JP6470296B2 - Biaxially stretched ethylene polymer film and package - Google Patents

Description

  The present invention relates to a biaxially stretched ethylene polymer film and a package that are excellent in bending resistance and transparency, and suitable for packaging materials having a specific range of heat shrinkability.

  Ethylene / α-olefin random copolymer, so-called linear low density polyethylene (LLDPE) is more transparent, stress cracking resistance, low temperature heat sealability, heat seal strength, impact resistance, etc. than high pressure method low density polyethylene It is widely used as a sealant for food packaging taking advantage of its characteristics. Among them, the ethylene / α-olefin random copolymer polymerized with a single site catalyst is further excellent in transparency, low-temperature heat sealability, contaminant sealability, and hot tack property.

  A method of biaxially stretching an ethylene / α-olefin random copolymer under specific conditions as a method for improving the transparency, mechanical strength, etc. of the ethylene / α-olefin random copolymer film (Patent Document 1), ethylene・ Proposed shrink film (Patent Document 2) formed by biaxial stretching of α-olefin random copolymer and ethylene / α-olefin random copolymer with high-density polyethylene or high-pressure low-density polyethylene added Has been.

  Further, as a method for improving easy tearability and bending resistance of a biaxially stretched ethylene polymer film, a biaxially stretched ethylene polymer film using an ethylene copolymer composition having specific melting characteristics (Patent Document 3) Or a laminated film (Patent Document 4, Patent Document 5) of the biaxially stretched polymer film and another polymer has been proposed.

However, the biaxially stretched ethylene polymer film obtained by such a method has a large heat shrinkage rate, or when the film is used as a packaging film, the film shrinks when heat sealed, and the appearance deteriorates. It turns out that there is a fear.
On the other hand, as a method of suppressing the heat shrinkage rate of the biaxially stretched ethylene polymer film, a method (Patent Document 6) has been proposed in which the stretched film is heat-treated so that the heat shrinkage rate at 100 ° C. is 30% or less. In Example 3, using an ethylene / α-olefin copolymer having a density of 0.922 g / cm ³ , the thermal contraction rate of MD at 120 ° C. is 48.6%, and the thermal contraction rate of TD is 50. It is described that a biaxially stretched film of 4% (MD + TD = 99.0%) was obtained.

JP 58-90924 A JP-A-57-181828 Japanese Patent No. 4601988 Japanese Patent No. 481438 Japanese Patent No. 4498913 Japanese Patent No. 3030128

  However, as a result of investigation by the present inventor, the heat shrinkage rate described in Example 3 of Patent Document 3 still does not improve the appearance of the heat seal part. It has been found that there is a trade-off relationship that easy tearability and flex resistance of the axially stretched ethylene polymer film are impaired.

The present invention is, bend resistance, excellent transparency, and even if the heat sealing, and to provide a biaxially oriented ethylene polymer film excellent in appearance of the heat-sealed portion.

The present invention has a density of 915 to 938 Kg / m ³ , a heat of fusion (ΔH _T ) obtained by a differential scanning calorimeter (DSC) of 100 to 200 J / g, and a heat of fusion (ΔH _{L) in} the range of the melting start temperature to 110 ° C. ) Is 50-80 J / g, the heat of fusion (ΔH _H ) in the range of 110 ° C. to the end of melting temperature is in the range of 35-100 J / g, and (ΔH _H ) / (ΔH _L ) is 0.5-1. A biaxially stretched ethylene polymer film obtained from the ethylene polymer composition (A) in the range of 5, wherein the heat shrinkage property (heat shrinkage rate) of the biaxially stretched ethylene polymer film is 120 ° C. The sum of the thermal shrinkage (MD) in the machine direction (MD) and the thermal shrinkage (%) in the transverse direction (TD) [MD + TD] is in the range of 15% <[MD + TD] <85%. A biaxially stretched ethylene polymer film characterized by To do.
Moreover, this invention relates to the package body containing said biaxially stretched ethylene polymer film.

Biaxially oriented ethylene polymer films of the present invention, bend resistance, excellent transparency, and even if the heat seal, is excellent in appearance of the heat seal portion, taking advantage of such properties, for various applications as packaging materials Can be used.

Hereinafter, the biaxially stretched ethylene polymer film according to the present invention will be described in detail.
[Ethylene polymer composition (A)]
The ethylene-based polymer composition (A) that forms the biaxially stretched ethylene polymer film of the present invention has a density of 915 to 938 Kg / m ³ , preferably 920 to 935 Kg / m ³ , and a differential scanning calorimeter (DSC). The heat of fusion (ΔH _T ) obtained is 100 to 200 J / g, preferably 130 to 200 J / g, and the heat of fusion (ΔH _L ) in the range of the melting start temperature to 110 ° C. is 50 to 80 J / g, preferably 55 to 80 J. / G, the heat of fusion (ΔH _H ) in the range of 110 ° C. to the end of melting temperature is 35-100 J / g, preferably 50-95 J / g, and (ΔH _H ) / (ΔH _L ) is 0.5. It is an ethylene polymer composition in the range of -1.5, preferably 0.65-1.4.

An ethylene polymer composition having a density outside the above range or (ΔH _T ) outside the above range may make it difficult to form a biaxially stretched film. Further, an ethylene polymer having (ΔH _H ) of less than 35 J / g or (ΔH _T ) / (ΔH _L ) of less than 0.5 is excellent in bending resistance even when a biaxially stretched film is formed. There is a possibility that an axially stretched film cannot be obtained.

  As long as the ethylene-based polymer composition (A) according to the present invention has film-forming ability, the melt flow rate (MFR: ASTM D1238 load 2160 g, temperature 190 ° C.) is not particularly limited. It is in the range of 10 g / 10 min, preferably 0.8-5 g / 10 min.

The density of the ethylene polymer composition (A) according to the present invention is measured by a density gradient tube as described later.
Each heat melting amount of the ethylene polymer composition (A) according to the present invention is a value measured by the following method using a differential scanning calorimeter (DSC).

Using a Q100 manufactured by TA Instruments as a differential scanning calorimeter (DSC), weigh accurately about 5 mg of the sample, and in accordance with JIS K 7122, from 10 ° C. to a heating rate of 10 ° C./min to 180 ° C. The sample was melted once by heating, then maintained at 180 ° C. for 10 minutes, cooled to 10 ° C. at a cooling rate of 10 ° C./minute, crystallized, then maintained at 10 ° C. for 5 minutes, and again Heating rate: The temperature was raised to 180 ° C. at 10 ° C./min to obtain a thermal melting curve. From the obtained thermal melting curve, the thermal melting amount (ΔH _T ) of the sample, and the obtained thermal melting curve was divided into 110 minutes at 110 ° C. Then, the heat of fusion (ΔH _L ) in the range from the melting start temperature to 110 ° C. and the heat of fusion (ΔH _H ) in the range from 110 ° C. to the end temperature of melting were determined.

(ΔH _L ) of the ethylene polymer composition (A) used in the present invention is mainly derived from a low density component contained in the ethylene polymer composition (A), and (ΔH _H ) is mainly ethylene-based. It is derived from the high-density component contained in the polymer composition (A), and (ΔH _H ) / (ΔH _L ) is in the above range, in other words, the ethylene-based polymer according to the present invention. The composition (A) can be said to be an ethylene polymer having a specific range of composition distribution.

Therefore, the ethylene polymer composition (A) according to the present invention can be obtained by appropriately selecting a Ziegler catalyst, a single site catalyst or the like and adjusting the composition distribution (density distribution) of the resulting ethylene polymer. It can also be obtained by appropriately mixing ethylene polymers having different densities. In that case, different ethylene polymer density, for example, the amount of the respective increase or decrease of the polymer amount and density of the polymer having a density in the range of 895~915kg / ^{m 3} is in the range of 915~965kg / ^{m 3} Can also be obtained.

  The ethylene polymer composition (A) used in the present invention is particularly obtained by mixing ethylene polymers having different densities, and the following ethylene copolymer composition (A-1) or ethylene copolymer The combined composition (A-2) is preferred. In addition, the density range of ethylene copolymer composition (A-1) and ethylene copolymer composition (A-2), each heat of fusion are the density range of ethylene polymer composition (A), each heat of fusion and The same.

[Ethylene copolymer composition (A-1)]
The ethylene copolymer composition (A-1) that can be used in the present invention has an ethylene / α-olefin random copolymer having a density in the range of 895 to 925 Kg / m ³ , preferably 900 to 920 Kg / m ³ ( a1) component and density 926~970Kg / ^{m 3,} preferably ethylene copolymer composition comprising ethylene polymer (a2) component in the range 930~965Kg / ^{m 3,} preferably, ethylene The α-olefin random copolymer (a1) component is 5-95 parts by weight, more preferably 20-80 parts by weight and the ethylene-based polymer (a2) component is 95-5 parts by weight, more preferably 80-20 parts by weight. [(A1) + (a2) = 100 parts by weight].

  As long as the ethylene copolymer composition (A-1) that can be used in the present invention has film-forming ability, the melt flow rate (MFR: ASTM D1238, load 2160 g, temperature 190 ° C.) is not particularly limited. 0.5 to 10 g / 10 min, preferably 0.8 to 5 g / 10 min.

[Ethylene copolymer composition (A-2)]
The ethylene copolymer composition (A-2) that can be used in the present invention has an ethylene / α-olefin random copolymer having a density in the range of 895 to 925 Kg / m ³ , preferably 900 to 920 Kg / m ³ ( a1) component, density 926~970Kg / ^{m 3,} preferably 930～965Kg / ethylene polymer in the range of ^{m 3} (a2) component and the density of 910~935Kg / ^{m 3,} preferably 915~930Kg / m ^3. An ethylene copolymer composition comprising high-pressure low-density polyethylene (a3) in the range of ³ .

  In the ethylene copolymer composition (A-2), among the components (a1), (a2) and (a3), the ethylene / α-olefin random copolymer (a1) component is preferably 5 to 95 parts by weight, More preferably, it is in the range of 20 to 80 parts by weight [(a1) + (a2) = 100 parts by weight]. In the ethylene copolymer composition (A-2), the ethylene polymer (a2) component is 95 to 5 parts by weight, more preferably 40 to 70 parts by weight [(a1) + (a2) = 100 parts by weight. Part] is desirable. In the ethylene copolymer composition (A-2), the ethylene / α-olefin random copolymer (a1) component + ethylene-based polymer (a2) component is preferably 50 to 95 parts by weight, preferably 60 parts. -90 parts by weight and high-pressure process low density polyethylene (a3) are in the range of 50-5 parts by weight, preferably 30-10 parts by weight [[(a1) + (a2)] + (a3) = 100 parts by weight]. It is desirable.

  As long as the ethylene copolymer composition (A-2) according to the present invention has a film forming ability, the melt flow rate (MFR: ASTM D1238, load 2160 g, temperature 190 ° C.) is not particularly limited, but is usually 0. .5 to 10 g / 10 min, preferably 0.8 to 5 g / 10 min.

[Ethylene / α-olefin random copolymer (a1)]
An ethylene / α-olefin random copolymer which is a component constituting the ethylene copolymer composition (A-1) or the ethylene copolymer composition (A-2) capable of forming the biaxially stretched ethylene polymer film of the present invention. The polymer (a1) has a density of 895 to 925 Kg / m ³ , preferably 900 to 920 Kg / m ³ , and an α-olefin having 4 or more carbon atoms, such as 1-butene, 1-heptene, 1 -Random copolymers with α-olefins such as hexene, 1-octene, 4-methyl-1-pentene, preferably α-olefins having 6 or more carbon atoms. The ethylene / α-olefin random copolymer (a1) according to the present invention may be one type or a mixture of two or more types as long as the density is in the above range.

  The melt flow rate (MFR: ASTM D1238, load 2160 g, temperature 190 ° C.) of the ethylene / α-olefin random copolymer (a1) according to the present invention is an ethylene copolymer with an ethylene polymer (a2) described later. When the composition (A-1) or the composition (A-2) of the ethylene-based polymer (a2) and the high-pressure method low-density polyethylene (a3) is used, there is no particular limitation as long as it has a film-forming ability. Usually, it is in the range of 0.01 to 10 g / 10 minutes, preferably 0.2 to 5 g / 10 minutes.

In addition, the ethylene / α-olefin random copolymer (a1) usually has a molecular weight distribution (weight average molecular weight: Mw, number average molecular weight: Mn, ratio expressed by Mw / Mn) of 1.5 to 4 in general. 0.0, preferably in the range of 1.8 to 3.5. This Mw / Mn can be measured by gel permeation chromatography (GPC).
The ethylene / α-olefin random copolymer (a1) has one or a plurality of sharp peaks determined from an endothermic curve measured at a heating rate of 10 ° C./min of a differential scanning calorimeter (DSC), The maximum temperature of the peak, that is, the melting point is usually in the range of 70 to 130 ° C, preferably 80 to 120 ° C.

  The ethylene / α-olefin random copolymer (a1) as described above can be prepared by a conventionally known production method using a Ziegler catalyst, a single site catalyst or the like, but is obtained by a single site catalyst (metallocene catalyst). The copolymers obtained are particularly preferred. The catalyst containing the metallocene compound is preferably formed from (a) a transition metal metallocene compound, (b) an organoaluminum oxy compound, and (c) a carrier, and if necessary, these components and (D) It may be formed from an organoaluminum compound and / or an organoboron compound.

  An olefin polymerization catalyst containing such a metallocene compound and a method for adjusting the ethylene / α-olefin random copolymer (a1) using the catalyst are described in, for example, JP-A-8-269270.

[Ethylene polymer (a2)]
An ethylene-based polymer (A-1) that can form the biaxially stretched ethylene polymer film of the present invention or an ethylene polymer that is another component constituting the ethylene copolymer composition (A-2) ( a2) has a density of 926~970Kg / ^{m 3,} preferably ethylene in the range of 930~965Kg / ^{m 3} homopolymer or ethylene and having 3 or more carbon α- olefins, for example, propylene, 1-butene, It is a random copolymer with α-olefin such as 1-heptene, 1-hexene, 1-octene, 4-methyl-1-pentene. The ethylene polymer (a2) according to the present invention may be one type or a mixture of two or more types as long as the density is in the above range.

  The melt flow rate (MFR: ASTM D1238, load 2160 g, temperature 190 ° C.) of the ethylene polymer (a2) is an ethylene copolymer composition (A1) with the ethylene / α-olefin random copolymer (a1). -1) and ethylene-based polymer (a1) and a composition (A-2) with a high-pressure method low-density polyethylene (a3) described later, the film is not particularly limited as long as it has a film-forming ability, but usually 0 0.01 to 100 g / 10 min, preferably 0.1 to 80 g / 10 min.

Ethylene polymer (a2) further has a density 926~945Kg / ^{m 3,} preferably 935～945Kg / ethylene polymer of the range of ^{m 3} (a2-1) density components 946~970Kg / m ³ , preferably 950 to 965 Kg / m ^{3 in} the range of the ethylene polymer (a2-2) component, the low density component and the high density component are used in combination. An axially stretched ethylene polymer multilayer film is obtained.

  When the ethylene polymer (a2-1) component and the ethylene polymer (a2-2) component are used as the ethylene polymer (a2), 1 to 99 parts by weight of the ethylene polymer (a2-1) component is used. , Preferably 30 to 70 parts by weight and 99 to 1 part by weight of ethylene polymer (a2-2) component, preferably 70 to 30 parts by weight [(a2-1) + (a2-2) = 100 parts by weight] It is desirable to make the ratio.

  Further, the ethylene polymer (a2) has a molecular weight distribution (weight average molecular weight: Mw, ratio of number average molecular weight: Mn: expressed as Mw / Mn) is usually 1.5 to 4.0, preferably It is in the range of 1.8 to 3.5. This Mw / Mn can be measured by gel permeation chromatography (GPC).

  The ethylene polymer (a2) has one or more sharp peaks determined from an endothermic curve measured at a heating rate of 10 ° C./min of a differential scanning calorimeter (DSC), the maximum temperature of the peak, That is, the melting point is usually in the range of 122 to 135 ° C.

  The ethylene polymer (a2) as described above can be prepared by a conventionally known production method using a Ziegler catalyst, a single site catalyst or the like. In particular, when the ethylene polymer (a2-1) is used as the ethylene polymer (a2), a copolymer obtained with a single site catalyst (metallocene catalyst) is particularly preferable. The catalyst containing the metallocene compound is preferably formed from (a) a transition metal metallocene compound, (b) an organoaluminum oxy compound, and (c) a carrier, and if necessary, these components and (D) It may be formed from an organoaluminum compound and / or an organoboron compound.

  An olefin polymerization catalyst containing such a metallocene compound and a method for preparing an ethylene polymer (a2) using the catalyst are described in, for example, JP-A-8-269270.

  On the other hand, when the ethylene polymer (a2-2) is used as the ethylene polymer (a2), a polymer obtained by a single site catalyst (metallocene catalyst) may be used, but a conventionally known Ziegler catalyst or the like may be used. The so-called high density polyethylene produced may be used.

[High pressure low density polyethylene (a3)]
The high-pressure low-density polyethylene (a3), which is another component constituting the ethylene copolymer composition (A-2) that can form the biaxially stretched ethylene polymer of the present invention, has a density of 910 to 935 Kg / m ^3, preferably in the range of 915~930Kg / ^{m 3.} The high-pressure method low-density polyethylene is a homopolymer of ethylene polymerized under high pressure, or a copolymer of 5% by weight or less with other α-olefin or vinyl compound such as vinyl acetate. It is an ethylene polymer that falls into the category.

The high-pressure low-density polyethylene having a density of less than 910 kg / m ³ is easy to block when the biaxially stretched multilayer film is molded as the ethylene copolymer composition (A-2), and has high tear strength. The object of the present invention may not be achieved.

  The melt flow rate (MFR: ASTM D1238, load 2160 g, temperature 190 ° C.) of the high-pressure low-density polyethylene (a3) is the same as that of the above-mentioned ethylene / α-olefin random copolymer (a1) and ethylene-based polymer (a2). The ethylene copolymer composition (A-2) is not particularly limited as long as it has a film-forming ability, but is usually 0.1 to 30 g / 10 minutes, preferably 0.1 to 10 g / 10 minutes. It is in the range.

  The ethylene copolymer composition (A-1) and the ethylene copolymer composition (A-2) according to the present invention are each independently an ethylene / α-olefin random copolymer (a1), an ethylene polymer ( After obtaining a2) and high-pressure method low density polyethylene (a3), dry blending with a Henschel mixer, tumbler blender, V-blender or the like, or after dry blending, single screw extruder, multi-screw extruder, Banbury mixer, etc. Obtained by melt kneading.

  The ethylene copolymer composition (A-1) according to the present invention can also be obtained by using a plurality of polymerizers by a continuous / multistage polymerization process to produce an ethylene / α-olefin random copolymer (a1) and an ethylene polymer. A method in which (a2) is polymerized and then mixed to obtain an ethylene copolymer composition (A-1). Using one polymerizer, an ethylene / α-olefin random copolymer (a1) Alternatively, various known polymerization methods such as a method of polymerizing the ethylene polymer (a2) and then polymerizing the ethylene polymer (a2) or the ethylene / α-olefin random copolymer (a1) can be employed.

  Ethylene-based polymer composition (A), ethylene copolymer composition (A-1), ethylene copolymer composition (A-2) or ethylene / α-olefin random constituting these compositions according to the present invention The copolymer (a1), ethylene-based polymer (a2) or high-pressure low-density polyethylene (a3) is used within a range that does not impair the purpose of the present invention, and generally used antioxidants, weathering stabilizers, antistatic agents, Additives such as antifogging agents, antiblocking agents, lubricants, nucleating agents, pigments or other polymers can be blended as necessary.

[Ethylene / α-olefin random copolymer (B)]
The biaxially stretched ethylene polymer film of the present invention is formed from the ethylene polymer composition (A), but is different from the ethylene polymer composition (A) on one or both sides of the ethylene polymer composition (A). You may have an alpha-olefin random copolymer (B).
The ethylene / α-olefin random copolymer (B) according to the present invention has a density of 890 to 945 Kg / m ³ , preferably 900 to 940 Kg / m ³ . When it has a layer made of an ethylene / α-olefin random copolymer (B) in such a density range, it is given low-temperature heat sealability, and seals at low-temperature sealability and low sealing pressure, such as high-speed filling and pillow packaging. It is superior to heat sealing at high speed and high speed.

The ethylene / α-olefin random copolymer having a density of less than 890 kg / m ³ is used to produce a biaxially stretched ethylene polymer multilayer film, particularly when it is biaxially stretched by the flat method (tenter method) described later, There is a possibility of fusion to the tenter clip, and the resulting biaxially stretched ethylene polymer multilayer film is also likely to be blocked. On the other hand, an ethylene / α-olefin random copolymer having a density exceeding 945 kg / m ³ has little effect of imparting a low temperature heat seal property to the resulting biaxially stretched ethylene polymer film.

As long as the ethylene / α-olefin random copolymer (B) according to the present invention has film-forming ability, the melt flow rate (MFR: ASTM D1238, load 2160 g, temperature 190 ° C.) is not particularly limited. It is in the range of 0.5 to 10 g / 10 minutes, preferably 0.8 to 5 g / 10 minutes.
Further, the ethylene / α-olefin random copolymer (B) according to the present invention can be prepared by a conventionally known production method using a Ziegler catalyst, a single site catalyst or the like in the same manner as the ethylene polymer (a2). it can.
The ethylene / α-olefin random copolymer (B) according to the present invention may be a single polymer or a composition comprising two or more types of ethylene / α-olefin random copolymers. Also good.

  In the ethylene / α-olefin random copolymer (B) according to the present invention, an antioxidant, a weathering stabilizer, an antistatic agent, an antifogging agent, and an antiblocking agent which are usually used within a range not impairing the object of the present invention. Additives such as agents, lubricants, nucleating agents, pigments, or other polymers can be blended as necessary.

[Biaxially stretched ethylene polymer film]
The biaxially stretched ethylene polymer film of the present invention is composed of the ethylene polymer composition (A), preferably the ethylene copolymer composition (A-1), or the ethylene copolymer composition (A-2). A biaxially stretched ethylene polymer film that can be formed.
The biaxially stretched ethylene polymer film of the present invention may be a single layer, a film having a layer structure of two layers or three layers or more. In addition, when it has a layer structure of two layers or three layers or more, the multilayer film in which each layer was comprised from the same mixing | blending may be sufficient as the said biaxially stretched ethylene polymer film.
When the biaxially stretched ethylene polymer film of the present invention is a single layer or two or more layers (hereinafter sometimes referred to as “base material layer 1”) composed of the same composition, for convenience. In addition, one side of the biaxially stretched ethylene polymer film is referred to as a heat fusion layer side, and the other side is referred to as a laminate layer side.
On the other hand, when the biaxially stretched ethylene polymer film of the present invention has a layer structure of at least two layers, a base material layer composed of at least an ethylene polymer composition (A), preferably an ethylene copolymer composition (A -1) or the base material layer 2 including a layer made of the ethylene copolymer composition (A-2).
The biaxially stretched ethylene polymer film of the present invention may have a film thickness ratio consisting only of the base material layer of 100% with respect to the whole. When a resin layer having a different composition from the base material layer is provided on the heat sealing layer side or the laminate layer side, the lower limit value of the film thickness ratio of the base material layer to the entire biaxially stretched ethylene polymer film is, for example, 70% or more. Preferably, 75% or more is more preferable, and 80% or more is more preferable. It is preferable that the base layer is in the above range from the viewpoint of setting the thermal shrinkage rate of the biaxially stretched ethylene polymer film within a predetermined range. The upper limit of the film thickness ratio of the base material layer is preferably 98% or less, more preferably 95% or less, and still more preferably 92% or less. Thereby, the characteristic of a multilayer structure can be exhibited.
In addition, when the biaxially stretched ethylene polymer film of the present invention has, for example, a three-layer structure, it is referred to as a heat fusion layer / base material layer / laminate layer for convenience. In that case, the base material layer is made of the ethylene-based polymer composition (A) according to the present invention, preferably the ethylene copolymer composition (A-1), or the ethylene copolymer composition (A-2). Although formed, the heat-sealing layer or the laminate layer may be formed of an ethylene polymer composition (A) having a different density, or formed of the ethylene / α-olefin random copolymer (B). May be. The heat-sealing layer or the laminate layer may be formed from a mixture of the ethylene polymer composition (A) and the ethylene / α-olefin random copolymer (B).

The biaxially stretched ethylene polymer film of the present invention has a corona treatment or flame treatment on the laminate side or the surface of the laminate layer in order to improve adhesion when printing with other thermoplastic resin films or to perform printing. Surface activation treatment such as treatment, plasma treatment, and undercoat treatment may be performed.
When the biaxially stretched ethylene polymer film of the present invention has a multilayer structure, the base material layer is the ethylene polymer composition (A), preferably the ethylene copolymer composition (A-1), or the ethylene copolymer. Although it is necessary to form from a polymer composition (A-2), it is a two layer which has the heat-fusion layer which consists of the said ethylene-alpha-olefin random copolymer (B) on the single side | surface of a base material layer, for example Configuration, or three-layer configuration having a laminate layer made of, for example, ethylene / α-olefin random copolymer (B) or other ethylene / α-olefin random copolymer on the other surface of the base material layer Can be adopted.

As the heat shrinkage characteristics (heat shrinkage rate) of the biaxially stretched ethylene polymer film of the present invention, the heat shrinkage rate (%) in the machine direction (MD) and the heat in the transverse direction (TD) at a heat shrinkage rate of 120 ° C. Sum of shrinkage (%) [MD + TD] ₁₂₀ is 15% <[MD + TD] ₁₂₀ <85%, preferably 25% <[MD + TD] ₁₂₀ <75%, more preferably 30% <[MD + TD] ₁₂₀ <70% More preferably, it satisfies the range of 35% <[MD + TD] ₁₂₀ <65%, and most preferably 37% <[MD + TD] ₁₂₀ <62% (however, the upper limit value and the lower limit value are included).
[MD + TD] ₁₂₀ biaxially oriented ethylene polymer film heat shrinkage rate is less than 15% of, for either a two resulting biaxially stretched ethylene polymer film oriented too is relieved of the stretching biaxially oriented ethylene polymer films There is a possibility that the bending resistance is remarkably lowered. On the other hand, when the biaxially stretched ethylene polymer film having a thermal shrinkage ratio of [MD + TD] ₁₂₀ exceeding 85% is heat-sealed, the heat-sealed portion may shrink and the appearance of the heat-sealed portion may be deteriorated.
Further, in the biaxially stretched ethylene polymer film of the present invention, the sum of the thermal shrinkage rate in the MD direction and the thermal shrinkage rate in the TD direction at a heat shrinkage rate of ₁₂₀ ° C. is [MD + TD] _120, and the heat shrinkage rate at 100 ° C. When the sum of the thermal shrinkage in the MD direction and the thermal shrinkage in the TD direction is [MD + TD] ₁₀₀ , the lower limit of [[MD + TD] _120- [MD + TD] ₁₀₀ ] is preferably 27% or more, for example, 30% The above is more preferable, and 40% or more is more preferable. On the other hand, the upper limit of [[MD + TD] _120- [MD + TD] ₁₀₀ ] is, for example, preferably 65% or less, more preferably 55% or less, more preferably 50% or less, and further preferably 45% or less. By setting the difference in heat shrinkage between 120 ° C. and 100 ° C. within the above range, it is possible to obtain excellent easy tearing, bending resistance, and appearance of the heat seal part.

The biaxially stretched ethylene polymer film of the present invention is preferably from the viewpoint of improving the seal appearance, and the range of the thermal shrinkage rate in at least one of the MD direction or TD direction at 120 ° C. is −0.5% or more and 50%. Or less, more preferably 0% or more and 40% or less, more preferably more than 0%, less than 35%, still more preferably more than 0%, 30% or less, most preferably more than 0% and 25% or less. . The other range of heat shrinkage at 120 ° C. is −10% or more and 65% or less, more preferably −5% or more and 60% or less, more preferably more than 0% and less than 55%, and still more preferably 10%. Thus, it is 53% or less, more preferably 20% or more and 52% or less, and most preferably 30% or more and 50% or less. The heat shrinkage rate increases in the direction of higher draw ratio. For example, when the draw ratio in the TD direction is higher than the draw ratio in the MD direction, the heat shrinkage rate in the TD direction is larger than the heat shrinkage rate in the MD direction also in the heat shrinkage rate.
Furthermore, from the viewpoint of significantly improving the bending resistance, the thermal shrinkage rate in one direction (for example, MD direction) is preferably more than 0%, more preferably 8% or more, and further preferably 15% or more. The thermal shrinkage rate in the other direction (for example, TD direction) is preferably more than −10%, more preferably 50% or less, more preferably 45% or less, and further preferably 35% or less.
In the biaxially stretched ethylene polymer film of the present invention, when the thermal shrinkage rate at 120 ° C. in one direction (for example, MD direction) is MD ₁₂₀ and the thermal shrinkage rate at 100 ° C. in the MD direction is MD ₁₀₀ , the lower limit of MD ₁₂₀ -MD _100], for example, preferably not less than -2%, more preferably at least 3%, more preferably at least 10%, more preferably 15% or more. On the other hand, the upper limit of [MD ₁₂₀ -MD ₁₀₀ ] in one direction (for example, MD direction) is, for example, preferably 20% or less, more preferably 18% or less, more preferably 15% or less, and further preferably 12% or less. . Even in the case of a biaxially stretched ethylene polymer film having a low stretch ratio in one direction (for example, MD direction) by making the difference in heat shrinkage between 120 ° C. and 100 ° C. in one direction (for example, MD direction) within the above range. Excellent tearability, bending resistance, and heat seal appearance can be obtained.

In the biaxially stretched ethylene polymer film of the present invention, preferably, one of the tear strength in the MD direction and the tear strength in the TD direction is (T _S ) and the other is (T _W ) (where T _S ≧ T _W. Yes.) In this case, the tear strength (T _S ) is, for example, 250 to 10 N / cm, preferably 230 to 20 N / cm, and particularly preferably 200 to 20 N / cm. The (T _W ) / (T _S ) is, for example, in the range of 0.10 to 1, preferably 0.20 to 1.
Further, in the biaxially stretched ethylene polymer film of the present invention, from the viewpoint of improving mechanical strength, the lower limit value of at least one tear strength in the MD direction or TD direction (for example, tear strength in the MD direction) is preferably 60 N / cm or more, more preferably 65 N / cm or more, more preferably 76 N / cm or more, more preferably 80 N / cm or more, and most preferably 84 N / cm or more. Further, the higher the tear strength, the better the mechanical strength. In addition, it is more preferable to provide an upper limit value from the viewpoint of ease of opening when the biaxially stretched ethylene polymer film of the present invention is used as a packaging film that is an application of, for example, a package. The upper limit of the tear strength is preferably 175 N / cm or less, more preferably 160 N / cm or less, more preferably 150 N / cm or less, more preferably 145 N / cm or less, and most preferably 135 N / cm or less.
Moreover, directionality can be provided to tearability by making the tear strength of the other (for example, MD direction) smaller than the above tear strength by an arbitrary value, which is preferable from the viewpoint of ease of cutting. The ease of cutting is very effective when the biaxially stretched ethylene-based film of the present invention is used as a packaging film that is used for a package or the like. When one tear strength is 60 N / cm or more, the other tear strength is preferably 20 N / cm or more from the viewpoint of maintaining mechanical strength, and a difference between one tear strength and the other tear strength is preferred. Is 20 N / cm or more and 120 N / cm or less, more preferably 25 N / cm or more and 100 N / cm or less, more preferably 30 N / cm or more and 80 N / cm or less, more preferably 32 N / cm or more and 70 N / cm or less. Most preferably, it is 35 N / cm or more and 60 N / cm or less.

A biaxially stretched ethylene polymer film having a tear strength (T _S ) of 250 N / cm or less is a film having an appropriate tear strength and excellent tearability, and a tear strength (T _S ) of 10 N / cm or more. The biaxially stretched ethylene polymer film has an appropriate tear strength and is excellent in durability as a packaging material. A biaxially stretched ethylene polymer film having (T _W ) / (T _S ) of 0.10 or more has a directionality in tearability and becomes a film that is easily torn in either the longitudinal or transverse direction. The biaxially stretched ethylene polymer film of the present invention preferably has a transparency (haze) in the range of 0.5 to 15%. By setting the haze to 15% or less, excellent transparency can be obtained. Further, the flex resistance is 1000 pieces / m ² or less, preferably 700 pieces / m ² or less. In the case of 1000 pieces / m ² or less, pinholes can be prevented from opening during transportation, storage, and display.

  Although the thickness of the biaxially stretched ethylene polymer film of the present invention can be variously determined depending on the application, the thickness is usually in the range of about 10 to 320 μm, preferably about 15 to 230 μm. In the case of having a biaxially stretched ethylene polymer film, the base material layer has a thickness of about 10 to 200 μm, preferably about 15 to 130 μm, and the heat fusion layer has a thickness of about 0.2 to 60 μm, preferably about 0 In the range of 4 to 40 μm, the total thickness of the biaxially stretched ethylene polymer film is in the range of about 10 to 320 μm, preferably about 15 to 230 μm.

When the biaxially stretched ethylene polymer film of the present invention has a multilayer structure, the heat-sealing layer may be formed on one side or both sides of the base material layer. The biaxially stretched ethylene polymer film having a heat-sealing layer formed on both sides can be used as an overlap packaging film, a water filling packaging sealant film, or a bonding base film.
In addition, when the biaxially stretched ethylene polymer film of the present invention has a multilayer structure, it may have a heat-sealing layer on one side of the base material layer and a laminate layer on the other side. A biaxially stretched ethylene polymer film with a heat-sealable layer on one side and a laminate layer on the other side can be a standing pouch bag, spout bag, or three-sided bag by laminating a thermoplastic resin film to the laminate layer. Can be used for Thus, the biaxially stretched ethylene polymer film of the present invention can be suitably used for a package.

In the biaxially stretched ethylene polymer film of the present invention, a thermoplastic resin film may be laminated on the laminate surface or the laminate layer.
Examples of the thermoplastic resin film include polyolefin (polyethylene, polypropylene, poly-4-methyl-1-pentene, polybutene, etc.), polyester (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyamide (nylon-6, Nylon-66, polymetaxylene adipamide, etc.), polyvinyl chloride, polyimide, ethylene / vinyl acetate copolymer or saponified product thereof, polyvinyl alcohol, polyacrylonitrile, polycarbonate, polystyrene, ionomer, or a mixture thereof. The film to be used can be exemplified.

The thermoplastic resin film may be an unstretched film or a stretched film, or a laminate obtained by one or more types of coextrusion molding, extrusion lamination, dry lamination, thermal lamination, and the like. It may be the body. Among them, a biaxially stretched thermoplastic film, particularly a biaxially stretched thermoplastic film made of polypropylene, polyethylene terephthalate, or polyamide is preferable.
In the biaxially stretched ethylene polymer film of the present invention, a substrate made of paper, aluminum foil or the like may be laminated on the laminate surface or laminate layer.

[Method for producing biaxially stretched ethylene polymer film]
The biaxially stretched ethylene polymer film of the present invention can be obtained by various known methods, for example, the ethylene polymer composition (A) for forming a biaxially stretched ethylene polymer film, or the above-mentioned for forming a heat fusion layer. Extrusion molding or coextrusion molding of ethylene / α-olefin random copolymer (B) or ethylene / α-olefin random copolymer constituting the laminate layer, tubular system or flat system (tenter system) ) Is obtained by biaxial stretching in the longitudinal (MD) direction and transverse (TD) direction within the above range. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. Among these methods, a biaxially stretched ethylene polymer film obtained by a flat method is preferable because it is more excellent in transparency. In the case of the flat method, the sheet obtained by extrusion molding is usually stretched 2 to 12 times, preferably 3 to 10 times in the longitudinal direction in a temperature range of 90 to 125 ° C, and then a temperature of 90 to 140 ° C. It is obtained by stretching 3 to 15 times, preferably 5 to 15 times in the transverse direction. For example, for a biaxially stretched ethylene polymer film, the stretch ratio in the transverse (TD) direction can be made larger than that in the longitudinal (MD) direction.

  The film obtained by biaxial stretching preferably has a heat shrinkage rate of 120 ° C. satisfying the above range by performing heat setting in a temperature range of 115 to 140 ° C. for 6 to 60 seconds. An axially stretched ethylene polymer film can be obtained. When performing heat setting, the inter-clip width of the tenter may be relaxed with respect to the film width.

  If the temperature of the heat set is 80 ° C. or lower, sufficient heat setting cannot be performed, and it may be difficult to adjust the heat shrinkage rate of 120 ° C. within the above range. The resulting biaxially stretched ethylene polymer film has a too small heat shrinkage rate, and it may be difficult to adjust the heat shrinkage rate at 120 ° C. within the above range.

Further, if the heat setting time is less than 6 seconds, sufficient heat setting cannot be performed, and if it exceeds 60 seconds, the heat shrinkage rate of the obtained biaxially stretched ethylene polymer film becomes too small, It may be difficult to adjust the heat shrinkage rate within the above range.
In addition, when heat-setting a film obtained by biaxial stretching, a sufficient heat-setting effect can be obtained by further heat-setting while relaxing the inter-clip width with respect to the film width.
That is, the heat shrinkage difference between 120 ° C. and 100 ° C. in the MD direction and the TD direction is achieved by adjusting the heating temperature and heating time of the heat set within the above range while relaxing the inter-clip width with respect to the film width, MD The difference in heat shrinkage between 120 ° C. and 100 ° C. in the direction, and the heat shrinkage at 120 ° C. in the biaxially stretched ethylene polymer film having a multilayer structure can be within the above-mentioned ranges.

  When another thermoplastic resin film is bonded to the laminate surface or the laminate layer surface of the biaxially stretched ethylene polymer film of the present invention, various known methods, for example, a biaxially stretched ethylene polymer film subjected to corona treatment as necessary After applying urethane type adhesive or isocyanate adhesive to the laminate surface or laminate layer surface, dry laminate with the thermoplastic resin film, or use the high pressure method low density polyethylene for the laminate surface or laminate layer surface and the thermoplastic resin film. It is possible to adopt an extrusion lamination method.

EXAMPLES Next, although this invention is demonstrated through an Example, this invention is not limited by these Examples.
Various test methods and evaluation methods in the present invention are as follows.
(1) Melt flow rate (g / 10 min)
Based on ASTM D1238, the load was 2160 g and the temperature was 190 ° C.
(2) Density (Kg / m ³ )
The polymer strand obtained by measuring MFR was treated at 120 ° C. for 2 hours, slowly cooled to room temperature (23 ° C.) over 1 hour, and then measured by the D method (density gradient tube) according to JIS K 7112. did.

(3) Haze (cloudiness value) (%)
The haze of one film was measured according to JIS K 7136 using Haze Meter (NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.).
(4) Tear strength (N / cm)
In accordance with JIS P8116 and ASTM 1922, using a light load tear tester (Type D manufactured by Toyo Seiki Seisakusho), the film has a length of 64 mm (long side) in the tear direction and a width of 50 mm (short side) in the direction perpendicular to the tear direction. A rectangular test piece was prepared, a 13 mm cut was made in the center of the short side, and the tear strength was measured.

(5) Thermal shrinkage (%)
A 100 mm wide and 100 mm long test piece was cut out so that the film length direction would be the film flow direction (MD) and the width direction (TD), sandwiched between filter papers, left in an oven at a predetermined temperature for 15 minutes, and then removed. Then, the dimensional change of the test piece after being allowed to cool to room temperature was measured, and the shrinkage rate was measured.
(6) Bending resistance Using a gelboflex tester manufactured by Tester Sangyo, a test piece of 210 mm width and 297 mm length was cut out from the film, and each of −30 ° C. at a bending angle of 440 degrees and a bending speed of 40 times / min. Under an atmosphere, after 3000 bending tests, a bag was made with the test piece after the bending test, and the number of pinholes was measured with an ageless seal check made by Mitsubishi Gas Chemical. And it evaluated by the number of pinholes per unit square meter.
(7) Heat seal strength 15 μm-thick Ny (brand: ONBC-15 manufactured by Unitika Co., Ltd.) and a dry-laminated film were used, and a 100 mm wide and 150 mm long test piece was removed from the film using a Toyo Seiki heat seal tester. Cut out and folded in half. Heat seal was performed at a heater temperature of 110 ° C to 140 ° C, a seal pressure of 1 Kgf / cm ² , and a seal time of 1 second, and the sealed test piece was converted into a test piece with a width of 15 mm. Cut out and measured for vertical peel strength using Tensilon RT1225 manufactured by Orientec.

(8) Heat seal appearance (laminated product)
A 15 μm thick Ny (brand: ONBC-15 manufactured by Unitika Co., Ltd.) and a dry-laminated film are sandwiched between fluoroglass sheets, and a heater temperature of 130 ° C. is sealed using a Toyo Seiki heat seal tester 10 mm wide seal bar. Sealing was performed at a pressure of 1 kgf / cm ² and a sealing time of 1 second. The case where no wrinkle was generated on the appearance of the seal was evaluated as ○, and the case where wrinkles were generated was evaluated as ×.
(Non-consolidated)
The film is sandwiched between 12 μm PET (brand: EMBLET manufactured by Unitika Co., Ltd.), a 10 mm wide seal bar of Toyo Seiki's heat seal tester is used, the heater temperature is 130 ° C., the seal pressure is 1 Kgf / cm ² , and the seal time is Sealed in 0.5 seconds. The seal appearance was evaluated as “◯” when no wrinkles or bubbles were generated, and “X” when wrinkles or bubbles were generated.
(Comprehensive evaluation)
The seal appearance in the table shows the results of the following comprehensive evaluation.
Comprehensive evaluation ◎; Evaluation of laminate products ○ and single unit evaluation ○
Comprehensive evaluation ○: Evaluation of laminate products ○ and single unit evaluation ×
Comprehensive evaluation ○: Evaluation of laminate product × and evaluation of single unit ○
Comprehensive evaluation ×: Evaluation of laminate product × and evaluation of single unit ×

The polymers and compositions used in the examples and comparative examples of the present invention are as follows.
(1) Ethylene / α-olefin random copolymer (a1)
Ethylene / 1-hexene random copolymer (a1-1): polymer using metallocene catalyst, density: 905 Kg / m ³ , MFR: 0.5 g / 10 min.

(2) Ethylene polymer (a2)
(I) Ethylene / 1-hexene random copolymer (a2-1): polymer using metallocene catalyst, density: 930 Kg / m ³ , MFR: 60 g / 10 min.
(Ii) Ethylene / propylene / 1-butene random copolymer (a2-2): polymer using Ziegler catalyst, density: 958 Kg / m ³ , MFR: 0.9 g / 10 min.

(3) High pressure method low density polyethylene (a3)
(I) High-pressure method low-density polyethylene (a3-2): density: 917 Kg / m ³ , MFR: 7 g / 10 min.

(4) Ethylene polymer composition (A-2)
(I) Ethylene polymer composition (A-2-1)
The ethylene / 1-hexene random copolymer (a1-1), ethylene / 1-hexene random copolymer (a2-1), ethylene / propylene / 1-butene random copolymer (a2-2) and high pressure method After dry blending low density polyethylene (a3-2) at a ratio of 36: 24: 25: 15 (parts by weight), using a twin screw extruder (46 mmφ) manufactured by Ikekai Tekko Co., Ltd., temperature 190 ° C., extrusion amount 50 kg. The mixture was melt-kneaded under the conditions of / hour to obtain an ethylene polymer composition (A-2-1).

The obtained ethylene polymer composition (A-2-1) had a density; 927 Kg / m ³ , MFR; 2.0 g / 10 minutes, heat of fusion (ΔH _T ); 127.1 J / g, melting start temperature to 110 Heat of fusion in the range of ° C. (ΔH _L ); 63.55 J / g, heat of fusion in the range of 110 ° C. to end of melting temperature (ΔH _H ); 63.55 J / g and (ΔH _H ) / (ΔH _L ); 1 0.00.

(5) Ethylene / α-olefin random copolymer (B)
(I) ethylene / 1-hexene random copolymer (b-1): polymer using metallocene catalyst, density: 903 Kg / m ³ , MFR: 3.8 g / 10 min,
(Ii) ethylene / 1-hexene random copolymer (b-2): polymer using metallocene catalyst, density: 913 Kg / m ³ , MFR: 3.8 g / 10 min.
(Iii) ethylene / 1-hexene random copolymer (b-3): polymer using metallocene catalyst, density: 918 Kg / m ³ , MFR: 3.8 g / 10 min.
(Iv) Ethylene / 1-hexene random copolymer (b-4): polymer using metallocene catalyst, density: 924 Kg / m ³ , MFR: 3.8 g / 10 min,
(V) ethylene / 1-hexene random copolymer (b-5): polymer using metallocene catalyst, density: 931 Kg / m ³ , MFR: 3.1 g / 10 min.

Example 1
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) ethylene / 1-hexene random copolymer (b-3), 50% ethylene polymer composition (A-2-1) in the laminate layer, ethylene / 1-hexene random copolymer ( b-3) 50% dry blended, melt extruded using a biaxially stretched film forming machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll to obtain a thickness An approximately 2.0 mm three-layer sheet ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio) was obtained. It was. This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 40 μm. Annealing was performed at 130 ° C. for 7 seconds while relaxing the width between the tenter clips by 8% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 1.

(Example 2)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) Ethylene / 1-hexene random copolymer (b-3) is used as the laminate layer, and 50% by weight of the ethylene polymer composition (A-2-1) is used for the laminate layer. Ethylene / 1-hexene random copolymer 50% by weight of the blend (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then on a cooling roll. Rapidly cooled three-layer sheet having a thickness of about 2.0 mm ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer Ratio). This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 40 μm. Annealing was performed at 127 ° C. for 7 seconds while relaxing the width between the tenter clips by 4% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 1.

(Example 3)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) ethylene / 1-hexene random copolymer (b-1), laminate layer 50% by weight of the ethylene polymer composition (A-2-1), ethylene / 1-hexene random copolymer 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. And a three-layer sheet having a thickness of about 2.0 mm ((b-1) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio ) This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 40 μm. Annealing was performed at 127 ° C. for 7 seconds while relaxing the width between the tenter clips by 4% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 1.

Example 4
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) is ethylene / 1-hexene random copolymer (b-3), the laminate layer is 50% by weight of the ethylene polymer composition (A-2-1), and ethylene / 1-hexene random copolymer. 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. A three-layer sheet having a thickness of about 2.0 mm ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio ) This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 40 μm. Annealing treatment was performed at 127 ° C. for 7 seconds without relaxing the tenter width with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 1.

(Example 5)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) An ethylene / 1-hexene random copolymer (A-2-1) is used as B), and the ethylene polymer composition (A-2-1) is used as the laminate layer in a biaxial structure including three extrusions. It is melt-extruded using a stretched film molding machine, shaped by a T-die, and then rapidly cooled on a cooling roll to obtain a three-layer sheet ((A-2-1) / (A-2) having a thickness of about 1.5 mm. -1) / (A-2-1) = 9/82/9 layer ratio). This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times was heated to 115 ° C. and stretched 10.0 times in the direction perpendicular to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 30 μm. Annealing treatment was performed at 132 ° C. for 7 seconds while relaxing the inter-clip width of the tenter by 4% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 2.

(Example 6)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) An ethylene / 1-hexene random copolymer (b-2) was used as B), and the ethylene polymer composition (A-2-1) was used as the laminate layer for the biaxially stretched film provided with three extrusions. Three-layer sheet ((b-2) / (A-2-1) / having a thickness of about 1.5 mm after being melt-extruded using a molding machine and shaped by a T-die and then rapidly cooled on a cooling roll. (A-2-1) = 9/82/9 layer ratio). This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times was heated to 115 ° C. and stretched 10.0 times in the direction perpendicular to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 30 μm. Annealing treatment was performed at 132 ° C. for 7 seconds while relaxing the inter-clip width of the tenter by 4% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 2.

(Example 7)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) An ethylene / 1-hexene random copolymer (b-3) is used as B), and the ethylene polymer composition (A-2-1) is used as a laminate layer for a biaxially stretched film provided with three extrusions. Three-layer sheet ((b-3) / (A-2-1) / having a thickness of about 1.5 mm after being melt-extruded using a molding machine and shaped with a T-die and then rapidly cooled on a cooling roll. (A-2-1) = 9/82/9 layer ratio). This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times was heated to 115 ° C. and stretched 10.0 times in the direction perpendicular to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 30 μm. Annealing treatment was performed at 132 ° C. for 7 seconds while relaxing the inter-clip width of the tenter by 4% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 2.

(Example 8)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) An ethylene / 1-hexene random copolymer (b-4) was used as B), and the ethylene polymer composition (A-2-1) was used as the laminate layer for the biaxially stretched film provided with three extrusions. Three-layer sheet ((b-4) / (A-2-1) / having a thickness of about 1.5 mm after being melt-extruded using a molding machine and shaped by a T-die and then rapidly cooled on a cooling roll. (A-2-1) = 9/82/9 layer ratio). This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times was heated to 115 ° C. and stretched 10.0 times in the direction perpendicular to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 30 μm. Annealing treatment was performed at 132 ° C. for 7 seconds while relaxing the inter-clip width of the tenter by 4% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 2.

Example 9
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) An ethylene / 1-hexene random copolymer (b-5) is used as B), and the ethylene polymer composition (A-2-1) is used as the laminate layer for the biaxially stretched film provided with three extrusions. Three-layer sheet ((b-5) / (A-2-1) / having a thickness of about 1.5 mm after being melt-extruded using a molding machine and shaped by a T-die and then rapidly cooled on a cooling roll. (A-2-1) = 9/82/9 layer ratio). This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times was heated to 115 ° C. and stretched 10.0 times in the direction perpendicular to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 30 μm. Annealing treatment was performed at 132 ° C. for 7 seconds while relaxing the inter-clip width of the tenter by 4% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 3.

(Example 10)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) is ethylene / 1-hexene random copolymer (b-3), the laminate layer is 50% by weight of the ethylene polymer composition (A-2-1), and ethylene / 1-hexene random copolymer. 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. And a three-layer sheet having a thickness of about 1.5 mm ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio ) This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times was heated to 115 ° C. and stretched 10.0 times in the direction perpendicular to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 30 μm. Annealing was performed at 130 ° C. for 7 seconds while relaxing the width between the tenter clips by 8% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 3.

(Example 11)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) is ethylene / 1-hexene random copolymer (b-3), the laminate layer is 50% by weight of the ethylene polymer composition (A-2-1), and ethylene / 1-hexene random copolymer. 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. A three-layer sheet having a thickness of about 2.0 mm ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio ) This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 40 μm. Annealing was performed at 130 ° C. for 7 seconds while relaxing the width between the tenter clips by 8% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 3.

(Example 12)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) is ethylene / 1-hexene random copolymer (b-3), the laminate layer is 50% by weight of the ethylene polymer composition (A-2-1), and ethylene / 1-hexene random copolymer. 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. And a three-layer sheet having a thickness of about 3.0 mm ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio ) This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction perpendicular to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 60 μm, and then the film Annealing was performed at 130 ° C. for 7 seconds while relaxing the width between the tenter clips by 8% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. The results are shown in Table 3.

(Example 13)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) is ethylene / 1-hexene random copolymer (b-3), the laminate layer is 50% by weight of the ethylene polymer composition (A-2-1), and ethylene / 1-hexene random copolymer. 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. And a three-layer sheet having a thickness of about 3.5 mm ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio ) This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 70 μm, and then the film Annealing was performed at 130 ° C. for 7 seconds while relaxing the width between the tenter clips by 8% with respect to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. Table 4 shows the results.

(Comparative Example 1)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) ethylene / 1-hexene random copolymer (b-1), laminate layer 50% by weight of the ethylene polymer composition (A-2-1), ethylene / 1-hexene random copolymer 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. And a three-layer sheet having a thickness of about 2.0 mm ((b-1) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio ) This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 40 μm. Annealing was performed at 110 ° C. for 7 seconds without relaxing the width between the tenter clips relative to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. Table 4 shows the results.

(Comparative Example 2)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) is ethylene / 1-hexene random copolymer (b-3), the laminate layer is 50% by weight of the ethylene polymer composition (A-2-1), and ethylene / 1-hexene random copolymer. 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. And a three-layer sheet having a thickness of 2.0 mm ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio) Got. This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 40 μm. Annealing was performed at 110 ° C. for 7 seconds without relaxing the width between the tenter clips relative to the width. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. Table 4 shows the results.

(Comparative Example 3)
As the ethylene polymer for the biaxially stretched ethylene polymer film substrate layer, the ethylene polymer composition (A-2-1) and the ethylene / α-olefin random copolymer ( B) is ethylene / 1-hexene random copolymer (b-3), the laminate layer is 50% by weight of the ethylene polymer composition (A-2-1), and ethylene / 1-hexene random copolymer. 50% by weight of (b-3) was dry blended, melt extruded using a biaxially stretched film molding machine equipped with three extrusions, shaped with a T-die, and then rapidly cooled on a cooling roll. A three-layer sheet ((b-3) / (A-2-1) / ((A-2-1) + (b-3)) = 9/82/9 layer ratio) having a thickness of about 2 mm. Obtained. This sheet was heated to 100 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated to 115 ° C. and stretched 10.0 times in the direction orthogonal to the flow direction (transverse direction) to obtain a biaxially stretched ethylene polymer multilayer film having a thickness of 40 μm. Annealing treatment was performed at 130 ° C. for 7 seconds while relaxing the inter-clip width of the tenter with respect to the width, and further annealed at 125 ° C. for 2 minutes using an oven. The physical properties of the biaxially stretched ethylene polymer multilayer film were measured by the method described above. Table 4 shows the results.

  The biaxially stretched ethylene polymer film of the present invention is excellent in mechanical strength such as film strength, pinhole resistance, and easy tearability, heat sealable, and excellent in film appearance during heat sealing. It is widely used as a flexible packaging material for industrial materials and other packaging materials. Above all, for packaging electronic parts with sharp protrusions, shells such as shrimp and crab, delicacy and skewered yakitori, frozen foods such as ice blocks, and dishes with sharp protrusions. Is suitable. Moreover, since it is excellent in bending resistance, it is also suitable for applications such as standing pouch bags and spout bags.

  This application is based on the priority based on Japanese Patent Application No. 2014-184239 filed on September 10, 2014 and the Japanese Patent Application No. 2015-081431 filed on April 13, 2015. All the disclosures of which are hereby incorporated by reference.

Claims (9)

The density is 915 to 938 Kg / m ³ , the heat of fusion (ΔH _T ) obtained by a differential scanning calorimeter (DSC) is 100 to 200 J / g, and the heat of fusion (ΔH _L ) in the range of the melting start temperature to 110 ° C. is 50 to 50 The heat of fusion (ΔH _H ) in the range of 80 J / g, 110 ° C. to the melting end temperature is in the range of 35 to 100 J / g, and (ΔH _H ) / (ΔH _L ) is in the range of 0.5 to 1.5. A biaxially stretched ethylene polymer film including a base material layer made of an ethylene polymer composition (A),
The heat shrinkage of the biaxially stretched ethylene polymer film is the sum of the heat shrinkage (%) in the machine direction (MD direction) and the heat shrinkage (%) in the transverse direction (TD direction) at a heat shrinkage of 120 ° C. Is a range of 15% <[MD + TD] <85%, where [MD + TD] is a biaxially stretched ethylene polymer film. The biaxially stretched ethylene polymer film according to claim 1,
A biaxially stretched ethylene polymer film having a tear strength of at least one of MD direction and TD direction of 60 N / cm or more. The biaxially stretched ethylene polymer film according to claim 1 or 2,
A biaxially stretched ethylene polymer film, wherein the biaxially stretched ethylene polymer film has a layer structure of at least two layers. The biaxially stretched ethylene polymer film according to claim 3,
The biaxially stretched ethylene polymer film, wherein the thickness ratio of the base material layer to the entire biaxially stretched ethylene polymer film is 70% or more. The biaxially stretched ethylene polymer film according to claim 3 or 4,
A biaxially stretched ethylene polymer film having a layer made of an ethylene / α-olefin random copolymer (B) having a density in the range of 890 to 945 kg / m ³ . A biaxially stretched ethylene polymer film according to any one of claims 1 to 5,
The thermal shrinkage rate at 120 ° C. in either the MD direction or the TD direction is −0.5% or more and 25% or less, and the other thermal shrinkage rate at 120 ° C. is 30% or more and 50% or less. Axial stretched ethylene polymer film. The biaxially stretched ethylene polymer film according to any one of claims 1 to 6,
The sum of the thermal contraction rate in the MD direction and the thermal contraction rate in the TD direction at 120 ° C. is [MD + TD] _120, and the thermal contraction rate in the MD direction and the thermal contraction rate in the TD direction at 100 ° C. A biaxially stretched ethylene polymer film in which [[MD + TD] _120- [MD + TD] ₁₀₀ ] is 27% or more and 65% or less when the sum is [MD + TD] ₁₀₀ . The biaxially stretched ethylene polymer film according to any one of claims 1 to 7,
When the thermal shrinkage rate at 120 ° C. in the MD direction is MD ₁₂₀ and the thermal shrinkage rate at 100 ° C. in the MD direction is MD ₁₀₀ , [MD ₁₂₀ -MD ₁₀₀ ] satisfies −2% or more and 20% or less.
Biaxially stretched ethylene polymer film.   A package comprising the biaxially stretched ethylene polymer film according to any one of claims 1 to 8.