Food packaging film

Abstract

To provide food packaging film suitable for automated packaging. [Solution] A food packaging film in which the neck-in ratio in the flow direction (MD direction) is 70% or more and less than 90% when stretched to 160% in the width direction (TD direction).

Description

Technical Field

[0001] Embodiments of the present invention relate to a film for food packaging and packaged foods.

Background Art

[0002] For food packaging, especially for fresh foods such as meat, fresh fish, and fruits and vegetables, many stretch films with excellent transparency, flexibility, and heat sealability have been developed and widely used as films for food packaging (for example, Patent Document 1). Food packaging methods using films for food packaging include hand packaging using a hand wrapper or automatic packaging using an automatic packaging machine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the supermarket market, etc., since it is necessary to package a large amount of food, improvement in the efficiency of packaging work by automatic packaging is required. Therefore, an embodiment of the present invention aims to provide a film for food packaging suitable for automatic packaging. Another embodiment of the present invention aims to provide a packaged food that is efficiently packaged.

Means for Solving the Problems

[0005] The present invention includes the following embodiments. The present invention is not limited to the following embodiments. (1) A film for food packaging in which the neck-in rate in the machine direction (MD direction) when stretched 160% in the transverse direction (TD direction) is 70% or more and less than 90%. (2) The film for food packaging according to (1), which contains polyvinyl chloride. (3) A food packaging film as described in (1) or (2) above, having a thickness of 9.0 μm or more and less than 20 μm. (4) A food packaging film according to any one of (1) to (3), comprising a polymer and a plasticizer, wherein the content of the plasticizer is 30 parts by mass or more and less than 45 parts by mass per 100 parts by mass of the polymer. (5) A food packaging film according to any of (2) to (4) above, wherein the degree of polymerization of the polyvinyl chloride is 900 or more and less than 1500. (6) A food packaging film containing polyvinyl chloride and a plasticizer, wherein the degree of polymerization of the polyvinyl chloride is 900 or more and less than 1500, the content of the plasticizer is 30 parts by mass or more and less than 45 parts by mass per 100 parts by mass of the polyvinyl chloride, and the thickness is 9.0 μm or more and less than 20 μm. (7) A packaged food comprising a food packaging film described in any of (1) to (6) above, and a food packaged in the food packaging film. [Effects of the Invention]

[0006] According to embodiments of the present invention, a food packaging film suitable for automated packaging can be provided. Furthermore, according to other embodiments of the present invention, efficiently packaged food products can be provided. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing an example of a measurement film before cutting in the method for measuring the neck-in rate (%). [Figure 2] Figure 2 is a schematic diagram showing an example of a measurement film before stretching in the method for measuring the neck-in rate (%). [Figure 3] Figure 3 is a schematic diagram showing an example of a measurement film after stretching in the method for measuring the neck-in rate (%). [Modes for carrying out the invention]

[0008] Embodiments of the present invention will now be described. The present invention is not limited to the following embodiments. <Food packaging film> In some embodiments of the present invention, the food packaging film is a film that satisfies the characteristic that the neck-in ratio in the flow direction (MD direction) when stretched to 160% in the width direction (TD direction) is 70% or more and less than 90%. According to the food packaging film that satisfies this characteristic, problems such as tearing or ripping of the film or damage to the tray can be suppressed in packaging operations using an automatic packaging machine, and food can be packaged efficiently. The food packaging film is a film used to package fresh foods (e.g., fresh meat, fresh fish, fruits and vegetables), processed foods, and food trays containing food using an automatic packaging machine. As an automatic packaging machine, a push-up type automatic packaging machine can be preferably used from the viewpoint of the packaging machine being compact, capable of handling a wide variety of products, and having a weighing and pricing mechanism. The food packaging film is generally installed in the automatic packaging machine in the form of a roll (winding body). The film is unwound from the roll by the automatic packaging machine and cut, and the items to be packaged, such as food trays, are packaged with the film.

[0009] In embodiments of the present invention, neck-in refers to the phenomenon in which the flow direction (MD direction) of a food packaging film shrinks when the food packaging film is stretched in the width direction (TD direction). The neck-in rate can be measured according to the following method. The measurement method will be explained with reference to the figures.

[0010] (1) A film for measurement 2 is prepared by unwinding and cutting a roll of food packaging film 1 (Figure 1). The length of the measurement film 2 in the width direction (Transversal Direction, TD direction) is T. (2) The ends of the measuring film 2 along the flow direction (Mold Direction, MD direction) are clamped by the clamping parts 3 (also called "chuck parts") (Figure 2). The length T0 between the chuck parts in the width direction (TD direction) of the measuring film and the length M0 in the flow direction (MD direction) of the measuring film are measured. The length T0 is the length in the width direction (TD direction) excluding the portion clamped by the chuck parts (i.e., T-2t). (3) Stretch the measuring film in the width direction (TD direction) so that the elongation rate calculated by the following formula 1 is 160% (Figure 3). In formula 1, T1 is the length between the chucks in the width direction (TD direction) of the stretched measuring film. Formula 1: Stretching rate (%)=(T1(mm) / T0(mm))×100 (4) Measure the length M1 in the flow direction (MD direction) of the measurement film stretched to an elongation rate of 160%, and calculate the neck-in ratio (%) using the following formula 2. The length M1 is the smallest length in the flow direction of the film. Formula 2: Neck-in percentage (%) = (M1 (mm) / M0 (mm)) × 100

[0011] The size of the measuring film may be, for example, a length T in the width direction (TD direction) of 250 to 500 mm and a length M0 in the flow direction (MD direction) of 250 to 1000 mm. The width t of the portion of the measuring film held by the chuck may be 10 to 20 mm. For example, in the case of a measuring film with a length T in the width direction (TD direction) of 300 mm, the measurement can be performed by setting the length M0 in the flow direction (MD direction) of the measuring film to 600 mm, the width t to 10 mm, and the length T0 in the width direction (TD direction) to 280 mm.

[0012] The stretching conditions are as follows: in an atmosphere with a temperature of 23°C and a relative humidity of 50%, a film chuck pressure of 2.1 to 2.4 MPa, and a film stretching speed of 120 mm / s. For stretching, an automatic packaging machine (for example, "WM-AI" manufactured by Ishida Co., Ltd.) can be used. When using "WM-AI", the settings are, for example, packaging speed: high speed, supply speed: high speed, lift switching: small.

[0013] The neck-in rate is 70% or more, and may be 75% or more. When the neck-in rate is 70% or more, the film has sufficient elongation resistance, and film tearing, breakage, etc. during packaging can be suppressed. The neck-in rate is less than 90%, and may be 85% or less, or 80% or less. When the neck-in rate is less than 90%, the shrinkage force of the film can be suppressed to be small, and deformation or breakage of the tray after packaging can be prevented.

[0014] The neck-in rate tends to decrease by reducing the degree of polymerization, increasing the plasticizer content rate, reducing the thickness, etc. The neck-in rate tends to increase by increasing the degree of polymerization, reducing the plasticizer content rate, increasing the thickness, etc. By utilizing these tendencies, the neck-in rate can be adjusted.

[0015] The film for food packaging may contain a polymer. Examples of the polymer include polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyesters such as polyethylene terephthalate and polyethylene naphthalate; styrenic polymers such as polystyrene and styrene-butadiene-styrene block copolymer; and chlorine-based polymers such as polyvinyl chloride and polyvinylidene chloride. The film for food packaging may contain only one kind of polymer or two or more kinds of polymers. The film for food packaging containing polyvinyl chloride tends to suppress the deformation of the tray during packaging because it is rich in stretchability. Also, the film for food packaging containing polyvinyl chloride has good properties as a wrap film in terms of transparency, flexibility, heat sealability, etc. In the embodiments of the present invention, polyvinyl chloride can be preferably used.

[0016] The degree of polymerization of polyvinyl chloride is preferably 900 or more and less than 1500. When the degree of polymerization of the polyvinyl chloride resin is 900 or more, the film is sufficiently stretched during packaging, so it is easy to prevent the film from breaking. The degree of polymerization of polyvinyl chloride may be 1000 or more, or 1200 or more. When the degree of polymerization of the polyvinyl chloride resin is less than 1500, it is easy to prevent the occurrence of deformation and breakage of the tray after packaging. The degree of polymerization of polyvinyl chloride may be 1450 or less, or 1400 or less. In the embodiments of the present invention, the degree of polymerization of polyvinyl chloride is the average degree of polymerization converted from the K value measured according to JIS K7367-2:1999.

[0017] Examples of polyvinyl chloride include TK-1000, TK-1300, TK-1400, etc. manufactured by Shin-Etsu Chemical Co., Ltd.; S1001N, S1003, etc. manufactured by Kaneka Corporation.

[0018] Food packaging films may further contain plasticizers. The plasticizer content is preferably 30 parts by mass or more and less than 45 parts by mass per 100 parts by mass of polymer. A plasticizer content of 30 parts by mass or more makes it easier to prevent the film from tearing during packaging. The plasticizer content may be 35 parts by mass or more, or 38 parts by mass or more. A plasticizer content of less than 45 parts by mass can suppress bleeding and prevent the film from coming off the chuck of an automatic packaging machine during packaging. The plasticizer content may be 42 parts by mass or less, or 40 parts by mass or less.

[0019] Examples of plasticizers include diisononyl adipate, epoxidized soybean oil, din-alkyl adipate, dioctyl adipate, and polyester compounds. Food packaging films may contain only one type of plasticizer or two or more types of plasticizers.

[0020] Food packaging films may further contain additives such as lubricants, antifogging agents, and stabilizers. Examples of lubricants include aliphatic hydrocarbon lubricants, higher aliphatic alcohol lubricants, fatty acid lubricants, aliphatic amide lubricants, fatty acid ester lubricants, metal soaps, and silicone oils. Examples of stabilizers include lead stabilizers, tin stabilizers, organometallic salt stabilizers, metal soap stabilizers, antimony stabilizers, phosphate stabilizers, and epoxidized oil stabilizers. Examples of antifogging agents include sorbitan fatty acid esters, polyglycerin fatty acid esters, and triethylene glycol. Food packaging films may contain each additive individually or in combination of two or more.

[0021] Food packaging films can be manufactured using molding materials for food packaging films. Preferably, the molding material is one that satisfies the characteristic of having a tensile elongation at break of 350-410% when a 13 μm thick food packaging film is made using the molding material and the tensile elongation at break is measured. A tensile elongation at break of 350% or more provides sufficient stretchability of the film, making it easier to prevent film breakage and tray deformation and damage. The tensile elongation at break may be 360% or more, or 370% or more. A tensile elongation at break of 410% or less makes it easier to prevent film sagging and wrinkles. The tensile elongation at break may be 400% or less, or 390% or less.

[0022] The tensile elongation at break can be measured in accordance with JIS K 6732:2006. The sample for measurement shall be a No. 1 dumbbell manufactured in accordance with JIS K6251:2017, with the width direction (TD direction) of the food packaging film being the longitudinal direction of the dumbbell. The measurement shall be performed in an atmosphere of 22°C and 49% relative humidity using a tensile breaking tester (for example, a Tensilon universal tester PTM-500 manufactured by Orientec Co., Ltd.) at a tensile speed of 250 mm / min.

[0023] The tensile elongation at break tends to increase when the degree of polymerization is reduced or the plasticizer content is increased. Conversely, the tensile elongation at break tends to decrease when the degree of polymerization is increased or the plasticizer content is decreased. These tendencies can be used to adjust the tensile elongation at break.

[0024] The thickness of the food packaging film is preferably 9.0 μm or more and less than 20 μm. A thickness of 9.0 μm or more can further reduce the occurrence of tearing, ripping, etc. of the film during packaging. The thickness may also be 10 μm or more, or 11 μm or more. A thickness of less than 20 μm makes it easier to keep the neck-in rate below 90%, and further reduces the occurrence of tray deformation and damage. The thickness may also be 15 μm or less, or 12 μm or less.

[0025] In some embodiments of the present invention, the food packaging film contains polyvinyl chloride and a plasticizer, wherein the degree of polymerization of the polyvinyl chloride is 900 degrees or more and less than 1500 degrees, the plasticizer content is 30 parts by mass or more and less than 45 parts by mass per 100 parts by mass of polyvinyl chloride, and the thickness is 9.0 μm or more and less than 20 μm. With this food packaging film, problems such as tearing or ripping of the film or damage to the tray can be suppressed during packaging operations using an automatic packaging machine, and food can be packaged efficiently.

[0026] The method for manufacturing food packaging film is not particularly limited and can be manufactured by known manufacturing methods such as melt extrusion, calendering, and casting. Considering handling ease and simplification of manufacturing equipment, the melt extrusion method is preferred. Food packaging film is generally manufactured in the form of a roll (winding body). The method for manufacturing food packaging film includes, for example, melting and kneading the molding material for the food packaging film, extruding the molding material from a die to form a film, and cooling the film and winding it up with a winding machine. The size of food packaging film can be set according to the application. The width of food packaging film can be selected according to the food, tray, etc. to be packaged, and can be, for example, 250 to 500 mm, and may be 250 mm, 280 mm, 300 mm, 330 mm, 350 mm, 400 mm, 450 mm, or 500 mm. The length of the roll should be, for example, 500 to 1200 m, and may be 500 m, 750 m, 1000 m, or 1200 m, from the standpoint of handling and workability.

[0027] <Packaging method> In an embodiment of the present invention, a packaging method for food, food trays containing food, etc., includes packaging the packaged object, including food, with the food packaging film of the embodiment using a push-up automatic packaging machine. In the push-up automatic packaging machine, the film is unwound from a roll, held by a chuck, cut to a predetermined length, and stretched in the width direction (TD direction). The packaged object is fed into the bottom of the film, pushed up toward the film, and packaged. The packaging method may be a method of packaging the packaged object by stretching the food packaging film of the embodiment such that the stretching ratio in the width direction (TD direction) is 150 to 170% and the neck-in ratio in the flow direction (MD direction) is 70% or more and less than 90%. The film chuck pressure is, for example, 2.1 to 2.4 MPa, and the film stretching speed is, for example, 100 to 150 mm / s, preferably 110 to 130 mm / s.

[0028] <Packaged food> In embodiments of the present invention, the packaged food comprises the food packaging film of the embodiment and the food packaged with the food packaging film. The packaged food may further include a food tray. The packaged food may, for example, include the food packaging film of the embodiment, the food packaged with the food packaging film and a food tray. [Examples]

[0029] Embodiments of the present invention will be specifically described by reference to examples. Embodiments of the present invention are not limited to the following examples.

[0030] <Film Production> [Example 1] A roll-shaped film (1000 m in the extrusion direction × 300 mm in the width direction) was produced by melt extrusion molding using a molding material containing polyvinyl chloride (degree of polymerization 1300) and a plasticizer (42 parts by mass per 100 parts by mass of polyvinyl chloride). The neck-in ratio and thickness of the film were measured using the following method. The results are shown in Table 1.

[0031] (Measurement of tensile elongation at break (%) of molded material) A 13 μm thick film was fabricated using a molding material by melt extrusion molding, cut, and a dumbbell-shaped test specimen was prepared in accordance with JIS K6251:2017. The longitudinal direction of the test specimen was aligned with the film's width direction (TD direction). Using the test specimen, the tensile elongation at break (%) was measured in accordance with JIS K 6732:2006 using a tensile breaking tester (Tensilon universal tester PTM-500 manufactured by Orientec Co., Ltd.) under conditions of a temperature of 22°C, relative humidity of 49%, and a tensile speed of 250 mm / min. The tensile elongation at break was 378 (%).

[0032] (Measurement of neck-in rate (%)) A film was unwound from the roll, cut, and prepared as a measurement film (width direction (TD direction): 300 mm, flow direction (MD direction): 600 mm). Following the method described above, the measurement film (T0: 280 mm, M0: 600 mm) was stretched using an automatic packaging machine (WM-AI, manufactured by Ishida Co., Ltd.) so that T1 was 448 mm, M1 (mm) was measured, and the neck-in ratio was calculated. The width t of the portion of the measurement film held by the chuck was 10 mm. The measurement was performed under the conditions of a temperature of 23°C, relative humidity of 50%, film chuck pressure of 2.2 MPa, and film stretching speed of 120 mm / s. The automatic packaging machine was set to packaging speed: high, feed speed: high, and lift switching: low.

[0033] (Measurement of film thickness (μm)) The film thickness was calculated from the film's mass, size, and density using the following formula 3. Formula 3: Film thickness (μm) = (Film mass (kg) × 10 6 ) / (Film width (mm) × Film length (m) × (Film density (g / cm³) 3 )))

[0034] [Examples 2-5 and Comparative Examples 1-7] Films with the neck-in ratios shown in Table 1 were prepared using the amounts of polymer and plasticizer shown in Table 1. In the table, "PVC" refers to polyvinyl chloride and "PO" refers to polyolefin.

[0035] <Film Evaluation> Using an automatic packaging machine (WM-AI, manufactured by Ishida Co., Ltd.), 50 trays were packaged per film. The automatic packaging machine settings were: packaging speed: high, feed speed: high, lift change: low. The film size was 300 mm in the width direction (TD direction) and 600 mm in the flow direction (MD direction). The trays used were "Food Tray CN20-20F" manufactured by Chuo Kagaku Co., Ltd., with dimensions of 20 cm in length, 20 cm in width, and 2.5 cm in depth. The automatic packaging machine stretched the film to a width direction (TD direction) elongation ratio of 160%, and then pushed the trays towards the stretched film to package the trays. Out of 50 trays, the number of trays with packaging defects such as tears, rips, or holes in the film, or damage or deformation of the tray was counted. Furthermore, the suitability of the film for automatic packaging was determined based on the number of defective trays. ○ indicates "suitable," and × indicates "unsuitable." Table 1 shows the number of trays with packaging defects and the determination results.

[0036] [Table 1] [Explanation of symbols]

[0037] 1. Film for food packaging 2. Measuring film 3. Clamping part (chuck part) T: Length in the width direction (TD direction) of the measuring film. Length between chuck parts in the width direction (TD direction) of the T0 measurement film T1 Length between chuck parts in the width direction (TD direction) of the stretched measuring film Length of the film used for M0 measurement in the flow direction (MD direction) M1 Length of the stretched measuring film in the flow direction (MD direction) t The width of the portion of the measuring film that is held by the chuck.

Claims

1. A food packaging film in which the neck-in ratio in the flow direction (MD direction) is 70% or more and less than 90% when stretched to 160% in the width direction (TD direction).

2. A food packaging film according to claim 1, comprising polyvinyl chloride.

3. A food packaging film according to claim 1, wherein the thickness is 9.0 μm or more and less than 20 μm.

4. A food packaging film according to claim 1, comprising a polymer and a plasticizer, wherein the content of the plasticizer is 30 parts by mass or more and less than 45 parts by mass per 100 parts by mass of the polymer.

5. The food packaging film according to claim 2, wherein the degree of polymerization of the polyvinyl chloride is 900 or more and less than 1500.

6. A packaged food comprising a food packaging film according to any one of claims 1 to 5, and a food packaged in the food packaging film.

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