JP2022063198A - Film for stretch packaging - Google Patents

Abstract

To provide a film for stretch packaging having a layer using a polypropylene resin as a major component, the film for stretch packaging excellent in a packaging aptitude (cutting properties, packaging wrinkle, bottom folding stability, tear strength), etc., hardly causing breakage in packaging, and having a transparent excellent appearance.SOLUTION: A film for stretch packaging includes at least one layer (I) containing, as a major component, a resin composition (Z) including: a polypropylene resin (A) having a glass-transition temperature of -15°C or lower, and a melting point of 130°C or lower, when raising a temperature again at 10°C/min. by differential scan calorimetry according to JIS K7121(2012), and an ethylene unit content of 6 mass% or more; and a polypropylene resin (B) having an ethylene unit content of less than 6 mass%. In the film, a loss tangent (tanδ) at 20°C measured with oscillation frequency of 10 Hz is 0.2 or more, and a storage elastic modulus (E') is 400 MPa or less.SELECTED DRAWING: None

Description

The present invention relates to a stretch wrapping film. More specifically, the present invention relates to a stretch wrapping film preferably used for food packaging, particularly a stretch wrapping film containing no chlorine or polyvinyl chloride plasticizer.

Conventionally, polyvinyl chloride-based films have been mainly used as films for stretch packaging for so-called pre-packaging, which are used by placing fruits and vegetables, meat, fish and shellfish, prepared foods, etc. on a lightweight tray and overlapping them. Polyvinyl chloride film has good packaging efficiency and is preferable for packaging such as a beautiful packaging finish. In addition, it has elastic recovery that returns to its original state when the film after packaging is pressed with a finger to deform it. It has excellent quality advantages recognized by both sellers and consumers that the product value does not decrease, such as excellent bottom folding stability, and film peeling is unlikely to occur during transportation display. It has. However, in recent years, with respect to polyvinyl chloride films, problems such as hydrogen chloride gas generated during incineration and elution of a large amount of plasticizer have been regarded as problems.

Therefore, various materials to replace the polyvinyl chloride-based film have been studied, and in particular, various stretch packaging films using the polyolefin-based resin have been proposed. Among them, ethylene-vinyl acetate copolymer is used as the main component for the front and back layers, and the intermediate layer is used for the reasons such as good surface characteristics as a stretch film, transparency, appropriate heat resistance, flexibility in material design, and economy. In addition, studies on stretch packaging films using various polypropylene-based resins as the main component are being actively conducted.

For example, a stretch for food packaging having a mixed resin layer containing three specific components including a polypropylene resin as a main component, and having a storage elastic modulus and loss tangent within a specific range by dynamic viscoelasticity measurement. A film has been proposed (Patent Document 1).

Further, in the mixed resin layer containing two kinds of polypropylene-based resins as main components, the crystallization curve shape, the crystallization peak temperature, the amount of heat of crystallization, etc. in the differential scanning calorimeter are defined by each polypropylene-based resin, and the two kinds are defined. A stretch packaging film in which the relationship between polypropylene-based resins is defined is proposed (Patent Documents 2 and 3).

Japanese Unexamined Patent Publication No. 9-165491 Japanese Unexamined Patent Publication No. 2011-68844 Japanese Unexamined Patent Publication No. 2012-162074

The stretch packaging film using various polypropylene-based resins as the main component in the intermediate layer as described above is a film having good various packaging suitability (cutting property, packaging wrinkle, bottom folding stability, tearing property) and the like. Even if two types of polypropylene-based resins having a crystallization curve shape, a crystallization peak temperature, a crystallization calorific value, etc. specified in Patent Documents 2 and 3 are selected, the film-formed film may be colored. In some cases, problems such as tearing of the film during film packaging were observed.

The present invention is a stretch wrapping film having a layer using a polypropylene-based resin as a main component in view of the above-mentioned problems of the prior art, and has packaging suitability (cutting property, packaging wrinkle, bottom folding stability, tearing property). It is an object of the present invention to provide a stretch wrapping film having a transparent and excellent appearance, which is good in quality and is less likely to be torn during packaging.

As a result of diligent studies, the present inventors have found that having at least one layer containing a resin composition containing a specific polypropylene-based resin as a main component provides packaging while maintaining transparency, good appearance, and packaging suitability. The present invention has been completed by investigating that it is an important factor for improving defects such as tearing of the film at the time.

That is, the gist of the present invention is as follows.

[1] Based on JIS K7121 (2012), the glass transition temperature when the temperature is re-heated at 10 ° C./min by differential scanning calorimetry is -15 ° C or lower, the melting point is 130 ° C or lower, and the ethylene unit content is At least a layer (I) containing a resin composition (Z) composed of a polypropylene-based resin (A) having an ethylene unit content of 6% by mass or more and a polypropylene-based resin (B) having an ethylene unit content of less than 6% by mass as a main component. A stretch packaging film having one layer, having a loss tangent (tan δ) of 0.2 or more at 20 ° C. measured at a vibration frequency of 10 Hz, and a storage elastic coefficient (E') at 20 ° C. measured at a vibration frequency of 10 Hz. A film for stretch packaging having a temperature of 400 MPa or less.

[2] The mass ratio of the resin composition (Z) when the total mass of the polypropylene-based resin (A) and the polypropylene-based resin (B) is 100% by mass is (A) / (B) =. The stretch packaging film according to [1], which is 10 to 60% by mass / 90 to 40% by mass.

[3] When the layer (I) further contains the following resin (C) and the total mass of the entire layer (I) is 100% by mass, the content of the resin (C) is 1 to 40% by mass. , [1] or [2] stretch packaging film.
Resin (C): At least one resin selected from petroleum resin, terpene resin, kumaron-inden resin, rosin-based resin, or hydrogenated derivatives thereof.

[4] When the layer (I) further contains the following resin (D) and the total mass of the entire layer (I) is 100% by mass, the content of the resin (D) is 1 to 45% by mass. , [1] to any one of [3].
Resin (D): At least one resin selected from a block copolymer of a vinyl aromatic compound and a conjugated diene, or a hydrogenated derivative thereof.

[5] Of [1] to [4], which comprises at least two layers having a layer (II) containing a polyethylene resin (E) as a main component on one or both surfaces of the layer (I). The stretch packaging film described in either.

[6] The polyethylene-based resin (E) is low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylate. The stretch packaging film according to [5], which is at least one selected from an ester copolymer and an ionomer resin.

The stretch wrapping film of the present invention is a stretch wrapping film having a transparent and excellent appearance, which has good packaging suitability and is less likely to be torn during packaging. The film for stretch wrapping of the present invention has good various packaging suitability (cutting property, packaging wrinkle, bottom folding stability, tearing property) when using an automatic wrapping machine, and also cleans the object to be packaged such as food. It can be suitably used as a non-chlorine-based stretch packaging film having a transparent and excellent appearance for display and display.

Hereinafter, the stretch wrapping film of the present invention as an example of the embodiment of the present invention will be described. However, the scope of the present invention is not limited to the embodiments described below.

In the present specification, when "X to Y" (X and Y are arbitrary numbers) is described, it means "X or more and Y or less", and "preferably larger than X" and ". "Preferably smaller than Y" is included.

Further, the "monomer component" refers to a repeating unit derived from a monomer which is a raw material for producing a resin and incorporated into the resin, and is also referred to as a "structural unit" or a "unit".
The "ethylene unit" refers to a repeating unit derived from ethylene, which is a raw material for producing a resin, and incorporated into the resin. The same applies to "vinyl acetate unit" and "propylene unit".
Further, "(meth) acrylic acid" represents one or both of "acrylic acid" and "methacrylic acid".

The stretch packaging film of the present invention (hereinafter, also referred to as “the film of the present invention”) is based on JIS K7121 (2012), and the glass transition temperature when the temperature is re-heated at 10 ° C./min by differential scanning calorific value measurement. A polypropylene-based resin (A) having an ethylene unit content of -15 ° C. or lower and a melting point of 130 ° C. or lower and an ethylene unit content of 6% by mass or more, and a polypropylene-based resin (B) having an ethylene unit content of less than 6% by mass. A stretch packaging film having at least one layer (I) containing the resin composition (Z) as a main component, wherein the loss tangent (tan δ) at 20 ° C. measured at a vibration frequency of 10 Hz is 0.2 or more. It is characterized in that the storage elastic coefficient (E') at 20 ° C. measured at a vibration frequency of 10 Hz is 400 MPa or less.
In the present invention, the ethylene unit content, the glass transition temperature, the loss tangent (tan δ), and the storage elastic modulus (E') are specifically measured by the method described in the section of Examples described later.

In the present invention, the "stretch packaging film" has a meaning that broadly includes a packaging film having extensibility and self-adhesiveness. Typically, a wrapping film for pre-packaging in which fruits and vegetables, meat, fish and shellfish, prepared foods, etc. are placed on a lightweight tray and overlapped, a wrapping film that overlaps to fix the luggage when carrying the luggage, and the like are mentioned. Can be done.

In addition, "sheet" generally refers to a product that is thin by definition in JIS and whose thickness is generally small for length and width, and "film" generally refers to length and width. It is a thin, flat product whose thickness is extremely small and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (Japanese Industrial Standards JIS K6900). For example, in terms of thickness, in a narrow sense, a film having a thickness of 100 μm or more may be referred to as a sheet, and a film having a thickness of less than 100 μm may be referred to as a film. However, since the boundary between the sheet and the film is not fixed and it is not necessary to distinguish between the two in the present invention, the term "film" or the term "sheet" is included, and the term "sheet" is referred to as "sheet". It shall include "film".

[Loss tangent (tanδ) / storage elastic modulus (E')]
The film of the present invention has a loss tangent (tan δ) of 0.2 or more at 20 ° C. measured at a vibration frequency of 10 Hz and a storage elastic modulus (E') of 400 MPa or less at 20 ° C. measured at a vibration frequency of 10 Hz. It is necessary.

<Loss tangent (tanδ)>
The loss positive tangent (tan δ) is the ratio of the loss elastic modulus (E ″) to the storage elastic modulus (E ′), that is, the loss positive tangent (tan δ = E ″ / E ′). It means that the loss elastic modulus (E ″), that is, the contribution rate of viscosity among the viscoelastic properties is large. The film of the present invention has a loss positive contact (tan δ) at 20 ° C. measured at a vibration frequency of 10 Hz. It is necessary to be 2 or more, preferably 0.25 or more, more preferably 0.3 or more. The loss positive contact (tan δ) is 0.2 or more, so that the film is packaged at room temperature. Since it deforms at a speed suitable for, packaging suitability is improved.

On the other hand, the upper limit of the loss tangent (tan δ) is not particularly limited, but is preferably 0.8 or less, more preferably 0.7 or less, and further preferably 0.6 or less. When the loss tangent (tan δ) is larger than 0.8, the packaging finish is good, but it shows plastic deformation, the tension of the packed product against the external force is too weak, and the tray is stacked during transportation or display. The film on the top surface tends to sag, and the commercial value tends to decrease. Further, in the case of automatic packaging, since it easily stretches vertically, problems such as chuck defects are likely to occur.

<Storage modulus (E')>
The film of the present invention needs to have a storage elastic modulus (E') at 20 ° C. measured at a vibration frequency of 10 Hz of 400 MPa or less, preferably 350 MPa or less, and more preferably 300 MPa or less. When the storage elastic modulus (E') is 400 MPa or less, the film of the present invention can be stretched appropriately without being too hard, so that the packaging suitability is improved.

On the other hand, the lower limit of the storage elastic modulus (E') is not particularly limited, but is preferably 80 MPa or more, more preferably 90 MPa or more, and further preferably 100 MPa or more. When the storage elastic modulus (E') is 80 MPa or more, the film does not easily adhere to each other at room temperature, so that workability is improved.

[Layer (I)]
The constituents of the film layer (I) of the present invention will be described below.

<Polypropylene resin (A)>
In the present invention, the polypropylene-based resin (A) has a glass transition temperature (hereinafter, simply “glass transition temperature” or simply, when the temperature is re-heated at 10 ° C./min by differential scanning calorimetry based on JIS K7121 (2012). It is necessary that the temperature is −15 ° C. or lower, the melting point is 130 ° C. or lower, and the ethylene unit content is 6% by mass or more.

The polypropylene-based resin (A) is a resin containing propylene as a main monomer component and having an ethylene unit content of 6% by mass or more. Here, the main monomer component refers to a monomer component that occupies 50% by mass or more and 94% by mass or less in the resin.
Therefore, the polypropylene-based resin (A) has a propylene component and an ethylene component as essential monomer components, and the propylene unit content in the polypropylene-based resin (A) is 50% by mass or more and 94% by mass or less. The ethylene unit content is 6% by mass or more and 50% by mass or less.

The ethylene unit content of the polypropylene-based resin (A) is preferably 6% by mass or more, preferably 8% by mass or more, and more preferably 10% by mass or more. When the ethylene unit content of the polypropylene resin (A) is 6% by mass or more, the flexibility of the film is improved, elastic recovery such as wrinkle suppression at the time of packaging is imparted, and adhesion such as bottom folding stability is imparted. Gender can be imparted. On the other hand, from the viewpoint of maintaining the rigidity of the film, the ethylene unit content of the polypropylene-based resin (A) is preferably 50% by mass or less, preferably 40% by mass or less, and particularly preferably 30% by mass or less.

The propylene unit content of the polypropylene-based resin (A) is particularly preferably 60 to 90% by mass from the viewpoint of maintaining the rigidity of the film and balancing the flexibility of the film.

The polypropylene-based resin (A) may have a monomer component other than propylene and ethylene as long as it satisfies the above-mentioned propylene unit content and ethylene unit content and also satisfies the above-mentioned glass transition temperature. .. Examples of other monomer components other than propylene and ethylene that the polypropylene-based resin (A) may have are 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene. , 1-octene and other α-olefins, vinyl acetate, (meth) acrylic acid, (meth) acrylic acid ester, (meth) glycidyl acrylate, vinyl alcohol, ethylene glycol, maleic anhydride, styrene, diene, cyclic olefin And so on. The polypropylene-based resin (A) may be a multiplex copolymer containing two or more of the above-mentioned other monomer components. When the polypropylene-based resin (A) has a monomer component other than propylene and ethylene, 1-butene is preferable as the monomer component.

The polypropylene-based resin (A) may be a block copolymer, a random copolymer, or a random copolymer as long as it satisfies the above-mentioned propylene unit content, ethylene unit content, and glass transition temperature. , It may be a graft copolymer.

The polypropylene-based resin (A) has a glass transition temperature of −15 ° C. or lower and -18 ° C. or lower when the temperature is reheated at 10 ° C./min by differential scanning calorimetry based on JIS K7121 (2012). It is preferably present, and more preferably −20 ° C. or lower. When the glass transition temperature of the polypropylene-based resin (A) is −15 ° C. or lower, the glass transition temperature of the resin composition (Z) can be lowered, and the low temperature suitability required for the film of the present invention and stretching at room temperature are required. Gender and flexibility can be imparted.

On the other hand, the lower limit of the glass transition temperature of the polypropylene-based resin (A) is not particularly limited, but is preferably −50 ° C. or higher, more preferably −40 ° C. or higher, and further preferably −35 ° C. or higher. preferable. When the glass transition temperature of the polypropylene-based resin (A) is −50 ° C. or higher, the glass transition temperature of the resin composition (Z) is not lowered too much, so that it is prevented from becoming too soft and appropriate packaging suitability is obtained. Can be done.

The polypropylene-based resin (A) was held at 200 ° C. for 1 minute by differential scanning calorimetry (DSC) measurement described in the section of Examples described later, and then cooled to −50 ° C. at a cooling rate of 10 ° C./min. It does not show the crystallization peak temperature (Tc) or the crystallization peak temperature (Tc) is preferably 100 ° C. or lower, more preferably 80 ° C. or lower, and 60 ° C. The following is more preferable. If the crystallization peak temperature (Tc) is not shown, or if the temperature is 100 ° C. or lower, the film of the present invention can be imparted with stretchability and flexibility.

The polypropylene-based resin (A) may exhibit a plurality of crystallization peak temperatures (Tc), but in that case, it is preferable that all of the plurality of peaks are within the above range. However, showing multiple peaks means that the polypropylene resin (A) has regions with different crystallization rates, that is, it is in a non-uniform state, resulting in a decrease in transparency, stickiness of raw material pellets, and storage. It is preferable to show a single peak because it may cause blocking in the inside.

The melting point of the polypropylene-based resin (A) was maintained at 200 ° C. for 1 minute by raising the temperature of about 10 mg of the resin from −50 ° C. to 200 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). After that, the temperature was lowered to -50 ° C at a cooling rate of 10 ° C./min, and the temperature was raised to 200 ° C. (re-heated) again at a heating rate of 10 ° C./min. (Tm) (° C.).
The crystal melting peak temperature (Tm) of the polypropylene-based resin (A) needs to be 130 ° C. or lower, preferably 125 ° C. or lower, and more preferably 120 ° C. or lower. It is preferable that the crystal melting peak temperature (Tm) of the polypropylene-based resin (A) is 130 ° C. or lower, which imparts appropriate flexibility to the film of the present invention and improves stretch suitability. On the other hand, the lower limit of the crystal melting peak temperature (Tm) of the polypropylene-based resin (A) is preferably 60 ° C. or higher, more preferably 80 ° C. or higher. When the crystal melting peak temperature (Tm) of the polypropylene-based resin (A) is 60 ° C. or higher, it is preferable because appropriate rigidity and heat resistance can be imparted to the film of the present invention.

The polypropylene-based resin (A) preferably has a crystal melting heat (ΔHm) of 35 J / g or less calculated from the crystal melting peak area observed when the temperature is re-heated as described above in the DSC measurement. .. When the heat of crystal melting (ΔHm) of the polypropylene-based resin (A) is 35 J / g or less, it is preferable because it is easy to secure the flexibility and packaging suitability of the film of the present invention. The amount of heat of crystal melting (ΔHm) of the polypropylene-based resin (A) is more preferably 30 J / g or less, and further preferably 25 J / g or less. The lower limit of the amount of heat of crystal melting (ΔHm) of the polypropylene-based resin (A) is not particularly limited, but 1 J / g or more is preferable from the viewpoint of preventing blocking.

When the polypropylene-based resin (A) has a weight average molecular weight (Mw) of 300,000 or more, it is possible to impart appropriate rigidity to the film of the present invention, and thus it is possible to prevent the film from being torn during packaging. It is preferable from the viewpoint of From such a viewpoint, the weight average molecular weight (Mw) of the polypropylene-based resin (A) is more preferably 310,000 or more, and particularly preferably 320,000 or more. The upper limit of the weight average molecular weight (Mw) of the polypropylene-based resin (A) is not particularly limited, but is preferably 1,500,000 or less, particularly preferably 1,000,000 or less, from the viewpoint of extrusion moldability.

The molecular weight distribution (Mw / Mn) calculated from the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene-based resin (A) is preferably 2.5 or less, and preferably 2.4 or less. It is more preferably 2.3 or less, and particularly preferably 2.3 or less. When the molecular weight distribution (Mw / Mn) is 2.5 or less, components having an extremely high molecular weight and components having an extremely low molecular weight can be excluded, and the peak of the crystallization curve tends to be single or less. Further, it is possible to eliminate the concern that the component having an extremely low molecular weight bleeds and the concern that the component having an extremely high molecular weight becomes an unmelted product at the time of molding.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the polypropylene-based resin (A) and the polypropylene-based resin (B) described later are polystyrene-equivalent values obtained by gel permeation chromatography (GPC), and are detailed. Is a value measured by the method described in the section of Examples described later.

As the polypropylene-based resin (A), one type may be used alone, or two or more types having different monomer compositions, physical properties, etc. may be mixed and used.

<Polypropylene resin (B)>
In the present invention, the polypropylene-based resin (B) needs to have an ethylene unit content of less than 6% by mass.

The polypropylene-based resin (B) is a resin containing propylene as a main monomer component and having an ethylene unit content of less than 6% by mass. In the present invention, the main monomer component in the resin means a monomer component that occupies 50% by mass or more in the resin, but in the polypropylene-based resin (B), it is preferably more than 94% by mass and 100% by mass or less. ..
Therefore, the polypropylene-based resin (B) has a propylene component or a propylene component and an ethylene component as essential monomer components, and the propylene unit content in the polypropylene-based resin (B) is usually more than 94% by mass. The ethylene unit content is less than 6% by mass.

The ethylene unit content of the polypropylene-based resin (B) is preferably less than 6% by mass, preferably less than 5% by mass, and more preferably less than 4% by mass. When the ethylene unit content of the polypropylene-based resin (B) is less than 6% by mass, it is possible to impart appropriate rigidity and heat resistance to the film of the present invention, and the cutability of the film when packaged and the tray can be obtained. The foldability of the product can be improved.

The propylene unit content of the polypropylene-based resin (B) is preferably more than 94% by mass and preferably 100% by mass or less from the viewpoint of maintaining the rigidity of the film.

The polypropylene-based resin (B) may have a monomer component other than propylene and ethylene as long as it satisfies the above-mentioned propylene unit content and ethylene unit content. Examples of other monomer components other than propylene and ethylene include α-olefins such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, and vinyl acetate. , (Meta) acrylic acid, (meth) acrylic acid ester, (meth) glycidyl acrylate, vinyl alcohol, ethylene glycol, maleic anhydride, styrene, diene, cyclic olefin and the like. The polypropylene-based resin (B) may be a multiplex copolymer containing two or more of the above-mentioned monomer components.

The polypropylene-based resin (B) may be a block copolymer, a random copolymer, or a graft copolymer as long as it satisfies the above-mentioned propylene unit content and ethylene unit content. It may be coalesced.

The polypropylene-based resin (B) is observed in the DSC measurement described in the section of Examples described later when the temperature is kept at 200 ° C. for 1 minute and then lowered to −50 ° C. at a cooling rate of 10 ° C./min. The crystallization peak temperature (Tc) is preferably 70 ° C. or higher. When the crystallization peak temperature (Tc) of the polypropylene-based resin (B) is 70 ° C. or higher, the compatibility with the polypropylene-based resin (A) described above is enhanced, and whitening is less likely to occur during stretch packaging, which is preferable. The crystallization peak temperature (Tc) of the polypropylene-based resin (B) is more preferably 80 ° C. or higher, and even more preferably 90 ° C. or higher. The upper limit of the crystallization peak temperature (Tc) of the polypropylene-based resin (B) is not particularly limited, but is preferably 150 ° C. or lower.

The polypropylene-based resin (B) has crystallization calculated from the crystallization peak area observed when the temperature is lowered to −50 ° C. at a cooling rate of 10 ° C./min after holding at 200 ° C. for 1 minute in DSC measurement. The calorific value (ΔHc) is preferably 35 J / g or more. When the crystallization heat quantity (ΔHc) of the polypropylene-based resin (B) is 35 J / g or more, appropriate rigidity and heat resistance can be imparted to the film of the present invention, and the film cutability and tray when packaged can be imparted. It is preferable because it can improve the foldability to. The calorific value (ΔHc) for crystallization of the polypropylene-based resin (B) is more preferably 40 J / g or more, and further preferably 45 J / g or more. The upper limit of the amount of heat of crystallization (ΔHc) of the polypropylene-based resin (B) is not particularly limited, but is preferably 100 J / g or less from the viewpoint of suppressing film whitening during stretching.

The melting point of the polypropylene-based resin (B) was maintained at 200 ° C. for 1 minute by raising the temperature of about 10 mg of the resin from −50 ° C. to 200 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). After that, the temperature was lowered to -50 ° C at a cooling rate of 10 ° C./min, and the temperature was raised to 200 ° C. (re-heated) again at a heating rate of 10 ° C./min. (Tm) (° C.).
The crystal melting peak temperature (Tm) of the polypropylene-based resin (B) is preferably 110 ° C. or higher, more preferably 120 ° C. or higher. When the crystal melting peak temperature (Tm) of the polypropylene-based resin (B) is 110 ° C. or higher, it is preferable because appropriate rigidity and heat resistance can be imparted to the film of the present invention. The upper limit of the crystal melting peak temperature (Tm) of the polypropylene-based resin (B) is not particularly limited, but is preferably 160 ° C. or lower.

The polypropylene-based resin (B) preferably has a crystal melting heat (ΔHm) of 35 J / g or more calculated from the crystal melting peak area observed when the temperature is re-heated as described above in the DSC measurement. .. When the heat of crystal melting (ΔHm) of the polypropylene-based resin (B) is 35 J / g or more, appropriate rigidity and heat resistance can be imparted to the film of the present invention, and the film's cutability and tray when packaged can be imparted. It is preferable because it can improve the foldability to. The amount of heat of crystal melting (ΔHm) of the polypropylene-based resin (B) is more preferably 40 J / g or more, and further preferably 45 J / g or more. The upper limit of the heat of crystal melting (ΔHm) of the polypropylene-based resin (B) is not particularly limited, but is preferably 100 J / g or less from the viewpoint of suppressing film whitening during stretching.

The polypropylene-based resin (B) preferably has a weight average molecular weight (Mw) of 350,000 or more from the viewpoint of suppressing tearing of the film during packaging and imparting appropriate slipperiness. From such a viewpoint, the weight average molecular weight (Mw) of the polypropylene-based resin (B) is more preferably 375,000 or more, and particularly preferably 400,000 or more. The upper limit of the weight average molecular weight (Mw) of the polypropylene-based resin (B) is not particularly limited, but is preferably 1,500,000 or less, particularly preferably 1,000,000 or less, from the viewpoint of extrusion moldability.

The molecular weight distribution (Mw / Mn) calculated from the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene-based resin (B) is preferably 4.5 or more. When the molecular weight distribution (Mw / Mn) is 4.5 or more, the moldability of the film is improved, tearing of the film can be suppressed, and appropriate slipperiness can be imparted to the film, which is preferable. The molecular weight distribution (Mw / Mn) of the polypropylene-based resin (B) is more preferably 5.0 or more, further preferably 5.5 or more. On the other hand, when this molecular weight distribution (Mw / Mn) is too large, a component having an extremely low molecular weight or a component having an extremely high molecular weight may be contained. Therefore, the molecular weight distribution (Mw / Mn) is 20 or less, particularly 15 or less, because there is a concern that a component having an extremely low molecular weight may bleed or a component having an extremely high molecular weight may become an unmelted product at the time of molding. Is preferable.

As the polypropylene-based resin (B), one type may be used alone, or two or more types having different monomer compositions, physical properties, etc. may be mixed and used.

<Resin composition (Z)>
The film layer (I) of the present invention is composed mainly of a resin composition (Z) of a polypropylene-based resin (A) and a polypropylene-based resin (B).
Here, the "main component" refers to a component that occupies the largest mass ratio among the components contained in the layer (I), and the content ratio of the resin composition (Z) in the layer (I) is 35% by mass. Above, it is particularly preferable that it is 40% by mass or more.

The resin composition (Z) is a mixture of the polypropylene-based resin (A) and the polypropylene-based resin (B), and the total mass of the polypropylene-based resin (A) and the polypropylene-based resin (B) is 100% by mass in the polypropylene-based resin. (A) / polypropylene resin (B) (in the present invention, this ratio is referred to as "(A) / (B)") = 10 to 60% by mass. It is preferably / 90 to 40% by mass.

Since the proportion of the polypropylene-based resin (A) in 100% by mass of the mixed polypropylene-based resin of the resin composition (Z) is 10 to 60% by mass, the flexibility of the film required for the stretch packaging film and the packaging It is possible to impart elastic recovery such as wrinkle suppression at the time of wrinkling, and to impart adhesiveness such as bottom folding stability. Further, since the proportion of the polypropylene-based resin (B) in 100% by mass of the mixed polypropylene-based resin of the resin composition (Z) is 90 to 40% by mass, the appropriate rigidity of the film required for the stretch packaging film is appropriate. It is possible to impart heat resistance, and it is possible to improve the cuttability of the film when it is packaged and the foldability into the tray.
The mass ratio of the polypropylene-based resin (A) to the polypropylene-based resin (B) is more preferably (A) / (B) = 15 to 55% by mass / 85 to 45% by mass, and (A) / (B). ) = 20 to 50% by mass / 80 to 50% by mass is more preferable.

<Resin (C)>
The film layer (I) of the present invention preferably contains the following resin (C).
Resin (C): At least one resin selected from petroleum resin, terpene resin, kumaron-inden resin, rosin-based resin, or hydrogenated derivatives thereof.

Here, the petroleum resin includes an alicyclic petroleum resin obtained from cyclopentadiene or a dimer thereof, an aromatic petroleum resin obtained from a C9 component, and a copolymerized petroleum resin of an alicyclic and aromatic petroleum resin. , Or their hydrogenated derivatives and the like.
Examples of the terpene resin include a terpene resin obtained from β-pinene, a terpene-phenol resin, and hydrogenated derivatives thereof.
As the kumaron-inden resin, a thermoplastic synthetic resin obtained by purifying a fraction of tar at 160 to 180 ° C. and polymerizing kumaron having 8 carbon atoms and indene having 9 carbon atoms as main monomers, or hydrogenated derivatives thereof, etc. Can be mentioned.
Examples of the rosin-based resin include rosin resins such as gum rosin and wood rosin, esterified rosin resins modified with glycerin and pentaerythritol, and hydrogenated derivatives thereof.

As the resin (C) as described above, it is preferable to use a hydrogenated derivative in terms of color tone, thermal stability, and compatibility. The resin (C) has various softening temperatures mainly depending on the molecular weight, but the softening temperature measured based on JIS K5601-2-2 (1990) is preferably 100 to 150 ° C, more preferably 110 to 140 ° C. ..

Specifically, as the resin (C), the product name "Highlets" and "Petrodin" of Mitsui Chemicals Co., Ltd., the product name "Arcon" of Arakawa Chemical Industry Co., Ltd., and the product name "Clearlon" of Yasuhara Chemicals Co., Ltd. , The trade name "Imarb" of Idemitsu Petrochemical Co., Ltd., and the trade name "Escolets" of Eastman Chemical Co., Ltd. can be used.

As these resins (C), only one kind may be used, or two or more kinds may be mixed and used.

When the layer (I) contains the resin (C), the content of the resin (C) is 1 to 40 mass when the total mass of the entire layer (I) is 100% by mass. % Is preferable.
When the content of the resin (C) is 1% by mass or more, the waist, cuttability, and bottom folding stability of the film of the present invention can be imparted. The content of the resin (C) is preferably 5% by mass or more, more preferably 10% by mass or more. Further, if the content of the resin (C) is 40% by mass or less, the low temperature suitability required for the stretch film is not easily impaired as the glass transition temperature rises, and the film is blocked by bleeding of small molecule substances. Hateful. The content of the resin (C) is preferably 35% by mass or less, more preferably 30% by mass or less.

<Resin (D)>
The film layer (I) of the present invention preferably contains the following resin (D) in addition to the resin composition (Z).
Resin (D): At least one resin selected from a copolymer of a vinyl aromatic compound and a conjugated diene, or a hydrogenated derivative thereof.

In the copolymer of the vinyl-based aromatic compound and the conjugated diene, as the vinyl-based aromatic compound, for example, styrene homologues such as styrene and α-methylstyrene can also be used. Further, examples of the conjugated diene include 1,3-butadiene, isoprene, 1,3-pentadiene and the like, and these can be used alone or in combination of two or more. Further, as the third component, a small amount of components other than the vinyl aromatic compound and the conjugated diene may be contained. However, the thermal stability and weather resistance are extremely poor when a double bond mainly composed of a vinyl bond in the conjugated diene portion remains, so in order to improve this, 80% or more of the double bond, and further 95%. It is preferable to use the one to which hydrogen is added.

Further, the ratio of the vinyl aromatic compound component and the conjugated diene component contained in such a copolymer is preferably 3 to 40% by mass / 97 to 60% by mass in terms of mass ratio. Here, it is preferable that the vinyl-based aromatic compound component in the copolymer composition is 3% by mass or more so that the rigidity of the film for stretch packaging does not decrease too much, while it is 40% by mass or less. The effect of imparting flexibility to the film and reducing the tensile elastic modulus is sufficient without the rigidity being too high.

As the resin (D), specifically, the styrene-butadiene block copolymer elastomer is manufactured by Asahi Kasei Co., Ltd. under the trade name "Tuffprene", and the styrene-butadiene block copolymer hydrogenated derivative is manufactured by Asahi Kasei Co., Ltd. "Tough Tech", as a hydrogenated derivative of styrene-isoprene block copolymer, trade name "Septon" manufactured by Kuraray, and as a styrene-vinylisoprene block copolymer elastomer, trade name "Hybuler" manufactured by Kuraray. Commercially available products such as can be used.

As these resins (D), only one kind may be used, or two or more kinds may be mixed and used.

When the layer (I) contains the resin (D), the content of the resin (D) is 1 to 45 mass when the total mass of the entire layer (I) is 100% by mass. % Is preferable.
When the content of the resin (D) is 1% by mass or more, the waist, cuttability, and bottom folding stability of the film of the present invention can be imparted. The content of the resin (D) is preferably 5% by mass or more, more preferably 10% by mass or more. Further, if the content of the resin (D) is 45% by mass or less, the low temperature suitability required for the stretch film is not easily impaired as the glass transition temperature rises, and the film is blocked by bleeding of small molecule substances. Hateful. The content of the resin (D) is preferably 40% by mass or less, more preferably 35% by mass or less.

<Resin (C) and resin (D)>
The layer (I) of the film of the present invention may contain only one of the above resin (C) and the resin (D), or may contain both, but the waist of the film and the like. It is preferable to contain both the resin (C) and the resin (D) from the viewpoint of imparting cutability and bottom folding stability.
In this case, when the total of the resin composition (Z), the resin (C), and the resin (D) is 100% by mass, the resin composition (Z) is 40 to 98% by mass, and the resin (C) and the resin (D). ) And 2 to 60% by mass in total are preferable.
Further, when the total mass of the polypropylene-based resin (A), the polypropylene-based resin (B), the resin (C), and the resin (D) is 100% by mass, the polypropylene-based resin (A), the polypropylene-based resin (B), The mass ratio of the resin (C) and the resin (D) is (A) / (B) / (C) / (D) = 5 to 45% by mass / 15 to 50% by mass / 1 to 40% by mass / 1 to. It is preferably 45% by mass, and more preferably (A) / (B) / (C) / (D) = 7 to 45% by mass / 17 to 45% by mass / 5 to 35% by mass / 5 to 40. It is mass%.

<Other resins>
In addition to the resin composition (Z), the resin (C), and the resin (D), the film layer (I) of the present invention may contain a resin other than these resins, and other resins may be used. Examples thereof include the polyethylene-based resin (E) described later.

When the polyethylene-based resin (E) is contained in the film layer (I) of the present invention, even if it is the same polyethylene-based resin as the polyethylene-based resin (E) constituting the surface layer described later, it is a different polyethylene-based resin. However, the same polyethylene-based resin is preferable. If the polyethylene-based resin (E) contained in the layer (I) and the ethylene-based resin (E) constituting the surface layer are the same polyethylene-based resin, the adhesion between the layer (I) and the surface layer can be enhanced. In addition to being able to improve the mechanical properties of the entire film, for example, trimming loss that occurs when both ends of the film-formed film are cut and trimmed is added as a constituent raw material for layer (I). Since it can be done, it is possible to eliminate waste of materials and reduce material costs.

When the polyethylene-based resin (E) is contained in the film layer (I) of the present invention, the content of the polyethylene-based resin (E) is usually 1 to 40% by mass. When the content of the polyethylene resin (E) is 1% by mass or more, the low temperature suitability required for the stretch film is sufficient. The content of the polyethylene-based resin (E) is preferably 5% by mass or more, more preferably 10% by mass or more. Further, when the content of the polyethylene-based resin (E) is 40% by mass or less, the bottom folding stability and heat resistance are sufficient. The content of the polyethylene-based resin (E) is preferably 35% by mass or less, more preferably 30% by mass or less.

<Additives>
The following various additives can be appropriately added to the film layer (I) of the present invention in order to impart performance such as anti-fog property, anti-fog property, slipperiness, and adhesiveness.

Here, as various additives, for example, a fat which is a compound of a fatty acid alcohol having a carbon number of usually 1 to 12, preferably 1 to 6, and a fatty acid having a carbon number of usually 0 to 22, preferably 12 to 18. Examples thereof include group alcohol fatty acid esters. Specifically, monoglycerin oleate, diglycerin oleate, polyglycerin oleate, glycerin trilysinolate, glycerin acetyl lysinolate, polyglycerin stearate, glycerin laurate, polyglycerin laurate, methylacetyl lysinolate, ethyl acetyl lysinolate. , Butylacetyllicinolate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol oleate, polypropylene glycol oleate, sorbitan oleate, sorbitan laurate, polyethylene glycol sorbitan oleate, polyethylene glycol sorbitan laurate, etc .; polyalkyl ether polyol (Specifically, polyethylene glycol, polypropylene glycol, etc.); Paraffin-based oil and the like can be mentioned. These can be used in combination of two or more.

The blending amount of these additives is usually 0.1 to 12 parts by mass, preferably 1 to 8 parts by mass with respect to 100 parts by mass of the resin composition constituting the layer (I).

[Surface layer]
The film of the present invention can be composed of at least two layers having a layer (II) containing a polyethylene resin (E) as a main component as a surface layer on one or both surfaces of the layer (I).
By providing the layer (II) containing the polyethylene resin (E) as a main component on one or both surfaces of the layer (I), heat sealability (bottom sealability), self-adhesiveness, and inflation, especially at low temperatures, are provided. It is possible to improve the moldability when the product is used.
Here, the content ratio of the polyethylene-based resin (E) contained as the main component in the layer (II) may be 50% by mass or more, particularly 55% by mass or more, particularly 60% by mass or more in the layer (II). preferable.

<Polyethylene resin (E)>
In the present invention, the polyethylene-based resin (E) is a resin containing ethylene as a main monomer component. Here, the main monomer component refers to a monomer component that occupies 50% by mass or more and 100% by mass or less in the resin. Therefore, the polyethylene-based resin (E) may be an ethylene homopolymer, or may be a copolymer containing ethylene as a main monomer component and containing other monomer components.

Examples of copolymers include low density polyethylene, linear low density polyethylene, linear low density polyethylene, ethylene / propylene copolymer, ethylene / (1-butene) copolymer, ethylene / (1-pentene). Polymers, ethylene (1-hexene) copolymers, ethylene (4-methyl-1-pentene) copolymers, ethylene (1-heptene) copolymers, ethylene (1-octene) copolymers Ethylene / (α-olefin) copolymers such as coalesced products, ethylene / vinyl acetate copolymers, ethylene / (meth) acrylic acid copolymers, ethylene / (meth) acrylic acid ester copolymers, ethylene / (meth) ) Glycidyl acrylate copolymer, ethylene / vinyl alcohol copolymer, ethylene / ethylene glycol copolymer, ethylene / maleic anhydride copolymer, ethylene / styrene copolymer, ethylene / diene copolymer, ethylene / cyclic Examples include olefin copolymers.

Further, the polyethylene-based resin (E) may be an ionomer resin containing metal ions in a resin containing ethylene as a main monomer component. Further, it may be a multiplex copolymer containing two or more kinds of monomer components other than ethylene, such as an ethylene / propylene / (1-butene) copolymer.

Among these, the polyethylene-based resin (E) includes ethylene homopolymers, low-density polyethylene, linear low-density polyethylene, linear low-density polyethylene, ethylene / (α-olefin) copolymers, and ethylene / vinyl acetate. Polymers and ionomer resins are preferred, low density polyethylene, linear low density polyethylene, linear ultra low density polyethylene, ethylene / vinyl acetate copolymers, ethylene / acrylic acid ester copolymers, ethylene / methacrylic ester copolymers, The ionomer resin is more preferable, and the polyethylene / vinyl acetate copolymer is particularly preferable.

When the polyethylene-based resin (E) is an ethylene-vinyl acetate copolymer, the vinyl acetate unit content is preferably 5 to 25% by mass. When the vinyl acetate unit content is 5% by mass or more, the obtained film is soft and not only can maintain flexibility and elastic recovery, but also can impart surface adhesiveness, which is preferable, 25% by mass. The following is preferable because the surface adhesiveness is not too strong and the unwinding property and the appearance can be maintained well.

The polyethylene-based resin (E) may be linear or branched. The method for producing the polyethylene-based resin (E) is not particularly limited, and a known polymerization method using a known catalyst for olefin polymerization, for example, a multisite catalyst typified by a Ziegler-Natta type catalyst or a metallocene-based catalyst. Examples thereof include a polymerization method using a single-site catalyst typified by.

The polyethylene-based resin (E) preferably has a melting point of 70 to 130 ° C, more preferably 80 to 120 ° C. When the melting point of the polyethylene resin (E) is 70 to 130 ° C., the tensile strength and dimensional stability of the film can be improved, which is preferable.
Here, the melting point was kept at 200 ° C. for 1 minute by raising the temperature of about 10 mg of the resin from −50 ° C. to 200 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC) as described above. After that, the temperature was lowered to -50 ° C at a cooling rate of 10 ° C./min, and the temperature was raised to 200 ° C. again at a heating rate of 10 ° C./min. ).

The polyethylene-based resin (E) preferably has a melt flow rate (MFR) of 0.1 to 20 g / 10 minutes, more preferably 0.5 to 10 g / 10 minutes. When the MFR is 0.1 g / 10 minutes or more, the extrudability of the film can be sufficiently maintained, which is preferable. Further, when the MFR is 20 g / 10 minutes or less, the film-forming stability of the film can be maintained, and unevenness in thickness and variation in mechanical strength can be suppressed, which is preferable.
Here, MFR is a value measured in accordance with JIS K7210-1 (2014), and the measurement conditions are 190 ° C. and a 2.16 kg load.

In the present invention, the polyethylene-based resin (E) contained in the layer (II) may be any resin as long as it is a resin containing ethylene as a main monomer component, and may be one kind, and the copolymerized monomer component and its composition. There may be two or more types having different physical properties.

<Other resins>
The film layer (II) of the present invention may contain a polyethylene-based resin (E) as a main component, and may contain other resins other than the polyethylene-based resin (E).
In this case, examples of the other resin that may be contained in the layer (II) include one or more of polypropylene-based resins, the above-mentioned resin (C), the above-mentioned resin (D), and the like. In order to sufficiently obtain the above-mentioned effect by containing the polyethylene-based resin (E), when the layer (II) of the film of the present invention contains a resin other than the polyethylene-based resin (E), the content thereof is the polyethylene-based resin. It is preferably 30% by mass or less, particularly preferably 0 to 15% by mass, in the total 100% by mass of (E) and other resins.

<Additives>
Similar to the layer (I), the layer (II) of the film of the present invention also has an addition that can be blended into the layer (I) in order to impart performance such as anti-fog property, anti-static property, slipperiness, and adhesiveness. As the agent, the above-mentioned various additives can be appropriately blended. Similar to the layer (I), the blending amount of the additive is usually 0.1 to 12 parts by mass, preferably 1 to 8 parts by mass with respect to 100 parts by mass of the resin composition constituting the layer (II).

[Film laminated structure]
The film of the present invention has at least one layer (I) described above, and is further composed of at least two layers having the above-mentioned layer (II) on one or both surfaces of the layer (I). It may be a laminated film.
Further, the film of the present invention has other layers such as an adhesive layer and a gas barrier layer (hereinafter, as required) for the purpose of improving mechanical properties and interlayer adhesiveness within a range not exceeding the gist of the present invention. , P layer) may be introduced as appropriate. Here, the layer (II) (hereinafter, may be abbreviated as the S layer) is a layer forming the film surface, but has a layer having the same composition as the layer forming the layer (II) inside. You may have more. Further, the layer (I) (hereinafter, may be abbreviated as M layer) may have at least one layer, and may have two or more layers.

The laminated structure of the film of the present invention is, for example, a three-layer structure consisting of (S layer) / (M layer) / (S layer), (S layer) / (P layer) / (M layer) / (S layer). A four-layer structure consisting of (S layer) / (P layer) / (M layer) / (P layer) / (S layer), (S layer) / (M layer) / (P layer) / (M layer) A five-layer structure consisting of / (S layer) and the like can be typically mentioned. In this case, the resin composition and the thickness ratio of each layer may be the same or different.

The thickness (total thickness) of the film of the present invention is in the range used as a normal stretch packaging film, that is, usually 5 to 100 μm, preferably 6 to 80 μm, and more preferably 7 to 50 μm. It is more preferably 8 to 30 μm, and particularly preferably 9 to 20 μm.

In the film of the present invention, the thickness of the layer (I) varies depending on the layer structure and the number of layers of the film of the present invention. For example, in the case of a single-layer film having one layer (I), the thickness of the layer (I) is The thickness of the above-mentioned stretch packaging film corresponds to this.

When the film of the present invention has a layer (II), the ratio of the thickness of the layer (II) is preferably 10 to 65% when the total thickness of the film is 100%. When the thickness ratio of the layer (II) is within the above range, stable film formation stability can be obtained, and suitable surface adhesiveness can be imparted to the stretch film. Here, the thickness ratio of the layer (II) refers to the total thickness ratio when the film of the present invention has layers (II) on both surfaces.

Further, when considering stable film forming processability, surface adhesiveness, various physical properties as a film for stretch packaging, and economy, the thickness ratio of the layer (II) is when the total thickness of the film is 100%. , 20-60% is more preferable.

The transparency of the film of the present invention may be in the range used as a normal stretch packaging film, and from the viewpoint of visibility, the larger the total light transmittance is, the more preferable it is, and usually 85% or more, preferably 88%. Yes, more preferably 90% or more. Similarly, the smaller the haze value, the more preferable it is, usually 15% or less, preferably 10% or less, and more preferably 8% or less.

[Film manufacturing method]
The film of the present invention may be a non-stretched film or a stretched film. When the film of the present invention is produced by inflation molding, it is usually a stretched film. The film of the present invention can be produced, for example, by melt-extruding a material from an extruder and forming it into a film by inflation molding or T-die molding.

In the case of a laminated film, it is preferable to coextrude with a multilayer die using a plurality of extruders. Practically, it is preferable to melt-extrude the material resin from the annular die for inflation molding, and the blow-up ratio (tube diameter / die diameter) at that time is usually 3 or more, preferably 4 to 7. At that time, the cooling method may be either a method of cooling from the outer surface of the tube or a method of cooling from both the outer surface and the inner surface of the tube.

Further, the obtained film is heated below the crystallization temperature of the resin and stretched 1.2 to 5 times in the vertical direction of the film by utilizing the speed difference between the nip rolls, or 1.2 in the vertical and horizontal directions of the film. Biaxial stretching may be performed up to about 5 times. As a result, it is possible to improve the cut property and impart heat shrinkage property.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples.

In the following, various measured values and evaluations of the film and its materials were performed as follows. Here, the flow direction of the film from the extruder is referred to as a vertical direction, and the direction perpendicular to the vertical direction is referred to as a horizontal direction or a width direction.

[Measurement of physical properties of propylene resin]
(1) Weight average molecular weight, molecular weight distribution The polypropylene-based resin used in Examples and Comparative Examples was used in a high-temperature GPC system (Viscotek triple detector HT-GPC model SG system) manufactured by Malvern Instruments, and the solvent used was: orthodichlorobenzene. The weight average molecular weight (Mw), the number average molecular weight (Mn), and the molecular weight distribution (Mw / Mn) were calculated by measuring temperature: 140 ° C., detector RI (reference flow method), and polystyrene-equivalent molecular weight. These values are summarized in Table 1.

(2) Ethylene unit content The polypropylene-based resin used in the Examples and Comparative Examples was measured with a ¹³ C-MMR spectrum using a nuclear magnetic resonance apparatus, and the spectral intensity of methyl carbon derived from the propylene unit and the ethylene unit were derived. The mass ratio of propylene unit and ethylene unit was calculated from the intensity ratio of the methyl carbon spectrum of. These values are summarized in Table 1.

(3) DSC measurement As the polypropylene-based resin used in Examples and Comparative Examples, about 10 mg of the resin was heated at a heating rate of 10 based on JIS K7121 (2012) and JIS K7122 (2012) using "DSC8500" manufactured by PerkinElmer. The temperature is raised from -50 ° C to 200 ° C at ° C / min, held at 200 ° C for 1 minute, then lowered to -50 ° C at a cooling rate of 10 ° C / min, and again to 200 ° C at a heating rate of 10 ° C / min. The temperature was raised again.
At this time, the amount of heat of crystallization (ΔHc) was calculated from the crystallization peak temperature (Tc) obtained in the temperature lowering process and the crystallization peak area. Further, the crystal melting peak temperature (Tm) obtained in the reheating process and the crystal melting heat quantity (ΔHm) were calculated from the crystal melting peak. The glass transition temperature (Tg) was defined as the temperature at the point where the straight line equidistant from the straight line extending the baseline and the curve of the stepwise change portion of the glass transition intersect. Based on the obtained crystallization curve, it was determined whether or not the peak of the crystallization temperature was single. These values are summarized in Table 1.

[Materials used other than propylene resin]
In the following examples and comparative examples, the following materials were used as the materials used other than the propylene-based resin.

<Resin (C)>
Hydrogenated petroleum resin (C1): ("Alcon P125" manufactured by Arakawa Chemical Industry Co., Ltd., softening temperature: 125 ° C.)

<Resin (D)>
Styrene-based elastomer (D1): Hydrogenated derivative of block copolymer of styrene and conjugated diene (MFR (JIS K7210-1 (2014), temperature 190 ° C., load 2.16 kgf) 0.5 g / 10 minutes, styrene unit Content 12% by mass)

<Polyethylene resin (E)>
Polyethylene resin (E1): Ethylene-vinyl acetate copolymer (vinyl acetate unit content: 15% by mass, melting point: 90 ° C., MFR (JIS K7210-1 (2014), temperature: 190 ° C., load 2.16 kgf) : 2.0g / 10 minutes)

[Evaluation of film]
(4) Transparency (total light transmittance, haze value)
The total light transmittance and the haze value were measured using a haze meter "NDH-5000" manufactured by Nippon Denshoku Industries Co., Ltd. by the measuring method described in JIS K7136 (2000).

(5) Packaging aptitude (5-1) Physical characteristics of film (storage elastic modulus / loss tangent)
According to the dynamic viscoelasticity measurement method described in JIS K7244 (1999), the storage elastic modulus (E') at 20 ° C. in the width direction of the films obtained in Examples and Comparative Examples at a vibration frequency of 10 Hz and a strain of 0.1%. ) And the loss tangent (tan δ) were measured.

(5-2) Stretchability The films obtained in Examples and Comparative Examples were fixed with a sample at a size of 50 mm square, and then stretched in the width direction of the film with a tabletop stretching machine at a rate of 100 mm / sec. The appearance, stretchability, tearing, and wrinkles were evaluated, and the stretchability of the film was evaluated.

(6) Comprehensive evaluation Based on the evaluation results of stretch aptitude and the value of loss tangent (tanδ), comprehensive evaluation was performed according to the following criteria.
○: Loss tangent (tan δ) is 0.3 or more, △ is 2 or less in the evaluation of stretch aptitude, and others are ○
Δ: Loss tangent (tan δ) is less than 0.3, △ is 2 or less in the evaluation of stretch aptitude, and others are ○
×: Those with × in the evaluation of stretch aptitude

[Example 1]
As the resin composition (Z), polypropylene-based resin (A1), polypropylene-based resin (B1), hydrogenated petroleum resin (C1), and styrene-based elastomer (D1) were used, and (A1) 12.5% by mass, (B1). It was melt-kneaded at 35% by mass, (C1) 25% by mass, and (D1) 27.5% by mass. Then, a film having a thickness of 80 μm was obtained with a test laminator. The packaging suitability (storage elastic modulus (E'), loss tangent (tan δ)) and stretch suitability of the obtained film were evaluated. The evaluation results are shown in Table 3.

[Example 2]
A film was obtained in the same manner as in Example 1 except that the polypropylene-based resin (A1) used in Example 1 was changed to 7.5% by mass and the polypropylene-based resin (B1) was changed to 40% by mass. The packaging suitability (storage elastic modulus (E'), loss tangent (tan δ)) and stretch suitability of the obtained film were evaluated. The evaluation results are shown in Table 3.

[Example 3]
A film was obtained in the same manner as in Example 2 except that the polypropylene-based resin (B1) used in Example 2 was changed to 35% by mass and the styrene-based elastomer (D1) was changed to 32.5%. The packaging suitability (storage elastic modulus (E'), loss tangent (tan δ)) and stretch suitability of the obtained film were evaluated. The evaluation results are shown in Table 3.

[Example 4]
A film was obtained in the same manner as in Example 1 except that the polypropylene-based resin (A1) used in Example 1 was changed to the polypropylene-based resin (A2). The packaging suitability (storage elastic modulus (E'), loss tangent (tan δ)) and stretch suitability of the obtained film were evaluated. The evaluation results are shown in Table 3.

[Example 5]
A film was obtained in the same manner as in Example 4 except that the polypropylene-based resin (A2) used in Example 4 was changed to 25% by mass and the polypropylene-based resin (B1) was changed to 22.5% by mass. The packaging suitability (storage elastic modulus (E'), loss tangent (tan δ)) and stretch suitability of the obtained film were evaluated. The evaluation results are shown in Table 3.

[Example 6]
The resin composition (Z) was changed to 40% by mass of polypropylene resin (A1), 35% by mass of polypropylene resin (B1), and 25% by mass of hydrogenated petroleum resin (C1), and no styrene elastomer (D1) was used. A film was obtained in the same manner as in Example 1 except for the above. The packaging suitability (storage elastic modulus (E'), loss tangent (tan δ)) and stretch suitability of the obtained film were evaluated. The evaluation results are shown in Table 3.

[Example 7]
As the resin composition (Z) of the layer (I), polypropylene-based resin (A1), polypropylene-based resin (B1), hydrogenated petroleum resin (C1), and styrene-based elastomer (D1) are used, and (A1) 12.5 mass. %, (B1) 35% by mass, (C1) 25% by mass, and (D1) 27.5% by mass.
As a molding material for the layer (II), 97% by mass of a polyethylene resin (E1) and 3% by mass of an antifog agent (diglycerin oleate) were melt-kneaded.
These melt-kneaded resins were subjected to co-pressing table inflation molding at an annular three-layer die at 190 ° C. and a blow-up ratio of 5.0 to have a total thickness of 10 μm, layer (II) / layer (I) / layer (II) (thickness 2 μm /). A three-layer film of 6 μm / 2 μm) was obtained.
The obtained film was evaluated as described above. The results are shown in Table 4.

[Example 8]
The total thickness is 10 μm, layer (II) / layer (I) / as in Example 7, except that the polypropylene-based resin (A1) of the resin composition (Z) of the layer (I) is changed to the polypropylene-based resin (A2). A three-layer film of layer (II) (thickness 2 μm / 6 μm / 2 μm) was obtained. The obtained film was evaluated as described above. The results are shown in Table 4.

[Comparative Example 1]
A film was obtained in the same manner as in Example 1 except that the polypropylene-based resin (A1) used in Example 1 was changed to the polypropylene-based resin (a1). The packaging suitability (storage elastic modulus (E'), loss tangent (tan δ)) and stretch suitability of the obtained film were evaluated. The evaluation results are shown in Table 3.

[Comparative Example 2]
Using 38% by mass of polypropylene-based resin (a1) and 42% by mass of polypropylene-based resin (B1) as the resin composition (Z), the hydrogenated petroleum resin (C1) was changed to 20% by mass, and the styrene-based elastomer (D1) was used. A film was obtained in the same manner as in Example 1 except that it was not used. The packaging suitability (storage elastic modulus (E'), loss tangent (tan δ)) and stretch suitability of the obtained film were evaluated. The evaluation results are shown in Table 3.

From the results in Table 3, it can be seen that the films of Examples 1 to 6 are transparent, have an excellent appearance, and are also excellent in packaging suitability.
On the other hand, in the films of Comparative Examples 1 and 2, the glass transition temperature of the polypropylene-based resin (a1) does not satisfy the provisions of the present invention, the transparency and appearance are inferior, and the storage elasticity of the film corresponding to the layer (I). Since the modulus (E') increases and the rigidity of the film increases, the packaging suitability is inferior. In particular, Comparative Example 2 has a very large storage elastic modulus (E'), and the loss tangent (tan δ) does not satisfy the provisions of the present invention, and the packaging suitability is significantly inferior.
Further, from the results in Table 4, it can be seen that even in Examples 7 and 8 of the three-layer film, the film is transparent, has an excellent appearance, and is excellent in packaging suitability.

Claims (6)

Based on JIS K7121 (2012), the glass transition temperature when the temperature is re-heated at 10 ° C./min by differential scanning calorimetry is -15 ° C or lower, the melting point is 130 ° C or lower, and the ethylene unit content is 6% by mass. It has at least one layer (I) containing the above-mentioned polypropylene-based resin (A) and the resin composition (Z) composed of the polypropylene-based resin (B) having an ethylene unit content of less than 6% by mass as a main component. A stretch packaging film having a loss tangent (tan δ) of 0.2 or more at 20 ° C. measured at a vibration frequency of 10 Hz and a storage elastic coefficient (E') of 400 MPa or less at 20 ° C. measured at a vibration frequency of 10 Hz. Is a stretch packaging film. The mass ratio of the resin composition (Z) when the total mass of the polypropylene-based resin (A) and the polypropylene-based resin (B) is 100% by mass is (A) / (B) = 10 to 60. The stretch packaging film according to claim 1, which is by mass% / 90 to 40% by mass. The claim that the layer (I) further contains the following resin (C), and the content of the resin (C) is 1 to 40% by mass when the total mass of the entire layer (I) is 100% by mass. 1 or the stretch packaging film according to claim 2.
Resin (C): At least one resin selected from petroleum resin, terpene resin, kumaron-inden resin, rosin-based resin, or hydrogenated derivatives thereof. The claim that the layer (I) further contains the following resin (D), and the content of the resin (D) is 1 to 45% by mass when the total mass of the entire layer (I) is 100% by mass. The stretch packaging film according to any one of claims 1 to 3.
Resin (D): At least one resin selected from a block copolymer of a vinyl aromatic compound and a conjugated diene, or a hydrogenated derivative thereof. Any one of claims 1 to 4, comprising at least two layers having a layer (II) containing a polyethylene-based resin (E) as a main component on one or both surfaces of the layer (I). The stretch packaging film described in the section. The polyethylene-based resin (E) is low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylate ester weight. The stretch packaging film according to claim 5, which is at least one selected from coalesced and ionomer resins.