JP2018062073A - Laminated film with heat-sealing property, rigidity and impact resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated film achieving all of heat-sealing property, rigidity and impact resistance while solving such a problem that, in a packaging material, tearing property during opening and rigidity required for toughness of a crystalline polymer such as polyethylene can be improved by using a resin having high density since a crystallinity degree increases, however, impact resistance and heat-sealing property are decreased, resulting in a trade-off relation.SOLUTION: A film comprising a sealing layer 12 and a base layer 11 different from each other in at least a heat of fusion, in which the sealing layer 12 disposed as an outermost layer has a smaller heat of fusion; both of the sealing layer 12 and the base layer 11 comprise, as constituent materials, at least one copolymer of α-olefin and ethylene and at least one low-density polyethylene produced by a high-pressure process, and a melt tension of the mixture of the sealing layer 12 and the base layer 11 is in the range from 0.015 to 0.055 N.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminated film having both rigidity and impact resistance.

  As a sealant film used for packaging materials such as foods, heat sealability such as polyethylene and polypropylene is generally good, and adhesiveness with other laminated base materials is good, and an inexpensive film is used. Physical properties required for packaging materials include filling properties at the time of filling contents, absence of damage to the bag when external force is applied to the packaging material, appropriate physical properties related to opening properties when opening the packaging material, In addition, good productivity at the time of manufacture is required.

  The aforementioned physical properties have been studied for a long time, and for crystalline polymers such as polyethylene, the tearability that shows openability and the rigidity that gives a soft feeling to the packaging material have high crystallinity using high-density resin. It is improved by raising. On the other hand, this method has a so-called trade-off relationship that the performance deteriorates with respect to impact resistance and heat sealability.

  For example, for compatibility of the physical properties described above, as in Patent Document 1, a low-density polyethylene resin is used on the seal layer side to impart impact resistance and heat sealability, and rigidity and tearability are imparted. In addition, a method is used in which high-density polyethylene is laminated on the laminate layer side to achieve both physical properties in a trade-off relationship.

Japanese Patent No. 4779822

  Patent Document 1 discloses a resin having a high density polyethylene on the laminate layer side and a molecular weight distribution (Mw / Mn) in the range of 2.0 to 3.5. However, since the resin has a uniform molecular weight distribution, rigidity can be imparted but tearability is not sufficient.

  In addition, since the resin has a narrow molecular weight distribution, when the processing speed during production is increased, the screw load due to the increase in shear viscosity may increase when the shear rate in the extruder increases. In addition, since the molecular weight distribution is uniform, the melt tension is lowered, and the productivity may be reduced, such as a decrease in film forming width and fluttering of the molten film during high-speed take-up.

In order to solve the above problems, one of the representative laminated films of the present invention is composed of a laminate in which a seal layer and a base layer are laminated, and the seal layer and the base layer are composed of a thermoplastic resin as a main material and a high pressure. Thermoplastic resin having a heat of fusion ΔH of 70 to 115 mJ / mg for the seal layer and a heat of fusion ΔH of 115 to 145 mJ / mg for the base layer. Is used.
In addition, the mixture of the seal layer and the base layer uses a material whose melt tension value is adjusted in the range of 0.015 to 0.055N.

  Furthermore, one of the other laminated films of the present invention is composed of at least two layers including a seal layer and a base layer, the seal layer is disposed as the outermost layer, and the heat of fusion of the seal layer is the above value. It is characterized by being in the range.

  Furthermore, one of the other laminated films of the present invention is a layer formed by mixing at least two kinds of resins in both the seal layer and the base layer, and the weight ratio of the main material is 70% or more. It is characterized by being less than 99%.

  Furthermore, in another laminated film of the present invention, the total layer thickness of the base layer and the seal layer is in the range of 40 μm to 200 μm, and the thickness of the seal layer is 7.5 μm to 30 μm. The ratio of the sealing layer in thickness is 30% or less.

  A crystalline polymer such as polyethylene is known to have a structure in which a lamellar crystal in a crystal part in which a molecular chain is folded and an amorphous phase serving as a random coil are mixed. If the density of the lamellar crystal, that is, the crystal phase is increased in the formed film, the rigidity is improved. At the same time, if the ratio of lamellar crystals in the film increases, the amount of heat required for melting increases and the amount of heat of fusion increases as the film rigidity increases. On the other hand, when calculating | requiring impact resistance, a softness | flexibility can be provided to a film by making the ratio of a lamellar crystal low and reducing rigidity. In this case, it is necessary to lower the heat of fusion. Further, when improvement in heat sealability is required, melting at a low temperature is required, and the heat of fusion must be lower than that of a layer requiring rigidity.

  In other words, as a prescription for achieving both trade-off physical properties, a flexible polyethylene layer with a low heat of fusion and a polyethylene layer with a high heat of fusion for imparting rigidity are laminated, and the resin has different branching properties. It becomes possible to improve impact resistance and tearability by including two or more kinds. At the same time, since the melting characteristics of the resin can be improved, productivity can also be improved.

1 shows a schematic view of a film obtained by the present invention.

  The present invention will be described in detail below. The basic structure of the laminated film in the present invention is a laminated film comprising a base layer 11 and a seal layer 12 and formed by an extruder.

  Since the laminated film in the present invention is formed by an extruder capable of heating up to 340 ° C., various thermoplastic resins can be used as the main material of the base layer 11, but a general packaging sealant In order to be used as a film, appropriate flexibility and workability are required. Therefore, low density polyethylene (LDPE) based on olefin, linear low density polyethylene (LLDPE) copolymerized with α-olefin and ethylene, medium density polyethylene (MDPE), high density polyethylene (HDPE) and homopolymer. Polymers, random copolymers, polypropylene and cycloolefin polymers with block random copolymers, cycloolefin copolymers obtained by copolymerizing cycloolefin and olefin, and ethylene vinyl acetate copolymers and olefin side chains obtained by copolymerizing the above olefins with vinyl acetate Obtained by modification of ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methacrylate Acid copolymer (EMAA) can be selected appropriately used alone and a plurality of such are suitable.

  In particular, for the base layer 11, the required properties of the sealant film for packaging materials, filling suitability at the time of filling the contents, no damage to the bag when an external force is applied to the packaging material, and when opening the packaging material It is necessary to satisfy openability. Specifically, it must have an appropriate melting point and heat of fusion in order to be processed into a bag shape when used as a suitable laminate with a sealant film alone or a film such as polyethylene terephthalate or polyamide such as 6 nylon or 66 nylon. It becomes. From the above requirements, it is preferable that both low-density polyethylene, linear low-density polyethylene copolymerized with α-olefin and ethylene are included.

The base layer 11 has a role of imparting rigidity to the sealant film, and it is necessary to select a material having appropriate rigidity and flexibility. In general, it is known that the rigidity increases as the ratio of the crystal part of polyethylene increases. In order to increase the crystallization ratio, it is important that the number of branches is small. Moreover, it is thought that crystallization is easy to advance, so that molecular weight is small. However, when the molecular weight is small and the number of branches is small, the impact resistance is likely to be lowered. Therefore, it is necessary to select a resin within the optimum range.
Since the crystallization ratio is related to the heat of fusion of the material, the molecular weight distribution (Mw / Mn) of the α-olefin and ethylene copolymer used in the base layer is in the range of 8.0 to 12.0. There is a need to select a material having a heat of fusion of 115 mJ / mg to 145 mJ / mg.
Similarly, the molecular weight distribution with respect to low-density polyethylene molecular weight distribution (Mw / Mn) 4.0 or more and 10.0 or less, 0.918 g / cm ³ or more in JISK7112 method in density, 0.925 g / cm ³ or less It is necessary to select from the range.
In this application, the heat of fusion is measured using a DSC (Differential Scanning Calorimeter), raised to 25 ° C. to 200 ° C. at 10 ° C./min as 1st run, held at 200 ° C. for 5 minutes, and kept at 30 ° C. The temperature is lowered at / min. 2nd run is a value obtained by measuring the heat of fusion of 2nd run when the temperature is increased from 25 ° C. to 200 ° C. at 10 ° C./min, held at 200 ° C. for 5 minutes, and then cooled at 30 ° C./min.

  Next, in the seal layer 12, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), which are materials that can be used in the base layer 11, and Polypropylene and cycloolefin polymers with homopolymers, random copolymers, block random copolymers, cycloolefin copolymers copolymerized with cycloolefin and olefin, and ethylene vinyl acetate copolymer or olefin side obtained by copolymerizing the above olefin with vinyl acetate Obtained by modifying the chain, ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methacrylic acid copolymer (EMAA) can be selected appropriately used alone and more of the like.

  As with the base layer 11, the sealing layer 12 also has the required properties of a sealant film for packaging materials, such as filling ability when filling the contents, no damage to the bag when an external force is applied to the packaging material, It is necessary to satisfy the openability when opening. Specifically, it has an appropriate melting point and heat of fusion for processing into a bag shape when used by appropriately laminating with a sealant film alone or a film of polyamide such as polyethylene terephthalate, 6 nylon or 66 nylon. Necessary. From the above requirements, it is preferable that both low-density polyethylene, linear low-density polyethylene copolymerized with α-olefin and ethylene are included.

About the sealing layer 12, it has a role which provides the softness | flexibility of a sealant film, especially heat-sealing property, and it is necessary to select the material which has a softness | flexibility. Generally, it is known that the flexibility increases as the ratio of the crystal part of polyethylene decreases. In order to decrease the crystallization ratio, crystallization is inhibited as the number of branches increases and the molecular weight increases. From this, the α-olefin and ethylene copolymer used in the seal layer have a molecular weight distribution (Mw / Mn) in the range of 2.0 to 4.0, and a heat of fusion of 70 mJ / mg to 115 mJ / mg. It is necessary to select the material to be.
As for the low density polyethylene, the molecular weight distribution (Mw / Mn) is 4.0 to 10.0 as in the case of the polyethylene used for the base layer 11, and the density is 0.918 g / cm ^{3 to} 0 by the JISK7112 method. It is necessary to select from the range of 925 g / cm ³ .
The heat of fusion is measured using a DSC (Differential Scanning Calorimeter) using the same method as for the base layer.

  Both the base layer 11 and the sealing layer 12 of the present invention use a mixture of at least one kind of α-olefin / ethylene copolymer and low density polyethylene. Generally, it is known that a copolymer of α-olefin and ethylene has a narrow molecular weight distribution and a relatively large number of single molecular weight components among polyethylene resins. When the molecular weight distribution is narrowed, molecules with a certain length of molecular weight are present in the film, so that the uniformity of the film increases and impact resistance increases, but the tearability, which is a required characteristic of packaging materials, decreases. . For this reason, in order to disturb the arrangement of uniform molecules to some extent, it is possible to improve tearability by mixing low density polyethylene having a relatively wide molecular weight distribution and having long chain branches.

  As for the α-olefin and ethylene copolymer used for the base layer 11 and the seal layer 12, the α-olefin includes propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, Nonene-1, decene-1, dodecene-1, 4-methyl-pentene-1, 4-methyl-hexene-1 and the like can be used, and polymerization methods such as gas phase method, solution method, and slurry method can be used. In any of the methods, the polymerization catalyst can be used without particular limitation, such as a Ziegler-Natta catalyst or a metallocene catalyst. From the availability of materials, butene-1, hexene-1, 4-methyl-pentene-1 can be suitably used for α-olefins.

  About the low density polyethylene used for the base layer 11 and the sealing layer 12, it is possible to use the low density polyethylene produced using the autoclave method and the tubular method which are high pressure methods, and there is no restriction | limiting in particular. Can be used.

  The effect of mixing low-density polyethylene with long chain branching is that the long chain branching ethylene is mixed with the uniform molecular weight distribution resin, so that the long chain branching ethylene is sufficiently entangled with the resin. It has the effect of increasing the extensional viscosity due to the effect, and reducing the motor load of the extruder by reducing the shear viscosity by increasing the free volume at the time of resin melting due to the presence of long chain branching. These effects are produced during extrusion film formation. It leads to improvement of sex.

  The effect of mixing low-density polyethylene with long chain branching into α-olefin and ethylene copolymer is described above, but impact resistance decreases among the physical properties of α-olefin and ethylene copolymer when the mixing amount is increased. To do. When the merit for physical properties and the merit for productivity are compared, the mixing ratio of the low density polyethylene to the α-olefin and the ethylene copolymer may be used in the range of 1.0% to 43.0% by weight. preferable. For the base layer 11 and the seal layer 12, the mixing ratio of the low density polyethylene to the α-olefin and the ethylene copolymer may be the same or different, but the thickness ratio accuracy during molding deteriorates. Are preferably mixed at the same ratio.

  The film and sheet obtained from the laminate of the base layer 11 and the seal layer 12 are not particularly limited as long as they are of a thickness used in general packaging materials, but are preferably used in the range of 40 μm to 200 μm. .

  Regarding the lamination ratio of the base layer 11 and the seal layer 12, when the seal layer thickness is insufficient, the heat sealability is not sufficient, and when it is too thick, the rigidity is lowered and the practicality is lowered. Therefore, the minimum thickness of the 12 seal layers is preferably in the range of 7.5 μm to 30 μm and 30% or less of the total thickness.

  The sealant film in the present invention is used by appropriately laminating a sealant film alone or a film of polyamide such as polyethylene terephthalate, 6 nylon or 66 nylon. It is important that the performance required at that time is in a range of a certain value or more in all physical properties such as rigidity, tearability, impact resistance, and heat sealability. Details of each physical property item are described below.

(About rigidity)
The rigidity of the sealant film needs to be an index value of a predetermined value or more from the viewpoint of the self-supporting property of the container and the ease of taking out the contents when a single film or a laminated film is used. In view of the above requirements, in the evaluation method of JISK7127, the index value of the tensile elastic modulus in the direction parallel to the film flow direction is preferably 300 MPa or more.

(About tearability)
The tearability of the sealant film needs to be an index value of a predetermined value or more from the viewpoint of easy opening of the container when a single film or a laminated film is used. In order to satisfy this requirement, in the tearability index described in JISK7128-2, the numerical value obtained by dividing the tear strength in the direction parallel to the film flow direction by the sealant film alone is in the range of 30 mN / μm to 80 mN / μm. It is preferable.

(About impact resistance)
The impact resistance of the sealant film needs to be a predetermined index value or more from the viewpoint of content protection suitability when used as a single film or a laminated film. In order to satisfy this requirement, the numerical value obtained by dividing the numerical value obtained in the impact resistance evaluation described in the JISK7124-1A method by the thickness is preferably 3.74 g / μm to 5.45 g / μm.

(About heat sealability)
The heat sealability of the sealant film needs to be an index value of a predetermined value or more from the viewpoint of the difficulty of damaging the container when the film is filled with contents. The index value of the heat seal strength of the sealant film alone after heat sealing with a seal bar at 140 ° C. for 1 second by the method described in JISZ0238 is preferably 5 N / 15 mm or more.

  To the base layer 11 and the seal layer 12, materials generally used for the film can be appropriately added in order to improve the suitability for forming the film and the sheet and the suitability for using the film and the sheet. For example, an anti-blocking agent such as a filler, a lubricant for improving slipperiness, an antioxidant for imparting processing stability, and the like can be appropriately added.

  Examples of anti-blocking agents such as fillers include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, polyurethane particles, polyester particles, silicon particles, fluorine particles, copolymers thereof, and pyrophyllite. , Clay compounds particles such as talc, smectite, vermiculite, mica, chlorite, kaolin mineral, sepiolite, silica, titanium oxide, alumina, silica alumina, zirconia, zinc oxide, strontium oxide, aluminum hydroxide, strontium carbonate, strontium chloride, Strontium sulfate, strontium nitrate, strontium hydroxide, glass particles, and the like can be used as appropriate.

  As a lubricant for improving slipperiness, for example, sucrose fatty acid ester, glycerin fatty acid ester, synthetic resin system is a hydrocarbon system such as liquid paraffin, paraffin wax, synthetic polyethylene wax, fatty acid system such as stearic acid, stearyl alcohol, Fatty acid amides such as stearic acid amide, oleic acid amide, erucic acid amide, and alkylene fatty acid amides such as methylene bis stearic acid amide and ethylene bis stearic acid amide can be suitably used.

  In order to improve the handling property at the time of forming as a film and a sheet, the handling property may be improved by imparting a concavo-convex shape to the film surface other than the additives described above.

  The method for producing the film of the present invention is not particularly limited, and a known method can be used. For example, a melt kneading method using a general mixer such as a single screw extruder, a twin screw extruder, or a multi-screw extruder, a method of heating and removing the solvent after each component is dissolved or dispersed and mixed, etc. Can be used. In consideration of workability, it is preferable to use a single screw extruder or a twin screw extruder. When a single screw extruder is used, a full flight screw, a screw having a mixing element, a barrier flight screw, a fluided screw, or the like can be used without particular limitation. The biaxial kneader is not particularly limited to the same direction rotating twin screw extruder, the different direction rotating twin screw extruder, and the screw shape is not limited to the full flight screw or kneading disc type.

  The method for laminating the base layer 11 and the seal layer 12 is not particularly limited, and a known method can be used. For example, a method of laminating the base layer 11 and the seal layer 12 by applying heat above the melting point to each film or sheet and pressurizing the base layer 11 and the seal layer 12 with different extruders. A method of obtaining a film by laminating in a heated and molten state can be used. In consideration of workability, a laminating method using a co-extruder for laminating in a molten state to obtain a film is preferable. As the coextrusion method, the thermoplastic resin that becomes each layer is melted with an extruder, then the molten resin is laminated with a feed block, and a laminated film is obtained from a T-die. Also, the plastic that becomes each layer is melted with an extruder. Thereafter, it is possible to use a multi-manifold method for obtaining a laminated film from a T-die by passing through a manifold and a multilayer inflation molding method.

The film cooling method of the base layer 11 and the seal layer 12 is not particularly limited. For example, in the case of the T-die method, an air cooling method such as an air chamber, a vacuum chamber, an air knife, etc., or a cooling roll is dipped into a cold water pan. It is possible to use a water cooling method such as.
When the inflation molding method is used, a method using room temperature, heated air, or the like can be appropriately selected at the blow unit.

  The sealant film obtained according to the present invention is not particularly limited with respect to use as a single film and other base materials, and the bag making mode. Even when used as a single film or laminated, the seal layer 12 side can be used as a content contact surface, and can be used for three-sided bags, jointed bags, gusset bags, standing pouches, pouches with spouts, pouches with beaks, and the like.

  As described above, in both cases of laminating with a single film and another base material, it is possible to appropriately carry out a surface modification treatment for improving the post-process suitability. For example, it is possible to perform a surface modification treatment on the base layer 11 side in order to improve the printing suitability when using a single film and the laminate suitability when using a laminate. For surface modification treatment, it is possible to suitably use methods such as corona discharge treatment, plasma treatment, flame treatment, etc. to express functional groups by oxidizing the film surface, or modification by wet processes such as coating of easy-adhesion layers. It is.

  Examples of the present invention will be described in detail below, but the present invention is not limited to the following examples.

As a main resin of the sealing layer 12, LLDPE made by Prime Polymer Co., Ltd. (Evolue sp1540 density 0.913 g / cm ³ MFR 3.8 g / 10 min) was used, and LDPE made by Nippon Polyethylene (Novatech LF342M1 density 0.924 g / cm ³ MFR 1 g / 10 min) is mixed by dry blending so as to contain 20%. The material of the seal layer mixed by dry blending is put into a single screw extruder and heated and melted to 250 ° C.

The main resin of the base layer 11, Ltd. using Prime Polymer Co. LLDPE (Evolue sp3530 density ^{0.931g / cm 3 MFR 3.2g / 10min} ), manufactured by Japan Polyethylene LDPE (Novatec LF342M1 density 0.924 g / cm ³ MFR 1 g / 10 min) is mixed to contain 20% by blending. The base layer material mixed by dry blending is charged into a single screw extruder and heated and melted to 250 ° C.

The heat-melted resin for the seal layer and the base layer is adjusted using a feed block T die so that the thickness of the seal layer and the base layer is 15 μm and 85 μm, respectively, so that the total thickness of the film is 100 μm. A laminated film was produced.
The seal layer and the base layer are a mixture of a thermoplastic resin as a main material and LDPE (low density polyethylene) produced by a high pressure method, and the mixture of the seal layer and the base layer has a melt tension value. The material adjusted to the range of 0.015-0.055N is used.
The melt tension is measured with a capillary rheometer at a temperature setting of 190 ° C., a Haul off speed of 20 m / min, and a die size D = φ1.5 mm × L = 24 mm.

Molding was performed in the same manner as in Example 1 except that Prime Polymer Co., Ltd. (Evolue sp2040 density 0.918 g / cm ³ MFR 3.8 g / 10 min) was used as the main resin for the seal layer.

It was molded in the same manner as in Example 1 except that Prime Polymer Co., Ltd. (Evolue sp0540 density 0.903 g / cm ³ MFR 3.8 g / 10 min) was used as the main resin for the seal layer.

It was molded in the same manner as in Example 1 except that Prime Polymer Co., Ltd. (Evolue sp2540 density 0.924 g / cm ³ MFR 3.8 g / 10 min) was used as the main resin for the seal layer.

  Molding was performed in the same manner as in Example 1 except that the thickness of the seal layer was 10 μm and the thickness of the base layer was 90 μm.

  Molding was performed in the same manner as in Example 1 except that the thickness of the seal layer was 30 μm and the thickness of the base layer was 70 μm.

  Molding was performed in the same manner as in Example 1 except that the total thickness was 50 μm and the thickness ratio of the seal layer and the base layer was the same.

  Molding was performed in the same manner as in Example 1 except that the total thickness was 150 μm and the thickness ratio of the seal layer and the base layer was the same.

  Molding was performed in the same manner as in Example 1 except that the LDPE ratio for mixing both the seal layer and the base layer was 5%.

  Molding was performed in the same manner as in Example 1 except that the ratio of LDPE mixed with the seal layer and the base layer was 30%.

Molding was carried out in the same manner as in Example 1 except that Ube Maruzen Polyethylene Co., Ltd. (Umerit 2525F density 0.926 g / cm ³ MFR 2.5 g / 10 min) was used as the main resin for the base layer.

Molding was performed in the same manner as in Example 1 except that Prime Polymer Co., Ltd. (Evolue sp4030 density 0.938 g / cm ³ MFR 3.8 g / 10 min) was used as the main resin for the base layer.

  Molding was performed in the same manner as in Example 1 except that the thickness of the seal layer was 5 μm and the thickness of the base layer was 95 μm.

  It was molded in the same manner as in Example 1 except that the thickness of the seal layer was 40 μm and the thickness of the base layer was 60 μm.

  Molding was performed in the same manner as in Example 1 except that the total thickness was 40 μm and the thickness ratio of the seal layer and the base layer was the same.

  It was molded in the same manner as in Example 1 except that the total thickness was 200 μm and the thickness ratio of the seal layer and the base layer was the same.

[Comparative Example 1]
Molding was performed in the same manner as in Example 1 except that Prime Polymer Co., Ltd. (Evolue sp2540 density 0.924 g / cm ³ MFR 3.8 g / 10 min) was used as the main resin for the base layer.

[Comparative Example 2]
It was molded in the same manner as in Example 1 except that Ube Maruzen Polyethylene Co., Ltd. (Umerit 2525F density 0.926 g / cm ³ MFR 2.5 g / 10 min) was used as the main resin for the seal layer.

[Comparative Example 3]
Molding was performed in the same manner as in Example 1 except that the LDPE ratio mixed with the seal layer and the base layer was 40%.

[Comparative Example 4]
Molding was performed in the same manner as in Example 1 except that the LDPE ratio mixed with the seal layer and the base layer was 1%.

  The resulting film was subjected to tensile modulus, impact resistance test, tear strength, and heat seal strength evaluation.

  In the tensile modulus test, the measurement was performed in accordance with the method described in JISK7127. The flow direction during film formation was the long side direction of the strip, and the film was cut into 15 mm width and 150 mm length. Evaluation was carried out with n = 5 using a tensile tester (model number AGS-500NX) manufactured by Shimadzu Corporation with a distance between marked lines of 50 mm and a tensile speed of 200 mm / min.

  In the impact resistance test, an impact test method based on the Dirty Dirt method of JISK7124-1 and the A method of the first part staircase method was used, and a Dart Impact Tester (model number IM-302) manufactured by Tester Sangyo Co., Ltd. was used. The% breaking weight was measured. The measured 50% fracture weight was measured by the method described in JISK7130, and the 50% fracture weight was divided by the measured thickness, and the 50% fracture weight per μm was calculated as the impact resistance value.

  In tearing evaluation, the tearing force with respect to the flow direction at the time of film formation was measured by n = 5 using the Elmendorf tearing method described in JISK7128-2. The tear force measured at n = 5 was divided by the thickness measured in μm units according to the method described in JISK7130, and calculated as a unit of mN / μm.

  In the measurement of heat seal strength, using a heat sealer (model number TP-701-B) manufactured by Tester Sangyo Co., Ltd., the seal pressure is 0.2 MPa, the seal time is 1 second, the seal width is 10 mm, and the seal temperature is 140 ° C. The seal layers were sealed. The sealed film was cut into 15 mm width x 80 mm, the distance between chucks was 20 mm, the tensile speed was 300 mm / min, and evaluation was performed with n = 5 using Shimadzu Corporation tensile tester (model number AGS-500NX). did.

  Table 1 shows the results of physical property evaluation performed on the films described in Examples 1 to 16 and Comparative Examples 1 to 4.

  In Examples 1 to 16 and Comparative Examples 1 to 4, the tensile modulus is 300 MPa or more, the impact resistance is 3.7 g / μm or more, the tear value is 100 mN / μm or less, and the heat seal strength is 10 N / 15 mm or more. It was evaluated as a criterion.

  From Table 1, it has confirmed that the result of Example 1-16 which is this embodiment was favorable. On the other hand, in Comparative Example 1, the heat of fusion of the base layer is low, and the rigidity is low throughout the film. In Comparative Example 2, the heat of fusion of the sealing layer is high, and the strength after heat sealing is reduced. In Comparative Example 3, the impact resistance is reduced. In Comparative Example 4, the tearability is not sufficiently obtained.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment. Further, the above-described embodiments are described for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

11 ... Base layer 12 ... Seal layer

Claims (4)

A laminated film in which at least a seal layer and a base layer are laminated,
The seal layer and the base layer are composed of a mixture of a thermoplastic resin as a main material and LDPE (low density polyethylene) manufactured by a high pressure method,
The sealing layer has a heat of fusion ΔH of 70 to 115 mJ / mg,
The base layer has a heat of fusion ΔH of 115 to 145 mJ / mg,
The mixture of the sealing layer and the base layer is a laminated film having a melt tension value of 0.015 to 0.055 N.   The laminated film according to claim 1, wherein the seal layer is disposed as an outermost layer. In the laminated film according to claim 1 or 2,
The sealing layer and the base layer are both layers formed by mixing at least two kinds of resins,
A laminated film having a weight ratio of a main material of 70% or more and less than 99%. In the laminated film according to any one of claims 1 to 3,
The total layer thickness of the base layer and the sealing layer is in the range of 40 μm to 200 μm,
The sealing layer has a thickness of 7.5 μm to 30 μm,
The laminated film, wherein a ratio of the sealing layer in the total layer thickness is 30% or less.

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