Catalyst systems of the ziegler-natta type and a process for...

Details Catalyst systems of the ziegler-natta type and a process for... Catalyst systems of the ziegler-natta type and a process for...

2001-08-28

2004-05-04

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...

C526S124600, C526S125300, C526S348000, C526S348100, C502S109000, C502S116000, C502S133000

Reexamination Certificate

active

06730753

ABSTRACT:

The present invention relates to catalyst systems of the Ziegler-Natta type, to a process for preparing them, to a process for the polymerization of olefins and to polymers and copolymers obtainable in this way.
Catalyst systems of the Ziegler-Natta type have been known for a long time. These systems are used, in particular, for the polymerization of C
2
-C
10
-alk-1-enes and comprise, inter alia, compounds of polyvalent titanium, aluminum halides and/or aluminum alkyls and also a suitable support material. The Ziegler-Natta catalysts are usually prepared in two steps. Firstly, the titanium-containing solid component is prepared. This is subsequently reacted with the cocatalyst. The polymerization is subsequently carried out with the aid of the catalysts obtained in this way.
To avoid the formation of hydrocarbon-soluble polymer in the (co)polymerization of ethylene with &agr;-olefins, a Lewis base is often used as a further component in the Ziegler-Natta catalysts. Thus, for example, siloxanes are used as further catalyst component in EP-A-225452, carboxylic esters, ketones and amines are used in DE-A-3538577 to 3538580 and aliphatic ethers are used in EP-A-212519.
The process known from EP-B-341539 gives, in the gas phase, polymers which have a comparatively low proportion of fines. The catalyst used comprises TiCl
3
.n
AlCl
3
, where n is from 0 to 0.5, as active component, a magnesium-containing component, a polysiloxane, silica gel as support component, an aluminum alkyl compound and a Lewis base. Although the use of the polysiloxane further reduces the proportion of hydrocarbon-soluble polymer and significantly improves the morphology of the polymer, the activity of the catalyst system is greatly reduced by the presence of the polysiloxane.
It is an object of the present invention to develop, starting from the catalyst system described in EP-B-341539, an improved catalyst system of the Ziegler-Natta type which no longer has the abovementioned disadvantage of a reduced activity when using polysiloxanes.
We have found that this object is achieved by a process for preparing catalyst systems of the Ziegler-Natta type, which comprises the following steps:
A) bringing an inorganic metal oxide on which a magnesium compound has been deposited into contact with a tetravalent titanium compound,
B) optionally, bringing the intermediate obtained in this way into contact with an electron donor compound and
C) bringing the intermediate obtained in step A) or B) into contact with a polysiloxane.
In view of the prior art, it was surprising that it was not only possible to overcome the disadvantage of the prior art by use of tetravalent titanium compounds in the process of the present invention, but the activity of the catalyst system is also significantly increased by the addition of the polysiloxane.
The present invention further provides catalyst systems of the Ziegler-Natta type which can be prepared by the process of the present invention and a process for the polymerization or copolymerization of olefins at from 20 to 150° C. and pressures of from 1 to 100 bar, wherein the polymerization or copolymerization is carried out in the presence of at least one catalyst system according to the present invention and an aluminum compound as cocatalyst.
Furthermore, the invention provides homopolymers of ethylene and copolymers of ethylene with &agr;-olefins obtainable by the polymerization process of the present invention, provides for their use for producing films, fibers and moldings and provides films, fibers and moldings which comprise homopolymers and copolymers of ethylene according to the present invention.
The inorganic metal oxide used in step A) has a magnesium compound deposited on it, where the amount of magnesium compound is generally from 1 to 200% by weight of the inorganic metal oxide, preferably from 1 to 100% by weight of the inorganic metal oxide and particularly preferably from 1 to 10% by weight of the inorganic metal oxide. The magnesium compound is generally uniformly distributed over the inorganic metal oxide. The inorganic metal oxide on which the magnesium compound has been deposited can be prepared by a process comprising the following steps:
a) optionally, bringing an inorganic metal oxide into contact with an organometallic compound of group 13 of the Periodic Table, (according to IUPAC 1985)
b) bringing the intermediate obtained in step a) or the inorganic metal oxide into contact with a magnesium compound MgR
n
X
2-n
,
where X are each, independently of one another, fluorine, chlorine, bromine, iodine, hydrogen, NR
2
, OR, SR, SO
3
R or OC(O)R, and R are each, independently of one another, a linear, branched or cyclic C
1
-C
20
-alkyl, a C
2
-C
10
-alkenyl, an alkylaryl having 1-10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part or a C
6
-C
18
-aryl and n is 1 or 2,
and subsequently
c) bringing the intermediate obtained in step b) into contact with an alcohol of the formula R—OH, where R is as defined under b).
R is an independent variable which is used a number of times in the description and has the following meanings for all compounds: R is in each case independently a linear, branched or cyclic C
1
-C
20
-alkyl such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl or n-dodecyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclododecyl, a C
2
-C
10
-alkenyl which may be linear, cyclic or branched and can have an internal or terminal double bond, e.g. vinyl, 1-allyl, 2-allyl, 3-allyl, butenyl, pentenyl, hexenyl, cyclopentenyl, cyclohexenyl, cyclooctenyl or cyclooctadienyl, an alkylaryl having 1-10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part, e.g. benzyl, o-, m-, p-methylbenzyl, 1- or 2-ethylphenyl, or a C
6
-C
18
-aryl which may bear further alkyl groups as substituents, e.g. phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl and 9-phenanthryl, 2-biphenyl, o-, m-, p-methylphenyl, 2,3-, 2,4-, 2,5- or 2,6-dimethylphenyl, 2,3,4-, 2,3,5-, 2,3,6-, 2,4,5-, 2,4,6- or 3,4,5-trimethylphenyl, and two radicals R may also be joined to form a 5- or 6-membered ring and the organic radicals R may also be substituted by halogens, e.g. fluorine, chlorine or bromine.
X is also a variable used a number of times in the description and is in each case independently a fluorine, chlorine, bromine, iodine or hydrogen atom or an amide group NR
2
, an alkoxide group OR, a thiolate group SR, a sulfonate group SO
3
R or a carboxylate group OC(O)R, where R is as defined above. Examples of NR
2
are dimethylamino, diethylamino and diisopropylamino, examples of OR are methoxy, ethoxy, isopropoxy, butoxy, hexoxy and 2-ethylhexoxy, examples of SO
3
R are methylsulfonate, trifluoromethylsulfonate and toluenesulfonate and examples of OC(O)R are formate, acetate and propionate.
The inorganic metal oxide is preferably firstly reacted in step a) with an organometallic compound MR
m
X
3-m
, where R is as defined above, M is a metal of group 13 of the Periodic Table, preferably B, Al or Ga and particularly preferably Al, and m is 1, 2 or 3.
The organometallic compound of group 13 of the Periodic Table which is used is preferably an aluminum compound AlR
m
X
3-m
, where the variables are as defined above. Examples of suitable compounds are trialkylaluminum compounds such as trimethylaluminum, triethylaluminum, triisobutylaluminum or tributylaluminum, dialkylaluminum halides such as dimethylaluminum chloride, diethylaluminum chloride or dimethylaluminum fluoride, alkylaluminum dihalides such as methylaluminum dichloride or ethylaluminum dichloride, or mixtures such as methylaluminum sesquichloride. The hydrolysis products of aluminum alkyls with alcohols can also be used. Preference is given to using dialkylaluminum halides and particular preference is given to using dimethylaluminum chloride or diethylaluminum chloride.
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