JPS6335163B2 - - 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 has been difficult to directly convert the resulting polymer into a product without separating and removing the catalyst residue. . 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 achieve an extremely narrow molecular weight distribution without having the above-mentioned drawbacks, for example, the ratio of weight average molecular weight (M _W ) to number average molecular weight (M _N ) (M _W /
An object of the present invention is to provide a catalyst suitable for producing polyethylene, in which M _N ) is smaller than 3. 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 discloses a solid catalyst obtained by reducing a transition metal compound in the maximum valence state, such as TiCl ₄ , with R Mg (OR') (R and R' are hydrocarbon residues). It provides: 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 a uniform dispersing agent for the transition metal compound in the solid Mg compound carrier, and in the latter case, the amount of Mg compound incorporated into the low-valent transition metal compound solid is stoichiometric. This seems to be due to the physical limitations, namely, the impossibility of synthesizing 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 a 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 ] <
3, x represents a number of 1<x<3. ) is brought 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 trihalide/tetrahydrofuran complex and a magnesium halide/tetrahydrofuran complex as precursors. The titanium trihalide/tetrahydrofuran complex has the general formula shown below. TiX ₃ · pY ... () (X: halogen atom, Y: tetrahydrofuran, p = 2 or 3). Regarding the synthesis of the complex,
It 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¨rwissenschafton (Jahrgang46,
171 (1959) Germany) That is, a tetrahydrofuran solution of the complex is prepared by dissolving or extracting titanium trihalide with an excess of tetrahydrofuran under reflux,
This is a method in which the complex crystals are precipitated by cooling or concentrating the mixture, or by adding a poor solvent such as a hydrocarbon solvent. It goes without saying that the purity can be increased by repeating recrystallization. The tetrahydrofuran complex of magnesium halide has the general formula MgX ₂ .p'Y (1p'2) ... () and is easily soluble in ether. _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 such as
The description of p′Y 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). Titanium trihalide is normally a solid, and in order to support it on a solid carrier, it can be prepared using a ball mill (Japanese Patent Publication No. 47-46269) or under reduced pressure.
Vaporize and support at ℃ (Special Publication No. 46-34092)
The following methods have been adopted. On the other hand, the titanium trihalide/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 these complexes can be precipitated from a tetrahydrofuran solution. By doing so, the complex of the general formula () can be easily produced. There is no particular restriction on the method of precipitating the titanium trihalide/tetrahydrofuran complex and the magnesium halide/tetrahydrofuran complex from an ether solution in which they are dissolved. For example, a method of cooling the solution, a method of adding a poor solvent such as a hydrocarbon, a method of removing tetrahydrofuran by evaporation, etc. can be adopted. In any case, it is preferable to remove excess tetrahydrofuran. Further, the complex of the above general formula () of the present invention is the above-mentioned complex.
It can be produced not only by the method of co-precipitating both Mg and Ti 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 Pall mill. However, the method of co-precipitation from the tetrahydrofuran solution is preferred because it is easy to operate. According to the present invention, the complex () 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. When used in combination with an organoaluminum compound in a polymerization system, this product exhibits excellent olefin polymerization activity and can yield a polymer with extremely high catalytic efficiency. 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. When the activated product of the complex of the general formula () obtained by the present invention is subjected to polymerization, the organoaluminum compound used as a cocatalyst may be one of the general formula AlR _o X _3-o (R; C number 1 to 14 saturated hydrocarbon residues, X;
halogen, n=2 or 1.5) and an alkylhaloaluminum compound represented by the general formula AlR _o (OR') _3-o (R, n; same as above, R'; a saturated hydrocarbon residue having 1 to 14 carbon atoms, and R The compound represented by the general formula AlRR′R″ (R, R′, R″ may be the same or different from each other) is preferable.
-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 ₆ 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, a suitable inert solvent such as n-hexane, n-heptane, etc. is used in the range of 60°C to 100°C. However, 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 due to 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. It is also possible to obtain these copolymers by copolymerizing ethylene with other α-olefins such as propylene, butene-1, hexene-1, etc. In the case of copolymerization, the α-olefin other than ethylene is preferably present at 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 (Mv), 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. Reference example 1 - TiCl ₃・3THF and TiCl ₃・2THF
Production - Using a Soxhlet extractor, 6g of titanium trichloride (titanium tetrachloride reduced with hydrogen) was extracted under reflux with 300ml of dehydrated and deoxygenated tetrahydrofuran (THF) under an argon gas atmosphere. about
After 10 hours, titanium trichloride was almost completely dissolved.
The THF phase became a deep purple-brown color. By cooling this all day and night, blue solid crystals precipitate out.
The mixture was washed with purified n-hexane and dried at room temperature under a stream of dry nitrogen gas to obtain a sky blue solid powder. The analytical values (% by weight) of the solid obtained by recrystallizing this twice using purified THF are shown.

[Table] Approximately twice the amount of purified n-hexane was added dropwise to the purplish-brown THF solution prepared by the above method while stirring, and the precipitate was further washed with n-hexane.
It was dried at room temperature under nitrogen gas flow to obtain a yellow-green powder.

[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 (weight %) were as follows.

[Table] Example 1 TiCl _3.3THF4.1gr produced in Reference Example 1 was placed in a 14-necked flask equipped with a stirrer under an argon seal.
Add 130 ml of purified THF and dissolve while stirring. To this was added 7.3g of the magnesium chloride complex powder produced in Reference Example 2, and the mixture was stirred and dissolved at 60°C for 2 hours. Purified n cooled to room temperature, dehydrated and deoxidized
- 500ml of hexane was added dropwise. The precipitate was separated by decantation, washed three times with purified hexane, and then dried. The analytical values (wt%) of the obtained complex were Ti5.0, Mg9.5, Cl41, C30, which corresponded to [Mg _0.8 ·Ti _0.2 ]Cl _2.2 ·(THF) _1.2 . In addition, when powder X-ray diffraction was measured on the obtained complex, 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 _3.3THF and MgCl _2.1.5THF . From this,
The complex of the present invention is TiCl _3.3THF and MgCl _2.1.5THF .
It can be seen that it is not a mixture of 500 in one autoclave purged with nitrogen gas
ml of purified n-hexane and Al (iso-
After adding 0.5 mmol of C ₄ H ₉ ) ₃ , 25 mg of the complex was added to activate the complex. After replacing the gas phase with hydrogen gas, the temperature was raised to 90°C and constant pressure polymerization was continued at a hydrogen pressure of 5 kg/cm ² and an ethylene pressure of 5 kg/cm ² for 1 hour, resulting in a bulk density of 0.31 g/cc and a molecular weight of 46,000. 232 gr of polyethylene powder was obtained. The polymerization activity per catalyst is K=1850 (gr-polymer/
gr-catalyst x P x hr) Polymerization activity per Ti is K _Ti = 37000 (gr-polymer/
gr―Ti×P×hr) However, P=ethylene pressure (Kg/cm ² ) The molecular weight distribution of the polymer is extremely narrow M _W /M _N =
It was 2.9. Example 2 The same treatment as in Example 1 was carried out using 2.5 gr of TiCl ₃ · 2 THF produced in Reference Examples 1 and 2 and 7.3 gr of magnesium chloride complex instead of TiCl ₃ · 3 THF,
A complex containing 3.9wt% Ti was produced. Using this complex, polymerization was performed under the same conditions as in Example 1, resulting in a polymer powder with a bulk density of 0.3 gr/cc and an average molecular weight of 48,000.
Got 190gr. K = 1520, K _Ti = 39000, M _W /M _N = of the polymer
3.1 The analytical value (weight%) of this complex is
Mg10.9, Ti3.9, Cl40.8, C29.5, which corresponds to [Mg0.85・Ti0.15]Cl2.10・(THF)1.15. Furthermore, when powder X-ray diffraction was measured for the obtained complex, the obtained X-ray diffraction image was completely different from the X-ray diffraction images of the raw materials TiCl _3.2THF and MgCl _2.1.5THF . Ta. This indicates that the complex of the present invention has TiCl ₃ 2THR and MgCl ₂
It can be seen that it is not a mixture with 1.5THF. Comparative Example 1 TiCl _3.3THF produced in Reference Example 1 was used as it was, and polymerization was carried out under the same conditions as in Example 1.
Only 5.8 gr of polymer with an average molecular weight of 76,000 was obtained. K=46 Example 3 The polymerization reaction of Example 1 was carried out by changing the hydrogen pressure, and the following results were obtained.

[Table] Example 4 In Example 1, a polymerization reaction was carried out by changing the amount and type of the organoaluminum compound used as a cocatalyst, and the following results were obtained.

[Table] Example 5 Under the same conditions as in Example 1, propylene was fed so that the molar concentration ratio of propylene to ethylene in the gas phase was 0.036, and a copolymerization reaction was carried out. 228 gr of a copolymer containing 4.7 methyl side chains per 1000 carbon atoms was obtained. (M _W /M _N ) of this copolymer
It was =2.8. Side chain methyl was measured using infrared absorption spectroscopy. Example 6 TiCl ₃ produced in advance and purified in Example 1
Instead of using a solution obtained by dissolving 3THF and MgCl _2.1.5THF in THF, TiCl ₃ (20 mmol) and 20 mmol of commercially available bulk anhydrous MgCl ₂ were used, respectively.
The following results were obtained by carrying out the same operation except that the solution obtained by extraction and dissolution with 130 ml of THF was mixed and concentrated to about half the volume.

【table】

[Table] The analysis values (weight%) of the complex are Ti9.2, Mg5.6,
Cl36, C33 [Mg _0.55・Ti _0.45 ]Cl _2.4 (THF) _1.
Corresponds to ₆ . In addition, when powder X-ray diffraction was measured for the obtained complex, the obtained X-ray diffraction image was TiCl ₃ .
The X-ray diffraction images were completely different from those of 3THF and MgCl ₂ .1.5THF. This shows that the complex of the present invention is not a mixture of TiCl ₃ .3THF and MgCl ₂ .1.5THF.

[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<3, 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.