JP6150687B2 - Multilayer sealant film - Google Patents

Description

 The present invention relates to a multilayer sealant film, a packaging material using the same, a packaging bag, and hermetic packaging. More specifically, the present invention relates to a multilayer sealant film that can form a hermetic package having a constant openability regardless of heat sealing conditions during packaging. The present invention relates to a packaging material and a packaging bag using the same.

  Conventionally, various packaging materials using a film made of a thermoplastic resin have been proposed. These packaging materials are used for packaging food, clothing, industrial parts, etc., and are used in a wide range of packaging bags that are sealed by heat sealing to preserve the contents and protect them from dust, dust, etc. It has been.

  Such a packaging bag is formed by forming a sheet-like packaging material including a sealant film having a sealing layer containing a polyolefin such as polypropylene and a base material layer into a bag shape so that the sealing layer is located inside. . After containing the contents, the opposing sealing layer is thermocompression bonded, the bag is heat sealed, and the food is sealed.

  When taking out the contents, the packaging material is cut with a scissors, or a notch serving as a tear starting point is formed at the end of the bag, and the bag is torn from the notch. In general, however, the opposing surfaces immediately below the heat-sealed bag mouth are gripped, both are pulled in the opposite direction with a strong force, the heat-sealed portion is peeled off, and the contents are taken out. The heat seal part is required to have sufficient strength so that the bag mouth does not open easily during transportation or sales, but if the heat seal strength is too strong, the purchaser can easily open the bag mouth. Disappear. As described above, it is generally considered that the heat seal strength and the easy-openability of the heat seal part are difficult to achieve at the same time.

  In order to form the heat seal part as described above, a film called a sealant film is laminated on one surface of the substrate. The sealant film includes a heat seal layer that is melted or softened by heat, and may be a multilayer film. As the sealant film, various configurations have been proposed from the viewpoint of sealing strength and easy opening (Patent Documents 1 and 2, etc.). When configuring hermetic packaging using such a sealant film, the base material is the outer layer, the packaging material is molded into a bag shape so that the heat seal layer is located inside the bag, and the contents are contained, The opposing heat seal layer is thermocompression bonded, the bag is heat sealed, and food or the like is enclosed. Since the heat seal layers are thermocompression bonded and integrated, it is difficult to delaminate the fused heat seal layers, and it is also difficult to peel the integrated heat seal layers due to cohesive failure.

  In the packaging bag using the sealant film described in Patent Documents 1 and 2, opening is performed by delamination between the base material and the seal layer or delamination between constituent layers of the sealant film. In the case where the sealant film includes an auxiliary layer to form a multilayer structure, it has also been proposed to perform delamination between the substrate and the auxiliary layer or between the seal layer and the auxiliary layer.

Patent No. 4040738 Japanese Patent No. 4300648

  In food business operators that use packaging bags, the contents should not be contaminated during product transportation. For this reason, after containing contents such as food in the packaging bag, it is necessary to completely perform thermocompression bonding between the seal layers. If the heat seal is insufficient, the seal layers may not be sufficiently fused together, and a gap may be generated in the heat seal portion. Moreover, even if it can heat seal, sealing strength becomes inadequate, a heat seal part peels at the time of transport, and a clearance gap may arise. This gap causes contamination of the contents. In order to avoid such a situation, the food business may perform thermocompression bonding at a high temperature near or exceeding the upper limit of the standard heat seal temperature, pressure, and time specified by the packaging bag provider.

 As the temperature and pressure at the time of heat sealing are higher and the time is longer, the heat sealing portion is more reliably fused and the sealing strength is improved. However, as a result of heat sealing under excessive conditions, the layers of the sealant film may adhere to each other, and the delamination property may be impaired. If the heat seal temperature is too high, for example, the substrate and the seal layer are excessively adhered, or between the substrate and the intermediate layer and between the seal layer and the intermediate layer are excessively adhered. As a result, peeling between these layers becomes difficult, and the openability may be significantly impaired.

 The present invention has been made in view of the prior art as described above, and an object of the present invention is to provide a multilayer sealant film that can form a packaging form with a constant unsealing property regardless of heat sealing conditions during packaging. .

 As a result of intensive research in order to solve the above problems, the present inventors have made a sealant film configuration, not a conventional delamination of a base material and a sealant film, or a delamination between constituent layers of a sealant film. It has been found that by performing cohesive failure of the layers, there is a possibility that a certain openability may be obtained regardless of the heat seal conditions during packaging and the adhesion between the layers, and the present invention has been completed. It was.

 That is, this invention which solves the said subject contains the following matter as a summary.

(1) Laminate layer (A) / intermediate layer (B) / seal layer (C) are laminated in this order,
The laminate layer (A) having a thickness of 3 to 50 μm includes 100 parts by mass of a linear low density polyethylene (A1) and 30 to 300 parts by mass of a polypropylene resin (A2) having a melting point of 140 to 165 ° C.
The intermediate layer (B) includes a polypropylene resin (B1) having a melting point of 140 to 165 ° C,
The sealing layer (C) includes a low melting point polypropylene resin (C1) having a melting point 15 to 60 ° C. lower than that of the polypropylene resin (B1) constituting the intermediate layer (B).
Multilayer sealant film.

(2) The laminate layer (A) contains low-density polyethylene (A3) having a melting point of less than 120 ° C in an amount of 300 parts by mass or less with respect to 100 parts by mass of linear low-density polyethylene (A1). 2. The multilayer sealant film according to 1.

(3) A packaging material obtained by laminating a base material and the multilayer sealant film according to (1) or (2) via a laminate layer (A).

(4) A packaging bag in which the packaging material according to (3) is formed into a bag shape having an opening with the seal layer (C) inside.

(5) Sealed packaging in which the contents are housed in the packaging bag described in (4) above, the opposing sealing layer (C) is thermocompression bonded, and the opening of the packaging bag is heat sealed.

(6) The sealed packaging according to (5), wherein the peeling mode at the time of opening is a cohesive failure of the laminate layer (A).

  ADVANTAGE OF THE INVENTION According to this invention, the packaging form which has fixed openability can be provided irrespective of the heat seal conditions at the time of packaging, and the adhesiveness between the structural layers of a sealant film.

FIG. 1 shows a cross-sectional view of a packaging material including the multilayer sealant film of the present invention. FIG. 2 shows a schematic view of one embodiment of the packaging bag and hermetic packaging of the present invention. FIG. 3 shows an outline of the opening mode of the sealed package of the present invention.

  Hereinafter, the present invention, including its best mode, will be described more specifically with reference to the drawings.

  As shown in FIG. 1, the multilayer sealant film 1 according to the present invention is formed by laminating a laminate layer (A) / intermediate layer (B) / seal layer (C) in this order. Moreover, the packaging material 2 of this invention laminates | stacks the base material 3 and the said multilayer sealant film 1 through a laminate layer (A). Hereinafter, the multilayer sealant film 1 and the substrate 3 composed of the laminate layer (A), the intermediate layer (B), and the seal layer (C) will be described.

Laminate layer (A)
The laminate layer (A) is a layer that is used for lamination with the substrate 3 and causes cohesive failure when the packaging bag is opened.

 The laminate layer (A) includes linear low density polyethylene (A1) and a polypropylene resin (A2) having a melting point of 140 to 165 ° C., and further includes low density polyethylene (A3) as necessary.

 The linear low density polyethylene (A1) is a thermoplastic resin obtained by copolymerizing ethylene and a small amount of α-olefin. As the comonomer, 1-butene, 1-hexene, 4-methyl-1- Although pentene, 1-octene, etc. are used, it is not limited to these.

The density of the linear low density polyethylene (A1) is preferably 0.900 to 0.945 g / cm ³ , more preferably 0.910 to 0.940 g / cm ³ . When the density of the linear low density polyethylene (A1) is too low, blocking is likely to occur in the multilayer sealant film 1, while when the density of the linear low density polyethylene (A1) is too high, Curling is likely to occur in the multilayer sealant film 1, and handling properties during lamination with the substrate 3 are reduced.

 Further, the melting point of the linear low density polyethylene (A1) is preferably 130 ° C. or lower, more preferably 100 to 130 ° C. If the melting point of the linear low density polyethylene (A1) is too low, blocking is likely to occur in the multilayer sealant film 1, while if the melting point of the linear low density polyethylene (A1) is too high, Curling is likely to occur in the multilayer sealant film 1, and handling properties during lamination with the substrate 3 are reduced. In the present specification, the melting point refers to a peak temperature showing the maximum endotherm in the measurement using a differential scanning calorimeter.

 Moreover, MFR in 190 degreeC of linear low density polyethylene (A1) becomes like this. Preferably it is 0.1-50.0 g / 10min, More preferably, it is the range of 1.0-30.0 g / 10min. When the MFR of the linear low density polyethylene (A1) is too low, the viscosity at the time of melting is high, so in the production of the multilayer sealant film 1, the resin pressure in the extruder rises and the productivity is significantly deteriorated. On the other hand, when the MFR of the linear low density polyethylene (A1) is too high, blocking is likely to occur in the multilayer sealant film 1.

 The melting point of the polypropylene resin (A2) is 140 to 165 ° C, more preferably 150 to 160 ° C. When the melting point of the polypropylene resin is too low, not only the multilayer sealant film 1 is likely to be blocked, but also when it is melted at the time of heat sealing, it cannot be agglomerated and destroyed. Strength cannot be obtained. On the other hand, when the melting point of the polypropylene resin is too high, the melting point difference from the linear low density polyethylene (A1) becomes large, and the heat seal temperature range in which a suitable opening strength can be obtained tends to be narrowed.

 In addition, the MFR at 230 ° C. of the polypropylene resin (A2) is not particularly limited, but considering the film forming property, the MFR is preferably 0.5 to 50.0 g / 10 min. The range of 1.0 to 30.0 g / 10 min is more preferable.

 As the polypropylene resin (A2), various polypropylene resins can be used without limitation as long as the melting point is satisfied. For example, random copolymerization of propylene homopolymer and propylene with ethylene and / or α-olefin having 4 to 10 carbon atoms such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc. Examples thereof include blends of a polymer, a block copolymer or a homopolymer of propylene and the above α-olefin (co) polymer having 2 to 10 carbon atoms, which may be appropriately selected from these. Among these, as the polypropylene resin (A2), a random copolymer of propylene and ethylene and / or an α-olefin having 4 to 10 carbon atoms is preferable, and in particular, a propylene-ethylene random copolymer, propylene-ethylene. -A butene random copolymer is preferably used.

 The content of propylene units in the polypropylene random copolymer preferably used is preferably 96.5 to 99.9% by mass, more preferably 98.0 per 100% by mass of the total amount of the polypropylene random copolymer. It is 99.5 mass%. The balance is the above-described ethylene and / or α-olefin. The copolymer composition can be measured using a nuclear magnetic resonance apparatus.

 The polypropylene resin (A2) is 30 to 300 parts by mass, preferably 35 to 270 parts by mass, and more preferably 40 to 250 parts by mass with respect to 100 parts by mass of the linear low density polyethylene (A1). Used.

 By constituting the laminate layer (A) from the linear low density polyethylene (A1) as described above and the polypropylene resin (A2) having a melting point of 140 to 165 ° C., the linear low density polyethylene (A1) ) And the polypropylene resin (A2) are incompatible with each other. Therefore, when the laminate layer (A) is pulled from above and below, it causes cohesive failure and becomes an opening start point of the packaging bag. The tensile force that causes cohesive failure is determined by the compatibility of the linear low-density polyethylene (A1) and the polypropylene resin (A2), so the packaging bag is opened with a constant tensile force regardless of the heat seal conditions. it can. Moreover, since it is incompatible, the surface of the laminate layer becomes uneven and the surface area is increased, so that the adhesion to the substrate 3 is enhanced. When the blending amount of the polypropylene resin (A2) is too small, the opening strength becomes too strong, and the opening property of the packaging bag 5 is impaired. Similarly, when the blending amount of the polypropylene resin (A2) is excessive, the unsealing strength becomes too strong and the unsealing property of the packaging bag 5 is impaired.

The laminate layer (A) may further contain low density polyethylene (A3) in addition to the above (A1) and (A2). The density of the low density polyethylene (A3) is preferably 0.900 to 0.945 g / cm ³ , more preferably 0.910 to 0.940 g / cm ³ . As such a low density polyethylene, a high pressure method low density polyethylene (HPLD) generally produced by a high pressure method is preferably used. When the density of the low density polyethylene (A3) is too low, blocking is likely to occur in the multilayer sealant film 1, while when the density of the low density polyethylene (A3) is too high, the multilayer sealant film 1 is curled. Is likely to occur, and the handling properties during lamination with the substrate 3 are reduced.

 The melting point of the low density polyethylene (A3) is preferably less than 120 ° C, more preferably 100 to 115 ° C. When the melting point of the low-density polyethylene (A3) is too low, blocking is likely to occur in the multilayer sealant film 1, while when the melting point of the low-density polyethylene (A3) is too high, curling occurs in the multilayer sealant film 1. Is likely to occur, and the handling properties during lamination with the substrate 3 are reduced.

 Moreover, MFR in 190 degreeC of low density polyethylene (A3) becomes like this. Preferably it is 0.5-15.0 g / 10min, More preferably, it is the range of 1.0-8.0 g / 10min. When the MFR of the low density polyethylene (A3) is too low, since the viscosity at the time of melting is high, in the production of the multilayer sealant film 1, the resin pressure in the extruder rises and the productivity is remarkably deteriorated. When the MFR of the density polyethylene (A3) is too high, blocking is likely to occur in the multilayer sealant film 1.

 The linear low density polyethylene (A1), polypropylene resin (A2) and low density polyethylene (A3) described above, and the density, melting point, MFR, etc. of each resin described later can be controlled by known means. For example, a material having desired physical properties may be selected from various commercial products, which can be controlled by the type of comonomer, its amount, molecular weight, and the like.

 When the low density polyethylene (A3) is blended in the laminate layer (A), the low density polyethylene (A3) is preferably 300 parts by mass or less with respect to 100 parts by mass of the linear low density polyethylene (A1). Preferably, it is used in an amount of 250 parts by mass or less.

 In the laminate layer (A), in addition to the linear low-density polyethylene (A1) and the polypropylene-based resin (A2) as described above, the low-density polyethylene (A3) is blended, so that the polypropylene-based resin (A2) is further added. Since the compatibility with the other resin material is reduced, the opening strength is reduced and the opening property of the packaging bag 5 is improved.

 In the laminate layer (A), in addition to the above (A1) to (A3), as long as the adhesion between the laminate layer and the substrate and the cohesive failure performance of the laminate layer are not impaired, petroleum resin, terpene resin, rosin, Antiblocking agents, antioxidants, light stabilizers, lubricants, antistatic agents, antifogging agents, coloring agents, nucleating agents, antibacterial agents and the like can be blended.

 The laminate layer (A) is obtained by melting and mixing each of the above components with an extruder as necessary, and forming a film.

 The thickness of the laminate layer (A) is not particularly limited as long as it does not impair the adhesion to the substrate and the cohesive failure performance of the laminate layer, and is preferably 3 to 50 μm, preferably 3 to 40 μm. . If the laminate layer (A) is too thin, it will melt at the time of heat sealing and cannot be coherently broken, and a predetermined opening strength cannot be obtained. On the other hand, if the laminate layer is too thick, not only a large amount of energy is required to destroy the layer that causes cohesive failure, but also the economy is low, and the weight of the packaging bag increases.

Middle layer (B)
The intermediate layer (B) is formed between the laminate layer (A) and the seal layer (C) for the purpose of firmly bonding the laminate layer (A) and the seal layer (C). The intermediate layer (B) includes a polypropylene resin (B1) having a melting point of 140 to 165 ° C. Examples of the polypropylene resin (B1) include the same resins as the polypropylene resin (A2) of the laminate layer (A). The polypropylene resin (B1) may be the same as or different from the polypropylene resin (A2) as long as it has a predetermined melting point.

 The intermediate layer (B) may be formed of the polypropylene resin (B1) alone. In addition to the polypropylene resin (B1), the above-mentioned linear low density polyethylene, low density polyethylene, and other thermoplastic resins. May be contained. The content of the resin other than the polypropylene resin (B1) in the intermediate layer (B) is preferably 100 parts by mass or less, and 30 parts by mass or less with respect to 100 parts by mass of the polypropylene resin (B1). More preferably.

 In addition, in addition to the polypropylene resin (B1), the intermediate layer (B) includes petroleum resin, terpene resin, rosin, as long as the adhesiveness to the laminate layer and the seal layer and the cohesive failure performance of the laminate layer are not impaired. Antiblocking agents, antioxidants, light stabilizers, lubricants, antistatic agents, antifogging agents, coloring agents, nucleating agents, antibacterial agents and the like can be blended.

 The intermediate layer (B) is obtained by melt-mixing the polypropylene resin (B1) and other components optionally blended with an extruder as necessary, and forming a film.

 The thickness of the intermediate layer (B) is not particularly limited as long as it does not impair the adhesion to the laminate layer or the seal layer and the cohesive failure performance of the laminate layer, and is usually about 3 to 50 μm, more preferably. It is about 4 to 45 μm. If the intermediate layer (B) is too thin, adhesion to the laminate layer or the seal layer may be insufficient. On the other hand, if the intermediate layer (B) is too thick, it is not economical and the weight of the packaging bag increases.

Seal layer (C)
The sealing layer (C) is provided to seal the packaging bag by thermocompression of the opposing sealing layers when the packaging bag is heat-sealed.

The sealing layer (C) includes a low melting point polypropylene resin (C1) having a melting point lower than that of the polypropylene resin (B1) constituting the intermediate layer (B).
The difference in melting point between the polypropylene resin (B1) and the low melting point polypropylene resin (C1) is in the range of 15 to 60 ° C, preferably 20 to 50 ° C. When the difference between the melting points is too small, the intermediate layer is melted during heat sealing, and when the sealing layer and the laminate layer are integrated, the sealing property and the opening strength are affected. On the other hand, when the difference between the melting points is too large, it means that the melting point of the low melting point polypropylene resin (C1) is too low, and the multilayer sealant film 1 is likely to be blocked.

 The melting point of the low melting point polypropylene resin (C1) is preferably 110 to 150 ° C, more preferably 110 to 140 ° C. When the melting point of the low melting point polypropylene resin (C1) is less than 110 ° C., the heat resistance of the heat seal part may be inferior. On the other hand, when the melting point of the low melting point polypropylene resin (C1) is too high, the low temperature heat sealability tends to be insufficient.

 Further, the MFR at 230 ° C. of the low melting point polypropylene resin (C1) is not particularly limited, but considering the film forming property, the MFR is 0.5 to 50.0 g / 10 min. Is preferable, and the range of 1.0 to 30.0 g / 10 min is more preferable.

 As the low melting point polypropylene resin (C1), various polypropylene resins can be used without limitation as long as the above melting point is satisfied. For example, random copolymerization of propylene homopolymer and propylene with ethylene and / or α-olefin having 4 to 10 carbon atoms such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc. Examples thereof include blends of a polymer, a block copolymer or a homopolymer of propylene and the above α-olefin (co) polymer having 2 to 10 carbon atoms, which may be appropriately selected from these. Among these, as the low melting point polypropylene resin (C1), a random copolymer of propylene and ethylene and / or an α-olefin having 4 to 10 carbon atoms is preferable, and in particular, a propylene-ethylene random copolymer, propylene An ethylene-butene random copolymer is preferably used.

 The content of propylene units in the polypropylene random copolymer preferably used is preferably 99.0-90.0% by mass, more preferably 98.0 per 100% by mass of the total amount of the polypropylene random copolymer. It is 90.0 mass%.

 The sealing layer (C) may be formed of the low melting point polypropylene resin (C1) alone, and besides the low melting point polypropylene resin (C1), the above-described linear low density polyethylene, low density polyethylene, and others The thermoplastic resin may be contained. The content of the resin other than the low melting point polypropylene resin (C1) in the seal layer (C) is preferably 20 parts by mass or less with respect to 100 parts by mass of the low melting point polypropylene resin (C1).

 In addition to the low melting point polypropylene resin (C1), the seal layer (C) includes petroleum resin, terpene resin, rosin, anti-resin within a range that does not impair the adhesion between the seal layers and the cohesive failure performance of the laminate layer. A blocking agent, an antioxidant, a light stabilizer, a lubricant, an antistatic agent, an antifogging agent, a coloring agent, a nucleating agent, an antibacterial agent and the like can be blended.

 The sealing layer (C) is obtained by melting and mixing the low-melting-point polypropylene resin (C1) and other components optionally blended with an extruder as necessary, and forming a film.

 The thickness of the sealing layer (C) is not particularly limited as long as it does not impair the adhesion between the sealing layers, and is usually about 3 to 50 μm, more preferably about 3 to 45 μm. If the sealing layer (C) is too thin, the adhesiveness when heat-sealing the packaging bag may be insufficient. On the other hand, when the sealing layer (C) is too thick, it is inferior in economic efficiency and the weight of the packaging bag increases.

Multilayer sealant film 1
The multilayer sealant film 1 according to the present invention is formed by laminating the above-described laminate layer (A), intermediate layer (B), and seal layer (C) in this order. The lamination method of each layer is not particularly limited, and a laminate layer (A), an intermediate layer (B), and a seal layer (C) are individually formed, and then each layer is dry-laminated using an adhesive described later. Or by extrusion lamination. Moreover, the resin raw material which comprises each layer may be separately kneaded and coextruded to obtain a multilayer sealant film.

 The film forming method may be a non-stretching method, a uniaxial stretching method, or a biaxial stretching method, but is preferably a non-stretching method. Illustrative examples of the non-stretching method include an extrusion molding method using a T die and an inflation molding method using an annular die. In the molding method, for example, a co-extrusion method using a T-die by a feed block method or a multi-manifold method is preferably used.

  About the extrusion method using the above-mentioned T dice, if specifically shown, the resin composition constituting each layer is extruded by the T dice method in each extruder and the temperature adjustable roll or the temperature adjustable Examples thereof include a method of cooling and winding in a water tank, and a method of cooling and winding the melt by an air cooling method or a water cooling method. The resulting multi-layer sealant film is a low-stretched film or a substantially unstretched film that is slightly stretched by a slight elongation until it is cooled from a melt extruded from a T-die or the like, or a tension during winding. It is.

 The laminate layer (A), the intermediate layer (B), and the seal layer (C) may be subjected to corona discharge treatment, flame treatment or the like for the purpose of improving the adhesion of each layer. Further, the surface to be surface-treated is not particularly limited, and may be either one side or both sides.

Packaging material 2
The packaging material 2 of the present invention is formed by laminating a base material 3 and the multilayer sealant film 1 via a laminate layer (A). The base material 3 may be printed with the product name of the contents, the name of the manufacturer, and the like.

 The base material 3 is appropriately selected according to the strength and hardness required of the packaging material 2, and for example, a biaxially stretched polyester film, a biaxially stretched polyamide film, a biaxially stretched polypropylene film, or the like is used. The vapor deposition film which vapor-deposited the metal film on this film may be sufficient. Moreover, the laminated film of these films and another thermoplastic resin film may be sufficient.

 The thickness of the substrate 3 varies depending on the use of the packaging material, but is generally about 10 to 300 μm. The surface of the substrate 3 on the side where the sealant film 1 is laminated may be subjected to corona discharge treatment, flame treatment or the like for the purpose of improving adhesion.

 The base material 3 and the multilayer sealant film 1 are laminated via the laminate layer (A) of the multilayer sealant film 1. Specifically, the multilayer sealant film 1 is placed so that the laminate layer (A) is in contact with one surface of the substrate 3, and both are thermocompression bonded. The thermocompression bonding temperature is equal to or higher than the softening temperature of the laminate layer (A), preferably pressurizing at 0.1 to 1.0 MPa, and preferably performing thermocompression bonding for 0.5 to 5 seconds.

 Alternatively, the packaging material 2 may be obtained by coextruding the resin composition constituting the laminate layer (A), the intermediate layer (B), and the seal layer (C) on one surface of the substrate 3.

 Further, the packaging material 2 can be obtained by laminating one side of the base material 3 and the laminate layer (A) with an adhesive.

 As the adhesive used here, a commercially available adhesive may be used, or a molten resin (for example, a molten polyethylene resin) may be used. Examples of the method for applying the adhesive include transfer means such as gravure, gravure reverse, and offset; scraping means such as a bar and a comma bar.

A schematic diagram of the packaging bag and hermetically sealed packaging bag 4 and hermetic packaging 5 is shown in FIG. The packaging bag 4 of this invention is obtained by shape | molding the packaging material 2 in the bag shape which has a sealing layer (C) inside, and has an opening part. Specifically, the packaging material is folded into an appropriate size, and the end portion is thermocompression bonded to form a bag shape. The thermocompression bonding temperature is a temperature at which the seal layer can be thermocompression bonded, and is usually 100 to 250 ° C, preferably 120 to 220 ° C. The pressure is preferably set at 0.1 to 1.0 MPa, and the thermocompression bonding is preferably performed for 0.5 to 5 seconds.

 The obtained packaging bag 4 contains contents 6 such as food, and the sealing layer facing the opening is thermocompression bonded, and the opening of the packaging bag is heat sealed to form a sealed package 5. The thermocompression bonding conditions are the same as described above.

 The peeling mode when the sealed package 5 is opened is a cohesive failure of the laminate layer (A). Specifically, as shown in FIG. 3, at the time of opening, when the opposite surface immediately below the heat-sealed bag mouth is gripped and pulled in the opposite direction with a strong force, the laminate layer (A) is cohesively broken. Opening is performed. By increasing the temperature, pressure, and time during thermocompression bonding, the seal layers (C) are firmly adhered to each other, but the state and properties of the laminate layer are not significantly changed. For this reason, the force required for cohesive failure of the laminate layer (A) is constant, and a stable opening property can be obtained regardless of the thermocompression bonding conditions. The opening strength is usually 40 to 75N, preferably 45 to 70N, and more preferably 50 to 65N.

  Hereinafter, the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, the characteristic of the resin raw material used, the physical property of a multilayer sealant film, and the physical property of a packaging bag were measured as follows.

(1) MFR
Based on JISK6758, MFR was measured at 230 ° C. for polypropylene and 190 ° C. for polyethylene.

(2) Melting point About 5 mg of resin sample was precisely weighed and sealed in an aluminum pan. This was mounted on a differential scanning calorimeter (model “SSC / 5200” manufactured by Seiko Instruments Inc.) and in a nitrogen stream at 20 mL / min. The temperature is raised to 230 ° C., held at this temperature for 10 minutes, cooled to −10 ° C. at a temperature lowering rate of 10 ° C./min, and then heated to 210 ° C. at a temperature rising rate of 10 ° C./min. In the endothermic curve, the peak temperature showing the maximum endotherm was taken as the melting point.

(3) Blocking strength As an index of blocking resistance, after the pressure and heating state under the following conditions, a tensile tester (manufactured by Shimadzu Corporation, autograph, model “AG-500D”) is used. The blocking strength was measured under the following conditions.
Test piece dimensions: 120 mm x 120 mm
Load condition: 10kg
Temperature and humidity conditions: 40 ° C. × 70% RH × 3 days Blocking measurement surface: 30 mm × 40 mm
Tensile speed: 50 mm / min Measuring temperature: 23 ° C. atmosphere

(4) Opening strength The opposing surface of the packaging bag 4 30 mm away from the upper part of the heat-sealed bag mouth is gripped by a chuck of a tensile tester and pulled in the opposite direction at a tensile speed of 500 mm / min to open the packaging bag 4. The maximum strength was measured. The measurement was performed 10 times, and the average value was defined as the opening strength.

(5) Occurrence frequency of film tearing at the time of opening, peeling appearance Gripping the facing surface 30 mm away from the upper part of the heat-sealed bag mouth of the packaging bag 4 by hand, and pulling each in the opposite direction with a strong force, Opened. The evaluation was performed 10 times, and the frequency with which the film was broken at the time of opening was shown as a percentage. Moreover, the external appearance of the peeling part was confirmed visually and the following determination was performed.
Peeling part appearance criteria ○: Good (no thread-like or layered peeled material was generated)
X: Defect (a filamentous or layered peeled material was generated)

(6) Rupture Strength Using a burst strength measuring machine (305-BP) manufactured by Sun Science Co., Ltd., 1.0 L / min of air was sent into the packaging bag 4 to measure the pressure at the time of rupture.

Example 1
3 types 3 consisting of a single screw extruder with a screw diameter of 75 mm for the intermediate layer and two single screw extruders with a screw diameter of 50 mm for both outer layers (laminate layer and seal layer). Using a layered T-die film-forming apparatus, linear low-density polyethylene (CW8003 manufactured by Sumitomo Chemical Co., Ltd., density 0.912 g / cm ³ , melting point 110 ° C., MFR as a raw material resin for the laminate layer (A) 9.0 g / 10 min) mixed resin blended with 100 parts by mass of propylene resin (FW3GT manufactured by Nippon Polypro Co., Ltd., melting point 148 ° C., MFR = 7.0 g / 10 min), intermediate layer ( Propylene polymer (FLX80G1, manufactured by Sumitomo Chemical Co., Ltd., melting point 158 ° C., MFR 11.0 g / 10 min) as a raw material resin for B) and propylene as a raw material resin for the seal layer (C) Tylene-1-butene random copolymer (manufactured by Prime Polymer Co., Ltd. F794NV, melting point 134 ° C., MFR 5.0 g / 10 min) was supplied to each, heated and melted at 230 ° C., and co-extruded by a feed block method Co-extruded from a T-die with a die lip gap of 1.5 mm and cooled and solidified on a cooling roll, so that the laminate layer (A) is 5 μm, the intermediate layer (B) is 11 μm, and the seal layer (C) is 4 μm. Adjustment was performed to obtain a multilayer film having a total thickness of 20 μm. Next, after applying a corona discharge treatment so that the wet tension of the surface of the laminate layer (A) becomes 40 mN / m, the laminate layer (A) / intermediate layer (B) / A multilayer sealant film 1 comprising the sealing layer (C) was obtained.
Evaluation of said (3) was performed using the multilayer sealant film 1 obtained above. The results are shown in Table 1.

 The surface of the laminate layer (A) on which the multilayer sealant film 1 has been subjected to corona discharge treatment and the corona-treated surface of the base material 3 (biaxially stretched polyester film E2001, thickness 12 μm, manufactured by Phutamura Chemical Co., Ltd.) are urethane-bonded. The packaging material 2 was obtained by pasting together via an agent.

Using a vertical pillow packaging machine (TWX1N, manufactured by Tokyo Automatic Machinery Co., Ltd.), the sealing layers (C) of the packaging material 2 are subjected to a heat seal temperature of 140 ° C., a time of 0.6 seconds, and a pressure of 0.5 MPa. The bag was heat-sealed under (bag making conditions: A) to prepare a packaging bag 4 (length 200 mm, width 130 mm).
Evaluation of said (4)-(6) was performed using the packaging bag 4 obtained above. The results are shown in Table 1.

(Example 2)
In the production of the multilayer sealant film 1 of Example 1, the mixing ratio of the linear low density polyethylene and the propylene resin in the mixed resin of the laminate layer (A) was changed to the values shown in Table 1, respectively. In the same manner as above, a multilayer sealant film 1 was obtained. Using this multilayer sealant film 1, the evaluation of (3) above was performed. The results are shown in Table 1. Further, in the same manner as in Example 1, a packaging material 2 was prepared using this multilayer sealant film 1, and then a packaging bag 4 was prepared in the same manner as in Example 1. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1.

(Example 3)
In the production of the packaging bag 4 (length 200 mm, width 130 mm) of Example 2 above, the bag making conditions were the heat seal temperature 200 ° C., the time 0.8 seconds, and the pressure 1.0 MPa (bag making conditions: B). Otherwise, the packaging bag 4 was prepared in the same manner as in Example 2. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1.

Example 4
In the production of the multilayer sealant film 1 of Example 1, the mixing ratio of the linear low density polyethylene and the propylene resin in the mixed resin of the laminate layer (A) was changed to the values shown in Table 1, respectively. In the same manner as above, a multilayer sealant film 1 was obtained. Using this multilayer sealant film 1, the evaluation of (3) above was performed. The results are shown in Table 1. Further, in the same manner as in Example 1, a packaging material 2 was prepared using this multilayer sealant film 1, and then a packaging bag 4 was prepared in the same manner as in Example 1. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1.

(Example 5)
In the production of the multilayer sealant film 1 of Example 1, in the mixed resin of the laminate layer (A), in addition to linear low density polyethylene and polypropylene resin, low density polyethylene (L405, manufactured by Sumitomo Chemical Co., Ltd., melting point) The multilayer sealant film 1 was obtained in the same manner as in Example 1 except that the blending ratio was 102 ° C. and MFR 4.0 g / 10 min), and the mixing ratio was set to the values shown in Table 1. Using this multilayer sealant film 1, the evaluation of (3) above was performed. The results are shown in Table 1. Further, in the same manner as in Example 1, a packaging material 2 was prepared using this multilayer sealant film 1, and then a packaging bag 4 was prepared in the same manner as in Example 1. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1. By blending the low density polyethylene, the unsealing strength was reduced, and the unsealing property of the packaging bag 4 was improved.

(Comparative Examples 1 and 2)
In the production of the multilayer sealant film 1 of Example 1, the mixing ratio of the linear low density polyethylene and the propylene resin in the mixed resin of the laminate layer (A) was changed to the values shown in Table 1, respectively. In the same manner as above, a multilayer sealant film 1 was obtained. Using this multilayer sealant film 1, the evaluation of (3) above was performed. The results are shown in Table 1. Further, in the same manner as in Example 1, a packaging material 2 was prepared using this multilayer sealant film 1, and then a packaging bag 4 was prepared in the same manner as in Example 1. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1. The opening strength was high, and the packaging bag 4 could not be opened easily.

(Comparative Example 3)
In the production of the multilayer sealant film 1 of Example 4, the propylene-based resin in the mixed resin of the laminate layer (A) was changed to a propylene-ethylene-1-butene random copolymer (F794NV, Prime Polymer Co., Ltd., melting point 134 ° C., A multilayer sealant film 1 was obtained in the same manner as in Example 4 except that the MFR was 5.0 g / 10 min. Using this multilayer sealant film 1, the evaluation of (3) above was performed. The results are shown in Table 1. Further, in the same manner as in Example 4, a packaging material 2 was prepared using this multilayer sealant film 1, and then a packaging bag 4 was prepared in the same manner as in Example 4. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1. The blocking phenomenon in the multilayer sealant film 1 was confirmed, the opening strength was increased, and stringing was observed.

(Comparative Example 4)
In the production of the multilayer sealant film 1 of Example 2, the raw material resin for the seal layer (C) was a propylene-ethylene random copolymer (manufactured by Nippon Polypro Co., Ltd. FW3GT, melting point 148 ° C., MFR 7.0 g / 10 min) A multilayer sealant film 1 was obtained in the same manner as in Example 2 except that. Using this multilayer sealant film 1, the evaluation of (3) above was performed. The results are shown in Table 1. Further, a packaging material 2 was prepared using the multilayer sealant film 1 in the same manner as in Example 2, and then a packaging bag 4 was prepared in the same manner as in Example 2. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1. The opening strength was slightly higher, and stringing was observed at the time of opening.

(Comparative Example 5)
In the production of the multilayer sealant film 1 of Example 2, the raw material resin for the intermediate layer (B) was propylene-ethylene-1-butene random copolymer (F794NV manufactured by Prime Polymer Co., Ltd., melting point 134 ° C., MFR 5.0 g). / 10 minutes), and the raw material resin for the seal layer (C) was a propylene polymer (FLX80G1, manufactured by Sumitomo Chemical Co., Ltd., melting point 158 ° C., MFR 11.0 g / 10 minutes). A multilayer sealant film 1 was obtained. Using this multilayer sealant film 1, the evaluation of (3) above was performed. The results are shown in Table 1. Further, a packaging material 2 was prepared using the multilayer sealant film 1 in the same manner as in Example 2, and then a packaging bag 4 was prepared in the same manner as in Example 2. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1. Sufficient heat seal strength could not be obtained, and both opening strength and burst strength were greatly reduced.

(Comparative Example 6)
In making the packaging bag 4 of Comparative Example 5 (length 200 mm, width 130 mm), the bag-making conditions were the conditions of heat-sealing temperature 200 ° C., time 0.8 seconds, and pressure 1.0 MPa (bag-making conditions: B). Otherwise, a packaging bag 4 was prepared in the same manner as in Comparative Example 5. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1.

(Comparative Example 7)
In the production of the multilayer sealant film 1 of Example 2, the thickness of each layer was the same as that of Example 2 except that the laminate layer (A) / intermediate layer (B) / seal layer (C) = 1 μm / 15 μm / 4 μm. Thus, a multilayer sealant film 1 was obtained. Using this multilayer sealant film 1, the evaluation of (3) above was performed. The results are shown in Table 1. Further, a packaging material 2 was prepared using the multilayer sealant film 1 in the same manner as in Example 2, and then a packaging bag 4 was prepared in the same manner as in Example 2. Using this packaging bag 4, the above evaluations (4) to (6) were performed. The results are shown in Table 1. The opening strength was strong and the packaging bag 4 could not be opened easily.

DESCRIPTION OF SYMBOLS 1 ... Multilayer sealant film A ... Laminate layer B ... Intermediate | middle layer C ... Sealing layer 2 ... Packaging material 3 ... Base material 4 ... Packaging bag 5 ... Sealing packaging 6 ... Contents

Claims (6)

Laminate layer (A) / intermediate layer (B) / seal layer (C) are laminated in this order,
The laminate layer (A) having a thickness of 3 to 50 μm includes 100 parts by mass of a linear low density polyethylene (A1) and 30 to 300 parts by mass of a polypropylene resin (A2) having a melting point of 140 to 165 ° C.
The intermediate layer (B) includes a polypropylene resin (B1) having a melting point of 140 to 165 ° C,
The sealing layer (C) includes a low melting point polypropylene resin (C1) having a melting point 15 to 60 ° C. lower than that of the polypropylene resin (B1) constituting the intermediate layer (B).
Multilayer sealant film.   The laminate layer (A) contains the low density polyethylene (A3) having a melting point of less than 120 ° C in an amount of 300 parts by mass or less with respect to 100 parts by mass of the linear low density polyethylene (A1). Multilayer sealant film.   A packaging material obtained by laminating a base material and the multilayer sealant film according to claim 1 or 2 via a laminate layer (A).   The packaging bag which shape | molded the packaging material of Claim 3 into the bag shape which has a sealing layer (C) inside and has an opening part.  Sealed packaging in which the contents are accommodated in the packaging bag according to claim 4, the opposing sealing layer (C) is thermocompression bonded, and the opening of the packaging bag is heat sealed.   The sealed packaging according to claim 5, wherein the peeling mode at the time of opening is cohesive failure of the laminate layer (A).

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