JP2022179043A - Heat-sealable laminated film - Google Patents

Abstract

To provide a carbon-neutral heat-sealable laminated film made of a biomass-derived raw material, with excellent heat resistance, impact resistance, and bending pinhole resistance.SOLUTION: There is provided a heat-sealable laminated film having a base layer and a sealant layer, in which the base material layer is a biaxially stretched polyamide film, and the biaxially stretched polyamide film contains 70 to 99 mass% of polyamide 6 and 1 to 30 mass% of polyamide whose raw material is at least partly derived from biomass as a polyamide resin, and the sealant layer is an unstretched polyolefin film, and the unstretched polyolefin film contains 70 to 95 mass% of a polypropylene resin and 5 to 30 mass% of a linear low-density polypropylene resin whose raw material is at least partly derived from biomass.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a heat-sealable laminated film suitably used for packaging films and the like.

A biaxially stretched film made of an aliphatic polyamide represented by polyamide 6 is excellent in impact resistance and bending pinhole resistance, and is widely used as various packaging materials.

In recent years, the use of biomass instead of fossil fuel raw materials has attracted attention in the field of materials for the construction of a recycling-oriented society. Biomass is an organic compound that is photosynthesised from carbon dioxide and water. By using it, it becomes carbon dioxide and water again. It is a raw material that can suppress the increase of carbon dioxide, which is a greenhouse gas. Biomass plastics using these biomass as raw materials have been rapidly put to practical use, and biaxially stretched polyamide films using biomass-derived raw materials have also been proposed (see, for example, Patent Document 1).

When used as a package, the biaxially stretched polyamide film is made into a laminated film by laminating a sealant film or the like, and then processed into a packaging bag or the like. As the sealant film, unstretched linear low-density polyethylene film, unstretched polypropylene film, etc. are used. From the viewpoint of carbon neutrality, a sealant film containing polyethylene polymerized using biomass-derived raw materials has been proposed. (See Patent Document 2, for example).

International Publication No. 2020/170714 JP 2018-001612 A

An object of the present invention is to provide a carbon-neutral heat-sealable laminate film using biomass-derived raw materials while being excellent in heat resistance, impact resistance, and bending pinhole resistance.

The present invention consists of the following configurations.
[1] A heat-sealable laminated film having at least a substrate layer and a sealant layer,
The base material layer is a biaxially stretched polyamide film, and the biaxially stretched polyamide film contains 70 to 99% by mass of polyamide 6 as a polyamide resin, and 1 to 30% of polyamide whose raw material is at least partly derived from biomass. including % by mass,
The sealant layer is an unstretched polyolefin film, and the unstretched polyolefin film contains 70 to 95% by mass of a polypropylene resin and 5 to 5 to 5 of a linear low-density polypropylene resin in which at least part of the raw material is derived from biomass. A heat-sealable laminated film containing 30% by mass.
[2] The heat-sealable laminated film of [1], wherein the content of carbon 14 in the substrate layer is 1 to 30% with respect to the total carbon in the substrate layer.
[3] The polyamide at least part of which is biomass-derived raw material in the base material layer is at least one polyamide selected from the group consisting of polyamide 11, polyamide 410, polyamide 610, and polyamide 1010, [1] Or the heat-sealable laminated film according to [2].
[4] The heat-sealable laminated film according to any one of [1] to [3], wherein the content of carbon 14 in the sealant layer is 3 to 30% with respect to the total carbon in the sealant layer.
[5] The sealant layer has a seal layer, a core layer and a laminate layer,
The resin composition constituting the sealing layer contains 94 to 100% by mass of a propylene-α-olefin random copolymer and 0 to 3% by mass of linear low-density polyethylene,
The resin composition constituting the core layer contains 25 to 97% by mass of a propylene-α-olefin random copolymer and 3 to 40% by mass of linear low-density polyethylene,
The resin composition constituting the laminate layer contains 25 to 70% by mass of a propylene-α-olefin random copolymer and 3 to 50% by mass of linear low-density polyethylene,
The heat-sealable laminated film according to any one of [1] to [4], wherein the sealant layer includes a laminate layer, a core layer, and a seal layer in this order from the surface in contact with the base layer.
[6] The heat-sealable laminated film according to any one of [1] to [5], wherein the carbon-14 content in the laminated film is 2 to 30% of the total carbon in the laminated film.
[7] A package using the heat-sealable laminated film according to any one of [1] to [6].

According to the present invention, a biaxially stretched polyamide film obtained by blending a polyamide resin polymerized from a specific biomass-derived raw material with polyamide 6 is laminated with a sealant film obtained by blending polyethylene using a biomass-derived raw material with polypropylene. A carbon-neutral heat-sealable laminated film having excellent heat resistance, impact resistance, and bending pinhole resistance can be obtained.

[Base material layer]
The substrate layer of the present invention is a biaxially oriented polyamide film. The biaxially stretched polyamide film contains 70 to 99% by mass of polyamide 6 and 1 to 30% by mass of polyamide whose raw material is at least partly derived from biomass as the polyamide resin. By containing 70% by mass or more of polyamide 6, excellent mechanical strength such as impact strength and gas barrier properties against oxygen, which are inherent to a biaxially stretched polyamide film made of polyamide 6, can be obtained. In addition, by containing 1 to 30% by mass of polyamide, at least part of which is derived from biomass, not only does it have little effect on the increase or decrease of carbon dioxide on the ground, but also bending pinhole resistance and abrasion resistance pinhole resistance improves.

<Polyamide 6>
Polyamide 6 used in the present invention is usually produced by ring-opening polymerization of ε-caprolactam. Polyamide 6 obtained by ring-opening polymerization is usually melt-extruded by an extruder after removing the lactam monomer with hot water and then drying.

The relative viscosity of polyamide 6 is preferably 1.8-4.5, more preferably 2.6-3.2. If the relative viscosity is less than 1.8, the impact strength of the film will be insufficient. If it is more than 4.5, the load on the extruder is increased, making it difficult to obtain an unstretched film before stretching.

As polyamide 6, in addition to those polymerized from commonly used fossil fuel-derived monomers, polyamide 6 chemically recycled from waste polyamide 6 products such as waste plastic products, waste tire rubber, fibers, and fishing nets can also be used. As a method of obtaining chemically recycled polyamide 6 from waste polyamide 6 products, for example, after collecting used polyamide products, depolymerization is performed to obtain ε-caprolactam, which is purified and then polyamide 6 is obtained. A method of polymerization can be used.

In addition, polyamide 6 obtained by mechanically recycling waste material from the production process of the polyamide film can be used together. Mechanically recycled polyamide 6 is, for example, a non-standard film that cannot be shipped when manufacturing a biaxially stretched polyamide film, and waste materials generated as cut ends (edge trim) are collected and melted extrusion or compression molding. It is a raw material pelletized by

<Polyamide at least part of which is derived from biomass>
Examples of the polyamide at least partly derived from biomass used in the present invention include polyamide 11, polyamide 410, polyamide 610, polyamide 1010, polyamide MXD10, and polyamide 11/6T copolymer resin.

Polyamide 11 is a polyamide resin having a structure in which monomers having 11 carbon atoms are bonded via amide bonds. Polyamide 11 is usually obtained using aminoundecanoic acid or undecanelactam as a monomer. In particular, aminoundecanoic acid is desirable from the viewpoint of carbon neutrality because it is a monomer obtained from castor oil. These structural units derived from monomers having 11 carbon atoms account for preferably 50 mol% or more, more preferably 80% mol or more, more preferably 80% mol or more, and 100 mol% of all structural units in polyamide 11. good too. Polyamide 11 is usually produced by the ring-opening polymerization of undecanelactam described above. Polyamide 11 obtained by ring-opening polymerization is usually melt-extruded by an extruder after removing the lactam monomer with hot water and then drying. The relative viscosity of polyamide 11 is preferably 1.8 to 4.5, more preferably 2.4 to 3.2. If the relative viscosity is less than 1.8, the impact strength of the film will be insufficient. If it is more than 4.5, the load on the extruder is increased, making it difficult to obtain an unstretched film before stretching.

Polyamide 410 is a polyamide resin having a structure in which a monomer having 4 carbon atoms and a diamine having 10 carbon atoms are copolymerized. Polyamide 410 typically utilizes sebacic acid and tetramethylene diamine. Sebacic acid is preferably made from castor oil, which is a vegetable oil, from an environmental point of view. Sebacic acid used here is preferably obtained from castor oil from the viewpoint of environmental protection (especially from the viewpoint of carbon neutrality).

Polyamide 610 is a polyamide resin having a structure in which a diamine having 6 carbon atoms and a dicarboxylic acid having 10 carbon atoms are polymerized. Hexamethylenediamine and sebacic acid are commonly used. Of these, sebacic acid is a monomer obtained from castor oil, and is desirable from the viewpoint of carbon neutrality. Structural units derived from these monomers having 6 carbon atoms and structural units derived from monomers having 10 carbon atoms, the total in PA610 is 50 mol of all structural units % or more, more preferably 80 mol % or more, and may be 100 mol %.

Polyamide 1010 is a polyamide resin having a structure in which a diamine having 10 carbon atoms and a dicarboxylic acid having 10 carbon atoms are polymerized. Polyamide 1010 typically utilizes 1,10-decanediamine (decamethylenediamine) and sebacic acid. Decamethylenediamine and sebacic acid are monomers obtained from castor oil, and thus are desirable from the carbon neutral point of view. These structural units derived from a diamine having 10 carbon atoms and structural units derived from a dicarboxylic acid having 10 carbon atoms account for 50 mol% or more of the total structural units in PA1010. It is preferably 80 mol % or more, more preferably 100 mol %.

The lower limit of the content of the polyamide, at least part of which is derived from biomass, in the substrate layer of the present invention is not particularly limited, but is preferably 1% by mass, more preferably 3% by mass or more. The upper limit of the content is 30% by mass, more preferably 20% by mass. If the content of the polyamide, at least part of which is derived from biomass, exceeds 30% by mass, the melt film may become unstable during casting, making it difficult to obtain a homogeneous unstretched film.

<Secondary materials, additives>
Various additives such as other thermoplastic resins, lubricants, heat stabilizers, antioxidants, antistatic agents, antifogging agents, ultraviolet absorbers, dyes, and pigments are added to the biaxially stretched polyamide film of the base layer. It can be contained as needed.

<Other thermoplastic resins>
The biaxially stretched polyamide film of the base layer may contain a thermoplastic resin in addition to the polyamide 6 and the polyamide resin at least part of which is derived from biomass, as long as the object of the present invention is not impaired. . Examples thereof include polyamide resins such as polyamide 12 resin, polyamide 66 resin, polyamide 6/12 copolymer resin, polyamide 6/66 copolymer resin, and polyamide MXD6 resin. Thermoplastic resins other than polyamides, for example, polyester polymers such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, and polyolefin polymers such as polyethylene and polypropylene, may be added as necessary. good. It is preferable that the raw materials of these thermoplastic resins are biomass-derived, since they do not affect the increase or decrease of carbon dioxide on the ground, thereby reducing the environmental load.

<Lubricant>
The biaxially stretched polyamide film of the substrate layer preferably contains fine particles or an organic lubricant such as fatty acid amide as a lubricant in order to improve the slipperiness and facilitate handling. As the fine particles, inorganic fine particles such as silica, kaolin, and zeolite, and polymer-based organic fine particles such as acryl-based and polystyrene-based organic fine particles can be appropriately selected and used. From the viewpoint of transparency and slipperiness, it is preferable to use fine silica particles. The fine particles preferably have an average particle size of 0.5 to 5.0 μm, more preferably 1.0 to 3.0 μm. If the average particle size is less than 0.5 μm, a large amount of addition is required to obtain good slipperiness. On the other hand, when it exceeds 5.0 μm, the surface roughness of the film tends to be too large and the appearance tends to be poor.

When the silica fine particles are used, the pore volume of silica is preferably 0.5 to 2.0 ml/g, more preferably 0.8 to 1.6 ml/g. When the pore volume is less than 0.5 ml/g, voids are likely to occur and the transparency of the film deteriorates. Tend.

The biaxially stretched polyamide film of the substrate layer may contain a fatty acid amide and/or a fatty acid bisamide for the purpose of improving slipperiness. Fatty acid amides and/or fatty acid bisamides include erucic acid amide, stearic acid amide, ethylene bis stearic acid amide, ethylene bis behenic acid amide, ethylene bis oleic acid amide and the like. The content of fatty acid amide and/or fatty acid bisamide is preferably 0.01 to 0.40% by mass, more preferably 0.05 to 0.30% by mass. If the content of the fatty acid amide and/or the fatty acid bisamide is less than the above range, the lubricity tends to deteriorate. On the other hand, when the above range is exceeded, the wettability tends to deteriorate.

For the biaxially stretched polyamide film of the base layer, polyamide resin such as polyamide MXD6 resin, polyamide 12 resin, polyamide 66 resin, polyamide 6/12 copolymer resin, polyamide 6/66 copolymer resin is used for the purpose of improving slipperiness. can be added.

<Antioxidant>
The biaxially stretched polyamide film of the substrate layer can contain an antioxidant. Phenolic antioxidants are preferred as antioxidants. The phenolic antioxidant is preferably a fully hindered phenolic compound or a partially hindered phenolic compound. For example, tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane, stearyl-β-(3,5-di-t-butyl-4-hydroxy phenyl)propionate, 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10- tetraoxaspiro[5,5]undecane and the like. By containing a phenolic antioxidant, the film-forming operability of the biaxially stretched polyamide film is improved. In particular, when a recycled film is used as a raw material, thermal deterioration of the resin tends to occur, resulting in film-forming operation failures, which tends to lead to an increase in production costs. On the other hand, by containing an antioxidant, the heat deterioration of the resin is suppressed and the workability is improved.

[Biaxially stretched polyamide film]
The thickness of the substrate layer is not particularly limited, but when used as a packaging material, it is usually 100 μm or less, generally 5 to 50 μm thick, and particularly 8 to 30 μm thick. be done.

The biaxially stretched polyamide film of the substrate layer preferably has a heat shrinkage rate of 0.6 to 3.0% in both the MD and TD directions at 160° C. for 10 minutes, more preferably 0.5%. 6 to 2.5%. If the heat shrinkage rate exceeds 3.0%, curling or shrinkage may occur when heat is applied in the next step such as lamination or printing. Moreover, the lamination strength with the sealant film may be weakened. Although it is possible to set the heat shrinkage to less than 0.6%, it may become mechanically brittle. Moreover, it is not preferable because productivity deteriorates.

The impact strength of the biaxially stretched polyamide film is preferably 0.7 J/15 μm or more. A more preferable impact strength is 0.9 J/15 μm or more.

The haze value of the biaxially stretched polyamide film is preferably 10% or less. More preferably 7% or less, still more preferably 5% or less. If the haze value is small, the transparency and gloss are good, so when used for packaging bags, clear printing can be performed and the product value is increased. Addition of fine particles to improve the slipperiness of the film increases the haze value. Therefore, when the film has two or more layers, the haze value can be reduced by adding fine particles only to the surface layer.

The dynamic friction coefficient of the biaxially stretched polyamide film is preferably 1.0 or less. It is more preferably 0.7 or less, still more preferably 0.5 or less. If the coefficient of dynamic friction of the film is small, the slipperiness is improved and the handling of the film is facilitated. If the coefficient of dynamic friction of the film is too small, the film will be too slippery and difficult to handle.

The biaxially stretched polyamide film has a biomass-derived carbon content (also referred to as biomass degree) measured by ASTM D6866-18 radioactive carbon (C ¹⁴ ), and contains 1 to 30% of the total carbon in the polyamide film. is preferred. Since carbon dioxide in the atmosphere contains a certain proportion of ^C14 (105.5 pMC), the ^C14 content in plants that grow by taking in carbon dioxide in the atmosphere, such as corn, is also about 105.5 pMC. is known to be It is also known that fossil fuels contain little ^C14 . Therefore, by measuring the proportion of ^C14 contained in the total carbon atoms in the film, the proportion of biomass-derived carbon can be calculated.

[Method for producing biaxially stretched polyamide film]
The biaxially stretched polyamide film of the substrate layer can be produced by a known production method. A typical production example is described below.

First, a raw material resin is melt extruded using an extruder, extruded in the form of a film through a T-die, cast on a cooling roll and cooled to obtain an unstretched film. The melting temperature of the resin is preferably 220-350°C. If it is less than the above range, unmelted materials may occur, resulting in appearance defects such as defects. The die temperature is preferably 250-350°C.

The cooling roll temperature is preferably -30 to 80°C, more preferably 0 to 50°C. In order to obtain an unstretched film by casting the film-shaped melt extruded from the T-die onto a rotating cooling drum and cooling it, for example, a method using an air knife or an electrostatic adhesion method in which an electrostatic charge is applied is preferably applied. can. Especially the latter is preferably used.

It is also preferable to cool the opposite side of the cast unstretched film to the cooling roll. For example, it is preferable to use a method of contacting the opposite side of the unstretched film to the cooling roll with a cooling liquid in a tank, a method of applying a liquid that transpires with a spray nozzle, a method of cooling by spraying a high-speed fluid, and the like. . The unstretched film thus obtained is biaxially stretched to obtain the biaxially stretched polyamide film of the present invention.

The stretching method may be a simultaneous biaxial stretching method or a sequential biaxial stretching method. In any case, as the stretching method in the MD direction, single-stage stretching or multi-stage stretching such as two-stage stretching can be used. As will be described later, multi-stage stretching in the MD direction such as two-stage stretching is preferable in terms of physical properties and uniformity (isotropy) of physical properties in the MD and TD directions, rather than single-stage stretching. Stretching in the MD direction in the sequential biaxial stretching method is preferably roll stretching.

The lower limit of the stretching temperature in the MD direction is preferably 50°C, more preferably 55°C, still more preferably 60°C. If the temperature is less than 50°C, the resin may not be softened, making stretching difficult. The upper limit of the stretching temperature in the MD direction is preferably 120°C, more preferably 115°C, still more preferably 110°C. If the temperature exceeds 120°C, the resin may become too soft to allow stable stretching.

The lower limit of the draw ratio in the MD direction (in the case of multistage drawing, the total draw ratio obtained by multiplying each draw ratio) is preferably 2.2 times, more preferably 2.5 times, and still more preferably 2.5 times. 8 times. If it is less than 2.2 times, the thickness accuracy in the MD direction may be lowered, and the crystallinity may be too low to lower the impact strength. The upper limit of the draw ratio in the MD direction is preferably 5.0 times, more preferably 4.5 times, and most preferably 4.0 times. If it exceeds 5.0 times, subsequent stretching may become difficult.

Further, when the stretching in the MD direction is performed in multiple stages, the stretching as described above is possible in each stretching. It is necessary to adjust the draw ratio. For example, in the case of two-stage stretching, the first stage stretching is preferably 1.5 to 2.1 times, and the second stage stretching is preferably 1.5 to 1.8 times.

A film stretched in the MD direction is stretched in the TD direction by a tenter, heat-set, and subjected to relaxation treatment (also referred to as relaxation treatment). The lower limit of the stretching temperature in the TD direction is preferably 50°C, more preferably 55°C, still more preferably 60°C. If the temperature is less than 50°C, the resin may not be softened, making stretching difficult. The upper limit of the stretching temperature in the TD direction is preferably 190°C, more preferably 185°C, still more preferably 180°C. If the temperature exceeds 190°C, crystallization may occur, making stretching difficult.

The lower limit of the draw ratio in the TD direction (in the case of multistage drawing, the total draw ratio obtained by multiplying each draw ratio) is preferably 2.8, more preferably 3.2, and still more preferably 3.5. times, particularly preferably 3.8 times. If it is less than 2.8, the thickness accuracy in the TD direction may be lowered, and the crystallinity may be too low to lower the impact strength. The upper limit of the draw ratio in the TD direction is preferably 5.5 times, more preferably 5.0 times, still more preferably 4.7 times, particularly preferably 4.5 times, and most preferably 4.5 times. Three times. If it exceeds 5.5 times, the productivity may be remarkably lowered.

The lower limit of the heat setting temperature is preferably 210°C, more preferably 212°C. When the heat setting temperature is low, the heat shrinkage rate becomes too large, and the appearance after lamination tends to deteriorate, and the lamination strength tends to decrease. The upper limit of the heat setting temperature is preferably 220°C, more preferably 218°C. If the heat setting temperature is too high, the impact strength tends to decrease.

The heat setting time is preferably 0.5 to 20 seconds. Furthermore, it is 1 to 15 seconds. The heat setting time can be set to an appropriate time in consideration of the heat setting temperature and the wind speed in the heat setting zone. If the heat setting conditions are too weak, crystallization and orientation relaxation become insufficient, causing the above problems. If the heat setting conditions are too strong, the toughness of the film will decrease.

Relaxation treatment after heat setting treatment is effective in controlling the thermal shrinkage rate. The temperature for the relaxation treatment can be selected in the range from the heat setting temperature to the glass transition temperature (Tg) of the resin, but the heat setting temperature -10°C to Tg + 10°C is preferable. If the relaxation temperature is too high, the shrinkage speed will be too fast, causing distortion and the like, which is not preferable. Conversely, if the relaxation temperature is too low, the relaxation treatment will not be performed, and the film will simply loosen, the heat shrinkage rate will not decrease, and the dimensional stability will deteriorate.

The lower limit of the relaxation rate of the relaxation process is preferably 0.5%, more preferably 1%. If it is less than 0.5%, the heat shrinkage rate may not sufficiently decrease. The upper limit of the relaxation rate is preferably 20%, more preferably 15%, still more preferably 10%. If it exceeds 20%, sagging may occur in the tenter, making production difficult.

Furthermore, the biaxially stretched polyamide film of the substrate layer can be subjected to heat treatment or humidity control treatment in order to improve the dimensional stability depending on the application. In addition, in order to improve the adhesiveness of the film surface, it is possible to perform corona treatment, coating treatment, flame treatment, etc., printing, vapor deposition of metals and inorganic oxides, etc. It is also possible. As the vapor deposition film formed by the vapor deposition process, a vapor deposition film of aluminum, a vapor deposition film of a single substance or a mixture of silicon oxide or aluminum oxide is preferably used. Furthermore, by coating a protective layer or the like on these vapor-deposited films, the oxygen barrier properties and the like can be improved.

[Sealant layer]
The sealant layer is an unstretched polyolefin film. The unstretched polyolefin film contains 70 to 95% by mass of polypropylene resin and 5 to 30% by mass of linear low-density polypropylene resin, at least part of which is derived from biomass.

The unstretched polyolefin film preferably has a laminated structure and has layers of a seal layer, a core layer and a laminate layer in this order. The seal layer and laminate layer are layers positioned on the surface side of the unstretched polyolefin film, and the core layer is positioned between them. The laminate layer is a layer suitable for laminating the biaxially oriented polyamide film, and in practice it is preferably laminated with the biaxially oriented polyamide film via an adhesive resin. The sealing layer is a layer suitable for heat sealing to produce a package. By adopting the above layer structure, it is possible to contain more biomass-derived linear low-density polyethylene resin while maintaining the properties of the unstretched polypropylene film, which is a sealant layer with excellent heat resistance.

<Seal layer>
In the present invention, the polypropylene-based resin composition constituting the seal layer contains a propylene-α-olefin random copolymer from the viewpoint of heat seal strength. The content of the propylene-α-olefin random copolymer in the polypropylene resin composition constituting the seal layer is preferably 94% by mass or more, more preferably 97% by mass or more, still more preferably 99% by mass or more, and 100% by mass. Especially preferred. Sufficient heat-sealing strength is obtained by making it 94 mass % or more.

In the present invention, the polypropylene-based resin composition that constitutes the seal layer may contain a propylene homopolymer from the viewpoint of improving slipperiness. The content of the propylene homopolymer is preferably 3% by mass or less, more preferably 2% by mass, even more preferably 1% by mass or less, and particularly preferably 0% by mass, from the viewpoint of heat seal strength. If the sealing layer contains a large amount of polyethylene-based resin such as linear low-density polyethylene, the heat-sealing strength may decrease due to poor mutual compatibility.

In the present invention, the polypropylene-based resin composition that constitutes the seal layer may contain linear low-density polyethylene from the viewpoint of improving bending resistance to pinholes. The content of the linear low-density polyethylene is preferably 3% by mass or less, more preferably 2% by mass, even more preferably 1% by mass or less, and particularly preferably 0% by mass, in terms of heat seal strength.

<Core layer>
In the present invention, the polypropylene-based resin composition constituting the core layer contains a propylene-α-olefin random copolymer from the viewpoint of heat seal strength. The content of the propylene-α-olefin random copolymer is preferably 25% by mass or more, more preferably 40% by mass or more, still more preferably 60% by mass or more, and particularly preferably 75% by mass or more, from the viewpoint of heat seal strength. 80% by mass or more is particularly preferred. From the viewpoint of bending pinhole resistance, it is preferably 97% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

In the present invention, the polypropylene-based resin composition constituting the core layer may contain a propylene homopolymer from the viewpoint of improving heat resistance. The content of the propylene homopolymer is preferably 30% by mass or more, more preferably 40% by mass or more, from the viewpoint of heat resistance. However, from the viewpoint of heat seal strength and bag breakage resistance, it is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, and particularly preferably 0% by mass.

In the present invention, the polypropylene-based resin composition constituting the core layer may contain linear low-density polyethylene from the viewpoint of improving bending pinhole resistance. The content of linear low-density polyethylene is preferably 3% by mass or more, more preferably 8% by mass or more, still more preferably 12% by mass or more, and particularly preferably 15% by mass or more, from the viewpoint of bending pinhole resistance. From the viewpoint of heat resistance, it is preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less.

<Laminate layer>
In the present invention, the polypropylene-based resin composition constituting the laminate layer contains a propylene-α-olefin random copolymer from the viewpoint of heat seal strength. The content of the propylene-α-olefin random copolymer is preferably 25% by mass or more, more preferably 40% by mass or more, further preferably 60% by mass or more, further preferably 80% by mass from the viewpoint of heat seal strength. % or more is particularly preferred. From the viewpoint of bending pinhole resistance, it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, particularly preferably 75% by mass or less, and particularly preferably 70% by mass or less.

In the present invention, the polypropylene-based resin composition constituting the laminate layer may contain a propylene homopolymer from the viewpoint of improving heat resistance. The content of the propylene homopolymer is preferably 30% by mass or more, more preferably 40% by mass or more, from the viewpoint of heat resistance. However, from the viewpoint of heat seal strength and bag breakage resistance, it is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, and particularly preferably 0% by mass.

In the present invention, the polypropylene-based resin composition that constitutes the laminate layer may contain linear low-density polyethylene from the viewpoint of improving bending resistance to pinholes. The content of the linear low-density polyethylene is preferably 3% by weight or more, more preferably 8% by weight or more, still more preferably 15% by weight or more, particularly preferably 20% by weight or more, particularly preferably 25% by weight or more, in terms of bending pinhole resistance. Weight percent or more is most preferred. From the viewpoint of heat resistance and heat seal strength, the content is preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less.

In the unstretched polyolefin film of the present invention, the difference in content of linear low-density polyethylene in the polypropylene-based resin composition constituting the sealing layer and the core layer is preferably 1 to 28% by mass. More preferably 1 to 23% by mass, still more preferably 1 to 18% by mass, particularly preferably 1 to 15% by mass. By setting the content difference to 28% by mass or less, the interlaminar strength at the interface between the seal layer and the core layer can be kept high, and high heat seal strength can be obtained.

In the unstretched polyolefin film of the present invention, the difference in content of the linear low-density polyethylene in the polypropylene-based resin composition constituting the core layer and the laminate layer is preferably 1 to 28% by mass. It is more preferably 1 to 23% by weight, still more preferably 1 to 18% by weight, and particularly preferably 1 to 15% by weight. By setting the content difference to 28% by mass or less, the interlaminar strength at the interface between the core layer and the laminate layer can be kept high, and high heat seal strength can be obtained.

In the unstretched polyolefin film of the present invention, the content of the linear low-density polyethylene in the polypropylene-based resin composition that constitutes the seal layer is more than the linear low-density polyethylene in the polypropylene-based resin composition that constitutes the core layer. The content of the linear low density polyethylene in the polypropylene resin composition constituting the laminate layer is higher than the content of the linear low density polyethylene in the polypropylene resin composition constituting the core layer. Larger ratios are preferred. By doing so, the linear low-density polyethylene in the film tends to be uniformly dispersed, which is advantageous in terms of bending pinhole resistance. In addition, high heat seal strength can be obtained due to the large ratio of the polypropylene-based resin in the resin near the heat seal surface.

Propylene-α-olefin random copolymer with a low melting point is used for the sealing layer, and propylene-α-olefin random copolymer with a high melting point is used for the layers and laminate layers, thereby improving the heat seal strength. , the heat resistance and bending pinhole resistance can be further enhanced.

<Propylene-α-olefin random copolymer>
Examples of the propylene-α-olefin random copolymer in the present invention include copolymers of propylene and at least one α-olefin having 2 or 4 to 20 carbon atoms other than propylene. Examples of α-olefin monomers having 2 or 4 to 20 carbon atoms include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1 and octene-1.

Ethylene is preferably used for the propylene-α-olefin random copolymer from the viewpoint of heat sealability. At least one type or more may be used, and two or more types may be mixed and used as needed. Particularly suitable is a propylene-ethylene-butene random copolymer in which the main monomer is propylene and certain amounts of ethylene and butene are copolymerized.

The lower limit of melt flow rate (MFR) of the propylene-α-olefin random copolymer is preferably 0.6 g/10 min, more preferably 1.0 g/10 min, still more preferably 1.2 g/10 min. Film thickness uniformity may be compromised. The upper limit of the melt flow rate of the random copolymer is preferably 12.0 g/10 min, more preferably 9.0 g/10 min, still more preferably 8.0 g/10 min.

<Propylene homopolymer)
The melt flow rate (MFR) of the propylene homopolymer (measured at 230° C. under a load of 2.16 kg) is not particularly limited, but is preferably 1.0 g/10 min or more and 10.0 g/10 min or less, and 2.0 g/min or more. 0 g/min or less is more preferable. If it is less than 1 g/10 min, the viscosity is too high and it is difficult to extrude with a T-die. may occur. As the propylene homopolymer, isotactic polypropylene, which has high crystallinity and can suppress deterioration of thermal shrinkage, is preferable.

<Linear low-density polyethylene>
Linear low-density polyethylene can be produced by a production method such as a high-pressure method, a solution method, or a gas phase method. Examples of linear low-density polyethylene include copolymers of ethylene and at least one α-olefin having 3 or more carbon atoms. As the α-olefin, what is generally called α-olefin may be used, and α- Olefins are preferred. Examples of copolymers of ethylene and α-olefin include ethylene/hexene-1 copolymer, ethylene/butene-1 copolymer, ethylene/octene-1 copolymer, etc. Ethylene-hexene copolymers are preferred from the viewpoint.

Linear low-density polyethylene is a biomass-derived linear low-density polyethylene polymerized using ethylene derived from plants such as sugar cane and ethylene derived from fossil fuels such as petroleum or plants as part of the raw material. can contain. From the viewpoint of carbon neutrality, biomass-derived linear low-density polyethylene is said to be effective in reducing the amount of carbon dioxide generated, and to be able to suppress global warming. When the biomass-derived ethylene of the biomass-derived linear low-density polyethylene is included, the content is preferably 50% by mass or more, more preferably 80% by mass or more. When it is 50% or more, the carbon dioxide reduction effect is good. The upper limit is preferably 98%, more preferably 96%. Since it is preferable to copolymerize an α-olefin other than ethylene from the viewpoint of bending pinhole resistance, it is preferably 98% by mass or less.

The lower limit of the MFR (measured at 190° C., 2.18 kg) of linear low-density polyethylene is preferably 1.0 g/10 min, more preferably 2.0 g/10 min. The upper limit is preferably 7.0 g/min, more preferably 5.0. Within the above range, good compatibility with the polypropylene-based resin and high seal strength can be obtained.

The lower limit of the density of linear low density polyethylene is preferably 910 kg/m ³ , more preferably 913 kg/m ³ . Good anti-blocking property can be obtained by making it 910 kg/m ³ or more. The upper limit is 935 kg/m ³ , more preferably 930 kg/m ³ . Good resistance to bag breakage can be obtained when it is 930 kg/m ³ or less.

<Additive>
In the unstretched polyolefin film, appropriate amounts of antiblocking agent, antioxidant, antistatic agent, antifogging agent, neutralizing agent, nucleating agent, Colorants, other additives, inorganic fillers, and the like may be included.

The polyolefin-based resin composition that constitutes the unstretched polyolefin film may contain an antiblocking agent. One type of anti-blocking agent may be used, but it is better to blend two or more types of inorganic particles with different particle sizes and shapes. be able to. The anti-blocking agent to be added is not particularly limited, but inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, aluminum borate, polymethyl methacrylate, ultra high molecular weight Organic particles such as polyethylene can be added.

The anti-blocking agent contained in the polypropylene-based resin composition constituting the seal layer is preferably 0.30% by mass or less, more preferably 0.25% by mass or less, relative to the polyolefin-based resin of the layer to which it is added. By making it 0.30% by mass or less, it is possible to reduce the shedding of the antiblocking agent. Moreover, it is preferably 0.05% by mass or more, and more preferably 0.10% by mass or more. Favorable anti-blocking property can be obtained by making it 0.05 mass % or more.

The anti-blocking agent contained in the polypropylene-based resin composition constituting the laminate layer is preferably 0.30% by mass or less, more preferably 0.25% by mass or less, relative to the polyolefin-based resin of the layer to be added. 0.10% by mass or less is more preferable, 0.05% by mass or less is particularly preferable, and 0.05% by mass or less is most preferable. By setting the amount to 0.30% by mass or less, it is possible to reduce detachment of the antiblocking agent from the surface of the laminate layer.

The polyolefin-based resin composition that constitutes the unstretched polyolefin film can contain an organic lubricant. By containing an organic lubricant, the lubricity and anti-blocking effect of the film are improved, and the handleability of the film is improved. It is believed that the reason for this is that the organic lubricant bleeds out and is present on the film surface, thereby exhibiting the lubricant effect and the release effect. The organic lubricant preferably has a melting point above room temperature. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specific examples include oleic acid amide, erucic acid amide, behenic acid amide, ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, and ethylenebisoleic acid amide. These may be used alone, but it is preferable to use two or more of them in combination because the lubricity and anti-blocking effect can be maintained even in a harsh environment. The content of the organic lubricant in the polypropylene-based resin composition is preferably 0.15% by mass or less, more preferably 0.10% by mass or less. By making it 0.15% by mass or less, blocking is less likely to occur even when stored in a place exposed to high temperatures such as a warehouse in summer. Moreover, it is preferably 0.02% by mass or more, and more preferably 0.025% by mass or more. Favorable lubricity can be obtained by making it 0.02% by mass or more.

The polyolefin-based resin composition that constitutes the unstretched polyolefin film can contain an antioxidant. Examples of antioxidants include phenolic antioxidants, phosphite antioxidants, combinations thereof, and those having phenolic and phosphite skeletons in one molecule. Calcium stearate etc. are mentioned as a neutralizing agent.

[Unstretched polyolefin film]
The lower limit of the thickness of the unstretched polyolefin film of the sealant layer is preferably 15 μm, more preferably 20 μm, still more preferably 25 μm. When the thickness is 15 μm or more, it is easy to obtain heat seal strength and bag breakage resistance. The upper limit of the film thickness is preferably 80 µm, more preferably 70 µm, still more preferably 60 µm, and particularly preferably 50 µm. When the thickness is 80 μm or less, the film does not have too strong a feeling of stiffness and is easy to process, and it is easy to manufacture a suitable package.

The haze value of the unstretched polyolefin film is preferably 20.0% or less. More preferably 15.0%, still more preferably 10.0%. If it is 20.0% or less, the visibility of the package can be easily obtained. Linear low-density polyethylene has high crystallinity and tends to increase haze, but if added within the above preferred range, increase in haze can be suppressed. The lower limit is preferably 1.0%, more preferably 2.0%. When it is 1.0% or more, the film surface does not have an extremely small unevenness, so blocking on the inner surface of the package is unlikely to occur.

The coefficient of static friction of the unstretched polyolefin film is preferably 0.70 or less, more preferably 0.50, still more preferably 0.40. When it is 0.70 or less, the surfaces that are not present when the package is filled with food or when the package is opened are slippery and the opening is good. The lower limit is preferably 0.10 or more, more preferably 0.20 or more, and particularly preferably 0.30. When it is 0.10 or more, it is difficult for the rolled film to collapse during transportation.

The impact strength of the unstretched polyolefin film is preferably 0.20J/15 μm or more, more preferably 0.25J, still more preferably 0.30J. By setting it to 0.20 J or more, it is possible to enhance the resistance to falling bag breakage of the package. An impact strength of 1.0 J is sufficient. Impact strength is highly dependent on the thickness and molecular orientation of the film. Moreover, the impact strength and the drop bag breakage resistance are not necessarily correlated.

The puncture strength of the unstretched polyolefin film is preferably 1.0N or more, more preferably 1.5N or more, and still more preferably 1.7N or more. When the thickness is 1.0 μm or more, the laminate has good pierce pinhole resistance.

The plane orientation coefficient of the unstretched polyolefin film is preferably 0.000 or more, more preferably 0.001 or more. The upper limit of the plane orientation of the film is preferably 0.010 or less, more preferably 0.008 or less, and still more preferably 0.006 or less. If it is more than the above, the film may be stretched unevenly and the thickness uniformity may be deteriorated.

The heat-seal initiation temperature of the unstretched polyolefin film is preferably 110°C or higher, more preferably 120°C or higher. When the temperature is 110°C or higher, it has a high stiffness and is easy to handle. The upper limit of the heat seal initiation temperature is 150°C, preferably 140°C, and still more preferably 130°C. When the temperature is 150°C or lower, the package can be produced at high speed, which is economically advantageous. The heat seal initiation temperature is greatly affected by the melting point of the seal layer. Therefore, if linear low-density polyethylene is used for the core layer and laminate layer, the change in heat sealing temperature can be suppressed.

The wet tension of the surface of the unstretched polyolefin film to be laminated with at least one film selected from the group consisting of polyamide resin film, polyester resin film, and polypropylene resin film is preferably 30 mN/m or more, more preferably. is 35 mN/m or more. When it is 30 mN/m or more, the laminate strength is less likely to decrease. The upper limit of the wetting tension is preferably 55 mN/m, more preferably 50 mN/m. If it is 55 mN/m or less, blocking between films is less likely to occur when the polyolefin resin film is wound on a roll.

The unstretched polyolefin film contains 3 to 30% of the biomass-derived carbon content (also referred to as biomass degree) measured by radioactive carbon (C14) of ASTM D6866-18 with respect to the total carbon in the unstretched polyolefin film. is preferred.

[Method for producing unstretched polyolefin film]
As the method for producing the unstretched polyolefin film in the present invention, for example, an inflation method or a T-die method can be used, but the T-die method is preferable in order to improve transparency. The inflation method uses air as a cooling medium, whereas the T-die method uses cooling rolls, and is therefore an advantageous manufacturing method for increasing the cooling rate. Since crystallization of the unstretched sheet can be suppressed by increasing the cooling rate, transparency is advantageous. For these reasons, it is preferable to use a non-oriented sheet in the T-die method.

A typical production example is described below. The raw materials of the polypropylene resin composition for the seal layer, core layer, and laminate layer are mixed, melt-mixed and extruded by separate extruders, and the laminated sheets of the seal layer, core layer, and laminate layer melted from the T-die are cooled. Cast on rolls to obtain non-oriented sheets. The lower limit of the temperature of the chill roll is preferably 15°C, more preferably 20°C. If it is less than the above, dew condensation may occur on the cooling roll, resulting in insufficient adhesion. The upper limit of the chill roll is preferably 60°C, more preferably 50°C. Transparency may deteriorate when the above is exceeded.

[Heat-sealable laminated film]
The heat-sealable laminated film of the present invention has a substrate layer and a sealant layer, but the laminated film may be constructed by interposing an adhesive layer, a printed layer, a metal layer, or the like between the substrate layer and the sealant layer. can. As a lamination method, known methods such as dry lamination and extrusion lamination can be used, but any lamination method may be used. Specific examples are shown below.

Example of layer structure of the laminated film of the present invention: ONY/adhesive/CPP, ONY/adhesive/Al/adhesive/CPP, PET/adhesive/ONY/adhesive/CPP, PET/adhesive/ONY/adhesive Agent/Al/adhesive/CPP, PET/adhesive/Al/adhesive/ONY/adhesive/CPP, ONY/adhesive/PET/adhesive/CPP, ONY/PE/CPP, ONY/adhesive/EVOH /adhesive/CPP, ONY/adhesive/aluminum-deposited PET/adhesive/CPP, CPP/adhesive/ONY/adhesive/LLDPE, ONY/adhesive/aluminum-deposited CPP.
The abbreviations used in the above layer structure are as follows.
/ : Boundary between layers ONY: biaxially oriented polyamide film PET: oriented polyethylene terephthalate film LLDPE: unoriented linear low density polyethylene film CPP: unoriented polypropylene film PE: extrusion laminate or unoriented low density polyethylene film Al: Aluminum foil EVOH: Ethylene-vinyl alcohol copolymer resin Adhesive: Adhesive layer for bonding films together Aluminum vapor deposition: Indicates that aluminum is vapor-deposited

[Characteristics of heat-sealable laminated film]
The flex resistance of the heat-sealable laminated film can be measured by pinhole evaluation. The number of pinholes after bending the heat-sealable laminated film 1,000 times at 1° C. is preferably 20 or less, more preferably 15, and particularly preferably 10 or less. If the number is 20 or less, pinholes are less likely to occur due to bending impact during transportation of the package.

The puncture strength of the heat-sealable laminated film is preferably 10 N or more, more preferably 12 N or more, and still more preferably 14 N or more. When the tension is 10 N or more, pinholes are less likely to occur when projections come into contact with the package.

The heat-sealing strength of the heat-sealable laminated film is preferably 20 N/15 mm or more, more preferably 25 N/15 mm or more, still more preferably 30 N/15 mm or more. When it is 20 N/15 mm or more, the resistance to bag breakage is likely to be obtained. A heat seal strength of 60 N/15 mm is very good, and 35 N/15 mm is sufficient.

The heat-sealable laminated film has a biomass-derived carbon content (also referred to as biomass degree) measured by ASTM D6866-18 for radioactive carbon (C14) of 2 to 30% of the total carbon in the heat-sealable laminated film. preferably included.

[Package]
The heat-sealable laminated film of the present invention is processed into a package intended to protect contents such as foodstuffs from dust and gas in the natural world. The package is manufactured by bonding the inner surfaces of the heat-sealable laminated film with a heat-seal bar or ultrasonic waves to form a bag. For example, two rectangular laminates are stacked so that the sealant side faces inside, and the four sides are heat-sealed to form a four-sided seal bag. The heat-sealable laminated film of the present invention can be processed into packages such as bottom-sealed bags, side-sealed bags, three-side-sealed bags, pillow bags, standing pouches, gusseted bags, and square-bottomed bags.

The package of the present invention preferably has a falling bag breakage resistance of 15 times or more, more preferably 20 times or more, and still more preferably 22 times or more. If the number of times is 15 or more, even if the package containing the food is accidentally dropped, the bag is less likely to break. About 30 times of falling bag breakage resistance is sufficient. The falling bag breakage resistance of the package is affected by the flex pinhole resistance, puncture strength, and heat seal strength of the laminate, and these characteristics are preferably set within a preferable range.

Film evaluation was performed by the following measurement methods. Unless otherwise specified, measurements were carried out in a measurement room at 23° C. and a relative humidity of 65%.

(1) Thickness of Film The film thus obtained is cut into a length of 100 mm in a stack of 10 sheets, and is conditioned at a temperature of 23° C. and a relative humidity of 65% for 2 hours or longer. After that, the width direction of the film is divided into 10 equal parts (for narrow films, the width is divided so that the width that can measure the thickness can be secured), and the thickness is measured using a thickness measuring instrument manufactured by Tester Sangyo. The thickness of the film was obtained by dividing the average value by the number of films stacked.
The thickness of the A layer (substrate layer) was calculated based on the ratio of the resin discharge amounts of the A layer, the B layer, and the C layer.

(2) Haze value The haze value of the film was measured according to JIS K7105 using a direct-reading haze meter manufactured by Toyo Seiki Seisakusho.

(3) Degree of biomass The degree of biomass of the film was determined by radiocarbon (C14) measurement shown in ASTM D6866-18 Method B (AMS).

(4) Thermal shrinkage rate The thermal shrinkage rate of the film is determined by the following formula according to the dimensional change test method described in JIS C2318, except that the test temperature is 160 ° C and the heating time is 10 minutes in each of the MD and TD directions. It was measured.
Thermal shrinkage = [(length before treatment - length after treatment) / length before treatment] x 100 (%)

(5) Impact strength The impact strength of the film was measured using a film impact tester manufactured by Toyo Seiki Seisakusho. The measured value was expressed as J (joule)/15 μm in terms of a thickness of 15 μm.

(6) Degree of Plane Orientation A sample was obtained from the central position in the width direction of the film. According to JIS K 7142-1996 A method for the sample, the refractive index (nx) in the film longitudinal direction and the refractive index (ny) in the width direction are measured with an Abbe refractometer using sodium D line as a light source, and the calculation formula of formula (1) The degree of plane orientation was calculated by
Planar orientation (ΔP) = (nx + ny) / 2-nz (1)

(7) Puncture strength The pierce strength of the film is determined according to the Food Sanitation Law, Standards and Standards for Foods, Additives, etc. No. 3: Utensils, Containers and Packaging (Ministry of Health and Welfare Notification No. 20, 1982), Section 2. Test methods for strength, etc. ” was measured in accordance with A needle having a tip diameter of 0.7 mm was pierced into the film at a piercing speed of 50 mm/min. The measurement was carried out at room temperature (23° C.), and the puncture strength (unit: N/μm) was obtained by dividing the puncture strength (unit: N) of the obtained film by the actual thickness of the film.

(8) Wetting Tension The wetting tension of the laminate layer surface was measured according to JIS-K6768 Plastics-Film and Sheet-Wet Tension Test Method.

(9) Heat-seal initiation temperature The heat-seal initiation temperature of the unstretched polyolefin film was measured according to JIS Z 1713 (2009). At this time, the film was cut into a rectangular test piece (for heat sealing) of 50 mm x 250 mm (width direction x length direction of film). The seal layer portions of the two test pieces are overlapped, and a thermal gradient tester (heat seal tester) manufactured by Toyo Seiki Seisakusho Co., Ltd. is used, with a heat seal pressure of 0.2 MPa and a heat seal time of 1.0 sec. did. Then, heat-sealing was performed under the condition that the temperature was increased with an inclination of 5°C. After heat-sealing, a test piece was cut out with a width of 15 mm. The test piece fused by heat sealing was opened at 180°, the unsealed portion was sandwiched between chucks, and the sealed portion was peeled off. Then, the temperature at which the heat seal strength reached 4.9 N was determined. A universal material testing machine 5965 manufactured by Instron Instruments was used as the testing machine. The test speed was 200 mm/min. Measurement was performed with N=5, and the average value was calculated.

[Heat seal strength]
The heat seal strength was measured according to JIS Z1707. Show specific steps. Using a heat sealer, two heat-sealable laminated films were used, and the seal layers of the unstretched polyolefin films were adhered to each other. The heat sealing conditions were an upper bar temperature of 120° C., a lower bar temperature of 30° C., a pressure of 0.2 MPa, and a time of 2 seconds. The adhesive sample was cut so that the seal width was 15 mm. The peel strength was measured using a tensile tester "AGS-KNX" (manufactured by Shimadzu Corporation) at a tensile speed of 200 mm/min. The peel strength is indicated by strength per 15 mm (N/15 mm).

(10) Bending Pinhole Resistance A heat-sealable laminated film was cut into a length of 280 mm and a width of 260 mm. It was made into a cylindrical shape with a diameter of 89 mm and a height of 260 mm so that the unstretched polyolefin film was on the inside, and was fixed with cellophane tape. The sample was attached to a gelboflex tester with a constant temperature bath manufactured by Tester Sangyo Co., Ltd., and subjected to a bending load of 1000 times at 1°C. The sample was removed and the number of pinholes was measured. The unstretched polyolefin film side was placed on a filter paper (Advantech, No. 50) with the unstretched polyolefin film side facing downward, and the four corners were fixed with Sellotape (registered trademark). Ink (pilot ink (product number INK-350-blue) diluted 5 times with pure water) was applied onto the test film and spread over the entire surface using a rubber roller. After wiping off the unnecessary ink, the test film was removed and the number of ink spots on the filter paper was counted. Measurement was performed with N=3, and the average value was calculated.

(11) Falling Bag Breakage Resistance Using a heat-sealable laminated film, a four-way seal bag having an inner dimension of 170 mm long and 120 mm wide was prepared, containing 200 ml of saturated saline. The heat sealing conditions at this time were a pressure of 0.2 MPa for 1 second, a seal bar width of 10 mm, and a heat sealing temperature of 160°C. After the bag-making process, the edges of the four-sided seal bag were cut off to give a seal width of 5 mm. Next, it was left in an environment of +5°C for 8 hours, and under this environment, the four-sided seal bag was dropped from a height of 1.2 m onto a flat concrete floor so that the surface became horizontal. Dropping was repeated until the bag broke, and the number of repeated drops was measured. Twenty samples were repeated and the average value was calculated.

[Production Example 1]
<Preparation of biaxially stretched polyamide film (ONY)>
(ONY1)
Using a device consisting of an extruder and a T-die with a width of 380 mm, the following resin composition A melted from the T-die is extruded in the form of a film, cast on a cooling roll temperature-controlled at 20° C. and electrostatically adhered to a thickness of 200 μm. of unstretched film was obtained.
Resin composition A:
Polyamide 6 (manufactured by Toyobo Co., Ltd., relative viscosity 2.8, melting point 220 ° C.) 97 parts by mass;
Polyamide 11 (manufactured by Arkema, relative viscosity 2.5, melting point 186 ° C.) 3.0 parts by mass;
0.45 parts by mass of porous silica fine particles (manufactured by Fuji Silysia Chemical Co., Ltd., average particle diameter 2.0 μm, pore volume 1.6 ml/g); 15 parts by mass

The obtained unstretched film was guided to a roll type stretching machine, stretched 1.73 times in the MD direction at 80°C by utilizing the peripheral speed difference of the rolls, and then further stretched 1.85 times at 70°C. Subsequently, this uniaxially stretched film was continuously guided to a tenter type stretching machine, preheated at 110°C, and stretched in the TD direction at 120°C for 1.2 times, 130°C for 1.7 times, and 160°C for 2.0 times. After stretching and heat setting treatment at 218° C., it was subjected to 7% relaxation treatment at 218° C., and then the surface of the side to be dry-laminated with the linear low density polyethylene film was subjected to corona discharge treatment to obtain a biaxially oriented polyamide film. rice field. Table 1 shows the evaluation results of the obtained biaxially stretched polyamide film.

(ONY2 to ONY13)
A biaxially stretched film was obtained in the same manner as ONY1 except that the film-forming conditions such as the raw material resin composition and the heat setting temperature were changed as shown in Table 1. Table 1 shows the evaluation results of the obtained biaxially stretched film. However, in ONY13, the molten resin could not be stably extruded in the form of a film from the T-die, and a homogeneous unstretched film could not be obtained, so biaxial stretching could not be performed.

Polyamide 410, polyamide 610, and polyamide 1010, which are polyamide resins at least partially containing raw materials derived from biomass, used the following.
Polyamide 410: (manufactured by DSM, ECOPaXX Q150-E, melting point 250°C)
Polyamide 610: (manufactured by Arkema, Rilsan S SMNO, melting point 222°C)
Polyamide 1010: (manufactured by Arkema, RilsanT TMNO, melting point 202°C)

[Production Example 2]
<Production of unstretched polyolefin film (CPP)>
(CPP1)
Based on the resin composition of each layer and its ratio shown in Table 2, raw materials were adjusted. With the content of each layer shown in Table 2 set to 100 parts by weight, 360 ppm of behenic acid amide as an organic lubricant and 2000 ppm of silica having an average particle size of 4 μm as an inorganic anti-blocking agent were added in a masterbatch to the sealing layer. did. A 2700 ppm masterbatch of behenic acid amide was added as an organic lubricant to the core layer.

(Raw material used in seal layer)
PP-1: Sumitomo Chemical propylene-ethylene-butene random copolymer FL6745A (MFR 6.0 g/10 min, melting point 130 ° C.)
LL-1: Braskem ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g/min, density 916 kg/m3, melting point 126° C.)
Silica particles: Shin-Etsu Chemical Co., Ltd. amorphous silica KMP130-4 (average particle size 4 μm)
Organic lubricant: Behenic acid amide BNT-22H manufactured by Nippon Fine Chemical Co., Ltd.

(Raw materials used in the core layer)
PP-2: Sumitomo Chemical propylene-ethylene-butene random copolymer FL8115A (MFR 7.0 g/10 min, melting point 148 ° C.)
PP-3: Propylene homopolymer FLX80E4 manufactured by Sumitomo Chemical Co., Ltd. (MFR 7.5 g/10 min, melting point 164° C.)
LL-1: Braskem ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g/min, density 916 kg/m3, melting point 126° C.)
LL-2: Sumitomo Chemical Co., Ltd. Ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0 g / min, density 923 kg / m3, melting point 118 ° C.)
LDPE-1: Braskem ethylene-hexene copolymer (plant-derived low-density polyethylene) SLH818 (MFR 8.1 g/min, density 918 kg/m3)
Organic lubricant: Behenic acid amide BNT-22H manufactured by Nippon Fine Chemical Co., Ltd.

(Raw materials used in laminate layer)
PP-2: Sumitomo Chemical propylene-ethylene-butene random copolymer FL8115A (MFR 7.0 g/10 min, melting point 148 ° C.)
PP-3: Propylene homopolymer FLX80E4 manufactured by Sumitomo Chemical Co., Ltd. (MFR 7.5 g/10 min, melting point 164° C.)
LL-1: Braskem ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g/min, density 916 kg/m3, melting point 126° C.)
LL-2: Sumitomo Chemical Co., Ltd. Ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0 g / min, density 923 kg / m3, melting point 118 ° C.)
LDPE-1: Braskem ethylene-hexene copolymer (plant-derived low-density polyethylene) SLH818 (MFR 8.1 g/min, density 918 kg/m3)
These raw materials were uniformly mixed at the ratios shown in Table 2 to obtain a mixed raw material for producing an unstretched polyolefin film.

A three-stage single screw extruder with a screw diameter of 90 mm is used for the mixed raw material used for the core layer, and a three-stage single screw extruder with a diameter of 65 mm and a diameter of 45 mm is used for the mixed raw material for the seal layer and the laminate layer, respectively. The resin is introduced in the order of layer/core layer/laminate layer, and the width of the resin is 800 mm, and the pre-land is divided into two stages. It was introduced into a T-slot type die designed as follows and extruded at a die outlet temperature of 230°C. The thickness ratios of the laminate layer/intermediate layer/heat seal layer were 25%/50%/25%, respectively.

The molten resin sheet discharged from the die was cooled with a cooling roll at 35° C. to obtain an unstretched polyolefin film having a thickness of 30 μm. When cooling on the cooling roll, both ends of the film on the cooling roll are fixed with air nozzles, the entire width of the molten resin sheet is pressed against the cooling roll with an air knife, and at the same time a vacuum chamber is applied between the molten resin sheet and the cooling roll. Prevents entrainment of air into Both ends of the air nozzle were installed in series in the film traveling direction. The die was surrounded by a sheet to prevent wind from hitting the molten resin sheet. Also, the direction of the suction port of the vacuum chamber was aligned with the traveling direction of the extruded sheet.

The surface of the laminate layer of the film was subjected to corona treatment (power density 20 W·min/m 2 ). The film forming speed was 20 m/min. The formed film was trimmed at the edges and wound into a roll.

(CPP2 to CPP14)
In CPP1, raw materials shown in Table 2 were used, and an unstretched polyolefin film having a thickness shown in Table 2 was obtained in the same manner.
However, for CPP12, the materials shown in Table 2 were used, and an unstretched polyolefin film with a single layer of 30 μm was obtained in the same manner using an extruder for the core layer only.
Table 2 shows the evaluation results of the films of CPP1 to 14.

[Examples and Comparative Examples]
<Preparation of heat-sealable laminated film>
The biaxially stretched polyamide film and the unstretched polyolefin film obtained in Production Examples 1 and 2 were mixed with 33.6 parts by mass of the main agent (TM569, manufactured by Toyo-Morton Co., Ltd.) and 4 parts of a curing agent (CAT10L, manufactured by Toyo-Morton Co., Ltd.). An ester adhesive obtained by mixing 0 parts by mass and 62.4 parts by mass of ethyl acetate was applied to the biaxially stretched polyamide film so that the coating amount was 3.0 g / m2, and dry laminated. did. After aging for 3 days at a temperature of 40° C., the heat-sealable laminated film was evaluated.
A heat-sealable laminated film was prepared by combining the biaxially stretched polyamide film and the unstretched polyolefin film shown in Table 3 and evaluated. Table 3 shows the results.

As shown in Table 3, the heat-sealable laminated films of Examples had good heat-seal strength, bending pinhole resistance, and drop bag breakage resistance even when the biomass content was increased.

On the other hand, the heat sealability using the biaxially stretched polyamide film containing no material that modifies the bending pinhole resistance of Comparative Examples 1 and 2 and the biaxially stretched polyamide film containing too little polyamide 11 of Comparative Example 3 The laminated film was inferior in bending pinhole resistance.
In Comparative Example 4, since linear low-density polyethylene was not added to the core layer and the laminate layer, the bending pinhole resistance was inferior.
In Comparative Examples 5 and 6, the difference in the content of linear low-density polyethylene between the seal layer and the core layer was large, so the heat seal strength was poor.
In Comparative Example 7, the content of the linear low-density polyethylene in the seal layer was large, so the heat seal strength was poor.
In Comparative Example 8, since a large amount of linear low-density polyethylene was contained over the entire film region, a large amount of linear low-density polyethylene was contained near the surface of the film, resulting in poor heat seal strength.
In Comparative Example 9, although the core layer contained linear low-density polyethylene, the lamination layer did not contain linear low-density polyethylene, and thus was inferior in bending pinhole resistance.
In Comparative Example 10, high-pressure low-density polyethylene (LDPE) was added as polyethylene, so the heat seal strength was poor.

The heat-sealable laminated film of the present invention is excellent in both impact resistance and bending pinhole resistance, and therefore can be suitably used for packaging materials such as food packaging.

Claims (7)

A heat-sealable laminated film having at least a substrate layer and a sealant layer,
The base material layer is a biaxially stretched polyamide film, and the biaxially stretched polyamide film contains 70 to 99% by mass of polyamide 6 as a polyamide resin, and 1 to 30% of polyamide whose raw material is at least partly derived from biomass. including % by mass,
The sealant layer is an unstretched polyolefin film, and the unstretched polyolefin film contains 70 to 95% by mass of a polypropylene resin and 5 to 5 to 5 of a linear low-density polypropylene resin in which at least part of the raw material is derived from biomass. A heat-sealable laminated film containing 30% by mass. 2. The heat-sealable laminated film according to claim 1, wherein the content of carbon 14 in the substrate layer is 1 to 30% with respect to the total carbon in the substrate layer. 3. The polyamide of which at least a part of the raw material in the base material layer is derived from biomass is at least one polyamide selected from the group consisting of polyamide 11, polyamide 410, polyamide 610, and polyamide 1010, according to claim 1 or 2 A heat-sealable laminate film as described. The heat-sealable laminated film according to any one of claims 1 to 3, wherein the content of carbon 14 in the sealant layer is 3 to 30% with respect to the total carbon in the sealant layer. The sealant layer has a seal layer, a core layer and a laminate layer,
The resin composition constituting the sealing layer contains 94 to 100% by mass of a propylene-α-olefin random copolymer and 0 to 3% by mass of linear low-density polyethylene,
The resin composition constituting the core layer contains 25 to 97% by mass of a propylene-α-olefin random copolymer and 3 to 40% by mass of linear low-density polyethylene,
The resin composition constituting the laminate layer contains 25 to 70% by mass of a propylene-α-olefin random copolymer and 3 to 50% by mass of linear low-density polyethylene,
The heat-sealable laminated film according to any one of claims 1 to 4, wherein the sealant layer includes a laminate layer, a core layer, and a seal layer in this order from the surface in contact with the base layer. The heat-sealable laminated film according to any one of claims 1 to 5, wherein the content of carbon 14 in the laminated film is 2 to 30% with respect to the total carbon in the laminated film. A package using the heat-sealable laminated film according to any one of claims 1 to 6.