JPS625063B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a package that has good gas barrier properties and can be heat sterilized. Furthermore, in detail, a polycarbonate resin layer is the outermost layer, a modified polyolefin adhesive resin layer,
A multilayer plastic film consisting of a saponified ethylene-vinyl acetate copolymer resin layer and a polyolefin resin layer, which has gas barrier properties, heat resistance,
After the food contents are degassed and packaged using a heat-shrinkable multilayer film with good transparency, etc.,
The present invention relates to a package that is heat sterilized in an atmosphere at ℃ for more than 5 minutes. In recent years, regulations on food additives have become stricter in the food processing industry, especially in the livestock meat processing and fish processing fields, and the amount of disinfectants used has been reduced or almost no longer used. In order to ensure freshness, packaging that has good oxygen gas barrier properties and can be heat sterilized is required.On the other hand, from the sales promotion aspect of market development, packaging that has excellent transparency and a good appearance without folds and wrinkles is required. There are demands for a package, and the present invention is a package that meets these needs. Conventionally, laminated heat-shrinkable films of ethylene-vinyl acetate copolymer resin and vinylidene chloride resin, or laminated films of combinations of polypropylene resin, polyamide resin, polyethylene resin, etc., have been used for packaging of processed meat products such as hams and sausages. etc. were used. However, although packaging using vinylidene chloride-based laminated heat-shrinkable film has excellent oxygen gas barrier properties, even when heat sterilized in hot water at 80℃ for 5 minutes after deaerating the food contents, However, there are drawbacks such as pinholes occasionally appearing in the package and delamination between films. Packaging bodies using a laminated film of polypropylene resin and polyethylene resin or a laminated film of polyamide resin and polyethylene resin are:
It is possible to withstand heat sterilization for 60 minutes in boiling water at 80°C to 100°C after deaerating the food contents, but the oxygen gas barrier properties are poor, and the contents of processed meat or fish meat products The edible shelf life of the packaged product is short, and at the same time, since the laminated film is not heat-shrinkable, the package after heat sterilization has the disadvantage that folds and wrinkles appear on the package, making it look unsightly. As such, it has good oxygen gas barrier properties, 80
It satisfies all the performance requirements such as being able to heat sterilize for more than 5 minutes in an atmosphere between 100°C and 100°C, and adding heat shrinkability to the plastic film in order to obtain a package with a good appearance and no folds or wrinkles. The packaging could not be found. The present inventor has discovered that a saponified ethylene-vinyl acetate copolymer resin with excellent oxygen gas barrier properties has stable and high gas barrier properties over a long period of time, exhibits high heat shrinkability in hot water, and We conducted research to create a package that can be heat sterilized, and we developed a package consisting of a polycarbonate resin layer as the outermost layer, a modified polyolefin adhesive resin layer, a saponified ethylene-vinyl acetate copolymer resin layer, and a polyolefin resin layer. The multilayer plastic sheet can be biaxially stretched at a temperature of 100℃ or less, and after degassing and packaging food contents using these heat-shrinkable multilayer plastic films, 80℃
It was discovered that heat sterilization for more than 5 minutes was possible in an atmosphere of 100°C to 100°C, and after further various studies, the present invention was completed. The purpose of the present invention is to ensure that the food contents can withstand heat sterilization for more than 5 minutes in an atmosphere of 80°C to 100°C after being degassed and packaged, and that their oxygen gas barrier properties and moisture proof properties remain stable for a long period of time. To provide a package using a heat-shrinkable multilayer plastic film for food packaging, which has excellent low-temperature heat-shrinkability, transparency, hygiene, etc. The present invention comprises a polycarbonate resin layer (A) as the outermost layer, a modified polyolefin adhesive resin layer (B),
Ethylene-vinyl acetate copolymer saponified resin layer (C)
A multilayer plastic film with a laminated structure including a polyolefin resin layer (D), etc., such as a multilayer plastic film, is formed from the outermost layer (A) - (B) - (C) - (B) -
It is a multilayer plastic film with a laminated structure in which the layers are stacked adjacent to each other in the order of (D), and the total thickness of the film is 10 μm or less.
The contents are degassed and packaged with a heat-shrinkable multilayer film that has a diameter of 200 μm and has a dimensional shrinkage rate of more than 10% in both length and width after 10 seconds when placed in an atmosphere at a temperature of 100°C. This package is characterized by being heat sterilized for more than 5 minutes in an atmosphere exceeding 80°C. Polycarbonate resins are various polycarbonate resins or copolymer resins obtained by reacting a dihydroxy compound with phosgene or cyphenyl carbonate by a known method. In addition, 1 to 50% by weight of polycarbonate resin
The thermoplastic resin may be melt-mixed, and the thermoplastic resin is preferably a thermoplastic polyester resin, a polyamide resin, a modified polypropylene adhesive resin, or the like. Modified polyolefin adhesive resin is modified polypropylene resin, modified polyethylene resin, or modified ethylene resin in which polar groups are graft copolymerized.
Vinyl acetate copolymer resins or blends thereof, among which modified ethylene-vinyl acetate copolymer adhesive resins have particularly good adhesive performance, and modified polypropylene adhesive resins have good heat resistance. and is preferable. The saponified ethylene-vinyl acetate copolymer resin has a softening temperature (flow tester method) of 150°C to 175°C, an ethylene content of 25 to 75 mol%,
Saponification degree of vinyl acetate in copolymer is 90%
As described above, it has extremely high oxygen gas barrier properties in a dry state. Polyolefin resins include low density polyethylene resin, medium density polyethylene resin, high density polyethylene resin, ethylene-vinyl acetate copolymer resin,
It is one of polypropylene resins, ionomer resins, copolymers of each resin, etc., or a blend thereof. The total thickness of the plastic film used in the present invention is from 10 μm to 200 μm, and plastic films with a thickness within this range are suitable for shrink-wrapping foods. The present invention is aimed at shrink packaging and heat sterilization packaging for food products, so items to be packaged, such as processed meat products, are filled into a bag made of a heat-shrinkable multilayer film, and after the inside is deaerated, the mouth part is Heat seal and heat to 80℃~
Heat sterilization is performed at the same time as shrink wrapping by placing the product in boiling water at 100°C or in a heating chamber for more than 5 minutes. When the food contents are packaged in a heat-shrinkable multilayer film and the inside is degassed, the food contents are heated, the multilayer film shrinks, the food contents and the multilayer film are brought into close contact, and the multilayer film is folded and wrinkle-free. A package with a good appearance can be obtained, and at the same time, the package with this appearance can be heat sterilized. The heat-shrinkable multilayer film for this purpose must be kept at a temperature of at least 10°C.
After 10 seconds, the vertical and horizontal directions will be 10
It is necessary to have a dimensional shrinkage rate exceeding 80%.
It can withstand heat sterilization in an atmosphere of 100°C to 100°C for more than 5 minutes without peeling of the heat-sealed part. The method of deaerating food contents is carried out by a single method or multiple methods, in which the food contents are filled into a bag-shaped bag made of a heat-shrinkable multilayer film,
After the inside of the bag is degassed with a degassing pressure of 760 mmHg, the opening is heat-sealed. The method for producing a heat-shrinkable multilayer film used in the present invention includes a polycarbonate resin layer as the outermost layer, a modified polyolefin adhesive resin layer, an ethylene-vinyl acetate copolymer saponified resin layer, a polyolefin resin layer, etc. A multilayer plastic sheet having a laminated structure, the multilayer plastic sheet is melt extruded from a laminated die using a coextrusion method using a plurality of extruders, cooled and solidified, and then stretched at a temperature of 70°C to 100°C. It is characterized in that it is reheated to a certain temperature, biaxially stretched by 1.5 times or more in the longitudinal direction and 1.5 times or more in the transverse direction, and then cooled. It is necessary for the laminated structure of the multilayer plastic sheet before stretching to have a polycarbonate resin layer as the outermost layer for packaging food contents,
For the method of coextruding the multilayer sheet, it is preferable to extrude it into a tube shape using a circular die or to extrude it into a flat shape using a T-die. Next, this tube-shaped sheet or flat-shaped sheet is reheated to a stretching temperature within the range of 70°C to 100°C, and subjected to simultaneous biaxial stretching in the longitudinal and lateral directions or sequential biaxial stretching by a known stretching method such as the Tubular method or the tenter method. By carrying out this process, it is possible to produce a film with a good appearance. Processed meat products are deaerated and packaged using the heat-shrinkable multilayer film of the present invention produced by the above-mentioned production method, and then heat sterilized by immersing them in boiling water at 100°C for 60 minutes. The processed meat product could be stored for a long period of time without any abnormalities such as folding and wrinkles that worsened the appearance or damage to the package. The main effect of the packaging body of the present invention is that polycarbonate resin and saponified ethylene-vinyl acetate copolymer resin, which are extremely difficult to biaxially stretch at temperatures below 100°C, are bonded to a polyolefin resin layer via an adhesive resin. This multilayer structure enables biaxial stretching of the polycarbonate resin layer and saponified ethylene-vinyl acetate copolymer resin layer at temperatures below 100°C, and the polycarbonate resin layer is the outermost layer. Therefore, as a package using these heat-shrinkable multilayer films, after deaerating the contents and packaging,
It was discovered that heat sterilization for more than a minute is possible. The stretching ratio of the biaxial stretching is 1.5 times or more in both length and width, preferably 2 times to 4 times. In order for the dimensional shrinkage rate to exceed 10% in both length and width after 10 seconds of being placed in a 100°C atmosphere, it is necessary to stretch the film by a factor of 1.5 or more in each direction. The dimensional shrinkage rate (α) is the length of the original film.
l ₀ , put it in an atmosphere at a constant temperature, and let the length of the film after a certain time be l, then α=100・(l ₀ −
l)/l ₀ (%). The heat-shrinkable multilayer film of the present invention can be heated from 70°C to 90°C.
The dimensional shrinkage rate after 10 seconds after being placed in an atmosphere at ℃ is 20
% to 50%. In order to obtain such a film, it is preferable to carry out biaxial stretching of 2 to 4 times both length and width at a temperature of 70°C to 90°C. Next, examples of the present invention will be described. Table 1 shows examples of the present invention.

[Table] The original film sheets of Examples No. 1 to No. 7 shown in Table 1 were all produced by the T-die coextrusion method, melt-extruded from a multilayer die, and
A sheet with a thickness of μm was produced. Next, the sheet was reheated using a biaxial stretching device, and then stretched twice in both length and width to form a film with a thickness of approximately 50 μm.The sheet was then subjected to stretchability, heat shrinkage, oxygen gas barrier properties, and package heating tests. We evaluated gender, etc. Regarding the film appearance, those with good transparency and smoothness and no stretching unevenness were evaluated as good, and those with stretching unevenness due to netting or with poor smoothness and transparency were evaluated as poor. The thickness of each layer of the film is shown in correspondence with the order of construction and the order of thickness construction from left to right. For heat shrinkage, put the film in boiling water,
After a second, take it out and cool it, and boil it before and after boiling.
Those exhibiting a dimensional shrinkage rate of more than % were considered good, and those showing less than that were considered poor. Oxygen gas barrier properties are determined using test method ASTM-D-
1434, measured in dry conditions at 20°C,
Oxygen gas barrier properties are good below ^30c.c./M2・24hr・ATM. The package heating testability was determined by vertically testing the various films mentioned above.
Processed into a three-sided sealed bag measuring 13 cm wide and 13 cm wide, the bag is filled with grilled pork, which is an amorphous processed meat product with protrusions weighing approximately 200 g, as the food content;
After the inside of the bag is degassed with a degassing pressure of 760 mmHg, the opening is heat-sealed in the degassed state. As a sealing method, a hot plate sealer heated to 130° C. is used, and sealing is performed with a hot plate pressure of 2 kg/cm ² and a heating time of 1 second. The package thus obtained is heated to 80°C.
Alternatively, heat the product in hot water at 100℃ for 5 minutes or 60 minutes at the same time as shrink wrapping, and the test quantity is 10 pieces at the same test level. After heating, a product with no degassing leak due to a broken seal or pinhole is considered good, and a product with even 1 out of 10 degassing leaks is considered bad. In the overall evaluation of the packaging, the appearance of the film,
Those that are good in all of the heat shrinkability, oxygen gas barrier properties, and packaging heat test properties are rated as good (○), and those that are defective in any of them are rated as poor (x). In Table 1, the polycarbonate resin is Teijin Kasei's Panlite, which has a melt viscosity of (10 ⁵ poise, 240°C), and the saponified ethylene-vinyl acetate copolymer resin has a softening temperature (flow tester method). ) is 170℃ manufactured by Kuraray Co., Ltd., and the modified ethylene-vinyl acetate copolymer adhesive resin, modified polypropylene adhesive resin, and modified polyethylene adhesive resin are Admer manufactured by Mitsui Petrochemical Co., Ltd. The ethylene-vinyl acetate copolymer resin is Evatate (vinyl acetate content 8% by weight) manufactured by Sumitomo Chemical Co., Ltd., and the low-density polyethylene resin is
Sumikasen manufactured by Sumitomo Chemical Co., Ltd. has a melting point of 105℃, and polypropylene resin is manufactured by Sumitomo Chemical Co., Ltd. with a softening temperature of 140℃.
It is an ethylene-propylene random copolymer polypropylene resin manufactured by Co., Ltd., and the ionomer resin is
Ethylene-methacrylic acid copolymer with a melting point of 99℃
It is a resin treated with Zn ions and is Himilan manufactured by Mitsui Polychemical Co., Ltd. As is clear from Examples No. 1 to No. 5, the packaging of the present invention has excellent transparency, an appearance of the packaging with no creases due to low-temperature heat shrinkability, and extremely good oxygen gas barrier properties. The package can be heated for 5 to 60 minutes in an atmosphere of 100°C to 100°C. As is clear from Examples No. 6 to No. 8, it was found that the package containing the saponified ethylene-vinyl acetate copolymer resin layer as the outermost layer did not withstand the package heat test. It was found that a package with resin as the outermost layer did not withstand the package heat test at 100°C for 60 minutes, and a package with an unstretched polypropylene resin layer as the outermost layer did not withstand the package heat test. However, it was found that these packages had no heat shrinkability and poor oxygen gas barrier properties.
This does not result in a package that satisfies all of the package heating test properties in an atmosphere of 100°C to 100°C for more than 5 minutes.

Claims (1)

[Claims] 1 Polycarbonate resin layer (A), modified polyolefin adhesive resin layer (B), saponified ethylene-vinyl acetate copolymer resin layer (C), polyolefin resin layer (D), and modified polyolefin adhesive resin layer ( B) is a biaxially stretched multilayer plastic film formed by laminating layers in this order, and the total thickness of the film is 10 to 10.
200μm, placed in a temperature atmosphere of 100℃,
Manufacture of a package characterized in that the contents are degassed and packaged with a heat-shrinkable film with a dimensional shrinkage rate of more than 10% in both length and width, and heat sterilized in an atmosphere of more than 80°C for more than 5 minutes. Method.