JP6863085B2 - Sealant film and packaging material - Google Patents

Description

The present invention is a sealant film used for retort packaging that can be sterilized and cooked by heating or pressurizing while food or the like is packaged, particularly retort packaging for range-up that can be heated in a microwave oven, and the sealant film. Regarding packaging materials using.

Flexible packaging using plastic materials is used worldwide as a packaging material for foods, and it is showing an increasing trend as it spreads to emerging countries. Under these circumstances, retort foods that have been pressurized and heat sterilized (retort sterilized) at high temperatures are expected to grow in demand in the food packaging market in the future due to their convenience.

These retort pouch foods are easy to cook, but in recent years, the convenience has been further improved by using a so-called range-up compatible retort packaging material that can be heated in a microwave oven. As a packaging material for such a range-up, for example, a packaging bag for a microwave oven using a sealant having a high sealing strength at room temperature and a decrease in sealing strength at high temperature is disclosed (Patent Documents 1 and 2). reference).

Japanese Unexamined Patent Publication No. 2013-079085 Japanese Unexamined Patent Publication No. 2013-079086

Since the sealant strength decreases at high temperatures, the sealant peels off due to internal pressure when heated in a microwave oven, and the internal pressure inside the packaging bag is reduced, so that the contents are safe without spilling during cooking in a microwave oven. It is disclosed that a cookable packaging bag can be formed. However, if the cuttability of the packaging bag is poor after cooking, the contents that have become hot at the time of opening are likely to scatter or spill. Therefore, in the case of microwave-compatible packaging materials, when cooking in a microwave oven, It has been required to have not only the suitability for removing steam but also the suitable tearability for easy opening.

An object to be solved by the present invention is to provide a sealant film having a suitable sealing property at room temperature, a steam bleeding property during cooking, and an excellent tearability.

Further, in the present invention, in addition to the above problems, it is an object to provide a laminated film having suitable bag breaking resistance.

In the present invention, one surface layer is a heat-sealing inner layer (A) and the other surface layer is an outer layer (B), and the inner layer (A) is a propylene-based block copolymer resin. The outer layer (B) contains 90% by mass or more of (a1) in the resin component, and the outer layer (B) contains 70% by mass or more of the propylene-based block copolymer resin (b1) in the resin component. When the contained propylene-based block copolymer resin (b1) is molded into a thickness of 60 μm on a cooling roll at 40 ° C. by the T-die film forming method, the cloudiness of the contained propylene-based block copolymer resin (b1) is 35% or less. Provided is a sealant film which is a coalesced resin.

The sealant film of the present invention has a suitable sealing property at room temperature due to the above configuration, and also has a suitable steam bleeding property during cooking, so that it can be suitably applied to a packaging material compatible with a microwave oven. Further, since it has a suitable straight-line cut property, it is likely to be torn in one direction, and it has a suitable tear property in which the tear strength is less likely to vary even after the tear is generated. Further, while realizing the suitable tearability, it is possible to realize the suitable sealing property without significantly increasing the sealing start temperature. Therefore, the packaging bag using the sealant film of the present invention is less likely to spill or scatter the contents at the time of opening or after the opening starts to occur.

Therefore, the sealant film of the present invention can be suitably used for packaging applications such as various foods, particularly as a sealant film for microwave oven-compatible retort packaging materials. Further, it is suitable for these applications because it is easy to realize suitable bag breaking resistance.

The sealant film of the present invention is a sealant film in which one surface layer is a heat-sealing inner layer (A) and the other surface layer is an outer layer (B), and the inner layer (A) is a propylene-based block co-weight. The combined resin (a1) is contained in an amount of 90% by mass or more in the resin component, and the outer layer (B) contains a propylene-based block copolymer resin (b1) in an amount of 70% by mass or more in the resin component. ) Is formed so that the propylene-based block copolymer resin (b1) has a thickness of 60 μm on a cooling roll at 40 ° C. in the T-die film forming method, and the degree of cloudiness is 35% or less. It is a sealant film which is a copolymer resin.

(Inner layer (A))
The inner layer (A) of the sealant film of the present invention is a heat-sealable layer, and is a layer containing 90% by mass or more of the propylene-based block copolymer resin (a1) in the resin component. In the present invention, by using the inner layer, it is possible to realize a high sealing property at room temperature without impairing the cut property, and an excellent steam in which the sealing layer is suitably destroyed by the internal pressure at the time of high temperature heating. Achieves pulling suitability.

As the propylene-based block copolymer resin (a1), a resin containing propylene and another α-olefin can be used. Examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. Among them, ethylene is preferable because it has excellent heat resistance and impact resistance. The propylene-ethylene block copolymer is not particularly limited, but is obtained, for example, by polymerizing a polymer block mainly composed of propylene in the first step and polymerizing a copolymer block of ethylene and propylene in the second step. Be done.

The α-olefin content in the propylene-based block copolymer resin (a1) is preferably 6 to 20 mol%, preferably 8 to 17 mol%, because impact resistance and heat seal strength can be easily obtained. Is more preferable.

The melting point of the propylene-based block copolymer resin (a1) is preferably 155 to 165 ° C., more preferably 157 to 163 ° C., in view of the balance between heat resistance and impact resistance.

The melt flow rate (MFR) of the propylene-based block copolymer resin (a1) is 0.5 to 10 g / 10 minutes (230 ° C., 21 minutes) because it is easy to mold and it is easy to obtain suitable impact resistance. It is preferably .18N), more preferably 2 to 5 g / 10 minutes.

The melt tension of the propylene-based block copolymer resin (a1) is preferably 0.006N to 0.05N, more preferably 0.007N to 0.045N, and 0.009N to 0.009N at 230 ° C. It is particularly preferably 0.04N. When the melt tension is within this range, the film forming property in various film forming methods such as the T-die method and the inflation method is excellent. The value of the melt tension can be measured by, for example, Capillograph manufactured by Toyo Seiki Co., Ltd. At this time, a piston speed of 20 mm / min and a capillary having a length of 40 mm and a diameter of 2 mm are used.

The propylene-based block copolymer resin (a1) used in the present invention has a degree of cloudiness when a molten resin is extruded from a T-die and cooled at a cooling roll temperature of 60 ° C. to form a single-layer film having a thickness of 60 μm. Is 30% or more, preferably 35% or more, and more preferably 40% or more of the propylene-based block copolymer resin. The propylene-based block copolymer resin is a resin containing propylene and other elastomer components such as α-olefin, and it is presumed that the elastomer-based domain of the resin having a degree of cloudiness is relatively large. .. Therefore, in the packaging material having the propylene-based block copolymer as the inner layer, the inner layer is likely to be smoothly broken when the internal pressure is increased by heating, and it is easy to realize particularly suitable steam removal suitability. The degree of cloudiness is measured based on JIS K7105.

The content of the propylene-based block copolymer resin (a1) in the resin component contained in the inner layer (A) is 90% by mass or more, preferably 95% by mass or more, and more preferably 97% by mass or more. By setting the content of the propylene-based block copolymer resin (a1) in the above range, it is possible to suitably realize suitable sealing properties at room temperature and suitable steam removal. When the inner layer has a multi-layer structure, the content of the propylene-based block copolymer resin (a1) in the inner layer is preferably in the above range.

In the sealant film of the present invention, it is preferable to use only the propylene-based block copolymer resin (a1) as the resin component of the inner layer (A), but other resins may be used in combination. Examples of the other resin include a propylene homopolymer, a propylene-α-olefin random copolymer (propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, metallocene). Polypropylene resin such as catalytic polypropylene, ultra-low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE) and other polyethylene resins, ethylene-vinyl acetate copolymer (EVA), ethylene -Methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH) ), Ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA) and other ethylene-based copolymers; Ionomer and the like.

Among them, ethylene-based elastomers, particularly copolymers of ethylene and α-olefins having 3 to 8 carbon atoms, can be preferably used because they have high vapor removal suitability and impact resistance. Further, the polypropylene resin having a high melt tension tends to improve the steam release suitability and the tearability. As these ethylene-based elastomers and polypropylene resins, for example, those described later can be preferably used.

When the other resin is used, the content of the other resin is 10% by mass, preferably 5% by mass or less, more preferably 1 to 3% by mass in the resin component contained in the inner layer (A). To do. Within this range, it becomes easy to improve steam removal suitability, impact resistance, and the like.

Various additives may be blended in the inner layer (A) as long as the effects of the present invention are not impaired. Examples of the additive include antioxidants, weather stabilizers, antistatic agents, antifogging agents, antiblocking agents, lubricants, nucleating agents, pigments and the like.

(Outer layer (B))
The outer layer (B) of the sealant film of the present invention is a propylene-based block copolymer resin having a cloudiness of 35% or less when molded to a thickness of 60 μm on a cooling roll at 40 ° C. in the T-die film forming method. (B1) is a layer containing 70% by mass or more of the resin component. In the present invention, by laminating the outer layer (B) on the inner layer (A), it is possible to realize a suitable tearing property as well as a sealing property at room temperature and a steam bleeding property.

As the propylene-based block copolymer resin (b1) used for the outer layer (B), a resin containing propylene and another α-olefin can be used as in the above (a1). Examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. Among them, ethylene is preferable because it has excellent heat resistance and impact resistance. The propylene-ethylene block copolymer is not particularly limited, but is obtained, for example, by polymerizing a polymer block mainly composed of propylene in the first step and polymerizing a copolymer block of ethylene and propylene in the second step. Be done.

The α-olefin content in the propylene-based block copolymer resin (b1) is preferably 6 to 20 mol%, preferably 8 to 17 mol%, because impact resistance and heat seal strength can be easily obtained. Is more preferable.

The melting point of the propylene-based block copolymer resin (b1) is preferably 155 to 165 ° C., more preferably 157 to 163 ° C., in view of the balance between heat resistance and impact resistance.

The melt flow rate (MFR) of the propylene-based block copolymer resin (b1) is 0.5 to 10 g / 10 minutes (230 ° C., 21 minutes) because it is easy to mold and it is easy to obtain suitable impact resistance. It is preferably .18N), more preferably 2 to 5 g / 10 minutes.

The melt tension of the propylene-based block copolymer resin (b1) is preferably 0.006N to 0.05N, more preferably 0.007N to 0.045N, and 0.009N to 0.009N at 230 ° C. It is particularly preferably 0.04N. When the melt tension is within this range, the film forming property in various film forming methods such as the T-die method and the inflation method is excellent.

The propylene-based block copolymer resin (b1) used in the present invention has a degree of cloudiness when a molten resin is extruded from a T-die and cooled at a cooling roll temperature of 60 ° C. to form a single-layer film having a thickness of 60 μm. Is 35% or less, preferably 30% or less, and more preferably 25% or less of the propylene-based block copolymer resin. The propylene-based block copolymer resin is a resin containing propylene and other elastomer components such as α-olefin, and the elastomer-based domain of the resin having a degree of cloudiness is finely dispersed, preferably in the form of streaks. It is a resin that is in a phase state. Therefore, it is presumed that the straightness at the time of tearing is less likely to be impaired with respect to the resin in the phase state in which a large domain is dispersed, and the resin can be preferably torn. The degree of cloudiness is measured based on JIS K7105.

The outer layer (B) contains 70% by mass or more of the propylene-based block copolymer resin (b1) in the resin component contained in the outer layer (B). Within this range, it is possible to realize suitable heat resistance and rupture resistance as well as tearing property suitable for a packaging bag. The content is preferably 75% by mass or more, and more preferably 85% by mass or more in the resin component. When the outer layer (B) has a multi-layer structure, it is preferable that the content of the propylene-based block copolymer resin (b1) in each layer is within the above range.

As the resin component used for the outer layer (B), it is preferable to use only the propylene-based block copolymer resin (b1), but it is also preferable to use the high melt tension polypropylene resin (b2) in combination. The high melt tension polypropylene resin (b2) has a structure in which a long chain branch is introduced into the main chain of the polypropylene resin or a crosslinked structure, and has an increased tension at the time of melting. By containing the polypropylene resin having a high melt tension, the rigidity of the film is increased by the orientation crystallization and the ease of tearing is promoted. In particular, when a film is formed by the inflation method, it is preferable in that stable film formation is possible even with a polypropylene-based resin, which has been difficult to form by inflation due to the weak melt tension in the past.

The content of the high melt tension polypropylene resin (b2) is preferably 0.1 to 30% by mass or less, more preferably 1 to 25% by mass, in the resin component contained in the outer layer (B). It is more preferably 2 to 20% by mass. Within the above range, it becomes easy to realize suitable film forming property and impact resistance.

The composition of the high melt tension polypropylene resin (b2) may be any of a propylene homopolymer, a propylene-ethylene random copolymer, or a propylene-ethylene block copolymer, but in terms of heat resistance, the propylene homopolymer Type is preferred. The melt flow rate (MFR) is preferably 0.1 to 18 g / 10 minutes (230 ° C., 21.18 N), more preferably 0.5 to 8 g / 10 minutes (230 ° C., 21.18 N), 0.8. ~ 6.0 g / 10 minutes (230 ° C., 21.18 N) is more preferable. It becomes easy to obtain suitable film forming properties and good compatibility with propylene-based block copolymers. The melt tension (230 ° C.) is preferably 0.05 to 0.4 N, more preferably 0.1 to 0.3 N.

It is also preferable to use a resin other than the above resin in combination with the outer layer (B). Examples of the other resin include a propylene homopolymer, a propylene-α-olefin random copolymer (propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, metallocene). Catalytic polypropylene, etc.), ultra-low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE) and other polyethylene resins, ethylene-vinyl acetate copolymer (EVA), ethylene-methylmetha Acrylic copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene Ethylene-based copolymers such as −acrylic acid copolymer (EAA) and ethylene-methacrylic acid copolymer (EMAA); further, ionomers of ethylene-acrylic acid copolymers, ionomers of ethylene-methacrylic acid copolymers and the like. Can be mentioned.

Among them, ethylene-based elastomers, particularly copolymers of ethylene and α-olefins having 3 to 8 carbon atoms, are preferably used because they have good compatibility with propylene-based block copolymers and have high impact resistance. it can.

When the other resin is used, the content of the other resin in the outer layer (B) is preferably 20% by mass or less, preferably 15% by mass or less in the resin component contained in the sealant film. Is even more preferable. The lower limit is not particularly limited, but is preferably 2% by mass or more, and more preferably 5% by mass or more. Within this range, it is easy to improve the impact resistance, and it is easy to obtain good heat resistance and rigidity.

The melt flow rate (MFR) of the ethylene-based elastomer is preferably 0.5 to 10 g / 10 minutes (190 ° C., 21.18 N), but is 3 to 10 g / 10 minutes because suitable tearability can be easily obtained. Is more preferable. In addition, it becomes easy to obtain good moldability when blended with a propylene-based block copolymer.

The density of the ethylene-based elastomer is preferably in the range of ^{0.870 to 0.943 g / cm 3.} It may be appropriately selected according to the purpose of modifying the propylene-based block copolymer, such as impact resistance or both impact resistance and rigidity. Particularly when it is desired to improve the impact resistance, it is preferably 0.870~0.910g / cm ^3, if you want particularly increase the rigidity is 0.910~0.943g / cm ³ preferable.

As described above, various resins can be appropriately used in the outer layer (B), but the melt tension of the melt-blended resin is 0.01 to 0.05 N because it is easy to obtain suitable tearability and vapor removal suitability. It is preferably 0.015 to 0.03N, more preferably 0.015 to 0.03N.

Various additives may be blended in the outer layer (B) as long as the effects of the present invention are not impaired. Examples of the additive include antioxidants, weather stabilizers, antistatic agents, antifogging agents, antiblocking agents, lubricants, nucleating agents, pigments and the like.

[Sealant film]
The sealant film of the present invention is a sealant film in which the inner layer (A) and the outer layer (B) form each surface layer, and the inner layer (A) has a heat-sealing property. The inner layer (A) and the outer layer (B) are usually single layers, but may have a multi-layer structure in which the resin compositions forming the inner layer (A) or the outer layer (B) are extruded by different extruders and laminated.

The sealant film of the present invention may have an intermediate layer (C) between the inner layer (A) and the outer layer (B). As the intermediate layer (C), any layer may be provided according to desired characteristics, and a plurality of layers having different characteristics or formulations may be provided. As the intermediate layer (C), for example, a layer containing an olefin resin can be preferably used, and suitable sealing properties, tearing properties, and vapor removal suitability can be easily obtained. A similar layer is preferable, and a layer similar to the outer layer (B) is particularly preferable.

As an example of a preferable configuration of the sealant film of the present invention, since it is easy to control the surface texture of both surface layers, a two-layer sealant film ((A) / (B) in which an inner layer (A) and an outer layer (B) are laminated is formed. )), And a three-layer sealant film ((A) / (C) / (B)) in which the inner layer (A), the intermediate layer (C), and the outer layer (B) are laminated can be exemplified. As described above, the inner layer (A) and the outer layer (B) in the configuration may be laminated by extruding the resin composition forming the inner layer (A) or the outer layer (B) with different extruders. ..

The sealant film of the present invention has an orientation function measured by infrared absorption (IR) of 0.05 to 0.6, preferably 0.1 to 0.5, more preferably 0.2 to 0.4. is there. Within the range of the orientation function, a suitable straight-line cut property at the time of film tearing can be obtained even though the orientation is weak, and since strong orientation does not occur due to stretching, the influence of high seal temperature is unlikely to occur, which is preferable. Easy heat sealing can be achieved.

The orientation function is the degree of orientation measured by the infrared absorption method (IR). Specifically, the following formula is used from the infrared dichroic ratio (D) measured using a transmission infrared spectrophotometer. It is calculated from.
Orientation F = (Dmax-1) / (Dmin + 2)
Dmax: Maximum transmittance measured by rotating the polarizer Dmin: Minimum transmittance measured in the same manner The value is calculated using absorption at ^{997 cm -1.}

The thickness of the sealant film of the present invention may be appropriately adjusted according to the intended use and mode, but it is easy to obtain suitable heat resistance for packaging applications, bag tear resistance during distribution, heat sealability, etc. The total thickness is preferably 20 to 150 μm, more preferably 40 to 100 μm.

As for the thickness of each layer, the thickness of the inner layer (A) is preferably 2 to 75 μm, preferably 5 to 30 μm, because it is easy to obtain suitable sealing properties and vapor venting properties without impairing the tearability. More preferred. Further, the thickness of the outer layer (B) is preferably 18 to 148 μm, more preferably 25 to 75 μm, because it is easy to obtain suitable tearing property and bag breaking resistance.

It is preferable that the thickness of the inner layer (A) is 5 to 50% of the total thickness of the sealant film because the thickness ratio of each layer can be easily adjusted in terms of sealing property, vapor removal suitability, and tearability. It is preferably 10 to 40%, more preferably 20 to 30%. In particular, when the sealant film is composed of an inner layer (A) and an outer layer (B), the thickness ratio represented by the inner layer (A) / outer layer (B) is preferably 50/50 to 5/95. , 40/60 to 10/90, more preferably 30/70 to 20/80.

The sealant film of the present invention has a structure of being laminated with a biaxially stretched polyamide film having a thickness of 25 μm, and a test piece heat-sealed with the sealant films of the present invention inside each other is heated at 121 ° C. for 30 minutes and then at room temperature ( The seal strength measured at 23 ° C.) is preferably 23 N / 15 mm or more. It is more preferably 30 N / 15 mm or more, and further preferably 40 N / 15 mm or more. The upper limit of the seal strength is not particularly limited, but is preferably about 100 N / 15 mm. By setting the heat seal strength at room temperature within this range, it can be safely distributed as a packaging material for retort pouches without breaking the bag. Further, it is preferable that the test piece obtained by heat-sealing the similarly prepared laminate film has a sealing strength in the range of 2 to 15 N / 15 mm measured in an atmosphere of 100 ° C. More preferably, it is 2 to 10 N / 15 mm, and particularly preferably 3 to 8 N / 15 mm. If the sealing strength in an atmosphere of 100 ° C is less than 2N / 15mm, peeling easily occurs from a place other than the steam bleeding mechanism part at the time of range up, and if it exceeds 15N / 15mm, steam bleeding occurs quickly. It may explode. When the sealing strength in an atmosphere of 100 ° C. is within the above range, steam can be released quickly and smoothly.

The method for producing the sealant film used in the present invention is not particularly limited, but for example, the resin used for each layer of the multilayer film (including a resin mixture containing two or more kinds of resins and additives) is used in separate extruders. Examples thereof include a co-extrusion method in which the mixture is heated and melted, laminated in a molten state by a method such as a co-extrusion multi-layer die method or a feed block method, and then formed into a film by an inflation method, a T-die chill roll method or the like. This coextrusion method is preferable because the thickness ratio of each layer can be adjusted relatively freely, and a film having excellent hygiene and excellent cost effectiveness can be obtained.

As a more preferable production method, it is preferable to produce by the inflation method because it is easy to control the range of the orientation function. As a manufacturing method using the inflation method, a resin for producing a film, or a resin used for each layer in the case of a multi-layer structure, is heated and melted by an extruder and coextruded into a film by an inflation method using a multi-layer circular die. It can be molded by doing.

As the inflation method, an air-cooled inflation method is preferable, and an upward air-cooled inflation method can be particularly preferably used. When the film is made into a single layer, one extruder and a single-layer circular die are used, and when the film is made into a multi-layer, a plurality of extruders and a multi-layer circular die are used. After extruding the cylindrical molten resin upward using these, the cylindrical molten resin is expanded and taken up as needed, and the molten resin is cooled and solidified by air cooling, and then appropriately cut to obtain the desired one. You can get the film.

In the present invention, it is preferable to adjust the magnification of stretching in the vertical direction and the horizontal direction with respect to the die gap and the desired film thickness by the air-cooled inflation method. As the magnification, it is preferable that the magnification stretched in the vertical direction (stretching magnification under air cooling when the molten resin is taken up) is 12 times or more, and 15 times or more, with respect to the outlet gap of the die. More preferably, it is more preferably 20 times or more, and particularly preferably 25 times or more. Further, the magnification stretched in the lateral direction is preferably 3 times or less, more preferably 2.5 times or less, further preferably 2 times or less, and preferably 1.5 times or less. Especially preferable. By setting the magnification in both directions within this range, it becomes easy to obtain suitable sealing property and straight-line cutting property. The upper limit of the magnification in the vertical direction and the lower limit of the stretching magnification in the horizontal direction are not particularly limited, but are preferably 80 times or less in the vertical direction and 1 time or more in the horizontal direction. The thickness of the die gap when extruding the molten resin is preferably 1 to 4 mm.

The blow ratio, which is a production condition in the inflation method, is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, and more preferably 1.1 to 2.0, from the above-mentioned magnification that is stretched in the lateral direction. It is more preferable to set it to 1.1 to 1.5, and it is particularly preferable to set it to 1.1 to 1.5. The line speed varies depending on the die diameter, the blow ratio, and the discharge amount, but is generally preferably 5 to 150 m / min. When the die diameter and the blow ratio are the same, the faster the line speed, the better the degree of orientation, which is preferable.

When the sealant film of the present invention is used as a packaging material for retort pouches, it can be used by being bonded to another base film. The other base film is not particularly limited, but from the viewpoint of easily exhibiting the effects of the present invention, it is preferable to use a plastic base film, particularly a biaxially stretched resin film. In addition, aluminum foil can be used in combination for applications that do not require transparency.

Examples of the stretched resin film include coextrusion with biaxially stretched polyester (PET), biaxially stretched polypropylene (OPP), biaxially stretched polyamide (PA), and ethylene vinyl alcohol copolymer (EVOH) as the central layer. Examples thereof include biaxially stretched polypropylene, biaxially stretched ethylene vinyl alcohol copolymer (EVOH), alumina vapor deposition PET, silica vapor deposition PET, alumina-silica dual vapor deposition PET, silica vapor deposition PA, and alumina vapor deposition PA. These may be used alone or in combination.

Two processing methods are mainly used as a method for laminating the sealant film of the present invention and various stretched base films. One is to apply an anchor coating agent to the laminated surface of the sealant film of the present invention or the base film as necessary, and heat-melt the polymer film (polyethylene, polypropylene, etc.) based on the sealant film of the present invention. This is an extrusion laminating method in which a thin film is extruded between the laminated surfaces of a material film, pressure-bonded, and laminated. The other is a dry laminating method in which an adhesive is applied to the laminated surface of the base film and then the sealant film of the present invention and the base film are pressure-bonded and laminated. However, when used for retort packaging, the dry laminating method is used. preferable.

Adhesives for laminating are generally cured with polyol / isocyanate, and are often used for high-performance applications such as retort applications. Conventionally, a combination of aluminum foil and a sealant film has been generally used for bonding, but various transparent vapor-deposited films are now on the market, and due to the demand for improving the visibility of the contents, the transparent vapor-deposited film The number of sealant films attached is also increasing.

Examples of the polyol used for the adhesive for lamination include the polyol itself described later, a polyester polyol obtained by reacting the polyol with polycarboxylic acids described later, ethylene glycol, diethylene glycol, triethylene glycol, and propylene glycol. Ethylene oxide, propylene oxide, butylene, starting from compounds having two active hydrogen atoms such as trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, etc. Examples thereof include polyesters obtained by addition-polymerizing monomers such as oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, and cyclohexylene.

Examples of the polyol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexane. Diol, neopentyl glycol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, bishydroxyethoxybenzene, 1,4-cyclohexanediol, 1 , 4-Cyclohexanedimethanol, triethylene glycol, polycaprolactone diol, dimerdiol, bisphenol A, glycols such as hydrogenated bisphenol A, propiolactone, butyrolactone, ε-caprolactone, δ-valerolactone, β-methyl-δ -Polyesters, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1 , 6-Hexanediol, neopentyl glycol and other compounds having two active hydrogen atoms were used as initiators, and monomers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran and cyclohexylene were added and polymerized. Polyethers and the like can be mentioned.

Examples of the polycarboxylic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecandicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and terephthal. Acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bis (phenoxy) ethane-p , P'-dicarboxylic acids and anhydrides or ester-forming derivatives of these dicarboxylic acids; p-hydroxybenzoic acid, p- (2-hydroxyethoxy) benzoic acid and ester-forming derivatives of these dihydroxycarboxylic acids, dimer acids, etc. Examples of polybasic acids.

Examples of the polyisocyanate include organic compounds having at least two isocyanate groups in the molecule. Examples of the organic polyisocyanate include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), lysine diisocyanate, trimethylhexamethylene diisocyanate, 1 , 3- (Isocyanatomethyl) cyclohexane, 1,5-naphthalenediocyanate, triphenylmethane triisocyanate and other polyisocyanates; adducts of these polyisocyanates, bullets of these polyisocyanates, or of these polyisocyanates Examples thereof include derivatives (modified products) of polyisocyanates such as isocyanurates.

Further, those obtained by reacting the isocyanate with the polyol at a mixing ratio in which the isocyanate group is excessive may be used.

In the adhesive, the equivalent ratio of the hydroxyl group equivalent of the polyol to the isocyanate equivalent of the polyisocyanate is preferably 0.5 to 5.0.

The packaging material of the present invention has a structure in which the sealant film is used as a sealant, so that in addition to good sealing property and steam bleeding suitability, good opening property due to suitable tearing property can be realized. Further, since suitable heat resistance and bag-breaking resistance can be realized, the packaging material formed by laminating the above-mentioned sealant film with various base materials is suitable as a packaging material for retort foods, particularly as a packaging material for microwave ovens. Can be applied to.

The packaging material of the present invention can be suitably used as a packaging bag by making a bag into various shapes such as a flat bag type, a self-supporting packaging bag (standing pouch) type, and a tube type. Specifically, for example, one film-shaped packaging material is folded so that the sealant layers face each other, or two film-shaped packaging materials of the present invention are overlapped so that the sealant layers face each other. The peripheral end can be heat-sealed and made into a packaging bag (retort pouch) for retort foods and the like. Further, if necessary, an opening start portion such as a V notch or an I notch may be provided.

Further, in the packaging bag using the packaging material of the present invention, it is preferable to provide a vapor venting portion. As the configuration of the steam venting portion, a known configuration, for example, a configuration disclosed in JP2013-079085, JP2013-079086, etc. can be appropriately used, and specifically, the body portion of the packaging bag can be used. An example is an example in which a punch hole is provided in the punch hole and a seal portion is provided to seal the periphery of the punch hole portion. In this configuration, by using the sealant film of the present invention at least in the portion that seals the periphery of the punched hole portion, suitable steam removal suitability can be realized.

The packaging material of the present invention and a packaging bag for retort foods using the packaging material can be suitably used for packaging foods that require treatment under high temperature hot water conditions such as boiling and retort sterilization. For example, curry and the like. It can be suitably applied to various retort food packaging applications such as stew, soup, and cooking sauce.

(Example 1)
Propylene-ethylene block copolymer (1) (haze 24% during film formation, MFR 2.5 g / 10 min (230 ° C, 21.18 N), melting point 163 ° C, melt tension 0.015 N) 97 parts by mass and ethylene- The resin for the inner layer (A) containing 3 parts by mass of the butene 1 random copolymer (1) (MFR 3.5 g / 10 min (190 ° C., 21.18 N), density 0.885 g / cm ^{3) is the first.} The resin for the outer layer (B) containing 100 parts by mass of the propylene-ethylene block copolymer (1) as a resin component is supplied to the second extruder and the third extruder at 250 ° C. Melted in. The molten resin is supplied to a T-die / chill-roll method co-extrusion multilayer film manufacturing apparatus (feed block and T-die temperature: 250 ° C.) having a feed block to perform melt extrusion of the copolymer, and the thickness of each layer is increased. An inner layer (A) / outer layer (B) = 12 μm / 48 μm (the thickness of the outer layer (B) is the total thickness of the layers supplied from the second and third extruders) was obtained.

(Example 2)
A sealant film was obtained in the same manner as in Example 1 except that the resin components used for the inner layer (A) and the outer layer (B) were as follows.
Inner layer (A): propylene-ethylene block copolymer (2) (haze 45% during film formation, MFR 2.0 g / 10 min (230 ° C, 21.18 N), melting point 161 ° C, melt tension 0.011 N) 100 Parts by mass Outer layer (B): propylene-ethylene block copolymer (1) 95 parts by mass, propylene homopolymer (1) (MFR 0.8 g / 10 min (230 ° C., 21.18 N), melting point 161 ° C., melt tension 0 .245N) 5 parts by mass, the melt tension of the resin in which the resin for the outer layer (B) was melt-blended was measured and found to be 0.019N.

(Example 3)
A sealant film was obtained in the same manner as in Example 2 except that the thickness of each layer was set to inner layer (A) / outer layer (B) = 21 μm / 39 μm.

(Example 4)
A sealant film was obtained in the same manner as in Example 2 except that the resin component used for the inner layer (A) was as follows.
Inner layer (A): 97 parts by mass of propylene-ethylene block copolymer (2), 3 parts by mass of propylene homopolymer (1)

(Example 5)
A sealant film was obtained in the same manner as in Example 2 except that the resin component used for the inner layer (A) was as follows.
Inner layer (A): propylene-ethylene block copolymer (2) 97 parts by mass, ethylene-butene 1 random copolymer (1) 3 parts by mass

(Example 6)
A sealant film was obtained in the same manner as in Example 2 except that the resin component used for the outer layer (B) was as follows.
Outer layer (B): 90 parts by mass of the propylene-ethylene block copolymer (1), 10 parts by mass of the propylene homopolymer (1), and the melt tension of the resin obtained by melt-blending the resin for the outer layer (B) are measured as 0. It was 021N.

(Example 7)
A sealant film was obtained in the same manner as in Example 2 except that the resin component used for the outer layer (B) was as follows.
Outer layer (B): propylene-ethylene block copolymer (3) (haze 12% at the time of film formation, MFR 4.0 g / 10 min (230 ° C., 21.18 N), melting point 162 ° C., melt tension 0.012 N) 85 Resin by mass, 15 parts by mass of propylene homopolymer (2) (MFR 3.3 g / 10 min (230 ° C., 21.18 N), melting point 161 ° C., melt tension 0.12 N), resin for outer layer (B) melt-blended When the melt tension of the above was measured, it was 0.018N.

(Example 8)
A sealant film was obtained in the same manner as in Example 2 except that the resin component used for the outer layer (B) was as follows.
Outer layer (B): 75 parts by mass of the propylene-ethylene block copolymer (3), 25 parts by mass of the propylene homopolymer (2), and the melt tension of the resin obtained by melt-blending the resin for the outer layer (B) are measured as 0. It was 025N.

(Example 9)
A sealant film was obtained in the same manner as in Example 8 except that the thickness of each layer was set to inner layer (A) / outer layer (B) = 21 μm / 39 μm.

(Example 10)
A sealant film was obtained in the same manner as in Example 8 except that the thickness of each layer was set to inner layer (A) / outer layer (B) = 30 μm / 30 μm.

(Example 11)
A resin for the inner layer (A) containing 97 parts by mass of the propylene-ethylene block copolymer (3) and 3 parts by mass of the ethylene-butene 1 random copolymer (1) was supplied to the first extruder. The resin for the outer layer (B) containing 95 parts by mass of the propylene-ethylene block copolymer (3) and 5 parts by mass of the propylene homopolymer (1) is used in the second extruder and the third extruder. It was fed and melted at 180-210 ° C. The molten resin is supplied to an air-cooled inflation coextrusion multilayer film manufacturing apparatus equipped with a spiral type three-layer die having a diameter of 200 mm and a die gap of 2 mm, and coextrusion is performed so that the blow ratio becomes 1.5. The sealant film having a thickness of each layer (A) / outer layer (B) = 12 μm / 48 μm (the thickness of the outer layer (B) is the total thickness of the layers supplied from the second and third extruders) is formed. Obtained. The melt tension of the resin obtained by melt-blending the resin for the outer layer (B) was measured and found to be 0.018 N.

(Example 12)
A sealant film was obtained in the same manner as in Example 11 except that the resin components used for the inner layer (A) and the outer layer (B) were as follows.
Inner layer (A): propylene-ethylene block copolymer (2) 100 parts by mass Outer layer (B): propylene-ethylene block copolymer (3) 95 parts by mass, propylene homopolymer (1) 5 parts by mass

(Example 13)
A sealant film was obtained in the same manner as in Example 2 except that the resin components used for the inner layer (A) and the outer layer (B) were as follows.
Inner layer (A): propylene-ethylene block copolymer (4) (haze 80% during film formation, MFR 2.0 g / 10 min (230 ° C, 21.18 N), melting point 164 ° C, melt tension 0.010 N) 97 Parts by mass, ethylene-butene 1 random copolymer (1) 3 parts by mass Outer layer (B): propylene-ethylene block copolymer (3) 75 parts by mass, propylene homopolymer (2) 15 parts by mass, ethylene-butene 1 Random copolymer (1) 10 parts by mass

(Comparative Example 1)
100 parts by mass of the propylene-ethylene block copolymer (2) resin was supplied to an extruder and melted, and the resin was used to produce a film having a thickness of 60 μm by the T-die chill roll method.

(Comparative Example 2)
A sealant film was obtained in the same manner as in Example 11 except that the resin components used for the inner layer (A) and the outer layer (B) were as follows.
Inner layer (A): 100 parts by mass of propylene-ethylene block copolymer (4) Outer layer (B): 100 parts by mass of propylene-ethylene block copolymer (4)

(Comparative Example 3)
A sealant film was obtained in the same manner as in Example 2 except that the resin component used for the inner layer (A) was as follows.
Inner layer (A): propylene-ethylene block copolymer (2) 85 parts by mass, propylene homopolymer (1) 15 parts by mass

(Comparative Example 4)
A sealant film was obtained in the same manner as in Example 2 except that the resin component used for the inner layer (A) was as follows.
Inner layer (A): propylene-ethylene block copolymer (2) 88 parts by mass, ethylene-butene 1 random copolymer (1) 12 parts by mass

The materials used in the above Examples and Comparative Examples and the obtained sealant film were evaluated as follows. The results obtained are shown in the table below.

(1) Haze value A propylene-ethylene block copolymer is supplied to an extruder having a diameter of 50 mm, melted at 250 ° C., and the melted resin is a film manufacturing apparatus (feed block and T-die chill roll method) having a feed block. It was supplied to a T-die temperature (250 ° C.) and melt-extruded to obtain a single-layer film having a total thickness of 60 μm at a cooling roll temperature of 40 ° C. The haze (cloudiness) of the obtained single-layer film was measured using a haze meter (manufactured by Nippon Denka Kogyo Co., Ltd.) based on JIS K7105 (unit:%).

(2) Degree of Orientation It was calculated from the following formula from the infrared dichroic ratio (D) measured using a transmission infrared spectrophotometer manufactured by JASCO Corporation.
Orientation F = (Dmax-1) / (Dmin + 2)
Dmax: Maximum transmittance measured by rotating the polarizer Dmin: Minimum transmittance measured in the same manner Also, it was calculated using absorption at ^{997 cm -1.}

(3) Tear strength The tear strength in the flow direction was measured in a thermostatic chamber at 23 ° C. and 50% Rh according to JIS K7128-1 (Truser method).
1.2N or less ◎: Excellent tearability 1.2-2.0N ○: Tearable but slightly heavy 2.0N or more ×: Inferior in tearability

(4) Straight cutability From the obtained sealant film, a test piece having a length of 150 mm in the flow direction and a length of 50 mm in the width direction was cut out, and a notch with a width of 15 mm was made in the center of the width direction by 10 mm, and the tip of the notch was cut. The width of was actually measured (W0). A polyester sheet having a thickness of 0.3 mm, a width of 15 mm, and a length of 160 mm prepared in advance was attached to the tip of the notch with tape. The pasted polyester sheet was folded back in the 180 ° direction, and the test piece excluding the notch on the opposite side to the tip was attached to the tensile tester, torn 100 mm at a speed of 300 mm / min, and the width of the end point was actually measured. (W1). Based on the obtained measured values, the retention rate was calculated from the following formula and used as an index of straight-line cutability.
Retention rate [%] = W1 / W0 × 100
100 ± 10% ◎: Excellent straightness cutability 100 ± 10 to 20% ○: Straight cutability but slightly inferior 100 ± 20% or more ×: No straightness

(5) Seal Strength A polyester adhesive was applied onto a biaxially stretched polyamide film having a thickness of 15 μm using a wire bar so that the coating thickness was 3.5 g / m ^2. After the adhesive was dried, the surface of the outer layer (A) of the sealant film obtained above was corona-treated and bonded, and dried at 40 ° C. for 24 hours to obtain a laminated film for testing. Using the obtained film, a test piece heat-sealed under the conditions of 190 ° C., 0.2 MPa, and 1 second was prepared, and heat-treated at 121 ° C. for 30 minutes using an autoclave. The test piece after the heat treatment was cut into a width of 15 mm, and the seal strength was measured with a tensile tester. Those having a thickness of 30 N / 15 mm or more were evaluated to have good sealing strength in packaging applications.

(6) Vapor removal suitability (5) A laminated film was obtained in the same manner as in the measurement of the seal strength. Using the obtained film, a three-way seal bag having an outer dimension of 10 cm × 12 cm and a seal width of 10 mm and one short side open was prepared so that the longitudinal direction was the MD direction of the sealant film. 20 ml of water was put into the obtained three-way seal bag, and the seal bar was sealed so that the protruding seal bar having a base of 20 mm and a tip of 90 degrees faced inward in the center. The steam escape condition when the obtained bag was microwaved at 500 W was evaluated.
⊚: Steam escapes smoothly from the protrusion seal part without making a sound.
〇: The sealant film on the protrusion breaks from the interface and steam escapes.
Δ: Steam escapes from the protruding portion, but the sealant at the peeled portion becomes whisker-like or string-like.
X: The seal retracts in places other than the protrusions, and steam escapes. Alternatively, the steam does not escape quickly and makes a plosive sound to break the bag.

As is clear from the above table, the sealant films of the present invention of Examples 1 to 13 had excellent tearability, suitable sealing properties, and excellent steam removal suitability. On the other hand, the sealant films of Comparative Examples 1 to 4 did not have good tearability and steam removal suitability.

Claims (10)

A sealant film in which one surface layer is a heat-sealing inner layer (A) and the other surface layer is an outer layer (B).
The inner layer (A) contains 90% by mass or more of the propylene-based block copolymer resin (a1) in the resin component.
The outer layer (B) contains 70% by mass or more of the propylene-based block copolymer resin (b1) in the resin component.
When the propylene-based block copolymer resin (b1) contained in the outer layer (B) is molded into a thickness of 60 μm on a cooling roll at 40 ° C. by the T-die film forming method, the degree of cloudiness is 35% or less. A sealant film characterized by being a propylene-based block copolymer resin. The sealant film according to claim 1, wherein the degree of orientation measured by an infrared absorption method (IR) is 0.05 to 0.6. When the propylene-based block copolymer resin (a1) of the inner layer (A) is molded into a thickness of 60 μm on a cooling roll at 40 ° C. by the T-die film forming method, the degree of cloudiness is 30% or more. The sealant film according to claim 1 or 2, which is a block copolymer resin. The sealant film according to any one of claims 1 to 3, wherein the thickness of the inner layer (A) is 5 to 50% of the total thickness of the sealant film. The sealant film according to any one of claims 1 to 4, wherein the outer layer (B) contains a polypropylene homopolymer (b2). The sealant film according to claim 5, wherein the difference in melt flow rate between the propylene-based block copolymer resin (b1) in the outer layer (B) and the polypropylene homopolymer (b2) is 4 or less. The sealant film according to claim 5 or 6, wherein the content of the polypropylene homopolymer in the resin component contained in the outer layer (B) is 2 to 30% by mass. The sealant film according to any one of claims 5 to 7, wherein the melt tension (230 ° C.) of the polypropylene homopolymer (b2) is 0.1 to 0.4 N. A packaging material using the sealant film according to any one of claims 1 to 8 as a sealant. The packaging material according to claim 9, which is used for retort packaging of food.