JP4792722B2 - Retort food container and manufacturing method thereof - Google Patents

Description

  The present invention relates to a retort food container and a method for producing the same.

Many processed foods are sold after being retorted for sterilization after enclosing the container, and the container is generally a pouch type or a plastic molded container with a sheet lid thermally bonded. However, since the heat insulation is not sufficient when the sheet lid is thermally bonded to a plastic molded container, there is a problem that heat is transmitted to the outer surface of the container in an application where reheating is performed using a microwave oven or the like. As a solution to this problem, there is a technique for forming a food container for retort by hot pressing a polypropylene resin foam sheet having high heat resistance.
Japanese Patent Laid-Open No. 11-245928 (pages 3 to 5, FIGS. 1 to 6)

  When retorting a food container sealed with food, a boil retort method is often employed in which the food container is placed in a retort kettle, heated and pressurized, and heated with hot water having a boiling point or higher. In this case, if the food container is made of a resin foam sheet, the following problems may occur. That is, this type of food container usually forms a flange portion at the mouth edge. The foam layer is exposed at the cut surface of the end of the flange portion. When this food container is immersed in hot water, water penetrates from the exposed surface of the foam layer into the foam. In the case of the boil retort treatment, the bubble wall is broken by heat and pressure, and the phenomenon that the closed cells communicate with each other also occurs, and water penetrates deep into the foam layer. Once permeated, the water that has permeated will remain on the flange even after the retort treatment is complete, causing mold generation and spots. Such mold and stains can damage the appearance of the product, and in some cases can lead to complaints from buyers.

  The present invention has been made in view of the above points, and even when the boil retort treatment is performed, mold and stains due to moisture penetration do not occur in the flange portion of the container mouth, and when reheated in a microwave oven or the like Another object of the present invention is to provide a retort food container in which heat is not easily transmitted to the outer surface of the container, and a method for producing the same.

(1) In order to achieve the above object, in the present invention, a container main body formed by hot-pressing a polypropylene resin foam sheet having a barrier layer on the surface and having a flange at the mouth, and the flange In the retort food container provided with a lid that seals the container body by welding to the part, the barrier layer has a three-layer configuration in which an ethylene-vinyl acetate copolymer resin is sandwiched between polypropylenes, and the lid is It has a PET film on which aluminum is vapor-deposited or a PET film or metal foil on which silicon oxide is vapor-deposited, and has an impervious area formed by compression at the periphery of the flange portion. and wherein the penetration of water into the interior is prevented with is formed in the wall end face withstand the heat or pressure during the boiling retort treatment are To have.

  According to this configuration, since the impervious region is provided at the periphery of the flange portion of the lip of the food container, hot water does not permeate from the cut surface of the flange portion. For this reason, even if hot water is dirty, the dirty water will not penetrate into the flange and cause mold or stains. You don't have to be injured.

(2) Further, in the present invention, a container body formed by hot-pressing a polypropylene resin foam sheet having a barrier layer on the surface and having a flange portion at the mouth, and the flange portion is welded to the flange portion. In the manufacturing method of the retort food container provided with the lid for sealing the container body, the barrier layer has a three-layer structure in which an ethylene-vinyl acetate copolymer resin is sandwiched between polypropylenes, and the lid is vapor-deposited with aluminum. A PET film or a metal foil on which silicon oxide is deposited, and compresses the periphery of the flange portion to form an impervious region. In the impervious region, the foam layer is crushed and boil retort treatment A wall that can withstand the heat or pressure of the time is formed on the end face to prevent water from penetrating into the interior.

  According to this configuration, a retort food container in which hot water does not permeate from the cut surface of the flange portion to cause mold and stains by compressing the peripheral edge of the flange portion of the lip of the food container to provide an impermeable region. Can be manufactured. In addition, it is sufficient to perform the compression in any step, and it can be easily performed.

(3) Moreover, in this invention, in the manufacturing method of the retort food container comprised as mentioned above, formation of the said impermeable area | region is performed by the hot press for forming a container main body shape, It is characterized by the above-mentioned. Yes.

  According to this structure, the impervious region can be formed together by one hot press for forming a food container, and the work efficiency is high.

  According to the present invention, in a retort food container having a flange portion at the lip, which is formed by hot-pressing a polypropylene resin foam sheet having a barrier layer on the surface, an impervious region is formed at the periphery of the flange portion. Since it is provided, hot water does not permeate from the end face of the flange portion and cause mold generation or stains. For this reason, the boil retort process can be performed in peace without worrying about the appearance of the product being damaged by mold and stains. Moreover, the impervious region can be formed at the same time as the container shape is formed by hot press, and the work efficiency is high.

  Hereinafter, the retort food container and the manufacturing method thereof according to the present invention will be described with reference to FIGS. 1 is a perspective view of a food container before being covered, FIG. 2 is a cross-sectional view of the food container in a state of being covered, FIG. 3 is a partially enlarged cross-sectional view of the food container, and FIG. 4 is a resin foam as a material of the food container FIG. 5 is a cross-sectional view showing another structure of the resin foam sheet, FIG. 6 is an explanatory view of the food container manufacturing process, and FIG. 7 is a cross-sectional view showing the structure of the hot press mold. .

  A food container 1 shown in FIG. 1 is obtained by hot-pressing a polypropylene resin foam sheet into a planar cup shape. On the surface of the polypropylene-based resin foam sheet, a barrier layer that prevents permeation of liquid or gas is formed.

  FIG. 4 shows a configuration example of a polypropylene resin foam sheet having one barrier layer. Here, a barrier layer 101 made of a PP / EVOH / PP film having a thickness of 40 to 150 μm is formed on the surface of a polypropylene resin foam sheet 100 having a thickness of 0.6 to 2.0 mm. “PP” of “PP / EVOH / PP” is polypropylene, and “EVOH” is an ethylene-vinyl acetate copolymer resin, a resin known as a trade name “EVAL”. That is, the PP / EVOH / PP film is a film having a three-layer structure in which Evar is sandwiched between polypropylene from both sides.

  FIG. 5 shows a configuration example of a polypropylene resin foam sheet having two barrier layers. Here, an adhesive layer 102 made of a PP film having a thickness of 15 to 50 μm and a PP / EVOH / PP film having a thickness of 40 to 150 μm are formed on the surface of a polypropylene resin foam sheet 100 having a thickness of 0.6 to 2.0 mm. A barrier layer 101 made of is formed.

  If only a barrier against water vapor is required, a PP / EVOH / PP film can be used, and a simple PP film can sufficiently achieve the object.

  A flange portion 2 is formed at the mouth edge of the food container 1. After putting food into the food container 1, as shown in FIG. 2, the lid body 10 is placed on the flange portion 2, and the flange portion 2 and the lid body 10 are welded by means such as thermocompression bonding or ultrasonic welding. The food container 1 is sealed.

  As the lid 10, a PET film on which aluminum is vapor-deposited, a PET film on which silicon oxide is vapor-deposited, a synthetic resin film such as polyethylene, polypropylene or polyethylene terephthalate and a metal foil such as aluminum are laminated to provide gas barrier properties and water vapor barrier properties. Use the one with higher For example, a laminate of a 12 μm thick polyester film deposited with silicon oxide, a 15 μm thick nylon film, and a 60 μm thick unstretched polypropylene film can be used.

  The food container 1 filled with food and sealed with the lid 10 is sterilized by boil retort. In the case of a normal foam container, it must be concerned that hot water permeates from the cut surface of the flange portion 2 to cause mold generation and stains. In the present invention, the flange portion This problem is addressed by compressing the periphery of 2 to form an impermeable region 3.

  As can be seen in FIG. 3, the foamed layer is crushed in the impervious region 3, and there is no room for water to enter the foam. Moreover, the impermeable area 3 forms a strong wall on the cut surface of the flange portion 2, and even if heat or pressure is applied during the boil retort treatment, the wall is broken and water does not penetrate inside. The compressibility and the horizontal width of the impervious region 3 are determined by experiments in order to withstand the heat and pressure of the boil retort process.

  In the experiment, the end of the 2.5 times expanded polypropylene resin foam sheet was crushed to a thickness of about 55%, and this was boiled and retorted with hot water at 120 ° C. for 30 minutes, but water absorption from the end surface was observed. There wasn't.

  The food container 1 is manufactured by a manufacturing line as shown in FIG. The polypropylene resin foam sheet 100 provided with a barrier layer on the surface drawn from the raw roll 110 passes through the oven 30 and is preheated. The polypropylene-based resin foam sheet 100 having a barrier layer on the preheated surface is hot-pressed by a hot-pressure press die 40 including a male die 41 and a female die 42 to form the shape of the food container 1. The polypropylene resin foam sheet 100 exiting the hot press mold 40 is sent to a trimming mold 50 comprising a male mold 51 and a female mold 52, where a portion of the food container 1 is punched from the sheet.

  FIG. 7 shows the structure of the hot press mold 40. The male mold 41 is provided with a protrusion 43 at the end of the portion forming the flange portion 2 of the food container 1, and the polypropylene resin foam sheet 100 is compressed between the protrusion 43 and the female mold 42, so An infiltration region 3 is formed. On the other hand, a vacuum passage 43 communicates with the female mold 42 at the bottom of the cavity, and the polypropylene resin foam sheet 100 is drawn into the cavity with a vacuum pressure. Thereby, the polypropylene resin foam sheet 100 is finished with high accuracy into the container shape as designed. Although the male mold 41 and the female mold 42 are each provided with a heater for temperature control, this is not shown.

  In this way, in the hot press process for forming the container shape of the food container 1, the impermeable region 3 is formed all at once, so there is no need to put a dedicated process for forming the impermeable region, High work efficiency.

  The shape of the food container 1 is not limited to a planar circular shape. It may be a square, a rectangle, another polygon, or an ellipse. Further, it may be a cup shape with a depth or a shallow tray shape.

  Although the embodiments of the present invention have been described above, various modifications can be made without departing from the spirit of the invention.

  INDUSTRIAL APPLICABILITY The present invention can be used to form a retort food container having a flange portion on a mouth edge by hot pressing a polypropylene resin foam sheet having a barrier layer on the surface.

Perspective view of the food container before the lid Cross section of food container with lid Partial enlarged sectional view of a food container Sectional view showing the configuration of the resin foam sheet that is the material of the food container Sectional drawing which shows the other structure of a resin foam sheet Illustration of food container manufacturing process Sectional view showing the configuration of the hot press mold

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Food container 2 Flange part 3 Impervious area 10 Lid body 30 Oven 40 Hot-pressing die 50 Trimming die 100 Polypropylene-based resin foam sheet provided with a barrier layer on the surface

Claims (3)

A container main body formed by hot-pressing a polypropylene-based resin foam sheet having a barrier layer on the surface and having a flange portion at a lip, and a lid body that is welded to the flange portion and seals the container main body. In a retort food container with
The barrier layer has a three-layer configuration in which an ethylene-vinyl acetate copolymer resin is sandwiched between polypropylenes,
The lid has a PET film deposited with aluminum or a PET film deposited with silicon oxide or a metal foil,
On the periphery of the flange portion, there is an impermeable region formed by compression,
In the impervious region, a foamed layer is crushed and a wall that withstands heat or pressure during boil retort treatment is formed on an end surface to prevent water penetration into the retort food container. A container main body formed by hot-pressing a polypropylene-based resin foam sheet having a barrier layer on the surface and having a flange portion at a lip, and a lid body that is welded to the flange portion and seals the container main body. In a method for producing a retort food container comprising:
The barrier layer has a three-layer configuration in which an ethylene-vinyl acetate copolymer resin is sandwiched between polypropylenes,
The lid has a PET film deposited with aluminum or a PET film deposited with silicon oxide or a metal foil,
Compressing the periphery of the flange to form an impermeable region;
In the impervious region, the foamed layer is crushed and a wall that withstands heat or pressure during boil retort treatment is formed on the end face to prevent water penetration into the retort food container. Production method.   The method for producing a retort food container according to claim 2, wherein the formation of the impermeable region is performed by a hot press for forming a container body shape.

Images