Stretched laminate film, bag, and fresh meat package

Abstract

To provide a stretched laminate film which is excellent in stretching stability and shrinkage performance, and has a low elastic modulus and excellent delamination, even when a vinylidene chloride copolymer is used as a barrier layer.SOLUTION: A stretched laminate film 100 has: an inner surface layer 10; an adhesive layer (A) 20 formed on the inner surface layer 10; a barrier layer 30 formed on the adhesive layer (A) 20; an adhesive layer (B) 40 formed on the barrier layer 30; and an outer surface layer 50 formed on the adhesive layer (B) 40. The outer surface layer contains a polyamide resin, a ratio of a thickness occupied by the outer surface layer 50 in the whole stretched laminate film 100 is 0.1% or more and less than 1.0%. The barrier layer contains a vinylidene chloride (VDC) copolymer. Both of tensile elastic moduli in the vertical direction and the lateral direction at 23°C are 50 MPa or more and less than 200 MPa, and both of thermal shrinkage factors in the vertical direction and the lateral direction at 80°C are 35% or more and less than 60%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a stretched laminated film, a bag, and a fresh meat package.

Background Art

[0002] Generally, stretched laminated films are used for packaging meats, processed meats, processed fishery products, machine parts, and the like. The stretched laminated film is provided with functions according to the application by each layer having various properties. The properties required for the stretched laminated film used for heat shrink packaging include the following.

[0003] (1) Heat shrinkability: The property that the film shrinks by heat. It is imparted by the layer that is easy to stretch. When heat is applied to a product vacuum-packed with a film having heat shrinkability by a warm water shower, hot air, a warm water bath, etc., the film adheres to the contents and the appearance of the product becomes good. (2) Barrier property: The property of blocking oxygen etc. It is imparted by the layer that does not allow oxygen etc. to pass through. For example, a laminated film having a layer of a vinylidene chloride copolymer, a saponified ethylene-vinyl acetate copolymer, an amide resin, etc. exhibits oxygen barrier property. Long-term storage of the contents becomes possible. (3) Transparency: The property indicating the transparency of the film. It is affected by the difference in the heat shrinkage rate of each layer of the film. It is an important property in terms of the appearance of the product. (4) Heat sealability: The property that the films adhere to each other by heat. It is imparted by the layer having a low melting temperature. It becomes possible to close the mouth of the bag made of the film by heat. (5) Multiple heat sealability: When heat-sealing the mouth of a bag made of a film, even if the heat-applied parts of a plurality of bags are overlapped and heat-sealed together, the bags do not weld to each other. The number of packaging bags per unit time can be increased.

[0004] To solve such problems, many technologies have been studied. For example, Patent Documents 1 and 2 describe films in which an ethylene-α-olefin copolymer is used as the surface layer of the film and the film is electron beam crosslinked. Such films can improve heat shrinkage and transparency, but have a problem of poor overlap sealing property. In addition, Patent Documents 3 and 4 describe heat-shrinkable laminated films in which the melting temperature of one surface layer is at least 20°C higher than the melting temperature of the other surface layer. The films of Patent Documents 3 and 4 are said to have good burn-through resistance and excellent impulse sealing property, but there is a problem that whitening becomes prominent and transparency deteriorates significantly when they are greatly heat-shrunk.

[0005] In addition, Patent Document 5 discloses a stretched laminated film in which at least four layers of a surface layer (A), an adhesive layer (A), a barrier layer, and a surface layer (B) are laminated in this order. A stretched laminated film is disclosed in which the melting temperature of the surface layer (A) is higher than that of the surface layer (B) by a specific range, the barrier layer is made of a vinylidene chloride copolymer, and the melting temperature of the barrier layer is within a specific range. According to the technology of this Patent Document 5, it is possible to achieve excellent effects in terms of heat shrinkage, barrier property, transparency, heat sealability, and overlap sealability described above.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, although the stretched laminated film disclosed in Patent Document 5 can exhibit excellent effects as described above, the vinylidene chloride copolymer used as the barrier layer may have a reduced shrinkage rate and thermal stability, and may also cause hardening of the film due to an increase in the elastic modulus. Therefore, further improvement has been desired in these aspects. Furthermore, when the thermal shrinkage property increases, the outer surface layer (surface layer (A)) tends to be easily peeled off, and further improvement has been desired for the interlayer adhesiveness (delamination property).

[0008] Therefore, an object of the present invention is to provide a stretched laminated film that is excellent in stretching stability and shrinkage performance, has a low elastic modulus, and is also excellent in delamination property even when a vinylidene chloride copolymer is used as the barrier layer. Another object of the present invention is to provide a bag using a stretched laminated film that is excellent in stretching stability and shrinkage performance, has a low elastic modulus, and is also excellent in delamination property even when a vinylidene chloride copolymer is used as the barrier layer, and a fresh meat package obtained by packaging fresh meat using the bag.

Means for Solving the Problems

[0009] The inventors of the present invention have intensively studied to solve the above-mentioned problems regarding a stretched laminated film including an inner surface layer, an adhesive layer (A) formed on the inner surface layer, a barrier layer formed on the adhesive layer (A), an adhesive layer (B) formed on the barrier layer, and an outer surface layer formed on the adhesive layer (B). As a result, by configuring the barrier layer from a specific vinylidene chloride (VDC) copolymer and optimizing the longitudinal and transverse tensile elastic moduli at 23°C and the longitudinal and transverse thermal shrinkage rates at 80°C, it has been found that even when using a vinylidene chloride (VDC) copolymer, good stretching stability and shrinkage performance can be ensured, and the elastic modulus can also be reduced. In addition, by making the ratio of the thickness occupied by the outer surface layer in the entire stretched laminated film as small as 0.1% or more and less than 1.0%, it has also been found that even when the shrinkage rate of the laminate is high, the outer surface layer does not peel off and good delamination properties can be obtained, thus completing the present invention.

[0010] The present invention has been made based on the above findings, and the gist thereof is as follows. (1) A stretched laminated film including an inner surface layer, an adhesive layer (A) formed on the inner surface layer, a barrier layer formed on the adhesive layer (A), an adhesive layer (B) formed on the barrier layer, and an outer surface layer formed on the adhesive layer (B), wherein the outer surface layer contains a polyamide resin, the ratio of the thickness occupied by the outer surface layer in the entire stretched laminated film is 0.1% or more and less than 1.0%, the barrier layer contains a vinylidene chloride (VDC) copolymer, and the longitudinal and transverse tensile elastic moduli at 23°C are both 50 MPa or more and less than 200 MPa, and the longitudinal and transverse thermal shrinkage rates at 80°C are both 35% or more and less than 60%.

[0011] (2) The stretched laminated film according to (1), wherein the content of vinyl chloride in the vinylidene chloride (VDC) copolymer is 10% by mass or more and less than 20% by mass.

[0012] (3) The barrier layer contains acetyl tributyl citrate (ATBC) in an amount of 0.1% by mass or more and less than 10% by mass, and the stretched laminated film according to (1) or (2).

[0013] (4) The content ratio of the rework vinylidene chloride (VDC) copolymer in the vinylidene chloride (VDC) copolymer is 20% by mass or more, and the stretched laminated film according to any one of (1) to (3).

[0014] (5) The barrier layer contains an alkaline earth metal salt of a fatty acid in an amount of 0.1% by mass or more and less than 1% by mass, and the stretched laminated film according to any one of (1) to (4).

[0015] (6) A bag using the stretched laminated film according to any one of (1) to (5), wherein the outer surface layer constitutes the outer surface of the bag, and the inner surface layer constitutes the inner surface of the bag.

[0016] (7) A fresh meat package characterized by packaging fresh meat using the bag according to (6). [Advantages of the Invention]

[0017] According to the present invention, even when a vinylidene chloride copolymer is used as the barrier layer, a stretched laminated film excellent in stretching stability and shrinkage performance, having a low elastic modulus and excellent delamination properties can be provided. Further, according to the present invention, even when a vinylidene chloride copolymer is used as the barrier layer, a bag using a stretched laminated film excellent in stretching stability and shrinkage performance, having a low elastic modulus and excellent delamination properties, and a fresh meat package packaging fresh meat using the bag can be provided. [Brief Description of the Drawings]

[0018]

Figure 1

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an exemplification for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be appropriately modified and implemented within the scope of its gist.

[0020] <Stretched laminated film> First, the stretched laminated film of the present embodiment (hereinafter sometimes referred to as "the film of the present embodiment") will be described. As shown in FIG. 1, the stretched laminated film of the present embodiment is a stretched laminated film 100 including an inner surface layer 10, an adhesive layer (A) 20 formed on the inner surface layer 10, a barrier layer 30 formed on the adhesive layer (A) 20, an adhesive layer (B) 40 formed on the barrier layer 30, and an outer surface layer 50 formed on the adhesive layer (B) 40.

[0021] (Inner surface layer) As shown in FIG. 1, the stretched laminated film of the present embodiment includes an inner surface layer 10. The inner surface layer is a layer that contacts the bactericidal object such as meat, processed meat, and processed fishery products among the multilayer films. When the stretched laminated film is processed into a bag shape, it becomes the innermost layer that contacts the bactericidal object.

[0022] The inner surface layer serves as a heat seal layer for sealing the bactericidal object. The resin used for such an inner surface layer is not particularly limited. For example, it can be selected from polyethylene, an ethylene copolymer such as ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, or a mixture thereof. Among them, ethylene-α-olefin copolymer is preferable because of its excellent stretchability and heat sealability.

[0023] Also, the melting temperature of the inner surface layer is preferably from 80°C to 130°C. As the ethylene-α-olefin copolymer, those polymerized using a catalyst called a single-site catalyst or a multi-site catalyst are preferable. Among them, those polymerized by a single-site catalyst are preferable in terms of good heat sealability. Further, a copolymer of ethylene and any one comonomer selected from butene comonomer, hexene comonomer, and octene comonomer is more preferable. Also, in terms of transparency and heat sealability, the density range of the ethylene-α-olefin copolymer is 0.88 to 0.92 g / cm 3 is preferably set to, and more preferably 0.89 to 0.918 g / cm 3 . Also, the value of the melt index measured under the measurement conditions (190°C, 21.2 N) conforming to the measurement conditions of JIS-K-7210 of the ethylene-α-olefin copolymer is preferably 0.5 to 7, and more preferably 1 to 4 in terms of heat shrinkage rate and suitable heat shrinkage stress.

[0024] When using an ethylene-α-olefin copolymer as the resin for the inner surface layer, it can be mixed with other resins such as ethylene-vinyl acetate copolymer, high-pressure low-density polyethylene, petroleum resin, and hydrogenated terpene resin in the range of 40% by weight or less. When these are mixed, physical properties such as kneadability with surfactants such as anti-fogging agents, transparency, and flexibility can be imparted. In terms of good heat sealability, the amount of the ethylene-α-olefin copolymer is preferably 60% by weight or more. The mixing amount range of other resins is preferably 5% by weight or more and 20% by weight or less.

[0025] Also, the inner surface layer preferably has an anti-blocking agent. The presence of the anti-blocking agent on the inner surface increases the opening property of the film. Here, the type of the antiblocking agent is not particularly limited as long as it can improve the openness of the film, and it can be appropriately selected according to the required performance and the material of the inner surface layer. As the antiblocking agent, for example, surfactants such as glycerin fatty acid esters, antioxidants, antistatic agents, petroleum resins, mineral oils, fatty acid amide lubricants, silicon oxide, calcium carbonate, talc, etc. can be used. Furthermore, among the above-mentioned antiblocking agents, it is preferable to have starch powder. This is because more excellent openness can be obtained.

[0026] In addition, having an antiblocking agent in the inner surface layer means that the antiblocking agent may be present on the inner surface layer of the film. For example, the antiblocking agent can also be contained in the inner surface layer, or the antiblocking agent can be adhered onto the inner surface layer, and it can be appropriately selected according to the use and the required performance.

[0027] The proportion (%) of the thickness occupied by the inner surface layer in the entire stretched laminated film of this embodiment is preferably 5 to 60%, more preferably 10 to 30% from the viewpoints of heat sealability and high heat shrinkability.

[0028] (Barrier layer) Furthermore, as shown in FIG. 1, the stretched laminated film of this embodiment further includes a barrier layer 30 on the inner surface layer 10 via an adhesive layer (A) 20 described later. By having the barrier layer, gas barrier properties, particularly oxygen barrier properties, can be obtained, thereby preventing oxidative deterioration of the contents.

[0029] And in the stretched laminated film of this embodiment, the barrier layer contains a vinylidene chloride (VDC) copolymer. Thereby, while maintaining good gas barrier properties, excellent heat shrinkability and reduction of elastic modulus can be realized.

[0030] The vinylidene chloride copolymer is a polymer of vinylidene chloride (VDC) and other monomers. As the vinylidene chloride copolymer, a vinylidene chloride (VDC) / vinyl chloride (VC) copolymer or a vinylidene chloride (VDC) / methyl acrylate (MA) copolymer is preferably used.

[0031] In addition, when the vinylidene chloride (VDC) copolymer is a vinylidene chloride (VDC) / vinyl chloride (VC) copolymer, increasing the vinyl chloride (VC) ratio results in more amorphous parts and improved shrinkage properties. However, when the VC ratio is increased, there is a concern that blocking between resins may occur and the transportability may deteriorate. On the other hand, when the vinyl chloride (VC) ratio in the vinylidene chloride (VDC) / vinyl chloride (VC) copolymer is lowered, the transportability is improved, but the thermal stability and draw stability deteriorate, and the elastic modulus also tends to increase. Therefore, when packaging a packaged object such as raw meat, it is considered that the unevenness of the packaged object cannot be sufficiently followed (the shrinkage performance deteriorates).

[0032] Therefore, in the drawn laminated film of the present embodiment, by adjusting the VDC / VC ratio of the vinylidene chloride (VDC) / vinyl chloride (VC) copolymer, high productivity and transportability can be achieved while also achieving high draw stability, shrinkage performance, and low elastic modulus. Specifically, the content of vinyl chloride in the vinylidene chloride (VDC) / vinyl chloride (VC) copolymer is preferably 10% by mass or more and less than 20% by mass. When the content of vinyl chloride (VC) in the copolymer is 10% by mass or more, blocking between polymers is reduced and the input amount into the extruder is stabilized. On the other hand, when the content of vinyl chloride (VC) in the copolymer is less than 20% by mass, the thermal stability is improved and the draw stability is enhanced.

[0033] When using a vinylidene chloride (VDC) / methyl acrylate (MA) copolymer as the vinylidene chloride copolymer, from the viewpoints of stretchability and thermal stability, the methyl acrylate (MA) content is preferably 5 to 12% by weight, more preferably 5 to 9% by weight.

[0034] Further, the barrier layer preferably contains 0.1% by mass or more and less than 10% by mass of acetyl tributyl citrate (ATBC). This is because, due to the plasticizing effect of the ATBC, even when the VDC ratio of the barrier layer is high, it is possible to achieve a reduction in elastic modulus and an improvement in shrinkage performance. When the content of the ATBC is 0.1% by mass or more, the effects of reducing the elastic modulus and improving the shrinkage performance can be more reliably exhibited. On the other hand, when the content of the ATBC is less than 10% by mass, it is possible to suppress the occurrence of phenomena such as the film turning white and the visibility decreasing.

[0035] Furthermore, as the vinylidene chloride (VDC) copolymer in the barrier layer, it is preferable to use a reworked vinylidene chloride (VDC) copolymer. This is because it is possible to achieve more excellent shrinkage properties and a reduction in elastic modulus. Here, the reworked vinylidene chloride (VDC) copolymer has undergone the process of melting and solidification one or more times. The reworked vinylidene chloride (VDC) copolymer has received a thermal history up to melting, and as a result, partial dehydrochlorination occurs within the molecule, and the crystallinity is moderately reduced. Therefore, it is considered to contribute to the improvement of shrinkage performance and the reduction in elastic modulus. It is considered that the more thermal history up to melting, the more it contributes to the improvement of shrinkage performance and the reduction in elastic modulus. However, since dehydrochlorination also progresses, the thermal history up to melting is preferably 5 times or less.

[0036] Furthermore, the content ratio of the reworked vinylidene chloride (VDC) copolymer in the vinylidene chloride (VDC) copolymer is preferably 20% by mass or more, more preferably 25% by mass or more. This is because it is possible to achieve more excellent shrinkage properties and a reduction in elastic modulus.

[0037] Further, it is preferable that the barrier layer contains 0.1% by mass or more and less than 1% by mass of an alkaline earth metal fatty acid salt. This is because the thermal stability can be improved. Here, the alkaline earth metal fatty acid salt may be any one that does not inhibit the gas barrier property and can ensure the thermal stability. Examples thereof include calcium stearate and magnesium stearate.

[0038] In addition, it is preferable that the melting temperature of the barrier layer is 140°C or more and less than 170°C. This is preferable because whitening after heat shrinkage caused by the difference in the heat shrinkage rate between the inner surface layer and the outer surface layer is less likely to occur, the haze degree is lowered, stickiness of the resin is less likely to occur, and stable production can be achieved. More preferably, it is 140°C or more and less than 165°C.

[0039] In addition, in order to facilitate melt processing and achieve stable production, a heat stabilizer and a plasticizer may be added to the barrier layer within a range that does not affect the effects of the present invention. It is preferable to add them in the range of 1 to 10% by weight. The heat stabilizer and the plasticizer hardly affect the melting temperature of the vinylidene chloride copolymer. Additives such as epoxidized linseed oil and epoxidized soybean oil may be used as a heat stabilizer and a plasticizer. These preferable addition amounts are 2 to 5% by weight. Further, a lubricant such as a fatty acid amide-based lubricant, and powders such as silicon oxide, calcium carbonate, and talc may be added to the vinylidene chloride copolymer. Among them, it is preferable to add 0.005 to 0.3% by weight of talc because the crystallization rate is increased as a crystal nucleus of the vinylidene chloride copolymer before stretching, and the heat shrinkability is improved. From the viewpoint of good oxygen permeability, the thickness ratio of the barrier layer to the entire layer is preferably 5 to 30%, and more preferably 6 to 20%.

[0040] Also, the oxygen permeability of the entire stretched laminated film of the present embodiment is preferably 1000 cc / (m 2 ·day·atm 23°C 0%RH) or less, and more preferably 900 cc / (m 2 ·day·atm 23°C 0%RH) or less. More excellent gas barrier properties can be obtained, and oxidation and deterioration of the bactericidal cells can be prevented.

[0041] (Outer surface layer) As shown in Fig. 1, the stretched laminated film of the present embodiment includes an outer surface layer 50. Among the laminated films, it is the layer that forms the outer surface. When the laminated film is processed into a bag shape, it constitutes the outer surface of the bag and becomes the layer in contact with the outside.

[0042] In order to maintain the strength of the laminated film, a resin with a relatively high melting temperature is used for the outer surface layer. In the stretched laminated film of the present embodiment, the outer surface layer contains a polyamide resin. This is because it has an excellent balance of ultraviolet transmittance, heat resistance, transparency, stretchability, etc. Here, as the polyamide resin, aliphatic amide resins such as nylon-6 and nylon-12, aliphatic amide copolymers such as nylon-6,66 and nylon-6,12, aliphatic ternary copolymers such as nylon-6,66,12, and among them, nylon-6,66 is preferable in terms of obtaining high heat shrinkability.

[0043] The melting temperature of the outer surface layer is not particularly limited, but is preferably from 140°C to 230°C. In the case of a polyamide resin, the melting temperature (Tm) of the resin is preferably from 140 to 220°C in terms of obtaining high heat shrinkability and preferable heat shrinkage stress, and from the same viewpoint, it is more preferably from 155 to 220°C.

[0044] In addition, it is preferable to mix 5 to 40% by weight of amorphous polyamide in the outer surface layer to obtain better stretchability and appropriate heat shrinkage stress.

[0045] Furthermore, it is preferable that the melting temperature of the outer surface layer is higher than that of the inner surface layer, preferably 65°C or more higher than that of the inner surface layer, and more preferably 90°C or more higher than that of the inner surface layer. When the melting temperature of the outer surface layer is somewhat higher than that of the inner surface layer, when the film is formed into a bag shape, even when heat is applied to the portions where multiple bags overlap during sealing of the inner surface layer and they are heat-sealed together, the bags (outer surface layers) do not weld to each other. That is, it is because the overlapping sealability is excellent. By having excellent overlapping sealability, the number of packaging bags per unit time can be increased, and productivity can be improved.

[0046] Here, regarding the difference in melting temperature between the outer surface layer and the inner surface layer, since the value of the melting temperature (Tm) measured with a differential scanning calorimeter (DSC) according to JIS-K7121 is the peak value, some crystals of the resin have started to dissolve even at the temperature until reaching Tm. Some of them may cause stickiness. If stickiness occurs, welding will occur between the overlapping film surface layers even before reaching the melting temperature, and they may adhere depending on the sealing pressure. However, if the melting temperature difference between the outer and inner layers is 65°C or more, even in such a case, almost no adhesion occurs. Also, if the difference is 100°C or more, no adhesion occurs, and the heat-sealing temperature range (usually set so that the heat-sealing temperature falls within the range of the melting temperature difference) may widen, which is preferable. In this case, the operating tolerance range such as the temperature and speed of the packaging machine will widen.

[0047] On the other hand, when the difference in melting temperature between the outer surface layer and the inner surface layer exceeds 150°C, generally, even if the melting temperature of the resin used as the sealing layer in the inner surface layer is low, it is about 80°C. Therefore, as the outer surface layer, a material with a melting temperature exceeding 230°C may be used in some cases. However, when the melting temperature exceeds 230°C, whitening may be observed after heat shrinkage. Considering the prevention of whitening after shrinkage to ensure good transparency and further suppressing the yellowing of the vinylidene chloride copolymer during coextrusion, the melting temperature difference is preferably 150°C or less and 70°C or more, and more preferably 150°C or less and 135°C or more.

[0048] In addition, when the stretched laminated film is made into a bag, even if the heat - applied parts of the bags are overlapped and heat - sealed, the bags will not weld to each other. Packaging of relatively bulky contents such as block meat can also be carried out efficiently. In addition, when a package vacuum - packed with a stretched laminated film is immersed in a hot water bath at 70 to 90 °C for several seconds, the stretched laminated film thermally shrinks to form a tight and beautiful package. For example, in the case of raw meat packaging, by tightly tension - packing, the appearance of the packaged meat is improved and the commercial value is increased. Also, the accumulation of gravy and blood can be suppressed, and the effect of suppressing the growth of bacteria can be obtained.

[0049] And in the stretched laminated film of the present embodiment, it is necessary that the ratio of the thickness occupied by the outer surface layer in the entire stretched laminated film is 0.1% or more and less than 1.0%, and preferably 0.3 to 0.9%. Even under conditions of high shrinkage rate, peeling of the outer surface layer can be suppressed, excellent delamination properties can be realized, high elastic modulus can be prevented, and the followability to meat during vacuum packaging is improved, so that the ultraviolet transmittance and appearance can also be improved.

[0050] Also, the outer surface layer preferably has an anti - blocking agent on the surface. The presence of an anti - blocking agent on the outer surface of the stretched laminated film can improve the handleability of the film and the peelability from other films.

[0051] Here, the anti - blocking agent is preferably fine particles. By reducing the contact points with the bactericidal cells due to the unevenness of the fine particles, the handleability of the film and the peelability from other films can be improved. Regarding the type of the antiblocking agent, there is no particular limitation as long as it can enhance the peelability from the other film, and it can be appropriately selected according to the required performance and the materials of the inner surface layer and the outer surface layer. As the antiblocking agent, for example, surfactants such as glycerin fatty acid esters, antioxidants, antistatic agents, petroleum resins, mineral oils, fatty acid amide lubricants, silicon oxides, calcium carbonates, talc, etc. can be used. Furthermore, among the above-described antiblocking agents, it is preferable that the outer surface layer has starch powder.

[0052] Note that having an antiblocking agent in the outer surface layer means that, as described for the inner surface layer, the antiblocking agent can be contained in the outer surface layer, or the antiblocking agent can be adhered onto the outer surface layer, and it can be appropriately selected according to the use and the required performance.

[0053] Furthermore, the antiblocking agent in the inner surface layer and the antiblocking agent in the outer surface layer may be the same or different.

[0054] (Adhesive layer) As shown in FIG. 1, the stretched laminated film of the present embodiment may further include an adhesive layer (A) 20 and an adhesive layer (B) 40 between the barrier layer 30 and the inner surface layer 10, and between the barrier layer 30 and the outer surface layer 50. By further providing these adhesive layers, the interlayer adhesiveness can be enhanced.

[0055] As the resin that can be used for the adhesive layers (A) and (B), an ethylene copolymer can be used. Preferably, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, a polyethylene ionomer, an ethylene-ethyl acrylate copolymer, an ethylene-maleic anhydride copolymer, etc. can be used. Among them, an ethylene-vinyl acetate copolymer is preferably used because the interlayer adhesion strength, stretchability, heat shrinkability, crosslinking characteristics when irradiated with electron beams, etc. between each surface layer and the barrier layer are good. Note that the resins used for the adhesive layers (A) and (B) may be the same or different, and can be appropriately selected according to the required performance and the components of other layers.

[0056] In addition, it is preferable to irradiate the stretched laminated film with ionizing radiation before stretching. Thereby, in particular, the outer surface layer is crosslinked and the stretchability of the film is enhanced. Since the vinylidene chloride copolymer becomes severely yellowed when strongly irradiated, it is preferable to adjust so that the radiation does not reach that layer. Generally, the effective depth of ionizing radiation is adjusted by the acceleration voltage. As the ionizing radiation irradiation, ionizing radiations such as α-rays, β-rays, γ-rays, neutron rays, and electron beams are irradiated.

[0057] Further, in the present embodiment, it is required that the tensile elastic modulus in the longitudinal and transverse directions of the stretched laminated film at 23°C is both 50 MPa or more and less than 200 MPa, and the heat shrinkage rate in the longitudinal and transverse directions at 80°C is both 35% or more and less than 60%. In the stretched laminated film, the tensile elastic modulus in the longitudinal and transverse directions at 23°C and the tensile elastic modulus in the longitudinal and transverse directions at 23°C are both very important parameters from the viewpoints of followability and strength when the killed cells are packaged by heat shrinkage using the stretched laminated film. Therefore, in the present embodiment, by the stretched laminated film satisfying the above-described relationship between the tensile elastic modulus and the heat shrinkage rate, the heat shrinkability, shape followability, film strength, etc. of the stretched laminated film can be enhanced well in balance.

[0058] Here, the reason for specifying the tensile elastic modulus in the longitudinal direction (film flow direction) and the transverse direction (film width direction) of the stretched laminated film at 23°C to be both not less than 50 MPa and less than 200 MPa is that when the tensile elastic modulus is not less than 50 MPa, the strength of the stretched laminated film can be maintained well, and when it is less than 200 MPa, the followability of the stretched laminated film can be enhanced. Note that the tensile elastic modulus can be measured in accordance with ASTM-D882.

[0059] Also, the reason for specifying the heat shrinkage rate in the longitudinal direction (film flow direction) and the transverse direction (film width direction) of the stretched laminated film at 80°C to be both not less than 35% and less than 60% is that when the heat shrinkage rate is not less than 35%, the followability between the stretched laminated film and the object to be packaged can be enhanced, and when it is less than 60%, the transparency after shrinkage of the stretched laminated film can be maintained well. Note that the heat shrinkage rate can be measured in accordance with ASTM D-2732.

[0060] <Bag, raw meat packaging body> The bag of this embodiment is a bag using the stretched laminated film of the above-described embodiment, in which the outer surface layer constitutes the outer surface of the bag, and the inner surface layer constitutes the inner surface of the bag. The barrier layer is composed of a specific vinylidene chloride (VDC) copolymer. By optimizing the tensile elastic modulus in the longitudinal and transverse directions at 23°C and the heat shrinkage rate in the longitudinal and transverse directions at 80°C, even when a vinylidene chloride (VDC) copolymer is used, good stretching stability and shrinkage performance can be ensured, and the elastic modulus can also be reduced. In addition, by making the ratio of the thickness occupied by the outer surface layer in the entire stretched laminated film small, not less than 0.1% and less than 1.0%, even when the shrinkage rate of the laminate is high, the outer surface layer does not peel off, and good delamination properties can be obtained.

[0061] When the stretched laminated film of this embodiment is used as a bag, it can generally be used as a two-side seal type bag called a bottom seal bag. The bag is mainly manufactured by sealing and cutting one side of a tubular, tube-shaped film in the width direction, putting the contents in, and sealing the mouth. Also, it can generally be used as a bag called a side seal bag. The bag is manufactured by fusion sealing or the like of the film.

[0062] In addition, the raw meat package using the bag of this embodiment has good followability to the object to be packaged due to the low tensile elasticity of the bag, and can package the object to be packaged without wrinkles by having a specific heat shrinkage rate, and the commercial value is increased by the improved appearance. Also, when sterilizing with ultraviolet rays or the like, since there are no wrinkled parts where the films overlap, the irradiation efficiency of ultraviolet rays can be improved. In addition, since the bag has high opening property, the initial bacterial count of raw meat can also be suppressed. As a result, the raw meat package of this embodiment has a small initial bacterial count and is suitable for sterilization by ultraviolet irradiation.

[0063] <Ultraviolet irradiation> After packaging foods such as raw meat using the stretched laminated film or bag of this embodiment, sterilization can be performed by irradiating ultraviolet rays with a wavelength range of 200 to 280 nm. Among the above ultraviolet rays, ultraviolet rays (UVC) with a wavelength range of 200 to 280 nm have the highest sterilization effect among ultraviolet rays and can be sterilized by inactivating bacteria. Therefore, they are effective in that no chemicals are used and no resistant bacteria are produced. Also, a large-scale device is not required, and there are advantages from the viewpoints of energy saving and the cost required for sterilization.

[0064] Here, it is preferable that the irradiation of ultraviolet rays with a wavelength range of 200 to 280 nm is performed after or during the packaging of the package. The effects of reducing the initial bacterial count and improving the irradiation efficiency by enhancing the shape followability according to this embodiment are exerted after or during the packaging of the package. Therefore, by irradiating ultraviolet rays at these timings, a higher sterilization effect can be obtained.

[0065] Regarding the irradiation conditions of the ultraviolet rays, there are no particular limitations. For example, it is preferable to irradiate from a position within 50 cm from the packaging body using a UVC-LED. This is because excellent sterilization performance can be achieved without using a large-scale device or causing a cost increase. From the same perspective, the distance between the UVC-LED and the packaging body is preferably within 40 cm, and more preferably within 30 cm.

Examples

[0066] Hereinafter, the present invention will be described in detail with specific examples and comparative examples, but the present invention is not limited to the following examples.

[0067] <Materials of the stretched laminated film> The components included in each sample of the examples and comparative examples are shown below.

[0068] (1) Stretched laminated film (1-1) As the surface layer (A) (outer surface layer), a 6 / 66 copolymer (Ny-1) was used. The melting point of the 6 / 66 copolymer was 192°C. Regarding the melting points of the surface layer (A), the adhesive layer (B), the adhesive layer (D), and the surface layer (E) described below, in accordance with JIS-K7121, a melting point was measured using a measuring device (DSC8500 manufactured by PerkinElmer). Specifically, after holding at 0°C for 1 minute, the temperature was raised from 0°C to 200°C at 10°C / minute and then held for 1 minute. Then, after cooling from 200°C to 0°C at 10°C / minute and holding for 1 minute, the melting point (the melting point during the second temperature rise) when the temperature was raised from 0°C to 200°C at 10°C / minute was measured. For those having multiple peaks, the maximum peak was taken as the melting point. (1-2) Both the adhesive layer (B) between the surface layer (A) and the barrier layer (C) and the adhesive layer (D) between the barrier layer (C) and the inner surface layer (E) used an ethylene / vinyl acetate copolymer (vinyl acetate content 20% by mass). The melting point of the ethylene / vinyl acetate copolymer was 85°C. As the barrier layer (1-3), a vinylidene chloride (VDC) / vinyl chloride (VC) copolymer (PVDC, manufactured by Asahi Kasei Corporation) was used as the following vinylidene chloride copolymer. Regarding the melting points of the following PVDCs, in accordance with JIS-K7121, the melting points were measured using a measuring device (DSC8500 manufactured by PerkinElmer). Specifically, since PVDC is prone to thermal decomposition, considering that the melting point may change when the temperature is repeatedly increased, it was held at 0°C for 1 minute, and then the melting point (the melting point at the first temperature increase) when the temperature was increased from 0°C to 200°C at a rate of 10°C / min was measured. Also, for those with multiple peaks, the maximum peak was taken as the melting point. · For PVDC-1, a copolymer with VDC / VC = 83 / 17 mass% and a melting point of 145°C was used. Note that PVDC-1 contains 3.0 mass% of dibutyl sebacate (DBS), 1.0 mass% of epoxidized linseed oil (ELO), and 0.03 mass% of talc as additives. · For PVDC-2, a copolymer with VDC / VC = 88 / 12 mass% and a melting point of 163°C was used. Note that PVDC-2 contains 5.0 mass% of acetyl tributyl citrate (ATBC) and 1.3% of epoxidized soybean oil (ESO) as additives. · For PVDC-3, a copolymer with VDC / VC = 88 / 12 mass% and a melting point of 163°C, and reworked products were used. Note that PVDC-3 is a product that has undergone the melting to solidification process of PVDC-2 once, pulverized so that the bulk density becomes 0.4 - 0.7 g / cc, and the pulverized product contains 0.3 mass% of calcium stearate. · For PVDC-4, a mixture of PVDC-1 and PVDC-3 at 80 mass% and 20 mass% respectively was used. (1-4) As the surface layer (E) (inner surface layer), an ethylene / hexene copolymer was used. The melting point of the ethylene / hexene copolymer was 98°C and the MI was 1.2 g / 10 min.

[0069] (2) Antiblocking agent The surface layer (A) and the surface layer (E) were adhered with starch powder containing amorphous silica at an adhesion amount of 50 to 2000 mg / m 2 .

[0070] [Examples 1 to 4 and Comparative Examples 1 to 3] (1) Production of Stretched Laminated Film Using the materials under the conditions shown in Table 1, the resin was melt-extruded from the extruders corresponding to the surface layer (A), the adhesive layer (B), the barrier layer (C), the adhesive layer (D), and the surface layer (E), and through a cylindrical die, a cylindrical laminated tube was created, and then cooled with a water-cooling ring to obtain an unstretched laminated tube (hereinafter referred to as "parison"). Subsequently, sampling was performed at eight equally spaced locations along a straight line in the width direction of the parison, and the thickness of each layer was measured by microscopic observation of its cross-section, and the average value of the eight locations was calculated. The obtained parison was irradiated with an electron beam at an acceleration voltage of 210 kV by adjusting the electron beam irradiation dose to reach a predetermined gel fraction, and cross-linking was performed. Subsequently, the irradiated parison was post-heated at 80 °C and heated with an infrared heater in the stretching section (heating adjustment in the range of 60 to 100 °C near the neck) to blow up the bubble. The blown-up tube was folded with a deflator while being cooled with an air-cooling ring to produce a tubular stretched laminated film. The thickness of the stretched laminated film was measured at this time and adjusted with the parison thickness to obtain a predetermined thickness. The stretching ratio was adjusted to 2.5 times in the longitudinal direction and 3.0 times in the transverse direction, and biaxially stretched to obtain a stretched laminated film with a width of 300 mm (stretched laminated film). Note that only the sample of Comparative Example 3 was heat-set by passing the blown-up tube through two heating rollers at 70 °C after folding with a deflator, and then cooled by passing through a cooling roller. (2) Production of Bag Samples of the obtained stretched laminated film were bottom-sealed with a bag-making machine so that the surface layer (A) became the outer layer to produce bag samples (bag width 300 mm, bag length 450 mm).

[0071] [Evaluation] Samples of the stretched laminated film and samples of the bag obtained as described above were evaluated as follows. The evaluation results are shown in Table 1.

[0072] (1) Stretch stability The state during bubble blow-up during the production of the stretched laminated film was observed for 1 hour, and the number of punctures was measured. The measured number of punctures was evaluated according to the following criteria. ◎: 0 punctures 〇: 1 puncture ×: 2 or more punctures

[0073] (2) Heat shrinkage rate at 80°C For samples of the stretched laminated film, the heat shrinkage rate at 80°C was measured according to ASTM D-2732. Specifically, after marking a 100-mm line or point in the longitudinal direction (MD direction) and the transverse direction (TD direction), the sample was immersed in a warm water bath at 80°C for 4 seconds for free heat shrinkage. After heat shrinkage, the distance between the marks was measured, and the heat shrinkage rate of the film was calculated from the following formula. Heat shrinkage rate at 80°C (%) = ((100 (mm) - dimension after shrinkage (mm)) / 100 (mm)) × 100

[0074] (3) Interlayer adhesion The presence or absence of interlayer delamination was visually confirmed in the samples whose heat shrinkage rate was measured at 80°C, and the evaluation was carried out according to the following criteria. 〇: No interlayer delamination occurred. ×: Interlayer delamination occurred (partially whitened).

[0075] (4) Tensile modulus at 23°C For samples of the stretched laminated film, the tensile modulus at 23°C was measured using a measuring device (Tensilon RTG-1210 manufactured by A&D Company) according to ASTM D-882. Specifically, a sample of the stretched laminated film was cut into strips with a width of 10 mm, and the tensile elastic modulus in the longitudinal direction (MD direction) and the transverse direction (TD direction) was measured from the load at 2% elongation under the conditions of a chuck distance of 50 mm, a tensile speed of 5 mm / min, and a temperature of 23°C. The number of test times was 5 times for both the MD direction and the TD direction, and the average value was taken as the tensile elastic modulus (%).

[0076] (5) Appearance of meat packaging After putting 4 - 7 kg of block - shaped beef (rib roast or sirloin) into each sample of the bag, vacuum packaging was performed. Then, it was immersed in a hot water bath at 80°C for 4 seconds for shrinkage and then cooled in a cooling bath. The appearance after cooling was evaluated according to the following criteria. ◎: The film follows the unevenness of the meat, has few wrinkles, and the cross - section of the meat can be clearly seen. 〇: The film follows the unevenness of the meat, but has wrinkles and the cross - section of the meat is slightly difficult to see. ×: The film does not fully follow the unevenness of the meat. Also, there are many wrinkles, the film sags, and the cross - section of the meat is difficult to see.

[0077]

Table 1

[0078] From the results in Table 1, it was found that each sample of the examples showed well - balanced and good results in all evaluation items. On the other hand, each sample of the comparative examples showed inferior results compared to the examples in at least one evaluation item.

Industrial applicability

[0079] According to the present invention, even when a vinylidene chloride copolymer is used as the barrier layer, a stretched laminated film excellent in stretching stability and shrinkage performance, having a low elastic modulus and excellent delamination property can be provided. Further, according to the present invention, even when a vinylidene chloride copolymer is used as the barrier layer, a stretched laminated film excellent in stretching stability and shrinkage performance, having a low elastic modulus, and excellent in delamination property is used, and a bag using the film, and a fresh meat package obtained by packaging fresh meat using the bag can be provided.

Claims

1. An extruded laminated film comprising an inner surface layer, an adhesive layer (A) formed on the inner surface layer, a barrier layer formed on the adhesive layer (A), an adhesive layer (B) formed on the barrier layer, and an outer surface layer formed on the adhesive layer (B), wherein: the outer surface layer contains a polyamide resin; the proportion of the thickness of the outer surface layer in the entire extruded laminated film is 0.1% or more and less than 1.0%; the barrier layer contains a vinylidene chloride (VDC) copolymer; the tensile modulus in both the longitudinal and transverse directions at 23°C is 50 MPa or more and less than 200 MPa, and the thermal shrinkage rate in both the longitudinal and transverse directions at 80°C is 35% or more and less than 60%.

2. The extruded laminated film according to Claim 1, wherein the content of vinyl chloride in the vinylidene chloride (VDC) copolymer is 10% by mass or more and less than 20% by mass.

3. The extruded laminated film according to Claim 1, wherein the barrier layer contains 0.1% by mass or more and less than 10% by mass of acetyl tributyl citrate (ATBC).

4. The extruded laminated film according to Claim 1, wherein the content ratio of the reworked vinylidene chloride (VDC) copolymer in the vinylidene chloride (VDC) copolymer is 20% by mass or more.

5. The extruded laminated film according to Claim 1, wherein the barrier layer contains 0.1% by mass or more and less than 1% by mass of a fatty acid alkaline earth metal salt.

6. A bag using the extruded laminated film according to any one of Claims 1 to 5, wherein: the outer surface layer constitutes the outer surface of the bag, and the inner surface layer constitutes the inner surface of the bag.

7. A fresh meat package, characterized by packaging fresh meat using the bag according to Claim 6.

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