Modified methylaluminoxane composition and method for producing the same, polymerization catalyst for olefins and method for producing polyolefins

Abstract

To provide a modified methylaluminoxane composition that can contribute to improving polymerization activity during the production of polyolefins.SOLUTION: There is provided a modified methylaluminoxane composition having a number of constituent units represented by formula (I) of x, a number of constituent units represented by formula (II) of y, and a number of constituent units represented by formula (III) of z, and having a ratio of Al-H bonds to the total of Al-H bonds, Al-CH3 bonds and Al-R bonds (where R is an alkyl group of C2 to 10) of less than 1.00 mol%. (R is an alkyl group of C2 to 10; * represents a binding site; x and y are each independently positive real numbers; provided that the ratio of x / y is between 0.1 and 25; z is a positive real number; When there are multiple R's in the modified methylaluminoxane, the multiple R's may be the same or different; The sequence of the structural units represented by formula (I), the structural units represented by formula (II), and the structural units represented by formula (III) in the modified methylaluminoxane may be any sequence.).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a modified methylaluminoxane composition and a method for producing the same, a polymerization catalyst for olefins, and a method for producing polyolefins. [Background technology]

[0002] Aluminoxanes are generally condensation products prepared by partial hydrolysis of organoaluminum compounds with water. In recent years, modified methylaluminoxanes having a methyl group and an alkyl group having two or more carbon atoms have been proposed (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-119278 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-119279 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-119280 Summary of the Invention [Problem to be solved by the invention]

[0004] Aluminoxanes are useful as co-catalyst components that efficiently activate transition metal compounds, which serve as main catalysts in the production of polyolefins (olefin polymers).

[0005] Patent Documents 1 to 3 propose a method for synthesizing modified methylaluminoxane by mixing a tetraalkyldialuminoxane having an alkyl group with two or more carbon atoms with trimethylaluminum, followed by a hydrolysis reaction. The modified methylaluminoxane obtained by these synthesis methods is soluble in not only aromatic hydrocarbon solvents but also aliphatic hydrocarbon solvents, making it widely applicable to the production of polyolefins for food applications where the inclusion of aromatic solvents is restricted. Furthermore, the modified methylaluminoxane obtained by these synthesis methods exhibits good storage stability. Meanwhile, improved polymerization activity is required for the production of polyolefins. Therefore, improving the polymerization activity when using modified methylaluminoxane as a cocatalyst component to produce polyolefins would be desirable, as it would further enhance the usefulness of modified methylaluminoxane.

[0006] An object of one aspect of the present invention is to provide a modified methylaluminoxane composition that can contribute to improving polymerization activity in producing polyolefins. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have discovered that reducing the Al-H bonds (hydride components) generated by β-hydrogen elimination from alkyl groups having two or more carbon atoms in the synthesis of modified methylaluminoxane leads to improved polymerization activity in the production of polyolefins.

[0008] That is, one aspect of the present invention is as follows. [1] A modified methylaluminoxane composition, The modified methylaluminoxane has x structural units represented by the following formula (I), y structural units represented by the following formula (II), and z structural units represented by the following formula (III): [ka] (In the above formula, R represents an alkyl group having 2 to 10 carbon atoms, and * represents a bonding position. x and y each independently represent a positive real number, with the proviso that the x / y ratio is 0.1 to 25, and z represents a real number of 0 or greater. When multiple Rs are present in the modified methylaluminoxane, the multiple Rs may be the same or different. The structural units represented by formula (I), formula (II), and formula (III) in the modified methylaluminoxane may be arranged in any order.) The modified methylaluminoxane composition, wherein the proportion of Al-H bonds to the total of Al-H bonds, Al-CH3 bonds, and Al-R bonds (R has the same meaning as R in formula (II)) in the modified methylaluminoxane composition (hereinafter also referred to as the "hydride component content") is less than 1.00 mol%. [2] The modified methylaluminoxane composition according to [1], wherein in formula (II), R represents an isobutyl group. [3] A method for producing the modified methylaluminoxane composition according to [1] or [2], a step (a) of adding 1.00 or more and less than 1.60 molar equivalents of water to a composition containing a trialkylaluminum represented by RAl (R has the same meaning as R in formula (II)), based on the amount of the trialkylaluminum, to thereby partially hydrolyze the trialkylaluminum and obtain an alkylaluminoxane composition; a step (b) of adding trimethylaluminum to the alkylaluminoxane composition obtained in the step (a); Including, The above production method, wherein in the step (a), the temperature of the composition after adding 1.00 or more equivalents of water on a molar basis relative to the amount of the trialkylaluminum is maintained at 10°C or lower. [4] The modified methylaluminoxane composition according to [1] or [2] and the following formula 1: MR 5 R 6 R 7 R 8 (In Formula 1, M represents a transition metal atom, and R 5 , R 6 , R 7and R 8 Among these, at least one is an organic group having a cycloalkadienyl skeleton, and the remaining groups each independently represent an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, an alkylsilyl group, an alkylamide group, an alkylimide group, an alkylamino group, an alkylimino group, or a halogen atom. 5 , R 6 , R 7 and R 8 When two or more of the above are organic groups having a cycloalkadienyl skeleton, at least two of the organic groups having a cycloalkadienyl skeleton may be bridged by carbon, silicon, or germanium. A polymerization catalyst for olefins, comprising a transition metal compound represented by the formula: [5] A method for producing a polyolefin, comprising polymerizing olefins in the presence of the polymerization catalyst according to [4]. [Effects of the Invention]

[0009] According to one aspect of the present invention, there are provided a modified methylaluminoxane composition that can contribute to improving polymerization activity in the production of polyolefins, and a method for producing the same. Furthermore, according to another aspect of the present invention, there are provided a polymerization catalyst for olefins that includes the modified methylaluminoxane composition, and a method for producing polyolefins. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Modified methylaluminoxane composition] One aspect of the present invention relates to a modified methylaluminoxane composition. The "modified methylaluminoxane composition" of the present invention and the present specification is a composition containing at least modified methylaluminoxane, and may further contain, for example, trimethylaluminum, a solvent, etc. The modified methylaluminoxane contained in the modified methylaluminoxane composition according to one aspect of the present invention is a modified methylaluminoxane having x structural units represented by the following formula (I), y structural units represented by the following formula (II), and z structural units represented by the following formula (III):

[0011] [ka]

[0012] In the above formula, R represents an alkyl group having 2 to 10 carbon atoms, and * represents a bonding position. x and y each independently represent a positive real number, provided that the x / y ratio is 0.1 to 25, and z represents a real number of 0 or greater. When multiple Rs are present in the modified methylaluminoxane, the multiple Rs may be the same or different. The structural units represented by formula (I), formula (II), and formula (III) in the modified methylaluminoxane may be arranged in any order. The modified methylaluminoxane contained in the composition may have a molecular weight distribution. Therefore, x, y, and z represent the average values of x, y, and z of the modified methylaluminoxane contained in the composition.

[0013] The Al-H bond (hydride component) contained in the structural unit represented by formula (III) can be generated by β-hydrogen elimination of the alkyl group R of trialkylaluminum RAl (where R is the same as R in formula (II)), which is used as a monomer for preparing modified methylaluminoxane. As a result of extensive research by the present inventors, it has been discovered that reducing this Al-H bond (hydride component) leads to improved polymerization activity in the production of polyolefins using the modified methylaluminoxane composition as a cocatalyst. Specifically, from the perspective of improving polymerization activity, the hydride component content of the modified methylaluminoxane composition, i.e., the ratio of Al-H bonds to the total of Al-H bonds, Al-CH3 bonds, and Al-R bonds (where R is the same as R in formula (II)), is less than 1.00 mol%. The hydride component content can be determined by gas chromatography (GC) analysis. The hydride component content of the modified methylaluminoxane composition is preferably 0.99 mol% or less, with 0.95 mol% or less, 0.90 mol% or less, 0.85 mol% or less, 0.80 mol% or less, 0.75 mol% or less, 0.70 mol% or less, 0.65 mol% or less, and 0.60 mol% or less being more preferred in this order. The hydride component content of the modified methylaluminoxane composition may be, for example, 0.00 mol%, greater than 0.00 mol%, 0.01 mol% or more, or 0.10 mol% or more. From the viewpoint of improving polymerization activity, a lower hydride component content is preferable. The hydride component content of the modified methylaluminoxane composition can be reduced, for example, by adding a predetermined amount or more of water in step (a), which will be described in detail below.

[0014] The modified methylaluminoxane contained in the modified methylaluminoxane composition will be described in more detail below.

[0015] The modified methylaluminoxane has x number of structural units represented by formula (I), y number of structural units represented by formula (II), and z number of structural units represented by formula (III).

[0016] In formula (II), R represents an alkyl group having a carbon number of 2 to 10. When the modified methylaluminoxane has a plurality of R, the plurality of R may be the same or different.

[0017] The alkyl group represented by R can be a linear alkyl group or a branched alkyl group. Specific examples of the alkyl group represented by R include an ethyl group, a propyl group, an n-butyl group, an isobutyl group, a t-butyl group, an amyl group, an isoamyl group, an n-hexyl group, an isohexyl group, an n-octyl group, and an isooctyl group. The alkyl group represented by R can be an unsubstituted alkyl group or a substituted alkyl group. Specific examples of the substituent possessed by the substituted alkyl group include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. In the alkyl group substituted with a halogen atom, the number of halogen atoms contained as a substituent can be, for example, 1 or more and 10 or less.

[0018] From the viewpoint of availability, the number of carbon atoms in the alkyl group represented by R is preferably 2 or more and 6 or less. The alkyl group represented by R may preferably be an ethyl group, an n-butyl group, an isobutyl group, or an n-hexyl group.

[0019] The number of structural units x of the structural unit represented by formula (I) and the number of structural units y of the structural unit represented by formula (II) each independently represent a positive real number. However, if the x / y ratio is below 0.1, the polymerization activity decreases significantly, and if the x / y ratio exceeds 25, the solubility in the solvent decreases, so the x / y ratio is 0.1 or more and 25 or less. From the viewpoint of suppressing a decrease in polymerization activity, the x / y ratio is preferably 0.5 or more. From the viewpoint of suppressing a decrease in solubility in the solvent, the x / y ratio is preferably 20 or less.

[0020] From the viewpoint of fully exhibiting catalytic performance, the sum of x and y (x+y) is preferably 2 or more, and more preferably 5 or more. From the above viewpoint, the sum of x and y (x+y) is preferably 50 or less, and more preferably 30 or less.

[0021] The number of structural units z of the structural units represented by formula (III) is a real number of 0 or more, and can be 0 or can be 1 or more. The upper limit of the number of structural units of the structural units represented by formula (III) is essentially the same as the upper limit of the hydride component content.

[0022] In formula (I), formula (II) and formula (III), * represents a bonding position. The constitutional unit represented by formula (I) can be bonded at the bonding position to, for example, another constitutional unit represented by formula (I), to a constitutional unit represented by formula (II), to a constitutional unit represented by formula (III), or to an end group of the modified methylaluminoxane. The constitutional unit represented by formula (II) can be bonded at the bonding position to, for example, a constitutional unit represented by formula (I), a constitutional unit represented by formula (II), a constitutional unit represented by formula (III), or an end group of the modified methylaluminoxane. The constitutional unit represented by formula (III) can be bonded at a bonding position to, for example, a constitutional unit represented by formula (I), a constitutional unit represented by formula (II), a constitutional unit represented by formula (III), or an end group of the modified methylaluminoxane. In the modified methylaluminoxane, the constitutional units represented by formula (I), formula (II), and formula (III) may be arranged in any order. For example, the constitutional units represented by formula (I), formula (II), and formula (III) may be arranged consecutively, or may be arranged alternately or randomly in any order.

[0023] For the modified methylaluminoxane, the methylaluminoxane integral ratio determined by the method described below can be used as an indicator of the remaining amount of trimethylaluminum used as a monomer for preparing the modified methylaluminoxane. When the remaining amount of trimethylaluminum is zero, the methylaluminoxane integral ratio is 1.000. A smaller value of the methylaluminoxane integral ratio indicates a larger amount of remaining trimethylaluminum. In one embodiment, the modified methylaluminoxane can exhibit a methylaluminoxane integral ratio of 0.800 or less. Although residual trimethylaluminum can cause a decrease in polymerization activity, the modified methylaluminoxane has a low hydride component content as described above, and therefore can contribute to improving polymerization activity even when it contains a predetermined amount of trimethylaluminum. In one embodiment, the methylaluminoxane integral ratio of the modified methylaluminoxane can be 0.300 or more or 0.400 or more.

[0024] [Method of producing modified methylaluminoxane composition] One aspect of the present invention relates to a method for producing the modified methylaluminoxane composition, which includes the steps of: (a) adding 1.00 to 1.60 molar equivalents of water to a composition containing a trialkylaluminum represented by RAl (R is the same as R in formula (II)) to partially hydrolyze the trialkylaluminum, thereby obtaining an alkylaluminoxane composition; and (b) adding trimethylaluminum to the alkylaluminoxane composition obtained in step (a), wherein the temperature of the composition after adding 1.00 or more molar equivalents of water to the trialkylaluminum in step (a) is maintained at 10°C or below. The above manufacturing method will be described in more detail below.

[0025] <Process (a)> (Preparation of a composition containing trialkylaluminum) The composition to which water is added in step (a) contains a trialkylaluminum represented by R3Al and usually does not contain trimethylaluminum. Hereinafter, a trialkylaluminum represented by R3Al will also be referred to simply as trialkylaluminum. Water may be added to the trialkylaluminum alone, or to a solution in which the trialkylaluminum is mixed with an organic solvent. The concentration of trialkylaluminum in such a solution is not particularly limited. The amount of trialkylaluminum used may be determined depending on the value of y of the modified methylaluminoxane to be produced.

[0026] Examples of organic solvents that can be mixed with trialkylaluminum to prepare the solution include electron-donating organic solvents, hydrocarbon compounds, and mixtures of two or more of these organic solvents.

[0027] Specific examples of the electron-donating organic solvent include ether solvents such as 1,2-diethoxyethane, 1,2-dibutoxyethane, diethyl ether, di-n-propyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, tetrahydrofuran, dioxane, glyme, diglyme, triglyme, anisole, and methoxytoluene; amine solvents such as diisopropylethylamine and triethylamine; and chain or cyclic amide compounds such as N,N-dimethylformamide, N,N-diethylformamide, 1,1,3,3-tetramethylurea, N-methyl-2-pyrrolidone, 1,3-dimethyl-imidazolidinone, and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

[0028] Examples of the hydrocarbon compound include linear hydrocarbon compounds, branched hydrocarbon compounds, or cyclic hydrocarbon compounds having 5 to 20 carbon atoms (preferably 6 to 12 carbon atoms), aromatic hydrocarbon compounds having 6 to 20 carbon atoms (preferably 6 to 12 carbon atoms), and mixtures thereof.

[0029] Specific examples of the hydrocarbon compound include aliphatic hydrocarbons such as pentane, hexane, heptane, isohexane, methylpentane, octane, 2,2,4-trimethylpentane (isooctane), n-nonane, n-decane, n-hexadecane, octadecane, eicosane, methylheptane, 2,2-dimethylhexane, and 2-methyloctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, and decalin; aromatic hydrocarbons such as benzene, toluene, xylene, cumene, and trimethylbenzene; and hydrocarbon solvents such as mineral spirits, solvent naphtha, kerosene, and petroleum ether.

[0030] (Addition of water) The addition of water to the composition in step (a) can be carried out without mixing water with another solvent, or can be carried out after mixing water with another solvent. The amount of water added to the composition in step (a) is 1.00 or more and less than 1.60 equivalents on a molar basis relative to the amount of trialkylaluminum. However, the temperature of the composition after adding 1.00 or more equivalents of water on a molar basis relative to the amount of trialkylaluminum in step (a) is maintained at 10°C or less. If the amount of water added in step (a) is less than 1.00 equivalents, the hydride component content of the resulting modified methylaluminoxane composition will exceed the range described above, and the use of such a modified methylaluminoxane composition as a cocatalyst will result in reduced polymerization activity in the production of polyolefins. Therefore, the amount of water added in step (a) is set to 1.00 equivalents or more, preferably 1.05 equivalents or more, more preferably 1.10 equivalents or more, 1.15 equivalents or more, and 1.20 equivalents or more in that order. On the other hand, if the amount of water added in step (a) is 1.60 equivalents or more, gelation occurs significantly, and it is difficult to obtain modified methylaluminoxane even if trimethylaluminum is added to the composition obtained in step (a) in step (b). Therefore, the amount of water added in step (a) is less than 1.60 equivalents, more preferably 1.55 equivalents or less, with 1.50 equivalents or less, 1.45 equivalents or less, 1.40 equivalents or less, 1.35 equivalents or less, and 1.30 equivalents or less being more preferred in that order. Furthermore, in step (a), gelation becomes more likely as the amount of water added increases. Therefore, to suppress gelation, the temperature of the composition after adding 1.00 or more equivalents of water on a molar basis relative to the amount of trialkylaluminum is maintained at 10°C or below. That is, after adding at least 1.00 or more equivalents of water on a molar basis relative to the amount of trialkylaluminum, the temperature of the composition is maintained at 10°C or below, preferably 5°C or below. The temperature can be, for example, -10°C or above or -5°C or above, but may be below the range exemplified herein. The temperature of the composition from the start of water addition until less than 1.00 equivalents of water is added may be 10°C or below or may be above 10°C. However, from the viewpoint of ease of temperature control during water addition, the temperature is preferably 10°C or below, and more preferably 5°C or below. The temperature of the composition from the start of water addition until less than 1.00 equivalents of water is added may be, for example, -10°C or above or -5°C or above, but may be below the range exemplified herein. The addition of water can be carried out over a period of time ranging from 60 seconds to 15 hours, depending on the scale of the reaction. After the addition of water, the composition to which water has been added can be left to stand without stirring for 1 minute to 48 hours, or can be stirred, in order to further promote the hydrolysis reaction. The temperature of the composition during and after the addition of water may be maintained at a constant temperature or within a predetermined range, or may be raised and / or lowered as appropriate. For example, the temperature of the composition after the addition of water may be raised, then maintained at a constant temperature or within a predetermined range, and then lowered, and this process may be repeated once or multiple times. Maintaining the temperature of the composition at a constant temperature or within a predetermined range is called "aging." In the present invention and this specification, the temperature of the composition is also referred to as the "internal temperature."

[0031] In step (a), a hydrolysis reaction proceeds in the composition after adding water, and the trialkylaluminum represented by R3Al is partially hydrolyzed to produce an alkylaluminoxane. In the modified methylaluminoxane produced by the above production method, the structural unit represented by formula (I) is derived from the partial hydrolysis product of trimethylaluminum, and the structural unit represented by formula (II) is derived from the trialkylaluminum represented by R3Al. Therefore, R in R3Al has the same meaning as R in formula (II). In R3Al, the three Rs may be the same or different.

[0032] Thus, an alkylaluminoxane composition is obtained by step (a). Such an alkylaluminoxane composition contains at least an alkylaluminoxane produced by partial hydrolysis of a trialkylaluminum represented by RAl, and may further contain, for example, water, a solvent, a trialkylaluminum represented by RAl, etc.

[0033] <Process (b)> In step (b), trimethylaluminum is added to the alkylaluminoxane-containing composition obtained in step (a). In step (b), trialkylaluminum is not usually added. The amount of trimethylaluminum used in step (b) can be determined depending on the value of x in the modified methylaluminoxane to be produced. Trimethylaluminum may be added alone, or as a solution in which trimethylaluminum is mixed with an organic solvent. For details of the organic solvent, please refer to the above description of the organic solvent that can be mixed with trialkylaluminum. The concentration of trimethylaluminum in such a solution is not particularly limited.

[0034] After adding trimethylaluminum to the alkylaluminoxane-containing composition obtained in step (a), the composition can be left to stand without stirring for 1 minute to 48 hours, or can be stirred. The temperature of the composition can be, for example, in the range of -90 to 150°C, and preferably in the range of -15 to 80°C. The temperature of the composition can be maintained at a constant temperature or within a predetermined range, or can be raised and / or lowered as appropriate. For example, the temperature of the composition after adding trimethylaluminum can be raised and then maintained at a constant temperature or within a predetermined range, and then lowered, once or multiple times.

[0035] In one embodiment of step (b), no water is added. Not adding water in step (b) is preferred from the viewpoint of further reducing the hydride component content of the modified methylaluminoxane produced.

[0036] Another embodiment of step (b) includes adding 0.60 or less molar equivalents of water relative to the amount of trimethylaluminum after the addition of trimethylaluminum. When water is added in step (b), it is preferable to add 0.60 or less molar equivalents of water relative to the amount of trimethylaluminum, from the viewpoint of further reducing the hydride component content of the modified methylaluminoxane produced. From the above viewpoint, the amount of water added in step (b) is preferably 0.55 or less molar equivalents relative to the amount of trimethylaluminum, with 0.50 or less, 0.45 or less, 0.40 or less, and 0.35 or less being more preferred in this order. When water is added in step (b), the amount of water added is more than 0.00 molar equivalents relative to the amount of trimethylaluminum, and can be 0.10 or more, or 0.20 or more.

[0037] The addition of water in step (b) can be carried out without mixing water with other solvents, or after mixing water with other solvents. The addition of water can be carried out over a period of time ranging from 60 seconds to 15 hours, depending on the scale of the reaction. The temperature of the composition during the addition of water can be, for example, in the range of -90 to 150°C, and from the viewpoint of the reactivity of the hydrolysis reaction, it is preferable to set the temperature in the range of -15 to 30°C.

[0038] After the addition of water, the composition to which water has been added can be left to stand without stirring for 1 minute to 48 hours, or can be stirred, in order to further promote the hydrolysis reaction. The internal temperature here can be, for example, in the range of -90 to 150°C, and preferably in the range of -15 to 80°C. The temperature of the composition can be maintained at a constant temperature or within a predetermined range, or can be raised and / or lowered as appropriate. For example, the temperature of the composition after the addition of water can be raised and then maintained at a constant temperature or within a predetermined range, and then lowered, and this process can be carried out once or multiple times.

[0039] In the above production method, the total amount of water added in step (a) and step (b) can be, for example, 0.50 equivalents or more, 0.60 equivalents or more, or 0.70 equivalents or more, based on the total amount of trialkylaluminum represented by RAl and trimethylaluminum. It can also be, for example, 1.00 equivalents or less, 0.95 equivalents or less, or 0.90 equivalents or less. When no water is added in step (b) as described above, the amount of water added in step (b) is zero.

[0040] The modified methylaluminoxane composition can be used as a polymerization catalyst in combination with a known catalyst for olefin polymerization. Examples of the olefin polymerization catalyst include transition metal compounds. Specific examples of such transition metal compounds include the transition metal compounds represented by the following formula 1:

[0041] [Olefin polymerization catalyst] One aspect of the present invention relates to an olefin polymerization catalyst comprising the above-mentioned modified methylaluminoxane and a transition metal compound represented by the following formula 1:

[0042] Formula 1:MR 5 R 6 R 7 R 8

[0043] In Formula 1, M represents a transition metal atom, R 5 , R 6 , R 7 and R 8 Among these, at least one is an organic group having a cycloalkadienyl skeleton, and the remaining groups each independently represent an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, an alkylsilyl group, an alkylamide group, an alkylimide group, an alkylamino group, an alkylimino group, or a halogen atom. 5 , R 6 , R 7 and R 8When two or more of the above are organic groups having a cycloalkadienyl skeleton, at least two of the organic groups having a cycloalkadienyl skeleton may be bridged by carbon, silicon, or germanium.

[0044] In the polymerization catalyst, the transition metal compound can function as a main catalyst, and the modified methylaluminoxane composition can function as a co-catalyst that contributes to the activation of the transition metal compound of the main catalyst.

[0045] Specifically, M in formula 1 can be titanium, zirconium, hafnium, chromium, vanadium, manganese, iron, cobalt, nickel, or palladium, and is preferably titanium, zirconium, chromium, iron, or nickel.

[0046] The transition metal compound represented by formula 1 is preferably a metallocene compound having one or two organic groups (ligands) with a cycloalkadienyl skeleton. Examples of the ligand with a cycloalkadienyl skeleton include alkyl-substituted cyclopentadienyl groups such as a cyclopentadienyl group, a methylcyclopentadienyl group, an ethylcyclopentadienyl group, a butylcyclopentadienyl group, a dimethylcyclopentadienyl group, and a pentamethylcyclopentadienyl group, an indenyl group, and a fluorenyl group. The cycloalkadienyl group may be crosslinked with a divalent substituted alkylene group, a substituted silylene group, or the like.

[0047] The ligands other than those having a cycloalkadienyl skeleton represent alkyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, alkylsilyl groups, alkylamide groups, alkylimido groups, alkylamino groups, alkylimino groups, or halogen atoms. The alkyl groups include cycloalkyl groups. The number of carbon atoms in the alkyl groups, cycloalkyl groups, aryl groups, and aralkyl groups can be, for example, 1 to 20. Specific examples of alkyl groups include methyl groups, ethyl groups, propyl groups, isopropyl groups, and butyl groups. Examples of cycloalkyl groups include cyclopentyl groups and cyclohexyl groups. Examples of aryl groups include phenyl groups and tolyl groups. Examples of aralkyl groups include benzyl groups. Examples of alkoxy groups include methoxy groups, ethoxy groups, and butoxy groups. Examples of aryloxy groups include phenoxy groups. These groups may be substituted with halogen atoms or the like. Examples of the alkylsilyl group include a trimethylsilyl group, a triethylsilyl group, etc. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0048] Specific examples of transition metal compounds containing a ligand having a cycloalkadienyl skeleton when M in formula 1 is zirconium are shown below. Bis(cyclopentadienyl)zirconium monochloride monohydride, bis(cyclopentadienyl)zirconium monobromide monohydride, bis(cyclopentadienyl)methylzirconium hydride, bis(cyclopentadienyl)ethylzirconium hydride, bis(cyclopentadienyl)phenylzirconium hydride, bis(cyclopentadienyl)benzylzirconium hydride, bis(cyclopentadienyl)neopentylzirconium hydride, Bis(methylcyclopentadienyl)zirconium monochloride hydride, bis(indenyl)zirconium monochloride hydride, bis(cyclopentadienyl)zirconium dichloride, bis(cyclopentadienyl)zirconium dibromide, bis(cyclopentadienyl)methylzirconium monochloride, bis(cyclopentadienyl)ethylzirconium monochloride, bis(cyclopentadienyl)cyclohexylzirconium monochloride, bis(cyclopentadienyl)phenyl Bis(cyclopentadienyl)benzylzirconium monochloride, bis(methylcyclopentadienyl)zirconium dichloride, bis(dimethylcyclopentadienyl)zirconium dichloride, bis(n-butylcyclopentadienyl)zirconium dichloride, bis(1-butyl-3-methylcyclopentadienyl)zirconium dichloride, bis(indenyl)zirconium dichloride, bis(indenyl)zirconium dibromide, bis(cyclopentadienyl) bis(cyclopentadienyl)zirconium dimethyl, bis(cyclopentadienyl)zirconium diphenyl, bis(cyclopentadienyl)zirconium dibenzyl, bis(cyclopentadienyl)zirconium monomethoxymonochloride, bis(cyclopentadienyl)zirconium monoethoxymonochloride, bis(methylcyclopentadienyl)zirconium monoethoxymonochloride, bis(cyclopentadienyl)zirconium monophenoxymonochloride, bis(fluorenyl)zirconium dichloride, and the like.

[0049] Specific examples of transition metal compounds in which M in Formula 1 is zirconium, the compound contains two or more ligands having a cycloalkadienyl skeleton, and the two or more ligands having a cycloalkadienyl skeleton are bonded via an alkylene group such as an ethylene group or a propylene group; a substituted alkylene group such as an isopropylidene group or a diphenylmethylene group; a silylene group; a substituted silylene group such as a dimethylsilylene group; or a substituted germanediyl group such as a dimethylgermanediyl group or a diphenylgermanediyl group are shown below. Ethylene bis(indenyl)dimethyl zirconium, ethylene bis(indenyl)diethyl zirconium, ethylene bis(indenyl)diphenyl zirconium, ethylene bis(indenyl)methyl zirconium monochloride, ethylene bis(indenyl)ethyl zirconium monochloride, ethylene bis(indenyl)methyl zirconium monobromide, ethylene bis(indenyl)zirconium dichloride, ethylene bis(indenyl)zirconium bromide, ethylene bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, dimethylsilylene bis(indenyl)zirconium dichloride diphenylsilylenebis(indenyl)zirconium dichloride, diphenylsilylenebis(indenyl)zirconium dichloride, dimethylsilylenebis(2-methyl-4-phenylindenyl)zirconium dichloride, dimethylsilylenebis(2-methyl-4-(1-naphthyl)indenyl)zirconium dichloride, dimethylgermanediylbis(indenyl)zirconium dichloride, diphenylgermanediylbis(indenyl)zirconium dichloride, dimethylgermanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride, dimethylgermanediylbis(2-methyl-4-(1-naphthyl)indenyl)zirconium dichloride, etc. These may be racemic or meso isomers, or mixtures thereof.

[0050] In homogeneous polymerization, only one type of the transition metal compound may be used, or two or more types may be used for the purpose of adjusting the molecular weight distribution, etc. In addition, when a solid catalyst is prepared in advance, only one type of the transition metal compound may be used, or two or more types may be used for the purpose of adjusting the molecular weight distribution, etc.

[0051] The contents of the modified methylaluminoxane composition and the transition metal compound in the polymerization catalyst are not particularly limited, and known techniques relating to olefin polymerization catalysts can be applied.

[0052] [Polyolefin manufacturing method] One aspect of the present invention relates to a method for producing a polyolefin, which comprises polymerizing olefins in the presence of the above-described polymerization catalyst.

[0053] Examples of polymerization methods using the above polymerization catalyst include solution polymerization using a solvent, bulk polymerization without using a solvent, gas phase polymerization, etc. The above polymerization catalyst can be used in both continuous polymerization and batch polymerization, and hydrogen or the like can also be used as a molecular weight modifier, if necessary.

[0054] The monomer used in the polymerization may be any compound that can be used for copolymerization of an olefinic monomer alone or in combination thereof. Specific examples include α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-decene, 1-hexadecene, 1-octadecene, and 1-eicosene, halogen-substituted olefins such as difluoroethylene, trifluoroethylene, tetrafluoroethylene, and hexafluoropropene, and cyclic olefins such as cyclopentene, cyclohexene, and norbornene.

[0055] Regarding the above production method, details regarding the polymerization of olefins, such as polymerization conditions, are not particularly limited, and known techniques regarding the polymerization of olefins can be applied. [Example]

[0056] The present invention will be described below based on examples, but the present invention is not limited to the embodiments shown in the examples.

[0057] In the following, "triisobutylaluminum" will be abbreviated as "TIBAL," "trimethylaluminum" as "TMAL," "methylcyclohexane" as "MCH," and "methylaluminoxane" as "MAO." The "equivalents" listed below are on a molar basis. "eq" is an abbreviation for equivalent.

[0058] [Example 1] Step (a): In a 500 mL flask, 1.21 equivalents of water (364 mmol) was added dropwise over 150 minutes to a mixture of TIBAL (300 mmol) and hexane (185 mL) while maintaining the internal temperature at -4±10°C, and the mixture was further aged at an internal temperature of 1±2°C for 90 minutes. Step (b): A mixture of TMAL (150 mmol) and hexane (10 mL) was added dropwise to the composition obtained in step (a) over 5 minutes while maintaining the internal temperature at 3±4°C. The internal temperature was then raised to 20°C over 30 minutes, and then further raised to 50±2°C over 20 minutes, and aged at the same temperature for 1 hour. The mixture was then allowed to cool to room temperature (20±5°C) over 1 hour and stirred overnight (18 hours) to obtain a modified methylaluminoxane composition. GC analysis of the modified methylaluminoxane composition revealed that the hydride component content was 0.15 mol %, the methyl group content was 60.5 mol %, and the isobutyl group content was 39.3 mol %.

[0059] Polymerization activity evaluation: The modified methylaluminoxane composition was diluted with toluene to a 0.6M Al concentration to prepare a cocatalyst solution. Toluene (1.0 L) was added to a 1.5 L autoclave under an ethylene atmosphere, and triethylaluminum (0.50 mmol, 0.5 M hexane solution) was added. The internal temperature was raised to 40±2°C, and bis(1-butyl-3-methylcyclopentadienyl)zirconium dichloride (2.5 μmol, 3.0 mM toluene solution) and the cocatalyst solution (0.50 mmol as Al) were sequentially added. Ethylene was then introduced at a flow rate of 5.0 L / min to increase the gauge pressure to 0.8 MPa, and the mixture was stirred at 50±2°C for 1 hour. The ethylene introduction was then stopped, and the atmosphere was replaced with nitrogen and allowed to cool. The resulting polyethylene was collected by suction filtration and dried. The polymerization activity was calculated from its dry mass and ethylene consumption to be 24.2 kg-PE / mmol-Zr. The polymerization activity is calculated by the following formula: The mass [kg] of consumed ethylene is determined using a mass flow meter, and the same results are obtained by using this as the mass [kg] of the obtained polymer. Mass of the obtained polymer (PE: polyethylene) [kg] / Amount of the main catalyst added [mmol] = Polymerization activity [kg-PE / mmol-Zr (main catalyst)]

[0060] [Example 2] Step (a): In a 5 L separable flask, 1.21 equivalents of water (3.73 mol) was added dropwise to a mixture of TIBAL (3.08 mol) and MCH (1.41 kg) over 11 hours while maintaining the internal temperature at 0±2°C, and the mixture was further aged at the same temperature for 90 minutes. Step (b): A mixture of TMAL (1.54 mol) and MCH (154 g) was added dropwise to the composition obtained in step (a) over 15 minutes while maintaining the internal temperature at -1±3°C. The internal temperature was then raised to 30°C over 45 minutes, then further raised to 50±1°C over 30 minutes, and aged at the same temperature for 1 hour. The mixture was then allowed to cool to room temperature (20±5°C) over 1 hour and stirred overnight (14 hours). The next morning, the mixture was heated to 60±1°C over 45 minutes, aged at the same temperature for 3 hours, and then allowed to cool to 25°C over 1 hour, yielding a modified methylaluminoxane composition. GC analysis of the resulting modified methylaluminoxane composition revealed that it had a hydride content of 0.42 mol%, a methyl group content of 59.4 mol%, and an isobutyl group content of 40.1 mol%. Ethylene polymerization was performed using this composition by the method described in Example 1, and the polymerization activity was calculated to be 26.4 kg-PE / mmol-Zr.

[0061] [Example 3] Step (a): To a mixture of TIBAL (360 mmol) and MCH (189 mL) in a 500 mL flask, 1.01 equivalents of water (364 mmol) was added dropwise over 150 minutes while maintaining the internal temperature at -4±6°C, and the mixture was further aged at the same temperature for 90 minutes. Step (b): A mixture of TMAL (90 mmol) and MCH (6.0 mL) was added dropwise to the composition obtained in step (a) over 10 minutes while maintaining the internal temperature at -6±4°C. The internal temperature was then raised to 20°C over 30 minutes, then further raised to 50±2°C over 20 minutes, and aged at the same temperature for 1 hour. The mixture was then allowed to cool to room temperature (20±5°C) over 1 hour and stirred overnight (18 hours). The next morning, the mixture was raised to 60±3°C over 30 minutes, aged at the same temperature for 3 hours, and then allowed to cool to 25°C over 1 hour, yielding a modified methylaluminoxane composition. GC analysis of the resulting modified methylaluminoxane composition revealed that it had a hydride content of 0.99 mol%, a methyl group content of 42.4 mol%, and an isobutyl group content of 56.6 mol%. Ethylene polymerization was performed using this composition by the method described in Example 1, and the polymerization activity was calculated to be 25.7 kg-PE / mmol-Zr.

[0062] [Example 4] Step (a): To a mixture of TIBAL (300 mmol) and MCH (185 mL) in a 500 mL flask, 1.21 equivalents of water (364 mmol) was added dropwise over 150 minutes while maintaining the internal temperature at -4±6°C, and the mixture was further aged at the same temperature for 90 minutes. Step (b): A mixture of TMAL (150 mmol) and MCH (10 mL) was added dropwise to the composition obtained in step (a) over 10 minutes while maintaining the internal temperature at -6±4°C. The internal temperature was then raised to 20°C over 30 minutes, then further raised to 50±2°C over 20 minutes, and aged at the same temperature for 1 hour. The mixture was then allowed to cool to room temperature (20±5°C) over 1 hour and stirred overnight (18 hours). The next morning, the mixture was heated to 60±3°C over 30 minutes, aged at the same temperature for 3 hours, and then allowed to cool to 25°C over 1 hour, yielding a modified methylaluminoxane composition. GC analysis of the resulting modified methylaluminoxane composition revealed that it had a hydride component content of 0.11 mol%, a methyl group content of 59.8 mol%, and an isobutyl group content of 40.0 mol%. Ethylene polymerization was performed using this composition by the method described in Example 1, and the polymerization activity was calculated to be 27.9 kg-PE / mmol-Zr.

[0063] [Example 5] Step (a): To a mixture of TIBAL (280 mmol) and MCH (184 mL) in a 500 mL flask, 1.15 equivalents of water (320 mmol) was added dropwise over 150 minutes while maintaining the internal temperature at -4±6°C, and the mixture was further aged at the same temperature for 90 minutes. Step (b): A mixture of TMAL (171 mmol) and MCH (11 mL) was added dropwise to the composition obtained in step (a) over 10 minutes while maintaining the internal temperature at -6±4°C. The internal temperature was then raised to 20°C over 30 minutes, and then further raised to 50±2°C over 20 minutes, and aged at the same temperature for 1 hour. The mixture was then allowed to cool to room temperature (20±5°C) over 1 hour, yielding a modified methylaluminoxane composition. A portion of the resulting modified methylaluminoxane composition was taken out and subjected to ethylene polymerization by the method described in Example 1, and the polymerization activity was calculated to be 26.4 kg-PE / mmol-Zr. Continuation of step (b): The composition in the flask was heated to 60±3°C over 30 minutes, aged at the same temperature for 3 hours, and then allowed to cool to 25°C over 1 hour to obtain a modified methylaluminoxane composition (after aging at 60°C). GC analysis of the modified methylaluminoxane composition (after aging at 60°C) revealed that the hydride component content was 0.28 mol%, the methyl group content was 64.0 mol%, and the isobutyl group content was 35.7 mol%.

[0064] [Example 6] Step (a): To a mixture of TIBAL (321 mmol) and MCH (186 mL) in a 500 mL flask, 1.27 equivalents of water (407 mmol) was added dropwise over 150 minutes while maintaining the internal temperature at -4±6°C, and the mixture was further aged at the same temperature for 90 minutes. Step (b): A mixture of TMAL (129 mmol) and MCH (8.6 mL) was added dropwise to the composition obtained in step (a) over 10 minutes while maintaining the internal temperature at -6±4°C. The internal temperature was then raised to 20°C over 30 minutes, then further raised to 50±2°C over 20 minutes, and aged at the same temperature for 1 hour. The mixture was then allowed to cool to room temperature (20±5°C) over 1 hour and stirred overnight (18 hours). The next morning, the mixture was heated to 60±3°C over 30 minutes, aged at the same temperature for 3 hours, and then allowed to cool to 25°C over 1 hour, yielding a modified methylaluminoxane composition. GC analysis of the resulting modified methylaluminoxane composition revealed that it had a hydride content of 0.17 mol%, a methyl group content of 56.9 mol%, and an isobutyl group content of 42.8 mol%. Ethylene polymerization was performed using this composition by the method described in Example 1, and the polymerization activity was calculated to be 24.3 kg-PE / mmol-Zr.

[0065] From the results of GC analysis of the modified methylaluminoxane compositions obtained in Examples 1 to 6, it was determined that the x and y of the modified methylaluminoxane contained in the modified methylaluminoxane composition obtained in each Example were each independently positive real numbers, the x / y ratio was 0.1 or more and 25 or less, and z was a real number of 0 or more.

[0066] [Comparative Example 1] Step (a): In a 5 L separable flask, water (1.24 mol) was added over 3.5 hours to a mixture of TIBAL (1.77 mol) and hexane (1.40 kg) while maintaining the internal temperature at 1±2°C, and the flask was aged at the same temperature for 1 hour. After that, the internal temperature was raised to 20±2°C over 1 hour to obtain a polyisobutylaluminoxane composition. Step (b): Next, TMAL (2.82 mol) and hexane (150 g) were added, and the internal temperature was raised to 50±2°C over 40 minutes, aged at the same temperature for 1 hour, and then cooled to 30°C. Subsequently, water (2.48 mol = 0.88 equivalents relative to TMAL) was added over 6 hours while maintaining the internal temperature at 1±2°C. Then, the internal temperature was raised to 50±2°C over 35 minutes, aged at the same temperature for 1 hour, and then cooled to 30°C. GC analysis of the resulting composition revealed that the hydride component content was as high as 1.49 mol%. Ethylene polymerization was carried out using this composition by the method described in Example 1, and the polymerization activity was calculated to be 23.9 kg-PE / mmol-Zr.

[0067] Comparative Example 2 Step (a): In a 5 L separable flask, water (1.24 mol) was added over 3.5 hours to a mixture of TIBAL (1.77 mol) and MCH (1.41 kg) while maintaining the internal temperature at 1±2°C, and the flask was aged at the same temperature for 1 hour. The internal temperature was then raised to 20±2°C over 1 hour, yielding a polyisobutylaluminoxane composition. Step (b): Next, TMAL (2.84 mol) and MCH (150 g) were added, and the internal temperature was raised to 50±2°C over 30 minutes, and the mixture was aged at the same temperature for 1 hour, and then cooled to 30°C. Subsequently, water (2.50 mol) was added over 5 hours while maintaining the internal temperature at 1±2°C, and the internal temperature was raised to 50±2°C over 30 minutes, and the mixture was aged at the same temperature for 1 hour, and then cooled to 30°C, thereby obtaining a modified methylaluminoxane composition. GC analysis of the resulting modified methylaluminoxane composition revealed a high hydride content of 1.23 mol%. After aging the composition at 60°C for 3 hours, ethylene polymerization was carried out in the same manner as in Example 1, and the polymerization activity was calculated to be 23.5 kg-PE / mmol-Zr.

[0068] Comparative Example 3 The procedure described for the comparative example was repeated except that the amount of TMAL added in step (b) was changed to 2.86 mol and the amount of water added to 2.06 mol. GC analysis of the resulting composition revealed that the hydride component content was as high as 1.11 mol%. Furthermore, ethylene polymerization was performed using this composition by the method described for Example 1, and the polymerization activity was calculated to be 21.6 kg-PE / mmol-Zr.

[0069] Comparative Example 4 Step (a): In a 500 mL flask, 0.70 equivalents of water (210 mmol) was added over 105 minutes to a mixture of TIBAL (300 mmol) and MCH (143 mL) while maintaining the internal temperature at 1±3°C, and the mixture was aged at the same temperature for 1 hour. After that, the internal temperature was raised to 20±2°C over 30 minutes, thereby obtaining a polyisobutylaluminoxane composition. Step (b): Next, a mixture of TMAL (149 mmol) and MCH (33 mL) was added, and the internal temperature was raised to 50±2°C over 20 minutes, aged at the same temperature for 1 hour, and then cooled to 25°C. Subsequently, water (154 mmol) was added over 2.5 hours while maintaining the internal temperature at 1±3°C, and then the internal temperature was raised to 50±2°C over 30 minutes, aged at the same temperature for 1 hour, and then cooled to 25°C. GC analysis of the resulting modified methylaluminoxane composition revealed that the hydride component content was as high as 2.51 mol%. Ethylene polymerization was performed using this composition by the method described in Example 1, and the polymerization activity was calculated to be 16.9 kg-PE / mmol-Zr.

[0070] [Reference example 1] Step (a): To a mixture of TIBAL (172 mmol) and MCH (177 mL) in a 500 mL flask, 2.10 equivalents of water (361 mmol) was added dropwise over 300 minutes while maintaining the internal temperature at -4±6°C (most of the mixture gelled when the amount of water added exceeded 1.6 equivalents). Step (b): To the composition obtained in step (a), a mixture of TMAL (275 mmol) and MCH (18.3 mL) was added dropwise over 10 minutes while maintaining the internal temperature at -6±4°C. The internal temperature was then raised to 50±2°C and aged at the same temperature for 1 hour, after which the mixture was allowed to cool to room temperature (20±5°C). The resulting composition was a heterogeneous composition containing a large amount of gel, and in NMR analysis it did not have an isobutyl group or a broad methyl group signal characteristic of modified methylaluminoxane.

[0071] [Reference example 2] Step (a): In a 500 mL flask, 1.21 equivalents of water (364 mmol) was added dropwise over 150 minutes to a mixture of TIBAL (300 mmol) and MCH (185 mL) while maintaining the internal temperature at -4±6°C. After that, an attempt was made to naturally raise the temperature (20±5°C). When the internal temperature reached 10°C, an endothermic reaction was observed and most of the mixture gelled. Step (b): When TMAL was added to the gel composition obtained in step (a) and the mixture was aged at an internal temperature of 50±2°C, no modified methylaluminoxane was obtained.

[0072] The results are shown in the table below.

[0073] The "MAO integral ratio" shown in the table below was calculated as the ratio of the integral value occupied by the modified methylaluminoxane to the methyl group signals detected in the vicinity of -0.2 ppm to -1.1 ppm in the NMR analysis results of the modified methylaluminoxane composition shown in the table below, measured using an ECA500 manufactured by JEOL Ltd., excluding the sharp signal detected in the vicinity of -0.9 ppm to -1.0 ppm (attributed to unreacted TMAL). Each peak can be easily extracted by curve fitting, baseline collection, etc.

[0074] [Table 1]

[0075] As shown in Table 1, in Examples 1 to 6, modified methylaluminoxanes with hydride component contents of less than 1.00 mol % could be produced, and high polymerization activity was obtained. In contrast, the results of Comparative Examples 1 to 4 show that when H2O / R3Al in step (a) is less than 1.00 equivalents, the resulting modified methylaluminoxane composition contains 1.00 mol% or more of hydride components as impurities, resulting in low polymerization activity. The results of Reference Example 1 show that when the HO / RAl ratio in step (a) is 1.60 equivalents or more, most of the mixture gels when it exceeds 1.60 equivalents, and even if TMAL is added in step (b), a modified methylaluminoxane composition cannot be obtained. The results of Reference Example 2 show that even if the HO / RAl ratio in step (a) is 1.00 equivalents or more but less than 1.60 equivalents, if the temperature of the composition exceeds 10°C after 1.00 equivalents or more of water is added, the composition will gel, and even if TMAL is added in step (b), a modified methylaluminoxane composition will not be obtained. [Industrial Applicability]

[0076] One aspect of the present invention is useful in the art of olefin polymerization.

Claims

1. 1. A modified methylaluminoxane composition comprising: The modified methylaluminoxane has x structural units represented by the following formula (I), y structural units represented by the following formula (II), and z structural units represented by the following formula (III): 【Chemical 1】 (In the above formula, R represents an alkyl group having 2 to 10 carbon atoms, * represents a bonding position, x and y each independently represent a positive real number, with the proviso that the x / y ratio is 0.1 to 25, and z represents a real number of 0 or greater. When a plurality of R's are present in the modified methylaluminoxane, the plurality of R's may be the same or different. The structural unit represented by formula (I), the structural unit represented by formula (II), and the structural unit represented by formula (III) may be arranged in any order in the modified methylaluminoxane.) Al—H bonds, Al—CH ３ the modified methylaluminoxane composition, wherein the proportion of Al—H bonds to the total of Al—H bonds and Al—R bonds (R has the same meaning as R in formula (II)) is less than 1.00 mol %.

2. 2. The modified methylaluminoxane composition of claim 1, wherein in formula (II), R represents an isobutyl group.

3. A method for producing the modified methylaluminoxane composition according to claim 1 or 2, comprising: R ３ a step (a) of adding 1.00 to 1.60 molar equivalents of water to a composition containing a trialkylaluminum represented by formula (II), wherein R has the same meaning as R in formula (II), to partially hydrolyze the trialkylaluminum, thereby obtaining an alkylaluminoxane composition; a step (b) of adding trimethylaluminum to the alkylaluminoxane composition obtained in the step (a); Including, The above-mentioned production method, wherein in the step (a), the temperature of the composition after adding 1.00 or more equivalents of water on a molar basis relative to the amount of the trialkylaluminum is maintained at 10°C or lower.

4. The modified methylaluminoxane composition according to claim 1 or 2 and a compound represented by the following formula 1: MR ５ R ６ R ７ R ８ (In Formula 1, M represents a transition metal atom, R ５ , R ６ , R ７ and R ８ Among these, at least one is an organic group having a cycloalkadienyl skeleton, and the remaining groups each independently represent an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, an alkylsilyl group, an alkylamide group, an alkylimide group, an alkylamino group, an alkylimino group, or a halogen atom. ５ , R ６ , R ７ and R ８ When two or more of the above are organic groups having a cycloalkadienyl skeleton, at least two of the organic groups having a cycloalkadienyl skeleton may be bridged by carbon, silicon, or germanium. A polymerization catalyst for olefins, comprising a transition metal compound represented by the formula:

5. A method for producing a polyolefin, comprising polymerizing olefins in the presence of the polymerization catalyst according to claim 4.

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