JPH0925314A - Production of ethylene polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a blow-moldable ethylene polymer excellent in a balance between rigidity and environmental stress cracking resistance and moldability at good efficiency by using a catalyst comprising a chromic ester, an inorganic oxide solid, an aluminoxane and a specified organoaluminum compound. SOLUTION: This production process comprises using a catalyst comprising a chromic ester, an inorganic oxide solid (e.g. silica or alumina), an aluminoxane (e.g. methylaluminoxane or isobutylaluminoxane) and an organoaluminum compound represented by formula I (wherein R<1> and R<2> are each a 1-18C hydrocarbon group; and n is in the range: 0<=n<=3) as the polymerization catalyst. It is desirable to use a catalyst obtained by impregnating the solid with the ester and treating the product with the aluminoxane and the compound. The chromic ester is more desirably a compound represented by formula II (wherein R<3> to R<8> are each a 1-18C hydrocarbon group; and M is C or Si).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an ethylene polymer. More specifically, chromic acid ester, inorganic oxide solid, alumoxane, general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² are the same or different and have 1 to 18 carbon atoms.
Represents a hydrocarbon group, and n is in the range of 0 ≦ n ≦ 3. )
The present invention relates to a method for producing an ethylene polymer for blow molding, which has excellent balance between rigidity and environmental stress crack resistance (ESCR) and moldability, using a catalyst composed of an organoaluminum represented by

[0002]

2. Description of the Related Art Ethylene polymers are generally and widely used as resin materials for various molded articles, and required characteristics differ depending on the molding method and application. For example, a polymer having a relatively low molecular weight and a narrow molecular weight distribution is suitable for a product molded by an injection molding method, but a product having a relatively high molecular weight is suitable for a product molded by inflation molding or blow molding. Polymers having a wide molecular weight distribution are suitable.

It is conventionally known that an ethylene polymer having a broad molecular weight distribution suitable for blow molding can be obtained by using a so-called Phillips catalyst in which chromium trioxide is supported on an inorganic oxide solid such as silica. is there. Also, US Pat. No. 3,324,101 and US Pat.
4,095, JP-A-53-91092, JP-B-47-
As described in 1766, a catalyst in which chromic acid esters are supported on an inorganic oxide solid such as silica also gives an ethylene polymer having a wide molecular weight distribution suitable for blow molding.

However, in recent years, there has been a demand for higher quality ethylene-based polymers suitable for large blow molded articles such as gasoline tanks, large tanks and water heaters. When a large blow molded product is produced using an ethylene-based polymer having a broad molecular weight distribution obtained by the above catalyst, the molded product is not necessarily satisfactory in any of the following points. (1) Environmental stress crack resistance (ESCR) is not sufficient. (2) Since the melt tension is not sufficient, not only the wall thickness of the large blow molded product is uneven, but also the surface of the molded product is uneven, which is not desirable in appearance.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned problems and to improve rigidity and resistance to environmental stress cracking (ESC).
The object of the present invention is to propose a method for efficiently producing an ethylene polymer for blow molding which is excellent in balance of R) and moldability.

[0006]

Means for Solving the Problems As a result of intensive studies in view of the above-mentioned problems, the present inventors have found that chromate ester, inorganic oxide solid, alumoxane, general formula R ¹ _n Al (OR ² ) _3-n ( R ¹ and R ² are the same or different and have 1 to 18 carbon atoms.
Represents a hydrocarbon group, and n is in the range of 0 ≦ n ≦ 3. )
The above-mentioned problems were solved by a method for producing an ethylene-based polymer characterized by using a catalyst composed of organoaluminum represented by

Hereinafter, the present invention will be described specifically. The chromic acid ester used in the present invention has a general formula

Embedded image (In the formula, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are the same or different hydrocarbon groups having 1 to 18 carbon atoms, and M represents a carbon atom or a silicon atom.). Those are preferable.

Specifically, when M is carbon, bis (te
rt-Butyl) chromate, bis (1,1-dimethylpropyl) chromate, bis (1,1-dimethyl-1-phenylmethyl) chromate, bis (1,1-diphenylethyl) chromate, bis (triphenylmethyl) chromate , Bis (texyl) chromate, bis (1,1,
2,2-tetramethylpropyl) chromate, bis (1,1,2-trimethylpropyl) chromate and the like can be mentioned, and among them, bis (tert-butyl) chromate is preferable. When M is silicon, bis (trimethylsilyl) chromate, bis (triethylsilyl) chromate, bis (tribenzylsilyl) chromate, bis (triphenylsilyl) chromate, bis (trinaphthylsilyl) chromate, bis (dimethylphenylsilyl) ) Chromate, bis (diphenylmethylsilyl) chromate, bis (dimethylthexylsilyl) chromate,
Examples thereof include bis (dimethylisopropylsilyl) chromate, bis (tert-butyldimethylsilyl) chromate, and bis (tri-tert-butylsilyl) chromate. Among them, bis (triphenylsilyl) chromate is preferable.

Examples of the inorganic oxide solid include silica, alumina, silica-alumina, aluminum phosphate and the like. It is desirable to remove the adsorbed moisture from the inorganic oxide solid before use. The inorganic oxide solid is usually dried under a nitrogen gas stream dried under molecular sieves flow in a temperature range of 100 to 900 ° C.
It is performed by arbitrarily selecting from the range of 0 minutes to 10 hours. It is preferable to dry under a fluidized state of a solid with a sufficient amount of nitrogen gas.

Examples of alumoxanes include methylalumoxane, ethylalumoxane, isobutylalumoxane, hexylalumoxane and chloroalumoxane. Among them, alkylalumoxane, particularly methylalumoxane or isobutylalumoxane is preferably used. . These are obtained by reacting water or a water-containing substance with a trialkylaluminum compound at a ratio of 0.5 to 1.2 equivalents per equivalent of trialkylaluminum by a known method. For example, Cam et al. (Makromomo
l. Chem. 191, 1641 (1990)) obtains an alkyl alumoxane by directly introducing water into a cooled toluene solution of trialkylaluminum.

The general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² are the same or different and have 1 to 18 carbon atoms)
Represents a hydrocarbon group, and n is in the range of 0 ≦ n ≦ 3. )
Examples of the organic aluminum represented by: trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri n-hexyl aluminum, dimethyl aluminum methoxide, dimethyl aluminum ethoxide, dimethyl aluminum isopropoxide, dimethyl aluminum n-butoxide, dimethyl aluminum iso Butoxide, diethylaluminum ethoxide, diethylaluminum isopropoxide, diethylaluminum n-butoxide, diethylaluminum isobutoxide, diisobutylaluminum ethoxide, diisobutylaluminum isopropoxide, diisobutylaluminum n-butoxide, diisobutylaluminum isobutoxide, di-n-hexyl. Aluminum ethoxide, di-n-hex Aluminum isopropoxide, di-n-hexyl aluminum n-butoxide, di-n-hexyl aluminum isobutoxide, methyl aluminum dimethoxide, methyl aluminum diethoxide, methyl aluminum diisopropoxide, methyl aluminum di n-butoxide, methyl aluminum dioxide Isobutoxide, ethyl aluminum diethoxide, ethyl aluminum diisopropoxide, ethyl aluminum di-
Butoxide, ethyl aluminum diisobutoxide, isobutyl aluminum diethoxide, isobutyl aluminum diisopropoxide, isobutyl aluminum di-n-butoxide, isobutyl aluminum diisobutoxide, n-hexyl aluminum diethoxide, n-hexyl aluminum diisopropoxide. , N-hexylaluminium di-n-butoxide, n-hexylaluminum diisobutoxide, aluminum trimethoxide,
Aluminum triethoxide, aluminum triisopropoxide, aluminum tri-n-butoxide, aluminum triisobutoxide and the like can be mentioned. Among them, trialkylaluminum, trialkylaluminum such as triisobutylaluminum or diethylaluminum ethoxide, diisobutylaluminum isobutoxide. Such dialkyl aluminum alkoxides are preferably used.

As a method of supporting a chromic acid ester on an inorganic oxide solid to obtain a solid component, the inorganic oxide solid is previously suspended in an inert hydrocarbon such as pentane, hexane, heptane, cyclohexane, decane, benzene and toluene. After making it turbid, the supporting reaction is carried out by adding the chromate ester or the above-mentioned inert hydrocarbon solution of the chromate ester,
There is a method of removing the solvent under a vacuum, or a method of separating after the reaction by filtration. The amount of chromic acid ester added to the inorganic oxide solid is such that chromium atoms are supported in an amount of 0.1 to 2.0 wt% with respect to the inorganic oxide solid. The reaction temperature is -78 ° C to the boiling point of the solvent, preferably 0 ° C to 60 ° C, and the reaction time is 10 minutes to 24 hours, preferably 30 minutes to 5 hours.

The above solid component is alumoxane and the general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² are the same or different and have 1 to 18 carbon atoms).
Represents a hydrocarbon group, and n is in the range of 0 ≦ n ≦ 3. )
As a method of obtaining a catalyst by treating with organoaluminum represented by: a) a solid component is treated with alumoxane, and then a compound represented by the general formula R ¹ _n Al
(OR ² ) _3-n (R ¹ and R ² represent the same or different hydrocarbon groups having 1 to 18 carbon atoms, and n is in the range of 0 ≦ n ≦ 3). A method of treating, b) a solid component represented by the general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² represent the same or different hydrocarbon groups having 1 to 18 carbon atoms, and n is 0 ≦ n ≦ 3.) A method of treating with organoaluminum represented by the formula ( ¹ ) and then treating with alumoxane, c) The solid component is treated with alumoxane and R ¹ _n Al (O 2).
R ² ) _3-n (R ¹ and R ² represent the same or different hydrocarbon groups having 1 to 18 carbon atoms, and n is in the range of 0 ≦ n ≦ 3). Any method of treating with a mixture may be used.

The solid component is previously suspended in an inert hydrocarbon such as pentane, hexane, heptane, cyclohexane, decane, benzene and toluene, and then alumoxane or the general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² represent the same or different hydrocarbon groups having 1 to 18 carbon atoms,
n is in the range of 0 ≦ n ≦ 3. ) The above-mentioned inert hydrocarbon solution of organoaluminum represented by 1) is added by any one of the methods a) to c) and treated. Alumoxane or the general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² represent the same or different hydrocarbon groups having 1 to 18 carbon atoms, and n is in the range of 0 ≦ n ≦ 3. The amount of the organoaluminum represented by) is such that the molar ratio of all aluminum atoms to chromium atoms in the solid component is 5 to 30.
If this ratio is 5 or less, or 30 or more, the polymerization activity is remarkably reduced, and problems such as a decrease in productivity occur. Alumoxane and the general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² represent the same or different hydrocarbon groups having 1 to 18 carbon atoms, and n is in the range of 0 ≦ n ≦ 3. The molar ratio with the organoaluminum represented by) is preferably used in the range of 100 to 0.1. The amount of solvent per 1 g of solid component is 5
~ 100 ml, reaction temperature 0 ~ 60 ° C, reaction time 10
Minutes to 10 hours, preferably 20 minutes to 5 hours. After the reaction, the solvent is removed under vacuum or separated by filtration to obtain the catalyst.

In carrying out the method of the present invention, a liquid phase polymerization method such as slurry polymerization or solution polymerization or a gas phase polymerization method can be used as a polymerization method of ethylene. The liquid phase polymerization method is usually carried out in a hydrocarbon solvent, and as the hydrocarbon solvent, an inert hydrocarbon such as butane, isobutane, hexane, cyclohexane, heptane, benzene or toluene may be used alone or in a mixture. The polymerization temperature is generally 0 to 300 ° C, and practically 20 to 200 ° C.
It is. Further, hydrogen or the like can be allowed to coexist in the polymerization system for controlling the molecular weight. Further, if necessary, propylene, 1-butene, 1-hexene, 4-methyl-1-
An α-olefin such as penten or 1-octene may be used alone or in combination of two or more kinds for polymerization.

[0016]

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The measurement methods used in Examples and Comparative Examples are shown below. -Pretreatment: Kneading was performed under nitrogen at 190 ° C for 7 minutes using a Plastograph manufactured by Toyo Seiki Co., Ltd. Melt flow rate: according to JIS-K-6760
The measured value at a temperature of 190 ° C. and a load of 10 kg is MLMF.
The measured value at R, a temperature of 190 ° C., and a load of 21.6 Kg is shown as HLMFR. Flow ratio: HLMFR / MLMFR, the larger this value, the wider the molecular weight distribution. Die swell ratio (SR): Using the same device as the melt flow rate, the expansion ratio (%) of the outer diameter of the extruded product at the time of HLMFR measurement to the orifice diameter (2.1 mm) is shown. -Density: measured according to JIS-K-6760. Melt tension (MT): using a melt tension tester manufactured by Toyo Seiki Co., Ltd., resin temperature 230 ° C., orifice diameter 2.1 mm, orifice length 8 mm, extrusion speed 15 m
The measurement was performed under the conditions of m / min and winding speed of 6.5 m / min. -Rigidity: The bending elastic modulus measured according to JIS-K-7203 was taken as the value of rigidity. ESCR: B measured according to JIS-K-6760
The F50 value determined by the TL method was used as the ESCR value.

Example 1 (1) Preparation of catalyst 35 ml of hexane was added to 3.70 g of DAVISON 952 grade silica calcined at 600 ° C. for 4 hours to form a slurry. Bis (triphenylsilyl) in this slurry
Chromate 108.6 mg (8.9 in terms of Cr atom)
mg; Cr loading 0.24 wt%) was added, and the mixture was stirred at 45 ° C. for 2 hours. The solvent was removed under vacuum to give a solid component. Subsequently, 35 ml of toluene was added to this solid component to form a slurry. A 2.7 mol / l toluene solution 0.32 of methylalumoxane manufactured by Tosoh Akzo Co., Ltd. was added to this slurry.
ml (Al / Cr molar ratio = 5) was added, and the mixture was stirred at 45 ° C. for 1 hour. Further, 0.86 ml of a 1.0 mol / l hexane solution of diethylaluminum ethoxide (Al /
Cr molar ratio = 5) was added, and the mixture was stirred at 45 ° C. for 1 hour.
The solvent was completely removed under vacuum to obtain the catalyst. (2) Polymerization Into a 1.5 L autoclave sufficiently replaced with nitrogen, 0.6 L of isobutane and 120 mg of the catalyst obtained in (1) were charged, and the internal temperature was raised to 95 ° C. Polymerization was carried out for 1 hour while introducing ethylene under pressure and keeping the ethylene partial pressure at 14 Kg / cm ² . Then, the content gas was discharged to the outside of the system to terminate the polymerization. As a result, 87 g of polyethylene was obtained. Polymerization activity is 730g polymer /
g catalyst / hour. The physical property measurement results are shown in Table 1. A polyethylene having a high balance of rigidity and ESCR and high melt tension was obtained.

Example 2 In Example 1, a catalyst prepared by adding 0.79 ml (Al / Cr mol = 5) of a 1.1 mol / l hexane solution of isobutylalumoxane manufactured by Tosoh Akzo Co. as an alumoxane was used. Polymerization was performed in the same manner as in Example 1 except for the above. The results are shown in Table 1.

Example 3 In Example 1, bis (te) was used as the chromate ester.
1.71 ml of 0.1 mol / l hexane solution of rt-butyl) chromate (8.9 mg in terms of Cr atom;
Polymerization was performed in the same manner as in Example 1 except that a catalyst prepared by adding a Cr loading amount of 0.24 wt%) was used. The results are shown in Table 1.

Example 4 In Example 3, a catalyst prepared by adding 1.57 ml (Al / Cr mol = 10) of a 1.1 mol / l hexane solution of isobutylalumoxane manufactured by Tosoh Akzo Co. as an alumoxane was used. Polymerization was performed in the same manner as in Example 1 except for the above. The results are shown in Table 1.

Example 5 Polymerization was carried out in the same manner as in Example 1 except that the catalyst prepared in the same manner as in Example 1 except that methylalumoxane and diethylaluminum ethoxide were added in the reverse order.
The results are shown in Table 1.

Example 6 Example 1 was repeated except that a catalyst prepared by adding the same amount of diisobutylaluminum isobutoxide was used instead of diethylaluminum ethoxide.
Polymerization was carried out in the same manner as described above. The results are shown in Table 1.

Example 7 Polymerization was carried out in the same manner as in Example 2 except that the catalyst prepared in Example 2 with the addition order of isobutylalumoxane and diethylaluminum ethoxide was reversed. The results are shown in Table 1.

Example 8 Example 2 was repeated except that a catalyst prepared by adding the same amount of diisobutylaluminum isobutoxide was used instead of diethylaluminum ethoxide.
Polymerization was carried out in the same manner as described above. The results are shown in Table 1.

Example 9 Polymerization was carried out in the same manner as in Example 3 except that the catalyst prepared in Example 3 by reversing the order of addition of methylalumoxane and diethylaluminum ethoxide was used.
The results are shown in Table 1.

Example 10 Example 3 was repeated except that a catalyst prepared by adding the same amount of diisobutylaluminum isobutoxide was used instead of diethylaluminum ethoxide.
Polymerization was carried out in the same manner as described above. The results are shown in Table 1.

Example 11 Polymerization was carried out in the same manner as in Example 4, except that the catalyst prepared in Example 4 with the addition order of isobutylalumoxane and diethylaluminum ethoxide was reversed. The results are shown in Table 1.

Example 12 Example 4 was repeated except that a catalyst prepared by adding the same amount of diisobutylaluminum isobutoxide in place of diethylaluminum ethoxide was used.
Polymerization was carried out in the same manner as described above. The results are shown in Table 1.

Example 13 Polymerization was carried out in the same manner as in Example 1 except that the catalyst prepared by previously mixing and adding methylalumoxane and diethylaluminum ethoxide in Example 1 was used. The results are shown in Table 1.

Example 14 Polymerization was carried out in the same manner as in Example 3 except that the catalyst prepared by previously mixing and then adding methylalumoxane and diethylaluminum ethoxide was used. The results are shown in Table 1.

Comparative Example 1 In Example 1, 0.86 ml of a 1.0 mol / l hexane solution of diethylaluminum ethoxide (Al /
Polymerization was carried out in the same manner as in Example 1 except that the catalyst prepared by adding only Cr mol = 5) was used and the polymerization temperature was 85 ° C. The results are shown in Table 1. The balance between the rigidity and the ESCR was worse than that of the first embodiment. The value of melt tension was also lower than in the case of Example 1.

Comparative Example 2 In Example 3, 0.86 ml of 1.0 mol / l hexane solution of diethylaluminum ethoxide (Al /
Polymerization was carried out in the same manner as in Example 3 except that the catalyst prepared by adding only Cr mol = 5) was used and the polymerization temperature was 85 ° C. The results are shown in Table 1. The balance between the rigidity and the ESCR was worse than that in the case of Example 3. The melt tension value was also lower than that in Example 3.

Comparative Example 3 W. R. Grace Corp
The 969ID catalyst (Cr loading 1.0 wt%) purchased from Oration was calcined in air at 600 ° C. for 30 hours. Polymerization was carried out in the same manner as in Example 1 except that 120 mg of this catalyst was used and the polymerization temperature was 105 ° C. The results are shown in Table 1. The balance between rigidity and ESCR is Examples 1 to 1.
The result was worse than the case of 4. The value of melt tension was also lower than that of Examples 1-14.

[0034]

[Table 1]

[0035]

EFFECTS OF THE INVENTION By carrying out the present invention, it is possible to efficiently produce an ethylene polymer for blow molding which has excellent balance between rigidity and environmental stress crack resistance (ESCR) and moldability, and is industrially valuable. There is.

[Brief description of drawings]

FIG. 1 is a flow chart of catalyst preparation in the production method of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshimitsu Yoshimitsu, Oita City, Oita Prefecture, No. 2 Nakasu, Showa Denko Oita Laboratory

Claims (6)

[Claims] 1. A chromate ester, an inorganic oxide solid, an alumoxane, a general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² are the same or different and have 1 to 18 carbon atoms.
Represents a hydrocarbon group, and n is in the range of 0 ≦ n ≦ 3. )
A method for producing an ethylene-based polymer, which comprises using a catalyst composed of organoaluminum represented by: 2. After supporting a chromic acid ester on an inorganic oxide solid, an alumoxane and a general formula R ¹ _n Al (OR ² ) _3-n (R ¹ and R ² are the same or different and have 1 to 18 carbon atoms).
Represents a hydrocarbon group, and n is in the range of 0 ≦ n ≦ 3. )
The method for producing an ethylene polymer according to claim 1, wherein a catalyst obtained by treating with an organoaluminum represented by 3. Chromates are represented by the general formula: (In the formula, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are the same or different hydrocarbon groups having 1 to 18 carbon atoms, and M represents a carbon atom or a silicon atom.). The method for producing an ethylene-based polymer according to claim 1, which is a compound. 4. The method for producing an ethylene-based polymer according to claim 1, wherein the chromate ester is bis (triphenylsilyl) chromate or bis (tert-butyl) chromate. 5. The method for producing an ethylene polymer according to claim 1, wherein the alumoxane is an alkyl alumoxane. 6. The method for producing an ethylene polymer according to claim 1, wherein the alumoxane is methyl alumoxane or isobutyl alumoxane.