Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2003-01-28
2004-11-09
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C525S240000
Reexamination Certificate
active
06815490
ABSTRACT:
The present invention relates to propylene polymers containing
a) from 50 to 95 parts by weight of a propylene homopolymer having a melt flow index of from 0.1 to 100 g/10 min. at 230° C. and under a weight of 2.16 kg, according to ISO standard 1133, and an isotacticity index of at least 98%,
b) from 5 to 50 parts by weight of an ethylene copolymer containing from 4 to 40% by weight of polymerized C
4
-C
20
-alk-1-ene and having a density of from 0.865 to 0.920 g/cm
3
and
c) from 0 to 1.5 parts by weight of a nucleating agent, the sum of the parts by weight of the propylene homopolymer a) and of the ethylene copolymer b) always being 100 parts by weight.
The present invention furthermore relates to a process for the preparation of these polymers and to their use as films, fibers and moldings.
The preparation of propylene homopolymers by Ziegler-Natta polymerization has long been known. The catalyst components used contain, inter alia, compounds of polyvalent titanium, aluminum halides and/or alkyls, as well as electron donor compounds, silanes, esters, ketones or lactones generally being used (DE-A 42 16 548, DE-A 44 19 438, EP-A 171 200, EP-A 530 599, U.S. Pat. No. 4,857,613).
In this process, propylene homopolymers having very different properties can be obtained, for example having substantially different rigidity, impact strength or flowability. Some applications in which propylene polymers are preferably used require in particular propylene polymers which, in addition to a high impact strength, also have, for optical reasons, a substantially reduced tendency to white fracture and high rigidity.
In addition to the preparation of propylene polymers by means of Ziegler-Natta catalysts, it is has also been possible for some years to prepare polymers of propylene and of ethylene with the use of metallocene catalysts having cyclic ligands (EP-A 519 237, EP-A 692 499).
DE-A 4407327 describes propylene polymers which consist of a propylene homopolymer and a nucleating agent and are distinguished, inter alia, by high rigidity and flowability. For certain applications of propylene polymers, however, even higher rigidity and improved white fracture behavior are of interest.
EP-A 593 221 discloses mixtures of propylene polymers and ethylene copolymers with polymerized C
4
-C
18
-alk-1-enes, whose density is less than or equal to 0.913 g/cm
3
. The blends mentioned therein have good impact strength and rigidity, but the manner in which the white fracture behavior of such products can be improved is not described.
Furthermore, WO-A 94/06859 claims blends of thermoplastic polymers and linear ethylene copolymers with polymerized C
3
-C
20
-alk-1-enes, which have, inter alia, high transparency and good impact strength at low temperatures. However, WO-A 94/06859 does not indicate how the white fracture behavior of such blends can be improved and at the same time their rigidity increased.
It is an object of the present invention to remedy the disadvantages described and to provide an improved propylene polymer which is distinguished by an advantageous property profile in terms of good impact strength, flowability and processability and moreover has high rigidity and very little tendency to white fracture.
We have found that this object is achieved by novel propylene polymers containing
a) from 50 to 95 parts by weight of a propylene homopolymer having a melt flow index of from 0.1 to 100 g/10 min. at 230° C. and under a weight of 2.16 kg, according to ISO standard 1133, and an isotacticity index of at least 98%,
b) from 5 to 50 parts by weight of an ethylene copolymer containing from 4 to 40% by weight of polymerized C
4
-C
20
-alk-1-ene and having a density of from 0.865 to 0.920 g/cm
3
and
c) from 0 to 1.5 parts by weight of a nucleating agent, the sum of the parts by weight of the propylene homopolymer a) and of the ethylene copolymer b) always being 100 parts by weight.
Propylene polymers which contain
a) from 60 to 90, in particular from 75 to 90, parts by weight of the propylene homopolymer a),
b) from 10 to 40, in particular from 10 to 25, parts by weight of the ethylene copolymer b) and
c) from 0 to 1.5, in particular from 0.05 to 1.5, parts by weight of the nucleating agent c) are particularly preferred.
The sum of the parts by weight of the propylene homopolymer and of the ethylene copolymer b) is always 100 parts by weight.
A preferably used propylene homopolymer a) is one which has a melt flow index of from 0.2 to 50 g/10 min at 230° C. and under a weight of 2.16 kg, according to ISO standard 1133. The melt flow index corresponds to the amount of polymer in grams which is forced, at 230° C. and under a weight of 2.16 kg, out of the test apparatus standardized according to ISO standard 1133.
The novel propylene polymer contains in particular a propylene homopolymer a) whose isotacticity index is at least 98.0%, preferably from 98.0% to 99.5%. The isotacticity index is to be understood as meaning that proportion of polymer which is insoluble in xylene according to ISO standard 6427 b). The isotacticity index is a measure of the stereospecificity of the propylene homopolymer.
The process leading to these propylene homopolymers a) can be carried out either batchwise or, preferably, continuously in the conventional reactors used for the polymerization of propylene. Suitable reactors include continuously operated stirred kettles. The reactors contain a fixed bed of finely divided polymer, which is usually kept in motion by stirring.
The process can be carried out with the Ziegler-Natta catalysts conventionally used in polymerization technology. In addition to a titanium-containing solid component, these also contain, inter alia, a cocatalyst. A suitable cocatalyst is an aluminum compound. In addition to this aluminum compound, an electron donor compound is also used as a further component of the cocatalyst.
For the preparation of the titanium-containing solid component, the titanium compounds used are in general halides or alcoholates of trivalent or tetravalent titanium, the chlorides of titanium, in particular titanium tetrachloride, being preferred. The titanium-containing solid component advantageously contains a finely divided carrier, for which silicas and aluminas as well as aluminum silicates of the empirical formula SiO
2
.aAl
2
O
3
, where a is from 0.001 to 2, in particular from 0.01 to 0.5, have proven useful.
The preferably used carriers have a particle diameter of from 0.1 to 1000 &mgr;m, in particular from 10 to 300 &mgr;mm, a pore volume of from 0.1 to 10, in particular from 1.0 to 5.0, cm
3
/g and a specific surface area of from 10 to 1000, in particular from 100 to 500, m
2
/g.
In particular, a finely divided inorganic oxide which has a pH of from 1 to 6, a mean particle diameter of from 5 to 200 &mgr;m, in particular from 20 to 70 &mgr;m and a mean primary particle diameter of from 1 to 20 &mgr;m, in particular from 1 to 5 &mgr;m, may be used as the finely divided carrier for the titanium-containing solid component. The primary particles are porous, granular oxide particles which are obtained from a corresponding hydrogel by milling, if necessary after sieving has been carried out. The hydrogel is produced in the acidic range, ie. at a pH of from 1 to 6, or is aftertreated with appropriately acidic wash solutions and purified.
Inter alia, the finely divided inorganic oxide also has cavities or channels having an average diameter of from 0.1 to 20 &mgr;m, in particular from 1 to 15 &mgr;m, whose macroscopic volume fraction is from 5 to 30%, in particular from 10 to 30%, based on the total particle. The finely divided inorganic oxide furthermore has in particular a pore volume of from 0.1 to 10, preferably from 1.0 to 4.0, cm
3
/g and a specific surface area of from 10 to 1000, preferably from 100 to 500, m
2
/g. The pH, ie. the negative decadic logarithm of the proton concentrations of the inorganic oxide is from 1 to 6, in particular from 2 to 5.
Preferred inorganic oxides are in particular oxides of silicon, of aluminum, of titanium or of one of the metals of ma
Rümpler Klaus-Dieter
Seelert Stefan
Basell Polyolefine GmbH
Keil & Weinkauf
Lipman Bernard
LandOfFree
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