Packaging material for food

Abstract

To provide a packaging material for food which exhibits enhanced food safety while using a polypropylene film containing isopropyl myristate as a substrate layer.SOLUTION: A packaging material for food comprises an anti-migration layer, a substrate layer, and a sealant layer, laminated in this order. The substrate layer is a polypropylene film containing isopropyl myristate. The anti-migration layer serves as a layer that inhibits the migration of isopropyl myristate from the substrate layer to the sealant layer when the substrate layer comes into contact with the sealant layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a packaging material for food.

Background Art

[0002] Polypropylene is commercially produced by polymerization of propylene monomers using a Ziegler-Natta catalyst. At the time of monomer polymerization, in addition to an external electron donor (for example, an alkoxysilane compound) and a cocatalyst (for example, an aluminum compound), an activity inhibitor may be used. The activity inhibitor is used for the purpose of improving film strength (tensile strength, elastic modulus, stiffness) by controlling stereoregularity, suppressing the disorder of the polymerization reactor, reducing particle aggregation, etc. Specific compounds include alkyl esters composed of monocarboxylic acids and monohydric alcohols such as propyl myristate, octyl acetate, ethyl propionate, ethyl butyrate, propyl butyrate, pentyl pentanoate, etc. Among these, isopropyl myristate is often used as a suitable activity inhibitor (Patent Document 1, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, regarding this isopropyl myristate, strict regulatory values are set in the Swiss Food Packaging Ordinance (SR 817.023.21). This ordinance, which was passed by the Swiss government and implemented in 2017, sets the strictest standards in the world for food packaging. It introduces a positive list system for packaging materials, including printing inks that do not come into contact with food, and regulates the elution amount of chemical substances from packaging materials. The positive list is classified into Part A and Part B, and isopropyl myristate is registered as Substance No. 498 in Part B (Migration Limit to Food (SML): 0.01 mg / kg (food)). Such regulations may be implemented globally, and it is desirable to promote the study of packaging materials that are safe according to global standards.

[0005] Regarding various commercially available polypropylene films, when the inventors conducted an ethanol immersion extraction test, the detection of isopropyl myristate was confirmed from a plurality of polypropylene films as described below.

[0006] This disclosure has been made in view of the above circumstances, and an object thereof is to provide a food packaging material that is excellent in food safety while including a polypropylene film containing isopropyl myristate as a base material layer.

Means for Solving the Problems

[0007] One aspect of the present invention provides a food packaging material in which a migration suppression layer, a base material layer, and a sealant layer are laminated in this order, the base material layer is a polypropylene film containing isopropyl myristate, and the migration suppression layer is a layer that suppresses the migration of isopropyl myristate from the base material layer to the sealant layer when the base material layer is in contact with the sealant layer. Such a packaging material includes a polypropylene film containing isopropyl myristate as a base material layer and is excellent in food safety. The reason for this will be briefly explained below. In the one-sided elution test in the European Plastic Regulation (EU No. 10 / 2011), the test is conducted by bringing the sealant layer side of the packaging material into contact with a pseudo-solvent, and at this time, the substrate layer and the pseudo-solvent are not in contact. However, when a packaging material having a substrate layer of a polypropylene film as the outermost layer was produced and the inventors conducted the above one-sided elution test, isopropyl myristate exceeding 0.01 mg / kg (food) was detected from the sealant layer. Since food packaging materials are generally processed roll-to-roll, the surface of the substrate layer and the surface of the sealant layer come into contact during processing and during storage in a rolled state. It is presumed that isopropyl myristate bled out from the surface of the substrate layer mainly due to this contact migrated to the sealant layer, and isopropyl myristate was detected from the sealant layer. Since the sealant layer comes into contact with the contents when used as a packaging material, in order to obtain a packaging material with better food safety, it is important to provide a migration suppression layer that suppresses the migration of isopropyl myristate from the substrate layer to the sealant layer as described above.

[0008] In one aspect, the migration suppression layer may be a layer formed on the substrate layer by the gravure coating method. By forming the migration suppression layer by the gravure coating method, the recyclability of the packaging material can be improved.

[0009] In one aspect, the migration suppression layer may contain at least one of a polypropylene-based resin, a polyurethane-based resin, and an acrylic-based resin. By including these resins in the migration suppression layer, it becomes easier to suppress the migration of isopropyl myristate from the substrate layer to the sealant layer.

[0010] In one aspect, the thickness of the migration suppression layer may be 0.5 to 3 μm. When the thickness of the migration suppression layer is 0.5 μm or more, it becomes easier to suppress the migration of isopropyl myristate from the substrate layer to the sealant layer. On the other hand, when the thickness is 3 μm or less, the material cost can be suppressed, and the recyclability of the packaging material can be improved.

[0011] In one aspect, the base material layer may be a stretched polypropylene film, and the sealant layer may be an unstretched polypropylene film. By using polypropylene films for both the base material layer and the sealant layer, the recyclability of the packaging material can be improved.

[0012] In one aspect, an intermediate layer, which is a gas barrier film, may be further laminated between the base material layer and the sealant layer. When isopropyl myristate migrates from the base material layer to the sealant layer inside the packaging material, it can be suppressed by using the gas barrier film.

Advantages of the Invention

[0013] According to the present disclosure, it is possible to provide a food packaging material that is excellent in food safety while including a polypropylene film containing isopropyl myristate as a base material layer.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present disclosure will be described. The same reference numerals are given to the same components, and redundant descriptions are omitted. Also, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0016] [Food Packaging Material] Embodiments of the food packaging material of the present disclosure will be described. The food packaging material can be referred to as a food packaging material film. Hereinafter, the food packaging material may sometimes be simply referred to as the "packaging material". FIG. 1 is a cross-sectional view schematically showing an embodiment of the food packaging material of the present disclosure. As shown in FIG. 1, the food packaging material 100 includes at least a migration suppression layer 10, a base material layer 20, and a sealant layer 30. The surface of the sealant layer 30 opposite to the base material layer 20 is a seal surface 30a, which is the surface in contact with the contents.

[0017] The packaging material 100 may further include an intermediate layer 40 between the base material layer 20 and the sealant layer 30. The food packaging material 100 may further include an adhesive layer between each layer as needed.

[0018] The content of polypropylene in the packaging material 100 is not particularly limited, but it is preferably 90% by mass or more, and more preferably 95% by mass or more. In this case, the packaging material 100 can be said to be a packaging material substantially made of a single material (monomaterial), and the recyclability of the packaging material 100 can be improved. The upper limit of the content is 100% by mass. Here, the "content of polypropylene" means the content of polypropylene contained in the packaging material 100. For a copolymer containing a comonomer other than propylene as a monomer unit, the amount of the monomer unit derived from the comonomer is not included in the content of polypropylene, and the amount of the monomer unit derived from the propylene monomer is taken as the polypropylene content. The content of polypropylene can be measured according to Raman spectroscopy.

[0019] From the viewpoint of further improving the recyclability, it is preferable that the base material layer and the sealant layer are polypropylene films, and it is more preferable that the base material layer, the resin film of the intermediate layer, and the sealant layer are polypropylene films.

[0020] (Migration suppression layer) The migration suppression layer 10 is a layer that suppresses the migration of isopropyl myristate from the base material layer 20 to the sealant layer 30 when the base material layer 20 and the sealant layer 30 are in contact. The migration suppression layer 10 can also be called a migration prevention layer.

[0021] The migration inhibiting layer 10 is not particularly limited as long as it is a material capable of expressing the above-described inhibiting function, and may include polypropylene-based resins, polyurethane-based resins, acrylic resins (polyacrylic acid and acrylic resins), polyester-based resins (such as polyethylene terephthalate and polyethylene naphthalate), and the like. From the viewpoint of the recyclability of the packaging material, it is preferable to contain a polypropylene-based resin as a main component. Further, from the viewpoint of imparting designability to the surface of the packaging material, it is preferable to contain a polyurethane-based resin or an acrylic resin, which is easy to adjust gloss and haze, as a main component. Furthermore, from the viewpoint of heat resistance and printing ink adhesion, it is preferable to contain a polyester-based resin as a main component. Here, the main component refers to a component contained in an amount exceeding 50% by mass based on the total amount of the components constituting the layer.

[0022] As a method for forming the migration inhibiting layer 10 on the base material layer 20, there are a gravure coating method in which a varnish or emulsion containing the above resin component is applied onto the base material layer 20, a dry lamination method in which a film containing the above resin component is laminated onto the base material layer 20 via an adhesive layer, an extrusion method in which the molten above resin component is extruded onto the base material layer 20, and the like. Among these, from the viewpoint of the recyclability of the packaging material, the gravure coating method, which is easier to form the migration inhibiting layer 10 thinner, is suitable.

[0023] The thickness of the migration inhibiting layer 10 is preferably 0.5 to 3 μm. When the thickness of the migration inhibiting layer 10 is 0.5 μm or more, it becomes easier to suppress the migration of isopropyl myristate from the base material layer 20 to the sealant layer 30. On the other hand, when the thickness is 3 μm or less, the material cost can be suppressed, and the recyclability of the packaging material can be improved.

[0024] (Base material layer) The base material layer 20 is a layer that supports the sealant layer 30 and is a polypropylene film containing a polypropylene-based resin.

[0025] Polypropylene-based resins are composed of resins containing propylene as a constituent unit. Examples of polypropylene-based resins include homopolypropylene, propylene copolymers obtained by copolymerizing propylene with α-olefins such as ethylene or butene, and ethylene-propylene rubber. These can be used alone or in combination of two or more. Examples of propylene copolymers include propylene-ethylene random copolymers, propylene-ethylene block copolymers, propylene-ethylene terpolymers, and the like. The polypropylene-based resin may be block polypropylene, which is a mixture of homopolypropylene and ethylene-propylene rubber.

[0026] Since the base material layer 20 is the layer that comes into contact with the heat-sealing bar during bag making, it is preferable to use a stretched film in view of heat resistance. The stretched film may be a uniaxially stretched film or a biaxially stretched film. From the viewpoint of improving the mechanical strength and dimensional stability of the packaging material 100, the base material layer 20 is preferably a biaxially stretched polypropylene film.

[0027] On the surface of the base material layer 20 on the side of the sealant layer 30, various pre-treatments such as corona treatment, plasma treatment, ozone treatment, and flame treatment may be performed, or a coating layer such as an easy-adhesion layer or the gas barrier layer described later may be provided. The base material layer 20 may contain resins other than polypropylene-based resins. Examples of such resins include polyolefin-based resins such as polyethylene-based resins. The base material layer 20 may contain at least one additive selected from fillers, antistatic agents, plasticizers, lubricants, antioxidants, etc., as necessary.

[0028] From the viewpoint of heat resistance (heat shrinkage during heat-sealing), the thickness of the base material layer 20 can be 15 μm or more, and may be 20 μm or more. On the other hand, from the viewpoint of reducing carbon dioxide emissions in the manufacturing process, it can be 50 μm or less, and may be 40 μm or less.

[0029] The base material layer 20 is a film containing isopropyl myristate. When a commercially available polypropylene film containing isopropyl myristate is subjected to the following immersion extraction test, the chromatogram peak area value of isopropyl myristate measured by gas chromatography-mass spectrometry (GC / MS analysis) is generally 100,000 to 20,000,000. From the perspective of improving the film strength of the polypropylene film as described above, the peak area value is preferably 1,000,000 or more. On the other hand, considering the migration limit (SML) to food, the peak area value is preferably 20,000,000 or less. However, the above numerical range does not limit the amount of isopropyl myristate that can be contained in the polypropylene film used as the base material layer 20. Also, for example, in the case of a stretched polypropylene film, the above numerical range is not necessarily satisfied with respect to the amount of isopropyl myristate. (Immersion extraction test) Cut out the target film to a size of 100 cm 2 and cut it into small pieces. After putting the cut pieces into a 100 mL PFA container, add 10 mL of 99.5 vol% ethanol, seal it, and heat it in a hot water bath at 60 °C for 8 hours. Then recover the ethanol and subject the 10-fold concentrated product to GC / MS analysis.

[0030] (Sealing layer) The sealing layer 30 is a layer that imparts heat-sealing properties to the packaging material 100 and contains, for example, a polypropylene-based resin. The polypropylene-based resin contains a resin containing propylene as a structural unit. Examples of the polypropylene-based resin include homopolypropylene, propylene copolymers obtained by copolymerizing propylene with an α-olefin such as ethylene or butene, and ethylene-propylene rubber. These can be used alone or in combination of two or more. Examples of the propylene copolymer include a propylene-ethylene random copolymer, a propylene-ethylene block copolymer, and a propylene-ethylene terpolymer. The polypropylene-based resin may be block polypropylene which is a mixture of homopolypropylene and ethylene propylene rubber.

[0031] From the viewpoint of reducing the heat seal temperature and enhancing the sealing property by heat sealing, the sealant layer 30 is preferably an unstretched polypropylene film.

[0032] From the viewpoint of exhibiting good heat sealability, the thickness of the sealant layer 30 can be 20 μm or more, and may be 60 μm or more. On the other hand, from the viewpoint of suppressing the amount of heat required for heat sealing and easily reducing the heat damage to other layers provided in the packaging material 100, it can be 150 μm or less, and may be 100 μm or less.

[0033] The sealant layer 30 is preferably a film that does not substantially contain isopropyl myristate. That is, as the film, when subjected to the immersion extraction test as described above, the chromatogram peak area value of isopropyl myristate measured by gas chromatography-mass spectrometry is preferably 0 (not detected).

[0034] (Intermediate layer) The intermediate layer 40 may be, for example, a resin film, or may be a resin film provided with a gas barrier layer (with gas barrier property imparted). The latter film can be referred to as a gas barrier film. By providing the packaging material 100 with a gas barrier film as the intermediate layer 40, when a packaging bag is manufactured using the packaging material 100 and the contents are accommodated in the packaging bag to manufacture a package, deterioration of the contents due to gases such as oxygen can be effectively suppressed. Also, inside the packaging material, when the migration of isopropyl myristate from the base material layer to the sealant layer occurs, it can be suppressed by using a gas barrier film. The gas barrier film can be provided with a gas barrier layer, that is, an adhesion layer, an inorganic oxide layer, and a gas barrier coating layer in this order on the resin film. The gas barrier layer of the gas barrier film may face the base material layer 20 side or the sealant layer 30 side.

[0035] From the perspective of recyclability, the resin film is, for example, a polypropylene film containing a polypropylene-based resin. The polypropylene-based resin contains a resin containing propylene as a constituent unit. Examples of the polypropylene-based resin include homopolypropylene, a propylene copolymer obtained by copolymerizing propylene with an α-olefin such as ethylene or butene, and ethylene propylene rubber. These can be used alone or in combination of two or more. Examples of the propylene copolymer include a propylene-ethylene random copolymer, a propylene-ethylene block copolymer, and a propylene-ethylene terpolymer. The polypropylene-based resin may be block polypropylene, which is a mixture of homopolypropylene and ethylene propylene rubber.

[0036] The resin film may be an unstretched film or a stretched film, but from the viewpoints of heat resistance and dimensional stability, a stretched film is preferable. The stretched film may be a uniaxially stretched film or a biaxially stretched film. When the stretched film is a biaxially stretched film, the strength and transparency of the packaging material 100 are further improved.

[0037] The thickness of the resin film may be appropriately set according to the use of the packaging material 100, and can be 10 μm or more, may be 15 μm or more, and can be 40 μm or less, may be 25 μm or less.

[0038] Examples of the inorganic compound constituting the inorganic oxide layer include silicon oxide (SiO X ), aluminum oxide (AlO X ), etc. From the viewpoints of excellent transparency and excellent tensile stretchability during processing, silicon oxide is preferable as the inorganic compound. By using the inorganic oxide layer, a very thin layer within a range that does not affect the recyclability of the packaging material can provide high barrier properties.

[0039] For example, when the inorganic compound is silicon oxide, the O / Si ratio of the inorganic oxide layer is desirably 1.7 or more. When the O / Si ratio is 1.7 or more, the content ratio of metallic Si is suppressed and good transparency is easily obtained. Further, the O / Si ratio is preferably 2.0 or less. When the O / Si ratio is 2.0 or less, the crystallinity of SiO becomes high and it is possible to prevent the inorganic oxide layer from becoming too hard, and good tensile resistance can be obtained. Thereby, it is possible to suppress the occurrence of cracks in the inorganic oxide layer when laminating the gas barrier coating layer. Also, although the polypropylene film may shrink due to heat during boiling or retort processing even after being formed into a packaging bag, when the O / Si ratio is 2.0 or less, the inorganic oxide layer easily follows the above shrinkage, and it is possible to suppress a decrease in barrier properties. From the viewpoint of obtaining these effects more sufficiently, the O / Si ratio of the inorganic oxide layer is preferably 1.75 or more and 1.9 or less, and more preferably 1.8 or more and 1.85 or less.

[0040] The O / Si ratio of the inorganic oxide layer can be determined by X-ray photoelectron spectroscopy (XPS). For example, using an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., trade name: JPS-90MXV), the X-ray source can be measured with non-monochromatized MgKα (1253.6 eV) and an X-ray output of 100 W (10 kV - 10 mA). For quantitative analysis to determine the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p can be used.

[0041] The inorganic oxide layer is SiO X or AlO X and the like can be formed by a vacuum deposition method using an inorganic compound. The thickness of the deposited layer may be, for example, 15 to 30 nm.

[0042] On the surface of the resin film where the inorganic oxide layer is to be laminated, an adhesion layer (anchor coat layer) is provided. The adhesion layer can achieve two effects: improving the adhesion performance between the resin film and the inorganic oxide layer and improving the smoothness of the resin film surface. Note that by improving the smoothness, it becomes easier to form a uniform inorganic oxide layer without defects, and it is easier to exhibit high barrier properties. The adhesion layer can be formed using an anchor coat agent.

[0043] Examples of the anchor coat agent include acrylic polyurethane resin, polyester polyurethane resin, polyether polyurethane resin, etc. From the viewpoints of heat resistance and interlayer adhesion strength, acrylic polyurethane resin is preferred as the anchor coat agent. The anchor coat agent may contain a silane coupling agent.

[0044] The thickness of the adhesion layer is not particularly limited, but it is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.03 to 3 μm, and particularly preferably in the range of 0.05 to 2 μm. When the thickness of the adhesion layer is equal to or greater than the above lower limit value, a more sufficient interlayer adhesion strength tends to be obtained. On the other hand, when it is equal to or less than the above upper limit value, the desired gas barrier property tends to be easily exhibited.

[0045] As a method for coating the adhesion layer on the resin film, known coating methods can be used without particular limitation, such as dipping method; methods using spray, coater, printing machine, brush, etc.

[0046] The coating amount of the adhesion layer is such that the mass per 1 m 2 after coating and drying the anchor coat agent is preferably 0.01 to 5 g / m 2 and more preferably 0.03 to 3 g / m 2 When the mass per 1 m 2 after coating and drying the anchor coat agent is equal to or greater than the above lower limit, the film formation tends to be sufficient. On the other hand, when it is equal to or less than the above upper limit, it tends to be easily dried sufficiently and the solvent is difficult to remain.

[0047] The method for drying the adhesion layer is not particularly limited, and examples thereof include a method by natural drying, a method of drying in an oven set at a predetermined temperature, and a method using a dryer attached to the coater, such as an arch dryer, a floating dryer, a drum dryer, an infrared dryer, etc. Further, the drying conditions can be appropriately selected according to the drying method. For example, in the method of drying in an oven, it is preferable to dry at 60 to 100°C for about 1 second to 2 minutes.

[0048] The gas barrier coating layer is a coating having gas barrier properties, and is formed using a gas barrier coating layer-forming composition (hereinafter also referred to as a coating agent) mainly composed of an aqueous solution or a water / alcohol mixed solution containing at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and their hydrolyzates. From the viewpoint of more sufficiently maintaining the gas barrier properties after heat treatment such as retort treatment, the coating agent preferably contains at least a silane coupling agent or its hydrolyzate, more preferably contains at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, and their hydrolyzates and a silane coupling agent or its hydrolyzate, and still more preferably contains a hydroxyl group-containing polymer compound or its hydrolyzate, a metal alkoxide or its hydrolyzate, and a silane coupling agent or its hydrolyzate. The coating agent can be prepared, for example, by mixing a metal alkoxide and a silane coupling agent (or their hydrolyzates) into a solution obtained by dissolving a hydroxyl group-containing polymer compound, which is a water-soluble polymer, in an aqueous (water or water / alcohol mixed) solvent.

[0049] Each component contained in the coating agent for forming the gas barrier coating layer will be described in detail. Examples of the hydroxyl group-containing polymer compound used in the coating agent include polyvinyl alcohol, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, and the like. Among these, when polyvinyl alcohol (PVA) is used, it is preferable because of its particularly excellent gas barrier properties.

[0050] From the viewpoint of obtaining excellent gas barrier properties, the gas barrier coating layer is preferably formed from a composition containing at least one selected from the group consisting of metal alkoxides represented by the following general formula (I) and their hydrolysis products. M(OR 1 ) m (R 2 ) n-m …(I) In the above general formula (I), R 1 and R 2 are each independently a monovalent organic group having 1 to 8 carbon atoms, and are preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer from 1 to n. When there are a plurality of R 1 or R 2 , R 1 may be the same or different from each other, and R 2 may be the same or different from each other.

[0051] Specific examples of the metal alkoxide include tetraethoxysilane [Si(OC 2 H 5 ) 4 , triisopropoxyaluminum [Al(O-2'-C 3 H 7 ) 3 , and the like. Tetraethoxysilane and triisopropoxyaluminum are preferable because they are relatively stable in an aqueous solvent after hydrolysis.

[0052] Examples of the silane coupling agent include compounds represented by the following general formula (II). Si(OR 11 )p (R 12 ) 3-p R 13 …(II) In the general formula (II) above, R 11 represents an alkyl group such as a methyl group or an ethyl group, and R 12 represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or an alkyl group substituted with a methacryloxy group. R 13 represents a monovalent organic functional group, and p represents an integer from 1 to 3. When there are a plurality of R 11 or R 12 , R 11 may be the same or different from each other, and R 12 may also be the same or different from each other. Examples of the monovalent organic functional group represented by R 13 include a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or a monovalent organic functional group containing an isocyanate group.

[0053] Specific examples of the silane coupling agent include silane coupling agents such as vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

[0054] In addition, the silane coupling agent may be a polymer obtained by polymerizing the compound represented by the general formula (II). As the polymer, a trimer is preferred, and more preferably 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate. This is a polycondensate of 3-isocyanatealkylalkoxysilane. By adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to a hydroxyl group-containing polymer compound, the water resistance of the gas barrier coating layer can be improved by hydrogen bonding.

[0055] 1,3,5-Tris(3-trialkoxysilylalkyl)isocyanurate may be produced by thermal condensation of 3-isocyanatopropylalkoxysilane, and may contain the starting material 3-isocyanatopropylalkoxysilane, but there are no particular problems. More preferably, it is 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate, and even more preferably 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate. This methoxy group has a high hydrolysis rate, and those containing a propyl group can be obtained relatively inexpensively, so 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is practically advantageous.

[0056] In addition, to the coating agent, within a range that does not impair the gas barrier property, it is also possible to add a known additive such as an isocyanate compound, a dispersant, a stabilizer, a viscosity modifier, a colorant, etc. as necessary.

[0057] The thickness of the gas barrier coating layer is preferably 50 to 1000 nm, and more preferably 100 to 500 nm. When the thickness of the gas barrier coating layer is 50 nm or more, there is a tendency to obtain a more sufficient gas barrier property, and when it is 1000 nm or less, there is a tendency to maintain sufficient flexibility.

[0058] The coating solution for forming the gas barrier coating layer can be applied, for example, by dipping method, roll coating method, gravure coating method, reverse gravure coating method, air knife coating method, comma coating method, die coating method, screen printing method, spray coating method, gravure offset method, etc. The coating film formed by applying this coating solution can be dried, for example, by hot air drying method, hot roll drying method, high frequency irradiation method, infrared irradiation method, UV irradiation method, or a combination thereof.

[0059] When drying the coating film, the temperature can be, for example, 50 to 150°C, preferably 70 to 100°C. By setting the drying temperature within the above range, the occurrence of cracks in the vapor deposition layer and the gas barrier coating layer can be further suppressed, and excellent barrier properties can be exhibited.

[0060] (Adhesive layer) The adhesive layer is provided between the above-mentioned layers as needed and is a layer for adhering the layers. As the adhesive constituting the adhesive layer, for example, polyester-isocyanate resin, urethane resin, polyether resin, etc. can be used. For using the packaging bag for retort applications, a two-component curable urethane-based adhesive with retort resistance can be preferably used.

[0061] The thickness of the adhesive layer can be, for example, 1.0 to 5.0 μm. When the thickness of the adhesive layer is 1.0 μm or more, it tends to be easy to ensure heat resistance that can withstand retort treatment, and when it exceeds 5.0 μm, the recyclability tends to decrease.

[0062] [Wound body] The wound body includes the above-mentioned food packaging material (film) and a core around which the food packaging material is wound. In this wound body (roll), during roll-to-roll processing and storage in a rolled state, the contact between the surface of the base material layer and the surface of the sealant layer is inhibited by the migration suppression layer. Therefore, the migration of isopropyl myristate bleeding out from the surface of the base material layer to the sealant layer is suppressed. Thereby, a packaging material with better food safety is provided.

[0063] [Package] An embodiment of the package using the packaging material of the present disclosure will be described with reference to FIG. 2. FIG. 2 is a cross-sectional view schematically showing an embodiment of the package of the present disclosure. As shown in FIG. 2, the package 500 includes a packaging bag 400 and the contents C accommodated in the packaging bag 400. Examples of the contents C include foods (food and drink), but may also be pharmaceuticals or the like. The packaging bag 400 is formed using the packaging material 100, and the seal surface 30a constitutes the inner surface of the packaging bag 400. Specifically, the packaging bag 400 is formed by overlapping two packaging materials 100 with the seal surfaces 30a facing each other and heat-sealing the peripheral edges of the seal surfaces 30a. The packaging bag 400 includes a main body portion 401 in which the contents C are accommodated and a seal portion 402 that surrounds the main body portion 401.

[0064] In the package 500 using the above packaging material 100, the elution of isopropyl myristate derived from the base material layer into the contents C from the sealant layer is sufficiently suppressed. Such a package 500 is excellent in food safety.

Example

[0065] The present invention will be described in more detail with the following examples, but the present invention is not limited to these examples.

[0066] <Preparation of various materials> (Preparation of polypropylene film etc.) The polypropylene film and the polyester film shown in Table 1 were prepared. Each film was subjected to the following immersion extraction test, and the chromatogram peak area value of isopropyl myristate was measured by gas chromatography-mass spectrometry (GC / MS analysis). (Immersion extraction test) The target film was cut into a size of 100 cm 2 and shredded. After putting the shredded material into a 100 mL PFA container, 10 mL of 99.5 vol% ethanol was added, sealed, and heated in a hot water bath at 60 °C for 8 hours. Then, the ethanol was recovered and concentrated 10 times, and the concentrated product was subjected to GC / MS analysis under the conditions shown in Table 2.

[0067]

Table 1

[0068] [Table 2]

[0069] As described above, isopropyl myristate was confirmed to be detected from the stretched polypropylene film used for measurement, but isopropyl myristate was not confirmed to be detected from the unstretched polypropylene film and the polyester film.

[0070] (Preparation of Composition for Forming Migration Inhibiting Layer) Ethyl acetate, a polyurethane resin (XGS-6116 Matt Medium R manufactured by Sakata Inx), and a curing agent (3% by mass of Lamior curing agent) were blended to prepare a varnish having a solid content of 15% by mass. This was used as the composition for forming a migration inhibiting layer.

[0071] (Preparation of Composition for Forming Adhesion Layer) An acrylic polyol and tolylene diisocyanate were mixed so that the number of NCO groups of tolylene diisocyanate was equal to the number of OH groups of the acrylic polyol, and diluted with ethyl acetate so that the total solid (total amount of acrylic polyol and tolylene diisocyanate) was 5% by mass. To the diluted mixture, β-(3,4-epoxycyclohexyl)trimethoxysilane was further added in an amount of 5 parts by mass with respect to 100 parts by mass of the total amount of the acrylic polyol and tolylene diisocyanate, and these were mixed to prepare a composition for forming an adhesion layer (anchor coating agent).

[0072] (Preparation of Composition for Forming Gas Barrier Coating Layer) The following Solution A, Solution B, and Solution C were mixed at a mass ratio of 65 / 25 / 10, respectively, to prepare a composition for forming a gas barrier coating layer. Solution A: A hydrolysis solution having a solid content of 5% by mass (in terms of SiO2) obtained by adding 72.1 g of 0.1N hydrochloric acid to 17.9 g of tetraethoxysilane (Si(OC2H5)4) and 10 g of methanol and stirring for 30 minutes for hydrolysis. Liquid B: 5 mass% aqueous / methanol solution of polyvinyl alcohol (mass ratio of water:methanol is 95:5). Liquid C: Hydrolysis solution obtained by diluting 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate with a mixture of water / isopropyl alcohol (mass ratio of water:isopropyl alcohol is 1:1) to a solid content of 5 mass%.

[0073] <Preparation of Packaging Material> (Example 1) On a stretched polypropylene film 1 (SFHS manufactured by Indopoly, thickness 20 μm) as a base material layer, a composition for forming a migration inhibition layer was applied by a gravure coating method and dried to produce a base material layer with a migration inhibition layer. The thickness of the migration inhibition layer was 0.7 μm. On the surface of the base material layer opposite to the surface on the migration inhibition layer side, a stretched polypropylene film 2 (thickness 20 μm) as an intermediate layer was laminated by a dry lamination method via a two-component curable adhesive (manufactured by Mitsui Chemicals, Inc., trade name: main agent A525 / hardener A52). The thickness of the adhesive layer was 2.0 μm. On the surface of the intermediate layer opposite to the surface on the base material layer side, an unstretched polypropylene film 1 (ZK207 manufactured by Toray, thickness 60 μm) as a sealant layer was laminated by a dry lamination method via a two-component curable adhesive (manufactured by Mitsui Chemicals, Inc., trade name: main agent A525 / hardener A52). The thickness of the adhesive layer was 2.0 μm. Thereby, a packaging material (laminate) having a laminated structure of migration inhibition layer / base material layer / adhesive layer / intermediate layer / adhesive layer / sealant layer was produced.

[0074] (Example 2) On a stretched polypropylene film 2 (thickness 20 μm) as a resin film constituting the intermediate layer, a composition for forming an adhesion layer was applied by a gravure roll coating method, dried and cured at 60 °C, and an adhesion layer made of an acrylic polyurethane resin with a coating amount of 0.1 g / m 2 was formed. On the adhesion layer, a transparent inorganic oxide layer (silica vapor deposition layer) made of silicon oxide with a thickness of 30 nm was formed by a vacuum evaporation apparatus using an electron beam heating method. As the silica vapor deposition layer, a vapor deposition layer with an O / Si ratio of 1.8 was formed by adjusting the vapor deposition material species. The O / Si ratio was measured with an X-ray photoelectron spectroscopy analyzer (manufactured by JEOL Ltd., trade name: JPS-90MXV), using a non-monochromatized MgKα (1253.6 eV) X-ray source and an X-ray output of 100 W (10 kV - 10 mA). For the quantitative analysis to obtain the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p were used respectively. On the inorganic oxide layer, a composition for forming a gas barrier coating layer was applied by a gravure roll coating method, and heated and dried in an oven under conditions of a tension of 20 N / m and a drying temperature of 120 °C to form a gas barrier coating layer with a thickness of 0.3 μm. In this way, an intermediate layer was prepared. In the same manner as in Example 1, a substrate layer with a migration suppression layer was prepared, and the surface of the intermediate layer on the gas barrier coating layer side was laminated on the surface of the substrate layer opposite to the side of the migration suppression layer by a dry lamination method via a two-component curable adhesive (manufactured by Mitsui Chemicals, Inc., trade name: main agent A525 / hardener A52). The thickness of the adhesive layer was 2.0 μm. On the surface of the intermediate layer on the resin film side, an unstretched polypropylene film 1 (thickness 60 μm) as a sealant layer was laminated by a dry lamination method via a two-component curable adhesive (manufactured by Mitsui Chemicals, Inc., trade name: main agent A525 / hardener A52). The thickness of the adhesive layer was 2.0 μm. Thereby, a packaging material having a laminated structure of migration suppression layer / substrate layer / adhesive layer / intermediate layer (gas barrier coating layer / inorganic oxide layer / adhesion layer / resin film) / adhesive layer / sealant layer was produced.

[0075] (Example 3) One side of the polyester film 1 (Lumirror #2-F51 manufactured by Toray Industries, Inc.) as the migration inhibition layer was subjected to corona treatment. The wetting tension of the treated surface was 38 mN / m. On this treated surface, a stretched polypropylene film 1 (SFHP manufactured by Indopoly, thickness: 20 μm) as the base material layer was laminated by the dry lamination method via a two-component curable adhesive (manufactured by Mitsui Chemicals, Inc., product name: main agent A525 / hardener A52). The thickness of the adhesive layer was 2.0 μm. Except for this, in the same manner as in Example 2, a packaging material having a laminated structure of migration inhibition layer / base material layer / adhesive layer / intermediate layer (gas barrier coating layer / inorganic oxide layer / adhesion layer / resin film) / adhesive layer / sealant layer was produced.

[0076] (Comparative Example 1) Except for not forming the migration inhibition layer, in the same manner as in Example 2, a packaging material having a laminated structure of base material layer / adhesive layer / intermediate layer (gas barrier coating layer / inorganic oxide layer / adhesion layer / resin film) / adhesive layer / sealant layer was produced.

[0077] <One-sided elution test> Two pieces of the packaging material obtained in each example were cut out to A4 size and laminated so that the front and back of the packaging material were in contact. This laminate was sandwiched between stainless steel plates with a thickness of 10 mm and left standing at 40 °C for 4 days under a pressure of 30 gf / cm 2 . The upper packaging material of the laminate was used as a sample for the elution test.

[0078] -Qualitative analysis- With the sealant layer side of the sample as the contact liquid surface, after setting it in a small one-sided extraction jig (contact area: 0.49 dm 2 ), 25 mL of 99.5 vol% ethanol was injected and sealed. After leaving this standing at 60 °C for 10 days, 50 μL of heptadecane (concentration: 100 μg / mL) was added as an internal standard substance to the recovered extract, and then concentrated 25-fold to 1.0 mL and subjected to GC / MS analysis under the conditions of Table 2 above. The chromatogram peak area value of isopropyl myristate obtained was described in Table 4.

[0079] -Quantitative analysis- Using ethanol, 950 μL of a standard substance solution of isopropyl myristate adjusted to concentrations of 0.1 μg / mL, 0.5 μg / mL, 1.0 μg / mL, and 5.0 μg / mL was injected into a 2-mL vial. Then, 50 μL of heptadecane (concentration: 100 μg / mL) was added as an internal standard substance, and the volume was made up to 1.0 mL. It was subjected to GC measurement under the conditions shown in Table 3. The extract obtained by qualitative analysis was subjected to GC measurement. Then, the obtained peak area values were applied to a calibration curve prepared from the measurement results of the standard substance, and quantification was carried out. Also, the lower limit of quantification and the elution amount were calculated using the following Equation -1. The elution amount of isopropyl myristate was described in Table 4. The detection limit of GC was 0.004 mg / kg (food).

[0080]

Table 3

[0081]

Equation

[0082] Food safety was evaluated according to the following criteria. ○: The elution amount of isopropyl myristate ester was 0.01 mg / kg (food) or less. ×: The elution amount of isopropyl myristate ester exceeded 0.01 mg / kg (food).

[0083] Recyclability was evaluated according to the following criteria based on the polypropylene content in the packaging material measured using Raman spectroscopy. ○: The polypropylene content in the packaging material was 95% by mass or more. △: The polypropylene content in the packaging material was 90% by mass or more and less than 95% by mass. ×: The polypropylene content in the packaging material was less than 90% by mass.

[0084]

Table 4

[0085] The summary of the present disclosure is as follows. [1] A migration inhibition layer, a base material layer, and a sealant layer are laminated in this order, the base material layer is a polypropylene film containing isopropyl myristate, the migration inhibition layer is a layer that inhibits the migration of isopropyl myristate from the base material layer to the sealant layer when the base material layer is in contact with the sealant layer, a food packaging material. [2] The food packaging material according to [1], wherein the migration inhibition layer is a layer formed on the base material layer by a gravure coating method. [3] The food packaging material according to [1] or [2], wherein the migration inhibition layer contains at least one of a polypropylene-based resin, a polyurethane-based resin, and an acrylic-based resin. [4] The food packaging material according to any one of [1] to [3], wherein the thickness of the migration inhibition layer is 0.5 to 3 μm. [5] The food packaging material according to any one of [1] to [4], wherein the base material layer is a stretched polypropylene film and the sealant layer is an unstretched polypropylene film. [6] The food packaging material according to any one of [1] to [5], wherein an intermediate layer, which is a gas barrier film, is further laminated between the base material layer and the sealant layer.

Explanation of reference numerals

[0086] 10... Migration inhibition layer, 20... Base material layer, 30... Sealant layer, 30a... Sealing surface, 40... Intermediate layer (barrier film), 100... Food packaging material, 400... Packaging bag, 500... Package, C... Contents.

Claims

1. A migration inhibiting layer, a base material layer, and a sealant layer are laminated in this order, wherein the base material layer is a polypropylene film containing isopropyl myristate, and the migration inhibiting layer is a layer that inhibits the migration of isopropyl myristate from the base material layer to the sealant layer when the base material layer is in contact with the sealant layer, a food packaging material.

2. The food packaging material according to claim 1, wherein the migration inhibiting layer is a layer formed on the base material layer by a gravure coating method.

3. The food packaging material according to claim 1 or 2, wherein the migration inhibiting layer contains at least one of a polypropylene-based resin, a polyurethane-based resin, and an acrylic-based resin.

4. The food packaging material according to claim 1 or 2, wherein the thickness of the migration inhibiting layer is 0.5 to 3 μm.

5. The food packaging material according to claim 1 or 2, wherein the base material layer is a stretched polypropylene film and the sealant layer is an unstretched polypropylene film.

6. The food packaging material according to claim 1 or 2, wherein an intermediate layer, which is a gas barrier film, is further laminated between the base material layer and the sealant layer.

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