JPH0112779B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyethylene composition having excellent molding processability and physical properties of molded products, and relates to a polyethylene composition having excellent molding processability such as melt extensibility, melt viscoelasticity, thin film processability, and physical properties such as impact resistance. This invention relates to a polyethylene composition suitable for molding applications. For applications such as polyethylene films, polymers with a relatively high molecular weight and a relatively wide molecular weight distribution are suitable. Several methods have been proposed as methods for producing polyethylene with a wide molecular weight distribution. As one method, a method of mixing high molecular weight polyethylene and low molecular weight polyethylene has been proposed. 1977-
161657, JP 55-60542, JP 55-60543, JP 56-57841, JP 57-133136). In addition, as another method, a multi-stage polymerization method of two or more stages has been attempted (Japanese Patent Publication No. 46-11349, Special Publication No. 11349, No. 48)
-42716, JP-A-51-47079, JP-A-52-19788). The inventors of the present application have examined in detail the polyethylene produced by the above-mentioned mixing and polymerization methods, and have found that it has excellent extrudability due to its wide molecular weight, but on the other hand, it has low melt extensibility and thin film. It has been found that there are some drawbacks such as difficulty in processability and the impact resistance of the thin film is not necessarily sufficient. The present invention improves these drawbacks of polyethylene consisting of a low molecular weight part and a high molecular weight part, and has excellent processability and physical properties, especially for thin film applications,
The present invention provides a polyethylene composition suitable for stretching purposes. That is, the present invention is a polyethylene composition consisting of polyethylene (A) and (B) selected from the group of ethylene homopolymers and copolymers of ethylene and α-olefin, (i) polyethylene (A) consists of a low molecular weight part (A-L) with a molecular weight of 50,000 to 50,000 and a high molecular weight part (A-H) with a molecular weight of 100,000 to 1.5 million, and (A-H)
The molecular weight of /(A-L) is 7 to 200, and the weight ratio of the amount of (A-L) to the amount of (A-H) is in the range of 60:40 to 40:60. (ii) Polyethylene (B) is polymerized using a Ziegler type catalyst, and the molecular weight of (B) is from 90,000 to 50
10,000, and the density exceeds 0.94 g/cm ³ and 0.97 g/cm ³
or less, and the amount of (B) in the composition is from 15% by weight
(iii) the melt index of the composition is 0.001 g/
10min. to 10g/10min. According to the present invention, polyethylene has a wide range of industrial applications, has excellent melt extensibility, thin film processability, thin film impact resistance, etc., and is particularly suitable for film forming, stretch forming, etc. A composition is provided. The present invention will be explained in detail below. Polyethylenes (A) and (B), which are the constituent components of the present invention, are selected from the group of homopolymers of ethylene and copolymers of ethylene and α-olefins. The α-olefin used for copolymerization has 3 to 14 carbon atoms.
Examples include propylene, butene, pentene, hexene, 4-methylpentene-1, octene, decene, and the like. Polyethylene (A) is a polymer consisting of a low molecular weight part (A-L) and a high molecular weight part (A-H),
The molecular weight (MW _AL ) of A-L is from 5,000 to 50,000, and the molecular weight (MW _AH ) of A-H is from 100,000 to 1,500,000. If the MW _AL is less than 50,000, the uniform dispersibility and physical properties of each component will deteriorate, while if it exceeds 50,000, it will be difficult to widen the molecular weight distribution within an appropriate molecular weight range of the composition, and processability will decrease. More preferably, it is from 10,000 to 40,000. On the other hand, if the MW _AH is less than 100,000, the molecular weight of the composition decreases and the impact resistance also decreases. If it exceeds 1,500,000, the balance between processability and physical properties becomes poor, such as the occurrence of hard eyes and a decrease in the uniform dispersibility of each component in the composition.
More preferably, it is 150,000 to 1,000,000. Also, the ratio between MW _AH and MW _AL (MW _AH /
MW _AL ) is 7 to 200, and if it is less than 7, the molecular weight distribution is narrow and processability is low, making it difficult to obtain the excellent physical properties of the present invention. On the other hand, if it exceeds 200, there is no advantage in improving moldability and physical properties, and it is also disadvantageous in terms of manufacturing. More preferably it is 10-150. In addition, the density of A-L is 0.91 to 0.98 g/ ^cm3 ,
-H has a density of 0.91 to 0.97 g/cm ³ . Especially A
When the density of -H is lower than both of the density of A-L and polyethylene (B) and is 0.91 to 0.95 g/cm ³ ,
It is preferable because both processability such as extrudable film formability and physical properties such as impact resistance are improved. The amount of A-L versus the amount of A-H in polyethylene (A) is
It ranges from 60/40 to 40/60. A-L or A
-When the amount of H exceeds 60%, the molecular weight distribution becomes narrow,
The balance between workability and physical properties deteriorates, and the occurrence of fish eyes increases. The polyethylene (A) can be produced by mixing the low molecular weight part and the high molecular weight part that have been prepared in advance, or by two-stage polymerization of the low molecular weight part and the high molecular weight part. Industrially, a two-stage polymerization method is preferred. Polyethylene (B) has a molecular weight (MW _B ) in the range of 90,000 to 500,000. In order to improve the balance between the moldability and physical properties of the composition, a particularly desirable embodiment is that the MW _B is from 100,000 to 400,000 MW _B /
MW _AL is 2 or more, and MW _AH /MW _B is 1.5 or more. Density exceeds 0.94g/ ^cm3 and 0.97g/ ^cm3
It is as follows. If the density is low, the rigidity and tensile strength of the composition will decrease, which is not preferable. Further, the amount of polyethylene (B) in the composition is in the range of 15 to 50% by weight, preferably 17% or more.
% or less. When the amount of (B) is less than 15%, workability and impact strength are not sufficiently improved. On the other hand, if it exceeds 50%, the molecular weight distribution of the composition becomes narrow, the processability and physical properties of the film deteriorate, and the characteristics of the polyethylene composition of the present invention are impaired. The polyethylene (A) is polymerized using a transition metal catalyst such as a Ziegler type catalyst or a chromium compound catalyst. Both the low molecular weight part and the high molecular weight part of (A) were polymerized using the same type of transition metal catalyst, or the low molecular weight part and the high molecular weight part were polymerized using different types of transition metal catalysts. Particularly preferred is one in which both the low molecular weight part and the high molecular weight part are produced using a magnesium compound-based Ziegler type catalyst. The polyethylene (B) is produced using a Ziegler-type catalyst, and particularly preferred is one produced using a magnesium compound-based Ziegler-type catalyst that can omit the decatalyst step. Polyethylene (B) produced using a magnesium compound-based Ziegler type catalyst is characterized by a relatively narrow molecular weight distribution, which enhances the effects aimed at in the present application. As the magnesium compound-based Ziegler type catalyst, any system based on organic magnesium or inorganic magnesium can be used. For example, magnesium chloride, hydroxymagnesium chloride, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium alkoxide, organic acid salts of magnesium, complexes of these with electron-donating compounds such as alcohols and organic acid esters, or complexes of these with electron-donating compounds such as alcohols and organic acid esters. mixtures, organomagnesium compounds having a carbon-magnesium bond, such as dialkylmagnesiums, alkylmagnesium chlorides, alkylmagnesium alkoxides, alkylmagnesium siloxides, or complexes of these organomagnesium compounds with electron donors such as ethers; organomagnesium components and halides, such as hydrochloric acid,
A reaction product of a chlorinated hydrocarbon, silicon tetrachloride, and tin tetrachloride is used as the magnesium component, and a catalyst is used that includes a component obtained by reacting this with titanium and/or a vanadium compound and an organometallic compound. Particularly preferred catalysts in the present invention include (1) general formula MαMgβR ¹ _p R ² _q X _r Y _s (where α is 0 or a number larger than 0, p, q, r,
s is 0 or a number greater than 0, p+q+r+s
=mα+2β, where M is a metal element belonging to a group or genus of the periodic table, R ¹ and R ² are hydrocarbon groups having the same or different numbers of carbon atoms, and X and Y are the same or different groups. and halogen, OR ³ ,
OSiR ⁴ R ⁵ R ⁶ , NR ⁷ R ⁸ , SR ⁹ represents a group, R ³ ,
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ are hydrogen atoms or hydrocarbon groups; R ⁹ is a hydrocarbon group); and (ii) containing at least one halogen atom. and (iii) a halide compound of Al, B, Si, Ge, Sn, Te, or Sb (i) and (ii) or (i) of (i) to (iii).
(ii)
It consists of a solid catalyst component [A] formed by reacting and (iii) and an organometallic compound [B]. The organometallic compound [B] is a compound of Groups 1 to 10 of the periodic table, and a complex containing an organoaluminum compound and an organomagnesium is particularly preferable. The reaction between the catalyst component [A] and the organometallic compound [B] component can be carried out under the polymerization conditions by adding both components to the polymerization system and as the polymerization progresses. You can.
In addition, the reaction ratio of the catalyst components is [A] component 1g
It is preferable to use the component [B] in an amount of 1 to 3000 mmol based on the amount of component [B]. Instead of the catalyst component [A], a Ti compound supported on an inorganic Mg compound may be used. Among these catalyst systems, the ones that are particularly desirable because they can omit the decatalyst step industrially are:
Special public 54-36788, 52-36790, 52-36791, 52-
36792, 52−50070, 52−36794, 52−36795, 52−
36796, 52-36915, 52-36917, 53-6019, JP-A-1987-21876, 50-31835, 50-72044, 50-
78619, No. 53-40696. The polyethylenes (A) and (B) can be polymerized by suspension polymerization, solution polymerization,
Manufactured by methods such as gas phase polymerization. Although it is industrially preferable to produce the polyethylene (A) by two-stage polymerization, several methods for two-stage polymerization have already been proposed. Examples of preferred methods used in the present invention are described below. The polymerization is carried out in saturated hydrocarbons having 4 to 10 carbon atoms. The order of polymerization is (A-L)-(A-
H) or (AH)-(AL). For simplicity, the (A-L)-(A-H) pattern will be explained with reference to the drawings. The low molecular weight part (A-L) has a polymerization pressure of 1 to 30 kg/
cm ² G, preferably 3 to 25 Kg/cm ² G, and the polymerization temperature is
It is carried out at 60-100°C, preferably 70-90°C. The high molecular weight part (A-H) has a polymerization pressure of 0.5 to 30 Kg/cm ² G,
Preferably 0.5-20Kg/cm ² G, polymerization temperature 40-
It is carried out at 110°C, preferably 60-90°C. In the polymerization vessel 1, ethylene, hexane, hydrogen, catalyst components, etc. are supplied from a line 2, and low molecular weight polyethylene (A-L) is polymerized. The slurry in the polymerization vessel 1 is led to a flash drum 3, where unreacted ethylene and hydrogen are removed. The removed ethylene and hydrogen are returned to the polymerization vessel 1 where the pressure is increased by the compressor 4. On the other hand, flash drum 3
The slurry inside is introduced into the second stage polymerization vessel 6 by the pump 5. In the polymerization vessel 6, ethylene, comonomer, hexane, catalyst components, etc. are supplied from the line 7, and polymerization of high molecular weight polyethylene (A-H) is performed, and the polymer in the polymerization vessel 6 is processed as a product through a post-processing process. Served. The flow explained above is one of the typical examples of the present invention. L) may be polymerized. In that case, the flash drum 3 can be omitted. Furthermore, the contents of the polymerization vessel may be circulated from the polymerization vessel 6 in the latter stage to the polymerization vessel 1 in the former stage. Polyethylene (A) can be continuously polymerized using such a flow sheet. The polyethylene (A) and (B) are mixed and kneaded to form the desired polyethylene composition. As for the mixing method of polyethylene (A) and (B), usual methods such as powder state, slurry state, pellet state, etc. are used. Kneading is carried out at a temperature of 150 to 300°C using a single-screw or twin-screw extruder, kneader, etc. In this way, the melt index (hereinafter referred to as MI) of the polyethylene composition produced is
From the range of 0.001g/10min. to 10g/10min.
Selected depending on the purpose. In particular, film compositions with comprehensively excellent processability and physical properties have MI in the range of 0.01 g/10 min. to 1 g/10 min. and density in the range of 0.935 g/cm ³ to 0.965 g/cm ³ . in range. The polyethylene composition contains substances that can be added or blended with polyolefins, such as heat stabilizers, antioxidants, ultraviolet absorbers, pigments, antistatic agents, lubricants, fillers, other polyolefins, thermoplastic resins, rubbers, etc. , can be used as needed. It is also possible to mix a foaming agent and perform foam molding. As detailed above, the polyethylene composition obtained by the present invention has the following characteristics. (1) It has a good balance of processing properties such as flow characteristics when melted, melt extensibility, and melt viscoelasticity, and also has excellent physical properties such as impact resistance, tensile strength, and surface photo-selectivity. (2) For film applications, it is difficult to produce extremely thin films of 6 microns or less, which was previously considered difficult.
Can be processed at ultra high speeds of m/min. or higher. (3) The molded product has high rigidity, impact resistance, and environmental stress cracking resistance, and all of these properties are well balanced for practical use. In particular, it provides excellent impact resistance for thin-walled molded products. (4) It has excellent physical properties and processability, making it easy to make thin-walled molded products. Therefore, it is suitable for the era of resource saving and energy saving. (5) Easy to manufacture. (6) Can be applied to various molding applications such as hollow, extrusion, injection, rotation and foaming. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. Symbols, measurement methods, and measurement conditions shown in Examples and Comparative Examples. (i) MI; represents melt index;
According to ASTMD-1238, temperature 190℃, load 2.16
Values measured under Kg conditions. (ii) MIR: Means the quotient obtained by dividing the value measured under MI measurement conditions at a load of 21.6 kg by MI, and is one measure of molecular weight distribution, and the larger this value is, the wider the molecular weight distribution is. (iii) Molecular weight (MW); using decalin solution, 135℃
The MW was determined from the intrinsic viscosity (η) measured in , and the formula described in Journal of Polymer Science, Vol. 36, p. 91 (1957), η=6.8×10 ⁻⁴ MW ^0.67 .
Note that all molecular weights in the present invention are determined by this method. (iv) Density: Measured according to ASTMD-1505. (v) Melt extensibility: Using a melt tension tester manufactured by Toyo Seiki Co., Ltd., stretch a strand made by melt extruding resin at a temperature of 150°C, and check the maximum drawing speed at which the strand can be stretched without breaking. The quotient divided by the linear velocity as it exits the nozzle. (vi) Film moldability; 50mm diameter screw, 75
Inflation film forming machine with mm diameter die, temperature 190℃, blow ratio 3.5 times, take-up speed
Form the film at 105m/min. and find the minimum thickness that can be formed. (vii) Impact resistance of the film; the above film forming machine,
A film with a thickness of 12 microns obtained by molding under the following conditions is measured using ASTMD-1709. (viii) Film fitting: Cut 700 cm ² of 12 micron thick film obtained by molding with the above film molding machine and conditions, and cut out the film with a diameter of 0.1 cm 2 on top of it.
Visually count all fisheyes larger than millimeters. Example 1-1 (1) Synthesis of catalysts for polyethylene (A) and (B) A hexane solution of 1 mole of trichlorosilane (HSiCl ₃ ) was placed in a 8-unit autoclave and heated to 50
It was kept at ℃. This has the composition AlAg _6.0 (C ₂ H ₅ ) _2.0 (n
-Organoaluminum _{with C4H9} ) _9.5 ( _{OC4H9 ) 3.5-}
A 1 mol/hexane solution 2 of the magnesium complex was added dropwise over 2 hours with stirring, and the reaction was further allowed to proceed at this temperature for 2 hours. The produced solid component was washed twice with hexane by the precipitation method. Titanium tetrachloride 2 was added to the slurry containing this solid component, and after reacting at 130°C for 2 hours, the solid catalyst was isolated and washed with hexane until no free halogen was detected. This solid catalyst contained 2.1% titanium. (2) Production of polyethylene (A) by two-stage polymerization First, in order to create a low molecular weight part, the reaction volume
Polymerization was carried out in 300 polymerization vessel 1. Polymerization temperature was 83℃,
The polymerization pressure was 11 kg/cm ² G. This polymerization vessel 1
Then, the above solid catalyst was added at a rate of 1.3 mmol (based on Ti atoms)/Hr, and triethylaluminum was added at a rate of 20 mmol (based on metal atoms)/Hr.
Polymerization is carried out by supplying purified hexane at a rate of 40/Hr, and also supplying ethylene at 7NM ³ /Hr and hydrogen as a molecular weight regulator such that the hydrogen concentration in the gas phase is about 90 mol%. The polymer slurry content in polymerization vessel 1 was heated to a pressure of 1 Kg/cm ² G and a temperature of
The slurry is introduced into a flash drum 3 at 75°C to separate unreacted ethylene and hydrogen, and then introduced into a polymerization reactor 6 after being pressurized with a slurry pump 5. In the polymerization vessel 6, polymerization is carried out at a temperature of 78° C. and a pressure of 6 kg/cm ² G. The polymerization vessel 6 has an internal volume of 250 ml. Triethylaluminum was added to the polymerization vessel 6 at a rate of 7.5 mmol (metal atom basis) Hr, and purified hexane was added at a rate of 40/Hr.
Polymerization was carried out by supplying ethylene at a rate of 7.1 NM ³ /Hr, and introducing hydrogen and butene-1 so that the concentrations in the gas phase were approximately 1 mol% and 2.5 mol%, respectively. . Two-stage polymerization was carried out in this way, and the polyethylene (A) powder obtained from polymerization vessel 6 had an MI of 014 g/10 min. and a density of 0.956 g/cm ³ . In addition, from the results of a separate homopolymerization experiment conducted under similar conditions, the low molecular weight part (A-L) of polyethylene (A) polymerized in the first stage polymerization vessel 1 has a molecular weight of about 13000 and a density of about 0.974. g/cm ³ , the high molecular weight (A-H) of the polyethylene (A) polymerized in the second stage polymerization vessel 2 has a molecular weight of approximately 620,000 and a density of approximately 0.939 g/cm 3 .
^cm3 , respectively. The low molecular weight part (A-L) and the high molecular weight part (A-L)
-H) was calculated from the density of the polyethylene produced in the first stage and the composition density at the outlet of the second stage polymerizer, and was determined to be (AL):(A-H) = 50:50. (3) Production of polyethylene (B) Polyethylene (B) was produced by homopolymerization using a polymerization vessel with a reaction volume of 200. The polymerization temperature was controlled at 83° C. and the polymerization pressure was controlled at 11 Kg/cm ² G. The catalyst used was similar to polyethylene (A), hydrogen was used as a molecular weight modifier, butene-1 was used as a comonomer, and the molecular weight
130,000, density is 0.950g/cm ³ , MI is 0.6g/
10 min., MIR produced 33 polyethylene (B). (4) Production and evaluation of polyethylene composition The polyethylene (A) and polyethylene (B) powders produced as described above were mixed in a weight ratio of 78:22, and then a stabilizer was added to this mixture. ditertiarybutylhydroxytoluene as
800ppm, tetrakis [methylene-3-(3′,
5'-di-t-butyl-4'hydroxyphenyl)
Propionate]Methane (1400 ppm) and calcium stearate (2300 ppm) were added and thoroughly stirred and mixed in a Henschel mixer to create a powder mixture.The mixture was kneaded in a Farel FCM at a temperature of 220℃, and then This kneaded material was extruded using a single screw extruder at a temperature of 250°C and pelletized to produce a polyethylene composition. The performance of this polyethylene composition is the first
As shown in the table, both moldability and physical properties are excellent. Example 1-2 Polyethylene (A) produced in Example 1-1 and
Example 1 except that (B) was mixed in the amount shown in Table 1.
A polyethylene composition was produced in the same manner as in Example 1-1. Its performance is shown in Table 1. Comparative Example 1-1 The performance was evaluated in the same manner as in Example 1-1 except that only the polyethylene (A) produced in Example 1-1 was used. Comparative Example 1-2 In Example 1-1, as shown in Table 1,
The performance was evaluated in the same manner as in Example 1-1 except that the blending amount was changed. Example 2-1 (1) Production of polyethylene (A) Using the catalyst used in Example 1-1, the polymerization vessel, polymerization temperature, and pressure used to polymerize polyethylene (B) in Example 1-1 So, the low molecular weight part (A-L) and the high molecular weight part (A-L) of polyethylene (A) are
-H) were separately polymerized. (A-L),
In both cases (A-H), butene-1 was used as a comonomer, and hydrogen was used as the molecular weight regulator as in Example 1-1. The produced (A-L) has a molecular weight of about 30,000 and a density of 0.963 g/cm ³ , and (A-H) has a molecular weight of about 450,000.
The density was 0.935 g/cm ³ . (2) Synthesis of catalyst for polyethylene (B) By feeding 138 g of di-n-butylmagnesium and 19 g of triethylaluminum into a stirring tank with a capacity of 4 with 2 n-heptane and reacting at 80°C for 2 hours, Composition AlMg ₆ (C ₂ H ₅ ) ₃
An organoaluminum-magnesium complex _of (n- _C4H9 ) ₁₂ was synthesized. 400 mmol (54
800 ml of n-heptane solution containing g) and 800 ml of n-heptane solution containing 400 mmol of titanium tetrachloride.
ml was subjected to dry nitrogen purging to remove moisture and oxygen, and then reacted at -20°C for 4 hours with stirring. The resulting hydrocarbon-insoluble solid was isolated and washed with n-heptane to yield 106 g of solid. (3) Production of polyethylene (B) Using the solid catalyst prepared as described above and triethylaluminum as catalysts, octene-1 as a comonomer and hydrogen as a molecular weight regulator, polyethylene (B) of Example 1-1 was produced. Polyethylene (B) as shown below was polymerized using the same polymerization vessel, polymerization temperature, and pressure used for production. That is, molecular weight 220,000, density 0.945g/cm ³ , MI 0.11g/
10min., MIR55. (4) Production and evaluation of polyethylene compositions (A-L) and (A-H) of polyethylene (A) produced as above and polyethylene (B)
were mixed at the blending ratio shown in Table 2, and then
As a stabilizer, 800 ppm of ditertiarybutylhydroxytoluene, n-octadecyl-β-
Add 1500 ppm of (4'-hydroxy-3',5'-di-t-butylphenyl)propionate and 2500 ppm of calcium stearate, and then thoroughly stir and mix using a Henschel mixer. The mixture was kneaded at a high temperature, and then the kneaded product was extruded using a single screw extruder at a temperature of 260°C and pelletized to produce a polyethylene composition. As shown in Table 2, this polyethylene composition exhibits excellent moldability and physical properties. Example 2-2 In Example 2-1, (A-L), (A-H)
The procedure was the same as in Example 2-1 except that the blending ratios of (B) and (B) were changed as shown in Table 2. Comparative Examples 2-1 to 2-2 The same procedure as Example 2-1 was carried out except that (A-L) and (A-H) were blended as shown in Table 2.

【table】

[Table] Examples 3-1 to 3-2 (1) Production of polyethylene (A) A using the same catalyst and the same method as in Example 2-1.
-L and A-H ₁ were polymerized separately. The produced A-L has a molecular weight of approximately 12,000 and a density of
A-H ¹ had a molecular weight of about 860,000 and _a density of 0.930 g/cm ³ . (2) Polyethylene (B) The same polymer as in Example 2-1 (B) was used. (3) Production and evaluation of polyethylene composition Compositions having the proportions shown in Table 3 were produced in the same manner as in Example 2-1. As shown in Table 3, this polyethylene exhibited very excellent performance in terms of moldability, physical properties, and firm eye level. Comparative Examples 3-1 to 3-3 Production of polyethylene (A) A-L and A- of polyethylene (A) of Example 3-1
H ₁ and A-H ₂ (with a molecular weight of about 190
10,000, density is 0.925). All other procedures were the same as in Example 3-1. Polyethylene A and B
Table 3 shows the percentage of As shown in Table 3, it can be seen that the moldability, physical properties, firm eye, etc. are inferior.

[Table] Note 1: Severe melt fracture occurred in the strand, making it unstable.
Note 2: The film becomes shark skin-like,
A film with normal appearance could not be obtained.
Note 3: Measurement could not be performed because a 12μ film could not be obtained.

[Brief explanation of drawings]

The drawing is a flow sheet showing an example of two-stage polymerization according to an embodiment of the present invention.

Claims (1)

[Claims] 1. Ethylene homopolymer and ethylene and α-
Consisting of polyethylene (A) and (B) selected from the group of olefin copolymers, (i) polyethylene (A) has a low molecular weight part (A-L) with a molecular weight of 50,000 to 50,000, and a low molecular weight part (A-L) with a molecular weight of 100,000. from 150
It consists of 10,000 high molecular weight parts (A-H), (A-
The molecular weight of H)/(the molecular weight of A-L is 7 to 200, and the weight ratio of the amount of (A-L) to the amount of (A-H) is in the range of 60:40 to 40:60. can be,
The amount of polyethylene (A) in the composition is from 85% by weight
(ii) Polyethylene (B) is polymerized using a Ziegler type catalyst, has a molecular weight of 90,000 to 500,000, and has a density of more than 0.94 and less than 0.97 g/cm ³ and the amount of polyethylene (B) in the composition is 15
(iii) the composition has a melt index of 0.001 g/wt.
A polyethylene composition characterized in that it has a yield of 10 min. or more and 10 g/10 min. or less. 2. The polyethylene composition according to claim 1, wherein the polyethylene (A) is produced by two-stage polymerization. 3. The polyethylene composition according to claim 1 or 2, wherein the polyethylene (A) and (B) are produced using a magnesium compound-based Ziegler type catalyst. 4 The molecular weight of polyethylene (B) is from 100,000 to 400,000, the molecular weight of polyethylene (B) / (A-L) is 2 or more, and the molecular weight of (A-H) / the molecular weight of polyethylene (B) The polyethylene composition according to claim 1, 2 or 3, wherein the polyethylene composition is 1.5 or more.