Multi-layered sheet and packaging container manufactured using same

Abstract

The present invention relates to a multi-layered sheet and a packaging container manufactured using the multi-layered sheet, the multi-layered sheet comprising: a first surface layer; a first core layer; a barrier layer; a second core layer; and a second surface layer, wherein each of the first core layer and the second core layer comprises a recycled polypropylene-based resin.

Description

Multilayer sheet and packaging container manufactured using the same

[0001] The present invention relates to a multilayer sheet capable of improving environmental issues while reducing the use of virgin plastic, and a packaging container manufactured using the multilayer sheet.

[0002] Many global CPG (Consumer Packaged Goods) companies are announcing sustainability strategies that include reducing plastic usage and minimizing the use of virgin plastics made from petroleum-derived naphtha. Among these plastics, plastic packaging containers are a key target for CPG companies, and recycling technologies for these containers are being developed to achieve this goal. Food packaging containers, in particular, come into direct contact with food, requiring careful consideration of recycling technologies and materials for safety reasons.

[0003] The above plastic recycling methods are broadly categorized into mechanical recycling (MR) and chemical recycling (CR). Mechanical recycling allows food contact of recycled products within constraints such as high-level prior screening, a limited supply chain for waste plastics, or a clear source of previous use. On the other hand, chemical recycling breaks waste plastics down into oligomers or monomers and then repolymerizes them to produce recycled products. Therefore, it offers a wide range of materials suitable for food contact.

[0004] Meanwhile, biomass-based plastics, utilizing plant resources, are emerging as a technology and material to replace petroleum-based naphtha-based plastics. Specifically, biomass-based plastics include polyethylene (PE) and polypropylene (PP), which are made by polymerizing ethanol extracted from plants like corn and sugarcane. These plastics are classified and applied as eco-friendly materials because they can be produced without the massive carbon dioxide emissions generated during crude oil extraction.

[0005] However, since the biomass-based plastic uses edible plant resources such as corn and sugarcane as its raw materials, it is not free from issues such as famine and food shortages due to regional imbalances in the world, and has limitations in its wide application due to limited production of materials.

[0006] In addition, when manufacturing plastic packaging containers using the above biomass-based plastic or the plastic obtained through the above recycling method, the emission of carbon dioxide is reduced, thereby improving environmental issues. However, the mechanical properties of the plastic packaging containers are not sufficient, so their use is limited.

[0007] Therefore, there is a need for a technology that can implement plastic packaging containers with secured mechanical properties while replacing the use of plastics based on petroleum naphtha raw materials and biomass-based plastics using edible plant resources.

[0008] In order to solve the above-mentioned conventional problems, the task of the present invention is to provide a multilayer sheet that can reduce the use of virgin plastic and reduce the emission of carbon dioxide by introducing a plastic that can replace plastic based on petroleum naphtha raw materials and plastic based on biomass using edible plant resources.

[0009] In addition, another object of the present invention is to provide a packaging container that is manufactured using the multilayer sheet and thus exhibits excellent mechanical properties and environmental friendliness.

[0010] To achieve the above object, the present invention provides a multilayer sheet comprising a first surface layer; a first core layer; a barrier layer; a second core layer; and a second surface layer, wherein each of the first core layer and the second core layer comprises a recycled polypropylene resin.

[0011] According to one embodiment of the present invention, the content of the recycled polypropylene resin included in the multilayer sheet may be 10 to 90 wt% based on the total weight of the multilayer sheet.

[0012] According to another embodiment of the present invention, each of the first core layer and the second core layer further includes a petroleum-based polypropylene resin, and the content ratio of the recycled polypropylene resin and the petroleum-based polypropylene resin included in each of the first core layer and the second core layer may be a weight ratio of 15 to less than 100: more than 0 to 85.

[0013] According to another embodiment of the present invention, the melt index (@230° C. and 2.16 kg) of the recycled polypropylene resin may be 0.3 to 3.0 g / 10 min.

[0014] According to another embodiment of the present invention, the recycled polypropylene resin may include a component derived from a non-petroleum naphtha raw material.

[0015] According to another embodiment of the present invention, the thickness ratio of the first core layer: the barrier layer: the second core layer may be 5 to 30: 1 to 3: 5 to 30.

[0016] According to another embodiment of the present invention, each of the first surface layer and the second surface layer includes a polypropylene-based resin, and the polypropylene-based resin may include a petroleum-based polypropylene-based resin, a recycled polypropylene-based resin, or a combination thereof.

[0017] According to another embodiment of the present invention, the barrier layer may include at least one selected from the group consisting of ethylene vinyl alcohol-based resin, polyvinyl alcohol-based resin, polyamide-based resin, polyketone-based resin, and metaxylene diamine-based resin.

[0018] According to another embodiment of the present invention, the multilayer sheet may further include a first adhesive layer provided between the first core layer and the barrier layer; and a second adhesive layer provided between the barrier layer and the second core layer.

[0019] According to another embodiment of the present invention, the multilayer sheet may have a thickness of 0.35 to 2.5 mm.

[0020] Meanwhile, the present invention provides a packaging container manufactured from the multilayer sheet.

[0021] The multilayer sheet of the present invention can reduce the amount of carbon dioxide emissions generated by the use of plastics based on petroleum naphtha raw materials by introducing recycled plastics (specifically, recycled polypropylene resins) containing components derived from non-petroleum naphtha raw materials, and can solve the limitations of biomass-based plastics using plant resources (e.g., food shortages, limited production, inability to be universally applied). In addition, the recycled plastic has equivalent physical properties to virgin plastic, so the multilayer sheet of the present invention into which the recycled plastic is introduced can exhibit mechanical properties equivalent to, or in some cases, superior to, those of sheets into which virgin plastic is introduced.

[0022] Therefore, when manufacturing a packaging container using the multilayer sheet of the present invention, an eco-friendly packaging container (specifically, a food packaging container) having excellent mechanical properties and solving issues of odor and safety can be provided.

[0023] FIG. 1 is a cross-sectional view illustrating a multilayer sheet according to one embodiment of the present invention.

[0024] FIG. 2 is a cross-sectional view illustrating a multilayer sheet according to another embodiment of the present invention.

[0025] Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the contents disclosed below, and may be modified in various forms as long as the gist of the invention is not changed.

[0026] The word "comprising" or "including" in this specification is intended to specify particular features, regions, steps, processes, elements and / or components, and does not exclude the presence or addition of other features, regions, steps, processes, elements and / or components, unless specifically stated to the contrary.

[0027] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification are to be understood as being modified by the term “about” in all cases unless otherwise specified.

[0028] In this specification, the terms first, second, etc. are used for the purpose of distinguishing one component from another, and the components are not limited by the terms.

[0029] The sizes of each component in this drawing may be exaggerated for illustration purposes and may differ from the sizes actually applied.

[0030]

[0031] multilayer sheet

[0032] The multilayer sheet of the present invention has the characteristic of introducing a plastic based on non-petroleum naphtha raw materials, which is classified into a different category from plastics based on petroleum naphtha raw materials and biomass-based plastics. Specifically, the multilayer sheet of the present invention comprises a first surface layer; a first core layer; a barrier layer; a second core layer; and a second surface layer, wherein each of the first core layer and the second core layer comprises a recycled polypropylene resin. The multilayer sheet may further optionally include a first adhesive layer and / or a second adhesive layer, as needed.

[0033] In the present invention, the plastic based on non-petroleum naphtha raw materials means recycled plastic obtained based on non-petroleum naphtha raw materials, rather than plastic (virgin plastic) obtained based on conventional petroleum naphtha raw materials.

[0034] The non-petroleum naphtha raw material is not particularly limited, but may include crude tall oil; palm oil refining by-products such as Palm Fatty Acid Distillate (PFAD); or waste oil such as used cooked oil. Accordingly, the plastic based on the non-petroleum naphtha raw material may be a plastic manufactured using the crude tall oil; the palm oil refining by-product; or a recycled raw material (e.g., recycled monomer) obtained by decomposing the waste oil by a method such as pyrolysis.

[0035] Additionally, the non-petroleum naphtha raw material may include waste plastic (waste plastic product). Accordingly, the plastic based on the non-petroleum naphtha raw material may be a plastic manufactured using a recycled raw material (e.g., recycled monomer) obtained by collecting and sorting the waste plastic and then decomposing it through a method such as pyrolysis.

[0036] Specifically, in the present invention, the recycled plastic obtained based on the non-petroleum naphtha raw material may be a recycled polypropylene-based resin, and the recycled polypropylene-based resin may be a polymer manufactured using a recycled monomer (e.g., recycled propylene) obtained from the non-petroleum naphtha raw material. Accordingly, the recycled polypropylene-based resin may include a component derived from the non-petroleum naphtha raw material.

[0037] Meanwhile, in the present invention, the petroleum-based polypropylene resin may be a polymer manufactured using a monomer (e.g., virgin propylene) obtained from a petroleum-based naphtha raw material.

[0038] Hereinafter, the multilayer sheet of the present invention will be described in detail with reference to FIGS. 1 and 2.

[0039]

[0040] First surface layer (10)

[0041] The first surface layer (10) included in the multilayer sheet of the present invention is a layer that serves as a base material in the multilayer sheet, and when manufacturing a packaging container using the multilayer sheet, it may be an inner layer that comes into contact with food, or conversely, an outer layer that is exposed to the outside. For example, when the first surface layer (10) is an inner layer, the second surface layer (50) may be an outer layer, and when the first surface layer (10) is an outer layer, the second surface layer (50) may be an inner layer.

[0042] When the first surface layer (10) is an outer layer, marking or printing may be performed on its surface to disclose brief product information, such as the expiration date and consumption date. This first surface layer (10) may be composed of one layer or two or more layers.

[0043] According to the present invention, the first surface layer (10) may include a polypropylene-based resin. The polypropylene-based resin may include a petroleum-based polypropylene-based resin (a), a recycled polypropylene-based resin (b), or a combination thereof (a+b). Specifically, the first surface layer (10) may be formed solely of the petroleum-based polypropylene-based resin (a) or solely of the recycled polypropylene-based resin (b). That the first surface layer (10) is formed solely of each of the resins means that, based on the total weight of the first surface layer (10), the content of the petroleum-based polypropylene-based resin (a) included in the first surface layer (10) is 100 wt%, or the content of the recycled polypropylene-based resin (b) included in the first surface layer (10) is 100 wt%.

[0044] The above petroleum-based polypropylene resin (a) may have a melting index (@230°C and 2.16 kg) of 0.3 to 3.0 g / 10 min. Specifically, the melting index (@230°C and 2.16 kg) of the petroleum-based polypropylene resin (a) may be, but is not limited to, 0.3 to 2.5 g / 10 min, 0.3 to 2.0 g / 10 min, 0.4 to 1.5 g / 10 min, or 0.4 to 1.0 g / 10 min.

[0045] In addition, the melt index of the recycled polypropylene resin (b) may be 0.3 to 3.0 g / 10 min (@230° C. and 2.16 kg). Specifically, the melt index of the recycled polypropylene resin (b) may be 0.3 to 2.0 g / 10 min, 0.3 to 1.5 g / 10 min, 0.3 to 1.0 g / 10 min, or 0.3 to 0.5 g / 10 min, but is not limited thereto.

[0046] The melt index of the petroleum-based polypropylene resin (a) may be the same as or different from the melt index of the recycled polypropylene resin (b). Specifically, the melt index of the petroleum-based polypropylene resin (a) may be greater than the melt index of the recycled polypropylene resin (b). In addition, the melt index of the petroleum-based polypropylene resin (a) may be less than the melt index of the recycled polypropylene resin (b).

[0047] Since the melting index of each of the above petroleum-based polypropylene resin (a) and the above recycled polypropylene resin (b) is within the above range, a multilayer sheet can be easily manufactured through coextrusion, and processability can be secured when manufacturing a packaging container by thermoforming the multilayer sheet.

[0048] The thickness of the first surface layer (10) is not particularly limited, but when considering the mechanical properties and manufacturing efficiency of the multilayer sheet, if the total thickness of the multilayer sheet is within 2.5 mm, it may be 65 to 90 ㎛, 68 to 88 ㎛, 70 to 86 ㎛, 72 to 84 ㎛, 74 to 82 ㎛, 74 to 80 ㎛, or 76 to 80 ㎛.

[0049]

[0050] 1st core layer (20)

[0051] The first core layer (20) included in the multilayer sheet of the present invention is a layer exhibiting the thickest extrusion thickness among the thicknesses of the multilayer sheet, and includes a recycled polypropylene-based resin (c). This first core layer (20) may be provided between the first surface layer (10) and the barrier layer (30), thereby providing a multilayer sheet that achieves reduction in carbon dioxide emissions while exhibiting mechanical properties equivalent to or superior to those of existing sheets. The first core layer (20) may be formed of one layer or two or more layers.

[0052] According to the present invention, the first core layer (20) may further include a petroleum-based polypropylene resin (d) together with the recycled polypropylene-based resin (c). Specifically, the first core layer (20) may be formed solely of the recycled polypropylene-based resin (c), or may be formed of a combination (c+d) of the recycled polypropylene-based resin (c) and the petroleum-based polypropylene-based resin (d). That the first core layer (20) is formed solely of the recycled polypropylene-based resin (c) means that the content of the recycled polypropylene-based resin (c) included in the first core layer (20) is 100 wt% based on the total weight of the first core layer (20).

[0053] When the first core layer (20) includes the recycled polypropylene-based resin (c) and the petroleum-based polypropylene-based resin (d), the content ratio (c:d) thereof is not particularly limited, but may be a weight ratio of 15 to less than 100: more than 0 to 85. Specifically, the first core layer (20) may include the recycled polypropylene-based resin (c) in an amount of 15 to less than 100 wt%, and the petroleum-based polypropylene-based resin (d) in an amount of more than 0 to 85 wt%, based on the total weight of the first core layer (20). For example, the content ratio (c:d) may be, but is not limited to, a weight ratio of 20 to 95: 5 to 80, a weight ratio of 25 to 90: 10 to 75, a weight ratio of 30 to 85: 15 to 70, a weight ratio of 35 to 80: 20 to 65, a weight ratio of 40 to 75: 25 to 60, a weight ratio of 45 to 70: 30 to 55, a weight ratio of 50 to 65: 35 to 50, or a weight ratio of 55 to 60: 40 to 45. When the content ratio (c:d) is within the above range, a multilayer sheet having mechanical properties equivalent to or higher than those of the above can be provided while achieving a reduction in carbon dioxide emissions.

[0054] The above recycled polypropylene resin (c) may have a melt index (@230°C and 2.16 kg) of 0.3 to 3.0 g / 10 min. Specifically, the melt index (@230°C and 2.16 kg) of the above recycled polypropylene resin (c) may be, but is not limited to, 0.3 to 2.0 g / 10 min, 0.3 to 1.5 g / 10 min, 0.3 to 1.0 g / 10 min, or 0.3 to 0.5 g / 10 min.

[0055] In addition, the petroleum-based polypropylene resin (d) may have a melting index (@230°C and 2.16 kg) of 0.3 to 3.0 g / 10 min. Specifically, the melting index (@230°C and 2.16 kg) of the petroleum-based polypropylene resin (d) may be, but is not limited to, 0.3 to 2.5 g / 10 min, 0.3 to 2.0 g / 10 min, 0.4 to 1.5 g / 10 min, or 0.4 to 1.0 g / 10 min.

[0056] The melt index of the recycled polypropylene resin (c) may be the same as or different from the melt index of the petroleum-based polypropylene resin (d). Specifically, the melt index of the recycled polypropylene resin (c) may be greater than the melt index of the petroleum-based polypropylene resin (d). In addition, the melt index of the recycled polypropylene resin (c) may be less than the melt index of the petroleum-based polypropylene resin (d).

[0057] Since the melting index of each of the above recycled polypropylene resin (c) and the above petroleum-based polypropylene resin (d) is within the above range, a multilayer sheet can be easily manufactured through coextrusion, and when manufacturing a packaging container by thermoforming the multilayer sheet, processability can be secured.

[0058] The thickness of the first core layer (20) is not particularly limited, but when considering the mechanical properties and manufacturing efficiency of the multilayer sheet, if the total thickness of the multilayer sheet is within 2.5 mm, it may be 200 to 500 ㎛, 210 to 450 ㎛, 220 to 400 ㎛, 230 to 350 ㎛, 230 to 300 ㎛, 240 to 260 ㎛, or 250 to 255 ㎛.

[0059]

[0060] Barrier layer (30)

[0061] The barrier layer (30) included in the multilayer sheet of the present invention is a layer that serves to block gases such as moisture and oxygen from penetrating or passing through the multilayer sheet. This barrier layer (30) may include a commonly known component capable of blocking the penetration and / or passage of gases.

[0062] Specifically, according to the present invention, the barrier layer may include at least one selected from the group consisting of ethylene vinyl alcohol (EVOH)-based resins, polyvinyl alcohol (PVOH)-based resins, polyamide-based resins (e.g., PA6, etc.), polyketone-based resins, and metaxylenediamine-based resins (e.g., MXDA, MXD6, etc.). As the barrier layer includes the above components, a multilayer sheet having superior gas barrier properties and improved environmental friendliness can be provided.

[0063] The thickness of the above barrier layer (30) is not particularly limited, but when the gas barrier property and mechanical properties of the multilayer sheet are taken into consideration, when the total thickness of the multilayer sheet is within 2.5 mm, it may be 5 to 35 ㎛, 7 to 30 ㎛, 9 to 25 ㎛, 10 to 25 ㎛, 12 to 25 ㎛, 15 to 25 ㎛, 15 to 20 ㎛, or 15 to 17 ㎛.

[0064]

[0065] Second core layer (40)

[0066] The second core layer (40) included in the multilayer sheet of the present invention is a layer that, together with the first core layer (20) described above, exhibits the thickest extrusion thickness among the thicknesses of the multilayer sheet, and includes a recycled polypropylene-based resin (e). This second core layer (40) may be provided between the barrier layer (30) and the second surface layer (50), thereby providing a multilayer sheet that exhibits mechanical properties equivalent to or superior to those of a conventional sheet while achieving reduction in carbon dioxide emissions. The second core layer (40) may be formed of one layer or two or more layers.

[0067] According to the present invention, the second core layer (40) may further include a petroleum-based polypropylene resin (f) together with the recycled polypropylene-based resin (e). Specifically, the second core layer (40) may be formed solely of the recycled polypropylene-based resin (e) or may be formed of a combination (e+f) of the recycled polypropylene-based resin (e) and the petroleum-based polypropylene-based resin (f). That the second core layer (40) is formed solely of the recycled polypropylene-based resin (e) means that the content of the recycled polypropylene-based resin (e) included in the second core layer (40) is 100 wt% based on the total weight of the second core layer (40).

[0068] When the second core layer (40) includes the recycled polypropylene-based resin (e) and the petroleum-based polypropylene-based resin (f), the content ratio (e:f) thereof is not particularly limited, but may be a weight ratio of 15 to less than 100: more than 0 to 85. Specifically, the second core layer (40) may include the recycled polypropylene-based resin (e) in an amount of 15 to less than 100 wt%, and the petroleum-based polypropylene-based resin (f) in an amount of more than 0 to 85 wt%, based on the total weight of the second core layer (40). For example, the content ratio (e:f) may be a weight ratio of 20 to 95: 5 to 80, a weight ratio of 25 to 90: 10 to 75, a weight ratio of 30 to 85: 15 to 70, a weight ratio of 35 to 80: 20 to 65, a weight ratio of 40 to 75: 25 to 60, a weight ratio of 45 to 70: 30 to 55, a weight ratio of 50 to 65: 35 to 50, or a weight ratio of 55 to 60: 40 to 45, but is not limited thereto. When the content ratio (e:f) is within the above range, a multilayer sheet having mechanical properties equivalent to or higher than those of the above can be provided while achieving a reduction in carbon dioxide emissions.

[0069] The above recycled polypropylene resin (e) may have a melt index (@230°C and 2.16 kg) of 0.3 to 3.0 g / 10 min. Specifically, the melt index (@230°C and 2.16 kg) of the above recycled polypropylene resin (e) may be, but is not limited to, 0.3 to 2.0 g / 10 min, 0.3 to 1.5 g / 10 min, 0.3 to 1.0 g / 10 min, or 0.3 to 0.5 g / 10 min.

[0070] In addition, the petroleum-based polypropylene resin (f) may have a melting index (@230°C and 2.16 kg) of 0.3 to 3.0 g / 10 min. Specifically, the melting index (@230°C and 2.16 kg) of the petroleum-based polypropylene resin (f) may be, but is not limited to, 0.3 to 2.5 g / 10 min, 0.3 to 2.0 g / 10 min, 0.4 to 1.5 g / 10 min, or 0.4 to 1.0 g / 10 min.

[0071] Since the melting index of each of the above recycled polypropylene resin (e) and the above petroleum-based polypropylene resin (f) is within the above range, a multilayer sheet can be easily manufactured through coextrusion, and processability can be secured when manufacturing a packaging container by thermoforming the multilayer sheet.

[0072] The thickness of the second core layer (40) is not particularly limited, but when considering the mechanical properties and manufacturing efficiency of the multilayer sheet, if the total thickness of the multilayer sheet is within 2.5 mm, it may be 200 to 500 ㎛, 210 to 450 ㎛, 220 to 400 ㎛, 230 to 350 ㎛, 230 to 300 ㎛, 240 to 260 ㎛, or 250 to 255 ㎛.

[0073] This second core layer (40) may have the same or different composition as the first core layer (20), and may also have the same or different thickness. Preferably, considering the mechanical properties of the multilayer sheet, the second core layer (40) may have the same composition and thickness as the first core layer (20).

[0074]

[0075] Meanwhile, in the multilayer sheet of the present invention, the thickness ratio between the first core layer (20), the barrier layer (30), and the second core layer (40) can be controlled within a specific range. Specifically, according to the present invention, the thickness ratio of the first core layer (20): the barrier layer (30): and the second core layer (40) can be 5 to 30: 1 to 3: 5 to 30. More specifically, the thickness ratio can be 10 to 30: 1 to 3: 10 to 30, 10 to 25: 1 to 2.5: 10 to 25, or 15 to 20: 1 to 2: 15 to 20 (for example, 10: 1: 10), but is not limited thereto. As the thickness ratio is within the above range, a multilayer sheet having improved mechanical properties while being environmentally friendly can be provided.

[0076]

[0077] Second surface layer (50)

[0078] The second surface layer (50) included in the multilayer sheet of the present invention is a layer that serves as a base material in the multilayer sheet together with the first surface layer (10), and when manufacturing a packaging container using the multilayer sheet, it may be an inner layer that comes into contact with food, or conversely, an outer layer that is exposed to the outside.

[0079] When the second surface layer (50) is an outer layer, marking or printing may be performed on its surface to disclose brief product information, such as the expiration date and consumption date. This second surface layer (50) may be composed of one layer or two or more layers.

[0080] According to the present invention, the second surface layer (50) may include a polypropylene-based resin. The polypropylene-based resin may include a petroleum-based polypropylene-based resin (g), a recycled polypropylene-based resin (h), or a combination thereof (g+h). Specifically, the second surface layer (50) may be formed solely of the petroleum-based polypropylene-based resin (g) or solely of the recycled polypropylene-based resin (h). That the second surface layer (50) is formed solely of each of the resins means that, based on the total weight of the second surface layer (50), the content of the petroleum-based polypropylene-based resin (g) included in the second surface layer (50) is 100 wt%, or the content of the recycled polypropylene-based resin (h) included in the second surface layer (50) is 100 wt%.

[0081] The above petroleum-based polypropylene resin (g) may have a melting index (@230°C and 2.16 kg) of 0.3 to 3.0 g / 10 min. Specifically, the melting index (@230°C and 2.16 kg) of the above petroleum-based polypropylene resin (g) may be, but is not limited to, 0.3 to 2.5 g / 10 min, 0.3 to 2.0 g / 10 min, 0.4 to 1.5 g / 10 min, or 0.4 to 1.0 g / 10 min.

[0082] In addition, the melt index of the recycled polypropylene resin (h) may be 0.3 to 3.0 g / 10 min (@230° C. and 2.16 kg). Specifically, the melt index of the recycled polypropylene resin (h) may be 0.3 to 2.0 g / 10 min, 0.3 to 1.5 g / 10 min, 0.3 to 1.0 g / 10 min, or 0.3 to 0.5 g / 10 min, but is not limited thereto.

[0083] Since the melting index of each of the above petroleum-based polypropylene resin (g) and the above recycled polypropylene resin (h) is within the above range, a multilayer sheet can be easily manufactured through coextrusion, and processability can be secured when manufacturing a packaging container by thermoforming the multilayer sheet.

[0084] The thickness of the second surface layer (50) is not particularly limited, but when considering the mechanical properties and manufacturing efficiency of the multilayer sheet, if the total thickness of the multilayer sheet is within 2.5 mm, it may be 65 to 90 ㎛, 68 to 88 ㎛, 70 to 86 ㎛, 72 to 84 ㎛, 74 to 82 ㎛, 74 to 80 ㎛, or 76 to 80 ㎛.

[0085] This second surface layer (50) may have the same or different composition as the first surface layer (10), and may also have the same or different thickness. Preferably, considering the mechanical properties of the multilayer sheet, the second surface layer (50) may have the same composition and thickness as the first surface layer (10).

[0086]

[0087] First adhesive layer (60) and second adhesive layer (70)

[0088] The multilayer sheet of the present invention may further include a first adhesive layer (60) and a second adhesive layer (70) to increase bonding strength between each layer. Specifically, the multilayer sheet may further include a first adhesive layer (60) provided between the first core layer (20) and the barrier layer (30); and a second adhesive layer (70) provided between the barrier layer (30) and the second core layer (40).

[0089] These first adhesive layer (60) and second adhesive layer (70) serve to strongly bond the first core layer (20), the barrier layer (30), and the second core layer (40), respectively, thereby improving the processability of the multilayer sheet.

[0090] Each of the first adhesive layer (60) and the second adhesive layer (70) may include an adhesive resin that can increase the bonding strength between each layer without deteriorating the physical properties of the multilayer sheet. The adhesive resin is not particularly limited as long as it is a commonly known adhesive resin, and may specifically include a polypropylene-based adhesive resin, but is not limited thereto.

[0091] The thickness of each of the first adhesive layer (60) and the second adhesive layer (70) is not particularly limited, but considering the bonding force between each layer and the thickness of the multilayer sheet, it may be 5 to 15 ㎛, 5 to 13 ㎛, 6 to 12 ㎛, 6 to 11 ㎛, 7 to 10 ㎛, or 8 to 9 ㎛.

[0092]

[0093] The multilayer sheet of the present invention can be environmentally friendly and have excellent mechanical properties while achieving reduction in carbon dioxide emissions by introducing recycled polypropylene resin into the first core layer (20) and the second core layer (40) interposed at specific locations (i.e., between the first surface layer (10) and the barrier layer (30) and / or between the barrier layer (30) and the second surface layer (50)).

[0094] Specifically, the multilayer sheet of the present invention may have a structure in which a first surface layer (10) / first core layer (20) / barrier layer (30) / second core layer (40) / second surface layer (50) are sequentially laminated, or a structure in which a first surface layer (10) / first core layer (20) / first adhesive layer (60) / barrier layer (30) / second core layer (40) / second adhesive layer (70) / second surface layer (50) are sequentially laminated.

[0095] A recycled polypropylene resin is necessarily introduced into each of the first core layer (20) and the second core layer (40), and a recycled polypropylene resin may be optionally introduced into each of the first surface layer (10) and the second surface layer (50).

[0096] Accordingly, the multilayer sheet of the present invention may have a content (total content) of recycled polypropylene-based resin of 10 to 90 wt% based on the total weight of the multilayer sheet. Specifically, the total content of the recycled polypropylene-based resin included in the multilayer sheet may be 15 to 90 wt%, 15 to 85 wt%, 20 to 80 wt%, 20 to 75 wt%, 25 to 70 wt%, 25 to 65 wt%, 30 to 60 wt%, or 30 to 55 wt% based on the total weight of the multilayer sheet, but is not limited thereto. When the content of the recycled polypropylene-based resin is within the above range, it is possible to provide a multilayer sheet having excellent mechanical properties while reducing the use of petroleum-based polypropylene-based resin, which is a cause of carbon dioxide emissions.

[0097] The multilayer sheet of the present invention can exhibit mechanical properties equivalent to or greater than those of a multilayer sheet in which each of the first surface layer (10), the first core layer (20), the second core layer (40), and / or the second surface layer (50) comprises a recycled polypropylene-based resin. Specifically, the multilayer sheet of the present invention can have a dart impact strength of 90 kgf or more, 95 kgf or more, 100 kgf or more, 105 kgf or more, 120 kgf or more, 150 kgf or more, 170 kgf or more, or 200 kgf or more (e.g., 90 to 250 kgf, 100 to 230 kgf, or 150 to 210 kgf), but is not limited thereto.

[0098] The multilayer sheet of the present invention may have a thickness of 0.35 to 2.5 mm. Specifically, the thickness of the multilayer sheet may be, but is not limited to, 0.4 to 2.3 mm, 0.45 to 2 mm, 0.5 to 1.8 mm, 0.55 to 1.5 mm, or 0.6 to 1.3 mm. As the thickness of the multilayer sheet is within the above range, it can be usefully used in the manufacture of a packaging container (specifically, a food packaging container) having a required level of physical properties.

[0099] The multilayer sheet of the present invention can be manufactured through a commonly known coextrusion method.

[0100]

[0101] Packaging container

[0102] The packaging container of the present invention is manufactured from the multilayer sheet described above. Specifically, the packaging container is manufactured through a thermoforming process of the multilayer sheet described above, and can be used to package various items. The thermoforming process can be performed using conventional methods such as extrusion molding, injection molding, vacuum molding, pressure molding, or pressure vacuum molding.

[0103] Since the packaging container of the present invention is manufactured using the multilayer sheet described above, it can have excellent mechanical properties. Specifically, the packaging container of the present invention can have a compressive strength of 20 kgf or more, 30 kgf or more, 32 kgf or more, 35 kgf or more, 38 kgf or more, 40 kgf or more, 45 kgf or more, 50 kgf or more, 55 kgf or more, or 60 kgf or more (e.g., 20 to 70 kgf, 40 to 65 kgf, or 50 to 60 kgf), but is not limited thereto.

[0104] In addition, the packaging container of the present invention has no unpleasant odor and is safe for people and environmentally friendly.

[0105] Therefore, the packaging container of the present invention can be usefully used as a container for packaging food (e.g., rice, side dishes, salad, etc.).

[0106] The present invention is described in more detail through the following examples. However, the scope of the present invention is not limited to these examples.

[0107]

[0108] [Example 1]

[0109] Petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.5 g / 10 min, block PP) was prepared to form the first surface layer and the second surface layer, respectively.

[0110] To form the first core layer and the second core layer, respectively, a mixed resin was prepared in which a petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.5 g / 10 min, block PP) and a recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.3 g / 10 min, block PP) were mixed in a weight ratio of 60:40. At this time, the recycled polypropylene resin was applied as a polymer of a recycled raw material (recycled propylene) obtained through the regeneration (pyrolysis) of crude tall oil, a by-product generated during the pulp manufacturing process.

[0111] Polypropylene-based adhesive resins were prepared to form the first and second adhesive layers, respectively.

[0112] Ethylene vinyl alcohol (EVOH) resin was prepared to form a barrier layer.

[0113] Using T-die coextrusion lamination, the prepared petroleum-based PP resin, mixed resin, polypropylene-based adhesive resin, EVOH resin, polypropylene-based adhesive resin, mixed resin, and petroleum-based PP resin were sequentially introduced into each of extruders A, B, C, D, E, F, and G, respectively, and melt coextruded (seven-stage extrusion). The temperatures during the melt coextrusion were set to 234°C, 225°C, 215°C, and 210°C for the petroleum-based PP resin, mixed resin, adhesive resin, and EVOH resin, respectively.

[0114] Through the above melt co-extrusion, a multilayer sheet having a laminated structure of first surface layer 80 ㎛ / first core layer 253 ㎛ / first adhesive layer 9 ㎛ / barrier layer 16 ㎛ / second adhesive layer 9 ㎛ / second core layer 253 ㎛ / second surface layer 80 ㎛, a total thickness of 0.7 mm, and a total content of recycled polypropylene resin of 30 wt% (based on the total weight of the multilayer sheet) was manufactured.

[0115]

[0116] [Example 2]

[0117] A multilayer sheet having a total thickness of 0.7 mm and a total content of recycled polypropylene resin of 50 wt% (based on the total weight of the multilayer sheet) was manufactured through the same process as Example 1, except that a mixed resin in which petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.5 g / 10 min, block PP) and recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.3 g / 10 min, block PP) were mixed in a weight ratio of 40:60 to form the first core layer and the second core layer, respectively, was manufactured.

[0118]

[0119] [Example 3]

[0120] A multilayer sheet having a total thickness of 0.7 mm and a total content of recycled polypropylene resin of 90 wt% (based on the total weight of the multilayer sheet) was manufactured through the same process as Example 1, except that only recycled polypropylene resin (melt index (@230°C and 2.16 kg): 0.3 g / 10 min, block PP) was used to form the first core layer and the second core layer, respectively.

[0121]

[0122] [Example 4]

[0123] A multilayer sheet having a total thickness of 0.7 mm and a total content of recycled polypropylene resin of 25 wt% (based on the total weight of the multilayer sheet) was manufactured through the same process as Example 1, except that a mixed resin in which petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.5 g / 10 min, block PP) and recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.3 g / 10 min, block PP) were mixed in a weight ratio of 65:35 to form the first core layer and the second core layer, respectively, was manufactured.

[0124]

[0125] [Example 5]

[0126] Petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.8 g / 10 min, block PP) was prepared to form the first surface layer and the second surface layer, respectively.

[0127] In order to form the first core layer and the second core layer, respectively, a mixed resin was prepared in which a petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.8 g / 10 min, block PP) and a recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 1.5 g / 10 min, block PP) were mixed in a weight ratio of 65:35. At this time, the recycled polypropylene resin was applied as a polymer of a recycled raw material (recycled propylene) obtained through the regeneration (pyrolysis) of waste cooking oil used in the cooking process or waste cooking oil (UCO, Used Cooking Oil) generated in the process washing process in the cooking oil production process.

[0128] Polypropylene-based adhesive resins were prepared to form the first and second adhesive layers, respectively.

[0129] Ethylene vinyl alcohol (EVOH) resin was prepared to form a barrier layer.

[0130] Using T-die coextrusion lamination, the prepared petroleum-based PP resin, mixed resin, polypropylene-based adhesive resin, EVOH resin, polypropylene-based adhesive resin, mixed resin, and petroleum-based PP resin were sequentially fed into each of extruders A, B, C, D, E, F, and G, respectively, and melt coextruded (seven-stage extrusion). The temperatures during the melt coextrusion were set to 232°C, 230°C, 220°C, and 225°C for the petroleum-based PP resin, mixed resin, polypropylene-based adhesive resin, and EVOH resin, respectively.

[0131] Through the above melt co-extrusion, a multilayer sheet having a laminated structure of first surface layer 75 ㎛ / first core layer 225 ㎛ / first adhesive layer 12 ㎛ / barrier layer 26 ㎛ / second adhesive layer 12 ㎛ / second core layer 225 ㎛ / second surface layer 75 ㎛, a total thickness of 0.65 mm, and a total content of recycled polypropylene resin of 25 wt% (based on the total weight of the multilayer sheet) was manufactured.

[0132]

[0133] [Example 6]

[0134] A multilayer sheet having a total thickness of 0.65 mm and a total content of recycled polypropylene resin of 50 wt% (based on the total weight of the multilayer sheet) was manufactured through the same process as Example 5, except that a mixed resin in which petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.8 g / 10 min, block PP) and recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 1.5 g / 10 min, block PP) were mixed in a weight ratio of 30:70 to form the first core layer and the second core layer, respectively, was manufactured.

[0135]

[0136] [Example 7]

[0137] Except that a mixed resin in which a petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.8 g / 10 min, block PP) and a recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 1.5 g / 10 min, block PP) were mixed in a weight ratio of 65:35 to form the first core layer and the second core layer, respectively, was used, a multilayer sheet having a total thickness of 1.2 mm (first surface layer 78 ㎛ / first core layer 493 ㎛ / first adhesive layer 15 ㎛ / barrier layer 28 ㎛ / second adhesive layer 15 ㎛ / second core layer 493 ㎛ / second surface layer 78 ㎛) and a total content of the recycled polypropylene resin of 25 wt% (based on the total weight of the multilayer sheet) was manufactured through the same process as in Example 5.

[0138]

[0139] [Example 8]

[0140] A multilayer sheet having a total thickness of 1.2 mm and a total content of recycled polypropylene resin of 50 wt% (based on the total weight of the multilayer sheet) was manufactured through the same process as Example 7, except that a mixed resin in which petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.8 g / 10 min, block PP) and recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 1.5 g / 10 min, block PP) were mixed in a weight ratio of 30:70 to form the first core layer and the second core layer, respectively, was used.

[0141]

[0142] [Example 9]

[0143] Recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.8 g / 10 min, block PP) was prepared to form the first surface layer and the second surface layer, respectively.

[0144] To form the first core layer and the second core layer, respectively, a mixed resin was prepared in which a petroleum-based polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.8 g / 10 min, block PP) and a recycled polypropylene resin (melt index (@230 ℃ and 2.16 kg): 0.8 g / 10 min, block PP) were mixed in a weight ratio of 65:35.

[0145] The above recycled polypropylene resin was applied as a polymer of recycled raw material (recycled propylene) obtained through the regeneration of waste plastic pyrolysis oil.

[0146] Polypropylene-based adhesive resins were prepared to form the first and second adhesive layers, respectively.

[0147] Ethylene vinyl alcohol (EVOH) resin was prepared to form a barrier layer.

[0148] Using T-die coextrusion lamination, the prepared recycled PP resin, mixed resin, polypropylene-based adhesive resin, EVOH resin, polypropylene-based adhesive resin, mixed resin, and recycled PP resin were sequentially fed into each of extruders A, B, C, D, E, F, and G, and melt coextruded (seven-fold extrusion). The temperatures during the melt coextrusion were set to 230-232°C, 230°C, and 225°C for the recycled PP resin, polypropylene-based adhesive resin, and EVOH resin, respectively.

[0149] Through the above melt co-extrusion, a multilayer sheet having a laminated structure of first surface layer 75 ㎛ / first core layer 225 ㎛ / first adhesive layer 12 ㎛ / barrier layer 26 ㎛ / second adhesive layer 12 ㎛ / second core layer 225 ㎛ / second surface layer 75 ㎛, a total thickness of 0.65 mm, and a total content of recycled polypropylene resin of 90 wt% (based on the total weight of the multilayer sheet) was manufactured.

[0150]

[0151] [Comparative Example 1]

[0152] A multilayer sheet having a total thickness of 0.7 mm was manufactured through the same process as Example 1, except that petroleum-based polypropylene resin (melt index (@230°C and 2.16 kg): 0.5 g / 10 min, block PP) was used alone to form the first core layer and the second core layer, respectively.

[0153]

[0154] [Comparative Example 2]

[0155] A multilayer sheet having a total thickness of 0.65 mm was manufactured through the same process as Example 5, except that petroleum-based polypropylene resin (melt index (@230°C and 2.16 kg): 0.8 g / 10 min, block PP) was used alone to form the first core layer and the second core layer, respectively.

[0156]

[0157] [Comparative Example 3]

[0158] A multilayer sheet having a total thickness of 1.2 mm was manufactured through the same process as Example 7, except that petroleum-based polypropylene resin (melt index (@230°C and 2.16 kg): 0.8 g / 10 min, block PP) was used alone to form the first core layer and the second core layer, respectively.

[0159]

[0160] The composition and thickness of the multilayer sheets of the above examples and comparative examples are summarized and shown in Table 1 below.

[0161]

[0162] First and second surface layersFirst and second core layersRecycled PP resinTotal content (wt%)Multilayer sheetTotal thickness (mm)Petroleum-based PP resin (wt%)Recycled PP resin (wt%)Petroleum-based PP resin (wt%)Recycled PP resin (wt%)Example 110006040300.7Example 210004060500.7Example 310000100900.7Example 410006535250.7Example 510006535250.65Example 610003070500.65Example 710006535251.2Example 810003070501.2Example 901006535900.65Comparative example 11000100000.7 Comparative Example 21000100000.65 Comparative Example 31000100001.2

[0163]

[0164] [Test Example 1] Measurement of dart impact strength

[0165] According to ASTM D7192, the dart impact strength of a multilayer sheet was measured by freely dropping a weight of a certain weight from a certain height onto the multilayer sheet to determine the peak force at the time of fracture of the multilayer sheet, and the results are shown in Table 2 below. Specifically, when evaluating a multilayer sheet having a thickness of 0.6 to 0.7 mm, a weight of 1.605 kg was dropped from a height of 800 mm, and when evaluating a multilayer sheet having a thickness of 1.2 mm, a weight of 4.105 kg was dropped from a height of 1000 mm.

[0166]

[0167] [Test Example 2] Compressive strength measurement

[0168] The surface temperature of the multilayer sheet was raised to 150-170 ℃ through a pre-heating process of less than 5 seconds at approximately 450-550 ℃, and a thermoformed container was manufactured through pressure vacuum forming.

[0169] The compressive strength of the thermoformed container was measured according to ASTM D695, and the results are shown in Table 2 below. Specifically, a compressive load was applied to the thermoformed container at a compression speed of 300 mm / min, and the maximum load value when the container was deformed and broken was measured, and this was applied as the compressive strength.

[0170]

[0171] Multilayer sheet dart impact strength (kgf) container compression strength (kgf) Example 1 10 6 4 9 Example 2 10 4 4 9 Example 3 9 8 3 9 Example 4 10 5 4 3 Example 5 10 1 3 3.5 Example 6 10 1 3 2.7 Example 7 20 4 6 4 Example 8 20 0 5 7.5 Example 9 10 5 3 1 Comparative Example 1 10 3 4 6 Comparative Example 2 10 5 3 2.2 Comparative Example 3 20 9 7

[0172] Referring to Table 2 above, the multilayer sheets of Examples 1 to 9 according to the present invention exhibit a dart impact strength equivalent to or higher than that of comparative examples having the same thickness but not including recycled PP resin, even when including recycled PP resin, and it can be confirmed that the containers manufactured using them exhibit a compressive strength at the desired level (quality standard: 20 kgf or more when the thickness is 0.7 mm / 40 kgf or more when the thickness is 1.2 mm). In addition, when manufacturing the multilayer sheets of Examples 1 to 9, phenomena such as imbalance in coextrusion extrusion amount and deterioration in appearance quality due to differences in melt index (MI) do not appear, and it can be seen that there is no problem in the manufacturing process even when using recycled PP resin.

[0173] [Explanation of symbols]

[0174] 10: First surface layer

[0175] 20: First core layer

[0176] 30: Barrier layer

[0177] 40: Second core layer

[0178] 50: Second surface layer

[0179] 60: First adhesive layer

[0180] 70: Second adhesive layer

Claims

1. A first surface layer; a first core layer; a barrier layer; a second core layer; and a second surface layer, A multilayer sheet, wherein each of the first core layer and the second core layer comprises a recycled polypropylene resin.

2. In paragraph 1, A multilayer sheet, wherein the content of recycled polypropylene resin contained in the multilayer sheet is 10 to 90 wt% based on the total weight of the multilayer sheet.

3. In paragraph 1, Each of the first core layer and the second core layer further comprises a petroleum-based polypropylene resin, A multilayer sheet, wherein the content ratio of the recycled polypropylene resin and the petroleum-based polypropylene resin contained in each of the first core layer and the second core layer is 15 to less than 100: 0 to 85 in weight ratio.

4. In paragraph 1, A multilayer sheet having a melting index (@230°C and 2.16 kg) of the above recycled polypropylene resin of 0.3 to 3.0 g / 10 min.

5. In paragraph 1, A multilayer sheet wherein the recycled polypropylene resin comprises a component derived from a non-petroleum naphtha raw material.

6. In paragraph 1, A multilayer sheet having a thickness ratio of the first core layer: the barrier layer: the second core layer of 5 to 30: 1 to 3: 5 to 30.

7. In paragraph 1, Each of the first surface layer and the second surface layer comprises a polypropylene resin, A multilayer sheet, wherein the polypropylene resin comprises petroleum-based polypropylene resin, recycled polypropylene resin, or a combination thereof.

8. In paragraph 1, A multilayer sheet, wherein the barrier layer comprises at least one selected from the group consisting of ethylene vinyl alcohol-based resin, polyvinyl alcohol-based resin, polyamide-based resin, polyketone-based resin, and metaxylene diamine-based resin.

9. In paragraph 1, A first adhesive layer provided between the first core layer and the barrier layer; and A multilayer sheet further comprising a second adhesive layer provided between the barrier layer and the second core layer.

10. In paragraph 1, A multilayer sheet having a thickness of 0.35 to 2.5 mm.

11. A packaging container manufactured from the multilayer sheet of paragraph 1.

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