JPH02125733A - Food storing container - Google Patents

Abstract

PURPOSE:To make durability for boiling or retort sterilization by providing copolymer films containing ethylene and unsaturated carboxylic acid on both sides of given polyamide resin film, sticking an olefinic/resin film and manufacturing laminate films of given ratio respectively. CONSTITUTION:Polyamide (MX) prepared by polycondensation reaction of methaxylenediamine and adipic acid is used. The difficulty of large permeability is solved by retaining polypropylene (PO) film. When a copolymer (EM) of ethylene and unsaturated carboxylic acid such as a copolymer of ethylene and maleic acid is interposed between said resin and film, bonding can be carried out to each other. PO films 1 and 5 of one film respectively occup two-thirds to 29/30 of the thickness of the whole laminate film. Although EM films 2 and 4 are used by bonding PO and MX and no restriction is applied to thickness, the same can be used as a thin one, and its thickness is around 1/20 of the laminate film thickness. The thickness of MX film 3 is 1/4 to 1/40 of the thickness of the entire laminate film.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) This invention relates to a food storage container. More specifically, the present invention relates to a container that can contain ready-to-eat foods such as instant foods, and which can be stored for a considerable period of time without deteriorating the quality of the foods.

(Prior Art) Containers have already been made that allow instant food to be stored for a long period of time without deterioration, and which also allow the food to be easily taken out. It is made from a laminated film made by laminating films of vinylidene chloride resin, ethylene-vinyl alcohol copolymer resin, olefin resin, styrene resin, amide resin, carbonate resin, etc. It is molded into. others,
Some were made of a laminated film with a metal foil such as aluminum or a vapor-deposited film interposed between these resins6. For example, Japanese Utility Model Publication No. 1983-29558 discloses a polycarbonate film with a vapor-deposited film of aluminum attached. We propose that a polyolefin and a polyethylene-vinyl alcohol copolymer film be laminated onto a film to form a laminated film, and then this can be formed into a container shape.

However, conventional laminated films are not perfect for storing instant foods. The reason for this is that instant foods are generally hygroscopic and easily oxidized, and although conventional laminated films have low moisture and oxygen permeability, they still have some permeability. This is because it provides moisture and oxygen to the food contained therein, thereby deteriorating the quality of the food. Therefore, it was desired to reduce the permeability of moisture and oxygen as much as possible.

Containers for food storage do not only need to have low moisture and oxygen permeability; they also need to be easy to form as a laminated film, the formed container must maintain a stable shape, and it must also be transparent. is also required. The above-mentioned Utility Model Publication No. 63-29558 contains a metal vapor deposited film, so its lack of transparency has sometimes been considered a drawback.

It also needed to be non-toxic since it would come into contact with food. In addition, it can be completely bonded by heating and melting, is easy to cut, and can withstand heat sterilization, which may seem contradictory to shape stability and ease of molding. Even the nature was sometimes required.

Food storage containers are required to have an extremely large number of characteristics, so it is impossible to meet all of them.
Therefore, depending on the nature of the food, containers have been made to satisfy only the most important characteristics, at the expense of other characteristics. Another important characteristic was the ability to withstand boiling or retort sterilization after containing food. To this end, it has become necessary to have low water vapor and oxygen permeability at high temperatures.

(Problems to be Solved by the Invention) This invention can withstand boiling or retort sterilization with food in it, is suitable for preserving food for a long time without deterioration, and is required as the food container mentioned above. This was done in an attempt to provide a container that satisfies all of the various requirements.

(Means for Solving the Problems) Among polyamide resins, the present invention is directed to a polyamide resin (hereinafter referred to as MX) obtained by polycondensation reaction of metaxylylene diamine and adipic acid.
The main point is to use MX is excellent in that it does not allow oxygen to pass through it, but on the other hand, it has the disadvantage of being hygroscopic and therefore having high moisture permeability. However, the disadvantage of this is that the MX film is sandwiched inside and on both sides, thicker polypropylene (hereinafter referred to as PO) is used.
It was discovered that this problem could be solved by laminating two films together. Furthermore, since MX and PO do not have adhesive properties to each other, they cannot be directly bonded together.
It has been found that when a copolymer of ethylene and unsaturated carboxylic acid (hereinafter referred to as EM) such as a copolymer of ethylene and maleic acid is interposed between the two, they can be bonded to each other. Furthermore, it was confirmed that the laminated film bonded in this way can be easily molded and has high shape stability, making it suitable for food containers. This invention was made based on such confirmation.

In this invention, an EM film is interposed on both sides of an MX film, and a PO film is bonded thereon to form a laminated film. 1
and 1/20 to 1/20, and 2/3 to 17/20, and the gist thereof is a food storage container formed by forming this laminated film into a container shape.

An example of implementing the present invention will be described below based on the drawings. FIG. 1 is a perspective view showing the state in which the container according to the present invention is used.

FIG. 2 is a sectional view taken along the line ■--■ of the container shown in FIG.

FIG. 3 is an enlarged sectional view of the portion marked ■ in FIG. 2.

In FIG. 1, A is a lidding film, B is a container, and C is a tightness protruding from the lidding film A. The lidding film A and the container B have a structure as shown in FIG.

On the side of the container in FIG. 3, 1 and 5 are PO films, 2 and 4 are 2M films, and 3MX films. Therefore, the WB is EM on both sides of the MX film 3.
Films 2 and 4 are interposed, and Po film 1 is placed thereon.
It is made of a laminated film made by laminating 5 and 5 together.

The thickness of these films is within the following range. Po films 1 and 5 have the same thickness, each having a thickness of 100 to 500 microns. EM films 2 and 4 are Po films 1 and 5 and M
Since it only serves to bond the X film 3 together, its thickness is thin (usually 10 to 50 microns).

Further, the MX film 3 is for preventing oxygen from permeating, and its thickness is 10 to 60 microns. Therefore, the total thickness of the laminated film is 230 to 116
It becomes 0 micron.

The reason why the PO film is made to have a thickness of 100 to 500 microns is that if the thickness is less than 100 microns, the strength will be poor and it will be insufficient to prevent the penetration of moisture.
This is because even if the thickness is 0 micron or more, there is no commensurate advantage. The reason why MX is set to 10 to 60 microns is that when MX is sandwiched between PO, even a small thickness can sufficiently prevent oxygen permeation. There is no need to do this, and on the contrary, 10
This is because it is difficult to manufacture small thicknesses of microns or less.

The relative thicknesses of these films are as follows. Both Po films 1 and 5 have the same thickness, and the total thickness accounts for approximately two-thirds to four-fifths of the total thickness of the laminated film. In terms of one film, Po films 1 and 5 each account for one-third to two-fifths of the thickness of the entire laminated film. Also, 2M
The film is 1. As mentioned above, since it only serves to bond PO and MX, its thickness is
Although there is no particular limitation, it may be as thin as possible, so it may be around 1/20 of the thickness of the laminated film. Moreover, the MX film 3 has a thickness of 1/4 to 1/20 of the entire laminated film.
becomes.

The Po films 1 and 5 may be made of polyethylene or polypropylene, but preferably polypropylene.

The resin constituting the EM films 2 and 4 is preferably a copolymer resin consisting of ethylene and maleic acid,
A copolymer resin of ethylene and an unsaturated carboxylic acid other than maleic acid may also be used.

In addition, a terpolymer containing another third component, such as a terpolymer of ethylene, maleic anhydride, and acrylic acid, may be used.

As described above, the resin constituting the MX film 3 is a resin obtained by polycondensation reaction of metaxylylene diamic acid and adipic acid. The resin is a crystalline resin having the following structural formula.

Although all conventional polyamide resins contain aliphatic carbon chains, this resin is unique in that it has an aromatic ring in its main chain. This resin is commercially available, for example, from Mitsubishi Gas Chemical Company under the name Nylon MXD6.

The laminated film used in the present invention can be produced, for example, as follows. Three extruders are used, each with PO,
Put EM and MX resins, extrude these resins into one nozzle, make both into a film inside the nozzle, and position MX in the center so that the MX film is sandwiched between them. An EM film is placed, and a PO film is placed on both sides of the EM film, and these resin films are superimposed within the die, or these resin films are superimposed immediately after exiting the die to form a laminated film.

Further, in order to mold the thus obtained laminated film into a container shape, for example, the following procedure is performed. The laminated film is heated and softened, pressed against a container-shaped mold by mechanical or pneumatic force, and then cooled to form a container. In addition,
Immediately after the laminated film is made by extrusion, the laminated film is softened and can be pressed into a mold immediately without heating to form a container.

(Effects of the Invention) The container according to the present invention is made of a laminated film consisting of a MX film at the center, an EM film interposed on both sides, and a PO film laminated thereon. The film is strongly adhered to the MX film1, so the laminated film is an integral, strong film that does not easily peel off, and has a strong and stable shape.

In addition, since the structure of the laminated film is such that the MX film is centered and the PO film is present on the surface, the MX film has the disadvantage of being highly hygroscopic; This is compensated for by a resin with low water permeability, resulting in an overall low moisture permeability. Furthermore, although the PO film has the drawback of high oxygen permeability, this drawback is compensated for by the MX film, which has low oxygen permeability, resulting in a low oxygen permeability as a whole. In this way, this laminated film becomes impermeable to both oxygen and moisture, making it suitable for storing foods.

Since the laminated film according to the present invention contains the MX film, it has a low oxygen permeability as described above, but it has a characteristic that the oxygen permeability is particularly low from low temperatures to high temperatures around 100°C. There is. Up until now, copolymer resins of ethylene and vinyl alcohol have been used as resins that are difficult for oxygen to permeate, but copolymer resins of ethylene and vinyl alcohol can be used at high temperatures of around 100"C.
Since the food suddenly becomes permeable to oxygen, when boiling or retort sterilization is performed, oxygen enters the container and oxidizes the food. However, the laminated film used in this invention has difficulty permeating oxygen even at high temperatures near 100'C, so even if boiling or retort sterilization is performed, the amount of oxygen that enters the container is small, so boiling or retort sterilization is not possible. It is suitable for

In addition, in the laminated film used in this invention, the MX film is 1/4 to 20% of the total thickness of the laminated film.
Since the MX film accounts for two-thirds to four-fifths of the total thickness and the PO film occupies the majority, the influence of PO appears strongly, and therefore it is only composed of PO. It can be easily molded, much like a container. Also,
Since the surface of the container formed in this way is PO, there is no risk of contaminating food even if it comes into direct contact with food (therefore,
Suitable as a food storage container. Also, the surface is PO
Therefore, by overlaying another PO film on this surface and heating it, it can be easily fused and, therefore, the food can be easily sealed by heat sealing. As described above, the container of the present invention has excellent characteristics as a food storage container.

Note that the same laminated film as for container B can be used as the IIA for the container base of this invention, but in addition, as shown in FIG.
It is also possible to use one in which an O film 8 is attached. It is preferable to use polypropylene as the PO film 8. The lid A can be easily adhered to the container iB by heat sealing, and therefore the food can be easily sealed. Lid A can be easily removed by lifting C and peeling it off. Therefore, this container is easy to seal and open.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the food storage container according to the present invention in use. Figure 2 shows the container shown in Figure 1.
FIG. FIG. 3 is an enlarged sectional view of the portion marked ■ in FIG. 2.

Claims (1)

[Claims] A film of a copolymer containing ethylene and an unsaturated carboxylic acid is interposed on both sides of a film of a polyamide resin obtained by polycondensation reaction of metaxylylene diamine and adipic acid, and an olefin resin is placed on top of the film of a copolymer containing ethylene and an unsaturated carboxylic acid. The films are bonded together to form a laminated film, of which the thickness of the polyamide resin and olefin resin film is 1/4 to 1/20 and 2/3 to 4/5 of the thickness of the entire laminated film, respectively, A food storage container made by forming this laminated film into a container shape.