JPS588644A - Heat-shrinkable multilayer film and its package - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-shrinkable multilayer plastic film that provides a heat-sterilizable package with good gas barrier properties and a package thereof.

More specifically, polypropylene resin layer, adhesive resin layer,
Using a heat-shrinkable multilayer film with good gas barrier properties, heat resistance, transparency, etc., consisting of a saponified ethylene-vinyl acetate copolymer resin layer, an adhesive resin layer, a polyolefin resin layer, etc., The present invention relates to a package that is heat sterilized for more than 5 minutes in an atmosphere of 80° C. to 100° C. after deaerating food contents.

In recent years, in the food processing industry, particularly in the livestock and fish processing fields, regulations on food additives have become stricter, and the amount of fungicides used has been reduced or almost completely eliminated. In order to ensure long-term shelf life and 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 wrinkle-free packaging is required. There is a demand for a package with a good appearance, and the present invention provides a heat-shrinkable multilayer film and a package thereof that meet these requirements.

Conventionally, for packaging of processed meat products such as hams and sausages, laminated heat-shrinkable films of ethylene-vinyl acetate copolymer resin and vinylidene chloride resin, or combinations of polypropylene resin, polyamide resin, polyethylene resin, etc. Laminated films were used.

However, although packaging using vinylidene chloride-based laminated heat-shrinkable film has excellent oxygen gas barrier properties, after deaerating the food contents and sterilizing them by heating for 5 minutes in hot water at However, there are also disadvantages in that pinholes occasionally occur in the package and delamination between films occurs.

Packaging bodies using a laminated film of polypropylene and a resin and a polyethylene resin, or a laminated film of a polyamide resin and a polyethylene resin, must be heated in boiling water at 80°C to 100°C for 60 minutes after deaerating the food contents. Although it is possible to withstand sterilization, it has poor oxygen gas barrier properties, the edible shelf life of the processed meat or fish meat products is short, and at the same time, the laminated film is not heat-shrinkable, so it cannot be used after heat sterilization. There is a drawback that folds and wrinkles occur on the appearance of the package, making it look unsightly.

In this way, we applied heat to the glass film in order to have good oxygen gas barrier properties, to be able to heat sterilize for more than 5 minutes in an atmosphere of 80°C to 100°C, and to obtain a package with a good appearance and no folds or wrinkles. 5- It has not been possible to find a plastic film or packaging that satisfies all of the required properties, including the ability to provide shrinkage.

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 shrinkage in hot water, and can be heated for long periods of time. Conducted research to obtain sterilizable glass packaging films and packaging bodies,
A laminated sheet including a laminated structure in which a polypropylene resin layer, an adhesive resin layer, an ethylene-vinyl acetate copolymer saponified resin layer, an adhesive resin layer, and a polyolefin resin layer are adjacent to each other in this order is heated at a temperature of 100°C or less. , can be biaxially stretched, and can be heat sterilized for more than 5 minutes in an atmosphere of 80°C to 100°C after deaerating food contents using these heat-shrinkable multilayer glass films. We discovered that this is possible, and after further various studies, we have completed the present invention.

The purpose of the present invention is to ensure that the food contents are kept at 80°C after being degassed and packaged.
It can withstand heat sterilization for more than 5 minutes in an atmosphere of 100°C, has oxygen gas barrier properties, and 6- has stable moisture resistance over a long period of time, and has excellent low-temperature heat shrinkability, transparency, and hygiene. An object of the present invention is to provide a heat-shrinkable multilayer plastic film for food packaging and a package using the heat-shrinkable multilayer plastic film.

The present invention is a multilayer plastic film having a laminated structure in which a polyzolopyrene resin layer, an adhesive resin layer, a saponified ethylene-vinyl acetate copolymer resin layer, an adhesive resin layer, and a polyolefin resin layer are adjacent to each other in this order. , the total thickness of the film is 10 μm to 150 μm, p, 100
A heat-shrinkable multilayer film characterized by a dimensional shrinkage of more than 10 inches in length and width after 10 seconds of being placed in an atmosphere at a temperature of The package is characterized by being heat sterilized for more than 5 minutes in an atmosphere of more than 80°C.

Polypropylene 4UW is a copolymer with ethylene, butene-1, pentene-1, etc., or a blend with polyethylene, polybutene-1, polypentene-1, etc., and is preferably an ethylene-globylene random copolymer polyglobylene. Resins are preferred.

The saponified ethylene-vinyl acetate copolymer resin has a softening temperature (flow tester method) of 150°C to 175°C, an ethylene content of 5 to 75 mol, and a saponification degree of vinyl acetate in the copolymer of (3). It has an extremely high oxygen gas barrier property in a dry state.

The adhesive resin layer is made of a modified polyethylene adhesive resin whose molecular chain ends are treated with a reactive functional group such as unsaturated carboxylic acid.
Modified polypropylene-based adhesive resins, modified ethylene-vinyl acetate copolymer-based adhesive resins, etc. Among these, modified ethylene-vinyl acetate copolymer-based adhesive resins have particularly good adhesive performance. Adhesive resin is
It has good heat resistance and is preferred.

, je IJ olefin resin layer is made of one type of low density polyethylene resin, medium density polyethylene resin, high density polyethylene resin, ethylene-vinyl acetate copolymer resin, polypropylene resin, copolymer of each resin, etc. It is a blend of these.

The total thickness of the plastic film used in the present invention is 10
Plastic films with a thickness in the range of μm to 150 μm are suitable for shrink wrapping food products.

It is preferable that the polypropylene resin layer has a volume of 10 or more, and the saponified ethylene-vinyl acetate copolymer resin layer has a volume of 10 or less with respect to the total film volume of the heat-shrinkable multilayer film.

The heat-shrinkable multilayer film of the present invention is intended for shrink wrapping and heat sterilization packaging of foods, so after filling a bag made of the film with an object to be packaged, such as processed meat products, and deaerating the inside. The mouth part is heat-sealed and placed in boiling water at 80°C to 100°C or in a heating chamber for more than 5 minutes to perform heat sterilization at the same time as shrink wrapping.

After wrapping the food contents in a heat-shrinkable multilayer film and deaerating the inside, the food contents are heated. 9- When the multilayer film shrinks, the food contents and the multilayer film come into close contact, and the multilayer film A package with a good appearance without folds and wrinkles can be obtained, and at the same time, a package with this appearance can be heat sterilized. The heat-shrinkable multilayer film for this purpose is placed in an atmosphere with a temperature of at least 100°C,
It is necessary to have a dimensional shrinkage rate of more than 10% in the vertical and horizontal directions after 10 seconds, and it can withstand heat sterilization in an atmosphere of 80°C to 100°C for more than 5 minutes without peeling of the heat-sealed part. .

The method for 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 the heat-shrinkable multilayer film of the present invention, and the food contents are packed at 760 wm.
The inside of the bag is degassed using the degassing pressure of Hg, and then the opening is heat-sealed.

In the method for producing a heat-shrinkable multilayer film of the present invention, a polyzolopyrene resin layer, an adhesive resin layer, an ethylene-vinyl acetate copolymer saponified resin layer, an adhesive resin layer, and a polyolefin resin layer are formed in this 10-order order. A multilayer plastic sheet having an adjacent laminated structure, the multilayer plastic sheet is melt-extruded from a laminated die in a co-extrusion method using multiple extruders, cooled and solidified, and then extruded at a temperature within the range of 70°C to 100°C. The film is characterized in that it is reheated to a stretching temperature of 1.5 times or more in the machine direction and biaxially stretched by 1.5 times or more in the transverse direction, and then cooled. The laminated structure of the multilayer plastic sheet before stretching must have a polypropylene resin layer as the outermost layer for packaging the food contents, and coextrusion methods for the multilayer sheet include extruding it into a tube shape using a circular die. , or extrusion into a flat shape using a T-die is preferred.

Next, this tubular sheet or flat 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 using a known tubular method or tenter method. By carrying out this process, it is possible to produce a film with a good appearance.

After deaerating and packaging processed meat products with the heat-shrinkable multilayer film of the present invention produced by the above production method, 10
After heat sterilization, the package was immersed in boiling water at 0℃ for 60 minutes.
The processed meat product could be stored for a long period of time without causing any abnormalities such as creases that degrade the appearance or damage to the package.

In order to produce the heat-shrinkable multilayer film of the present invention, it is necessary to heat the raw multilayer sheet to 70°C to 100°C and biaxially stretch it. For the first time, biaxial stretching at such low temperatures became possible.

A single-layer sheet of saponified ethylene-vinyl acetate copolymer resin can be stretched by heating it to 140°C to 170°C, near its softening temperature, but a plastic film biaxially stretched at such high temperatures has a It shows almost no shrinkage even when heated to ℃. Even if this single-layer sheet is heated to a temperature of 100° C. or lower and an attempt is made to stretch it, because the resin is hard, a so-called necking phenomenon occurs or the sheet breaks during stretching.

Therefore, it is extremely difficult to stretch a monolayer sheet of saponified ethylene-vinyl acetate copolymer resin to produce a low-temperature heat-shrinkable plastic film that shrinks at temperatures below 100°C.

The main effect of the heat-shrinkable multilayer film of the present invention is that polyolefin resin and saponified ethylene-vinyl acetate copolymer resin, which is extremely difficult to biaxially stretch at temperatures below 100°C, can be bonded together through an adhesive resin. This multilayer structure allows one of the saponified ethylene-vinyl acetate copolymer resin layers to
Because biaxial stretching is possible at temperatures below 00°C and the polypropylene resin layer is the outermost layer, after the contents are degassed and packaged as a package using these heat-shrinkable multilayer films, 5 in an atmosphere of 80℃ to 100℃
The reason for this is the discovery that heat sterilization for more than a minute is possible.

In the case of this configuration, in order to obtain a better biaxially stretched film, the capacity of the polypropylene resin layer must be 10 or more by volume with respect to the total capacity of the film, and the capacity of the saponified ethylene-vinyl acetate copolymer resin layer must be It is desirable that the capacitance is less than or equal to the capacitance of the film relative to the total capacitance of the film.

The stretching ratio of biaxial stretching is 1.5 times or more in both length and width,
Preferably it is 2 to 4 times.

In order for the dimensional shrinkage rate after 10 seconds to exceed 10 inches in the vertical and horizontal directions after being placed in an atmosphere at 100°C, it is necessary to stretch the film by 1.5 times or more in each direction.

The dimensional shrinkage rate (α) is α = 100・(to-t)/to (4)
This is the value defined by .

The heat-shrinkable multilayer film of the present invention can be heated from 70°C to 90'C.
It is preferable that the dimensional shrinkage rate after 10 seconds after being placed in the atmosphere is 20 inches to 50%.

In order to obtain such a film, it is preferable to carry out biaxial stretching at a rough temperature of 0°C to (3)°C in both length and width by 2 to 4 times.

Next, examples of the present invention will be described.

Table 1 shows examples of the present invention.

14- The raw sheets of the films of Na1 to N[L7 examples shown in Table 1 were all produced by the T-die coextrusion method,
A 200 μm thick sheet was produced by melt extrusion from a multilayer die.

The film of Example 8 was produced by T-die coextrusion method.
I made a pm sheet.

Next, after reheating the sheet using a biaxial stretching device,
A film having a thickness of approximately 50 μm was prepared by stretching the film twice in both length and width, and its stretchability, heat shrinkability, oxygen gas barrier property, package heat testability, etc. were evaluated.

Films with good transparency and smoothness and no stretching unevenness were evaluated as good, and films with stretching unevenness due to necking or poor smoothness and transparency were evaluated as poor.

The thickness of each layer of the film is determined by the order of composition and the order of thickness composition.
They are shown correspondingly from left to right.

- Heat shrinkability is considered good if the film is placed in boiling water, taken out after 10 seconds and cooled, and exhibits a dimensional shrinkage of more than 10% in both length and width before and after boiling.
Anything less than that was considered defective.

Oxygen gas barrier property was determined using test method ASTM-D-14.
34, measured in dry condition at 20C, with added C
C/M' -24hr -ATV or less, the oxygen content is good.

The package heating test property was determined by testing the above-mentioned films at 13o+ vertically.
+Processed into a three-sided sealed bag with a width of 13 crn, grilled pork, which is an amorphous processed meat product with a protrusion of 2002 mm in weight, was filled as food content into the cough bag, and the inside of the bag was degassed at a degassing pressure of 760 mHg. After complete deaeration, heat seal the mouth in a deaerated 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 K5/d and a heating time of 1 second.

The package thus obtained ￥1l - 80℃ or 10
Heating is performed simultaneously with shrink wrapping in hot water at 0°C for 5 minutes or 60 minutes, and the test quantity is 10 pieces at the same test level.

17- Items with no degassing leaks due to seal breakage, pinholes, etc. after heating are considered good, and items with even 1 out of 10 degassing leaks are considered defective.

In the overall evaluation of the package, a film that is good in all of the film appearance, heat shrinkability, oxygen gas barrier property, and package heat testability is considered good (○ mark), and a film that is defective in any of them is considered poor (X mark). ).

In Table 1, polypropylene resin has a softening temperature of 14
The ethylene-propylene random copolymer polypropylene resin manufactured by Sumitomo Chemical ■ is at 0°C, and the saponified ethylene-vinyl acetate copolymer resin is Epal manufactured by Kuraray ■, which has a softening temperature (flow tester method) of 170°C. The modified polypropylene adhesive resin, modified ethylene-vinyl acetate copolymer adhesive resin, and modified polyethylene adhesive resin are all manufactured by Mitsui Petrochemical Co., Ltd., Atmer Ashi, and the low-density polyethylene resin is manufactured by Sumitomo Chemical, which has a melting point of 105°C. The ethylene-vinyl acetate copolymer resin is Sumikasen made by Sumitomo Chemical Co., Ltd. and is not used in the packaging.

Pathate (vinyl acetate content 8% by weight).

As is clear from Examples 111a1 to 111a1 to No. 5, the package using the heat-shrinkable multilayer film of the present invention has excellent transparency, a package appearance with no creases due to low-temperature heat-shrinkability, and excellent oxygen gas barrier properties. Good p1 and 80℃~1
The package can be heated for 5 to 60 minutes in an atmosphere of 00°C.

As is clear from Examples Nα6 to Nα8, the package containing the unstretched polypropylene resin layer as the outermost layer can withstand the package heat test, but has no heat shrinkage and has poor oxygen gas barrier properties. It was found that even in packages containing a polypropylene resin layer inside the film, the outer layer of the heat-shrinkable film peeled off, resulting in poor packaging heat test properties. It has been found that the packaging bodies cannot withstand the package heating test at 100°C for 60 minutes, and these packaging bodies have poor appearance, low-temperature heat shrinkability, oxygen gas barrier properties, and in an atmosphere of leap temperature to 100°C. Package 19 that satisfies all of the package heating test properties for over 5 minutes - Patent applicant Sumitomo Bakelite Co., Ltd. - Sukeichi

Claims (8)

[Claims] (1) A multilayer plastic film including a laminated structure in which a polypropylene resin layer, an adhesive resin layer, a saponified ethylene-vinyl acetate copolymer resin layer, an adhesive resin layer, and a polyolefin resin layer are adjacent in this order, The total thickness of the film is 10 μm to 150 μm, and 6.io
A heat-shrinkable multilayer film characterized by having a dimensional shrinkage of more than 10 inches in both length and width after 10 seconds of being placed in an atmosphere at a temperature of 0°C. (2) The heat-shrinkable multilayer film according to claim (1), wherein the polypropylene resin layer is an ethylene-nolopylene random copolymer polypropylene resin. (3) The heat-shrinkable multilayer film according to claim (1), wherein the adhesive resin layer is a modified polyethylene resin, a modified ethylene-vinyl acetate copolymer resin, or a modified polynolopyrene resin. (4) Claim No. 1, wherein the ethylene-vinyl acetate copolymer saponified resin layer is a resin having an ethylene content of 5 to 75 mole and a saponification degree of vinyl acetate in the copolymer of more than 40%. The heat-shrinkable multilayer film described in . (5) The heat-shrinkable multilayer film according to claim (1), wherein the polyolefin resin is a polyethylene resin, an ethylene-vinyl acetate copolymer resin, or a polyethylene resin. (6) Claim (1) in which the polypropylene resin layer has a capacity of 10 or more with respect to the total capacity of the film.
A heat-shrinkable multilayer film according to items (5) to (5). (7) Heat shrinkability according to claims (1) to (6), wherein the saponified ethylene-vinyl acetate copolymer resin layer has a shrinkage capacity of less than 100% relative to the total volume of the film. multilayer film. (8) The polypropylene resin layer, the adhesive resin layer, the saponified ethylene-vinyl acetate copolymer resin layer, the adhesive resin layer, and the polyolefin resin layer have a laminated structure adjacent to each other in this order, and the total of the film is Thickness is 10 μm to 15
0 μm, placed in an atmosphere at a temperature of 100°C,
The contents are degassed and packaged using a heat-shrinkable film that has a dimensional shrinkage rate of over 10% in both length and width after 0 seconds, and is heat sterilized for more than 5 minutes in an atmosphere exceeding 80°C. packaging.