Multi-layer blow-molded container

Abstract

To provide a multi-layer blow-molded container that is allowed to inhibit a component of a content from infiltrating from an inner layer into an outer layer, excellent in drop strength of a container body and easy to recover by separating the outer layer from the inner layer after using the content.SOLUTION: A multi-layer blow-molded container, having a container body forming a receiving region structured with a laminate of three or more layers consisting of a resin material, includes an inner layer that is constituted of a polyolefin virgin resin material, an outer layer that is constituted of a polyolefin-virgin or polyolefin-reclaimed resin material and is arranged closer to a container exterior than the inner layer, and an intermediate layer that is constituted of a resin material having gas-barrier properties and is arranged between the inner layer and the outer layer. The inner layer has a thickness of 1% or more and 15% or less than a thickness of the outer layer, the intermediate layer has at least one surface abutting against the inner or outer layer without interposing an adhesion layer. The resin materials making up the inner and outer layers each have an elastic modulus as measured conforming to JIS K 7171 of 800 MPa or greater.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multi-layer blow-molded container, a method for separating and recovering the same, and the like. [Background technology]

[0002] 2. Description of the Related Art Resin molded containers formed by blow molding (blow molded containers) are widely used as containers for storing everyday products such as shampoo, hand soap, detergent, and fabric softener.

[0003] In addition, against the background of environmental issues and the need to reduce the amount of plastic resource used, blow molded containers using recycled resins have also been developed. For example, Patent Document 1 discloses a multi-layer blow container having at least an outer layer and an inner layer, in which at least one of the outer layer and the inner layer is a resin composition containing a specific metallocene-based polyethylene, and an intermediate layer between the outer layer and the inner layer is a specific recycled polyolefin resin, and the multi-layer blow container contains 5% by mass or more of the resin composition containing the metallocene-based polyethylene relative to the total mass. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-95144 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, when recycling used blow-molded containers as container raw materials (material recycling), it is often the case that the aroma components (fragrant components, etc.) and surfactant components contained in the contents as described above permeate and are adsorbed into the used blow-molded container. In particular, containers made of polyolefin-based resin materials are prone to adsorb the aroma components, etc., while it is not easy to remove the aroma components, etc. from the resin, so that it tends to be difficult to obtain high-grade recycled raw materials from such used blow-molded containers. One method for solving this problem is to separate and recover the layer (inner layer) arranged on the inside side of the container from the layer (outer layer) arranged on the outside side of the container for the used multi-layer blow-molded container, but it tends to be difficult to achieve both the ease of separating and recovering the inner layer and the outer layer of the multi-layer blow-molded container and the drop strength of the container body (drop strength when the contents are contained in it). In addition, if the aroma components, etc. have permeated to a certain extent into the outer layer, this method cannot solve the above problem.

[0006] The present invention has been made in consideration of the above-mentioned problems, and relates to a multi-layer blow-molded container that can suppress penetration of components of the contained contents from the inner layer to the outer layer, has excellent drop strength of the container body, and further allows the inner layer and outer layer to be easily separated and recovered after use of the contained contents. [Means for solving the problem]

[0007] The present invention relates to a multi-layer blow-molded container in which a container body forming a storage area has a laminated structure formed by laminating three or more layers made of resin materials, the laminated structure including an inner layer made of a polyolefin-based virgin resin material, an outer layer made of a polyolefin-based virgin resin material or a polyolefin-based recycled resin material and disposed outside the container relative to the inner layer, and an intermediate layer made of a resin material having gas barrier properties and disposed between the inner layer and the outer layer, the layer thickness of the inner layer being 1% to 15% of the layer thickness of the outer layer, at least one surface of the intermediate layer being in contact with the inner layer or the outer layer without an adhesive layer, and the resin material constituting the inner layer and the resin material constituting the outer layer both having a modulus of elasticity of 800 MPa or more, measured in accordance with JIS K 7171. Effect of the Invention

[0008] According to the present invention, it is possible to provide a multi-layer blow-molded container which can suppress the penetration of components of the contained contents from the inner layer to the outer layer, has excellent drop strength of the container body, and further allows the inner layer and outer layer to be easily separated and recovered after use of the contained contents. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a multilayer blow-molded container according to an embodiment of the present invention, with a part of the container body cut away, and a cross-sectional view showing the layered structure of the container body. [Diagram 2] 10 is a cross-sectional view of a layered structure of a container body in a modified example of a multilayer blow-molded container according to an embodiment of the present invention. FIG. [Diagram 3] 10 is a cross-sectional view of a layered structure of a container body in a further modified example of a multilayer blow-molded container according to an embodiment of the present invention. FIG. [Figure 4] FIG. 1 is a cross-sectional view of the laminated structure of a container body of a multilayer blow-molded container according to an embodiment of the present invention, and plastic flakes obtained by crushing or shredding the same. [Diagram 5] FIG. 2 is a list showing the layer configuration of the laminate structure of the multilayer blow-molded container sample produced in the Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are given the same reference numerals, and duplicated descriptions are omitted as appropriate. In addition, in some drawings, there are some parts that are not given reference numerals (omitted) for convenience. Furthermore, the dimensional ratios of each member shown in the drawings may differ from the actual dimensional ratios in order to facilitate understanding of the invention.

[0011] [Overall structure] First, the overall configuration of an embodiment of a multilayer blow molded container and a containerized product using the same according to the present invention will be described with reference to Figs. 1 to 3 and the like. The multi-layer blow molded container according to the present invention includes the following embodiments.

[0012] The multilayer blow molded container 100 according to the present embodiment includes a container body 11 forming a storage area 41 for storing contents, and a laminated structure 20 formed by laminating three or more layers made of resin materials. The laminated structure 20 includes an inner layer 21 made of a polyolefin virgin resin material, an outer layer 25 made of a polyolefin virgin resin material or a polyolefin recycled resin material and disposed on the outer side of the container than the inner layer 21, and an intermediate layer 23 made of a resin material having gas barrier properties and disposed between the inner layer 21 and the outer layer 25. The thickness of the inner layer 21 is 1% to 15% of the thickness of the outer layer 25, and at least one surface of the intermediate layer 23 is laminated in contact with the inner layer 21 or the outer layer 25 without an adhesive layer 27. The elastic modulus (flexural modulus) of the resin material constituting the inner layer 21 and the resin material constituting the outer layer 25 measured in accordance with JIS K 7171 is 800 MPa or more.

[0013] For example, a multi-layer blow molded container 100 according to this embodiment may be an embodiment as shown in FIG. Specifically, the container body 11 forming the storage area 41 and the opening 31 integrated therewith may be a multilayer blow molded container 100 having a laminated structure 20 formed by laminating three layers made of a predetermined resin material. The laminated structure 20 includes a predetermined inner layer 21, a predetermined outer layer 25 disposed on the outer side of the container than the inner layer 21, and a predetermined intermediate layer 23 disposed between the inner layer 21 and the outer layer 25. In the embodiment of FIG. 1, both sides of the intermediate layer 23 are in contact with the inner layer 21 and the outer layer 25 without an adhesive layer 27 therebetween. As a modified example, the laminated structure 20 provided in the container body 11 of the multilayer blow molded container 100 according to the present embodiment may be an embodiment in which the intermediate layer 23 is bonded to the inner layer 21 via the adhesive layer 27 (for example, a four-layer structure as shown in FIG. 2 ) or an embodiment in which the intermediate layer 23 is bonded to the outer layer 25 via the adhesive layer 27 (for example, a four-layer structure as shown in FIG. 3 ) as long as one surface of the intermediate layer 23 is in contact with the inner layer 21 or the outer layer 25 without the adhesive layer 27. Furthermore, as long as the above configuration is satisfied, the laminated structure 20 may be an embodiment further including a layer (resin layer) made of a resin material other than the inner layer 21, the intermediate layer 23, the outer layer 25, and the adhesive layer 27. The details of the laminated structure 20 and the inner layer 21, the intermediate layer 23, the outer layer 25, the adhesive layer 27, etc. will be described later.

[0014] Furthermore, the multilayer blow molded container 100 according to this embodiment is provided with an opening 31 through which contents can be accommodated (injected, etc.) and discharged, together with the container body 11. It is more preferable that this opening 31 has a plug structure that can be repeatedly opened and closed as shown in Fig. 1, but is not limited thereto. It is preferable that this plug structure has a screw thread that can be sealed with a cap, a cap with a pump, a spout, or the like. In other words, it is preferable that the opening 31 of this multilayer blow molded container 100 has a screw thread and can be sealed with a cap of a separate member that also has a screw thread. Furthermore, the multilayer blow molded container 100 according to this embodiment may further include other members as long as the effects of the present invention are not adversely affected. However, from the viewpoints of the drop strength of the container body 11 and the difficulty of peeling of the layers of the laminated structure 20 when the contents are used, it is more preferable that the multilayer blow molded container 100 according to this embodiment is an embodiment that does not include a member (such as an air hole) that can introduce outside air between the layers of the laminated structure 20.

[0015] The capacity of the multilayer blow molded container 100 according to this embodiment (the volume of the storage area 41 for storing the contents, i.e., the maximum amount of the contents that can be stored, the filling amount) is not limited, but from the viewpoint of maintaining a high level of drop strength, it is preferably 1000 ml or less, more preferably 800 ml or less, and even more preferably 600 ml or less. The lower limit is preferably 50 ml or more, and more preferably 100 ml or more.

[0016] Then, by using such a multi-layer blow molded container 100 according to the present embodiment, a containerized product can be obtained in which the contents are accommodated in the accommodation area 41 of the container body 11 and sealed with a cap or the like. When using the contents accommodated in this containerized product, for example, if the contents are liquid contents (liquid), the liquid can be pumped out using a cap with a pump or the like and used. In addition, the cap or the like may be removed and the container body 11 may be tilted to discharge the contents. The type of contents accommodated in the multi-layer blow molded container 100 according to the present embodiment is not particularly limited, but examples include shampoo, rinse, conditioner, hand soap, body soap, facial cleanser, detergent, fabric softener, bleach, disinfectant, etc., and liquid (including paste-like) contents are preferable. When the content is liquid, the viscosity is preferably, for example, 1 mPa s or more at 30°C, and is preferably 120,000 mPa s or less, and more preferably 60,000 mPa s or less (both measured with a B-type viscometer (e.g., Viscometer TV-10 or Viscometer TVB-10 manufactured by Toki Sangyo Co., Ltd.)). However, it may also be possible to store and use content other than liquid (powders, granular materials, granular materials, etc.).

[0017] [Laminated structure] Next, an embodiment of a laminate structure provided at least in a container body of a multilayer blow molded container according to the present invention will be described in detail with reference to Figs. 1 to 3 and the like.

[0018] The laminated structure 20 provided at least in the container body 11 of the multilayer blow molded container 100 according to this embodiment includes an inner layer 21, an outer layer 25, and an intermediate layer 23, all of which are layers made of a resin material. The multilayer blow molded container 100 according to this embodiment is formed by blow molding so that at least the container body 11 has such a laminated structure 20. Therefore, the container body 11 surrounding the storage area 41 in which the contents are stored in the multilayer blow molded container 100 is formed by laminating three or more layers made of a resin material. Note that members other than the container body 11 of the multilayer blow molded container 100 according to this embodiment (e.g., the opening 31, etc.) may also have this laminated structure 20, and for example, the entire member formed integrally with the container body 11 of the multilayer blow molded container 100 according to this embodiment (blow molded integrally) may substantially have this laminated structure 20. In this laminated structure 20 , the outer layer 25 is disposed closer to the outside of the container than the inner layer 21 , and the intermediate layer 23 is disposed between the inner layer 21 and the outer layer 25 . Here, "made of a resin material" means that the mass ratio of the resin material to the total mass is 70% or more, more preferably 75% or more, even more preferably 80% or more, even more preferably 85% or more, and even more preferably 90% or more. Therefore, these layers may partially contain materials (e.g., antistatic agents) other than the resin material (polymer resin material). In addition, the "outer side of the container" refers to the outer surface side opposite to the storage area 41 side of the container body 11 of the multilayer blow molded container 100 as shown in FIG. 1. The same applies to other cases. The inner layer 21, the outer layer 25, and the intermediate layer 23, as well as embodiments of their joining or abutting, will be described in detail below.

[0019] <Inner layer> The inner layer 21 is a layer made of a polyolefin-based virgin resin material. The inner layer 21 does not substantially contain recycled resin materials or resin materials other than polyolefin-based resins. The inner layer 21 is disposed closer to the inside of the container than the outer layer 25 and the intermediate layer 23 in the laminated structure 20. For example, in the embodiment of FIG. 1, the inner layer 21 is disposed as the innermost layer that directly contacts the contents contained in the containing area 41 of the multilayer blow-molded container 100. Here, "polyolefin-based (resin material)" refers to a polymer resin material in which an olefin-based hydrocarbon skeleton (e.g., an ethylene skeleton, a propylene skeleton, etc.) accounts for more than 50% of the molecular weight (the "polyethylene-based" and "polypropylene-based" described below have the same definition). Also, "virgin resin material" refers to a new resin material (a resin material that does not include recycled products) produced from raw materials such as petroleum. Furthermore, "inner side of the container" refers to the inner side of the container body 11 on the side of the storage area 41 of the multilayer blow-molded container 100 as shown in FIG. 1. The same applies to other cases.

[0020] The polyolefin-based virgin resin material constituting the inner layer 21 is not limited as long as it is a material having a predetermined flexural modulus described later and does not include recycled resin materials or resin materials other than polyolefins. For example, virgin resin materials such as polyethylene-based resin, polypropylene-based resin, and adhesive polyolefin capable of constituting an adhesive layer described later can be mentioned. Two or more of these may be mixed and used. The polyethylene-based resin includes high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra-low density polyethylene (ULDPE), and the like. Biopolyethylene (BioPE) obtained by dehydrating and polymerizing bioethanol produced from sugarcane molasses and the like is also included. Furthermore, two or more of these may be mixed and used. In particular, from the viewpoint of the strength of the container itself (such as the difficulty of deformation when the contents are used), it is more preferable that the inner layer 21 is made of high density polyethylene (HDPE) which is a virgin resin material (containing 70% or more of HDPE by mass).

[0021] The polyolefin-based virgin resin material (or the mixed material in the case of a mixture) constituting the inner layer 21 has a modulus of elasticity (flexural modulus) of 800 MPa or more as measured in accordance with JIS K 7171. The flexural modulus of the resin material constituting the specified inner layer 21 and the flexural modulus of the resin material constituting the specified outer layer 25 described later are both at least a specified value, so that the multilayer blow molded container 100 according to this embodiment has excellent drop strength of the container body 11. In addition, when the contents are used, the layers of the laminated structure 20 are less likely to peel off (such as peeling between layers due to use of the contents). The flexural modulus of the polyolefin-based virgin resin material constituting the inner layer 21 is more preferably 880 MPa or more, more preferably 1000 MPa or more, and even more preferably 1200 MPa or more.

[0022] In addition, since it is easy to increase the ease of peeling between the inner layer 21 and the outer layer 25 and the ease of separation and recovery (recyclability) while maintaining a high drop strength of the container body 11, it is preferable that the polyolefin-based virgin resin material constituting the inner layer 21 contains less than 50% by mass of an adhesive polyolefin, which will be described later. For example, the polyolefin-based virgin resin material constituting the inner layer 21 contains a polyethylene-based virgin resin material and an adhesive polyolefin of the virgin resin material, and the polyethylene-based virgin resin material is more than 50% by mass, more preferably 60% by mass or more, and even more preferably 70% by mass or more of the total amount of the polyolefin-based virgin resin material, and the adhesive polyolefin of the virgin resin material is less than 50% by mass, more preferably 40% by mass or less, and even more preferably 30% by mass or less. The lower limit of the mass ratio of this adhesive polyolefin may be 5% by mass or more, or may be 10% by mass or more. In the co-extrusion of the parison used in blow molding, the material for the inner layer 21 may be, for example, a dry blend of a predetermined amount of a polyethylene-based virgin resin material and an adhesive polyolefin of the virgin resin material.

[0023] The inner layer 21 may be a multi-layer structure in which a plurality of layers made of a polyolefin-based virgin resin material are laminated, but from the viewpoint of ease of manufacture, it is more preferable that the inner layer 21 is a single layer (single layer) made of a polyolefin-based virgin resin material. Here, the terms "single layer" and "multi-layer" are based on the layer structure in blow molding. The same applies to the outer layer 25 and intermediate layer 23 described below.

[0024] The thickness of the inner layer 21 is 1% to 15% of the thickness of the outer layer 25. This allows the plastic flakes 51 including the inner layer 21 and the plastic flakes 51 including the outer layer 25 to be easily separated by wind sorting or the like after the container body 11 or the like is crushed or shredded. Even in an embodiment in which both sides of the intermediate layer 23 are in contact with the inner layer 21 and the outer layer 25 without the adhesive layer 27, as described below, the intermediate layer 23 is more likely to be separated from the contact surface between the inner layer 23 and the outer layer 25 by crushing or shredding, etc., due to differences in the concentration of physical stress caused by the difference in layer thickness. In addition, even in the above embodiment, the moldability during blow molding can be maintained high and appearance disturbance can be highly suppressed due to the difference in layer thickness. In order to easily achieve both moldability and separation and recovery, the thickness of the inner layer 21 is preferably 2% or more, more preferably 3% or more, and the upper limit is preferably 12% or less, more preferably 10% or less, more preferably 8% or less, and even more preferably less than 5% of the thickness of the outer layer 25. The specific thickness of the inner layer 21 is not limited as long as it satisfies the above ratio, but is preferably 15 μm or more and 100 μm or less, with the lower limit being more preferably 20 μm or more, more preferably 25 μm or more, and the upper limit being 80 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less. Here, the “layer thickness” refers to the linear distance between both surfaces (main surface, outer surface) of the inner layer 21 (D2 in FIG. 1), and is a value obtained by measuring the layer thickness of the inner layer 21 at any 10 points by, for example, observing the cross section of the laminated structure 20 under an optical microscope, and calculating the average value.

[0025] <Outer layer> The outer layer 25 is a layer made of a polyolefin-based virgin resin material or a polyolefin-based recycled resin material. The outer layer 25 does not substantially contain any resin material other than polyolefin. The outer layer 25 is disposed on the outer side of the container than the inner layer 21 and the intermediate layer 23 in the laminated structure 20. Here, the term "recycled resin material" refers to a resin material (recycled resin material) obtained by recycling resin products such as used resin containers. The same applies to other materials.

[0026] The resin material constituting the outer layer 25 is not limited as long as it has a predetermined flexural modulus described later and does not contain a resin material other than polyolefin-based, and examples thereof include the polyethylene-based resin and polypropylene-based resin described above. Two or more of these may be mixed and used. Also, a polyolefin-based virgin resin raw material and a polyolefin-based recycled resin raw material may be mixed and used. In particular, from the viewpoint of the strength of the container itself, it is preferable that the outer layer 25 is made of high density polyethylene (HDPE). Furthermore, in addition to the viewpoint of the strength of the container itself, it is more preferable that the inner layer 21 and the outer layer 25 are both made of high density polyethylene (HDPE) because it makes multilayer blow molding easier.

[0027] The polyolefin virgin resin material or polyolefin recycled resin material (mixture of materials in the case of a mixture) constituting the outer layer 25 also has a modulus of elasticity (flexural modulus) of 800 MPa or more as measured in accordance with JIS K 7171. The flexural modulus of the resin material constituting the specified outer layer 25 and the flexural modulus of the polyolefin virgin resin material constituting the specified inner layer 21 described above are both equal to or greater than a predetermined value, so that the multilayer blow molded container 100 according to this embodiment has excellent drop strength of the container body 11. Furthermore, when the contents are used, the layers of the laminated structure 20 are less likely to peel off (such as peeling off between layers due to use of the contents). The flexural modulus of the resin material constituting the outer layer 25 is more preferably 880 MPa or more, more preferably 1000 MPa or more, and even more preferably 1200 MPa or more.

[0028] Furthermore, this outer layer 25 may be a multi-layer consisting of multiple layers made of polyolefin-based virgin resin material, layers made of polyolefin-based recycled resin material, or layers made of a mixed material of polyolefin-based virgin resin material and polyolefin-based recycled resin material (for example, a multi-layer consisting of a layer made of polyolefin-based virgin resin material and a layer made of polyolefin-based recycled resin material), but from the standpoint of ease of manufacture, it is more preferable for it to be a single layer (single layer) made of a specified polyolefin-based resin material.

[0029] The thickness of this outer layer 25 is not limited, but from the standpoint of container strength and ease of separation and recovery, it is preferably 500 μm or more and 1000 μm or less, with the upper limit being preferably 900 μm or less, even more preferably 800 μm or less, and even more preferably 700 μm or less. Here, this “layer thickness” also refers to the linear distance between both surfaces (main surface, outer surface) of the outer layer 25 (D4 in FIG. 1), and is a value obtained by measuring the layer thickness of the outer layer 25 at any 10 points by observing the cross section of the laminated structure 20 with an optical microscope or the like, and calculating the average value.

[0030] <Middle Class> The intermediate layer 23 is a layer made of a resin material having gas barrier properties. Therefore, the intermediate layer 23 has gas barrier properties, and is disposed between the inner layer 21 and the outer layer 25 in the laminated structure 20, suppressing the penetration of components contained in the contents (permeation of aroma components such as perfume components, surfactant components, etc.) from the inner layer 21 side to the outer layer 25 side.

[0031] The resin material having gas barrier properties constituting the intermediate layer 23 is not limited as long as the intermediate layer 23 is a resin material that can provide gas barrier properties, but ethylene vinyl alcohol copolymer (EVOH) is shown as a preferred resin material. This is because even if a part of the resin remains in the outer layer 25 during separation and recovery, it has very little effect on material recycling. In addition, nylon (Ny) and the like can also be used. Furthermore, polyvinyl alcohol (PVA), polyvinylidene chloride (PVDC), and the like may also be used. Note that the resin material constituting the intermediate layer 23 does not need to be a polyolefin-based resin material, but from the viewpoint of the recyclability of the outer layer 25 made of a polyolefin-based resin material, it is preferable to use the above-mentioned ethylene vinyl alcohol copolymer (EVOH) that contains a certain amount of ethylene skeleton in the polymer molecule. In addition, this may contain a recycled resin material as long as the intermediate layer 23 can provide gas barrier properties, but it is more preferable to use a virgin resin material because it is easy to maintain high gas barrier properties. The gas barrier property (gas permeability) of the intermediate layer 23 is, but is not limited to, 100 mL / m at 23° C. and 65% RH. 2 ·day·atm or less (measured using a MOCON OX-TRAN2 / 21ML in accordance with a method conforming to JIS K7126), and 2 ·day·atm or less is preferable, and 10mL / m 2 It is even more preferable that the temperature is 100°C or less.

[0032] In addition, this intermediate layer 23 may be a multi-layer structure in which multiple layers made of resin material having gas barrier properties are laminated together, but from the standpoint of ease of manufacture, it is more preferable that it be a single layer (single layer) made of resin material having gas barrier properties.

[0033] The thickness of the intermediate layer 23 is preferably 1% to 5% of the total thickness of the laminated structure 20, and more preferably 1% to 4%. This is because the intermediate layer 23 can be easily separated from the vicinity of the intermediate layer 23 by crushing or shredding. This also increases the polyolefin resin content of the multilayer blow molded container 100 according to the present embodiment. In addition, even in the case of an embodiment in which the intermediate layer 23 is bonded to the outer layer 25 via the adhesive layer 27 as described below, the effect on the recyclability of the outer layer 25 can be extremely reduced. The specific thickness of the intermediate layer 23 is not limited, but is preferably 15 μm to 50 μm, and more preferably 20 μm to 40 μm. In the case of an embodiment in which the intermediate layer 23 is bonded to the outer layer 25 via the adhesive layer 27 as described below, the thickness of the intermediate layer 23 is preferably 5% or less of the total thickness of the outer layer 25, and more preferably 4% or less. Here, this "layer thickness" is also the linear distance between both surfaces (principal surface, outer surface) of intermediate layer 23 (D3 in FIG. 1), and is a value obtained by measuring the layer thickness of intermediate layer 23 at any 10 points by observing the cross section of laminate structure 20 with an optical microscope or the like, and calculating the average value. Similarly, the "total thickness" of laminate structure 20 is also the linear distance between both outermost surfaces of laminate structure 20 (D1 in FIG. 1), and is also a value obtained by measuring the total thickness (the thickness of the entire laminate structure 20) at any 10 points by observing the cross section of laminate structure 20 with an optical microscope or the like, and calculating the average value.

[0034] Furthermore, in this laminated structure 20, if the total thickness (D2+D3 in FIG. 1), which is the sum of the layer thickness of the intermediate layer 23 and the layer thickness of the inner layer 21, is 15% or less of the layer thickness of the outer layer 25, it is preferable because the separation and recovery property of the outer layer 25 (separation and recovery of the outer layer 25, the inner layer 21, and the intermediate layer 23) is easily improved. The upper limit is more preferably 12% or less, and more preferably 10% or less. The lower limit may be 3% or more, or may be 5% or more. In addition, it is more preferable that the layer thickness of the intermediate layer 23 satisfies the ratio to the total thickness of the laminated structure 20 described above. In the case of an embodiment in which the intermediate layer 23 is bonded to the inner layer 21 via the adhesive layer 27 as described later, it is more preferable that the total thickness of the layer thickness of the intermediate layer 23, the layer thickness of the inner layer 21, and the layer thickness of the adhesive layer 27 therebetween is within the above range.

[0035] <Adhesive layer> The laminated structure 20 provided in the container body 11 of the multilayer blow molded container 100 according to this embodiment may have, in addition to the inner layer 21, the outer layer 25, and the intermediate layer 23 described above, an adhesive layer 27 made of a resin material having a function of bonding the intermediate layer 23 to the inner layer 21 or the outer layer 25. The material constituting the adhesive layer 27 is not limited as long as the adhesive layer 27 is a resin material capable of bonding the above-mentioned layers together, but adhesive polyolefin (modified polyolefin in which a functional group is introduced into polyolefin to impart adhesiveness, such as NB508 manufactured by Mitsui Chemicals, Inc.) is shown as a preferred resin material. This is because even if a portion of the polyolefin remains in the outer layer 25 during separation and recovery, it has very little effect on recyclability. In addition, an adhesive polyolefin-based polymer alloy (such as Modic manufactured by Mitsubishi Chemical Corporation) in which polyolefin is chemically modified with a polymerizable vinyl monomer can also be used. On the other hand, from the viewpoint of recyclability, it is more preferable that the adhesive layer 27 is substantially free of polyester resin (adhesive polyester resin).

[0036] In the laminated structure 20 provided in the container body 11 of the multilayer blow-molded container 100 according to this embodiment, as described above, at least one surface of the intermediate layer 23 abuts against the inner layer 21 or the outer layer 25 without an adhesive layer 27. That is, in this laminated structure 20, the inner layer 21 and the intermediate layer 23 abut against each other without an adhesive layer 27, and / or the outer layer 25 and the intermediate layer 23 abut against each other without an adhesive layer 27. Therefore, the multilayer blow-molded container 100 according to this embodiment does not include an embodiment in which the inner layer 21 and the intermediate layer 23 are bonded to each other via the adhesive layer 27 and the outer layer 25 and the intermediate layer 23 are bonded to each other via the adhesive layer 27 in the laminated structure 20. Here, when the layers are "in contact" with each other, it means that the surfaces (main surfaces, outer surfaces) of the layers are in physical contact with each other. When the layers (layer surfaces) are "in contact" with each other without an adhesive layer, it means that the layers (layer surfaces) are not bonded to each other by an adhesive layer (for example, a layer made of an adhesive material, or a fusion interface formed by thermal melting of layers), and are in contact with each other in an unfixed state. The layers in the laminated structure 20 that are in contact with each other without an adhesive layer 27 have an adhesive force that provides the container body 11 of the multilayer blow molded container 100 according to this embodiment with a predetermined drop strength by being combined with other configurations, etc.

[0037] An example of an embodiment in which the laminate structure 20 has the adhesive layer 27 is an embodiment in which the intermediate layer 23 in the laminate structure 20 is bonded to the inner layer 21 via the adhesive layer 27, as shown in FIG. 2. In this embodiment, the outer layer 25 and the intermediate layer 23 are in contact with each other without the adhesive layer 27. This makes it easier for the intermediate layer 23 to form plastic flakes 51 together with the inner layer 21 when separated from the contact area between the outer layer 25 and the intermediate layer 23 by crushing or shredding, and makes it easier to separate and recover the outer layer 25. In other words, the intermediate layer 23 is less likely to remain in the inner layer 21. For example, in the above embodiment, when adhesive layer 27 is made of adhesive polyolefin, intermediate layer 23 made of a resin material having gas barrier properties and functional groups of the adhesive polyolefin of adhesive layer 27 chemically react with each other to bond, while inner layer 21 made of a polyolefin-based virgin resin material and adhesive layer 27 are compatible with each other to bond, and it is presumed that these bond intermediate layer 23 and inner layer 21 via adhesive layer 27.

[0038] 3, an embodiment is also exemplified in which the intermediate layer 23 in the laminated structure 20 is bonded to the outer layer 25 via an adhesive layer 27. In this embodiment, the inner layer 21 and the intermediate layer 23 are in contact with each other without the adhesive layer 27. This makes it easier to maintain high drop strength of the container body 11. In this embodiment, it is presumed that the same bonding as above is performed when the adhesive layer 27 is made of adhesive polyolefin.

[0039] Here, the thickness of the adhesive layer 27 is not limited, but is preferably 5 μm or more and 25 μm or less, and more preferably 10 μm or more and 20 μm or less. This "layer thickness" is also the straight-line distance between both surfaces (main surface, outer surface) of adhesive layer 27, and is a value obtained by measuring the layer thickness of adhesive layer 27 at any 10 locations by observing the cross section of laminated structure 20 with an optical microscope, for example, and calculating the average value.

[0040] On the other hand, from the viewpoint of achieving a high level of compatibility between suppression of appearance disturbance during blow molding and improvement of separation and recovery, it is preferable that the laminated structure 20 does not include this adhesive layer 27. In other words, it is preferable that both sides (both main sides) of the intermediate layer 23 in the laminated structure 20 are in contact with the inner layer 21 and the outer layer 25 without the adhesive layer 27. For example, as shown in Fig. 1, it is preferable that the laminated structure 20 is composed of three layers, the inner layer 21, the outer layer 25, and the intermediate layer 25, and both sides of the intermediate layer 23 are laminated in contact with the inner layer 21 and the outer layer 25 without the adhesive layer 27, because this makes it easier to exhibit the above-mentioned effects. In addition, the adhesion (adhesion or adhesion without an adhesive material) between a layer made of ethylene vinyl alcohol copolymer (EVOH) and a layer made of polyethylene resin (PE) or polypropylene resin (PP) is low in co-extrusion, and an adhesive layer made of an adhesive material is usually required between these layers. However, in the multilayer blow molded container 100 according to this embodiment, by satisfying the above-mentioned predetermined layer thickness ratio and bending elastic modulus of the constituent materials, even if the intermediate layer 23 is made of EVOH, and the inner layer 21 and the outer layer 25 are made of PE or PP, and further the adhesive layer 27 is not included, they are in close contact and blow molding can be performed without problems, and in this case, the number of layers can be reduced, making it easier to suppress appearance disturbance during blow molding. In addition, the drop strength is also excellent. In particular, it is preferable that the laminated structure 20 is a three-layer structure of the inner layer 21, the outer layer 25, and the intermediate layer 25, all of which are single layers, because the above-mentioned effect is more easily exhibited.

[0041] <Other configurations> The laminated structure 20 of the multilayer blow molded container 100 according to this embodiment may further include other layers (layers made of materials other than resin materials) in addition to the above-mentioned inner layer 21, outer layer 25, intermediate layer 23, adhesive layer 27, and other resin layers. For example, the outermost layer of the laminated structure 20 may include a printed layer on which the name and ingredients of the contents are printed or a pattern is applied, or a coating layer coated with cellulose nanofibers (CNF) or the like as a functional layer having functions such as water resistance, abrasion resistance, mold resistance, and light resistance (especially ultraviolet resistance) for the purpose of protecting the multilayer blow molded container 100 during distribution, etc. However, from the viewpoint of making the material recycling of the multilayer blow molded container 100 easier, it is more preferable that the laminated structure 20 does not include the printed layer or functional layer. On the other hand, the multilayer blow-molded container 100 of this embodiment may also be provided with a separate component formed separately from the container body 11, such as a shrink film or a roll-up label wrapped around the container body 11 to cover it, which performs the same function as the printed layer and functional layer described above.

[0042] The total thickness of the laminated structure 20 of the multilayer blow molded container 100 of this embodiment (the total thickness of the entire laminated structure 20 including printed layers, coating layers, etc. if they are included, the aforementioned D1) is not limited, but is preferably 550 μm or more, more preferably 600 μm or more, even more preferably 700 μm or more, and is preferably 1000 μm or less, more preferably 900 μm or less.

[0043] The laminated structure 20 provided in the container body 11 of the multilayer blow molded container 100 according to this embodiment configured as described above can suppress the penetration of components of the contents from the inner layer 21 to the outer layer 25, and the drop strength of the container body 11 (drop strength when the contents are contained therein) is excellent, and further, the inner layer 21 and the outer layer 25 can be easily separated and recovered after the contents are used. Then, a high-grade recycled material (material recycled material) can be obtained from the separated and recovered outer layer 25.

[0044] [Method for separating and recovering multi-layer blow molded containers] Next, an embodiment of the method for separating and recovering a multilayer blow molded container according to the present invention will be described in detail with reference to FIG.

[0045] The multilayer blow-molded container 100 of this embodiment, configured as described above, not only has excellent drop strength for the container body 11 when it contains the contents, but also makes it easy to separate and recover the inner layer 21 and outer layer 25 by crushing or shredding after the contents have been used. Furthermore, since penetration of the components of the contents from the inner layer 21 to the outer layer 25 is suppressed, the outer layer 25 can be separated and recovered for recycling to obtain high-grade recycled raw material. As a method for separating and recovering the multi-layer blow-molded container 100 of this embodiment, for example, an embodiment is shown that includes a plastic flake formation process in which the used multi-layer blow-molded container 100 of this embodiment is crushed or shredded to form plastic flakes 51, and a separation and recovery process in which the plastic flakes 51 including the inner layer 21 and the plastic flakes 51 including the outer layer 25 are separated from the plastic flakes 51 by sorting, and the plastic flakes 51 including the outer layer 25 are recovered.

[0046] The method of crushing or shredding the multilayer blow molded container 100 according to this embodiment in the plastic flake formation step is not particularly limited, and a method is shown in which the used multilayer blow molded container 100 according to this embodiment is crushed or shredded into small pieces, for example, several mm square, by a known crusher or shredder after cleaning the storage area 41 if necessary. By this crushing or shredding, layers that are in contact with each other without the adhesive layer 27 tend to be easily separated from each other (for example, FIG. 4), but in order to make this separation easier, a process of applying vibration during, before, or after the crushing or shredding may be performed. Furthermore, in cases where the crushing or shredding is performed without cleaning the storage area 41, the obtained plastic flakes 51 may be washed.

[0047] The sorting method in the separation and recovery step is not limited, but since there is a difference in thickness between the plastic flakes 51 including the inner layer 21 and the plastic flakes 51 including the outer layer 25 due to the above-mentioned structure, it is preferable to perform wind sorting by utilizing this difference in thickness (weight difference). Also, in cases where the intermediate layer 23 is made of EVOH, separation and sorting can also be performed based on the functional groups using optical methods such as near-infrared. The above-mentioned washing of the plastic flakes 51 may be performed after this sorting.

[0048] Furthermore, the method for separating and recovering the multilayer blow molded container 100 according to this embodiment may include any other steps than those described above, provided that the effects of the present invention are not affected. For example, the method may include a washing step, a drying step, or the like, as described above. Note that, in the method for separating and recovering the multilayer blow molded container 100 according to this embodiment, since the multilayer blow molded container 100 according to this embodiment has the configuration described above, a step for removing aroma components, etc. (such as a deodorizing step) is not required.

[0049] The plastic flakes 51 including the outer layer 25 thus obtained can be used to form a high-grade recycled resin material (polyolefin-based recycled resin material) by, for example, dissolving, pelletizing, and drying. The multilayer blow-molded container 100 according to this embodiment can also be manufactured using this recycled resin material for the outer layer 25. In other words, a horizontal recycling system for the multilayer blow-molded container 100 can be constructed in which the multilayer blow-molded container 100 after the contents contained therein have been used up is recycled into a material to be used for manufacturing a similar multilayer blow-molded container 100.

[0050] [Method for manufacturing multi-layer blow molded containers] Next, an embodiment of a method for producing a multi-layer blow molded container according to the present invention will be described.

[0051] The multilayer blow-molded container 100 of this embodiment can be manufactured by a method including a container molding step in which the multilayer blow-molded container 100 is formed by blow molding from these materials, for example, by making the inner layer 21 of the laminated structure 20 forming the container body 11 etc. out of a polyolefin-based virgin resin material, making the intermediate layer 23 out of a resin material having gas barrier properties, and making the outer layer 25 out of a polyolefin-based virgin resin material or a polyolefin-based recycled resin material (such as the recycled resin material described above).

[0052] An example of blow molding is a method in which the resin materials (melt of resin materials) that make up each layer are co-extruded through a multilayer extrusion die to extrude a cylindrical parison (a laminated parison of three or more layers), and then this is blown into shape using a blow molding die positioned below the die.

[0053] As described above, the resin material constituting the outer layer 25 may contain polyolefin-based recycled resin material. From the viewpoint of further increasing the efficiency of material recycling, it is preferable to adjust the content of polyolefin-based recycled resin material in the resin material constituting the outer layer 25 to be 30% by mass or more and 70% by mass or less.

[0054] Hereinafter, examples of the present invention will be described, however, the present invention is not limited to the following examples, and various modifications are possible within the technical concept of the present invention. EXAMPLES

[0055] Using predetermined materials, four types of multilayer blow molded containers were produced, each having a container body and an opening with a predetermined laminated structure (samples 1 to 4, capacity (filled amount) of 500 ml). Specifically, the resin materials (melt) constituting each layer were co-extruded from a multi-layer extrusion die to extrude each cylindrical parison (laminated parison) so that the resin materials constituting the inner layer, intermediate layer, and outer layer were configured as shown in Figure 5, and then blow molded using a blow molding die positioned below the die. As shown in Figure 5, an adhesive layer (Admer) was disposed between the inner layer and intermediate layer in the laminated structure of Sample 3, and between the intermediate layer and outer layer in the laminated structure of Sample 4. The inner layer in the laminated structure of Sample 2 was made of a resin material in which HDPE and Admer were mixed in a mass ratio of 3:1.

[0056] Here, HDPE shown in FIG. 5 is high density polyethylene (Hi-Zex 6008B manufactured by Prime Polymer Co., Ltd., with a modulus of elasticity measured according to JIS K 7171 of 1260 MPa), EVOH is an ethylene vinyl alcohol copolymer (F171B manufactured by Kuraray Co., Ltd.), and Admer is an adhesive polyolefin (NB508 manufactured by Mitsui Chemicals Co., Ltd.). The modulus of elasticity measured according to JIS K 7171 of a resin material in which HDPE and Admer are mixed at a mass ratio of 3:1 is 1220 MPa. In addition, in each sample, the layer thickness of the inner layer in the laminated structure was 30 to 40 μm, the layer thickness of the intermediate layer was 30 μm, the layer thickness of the outer layer was 700 μm, and the layer thickness of the adhesive layer was 10 to 20 μm. Then, for each multilayer blow-molded container sample, the moldability (lack of disturbance in appearance), ease of peeling of the laminated structure, recyclability, drop strength, and lack of odor transfer of the contained liquid to the outer layer (penetration of aroma components) were confirmed as follows.

[0057] The moldability (absence of appearance disturbance) of the produced multilayer blow molded containers was evaluated as follows: ◯: those with no appearance disturbance, △: those with slight appearance disturbance, and ×: those with noticeable appearance disturbance. The ease of peeling of the laminated structure was evaluated by crushing the resulting multilayer blow-molded containers, drying them, and then air sorting them. If the outer layer was separated and recovered at 90 wt% or more of the theoretical value, it was evaluated as ◎; if the outer layer was separated and recovered at 70-80 wt% of the theoretical value, it was evaluated as 〇; if the outer layer was separated and recovered at 50-60 wt% of the theoretical value, it was evaluated as △; and if the outer layer was separated and recovered at less than 50 wt% of the theoretical value, it was evaluated as ×. Recyclability was evaluated by comparing the MFR (melt flow rate) value at 190°C of the recycled resin material obtained from the plastic flakes including the outer layer recovered after crushing and drying the obtained multilayer blow molded containers and air sorting them with the outer layer resin material before molding the multilayer blow container. If the change rate was within 5% it was rated as ◎, if the change rate was within 10% it was 〇, if the change rate was within 20% it was △, and if the change rate was more than 20% it was rated as ×. The MFR at 190°C was measured at 190°C under a load of 2.16 kg in accordance with JIS K 7210. The drop strength was evaluated by pouring 500 ml of water into the storage area of ​​the obtained multilayer blow molded container and allowing it to fall naturally from a height of 1 m. Those for which no peeling or cracking was observed were rated as ◎, those for which no cracking or almost no peeling was observed were rated as △, and those for which peeling or cracking was observed were rated x. To evaluate the lack of odor transfer of the contained liquid to the outer layer, 500 ml of fabric softener liquid (Kao Corporation's Humming Deodorizer Rose & Floral Scent) was placed in the storage area of ​​the resulting multilayer blow-molded container and stored at 40°C for one month. The resulting plastic flakes including the outer layer were then washed, crushed, dried, and air-sorted. A sensory evaluation was conducted by multiple panelists on the plastic flakes, with those that had no detectable odor being rated as ◯, those that had a slight detectable odor being △, and those that had a strong detectable odor being rated as ×.

[0058] The results of these evaluations are also shown in Table 1 below. These results show that all of the multilayer blow molded containers of Samples 1 to 4 are capable of suppressing the penetration of aroma components of the contents from the inner layer to the outer layer, have excellent drop strength for the container body, etc., and are multilayer blow molded containers that are easy to separate and recover the inner and outer layers after the contents have been used. In particular, all of the multilayer blow molded containers of Sample 1, which does not use Admer, received very favorable evaluation results.

[0059] [Table 1] [Explanation of symbols]

[0060] 100 Multi-layer blow molded container 11 Container body 20 Laminated structure 21 Inner layer 23 Middle Class 25 Outer layer 31 Opening 41 Containment Area 51 Plastic Flakes D1 Total thickness of the laminate D2 Inner layer thickness D3 Thickness of the intermediate layer D4 Outer layer thickness

Claims

1. A multi-layer blow-molded container having a laminated structure in which a container body forming a storage area is formed by laminating three or more layers made of a resin material, The laminated structure includes an inner layer made of a polyolefin-based virgin resin material, an outer layer made of a polyolefin-based virgin resin material or a polyolefin-based recycled resin material and disposed on the outer side of the container than the inner layer, and an intermediate layer made of a resin material having gas barrier properties and disposed between the inner layer and the outer layer, The thickness of the inner layer is 1% or more and 15% or less of the thickness of the outer layer, At least one surface of the intermediate layer is in contact with the inner layer or the outer layer without an adhesive layer therebetween; The elastic modulus of the resin material constituting the inner layer and the resin material constituting the outer layer, as measured in accordance with JIS K 7171, is 800 MPa or more. Multi-layer blow molded container.

2. 2. The multilayer blow-molded container according to claim 1, wherein both sides of the intermediate layer in the laminated structure are in contact with the inner layer and the outer layer without an adhesive layer therebetween.

3. The multi-layer blow-molded container according to claim 1 , wherein the intermediate layer in the laminate structure is bonded to the inner layer via an adhesive layer.

4. The multi-layer blow-molded container according to claim 1 , wherein the intermediate layer in the laminate structure is bonded to the outer layer via an adhesive layer.

5. The multilayer blow molded container according to any one of claims 1 to 4, wherein the layer thickness of the intermediate layer is 1% or more and 5% or less of the total thickness of the laminated structure.

6. The multilayer blow molded container according to any one of claims 1 to 5, wherein the total thickness of the intermediate layer and the inner layer is 15% or less of the thickness of the outer layer.

7. The multilayer blow molded container according to any one of claims 1 to 6, wherein the polyolefin-based virgin resin material constituting the inner layer contains less than 50% by mass of adhesive polyolefin.

8. The multilayer blow molded container according to any one of claims 1 to 7, wherein the intermediate layer is composed of an ethylene-vinyl alcohol copolymer.

9. The multilayer blow-molded container according to any one of claims 1 to 8, wherein the inner layer and the outer layer are both made of high-density polyethylene.

10. A containerized product comprising the multilayer blow molded container according to any one of claims 1 to 9, and an item accommodated in the accommodation region of the multilayer blow molded container.

11. A plastic flake forming step of crushing or shredding the used multilayer blow molded container according to any one of claims 1 to 9 into plastic flakes; A separation and recovery process for separating the plastic flakes including the inner layer and the plastic flakes including the outer layer from the plastic flakes by sorting, and recovering the plastic flakes including the outer layer. A method for separating and recovering multi-layer blow molded containers.

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