DE2128479C3 - Process for polymerizing gaseous α-olefins - Google Patents

Description

dung to titanium compound from 1 to 20, made grease used. The extraction takes place at a temperature of 25 to 120 ⁰ C and contains 50Ü to 10,000 parts per million parts by leaching or titanium, optionally in the presence of hydrogen simply by suspending the prepolymer in the hydrogen, which is characterized by the fact that the Solvent and allow the prepolymer polymerization to settle in the absence of a liquid dispersion, as well as removal of the used solvent, grease agent and a prepolymer Extraction treatment with an ali- minutes in contact with the solvent phatic or cycloaliphatic !! Will let hydrocarbon. The extraction is terminated as soon as it is subjected to a solvent at 25 to 120 ° C., so that there is no low build-up of a small amount of solvent in the extraction medium in the cold, which precipitates out one more time. All in all, an organoaluminum bond in a molar ratio of 2 to 8 ml of solvent per gram of prepolymer from 1 to 20 is generally sufficient, based on that in the prepolymer for this measure. After the extraction has ended, a dissolved titanium compound is revealed, the prepolymer is resuspended in a small amount and has then been dried. 15 Solvent suspended, which as an activator an Or-

In this catalyst system, the Moherganoaluminum compound is in a molar ratio of

ratio of the organoaluminum compound to the titanium ratio 1 to 20, based on the amount in the prepolymer

binding 1 to 20. dene titanium compound. The lo-

It has been shown that it is advantageous if a solvent is removed in vacuo. The received Titanium compound, in which the titanium in a valuable io prepolymer can either be used directly for the

keitsstufc under 4 is used. So polymer production are used or during several

For example, good results when polymerizing can be kept for weeks.

of ethylene when the polymerization takes place in a process. It is important that the

In the presence of titanium trichloride, obtained by reducing the following operations, production of the catalyst

tion of titanium tetrachloride with an organoaluminium as systems, prepolymerization, extraction and processing

compound and in the presence of an aluminum trialkyl preserve the prepolymer to the exclusion of

of the formula AlR ₃ , in which R is an alkyl group with 2 air and moisture, so that

to 8 carbon atoms. the catalyst system is not affected.

As a dispersant in the preparation of the pre-It has been shown that the extraction of the Polymer are the in the case of the Niederdruckpoly- 3 »prepolymer with a solvent in the interior

merization of olefins customary aliphatic prepolymer particles have a certain porosity

or cycloaliphatic hydrocarbons is generated. This porosity is mainly due to

selects, for example η-butane, n-pentane, η-hexane, measuring the specific surface area according to the BET-

n-heptane or isooctane; Mixtures method (J. Am. Soc. 60 [1938], p. 309) are also suitable,

of aliphatic and / or cycloaliphatic carbon, namely on a simply dried prepolymer

lenhydrogen, such as the petroleum distillates with boiling sat and on the same prepolymer that was previously the

range 35 to 250 ° C. The amount used had been subjected to extraction. The specific

Dispersant depends in practice on the amount of surface area of the simply dried prepolymer

of the prepolymer produced. To the medium, corresponds essentially to the outer surface of the partial

in which the prepolymer is formed, more easily 4 »chen and can be, for example, 0.1 m '/ g, while

To be able to stir, it is expedient to double the specific surface of the corresponding

pelte amount of dispersant used, based on traded, ie extracted prepolymer 1 m ² / g

on the weight of prepolymer that is formed exceeds.

shall be. In practice, there has been a weight loss. The formation of this porosity in the prepolymer

The ratio of dispersant to prepolymer of 45 has very important effects. The on

about 2.5: 1 has been found to be very satisfactory. Activator added at the end of the extraction can be added to the

The polymerisation of the prepolymer will penetrate from particles themselves of the prepolymer, so broken as soon as about 5 to 100 g of prepolymer that the polymerisaje mmoles of transition metal compound of the catalyst have been formed at least partially in the interior of the prepolymer in the subsequent operation. The breakdown of the polysolate itself takes place. It has also been shown merization can be effected in a simple manner in that no additional that the amount of catalyst had to be added to the reactor from the outset, since the polyolefin to be prepolymerized is given up on the merization rate during this operation; or the continuous feed of ganges will not decrease significantly. However, it became a like Olefin stopped. 55 described above, but not the extra

The reaction vessel is then rinsed in prepolymer for allion treatment

common with an inert gas stream; then the polymerization is started, so the polymer

the prepolymer separated from the dispersant, sation speed very quickly, and it had to

for example by distillation or even better, therefore, from time to time new catalyst into the poly-

can be fed in by filtering or by decanting the dispersion vessel. In addition

greedy. from can be obtained by using a previously extracted

The prepolymer is then to a large extent extracted from the solvent with a water prepolymer, specifically avoiding the occurrence of polymer agglomerates in the polymeric or cycloparaffinic hydrocarbon tank. This is an important advantage material. In practice, it is expedient to use a hydrocarbon or a carbon dioxide as an ex- 65 because these agglomerates make it difficult to carry out the contracting agent and, moreover, are too heterogeneous Hydrogen mixture of the same type as in the case of polymers. Preparation of the prepolymer used dispersant The prepolymer is then used in the actual

The polymerization stage is used and, in the course of this, is brought into direct contact with the olefin that is to be polymerized, in the absence of dispersants such as saturated hydrocarbons. This operation is carried out as a fluidized bed process, the olefin to be polymerized flowing as a gas in a column from bottom to top which contains a prepolymer layer which is spread out by the gas stream and kept in a fluidized bed. The olefin ίο is introduced into the device at a temperature that the temperature of the reaction medium is at least 60 "C, advantageously about 80 ⁰ C, and at a feed pressure that is slightly higher than the gas pressure above the fluidized bed, so that the pressure losses in As it flows through the fluidized bed, part of the olefin polymerizes on contact with the prepolymer, the particles of which gradually grow.

The non-polymerized olefin component emerges from the fluidized bed and enters a cooling device, in which the heat of polymerisation is given off before it is preferably fed into the fluidized bed device is fed back. »5

In the entire circuit, consisting of a column with a fluidized bed, a cooling device for the gas and flow means to circulate the gas can maintain the olefin under moderate pressure which is approximately equal to atmospheric pressure or, preferably, under significantly increased pressure, which preferably reaches 30 bar in order to accelerate the rate of polymerization.

The polymerization is terminated as soon as the polymer has the desired mean molecular weight which is generally between 100,000 and 1,000,000. To better control this To achieve molecular weight, can in the preparation of the prepolymer and in the actual Polymerization stage the olefin to be polymerized with a chain terminator such as Hydrogen, mixed in a molar ratio of hydrogen to olefins of, for example, 10 to 80% will.

In some cases, especially if only a small amount of prepolymer is used for polymerizing, it can be useful to mix this prepolymer with polymer already formed in an earlier operation in order to start the polymerization in the fluidized bed . which corresponds to a layer at least 10 cm high.

The polymer obtained can, if appropriate, be aftertreated in the manner customary for polyolefins in order to remove catalyst residues. The process according to the invention can, however, also be carried out with catalyst systems of high productivity, for example with the system TiCl ₃ , AIR ₃ , where R is an alkyl group with 2 to 8 carbon atoms, in order to polymerize ethylene. The polymers obtained in this way, which contain, for example, less than 100 ppm of titanium, can be used further immediately without any cleaning treatment.

The inventive method can be with a single gaseous olefin, such as Ethyien or Propylene, or with several gaseous olefins in a mixture with one another or one behind the other (in blocks) execute. For example, the poly-

merization started with propylene and then continued with ethylene.

The inventive method is particularly suitable for the polymerization of ethylene, in particular with the high-performance catalyst systems already mentioned. The polyethylene falls as practically spherical, non-baking granules with a particle diameter of a few 100 μΐη, where the particle diameter from the degree of polymerization depends. The polymer has a small particle size distribution and looks better than that produced by polymerisation Polyethylenes obtained in the presence of a dispersing agent because the inventionsucmäP. manufactured products generally no Sp; iii η ii! ci Have cavities.

example 1

In a 5-1 stainless steel reactor equipped with a mechanical stirrer and heater, 1 liter of n-heptane, 80 mmoles of diethylchloroaluminum and 6 mmoles of titanium trichloride obtained by reducing titanium tetrachloride with an organoaluminum compound were successively charged. Then hydrogen was passed in up to a pressure of 1.5 bar, the reaction mixture was brought to 75 ^° C. and ethylene was passed in in an amount of 150 g / hour. After a 2-hour reaction, the prepolymer was spun off and extracted twice in succession with a total of 2 liters of boiling heptane, each heptane fraction being separated off by allowing it to settle or pour it off. Before the last pouring off, 500 ecm of heptane containing 20 mmol of diethylchloroaluminum were added and the solvent was then evaporated. 300 g of a brown prepolymer with an average grain size of 150 μm and containing 960 ppm of titanium were obtained.

125 g of this prepolymer were then introduced into a reactor with a fluidized bed, which consisted of a Pyrex glass tube with a diameter of 10 cm, which was closed at the bottom by a perforated plate containing four holes with a diameter of 0.3 mm ^{per cm 2.}

The reactor was heated to 80 ° C. and the prepolymer with an ascending stream of ethylene, speed 7 cm / sec and relative pressure 3 bar, swirled. The unconverted ethylene was cooled in a subsequent cooler and then returned to the fluidized bed reactor with the aid of a positive pressure blower. After 18 hours of polymerization 1100 g of polyethylene with an average grain size of 350 μm were obtained. The catalytic yield was 440 g of polymer per mmol of titanium, and the mean rate of polymerization was 24.6 g / mmole titanium and per hour.

Example 2

A prepolymer was prepared as in Example 1, with the difference that the catalyst system was formed from 7 mmoles of titanium trichloride and 7 mmoles of triethylaluminum. The fed ethylene polymerized at a rate of 100 g / hour. After 2 '/ ₂ hours 25Og were obtained prepolymer was extracted at 8O ⁰ C with total 2 i solvent. After the last extraction, 500 ecm of heptane containing 17.5 mmol of triethylaluminum were added and the solvent was removed in vacuo.

35 g of prepolymer and 250 g were placed in a steel fluidized bed actuator with a diameter of 11 cm Powdered polyethylene brought in from another manufacturing process that owned polyethylene a grain size similar to that of the prepolymer. The bed was filled with ethylene, flow rate 10 cm / sec under a pressure of 15 bar, vortex. The unreacted ethylene was cooled and then returned to the reactor, its Temperature was kept at 80 C. After 5 hours, 1300 g of polymer were obtained, which is a catalytic Yield of 1050 g of polymer per mmol of titanium and an average rate of polymerization of 210 g of polymer per mmole of titanium and per hour.

The polymer obtained was obtained as spherical granules with a particle diameter of about 450 μm.

Example 3

A prepolymer was prepared as in the previous example with the difference that instead of aluminum triethyl equivalents, all molar amounts of aluminum triisobutyl were used.

29 g of prepolymer, mixed with 500 g of inert polymer, were used for the polymerization of ethylene used in the fluidized bed at 80 C and under a pressure of 20 bar. After 4 hours of polymerization 2400 g of polymer were obtained, corresponding to a catalytic yield of 2400 g Polymer per millimole of titanium and a medium polymerization wedge of 600 g of polymer per mmol of titanium and per hour. The polymer fell as spherical granules with a diameter of about 600 μm.

Example 4

The procedure was as in Example 2, but instead of aluminum triethyl the equivalent molar amount Aluminum trioctyl used. For the polymerization of ethylene, 22 g Vorpolymcrisal with 500 g inert polymer mixed and vortexed and the polymerization at 80 "C under a pressure of 20 bar accomplished. After 6 hours of polymerization, 1800 g of polymer were obtained; this corresponded to one Catalylic yield of 2020 g of polymer per mmol of titanium and an average polymerization rate of 337 g of polymer per mmol of titanium and per hour.

The polymer was obtained as spherical granules with a diameter of about 560 μm.

Comparative experiments A and B and example 5

It was the polymerization of ethylene in the presence of an unbchandcllcn, a simply washed and an extracted prepolymer carried out and the effect of the Vorpolymcrisalc in the polymerization examined.

1. Preparation of the prepolymer

In a stainless steel reactor with mechanical Agitator and heating or cooling jacket were introduced one after the other: 21 n-Hcptane, 5.12 g (14 mmol) of tri-n-oclylaluminum, 2.16 g (14 mmol) Tilanlrichlorid obtained by reducing titanium tetrachloride by means of diethylaluminum chloride.

Hydrogen was then injected until the pressure in the reactor reached 6 bar and the reaction mixture heated to a temperature of 80 "C and this temperature during the entire manufacture of the prepolymer retained. Ethylene was used for two and a half hours at a rate of 200 g per hour initiated.

The reaction was then interrupted; Ethylene and hydrogen were relaxed and then with one Nitrogen stream removed. The yield was 485 g of prepolymer. The suspension of the prepolymer In the reaction medium, kept under nitrogen, polymer was divided into three parts, each containing 160 g of V01 divided.

2. Treatment of the prepolymer

ao la The first 160 g prepolymer sample was decanted from the liquid suspension medium and then dried under vacuum. 160 g of sticky powder containing lumps of crude prepolymer were obtained.

2 b The second prepolymer sample weighing 160 g was decanted from the liquid suspension medium; Then 1300 cm ^{3 of} n-heptane at 25 ° C. containing 3.40 g (12 mmol) of tri-n-octylaluminum were mixed with the slurry and this was dried under vacuum. This gave 157 g of a sticky powder which contained lumps of prepolymer.

2c The third prepolymer sample weighing 160 g was separated from the liquid suspension medium by allowing it to settle; then 1300 cm ^{3 of} n-heptane at 80 "C were mixed with the slurry and this was decanted. This measure was repeated twice, each time with 1300 cm ^{3 of} n-heptane at 80" C. To the third amount of solvent was added 3.40 g (12 mmoles) of tri-n-octylaluminum. The slurry was dried under vacuum. The result was 148.5 g of a friable powder which did not contain any lumps.

For all three samples, the prepolymer porosity determined according to the B.E.T. method.

3. Polymerization

A tube made of stainless steel was used as the fluidized-layer reactor Steel with an inner diameter of 7 cm and a porous stainless steel plate at its lower

Used end.
8 g of prepolymer (ohm

Lump) mixed with 100 g of a previously prepared polyethylene powder which is not a catalyst contained, placed on the plate.

The reaction tube was heated to 90 "C and there

Prepolymer with a carrier gas

Ethyl stream, speed 10 cm / s, relative pressure 6 bar, swirl. The unreacted ethy leu was called off. After 2 hours of polymerization, the G contained in the reaction tube was; flushed with a stream of nitrogen. The Polymcris; was weighed and the polymerization rate speed as well as the howling of polymer, based ai the Tilanlrichlorid contained in the Vorpolymcrisal b right! and calculated. The results are summarized in the table below.

709 636/14 '

-ö *

Prepolymer Porosity of the Polymer Polymeri Polyincr Prepolymer sat ionsratc aushcutc, sats (g / mmol TiCl ₃ based x hour on TiCI, (m '/ g) (G) - γ bar) (g / m mol TiCl ₃ I.

2a (comparative experiment Λ) 0.3
2b (comparative experiment B) 0.7
2c (Example 5) 2.8

86 31 370 93 33.5 400 148 53.5 640

The results obtained with a prepolymer simply washed with a solvent at 25 ° C. (according to 2b) (comparative experiment B) do not differ significantly from the results obtained with a crude prepolymer (according to 2a) (comparative experiment A). In contrast, lie (Example 5) in Ge _o of the extracted results obtained prepolymer enwart by more than 50% higher. It should be noted that the presence of only a single lump of prepolymer in the fluidized bed of the reaction tube causes the agglomeration of all of the polymer contained in the reaction tube. This is due to the fact that heat or heat is not easily removed from the polymer lumps by rising ethylene. Since the lump is at a higher temperature than the surrounding powder, the rate of polymerization around the lump is higher. This phenomenon causes rapid growth of the lump and consequently agglomeration of the polymer.

The polymerization of olefins in the presence of crude or simply washed prepolymers is therefore not possible on an industrial scale.

Example 6
Copolymerization of ethylene and propylene

A prepolymer was prepared from ethylene and propylene and the same procedure as in Example 3 was used with a catalyst made from titanium trichloride and triisobutylaluminum.

25 g of the prepolymer obtained were mixed with 500 g of polyethylene powder from a previous operation. The mixture was introduced into a fluidized bed reactor with a diameter of 15 cm and swirled with an ascending gas stream of 82% by volume of ethylene and 18% by volume of propylene; Pressure 11 bar, polymerization ^{temperature 80 °} C., polymerization time 2 hours.

2200 g of copolymer were obtained in the form of a powder with regular grain with a diameter of> 0.5 mm. The copolymer contained 6 % by weight of propylene units, determined by 1R spectrography.

Example 7

Copolymerization from ethylene and l-butene

The procedure was as in Example 6, with the modification that the carrier mixture was 85% by volume of ethylene and contained 15% by volume 1-butene. 2100 g of copolymer were obtained, as in Example 6 as a powder with a regular grain, diameter ^> 0.5 mm. The copolymer contained 4% by weight of 1-butene : units determined by IR spectrography.

Comparative experiments C and example 8
a) Preparation of the prepolymer

The same general conditions as in Example I were used, in a 5 l reactor made of stainless steel. There were 11 n-heptane, ao 6 mmol TiCl, and 18 mmol diethylaluminum chloride submitted; then hydrogen was pressurized brought up to a pressure of 1 bar and the reaction medium to 80 ° C; eventually were 200 g / hour of ethylene introduced; Polymerization time 2 hours.

The prepolymer obtained was divided into two equal parts.

The solvent of the first part was simply evaporated after the addition of 7 mmoles of tri-n-octylaluminum; 200 g of non-sticky or non-baking powder were obtained.

The second part of the prepolymer was washed twice by settling with 2 I of n-heptane of 8O ⁰ C and then once with 2 1 of n-heptane of 25 ° C. 7 mmoles of tri-n-octylaluminum were added; the solvent was then drawn off. The prepolymer obtained was of the same ^{Beschaffenhe:} t as the prepolymer of the first part.

b) polymerization

A fluidized bed reactor with a diameter of 10 cm was used. Any part of the prepolymer was each with 180 g of previously prepared poly

ethylene powder mixed and then introduced into the ^{reactor heated to 8O 0} C, together with an ascending stream of ethylene under a pressure of 6 bar.

When polymerizing in the presence of the not extra-

With this prepolymer, it was very difficult to control the temperature in the reactor. The reactor was open after 2 hours. The reactor walls were covered with caked polymer powder. The polymer contained in the reactor itself was closed

a large part agglomerated in the form of spheres

with a diameter of 1 to 2 cm (comparative experiment C).

The polymerization in the presence of the extracted

The prepolymer was somewhat easier to control. After opening the reactor, agglomerates were also

merate found, but in a smaller amount than when working with the non-extracted prepolymer (Example 8).

Example 9

A prepolymer was prepared according to Example 1 with the modification that the catalyst system was composed of 50 mmol sesquiathylchloraluminum, 40 mmol dichloromonopropoxy-

" Ί-

itane (obtained by reducing dichlorodiprop- After 6 hours of polymerization, 650 g of poly-

jxytitan with Monochlorodiethylaluminium) and 20MoI ethylene with an average grain size of 230 μm

Oichlorodipropoxytitanium. 300 g of preliminary obtained were obtained. The yield based on the catalyst

j & lymerisat. was 65 g of polymer per mg of titanium; the middle

50 g of this prepolymer were in a reactor 5 lere polymerization rate was 11 g each

or introduced with a fluidized bed according to Example I. mgAtom Titan and per hour.

Claims (1)

tetrac'ilorid and the ahiminiumorganischen Verbin patent claim: fertilizers are volatile and become one largely due to the evaporating or evaporating Process for polymerizing gaseous dispersants entrained; In order to maintain usable gen-olefins in a fluidized bed at counter-polymerization rates, there was a prepolymer which, through polymer, must then be added at periodic intervals to the re: ionization of a gaseous O! efm under a pressure medium, fresh catalyst system: under 10 bar in a liquid, saturated carbon - in addition, the polymer substance tends to stick together due to its hydrogen as a dispersant by means of a cata- sticky nature in the course of the desiccant lysis of one or more titanium compounds, and the polymerization genes of the general formula Ti (OR) _1n X _1,, ", in then, in the agglomerates formed, the R being an alkyl group with 1 to 8 carbon quickly comes to a standstill. atoms, X stands for chlorine, /> the number 3 or 4 In the process according to DT-OS! 5 20 852 is or a fractional number between 3 and 4 and Hi represents a polymerization of the Oleline, for example, propene, integer or a fractional number between 0 and "5 in the fluidized bed in Gegenwari a prepolymerized p and an organoaluminum compound sats of the same olefin carried out, the a of the general formula AIR "C1 ₃ ", in which R contains a titanium and / or vanadium trihalide and an alkyl group with 1 to 8 carbon atoms and an aluminum alkyl compound as a catalyst system containing a whole or fractional number from 1 to 3; The prepolymer is prepared in the presence of a significant! in a molar ratio of organo-20 conventional dispersant and without white aluminum compound to titanium compound of 1 tere pretreatment in the form of this with further up to 20, and 500 to 10,000 saturated hydrocarbon diluted dispersion parts per million Contains parts of titanium, given- used in the main polymerization stage. The difference in the presence of hydrogen, thereby dispersing agent, is shown under the polymerization conditions η η that the polymer is evaporated and contributes to the turbulence of the ion in the absence of a liquid dispersing prepolymer. If necessary, a layer is additionally carried out and a prepolymer is added to the vortex and an aluminum alkyl compound, which is separated from the dispersant, is introduced in order to then improve the polymerization results with an extraction treatment with an aluminum. phatic or cycloaliphatic carbon than 30 The method according to DT-AS 10 76 375 and FR-PS solvent at 25 to 120 "C subjected, dar- 11 40 768 for polymerizing ethylene are carried out in a small amount of solvent in the fixed bed. Here, too, the previously pure organoaluminum compound is dissolved in a molar, TiCl ₄ and monochlorodiethylaluminum in a ratio of 1 to 20, based on the prepolymer or polymer present in the pre-catalyst system, which contains the titanium compound impregnated with these catalyst components, suspended and then dried polymer without further pretreatment, after evaporation of the dispersant used used. Comparative tests have shown that - prepolymers produced in this way nichl 4 ° are suitable for fluidized bed polymerization because they lead to the formation of lumps in the polymer, too The low pressure polymerization of olefins, if they are not sticky themselves, usually in the presence of Ziegler catalysts. It has now been shown that the polymerization of carried out, which overalle from a compound of the gaseous Λ-olefins in the fluidized bed of the subgroups IVb, Vb or VIb of the period can be improved surprisingly if one has a Vorodal system, preferably of titanium, and a re-polymerisate is used, which in a certain way preduction agent, for example an aluminum organ has been traded. A solid polymer is obtained niche connection, put together. Is used in with an average molecular weight over 50 00C a liquid, usually a solvent, in a yield that is many times higher than that of a liquid th dispersant worked that a saturated 50 indicated the method according to DT-OS 15 20 852 Hydrocarbon or a mixture of saturated is. Is hydrocarbons, so according to the polymer- The invention is a process for sation the dispersant or the solvent polymerizing of gaseous -olefins recovered in one. Before it is used in a white fluidized bed in the presence of a prepolymer, this must be subjected to a circumstance- 55 borne by the polymerization of a gaseous Λ-olefin and costly purification process at a pressure of less than 10 bar in a liquid. In order to avoid this disadvantage, one has already tried the polymerization in a dispersant compounds of the general formula Ti (OR) _m Xp-m, in the presence of a catalyst system consisting of 60 in R is an alkyl group with 1 to 8 carbon titanium tetrachloride and an organoaluminum atom, X stands for chlorine, ρ the numbers 3 or A to start the compound and then the dispersant or a fraction between 3 and 4 and m to escape from the reaction medium leave; the whole or a fraction between 0 and ρ polymerization is then denoted in the same apparatus and an organoaluminum compound dei continued in the mass of the polymer formed, 65 general formula AIR _n CI ₁ », where R is an alkyd with increasing evaporation or evaporation group with 1 to 8 carbon atoms and η one of the dispersant dries. This mode of operation is a whole or fractional number from 1 to 3, but is associated with several disadvantages: Titanium - a molar ratio of organoaluminum compounds