JP2023163378A - Sealant film, packaging material, and package - Google Patents

Abstract

To provide a sealant film that is a polypropylene film but is superior in both heat resistance and low-temperature sealability.SOLUTION: A sealant film includes a first layer, which comprises a propylene homopolymer (A), a propylene/ethylene random copolymer (B), and a propylene/ethylene/α-olefin copolymer elastomer (C). The content of the propylene/ethylene/α-olefin copolymer elastomer (C) is 5.0-14.5 pts.mass relative to 100 pts.mass of the total amount of the propylene homopolymer (A) and the propylene/ethylene random copolymer (B).SELECTED DRAWING: Figure 1

Description

The present invention relates to a sealant film, a packaging material, and a packaging body. Specifically, the present invention provides a sealant film that is a polypropylene film but has excellent heat resistance and low-temperature sealing properties, and can be suitably used for packaging materials even in harsh treatments such as boiling water treatment and retort treatment. The present invention also relates to packaging materials and packaging bags obtained using the sealant film.

Polypropylene-based unstretched films have excellent rigidity and heat resistance, and are inexpensive, so they are sometimes used as sealant films in various packaging materials such as food packaging.

Patent Document 1 discloses that the polymer is selected from a crystalline propylene polymer having a melting point of 120 to 165°C, an ethylene/α-olefin copolymer, ethylene and an α-olefin having 3 to 20 carbon atoms, a cyclic olefin, or a cyclic polyene. A polypropylene film containing a copolymer with at least one kind has been proposed.

Patent Document 2 proposes a polypropylene film characterized by comprising a crystalline propylene/α-olefin random copolymer and an ethylene/α-olefin random copolymer.

Patent Document 3 discloses a polypropylene-based composite film composed of three layers, characterized in that the middle layer is made of a propylene-ethylene block copolymer and both surface layers are made of a propylene-based random copolymer. Composite films have been proposed.

Japanese Patent Application Publication No. 2003-119298 Japanese Patent Application Publication No. 2004-359711 Japanese Patent Application Publication No. 2017-132186

When used as a sealant film, a polypropylene-based unstretched film is required to have heat resistance that can withstand retort treatment, which involves sterilization and sterilization by pressure treatment at a high temperature of 135° C., which is a high retort condition.
Furthermore, in recent years, with the aim of improving the recyclability of packaging materials, studies have been progressing on packaging materials with a monomaterial structure using a biaxially oriented polypropylene film (OPP) base material and an unstretched polypropylene film. However, biaxially oriented polypropylene film has a lower melting point than biaxially oriented polyamide film (ONy), biaxially oriented polyester film (PET), etc. that have been conventionally used as base materials, so it cannot be used at high temperatures during bag making. There are circumstances that prevent heat sealing. Therefore, low-temperature sealing properties are also required for polypropylene-based unstretched films so that heat-sealing can be performed appropriately even if the heat-sealing temperature is lowered.
However, it is currently difficult to achieve both excellent heat resistance and low-temperature sealability with conventional unstretched polypropylene films.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sealant film that is a polypropylene film but can have both excellent heat resistance and low-temperature sealability. Another object of the present invention is to provide a packaging material and a packaging body obtained using the sealant film.

As a result of intensive studies to solve the above problems, we found that a predetermined amount of a propylene-ethylene-α-olefin copolymer elastomer was added to a resin composition containing a propylene homopolymer (A) and a propylene/ethylene random copolymer (B). The inventors discovered that it is important to include (C) and completed the present invention.

The sealant film according to one aspect of the present invention contains a propylene homopolymer (A), a propylene/ethylene random copolymer (B), and a propylene-ethylene-α-olefin copolymer elastomer (C), and includes a propylene- The content of the ethylene-α-olefin copolymer elastomer (C) is 5.0 to 14.0 parts by mass based on 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene/ethylene random copolymer (B). 5 parts by weight of the first layer.

The above-mentioned sealant film can have both excellent heat resistance and low-temperature sealability. Such effects can be obtained by copolymerization of a crystalline propylene polymer, an ethylene/α-olefin copolymer, and ethylene with at least one member selected from α-olefins having 3 to 20 carbon atoms, cyclic olefins, or cyclic polyenes. (For example, Patent Document 1 above), when using a resin composition comprising a crystalline propylene/α-olefin random copolymer and an ethylene/α-olefin random copolymer, This cannot be obtained when a propylene-based random copolymer is used in the surface layer (e.g., Patent Document 3). This effect is suitable for use as a packaging material for retorts.

In one embodiment, the mass ratio of the content of the propylene homopolymer (A) to the content of the propylene/ethylene random copolymer (B) is preferably in the range of 0.10 to 0.95. This makes it easier to obtain better low-temperature sealing properties while maintaining heat resistance.

In one embodiment, the sealant film may include the first layer and a second layer containing a propylene/ethylene block copolymer (D) and an ethylene/propylene copolymer elastomer (E). This makes it easy for the film to have excellent cold impact resistance.

In one embodiment, the sealant film includes the first layer, the second layer, and a third layer containing a propylene homopolymer (A) and a propylene/ethylene random copolymer (B). You can prepare in this order. Thereby, distortion and warping of the film can be easily suppressed.

In one embodiment, the second layer may contain 90 to 50% by mass of the propylene/ethylene block copolymer (D) and 10 to 50% by mass of the ethylene/propylene copolymer elastomer (E). This makes it easier for the film to obtain better cold impact resistance.

In one embodiment, the second layer may have a thickness of 20 μm or more. This makes it easier for the film to obtain better cold impact resistance.

A packaging material according to one aspect of the present invention includes the above sealant film and a resin film having a metal oxide vapor deposited layer.

A packaging material according to one aspect of the present invention includes the above sealant film and a biaxially stretched polypropylene film.

A package according to one aspect of the present invention is made from the above-mentioned packaging material.

According to the present invention, it is possible to provide a sealant film that is a polypropylene film but can achieve both excellent heat resistance and low-temperature sealability at a high level in a well-balanced manner. Moreover, according to the present invention, it is possible to provide a packaging material and a package obtained using the sealant film.

The sealant film of the present invention has heat resistance that can withstand retort treatment that performs sterilization and sterilization at a high temperature of 135°C, which is a high retort condition, and can be used with a biaxially oriented polypropylene film (OPP) base material. It also has excellent heat-sealable low-temperature sealability (even if the packaging material is made of the same material as polypropylene).

FIG. 1 is a cross-sectional view of a sealant film according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of a sealant film according to one embodiment of the present invention. FIG. 3 is a cross-sectional view of a sealant film according to one embodiment of the present invention. FIG. 4 is a sectional view of a packaging material according to an embodiment of the present invention. FIG. 5 is a sectional view of a packaging material according to an embodiment of the present invention. FIG. 6 is a sectional view of a packaging material according to an embodiment of the present invention.

<Sealant film 100>
FIG. 1 is a cross-sectional view of a sealant film 100 according to an embodiment of the invention. The sealant film 100 includes a first layer 10 containing a propylene homopolymer (A), a propylene/ethylene random copolymer (B), and a propylene-ethylene-α-olefin copolymer elastomer (C).

(Propylene homopolymer (A))
The propylene homopolymer (A) can be obtained by a method of homopolymerizing propylene using, for example, a Ziegler-Natta type catalyst, a metallocene catalyst, or a half metallocene catalyst. By containing the propylene homopolymer (A) in the sealant film, excellent heat resistance can be imparted to the first layer. This makes it difficult for fusion to occur on the inner surface of the packaging bag after the pressure and heat treatment is performed under high retort conditions of, for example, 135°C.

As the propylene homopolymer (A), one can be used that has a melting start temperature of 150° C. or higher and a melting point of 155° C. or higher when measured by differential scanning calorimetry (JIS K 7121). When both the melting start temperature and the melting point are within this range, superior heat resistance can be imparted to the first layer. This makes it more difficult for fusion to occur on the inner surface of the packaging bag after the pressure and heat treatment is performed under high retort conditions of, for example, 135°C. The conditions for differential scanning calorimetry are as follows.
[Differential scanning calorimetry conditions]
When the temperature is raised from 25°C to 230°C at a rate of 10°C/min, the straight line extending the low-temperature side baseline of the DSC curve to the high-temperature side touches the low-temperature side curve of the melting peak, and the slope is maximized. The point of intersection with the tangent line drawn on is the melting start temperature, and the temperature at the top of the melting peak is the melting point.

As the propylene homopolymer (A), one having a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 2.0 to 7.0 g/10 minutes can be used. . When the melt flow rate is equal to or higher than the lower limit, the load on the extruder during molding is reduced, the processing speed is less likely to decrease, and excellent productivity can be easily maintained. Moreover, since the melt flow rate is below the upper limit, the first layer tends to have excellent impact resistance.

(Propylene/ethylene random copolymer (B))
The propylene/ethylene random copolymer (B) can be obtained by copolymerizing ethylene as a comonomer into a main monomer consisting of propylene using, for example, a Ziegler-Natta type catalyst, a metallocene catalyst, or a half metallocene catalyst. . By containing the propylene/ethylene random copolymer (B) in the first layer, excellent low-temperature sealing properties can be easily obtained while maintaining heat resistance.

As the propylene/ethylene random copolymer (B), one having a melting point in the range of 132 to 150° C. when measured by differential scanning calorimetry (JIS K 7121) can be used. By using a material having a melting point within this range, it is easy to obtain excellent low-temperature sealing properties while maintaining heat resistance. The conditions for differential scanning calorimetry are as follows.
[Differential scanning calorimetry conditions]
The melting point is defined as the temperature at the top of the melting peak of the DSC curve when the temperature is raised from 25°C to 230°C at a rate of 10°C/min.

The ethylene content of the propylene/ethylene random copolymer (B) may be 6% by mass or less. When the ethylene content is below the upper limit, heat resistance is not likely to decrease excessively while maintaining low-temperature sealing properties. This makes it easier to suppress fusion on the inner surface of the packaging bag after the pressure and heat treatment under high retort conditions of 135°C. From this point of view, the ethylene content may be 5.5% by mass or less, and may be 4.5% by mass or less. The lower limit of the ethylene content is not particularly limited, but from the viewpoint of low-temperature sealing properties, it can be set to 3% by mass.

The ethylene content of the propylene/ethylene random copolymer (B) is listed on pages 412 to 413 of the Polymer Analysis Handbook (May 10, 2013, 3rd printing) edited by the Japan Society for Analytical Research, Polymer Analysis Roundtable. It can be measured according to the ethylene content quantitative method (IR method).

(Propylene-ethylene-α-olefin copolymer elastomer (C))
The propylene-ethylene-α-olefin copolymer elastomer (C) can be obtained by copolymerizing propylene, ethylene, and α-olefin using, for example, a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst. I can do it. By containing the propylene-ethylene-α-olefin copolymer elastomer (C) in the first layer, excellent low-temperature sealing properties can be obtained. Furthermore, since the first layer contains the propylene-ethylene-α-olefin copolymer elastomer (C), it is easy to obtain excellent bending whitening resistance and scratch resistance.

The propylene-ethylene-α-olefin copolymer elastomer (C) has a structural unit derived from propylene and ethylene and a structural unit derived from an α-olefin having 4 to 20 carbon atoms. An olefin copolymer elastomer can be used. This makes it easy to obtain excellent low-temperature sealing properties. The propylene-ethylene-α-olefin copolymer elastomer (C) may be a random copolymer.

Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-hexadecene, 1-eicosene, 4- Examples include methyl-1-pentene and 4-methyl-1-hexene. The α-olefin having 4 to 20 carbon atoms is preferably 1-butene or 1-hexene. The propylene-ethylene-α-olefin copolymer elastomer (C) may have two or more types of structural units derived from these α-olefins having 4 to 20 carbon atoms.

In the propylene-ethylene-α-olefin copolymer elastomer (C), the content of structural units derived from propylene is determined by the total amount of the propylene-ethylene-α-olefin copolymer elastomer (C) (total amount of structural units). It is possible to use 60 to 85% by weight, preferably 65 to 80% by weight based on 100% by weight. When the content of structural units derived from propylene is at least the lower limit, it is easy to maintain excellent heat resistance. Furthermore, when the content of structural units derived from propylene is below the upper limit, excellent low-temperature sealing properties can be easily obtained.

In the propylene-ethylene-α-olefin copolymer elastomer (C), the content of structural units derived from ethylene is determined by the total amount of the propylene-ethylene-α-olefin copolymer elastomer (C) (total amount of structural units). A content in the range of 1 to 10% by weight based on 100% by weight can be used. When the content of structural units derived from ethylene is at least the lower limit, low-temperature sealing properties can be easily obtained. Further, since the content of structural units derived from ethylene is below the upper limit, it is easy to suppress a decrease in heat resistance.

As for the propylene-ethylene-α-olefin copolymer elastomer (C), the content of structural units derived from α-olefin is the same as the total amount of the propylene-ethylene-α-olefin copolymer elastomer (C) (the content of structural units derived from α-olefin). Total amount) may be used in a range of 10 to 30% by mass based on 100% by mass. When the content of structural units derived from α-olefin is at least the lower limit, a low-temperature seal can be easily obtained. Furthermore, since the content of the structural unit derived from α-olefin is below the upper limit, it is easy to suppress a decrease in heat resistance.

As the propylene-ethylene-α-olefin copolymer elastomer (C), one having a density (JIS K 7112) in the range of 850 to 900 kg/m ³ can be used. When the density is at least the lower limit, the tackiness of the film can be suppressed. Furthermore, since the density is below the upper limit, low-temperature sealing properties can be easily obtained.

The propylene-ethylene-α-olefin copolymer elastomer (C) has a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) of 0.5 to 15 g/10 minutes, preferably A range of 1 to 10 g/10 minutes or 2 to 7 g/10 minutes can be used. When the melt flow rate is equal to or higher than the lower limit, the load on the extruder during molding is reduced, the processing speed is less likely to decrease, and excellent productivity can be easily maintained. Furthermore, when the melt flow rate is below the upper limit, compatibility with the propylene homopolymer (A) and the propylene/ethylene random copolymer (B) becomes good, and heat resistance is easily maintained.

The first layer consists of 5.0 parts of propylene-ethylene-α-olefin copolymer elastomer (C) per 100 parts by mass of the propylene homopolymer (A) and propylene/ethylene random copolymer (B). Contains ~14.5 parts by mass. When the content of the propylene-ethylene-α-olefin copolymer elastomer (C) is within the above range, low-temperature sealing properties can be easily obtained while maintaining excellent heat resistance. From the above viewpoint, the content may be 6.0 to 12.0 parts by mass, and may be 7.0 to 9.0 parts by mass.

In the first layer, the mass ratio (A)/(B) of the content of propylene homopolymer (A) to the content of propylene/ethylene random copolymer (B) is in the range of 0.10 to 0.95. It may be. When the mass ratio (A)/(B) is at least the lower limit, it is easy to maintain excellent heat resistance. Furthermore, when the mass ratio (A)/(B) is less than or equal to the upper limit value, excellent low-temperature sealing properties can be easily obtained. From this point of view, the mass ratio (A)/(B) may be from 0.30 to 0.94, and may be from 0.40 to 0.93.

<Sealant film 101>
FIG. 2 is a cross-sectional view of the sealant film 101 according to one embodiment of the present invention. The sealant film 101 includes a first layer 10 that is a heat seal layer, and a second layer 1 containing a propylene/ethylene block copolymer (D) and an ethylene/propylene copolymer elastomer (E). . By providing the second layer, the sealant film can easily obtain excellent cold impact resistance.

(Propylene/ethylene block copolymer (D))
The propylene-ethylene block copolymer (D) is produced by producing a propylene polymer (D1) in the first step, and then producing an ethylene-propylene copolymer (D2) by gas phase polymerization in the second step. It is a copolymer that can be obtained. The propylene/ethylene block copolymer (D) is not a block copolymer in which a propylene polymer terminal and an ethylene-propylene copolymer terminal are bonded together, but is a type of blend copolymer. By containing the propylene/ethylene block copolymer (D) in the second layer, excellent cold impact resistance can be easily obtained.

As the propylene/ethylene block copolymer (D), one whose melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) is in the range of 0.5 to 2.5 g/10 minutes is used. be able to. When the melt flow rate is equal to or higher than the lower limit, the load on the extruder during molding is reduced, the processing speed is less likely to decrease, and excellent productivity can be easily maintained. When the melt flow rate is below the upper limit, the second layer can easily obtain excellent cold impact resistance.

The propylene/ethylene block copolymer (D) may contain 90 to 60% by mass of the propylene polymer (D1) and 10 to 40% by mass of the ethylene-propylene copolymer (D2). By having each component within this range, it is easy to obtain excellent cold impact resistance. From this point of view, the propylene-ethylene block copolymer (D) contains 87.5-65% by mass of the propylene polymer (D1) and 12.5-35% by mass of the ethylene-propylene copolymer (D2). It may well contain 85-70% by weight of propylene polymer (D1) and 15-30% by weight of ethylene-propylene copolymer (D2).

The ethylene content of the ethylene-propylene copolymer (D2) is not particularly limited, but can be in the range of 20 to 40% by mass. When the ethylene content is below the upper limit, the tackiness of the product can be suppressed, and the product is less likely to be contaminated by tack during production, making it easy to maintain excellent productivity. When the ethylene content is at least the lower limit, it is easy to obtain excellent cold impact resistance.

(Ethylene-propylene copolymer elastomer (E))
The ethylene/propylene copolymer elastomer (E) can be produced by slurry polymerization in the presence of an inert hydrocarbon such as hexane, heptane, kerosene, or a liquefied α-olefin solvent such as propylene, or by gas phase polymerization without a solvent. It can be obtained legally. Specifically, the ethylene-propylene copolymer elastomer (E) is obtained using a known multistage polymerization method. That is, after polymerizing propylene and/or propylene-α-olefin polymer in the first stage reactor, a polymerized high rubber can be obtained by copolymerizing propylene and α-olefin in the second stage reaction. Contains polypropylene resin. By containing the ethylene-propylene copolymer elastomer (E) in the second layer, even better cold impact resistance can be easily obtained.

As the ethylene/propylene copolymer elastomer (E), one whose melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) is in the range of 0.5 to 3.5 g/10 minutes is used. be able to. When the melt flow rate is equal to or higher than the lower limit, the load on the extruder during molding is reduced, the processing speed is less likely to decrease, and excellent productivity can be easily maintained. When the melt flow rate is below the upper limit value, the compatibility between the propylene/ethylene block copolymer (D) and the ethylene/propylene copolymer elastomer (E) becomes good, and impact resistance is easily obtained.

As the ethylene/propylene copolymer elastomer (E), one having a mass ratio of propylene content to ethylene content (propylene content/ethylene content) in the range of 1.5 to 4 can be used. Within the above range, even better cold impact resistance can be easily obtained.

The second layer may contain 90-50% by weight of the propylene-ethylene block copolymer (D) and 10-50% by weight of the ethylene-propylene copolymer elastomer (E). When the content of the propylene/ethylene block copolymer (D) is 50% by mass or more, excellent heat resistance can be easily maintained. From this point of view, the content may be 60% by mass or more, and may be 70% by mass or more. The content of the propylene/ethylene block copolymer (D) is 90% by mass or less, that is, the content of the ethylene/propylene copolymer elastomer (E) is at least 10% by mass or more. It is possible to exhibit cold shock resistance. From this point of view, the content of the propylene/ethylene block copolymer (D) may be 87.5% by mass or less, and may be 85% by mass or less. From the above viewpoint, the content of the ethylene-propylene copolymer elastomer (E) may be 12.5 to 40% by mass, and may be 15 to 30% by mass.

<Sealant film 102>
FIG. 3 is a cross-sectional view of a sealant film 102 according to one embodiment of the invention. The sealant film 102 includes a first layer 10 that is a heat seal layer, a second layer 1, and a third layer 2 containing a propylene homopolymer (A) and a propylene/ethylene random copolymer (B). and are provided in this order. By providing the third layer, distortion and curling of the film can be easily suppressed.

Although there is no particular restriction on the mixing ratio (mass ratio) of the propylene homopolymer (A) and the propylene/ethylene random copolymer (B) in the third layer, the first layer is Preferably, the ratio is similar to that of the layers.

The sealant film is a non-stretched film and can be mainly composed of a polypropylene-based material, so it can be referred to as a polypropylene-based non-stretched film.

The thickness of the sealant film is not particularly limited as long as it can be used as a film for packaging materials, for example. However, if the film is too thick, there will be a cost disadvantage, so the thickness of the film can be 100 μm or less, and may be 50 to 70 μm.

The thickness percentage of the first layer in the sealant films 101 and 102 may be 8-30% based on the thickness of the sealant film. When the thickness ratio of the first layer is at least the lower limit value, it is easy to develop excellent heat-sealing strength, and when it is at most the upper limit value, it is easy to obtain cold impact resistance of the film and it is practical. It's easy to get caught. From this point of view, the thickness percentage of the first layer may be between 10 and 25%.

The thickness of the second layer in sealant films 101 and 102 may be 20 μm or more. This maintains the cold impact resistance of the film, making it difficult to break the bag even when stored at low temperatures. From this point of view, the thickness of the second layer may be greater than or equal to 25 μm, and may be greater than or equal to 30 μm. Although the upper limit of the thickness of the second layer is not particularly limited, it can be set to 50 μm since it is a cost disadvantage.

The percentage of the total thickness of the first layer and the third layer in the sealant film 102 may be 16-42% based on the thickness of the sealant film. When the ratio of the total thickness of the first layer and the third layer is at least the lower limit, it is easy to develop excellent heat sealing strength, and when it is at most the upper limit, it is easy to obtain cold impact resistance of the film. , it is easy to obtain practicality. From this point of view, the proportion of the total thickness of the first layer and the third layer may be 20-35%.

<Method for manufacturing sealant film>
The method for manufacturing the sealant film is not particularly limited, and any known method can be used.
For example, methods for thermoforming each of the first to third layers include a melt-kneading method using a general mixing machine such as a single-screw extruder, a twin-screw extruder, a multi-screw extruder, etc.; Examples include a method of dissolving or dispersing and mixing the components and then removing the solvent by heating. When workability is considered, a single screw extruder or a twin screw extruder can be used. When using a single-screw extruder, examples of the screw include a full-flight screw, a screw with a mixing element, a barrier-flight screw, a fluted screw, and the like, and these can be used without particular restriction. As the twin-screw kneading device, a co-rotating twin-screw extruder, a counter-rotating twin-screw extruder, etc. can be used, and the screw shape can be used without particular limitation, such as a full-flight screw or a kneading disk type. I can do it.

In the above method, each layer can be formed and laminated by melting the raw materials for each layer and then forming a film using a T-die through a feed block or multi-manifold.

The obtained sealant film may be subjected to a surface modification treatment to improve suitability for post-processing as necessary. For example, in order to improve the printability when using a single film or to improve the lamination suitability when using a laminated film, surface modification treatment may be performed on the printing surface or the surface that comes into contact with the base material. Examples of surface modification treatments include treatments that generate functional groups by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and flame treatment, and wet process modification treatments that form an easy-to-adhesion layer through coating. .

<Packaging material>
The packaging material includes the above sealant film. The packaging material may include only the above sealant film, or may further include other layers. The sealant film is provided in the packaging material so that the first layer, which is a heat-sealing layer, faces the contents.

<Packaging materials 200-202>
4 to 6 are cross-sectional views of packaging materials according to one embodiment of the present invention. In the packaging material 200, a sealant film 100 and a base material 4 are laminated with an adhesive layer 3 interposed therebetween. In the packaging material 201, a sealant film 101 and a base material 4 are laminated with an adhesive layer 3 interposed therebetween. In the packaging material 202, a sealant film 102 and a base material 4 are laminated with an adhesive layer 3 interposed therebetween.

As the base material, resin films such as biaxially oriented polyamide film (ONy), biaxially oriented polyester film (PET), biaxially oriented polypropylene film (OPP), etc., and metal oxide vapor deposited layers were provided on the surfaces of these resin films. Examples include a resin film (transparent vapor-deposited film) having a metal oxide vapor-deposited layer, printing paper, metal foil (AL foil), and the like. The base material may be a single layer of any of these materials, or may be a laminate comprising two or more of these materials. When the base material is a laminate, each layer may be laminated via an adhesive layer.

From the viewpoint of gas barrier properties of the packaging material, the base material may be a resin film having a metal oxide vapor deposited layer, that is, the packaging material may include a sealant film and a resin film having a metal oxide vapor deposited layer. I can do it. Examples of the metal oxide constituting the metal oxide vapor deposited layer include silicon oxide and aluminum oxide. From the viewpoint of protecting the metal oxide vapor deposited layer, the resin film may be laminated with the metal oxide vapor deposited layer facing the sealant layer side. The resin film may have metal oxide vapor deposited layers on both sides thereof.

From the viewpoint of recyclability of the packaging material, the base material can be a biaxially oriented polypropylene film, that is, the packaging material can include a sealant film and a biaxially oriented polypropylene film. A packaging material obtained using a biaxially stretched polypropylene film as a base material can be referred to as a packaging material made of the same material.

From the viewpoint of gas barrier properties and recyclability of the packaging material, the base material can be a laminate of a resin film having a metal oxide vapor-deposited layer and a biaxially oriented polypropylene film. A resin film having a substance vapor deposition layer and a biaxially stretched polypropylene film can be provided in this order. Particularly from the viewpoint of recyclability of the packaging material, the resin film having the metal oxide vapor-deposited layer may be a biaxially stretched polypropylene film having the metal oxide vapor-deposited layer.

As the material for the adhesive layer, for example, polyester-isocyanate resin, urethane resin, polyether resin, acid-modified polyolefin, etc. can be used.

The packaging material can be manufactured by a normal dry lamination method in which a sealant film and a base material are laminated via an adhesive layer as described above. However, the packaging material may be manufactured by a method of directly extruding and laminating a sealant film onto a base material.

The composition of the packaging material is determined according to the required characteristics of the package, such as barrier properties that satisfy the quality retention period of the food to be packaged, size and impact resistance that can accommodate the weight of the contents, visibility of the contents, recyclability, etc. It can be adjusted as appropriate.

<Package>
The package may be made into a bag from the above-mentioned packaging material, and there are no particular restrictions on the bag-making style. For example, the above packaging material (laminate) can be used for flat bags, three-sided bags, gassho bags, gusset bags, standing pouches, pouches with spouts, pouches with beaks, etc. that use a sealant film as a sealant.

<Overview of this embodiment>
[Invention 1]
Contains a propylene homopolymer (A), a propylene/ethylene random copolymer (B), and a propylene-ethylene-α-olefin copolymer elastomer (C),
The content of the propylene-ethylene-α-olefin copolymer elastomer (C) is 5 parts by mass based on 100 parts by mass of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B). .0 to 14.5 parts by weight of a first layer.
[Invention 2]
The sealant film according to invention 1, wherein the mass ratio of the content of the propylene homopolymer (A) to the content of the propylene/ethylene random copolymer (B) is 0.10 to 0.95.
[Invention 3]
the first layer;
The sealant film according to invention 1 or 2, comprising a second layer containing a propylene/ethylene block copolymer (D) and an ethylene/propylene copolymer elastomer (E).
[Invention 4]
the first layer;
the second layer;
The sealant film according to invention 3, comprising a propylene homopolymer (A) and a third layer containing a propylene/ethylene random copolymer (B) in this order.
[Invention 5]
According to invention 3 or 4, the second layer contains 90 to 50% by mass of the propylene/ethylene block copolymer (D) and 10 to 50% by mass of the ethylene/propylene copolymer elastomer (E). sealant film.
[Invention 6]
The sealant film according to any one of inventions 3 to 5, wherein the second layer has a thickness of 20 μm or more.
[Invention 7]
A packaging material comprising the sealant film according to any one of inventions 1 to 6 and a resin film having a metal oxide vapor-deposited layer.
[Invention 8]
A packaging material comprising the sealant film according to any one of inventions 1 to 6 and a biaxially oriented polypropylene film.
[Invention 9]
A package made from the packaging material according to invention 7 or 8.

Hereinafter, the present invention will be explained in detail using Examples and Comparative Examples, but the present invention is not limited only to the following Examples.

<Preparation of sealant film>
(Example 1)
A propylene homopolymer (A), a propylene/ethylene random copolymer (B), and a propylene-ethylene-α-olefin copolymer elastomer (C) shown below were prepared.

(Propylene homopolymer (A))
When performing differential scanning calorimetry (JIS K 7121), the melting start temperature is 153 °C, the melting point is 159 °C, and the melt flow rate (MFR: ISO 1133) (temperature 230 °C, load 2.16 kg) is 3. .0 g/10 min of propylene homopolymer.

(Propylene/ethylene random copolymer (B))
A propylene/ethylene random copolymer having a melting point of 147°C and an ethylene content of 3.4% by mass when measured by differential scanning calorimetry (JIS K 7121).

The ethylene content can be measured using the method for quantifying ethylene content described on pages 412-413 of the Polymer Analysis Handbook (May 10, 2013, 3rd edition) edited by the Polymer Analysis Roundtable of the Japan Analytical Society. IR method).

(Propylene-ethylene-α-olefin copolymer elastomer (C))
Tafmer PN-3560 (trade name, manufactured by Mitsui Chemicals, Inc.), which is a propylene-ethylene-1-butene copolymer elastomer, was used. Melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) is 6.0 g/10 minutes, density is 866 kg/m ³ , content of structural units derived from propylene is 73% by mass, The content of structural units derived from ethylene was 5% by mass, and the content of structural units derived from 1-butene was 22% by mass.

After mixing 47.4 parts by mass of propylene homopolymer (A) and 52.6 parts by mass of propylene/ethylene random copolymer (B) in pellet form, the propylene homopolymer (A) and propylene/ethylene random copolymer A resin mixture was prepared in which 5.3 parts by mass of the propylene-ethylene-α-olefin copolymer elastomer (C) was mixed with 100 parts by mass of the total amount of the composite (B). Thereafter, the resin mixture was supplied to an extruder temperature-controlled at 250°C, kneaded in a molten state, and formed into a film with a thickness of 60 μm using a T-die extruder equipped with a feed block. , the sealant film of Example 1 was produced.

(Examples 2 to 5 and Comparative Examples 1 to 5)
A film was produced in the same manner as in Example 1, except that the mixing ratio of each raw material compound was changed as shown in Table 1.

(Example 6)
As materials used for the second layer, a propylene/ethylene block copolymer (D) and an ethylene/propylene copolymer elastomer (E) shown below were prepared.

(Propylene/ethylene block copolymer (D))
The melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) is 1.8 g/10 minutes, and the propylene polymer is 81.5% by mass and the ethylene-propylene copolymer is 18.5% by mass. A propylene/ethylene block copolymer containing 36.2% by weight of ethylene in the ethylene/propylene copolymer.

(Ethylene-propylene copolymer elastomer (E))
Both ethylene and propylene have a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) of 0.6 g/10 minutes and a propylene content/ethylene content mass ratio of 2.7. Polymeric elastomer.

For forming the first layer, 47.4 parts by mass of propylene homopolymer (A) and 52.6 parts by mass of propylene/ethylene random copolymer (B) were mixed in pellet form, and then the propylene homopolymer (A) was mixed in pellet form. ) and a total of 100 parts by mass of the propylene/ethylene random copolymer (B), and 5.3 parts by mass of the propylene-ethylene-α-olefin copolymer elastomer (C) were prepared to prepare a resin mixture.
For forming the second layer, a resin mixture was prepared in which 70% by mass of a propylene/ethylene block copolymer (D) and 30% by mass of an ethylene/propylene copolymer elastomer (E) were mixed in pellet form.
Each resin mixture was supplied to an extruder temperature-controlled at 250°C, kneaded in a molten state, and then processed into a T-die extruder with a feed block to form a first layer with a thickness of 15 μm and a second layer with a thickness of 15 μm. were laminated to have a thickness of 45 μm to produce the sealant film of Example 6.

(Example 7)
A film was produced in the same manner as in Example 6, except that the mixing ratio of each raw material compound was changed as shown in Table 2.

(Example 8)
A resin mixture prepared by mixing 47.4 parts by mass of propylene homopolymer (A) and 52.6 parts by mass of propylene/ethylene random copolymer (B) in pellet form for forming the first layer and the third layer. prepared. Only in the resin mixture for forming the first layer, propylene-ethylene-α-olefin copolymer was added to 100 parts by mass of the total amount of propylene homopolymer (A) and propylene/ethylene random copolymer (B). 5.3 parts by mass of elastomer (C) was added.
For forming the second layer, a resin mixture was prepared in which 70% by mass of a propylene/ethylene block copolymer (D) and 30% by mass of an ethylene/propylene copolymer elastomer (E) were mixed in pellet form.
Each resin mixture is supplied to an extruder temperature-controlled at 250°C, kneaded in a molten state, and then passed through a T-die extruder equipped with a feed block until the thickness of the first layer and the third layer are adjusted respectively. The sealant film of Example 8 was produced by laminating the first layer to have a thickness of 10 μm and the second layer having a thickness of 40 μm.

(Example 9)
A film was produced in the same manner as in Example 8, except that the mixing ratio of each raw material compound was changed as shown in Table 2.

(Comparative Examples 6-7)
A film was produced in the same manner as in Example 6, except that the mixing ratio of each raw material compound was changed as shown in Table 2.

(Comparative Examples 8-9)
A film was produced in the same manner as in Example 8, except that the mixing ratio of each raw material compound was changed as shown in Table 2.

<Various evaluations>
The films obtained in each example were evaluated as follows. The results are shown in Tables 1 and 2.

[Low temperature sealability evaluation]
The films obtained in each example (the first layer if the film is a laminate) were placed facing each other, and sealed using a heat sealer manufactured by Tester Sangyo Co., Ltd. at a sealing pressure of 0.2 MPa and a sealing time of 1 second. Heat sealing was performed under the condition that the width was 5 mm. The sealing temperature was adjusted in 2°C increments between 140°C and 160°C. Thereafter, the films heat-sealed at each temperature were cut into 15 mm wide x 80 mm pieces, and T-peel was performed at a tensile speed of 300 mm/min using a tensile testing machine manufactured by Shimadzu Corporation. Seal strength was measured. The temperature at which the heat seal strength reached 15 N/15 mm or more was defined as the heat seal start-up temperature, and it was determined that the lower the heat seal start-up temperature, the better the low-temperature sealability.

[Heat resistance evaluation]
The films obtained in each example (the first layer if the film is a laminate) were placed facing each other, and sealed using a heat sealer manufactured by Tester Sangyo Co., Ltd. at a sealing pressure of 0.05 MPa and a sealing time of 30 seconds. Heat sealing was performed under conditions of a width of 10 mm and a sealing temperature of 135°C. After that, the heat-sealed film was cut into 15 mm width x 80 mm, and T-peel was performed at a tensile speed of 300 mm/min using a tensile tester manufactured by Shimadzu Corporation to test the thermal bonding strength of the heat-sealed part. It was measured. It was determined that the heat resistance was good if the heat fusion strength was 2.0 N/15 mm or less.

Although the sealant film of the present invention is a polypropylene film, it can achieve both high levels of heat resistance and low-temperature sealability. Therefore, the sealant film of the present invention can be suitably used in polypropylene monomaterial packaging materials (retort packaging materials).

DESCRIPTION OF SYMBOLS 1...Second layer, 2...Third layer, 3...Adhesive layer, 4...Base material, 10...First layer, 100-102...Sealant film, 200-202...Packaging material.

Claims (12)

Contains a propylene homopolymer (A), a propylene/ethylene random copolymer (B), and a propylene-ethylene-α-olefin copolymer elastomer (C),
The content of the propylene-ethylene-α-olefin copolymer elastomer (C) is 5 parts by mass based on 100 parts by mass of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B). .0 to 14.5 parts by weight of a first layer. The sealant film according to claim 1, wherein the mass ratio of the content of the propylene homopolymer (A) to the content of the propylene/ethylene random copolymer (B) is 0.10 to 0.95. the first layer;
The sealant film according to claim 1, comprising a second layer containing a propylene/ethylene block copolymer (D) and an ethylene/propylene copolymer elastomer (E). the first layer;
the second layer;
The sealant film according to claim 3, comprising a propylene homopolymer (A) and a third layer containing a propylene/ethylene random copolymer (B) in this order. 4. The second layer contains 90 to 50% by mass of the propylene/ethylene block copolymer (D) and 10 to 50% by mass of the ethylene/propylene copolymer elastomer (E). Sealant film. 5. The second layer contains 90 to 50% by mass of the propylene/ethylene block copolymer (D) and 10 to 50% by mass of the ethylene/propylene copolymer elastomer (E). Sealant film. The sealant film according to claim 3, wherein the second layer has a thickness of 20 μm or more. The sealant film according to claim 4, wherein the second layer has a thickness of 20 μm or more. A packaging material comprising the sealant film according to any one of claims 1 to 8 and a resin film having a metal oxide vapor deposited layer. A packaging material comprising the sealant film according to any one of claims 1 to 8 and a biaxially oriented polypropylene film. A package made from the packaging material according to claim 9. A package made from the packaging material according to claim 10.

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