JPH0745532B2 - Method for producing ethylene / α-olefin copolymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to copolymerization of ethylene and α-olefin. More specifically, it relates to a method for obtaining a rubbery copolymer of ethylene and an α-olefin using a Ti-based catalyst.

2. Description of the Related Art As a method for copolymerizing ethylene and α-olefin to polymerize a rubber-like polymer, a method using a vanadium compound and an organoaluminum compound as a catalyst is generally used.

However, vanadium-based catalysts have drawbacks such as low catalytic activity, large activity decay, and reduced activity at high temperatures.

As for another catalyst system for copolymerizing olefins, a method using a Ti compound and an organoaluminum compound is known, and the activity is relatively high. In the case where a rubber-like copolymer is polymerized, a titanium-based catalyst cannot be used in practice and a vanadium-based catalyst having a low catalytic performance is industrially used because of its low randomness with an α-olefin.

Problems to be Solved by the Invention The inventor of the present application investigated a method for obtaining a copolymer of ethylene and α-olefin having good randomness by using a Ti-based catalyst.

As a result, a copolymer having good randomness can be obtained by copolymerizing ethylene and α-olefin with a catalyst system in which a component obtained by reducing titanium tetrahalide with an organomagnesium compound and an organoaluminum compound are combined. And applied for a patent.

However, since this catalyst system contains a large amount of titanium metal, it was considered necessary to improve the activity per titanium metal in terms of the quality of the produced polymer.

Means for Solving the Problems The inventors of the present application have conducted intensive research to solve the above problems, and completed the present invention.

That is, according to the method of the present invention, titanium tetrahalide represented by the general formula (A) TiX ₄ (X represents a halogen atom) is reduced with an organomagnesium compound as a catalyst system when polymerizing ethylene and α-olefin. Copolymerizing ethylene and an α-olefin in the presence of a catalyst composed of activated titanium obtained by supporting the low valent titanium component obtained on magnesium halide and (B) an organoaluminum compound. Depending on the method, a copolymer having good randomness can be efficiently obtained.

The low-valent titanium component which is the raw material of the component (A) used in the method of the present invention is obtained by reducing titanium tetrahalide represented by the general formula TiX ₄ (X represents a halogen atom) with an organomagnesium compound.

The titanium tetrahalide is preferably titanium tetrachloride or titanium tetrabromide, and particularly preferably titanium tetrachloride.

The organomagnesium compound has the general formula MgR ₂ or MgRX
(Wherein R represents a hydrocarbon residue and X represents a halogen atom) can be used as an essential component, or an organomagnesium compound forming a complex compound with an organoaluminum compound can be used. .

As the organomagnesium compound, ethylbutyl magnesium, diisobutyl magnesium, dihexyl magnesium, diphenyl magnesium, ethyl allyl magnesium, ethyl magnesium chloride, phenyl magnesium chloride, etc. are used. Particularly, a complex compound of ethyl butyl magnesium, dihexyl magnesium, etc. and triethyl aluminum is used. Especially preferred.

The method for reducing titanium tetrahalide with an organomagnesium compound is 0.5 mol or more, preferably 1.0 mol or more, based on titanium tetrahalide of the organomagnesium compound.
The reaction is carried out at a temperature of 70 ° C. to 200 ° C., preferably −70 ° C. to 150 ° C. for a few minutes to a few hours, in which case hydrocarbons such as n-hexane and n-heptane are generally made to coexist.

Magnesium chloride is preferable as the magnesium halide used in the component (A) adjustment.

The method of supporting the magnesium halide and the low valent titanium component is not particularly limited, but a method of co-milling both is preferable. The temperature at that time is -30 ° C to 100 ° C, and the crushing time is about several hours to 100 hours.

The ratio of both when co-milling is 0.3wt% to 10w as titanium metal
It is mixed and pulverized so as to be t%, preferably 0.5 wt% to 7 wt%.

When a liquid compound such as toluene, heptane, α-methylstyrene, ethylene chloride, silicon tetrachloride, or dimethylpolysiloxane is coexisted during co-milling,
This is preferable because the activity of the catalyst is improved.

The organoaluminum compound used as the catalyst (B) component is represented by the general formula AlRnX _3-n (wherein R is a hydrocarbon residue, X is a halogen atom, an alkoxy group, a hydrogen atom or a siloxy group, and n is 1 to 3). Are shown), for example, trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-iso-butylaluminum, diethylaluminum chloride, diethylaluminum monoethoxide, and the like, and mixtures thereof may be used. .

The amount of the component (B) used is 0.5 to 200 times, preferably 1 to 100 times, the amount of Ti mole atoms in the component (A).

Examples of the α-olefin copolymerizable with ethylene include propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, octene-1 and the like.

The polymerization temperature is 0 to 150 ° C., preferably 10 to 100 ° C. The polymerization pressure is atmospheric pressure to 100 kg / cm ² .

Polymerization can be carried out by solution polymerization and suspension polymerization. In solution polymerization, hexane, heptane, toluene and the like are used as a solvent, and in suspension polymerization, it is carried out in a poor solvent such as propylene.

The molecular weight of the copolymer can be adjusted, if necessary, by using a chain transfer agent such as hydrogen.

Example 1 (a) Preparation of titanium component In a 200 ml flask whose atmosphere was replaced with nitrogen, 50 ml of n-heptane and 79.5 mM of titanium tetrachloride were placed. On the other hand, ethyl butyl magnesium (2.8 mol% of triethyl aluminum was added to the dropping funnel.
135 ml of n-heptane solution (containing 159 mM as ethylbutyl magnesium) was added to the titanium tetrachloride solution at 5 ° C., and then stirred at 70 ° C. for 1 hour. Next, after washing 5 times with 100 ml of n-heptane, the supernatant was removed and vacuum dried at 60 ° C. to obtain a low-valent titanium component.

Put 15g of magnesium chloride and 5g of low-valent titanium component mentioned above into 3ml of toluene in a vibration mill pot with an internal volume of 600ml.
After pulverizing for a period of time and removing the pulverized product in a nitrogen stream, an activated titanium component (A) having a titanium content of 4.1 wt% was obtained.

(B) Copolymerization of ethylene and propylene 30 ml of n-heptane, 50 mg of the component (A) adjusted in (a) and 0.08 ml of triethylaluminum were charged in a N ₂ stream into an autoclave made of SUS-32 having an internal volume of 6. . After replacing the gas phase of the autoclave with propylene, liquefied propylene (1.5 kg) and hydrogen (2.5 kg / cm ²⁾ were charged at a partial pressure, and the ethylene partial pressure was maintained at 5 kg / cm ² to carry out polymerization at 50 ° C. for 1 hour. It was

After the reaction was completed, unreacted monomers were removed to obtain 420 g of an ethylene-propylene copolymer.

The [η] of the obtained copolymer was 1.78 (in tetralin at 153 ° C), and the ethylene content was 47.7%. In addition, the absorption at 730 cm ^{-1 due} to polyethylene was not found at all in the IR absorption spectrum.

The amount of polymer obtained in this polymerization was 8400 g / g- (A), 250
It was kg / g-Ti.

Examples 2 to 4 Table 1 shows the results of polymerization using the activated titanium component (A) synthesized in Example 1 (a) while changing the polymerization temperature, ethylene and hydrogen partial pressure, the type and amount of the organoaluminum compound, and the like.
Shown in.

Comparative Example 1 Polymerization was repeated under exactly the same conditions as in Example 1 except that the low-valent titanium component prepared in Example 1 was used instead of the activated titanium component (A).

The yield of the copolymer obtained by polymerization was 480 g and [η] was 1.7.
7. The ethylene content was 49.3%.

Polymer acquisition amount is 9600g / g-Low valent titanium component, 56k
It was g / g-Ti.

Comparing this result with Example 1, the activity per catalyst is almost the same, but Ti g remains in the polymer and exerts a bad influence.
The amount of acquisition per unit has reached about 3.78 times.

[Brief description of drawings]

FIG. 1 is a flow chart for facilitating the understanding of the present invention.

Claims (1)

[Claims] 1. A low-valent titanium component obtained by reducing (A) titanium tetrahalide represented by the general formula TiX ₄ (where X represents a halogen atom) with an organomagnesium compound is supported on magnesium halide. A process for producing a copolymer, which comprises copolymerizing ethylene and an α-olefin in the presence of a catalyst comprising the resulting activated titanium and (B) an organoaluminum compound.