JPS638122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention describes the use of α-alkenes having 2 to 8 carbon atoms, in particular ethene or propene, optionally containing at least one other α-alkene having 2 to 10 carbon atoms.
- together with a small amount of up to 10 mol % of alkenes, at least one compound of a transition metal from groups 4 to 6 or 8 of the periodic table and generally also from group 1 of the periodic table.
and an organometallic compound of a metal from the group III. The catalyst may be of the type described in GB Patent Specifications Nos. 799392 and 799823, but the catalysts to be used are not limited to the catalyst systems disclosed in these specifications. The polymerization is carried out in α-alkenes having 3 to 8 carbon atoms, in a liquid diluent (which can also be the monomer itself, especially in the polymerization of propene) at pressures up to 100 Kg/cm ² and with a melt index according to ASTMD-1238 of less than 100. and at least 1
Using similar catalyst systems under conditions such that the polymerization conditions in one reactor form a polymer with a high molecular weight and the polymerization conditions in at least one other reactor form a polymer with a lower molecular weight than the other. The polymerization is carried out in at least two reactors in which a polymer having a broad molecular weight distribution is produced.

The invention also includes connections for discharging the contents from one reactor to another, and supply pipes for components forming the polymerization medium, such as monomers, catalysts or catalyst components, if desired. Polymers with a broad molecular weight distribution, in particular polyalkenes, in particular polyalkenes, are prepared by means of two polymerization reactors equipped with a supply pipe for the molecular weight regulator, a discharge pipe for the polymer suspension and a cooling element for removing the heat of polymerization. It relates to equipment for producing polymers such as polyethylene or polypropylene.

Polyalkenes with a broad molecular weight distribution are desirable for many applications in extrusion and blow molding of polyalkenes, particularly polyethylene, such as bottles, cable tubing, and the like. When processing polyethylenes with similar melt indexes, polyethylenes with the broadest molecular weight distribution have good surface gloss, but products are produced that sometimes suffer from surface defects including melt fractures. By using polyalkenes with low molecular weight, ie, high melt index, higher flow rates in extrusion can be obtained with less or no melt fracture. However, in that case the mechanical properties due to molecular weight, such as tensile strength, toughness, stress-cracking resistance, etc., become poorer. For the production of products by extrusion or blow molding, it is desirable to use polyalkenes with high molecular weight, especially high molecular weight polyethylene or polypropylene, in order to obtain favorable properties of the finished product. The disadvantages of poor flow, low surface gloss, and surface imperfections can be eliminated, or at least greatly reduced, by using polyalkenes with high molecular weight and broad molecular weight distribution.

The desired molecular weight distribution and molecular weight value is Modern
Plastics, December 1957, pp. 109-112 and the
Technical papers of the 17th Annual Technical Conference of the Society of Plastics Engineers, Volume 7, 28-1, 1-
Further explanation is provided on page 4.

A number of methods have been described for the production of polyalkenes, especially polyethylenes with a broad molecular weight distribution.

In order to obtain polyethylene with the desired properties, Belgian Patent Specification No. 551,931 recommends mixing polyethylene with very high molecular weight with polyethylene of considerably lower molecular weight.
A similar method has been proposed in British Patent Specification No. 1233599. However, this has the disadvantage that the homogeneity of such mechanical mixtures is far from what is desired, which disadvantages are particularly evident and cannot be tolerated in the production of thin-walled products such as films, bottles and similar products. .

Attempts have also been made to directly produce high molecular weight polyalkylenes with a broad molecular weight distribution by selecting appropriate catalyst systems. This type of method is known, namely British Patent Specification No. 1154884, no.
No. 1114019, No. 1114020 and No. 1170299.

The disadvantage of these methods is slow polymerization and therefore low polymer yields, so that catalyst residues have to be removed by washing. The large amount of catalyst required and catalyst washing made these processes uneconomical. Compared to the said process described in the above patent application series, British Patent Specification No.
Even by the method of No. 1170299, polymerization for 7 hours at 5 atmospheres absolute pressure yields a polymer containing 195 p.p.m. titanium, which typically has a titanium content of 30 p.p.
This far exceeds the present requirement that it be less than m. Therefore, British Patent Specification No.
In the method according to No. 1170299, it is also necessary to wash the catalyst residue.

Furthermore, polyalkenes, especially polyethylenes with different molecular weights, are obtained in different zones or reactors, thus e.g.
3074922, German Patent Specification No. 1138940, French Patent Specification No. 1236365 and British Patent Specification No. 1057728 and No. 1174542 for carrying out the polymerization of α-alkenes in two or more stages. It has been suggested repeatedly.

This type of polymerization is carried out in at least two reactors connected in series and is used to obtain polymers with a broad molecular weight distribution, ie the polyolefins in the said patent. Broad molecular weight distribution is also desired for polymers other than olefins,
These polymers can be prepared by the corresponding method of mixing low and high molecular weight polymers, or by other known methods, for example in reactors connected in series, in which polymers of different average molecular weights are formed in separate reactors. It is produced by polymerization under conditions such as

According to the above-mentioned British patent specification, ethene is polymerized in two stages, in one stage with 5-30% by weight of the total polymer in a gas chamber with a hydrogen content of 0-10% by volume, and in the other stage with a hydrogen content of 0-10% by volume. In this case, 70-95% by weight of the total amount of polymer is in the gas phase and 20-80% of hydrogen is
Polyethylene of different molecular weights can be obtained by manufacturing with volume percentages.

The polymerization of propene to polypropylene, which has a broad molecular weight distribution, is described in Luxembourg Patent Specification No.
43556, in which also different amounts of hydrogen are used during the polymerization.

Polyalkylenes, in particular polyethylene, with favorable properties are obtained by hitherto known multi-step polymerization processes, but this material, when formed into articles, in particular blow molded into bottles, formed into sheets or films. It is clear that when doing so, it still has a heterogeneity, the so-called gel. This inhomogeneity manifests itself as small grain irregularities in the molded product.

The cause of this is not clear at all. The extreme values of polymer molecular weights from the various reaction stages vary widely, and considering the molecular weight distribution of the polymer formed at each stage, a small amount of material with a very high molecular weight is formed, which Although it is presumed that the polyalkylenes cannot be homogeneously mixed with other polyalkylenes or are very difficult to mix, this presumption is not to be considered a binding statement.

Polyalkenes with a wide molecular weight distribution and very good homogeneity are α-
carrying out the polymerization by circulating the alkene, in particular ethene or propene, in two reactors, if desired with a small amount of up to 10 mol % of at least one other α-alkene having from 2 to 10 carbon atoms; during which the monomers, catalyst and dispersant are fed into one reactor, and the polymer suspension is discharged from this reactor and fed into another reactor, which, if desired, is fed with the monomers. and dispersant can be fed, the polymer suspension is discharged from the later reactor and fed again to the earlier reactor, and a part of the circulating polymer suspension passes through the drain in the system. The polymerization conditions in one reactor are selected such that a polymer having a relatively low molecular weight forms therein, and the polymerization conditions in the other reactor are withdrawn from circulation and treated according to known methods, and the polymerization conditions in the other reactor are selected such that a polymer having a relatively low molecular weight forms therein. It has now been discovered that polymers are selected to form polymers having a higher molecular weight than that of the reactor described in .

a manifold for transporting the contents from one reactor to another; and a second manifold between the reactors, which is fitted in such a way that the reactor and manifold constitute a recirculation system. an apparatus consisting of two polymerization reactors and one or more devices for recycling the contents of a recirculation system having a broad molecular weight distribution and extremely high homogeneity. It has also now been discovered that it is particularly suitable for use in polymer production.

In the polymerization of α-olefins in the presence of catalysts containing transition metal compounds, the molecular weight is regulated by the choice of temperature. As the temperature decreases, polymers with higher molecular weights are formed. Molecular weight can also be adjusted by the addition of molecular weight modifiers, of which hydrogen is the most common. If polymers of different molecular weights are to be prepared by means of molecular weight regulators in an apparatus of the above-mentioned type, the ratio of monomers to molecular weight which determines the molecular weight is different in the reactor. Different monomer pressures can be selected.

However, here a molecular weight regulator is added to one of the reactors so that a polymer with a relatively low molecular weight is formed, and a polymer with a relatively high molecular weight is formed in the second reactor in the circulation. The polymer suspension discharged from this reactor into another reactor is completely or substantially free of the molecular weight regulator, and if desired together with the molecular weight regulator, the monomer and dispersion withdrawn from said discharge stream are removed. by feeding the molecular weight modifier along with the agent into the part of the system feeding the reactor where the polymer with a relatively low molecular weight is formed and incorporating it into the reaction mixture entering the last mentioned reactor. It is desirable to form polymers of different molecular weights in different reactors.

If necessary, a molecular weight regulator is added to the reactor feed or the reactor itself in which the polymer having a relatively low molecular weight is formed.

It is also possible, if desired, to use a combination of the last mentioned embodiments, eg different temperatures and/or pressures in the two reactors.

The device according to the invention for realizing the above-mentioned process naturally comprises a catalyst or catalyst components in the monomers, dispersants and other components to be present in the polymerization medium, such as molecular weight regulators, suspending agents and/or It was equipped with a feeding element for feeding other additives, a discharge channel for discharging the polymer suspension and a cooling element for removing the heat of polymerization.

Apparatus for polymerization in recirculating systems are described, for example, in U.S. Pat.
No. 3405109 is well known, but these are all
It concerns so-called loop reactors, in which the polymerization takes place under identical conditions in all reactors.

In the polymerization apparatus according to the invention, the polymerization in each reactor is carried out under different conditions. This makes it possible to produce polymers of different average molecular weights in the reactor, so that a homogeneous polymer with a broad molecular weight distribution is finally obtained.

The process according to the invention in the apparatus described above comprises the polymerization of α-alkenes with 2 to 8 carbon atoms, such as ethene, propene, butene-1, pentene-1, hexene-1 or 4-methylpentene-1, in particular ethene. Alternatively, it may be used in the polymerization of propene.
If desired, other α with 3 to 10 carbon atoms
- Alkenes may be used as comonomers in an amount of up to 10 mol % calculated on the main monomer.

The monomer is supplied to one or two of the reactors in the circulation.
It may be added to one reactor.

In a general sense, among the useful catalysts listed below are those obtained by activating the reaction products of tetravalent titanium compounds, if desired together with other transition metal compounds and organometallic compounds with organo-aluminum compounds. It is preferable to do so. This type of catalyst is described in British Patent Specification No. 1373981.

The present invention is of course not limited to the catalytic polymerizations described in these applications. The amount of catalyst to be used is generally from 0.001 to 10 moles of transition metal per dispersant, preferably from 0.01 to 1 mole, more particularly
Corresponds to 0.01-0.05 mol. The catalyst is preferably supplied at one or several locations, preferably suspended or dissolved in a dispersant. Catalyst is thus fed into this reactor, which is also fed with molecular weight regulator.

The dispersant can be any liquid that is inert to the catalyst system and other compounds present in the circulation. Examples of this are saturated aliphatic hydrocarbons such as butane, isobutane, pentane, hexane, heptane, pentamethylheptane or petroleum distillates such as light naphtha, gasoline, kerosene, gas oil, aromatic carbonates such as benzene and toluene. Hydrogen and halogenated aliphatic or aromatic hydrocarbons such as tetrachloroethane. The dispersant can be supplied in one or several locations, either in pure form or in admixture with other components such as catalyst and/or monomer. It is also possible to use monomers as dispersants for the polymerization of α-alkenes having 3 or more carbon atoms.

The molecular weight regulator to be used can be any compound which in combination with the catalyst system used and the monomer or monomer mixture to be polymerized forms a polymer with a low molecular weight, which compound can be removed from the reaction mixture in a relatively simple manner. Can be made inert or inert by other means. The simplest method of removing all or part of the molecular weight modifier from a polymer suspension stream is evaporation. For this purpose, a relief valve may be provided at the outlet of the reactor in which the relatively low molecular weight polymer is formed. Further pressure reduction causes a portion of the dispersant and monomer to convert to the vapor phase. The volatile molecular weight regulator then also partially or completely converts into the vapor phase. Among the molecular weight regulators used, hydrogen is particularly suitable for this purpose.

This hydrogen is generally most easily removed from the circulation by lowering the pressure in the system to a value such that the hydrogen, along with the dispersant and a portion of the monomer, escapes wholly or mostly as a gas. If the polymerization is carried out under pressure, a reduction in pressure to at least atmospheric pressure is sufficient. Although in principle it is possible to reduce the pressure below atmospheric pressure, it is generally not recommended because the compression energy that would increase the pressure within the system is unnecessarily large. The hydrogen released as a gas and any other components are separated from the liquid phase in known manner. The gas is then raised to polymerization pressure, or to a slightly higher pressure if desired,
It is then passed through an absorption device to the part of the system that feeds the reactor where the polymer with low molecular weight is obtained. Sufficient additional hydrogen is supplied to this part of the system to maintain the hydrogen reference at a given value. The amount of hydrogen present in this "low molecular weight part" of the system depends on the sensitivity of the system to the action of hydrogen. For example, in rather sensitive systems, the molar ratio between hydrogen and monomers, especially ethene or propene, may range from about 75:25 to 85:15 at about 85°C in the gas phase in equilibrium with the liquid phase. A lot of hydrogen is added.

Polymerization of the "high molecular weight portion" can be carried out without hydrogen or with relatively little hydrogen. In the above system, the molar ratio of hydrogen to monomer in the gas phase can vary, for example from a negligible amount of hydrogen or from 0 to 10:90 and even 25:75 hydrogen.

Since the polymer particles contained in the suspension are a recirculating system consisting of relatively low molecular weight polymer and higher molecular weight polymer, the molecular weight of the polymer formed in each reactor and other It is not fully possible to state exactly what the nature of is. What can be said is that the reaction conditions chosen in the "low molecular weight part" of the system, if the polymerization is carried out only therein, can lead to melts of up to 100, and more especially between 40 and 80, in the case of ethene polymerization. The conditions are such that index polyethylene can be obtained.

Similarly, the reaction conditions in the "high molecular weight part" of the system are such that, if polymerization is carried out only therein, polyethylene with a melt index of less than 1, e.g. between 0.005 and 0.05, is generally obtained in the case of ethene polymerization. It is something.

A portion of the recycled polymerization mixture is withdrawn and further processed in a conventional manner to recover the polymer. Generally, a portion of the polymerization mixture of 1/3 to 1/15, preferably 1/7 to 1/12 is withdrawn. The preferred location for withdrawal is the "high molecular weight part" of the system, and more specifically, after the removal of the molecular weight modifier, if such removal is possible.

In addition to the above ingredients, α
-Other components commonly used in the polymerization of alkenes can also be fed into the system.

The process according to the invention produces polymers with a broad molecular weight distribution and a melt index of less than 100. In the polymerization of ethene, the melt index of the resulting product is generally in the range of 0.1 to 0.5 for extrusion and blowing grades. Another important quantity for processing power is the flow index, which is
Defined as MI ₃₀ / (mi) ^3/4 . mi is load
Melt index measured by ASTMD-1238 at 2.16Kg. MI ₃₀ exhibits similar parameters, but it is also measured according to ASTM D-1238, but at a load of 30 Kg. In extrusion and blow molding grades, the flow index of the polyethylene produced according to the invention amounts to 10-20, more particularly 12-16.

The polymers obtained by the process according to the invention can be processed into thin-walled products and films with extremely low gel contents.

The method according to ^the invention is characterized in that ^a
It can be carried out at a pressure of Kg/cm ² . If the molecular weight regulator is removed by lowering the pressure, it is clear that a low pressure zone exists within the system.
The liquid phase from this zone, containing no or mostly molecular weight regulator, is then raised again to the desired polymerization pressure. The temperature at which polymerization is carried out is generally 10-110℃,
Preferably 50-100℃, more specifically 70-90℃
is within the range of The released heat of polymerization can be removed by cooling the reactor and/or other parts of the recycle system or, if desired, by evaporating and condensing portions of the dispersant and/or monomer.

The method according to the invention described above relates to the preparation of polyalkenes with a broad molecular weight distribution. In general, in an apparatus of the type described herein in which the process can be carried out, other polymers with a broad molecular weight distribution can also be produced, and this apparatus is therefore suitable for the production of polyalkenes with a broad molecular weight distribution. Not limited to devices.

In this method, it is desirable to control the molecular weight using a molecular weight regulator. Different monomer pressures are also selected in the reactor, so that different ratios between monomer and molecular weight regulator can be set.

In this case, the apparatus according to the invention must be equipped with a device for maintaining different pressures within the reactor. Suitable devices are a relief valve in one of the manifolds and a compressor in the other manifold.

However, preferentially polymers with a broad molecular weight distribution are produced in the presence of different amounts of molecular weight regulator. If desired, this measurement may be used in conjunction with the measurements described above, and the method generally provides that these measurements detail each other. For example, polymerization may be carried out with a higher concentration of molecular weight regulator in one reactor than in another. If the polymerization is also carried out under lower pressure, the molar ratio of monomer to molecular weight regulator is further reduced and the effect of molecular weight is further enhanced, ie polymers with lower molecular weights can be produced.

In order to be able to perform polymerizations in two reactors in the presence of different amounts, or rather different concentrations, of molecular weight regulators, the apparatus according to the invention must be equipped with suitable equipment. In the polymerization of α-olefins, hydrogen is a commonly used molecular weight regulator. Gaseous or volatile molecular weight regulators are also used in other types of polymerizations. In order to be able to use such gaseous or volatile molecular weight regulators in different concentrations in the reactor, the device according to the invention is equipped with a relief valve in one of the connecting lines and subsequently in the recirculation direction. That is, a liquid-vapor separator must be provided as seen in the direction of pressure drop across the relief valve. The liquid outlet of the separator is connected to the recirculation system, and its vapor outlet is connected to another connecting pipe between the reactors, so that the vapor outlet of the liquid-vapor separator is connected to the reactor before the relief valve. is supplied in reverse. For this purpose a compressor must be installed between the vapor discharge and the feedback to the reactor. Compression will cause the exhausted vapor to condense, at least to a significant extent.

Feedback to the circulation system is preferably provided by a mixing device in which the streams from the steam effluent are combined and mixed with the recycle stream. The stream from the vapor effluent is at least partially in the vapor phase, so the mixing device is preferably an absorption device, ie, a device that absorbs vapor or gas in a liquid. If hydrogen is used as a molecular weight regulator, it is difficult to mix the hydrogen back into the recycle stream. This is because it is desirable for the vapor discharge of the liquid-vapor separator to be connected to a compressor, so that the mixing or absorption is carried out at high pressures, in particular equal to or equal to the pressure in the reactor to which the mixture is fed back. or at nearly equal pressures. The desired hydrogen concentration in the reactor 1 can then be easily achieved in the absorption device 6 (see drawing) in the liquid phase.

The liquid discharge pressure of the vapor-liquid separator is of course lower than before the relief valve. In order to be able to recycle the reaction mixture, another compressor must be installed within the recirculation system. This is preferably installed before and after the reactor through which the liquid discharge from the liquid-vapor separator passes. If the compressor is subsequently installed,
The pressure inside this reactor will always be lower than the others.
If a compressor is placed in front of it, the pressures in the two reactors will be almost equal. This example is rather preferred, since it does not require too much donation and offers a great possibility of creating polymerization conditions in two different reactors. If the pressure in the reactor with a low concentration of molecular weight regulator, in this case reactor 2, is lower than in the other reactors,
The monomer pressure is also lower here and the increase in monomer to molecular weight regulator ratio is reversed. This is also another reason why this pre-reactor compression is better than post-reactor compression. Although the pressure is even higher than in other reactors, a relief valve must be installed in the system after this reactor.

The apparatus according to the invention illustrates, by way of example, an embodiment of the process in which the removal of hydrogen is carried out by lowering the pressure and the feedback is carried out by absorption at a higher pressure, as well as by the description of the facility according to the invention. The invention will now be described by reference to the accompanying drawings in which:

The stirred reactor 1, which is substantially completely filled with liquid, is fed through line 10 with ethene, which has been dissolved in a dispersant, and with the catalyst dissolved in the dispersant through line 11. The reaction mixture is withdrawn through conduit 12 fitted with relief valve 3. The gas-liquid mixture obtained by reducing the pressure is separated in separator 4. The liquid phase consisting of the polymer suspension is sent through conduit 13 to pump 5 which raises the pressure of the liquid phase to the polymerization pressure and then through conduit 14 installed in cooler 8 to reactor 2. sent to Reactor 2 is of the same type as reactor 1. A portion of the polymer suspension is continuously withdrawn through conduit 15 and sent to a processing section (as shown) where the catalyst is deactivated and the polymer is recovered, where the solvent is recovered. is conduit 17
After being mixed with ethene fed through conduit 1
6 and is supplied to the reactor 2. From reactor 2 the reaction mixture is passed through conduit 1 installed in condenser 9
8 and is sent to the absorber 6. This absorber is also connected via conduit 19 to hydrogen, dispersant and separator 4.
The mixture with ethene is separated as a gas at , and brought to the polymerization pressure by means of a compressor 7 . If required, additional hydrogen is supplied via conduit 20. From the absorber the reaction mixture is returned to reactor 1. In the recirculation system described, therefore, low molecular weight polyethylene is formed in reactor 1 and polyethylene with high molecular weight is formed in reactor 2. The two reactors may be of equal size, but it is also possible to use reactors of different sizes. Naturally, reactor 1 and/or reactor 2 may also be replaced by two or more smaller reactors connected in parallel or in series.

Although the pressure and temperature in the two reactors need not be equal, this is often the case for practical reasons. Additionally, a small amount of comonomer may be added to one ethylene feed and not to the other. A person of ordinary skill in the art will not find it difficult to conceive of this embodiment within the scope of the present invention.

The polymerization reactor can be of any conventional type, for example a multistage reactor connected optionally in parallel or in series, or a reactor divided into zones, and equipped with a stirrer. The reactor may also be a gas-stirred reactor in which the gas consisting of all or part of the gaseous monomer is blown to the bottom of the reactor. The two reactors are not of the same type or size.

10 and 11 are feed pipes for monomers and catalysts in the dispersant. These feed lines may be manifold so that the monomer, dispersant and catalyst components can be fed separately. This drawing is only schematic and the feed tubes may terminate both at the top and bottom of the reactor, or somewhere in the middle.
It is not necessary that all supply pipes terminate at the same location. In this diagram, the catalyst is fed to reactor 1, which can produce low molecular weight polymers as explained below, but the catalyst can also be fed to reactor 2, or to both reactors, which requires the necessary Requires tube. The same applies to the monomers and dispersants and any other components of the polymerization mixture. Reactor 1
is emptied through relief valve 3, causing a pressure drop through the valve, and the reaction mixture discharged from reactor 1 through valve 3 flows through conduit 12 to liquid-vapour separator 4. Polymerization conditions are generally such that as a result of the pressure drop (through valve 3) some of the dispersant and monomer are converted to the vapor phase and all or a significant amount of the molecular weight modifier is in the vapor phase. The vapor phase is passed through conduit 19 to compressor 7 and from there to absorber 6 .

The liquid phase is sent from the liquid-vapor separator through line 13, compressor 5 and line 14 to reactor 2. Cooler 8 is attached to conduit 14 . cooling in any other suitable location and in any other suitable manner;
This is carried out, for example, in a wall-cooled reactor by cooling the equipment within the reactor by means of a condenser for condensation of the evaporated dispersant. The drawing shows supply pipes 16 and 17 for monomer and dispersant. As mentioned above, monomer and/or dispersant and/or catalyst or catalyst components are fed to reactor 1, or reactor 2, or both, and the necessary equipment must be installed.

A conduit 18, which can be connected to both the top and the bottom of the reactor 2, but preferably to the top, serves to discharge the reaction mixture. Cooler 9 is attached to conduit 18 . The above notes for cooler 8 also apply to cooler 9. In the absorber 6,
The flow from conduit 19, which may be wholly or partially liquid after compressor 7, is mixed with the reaction mixture flow from conduit 18. Conduit 20 serves to control the molecular weight regulator. The reaction mixture is returned to reactor 1 through conduit 21. The reaction mixture consisting of dispersant, polymer and other ingredients, if any, is transferred to conduit 15.
The polymer can then be removed in a manner known per se. Attention to the feed and discharge conduits of reactor 1 is also given to conduits 14, 16, 17 and 18 in that each of these may terminate at the top or bottom of the reactor, or somewhere in between. This is strikingly true.

A number of parts are shown in the drawings which are not essential to the device according to the invention, but cannot be ignored for a better understanding. The essence of the device according to the invention consists in reactors 1 and 2 which are arranged in a recirculation system by conduits 12, 13 and 14 and also by 18 and 21. Devices for passing the molecular weight regulator into side channels around the reactor 2, namely the relief valve 3, the vapor-liquid separator 4, the compressors 5 and 7, and the mixing device 6, which can be an absorber, are preferred in the device according to the invention. belongs to the aspect.

The discharge pipe 15 may be connected at any point in the recirculation system, both in the reactor and in the connecting line, and the connection after the compressor 5 shown in the drawings only represents an example. A part that is very suitable for connection is also the conduit 13
It is. The fraction to be discharged is then not compressed, which saves compression energy. On the other hand, some homogenization generally occurs within the compressor, resulting in
Discharge after the compressor 5 is also advantageous. However, this is conditional and in itself has no essential importance to the device.

In the embodiment diagrammatically shown in the drawings, reactor 1
The pressures in and 2 are equal or at least approximate.

To enable polymerization at different pressures,
Compressor 5 may be placed in conduit 21 after reactor 2, so that compressor 7 may be omitted. However, the pressure in reactor 2 cannot be adjusted independently of the applied pressure reduction to lower the molecular weight regulator concentration as desired. An unrelated adjustment is that the stepwise pressure increase is caused by compressor 5 and
It would be possible if this were done across the compressor.

The possibility of producing polymers of different molecular weights by carrying out the polymerizations at different molecular weight regulator concentrations and at different temperatures in reactors 1 and 2 is usually sufficient, so that polymers of different molecular weights can be produced at different pressures. It is not worth considering the polymerization of In contrast, for polymerizations at variable pressures, the pressure in reactor 2 must be higher than the pressure in reactor 1 in order to enhance the effect of the molecular weight regulator. Compressor 5 must then raise the pressure above the pressure in reactor 1. and a relief valve for pressure relief, e.g. conduit 18.
must be attached to. In many cases this is not done. Therefore only different concentrations of the molecular weight regulator and different temperatures are possible, but as mentioned above these possibilities are usually sufficient.

EXAMPLE Ethene was polymerized in an apparatus of the type described in the accompanying drawings. Small amounts of ethene as a comonomer
Mixed with 1.5 mol% butene. The dispersant used was a low boiling gasoline with a boiling range of 60-80°C.
Polymerization temperature was 50℃ in reactor 2 and 85℃ in reactor 1.
The working pressure was 20 atmospheres absolute. The pressure was reduced to 5 atmospheres absolute across relief valve 3. The molecular weight regulator was hydrogen.

2.72 Kg/h of ethene and 3.34 Kg/h of low boiling gasoline were fed into the system through conduits 16 and 17. If necessary, the hydrogen to be supplied is passed through line 20 and after the absorption device 6 a weight ratio of hydrogen:ethene in the liquid phase in reactor 1 of 1:35 is reached and the hydrogen is fed through line 11.
The ethene feed through -2.28 Kg/hr was adjusted to account for this.

A catalyst prepared by the following method was added through conduit 10.

In a pure nitrogen atmosphere, 264 ml of a 2 molar solution of monoethylaluminum dichloride (MEAC) dissolved in low-boiling gasoline (boiling range 62-82°C) was
Place in a reactor equipped with a stirrer and feed tube. 40℃
440 ml of a 0.3 molar solution of dibutylmagnesium (DBM) dissolved in low-boiling gasoline was gradually added with stirring. After the dibutylmagnesium addition is complete, stirring is continued at 40° C. for 20 minutes more. Next, 25 ml of a 4 molar solution of TiCl ₄ dissolved in low boiling point gasoline was added dropwise, and finally 271 ml of low boiling point gasoline was added dropwise.
was added to adjust the total amount to 1. The temperature is constantly kept at 40°C and stirring is continued for an additional 45 minutes at 40°C after the TiCl ₄ addition is complete. The suspension thus obtained had a MEAC of 528 mmol/mole;
DBM; Contains 100 mmol/TiCl ₄ or its reaction product.

Catalyst feed was adjusted such that 86 mg (1.79 mmol) of titanium in the form of a titanium compound was added every hour. As a result of the pressure reduction across safety valve 3 and the hydrogen, ethene and dispersant vapor discharge through conduit 19, a hydrogen/ethene weight ratio in the liquid phase of 1:436 was established in reactor 2. 5Kg/hour polyethylene and 6.13
A polymer suspension consisting of Kg/h of low-boiling gasoline was discharged through line 15. butanol suspension
The catalyst was deactivated by adding 0.18/hr and then the polyethylene was separated from the gasoline and dried.

Polyethylene containing only 10 p.pm of Ti, and therefore no need to remove catalyst residue, has a melt index (mi) of 0.19 and a flow index of 16.5 as defined above.
It had If polyethylene with a melt index of 0.19 is produced in one reactor with the same catalyst system and the same polymerization temperature, the flow index will
When the polymerization was carried out at 85°C, it was only 4.7, and when the polymerization was carried out at 60°C, it was only 6.4.

[Brief explanation of the drawing]

The attached drawing is an explanatory drawing for showing one embodiment of the α-alkene polymerization method according to the present invention, and in this drawing, 1 and 2 are reactors, 3 is a relief valve, 4 is a separator, and 5 is a reactor.
is a compressor, 6 is an absorber, 7 is a compressor, 8 and 9 are coolers, 10 is a conduit for supplying ethene in the dispersant,
11 is a conduit for supplying the catalyst in the dispersant, 12 is a conduit for removing the reaction mixture, 13 and 14 are conduits, 1
5 is a conduit for removing the polymer suspension, 16 is a conduit, 17 is an ethene introduction tube, 18 is a conduit, 19 is a conduit for ethene, dispersant, hydrogen, and mixture separated in the separator 4, and 20 is a conduit for hydrogen. It is a conduit.

Claims (1)

[Claims] 1 α-alkene having 2 to 8 carbon atoms,
one compound of one or more transition metals from groups 4 to 6 or 8 of the Periodic Table, optionally together with small amounts of up to 10 mol % of other α-alkenes having 2 to 10 carbon atoms; In the polymerization of α-alkenes with 3 to 8 carbon atoms, using catalysts containing
Polymerization is carried out at a pressure of 100Kg/ ^cm2 , and this polymerization is
The polymerization conditions in at least one reactor form a polymer having a high molecular weight;
By carrying out the polymerization in at least two reactors under such reaction conditions that the polymerization conditions in one other reactor form a polymer with a lower molecular weight than the other, the melt index according to ASTM D-1238 is 0.005 to 100. and a method for forming polymers with a broad molecular weight distribution, in which monomers, catalysts and dispersants are fed into one reactor 1 and the polymer suspension is discharged from this reactor 1 and fed into another reactor 2. However, this reactor may also be fed with monomers and dispersants if desired, and the polymer suspension is discharged from the rear reactor 2 and fed again to the front reactor 1 and recycled polymer suspension. A portion of the suspension is removed from the circulation system through an internal discharge pipe and is worked up in a customary manner, adjusting the polymerization conditions in one reactor (1 or 2) such that a polymer with a relatively low molecular weight is formed therein. the other reactor (2 or 1)
Reactor (1 or 2) in which the polymerization conditions are first stated
A process for the polymerization of α-alkenes, characterized in that the polymerization is carried out in cycles in two reactors, chosen such that a polymer with a higher molecular weight than that in the reactor is formed. 2. Add the molecular weight regulator to one reactor, completely or substantially remove the molecular weight regulator from the polymer discharged from this reactor, feed to another reactor, and add the molecular weight regulator to the desired amount. If so, the monomer and dispersant which can be removed from the discharge pipe are fed into the part of the system flowing from the later reactor to the earlier reactor and mixed into the reaction mixture flowing therein. The method described in Section 1. 3. The method according to claim 2, wherein the molecular weight regulator used is hydrogen. 4 In one stage the hydrogen/ethene molar ratio in the gas phase is between 75:25 and 85:15 and in the other stage 0.
~25:75, Claims 1 to 3
The method described in any one of the preceding paragraphs. 5. Process according to claim 4, wherein the hydrogen/ethene molar ratio in the gas phase in the hydrogen-poor reaction stage is in the range of 10:90 to 25:75. 6. The method according to any one of claims 1 to 5, wherein the polymerization is carried out at a temperature of 10 to 110°C. 7. The method according to claim 6, wherein the polymerization is carried out at a temperature of 50 to 100°C. 8. Claims 1 to 7, wherein the polymerization in the reactor in which polyethylene having a relatively high molecular weight is produced is carried out at a lower temperature than in other reactors.
The method described in any one of the preceding paragraphs. 9 Connections for conveying the contents from one reactor 1 to another reactor 2 and feed pipes for components forming the polymerization medium, such as monomers, catalysts or catalyst components and, if desired, molecular weight regulators. α-, which consists of two polymerization reactors equipped with a supply pipe for polymer suspension, a discharge pipe for polymer suspension, and a cooling member for removing heat of polymerization.
In an apparatus for polymerizing alkenes, this apparatus:
characterized in that it has a second connecting line in which the reactor and the connecting line are fitted in such a way as to form a recirculating system, and one or more devices for recycling the contents of the recirculating system. Equipment for α-alkene polymerization. 10. Device according to claim 9, having a relief valve in one of the connecting pipes and a compressor in the other connecting pipe. 11 A relief valve in one connecting line and behind the relief valve, looking in the direction of the pressure drop across the relief valve, a liquid outlet is connected to the recirculation system and a vapor outlet is connected to the other connecting line. and one or more compressors arranged to maintain the pressure in the reactor before the relief valve. The device according to any one of the preceding items. 12. The device according to claim 11, comprising a compressor placed on the liquid outlet side and the vapor outlet side of the liquid-vapor separator. 13. Apparatus according to any one of claims 10 to 11, comprising a device for mixing the recirculation stream and the stream from the vapor outlet of the liquid-vapor separator. 14. Apparatus according to claim 13, comprising an absorber for absorbing or mixing the recycle stream of both gas and liquid components in the stream from the vapor outlet of the liquid-vapor separator.