JP7362221B2 - Vacuum and/or pressure formed container and method for manufacturing the same - Google Patents

Description

The present invention relates to vacuum and/or pressure formed containers. More specifically, it relates to a vacuum and/or pressure-formed container with a foam layer on the side.

Currently, a wide variety of containers are on the market. Containers are required to have various functions depending on their use. For example, in the case of containers containing food, functions such as gas barrier properties, water leakage resistance, and heat resistance are required. These functions are achieved by combining one or more materials.

An example of using a container to enclose food is instant foods such as instant noodles and instant soup. These instant foods can be eaten by pouring a specified amount of boiling water into the container. Therefore, these instant foods are required to have water leakage resistance.

Containers made of thermoplastic resins such as polypropylene and polystyrene are known as containers having water leakage resistance. Containers made of thermoplastic resin have excellent water leakage resistance, but they also have the characteristic that the heat inside the container is easily transmitted to the outside of the container. Therefore, when pouring hot water or the like into the container, it is difficult to directly grip the container.

Therefore, we have developed a method of wrapping corrugated paper around the outside of the thermoplastic resin container, and a so-called method of fitting a paper container that is slightly larger than the thermoplastic resin container so that an air layer is created between the thermoplastic resin container and the thermoplastic resin container. A method of using a double container has been conventionally used (see Patent Documents 1 and 2).

Publication No. 05-084621 Japanese Patent Application Publication No. 2000-062753

By the way, when corrugated paper is wrapped, heat resistance is improved, but a new problem arises, such as poor aesthetic appearance. Therefore, it may be possible to print on the surface of corrugated paper. However, in the case of corrugated paper, there may be a limit to the number of colors that can be used. Furthermore, if a thermoplastic resin container is wrapped with corrugated paper or made into a double container, problems such as bulkiness and difficulty in stacking arise. Furthermore, since the weight increases, there is also the problem of increased transportation costs. Furthermore, in order to attach corrugated paper to a thermoplastic resin container or to integrate double containers, there arises the problem that a separate process apparatus is required.

The present inventors investigated whether it is possible to make a container made of a thermoplastic resin that has excellent printability, is not bulky or significantly increases in weight, and is heat resistant using existing equipment. The inventors have newly discovered that the above problem can be solved by providing a foam layer on the side surface of the container, and have completed the present invention.

In order to solve the above problems, the present invention provides a vacuum and/or pressure molded container having a foam layer on the side surface. Furthermore, in order to solve the above problems, the present invention integrates a container side surface made of a vacuum- and/or pressure-molded thermoplastic resin and a laminate having paper as the main strength material and a foam layer as the outermost layer. vacuum and/or pressure formed containers. Furthermore, in order to solve the above problems, the present invention provides a step of arranging a laminate before foaming formed into an inverted truncated pyramid shape or a cylindrical shape along the inner wall surface of a mold, A vacuum and/or pressure processing step for processing a thermoplastic resin sheet under vacuum and/or pressure, and heating the laminate so that a container made of thermoplastic resin is placed inside the laminate before foaming formed in and a foaming step of foaming the outermost layer of the laminate.

According to this configuration, since the container made of thermoplastic resin and the laminate including the foam layer are integrally molded, it has better printability than wrapping corrugated paper around a container made of thermoplastic resin, and is less bulky and bulky. Significant weight increases can also be prevented. Further, by using a mold, it is possible to easily integrally mold a container made of a thermoplastic resin and a laminate including a foam layer.

According to the present invention, a container made of a thermoplastic resin with excellent printability and heat resistance can be provided using existing equipment. Furthermore, since the container and the laminate are integrally molded, they are difficult to separate. Furthermore, since the laminate is not foamed during integral molding and can be foamed after integral molding, bulkiness can be suppressed.

Embodiments of the present invention will be described below. The molded container according to the present embodiment will be explained by taking as an example a bowl-shaped container in which a container body made of a thermoplastic resin and a laminate having a foamed layer as the outermost layer are integrated.

The container main body in this embodiment has a bowl-shaped shape with a tail end and a flange extending outward from the opening.

Thermoplastic resins that can be used for the container body include polyester resin, polyethylene resin, polypropylene resin, polystyrene resin, polyamide resin, polycarbonate resin, polyacrylonitrile resin, polyimide resin, polyvinyl chloride resin, polyvinylidene chloride resin, and polyvinyl alcohol. Examples include resin, ethylene vinyl alcohol resin, and polyurethane resin. The thermoplastic resin layer may be a single layer or a laminate. Among these, polystyrene resin or polypropylene resin is preferred from the viewpoint of ease of molding.

As a method for molding the thermoplastic resin container according to this embodiment, conventional molding methods such as injection molding, vacuum forming, pressure forming, vacuum pressure forming, hot plate molding, etc. can be used. In this embodiment, vacuum forming, pressure forming, or vacuum pressure forming is preferable.
Here, vacuum forming refers to a method of forming a thermoplastic resin sheet into a predetermined shape by suctioning a heated thermoplastic resin sheet to increase its flexibility and bringing it into close contact with a mold. Compression molding is a thermoplastic resin sheet that has been heated to increase its flexibility and is sandwiched between a lower mold and an upper compressed air box, and the thermoplastic resin sheet is brought into close contact with the mold by pressure, forming it into the desired shape. Tell me how to shape it. Vacuum and pressure forming refers to a forming method that combines vacuum forming and pressure forming.

The laminate according to this embodiment uses paper as the main strength material and includes a foam layer as the outermost layer. Specifically, the paper base material is composed of a layer of polyethylene A on one side and a layer of polyethylene B, which has a higher melting point than polyethylene A, on the other side. Here, the thickness of the laminate before foaming is preferably 30 to 100 μm. If it is less than 30 μm, a sufficient thickness of the paper base material or polyethylene layer cannot be ensured, and as a result, a sufficient foam layer cannot be obtained. On the other hand, if it is too thick than 100 μm, it becomes bulky. Further, the thickness of the laminate after foaming is preferably less than 1200 μm. If it is 1200 μm or more, it becomes bulky and difficult to stack. Furthermore, the thickness of the foam layer is preferably 400 μm or more.

The basis weight of the paper base material can be selected as appropriate depending on ease of handling, etc., but it is usually preferably about 200 g/m ² or more and 400 g/m ² or less, and 250 g/m ² or more and 350 g/m ² or less. More preferred. In the present invention, the foamed layer before foaming (hereinafter also simply referred to as "unfoamed layer") is foamed to form a foamed layer using the water contained in the paper base material. Moisture is important. The moisture content of the paper base material is preferably within the range of about 5 to 10% by weight.

Next, polyethylene will be explained. Although various polyethylenes can be used in the present invention, it is preferable to use low to medium density polyethylene as polyethylene A, and medium to high density polyethylene as polyethylene B. As a rough definition, low-density polyethylene refers to polyethylene with a melting point of 95 to 130°C and a density of 0.91 to 0.929 g/cm ³ . Medium density polyethylene refers to polyethylene with a melting point of 110 to 135 and a density of 0.93 to 0.941 g/cm ³ . High-density polyethylene refers to polyethylene with a melting point of 120 to 140°C and a density of 0.942 to 0.97 g/cm ³ .

Note that the difference in melting point between polyethylene A and polyethylene B is preferably 5°C or more, more preferably 10°C or more. If the difference in melting point between polyethylene A and polyethylene B is small, it will be difficult to control the temperature during foaming.

Furthermore, in the present invention, in order to integrate the container body and the laminate, it is preferable to add the same material as the container body to polyethylene B. By using the same material as the container body, the adhesive strength between the laminate and the container body increases, allowing them to be integrated. In this embodiment, it is preferable to add polypropylene to polyethylene B. Here, the amount of polypropylene added to polyethylene B is preferably 10 to 50% by weight. If it is less than 10%, the adhesion to the container body is insufficient, and if it is more than 50%, it may interfere with the formation of the laminate.

In addition to adding the same material as the container body to polyethylene B, a layer made of the same material as the container body may be provided on the polyethylene B layer. In this embodiment, it is preferable to provide a polypropylene layer on the polyethylene B layer. The thickness of the polypropylene layer is preferably 5 to 15 μm. If it is less than 5 μm, the adhesiveness will not be stable. When it is thicker than 15 μm, workability deteriorates.

A method for manufacturing the laminate will be explained. Here, an example will be described in which a T-die is used as a polyethylene coating method, but the method is not limited to this. In the laminate, the paper base material (base paper) wound into a roll is unwound, and the paper base material is sent to the first T-die according to the guide rollers. Extrusion lamination is performed through a T-die, and molten polyethylene A is applied to one side of the paper base material. The surface coated with polyethylene A is cooled with a chill roller to form a polyethylene A layer. Note that the thickness of the polyethylene A layer is preferably 40 to 200 μm. Within this range, sufficient heat insulation properties can be achieved after foaming.

After providing a polyethylene A layer on one side of the paper base material, a polyethylene B layer is then provided on the opposite side from the polyethylene A layer. Specifically, extrusion lamination is performed through a T-die, and molten polyethylene B is applied to the paper base material on the opposite side from the polyethylene A layer. The surface coated with the polyethylene B layer is cooled with a chill roller to provide the polyethylene B layer. This yields a laminate in which polyethylene layers are provided on both sides of the paper base material. The thickness of the polyethylene B layer is preferably 25 to 80 μm. In this embodiment, polyethylene A was applied first, but polyethylene B may be applied first. Further, it is preferable that the (time) interval between providing the polyethylene A layer and the polyethylene B layer is short. This is because if the interval is too long, moisture will escape from the paper base material, making it difficult for the polyethylene to foam.

Printing can also be performed on the surface of the polyethylene A layer of the obtained laminate. By printing, it is possible to add decoration and improve the appearance. Preferably, printing is performed on the unfoamed layer. An unfoamed layer is easy to print.

Next, a method for manufacturing a molded container according to this embodiment will be explained. Here, vacuum forming will be explained as an example. First, the printed laminate described above is punched out into a predetermined shape. When the punched laminate is glued end to end with the printed side facing outward, it has a shape that matches the side surface of the bowl-shaped container.

First, a laminate with its ends bonded together is placed in a mold of a vacuum forming apparatus. Subsequently, the heated polypropylene sheet is placed on top of the mold, and the polypropylene sheet is sucked through a suction port provided on the surface of the mold. The polypropylene sheet is brought into close contact with the mold by suction and is deformed into a predetermined shape of the container body. Further, when the polypropylene sheet is deformed by suction, the inner surface of the laminate and the body of the container body come into contact. Since the inner surface of the laminate contains polypropylene, when the heated polypropylene sheet comes into contact with the inner surface of the laminate, the laminate and the polypropylene sheet adhere and become integrated. Thereby, the laminate and the container body can be integrated without using an adhesive. In addition, when vacuum forming a polypropylene sheet, you may press a polypropylene sheet with a jig. By using the jig, the polypropylene sheet can be more reliably shaped into the desired shape of the container body. Moreover, by pressing with a jig, the adhesion between the laminate and the polypropylene sheet can be ensured.

Next, the molded container in which the laminate and the container body are integrated is removed from the mold and transported into an oven. The temperature inside the oven is set to be higher than the melting point of polyethylene A and lower than the melting point of polyethylene B. Thereby, the outer surface of the laminate is heated and foamed. Note that if the heating temperature is lower than the melting point of polyethylene A, a foam layer cannot be provided. On the other hand, if the heating temperature exceeds the melting point of polyethylene B, it is not preferable because all the inner and outer surfaces of the laminate may foam or sufficient foaming may not be obtained. Furthermore, there is a possibility that the shape of the container body may be distorted.

As explained above, the vacuum-formed container according to this example is less bulky and lighter than a container wrapped in corrugated paper. Furthermore, since the laminate can be printed, it has an excellent appearance. Furthermore, an extremely excellent effect is achieved in that the container body and the laminate can be integrated without using a new device.

Although a vacuum forming apparatus was used in the above embodiments, the present invention is not limited to vacuum forming, and can be manufactured using other forming methods. For example, a pressure forming device may be used instead of a vacuum forming device. When using a pressure forming apparatus, it is the same as a vacuum forming apparatus until the heated thermoplastic resin sheet is placed on the mold. In the pressure forming apparatus, pressure is applied from above the thermoplastic resin sheet using a pressure box, so that the polypropylene sheet is brought into close contact with the mold, forming a predetermined shape of the container body. Further, when the polypropylene sheet is deformed by pressure, the inner surface of the laminate and the body of the container body come into contact and become integrated. Furthermore, it can also be manufactured using a vacuum pressure forming apparatus. In the case of vacuum-pressure forming equipment, suction is drawn from the mold and pressure is applied from the compressed air box.

Claims (2)

A container consisting of a container body made of a thermoplastic resin molded in vacuum and/or pressure, and a laminate in which polyethylene layers are provided on both sides of paper, which is the main strength material, by extrusion lamination,
The container body and the laminate are integrated by thermally adhering the thermoplastic resin of the container body and the polyethylene layer inside the laminate,
The laminate is a vacuum and/or pressure molded container, wherein the laminate includes a printed layer on the outer polyethylene layer, and the outer polyethylene layer of the laminate forms a foam layer by foaming. A method for manufacturing a vacuum and/or pressure-formed container with a foam layer on the side, the method comprising:
An arrangement step of forming and arranging a pre-foamed laminate in which polyethylene layers are provided on both sides of paper, which is the main strength material, by extrusion lamination into an inverted truncated cone shape or a cylindrical shape along the inner wall surface of the mold;
A container body made of a thermoplastic resin is placed inside the laminate before foaming formed into an inverted truncated pyramid shape or a cylindrical shape , and at the same time, a thermoplastic resin is placed so that the inside of the laminate and the container body are thermally bonded. a vacuum and/or pressure processing step of processing a resin sheet under vacuum and/or pressure;
a foaming step of heating the laminate to foam the outermost layer of the laminate;
A method for manufacturing a vacuum and/or pressure-formed container, comprising: