JPH07116251B2 - Method for producing modified polyethylene - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a modified polyethylene having a wide molecular weight distribution. More specifically, it relates to a hollow molding having excellent physical properties and processability, and a method for producing polyethylene for extrusion molding.

[Conventional technology]

For blow molding and extrusion molding applications, polyethylene having a relatively high molecular weight and a wide molecular weight distribution is required. Heretofore, attempts have been made to produce the compound in one 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 characteristic of being able to obtain polyethylene having a wide molecular weight distribution, and the molecular weight distribution is defined by the properties of the catalyst. It is also disadvantageous in obtaining. From such a viewpoint, a method of sequentially producing high-molecular-weight polyethylene and low-molecular-weight polyethylene in two or more continuous polymerization steps is conceivable, and is proposed as a multi-stage polymerization method. According to this method, polyethylene having a wide molecular weight distribution and therefore good fluidity even with a relatively high molecular weight can be obtained with high productivity. In addition, α-olefin is copolymerized as a comonomer to control the rigidity of polyethylene, but by distributing the α-olefin content in the high molecular weight polymer higher than that of the low molecular weight polymer, the rigidity and stress cracking property (ESCR) can be improved. It is also known that the balance is significantly increased.

Regarding these multi-stage polymerization methods, Japanese Patent Publication No.
It is known from Japanese Patent Publication No. 48-42716, Japanese Patent Publication No. 56-161405.

However, while the polyethylene produced by the multi-stage polymerization method has the above-mentioned excellent properties, it also has some drawbacks in processing and molding. That is, the melt tension of the molten polymer is small and the die swell is small. When performing blow molding, in addition to the properties of molecular weight and molecular weight distribution, the viscoelastic properties of the molten polymer, that is, melt tension and die swell properties are important. 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 and is brought into close contact with a mold to obtain a molded product. At this time, if the melt tension of the molten polymer is low, the parison may hang down due to its own weight (drawdown), or even if an attempt is made to mold a large product, the parison may fall off from the die due to its own weight. become. 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 blow molding, bottles and the like are molded from the parison of a certain length, but with polyethylene with a small die swell, the wall thickness of the product becomes thin, and it becomes difficult to obtain a product of a constant weight. For this reason, it is necessary to replace the die in order to adjust the wall thickness, which is industrially extremely disadvantageous in that manufacturers of various products have low productivity and need a preliminary die. In addition, the die swell depends on the shear rate, and changing the shear rate also changes the die swell. If the shear rate dependency of the die swell is large, the wall thickness changes due to slight changes in the shear rate, making it difficult to obtain a product of a constant weight, which impairs the molding stability and is industrially extremely disadvantageous. On the other hand, even when a film is formed by inflation as extrusion molding, the bubble becomes unstable if the melt tension is small.

A method for improving die swell, which is one of such viscoelastic properties, has been proposed. According to this, in a multi-stage polymerization method consisting of three polymerization steps, it is characterized in that a polymer having a remarkably high molecular weight is produced in that one polymerization step. It has been shown to make polymers with 1% to 10% of the total yield, and the examples show attempts to improve die swell by producing 5% of the 3 million molecular weight polymer. ing. Further, JP-A-57-141409 shows that a high molecular weight polymer having an intrinsic viscosity [η] of 7 to 40 is produced. In Examples, the intrinsic viscosity [η] of 7.69 to
Vary within the range of 14.8, and the production amount to the total production amount
It shows an attempt to adjust the die swell over a wide range by adjusting at 10% or less. However, according to the study of the present inventors, it is confirmed that the die swell is certainly large, but it is not sufficient, and as the die swell is improved, the dependency on the shear rate of the die swell becomes significantly large, and the die Well improvement is inadequate. Furthermore, polyethylene containing a small amount of a polymer having a remarkably high molecular weight has a lump and a gel, resulting in insufficient homogeneity and significantly impairing the value of the product.

Further, in the above proposal, melt tension, which is an important characteristic of viscoelasticity, is not mentioned at all, and in the technique proposed as a conventional multistep polymerization method, high melt tension, high die swell and die Polyethylene, which has a characteristic that the shear rate dependence of wells is low, has not been manufactured.

[Problems to be solved by the invention]

In molding polyethylene, the flow and viscoelastic properties of the molten polymer are important. Polyethylene for blow molding and extrusion molding has a wide molecular weight distribution and therefore is required to have high fluidity even at a relatively large molecular weight.

In addition, as a viscoelastic property, in blow molding applications, it is necessary to have a high melt tension to prevent drawdown, a large die swell in molding, and a small dependence on the shear rate. In molding applications, high melt tension is required for bubble stability. Therefore, as a result of intensive studies by the present inventors, a polyethylene powder obtained by a multi-step process consisting of three or three or more specific polymerization steps is brought into contact with a radical generator to modify the polyethylene powder, thereby obtaining excellent flow characteristics. As a result, a method for producing polyethylene having viscoelastic properties such as high melt tension, large die swell and small dependence on shear rate has been found.

[Means for solving problems]

That is, the present invention, in the presence of Ziegler type catalyst, the polymerization of ethylene or the copolymerization of ethylene and α-olefin,
Step ((H) step) for producing polyethylene having an intrinsic viscosity [η] of 5 to 20 and an α-olefin content of 20% by weight or less based on the total polymerization amount (step (H)), and an intrinsic viscosity [η] of 0.2 to 1.
0, a step of producing polyethylene having an α-olefin content of 10% by weight or less by 20 to 70% by weight based on the total polymerization amount ((L) step) and an intrinsic viscosity [η] of 1 to 5, and an α-olefin content of 20 20% by weight or less of the total polymerization amount of polyethylene
A multi-step process consisting of a step of producing 70% by weight (step (M)) is performed as at least three polymerization steps in any order, or steps (H) and (L) are carried out in parallel, and then each step is carried out. The method for producing a modified polyethylene characterized in that the radical generating agent is brought into contact with the obtained polyethylene powder, which is carried out through the step (M) which is carried out by mixing the reaction mixture containing the polymer in the above. .

[Action]

It is particularly preferred that the catalyst used in the present invention is one which has a sufficiently high activity and gives a polymer having a molecular weight distribution in a specific range. That is, if the catalytic activity is too low in the present invention, high productivity, which is one of the features of the multistage polymerization method, is impaired. Further, if the molecular weight distribution of the catalyst deviates from the following range, it is difficult to sufficiently bring out the effect of the present invention. Specifically, the catalyst used in the present invention is required to have a characteristic of a relatively wide molecular weight distribution, and when producing polyethylene specified in the step (M), w / n is 5 or less.
Catalysts that give polyethylene with a molecular weight distribution of -15 are preferred. With a narrow molecular weight distribution catalyst having a w / n of less than 5, the improvement of melt tension and die swell, which are the great effects of the present invention, are insufficient.

On the other hand, a catalyst having a w / n of more than 15 requires a large amount of a molecular weight regulator (for example, hydrogen) when carrying out the step (L), and as a result, the catalytic activity is remarkably reduced and the productivity is impaired.

The catalyst used in the present invention is not particularly limited as long as it satisfies the above, but the following catalysts can be used, for example.

(I) at least one magnesium-containing reactive agent and at least one transition metal-containing reactive agent containing a titanium compound, and at least one reactive agent is represented by the chemical formula C--O--M.
(Wherein M represents magnesium or a transition metal) selected to have a bond and reacting the product obtained by the reaction with (ii) at least one aluminum halide compound. Of the periodic table of the solid catalyst (A) obtained by Ia, IIa, IIb, IIIb and IVb
A catalyst composed of an organometallic compound (B) of a group metal can be used. Examples of the magnesium-containing reaction agent include a reaction agent composed of metal magnesium and alcohols such as ethanol and n-butanol, or an organic silanol, an oxygen-containing organic compound of magnesium such as magnesium alkoxide, a magnesium halide, an organic magnesium compound. And so on. Examples of the transition metal-containing reactive agent containing a titanium compound include an oxygen-containing organic compound of titanium such as titanium tetrabutoxide or a halogenated compound of titanium such as titanium tetrachloride. Further, the solid catalyst (A) may contain a silicon compound in order to give a polymer having good particle properties. Examples of the silicon compound include polysiloxanes such as dimethylpolysiloxane and methylhydropolysiloxane. Examples of the dialkyl aluminum chloride or alkyl aluminum dichloride include diethyl aluminum chloride, ethyl aluminum dichloride, i-butyl aluminum dichloride and the like. Suitable examples of the production method for providing such a solid catalyst (A) are Japanese Patent Application Nos. 59-102661, 59-118120 and 59-2516.
It is shown in detail in No. 37. In the present invention, as the organometallic compound (B) of Group Ia, IIa, IIb, IIIb, IVb metal of the periodic table, triethylaluminum, tri-
Examples thereof include i-butylaluminum.

In carrying out the present invention, the amount of the solid catalyst (A) used is 0.1 titanium atom per solvent or 1 reactor.
Preference is given to using amounts corresponding to 001 to 25 mmol.
The organometallic compound (B) is used in a concentration of 0.02 to 50 mmol, preferably 0.2 to 5 mmol, per solvent or reactor 1.

In the present invention, ethylene polymerization or copolymerization of ethylene and α-olefin is carried out in at least three polymerization stages under different polymerization conditions in the same or different polymerization zones. In the step (H), a polyethylene having an intrinsic viscosity [η] of 5 to 20, preferably 5 to 15 and an α-olefin content of 20 wt% or less is produced, and in the step (L), [η] is 0.2 to 1.0 to produce a polyethylene having an α-olefin content of 10 to 10% by weight, preferably 0.4 to 1.0,
In the step (M), [η] is 1 to 5, preferably 1 to
In 4, a polyethylene having an α-olefin content of 20% by weight or more is produced. When the [η] of the polyethylene produced in the step (H) is less than 5, the effect of increasing the melt tension and die swell, which are the effects of the present invention, is small. Also,
If [η] exceeds 20, the uniformity of the product will be impaired, and spots and gel will be generated, which is not preferable. When the [η] of the polyethylene produced in the step (L) is less than 0.2, the molecular weight is too small and the amount of polymer soluble in the solvent is significantly increased. On the other hand, [η]
When the value exceeds 1, the molecular weight distribution becomes narrow and the workability deteriorates.

When carrying out the copolymerization reaction of ethylene and α-olefin in the method of the present invention, α-olefin is propylene,
It is selected from butene-1, hexene-1, octene-1,4 methylpentene-1, etc., and one kind or a combination of two or more kinds can be used. The content of the α-olefin is adjusted within the above range, but it is preferable that the α-olefin content is more distributed to the high molecular weight side. By doing this, the rigidity of the obtained polyethylene and
The balance of ESCR is significantly improved.

The polymerization ratio in the present invention is adjusted by adjusting the cumulative amount of ethylene charged in each step in a batch type polymerization vessel, and when continuously performed, the flow rate of ethylene fed to three polymerization vessels is adjusted. Done by that. (H)
The ratio of polyethylene produced in the process is 2 of the total polymerization amount.
When the amount is up to 40% by weight and less than 2%, the effect of increasing the melt tension and the die swell, which are the effects of the present invention, are small. Again 40
% Or more, the molecular weight becomes too large and the fluidity deteriorates. The ratio of polyethylene produced in the step (L) is 20 to 70% by weight of the total polymerization amount, and if it is less than 20%, the processability decreases, If it exceeds%, the physical properties of the product deteriorate. The ratio of polyethylene produced in step (M) is 20 to 70 of the total polymerization amount.
If it exceeds 70% by weight, the workability is deteriorated.

The intrinsic viscosity [η] and the polymerization ratio in each of these steps can be arbitrarily adjusted within the above range, but it is preferable that the final product has an intrinsic viscosity of 1 to 5.

The above-mentioned three or more polymerization steps may be carried out in any order, or (H) step and (L) step may be carried out in parallel, and then the reaction mixture containing the polymer in each step. It is also possible to carry out the step (M) by mixing. However, when adjusting the molecular weight with hydrogen concentration, if the hydrogen concentration in the previous stage is higher than in the latter stage,
It is necessary to provide a hydrogen purge step between both stages.

Polymerization of ethylene or copolymerization of ethylene and α-olefin is performed in the liquid phase or the gas phase in the presence or absence of an inert solvent. The liquid phase polymerization is preferably performed by slurry polymerization.

The polymerization temperature in the present invention may be any temperature below the melting point of the polymer, but a temperature range of 40 to 100 ° C. is particularly preferable. Reaction pressure is atmospheric pressure to 100 kg / cm ² , especially atmospheric pressure to 5
The range of 0 kg / cm ² is preferred.

In the polymerization, in order to adjust the intrinsic viscosity [η] of the polymer, it is generally done by a molecular weight modifier (for example, hydrogen), but when producing a polymer having a large intrinsic viscosity [η],
It can also be carried out in the substantial absence of molecular weight regulators. In this case, the molecular weight can be adjusted by changing the polymerization temperature.

As the inert solvent that can be used for the polymerization in the liquid phase polymerization, any of those commonly used in the art can be used, but in particular, an alkane having 4 to 20 carbon atoms, Cycloalkanes such as isobutane, pentane, hexane, heptane, cyclohexane are suitable.

The polyethylene obtained as described above has improved melt tension and die swell by itself, but it is not yet sufficient. Also,
On the other hand, improving the die swell has a drawback that the shear rate dependence of the die swell becomes large.

This modification of polyethylene is carried out by bringing the polyethylene powder obtained by the polymerization method of the present invention into contact with a radical generator. As one of the concrete methods,
When strict and uniform quality is required for reforming, the method disclosed in JP-A-59-68350 by the inventors of the present invention is suitable.

That is, by infiltrating a raw material polyethylene powder with a solvent, adding and mixing a liquid radical agent, and drying,
It is carried out by obtaining a polyethylene powder that uniformly contains a radical generating agent and heat-treating at a temperature not lower than the decomposition temperature of the radical generating agent. According to this method, the radical generator is evenly attached even within the pores of the polyethylene powder,
The modified polyethylene thus obtained does not generate gel or fish eyes during film formation.

Further, in the case of not requiring such a strict and uniform quality at the time of modification, a method of impregnating a polymer with a liquid radical generator and adding it as a so-called masterbatch to make contact,
The method of impregnating the radical generating agent with the radical generating agent in advance and adding it to the stabilizer to bring them into contact is not particularly limited.

The radical generator used in the present invention is preferably an organic peroxide such as hydroperoxides, dialkyl peroxides, peroxyesters,
Among them, those having a decomposition temperature of 150 ° C. or higher that gives a one-minute half-life are preferable. Particularly preferred examples include dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5-, which belongs to dialkyl peroxides. Examples include di (t-butylperoxy) hexane and α, α′-bis (t-butylperoxyisopropyl) benzene.

The amount of the radical generator added is preferably in the range of 5 to 1000 ppm with respect to the polyethylene powder. If the added amount is 5 ppm or less, the results of polyethylene modification will not be noticeable.
Further, when the addition amount is 1000 ppm or more, the reforming reaction proceeds excessively, and therefore polyethylene deteriorates the quality of the molded product.

When it is necessary to dry the polyethylene powder to which the radical generator has been added and mixed, raising the temperature promotes decomposition of the radical generator, and also causes adverse effects such as melting and agglomeration of the polyethylene powder. It is preferred to operate at a temperature of at least 120 ° C or lower.

On the other hand, it can also be modified by a method of using air or oxygen as a radical generator and bringing it into contact with polyethylene powder and heat treatment.

As the heat treatment method, it is sufficient to simply pass through a commonly used extruder for pelletizing polyethylene powder. 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 powder as the reaction mixture, for example, 150 to 350 ° C.
Normal extruder operating temperature ranges of the order of magnitude may be used.

[Effect of the present invention]

According to the present invention, a technique for producing polyethylene in at least three specified polymerization steps using a Ziegler-type catalyst modified to produce a polymer having high activity and a specific range of molecular weight distribution The first is to improve the viscoelastic property of the molten polymer by using the technique of modifying with a radical generator and to produce polyethylene having high compatibility by blow molding and extrusion molding.

That is, by increasing the melt tension, the drawdown of the parison and the phenomenon that the parison is cut off from the die due to its own weight in the hollow molding can be greatly improved, and a larger product can be molded. Further, in the film formation by inflation, the stability of bubbles is improved. On the other hand, the die swell is also greatly improved, and a thick parison can be obtained without using a die having a large diameter, and a product having a constant wall thickness can be easily obtained.

The second effect of the present invention is that the radical generator can significantly reduce the dependency of the die swell on the shear rate. Although the polyethylene obtained by the multi-step polymerization method containing a polymer having a remarkably large molecular weight has an improved die swell, the shear rate dependence of the die swell becomes remarkably large, and when the shear rate on molding is changed, the die swell also increases. Change. The present invention greatly improves this drawback.

The third effect of the present invention is not particularly required to significantly improve the viscoelastic properties such as die swell by producing a polymer having a remarkably large molecular weight as shown in the prior art upon polymerization. This is because the melt tension and die swell can be sufficiently improved by the subsequent modification with the radical generator. That is, according to the present invention, it is not necessary to remarkably increase the molecular weight of the high molecular weight polymer, and therefore it is possible to increase the ratio of the high molecular weight polymer. This improves the balance of the proportions of the components, which makes it possible to produce homogeneous polymers.

The fourth effect of the present invention is to obtain polyethylene having a wide molecular weight distribution and good processability.

The fifth effect of the present invention is that since the yield of the polymer obtained per catalyst component is high by using a highly active catalyst, it is not necessary to take a special means from the polymer to remove the catalyst residue, In addition, problems such as deterioration and coloring of the polymer during molding can be avoided.

〔Example〕

Hereinafter, the present invention will be shown by examples, but the present invention is not limited to these examples.

The properties of 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: high load melt index according to ASTM D-1238 condition F (H
LMI) to MI ratio HLMI / MI _{0 As} one measure of the molecular weight distribution, the larger this value is, the wider the molecular weight distribution is.

Density: True density according to JIS K-6760 Melt tension: Using a melt tension tester (manufactured by Toyo Seiki Co., Ltd.), with a nozzle diameter of 2.095 mm and an orifice of 8 mm, a polymer at 190 ° C. and a descending speed of 10 mm / min. Tension when extruding and winding into a monofilament form Die swell: Die swell (SR-I) and shear rate 50 sec measured at 190 ° C. under a shear rate of 15 sec ⁻¹ using the above melt tension tester and orifice. ^-1 Die swell (SR-II) measured under the condition of ^-1 Dependence of die swell on shear rate (K): value calculated by the following formula: K = (SR-II-SR-I) / log (50 / 15) w / n = value measured by GPC (150C type manufactured by Waters Co.) with o-dichlorobenzene as a solvent at a temperature of 140 ° C [Example] Example 1a) [Production of solid catalyst component] Stirrer 1000 ml container with Under a nitrogen atmosphere score, metallic magnesium powder 4.9g of (0.20 mol) of titanium tetrabutoxide 27.2 g (0.08 mol) was added, the temperature was raised to 80 ° C., n-butanol 15, further dissolved iodine 0.25 g.
6g (0.21mol) and 12.6g (0.21mo) of i-propanol
The mixture of l) was added dropwise over 2 hours and then heated to 120 ° C. for reaction. To the reaction product thus obtained, 340 ml of hexane was added at room temperature, and then the mixture was stirred at 70 ° C. for 1 hour. To this solution, 220 ml (0.4 mol) of a 30 wt% diethylaluminum chloride hexane solution was added at 45 ° C over 2 hours, and the mixture was stirred at 60 ° C for 1 hour. Next, 24.0 g (0.4 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., 408 ml of a 50 wt% hexane solution of i-butylaluminum dichloride was added over 2 hours. After adding all, stirring was carried out at 70 ° C. for 1 hour. Hexane was added to the product, and the product was washed 15 times by the 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, the sample was dried under a nitrogen atmosphere, and elemental analysis revealed that Ti was 9.0% by weight.

b) [Evaluation of molecular weight distribution of catalyst] When the single polymerization was carried out under the same polymerization conditions as in the step (M) shown in the following item c), [η] of the produced polyethylene was
It was 1.9, and w / n was 9.0, which was a relatively wide molecular weight distribution.

c) [Polymerization] A stirring reactor having an internal capacity of 10 was charged with 6 n-hexanes, the internal temperature was adjusted to 65 ° C., and then 0.87 g (4.4 mmol) of triisobutylaluminum and the solid catalyst obtained in the above a) were added. 11
5 mg was added. After adjusting the internal pressure of the reactor to 1 kg / cm ² with nitrogen gas, ethylene was introduced to start polymerization and 8 g of 1-butene was introduced, and further ethylene was continuously added so that the total pressure was 2.6 kg / cm ^2. Was added and polymerized for 20 minutes ((H) step). Next, the gas phase was replaced with nitrogen and the internal temperature was adjusted to 85
℃, adjust the internal pressure to 1kg / cm ² , hydrogen partial pressure 12.8kg / cm
After adding ² , the polymerization was started by introducing ethylene and at the same time, 3.6 g of 1-butene was introduced and ethylene was continuously added so that the total pressure was 17.0 kg / cm ² and polymerization was carried out for 58 minutes ((L)). Process). The gas phase was replaced with nitrogen again, the internal temperature was 80 ° C, and the internal pressure was 1k.
After adjusting to g / cm ² and adding hydrogen partial pressure of 1.5 kg / cm ² ,
Introduce ethylene to start the polymerization and at the same time to 1-butene
After introducing 48 g, ethylene was continuously added so that the total pressure would be 7.0 kg / cm ^2, and polymerization was performed for 51 minutes ((M) step).

The supply ratios of ethylene in the steps (H), (L) and (M) were 18%, 43% and 39%, respectively. About half of the polyethylene powder slurry thus obtained was discharged, filtered and dried to obtain 950 g of polyethylene powder (Comparative Example 1).

On the other hand, 31.5 mg of α, α′-bis (t-butylperoxyisopropyl) benzene as a radical generator was supplied to the polyethylene powder slurry remaining in the reactor and stirred for 15 minutes. Then, the contents were taken out and dried at a temperature of 90 ° C. in a batch-type ventilation dryer to obtain 1050 g of polyethylene powder in contact with the radical generator. The content of the radical generator was 30 ppm. The catalyst efficiency in this polymerization is 17400 g /
g It is a solid catalyst, and the bulk density of the polymer is 0.38 g / cm ³
Met. The [η] of the polymer extracted in a small amount at the end of the polymerization in the (H) step is 9.9, and the [η] of the polymer extracted in a small amount at the end of the polymerization in the (L) step is 3.4, and the [η] of the final product is From 2.8, it can be seen that the [η] of the polymer produced in the step (L) is 0.7, and the [η] of the polymer produced in the step (M) is 1.9. Also,
The α-olefin content in the polymer produced in each step was 0.6% by weight in the (H) step, and the 1- ▲ C ⁼ ₄ ▼ charge and the ethylene partial pressure in the (L) step and the (M) step. It is estimated that they are 0.9% by weight and 0.4% by weight, respectively. To this polyethylene powder, 700 ppm of Irganox B220 (manufactured by Ciba Geigy) was added as a stabilizer, and pelletized at a resin temperature of 200 ° C. with an extruder having a screw diameter of 25 mmφ to complete the modification. The physical properties of the modified polyethylene are as follows. The MI was 0.026 g / 10 min, the N value was 250, the density was 0.947, and the melt tension was 31 g, which was significantly higher than those of Comparative Example 1 (unmodified polyethylene) and Comparative Example 2 (two-step polymerization). Also, the die swell is 3.08 as SR-I.
The SR-II was as large as 3.40, and the dependency of the die swell on the shear rate: K was 0.61, which was significantly smaller than the result of Comparative Example 1.

Furthermore, when it was formed into an inflation film by an extruder with a screw diameter of 25 mmφ, it was shown that the fish eye of 0.2 mm or more was 600 polymers / m ² and it was a uniform polymer.

Comparative Example 1 (Unmodified Polyethylene) In the same manner as in Example 1, a stabilizer was added to the polyethylene powder containing no radical generator obtained by the polymerization of Example 1 to form a pellet. The physical properties of this unmodified polyethylene are as follows. MI is 0.038g / 10min, N value is 22.5, and density is 0.9.
It was 47 g / cm ³ , and the melt tension was 22.9 g, which was higher than that of Comparative Example 2, but was insufficient. The die swell was 2.74 for SR-I and 3.42 for SR-II, and the dependency of the die swell on the shear rate: K was 1.30, which was extremely large.

Comparative Example 2 (two-stage polymerization) The same reactor as in Example 1 was charged with 6 n-hexanes,
After adjusting the internal temperature to 85 ℃, triisobutylaluminum
0.87 g (4.4 mmol) and 95 mg of the solid catalyst obtained in Example 1 were added. After adjusting the reactor internal pressure by nitrogen gas to 1 kg / cm ² and further adding hydrogen partial pressure 12.8 kg / cm ² , ethylene was introduced to start polymerization and 1-butene 20 g was introduced,
Add ethylene continuously so that the total pressure is 17 kg / cm ^2.
Polymerization was carried out for 65 minutes ((L) step). Subsequently 80 ° C. was the temperature replacing gas phase with nitrogen, after the addition of a 1 kg / cm ² adjusted further hydrogen partial pressure 0.2 kg / cm ² in pressure, as well as initiate the polymerization ethylene was introduced 1 -Introduced 32g of butene, total pressure is 4.2kg
Ethylene was continuously added so as to be / cm ² and polymerization was performed for 45 minutes ((M) step). Next, the same radical generator as in Example 1 was added, and in the same manner as in Example 1, 1800 g of polyethylene powder in contact with the radical generator was obtained. The content of the radical generator was 30 ppm. This polyethylene powder was pelletized and modified. Of this modified polyethylene
The MI was 0.025 g / 10 min, the N value was 244, the density was 0.950 g / cm ³ , and the melt tension was 21.3 g, which is lower than in Example 1, and the die swell was 2.25 as SR-I and 2.54 as SR-II. And the dependence of die swell on shear rate: K is 0.55
Met.

Examples 2 to 7 Polyethylene was produced in the same manner as in Example 1 except that the reaction conditions were variously changed using the catalyst prepared in Example 1a). The reaction conditions are shown in Table 1. In Example 5, 1-hexene was used as the α-olefin, and in Example 6, 1-octene was used. In Example 7, the polymerization order was changed to (L)
Polymerization was carried out as step → (M) step → (H) step.
In the same manner as in Example 1, the polyethylene powders obtained by these polymerizations were modified by adding the same type of radical generator. The results of this modified polyethylene are shown in Table 2.

Comparative Example 3 (Unmodified Polyethylene) Without modifying the polyethylene obtained in Example 3,
Pelletized.

Comparative Example 4 (Unmodified Polyethylene) Without modifying the polyethylene obtained in Example 4,
Pelletized.

Comparative Example 5 (two-stage polymerization) Comparative Example 2 except that the hydrogen partial pressure in the (M) step was changed.
Two-step polymerization was carried out in the same manner as in. Table 1 shows the reaction conditions
Table 2 shows the physical properties of the modified polyethylene.

Example 8 Two stirring reactors having an internal capacity of 5 were used, and one reactor was charged with hexane 3, and 0.44 of triisobutylaluminum was added.
g (2.2 mmol) and 65 mg of the solid catalyst obtained in Example 1a) above
Was added. Then, under the same conditions as in step (H) of Example 3,
Polymerized for 40 minutes.

Hexane 3 was charged into the other reactor, and 0.44 g (2.2 mmol) of triisobutylaluminum and 100 mg of the solid catalyst obtained in the above Example 1a) were added. Then, (L) of Example 3
Polymerization was carried out for 55 minutes under the same conditions as the process.

The reaction mixture containing these polymers was pressure-fed through a connecting pipe to a stirring reactor having an internal volume of 10 to replace the gas phase portion with nitrogen, and then under the same conditions as in the step (M) of Example 3 for 35 minutes. Polymerized.

The ratios and intrinsic viscosities of the polymers produced in each step are shown in Table 1. The physical properties of polyethylene modified in the same manner as in Example 1 are shown in Table 2.

Comparative Example 6 a) [Catalyst production] 3.7 g (0.15 mol) of magnesium metal powder and Ti (O-n) were placed in a 1000 ml flask equipped with a stirrer under a nitrogen atmosphere.
-C ₄ H ₉ ) ₄ 102 g (0.3 mol) was added, the temperature was raised to 80 ° C, and 1.8 g of n-butanol 23.7 g (0.3 mol) was dissolved.
(2 mol) was added dropwise over 1 hour, and then heated to 120 ° C. for reaction. To the reaction product thus obtained, 400 ml of hexane was added at room temperature, and then 95.8 g (0.75 mol) of Al (C ₂ H ₅ ) Cl ₂ diluted to 50 wt% with hexane was added dropwise at 45 ° C. for 2 hours. , A solid product was obtained. Hexane was added to this product, and the product was washed by a gradient method, that is, stirring, standing, and removal of the supernatant liquid repeatedly until chlorine ions were not detected in the supernatant liquid. The Ti content of this solid product was 17.8 wt%.

b) [Evaluation of molecular weight distribution of catalyst] When the single polymerization was carried out under the same conditions as the step (M) shown in the following item c), the polyethylene [η] produced was 2.0.
And w / n was 4.5, which was a narrower molecular weight distribution than the catalyst system used in Example-1.

c) [Polymerization] Polyethylene was produced in the same manner as in Example 1 except that the reaction conditions shown in Table 1 were variously changed using the catalyst obtained in the above a).

To the obtained polyethylene powder, in the same manner as in Example-1,
The same type of radical generator was added for modification. The results of this modified polyethylene are shown in Table-2.

As a result, the melt tension was remarkably small as compared with the results of Example 1 using the catalyst that yielded a polymer having a wide molecular weight distribution, and the effects shown in the present invention were not obtained.

Example 9 a) [Production of solid catalyst component] 21.3 g (0.2 mol) of diethoxymagnesium and 68 g (0.2 mol) of titanium tetrabutoxide were added to an autoclave having a stirrer and a capacity of 1.6 l, and heated to 120 ° C. Stir for 1 hour. Then 340 ml of hexane was added to obtain a solution. 50% isobutylaluminum dichloride at 45 ° C
186 g (1.2 mol) of hexane solution was added over 2 hours. After adding all, stirring was carried out at 60 ° C. for 1 hour. Hexane was added to the product and the product was washed 10 times by the gradient method. Thus,
A slurry of the solid catalyst component suspended in hexane was obtained. The Ti content of this solid catalyst component was 11.8% by weight.

b) [Evaluation of molecular weight distribution of catalyst] When the single polymerization was carried out under the same polymerization conditions as in the step (M) shown in the following item c), [η] of the produced polyethylene was
The molecular weight distribution was 1.8 and w / n was 7.9, which was a relatively wide molecular weight distribution.

c) [Polymerization] 6 l of hexane was charged into a stirring reactor having an inner volume of 10 l, the inner temperature was adjusted to 65 ° C, and then triisobutylaluminum 1.
0 g (5 mmol) and 110 mg of the solid catalyst obtained in a) above were added. After adjusting the internal pressure of the reactor to 1 kg / cm ² by nitrogen gas, ethylene was introduced to start the polymerization and 8 g of 1-butene was introduced, and the total pressure was continuously adjusted to 2.6 kg / cm ^2. Ethylene was added and polymerization was carried out for 20 minutes ((H) step). Next, replace the gas phase with nitrogen and set the internal temperature to 85 ° C and the internal pressure.
Was adjusted to 1 kg / cm ^2, further after the addition of hydrogen partial pressure 12.8 kg / cm ^2, so that the total pressure introducing 1-butene 3.6g starts the polymerization ethylene was introduced is 17 kg / cm ² Ethylene was continuously added to and polymerized for 60 minutes ((L) step). The gas phase was replaced with nitrogen again, the internal temperature was adjusted to 80 ° C, the internal pressure was adjusted to 1 kg / cm ² , and the hydrogen partial pressure was further added to 1.5 kg / cm ² , and then ethylene was introduced to bring the total pressure to 7.0 kg / cm 2. Ethylene was continuously added so as to be ² and polymerized for 50 minutes ((M) step).

The feed rates of ethylene in the steps (H), (L) and (M) were 19%, 41% and 40%, respectively.

Then, 60 mg of α, α′-bis (t-butylperoxyisopropyl) benzene as a radical generator was added to the reactor.
And was stirred for 15 minutes. The contents were extracted and dried at 90 ° C. in a batch-type ventilation dryer to obtain 2250 g of polyethylene powder in contact with the radical generator. The content of the radical generator was 27 ppm. The catalyst efficiency in this polymerization is 2050 g / g solid catalyst, and the bulk density of the polymer is 0.39 g.
It was / cm ³ . [Η] of the polymer extracted in a small amount at the end of the polymerization in the (H) step was 9.6, [η] of the polymer extracted in a small amount at the end of the polymerization in the (L) step was 3.4, and [η] of the final product was From 2.8, it can be seen that the [η] of the polymer produced in the step (L) is 0.5 and the [η] of the polymer produced in the step (M) is 1.8.

The content of α-olefin in the polymer produced in each step was 0.6% by weight in the step (H) (L)
In the process and (M) process, 0.9% by weight and 0.4% by weight, respectively, due to the relationship between the charged amount of 1-butene and the ethylene partial pressure.
It is estimated to be.

As a stabilizer to this polyethylene powder, Irganox
B220 (manufactured by Ciba-Geigy) was added at 700 ppm and the screw diameter
The reforming was completed by pelletizing at a resin temperature of 200 ° C. with a 25 mmφ extruder. The physical properties of the modified polyethylene are as follows. MI is 0.025g / 10min, N value is 250, and density is 0.948.
g / cm ³ , melt tension 31.1 g, die swell SR-I
Was 3.06, SR-II was 3.38, and dependence on shear rate: K was 0.61. Furthermore, screw diameter 25 mm
When the film was blown into an inflation film using a φ extruder, it showed that the number of fish eyes of 0.2 mm or more was 560 particles / m ² and the polymer was uniform.

Example 10 a) [Production of solid catalyst component] 19.0 g (0.2 mol) of anhydrous magnesium chloride and 47.6 g (0.14 mol) of titanium tetrabutoxide were added to an autoclave having a stirrer and a capacity of 1.6 l, and heated to 120 ° C. And stirred for 2 hours. Then, 300 ml of hexane was added to obtain a solution.
Subsequently, 305 g (1.2 mol) of a 50% hexane solution of ethylaluminum diglolide was added at 45 ° C over 2 hours. After adding all, stirring was carried out at 60 ° C. for 1 hour. Hexane was added to the product and the product was washed 10 times by the gradient method. Thus, a slurry of the solid catalyst component suspended in hexane was obtained. The Ti content of this solid catalyst component was 9.8% by weight.

b) [Evaluation of molecular weight distribution of catalyst] When the single polymerization was carried out under the same polymerization conditions as in the step (M) shown in the following item c), [η] of the produced polyethylene was
It was 1.9 and w / n was 8.4, which was a relatively wide molecular weight distribution.

c) [Polymerization] 6 l of hexane was charged into a stirring reactor having an inner volume of 10 l, the inner temperature was adjusted to 65 ° C, and then triisobutylaluminum 1.
0 g (5 mmol) and 100 mg of the solid catalyst obtained in a) above were added. After adjusting the internal pressure of the reactor to 1 kg / cm ² by nitrogen gas, ethylene was introduced to start the polymerization and 8 g of 1-butene was introduced, and the total pressure was continuously adjusted to 2.6 kg / cm ^2. Ethylene was added and polymerized for 15 minutes ((H) step). Next, replace the gas phase with nitrogen and set the internal temperature to 85 ° C and the internal pressure.
Was adjusted to 1 kg / cm ^2, further after the addition of hydrogen partial pressure 12.8 kg / cm ^2, so that the total pressure introducing 1-butene 3.6g starts the polymerization ethylene was introduced is 17 kg / cm ² Ethylene was continuously added to and polymerized for 60 minutes ((L) step). The gas phase was replaced with nitrogen again, the internal temperature was adjusted to 80 ° C, the internal pressure was adjusted to 1 kg / cm ² , and the hydrogen partial pressure was further added to 1.5 kg / cm ² , then ethylene was introduced and the total pressure was 7.0 kg / cm 2. Ethylene was continuously added so as to be ² and polymerized for 60 minutes ((M) step).

The supply ratios of ethylene in the steps (H), (L) and (M) were 15%, 42% and 43%, respectively.

Then, 60 ml of α, α'-bis (t-butylperoxyisopropyl) benzene as a radical generator in the reactor
And was stirred for 15 minutes. The contents were extracted and dried at 90 ° C. in a batch-type aeration dryer to obtain 2480 g of polyethylene powder in contact with the radical generator. The content of the radical generator was 24 ppm. The catalyst efficiency in this polymerization is 2480 g / g solid catalyst, and the bulk density of the polymer is 0.37 g.
It was / cm ³ . The [η] of the polymer extracted in a small amount at the end of the polymerization in the (H) step is 10.1, and the [η] of the polymer extracted in a small amount at the end of the polymerization in the (L) step is 3.2, and the [η] of the final product is From 2.6, it can be seen that the [η] of the polymer produced in the (L) step is 0.8, and the [η] of the polymer produced in the (M) step is 1.9.

The content of α-olefin in the polymer produced in each step was 0.6% by weight in the step (H) (L)
In the process and (M) process, 0.9 wt% and 0.4 wt% respectively from the relationship between the charged amount of 1-butene and the ethylene partial pressure.
It is estimated to be.

As a stabilizer to this polyethylene powder, Irganox
B220 (manufactured by Ciba-Geigy) was added at 700 ppm and the screw diameter
The reforming was completed by pelletizing at a resin temperature of 200 ° C. with a 25 mmφ extruder. The physical properties of the modified polyethylene are as follows. MI is 0.040g / 10min, N value is 235, and density is 0.949.
g / cm ³ , melt tension 25.4 g, die swell SR-I
Was 2.86, SR-II was 3.17, and dependence on shear rate: K was 0.59.

Example 11 a) [Manufacture of solid catalyst component] 5.0 g (0.2 mol) of magnesium metal powder and 27.3 g (0.05 mol) of tetrakis (2-ethylhexoxy) silane were placed in a flask having a volume of 1 l equipped with a stirrer, and iodine 0.2 was added. 35.0 g (0.47 mol) of n-butanol in which g was dissolved was added at 100 ° C. over 2 hours, and the mixture was stirred at 140 ° C. for 2 hours under a nitrogen blanket while eliminating generated hydrogen gas. Then decane 350
ml and 30 ml of a 30% by weight solution of diethylaluminum chloride were added to obtain a solution of a component having a CO-Mg bond. 4 g (0.02 mol) of titanium tetrachloride was added to this solution, and subsequently 25.4 g (0.1 mol) of a 50% hexane solution of ethylaluminum dichloride was added at 45 ° C. over 2 hours. After adding all, stirring was carried out at 60 ° C. for 1 hour. Hexane was added to the product and the product was washed 10 times by the gradient method. Thus, a slurry of the solid catalyst component suspended in hexane was obtained. The Ti content of this solid catalyst component was 2.7% by weight.

b) [Evaluation of molecular weight distribution of catalyst] When the single polymerization was carried out under the same polymerization conditions as in the step (M) shown in the following item c), [η] of the produced polyethylene was
It was 1.6 and w / n was 6.8, which was a relatively wide molecular weight distribution.

c) [Polymerization] 6 l of hexane was charged into a stirring reactor having an inner volume of 10 l, and the inner temperature was adjusted to 65 ° C.
87 g (4.4 mmol) and 100 mg of the solid catalyst obtained in a) above were added. After adjusting the reactor internal pressure to 1 kg / cm ² with nitrogen gas, ethylene was introduced to start the polymerization and
-Introducing 8 g of butene, further continuously adding ethylene so that the total pressure was 2.6 kg / cm ^2, and polymerizing for 15 minutes ((H)
Process). Subsequently 85 ° C. was the temperature replacing gas phase with nitrogen, to adjust the internal pressure to 1 kg / cm ^2, was further added hydrogen partial pressure 12.8 kg / cm ^2, as well as initiate the polymerization ethylene was introduced 1-
3.6 g of butene was introduced, ethylene was continuously added so that the total pressure was 17 kg / cm ^2, and polymerization was carried out for 60 minutes ((L) step). The gas phase was replaced with nitrogen again, the internal temperature was adjusted to 80 ° C, the internal pressure was adjusted to 1 kg / cm ² , and the hydrogen partial pressure was further added to 1.5 kg / cm ² , then ethylene was introduced and the total pressure was 7.0 kg / cm 2. Ethylene was continuously added so as to be ² and polymerized for 70 minutes ((M) step).

The supply ratios of ethylene in the steps (H), (L) and (M) were 17%, 44% and 39%, respectively.

Then, 60 mg of α, α′-bis (t-butylperoxyisopropyl) benzene as a radical generator was added to the reactor.
And was stirred for 15 minutes. The contents were taken out and dried at 90 ° C. in a batch-type ventilation dryer to obtain 1980 g of polyethylene powder in contact with the radical generator. The content of the radical generator was 30 ppm. The catalyst efficiency in this polymerization is 1980 g / g solid catalyst, and the bulk density of the polymer is 0.36 g.
It was / cm ³ . The [η] of the polymer extracted in a small amount at the end of the polymerization in the (H) step was 9.0, and the [η] of the polymer extracted in a small amount at the end of the polymerization in the (L) step was 2.9, and the [η] of the final product was From 2.4, it can be seen that the [η] of the polymer produced in the step (L) is 0.5, and the [η] of the polymer produced in the step (M) is 1.6.

The content of α-olefin in the polymer produced in each step was 0.6% by weight in the step (H) (L)
In the process and (M) process, 0.9 wt% and 0.4 wt% respectively from the relationship between the charged amount of 1-butene and the ethylene partial pressure.
It is estimated to be.

As a stabilizer to this polyethylene powder, Irganox
B220 (manufactured by Ciba-Geigy) was added at 700 ppm and the screw diameter
The reforming was completed by pelletizing at a resin temperature of 200 ° C. with a 25 mmφ extruder. The physical properties of the modified polyethylene are as follows. MI 0.055g / 10min, N value 210, density 0.951
g / cm ³ , melt tension is 22.8 g, and die swell is SR-I.
Was 2.79, SR-II was 3.10, and dependence on shear rate: K was 0.59.

[Brief description of drawings]

FIG. 1 is a flow chart showing the catalyst preparation process according to the present invention.

Continuation of the front page (56) Reference JP-A-59-227913 (JP, A) JP-A-57-141409 (JP, A) JP-A-54-70388 (JP, A) JP-B-59-10724 (JP) , B2)

Claims (2)

[Claims] 1. (i) At least one magnesium-containing reactant and at least one transition metal-containing reactant containing a titanium compound, wherein at least one of the reactants is C--O-- M (wherein M represents magnesium or a transition metal) selected to have a bond and the product obtained by reacting with (ii) at least one dialkylaluminum chloride or alkylaluminum dichloride The solid catalyst (A) obtained by reacting with and Ia, IIa, IIb, II of the periodic table
Polymerization of ethylene or copolymerization of ethylene with α-olefin in the presence of a Ziegler type catalyst consisting of an organometallic compound (B) of Group I b and IV b metal, intrinsic viscosity [η] 5-20, α-olefin A step of producing 2-40% by weight of the total polymerization amount of polyethylene having a content of 20% by weight or less (step (H)), an intrinsic viscosity [η] of 0.2-1.0, and an α-olefin content of 10% by weight or less. A step of producing a certain polyethylene in an amount of 20 to 70% by weight of the total polymerization amount (step (L)) and an intrinsic viscosity [η] of 1 to 5, and an α-olefin content of 20% by weight.
The following multi-steps comprising polyethylene (20 to 70% by weight based on the total polymerization amount) (step (M)) are carried out in any order as at least three polymerization steps, or steps (H) and (L ) Are carried out in parallel, and then the reaction mixture containing the polymer in each step is mixed (M), and the resulting polyethylene powder is contacted with a radical generator. A method for producing modified polyethylene. 2. As a catalyst, the molecular weight distribution w / in step (M)
The method for producing polyethylene according to claim 1, wherein a polyethylene for which n is in the range of 5 to 15 is used.