JPH0559122B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an ethylene polymer,
Specifically, by using a catalyst mainly composed of a specific activated titanium catalyst component and an organometallic compound, and by prepolymerizing α-olefin, an ethylene polymer with high bulk density and uniform particle size can be produced with high activity. Relating to a method of polymerization. Various methods have been known for producing stereoregular polyolefins, particularly polypropylene, using catalysts consisting of solid catalyst components containing magnesium and titanium and organometallic compounds. However, when these catalysts are used to polymerize ethylene or copolymerize ethylene with an α-olefin having 3 or more carbon atoms, the resulting polymer has a very low density and a wide particle size distribution. In particular, a large amount of fine powder is produced, and the shape of the particles is also microscopically uneven. For this reason, there are major drawbacks in that post-polymerization treatment, storage and transportation of the polymer product require time and effort, and handling is inconvenient. Moreover, these catalysts did not necessarily have sufficient catalytic activity. On the other hand, in the polymerization of olefins, methods such as two-stage polymerization have been proposed, for example, in order to improve the stereoregularity of polypropylene.
However, when polymerizing ethylene with the above catalyst system,
Even if two-stage polymerization with prepolymerization is employed, although the activity is improved to some extent, the bulk density of the resulting polyethylene is not improved at all. The present inventors have conducted extensive research in order to produce a highly active polyethylene resin with a large bulk density, good particle distribution, and particle shape. As a result, the purpose can be achieved by using a specific catalyst, prepolymerizing α-olefins other than ethylene prior to main polymerization, and then performing main polymerization of ethylene or ethylene and other α-olefins. This discovery led to the completion of the present invention. That is, the present invention provides a method for producing an ethylene polymer by polymerizing ethylene using (A) a reaction product of a magnesium compound and a titanium compound and (B) a catalyst containing an organoaluminum compound as a main component. Formula Mg(OR ¹ ) _o X ¹ _2-o [In the formula, R ¹ represents an alkyl group having 1 to 20 carbon atoms, X ¹ represents a halogen atom, and n represents 0<n≦2
indicates the real number of ] A solid product obtained by reacting a magnesium compound represented by the above, an electron-donating compound consisting of an aromatic carboxylic acid ester, and titanium tetrahalide is used as the component (A) of the above catalyst, and is also used in the main polymerization of ethylene. The present invention provides a method for producing an ethylene polymer, which comprises prepolymerizing an α-olefin having 3 or more carbon atoms prior to the process. The magnesium compound used in the present invention has the general formula
It is expressed as Mg(OR ¹ ) _o X ¹ _2-o . Here, R ₁ represents an alkyl group of 1 to 20, X ¹ is chlorine,
Indicates a halogen atom such as bromine, and n is 0<n
It is a real number satisfying ≦2. Specifically, these magnesium compounds include magnesium dimethoxide,
Examples include magnesium diethoxide, magnesium monochloromonomethoxide, and magnesium monochloromonoethoxide, and these may be used alone or in an appropriate mixture. Further, as the electron-donating compound, aromatic carboxylic acid ester is used. Examples of aromatic carboxylic acid esters include methyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, octyl acetate, cyclohexyl acetate, ethyl propionate, methyl acetate, ethyl valerate, methyl chloroacetate, ethyl dichloroacetate, and methacryl. Methyl acid, ethyl crotonate, ethyl pivalate, dimethyl maleate, ethyl cyclohexanecarboxylate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, octyl benzoate,
Cyclohexyl benzoate, phenyl benzoate, benzyl benzoate, methyl toluate, ethyl toluate, amyl tolyate, ethyl ethylbenzoate, methyl anisate, ethyl anisate, ethyl ethoxybenzoate, ethyl p-p-ptoxybenzoate,
Examples include ethyl o-chlorobenzoate and ethyl naphthoate. Among such aromatic carboxylic acid esters, for example, benzoic acid, p
- Aromatic carboxylic acids having 1 to 4 carbon atoms such as methoxybenzoic acid, p-ethoxybenzoic acid, and toluic acid.
The alkyl esters of are particularly preferred. Next, in the present invention, titanium tetrahalide is used as the titanium compound. in particular
Examples include TiCl ₄ , TiBr ₄ , Til ₄ and the like, and it is particularly preferable to use titanium tetrachloride (TiCl ₄ ). Component (A) of the catalyst used in the present invention is prepared by reacting the above-mentioned magnesium compound, electron donating compound, and titanium halide, and various methods can be considered for its preparation. For example, the following methods (1) to (3) can be cited. (1) There is a method in which the magnesium compound is first brought into contact with an electron-donating compound and then reacted with titanium tetrahalide. There are no particular restrictions on the conditions for contacting the magnesium compound with the electron-donating compound, but usually 0.001 to 10 of the electron-donating compound is added to 1 mole of the magnesium compound.
Add moles, preferably 0.05 to 5 moles, 0 to
5 minutes to 10 hours at 200℃, preferably 30 to 150℃
The contact reaction may be carried out for 30 minutes to 3 hours. Note that an inert hydrocarbon such as pentane, hexane, heptane, octane, etc. can also be added to this reaction system as a solvent. Next, after this contact reaction, the obtained product is reacted with the titanium halide, but the conditions at this time are usually such that 1 magnesium in the product is
Titanium tetrahalide is added in an amount of 1 to 5 moles, preferably 2 to 20 moles per mole, and
5 minutes to 10 hours at 200℃, preferably 30 to 150℃
Allow to react for 30 minutes to 5 hours. This reaction can also be carried out using an inert solvent such as pentane, hexane, heptane, etc., if necessary. Furthermore, this
In method (1), the reaction with titanium tetrahalide can be repeated not only once but twice or more, and by doing so, a product with even better catalytic activity can be obtained. (2) Component (A) of the catalyst can also be prepared by reacting the magnesium compound with an alcohol and then reacting it with an electron-donating compound and titanium tetrahalide. The conditions for the alcohol treatment here are usually 0.01 to 10% alcohol per mole of magnesium compound.
moles, preferably 0.1 to 5 moles, 0 to 200
5 minutes to 5 hours at a temperature of ℃, preferably 20 to 100℃
What is necessary is just to make it react at ℃ for 20 minutes to 3 hours. Also,
Suitable alcohols include primary, secondary or tertiary alcohols having 1 to 10 carbon atoms;
More specifically, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, amyl alcohol, octanol, etc. can be mentioned. In method (2), an alcohol-treated magnesium compound is reacted with an electron-donating compound and titanium tetrahalide. In this case, the electron-donating compound is first reacted, and then the titanium tetrahalide is reacted. They may be added and reacted, or both compounds may be added simultaneously and reacted with the alcohol-treated magnesium compound.
In these cases, the addition ratio of each compound, reaction temperature, time, etc. may be in accordance with the conditions of the method (1) above. (3) First, the magnesium compound is mixed with one or more halogen-containing compounds selected from the group consisting of halogenated hydrocarbons, oxygen-containing halogenated hydrocarbons, thionyl halides, halogenated phosphorous compounds, and halogen-containing nitrogen compounds; General formula Ti(OR ³ ) ₄ [In the formula, R ³ has a carbon number of 1 to
10 alkyl, cycloalkyl, aryl or aralkyl groups. ], and then treated with an oxygen-containing titanium compound represented by
Component (A) of the catalyst can also be obtained by the method of reacting with titanium tetrahalide as described above. In this case, the electron-donating compound may be added to the reaction system at any stage of the method (3) above. The timing of addition is not particularly limited, and it may be present in the reaction meter from the beginning, or may be added at an intermediate stage. The halogen-containing compound used in method (3) is as described above, and the halogenated hydrocarbons include alkyl halides, allyl halides, aryl halides, aralkyl halides, etc. Examples include n-butyl chloride, monochlorobenzene, allyl chloride, carbon tetrachloride, and ethyl iodide. Examples of oxygen-containing halogenated hydrocarbons include halogenated benzoyl, halogenated epoxy, and halogenated alkoxycarbonyl, and specific examples include epichlorohydrin and ethyl chloroformate. Thionyl halides include thionyl chloride and thionyl bromide, and phosphorus halides include phosphoryl halides such as phosphoryl chloride, phosphorus trihalides such as phosphorus trichloride, and pentahalides such as phosphorus pentachloride. You can give things like phosphorus. Examples of the halogen-containing nitrogen acid compound include halogen-containing acetonitrile such as trichloroacetonitrile, and halogen-containing nitrosyl such as nitrosyl chloride. On the other hand, as an oxygen-containing titanium compound,
Ti(OCH ₃ ) ₄ , Ti(OC ₂ H ₅ ) ₄ , Ti(O・n−
C ₃ H ₇ ) ₄ , Ti (O・n-C ₄ H ₉ ) ₄ , Ti (OC ₆ H ₁₁ ) ₄ ,
Examples include Ti(O・C ₆ H ₅ ) ₄ . Regarding reaction conditions, etc., it is sufficient to follow Japanese Patent Application Laid-open No. 166205/1983. The method of the present invention uses both (A) and (B) as the component (A), which is the solid product prepared by the methods (1) to (3) above, and an organoaluminum compound as the component (B). Polymerization of ethylene is carried out using a catalyst whose main component is
The shape of component (A), which is a solid catalyst component, is not particularly limited, but it should preferably be adjusted to have a particle size of 5 to 100 μm and a specific surface area of 5 to 35 m ² /g. In addition, as component (B) of the catalyst, an organoaluminum compound is used, and has the general formula AlR ⁴ _K
The one represented by X ³ _3-K is widely used. R ₄ is an alkyl group, cycloylkyl group, or aryl group having 1 to 10 carbon atoms, k is a real number between 1 to 3, and X ³ represents a halogen atom such as chlorine or bromine. Specifically, trialkylaluminum compounds such as trimethylaluminum, triethyloaluminum, triisopropylaluminium, triisobutylaluminum, trioctylaluminum, and diethylaluminium monochloride,
Dialkyl aluminum monohalides such as diisopropylaluminum monochloride, diisobutyl aluminum monochloride, and dioctyl aluminum monochloride are preferred, and mixtures thereof are also preferred. In polymerizing ethylene by the method of the present invention, first, a dispersion of the above-mentioned solid product as component (A) and an organoaluminum compound as component (B) are added to the reaction system, and if desired, an electron donor is added to the reaction system. Then, an α-olefin having 3 or more carbon atoms is added to this system to carry out preliminary polymerization, and then main polymerization of ethylene is carried out. The prepolymerization carried out here involves α-olefins other than ethylene, in other words α-olefins having 3 or more carbon atoms, preferably α-olefins having 3 to 12 carbon atoms, specifically propylene, butene-1, pentene-1 , hexene-1, octene-1, etc. should be used as raw materials. This preliminary polymerization is usually carried out at a lower temperature than the subsequent main polymerization of ethylene to keep the polymerization rate low.Generally, the polymerization is carried out at a temperature below 40℃, preferably about 10 to 30℃. Prepolymerization is carried out so that the amount is in the range of 0.01 to 30 g per 1 g of titanium atoms. There is no particular restriction on the form of this preliminary polymerization, and solution polymerization, suspension polymerization, gas phase polymerization, etc. are all possible, but solution polymerization is preferred in order to control the polymerization rate. In this solution polymerization, benzane, hexane, heptane, benzene, toluene,
An inert solvent such as xylene is used, and the amount of catalyst added is calculated by converting component (A) into titanium atoms.
0.001 to 5 mmol/, preferably 0.005 to 1 mmol/, while component (B) has a molar ratio of 1 to 1000 (molar ratio) to the titanium atoms in component (A), preferably 10 to 1 mmol/.
500 (molar ratio). Furthermore, during this prepolymerization, the molecular weight can be controlled by known means such as hydrogen. In the present invention, as mentioned above, it is necessary to carry out preliminary polymerization prior to the main polymerization of ethylene.
If the main polymerization is started immediately without prepolymerization, the catalyst activity will be low, and the resulting ethylene polymer will have a low bulk density and a large amount of fine powder. Note that if preliminary polymerization is performed using ethylene as a raw material, the resulting ethylene polymer will have a low bulk density, which is not preferable. In the present invention, after the preliminary polymerization is completed, the main polymerization of ethylene is carried out. In this main polymerization, the catalyst used in the prepolymerization may be used as is, and the process proceeds by introducing ethylene into the reaction system in which the prepolymerization was performed. At this time, the reaction system may be newly supplemented with components (A) and (B) of the catalyst, as well as an electron-donating compound and the like. Moreover, in this main polymerization, ethylene is polymerized alone. There are no particular restrictions on the polymerization method and conditions, and slurry polymerization using an inert hydrocarbon solvent, liquid phase polymerization without a solvent, gas phase polymerization, etc. are all possible, and both continuous and discontinuous polymerization are possible. be. For example, in the case of slurry polymerization using an inert hydrocarbon solvent or liquid phase polymerization without a solvent, the amount of the catalyst component added is 0.001 to 5 mmol/, preferably 0.005 mmol/component (A) in terms of titanium atoms. ~1 mmol/. On the other hand, (B)
The component is 1 to 1000 to the titanium atom in component (A).
(molar ratio), preferably 10 to 500 (molar ratio).
The ethylene pressure in the reaction system is preferably normal pressure to 50 kg/ ^cm2 , and the reaction temperature is 45°C or higher, preferably 50 to 100 kg/cm2.
It is ℃. Molecular weight adjustment during polymerization can be carried out by known means, such as hydrogen. Note that the reaction time may be appropriately determined within the range of 5 minutes to 10 hours. According to the method of the present invention, since prepolymerization is carried out, the catalytic activity is extremely high, and the obtained ethylene polymer has a large bulk density, a narrow particle distribution, and very little fine powder, and has a microscopic particle size. The target shape is spherical. Moreover, since this ethylene polymer has a narrow molecular weight distribution, it can be easily stored and transported efficiently and without any trouble. Therefore, the method of the present invention can be effectively used for producing polyethylene of high product value, particularly high-density polyethylene or linear low-density polyethylene (LLDPE). Next, the method of the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 (1) Production of solid catalyst component In a well-dried 500 ml four-necked flask, 150 ml of dehydrated n-heptane, 10.0 g (88 mmol) of magnesium diethoxide, and 2.64 g (17.6 mmol) of n-butyl benzoate were added. was added and the reaction was carried out under reflux for 1 hour. Then, the temperature was raised to 70°C and 83 g (440 mmol) of titanium tetrachloride was added.
was added dropwise over 30 minutes, and the reaction was further carried out under reflux for 3 hours. After the reaction was completed, washing was repeated by decanting with n-heptane until no chlorine ions were detected, thereby obtaining a solid catalyst component. The amount of titanium supported in this solid catalyst component was measured by a colorimetric method and was found to be 45 mg-Ti/g support. The solid catalyst component had an average particle size of 24 μm and a specific surface area of 20 m ² /g. (2) Production of ethylene polymer 400 ml of dehydrated and purified n-heptane, 2 mmol of triethylaluminum, and 0.01 mmol of the solid catalyst component obtained in the above (1) as titanium were added to a 1-volume stainless steel autoclave. Then, at 25℃, propylene was added at a partial pressure of 0.8Kg/
cm ² G was supplied and prepolymerization was carried out for 15 minutes. Next, the temperature of the reaction system was raised to 70℃, and 3
Kg/cm ² G after inserting, the total pressure is 9Kg/cm2.
Ethylene was introduced continuously to give cm ² G, and 1
Time polymerization was carried out. After the polymerization was completed, unreacted monomers were removed to obtain an insoluble polymer. Results first
Shown in Table and Table 2. Example 2 The same procedure as in Example 1(2) was carried out except that octene-1 was used instead of propylene as the prepolymerized monomer. The results are shown in Table 1. Example 3 The same procedure as in Example 1(2) was carried out except that 0.2 mmol of methyl p-toluate was added during prepolymerization. The results are shown in Table 1. Comparative Example 1 In Example 1(2), the same operation as in Example 1(2) was performed except that preliminary polymerization was not performed. The results are shown in Tables 1 and 2. Comparative Example 2 The same operation as in Example 1 (2) was carried out except that the prepolymerization was carried out using ethylene instead of propylene and supplying 2 kg/cm ² G at a partial pressure. I did it. The results are shown in Table 1.

【table】

[Table] * Shown as weight average molecular weight/number average molecular weight.

[Brief explanation of the drawing]

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 method for producing an ethylene polymer by polymerizing ethylene using (A) a reaction product of a magnesium compound and a titanium compound and (B) a catalyst containing an organoaluminum compound as a main component. , general formula
Mg(OR ¹ ) _o X ¹ _2-o [In the formula, R ¹ represents an alkyl group having 1 to 20 carbon atoms,
X ¹ represents a halogen atom, and n represents a real number satisfying 0<n≦2. ] A solid product obtained by reacting a magnesium compound represented by the above, an electron-donating compound consisting of an aromatic carboxylic acid ester, and titanium tetrahalide is used as the component (A) of the above catalyst, and is also used in the main polymerization of ethylene. 1. A method for producing an ethylene polymer, which comprises prepolymerizing an α-olefin having 3 or more carbon atoms prior to the step. 2. The method according to claim 1, in which n is 2 as the magnesium compound represented by general Mg(OR ¹ ) _o X ¹ _2-o .