyridine moiety-containing single-site catalyst in the presence of clay.
BACKGROUND OF THE INVENTION
Pyridine based single-site catalysts are known. See U.S. Pat. No. 5,637,660. These catalysts are particularly useful for making ultra-high molecular weight polyethylene (UHMWPE). See U.S. Pat. No. 6,265,504. Unlike the conventional UHMWPE made with the Ziegler catalysts, the single-site UHMWPE has narrow molecular weight distribution. The catalysts, however, have relatively low activity and the UHMWPE produced has relatively low bulk density.
Low catalyst activity means low efficiency and high cost of the polymer production. Similarly, low bulk density means low productivity per reactor unit. Polyethylene of low bulk density also dries slowly because it absorbs solvent and residual monomers. Further, low bulk density may result in inferior product quality.
New ethylene polymerization processes are needed. Ideally, the process would use the readily available pyridine based single-site catalysts, give high catalyst activity, and produce UHMWPE having increased bulk density.
SUMMARY OF THE INVENTION
The invention is an olefin polymerization process. The process is performed in the presence of a clay, an activator, and a transition metal complex having at least one pyridine moiety-containing ligand. I surprisingly found that the use of clay in the process significantly increases the catalyst activity.
The invention also includes a process for preparing an ultra-high molecular weight polyethylene (UHMWPE). The process comprises polymerizing ethylene in the presence of a clay, a supported transition metal complex having at least one pyridine moiety-containing ligand, and a non-alumoxane activator. The process is performed in the absence of aromatic solvent, &agr;-olefin comonomer, and hydrogen. The process produces UHMWPE having an increased bulk density.
DETAILED DESCRIPTION OF THE INVENTION
The process of the invention comprises polymerizing an olefin in the presence of a clay, an activator, and a transition metal complex having at least one pyridine moiety-containing ligand.
Suitable olefins include C
2-20
&agr;-olefins. Suitable olefins also include cyclic olefins and conjugated and non-conjugated dienes. Examples of suitable olefins are ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, butadiene, isoprene, cyclopentene, cyclohexene, norbornene, 1-methylnorbornene, 5-methylnorbornene, the like, and mixtures thereof. Preferred olefins are C
2-10
&agr;-olefins. More preferred olefins are ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene. Most preferred olefins are ethylene and mixtures of ethylene with a C
3-10
&agr;-olefin.
Suitable clays include montmorillonite, saponite, hectorite, mica, vermiculite, bentonite, nontronite, beidellite, volkonskoite, magadite, and kenyaite, the like, and mixtures thereof. Preferably, the clays are modified, for example, with quaternary ammonium compounds. The modified clays are called organoclays. Organoclays are commercially available, for example, from Southern Clay Products, Inc., and Co-Op Chemical Co., LTD.
Preferably, the clay is heat-treated prior to the use in the polymerization. More preferably, the clay is heat-treated in the polymerization reactor prior to the use in the polymerization. The heat treatment is preferably conducted at a temperature within the range of 100° C. to 200° C.; more preferably from 125° C. to 165° C. The heat treatment removes moisture and other impurities from the clay.
Suitable activators include alumoxanes, alkyl aluminums, alkyl aluminum halides, anionic compounds of boron or aluminum, trialkylboron and triarylboron compounds. Examples include methyl alumoxane (MAO), polymeric MAO (PMAO), ethyl alumoxane, diisobutyl alumoxane, triethylaluminum, diethyl aluminum chloride, trimethylaluminum, triisobutyl aluminum, lithiumtetrakis(pentafluorophenyl) borate, lithium tetrakis(pentafluoro-phenyl)aluminate, dimethylanilinium tetrakis (pentafluorophenyl)borate, trityl tetrakis (pentafluorophenyl)borate, tris(pentafluorophenyl)borane, triphenylborane, tri-n-octylborane, the like, and mixtures thereof. MAO, PMAO, and tris-(pentafluorophenyl)borane are preferred.
Suitable transition metal complexes include those which have at least one pyridine moiety-containing ligand. By “pyridine moiety-containing ligand,” I mean any ligand that includes a pyridine ring structure. Preferably, the complex has the general structure:
M is a transition metal. Preferably, M is Group 4 transition metal. More preferably, M is Ti or Zr. Most preferably, M is Ti.
L
1
is a pyridine moiety-containing ligand. Preferably, L
1
has the general structure:
Wherein Y is bonded to M and is selected from the group consisting of O, S, and NR wherein R is hydrogen or an alkyl group. One or more of the remaining ring atoms are optionally and independently substituted by alkyl, aryl, aralkyl, alkylaryl, silyl, halogen, alkoxy, aryloxy, siloxy, nitro, dialkyl amino, or diaryl amino groups and two adjacent substituents optionally form a ring structure.
L
2
is a ligand selected from the group consisting of L
1
ligands, cyclopentadienyls, indenyls, fluorenyls, boraaryls, azaborolinyls, indenoindolyls, and phosphinimines. Preferably, L
2
is selected from the group consisting of L
1
ligands and cyclopentadienyls. More preferably, L
2
is an L
1
ligand. Most preferably, L
2
is the same as L
1
.
X is a ligand selected from the group consisting of halides, alkyl, aryl, alkoxy, aryloxy, dialkylamino, and siloxy groups. Preferably, X is selected from the group consisting of halides, aralkyl, and alkylaryl groups. More preferably, X is selected from chloride and benzyl. Either m or n can be zero; the sum of n and m satisfies the valence of M.
Example of suitable complexes are bis(2-pyridinoxy)ttanium dichloride, (cyclopentadienyl)(2-pyridinoxy)titanium dichloride, 8-quinolinoxy titanium trichlorde, 8-(2-methyl-5,7-dichloroquinolinoxy)titanium trichloride, bis(8-(2-methyl-5,7-dichloroquinolinoxy))titanium dichloride, and 8-Quinolinoxytitanium tribenzyl.
Activators are generally used in an amount within the range of about 0.01 to about 100,000, preferably from about 0.1 to about 1,000, and most preferably from about 0.5 to about 50, moles per mole of the complex.
The complex is preferably supported. The support is preferably a porous material such as inorganic oxides and chlorides, and organic polymer resins. Preferred inorganic oxides include oxides of Group 2, 3, 4, 5, 13, or 14 elements. Preferred supports include silica, alumina, silica-aluminas, magnesias, titanias, zirconias, magnesium chloride, and crosslinked polystyrene. Silica is most preferred.
Preferably, the support has a surface area in the range of about 10 to about 900 m
2
/g, a pore volume in the range of about 0.1 to about 4.0 mL/g, an average particle size in the range of about 10 to about 500 &mgr;m, and an average pore diameter in the range of about 10 to about 1000 Å. The support is preferably modified by heat treatment, chemical modification, or both. For heat treatment, the support is preferably heated at a temperature from about 50° C. to about 800° C. More preferably, the temperature is from about 100° C. to about 400° C.
Suitable chemical modifiers include organoaluminum, organosilicon, organomagnesium, and organoboron compounds. Organosilicon and organoboron compounds, such as hexamethyidisilazane (HMDS) and triethylborane, are preferred. Suitable techniques for treating a support are taught, for example, by U.S. Pat. No. 6,211,311, the teachings of which are incorporated herein by reference.
Preferably, the supporting involves treating a support with organosilicon compounds, calcining the treated support, treating the calcined support with organomagnesium compounds, mixing the organomagnesium-treated support with a pyridine moiety-cont
Choi Ling-Siu
Equistar Chemicals LP
Guo Shao-Hua
LandOfFree
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