JP2003192705A - Method for producing olefin polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which can polymerize an olefin in the presence of a metallocene catalyst to control rapidly a hydrogen concentration in the polymerization system so that an olefin polymer having a desired molecular weight may be easily produced. <P>SOLUTION: The method for polymerizing the olefin in the presence of a metallocene catalyst to produce an olefin polymer comprises controlling a hydrogen concentration in the polymerization system so that the olefin polymer may have an adjusted molecular weight, wherein (1) an amount of gas to be purged from the system is increased to decrease the hydrogen concentration in the polymerization system so that the olefin polymer may be converted from the lower to the higher in its molecular weight, while (2) the amount of the gas to be purged from the system is decreased to increase the hydrogen concentration in the polymerization system so that the olefin polymer may be converted from the higher to the lower in its molecular weight. The method is particularly effective for continuously producing a product group of polymers with various molecular weights. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an olefin polymer. Specifically, when polymerizing an olefin using a metallocene catalyst to produce an olefin polymer,
The present invention relates to a method for producing an olefin polymer, which allows an olefin polymer having a desired molecular weight to be easily and efficiently obtained.

[0002]

BACKGROUND OF THE INVENTION Homopolymers of ethylene and propylene, or olefin polymers which are copolymers of these with other α-olefins are widely used as various molding materials. Such olefin polymers have been conventionally produced by solution polymerization, suspension polymerization, bulk polymerization or gas phase polymerization.
It is produced by polymerizing an olefin in the presence of a so-called Ziegler catalyst containing titanium, magnesium and halogen as main components. One of the important target product indexes of olefin polymers is molecular weight, which includes, for example, reaction temperature, in-system α-olefin concentration,
It is controlled by the hydrogen concentration in the system. It is known that the hydrogen concentration in the system has a significant influence on the molecular weight of the product. Here, the term "inside the polymerization reaction system" refers to a polymerization reaction system including a polymerization reactor and a circulation system, if any, and will be described below using this definition.

Usually, in order to control the hydrogen concentration in the system, the hydrogen concentration in the system is measured by a measuring device such as gas chromatography, and the amount of hydrogen fed into the reactor is determined manually or automatically based on the measured hydrogen concentration. The method of changing is conventionally adopted. By the way, recently, in addition to Ziegler catalyst as a catalyst for olefin polymerization, zirconium,
A catalyst system has been developed which comprises a catalyst component containing a metallocene complex compound of a Group 4 metal of the periodic table such as titanium and a promoter component such as an organoaluminum compound. These are commonly referred to as metallocene catalysts (or metallocene catalysts), and compared with conventional Ziegler catalysts (or Ziegler catalysts),
The catalyst design has the advantage that the molecular weight distribution and various regularities can be controlled.

When the olefin is polymerized in the presence of a metallocene catalyst, the molecular weight of the product can be controlled industrially in the same manner as the Ziegler catalyst, the reaction temperature and the α-in-system.
It can be performed by controlling the olefin concentration, the hydrogen concentration in the system, and the like. However, in the case of the metallocene catalyst, the hydrogen present in the polymerization tank has a greater effect on the molecular weight of the produced polymer, as compared with the Ziegler catalyst. It is necessary to polymerize Furthermore, the polymerization reaction using a metallocene catalyst has a peculiar problem that hydrogen is generated during polymerization. Due to the generated hydrogen, the concentration of hydrogen in the polymerization tank increases, and the desired molecular weight cannot be obtained easily.

The hydrogen concentration in the polymerization tank is controlled by the amount of hydrogen fed into the polymerization system even in the polymerization with a metallocene catalyst. In consideration of the amount of hydrogen generated, in order to obtain a product having a desired molecular weight, the polymerization is carried out at a much lower hydrogen concentration than that of the Ziegler catalyst. In addition, it is not uncommon for the molecular weight to change greatly within a very small hydrogen concentration range. Since the metallocene catalyst has a higher hydrogen concentration dependence than the Ziegler catalyst, it is extremely important to control the hydrogen concentration in the system. If the hydrogen concentration is too high, it becomes difficult to form a high molecular weight polymer, and thus it becomes difficult to form a desired polymer.

It can be said that in the metallocene catalyst, when the control of the hydrogen concentration in the system is insufficient and the hydrogen concentration fluctuates, the molecular weight or molecular weight distribution of the produced polymer tends to be unstable. This problem is serious in a so-called continuous polymerization method in which the raw material olefin is continuously supplied to the polymerization system to continuously carry out the polymerization reaction and the withdrawal of the produced polymer. That is, in the continuous polymerization method, unpolymerized (unreacted) olefin is generally recovered and circulated in the polymerization reactor, and the hydrogen concentration in the circulating olefin must also be considered.

JP-A-9-216913 describes an invention for selectively removing hydrogen in a polymerization reaction system in the polymerization of olefins using a metallocene catalyst. The hydrogen in the system is catalytically hydrogenated. It has been proposed to remove with a hydrogenation catalyst having. In addition, JP-A-10-204
No. 123 publication discloses that a part of the gas in the polymerization tank is extracted,
A method is disclosed in which hydrogen in the extracted gas is subjected to an addition reaction with an olefin using a hydrogenation catalyst to reduce the hydrogen concentration in the polymerization tank and control the amount of hydrogen. However, control by such methods is not stable due to changes in the performance of the hydrogenation catalyst, and is only for maintaining a low concentration of hydrogen in the system, and a polymer having exactly the desired molecular weight is obtained. Is still insufficient to obtain. Also from an industrial point of view, clogging due to the adhesion of polymers and catalysts to hydrogenation catalysts, deterioration of hydrogenation catalysts due to scattered polymers and catalysts, and reduction in capacity were observed, which is not sufficient for long-term continuous operation. is there.

[0008]

Therefore, in polymerizing an olefin in the presence of a metallocene catalyst, a technique for controlling the hydrogen concentration in the system so as to obtain a desired molecular weight, that is, in obtaining a product having a high molecular weight Therefore, it is desired to develop a control technique capable of immediately attaining a hydrogen concentration matching with the hydrogen concentration and immediately obtaining the hydrogen concentration matching with the hydrogen concentration when obtaining a low molecular weight product.

[0009]

Means for Solving the Problems In the method for producing an olefin polymer using such a metallocene catalyst, the present inventors immediately develop a hydrogen concentration corresponding to a desired product molecular weight if the desired product molecular weight is set. As a result of diligent research on the driving method that can accurately obtain the desired molecular weight,
By applying and controlling the method of purging the gas in the system, it became possible to control the hydrogen concentration in accordance with the desired hydrogen concentration setting, and found that an olefin polymer having a desired molecular weight can be obtained. The present invention has been completed. Therefore, the present invention provides a method for producing an olefin polymer, which comprises polymerizing an olefin using a metallocene catalyst and controlling the molecular weight of the olefin polymer produced according to the hydrogen concentration in the polymerization reaction system. When the molecular weight of the polymer is changed from the lower one to the higher one, the hydrogen concentration in the polymerization reaction system is decreased by increasing the gas purge amount outside the polymerization reaction system, and (2) the molecular weight of the polymer is increased. When changing from one to a lower one, the method is a process for producing an olefin polymer characterized by increasing the hydrogen concentration in the polymerization reaction system by decreasing the amount of gas purged to the outside of the polymerization reaction system.

Further, the present invention is a method for producing an olefin polymer, in which an olefin polymer is produced by polymerizing an olefin using a metallocene catalyst, and the molecular weight of the produced olefin polymer is controlled by the hydrogen concentration in the polymerization reaction system. In order to obtain an olefin polymer having a desired molecular weight, a method for producing an olefin polymer is characterized in that the amount of gas purged to the outside of the polymerization reaction system is determined in accordance with the amount of hydrogen generated in the polymerization reactor. According to the present invention, in the presence of a metallocene catalyst, when polymerizing an olefin, the hydrogen concentration in the system can be rapidly controlled to a hydrogen concentration that achieves a desired molecular weight, and particularly, a product group having various molecular weights. The effect is great when the is manufactured by continuous operation. The molecular weight as used in the present invention is described as meaning all weight average molecular weights.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrogen concentration in a polymerization system consists of a hydrogen balance as described below. The hydrogen balance is divided into (1) hydrogen that flows in and out and (2) hydrogen that flows out and consumes. (1) is the sum of hydrogen fed into the system and hydrogen generated in the system, and (2) is the sum of hydrogen going out of the system and hydrogen consumed in the system. It is as follows when this is further classified according to the contents.

(1) Inflowing / generating hydrogen The sum of the following (a) to (d) is obtained. (A) Amount of generated hydrogen: _HEV (mol / kg-Polymer) × W (kg /
hr) _HEV is the hydrogen generation amount (mol) per unit weight of the produced polymer.
/ kg-Polymer), and W is the polymer production amount (kg / hr). (B) Brought-in hydrogen amount from the previous stage: C (mol / hr) When the olefin polymerization is carried out by two-stage polymerization, there is hydrogen introduced from the preceding stage, and this is the carried-in hydrogen amount C. It can be measured. In the first-stage polymerization, C = 0. (C) Amount of hydrogen mixed with monomer: ΣMi (mol / hr) ×
[H ₂ ] _Mi (molar fraction) The amount of hydrogen brought in by mixing in the raw material olefin monomer is the i-th monomer feed amount Mi and the hydrogen concentration in the i-th monomer when i kinds of olefin monomers are used. It is the sum of products with H ₂ ] _Mi. When there is a circulating system of unreacted olefin, it is necessary to consider both the newly supplied olefin and the circulating olefin as the monomer. (D) Hydrogen feed amount: H _FD (mol / hr) alone represents the amount of hydrogen introduced into the polymerization system.

(2) Hydrogen that flows out and is consumed The sum of the following (e) to (g) is obtained. (E) Hydrogen consumption: H _CS (mol / kg-Polymer) × W (kg /
hr) Hydrogen consumed by chain transfer to the polymer in the polymerization reaction system, which is the hydrogen consumption amount H per unit weight of the produced polymer.
_CS (unit: mol / kg-Polymer) and polymer production amount W (unit:
kg / hr). (F) Amount of purged hydrogen outside the system: G _PG (mol / hr) × [H ₂ ]
_RA (molar fraction) The amount of hydrogen carried out by gas purging to the outside of the system is the product of the gas purge amount G _PG and the hydrogen concentration [H ₂ ] _{RA in} the reactor. (G) Amount of hydrogen accompanying polymer extraction: G _AC (mol / hr) ×
[H ₂ ] _RA (molar fraction) The amount of hydrogen generally lost when the produced polymer is extracted from the system is the amount of entrained gas G _AC and the hydrogen concentration in the reactor [H ₂ ] It is the product of _RA .

In the steady state, (1) inflowing / generating hydrogen and (2) outflowing / consuming hydrogen are balanced, so that (H _EV × W) + C + (ΣMi × [H ₂ ] _Mi ) + H _FD = a _{(H CS × W) + (} G PG × [H 2] RA) + (G AC × [H 2] RA) ··· (I). In the polymerization reactor, actually observable hydrogen generation amount H _EVOBS The apparent, H _EVobs = H _EV - since it is H _CS, By transforming the above formula _{(I), (H EVobs ×} W) + C + ( ΣMi × [H ₂ ] _Mi ) + H _FD = [(G _PG + G _AC ) × [H ₂ ] _RA ] ... (II)

In the formula (II), C, Mi, [H ₂ ]
_Mi , H _FD , G _PG and [H ₂ ] _RA can be measured respectively, G _AC can be calculated from the overall mass balance, and _{HE Vobs} can be measured in advance by experiments. Of these, C, [H ₂ ] _Mi , G _AC , and _HEVObs are values determined by the catalyst and process used, and thus if they are determined, the values are determined. Other M
i, H _FD , G _PG, and [H ₂ ] _RA change depending on the polymerization conditions, but if variables other than two of these are fixed, the remaining two variables are in a 1: 1 correspondence. Become. For example, if Mi and G _PG are fixed, [H ₂ ] _RA and H _FD are 1: 1.
Correspondingly, adjust [H ₂ ] by moving H _FD . In the Ziegler catalyst, the values of H _FD and [H ₂ ] _RA are sufficiently larger than the others, so it is common sense to control the hydrogen concentration with the hydrogen feed amount H _FD . But,
The metallocene catalyst, the value of H _EVOBS is or H _FD [H _2]
The value is _almost the same as the value of _RA , and in the more extreme case, the condition of H _FD = 0 is also possible. Therefore, depending on the gas purge amount G _PG
The aspect of controlling [H ₂ ] _RA has an important meaning as a delicate and precise hydrogen concentration control.

In the case of using a metallocene catalyst, the amount of hydrogen C introduced from the polymerization reactor of the previous stage even in the two-stage polymerization
Is extremely less than the Ziegler catalyst, for example,
In terms of concentration, 100 mol ppm (since the hydrogen concentration in the gas in the present specification is on a molar basis, hereinafter simply referred to as p
(displayed as pm)), which can be almost ignored. Further, since the olefin monomer as a raw material is usually for a polymer grade, the hydrogen concentration thereof is 0 or almost negligible. Therefore, C = 0, ΣMi
Since [H ₂ ] _Mi = 0, the formula (II) can be approximated as _HEVObs × W + H _FD = (G _PG + G _AC ) × [H ₂ ] _RA ... (III). Here, if the fed hydrogen amount H _FD is controlled to 0 or a constant amount, H _EVobs becomes a constant value in the metallocene catalyst used if the polymerization conditions are determined. Also, the polymer production amount W is almost constant under steady-state polymerization conditions. Also, since the amount of accompanying gas G _AC carried in withdrawing the polymer is almost constant, it is possible to control the hydrogen concentration [H ₂ ] _RA in the reactor with the gas purge amount G _PG after all. It means that

The production method of the present invention was carried out based on such a polymerization reaction analysis and many trials and errors. In the method for producing an olefin polymer using a metallocene catalyst, which has been difficult until now, the desired molecular weight can be accurately determined. The technology that can be controlled is provided.

The present invention will be described in more detail below. As the metallocene catalyst in the present invention, a conventionally known one can be used. As the metallocene catalyst, a metallocene (A) metallocene transition metal compound (metallocene complex) and a promoter component or other component are usually used. They are,
All of them are known, and for example, JP-A-9-216913.
All of those described in paragraph numbers 0015 to 0053 of the publication can be used. As a specific example of the metallocene-based transition metal compound (component A), when the transition metal is Zr, isopropylidene-bis (indenyl) zirconium dichloride, isopropylidene-bis (indenyl) zirconium dimethyl, dimethylsilyl (cyclo Pentadienyl) (fluorenyl) zirconium dimethyl, ethylene-bis (cyclopentadienyl) zirconium dichloride, dimethylsilyl-bis (cyclopentadienyl) zirconium dichloride, isopropylidene-bis (indenyl) zirconium (chloride) (tetraphenylborate) ) Tetrahydrofuran,
Examples thereof include dimethylsilylene bis [2-methyl-4- (2-fluoro-4-biphenyl) -4H-azurenyl] zirconium dichloride complex and the like. Also,
Of the metals of Groups 4, 5 and 6 of the periodic table other than zirconium, titanium and hafnium are particularly preferable metals, and also for the complexes thereof, the same compounds as mentioned above can be mentioned.

As the cocatalyst component and the like (component B) used in combination with the metallocene type transition metal compound, known compounds can be used, typically, an organoaluminum compound such as trialkylaluminum and an organoaluminum such as aluminoxane. An oxy compound, a 2: 1 reaction product of trimethylaluminum and methylboronic acid, aluminum chloride, tetraphenylboron, tetrakis (pentafluorophenyl) phosphorus, reacts with [A] such as a component to exchange the component [A] for a cation. It is preferable to use an ionic compound, a clay mineral, or the like that can be used. Examples of clay minerals include kaolin, bentonite, hummo group, montmorillonite group, vermiculite, ryokdeite group, kaolinite, nacrite, dickite, and halloysite.

<Catalyst Formation> The metallocene catalyst used in the present invention can be prepared by bringing the catalyst component A into contact with the catalyst component A, if necessary, in the polymerization tank or outside the polymerization tank. I can. In some cases
A prepolymerized product obtained by contacting this in the presence of an olefin such as ethylene, propylene, butene, and hexene to polymerize a small amount can also be preferably used.

<Production of Olefin Polymer> In the process for producing an olefin polymer according to the present invention, an olefin is polymerized in the presence of the above-mentioned metallocene catalyst. As the polymerization form,
Gas phase polymerization, bulk polymerization, slurry polymerization, etc. can be adopted. When the polymerization medium is a liquid or supercritical fluid, bulk polymerization or slurry polymerization is performed, and when the polymerization medium is gas, vapor phase polymerization is performed. In the present invention, it is particularly preferable to use gas phase polymerization. In the present invention, the polymerization reaction system includes a polymerization reactor and, if necessary, an external circulation system, and the polymerization reaction system may be provided outside the equipment having these two functions. Needless to say, a stirring device for the contents of the container, a device for discharging the produced polymer, a device for pumping fluid in the system of the external circulation system, and other devices are attached, and these devices, particularly the polymerization reactor and the external circulation, are attached. As described above, the entire system including the system may be referred to as “inside the system”.

In the present invention, (1) when changing the molecular weight of a polymer to be produced from a low molecular weight to a high molecular weight, the hydrogen concentration in the polymerization reaction system is increased by increasing the gas purge amount outside the polymerization reaction system. (2) When changing the molecular weight of the polymer to be produced from the higher one to the lower one, the hydrogen concentration in the polymerization reaction system is increased by decreasing the gas purge amount outside the polymerization reaction system. Here, it is assumed that the polymer having a low molecular weight has a weight average molecular weight of about 100,000 to 200,000 and the polymer having a high molecular weight has a molecular weight of about 200,000 to 1,000,000. The gas purge amount depends on the physical properties of the polymer being manufactured and the manufacturing environment. For example, if the purge rate of the circulating gas mainly composed of unreacted ethylene outside the polymerization reaction system is 10%,
In the process of continuously producing polyethylene having a weight average molecular weight of 150,000, when the molecular weight is changed to 300,000, a method of increasing the purge rate to 20 to 30% can be used. The rate of increase depends on the type of catalyst, polymerization temperature,
It is not unique because it depends on the residence time in the polymerization tank.
The hydrogen concentration in the newly supplied ethylene monomer may be changed along with the change of the purge rate, but it is preferable and convenient to deal with only the change of the purge rate.
At this time, the hydrogen concentration in the newly supplied ethylene monomer is preferably kept constant within the range of 0.01 to 10 ppm by mole (the hydrogen concentration in the gas in the present specification is on a molar basis). Further, in the present invention, in order to obtain an olefin polymer having a desired molecular weight, the amount of gas purged to the outside of the polymerization reaction system is determined according to the amount of hydrogen generated in the polymerization reaction tank.

The olefins used in the present invention include:
Α-Olefins having 2 to 18 carbon atoms are preferable, and examples thereof include ethylene, propylene, 1-butene, 1-pentene,
1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1
-Tetradecene, 1-hexadecene, 1-octadecene and the like. Polyenes such as butadiene, isoprene, 1,4-hexadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene may be copolymerized with these olefins. The copolymerization ratio when these polyenes are used is 10% of that of the copolymer.
It is not more than wt%, preferably 0.1 to 5.0 wt%.
In the present invention, among these, ethylene and a carbon number of 3 to
It is preferable to apply it to a process for continuously producing a propylene block copolymer in which 18-α-olefin is copolymerized or propylene is polymerized in the first stage and then ethylene-propylene is subsequently copolymerized.

As an example of the present invention, the olefin polymerization method (gas phase polymerization method) when the circulating fluid is a gas will be described in detail with reference to FIG. The polymerization method to which the present invention is applied is not particularly limited to a gas phase polymerization method, a slurry polymerization method, a solution polymerization method, a bulk polymerization method, or the like. Therefore, the gas phase reactor illustrated in FIG. 1 may be another type of fluidized bed reactor. For example, it may be a fluid contact reactor or a liquid phase reactor between two phases of solid gas or solid liquid. Known reactors can be used as these reactors, but as a gas phase polymerization reactor, a mechanically stirred fluidized bed reactor that mechanically stirs, and a gas is dispersed in the form of bubbles through a dispersion plate. Both bubbling fluidized bed reactors that perform the fluidization are included.

A gas phase reactor 1 shown in FIG. 1 is a stirring type fluidized bed type polymerization reactor, which is connected to a gas circulation line 2, a blower 3 and a powder withdrawal line 4, and is provided in the middle of the gas circulation line 2. A cyclone 5 and a gas purge line 6 are installed. During the olefin polymerization, a balance is maintained in the gas circulation line 2 such that the raw material monomer or (and) an inert gas such as nitrogen and hydrogen, if necessary, from the raw material feed line 7 maintain the pressure and composition in the reaction system. The blower 3 is driven to circulate these gases. Finally, the circulating gas is again used in the gas phase reactor 1
Is blown into. In the polymerization reactor, a fluidized bed is formed by particles introduced in advance or polymer particles generated by the polymerization, a raw material monomer, a fluid gas composed of an inert gas and the like, and a mechanically agitating stirring blade. This stirring blade
It is forcibly rotated by the motor installed at the bottom. It goes without saying that a fluidized bed system in which a fluidized gas is blown up outside the fluidized bed by such a stirring blade is also possible. In the gas phase reactor 1, the catalyst component A
Polymerization of the olefin is carried out by feeding separately and after pre-contacting B and B, or by feeding the polymer previously polymerized in the previous stage. The produced polymer is continuously or intermittently extracted via the powder extraction line 4.

The pressure in the gas phase reactor 1 is usually 1 to 100.
kg / cm ^2, preferably used at 1 to 50 kg / cm ^2, the temperature is usually 10 to 100 ° C., preferably 30 to 10
It is used at 0 ° C, more preferably 50 to 100 ° C. When the olefin is polymerized under a certain condition and the molecular weight of the produced polymer is lower than the desired value, the gas purge amount from the purge line 5 is increased to the amount calculated from the formula (I), By reducing the hydrogen concentration, a polymer having a desired molecular weight can be obtained. On the contrary, when the molecular weight of the produced polymer is higher than the desired value, the amount of gas purged from the purge line 5 is reduced to the amount calculated from the formula (I) to increase the hydrogen concentration in the reaction system. Thus, a polymer having a desired molecular weight can be obtained. Thus, the present invention can be applied to the case where the molecular weight of the produced polymer is changed from a predetermined value to a different predetermined value, and the desired molecular weight is maintained and managed, and also as a rapid response method in the case of deviation from the desired value. It can be applied effectively. Although the gas purged from the polymerization system may be discarded as it is by incineration, etc., it is usually separated into each raw material through a purification process such as distillation, and a part of it is reused for polymerization. It

[0027]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, the measuring method and apparatus of each physical-property value in an Example are shown below. (1) Hydrogen concentration The concentration of hydrogen in the monomer and in the polymerization tank was determined by gas chromatography (manufactured by Alignment Co., Intelligent Micro G).
It was measured using C). (2) The molecular weight of the rubber part The obtained polymer is heated and eluted by a fractionation device (manufactured by Mitsubishi Chemical Co.,
CFC-T-102L) was used to separate soluble components below 40 ° C by a cross fractionation method (TREF), followed by gel permeation chromatography (GPC150C manufactured by Waters).
Type apparatus and three columns of AD80M / S manufactured by Showa Denko were used), and orthodichlorobenzene was used as a solvent at a measurement temperature of 140 ° C. (3) Melt Flow Rate (MFR) Based on JIS-K6758 (230 ° C., 2.16 kg load), it was measured using a melt indexer (manufactured by Techno Seven).

Example 1 (1) As the metallocene complex of the metallocene catalyst component (A), dichloro {1,
1'-Dimethylsilylenebis [2-ethyl-4- (2-
Fluoro-4-biphenylyl) -4H-azulenyl]}
Hafnium was used. As a co-catalyst for the component (B), commercially available granulated montmorillonite (manufactured by Mizusawa Chemical Co., Inc., Benclay SL, average particle size: 28.0 μm) was used after being chemically treated with lithium hydroxide and excess sulfuric acid. When composition analysis was performed by fluorescent X-ray, the molar ratio of the constituent elements to silicon as the main component was Al / Si = 0.21, Mg / Si
= 0.046, Fe / Si = 0.022. In addition to the components (A) and (B), propylene was prepolymerized at 40 to 50 ° C. using triethylaluminum as the component (C), and polypropylene per 1 g of the component (B) was polypropylene 2.
A prepolymerized catalyst containing 0 g was obtained.

(2) First Stage Polymerization The prepolymerized metallocene catalyst was supplied to a liquid phase polymerization reactor together with liquefied propylene, hydrogen and triisobutylaluminum (TIBA) to produce a propylene homopolymer. The polymerization conditions are a polymerization temperature of 65 ° C. and a hydrogen concentration of 3
00 ppm, TIBA / propylene (weight ratio) is 21.
It was 2/90000 and the average residence time was 1.25 hours. The MFR of the obtained propylene homopolymer was 59.5 g /
After 10 minutes, the yield of polypropylene per 1 g of the component (A) was 7900 g.

(3) Second stage polymerization The polymerization system shown in FIG. 1 was used. In the gas phase reactor 1,
Propylene alone polymerized with metallocene catalyst in the first stage
The polymer was continuously fed at 17 kg / hr. Well
In addition, the gas entrained with the propylene polymer is sampled.
When ringing and measuring the hydrogen concentration, it was zero.
It was That is, C = 0 in the formula (I). Conflict
In the reactor 1, ethylene and propylene are passed through the route 6.
Is the gas composition ethylene 55 mol% in the gas phase reactor 1,
Propylene 45 mol%, polymerization temperature 65 ° C., pressure 1.
It was continuously supplied so as to be kept constant at 2 MPa. This d
When the hydrogen concentration in the ethylene and propylene gas was measured
It was zero. That is, in the formula (I)
[H₂]_Mi Was 0. Note that hydrogen was not supplied
However, due to the hydrogen generated during the polymerization, the water in the gas phase reactor 1
The elementary concentration was 50 ppm. Polymer produced is 1
Extracted from the extraction line 4 at 9.3 kg / hr
It was At this time, it is discharged from the gas phase reactor 1 along with the powder.
The gas discharged was 4.2 kg / hr. Sanawa
The polymer production amount W in the gas phase reactor 1 is 2.3 kg.
/ Hr, the residence time of the powder in the gas phase polymerization tank is 1
Time, at this time purged from the purge line 5 to the outside of the system
The gas purge amount was 18.5 kg / hr. this
From these data and formula (I), H under these conditions_EVobs
Is 14.4 × 10 ^-3mol / kg-polymer
Calculated. Hydrogen concentration whose correlation was measured in advance
When the hydrogen concentration is 50ppm from the relationship between the molecular weight and
Was predicted to have a molecular weight of 370,000, but actually measured 3
It is 60,000, and it is confirmed that it almost matches the predicted value.
It was

<Example 2> Propylene according to Example 1
The production of the ethylene block copolymer was stably operated for 24 hours continuously. Then in the second stage polymerization of Example 1, the catalyst,
The operating conditions were changed in the gas circulation system in order to obtain a polymer having a molecular weight of 420,000 without changing the polymerization conditions (gas composition, temperature, pressure, etc.) and other conditions at all. First, FIG.
It was found that the more necessary hydrogen concentration was 15 ppm. Next, the hydrogen concentration and other values were substituted into the formula (I), and the gas purge amount was increased to the calculated 71.5 kg / hr. About 30 minutes after the gas purge amount became stable, the hydrogen concentration in the gas phase reactor was measured, and the hydrogen concentration in the reactor was 16 ppm. The molecular weight of the powdery polymer obtained after about 3 hours when the gas phase concentration was stable was 41.
It was confirmed that a polymer having a molecular weight close to the target was obtained.

<Example 3> Propylene according to Example 2
The production of the ethylene block copolymer was stably operated for 24 hours continuously. Then, in the second stage polymerization of Example 2, the catalyst,
In order to obtain a polymer having a molecular weight of 310,000 without changing the polymerization conditions (gas composition, temperature, pressure, etc.) and other conditions at all, the operating conditions were changed in the gas circulation system. First, FIG.
It was found that the more necessary hydrogen concentration was 100 ppm. Next, each value including the hydrogen concentration was substituted into the formula (I), and the gas purge amount was reduced to the calculated 7.2 kg / hr. About 30 minutes after the gas purge amount became stable, the hydrogen concentration in the gas phase reactor was measured and found to be 98 ppm.
Also, the powdery polymer obtained after about 3 hours with stable gas phase concentration had a molecular weight of 310,000, and it was confirmed that a polymer close to the target molecular weight was obtained.

[0033]

According to the present invention, in the presence of a metallocene catalyst, when polymerizing an olefin, the hydrogen concentration in the system can be rapidly controlled, and an olefin polymer having a desired molecular weight can be easily produced. can do. In particular, the effect is great when a product group of various molecular weights is manufactured by continuous operation.

[Brief description of drawings]

FIG. 1 shows an example of a polymerization system (gas phase polymerization method).

FIG. 2 shows an example of a correlation diagram between hydrogen concentration and weight average molecular weight.

[Explanation of symbols]

1: Gas phase reactor 2: Gas circulation line 3: Blower 4: Powder extraction line 5: Cyclone 6: Gas purge line 7: Raw material feed line

Claims (5)

[Claims] 1. A process for producing an olefin polymer, which comprises polymerizing an olefin using a metallocene catalyst, wherein the molecular weight of the olefin polymer produced is controlled by the concentration of hydrogen in a polymerization reaction system. When changing the molecular weight of the coalescence from low to high, decrease the hydrogen concentration in the polymerization reaction system by increasing the amount of gas purged to the outside of the polymerization reaction system,
(2) When the molecular weight of the polymer is changed from a higher one to a lower one, the hydrogen concentration in the polymerization reaction system is increased by decreasing the amount of gas purged to the outside of the polymerization reaction system. How to make a coalesce. 2. A method for producing an olefin polymer in which an olefin polymer produced by polymerizing an olefin using a metallocene catalyst is controlled by the concentration of hydrogen in a polymerization reaction system, the olefin having a desired molecular weight. A process for producing an olefin polymer, characterized in that the amount of gas purged to the outside of the polymerization reaction system in order to obtain the polymer is determined according to the amount of hydrogen generated in the polymerization reactor. 3. The method for producing an olefin polymer according to claim 1, wherein the polymerization of the olefin is carried out in a gas phase in which the metallocene catalyst flows. 4. The olefin polymer according to claim 1, wherein at least a part of the gas flowing out from the polymerization reactor is circulated to the original polymerization reactor as unreacted olefin. Manufacturing method. 5. The olefin polymer according to any one of claims 1 to 4, wherein the hydrogen concentration in the olefin newly supplied to the polymerization reactor is constant in the range of 0.01 to 10 ppm. How to make a coalesce.