JP2629808B2 - Method for producing modified ethylene copolymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for modifying a copolymer of ethylene and α-olefin having a density of 0.945 g / cm ³ or less with a radical generator. More specifically, linear low-density polyethylene (LLDP) by copolymerization of specific ethylene and α-olefin
The present invention relates to a method for producing a homogeneous polyethylene resin having improved moldability and mechanical properties by uniformly mixing and reacting E) and a radical generator by a specific method.

[Prior art] LLDPE obtained by copolymerizing ethylene and an α-olefin having 3 or more carbon atoms in the presence of a Ziegler-type catalyst has higher heat resistance and tensile strength than low-density polyethylene (LDPE) obtained by a radical polymerization method. Excellent in various mechanical properties such as strength, rigidity and impact resistance. In particular, the characteristics can be exploited in molding fields such as film and hollow extrusion, and can be substituted for conventional LDPE. LLDPE is extremely advantageous in terms of production cost as compared with LDPE in terms of production cost and energy consumption, which are extremely low.

However, since LLDPE has a linear skeleton in the molecular structure, it has inferior flow characteristics, melt elasticity and melt tension as compared with LDPE which is said to have long chain branches. This means that in hollow molding, extrusion molding, film molding, etc., the consumption of motor current at the time of molding is large, and the appearance and dimensions of molded products are not uniform, and the commercial value is poor. Extremely disadvantageous. Techniques for chemically cross-linking polyethylene have been developed for a long time, and are used, for example, for covering electric wires and foaming molded products. However, these methods use a relatively large amount of a radical generator, and do not reshape a product once crosslinked. As a method of using a relatively small amount of a radical generator, for example,
52-82964 proposes a method for producing a tubular film by adding a radical generator to specific polyethylene. This method relates to a high density ethylene polymer, and this specific method involves directly blending a radical generator into polyethylene pellets or simply blending polyethylene pellets with a master patch pellet containing a radical generator. In such a method, quality variation and heterogeneity occur in the modified product. JP-B-62-42921 proposes a method of modifying a specific ethylene copolymer with a radical generator. In this method, a flammable solvent is used in order to alleviate the non-uniform reaction of the radical generator, and therefore there is a problem in terms of work safety or production cost, which is extremely disadvantageous industrially. Furthermore, the proposal is a partial modification technique which aims to alleviate the disadvantages of the copolymer before modification. Therefore, the product quality such as moldability and mechanical properties has not reached the range intended by the present inventors.

[Problems to be Solved by the Invention] The present inventors have studied the problems of heat resistance and mechanical properties of LLDPE, the flow properties of LLDPE, the problems of melt elasticity and melt tension, and the problem of products using radical generators. We worked hard to solve the problem of inhomogeneity and to obtain an ethylene copolymer with better mechanical properties and moldability.

[Means for Solving the Problems] As a result, the present invention has been completed by reacting a specific ethylene copolymer obtained by employing a specific process with a radical generator by a specific method. Was.

That is, the present invention relates to a copolymer of ethylene and α-olefin having a density of 0.945 g / cm ³ or less,
0.005% by weight or more and 1.0% by weight or less of a radical generator,
In producing the modified ethylene copolymer by reacting at a temperature not lower than the melting point of the copolymer and lower than the thermal decomposition temperature, (i) the step of polymerizing the copolymer of ethylene and α-olefin is a step of low molecular weight polymerization. Consisting of a high molecular weight polymerization step,
Powdery ethylene having an α-olefin content in the copolymer produced in the high molecular weight polymerization step which is equal to or more than the α-olefin content in the copolymer produced in the low molecular weight polymerization step;
A method for producing a modified ethylene copolymer, which comprises reacting an α-olefin copolymer with (ii) a radical generator previously dispersed in an inorganic filler as a radical generator.

[Effect] The copolymer of ethylene and α-olefin used in the present invention comprises a low molecular weight polymerization step and a high molecular weight polymerization step, and the copolymer formed in the high molecular weight polymerization step has a low α-olefin content. It is essential that the polymer is produced by at least a two-stage polymerization process in which the polymerization is carried out at a content of α-olefin or more in the molecular weight polymerization process. Preferably, in the presence of a Ziegler-type catalyst, the copolymer to be formed has an α-olefin content of 10% by weight or less and a melt index of 0.1 to 3%.
000 g / 10 minutes and a low molecular weight polymerization step in a pre-stage in which the polymerization amount is 10 to 70% by weight of the total polymerization amount, and an α-olefin content in the copolymer to be produced is in the pre-stage polymerization step. The high-molecular-weight polymerization at a later stage where the polymerization is performed so that the ratio of the α-olefin content generated in the above is not less than 20% by weight, the melt index is 0.001 to 50 g / 10 minutes, and the polymerization amount is 90 to 30% by weight of the total polymerization amount. A powder having a density of 0.945 g / cm ³ or less, which is produced by a gas phase polymerization method or a suspension polymerization method using at least two stages of polymerization steps, is used.

Regarding the production method using this two-stage polymerization process,
This is described in detail in JP-A-59-59704.

Ethylene copolymer is produced in one-stage polymerization process or produced by polymerizing and mixing polymers with different molecular weights in each polymerization vessel using two or more polymerization vessels to expand the molecular weight distribution In such a case, heat resistance, mechanical properties and work-forming are insufficient.

The starting ethylene copolymer powder used in the present invention needs to be an ethylene copolymer powder precipitated as a particulate solid by copolymerization of ethylene. As such an ethylene copolymer powder, an ethylene copolymer powder extracted as a particulate precipitate from a polymerization reactor in a polymerization step is suitably used. Once the ethylene copolymer powder has been melted, it is not suitable for use in the present invention unless it is extremely finely powdered. The particle size of the ethylene copolymer powder is not particularly limited, but usually the average particle size is 50μ or more.
3 mm.

If the copolymer is not in powder form, a gel or fish eye will frequently occur during hollow molding, extrusion molding or film molding, or a partial difference in product strength due to inhomogeneous modification will result in a radical generator. Instead, the quality of the product is impaired by the reforming. The reason is not clear, but the reason is that the raw ethylene copolymer powder has pores and the radical generator dispersed in the inorganic filler added next adheres to all of these pores. ,
This is presumably because the state of dispersion of the radical generator in the copolymer becomes uniform.

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. A particularly preferred example is dicumyl peroxide, which belongs to dialkyl peroxides, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5-. Di (t-butylperoxy) hexane, α, α′-bis (t-butylperoxyisopropyl) benzene and the like.

As the inorganic filler, any material may be used as long as it is not reactive with the radical generator. Usually, however, the oxidation of the Group I to IV metals of the periodic table added to the difference in the molding of thermoplastics such as polyethylene. Products, hydroxides, carbonates, sulfates and fatty acid salts. Among them, it is preferable to use an aliphatic salt of a metal of Groups I to IV, which is most frequently used as a lubricant.

Examples of the metals in Groups I to IV of the periodic table include sodium, magnesium, aluminum, silicon, calcium, zinc, barium, and titanium. Oxides of these metals,
Specific examples of hydroxides, carbonates, and sulfates include magnesium oxide, calcium oxide, zinc oxide, titanium oxide, alumina, silica, talc, kaolin, mica, diatomaceous earth, magnesium hydroxide, and calcium hydroxide. , Magnesium carbonate, calcium carbonate, barium carbonate, magnesium sulfate, calcium sulfate, barium sulfate, glass powder, zeolite and the like.

As the fatty acid salt, a fatty acid salt having 8 or more carbon atoms, preferably 8 to 24 carbon atoms is used.

Fatty acids having 8 or more carbon atoms include pelargonic acid, lauric acid, myristic acid, palmitic acid, stearic acid,
Oleic acid and the like can be mentioned. These fatty acid salts include, for example, zinc stearate, barium stearate,
Calcium stearate, aluminum stearate,
Magnesium stearate, calcium pelargonate,
Examples include calcium laurate, calcium myristate, calcium palmitate, calcium oleate and the like.

 A plurality of mixtures of these compounds are also suitably used.

As the shape of the inorganic filler, any commonly used shape can be used, but usually, a powder having an average particle size of 0.1 μm to 10 μm is used.

In the present invention, a radical generator previously dispersed in an inorganic filler is used.

As a method of dispersing the radical generator in the inorganic filler, a commonly used mixing method can be used, and the inorganic filler and the radical generator are sufficiently mixed with a stirrer such as a ribbon blender or a Henschel mixer.

If the radical generator is not dispersed in the inorganic filler in advance,
In particular, a gel or fish eye is generated, the homogeneity of the product quality is poor, and the modifying effect is insufficient.

The mixing ratio of the inorganic filler and the radical generator is 100 parts by weight or less, preferably 50 parts by weight or less based on 100 parts by weight of the inorganic filler. If the amount of the radical generator exceeds 100 parts by weight, the homogeneity of the product quality deteriorates. From an industrial standpoint, it is preferable that the inorganic filler in which the radical generator is dispersed retains fluidity as a powder to such an extent that handling in the process is not difficult. Since this situation varies depending on the types and amounts of the radical generator and the inorganic filler used, it is preferable to observe the state of mixing by a preliminary mixing test.

When handling is difficult due to extremely poor fluidity, the mixing ratio of the radical generator to the inorganic filler is reduced.

Next, the ethylene copolymer and the radical generator dispersed in the inorganic filler are mixed and reacted. As a method, a radical generator dispersed in an inorganic filler is added to an ethylene copolymer, and a mixture obtained by mixing with a ribbon blender, a Henschel mixer or the like is reacted by heating at a temperature equal to or higher than the decomposition temperature of the radical generator. . During this mixing, it is preferable to add an appropriate amount of a commonly used stabilizer for ethylene copolymer. For example, an addition amount of 100 times or less with respect to the radical generator is appropriate. Otherwise, the action of the radical generator may be inhibited, and good reforming results may not be obtained.

In practicing the present invention, the type of radical generator and the properties of the ethylene copolymer used for renovation are considered, so that the crystallization temperature of the modified ethylene copolymer is 105 ° C. or higher. It is preferable to select the amount to be used appropriately.

However, as a condition to be implemented, the mixing ratio of the ethylene copolymer and the inorganic filler in which the radical generator is dispersed is usually 1.0% by weight based on the ethylene copolymer.
It is as follows. The ratio of the radical generator to the ethylene copolymer is selected to be 0.005% by weight or more and 1.0% by weight or less, preferably 0.01% by weight or more and 0.5% by weight.
If the used amount of the radical generator is less than 0.005% by weight, the modifying effect is insufficient, and if the used amount exceeds 1.0% by weight, there is a possibility that there is a problem in workability and product quality.

As a method of the above-mentioned heat treatment, since the ethylene copolymer powder and the radical generator are already uniformly and intimately mixed, no special means is required in order to achieve a uniform mixing, and only a general method is used. It is sufficient to pass through an extruder for pelletizing the polyethylene powder used. 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 ethylene copolymer powder as the reaction mixture, and for example, a normal extruder operating temperature range of about 150 to 350 ° C. is used. I just need. It is preferable to carry out the heat treatment in an atmosphere having an oxygen concentration as low as possible, for example, an atmosphere with a nitrogen seal or the like, in order to prevent oxidation deterioration of the product.

[Effects of the Invention] According to the method of the present invention, after the desolvation step of the ethylene copolymer slurry employed in many industrial processes, or after the degassing step of the gas phase polymerized ethylene copolymer powder. Since the existing process can be performed almost as it is, a new device other than the device for dispersing the radical generator in the inorganic filler for carrying out the present invention,
With very little additional energy or effort, the present invention can be implemented very simply, easily and efficiently.

The modified ethylene copolymer obtained in the present invention has excellent moldability such as high melt tension and melt elasticity at the time of molding and a high discharge rate of an extruder. Further, the modified ethylene copolymer obtained in the present invention has extremely good heat resistance. Generally, LLDPE tends to have better heat resistance than LDPE, but the modified ethylene copolymer obtained in the present invention has much higher heat resistance. Therefore, it can be used in applications that require higher temperature conditions and can be a highly functional product, and thus has extremely high industrial value.

Further, the modified ethylene copolymer obtained in the present invention is excellent in mechanical properties such as impact strength, rigidity, and cracking stress against environment.

Further, because the modified ethylene copolymer has good modifying properties,
In film forming, it is possible to provide a good quality film with few gels and fish eyes, and in hollow forming, it is possible to provide a hollow molded product having a good surface texture.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, HLMI / MI is a high-load melt index (HLMI, according to ASTM D-1238 Condition F).
And the melt index (MI, according to ASTM D-1238 condition E), and the density was determined by measuring according to ASTM D-1505.

The melt tension was measured by measuring the reaction when the melted polymer was stretched at a constant speed. That is, using a melt tension measuring device manufactured by Toyo Seiki Seisaku-sho, resin temperature 190 ° C, extrusion speed 10mm / min, winding speed 11m / min, nozzle diameter 2.0
The test was performed under the conditions of 9 mmφ and a nozzle length of 8 mm.

Die swell uses the same equipment as melt tension, resin temperature 19
The cooled diameter of the melt extruded to 10 cm at 0 ° C and an extrusion speed of 10 mm / min was measured (die swell has a nozzle diameter of 2.
90 mmΦ).

The crystallization temperature (Tc) and melting temperature (Tm) of the copolymer were measured as follows. That is, Seiko Electronic Industry Co., Ltd.
Using a DSC-200 type differential scanning calorimeter, 10 mg of the sample was placed in a sample container, heated and melted at 200 ° C. for 10 minutes, cooled at a rate of 10 ° C./minute, and the exothermic peak (Tc) was recorded.

Example 1 to 3 (a) with capacity 1 flask of catalyst preparation stirrer, metallic magnesium 2.0g and _{Ti- (O-nC 4 H 9} ) 4 56g was added, 80 ° C.
While stirring and heating, the n-
12.5 g of butanol was added dropwise over 1 hour. Then 140 ° C
, And the mixture was maintained for 2 hours. Then, 23 g of diphenyldiethoxysilane was added, and the mixture was maintained for 2 hours. The reaction product thus obtained was cooled to 60 ° C. and diluted with 150 ml of hexane. Then at 45 ° C 50 ml of ethylaluminum dichloride
After adding 365 ml of a 3% hexane solution over 2 hours,
Aged for 0 minutes. Subsequently, the product was washed with hexane until no chloride ion was detected in the supernatant to obtain a solid catalyst.

(B) Polymerization (b-1) Pre-stage polymerization A polymerization reactor equipped with a stirrer having an internal volume of 200 was sufficiently replaced with nitrogen, 1-hexene 100 was charged, and 1.3 g of the solid catalyst and 20 g of triisobutylaluminum were further added. Supplied. The temperature was set to 65 ° C and the internal pressure of the polymerization reactor was set to 1.0 kg / cm ²
After adjusting the pressure to 6.0 kg / cm ² , ethylene was continuously supplied so that the total pressure became 17.0 kg / cm ^2.
Polymerized for 35 minutes. A part of the produced copolymer was collected, and the 1-hexene content was measured by an infrared absorption spectrum. As a result, the content was 2.4% by weight, and the MI was 2.0 g / 10 minutes.

(B-2) Post-stage polymerization After the pre-stage polymerization, the gas phase was replaced with nitrogen, the temperature was again raised to 65 ° C., and a hydrogen partial pressure of 2.0 kg / cm ² was charged.
Ethylene was continuously supplied so as to obtain m ^2, and polymerization was carried out for 60 minutes so that the polymerization amount ratio between the former stage and the latter stage became equal. As a result, 16.8 kg of a polymer was obtained. MI of copolymer
Was 0.95 g / 10 min, HLMI / MI was 30, density was 0.921 g / cm ³ .
The 1-hexene content of this copolymer was 7.2% by weight.
It is estimated that the 1-hexene content of the copolymer formed in the post-stage polymerization was 12% by weight.

(C) Dispersion of Radical Generator in Inorganic Filler 4.0 g of calcium stearate as an inorganic filler and 0.4 g of dicumyl peroxide as a radical generator in Example 1, 1.0 g in Example 2, and 1.0 g in Example 2. Then
1.6g is weighed and a small mixer (SK-M2 manufactured by Kyoritsu Riko Co., Ltd.)
Mold). Next, stirring by an intermittent operation is performed,
Mixed.

Stirring was performed for 10 minutes by intermittent operation of stirring for 5 seconds and stopping for 10 seconds in order to prevent mutual adhesion of contents due to frictional heat of stirring.

(D) Modification In Examples 1 to 3, 2 kg of the copolymer powder obtained above was used, and tetrakis [methylene-3 (3,5-di-t-butyl-4-hydroxyphenyl) was used as a stabilizer. Propionate] methane 0.6 g (300 ppm) and tris (2,4-di-t-butylphenyl) phosphite, 1.0 g
g (500 ppm) and 2,6-di-t-butyl-p-gresol 1.
0 g (500 ppm) and the radical generator homogeneously dispersed in the calcium stearate were added, and dry-blended with a Henschel mixer. Then the screw diameter
The reforming was completed when pelletizing at an extrusion temperature of 200 ° C. using a 25 mm extruder.

This modified polyethylene pellet was used in each of the examples.
A film having a thickness of 30 μm and a blow ratio of 1.5 was formed and evaluated using an inflation film forming machine having a screw diameter of 25 mm using 800 g.

Further, the melt tension and die swell of the modified polyethylene pellet were measured. These results are shown in Table 1.

In the evaluation, fish eyes (FE) were visually evaluated as "small", "medium",
"Many".

As for film forming properties, bubble stability (bubble swing and degree of strain) was evaluated.

Comparative Examples 1 to 3 Example 2 was repeated using 2 kg of the copolymer powder obtained in Example 1.
Pelletization was performed in the same manner as described above. However, in Comparative Example 1, no radical generator was used, and in Comparative Example 2, dicumyl peroxide 0.04 g was added to calcium stearate 4.0 g.
In Comparative Example 3, 1.0 g of dicumyl peroxide was added directly without dispersing in calcium stearate, and each was modified.

Using the same method as in Example 1, the obtained copolymer pellets were subjected to film forming evaluation, and melt tension and die swell were measured. As shown in Table 1, the results were unsatisfactory as compared with Example 1.

Comparative Example 4 Using the copolymer powder obtained in Example 1, pellets were added by adding only the same stabilizer as in Example, and then dicumyl peroxide (equivalent to 200 ppm) dispersed in calcium stearate was added. Modification was performed by adding and pelletizing.

The obtained copolymer pellets were evaluated in the same manner as in Example 1. As shown in Table 1, the results were unsatisfactory as compared with Example 1.

Comparative Example 5 Using the solid solvent component prepared in Example 1, a copolymer powder was obtained in only one polymerization step.

That is, the inside of a stainless steel electromagnetic stirring reactor having an internal volume of 10 was sufficiently replaced with nitrogen, 1-hexene 5 was charged, and 168 mg of a solid catalyst component and 1.2 g of triisobutylaluminum were supplied. After adjusting the temperature to 65 ° C and adjusting the internal pressure of the autoclave to 1.0 kg / cm ² , the hydrogen partial pressure was 4.5 kg.
/ cm ^2, and then ethylene was continuously supplied so that the total pressure became 12.5 kg / cm ^2, and polymerization was carried out for 120 minutes. The obtained copolymer was 1.57 kg, its MI was 1.4 g / 10 min, HLMI / MI was 27, and density was 0.924 g / cm ³ .

This copolymer was pelletized in the same manner as in Example 1 after adding a stabilizer and dicumyl peroxide dispersed in calcium stearate, and then evaluated. As shown in Table 1, the results were inferior to those of the examples because of the single-stage polymerization step.

Comparative Example 6 Using 0.5 g of the solid catalyst component prepared in Example 1, in the pre-stage polymerization, the hydrogen partial pressure was 6.0 kg / cm ² , the total pressure was 12.0 kg / cm ^{2, the} polymerization time was 60 minutes, and In stage polymerization, the hydrogen partial pressure is 2.
Copolymerization of ethylene and 1-hexene was carried out in the same manner as in Example 1 except that 5 kg / cm ² , the total pressure was 13.5 kg / cm ^2, and the polymerization time was 50 minutes.

As a result, a copolymer having an MI of 5.6 g / 10 min and a 1-hexene content of 11.3% by weight was obtained in the pre-stage polymerization, and after the end of the post-stage polymerization, the MI was 1.0 g / 10 min and the density was 1. 0.923g / cm
^{In 3} , a copolymer having a 1-hexene content of 6.8% by weight was obtained. Therefore, it is estimated that the 1-hexene content of the copolymer formed in the later stage was 2.3% by weight.

The pelletized and modified polyethylene was evaluated in the same manner as in Example 1 using the obtained copolymer powder. As shown in Table 1, the results were unsatisfactory as compared with the examples.

Comparative Example 7 Commercially available high-pressure LDPE, Petrocene 170 (Tosoh Corporation) having MI and density almost equal to the copolymer used in Example 1
Was modified by adding a stabilizer and dicumyl peroxide (equivalent to 500 ppm) dispersed in calcium stearate in the same manner as in Example 1. As a result, the crystallization temperature (Tc) was 98 ° C., and the heat resistance was low.

Example 4 (a) Polymerization Using the solid catalyst component prepared in Example 1, a copolymer powder was obtained using 1-butene as an α-olefin.

That is, the same polymerization reactor as in Example 1 was sufficiently replaced with nitrogen, hexane 100 was charged, and 1.1 g of a solid catalyst component and 20 g of triisobutylaluminum were supplied. After the temperature was adjusted to the polymerization reactor internal pressure and 65 ° C. to 1.0 kg / cm ^2,
1-Butene 5 and a hydrogen partial pressure of 6.5 kg / cm ² were charged, and then ethylene was continuously supplied so that the total pressure became 12.5 kg / cm ^2, and polymerization was carried out for 90 minutes. A part of the produced copolymer was sampled, and the 1-butene content was measured. As a result, it was 2.0% by weight, and the MI was 7.0 g / 10 minutes.

Next, the gas phase in the polymerization reactor was replaced with nitrogen, and the temperature was again raised to 65 ° C., 1-butene 25 and a hydrogen partial pressure of 0.5 kg / cm ² were charged, and then the total pressure was 6.5 kg / cm ² . As a result, ethylene was continuously supplied, and polymerization was carried out for 50 minutes so that the polymerization amount ratio of the former stage and the latter stage became equal. As a result, 11.3 kg of a copolymer was obtained. MI of copolymer is 2.8g / 10min, HLMI / MI
28, a density of 0.921 g / cm ^3. It is estimated that the 1-butene content of this copolymer was 8.8% by weight, and the 1-butene content of the copolymer produced at a later stage was 15.6% by weight.

(B) Modification In the same manner as in Example 1, a stabilizer and calcium stearate in which α, α′-bis (t-butylperoxydiisopropyl) benzene was dispersed in advance were added, and the mixture was uniformly dry-blended. . The amounts used were the same as in Example 1.

Next, pelletization and modification were performed in the same manner as in Example 1. This modified polyethylene was evaluated in the same manner as in Example 1. The results were good as shown in Table 3.

Comparative Example 8 The copolymer powder obtained in Example 4 was pelletized in the same manner as in Example 1. However, pelletization was performed without using α, α-bis (t-butylperoxydiisopropyl) benzene as a radical generator.

The obtained copolymer was evaluated in the same manner as in Example 1. As shown in Table 1, the results were unsatisfactory as compared with the examples.

Comparative Example 9 Using the solid catalyst component prepared in Example 1 and 1-butene as the α-olefin, the modified M of Example 4 was used.
Copolymer powders with I, HLMI / MI and density were obtained.

That is, the inside of a stainless steel electromagnetic stirring type reactor having an internal volume of 10 was sufficiently replaced with nitrogen, hexane 5 was charged, and 175 mg of a solid catalyst component and 1.2 g of triisobutylaluminum were supplied. After adjusting the temperature to 65 ° C. and adjusting the internal pressure of the autoclave to 1.0 kg / cm ² , 250 ml of 1-butene and a partial pressure of hydrogen of 6.5 kg / cm ² were charged, and then ethylene was added so that the total pressure became 12.5 kg / cm ^2. Was continuously fed and polymerized for 90 minutes. A part of the produced copolymer was sampled, and the 1-butene content was measured by an infrared absorption spectrum. As a result, the content was 2.0% by weight, and the MI was 7.1 g / 10 minutes.

Then, the gas phase was replaced with nitrogen, and again at 65 ° C for 1 hour.
- charged butene 1250ml and hydrogen partial pressure of 0.3 kg / cm ^2, followed by the total pressure is polymerized continuously fed to 50 minutes of ethylene such that 6.3 kg / cm ^2. As a result, 1.72 kg of a copolymer was obtained, MI was 0.9 kg / 10 minutes, HLMI / MI was 53, and density was 0.992 g / cm ³ .

This copolymer was pelletized in the same manner as in Example 1 except that only the stabilizer and calcium stearate were added. The obtained pellets were evaluated by the same method as in the example. As shown in Table 2, the results were inferior to example 4 in melt tension, die swell, and film forming property.

Examples 5 to 7 In the pre-stage polymerization using 1.5 g of the solid catalyst component prepared in Example 1, the hydrogen partial pressure was 8.0 kg / cm ² , the total pressure was 19 kg / cm ^{2, the} polymerization time was 40 minutes, and the post-stage was performed. In the polymerization, the hydrogen partial pressure was set to 2.5 kg /
Copolymerization of ethylene and 1-hexene was carried out in the same manner as in Example 1 except that cm ² , the total pressure was 8.5 kg / cm ^2, and the polymerization time was 60 minutes. As a result, 18.3 kg of a good powdery copolymer was obtained. MI of copolymer is 3.2g / 10min, or HLMI / MI
Was 26 and the density was 0.922 g / cm ² .

2 kg of this ethylene copolymer powder was homogeneously mixed with α, α'-bis (t-butylperoxydiisopropyl) benzene as a radical generator dispersed in calcium stearate as an inorganic filler in the same manner as in the example. It was pelletized and modified at 200 ° C. This modified polyethylene was evaluated in the same manner as in Example 1. The results were good as shown in Table 3.

Comparative Examples 10 to 12 The copolymer powder obtained in Example 5 was pelletized in the same manner as in Example 1. However, in Comparative Example 10, no radical generator was used, and in Comparative Examples 11 and 12, Table 3 was used.
The modification was performed using the radical generator described in (1). The obtained polyethylene pellets were evaluated in the same manner as in Example 1. The results were unsatisfactory as shown in Table 2.

Example 8 Silica as an inorganic filler (Fuji Davison Co., Ltd.)
And 0.49 g of α, α'-bis (t-butylperoxydiisopropyl) benzene as a radical generator were dispersed in 4.0 g of SYLOD 244) in the same manner as in (C) of Example 1, and dispersed in silica. A radical generator was obtained.

Then, 2 kg of the radical generator dispersed in the silica and the copolymer powder obtained in (B) of Example 1 were used,
Pelletization was performed in the same manner as in Example 1 (D).

When this modified ethylene copolymer was evaluated by the method of (D) in Example 1, MI was 0.30 g / 10 min, HLMI / MI65, density was 0.921.
g / cm ³ , Tc 108.2 ° C., melt tension 21.2 g, die swell 1.7 were obtained.
There were few fish eyes in the film.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-8740 (JP, A) JP-A-59-6241 (JP, A) JP-A-58-194904 (JP, A) JP-A-58-194904 71904 (JP, A) JP-A-57-38837 (JP, A)

Claims (4)

(57) [Claims] 1. A copolymer of ethylene and α-olefin having a density of 0.945 g / cm ³ or less and a radical generator of 0.005 to 1.0% by weight based on the copolymer. In producing a modified ethylene copolymer by reacting at a temperature not lower than the melting point of the above and below the thermal decomposition temperature, (i) a polymerization step of a copolymer of ethylene and an α-olefin comprises a low molecular weight polymerization step and a high molecular weight polymerization step Consisting of
Powdery ethylene having an α-olefin content in the copolymer produced in the high molecular weight polymerization step which is equal to or more than the α-olefin content in the copolymer produced in the low molecular weight polymerization step;
A method for producing a modified ethylene copolymer, comprising reacting an α-olefin copolymer with (ii) a radical generator previously dispersed in an inorganic filler as a radical generator. 2. The method according to claim 1, wherein the polymerization step comprises:
A low-molecular-weight polymerization step in a pre-stage in which the olefin content is 10% by weight or less, the melt index is 0.1 to 300 g / 10 minutes, and the polymerization amount is 10 to 70% by weight of the total polymerization amount;
The α-olefin content of the copolymer to be produced is at least 20% by weight of the α-olefin content ratio produced in the previous polymerization step, and the melt index is 0.001 to 50 g / 10.
Claims (1) to (4) wherein at least two stages of a high-molecular-weight polymerization step, which is a step of polymerizing so that the amount and the polymerization amount are 90 to 30% by weight of the total polymerization amount, are used. 1) The method according to the above. 3. A radical generator dispersed in an inorganic filler prepared by previously mixing a radical generator of 100 parts by weight or less with respect to 100 parts by weight of the inorganic filler. The method according to any of paragraphs (1) and (2). 4. The method according to claim 1, wherein the crystallization temperature of the copolymer of ethylene and α-olefin is 105 ° C. or higher. the method of.