DE2050373B2 - Process for the polymerization of propylene from the gas phase - Google Patents

Description

20th

The invention relates to a process for the polymerization of propylene from the gas phase Use of Ziegler-type catalysts.

The known polymerization processes of this type have disadvantages. These are based on this reasons that one must on the one hand strive to achieve the highest possible catalyst yield in order to removal of the catalyst residues remaining in the polymer by a cleaning aftertreatment to avoid. On the other hand, the content of the polymer in in n-heptane soluble proportions should be as low as possible. js So far, the fulfillment of one requirement has excluded that of the other. So you could either if the appropriate catalysts are selected, do without a cleaning post-treatment of the polymers, but then had to intervene n-heptane-soluble components Take 20 and 30 percent by weight into account or you were with polymers with low in N-heptane soluble components forced to remove the catalyst residues from the polymer.

The invention is based on the object of creating a process for the polymerization of propylene, that meets both of the above requirements.

The object set is achieved according to the invention with what is characterized by the claim Procedure; - whereby it is advantageous if the w Cs hydrocarbon fraction more than 5 percent by volume containing inert gases

From the designed documentation of the Belgian patent 7 19156 Although the process set out in the preamble of claim is already known but v> is this document makes no reference to refer to the essential for the present invention using the - under polymerization - inert additional gas shares. This is to intervene in the heat exchange between the active catalyst surface m and the surrounding gas. This avoids the sometimes extremely high temperature peaks at the reaction site, which are the reason for the formation of extremely low molecular weight - ie the sticky - components in the polypropylene. i >>

The teaching from DE-OS 15 20 852 can not lead to the subject of the present invention, since according to this laid-open specification with catalyst activities worked in the order of 100 g / g-h will. With such, comparatively very small Activities occurs the problem to be overcome with the present invention, namely the undesirable To avoid the formation of high temperature peaks, not at all noticeable.

The process according to the invention can be carried out with the usually used catalysts of the Segler type, for example the combination of titanium trichloride and aluminum triethyi. Here, additions of third substances can be present, for example hexamethylphosphoric acid triamide or triphenylphosphine oxide, which intervene in the redox process of the Ziegler catalyst. The monomer pressure and reaction temperature are in the ranges customary for low-pressure polymerizations from about normal pressure to about 100 atm and from about room. : emperature to about 150 ⁰ C. In this case, however, it is essential that the polymerization is carried out with respect to the pressure-temperature relationship in the thermodynamic gas state area.

Those to be used according to the invention for the polymerization Cs hydrocarbon fraction must be pre-cleaned have been subjected. This can, for example, according to the procedure of the German Patents 1183491 and 1262,261 have been made. Whether the required level of catalyst activity is guaranteed as a result of the cleaning pretreatment of the Cr hydrocarbon fraction easily by a batch run experiment in a small test reactor under the pressure and Temperature conditions of the desired polymerization are determined.

The reduction in the content of n-heptane-soluble fractions in the polyizate achieved by the process according to the invention is particularly pronounced when the polymerization is carried out in batches.For example, in a polymerization carried out for comparison purposes with more than 99 percent pure propylene, 20 to 22 percent by weight of heptane-soluble fractions in the polymer were found When using a Cr hydrocarbon fraction which had about 7 percent by volume of inert gas in the form of propane, the content of heptane-soluble components in the polymer was, however, only 7 to 10 percent by weight The proportion is still in the order of magnitude of 5 percent by weight, based on the total weight of the polymer.

The process according to the invention is particularly suitable for the polymerization of the crude gas in cracked gas separation accruing Cj fraction which generally contains considerable amounts of propane, which is inert towards the polymerization components. The use this crude Cr fraction, which is possible without further distillative aftertreatment, arouses economic benefits Reasons of particular interest.

According to a special embodiment of the invention is carried out in the presence of hydrogen. This enables the average to be reduced Molecular weight without the proportion of soluble products being increased significantly.

In Example 1 below and Comparative Experiments A and B, propylene-containing gases are used are used, the composition of which - after cleaning - can be found in the table below is.

Tabel Purified Purified

Crude CrFraküon Reiim-Propylen [TpM] ITpM]

A than

propane

Propene

Propadien

Propyne

Butadieu-1,3

0.24% by volume

5.9% by volume

93.5% by volume

20th

27

example 1

510

1.5% by volume

98.8% by volume

10

A continuously operated gas phase polymerization reactor eRtMlt 200,000 parts powdery Polypropylene. At 35 atm pressure of the purified, raw Cr hydrocarbon fraction from the table above and at 90 ° C polymerization temperature are below permanent mechanical pipes every hour 2 parts of a solid catalyst component suspended in cyclohexane added, which consists essentially of TiCb ■ i AICI3 and also 15 percent by weight Their total mass contains hexamethylphosphoric triamide. Next, 7 parts per hour are used Triethyl aluminum added

Every hour about 3C 000 bb 35 000 parts of a powdery to fine-grained polypropylene discharged, corresponding to a medium Ki alysatoraktivitaet of about 3,000 parts polymer / part heavy metal component and hour.

After cooling, the polymer exhibits a well-developed flow behavior and a "dry" appearance Handle". The intrinsic viscosity fluctuates approximately between 7.6 and 8.3 [dl / g} the soluble fraction in boiling n-heptane is about 20 to 22 percent by weight

Comparative experiment A

In the same reactor and under the same conditions as in Example 1, instead of the Cj fraction polymerized the purified pure propylene from the table above.

Here, every hour 36,000 to 42,000 parts of one powdery to coarse-grained polypropylene discharged. An average catalyst activity is then determined of about 4,000 parts polymer / part heavy metal component and hour. After cooling, this polymer shows a "sticky handle" as well poor flow behavior and, when stored in sacks, a strong tendency towards compactness Solidification of the entire contents of the sack. The polymer has an intrinsic viscosity of about 7.2 to 7.8 dl / g, the Solubility in boiling n-heptane is 25.5 to 26.5 percent by weight

Example 2

The reactor of Example 1 is filled with 50,000 parts of powdered polypropylene. Simultaneously 8 parts of the example! 1 heavy metal catalyst component used and 20 parts Triethyl aluminum added. At 35 atm and 90 ° C is a purified crude C3 fraction, which 10.5 percent by volume Contains propane, polymerized as in Example 1.

After four hours, 120,000 to 150,000 parts of a very finely powdered polymer are discharged Remainder of about 50,000 parts remains in the reactor. As described at the beginning of this example, is again

the polymerisation is started in constant alternation every four hours between 120,000 and 150,000 Parts of polymer discharged, corresponding to an average catalyst activity of about 4200 Te'len Polymer / part heavy metal component and hour.

ίο The polymer has an intrinsic viscosity of 9 to 9.7 [dl / g] and an n-heptane-soluble fraction of about 8 to 11 percent by weight

Comparative experiment B

In the operating mode corresponding to Example 2 ("periodically - batchwise"), the purified ultra-fine propylene from the table above is polymerized instead of the C _{3 fraction}
About 155,000 parts of a powdered polymer are discharged in a four-hour operating cycle, ie the average catalyst activity is about 5000 parts of polymer / part of heavy metal component per hour.
The powdery polymer obtained shows after

a very good flow behavior and a noticeably weaker tendency to cake when stored in sacks compared to the polymer Comparative experiment A. The polymer has an intrinsic viscosity of 73 to 8 [dl / g} the solubility in n-heptane is 193 to 22 pounds percent by weight

Example 3

A continuously operated gas phase polymerization reactor contains 200,000 parts of powder

J5 polypropylene. After prior cleaning according to the method of German patent 1183491, a crude Cr cut, which contains about 7 percent by volume of propane and to which about 0.2 to 03 percent by volume of hydrogen is added, is fed to the polymerization reactor, which is operated at about 35 atm and 90 ° C. With constant mechanical stirring, 2 parts per hour of a solid catalyst component suspended in cyclohexane, essentially consisting of TiCl ₃ · j MO3, are added

and also contains 15 percent by weight of its total mass hexamethylphosphoric acid triamide 7 parts of aluminum triethyl are also added every hour

30,000 to 33,000 parts of a powdery to coarse-grained polypropylene are discharged every hour. The average polymerization or catalyst activity is about 2,500 parts polymer / part Heavy metal component and hour.

After cooling, the product has a somewhat “sticky feel”. When stored in sacks, the tends to Content to solidify. The polymer obtained has an intrinsic viscosity of 23 to 33 dl / g and a soluble fraction in this n-heptane from about 25 to

w) 27 percent by weight

Comparative experiment C

In the same reactor and under the same conditions as in Example 3, instead of the C3 fraction a purified high-purity propylene with a propylene content of about 99 percent by volume is used for the polymerization, about 0.15 to 0.2 percent by volume of hydrogen being added to the propylene.

Compared to example 3, the drive of the mechanical tubes shows a significantly increased power consumption (Corresponding to 19.5 to 20 amps compared to about 15.5 to 16 amps and tends to "Stand still".

The constant product discharge is with strong Variations about 25,000 to 36,000 parts of polymer. The product is hen's egg-sized, firmly caked Tubers interspersed, is very soft and shows strong stickiness; the intrinsic viscosity is about 3.5 to 3.7 dl / g, the n-heptane solubility is about 29 to 32 Weight percent

Example 4

The reactor dec Example 3 A 50 000 parts of powdered polypropylene filled same 12 parts of the heavy metal catalyst component used in Example 3 and 25 parts AJuminiumtriäthyl be added atm at 35 and 90 ⁰ C ^ after cleaning, as in Example 3, a raw C Schnht which contains about 7 percent by volume of propane and to which 0.25 percent by volume of hydrogen has been added, polymerized

After 4 hours, 178,000 parts of a powdery polymer are discharged, a remainder of about 50,000 parts remain in the reactor. As described at the beginning of this example, the

Polymerization started, alternating between 150,000 and 200,000 TeUe every four hours Polymer discharged, d. H. the mean catalyst activity is about 3500 parts polymer / part Heavy metal component and hour.

ίο The powdery polymer obtained shows after very good trickling behavior when cooling down, and a "dry handle" when storing the bags in the Pallet stacks do not show the solidification of the sack hold, as is the case with the polymers

Example 3 is usually still observed. The polymer has an intrinsic viscosity of about 22 to 2.7 [dl / g] and can be easily processed by conventional methods. The n-heptane solubility is about 18 to 22 percent by weight. When processed as an injection-molded article, the polymer exhibits a surprising degree of rigidity, so the torsional modulus at 25 ° C. reaches about 6.1O ⁹ [dynes / cm ² ].

Claims (1)

Claim; Process for the polymerization of propylene from the gas phase using catalysts of the Ziegler type, the gas mixture having a has such a degree of purity that a catalyst activity of more than 1000 parts of polymer to 1 part of the heavy metal component of the catalyst is achieved per hour, characterized in that propylene is in the form a propylene containing, in the cracked gas separation accruing Cj hydrocarbon fraction is used that contains more than 3 percent by volume of inert gases, the inert gases being predominantly Ethane and propane are.