JPH10139954A - Wrap stretch film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefinic wrap stretch film excellent in wrapping properties and retention of wrapping. SOLUTION: This film is obtd. from a polyolefin compsn. comprising 40-90wt.% propylene polymer and 10-60wt.% ethylene/4C or higher α-olefin copolymer having a content of α-olefin-derived monomer unit of 1-15mol%, an MI ratio given by the formula of 7-20, and a ratio of wt. average mol.wt. (Mw) to number average mol.wt. (Mn) of 1.0-2.5. The formula expressing the MI ratio is, MI ratio=(melt index measured with 10kgf)/(melt index measured with 2kgf).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wrap stretch film, and more particularly, to a polyolefin wrap stretch film having excellent lapping properties and wrapping retention properties.

[0002]

2. Description of the Related Art Conventionally, excellent optical properties, deformation recovery properties and flexibility have been applied to wrap packaging for business use such as food packaging.
A vinyl chloride film has been frequently used due to adhesion and the like. However, in recent years, as environmental problems have come to the fore, packaging materials have been required to replace vinyl chloride, which generates harmful gases by incineration.

On the other hand, general-purpose polyolefin resins are not only inferior in optical properties but also poor in recovery from deformation after stretching and self-adhesiveness, and are not suitable for wrap films.

Therefore, it has been proposed to use an ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) or an ethylene-α-olefin copolymer alone or as a mixture as a material resin for a wrap stretch film. If these polyethylene-based soft resins are used with a low degree of crystallinity, those having excellent deformation recovery properties can be obtained.However, since the stress relaxation is reduced at the same time and the film tension is strongly maintained even after lapping, There is a disadvantage that the tray is easily deformed and the adhesive portion is easily peeled off. Furthermore, since the yield stress becomes smaller as the degree of crystallinity decreases, it is necessary to suppress the adhesive force in consideration of the unwinding property, and thus the peeling of the adhesive portion has been more likely to occur. In addition, the polyethylene-based film has a dissatisfaction that it cannot withstand use in a microwave oven due to its low melting point.

On the other hand, it has been proposed to use a polypropylene-based soft resin such as ethylene-propylene rubber, ethylene-propylene-diene rubber, or a polyolefin elastomer obtained by mixing styrene-butadiene rubber with polypropylene. These have problems such as inferior transparency and accuracy of thickness and thinness of the film and insufficient deformation recovery after stretching due to problems such as low fluidity. For example, Japanese Unexamined Patent Publication No. Hei 6-256439 proposes a three-layer film using a propylene-ethylene copolymer as a base layer, but it cannot be said that deformation recovery after stretching is sufficient, and wrapping is not sufficient. I am dissatisfied with the tightness afterwards and the return of the film after pressing the wrapped film with a finger.

[0006]

SUMMARY OF THE INVENTION Under the above circumstances, the present invention can perform lapping with a good appearance, has excellent shape retention after lapping, and has excellent transparency and film unwinding properties. An object of the present invention is to provide a polyolefin-based wrap stretch film which is excellent and can be substituted for a vinyl chloride wrap stretch film.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to obtain a film free from the above-mentioned drawbacks. As a result, a film composed of a specific ethylene-α-olefin copolymer and a propylene-based polymer has been obtained. The inventors have found that the above problems can be solved, and have completed the present invention.

That is, the present invention relates to (a) 40 to 90% by weight of a propylene polymer, (b) a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, and Ii) an MI ratio of 7 to 20 represented by the following formula:

[0009]

(Equation 2)

Iii) Wrap stretch comprising a polyolefin composition comprising 10 to 60% by weight of an ethylene-α-olefin copolymer having a weight average molecular weight (Mw) / number average molecular weight (Mn) of 1.0 to 2.5. Film.

Hereinafter, the present invention will be described in detail.

In the wrap stretch film, it is necessary that the elasticity of the film, that is, the strain relaxation is small, from the viewpoint of preventing wrinkles from occurring during packaging and maintaining a tight feeling after packaging. However, it is necessary that the stress is relieved to a large extent in order to prevent the deformation of the tray. Although it is difficult to balance the above-mentioned small strain relaxation and large stress relaxation because of their contradictory properties, we have found that the propylene-based polymer described below contains 40 to 90% by weight, preferably 60 to 90% by weight. A specific ethylene-α-olefin copolymer is 10 to 60% by weight, preferably 10 to 40% by weight.
The present inventors have found that a film comprising a polyolefin composition comprising a weight% of the composition has a good balance between strain relaxation and stress relaxation, and is suitable for a wrap stretch film. When the blending ratio of the ethylene-α-olefin polymer is less than 10% by weight, the film lacks elasticity and is not suitable for generating wrinkles and necking at the time of packaging. If the amount is less than 10% by weight, the film is too rubbery to cause deformation of the tray after packaging and to cause blocking during film formation, which is not preferable.

In the present invention, the propylene polymer is a homopolymer of propylene or a copolymer with another monomer copolymerizable with propylene. Other copolymerizable monomers include those having 4 carbon atoms such as ethylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and 1-decene. To α-olefins and diene such as divinylbenzene, 1,4-cyclohexadiene, dicyclopentadiene, cyclooctadiene, and ethylidene norbornene, among which ethylene is preferred.

The method for producing these propylene-based polymers is not particularly limited, and generally, a Ziegler-Natta catalyst using a combination of a so-called titanium-containing solid transition metal portion and an organic component, particularly a transition metal component Is a solid component or titanium trichloride containing titanium, magnesium and halogen as essential components and an electron donating compound as an optional component, using a catalyst in which an organometallic component is an organoaluminum compound, using slurry polymerization, gas phase polymerization, and bulk polymerization. ,
It can be obtained by one-stage or multi-stage polymerization using a solution polymerization or a combination thereof. In addition, these propylene-based polymers may be random polymers or block copolymers, but preferred are random copolymers. In addition, two or more of these propylene polymers may be used.

Further, the propylene polymer preferably satisfies the following conditions with respect to the melt index (hereinafter abbreviated as MI) and the content of other copolymerizable monomers.

I) MI The MI of the propylene-based polymer of the present invention measured at 230 ° C. under 2 kgf is preferably 0.01 to 50 g / 10
Min, more preferably 0.1 to 30 g / 10 min, even more preferably 1 to 20 g / 10 min. When the MI is in the above range, a film excellent in film appearance without particular surface roughness and excellent in film strength can be obtained.

Ii) Content of other copolymerizable monomer When the propylene-based polymer of the present invention is a copolymer of propylene with another monomer copolymerizable with propylene, another monomer is used. The body content is preferably up to 40% by weight, more preferably up to 30% by weight. Within such a range of the content of the other monomer, it is possible to obtain a film having particularly small troubles such as partial elongation at the time of unwinding the film.

Next, the ethylene-α-olefin copolymer in the present invention is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms. The α-olefin in the present invention is a hydrocarbon consisting of only 4 or more, preferably 4 to 20 carbon atoms and hydrogen atoms, and having an unsaturated bond at its terminal. Hexene, 4-methylpentene, octene, decene and the like. These α-olefins may be used alone or in combination of two or more.

Further, as the ethylene-α-olefin copolymer, those satisfying the following conditions with respect to the monomer unit, MI ratio and molecular weight distribution based on α-olefin are used.

I) Monomer unit based on α-olefin The monomer unit based on α-olefin in the ethylene-α-olefin copolymer of the present invention accounts for 1 to 15 mol%, preferably 5 to 15 mol%. %. When the monomer unit based on α-olefin is lower than the above, the flexibility and deformation recovery of the film become insufficient, which is not preferable. On the other hand, when the monomer unit based on α-olefin is higher than the above range, the unwinding resistance of the film becomes large and not only can not be smoothly wrapped, but also a low molecular weight material is easily generated, and bleeding of the film is caused. Cause.

Ii) MI ratio In the ethylene-α-olefin copolymer of the present invention,
The following formula

[0022]

(Equation 3)

The MI ratio represented by the following formula is preferably 7 to 2
0, more preferably 8 to 15. Here, each MI
Is a value measured at 190 ° C. When the MI ratio is higher than the above range, bleeding is caused due to a large amount of low molecular weight components, and unwinding property is deteriorated, and since there are many branches in the molecular chain, stress relaxation is increased, and lap adhesion is increased. This is not preferable because the exfoliation tends to occur easily and the transparency tends to deteriorate due to lack of compatibility with the propylene-based polymer. On the other hand, when the MI ratio is lower than the above, the fluidity is inferior and the processability deteriorates, which is not preferable.

Iii) Molecular weight distribution In the ethylene-α-olefin copolymer of the present invention,
The molecular weight distribution represented by weight average molecular weight (Mw) / number average molecular weight (Mn) is 1.0 to 2.5, preferably 1.2.
~ 2.0. When the molecular weight distribution is larger than the above, the unwinding property of the low molecular weight material due to bleeding tends to deteriorate with time. Furthermore, in general, ethylene-α-olefin copolymers having a wide molecular weight distribution tend to have a wide composition distribution, and an increase in heat sealing temperature due to the formation of polyethylene crystals deteriorates sealing properties in a pillow package, or causes bleeding of low molecular weight components. This tends to cause problems such as deterioration of unwinding property over time and blocking, which is not preferable.

The ethylene-α-olefin copolymer has an MI of 0.01 to 50 g / 10 minutes, preferably 0.1 to 30 g, measured at 190 ° C. under 2 kgf.
/ 10 minutes, more preferably 1 to 20 g / 10 minutes. When the MI is in the above range, a film excellent in film appearance without any surface roughness and excellent in film strength can be obtained.

Further, the ethylene-α-olefin copolymer has a density of 0.85 to 0.95 kg / l, preferably 0.85 to 0.93 kg / l. When the density is in the above range, a film having particularly excellent deformation recovery and transparency can be obtained.

In the present invention, the method for producing the ethylene-α-olefin copolymer is not particularly limited. Choosing conditions known in the prior art for Ziegler-Natta or Kaminsky-Sin type polymerization reactions,
It may be polymerized by bulk polymerization, suspension method, solution method, slurry method, gas phase method or other methods. These polymerizations may be a batch method or a continuous method. Also,
A method for obtaining an ethylene-α-olefin copolymer suitably used in the present invention is described in, for example,
A method as proposed in Japanese Patent Publication No. 306121 is cited. That is, a catalyst comprising a metallocene transition metal complex having a specific ligand and an organoaluminum compound may be used as the catalyst, and the catalyst component may be supported on an inorganic substance. As the metallocene-based transition metal complex, a transition metal selected from the group IVB [titanium,
And a coordination compound in which a ligand having a cyclopentadienyl group and an amidosilane group or an amidoalkanediyl, and a halogen atom or an alkyl group are bonded. Examples of the organoaluminum compound include alkylaluminum, and a chain or cyclic aluminoxane. The chain or cyclic aluminoxane is produced by bringing alkyl aluminum into contact with water.For example, alkyl aluminum is added during polymerization and water is added later, or water of crystallization of complex salt or water of adsorption of organic and inorganic compounds is added. It is obtained by reacting with alkyl aluminum. Examples of the inorganic substance for supporting the catalyst include silica gel, zeolite, and diatomaceous earth.

In the present invention, the film made of the above-mentioned polyolefin composition achieves the object of the present invention sufficiently as a wrap stretch film, even if it is a single-layer film. Alternatively, another resin layer may be laminated on at least one film surface to use as a multilayer film. In that case, the film layer composed of the above-mentioned polyolefin composition comprises 5% of the total film.
It is preferable to make it 0% or more.

The thickness of the film is preferably 5 to 30 μm, and 7 to 20 μm.
Is more preferable, and further preferably 10 to 15 μm. If the film is too thin, it is not only difficult to form an accurate film,
Due to the adhesiveness of the film, the film is likely to be stretched or broken at the time of being pulled out from a roll.On the other hand, if the film is excessively thick, the adhesive portion becomes a large lump, impairing the aesthetic appearance and cost. Since it is disadvantageous, the thickness of the film is most preferably in the above range.

In the present invention, when the wrap stretch film is to have more excellent optical properties such as transparency and transparency, the surface layer is preferably made of a resin comprising linear low-density polyethylene or ethylene-vinyl acetate copolymer. Preferably, the layers are stacked.

Here, the linear low-density polyethylene refers to a polymer mainly composed of ethylene which is generally recognized as a linear low-density polyethylene, and is usually obtained by a method such as a gas phase method, a slurry method or a solution method. And a random copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms or a block copolymer thereof.

The above linear low density polyethylene was heated at 190 ° C.
The MI under 2 kgf is preferably 0.1 to 20 g / min.
When the MI is in the above range, a film excellent in film appearance without any surface roughness, and excellent in transparency and film strength can be obtained.

The α-olefin constituting the linear low-density polyethylene is, for example, 1-butene, 3-methyl-1
-Butene, 4-methyl-1-pentene, 1-hexene,
Examples thereof include those having 3 to 20 carbon atoms such as 1-octene and 1-decene. These α-olefins may be used alone or in combination of two or more. Also, α-
The monomer unit amount based on the olefin is preferably from 1 to 15 mol%. When the amount of the monomer unit based on the α-olefin is in the above range, there is no problem such as blocking, and a film excellent in film spreadability can be obtained.

The density of the linear low-density polyethylene is:
0.89 to 0.94 kg / l is preferred. When the density is in the above range, particularly, a film that hardly causes blocking of the film and has excellent extensibility of the film is obtained.

In the present invention, as the ethylene-vinyl acetate copolymer, a random copolymer or a block copolymer of ethylene and vinyl acetate can be used without limitation. Further, the amount of the monomer based on vinyl acetate is preferably 1 to 15 mol%. When the amount of the monomer based on vinyl acetate is in the above range, in particular, a film which hardly causes blocking of the film and has excellent extensibility of the film can be obtained.

The ethylene-vinyl acetate copolymer of 19
The MI at 0 ° C. and 2 kgf is preferably 0.1 to 20. In particular, when the MI is in the above range, a film excellent in film appearance without surface roughness or the like and excellent in transparency and film strength can be obtained.

The density of the ethylene-vinyl acetate copolymer is preferably from 0.91 to 0.97 kg / l. When the density is in the above range, particularly, a film that hardly causes blocking of the film and has excellent extensibility of the film is obtained.

The above-mentioned linear low-density polyethylene and ethylene-vinyl acetate copolymer may be used alone or in combination. Further, for the purpose of improving fluidity and moldability, a polyolefin such as ultra-low density polyethylene, low density polyethylene, or high density polyethylene is used in the corresponding layer as long as the transparency and flexibility of the film are not impaired.
0% or less may be mixed.

In the present invention, additives suitable for imparting certain properties to the film to be produced can be added. For example, antioxidants, weathering agents such as ultraviolet absorbers, antiblocking agents, flame retardants, antifoggants, adhesives,
Examples include coloring agents, matting agents, antistatic agents, oxygen and carbon dioxide gas absorbents, gas adsorbents, freshness preserving agents, enzymes, deodorants, and fragrances. In addition, other components may be added as needed as long as the features of the present invention are not impaired.

The film of the present invention can be produced by using any known molding method. Specifically, methods such as an extrusion casting method, an upward inflation method, a downward water-cooling inflation method, a biaxial tenter method, and a tubular biaxial stretching method can be used without any limitation. In the case of a multilayer film, it may be manufactured by a coextrusion method or the like. The film thus obtained may be unstretched, or may be uniaxially or biaxially stretched after film formation, but the stretching magnification should be 40 times or less in area magnification. Is preferred.

[0041]

As described above, the wrap stretch film of the present invention comprising a propylene-based polymer and a specific ethylene-α-olefin copolymer has a moderate content binding force, so that deformation of the tray or It is difficult for the adhesive part to be loosened. At the same time, since the strain recovery property satisfies the required amount, it is possible to suppress wrinkles during wrapping and depressions after acupressure of the wrapped film. Furthermore, it has good bottom sealing properties.

Therefore, the wrap stretch film of the present invention has such excellent properties as described above, so that it can wrap articles very well regardless of fruits and vegetables, prepared dishes, meat, fresh fish and the like.

[0043]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention.

(1) Measurement method Ratio of number average molecular weight and weight average molecular weight Measured by GPC (gel permeation chromatography). Water-based GPC-150C was carried out at 135 ° C. using o-dichlorobenzene as a solvent. The column used was Tosoh TSK gel GMH
6-HT, gel size 10-15 μm. The calibration curve has a weight average molecular weight of 950, 2900,
It was prepared using 10,000, 50,000, 49,980, 2.7, and 6.75 million polystyrene.

Method for measuring the proportions of the monomer units based on ethylene and the monomer units based on propylene in the propylene-ethylene random copolymer component was calculated using a 13C-NMR spectrum chart. That is, the respective proportions of the monomer units based on ethylene and the monomer units based on propylene in the propylene-ethylene random copolymer component are as follows: First, Polymer (Polymer) Vol. 29 (1988) 1848
The assignment of the peaks was determined by the method described on page 2, then Macromolecules (Macromolecules).
s) The respective ratios of the monomer units based on ethylene and the monomer units based on propylene were calculated by the method described in Volume 10 (1977), page 773.

The measurement was carried out according to MI JIS-K7210.

MI ratio The value (I) at a load of 10 kg according to JIS-K7210
10) and the value (I2) at a load of 2.16 kg (I2).
/ I2).

The density was measured according to JIS-K7112.

Haze Measured according to JIS-K7105.

Wrapping property Three apples were placed on a tray and wrapped using an ARC handler (205-U), and the appearance was evaluated on a three-point scale.

○ → good, △ → partial sag, × →
Unwrinkling or adhesion does not work well. Unwinding resistance A roll of 300 m of film wound around a 3 inch inside diameter paper tube is placed on two rollers with low resistance, and the film end is unwound at a head speed of 300 mm / min. Tensile tension was measured.

Finger push-back property The film was wrapped in a tambourine shape on an iron cylinder having an inner diameter of 100 mm and a height of 10 mm, and the center (center of the circle) of the wrapped film was pressed with the middle finger by the height of the cylinder (10 mm). The state of the impression after one minute was evaluated on a three-point scale.

○ → Pressed marks disappeared, Δ → Wrinkles generated, × → Pressed marks remained (2) Constituent resin

[0054]

[Table 1]

(3) Molding of Multilayer Film Examples of film formation are described below. Table 2 shows the composition and constitution of each multilayer film, and the haze value, wrapping property and unwinding property of the obtained film were evaluated. Table 3 summarizes the results.

Example 1 A propylene polymer (PP-3) and an ethylene-octene copolymer (PE-1) were mixed at a ratio of 75:25, extruded into a circular die, and extruded into a film at 190 ° C. did. Next, air is blown into the inside of the molten cylindrical film, and air is blown annularly from outside to solidify by air cooling, and the draft 30, the blow-up ratio 3, and the take-up speed 40
The film was taken at m / min to obtain a film having a thickness of 13 μm. Table 3 shows the measurement results of the physical properties of the obtained film.

The obtained film had good lapping and drawing properties.

Example 2 In Example 1, random polypropylene (PP-2) and propylene-based polymer (PP-4) were used as constituent resins.
And ethylene-octene copolymer (PE-1)
The same operation as in Example 1 was performed except that the mixture was mixed at a ratio of 5:50:25.

The obtained film had good lapping and drawing properties.

Example 3 In Example 1, homopolypropylene (PP-1), propylene-based polymer (PP-4) and ethylene-octene copolymer (PE-1) were used as constituent resins in a ratio of 25: 5.
The same operation as in Example 1 was performed except that the components were mixed at a ratio of 0:25.

The obtained film had good lapping and drawing properties.

Example 4 In Example 1, the propylene polymer (PP-3) and the ethylene-octene copolymer (P
Example 1 except that E-2) was mixed at a ratio of 75:25.
The same was done.

The obtained film had good lapping and drawing properties.

Example 5 In Example 1, random polypropylene (PP-2) and propylene-based polymer (PP-4) were used as constituent resins.
And ethylene-octene copolymer (PE-2)
The same operation as in Example 1 was performed except that the mixture was mixed at a ratio of 5:50:25.

The obtained film had good lapping and drawing properties.

Example 6 In Example 1, propylene polymer (PP-3) and ethylene-octene copolymer (P
Example 1 except that E-1) was mixed at a ratio of 85:15.
The same was done.

The obtained film had good lapping and drawing properties.

Example 7 In Example 1, the propylene polymer (PP-3) and the ethylene-octene copolymer (P
Example 1 except that E-1) was mixed at a ratio of 65:35.
The same was done.

The obtained film had good lapping and drawing properties.

Example 8 A three-layer three-layer multilayer inflation die was used. From the inner surface layer and outer surface layer extruder, ethylene-butene copolymer (PE-
3) was extruded, and a mixture comprising 75% by weight of a propylene-based polymer (PP-3) and 25% by weight of an ethylene-octene copolymer (PE-1) was extruded from a substrate layer extruder, and 19
Extruded into a film at 0 ° C. Next, air is blown into the inside of the molten cylindrical film, air is blown annularly from the outside to solidify by air cooling, and the draft is taken up, the blow-up ratio is 3. The take-up speed is 40 m / min, and the thickness is 13 μm.
Was obtained. Table 3 shows the measurement results of the physical properties of the obtained film.

The obtained film had good lapping and unwinding properties.

Example 9 In Example 8, except that propylene-based polymer (PP-4) and ethylene-octene copolymer (PE-1) were mixed at a ratio of 75:25 as constituent resins of the base material layer. Was performed in the same manner as in Example 8. Table 3 shows the measurement results of the physical properties of the obtained film.

The obtained film had good lapping and drawing properties.

Example 10 Example 10 was carried out in the same manner as in Example 8, except that an ethylene-vinyl acetate copolymer (PE-5) was used as the constituent resin of the inner surface layer and the outer surface layer.

The obtained film had good lapping and drawing properties.

Example 11 In Example 8, propylene-based polymer (PP-2) and propylene-based polymer (PP-
Example 8 was repeated except that 3) and the ethylene-octene copolymer (PE-1) were mixed at a ratio of 25:50:25.

The obtained film had good lapping and drawing properties.

Example 12 In Example 8, except that propylene-based polymer (PP-3) and ethylene-octene copolymer (PE-2) were mixed at a ratio of 75:25 as the constituent resin of the base material layer. Was performed in the same manner as in Example 8.

The obtained film had good lapping and drawing properties.

Comparative Example 1 In Example 1, propylene-based polymer (PP-3) and ethylene-octene copolymer (P
Example 1 except that E-1) was mixed at a ratio of 25:75.
The same was done.

At the time of film formation, the film tube was blocked and could not be opened.

Comparative Example 2 In Example 1, the constituent resin was a propylene-based polymer (P
Except having changed to P-3), it carried out similarly to Example 1.

The recovery of deformation after stretching and opening is insufficient.
The finger push-back property was insufficient.

Comparative Example 3 In Example 1, the propylene-based polymer (PP-3) and the ethylene-butene copolymer (PE
-3) was carried out in the same manner as in Example 1, except that 75:25 was mixed.

The recovery of deformation after stretching and opening is insufficient.
The finger push-back property was insufficient.

Comparative Example 4 In Example 1, propylene-based polymer (PP-3) and low-density polyethylene (PE-4) were used as constituent resins.
Was carried out in the same manner as in Example 1 except that was mixed at a ratio of 75:25.

The dispersion of the two resins was insufficient, and the transparency of the film was insufficient.

In Examples 1 to 11, the unwinding property, the lapping property, and the finger push-back property were all good.

On the other hand, in Comparative Example 1, the crushed tubular film was blocked during the inflation film formation and could not be opened, and could not be evaluated as a single film. In Comparative Examples 2 and 3, as a result of the finger push-back test, dents of the film remained or wrinkles occurred after finger pushing. Furthermore, in Comparative Example 4, the transparency deteriorated, and the tightness after lapping was insufficient due to the lack of self-adhesiveness of the film.

[0090]

[Table 2]

[0091]

[Table 3]

Claims (2)

[Claims] 1. A copolymer of (a) 40 to 90% by weight of a propylene-based polymer and (b) a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, wherein i) a monomer unit based on the α-olefin Ii) the MI ratio represented by the following formula is 7 to 20, iii) A wrap stretch film comprising a polyolefin composition comprising 10 to 60% by weight of an ethylene-α-olefin copolymer having a weight average molecular weight (Mw) / number average molecular weight (Mn) of 1.0 to 2.5. 2. The wrap stretch film according to claim 1, wherein a surface layer made of linear low-density polyethylene or ethylene-vinyl acetate copolymer is laminated on at least one film surface.