plastic containers

Abstract

To provide a plastic container with excellent recyclability.SOLUTION: According to the present invention, a plastic container for storing content includes, in order from the inner surface of the container, an inner layer, an inner adhesive layer, a gas barrier layer, an outer adhesive layer, and an outer layer, and the content of EVOH resin in the container is 5% by mass or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a plastic container.

Background Art

[0002] Patent Document 1 discloses a plastic container capable of containing contents such as mayonnaise. [[ID=十三]]<00000十>

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a plastic container such as that of Patent Document 1, a large amount of plastic is consumed, and from the perspective of environmental measures, it is strongly desired to make the material monomaterial (single material) and thus improve the recyclability by monomaterialization.

[0005] The present invention has been made in view of such circumstances, and provides a plastic container having excellent recyclability.

Means for Solving the Problems

[0006] According to the present invention, there is provided a plastic container for containing contents, which includes, in order from the inner surface side of the container, an inner layer, an inner adhesive layer, a gas barrier layer, an outer adhesive layer, and an outer layer, and the content rate of EVOH resin in the container is 5% by mass or less.

[0007] By adopting this configuration, the content of dissimilar constituent materials (EVOH resin) is reduced, or in other words, the content of similar constituent materials is increased. This allows for the monomaterialization of plastic containers and improves their recyclability. In other words, it is possible to provide plastic containers with excellent recyclability.

[0008] The following are examples of various embodiments of the present invention. The embodiments shown below can be combined with each other. Preferably, the plastic container is as described above, wherein a reproduction layer is provided between the inner layer and the inner adhesive layer, and the thickness of the inner adhesive layer is less than the thickness of the outer adhesive layer. Preferably, the plastic container is as described above, wherein a reproduction layer is provided between the inner layer and the inner adhesive layer, and the ratio of the thickness of the gas barrier layer to the thickness of the inner adhesive layer or the outer adhesive layer is 4.0 or more. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view showing the plastic container 1 and cap 13. [Figure 2] This is a diagram showing the layer structure of plastic container 1. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature can stand alone as an independent invention.

[0011] 1. Composition of plastic containers

[0012] Figure 1 shows a schematic diagram of a plastic container 1 according to one embodiment of the present invention. As shown in Figure 1, the plastic container 1 is a container for holding contents. Examples of contents include viscous substances such as mayonnaise and ketchup.

[0013] The plastic container 1 dispenses its contents by constricting the body 14, etc., through a spout 12 with a screw thread 11. The spout 12 is usually sealed with a cap 13. The plastic container 1 is a blow-molded body formed by blow molding. Details of blow molding will be described later.

[0014] The plastic container 1 has a multilayer structure. Figure 2 shows an example of the layer structure of the plastic container 1, and from the inner side of the plastic container 1, it comprises, in order, the innermost layer 2 (corresponding to the "inner layer" of the present invention), the repro layer 3, the adhesive resin layer 4 (corresponding to the "inner adhesive layer" of the present invention), the gas barrier layer 5, the adhesive resin layer 6 (corresponding to the "outer adhesive layer" of the present invention), and the outermost layer 7 (corresponding to the "outer layer" of the present invention). The layer structure of the plastic container 1 may also include other layers in addition to these layers.

[0015] The EVOH (ethylene vinyl alcohol copolymer) resin content in the plastic container 1 is 4.5 to 5% by mass, i.e., 5% by mass or less. Specifically, the EVOH resin content in the plastic container 1 may be, for example, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0% by mass, and may be within the range of any two of the values ​​exemplified here. By adopting such a configuration, the content of dissimilar constituent materials (EVOH resin) is reduced, in other words, the content of the same type of constituent material is increased, thereby promoting monomaterialization of the plastic container 1 and improving its recyclability. This is particularly useful when promoting monomaterialization of relatively large plastic containers 1, such as those with a capacity of 300g or more. In other words, it is possible to provide a plastic container 1 with excellent recyclability.

[0016] The ratio of the thickness of each layer to the thickness of the plastic container 1 (side wall) is, for example, as follows: Innermost layer 2: 5-20% Reproductive stage 3:30-60% Adhesive resin layer 4: 0.2~3% Gas barrier layer 5:1-4% Adhesive resin layer 6:0.2~3% Outermost layer 7: 20% - 50%

[0017] The following will explain each layer.

[0018] (Innermost layer 2) The innermost layer 2 is the layer arranged on the innermost side of the plastic container 1 and in contact with the contents, and is composed of a resin composition containing a resin (preferably a thermoplastic resin). Examples of the resin include polyolefin (e.g., polyethylene, polypropylene), polyester (e.g., PET), EVOH, nylon, etc. The resin composition may contain only the resin or may contain the resin and additives. Examples of the additives include lubricants and fillers.

[0019] (Outermost layer 7) The outermost layer 7 is the layer arranged on the outermost side of the plastic container 1 and is composed of a resin composition containing a resin (preferably a thermoplastic resin). Examples of the resin include polyolefin (e.g., polyethylene, polypropylene), polyester (e.g., PET), EVOH, nylon, etc. The resin composition may contain only the resin or may contain the resin and additives. Examples of the additives include lubricants and fillers. The outermost layer 7 and the innermost layer 2 are composed of the same kind of material.

[0020] (Repro layer 3) The repro layer 3 is disposed between the innermost layer 2 and the outermost layer 7. The repro layer 3 is composed of a resin composition containing a repro material obtained by recycling the scrap generated during the molding of the plastic container 1. Since the scrap includes all the layers of the plastic container 1 (the innermost layer 2, the repro layer 3, the adhesive resin layers 4 and 6, the gas barrier layer 5, the outermost layer 7), the repro material is a mixture of the resin compositions constituting each of all the layers of the plastic container 1. The repro layer 3 may also be composed of, in addition to the repro material, the same resin as the innermost layer 2 (the outermost layer 7). Further, the repro layer 3 may be separately composed of the same kind of material as the innermost layer 2 (the outermost layer 7), which is the main component of the repro material. In particular, by composing it to include a biomass resin as the same kind of material as the repro material, a more environmentally considerate plastic container 1 can be obtained.

[0021] (Gas barrier layer 5) The gas barrier layer 5 is composed of a resin having high gas barrier properties. Examples of such resins include EVOH and aromatic polyamides. By providing the gas barrier layer 5, oxidative degradation of the contents due to oxygen permeation can be effectively suppressed.

[0022] The gas barrier layer 5 is preferably disposed between the repro layer 3 and the outermost layer 7. By disposing the gas barrier layer 5 closer to the outermost layer 7 than the repro layer 3, an increase in the relative humidity of the gas barrier layer 5 due to the moisture of the contents is suppressed. Since the oxygen permeation rate of EVOH increases when the relative humidity increases, by disposing the gas barrier layer 5 closer to the outermost layer 7 than the repro layer 3, an increase in the oxygen permeation rate can be suppressed. The ethylene content of EVOH is more preferably 27 mol% or less.

[0023] (Adhesive resin layers 4, 6) The adhesive resin layers 4 and 6 are composed of an adhesive resin. Examples of the adhesive resin include acid-modified polyolefin resins (e.g., maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene). By providing the adhesive resin layers 4 and 6, the adhesiveness between the gas barrier layer 5 and the outermost layer 7 or the repro layer 3 is improved.

[0024] From the viewpoint of improving recyclability by promoting the monomaterialization of the plastic container 1, it is preferable to reduce the amount of adhesive resin layer 4 in the plastic container 1 by making the thickness of adhesive resin layer 4 smaller than the thickness of adhesive resin layer 6. Since the repro layer 3 is composed of the resin composition that makes up adhesive resin layers 4 and 6, even if the thickness of adhesive resin layer 4 is smaller than the thickness of adhesive resin layer 6, adhesion between the gas barrier layer 5 and the repro layer 3 can be ensured.

[0025] Furthermore, from the viewpoint of promoting the monomaterialization of the plastic container 1 and improving recyclability, it is preferable to set the ratio of the thickness of the gas barrier layer 5 to the thickness of the adhesive resin layers 4 and 6 to 4.0 or more, that is, to reduce the amount of adhesive resin layers 4 and 6 in the plastic container 1 by making the thickness of the adhesive resin layers 4 and 6 smaller than that of the gas barrier layer 5. Since the repro layer 3 is composed of the resin composition that makes up the adhesive resin layers 4 and 6, even if the thickness of the adhesive resin layer 4 is reduced, the adhesion between the gas barrier layer 5 and the repro layer 3 can be ensured. The ratio of the thickness of the gas barrier layer 5 to the thickness of the adhesive resin layers 4 and 6 is preferably 4.0 to 10.0, specifically for example 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0, and may also be within the range of any two of the values ​​exemplified here.

[0026] 2. Method for manufacturing plastic containers The plastic container 1 can be formed by blow molding a parison. The blow molding may be direct blow molding or injection blow molding. In direct blow molding, the plastic container 1 is manufactured by sandwiching a molten cylindrical parison extruded from an extruder between a pair of split molds and blowing air into the parison. In injection blow molding, a test tube-shaped bottomed parison called a preform is formed by injection molding, and blow molding is performed using this parison.

[0027] In any blow molding process, the layer structure of the parison is the same as that of the plastic container 1. Multilayer parisons can be formed by co-extrusion molding, multilayer injection molding, or the like.

[0028] When forming a plastic container 1 by direct blow molding, the portion of the cylindrical parison within the cavity formed by a pair of split molds becomes the plastic container 1, while the portion other than the plastic container 1 becomes scrap. This scrap contains the constituent materials of all the layers that make up the plastic container 1. By subjecting this scrap to recycling treatment such as crushing, a reproducible material can be obtained. [Examples]

[0029] 1. Manufacturing of plastic container 1 (Example 1) A plastic container 1 (with a capacity of 400g) having the shape shown in Figure 1 and the layer structure shown in Figure 2 was manufactured. The plastic container 1 was manufactured by extruding a cylindrical parison from a multilayer die head using co-extrusion molding of the constituent resin or resin composition, and performing known direct blow molding. The EVOH resin content in the plastic container 1 is 4.5% by mass. From the viewpoint of improving recyclability by promoting monomaterialization of the plastic container 1, the amount of adhesive resin layer 4 in the plastic container 1 was reduced by making the thickness of adhesive resin layer 4 smaller than the thickness of adhesive resin layer 6. Since the repro layer 3 is composed of the resin composition that makes up adhesive resin layers 4 and 6, adhesion between the gas barrier layer 5 and the repro layer 3 can be ensured even if the thickness of adhesive resin layer 4 is smaller than the thickness of adhesive resin layer 6. The ratio of the thickness of each layer (composition) to the thickness of the plastic container 1 (side wall) is as follows. Note that the ratio of the thickness of each layer to the thickness of the plastic container 1 refers to the average value of the ratio measured at 12 points in the circumferential direction at a height of 90 mm from the bottom of the plastic container 1. Innermost layer 2 (low-density polyethylene (LDPE)): 14.4% Reproduction layer 3 (reproduction material): 48.1% Adhesive resin layer 4 (acid-modified polyolefin resin): 1.3% Gas barrier layer 5 (EVOH, ethylene ratio: 27 mol%): 2.9% Adhesive resin layer 6 (acid-modified polyolefin resin): 2.0% Outermost layer 7 (low-density polyethylene (LDPE)): 31.3%

[0030] The properties of plastic container 1 are as follows: Container weight: 16.26g Bottle height: 200.60mm Nozzle height: 195.72 mm Height of screw part: 192.10mm Shoulder height: 178.06 mm Shoulder-to-nozzle height: 17.66mm Shoulder-to-twist joint height: 14.03mm Nozzle height: 22.54mm Mouth outer diameter: 17.68mm Nozzle inner diameter: 14.91 mm Seal thickness: 1.39mm Nozzle lower diameter: 16.64 mm Screw thread diameter: 22.34mm Screw valley diameter: 20.33mm Shoulder diameter: 28.28mm Body width (long diameter / short diameter): 76.0mm / 53.3mm Body width major axis / mouth outer diameter: 76.0mm / 17.68mm(4.3) Minimum wall thickness: 0.24mm Buckling strength: 3.70 kgf (measured by compressing the mouth of an empty container (compression strength: 50 mm / min))

[0031] The thickness distribution of plastic container 1 is shown in Table 1 below. The thickness distribution was measured at 16 locations at 10 mm intervals from the bottom of plastic container 1, and at 12 locations in the circumferential direction. [Table 1]

[0032] (Example 2) A plastic container 1 (360g capacity) having the shape shown in Figure 1 and the layer structure shown in Figure 2 was manufactured. The plastic container 1 was manufactured by co-extrusion molding of the constituent resin or resin composition, extruding a cylindrical parison from a multilayer die head, and performing known direct blow molding. The EVOH resin content in the plastic container 1 is 5.0% by mass. The ratio of the thickness of the gas barrier layer 5 to the thickness of the adhesive resin layers 4 and 6 was set to 5.0. In other words, from the viewpoint of promoting monomaterialization of the plastic container 1 and improving recyclability, the amount of adhesive resin layers 4 and 6 in the plastic container 1 was reduced by reducing the thickness of the adhesive resin layers 4 and 6 relative to the gas barrier layer 5. Since the repro layer 3 is composed of the resin composition that makes up the adhesive resin layers 4 and 6, adhesion between the gas barrier layer 5 and the repro layer 3 can be ensured even if the thickness of the adhesive resin layer 4 is reduced. The ratio of the thickness of each layer to the thickness of the plastic container 1 (side wall) is as follows. The ratio of the thickness of each layer to the thickness of the plastic container 1 represents the average value of the ratios measured at four points in the circumferential direction at a height of 50 mm from the bottom of the plastic container 1. Innermost layer 2 (low-density polyethylene (LDPE)): 12.4% Reproduction layer 3 (reproduction material): 46.6% Adhesive resin layer 4 (acid-modified polyolefin resin): 0.6% Gas barrier layer 5 (EVOH, ethylene ratio: 27 mol%): 3.0% Adhesive resin layer 6 (acid-modified polyolefin resin): 0.6% Outermost layer 7 (low-density polyethylene (LDPE)): 36.8%

[0033] The properties of plastic container 1 are as follows: Container weight: 14.81g Bottle height: 189.60mm Nozzle height: 185.05 mm Height above screw section: 181.46 mm Shoulder height: 167.47mm Shoulder-to-nozzle height: 17.58mm Shoulder-to-twist joint height: 13.99mm Nozzle height: 22.12mm Mouth outer diameter: 17.69mm Nozzle inner diameter: 14.80 mm Seal thickness: 1.43mm Nozzle lower diameter: 16.76 mm Screw thread diameter: 22.35mm Screw root diameter: 20.28mm Shoulder diameter: 28.54mm Body width (long diameter / short diameter): 70.7mm / 47.7mm Body width major axis / mouth outer diameter: 70.7mm / 17.69mm(4.0) Minimum wall thickness: 0.27mm Buckling strength: 4.80 kgf (measured by compressing the mouth of an empty container (compression strength: 50 mm / min))

[0034] The thickness distribution of plastic container 1 is shown in Table 2 below. The thickness distribution was measured at 17 locations at 10 mm intervals from the bottom of plastic container 1, and at 12 locations in the circumferential direction. [Table 2]

[0035] 2. Drop test A drop test was conducted on the plastic container 1 of Examples 1 and 2. In the drop test, the plastic container 1 was filled with room temperature water, and then the cap 13 was attached to the spout 12 to seal the plastic container 1. The sample was then dropped three times from a height of 1.2 m with the bottom facing downwards. As a result, no samples cracked in either Example 1 or 2, and good results were obtained. [Explanation of Symbols]

[0036] 1: Plastic container 2: Innermost layer 3: Reproductive layer 4: Adhesive resin layer 5: Gas barrier layer 6: Adhesive resin layer 7: Outermost layer 11: Screw thread 12: Outlet 13: Cap 14: Torso

Claims

1. A plastic container for holding contents, The container comprises, in order from the inner surface side, an innermost layer, an inner adhesive layer, a gas barrier layer, an outer adhesive layer, and an outermost layer. The container has a reproduction layer only between the innermost layer and the inner adhesive layer. The EVOH resin content in the container is 4.5 to 5.0% by mass. The innermost layer and the outermost layer are each composed of a resin composition containing polyolefin. The aforementioned gas barrier layer is made of EVOH resin. The reproduction layer is composed of a resin composition containing reproduction material. The aforementioned repro material is a material obtained by recycling scrap generated during the molding of the plastic container. A plastic container in which the thickness of the inner adhesive layer is less than the thickness of the outer adhesive layer.

2. A plastic container according to Claim 1, The resin composition constituting the repro layer is a plastic container containing a biomass resin.

3. A plastic container according to claim 1 or claim 2, A plastic container in which the ratio of the thickness of the gas barrier layer to the thickness of the inner adhesive layer or the outer adhesive layer is 4.0 or more.

4. A plastic container according to any one of Claims 1 to 3, A plastic container in which the EVOH resin has an ethylene content of 27 mol% or less.

5. A plastic container according to any one of Claims 1 to 4, A plastic container with a net weight of 300g or more.

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