JP3305486B2 - Method for producing ethylene copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an ethylene copolymer. More specifically, the present invention relates to a method for providing an ethylene copolymer excellent in extrusion characteristics and melt properties and suitable for inflation molding.

[0002]

2. Description of the Related Art In the field of inflation molding, an ethylene copolymer having a high molecular weight and a wide molecular weight distribution is required. Heretofore, there have been many proposals for a method for producing an ethylene copolymer for inflation molding having a wide molecular weight distribution by two-stage polymerization. In particular, there is a method disclosed in Japanese Patent Publication No. 3-18645. this is,
In this method, continuous two-stage polymerization is performed using a volatile hydrocarbon solvent such as propane or isobutane to produce a high-molecular-weight component in the first stage and a low-molecular-weight component in the second stage. When adjusting the molecular weight with hydrogen, in the transition 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.

As a solid catalyst component used in the production of an ethylene copolymer by two-stage polymerization, Japanese Patent Application Laid-Open No.
78287, JP-A-53-13282, JP-A-54-
75491, JP-A-54-81190, JP-A-55-3
459, JP-A-57-205410, JP-A-58-14
9906 and JP-A-58-225105.

[0004]

However, the ethylene copolymer obtained by performing the two-stage polymerization by the above-mentioned method using the catalyst system comprising the above-mentioned solid catalyst component has a high catalytic activity and a very high productivity. Although high, there was a problem that the extrusion characteristics and 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 to provide a method for producing an ethylene copolymer having excellent extrusion characteristics and melt properties during molding.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned problems, and as a result, have found that ethylene and α-olefin are mixed with a high molecular weight component in the first polymerization zone and low in the second polymerization zone. In producing an ethylene-based copolymer by two-stage polymerization in which a molecular weight component is polymerized, (1) a co-pulverized product obtained by co-pulverizing aluminum trihalide, an organic compound having a Si—O bond, and magnesium alcoholate And a solid component obtained by contacting (2) a tetravalent titanium compound having at least one halogen atom in a liquid phase with an organoaluminum compound to obtain a prepolymerized amount of O.O./g of the solid component.
A prepolymerized catalyst pre-polymerized with ethylene so as to have a weight of from 0.1 to 100 g is prepared by reacting a 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 obtained by treating with a dihalogenated organoaluminum compound represented by the following formula: Al / Ti = 2 to 20 mol ratio with respect to titanium atom in the prepolymerization catalyst; The object has been solved by a method for producing an ethylene copolymer using a catalyst system comprising a compound.

Hereinafter, the present invention will be described specifically. Solid Component As the solid component used in the production of the ethylene 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-milled product obtained by co-milling an aluminum trihalide, an organic compound having a Si—O bond and magnesium alcoholate, and (2) a tetravalent having at least one halogen atom Is a solid component obtained by bringing the titanium compound into contact with a liquid phase.

[0007] Aluminum trihalide is an anhydride and includes aluminum trichloride, aluminum tribromide, and aluminum trifluoride. Particularly, aluminum trichloride is preferable. The shape of the aluminum trihalide may be a powder or a granular material.

[0008] Typical examples of organic compound having a SiO bond 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 hydrocarbon groups selected from the group consisting of alkyl groups, cycloalkyl groups, aryl groups and aralkyl groups having at most 20 carbon atoms. (These may be unsaturated, may be substituted with a halogen atom or an alkoxy group having at most 20 carbon atoms, or may have an epoxy ring such as a glycidyl group.) (R ³ is a hydrogen atom or a halogen atom.) R ⁷ may be a hydrogen atom), R ⁴ , R ⁵ and R ⁶
May be the same or different and are the above-mentioned hydrocarbon groups (which may be unsaturated or substituted) or halogen atoms, p + q is 4 (provided that p ≠ 0), and r is 1 to 1000 Where s is 2 to 1000
Is an integer.

Representative compounds of 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-
(Glycidoxy) propyltrimethoxysilane and the like.

Representative compounds represented by 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
4,4-tetraphenyl-2,4-disilane-1-oxacyclopentane, 1,1,3,3-tetramethyldisiloxane, hexachlorodisiloxane and the like.

Further, typical compounds represented by the formula (III) include 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 represented by an alkyl group having at most 8 carbon atoms, a phenyl group or an aralkyl group are preferred. . In the formula (II), R ⁴ , R ⁵ and R ⁶ are preferably represented by an alkyl group, a phenyl group or a halogen atom having at most 4 carbon atoms. preferable.
Moreover, in the 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. Preferred examples of the organic compound having a Si—O bond include tetramethoxysilane, tetraethoxysilane, tetracresylsilane, hexamethyldisiloxane, diethoxydiphenylsilane, dimethoxydiphenylsilane, and vinyl (tributoxy) silane. Can be

Typical magnesium alcoholates are 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 crecolate. Zolate and the like. Among these magnesium alcoholates, those in which R ⁸ in the above formula (IV) is represented by an alkyl group or phenyl group having at most 3 carbon atoms are desirable. These preferred 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 mole is generally 0.02 to 2.0.
The molar ratio is 1.0, particularly preferably 0.05 to 0.20. Further, the ratio of the aluminum atom of the aluminum trihalide to the silicon atom of the organic compound having a Si—O bond is important. The ratio is preferably from 0.25 to 4, particularly preferably from 0.5 to 2. As a method of the co-milling, a method usually used using a commonly used mill such as a ball mill, a vibrating ball mill, an impact mill and a colloid mill may be applied.
The co-milling may be carried out at room temperature, but if heat generation is large, cooling may be carried out. The pulverization is performed in a dry inert gas (eg, nitrogen, argon) atmosphere. The time required for co-grinding cannot be specified unconditionally depending on the type and capacity of the crusher used and the amount, type and proportion of the material to be crushed, but the particle size and particle size distribution of the co-ground product are uniform. The crushing time should be selected so that it becomes as follows. Therefore, generally 10
Although it is more than a minute, even if co-milling is performed for 20 hours or more, further improvement of the effect cannot be expected, and the yield of the co-milled product may be reduced. The co-ground product obtained in this way is a complex containing aluminum, silicon and magnesium. The average particle size of the co-ground product obtained in this way is usually from 50 to 200 microns and the specific surface area is from 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 a liquid phase. In this case, it may be carried out in the presence of a hydrocarbon-based solvent, or in the case where the titanium-based compound is in a liquid state, it may be carried out 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). TiX _t (OR ⁹ ) _u (NR ¹⁰ R ¹¹ ) _v (OCOR ¹² ) _w (V) In the formula (X), X is a chlorine atom, a bromine atom or an iodine atom, and 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 of 1-4, and u, v and w are 0
And t + u + v + w is 4.

Representative examples of titanium compounds include titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, methoxytitanium trichloride, dimethoxytitanium dichloride, trimethoxytitanium chloride, ethoxytitanium trichloride, diethoxytitanium dichloride, triethoxytitanium 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 0). 4) is preferable, and titanium tetrachloride, methoxy titanium trichloride, ethoxy titanium trichloride and butoxy titanium trichloride are particularly preferable.

When the solid component is produced, it is not always necessary to carry out the reaction in the presence of a hydrocarbon solvent. However, when the solid component is produced in the presence of a hydrocarbon solvent, the hydrocarbon solvent used is 0 to 140 ° C. Those that are liquid are preferred.
Representative 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 ratio of contact between the co-ground product and the titanium compound may be selected under appropriate conditions such that the amount of titanium atoms is generally 0.5 to 15% by weight on the co-ground product. . Therefore, the ratio of the titanium compound to one atom of magnesium in the co-milled product is 0.5 to 5%.
The molar ratio is 0, preferably 0.5 to 40, more preferably 1.0 to 20. The contact temperature is usually from room temperature to 150 ° C., especially from 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. In addition, the contact time is generally 10 minutes to 5 hours, but in particular, the contact is preferably performed for 10 minutes to 3 hours.
It is desirable from the viewpoint of polymerization activity. If 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 completely, but the obtained solid component 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 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 the contact product. In order to carry out the purification, the supernatant liquid is decanted or filtered by using the hydrocarbon solvent used at the time of contact or another hydrocarbon solvent (especially, one having a relatively low boiling point is preferable), and the washing liquid is used. It is desirable to repeat the washing until the presence of halogen is no longer observed. The slurry containing the solid component obtained may be washed with the above-mentioned hydrocarbon solvent, provided that the slurry contains substantially no unreacted titanium compound.
Can be supplied to a polymerization vessel described later. Alternatively, the hydrocarbon solvent used for washing may be removed under reduced pressure, and then mud-fed to a polymerization vessel as a solid component.
The above 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 prepolymerization amount 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.
As the inert hydrocarbon solvent, hexane, heptane, octane, decane, aliphatic hydrocarbons such as cyclohexane,
Aromatic hydrocarbons such as benzene, toluene and xylene

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

Typical examples of the organoaluminum compounds represented by the formula (VI) include trialkylaluminums such as triethylaluminum, tripropylaluminum, tributylaluminum, trihexylaluminum and trioctylaluminum, diethylaluminum hydride and the like. Examples include dialkylaluminum hydrides such as diisobutylaluminum hydride and dialkylaluminum halides such as diethylaluminum chloride.

Typical examples of the organoaluminum compound represented by the formula (VII) include alkylalumoxanes such as tetraethyldialumoxane and tetrabutyldialumoxane. Of these organoaluminum compounds, trialkylaluminums are preferable, and trialkylaluminums having an alkyl group of at most 6 carbon atoms (eg, triethylaluminum, triisobutylaluminum) are particularly preferable.

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

The aluminum trihalide used in obtaining the catalyst system used in the present invention, Si--O
The organic compound having a bond, the magnesium alcoholate, the titanium compound and the organic aluminum compound may 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 pre-polymerized catalyst and the unreacted product is washed with the hydrocarbon solvent or another hydrocarbon solvent used during the reaction, and the supernatant is withdrawn by a gradient method or a filtration method, and washed with the hydrocarbon solvent. . The slurry containing the obtained prepolymerized catalyst is supplied to a reactor described below. Further, after removing the hydrocarbon solvent used for washing under reduced pressure, the hydrocarbon solvent may be added to the reactor after supply to the reactor to form a slurry.

The slurry containing the above prepolymerized catalyst is cooled to 30 ° C. or lower, and then cooled to a general formula 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. )).

Specific examples of the organoaluminum dihalide include methylaluminum dichloride, ethylaluminum dichloride, isobutylaluminum dichloride,
Hexylaluminum dichloride, methylaluminum dibromide, ethylaluminum dibromide, isobutylaluminum dibromide, etc., among which the above-mentioned alkylaluminum dichloride is preferably used.

As the processing conditions, the processing temperature is 30 ° C. or higher and the boiling point of the solvent, 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. The ratio of the organoaluminum dihalide to the titanium atom in the prepolymerization catalyst is Al / Ti
= 2 to 20 molar ratio is preferred. Ethylene copolymers produced using the solid catalyst component obtained at a ratio of 2 or less have poor extrusion characteristics and melt properties. When an ethylene copolymer is produced using the solid catalyst component obtained at a ratio of 20 or more, the activity is very low, and the productivity is reduced. After the treatment with the organic aluminum dihalide, washing with the 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 as described above and an organoaluminum compound. The polymerization of the present invention can be achieved by homopolymerizing ethylene or copolymerizing ethylene with an 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 in particular, trialkylaluminums are preferable, and particularly, the alkyl group has at most 6 carbon atoms. (For example, triethylaluminum, triisobutylaluminum) are preferred.

Using the above catalyst system, copolymerization of ethylene and α-olefin is carried out at a temperature of 50 to 100 ° C. in a hydrocarbon solvent. 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. A hydrocarbon solvent which is easily volatile from the treatment, propane, n-butane, isobutane, isopentane, n-pentane and the like are preferable.

The α-olefin used in the copolymerization with ethylene is selected from chain or branched α-olefins having at most 20, 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 from 0.2 to 5% by weight.

The polymerization reaction is carried out in two or more stages in a single or a plurality of reactors, and in the case of using a plurality of reactors, the reaction mixture obtained by polymerization in the first stage reaction zone is successively used. To feed the second stage reaction zone continuously. The transfer from the first-stage reaction zone to the second-stage reaction zone takes place through a connecting pipe and is effected by a differential pressure due to continuous discharge of the polymerization reaction mixture from the second-stage reaction zone. When performing multi-stage polymerization using a readily volatile hydrocarbon solvent, the high molecular weight component formed under low hydrogen concentration conditions is used in the first stage, and the low molecular weight component under high hydrogen concentration conditions is used in the second stage. It is necessary for the process to polymerize in stages.

In the case of industrial continuous production in a two-stage polymerization process, the specific polymerization activity in the two polymerization zones (solid catalyst component, polymerization time, amount of polymer produced per ethylene partial pressure is expressed as Rsp). Are ideally the same, ideally speaking, but for the intended purpose of widening the molecular weight distribution, the activity of the specific activity Rsp, L for producing a high molecular weight component and the specific activity Rsp, H for producing 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 having a volume ratio that does not vary much depending on the production ratio, but Rsp and H are extremely high. If it is lower than Rsp, L, it is necessary to cover the decrease in activity with another design or condition by making a difference in volume ratio. Also, Rs
When the absolute values of p and H are low, the amount of the catalyst residue increases, which is not suitable for a deashless process. In the process, if Rsp and H are low, the catalyst efficiency can be increased by increasing the ethylene concentration and the residence time. However, under the condition of high hydrogen concentration, if the monomer concentration is increased, the hydrogen concentration is increased. And the operating pressure naturally increases. Specific activity (Rs) of a catalyst for forming a relatively low molecular weight ethylene polymer having [η] = 1
p, H) is not less than 800 g / g · hr · kg / cm ² , and the specific activity (Rsp, L) of the catalyst for forming a relative high molecular weight polymer satisfying [η] ≧ 2.0, The catalyst is not particularly limited as long as it has a high activity with an activity ratio of 1 <Rsp, L / Rsp, and H <3, but the above-mentioned catalyst system is particularly preferable.

When a polymer mixture is produced in the first stage with the low molecular weight component and in the second stage with the high molecular weight component, for example, if the above catalyst system is used, Rsp, L / Rsp, H
= 3, but in the reverse order, that is, when a high molecular weight component is produced in the first stage and a low molecular weight component is produced 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 produce a high molecular weight component in the first stage and a low molecular weight component in the second stage.

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

In the second stage, [η] is 0.3-1.
The copolymer of ethylene and α-olefin in the range of 0 was prepared by adjusting the concentration ratio of the hydrogen concentration to the ethylene concentration in the liquid phase to 1
The reaction is carried out by copolymerizing the α-olefin in the reaction mixture flowing from the first stage while maintaining it at 0 to 50 × 10 ⁻³ (weight ratio), or by supplying the α-olefin to the second stage if necessary. good. Therefore, in the second stage, a copolymer having a relatively low molecular weight and a lower branching degree than the comonomer content of the copolymer of ethylene and α-olefin produced in the first stage is produced.

The ratio of the high molecular weight copolymer of the first stage and the low molecular weight polymer of the second stage in the total polymer mixture was 3
Polymerization is performed in each reaction step so as to be 0 to 70% by weight and 70 to 30% by weight. The polymerization in the first and second stages may be performed in a batch system, but is preferably performed in a continuous polymerization system from the viewpoint of productivity.

In the present specification, the intrinsic viscosity [η] is 13
Represents the intrinsic viscosity in a decalin solvent at 5 ° C. Since the weight additivity with respect to the intrinsic viscosity is satisfied, [η] b of the ethylene polymer formed in the second-stage reaction zone can be obtained by the following equation. [[Eta]] b = ([[eta]] c-Wa [[eta]] a) / Wb where [[eta]] c is the intrinsic viscosity of the whole polymer, and [[eta]] a is the ethylene copolymer produced in the first-stage reaction zone. Intrinsic viscosity of
Wa and Wb each indicate the weight fraction of the polymer formed in the first and second reaction zones, and Wa + Wb = 1.0.
[Η] a of the copolymer formed 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 formed in the second stage is 0. A molecular weight in the range of greater than .40 and less than 0.75 is selected. further,
The molecular weight [η] c of all copolymers is preferably in the range of 2.0 to 3.5. The ratio of the polymer formed in the first stage and the second stage is preferably 30 to 70% by weight of the total polymer, and particularly, the ratio of the high molecular weight copolymer formed in the first stage is 40 to 60% by weight. , 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 at a pressure of 0.5 to 100 kg / cm ² , depending on the solvent used. . The reactor type may be a tank type (vessel type) or an annular type (loop type). In each stage of the reactor, the polymer concentration is generally 5 to 60% by weight, preferably 35 to 55% by weight from the viewpoint of productivity. The polymer obtained as above is 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 less fish eyes.

[0040]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The method of the physical property test is as follows. The polymer powder was 65 mmφ, L / D = 26, full flight screw extruder (50 rpm, C ₁ = 160
_{℃, C 2 = 200 ℃,} C 3 = 220 ℃, D = 210 ℃)
, And physical properties were measured using the pelletized sample. 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 Seisaku-sho, Ltd. A molten resin at 190 ° C. is extruded from an orifice having 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 at the time of elongation and solidification 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 Iron Works. The discharge amount per hour at a screw rotation speed of 90 rpm when a full flight screw with L / D = 26 was used was defined as the extrusion amount. A die for blown film having a diameter of 750 mm and a lip gap of 1.0 mm was attached to the extruder tip. Set temperature is below cylinder 1
At 240 ° C, cylinder 2 at 230 ° C, cylinder 3,
The crosshead and die were at 220 ° C.

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

An n-hexane slurry containing 20 kg of the solid component was placed in a 400 L reactor purged with nitrogen.
L and triisobutylaluminum were added at a molar ratio of Al / Ti = 0.03 to 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 performed. After stopping the supply of hydrogen and ethylene, the reaction system was cooled, and the supernatant was taken out and n-hexane was added. This operation was repeated three times. A part of the slurry containing the obtained pre-polymerized catalyst was withdrawn, the solvent was removed under reduced pressure, and the pre-polymerized catalyst was analyzed.
0.42 g, and the Ti content was 11% by weight.

400 L of an n-hexane slurry containing 20 kg of the above prepolymerized catalyst was placed in an 800 L reactor purged with nitrogen, and cooled to 30 ° C. or lower. Ethyl aluminum dichloride was added at a molar ratio of Al / Ti = 5 to titanium atoms in the prepolymerization catalyst, and then 60 ° C.
And reacted for 2 hours. After cooling to room temperature, the solid was washed with n-hexane until no halogen component was detected in the washing liquid to obtain a solid catalyst component. A part of the slurry containing the obtained solid catalyst component was withdrawn, the solvent was removed under reduced pressure, and the solid catalyst component was analyzed. The prepolymerization amount of polyethylene was 0.34 g per 1 g of the solid catalyst component, and the Ti content was 10 wt. %, 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 purified isobutane and 1 L of triisobutylaluminum were added.
At a rate of 75 mmol / hr, 2.
At a rate of 55 g / hr, ethylene was discharged at 80 ° C. while discharging the contents of the polymerization vessel at a required rate.
1.0 kg / hr, hexene-1 is 0.910 kg / h
r, and the hydrogen concentration in the liquid phase is 0.35 × 10 ^-3
(W / w), the ratio of hexene-1 to ethylene concentration was 1.3.
(W / w), the first-stage copolymerization is continuously performed in a liquid-filled state under the conditions of a total pressure of 41 kg / cm ² and an average residence time of 0.80 hr. Isobutane slurry containing ethylene-hexene-1 copolymer produced by copolymerization (polymer concentration 23% by weight, intrinsic viscosity [η] of polymer 5.47, hexene content 1.07% by weight, copolymer weight The coalescence density is 0.9
29 g / cm 3) was introduced into a second-stage polymerization vessel having an internal volume of 400 L as it was through a continuous tube having an inner diameter of 50 mm. Without adding a catalyst, 55 L / hr of isobutane and hydrogen were supplied, and the contents of the polymerization vessel were required. 9 while discharging at speed
At 0 ° C., ethylene was supplied at a rate of 23.7 kg / hr, the ethylene concentration was 1.20% by weight, the ratio of hydrogen to ethylene concentration was 15 × 10 ⁻³ (w / w), and the total pressure was 4%.
The second-stage polymerization is performed under the conditions of 1.0 kg / cm ³ and a residence time of 1.05 hr.

The effluent from the second stage polymerization vessel contains 31% by weight of an ethylene polymer mixture, the intrinsic viscosity [η] of the polymer is 2.83 and the hexene-1 content of the comonomer is 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 corresponds to 47:53, the intrinsic viscosity [η] of the ethylene copolymer produced only in the second-stage polymerization vessel is 0.50, and the hexene-1 content is 0. .40% by weight,
The density corresponds to 0.965 g / cm ³ . The extrusion rate in blown film molding is 30.8 kg / h
r, the melt tension of the film was excellent at 16.2 g, and an ethylene copolymer excellent in extrusion characteristics and melt properties was obtained. The specific activities of the first and second stages are Rsp, 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 ethyl aluminum dichloride used was changed to Al / Ti = 15 with respect to titanium atom.
A solid catalyst component was prepared in the same manner as in Example 1 except that the molar ratio was changed, and two-stage polymerization was performed. Table 1 shows the results. An ethylene copolymer having excellent extrusion properties and melt properties was obtained.

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

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

Example 3 A solid catalyst component was prepared in the same manner as in Example 1 (1) except that dimethoxydiphenylsilane was used instead of diethoxydiphenylsilane, and two-stage polymerization was carried out. Table 1 shows the results. An ethylene 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 (1) except that a prepolymerized catalyst prepolymerized with ethylene was used so that the prepolymerization amount was 500 g per 1 g of the solid component. , A two-stage polymerization. Table 1 shows the results. The results were inferior in extrusion characteristics and melt properties.

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

Comparative Example 4 In Example 1 (1), the solid component was ethyl aluminum dichloride in such a manner that Al / Ti = 5 mole ratio with respect to the titanium atom in the solid component without any prepolymerization with ethylene. A solid catalyst component was prepared in the same manner as in Example 1 except that the treatment was carried out, and two-stage polymerization was carried out. Table 1 shows the results. 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 instead of hexene-1 as a comonomer. Table 1 shows the results. An ethylene 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. Table 1 shows the results. An ethylene copolymer having excellent extrusion properties and melt properties was obtained.

[0055]

[Table 1]

[0056]

According to the present invention, an ethylene copolymer having excellent extrusion properties and melt properties can be produced, which is industrially valuable.

[Brief description of the drawings]

FIG. 1 is a flowchart of catalyst preparation in a production method of the present invention.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuya Maki No. 2 in Oita, Oita City, Oita Prefecture Showa Denko KK Oita Research Laboratory (56) References JP-A-55-71707 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) C08F 4/65-4/658

Claims (1)

(57) [Claims] 1. An ethylene-based copolymer is produced by two-stage polymerization of ethylene and an α-olefin in a first polymerization zone and a low-molecular weight component in a second polymerization zone. (1) Aluminum trihalide, Si-
A co-ground product obtained by co-ground an organic compound having an O bond and magnesium alcoholate, and (2) a solid obtained by contacting a tetravalent titanium compound having at least one halogen atom in a liquid phase The component is combined with an organoaluminum compound and the prepolymerization amount is 0.01 to 10 per gram of the solid component.
A pre-polymerized catalyst prepolymerized with ethylene so as to be 0 g is a dihalogen 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, and X is a halogen atom) Organoaluminum compound and titanium atom in the prepolymerization catalyst
A method for producing an ethylene-based copolymer using a catalyst system comprising a solid catalyst component and an organoaluminum compound obtained by treating at a molar ratio of / Ti = 2 to 20.