Packaging bags and multilayer packaging films used to make the packaging bags

Abstract

The present invention relates to a packaging bag (10), characterized in that a multilayer film (5) for packaging with a heat-sealable resin layer (3) on its surface is used, which is formed by bonding the heat-sealable resin layers (3) of the film (5) together, and in the packaging bag (10), there are oriented crystals in the sealing part (7) formed by bonding the heat-sealable resin layers (3) together.

Description

Technical Field

[0001] This invention relates to a packaging bag, and also to a multilayer film for making the packaging bag. Background Technology

[0002] CPP film (also known as unstretched polypropylene film or cast PP film), formed from polypropylene and possessing heat-sealable properties, has excellent heat resistance and is used to make bags for containing various foods. Furthermore, in recent years, higher heat resistance and impact resistance have been required for processes such as retort sterilization (heated steam sterilization). Therefore, impact-resistant polypropylene (hereinafter, sometimes referred to as impact-resistant PP) has been used to make CPP film.

[0003] Impact-resistant PP, also known as block PP, impact-resistant copolymer, or high-impact polypropylene, contains rubber components such as ethylene-propylene copolymer (EPR) and styrene-butadiene copolymer (SBR) dispersed in a homopolymer or atactic polypropylene matrix. The presence of these rubber components significantly improves its impact resistance.

[0004] Furthermore, traditional retort pouches use multilayer films with a layered structure of biaxially stretched PET / biaxially stretched nylon / Al / CPP, which offer high impact resistance and rarely break when dropped from a height. However, due to their multilayered composition of different materials, they lack recyclability. Therefore, in recent years, there has been a demand for single-material polypropylene bags in response to recycling needs. However, such single-material bags do not use biaxially stretched PET or biaxially stretched nylon, so while they are suitable for recycling, they have low impact resistance.

[0005] For example, Patent Documents 1 and 2 disclose propylene resin compositions in which linear low-density polyethylene (LLDPE) is incorporated into propylene-based impact-resistant copolymers (equivalent to impact-resistant PP), and disclose that heat-sealing films with various excellent properties can be obtained from these resin compositions.

[0006] In patent documents 1 and 2, the physical properties of heat-sealing films formed from impact-resistant PP are improved by incorporating linear low-density polyethylene into impact-resistant PP, but the drop strength of packaging bags obtained using such heat-sealing resin layers is still not satisfactory.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 4844091

[0010] Patent Document 2: WO2017 / 038349 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] Therefore, the problem of the present invention is to provide a packaging bag with significantly improved bag drop strength and a multilayer film for obtaining the packaging bag.

[0013] Another problem with the present invention is to provide a packaging bag with improved bag strength without compromising recyclability, and a multilayer film for obtaining the packaging bag.

[0014] Technical solution

[0015] The inventors have discovered that when a multilayer film for packaging with a heat-sealable resin layer on its surface is used to make a packaging bag by stacking the multilayer film with the heat-sealable resin layers facing each other, the bag drop strength is improved without compromising recyclability when oriented crystals are present in the sealing part (i.e., the joint part of the multilayer film).

[0016] According to the present invention, a packaging bag is provided, characterized in that it is formed by bonding the heat-sealable resin layers of the packaging multilayer film having heat-sealable resin layers on its surface, wherein oriented crystals are present in the sealing portion formed by the bonding of the heat-sealable resin layers to each other in the packaging bag.

[0017] The following scheme is preferably applied in the packaging bag of the present invention.

[0018] (1) The multilayer film for packaging includes a strength-enhancing stretch film for presenting the oriented crystals in the sealing portion.

[0019] (2) The strength-enhancing stretch film comprises an olefin resin and a reinforcing resin with a melting point higher than that of the olefin resin.

[0020] (3) The strength-enhancing stretch film is formed from a mixture of the olefin resin and the reinforcing resin.

[0021] (4) The strength-enhancing stretch film is a laminate of the olefin resin layer and the reinforcing resin layer.

[0022] (5) The reinforcing resin is polyamide, polyester or ethylene-vinyl alcohol copolymer.

[0023] (6) In addition to the strength-enhancing stretch film, the multilayer film for packaging also includes a substrate film for improving recyclability.

[0024] (7) Contains olefin resin in an amount of 80% or more by mass.

[0025] (8) The heat-sealing resin layer is an unstretched molded body containing impact-resistant polypropylene, and the loss tangent (tanδ) at 5°C in the dynamic viscoelasticity test exceeds 0.0594 and the storage modulus (E') at 110°C exceeds 1MPa.

[0026] (9) The unstretched molded body comprises an impact-resistant polypropylene component (A) formed by dispersing an ethylene-propylene copolymer and linear low-density polyethylene (B) in polypropylene.

[0027] (10) The unstretched molded body contains more than 8% by mass of xylene-soluble components derived from ethylene-propylene copolymer.

[0028] (11) The unstretched molded body contains the linear low-density polyethylene (B) in an amount of less than 20% by mass.

[0029] According to the present invention, a multilayer film for packaging is provided, characterized in that it comprises a heat-sealable resin layer and a support film laminated thereon with an adhesive layer, wherein the support film has a strength-reinforcing stretch film comprising an olefin resin and a reinforcing resin having a melting point higher than that of the olefin resin.

[0030] That is, the packaging bag can be obtained by heat-sealing the multilayer film used for packaging described above.

[0031] Invention Effects

[0032] The packaging bag of the present invention is obtained by heat-sealing a multilayer film for packaging, comprising a substrate layer and a heat-sealable resin layer. It is characterized by the presence of oriented crystals in the sealing portion (the portion formed by the bonding of the heat-sealable resin layers). The presence of oriented crystals in the sealing portion means that there are stretched portions in the multilayer film for packaging, and the orientation caused by stretching during heat sealing is not completely eliminated.

[0033] That is, the orientation crystals in the sealing portion of the recyclable packaging bag of the present invention do not disappear, resulting in a significant increase in the bag's tear resistance. For example, if the examples and comparative examples that were tested by filling a certain amount of water (horizontal drop test) are compared, in the packaging bag of Comparative Example 1 where there are no orientation crystals in the sealing portion, the number of times the bag did not break during horizontal drop was 5, while in the packaging bag of Example 1 where there are orientation crystals in the sealing portion, the number of times the bag did not break during horizontal drop exceeded 10.

[0034] The greatest advantage of the packaging bag of the present invention, which improves the bag-drying strength by having oriented crystals present in the sealing portion, is that it can be made using a multilayer film for packaging composed primarily of the same resin material, thereby significantly improving recyclability. For example, by having oriented crystals present in the sealing portion of a packaging bag formed using a multilayer film composed primarily of olefin-based resins such as polypropylene, more than 80% by mass of the packaging bag can be made of olefin-based resin, ensuring extremely high recyclability. Attached Figure Description

[0035] Figure 1 This is a schematic cross-sectional view of the packaging bag of the present invention.

[0036] Figure 2 This is a schematic cross-sectional view showing an example of a multilayer film for packaging according to the present invention.

[0037] Figure 3 This is a schematic cross-sectional view showing another example of the multilayer film for packaging according to the present invention. Detailed Implementation

[0038] Reference Figure 1 The packaging bag of the present invention, generally indicated by 10, is obtained by heat-sealing a multilayer film 5 for packaging, which includes a support film 1 for ensuring the shape of the bag and a heat-sealable resin layer 3. Figure 1 It is understood that the periphery of the packaging bag 10 has a sealing part 7 formed by heat sealing (heat fusion) between the heat-sealable resin layers 3.

[0039] The inside of such a packaging bag 10 is filled with various contents 9 such as liquid, paste, powder or granules, so it is required to have high drop strength in order not to break the bag when it falls.

[0040] In the packaging bag 10 of the present invention, oriented crystals are present in the sealing portion 7, thereby ensuring high drop strength. That is, when the packaging bag 10 is dropped, stress is generated in the direction of opening the sealing portion 7 due to the contents 9. In the present invention, since oriented crystals are present in the sealing portion 7, damage to the sealing portion 7 caused by such stress is effectively suppressed, resulting in high drop strength.

[0041] It should be noted that the oriented crystals present in the sealing part 7 can be confirmed, for example, by two-dimensional X-ray diffraction.

[0042] In this invention, the layer structure of the multilayer film 5 used to form the packaging bag 10 is designed to prevent the loss of orientation crystals caused by heat sealing. Based on this layer structure, heat sealing conditions can be achieved using a sealing strip within the same temperature range as usual, further imparting heat resistance and impact resistance to the packaging bag 10.

[0043] In this invention, the support film 1 laminated on the heat-sealing resin layer 3 includes: a strength-enhancing stretch film for ensuring the presence of the aforementioned oriented crystals in the sealing portion 7 and a substrate film for ensuring recyclability, having a layer structure that varies depending on the positional relationship between the strength-enhancing stretch film and the substrate film.

[0044] exist Figure 2 and Figure 3 The layer structure of such a multilayer film 5 is shown in the figure.

[0045] Figure 2 The multilayer film 5 shown has a support film 1 with the following layer structure: between the substrate film 11 and the heat-sealing resin layer 3, a strength-reinforcing stretch film 21 is sandwiched between adhesive layers 23, 23.

[0046] In addition, Figure 3 In the middle, there is the following layer structure: between the strength-reinforcing tensile film 21 and the heat-sealing resin layer 3, the substrate film 11 is sandwiched by adhesive layers 23, 23.

[0047] exist Figure 2 and Figure 3 In any of the schemes, the oriented crystal can remain in the sealing part 7, thereby improving the bag dropping strength.

[0048] Substrate film 11;

[0049] The substrate film 11 is designed to ensure recyclability, and is therefore primarily composed of an olefin-based resin, similar to the heat-sealing resin layer 3, and is manufactured using known methods such as extrusion molding. In particular, when gas barrier properties are required, an propylene-based film with an inorganic film is used; when gas barrier properties are not required, a conventional propylene-based film is used, considering factors such as strength, heat resistance, cost, and formability.

[0050] Of course, the substrate film 11 can be omitted if recyclability is not required.

[0051] Acrylic resins are represented by polypropylene (a homopolymer of propylene), but as long as the properties of polypropylene are not compromised, they can also be random or block copolymers formed by copolymerizing α-olefins or cyclic olefins such as ethylene, 1-butene, and 4-methyl-1-pentene.

[0052] Furthermore, the substrate film 11, formed from acrylic resin, is preferably stretched along a uniaxial or biaxial direction. This substrate film 11 is not used to ensure the presence of oriented crystals in the sealing portion 7, but its strength is further improved by stretching. The stretching ratio of the stretched film forming the substrate film 11 is only required to prevent film breakage due to overstretching, typically around 2 to 5 times.

[0053] The thickness of the substrate film 11 can be appropriate depending on the capacity of the final manufactured bag, and generally, a thickness of 10 μm or more is sufficient.

[0054] Furthermore, in the substrate film 11, especially in the substrate film 11 formed of acrylic resin, in order to improve the gas barrier properties, gas barrier resins such as ethylene-vinyl alcohol copolymers may be laminated, or an inorganic coating may be formed on its surface.

[0055] Such a barrier resin layer is laminated onto the substrate film 11 using a dry lamination adhesive, such as an olefin resin (e.g., polyethylene, polypropylene) modified with unsaturated carboxylic acids like maleic acid, urethane-based, or epoxy-based adhesives. Furthermore, the inorganic coating is primarily formed of: an inorganic vapor-deposited film formed by physical vapor deposition (e.g., sputtering, vacuum evaporation, ion plating), or chemical vapor deposition (e.g., plasma CVD); or an inorganic coating formed by wet coating, such as silicon compounds, aluminum oxides, or various metals or metal oxides. Moreover, the aforementioned inorganic coating can also be applied to the vapor-deposited film. Because such an inorganic coating is formed from inorganic materials, it exhibits higher oxygen barrier properties compared to barrier resins such as ethylene-vinyl alcohol copolymers.

[0056] Strength-enhancing stretch membrane 21;

[0057] Strength-enhancing stretch membrane 21, etc. Figure 2 and Figure 3 As shown, it is disposed between the substrate film 11 and the heat-sealing resin layer 3 or on the outermost side of the packaging bag 10. In order to form such a multilayer film 5, the substrate film 11 is bonded to the strength-reinforcing stretch film 21, and an adhesive layer 23 is provided to bond the stretch film 21 or the substrate film 11 to the heat-sealing resin layer 3.

[0058] As the adhesive for forming such an adhesive layer 23, adhesive resins such as olefin resins modified with unsaturated carboxylic acids such as maleic acid, urethane-based or epoxy-based dry lamination adhesives can be used.

[0059] Examples of urethane-based dry lamination adhesives include those composed of reactants of isocyanates with (meth)acrylic compounds and polyester polyols. These adhesives typically include known curing catalysts such as amine catalysts, metal catalysts, or phosphoric acid-modified compounds. The amount of curing catalyst is determined based on the type of catalyst, aiming to form a dense cured film (adhesive layer) at the temperature and time without thermal deformation of the base resin.

[0060] In addition, epoxy adhesives include liquid resins with epoxy groups in their molecules and epoxy curing agents.

[0061] Liquid resins containing epoxy groups in their molecules are exemplified by those obtained through the reaction of epichlorohydrin with phenolic compounds, amine compounds, carboxylic acids, etc., and those obtained by oxidizing unsaturated compounds such as butadiene with organic peroxides, etc. Any type of liquid resin can be used. Specific examples 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, and glycidylamine type epoxy resins.

[0062] Furthermore, known epoxy curing agents such as amines, acid anhydrides, and polyamides can be used, with aromatic polyamines, particularly m-phenylenediamine, being the most preferred. The ratio of epoxy resin to curing agent should be set according to the epoxy equivalent of the epoxy resin to form a sufficiently cured film.

[0063] Therefore, at least one of the strength-enhancing stretch film 21 contains an adhesive layer 23 formed of the adhesive. Regarding the thickness of the adhesive layer 23 thus formed, it is typically 5–30 μm in adhesive layers represented by modified olefin resins, and about 0.1–10 μm in urethane and epoxy adhesive layers.

[0064] In this invention, the oriented crystals in the strength-enhancing stretch film 21 remain in the sealing part 7, which can greatly improve the bag drop strength.

[0065] Such a strength-reinforcing stretch film 21 is a stretched molded body of a mixture or laminate of an olefin-based resin and a reinforcing resin with a melting point higher than that olefin-based resin. That is, when the packaging bag 10 is formed by heat sealing with the heat-sealing resin layer 3 (described later), the molecular orientation of the strength-reinforcing stretch film 21 remains due to the heat sealing, and high strength is achieved through this molecular orientation, which can significantly improve the bag drop strength compared to a bag made only of acrylic resin.

[0066] Examples of olefin-based resins include: low-density polyethylene, high-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. Examples of olefin copolymers and impact-resistant polypropylene are also included. In particular, considering heat resistance, propylene-based resins such as polypropylene or copolymers of propylene with other α-olefins are preferred.

[0067] Furthermore, as a reinforcing resin, there are no particular restrictions as long as the melting point is higher than that of olefin resins. In fact, considering the ability to perform stretching in the presence of olefin resins, polyamide resins, polyester resins, and ethylene-vinyl alcohol copolymer resins are preferred.

[0068] Examples of polyamide resins include: nylon 6, nylon 6-6, nylon 6-10, nylon 11, nylon 12, nylon 13, nylon 6 / nylon 6,6 copolymer, aromatic nylons (e.g., poly(m-phenylene adipamide)), and amorphous nylons (e.g., nylon 6I / 6T). Examples of polyester resins include: polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate (PEN). For ethylene-vinyl alcohol copolymer resins, resins with an ethylene copolymerization rate in the range of 20 mol% to 40 mol% are preferred.

[0069] In the mixture of olefin resin and reinforcing resin used to form such a strength-reinforcing stretch film 21, the mass ratio of olefin resin to reinforcing resin is typically in the range of about 50:50 to 90:10. That is, if the amount of reinforcing resin is too large, stretching becomes difficult, and the recyclability of the packaging bag is significantly reduced; if the amount of reinforcing resin is too small, the amount of oriented crystals present in the sealing part may decrease, and the improvement in bag strength is insufficient.

[0070] Furthermore, a compatibilizer for uniformly dispersing the olefin resin and the reinforcing resin can also be used in the above mixture. Examples of such compatibilizers include acid-modified olefin resins or imine-modified olefin resins. It is generally preferred that about 10 to 60% by mass of the compatibilizer be incorporated into the mixture, thereby enabling stable stretching.

[0071] The above mixture is prepared by stretching a film formed by extrusion at a temperature above the glass transition temperature (Tg) of an olefin resin but below its melting point, for example, by stretching the film obtained by melt mixing in an extruder. The stretching can be performed in a uniaxial or biaxial direction, and the stretching ratio is preferably 2 times or more.

[0072] The thickness of the aforementioned strength-enhancing stretch film 21 is not particularly limited, and can be appropriately set according to the thickness of the substrate layer 1, which is determined based on the target bag capacity, etc. Generally, a thickness of 5 μm or more is preferred, and a thickness in the range of about 10 to 20 μm is particularly preferred.

[0073] The strength-reinforcing stretch film 21 can, for example, 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 about 1 / 1 to 3 / 1. That is, if the thickness of the reinforcing resin is too large, the recyclability of the packaging bag will be significantly lost; if the amount of reinforcing resin is too small, the amount of oriented crystals present in the sealing part may be reduced, and the improvement in bag strength will be insufficient.

[0074] The strength-reinforcing stretch film 21 having the above-described laminated structure is manufactured by: co-extruding an olefin resin and a reinforcing resin with a melting point higher than that of the olefin resin, sandwiching the adhesive between them as needed, and then stretching it, for example, at a temperature above the glass transition temperature (Tg) of the olefin resin but below its melting point. Stretching can be performed in a uniaxial or biaxial direction, and the stretching ratio is preferably 2 times or more.

[0075] In other words, from a recycling perspective, the amount of reinforcing resin used cannot be excessive. Therefore, by using an olefin-based resin as a support material and performing co-extrusion / co-stretching, the amount of reinforcing resin used can be suppressed. For example, in the strength-reinforcing stretch film 21 of this laminated structure, the thickness of the reinforcing resin stretch film can be controlled to about 5 μm, which can ensure recycling while leaving oriented crystals and significantly improving bag strength.

[0076] It should be noted that, in the case of this type of laminated strength-enhancing stretch film, the reinforcing resin layer side can also be located on the heat-sealing resin layer side, and the olefin resin layer side can also be located on the heat-sealing resin layer side.

[0077] 3. Heat-sealable resin layer (sealant);

[0078] The heat-sealable resin layer 3 is laminated by overlapping and pressing it onto the adhesive layer 23 coated on the stretch film 21, and the adhesive is then heated and cured in this state. The heat-sealable resin layer 3 melts easily by heating and cures immediately by cooling, so it can be used to produce a packaging bag (bag 10) by heat-bonding (heat-sealing) the multilayer film 5 (heat-sealable resin layer 3) to each other.

[0079] In this invention, the aforementioned heat-sealing resin layer 3 can also be formed from a common polyolefin such as polypropylene. To impart impact resistance and heat resistance to the packaging bag 10, it is ideal to have dynamic viscoelastic properties. For example, preferably, the loss tangent (tanδ) at 5°C in a dynamic viscoelasticity test at 10 Hz exceeds 0.0594, thereby improving impact resistance in low-temperature regions. That is, by having such viscoelasticity at 5°C, the heat-sealing resin layer 3 achieves good low-temperature impact resistance in low-temperature regions (around 5°C), becoming a packaging bag that is very difficult to break. Furthermore, the storage modulus (E') at 110°C in the dynamic viscoelasticity test at 10 Hz must still be greater than 1 MPa. That is, with such a large storage modulus (E') at 110°C, the heat-sealing resin layer 3 exhibits moderate elasticity in high-temperature regions (around 110°C), maintaining sufficient sealing strength to seal the bag even at high temperatures. Therefore, the packaging bag 10 has high sealing strength at high temperatures, which can effectively prevent the seal from being damaged by microwave heating and effectively carry out microwave heating.

[0080] In this invention, the heat-sealing resin layer 3 having the viscoelasticity described above can be made simply by using a cast film containing impact-resistant polypropylene (hereinafter referred to as CPP film), adjusting the composition of the impact-resistant PP, and the type and amount of the modified resin components used.

[0081] That is, the CPP film with the above-mentioned viscoelasticity is obtained by melt extrusion of a resin composition containing an impact-resistant PP component (A) and a modified resin component (B).

[0082] Impact-resistant PP component (A);

[0083] The impact-resistant PP component (A) is composed of impact-resistant polypropylene (impact-resistant PP), which specifically has a structure in which ethylene-propylene copolymer (EPR) is dispersed in homopolymer or atactic polypropylene. That is, impact resistance is imparted by dispersing EPR in polypropylene. Besides EPR, other rubber components dispersed in polypropylene include styrene-butadiene copolymer (SBR) and ethylene-propylene-butene copolymer (EPBR). Even rubber components other than EPR can improve impact resistance at low temperatures (tanδ greater than 0.0594 at 5°C), but EPR is the best.

[0084] From the perspective of film formability (extrusion formability), the MFR (melt flow rate, 230°C) of the impact-resistant PP, as mentioned above, is in the range of about 0.5 to 10 g / 10 min.

[0085] Furthermore, the EPR content in the aforementioned impact-resistant PP can be expressed by the ratio of xylene-soluble components when the CPP film used to form the heat-sealable resin layer 3 is dissolved in boiling xylene. Ideally, this xylene-soluble component ratio is in the range of 8% by mass or more, and particularly ideally, it is 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 bag will decrease. In addition, if the soluble component ratio is too high, it may sometimes result in insufficient heat resistance and poor bag appearance.

[0086] Furthermore, the intrinsic viscosity of the xylene-soluble component (EPR) measured (using tetrahydronaphthalene at 135°C as a solvent) is preferably in the range of 1.0 to 2.9 dl / g. This intrinsic viscosity is a parameter corresponding to the molecular weight of EPR in the impact-resistant PP. When this value is outside the above range, there is a tendency for the impact resistance to be unsatisfactory. This is thought to be because the size of the EPR molecules is either larger or smaller than required, and therefore, the properties of the modified resin component (B) described below are not fully utilized.

[0087] Modified resin component (B);

[0088] The modified resin component (B) is used to significantly improve the dispersibility of EPR in PP by increasing the compatibility between polypropylene (PP) and ethylene-propylene copolymer (EPR) in the above-mentioned impact-resistant PP, thereby maximizing the impact resistance improvement effect of EPR.

[0089] As the modified resin component (B), linear low-density polyethylene (LLDPE) is preferably used. This LLDPE has a density in the range of 0.860–0.925 g / cm³. 3 The range of linear low-density polyethylene, for example, is produced by copolymerizing trace amounts of α-olefins such as butene-1, hexene-1, and 4-methylpentene-1 with ethylene to reduce density. The linearity of the molecules is extremely high.

[0090] 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 compromise the film formability.

[0091] Furthermore, it is preferable that the LLDPE contains 12 mol% or less of α-olefins as comonomers, and that the number-average molecular weight of the polystyrene, as determined by GPC, is 10,000 or more. That is, if the content of α-olefins as comonomers is high, or if the number-average molecular weight is low and contains a large number of low molecular weight components, the oil resistance and flavor imparted to the contents will be poor when used as a bag.

[0092] Regarding the LLDPE(B) mentioned above, it is preferable to design the membrane composition such that the amount of LLDPE in the CPP membrane (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 an excessive amount of LLDPE is included, it may impair the membrane's anti-blocking properties and heat resistance.

[0093] It should be noted that the resin composition used to form the CPP film may also be combined with its own known additives.

[0094] The CPP film containing the above-mentioned impact-resistant PP is manufactured by the following method: the components are dry-mixed, fed into an extruder for melt mixing, the mixture is melt-extruded from a T-die into a film shape, the extruded film-shaped melt is solidified by contact with a cooling roller, and then wound.

[0095] 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 20 to 100 μm, and particularly preferred to be in the range of 50 to 80 μm.

[0096] As described above, the multilayer film 5, which significantly improves the bag-dropping strength by arranging oriented crystals in the sealing portion 7, has... Figure 2 and Figure 3 The layered structure shown is preferred, but the structure described below is particularly desirable.

[0097] It should be noted that the following abbreviations are used in the following structure.

[0098] SUB: Substrate film 11.

[0099] STRG: Strength-enhancing stretch membrane 21.

[0100] SEAL: A heat-sealable resin layer, preferably a CPP film.

[0101] AD: Adhesive.

[0102] SUB (Inorganic Coating) / AD / STRG / AD / SEAL;

[0103] or

[0104] STRG / AD / SUB (Inorganic Coating) / AD / SEAL.

[0105] In the above example, the inorganic coating can be disposed on any side of the substrate film 11 (SUB).

[0106] In addition, in this invention, a printing layer may also be laminated on the outer surface of the substrate film 11.

[0107] <Production of Packaging Bag 10>

[0108] The multilayer film 5 having the above-mentioned layer structure is bonded by heat sealing in the heat-sealable resin layer 3 to form a bag, thereby obtaining a packaging bag 10.

[0109] Bag making can be carried out using known methods. For example, an empty bag can be made by using a three-way seal of two multilayer films 5, filling the contents from the opening, and finally sealing the opening by heat sealing.

[0110] Alternatively, an empty bag can be made by folding back a multilayer film 5 and heat-sealing both ends. In this case, heat sealing is not required in one of the three directions described above. Furthermore, a dedicated multilayer film 5 for the sides or bottom can be used to make the empty bag. This method is advantageous in increasing the bag's volume or providing upright posture.

[0111] The heat sealing during bag making is performed by heating the heat-sealing resin layer 3 by melting it and pressing it with a sealing strip. This forms a sealing part 7 formed by bonding the peripheries of the multilayer film 5 together. In this sealing part 7, at least one of the olefin resin in the strength-reinforcing tensile film 21 (or the multilayer strength reinforcement) and the reinforcing resin with a melting point higher than that of the olefin resin has oriented crystals.

[0112] The resulting packaging bag 10, filled with contents, is for sale, for example, if the contents are food, after being subjected to a cooking process (sterilization by heated steam at 100–130°C).

[0113] In the packaging bag 10 of the present invention, particularly to ensure recyclability, the multilayer film 5 employs a layer composition that increases the olefin resin content in the base film 11 and the olefin resin content in the strength-reinforcing stretch film 21 (minimizing the amount of reinforcing resin used). The olefin resin content in the packaging bag 10 is preferably 80% by mass or more, and particularly preferably 85% by mass or more. That is, in the present invention, even with such a large amount of olefin resin used, the strength reduction caused by retort sterilization can be effectively avoided, and the bag-drying strength can be improved.

[0114] Example

[0115] The superior effects of the present invention will be illustrated by the following examples.

[0116] It should be noted that the various materials and measurement methods used in the following experiments are as follows.

[0117] <Substrate Film A>

[0118] Transparent vapor-deposited stretched polypropylene film.

[0119] Thickness 20μm.

[0120] Melting point: 163.8℃.

[0121] <Strength-reinforcing tensile membrane material>

[0122] Olefin resins;

[0123] Polypropylene resin (a1);

[0124] Prime polymer manufactures E-200GV (homopolymer PP).

[0125] Melting point: 164.1℃.

[0126] MFR: 1.6g / 10min (230℃, 2.16kg).

[0127] Adhesive resin (b1);

[0128] Mitsui Chemicals Co., Ltd. QB550.

[0129] Melting point: 141.6℃.

[0130] MFR: 2.8g / 10min (230℃, 2.16kg).

[0131] Density: 890 kg / m³ 3 .

[0132] Adhesive resin (b2);

[0133] Mitsui Chemicals Co., Ltd. QB500.

[0134] Melting point: 160.1℃.

[0135] MFR: 3.0g / 10min (230℃, 2.16kg).

[0136] Reinforcing resin;

[0137] Polyamide resin (c1);

[0138] Unitika Production A1030BRT.

[0139] Melting point: 219.7℃.

[0140] MFR: 8.2g / 10min (250℃, 2.16kg).

[0141] Density: 1130 kg / m³ 3 .

[0142] Polyamide resin (c2);

[0143] Ube Kosan Co., Ltd. 1013B.

[0144] Melting point: 221.0℃.

[0145] MFR: 51.2g / 10min (250℃, 2.16kg).

[0146] Density: 1140 kg / m³ 3 .

[0147] Ethylene-vinyl alcohol copolymer (c3);

[0148] Kuraray Production J171B.

[0149] Melting point: 180.1℃.

[0150] MFR: 6.2g / 10min (230℃, 2.16kg).

[0151] Density: 1140 kg / m³ 3 .

[0152] <Fabrication of Composite Membranes (A) to (C)>

[0153] Polypropylene resin (a1), adhesive resin (b1), and reinforcing resin were fed into the hopper of a twin-screw extruder with a T-die. Melt mixing was performed inside the extruder, with the screw speed set to 100 rpm. The mixture was discharged from the T-die as a film, which was then cured upon contact with cooling rollers and wound to obtain a composite film with an average thickness of 170 μm. This film is an unstretched film used to produce a strength-reinforcing layer (strength-reinforcing stretched film).

[0154] The type of reinforcing resin used, the temperature settings (C1 to C4) of the extruder barrel, the temperature setting of the T-die, and the setting of the cooling roller are as shown in Tables 1 and 2 below.

[0155] [Table 1]

[0156] Composition ratio (by weight) Composite membrane (A) a1 / b1 / c1=1 / 1 / 1 Composite membrane (B) a1 / b1 / c2 = 2 / 0.15 / 0.85 Composite membrane (C) a1 / b1 / c3=1 / 1 / 1

[0157] [Table 2]

[0158]

[0159] <Preparation of Co-extruded Films A and B>

[0160] Resin was fed into the hopper of a single-shaft extruder with a three-layer T-die. The resin was melt-mixed within the extruder, discharged from the T-die as a film, and solidified upon contact with the cooling rollers. The film was then wound to obtain a co-extruded film with an average thickness of 190 μm. This film is an unstretched film used to produce multilayer strength-reinforced films D and E. The resin material, extruder barrel temperature (C1–C4), T-die temperature, cooling rollers, and screw speed were set to the conditions shown in Table 3 below.

[0161] [Table 3]

[0162]

[0163] <Preparation of Strength-Enhancing Stretch Membranes A-E>

[0164] Strength-enhancing stretch films A to E were obtained using a biaxial stretching apparatus (manufactured by Toyo Seiki Co., Ltd.). The stretching conditions are shown in Table 4 below.

[0165] Heat setting was performed by placing a plate at 200°C (or 210°C) close to the film at a distance of 1.5 cm for 2 minutes (or 3 minutes). The resulting strength-enhancing stretch film (hereinafter, sometimes simply referred to as stretch film) was then subjected to corona discharge treatment to achieve surface hydrophilicity.

[0166] [Table 4]

[0167]

[0168]

[0169] <Strength-enhancing tensile membrane F>

[0170] Stretch nylon film;

[0171] EMBLEM (15μm thickness) manufactured by Unitika.

[0172] <Film (Sealant) for Heat-Sealable Resin Layers>

[0173] CPP(A);

[0174] Polypropylene resin is a sealant film.

[0175] ZK401 manufactured by TORAY Film Processing Co., Ltd.

[0176] Thickness: 70μm.

[0177] CPP(B);

[0178] Polypropylene resin is a sealant film.

[0179] ZK500 manufactured by TORAY Film Processing Co., Ltd.

[0180] Thickness: 70μm.

[0181] CPP(C) and (D);

[0182] CPP(C) and CPP(D), as polypropylene resin-based sealant films, are manufactured using the following materials as described below.

[0183] Block PP(d1);

[0184] PC480A manufactured by Sun Allomer.

[0185] MFR (230℃): 2.0g / 10min.

[0186] LLDPE(e1);

[0187] ULTZEX 2022L manufactured by PRIMEPOLYMER Co., Ltd.

[0188] MFR (190℃): 2.0g / 10min.

[0189] Density: 919 kg / m³ 3 .

[0190] Alpha-olefin species: 4-methylpentene-1.

[0191] LLDPE(e2);

[0192] TAFMER A1085S manufactured by Mitsui Chemicals Co., Ltd.

[0193] MFR (190℃): 1.2g / 10min.

[0194] Density: 885 kg / m³ 3 .

[0195] Alpha-olefin species: Butene-1.

[0196] The resin components were dry-mixed and fed into the hopper of a single-shaft extruder with a T-die. Melt-mixing was performed inside the extruder, and the mixture was discharged from the T-die as a film, which was then cured by contact with a cooling roller at 60°C to produce a 70 μm thick film. The resin components and the extruder barrel temperature settings are shown in Tables 5 and 6 below. The obtained CPP was subjected to corona discharge treatment to hydrophilize its surface.

[0197] [Table 5]

[0198] Composition ratio (by weight) CPP(C) d1 / e1 = 86 / 14 CPP(D) d1 / e2 = 95 / 5

[0199] [Table 6]

[0200]

[0201] <Melt Point Determination>

[0202] Use TA Instruments' DSC2500.

[0203] The heating rate is 10℃ / min, and the melting point is determined at the peak.

[0204] <Film Thickness Measurement>

[0205] The film thicknesses of composite films (A) to (C), multilayer films, strength-reinforcing layers (A) to (D), CPP (C), and (D) were evaluated using a film thickness gauge.

[0206] Furthermore, the film thickness of each layer of the multilayer film and the strength-reinforcing layer (D) is calculated using the following method.

[0207] An ultramicrotome (Ultramikrotom) manufactured by Leica, equipped with an ultramicrotome preparation device (EM UC7) and a freezing system (EM FC7), was used. Sections were cooled and cut at -140°C. The samples were observed at 400x and 1000x magnification using a SEM (S-3400N) manufactured by Hitachi High Technologies, Ltd.

[0208] The film thickness of each layer of the strength-enhancing layer (D) is derived from the following formula.

[0209] The thickness of each layer of the strength-reinforcing layer (D) = a·b / c

[0210] In the formula, a is the thickness of each layer of the multilayer film, b is the thickness of the stretched multilayer film, and c is the thickness of the multilayer film.

[0211] <The existence of oriented crystals>

[0212] The presence or absence of oriented crystals at the sealing location was determined using a fully automated multi-object X-ray diffraction apparatus (SmartLab) manufactured by Rigaku Co., Ltd. The measurement range was set to 5–40 degrees. Samples were prepared by heating a strength-enhancing film at 190°C, and samples exhibiting an arc shape during X-ray diffraction were considered to have oriented crystals.

[0213] <Adhesive>

[0214] Carbamate adhesive; manufactured by Toyo Morton Co., Ltd.

[0215] Coating liquid;

[0216] Polyester polyol / polyisocyanate / ethyl acetate

[0217] =66 / 6.3 / 70.

[0218] Epoxy adhesive; MAXIVE manufactured by Mitsubishi Gas Chemical Co., Ltd.

[0219] Coating liquid;

[0220] Epoxy resin M-100 / Polyamine C-93T / Mixed solvent

[0221] =5.4 / 18.6 / 60.

[0222] Mixed solvent: methanol / ethyl acetate = 9 / 1.

[0223] Lamination, bag making, and cooking are carried out using the following methods.

[0224] Lamination

[0225] The adhesive coating solution is applied to the film using a doctor blade coater. The coating amount, based on solids mass, is approximately 3.5 g / m². 2 .

[0226] Multilayer films were obtained by laminating a substrate film, strength-reinforcing stretch films A-F, and CPP(A)-(D) using a dry lamination method. The laminated films were then cured at 50°C for 4 days.

[0227] It should be noted that the strength-reinforcing stretch films D and E are composed of Ny / ad / PP stretch films. Strength-reinforcing stretch film D is laminated with CPP and PP in opposite configurations, and strength-reinforcing stretch film E is laminated with CPP and Ny in opposite configurations.

[0228] <Bag Manufacturing>

[0229] Two sheets of the multilayer film obtained above were cut into 140mm × 180mm pieces and filled with 200g of water to make bags. Bag making was carried out using an Impulse sealing machine manufactured by Fuji Impulse Co., Ltd., under the following conditions.

[0230] Sealing conditions;

[0231] Heating temperature: 190℃.

[0232] Heating time: 1.4s.

[0233] Cooling: 3.0s.

[0234] Sealing width: 5mm.

[0235] <Bags for sealing strength testing (bags for sealant heat resistance testing)>

[0236] A multilayer film consisting of the following layers was produced by dry lamination using a urethane-based adhesive.

[0237] Stretched PET film (12μm) / Stretched Ny film (15μm)

[0238] / Aluminum foil (7μm) / CPP film (70μm)

[0239] The value in parentheses is the thickness.

[0240] Two sheets of the above multilayer film were cut into 140mm×180mm pieces, filled with 200g of water to make bags. The bags were manufactured under the following conditions and then subjected to a boiling treatment to obtain a reference bag for the sealing strength test.

[0241] Sealing conditions;

[0242] Heating temperature: 220℃.

[0243] Heating time: 1.4s.

[0244] Cooling: 3.0s.

[0245] Sealing width: 5mm.

[0246] Steaming / cooking conditions;

[0247] Spray type.

[0248] 121℃ for 30 minutes.

[0249] <Bag Drop Test>

[0250] The test was conducted by dropping two bags, each cooled overnight at 5°C, horizontally stacked, from a height of 120 cm. The lower bag was used as the test bag. The average number of times the bag did not break was recorded as N3.

[0251] <Sealing Strength Measurement>

[0252] A universal testing machine (AG-I / 30N-10KN) manufactured by Shimadzu Corporation was used as the sealing strength testing machine. The test conditions are as follows.

[0253] Test film:

[0254] The heat-sealed section is made by cutting a 15mm wide strip at a right angle from the short side (140mm) of the bag used for the sealing strength test.

[0255] For the test pieces, six samples were produced.

[0256] Atmospheric temperature: 110℃.

[0257] Stretching speed: 300mm / min.

[0258] Based on the sealing strength, the heat resistance of the sealant is determined using the following criteria.

[0259] 〇: The sealing strength is above 10N.

[0260] ×: Sealing strength is less than 10N.

[0261] <Methods for determining dynamic viscoelasticity>

[0262] A dynamic viscoelasticity measuring apparatus manufactured by Seiko Instruments Co., Ltd. was used. The test conditions are as follows.

[0263] Test film: 20mm in length and 10mm in width.

[0264] The clamp spacing is 5mm.

[0265] Temperature range: -70℃~150℃.

[0266] Heating rate: 3℃ / min.

[0267] Frequency: 10Hz.

[0268] tanδ (loss tangent): Calculated from the loss modulus / storage modulus at 5℃.

[0269] E' (storage modulus): Calculated from the value at 110℃.

[0270] <Olefin content in the bag>

[0271] The olefin content (mass%) in the bag can be calculated using the following formula.

[0272] Olefin resin content (%) of the entire bag

[0273] = [1-(A+B) / C]×100

[0274] In the formula, A is the amount of adhesive applied, B is the amount of reinforcing resin in the strength reinforcement layer, and C is the weight of the bag.

[0275] <Example 1>

[0276] A multilayer film consisting of the following layers is produced by laminating with a urethane-based adhesive.

[0277] Substrate film A / Stretch film A / CPP(A)

[0278] Using this multilayer film, bags are manufactured by the method described above, subjected to a cooking process under the conditions described above, and then subjected to a bag drop test.

[0279] In addition, the sealing strength of the sealant was tested, and the heat resistance of the sealant was evaluated.

[0280] The experimental results are shown in Table 7.

[0281] <Example 2>

[0282] Replace CPP(A) with CPP(B), and otherwise perform the same multilayer film fabrication, bag manufacturing, and cooking treatment as in Example 1. Perform the same various measurements as in Example 1, and the test results are shown in Table 7.

[0283] <Example 3>

[0284] Replace CPP(A) with CPP(C), and otherwise perform the same multilayer film fabrication, bag manufacturing, and cooking treatment as in Example 1. Perform the same various measurements as in Example 1, and the test results are shown in Table 7.

[0285] <Example 4>

[0286] Replace CPP(A) with CPP(D), and otherwise perform the same multilayer film fabrication, bag manufacturing, and cooking treatment as in Example 1. Perform the same various measurements as in Example 1, and the test results are shown in Table 7.

[0287] <Example 5>

[0288] The stretch film A used in Example 1 was replaced with stretch film B. Otherwise, the production of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Example 1. All the same tests were performed as in Example 1. The test results are shown in Table 7.

[0289] <Example 6>

[0290] The stretch film A used in Example 1 was replaced with stretch film C. Otherwise, the production of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Example 1. All the same tests were performed as in Example 1. The test results are shown in Table 7.

[0291] <Example 7>

[0292] Replace CPP(A) with CPP(B), and otherwise perform the same multilayer film fabrication, bag manufacturing, and cooking treatment as in Example 6, and conduct the same various measurements as in Example 1. The test results are shown in Table 7.

[0293] <Example 8>

[0294] The stretch film A used in Example 1 was replaced with stretch film D. Otherwise, the production of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Example 1. All the same tests were performed as in Example 1. The test results are shown in Table 7.

[0295] <Example 9>

[0296] Replace CPP(A) with CPP(B), and otherwise perform the same multilayer film fabrication, bag manufacturing, and cooking treatment as in Example 8, and conduct the same various measurements as in Example 1. The test results are shown in Table 7.

[0297] [Table 7]

[0298]

[0299] <Example 10>

[0300] The stretch film A used in Example 1 was replaced with stretch film F. Otherwise, the production of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Example 1. All the same tests were performed as in Example 1. The test results are shown in Table 8.

[0301] <Example 11>

[0302] The CPP(A) was replaced with CPP(C), and the multilayer film was made, the bag was manufactured, and the cooking process was carried out in the same manner as in Example 10. All the same measurements were performed as in Example 1, and the test results are shown in Table 8.

[0303] <Example 12>

[0304] The layer composition of the multilayer film was changed as described below. Otherwise, the fabrication of the multilayer film, bag manufacturing, and cooking treatment were carried out in the same manner as in Example 10. Various tests were performed in the same manner as in Example 1, and the test results are shown in Table 8.

[0305] Stretch film F / Substrate film (A) / CPP (A)

[0306] <Example 13>

[0307] The urethane adhesive was replaced with an epoxy adhesive for lamination. Otherwise, the multilayer film was made, the bag was manufactured, and the cooking process was carried out in the same manner as in Example 2. All the tests were performed in the same manner as in Example 1. The test results are shown in Table 8.

[0308] <Example 14>

[0309] The CPP(B) was replaced with CPP(C), and the multilayer film was made, the bag was manufactured, and the cooking process was carried out in the same manner as in Example 13. All the same measurements were performed as in Example 1, and the test results are shown in Table 8.

[0310] <Example 15>

[0311] The urethane adhesive was replaced with an epoxy adhesive, and CPP(A) was replaced with CPP(C) for lamination. Otherwise, the multilayer film was made, the bag was manufactured, and the cooking process was carried out in the same manner as in Example 6. All the tests were performed in the same manner as in Example 1, and the test results are shown in Table 8.

[0312] <Example 16>

[0313] The stretch film A was replaced with stretch film E. Otherwise, the production of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Example 13. The same various tests were performed as in Example 1. The test results are shown in Table 8.

[0314] <Example 17>

[0315] The stretch film A was replaced with stretch film E. Otherwise, the production of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Example 14. All the same tests were performed as in Example 1. The test results are shown in Table 8.

[0316] <Example 18>

[0317] The layer composition of the multilayer film was changed as described below. Otherwise, the fabrication of the multilayer film, bag manufacturing, and cooking treatment were carried out in the same manner as in Example 13. Various tests were performed in the same manner as in Example 1, and the test results are shown in Table 8.

[0318] Substrate film (A) / Stretch film F / CPP (B)

[0319] <Example 19>

[0320] The layer composition of the multilayer film was changed as described below. Otherwise, the fabrication of the multilayer film, bag manufacturing, and cooking treatment were carried out in the same manner as in Example 13. Various tests were performed in the same manner as in Example 1, and the test results are shown in Table 8.

[0321] Stretch film E / Substrate film (A) / CPP (B)

[0322] [Table 8]

[0323]

[0324] <Comparative Example 1>

[0325] Without using a stretch film, the layer composition of the multilayer film was changed as described below. Otherwise, the production of the multilayer film, bag manufacturing, and cooking treatment were carried out in the same manner as in Example 1. Various tests were performed in the same manner as in Example 1, and the test results are shown in Table 9.

[0326] Substrate film (A) / CPP (A)

[0327] <Comparative Example 2>

[0328] CPP(A) was replaced with CPP(B). Otherwise, the fabrication of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Comparative Example 1. All the same measurements were performed as in Example 1, and the test results are shown in Table 9.

[0329] <Comparative Example 3>

[0330] The CPP(A) was replaced with CPP(C), and the production of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Comparative Example 1. The same various tests as in Example 1 were performed, and the test results are shown in Table 9.

[0331] <Comparative Example 4>

[0332] CPP(A) was replaced with CPP(D). Otherwise, the fabrication of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Comparative Example 1. All the same measurements were performed as in Example 1, and the test results are shown in Table 9.

[0333] <Comparative Example 5>

[0334] Lamination was performed using an epoxy adhesive. Otherwise, the fabrication of the multilayer film, bag manufacturing, and cooking treatment were carried out in the same manner as in Comparative Example 2. Various tests were performed in the same manner as in Example 1, and the test results are shown in Table 9.

[0335] <Comparative Example 6>

[0336] CPP(B) was replaced with CPP(C). Otherwise, the fabrication of the multilayer film, bag manufacturing and cooking treatment were carried out in the same manner as in Comparative Example 2. All the same measurements as in Example 1 were performed, and the test results are shown in Table 9.

[0337] [Table 9]

[0338]

[0339] It should be noted that, regarding the CPP membranes (A) to (D) used to form multilayer membranes, the loss tangent (tanδ) at 5°C and the storage modulus (E') at 110°C in the dynamic viscoelasticity determination are shown in Table 10.

[0340] [Table 10]

[0341] CPP film tanδ E'(MPa) Heat resistance of sealant CPP(A) 0.059 >1 〇 CPP(B) 0.083 Less than 1 × CPP(C) 0.072 >1 〇 CPP(D) 0.065 >1 〇

[0342] Explanation of reference numerals in the attached figures

[0343] 1: Support membrane;

[0344] 3: Heat-sealable resin layer;

[0345] 5: Multi-layer film for packaging;

[0346] 7: Sealing part;

[0347] 9: Contents;

[0348] 10: Packaging bags;

[0349] 11: Substrate film;

[0350] 21: Strength-enhancing stretch membrane;

[0351] 23: Adhesive layer.

Claims

1. A packaging bag, characterized in that, The packaging bag is formed by bonding the heat-sealable resin layers of the packaging multilayer film together. In the packaging bag, oriented crystals are present in the sealed portion formed by the bonding of the heat-sealable resin layers together. The multilayer film for packaging includes a strength-enhancing stretch film for ensuring the presence of the oriented crystals in the sealing portion. The strength-enhancing tensile film is formed from a mixture of an olefin-based resin and a reinforcing resin with a melting point higher than that of the olefin-based resin. The packaging bag contains olefin resin in an amount of more than 80% by weight.

2. The packaging bag according to claim 1, wherein, The reinforcing resin is a polyamide, polyester, or ethylene-vinyl alcohol copolymer.

3. The packaging bag according to claim 1, wherein, In addition to the strength-enhancing stretch film, the multilayer film for packaging also includes a substrate film for improving recyclability.

4. The packaging bag according to claim 1, wherein, The heat-sealable resin layer is an unstretched molded body containing impact-resistant polypropylene, and the loss tangent tanδ at 5°C exceeds 0.0594 and the storage modulus E' at 110°C exceeds 1MPa in the dynamic viscoelasticity test.

5. The packaging bag according to claim 4, wherein, The unstretched molded body comprises an impact-resistant polypropylene component (A) formed by dispersing an ethylene-propylene copolymer in polypropylene and linear low-density polyethylene (B).

6. The packaging bag according to claim 5, wherein, The unstretched molded body contains more than 8% by mass of xylene-soluble components derived from ethylene-propylene copolymer.

7. The packaging bag according to claim 5, wherein, The unstretched molded body contains linear low-density polyethylene (B) in an amount of less than 20% by mass.

8. A multilayer film for packaging, characterized in that, The multilayer film for packaging includes: a heat-sealable resin layer and a support film laminated to the heat-sealable resin layer, separated by an adhesive layer. In the multilayer film for packaging, the support film has a strength-reinforcing tensile film formed from a mixture of an olefin resin and a reinforcing resin with a melting point higher than that of the olefin resin. The strength-enhancing stretch film is a strength-enhancing stretch film used to ensure that oriented crystals exist in the joint formed by the bonding of the heat-sealing resin layers. The multilayer film for packaging contains olefin resin in an amount of 80% by mass or more.

9. The multilayer film for packaging according to claim 8, wherein, In addition to the strength-enhancing tensile membrane, the support membrane also has a substrate membrane for improving recyclability.

10. The multilayer film for packaging according to claim 9, wherein, The substrate film includes at least a stretched film made of acrylic resin.

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