JPH11116691A - Production of polyolefin hardly containing fisheye - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyolefin resin hardly containing fisheyes. SOLUTION: This method for producing a polyolefin hardly containing fisheyes comprises dividing a melt kneader into plural mixing regions, carrying out the melt kneading of the polyolefin at >=180 deg.C temperature in the first mixing region, then performing the melt kneading at a resin temperature below 180 deg.C in the mixing regions of the second mixing region or thereafter for a time of >=40% based on the total residence time of the resin in the melt kneader when conducting the melt kneading of the polyolefin with the melt kneader.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for eliminating fish eyes from a polyolefin produced by a continuous polymerization method. In particular, when granulating by melt-kneading,
The present invention relates to an improvement in a technique for producing a polypropylene block copolymer or a polypropylene block copolymer composition, in which a kneading apparatus controls a melting temperature and a kneading temperature of a resin.

[0002]

2. Description of the Related Art A fisheye of a polypropylene block copolymer used for impact resistance has been conventionally known as a factor of impairing the impact strength and appearance when it is formed into a film or a molded product. In order to control the fisheye, see, for example, Japanese Patent Application Laid-Open No. Sho 58-4971.
No. 6 and Japanese Patent Application Laid-Open No. 61-6982.
No. 1 discloses a method in which alcohols are used as a polymerization deactivator. However, with the recent development of catalyst development technology, the polymerization activity has been dramatically improved.As a result, the control of fish eyes is insufficient with the conventional classifier alone. Since the polymerization activity of the catalyst also decreases, it cannot be said that this is a very effective means from the viewpoint of productivity. Therefore, attempts have been made to reduce the fish eyes in the melt-kneading and granulating step. For example, Japanese Unexamined Patent Publication
No. 339920 discloses that the temperature of the molten resin during kneading is 230.
There has been proposed a method of reducing fish eyes by controlling the residence time at 20 ° C. or less to 20 seconds or more.

[0003]

However, although the fisheye of the polypropylene block copolymer shows a tendency to decrease in the above-mentioned proposed method, the effect of decreasing the fisheye is not sufficient, and the fisheye is more efficiently produced. There is a need for the development of improved techniques to reduce them.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies on the behavior of fish eyes of a polypropylene block copolymer in a melt-kneading apparatus, and found that the resin temperature in the melt-kneading section and the resin temperature in the kneading section were controlled. By
The present inventors have found that fish eyes in a polypropylene block copolymer can be significantly reduced, and have completed the present invention.

[0005] The gist of the present invention is that when melt-kneading a polyolefin using a melt-kneading apparatus, the melt-kneading apparatus is divided into a plurality of mixing zones, and the polyolefin is placed in a first mixing zone arranged sequentially from the polyolefin supply side. 180
Melt-kneading treatment at a resin temperature of not less than 180 ° C., and then, at a resin temperature of less than 180 ° C. in a mixing region below the second mixing region, and a time of 40% or more of the total residence time of the resin in the melt-kneading device And a kneading treatment.

Hereinafter, the present invention will be described in more detail. In the present invention, the present inventors studied the behavior of polyolefin fish eyes in the melt kneading apparatus,
The following findings were obtained.

[0007] 1. In the case of polyethylene, for example, in the case of high-density polyethylene, when ethylene is polymerized, an ultra-high-molecular-weight resin portion mixed in the polymer or an apparent ultra-high-molecular-weight resin portion called entanglement causes fisheye. In order to finish this high-density polyethylene resin as a finished resin (product), the non-uniform resin part is depolymerized so as to have the same physical properties as the uniform high-density polyethylene part occupying many parts, Alternatively, it is necessary to disentangle and disperse the entanglement.

This non-uniform portion which must be dispersed is generally present in the form of particles, but when a polymer is formed while containing the same, fish eyes (Fish E) are formed on the product.
ye) or aggregates called gels appear. Fisheye is so named because when it is formed into a thin film from high-density polyethylene, it remains like a fisheye. The size of the fish eye that adversely affects the physical properties of the product is generally a size of 50 μm or more, and the generation of the fish eye of this size or more significantly lowers the product quality. In the case of the above high-density polyethylene resin, it is known that fish eyes have exited from the polymerization stage, that is, exist from the beginning of the melt-kneading stage, which is different from the case of polypropylene described below. Fish eyes existing from the beginning have the property that the amount thereof is reduced by the melt-kneading operation.

[0009] 2. The polypropylene block copolymer contains an elastomer component composed of a copolymer of propylene and α-olefin, for example, EPR (ethylene / propylene copolymer rubber), and has a heterogeneous dispersion structure in which the EPR phase and the polypropylene phase coexist. doing. In other words, it has a structure in which an EPR phase having a size of several μm or less floats in a polypropylene phase which occupies most of the polymer, but is molded using a resin partially containing particles in which the EPR phase is largely solidified. In this case, for example, when a thin film is formed, a fish-eye-like form appears as in the case of high-density polyethylene. Thus, in the case of polypropylene as well, this non-uniform part is called fisheye or gel.

[0010] The fish eye of such an uneven portion is
It is the same as in the case of high-density polyethylene that the amount is reduced by the melt-kneading operation applied to the resin, but in the case of the polypropylene block copolymer,
Recent studies have shown that fish eyes have left the polymerization stage, ie, are not significantly present from the initial stages of the melt kneading operation. This is different from the case of high density polyethylene. When the powder of the polypropylene block copolymer supplied from the polymerization step is melted, fish eyes of EPR are observed. Conventionally, it was a general view that only the fish eyes of the EPR after melting were observed and it was presumed that the fish eyes existed from the stage of the powder raw material. Estimated the cause of this fish eye as follows. That is, since the polypropylene block copolymer is generally designed so that the molecular weight of an elastomer component, for example, EPR, is higher than that of polypropylene in order to impart its impact strength, the melt viscosity of EPR is higher. Since the melting point of polypropylene is about 165 ° C, the resin temperature is 16 ° C.
From the point where the temperature exceeds 5 ° C., the polypropylene phase having a low melt viscosity starts to flow (flow) through the gap between the EPR components. Even when the proportion of polypropylene is high (EPR content is low), EPR cannot keep up with the flow of polypropylene, and the EPR component is left behind and agglomerates, approaching a thermodynamically stable sphere, resulting in a large lump, This may cause the generation of fish eyes in EPR. The mechanism of this fish eye generation was confirmed from the examination results.

That is, as shown in the above 1 and 2, it can be seen that the mechanism of fisheye generation is different between high density polyethylene and polypropylene block copolymer. In the former, fish eyes are generated in the polymerization stage, and fish eyes are already present in the raw material immediately after the polymerization stage. Will come. Conventionally, it has been considered that the case of the polypropylene block copolymer is the same as the case of the high-density polyethylene, but it has been found that the case is different.

Hereinafter, the case (2) of the polypropylene block copolymer which generates fish eyes will be described in detail. In the conventional technology, even in the case of a polypropylene block copolymer, erasing fish eyes is simply by applying a shearing force to the melted resin and kneading, and dividing the fish eyes into smaller portions using the dispersion effect. ,
This problem has been dealt with only by the operation of reducing the particle size to below the limit fisheye particle size.

In the present invention, the following two items are required to reduce or eliminate the generation of fish eyes during melt-kneading of the polypropylene block copolymer based on the mechanism of fish eye generation of the polypropylene block copolymer described above. It is necessary to satisfy In other words, as a method of reducing or eliminating the generation of fish eyes during melt kneading, the number of fish eyes having a specified diameter or more should not be generated as much as possible when melt kneading a resin. Fish eyes that are unexpectedly generated during melt kneading are reduced or eliminated by effective means. It has been found that it is important to make these two methods coexist.

By using a technique that does not generate a large number of fish eyes, there is an effect that less energy is required for finishing the resin in the final form. The above can be controlled by melting and kneading the polypropylene block copolymer at a resin temperature (material temperature) of 180 ° C. or higher and in a short time. For the above, the molten resin obtained above is
It can be controlled by kneading at a resin temperature of less than 0 ° C. for a predetermined time.

According to the present invention, based on the above findings, when melt-kneading a polyolefin using a melt-kneading apparatus, the melt-kneading apparatus is divided into a plurality of mixing regions, and the first and second mixing sections are sequentially arranged from the polyolefin supply side. The polyolefin is melt-kneaded in the mixing zone at a resin temperature of 180 ° C. or higher, and then in the mixing zone below the second mixing zone at a resin temperature of less than 180 ° C. and the total residence time of the resin in the melt-kneading apparatus. And a kneading treatment over 40% or more of the above-mentioned process, thereby producing a method for producing a polyolefin with less fish eyes.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION As the polyolefin in the present invention, homopolypropylene, ethylene propylene random copolymer, propylene ethylene block copolymer,
Includes copolymers of propylene and α-olefins such as propylene butene-1 copolymer. Also included are blends based on these homopolymers and copolymers, polymer alloys, systems containing fillers, fiber reinforcements and additives. Especially in propylene ethylene copolymer,
The present invention is very effective in a high ethylene-containing copolymer and a system in which the molecular weight of the ethylene-propylene copolymer component in the copolymer is high and the molecular weight of the propylene homopolymer component is low. Furthermore, the effect of the present invention is remarkably exhibited when a polypropylene block copolymer such as a propylene ethylene block copolymer used for impact resistance is used.

The polypropylene block copolymer comprises 40 to 95% by weight of a matrix polypropylene portion and 5 to 60% by weight of an elastomer portion. The matrix polypropylene portion substantially comprises a propylene homopolymer, The elastomer portion is required to be composed of an ethylene / propylene random copolymer having an ethylene content of 30 to 70% by weight in order to secure required physical properties of the polymer. Such a polypropylene block copolymer is produced by a known method by block copolymerizing propylene and ethylene in the presence of a stereoregular catalyst in a continuous polymerization apparatus having two or more polymerization reactors. . For example, in the first step, propylene alone or propylene and ethylene are polymerized in a gas phase or a liquid phase, preferably in a gas phase to produce the matrix polypropylene portion, and in the second step, the propylene polymer is produced in the first step. In the presence of the polymer, propylene and ethylene are copolymerized in the gas phase to produce the above-mentioned elastomer portion.

The ethylene content in the polypropylene block copolymer is preferably 1.5 to 42% by weight from the viewpoints of impact resistance, paintability and surface gloss. Further, from the viewpoint of impact resistance, surface gloss, and moldability, the ratio of the weight average molecular weight Mw (λ = Mw (elastomer) / Mw (matrix)) of the elastomer portion and the matrix polypropylene portion is 1.0 to 10 And the melt flow rate (MFR) at 230 ° C. is preferably 0.5 to 100 (g / 10 min).

In the present invention, the polypropylene block copolymer powder to be melt-kneaded is a polymer powder of the above-described polypropylene block copolymer or a polypropylene blended with additives such as an antioxidant and a neutralizing agent. It may be a block copolymer composition powder. Specific additives include an antioxidant, an ultraviolet absorber, a light stabilizer, a lubricant, an antistatic agent, a colorant, a conductive agent, a dispersant, a printability-imparting agent, a molecular weight modifier, a crosslinking agent, and a crosslinking assistant. Filler, flame retardant, flame retardant auxiliary, foaming agent, processing aid, neutralizing agent, heavy metal deactivator, plasticizer, granulating agent and the like.

The melt-kneading apparatus used in the present invention is not particularly limited, and examples thereof include a single-screw extruder, a twin-screw co-rotating extruder, and a twin-screw different-direction rotating extruder. . As a specific example, as a single-screw extruder, a co-kneader manufactured by Buss Co., Ltd., as a twin-screw co-rotating extruder, a TEM series manufactured by Toshiba Machine Co., Ltd., a TEX series manufactured by Japan Steel Works, Ltd., Kobe Steel Co., Ltd. Manufacturing KT
X-series and other twin-screw bi-directional rotary extruders include Nippon Steel Corporation TEX series, CMP series, Co., Ltd.
Kobe Steel FCM series, NCM series, LC
M series and the like.

Hereinafter, a method for reducing or eliminating the number of fish eyes in a polypropylene block copolymer using a twin screw extruder will be described as an example of an embodiment of the present invention. In each screw piece (Screw piece) constituting the screw of the twin screw extruder, kneading,
Full flight scr (Flight flight scr
The screw piece that mainly controls kneading and dispersion, excluding the ew) portion, is referred to as a mixing piece. The mixing piece does not exist over the entire length of the screw of the twin-screw extruder, but rather works by a method in which several mixing pieces are continuously formed during a certain length. A part that continuously configures several mixing pieces is called a mixing zone.
It is common that a plurality of mixing zones exist on a set of screws. The first mixed area and the second mixed area are sequentially referred to from the hopper (Hopper) side. FIG.
The outline is shown below. In the figure, 1 is the first mixed region, 2, 3, 4
Are the second, third, and fourth mixing regions, 5 is a hopper, and 6 is a vent port.

In general, the first mixing zone plays a role of melting and kneading the solid resin (polypropylene block copolymer powder) supplied from the hopper. This operation causes fish eyes to appear from inside the resin. As a result of the examination, it has been found that the appearance of fish eyes can be controlled by the melt-kneading treatment in the first mixing region. On the other hand, in each of the mixing regions below the second mixing region, the molten resin is kneaded to apply an effective shearing force to the resin for the purpose of reducing the number of fish eyes. The latter is the same operation as the conventional purpose of reducing or eliminating the number of fish eyes, while the former is based on a completely new idea. In order to make the latter work more effectively, it is important to select the former mechanism and operating conditions. Hereinafter, the process for completing the present invention will be described in steps.

(1) The first arranged sequentially from the hopper side
A method and apparatus for controlling the generation of fish eyes in the mixed region and controlling the reduction or elimination of the number of fish eyes in the mixed region below the second mixed region. This method and apparatus are effective in reducing or eliminating the number of fish eyes in a fish-eye-generating type polymer material such as a polypropylene block copolymer with lower energy, which is effective. I understood that.

(2) The resin temperature is set to 180 ° C. in the first mixing region.
A method and an apparatus for reducing or eliminating the number of fish eyes, wherein the resin temperature is reduced to 180 ° C. or lower in a mixed region below the second mixed region. The experiment was performed using a twin screw extruder manufactured by Kobe Steel Ltd. In the experimental results, the remaining ratio of fish eyes was as follows.

[0025]

[Table 1]

The complete melting temperature of the polypropylene block copolymer is 166 ° C. From this result, it was found that it is necessary to completely melt the polypropylene block copolymer in the first mixing region where the resin is melted, in order to reduce or eliminate the number of fish eyes. At the same time, it was also found that if the unmelted resin was left at the outlet of the first mixing region and was poured into the mixing region below the second mixing region, the melting was delayed and the number of fish eyes was not easily reduced. And
It was also found that raising the resin temperature to 180 ° C. or more is effective for completely melting the entire resin in the first mixing region.

On the other hand, it is well known that a smaller resin viscosity difference between polypropylene and EPR is more effective in reducing or eliminating fish eyes in a completely melted resin. This is for facilitating transmission of the shearing force to the mating resin. In the case of a polypropylene block copolymer, 166 ° C. in a region above 166 ° C. where both resins are molten.
However, under the best conditions, the viscosity difference increases as the temperature increases. Therefore, 16 in the mixed region below the second mixed region.
It is desirable to keep the temperature at 6 ° C or higher and as low as possible,
It is important to reduce the resin temperature to at least 180 ° C. Thus, it was confirmed that fish eyes could be reduced or eliminated by completely melting the polypropylene block copolymer in the first mixed region.

(3) The resin temperature is set to 180 ° C. in the first mixing region.
It is as described in the above (2) that the resin temperature is lowered to 180 ° C. or lower in the mixing region below the second mixing region as described above. However, as a more preferable condition, the mixing below the second mixing region is limited. A method and an apparatus for reducing or eliminating fish eyes, characterized in that the resin temperature is set at around 166 ° C. in a region. Similarly, an experiment was performed using a twin-screw extruder manufactured by Kobe Steel Ltd. In the experimental results, the remaining ratio of fish eyes was as follows.

[0029]

[Table 2]

As described above, completely melting the polypropylene block copolymer in the first mixing region and keeping the resin temperature as low as possible above the melting point in the first mixing region reduces or eliminates fish eyes. . That is, in the present invention, as the conditions for the melt-kneading treatment in the first mixing region, the resin temperature is 180 ° C. or more, preferably 180 to 230 ° C.
° C, more preferably in the range of 180-210 ° C,
The residence time of the resin in the region is less than 60% of the total residence time, preferably 50% or less, in the range of 10 to 30 seconds. If the resin temperature is lower than 180 ° C., it is difficult to completely melt the resin (polypropylene block copolymer), and the generation of fish eyes is undesirably increased. On the other hand, if the residence time of the resin is longer than the above, fish eye generation increases, which is not preferable.

On the other hand, as the kneading treatment conditions in the second mixing region, the resin temperature is lower than 180 ° C., preferably 165 ° C. or higher.
Less than 80 ° C., and the residence time of the resin in the region is at least 40% of the total residence time, preferably at least 50%,
The range is 10 to 120 seconds. The resin temperature is 180 ° C
Above is undesirable because the effect of reducing fish eyes or erasing is small. If the residence time of the resin is shorter than the above, fish eyes are reduced or the erasing effect is reduced, which is not preferable.

(4) The ratio of the energy required to melt the resin from room temperature to the first mixing region and the energy required to reduce or eliminate fish eyes in the mixing region below the second mixing region is 1: 0.3. The following is a study of a method and apparatus for reducing or eliminating fish eyes to reduce total energy. (4) is added as a condition for limiting (1) to (3). The energy required to melt the resin from room temperature can be theoretically calculated from the value of the increase in enthalpy for raising the temperature of the resin from room temperature to the melting temperature and the latent heat required for melting. Therefore, this value is a heat value specific to the resin.

When (1) to (3) are used, the energy required for reducing or eliminating fish eyes in the mixed region below the second mixed region can be made extremely smaller than the former energy. How to lower the energy level in the latter half depends on reducing the energy required to obtain a product with a high level of molten quality. In the conventional fish eye reduction or erasing technique that generates many fish eyes when the resin is melted, a large amount of energy required for erasing fish eyes is required in a mixed region below the second mixed region, and their energy ratio is reduced by one. It could not be kept below 0.3.
According to the methods (1), (2) and (3), there is an effect that the energy of the latter can be suppressed to 30% or less of that of the former after achieving the target fisheye level.

(5) Examination of a method and an apparatus for achieving a technique for reducing the L / D of a mixing extruder to 18 or less. (5) is (1)
To (4).
Regarding the method (4) for reducing the total energy required for erasing fish eyes, the energy required for erasing fish eyes in the second mixing region can be reduced, so that the L / D of the kneading extruder is reduced to 18 or less. The cost could be reduced and the cost of the equipment improved.

[0035]

EXAMPLES The present invention will be described in more detail with reference to the following specific examples.
It is not limited by this. Evaluation of the physical properties of the propylene block copolymers (pellets) obtained in the examples and comparative examples is based on the following methods.

<Number of Fish Eyes> Using the obtained pellets as a raw material, a 30 mm single screw extruder (screw diameter 3
(0 mm), a film having a thickness of 35 μm is formed using a film forming machine having a T-shaped die at the tip, and scanning is performed using a GX40 automatic gel counting device manufactured by Dia Instruments Inc. so that the accumulated signal voltage becomes 600 mV. The period was adjusted, and the number of fish eyes having a diameter of 0.05 mm or more, which were observed per 250 cm ^{2 of} the film, was measured while passing the film at a film passing speed of 5 m / min.

<Preparation of Polypropylene Block Copolymer Powder> The polypropylene block copolymer powder used in Examples and Comparative Examples was prepared by polymerization and blending according to the following method. Preparation Example 1 Using a continuous process of polymerizing propylene in the first reactor and polymerizing the elastomer component in the second reactor, the polypropylene of the first stage and the elastomer component of the second stage were polymerized. The polypropylene block copolymer was polymerized so that the weight ratio became polypropylene: elastomer = 83: 17. At this time, the weight average molecular weight of each component was 200,000 for the polypropylene component and 5 for the elastomer component.
The polymerization was carried out so as to be 0,000, and finally the polymerization was carried out such that the MFR of the polypropylene block copolymer became 30 g / 10 minutes. Based on 100 parts by weight of the obtained polymerization powder, 0.05 parts by weight of Irganox 1010 manufactured by Ciba-Geigy as a phenolic antioxidant, and 0.05 parts by weight of Irgafos 168 manufactured by Ciba-Geigy as a phosphorus-based antioxidant. As a neutralizing agent, 0.05 parts by weight of calcium stearate manufactured by NOF Corporation was added, and the mixture was uniformly blended with a tumbler for 15 minutes to obtain a polypropylene block copolymer powder.

Example 1 <Molten Kneading and Granulation> The cylinder temperature of the polypropylene block copolymer powder obtained in Preparation Example 1 was first mixed using a twin screw extruder KTX-46 manufactured by Kobe Steel Ltd. The screw speed was adjusted so that the resin temperature in the region and the mixed region below the second mixed region was adjusted to the temperature shown in Table 3 and the residence time of the resin in the region was the condition shown in Table 3.
The resin composition was extruded at 0 rpm and a resin extrusion rate of 50 kg / hour to obtain a pellet-shaped resin composition. <Evaluation of Physical Properties> The number of fish eyes in the film was 463 as a result of measuring the number of fish eyes of the obtained pellets based on the physical property evaluation method described above.

COMPARATIVE EXAMPLE 1 In Example 1, the cylinder temperature was changed to the first mixed region and the second mixed region.
The same operation was performed except that the resin temperature in the mixed region below the mixed region was adjusted to the temperature shown in Table 3. As a result, as a result of evaluating the physical properties of the obtained pellet, the number of fish eyes in the film was 715.

Example 2 and Comparative Example 2 In Example 1, the cylinder temperature was changed to the first mixing region and the second mixing region.
The same procedure was performed except that the resin temperature in the mixed region below the mixed region was adjusted to the temperature shown in Table 3. Table 3 shows the results.

[0041]

[Table 3] * 1: Cylinder temperature set value in the first mixed area * 2: Cylinder temperature set value after the second mixed area

[0042]

According to the present invention, fish eyes in a polyolefin, particularly a polypropylene block copolymer, can be remarkably reduced with less energy by adjusting the resin temperature in the melt kneading apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an apparatus used for carrying out the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinji Hashizume 1-6-14 Edobori, Nishi-ku, Osaka Co., Ltd. Inside Kobe Steel Ltd. (72) Inventor Makoto Ichinomiya 1-6-14, Edobori, Nishi-ku, Osaka Co., Ltd. Inside Kobe Steel (72) Inventor Fumihisa Watanabe 1 Tohocho, Yokkaichi-shi, Mie Pref. Inside Yokkaichi Resin Technology Development Center, Mitsubishi Chemical Corporation (72) Inventor Shogo Okumura 3-10, Shiodori, Kurashiki-shi, Okayama Japan Polychem Mizushima Technical Center Co., Ltd.

Claims (8)

[Claims] 1. When melt-kneading a polyolefin using a melt-kneading apparatus, the melt-kneading apparatus is divided into a plurality of mixing zones, and the polyolefin is heated to 180 ° C. or higher in a first mixing zone sequentially arranged from the polyolefin supply side. Melt kneading treatment at a resin temperature of less than 180 ° C. in a mixing region below the second mixing region, and over 40% or more of the total residence time of the resin in the melt kneading device. A method for producing a polyolefin having less fish eyes, which comprises kneading. 2. The method according to claim 1, wherein the polyolefin is a polypropylene block copolymer. 3. The temperature of the resin in the first mixing region is from 180 to 2
The method for producing a polyolefin having less fish eyes according to claim 1 or 2, wherein the temperature is in a range of 30 ° C. 4. The resin temperature in the mixing zone below the second mixing zone is in the range of 165 ° C. or more and less than 180 ° C.
3. The method for producing a polyolefin having less fish eyes according to any one of 3. 5. The residence time in the first mixing zone is from 10 to 30.
The method for producing a polyolefin having a low fish eye according to any one of claims 1 to 4, which is in a range of seconds. 6. The method according to claim 1, wherein the residence time in the mixing zone below the second mixing zone is in the range of 10 to 120 seconds. 7. The ratio of the energy required for melt-kneading the polyolefin resin in the first mixing zone to the energy required for kneading the polyolefin resin in the mixing zone below the second mixing zone is 1: 0.1. The method for producing a polyolefin having a low fish eye according to any one of claims 1 to 6, which is in a range of 3 or less. 8. The method according to claim 1, wherein the L / D of the melt kneading apparatus is 18 or less.