JP5660980B2 - Film for stretch wrapping - Google Patents

Description

  The present invention relates to a stretch packaging film that is suitably used for food packaging, and more particularly to a stretch packaging film that does not contain chlorine or a plasticizer for polyvinyl chloride.

  Conventionally, a polyvinyl chloride film has been mainly used as a film that overlaps by placing fruits and vegetables, meat, side dish, etc. on a lightweight tray, that is, a stretch packaging film for so-called pre-packaging. The reason for this is that the polyvinyl chloride film has good packaging efficiency such as good packaging efficiency and a good packaging finish, and returns to its original state when the film after packaging is deformed by pressing with a finger. Quality recognized by both sellers and consumers that the product value does not decrease, such as excellent elasticity recovery, bottom folding stability, and film peeling during transportation display. It was because of having the advantage of.

  However, in recent years, with respect to polyvinyl chloride films, problems such as elution of hydrogen chloride gas generated during incineration and plasticizers contained in large quantities have been regarded as problems. For this reason, various alternatives to polyvinyl chloride films have been studied, and various stretch packaging films using polyolefin resins have been proposed. Above all, for reasons such as good surface properties as a stretch film, transparency, moderate heat resistance, freedom of material design, economy, etc., an ethylene-vinyl acetate copolymer is used as the main component for the front and back layers, and the intermediate layer In addition, a study is being actively made on a film for stretch packaging having two types and three layers comprising various polypropylene resins as main components.

  For example, Patent Document 1 has at least one layer containing a propylene-based resin and a petroleum resin, a terpene resin, a coumarone-indene resin, a rosin resin, or a hydrogenated derivative thereof having a crystallization heat amount of 10 to 60 J / g. However, a stretch film for food packaging having a specific storage elastic modulus has been proposed.

  When a film for stretch packaging is set and packaged in an automatic packaging machine, a film having a predetermined width may be packaged by changing the degree of stretching according to the size of the tray. At this time, in order to wrap a large tray, the degree of stretching at the time of overlapping is increased and packaged (high stretch packaging).

  In the above-mentioned Patent Document 1, a new polyolefin-based stretch packaging film has been proposed as a non-chlorine-based stretch packaging film that does not contain chlorine or polyvinyl chloride plasticizer, but the film used an automatic packaging machine. Although the suitability of various packaging machines (cutability, packaging wrinkles, bottom folding stability, tearability) is good, whitening of the film after packaging that occurs when carrying out high stretch packaging as described above is an issue ing.

JP-A-9-154479

  The present invention has been made in view of the above circumstances, and its solution is to provide a novel non-chlorine stretch packaging film that is less likely to be whitened after packaging even when subjected to high stretch when overlapping. There is to do.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be easily solved by adopting a specific configuration, and the present invention has been completed.

That is, the gist of the present invention is a laminated film comprising at least three layers of both outermost layers containing an ethylene resin (A) component as a main component and an intermediate layer containing a propylene resin (B) component as a main component. The ethylene resin (A) component has a vinyl acetate unit content of 5 to 25% by mass, a melt flow rate of 0.2 to 10 g / 10 minutes, and an extrapolation crystallization start temperature and crystallization. It exists in the film for stretch packaging characterized by consisting of the ethylene-vinyl acetate copolymer whose difference in peak temperature is 5 degreeC or more .

  According to the present invention, the suitability of various packaging machines when using an automatic packaging machine (cutability, packaging wrinkles, bottom folding stability, tearability) is good, and high stretch is applied when overlapping. In addition, it is possible to provide a non-chlorine stretch packaging film in which whitening of the post-packaging film hardly occurs.

  Hereinafter, a stretch packaging film (hereinafter referred to as “the stretch film”) 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 this stretch film, a surface layer mainly composed of an ethylene-based resin (A) component is formed and a laminated structure is adopted, so that heat sealability (bottom sealability) at low temperatures, self-adhesion, and inflation are achieved. The moldability at the time can be improved.

  Here, examples of the ethylene-based resin (A) include low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, and copolymers containing ethylene as a main component, for example Ethylene, α-olefins having 3 to 10 carbon atoms such as propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, vinyl acetate, vinyl propionate, etc. One or two selected from unsaturated carboxylic acid esters such as vinyl esters, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate and the like, and ionomers thereof, unsaturated compounds such as conjugated dienes and non-conjugated dienes Copolymers or multi-component copolymers with more than one comonomer, or their If the composition, and the like. The content of ethylene units in the ethylene polymer is usually more than 50% by mass.

  Among these ethylene-based resins (A), low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylate copolymer, and ethylene -At least one ethylene-based polymer selected from methacrylic acid ester copolymers is preferred.

  Examples of the acrylic acid ester of the ethylene-acrylic acid ester copolymer include methyl acrylate and ethyl acrylate. Examples of the acrylic acid ester of the ethylene-methacrylic acid ester copolymer include methyl methacrylate. And ethyl methacrylate.

Among them, as the ethylene resin (A), a resin having a difference between the extrapolation crystallization start temperature described in JIS K 7122 and the crystallization peak temperature of 5 ° C. or more is used in the present invention, and the vinyl acetate unit content is 5 ~ 25% by mass, melt flow rate (JISK7210, temperature: 190 ° C,
An ethylene-vinyl acetate copolymer having a load of 21.18 N) of 0.2 to 10 g / 10 min is preferable, particularly 0.5 to 8 g / 10 min, and particularly 1 to 6 g / 10 min of ethylene-vinyl acetate copolymer. More preferred are polymers.

Here, if the difference between the extrapolation crystallization start temperature and the crystallization peak temperature is 5 ° C. or more , the whitening of the film after packaging is good, and if the vinyl acetate unit content is 5% by mass or more, it is obtained. The film is soft and not only can maintain flexibility and elastic recovery, but also can impart surface tackiness. On the other hand, if it is 25 mass% or less, surface tackiness will not be too strong and unwinding property and an external appearance can be maintained favorable. The melt flow rate is 0.
If it is 2 g / 10 min or more, the extrudability can be maintained well, while 10 g / 1
If it is 0 minute or less, the film-forming stability can be maintained, and it is possible to suppress the occurrence of unevenness in thickness, variation in mechanical strength, and the like.

  The intermediate layer is a layer containing a predetermined propylene resin (B) component as a main component.

  In the present invention, it is preferable to set the crystallization heat amount (ΔHc) of the intermediate layer within a predetermined range (10 J / g or more and 60 J / g or less). If the heat of crystallization is less than 10 J / g, in addition to the crystallinity being too low and the film forming property being poor, the film may be too soft or the strength may be insufficient at room temperature. In addition, when the amount of heat of crystallization exceeds 60 J / g, a large force is required at the time of film extension, and only non-uniform elongation is exhibited, which may not be suitable for a stretch film. The method for adjusting the crystallization heat amount (ΔHc) to a predetermined range is not particularly limited, but a method of mixing a resin different from the propylene resin (B) is preferably used. Among these, it is more preferable to mix the resin described later in terms of imparting various packaging machine aptitudes (cutability, packaging wrinkles, bottom folding stability, tearability, and transparency after packing).

  Examples of the propylene-based resin (B) include a propylene homopolymer, a random copolymer or a block copolymer of propylene and “another copolymerizable monomer”, and the like.

  By using such a propylene-based resin (B) as a main component of the intermediate layer, various packaging suitability such as bottom folding and cutability can be improved, and in addition to pellet storage stability, the resin composition constituting the intermediate layer The strength and heat resistance of the object can be increased.

  In this case, examples of other copolymerizable monomers include ethylene, 1-butene, 1-hexene, 4-methylpentene-1, 1-octene and other α-olefins having 4 to 20 carbon atoms and divinylbenzene, Although dienes, such as 1, 4- cyclohexadiene, dicyclopentadiene, cyclooctadiene, ethylidene norbornene, etc. are mentioned, 2 or more types of these may be copolymerized.

  From the viewpoint of imparting appropriate flexibility necessary for the stretch film, a propylene-ethylene random copolymer, a propylene-ethylene-butene-1 copolymer, a reactor type polypropylene elastomer, and a propylene-ethylene copolymer It is preferable to use one or two kinds of mixed components selected from a polymer or a propylene-α-olefin copolymer.

  In addition, in 1 type or 2 types of mixed components chosen from propylene-type resin (B), crystallization calorie | heat_amount ((DELTA) Hc) when it measures at the temperature decrease rate of 10 degree-C / min with a differential scanning calorimeter (DSC). If it is 30 J / g or more, strength and heat sealability can be maintained.

  Here, the amount of heat of crystallization (ΔHc) depends on the molecular weight of the resin used, the ethylene content (copolymerization ratio), the degree of randomness (dispersibility in the copolymer of ethylene components), stereoregularity, and the like. In general, it can be said that the higher the crystallization heat amount, the higher the peak temperature tends to increase, and the heat resistance is generally excellent. From such a viewpoint, the crystallization heat quantity (ΔHc) is preferably 30 J / g or more, more preferably 40 J / g or more, and particularly preferably 50 J / g or more. The upper limit is not particularly limited, but is practically 150 J / g or less.

  Moreover, when the peak of the crystallization curve when measured at a temperature decrease rate of 10 ° C./min with a differential scanning calorimeter (DSC) of the propylene-based resin (B) used in the present invention is not single, specifically, The case of a double peak will be described. When the peak of the crystallization curve is a double peak, there are regions with different crystallization speeds in the resin, that is, it is inhomogeneous so that the transparency is lowered, the raw material pellets are sticky or stored. May cause blocking and may not be suitable for the present invention.

  The melt flow rate (MFR) of one or two kinds of mixed components selected from the propylene-based resin (B) is not particularly limited, but usually MFR (JISK7210, temperature: 230 ° C., load: 21.18N) is 0.2 g / 10 min or more, preferably 0.5 to 18 g / 10 min, and more preferably 1 to 15 g / 10 min. If the MFR is 0.2 g / 10 min or more, the extrusion processability is stable. If the MFR is 20 g / 10 min or less, stable film formation is possible at the time of molding, as well as unevenness in thickness, decrease in mechanical strength, and variation. Etc. are preferable.

  Examples of the propylene-based resin (B) include, for example, trade names “Novatech PP” and “WINTEC” of Nippon Polypro Co., Ltd., trade names “Noblen” of Sumitomo Chemical Co., Ltd., and trade names “Prime Polypro” of Prime Polymer Co., Ltd. “Prime TPO”, trade name “Versify” of Dow Chemical Co., Ltd., and the like.

  Examples of the resin (C) include a block copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated derivative thereof. Since such a copolymer generally has rubber elasticity and is flexible, it gives an elastic recovery property to the film and effectively acts to reduce the tensile elastic modulus of the polypropylene resin as the component (B). .

  Here, styrene is a typical vinyl aromatic compound, but styrene homologues such as α-methylstyrene may also be used. Examples of the conjugated diene include 1,3-butadiene, isoprene, 1,3-pentadiene, and the like. These may 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 when a double bond mainly consisting of vinyl bonds in the conjugated diene moiety remains are extremely poor. To improve this, 80% or more of the double bond, and further 95% It is preferable to use one added with hydrogen.

  Moreover, it is preferable that the ratio of the vinyl aromatic-type compound and conjugated diene of such a copolymer is 3 / 97-40 / 60 by weight ratio. Here, if the vinyl aromatic compound in the copolymer composition is less than 3% by weight, the rigidity of the copolymer itself tends to be too low, and the polymerization productivity tends to decrease, such as difficulty in pelletization. If it exceeds wt%, the rigidity of the copolymer itself becomes high, and the film, which is the purpose of the addition of the component (B), is imparted with an elastic recovery property, or the effects such as reduction of the tensile modulus are insufficient. Sometimes.

  Specifically, styrene-butadiene block copolymer elastomer (Asahi Kasei Kogyo Co., Ltd. trade name “Tufprene”), hydrogenated derivative of styrene-butadiene block copolymer (Asahi Kasei Kogyo Co., Ltd. trade name “Tuftec”), styrene -Use of commercial products such as hydrogenated derivatives of isoprene block copolymer (Kuraray brand name "Septon"), styrene-vinylisoprene block copolymer elastomer (Kuraray brand name "Hibler"), etc. it can.

  In the resin composition constituting the intermediate layer, the content of the resin (C) is preferably 1 to 50% by mass. If content of resin (C) is 1 mass% or more, the elastic recovery property of a film required for a stretch film can be provided. Especially, it is more preferable that content of resin (C) is 5 mass% or more, and it is further more preferable that it is 10 mass% or more. Moreover, if it is 50 mass% or less, compatibility with a propylene resin (B) will improve and transparency can be improved. Therefore, from the viewpoint of achieving both imparting elasticity and improving transparency, the content of the resin (C) is more preferably 40% by mass or less.

  The resin composition constituting the intermediate layer may contain a predetermined resin (D) component in addition to the component (B) and the component (C).

Examples of the resin (D) include petroleum resins, terpene resins, coumarone-indene resins, rosin resins, and hydrogenated derivatives thereof. (Also referred to as “petroleum resins”).
Such a resin (D) component effectively acts on further improvement of packaging suitability such as film waist and cutability, bottom folding stability, and transparency.

  Here, as the petroleum resin, cyclopentadiene or an alicyclic petroleum resin obtained from the dimer thereof, an aromatic petroleum resin obtained from the C9 component, or a copolymer of alicyclic and aromatic petroleum resin A petroleum resin etc. can be mentioned.

  Examples of the terpene resin include a terpene resin obtained from β-pinene and a terpene-phenol resin.

  Examples of the coumarone-indene resin include a thermoplastic synthetic resin obtained by purifying a 160 to 180 ° C. fraction of tar and polymerizing coumarone having 8 carbons and indene having 9 carbons as main monomers.

Examples of the rosin resin include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin, pentaerythritol, and the like.
The petroleum resin as described above is preferably a hydrogenated derivative from the viewpoints of color tone, thermal stability, and compatibility.

  Moreover, although what has various softening temperatures mainly by molecular weight is obtained as said petroleum resin, what has a softening temperature in 100-150 degreeC, Preferably it is 110-140 degreeC is more suitable.

  Specifically, Mitsui Chemicals' product names “Hilets” and “Petrogin”, Arakawa Chemical Industries' product name “Arcon”, Yashara Chemicals' product name “Clearon”, Idemitsu Petrochemical Co., Ltd. ) And trade name “Escoretz” of Eastman Chemical Co., Ltd. can be used.

  In the resin composition constituting the intermediate layer, the content of the resin (D) is preferably 1 to 40% by mass. If content of resin (D) is 1 mass% or more, the cut property and bottom folding stability required for a stretch film can be provided. Especially, it is more preferable that content of resin (D) is 5 mass% or more, and it is further more preferable that it is 10 mass% or more. Moreover, if it is 40 mass% or less, the low temperature aptitude required for a stretch film will not be spoiled with a raise of a glass transition temperature, and the blocking of the film by the bleed | bleed of a low molecular weight substance will not be caused easily. Therefore, from this viewpoint, the content of the resin (D) is more preferably 35% by mass or less, and further preferably 30% by mass or less.

  The resin composition constituting the intermediate layer may contain an ethylene-based resin (E) in addition to the component (B), the component (C), and the component (D).

  The ethylene resin (E) may be the same polymer as the ethylene resin (A) constituting the surface layer or may be a different ethylene resin, but is preferably the same ethylene resin. It is good. If the ethylene-based resin (E) and the ethylene-based polymer (A) constituting the surface layer are the same ethylene-based polymer, the adhesion between the intermediate layer and the surface layer can be improved, and the dynamics of the entire film In addition to improving the characteristics, for example, trimming loss that occurs when trimming by trimming both ends of the formed film can be prepared by adding it as a constituent material of the intermediate layer, eliminating waste of materials, Material costs can be reduced.

As the most preferred ethylene-based resin (E), the vinyl acetate unit content is 5 to 25% by mass, and the melt flow rate (JISK7210, temperature: 190 ° C., load: 21.18 N) is 0.2 to 10 g / 10 min. The ethylene-vinyl acetate copolymer is preferably 0.5 to 8 g / 10 min, more preferably 1 to 6 g / 10 min.
Here, if the vinyl acetate unit content is 5% by mass or more, the resulting film is not only soft and can maintain flexibility and elastic recovery, but also when the ethylene resin (E) is a surface layer. Can be given surface tackiness. On the other hand, if it is 25 mass% or less, even if it is a case where ethylene-type resin (E) is a surface layer, it can maintain unwinding property and an external appearance favorably, without surface adhesiveness being too strong. it can. Moreover, if the melt flow rate is 0.2 g / 10 min or more, the extrudability can be maintained satisfactorily, while if it is 10 g / 10 min or less, the film forming stability can be maintained, This is preferable because it is possible to suppress the occurrence of thickness unevenness and variations in mechanical strength.

  In the resin composition constituting the intermediate layer, the content of the ethylene resin (E) is preferably 1 to 40% by mass. If content of ethylene-type resin (E) is 1 mass% or more, the low temperature aptitude required for a stretch film can be provided. Especially, it is more preferable that content of ethylene-type resin (D) is 5 mass% or more, and it is further more preferable that it is 10 mass% or more. Further, if it is 40% by mass or less, the bottom folding stability and heat resistance are sufficient, and from this viewpoint, the content of the ethylene resin (E) is more preferably 35% by mass or less, and 30% by mass or less. More preferably.

  In the surface layer and / or the intermediate layer of the stretch film, the following various additives can be appropriately blended in order to impart performances such as antifogging property, antistatic property, slipperiness and adhesiveness.

  Here, as various additives, for example, an aliphatic alcohol system which is a compound of a fatty acid alcohol having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms, and a fatty acid having 10 to 22 carbon atoms, preferably 12 to 18 carbon atoms. Fatty acid esters, specifically, monoglycerylate, polyglycerin oleate, glycerin triricinoleate, glycerin acetylricinoleate, polyglycerin stearate, glycerin laurate, polyglycerin laurate, methylacetylricinoleate, ethylacetylricinoleate, Butylacetylricinoleate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol oleate, polypropylene glycol oleate, sorbitan oleate, sorbitan laurate, Reethylene glycol sorbitan oleate, polyethylene glycol sorbitan laurate, and the like, and polyalkyl ether polyols, specifically, polyethylene glycol, polypropylene glycol, and the like, and paraffinic oils can be mentioned, one or two of these The above can be used together.

  And these additives are 0.1 to 12 mass parts with respect to 100 mass parts of resin components which comprise a surface layer and / or an intermediate | middle layer, It is preferable to mix | blend 1-8 mass parts suitably.

  In this stretch film, the surface layer is an ethylene polymer (A), and the intermediate layer includes at least 3 an intermediate layer made of a resin composition containing a predetermined propylene resin (B) component as a main component. It may be a laminated film composed of layers, and may be abbreviated as other layer (hereinafter referred to as P layer) as necessary, such as improvement of mechanical properties and interlayer adhesion, within the range not exceeding the gist of the present invention. ) May be introduced as appropriate. Here, the surface layer (hereinafter sometimes abbreviated as S layer) may have the same layer other than both surface layers, that is, an intermediate layer. Further, the intermediate layer (hereinafter sometimes abbreviated as “M layer”) may have at least one layer between both surface layers, and may have two or more layers. For example, a three-layer structure composed of (S layer) / (M layer) / (S layer), a four-layer structure composed of (S layer) / (P layer) / (M layer) / (S layer), (S layer) 5 layers consisting of / (P layer) / (M layer) / (P layer) / (S layer), (S layer) / (M layer) / (P layer) / (M layer) / (S layer) A typical configuration can be given. In this case, the resin composition and thickness ratio of each layer may be the same or different.

  In this stretch film, the preferred range of the thickness ratio between the surface layer and the intermediate layer is preferably 10 to 65% for the front and back layers and 90 to 35% for the intermediate layer. If the thickness ratio is within such a range, stable film forming stability can be obtained, and suitable surface tackiness can be imparted to the stretch film.

  Furthermore, when considering stable film forming processability, surface tackiness, various physical properties as a stretch wrapping film, and economic efficiency, it is more preferable that the front and back layers are 20 to 60% and the intermediate layer is 80 to 40%. .

  The thickness of this stretch film should just be the range used as a film for normal stretch packaging, ie, about 8-30 micrometers, typically about 9-20 micrometers.

  The stretch film can be produced by, for example, melt-extruding a material from an extruder and molding the material into a film by inflation molding or T-die molding.

  When making a laminated film, it is preferable to co-extrusion with a multilayer die using a plurality of extruders. Practically, it is preferable to melt-extrude the material resin from an annular die and perform inflation molding, and the blow-up ratio (tube diameter / die diameter) at that time is preferably 3 or more, particularly preferably in the range of 4 to 7. . As a cooling method in that case, 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 may be used.

  Further, the obtained film is heated to a temperature lower than the crystallization temperature of the resin, and stretched by about 1.2 to 5 times in the longitudinal direction of the film by utilizing a speed difference between nip rolls, or 1.2 in the longitudinal and lateral directions of the film. It may be biaxially stretched to about 5 times. Thereby, improvement of cut property, provision of heat shrinkability, etc. can be performed.

  The storage elastic modulus of this stretch film is such that the storage elastic modulus (E ′) at 20 ° C. measured at a vibration frequency of 10 Hz and a strain of 0.1% by the dynamic viscoelasticity measurement method described in JIS K-7198A method is 100 MPa to 1 GPa. It is preferable that it exists in the range. When the film is used as a soft film, the value of the elastic modulus near room temperature is an index. When the storage elastic modulus (E ′) at 20 ° C. is 100 MPa or more, problems such as poor film workability due to close contact between the films at room temperature are unlikely to occur. On the other hand, if it is 1 GPa or less, the film does not become too hard and is appropriately stretched, which is advantageous for soft film applications.

The stretch film has a flexibility of 100% elongation tensile stress in the transverse direction (TD) of 40 to 140 kgf / cm ² measured by conducting a tensile test at a temperature of 20 ° C. and a tensile speed of 200 mm / min according to JIS Z1702. It is preferable that it exists in the range of this, More preferably, it is 50-130 kgf / cm < ² >.

  In the present invention, the “stretch film” is meant to encompass a wide range of packaging films having stretchability and self-adhesiveness. Typically, a pre-packaging packaging film that overlaps fruits and vegetables, meat, side dish, etc. on a lightweight tray, or a packaging film that overlaps in order to fix the baggage during transportation. .

  In the present invention, the “main component” includes the meaning of allowing other components to be contained within a range that does not interfere with the function of the main component, unless otherwise specified. At this time, the content ratio of the main component is not specified, but the main component (when two or more components are main components, the total amount thereof) is 50% by mass or more, particularly 70% by mass in the composition. %, More preferably 90% by mass or more (including 100% by mass).

  In general, “sheet” is a thin product as defined by JIS, and generally its thickness is small and flat instead of length and width, and “film” is generally defined as length and width. A thin flat product having an extremely small thickness and an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). For example, in terms of thickness, in the narrow sense, a film having a thickness of 100 μm or more is sometimes referred to as a sheet, and a film having a thickness of less than 100 μm is sometimes referred to as a film. However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, the various measured value and evaluation about the film displayed in this specification and its material were performed as follows. Here, the flow direction of the film from the extruder is called the vertical direction, and the perpendicular direction is called the horizontal direction.

(1) Crystallization peak temperature (Tc) and crystallization heat (ΔHc)
Using DSC-7 manufactured by PerkinElmer, Inc., according to JISK7121, JISK7122, the measurement sample was heated to 200 ° C at a temperature increase rate of 10 ° C / min, held for 1 minute, and then the temperature decrease rate was 10 ° C / min. And determining whether or not the peak of the crystallization temperature is single based on the obtained crystallization curve, and determining the crystallization peak temperature (Tc) and the crystallization heat quantity (ΔHc).

(2) Storage elastic modulus (E ')
According to the dynamic viscoelasticity measurement method described in the JISK-7198A method, using a dynamic viscoelasticity measurement device “DVA-200” manufactured by IT Measurement Control Co., Ltd., the vibration frequency is 10 Hz in the transverse direction (TD). Measurement was performed from −50 ° C. to 150 ° C. at a rate of temperature increase of 1 ° C./min at a strain of 0.1%, and the storage elastic modulus (E ′) at a temperature of 20 ° C. was determined from the obtained data.

(3) Flexibility According to JIS Z1702, a tensile test is performed at a temperature of 20 ° C. and a tensile speed of 200 mm / min, and a 100% elongation tensile stress (kgf / cm ² ) in the transverse direction of the film is measured. Flexibility was evaluated according to the following criteria.
A: Tensile stress value (kgf / cm ² ) is 50 or more and less than 80 B: Tensile stress value (kgf / cm ² ) is 40 or more and less than 50, or 80 or more and less than 90 Δ: Tensile stress value (kgf / cm ² ) is 20 or more and less than 40, or 90 or more and less than 140 ×: Tensile stress value (kgf / cm ² ) is less than 20, or 140 or more

(4) Suitability for packaging machine Using the film (width 350 mm) obtained in the examples and comparative examples, using an automatic packaging machine (ISHIDA / Wmini-UNI manufactured by Ishida Co., Ltd.), expanded polystyrene tray (length 330 mm, width 230 mm, 38 mm in height) was packaged, and the transparency, cutability, packaging wrinkle, bottom folding stability and tearability after packing were evaluated according to the criteria shown in Table 2, and the results are shown in Table 1.

Example 1:
For the resin composition forming both surface layers, EVA (vinyl acetate content: 15% by mass, crystallization heat: 81.4 J / g, extrapolation crystallization start) as the ethylene-based polymer as component (A) Temperature: 81.1 ° C., crystallization peak temperature: 75.1 ° C., melt flow rate (JIS K7210, temperature: 190 ° C., load: 21.18 N) 2.3 g / 10 min) and 97 parts by mass as an antifogging agent 3 parts by mass of diglycerin oleate was melt-kneaded.
On the other hand, for the resin composition forming the intermediate layer, the propylene-based resin (B) component (crystallization peak: single, crystallization heat: 69.0 J / g, crystallization peak temperature: 95.9 ° C., melt A block copolymer of a flow rate (JISK7210, temperature: 230 ° C., load: 21.18 N) 7.0 g / 10 min) and a vinyl aromatic compound and a conjugated diene as component (C) or a hydrogenated derivative thereof (Melt flow rate (JISK7210, temperature: 190 ° C., load: 21.18N) 0.7 g / 10 min) and hydrogenated petroleum resin (softening temperature 125 ° C., manufactured by Arakawa Chemical Industries, Ltd.) as component (D), Alcon P125) is melt-kneaded so that the mass ratio is (B) / (C) / (D) = 51.4 / 32.4 / 16 · 2, and these melt-kneaded resins are made into an annular three-layer die 190. , By co-extrusion inflation molding at a blow-up ratio of 5.0 to obtain a three-layer film having a total thickness of 12μm (2μm / 8μm / 2μm).

Example 2:
The composition of component (A) forming both surface layers in Example 1 is EVA (vinyl acetate content: 15% by mass, crystallization heat amount: 66.3 J / g, extrapolation crystallization start temperature: 80.3 ° C. The total thickness was the same as in Example 2 except that the crystallization peak temperature was changed to 75.2 ° C and the melt flow rate (JISK7210, temperature: 190 ° C, load: 21.18N) 2.0 g / 10 min). A 12 μm three-layer film was obtained.

Comparative Example 1:
The composition of the component (A) forming both surface layers in Example 1 is EVA (vinyl acetate content: 15 mass%, crystallization heat amount: 66.3 J / g, extrapolation crystallization start temperature: 77.4 ° C. The total thickness was the same as in Example 2 except that the crystallization peak temperature was 72.7 ° C. and the melt flow rate (JISK7210, temperature: 190 ° C., load: 21.18 N) 2.2 g / 10 min). A 12 μm three-layer film was obtained.

From the results of Table 1, Examples 1 to 3 show that (1) the difference between the extrapolation crystallization start temperature and the crystallization peak temperature of the ethylene-based resin (A) of both surface layers is 5 ° C. or more , (2) Differential scanning calorimeter (DSC)
The peak of the crystallization curve when measured at a rate of temperature decrease of 10 ° C./min.
) The crystallization peak temperature (Tc) in (3) above is 70 ° C. or higher, and the crystallization heat quantity (ΔHc)
) Is 10 J / g or more and 60 J / g or less as component (B) as a main component of the intermediate layer, the transparency after packing when a large tray is packaged in an automatic packaging machine is good, and By setting the storage elastic modulus (E ′) within the specified range, it can be confirmed that good results can be obtained in any of suitability for packaging machine, flexibility and low temperature suitability. Further, in Example 2, in addition to the resin composition (B) component and the (C) component forming the intermediate layer, by including a hydrogenated petroleum resin as the (D) component, flexibility, suitability for packaging machines, low temperature It is excellent in suitability and is a particularly preferred embodiment. On the other hand, when the difference between the extrapolation crystallization start temperature and the crystallization peak temperature was less than 5 ° C., the result of inferior transparency after packing when a large tray was packaged in an automatic packaging machine (Comparative Example) 1).

  The film of the present invention can be suitably used, for example, as a stretch film for food packaging.

Claims (4)

And both outermost layers containing ethylene-based resin component (A) as a main component, a laminate film comprising at least three layers of an intermediate layer mainly containing propylene-based resin (B) component, an ethylene-based resin (A ) The component has a vinyl acetate unit content of 5 to 25% by mass, a melt flow rate of 0.2 to 10 g / 10 min, and a difference between the extrapolation crystallization start temperature and the crystallization peak temperature of 5 ° C. or more. A stretch packaging film comprising an ethylene-vinyl acetate copolymer .   The film for stretch packaging according to claim 1, wherein the storage elastic modulus (E ') at 20 ° C measured at a vibration frequency of 10 Hz and a strain of 0.1% is 100 MPa to 1 GPa. Stretch packaging film according to the intermediate layer, any of the following (1) and of satisfying claims 1-2 (2).
(1) Single peak of crystallization curve when measured with a differential scanning calorimeter (DSC) at a temperature drop rate of 10 ° C./min (2) Crystallization peak temperature (Tc) in (1) above is 70 ° C. or higher And the amount of crystallization (ΔHc) is 10 to 60 J / g. The film for stretch packaging according to any one of claims 1 to 3 , wherein the propylene resin (B) component comprises the following components, and the intermediate layer contains the following components (C) and / or (D) .
(B) From among homopolypropylene, propylene-ethylene copolymer, propylene-ethylene-butene-1 copolymer, reactor-type polypropylene elastomer, propylene-ethylene copolymer, and propylene-α-olefin copolymer At least one selected component (C) a component comprising a block copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated derivative thereof (D) a petroleum resin, a terpene resin, a coumarone-indene resin, a rosin resin, And at least one resin selected from hydrogenated derivatives thereof