JPH0352781B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyethylene composition suitable for use in films that are strong and have excellent transparency. Among polyethylenes, high-density polyethylene has a high degree of crystallinity, so a film with high rigidity and firmness can be obtained, but its transparency is poor and its use as a packaged product is limited. On the other hand, low-density polyethylene has a lower crystallinity than high-density polyethylene, so it has excellent transparency, but it lacks rigidity and is difficult to make thin when molded into a film. In recent years, the wave of resource and energy conservation has been reflected in the packaging industry, and strong, thin films with excellent transparency are required for films used in packaging. This demand is particularly high for polyethylene, which has a large impact on film applications, and resin manufacturers are conducting research to meet this demand. However, as mentioned above, both high-density polyethylene and low-density polyethylene have their own problems.
It is difficult to provide polyethylene with highly desired properties. The present invention provides a type of polyethylene that satisfies such demands, and particularly relates to a polyethylene suitable for the field of air-cooled blown films. That is, the present invention provides: [] 70 to 95 parts by weight of an ethylene polymer or ethylene/α-olefin copolymer having the following properties (A) to (C): (A) a density based on the ASTM D 1505 measurement method; (B) Melt flow index based on ASTM D 1238E measurement method is 1 g/10 ^min or less, (C) Melt flow index based on ASTM D 1238E measurement method and ASTM D
Melt flow index ratio HLMI/MI based on the measurement method of 1238F is 40 or less, [] Low density polyethylene, vinyl acetate content is 20
Ethylene-vinyl acetate copolymer of less than % by weight,
At least one selected from the group consisting of an ionomer and an ethylene/α-olefin copolymer
5 to 30 parts by weight of seeds (however, + is 100 parts by weight), [] 0.01 to 5 parts by weight of at least one magnesium salt or calcium salt of a sulfonic acid selected from alkyl sulfonic acids or alkylbenzene sulfonic acids, and If necessary, at least one selected from dibenzylidene sorbitol or its nuclear substituted product.
The present invention provides a polyethylene composition characterized in that the seed comprises 0.05 to 0.5 parts by weight. The first component of the present invention has a density of 0.94 g/cm ³ or more,
Preferably 0.95g/cm3 or ^more , melt flow index (hereinafter abbreviated as MI) 1g/10min
Below, preferably below 0.8g/10min, HLMI/
Ethylene homopolymer with MI of 40 or less, preferably 35 or less, or ethylene and α- having 3 to 12 carbon atoms
Olefins such as propylene, 1-butene,
Copolymers with 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene are preferred. Density was determined by ASTM D 1505 density gradient tube method measurement, and MI was determined by ASTM D 1238E (temperature 190℃,
It was determined by measurement at a load of 2.16 kg), and HLMI/
MI is ASTM D 1238F (temperature 190℃, load 21.6
It was determined by the ratio of the HLMI determined by measurement in kg) and the above MI. Even if an ethylene homopolymer or an ethylene/α-olefin copolymer is used outside the above range, a polyethylene composition excellent in rigidity, stiffness, and valve stability during inflation molding cannot be obtained. The second component of the present invention compensates for the shortcomings of the first component, such as impact strength and transparency, and is a compound having a lower melting point, better compatibility, and similar refractive index than the first component, Specifically, the density is 0.935g/ ^cm3
Below, high-pressure low density polyethylene with MI5.0g/10min or less, vinyl acetate content of 20% by weight or less, MI5
g/10min or less ethylene/vinyl acetate copolymer, ionomer or density 0.85 to 0.935
^At least one compound selected from copolymers of ethylene and a small proportion of α-olefin having 3 to 18 carbon atoms can be selected. Among these, ethylene/α-olefin copolymer is preferred, with a density of 0.85 to 0.91 g/
cm ³ MI5.0g/10min or less, crystallinity by X-ray
20% or less of ethylene/α-olefin copolymer is preferred, more preferably ethylene and 6 carbon atoms.
A copolymer with 1 to 16 α-olefins, with an ethylene content of 75 to 95 mol% and a density of
Ethylene α with 0.85 to 0.91g/10min, MI4.0g/10min or less, ratio w/n of weight average molecular weight w to number average molecular weight n by GPC method is 4 or less, and crystallinity by X-ray is 20% or less -Olefin copolymers are preferred in the present invention. The blending ratio of these above-mentioned polymers is such that the second component is 5 to 30 parts by weight, and the total amount of the first and second components is 5 to 30 parts by weight, considering the balance of rigidity, stiffness, impact resistance, moldability, etc. Use in such a proportion that it is 100 parts by weight. The third component of the present invention improves molding processability during film molding to produce a film with a smooth surface,
This is a necessary component to produce a film with excellent transparency. Specifically, it is a magnesium salt or calcium salt of a sulfonic acid selected from alkylsulfonic acids and alkylbenzenesulfonic acids. The number of carbon atoms in the alkyl sulfonic acid is preferably 8 to 30, particularly preferably 10 to 25,
On the other hand, the alkyl group of the alkylbenzenesulfonic acid preferably has 4 to 30 carbon atoms, particularly 8 to 15 carbon atoms. When used in the present invention, these sulfonic acid compounds are used in the form of magnesium salts or calcium salts. Other metal salt forms, ie, lithium salts, sodium salts, and potassium salts, are hygroscopic and may cause foaming during molding, making it difficult to mold them properly. The usage ratio of the third component of the present invention is 0.01 to 5 parts by weight based on the total amount (100 parts by weight) of the first component and the second component, particularly
0.05 to 2 parts by weight is preferred. If used outside the above range, bubble stability during inflation molding may be impaired, and printability, heat sealability, and transparency may be impaired. In the present invention, in addition to the above [] to [], in order to further improve transparency, dibenzylidene sorbitol or its nuclear substituted product may be added as a fourth component. Dibenzylidene sorbitol may be in the D-form, L-form or racemic form, and the nuclear substituent of dibenzylidene sorbitol includes an alkyl group; for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, etc., or an alkoxy group. group; for example, methoxy group,
Examples include ethoxy group, propoxy group, butoxy group, and derivatives whose nucleus is substituted with halogen such as chlorine. Further, this nuclear-substituted dibenzylidene sorbitol may be substituted at any of the ortho, meta, and para positions.
One or more of these dibenzylidene sorbitol or its nuclear substituted product can be combined with []+[]
0.01 to 1 part by weight per 100 parts by weight, especially
Add 0.05 to 0.5 parts by weight. The polyethylene composition of the present invention can be obtained by mixing the above-mentioned first to third components and, if necessary, dibenzylidene sorbitol or its nuclear substituted product using a ribbon blender, tumble blender, Henschel mixer, or the like; Examples include a method of melt-mixing using an extruder, Banbury mixer, two rolls, etc. after mixing. In addition, the composition of the present invention may contain various known additives, such as heat stabilizers, weather stabilizers, antistatic agents, antifogging agents, antiblocking agents, pigments, dyes, and inorganic or organic additives. Fillers and the like may also be added. The composition of the present invention obtained in this way has high rigidity, strong elasticity, excellent impact resistance and moldability, and has good transparency, so it can be used in the packaging field. We can expect the development of The present invention will be explained below using examples, but the present invention is not limited to these examples as long as the purpose thereof is not impaired. Examples 1 to 10 MI0.45g/10min (ASTM D 1238E), density
0.965g/ ^cm3 (ASTM D 1505), HLMI/MI28
90 parts by weight of high-density polyethylene, 10 parts by weight of the polymer shown in Table 1, and the formulation shown in Table 2 were mixed in an Enciel mixer and then granulated in a 20 mmφ extruder. The obtained pellets were extruded using a 50 mmφ extruder equipped with an inflation die with a die grip diameter of 75 min and a lip clearance of 1.2 mm.
The film was formed at 200℃ and the swelling ratio was 4.0.
A film of 480 mm and 20 μm in thickness was obtained. Table 2 shows the physical properties of the obtained film. The physical properties were measured by the method shown below. Haze: ASTM D 1003-52 (%) Impact strength: Using a film impact tester made by Toyo Seiki Seisakusho, 23℃, impact ball diameter 1
Young's modulus measured using inches: Average value in the vertical and horizontal directions calculated from the initial slope according to JIS K 6781

[Table] Comparative Example 1 The same procedure as in Example 1 was conducted except that the magnesium hexadecyl sulfonate used in Example 1 was not used. The results are shown in Table 2. Comparative Example 2 The same procedure as in Example 1 was conducted except that the ethylene-decene-1 copolymer of Example 1 was not used. The results are shown in Table 2. Comparative Example 3 Instead of high density polyethylene of Example 1
MI0.5g/10min, density 0.962g/ ^cm3 , HLMI/
The same procedure was carried out except that MI60 high-density polyethylene was used. The results are shown in Table 2.

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Claims (1)

[Claims] 1 [] Ethylene polymer or ethylene/α-olefin copolymer having the following properties (A) to (C):
70 to 95 parts by weight, (A) Density is 0.94 g/cm ³ or more based on ASTM D 1505 measurement method, (B) Melt flow index is 1 g/10 min or less based on ASTM D 1238E measurement method, (C) Melt flow index based on ASTM D 1238E measurement method and ASTM D
Melt flow index ratio HLMI/MI based on the measurement method of 1238F is 40 or less, [] High pressure low density polyethylene, ethylene-vinyl acetate copolymer with vinyl acetate content of 20% by weight or less, ionomer and density 0.935g / ^cm3
At least one selected from the group consisting of the following ethylene/α-olefin copolymers.
30 parts by weight (however, + is 100 parts by weight), [] 0.01 to 5 parts by weight of at least one magnesium salt or calcium salt of a sulfonic acid selected from alkyl sulfonic acids or alkylbenzenesulfonic acids, and if necessary. At least one selected from dibenzylidene sorbitol or its nuclear substituted product
A polyethylene composition comprising 0.05 to 0.5 parts by weight of seeds. 2 The component [] is a copolymer of ethylene and α-olefin having 6 to 16 carbon atoms, and the ethylene content is
75 to 95 mol%, density 0.85 to 0.91 g/
2. The polyethylene composition according to claim 1, which is an ethylene/α-olefin copolymer having a cm ³ , MI of 4.0 g/10 min or less, and a degree of crystallinity measured by X-rays of 20% or less.