JPH06199943A - Method for initiating polymerization of α-olefin - Google Patents

Abstract

(57) [Abstract] [Purpose] When a polyolefin composed of a solid catalyst component containing titanium and / or vanadium and an organoaluminum compound is used to produce a polyolefin in a gas phase,
Provided is a method for starting an operation without generating a sheet-shaped polymer or other abnormalities in the initial stage of polymerization. [Constitution] After filling the reactor with seed polymer, (I)
The electrostatic voltage between the polyolefin particles and the ground at the position where the sheet-like polymer can be formed in the reactor is adjusted to zero or a positive value, and then (II) the solid catalyst component and the organoaluminum compound and the olefin are placed. A fixed amount is supplied to start the reaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation method for polymerizing .alpha.-olefin by a gas phase method. For more details,
The present invention relates to a start-up method for reducing the generation of a sheet-like polymer when polymerizing or copolymerizing an α-olefin using a gas-phase fluidized bed, and for continuing the polymerization stably.

[0002]

2. Description of the Related Art In order to prevent the formation of a sheet polymer, it is necessary to keep the electrostatic voltage level at zero during the polymerization reaction, that is, to keep the voltage polarity neutral, for example, Japanese Patent Publication No. 63-500176. Have been proposed to.
However, all of them are methods focusing on the electrostatic voltage during the polymerization and not focusing on the state before the initiation of the polymerization.

[0003]

[Problems to be Solved by the Invention]
-In the case of carrying out the polymerization of olefins, a sheet-shaped polymer may be produced in the initial stage of the polymerization, which may block the polymer outlet or the pipes downstream thereof, making it substantially impossible to continue the polymerization reaction. is there. The sheet-like polymer is produced from the time when the solid catalyst component is supplied into the reactor in a state where the polymerization reaction does not substantially occur and the polymerization is initiated until a polymer having a certain multiple of the reaction part volume of the fluidized bed is produced. To be observed. After shifting to a stationary reaction, a sheet polymer is not usually formed.

At the beginning of the polymerization, not only a sheet polymer is formed, but the polymerization itself is extremely unstable.
In particular, the bulk density of the produced polymer is reduced as compared with the steady state in the stable state. In a polymerization reaction using a gas-phase fluidized bed, one of the factors affecting productivity is the bulk density of the polymer. Since the productivity depends on how much polymer can be produced in a unit time in a given reaction zone volume, the higher the bulk density, the higher the productivity. Therefore, it is preferable to maintain the same bulk density from the initial stage of the polymerization as in the steady state. Further, the product polymer is intermittently extracted, but the amount of the polymer extracted at one time is set to a predetermined volume. When the bulk density of the polymer is reduced, the amount of polymer particles in the gas at the time of withdrawing is reduced, so that the amount of entrained gas discharged together with the predetermined volume of polymer is increased. The accompanying gas is an unreacted gas and contains nitrogen, ethylene, etc., but it is difficult to separate ethylene from nitrogen and recover ethylene. Therefore,
If the bulk density can be maintained at a stable value from the initial stage of polymerization, the amount of unreacted gas entrained at the time of extraction can be reduced, and the economical efficiency is improved. As mentioned above,
By preventing a decrease in bulk density of the polymer produced in the initial stage of polymerization, productivity can be improved and economic efficiency can be increased.

In addition, in the initial stage of the polymerization, the MFR (melt flow rate) of the obtained polymer may be different from the MFR of the polymer at the steady state even though hydrogen is supplied at a predetermined gas amount ratio. . That is, there is a phenomenon in which the molecular weight regulation function of hydrogen is abnormal. When such a phenomenon occurs, it is practically difficult to obtain a polymer having predetermined physical properties, and the trial and error of changing the gas composition, measuring the MFR of the obtained polymer, and feeding back to the gas composition. It is necessary to repeat. However, in the case of a gas-phase fluidized bed reactor, the residence time of the polymer particles is generally several hours, and therefore it takes a long time until the entire polymer in the reactor is replaced with a new one.
Therefore, if the MFR at the beginning of polymerization is kept normal,
It is possible to start production in a steady state without producing off-spec or secondary polymer, and productivity is improved.

The present invention solves the problems such as the production of a sheet polymer in the early stage of olefin polymerization using a gas phase fluidized bed reactor, the decrease in the bulk density of the polymer and the decrease in the MFR, thereby improving the productivity. The purpose is to provide a high driving method.

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies in accordance with the above-mentioned object, and as a result, at the beginning of the polymerization, before starting the supply of the catalyst in the steady state, the specific position in the reactor was changed. By adjusting the electrostatic voltage within a certain range,
The present invention has been accomplished by finding that it is possible to suppress the formation of a sheet-shaped polymer and suppress the deviation of other polymerization characteristics from the steady state. That is, according to the present invention, a catalyst composed of a solid catalyst component containing at least titanium and / or vanadium and magnesium and an organoaluminum compound is supplied to a reactor, and α-olefin is constantly polymerized or copolymerized in a gas phase. In the method, after charging the seed polymer into the reactor, (I) adjusting the electrostatic voltage between the polyolefin particles and the ground at a position in the reactor where the sheet polymer can be formed to zero or a positive value. Then, (II) a solid catalyst component, an organoaluminum compound, and a predetermined amount of an olefin are supplied to start the reaction, and a method for initiating polymerization of an olefin is provided.

The present invention will be described in detail below. In the present invention, the reactor used for polymerizing or copolymerizing the α-olefin in a gas phase includes a fluidized bed system and a stirred bed system which are operated substantially in a gas-solid system,
It may or may not have a stirrer.

As the α-olefin used in the present invention,
Usually an olefin having 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms, for example, ethylene, propylene, butene-1, pentene-
1, hexene-1, 4-methylpentene-1 and the like. These can be homopolymerized or copolymerized with two or more kinds at an appropriate mixing ratio. Examples of the combination of copolymerization include ethylene / propylene, ethylene / butene-1, ethylene / hexene-1, ethylene / 4-methylpentene-1 and the like, and ethylene and a carbon number of 3 to 3.
Copolymerization of 12 with α-olefins, propylene with butene-1, and ethylene with two or more other α-
Examples thereof include copolymerization with olefins. Further, copolymerization with a diene is also possible for the purpose of modifying the polyolefin. Such dienes include butadiene, 1,4-
Examples include hexadiene, ethylidene norbornene, dicyclopentadiene and the like. The olefin can be fed to the reaction system preferably with a suitable inert carrier gas such as nitrogen.

As the catalyst used for the above-mentioned polymerization of α-olefin, a catalyst comprising a solid catalyst component containing at least titanium and / or vanadium and magnesium and an organoaluminum compound is used. As the solid catalyst component containing at least titanium and / or vanadium and magnesium, a solid catalyst component containing titanium and magnesium used in a Ziegler-based catalyst conventionally known as a catalyst for olefin polymerization, and a solid catalyst component containing vanadium and magnesium Alternatively, a solid catalyst component containing titanium, vanadium and magnesium can be used.

Examples of the solid catalyst component include magnesium metal, magnesium hydroxide, magnesium carbonate,
Magnesium oxide, magnesium chloride, etc., also silicon,
Double salts, double oxides, carbonates, chlorides, hydroxides, etc. containing an element selected from aluminum and calcium and magnesium atom, and further these inorganic solid compounds are oxygen-containing compounds, sulfur-containing compounds, aromatic carbon Examples thereof include inorganic solid compounds containing magnesium such as those treated or reacted with a substance containing hydrogen or halogen and having a titanium compound and / or a vanadium compound supported by a known method.

Examples of the oxygen-containing compound include water; polysiloxane; organic oxygen-containing compounds such as alcohols, phenols, ketones, aldehydes, carboxylic acids, esters and acid amides; metal alkoxides; inorganic compounds such as metal oxychlorides. An oxygen compound can be illustrated. Examples of the sulfur-containing compound include organic sulfur compounds such as thiol and thioether, and inorganic sulfur compounds such as sulfur dioxide, sulfur trioxide and sulfuric acid. Examples of aromatic hydrocarbons include various monocyclic or polycyclic aromatic hydrocarbons such as benzene, toluene, xylene, anthracene, and phenanthrene. Examples of the halogen-containing substance include chlorine, hydrogen chloride, metal chlorides and organic halides.

Examples of the titanium compound include titanium halides, alkoxy halides, alkoxides,
Examples thereof include halogenated oxides. Of these, a tetravalent titanium compound and a trivalent titanium compound are preferable, and the tetravalent titanium compound is specifically represented by the general formula Ti (OR) _n X _4-n (where R is a carbon atom). A hydrocarbon group such as an alkyl group, an aryl group or an aralkyl group of the formulas 1 to 20, X represents a halogen atom, and n is a number in the range of 0 ≦ n ≦ 4.), Specifically, titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, monomethoxytrichlorotitanium, dimethoxydichlorotitanium, trimethoxymonochlorotitanium, tetramethoxytitanium, monoethoxytrichlorotitanium, diethoxydichlorotitanium, triethoxymonochlorotitanium. , Tetraethoxy titanium, monoisopropoxytrichlorotitanium, diisopropoxydichlorotitanium, triisopropoxymonoc Rhotitanium, tetraisopropoxytitanium, monobutoxytrichlorotitanium, dibutoxydichlorotitanium, tributoxymonochlorotitanium, tetrabutoxytitanium, monopentoxytrichlorotitanium, monophenoxytrichlorotitanium, diphenoxydichlorotitanium, triphenoxymonochlorotitanium, tetraphenoxytitanium. Etc. can be mentioned. Examples of the trivalent titanium compound include Ti (OR) _m X _4-m (wherein R represents a hydrocarbon group such as an alkyl group, an aryl group or an aralkyl group having 1 to 20 carbon atoms, and X represents a halogen). Represents an atom, and m is a number in the range of 0 <m <4.) 4
Examples thereof include trivalent titanium compounds obtained by reducing a valent titanium oxide halide with hydrogen, aluminum, titanium, or an organometallic compound of Group I to III metal of the periodic table.

Of the above titanium compounds, tetravalent titanium compounds are particularly preferable. Specific examples of these catalysts include, for example, MgO-RX-TiCl ₄ system (Japanese Patent Publication No. 51-
3514 _{JP), Mg-SiCl 4 -ROH-} TiCl 4 type (JP-B 50-23864 discloses), MgCl ₂ -Al (O
R) ₃ -TiCl ₄ system (Japanese Patent Publication No. 51-152, Japanese Patent Publication No. 52-15111), MgCl ₂ -SiCl ₄ -RO
H-TiCl ₄ system (JP-A-49-106581), M
_{g (OOCR) 2 -Al (OR} ) 3 -TiCl 4 system (JP-B 52-
11710 JP), Mg-POCl ₃ -TiCl ₄ system (JP-B 51-153 discloses), MgCl ₂ -AlOCl-TiCl ₄
System (Japanese Patent Publication No. 54-15316), MgCl ₂ -Al
(OR) _n -X _3-n -Si (OR ') _m -TiCl ₄ system (JP-A-56)
As a preferable example, a solid catalyst component (in the above formula, R and R ′ are organic residues, and X is a halogen atom) in combination with an organoaluminum compound is preferable.

Examples of the vanadium compound include tetravalent vanadium compounds such as vanadium tetrachloride, vanadium tetrabromide and vanadium tetraiodide, and pentavalent vanadium compounds such as vanadium oxytrichloride and orthoalkylvanadate.
Examples thereof include trivalent vanadium compounds such as vanadium trichloride and vanadium triethoxide. The vanadium compound is used alone or in combination with the titanium compound.

Another example of the catalyst system is a catalyst system in which a reaction product of an organomagnesium compound such as a so-called Grignard compound and a titanium compound and / or a vanadium compound is used as a solid catalyst component, and an organoaluminum compound is combined therewith. Can be illustrated. Examples of the organomagnesium compound include the general formula RMgX,
Magnesium compounds represented by R ₂ Mg, RMg (OR) and the like (wherein R represents an organic residue having 1 to 20 carbon atoms, X represents a halogen atom), ether complexes thereof, or organomagnesium compounds thereof In addition, other organometallic compounds, such as organosodium, organolithium, organopotassium, organoboron, organocalcium, organozinc, and the like, which have been modified and added can be used. Specific examples of the catalyst systems, for example, RMgX-TiCl ₄ type (JP-B 50-39470 discloses), RMgX- phenol -TiCl ₄ system (JP-B 54-12953 discloses), RMg
X-halogenated phenol-TiCl ₄ system (Japanese Patent Publication No. 54-
No. 12954), RMgX—CO ₂ —TiCl ₄ system (JP-A-57-73009), and the like, and a combination of an organoaluminum compound with a solid catalyst component.

As another example of the catalyst system, an inorganic oxide such as SiO ₂ , Al ₂ O ₃ and SiO ₂ .Al ₂ O ₃ and the above-mentioned titanium and / or vanadium and magnesium are contained as solid catalyst components. A solid substance obtained by contacting with a solid catalyst component is used, and an organoaluminum compound in combination therewith can be exemplified. As the inorganic oxide, the above-mentioned SiO ₂ , Al ₂ O ₃ and SiO ₂ .Al can be used.
_In addition to ₂ O _3, etc., CaO, B ₂ O ₃ , SnO _2, etc. can be mentioned, and a double oxide of these oxides can also be used. As a method of bringing these various inorganic oxides into contact with a solid catalyst component containing titanium and / or vanadium and magnesium, a known method can be adopted. That is, in the presence or absence of an organic solvent such as an inert hydrocarbon, alcohols, phenols, ethers, ketones, esters, amines, nitriles, or a mixture thereof, at a temperature of 20 to 400.
5 minutes to 20 ° C., preferably 50 to 300 ° C.
Although a method of reacting for a time is used, the reaction may be carried out by a method of co-grinding treatment or a method of appropriately combining these. Specific examples of the above catalyst system include:
For example, SiO ₂ --ROH--MgCl ₂ --TiCl ₄ (JP-A-56)
-47407), SiO ₂ -ROR'-MgO-AlC.
l ₃ -TiCl ₄ (JP 57-187305 JP), Si
_{O 2 -MgCl 2 -Al (OR)} 3 -TiCl 4 -Si (OR ') 4
(Japanese Unexamined Patent Publication No. 58-21405), SiO ₂ -TiCl _{4
-R n AlCl 3-n -MgCl 2} -Al (OR ') n Cl 3-n ( _{JP-A-3-35004), SiO 2 -TiCl 4 -R} n AlX
_{3-n -MgCl 2 -Al (OR} ') n Cl 3-n -Si (OR'') m Cl
_4-m (JP-A-3-64306), SiO ₂ -MgCl
_{2 -Al (OR ') n Cl} 3-n -Ti (OR'') 4 -R n AlCl
_3-n (JP-A-3-153707), SiO ₂ -MgC
_{l 2 -Al (OR ') n} Cl 3-n -Ti (OR'') n Cl 4-n -R n Al
Cl _3-n (JP-A-3-185004), SiO ₂ -Ti
_{Cl 4 -R n AlCl 3-n} -MgCl 2 -Al (OR ') n Cl 3-n -
R '' _m Si (OR ''') _n X _{4- (m + n)} (Japanese Patent Application No. 2-41526
5 JP), SiO ₂ -R _n MgX _{2 over n -Al (OR ') n Cl} 3-n
_{-Ti (OR '') n Cl} 4-n -R '''OH-R n AlX 3-n ( Japanese Patent Application No. _{3-94983), SiO 2 -MgCl 2 -Al} (O
_{R ') n Cl 3-n} -Ti (OR'') n Cl 4-n -R''' OH-R n Al
Cl _3-n -Al (OR ') _n Cl _3-n (Japanese Patent Application No. 3-48643) (wherein R, R', R "and R"'represent a hydrocarbon residue) .) Etc. in combination with an organoaluminum compound.

In these catalyst systems, a titanium compound and / or a vanadium compound can be used as an adduct with an organic carboxylic acid ester, and the above-mentioned inorganic solid compound containing magnesium is contact-treated with the organic carboxylic acid ester. It can be used later. Furthermore, an organoaluminum compound can also be used as an adduct with an organic carboxylic acid ester. Also, in all cases it is possible to use catalyst systems prepared in the presence of organic carboxylic acid esters. Examples of the organic carboxylic acid ester used here include various esters of aliphatic, alicyclic and aromatic carboxylic acids, and preferably an aromatic carboxylic acid ester having 7 to 12 carbon atoms is used.
Specific examples thereof include alkyl esters of benzoic acid, anisic acid, toluic acid such as methyl and ethyl.

The organoaluminum compound used together with the solid catalyst component in the present invention means an organoaluminum compound having at least one aluminum-carbon atom bond in the molecule. For example, (i) the general formula R _m Al (O
R ') _n H _p X _q (wherein R and R'are carbon atoms usually 1
A hydrocarbon group containing 1 to 15, preferably 1 to 4, for example, an alkyl group, an aryl group, an alkenyl group, a cycloalkyl group and the like, and in the case of an alkyl group, methyl, ethyl, propyl, isopropyl, isobutyl, sec. -Butyl, tert-butyl, hexyl, octyl and the like. R and R'may be the same or different. X
Represents a halogen atom, and m, n, p and q are 0 <m ≦ 3, 0 ≦ n <3, 0 ≦ p <3 and 0 ≦ q <3, respectively.
And is a number that satisfies m + n + p + q = 3. ), And (ii) a general formula MAlR ₄ (wherein M is a metal selected from Li, Na or K, and R is the same hydrocarbon group as described above). , And complex alkylated products of Group I metals and aluminum in the periodic table.

Examples of the organoaluminum compound belonging to the above (i) include, for example, R _m Al (OR ′) _{3 —m} represented by the general formula (wherein R and R ′ are the same hydrocarbon groups as above. M is preferably 1.5 ≦ m ≦ 3.), A general formula R _m AlX _{3 —m} (wherein R is the same hydrocarbon group as described above, X is a halogen atom, and m is preferably m). 0 <m <3.), R _m AlH _{3 −m} (wherein R is the same hydrocarbon group as described above, and m is preferably a number in the range of 2 ≦ m <3). And R _m Al (OR ′) _n X _q (wherein R and R ′ are the same hydrocarbon groups as described above. X is a halogen atom, and m, n and q are preferably M0 <m ≦ 3, 0 ≦ n <3, 0 ≦ q <3, respectively
And is a number that satisfies m + n + q = 3. ) And the like can be exemplified.
Specific examples of the organoaluminum compound belonging to (i) include trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, tri-sec-butylaluminum, tri-aluminum.
Trialkylaluminums such as tert-butylaluminum, trihexylaluminum and trioctylaluminum; trialkenylaluminums; dialkylaluminum alkoxides such as diethylaluminum ethoxide and dibutylaluminum butoxide; alkylaluminums such as ethylaluminum sesquiethoxide and butylaluminum sesquibutoxide. In addition to sesquialkoxide, partially alkoxylated alkylaluminum having an average composition represented by R _2.5 Al (OR) _0.5, etc .; Dialkylaluminum halides such as diethylaluminum chloride, dibutylaluminum chloride, diethylaluminum bromide; ethyl Aluminum sesquichloride, butyl aluminum sesquichloride, ethyl aluminum sesquichloride Partially halogenated alkyl aluminum such as alkyl aluminum sesquihalide such as bromide; diethyl aluminum hydride, dialkyl aluminum hydride such as dibutyl aluminum hydride and ethyl aluminum dihydride, alkyl aluminum dihydride such as propyl aluminum dihydride, and the like, Partially hydrogenated alkylaluminum; partially aluminumized and halogenated alkylaluminums such as ethylaluminum ethoxy chloride, butylaluminum butoxycyclolide, ethylaluminum ethoxy bromide and the like can be exemplified. Examples of the organoaluminum compound belonging to (ii) above include LiAl (C ₂ H ₅ ) ₄ and LiAl (C ₇ H ₁₅ ).
₄ etc. Further, as the organoaluminum compound similar to (i), an organoaluminum compound in which two or more aluminum atoms are bonded via an oxygen atom or a nitrogen atom can also be used. Examples of these compounds include (C ₂ H ₅ ) ₂ AlOAl (C ₂ H ₅ ) ₂ and (C ₄ H ₉ ) ₂ AlOAl.
(C ₄ H _{9) 2,} can be exemplified _{(C 2 H 5) 2 AlN} (C 2 H 5) Al (C 2 H 5) 2 and the like. Among these, trialkylaluminum is preferable.

The amount of the organoaluminum compound used during steady operation is not particularly limited, but normally, it can be used in an amount of 0.05 to 1000 mol per mol of the titanium compound.

The polymerization reaction is carried out in the same manner as the polymerization reaction of olefins using a conventional Ziegler type catalyst. That is, the reaction occurs substantially in the gas phase. As the polymerization condition of α-olefin, the temperature is 20 to 300 ° C., preferably 4
The pressure is 0 to 200 ° C., and the pressure is atmospheric pressure to 70 kgf / cm ² · G, preferably ^{2 to} 60 kgf / cm ² · G. The regulation of molecular weight is
Although it can be carried out to some extent by changing the polymerization conditions such as the polymerization temperature and the molar ratio of the catalyst, it is effectively carried out by adding hydrogen to the polymerization system. During steady operation,
The α-olefin, the solid catalyst component, and the organoaluminum compound are constantly introduced into the reaction system, while the produced polymer particles are extracted.

In the polymerization reaction of the α-olefin in the gas phase fluidized bed, the fluidized bed reactor is filled with a resin powder called a seed polymer in advance to start the fluidization, and the raw material mixed gas, the solid catalyst component and the auxiliary catalyst are added thereto. A polymerization reaction is performed by continuously supplying an organoaluminum compound as a catalyst.
If the above seed polymer is not used, a granular resin will not be generated because the supplied catalyst is difficult to disperse, and thus a fluidized bed will not be formed. used. In the present invention, the seed polymer to be charged in advance in the reactor before starting the reaction is not particularly limited as long as it is a particle capable of forming a fluidized bed or a stirred bed. However, polyolefin particles are usually preferred, especially those having the same properties as the target product in steady state operation. The seed polymer used in the present invention has an average particle size of 500 to 15
It is in the range of 00 μm and has a density of 0.25 to 0.5.
It is preferably g / cm ³ . The smaller the number of fine particles having an average particle size of less than 500 μm, the better. The filling amount of the seed polymer is not particularly limited as long as it can form a fluidized bed or a stirring bed.

After the seed polymer is filled, a nitrogen purge is carried out to remove entrained oxygen and the like or to dry it, and the temperature and pressure are raised to reach the temperature and gas composition of the polymerization conditions. Then, the polymerization is started by supplying the olefin gas, the solid catalyst component and the organoaluminum compound at an amount and a rate separately specified as steady operation. After the seed polymer is added, the order of supplying the fixed catalyst component, the organoaluminum compound and the olefin can be appropriately selected. For example, a method of simultaneously supplying a fixed catalyst component, an organoaluminum compound and an olefin gas appropriately diluted with an inert gas, a method of starting the supply of the organoaluminum compound first, and then a supply of the fixed catalyst component or the like, or Any method such as first starting the supply of the fixed catalyst component and then starting the supply of the organoaluminum compound or the like can be employed.

Before supplying the catalyst or the like to start the polymerization, the inventors of the present invention set the electrostatic voltage between the position in the reactor where the sheet-like polymer can be formed and the ground to zero or a positive value. By adjusting the pretreatment and conditions so that the catalyst does not form a sheet polymer after the polymerization is started and the bulk density and the MFR are not deteriorated, it is stable and stable. It was found that the polymerization reaction started. This is a previously unknown fact.

In the above, in order to adjust the electrostatic voltage in the reactor before the start of polymerization to zero or a positive value, any method can be adopted. For example, a method of providing a discharge passage by increasing the conductivity of particles using an additive such as an antistatic agent or other polar compound, a method of providing a ground device in the fluidized bed to discharge the electric charge to the ground,
A method of neutralizing the electrostatic charge of particles by ionizing gas or particles by electric discharge to generate ions, or generating radiation using a radiation source, and neutralizing the electrostatic charge of particles by the ions generated by the radiation There are ways.

The method of using the additive is, for example, water;
Examples thereof include chromium compounds such as bis (cyclopentadienyl) chromium; alcohols such as methanol, ethanol and isopropanol; oxygen; nitrogen oxides such as nitric oxide; ketones such as acetone and methyl isobutyl ketone. These polar compounds are 0.001-1000 pp
It is fed into the olefin gas, for example ethylene, in the range of m. In addition, the electrostatic voltage can be adjusted by changing the method of introducing the seed polymer, the drying conditions thereof, the concentration of olefin gas supplied to the reactor, and the conditions such as reaction pressure and gas flow rate.

The electrostatic voltage is measured at a position where a sheet-like polymer can be produced in the gas phase polymerization, but it is usually a position on the upper side of the gas dispersion plate used in the fluidized bed and close to the same. This position is previously determined empirically and is usually a distance from the dispersion plate of ½ or less of the diameter of the fluidized bed. Further, as the device for measuring the electrostatic voltage, any conventionally known device can be used. However, it must be a voltmeter capable of measuring the electrostatic voltage between the polyolefin particles and ground.

[0029]

Although the reason is not clear, the solid catalyst component, organoaluminum, is used when the electrostatic voltage between the electrode and the ground, which is placed at a position where the sheet polymer can be formed before the initiation of polymerization, is zero or positive. When the compound and the olefin gas are supplied to start the polymerization, the production of the sheet polymer is not observed in the subsequent steady operation.

[0030]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples. <Preparation Example of Solid Catalyst Component> 50 g of SiO ₂ calcined at 600 ° C. was placed in a 500 ml three-necked flask equipped with a stirrer and a reflux condenser, and 160 ml of dehydrated hexane was added,
Add 2.2 ml of titanium tetrachloride, and add 3 ml under reflux of hexane.
Reacted for hours. After cooling, 30 ml of a hexane solution of diethylaluminum chloride (1 mmol / cc) was added, the mixture was reacted again under reflux of hexane for 2 hours, and dried under reduced pressure at 120 ° C. to remove hexane. The obtained reaction product is referred to as component (I). Separately, an internal volume of 400 m containing 25 stainless steel balls of 1/2 inch diameter
A commercially available anhydrous magnesium chloride (10 g) and aluminum triethoxide (4.2 g) were placed in a stainless steel pot (1) and subjected to ball milling for 16 hours at room temperature under a nitrogen atmosphere to obtain a reaction product. This is designated as component (II). 5.4 g of the above component (II) was dissolved in 160 ml of dehydrated ethanol, and the whole amount of the solution was added to a three-necked flask containing the component (I), and the mixture was reacted under reflux of ethanol for 3 hours, then at 150 ° C. It was dried under reduced pressure for 6 hours to obtain a solid catalyst component. The content of titanium in 1 g of the obtained solid catalyst component was 15 mg.

<Comparative Example 1> In a cylindrical gas-phase fluidized bed type polyethylene polymerization reactor having an inner diameter of 25 cm, a stainless steel electrode is placed at a position 10 cm above a gas dispersion plate, which is considered to produce a sheet polymer in the fluidized bed. Was installed and the electrostatic voltage between it and the ground was measured. As seed polymer, the amount of polyethylene particles required to form a fluidized bed (linear low density polyethylene having an average particle size of 780 μm)
Was charged and dried with nitrogen gas, and then nitrogen gas was circulated to form a fluidized bed. At this time, the electrostatic voltage was measured and found to be -5 kV. In that state, the solid catalyst component containing Ti and Mg obtained in the preparation example of the solid catalyst component, triethylaluminum, and olefin were started to be supplied to carry out the polymerization reaction of polyethylene. However, soon after, the polyethylene outlet and the piping downstream of the polyethylene were blocked, and the polymerization reaction had to be stopped. When the inside of the apparatus was inspected after the operation was stopped, the cause of the blockage of the extraction system was the sheet polymer.

Example 1 Using the same reactor and electrode as in Comparative Example 1, the seed polymer was charged with polyethylene particles in an amount necessary for forming a fluidized bed, and the mixture was dried with nitrogen gas and then statically charged. When the electric voltage was measured, it showed -5 kV. Then, after increasing the electrostatic voltage to +0.1 kV by supplying 0.41 mol of butene-1 to 1 mol of ethylene in the gas, an adjustment example of the solid catalyst component in the same manner as in Comparative Example 1 The polymerization reaction was started by supplying the solid catalyst component containing Ti and Mg obtained in step 3 and triethylaluminum. As a result, the steady operation could be continued for 48 hours without generating the sheet polymer.

Example 2 Copolymerization of ethylene and butene-1 was carried out using the same apparatus and electrodes as above.
The electrostatic voltage after filling the seed polymer was -8 kV, but as it was, the solid catalyst component containing Ti and Mg obtained in the preparation example of the solid catalyst component and triethylaluminum were supplied as in Comparative Example 1. By doing so, the polymerization reaction was started. Since the generation of a sheet-like polymer was soon seen in the produced polyethylene, the supply of the solid catalyst component and triethylaluminum was temporarily stopped.
Next, when the concentration of the comonomer in the supplied olefin gas was increased from 0.3 mol to 0.41 mol per 1 mol of ethylene, the electrostatic voltage showed an increase and reached +3 kV. Then, the supply of the solid catalyst component and the organoaluminum compound was restarted. After that, the sheet-like polymer was not generated, and the steady operation could be continued for 48 hours.

[0034]

According to the present invention, α in a fluidized bed reactor is
-In the gas phase polymerization of olefins, by adjusting the electrostatic voltage before the start of polymerization, it is possible to continuously and stably carry out the polymerization without producing a sheet polymer.

Claims (2)

[Claims] 1. A catalyst comprising a solid catalyst component containing at least titanium and / or vanadium and magnesium and an organoaluminum compound is supplied to a reactor, and α-olefin is constantly polymerized or copolymerized in a gas phase. In the method, after charging the seed polymer into the reactor, (I) adjusting the electrostatic voltage between the polyolefin particles and the ground at a position in the reactor where the sheet polymer can be formed to zero or a positive value. Then, (II) a solid catalyst component, an organoaluminum compound, and an olefin are supplied in a predetermined amount to start the reaction, and a polymerization initiation method for an α-olefin. 2. The method for initiating the polymerization of an α-olefin according to claim 1, wherein the organoaluminum compound is alkylaluminum.