Easy-open packaging bags

Abstract

To provide an easy-openable container which is excellent in a tearing property, productivity, and appearance.SOLUTION: There is provided an easy-openable packaging bag which is sealed by heat-sealing a lamination film. The lamination film includes: an inner layer film; an intermediate layer film where an opening induction cut is formed; and an outer layer film formed by a biaxially-oriented film in which fine scratches are formed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a packaging bag having excellent tear-openability, which is sealed by heat-sealing a laminated film. [Background technology]

[0002] It is a widely used technique to form an easy-open line on a soft packaging bag in order to make it easier to open the bag by breaking the film. However, it is known that when a biaxially oriented film with a large molecular orientation angle is used for a packaging bag, the tearability is impaired. In biaxially stretched films, the cross angle between the molecular orientation direction and the film's machine direction or width direction is called the molecular orientation angle. When the machine direction of the film is set as an angle of 0°, the molecular orientation angle generally tends to be small in the center of the film and large in the outermost parts. In other words, if only films with small molecular orientation angles could be used, only the central part would be used, leading to increased costs. Patent Document 1 proposes using a biaxially stretched film with a molecular orientation angle of 15 degrees or less to impart easy-open properties, and Patent Document 2 discloses that a biaxially stretched film with a molecular orientation angle of less than 49 degrees can be used by providing an opening-inducing defect in the middle layer. Thus, in order to avoid impairing tearability, it is necessary to use a biaxially stretched film with a small molecular orientation angle, which places restrictions on the choice of materials and inevitably increases costs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2-219749 [Patent Document 2] JP 2020-75748 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an easy-open container that is excellent in tearability, productivity and appearance. [Means for solving the problem]

[0005] The invention of claim 1 is an easy-open packaging bag that is sealed by heat sealing a laminated film, the laminated film comprising an inner layer film, a middle layer film having opening-inducing defects formed therein, and an outer layer film made of a biaxially oriented film having a plurality of fine defects formed therein.

[0006] The invention of claim 2 is the packaging bag according to claim 1, in which the tip of the opening-inducing defect reaches the inside of the inner layer film or the outer layer film.

[0007] The invention of claim 3 is the packaging bag according to claim 1 or 2, in which the width of the opening-induced defect is 0 μm or more and 20 μm or less.

[0008] The invention of claim 4 is the packaging bag according to any one of claims 1 to 3, in which a plurality of opening-inducing defects are formed.

[0009] The invention of claim 5 is the packaging bag according to any one of claims 1 to 4, wherein the outer layer film is a biaxially stretched film having a molecular orientation angle of 49 degrees or more.

[0010] The invention of claim 6 is the packaging bag according to any one of claims 1 to 5, wherein the outer layer film is polyamide or polyester.

[0011] The invention of claim 7 is the packaging bag according to any one of claims 1 to 6, wherein the intermediate layer film is polyamide or polyester.

[0012] An eighth aspect of the present invention is the packaging bag according to any one of the first to sixth aspects, wherein the intermediate layer film is nylon or polybutylene terephthalate.

[0013] The invention of claim 9 is the packaging bag according to any one of claims 1 to 8, which has a steam release mechanism. Effect of the Invention

[0014] According to the present invention, it is possible to provide an easy-open container that is excellent in tearability, productivity and appearance.

[0015] In the present invention, by using a biaxially stretched film having a plurality of fine defects on the outer layer and a film having an opening-inducing defect on the middle layer, a packaging bag with good tearability can be obtained regardless of the molecular orientation angle of the biaxially stretched film. Furthermore, when the tip of the opening-inducing defect reaches the inside of the inner layer film or the outer layer film, even higher tearability can be obtained. Furthermore, by controlling the width of the opening-induced flaw to within the range of 0 μm or more and 20 μm or less, a packaging bag with excellent appearance can be obtained. Furthermore, by providing a plurality of opening-inducing defects, a packaging bag with excellent productivity can be obtained.

[0016] When the outer layer film is a biaxially oriented film having a molecular orientation angle of 49 degrees or more, the advantages of the present invention are further enhanced. By using polyamide or polyester for the outer layer film, the packaging bag can be provided with the necessary strength and heat resistance.

[0017] By using polyamide or polyester for the intermediate layer film, the necessary strength and heat resistance can be imparted to the packaging bag, and in particular, by using nylon or polybutylene terephthalate, strong impact resistance can be imparted.

[0018] Furthermore, by providing a steam release mechanism, the bag can be heated easily in a microwave oven without breaking, and the heated contents can be easily removed. [Brief description of the drawings]

[0019] [Figure 1]FIG. 1 is a diagram showing a laminate film used in one embodiment of the present invention. [Diagram 2] 1 is a photograph showing the appearance (cut portion) of a pouch according to one embodiment of the present invention, for illustrating defects in the outer layer film of the packaging bag of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] (Laminated film) An important feature of the easy-open packaging bag of the present invention is that it is made of a laminated film having an inner layer film, a middle layer film having opening-inducing defects formed therein, and an outer layer film made of a biaxially oriented film having a plurality of fine defects formed therein. 1 is a cross-sectional view of a laminated film 1 used in one example of the packaging bag of the present invention, and this laminated film 1 is composed of an outer layer film 2, an intermediate layer film 3, and an inner layer film 4, and the intermediate layer film 3 has a V-shaped opening guide flaw 5 with an opening width of L formed from the outer layer film 2 side to the inner layer film 4. In addition, the surface of the outer layer film 2 has a plurality of fine flaws 6, 6, 6... formed by flaw processing described below.

[0021] <Inner layer film> The inner layer film, which is the innermost layer of the packaging bag of the present invention, can be made of various known materials, for example, polyolefins having heat sealability. Examples of such polyolefins include low-density, medium-density, or high-density polyethylene, linear low-density polyethylene, isotactic polypropylene, syndiotactic polypropylene, ethylene-propylene copolymers, polybutene-1, poly4-methyl-1-pentene, ethylene-butene-1 copolymers, propylene-butene-1 copolymers, ethylene-propylene-butene-1 copolymers, ethylene-vinyl acetate copolymers, ionically crosslinked olefin copolymers (ionomers), and ethylene-acrylic acid ester copolymers. These can be used alone or as a blend of two or more kinds. In particular, from the viewpoint of heat resistance, propylene-based polymers are suitable, and homopolypropylene, random copolymers and block copolymers mainly composed of propylene can be used.

[0022] <Intermediate layer film> In the present invention, at least one intermediate layer can be provided between the inner layer film and the outer layer film. As the intermediate layer film, various known materials can be used, such as polyamide and polyester. Examples of polyamide include nylon 6, nylon 66, nylon 46, nylon 69, nylon 610, nylon 612, nylon 11, nylon 12, and nylon MXD6. From the viewpoint of ease of handling, nylon 6 or nylon 66 is preferred. As the polyester, preferred are condensation polymers obtained by polymerization of monomers having aromatic dicarboxylic acid or aliphatic dicarboxylic acid and diol as constituent components, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. Among these, it is particularly preferred to use polybutylene terephthalate (PBT) or polyethylene terephthalate (PET), which has low hygroscopicity, or blends thereof. It is further preferable to use PBT, which has impact resistance that is effective in preventing the packaging bag from falling and breaking.

[0023] <Opening Induction Defect> It is preferable to form an opening-inducing defect in the intermediate layer film at a location corresponding to the tear-open location of the packaging bag.

[0024] Methods for forming opening-inducing defects include groove processing using a rotary cutter, perforation processing, laser processing, and the like, but in the present invention, groove processing using a cutter is preferred. Laser processing can cause the molten film around the cut area to form protrusions, creating gaps in the laminate and potentially creating spine-like undulations when wound up, and there are also safety concerns when using organic solvents, so it is preferable to use a cutter that can easily create an opening-inducing defect of the desired opening width without causing such problems.

[0025] In addition, the opening-inducing defect is preferably processed by performing half-cut processing from the intermediate layer side after laminating the intermediate layer and the inner layer or the outer layer. The tip of the defect may remain in the intermediate layer or may reach the inner layer or the outer layer, but it is preferable that it reaches the inner layer or the outer layer in order to obtain higher tearability. In addition, when the intermediate layer is composed of a laminate of two or more layers, it is preferable that the tip reaches the layer of the intermediate layer that is closest to the inner layer or the outer layer, and it is more preferable that it reaches the inner layer or the outer layer.

[0026] When processing is performed after laminating the intermediate layer and the inner or outer layer, the thickness of the film makes it possible to stably form defects of a certain shape in a stiff film. Furthermore, in half-cut processing, a part of the film is not completely cut, so the film is less likely to meander and has good transportability. Therefore, when laminating the processed film to the outer layer film, unlike when a single intermediate layer is cut, the periphery of the cut part does not overlap and a spine-like undulation does not occur during winding, and a laminated film with a certain shape of opening-induced defects can be stably formed.

[0027] When the inner layer is thicker than the outer layer or when a highly flexible material such as polyolefin is used for the inner layer, performing the opening-inducing defect processing after laminating the intermediate layer and the inner layer can achieve more stable molding. In addition, when forming opening-inducing defects in a laminated film in which the outer layer and the intermediate layer are laminated, it is necessary to adjust the incision depth so as not to impair the performance required for the outer layer, such as barrier properties and impact resistance, and it is more preferable from the viewpoint of productivity to perform the opening-inducing defect processing on a laminated film in which the intermediate layer and the inner layer are laminated.

[0028] In the present invention, the width of the tear-inducing defect means the opening width of the defect at the interface between the surface of the intermediate layer on which the tear-inducing defect is provided and the adjacent layer bonded to that surface (L in FIG. 1). The opening of the tear-inducing defect is smaller and closed after lamination of the film or heat treatment than before lamination. For example, a tear-inducing defect with a defect width of 0 μm is in a state where the defect is completely closed by lamination of the film or heat treatment. The width of the opening induced flaw is preferably 0 μm or more and 80 μm or less, particularly preferably 0 μm or more and 20 μm or less, and further preferably 0 μm or more and less than 10 μm. A laminated film having opening-inducing defects with a defect width of 0 μm or more and 20 μm or less has an excellent appearance, and in particular, a laminated film having defects with a defect width of 0 μm or more and less than 10 μm is unable to visually determine whether processing has been performed or not, and a highly attractive packaging bag can be obtained. That is, by controlling the width of the flaw, it is possible to provide a packaging bag that has a good appearance and is easy to open.

[0029] In the present invention, it is preferable that the number of opening induced defects is plural. Conventional packaging bags with a single cut line formed in the intended opening area cannot be easily opened unless the cut lines on the front and back are perfectly aligned. Furthermore, if an opening-assist notch is provided in the heat-sealed area, the notch must also be aligned. These adjustments take time and are thought to increase the failure rate, reducing productivity. However, in the packaging bag of the present invention, which has multiple opening-guiding defects, the bag is opened at any one of the multiple defects and the closest defect on the opposite side, making it easy to adjust the position, resulting in fewer defects and higher productivity. In other words, a packaging bag with excellent productivity and easy-openability can be provided.

[0030] In the present invention, the number of opening-inducing defects is not particularly limited as long as it is more than one, but if there are too few, the purpose of facilitating position adjustment cannot be achieved, and if there are too many, the strength of the substrate is impaired, so 3 to 5 defects are preferable. In addition, the distance between each opening guide defect can be determined arbitrarily, but if the distance is too far, the openability is impaired, so it is preferable that the distance be 2 mm or less.

[0031] The cross-sectional shape of the opening induced flaw may be a V-shape as shown in FIG. 1 or a rectangle, but is not limited thereto. The tear line caused by the opening induced flaw may be linear, arcuate, or curved, but is not limited thereto. Furthermore, the tear line caused by the opening induced flaw may be formed continuously or intermittently. When the tear line is formed intermittently, the processing gap between the flaws is preferably 1 mm or less, more preferably 0.5 mm or less, in order to prevent the flaw from tearing in an unintended direction from the part where the flaw is removed.

[0032] <Outer film> For the outer layer film of the present invention, various known materials can be used, such as polyamide and polyester. Examples of polyamide include nylon 6, nylon 66, nylon 46, nylon 69, nylon 610, nylon 612, nylon 11, nylon 12, and nylon MXD6. From the viewpoint of ease of handling, nylon 6 or nylon 66 is preferred. As the polyester, preferred are condensation polymers obtained by polymerization of monomers having aromatic dicarboxylic acid or aliphatic dicarboxylic acid and diol as constituent components, such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Among these, PBT and PET are more preferred, and PET is particularly preferred.

[0033] The outer layer film may have a barrier layer formed thereon. The barrier layer may be formed on either the outer surface side or the intermediate layer side of the outer layer film, but is preferably formed on the intermediate layer film side in order to protect the barrier layer from damage from the outside of the packaging bag. The barrier layer is formed by depositing inorganic substances such as silicon oxide, ceramics such as alumina, carbon, etc., by chemical vapor deposition (CVD), vacuum deposition, sputtering, ion plating, etc. Alternatively, a coating layer containing a barrier resin coating agent made of polycarboxylic acid polymer, vinylidene chloride, ethylene-vinyl alcohol copolymer, etc. may be formed.

[0034] <Fine scratch processing of outer film> By applying multiple fine flaws to the surface of the outer layer film, although delamination occurs between the fine flaws, the opening is connected from flaw to flaw, so no major delamination occurs and good openability is obtained. In addition, because the shape is different from the opening-inducing flaw processing of the intermediate layer, easy opening can be achieved without compromising impact resistance or barrier properties.

[0035] The shape of the multiple fine defects on the outer layer film may be, but is not limited to, a circle, a crescent, a polygon, etc. The defects may be through holes, semi-through holes, or crack holes. The defect processing on the outer layer film may be performed on the entire surface of the film, or may be performed only around the intended opening portion. Also, the defect processing may be performed so as to form a tear line consisting of multiple fine defects at approximately the same position as the above-mentioned opening-inducing defect. The size of the flaw is selected as appropriate to achieve the above purpose, and is, for example, 0.1 mm to 1 mm, but is not limited thereto. If the width between the flaws is too large, there is a risk of the package being opened in an unintended direction, so the size is preferably 0.1 mm to 2 mm, and more preferably 0.1 mm to 1 mm.

[0036] Furthermore, as mentioned above, when a tear line is formed in the outer layer film by multiple fine defects, if the tear line is too far away from the tear line formed by the opening-inducing defects, the openability will be impaired. Therefore, it is preferable that these tear lines are approximately parallel, and even if the tear lines do not overlap, the distance between the lines is 2 mm or less.

[0037] As the outer layer film, a film subjected to a so-called magic cut or a film subjected to a porous processing can also be used.

[0038] 2 is a polarizing microscope photograph of the vicinity of cut portion 7 of an example of the packaging bag of the present invention (C of Example 4; a pouch having a plurality of fine defects in the outer layer and opening-inducing defects in the middle layer) taken from the outside. Regular dot-like defects are formed at intervals of about 1 mm over the entire surface of the outer layer film 2.

[0039] <Film lamination> The laminated film used in the present invention can be obtained by a normal dry lamination method. The adhesive used can be any adhesive commonly used in the manufacture of film packaging, such as a polyurethane adhesive. The opening-inducing flaw processing of a film formed by bonding an inner layer and an intermediate layer and laminating it with an outer layer film, or the opening-inducing flaw processing of a film formed by bonding an outer layer and an intermediate layer and laminating it with an inner layer film, can be performed in-line, or the film stored after the flaw processing can be laminated later. Depending on the types of resins constituting each film, lamination may be performed by known co-extrusion lamination, such as lamination of an inner layer film and an intermediate layer film, or lamination of the intermediate layer films when there are a plurality of intermediate layer films.

[0040] <Forming packaging bags> The packaging bag according to the present invention can be formed by overlapping the laminated film so that the inner layer films face each other and heat sealing the laminated film. Examples of the form of the pouch include, but are not limited to, a four-sided sealed pouch and a standing pouch.

[0041] The packaging bag according to the present invention may have a steam release mechanism. This makes it possible to release the internal pressure in the packaging bag during microwave heating and prevent the bag from breaking. When removing the contents after heating, by using a packaging bag with excellent tearability, the bag can be opened without the contents adhering to the opening part scattering and soiling the surroundings.

[0042] In addition, an opening-assist notch may be provided in the heat-sealed portion. The notch shape may be an I-notch, U-notch, multi-notch, or any other shape commonly used in film packaging.

[0043] In one embodiment of the present invention, an easy-open packaging bag with excellent tearability, productivity, and appearance can be obtained by using a vapor-deposited PET outer layer film with multiple fine defects, a PBT intermediate layer film with opening-inducing defects of 0 μm or more and 20 μm or less, and a polypropylene inner layer film.

[0044] In yet another embodiment, an easy-open packaging bag with excellent tearability, productivity, and appearance can be obtained by using a vapor-deposited PET outer layer film with multiple fine defects, a nylon intermediate layer film with opening-inducing defects of 0 μm or more and 20 μm or less, and a polypropylene inner layer film. EXAMPLES

[0045] The present invention will now be described in detail with reference to examples. However, the examples are merely embodiments of the present invention and the present invention is not limited thereto.

[0046] <Examples 1 to 5> Packaging bags were produced using five types of vapor-deposited biaxially stretched polyethylene terephthalate films having molecular orientation angles ranging from 40 degrees to 56 degrees by the following methods A to C, and the ease of opening the bags was evaluated.

[0047] [Pouch production] A: No scratches In the first lamination step, a polybutylene terephthalate film having a thickness of 15 μm as an intermediate layer film and a polypropylene film having a thickness of 70 μm as an inner layer film were laminated by a dry lamination method using a polyurethane adhesive. In the second lamination step, a 12 μm vapor-deposited biaxially stretched polyethylene terephthalate film coated with a polyurethane adhesive was laminated on the polybutylene terephthalate film surface of the laminated film by dry lamination to produce a laminated film. The laminated film produced in the second lamination step was heat sealed so that the machine direction of the laminated film was the opening direction, to produce a flat pouch having a height of 170 mm and a width of 130 mm. B: Opening induced flaws in the middle layer In the first lamination step, a polybutylene terephthalate film having a thickness of 15 μm as an intermediate layer film and a polypropylene film having a thickness of 70 μm as an inner layer film were laminated by a dry lamination method using a polyurethane adhesive. A half-cut opening-induced defect of 10 μm was formed using a rotary cutter on the polybutylene terephthalate film side of the laminated film produced in the first lamination step. In the second lamination process, a 12 μm vapor-deposited biaxially oriented polyethylene terephthalate film coated with a polyurethane adhesive was laminated by dry lamination to the polybutylene terephthalate film surface of the laminated film on which the opening-induced defects had been formed, to produce a laminated film. The laminated film produced in the second lamination step was heat sealed so that the machine direction of the laminated film was the opening direction, to produce a flat pouch having a height of 170 mm and a width of 130 mm. C: Multiple small scratches on the outer layer / opening induced scratches on the middle layer In the second lamination step, a flat pouch was produced in the same manner as in B, except that a 12 μm vapor-deposited biaxially stretched polyethylene terephthalate film was subjected to a multiple minute flaw processing.

[0048] [Heating the pouch in a water bath] The pouch was placed in hot water set to 100°C in a Yamato high-temperature water bath (BF600) and heated for 20 minutes.

[0049] [Delamination evaluation when opening pouch] The cut portion of each pouch that had been torn open after warming in hot water was visually evaluated. Those that had been opened along the opening induced defect were marked with an ◯, those in which a part of the outer film had deviated from the opening induced defect were marked with a △, and those in which the outer film had completely deviated from the opening induced defect were marked with an ×.

[0050] [Measurement of molecular orientation angle of outer layer film] Using a phase difference measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments, the outer layer film (biaxially oriented polyethylene terephthalate film) was cut out from the center of the film width direction to a size of 5.0 cm in the width direction x 4.0 cm in the machine direction. The film was set in the device so that the machine direction was at an angle of 0° defined by this measuring device, and the absolute value was taken as the measurement result.

[0051] Table 1 shows the evaluation results of the openability of each pouch.

[0052] [Table 1]

[0053] As shown in Table 1, pouches with opening-inducing flaws on the middle layer had good openability when the molecular orientation angle was less than 49 degrees. On the other hand, pouches with fine flaws on the outer layer in addition to flaws on the middle layer showed good openability even at 56 degrees. Since the upper limit of the molecular orientation angle of actual biaxially oriented films is around 56 degrees, it can be said that good openability is exhibited regardless of the orientation angle. That is, when a biaxially oriented film having an orientation angle of 49 degrees or more is used for the outer layer, there is an advantage to using a film having fine flaws applied thereto, particularly for the outer layer. [Industrial Applicability]

[0054] According to the present invention, it is possible to obtain an easily openable container that is excellent in tearability, productivity and appearance. [Explanation of symbols]

[0055] 1 laminated film, 2 outer layer film, 3 middle layer film, 4 inner layer film, 5 opening induced defects, 6 micro-processing defects, 7 cut area.

Claims

1. A packaging bag sealed by heat sealing a laminated film, The laminated film comprises an inner layer film, an intermediate layer film having an opening-inducing defect formed thereon, and an outer layer film made of a biaxially oriented film having a plurality of fine defects formed thereon; The opening induction flaw and the plurality of fine flaw processes are formed separately, The plurality of fine flaws are formed within a thickness range of the outer layer, The plurality of fine defects formed by the plurality of fine defect processing have an interval between the defects of 0.1 mm to 2 mm, The plurality of microscopic flaws are formed into a tear line consisting of a plurality of microscopic flaws, The tear line formed by the opening-inducing defect and the tear line composed of the plurality of fine defects are approximately parallel to each other, An easy-open packaging bag, characterized in that the distance between the tear line formed by the opening-inducing defect and the tear line consisting of the plurality of fine defects is 2 mm or less.

2. The packaging bag according to claim 1 , wherein a tip of the opening-inducing defect reaches an inside of the inner layer film or the outer layer film.

3. The packaging bag according to claim 1 or 2, wherein the width of the opening-induced defect is 0 μm or more and 20 μm or less.

4. The packaging bag according to any one of claims 1 to 3, wherein a plurality of the opening-inducing defects are formed.

5. The packaging bag according to any one of claims 1 to 4, wherein the outer layer film is a biaxially oriented film having a molecular orientation angle of 49 degrees or more.

6. The packaging bag according to any one of claims 1 to 5, wherein the outer layer film is polyamide or polyester.

7. The packaging bag according to any one of claims 1 to 6, wherein the intermediate layer film is polyamide or polyester.

8. The packaging bag according to any one of claims 1 to 6, wherein the intermediate layer film is nylon or polybutylene terephthalate.

9. The packaging bag according to any one of claims 1 to 8, having a steam venting mechanism.

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