JPS584932B2 - Method for producing polyethylene with controlled molecular weight distribution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyethylene with a controlled molecular weight distribution, and more particularly to a method for producing polyethylene with a wide molecular weight distribution and excellent moldability by using a specific catalyst.

Conventionally, as a method for producing polyethylene with a wide molecular weight distribution and excellent moldability, there is a method known as JP-A No. 48-4858.
A method described in Publication No. 4 is known.

According to this method, one of the components of the catalyst used is prepared by reacting an inorganic magnesium compound with an inorganic compound of a Group 2 to 8 metal in a titanium halide in the presence of an electron donor.

However, since this catalyst uses various compounds as raw materials, it is difficult and time-consuming to prepare, and the quality of the catalyst obtained is uneven.Therefore, it is difficult to reproducibly prepare a catalyst with a certain performance and stable quality. was difficult.

Therefore, the present inventors have conducted extensive research in order to develop a method for efficiently producing polyethylene with a wide molecular weight distribution using a melting medium that has good reproducibility and is easy to operate.

As a result, they found that the object could be achieved by using a reaction product of magnesium hydroxide and ariminium alkoxide as a magnesium compound, which is one of the catalyst components, and completed the present invention.

That is, the present invention provides a method for polymerizing ethylene using a catalyst containing a reaction product of a magnesium compound and a titanium halide and an organoaluminum compound, which is obtained by contacting magnesium hydroxide with an aluminum alkoxide as the magnesium compound. The present invention provides a method for producing polyethylene with a controlled molecular weight distribution, which is characterized by using a substance.

The aluminum alkoxide used in the present invention is generally 2Al(OR)3 [R represents an alkyl group.

] Specific examples thereof include aluminum methoxide, aluminum ethoxide, aluminum isopropoxide, aluminum benzoxide, and the like.

These can be obtained by known methods such as adding aluminum powder to anhydrous alcohol and heating it, or reacting mercury chloride and iodine as a catalyst in a xylene solution.

The substance used as the magnesium compound in the present invention is obtained by contacting magnesium hydroxide with the above-mentioned aluminum alkoxide.

This reaction is carried out by dispersing a predetermined amount of magnesium hydroxide and aluminum alkoxide in an inert hydrocarbon solvent such as hepkune, kerosene, decalin, etc. or in a molten state at a temperature of 100 to 180°C for 30 minutes to 3 hours. .

At this time, although there are particular restrictions on the addition ratio of magnesium hydroxide and aluminum alkoxide, usually 0.0 aluminum alkoxide is added to 1 mole of magnesium hydroxide.
The amount should be 5 to 5 moles.

If it is outside this range, the activity of the catalyst will not be improved sufficiently.

This reaction can also be carried out in a method using aluminum powder.

For example, when aluminum alkoxide is produced from anhydrous alcohol and aluminum powder, the reaction is carried out in the presence of magnesium hydroxide.
Next, a method such as removing excess alcohol or solvent may be mentioned.

One component of the catalyst used in the present invention can be obtained by reacting the above magnesium compound (reactant of magnesium hydroxide and aluminum alkoxide) with titanium halide.

Prior to this reaction, it is preferable to crush the magnesium compound in advance using a ball mill or the like. In the reaction between the magnesium compound and titanium halide, the magnesium compound is usually first dispersed in an inert hydrocarbon solution, Next, titanium halide was added and the mixture was stirred for 6 hours.
The reaction is carried out at a temperature of 0 to 140°C for 0.5 to 5 hours.

Note that this reaction may be carried out without a solvent when the titanium halide is in a liquid state.

The amount of titanium halide to be added at this time is preferably in the range of 0.5 to 25 moles per mole of the magnesium compound.

Further, the titanium halides that can be used here include tetravalent, trivalent or divalent titanium halides, more specifically TiBr4, TiCl4Tt (O}
() Cl3,T i(OR) Cl2,Ti(
ORj)3Cl tTiBr3,TiC4,Ti
C4 (where W represents an alkyl group).

) can be given. By carrying out the above reaction, a reaction product of a magnesium compound, which is a component of the catalyst used in the present invention, and a titanium halide can be obtained.

After the reaction is completed, free titanium compounds are removed from the reaction product by washing.

At this time, the washing is preferably carried out using an inert hydrocarbon solvent having 5 to 10 carbon atoms, such as pentane, hexane, cyclohexane, heptane, benzene, toluene, xylene, and the like.

The reaction product from which free titanium compounds have been washed away is further suspended in an inert solvent such as a hydrocarbon in an inert gas at an appropriate concentration to prepare a catalyst component.

Note that the washed reaction product may be further treated with organoaluminium and then made into a suspension in the same manner as above.

The method of the present invention is carried out using a catalyst containing the reaction product of the above-mentioned magnesium compound and titanium halide and an organoaluminum compound.

In polymerizing ethylene, a suspension of the above reaction product and an organoaluminum compound are added as a catalyst to the reaction system, and then ethylene is introduced into the system.

There are no particular restrictions on the polymerization method and conditions, and solution polymerization,
Both suspension polymerization and gas phase polymerization are possible, and both continuous polymerization and discontinuous polymerization are possible.

For example, in the case of solution polymerization or suspension polymerization, the amount of catalyst components added is 0.01 to 10 mmol/l for the reaction product of magnesium compound and titanium halide, and 0.05 to 10 mmol/l for the organoaluminum compound. Preferably it is 50 mmol/l.

The solvent for the reaction system is preferably an inert hydrocarbon such as n-hexane or n-heptane, and the ethylene pressure in the reaction system is selected to be in the range of normal pressure to 50 kg/cm', and the reaction temperature is 8.
It is desirable to react at around 0°C for 1 to 2 hours.

Molecular weight adjustment during polymerization can be carried out by known means, such as hydrogen.

The hydrogen pressure is usually preferably about 60% of the ethylene pressure.

Examples of organoaluminum compounds that are one component of the catalyst used in the method of the present invention include trialkylaluminum compounds such as trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, trioctylaluminum, and diethylaluminum monochloride, diisopropylaluminum, etc. Dialkyl aluminum monohalides such as aluminum monochloride, diisobutyl aluminum monochloride, and dioctyl aluminum monochloride are suitable.

The types of polyethylene that can be polymerized by the method of the present invention include not only ethylene homopolymers but also copolymers of ethylene and a small amount of α-olefin.

Note that the catalyst used in the method of the present invention may further contain an organic metal such as organic zinc.

Since the method of the present invention uses the catalyst described above, the reproducibility of the catalyst preparation is better than that of the catalyst described in JP-A-48-48584, and the catalyst activity is also as follows: 1 g of titanium atom, 1 g of titanium atom. 1,000 to 5,000 per hour
g and is not inferior in any way.

Furthermore, the polyethylene produced by the method of the present invention has a melt index of 0.01 to 50 and a melt flow ratio of F. R. (The value of the ratio of the melt index at a load of 10 kg to the melt index at a load of 2.16 k9) is 10 to 20, and the molecular weight distribution is wide.

Therefore, this polyethylene has very good moldability and also has excellent physical properties.

Moreover, the method of the present invention is an extremely effective method because the molecular weight distribution of the polyethylene obtained can be adjusted to a desired range by appropriately selecting the blending ratio of catalyst components, polymerization conditions, etc.

Next, the method of the present invention will be explained in more detail with reference to Examples.

Example 1 (1) Preparation of catalyst 4.5.9 (78 mmol) of magnesium hydroxide and 20 g (9.8 mmol) of aluminum isoproboxide were
-The mixture was suspended in 100 ml of hebutane and reacted under reflux (~98°C) for 60 minutes.

Next, 48.7 ml (80 mmol) of Tick was added and reacted at 98°C for 60 minutes.

The temperature was lowered, the supernatant liquid was drained, and 100 ml of n-hebutane was newly added to perform washing by the decanting method.

After washing three times, 200 ml of n-hebutane was added to obtain a catalyst slurry.

The amount of titanium supported was determined by colorimetric method and was 220cm.
TI/g・Carrier.

(2) Polymerization of ethylene A 1-liter autoclave was purged with argon, and 400 ml of n-hebutane, 4 mmol of triethylaluminum, and the above slurry equivalent to 1.0 mmol of titanium atoms were added, and the temperature was raised to 80°C. .

Hydrogen at 4 kg/cm' and ethylene were continuously supplied at a total pressure of 8 kg/cm', and polymerization was carried out at 80° C. for 1 hour.

As a result, 105 g of polyethylene was obtained, and the catalyst activity was 1 g of titanium, 2.0 g per hour. It is 190g.

Measurement of molecular weight distribution was performed by melt flow ratio (F.R.).

Melt index (MI) at 190℃ and 10kg load
IO ) and 2.16 kg melt index (M■2
) is the ratio of F. a. (=M Ito/MI2) then F. R. = 18.5, M■2 was 0.022.

Comparative Example 1 4.5 g (78 mmol) of magnesium hydroxide was dispersed in 30 cc of decalin and heated to 100°C. +c45
ml (approximately 46 mmol) and reacted for 60 minutes.

Washing was carried out in the same manner as in Example 1, and the supported amount was 120
A catalyst slurry (in n-heptane) of mg·T i/g·support was obtained.

Ethylene polymerization was carried out in the same manner as in Example 1, except that 0.2 mmol of titanium and 3 mmol of triethylaluminum were used as the catalyst.

As a result, 23 g of polyethylene was obtained, and the activity was 1 titanium.
g, 2,400 g per hour, melt index 0.
24, F. R. 1 2.8, the distribution was relatively narrow.

Example 2 (1) Preparation of catalyst 4.0 g (69 mmol) of magnesium hydroxide and 0.4 g (2 mmol) of aluminum isoproboxoxide were suspended in 40 cc of decalin, and heated at 130 to 140°C with Tic.
45 ml (46 mmol) was added dropwise and reacted for 90 minutes.

After completion, the temperature was lowered and a washing operation was performed in the same manner as in Example 1 to obtain a catalyst slurry with a supported amount of 150 mg Ti/g carrier.

(2) Polymerization of ethylene 4 mmol of tochetylaluminium, 0.0 mmol of titanium.
Ethylene polymerization was carried out in the same manner as in Example 1 except that the above slurry was used in an amount equivalent to 6 mmol.

As a result, 52 g of polyethylene was obtained.

This polyethylene has a melt index of 0.05, F
．． R. was 18.8, indicating a wide molecular weight distribution.

Example 3 (1) Production of catalyst 4.3 g (74 mmol) of magnesium hydroxide and 3.0 g (14.7 mmol) of aluminum isoproboxoxide were dispersed in 30 ml of decalin, and the temperature was raised to 140°C.

This is TicA4 8. 7 ml (80 mmol) was added dropwise and the reaction was carried out for 90 minutes.

Thereafter, washing was carried out in the same manner as in Example 1 to obtain a catalyst slurry (in n-heptane) having a titanium loading of 150 .mu.Ti/g.

(2) Polymerization of ethylene Ethylene was polymerized in the same manner as in Example 1, except that the above slurry was used in an amount equivalent to 4.0 mmol of triethylaluminum and 0.25 mmol of titanium, and the polymerization was carried out for 2 hours.

As a result, 111 g of polyethylene were obtained, an activity of 4.630 g per g of titanium per hour, a melt index of 0.096, an F. R. was 14.8.

Claims (1)

[Claims] 1. When polymerizing ethylene using a catalyst containing a reaction product of a magnesium compound and a titanium halide and an organoaluminum compound, a substance obtained by contacting magnesium hydroxide with an aluminum alkoxide is used as the magnesium compound. A method for producing polyethylene with a characteristically controlled molecular weight distribution.