Aluminoxane-containing solution capable of long-term stable storage and method for producing the same

Abstract

To provide an aluminoxane-containing solution capable of long-term stable storage and a method for producing the same.SOLUTION: The present invention provides a cyclic ether solution containing aluminoxane and a polar additive, and a method for producing the same. Preferably, the aluminoxane is methylaluminoxane, the cyclic ether is tetrahydrofuran, and the polar additive is selected from the group consisting of amine compounds, amide compounds, and sulfoxide compounds.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aluminoxane-containing solution that can be stably stored for a long time and a method for producing the same.

Background Art

[0002] It is widely known that methylaluminoxane, which is a condensation product of water and trimethylaluminum, exhibits high activity for ethylene polymerization as a cocatalyst for metallocene catalysts (Non-Patent Document 1). In the reaction of water and trimethylaluminum, it is impossible to avoid the formation of solids or gels in the form of trimethylaluminum that has undergone excessive hydrolysis, resulting in a decrease in the reaction yield based on aluminum. In addition, the gel itself accumulates in the production line or tank, interfering with the smooth operation of the production plant and causing a decrease in the yield and purity of the final product. Furthermore, if impurities are present in the polyolefin, it will cause adverse effects such as a decrease in the functionality of the polyolefin itself, coloring, and physiological activity to the human body. Therefore, it is desirable that there are no impurities in the cocatalyst methylaluminoxane itself (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since it is necessary to completely eliminate the aluminum-containing gel that is by-produced during the production of aluminoxanes such as methylaluminoxane in its manufacturing process, it is conceivable to dissolve and handle aluminoxane in a polar solvent such as tetrahydrofuran (THF). Tetrahydrofuran is known to undergo ring-opening polymerization in the presence of a Lewis acid to form polytetramethylene ether glycol (Non-Patent Document 2). It is described that when only ethylaluminoxane (EAO) is used as a catalyst as the Lewis acid, the reaction does not proceed, and the addition of an epoxide such as epichlorohydrin promotes the reaction.

[0006] However, it has been found that a tetrahydrofuran solution containing methylaluminoxane (MAO) polymerizes even without the addition of an epoxide, and the viscosity of the solution increases. Tetrahydrofuran has a high solubility in aluminoxane and is easy to remove due to its low boiling point, so it is used as a cleaning solvent. The cleaning liquid is preferably a liquid with fluidity for a certain period until it is discarded. Therefore, a method for suppressing the polymerization of tetrahydrofuran in a tetrahydrofuran solution containing methylaluminoxane is desired.

Means for Solving the Problems

[0007] Therefore, the problem to be solved by the present invention is to provide a method for stabilizing a tetrahydrofuran solution containing methylaluminoxane and a composition. The inventor has found that when aluminoxane is dissolved in a cyclic ether solution and stored, the solution can be stored for a long time by adding a polar additive, leading to the completion of the present invention.

[0008] This application includes the following inventions. (1) A cyclic ether solution containing aluminoxane and a polar additive. (2) The solution of (1), wherein the aluminoxane is methylaluminoxane. (3) The solution of (1) or (2), wherein the cyclic ether is a cyclic ether having 5 or more members. (4) The solution of (3), wherein the cyclic ether is tetrahydrofuran. (5) The solution of any one of (2) to (4), wherein the content of the polar additive is 0.14 molar equivalent ratio or more with respect to aluminum in methylaluminoxane. (6) The solution of any one of (1) to (5), wherein the polar additive is a compound selected from the group consisting of an amine compound, an amide compound, and a sulfoxide compound. (7) A method for producing a cyclic ether solution containing an aluminoxane and a polar additive, using an aluminoxane, a polar additive, and a cyclic ether. (8) The production method of (7), wherein the aluminoxane is methylaluminoxane. (9) The production method of (7) or (8), wherein the cyclic ether is a cyclic ether having 5 or more members. (10) The production method of (9), wherein the cyclic ether is tetrahydrofuran. (11) The production method of any one of claims (8) to (10), wherein the content of the polar additive is 0.14 molar equivalent ratio or more with respect to aluminum in methylaluminoxane. (12) The production method of any one of (7) to (11), wherein the polar additive is a compound selected from the group consisting of an amine compound, an amide compound, and a sulfoxide compound. [Effect of the Invention]

[0009] According to the present invention, it is possible to provide an aluminoxane-containing solution that can be stably stored for a long time and a method for producing the same. [Embodiments for Carrying Out the Invention]

[0010] The present invention provides an aluminoxane-containing solution, a cyclic ether solution containing an aluminoxane and a polar additive in a cyclic ether, and a method for producing the same.

[0011] Examples of the aluminoxane include methylaluminoxane, ethylaluminoxane, triisobutylaluminoxane, tert-butylaluminoxane, and mixtures thereof. Particularly preferred is methylaluminoxane.

[0012] Methylaluminoxane is a condensation product obtained by partially hydrolyzing highly reactive trimethylaluminum and has a structural unit represented by the formula: [(CH3)AlO]. Methylaluminoxane is generally a mixture of two or more compounds with different molecular weights, and the compounds have a linear structure, a cyclic structure, or a combination thereof. The average degree of oligomerization (average degree of polymerization) of methylaluminoxane is generally 60 or less. Methylaluminoxane may contain a branched structure or a crosslinked structure. Although there is thought to be a close relationship between the composition and structure of methylaluminoxane and its stability, since methylaluminoxane has a very complex structure as described above, it is difficult to specify the difference in the stability of methylaluminoxane compositions from the viewpoints of the composition and structure of methylaluminoxane.

[0013] Methylaluminoxane can be obtained by reacting trimethylaluminum with water. The reaction is preferably carried out in a solvent. Examples of the solvent include aliphatic hydrocarbons and aromatic hydrocarbons that are inert to trimethylaluminum and methylaluminoxane. Examples of the aliphatic hydrocarbons include saturated hydrocarbon compounds such as n-pentane, n-hexane, n-heptane, n-octane, isooctane, and purified kerosene; and cyclic hydrocarbon compounds such as cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, and cycloheptane. Examples of the aromatic hydrocarbons include benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, propylbenzene, and cumene. The solvent is preferably toluene.

[0014] The reaction temperature is generally 0°C to 100°C, preferably 10°C to 40°C.

[0015] The reaction time is generally 0.5 hours to 100 hours, preferably 1 hour to 10 hours.

[0016] The molar ratio of trimethylaluminum to water (number of moles of trimethylaluminum / number of moles of water) is preferably from 1.0 to 5.0, more preferably from 1.2 to 4.0, and still more preferably from 1.5 to 3.0.

[0017] Trimethylaluminum is preferably mixed with the solvent to form a trimethylaluminum solution and then reacted with water. The concentration of trimethylaluminum in the trimethylaluminum solution is preferably from 1% by mass to 20% by mass, more preferably from 5% by mass to 15% by mass.

[0018] Water is preferably added in the form of an aqueous dispersion. By using an aqueous dispersion, the addition rate can be easily adjusted. The aqueous dispersion can be prepared by mixing the solvent with water. The medium of the aqueous dispersion is preferably the same as the solvent of the trimethylaluminum solution. The water concentration in the aqueous dispersion is preferably from 1% by mass to 20% by mass, more preferably from 5% by mass to 15% by mass.

[0019] The reaction between trimethylaluminum and water to produce methylaluminoxane is preferably stirred using a stirrer. The stirrer is not particularly limited, but it is preferable to use a high-speed homogenizer. By using a high-speed homogenizer, trimethylaluminum and water can be reacted quickly. The rotation speed of the high-speed homogenizer can be, for example, from 1000 rpm to 20000 rpm.

[0020] The low-molecular-weight methylaluminoxane generated at the initial stage of the reaction between trimethylaluminum and water still has a very high reactivity with water, similar to trimethylaluminum. Therefore, if the reaction is carried out with all the water present in the reaction field in advance, the reaction proceeds irregularly and a gel-like substance is likely to be generated. Therefore, it is preferable to gradually add water or an aqueous dispersion to the trimethylaluminum solution. Thereby, the reaction can be carried out while controlling the amount of water coexisting with trimethylaluminum or low-molecular-weight methylaluminoxane, and as a result, the generation of the gel-like substance can be somewhat suppressed.

[0021] The reaction product containing the aluminoxane produced as described above is dried to remove the water and organic solvent used, and a solid aluminoxane is obtained. Examples of the drying procedure for aluminoxane include methods such as drying the aluminoxane solution under reduced pressure or by degassing. In the case of drying under reduced pressure, for example, the degree of reduced pressure can be set to 1 to 50 kPaA, preferably 2 to 10 kPaA, the drying temperature can be set from 10°C to 40°C, preferably 15 to 25°C. The drying time is not particularly limited, but is preferably 1 to 100 hours, more preferably 2 to 20 hours.

[0022] The solid aluminoxane dried as described above is dissolved in a cyclic ether solution so as to enable long-term storage. Cyclic ethers such as THF can dissolve the solids and gels when solid or gel-like trimethylaluminum is mixed, so it is preferable to use them as a solvent for dissolving aluminoxane. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, and 1,4-dioxane. In particular, cyclic ethers with a ring size of 5 or more are preferred, and tetrahydrofuran is most preferred. The amount of the cyclic ether solution used is not particularly limited, but for example, a molar equivalent ratio of 0.1 to 30, more preferably about 1 to 10, based on aluminum in the aluminoxane may be sufficient.

[0023] As described at the beginning, the tetrahydrofuran solution containing methylaluminoxane polymerizes even in the absence of a ring-opening polymerization accelerator such as epichlorohydrin, and the viscosity of the solution increases. The present inventor has found that this polymerization can be suppressed by the addition of a predetermined polar additive. Examples of such polar additives that can be used include amine compounds, amide compounds, and sulfoxide compounds.

[0024] Examples of the amine compound include aliphatic amine compounds and aromatic amine compounds. Examples of the aliphatic amine compounds include primary amines such as methylamine, ethylamine, butylamine, amylamine, isoamylamine, cyclohexylamine, hexamethylenediamine, spermidine, spermine, and amantadine; secondary amines such as dimethylamine, diethylamine, diisopropylamine, dibutylamine, diisobutylamine, diamylamine, and dicyclohexylamine; and tertiary amines such as trimethylamine, triethylamine, tributylamine, triisobutylamine, triethanolamine, tricyclohexylamine, and N,N-diisopropylethylamine. Examples of the aromatic amine compounds include aniline, N,N-dimethylaniline, phenethylamine, toluidine, catecholamine, 1,8-bis(dimethylamino)naphthalene, and the like. Triethylamine (Et3N) and dimethylamine (Et2NH) are particularly preferred.

[0025] Examples of the heterocyclic compound containing a nitrogen atom include saturated heterocyclic compounds such as pyrrolidine, piperidine, piperazine, morpholine, quinuclidine, and 1,4-diazabicyclo[2.2.2]octane; and unsaturated heterocyclic compounds such as pyrazole, imidazole, pyridine, 2-methylpyridine, 4-methylpyridine, 2,6-dimethylpyridine, 2,4,6-trimethylpyridine, 2,6-diethylpyridine, 2,6-diisopropylpyridine, 2,2-bipyridine pyridazine, pyrimidine, pyrazine, pyrrole, oxazole, thiazole, 4-dimethylaminopyridine, indole, quinoline, isoquinoline, purine, 1-methylimidazole, 1-ethylimidazole, and 1-butylimidazole. 2,6-Dimethylpyridine (2,6-lutidine) is particularly preferred.

[0026] Examples of the amide compound include chain amide compounds such as formamide, acetamide, N,N-dimethylacetamide, and N,N-dimethylformamide, and cyclic amide compounds such as N-methylpyrrolidone, benzamide, and acetanilide. Particularly preferred are N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP).

[0027] Examples of the sulfoxide compound include dimethyl sulfoxide and diethyl sulfoxide. Particularly preferred is dimethyl sulfoxide (DMSO).

[0028] The content of the polar additive in the aluminoxane-containing solution cyclic ether solution of the present invention is not particularly limited, but it is preferably blended in an amount such that the solution does not thicken when stored for a long time. For example, when blended in the aluminoxane-containing solution cyclic ether solution of the present invention at a molar equivalent ratio of 0.14 or more with respect to aluminum in the aluminoxane, long-term storage can be achieved. The upper limit is not particularly limited either. For example, an amount at which the thickening suppression effect reaches a plateau, for example, about 1 molar equivalent ratio or less with respect to aluminum in the aluminoxane may be sufficient, and the lower limit may be, for example, about 0.01 molar equivalent.

[0029] The "stable long-term storage" of the aluminoxane-containing solution as referred to in the present invention means that, for example, even when the solution is stored at room temperature for 1 day or more, preferably 1 week or more, more preferably 1 month or more, the viscosity does not increase by, for example, 10% or more, preferably 20% or more, more preferably 50% or more, and even more preferably 100% or more. The viscosity can be measured, for example, with a rotational viscometer.

[0030] All documents referred to in this specification are hereby incorporated by reference in their entirety into this specification.

[0031] The embodiments of the present invention described below are for illustrative purposes only and do not limit the technical scope of the present invention. The technical scope of the present invention is limited only by the description in the claims. Changes to the present invention, such as addition, deletion, and substitution of the constituent elements of the present invention, can be made on the condition that the gist of the present invention is not deviated from.

Example

[0032] The present invention will be described in more detail based on examples below, but these do not limit the present invention in any way.

[0033] Example 1 A methylaluminoxane toluene solution (product name TMAO-312, manufactured by Tosoh Finechem Corporation) was dried under a reduced pressure of 2.0 kPaA at 25°C or lower to obtain dry MAO (MAO 99.2 wt%, TMAL 0.6 wt%, Toluene 0.2 wt%, Al concentration 41.5 wt%). Subsequently, 0.406 g (6.24 mmol as Al) of the obtained dry MAO was put into a 50 ml Schlenk tube and dissolved in 22.9 g (260 mmol) of 1,4-dioxane, and the freezing point depression was measured. As a result, the freezing point was 11.5959°C. Since the freezing point measured with only 1,4-dioxane was 11.7830°C, the freezing point depression was 0.1871°C. As a result of calculating the MAO molecular weight from this freezing point depression, the molecular weight was 810. 0.550 g (8.45 mmol as Al) of dry MAO, 2.44 g (33.8 mmol) of tetrahydrofuran, and 0.940 g (8.77 mol) of 2,6-lutidine were put into a 50 ml heat-resistant flask under a nitrogen atmosphere and dissolved until homogeneous. The solution was left standing in a constant temperature bath at 50°C for 1.8 days for testing, and 3.75 g of the test solution was obtained. 1.1 ml was taken from the test solution, and the viscosity was measured at 25°C and a rotor rotation speed of 20 rpm (Tokyo Keiki Industry TV-25L type, rotor 1°34’×R24, measurement range 2.5 M). As a result, the viscosity was 2.0 mPas.

[0034] Comparative Example 0.550 g of dry MAO (8.45 mmol as Al), 2.46 g of tetrahydrofuran (34.1 mmol), and the study was conducted in the same manner as in Example 1 except that no additive was added, and 2.85 g of the test solution was obtained. 1.1 ml was collected from the test solution and the viscosity was measured at 25 °C with a rotor rotation speed of 10 rpm (Tokyo Keiki Co., Ltd. TV-25L type, rotor 1°34’×R24, measurement range 5 M). As a result, the viscosity was 350 mPas. The test results of Example 1 and the comparative examples are shown in Table 1.

[0035] Examples 2 to 10 Using dry MAO and tetrahydrofuran in the same manner as in Example 1, except that an additive other than 2,6-lutidine was used as the polar additive to prepare an aluminoxane-containing solution, and the viscosity was measured. The amount of dry MAO, tetrahydrofuran, additive used, the type of additive, and the viscosity measurement results are also summarized in Table 1. Compared with the comparative examples, in the examples where the polar additive was added, no significant thickening was observed even after storing the solution for 1.8 days. In addition, in the addition of Et3N in Examples 3 and 4, two-layer separation was observed, presumably due to salt formation with dry MAO. The salt mainly existed in the lower layer, and a slight increase in viscosity occurred due to the influence of the salt itself, rather than thickening due to the polymerization of tetrahydrofuran.

[0036] [Table 1]

[0037] As described above, the embodiments of the present invention have been explained, but the present invention is not limited to these, and the materials used, various conditions, etc. can be appropriately changed without departing from the spirit of the invention.

Claims

1. A cyclic ether solution containing an aluminoxane and a polar additive.

2. The solution according to claim 1, wherein the aluminoxane is methylaluminoxane.

3. The solution according to claim 2, wherein the cyclic ether is a cyclic ether having 5 or more members in the ring.

4. The solution according to claim 3, wherein the cyclic ether is tetrahydrofuran.

5. The solution according to claim 2, wherein the content of the polar additive is 0.14 molar equivalent ratio or more with respect to aluminum in the aluminoxane.

6. The solution according to claim 1, wherein the polar additive is a compound selected from the group consisting of an amine compound, an amide compound, and a sulfoxide compound.

7. A method for producing a cyclic ether solution containing an aluminoxane and a polar additive using an aluminoxane, a polar additive, and a cyclic ether.

8. The production method according to claim 7, wherein the aluminoxane is methylaluminoxane.

9. The production method according to claim 7, wherein the cyclic ether is a cyclic ether having 5 or more members in the ring.

10. The production method according to claim 9, wherein the cyclic ether is tetrahydrofuran.

11. The production method according to claim 8, wherein the content of the polar additive is 0.14 molar equivalent ratio or more with respect to aluminum in the aluminoxane.

12. The production method according to claim 7, wherein the polar additive is a compound selected from the group consisting of an amine compound, an amide compound, and a sulfoxide compound.

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