Antibacterial film

Abstract

To provide an antibacterial film having a high effect for suppressing breeding of bacteria adhering to contents.SOLUTION: An antibacterial film has a base material layer, and a seal layer laminated on the base material layer, wherein the base material layer is composed of a material containing a propylene-based resin, the seal layer is composed of a material containing a propylene-based random copolymer and an antibacterial agent, the antibacterial agent contains particles, and a modal particle size of the particles of the antibacterial agent is larger than the thickness of the seal layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antimicrobial film. [Background technology]

[0002] Patent Document 1 discloses an antibacterial film used in a package containing contents such as cut vegetables. This antibacterial film includes a base layer and a sealing layer laminated on the base layer. The sealing layer is made of a material containing an antibacterial agent. This makes it possible to inhibit the proliferation of bacteria adhering to the contents inside the package. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-49657 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an antibacterial film that is highly effective in inhibiting the growth of bacteria adhering to contents. [Means for solving the problem]

[0005] An antibacterial film according to a first aspect of the present invention comprises a base layer and a sealing layer laminated on the base layer, wherein the base layer is made of a material containing a propylene-based resin, and the sealing layer is made of a material containing a propylene-based random copolymer and an antibacterial agent, the antibacterial agent containing particles, and the mode particle size of the antibacterial agent particles is larger than the thickness of the sealing layer.

[0006] The antibacterial film is produced by, for example, heat-sealing the sealing layers on the back and bottom of a cylindrical antibacterial film using a vertical pillow packaging machine. Next, contents such as cut vegetables are placed in the upper opening, and while degassing, the sealing layers are heat-sealed to close the upper opening, producing a package containing the contents.

[0007] In the above antibacterial film, the mode particle diameter of the antibacterial agent particles is larger than the thickness of the sealing layer, so the antibacterial agent particles are exposed from the sealing layer. As a result, the contents contained in the package come into contact with the particles contained in the antibacterial agent, or the distance between the contents and the particles contained in the antibacterial agent is short. Therefore, the antibacterial agent particles are more effective in suppressing the growth of bacteria adhering to the contents than when they are present within the sealing layer.

[0008] In the antibacterial film according to the second aspect of the present invention, the ratio of the mode particle size of the antibacterial agent to the thickness of the sealing layer is 20 / 3 or less.

[0009] The antibacterial film enhances the effect of suppressing bacterial growth while maintaining good sealing properties of the sealing layer.

[0010] In the antibacterial film according to a third aspect of the present invention, the ratio of the mode particle size of the antibacterial agent particles to the thickness of the sealing layer is 4 or less.

[0011] The antibacterial film can further enhance the effect of suppressing bacterial growth while maintaining good sealing properties of the sealing layer.

[0012] In the antibacterial film according to a fourth aspect of the present invention, the ratio of the mode particle size of the antibacterial agent particles to the thickness of the sealing layer is 4 / 3 or less.

[0013] The antibacterial film can further enhance the effect of suppressing bacterial growth while maintaining good sealing properties of the sealing layer.

[0014] In the antibacterial film according to a fifth aspect of the present invention, the ratio of the antibacterial agent in the material constituting the sealing layer is in the range of 0.02% by weight to 2.00% by weight.

[0015] The antibacterial film can further enhance the effect of inhibiting bacterial growth.

[0016] In the antibacterial film according to a sixth aspect of the present invention, the mode particle size of the antibacterial agent particles is in the range of 0.5 μm to 6.0 μm.

[0017] According to the above antibacterial film, when the material constituting the sealing layer contains an antibacterial agent, the sealing layer has good sealing properties while maintaining the thickness generally required for the sealing layer of an antibacterial film used in a package. [Effects of the Invention]

[0018] The antibacterial film according to the present invention is highly effective in inhibiting the proliferation of bacteria adhering to the contents. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view of an antibacterial film according to an embodiment. [Figure 2A] 1 is a table showing the specifications of the antibacterial films of Examples 1 to 4. [Figure 2B] 1 is a table showing the specifications of the antibacterial films of Examples 5 to 9. [Figure 2C] 1 is a table showing the specifications of the antibacterial films of Comparative Examples 1 and 2 and the film of the Reference Example. [Figure 3A] 1 is a table showing the results of the first to third tests of the antibacterial films of Examples 1 to 4. [Figure 3B] 1 is a table showing the results of the first to third tests of the antibacterial films of Examples 5 to 9. [Figure 3C] 1 is a table showing the results of the first to third tests of the antibacterial films of Comparative Examples 1 and 2 and the film of Reference Example. [Figure 4A]1 is a table showing the results of the second additional test of the antibacterial films of Examples 1 to 4. [Figure 4B] 1 is a table showing the results of the second additional test of the antibacterial films of Examples 5 to 9. [Figure 4C] 1 is a table showing the results of a second additional test on the antibacterial films of Comparative Examples 1 and 2 and the film of the Reference Example. [Figure 5] Table showing the results of the fifth test. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an antibacterial film according to one embodiment of the present invention will be described with reference to the drawings.

[0021] <1. Composition of antibacterial film> Fig. 1 is a cross-sectional view showing an example of the layer structure of an antibacterial film 10. The antibacterial film 10 is used in a package that contains contents. The contents are, for example, fruits and vegetables. The fruits and vegetables include, for example, cut vegetables such as cabbage, lettuce, or carrots, as well as vegetables such as green onions, bean sprouts, spinach, broccoli, or bell peppers.

[0022] The antibacterial film 10 includes a base layer 20 and a sealing layer 30. Note that the materials constituting the base layer 20 and the sealing layer 30 shown below, and the specifications relating to the content of the materials, etc., can be applied to the matters described in the prior art document (JP 2021-49657 A), and therefore detailed explanations thereof will be omitted.

[0023] It is possible to select any thickness for the antibacterial film 10. From the viewpoint that the antibacterial film 10 is used in the production of packaging, the thickness of the antibacterial film 10 is preferably in the range of 10 μm to 50 μm.

[0024] When a package is manufactured using the antibacterial film 10, the base layer 20 is the outermost layer, in other words, the layer that faces the external space. The thickness of the base layer 20 can be selected arbitrarily. From the viewpoint that the antibacterial film 10 is used to manufacture a package, the thickness of the base layer 20 is preferably in the range of 2 μm to 49 μm. In this embodiment, the thickness of the base layer 20 is 26 μm.

[0025] The material constituting the base layer 20 is a material containing a propylene-based resin. The propylene-based resin is, for example, a homopropylene polymer (HPP) or a propylene-based random polymer. The propylene-based random copolymer is a copolymer of propylene and another α-olefin. Examples of the α-olefin other than propylene include α-olefins other than propylene having 2 to 10 carbon atoms, and specific examples include α-olefins such as ethylene, 1-butene, 1-pentene, and 1-hexene. The material constituting the base layer 20 may contain at least one of a hydrogenated styrene-based thermoplastic elastomer (SEBS) and a styrene-based thermoplastic elastomer (SBC) in addition to the propylene-based resin.

[0026] When a package is manufactured using the antibacterial film 10, the sealing layer 30 is the innermost layer, in other words, the layer facing the internal space that accommodates the contents. The sealing layer 30 is laminated on the base layer 20. In this embodiment, the sealing layer 30 is laminated directly on the base layer 20. The sealing layer 30 may be laminated on the base layer 20 via an optional intermediate layer. The thickness of the sealing layer 30 can be selected arbitrarily. From the viewpoint that the antibacterial film 10 is used in the manufacture of a package, the thickness of the sealing layer 30 is preferably in the range of 1 μm to 8 μm. In this embodiment, the thickness of the sealing layer 30 is 1.5 μm.

[0027] The material constituting the sealing layer 30 is a material containing a propylene-based random copolymer and an antibacterial agent. The propylene-based random copolymer contained in the material constituting the sealing layer 30 is a binary copolymer or a terpolymer. In this embodiment, the propylene-based random copolymer contained in the material constituting the sealing layer 30 is a terpolymer. The antibacterial agent is, for example, an inorganic antibacterial agent or an organic antibacterial substance. Examples of inorganic antibacterial agents include metal compounds containing metal ions, and specific examples include metal compounds containing silver ions, copper ions, or zinc ions.

[0028] In this embodiment, the mode particle diameter of the particles, such as the metal compound, contained in the antibacterial agent is larger than the thickness of the sealing layer 30 so that the particles contained in the antibacterial agent are exposed to the interior space from the sealing layer 30. From the perspective of enhancing antibacterial performance alone, the larger the mode particle diameter of the particles contained in the antibacterial agent, the higher the antibacterial performance. However, if the mode particle diameter of the particles contained in the antibacterial agent is too large relative to the thickness of the sealing layer 30, the sealing performance of the sealing layer 30 may be reduced, and good sealing performance may not be achieved under normal heat-sealing temperature conditions. From this perspective, the ratio of the mode particle diameter of the antibacterial agent particles to the thickness of the sealing layer 30 (hereinafter referred to as the "ratio RA") is preferably 20 / 3 or less. The ratio RA is more preferably 4 or less. The ratio RA is even more preferably 4 / 3 or less. The mode particle diameter is the particle diameter at the maximum value of the particle distribution and can be measured using, for example, a flow particle image analyzer or a laser diffraction particle size analyzer.

[0029] Furthermore, when the material constituting the sealing layer 30 contains an antibacterial agent, it is preferable to obtain good sealing properties for the sealing layer 30 while maintaining the thickness generally required for the sealing layer 30 of the antibacterial film 10 used in the package. From this perspective, it is preferable that the mode particle size of the antibacterial agent particles be in the range of 0.5 μm to 6.0 μm.

[0030] The proportion of the antibacterial agent in the material constituting the sealing layer 30 can be selected arbitrarily. In a preferred example, the proportion of the antibacterial agent in the material constituting the sealing layer 30 is preferably in the range of 0.02 wt % to 2.00 wt %.

[0031] <2. Action and effect of antibacterial film> The antibacterial film 10 is heat-sealed, for example, by a vertical pillow packaging machine, at the sealing layers 30 on the back and bottom of the cylindrical antibacterial film 10. Next, contents such as cut vegetables are placed in the upper opening, and while degassing, the sealing layer 30 is heat-sealed to close the upper opening, thereby producing a package containing the contents.

[0032] In the antibacterial film 10, the mode particle diameter of the antibacterial agent particles is larger than the thickness of the sealing layer 30, so the antibacterial agent particles are exposed from the sealing layer 30. As a result, the contents contained in the package come into contact with the particles contained in the antibacterial agent, or the distance between the contents and the particles contained in the antibacterial agent is short. Therefore, the particles contained in the antibacterial agent are more effective in suppressing the growth of bacteria adhering to the contents than when they are present within the sealing layer 30.

[0033] <3. Example> The inventor(s) of the present application manufactured antibacterial films of Examples, Comparative Examples, and Reference Examples, and conducted tests to evaluate the properties of the antibacterial films. The tests included Test 1, Test 2, Test 3, Test 4, and Test 5. For ease of explanation, the following describes the elements constituting the antibacterial films of Examples and Comparative Examples that are the same as those in the embodiment, using the same reference numerals as in the embodiment. In the antibacterial films of Examples and Comparative Examples, an Ag-Zn-based antibacterial agent was used as the antibacterial agent.

[0034] 2A to 2C are tables showing the specifications of the antibacterial films 10 of Examples 1 to 9, the antibacterial films 10 of Comparative Examples 1 and 2, and the film of the Reference Example. As shown in FIG. 2C, the antibacterial films 10 of Comparative Examples 1 and 2 have a ratio RA of 1 or less. The film of the Reference Example does not contain an antibacterial agent in the material constituting the sealing layer 30. FIGS. 3A to 3C are tables showing the results of Tests 1 to 3. Tests 1 to 3 are tests to evaluate the properties of the antibacterial films 10 of Examples 1 to 9, the antibacterial films 10 of Comparative Examples 1 and 2, and the film of the Reference Example before packaging is produced, i.e., in the state of the film alone.

[0035] <3-1. First Exam> The first test was a test to evaluate the antibacterial properties of the film. In the first test, the antibacterial properties of the antibacterial films 10 of Examples 1 to 9, the antibacterial films 10 of Comparative Examples 1 and 2, and the film of the Reference Example were evaluated based on JIS Z2801. In the antibacterial property section of FIGS. 2A to 2C, "◯" indicates an antibacterial activity value of 2.0 or more, and "×" indicates an antibacterial activity value of less than 2.0. In the antibacterial films 10 of Examples 1 to 9 and Comparative Examples 1 and 2, the material constituting the sealing layer 30 contains an antibacterial agent, and therefore it can be seen that the antibacterial properties were evaluated to be high.

[0036] <3-2. Second Exam> The second test was a test to confirm the seal strength when two films were heat-sealed. For each of the antibacterial films 10 of Examples 1 to 9, Comparative Examples 1 and 2, and the Reference Example film, two films were cut into 70 mm MD (machine direction) × 200 mm TD (transverse direction) pieces. The two pieces were then stacked with the seal layers facing each other, and heat-sealed under specified conditions using a heat-sealing machine (HG-100-2, manufactured by Toyo Seiki Seisakusho) to produce measurement samples. The specified conditions were a sealing temperature of 150°C, a gauge pressure of 0.26 MPa, and a sealing time of 0.5 seconds.

[0037] Next, measurement samples were cut to a size of 10 mm in the MD and 50 mm in the TD, with the heat-sealed portion at the very edge of the sample, and the area of ​​the heat-sealed portion being 10 mm in the MD and 10 mm in the TD. The cut measurement samples were pulled in the TD using a digital force gauge (Imada ZTS-100N) attached to a measurement stand (Imada MX-500N), and the heat-sealed portion was peeled off. The heat-seal strength was measured five times for each measurement sample. The seal strength values ​​shown in Figures 3A to 3C are the average of the five measurements, each multiplied by 1.5.

[0038] 3B, it was confirmed that under the heat sealing conditions in the second test, the seal strength of the antibacterial film 10 of Example 9 was slightly low. This is thought to be due to the relatively large ratio RA.

[0039] Additionally, as an additional test to the second test, the inventors also measured the seal strength using the same method as in the second test under the specified heat sealing conditions, where the seal temperatures were 135°C, 140°C, and 145°C. Figures 4A to 4C show the results of the additional test to the second test.

[0040] As shown in Figures 4A and 4B, it was confirmed that the antibacterial films 10 of Examples 1, 4, 5, and 8, which have a ratio RA of 4 / 3, had good sealing properties even when the sealing temperature during heat sealing was relatively low.

[0041] <3-3. Third Exam> The third test was a test to evaluate the permeability of the film. In the third test, the antibacterial films 10 of Examples 1 to 9, Comparative Examples 1 and 2, and the film of the Reference Example were each cut into strips measuring 1 cm in the MD direction and 10 cm in the TD direction to produce measurement samples. Each measurement sample was set with the sealing layer facing the light source, and the haze value (%) was measured using a haze meter (NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.). The measurement was performed four times. The haze value items shown in Figures 3A to 3C are the average values ​​of the four measurements.

[0042] As shown in Figures 3A to 3C, it was confirmed that the antibacterial films 10 of Examples 1 to 9, the antibacterial films 10 of Comparative Examples 1 and 2, and the film of the Reference Example had transmittance at a level generally required for packaging.

[0043] <3-4. Fourth Exam> The fourth test is a test to confirm the Young's modulus, oxygen permeability, and carbon dioxide permeability of the film. In the fourth test, the Young's modulus, oxygen permeability, and carbon dioxide permeability of the antibacterial films 10 of Examples 1 and 4 were measured.

[0044] The Young's modulus of the antibacterial film 10 of Example 1 was MD / TD = 0.9 / 2.2 (GPa). The Young's modulus of the antibacterial film 10 of Example 4 was MD / TD = 2.1 / 5.0 (GPa). Because the base layer 20 of the antibacterial film 10 of Example 1 contains SEBS, it was confirmed to have softer properties than the antibacterial film 10 of Example 4, whose base layer 20 is composed solely of HPP. For this reason, it is thought that the antibacterial film 10 of Example 1 can be degassed more suitably after the production of a package than the antibacterial film 10 of Example 4.

[0045] The oxygen permeability of the antibacterial film 10 of Example 1 was 3110 (cm 3 / m 2 ·24h·atm), and the dioxide permeability is 11100 (cm 3 / m 2The oxygen permeability of the antibacterial film 10 of Example 4 was 1920 (cm 3 / m 2 ·24h·atm), and the dioxide permeability is 5400 (cm 3 / m 2 It was confirmed that the antibacterial film 10 of Example 1 had higher breathability than the antibacterial film 10 of Example 4.

[0046] <3-5. Fifth Exam> The fifth test was a test to confirm the effect of inhibiting bacterial growth when a package was manufactured using the film. In the fifth test, 130 g of cut cabbage was placed in the package for each of the antibacterial films 10 of Examples 1 to 9, the antibacterial films 10 of Comparative Examples 1 and 2, and the film of the Reference Example. The packages were then placed in a vertical pillow packaging machine (Daisei Machinery Co., Ltd.) and degassed to produce packages with the contents sealed inside. The resulting packages were 240 mm long and 195 mm wide, and five were produced for each degassing level described below. The seal widths of the top, bottom, and back panel (back) of the resulting packages were all 10 mm. These packages were stored in an environment of 10°C for 120 hours (5 days). After 5 days, the contents were removed from the package, and 10 g of the contents were homogenized with 90 cc of phosphate buffer. 1 mL of the resulting 10-fold diluted solution was taken and diluted with 9 mL of phosphate buffer to obtain a further 10-fold diluted sample solution. Next, the diluted solution was diluted to an appropriate dilution ratio and cultured in Petrifilm medium (3M) at 35°C for 48 hours, and the general viable bacterial count was counted.

[0047] In the fifth test, the relationship between the degassing index of the package containing the contents and the total viable bacterial count was confirmed. The degassing index of the package is an index uniquely defined by the inventor(s) and is defined by the following formula (1) as the volume of the internal space of the package per gram of contents enclosed in the package. Degassing index = Degree of degassing / Weight of contents to be sealed (130g in this test) (1)

[0048] The degree of degassing in formula (1) is calculated based on the inner surface area S (mm 2 The volume of the package can be determined, for example, by submerging the package in a bucket of water and measuring the volume of the water that overflows from the bucket.

[0049] Figure 5 is a table showing the results of Test 5. Figure 5 shows the ratio of the general viable bacterial count in the packages produced using the antibacterial films 10 of Examples 1 to 9 and the antibacterial films 10 of Comparative Examples 1 and 2, when the general viable bacterial count in the package produced using the film of the Reference Example is set to 1.

[0050] As shown in FIG. 5 , it was confirmed that the packages produced using the antibacterial films 10 of Examples 1 to 9 had a lower viable bacterial count than the packages produced using the antibacterial films 10 of Comparative Examples 1 and 2; in other words, they had a higher effect of inhibiting bacterial growth. This is thought to be because the antibacterial films 10 of Examples 1 to 9 had a ratio RA greater than 1. It was also confirmed that the smaller the degassing index, the lower the viable bacterial count. This is thought to be because the smaller the degassing index, in other words, the smaller the volume of the internal space of the package per gram of contents enclosed in the package, the closer the distance between the antibacterial agent particles exposed from the seal layer 30 of the package and the contents, or the closer the contact between the antibacterial agent particles exposed from the seal layer 30 of the package and the contents.

[0051] <4. Modifications> The above-described embodiments are merely examples of possible forms of the antibacterial film of the present invention, and are not intended to limit the forms. The antibacterial film of the present invention may take forms different from those exemplified in the embodiments. Examples include forms in which part of the configuration of the embodiments is replaced, modified, or omitted, or forms in which a new configuration is added to the embodiments. Some examples of modifications of the embodiments are shown below.

[0052] <4-1> The material constituting the sealing layer 30 can be changed as desired. For example, the material constituting the sealing layer 30 may contain a deodorizer. Examples of the deodorizer include inorganic deodorizers. Examples of the inorganic deodorizer include zirconium phosphate; aluminosilicate (zeolite); zinc aluminosilicate; carbonates such as sodium carbonate, sodium bicarbonate, and calcium carbonate; and metal oxides such as calcium oxide, magnesium oxide, aluminum oxide, zinc oxide, copper oxide, iron oxide, titanium oxide, and alum.

[0053] <4-2> In the above embodiment, a package is produced from one antibacterial film 10 using a vertical pillow packaging machine, but a package may also be produced by heat sealing two or more antibacterial films 10, for example.

[0054] <4-3> In the above embodiment, the sealing layers 30 of the antibacterial film 10 are joined together by heat sealing, but the means for sealing the sealing layers 30 of the antibacterial film 10 together can be changed as desired. For example, the sealing layers 30 of the antibacterial film 10 may be sealed together by impulse sealing, high frequency sealing, or ultrasonic sealing. [Explanation of symbols]

[0055] 10: Antibacterial film 20: Base material layer 30: Sealing layer

Claims

1. a substrate layer; a seal layer laminated on the base material layer, the base layer is made of a material containing a propylene-based resin, the sealing layer is made of a material containing a propylene-based random copolymer and an antibacterial agent, the antimicrobial agent comprises particles; The mode particle size of the antibacterial agent particles is larger than the thickness of the sealing layer. Antibacterial film.

2. The ratio of the mode particle diameter of the antibacterial agent particles to the thickness of the sealing layer is 20 / 3 or less. The antibacterial film of claim 1.

3. The ratio of the mode particle size of the antibacterial agent particles to the thickness of the sealing layer is 4 or less. The antibacterial film according to claim 2.

4. The ratio of the mode particle diameter of the antibacterial agent particles to the thickness of the sealing layer is 4 / 3 or less. The antibacterial film according to claim 3.

5. The proportion of the antibacterial agent in the material constituting the sealing layer is in the range of 0.02% by weight to 2.00% by weight. The antibacterial film according to any one of claims 1 to 4.

6. The mode particle size of the antibacterial agent particles is in the range of 0.5 μm to 6.0 μm. The antibacterial film according to any one of claims 1 to 5.

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