JPH09208759A - Polyethylene composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyethylene composition capable of producing a film excellent in transparency and mechanical characteristics by bringing the composition to comprise each specific ethylene-α-olefin copolymer and high pressure low density polyethylene in a specific ratio. SOLUTION: This polyethylene composition comprises (A) 94.5-99.5wt.% of an ethylene-α-olefin copolymer having 0.880-0.960g/cm<3> density, 0.01-200g/10 minutes melt flow rate under 2.16kg load (MFR2.16 ) at 190 deg.C, a ratio expressed by MFR21.6 /MFR2.16 (MFR21.6 is the melt flow rate under 21.6kg load at 190 deg.C) in 10-20 and 2.0-4.0 molecular weight distribution (Mw/Mn) and (B) 0.5-5.5wt.% low density polyethylene obtained by a high pressure method having 0.05-50g/10min. MFR2.16 , the ratio MFR21.6 /MFR2.16 in >=30 and a melt tension at 190 deg.C, MT190 , expressed by-8log(MFR2.16 )+5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene composition, and more particularly, to a polyethylene composition capable of producing a film having excellent transparency and mechanical properties.

[0002]

2. Description of the Related Art Polyethylene is used in various applications after being formed into a film by a T-die method, an inflation method or the like.

[0003] The characteristics of polyethylene vary depending on the molding method and application, but in recent years, a low-density linear ethylene-α-olefin copolymer (LLDPE) using a Ziegler catalyst comprising a transition metal component has been widely used. But,
In LLDPE, low molecular weight components are produced depending on polymerization conditions, and the composition distribution of α-olefins in the copolymer is wide, so if the molded film has adhesiveness, or if the molecular weight distribution of the copolymer is wide, mechanical The strength sometimes decreased.

On the other hand, films produced from LLDPE obtained using a so-called metallocene compound as a polymerization catalyst have been developed.

For example, JP-A-6-65442 and JP-A-6-65442
In JP-A-65443 and JP-A-6-207056, a polyethylene composition obtained by mixing (A) a metallocene-based LLDPE having specific physical properties with (B) a low-density polyethylene by a high-pressure radical method having specific physical properties is a film. It is disclosed that it is suitable for manufacturing.

The physical properties of the low-density polyethylene of component (B) in these compositions by a high-pressure radical method are as follows:
The above publication describes suitable ranges such as density, melt flow rate (MFR), molecular weight distribution, and swell ratio. Also, regarding the composition ratio of the component (B), 1 to 40 wt
It is described that the composition is used in the range of%, and in the examples, 10 wt% or more of the composition is described in the above publication.

A polyethylene composition comprising LLDPE with a metallocene catalyst may not always have a balance between transparency and mechanical properties, and improvement is desired.

[0008]

The present invention relates to an ethylene-
A polyethylene composition comprising an α-olefin copolymer component and a high-pressure process low-density polyethylene component, wherein the physical properties of these components are specified, and further, the blending ratio thereof is specified to obtain transparency and mechanical properties. An object of the present invention is to provide a polyethylene composition capable of producing an excellent film.

[0009]

The present invention comprises (A) an ethylene-α-olefin copolymer 94.5 to 99.5% by weight and (B)
A polyethylene composition comprising 0.5 to 5.5% by weight of high-pressure low-density polyethylene, which comprises (A) ethylene-α
-The olefin copolymer and the high-pressure method low-density polyethylene (B) have the following characteristics, respectively.

(A) Ethylene-α-olefin copolymer: (A-1) Density (d) = 0.880 to 0.960 (g / cm ³ ) (A-2) Melt flow rate at 190 ° C under a load of 2.16 kg.
(MFR _2.16 ) = 0.01 to 200 (g / 10 min) (A-3) Melt flow rate at 190 ° C and 21.6kg load
(MFR _21.6) and 190 ° C., the ratio of the melt flow rate (MFR _2.16) of 2.16kg load _{(MFR 21.6) / (MFR 2.16} ) = 10
-20 (A-4) Molecular weight distribution (Mw / Mn) = 2.0-4.0

(B) High-pressure low-density polyethylene: (B-1) Melt flow rate at 190 ° C. under 2.16 kg load
(MFR _2.16 ) = 0.05 to 50 (g / 10min) (B-2) Melt flow rate at 190 ℃, 21.6kg load
(MFR _21.6) and 190 ° C., the ratio of the melt flow rate (MFR _2.16) of 2.16kg load _{(MFR 21.6) / (MFR 2.16} ) ≧ 30 (B-3) a melt tension MT at ₁₉₀ ℃ 190 ≧ -8 lo
g (MFR _2.16 ) + 5

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The ethylene-α-olefin copolymer which is the component (A) of the polyethylene composition of the present invention is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms.

As the α-olefin, propylene, butene-1, pentene-1, hexene-1,4-methylpentene-
1, octene-1 and the like.

The repeating unit derived from the α-olefin in the copolymer of ethylene and α-olefin is usually contained in an amount of 30 wt% or less. The α-olefin may be used alone or in combination of two or more in the ethylene-α-olefin copolymer.

The ethylene-α-olefin copolymer as the component (A) has physical properties in the following specific ranges.

(A-1) Density (d) = 0.880 to 0.960 (g / c
m ³ ), preferably 0.895 to 0.945 (g / cm ³ ) (A-2) 190 ° C., melt flow rate at 2.16 kg load
(MFR _2.16 ) = 0.01 to 200 (g / 10 min), preferably 0.1
~ 20 (g / 10min) (A-3) Melt flow rate at 190 ℃, 21.6kg load
(MFR _21.6) and 190 ° C., the ratio of the melt flow rate (MFR _2.16) of 2.16kg load _{(MFR 21.6) / (MFR 2.16} ) = 10
-20 (A-4) Molecular weight distribution (Mw / Mn) = 2.0-4.0

Of the above properties, if the (A-1) density is higher than the above range, ethylene-α
-The impact strength peculiar to the olefin copolymer is impaired, which is not preferable.

When (A-2) MFR _2.16 is lower than the above range, the motor load current during molding of the polyethylene composition increases and the resin pressure also increases, which is not preferable. MFR
_{When 2.16} is higher than the above range, the impact strength of the film obtained from the polyethylene composition is lowered, and the stability of bubbles during inflation molding is lowered.

When (A-3) (MFR _21.6 ) / (MFR _2.16 ) is larger than the above range, the mechanical properties of the polyethylene composition are deteriorated, which is not preferable.

(A-4) If the molecular weight distribution (Mw / Mn) is larger than the above range, the mechanical properties of the polyethylene composition are undesirably deteriorated.

The ethylene-α-olefin copolymer as the component (A) is obtained by polymerizing ethylene or copolymerizing ethylene and α-olefin in the presence of a single site catalyst.

As the single-site catalyst, a combination of a metallocene compound of a transition metal of Group IV or V of the periodic table with an organic aluminum compound and / or an ionic compound is used.

As the transition metal of Group IV or V of the periodic table,
Titanium (Ti), zirconium (Zr), hafnium (H
f) and vanadium (V) are preferred.

The metallocene compound is a compound bridged by at least one cyclopentadienyl group, a substituted cyclopentadienyl group, hydrocarbyl silicon, etc., and a cyclopentadienyl group bridged by oxygen, nitrogen and phosphorus atoms. Any known metallocene compound having the above as a ligand can be used.

Specific examples thereof are disclosed in JP-A-58-19309.
No. 60-35006, No. 61-130314, No. 61
JP-A-264010, JP-A-61-296008, JP-A-63-222177, JP-A-63-251405, JP-A-1-66214,
Nos. 1-74202, 1-275609, 1-301704, 1-319489, 2-41303 and 2-131488
Publication Nos., 3-12406, 3-139504, 3-17
9006 gazette, the same 3-185005 gazette, the same 3-18809 gazette, the same
No. 3-197514, No. 3-207703, No. 5-2009013, Japanese Translation of PCT International Publication No. 1-501950, No. 1-502036, and
Examples thereof include those described in JP-A-5-505593.

In the present invention, as single-site catalysts other than the above, Japanese Patent Laid-Open Nos. 61-130314 and 61-264 are used.
No. 010, No. 63-142004, No. 1-129004, No. 1-301704, No. 2-75605, No. 3-12406
Publication Nos., 3-12407, 4-227708, 4-26
Examples thereof include metallocene compounds described in JP-A-8308, JP-A-4-3000088, JP-A-6-25343 and the like.

Specific examples of these metallocene compounds include dimethylsilyl (2,4-dimethylcyclopentadienyl) (3 ', 5'-dimethylcyclopentadienyl) zirconium dichloride and dimethylsilyl (2,4-dimethyl). Cyclopentadienyl) (3 ', 5'-dimethylcyclopentadienyl) Silicon bridged metallocene compounds such as hafnium dichloride, ethylenebisindenylzirconium dichloride, ethylenebisindenylhafnium dichloride, ethylenebis (methylindenyl) Examples thereof include indenyl-based cross-linking metallocene compounds such as zirconium dichloride and ethylenebis (methylindenyl) hafnium dichloride.

The organoaluminum compound used in combination with the metallocene compound in the present invention has a general formula (-
Al (R) O-) _{n represents} a linear or cyclic polymer (R
Is a hydrocarbon group having 1 to 10 carbon atoms, including those partially substituted with a halogen atom and / or an RO group. n is the degree of polymerization and is 5 or more, preferably 10 or more), and specific examples include methylalumoxane, ethylalumoxane, and isobutylethylalumoxane, each of which is a methyl, ethyl, or isobutyl group. Can be

Examples of other organic aluminum compounds include trialkylaluminum, dialkylhalogenoaluminum, sesquialkylhalogenoaluminum, alkenylaluminum, dialkylhydroaluminum and sesquialkylhydroaluminum.

Specific examples thereof include trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, etc., dialkylhalogenoaluminums such as dimethylaluminum chloride and diethylaluminum chloride, sesquimethylaluminum chloride, Examples include sesquialkylhalogenoaluminum such as sesquiethylaluminum chloride, ethylaluminum dichloride, diethylaluminum hydride, and sesquiethylaluminum hydride. These organic aluminum compounds can be used in combination with the aforementioned organic aluminum oxy compounds.

Examples of the ionic compound include those represented by the general formula: C ⁺ A
^- , C ⁺ is an oxidizing cation of an organic compound, an organometallic compound, or an inorganic compound, or a Bronsted acid comprising a Lewis base and a proton, and reacts with an anion of a metallocene ligand to form a metallocene cation. Can be generated. Specific examples thereof are disclosed in
4-253711 JP, 4-305585 JP, JP-A-5-507756
And JP-A-5-502906 can be used.

In particular, an ionic compound of a tetrakis (pentafluorophenyl) borate anion and a triphenylcarbonium cation or a dialkylanilinium cation is preferable. These ionic compounds can be used in combination with the above-mentioned organoaluminum compound.

As a method for copolymerizing ethylene and α-olefin using a single-site catalyst, various well-known methods can be adopted, and fluidized bed gas phase polymerization in an inert gas or stirred gas polymerization can be used. Phase polymerization, slurry polymerization in an inert solvent, bulk polymerization using a monomer as a solvent and the like can be mentioned.

The high-pressure low-density polyethylene, which is the component (B) of the polyethylene composition of the present invention, has the following characteristics. (B-1) Melt flow rate at 190 ℃, 2.16kg load
(MFR _2.16 ) = 0.05 to 50 (g / 10 minutes), preferably 0.1 to
20 (g / 10min) (B-2) Melt flow rate at 190 ℃, 21.6kg load
(MFR _21.6) and 190 ° C., the ratio of the melt flow rate (MFR _2.16) of 2.16kg load _{(MFR 21.6) / (MFR 2.16} ) ≧ 30 (B-3) a melt tension MT at ₁₉₀ ℃ 190 ≧ -8 lo
g (MFR _2.16 ) + 5

When (B-1) MFR _2.16 is out of the above range among the above characteristics, the compatibility with the ethylene-α-olefin copolymer as the component (A) is remarkably poor and a normal film is obtained. I can't.

(B-3) When MT ₁₉₀ is out of the above range, the transparency of the film obtained from the polyethylene composition is lowered, which is not preferable.

The high-pressure low-density polyethylene as the component (B) can be produced by high-pressure radical polymerization.

As the high-pressure low-density polyethylene, a homopolymer of ethylene or a copolymer with another monomer such as an ethylene-vinyl acetate copolymer can be used.
When an ethylene-vinyl acetate copolymer is used, the amount of the repeating unit derived from vinyl acetate in the copolymer is usually preferably 20% by weight or less.

The blending ratio of each component in the present invention is 99.5 to (A) ethylene-α-olefin copolymer.
95% by weight, and (B) high pressure method low density polyethylene
0.05 to 5% by weight. When the proportion of the component (B) is less than the above range, the transparency is lowered, and when the proportion is large, the impact strength and the tear strength are lowered.

The polyethylene composition of the present invention is prepared by mixing and kneading the respective components by using various kneading machines such as Banbury mixer, roll mixer, kneader, high speed rotary mixer, extruder, etc., preferably single-screw or twin-screw extruder. Can be obtained. It is also possible to knead during film inflation or T-die molding. It is also possible to mix by solution blending using a suitable good solvent.

The polyethylene composition of the present invention may be added with a lubricant, an anti-blocking agent, an antioxidant, an ultraviolet absorber, a flame retardant, an inorganic / organic filler, a pigment, an antistatic agent, etc., depending on the intended use. it can.

The polyethylene composition of the present invention can be processed into various shapes such as films, pellets, sheets and fibers. For example, various types of packaging films such as standard bags, heavy bags, wrap films, raw paper, sugar bags, oil packaging bags, water packaging bags, food packaging, infusion packs, agricultural multi-films and house films, etc. It is suitable for agricultural materials. Further, it can be used as a multilayer film by being bonded to a substrate such as nylon or polyester.
In addition, it can be used for blow infusion bags, blow bottles, tubes, pipes, tear-off caps by extrusion molding, injection molded products such as daily necessities, fibers, and large molded products by rotational molding.

Examples of the method for producing a film include inflation molding and T-die film molding.

The film obtained from the composition of the present invention can be used as a packaging film or a multilayer film with other films such as nylon.

[0045]

EXAMPLES The characteristic values were measured as follows.

Method for measuring polyethylene properties (1) Density: 2.16k at 190 ° C according to JIS K7112
g Strand obtained during MFR measurement under load is 100
The sample was heat-treated at ℃ for 1 hour, and gradually cooled to room temperature over 1 hour, and measured using a density gradient tube. (2) Melt flow rate (MFR _2.16 ): 2.1 at 190 ° C using a melt indexer according to JIS K7210.
It is determined by measuring the weight of the resin extruded into a strand in 10 minutes under a load of 6 kg. (3) Melt flow rate ratio (MFR _21.6 ) / (MFR _2.16 ):
MFR _21.6 obtained with a _21.6 kg load in the same manner as in method (2) above
Divided by MFR _2.16 . (4) Molecular weight distribution: The molecular weight distribution was measured using WATERS 150CV as a measuring device under the conditions of column PL Mixed B, temperature 135 ° C, and solvent ODCB. (5) Melt tension at 190 ℃ MT ₁₉₀ : Co., Ltd.
Using a Capillograph IC manufactured by Toyo Seiki Seisaku-sho, Ltd., the resin temperature was 190 ° C., the extrusion speed was 10 mm / min, the winding speed was 20 m / min, the nozzle diameter was 2.09 mmφ, and the nozzle length was 8 mm.

Evaluation Method of Film Characteristics (1) Film Impact: A film impact tester manufactured by Toyo Seiki Seisaku-sho, Ltd. was used to measure the impact spherical surface with 0.5 inch hemisphere or 1.0 inch hemisphere. (2) Transparency: Haze was measured according to JIS K7105. (3) Tear strength: Measured by Elmendorf method according to JIS K7128.

Examples 1 to 18 and Comparative Examples 1 to 7 Tables 1 and 2 show the characteristics of each component of the polyethylene composition. Tables 3 and 5 collectively show the types of polyethylene components used, the blending ratio, and the molding temperature. The mixing method was kneading using a twin-screw kneader manufactured by Ikegai Iron Works to obtain pellets. The film was manufactured using a Modern Machinery 50 mmφ inflation molding machine to obtain a 40 μ film. The molding conditions and the like are as follows.

Die diameter: 150 mm, lip clearance:
2 mm, molding temperature: 150 to 200 ° C., BUR: 2.0 The properties of the obtained film are summarized in Tables 4 and 6.

Examples 19 to 36, Comparative Examples 8 to 14 The same procedure was carried out except that the kind of the polyethylene component (A) was changed. Tables 7 and 9 show the types of polyethylene components used, the blending ratios, and the molding temperatures. The mixing method was kneading using a twin-screw kneader manufactured by Ikegai Iron Works to obtain pellets. A 40μ film was obtained in the same manner as in Example 1. The characteristics of the obtained film are summarized in Tables 8 and 10.

Examples 37 to 38 and Comparative Examples 15 to 17 40 μ film films were produced in the same proportions as shown in Table 11 in the same manner except that a 40 mmφT die forming machine was used. The molding conditions and the like are as follows. Die width: 300mm, molding temperature: 230 ℃, take-up speed: 1
5 m / min. Cooling roll temperature: 70 ° C., using air chamber Table 12 summarizes the characteristics of the obtained film.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

[0056]

[Table 5]

[0057]

[Table 6]

[0058]

[Table 7]

[0059]

[Table 8]

[0060]

[Table 9]

[0061]

[Table 10]

[0062]

[Table 11]

[0063]

[Table 12]

[0064]

By the composition of the present invention, a film having excellent transparency and mechanical properties can be produced.

Claims (1)

[Claims] 1. An (A) ethylene-α-olefin copolymer (94.5-99.5% by weight) and (B) a high-pressure low-density polyethylene
A polyethylene composition comprising 0.5 to 5.5% by weight, wherein the (A) ethylene-α-olefin copolymer and the (B) high-pressure low-density polyethylene have the following characteristics, respectively: Polyethylene composition. (A) Ethylene-α-olefin copolymer: (A-1) Density (d) = 0.880 to 0.960 (g / cm ³ ) (A-2) Melt flow rate at 190 ° C and 2.16 kg load
(MFR _2.16 ) = 0.01 to 200 (g / 10 min) (A-3) Melt flow rate at 190 ° C and 21.6kg load
(MFR _21.6) and 190 ° C., the ratio of the melt flow rate (MFR _2.16) of 2.16kg load _{(MFR 21.6) / (MFR 2.16} ) = 10
~ 20 (A-4) Molecular weight distribution (Mw / Mn) = 2.0 to 4.0 (B) High-pressure low density polyethylene: (B-1) Melt flow rate at 190 ° C, 2.16 kg load
(MFR _2.16 ) = 0.05 to 50 (g / 10min) (B-2) Melt flow rate at 190 ℃, 21.6kg load
(MFR _21.6) and 190 ° C., the ratio of the melt flow rate (MFR _2.16) of 2.16kg load _{(MFR 21.6) / (MFR 2.16} ) ≧ 30 (B-3) a melt tension MT at ₁₉₀ ℃ 190 ≧ -8 lo
g (MFR _2.16 ) + 5