DE1147755C2 - Process for working up solutions or dispersions of low-pressure polymers - Google Patents

Description

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It is known that polymers, as they are in the low-thickness polymerization of olefins, Diolefins and their derivatives, such as ethylene,

60

65 propylene, a-butylene, butadiene or styrene, etc., as well as their mixtures with the help of mixed catalysts made from compounds of the elements of IV. To VI. and VIII. Nebengrappe of the periodic system on the one hand and organometallic compounds of the metals of the I. to III. Group of the Periodic Table, on the other hand, in the presence of inert solvents, can be worked up by converting the mixed catalyst residues with decomposing agents into soluble compounds and then washing and drying the separated low-pressure polymer. However, the work-up is only incomplete because the polymer particles present or which precipitate out contain undesired mixed catalyst residues and atactic or low molecular weight polymer components.

Therefore, one keeps in the polymers, provided that one works with the usual Rührcra and not special ones Effort drives back ash content to around 0.2%. Which so pollutes remaining polymers have unfavorable color numbers and inferior mechanical properties; the acidic catalyst residues also often cause corrosion in the processing machines.

It has now been found that low-pressure polymer solutions or dispersions, such as those used in the low-pressure polymerization of olefins, diolefins, can be used. their derivatives or mixtures with the aid of mixed catalysts from compounds of the elements of IV. to VI. and VIII. Subgroup of the periodic system on the one hand and aluminum, aluminum hydride, alkali metals or organometallic compounds of the metals of the I. to III. Group of the periodic system, on the other hand, in the presence of inert solvents, by treating the polymer solutions or dispersions at temperatures between -50 and +200 ⁰ C below the softening range of the polymers with agents which convert the mixed catalyst residues into soluble compounds and, if polymer solutions are present, the The polymer can be precipitated out, and by subsequent separation of the polymers, using shear and vibration forces which have a crushing effect, it can be worked up more advantageously if the existing or resulting polymer materials are exposed to the shear and vibration forces which have a crushing effect during the treatment with the solvents and precipitants mentioned.

As mixed catalysts, their removal according to the invention is improved, for example, the reaction products from compounds are suitable of titanium, zirconium, vanadium, thorium or uranium, such as titanium halides or halogen orthotitanic acid esters, with aluminum, aluminum hydride, organometallic compounds of aluminum, such as halogen-containing or halogen-free aluminum alkyls, -aryls and -aralkyls, also with organometallic ones Compounds of magnesium, zinc or the alkali metals or with the alkali metals self.

The polymer solutions and dispersions to be worked up contain inert diluents Aliphatic, cycloaliphatic or aromatic liquids that are liquid under the working conditions Hydrocarbons or hydrocarbon mixtures, such as butane, hexane, gasoline fractions, diesel oil

fractional, benzene, xylene, cyclohexane.

Suitable decomposition agents which are added to convert the mixed catalyst residues into soluble compounds are those which are capable are to precipitate the polymers from their solutions, especially alcohols such as methanol, ethanol, Isopropyl alcohol, n-butanol, the pentanols. Polyhydric alcohols such as glycols, and further usable such liquid organic oxygen-containing compounds in which both valences of oxygen are bound to carbon, e.g. ether, glycol dimethyl ether, Tetrahydrofuran, dioxane, furan and pyran, also aldehydes such as acetaldehyde and butyraldehyde, also ketones, such as acetone, methyl ethyl ketones, cyclopentanones, cyclohexanones and pyrone, further Esters, such as ethyl acetate, butyl acetate and acetoacetic ester, and finally lactones, such as Propioactone and butyrolactone. But also organic and inorganic acids and complexes organic and inorganic salts are suitable. There are also mixtures of the specified Compounds and, if appropriate, their aqueous solutions are suitable.

For the mechanical breakdown of the existing or in the presence of the decomposition agent from the Dispersions produced from polymer solutions are used such comminution devices which not only are able to homogenize the dispersions by breaking them into agglomerates Dividing the dispersion particles, but also by exerting strong shear and vibration forces, the individual particles are still further comminuted; this is based on the rotor-stator or rotor-air-rotor principle , working disintegrators, such as Schiag pin mills or disk mills, which z. B. under the name Ulira ^ Turrax, mixed siren or Supraton mill are known.

Among the devices that have an extraordinary degree of freedom, in particular those arising from solution Effect dispersions also include nozzles, which atomize the polymers allow. It may be advantageous to to design a nozzle in such a way that the resulting vibrations of the liquid and steam jets a further explanation takes place.

The mechanical pulping, which is carried out simultaneously with the mixed catalyst decomposition and, optionally, precipitation of the solution or even begun before the addition of the decomposing agent may be at temperatures between -50 and + 200 ° C, preferably 30 and 8O ⁰ C, below the softening range of the Polymer can be carried out batchwise or continuously. All that is required is that the treatment is continued until the isotactic polymer has precipitated out completely, so that the fine dispersion does not stick together as a result of the polymer which subsequently precipitates. A treatment time of 10 to 60 minutes is generally sufficient for this. It has proven to be advantageous in some cases to carry out the filling in cascade-like cascading containers, it being possible for the decomposing or precipitating agents to be added both to each and to a specific kettle.

, The breakdown of the polymer and the conversion and dissolution of the mixed catalysts can be improved and accelerated by the polymer solution or dispersion of the mechanical crushing device fed through a nozzle, with the decomposition agent presented can be or can be injected at the same time as the polymer; blows as an additional pumped medium one through the same or a further nozzle an inert gas or a vaporous solution or A decomposition agent. In this case the digestion vessel is equipped with a reflux condenser.

Then the polymer is in the usual manner, for. B. by filtration, from the solvents separated off, washed, optionally also

, ₅ mashed with a washing solution, filtered again and dried.

The procedure according to the invention gives polymers whose grain size is considerably smaller than those who, under otherwise comparable

conditions can be obtained, but instead of mechanical digestion have only been intensively stirred in the usual manner. The ash content will be 0.01 to 0.03 ° / ₀ and thus meet the requirements of the art.

A further advantage of the process is that the mechanical digestion also enables the undesired substances to be separated off atactic components, which significantly improves the flow strength of the products. Flow strength is also called the stretching To understand the property of thermoplastics designated voltage, which according to DIN 53 455, which consists of DIN 53 371 emerged, on test bars punched from press plates with a thickness of 1 mm at a feed rate measured at 500 mm / min

would. Furthermore, due to the more intensive digestion, significantly less contact decomposition agent is required, so that here, too, the procedure is cheaper.

It is known from French patent specification 1215 709 that the polymer dispersions can be used first crushed and then decomposed. This corresponds to the general technique, as small as possible Using parts to achieve the desired success. Surprisingly, however, it succeeds this approach does not improve the processing. As the table shows, the work-up can be done a crude low pressure polybutene-1 dispersion in hexane, because of the clumping, the high ash content, the low flow strength and the low bulk density of the polymer is completely unsatisfactory (Experiment I), by application the previous comminution specified in French Patent 1,215,709 improve (experiment II). If, on the other hand, you work

according to the invention (experiment III), 'so are all difficulties remedied: The polymer has an extremely narrow grain size distribution, low ash content, high bulk density and high flow strength. The method according to the invention is even capable, like experiments IV and V show that after treatment according to French patent 1,215,709 it clumped To process material, regardless of whether the pretreatment was carried out once or 20 to 30 times. It is Surprisingly and could not have been foreseen that the known process, which during the polymerization or fails before the work-up, then brings a progressive result if you get it during the work-up begins.

Experiment no.

II III

IV

Treatment of the dispersion
with Reaktron device
the work-up according to
French patent specification
1215 709

Treatment of the dispersion
with Reaktron device during work-up according to the present invention

Grain size distribution (° / o)

0.8 mm

0.65

0.5

0.4

0.1

Ash content (%>)

Bulk weight (g / l)

Yield strength (kg / cm ² )

cannot be determined, product clumped and caked together, 95% over 0.5 mm

0.20 to 0.30

Part sieved from the clumped product: 80 to 100

120

cannot be determined, product clumped and caked, 97% over 0.5 mm

0.2 to 0.5 distribution uneven

Part sieved from the clumped product: 80 to

120 0.2 to 1.4
0.2 to 3.0
0.2 to 6.0
3.2 to 8.8
85 to 94
0.4 to 4.4

0.01 to 0.03

220 to 330

200 to 225

0.2

0.4 to 1.2 1.2 to 2.0 3.8 to 5.4 90 to 96 0.2 to 1.2

0.02 to 0.03

200 to 250

200 to 210

+, 20 to 30 passes

0.2 to 0.6 0.4 to 0.8 1.2 to 1.6 7.4 to 9.0 69 to 90 0.2 to 2.0

0.02 to 0.03

200 to 290

200 to 220

example 1

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Example 2

A solution of 15 parts by weight of poly-a-butylene in 100 parts by weight of heptane, which is obtained by polymerizing 15 parts by weight of a-butylene in 100 parts by weight of heptane, to which 0.06 parts by weight of titanium trichloride and 0.12 parts by weight of diethylaluminum monochloride has been obtained, is obtained at optionally 30 ° C in a stirred vessel, in which 50 parts by weight of methanol at 30 ⁰ C are over 10 minutes directly into the feed openings of a high speed Ultra-Turrax stirrer and outgoing total of 30 minutes. The polymer is then filtered off and washed on the filter with 20 parts by weight of methanol. It is then mashed in 75 parts by weight of methanol for 2 hours at 70 ° C. and again separated from the methanol. After drying, the purified polymer is finely divided and has an ash content of 0.02% and a flow strength of 220 kg / cm ² .

If the precipitation is carried out in a customary, normal stirred tank under otherwise identical conditions, a coarse flocculent polymer is obtained, some of which is baked together. The ash content is 0.24%, the flow strength is 120 kg / cm ² .

A solution of 15 parts by weight of poly-a-butylene in 100 parts by weight of heptane, which was obtained as described in Example 1, is blown at 70 ° C. through a mixing nozzle through which 50 parts by weight of gaseous n-propanol at 120 ° C. are, in a stirred vessel in which there are 10 parts by weight of n-propanol and 10 ^{parts by weight of heptane at 70 0} C, placed in the intake part of a high-speed Kothoff mixed siren. After 20 minutes of digestion and work-up as in Example 1, a finely flaky polybutylene is obtained which has the following particle size distribution:

> 0.5 mm 0.88%

0.4 mm 0.31%

0.3mm 0.17%

0.25mm 0.27%

0.20 mm 0.69%

0.16 mm 30.6%

0.10 mm 38.2%

0.06 mm 15.81%

0.04 mm 7.25%

<0.04 mm 5.82%

The ash content is 0.025%. The precipitation is carried out in a normal stirred tank and without use

carried out through a nozzle, a coarse flaky polymer is obtained even with intensive stirring, the grain size of which is 97% over 0.5 mm; Ash content: 0.2%.

Example ^

A suspension of 25 parts by weight of polypropylene in 100 parts by weight of hexane, which has been obtained by polymerization of 25 parts by weight of propylene in 100 parts by weight of hexane, to which 0.05 parts by weight of titanium trichloride and 0.1 part by weight of diethylaluminum monochloride are added, is, at 30 ⁰ C in a stirred vessel given, in which 5 parts by weight of n-butanol are presented, and with a comminution unit that works on the rotor-stator principle (Supraton pass-through device), pumped around and digested. After 15 minutes, the suspension is filtered off and washed on the filter with 20 parts by weight of n-butanol at 60.degree. A fine-grained polypropylene with an ash content of 0.01% and the following grain size distribution is obtained:

> 0.25mm 3.2%

0.20 mm 2.4%

0.15mm 3.0%

0.10 mm 12.4%

0.075mm 50.4%

0.06 mm 20.4%

0.04 mm 6.2%

<0.04 mm 2.0%

ίο If the decomposition is carried out in a normal stirred tank, a coarse-grained polypropylene is obtained even with intensive stirring an ash content of 0.025%, which has the following grain size distribution:

> 0.25mm 16.0%

0.20 mm 15.2%

0.15 mm 17.4%

0.10 mm 21.4%

0.075 mm ....... 13.2%

^ao 0.06 mm ... 10.6%

0.04 mm 5.2%

<0.04mm 1.2%

309630/454

Claims (3)

Claims: 10 1. Process for working up solutions or dispersions of low-pressure polymers, such as those used in the low-pressure polymerization of olefins, diolefins, their derivatives or mixtures with the aid of mixed catalysts made from compounds of the elements of IV. To VI. and VIIL subgroup of the periodic system on the one hand and aluminum, aluminum hydride, alkali metals or organometallic compounds of metals from I to III. Group of the periodic system, on the other hand, arise in the presence of inert solvents, by treating the polymer solutions or dispersions at temperatures between -50 and + 200 ⁰ C below the softening range of the polymers with agents which convert the mixed catalyst residues into soluble compounds and, if polymer solutions are present, the Precipitate polymers, and by subsequent separation of the polymers, using shear and vibration forces which have a crushing effect, characterized in that the existing or resulting polymer particles are exposed to the shear and vibration forces which have a crushing effect during the treatment with the solvents and precipitants mentioned. 2. The method according to claim 1, characterized in that that one crushes the Polyrnerisatteifcherf with a disintegrator. 3. The method according to claim 1 and 2, characterized in that one in the polymerization resulting solution or dispersion before treatment with the disintegrator for itself or atomized together with the decomposition agent. 50