Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1997-01-28
2001-01-16
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S124300, C526S124900, C502S103000, C502S104000, C502S110000, C502S111000, C502S115000, C502S119000, C502S126000
Reexamination Certificate
active
06174971
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to catalyst system for the polymerization of olefins, particularly, to a catalyst system comprising a supported Ziegler-Natta catalyst. The catalyst system is used to polymerize olefins, such as ethylene.
2. Description of the Prior Art
Polyolefin manufacturing processes typically involve the polymerization of olefin monomer with a Ziegler-Natta type catalyst. Catalyst systems for the polymerization of olefins are well known in the art. Typically, these systems include a Ziegler-Natta type polymerization catalyst component and a co-catalyst, usually an organoaluminum compound. Examples of such catalyst systems are shown in the following U.S. Pat. Nos. 3,574,138; 4,316,966; and 5,173,465, the disclosures of which are hereby incorporated by reference.
A Ziegler-Natta type polymerization catalyst is basically a complex derived from a halide of a transition metal, for example, titanium or vanadium, with a metal hydride and/or a metal alkyl, typically an organoaluminum compound, as a co-catalyst. The catalyst is usually comprised of a titanium halide supported on a magnesium compound complexed with an alkylaluminum co-catalyst.
SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to synthesize a supported Ziegler-Natta catalyst for the polymerization of ethylene.
Also, an object of this invention is to produce a polyolefin having large particle size, a low amount of small particles or “fines” and low wax.
In addition, an object of this invention is to produce a catalyst with high activity and better hydrogen response.
These and other objects are accomplished by a catalyst system comprising a supported Ziegler-Natta catalyst used in a polymerization process for polymerizing olefins, especially ethylene.
The present invention provides for a catalyst for polymerization of olefins having high activity and better hydrogen response comprising:
a) a supported Ziegler-Natta transition metal catalyst component; and
b) an organoaluminum co-catalyst.
The present invention provides for a catalyst component comprising:
a) a soluble magnesium compound of magnesium dialkoxide of the general formula Mg(OR)
2
where R is a hydrocarbyl or substituted hydrocarbyl of 1 to 20 carbon atoms;
b) a mild chlorinating agent;
c) a titanating agent; and
d) an organoaluminum compound.
The present invention provides for a process for synthesizing a catalyst component comprising:
a) synthesizing magnesium di(alkoxide) from magnesium dialkyl and alcohol;
b) adding a mild chlorinating agent;
c) adding a titanating agent;
d) adding a second titanating agent;
e) adding an organoaluminum compound.
The present invention also provides a process for the polymerization of olefins using the catalyst system described above to produce a polymer product having a narrow molecular weight distribution, a low amount of small particles and low wax comprising:
a) selecting a conventional Ziegler-Natta transition metal catalyst component;
b) contacting the catalyst component with an organoaluminum co-catalyst compound;
c) introducing the catalyst system into a polymerization reaction zone containing a monomer under polymerization reaction conditions to form a polymer product; and
e) extracting polymer product from the polymerization reaction zone.
DETAILED DESCRIPTION OF THE INVENTION
The synthesis procedure for Ziegler-Natta type catalysts for the polymerization of olefins is disclosed in U.S. Pat. Nos. 3,644,318, the disclosure of which is hereby incorporated, The standard synthesis procedure is:
a) selecting a magnesium compound;
b) adding a chlorinating agent;
c) adding a titanating agent; and
d) optionally, adding a preactivating agent.
The chlorinating agent and the titanating agent ma compound.
Mg(OEt)
2
+TiCl
4
→titanium catalyst on magnesium support
The present invention modifies the synthesis procedure, and thus modifies the catalyst and the polymer product. The present invention is characterized by the following:
1) a soluble magnesium compound;
2) a mild chlorinating agent;
3) simultaneous chlorination-titanation steps with a mild reagent;
4) a second chlorination-titanation with a stronger reagent;
5) a preactivation step.
A proposed mechanism for the modified synthesis procedure is as follows:
1) MgRR′+2R″OH→Mg(OR″)
2
2) Mg(OR″)
2
+ClAR′″
x
“A”
3) “A”+TiCl
4
/Ti(OR″″)
4→“B”
4) “B”+TiCl
4
→“C”
5) “C”+TEAl→preactivated catalyst
While the exact composition of “A” is unknown, it is believed that it contains a partially chlorinated magnesium compound, one example of which may be ClMg(OR″). The first chlorination-titanation produces a catalyst (“B”) which is probably a complex of chlorinated and partially chlorinated magnesium and titanium compounds and may possibly be represented by (MgCl
2
)
y
.(TiCl
x
(OR)
4-x
)
z
. The second chlorination-titanation produces a catalyst (“C”) which is also probably a complex of chlorinated and partially chlorinated magnesium and titanium compounds but different from “B” and may possibly be represented by (MgCl
2
)
y′
.(TiCl
x′
(OR)
4-x′
)
z′
. It is expected that the level of chlorination of “C” would be greater than that of “B”. This greater level of chlorination would produce a different complex of different compounds. While this description of the reaction products offers the most probable explanation of the chemistry at this time, the invention as described in the claims is not limited by this theoretical mechanism.
The soluble magnesium compound is preferably a non-reducing compound such as magnesium dialkoxide of the general formula Mg(OR″)
2
where R″ is a hydrocarbyl or substituted hydrocarbyl of 1 to 20 carbon atoms. A non-reducing compound has the advantage of forming MgCl
2
instead of insoluble Ti
+3
species formed by reduction of compounds such as MgRR′ which tend to form catalysts having a broad particle size distribution. In addition, Mg(OR″)
2
is less reactive than MgRR′ and the chlorination with a mild chlorinating agent, followed by a simultaneous chlorination-titanation with a mild reagent and a second chlorination-titanation with a stronger reagent are gradual and successively stronger reactions which may result in more uniform product, i.e., larger catalyst particles and better catalyst particle size control.
Magnesium dialkoxide, such as magnesium di(2-ethylhexoxide), may be produced by reacting an alkyl magnesium compound (MgRR′), such as butyl ethyl magnesium (BEM), with an alcohol (ROH), such as 2-ethylhexanol.
MgRR′+2 R″OH→Mg(OR″)
2
+RH+R′H
In the case of BEM, RH and R′H are butane and ethane, respectively. The reaction takes place at room temperature and the reactants form a solution.
The magnesium dialkyl [MgRR′] may be any magnesium dialkyl where R and R′ are alkyl groups of 1-10 carbon atoms. R and R′ may be the same or different. Examples of the magnesium dialkyl are magnesium diethyl, magnesium dipropyl, magnesium dibutyl, butylethylmagnesium, etc. Butylethylmagnesium (BEM) is the preferred magnesium dialkyl.
The alcohol may be any alcohol of the general formula R″OH where R″ is an alkyl group of 4-20 carbon atoms. The alcohol may be linear or branched. Examples of the alcohol are butanol, isobutanol, 2-ethylhexanol, etc. The preferred alcohol is 2-ethylhexanol.
Alkyl magnesium compounds are highly associative due to electron-deficient bonding which results in a high molecular weight species which is very viscous in solution. This high viscosity may be reduced by the addition of an aluminum alkyl, such as triethylaluminum, which disrupts the association between the individual alkyl magnesium molecules. The preferred molar ratio of alkyl aluminum to magnesium is 0.001:1 to 1:1, more preferably 0.01 to 0.1:1 and most preferably 0.03:1 to 0.05:1. In addition, an electron donor such as an ether, e.g., dii
Chen Hong
Coffy Tim J.
Shamshoum Edwar S.
Fina Technology, Inc.
Rabago R.
Wheelington Jim D.
Wu David W.
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