JP5741084B2 - Paper tray container - Google Patents

Description

  The present invention relates to a tray-shaped paper tray-like container in which a synthetic resin film is integrated by vacuum molding or the like on the inner surface of an outer container whose base material is paper that is filled with uncooked and cooked food. It is.

As a container for storing frozen foods and the like, a tray-like container in which a blank made of paperboard coated with a synthetic resin is assembled has been proposed and put into practical use.
This tray-like container is coated with synthetic resin on the inner surface, and is folded and molded so as to be overlapped so that the end face of the blank is not exposed at the corner portion. It could also be used for the contents.

On the other hand, in particular, in particular, such a paper tray-shaped container is filled with sealed food or semi-cooked food and sealed, and when used, the tray-shaped container is directly heated or heated by a microwave oven or oven. There is an increasing demand for cooking and using it as a tableware as it is.
As the synthetic resin provided on the inner surface of such a tray container, polypropylene having both the required heat resistance and heat sealability is suitable, but in order to withstand the heating process by a microwave oven or an oven, the film thickness is For example, a film having a thickness of 100 μm or more is preferably used.

  However, if a synthetic resin film such as a thick polypropylene film is used on the inner surface of a tray-like container, it is difficult to fold and form at the corner portion, and the flange produced when the corner portion is folded and formed. After the contents were stored, it was difficult to seal the flange with the flange.

  In forming such a tray-like container, several tray-like containers have been proposed in which a synthetic resin film is heat-softened on the inner surface of a paper outer container and laminated and bonded by means such as vacuum forming. According to this method, it is possible to manufacture a tray-like container that is superior in view of the cover of the inner surface of the outer container and the ease of molding as compared with the method using a blank laminated with a synthetic resin film.

  However, in the process of laminating and bonding the synthetic resin film to the inner surface of the tray-like container using vacuum molding, the inner surface of the paper outer container and the synthetic resin film have the necessary adhesive strength without causing defects such as pinholes. It was not always easy to form the layers. In particular, in the deep drawing vacuum forming process, it is difficult to stably and firmly laminate the film in the vicinity of the bottom of the container.

FIG. 7 is a schematic cross-sectional view of an example of a paper tray-like container in a vacuum forming step (before suction), and FIG. 8 is a schematic cross-sectional view after suction.
In FIG. 7, a paper outer container (10) molded in a tray shape is set inside a vacuum molding die (30). The synthetic resin film (20) is heated by a heating device (not shown) and is carried above the mold (30). The white arrow in the figure indicates the film's future deformation direction and air suction direction (D).

FIG. 8 shows a state in which suction is started from the above state and the synthetic resin film (20) is deformed and adhered along the inner surface of the outer container (10). The synthetic resin film on the upper side of the outer container (10) adheres uniformly, but the only part where the air escapes when the air is released is the corner (E) at the bottom of the container. As a result, a load is applied to the film and pinholes are easily formed, and as the film cools, the adhesion is weakened.

Thus, in the conventional tray-shaped container molding, when the outer container is placed in a mold and the synthetic resin film softened by heating is integrated by vacuum molding or the like, the synthetic resin film is attached to the outer container. Since it was immediately cooled at the contact stage, sufficient adhesive strength with the outer container could not be obtained. In particular, in the case of a polypropylene film having heat resistance and heat sealability, satisfactory adhesive strength was not obtained.

Several proposals have heretofore been made in order to alleviate such problems when laminating and bonding a synthetic resin film on the inner surface of a paper outer container by heat softening and vacuum forming or the like.
For example, as shown in Patent Document 1 and Patent Document 2, a tray-like container has been proposed in which a synthetic resin film is heated and softened on the inner surface of a paper outer container and laminated and bonded by means such as vacuum forming. .

  In Patent Document 1, a sealed container formed integrally with an outer box made of cardboard having a slit in the lower part and an inner box formed by degassing and sealing a synthetic resin film from the slit on the inner surface of the outer box Has been proposed.

Further, in Patent Document 2, a plastic film is in close contact with the inner surface of an outer box made of paperboard, and this plastic film is extended to the outer surface of the flap that is continuous with the outer periphery of the opening of the outer box. In doing so, it is possible to make a sealed package with no hook-shaped piece by folding the flap inside, and applying a heat-adhesive lid on top of this to heat and pressurize, and when storing and transporting the package Containers that take up little space and are easy to handle have been proposed.

  These tray-like containers can have a structure in which no step is generated in the flange part, and can be used as a container having good sealing performance. However, only the structure for promoting deaeration from the lower slit is used in the corner part. It has been difficult to reliably prevent defects that are likely to occur.

  Furthermore, in Patent Document 3, a small-diameter hole is appropriately provided on the bottom surface portion of the outer layer container, and the small hole opened in the outer layer container is used as a vacuum hole when vacuum suction is applied with a plastic sheet heated in another line. A method for manufacturing a composite container has been proposed in which deaeration can be performed smoothly.

Further, in Patent Document 4, a tray-like container having a good sealing property, in which the polypropylene film heated and softened as described above is integrated on the inner surface of a paper outer container by means of vacuum forming or the like, A tray-like container has been proposed in which a specific low-melting point plastic film is interposed in the inner layer to enhance the adhesive strength between the outer container and the polypropylene film. Thereby, also in a corner part etc., when opening a cover material, the danger that the synthetic resin film integrated with the outer container will peel from an outer container decreases.
Even in the case of a deep-drawn tray even when using the above-described means, the container bottom and corners ensure the close contact between the outer container and the inner layer film during vacuum forming, and prevent the occurrence of pinholes and the like. It was difficult.

Japanese Utility Model Publication No. 51-31202 Japanese Utility Model Publication No. 54-42830 JP 55-34910 A JP-A-10-114327

  The present invention has been made to solve the above-described conventional problems, and ensures that the outer container and the inner layer film are in close contact with each other at the bottom and corners of the container even in the deep drawing tray during vacuum forming. It is an object of the present invention to provide a paper tray-like container that can prevent the occurrence of pinholes and the like.

The invention described in claim 1 of the present invention
After the contents are filled into a paper-based tray-like container, the tray-like container is composed of a lid material and a tray-like container that are sealed and sealed with a paper-based base material. However, a synthetic resin film is laminated and bonded to the inner surface of the outer container made of a paper base material having a flange surface at the periphery of the opening by vacuum molding or a combination of vacuum molding and pressure molding. In the paper tray-like container in which the lid material is overlapped on the flange surface of the container and the inner surface of the overlap is heat-sealed and sealed, the blank side plate forming the outer container and the side plate are connected to the same. A linear concave or convex portion with one end of a crease line at the boundary of the polymer piece is provided on the polymer piece ,
A plurality of fine holes are formed on the crease line of the boundary between the side plate of the blank and the polymer piece forming the outer container,
The paper tray-like container is characterized in that the density of arrangement increases or the size of the micro-holes increases as the fine holes go to the bottom of the paper tray-like container.

  The paper tray-like container according to the present invention is a paper product in which a synthetic resin film is laminated and bonded together by vacuum forming or a combination of vacuum forming and pressure forming on the inner surface of an outer container made of a paper base material. In a tray-like container, a paper is characterized in that a linear concave portion or convex portion having a folded ruled line at the boundary between a blank side plate forming an outer container and a continuous polymer piece connected thereto is provided on the polymer piece. A tray-shaped container.

The folded side line of the boundary between the blank side plate forming the outer container of the paper tray-like container according to the present invention and the polymer piece connected thereto serves as an air passage during vacuum suction.
By providing a linear concave or convex portion connected to the bent ruled line on the polymer piece, the end of the polymer piece passes through a slight gap formed in the overlapping region of the side plate and the polymer piece by the linear concave or convex portion. Since air at the time of suction can move from the crease to the crease line, even in the deep-drawn tray, at the bottom and corner of the container, the adhesion between the outer container and the inner layer film is ensured during vacuum molding, and It becomes possible to prevent the occurrence of pinholes.

In this case, of course, the end opposite to the linear concave portion or convex portion connected to the folded ruled line formed on the superposed piece must be opened inside the outer container.
In addition, since a plurality of fine holes are formed on the bent ruled line, the movement of the air is further promoted, and the above-described effect is manifested more quickly and remarkably.

The plurality of micro holes are most necessary to be deaerated during air suction because the density of arrangement increases toward the bottom of the paper tray-like container according to the present invention or the size of the micro holes increases. In particular, the suction from the bottom is accelerated, and the above-described effect is realized more quickly.
Thus, according to the paper tray-like container according to the present invention, not only the non-defective product rate is improved by the reduction of defective products due to the occurrence of pinholes in the synthetic resin film on the inner surface, but also at the time of film forming The effect of increasing the molding efficiency can be expected by stabilizing the vacuum suction speed.

  Furthermore, since a synthetic resin film adhered to the inner surface of the paper tray container by vacuum molding or a combination of vacuum molding and compressed air molding is used, the inner surface of the tray-shaped container has complete water resistance. It allows food containing moisture to be stored, and the contents can be cooked without changing the container in a microwave oven, oven, etc., so consumers can easily cook without preparing cooking utensils such as pans. It became possible. Moreover, since the container is not damaged by these cooking, it can be used as it is.

Blank drawing of an example of the paper tray-like container of the present invention The schematic diagram which looked at an example of the paper tray-shaped container of this invention from the side surface 3 The blank figure of other examples of the paper tray-like container of the present invention Partial enlarged view of a blank of another example of the paper tray-like container of the present invention Partial enlarged view of a blank of another example of the paper tray-like container of the present invention Partial enlarged view of a blank of another example of the paper tray-like container of the present invention Schematic of vacuum forming process (before suction) of an example of paper tray-like container Schematic of vacuum forming process (after suction) of an example of paper tray-like container

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a blank view of an example of a paper tray-like container of the present invention, and FIG. 2 is a schematic view of a paper tray-like container assembled from the blank shown in FIG. .
The paper tray-like container of the present invention is a paper tray-like shape in which a synthetic resin film is laminated and bonded together by vacuum forming or a combination of vacuum forming and pressure forming on the inner surface of an outer container made of a paper base material. It is a container.

  The outer container made of a paper base is a tray-like container assembled from a paper blank as shown in the blank diagram of FIG. 1 by a well-known manufacturing method, and has two pairs of side surfaces raised from the bottom surface (1) ( 2) and a side wall (3) and a paper container having a flange provided with two pairs of flanges (4) and (5) connected to the outer periphery of the side surface.

  As parts to be bonded to assemble and fix the paper blank, the polymer pieces (7) are connected to the both side ends of the left and right side surfaces (2) via the crease lines (A), and the polymer pieces (7) On the top, a linear unevenness (C) in which one end thereof is bent and connected to a ruled line (A) is formed by embossing. The polymer piece (7) is adhered and fixed to the inner side surface with the side surface (3) raised at the time of assembly.

  The linear unevenness (C) formed on the polymer piece (7) has the opposite end connected to the crease line (A) communicating with the gap toward the inside of the outer container. When the synthetic resin film is vacuum-adsorbed inside the container, it plays an auxiliary role for extracting air from the space between the outer container and the film. Since the outline of the state of the cross section of the container at the time of vacuum forming has already been described with reference to FIGS.

  Another embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 is a blank view of an example of the paper tray-like container of the present invention, and FIG. 4 is a view of the vicinity of the polymerization piece (B) when the paper tray-like container assembled from the blank shown in FIG. Partial enlarged views are shown respectively.

  The outer container made of a paper base material is a tray-like container assembled from a paper blank as shown in the blank diagram of FIG. 3 by a known manufacturing method, and two pairs of side surfaces (1) rising from the bottom surface (1) ( 2) and a side wall (3) and a paper container having a flange provided with two pairs of flanges (4) and (5) connected to the outer periphery of the side surface.

  As parts to be bonded to assemble and fix the paper blank, the polymer pieces (7) are connected to the both side ends of the left and right side surfaces (2) via the crease lines (A), and the polymer pieces (7) On the top, a linear unevenness (C) in which one end thereof is bent and connected to a ruled line (A) is formed by embossing. The polymer piece (7) is adhered and fixed to the inner side surface with the side surface (3) raised at the time of assembly.

  Further, a plurality of fine holes (6) are formed on the folded ruled line (A), and one end is connected to the folded ruled line (A) when the synthetic resin film is vacuum-adsorbed inside the outer container. In addition to the suction effect due to the unevenness (C), it also plays an auxiliary role for extracting air from the space between the outer container and the film.

The plurality of fine holes (6) need not be arranged at substantially equal intervals on the folded ruled line (A) as shown in FIG.
As shown in FIG. 5, the plurality of micropores (6) are arranged at a narrow interval at the bottom of the container where air suction needs to be enhanced, and at a large interval at the top of the container, deaeration is performed. It is desirable for effective execution.
Further, for the same reason, the size of each of the plurality of micro holes (6) does not need to be the same, and as shown in FIG. 6, the hole diameter at the bottom of the container that requires particularly enhanced air suction is large. A state where the upper part of the container is formed with a small hole diameter is desirable for effective deaeration.

  Although not shown, for the same reason, it is also possible to add a fine hole around the corner of the bottom where pinholes are likely to be vacant in the synthetic resin film, or to provide small irregularities on the boundary with the side surface where the polymer piece is cut off.

Usually, a paperboard such as a cup base paper is used as the paper base material to be the outer container. Although the basis weight and density is appropriately selected depending on vessel capacity and design, usually density 0.8 before and after the cup base paper is often used in a range of basis weight ^{200g / m 2 ~500g / m 2} .
As a paper base material, it is necessary to use a material that does not generate odor due to heating or has low rigidity in order to have rigidity against heating by a microwave oven, an oven, etc. as well as having an appropriate rigidity. . A material made of virgin pulp is suitable as a material that satisfies this requirement. In addition, it is necessary to use a material that is water resistant and has no absorbability of moisture adhering from the end face or a low material because it is necessary to prevent the moisture adhering to cooking. As a material satisfying this requirement, what is generally called cup base paper is suitable.

These required qualities are intended to prevent deterioration of the container due to condensation on the surface of the sealed paper container when it is frozen and refrigerated in a refrigerator, etc., and before the consumer purchases and takes it away from the storage state. It will also be effective. Moreover, oil resistance can also be given as needed. Furthermore, it is necessary that the material does not peel off in terms of peel strength from the lid when opened.
The paper substrate may be a single body, but may be a laminate in which other layers are combined as necessary. Commonly used composite layers include a printed layer, a sealant layer, a gas barrier layer, an adhesive layer for ensuring adhesion between layers, an anchor layer, and the like.

  The printing layer provided on the surface of the outer container as needed is a layer containing a pattern, product information, and the like that can be applied by a method such as gravure printing using a known ink. When a polyolefin resin is used as the thermoplastic resin layer on the paper substrate surface, an easy adhesion treatment such as a corona treatment is usually performed on the surface in order to improve the adhesion of the ink.

  When the outer container is assembled by heat sealing, a sealant layer is required. The sealant layer is a layer made of polyethylene resin, polypropylene resin, or the like, and usually serves as a hermetic seal for the lid after the contents are sealed. Specifically, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, ethylene-α-olefin copolymer and other ethylene resins, homo-block / random polypropylene resins, propylene -Propylene resins such as α-olefin copolymers, ethylene-α, β unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, ethylene-methyl acrylate and ethylene- Esterified products of ethylene-α, β unsaturated carboxylic acid copolymers such as ethyl acrylate, ethylene-methyl methacrylate and ethylene-ethyl methacrylate, ethylene-α, cross-linked carboxylic acid sites with sodium ion, zinc ion, β-unsaturated carboxylic acid copolymer ionic cross-linked product, ethylene-maleic anhydride Epoxy compound-modified polyolefins such as acid anhydride-modified polyolefins, ethylene-glycidyl methacrylate copolymers, etc. represented by terpolymers such as inacid graft copolymers and ethylene-ethyl acrylate-maleic anhydride, ethylene- It is provided by a single substance or a blend of two or more resins selected from vinyl acetate copolymers. The thickness of the sealant layer (5) is not particularly limited.

As the gas barrier layer, stretched films of plastics such as polyester, polypropylene, polyamide, etc., processed films in which polyvinyl alcohol is applied to various plastic films, or thin films of metals such as aluminum and metal oxides such as silicon oxide are deposited, Furthermore, aluminum foil or the like can be applied. Moreover, although it does not specifically limit regarding the thickness, Usually, the stretched film of the range of 6 micrometers-25 micrometers is often used.
As the adhesive layer and the anchor layer, a layer of a commonly used material can be appropriately selected from the properties of the layers to be laminated.

  As mentioned above, although the paper base material used for the tray-shaped paper container concerning this invention was demonstrated, these laminated bodies are not limited to the thing of the above structures, In consideration of the use as a packaging material, it is packaging. For the purpose of improving the rigidity and durability required as a material, a configuration in which another layer is interposed may be used.

Moreover, the outer container used for the tray-shaped paper container of this invention can be produced as follows, for example from a paper base material.
The printed paper base material is punched into a predetermined shape according to the shape of the container, and simultaneously cut as a blank with a ruled line for bending. The blank is bent along a ruled line, assembled, and necessary parts are adhered to produce an outer container.

  In the paper tray-shaped container according to the present invention, it is necessary to provide a synthetic resin film only on the inner surface of the outer container and the cover material. This is because, when the container is heated by a microwave oven, an oven, or the like, a phenomenon occurs in which the moisture of the paper, which is the base material, evaporates and comes out on the surface of the paper. For this reason, when a synthetic resin film is provided on both sides of the paper, there arises a problem that the adhesion between the paper and the synthetic resin film is peeled off by the vapor. At this time, if a synthetic resin film having a low melting point is disposed, there arises a problem that the synthetic resin film foams due to melting of the synthetic resin film itself and ejection of the vapor.

  Therefore, in the paper tray-like container according to the present invention, the synthetic resin film is provided only on the inner surface of the paper base material and is not provided on the outer surface so as not to hinder the release of vapor. In addition, when a synthetic resin film is also arranged on the outside, another means that does not hinder the release of such vapor is possible by laminating and bonding a highly breathable synthetic resin film, such as having fine through holes. is there.

  The synthetic resin film used in the paper tray-like container of the present invention is excellent in water resistance, maintains sufficient hermeticity during storage such as refrigeration after filling and sealing the contents, and is excellent in heat-fusibility. Of course, resistance to heating such as a microwave oven and an oven is required. That is, high water resistance and heat resistance are required.

For example, the layer in contact with the contents is a polypropylene (PP) resin, specifically, a homopolypropylene, a random polypropylene copolymer, or a block polypropylene copolymer, and it is particularly preferable to use a random polypropylene copolymer.
The layer in contact with the outer container is preferably a synthetic resin film comprising at least two layers using an ethylene copolymer layer having a carbonyl group. The thickness of the synthetic resin film is required to be 100 μm or more for moldability, heat resistance, and content protection, and is preferably in the range of 100 to 200 μm.

Specific examples of the ethylene copolymer containing a carbonyl group include an ethylene-methyl methacrylate copolymer, an ethylene-vinyl acetate copolymer, or an ethylene-acrylic acid ester-maleic anhydride terpolymer. Is mentioned.
In addition to the above structure, this synthetic resin film may have a multi-layer structure in which PP layers other than a single PP are combined with PP, polyethylene, or amorphous polyester other than PP used on the side in contact with the contents. .
Each of the synthetic resin films may be laminated by a dry laminating method, but a film formed by a coextrusion method in which melt extrusion is simultaneously performed is preferable.

On the other hand, the lid material that seals the opening of the paper tray-shaped container needs to have both sealing properties and unsealing properties, and a peelable resin is laminated as a synthetic resin film in order to improve easy unsealing at the time of opening. It is preferable to do.
As this peelable resin, polyethylene polymerized by a single site catalyst, or ethylene-α olefin copolymer, polyethylene polymerized by a single site catalyst, or polyethylene polymerized by ethylene-α olefin copolymer by a multi-site catalyst, Or it is preferable to use resin which mixed ethylene-alpha olefin copolymer.

  When a printing layer is provided on the paper tray-like container, the ink needs to have resistance to heating by a microwave oven, an oven, or the like. That is, high heat resistance is required. Further, it is necessary that odor is not generated or low due to heating. Furthermore, air permeability is required in order not to hinder the release of vapor from the paper due to the heating described above.

  The printing layer used for the tray-like container can be provided with an overcoat varnish (OP varnish) on the outermost surface of the printing layer in addition to the ink for forming the pattern. By providing this OP varnish, when producing a tray-like container, the synthetic resin film is laminated with a paper base material and integrated in a mold by vacuum forming or vacuum / pressure forming in combination. The tray-like container can be easily taken out from the mold, and the tray-like container can be prevented from being deformed or broken in the taking-out process. Also, this OP varnish needs to be simultaneously provided with the properties of heat resistance, air permeability, and no odor due to heating, like other inks.

The paper tray-like container of the present invention is manufactured by laminating and integrating a synthetic resin film on the inner surface of the outer container by vacuum molding or a combination of vacuum molding and pressure molding.
On the other hand, a lid member (not shown) for sealing the opening of the tray-like container is a paper lid member having a shape and size matching the flanges (4) and (5) of the paper tray-like container. A synthetic resin film is laminated and adhered, and a printed layer is provided on the entire outer surface or an appropriate portion.

  Then, after filling the paper tray-shaped container with contents such as food, the lid material is stacked on the flanges (4) and (5) of the tray-shaped container, and the synthetic resin films on the inner surfaces of both members are heated. Seal and use by fusing.

  The method of the present invention, which enables stable production during vacuum forming by changing the shape of the carton blank as a member, is widely applied not only to paper tray containers but also to the field of paper primary containers as a packaging container manufacturing technology It is thought that this is a possible technology.

DESCRIPTION OF SYMBOLS 1 ... Bottom 2 ... Side 3 ... Side 4 ... Flange 5 ... Flange 6 ... Fine hole 7 ... Polymerization piece 10 ... Outer container 20 ... Synthetic resin film 30 ... Mold A ... Folding ruled line B ... Polymerization piece vicinity C ... Linear shape Concavity and convexity D ... Suction direction E ... Corner

Claims (1)

After the contents are filled into a paper-based tray-like container, the tray-like container is composed of a lid material and a tray-like container that are sealed and sealed with a paper-based base material. However, a synthetic resin film is laminated and bonded to the inner surface of the outer container made of a paper base material having a flange surface at the periphery of the opening by vacuum molding or a combination of vacuum molding and pressure molding. In the paper tray-like container in which the lid material is overlapped on the flange surface of the container and the inner surface of the overlap is heat-sealed and sealed, the blank side plate forming the outer container and the side plate are connected to the same. A linear concave or convex portion with one end of a crease line at the boundary of the polymer piece is provided on the polymer piece ,
A plurality of fine holes are formed on the crease line of the boundary between the side plate of the blank and the polymer piece forming the outer container,
A paper tray-like container, characterized in that the density of arrangement increases or the size of the micropores increases as the fine holes go to the bottom of the paper tray-like container.

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