JP2002019063A - Synthetic resin sheet material for molding container and food container made thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic resin sheet material for molding suitable for a packaging container of food or the like and having properties such as excellent impact strength, heat resistance and moldability, and a food container having excellent sealability. SOLUTION: The synthetic resin sheet material comprises an intermediate layer 1 made of a polybutylene terephthalate resin, one side or both side surfaces of which are covered with a coating layer 2 made of a polyethylene terephthalate resin or a copolyester resin. The food container is made of the sheet material and comprises a container body 3, and a cover 4 in such a manner that a protruding strip (a) and a groove (b) for sealing the container by engaging the strip (a) with the groove (b) each other on overall peripheries of outer peripheral edges 31 and 41 of the body 3 and the cover 4.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a synthetic resin sheet material mainly used as a material for packaging tools such as lunch boxes, side dishes, small articles and the like, and a food container using the sheet material.
In particular, it relates to a hygienic and inexpensive synthetic resin sheet material having excellent heat resistance, high mechanical strength, and low cost.

[0002]

2. Description of the Related Art Packaging tools for such applications are manufactured by blow molding a synthetic resin sheet, and the material is polyethylene terephthalate resin (hereinafter abbreviated as PET) from the standpoint of price, environmental hygiene and recycling. It is heavily used.

[0003]

The above-mentioned PET has excellent electrical properties and chemical resistance, but does not have sufficient impact strength, heat resistance, and moldability required for packaging, and cracks due to insufficient impact strength. It may easily enter or be scratched, impairing its appearance and losing its function as a wrapper.It also has low heat resistance, so it may be exposed to hot water or deformed by microwave heating, etc. However, there was a drawback that an accurate shape could not be obtained due to poor quality. In order to solve this drawback, it has been proposed to use a reinforced plastic filled with glass fiber, but because transparency deteriorates, it cannot be used depending on the application,
There was a problem to be solved in that there were difficulties in recycling.

Therefore, the present inventor has proposed that by using a copolymer containing a polybutylene terephthalate resin as a main component and a polyethylene terephthalate resin in combination as a surface layer, the outer surface is beautiful and suitable for packaging containers of goods. An object of the present invention is to develop a synthetic resin sheet having properties excellent in strength, heat resistance, and moldability, and to provide a food container using the sheet together with the sheet.

[0005]

The synthetic resin sheet material for container molding and the food container of the present invention for achieving the above object will be described with reference to the same reference numerals as in the drawings of the embodiments. One or both surfaces of an intermediate layer 1 made of polybutylene terephthalate resin are covered with a coating layer 2 made of polyethylene terephthalate resin or copolyester resin. or,
The food container is a food container made of a synthetic resin sheet molded from the synthetic resin sheet material for forming a container, and is closely fitted to the outer peripheral edge 31 of the container body 3 and the outer peripheral edge 41 of the lid 4. Either the substantially U-shaped ridge a or the concave groove b is formed over the entire periphery of the outer peripheral edges 31 and 41.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In carrying out the present invention,
The material of the intermediate layer 1 is a polybutylene terephthalate resin (hereinafter abbreviated as PBT), and its thickness for forming a container is generally 0.1 mm to 0.1 mm depending on the use of the packaging tool.
It is about 4 mm. Recycled raw materials may be used as raw materials to reduce material costs. This PBT
Has a high melting point of 225 ° C., a small water absorption, no deformation due to moisture absorption, a low dielectric loss tangent value, and a low specific gravity and excellent chemical resistance. . In addition, since it is an olefin-based resin, good adhesion to a coating layer described later is also a favorable point.

The coating layer 2 is made of non-recycled raw material PET or copolyester resin, which is not a recycled material, from the viewpoint of the appearance of the surface in contact with the article to be packaged, moldability as a container, and hygiene. The copolyester resin uses cyclohexanedimethanol, ethylene glycol and terephthalic acid as raw materials. Coating layer 2 is intermediate layer 1
When applied to only one side, it is needless to say that consideration must be given to the production of the container so that the inside of the container is coated. Both of these resins have high transparency, low haze, and excellent gloss. The glass transition temperature of PET is 69 ° C., and the glass transition temperature of the copolyester resin is 81 ° C., which is lower than that of the intermediate layer 1. However, when blow molding or vacuum molding is performed, the moldability of the intermediate layer 1 is hindered. The intermediate layer 1 can be prevented from being cracked or cracked because the flexibility can be prevented without lowering the productivity. Suitably, the thickness of these coating layers 2 is between 15 and 20 microns. The coating layer 2 may be formed by forming a thin film of PET or copolyester resin having a predetermined thickness and performing thermocompression bonding. However, by extruding the surface of the intermediate layer 1 at the same time as extruding the intermediate layer 1, the production efficiency is reduced. It is possible to increase.

In the above-mentioned synthetic resin sheet material for molding a container according to the present invention, since the main intermediate layer 1 is PBT having a melting point of 225 ° C., the softening temperature is higher than that of a conventional PET resin alone. As heat resistance. The melting point of PBT is within the range of the molding temperature commonly used in conventional blow molding and vacuum molding, and does not impair moldability and container productivity. Further, the intermediate layer 1 and the coating layer 2 have high transparency and thermal stability, have a small water supply rate, do not undergo moisture absorption deformation, and have excellent chemical resistance.
Further, since the dielectric loss tangent value is low, the container itself generates little heat and does not deform even when heated by, for example, a microwave oven. The use of recycled PBT by resource recycling as the main raw material PBT can reduce material costs.

The coating layer 2 made of non-recycled raw material PET or copolyester resin prevents the intermediate layer 1 from cracking or cracking due to its flexibility without impairing the moldability. It has the effect of completely maintaining the appearance and sanitary condition of the surface that comes into contact with the article to be packaged.

Next, the food container made of the synthetic resin sheet of the present invention uses the synthetic resin sheet of the present invention having the above-described composite layer structure, and is provided on the outer peripheral edge 31 of the container body 3 and the outer peripheral edge 41 of the lid 4. Either a substantially U-shaped convex ridge a or a concave groove b that is closely fitted to each other is formed over the entire outer periphery 31, 41. After the food is stored, the ridge a and the concave groove b are fitted to each other to close the lid, and the container is sealed, whereby contamination and leakage of the contents from the outside can be prevented. The melting point of the raw material sheet is higher than the normal food heating temperature,
In addition, since the value of the dielectric loss tangent is extremely small, heating with a microwave oven is possible with peace of mind, and since the synthetic resin sheet retains the above-mentioned excellent mechanical properties and maintains a hygienic condition, it can be packed in a pack. It is highly convenient and excellent as a food container. Means such as spot welding, ultrasonic sealing, or high frequency welding may be used in combination to complete the closed state.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an enlarged perspective view showing a cross section of the first embodiment of the present invention, FIG. 2 is an enlarged perspective view showing a cross section of the second embodiment, and FIG. 3 uses the synthetic resin sheet material for container molding of the first embodiment. It is a perspective view of a food container of a 3rd example in an open state.

A first embodiment of the present invention shown in FIG. 1 is a synthetic resin sheet having a composite layer structure in which both surfaces of an intermediate layer 1 are coated with a coating layer 2 and developed mainly for blow molding or vacuum molding. Material. The mid layer 1 is made of PBT. The coating layer 2 uses a copolyester resin containing cyclohexanedimethanol, ethylene glycol and terephthalic acid as raw materials.
The thickness of the intermediate layer 1 is 0.2 mm, and the thickness of the coating layer 2 is 15 microns. Since the synthetic resin sheet material of this embodiment has heat resistance that can be used even at 130 ° C. or higher and has a small dielectric loss tangent value, it is not deformed by hot water or microwave heating.

The second embodiment shown in FIG.
The raw materials of the coating layer 2 are the same as those of the first embodiment, but the coating layer 2 is formed on only one surface of the intermediate layer 1. The synthetic resin sheet material of such an embodiment is used such that the coating layer 2 is located inside the container.

In each of the first and second embodiments,
There is a modification in which the material of the coating layer 2 is PET. Since the layered structure is the same as that of each embodiment in each of the modified examples, the illustration is omitted.

FIG. 3 shows, as a third embodiment, a lunch container molded using the synthetic resin sheet material of the first embodiment or the second embodiment. A lunch container having a well-known internal structure, comprising a container body 3 and a lid 4, both manufactured by blow molding or vacuum molding, and a partition 3 is provided inside the container body 3.
In the figure, there are formed three large and small recesses 32 for accommodating foods separated by 3. Outer edge 3 of container body 3
Either a substantially U-shaped convex ridge a or a concave groove b, which is closely fitted to each other, is formed over the entire outer periphery 31, 41 of the outer periphery 1, 1 and the outer periphery 41 of the lid 4. . In the third embodiment shown in FIG. 3, the ridge a is formed on the container body 3 and the concave groove b is formed on the lid 4. On the contrary, the concave groove b is formed on the container main body 3 and the concave groove b is formed on the lid 4. Needless to say, the article a may be formed. Also, the cross-sectional shapes of the ridges a and the concave grooves b are not limited to a perfect U-shape, but may be a U-shape that is close to the U-shape. After the rice and the side dish are stored in the storage recess 32, the ridges a and the grooves b are fitted and closed, and the container is closed to prevent contamination and leakage of contents from the outside. can do.

Although the embodiments which are considered to be representative of the present invention have been described above, the present invention is not necessarily limited to only the structures of these embodiments, but includes the structural requirements of the present invention and is referred to as the present invention. The present invention can be implemented by appropriately modifying it within the range of achieving the object and having the following effects.

[0017]

As is clear from the above description, the first invention is a synthetic resin sheet material for molding a container,
PBT, which is a material constituting the main intermediate layer 1, has a high melting point of 225 ° C., and has a higher softening temperature than conventional PET simple resin, and has excellent heat resistance as a packaging container. Since the increased softening temperature is within the range of the molding temperature commonly used in conventional blow molding and vacuum molding, the moldability is not impaired and the productivity does not decrease. In addition, it has high transparency and thermal stability, has no moisture absorption deformation, is excellent in chemical resistance, and has a low dielectric loss tangent, so that it does not undergo thermal deformation even when heated in a microwave oven. In addition, if PBT forming the intermediate layer is made of recycled material by resource recycling, it is possible to reduce the material cost in addition to the above-mentioned effects, and to obtain a characteristic that is environmentally advantageous by recycling the resource. I have. In addition, since the coating layer 2 is made of non-recycled raw material PET or copolyester resin which is not a recycled material, the flexibility of the intermediate layer 1 is prevented from cracking or cracking without impairing the moldability, and the packaging This has the effect of maintaining the appearance and hygiene of the surface in contact with the article in a perfectly good state.

[Brief description of the drawings]

FIG. 1 is an enlarged perspective view showing a structural cross section of a first embodiment.

FIG. 2 is an enlarged perspective view showing a structural cross section of a second embodiment.

FIG. 3 is a reference perspective view showing a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intermediate layer 2 Coating layer 3 Container main body 31 Outer peripheral edge 32 Housing recess 33 Partition 4 Lid 41 Outer peripheral edge a Protrusion b groove

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E033 AA10 BA17 BA18 BB08 CA03 CA07 CA09 CA11 DA04 DA08 DD01 DE12 EA10 FA03 FA04 GA03 4F100 AK42A AK42B AK42C AL01A AL01C BA03 BA06 BA10A BA10C BA15 DA01 DA03 DA04 DB13 GB18 GB46 GB JJ03 JK10 JL01

Claims (8)

[Claims] 1. A container-forming synthetic resin sheet material in which one or both surfaces of an intermediate layer (1) made of polybutylene terephthalate resin are covered with a coating layer (2) made of polyethylene terephthalate resin or copolyester resin. 2. The coating layer (2) has a thickness of 15 to 20.
The synthetic resin sheet material for container molding according to claim 1, which has a micron diameter. 3. The synthetic resin sheet material for molding a container according to claim 1, wherein said coating layer (2) is a polyethylene terephthalate resin as a non-recycled raw material. 4. The synthetic resin sheet material for molding a container according to claim 1, wherein said coating layer (2) is a copolyester resin having cyclohexanedimethanol, ethylene glycol and terephthalic acid as raw materials. 5. An intermediate layer (1) made of polybutylene terephthalate resin is molded from a synthetic resin sheet material for container molding in which one or both surfaces are covered with a coating layer (2) made of polyethylene terephthalate resin or copolyester resin. It is a synthetic resin sheet food container, which has a substantially U-shape that is closely fitted to the outer peripheral edge (31) of the container body (3) and the outer peripheral edge (41) of the lid (4). A food container made of a synthetic resin sheet, wherein one of the ridges (a) and the concave grooves (b) is formed over the entire periphery of the outer peripheral edges (31), (41). 6. The coating layer (2) has a thickness of 15 to 20.
The synthetic resin sheet material for container molding according to claim 5, which is a micron. 7. The synthetic resin sheet material for molding a container according to claim 5, wherein the coating layer (2) is a polyethylene terephthalate resin as a non-recycled raw material. 8. The food container made of a synthetic resin sheet according to claim 5, wherein the coating layer (2) is a copolyester resin having cyclohexanedimethanol, ethylene glycol and terephthalic acid as raw materials.