DE1105171B - Process for the production of uniform polymers - Google Patents

Description

Process for the production of uniform polymers It is well known, the most diverse, powdery or granular substances with different particle sizes by sieving or other mechanical processes in To break down fractions with uniform particle size. This will cause the disconnection intended for fractions with very small or very coarse particles, because these at can interfere with the mechanical processing of such substances.

On the other hand, it is known that it is technically not possible to use macromolecular Making compounds with molecules of exactly the same size. Polymerization products rather, they are composed of molecules of different sizes, their distribution can generally be represented by a distribution curve. It is therefore Measures have often been proposed to improve the polymer uniformity of To improve polymerization products. So you can influence the polymerization Keeping factors constant or the polymers by fractional dissolving or precipitating disassemble from their solution.

The present invention is based on the knowledge that the Size of particles of polyethylene produced in suspension in a given It is related to the molecular weight.

To polymer uniform from polyethylene made in suspension To obtain substances, it is suggested that the suspended or from the suspending agent separate polymer particles mechanically in fractions of the same or similar Particle size decompose. The particles can, for example, by sedimentation or Flotation processes are fractionated.

Even if you have the polymer particles separated from the suspension medium in a hot air or nitrogen stream, for example in a flotation dryer, dries, so is the grain size distribution the same as in aqueous suspension. By using suitable classifiers, e.g. B. centrifugal separator or air separator, the separation into fractions of different particle size and thus different Degree of polymerization take place in a technically simple manner.

EXAMPLE 1 A polyethylene produced in suspension in a known manner is broken down into sieve fractions after washing and drying with the aid of a vibrating sieve with various sieve inserts. The results are shown in Table 1 below: Table 1 Fraction quantity, grain sizes, intrinsic melting point tion in 0/0 | in micron viscosity in oC 1 7)> 600 2.16 127 2 16 400 to 600 1.75 126.5 3 10 200 to 400 1.57 126.0 to 1265 4 67 75 to 200 1.39 123.5 to 125 Example 2 A polyethylene produced in suspension in the usual way is sieved for 1 minute with the aid of a vibrating sieve with various standardized sieve inserts. The six fractions obtained (1 to 6) are then sieved for another 5 minutes, each for itself.

In this case, one more fraction is obtained from each fraction (la to 6a). The grain sizes of the various fractions and their intrinsic viscosity are given in Table 2 below.

Table 2 Weight Fractional grain sizes percent of intrisic viscosity No. in microns Initial weight 1 3.30> 600 5.91 1 a 35.03 400 to 600 3.07 2 36.50 400 to 600 2.92 2a 14.38 300 to 400 2.84 3 4.52 300 to 400 2.73 3a 2.37 200 to 300 2.77 4 1.85 200 to 300 2.68 4a 0.60 150 to 200 2.69 5 0.60 150 to 200 2.60 5a 0.29 120 to 150 2.60 6 0.29 120 to 150 2.55 6a 0.27 <120 2.74

Claims (1)

PATENT CLAIM: Process for the production of uniform polymer materials made of polyethylene produced in suspension len, characterized in that the suspended or polymer particles separated mechanically from the suspension medium into fractions are broken down with the same or similar particle size.