Laminate for packaging

Abstract

The packaging laminate of the present invention is characterized by having: a barrier film (1) having an inorganic film (1b) formed on the surface of a thermoplastic resin film (1a); and an adhesive layer (3) disposed on the inorganic film (1b), the adhesive layer (3) being formed of an epoxy adhesive.

Description

[0001] This application is a divisional application of the application filed on September 10, 2021, with application number 202180061851.5 and invention title "Laminated Body for Packaging". Technical Field

[0002] This invention relates to laminates for packaging, and more specifically, to laminates for packaging that exhibit excellent oxygen barrier properties. Background Technology

[0003] Resin films, represented by olefin resin films such as polypropylene film and polyethylene film, are inexpensive and have the advantage of being easily bonded together by heat sealing to form pouches, and have long been widely used as packaging materials.

[0004] Such resin films have poor gas barrier properties. Therefore, as a method to improve gas barrier properties, it is known to form an inorganic film on the surface of the resin film. Known methods include vapor-deposited films of aluminum or silicon oxide, coatings primarily composed of silicon oxide, coatings formed by the crosslinking reaction of carboxylic acids and metals, and coatings formed by dispersing metal oxides. Furthermore, it is also known to form the aforementioned coatings on the aforementioned vapor-deposited films. Resin films with such inorganic films on their surfaces exhibit high gas barrier properties and are therefore commercially available as barrier films.

[0005] However, when using the aforementioned barrier film to make small bags, a heat-sealable resin layer is typically included. This heat-sealable resin layer is adhered to the barrier film using an adhesive.

[0006] For example, Patent Document 1 discloses a packaging laminate comprising: a substrate film having a vapor-deposited film, and a heat-sealable resin layer disposed on the vapor-deposited film with an adhesive layer in between, wherein the adhesive layer is formed of a cured product of a two-component curable adhesive comprising a polyester polyol, an isocyanate compound, and a phosphoric acid modified compound.

[0007] It should be noted that the adhesive layer is designed to bond layers formed of different materials, while the heat-sealing resin layer is designed to bond layers of the same type of resin (heat-sealing resin), and they are different layers from the adhesive layer.

[0008] However, while the pouches obtained using this packaging laminate maintain sufficient oxygen barrier properties without retort sterilization, their oxygen barrier properties decrease significantly upon retort sterilization. Therefore, it is difficult to use this packaging laminate as pouches for retortable foods. The decrease in oxygen barrier properties after retort sterilization can be attributed to the shrinkage of the substrate film and defects in the vapor-deposited layer caused by heating during the process. This reduction in oxygen barrier properties due to heating is not limited to cases with vapor-deposited films; it also occurs when other inorganic films are present. Therefore, it is required that the excellent oxygen barrier properties provided by inorganic films be maintained even after retort sterilization.

[0009] Furthermore, Patent Document 2 discloses a gas-barrier polyolefin laminated film having a polyolefin film layer and a gas barrier layer. In this laminated film, the gas barrier layer is a film layer formed by curing epoxy resin containing aromatic rings within the molecule with an epoxy resin curing agent, exhibiting excellent oxygen barrier properties. However, it does not have inorganic films such as vapor-deposited films, so regardless of whether it is sterilized by boiling, it is impossible to obtain the level of oxygen barrier properties of a barrier film with an inorganic film.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2020-37187

[0013] Patent Document 2: Japanese Patent No. 4117461 Summary of the Invention

[0014] The problem the invention aims to solve

[0015] Therefore, the present invention addresses the problem of providing a packaging laminate that exhibits excellent oxygen barrier properties even when subjected to heat treatment such as retort sterilization.

[0016] Solution for solving the problem

[0017] According to the present invention, a packaging laminate is provided, characterized in that the packaging laminate comprises: a barrier film having an inorganic film formed on the surface of a thermoplastic resin film; and an adhesive layer disposed on the inorganic film.

[0018] The adhesive layer is formed of an epoxy-based adhesive.

[0019] In the packaging laminate of the present invention, the following scheme is preferably applied.

[0020] (1) The packaging laminate according to technical solution 1, wherein the energy storage modulus of the adhesive layer is higher than 39 MPa at 120°C.

[0021] (2) The epoxy adhesive comprises epoxy resin and amine curing agent, and the adhesive layer is formed by curing the epoxy resin using the amine curing agent.

[0022] (3) A heat-sealing resin layer is stacked on the adhesive layer.

[0023] (4) The heat-sealing resin layer is composed of an propylene resin composition, which contains an impact polypropylene component (A) of ethylene-propylene copolymer dispersed in polypropylene and linear low-density polyethylene (B).

[0024] (5) The xylene-soluble component of the propylene resin composition is derived from ethylene-propylene copolymer at a rate of 8% or more by mass.

[0025] (6) The linear low-density polyethylene (B) contains methylpentene as a copolymer.

[0026] (7) The thermoplastic resin film is a stretched polypropylene film.

[0027] (8) In addition to the thermoplastic resin film, a strength-reinforcing layer is provided, which is composed of a stretch film comprising at least one selected from olefin resins, polyamide resins and ethylene-vinyl alcohol copolymers.

[0028] (9) The tensile film having the strength-reinforcing layer is formed of polypropylene.

[0029] (10) The inorganic film is a vapor-deposited film.

[0030] According to the present invention, a small bag obtained by heat-sealing the above-mentioned packaging laminate is also provided.

[0031] Preferably, the pouch contains 80% by mass or more of an olefin resin.

[0032] According to the present invention, a packaging laminate is also provided, characterized in that the packaging laminate includes a barrier film on which an inorganic film is formed on the surface of a thermoplastic resin film, and an adhesive layer is provided on the inorganic film, wherein the storage modulus of the adhesive layer is higher than 39 MPa at 120°C.

[0033] The effects of the invention

[0034] The packaging laminate of the present invention has a basic structure comprising a barrier film having an inorganic film and a heat-sealing resin layer, but it is characterized by the fact that the adhesive layer between the barrier film (inorganic film) and the heat-sealing resin layer is formed by an epoxy adhesive, thereby achieving excellent oxygen barrier properties even after cooking.

[0035] Excellent oxygen barrier properties can be achieved even after boiling by forming an adhesive layer with an epoxy-based adhesive, as confirmed by numerous experimental results and phenomena, although the exact reasons for this remain to be clarified. However, the inventors presume that one possible reason is that the adhesive layer formed with the epoxy-based adhesive exhibits a large storage modulus at high temperatures, particularly at 120°C.

[0036] For example, as shown in Example 1 described later, when the adhesive layer formed between the heat-sealing film and the inorganic film is composed of an epoxy adhesive, its storage modulus is as high as 57 MPa (@120°C). When this layer is stacked and bagged (filled with water as the contents), the oxygen permeability before boiling is 0.05 cc / m³. 2 / day / atm, after steaming / boiling is 1.75cc / m 2 / day / atm indicates a slight increase in oxygen permeability. On the other hand, as in Comparative Example 1, the storage modulus of the adhesive layer formed with a polyurethane-based adhesive is 2.4 MPa (@120°C), significantly lower than that of the adhesive layer of Example 1 formed with an epoxy-based adhesive. It can be seen that in the pouches obtained by laminating the materials of Comparative Example 1, not only does it show 1.04 cc / m² before cooking... 2 The oxygen permeability is slightly higher than that of Example 1, at / day / atm, and it significantly increases to 12.54cc / m after cooking. 2 / day / atm. Similarly, the storage modulus of the adhesive layer of Comparative Example 3, formed with a polyurethane-based adhesive of a different type than Comparative Example 1, was 39 MPa (@120°C), which was greater than that of the adhesive layer of Comparative Example 1, but still lower than that of the adhesive layer of Example 1 formed with an epoxy-based adhesive. In the pouches obtained from such a laminate of Comparative Example 3, the oxygen permeability increased significantly by 11.58 cc / m after cooking. 2 / day / atm.

[0037] That is, the adhesive layer formed by the epoxy adhesive exhibits a large storage modulus value at 120°C, for example, greater than 39 MPa.

[0038] That is, as demonstrated in the experiments of the embodiments described later, the laminate of the barrier film and adhesive layer having an inorganic film such as an evaporated film has a high thermal shrinkage rate and shrinks significantly during heating in the cooking process. However, it can be considered that the adhesive layer formed by the epoxy adhesive has a high storage modulus at high temperatures, so it is possible that the thermal shrinkage of the laminate of the barrier film and adhesive layer is suppressed, effectively suppressing the generation of cracks and pinholes on the inorganic film caused by shrinkage.

[0039] In this way, the packaging laminate of the present invention not only exhibits excellent oxygen barrier properties before cooking, but also after cooking, and is therefore preferably used as a pouch for cooked foods. Attached Figure Description

[0040] Figure 1 This is a schematic side sectional view showing the basic structure of the packaging laminate of the present invention.

[0041] Explanation of reference numerals in the attached figures

[0042] 1: Barrier membrane;

[0043] 1a: Thermoplastic resin film;

[0044] 1b: Inorganic membrane;

[0045] 3: Adhesive layer;

[0046] 5: Heat-sealing resin layer. Detailed Implementation

[0047] <Layer Structure of Packaging Laminates>

[0048] like Figure 1 As shown, the packaging laminate of the present invention has a basic structure in which an adhesive layer 3 is formed on a barrier film 1, and a heat-sealing resin layer 5, for example, is bonded to the adhesive layer 3.

[0049] In this basic structure, regarding the barrier film 1, an inorganic film 1b is formed on the surface of the thermoplastic resin film 1a. A heat-sealing film is attached to the inorganic film 1b of the barrier film 1 using an adhesive, thereby forming, for example, a heat-sealing resin layer 5 through the adhesive layer 3.

[0050] <Barrier Membrane 1>

[0051] Thermoplastic resin film 1a;

[0052] In the barrier film 1, the thermoplastic resin film 1a serves as the substrate of the inorganic film 1b and is manufactured using known methods such as extrusion or co-extrusion molding.

[0053] As such thermoplastic resins are not limited by principles, various thermoplastic resins can be used, such as representative low-density polyethylene, high-density polyethylene, medium-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene, as well as olefin-based resins such as cyclic olefin copolymers.

[0054] In addition to the olefin resins mentioned above, the following resins can also be used to form the thermoplastic resin film 1a.

[0055] Ethylene-vinyl compound copolymers, such as ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, and ethylene-vinyl chloride copolymers;

[0056] Styrene-based resins, such as polystyrene, acrylonitrile-styrene copolymer, ABS (Acrylonitrile Butadiene Styrene), and α-methylstyrene-styrene copolymer;

[0057] Polyethylene-based resins, such as polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymer, polymethyl methacrylate, and polymethyl methacrylate;

[0058] Polyamides, such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12;

[0059] Thermoplastic polyesters, such as polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate (PEN).

[0060] Other resins, such as polycarbonate, polyphenylene ether, polyimide resin, polyamide-imide resin, polyether-imide resin, fluororesin, allyl resin, polyurethane resin, cellulose resin, polysulfone resin, polyethersulfone resin, ketone resin, amino resin, polylactic acid, etc.

[0061] Furthermore, it can also be a blend of the resins exemplified above, or a substance formed by modifying these resins through appropriate copolymerization (e.g., acid-modified olefin resins, etc.).

[0062] In the packaging laminate of the present invention, from the viewpoint of forming retort pouches with high recyclability, the thermoplastic resin film 1a is preferably a film of olefin resin, and especially from the viewpoint of the strength of the pouch, it is more preferably polypropylene.

[0063] Furthermore, considering its heat resistance to withstand boiling sterilization, the thermoplastic resin film 1a is preferably stretched in a uniaxial or biaxial direction. The stretch ratio is only required to prevent film breakage due to overstretching, and is usually more than two times.

[0064] The thermoplastic resin film 1a described above only needs to have an appropriate thickness depending on the capacity of the final manufactured bag, etc. However, if it is too thin, the strength may be reduced due to the loss of orientation when the inorganic film 1b described later is formed. Therefore, it is preferable to have a thickness of at least 10µm.

[0065] Inorganic membrane 1b;

[0066] The inorganic film 1b disposed on the surface of the aforementioned thermoplastic resin film 1a is provided to ensure oxygen barrier properties, and includes vapor-deposited films of various metals or metal oxides, coatings mainly composed of silicon oxides, coatings formed by the cross-linking reaction of carboxylic acids and metals, and coatings formed by the dispersion of metal oxides, etc. Moreover, sometimes the aforementioned coatings are also disposed on the aforementioned vapor-deposited films.

[0067] In this invention, the formed film is dense and has high oxygen barrier properties. Therefore, the inorganic film 1b is preferably a film with a coating mainly composed of silicon oxide on the vapor-deposited film.

[0068] This vapor-deposited film is an inorganic film formed through physical vapor deposition methods such as sputtering, vacuum evaporation, and ion plating, or chemical vapor deposition methods such as plasma CVD (Chemical Vapor Deposition). For example, it may be a film formed from various metals or metal oxides. Because such vapor-deposited films are formed from inorganic materials, they exhibit higher oxygen barrier properties compared to gas-barrier resins such as ethylene-vinyl alcohol copolymers.

[0069] In this invention, from the viewpoint of ensuring particularly high oxygen barrier properties, vapor-deposited films formed of silicon oxide, aluminum oxide, and especially silicon oxide exhibit the highest oxygen barrier properties and are therefore the most preferred.

[0070] Furthermore, the thickness of the aforementioned inorganic film 1b varies depending on the required level of oxygen barrier properties. However, in the case of vapor-deposited films, the thickness is designed to ensure that the properties of the thermoplastic resin film 1a, which serves as the substrate during vapor deposition, are not impaired, and that 1cc / m is maintained. 2 A thickness with an oxygen permeability of less than / day / atm is preferable, typically ranging from 1000nm to 10nm, especially around 100nm to 10nm.

[0071] <Adhesive layer 3>

[0072] The adhesive layer 3 is formed of an epoxy-based adhesive. In addition to exhibiting adhesive properties, the adhesive layer 3 formed in this way also exhibits a large storage modulus, as described above, for example, a storage modulus greater than 39 MPa (@120°C), and particularly greater than 45 MPa, at 120°C. That is, the adhesive layer 3 formed of the epoxy-based adhesive exhibits a large storage modulus at 120°C, thus effectively preventing the reduction of oxygen barrier properties during heat treatments such as sterilization at temperatures between 100°C and 120°C.

[0073] The aforementioned epoxy adhesive is a so-called dry lamination adhesive, which is an adhesive that uses an epoxy curing agent to cure liquid epoxy resin for bonding. The adhesive layer 3 formed by using this epoxy adhesive is used to bond and fix the heat-sealable resin layer 5 and other layers onto the inorganic film 1b.

[0074] The epoxy resins mentioned above are liquid resins with epoxy groups in their molecules. Representative examples include resins obtained by reacting epichlorohydrin with phenolic compounds, amine compounds, carboxylic acids, etc., and resins obtained by oxidizing unsaturated compounds such as butadiene using organic peroxides, etc. Any type of resin can be used.

[0075] Specific examples, and not limited to these, include: bisphenol A or bisphenol F type epoxy resins, linear phenolic epoxy resins, cyclic aliphatic epoxy resins, long-chain aliphatic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, etc.

[0076] In this invention, glycidylamine type epoxy resins are particularly preferred in terms of their ability to form adhesive layers with high elastic modulus.

[0077] Furthermore, known epoxy curing agents such as amines, acid anhydrides, and polyamides can be used as epoxy curing agents. In particular, from the viewpoint of forming a coating (adhesive layer) with high elastic modulus and easy to follow thermal shrinkage, amine curing agents are preferred, among which aromatic polyamines, represented by m-phenylenediamine, are preferred.

[0078] The ratio of epoxy resin to curing agent can be set according to the epoxy equivalent of the epoxy resin to form a sufficiently cured film.

[0079] The epoxy adhesive described above forms an adhesive layer 3 on the inorganic film 1b by applying and drying a volatile organic solvent such as a hydrocarbon-based, alcohol-based, ketone-based, ester-based, or ether-based solvent on the inorganic film 1b.

[0080] It should be noted that, after extensive laboratory testing, it was determined that, in order to effectively avoid the reduction in oxygen barrier properties during heat treatments such as sterilization, the high storage modulus at 120°C shown in adhesive layer 3 is currently only achievable with epoxy resins; high storage modulus cannot be obtained with polyurethane adhesives. However, it is believed that even other adhesives, as long as they exhibit a high storage modulus at 120°C similar to those of this invention, can effectively prevent the reduction in oxygen barrier properties during heat treatments such as sterilization.

[0081] <Heat-sealing resin layer 5>

[0082] The heat-sealable resin layer 5 is formed by overlapping and pressing a heat-sealable film onto the adhesive layer 3, and then curing the adhesive in this state. That is, the resin layer 5 is easily melted by heating and immediately cured by cooling. Therefore, by utilizing this property, the laminate can be heat-bonded to various objects, and furthermore, small bags can be made by heat-bonding (heat-sealing) the laminates together.

[0083] It should be noted that the adhesive is cured by maintaining a temperature of approximately 30℃ to 50℃ for more than 24 hours.

[0084] In this invention, the heat-sealing film used in the formation of the heat-sealing resin layer 5 described above can be a film made of various thermoplastic resins. In terms of cost, films made of olefin resins are preferred. Especially in the case of making small bags for retorting, heat resistance and impact resistance need to be guaranteed. Therefore, CPP film (also known as unstretched polypropylene film or cast PP film) is preferred. In particular, CPP film made of impact-resistant polypropylene (impact PP) is most preferred in terms of ensuring excellent impact resistance and heat resistance.

[0085] CPP films using the aforementioned impact-resistant PP are formed by melt extrusion of an propylene resin composition comprising an impact-resistant PP component (A) and linear low-density polyethylene (B).

[0086] Impact-resistant PP component (A);

[0087] The impact-resistant PP component (A) is composed of impact-resistant polypropylene (impact-resistant PP), which in this invention has a structure in which ethylene-propylene copolymer (EPR) is dispersed in homopolymer or atactic polypropylene. That is, impact resistance is imparted to polypropylene by dispersing EPR in it. Besides EPR, styrene-butadiene copolymer (SBR), ethylene-propylene-butene copolymer (EPBR), and other rubber components dispersed in polypropylene are known. Even substances other than EPR can improve impact resistance, but EPR is particularly preferred in terms of improving impact resistance at low temperatures.

[0088] From the perspective of film formability (extrusion formability), the MFR (melt flow rate, 230°C) of impact PP, as mentioned above, is in the range of about 0.5 to 10 g / 10 min.

[0089] Furthermore, the EPR content in the aforementioned impact-resistant PP can be expressed as the ratio of xylene-soluble components when the CPP film used in the formation of the heat-sealable resin layer 5 is dissolved in boiling xylene. This xylene-soluble component ratio is 8% by mass or more, and particularly preferably in the range of 8% to 20% by mass. That is, if the xylene-soluble component ratio is less than the above range, the EPR content is low, and therefore the impact resistance of the pouch is reduced. In addition, if the soluble component ratio is too high, it may sometimes result in poor appearance of the pouch.

[0090] Straight-chain low-density polyethylene (B);

[0091] This linear low-density polyethylene (LLDPE) is used as a compatibilizer for polypropylene (PP) and ethylene-propylene copolymer (EPR) when blended with the aforementioned impact-resistant PP. It is a component that fully utilizes the impact-improving effect of EPR by significantly increasing the dispersibility of EPR in PP.

[0092] This type of LLDPE has a density of 0.860 g / cm³. 3 ~0.925g / cm 3 Linear low-density polyethylene within the range of [specific types], such as substances copolymerized with ethylene from α-olefins such as butene-1, hexene-1, 4-methylpentene-1, and octene-1; substances that are low-density by introducing short-chain α-olefin chains as branches into long-chain ethylene chains, and have extremely high molecular linearity.

[0093] Furthermore, since this LLDPE is used in combination with impact-resistant PP, it is preferable to use LLDPE with an MFR (190°C) of 1.0 to 15 g / 10 min in order not to impair the film formability. In addition, as comonomer components, hexene-1 and 4-methylpentene-1 (methylpentene) are preferred, with methylpentene being the most preferred.

[0094] Furthermore, the LLDPE preferably contains 10 mol% or less of the α-olefin as a comonomer and has a number-average molecular weight of 10,000 or more when converted to polystyrene by GPC (Gel Permeation Chromatography). That is, when the content of the α-olefin as a comonomer is high, or when the number-average molecular weight is low and contains a high proportion of low molecular weight components, the oil resistance and flavor profile of the contents deteriorate when used in small pouches.

[0095] The LLDPE (B) described above is preferably designed in a manner where the amount of LLDPE in the CPP film (equivalent to the amount of LLDPE in the heat-sealing resin layer 5) is 20% by mass or less. That is, this is because if the LLDPE content is excessive, it may impair the film's anti-blocking properties and heat resistance.

[0096] It should be noted that in the acrylic resin composition used in the formation of CPP membrane, additives known to the public can also be added in an amount that does not impair recyclability.

[0097] CPP films containing the aforementioned impact-resistant PP components are manufactured by: dry mixing the components, feeding them into an extruder for melt mixing, extruding the blend into a film shape from a T-die, contacting the extruded molten film with a cooling roller to solidify it, and then winding it up.

[0098] There is no particular limitation on the thickness of such CPP film. However, considering rigidity, openability, etc., it is usually preferred to be in the range of 20µm to 100µm, especially 50µm to 80µm.

[0099] Regarding the packaging laminate of the present invention obtained by laminating the above-mentioned layers or films, for example, a printed layer and a transparent protective layer (PET film) can be laminated on the outer surface of the barrier film 1.

[0100] <Other Layers>

[0101] In this invention, it is preferable that, when the aforementioned polypropylene stretch film is used as the thermoplastic resin film 1a serving as the substrate of the inorganic film 1b, a stretch film layer comprising at least one selected from olefin resins, polyamide resins, and ethylene-vinyl alcohol copolymers is provided as a strength reinforcing layer on the outer surface of the stretch film (thermoplastic resin film 1a) or between the inorganic film 1b and the adhesive layer 3. That is, this strength reinforcing layer, unlike the thermoplastic resin film 1a (the film serving as the substrate of the inorganic film 1b) in the barrier film 1, is a layer designed to mitigate the loss of orientation caused by heat treatment such as heat sealing, and effectively suppress strength reduction.

[0102] Such a strength-reinforcing layer is a stretched molded body of a blend or laminate of an olefin resin and a reinforcing resin with a higher melting point than the olefin resin. Stretch films of blends of olefin resin and polyamide resin or ethylene-vinyl alcohol copolymers are particularly preferred. Typically, the mass ratio of olefin resin to reinforcing resin is in the range of approximately 50:50 to 90:10. That is, if the amount of reinforcing resin is excessively high, the strength-reinforcing effect is excellent but the recyclability is low; if the amount of reinforcing resin is low, the strength-reinforcing effect of the layer will be compromised.

[0103] Furthermore, the strength-reinforcing layer can have a laminated structure consisting of an olefin resin layer and a reinforcing resin layer. In such a laminated structure, the thickness ratio of the olefin resin layer to the reinforcing resin layer is typically in the range of approximately 1 / 1 to 3 / 1. That is, if the thickness of the reinforcing resin is too thick, the recyclability of the packaging bag will be significantly reduced; if the amount of reinforcing resin is too small, the amount of oriented crystals present in the sealing part will be less, and the improvement in bag strength may be insufficient.

[0104] Furthermore, the olefin resin used for forming the strength reinforcing layer described above is preferably the same type of olefin resin as the olefin resin used for forming the thermoplastic resin film 1a described above, and polypropylene is particularly preferred.

[0105] Furthermore, there are no particular limitations on the polyamides that can be blended with the aforementioned olefin resins. Various polyamides can be exemplified, with the following generally preferred: nylon 6, nylon 6,6, nylon 11, nylon 12, nylon 13, nylon 6 / nylon 6,6 copolymers, aromatic nylons (e.g., poly(m-phenylene adipamide)).

[0106] The aforementioned strength-reinforcing layer is formed by co-extruding and stretching the blend, or by extruding multiple layers of the blend and stretching them. Stretching is achieved by stretching along a uniaxial or biaxial direction.

[0107] There is no particular limitation on the thickness of this strength-reinforcing layer, as long as it is appropriately set to the thickness of the thermoplastic resin film 1a according to the capacity of the target pouch, etc. Generally speaking, a thickness of 5µm or more is preferred, and it is particularly preferred to be in the range of about 5µm to 30µm.

[0108] It should be noted that the various resins and polymers used in the formation of the thermoplastic resin film 1a and the strength reinforcing layer mentioned above only need to have a molecular weight sufficient to form a film.

[0109] Furthermore, when the aforementioned strength-reinforcing layer is formed between the adhesive layer 3 and the heat-sealing resin layer 5, an adhesive layer 3 is also provided between the strength-reinforcing layer and the heat-sealing resin layer 5. That is, the layer structure of the packaging laminate at this time is barrier film / adhesive layer / strength-reinforcing layer / adhesive layer / heat-sealing resin layer.

[0110] <Application Forms of Packaging Laminates>

[0111] The above-described packaging laminate of the present invention is used to make bags by bonding heat-sealing resin layers, and is used as small bags (bag-shaped containers).

[0112] Bag making is carried out using known methods. For example, an empty pouch is made by using a three-sided seal on two laminated pieces, filling the contents through the opening, and finally closing the opening by heat sealing.

[0113] Alternatively, an empty pouch can be made by folding a single laminate in half and heat-sealing both ends. In this case, it is not necessary to heat-seal the bottom. Furthermore, a laminate specifically designed for the sides or bottom can be used to create the empty pouch. This method is advantageous in terms of increasing the pouch's volume or providing it with a standing position.

[0114] By using the packaging laminate of this invention to manufacture bags, the pouches filled with contents not only possess excellent oxygen barrier properties, but also excellent heat resistance and impact resistance. Even when sterilized by heated steam at 100°C to 130°C (cooking treatment), the reduction in oxygen barrier properties is effectively avoided and excellent oxygen barrier properties are maintained. Therefore, such pouches are extremely suitable, especially for food packaging.

[0115] Furthermore, from a recycling point of view, it is preferable to adjust the types of various materials and the thickness of various layers in the aforementioned pouches so that the content of olefin resin is 80% by mass or more.

[0116] Example

[0117] The superior effects of the present invention will be illustrated by the following embodiments.

[0118] It should be noted that the following materials were used in the following experiments.

[0119] <Sealing film (heat sealing film)>

[0120] CPP membrane-1;

[0121] TORAYFAN ZK500 manufactured by Toray Film Processing Co., Ltd.

[0122] Thickness: 70µm.

[0123] Xylene soluble component ratio: 16.9% by mass.

[0124] CPP membrane-2;

[0125] TORAYFAN SH41E manufactured by Toray Film Processing Co., Ltd.

[0126] Thickness: 70µm.

[0127] Xylene soluble component ratio: 19.5% by mass.

[0128] CPP membrane-3;

[0129] TORAY FAN3951 manufactured by Toray Film Processing Co., Ltd.

[0130] Thickness: 70µm.

[0131] LLDPE (linear low-density polyethylene) film;

[0132] TUXHZ is manufactured by Mitsui Chemicals Tohcello, Inc.

[0133] Thickness: 70µm.

[0134] Barrier membrane

[0135] Barrier stretched polypropylene film-1 (barrier film-1);

[0136] Thickness: 20µm.

[0137] Inorganic film: A film formed by applying a coating mainly composed of silicon oxide onto a vapor-deposited film mainly composed of silicon oxide.

[0138] Barrier stretched polypropylene film-2 (barrier film-2)

[0139] Thickness: 20µm.

[0140] Inorganic film: A film formed by depositing a coating mainly composed of silicon oxide on a vapor-deposited film mainly composed of aluminum oxide.

[0141] <Other membranes>

[0142] Stretched polypropylene film (OPP film);

[0143] BAIREN P2271 manufactured by Toyobo Co., Ltd.

[0144] Thickness: 20µm.

[0145] <Adhesive>

[0146] Epoxy adhesive; MAXIVE manufactured by Mitsubishi Gas Chemical Co., Ltd.

[0147] Coating liquid

[0148] Epoxy resin M-100 / Polyamine C-93T / Mixed solvent

[0149] =5.4 / 18.6 / 60

[0150] Mixed solvent: Methanol / ethyl acetate = 9 / 1

[0151] Polyurethane adhesive A; manufactured by Toyo-Morton, Ltd.

[0152] Coating liquid a

[0153] Polyester polyol / polyisocyanate / ethyl acetate

[0154] =66 / 6.3 / 70

[0155] Coating liquid b

[0156] Polyester polyol / polyisocyanate / ethyl acetate

[0157] =34 / 17 / 55

[0158] Polyurethane adhesive B; PASLIM manufactured by DIC Corporation.

[0159] Coating liquid

[0160] Polyester polyol VM001 / polyisocyanate VM108CP / ethyl acetate

[0161] =10 / 3.8 / 16.2

[0162] The lamination process, bag making, and cooking of the laminated film are described below.

[0163] <Layer Composition>

[0164] To produce two-layer products made by laminating a barrier film (barrier stretched polypropylene) / adhesive / sealing film, and three-layer products made by laminating other films (stretched polypropylene) / barrier film / sealing film.

[0165] It should be noted that the adhesive is not included in the number of layers.

[0166] Lamination

[0167] Lamination was performed using a dry lamination method to obtain a laminate. An adhesive (coating liquid) was applied using a doctor blade coater. The coating amount was set to approximately 4 g / m³ (solids weight). 2 .

[0168] In two-layer compositions, the inorganic film side is laminated with the sealing side facing towards it. In three-layer compositions, to use the barrier film as an intermediate layer, the non-inorganic film side is subjected to corona discharge treatment to hydrophilize its surface. Furthermore, the films are laminated with the inorganic film side facing towards the other film sides. After lamination, they are cured at 50°C for 4 days.

[0169] Bag Making

[0170] Two laminated films (laminated bodies) are cut into 140mm × 180mm pieces and filled with 200g of water to make bags. These bags are then sealed using a pulse sealing machine manufactured by Fuji Impulse Co., Ltd.

[0171] Sealing conditions: 180℃, 1.4 (s), cooling 3.0 (s).

[0172] Sealing width: 5mm.

[0173] <Steaming / Cooking Conditions>

[0174] 121℃×30 minutes spray type

[0175] The evaluation of various physical properties is carried out using the following methods.

[0176] <Determination of Elastic Modulus of Adhesive Coating Monomers>

[0177] Method for preparing adhesive coatings;

[0178] Adhesive coatings are made by preparing individual coating solutions and applying them onto a silicon substrate.

[0179] Methods for determining elastic modulus;

[0180] The dynamic viscoelasticity measuring apparatus manufactured by Seiko Instruments Inc. was used.

[0181] Test film: 5.0 mm in length and 10 mm in width.

[0182] Temperature range: 20℃~150℃.

[0183] Heating rate: 3℃ / min.

[0184] Frequency: 10Hz.

[0185] The energy storage modulus E' at 120℃ is used for evaluation.

[0186] <Preparation of the laminate of barrier film and adhesive layer and evaluation of its heat shrinkage>

[0187] Fabrication of barrier films made of laminated adhesives;

[0188] The adhesive coating solution is applied to the vapor-deposited surface of the barrier film using a doctor blade coater. The coating amount is set to approximately 4 g / m² (solids weight). 2 .

[0189] <Determination of Oxygen Permeability>

[0190] The measurements were performed using MOCON's OX-TRAN2 / 22 at 40°C and 90% RH.

[0191] The small bags before and after the steaming / cooking treatment were cut out for testing.

[0192] <Example 1>

[0193] The elastic modulus of the epoxy adhesive (MAXIVE) coating was determined.

[0194] Next, an epoxy adhesive coating solution is applied to the vapor-deposited surface of the barrier stretched polypropylene film-1 (coating amount in solids conversion: approximately 4 g / m²). 2 A two-layer laminate was obtained by laminating a sealing film (CPP film-1) on top of it using a dry lamination method.

[0195] After curing the laminate at 50°C for 4 days, the laminate was used to make small bags (filled with 200g of water) and then subjected to a boiling treatment. At this time, the oxygen permeability before and after the boiling treatment was measured.

[0196] The experimental results are shown in Table 1.

[0197] <Example 2>

[0198] Using the same epoxy adhesive as in Example 1, a three-layer laminate consisting of OPP film / adhesive / barrier film-1 / adhesive / CPP film-1 was fabricated.

[0199] The laminated material was used to make small bags, which were then subjected to a cooking process, and the oxygen permeability after the cooking process was measured.

[0200] The experimental results are shown in Table 1.

[0201] <Example 3>

[0202] Using the same epoxy adhesive as in Example 1, a three-layer laminate consisting of OPP film / adhesive / barrier film-1 / adhesive / CPP film-2 was fabricated.

[0203] The laminated material was used to make small bags, which were then subjected to a cooking process, and the oxygen permeability after the cooking process was measured.

[0204] The experimental results are shown in Table 1.

[0205] <Example 4>

[0206] Using the same epoxy adhesive as in Example 1, a three-layer laminate consisting of OPP film / adhesive / barrier film-1 / adhesive / CPP film-3 was fabricated.

[0207] The laminated material was used to make small bags, which were then subjected to a cooking process, and the oxygen permeability after the cooking process was measured.

[0208] The experimental results are shown in Table 1.

[0209] <Example 5>

[0210] Using the same epoxy-based adhesive as in Example 1, a three-layer laminate consisting of an OPP film, an adhesive, a barrier film-1, an adhesive, and an LLDPE film was fabricated. This laminate was used to make small bags, which were then subjected to a retort treatment, and the oxygen permeability after the retort treatment was measured.

[0211] The experimental results are shown in Table 1.

[0212] <Example 6>

[0213] Using the same epoxy-based adhesive as in Example 1, a two-layer laminate consisting of barrier film-2, adhesive, and CPP-1 film was fabricated. This laminate was used to make small bags, which were then subjected to a retort treatment, and the oxygen permeability after the retort treatment was measured.

[0214] The experimental results are shown in Table 1.

[0215] <Comparative Example 1>

[0216] The elastic modulus of the coating obtained from coating solution a of polyurethane adhesive A was determined.

[0217] In addition to using the adhesive mentioned above, a laminate consisting of two layers, barrier film-1 / adhesive / CPP film-1, was prepared in the same manner as in Example 1. The laminate was used to make small bags, which were then subjected to a cooking process, and the oxygen permeability before and after the cooking process was measured.

[0218] The experimental results are shown in Table 1.

[0219] <Comparative Example 2>

[0220] The elastic modulus of the coating obtained by polyurethane adhesive B was determined.

[0221] In addition to using the adhesive mentioned above, a laminate consisting of two layers, barrier film-1 / adhesive / CPP film-1, was prepared in the same manner as in Example 1. The laminate was used to make small bags, which were then subjected to a cooking process, and the oxygen permeability before and after the cooking process was measured.

[0222] The experimental results are shown in Table 1.

[0223] <Comparative Example 3>

[0224] The elastic modulus of the coating obtained from coating solution b of polyurethane adhesive A was determined.

[0225] In addition to using the adhesive mentioned above, a laminate consisting of a barrier film-1, an adhesive, and a CPP film-1 was prepared in the same manner as in Example 1. The laminate was used to make small bags, which were then subjected to a boiling treatment, and the oxygen permeability before and after the boiling treatment was measured.

[0226] The experimental results are shown in Table 1.

[0227] <Comparative Example 4>

[0228] Using the same adhesive as Comparative Example 1, a three-layer laminate consisting of OPP film / adhesive / barrier film-1 / adhesive / CPP film-1 was prepared. Small bags were made using this laminate, and a retorting treatment was performed to determine the oxygen permeability after the retorting treatment.

[0229] The experimental results are shown in Table 1.

[0230] <Comparative Example 5>

[0231] Using the same adhesive as Comparative Example 1, a three-layer laminate consisting of an OPP film, an adhesive, a barrier film-1, an adhesive, and an LLDPE film was prepared. This laminate was used to make small bags, which were then subjected to a retort treatment, and the oxygen permeability after the retort treatment was measured.

[0232] The experimental results are shown in Table 1.

[0233] <Comparative Example 6>

[0234] Using the same adhesive as Comparative Example 1, a two-layer laminate consisting of barrier film-2, adhesive, and CPP film-1 was prepared. This laminate was used to make small bags, which were then subjected to a retort treatment, and the oxygen permeability after the retort treatment was measured.

[0235] The experimental results are shown in Table 1.

[0236] It should be noted that the abbreviations used in Table 1 regarding layer composition have the following meanings.

[0237] CPP1: CPP membrane-1.

[0238] CPP2: CPP membrane-2.

[0239] CPP3: CPP membrane-3.

[0240] LLDPE: LLDPE membrane.

[0241] BA1: Barrier membrane-1.

[0242] BA2: Barrier membrane-2.

[0243] OPP: OPP film (stretched polypropylene film).

[0244] AD: Adhesive.

[0245] [Table 1]

[0246]

Claims

1. A laminated body for packaging, characterized in that, The packaging laminate comprises: a barrier film, an inorganic film formed on the surface of a thermoplastic resin film; an adhesive layer disposed on the inorganic film; and a heat-sealable resin layer. The adhesive layer is formed of an epoxy-based adhesive and has a storage modulus higher than 39 MPa at 120°C. The heat-sealable resin layer is composed of an propylene-based resin composition, which includes an impact polypropylene component (A) of ethylene-propylene copolymer dispersed in polypropylene, wherein the proportion of xylene-soluble components derived from the ethylene-propylene copolymer in the propylene-based resin composition is in the range of 8% by mass or more. The thermoplastic resin film is a stretched polypropylene film. The packaging laminate contains 80% by mass or more of an olefin-based resin. A strength-reinforcing layer is formed by an adhesive layer disposed on the inorganic film of the barrier membrane.

2. The packaging laminate according to claim 1, wherein, The strength-enhancing layer is composed of a stretch film containing at least one selected from olefin resins, polyamide resins, and ethylene-vinyl alcohol copolymers.

3. The packaging laminate according to claim 1, wherein, The strength-reinforcing layer is formed from a stretched polypropylene film.

4. The packaging laminate according to claim 1, wherein, A heat-sealable resin layer is formed on one side of the non-inorganic film surface of the barrier membrane by means of an adhesive layer.

5. The packaging laminate according to claim 1, wherein, The inorganic film is a vapor-deposited film.

6. A pouch obtained by heat-sealing a packaging laminate according to claim 1.

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