JPH028898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a container, and more particularly to a container in which a plastic inner container is inserted into a paper outer container, and the object thereof is to stably block oxygen gas over a long period of time. It is an object of the present invention to provide a container which has excellent properties, excellent heat shrinkage resistance, and good moldability.

It is already known that paper containers and plastic containers can be integrated to make containers for various foods.In particular, paper containers have been developed for the purpose of making containers with high gas barrier properties suitable for soft drinks, youth drinks, etc. For the plastic container, a saponified ethylene vinyl acetate copolymer film is laminated on styrene or polypropylene, and a polyethylene film is further laminated. A structure constructed as an inner layer has been proposed in JP-A No. 57-68363, but according to this, the disadvantage of poor gas barrier properties of paper and polyethylene film can be overcome by using saponified ethylene-vinyl acetate copolymer film. In addition, the rigidity of the container can be increased by using styrene or polypropylene, and specifically, the thickness of the styrene or polypropylene in its original form is 300 to 500μ, and the saponified ethylene-vinyl acetate copolymer film is used. The thickness of 20~
50μ, and the thickness of the polyethylene film is 40 to 120μ, including the adhesive layer between each film.
A material with a diameter of 400 to 620μ is to be used.

However, although this product claims to have improved gas barrier properties, the gas barrier properties remain high for a relatively short period of time.
After liquids such as soft drinks and juices are contained, the gas barrier properties are forced to deteriorate rapidly within a relatively short period of time. In addition, when filling the contents, especially those such as youth products, they are heated to a high temperature of 80°C or 95°C, for example, and this temperature causes the inner resin layer to shrink due to heat. result.

Furthermore, this proposed product is constructed by laminating a saponified ethylene-vinyl acetate copolymer film on styrene or polypropylene, and then laminating a polyethylene film, which is an extremely inefficient production method. Therefore, this point also has its drawbacks.

The inventors of the present invention have created a product that is easy to mold and has high efficiency even though it has almost the same resin layer structure: a polyethylene resin layer for the inner layer, a saponified ethylene vinyl acetate copolymer layer for the middle layer, and a polyolefin resin layer for the outer layer. Moreover, it has a long-term stable high oxygen gas barrier property and excellent heat shrinkage resistance.
Moreover, as a result of intensive research and various experiments to obtain a container with good moldability, we were able to create an outer container made of paper with plastic coating on both sides, with a specific gravity of 0.92 to 0.95.
Melt index 1-7, thickness 0.2mm-0.5
A polyethylene resin layer (hereinafter simply referred to as a polyethylene resin layer) having a thickness of 0.01 mm to 0.1 mm, a saponified ethylene vinyl acetate copolymer layer (hereinafter simply referred to as an EVAL layer) having a thickness of 0.01 mm to 0.1 mm, and a melt index of 3 or less. It consists of three layers: a polyolefin resin layer (hereinafter simply referred to as a polyolefin resin layer) with a thickness of 0.1 mm to 0.25 mm, and these three layers are formed using a molded material that is integrated in this order. , by making the container into which a plastic inner container is inserted, which is molded so that the polyethylene resin layer becomes the inner layer and the drawing ratio is within the range of 0.7 to 1.5, the purpose can be easily achieved. This is the result of the present invention.

An example of the implementation of the present invention will be described below with reference to the accompanying drawings. Reference numeral 1 is a piece of paper in the shape of a pot. 2 is plastic coated on both sides of the paper 1, and is used as a paper outer container 3. 4 is a polyethylene resin layer, the specific gravity of the polyethylene resin used for this is 0.92 to 0.95, and the melt index (when the resin is heated to 190±2℃ and an actual load is applied, The amount of resin flowing out in 10 minutes (expressed in gr) is 1 to 7,
The thickness of forming the layer is 0.2 mm to 0.5 mm. 5 is the Eval layer, and the thickness of that layer is 0.01
mm~0.1mm. 6 is a polyolefin resin layer, the melt index of this polyolefin resin is 3 or less, and the thickness of this layer is 0.1 mm to 0.25 mm. These three layers, the polyethylene resin layer 4, the EVAL layer 5, and the polyolefin resin layer 6, are integrated in this order to form the molding material 7.
becomes. A plastic inner container 8 is molded using this molding material 7. At this time, the polyethylene resin layer 6 is molded as the inner layer of the plastic inner container 8, and its drawing ratio (depth/diameter)
is molded so that it is within the range of 0.7 to 1.5. Plastic inner container 8 molded in this way
is inserted into the paper outer container 3 to form a container. Note that the means for sealing this container is optional, but
In order to obtain high and stable oxygen gas barrier properties, it is preferable to use the following method. For example, the inner lid 11 may be formed by laminating a polyethylene film 10 on the aluminum foil 9, and the polyethylene film 10 of the inner lid 11 may be heat-sealed so as to be in contact with the container. The outer cover 12 is made of a suitable plastic molded product and is fitted over the inner cover 11 described above.

FIG. 3 shows a state in which when the plastic inner container 8 is inserted into the paper outer container 3, there is a slight gap 13 between the paper outer container 3 and the plastic inner container 8. The specific gravity of the polyethylene resin used in the present invention is within the range of 0.92 to 0.95, and the specific gravity is 0.92 to 0.95.
Resins with smaller specific gravity have poor rigidity, so when molded products are made, they lack stiffness, have poor shape retention, and have poor impact resistance, making them more likely to break if accidentally dropped, as well as lower water vapor permeability. It is high and has poor moisture resistance, so it is necessary to have a value within the range of 0.95 to 0.95. In addition, a melt index in the range of 1 to 7 is used, but if the melt index is low, the molding temperature range is narrow and molding is difficult, and when the sheet is heated and molded, internal distortion is large, resulting in poor product quality. After the sheet is old, thermal deformation is likely to occur when heated at a low temperature of 100℃ or less for sterilization, etc. On the other hand, if the melt index is large, the sheet will sag when heated and wrinkles will occur during molding. A range of 7 is required. Furthermore, the thickness of the polyethylene resin layer that makes up the molding material needs to be in the range of 0.2 mm to 0.5 mm. If the thickness is too thin, cold impact resistance will be weak, which is undesirable, and water vapor will easily pass through, so water vapor will not be able to penetrate into the adjacent EVAL layer. Sufficient thickness is also required to reduce transmission as much as possible. In other words, although the EVAL layer has excellent gas barrier properties, it also has the property of easily absorbing moisture, and when it absorbs moisture, its gas barrier properties deteriorate rapidly. When storing liquid, it is necessary to block future water vapor transmission as much as possible, and for this reason, it is necessary that the thickness is 0.2 mm to 0.5 mm.

The thickness of the EVAL layer, which is the molding material used in the present invention, must be in the range of 0.01 mm to 0.10 mm. If the thickness is too thin, the oxygen gas barrier properties after molding will be poor, and if it is too thick, a large amount of heat will be generated during molding. need,
This heat has an adverse effect on other resin layers, and if this heat is insufficient, cracks will appear in EVAL, resulting in extremely poor gas barrier properties.

Examples of the polyolefin resin used in the present invention include polyethylene and polypropylene resins, but polyethylene and polypropylene may not only be used alone, but also a mixture of polyethylene and polypropylene. The polyolefin resin used has a melt index of 3 or less, but a polyolefin resin having a melt index higher than this is not preferred because the sheet sags when heated and wrinkles tend to occur around the sheet during molding. In particular, when polypropylene is used, it is preferable to use a blend of rubber-based resin in order to improve cold impact resistance. Furthermore, the thickness of the polyolefin resin layer that forms the molding material must be in the range of 0.1 mm to 0.25 mm; if it is too thin, the molded product will lack rigidity and will be easily deformed by external force, and if it is too thick, the oxygen gas in the EVAL layer will It also causes a sudden decrease in barrier properties. In other words, the EVAL layer easily absorbs moisture;
Moreover, as mentioned earlier, the gas barrier property deteriorates rapidly when moisture is absorbed, but even if water vapor from the contained contents such as soft drinks and juices is permeated and absorbed by the EVAL layer, this water vapor The gas barrier properties of the EVAL layer will not deteriorate rapidly unless a large amount of the EVAL layer accumulates in the EVAL layer. Therefore, making the polyolefin resin layer, which is the outer layer of the plastic inner container, thicker in order to maintain its shape, etc. will force the water vapor absorbed in the EVAL layer to accumulate in the EVAL layer without letting it escape to the outside. As a result, the gas barrier properties of the EVAL layer will decrease rapidly in a short period of time.In this regard, by thinning the outer polyolefin resin layer, water vapor from inside the container will be able to reach the EVAL layer. Since the gas is not forced to stagnate and is allowed to pass out easily, the gas barrier properties of the EVAL layer do not deteriorate rapidly.

In the molding material of the present invention, an adhesive layer may be formed between each layer constituting the material by coextrusion, or each layer may be formed separately and then integrated.

Any method may be used to mold the plastic inner container of the present invention from a molding material, and for example, pressure molding is an example of a preferred molding method.

The thickness of the polyethylene resin layer in the molding material used in the present invention is 0.2 mm to 0.5 mm, the thickness of the EVAL layer is 0.01 mm to 0.1 mm, and the thickness of the polyolefin resin layer is 0.1 mm to 0.25 mm. , between these resin layers, especially the polyethylene resin layer that is to become the inner layer of the container, and the polyolefin resin layer, even if the thickness is within the above thickness range, the polyethylene resin layer is always thicker than the polyolefin resin layer. The thickness of the layer must be increased. By doing so, the polyethylene resin layer provides shape retention and prevents water vapor from permeating into the EVAL layer, while the polyolefin resin layer prevents water vapor from escaping from the EVAL layer. It is something that can be played.

The container obtained by the present invention can store any item, and is suitable for storing all kinds of things such as liquids, solids, granules, powder fluids, etc.
Containers specifically intended to block oxygen gas,
Alternatively, it is extremely preferable as a container or the like which is intended to be housed in a container together with oxygen gas to prevent the oxygen gas filled inside from escaping.

The container of the present invention, especially the plastic inner container, can be molded very easily despite the drawing ratio being 0.7 to 1.5, and the polyethylene resin that forms the inner layer has a specific gravity of 0.92 to 1.5. 0.95, with a melt index of 1 to 7, and the thickness of the molding material layer was 0.2 mm to 0.5 mm, so the shape retention of the inner container was extremely good.
It also has excellent impact resistance and has a low water vapor permeability, so the water vapor in the contents is less likely to be absorbed into the EVAL layer, so there is no sudden drop in oxygen gas barrier properties due to absorption of water, and it can be used for a long period of time. In addition, stable oxygen gas barrier properties can be maintained, and concerns about deterioration of the contents have been completely eliminated.

In addition, the polyolefin resin layer that is the outer layer sufficiently plays the role of a heat insulating layer because the EVAL layer is easy to mold, and is also thick enough to allow water vapor absorbed by the EVAL layer to easily pass through. There was no possibility of any sudden loss of gas barrier properties.

The container obtained according to the present invention can be molded to a uniform thickness without any local unevenness in thickness, and can be molded by high-temperature filling, which is used when filling with juice or other liquids. However, no heat shrinkage occurred. That is, the filling material is heated mainly for the purpose of sterilizing the filling material itself, and then filled into containers in the heated state, and the temperature at the time of filling is around 80°C for youth products. In some cases, it is heated to a temperature of around 95°C, and when the filling heated to this temperature is filled into a container, the resin layer that makes up the container,
In particular, conventional containers have had problems such as heat shrinkage of the resin in the inner layer and deformation of the container, but the container obtained by the present invention has good heat shrinkage resistance and can be filled at high temperatures. also does not cause heat shrinkage,
Therefore, there is no risk of deformation of the container, and it has good heat shrinkage resistance that cannot be obtained with conventional containers of this type.
Moreover, it is an extremely excellent invention that can easily provide a container that has excellent moldability and can be stored stably for a long period of time.

[Brief explanation of drawings]

The accompanying drawings show an example of the implementation of the present invention,
FIG. 1 is a longitudinal sectional view showing an example of a molding material, FIG. 2 is a longitudinal sectional view showing an example of a container, and FIG. 3 is a longitudinal sectional view showing another example of a container. 1: paper, 2: plastic coat layer, 3: paper outer container, 4: polyethylene resin layer, 5: EVAL layer, 6: polyolefin resin layer, 7: molding material,
8: Plastic inner container.

Claims (1)

[Claims] 1 A paper outer container coated with plastic on both sides has a specific gravity of 0.92 to 0.95 and a melt index of 1.
~7. A polyethylene resin layer with a thickness of 0.2 mm to 0.5 mm, a saponified ethylene vinyl acetate copolymer layer with a thickness of 0.01 mm to 0.1 mm, and a melt index of 3 or less and a thickness of It consists of three layers, including a polyolefin resin layer with a thickness of 0.1 mm to 0.25 mm, and these three layers are integrated in this order using a molded material, so that the polyethylene resin layer becomes the inner layer, and the drawing ratio is adjusted. 1. A container characterized in that a plastic inner container is inserted, which is molded so that the value is within the range of 0.7 to 1.5.