Manufacture of polyethylenes

Details Manufacture of polyethylenes Manufacture of polyethylenes

2000-09-28

2003-04-29

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...

C526S114000, C526S115000, C526S117000, C526S118000, C526S119000, C502S113000, C502S117000, C502S129000, C502S152000, C502S155000, C502S167000, C525S240000

Reexamination Certificate

active

06555631

ABSTRACT:

FIELD OF THE INVENTION
Blends of polyethylenes may be manufactured by using various combinations of ethylene polymerization catalysts what may or may not copolymerize &agr;-olefins and ethylene, and ethylene oligomerization catalysts that produce &agr;-olefins.
TECHNICAL BACKGROUND
Polyethylenes are important items of commerce, these being produced in larger volumes than any other polymer. Many different grades of this polymer type are produced, these differing grades varying in many properties, including cost. For an overview of polyethylenes, see B. Elvers, et al., Ed.,
Ullmann's Encyclopedia of Industrial Chemistry,
5
th
Ed., Vol. A21, VCH Verlagsgesellschaft, Weinheim, 1992, p. 488-518; and H. Mark et al., Ed.,
Encyclopedia of Polymer Science and Engineering
, Vol. 6, John Wiley & Sons, New York, 1986, p. 383-489.
Aside from cost the two major property areas of concern to most users (polymer processors) are final polymer physical properties, that is does the polymer have physical properties suitable for the end use, and how difficult is it to form the polymer into the final article, often called processability. In some instances polyethylene compositions having desirable properties are obtained by blending two or more polyolefins, at least one of which is a polyethylene, together. These blends may be formed by melt blending the separate blend polymers, or by forming two or more of the blend polymers in a single polymerization system (these may be sequential or simultaneous polymerizations). The latter is often preferred because such blends are often more uniform, and the cost of a separate mixing step is avoided.
Blends may be formed to improve physical properties and/or processing properties. For instance, high density polyethylene is sometimes not as tough as desired, so it may be blended with a less crystalline polymer, such as a lower melting (even elastomeric) copolymer of ethylene and an &agr;-olefin (or other polyolefin), to toughen the resulting product. Therefore improved methods of making blends of polyethylene polymers are of interest.
Various reports of “simultaneous” oligomerization and polymerization of ethylene to form (in most cases) branched polyethylenes have appeared in the literature, see for instance WO90/15085, WO99/50318, U.S. Pat. Nos. 5,753,785, 5,856,610, 5,686,542, 5,137,994 and 5,071,927; C. Denger, et al,
Makromol. Chem. Rapid Commun.
, vol. 12, p. 697-701 (1991), and E. A. Benham, et al.,
Polymer Engineering and Science
, vol. 28, p. 1469-1472 (1988). All of the above are incorporated by reference herein for all purposes as if fully set forth.
None of these references specifically describes any of the processes or branched homopolyethylenes of the present invention.
SUMMARY OF THE INVENTION
This invention concerns a process for producing a blend of two or more polyethylenes, comprising the step of contacting:
(1) ethylene;
(2) an active ethylene oligomerization catalyst under conditions to oligomerize at least a portion of the ethylene to one or more &agr;-olefins of the general formula R
18
CH═CH
2
, wherein R
18
is an alkyl containing an even number of carbon atoms;
(3) a first active polymerization catalyst under conditions to copolymerize ethylene and the &agr;-olefins generated from the active ethylene oligomerization catalyst; and
(4) a second active polymerization catalyst under conditions to polymerize ethylene, but not readily copolymerize ethylene and &agr;-olefins.
This invention also concerns a polymerization catalyst component, comprising:
(a) an oligomerization catalyst that oligomerizes ethylene to one or more &agr;-olefins of the formula H
2
C═CHR
18
, wherein R
18
is an alkyl containing an even number of carbon atoms;
(b) a first polymerization catalyst that is capable of copolymerizing ethylene and one or more &agr;-olefins of the formula H
2
C═CHR
18
;
(c) a second polymerization catalyst chemically distinct from the first polymerization catalyst, that is capable of polymerizing ethylene but does not readily copolymerize ethylene and &agr;-olefins;
(d) optionally one or more catalyst supports onto which one or more of (a), (b) and/or (c) has been supported; and
(e) optionally one or more catalyst activators for (a), (b) and/or (c).
This invention also concerns a first polymer blend comprising:
(a) a first polyethylene that contains at least three different branches of the formula —(CH
2
CH
2
)
n
H, wherein n is an integer of 1 or more, and
(b) a second polyethylene that is different from the first polyethylene, in a weight ratio of about 1:4 to about 4:1 based on the total weight of the first and second polyethylenes, and provided that said second polyethylene has a melting point at least 20° C. higher than said first polyethylene, or said second polyethylene has a heat of fusion at least 50 J/g greater than said first polyethylene, or both.
Also described herein is a second polymer blend comprising:
(a) a third polyethylene having a density of less than 0.93 g/mL, containing at least 2 ethyl branches, at least 2 hexyl or longer branches and at least one butyl branch per 1000 methylene groups, and provided that said third polyethylene has fewer than 5 methyl branches per 1000 methylene groups; and
(b) a fourth polyethylene having a density of 0.93 g/mL or more.
This invention also includes a third polymer blend comprising:
(a) a fifth polyethylene containing about 20 to about 150 branches of the formula —(CH
2
CH
2
)
n
H per 1000 methylene groups, wherein n is an integer of 1 to 100, provided that said fifth polyethylene has less than about 20 methyl branches per 1000 methylene groups; and
(b) a sixth polyethylene that is different from the fifth polyethylene and has a density of about 0.93 g/mL or more.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Herein certain terms are used which are defined below.
By “hydrocarbyl” is meant a univalent radical containing only carbon and hydrogen. As examples of hydrocarbyls may be mentioned unsubstituted alkyls, cycloalkyls and aryls. If not otherwise stated, it is preferred that the hydrocarbyl groups herein contain 1 to 30 carbon atoms, and more preferably 1 to 20 carbon atoms.
By “substituted hydrocarbyl” herein is meant a hydrocarbyl group that contains one or more “inert functional groups” that are inert under the process conditions to which the compound containing these groups is subjected. The inert functional groups also do not substantially interfere with the oligomerization/polymerization process. For example, in cases in which the inert functional group may be near the complexed iron atom, such as R
4
or R
5
in formula (I) (shown below), or as a substituent on R
4
, R
5
, R
6
or R
7
, the inert functional group should not coordinate to the iron atom more strongly than the three depicted N groups in (I) which are the desired coordinating groups—that is, the functional group should not displace one or more of the desired coordinating N groups. The hydrocarbyl may be completely substituted, as in trifluoromethyl. If not otherwise stated, it is preferred that substituted hydrocarbyl groups herein contain 1 to about 30 carbon atoms. Included in the meaning of “substituted” are heterocyclic rings.
Examples of inert functional groups include halo (fluoro, chloro, bromo and iodo), ester, keto (oxo), amino, imino, carboxyl, phosphite, phosphonite, phosphine, phosphinite, thioether, amide, nitrile, and ether. Preferred inert functional groups are halo, ester, amino, imino, carboxyl, phosphite, phosphonite, phosphine, phosphinite, thioether, and amide. With respect to catalysts based on ligands (I) and (II) described below, which inert functional groups are useful in which oligomerizations/polymerizations may in some cases be determined by reference to U.S. Pat. Nos. 5,955,555, 6,103,946 and WO98/30612, all of which are hereby incorporated by reference for all purposes as if fully set forth.
By an oligomerization or polymerization “catalyst activator” is meant a compound that reacts with a transition metal compound to form an activated catalyst specie

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