JPH06199944A - Vapor-phase polymerization of olefins - Google Patents

Abstract

PURPOSE:To polymerize an olefin in vapor phase without causing the lowering of the bulk density of polymer by filling a seed polymer in a reactor, introducing an organic aluminum compound into the reactor under a specific condition and starting the reaction while supplying a solid catalyst component and an organic Al compound. CONSTITUTION:A seed polymer is filled in a reactor, an organic Al compound (preferably alkyl Al) is introduced into the reactor until the indications of long and short thermometers inserted into the reactor show abrupt depression, the reactor is supplied with an organic aluminum compound of an amount determined by the formula A=0.044XV<2/3>+aW (A is amount of supplied organic Al compound; V is volume of the total system including the gas circulation pipe; W is weight of the seed polymer; (a) is coefficient of 0-89) and the reaction is started while further supplying the organic Al compound and a solid catalyst component containing titanium and/or vanadium and magnesium to the reactor to start the reaction and effect the vapor-phase polymerization of an olefin. Preferably, the polymerization temperature is 40-200 deg.C and the polymerization pressure is 2-60kgf/.cm<2>.G.

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 an olefin by a gas phase method. More specifically, when the α-olefin is polymerized or copolymerized using a gas phase fluidized bed, the generation of a sheet polymer at the initial stage of the polymerization is reduced, and an operation start method for preventing an unstable polymerization reaction is provided. It is a thing.

[0002]

[Problems to be Solved by the Invention]
-When carrying out the polymerization of olefins, in the initial stage of the polymerization, a sheet-shaped polymer is produced, and the polymer outlet and the pipes downstream thereof are blocked, making it substantially impossible to continue the polymerization reaction. There is. It should be noted that it is generally difficult to produce a sheet-like polymer after shifting to a steady reaction.
Therefore, the cause of the formation of the sheet polymer is
It is considered that some conditions in the system greatly differ from those in the steady state before reaching the steady state.

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 may be reduced as compared with the steady state in which the polymer is in a stable state. One of the factors that affect productivity in the polymerization reaction using a gas-phase fluidized bed
The first 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 can be improved. As described above, productivity can be improved and economic efficiency can be improved by preventing a decrease in bulk density of the polymer formed in the initial stage of polymerization.

In addition, in the initial stage of polymerization, the MFR (melt flow rate) of the obtained polymer may be different from the MFR of the polymer in the steady state, even though hydrogen is supplied at a predetermined gas ratio. . That is, there is a phenomenon in which the function of regulating the molecular weight 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 initial stage of polymerization is kept normal, steady-state production can be started without producing an 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 initial stage of olefin polymerization using a gas phase fluidized bed reactor, the decrease in the bulk density of the polymer and the decrease in MFR, thereby improving the productivity. The purpose is to provide a high driving method.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in accordance with the above-mentioned object, and as a result, they have been used in combination with a fixed catalyst component at the beginning of polymerization and before starting the supply of the catalyst in a steady state. The present inventors have found that by supplying only the organoaluminum compound described above into the reactor, it is possible to suppress the production of the sheet-like polymer and to suppress the deviation of the other polymerization characteristics from the steady state, and arrived at the present invention. That is, according to the present invention, 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 olefin polymerization or copolymerization is constantly initiated in a gas phase. In the method, first, after charging the seed polymer into the reactor, (I) the organoaluminum compound is charged into the reactor until the difference (ΔT) between the indicated values of the thermometers inserted into the reactor shows a sharp decrease. Then, (II) the amount of the organoaluminum compound calculated by the following formula (1) is fed into the reactor: A = 0.044 × V ^2/3 + aW (1) (where A is an organoaluminum) Compound supply (mo
l), V is the volume (m ³ ) of the entire system including the gas circulation pipe, W is the weight (ton) of the seed polymer, and a is a coefficient (mol / ton) in the range of 0 to 89. ), And thereafter, the reaction is started while further supplying the solid catalyst component (III) and the organoaluminum compound, and a gas phase polymerization method for olefins is provided.

The present invention will be described in detail below. The gas phase fluidized bed used in the present invention includes all fluidized bed systems and agitated bed systems which are substantially operated in a gas-solid system, and may or may not have a stirrer.

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

As the catalyst used for the polymerization of the above-mentioned olefins, 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.

As the vanadium compound, a tetravalent vanadium compound such as vanadium tetrachloride, vanadium tetrabromide and vanadium tetraiodide, a pentavalent vanadium compound 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, a solid catalyst component contains inorganic oxides 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. 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 catalytically 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, the general formula R _m Al (OR ′) _{3 —m} (wherein R and R ′ are the same hydrocarbon groups as described 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. As such a compound,
For example, (C ₂ H ₅ ) AlOAl (C ₂ H ₅ ), (C ₄ H ₉ ) AlOAl
Examples thereof include (C ₄ H ₉ ), (C ₂ H ₅ ) AlN (C ₂ H ₅ ) Al (C ₂ H ₅ ), 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 usual olefin polymerization reaction using a Ziegler type catalyst. That is, the reaction occurs substantially in the gas phase. As the olefin polymerization conditions, the temperature is 20 to 300 ° C., preferably 40 to
The temperature is 200 ° C., and the pressure is atmospheric pressure to 70 kgf / cm ² · G, preferably ^{2 to} 60 kgf / cm ² · G. The molecular weight can be adjusted to some extent by changing the polymerization conditions such as the polymerization temperature and the molar ratio of the catalyst, but it is effectively performed by adding hydrogen to the polymerization system. During steady operation, the 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 an olefin in a gas-phase fluidized bed, a fluidized bed reactor is filled with a resin powder called a seed polymer in advance to start fluidization, and a raw material mixed gas, a solid catalyst component and an organic material as a co-catalyst are used. The aluminum compound is continuously supplied to carry out the polymerization reaction. 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 the reactor in advance 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 physical properties as the target product in steady-state operation. The seed polymer used in the present invention is preferably particles having an average particle size in the range of 500 to 1500 μm and a bulk density of 0.25 to 0.5 g / cm ³ . It is better that the amount of fine powder having an average particle diameter of less than 500 μm is small. The seed polymer may be packed in any amount as long as it can form a fluidized bed or a stirred bed, and is not particularly limited.

At the initial stage of the polymerization, in addition to the production of the sheet-shaped polymer, a decrease in the bulk density of the polymer and a decrease in the MFR are observed as described above. One of the reasons why the above-mentioned abnormal phenomenon occurs after the catalyst supply is started and before the polymerization reaches a steady state is considered to be a decrease in the concentration of the organoaluminum compound as a co-catalyst near the active point of the solid catalyst component. . There are three reasons for this. (1) When the reaction system is opened or the cleaning operation is performed, impurities remain in the system and accumulate in the dead space in the system, which is continuously released to consume the organoaluminum compound, which is effective. Reduce the concentration. (2) Impurities contained in the seed polymer supplied from the outside of the reactor are released into the system to consume the organoaluminum compound and reduce the effective concentration. (3) The seed polymer supplied from the outside adsorbs the organoaluminum compound to reduce the effective concentration.

Considering the case where the solid catalyst component is supplied in the state where there is not enough organoaluminum compound for carrying out the reaction, the charged solid catalyst component accumulates near the inner wall of the reactor without causing a reaction. So after that,
When an organoaluminum compound is supplied into the system, the reaction mainly starts in the vicinity of the vessel wall to form a sheet polymer. And at the same time, the decrease in bulk density of the polymer and the MF
A decrease in R is also observed. Next, the organoaluminum compound is present, but if the amount is insufficient with respect to the solid catalyst component, the polymerization activity becomes extremely unstable. That is, the polymerization activity greatly varies depending on the change in the amount ratio of the organoaluminum compound to the solid catalyst component. Furthermore, in this case, the polymerization reaction starts immediately after the solid catalyst component is supplied, but the bulk density of the polymer decreases, the reaction becomes unstable, and a decrease in MFR is observed. A polymer is produced. Finally, when the amount of the organoaluminum compound is large with respect to the solid catalyst component, no particular problem occurs. The decrease in bulk density of the polymer and the decrease in MFR are extremely small. In this case, the polymerization reaction is confirmed immediately after the catalyst supply is started. Then, although the initial polymerization activity is lower than that in the steady state, no decrease in bulk density of the polymer and no decrease in MFR are observed, and thereafter, a sheet polymer is not formed. Therefore, if the organoaluminum compound is present to some extent in excess of the solid catalyst component at the time of starting the catalyst supply in the reactor, the production of the sheet polymer is suppressed, and other abnormalities observed at the start of the reaction are suppressed. The phenomenon can also be avoided.

At the start of the polymerization reaction, the amount of the organoaluminum compound to be supplied after filling the seed polymer largely changes depending on the impurities before filling the seed polymer and the impurities contained in the seed polymer as described above. Furthermore, the required amount of the organoaluminum compound varies greatly depending on the supply rate. Therefore, in order to always initiate the polymerization in a stable state, it is extremely important to find a simple method for detecting that the supply amount of the organoaluminum compound has reached the above required amount.

The present inventors have found that the difference (ΔT) between the indicated values of two types of thermometers, long and short, inserted at almost the same height in the reaction system changes greatly at the same time when the polymerization reaction starts, and It was found that this change can be used to determine the optimum supply amount of the organoaluminum compound. The above ΔT is
It is generated because polymer particles and catalyst components adhere to the inner wall of the reactor. That is, the longer thermometer is inserted inside the reactor to directly measure the temperature of the gas stream and particles. Therefore, there is no particular obstacle at the measurement site because the moving polymer particles collide with the thermometer. On the other hand, since the shorter thermometer is installed near the inner wall of the reactor, it is easily affected by the temperature of the inner wall of the reactor, and the polymer particles adhering to the inner wall of the reactor are measured by the thermometer. Easy to adhere to. The attached polymer particles function as a heat insulating material, and as a result, a temperature difference occurs between the indicated values of the long and short thermometers. At steady state, ΔT is small. That is, it is considered that since there is almost no adhesion of polymer particles to the inner wall of the reactor in a steady state, the heat insulating effect does not occur and ΔT is small.

After the seed polymer is filled, nitrogen purge is carried out to remove entrained oxygen and the like, and the temperature and pressure are raised to reach the temperature and gas composition of the polymerization conditions. At this point, ΔT is 3 to 10. ℃. This value changes depending on the water concentration in the seed polymer. The ΔT during the steady reaction is 0.5 to 1 ° C. Further, when the organoaluminum compound is supplied into the reactor in which the organoaluminum compound is substantially absent, ΔT initially shows a value of 3 to 10 ° C., but when it is continuously supplied, ΔT rapidly increases at a certain point. To 0.5 to 1 ° C. The above phenomenon is observed regardless of the presence or absence of a catalyst in the system. Also, in the presence of a catalyst, the start of the reaction is confirmed when ΔT shows a sharp decrease. That is, two types of thermometers, long and short, were installed in the fluidized bed in the reactor, and the difference in the measured values was traced to confirm that the organoaluminum compound was supplied to the minimum amount necessary for starting the reaction. Can be detected indirectly.

In the above, the feed rate of the organoaluminum compound is 0.01 to 50 mol / (h · ton-species polymer). More preferably, it is 0.2 to 40 mol / (h · ton).
-Seed polymer). Further, in the present invention, the organoaluminum compound is supplied in two stages. However, the actual supply operation will continue. It may be appropriately divided into two or more times and intermittently supplied. The organoaluminum compound supplied here is usually the same as the organoaluminum compound supplied during steady operation.

The amount of organoaluminum compound to be initially supplied is determined according to the change in the value of ΔT. As mentioned above, when the seed polymer is packed in the reactor,
When the organoaluminum compound is substantially absent in the system, ΔT in the fluidized bed shows a constant value, but when the organoaluminum compound is supplied, ΔT shows a sharp decrease at a certain point. The feeding of the organoaluminum compound must be continued at least until the ΔT shows a sharp decrease. Here, the time point when ΔT shows a sharp decrease is a value obtained by the following method. (1) Plot the variation of ΔT with respect to the time axis and draw a curve. (2) A tangent line is drawn on the above curve at the point where the decreasing rate of ΔT shows the maximum. (3) The point corresponding to the intersection of the tangent line and the time axis is “ΔT
Is a point at which a sharp decrease occurs.

After the time point when ΔT suddenly decreases according to the above, the amount of the organoaluminum compound to be further supplied is calculated by the following equation (1) using the total system volume including the gas circulation pipe and the weight of the seed polymer. ) Can be obtained. A = 0.044 × V ^2/3 + aW (1) (where A is the supply amount of the organoaluminum compound (mo
l), V is the volume (m ³ ) of the entire system including the gas circulation pipe, W is the weight (ton) of the seed polymer, and a is a number in the range of 0 to 89 (mol / ton). ) The value of a is preferably 0.
The range is 7 to 21, and more preferably 0.7 to 9.5. When a is a negative value, a sheet polymer is likely to be produced, and the bulk density and MFR are low. On the other hand, when the value of a exceeds 89, the catalytic activity decreases and the amount of low-molecular weight polymer increases, which is not preferable.

After supplying the organoaluminum compound, the operation is started according to a conventional method. That is, when the organoaluminum compound is supplied without supplying the olefin, the solid catalyst component and the olefin are supplied to start the polymerization reaction. Further, when the olefin has already been supplied, the polymerization reaction is started by supplying the solid catalyst component. The supply amount of the organoaluminum compound is appropriately changed to a predetermined supply amount during steady operation. The olefin can be appropriately supplied together with an inert gas for dilution, for example, nitrogen, and hydrogen gas for adjusting the molecular weight can also be supplied together.

[0032]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples, but the present invention is not limited thereto.

<Preparation example of solid catalyst component> 600 in a 500 ml three-necked flask equipped with a stirrer and a reflux condenser.
Add 50 g of SiO ₂ baked at ℃, and add dehydrated hexane 1
60 ml and titanium tetrachloride 2.2 ml were added, and the mixture was reacted under reflux of hexane for 3 hours. After cooling, a hexane solution of diethylaluminum chloride (1 mmol / cc) was added to 30 m.
l was added, and 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, diameter 1 /
Commercially available anhydrous magnesium chloride (10 g) and aluminum triethoxide (4.2 g) were placed in a stainless steel pot with an internal volume of 400 ml containing 25 2-inch stainless steel balls, and ball milling was performed for 16 hours at room temperature under a nitrogen atmosphere. The reaction product was obtained. This is designated as component (II). 5.4 of the above component (II)
g was dissolved in 160 ml of dehydrated ethanol, the whole amount of the solution was added to a three-necked flask containing the component (I), reacted under reflux of ethanol for 3 hours, and dried under reduced pressure at 150 ° C. for 6 hours to give a solid. A catalyst component was obtained. The content of titanium in 1 g of the obtained solid catalyst component was 15 mg.

<Method of measuring ΔT> As the thermometer, any of a thermoelectric thermometer, a resistance thermometer and a mechanical thermometer can be used. A thermoelectric thermometer is usually convenient. Since the longer thermometer is intended to measure the temperature of the gas flow and the particle flow itself in the central part of the reactor, its measurement position only needs to be sufficiently separated from the inner wall of the reactor, and there are no special restrictions. Absent. Polymerization of polyolefin is an exothermic reaction, but the temperature distribution in the diameter direction of the reactor has a large temperature gradient near the inner wall of the reactor and a relatively gentle temperature gradient in the central part of the reactor. Therefore, in order to measure the temperature of the central portion, it is sufficient that the distance from the inner wall of the reactor is sufficiently large. In a normal reactor, the temperature measurement site is located 1
It is sufficient to define a distance of more than 00 mm inside.
On the other hand, the shorter thermometer does not measure the temperature of the vessel wall itself, but the temperature of the gas phase portion in the reactor which is in contact with the inner wall of the reactor. The thermometer preferably has its measurement site as close as possible to the inner wall of the reactor. Usually, the measurement site is set at a short distance of 100 mm or less, preferably 50 mm or less from the inner wall of the reactor. If it is too close to the inner wall, it is affected by the temperature of the vessel wall or the temperature of the outside air. In such a case, a heat insulating material such as calcium oxide is appropriately used to block the heat conduction from the vessel wall or the outside air. The installation positions of the two types of thermometers, long and short, are suitable at a place where the sheet-like polymer is easily generated in the reactor. Usually, it is located above the gas dispersion plate used in the fluidized bed and close to the same. This position is determined beforehand based on experience. The positions of the two thermometers are substantially the same height. In the case of a reactor having a cylindrical cross section, as long as they have the same height, they can be installed at facing positions. Example of the present invention (inner diameter 1.4)
m of a cylindrical fluidized bed reactor), two types of thermocouple type thermometers, long and short, were installed at positions 40, 70 and 130 cm above the gas dispersion plate, and a recorder was connected to each of them. . The measurement site of the longer thermometer was at a distance of 28 cm from the inner surface of the reactor, and the shorter thermometer was set at a distance of 5 cm from the inner wall of the reactor.

<Operation start method> Until the reaction start when the copolymerization reaction of ethylene and butene-1 is carried out using a fluidized bed reactor having an inner diameter of 1.4 m and a total volume of 48 m ³ including a gas circulation pipe. The operation is as follows. (1) Nitrogen is allowed to flow in the reaction system under conditions of 95 ° C., 0.5 MPa and a flow rate of 60 Nm ³ / h for 1 day to carry out the first drying. (2) Charge 2 tons of the seed polymer into the reactor. (3) Nitrogen in the system is pressurized to 0 to 0.5 MPa · G and then depressurized, and this is repeated three times to remove oxygen. (4) After supplying an initial amount of triethylaluminum (TEA) as shown below and in Table 1, the solid catalyst component containing Ti and Mg obtained in the preparation example of the solid catalyst component was fed at a feed rate of 50 g / h. The catalyst is continuously fed at a weight ratio of TEA to solid catalyst components of 0.05 to 2 to start the reaction. The temperature of the raw material gas is 60 to 95 ° C., the composition is hydrogen / ethylene ratio = 0.1 to 0.4, and butene-1 / ethylene ratio =
It is set to 0.05 to 0.8. The reaction pressure is 1.96 MPa.
・ G.

Examples 1 to 3 Horizontally at a height of 1.3 m from the gas dispersion plate in the reactor, lengths of 5 cm and 2
Two thermometers of 8 cm were inserted to determine ΔT. While measuring the temperature in the reactor, TEA was added at a feed rate of 0.8 mol / (h · ton-species polymer) until ΔT showed a sharp decrease, and a of the formula (1) shown in Table 1 was added. After supplying TEA in an amount corresponding to the value of, the solid catalyst component and TEA were continuously supplied to start the reaction. The results are shown in Table 1.

<Comparative Example 1> The procedure of Example 1 was repeated, except that the continuous supply of the catalyst was started before ΔT sharply decreased. The results are shown in Table 1.

[0038]

[Table 1]

[0039]

INDUSTRIAL APPLICABILITY According to the present invention, in a polymerization reaction of an olefin in a gas-phase fluidized bed, after a seed polymer is charged, a specific amount of an organoaluminum compound is supplied in advance and then the reaction is started, whereby the sheet-shaped polymer at the initial stage of polymerization It is possible to reduce production and prevent decrease in polymer bulk density and decrease in MFR.

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 fed to a reactor to constantly initiate polymerization or copolymerization of olefins in a gas phase. In the method, first, after charging the seed polymer into the reactor, (I) the organoaluminum compound is charged into the reactor until the difference (ΔT) between the indicated values of the thermometers inserted into the reactor shows a sharp decrease. Then, (II) the amount of the organoaluminum compound calculated by the following formula (1) is fed into the reactor: A = 0.044 × V ^2/3 + aW (1) (where A is an organoaluminum) Compound supply (mo
l), V is the volume (m ³ ) of the entire system including the gas circulation pipe, W is the weight (ton) of the seed polymer, and a is a coefficient (mol / ton) in the range of 0 to 89. ), And thereafter, the reaction is initiated while further supplying (III) the solid catalyst component and the organoaluminum compound, and a vapor phase polymerization method for olefins. 2. The method for vapor phase polymerization of olefins according to claim 1, wherein the organoaluminum compound is alkylaluminum.