JP2008247999A - Polypropylene production method - Google Patents

Abstract

An object of the present invention is to provide a method for producing polypropylene capable of sufficiently suppressing the agglomeration of polypropylene particles due to melting and capable of producing polypropylene particles having a sufficiently uniform particle size.
The method for producing polypropylene according to the present invention comprises a liquid phase polymerization step of obtaining an intermediate product from a monomer for liquid phase polymerization by a liquid phase polymerization reaction, and a polymerization of polypropylene by a gas phase polymerization reaction from the intermediate product and the monomer gas. A first gas phase polymerization step for obtaining a coalescence, and a calorific value per unit volume of a region where a gas phase polymerization reaction occurs in the first gas phase polymerization region to which an intermediate product is first supplied is 8.0 × 10 The production amount of the intermediate product obtained through the liquid phase polymerization step so as to be ^{8 to} 1.25 × 10 ⁹ joules / hour / m ^3, and the production amount of the polypropylene polymer in the first gas phase polymerization zone, , Are adjusted.
[Selection] Figure 1

Description

  The present invention relates to a method for producing polypropylene.

  Polypropylene is used as a material for home appliance parts, packaging materials, daily necessities, and the like, and has a wide variety of uses. In addition, for the purpose of improving impact strength and the like, a polypropylene polymer using a block copolymer of propylene and ethylene has been developed and used for automobile parts and the like.

  As a method for producing a polypropylene polymer, a liquid phase polymerization method such as a slurry polymerization method, a solution polymerization method and a bulk polymerization method, and a gas phase polymerization method using a stirring type or fluidized bed type reactor are known. Among these production methods, a gas phase polymerization method or a combination of a bulk polymerization method and a gas phase polymerization method has been widely adopted in recent years.

  The block copolymer of propylene and ethylene is produced through the following steps. First, polypropylene is produced from a raw material propylene by a polymerization reaction. A block copolymer is then produced by copolymerizing ethylene and propylene in the presence of this polypropylene.

  In order to produce a high-quality block copolymer, it is required that variation in the content of the copolymer contained in each particle is sufficiently small. The use of polymer particles having variations in content causes an increase in the amount of non-standard quality products that deviate from normal quality standards.

As a means for suppressing the variation in the content of the copolymer in each particle, it is possible to narrow the residence time distribution of the polymer in the polymerization reactor for producing it and to make the degree of polymerization uniform. As such a technique, for example, Patent Documents 1 to 4 describe a method and an apparatus for circulating a fluid to be processed through a plurality of polymerization reactors or reaction regions arranged in series.
Japanese Patent Laid-Open No. 2003-277412 JP-A 63-218245 JP-T-2001-525242 Japanese Patent No. 3304462

  By the way, in the gas phase polymerization method, the monomer gas itself is a polymerization medium, and a medium for diluting the produced polymer is not used. Therefore, the monomer gas and the solid catalyst are first contacted with each other upstream of the reaction process. High temperature parts are easily formed. In addition, in the case of the gas phase polymerization method, there is a problem that it is difficult to remove heat accompanying the polymer formation reaction.

  Therefore, in the methods of Patent Documents 1 to 4 in which a polymer is produced by a gas phase polymerization method, the polymer is easily melted and agglomerated on the upstream side of the reaction process, and it is difficult to perform the polymerization reaction stably. Further, when the polymerization reaction is unstable, the particle size of the produced polymer particles becomes non-uniform.

  The present invention has been made in view of such circumstances, and a method for producing polypropylene capable of sufficiently suppressing the agglomeration of polypropylene particles by melting and capable of producing polypropylene particles having a sufficiently uniform particle size. The purpose is to provide.

The method for producing polypropylene according to the present invention includes a liquid phase polymerization step of obtaining an intermediate product from a liquid phase polymerization monomer having a propylene content of 95% by mass or more by a polymerization reaction in a liquid phase, an intermediate product, and a propylene content A first gas phase polymerization in which a monomer gas having an amount of 95% by mass or more is introduced into one gas phase polymerization zone or a gas phase polymerization zone in which a plurality of monomer gases are arranged in series to obtain a polypropylene polymer by a polymerization reaction in the gas phase. And a calorific value per unit volume of a region where a gas phase polymerization reaction occurs in the first gas phase polymerization region to which the intermediate product is first supplied among the gas phase polymerization regions. The production amount per unit mass of the intermediate product obtained through the liquid phase polymerization step so as to be 0 × 10 ^{8 to} 1.25 × 10 ⁹ joules / hour / m ³ , Polypropy And adjusting the polymer produced per catalyst unit weight of the emissions, the.

  In order to prevent the melting of the polymer in the gas phase polymerization reactor, the present inventors do not directly introduce the polymerization catalyst into the gas phase polymerization reactor, It has been found that it is very useful to produce an intermediate product by liquid phase polymerization of a monomer (monomer for liquid phase polymerization) and introduce it into a gas phase polymerization reactor.

  The intermediate product obtained through the liquid phase polymerization process has progressed to some extent. Therefore, by introducing the intermediate product into the gas phase polymerization reactor, a local temperature rise on the upstream side of the reactor can be prevented. The liquid phase polymerization method has an advantage that the reaction heat can be easily removed as compared with the gas phase polymerization method because a liquid medium is used. Therefore, in the liquid phase polymerization method, even when a monomer having a high polymerization reaction rate is introduced, the reaction temperature can be easily controlled, and an intermediate product can be produced stably. In addition, by continuously performing gas phase polymerization in a plurality of gas phase polymerization zones arranged in series, each residence time distribution of the polymer in each gas phase polymerization zone can be set narrow, and the particle size is sufficiently Uniform polypropylene particles can be obtained.

Furthermore, the present inventors adjust the reaction ratio in the liquid phase polymerization reactor and the first gas phase polymerization zone of the gas phase polymerization reactor to produce a gas phase polymerization reaction in the first gas phase polymerization zone, The calorific value per unit volume of the so-called reaction mass is 8.0 × 10 ^{8 to} 1.25 × 10 ⁹ Joules / hour / m ³ (more preferably 8.0 × 10 ^{8 to} 1.1 × 10 ⁹ Joules / It was found that high-quality polypropylene particles can be produced by adjusting the time / m ³ ).

According to the study by the present inventors, for example, when the polymerization reaction of propylene proceeds excessively in the liquid phase polymerization step, the calorific value becomes less than 8.0 × 10 ⁸ joules / hour / m ³ . In such a case, due to the wide residence time distribution of the polymer in the liquid phase polymerization reactor, the particle size of the intermediate product becomes non-uniform, and as a result, the polypropylene obtained through the first gas phase polymerization step The particle size of the particles is also non-uniform. On the other hand, when the polymerization reaction of propylene in the liquid phase polymerization step is insufficient or the polymerization reaction rate in the first gas phase polymerization step is excessively high, the calorific value is 1.25 × 10 ⁹ joules / hour. / more than ^{m 3.} In such a case, problems such as agglomeration due to melting occur, and the reaction in the gas phase polymerization reactor becomes unstable.

  In the method for producing polypropylene according to the present invention, the second gas is formed by copolymerizing ethylene with propylene and / or an α-olefin having 4 or more carbon atoms in the presence of a polypropylene polymer obtained through the first gas phase polymerization step. It is preferable to provide a phase polymerization step. A high-quality block copolymer can be produced by further performing the second gas phase polymerization step following the first gas phase polymerization step. Further, by using a polypropylene polymer obtained by continuous gas phase polymerization in a gas phase polymerization region in which a plurality are arranged in series, polypropylene particles having a sufficiently uniform copolymer content and particle size can be obtained. Obtainable.

  In the present invention, a bulk polymerization reaction is preferably employed in the liquid phase polymerization step as the liquid phase polymerization reaction. This is because the bulk polymerization method has advantages such as no need to recover the solvent and a small amount of unreacted monomer. In the present invention, it is preferable to employ a fluidized bed type reactor in the first gas phase polymerization step as the gas phase polymerization reactor. This is because the fluidized bed type gas phase polymerization reactor has advantages such as high contact efficiency between the solid catalyst and the polymer and uniform temperature in the reactor. In the second gas phase polymerization step, it is preferable to employ a fluidized bed type gas phase polymerization reactor.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to fully suppress that a polypropylene particle aggregates by melting, the manufacturing method of the polypropylene which can manufacture a polypropylene particle with a sufficiently uniform particle size can be provided.

  Hereinafter, preferred embodiments of a method for producing polypropylene according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing a polypropylene production system according to the present embodiment. A polypropylene production system 10 shown in FIG. 1 includes a bulk polymerization reaction apparatus 1 that performs a liquid phase polymerization process and a gas phase polymerization reaction apparatus 2 that performs a first gas phase polymerization process. The bulk polymerization reaction apparatus 1 is an apparatus for producing an intermediate product by polymerizing a monomer for liquid phase polymerization by a bulk polymerization method. The gas phase polymerization reaction apparatus 2 is an apparatus that is disposed in the subsequent stage of the bulk polymerization reaction apparatus 1 and further polymerizes the intermediate product to produce polypropylene.

  The bulk polymerization reaction apparatus 1 includes two reactors 1a and 1b. A supply pipe L1 communicates with the lower part of the reactor 1a of the bulk polymerization reaction apparatus 1, and a liquid phase polymerization monomer to which a solid catalyst is added is supplied through the supply pipe L1. The tops of the two reactors 1a and 1b communicate with each other through a connecting pipe L2, while the bottoms of the reactors 1a and 1b communicate with each other through another connecting pipe L3.

  In the bulk polymerization reaction apparatus 1 having the above configuration, the liquid phase polymerization monomer supplied to the reactor 1a repeatedly flows through the reactor 1a and the reactor 1b together with the solid catalyst. More specifically, the liquid phase polymerization monomer supplied from the lower part of the reactor 1a flows upward in the reactor 1a in the presence of the polymerization solid catalyst, and then to the reactor 1b through the connecting pipe L2. And introduced. Then, after flowing downward in the reactor 1b, it is again introduced into the reactor 1a through the connecting pipe L3. By repeating such a flow for a predetermined time, the polymerization reaction proceeds, and an intermediate product having a predetermined polymerization degree is continuously produced. The intermediate product containing polypropylene particles is sent to the gas phase polymerization reactor 2 through an intermediate product transfer pipe L4 connected to the lower part of the reactor 1b.

  The gas phase polymerization reaction apparatus 2 includes two fluidized bed reactors 2a and 2b, and the upper reactor 2a and the lower reactor 2b are first gas dispersions having a large number of through holes in the thickness direction. The first gas dispersion plate 2c is divided by the plate 2c and forms the bottom surface of the upper reactor 2a. The bottom surface of the lower reactor 2b is also composed of a second gas dispersion plate 2d having the same structure as the first gas dispersion plate 2c.

  The tip of the intermediate product transfer pipe L4 communicates with the upper reactor 2a, and the intermediate product is supplied into the upper reactor 2a through this. The upper reactor 2a and the lower reactor 2b are communicated with each other through a connecting pipe L5. Through this, the polypropylene particles grown in the upper reactor 2a can be supplied to the lower reactor 2b.

  Further, a gas supply pipe L6 for supplying a monomer gas having a propylene content of 95% by mass or more to the reactors 2a and 2b is connected to the bottom of the gas phase polymerization reaction apparatus 2. The monomer gas supplied through the gas supply pipe L6 is supplied into the lower reactor 2b through the through hole of the second gas dispersion plate 2d. Further, this monomer gas is supplied from the lower reactor 2b into the upper reactor 2a through the through holes of the first gas dispersion plate 2c. With this monomer gas, the polypropylene particles on the gas dispersion plate are fluidized to form a fluidized bed of polypropylene particles. The gas phase polymerization reaction apparatus 2 may have a configuration capable of forming three or more fluidized beds therein.

  One end of a gas circulation pipe L7 is connected to the top of the upper reactor 2a for extracting and recirculating gas containing unreacted monomer gas. The other end of the gas circulation pipe L7 communicates with the gas supply pipe L6 so that unreacted monomer gas can be supplied again to the lower reactor 2b. A compressor 5 for boosting the gas and a heat exchanger 8 for cooling the gas are disposed in the middle of the gas circulation pipe L7. The polypropylene particles in the lower reactor 2b are discharged out of the system through the discharge pipe L8.

A method for producing polypropylene using the polypropylene production system 10 having the above-described configuration is a region in which a gas phase polymerization reaction occurs in the upper reactor 2a of the gas phase polymerization reactor 2 (hereinafter referred to as "reaction region of the upper reactor 2a"). ) Of 8.0 × 10 ^{8 to} 1.25 × 10 ⁹ joules / hour / m ³ (more preferably 8.0 × 10 ^{8 to} 1.1 × 10 ⁹ joules / hour). / M ³ ), the polymerization degree of the intermediate product produced by the bulk polymerization reactor 1 and the polymerization degree of the polypropylene produced by the upper reactor 2a are adjusted.

  The “reaction region of the upper reactor 2a” here refers to a region in which a fluidized bed (concentrated layer) 2A of polypropylene is formed on the first gas dispersion plate 2c forming the bottom surface of the upper reactor 2a. Similarly, the region in which the gas phase polymerization reaction occurs in the lower reactor 2b of the gas phase polymerization reactor 2 (hereinafter referred to as “the reaction region of the lower reactor 2b”) is the second that forms the bottom surface of the lower reactor 2b. This refers to a region where a fluidized bed (concentrated layer) 2B of polypropylene is formed on the gas dispersion plate 2d. The amount of heat generated in these regions can be calculated based on the balance between the amount of heat supplied into the reactor and the amount of heat discharged from the reactor. In the present embodiment, the inside of the upper reactor 2a is the first gas phase polymerization zone.

  Hereinafter, the manufacturing method of the polypropylene which concerns on this embodiment is demonstrated.

  In the present embodiment, as the liquid phase polymerization monomer supplied to the bulk polymerization reactor 1, a propylene content of 95% by mass or more based on the total mass of the liquid phase polymerization monomer is used. When a liquid phase polymerization monomer having a propylene content of less than 95% by mass is used, the heating value per unit volume of the reaction region of the upper reactor 2a is within the above range due to the influence of components other than propylene. Even if it adjusts, the productivity of the manufactured polypropylene will fall.

  From the viewpoint of efficiently producing higher quality polypropylene particles, the monomer for liquid phase polymerization preferably has a propylene content of 98% by mass or more, and more preferably consists essentially of propylene. From the same viewpoint, the monomer gas supplied to the gas phase polymerization reaction apparatus 2 preferably has a propylene content of 95% by mass or more and 98% by mass or more based on the total mass of the monomer gas. More preferred are those consisting essentially of propylene.

  As the solid catalyst used in the present embodiment, a solid catalyst containing titanium, magnesium and halogen (hereinafter referred to as “solid catalyst (A)”); organoaluminum compound, organoaluminum oxy compound, boron compound, organozinc A solid catalyst obtained by supporting a promoter such as a compound on a particulate carrier (hereinafter referred to as “solid catalyst (B)”); a promoter such as an organoaluminum compound, an organoaluminum oxy compound, a boron compound, and a metallocene system A solid catalyst (hereinafter, referred to as “solid catalyst (C)”) in which a compound is supported on a particulate carrier can be used. These solid catalysts can also be used in combination.

As the particulate carrier, a porous substance is preferable. Suitable examples include inorganic oxides such as SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , B ₂ O ₃ , CaO, ZnO, BaO, ThO ₂ ; smectite, montmorillonite, hectorite, laponite. And clays such as saponite and clay minerals; organic polymers such as polyethylene, polypropylene, and styrene-divinylbenzene copolymers.

  Examples of the solid catalyst (A) include, for example, JP-A-63-142008, JP-A-4-227604, JP-A-5-339319, JP-A-6-179720, JP-B7-116252. Solid catalysts described in JP-A-8-134124, JP-A-9-31119, JP-A-11-228628, JP-A-11-80234, JP-A-11-322833, and the like. Is mentioned. When this solid catalyst (A) is used, it is preferable to use an organoaluminum compound in combination, and an electron donating compound is used as necessary.

  As said solid catalyst (B), the solid catalyst described in Unexamined-Japanese-Patent No. 61-276805 and Unexamined-Japanese-Patent No. 2003-171415 is mentioned, for example. When using this solid catalyst (B), it is preferable to use together catalyst components, such as a metallocene compound and an organoaluminum compound.

  Examples of the solid catalyst (C) include those described in JP-A-61-108610, JP-A-61-296008, JP-A-63-89505, JP-A-3-234709, and the like. Solid catalyst. When using this solid catalyst (C), it is preferable to use together catalyst components, such as an organoaluminum compound and a boron compound.

  A mixture of a monomer for liquid phase polymerization and a solid catalyst is supplied to the bulk polymerization reactor 1 to produce an intermediate product by the bulk polymerization method (liquid phase polymerization step). In the bulk polymerization method, the propylene monomer itself is a polymerization solvent, and a solid catalyst is dispersed in the polymerization solvent to perform polymerization. Polymerization by the bulk polymerization method is preferably carried out under conditions where the polymerization solvent can be kept in a liquid state and the produced polymer is not dissolved in the polymerization solvent. The temperature condition of the bulk polymerization reaction is usually 30 to 100 ° C, preferably 50 to 80 ° C. The polymerization conditions for the bulk polymerization reaction are usually 1.0 to 10 MPaG, preferably 2.0 to 5 MPaG.

  The intermediate product is supplied to the gas phase polymerization reactor 2 through the intermediate product supply pipe L4 to perform gas phase polymerization (first gas phase polymerization step). More specifically, the intermediate product is supplied into the upper reactor 2a through the intermediate product supply pipe L4, and the monomer gas is supplied into the upper reactor 2a through the through holes of the first gas dispersion plate 2c. In the upper reactor 2a, polypropylene is polymerized by a fluidized bed gas phase polymerization method. This fluidized bed gas phase polymerization method is a method in which a monomer gas is a medium and polymerization is performed by fluidizing polypropylene particles containing a solid catalyst in the medium. The polymerization by the fluidized bed gas phase polymerization method is preferably performed under conditions in which propylene can exist in a gas state in the upper reactor 2a. The temperature condition of the fluidized bed gas phase polymerization method is usually 50 to 110 ° C, preferably 60 to 100 ° C. The pressure condition of the fluidized bed gas phase polymerization method is usually normal pressure to 5 MPaG, preferably 1.5 to 3.5 MPaG.

  The polypropylene particles grown in the upper reactor 2a are supplied into the lower reactor 2b through the connecting pipe L5, and the monomer gas is supplied into the lower reactor 2b through the through holes of the second gas dispersion plate 2d. In the lower reactor 2b, polypropylene is polymerized by a fluidized bed gas phase polymerization method. The polymerization by the fluidized bed gas phase polymerization method performed in the lower reactor 2b can be performed under the same conditions as those of the upper reactor 2a.

Next, it manufactures with the block polymerization reactor 1 so that the emitted-heat amount per unit volume of the reaction area | region of the upper stage reactor 2a may be 8.0 * 10 < ⁸ > -1.25 * 10 < ⁹ > joule / hour / m < ³ >. A method for adjusting the production amount of the intermediate product per catalyst unit mass and the production amount of the polypropylene produced in the upper reactor 2a per catalyst unit mass will be described.

  In the bulk liquid phase polymerization method in the bulk polymerization reactor 1, for example, by adjusting the temperature and pressure conditions of the polymerization reaction, or by adjusting the amount of the solid catalyst added to the polymerization solvent or the activity of the solid catalyst, The calorific value per unit volume of the reaction region of the upper reactor 2a can be adjusted. Further, by adjusting the supply amount of the monomer for liquid phase polymerization to the bulk polymerization reactor 1, the average residence time of the polymer in the device is adjusted, and the calorific value per unit volume of the reaction region of the upper reactor 2a is increased. You may control so that it may become a desired numerical value.

  On the other hand, in the fluidized bed gas phase polymerization method in the gas phase polymerization reaction apparatus 2, for example, by adjusting the temperature and pressure conditions of the polymerization reaction or adjusting the hold-up amount of the upper reactor 2a, the polymer in the apparatus It is possible to adjust the calorific value per unit volume of the reaction region of the upper reactor 2a by adjusting the average residence time.

  In addition, when the average residence time of the polymer in the upper reactor 2a is Ta (hour) and the average residence time of the polymer in the lower reactor 2b is Tb (hour), the ratio (Ta / Tb) is less than 3. Is preferably set to be less than 2. On the other hand, the lower limit of the ratio is preferably 1.

  When the ratio exceeds 3, the average particle residence time of the polymer in the upper reactor 2a is long, and the particle size of the polypropylene particles discharged from the lower reactor 2b tends to be uneven. On the other hand, when the ratio is less than 1, the calorific value per unit volume of the reaction region of the upper reactor 2a tends to increase.

  According to the method for producing polypropylene according to the present embodiment, since the generation of polymer lumps can be sufficiently suppressed in the upper reactor 2a in which local high temperature portions are easily formed, gas phase polymerization can be stably performed. . Specifically, polypropylene particles can be stably flowed in the reactors 2a and 2b. In addition, the transfer of polypropylene particles from the upper reactor 2a to the lower reactor 2b can be performed stably.

  As the degree of polymerization of polypropylene increases, the calorific value associated with the polymerization reaction decreases. Therefore, if the calorific value of the upper reactor 2a is adjusted within the above range, the lower reactor 2b and the latter reactor are more downstream. In the gas phase reactor, it can be said that there is a low possibility that a local high temperature portion that causes generation of a polymer mass is formed.

(Second Embodiment)
FIG. 2 is a schematic configuration diagram showing a polypropylene production system according to the present embodiment. The polypropylene production system 20 shown in FIG. 2 includes a bulk polymerization reaction apparatus 1 that performs a liquid phase polymerization process and a gas phase polymerization reaction apparatus 2 that performs a first gas phase polymerization process, in addition to a second gas phase polymerization process. The polypropylene production system 10 according to the first embodiment is different from the polypropylene production system 10 according to the first embodiment in that the vapor phase polymerization reaction apparatus 3 is implemented. The gas phase polymerization reaction apparatus 3 is an apparatus that is disposed in the subsequent stage of the gas phase polymerization reaction apparatus 2 and performs copolymerization of ethylene and propylene in the presence of the polypropylene polymer from the gas phase polymerization reaction apparatus 2.

  The gas phase polymerization reaction apparatus 3 includes two fluidized bed reactors 3a and 3b above and below, and the upper reactor 3a and the lower reactor 3b have a first gas dispersion having a number of through holes in the thickness direction. The first gas dispersion plate 3c is divided by the plate 3c and forms the bottom surface of the upper reactor 3a. The bottom surface of the lower reactor 3b is also composed of a second gas dispersion plate 3d having the same structure as that of the first gas dispersion plate 3c. In the upper reactor 3a, a polypropylene fluidized bed 3A is formed on the first gas dispersion plate 3c, and in the lower reactor 3b, a polypropylene fluidized bed 3B is formed on the second gas dispersion plate 3d.

  A polypropylene polymer is transferred from the gas phase polymerization reactor 2 to the upper reactor 3a through the discharge pipe L8. The upper reactor 3a and the lower reactor 3b communicate with each other through a connecting pipe L9, and the polypropylene particles grown in the upper reactor 3a are supplied to the lower reactor 3b through this.

  In addition, a mixed gas supply pipe L10 for supplying a mixed gas of ethylene and propylene to the reactors 3a and 3b is connected to the bottom of the gas phase polymerization reaction apparatus 3. The mixed gas supplied through the gas supply pipe L10 is supplied into the lower reactor 3b through the through hole of the second gas dispersion plate 3d. Further, the mixed gas is supplied from the lower reactor 3b to the upper reactor 3a through the through holes of the first gas dispersion plate 3c. With this mixed gas, the polypropylene particles on the gas dispersion plate are fluidized to form a fluidized bed of polypropylene particles. The gas phase polymerization reaction apparatus 3 may have a configuration capable of forming three or more fluidized beds therein.

  One end of a gas circulation pipe L11 for extracting and recirculating a gas containing an unreacted mixed gas is connected to the top of the upper reactor 3a. The other end of the gas circulation pipe L11 communicates with the mixed gas supply pipe L10 so that the unreacted mixed gas can be supplied again to the lower reactor 3b. In the middle of the gas circulation pipe L11, a compressor 5 for boosting the gas and a heat exchanger 8 for cooling the gas are disposed. The polypropylene particles in the lower reactor 3b are discharged out of the system through the discharge pipe L12.

  In the method for producing polypropylene according to the present embodiment, polypropylene particles discharged from the gas phase polymerization reaction apparatus 2 are introduced into the gas phase polymerization reaction apparatus 3. The polypropylene particles obtained through the first gas phase polymerization step in the gas phase polymerization reactor 2 have a sufficiently uniform particle size. Therefore, by carrying out the second gas phase polymerization step in which ethylene and propylene are subsequently copolymerized in the gas phase polymerization reactor 3, polypropylene particles having a sufficiently uniform copolymer content can be produced. In this case, by setting each residence time distribution of the polymer in each reactor narrowly in the gas phase polymerization reactor 3, polypropylene particles having a more uniform copolymer content and particle size can be obtained.

  As mentioned above, although embodiment of the manufacturing method of the polypropylene which concerns on this invention was described in detail, the following forms may be sufficient as this invention.

  For example, in the above embodiment, the bulk polymerization reaction apparatus 1 is exemplified as an apparatus for performing liquid phase polymerization. Instead of this, a conventionally known stirred tank reactor or other loop reactor is used. (See Japanese Patent Publication No. 41-12916, Japanese Patent Publication No. 46-11670, Japanese Patent Publication No. 47-42379). Moreover, the apparatus which performs liquid phase polymerization is not limited to a continuous type, You may use a batch type and a semibatch type.

  The polymerization of the monomer for liquid phase polymerization may be performed by a slurry polymerization method instead of the bulk polymerization method, or the slurry polymerization method and the bulk polymerization method may be used in combination. For example, prepolymerization by a slurry polymerization method may be performed on the monomer for liquid phase polymerization, and the product obtained thereby may be supplied to the bulk polymerization reaction apparatus 1.

  In the slurry polymerization method, an aliphatic solvent such as propane, butane, isobutane, pentane, hexane, heptane, and octane; an inert solvent such as cycloaliphatic hydrocarbon such as cyclopentane and cyclohexane added with a propylene monomer In this method, polymerization is performed by using a polymerization solvent and dispersing a solid catalyst in the polymerization solvent.

  In the slurry polymerization method, for example, by adjusting the amount of propylene monomer or solid catalyst added to the polymerization solvent or the activity of the solid catalyst, the calorific value per unit volume of the reaction region of the upper reactor 2a at the subsequent stage is adjusted. Can be adjusted. Further, by adjusting the supply amount of the monomer for liquid phase polymerization supplied into the reactor for performing the slurry polymerization, the average residence time of the polymer in the reactor is adjusted, and the unit volume of the reaction region of the upper reactor 2a is adjusted. The amount of generated heat may be controlled to a desired value. However, when the slurry polymerization method is adopted, it is necessary to sufficiently remove the inert solvent before supplying the intermediate product to the upper reactor 2a.

  The polymerization reaction by the slurry polymerization method is preferably carried out under conditions where the polymerization solvent can be kept in a liquid state and the produced polymer is not dissolved in the polymerization solvent. The temperature condition of the slurry polymerization reaction is usually 30 to 100 ° C, and preferably 50 to 80 ° C. The pressure condition of the slurry polymerization reaction is usually normal pressure to 10 MPaG, and preferably 0.3 to 5 MPaG.

  As the slurry polymerization reactor used in the slurry polymerization method, a known polymerization reactor such as a stirred tank reactor or a loop reactor can be used (Japanese Patent Publication No. 41-12916, Japanese Patent Publication No. 46-). 11670 and Japanese Examined Patent Publication No. 47-42379).

  Moreover, in the said embodiment, although the vapor phase polymerization reaction apparatus 2 and 3 were illustrated as an apparatus which performs vapor phase polymerization, in order to accelerate | stimulate the flow in a reactor, the stirrer was provided auxiliary. May be used. Furthermore, instead of the gas phase polymerization reaction apparatus 2, a conventionally known reactor may be used (refer to Japanese Patent Laid-Open Nos. 58-201802, 59-126406, and 2-233708). ).

  Further, instead of the fluidized bed gas phase polymerization method, a stirring tank type gas phase polymerization method and / or a moving bed type gas phase polymerization method may be used.

  The stirred tank type gas phase polymerization method is a method in which a monomer gas is a medium, and a solid catalyst and polypropylene are fluidized in the medium by a stirrer to perform polymerization. The polymerization reaction is preferably performed under conditions where propylene can exist in a gaseous state in the reactor. The temperature condition of the stirred tank type gas phase polymerization method is usually 50 to 110 ° C, preferably 60 to 100 ° C. The pressure condition of the stirred tank gas phase polymerization method is usually normal pressure to 5 MPaG, preferably 0.5 to 3 MPaG.

  As the reactor used in the stirred tank type gas phase polymerization method, conventionally known reactors can be used (see JP-A-46-31969 and JP-A-59-21321).

  The moving bed type gas phase polymerization method is a method of performing polymerization by moving solid particles for propylene polymerization in a gas phase polymerization medium containing propylene without substantially mixing them. The temperature condition of the moving bed type gas phase polymerization method is usually 50 to 110 ° C, preferably 60 to 100 ° C. The pressure condition of the moving bed gas phase polymerization method is usually normal pressure to 6 MPaG, and preferably 1.5 to 5 MPaG. An inert gas such as nitrogen and a chain transfer agent such as hydrogen may be added to the polymerization medium.

  The solid particles for propylene polymerization used in the moving bed type gas phase polymerization method move in the polymerization medium by gravity, a mechanical mechanism, and the like, and move in various directions such as horizontal, vertical, and diagonal directions. The moving bed type gas phase polymerization method is classified into a flat flow type, a counter flow type, a cross flow type, and the like depending on the relationship between the moving direction of the solid particles for propylene polymerization and the flow direction of the polymerization medium. Of these, any type may be adopted. However, in the countercurrent type in which the solid particles for propylene polymerization fall vertically, the flow rate of the polymerization medium needs to be suppressed to a fluidization start speed or less.

  The removal of the polymerization heat generated during the polymerization in the moving bed type gas phase polymerization method is usually performed by discharging the gas as the polymerization medium from the reactor, and using a heat exchanger or the like installed outside the reactor. After cooling, a method is used in which this gas is supplied again to the reactor as a circulating gas. The circulating gas may be cooled to a temperature lower than the dew point and supplied as a gas / liquid two-phase mixed gas.

  As the reactor used in the moving bed type gas phase polymerization method, a conventionally known reactor can be used (for example, Journal of Powder Engineering, Vol. 28 No. 12, p. 772 to p. 773 (1991)). reference).

  In the polypropylene production system 20 according to the above-described embodiment, the case where ethylene and propylene are copolymerized in the presence of polypropylene is exemplified. However, another olefin monomer and propylene are copolymerized to produce a block copolymer. Also good. Further, ethylene and other olefin monomers may be copolymerized with propylene in the presence of polypropylene. The other olefin monomer is preferably an α-olefin having 4 or more carbon atoms, and the upper limit of the number of carbon atoms is preferably 12, and more preferably 8.

  Other olefin monomers include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, 1-hexene, 1-heptene, 1-octene and the like. Among these olefin monomers, one type may be used alone, or two or more types may be used in combination.

  In addition, using a multistage polymerization method, propylene-propylene / ethylene block copolymer, propylene / propylene / ethylene / propylene / ethylene block copolymer, propylene / ethylene / propylene / ethylene block copolymer, propylene / propylene / A block copolymer such as an ethylene / 1-butene block copolymer may be produced. Here, “-” indicates a boundary between blocks, and “•” indicates that two or more olefins are copolymerized in one block.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

Example 1
(1) Preparation of solid catalyst precursor A cylindrical reactor (with an internal volume of 200 liters) equipped with stirring blades and baffle plates was prepared, and the interior thereof was replaced with nitrogen. In this reactor, 54 liters of hexane, 100 g of diisobutyl phthalate, 20.6 kg of tetraethoxysilane and 2.23 kg of tetrabutoxy titanium were charged. After stirring, 51 liters of dibutyl ether solution of butylmagnesium chloride (concentration 2.1 mol / liter) was added dropwise to the resulting stirred mixture over 4 hours. The temperature in the reactor during dropping was kept at 7 ° C. and the stirring rotation speed was 150 rpm. After completion of the dropwise addition, the mixture was stirred at 20 ° C. for 1 hour, and then the solid obtained by filtration was washed with 70 liters of toluene at room temperature. After cleaning with toluene three times in total, toluene was added again to obtain a slurry containing a solid catalyst precursor.

  The solid catalyst precursor contained Ti: 1.9% by mass, OEt (ethoxy group): 35.6% by mass, and OBu (butoxy group): 3.5% by mass. The average particle size of the precursor was 39 μm, and the amount of fine powder components having a particle size of 16 μm or less was 0.5% by mass.

(2) Preparation of solid catalyst A cylindrical reactor (with an internal volume of 200 liters) having the same shape as that used for the preparation of the precursor of the solid catalyst was prepared, and the inside thereof was replaced with nitrogen. The slurry containing the above-mentioned solid catalyst precursor was transferred into the reactor. After standing, toluene was extracted so that the volume of the slurry was 49.7 liters, and stirred at 80 ° C. for 1 hour, and then the slurry was cooled to 40 ° C. or lower. Next, a mixed liquid of 30 liters of tetrachlorotitanium and 1.16 kg of dibutyl ether was added, and 4.23 kg of orthophthalic acid chloride was further added. After stirring for 3 hours at 110 ° C. in the reactor, the solid obtained by filtration was washed with 90 liters of toluene at 95 ° C.

  After washing with toluene three times in total, toluene was added again to obtain a slurry. After standing, toluene was extracted so that the volume of the slurry was 49.7 liters, and a mixed solution of 15 liters of tetrachlorotitanium, 1.16 kg of dibutyl ether and 0.87 kg of diisobutyl phthalate was added with stirring. After stirring for 1 hour at a temperature of 105 ° C. in the reactor, the solid obtained by filtration was washed with 90 liters of toluene at 95 ° C.

  After washing with toluene twice in total, toluene was added again to obtain a slurry. After standing, toluene was extracted so that the volume of the slurry was 49.7 liters, and a mixed liquid of 15 liters of tetrachlorotitanium and 1.16 kg of dibutyl ether was added with stirring. After stirring for 1 hour at a temperature of 105 ° C. in the reactor, the solid obtained by filtration was washed with 90 liters of toluene at 95 ° C.

  After washing with toluene twice in total, toluene was added again to obtain a slurry. After standing, toluene was extracted so that the volume of the slurry was 49.7 liters, and a mixed liquid of 15 liters of tetrachlorotitanium and 1.16 kg of dibutyl ether was added with stirring. After stirring for 1 hour at a temperature of 105 ° C. in the reactor, the solid obtained by filtration was washed with 90 liters of toluene at 95 ° C. After a total of 3 washes with toluene, the solid was further washed with 90 liters of hexane. After washing twice with hexane, the solid was dried to obtain a solid catalyst. This solid catalyst contained Ti: 2.2% by mass and phthalate ester component: 9.4% by mass.

(3) Production of polypropylene <preliminary polymerization>
An SUS autoclave (with an internal volume of 3 liters) equipped with a stirring blade was prepared, and 1.5 liters of n-hexane, 37.5 mmol of triethylaluminum, which had been sufficiently dehydrated and degassed, and 3.75 mmol of tert-butyl-n-propyldimethoxysilane and 15 g of the above solid catalyst were charged. While maintaining the temperature in the autoclave at about 10 ° C., 37.5 g of propylene was continuously supplied over about 30 minutes to carry out slurry polymerization of 2.5 g of propylene per 1 g of the solid catalyst.

  After the slurry liquid after the reaction was transferred to a SUS autoclave (with an internal volume of 150 liters) equipped with a stirring blade, 100 liters of liquid butane was further added to obtain a prepolymerized catalyst slurry for use in the liquid phase polymerization step.

<Liquid phase polymerization>
In the liquid phase polymerization reactor (total internal volume 30 liters) having the same configuration as the bulk polymerization reactor 1 shown in FIG. 1, propylene, hydrogen, triethylaluminum and tert-butyl-n-propyldimethoxysilane and the above prepolymerization The catalyst slurry was continuously supplied, and an intermediate product was continuously produced by a bulk polymerization method (liquid phase polymerization step). The reaction conditions were set as follows.
Polymerization temperature: 70 ° C.
Polymerization pressure: 4.3 MPaG,
Supply amount of liquid propylene: 270 liter / hour,
Feed rate of prepolymerized catalyst slurry: 23 liters / hour,
Supply amount of solid catalyst contained in the prepolymerized catalyst slurry: 3.5 g / hour,
Hydrogen concentration in the reactor: 10% by volume,
Triethylaluminum feed rate: 197 mmol / hour,
Feed rate of tert-butyl-n-propyldimethoxysilane: 31 mmol / hour,
Average residence time: 0.11 hours.

<Gas phase polymerization>
A gas phase polymerization reaction apparatus (total internal volume 1440 liters) having the same configuration as that of the gas phase polymerization reaction apparatus 2 shown in FIG. 1 is installed at the subsequent stage of the liquid phase polymerization reaction apparatus. The intermediate product can be fed into the upper reactor.

The intermediate product, propylene and hydrogen were continuously supplied to the upper reactor of the gas phase polymerization reactor to perform gas phase polymerization. Further, the polypropylene extracted from the upper reactor was transferred to the lower reactor to perform gas phase polymerization. The reaction conditions were set as follows.
Polymerization temperature: 80 ° C.
Polymerization pressure: 1.8 MPaG
Monomer gas circulation air volume: 100 m ³ / hour,
Hydrogen concentration in the reactor: 10% by volume,
Reaction area of upper reactor: 0.04 m ³ ,
Reaction zone of lower reactor: 0.06 m ³ ,
Calorific value per unit volume of the reaction zone of the upper reactor: 9.48 × 10 ⁸ joules / hour / m ³ ,
Calorific value per unit volume in the reaction region of the lower reactor: 5.70 × 10 ⁸ joules / hour / m ³ ,
Hold up (upper reactor): 14kg
Hold up (lower reactor): 22 kg.

  When the polypropylene particles extracted from the lower reactor were observed with the naked eye, no polypropylene particles were melted and the particles were agglomerated.

  In addition, the particle size uniformity of the polypropylene particles was evaluated using a laser diffraction particle size measuring device (manufactured by Sympatec Helos & Rodos, trade name: Type Rodos SR). The n value (equal number) was determined on the assumption that the particle size distribution of the polypropylene particles follows a Rosin-Ramler distribution. As a result, the n value of the polypropylene particles obtained in this example was 4. The average particle size was 753 μm. The n value of the rosin-Lambler distribution means that the larger the numerical value, the smaller the spread of the particle size distribution, and the more uniform the particle size of the polypropylene particles. Table 1 shows part of the evaluation results and conditions for the polymerization reaction.

(Comparative Example 1)
The liquid phase polymerization reactor and the upper reactor for performing the first gas phase polymerization were operated under the conditions shown in Table 1, and the calorific value per unit volume of the reaction region of the upper reactor was 1.34 × 10 ⁹ joules / Polypropylene was produced in the same manner as in Example 1 except that the time / m ³ was set. The evaluation of the obtained polypropylene particles was also performed in the same manner as in Example 1. Table 1 shows part of the evaluation results and conditions for the polymerization reaction.

(Comparative Example 2)
The liquid phase polymerization reactor and the upper reactor for performing the first gas phase polymerization were operated under the conditions shown in Table 1, and the calorific value per unit volume of the reaction region of the upper reactor was 7.46 × 10 ⁸ joules / Polypropylene was produced in the same manner as in Example 1 except that the time / m ³ was set. The evaluation of the obtained polypropylene particles was also performed in the same manner as in Example 1. Table 1 shows part of the evaluation results and conditions for the polymerization reaction.

It is a schematic block diagram which shows the polypropylene manufacturing system which concerns on 1st Embodiment of this invention. It is a schematic block diagram which shows the polypropylene manufacturing system which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bulk polymerization reaction apparatus, 2, 3 ... Gas phase polymerization reaction apparatus, 2a ... Upper stage reactor (1st gas phase polymerization area) 10, 20, ... Polypropylene production system.

Claims (5)

A liquid phase polymerization step of obtaining an intermediate product from a monomer for liquid phase polymerization having a propylene content of 95% by mass or more by a polymerization reaction in the liquid phase;
The intermediate product and a monomer gas having a propylene content of 95% by mass or more are introduced into one gas phase polymerization zone or a gas phase polymerization zone in which a plurality of them are arranged in series. A first gas phase polymerization step to obtain a polymer;
A method for producing polypropylene comprising:
The calorific value per unit volume of a region where a gas phase polymerization reaction occurs in the first gas phase polymerization region to which the intermediate product is first supplied is 8.0 × 10 ^{8 to} 1.25. × 10 ⁹ Joules / hour / m ³ The production amount per unit mass of the intermediate product obtained through the liquid phase polymerization step and the polypropylene polymer in the first gas phase polymerization zone A production method of polypropylene, characterized in that the production amount per unit mass of the catalyst is adjusted.   A second gas phase polymerization step of copolymerizing ethylene and / or an α-olefin having 4 or more carbon atoms and propylene in the presence of the polypropylene polymer obtained through the first gas phase polymerization step. The method for producing polypropylene according to claim 1, characterized in that it is characterized in that   The method for producing polypropylene according to claim 1 or 2, wherein the polymerization reaction in the liquid phase is a bulk polymerization reaction.   The method for producing polypropylene according to any one of claims 1 to 3, wherein the gas phase polymerization reactor is a fluidized bed type. The calorific value per unit volume of the reaction region is 8.0 × 10 ^{8 to} 1.1 × 10 ⁹ joules / hour / m ³ , according to any one of claims 1 to 4. The manufacturing method of the polypropylene of description.

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