JP2535914B2 - Method for producing polyethylene - Google Patents

Description

The present invention relates to a method for producing polyethylene by polymerizing ethylene or ethylene and an α-olefin in the presence of a novel catalyst system. More specifically, it relates to a method for producing polyethylene having a large melt tension and a large expansion ratio (die swell) during molding.

<Prior Art> Polyethylene is molded and used by various molding methods according to the use. Therefore, polyethylene is required to have characteristics corresponding to the molding method and the intended use. For example, in the case of performing hollow molding, polyethylene having a large melt swell and a cylindrical melt from an extruder does not hang down or break, and polyethylene having a large die swell to some extent is required for molding a large bottle.

Although many proposals have been made so far regarding the production of polyolefins using Ziegler-type catalysts, there are only a few proposals regarding the catalyst modification for the purpose of improving the melt tension and die swell.

For example, according to the proposal of JP-A-56-90810, a halogen-containing titanium compound and an OR group, which are supported and bound on a solid reaction product formed by the reaction of an inert hydrocarbon-soluble organomagnesium component and a halogenating agent, It is stated that it is possible to adjust the die swell of the olefin polymer in a wide range by using a solid catalyst component containing substantially no OR group, which is produced by thermally decomposing a reaction solid containing a. Further, according to the proposal of JP-A-59-56406,
It is said that it is possible to produce an olefin polymer having large melt tension and die swell by heat-treating a highly active titanium catalyst component containing magnesium, titanium and halogen as essential components in the presence of a specific organic polyvalent metal compound. There is. However, the solid catalyst component obtained by such heat treatment has a problem in that although the die swell is improved to some extent as compared with that before the heat treatment, the catalytic activity is lowered.

The present inventors have studied the method for producing polyethylene having a large melt tension and a large die swell while avoiding the above problems, and as a result, in Japanese Patent Application No. Sho 61-280893, metal enolates, organomagnesium compounds and halogen-containing titanium. We proposed a method using the reaction product of the compound as a catalyst component.

<Problems to be Solved by the Invention> However, although this catalyst component is improved in melt tension and die swell, it is insufficient in catalytic activity and polymer powder properties which have industrial significance. It was Still, since the halogen-containing titanium compound is used in the catalyst production, there is a problem that the catalyst preparation machine is corroded. Therefore, as a result of further intensive studies, the present inventors have found the present invention.

<Means for Solving Problems> That is, the present invention provides a method for producing polyethylene in which ethylene or ethyleneto α-olefin is polymerized and polymerized in the presence of a Ziegler type catalyst, wherein the catalyst is (i).
From a metal enolate selected from iron, nickel, cobalt, magnesium, beryllium, (ii) an organomagnesium compound, (iii) an oxygen-containing organic compound of titanium, (iv) a halogenated organoaluminum compound, and (v) a polysiloxane and silanes. The present invention relates to a method for producing polyethylene, which comprises a catalyst component (A) which is a reaction product of a selected silicon compound and a catalyst component (B) selected from an organoaluminum compound.

<Action> The metal enolate (i) used in the preparation of the catalyst component (A) of the present invention includes iron, nickel, cobalt, magnesium and beryllium as metal atoms, and also has an enol type structure such as acetylaceto. Examples include nato and dipivaloyl methanate. More specifically, iron (II) acetylacetonate, iron (III) acetylacetonate, nickel acetylacetonate,
Cobalt (II) acetylacetonate, cobalt (II
I) Acetylacetonate, magnesium acetylacetonate, chromium acetylacetonate, iron dipivaloyl methanate, cobalt dipivaloyl methanate and the like.

Further, (ii) as the organic magnesium compound, a compound represented by the general formula R ¹ R ² Mg, R ³ MagX (wherein R ¹ , R ² and R ³ may be the same or different and has 1 to 20 carbon atoms) , X represents a halogen atom), and dialkyl magnesium and alkyl magnesium halide. More specifically, diethyl magnesium, dibutyl magnesium, butyl ethyl magnesium, butyl propyl magnesium, di-n-hexyl magnesium, etc., ethyl magnesium chloride, ethyl magnesium bromide, ethyl magnesium iodide, butyl magnesium chloride, butyl magnesium bromide, butyl magnesium Examples include iodide. Also, a mixture of these organomagnesium compounds and organoaluminum compounds can be used.

(Iii) The oxygen-containing organic compound of titanium is represented by the general formula [TiOa (OR ⁴ ) _b ] _m (wherein R ⁴ represents a hydrocarbon group having 1 to 20 carbon atoms. The valence of Ti is 4, a And b are a ≧
0, b> 0, and m is an integer. ) Is used. For example, titanium tetraethoxide, titanium tetra-n-propoxide, titanium tetra-i-propoxide, titanium tetra-n-butoxide, hexa-i.
-Propoxydititanate and the like.

The (iv) halogenated organic aluminum compound represented by the general formula AlR ⁵ _n X _3-n (wherein R ⁵ is .n is the number made 0 <n <3 representing a hydrocarbon group having 1 to 20 carbon atoms ) Is used.

For example, ethyl aluminum dichloride, n-propyl aluminum dichloride, butyl aluminum dichloride, i-butyl aluminum dichloride, sesquiethyl aluminum chloride, sesquiisobutyl aluminum chloride, sesqui-i-propyl aluminum chloride, sesqui-n-propyl aluminum chloride, diethyl aluminum Examples thereof include chloride, di-i-propylaluminum chloride, di-n-propylaluminum chloride, di-i-butylaluminum choroid, diethylaluminum bromide, diethylaluminum iodide and the like.

The following compounds are used as the silicon compound (v) selected from polysiloxanes and silanes.

The polysiloxane has the general formula (In the formula, R ⁶ and R ⁷ are hydrocarbon groups such as alkyl groups and aryl groups having 1 to 12 carbon atoms, hydrogen, halogen, and 1 to 12 carbon atoms.
Represents a silicon-bondable atom or residue such as 12 alkoxy groups, allyloxy groups, and fatty acid residues, and represents R ⁶ and R ⁷
May be the same kind or different kinds, and p represents an integer of 2 to 10,000, which is abnormal, and is one or two of the repeating units represented by
Siloxane polymer having a chain, cyclic or three-dimensional structure containing at least one species in various ratios and distributions in the molecule (except when all R ⁶ and R ⁷ are hydrogen or halogen) Can be given.

Specifically, as the chain polysiloxane, for example, hexamethyldisiloxane, octamethyltrisiloxane, dimethylpolysiloxane, diethylpolysiloxane, methylethylpolysiloxane, methylhydropolysiloxane, ethylhydropolysiloxane, butylhydrosiloxane, Hexaphenyldicycloxane, octaphenyltrisiloxane, diphenylpolysiloxane, phenylhydropolysiloxane, methylphenylpolysiloxane, 1,5-dichlorohexamethyltrisiloxane, 1,7
-Dichlorooctamethyltetrasiloxane, dimethoxypolysiloxane, diethoxypolysiloxane, diphenoxypolysiloxane and the like.

Examples of the cyclic polysiloxane include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, 2,4,6-trimethylcyclotrisiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, Examples thereof include triphenyltrimethylcyclotrisiloxane, tetraphenyltetramethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane, octaphenylcyclotetrasiloxane.

As the polysiloxane having a three-dimensional structure, for example, the above chain-like or cyclic polysiloxane having a crosslinked structure by heating or the like can be mentioned.

It is desirable that these polysiloxanes be liquid for handling, and the viscosity at 25 ° C. is 1 to 10,000 centistokes, preferably 1 to 1000 centistokes. However, it is not necessary to limit it to a liquid state, and a solid substance generally called a silicone grease may be used.

Examples of silanes include the general formula H _q Si _r R ⁸ _s X _t (wherein R ⁸ is a hydrocarbon group such as an alkyl group or an aryl group having 1 to 12 carbon atoms,
Represents a group capable of bonding to silicon such as an alkoxy group having 1 to 12 carbon atoms, an allyloxy group, a fatty acid residue, etc., and each R ⁸ may be different from each other or the same kind, and X represents halogens different from each other or the same kind. , Q, s and t are integers of 0 or more,
r is a natural number and is q + s + t = 2r + 2).

Specifically, for example, silahydrocarbons such as trimethylphenylsilane and allyltrimethylsilane, chain and cyclic organic silanes such as hexamethyldisilane and octaphenylcyclotetrasilane, organic silanes such as methylsilane, dimethylsilane and trimethylsilane, Silicon halides such as silicon tetrachloride and silicon tetrabromide, alkyl and aryl halogenosilanes such as dimethyldichlorosilane, diethyldichlorosilane, n-butyltrichlorosilane, diphenyldichlorosilane, triethylfluorosilane and dimethyldibromosilane, trimethylmethoxysilane. Alkoxysilane such as dimethyldiethoxysilane, tetramethoxysilane, diphenyldiethoxysilane, tetramethyldiethoxydisilane, dimethyltetraethoxydilane, Chloro diethoxy silane, dichlorodiphenylsilane, haloalkoxy and phenoxy silanes such as tri-bromoethoxy silane, acetoxytrimethylsilane, diethyl diacetoxy silane, silane compounds containing fatty acid residue such ethyltriacetoxysilane, and the like.

The above organosilicon compounds may be used alone, or may be used by mixing or reacting two or more kinds.

The catalyst component (A) is preferably prepared in an inert hydrocarbon solvent such as hexane, heptane, octane, decane or cyclohexane, or in a halohydrocarbon cell such as carbon tetrachloride or dichloroethane.

The catalyst component (A) may be prepared by any method, but the following method is preferable.

After reacting I (i) a metal enolate with (ii) an organomagnesium compound, (iii) reacting with an oxygen-containing organic compound of titanium, and (v) in the presence of a silicon compound selected from polysiloxane and silanes ( iv) A method of reacting an organoaluminum halide compound.

II (i) After reacting a metal enolate with (ii) an organomagnesium compound, (v) reacting with a silicon compound selected from polysiloxane and silanes (iii) reacting with an oxygen-containing organic compound of titanium, and then (Iv) A method of reacting an organoaluminum halide compound.

An inorganic carrier can also be used in the preparation.
As the inorganic carrier, metal oxides such as alumina,
Examples thereof include silica, metal halides such as magnesium chloride and magnesium bromide, and metal alcoholates such as methoxymagnesium and ethoxymagnesium.

The amount of each component used in the preparation of the catalyst component (A) is not limited, but for example, (ii) about 1 to 100 mol of the metal enolate, (ii) an organomagnesium compound of about 0.01 to 100 mol, preferably 0.1 to 10 mol. It is a degree. Also, (i) about 0.01 to 20 mol of an oxygen-containing organic compound of titanium (iii) with respect to 1 mol of metal enolate, preferably
It is about 0.1 to 5 moles, (iv) about 0.1 to 100 moles of organoaluminium halide compound, preferably about 1 to 20 moles, and (v) a silicon compound selected from polysiloxanes and silanes (converted to silicon atom). ) It is about 0.01 to 20 mol, preferably about 0.05 to 5 mol.

The reaction temperature is not limited, but may be 0 to 200.
C., preferably 0 to 150.degree.

In the present invention, the organoaluminum compound which is the catalyst component (B) is represented by the general formula R ⁹ _m AlX _3-m (wherein R ⁹ is a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen atom, and m is 0). And a number of 3 or less is shown in the table). Examples of such compounds include trialkylaluminums such as triethylaluminum and tributylaluminum, organoaluminum halides such as diethylaluminum chloride, ethylaluminum sesquichloride and ethylaluminum dichloride.

Further, it is also possible to use an aluminoxane compound in which two or more aluminum atoms are bound via an oxygen atom or a nitrogen atom, for example, a polymer such as tetramethylaluminoxane or polymethylaluminoxane.

In the practice of the present invention, the catalyst component (A) is used in an amount of 0.001 titanium atom per solvent or reactor.
It is preferable to use in an amount corresponding to ˜2.5 mmol, and higher concentration can be used depending on the conditions.

The catalyst component (B) can be used in a concentration of 0.02 to 50 mmol, preferably 0.2 to 5 mmol of aluminum atom per solvent or reactor 1.

Polymerization of ethylene or ethylene and α-olefin is carried out in a liquid phase or a gas phase. When the polymerization is carried out in the liquid phase, it is preferable to use an inert solvent. The inert solvent may be any of those commonly used in the art, particularly alkanes and cycloalkanes having 4 to 20 carbon atoms, such as isobutane, pentane, hexane, Heptane, cyclohexane, etc. are suitable.

The polymerization of the present invention includes not only homopolymerization of ethylene but also copolymerization of ethylene and α-olefin. The α-olefin used for copolymerization includes propylene, 1-butene, 1
-Pentene, 1-hexane, 1-octene, 4-methyl-1-
Examples include pentene or a mixture thereof. α
-The amount of olefin used must be selected according to the density of the target polymer. The density of the polymer according to the invention is 0.
It can be manufactured in the range of 900 to 0.970 g / cm ³ .

The polymerization operation of the present invention can be carried out not only in ordinary one-step polymerization carried out under one polymerization condition, but also in multi-step polymerization carried out under a plurality of polymerization conditions.

The polymerization conditions in the present invention are not particularly limited, but the polymerization temperature is, for example, 20 to 300 ° C., and the polymerization pressure is, for example, ^{2 to} 50 kg / cm ² G.

<Example> The present invention will be shown below by examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, HLMI / MI is high load melt index (HLMI, ASTM D-1238 condition E).
And the melt index (MI, according to ASTM D-1238 condition E), and the density was measured and determined according to ASTM D-1505. The catalyst activity is represented by the polyethylene production amount (g) per 1 g of the catalyst component (A).

As the melt tension, the stress when the melted polymer was stretched at a constant speed was measured. That is, using a melt tension measuring machine manufactured by Toyo Seiki Seisakusho, resin temperature 190 ° C, extrusion speed 10 mm / min, winding speed 11 m / min, nozzle diameter 2.0
The conditions were 9 mmφ and 8 mm nozzle length.

The die swell uses the same equipment as the melt tension, and the resin temperature
The diameter of the extruded melt after cooling to 190 cm at an extrusion rate of 10 mm / min was measured (the die swell is the nozzle diameter
Expressed as a ratio to 2.09 mmφ).

Example 1 [Preparation of catalyst component (A)] Finely powdered magnesium acetylacetonate was added to a flask having an inner volume of 500 ml equipped with a stirrer and a water-cooled reflux condenser.
After adding 2.2 g (10 mmol) and adding 200 ml of hexane, 45 ℃
Solution of butylethylmagnesium in heptane (concentration 20wt
%) 17 ml (21 mmol) was slowly added dropwise. After adding all, the mixture was stirred at 68 to 70 ° C. for 1 hour to obtain a pale yellow slurry.
Subsequently, 1.8 ml of methylhydropolysiloxane (viscosity of about 30 centistokes at 25 ° C.) (30 mg of silicon-atom) was added and stirred for 1 hour. After cooling to 45 ° C, tetra-
1.7 g (5 mmol) of n-butoxide was added, and then a hexane solution of i-butylaluminum dichloride (concentration: 50 wt
%) 37 ml (0.1 mol) was slowly added dropwise, and after all were added, the mixture was again stirred at 68 to 70 ° C. for 1 hour. Hexane was added to the product, and the product was washed seven times by a gradient method to obtain a slurry of the catalyst component (A) suspended in hexane (containing 3.0 g of the catalyst component (A)). A part of the sample was sampled, dried in a nitrogen atmosphere, and analyzed by elemental analysis. As a result, titanium was 6.5 wt%.

[Polymerization] The interior of the stainless steel electromagnetic stirring reactor with an internal volume of 2 was sufficiently replaced with nitrogen, and hexane 1.2 was charged to adjust the internal temperature to 8
Adjusted to 0 ° C. Then, 0.23 g (1.2 mmol) of triisobutylaluminum as the catalyst component (B) and 9 mg of the above catalyst component (A) were sequentially added. After adjusting the inside of the reactor to 1 kg / cm ² G with nitrogen, add 4 kg / cm ² of hydrogen to bring the total pressure to 1
Polymerization was carried out for 1.5 hours while adding ethylene so that the concentration became 1 kg / cm ² G. Polyethylene was taken out of the reactor by filtration and dried. As a result, MI was 0.41 g / 10 minutes, HLMI / MI
As a result, 234 g of polyethylene of 52 was obtained. Catalytic activity is 26000g
/ g, and the bulk density was 0.39 g / cm ³ . The melt tension of this polyethylene was 1.0 g and the die swell was 1.91.

Comparative Examples 1 to 3 In the method of Example 1, the use of each component in the preparation of the catalyst component (A) was changed as shown in Table 1.

That is, in Comparative Example 1, methylhydropolysiloxane was used, in Comparative Example 2, butylethylmagnesium was used, and in Comparative Example 3, magnesium acetylacetonate was not used. Polymerization was carried out under the same conditions as in Example 1. As is clear from the results shown in Table 1, by making the five components essential during the preparation of the catalyst component (A), the activity is high, the powder properties are good, and the effect of improving the melt tension and die swell is recognized. .

Examples 2 to 4 In the method of Example 1, the kind of each component in preparing the catalyst component A) was changed as shown in Table 2. That is, iron (III) acetylacetonate was used as the (i) metal enolate in Example 2, cobalt (III) acetylacetonate was used as the (i) metal enolate in Example 3, and (ii) organomagnesium compound was used in Example 4. Catalysts were prepared by using di-n-hexylmagnesium as the above. Polymerization was carried out under the same conditions as in Example 1.

Examples 5 to 7 The method of Example 1 was carried out by changing the type of the silicon compound selected from (v) polysiloxane and silane in the preparation of the catalyst component (A) as shown in Table 3. . That is, in place of the methylhydropolysiloxane in Example 1, dimethylpolysiloxane was used in Example 5, diphenyldiethoxysilane was used in Example 6, and tetramethoxysilane was used in Example 7, respectively. I went. Polymerization was carried out under the same conditions as in Example 1.

Examples 8 and 9 In the method of Example 1, the types and amounts of (iii) the oxygen-containing organic compound of titanium and (iv) the halogenated organic compound in the preparation of the catalyst component (A) are shown in Table 4. I changed each to.

Polymerization was carried out under the same conditions as in Example 1.

Example 10 Using the catalyst component (A) prepared in Example 1, polyethylene was produced by copolymerizing ethylene and 1-butene. That is, hexane 1. was added to the same polymerization apparatus as in Example 1.
2 was charged and the internal temperature was adjusted to 80 ° C. Then, 0.23 g (1.2 mm) of triisobutylaluminum as a catalyst component (B)
ol) and 7 mg of catalyst component (A) prepared in Example 1 were added. After adjusting the inside of the reactor with nitrogen to 1 kg / cm ² G, hydrogen
Polymerization was carried out for 1.5 hours while adding 100 ml of 3 kg / cm ² , 1-butene and adding ethylene so that the total pressure was 10 kg / cm ² G.
The polyethylene was taken out from the reactor by filtration and dried. As a result, MI was 1.5g / 10 minutes, HLMI / MI was 32, and density was 0.
140 g of polyethylene with 932 g / cm ³ were obtained.

This polyethylene has a melt tension of 4.2 g and a die swell
It was 1.62.

Comparative Example 4 Using the catalyst component prepared in Comparative Example 3, the same copolymerization of ethylene and 1-butene as in Example 10 was performed. as a result
116 g of polyethylene with MI of 1.2 g / 10 min, HLMI / MI of 30 and density of 0.932 g / cm ³ were obtained.

This polyethylene has a melt tension of 1.8 g and a die swell
It was 1.46.

<Effects of the Invention> According to the present invention, by polymerizing ethylene or ethylene and an α-olefin using a novel catalyst, polyethylene having a large melt tension and a large die swell can be produced with high productivity. That is, the first effect of the present invention is that polyethylene having a large melt tension and a large die swell can be produced. Therefore, in the hollow molding, the cylindrical melt can be smoothly molded without hanging or breaking. In addition, since the die swell is large even when molding a large bottle, a complicated shape can be molded. The second effect of the present invention is that it is not necessary to perform heat treatment at the time of catalyst preparation and can be used without lowering the catalyst activity, so that high productivity can be maintained.

The third effect of the present invention is that the powder properties of the polymer are remarkably good. That is, it is possible to obtain polyethylene having a high bulk density, which is of great significance industrially.
This prevents the formation of deposits in the polymerization apparatus in the polymerization step, facilitates the separation / excess of the polymer slurry in the polymer separation / drying step, and the silo in the transfer step. There are no bridges and the troubles in transportation are eliminated.

A fourth effect of the present invention is that since a halogen-containing titanium compound is not used in the production of the catalyst component, troubles in the catalyst production process and the catalyst cleaning liquid treatment process can be avoided. Titanium tetrahalide easily decomposes even when contacted with an extremely small amount of air or moisture to generate a large amount of hydrogen chloride and solid deposits which are decomposition products, so it corrodes the equipment and piping, and However, it causes problems such as blocking the piping. According to the method for producing a catalyst component of the present invention, these problems caused by using titanium tetrahalide as a starting material can be improved or eliminated.

[Brief description of drawings]

FIG. 1 is a catalyst preparation diagram (flow chart) in the present invention.
Indicates.

Claims (1)

(57) [Claims] 1. A method for producing polyethylene in which ethylene or ethylene and an α-olefin are polymerized in the presence of a Ziegler type catalyst, wherein the catalyst is i) a metal enolate selected from iron, nickel, cobalt, magnesium and beryllium and ii). An organomagnesium compound and iii) a general formula [TiO _a (OR ⁴ ) _b ] _m (wherein R ⁴ represents a hydrocarbon group having 1 to 20 carbon atoms, the valence of Ti is tetravalent, and a and b are , A ≧ 0, b> 0, and m is an integer), the reaction formation of an oxygen-containing compound of titanium with iv) an organoaluminum halide compound, and v) a silicon compound selected from polysiloxane and / or silanes. A process for producing polyethylene, comprising a catalyst component (A) which is a product and a catalyst component (B) selected from organoaluminum compounds.