JPS59230010A - Vapor-phase multi-stage polymerization process - Google Patents

Abstract

PURPOSE:To produce a block copolymer giving a molded article free from fish- eye, by polymerizing propylene with a Ziegler-Natta catalyst, extracting the polymer intermittently from the system, separating the entrained gas, and copolymerizing ethylene and propylene at a specific ratio. CONSTITUTION:A Ziegler-Natta catalyst and propylene are supplied through the lines 1 and 5, respectively to the first polymerization zone 2 of a horizontal stirring-bed reactor, etc., and subjected to the vapor-phase polymerization. The produced polymer is extracted intermittently from the reactor through the discharge valve 14 to the receptor 15, and the entrained gas is expelled from the receptor 15 by opening the gas-discharge valve 18. The pressure in the receptor 15 containing the polymer is increased by opening the pressurizing gas inlet valve 17 until the ethylene/propylene molar ratio of the gas in the receptor 15 reaches <=0.1 or >=0.9, and then the polymer is transferred through the line 20 into the second polymerization zone 22 and polymerized to obtain the objective block copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas phase multistage polymerization method suitable for producing ethylene-propylene copolymers. More specifically, the present invention relates to a method for transferring a polymer between polymerization zones in the multistage polymerization method.

With the progress in the development of highly active catalysts for olefin polymerization, it has become possible to omit the catalyst removal operation after polymerization, and thus gas phase polymerization is attracting attention because of its simple operation. In addition, in order to improve the physical properties of polyolefin, there has been a proposal to carry out a multi-stage polymerization method in the gas phase, in which two or more polymerization zones are provided and a series of polymerization reactions are carried out under different reaction conditions. 6570
No. 8 is one example.

:f-f V 7.Propylene block copolymer C is usually produced by homopolymerizing propylene and then subsequently polymerizing a mixture of ethylene and propylene. When carrying out such ethylene/propylene block copolymerization in the gas phase, it is important to independently control the hydrogen used as a molecular weight control agent and the concentrations of ethylene and propylene in each polymerization zone. be.

In JP-A-57-65708, as a method of controlling hydrogen concentration in a gas phase multi-stage polymerization method for producing propylene homopolymer, the polymer extracted from the first polymerization zone is temporarily held in an inert gas atmosphere area. After that, a method is disclosed in which the polymer is introduced into a second polymerization zone using the pressure of the raw material gas supplied to the second polymerization zone.

However, when this method is used to produce ethylene-propylene block copolymers, a sticky copolymer forms and accumulates in the inert atmosphere area and in the transfer piping to the second polymerization zone. In addition, the polymerization zone is easily clogged, making long-term continuous operation difficult. In addition, the polymer that has grown on the accumulated sticky copolymer and whose degree of polymerization is not controlled enters the second polymerization zone, making it difficult to complete the final molding. A new problem arises in that the surface of the product is damaged by scratches.

As a result of intensive research to solve the above problems when producing ethylene-propylene block copolymer using a gas phase multi-stage polymerization method, the present inventors have found that the polymer extracted from the first polymerization zone into a receiver and The above problems are solved by separating the gas extracted along with the polymer and then introducing the polymer into the second polymerization zone at a gas pressure where the concentrations of ethylene and propylene are in a specific range. Having learned that this is the case, we have completed the present invention.

That is, the present invention performs gas phase polymerization of propylene in the first polymerization zone in the presence of a Chive 2-Natsuta catalyst, and then continues gas phase copolymerization of ethylene and propylene in the second polymerization zone to form ethylene and propylene copolymer. In a gas phase multi-stage polymerization method for producing a polymer, there is a Z step in which the polymer is intermittently extracted from the polymerization zone into a receiver; however, the gas introduced along with the polymer is transferred to the receiver. Φ←
(6) introducing the polymer in the receiver into a second polymerization zone.

The first effect obtained by carrying out the method of the present invention is that the formation of a sticky copolymer in the polymer transfer path from the first polymerization zone to the second polymerization zone is prevented. By completely preventing clogging, the production of ethylene-propylene copolymers by gas phase multi-stage polymerization can be carried out stably for a long period of time.

The second effect obtained by carrying out the method of the present invention is that leakage of gas from the first polymerization zone to the second polymerization zone is substantially prevented, and the gas concentration in each polymerization zone can be adjusted arbitrarily and , in that it can be controlled independently. This makes it possible to arbitrarily and independently control the molecular weight of the polymer produced in each polymerization zone and the composition of the copolymer components, increasing the degree of freedom in polymer design.

The third effect obtained by carrying out the method of the present invention is that since no adhesive copolymer is generated in the transport path, molecules fi-? To obtain a high-quality ethylene-propylene polymer copolymer that does not mix foreign polymers whose composition is not controlled into the product and has extremely low occurrence of surface roughness or fissure eyes in the final molded product. be able to.

In carrying out the process of the invention, a catalyst system containing a titanium trichloride composition and an organoaluminum compound can be used as the polymerization catalyst, and not only when it consists of only the two components of a titanium trichloride composition and an organoaluminum compound. This means that in addition to the two components, an auxiliary component such as an electron-donating compound or a carrier may coexist.

Furthermore, it does not matter what form these components are present in the catalyst system.

The above-mentioned titanium trichloride composition includes titanium trichloride obtained by reducing titanium tetrachloride with aluminum or an organoaluminum compound, a titanium trichloride obtained by pulverizing and activating the titanium trichloride, and titanium trichloride and an electron A pulverized product with a donor compound, a product obtained by precipitation from liquefied titanium trichloride in the presence of an ether compound, a product obtained by the method described in Japanese Patent Publication No. 8856/1983, titanium tetrachloride , a mutually compatible type obtained by bringing a magnesium compound and an electron-donating compound into contact with each other.

As an example of a preferred titanium trichloride composition, a product obtained by reacting titanium tetrachloride, an organoaluminum compound, and an ether compound is subsequently reacted with titanium tetrachloride and an ether compound, or with titanium tetrachloride and an ether compound. Mention may be made of titanium trichloride compositions obtained by treatment with reaction products.

The organoaluminum compound has the general formula AtRmXg
-m (R = hydrogen or a hydrocarbon group having 1 to 10 carbon atoms,
In particular, it is an alkyl group, X-halogen or an alkoxy group having 1 to 12 carbon atoms (1<m<3). Specifically, triethylaluminum, l-li-n-7'ropylaluminum, tri-1so-propylaluminum, tri-iso-fluoraluminum, diethylaluminium chloride, di-1so-butylaluminum chloride, diethylaluminium iodide. etc. Moreover, a mixture of those selected from these can be used.

It is also possible to add each set of electron-donating compounds as a third component of the polymerization catalyst system during polymerization to improve the performance of the catalyst. Examples of such electron-donating compounds include (a) ethers such as diethyl needle, di-n-butyl ether, diynamyl ether, tetrahydrofuran, dioxane, diethylene, and glycol dimethyl ether;

diphenyl ethers, (b)carboxylic acid esters,
For example, methyl formate9. Ethyl acetate, ethyl benzoate, ethyl toluate, methyl methacrylate, etc., e→taketones such as methyl ethyl ketone, acetophenone, etc.) aldehydes, such as acetaldehyde,
Inbutyraldehyde, benzaldehyde, etc. (e)
Amines, nitriles, acid amides such as diethylamine.

Aniline, acetonitrile, acrylamide.

(he)phosphoric acid compounds such as tetramethylurea, such as triphenylphosphine, triphenylphosphite,
triphenyl phosphate, (t)i'sulfur compounds such as carbon disulfide, methyl phenyl sulfone, etc.
can be given.

The polymerization catalyst system can be subjected to a preactivation treatment as disclosed in JP-A-57-209904.

The polymer produced in the first polymerization zone is preferably a homopolymer of propylene, but ethylene or
A propylene-based random copolymer having an α-olefin content of 10% by weight or less may also be used. The molecular weight of the polymer is preferably in the range of 0.5 to 9 in terms of intrinsic viscosity ((η) value measured in a tetralin solution at 185° C.).

The polymer produced in the second polymerization zone has an ethylene content of 5 to
It can be selected from ethylene/propylene and random copolymers in the range of 95% by weight, and these copolymers also contain 10% by weight of a vinyl compound such as olefin having 4 to 11 carbon atoms or styrene as the eighth component. The following can be contained. If the ethylene content is outside the above range, less sticky copolymer will be produced, and even if the method of the present invention is not applied, the method of JP-A-57-65708 can be used to transfer the copolymer between each polymerization zone. This is excluded from the scope of the present invention. Intrinsic viscosity of the above polymer produced in the second polymerization zone [
η] is the intrinsic viscosity of the polymer produced in the first polymerization zone [η
] Higher is preferable.

Hydrogen can coexist as a molecular weight regulator in each polymerization zone, and its concentration is approximately 1 mole of olefin.
The amount is in the range of 5 moles or less. In addition, the polymerization temperature in each polymerization zone is lower than the sintering temperature of the resulting polymer, and
It is set higher than the dew point of the gas mixture in the reactor. Specifically, the temperature can be selected from the range of 30 to 90°C, preferably 40 to 80°C, and more preferably 50 to 75°C. The polymerization pressure can be selected from the range of 1 to 40 kf/dG. The polymerization time can be selected from the range of 10 minutes to 10 hours, preferably 80 minutes to 5 hours. Reaction conditions such as polymerization pressure, polymerization temperature, polymerization time, hydrogen concentration, etc. may be different for each polymerization zone, and the present invention can be achieved even if the pressure in the second polymerization zone is set higher than that in the first polymerization zone. objective is achieved.

Both the first polymerization zone and the second polymerization zone may be composed of one polymerization vessel, or may be composed of two or more polymerization vessels, and the plurality of polymerization vessels constituting the same polymerization zone are connected in series. It is desirable that the vehicle be operated in the following manner. The present invention can also be applied to transfer of polymer between polymerization vessels within the same polymerization zone.

Note that in carrying out the present invention, it is of course possible to add any olefin polymerization step before the first polymerization zone and/or after the second polymerization zone, and the present invention also applies to these additional steps. can be applied.

There are no particular restrictions on the type of reactor used when carrying out the method of the present invention, including a fluidized bed reactor.

Any of a stirred unreactor, a stirred fluidized bed reactor, a tubular reactor, etc. can be used, and these may be either vertical or horizontal. As a reactor that can be preferably used, JP-A-51-
Horizontal reactor No. 86584 or JP-A-57-155
An example is a stirred fluidized bed reactor No. 204.

In the present invention, polymer is intermittently extracted from the first polymerization zone into a receiver. Since the extraction of this polymer involves the leakage of gas components from the first polymerization zone, the leaked gas is removed from the receiver by cutting off communication with the first polymerization zone and then reducing the pressure. do. Falling pressure does not need to be a vacuum,
It may be about atmospheric pressure or about 0.5 to 9/d-G. Next, the pressure of the receiver containing the polymer is increased with gas. The gas used for pressurization must be an inert gas that does not poison the catalyst, such as nitrogen, saturated hydrocarbons having 1 to 4 carbon atoms, ethylene or propylene, or mixtures of these gases. This molar ratio is 0.1 and 0.
If a mixture between 9 and 9 is used, a sticky copolymer will be formed in the receiver and in the polymer transport system thereafter, which is not preferable. Examples of preferable pressurizing gases include globylene or ethylene gas alone, and furthermore the atmospheric gas in the first polymerization zone as long as the above molar ratio conditions are met. In order to facilitate the transfer of the polymer to the second polymerization zone, the pressure increase is desirably set higher than the polymerization pressure in the second polymerization zone, preferably 2 ky/dG or higher. After the receiver is pressurized to a predetermined value, it is brought into communication with the second polymerization zone, the polymer is transferred to the second polymerization zone, and polymerization is carried out in the zone. The above-mentioned series of procedures are automatically carried out by a series of sea fence operations of each cut-off pulp.

The method of the present invention will be explained in more detail below with reference to the accompanying drawings showing an example of an embodiment.

FIG. 1 is a flow sheet showing one embodiment of the method of the present invention. In this example, the first polymerization zone and the second polymerization zone each consist of one polymerization vessel.

A catalyst suspension obtained by prepolymerizing a titanium trichloride composition and a small amount of an olefin such as an organoaluminum compound in a saturated hydrocarbon having 4 to 7 carbon atoms in a separate container (not shown) is supplied as a catalyst. Spray feed from pipe 1 into first polymerization vessel 2. In this example, the polymerization vessel 2 is a horizontal stirring unreactor;
The stirring blade 4 is rotated by a motor 8 to perform gas phase polymerization of propylene. Liquefied propylene is sprayed into the first polymerization vessel 2 through the pipe 5 to remove polymerization heat. Unreacted gas is pipe 6
It is then extracted from the reaction system, and a portion of it is liquefied by a cooler 8 and enters a reservoir 9. The liquefied gas in the reservoir 9 is extracted by the pump 10 and returned to the reactor 2 via the pipe 5', while the gas in the gas phase is extracted by the blower 18-1 to the first polymerizer 2. Blown into the bottom. Hydrogen and propylene consumed in the reaction system, and if necessary a small amount of ethylene, are replenished through pipe 7 and/or pipe 12.

The polymer produced in the first polymerization vessel 2 is intermittently introduced into the receiver 15 by opening the polymer discharge valve 14 for a predetermined period of time. The gas introduced into the receiver 16 with the polymer is discharged to a gas recovery system (not shown) by opening the gas discharge valve 18. After closing the gas exhaust valve 18, the pressurized gas introduction valve 17 is opened to introduce pressurized gas into the receiver 16 through the pipe 16, and then the valve 17 is closed.

Next, open the polymer transfer valve 19 to remove the receiver 15 and the transfer pipe 2.
The polymer in 0 is transferred to the second polymerizer 22 by pressurized gas. If the pressure of the pressurized gas is higher than the polymerization pressure in the second polymerization vessel 22, the flashing into the reactor 15 will be
Beneficially, less polymer remains in the receiver 15 and transfer tube 20. When the transfer of the polymer is completed, the polymer transfer valve 19 is closed, thereby completing one cycle of the operation of transferring the polymer from the first polymerizer 2 to the second polymerizer 22.

Note that after this, before opening the exhaust valve 14, open the gas exhaust valve 1.
8 is opened, the residual gas in the receiver 15 is discharged to the recovery system, and then the discharge valve 18 is closed.Then, the pressurized gas introduction valve 17 is opened to introduce pressurized gas, and the pressure in the receiver 16 is reduced. It is possible to add a step of increasing the pressure to the same pressure as the polymerization pressure of the first polymerization vessel 20 and then closing it.

By repeating the above series of operations, the first polymerization vessel 2
The polymer can be smoothly transferred from the polymerizer to the second polymerizer 22 without clogging the transfer path.

In the second polymerization vessel 22, gas phase copolymerization of ethylene and propylene is carried out in a flow similar to that in the first polymerization vessel 2).

[Brief explanation of the drawing]

FIG. 1 is a 170-sheet diagram illustrating one embodiment of the method of the present invention. More than 1 day

Claims (3)

[Claims] (1) In the presence of a Chive 2-Nanta catalyst, gas phase polymerization of propylene is carried out in the first polymerization zone, followed by gas phase copolymerization of ethylene and propylene in the second polymerization zone to produce ethylene-propylene copolymerization. In the gas phase multi-stage polymerization method for producing a polymer, the gas introduced along with the polymer (in the step of intermittently withdrawing the polymer from the AJ first polymerization zone to the receiver) is removed from the receiver. (Q) Next, the receiver containing the polymer is pressurized such that the gas composition in the receiver is such that the molar ratio of (ethylene/propylene) is 0.1 or less or 0.9 or more. A gas phase multi-stage polymerization method comprising the following steps: - (6) introducing the polymer in the receiver into a second polymerization zone. (2) The gas phase multi-stage polymerization method according to claim 1, wherein the pressurized gas in step 0 is propylene. (3) The gas phase multi-stage polymerization method according to claim (1), characterized in that the pressure after increasing the pressure in the step (Q) is higher than the polymerization pressure in the second polymerization zone by J2#/d or more.