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
1999-12-06
2002-08-06
Wu, David W. (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...
C524S515000, C525S240000
Reexamination Certificate
active
06429250
ABSTRACT:
The present invention relates to a talc-reinforced polypropylene molding composition with high impact strength, comprising
a) from 35 to 90% by weight of a propylene polymer (A) with a melt flow rate of from 15 to 100 g/10 min at 230° C. and under a load of 2.16 kg in accordance with ISO 1133 and a content of from 0 to 25% by weight of other C
2
-C
10
1-alkenes,
b) from 5 to 40% by weight of an ethylene polymer (B) with from 20 to 30% by weight of copolymerized C
4
-C
10
1-alkenes, a melt flow rate of from 0.2 to 30 g/10 min at 190° C. and under a load of 2.16 kg in accordance with ISO 1133, a density of from 0.850 to 0.880 g/cm
3
and a Mooney viscosity (ML 1+4; 121° C.) of from 5 to 50 in accordance with DIN 53523/T1, and
c) from 5 to 25% by weight of talc whose average particle size by the Sedigraph method is from 1.0 to 10 &mgr;m.
The present invention further relates to a process for producing talc-reinforced polypropylene compositions of this type, and also to their use as films, fibers or moldings, in particular in the automotive sector.
Blends, i.e. mixtures of high-impact-strength polypropylene with other polyolefins, have for more than 20 years been the most important class of materials for producing automobile bumpers and dashboards. Whereas at the start of this development the blends used were mainly made from polypropylene and ethylene-propylene rubbers produced in extruders, 10 years later the blends used included in particular those obtained from a reactor cascade. For these a polypropylene is first prepared in a first reactor, and ethylene and propylene are then polymerized onto this once it has been transferred into the second reactor. The polymerization usually takes place with the aid of Ziegler-Natta catalysts, as described, for example, in EP-A 45975, U.S. Pat. No. 4,857,613 or U.S. Pat. No. 5,288,824.
For some years there has also been increasing use of mineral-reinforced blends made from polypropylene with ethylene-propylene rubbers, and particular attention has been given to talc-reinforced blends (EP-A 9276, EP-A 430490, EP-A 476926, DE-A 3319619). Talc-reinforced blends of this type have, inter alia, low linear expansion and are therefore very suitable for jointless connections (zero-gap), for example of a bumper to the bodywork. They also feature, inter alia, high stiffness.
EP-A 519725 describes a highly crystalline polyolefin material suitable for producing automotive bumpers. This material is prepared by blending in an extruder and is composed of the following four components: an ethylene-propylene rubber, an ethylene-propylene block copolymer, an ethylene-butene copolymer and from 3 to 10% by weight of talc. The preparation of this complicated mixture in an extruder is very laborious and results in inhomogeneity. The mechanical properties of this mixture do not meet the latest technical requirements and the talc reinforcement makes the density of the material too high for many applications.
EP-A 496625 also discloses a highly crystalline polyolefin material suitable for producing automotive bumpers. For this, still higher stiffness is achieved by adding up to 30% by weight of talc. These materials, too, are characterized by densities of more than 1.05 kg/cm
3
, too high for many applications.
For weight-saving it is advantageous for moldings such as bumpers to have thin walls. However, if a large-surface-area bumper with thin walls is to be produced by injection molding, the material used must be very free-flowing as well as meeting the usual requirements for high stiffness, adequate low-temperature impact strength and low linear expansion. In addition, the cost of the material must be low. This is not achievable with currently known polypropylene blends since the flowability (melt flow rate) of known bumper materials in accordance with ISO 1133 is only in the range from 2.5 to 9 g/10 min at 230° C. and 2.16 kg.
However, the increase in the melt flow rate of polypropylene blends which would be needed to produce thin-walled moldings is associated with loss of impact strength at low temperatures. Furthermore, substantial viscosity differences mean that blends of free-flowing polypropylene with ethylene-propylene rubber have very poor dispersion, as well as poor impact strength at low temperatures. If organic peroxides are used for chemical degradation of polypropylene blends of this type in order to increase flowability the result is a drastic deterioration in impact strength and stiffness. Reinforcement of blends of this type using talc, furthermore, reduces ultimate elongation as well as flowability.
It is an object of the present invention to overcome the disadvantages described and to develop a polypropylene molding composition which, due to its melt flow rate of at least 10 g/10 min at 230° C. and 2.16 kg in accordance with ISO 1133, is suitable for producing relatively thin-walled moldings and has low linear expansion and high ultimate elongation as well as good stiffness and impact strength at low temperatures. A further object is to find a very simple and cost-effective process for preparing polypropylene molding compositions of this type.
We have found that this object is achieved by means of the novel polypropylene molding composition defined at the outset.
The novel talc-reinforced polypropylene molding composition is composed of
a) from 35 to 90% by weight of a propylene polymer (A) with a melt flow rate of from 15 to 100 g/10 min at 230° C. and under a load of 2.16 kg in accordance with ISO 1133 and a content of from 0 to 25% by weight of other C
2
-C
10
1-alkenes,
b) from 5 to 40% by weight of an ethylene polymer (B) with from 20 to 30% by weight of copolymerized C
4
-C
10
1-alkenes, a melt flow rate of from 0.2 to 30 g/10 min at 190° C. and under a load of 2.16 kg in accordance with ISO 1133, a density of from 0.850 to 0.880 g/cm
3
and a Mooney viscosity (ML 1+4; 121° C.) of from 5 to 50 in accordance with DIN 53523/T1, and
c) from 5 to 25% by weight of talc whose average particle size by the Sedigraph method is from 1.0 to 10 &mgr;m.
The total here of the individual components (A), (B) and (C) is always 100% by weight.
Particularly preferred talc-reinforced polypropylene molding compositions comprise
a) from 40 to 70% by weight, in particular from 45 to 65% by weight, of a propylene polymer (A),
b) from 15 to 35% by weight, in particular from 15 to 33% by weight, of an ethylene polymer (B), and
c) from 10 to 25% by weight, in particular from 10 to 22% by weight, of talc (C),
where the total of the individual components (A), (B) and (C) is again always 100% by weight.
The melt flow rate of the novel talc-reinforced polypropylene molding composition in accordance with ISO 1133, at 230° C. and under a load of 2.16 kg, is preferably from 10 to 40 g/10 min, in particular from 15 to 25 g/10 min and particularly preferably from 15 to 20 g/10 min. The melt flow rate may also be adjusted by chemical degradation during the preparation process of the novel polypropylene molding composition, with the aid of peroxides.
The novel talc-reinforced polypropylene molding composition comprises, inter alia, the propylene polymer (A), which has a melt flow rate in accordance with ISO 1133, at 230° C. and under a load of 2.16 kg, of from 15 to 100 g/10 min, in particular from 30 to 60 g/10 min, and a content of from 0 to 25% by weight, in particular from 5 to 10% by weight, of other C
2
-C
10
1-alkenes.
For the purposes of the present invention, C
2
-C
10
1-alkenes include in particular C
4
-C
10
-1-alkenes, such as 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene, as well as ethylene. Preference is given to the use of ethylene or 1-butene. It is also possible to use mixtures of two different C
2
-C
10
1-alkenes, for example of ethylene and 1-butene. The C
2
-C
10
1-alkene used in the propylene polymer (A) comprises in particular ethylene.
The propylene polymer (A) may therefore be either a propylene homopolymer or a propylene copolymer with up to 25% by weight of other copolymerized C
2
-C
10
1-alkenes. The propylene polymer (A
Harlan R.
Keil & Weinkauf
Targor GmbH
Wu David W.
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