JP2712307B2 - Method for producing polyethylene - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing polyethylene having a wide molecular weight distribution. More particularly, the present invention relates to a method for producing polyethylene for use in hollow molding and extrusion molding having excellent melt properties and processability.

[Problems to be solved by conventional technology and invention]

In blow molding and extrusion molding applications, polyethylene having a relatively high molecular weight and a broad molecular weight distribution is required. Heretofore, attempts have been made to produce a single polymerization step by selecting an appropriate catalyst in order to broaden the molecular weight distribution. However, in general, it is difficult to obtain sufficiently high productivity with a catalyst having a performance capable of obtaining polyethylene having a wide molecular weight distribution, and since the molecular weight distribution is regulated by the properties of the catalyst, a polyethylene having a molecular weight distribution suitable for the application is used. It is also disadvantageous in obtaining From such a viewpoint, a method of sequentially producing a high-molecular-weight polyethylene and a low-molecular-weight polyethylene in two or more successive polymerization steps has been considered, and has been proposed as a multi-stage polymerization method. According to this method, the molecular weight distribution is wide,
Therefore, polyethylene having good flowability even with a relatively high molecular weight can be obtained with high productivity. In addition, α-olefins are copolymerized as comonomers to adjust the rigidity of polyethylene.However, by allocating the α-olefin content in high-molecular-weight polymers higher than that in low-molecular-weight polymers, rigidity and stress cracking resistance are improved. It is also known that sex (ESCR) balance is significantly enhanced.

However, while the polyethylene produced by the multi-stage polymerization method has the above-mentioned excellent properties, it also has some drawbacks in processing. The low melt tension of the polymer and the small die swell. When performing hollow molding, the melt properties of the polymer, that is, the melt tension, and the properties of the die swell are important in addition to the properties of the molecular weight and the molecular weight distribution. In the hollow molding, a cylindrical molten polymer (parison) is extruded from a die, and when a predetermined length is reached, a gas such as air is blown into the parison to be in close contact with a mold to obtain a molded product. At this time, if the melt tension of the polymer is small, the parison may hang down due to its own weight (drawdown),
Further, even if an attempt is made to form a large product, the parison will be cut off from the die by its own weight. on the other hand,
When the molten polymer is extruded from the die of the molding machine, swelling occurs due to the ballast effect. The ratio of the parison diameter to the die diameter is called the die swell and is used as an index of the degree of swelling. In the blow molding, a bottle or the like is formed from the parison having a certain length. However, in the case of polyethylene having a small die swell, the wall thickness of the product becomes thin, and it is difficult to obtain a product having a certain weight. For this reason, it is necessary to replace the dies in order to adjust the wall thickness, and this is extremely disadvantageous industrially for manufacturers who mold various products, such as a decrease in productivity and a need for spare dies. In addition, the die swell is dependent on the shear rate, and changing the shear rate changes the die swell. If the shear rate dependence of the die swell is large, the wall thickness changes due to a slight change in the shear rate, and it becomes difficult to obtain a product with a constant weight, which impairs the molding stability and is extremely disadvantageous industrially. on the other hand,
Even when a film is formed by inflation as extrusion molding, bubbles become unstable when the melt tension is small.

As a method for improving the die swell which is one of such viscoelastic properties, in a multi-stage polymerization method comprising three polymerization steps, a method for producing a polymer having a remarkably high molecular weight in one polymerization step has been proposed. I have. For example,
Japanese Patent Publication No. 59-10724 discloses that a polymer having a molecular weight of 1,000,000 or more is produced in an amount of 1 to 10% of the total production amount. In Examples, a polymer having a molecular weight of 3,000,000 is produced in an amount of 5% of the total production amount. Attempts have been made to improve die swell by manufacturing.

In JP-A-57-141409, the intrinsic viscosity [η] is 7 to 40.
It is shown that a high molecular weight polymer is produced, and in Examples, the intrinsic viscosity [η] is changed in the range of 7.69 to 14.8,
Attempts have been made to adjust the die swell over a wide range by adjusting the production to 10.5% or less of the total production. However, according to the study by the present inventors, there is still room for improvement of the die swell, and the tendency of the die swell to depend on the shear rate tends to increase with the improvement of the die swell. Furthermore, polyethylene containing a small amount of a polymer having a remarkably high molecular weight has a problem in homogeneity due to the presence of bumps and gels. Also,
In the above proposals, there is no mention of melt tension, which is an important property of melt properties.

In JP-A-59-227913, an ultra-high amount of a polymer having an intrinsic viscosity [η] of 11 to 26 measured in a decalin solvent at 135 ° C. is polymerized in a first stage at 5 to 23% by weight, followed by polymerization. [Η]
Shows a method of polymerizing a polymer having 0.25 to 1.6 and a polymer having [η] of 2.9 to 5.1 in an arbitrary order, and shows an example of a batch system and an attempt to improve mechanical strength. However, high productivity cannot be expected in a batch system, and many difficult problems such as non-uniformity caused by differences in the distribution of particle residence times differ from the batch system in a continuous system capable of high productivity. Need to be resolved.

Furthermore, Japanese Patent Application Laid-Open No. 62-25105-25109 discloses a multi-stage polymerization method by a continuous system, but in all of these examples, the ultrahigh molecular weight component, that is, the intrinsic viscosity measured in a decalin solvent at 135 ° C. The component having [η] of 15 or more is less than 5% by weight. It is stated that when the content exceeds 5% by weight, gels and lumps are generated.

In each of the above prior arts, the nonuniformity of the polymer (generation of gels and bumps) is not a particular problem because the production ratio of the ultrahigh molecular weight component is low or because of batch polymerization.

Further, in JP-A-58-138719, the intrinsic viscosity (η)
Are high molecular weight ethylene (co) polymers having a molecular weight of 1.5 to 11, preferably 1.5 to 7, and [η] of 0.5 to 8 and [η] of 0.2 to
3 shows a method of polymerizing each component of the ethylene (co) polymer in multiple stages. In the same publication, the batch type and the continuous type have been studied in the comparatively low molecular weight range of [η] of the high molecular weight component of 2.60 to 6.72, and three components of a high molecular weight component, a low molecular weight component, and an intermediate component thereof have been studied. Since it is an ethylene (co) polymer consisting of However, no effect on the melt properties required for the hollow molded article is described. According to the study of the present inventors, the conventional continuous multi-stage polymerization method, high molecular weight [η]
If the number exceeds 6, the product is likely to be bumpy, and some countermeasures are required.

The present inventors have already disclosed JP-A-61-207404, but they were insufficient in terms of continuous polymerization. Further, as shown in the present invention, the molecular weight and production ratio of each component are determined by the molecular weight [η] W of the finally produced polyethylene.
, The melt tension, die swell, and drawdown of the resulting polyethylene were not sufficiently improved, and the effects of the radical generator described in the publication were difficult to appear.

Including the step of polymerizing ultra-high molecular weight polyethylene as described above, it is necessary to continuously produce polyethylene having excellent melt tension, die swell and drawdown with high productivity, and the ratio of ultra-high molecular weight components is high. However, there is a demand for a method for producing polyethylene which is excellent in uniformity of the polymer, generates few gels and bumps, and is suitable for hollow molding.

[Means for solving the problem]

That is, the present invention provides a method for polymerizing ethylene or ethylene and an α-olefin in a continuous multi-stage in the presence of a Ziegler-type catalyst, using a polymerization apparatus comprising three or more polymerization vessels, (U component): α-olefin The content α _U is 0.1 to 10% by weight, and the intrinsic viscosity [η] _U is 2 × [η] _W ≦ [η] _U ≦ 5 × with respect to the intrinsic viscosity [η] _{W of} all ethylene polymers.
[Η] _W , and the ratio R _{U of the} U component in the total ethylene polymer is 0.3 × [η] _W ≦ [η] _U × R _U ≦ 0.8 × [η]
Component that satisfies _W : (H component): α-olefin content α _H is 20% by weight or less, and intrinsic viscosity [η] _H is ([η] _W ) ^1/2 ≦ [η] _H ≦ 1.5 × [Η] _W , and the ratio RH of the H component in the total ethylene polymer is 0.25 ×
[Η] _W ≦ [η] _H × R _H ≦ 0.7 × [η] _W , component that satisfies _W , (L component): α-olefin content α _L is 10% by weight or less, intrinsic viscosity [η] _L Is 0.2 ≦ [η] _L ≦ 2.0, and the proportion R _{L of the} L component in the total ethylene polymer is a component satisfying [η] _L × R _L ≧ 0.05 × [η] _W ,
Further, when R _U + R _H + R _L = 1.0, R _U , R _H , and R _L are all less than 1, and α _U × R _U ≧ 0.2 × (α _U × R _U + α _H × R _H + α _L ×
R _L ) is produced in any order, and as a catalyst, (I) a transition metal-containing reactant containing at least one tetravalent titanium compound, metallic magnesium and a hydroxylated organic compound And a reaction product obtained by reacting at least one selected from oxygen-containing organic compounds of magnesium and oxygen with (II) at least one of the general formula AlR _n
X _3-n (wherein, R represents an alkyl group having 1 to 20 carbon atoms, X represents a halogen atom, and n represents 0 ≦ n ≦ 3
A solid catalyst obtained by reacting an organoaluminum compound represented by the formula (III) with at least one kind of polysiloxane, and a trialkylaluminum, the polymer corresponding to the H component being used alone. When polymerized, polyethylene having a molecular weight distribution Mw / Mn in the range of 7 to 17 is obtained, and the deactivation rate constant Kd> 0.
3 (Hr ^-1 ), using a catalyst having a intrinsic viscosity [η] _{W of} all ethylene polymers of 1.5 ≦ [η] _W ≦ 4.0, a method for producing polyethylene,
And a method for producing polyethylene, comprising contacting a radical generator with the obtained polyethylene.

In the present invention, the polymerization of ethylene or the copolymerization of ethylene and an α-olefin is carried out in multiple stages under polymerization conditions comprising at least three polymerization vessels. The polyethylene obtained in the present invention comprises three components: an ultrahigh molecular weight component (U component), a high molecular weight component (H component), and a low molecular weight component (L component).

It is known that the melt tension, die swell, drawdown and the like of polyethylene are greatly improved by containing an ultrahigh molecular weight component as described above. However,
The polymer containing the ultrahigh molecular weight component has a large difference in molecular weight from the other components, and therefore has poor compatibility, becomes non-uniform, and is liable to generate gels, bumps, and fish eyes. Further, unlike the batch type, the continuous type is likely to induce non-uniformity due to the difference in the residence time distribution of the particles. Therefore, the molecular weight and production ratio of each component are determined based on the molecular weight [η] _W of the finally produced polyethylene, and by selecting the type and amount of α-olefin according to the use of the product, It is possible to optimize the melt tension, die swell, drawdown, workability, and uniformity of the obtained polyethylene.

In the U component, the intrinsic viscosity [η] _U is 2 × [η] _W
≦ [η] _U ≦ 5 × [η] _W , preferably 2.5 × [η] _W
≦ [η] _U ≦ 4 × [η] _W and the production ratio R _U is 0.3 ×
[Η] _W ≤ [η] _U x _RU ≤ 0.8 x [η] _W , preferably
0.35 × [η] _W ≦ [η] _U × R _U ≦ 0.7 × [η] _W If [η] _U and _RU are each smaller than the above range, sufficient melt tension, die swell and drawdown cannot be obtained,
[Η] If _U is larger than the above range, the uniformity of the product is impaired, and dust and gel are generated, which is not preferable. Also,
If each of [η] _U and R _U is larger than the above range, the molecular weight [η] _{W of the} product becomes large and the workability is significantly impaired.

In the H component, the intrinsic viscosity [η] _H is
([Η] _W ) ^1/2 ≦ [η] _H ≦ 1.5 × [η] _W , preferably ([η] _W ) ^3/4 ≦ [η] _H ≦ 1.3 × [η] _W The ratio _RH is 0.25 × [η] _W ≦ [η] _H × _RH ≦ 0.
7 × [η] _W , preferably 0.3 × [η] _W ≦ [η] _H × R _H
≦ 0.6 × [η] _W. [Η] _H, and the melt tension R _H is smaller than each said range, die swell, drawdown, small effect of improving the uniformity, conversely [η] _H, R _H are each, the range is greater than the product Has an excessively large molecular weight or has low fluidity.

In the L component, the limiting viscosity [η] _L is 0.2 ≦
[Η] _L ≦ 2.0 and the production ratio _RL is [η] _L × R _L ≧ 0.0
5 × [η] _W. When [η] _L <0.2, the molecular weight is too small, and the amount of the polymer soluble in the solvent is remarkably increased, and the melt tension and the drawdown are reduced. If [η] _L > 2.0, the molecular weight distribution becomes narrow, and the fluidity decreases.

The intrinsic viscosity [η] and the polymerization ratio of each of these components can be arbitrarily adjusted within the above ranges, but it is preferable that the intrinsic viscosity of the final product is 1.5 to 4.

When a copolymerization reaction of ethylene and an α-olefin is carried out in the method of the present invention, the α-olefin is selected from propylene, butene-1, hexene-1, octene-1, 4methylpentene-1 and the like. Species or two or more of them can be used in combination. It is preferable that the α-olefin is distributed more to the high molecular weight side. By doing so, the balance between rigidity and ESCR of the obtained polyethylene is remarkably improved. Further, according to the studies by the inventors, U, H, L,
Α-olefin content α _U , α _H , α _L in each component is α
_{U × R U ≧ 0.2 × (} α U × R U + α H × R H + α L × R L) is _{preferably, α U × R U ≧ 0.3} × (α U × R U + α H × R H + α L
× R _L ). If α _U satisfies the above relationship, the uniformity of the obtained polyethylene can be remarkably improved even in a continuous multistage polymerization. This is because ultrahigh molecular weight polyethylene becomes a copolymer and the melting point decreases,
It is also considered that compatibility with other components is increased due to easy melting. And the melt tension is also improved by the improvement of the uniformity. If the limiting viscosity, production ratio, and α-olefin content of each component are adjusted within the above ranges, the effects of the present invention can be sufficiently exerted.

For the above three components, three or more polymerization steps are continuously performed in an arbitrary order, but the polymerization of the components (U) and (L) is performed in parallel, and then the polymer of each component is mixed. Then, the polymerization of the component (H) can be carried out. In polymerization, the intrinsic viscosity [η] of the polymer is generally adjusted by a molecular weight modifier (for example, hydrogen). However, when the molecular weight is adjusted by the hydrogen concentration, if the hydrogen concentration in the preceding stage is higher than that in the subsequent stage, it is necessary to provide a hydrogen purging step between both stages. When a polymer having a large intrinsic viscosity [η] is produced, it can be carried out in a state where a molecular weight modifier is substantially absent. In this case, the molecular weight can be adjusted by changing the polymerization temperature.

A polymer containing an ultra-high molecular weight has a large difference in molecular weight from other components, so that it has poor compatibility and becomes non-uniform, and gels, lumps, and fish eyes are easily generated. In order to solve this, the molecular weight and the production ratio of each component are determined as described above, but this alone is still insufficient.

As a result of intensive studies by the present inventors, the catalyst used in the present invention has a sufficiently high activity and gives a polymer having a molecular weight distribution in a specific range, and has a relatively low deactivation rate constant (Kd) of the catalyst. Larger ones are preferred.

That is, in the present invention, if the catalyst activity is too low, high productivity is impaired. Specifically, the catalyst used in the present invention is required to have relatively wide molecular weight distribution characteristics, and Mw / Mn is 7 when the polyethylene specified in (H component) is independently homopolymerized. Preferred are those catalysts which give polyethylene having a molecular weight distribution of 1717. A catalyst having a narrow molecular weight distribution of Mw / Mn of less than 7 does not sufficiently improve the uniformity, melt tension and die swell, which are great effects of the present invention. On the other hand, a catalyst having a Mw / Mn of more than 17 requires a large amount of a molecular weight regulator (for example, hydrogen) at the time of polymerization of the component (L), and as a result, the catalytic activity is remarkably reduced and productivity is impaired.

The deactivation rate constant of the catalyst is desirably Kd> 0.3 (Hr ^-1 ), preferably Kd> 0.4 (Hr ^-1 ). When Kd is small, uniformity becomes insufficient. The reason for this is not clear, but is considered as follows. For example, Kd <0.3 (Hr ^-1 )
It is conceivable that the catalyst of the formula (1) has an active site that appears during the progress of the polymerization, different from the active site that appears at the start of the polymerization. As described above, if an active site is generated later, Kd becomes smaller, and the polymerization composition is different because the polymerization time is different from the active site generated from the start, which may contribute to the induction of non-uniformity. As the catalyst used in the present invention, the following Ziegler type catalysts can be used.

(I) Reaction obtained by reacting a transition metal-containing reactant containing at least one tetravalent titanium compound with at least one selected from metal hydroxide, an organic hydroxide compound and an oxygen-containing organic compound of magnesium. The product and (II) at least one of the general formulas AlRnX3-n where R is 1
X represents a halogen atom, n represents a number satisfying 0 ≦ n ≦ 3) and (III) at least one polysiloxane. A catalyst comprising a solid catalyst obtained by the reaction and a trialkylaluminum may be mentioned. Examples of the transition metal-containing reactant containing a tetravalent titanium compound include an oxygen-containing organic compound of titanium such as titanium tetrabutoxide and a halogenated compound of titanium such as titanium tetrachloride. Examples of the magnesium-containing reactant include a reactant comprising metal magnesium and an alcohol such as ethanol and n-butanol, or an organic silanol, and an oxygen-containing organic compound of magnesium such as a magnesium alkoxide. As the organic aluminum compound, diethyl aluminum chloride, ethyl aluminum dichloride, i-butyl aluminum dichloride, tri-i-
Butyl aluminum and the like. Examples of the polysiloxane include dimethylpolysiloxane and methylhydropolysiloxane. Examples of trialkylaluminum include triethylaluminum, tri-i
-Butyl aluminum and the like. A preferred example of a production method for providing such a solid catalyst is described in JP-A-62-13550.
1, detailed in JP-A-60-262802.

Thus, the catalyst needs to satisfy Kd> 0.3 and Mw / Mn of 7 to 17, and it is preferable to conduct a polymerization experiment using Kd and Mw / Mn alone and to grasp experimentally.

In the practice of the present invention, the amount of the solid catalyst used is
Per atom or per reactor, titanium atom 0.001-25m
Preferably, it is used in an amount corresponding to mol. The organic metal catalyst is used in an amount of 0.02 to 50 mmol, preferably 0.2 to 50 mmol per solvent.
Used at a concentration of の 5 mmol.

The polymerization of ethylene or the copolymerization of ethylene and α-olefin is carried out in the presence or absence of an inert solvent in a liquid phase or a gas phase. In liquid phase polymerization, it is preferable to carry out slurry polymerization.

As the inert solvent that can be used for the polymerization in the liquid phase polymerization, any inert solvent that is usually used in the art can be used, and in particular, 4 to 20
Alkanes and cycloalkanes having two carbon atoms, such as isobutane, pentane, hexane, heptane, cyclohexane and the like are suitable.

As the polymerization temperature in the present invention, any temperature lower than the melting point of the polymer can be selected, but a temperature range of 30 to 100 ° C. is preferable. In particular, when the component (U) is polymerized in the first stage, the temperature is preferably in the range of 30 to 60 ° C because of the high polymerization activity of the reaction. The reaction pressure is preferably in the range of normal pressure to 100 kg / cm ² G, particularly preferably normal pressure to 50 kg / cm ² G.

The polyethylene obtained as described above is itself an improved melt tension and die swell.
However, depending on the application of the product, further modification is possible by contacting the polyethylene powder with a radical generator. As a specific method, when strict and uniform quality is required for reforming, the method disclosed in JP-A-59-68530 is preferable. That is, the raw polyethylene powder is impregnated with a solvent, a liquid radical agent is added, mixed, and dried to obtain a polyethylene powder containing the radical generator uniformly, and heat-treated at a temperature equal to or higher than the decomposition temperature of the radical generator. It is done by doing. According to this method, the radical generator uniformly adheres to the pores of the polyethylene powder, and the modified polyethylene thus obtained does not generate gels or fish eyes during film formation.

In the case where uniform quality is not so strictly required for the modification, a method in which a liquid radical generator is impregnated into a polymer and added as a so-called masterbatch and brought into contact with the polymer, or the stabilizer is impregnated with the radical generator in advance. There is no particular limitation on the method of adding and bringing into contact.

As the radical generator used in the present invention, organic peroxides such as hydroperoxides, dialkyl peroxides, and peroxyesters are preferable,
Among them, those having a decomposition temperature giving a half life of 1 minute of 150 ° C. or more are preferable. Particularly preferred are dicumyl peroxide belonging to dialkyl peroxides and 2,5-dimethyl-2,5-di (t-butylperoxy).
Hexin-3,2,5-dimethyl-2,5-di (t-butylperoxy) hexane, d, d'-bis (t-butylperoxyisopropyl) benzene and the like.

The amount of the radical generator is preferably in the range of 2 to 500 ppm based on polyethylene. If the amount is less than 2 ppm, the effect of the modification of polyethylene will not be remarkably exhibited. Also,
If the addition amount exceeds 500 ppm, the reforming reaction proceeds excessively, so that polyethylene impairs the quality of the molded article.

If it is necessary to dry the polyethylene mixed with the radical generator, increasing the temperature promotes the decomposition of the radical generator and causes adverse effects such as inducing agglomeration of the polyethylene. It is preferred to operate at a temperature of at least 120 ° C. or less.

On the other hand, using air or oxygen as a radical generator,
It can also be modified by a method of heating by contacting with polyethylene.

As a heat treatment method, it is sufficient to simply pass through a commonly used extruder for pelletizing. The operating temperature in this heat treatment may be a temperature equal to or higher than the decomposition temperature of the radical generator contained in the polyethylene as a reaction mixture, and for example, the operating temperature range of a usual extruder of about 150 to 350 ° C. may be used.

〔The invention's effect〕

According to the present invention, utilizing a Ziegler-type catalyst, which has a high activity, a large catalyst deactivation rate constant, and which has been modified to produce a polymer having a specific range of molecular weight distribution, (U), The technology of producing polyethylene consisting of the three components (H) and (L) in at least three polymerization vessels firstly improves the viscoelastic properties of the molten polymer, and is more compatible with hollow molding and extrusion. In the production of polyethylene having a high viscosity.

The second effect of the present invention is that, when the above-mentioned polyethylene is produced in a continuous manner, the molecular weight of each component and the production ratio are determined based on the molecular weight [η] _W of the finally produced polyethylene, and Is determined on the basis of the ratio of each component, and the use of a catalyst having the above characteristics significantly improves the homogeneity of the obtained polyethylene.

A third effect of the present invention resides in that the obtained polyethylene powder can be modified with a radical generator according to the use of the product to improve the melt tension and die swell.

A fourth effect of the present invention is that a polyethylene having a wide molecular weight distribution and good processability can be obtained.

〔Example〕

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

The properties of the polymers in Examples, Reference Examples and Comparative Examples were measured by the following methods.

MI: melt index according to ASTM D-1238 condition E N value: ratio of high load melt index (HLMI) according to ASTM D-1238 condition F to MI HLMI / MI As one measure of molecular weight distribution, the larger the value, the higher the molecular weight distribution. Indicates that it is wide.

Density: True density according to JIS K-6760 Melt tension: Using a melt tension tester (manufactured by Toyo Seiki Co., Ltd.), a polymer with an orifice with a nozzle diameter of 2.095 mm and a length of 8 mm at 190 ° C and a descent rate of 10 mm / min. Tension when extruding and winding into a monofilament Die swell: Die swell (SR-I) and shear rate 50se measured at 190 ° C under a shear rate of 15 sec-1 using the above melt tension tester and orifice
Die swell measured under the condition of c ^-1 (SR-II) Dependence of die swell on shear rate (K): value calculated by the following equation K = (SR-I-SR-II) / log ( 50/15) Intrinsic viscosity [η]: Measured in orthodichlorobenzene at 140 ° C., there is the following formula between intrinsic viscosity [η] and viscosity average molecular weight M.

[Η] = 3.56 × 10 ⁻⁴ M ^{0.725 Deactivation} rate constant Kd: When the time-dependent change of the ethylene consumption Nl / Hr) is plotted on a logarithmic scale of a semilogarithmic graph, the slope approximates to a straight line, and the slope thereof is obtained.

Reference Example 1 a) Production of a solid catalyst component Under a nitrogen atmosphere, 40 g (1.65 mol) of metallic magnesium powder and 28.3 g (0.083 mol) of titanium tetrabutoxide were added to a catalyst preparation device of 10 l container equipped with a stirrer, and the mixture was heated to 80 ° C. The temperature was raised, and n-butanol 140 further dissolved 2.0 g of iodine.
4 g (1.89 mol) and 2-ethyl-hexanol 246.4
g (1.89 mol) of the mixture was added dropwise over 2 hours.
The reaction was performed by heating to 0 ° C. After adding 2720 ml of hexane at room temperature to the reaction product thus obtained, the mixture was stirred at 70 ° C. for 1 hour. To this solution, 907 ml (1.65 mol) of a 30% by weight solution of diethylaluminum chloride in hexane was added at 45 ° C for 2 hours.
It was added over time and stirred at 60 ° C. for 1 hour. Next, 198 g (1.65 g atom of silicon) of methylhydropolysiloxane (viscosity of about 30 centistokes at 25 ° C.) was added, and the mixture was reacted under reflux for 1 hour. After cooling to 45 ° C., 3670 ml of a 50% by weight hexane solution of i-butylaluminum dichloride was added over 2 hours. After the addition, the mixture was stirred at 70 ° C. for 1 hour. Hexane was added to the product, and the product was washed 15 times by a gradient method. Thus, a slurry of the solid catalyst component suspended in hexane was obtained. A part of the sample was collected, the supernatant was removed, and the sample was dried under a nitrogen atmosphere and subjected to elemental analysis.
% By weight.

b) Polymerization of ethylene The inside of a stainless steel electromagnetically stirred autoclave having a capacity of 2 l was sufficiently replaced with nitrogen, and 1.2 l of hexane was charged.
The internal temperature was adjusted to 80 ° C. Then, the catalyst component
A slurry containing 0.23 g (1.2 mmol) of i-butylaluminum and 10 mg of the solid catalyst component obtained in the above (a) was sequentially added. After adjusting the internal pressure of the autoclave to 1Kg / cm ² G, hydrogen 1.5 Kg / cm ² G was added, followed so that the internal pressure of the autoclave to 8.5 kg / cm ² G, subjected to 1.5 hour of polymerization while continuously ethylene was added Was. After polymerization, cool
The unreacted gas was expelled to remove the polyethylene, separated from the solvent by filtration and dried.

As a result, melt index 0.04g / 10min, HLMI / MI9
9. 279 g of polyethylene having a bulk density of 0.30 g / cm ³ was obtained. Production volume per 1g of solid catalyst component (A) (decrease, activity)
Is equivalent to 27900 g / g. The average particle size was 211 μ, and the ratio of fine particles having a particle size of 105 μ or less was 5.7% by weight.

Further, Mw / Mn is 8.0, and the deactivation rate constant of polymerization Kd is 0.
It was 62 Hr ^-1 .

Reference Example 2 a) Production of a solid catalyst component Under a nitrogen atmosphere, 40 g (1.65 mol) of metallic magnesium powder and 224 g (0.66 mol) of titanium tetrabutoxide were added to a catalyst preparation device having a volume of 10 l equipped with a stirrer, and heated to 80 ° C. Warm,
Further, 134 g of n-butanol in which 2.0 g of iodine was dissolved (1.
A mixture of 82 mol) and 109 g (1.82 mol) of i-propanol was added dropwise over 2 hours, and then heated to 120 ° C. to react. After adding 2720 ml of hexane at room temperature to the reaction product thus obtained, the mixture was stirred at 70 ° C. for 1 hour. To this solution, 1820 ml (3.3 mol) of a 30% by weight diethylaluminum chloride in hexane solution was added at 45 ° C. over 1 hour. After the addition, the mixture was stirred at 70 ° C. for 1 hour. 45 ℃
After cooling, 1,25 ml of a 50% by weight solution of isobutylaluminum chloride in hexane was added over 1 hour. After the addition, the mixture was stirred at 70 ° C. for 1 hour.

Hexane was added to the product, and the product was washed 15 times by a gradient method. Thus, a slurry of the solid catalyst component suspended in hexane was obtained. A part thereof was collected, the supernatant was removed, and the resultant was dried under a nitrogen atmosphere and subjected to elemental analysis. As a result, it was found that Ti was 10.8% by weight.

b) Polymerization of ethylene Using the solid catalyst component obtained in (a), ethylene was polymerized in the same manner as in b) of Reference Example 1.

As a result, melt index 0.09g / 10min, HLMI / MI5
7, 280 g of polyethylene having a bulk density of 0.33 g / cm ³ was obtained. The production per g of solid catalyst is equivalent to 28000 g. The average particle size is 395μ, the proportion of fine particles having a particle size of 105μ or less is
It was 0.6% by weight. Further, Mw / Mn was 5.5, and the deactivation constant Kd of the polymerization was 0.23 (Hr ^-1 ).

Example 1 [Three-stage polymerization] (Polymerization of L component) Continuous polymerization was performed by connecting three polymerization units in series. In a first polymerization vessel having an internal volume of 300 liters, hexane (150 kg / Hr), ethylene (15.0 kg / Hr), hydrogen (480 Nl / Hr), and the solid catalyst component obtained in Reference Example 1 were continuously fed at a rate of 0.8 g / Hr. Supplied. In addition, the concentration of triisobutylaluminum in the liquid was set to 1.0 mmol / kg.
Triisobutylaluminum and butene-1 were continuously supplied to hexane so that the weight ratio of butene-1 to ethylene was 0.4 g / g. The polymerization temperature was adjusted to 85 ° C.

The slurry containing the polymer produced in the first polymerization reactor was continuously introduced into the second polymerization via a flash tank and a pump.

(Polymerization of H component) 27 kg / Hr of hexane was added to the second
Ethylene was supplied at a rate of 15.8 kg / Hr, hydrogen was supplied at a rate of 90 Nl / Hr, and butene-1 was continuously supplied such that the polymerization ratio of butene-1 and ethylene in the liquid became 0.5 g / g. The temperature was adjusted to 85 ° C.

The slurry containing the polymer produced in the second polymerization reactor was continuously supplied to the third polymerization reactor by obtaining a flash tank and a pump.

(Polymerization of U component) In a third polymerization vessel having an inner volume of 500 l, hexane was 8 kg / Hr, ethylene was 9.0 kg / Hr, and butene-1 was 1.7 g / g in weight ratio of butene-1 to ethylene in the liquid. Each was continuously supplied so that A small amount of hydrogen was continuously supplied to control the molecular weight. The temperature was adjusted to 50 ° C.

The slurry containing the polymer produced in the third polymerization vessel was separated into polymer and hexane by a centrifugal separator, and the polymer was dried.

When a small amount of the polymer discharged from each polymerization unit was extracted, [η] of the polymer in the first polymerization unit was 0.65,
The polymer [η] of the polymerization vessel is 1.78, and the final product [η] is
It was 2.45. In addition, as a result of analyzing the unreacted gas in each polymerization reactor, the production ratio in each of the first, second, and third polymerization reactors was 41%.
%, 42% and 17%. From these facts, it can be seen that [η] of each of the H and U components is 2.88,5.7.

The content of α-olefin in the polymer produced in each step is 0.3% by weight in the step (L),
In the steps (H) and (U), 0.4 wt% and 0.8 wt%, respectively, were obtained from the relationship between the charged amount of butene-1 and ethylene partial pressure.
% By weight.

(Modification of polyethylene)

40 kg of polyethylene obtained as above was used for an internal volume of 20
Placed in a 0 l autoclave. Separately, a solution of a radical generator containing 0.40 g (corresponding to 10 ppm) of α, α'-bis (t-butylperoxyisopropyl) benzene as a radical generator and 40 kg of hexane as an inert organic solvent was prepared.

While stirring the polyethylene powder in the autoclave, the entire amount of the radical generator solution was injected and added, and stirring was continued for 15 minutes. Next, the content was extracted and dried at an internal temperature of 90 ° C. in a batch-type air-flow drier to obtain a reaction mixture.

700 ppm of Irganox B-220 (manufactured by Ciba-Geigy) was added as a stabilizer to the polyethylene powder, and granulation was performed at a resin temperature of 200 ° C. with an extruder having a screw diameter of 65 mmφ to complete the modification. The physical properties of the modified polyethylene are as follows. MI is 0.028g / 10min, N value is 265, density is 0.950
g / cm ³ , and the melt tension was 38.0 g. The die swell was 1.71 as SR-I and 1.80 as SR-II, and the dependency K on the shear rate of the die swell was 0.17.

Further, when formed into an inflation film by an extruder having a screw diameter of 25 mmφ, the number of fish eyes of 0.3 mm or more was as small as 760/10 m ² , indicating that the polymer was a uniform polymer.

Comparative Example 1 [Two-stage polymerization] (Polymerization of L component) Two-stage polymerization was performed using the same first and second polymerization reactors as in Example 1. Hexane was fed at a rate of 150 kg / Hr, ethylene at 180 kg / Hr, hydrogen at 460 Nl / Hr, and the solid catalyst component obtained in Reference Example 1 at a rate of 0.8 g / Hr to the first polymerization reactor. Further, triisobutylaluminum and butene-1 were continuously supplied so that the concentration of triisobutylaluminum in the liquid was 1.0 mmol / kg hexane and the weight ratio of butene-1 to ethylene was 0.7 g / g.

The slurry containing the polymer produced in the first polymerization reactor was continuously introduced into the second polymerization reactor via a flash tank and a pump.

(Polymerization of H component) In the second polymerization vessel, 27 kg / Hr of hexane and 20.0 k of ethylene
g / Hr, 25Nl / Hr of hydrogen, and butene-1 in the solution.
And ethylene were continuously supplied such that the weight ratio of ethylene and ethylene became 0.7 g / g. The temperature was adjusted to 80 ° C.

The slurry containing the polymer formed in the second polymerization vessel was separated into polymer and hexane by a centrifugal separator, and the polymer was dried.

When a small amount of the polymer discharged from each polymerization vessel was extracted, the [η] of the polymer in the first polymerization vessel was 0.7, and the [η] of the final product was 2.35. Further, as a result of analyzing the unreacted gas in each polymerization reactor, the production ratio in each of the first and second polymerization reactors was 50% and 50%. From these results, it can be seen that [η] of the polymer produced in the second polymerization vessel is 4.0. The obtained polymer was treated in the same manner as in Example 1,
After modification, granulation was performed. The results are shown in Table 2.

Examples 2 to 17, Comparative Examples 2 to 7 Using the solid catalyst prepared in Reference Example 1, three-stage polymerization was carried out in the same manner as in Example 1 except that polymerization conditions were variously changed. Table 1 shows the reaction conditions. Examples 8 to 10, and 12, 13
And Comparative Example 6 changed the polymerization order from the component (U) to the component (L)
(H) Component is changed. Table 2 shows the measurement results of the physical properties of the obtained polyethylene. In addition, about what was modified by the radical generator, the addition amount was shown.

In Comparative Example 7, since the solid catalyst obtained in Reference Example 2 was used, fish eyes were significantly increased.

Claims (2)

(57) [Claims] In a method for continuously polymerizing ethylene or ethylene and an α-olefin in a continuous multistage process in the presence of a Ziegler-type catalyst, a polymerization apparatus comprising three or more polymerization units is used. The olefin content α _U is 0.1 to 10% by weight, and the intrinsic viscosity [η] _U is 2 × [η] _W ≦ [η] _U ≦ 5 × [η with respect to the intrinsic viscosity [η] _{W of} all ethylene polymers. ]
_W , the ratio of the U component in the total ethylene polymer R _U
Is a component that satisfies 0.3 × [η] _W ≦ [η] _U × R _U ≦ 0.8 × [η] _W , (H component): α-olefin content α _H is 20% by weight or less, intrinsic viscosity [Η] _H is ([η] _W ) ^1/2 ≦
[Η] _H ≦ 1.5 × [η] _W , and the ratio R _{H of the} H component in the total ethylene polymer is 0.25 × [η] _W ≦ [η] _H
× R _H ≦ 0.7 × [η] _W , component that satisfies _W , (L component): α-olefin content α _L is 10% by weight or less, intrinsic viscosity [η] _L is 0.2 ≦ [η] _L ≦ 2.0, the proportion R _{L of the} L component in the total ethylene polymer is
[Η] _L × R _L ≧ 0.05 × [η] is a component that satisfies _W ,
In addition, when R _U + R _H + R _L = 1.0, R _U , R _H , and R _L are all less than 1, and [α] _U × R _U ≧ 0.2 × ([α] _U × R _U + [α] _H × R
_H + [α] _L × R _L ) are produced in any order, and as a catalyst, at least one of (I)
A transition metal-containing reactant comprising a species of tetravalent titanium compound;
A reaction product obtained by reacting metallic magnesium with at least one selected from an organic compound of hydroxide and an oxygen-containing organic compound of magnesium; and (II) at least one kind of general formula AlR _n X _3-n , R represents an alkyl group having 1 to 20 carbon atoms, X represents a halogen atom,
n represents a number satisfying 0 ≦ n ≦ 3), and a solid catalyst obtained by reacting an organoaluminum compound represented by the formula (III) with at least one kind of polysiloxane; Is obtained by homopolymerizing a polymer having a molecular weight distribution _Mw / _Mn in the range of 7 to 17, and a catalyst having a deactivation rate constant Kd> 0.3 (Hr ^-1 ) at that time. A method for producing a polyethylene having an intrinsic viscosity [η] _W of 1.5 ≦ [η] _W ≦ 4.0 using a total ethylene polymer. 2. A method for polymerizing ethylene or ethylene and an α-olefin in a continuous multistage process in the presence of a Ziegler-type catalyst, using a polymerization apparatus comprising three or more polymerization units, wherein (U component): α- The olefin content α _U is 0.1 to 10% by weight, and the intrinsic viscosity [η] _U is 2 × [η] _W ≦ [η] _U ≦ 5 × [η with respect to the intrinsic viscosity [η] _{W of} all ethylene polymers. ]
_W , the ratio of the U component in the total ethylene polymer R _U
Is a component that satisfies 0.3 × [η] _W ≦ [η] _U × R _U ≦ 0.8 × [η] _W , (H component): α-olefin content α _H is 20% by weight or less, intrinsic viscosity [Η] _H is ([η] _W ) ^1/2 ≦
[Η] _H ≦ 1.5 × [η] _W , and the ratio R _{H of the} H component in the total ethylene polymer is 0.25 × [η] _W ≦ [η] _H
× R _H ≦ 0.7 × [η] _W component (L component): α-olefin content α _L is 10% by weight or less, intrinsic viscosity [η] _L is 0.2 ≦ [η] _L ≦ 2.0, the proportion R _{L of the} L component in the total ethylene polymer is
[Η] _L × R _L ≧ 0.05 × [η] is a component that satisfies _W ,
In addition, when R _U + R _H + R _L = 1.0, R _U , R _H , and R _L are all less than 1, and [α] _U × R _U ≧ 0.2 × ([α] _U × R _U + [α] _H × R
_H + [α] _L × R _L ) are produced in any order, and as a catalyst, at least one of (I)
A transition metal-containing reactant comprising a species of tetravalent titanium compound;
A reaction product obtained by reacting metal magnesium with at least one selected from an organic compound of hydroxide and an oxygen-containing organic compound of magnesium; and (II) at least one kind of a general formula AlR _n X _3-n , R represents an alkyl group having 1 to 20 carbon atoms, X represents a halogen atom,
n represents a number satisfying 0 ≦ n ≦ 3), a solid catalyst obtained by reacting an organoaluminum compound represented by the formula (III) with at least one kind of polysiloxane, and a trialkylaluminum. Is obtained by homopolymerizing a polymer having a molecular weight distribution _Mw / _Mn in the range of 7 to 17, and a catalyst having a deactivation rate constant Kd> 0.3 (Hr- ¹ ) at that time. , A polyethylene having an intrinsic viscosity [η] _W of 1.5 ≦ [η] _W ≦ 4.0, and contacting a radical generator with the obtained polyethylene, thereby producing a polyethylene. .