JPH0319844B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an ethylene polymer having a narrow molecular weight distribution. More specifically, the present invention relates to a method for producing an ethylene polymer with a narrow molecular weight distribution using a novel catalyst containing a titanium compound and a zirconium compound. Many methods have been proposed to produce ethylene polymers with a narrow molecular weight distribution suitable for injection molding. Even in the case of polymers that are
Significant amounts of extractables (very low molecular weight polymers) are present. The presence of these extremely low molecular weight polymers causes smoke, smear, or bad odor when the polymer is molded, and also causes fouling (polymer adhesion to the walls of the polymerization vessel, etc.) during the production of the polymer. ) and bridging. The above phenomenon becomes even more remarkable in a copolymer obtained by copolymerizing ethylene and α-olefin. In particular, in medium-density polyethylene and low-density polyethylene obtained by copolymerizing ethylene and a relatively large amount of α-olefin, the amount extracted by a solvent such as cyclohexane or n-hexane increases. The extract is composed of an extremely low molecular weight polymer and/or an extremely low density polymer, and the amount of the extremely low density portion is determined by the width of the density distribution (branching degree distribution) that occurs during copolymerization. be done. Based on the above, the present inventors conducted various searches to produce a polymer having a narrow molecular weight distribution and improving the above-mentioned drawbacks. As a result, (A) (1) General formula Mg ( OR ¹ ) _l X ¹ _2-l magnesium compound M; (2) alkoxytitanium compound T represented by the general formula Ti(OR ² ) ₄ ; and (3) alkoxy titanium compound T represented by the general formula Zr(OR ³ ) ₄ . A hydrocarbon-insoluble solid catalyst component obtained by reacting a zirconium compound Z and (4) an aluminum halide compound E represented by the general formula Al R ⁴ _n X ² _3-n in a specific quantitative ratio, and (B) an organoaluminum compound. The present inventors have discovered that an ethylene polymer that has improved all of these problems can be obtained by copolymerizing ethylene alone or ethylene and α-olefin using a catalyst system obtained from the above methods, and has arrived at the present invention. Many catalyst systems that use titanium compounds and zirconium compounds in combination have been known, but all of them are aimed at broadening the molecular weight distribution (for example,
It is surprising that a polymer having a significantly narrow molecular weight distribution can be obtained by using a titanium compound and a zirconium compound in combination, as in the present invention. The characteristic effects of the present invention are that the ethylene polymer obtained by the polymerization method of the present invention has a narrow molecular weight distribution and an extremely small content of extremely low molecular weight polymers, and is most suitable for injection molding. Even during molding, there is almost no generation of smoke, dirt, or bad odor. Further, in the production of the polymer, phenomena such as fouling and bridging hardly occur, so stable operation can be carried out not only in ethylene homopolymerization but also in copolymerization with α-olefin, which provides low density. The general formula of the magnesium compound used to produce the solid catalyst component is shown by the following formula. Mg (OR ¹ ) _l X ¹ _2-l () In the () formula, R ¹ has at most 16 carbon atoms.
is a saturated or unsaturated aliphatic, alicyclic or aromatic hydrocarbon group, X ¹ represents a halogen atom, and 1 is 0.1 or 2. Among the magnesium compounds represented by the formula ( ), representative examples of preferred compounds include magnesium chloride, magnesium bromide, magnesium ethylate, magnesium butyrate, ethoxymagnesium chloride, butoxymagnesium chloride, and the like. The titanium compound used to produce the solid catalyst component has the general formula shown below. Ti(OR ² ) ₄ () In the () formula, R ² is an aliphatic, alicyclic, or aromatic hydrocarbon group having at most 16 carbon atoms, and among the alkoxytitanium compounds represented by the () formula, Representative examples of suitable ones include ethyl titanate, isopropyl titanate, n-butyl titanate, isobutyl titanate, phenyl titanate, and the like. Furthermore, the general formula of the zirconium compound is represented by the following formula. Zr(OR ³ ) ₄ () In the () formula, R ³ is an aliphatic, alicyclic, or aromatic hydrocarbon group having at most 16 carbon atoms, and among the alkoxyzirconium compounds represented by the () formula, Representative examples of suitable ones include ethyl zirconate, n-propyl zirconate, n-butyl zirconate, and phenyl zirconate. The general formula of the aluminum halide compound is represented by the following formula. _AlR ^{4 n} _{_} ^{_ _} It represents an atom, and m represents a number of 0≦m≦2. Among the aluminum halide compounds represented by the formula (), representative examples of suitable compounds include methylaluminum dichloride, ethylaluminum dichloride, ethylaluminum sesquichloride, diethylaluminum chloride, butylaluminum dichloride, butylaluminum sesquichloride, aluminum chloride, Aluminum chloride, etc. The solid catalyst component of the present invention comprises the above reactant (),
(), () and () by any method that results in a chemical reaction of these reactants. The reaction for producing the solid catalyst component is preferably carried out in a liquid diluent. As a liquid diluent,
Aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene, toluene and xylene are used. It is also possible to use polar solvents such as ethers and alcohols. The order of addition of the reactants is arbitrary, but reactant () is added to the reaction mixture of reactants (), (), ().
It is most preferable to add. Reactant (),
The reaction temperature and time for () and () vary depending on the type of reactants and their proportions, and are not particularly limited, but are generally 10 minutes to 3 minutes at 40 to 180°C.
The time is particularly preferably 30 minutes to 2 hours at 60 to 140°C. The reaction temperature and time between the reaction mixture of the reactants and the reactants () are generally -40
It is preferably 10 minutes to 5 hours at a temperature of .degree. C. to 120.degree. C., and particularly preferably 30 minutes to 2 hours at a temperature of -30.degree. C. to 80.degree. The usage amount of each reactant is strict, and the usage amount of compounds (), (), () and () is according to the formula Zr/Ti×X ¹ +X ² /Mg+Ti+Zr≦1.5, 0.5≦Zr/Ti≦1.0
, 0.2≦Mg/Ti+Zr≦1.3 (). Here, Mg, Ti, Zr and X ¹ , X ² each represent the amounts of magnesium, titanium, zirconium and halogen used, and these amounts are expressed in gram equivalents. Therefore, in order to obtain a catalyst solid component according to the present invention, it is necessary to use these compounds so as to satisfy the above formula (). The product in formula () needs to be 1.5 or less, and if this product is larger than 1.5, a polymer with a sufficiently narrow molecular weight distribution cannot be obtained. The solid catalyst component obtained in the above manner may be thoroughly washed with an inert hydrocarbon such as n-hexane or n-heptane, and may be directly supplied to the polymerization system as a slurry, or after drying, it may be powdered. It may be used in a form. The content of titanium atoms in the solid component obtained as described above is generally 0.1 to 30% by weight,
The content of zirconium atoms is 0.1-20% by weight. In addition, the content of magnesium atoms is 0.1 to 30
% by weight, and the content of halogen atoms is at most
It is 70% by weight. Using the solid catalyst component purified as described above, homopolymerization of ethylene or ethylene and α- The present invention can be achieved by copolymerizing with olefin. As the organoaluminum compound used in the polymerization, an organoaluminum compound represented by the general formula Al R ⁵ _o X ³ _3-o () is used. In formula (), R ⁵ is an aliphatic, alicyclic or aromatic hydrocarbon group having at most 12 carbon atoms,
X ³ is a halogen atom or hydrogen atom, n is 2≦n≦
The number is 3. Typical examples include trialkylaluminum such as toluethylaluminum, tripropylaluminum, triisobutylaluminum, trihexylaluminum, alkylaluminum hydride such as diethylaluminum hydride and diisobutylaluminum hydride, and diethylaluminum chloride, diethylaluminum bromide, etc. Examples include dialkyl aluminum halides. The amount of the organoaluminum compound used is generally 0.1 to 10 mmol, preferably 0.3 to 3 mmol, per 1 inert solvent. Inert solvents include unsaturated aliphatic hydrocarbons such as butane, pentane, hexane, heptane, cyclohexane and methylcyclohexane, and aromatic hydrocarbons such as benzene, toluene and xylene. In addition, the third component is
It is an electron-donating compound and is well known as a modifier for polymerization activity, crystallinity, etc. in the polymerization of olefins. When copolymerizing with ethylene, the α-olefin used is an α-olefin having at most 20 carbon atoms, preferably 12 carbon atoms, and a typical example thereof is propylene butene-1,4-methylpentene- 1, hexene-1
and octene-1. The proportion of the above α-olefin in the obtained ethylene copolymer is generally preferably 20 mol% or less, particularly
The content is preferably 15 mol% or less. In carrying out the method of the present invention, the polymerization temperature and pressure are not particularly limited, and commonly used conditions can be applied, but generally a temperature range of room temperature to 300°C and a polymerization pressure of 1 to 200 atm are adopted. It is carried out by a phase method, suspension method or solution method. Further, if necessary, hydrogen or the like may be allowed to coexist in the polymerization reaction system in order to adjust the molecular weight. Next, the present invention will be explained in more detail by referring to Examples and Comparative Examples. Examples 1 to 5, Comparative Examples 1 to 4 (1) Production of solid catalyst components Magnesium ethylate, n-butyl titanate, n-butyl zirconate and n-heptane were used as a solvent in the proportions shown in Table 1. ,70℃
The reaction was carried out for 1.5 hours. Then, a predetermined amount of ethylaluminum dichloride was added at 80°C. After thoroughly washing the generated precipitate with n-hexane, it was vacuum dried at 40°C to obtain a solid catalyst powder. (2) Polymerization of ethylene In a 3.0 stainless steel autoclave,
Hexane 2, the amount of the above solid catalyst component shown in Table 1, and 0.8 m of triisobutylaluminum.
mol was added and the internal temperature was raised to 90°C. Next, add hydrogen in the amount shown in Table 1, and then pressurize ethylene.
Polymerization was carried out for 1 hour while maintaining the ethylene partial pressure at 5.0 Kg/cm ² . Polymerization was then terminated by discharging the contained gas to the outside of the system. The results obtained are shown in Table 1. Example 6 A solid catalyst component was obtained in exactly the same manner as in Example 4 except that isopropyl titanate was used instead of n-butyl titanate, and using this material, ethylene polymerization was carried out in the same manner as in Example 4. Ta. The results are shown in Table 1. Example 7 A solid catalyst component was obtained in exactly the same manner as in Example 1 except that magnesium chloride was used instead of magnesium ethylate. Ethylene polymerization was carried out in exactly the same manner as in Example 1, except that a predetermined amount of this solid catalyst component was used. The results are shown in Table 1. Examples 8 to 11 In the polymerization of ethylene in Example 1, when ethylene was press-ined and polymerization was started, α-olefin (types and supply amounts are shown in Table 2) was press-ined together with ethylene, and ethylene and α-olefin were combined. The copolymerization was carried out for 1 hour. The polymerization results are shown in Table 2. Example 12 22.1 mg of the solid catalyst component prepared in Example 1, 0.5 mmol of triisobutylaluminum and 1 kg of isobutane were placed in a 3.0 mm stainless steel autoclave, and the internal temperature was raised to 80°C. Hydrogen was injected to a partial pressure of 1.0 Kg/cm ² , 90 g of butene-1 was charged, and then ethylene was injected to a partial pressure of 5.0 Kg/cm ² . Polymerization was carried out for 1 hour while feeding ethylene to maintain the pressure. The obtained polymer weighed 510g, and the polymerization activity was 4620
g/g, solid catalyst, time, and ethylene pressure.
The MI of this polymer is 6.2 g/10 min, and the HLMI/
The MI was 21 and the density was 0.921 g/cc.
Further, the amount of n-hexane extracted was 9.5%. Comparative Example 5 23.6 mg of solid catalyst component prepared in Comparative Example 1
Copolymerization of ethylene and butene-1 was carried out in the same manner as in Example 12, except that ethylene and butene-1 were used. The weight of the obtained polymer was 290 g, and the polymerization activity was 2460 g/g-solid catalyst/time/ethylene pressure. The MI of the polymer is
5.9 g/10 minutes, HLMI/MI was 45, and density was 0.923 g/cc. The amount of n-hexane extracted is
The percentage was as high as 35%.

【table】

[Table] *) Ethylaluminum dichloride **) Polymerization activity (g = polymer / g - solid catalyst = time = ethylene pressure)
＊＊＊) According to JIS K-6760 (190℃, MI load is 2.
16Kg, HLMI load is 21.6Kg)

【table】 [Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of the catalyst preparation and polymerization steps according to the present invention.

Claims (1)

[Claims] 1 (A) (1) ^General formula _Mg (OR ^{1 )} _l group or aromatic hydrocarbon group, X ¹ represents a halogen atom, and l is 0,1
or 2) and (2) a magnesium compound M represented by the general formula Ti(OR ² ) ₄ (wherein R ² is an aliphatic, alicyclic or aromatic hydrocarbon group having at most 16 carbon atoms). ) and (3) an alkoxytitanium compound T represented by the general formula Zr(OR ³ ) ₄ (wherein R ³ is
(16 aliphatic, alicyclic or aromatic hydrocarbon groups) and (4) the general formula Al R ⁴ _n X ² _3-n (wherein R ⁴ is a carbon number At most 12 saturated or unsaturated aliphatic, alicyclic or aromatic hydrocarbon groups, X ² represents a halogen atom, m represents a number of 0≦m≦2) In a method of copolymerizing ethylene alone or with ethylene and α-olefin using a catalyst system obtained from a hydrocarbon-insoluble solid catalyst component obtained by reacting aluminum compound E and (B) an organoaluminum compound, the above compound M, T, Z and E are expressed by the following ^formulas Zr/Ti×X ^{1 +} X ² represents the amount of magnesium, titanium, zirconium and halogen used, each expressed in gram equivalent.