JPH07258327A - Manufacture of ethylene copolymer - Google Patents

Abstract

PURPOSE:To obtain an ethylene copolymer excellent in extrusion properties, melt properties, etc., by copolymerizing ethylene with an alpha-olefin in the presence of a catalyst system comprising a specific solid catalyst component and an organoaluminum compd. through specific 2 stages. CONSTITUTION:A mixture (A) obtd. by pulverizing an aluminum trihalide together with an org. compd. having an SiO bond and a magnesium alcoholate is brought into contact with a tetravalent-titanium compd. (B) having at least 1 halogen atom in a liq. phase. The resultant solid component is used in combination with an organoaluminum compd. to effect prepolymn. of ethylene to such an extent that the amt. of the resultant prepolymer is 0.01 to 100g per g of the solid component. The resultant catalyst is treated with a compd. of the formula provided that the Al/Ti molar ratio is in the range of 2 to 20. The resultant solid catalyst component is combined with an organoaluminum compd. to form a catalyst system, in the presence of which ethylene and an alpha-olefin are copolymerized according to two-stage polymn. wherein a high-molecular component is formed in the first polymn. zone and a low-molecular component is formed in the second polymn. zone.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an ethylene copolymer. More specifically, it relates to a method for providing an ethylene-based copolymer having excellent extrusion properties and melt properties, which is suitable for inflation molding.

[0002]

2. Description of the Related Art In the field of inflation molding, an ethylene-based copolymer having a high molecular weight and a wide molecular weight distribution is required. Up to now, there have been many proposals for a method for producing an ethylene copolymer for inflation molding having a wide molecular weight distribution by two-step polymerization. Particularly, there is a method disclosed in Japanese Patent Publication No. 3-18645. this is,
This is a method of producing a high molecular weight component in the first stage and a low molecular weight component in the second stage by carrying out continuous two-stage polymerization using an easily volatile hydrocarbon solvent such as propane and isobutane. When adjusting the molecular weight with hydrogen, when moving from the first stage to the second stage,
It does not require an intermediate hydrogen flash tank and is highly desirable in terms of productivity.

Further, as a solid catalyst component used in the production of an ethylene-based copolymer by two-step polymerization, Japanese Patent Laid-Open No.
78287, JP-A-53-132082, JP-A-54-
75491, JP-A-54-81190, JP-A-55-3
459, JP-A-57-205410, JP-A-58-14
9906, the highly active supported solid catalyst component disclosed in JP-A-58-225105 and the like.

[0004]

However, the ethylene-based copolymer obtained by carrying out the two-step polymerization by the above-mentioned method with the catalyst system comprising the above-mentioned solid catalyst component has a high catalyst activity and very high productivity. Although high, there was a problem that the extrusion characteristics and the melt properties during inflation molding were not always satisfactory. An object of the present invention is to solve these problems of the prior art and provide a method for producing an ethylene-based copolymer having excellent extrusion properties and melt properties during molding.

[0005]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the inventors of the present invention have found that ethylene and α-olefin have low molecular weight components in the first polymerization zone and low amounts in the second polymerization zone. In producing an ethylene-based copolymer by a two-step polymerization of polymerizing a molecular weight component, (1) a co-milling product obtained by co-milling an aluminum trihalide, an organic compound having a Si—O bond and a magnesium alcoholate And (2) a solid component obtained by contacting a tetravalent titanium compound having at least one halogen atom in a liquid phase in combination with an organoaluminum compound so that the amount of prepolymerization is 0.
The prepolymerization catalyst preliminarily polymerized with ethylene so as to have a weight of 01 to 100 g is represented by the general formula R ¹ AlX ₂ (R ¹ is an alkyl group, a cycloalkyl group, an aryl group and an aralkyl group,
Represents a halogen atom), and a solid catalyst component and an organoaluminum obtained by treating with a dihalogenated organoaluminum compound in the range of Al / Ti = 2 to 20 molar ratio with respect to titanium atom in the prepolymerization catalyst. The above problems have been solved by a method for producing an ethylene-based copolymer using a catalyst system composed of a compound.

The present invention will be specifically described below. Solid Component As the solid component used in the production of the ethylene-based copolymer of the present invention, a solid component containing at least magnesium, titanium and halogen is used. For example, those described in JP-A-58-225105 can be used. Specifically, (1) a co-ground product obtained by co-ground aluminum trihalide, an organic compound having a Si—O bond and magnesium alcoholate, and (2) a tetravalent having at least one halogen atom. It is a solid component obtained by contacting the titanium compound of 1) in the liquid phase.

Aluminum trihalides are anhydrous and include aluminum trichloride, aluminum tribromide, and aluminum trifluoride. Aluminum trichloride is particularly preferable. The aluminum trihalide may be in the form of powder or particles.

A typical organic compound having a Si--O bond is represented by the general formula: Si (OR ² ) _p R ³ _q (I) R ⁴ (R ⁵ ₂ SiO) _r SiR ⁶ ₂ (II) (R ⁷ ₂ SiO) _s (III). In the formula, R ² , R ³ and R ⁷ may be the same or different and are a hydrocarbon group selected from the group consisting of an alkyl group having at most 20 carbon atoms, a cycloalkyl group, an aryl group and an aralkyl group. (These may be unsaturated, may be substituted with a halogen atom or an alkoxy group having at most 20 carbon atoms, and may have an epoxy ring such as a glycidyl group) (R ³ is a hydrogen atom or a halogen atom). Atom, R ⁷ may be a hydrogen atom), R ⁴ , R ⁵ and R ⁶
May be the same or different, are the above hydrocarbon groups (which may be unsaturated or substituted) or halogen atoms, p + q is 4 (where p ≠ 0), and r is 1 to 1000. Is an integer and s is 2 to 1000
Is an integer.

Typical compounds represented by the formula (I) include tetramethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, tetraethoxysilane, triethoxyethylsilane, diethoxydiethylsilane, ethoxytriethylsilane, Tetrapropoxysilane, dipropoxydipropylsilane, tetraisopropoxysilane, diisopropoxydiisopropylsilane, dimethoxydiethylsilane, diethoxydibutylsilane, tetra-n-butoxysilane, di-n-butoxy-di-n-butylsilane, tetrasec-butoxy Silane, tetrahexoxysilane, tetraoctoxysilane, tetraphenoxysilane, tetracresylsilane, diphenyldiethoxysilane, diphenyldimethoxysilane, trimethoxychloro Orchids, dimethoxy dichlorosilane,
Dimethoxydibromosilane, triethoxychlorosilane, diethoxydibromosilane, dibutoxydichlorosilane, dicyclopentoxydiethylsilane, diethoxydiphenylsilane, 3,5-dimethylphenoxytrimethylsilane, methylphenyl-bis (2-chloroethoxy) silane , Dimethoxydibenzylsilane, tri-n-propylallyloxysilane, allyltris (2-chloroethoxy) silane, trimethoxy-3-ethoxypropylsilane, vinyl (tributoxy) silane and 3-
Examples thereof include (glycidoxy) propyltrimethoxysilane.

Representative examples of the compound represented by the formula (II) include hexamethyldisiloxane, octamethyltrisiloxane, tetracosamethylundecasiloxane, 8-hydroheptamethyltrisiloxane and hexaphenyldisiloxane. , Hexacyclohexyldisiloxane, 1,8-dimethyldisiloxane, hexaethyldisiloxane, octaethyltrisiloxane, hexapropyldisiloxane, 1,3-dichlorotetramethyldisiloxane, 1,3-bis (p-phenoxydiphenyl)
-1,3-dimethyl-1,3-diphenyldisiloxane, 1,3-diallyltetramethyldisiloxane, 1,
3-dibenzyltetramethyldisiloxane, 2,2
Examples include 4,4-tetraphenyl-2,4-disilane-1-oxacyclopentane, 1,1,3,3-tetramethyldisiloxane, and hexachlorodisiloxane.

Further, as typical compounds represented by the formula (III), 1,3,5-trimethylcyclotrisiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane and pentamethylchlorocyclotrisiloxane. , 1,3,5-trimethyltriphenylcyclotrisiloxane, hexaphenylcyclotrisiloxane, 1,3,5-tribenzyltrimethylcyclotrisiloxane and 1,3,5-triallyltrimethylcyclotrisiloxane.

Among these compounds having a Si--O bond, those in which R ² and R ³ in the above formula (I) are each represented by an alkyl group having at most 8 carbon atoms, a phenyl group or an aralkyl group are preferable. . Further, in the formula (II), it is preferable that R ⁴ , R ⁵ and R ⁶ are each represented by an alkyl group having at most 4 carbon atoms, a phenyl group or a halogen atom, and further, r having 4 or less. preferable.
Further, in the above formula (III), R ⁷ is preferably a hydrogen atom, an alkyl group having 4 or less carbon atoms, a phenyl group or a vinyl group, and more preferably s is 10 or less. Examples of these suitable organic compounds having a Si-O bond include tetramethoxysilane, tetraethoxysilane, tetracresylsilane, hexamethyldisiloxane, diethoxydiphenylsilane, dimethoxydiphenylsilane and vinyl (tributoxy) silane. To be

A typical magnesium alcoholate has a general formula represented by the following formula (IV). Mg (OR ⁸ ) ₂ (IV) In the formula (IV), R ⁸ is a hydrocarbon group having at most 8 carbon atoms selected from the group consisting of an alkyl group, a cycloalkyl group, an aryl group and an aralkyl group. . Typical of these magnesium alcoholates are magnesium methylate, magnesium ethylate, magnesium propylate, magnesium butyrate, magnesium hexylate, magnesium phenolate, magnesium cyclohexanolate, magnesium benzyl alcoholate and magnesium crelate. Examples include zolate. Of these magnesium alcoholates, those in which R ⁸ in the above formula (IV) is represented by an alkyl group or a phenyl group having at most 3 carbon atoms are preferable. These suitable magnesium alcoholates include magnesium methylate, magnesium ethylate and magnesium phenolate.

In producing the above co-ground product,
The addition ratio of the aluminum trihalide and the organic compound having a Si—O bond to the magnesium alcoholate per mol is generally 0.02 to
The molar ratio is 1.0, and a molar ratio of 0.05 to 0.20 is particularly preferable. Further, the ratio of aluminum atoms of aluminum trihalide to silicon atoms of the organic compound having a Si—O bond is important. The ratio is preferably 0.25 to 4, and particularly preferably 0.5 to 2. As a method of co-milling, a commonly used method using a mill such as a commonly used ball mill, vibrating ball mill, impact mill or colloid mill may be applied.
The co-grinding temperature may be room temperature, but when the heat generation is large, it may be cooled. The pulverization is performed in a dry inert gas (for example, nitrogen, argon) atmosphere. The time required for co-pulverization cannot be unconditionally specified by the type and capacity of the pulverizer used and the filling amount, type and proportion of the pulverized product, but the particle size and particle size distribution of the co-pulverized product are uniform. The grinding time should be selected to the extent that Therefore, generally 10
Although it is more than a minute, even if co-milled for 20 hours or more, the effect cannot be expected to be further improved, and the yield of the co-milled product may rather be lowered. The co-ground product thus obtained is a complex containing aluminum, silicon and magnesium. The average particle size of the co-ground product thus obtained is usually 50 to 200 microns and the specific surface area is 20 to 200 m ² / g.

The solid component of the present invention can be obtained by bringing the co-ground product obtained as described above into contact with the titanium compound in the liquid phase. In this case, it may be carried out in the presence of a hydrocarbon solvent, or when the titanium compound is in a liquid state, it may be carried out as it is without a solvent. The titanium-based compound used for producing the solid component is a tetravalent titanium compound having at least one halogen atom, and its general formula is represented by the following formula (V). In ^{_{TiX t (OR 9) u (}} NR 10 R 11) v (OCOR 12) w (V) (V) Formula, X is chlorine atom, a bromine atom or an iodine ^{atom, R 9, R 10, R} 11 and R ¹² is an aliphatic, alicyclic or aromatic hydrocarbon having at most ¹² carbon atoms, t is a number from 1 to 4 and u, v and w are 0.
To 3 and t + u + v + w is 4.

Typical examples of titanium compounds are titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, methoxytitanium trichloride, dimethoxytitanium dichloride, trimethoxytitanium chloride, ethoxytitanium trichloride, diethoxytitanium dichloride and trititanium. Examples include ethoxytitanium chloride, propoxytitanium trichloride, butoxytitanium trichloride, dimethylaminititanium trichloride, bis (dimethylamino) titanium dichloride, diethylaminotitanium trichloride, titanium propionate trichloride and titanium benzoate trichloride. Among them, in the formula (V), u, v and w are 0, R ⁹ is an alkyl group having at most 6 carbon atoms, and t is 3 or u is 0 (that is, t is Those of 4) are preferable, and titanium tetrachloride, methoxytitanium trichloride, ethoxytitanium trichloride and butoxytitanium trichloride are particularly preferable.

The solid component does not necessarily have to be produced in the presence of a hydrocarbon solvent, but when it is produced in the presence of a hydrocarbon solvent, the hydrocarbon solvent used is 0 ° C to 140 ° C. It is preferably liquid.
Typical examples are aliphatic hydrocarbons (eg, isobutane, n-pentane, n-hexane, n-heptane, paraffin), alicyclic hydrocarbons (eg, cyclohexane, methylcyclohexane, dimethylcyclohexane).
And aromatic hydrocarbons (eg benzene, toluene, xylene).

The proportion of the co-ground product and the titanium compound to be brought into contact with each other may be appropriately selected so that the amount of titanium atoms supported on the co-ground product is generally 0.5 to 15% by weight. . Therefore, the ratio of the titanium-based compound to one atom of magnesium in the co-ground product is 0.5 to 5
The molar ratio is 0, preferably 0.5 to 40, and more preferably 1.0 to 20. The contact temperature is usually room temperature to 150 ° C, especially room temperature to 130 ° C.
Is desirable. If the contact is made at room temperature or lower, the contact is insufficient. On the other hand, at 150 ° C or higher, a satisfactory solid component cannot be obtained. The contact time is generally 10 minutes to 5 hours, but especially 10 minutes to 3 hours,
It is desirable from the viewpoint of polymerization activity. When the contact time is 10 minutes or less, the contact is insufficient. On the other hand, even if the contact is carried out for 5 hours or more, the contact does not proceed further and the solid component obtained may be deactivated. To carry out this contact in the presence of the hydrocarbon solvent, the hydrocarbon solvent is at most 10 parts by weight per 1 part by weight of the co-ground product, depending on the solubility of the titanium compound.

The contact product obtained as described above contains an unreacted titanium compound in addition to the solid component. The solid component of the present invention is obtained by purifying this contact product. In order to carry out this purification, the supernatant liquid is extracted by a gradient method or a filtration method using the hydrocarbon solvent used at the time of contact or another hydrocarbon solvent (particularly, one having a relatively low boiling point is preferable), and the washing solution is washed. It is desirable to repeat the wash until no halogen is present in it. It may be washed with the above hydrocarbon solvent, and a slurry containing the obtained solid component (however, it does not substantially contain unreacted titanium-based compound)
Can also be supplied to the polymerization vessel described later. It is also possible to remove the hydrocarbon solvent used for washing under reduced pressure and then mud-feed it to the polymerization vessel as a solid component.
The solid component is combined with an organoaluminum compound and prepolymerized with ethylene in an inert hydrocarbon solvent to produce 0.01 to 100 g of an ethylene polymer per 1 g of the solid component. Even if the amount of prepolymerization is smaller or larger than the above range, no improvement effect is observed in the extrusion properties and melt properties of the ethylene copolymer finally obtained by the two-stage polymerization.
Inert hydrocarbon solvents include hexane, heptane, octane, decane, cyclohexane and other aliphatic hydrocarbons,
Aromatic hydrocarbons such as benzene, toluene and xylene

The general formula of the organoaluminum compound is represented by the following formulas [(VI) and (VII)]. AlR ¹³ R ¹⁴ R ¹⁵ (VI) R ¹⁶ R ¹⁷ Al-O-AlR ¹⁸ R ¹⁹ (VII) In formula (VI), R ¹³ , R ¹⁴ and R ¹⁵ may be the same or different and have at most carbon atoms. Twelve aliphatic, alicyclic or aromatic hydrocarbon groups, halogen atoms or hydrogen atoms, at least one of which is the above hydrocarbon group, and when a halogen atom is contained, the halogen atom is It is one. In the formula (VII), R ¹⁶ , R
¹⁷ , R ¹⁸ and R ¹⁹ are the above hydrocarbon groups.

Among the organoaluminum compounds represented by the formula (VI), typical ones include trialkylaluminum, tripropylaluminum, tributylaluminum, trihexylaluminum and trioctylaluminum, trialkylaluminum, diethylaluminum hydride and Examples thereof include dialkyl aluminum hydride such as diisobutyl aluminum hydride and dialkyl aluminum halogenide such as diethyl aluminum chloride.

Among the organoaluminum compounds represented by the formula (VII), typical ones include alkylalumoxanes such as tetraethyl dialumoxane and tetrabutyl dialumoxane. Of these organoaluminum compounds, trialkylaluminums are preferable, and trialkylaluminums having an alkyl group having at most 6 carbon atoms (eg, triethylaluminum, triisobutylaluminum) are preferable.

In the prepolymerization, the ratio of Al atoms in the organoaluminum to titanium atoms in the solid component is Al / T.
It is preferably used in a ratio such that i = 0.01 to 0.1 molar ratio. The temperature of the prepolymerization is -20 ° C to 60
C., preferably 40.degree. C., is preferred. Further, a molecular weight modifier such as hydrogen may be used if necessary.

Aluminum trihalide, Si--O, used in obtaining the catalyst system used in the present invention.
The organic compound having a bond, the magnesium alcoholate, the titanium compound and the organoaluminum compound may each be used alone or in combination of two or more.

The prepolymerized catalyst obtained by the above method is generally purified by the following method. That is,
The mixture of the prepolymerization catalyst and the unreacted material is extracted with the hydrocarbon solvent used during the reaction or another hydrocarbon solvent by a gradient method or a filtration method, and washed with the hydrocarbon solvent. . The slurry containing the obtained prepolymerized catalyst is supplied to the reactor described later. Alternatively, the hydrocarbon solvent used for washing may be removed under reduced pressure, and then the hydrocarbon solvent may be added to the reactor to form a slurry.

After cooling the slurry containing the above-mentioned prepolymerization catalyst to 30 ° C. or lower, R ¹ AlX ₂ (R ¹ represents an alkyl group, a cycloalkyl group, an aryl group and an aralkyl group, and X represents a halogen atom. ) Is treated with a dihalogenated organoaluminum compound.

Specific examples of the dihalogenated organoaluminum include methyl aluminum dichloride, ethyl aluminum dichloride, isobutyl aluminum dichloride,
Hexylaluminum dichloride, methylaluminum dibromide, ethylaluminum dibromide, isobutylaluminum dibromide and the like can be mentioned. Among them, the above alkylaluminum dichloride is preferably used.

The treatment conditions include a treatment temperature of 30 ° C. or higher and a boiling point of the solvent or lower, preferably 40 ° C. or higher and 90 ° C. or lower.
The treatment time is 15 minutes or more and 5 hours or less, preferably 30 minutes or more and 3 hours or less. In addition, the ratio of the dihalogenated organoaluminum and the titanium atom in the prepolymerization catalyst is Al / Ti.
= 2 to 20 molar ratio is preferred. The ethylene-based copolymer produced using the solid catalyst component obtained with this ratio of 2 or less is inferior in extrusion properties and melt properties. When an ethylene copolymer is produced using the solid catalyst component obtained at this ratio of 20 or more, the activity is extremely low and the productivity is reduced. After treatment with the organoaluminum dihalide, wash with the above-mentioned inert hydrocarbon until the halogen component in the washing liquid is no longer detected,
A solid catalyst component is obtained.

The catalyst system used in the present invention is obtained from the solid catalyst component obtained by the above and an organoaluminum compound. The polymerization of the present invention can be achieved by carrying out homopolymerization of ethylene or copolymerization of ethylene and α-olefin using this catalyst system. As the organoaluminum compound used in the polymerization, the same compound as the organoaluminum compound used in the prepolymerization of the solid component is used, and particularly trialkylaluminums are preferable, and particularly, the alkyl group has at most 6 carbon atoms. Trialkylaluminum of (e.g., triethylaluminum, triisobutylaluminum) are preferred.

Copolymerization of ethylene and α-olefin is carried out at a temperature of 50 to 100 ° C. in a hydrocarbon solvent using the catalyst system as described above. Examples of the hydrocarbon solvent include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, hexane and heptane, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. From the treatment, an easily volatile hydrocarbon solvent, propane, n-butane, isobutane, isopentane, n-pentane and the like are preferable.

The α-olefin used for the copolymerization with ethylene is selected from chain or branched α-olefins having at most 20, and preferably 12 carbon atoms. For example, propylene, butene-1, pentene-
1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, dodecene-1,4-methylpentene-1, and mixtures thereof. The comonomer content is usually in the range of 0.2 to 5% by weight.

The polymerization reaction is carried out in two steps in a single reactor or in a plurality of reactors. When a plurality of reactors are used, the reaction mixture obtained by the polymerization in the reaction zone in the first stage is continuously used. Are continuously fed to the second reaction zone. The transfer from the reaction zone of the first stage to the reaction zone of the second stage is carried out through a connecting pipe, and is carried out by a differential pressure due to continuous discharge of the polymerization reaction mixture from the reaction zone of the second stage. When carrying out multi-stage polymerization using an easily volatile hydrocarbon solvent, the high-molecular weight component formed under conditions of low hydrogen concentration is the first stage, and the low-molecular weight component under conditions of high hydrogen concentration is the second stage. It is necessary for the process to polymerize in stages.

When industrially continuously producing by a two-stage polymerization process, polymerization specific activity in two polymerization zones (solid catalyst component, polymerization time, amount of polymer produced per ethylene partial pressure by Rsp) From the ideal, it is desirable that they are the same, but for the intended purpose of broadening the molecular weight distribution, the specific activity Rsp, L that produces a high molecular weight component and the specific activity Rsp, H that produces a low molecular weight component Ratio Rsp, L / Rs
Ideally, p and H are close to 1. Otherwise, a value as close as possible is desirable. If it is close to 1, it is sufficient to use a reactor having the same monomer concentration and the same residence time in each polymerization zone, and a volume ratio in which the ratio is not so different according to the production amount ratio, but Rsp and H are extremely high. When it is lower than Rsp and L, it becomes necessary to make a difference in volume ratio to cover the lowering of the activity with another design or condition. Also, Rs
When the absolute values of p and H are low, the amount of catalyst residue is large, which is not suitable for the deashing-free process. Also in the process, if Rsp and H are low, it is possible to increase the catalytic efficiency (productivity) by increasing the ethylene concentration and the residence time, but under high hydrogen concentration conditions, when the monomer concentration is increased, the hydrogen concentration is accompanied. However, there is a demerit that the operating pressure also rises. The specific activity (Rs) of the catalyst for producing a relatively low molecular weight ethylene polymer with [η] = 1
p, H) is 800 g / g · hr · kg / cm ² or more, and the specific activity (Rsp, L) of the catalyst that forms a relative high molecular weight polymer of [η] ≧ 2.0 and the above Rsp, It is not limited as long as it is a highly active catalyst having an activity ratio with H satisfying the ranges of 1 <Rsp, L / Rsp, H <3, but the above catalyst system is particularly preferable.

Further, when a polymer mixture is produced by using a low molecular weight component in the first stage and a high molecular weight component in the second stage, for example, when the above catalyst system is used, Rsp, L / Rsp, H
However, when the order is reversed, that is, when a high molecular weight component is formed in the first stage and a low molecular weight component is formed in the second stage, Rsp, L / Rsp, H = 1.2. ~ 2
It was found that the activity ratio in both stages was very close to 1. From both sides, it is necessary to make a high molecular weight component in the first stage and a low molecular weight component in the second stage.

In the first step, the copolymerization reaction of ethylene and α-olefin of [η] ≧ 2.0 is controlled by adjusting the weight ratio of hydrogen concentration in the liquid phase to ethylene concentration. To do. The concentration ratio of hydrogen to ethylene in this liquid phase is generally 1.0 × 10 ⁻³ (weight ratio) or less in the presence of hydrogen. Further, the copolymer of ethylene and α-olefin produced in the first step is [η]
Is a high molecular weight compound of 2.0 or more, and the content of α-olefin in the copolymer is generally 0.2 to 5% by weight.
0.5 to 2.5% by weight is preferable.

In the second stage, [η] is 0.3-1.
A copolymer of ethylene and α-olefin in the range of 0 has a concentration ratio of hydrogen concentration to ethylene concentration of 1 in the liquid phase.
It is maintained at 0 to 50 × 10 ⁻³ (weight ratio) and copolymerized with α-olefin in the reaction mixture flowing in from the first stage, or if necessary, even if α-olefin is supplied to the second stage. good. Therefore, in the second stage, a relatively low molecular weight copolymer having a branching degree lower than the comonomer content of the ethylene-α-olefin copolymer produced in the first stage is produced.

The proportion of the first stage high molecular weight copolymer and the second stage low molecular weight polymer in the total polymer mixture is 3 respectively.
Polymerization is performed in each reaction step so as to be 0 to 70% by weight and 70 to 30% by weight. The first-stage and second-stage polymerizations may be carried out batchwise, but continuous polymerization is preferred from the viewpoint of productivity.

In this specification, the intrinsic viscosity [η] is 13
It represents the intrinsic viscosity in decalin solvent at 5 ° C. Since the weight additivity regarding the intrinsic viscosity is established, [η] b of the ethylene polymer produced in the second reaction zone can be calculated by the following equation. [Η] b = ([η] c-Wa [η] a) / Wb where [η] c is the intrinsic viscosity of the entire polymer and [η] a is an ethylene copolymer produced in the first-stage reaction zone. The intrinsic viscosity of
Wa and Wb respectively represent the weight fraction of the polymer formed in both the first and second reaction zones, and Wa + Wb = 1.0.
[Η] a of the copolymer produced in the first stage has an intrinsic viscosity of 2.0 or more and 6.2 or less, and [η] b of the low molecular weight polymer produced in the second stage is 0. A molecular weight in the range of greater than 0.40 and less than 0.75 is selected. further,
The molecular weight [η] c of all the copolymers is preferably in the range of 2.0 to 3.5. Further, the proportion of the polymer formed in the first stage and the second stage is preferably 30 to 70% by weight in the whole polymer, but the proportion of the high molecular weight copolymer formed in the first stage is 40 to 60% by weight. It is preferable in terms of impact strength, environmental stress crack resistance, and moldability.

The polymerization reaction is carried out at a temperature of 50 ° C. to 100 ° C. for 20 minutes to 10 hours under a pressure of 0.5 to 100 Kg / cm ² , although the pressure depends on the solvent used. . The reactor type may be a tank type (bessel type) or an annular type (loop type). In each stage of the reactor, the polymer concentration is generally 5 to 60% by weight, and preferably 35 to 55% by weight is suitable from the viewpoint of productivity. The polymer obtained as described above is then preferably kneaded. It is also possible to use a single-screw or twin-screw extruder or a continuous kneader. After kneading, the obtained polymer has few fish eyes.

[0040]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. The method of physical property test is as follows. Polymer powder 65 mmφ, L / D = 26, full flight screw extruder (50 rpm, C ₁ = 160
℃, C ₂ = 200 ℃, C ₃ = 220 ℃, D = 210 ℃)
Physical properties were measured using a sample that was kneaded in and pelletized. The density was measured according to JIS-K-6760. The melt tension was measured by a melt tension tester type II manufactured by Toyo Seiki Seisakusho. 190 ° C molten resin is extruded from an orifice with a diameter of 2.095 mm and a length of 8.000 mm at a flow rate of 17.9 mm ² / sec, and the tension when it is stretched and solidified at room temperature at a rate of 108 mm / sec is melted. The tension was used. The extrusion amount was measured by a 50 mmφ inflation molding machine manufactured by Yoshii Tekko. When a full flight screw of L / D = 26 was used, the discharge amount per hour at a screw rotation speed of 90 rpm was defined as the extrusion amount. An inflation film die having a diameter of 750 mm and a lip gap of 1.0 mm was attached to the tip of the extruder. The set temperature is from the bottom of the hopper to cylinder 1.
240 ℃, cylinder 2 230 ℃, cylinder 3,
The crosshead and die were set at 220 ° C.

Example 1 (1) Preparation of catalyst A commercially available magnesium ethylate (average particle size: 860) was placed in a nitrogen atmosphere in a pot (crushing container) having an internal volume of 160 L containing about 260 kg of porcelain balls having a diameter of 15.4 mm. Micron) 20 kg (17.5 mol), granular aluminum trichloride 1.66 kg (12.5 mol) and diethoxydiphenylsilane 2.72 kg (10 mol).
Using a vibrating ball mill, these were co-ground for 4 hours under the conditions of an amplitude of 8 mm and a frequency of 1200 rpm.
After co-milling, the contents were separated from the porcelain balls under a nitrogen atmosphere. 20 Kg of the co-ground product obtained as described above and 80 L of n-heptane were added to 800 L of a nitrogen-substituted reactor. While stirring, 41.6 L of titanium tetrachloride was added dropwise at room temperature, and the temperature of the reaction system was raised to 90 ° C.
Stirring was continued for 0 minutes. Then, after cooling the reaction system, the supernatant was withdrawn and n-hexane was added. This operation was repeated 3 times. A part of the obtained slurry containing the solid component was sampled, the solvent was removed under reduced pressure, and the solid component was analyzed. As a result, the Ti content in the solid component was 11% by weight, and Cl
The content was 59% by weight.

220 n-hexane slurry containing 20 kg of the above solid component was placed in a reactor of 400 L nitrogen substitution.
L and triisobutylaluminum were added so that the Al / Ti = 0.03 molar ratio with respect to the titanium atoms in the solid component. Stirring was warmed to 40 ° C., the hydrogen partial pressure is added hydrogen such that 0.8 Kg / cm ^2, further ethylene partial pressure added ethylene so that 1.7Kg / cm ^2, 40 minutes pre Polymerization was carried out. After the supply of hydrogen and ethylene was stopped, the reaction system was cooled, the supernatant liquid was extracted, and n-hexane was added. This operation was repeated 3 times. A part of the obtained slurry containing the prepolymerized catalyst was withdrawn, the solvent was removed under reduced pressure, and the prepolymerized catalyst was analyzed. As a result, the prepolymerized amount of polyethylene was 1 g of the solid component.
0.42 g, and the Ti content was 11% by weight.

400 L of n-hexane slurry containing 20 kg of the above-mentioned prepolymerization catalyst was placed in a reactor in which 800 L of nitrogen had been replaced, and cooled to 30 ° C. or lower. Ethyl aluminum dichloride was added to the titanium atom in the prepolymerization catalyst so as to have an Al / Ti = 5 molar ratio, and then added at 60 ° C.
The temperature was raised to 2, and the reaction was performed for 2 hours. After cooling to room temperature, the solid was washed with n-hexane until the halogen component in the washing liquid could not be detected to obtain a solid catalyst component. A part of the obtained slurry containing the solid catalyst component was sampled, the solvent was removed under reduced pressure, and the solid catalyst component was analyzed. As a result, the prepolymerization amount of polyethylene was 0.34 g per 1 g of the solid catalyst component, and the Ti content was 10% by weight. %, Cl content was 60% by weight.

(2) Two-stage polymerization In a first-stage polymerization vessel having an internal volume of 200 L, 117 L / hr of dehydrated and refined isobutane and 1 part of triisobutylaluminum were used.
2. The above solid catalyst component was added at a rate of 75 mmol / hr.
It was continuously fed at a rate of 55 g / hr, and while the contents of the polymerization vessel were discharged at a required rate, ethylene was added at a rate of 2 at 80 ° C.
1.0 kg / hr, hexene-1 0.910 kg / h
It is supplied at a rate of r and the hydrogen concentration in the liquid phase is 0.35 × 10 ⁻³
(W / w), the concentration ratio of hexene-1 to ethylene is 1.3.
(W / w), the total pressure is 41 Kg / cm ² , and the average residence time is 0.80 hr, and the first stage copolymerization is continuously performed in a liquid-filled state. Isobutane slurry containing ethylene-hexene-1 copolymer produced by copolymerization (polymer concentration 23 wt%, polymer intrinsic viscosity [η] 5.47, hexene content 1.07 wt%, copolymer weight Coalescence density is 0.9
29 g / cm3) was introduced as it was into a second-stage polymerization vessel having an internal volume of 400 L through a continuous tube having an inner diameter of 50 mm, and 55 L / hr of isobutane and hydrogen were supplied without adding a catalyst to obtain the content of the polymerization vessel. 9 while discharging at a speed
At 0 ° C., ethylene was fed at a rate of 23.7 Kg / hr, the ethylene concentration was maintained at 1.20% by weight, the hydrogen to ethylene concentration ratio was kept at 15 × 10 ⁻³ (w / w), and the total pressure was 4%.
Second-stage polymerization is carried out under the conditions of 1.0 Kg / cm ³ and residence time of 1.05 hr.

The discharge from the second-stage polymerizer contained 31% by weight of the ethylene polymer mixture, the intrinsic viscosity [η] of the polymer was 2.83, and the hexene-1 content of the comonomer was 0.71% by weight. And the density of the ethylene copolymer mixture was 0.951 g / cm ³ . The production ratio of the first-stage and second-stage polymers is equivalent to 47:53, the intrinsic viscosity [η] of the ethylene copolymer produced only in the second-stage polymerizer is 0.50, and the hexene-1 content is 0. 40% by weight,
The density corresponds to 0.965 g / cm ³ . Extrusion rate in blown film molding is 30.8 Kg / h
r, the melt tension of the film was 16.2 g, which was excellent, and an ethylene-based copolymer having excellent extrusion properties and melt properties was obtained. The first stage and second stage specific activities are Rsp and L = 68, respectively.
00g / g · hr · Ethylene pressure Kg / cm ² , Rsp,
H = 4800 g / g · hr · Ethylene pressure Kg / cm ² .

Example 2 In Example 1 (1), the amount of ethylaluminum dichloride used was Al / Ti = 15 with respect to titanium atoms.
A solid catalyst component was prepared and two-stage polymerization was carried out in the same manner as in Example 1 except that the molar ratio was changed. The results are shown in Table 1. An ethylene-based copolymer having excellent extrusion properties and melt properties was obtained.

Comparative Example 1 In Example 1 (1), the amount of ethyl aluminum dichloride used was Al / Ti = 0.
A solid catalyst component was prepared and two-stage polymerization was carried out in the same manner as in Example 1 except that the molar ratio was changed to 5. The results are shown in Table 1. The result was inferior extrusion property and melt property.

Comparative Example 2 In Example 1 (1), the amount of ethyl aluminum dichloride used was Al / Ti = 30 with respect to titanium atoms.
A solid catalyst component was prepared and two-stage polymerization was carried out in the same manner as in Example 1 except that the molar ratio was changed. The results are shown in Table 1. Although the extrusion properties and melt properties were excellent, the polymerization activity was extremely low, resulting in poor productivity.

Example 3 A solid catalyst component was prepared and two-stage polymerization was carried out in the same manner as in Example 1 except that dimethoxydiphenylsilane was used instead of diethoxydiphenylsilane in Example 1 (1). The results are shown in Table 1. An ethylene-based copolymer having excellent extrusion properties and melt properties was obtained.

Comparative Example 3 A solid catalyst component was prepared in the same manner as in Example 1 except that a prepolymerized catalyst prepolymerized with ethylene was used in Example 1 (1) so that the prepolymerization amount was 500 g per 1 g of the solid component. , Two-stage polymerization was performed. The results are shown in Table 1. The result was inferior extrusion property and melt property.

Example 4 A solid catalyst component was prepared and two-stage polymerization was carried out in the same manner as in Example 1 except that butoxytitanium trichloride was used instead of titanium tetrachloride in Example 1 (1). The results are shown in Table 1. An ethylene-based copolymer having excellent extrusion properties and melt properties was obtained.

Comparative Example 4 In Example 1 (1), ethyl aluminum dichloride was used as the solid component without prepolymerization with ethylene so that Al / Ti = 5 mol ratio to titanium atom in the solid component. A solid catalyst component was prepared in the same manner as in Example 1 except that the above treatment was carried out, and two-stage polymerization was carried out. The results are shown in Table 1. The extrusion properties and melt properties were poor, and the polymerization activity was also very low, resulting in poor productivity.

Example 5 Using the same catalyst and the same polymerization reactor as in Example 1, butene-1 was used as a comonomer instead of hexene-1. The results are shown in Table 1. An ethylene-based copolymer having excellent extrusion properties and melt properties was obtained.

Example 6 Using the same catalyst and the same polymerization reactor as in Example 1, two-stage polymerization was carried out while changing the production ratio of the first-stage and second-stage polymers. The results are shown in Table 1. An ethylene-based copolymer having excellent extrusion properties and melt properties was obtained.

[0055]

[Table 1]

[0056]

EFFECT OF THE INVENTION By carrying out the present invention, an ethylene-based copolymer having excellent extrusion properties and melt properties can be produced, which is industrially valuable.

[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 Tetsuya Maki No.2 Nakasu, Oita City, Oita Prefecture Showa Denko Oita Research Center

Claims (1)

[Claims] 1. An ethylene-based copolymer is produced by a two-step polymerization in which ethylene and an α-olefin are polymerized in a first polymerization zone to a high molecular weight component and in a second polymerization zone to a low molecular weight component. (1) Aluminum trihalide, Si-
Co-milling product obtained by co-milling organic compound having O bond and magnesium alcoholate, and (2) solid obtained by contacting tetravalent titanium compound having at least one halogen atom in liquid phase The component is combined with the organoaluminum compound and the amount of prepolymerization is 0.01 to 10 per 1 g of the solid component.
A dihalogen represented by the general formula R ¹ AlX ₂ (R ¹ represents an alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, and X represents a halogen atom) was prepared by prepolymerizing ethylene with 0 g. Organoaluminum compound with Al for titanium atom in prepolymerization catalyst
A method for producing an ethylene-based copolymer using a catalyst system composed of a solid catalyst component and an organoaluminum compound obtained by treating in a molar ratio of / Ti = 2 to 20.