JPH0822888B2 - Method for producing olefin polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to polypropylene, polybutene-
More specifically, it relates to a method for producing an olefin polymer having good stereoregularity and capable of producing a high molecular weight olefin polymer in a high yield.

[Prior Art and Its Problems] Conventionally, a solid catalyst component containing magnesium, titanium, halogen and an electron donor as essential components is combined with an external electron donor such as an organoaluminum compound and an ester or an organosilicon compound. A method for producing an olefin polymer using a highly active catalyst is known (Japanese Patent Publication No. 56-39767, Japanese Patent Publication No. 55-104303, Japanese Patent Publication No. 56-115301, Japanese Patent Publication No. 57-63312). No. 59-6205
No.

However, many of them have not been able to completely omit the washing step and the deashing step for removing the atactic polymer, and the catalytic activity is not satisfactory, and the physical properties of the obtained polymer are also three-dimensional. Further improvement in regularity and molecular weight has been desired.

On the other hand, a method using a phosphite ester as an internal or external electron donor in the catalyst (see JP-A-55-104303 and JP-A-58-138711) is also known. However, the stereoregularity of the polymer was insufficient.

Further, a method using an ether containing an aromatic hydrocarbon group as an external electron donor (JP-A-61-78804, JP-A-61-145206) is also known, but the activity persistence is known. There is a drawback that it is insufficient and the catalyst cost is high, which is industrially disadvantageous.

The present invention has been made based on the above circumstances.

That is, an object of the present invention is to provide a method for efficiently producing an olefin polymer having high stereoregularity in a high yield and in a stable process by using a catalyst having high activity and excellent activity sustainability. Is to provide.

[Means for Solving the Problems] The outline of the present invention for solving the problems is a high activity catalyst component (A) containing magnesium, tetravalent titanium, halogen and an electron donor as essential components. In the method for producing an olefin polymer in the presence of a catalyst obtained from an organoaluminum compound (B) and an external electron donor (C), the following formula [1a] is used as the external electron donor (C); (However, in the formula [1a], R ¹ , R ² , R ³ and R ⁴ have 1 carbon atoms.
~ 7 saturated or unsaturated aliphatic hydrocarbon groups. ) Or the following formula [1b]; (However, R ⁵ represents a hydrogen atom or an aliphatic hydrocarbon group having 1 to 6 carbon atoms, R ⁶ represents a group similar to R ³ in formula [1a], and R ⁷ represents formula [1a ] Represents the same group as R ^{4 in the above} ).) Is a method for producing an olefin polymer, characterized by carrying out homopolymerization or copolymerization of an olefin.

The catalyst used in the process of the invention is magnesium, 4
For highly active polymerization obtained from a solid catalyst component (A) containing a valent titanium, a halogen and an electron donor as essential components, an organoaluminum compound (B) and a specific ether compound as an external electron donor (C) Is a catalyst,
It can be obtained as follows.

-A solid catalyst component (A) -The solid catalyst component (A) is a magnesium compound (A).
-1), the halogenated tetravalent titanium compound (A-2) and the electron donor (A-3) are brought into contact with each other. Examples of the magnesium compound (A-1) include magnesium dihalide, magnesium oxide, magnesium hydroxide, hydrotalcite, magnesium carboxylate, alkoxymagnesium, aryloxymagnesium, alkoxymagnesium halide, and aryloxymagnesium halide. , Alkylmagnesium, alkylmagnesium halides, organomagnesium compounds and electron donors, halosilanes, alkoxysilanes,
Reactants with silanols, aluminum compounds and the like are included.

Among these various magnesium compounds, magnesium halide, alkoxy magnesium, alkyl magnesium, and alkyl magnesium halide are preferable.

The tetravalent titanium compound (A-2), which is one of the raw materials of the solid catalyst component (A), is specifically TiCl
Tetrahalogenated titanium such as ₄ , TiBr ₄ , TiI ₄ ; Ti (OCH
₃ ) Cl ₃ , Ti (OC ₂ H ₅ ) Cl ₃ , (nC ₄ H ₉ O) TiCl ₃ , Ti (OC ₂ H ₅ ) Br ₃ and other trihalogenated alkoxytitanium; Ti (OCH ₃ ) ₂ Cl ₂ , Ti
Dihalogenated alkoxy titanium such as (OC ₂ H ₅ ) ₂ Cl ₂ , (nC ₄ H ₉ O) ₂ TiCl ₂ , Ti (OC ₃ H ₇ ) ₂ Cl ₂ ; Ti (OCH ₃ ) ₃ Cl, Ti (OC ₂ H ₅ ) ₃
Cl, (nC ₄ H ₉ O) ₃ TiCl, monohalogenated trialkoxy titanium such as Ti (OCH ₃ ) ₃ Br, Ti (OCH ₃ ) ₄ , Ti (OC ₂ H ₅ ) ₄ , Ti (nC ₄
Examples thereof include tetraalkoxy titanium such as H ₉ O) ₄ .

These may be used alone or in combination of two or more.

Of these, it is preferable to use a high halogen content substance, and it is particularly preferable to use titanium tetrachloride.

The electron donor (A
As 3), an organic compound containing oxygen, nitrogen, phosphorus or sulfur can be used.

Examples of the electron donor (A-3) include esters, thioesters, amines, amides, ketones, nitriles, phosphines, ethers, thioethers, esters, thioesters, acid anhydrides. , Acid halides, acid amides, aldehydes, organic acids and the like.

More specifically, dimethyl phthalate, diethyl phthalate, dipropyl phthalate, diisobutyl phthalate, methyl ethyl phthalate, methyl propyl phthalate, methyl isobutyl phthalate, ethyl propyl phthalate, ethyl isobutyl phthalate, propyl isobutyl phthalate, dimethyl terephthalate, diethyl terephthalate, di Propyl terephthalate, diisobutyl terephthalate, methyl ethyl terephthalate, mail propyl terephthalate, methyl isobutyl terephthalate, ethyl propyl terephthalate, ethyl isobutyl terephthalate, propyl isobutyl terephthalate, dimethyl isophthalate, diethyl isophthalate, dipropyl isophthalate, diisobutyl isophthalate, methyl ethyl Aromatic dicarboxylic acid diesters such as sophthalate, methylpropylisophthalate, methylisobutylisophthalate, ethylpropylisophthalate, ethylisobutylisophthalate and propylisobutylisophthalate, methyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, acetic acid Octyl, cyclohexyl acetate, ethyl propionate, ethyl acetate, ethyl valerate, methyl chloroacetate, ethyl dichloroacetate, methyl methacrylate, ethyl crotonate,
Ethyl pivalate, dimethyl maleate, ethyl cyclohexanecarboxylate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, octyl benzoate, cyclohexyl benzoate, phenyl benzoate, benzyl benzoate, methyl toluate, toluyl. Monoesters such as ethyl acidate, amyl toluate, ethyl anisate, ethyl ethoxybenzoate, ethyl p-butoxybenzoate, ethyl o-chlorobenzoate and ethyl naphthoate, γ-butyrolactone, δ-valerolactone, coumarin, phthalide. , C2-18 esters such as ethylene carbonate; organic acids such as aromatic carboxylic acids such as benzoic acid and p-oxybenzoic acid; such as succinic anhydride, benzoic anhydride and p-toluic anhydride Acid anhydrides; acetone, methyl ethyl ketone Methyl isobutyl ketone, acetophenone, benzophenone, number 3-15 ketones carbon atoms such as benzoquinone; acetaldehyde, propionaldehyde, octyl aldehyde, benzaldehyde,
2 to 2 carbon atoms such as tolualdehyde and naphthylaldehyde
15 aldehydes; C2 to C15 acid halides such as acetyl chloride, benzyl chloride, triyl acid chloride, and anisic acid chloride; methyl ether, ethyl ether, isopropyl ether, n-butyl ether, amyl ether, tetrahydrofuran, anisole, Ethers having 2 to 20 carbon atoms such as diphenyl ether and ethylene glycol butyl ether; acid amides such as acetic acid amide, benzoic acid amide and toluic acid amide; tributylamine, N, N'-dimethylpiperazine, tribenzylamine, aniline, polyzine , Picoline, tetramethylethylenediamine, and other amines; acetonitrile, benzonitrile, tolunitrile, and other nitriles.

Of these, preferred are esters, ethers, ketones, acid anhydrides and the like. Particularly, aromatic dicarboxylic acid diesters such as diisobutyl phthalate or alkyl esters of aromatic carboxylic acids, for example, aromatic carboxylic acids such as benzoic acid, p-methoxybenzoic acid, p-ethoxybenzoic acid and toluic acid having 1 carbon atom.
Alkyl esters of -4 are preferred. Aromatic dicarboxylic acid diesters are particularly preferable because they can improve the catalytic activity and activity sustainability as well as the stereoregularity of the resulting polymer.

--Preparation of Solid Catalyst Component (A) ---- The solid catalyst component (A) is described in JP-A-53-43094 and JP-A-5-43094.
It can be prepared according to the methods described in JP-A-5-135102, JP-A-55-135103, JP-A-56-811, JP-A-56-11908 and JP-A-56-18606.

Regarding some examples of the method for producing the solid catalyst component (A),
A brief description will be given below.

(1) Grinding or crushing the magnesium compound (A-1) or a complex compound of the magnesium compound and the electron donor (A-3) in the presence or absence of an electron donor, a grinding aid or the like. Instead, it is reacted with a tetravalent titanium compound (A-2) forming a liquid phase under the reaction conditions. However, the electron donor is used at least once.

(2) Magnesium compound (A-1) having no reducing ability
And the liquid tetravalent titanium compound (A-2) are reacted in the presence of the electron donor (A-3) to precipitate a solid tetravalent titanium complex.

(3) The tetravalent titanium compound (A-2) is reacted with the compound obtained in (1) or (2).

(4) The electron donor (A
-3) and the tetravalent titanium compound (A-2) are reacted.

(5) The magnesium compound (A-1) or a complex compound of the magnesium compound (A-1) and the electron donor (A-3), in the presence or absence of an electron donor, a grinding aid, or the like, And a tetravalent titanium compound (A-2) in the presence of the pulverized product, and treated with halogen or a halogen compound. However,
The electron donor (A-3) is used at least once.

(6) The compound obtained in (1) to (4) above is treated with halogen or a halogen compound.

Furthermore, for example, JP-A-56-166205 and JP-A-57
-63309, JP-A-57-190004, JP-A-57-3
The preparation methods described in JP-A-00407 and JP-A-58-47003 can also be included as suitable preparation methods of the solid catalyst component (A) in the present invention.

Further, oxides of elements belonging to groups II to IV of the periodic table, for example, oxides of silicon oxide, magnesium oxide, aluminum oxide, etc., preferably silicon oxide, or II to
A complex oxide containing at least one oxide of an element belonging to Group IV, for example, a solid substance obtained by supporting the magnesium compound on silica-alumina or the like, an electron donor, and a titanium halide in a solvent are added in an amount of 0 to 200. ℃, preferably 10
The solid catalyst component (A) can also be prepared by contacting at a temperature of 150 ° C for 2 minutes to 24 hours (preparation method described in Japanese Patent Application No. 61-43670).

In preparing the solid catalyst component (A), an organic solvent inert to the magnesium compound, the electron donor and the tetravalent titanium compound as a solvent, for example, an aliphatic hydrocarbon such as hexane or heptane, benzene or toluene. And the like, or halogenated hydrocarbons such as mono- or polyhalogen compounds of saturated or unsaturated aliphatic, alicyclic and aromatic hydrocarbons having 1 to 12 carbon atoms can be used.

--- Composition of Solid Catalyst Component (A) --- Regarding the composition of the solid catalyst component (A), the atomic ratio of magnesium / titanium is 2 to 100, the atomic ratio of halogen / titanium is 5 to 200, the electron donor / titanium ( 0.1-10 by molar ratio)
Is.

-Regarding the organoaluminum compound (B) -The organoaluminum compound (B) is not particularly limited and may be represented by the general formula AlR ⁸ _v X _3-v [wherein R ⁸ is an alkyl group having 1 to 10 carbon atoms, cycloalkyl Is a group or an aryl group, v is a real number of 1 to 3, and X represents a halogen atom such as chlorine or bromine. ] Are widely used.

Specifically, trialkylaluminums such as trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, trioctylaluminum, etc., and dialkylaluminums such as diethylaluminum monochloride, diisopropylaluminum monochloride, diisobutylaluminum monochloride, dioctylaluminum monochloride. Alkylaluminum sesquihalides such as monohalides and ethylaluminum sesquichloride are preferable, and a mixture thereof is also preferable.

-Regarding External Electron Donor (C) -One of the important points of the present invention is to use an ether compound represented by the above formula [1a] or [1b] as the above external electron donor (C). is there.

In the above formula [1a], specific examples of R ¹ , R ² , R ³ and R ⁴ include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, Examples thereof include alkyl groups such as 1-methylpropyl group, t-butyl group, pentyl group, hexyl group and heptyl group; alkenyl groups such as vinyl group, propenyl group, butenyl group, pentenyl group and hexenyl group.

Of these, a lower alkyl group such as a methyl group and an ethyl group is preferable as R ¹ and R ² , and a methyl group is particularly preferable, and a methyl group, an ethyl group, an n-propyl group, and an n-type are preferable as R ^3. A butyl group, an n-pentyl group or an n-hexyl group, particularly a methyl group or an ethyl group is preferable, and R ⁴
As, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, 1-methylpropyl group, 2
-Methylpropyl group, tert-butyl group, pentyl group, 1
-Methylbutyl group and hexyl group, particularly methyl group and ethyl group are preferred.

The R ¹ , R ² , R ³ and R ⁴ may be the same type of groups or different types of groups.

Specific examples of the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵ in the above formula [1b] include alkyl groups such as methyl group, ethyl group, propyl group and butyl group.

Examples of R ⁷ include the same groups as those of R ⁴ .

The ether compounds represented by the above formula [1a] or formula [1b] can be used alone or in combination of two or more as the component (C).

Specific examples of the ether compound represented by the above formula [1a] include, for example, tert-butyl methyl ether and tert-butyl methyl ether.
Butylethyl ether, tert-butyl-n-propyl ether, tert-butyl isopropyl ether, tert-butyl n-butyl ether, tert-butyl-1-methylpropyl ether, tert-butyl-2-methylpropyl ether, ditert-butyl ether , Tert-butyl-n-
Pentyl ether, tert-butyl-1-methylbutyl ether, tert-butyl-2-methylbutyl ether, te
rt-butyl-3-methylbutyl ether, tert-butyl-tert-amyl ether, tert-butyl neopentyl ether, tert-butyl-1-ethylpropyl ether,
tert-butylhexyl ether, tert-butyl isohexyl ether, tert-butyl neohexyl ether, te
rt-butylheptyl ether, tert-amyl methyl ether, tert-amyl ethyl ether, tert-amyl-n
-Propyl ether, tert-amyl isopropyl ether, tert-amyl-n-butyl ether, tert-amyl-1-methylpropyl ether, tert-amyl-2-methylpropyl ether, tert-amyl-n-benzyl ether, tert-amyl -1-methylbutyl ether, te
rt-amyl-2-methylbutyl ether, tert-amyl-3-methylbutyl ether, tert-amyl-1-ethylpropyl ether, tert-amyl neopentyl ether, di-tert-amyl ether, tert-amylhexyl ether, tert- Amyl-isohexyl ether, tert
-Amylheptyl ether, tert-hexyl methyl ether, tert-hexyl ethyl ether, tert-heptyl methyl ether, tert-heptyl ethyl ether, tert
-Octyl methyl ether, saturated ether compounds such as tert-octyl ethyl ether; tert-butyl vinyl ether, tert-butyl allyl ether, tert-butyl cutyl ether, tert-butyl butenyl ether, tert-
Amyl vinyl ether, tert-amyl allyl ether,
Mention may be made of unsaturated ether compounds such as tert-amyl butenyl ether.

Specific examples of the ether compound represented by the formula [1b] include, for example, 1-methyl-1-propenyl methyl ether, 1-methyl-1-propenyl ethyl ether,
Unsaturated ethers such as 1-methyl-1-propenyl allyl ether can be mentioned.

Among these, saturated aliphatic ether represented by the formula [1a], specifically, tert-butyl methyl ether, tert.
-Butyl ethyl ether, tert-butyl-n-propyl ether, tert-butyl-n-butyl ether, tert-
Amyl methyl ether, tert-amyl ethyl ether,
tert-amyl-n-propyl, tert-amyl-n-butyl ether and the like are preferable, and tert-butyl methyl ether, tert-butyl ethyl ether, tert-amyl methyl ether, tert-amyl ethyl ether are particularly preferable. .

In the method of the present invention, when an ether compound other than the ether compound represented by the above formula [1a] or the above formula [1b] is used alone as the external electron donor (C), the activity of the catalyst is unsatisfactory. It is not preferable because it is sufficient, the activity persistence is insufficient, and the stereoregularity of the obtained polymer is low.

However, as long as the object of the present invention is not impaired, the above formula [1
a] or an ether compound other than the ether compound represented by [1b], or a fourth component such as another electron donating compound such as an organic phosphorus compound, in combination with the component (C) as appropriate. Is also possible.

-Catalyst component composition-As the composition of each component of the olefin polymerization catalyst,
Usually, the solid catalyst component (A) is in an amount of 0.0005 to 1 mmol per reaction volume in terms of thyrane atom, and the organoaluminum compound (B) has an aluminum / titanium atomic ratio of 1 to 1000, Preferably 5
The amount is 500.

Regarding the external electron donor (C), the molar ratio of the ether compound represented by the formula [1a] and the ether compound represented by the formula [1b]) / titanium is usually 0.1 to 50.
0, preferably 1-100. When this molar ratio is less than 0.1, the sustainability of the catalytic activity is insufficient, or the stereoregularity of the resulting polymer is insufficient, while
If it exceeds, the catalytic activity may decrease.

-Polymerization- The method of the present invention is a method for producing an olefin homopolymer or copolymer in which olefins are homopolymerized or olefins are copolymerized in the presence of the catalyst.

In the case of producing a homopolymer, a single olefin may be supplied to a polymerization vessel and polymerized at a temperature of 40 to 90 ° C. and a pressure of 1 to 100 kg / cm ² G.

When a random copolymer is produced, a plurality of types of olefins may be supplied to the polymerization vessel and copolymerized.

In the case of producing a so-called block copolymer, after the first-stage polymerization treatment for homopolymerizing an olefin, the second-stage polymerization treatment is carried out to obtain the olefin homopolymer obtained in the first stage. In the presence, copolymerization with other single olefin or multiple types of olefins can be carried out.

As the olefin, for example, the general formula; R ⁸ -CH = CH ₂ [wherein, R ⁸ represents an alkyl group or a cycloalkyl group of which a hydrogen or 1,3～12 carbon atoms. ],
Specific examples thereof include linear monoolefins such as ethylene, propylene, butene-1, pentene-1, and octene-1, branched monoolefins such as 4-methyl-pentene-1, and vinylcyclohexene.

The polymerization method may be any of a slurry polymerization method, a gas phase polymerization method, a bulk polymerization method using a liquid monomer itself as a solvent, and the like.

In the case of producing a so-called block copolymer, the first and second polymerization vessels are connected in series and heated to a temperature of 90 ° C or lower and a single olefin is supplied under a pressure of 1 to 100 kg / cm ² G. Then, the first stage polymerization reaction is performed to produce 1 to 20% by weight of the total amount of the polymer finally obtained,
In the second polymerization reactor, the reaction product transferred from the first polymerization reactor or a degassing device is provided between the first polymerization reactor and the second polymerization reactor to provide the reaction product of the first stage. To the product obtained by degassing the unreacted olefin vaporized component from the above, only one other olefin or a plurality of other olefins are supplied, and the temperature is kept at 90 ° C while keeping the reaction system in a fluid state. A second stage polymerization reaction is carried out below and under a pressure of 1 to 100 kg / cm ² G to produce a copolymer containing 1 to 30% by weight of another olefin. If necessary, preliminary polymerization may be carried out in which a small amount of another olefin is polymerized before the first stage polymerization reaction.

The molecular weight of the polymer can be controlled by adjusting the hydrogen concentration in the polymerization vessel. Further, the catalyst component can be supplied by suspending it in an inert solvent or olefin.

In the method of the present invention, post-treatment after polymerization can be carried out by a conventional method. That is, in the gas phase polymerization method, after the polymerization, the polymer powder derived from the polymerization vessel,
A nitrogen stream or the like may be passed through to remove olefins and the like contained therein. If desired, pelletizing may be carried out by an extruder, and in this case, a small amount of water, alcohol, etc. may be added to completely deactivate the catalyst. Further, in the bulk polymerization method, after the polymerization, the monomer can be completely separated from the polymer discharged from the polymerization vessel, and then pelletized.

As described above, the olefin polymer obtained by the method of the present invention usually has an intrinsic viscosity [η] (tetralin solution, 135 ° C) of 1.0 to 6 dl / g, particularly 1.3 dl / g or more. The stereoregularity was II (92% after extraction of the obtained polymer with Soxhlet extraction for 6 hours with n-heptane).
That is all.

[Effects of the Invention] According to the present invention, (1) a molded product having a good appearance can be obtained because the obtained polymer has excellent stereoregularity, and (2) a polymer powder having a high molecular weight is used. Since it is possible to obtain an olefin polymer having excellent fluidity characteristics, it is convenient for powder transportation. (3) Since the yield of the olefin polymer is high, it is excellent in economic efficiency. Since it is excellent, the polymerization process can be made stable, and it is particularly advantageous in multi-stage polymerization, etc. (5) Further, if a gas phase polymerization method is adopted, the step of collecting the polymerization solvent can be omitted, The drying process of the produced polymer can be greatly simplified.

It is possible to provide a method for producing an olefin polymer having advantages such as the following.

EXAMPLES Next, the present invention will be described more specifically by showing Examples and Comparative Examples of the present invention.

(Example) Preparation of solid catalyst component 200 ml of butyloctylmagnesium (20% heptane solution, manufactured by Schering Co., Ltd. in Germany) and 150 ml of heptane were placed in a 2 l flask substituted with argon, and about 4 l of chlorine gas was added at room temperature over 30 minutes. It was This was heated to 90 ° C., 24 ml of ethanol was added, and the mixture was stirred at 90 ° C. for 10 minutes. The product was washed twice with 200 ml heptane and the supernatant was removed. Kerosene 4
A dispersion was obtained by adding 00 ml and 24 ml of ethanol and stirring at 100 ° C. for 2 hours. This dispersion was transferred by siphoning to a solution of TiCl ₄ 500 ml / heptane 200 ml cooled to −20 ° C. After warming to room temperature, 3 ml of di-n-butyl phthalate was added, and the mixture was stirred at 110 ° C for 1 hour. After removing the supernatant, 600 ml of TiCl ₄ was added and the mixture was further stirred at 110 ° C. for 1 hour. After removing the supernatant, the solid catalyst component was sufficiently washed with heptane.

Manufacture of olefin polymer 400m of heptane in the stainless steel autoclave
l, then triisobutylaluminum 1 mmol, te
rt-Butyl methyl ether 0.1 mmol and the solid catalyst component obtained above were converted into titanium atoms and 0.0025 mmol, which were added in this order, hydrogen pressure was 0.2 kg / cm ² , propylene pressure was 7 kg / cm.
While maintaining at ² , polymerization was carried out at 70 ° C. for 4 hours.

 The results are shown in Table 1.

(Example 2, Comparative Examples 1 and 2) The same procedure as in Example 1 was repeated except that the other external electron donor shown in Table 1 was used instead of tert-butyl methyl ether. . The results are shown in Table 1.

[Brief description of drawings]

FIG. 1 is a flow chart of the method for producing an olefin polymer according to the present invention.

Claims (1)

[Claims] 1. A catalyst obtained from a highly active catalyst component (A) containing magnesium, tetravalent titanium, halogen and an electron donor as essential components, an organoaluminum compound (B) and an external electron donor (C). In the process of producing a polymer of an olefin in the presence of an external electron donor (C)
As the following formula [1a]; (However, in the formula [1a], R ¹ , R ² , R ³ and R ⁴ have 1 carbon atoms.
~ 7 saturated or unsaturated aliphatic hydrocarbon groups. ) Or the following formula [1b]; (However, in the formula [1b], R ⁵ is a hydrogen atom or a carbon number 1
~ 6 represents an aliphatic hydrocarbon group, R ⁶ is R ³ in the formula [1a]
And R ⁷ represents the same group as R ⁴ in the formula [1a]. ) Homopolymerization or copolymerization of an olefin is carried out using an ether compound represented by