Polymer mixture

Details Polymer mixture Polymer mixture

1999-12-01

2001-10-02

Nutter, Nathan M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S240000

Reexamination Certificate

active

06297323

ABSTRACT:

The present invention relates to polymer blends containing at least 85% by weight of ethylene/&agr;-olefin copolymers (A) prepared by metallocene catalysis and from 1 to 15% by weight of essentially linear ethylene/&agr;-olefin copolymers (B) prepared using another catalyst, the percentages in each case being based on the total weight of the polymer blend.
The present invention furthermore relates to the use of these polymer blends for the production of films and to films which contain these polymer blends.
Ethylene/&agr;-olefin copolymers which are prepared by metallocene catalysis have some advantageous properties compared with copolymers prepared by means of conventional catalyst systems. Thus, the metallocene copolymers are often superior in their mechanical properties, such as toughness, compared with copolymers of similar composition prepared by a different method. The excellent mechanical properties make metallocene copolymers appear particularly suitable for the production of films. Especially for the production of films, high requirements are also set with regard to the optical properties of the polymers used. In the case of pure metallocene copolymers, as well as in conventionally prepared LLDPE, a slight haze and insufficient gloss are often evident.
In order to improve the optical properties of LLDPE copolymers, these copolymers are mixed with other polymers. U.S. Pat. No. 4,587,303 describes a polymer blend comprising LLDPE and LDPE or ethylene copolymers obtained by high-pressure free radical polymerization processes. These high-pressure polymers are distinguished by long-chain branches, giving rise to, inter alia, their low density. WO 95/27005 describes a polymer blend of LLDPE, which was prepared by metallocene catalysis, and low density polyethylene. It is true that the stated polymer blends have improved optical properties compared with pure metallocene copolymers. However, this improvement is accompanied by a dramatic deterioration in the mechanical properties.
It is an object of the present invention to provide polymer blends which are based on ethylene/&agr;-olefin copolymers prepared by metallocene catalysis and which, on the one hand, have better optical properties than pure metallocene copolymers and, on the other hand, exhibit good mechanical properties.
We have found that this object is achieved by the polymer blends stated at the outset, their use for the production of films, and films which contain these polymer blends.
Suitable copolymers (A) are in principle all ethylene/&agr;-olefin copolymers prepared by metallocene catalysis.
The polymerization can be carried out, for example, in the gas phase, in suspension, in solution or in the high-pressure process, the catalyst system used in the suspension or gas-phase process preferably being one which contains
a) an inorganic or organic carrier,
b) a metallocene complex and
c) a compound forming metallocenium ions.
Preferably used carrier materials a) are finely divided carriers which preferably have a particle diameter of from 1 to 300 &mgr;m, in particular from 30 to 70 &mgr;m. Suitable inorganic carriers are, for example, magnesium chloride or silica gels, preferably those of the formula SiO
2
.a Al
2
O
3
, where a is from 0 to 2, preferably from 0 to 0.5; these are therefore aluminosilicates or silica. Such products are commercially available, for example Silica Gel 332 from Grace. Suitable organic carriers are, for example, finely divided polyolefins, for example finely divided polypropylene.
The amount of carrier is preferably from 50 to 99.9% by weight, based on the total weight of carrier and metallocene complex (component b).
Particularly suitable metallocene complexes b) are those of the general formula I
where
M is titanium, zirconium, hafnium, vanadium, niobium or tantalum,
X is fluorine, chlorine, bromine, iodine, hydrogen, C
1
-C
10
-alkyl, C
6
-C
15
-aryl, alkylaryl having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, —OR
7
or —NR
7
R
8
,
R
7
and R
8
are each CH
1
-C
10
-alkyl, C
6
-C
15
-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical,
R
2
to R
6
are each hydrogen, C
1
-C
10
-alkyl, 5- to 7-membered cycloalkyl which in turn may carry C
1
-C
10
-alkyl as substituent, C
6
-C
15
-aryl or arylalkyl, where, if desired, two neighboring radicals together may furthermore be a saturated or unsaturated cyclic group of 4 to 15 carbon atoms, or Si(R
9
)
3
,
R
9
is C
1
-C
10
-alkyl, C
3
-C
10
-cycloalkyl or C
6
-C
15
-aryl,
R
10
to R
14
are each hydrogen, C
1
-C
10
-alkyl, 5- to 7-membered cycloalkyl which in turn may carry C
1
-C
10
-alkyl as a substituent, C
6
-C
15
-aryl or arylalkyl, where, if desired, two neighboring radicals together may furthermore be a saturated or unsaturated cyclic group of 4 to 15 carbon atoms, or Si(R
15
)
3
,
R
15
is C
1
-C
10
-alkyl, C
6
-C
15
-aryl or C
3
-C
10
-cycloalkyl,
or R
5
and Z together form a group —R
16
—A—,
═BR
17
, ═AlR
17
, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO
2
, ═NR
17
, ═CO, ═PR
17
or ═P(O)R
17
,
R
17
, R
18
and R
19
are identical or different and are each hydrogen, halogen, C
1
-C
10
-alkyl, C
1
-C
10
-fluoroalkyl, C
6
-C
10
-fluoroaryl, C
6
-C
10
-aryl, C
1
-C
10
-alkoxy, C
2
-C
10
-alkenyl, C
7
-C
40
-arylalkyl, C
8
-C
40
-arylalkenyl or C
7
-C
40
-alkylaryl, or two neighboring radicals in each case, together with the atoms linking them, form a ring, and
M
2
is silicon, germanium or tin,
R
20
is C
1
-C
10
-alkyl, C
6
-C
15
-aryl, C
3
-C
10
-cycloalkyl, alkylaryl or Si(R
21
)
3
,
R
21
is hydrogen, C
1
-C
10
-alkyl, C
6
-C
15
-aryl, which in turn may be substituted by C
1
-C
4
-alkyl, or C
3
-C
10
-cycloalkyl
or R
5
and R
13
together form a group —R
16
—.
Among the metallocene complexes of the general formula I,
are preferred.
Particularly preferred transition metal complexes are those which contain, as ligands, two aromatic ring systems linked to one another by a bridge, ie. the transition metal complexes of the general formula Ic.
The radicals X may be identical or different but are preferably identical.
Among the compounds of the formula Ia, those in which
M is titanium, zirconium or hafnium,
X is chlorine, C
1
-C
4
-alkyl or phenyl and
R
2
to R
6
are each hydrogen or C
1
-C
4
-alkyl are preferred.
Examples of preferred compounds of the formula Ib are those in which
M is titanium, zirconium or hafnium,
X is chlorine, C
1
-C
4
-alkyl or phenyl,
R
2
to R
6
are each hydrogen, C
1
-C
4
-alkyl or Si(R
9
)
3
,
R
10
to R
14
are each hydrogen, C
l
-C
4
-alkyl or Si(R
15
)
3
.
The compounds of the formula Ib in which the cyclopentadienyl radicals are identical are particularly suitable.
Examples of particularly suitable compounds include: bis(cyclopentadienyl)zirconium dichloride, bis(pentamethylcyclopentadienyl)zirconium dichloride, bis(methylcyclopentadienyl)zirconium dichloride, bis(ethylcyclopentadienyl)zirconium dichloride, bis(n-butylcyclopentadienyl)zirconium dichloride and bis(trimethylsilylcyclopentadienyl)zirconium dichloride and the corresponding dimethylzirconium compounds.
Particularly suitable compounds of the formula Ic are those in which
R
2
and R
10
are identical and are each hydrogen or C
1
-C
10
-alkyl,
R
6
and R
14
are identical and are each hydrogen, methyl, ethyl, isopropyl or tert-butyl,
R
4
and R
12
are each C
1
-C
4
-alkyl
R
3
and R
11
are each hydrogen or two neighboring radicals R
3
and R
4
on the one hand and R
11
and
R
12
on the other hand together are a cyclic group of 4 to 12 carbon atoms,
M is titanium, zirconium or hafnium and
X is chlorine, C
1
-C
4
-alkyl or phenyl.
Examples of particularly suitable complex compounds include dimethylsilanediylbis(cyclopentadienyl)zirconium dichloride, dimethylsilanediylbis(indenyl)zirconium dichloride, dimethylsilanediylbis(tetrahydroindenyl)zirconium dichloride, ethylenebis(cyclopentadienyl)zirconium dichloride, ethylenebis(indenyl)zirconium dichloride, ethylenebis(t

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