Laminate and standing pouch using the same

Abstract

To provide a laminate having gas barrier properties, excellent in reuse properties, and appropriately usable specifically for a standing pouch.SOLUTION: A laminate includes at least a barrier film layer and a sealant layer laminated in order. The barrier film layer includes a high-density polyethylene film with a density of 0.940-0.980 g / cm3 and a thickness of 20-40 μm, and a barrier layer formed on the high-density polyethylene film. The sealant layer includes a linear low-density polyethylene film with a density of 0.910-0.920 g / cm3 and a thickness of 100-150 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to laminates for packaging, and more particularly to laminates applicable to standing pouches. [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 transporting the packaging, the method of opening the packaging, and the method of disposal.

[0003] For example, standing pouches can make products stand out on store shelves, and their range of use is expanding. For a standing pouch to remain fully visible without bending, the laminated structure that makes up the pouch needs to be rigid. Furthermore, if the contents are liquid, it needs to be strong enough to prevent tearing when dropped. To meet these requirements, laminated structures combining polyester film, nylon film, and polyolefin film 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 laminated materials used in packaging.

[0005] One method for reusing laminates composed of various materials is to separate each material again. However, separating a laminate that has been given a certain strength as a packaging material requires various thermal, chemical, and mechanical processes. Furthermore, separating the separated materials requires physical processes based on specific gravity, as well as different spectroscopic methods for each material. However, the more precision one tries to increase in these separation and sorting processes, the more energy is consumed, making them inefficient.

[0006] Another approach involves reconstructing the original laminate using materials of the same type, thereby reusing the laminate as a single integrated material. Thermoplastic resins, in particular, include various types of materials such as polyolefins, polyesters, and polyamides. Each of these materials can be given various properties depending on its molecular weight, molecular weight distribution, heat treatment, orientation, stretching, and other states and treatments. Polyolefin materials, in particular, have good processability due to their low melting point, and are easy to use because various materials can be manufactured using copolymers, etc. For this reason, various methods have been proposed to date.

[0007] Patent Document 1 proposes a laminate in which two films, referred to as an outer web and an inner web, are laminated with a printed layer in between. Both the outer and inner webs have a multilayer structure of high-density polyethylene and low-density polyethylene, but since they are co-extruded films, special equipment is required. In addition, the inner web acts as a sealant layer in the packaging, and ethylene vinyl acetate (EVA) and ionomers are also recommended for this layer. However, these resins are prone to chemical changes such as crosslinking during recycling, and repeated recycling tends to produce impurities such as gels.

[0008] Furthermore, laminates for packaging often require properties such as oxygen barrier and water vapor barrier properties. Patent Document 1 recommends resins such as EVOH, but in that case, adhesive strength between the upper and lower layers cannot be obtained without an adhesive resin intermediary. Moreover, similar to EVA, repeated heat treatment tends to generate gel, which can hinder reuse.

[0009] Patent Document 2 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, and as a result, the laminate is made of the same type of resin. 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 environmental issues. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Special publication 2018-511504 [Patent Document 2] Patent No. 5197952 [Overview of the project] [Problems that the invention aims to solve]

[0011] The problem that the present invention aims to solve is to provide a laminate having gas barrier properties, excellent reusability, and particularly suitable for use in standing pouches. [Means for solving the problem]

[0012] To solve the above problems, the invention according to claim 1 of the present invention is characterized in which at least a barrier film layer, an adhesive layer, and a sealant layer are laminated in this order, and the barrier film layer has a density of 0.940 to 0.980 g / cm³ 3 It consists of a film made of high-density polyethylene with a thickness of 20-40 μm and a barrier layer formed on the film, wherein the sealant layer has a density of 0.910-0.920 g / cm³ 3 This laminate is characterized by being composed of a film with a thickness of 100 to 150 μm made of linear low-density polyethylene.

[0013] Furthermore, in the invention according to claim 2 of the present invention, the difference between the heat-sealing initiation temperature between the high-density polyethylene films of the laminate and the heat-sealing saturation temperature at which the heat-sealing strength between the linear low-density polyethylenes of the laminate becomes saturated is 30°C or more, which is the laminate according to claim 1.

[0014] Furthermore, in the invention according to claim 3 of the present invention, the barrier layer of the barrier film layer consists of a metal oxide layer formed by a vapor deposition method and a gas barrier coating layer formed on the metal oxide layer, wherein the gas barrier coating layer contains a water-soluble polymer and one or more metal alkoxides or hydrolysis products thereof, which is the laminate according to claim 1 or 2.

[0015] Furthermore, in the invention according to claim 4 of the present invention, the metal oxide layer contains either Al or Si, which is the laminate according to claim 3.

[0016] Furthermore, in the invention according to claim 5 of the present invention, an adhesive layer containing an anchor coating agent is provided between the high-density polyethylene film and the barrier layer of the barrier film layer, which is the laminate according to any one of claims 1 to 4.

[0017] Furthermore, the invention according to claim 6 of the present invention is a standing pouch using the laminate according to any one of claims 1 to 5. [Advantages of the Invention]

[0018] By providing a polyolefin-based laminate having gas barrier properties, a packaging body excellent in recyclability can be produced. In particular, a laminate suitable for a standing pouch can be produced based on the heat-sealing properties between the barrier film layer and the sealant layer. [Mode for Carrying Out the Invention]

[0019] Hereinafter, embodiments of the present invention will be described in detail.

[0020] The barrier film layer in this invention is formed by laminating a film made of high-density polyethylene with a barrier layer.

[0021] High-density polyethylene can be used in various densities and MFRs, but the density is 0.940-0.980 g / cm³. 3 A density of 0.940 g / cm³ is preferred. 3 If the size is smaller, the film will lack sufficient rigidity and its density will be 0.980 g / cm³. 3 If the density is too large, transparency will be insufficient. Transparency may also be adjusted by adding nucleating agents to the high-density polyethylene. Furthermore, the mechanical strength of the high-density polyethylene film may be adjusted by stretching or heat treatment, and the adhesion of the surface may be adjusted by surface treatment such as corona treatment.

[0022] For the barrier layer used in the barrier film layer, coating materials such as polyvinyl alcohol (PVA) or EVOH with added inorganic fillers can be used. When using these materials, the coating layer can be made to a thickness of several micrometers.

[0023] More preferably, a vapor-deposited layer made of a metal oxide is used as the barrier layer. As the metal oxide, silicon oxide, aluminum oxide, tin oxide, magnesium oxide, or mixtures thereof can be used, but silicon oxide and aluminum oxide are preferred. Vacuum deposition, sputtering, ion plating, or plasma vapor deposition can be used to form the vapor-deposited layer.

[0024] If the vapor-deposited layer is too thin, it becomes difficult to form a uniform, continuous film, and sufficient gas barrier properties cannot be obtained. If the thickness is too thick, the flexibility is low, making it prone to cracking under bending and tension, which also reduces gas barrier properties. The vapor-deposited layer thickness is preferably in the range of 5 nm to 500 nm.

[0025] Furthermore, a gas barrier film layer can be provided on the barrier layer made of the metal oxide. The gas barrier film layer provides a higher barrier function by protecting the barrier layer made of the metal oxide from mechanical degradation, and can be composed of a material containing a water-soluble polymer and one or more types of metal alkoxides or their hydrolysis products. The gas barrier film layer can be obtained by applying and drying a coating agent mainly composed of an aqueous solution or a water-alcohol mixture solution containing a water-soluble polymer and one or more types of metal alkoxides or their hydrolysis products.

[0026] Examples of the water-soluble polymers that can be used include polyvinyl alcohol (PVA), polyvinylpyrrolidone, starch, methylcellulose, carboxymethylcellulose, sodium alginate, or mixtures thereof. In particular, when PVA is used, a gas barrier film layer with the best gas barrier properties can be formed.

[0027] The aforementioned PVA is obtained by saponifying polyvinyl acetate, and various types of saponified PVA can be used, ranging from partially saponified PVA with several tens of percent of acetyl groups remaining to fully saponified PVA with only a few percent of acetyl groups remaining. There are no restrictions on the molecular weight of the PVA; for example, those with a degree of polymerization ranging from 300 to several thousand can be used.

[0028] Metal alkoxides have the general formula M(OR) n This is a compound represented by the formula shown. Here, M represents a metal such as Ti, Al, or Zr sugar, or Si, and R represents an alkyl group such as a CH3 group or a C2H5 group. n represents the valency of element M. Examples of metal alkoxides include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [AL(O-2'-C3H7)3], among which tetraethoxysilane and triisopropoxyaluminum can exist relatively stably in a water-containing solution after hydrolysis.

[0029] When alkoxysilane is used as the metal alkoxide, examples of the alkoxysilane include Si(OR 1 )4 or R 2 Si(OR 3 )3 represented compounds or mixtures thereof. Herein, R 1 and R 3 represent hydrolyzable groups such as CH3 group, C2H5 group, C2H4OCH3 group, and R 2 represents an organic functional group.

[0030] Furthermore, an adhesive layer containing an anchor coating agent may be provided between the high-density polyethylene film used in the present invention and the barrier layer. The adhesive layer can improve the adhesion between the high-density polyethylene film and the barrier layer made of metal oxide, improve the smoothness of the film, and reduce defects in the vapor-deposited layer in the subsequent process. Examples of the material for the adhesive layer include polyester-based polyurethane resins, polyether-based polyurethane resins, and the like. Among these, polyester-based polyurethane resins are preferred from the viewpoints of heat resistance and interlayer adhesion strength.

[0031] The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 0.05 to 2 µm. If the film thickness is too thin, improvement in adhesion cannot be expected, and if it is thick, impurities increase during reuse of the laminate.

[0032] As the sealant layer that can be used in the present invention, linear low-density polyethylene with a density of 0.910 to 0.920 g / cm 3 can be used, and the thickness of the sealant layer is preferably 100 to 150 µm. When the density is lower than 0.910 g / cm 3 , the film is prone to blocking, and when the density is higher than 0.920 g / cm 3 , the melting point increases, and the melting point becomes close to that of the laminated high-density polyethylene, making it difficult to form a package into a bag. In addition, when the thickness of the sealant is too thin, the strength of the package for contents such as liquids is insufficient, and when it is too thick, heat sealing as a package becomes difficult.

[0033] The heat-sealing properties of the high-density polyethylene film constituting the barrier film layer and the linear low-density polyethylene film constituting the sealant layer in this invention have the following relationship, which is when the bag-making process for packaging using the laminate according to this invention becomes highly productive. That is, the heat-sealing start temperature T between the high-density polyethylene film sides of this laminate (hereinafter referred to as between the substrates) HD The heat seal saturation temperature T is the point at which the heat seal strength between the linear low-density polyethylene film sides of this laminate (hereinafter referred to as "between sealants") saturates. LL This is the case when the difference between the two is 30°C or more. That is, T HD and T LL This laminate is characterized by having a temperature difference of 30°C or more.

[0034] Here, the heat seal start temperature is the temperature at which the heat seal strength becomes greater than 0 when measured. The heat seal saturation temperature is the heat seal temperature at which the heat seal curve rises to saturation strength when measured, and can also be considered the condition under which the sealant undergoes cohesive failure during heat seal strength measurement.

[0035] T HD and T LL When the difference is small, it means that there is a sufficient difference between the melting point of high-density polyethylene and the melting point of linear low-density polyethylene, but the sealant layer is thick. Because a certain amount of time is required to increase the heat seal strength between the sealants, softening and melting of the high-density polyethylene layer may occur during that time, causing the polymer polyethylene film to become thin or blocking with the heat seal bar, resulting in defects in the sealed part of the packaging.

[0036] In other cases, even if the sealant layer is thin, there is not a sufficient difference between the melting point of high-density polyethylene and the melting point of linear low-density polyethylene. In this case as well, softening and melting of the high-density polyethylene layer occurs before the heat seal strength between the sealants can be increased.

[0037] The laminate according to the present invention can be manufactured by laminating and bonding a barrier film layer and a sealant layer using a lamination method such as a dry lamination method or a non-solvent lamination method. The adhesive used to form the adhesive layer can be selected according to the bonding method, but urethane-based adhesives, polyester-based adhesives, etc., can be used.

[0038] Furthermore, text information, designs, and other images may be printed on the barrier film layer of the laminate according to the present invention, and gravure printing, flexographic printing, and other methods are possible.

[0039] The packaging form using the laminate according to the present invention is not particularly limited and can include pillow packaging, four-sided sealed packaging, etc., but it is suitable for standing pouches filled with liquid due to the design of the sealant thickness.

[0040] Further details will be explained below based on the following examples. [Examples]

[0041] The materials shown in Table 1 were used as the high-density polyethylene film and sealant layer constituting the laminate.

[0042] [Table 1]

[0043] The barrier layer formed on the high-density polyethylene film was fabricated as follows, common to all laminate configurations.

[0044] The adhesion layer was prepared using the following procedure. [Coating Solution 1]: Adhesive solution manufactured by Mitsui Chemicals, Inc. (polyester-based polyurethane resin solution) Main component: Takelac A-525 (50% by mass of urethane resin precursor, 50% by mass of ethyl acetate) Hardener: Takenate A-52 (55% by mass of urethane resin hardener, 45% by mass of ethyl acetate) Solvent: Ethyl acetate These were blended in the ratio A-525:A-52:ethyl acetate = 9:1:165 (solid content concentration 3% by mass).

[0045] The gas barrier coating layer was prepared using the following procedure. [Coating liquid 2] (a) A hydrolysis solution with a solid content of 5% (by weight, calculated as SiO2) obtained by adding 17.9 g of tetraethoxysilane (Si(OC2H5)4; hereafter abbreviated as TEOS) and 10 g of methanol to 72.1 g of 0.1 N hydrochloric acid and stirring for 30 minutes.

[0046] (b) A 5% (by weight) solution of polyvinyl alcohol (PVA) in water / methanol = 95 / 5 (by weight).

[0047] (c) 1,3,5-Tris(3-trimethoxysilylpropyl) isocyanurate in a water / isopropyl alcohol = 1 / 1 solution with a solid content of 5% (by weight R 2 Hydrolysis solution prepared in terms of Si(OH)3.

[0048] The above solutions (a) to (c) were mixed in a ratio of a / b / c = 70 / 20 / 10 (solid weight ratio) to obtain [coating solution 2].

[0049] On the corona-treated side of each high-density polyethylene film, the coating liquid 1 is applied using a gravure coating machine by gravure roll coating with a tension of 70 N / m and a drying temperature of 60°C, and polyurethane resin is applied at a rate of 0.1 g / m². 2 The amount applied was cured.

[0050] Next, an AlOx vapor deposition film with a thickness of 10 nm was formed by evaporating aluminum while introducing oxygen using an electron beam vacuum deposition method as the deposition layer. Then, the coating solution 2 was sequentially applied under conditions of a tension of 60 N / m and a drying temperature of 70°C.

[0051] This creates an adhesion layer (0.1g / m 2 ) / AlOx layer (10nm) / Gas barrier film layer (0.3g / m²) 2A transparent gas barrier laminate consisting of the above was obtained.

[0052] The resulting barrier film exhibits an oxygen permeability of 0.7 cc / m², regardless of the density and thickness of the high-density polyethylene film. 2 • day • MPa, water vapor transmission rate 4.5 g / m 2 It was a day.

[0053] Next, the combinations of high-density polyethylene film and sealant layer shown in Table 1 were laminated under common conditions using the non-solvent lamination method. ADN-369AF:ADN-369B=3:1 (manufactured by Toyo Morton Co., Ltd.) was used as the adhesive, with an application rate of 1.8 g / m². 2 (Wet) was used. Through the above process, laminates of components 1 to 6 were obtained.

[0054] Next, the heat seal strength between the substrates and between the sealants of the laminates from configurations 1 to 6 was measured. For the heat seal, the heat seal pressure was fixed at 0.2 MPa and the heat seal time at 1 second, while the temperature of the heat seal bar was varied. The heat seal strength was measured using a test specimen with a width of 15 mm under conditions of 90° peeling at a tensile speed of 300 mm / min. The results are shown in Table 2.

[0055] [Table 2]

[0056] Next, standing pouches were manufactured using the laminates from Composition 1 to Composition 6. The size of the standing pouches was 235 mm (length) x 130 mm (width). The sealing temperature during pouch manufacturing was set to 130°C for the bottom seal, 150°C for the side seal, and 150°C for the point seal, with three conditions where each temperature was varied by 10°C above and below. Heat seal characteristics were evaluated based on whether the seal was good or bad. In addition, 350 ml of water was filled as the contents. Pressure resistance was evaluated by holding a load of 80 kgf for 1 minute at room temperature and checking whether the pouch ruptured. Drop strength was evaluated by dropping the pouch vertically three times and horizontally three times from a height of 1.2 m and checking whether the pouch ruptured. The results for each are shown in Table 3.

[0057] [Table 3]

[0058] From the results in Tables 2 and 3 above, it can be seen that the pressure resistance of the standing pouch is weak in configurations 1 and 2, and the drop strength is weak in configurations 5 and 6, indicating that configurations 3 and 4 are the preferred configurations.

Claims

1. A laminate for a standing pouch in which at least a barrier film layer, an adhesive layer, and a sealant layer are laminated in this order, The barrier film layer has a density of 0.940 to 0.980 g / cm³. ３ The system comprises a high-density polyethylene film having a thickness of 20 to 40 μm and a barrier layer formed on the high-density polyethylene film. The sealant layer has a density of 0.910 to 0.920 g / cm³. ３ It comprises a linear low-density polyethylene film having a thickness of 100 to 150 μm, A laminate for a standing pouch, characterized in that the barrier layer side of the barrier film layer is laminated to the sealant layer side.

2. The standing pouch laminate according to claim 1, characterized in that the difference between the heat-sealing start temperature of the high-density polyethylene films of the standing pouch laminate and the heat-sealing saturation temperature at which the heat-sealing strength of the linear low-density polyethylenes of the standing pouch laminate becomes saturated is 30°C or more.

3. The laminate for standing pouch according to claim 1 or 2, characterized in that the barrier layer of the barrier film layer has a metal oxide layer formed by vapor deposition.

4. The laminate for a standing pouch according to claim 3, wherein the thickness of the metal oxide layer is 5 nm to 500 nm.

5. The laminate for standing pouch according to claim 3 or 4, characterized in that the barrier layer comprises the metal oxide layer and a gas barrier film layer formed on the metal oxide layer, and the gas barrier film layer contains a water-soluble polymer and one or more metal alkoxides or their hydrolysis products.

6. The laminate for a standing pouch according to any one of claims 3 to 5, characterized in that the metal oxide layer contains either Al or Si.

7. The laminate for standing pouch according to claim 1 or 2, wherein the barrier layer of the barrier film layer has a coating layer containing PVA or EVOH.

8. The laminate for a standing pouch according to claim 7, wherein the coating layer further contains an inorganic filler.

9. The laminate for a standing pouch according to any one of claims 1 to 8, characterized in that it comprises an adhesive layer containing an anchor coating agent between the high-density polyethylene film of the barrier film layer and the barrier layer.

10. The laminate for a standing pouch according to any one of claims 1 to 9, wherein the high-density polyethylene film is a stretched film.

11. The laminate for standing pouch according to any one of claims 1 to 10, wherein the adhesive forming the adhesive layer is a non-solvent adhesive.

12. The laminate for a standing pouch according to any one of claims 1 to 11, wherein the barrier film layer is printed by flexographic printing.

13. A standing pouch using the laminate for standing pouches described in any one of claims 1 to 12.

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