JP5823212B2 - Polyolefin-based multilayer wrap film and food packaging film - Google Patents

Description

  The present invention relates to a wrap film, and more particularly to a polyolefin-based multilayer wrap film that can be suitably used for packaging foods and the like.

  Conventionally, polyvinyl chloride-based films have been mainly used as wrap films for so-called prepackages in which fruits and vegetables, meat, side dishes, etc. are placed on a lightweight tray and overlapped with a film. In addition to packaging suitability such as good packaging efficiency and beautiful packaging finish, it also has excellent resilience to return to its original shape even when it is deformed, such as pressing the film after packing, and also has a bottom seal. This is because it has a quality advantage that is recognized by both the seller and the consumer that the value of the packaged product does not decrease because the film is not peeled off during transportation display. is there.

  However, in recent years, problems such as hydrogen chloride gas generated during incineration and elution of a large amount of plasticizer have been regarded as problems for polyvinyl chloride films.

  On the other hand, as a material to replace the vinyl chloride stretch film, there is a polyolefin wrap film that can be produced without generating toxic gas during incineration and without using a plasticizer that easily dissolves in the packaged food. Has been developed.

  For example, Patent Document 1 discloses a copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated derivative thereof, and a resin having a glass transition temperature of −20 ° C. or higher and a propylene-based resin and a petroleum resin component. A stretch film for food packaging having at least one mixed resin layer mixed is disclosed.

  Specifically, Patent Document 1 discloses, as an example, a styrene-isoprene-styrene triblock copolymer (glass transition temperature) composed of 80% by weight of polyisoprene having 20% by weight of styrene and 55% of 3,4-bond ratio. -19 ° C) 49 wt%, hydrogenated derivative of cyclopentadiene petroleum resin (glass transition temperature 81 ° C, softening temperature 125 ° C) 21 wt%, propylene-ethylene random copolymer (ethylene content 4 mol%, 230 MFR at 0.5 ° C. = 0.5 g / 10 min) and a composition in which 3.0 parts by weight of diglycerin monooleate as an antifogging agent was mixed as an intermediate layer having a thickness of 11 μm and EVA (vinyl acetate) on both sides 15% by weight, MFR at 190 ° C. = 2.0 g / 10 min) 3 parts diglycerin monooleate as an antifogging agent in 100 parts by weight 0 coextruded inflation molded to each a 2μm layer of parts kneaded composition, a film having a total thickness of 15μm have been disclosed.

  However, the stretch film having the above configuration is inferior in rigidity to the load from the upper surface when the film is stretched on the tray, and when the prepackage is transported by multi-stacking, the package disposed in the lower part is The commercial value may decrease in appearance due to the load received from the package. Furthermore, because the heat resistance of the film is inferior, when heat-sealing the bottom of the packaging body with a horizontal pillow type packaging machine, defects such as holes in the film occur due to melting by the heat received from the heat-sealing hot plate. there's a possibility that.

Patent Document 2 discloses a heat seal layer made of at least one ethylene-α-olefin random copolymer having a density of 0.900 to 0.930 g / cm ³ and a density of 0.900 to 0.00. Including at least one ethylene-α-olefin random copolymer consisting of 930 g / cm ³ and at least one ethylene-α-olefin block copolymer having a density of 0.860 to 0.890 g / cm ^3. A multilayer film for shrink wrapping composed of layers comprising a composition is disclosed.

  It is possible to make it hard to produce indentation traces due to indentation load by shrinking the packaging body using the film having the above structure by a heat process such as hot air. It is necessary to provide a margin for the width of the film relative to the package, and it is necessary to prepare a film having a wider width than a film that does not require a shrinking process.

  In addition, special equipment such as a shrink tunnel for sending hot air is required. Furthermore, in order to manufacture said film, a extending | stretching process is needed in order to provide a heat-shrink function, The extending | stretching equipment for that, Furthermore, the electron beam irradiation equipment for electron beam bridge | crosslinking is needed. Therefore, there exists a problem that the manufacturing cost of the said film and the package using the said film rises.

JP-A-9-165492 JP 2009-298119 A

  This invention is made | formed in view of the said situation, The solution subject is providing the polyolefin-type multilayer wrap film which is excellent in the heat resistance characteristic in rigidity, a heat seal, etc., and has a favorable mechanical characteristic.

  As a result of intensive studies, the present inventors have found that the above problems can be easily solved by a multilayer film having a specific configuration, and have completed the present invention.

That is, the gist of the present invention is that both surface layers (A) are mainly composed of an ethylene polymer (a), and one of the layers sandwiched between both surface layers (B) is a soft resin polymer. ( B1) and a crystalline propylene polymer having a heat of crystallization (ΔHc) of 80 J / g or more and 120 J / g or less when measured at a temperature drop rate of 10 ° C./min with a differential scanning calorimeter (DSC) ( b2) and the tackifier (b3) only, and (b1) is 1% by mass to 15% by mass, (b2) is 40% by mass to 80% by mass, and (b3) is 5% by mass. and also contains 30 wt% or less, the total thickness of a multilayer film of 5 to 20 [mu] m, and the indentation load of the multilayer film 160gf above, loss tangent in a dynamic viscoelasticity measured at frequencies 10 Hz (tan [delta) is and wherein a 0.13 to a 0.18 It exists in the polyolefin-type multilayer wrap film.

  ADVANTAGE OF THE INVENTION According to this invention, the polyolefin-type multilayer wrap film which is excellent in rigidity, has the heat-resistant characteristic in heat seal etc., and a favorable mechanical characteristic, and the film for food packaging can be provided.

FIG. 1 is a schematic explanatory view of an indentation load measuring instrument to which pins are attached for evaluating the characteristics of the film of the present invention. FIG. 2 is a schematic diagram of a process of pushing the wrap film of the present invention with a pin.

  In the present invention, “configured as a main component” is intended to permit the inclusion of other components within a range that does not interfere with the action and effect of the resin that constitutes each layer. Further, this term does not limit the specific content, but it is 70% by mass or more and 100% by mass or less, preferably 85% by mass or more and 100% by mass or less, more preferably 95% by mass of the total components of each layer. It means that it occupies% or more and 100 mass% or less.

Wrap film of the present invention, the surface layer (A), intermediate layer (B) is then required and to be stacked in the order of the surface layer (A) / intermediate layer (B) / the surface layer (A), surface layer ( Another layer may be provided between A) and the intermediate layer (B). Further, both surface layers (A) are composed mainly of an ethylene polymer (a), and the intermediate layer (B) is a soft resin polymer (b1) of 1% by mass to 15% by mass, a crystalline propylene-based polymer. The polymer (b2) contains 40% by mass to 80% by mass and the tackifier (b3) contains 5% by mass to 30% by mass, and is a multilayer film having a total thickness of 5 to 20 μm, The indentation load of the multilayer film is 160 gf or more, and the loss tangent (tan δ) in dynamic viscoelasticity measured at a frequency of 10 Hz is 0.13 to 0.18 .

  The resin used as the main component of the surface layer (A) can be appropriately selected in consideration of the resin used as the main component of the intermediate layer (B), but when using the wrap film of the present invention, the surface layer There is no particular limitation as long as the delamination phenomenon does not occur between (A) and the intermediate layer (B).

  As the resin used for the surface layer (A), since the melt extrusion temperature is 180 to 300 ° C., a thermoplastic resin that can be melt-extruded in that range is suitably used. Specific examples of the thermoplastic resin include ethylene polymers, propylene polymers, cyclic olefin polymers, saponified ethylene-vinyl acetate copolymers, and styrene polymers. These thermoplastic resins can be used alone or as a mixed resin component of two or more.

  In the present invention, an ethylene polymer (a) is used as a resin contained as a main component in the surface layer (A) in view of low-temperature sealability (bottom sealability), self-adhesiveness, and inflation moldability.

  Examples of the ethylene polymer (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. And α-olefins having 3 to 10 carbon atoms such as propylene, butene-1, hexene-1, 4-methylpentene-1 and octene-1, vinyl esters such as vinyl acetate and vinyl propionate, methyl acrylate, acrylic Copolymer composed of one or more comonomers selected from the group consisting of unsaturated carboxylic acid esters such as ethyl acrylate, methyl methacrylate and ethyl methacrylate, and unsaturated compounds such as conjugated dienes and non-conjugated dienes Examples thereof include a polymer, a multi-component copolymer, or a mixed composition thereof. The ethylene unit content of the ethylene polymer is usually more than 50% by weight.

  Among these ethylene polymers (a), low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid ester copolymer, and At least one ethylene polymer selected from ethylene-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 these, as the ethylene polymer (A), the vinyl acetate unit content is 5 to 25% by mass, and the melt flow rate (JIS K 7210, 190 ° C., load 21.18N) is 0.2 to 10 g / 10. Minute ethylene-vinyl acetate copolymer is preferred, especially 0.5 to 8 g / 10 min, especially 1 to 6 g / 10 min ethylene-vinyl acetate copolymer is more preferred.

  Here, if the vinyl acetate unit content is 5% by mass or more, the resulting 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. 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.

  The intermediate layer (B) is a layer containing a soft resin polymer (b1), a crystalline propylene polymer (b2), and a tackifier (b3) as main components.

  As the soft resin polymer (b1), a resin that imparts flexibility to the wrap film of the present invention and is compatible with the crystalline propylene polymer (b2) and the tackifier (b3), in particular. It is not limited.

  Specific examples of the soft resin polymer (b1) include α-olefins having 2 to 10 carbon atoms such as ethylene, propylene, butene-1, hexene-1, 4-methylpentene-1, and octene-1, and vinyl acetate. And vinyl esters such as vinyl propionate, vinyl aromatic compounds such as styrene, α-methyl styrene, p-methyl styrene, vinyl xylene, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, methyl acrylate, ethyl acrylate, Unsaturated carboxylic acid esters such as methyl methacrylate and ethyl methacrylate, conjugated dienes such as 1,3-butadiene, isoprene, and 2-ethyl-1,3-butadiene, 1,4-hexadiene, 1,5-hexadiene, 1, Amorphous if composed of one or more comonomers selected from non-conjugated dienes such as 6-heptadiene Alternatively, a low crystalline copolymer or a multi-component copolymer, or a mixed resin component thereof may be used.

  In the present invention, it is easy to obtain from the market a resin that is compatible with the crystalline propylene polymer (b2) and the tackifier (b3) and can impart desired viscoelasticity to the wrap film of the present invention. Therefore, a styrene-based thermoplastic elastomer (b1-a) can be preferably used as the soft resin-based polymer (b1).

  The styrenic thermoplastic elastomer (b1-a) is preferably styrene, a copolymer of a vinyl aromatic compound such as α-methylstyrene and a conjugated diene, or a hydrogenated derivative thereof. Here, examples of the conjugated diene constituting the conjugated diene moiety include 1,3-butadiene, isoprene, 1,3-pentadiene, and the like. These are polymerized in a copolymer alone or in combination of two or more. It may be.

  Among these styrene thermoplastic elastomers, hydrogenated styrene-butadiene block copolymer (SB), hydrogenated styrene-isoprene block copolymer (SI), styrene-butadiene-styrene block copolymer (SBS). ), Hydrogenated product of styrene-isoprene-styrene block copolymer (SIS), hydrogenated product of styrene-isoprene-butadiene-styrene block copolymer (SIBS), styrene-butadiene random copolymer ( SBR) and styrene-isoprene random copolymer (SIR) hydrogenated products are excellent in thermal stability during molding processing, generation of deteriorated products, and generation of odors. It can use suitably at the point which suppresses. The hydrogenation ratio of the hydrogenated product of these styrenic thermoplastic elastomers is preferably such that hydrogen is added to 80% or more, more preferably 95% or more of the double bonds.

  The styrene content of these styrenic thermoplastic elastomers is usually 1% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, and usually 40% by mass or less, preferably 20% by mass or less. More preferably, it is 15 mass% or less. If the styrene content of the styrene-based thermoplastic elastomer (b1-a) is 1% by mass or more and 40% by mass or less, a desired dynamic viscoelastic behavior can be imparted to the wrap film of the present invention, and at the time of molding. It is preferable from the viewpoint that thermal stability can be obtained.

  Specific examples of such a styrenic thermoplastic elastomer include the product names “Hibler 7311” and “Septon 2063” manufactured by Kuraray Co., Ltd., the product names “Tuftec H1221” manufactured by Asahi Kasei Co., Ltd., and JSR Corp. Product name “Dynalon 1320P” or the like.

  The crystalline propylene polymer (b2) used for the wrap film of the present invention has a crystallization calorific value (ΔHc) of 30 J measured by a differential scanning calorimeter (DSC) at a temperature decreasing rate of 10 ° C./min. / G or more of a homopolymer of propylene, or a random copolymer or block copolymer of propylene and "other copolymerizable monomers". Examples of other copolymerizable monomers include α-olefins having 2 to 4 to 10 carbon atoms such as ethylene, 1-butene, 1-hexene, 4-methylpentene-1, 1-octene, and divinylbenzene, 1 , 4-cyclohexadiene, dicyclopentadiene, cyclooctadiene, dienes such as ethylidene norbornene, and the like, and two or more of these may be copolymerized. Among these, a propylene homopolymer, a propylene-ethylene random copolymer, and a propylene-ethylene block copolymer are preferable in that they can be procured at a relatively low cost.

  Here, the heat of crystallization (ΔHc) is the molecular weight, the ethylene content (copolymerization ratio), the randomness (dispersibility of the ethylene component in the copolymer) and the stereoregulation of the crystalline propylene polymer (b2) used. Depends on sex etc. In general, it can be said that the higher the amount of crystallization heat, the higher the peak temperature tends to be, so that the heat resistance is excellent. If the heat of crystallization (ΔHc) of the crystalline propylene polymer (b2) measured by a differential scanning calorimeter (DSC) at a temperature decrease rate of 10 ° C./min is 30 J / g or more, the crystallinity In addition to the pellet storage stability of the propylene polymer (b2), the strength and heat resistance of the resin composition constituting the intermediate layer of the wrap film of the present invention can be increased. The upper limit is not particularly limited, but is practically 150 J / g or less. From this point of view, the amount of crystallization heat (ΔHc) is 30 to 140 J / g, preferably 40 to 130 J / g, and more preferably 50 to 120 J / g.

  The calorific value of crystallization measured by a differential scanning calorimeter (DSC) was measured by using Pyris 1 manufactured by Perkin Elmer Co., Ltd. as an apparatus, packing about 10 mg of sample into an aluminum pan, holding at -10 ° C. for 1 minute, and then rising to 200 ° C. Warm, hold again at 200 ° C for 1 minute, measure the crystallization curve when the temperature drops to -10 ° C, and straight line between the point where the crystallization curve rises from the baseline and the 0 ° C point of the crystallization curve In conclusion, the amount of crystallization heat was determined from the total area of the portion surrounded by the straight line and the crystallization curve.

  When the crystalline propylene polymer (b2) is a propylene-ethylene random copolymer, the ethylene content is preferably less than 5% by mass, and is 4.5% by mass or less. More preferably, it is more preferably 4% by mass or less.

  The melt flow rate (MFR) of the crystalline propylene polymer (b2) is not particularly limited, but usually MFR (JIS K7210, temperature: 230 ° C., load: 21.2 N) is 0.2 g / 10 minutes or more, preferably 0.5 to 18 g / 10 minutes, and more preferably 1 to 15 g / 10 minutes.

  Examples of the crystalline propylene polymer (b2) include “NOVATEC PP” and “WINTEC” manufactured by Nippon Polypro Co., Ltd., “NOBREN” manufactured by Sumitomo Chemical Co., Ltd., “Prime Polypro” “Prime TPO” manufactured by Prime Polymer Co., Ltd., Dow Chemical Co., Ltd. "DOW" made by the company etc. can be mentioned.

  The mass% of the crystalline propylene polymer (b2) contained in the intermediate layer (B) is usually 80% by mass or less, preferably 75% by mass or less, more preferably 70% by mass or less, and usually 40% by mass. % Or more, preferably 45 mass% or more, more preferably 50 mass% or more. If the content of the crystalline propylene-based polymer (b2) is 80% by mass or less, good mechanical properties such as good transparency and prevention of wrinkling of the package can be obtained in the film of the present invention, If it is 40 mass% or more, favorable heat resistance and film cut property can be obtained.

  The tackifier (b3) used in the film of the present invention may be any resin having a tackiness at room temperature made of natural resin or synthetic resin. Natural resin rosin, polymerized rosin, hydrogenated rosin, rosin pentaerythritol, Rosin resins such as glycerol and esters of esters and rosins; Terpene resins such as terpene / phenol resins, terpene resins (α-pinene resins, β-pinene resins), aromatic modified terpene resins and hydrogenated terpene resins; Hydrocarbon resin, aliphatic hydrocarbon resin, aliphatic cyclic hydrocarbon resin, aliphatic / alicyclic petroleum resin, aliphatic / aromatic petroleum resin, unsaturated hydrocarbon copolymer and hydrogenated carbon Petroleum hydrocarbon resins such as hydrogen resins; phenol / formaldehyde resins and xylene / formaldehyde resins Enol resin; chroman resin such as chroman indene resin; and the like.

  Among these, rosin-based resins, terpene-based resins, and petroleum-based hydrocarbon resins can be suitably used because of their good compatibility with the styrene-based thermoplastic resin (b1). Specific examples of such tackifiers include Mitsui Chemicals 'brand names “Hilets” and “Petrogin”, Arakawa Chemical Industries' brand name “Arcon”, and Yashara Chemicals ’brand name“ Clearon ”. ", Idemitsu Petrochemical Co., Ltd. trade name" Imabe ", Eastman Chemical Co., Ltd. trade name" Escolez ", and the like.

  The mass% of the tackifier (b3) contained in the intermediate layer (B) is usually 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, and usually 5% by mass or more. Preferably it is 8 mass% or more, More preferably, it is 10 mass% or more. If the content of the tackifier (b3) is 30% by mass or less, excessive bleeding of the tackifier from the wrap film of the present invention can be prevented, and the process for producing the wrap film of the present invention can be prevented. Sometimes, it becomes possible to stably extrude the blend of the intermediate layer (B) with an extruder. Moreover, if it is 5 mass% or more, favorable rigidity and transparency can be provided to the film of this invention.

  In the surface layer and / or intermediate layer of the film of the present invention, for example, a recycled resin, an antifogging agent, an antistatic agent, slipperiness, self-adhesiveness, etc. generated from trimming loss or the like within a range not exceeding the gist of the present invention. In order to impart the above performance, various additives as described below can be appropriately blended in the resin layer. 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, etc., and polyalkyl ether polyols, specifically, polyethylene glycol, polypropylene glycol, etc., and at least one compound selected from paraffinic oil, etc. It is preferable to add 0.1 to 12 parts by mass, preferably 1 to 8 parts by mass with respect to 100% by mass of the resin component to be produced.

  The indentation load strength of the wrap film of the present invention is 160 gf or more, preferably 170 gf or more, and more preferably 180 gf or more. If the indentation load strength is 160 gf or more, good rigidity can be imparted to the film of the present invention, and when the prepackage is stacked in multiple stages, the load placed on the lower package from the upper package Therefore, it is possible to prevent the film stretched on the tray from being distorted and reducing the commercial value of the appearance.

  When measuring indentation load in this invention, the instrument shown in FIG. 1 is used. 1, the upper plate 1 and the lower plate 2 of 30 mm in length and 180 mm in width are respectively fixed by two iron rods 3 so as to have a vertical width of 180 mm, and the tip of the lower plate has a radius of 10 mm. It is an instrument having a total weight of 500 g to which a hemispherical pin 4 is attached. As shown in FIG. 2, a circular sample film having a diameter of 40 mm is fixed to the film fixing jig 5, and the upper plate 1 of the instrument of FIG. The tensile tester upper chuck 6 is lifted up with the temperature of 23 ° C. and a tensile speed of 200 mm / min, and the central portion of the sample film is pushed in with a hemispherical pin 4 fixed to the device of FIG. The maximum load until the sample film is displaced by 5 mm is defined as the indentation load of the wrap film of the present invention.

  When the dynamic viscoelasticity at 10 Hz of the film of the present invention is measured, the value of loss tangent (tan δ) at 0 ° C. to 30 ° C. is 0.13 or more, preferably 0.14 or more, more preferably 0.8. It is 15 or more and 0.60 or less, preferably 0.50 or less, more preferably 0.40 or less. If the value of the loss tangent is 0.13 or more, in the stretch process when the plastic tray is packaged with the film of the present invention, a sufficient elongation is exhibited and a clean package without wrinkles can be produced. Further, if the value of the loss tangent is 0.60 or less, the plastic behavior of the film can be suppressed, and the folding failure to the tray bottom due to repulsion when the film is cut can be suppressed.

  When the total heat of fusion of the stretch film of the present invention is measured by a differential scanning calorimeter (DSC), the ratio of the heat of fusion of 120 ° C. or higher to the total heat of fusion is usually 20% or higher, preferably 20% or higher, more preferably Is 23% or more. If the ratio of the heat of fusion of 120 ° C. or higher to the total heat of fusion is 20% or higher, the flexibility of the film is imparted and the tear resistance of the film can be improved. Further, if the ratio of the heat of fusion is 20% or more, good heat resistance is imparted to the film, and the film is completely melted by the excessive heat amount of the heat seal hot plate, and a hole is formed in the heat seal portion. The appearance defects such as can be prevented.

  The heat of fusion measured by a differential scanning calorimeter (DSC), the heat of heat ratio of 120 ° C. or higher was measured by using Pyris 1 manufactured by Perkin Elmer Co., Ltd. After holding, raise the temperature to 200 ° C and measure the melting curve. Connect the point where the melting curve returns to the baseline and the 0 ° C point of the melting curve with a straight line, and the total area of the part surrounded by this straight line and the melting curve Then, the heat of fusion is determined, the total area is divided into two at 120 ° C., and the area ratio of the portion of 120 ° C. or higher relative to the total area is defined as the heat of fusion ratio of 120 ° C. or higher.

  The total thickness of the film of the present invention is 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less, 5 μm or more, preferably 7 μm or more, and more preferably 9 μm or more. If the total thickness is 20 μm or less, flexibility can be imparted to the film, and excellent cut properties can be maintained. Moreover, if it is 5 micrometers or more, pinhole-proof property will improve and it can prevent that problems, such as a hole opening at the time of handling the said film, generate | occur | produce.

  The thickness of each layer of the film of the present invention can be appropriately adjusted within a range showing predetermined dynamic viscoelastic behavior, indentation load strength, and thermal behavior by a differential scanning calorimeter (DSC). When considering the film-forming stability and the adhesiveness of the surface layer, the ratio of the thickness ratio is preferably 10 to 65% for the front and back layers and 35 to 90% for the intermediate layers, 20 to 60% for the front and back layers, and the intermediate layer More preferably, it is 80 to 40%.

  The film of the present invention can be produced, for example, by melt-extruding a material from an extruder and forming the film 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 film of the present invention can be used as a package for various substances, and its use is not particularly limited. For example, foods such as fruits and vegetables, fresh fish, and meat that are susceptible to deterioration such as moisture absorption and drying. Can be suitably used as a food packaging body for storing food.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. In addition, the various measured value and evaluation about the film displayed in this specification were performed as follows.

(1) Indentation load strength Using the device shown in FIG. 1, a film is fixed as shown in FIG. 2, and a pin having a hemispherical shape with a radius of 10 mm is attached to a universal tensile testing machine (Autograph manufactured by Shimadzu Corporation) AGS-H) was mounted and the sample film was pushed in at a speed of 200 mm / min until the sample film was displaced by 5 mm, and the maximum load was measured.

(2) Loss tangent (tan δ)
A sample was cut into a length of 4 mm and a width of 60 mm, using a viscoelastic spectrometer DVA-200 (manufactured by IT Measurement Co., Ltd.), with a vibration frequency of 10 Hz, a strain of 0.1%, a heating rate of 3 ° C./min, and a chuck spacing of 25 mm. About the horizontal direction, it measured from -60 degreeC and calculated | required the value of loss tangent (tan-delta) from the obtained data.

(3) Heat of fusion, ratio of heat of fusion Using Pyris1 manufactured by Perkin Elmer Co., Ltd., about 10 mg of sample was packed in an aluminum pan, held at −10 ° C. for 1 minute, and then heated to 200 ° C. to obtain a melting curve. Measure, connect the point at which the melting curve returns to the baseline and the 0 ° C point of the melting curve with a straight line, calculate the heat of fusion from the total area of the part surrounded by this line and the melting curve, It divided | segmented and the area ratio of the part 120 degreeC or more with respect to the total area was made into the calorie | heat amount rate of 120 degreeC or more.

(4) Stacking test 40 g of towels containing water and 300 g of pseudo food are placed in a foamed polystyrene tray (length 250 mm, width 180 mm, height 25 mm) and hand-wrapped with a handler wrapper. Make five. The package is stacked in five layers and stored at 10 ° C. for 5 hours. The state of the tension part of the lowermost package after storage was evaluated according to the following criteria.
○: Deformation is not seen at all, or a slight slack is observed in the tensing part, but a pass level △: The slack in the zenith part is conspicuous, and the commercial value of the pack product is deteriorated. And there is no commercial value of the pack product

(5) Heat resistance One sheet of film is brought into contact with the heat sealing hot plate attached to the horizontal pillow type packaging machine (tray wrapper) (Omori Machine Industry Co., Ltd., Stretch Wrapper STN-7500) for 2 seconds. The maximum hot plate temperature that does not open was measured and defined as the heat resistant temperature.

(6) Packaging wrinkle Using a stretch packaging film with a width of 350 mm, a polystyrene foam tray (length: 200 mm, width: 150 mm, with a horizontal pillow type packaging machine (tray wrapper) (Omori Machine Industry Co., Ltd., Stretch Wrapper STN-7500). 30 mm in height) was packaged, the appearance of the package was confirmed, and evaluated according to the following criteria.
○: No wrinkles occur under normal use conditions, or there are slight wrinkles but no problem at all. Δ: Wrinkles occur in 30% or more of the zenith area, and cannot be removed even after adjustment. Wrinkles occur on the entire surface

(7) Cutability and bottom folding stability Expanded polystyrene tray (length) using a horizontal pillow type packaging machine (tray wrapper) (Omori Machine Industry Co., Ltd., Stretch wrapper STN-7500) using a stretch packaging film with a width of 350 mm 200 mm, width 150 mm, and height 30 mm), the state of the bottom portion of the package was confirmed, and evaluated according to the following criteria.
○: The film can be cut with a beautiful cross section without any problems, so that it can be folded neatly. △: A slight rebound occurs when the film is cut, and the bottom surface is stiff. ×: A large rebound occurs when the film is cut. Can't put

Example 1:
About the resin composition which forms both surface layers (A), EVA (vinyl acetate content 15 mass%, melt flow rate (JIS K 7210, 190 ° C., load 21) as the ethylene-based polymer as component (a) .18N) 2.0 g / 10 min) 97 parts by mass and 3 parts by mass of diglycerin oleate as an antifogging agent were melt-kneaded. On the other hand, for the resin composition forming the intermediate layer (B), a hydrogenated styrene-isoprene-styrene block copolymer (styrene content: 12 wt.%) As the styrene-based thermoplastic elastomer as the component (b1-a). % (Manufactured by Kuraray Co., Ltd., trade name “HIBLER 7311”) and (b2) propylene polymer as component (propylene-ethylene random copolymer (ethylene content 3%, crystallization peak: single, crystallization) Heat amount 80 J / g, crystallization peak temperature 115.9 ° C., melt flow rate (JIS K 7210, 230 ° C., load 21.18 N) 3 g / 10 min), and hydrogenation as a tackifier as component (b3) Petroleum resin (softening temperature 125 ° C., Arakawa Chemical Industries, Ltd., Alcon P125) is mass ratio (b1-a) / (b2) / (b3) = 1 These melt-kneaded resins were co-extruded and blow molded at an annular three-layer die of 190 ° C. and a blow-up ratio of 5.0 so that the average thickness of each layer was 3.5 μm. A three-layer film (sample) having a total thickness of 14 μm of / 7 μm / 3.5 μm was obtained.

Comparative Example 5 :
In Example 1, with respect to the resin composition forming the intermediate layer (B), a hydrogenated styrene-butadiene-styrene block copolymer (styrene content: styrene-based thermoplastic elastomer as the component (b1-a)): 12% by weight (produced by Asahi Kasei Chemicals Co., Ltd., trade name “Tuftec H1221”), and propylene-ethylene random copolymer (ethylene content 3%, crystallization) as component (b2) propylene polymer Peak: Single, heat of crystallization 80 J / g, crystallization peak temperature 115.9 ° C., melt flow rate (JIS K 7210, 230 ° C., load 21.18 N) 3 g / 10 min), and adhesion as component (b3) Hydrogenated petroleum resin (softening temperature 125 ° C., Arakawa Chemical Industries, Ltd., Alcon P125) as an imparting agent (b1 a) / (b2) / (b3) = 23/57/20 and except that the melt 混練Ru so so in the same manner as in Example 1, the total thickness to obtain a multi-layer film of 14 [mu] m.

Comparative Example 1:
In Example 1, with respect to the resin composition forming the intermediate layer (B), a hydrogenated styrene-isoprene-styrene block copolymer (styrene content: styrene-based thermoplastic elastomer as the component (b1-a)) 12% by weight (manufactured by Kuraray Co., Ltd., trade name “HIBLER 7311”), and propylene-based polymer as component (b2), propylene-ethylene random copolymer (ethylene content 3%, crystallization peak: single, The amount of heat of crystallization 80 J / g, the peak temperature of crystallization 115.9 ° C., the melt flow rate (JIS K 7210, 230 ° C., load 21.18 N) 3 g / 10 min), and the tackifier as component (b3) Hydrogenated petroleum resin (softening temperature 125 ° C., Arakawa Chemical Industry Co., Ltd., Alcon P125), by mass ratio, (b1-a) / (b2) / ( b3) A multilayer film having a total thickness of 14 μm was obtained in the same manner as in Example 1 except that the melt kneading was performed so that the ratio was 50/30/20.

Comparative Example 2:
In Example 1, for the resin composition forming the intermediate layer (B), a propylene-ethylene random copolymer (ethylene content 3%, crystallization peak: single, The amount of heat of crystallization 80 J / g, the peak temperature of crystallization 115.9 ° C., the melt flow rate (JIS K 7210, 230 ° C., load 21.18 N) 3 g / 10 min), and the tackifier as component (b3) The hydrogenated petroleum resin (softening temperature 125 ° C., Arakawa Chemical Industries, Ltd., Alcon P125) was changed except that it was melt kneaded so that the mass ratio was (b2) / (b3) = 80/20. In the same manner as in Example 1, a multilayer film having a total thickness of 14 μm was obtained.

Comparative Example 3:
In Example 1, with respect to the resin composition forming the intermediate layer (B), a hydrogenated styrene-isoprene-styrene block copolymer (styrene content: styrene-based thermoplastic elastomer as the component (b1-a)) 12% by weight (manufactured by Kuraray Co., Ltd., trade name “HIBLER 7311”), and propylene-based polymer as component (b2), propylene-ethylene random copolymer (ethylene content 3%, crystallization peak: single, The amount of heat of crystallization 80 J / g, the peak temperature of crystallization 115.9 ° C., the melt flow rate (JIS K 7210, 230 ° C., load 21.18 N) 3 g / 10 min), and the tackifier as component (b3) Hydrogenated petroleum resin (softening temperature 125 ° C., Arakawa Chemical Industry Co., Ltd., Alcon P125), by mass ratio, (b1-a) / (b2) / ( b3) A multilayer film having a total thickness of 14 μm was obtained in the same manner as in Example 1 except that the melt kneading was performed so that the ratio was 70/10/20.

Comparative Example 4:
A multilayer film having a total thickness of 60 μm was obtained in the same manner as in Example 1 except that the average thickness of each layer was changed to 15 μm / 30 μm / 15 μm in Example 1.

  Table 1 below shows the measurement results of the characteristics and performance of the film thus obtained.

From Table 1, it was confirmed that the package using the film of the present invention had no problems in all the characteristics of rigidity, heat resistance, and proper packaging and was practical (Example 1) . In contrast, in the case of using a film having a indentation load intensities outside the range defined in the present invention, the rigid like loose TenCho portion of the lowermost package occurs insufficient in stacking test ( Comparative Examples 1 and 3) . When a film having dynamic viscoelastic properties (loss tangent) outside the range specified in the present invention is used, wrinkles are generated when the package is finished, and the film is not cut properly when cut. Was insufficient (Comparative Examples 2 and 3).

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

1 Upper plate 2 Lower plate 3 Iron bar 4 Pin 5 Film fixing jig 6 Tensile tester upper chuck

Claims (10)

Both surface layers (A) are mainly composed of an ethylene polymer (a), and one of the layers sandwiched between both surface layers is a soft resin polymer (b1), and a differential scanning calorific value. A crystalline propylene polymer (b2) having a heat of crystallization (ΔHc) of 80 J / g or more and 120 J / g or less when measured at a temperature drop rate of 10 ° C./min with a total (DSC), and a tackifier ( comprises only three components b3), (b1) more than 15 wt% 1 wt% or more, (b2) over 40 wt% 80 wt% or less, 5 wt% to 30 wt% or less including have a (b3) It is a multilayer film with a total thickness of 5 to 20 μm, the indentation load of the multilayer film is 160 gf or more, and the loss tangent (tan δ) in dynamic viscoelasticity measured at a frequency of 10 Hz is 0.13 to 0.00 . Polyolefin-based multilayer characterized by being 18 Wrapped film.   2. The polyolefin according to claim 1, wherein the ratio of the heat of fusion of 120 ° C. or higher measured by a differential scanning calorimeter (DSC) at a temperature rising rate of 10 ° C./min is 20% or higher with respect to the total heat of dissolution of the multilayer film. -Based multilayer wrap film.   The polyolefin multilayer wrap film according to claim 1 or 2, wherein the soft resin polymer (b1) is a styrene thermoplastic elastomer (b1-a).   The styrenic thermoplastic elastomer (b1-a) is a hydrogenated styrene-butadiene block copolymer (SB), a hydrogenated styrene-isoprene block copolymer (SI), a styrene-butadiene-styrene copolymer. At least one selected from a hydrogenation product of a combination (SBS), a hydrogenation product of a styrene-isoprene-styrene copolymer (SIS), and a hydrogenation product of a styrene-isoprene-butadiene-styrene copolymer (SIBS) The polyolefin multilayer wrap film according to claim 3, which is a seed.   The polyolefin multilayer wrap film according to claim 3 or 4, wherein a styrene content in the styrene thermoplastic elastomer (b1-a) is 1 to 40% by weight. The crystalline propylene polymer (b2) is composed of one or more mixed components selected from homopropylene, propylene-ethylene random copolymer, and propylene-ethylene block copolymer. The polyolefin multilayer wrap film according to any one of 5 . The polyolefin multilayer wrap film according to any one of claims 1 to 6 , wherein the tackifier (b3) is at least one selected from rosin resins, terpene resins, and petroleum hydrocarbon resins. The ethylene polymer (a) is low density polyethylene, linear low density polyethylene, linear ultra-low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate. The polyolefin multilayer wrap film according to any one of claims 1 to 7, which is at least one selected from a copolymer, an ethylene-methyl methacrylate, and an ethylene-ethyl methacrylate copolymer. Ethylene-based polymer (a) has a vinyl acetate unit content of 5 to 25% by weight and an ethylene having a melt flow rate (JIS K 7210 190 ° C. load: 21.18 N) of 0.2 to 10 g / 10 min. The polyolefin-based multilayer wrap film according to any one of claims 1 to 8 , which comprises a vinyl acetate copolymer as a main component. A film for food packaging, comprising the polyolefin-based multilayer wrap film according to any one of claims 1 to 9 .

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