JPS6335164B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new catalyst for olefin polymerization. Traditionally, polymerization of olefins such as ethylene requires
It is well known that a so-called Ziegler catalyst, which is a combination of a transition metal compound of groups a to a of the periodic table and an organometallic compound of a metal of groups a to a of the periodic table, is effective. However, many of the catalysts known so far have insufficient polymerization activity for industrial production, and it is difficult to use them as products without separating and removing catalyst residue from the obtained polymer. Ta. Furthermore, when producing polyethylene by so-called slurry polymerization, in which the polymerization reaction is carried out in a temperature range such as 90°C, where the polymer does not substantially dissolve in the hydrocarbon dispersant, and the polymer is recovered in the form of a solid powder, Productivity is determined by the bulk density of the polyethylene powder produced, and hitherto known catalysts have not always given satisfactory results. The object of the present invention is to provide a polymer having an extremely narrow molecular weight distribution, for example, a ratio (M _W /M _{N ) of weight average molecular weight (M W ) to number average molecular weight (M N ) of} less than 3, without having the above-mentioned drawbacks. The object of the present invention is to provide a catalyst suitable for producing polyethylene. That is, an object of the present invention is to provide a highly active catalyst for producing polyethylene powder with an extremely narrow molecular weight distribution and high bulk density. A typical method for manufacturing Ziegler catalysts with extremely high catalytic efficiency is to use elements from Group Group of the periodic table,
In particular, a method is known in which a transition metal compound is supported on a solid compound containing Mg. For example, a typical catalyst comprising magnesium chloride or a product based on magnesium chloride, which is closely related to the present invention, as a carrier, and a chloride or chlorine compound of a transition metal such as titanium is disclosed in Japanese Patent Publication No. 12105/1983. , 46-
Publication No. 34092, Publication No. 47-41676, Publication No. 47-46269
There are publications etc. These provided catalysts have considerably improved activity per transition metal as a result of the effective use of transition metal compounds, but the activity of the catalyst including the carrier is still insufficient, and the polyethylene produced It is difficult to say that the molecular weight distribution of is extremely narrow. All of the methods described here are methods in which a solid carrier having solid physical properties or composition is brought into contact with a gaseous, liquid, or solid transition metal compound. Dispersibility can be considered to have its own limits. On the other hand, a method is also known in which a liquid (ie, solution) Mg compound is used as a reducing agent and a liquid transition metal compound is brought into contact with the reducing agent. For example, Japanese Patent Publication No. 47-40959 usually uses a solid catalyst obtained by reducing a transition metal compound in the maximum valence state, such as TiCl ₄ , with RMg (OR') (R and R' are hydrocarbon residues). This is what we provide. Although the activity of the catalyst obtained here is considerably higher than that of low-valent transition metal compounds obtained by reduction with ordinary organoaluminum compounds, it is still not sufficient. As described above, the so-called Ziegler-Natsuta type catalyst, which has a group metal compound mainly composed of Mg, is produced by contacting the Mg compound as a solid with a transition metal compound or by contacting the liquid Mg compound as a reducing agent. It is broadly divided into methods. However, neither of these methods can achieve the object of the present invention. The reason for this is that in the former case, there is a lack of uniform dispersion of the transition metal compound into the solid Mg compound carrier, and in the latter case, there is an upper limit on the amount of Mg compound that can be incorporated into the solid low-valent transition metal compound. This seems to be due to the fact that it is impossible to synthesize a solid containing a sufficient amount of Mg to uniformly disperse Ti(). From the above-mentioned point of view, _the present inventors first discovered that two types of transition metals represented by the general formula (Ti _n V _1-n ) Complex i.e. TiX ₃・n′Y
The present inventors have revealed that a complex obtained by precipitating from an _ether solution containing Furthermore, Mg and Ti as shown below
The product obtained by contacting the tetrahydrofuran complex of halide () with an organoaluminum compound in an inert medium is excellent as a catalyst component for olefin polymerization, and has an extremely narrow molecular weight distribution and bulk density in polymerization in the coexistence of an organoaluminum compound. It has been found that a polymer with high yield can be obtained in high yield. That is, the present invention is based on the general formula [ _{Mg o} Ti () _1-o ] <
4, x represents a number of 1<x<3. ) The present invention relates to a method for activating a complex, which comprises bringing the complex represented by the following formula into contact with an organoaluminum compound in an inert medium. Next, the present invention will be explained in more detail. The complex of the general formula () can be produced using a titanium tetrahalide tetrahydrofuran complex and a magnesium halide tetrahydrofuran complex as precursors. The tetrahalogenated titanium tetrahydrofuran complex has the general formula shown below. TiX ₄ ·pY ... () (X: halogen atom, Y: tetrahydrofuran, p=2) The synthesis of this complex has already been reported in detail in the literature. For example (A) Journal of Inorganic & Nuclear
Chemistry (Pergamon Press Ltd, Vol24,
1105-1109 (1962) United Kingdom) (B) Die Natu¨rwissenschaften (Jahrgang46,
171 (1959) Germany) That is, a tetrahydrofuran solution of the complex is prepared by dissolving titanium tetrahalide in an excess of tetrahydrofuran, and the complex is prepared by cooling or concentrating it or adding a poor solvent such as a hydrocarbon solvent. This is a method of precipitating crystals. It goes without saying that the purity can be increased by repeating recrystallization. The tetrahydrofuran complex of magnesium halide is an ether-easily soluble complex having the general formula MgX ₂ .p'Y (1p'2)...(). _ZnCl2・
2THF (THF: Tetrahydrofuran), _NiCl2・
2THF and MnCl ₂・1.5THF, FeCl ₂・1.5THF
Although the synthesis and physical properties of ether complexes of divalent metal halides are known (see the above-mentioned document (A)), the description of these compounds in the literature is not comprehensive. However, as shown in the reference examples, it can be synthesized according to a similar method. The compound used as complexing agent and solvent in the preparation of the above complexes is tetrahydrofuran (THF). The titanium tetrahalide tetrahydrofuran complex of the general formula () is easily soluble in tetrahydrofuran, and the magnesium halide tetrahydrofuran complex of the general formula () is also easily soluble in tetrahydrofuran, so by coprecipitating these complexes from an ether solution, The complex of the general formula () can be easily produced. Methods for co-precipitating a titanium tetrahalide tetrahydrofuran complex and a magnesium halide tetrahydrofuran complex from a tetrahydrofuran solution in which they are dissolved include, for example, a method of cooling the solution, a method of adding a poor solvent such as a hydrocarbon, and a method of removing tetrahydrofuran by evaporation. method etc. can be adopted. In any case, it is preferable to remove excess tetrahydrofuran. What is interesting here is that when tetrahydrofuran solutions, especially saturated solutions, of the titanium tetrahalide tetrahydrofuran complex and the magnesium halide tetrahydrofuran complex are brought into contact with each other, a precipitate is formed. Needless to say, no reduction reaction occurs during contact between the two. Nor is it conceivable that precipitation may occur due to common ion effects or other causes. After all, it is presumed that a different type of complex with inferior solubility is formed by contact between the two complexes. Further, the complex of the general formula () is the Mg, Ti
It can be produced not only by a method of co-precipitating both components from a tetrahydrofuran solution, but also by other methods. As a specific method, it can be produced, for example, by pulverizing both components of the tetrahydrofuran complex together in a ball mill. However, the method of co-precipitation from the above-mentioned tetrahydrofuran solution is preferred because it is easy to perform. According to the present invention, the complex of the general formula () synthesized according to the above method becomes an extremely useful catalyst component by contacting it with an organoaluminum compound in a known inert medium such as hexane. By using this compound in combination with an organoaluminum compound in a polymerization system,
Shows excellent olefin polymerization activity. In this respect, titanium tetrahalide ether complexes exhibit similar behavior. However, the titanium tetrahalide ether complex not only has extremely low activity, but also cannot be recovered even if polymerization is carried out using a hydrocarbon solvent at a temperature such as 80°C, i.e., under conditions where the polymer is not substantially dissolved. The polymer exhibits a fibrous form with a significantly low bulk density. If such a fibrous polymer is produced, it not only becomes undesirable in terms of the properties of the polymer itself, but also undesirable in terms of the polymerization process, such as increased stirring torque and difficulty in controlling internal temperature, as is clear from comparative examples. More points. What the present inventors could not have predicted was that when the complex obtained by activating the complex of the general formula () according to the present invention is used, not only the polymerization activity is significantly improved, but also the polymerization conditions described above are improved. When so-called slurry polymerization is carried out, the recovered polymer is in the form of a powder with a high bulk density. A further interesting fact is that the molecular weight distribution of the obtained polymer is extremely narrow. When an activated product of the complex obtained by the method of the present invention is used together with an organoaluminum compound to polymerize an olefin according to the method described below, a polymer can be obtained with extremely high catalytic efficiency. That is, for example, it is easy to obtain 30,000 gr or more of polymer per hour at 90° C. per 1 gr of Ti, per 1 kg/cm ² pressure of ethylene. The molecular weight distribution of this polymer is extremely narrow, and a preferable value such as (M _W /M _N )3 can be achieved, for example. As the organoaluminum compound used to activate the complex of general formula () according to the present invention, known organoaluminum compounds used as cocatalysts in polymerization reactions can be used. In addition, when the activated product of the complex of the general formula () obtained by the present invention is subjected to polymerization, the organoaluminum compound used in combination as a cocatalyst is one of the general formula AlR _o X _3-o (R; C number 1 _to 14 saturated _hydrocarbon residues, A compound represented by the general formula AlRR′R″ (where R, R′, and R″ are the same or different from each other) is preferable. C number 1
-14 saturated hydrocarbon residues) Most preferred are trialkylaluminums represented by: -14 saturated hydrocarbon residues. For example, Al(C ₂ H ₅ ) ₃ , Al(n-C ₄ H ₉ ) ₃ , Al
Examples include (iso-C ₄ H ₉ ) ₃ and Al(n-C ₈ H ₁₇ ) ₃ . The amount of these organoaluminum compounds used is per mole of transition metal contained in the complex used.
A range of 0.5 to 100 mol is preferred, particularly a range of 2 to 50 mol. The polymerization of ethylene using a catalyst comprising an activated product of the complex obtained according to the method of the present invention in combination with an organoaluminum compound is carried out in exactly the same manner as when using a conventional Ziegler type catalyst. The polymerization temperature is in the range of room temperature to 200°C, but in order to fully exhibit the characteristics of the catalyst of the present invention, an appropriate inert solvent such as n-hexane, n-heptane, etc. should be used in the range of 60°C to 100°C. It is preferable to carry out so-called slurry polymerization to recover a powdery polymer having a high bulk density. Although there are no particular restrictions on the polymerization pressure, a pressure of 20 kg/cm ² or less is usually sufficient because of the high activity. When polymerizing ethylene, control of the degree of polymerization is achieved by introducing an appropriate amount of hydrogen into the polymerization zone. In addition, ethylene and other α-
It is also possible to obtain these copolymers by copolymerizing olefins such as propylene, butene-1, hexene-1, etc. In the case of copolymerization,
It is preferable that α-olefin other than ethylene be present in a molar concentration of 5% or less in the gas phase. The catalyst obtained by combining the activated product of the complex obtained according to the method of the present invention with an organoaluminum compound has extremely high activity as described above, so it is sufficient to use a small amount. This method is extremely advantageous industrially since the catalyst removal step can be omitted. FIG. 1 shows a flowchart of the present invention,
The gist of the present invention is not limited to this. Next, the present invention will be described in more detail with reference to Examples and Reference Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded. In addition, the molecular weight in the examples of the present invention is a viscosity average molecular weight (M _V ), and was calculated based on the following formula. [η] 4.60×10 ^-4 M ^0.725 However, [η] is the intrinsic viscosity measured at 130°C in tetrahydronaphthalene solvent. The molecular weight distribution (M _W /M _N ) was determined by the column fraction method. The measurement method for MI (Melt Index) is ASTM D-
Measured at 190°C in accordance with 1238T. Reference example 1 - Production of TiCl _4.2THF - Dehumidifying in a four-necked flask under an argon gas atmosphere.
300ml of deoxygenated n-hexane and
Supply 60 mmol of _TiCl4 . The flask is placed in a water bath, and 180 mmol of tetrahydrofuran (THF) is added dropwise with stirring while maintaining the internal temperature at 0 to 5°C, producing a yellow precipitate. Continue stirring for about 30 minutes,
The resulting solid powder is thoroughly washed repeatedly with purified n-hexane. This was dried under reduced pressure at room temperature to obtain a yellow powder. The analytical values (weight %) are as follows.

[Table] Reference Example 2 - Production of MgCl ₂ 1.5THF - Using a Soxhlet extractor, 10 gr of commercially available bulk anhydrous MgCl ₂ was extracted under reflux with 250 ml of dehydrated and deoxygenated THF under an argon gas atmosphere. After about 20 hours, almost no MgCl ₂ solids are visible. Concentrate the extract to approximately 100ml. This was allowed to cool to room temperature and then dried under a stream of dry nitrogen gas to reach a constant weight. The analytical values were as follows.

[Table] Example 1 TiCl _4.2THF (synthesized in Reference Example 1) in a 100ml four-necked flask with a stirrer under an argon gas atmosphere.
7.0 mmol (2.26 gr) is collected, and 45 ml of THF, which has been dehumidified and further removed from dissolved oxygen gas, is supplied and stirred at room temperature. A clear yellow solution was obtained. On the other hand, in a 200ml four-necked flask with a stirrer immersed in a constant temperature bath at 25℃ under an argon gas atmosphere.
MgCl ₂・1.5THF (synthesized in Reference Example 2) 8.4 mmol
(1.84gr) and supplied 20ml of the above THF.
Stirring at room temperature gave a clear colorless solution. Add the above TiCl _4.2THF to this under stirring.
When the solution is gradually added dropwise, a pale yellow precipitate forms.
After continuing to stir for 1 hour, the precipitate was filtered off.
After thoroughly washing this with purified n-hexane, it is dried under reduced pressure at room temperature. The elemental analysis value (weight %) and the formula of the powder obtained here are shown below.

[Table] In addition, when powder X-ray diffraction was measured on the obtained powder, the obtained X-ray diffraction image showed that it was the raw material.
The X-ray diffraction images were completely different from those of TiCl _4.2THF and MgCl _2.1.5THF . This shows that the complex of the present invention is not a mixture of TiCl _4.2THF and MgCl _2.1.5THF . After replacing an autoclave with a stirrer with a capacity of 1 with sufficient nitrogen gas, 25 mg of the above solid powder and Ali
-Bu ₃ [Al(iso-C ₄ H ₉ ) ₃ ] 0.45 mmol (i.e. Al/Ti
=15/1 (mol/mol)] and 500 ml of purified n-hexane to activate the above complex.
After heating to 90℃, ethylene 5Kg/cm ² and hydrogen 4
Polymerize ethylene at Kg/cm ² and after 1 hour
119.5gr of polyethylene powder was obtained. The polymerization activity and properties of the polymer were as follows. K=960 (gram polymer/gram catalyst・Kg/cm ² ethylene pressure・time) K _Ti =16400 (gram polymer/gram Ti・Kg/cm ² ethylene pressure・time) Bulk density=0.35gr/cc MI= 4.3 M _W /M _N = 2.9 Example 2 In the complex production of Example 1, twice the amount of each
_MgCl2・1.5THF (16.8mmol) and double amount of THF
A THF solution of MgCl _2.1.5THF containing (40 ml) was used, and a solution of TiCl _4.2THF equivalent to that in Example 1 was added to this.
By dropping the THF solution, a yellow complex with the following composition (% by weight) and the following formula was obtained.

[Table] In addition, when powder X-ray diffraction was measured on the obtained complex, the obtained X-ray diffraction image showed that the raw material
The X-ray diffraction images were completely different from those of TiCl _4.2THF and MgCl _2.1.5THF . This shows that the complex of the present invention is not a mixture of TiCl _4.2THF and MgCl _2.1.5THF . This complex was activated under the same conditions as in Example 1, and ethylene polymerization was carried out to obtain 80 gr of polyethylene powder. The polymerization results are as follows. K = 640 K _Ti = 18800 Bulk density = 0.33gr/cc MI = 4.8 M _W /M _N = 2.8 Example 3 The same operations as in Example 1 were carried out except that the amount of Ali-Bu ₃ was changed, and the following procedure was carried out. Got the results.

[Table] Example 4 The same operations as in Example 1 were performed except that the type of organoaluminum compound was changed, and the following results were obtained.

[Table] Example 5 In Example 1, the partial pressure in the polymerization zone was 0.4
Propylene equivalent to Kg/cm ² was fed, and an ethylene-propylene copolymerization reaction was carried out. number of carbons
128.3 gr of a copolymer having 4.3 side chain methyl groups per 1000 pieces was obtained. Side chain methyl was measured using infrared absorption spectroscopy.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing one embodiment of the present invention.

Claims (1)

[Claims] 1. General formula [Mg _o Ti() _1-o ]X _n ·xY (in the formula,
is a halogen atom, Y is tetrahydrofuran, n is 0.01 to 0.99, m is 2<m<4, x is 1<
Indicates the number of x<3. ) A method for activating a complex, which comprises bringing the complex represented by the following formula into contact with an organoaluminum compound in an inert medium.