Laminates and packaging bags

Abstract

This laminate comprises, in order, a substrate layer, a first polyethylene resin layer that includes a first polyethylene resin and that has a melt flow rate of less than 5 g / 10 min, and a second polyethylene resin layer that includes a second polyethylene resin and that has a melt flow rate of 5-12 g / 10 min, the ratio R2 (Mw / Mn) of the weight-average molecular weight Mw of the second polyethylene resin and the number-average molecular weight Mn thereof being 7 or lower.

Description

[Technical Field]

[0001] This disclosure relates to laminates and packaging bags. [Background technology]

[0002] Packaging materials are used in various combinations depending on the nature and quantity of the contents being packaged, post-processing to protect the contents from deterioration, the method of disposal of the packaging materials, the form in which the package is transported, and the method of opening the package. Here, "packaging" refers to an article composed of packaging materials and the contents contained therein.

[0003] One example of packaging bag is the standing pouch. Standing pouches can make products stand out on store shelves, and their range of use is expanding. In order for the entire contents of a standing pouch to be visible without bending, the laminated material that makes up the pouch needs to have a certain degree of rigidity. Also, if the contents are liquid, it needs to be strong enough not to tear when dropped. To meet these functions, laminated materials combining polyester film, nylon film, polyolefin film, etc. have been used.

[0004] However, with the growing awareness of environmental issues in recent years, there is a demand for resource-saving and reusable functions in various products, and similar functions are now required for laminates used in packaging materials.

[0005] One method for reusing laminates composed of various materials is to separate each material individually. However, separating laminates that have been given a certain strength for use as packaging material requires various thermal, chemical, and mechanical processes. Furthermore, separating the separated materials requires physical processes based on specific gravity or different spectroscopic methods for each material, which is inefficient.

[0006] Another approach involves monomaterialization of packaging materials. This means constructing a laminate from materials of the same type and reusing the laminate as a single material. Patent Document 1 discloses a laminate consisting of a uniaxially oriented polyolefin resin film and a polyolefin heat-seal layer. The main focus of this invention is a laminate with easy tearing properties due to the uniaxially oriented film, but as a result, it is a laminate made of resins of the same type. However, there are no specifications regarding the strength as a packaging material, and it is possible to laminate films such as biaxially oriented nylon or polyester as needed, so it does not address the challenges of achieving monomaterialization. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5197952 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The inventors selected polyethylene resin as the material to achieve monomaterial packaging. Under the constraint that various resin materials could not be used in combination, they fabricated a laminate containing a base layer and a sealant layer, and repeatedly prototyped standing pouches using this laminate. As a result, they found a problem in the process of fabricating standing pouches from the laminate: the laminates would stick together, making it difficult to supply the laminate to the pouch-making machine. In addition, they found a problem in the process of filling the standing pouches with contents: the inner surfaces (sealant layers) of the standing pouches would stick together, making it difficult to open them.

[0009] This disclosure provides a laminate applicable to the manufacture of packaging bags that should be monomaterialized, which enables efficient bag making and efficient filling of the packaging bags with contents. This disclosure also provides a packaging bag including the above laminate. [Means for solving the problem]

[0010] One aspect of this disclosure relates to a laminate. This laminate comprises, in this order, a base layer, a first polyethylene resin layer containing a first polyethylene resin with a melt flow rate of less than 5 g / 10 min, and a second polyethylene resin layer containing a second polyethylene resin with a melt flow rate of 5 to 12 g / 10 min, wherein the ratio R2 (Mw / Mn) of the weight-average molecular weight Mw to the number-average molecular weight Mn of the second polyethylene resin is 7 or less. In this disclosure, the melt flow rate refers to the value measured under conditions of a load of 2.16 kg and a temperature of 190 °C, in accordance with the method described in JIS K7210. The Mw / Mn of the polyethylene resin can be measured using gel permeation chromatography (GPC).

[0011] In the above laminate, the base layer constitutes the outermost surface, and the second polyethylene resin layer constitutes the innermost surface. The second polyethylene resin layer acts as a sealant layer and also prevents adhesion. That is, because the molecular weight distribution of the second polyethylene resin constituting the second polyethylene resin layer is relatively sharp, there are few low molecular weight components that tend to exhibit surface stickiness. Therefore, even if a certain amount of heat is applied while the base layer of another laminate is in contact with the second polyethylene resin layer, adhesion between the two can be suppressed. Furthermore, even if a certain amount of heat is applied while the second polyethylene resin layers are in contact with each other after bag formation, adhesion between the two can be suppressed. The first polyethylene resin layer also acts as a sealant layer. Examples of low molecular weight components that may be included in the second polyethylene resin layer include waxy components with a molecular weight of several thousand.

[0012] Whether the molecular weight distribution of a polyethylene resin is sharp or broad can be evaluated by the ratio of its weight-average molecular weight (Mw) to its number-average molecular weight (Mn) (Mw / Mn). The closer this value is to 1, the sharper the molecular weight distribution; the larger the value, the broader the molecular weight distribution. If the ratio R2 (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the second polyethylene resin is 7 or less, the molecular weight distribution of the second polyethylene resin is relatively sharp. By keeping the ratio R2 of the second polyethylene resin below this value, the second polyethylene resin layer can adequately perform its role in preventing adhesion.

[0013] The thickness Ta of the first polyethylene resin layer and the thickness Tb of the second polyethylene resin layer preferably satisfy the following conditions: The first polyethylene resin layer is sufficiently thinner than the second polyethylene resin layer, which allows for the efficient production of the sealant layer, for example, by the inflation method. 2 ≤ Tb / (Ta+Tb) × 100 ≤ 30

[0014] From the viewpoint of heat resistance of the base layer, it is preferable that the base layer includes at least a high-density polyethylene resin layer. When the polyethylene content in the laminate is 90% by mass or more, it can be said that it consists substantially of a single material (monomaterial). In this disclosure, a monomaterial laminate refers to one in which the mass ratio of a specific material (polyethylene resin) is 90% by mass or more (preferably 95% by mass or more). The polyethylene resin content in the laminate can be measured using a Fourier transform infrared spectrophotometer (FT-IR).

[0015] One aspect of this disclosure relates to a packaging bag including the above-mentioned laminate. This packaging bag can realize a monomaterial structure and efficiently carry out the process of filling the contents. [Effects of the Invention]

[0016] According to the present disclosure, there is provided a laminate that is applicable to the manufacture of a packaging bag that is to be made of a single material, enables efficient bag making, and allows the step of filling contents into the packaging bag to be efficiently carried out. Further, according to the present disclosure, there is provided a packaging bag including the laminate. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0017] [Figure 1] Figure 1 is a front view schematically showing one embodiment of a standing pouch according to the present disclosure. [Figure 2] Figure 2 is a cross-sectional view schematically showing the configuration of the standing pouch shown in Figure 1. [Figure 3] Figure 3 is a perspective view schematically showing a pair of side trunk portions and a bottom tape that constitute the standing pouch shown in Figure 1. [Figure 4] Figure 4 is a cross-sectional view schematically showing one embodiment of a laminate according to the present disclosure. [Figure 5] Figure 5 is a graph showing the relationship between sealing temperature and sealing strength. [MODE FOR CARRYING OUT THE INVENTION]

[0018] Hereinafter, embodiments of the present disclosure will be described in detail. Here, a standing pouch will be described as an example of a packaging bag that is realized to be made of a single material. A standing pouch is used as a refill pouch for shampoo, hand soap, detergent, and the like, or as a pouch for soup, seasonings, and the like. Note that the present disclosure is not limited to the following embodiments.

[0019] <Standing Pouch> Figure 1 is a schematic front view showing the standing pouch according to this embodiment. Figure 2 is a schematic cross-sectional view showing the configuration of the standing pouch according to this embodiment. The standing pouch 10 shown in these figures is formed by heat sealing a pair of side sections 1 and 2 and a bottom tape 3. Both the pair of side sections 1 and 2 and the bottom tape 3 are composed of a laminate including at least a base layer L1 and a sealant layer L2 (see Figure 2). The formation of the standing pouch by heat sealing can be carried out in the same way as conventional methods.

[0020] The bottom tape 3 has one mountain fold portion 3a. That is, when the standing pouch 10 is standing upright, the bottom tape 3 is arranged in an inverted V shape (see Figures 2 and 3). The bottom of the standing pouch 10 is composed of a heat-sealed portion 5 and a heat-sealed portion 6, as shown in Figure 2. The heat-sealed portion 5 is the portion where the bottom 1a of the side body portion 1 and one bottom portion 3b of the bottom tape 3 are heat-sealed. The heat-sealed portion 6 is the portion where the bottom 2a of the side body portion 2 and the other bottom portion 3c of the bottom tape 3 are heat-sealed. As shown in Figure 1, the side body portions 1 and 2 and the bottom tape 3 are heat-sealed so that the bottom of the area that contains the contents is curved and the upper side is arc-shaped.

[0021] The sides of the standing pouch 10 are composed of heat-sealed sections 7. The width of the heat-sealed section 7 is, for example, 5 to 18 mm, or it may be 7 to 15 mm. A width of 5 mm or more for the heat-sealed section 7 tends to achieve sufficient seal strength, while a width of 18 mm or less tends to make it easier to ensure a sufficient volume of contents in the standing pouch 10.

[0022] As shown in Figure 1, the standing pouch 10 has fused portions 9 on both sides of the bottom portion 10b. In this embodiment, two fused portions 9 are formed vertically on one side of the standing pouch 10, and two fused portions 9 are also formed vertically on the other side. The fused portions 9 join the side body portion 1 and the side body portion 2. The fused portions 9 are the areas where the sealant layers L2 of the side body portions 1 and 2 are locally fused together through notches 8a and 8b provided in the bottom tape 3. As shown in Figure 3, the notches 8a and 8b of the bottom tape 3 are located in the region between the mountain fold portion 3a and the bottom edges 3d and 3d, and are provided on the sides of the bottom tape 3. By providing fused portions 9 on both sides of the bottom portion 10b, the self-supporting ability and drop resistance of the standing pouch 10 can be further improved. In this example, two pairs of notches 8a and 8b are provided on one side of the bottom tape 3 to form two fused portions 9. However, for example, a pair of notches may be provided on one side of the bottom tape 3 to form one fused portion 9.

[0023] From the viewpoint of recyclability, it is preferable that the polyethylene resin content in the standing pouch 10 be 90% by mass or more. From the viewpoint of achieving a higher degree of monomaterialization, it is more preferable that the polyethylene resin content in the standing pouch 10 be 92% by mass or more, and even more preferable that be 95% by mass or more.

[0024] <Laminate> The pair of side sections 1, 2 and the bottom tape 3 of the standing pouch 10 are all substantially made of polyethylene resin. Figure 4 is a schematic cross-sectional view showing the laminate according to this embodiment. The laminate 20 shown in this figure includes a base layer L1 and a sealant layer L2. The sealant layer L2 is composed of a first polyethylene resin layer L2a and a second polyethylene resin layer L2b. The second polyethylene resin layer L2b constitutes the innermost surface of the laminate 20.

[0025] The polyethylene resin content in the laminate 20 is preferably 90% by mass or more. A polyethylene resin content of 90% by mass or more in the laminate 20 is preferable because it facilitates the realization of monomaterialization. From this viewpoint, the polyethylene resin content in the laminate 20 is more preferably 92 to 100% by mass, and even more preferably 95 to 100% by mass. Realization of monomaterialization is preferable because it facilitates resin regeneration. The laminate 20 has excellent impact resistance because it is flexible and easily stretchable.

[0026] [Base material layer] The base layer L1 is preferably composed of an unstretched polyethylene resin film. Because the base layer L1 is unstretched, the resin has almost no orientation, making it easily stretchable and resistant to breakage under external stresses such as tension and shear. The thickness of the base layer L1 is, for example, 5 to 800 μm, and may be 5 to 500 μm or 10 to 50 μm. The base layer L1 has a melting point 20°C or more higher than the second polyethylene resin layer L2b, preferably 25°C or more higher. The difference in melting points between the two suppresses the melting of the base layer L1 during the heat sealing process. The difference in seal rise temperature between the base layer L1 and the sealant layer L2 is preferably 25°C or more, more preferably 30°C or more. The seal rise temperature, as shown in Figure 5, refers to the temperature at which seal strength is achieved. The melting point of the polyethylene resin can be measured using a differential scanning calorimeter (DSC).

[0027] The melting point of the base layer L1 is preferably 120°C or higher, and more preferably 125°C or higher. Examples of polyethylene resins constituting the base layer L1 include high-density polyethylene resin (HDPE) and medium-density polyethylene resin (MDPE). Of these, HDPE and MDPE with a density of 0.925 g / cm³ are preferred from the viewpoint of heat resistance. 3 It is preferable to use the above materials. In particular, materials with a density of 0.93 to 0.98 g / cm³ are preferred. 3 It is preferable to use a high-density polyethylene resin within the specified range.

[0028] The polyethylene resin constituting the base layer L1 is not limited to petroleum-derived materials, and may be partially or entirely made of bio-derived resin materials (for example, biomass polyethylene using biomass-derived ethylene as a raw material). A method for producing biomass-derived polyethylene resin is disclosed, for example, in Japanese Patent Publication No. 2010-511634. The base layer L1 may include commercially available biomass polyethylene (such as Green PE manufactured by Braschem), or it may include mechanically recycled polyethylene made from used polyethylene products or resin (so-called burrs) generated during the manufacturing process of polyethylene products.

[0029] The base layer L1 may contain components other than polyethylene resin. Examples of such components include polyamide, polyethylene terephthalate, polypropylene, polyvinyl alcohol, and biodegradable resin materials (e.g., polylactic acid, polycaprolactone, polyhydroxyalkanoate, polyglycolic acid, modified polyvinyl alcohol, casein, modified starch, etc.). The base layer L1 may also contain additives such as antistatic agents, ultraviolet absorbers, plasticizers, lubricants, and colorants. The amount of components other than polyethylene resin in the base layer L1 is preferably 0 to 15% by mass, and more preferably 0 to 10% by mass, based on the total amount of the base layer L1.

[0030] The base layer L1 may be a single layer or may be formed of multiple layers. From the viewpoint of heat resistance, it is preferable that the base layer L1 includes at least a high-density polyethylene resin layer (a layer containing high-density polyethylene resin).

[0031] [Sealant layer] As described above, the sealant layer L2 is composed of a first polyethylene resin layer L2a and a second polyethylene resin layer L2b. The thickness of the sealant layer L2 is, for example, 40 to 150 μm, and may also be 20 to 250 μm.

[0032] (First polyethylene resin layer) The first polyethylene resin layer L2a contains the first polyethylene resin and has a melt flow rate of less than 5 g / 10 min. The melt flow rate of the first polyethylene resin layer L2a is preferably 0.5 g / 10 min or more and less than 5 g / 10 min, and more preferably 2 g / 10 min or more and less than 5 g / 10 min. A melt flow rate of less than 5 g / 10 min results in a higher melt tension, which has the effect of suppressing wrinkles during processing by methods such as inflation. In other words, when the sealant layer L2 is heated to melt, the first polyethylene resin layer L2a is less fluid than the second polyethylene resin layer L2b, so it is presumed that the first polyethylene resin layer L2a plays a supporting role in maintaining high film formation accuracy, resulting in a smooth and transparent film.

[0033] The ratio R1 (Mw / Mn) of the weight-average molecular weight Mw to the number-average molecular weight Mn of the polyethylene resin constituting the first polyethylene resin layer L2a may be, for example, 1 to 12, 1 to 8, 1 to 6, 1 to 5, 1 to 4.5, or 1 to 4. The molecular weight distribution of the first polyethylene resin may be sharper than that of the second polyethylene resin. If the molecular weight distribution of the first polyethylene resin is sharp, there will be fewer low molecular weight components, and it will be possible to suppress the emergence of such components onto the surface of the sealant layer L2 via the second polyethylene resin layer L2b. When the first polyethylene resin layer L2a and the second polyethylene resin layer L2b are each composed of a single polyethylene resin, if the ratio R1 of the first polyethylene resin is smaller than the ratio R2 of the second polyethylene resin, it can be determined that the molecular weight distribution of the first polyethylene resin is sharper than that of the second polyethylene resin.

[0034] The melting point of the first polyethylene resin layer L2a is preferably 120°C or lower, and more preferably 95 to 110°C. That is, the first polyethylene resin layer L2a is preferably composed of polyethylene resin with a melting point of 120°C or lower, and more preferably composed of polyethylene resin with a melting point of 95 to 110°C. The density of the first polyethylene resin layer L2a is 0.925 g / cm³.3 Less than (more preferably 0.900~0.920 g / cm³) 3 It is preferable that the material be composed of polyethylene resin. Specific examples include linear low-density polyethylene resin (LLDPE) and very low-density polyethylene resin (VLDPE). These polyethylene resins may also be used in blend form.

[0035] The first polyethylene resin layer L2a may contain multiple polyethylene resins as the first polyethylene resin. When the first polyethylene resin layer L2a contains multiple polyethylene resins, it is preferable that the first polyethylene resin layer L2a contains at least one polyethylene resin that satisfies at least one of the above-mentioned range of ratio R1, melting point, and density.

[0036] The content of polyethylene resin that satisfies at least one of the above ranges of ratio R1, melting point, and density may be 60-100% by mass, 80-100% by mass, 90-100% by mass, or 95-100% by mass, based on the total mass of polyethylene resin constituting the first polyethylene resin layer L2a. The content of polyethylene resin that satisfies at least one of the above ranges of ratio R1, melting point, and density may be substantially 100% by mass, based on the total mass of polyethylene resin constituting the first polyethylene resin layer L2a (in which case the first polyethylene resin layer L2a consists of polyethylene resin that satisfies at least one of the above ranges of ratio R1, melting point, and density).

[0037] The first polyethylene resin layer L2a may contain additives such as antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, nucleating agents, and plasticizers. The amount of components other than polyethylene resin in the first polyethylene resin layer L2a is preferably 0 to 15% by mass, and more preferably 0 to 10% by mass, based on the total amount of the first polyethylene resin layer L2a.

[0038] The first polyethylene resin layer L2a is preferably sufficiently thicker than the second polyethylene resin layer L2b. That is, the ratio of the thickness of the first polyethylene resin layer L2a to the total thickness of the sealant layer L2 is preferably 70-98%. A ratio of 70% or more increases the stability of film formation and allows for the supply of a wrinkle-free, smooth film. On the other hand, a ratio of 98% or less allows the second polyethylene resin layer L2b to adequately perform its role in preventing adhesion. This ratio is more preferably 75-95%, and even more preferably 80-90%.

[0039] (Second polyethylene resin layer) The second polyethylene resin layer L2b contains the second polyethylene resin and has a melt flow rate of 5 to 12 g / 10 min. The melt flow rate of the second polyethylene resin layer L2b is preferably 5 to 10 g / 10 min, and more preferably 6 to 9 g / 10 min. A melt flow rate of 5 g / 10 min or more results in a low extrusion load during manufacturing, less heat generation inside the extruder, and reduced resin degradation. In other words, when heated to melt the sealant layer L2, the second polyethylene resin layer L2b is more fluid than the first polyethylene resin layer L2a, which is thought to provide low-temperature sealing properties and reduce low molecular weight components generated by resin decomposition due to thermal degradation.

[0040] The ratio R2 (Mw / Mn) of the weight-average molecular weight Mw to the number-average molecular weight Mn of the second polyethylene resin constituting the second polyethylene resin layer L2b is 7 or less, and may be 1.5-7, 2-6, 3-6, 4-6, 4.5-6, or 5-6. A ratio R2 of 7 or less allows the second polyethylene resin layer L2b to adequately perform its anti-adhesion role. In other words, a sharp molecular weight distribution means a low content of low molecular weight components. A low content of low molecular weight components results in lower tackiness and a steeper melting point, thus preventing adhesion even when a certain amount of heat is applied while the sealing surfaces are in contact. Note that polyethylene resins with a sharp molecular weight distribution can be obtained, for example, by a gas-phase polymerization method using a metallocene catalyst.

[0041] The melting point of the second polyethylene resin layer L2b is preferably 120°C or lower, and more preferably 95 to 110°C. That is, the second polyethylene resin layer L2b is preferably composed of polyethylene resin with a melting point of 120°C or lower, and more preferably of polyethylene resin with a melting point of 95 to 110°C. The density of the second polyethylene resin layer L2b is 0.925 g / cm³. 3 Less than (more preferably 0.900~0.920 g / cm³) 3 It is preferable that the material be composed of polyethylene resin. Specific examples include linear low-density polyethylene resin (LLDPE) and very low-density polyethylene resin (VLDPE). These polyethylene resins may also be used in blend form.

[0042] The second polyethylene resin layer L2b may contain multiple polyethylene resins as the second polyethylene resin. When the second polyethylene resin layer L2b contains multiple polyethylene resins, it is preferable that the second polyethylene resin layer L2b contains at least one polyethylene resin that satisfies at least one of the above-mentioned ranges of ratio R2, melting point, and density.

[0043] The content of polyethylene resin that satisfies at least one of the above ranges of ratio R2, melting point, and density may be 60-100% by mass, 80-100% by mass, 90-100% by mass, or 95-100% by mass, based on the total mass of polyethylene resin constituting the second polyethylene resin layer L2b. The content of polyethylene resin that satisfies at least one of the above ranges of ratio R2, melting point, and density may be substantially 100% by mass, based on the total mass of polyethylene resin constituting the second polyethylene resin layer L2b (an embodiment in which the second polyethylene resin layer L2b consists of polyethylene resin that satisfies at least one of the above ranges of ratio R2, melting point, and density).

[0044] When the second polyethylene resin layer L2b contains multiple polyethylene resins, the content of polyethylene resins with a ratio R2 greater than 6 among the second polyethylene resins constituting the second polyethylene resin layer L2b is preferably 0 to 5% by mass, and more preferably 0 to 1% by mass, based on the total mass of polyethylene resins constituting the second polyethylene resin layer L2b. The second polyethylene resin layer L2b does not have to contain polyethylene resins with a ratio R2 greater than 6.

[0045] When the first polyethylene resin layer L2a and / or the second polyethylene resin layer L2b contain multiple polyethylene resins, the fact that the molecular weight distribution of the first polyethylene resin is sharper than that of the second polyethylene resin can be confirmed by the fact that the weighted average value calculated from the ratio R1 of each polyethylene resin in the first polyethylene resin layer L2a, taking into account the content of each polyethylene resin relative to the total amount of the first polyethylene resin, is smaller than the weighted average value calculated from the ratio R2 of each polyethylene resin in the second polyethylene resin layer L2b, taking into account the content of each polyethylene resin relative to the total amount of the second polyethylene resin.

[0046] The second polyethylene resin layer L2b may contain additives such as antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, nucleating agents, and plasticizers. The amount of components other than polyethylene resin in the second polyethylene resin layer L2b is preferably 0 to 15% by mass, and more preferably 0 to 10% by mass, based on the total amount of the second polyethylene resin layer L2b.

[0047] The second polyethylene resin layer L2b is preferably sufficiently thinner than the first polyethylene resin layer L2a. That is, the ratio of the thickness of the second polyethylene resin layer L2b to the total thickness of the sealant layer L2 is preferably 2 to 30%. A ratio of 2% or more allows the second polyethylene resin layer L2b to adequately perform its role in preventing adhesion, while a ratio of 30% or less facilitates the formation of the sealant layer L2. This ratio is more preferably 5 to 25%, and even more preferably 10 to 20%.

[0048] Biomass polyethylene, which uses biomass-derived ethylene as a raw material, may be used as part or all of the polyethylene resin constituting the sealant layer L2. Such a sealant film is disclosed, for example, in Japanese Patent Application Publication No. 2013-177531. The sealant layer L2 may also contain mechanically recycled polyethylene, which is made from used polyethylene products or resin (so-called burrs) generated during the manufacturing process of polyethylene products.

[0049] (Other layers) The laminate may have an adhesive layer (not shown) between the base material layer L1 and the sealant layer L2. The adhesive forming the adhesive layer can be selected according to the bonding method, but urethane-based adhesives, polyester-based adhesives, etc., can be used. By providing such an adhesive layer, the interlayer adhesion between the base material layer L1 and the sealant layer L2 is increased, making delamination less likely and maintaining the pressure resistance and impact resistance of the pouch.

[0050] Preferably, the adhesive layer contains no chlorine. When the adhesive layer contains no chlorine, it is possible to prevent coloration of the adhesive and the recycled resin after recycling, and the generation of odor caused by heat treatment. From the viewpoint of environmental consideration, it is preferable to use a biomass material for the adhesive layer. Further, biomass polyethylene can be used for the polyethylene resin. From the viewpoint of environmental consideration, the adhesive preferably contains no solvent.

[0051] The laminate may further include a gas barrier layer, for example, from the viewpoint of improving gas barrier properties against water vapor and oxygen. The gas barrier layer may be provided between the base material layer L1 and the sealant layer L2, or may be provided on the surface of the base material layer L1 opposite to the sealant layer L2. The water vapor transmission rate of the laminate is, for example, 5 g / m 2 ·day or less, and 1 g / m 2 ·day or less, or 0.5 g / m 2 ·day or less. The oxygen transmission rate of the laminate is, for example, 1 cc / m 2 ·day·atm or less, and 0.5 cc / m 2 ·day·atm or less, or 0.2 cc / m 2 ·day·atm or less. When the laminate includes a gas barrier layer, it can protect the content from deterioration caused by water vapor and oxygen, and facilitates maintaining the quality over a long period of time.

[0052] An example of a gas barrier layer is a vapor-deposited inorganic oxide layer. By using a vapor-deposited inorganic oxide layer, high barrier properties can be obtained with a very thin layer that does not affect the recyclability of the laminate. Examples of inorganic oxides include aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoint of transparency and barrier properties, the inorganic oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. The thickness of the vapor-deposited inorganic oxide layer can be, for example, 5 nm to 100 nm, or 10 nm to 50 nm. A thickness of 5 nm or more tends to exhibit good barrier properties, while a thickness of 100 nm or less tends to maintain the flexibility of the laminate. The vapor-deposited layer can be formed by, for example, physical vapor deposition or chemical vapor deposition.

[0053] The laminate may include a metal layer (metal foil) in addition to, or instead of, the inorganic oxide vapor deposition layer. Various metal foils made of aluminum, stainless steel, etc., can be used as the metal layer, and among these, aluminum foil is preferred in terms of moisture resistance, processability such as ductility, and cost. As the aluminum foil, general soft aluminum foil can be used. Among these, aluminum foil containing iron is preferred in terms of excellent pinhole resistance and ductility during molding. When a metal layer is provided, its thickness may be 7 to 50 μm or 9 to 15 μm in terms of barrier properties, pinhole resistance, processability, etc.

[0054] The laminate may have an anchor coat layer between the base layer L1 and the sealant layer L2. The anchor coat layer may be a very thin layer that does not affect the recyclability of the laminate, and can be formed using an anchor coat agent. Examples of anchor coat agents include acrylic resin, epoxy resin, acrylic urethane resin, polyester polyurethane resin, polyether polyurethane resin, and polyvinyl alcohol resin. From the viewpoint of heat resistance and interlayer adhesion strength, acrylic urethane resin and polyester polyurethane resin are preferred as anchor coat agents.

[0055] The laminate may further include, for example, a printed layer. The printed layer may be provided between the substrate layer L1 and the sealant layer L2, or on the side of the substrate layer L1 opposite to the sealant layer L2. When a printed layer is provided, it is preferable to use a printing ink that does not contain chlorine to prevent discoloration or odor generation when the printed layer is remelted. Furthermore, it is preferable from an environmental perspective to use biomass materials for the compounds contained in the printing ink.

[0056] Although embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above embodiments. For example, in the above embodiments, a standing pouch was given as an example of an application target for the laminate, but the laminate according to the embodiment may be applied to the manufacture of other packaging bags. For example, one laminate may be folded in half so that the sealant layers face each other, and then sealed on three sides to form a bag shape, or two laminates may be stacked so that the sealant layers face each other, and then heat-sealed on all four sides to form a bag shape. The packaging bag can contain contents such as food or pharmaceuticals. The packaging bag can be subjected to heat sterilization treatment such as boiling. [Examples]

[0057] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples.

[0058] (Example 1) The laminate was fabricated using the following materials. • Substrate layer: Unstretched HDPE film (thickness: 35 μm, density: 0.948 g / cm³) 3 (Melting point: 135℃) • Adhesive layer: Urethane-based adhesive • First sealing layer: Low-temperature sealing LLDPE (density: 0.916 g / cm³) 3 (MFR: 4.0g / 10 min, Melting point: 102℃, Mw / Mn: 4.0) • Second sealing layer… Anti-adhesion VLDPE (density: 0.913 g / cm³)3 (MFR: 10.0g / 10min, Melting point: 104℃, Mw / Mn: 5.5) On the surface of the support film two A sealing layer (thickness: 80 μm) was provided. two The seal layer on the surface of the one A two-layer sealant layer was obtained by providing a sealing layer (thickness: 20 μm). The laminate according to Example 1 was obtained by bonding this sealant layer and the substrate layer via an adhesive layer (thickness: 1-2 μm). After bonding the substrate layer and the sealant layer, the support film was removed. The resin used to constitute the first sealing layer had a sharper molecular weight distribution than the resin used to constitute the second sealing layer.

[0059] (Example 2) A blend of the following two types of polyethylene resin (density: 0.912 g / cm³) 3 A laminate according to Example 2 was obtained in the same manner as in Example 1, except that a second sealing layer was formed using (MFR: 5.0 g / 10 min, melting point: 103°C). ·LLDPE (density: 0.915g / cm 3 (MFR: 7g / 10min, Melting point: 102℃, Mw / Mn: 4.0) ·VLDPE (density: 0.913g / cm 3 (MFR: 8g / 10min, Melting point: 104℃, Mw / Mn: 5.5) Furthermore, 5 parts by mass of LLDPE and 5 parts by mass of VLDPE were blended. As the resin constituting the first seal layer, a resin with a sharper molecular weight distribution than the resin constituting the second seal layer was used.

[0060] (Comparative Example 1) A laminate according to Comparative Example 1 was obtained in the same manner as in Example 1, except that instead of providing a two-layer sealant layer, a single-layer sealant layer (thickness: 100 μm) was provided using the following polyethylene resin. • Sealant layer: Low-temperature sealing LLDPE (density: 0.916 g / cm³) 3 (MFR: 4.0g / 10 min, Melting point: 105℃, Mw / Mn: 10.0)

[0061] (Comparative Example 2) A laminate according to Comparative Example 2 was obtained in the same manner as in Example 1, except that instead of providing a two-layer sealant layer, a single-layer sealant layer (thickness: 100 μm) was provided using the following polyethylene resin. • Sealant layer: Low-temperature sealing LLDPE (density: 0.915 g / cm³) 3 (MFR: 2.0g / 10min, Melting point: 102℃, Mw / Mn: 11.0)

[0062] <Seal strength> The seal strength of the laminates in the examples and comparative examples was measured as follows. Specifically, the laminates were stacked so that the sealant layers faced each other, and sealed using a 10 mm wide heat sealer. The sealing conditions were pressure: 0.2 MPa, time: 1.0 second. Sealing was performed at a predetermined sealing temperature (from 80°C to 200°C in 10°C increments). After sealing, the packaging material was cut to a width of 15 mm to obtain test specimens. A T-type peel test was performed using a tensile testing machine at a speed of 300 mm / min. Figure 5 shows the relationship between sealing temperature and seal strength (N / 15 mm). Table 1 shows the peel modes of the test specimens after the T-type peel test (seal temperatures: 120°C and 140°C). The peel mode was confirmed visually.

[0063] [Table 1]

[0064] <Making a standing pouch> The laminates described in the examples and comparative examples were used as the main body and bottom material, respectively, and standing pouches were manufactured using a pouch-making machine manufactured by Totani Giken Kogyo Co., Ltd. The pouch sizes were as follows. ·Top and bottom: 230mm ·Width: 150mm • Fold width: 40mm In the case of Comparative Example 3, the laminate layer was heat-fused to the sealing bar of the bag-making machine, making it impossible to form bags.

[0065] (Evaluation of mouth opening) Standing pouches according to the examples and comparative examples were passed through a nip roll heated to 60°C under a pressure of 0.5 MPa. The force required to open the opening of the standing pouches was then measured. The results are shown in Table 2.

[0066] (Pressure resistance test) Approximately 400 ml of room temperature water was sealed into the standing pouches of the examples and comparative examples, respectively. The rupture of the pouches was observed when a static load of 80 kgf was applied to the sealed pouch for 1 minute. This test was repeated 10 times, and the number of ruptured pouches was counted. The results are shown in Table 2.

[0067] (Drop test) Each standing pouch was sealed with approximately 400 ml of room temperature water. The pouches were dropped 10 times from a height of 1 m while standing upright, and the number of pouches that ruptured was observed. This test was performed 5 times, and the number of ruptured pouches was counted. The results are shown in Table 2.

[0068] [Table 2] [Explanation of Symbols]

[0069] 1,2...side body section, 1a,2a,3b,3c,10b...bottom section, 3...bottom tape, 3a...mountain fold section, 3d...bottom edge, 5,6,7...heat seal section, 8a,8b...notch section, 9...fusion section, 10...standing pouch, 20...laminated body, L1...base layer, L2...sealant layer, L2a...first polyethylene resin layer, L2b...second polyethylene resin layer.

Claims

1. A base layer and A first polyethylene resin layer containing a first polyethylene resin and having a melt flow rate of less than 5 g / 10 min, A second polyethylene resin layer containing a second polyethylene resin and having a melt flow rate of 5 to 12 g / 10 min, They are provided in this order, The ratio R of the weight-average molecular weight Mw to the number-average molecular weight Mn of the second polyethylene resin ２ A laminate with (Mw / Mn) of 4 to 6.

2. The laminate according to claim 1, wherein the molecular weight distribution of the first polyethylene resin is sharper than the molecular weight distribution of the second polyethylene resin.

3. The laminate according to claim 1 or 2, wherein the thickness Ta of the first polyethylene resin layer and the thickness Tb of the second polyethylene resin layer satisfy the following conditions. 2≦Tb / (Ta+Tb)×100≦30

4. The laminate according to any one of claims 1 to 3, wherein the base material layer includes at least a high-density polyethylene resin layer.

5. A laminate according to any one of claims 1 to 4, wherein the polyethylene resin content is 90% by mass or more.

6. A packaging bag comprising the laminate according to any one of claims 1 to 5.

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