High-molecular polypropylene with a broad distribution of...

Details High-molecular polypropylene with a broad distribution of... High-molecular polypropylene with a broad distribution of...

2002-05-13

2004-07-06

Rabago, Roberto (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S348000, C526S065000, C526S160000, C525S053000, C525S240000

Reexamination Certificate

active

06759500

ABSTRACT:

The present invention relates to propylene polymers containing from 0 to 2.5% by weight of C
2
-C
10
-olefin comonomers and having an M
w
of from 350,000 to 1,000,000 g/mol, an M
w
/M
n
of from 4 to 10, a proportion by weight of the polymer fraction having a viscosity number of from 500 to 1400 ml/g of from 20 to 80% of the total polymer and a proportion by weight of a polymer fraction having a viscosity number of from 200 to 400 ml/g, of from 80 to 20% of the total polymer and an isotactic sequence length of from 50 to 100.
The present invention further relates to the use of such propylene polymers (hereinafter referred to as “propylene polymers of the present invention”) for producing fibers, films and moldings, in particular for producing tubes having a high creep rupture strength under internal pressure (creep rupture strength hereinafter referred to as “CRS”), the fibers, films and moldings, in particular the tubes having a high CRS, made from the propylene polymers of the present invention and the use of the moldings, in particular the tubes having a high CRS, in the construction of chemical apparatus, as drinking water pipe and as wastewater pipe.
High molecular weight propylene polymers can be prepared using conventional Ziegler catalysts based on a titanium compound/an aluminum alkyl, as is described, for example, in DE-A 40 19 053. The expression “high molecular weight propylene polymers” usually refers to propylene polymers which have a molecular weight M
w
measured by GPC (gel permeation chromatography) of more than about 500,000 g/mol and a corresponding melt flow rate at 230° C. under a load of 5 kg (MFR 230/5, measured in accordance with ISO 1133) of at least about 3 dg/min. In contrast thereto, customary propylene polymers have an M
w
of from about 100,000 g/mol to about 300,000 g/mol and correspondingly an MFR (230/5) of more than 4 dg/min.
The high molecular weight propylene polymers obtainable using Ziegler catalysts (hereinafter referred to as “high molecular weight Ziegler propylene polymers”) generally have a large mean length of isotactic sequences “n-iso”, (measured using the
13
C-NMR method as described by zambelli et al. Macromolecules 8, 687-689(1975); the value is usually over 100. Further properties of such high molecular weight Ziegler propylene polymers are a comparatively high proportion of xylene-soluble substances “XS value” (XS value determined as described in the examples) and a comparatively high melting point of generally more than 160° C. (determined by the DSC method, as described in the examples). When processed, for example by extrusion, to produce shaped articles such as tubes, etc., such high molecular weight Ziegler propylene polymers display poor processability (in particular poor flow) and the articles produced often have poor organoleptic properties (odor, taste). The unsatisfactory organoleptic properties are caused, on the basis of present-day knowledge, by low molecular weight, oily propylene oligomers.
Attempts are usually made to circumvent the unsatisfactory processability of the high molecular weight Ziegler propylene (homo)polymers by changing to high molecular weight Ziegler propylene-olefin copolymers which have a lower melting point and therefore flow more readily at a given temperature during extrusion than do the analogous homopolymers. However, the copolymers have an increased content of readily soluble propylene oligomers, again resulting in high proportions of xylene-soluble material and unfavorable organoleptic properties of the high molecular weight Ziegler propylene copolymers.
In addition, the tubes produced from high molecular weight Ziegler propylene polymers, for example as described in DE-A 40 19 053, have high brittleness (low CRS) and a rough (internal) surface. The rough surface provides, on the basis of present-day knowledge, a large surface area for attack by liquids, and the liquids leach out the polymer stabilizer present in the tube, which once again reduces the CRS of the tubes.
It is an object of the present invention to find propylene polymers which can easily be processed (inter alia due to improved flow) by means of conventional manufacturing tools to give shaped bodies, in particular tubes, which have not only low brittleness and a smooth surface but also a high toughness and good stiffness combined with a good CRS of the shaped bodies, in particular tubes.
We have found that this object is achieved by the propylene polymers of the present invention, the use of such propylene polymers for producing fibers, films and moldings, the fibers, films and moldings made of the propylene polymers of the present invention and the use of the tubes in the construction of chemical apparatus, as drinking water pipes and as wastewater pipes.
The propylene polymers of the present invention are generally obtained by means of at least two-stage polymerization (known as the cascade method) of propylene together with from 0 to 2.5% by weight of C
2
-C
10
-olefin comonomers, preferably from 0 to 1.5% by weight of C
2
-C
10
-olefin comonomers and in particular from 0 to 1% by weight of C
2
-C
10
-olefin comonomers, in the presence of metallocene catalyst systems (as described below).
Suitable C
2
-C
10
-olefin comonomers are ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene. It is possible to copolymerize a plurality of comonomers or only one comonomer with the propylene. The abovementioned % by weight are then based on the sum of the comonomers. Preferred C
2
-C
10
-olefin comonomers are ethylene, 1-butene and 1-hexene. Preferred propylene-olefin copolymers are propylene-ethylene copolymers, propylene-1-butene copolymers and propylene-ethylene-1-butene terpolymers. The total amount of comonomers in these cases, too, is in the range from 0.1 to 2.5% by weight, preferably in the range from 0.1 to 1.5% by weight, in particular in the range from 0.1 to 1% by weight.
The polymerization reactions, generally at least two-stage reactions, can essentially be carried out continuously or batchwise by all suitable olefin polymerization methods. They can be carried out in the gas phase, for example in a fluidized-bed reactor or a stirred gas phase, in the liquid monomers, in solution or in suspension in suitable reaction vessels or in loop reactors. The polymerization temperature is usually in the range from 0 to 150° C., preferably in the range from 30 to 100° C., the pressure is in the range from 5 to 500 bar, preferably from 10 to 100 bar, and the mean residence time is in the range from 0.5 hour to 6 hours, preferably from 0.5 to 4 hours.
A well-suited polymerization method is the two-stage bulk polymerization process.
Here, a high molecular weight propylene homopolymer or copolymer of the composition described above, preferably a propylene homopolymer, having a viscosity of from 500 to 1400 ml/g (determined by the method disclosed in the examples) and a proportion of the total polymer of from 20 to 80% by weight, preferably from 45 to 75% by weight, particularly preferably from 48 to 65% by weight, is prepared in the first reaction step, while in the second, usually downstream reaction step, a low molecular weight propylene homopolymer or copolymer of the composition described above, preferably a propylene homopolymer, having a viscosity of from 200 to 400 ml/g and a proportion of from 20 to 80% by weight, preferably from 25 to 55% by weight, particularly preferably from 35 to 52% by weight, is prepared.
The first and second reaction steps can be carried out batchwise or continuously. Preference is given to continuous operation. The first polymerization step is generally carried out in liquid propylene at from 55 to 100° C. and a residence time of from 0.5 to 3.5 hours. A phase ratio in the range from 2.5 to 4 l of liquid propylene per kg of PP, preferably 3.3 l of liquid propylene per kg of PP, is usually set. To regulate the molar mass, hydrogen is generally metered in.
After the first reaction step, the multiphase system is generally transferred to the second reaction step and po

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