DE102006029920A1 - Polypropylene blend, useful e.g. to prepare film, fiber, tube, hose, molded bodies, textile/fabrics, preferably protective clothing, and in medicine and automobile, comprises two fractions of polypropylene with different molecular weight - Google Patents

Abstract

Polypropylene blend (I) comprises at least two fractions of polypropylene with different molecular weight, where the lighter- and heavier fractions exhibit an average molecular weight of 100000-400000 g/mol, and 450000-2000000 g/mol, respectively; and the weight ratio (in wt.%) of lighter fraction to heavier fraction is 55 to less than 90, to greater than 10 to 45.

Description

This The invention relates to polyethylene blends consisting of a proportion low molecular weight and a proportion of high molecular weight polypropylene in a very specific mixing ratio.

task The present invention is a Polypropylenblend with outstanding providing physical properties, being the goal was, in particular polypropylene blends with high tear and tensile strength manufacture.

The Task is solved with the polypropylene blend according to claim 1. Uses of the inventive polypropylene blends give the claims 13 to 19. The dependent ones claims describe advantageous developments.

According to the invention, a polypropylene blend is provided containing at least two fractions of polypropylene but of different molecular weight, the lighter fraction having an average molecular weight (M _w ) between 100,000 and 400,000 g / mol and the heavier fraction having an average molecular weight (M _w ) between 450,000 and 2,000,000 g / mol, and the light fraction is in a weight ratio of 55 to <90% by weight to the heavy fraction of 45 to> 10% by weight.

Prefers For example, the polypropylene blend has a weight ratio of the light fraction to the heavy fraction of 65 to 85 wt .-% to 35 to 15 wt .-% to.

Further it is preferred if the polypropylene blend is a weight ratio of light fraction to the heavy fraction of 75 to 85 wt .-% to 25 to 15 wt .-%.

All is particularly preferred the weight ratio of the light fraction to the heavy fraction of 78 to 82% by weight to 22 to 18 wt .-%.

Especially join the outstanding physical described below Properties of the polypropylene blends according to the invention when the heavy fraction of the polypropylene is at least 95% isotacticity preferably has at least 98% isotacticity.

alternative it is also possible when the heavy fraction of polypropylene has variable tacticity. According to the invention is under variable tacticity a polypropylene polymer understood that the polymer due a statistical distribution of stereo errors in the polymer chain, in a range of 25 to 60% [mmmm] pentane concentration, being excluded according to the invention Will that polymer be arbitrary or regular Contains sequences of isotactic and atactic blocks.

Farther it is advantageous if the light fraction of the polypropylene at least 95% isotacticity, preferably has at least 98% isotacticity.

In an advantageous embodiment, it is preferred if the lighter fraction has an average molecular weight (M _w ) of between 150,000 and 300,000 g / mol and the heavier fraction has an average molecular weight (M _w ) of between 800,000 and 1,500,000 g / mol.

In a most preferred embodiment, the lighter fraction has an average molecular weight (M _w ) of between 150,000 and 250,000 g / mol and the heavier fraction has an average molecular weight (M _w ) of between 1,000,000 and 1,500,000 g / mol.

The produced polypropylene blends according to the invention have at a temperature of 100 ° C preferably a degree of stretching λ between 8 to 20, preferably between 10 to 18, most preferably between 12 to 16 on.

The Tear strength σ of the polypropylene blend according to the invention amounts It is at a temperature of 100 ° C to at least 10 MPa, preferably at least 12 MPa, most preferably at least 13 MPa.

optional can other additives selected from the group consisting of pigments, plasticisers, antioxidants, Radiation absorbers, reinforcing Fibers, flame retardants, other polymers, nanotubes, carbon black and / or silica gel.

use finds inventive polypropylene blend in the manufacture of films, fibers, pipes, hoses and / or Moldings, which advantageously by extrusion and / or injection molding being represented.

moreover is a use in medicine, e.g. in dentures, implants, Fittings for bone fractures, Intramedullary nails, Rails, and / or artificial Sinews conceivable.

The predestine excellent properties of the polymer blends a use in the automotive industry. Conceivable here is a use for all possible, plastic molded parts of a car, such as e.g. bumpers, Parts of the body (fenders, Bonnet etc.), parts of the interior lining, but also functional Parts, such as ventilation hoses, fuel, Lubricant and / or coolant lines, without a limitation to want to make on the examples mentioned.

As well It is conceivable that the polymer blends according to the invention in the preparation of fibers, textiles and / or fabrics. Especially for the production of protective clothing are the polymer blends according to the invention best for.

Farther is the use of the polymer blends according to the invention in the preparation of protective panels advantageous.

Example 1: Polymers used:

• a) low molecular weight polypropylene: Montell SM 6150 (iPP), tacticity [mmmm]> 98%, M _w = ~ 200,000 g / mol
• b) high molecular weight, isotactic polypropylene (hiPP) ·: Tacticity [mmmm]> 96%, M _w = ~ 1,100,000 g / mol, T _m = 162 ° C

Example 2: Extruder used and settings:

A mini-extruder from Daca-Instruments is used for all blended experiments. The capacity of the extruder is 0.5-4.5 ml. The extruder is operated at the following settings: Temperature: 180 ° C Speed of the worm gear: 50 rpm

Example 3: Sample preparation:

3.00 g of low molecular weight polypropylene (iPP) are weighed. Depending on the desired percentage of the high molecular weight polypropylene (hiPP) with respect to the low molecular weight PP (iPP) forming the matrix, appropriate amounts of the high molecular weight polypropylene (hiPP) are weighed in (see Table 1): Share of hiPP [%] iPP [g] iPP [g] sample name 0 3.00 0.00 PB00 2 3.00 0.06 PB02 5 3.00 0.15 PB05 20 3.00 0.60 PB20 100 3.00 0 PB100 Tab.1: Shares of hiPP

in the next Step are the low and the high molecular weight polypropylene of Hand mixed together.

Example 4: Melting, mixing and extrusion

After the extruder reaches the preset temperature of 180 ° C and the rotational speed of the worm gear has stabilized at 50 rpm, the sample mixture is rapidly added using a hand press. The melting and mixing of the two polymer fractions lasts 15 min. At closing the outlet cock of the extruder is opened and the polymer drained. The forming polymer strand is rolled up with the aid of a glass rod.

Example 5: Description of shoulder sample preparation

In order to be able to perform reproducible stress-strain experiments, the material to be analyzed must have a specific, always identical shape. (RP Brown, Physical Testing of Rubbers, Applied Science Publishers Ltd., London, 1979). This is a piece of polymer similar in appearance to a dog bone (cf. 7 ). Due to the shape, there is an inherent reinforcement of the stress and strain forces in the material. To prepare the specimens, the sample polymer is placed in a heatable high pressure press. At 200 ° C, the sample is subjected to a special pressing process with time-varying pressure (see Table 2). Time [min] Pressure [MPa] 5 0 60 25 Table 2: Time-pressure history

Subsequently, the heating plates are switched off and cooled under constant pressure with the help of a water cooling system. After the hotplates reach 50 ° C, the polymer is removed and further cooled at RT. Due to the aluminum stencil used, one obtains polymer plates with the dimensions: 40 × 60 × 1 mm. In the next step, 50 mm long and 8 mm wide shoulder samples (dogbones) are used with the aid of a special punching tool ( 7 ) punched out. These can then be subjected to tensile-strain experiments.

Example 6: Carrying out the tensile-strain experiments

The Tensile-strain tests are performed by the company using the tensile-strain apparatus (1435) Zwick performed. Since iPP tends to be at room temperature, even at low expansion To break, the train-strain experiments are in a heating chamber at 100 ° C carried out. This ensures that to obtain a complete set of tensile-strain experiments. The sample is loaded until it breaks.

The following Figures illustrate the superior Physical properties of the polypropylene blend according to the invention:

1 shows an electron micrograph of the fracture of a stretched polymer sample consisting of 100 wt .-% low molecular weight PP (200 times).

2 shows an electron micrograph of the fracture of a stretched polymer sample consisting of 80 wt .-% low molecular weight and 20 wt .-% high molecular weight PP (200 times).

3 shows an electron micrograph of the fracture of a stretched polymer sample consisting of 100 wt .-% low molecular weight PP (1000 times).

4 shows an electron micrograph of the fracture of a stretched polymer sample consisting of 80 wt .-% low molecular weight and 20 wt .-% high molecular weight PP (1000 times).

5 shows characteristic tensile-strain curves of the investigated polyproplene blends with different mixing ratios of low molecular weight to high molecular weight fraction of the polypropylene. The various imaged samples therein are characterized by their content of high molecular weight polypropylene (iPP). Representative of all samples, PB20, for example, means the sample whose proportion of low molecular weight polypropylene is 80% by weight and the proportion of high molecular weight polypropylene (iPP) is 20% by weight.

6 shows a comparison of the tensile strain data (λ rupture) depending on the proportion of high molecular weight PP. Shown is the maximum load capacity of the examined samples until a break of the test specimen took place.

7 shows a shoulder sample used in the tensile-elongation experiments.

8th shows measurement results of tensile elongation experiments of various samples consisting of 100% low molecular weight polypropylene.

9 shows measurement results of tensile elongation experiments of various samples consisting of 80% by weight of low molecular weight and 20% by weight of high molecular weight polypropylene.

10 shows the direct comparison of the in the 8th and 9 shown measurement results.

σ:

wirksame Zugkraft auf die Querschnittsfläche des Testkörpers (dogbone).

λ:

Ausdehnungsrate des Testkörpers (dogbone), gemessen in einem Vielfachen der ursprünglichen Beabstandung der zwei am Testkörper im Abstand von 12 mm angebrachten Referenzpunkte.

In the figures mean:

σ:

effective tensile force on the cross-sectional area of the test body (dogbone).

λ:

Extension rate of the test body (dogbone) measured in a multiple of the original spacing of the two reference points attached to the test body at a distance of 12 mm.

The electron micrographs (shown in the 1 - 4 ) illustrate the experimentally found high load capacities of the polypropylene blends according to the invention. It can be seen that the increased tensile strain values are due to the high partial crystallinity of the blends. While low molecular weight polypropylene is in an amorphous state, the melting of 20% by weight of a high molecular weight polypropylene leads to a greatly increased crystallinity, which causes the high mechanical resistance of moldings formed from this polypropylene blend.

In 5 Comparative are the tensile-strain curves of the examined polypropylene blends listed. This shows the superior tensile-elongation properties of the present invention polypropylene blend. Surprisingly, the polypropylene blends with a lower proportion of high molecular weight polypropylene and the sample of pure, high molecular weight PP have significantly poorer tensile-strain properties than the sample made from the PP mixture according to the invention.

Another way of representation is in 6 selected. Here, λ is shown as a function of the percentage by weight of high molecular weight PP. As in 5 It becomes clear that the sample with the PP mixture according to the invention has significantly improved material properties than all the other samples investigated. This can be seen from the significantly increased strain rate λ until the fracture occurs.

In 8th are measured curves for tensile-strain experiments of various samples of low molecular weight PP (Montell SM 6150), while 9 shows the same measurement results for samples of the PP blend according to the invention. By performing several traces of different batches, the good reproducibility of the invention is illustrated. In 10 the two measured curves of the pure, low molecular weight PP and of the PP blend according to the invention are compared. It can be seen that the PP blend according to the invention has properties with respect to the tensile-elongation behavior which are many times superior to those of the pure low-molecular weight PP.

Claims (19)

Polypropylene blend containing at least two fractions of polypropylene, but of different molecular weight, characterized in that the lighter fraction has an average molecular weight (M _w ) between 100,000 and 400,000 g / mol and the heavier fraction has an average molecular weight (M _w ) between 450,000 and 2,000 .000 g / mol and the light fraction in a weight ratio of 55 to <90% by weight to the heavy fraction of 45 to> 10 wt .-%. Polypropylene blend according to claim 1, characterized in that that it's a weight ratio the light fraction to the heavy fraction of 65 to 85% by weight to 35 to 15 wt .-% has. Polypropylene blend according to claim 1, characterized in that that it's a weight ratio of the light fraction to the heavy fraction of 75 to 85% by weight to 25 to 15 wt .-% has. Polypropylene blend according to claim 1, characterized in that that it's a weight ratio of the light fraction to the heavy fraction of 78 to 82% by weight to 22 to 18 wt .-% has. Polypropylene blend according to one of the preceding claims, characterized in that the heavy Fraction has at least 95% isotacticity, preferably at least 98% isotacticity. Polypropylene blend according to one of claims 1 to 4, characterized in that the heavy fraction has variable tacticity. Polypropylene blend according to one of the preceding claims, characterized in that the light fraction has at least 95% isotacticity, preferably at least 98% isotacticity having. Polypropylene blend according to one of the preceding claims, characterized in that the lighter fraction has an average molecular weight (M _w ) of between 150,000 and 300,000 g / mol and the heavier fraction has an average molecular weight (M _w ) of between 800,000 and 1,500,000 g / mol. Polypropylene blend according to one of Claims 1 to 7, characterized in that the lighter fraction has an average molecular weight (M _w ) of between 150,000 and 250,000 g / mol and the heavier fraction has an average molecular weight (M _w ) of between 1,000,000 and 1,500,000 g / mol. Polypropylene blend according to one of the preceding Claims, characterized in that it at a temperature of 100 ° C, a degree of stretching λ between 8 to 20, preferably between 10 to 18, most preferably between 12 to 16. Polypropylene blend according to one of the preceding Claims, characterized in that it has a tensile strength at a temperature of 100 ° C. of at least 10 MPa, preferably at least 12 MPa, especially preferably at least 13 MPa. Polypropylene blend according to one of the preceding Claims, characterized in that further additives selected from the group consisting of pigments, plasticisers, antioxidants, Radiation absorbers, reinforcing Fibers, flame retardants, other polymers, nanotubes, carbon black and / or Silica gel can be included. Use of a polypropylene blend according to one of claims 1 to 12 for the production of films, fibers, pipes, hoses and / or Moldings. Use according to the preceding claim, characterized characterized in that films, fibers, tubes, hoses and / or molded parts Extrusion and / or injection molding can be produced. Use of a polypropylene blend according to one of claims 1 to 12 in medicine. Use of a polypropylene blend according to one of claims 1 to 12 in automotive engineering. Use of a polypropylene blend according to one of claims 1 to 12 for the production of fibers, textiles and / or fabrics. Use according to the preceding claim, characterized characterized in that the textile is protective clothing. Use of a polypropylene blend according to one of claims 1 to 12 for the production of protective panels.