Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-06-21
2001-02-20
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
06191223
ABSTRACT:
TITLE OF THE INVENTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polymer blends comprising
a) from 50 to 85% by weight of a copolymer of propylene (A) with 1-alkenes comprising from 20 to 80% by weight of a high molecular weight copolymer of propylene (I) containing from 2.0 to 7.0% by weight of copolymerized 1-alkene and having a viscosity of from 500 to 1200 ml/g and from 20 to 80% by weight of a low molecular weight copolymer of propylene (II) containing from 4.0 to 10.0% by weight of copolymerized 1-alkene and having a viscosity of from 200 to 450 ml/g,
b) from 5 to 10% by weight of a polymer of ethylene (B) and
c) from 10 to 40% by weight of a rubber-like copolymer of propylene and a 1-alkene (C) containing from 30 to 70% by weight of copolymerized 1-alkene,
and having a melt flow index (MFI) at 230° C. under a weight of 5 kg of from 0.1 to 5 g/10 min, a molecular weight distribution (M
w
/M
n
) of from 6 to 20 and a total 1-alkene content of from 4 to 15% by weight.
The present invention further relates to a process for preparing such polymer blends, also moldings, hollow bodies and stamping plates comprising the polymer blends of the present invention and also a process for producing die stamping plates.
2. Description of the Related Art
Thermoplastic polymers, for ex ample propylene polymers, can generally be readily processed to produce moldings or hollow bodies. In the production of die stamping plates, however, there are sometimes difficulties resulting from, inter alia, the fact that the stamping plates frequently become brittle after prolonged use.
DE-A 4019053 discloses homopolymers of propylene having a broad molecular weight distribution (M
w
/M
n
) which are suitable, in particular, for producing films and moldings. However, die stamping plates produced therefrom have a certain brittleness and a relatively rough surface, which restricts their practical use.
Furthermore, EP-A 573862 describes crystalline polymers of propylene which likewise have a broad molecular weight distribution (M
w
/M
n
). These polymers are prepared by gas-phase polymerization in the presence of Ziegler-Natta catalysts. However, the propylene polymers obtained in this way have a relatively unsatisfactory brittleness during further processing and are not completely homogeneous. The production of die stamping plates from such propylene polymers by means of a customary platen pressing process is virtually impossible since the viscosity of the melt obtained is not sufficient.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to remedy the disadvantages indicated and to find an improved molding composition which can be converted using customary manufacturing tools into fracture-resistant moldings and hollow bodies which have a smooth surface, a high toughness and good stiffness together with a high durability on prolonged use. Furthermore, the present object also extends to a simple and economical process for producing such moldings, and also to moldings, hollow bodies and die stamping plates comprising the molding compositions of the present invention.
The polymer blends of the present invention comprise
a) from 50 to 85% by weight of a copolymer of propylene (A) with 1-alkenes comprising from 20 to 80% by weight of a high molecular weight copolymer of propylene (I) containing from 2.0 to 7.0% by weight of copolymerized 1-alkene and having a viscosity of from 500 to 1200 ml/g and from 20 to 80% by weight of a low molecular weight copolymer of propylene (II) containing from 4.0 to 10.0% by weight of copolymerized 1-alkene and having a viscosity of from 200 to 450 ml/g,
b) from 5 to 10% by weight of a polymer of ethylene (B) and
c) from 10 to 40% by weight of a rubber-like copolymer of propylene and a 1-alkene (C) containing from 30 to 70% by weight of copolymerized 1-alkene,
and have a melt flow index (MFI) at 230° C. under a weight of 5 kg of from 0.1 to 5 g/10 min, a molecular weight distribution (M
w
/M
n
) of from 6 to 20 and a total 1-alkene content of from 4 to 15% by weight.
DETAILED DESCRIPTION OF THE INVENTION
The polymer blends of the present invention preferably consist of
a) from 50 to 85% by weight, in particular from 60 to 85% by weight, of the copolymer (A),
b) from 5 to 10% by weight, in particular from 5 to 7% by weight, of the polymer of ethylene (B) and
c) from 10 to 40% by weight, in particular from 10 to 35% by weight, of the rubber-like copolymer of propylene and a 1-alkene (C), where the sum of the three polymers (A), (B) and (C) is always 100% by weight.
The melt flow index (MFI) of the polymer blends of the present invention at 230° C. under a weight of 5 kg, in accordance with DIN 53735, is preferably from 0.3 to 3.0 g/10 min. The polymer blends of the present invention also preferably have a molecular weight distribution (M
w
/M
n
) of from 6 to 15 and a total 1-alkene content of from 5 to 12% by weight.
For the purposes of the present invention, 1-alkenes include ethylene and, in particular, C
4
-C
12
-alk-1-enes such as 1-butene,. 1-pentene, 1-hexene, 1-heptene and 1-octene, with preference being given to using ethylene and 1-butene. It is also possible to use mixtures of two different 1-alkenes, for example ethylene and 1-butene.
One constituent of the polymer blends of the present invention is the copolymer of propylene (A) with 1-alkenes, which preferably comprises from 45 to 75% by weight, in particular from 48 to 65% by weight, of a high molecular weight copolymer of propylene (I) and from 25 to 55% by weight, in particular from 35 to 52% by weight, of a low molecular weight copolymer of propylene (II). The high molecular weight copolymer of propylene (I) preferably contains from 2.0 to 7.0% by weight, in particular from 3.0 to 5.0% by weight, of copolymerized 1-alkene and preferably has a viscosity (viscosity number) of from 400 to 1200 ml/g, in particular from 450 to 700 ml/g, in each case determined at 135° C. in decalin. The low molecular weight copolymer of propylene (II) preferably contains from 4.0 to 10.0% by weight, in particular from 4.5 to 8.0% by weight, of copolymerized 1-alkene and preferably has a viscosity (viscosity number) of from 200 to 450 ml/g, in particular from 220 to 400 ml/g, in each case determined at 135° C. in decalin. As 1-alkene, preference is giving to using ethylene, if desired together with 1-butene. In particular, use is made of a copolymer of propylene (A) in which the low molecular weight copolymer of propylene (II) has a higher ethylene content than the high molecular weight copolymer of propylene (I).
The process leading to these copolymers (A) can be carried out in the customary reactors used for the polymerization of 1-alkenes, either batchwise or preferably continuously, for example in solution, as a suspension polymerization or as a gas-phase polymerization. Suitable stirred reactors are, for example, continuous stirred reactors, loop reactors or fluidized-bed reactors. Of course, the reaction can also be carried out in a plurality of reactors connected in series. The polymerization is preferably carried out in the gas phase or in suspension (bulk polymerization). Suitable gas-phase reactors are fluidized-bed reactors and horizontal or vertical stirred powder bed reactors. Particular preference is giving to using powder bed reactors in which the reaction bed is kept in motion by vertical stirrers. The reaction bed generally comprises the polymer which is produced in the respective reactor. Suitable suspension reactors are, inter alia, loop reactors.
The polymerization of the copolymers of propylene to be used according to the present invention is preferably carried out at from 30 to 150° C. and pressures in the range from 10 to 100 bar in the presence of a Ziegler-Natta catalyst system comprising
a) a titanium-containing solid component comprising at least one halogen-containing magnesium compound and an electron donor,
b) an aluminum compound and
c) a further electron donor compound.
A preferred titanium-containing solid component is, for example, pr
Dolle Volker
Terwyen Herbert
Keil & Weinkauf
Nutter Nathan M.
Tagor GmbH
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