JPH0216763B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyethylene, and more particularly, to a method for efficiently producing polyethylene with a wide molecular weight distribution by using a specific catalyst and allowing a molecular weight distribution regulator to be present during the polymerization reaction. Recently, in producing polyethylene, highly active catalysts have been used to increase production efficiency. However, polyethylene produced using the above-mentioned highly active catalysts has a narrow molecular weight distribution, resulting in low fluidity and high resin pressure during molding, and the resulting molded products are susceptible to the so-called shark skin phenomenon. There are various problems. Therefore, in order to solve these problems, various efforts are being made and implemented, such as improving the selection of catalysts, operating conditions such as hydrogen concentration and polymerization temperature, and carrying out polymerization in multiple stages. However, all of these methods require new equipment and are complicated to operate, resulting in poor workability and high manufacturing costs. In order to solve these practical problems, a method described in Japanese Patent Application Laid-open No. 41207/1983 has been developed. Although this method is effective in controlling the molecular weight distribution of the resulting polyethylene, it is still insufficient. The object of the present invention is to efficiently produce polyethylene having a controlled molecular weight distribution, in particular, a polyethylene having a wide molecular weight distribution without such drawbacks, and the present invention is composed of (A) at least magnesium alkoxy, magnesium sulfate; and a solid catalyst component obtained by reacting a chlorine-containing titanium compound, (B) trialkylaluminum represented by the general formula R ¹ ₃ Al (R ¹ represents an alkyl group or a cycloalkyl group having 1 to 8 carbon atoms) and (C) general formula R ² _o AlCl _3-o (R ² represents an alkyl group or cycloalkyl group having 1 to 8 carbon atoms, and n is 0<n≦2
Indicates a real number that satisfies. ) When producing polyethylene using a catalyst prepared from a chlorine-containing aluminum compound represented by This is a method for producing polyethylene, characterized in that the polyethylene is made to exist. The catalyst used in the method of the present invention is prepared from the above components (A), (B) and (C), of which component (A) contains at least alkoxymagnesium, magnesium sulfate and chlorine-containing components. A solid catalyst component obtained by reacting a titanium compound is used, and for example, one obtained by reacting alkoxymagnesium with a chlorine-containing titanium compound in the presence of magnesium sulfate is preferably used. Examples of the alkoxymagnesium include methoxymagnesium, ethoxymagnesium, propoxymagnesium, butoxymagnesium, diethoxymagnesium (magnesium diethoxide), and the like. On the other hand, examples of the chlorine-containing titanium compound include titanium tetrachloride (TiCl ₄ ), titanium trichloride (TiCl ₃ ), an adduct of titanium trichloride and aluminum chloride (TiCl ₃ 1/3 AlCl ₃ ), dichloromethoxy Titanium ( _{CH3OTiCl2 ) ,} trichloroethoxytitanium ( _{C2H5OTiCl3 )} , trichloropropoxytitanium ( _{C3H7OTiCl3 )} , dichlorodipropoxytitanium (( _{C3H7O ) 2TiCl2 )} , _dichloro Examples include diethoxytitanium ((C ₂ H ₅ O) ₂ TiCl ₂ ) and monochlorotriethoxytitanium ((C ₂ H ₂ O) ₃ TiCl). Although the solid catalyst component (A) may be produced as described above, it is more preferable to first modify the alkoxymagnesium using silicon tetrachloride or the like, and then react it with a chlorine-containing titanium compound. It can be obtained by letting Next, in the trialkylaluminum represented by the general formula R ¹ ₃ Al, which is the component (B) of the catalyst, R ¹ may be an alkyl group or a cycloalkyl group having 1 to 8 carbon atoms, and a preferable example is trimethyl. Examples include aluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, and trioctylaluminum. Next, in the chlorine-containing aluminum compound represented by the general formula R _2o AlCl _3-o , which is the component (C) of the catalyst, R ₂ is an alkyl group or a cycloalkyl group having 1 to 8 carbon atoms, and n is 0< Any real number satisfying n≦2 may be used. Suitable examples of this compound include diethylaluminum monochloride, diisopropylaluminum monochloride, diisobutylaluminum monochloride, dioctylaluminum monochloride, ethylaluminum dichloride, isopropylaluminum dichloride, ethylaluminum sesquichloride, and the like. In the method of the present invention, it is essential to use a catalyst prepared from each of the components (A), (B), and (C) above, and to have a specific molecular weight distribution regulator present in the polymerization reaction system. be. Here, water is used as the molecular weight distribution regulator, and the amount of water present during the polymerization reaction is 0.05% relative to the component (C) of the catalyst.
It should be in the range of ~0.3 times molar. If the amount of molecular weight distribution regulator in the reaction system is too small,
The effect of controlling the molecular weight distribution is not sufficient, and conversely, if the amount is too large, the polymerization activity of the catalyst will be significantly reduced, resulting in disadvantages such as the need for a deashing step. When producing polyethylene by the method of the present invention, a catalyst prepared from the above components (A), (B), and (C) and a molecular weight distribution regulator are added to the reaction system,
Furthermore, ethylene is introduced and reacted. There are no particular restrictions on the polymerization method and conditions, and solution polymerization, suspension polymerization, gas phase polymerization, etc. are all possible, and both continuous and discontinuous polymerization are possible, as well as one-stage polymerization. Multistage polymerization can also be carried out. Butane,
Inert solvents such as pentane, n-hexane, cyclohexane, heptane, benzene, toluene and the like are preferred. Furthermore, the ethylene pressure in the reaction system is 0.5 to 15
Kg/cm ² G, preferably 1 to 10 Kg/cm ² G, and the reaction temperature is 50 to 95°C, preferably 60 to 90°C.
The desired polyethylene can be obtained by stirring for minutes to 5 hours, preferably 30 minutes to 3 hours. The molecular weight during polymerization may be controlled by known means such as hydrogen. The types of polyethylene that can be polymerized by the method of the present invention include not only ethylene homopolymers, but also ethylene and a small amount of α-olefin, especially propylene, butene-1, pentene-1, etc. having 3 to 10 carbon atoms.
Examples include copolymers with α-olefin. Since the method of the present invention uses the above-mentioned catalyst, the catalyst activity is extremely high, and a sufficient effect can be obtained even with a small amount of use, and as a result, the deashing step (catalyst removal step) can be omitted. Moreover, according to the method of the present invention, the molecular weight distribution of the obtained polyethylene can be easily adjusted simply by adding a molecular weight distribution regulator without changing the catalyst or adding equipment. It is possible to improve the performance and workability. Furthermore, the resulting polyethylene, particularly polyethylene with a wide molecular weight distribution, has excellent moldability, particularly extrusion moldability into films, sheets, etc., and the surface of the molded product is also very beautiful. Next, examples of the present invention will be shown. In addition, in the following examples, all operations were performed under an argon stream. In addition, the evaluation of molecular weight distribution was performed at 190℃, 2.16
Kg load for melt index (MI _2.16 )
The melt flow ratio (FR) was the ratio of the melt index (MI _21.6 ) at a load of 21.6 kg. moreover,
The evaluation of resin pressure shows the measured output value of breaker plate out using an inflation molding machine with a diameter of 20 mm, a die at 195°C, and a discharge rate of 20/min. Examples 1 to 4 and Comparative Examples 1 to 4 (1) Production of solid catalyst component 1.0 g (8.8 mmol) of magnesium diethoxide and 1.06 g (8.8 mmol) of commercially available anhydrous magnesium sulfate were suspended in 50 ml of n-heptane. Then, 1.5 g (8.8 mmol) of silicon tetrachloride and 1.6 g (35.2 mmol) of ethanol were added, and the reaction was carried out at 80° C. for 1 hour. Next, 5 ml (45 mmol) of titanium tetrachloride was added and the mixture was heated at 98°C for 30 minutes.
Allowed time to react. After the reaction, the mixture was cooled and left to stand, and the supernatant liquid was removed by a decanting method. Next, 100 ml of n-heptane was added and the washing operation of stirring, standing, and removing the supernatant liquid was performed three times, and then 200 ml of n-heptane was added.
ml was added to obtain a dispersion of solid catalyst components. The amount of titanium supported on this product was determined by a colorimetric method and was found to be 12 mg-Ti/g-support. (2) Polymerization of ethylene In a 7-volume stainless steel autoclave, 55% of dry hexane, the solid catalyst component prepared above as the (A) component, triethylaluminum as the (B) component, diethylaluminum as the (C) component, and molecular weight distribution adjustment. Add a certain amount of water as a agent,
Furthermore, hydrogen was metered so that the polyethylene had the melt index (MI) shown in Table 1, and ethylene was continuously supplied so that the total pressure of the reactor was 8.3 Kg/cm ² G. The reaction was carried out with stirring for a minute. After the reaction was completed, the obtained polyethylene was washed and dried, and its FR and resin pressure were measured. The results are shown in Table 1. Examples 5-7 and Comparative Examples 5-7 In a 7-volume stainless steel autoclave was added 2.7 g of dry hexane and the same as in Examples 1-4 above.
(A), (B), and (C) catalyst components were added, hydrogen was measured so that the resulting polyethylene had the intrinsic viscosity [η] shown in Table 2, and the total pressure of the reactor was 8.7.
Continuously supply ethylene so that the amount is 90 kg/cm ² G.
After reacting at ℃ for 120 minutes with stirring, the temperature was lowered to 40℃. Next, the reactor was degassed, hydrogen was metered so that the polyethylene reached the MI shown in Table 2, and ethylene was continuously fed so that the total pressure of the reactor was 8.3 Kg/cm ² G, and the molecular weight A predetermined amount of water as a distribution regulator shown in Table 2 was added to the autoclave, and a polymerization reaction was carried out at 80°C for 30 minutes with stirring. After the reaction was completed, the obtained polyethylene was washed and dried, and its FR and resin pressure were measured. The results are shown in Table 2. Example 8 and Comparative Example 8 In a 7 volume stainless steel autoclave was added 2.7 g of dry hexane and the same as in Examples 1 to 4 above.
(A), (B), and (C) catalyst components were added, hydrogen was measured so that the resulting polyethylene had the intrinsic viscosity [η] shown in Table 3, and the total pressure of the reactor was 8.7.
Continuously supply ethylene so that the amount is 90 kg/cm ² G.
After reacting at ℃ for 120 minutes with stirring, the temperature was lowered to 40℃. Then, after degassing the reactor,
Hydrogen, 50 g of butene-1, and ethylene were continuously fed so that the resulting polyethylene had the MI shown in Table 3, and ethylene was added so that the total pressure of the reactor was 8.3 Kg/cm ² G, while molecular weight distribution was adjusted. A predetermined amount of water as a reagent shown in Table 3 was placed in the autoclave, and a polymerization reaction was carried out at 80° C. for 30 minutes with stirring. After the reaction was completed, the polyethylene was washed and dried, and its FR and resin pressure were measured. The results are shown in Table 3.

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【table】 [Brief explanation of drawings]

FIG. 1 is a drawing showing the steps for preparing a catalyst used in the method of the present invention.

Claims (1)

[Claims] 1 (A) A solid catalyst component obtained by reacting at least alkoxymagnesium, magnesium sulfate, and a chlorine-containing titanium compound, (B) General formula R ¹ ₃ Al
(R ¹ represents an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group.) and (C) the general formula R ² _o AlCl _3-o (R ² is an alkyl group having 1 to 8 carbon atoms. or a cycloalkyl group, and n is a real number satisfying 0<n≦2. A method for producing polyethylene, characterized in that water is present in a molar ratio of 0.05 to 0.3 times the mole of component (C) of the catalyst.