Biodegradable multilayer film, method of manufacturing the same, and environmentally friendly packaging material comprising the same

Abstract

The present invention provides a biodegradable multilayer film, a method for manufacturing the same, and an environmentally friendly packaging material including the same, the biodegradable multilayer film including a base layer and a biodegradable resin layer, wherein the biodegradable resin layer includes a polyhydroxyalkanoate (PHA) resin, and the biodegradable resin layer has a heat bonding strength of 0.5 kgf / 15 mm to 15 kgf / 15 mm, a water permeability of 3 g / m2·atm·day or less, and an oxygen permeability of 10 cc / m2·atm·day or less. The biodegradable multilayer film can be biodegradable under natural conditions such as soil and the ocean, can improve barrier properties against moisture and oxygen without including aluminum or nylon materials, and can further improve adhesion properties. Accordingly, the biodegradable multilayer film can be used as a packaging material in various fields, thereby providing a high-quality and environmentally friendly packaging material.

Description

Technical Field

[0001] This invention relates to biodegradable multilayer films, methods for preparing said biodegradable multilayer films, and environmentally friendly packaging materials comprising said biodegradable multilayer films. Background Technology

[0002] Commonly used packaging materials consist of a base layer for printing and surface protection, a barrier layer (barrier film) for blocking moisture and oxygen, and an inner layer for heat-melt lamination and storage of contents.

[0003] Packaging materials are designed for their purpose such that the base layer typically consists of polyethylene terephthalate (PET) film or polypropylene (PP) film and is used for packaging printing applications (such as gravure printing, flexographic printing, and screen printing) and serves as a support layer to maintain the strength of the multilayer film structure. The barrier layer contains aluminum foil or nylon layers and serves as a blocking layer. The inner layer consists of low-density polyethylene (LDPE) layers, linear low-density polyethylene (LLDPE) layers, or cast polypropylene (CPP) layers for hot melt lamination and is used to store food and objects and maintain their shape.

[0004] However, these packaging materials are difficult to recycle. Their problem lies in their slow and incomplete natural decomposition during landfill processes, or, depending on their type, taking hundreds of years to decompose. In particular, they hardly decompose in soil or ocean, contributing to air and marine pollution problems.

[0005] To address these issues, there has been a growing demand in recent years for environmentally friendly packaging materials that do not use non-degradable plastics (such as PET and nylon) or aluminum as a metallic component (neither of which is environmentally friendly). These materials can easily maintain the lifespan and storage of the contents and can completely decompose in nature or through landfills after use without harming the natural environment.

[0006] Although various biodegradable materials (such as paper and biodegradable polymers such as polylactic acid (PLA)) have been studied as environmentally friendly packaging materials, the problem is that they are almost unusable as packaging materials due to their poor barrier properties against oxygen or moisture and their biodegradability.

[0007] Therefore, there is a need to develop biodegradable films and environmentally friendly packaging materials that are biodegradable in soil and ocean and have excellent barrier properties against oxygen and moisture.

[0008] [Existing Technical Documents]

[0009] [Patent Literature]

[0010] (Patent Document 1) Korean Patent Publication No. 2012-0103158. Summary of the Invention

[0011] Technical issues

[0012] The purpose of this invention is to provide a biodegradable multilayer film that is biodegradable under natural conditions (e.g., soil and ocean), has excellent barrier properties against moisture and oxygen without containing aluminum or nylon materials, and has excellent adhesive properties.

[0013] Another object of the present invention is to provide a method for preparing biodegradable multilayer films having the above-mentioned properties in an efficient manner.

[0014] Another object of the present invention is to provide an environmentally friendly packaging material comprising the above-mentioned multilayer film, which has excellent lifespan characteristics and can safely store perishable products.

[0015] Solutions to technical problems

[0016] This invention provides a biodegradable multilayer film comprising a substrate layer and a biodegradable resin layer, wherein the biodegradable resin layer comprises polyhydroxyalkanoate (PHA) resin, the heat-sealing strength of the biodegradable resin layer is 0.5 kgf / 15 mm to 15 kgf / 15 mm, and the biodegradable multilayer film has a density of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 • atm • day or less oxygen transfer rate.

[0017] Furthermore, the present invention provides a method for preparing a biodegradable multilayer film, the method comprising melt extruding polyhydroxyalkanoate (PHA) resin to form a biodegradable resin layer on a substrate layer, wherein the heat-sealing strength of the biodegradable resin layer is 0.5 kgf / 15 mm to 15 kgf / 15 mm, and the biodegradable multilayer film has a strength of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 • atm • day or less oxygen transfer rate.

[0018] In addition, the present invention provides an environmentally friendly packaging material, which includes the above-mentioned biodegradable multilayer film.

[0019] Advantages of the present invention

[0020] Because the biodegradable multilayer film according to embodiments of the present invention has a specific structure comprising a base layer and a biodegradable resin layer and contains specific biodegradable components, it is biodegradable under natural conditions (e.g., soil and ocean), has improved barrier properties against moisture and oxygen without containing aluminum or nylon materials, and has further improved adhesive properties.

[0021] Meanwhile, the method for preparing biodegradable multilayer films according to embodiments of the present invention can provide a method for preparing biodegradable multilayer films with the above-mentioned properties in an efficient manner.

[0022] Furthermore, various structures can be designed by easily combining biodegradable resin layers and barrier layers with various functions, depending on the intended purpose. In particular, when using the co-extrusion method according to embodiments of the present invention, single materials or different materials can be extruded simultaneously to combine materials with various functions, and processability and productivity can be further improved.

[0023] Furthermore, biodegradable multilayer films are environmentally friendly because they are completely decomposed in soil and ocean and can safely store perishable products; therefore, they can be used as packaging materials in various fields to provide high-quality, environmentally friendly packaging materials. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of a biodegradable multilayer film according to an embodiment of the present invention.

[0025] Figure 2 This is a cross-sectional view of a biodegradable multilayer film according to another embodiment of the present invention.

[0026] Figure 3 This is a cross-sectional view of a biodegradable multilayer film according to another embodiment of the present invention.

[0027] Figure 4 This is a cross-sectional view of a biodegradable multilayer film according to another embodiment of the present invention. Detailed Implementation

[0028] The invention will be described in more detail below.

[0029] The implementation scheme is not limited to the scheme described below. Rather, it can be modified in various forms as long as the spirit of the invention is not changed.

[0030] In this specification, unless otherwise expressly stated, when a component is referred to as a “comprising” element, it is understood to include other elements rather than exclude other elements.

[0031] In this specification, unless otherwise stated, the singular form is to be interpreted as the singular or plural as described in the context.

[0032] Furthermore, unless otherwise stated, all numerical values ​​used herein to represent the physical properties, dimensions, reaction conditions, etc. of elements are understood to be modified by the term “about”.

[0033] In this specification, the terms first resin layer, second resin layer, first adhesive layer, second adhesive layer, or first, second, etc., are used to describe various components. However, the components should not be limited by these terms. These terms are used only to distinguish one component from another.

[0034] In this specification, when referring to an element being formed "on" or "below" another element, it means not only that an element is formed directly "on" or "below" another element, but also that an element is formed indirectly on or below another element, with other elements inserted between them.

[0035] Furthermore, the references to "one side" and "the other side" or "upper" and "lower" for each component are explained based on the accompanying drawings. These terms are used only to distinguish components and are interchangeable in practical application.

[0036] Furthermore, for descriptive purposes, the dimensions of the various elements in the accompanying drawings may be exaggerated and do not represent actual dimensions. Additionally, in the specification, the same reference numerals denote the same elements.

[0037] [Biodegradable multilayer film]

[0038] A biodegradable multilayer film according to an embodiment of the present invention comprises a substrate layer and a biodegradable resin layer, wherein the biodegradable resin layer comprises polyhydroxyalkanoate (PHA) resin, the heat-sealing strength of the biodegradable resin layer is 0.5 kgf / 15 mm to 15 kgf / 15 mm, and the biodegradable multilayer film has a density of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 • atm • day or less oxygen transfer rate.

[0039] Because the biodegradable multilayer film according to embodiments of the present invention has the specific structure described above and contains specific biodegradable components, the biodegradable multilayer film and the environmentally friendly packaging material including the biodegradable multilayer film are biodegradable under natural conditions (e.g., soil and ocean), have improved barrier properties against moisture and oxygen, and do not contain aluminum or nylon materials, thus enabling the safe storage of perishable products and exhibiting excellent adhesive properties. Therefore, its technical significance lies in providing high-quality, environmentally friendly packaging materials.

[0040] Furthermore, according to embodiments of the present invention, the biodegradable multilayer film may also include a barrier layer, wherein the barrier layer may contain ethylene vinyl alcohol (EVOH) resin.

[0041] Specifically, the biodegradable multilayer film includes a substrate layer, a barrier layer, and a biodegradable resin layer, wherein the biodegradable resin layer comprises polyhydroxyalkanoate (PHA) resin, the barrier layer comprises ethylene vinyl alcohol (EVOH) resin, the heat-sealing strength of the biodegradable resin layer is 0.5 kgf / 15 mm to 15 kgf / 15 mm, and the biodegradable multilayer film has a strength of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 • atm • day or less oxygen transfer rate.

[0042] When a biodegradable multilayer film comprises a barrier layer containing ethylene vinyl alcohol (EVOH) resin and a biodegradable resin layer containing polyhydroxyalkanoate (PHA) resin, not only can the heat-sealing strength of the barrier layer and the biodegradable resin layer be improved, but also, since both the barrier layer and the biodegradable resin layer contain hydroxyl (OH) functional groups, interlayer delamination can be minimized. Therefore, the barrier layer and the biodegradable resin layer have excellent compatibility with each other and can further improve the adhesive properties.

[0043] Each layer of the biodegradable multilayer film will be described in detail below.

[0044] basal layer

[0045] The biodegradable multilayer film of the present invention may include a substrate layer.

[0046] Because biodegradable multilayer films include a substrate layer, they are easy to print product information and designs, and may be more beneficial for surface protection.

[0047] The base layer may include at least one selected from paper, polyethylene terephthalate (PET) film, polyimide (PI) film, polypropylene (PP) film, and polyethylene (PE) film. Specifically, it may include paper.

[0048] When the base layer includes paper, it may be more advantageous to provide environmentally friendly packaging materials because paper has better biodegradability than other plastic materials.

[0049] The basis weight of the base layer (e.g., paper layer) can be 30 g / m³. 2 Up to 200g / m 2The thickness of the substrate can vary depending on the thickness of the biodegradable multilayer film, but it can be, for example, 30 μm to 1000 μm, 30 μm to 500 μm, or 40 μm to 300 μm.

[0050] Meanwhile, a barrier layer or a biodegradable resin layer can be disposed on at least one side of the substrate.

[0051] In addition, an environmentally friendly barrier layer can be coated on the surface of the substrate to have moisture and / or oxygen barrier properties, or it can be further formed into a functional coating with antistatic or adhesive properties.

[0052] The functional coating may include a primer coating and an adhesive coating, which may have commonly used materials and physical properties, as long as they do not impair the desired effects of the invention.

[0053] For example, a functional coating may include a primer coating. In this case, barrier properties against moisture and / or oxygen can be further improved, adhesion to the barrier layer or biodegradable resin layer can be enhanced, and antistatic properties can be improved. Furthermore, when another layer (e.g., an adhesive coating or release layer) is applied on the other side of the primer coating, these coating liquids can be prevented from penetrating to the surface of the substrate (liquid permeation).

[0054] The primer coating may contain at least one of the following, selected from ammonium compounds, phosphate compounds, and polymers (such as acrylic resins and urethane resins), which have antistatic properties.

[0055] An adhesive coating is a coating used to improve adhesion and contains at least one selected from, for example, polyhydroxyalkanoates (PHA), polysiloxane compounds, polyvinyl alcohol (PVA), ethylene vinyl acetate (EVA), acrylic resins, and urethane resins.

[0056] The thickness of the functional coating can be appropriately adjusted according to the use and purpose of the biodegradable multilayer film, and can be specifically 15nm to 50nm, 20nm to 45nm, 25nm to 40nm or 30nm to 35nm, but is not limited thereto.

[0057] Biodegradable resin layer

[0058] The biodegradable multilayer film of the present invention may include a biodegradable resin layer comprising a polyhydroxyalkanoate (PHA) resin.

[0059] PHA resins have similar physical properties to conventional petroleum-derived synthetic polymers (such as polybutylene terephthalate (PBAT), polybutylene succinate (PBS), polybutylene terephthalate (PBST), and polybutylene adipate (PBSA)), exhibiting complete biodegradability and excellent biocompatibility.

[0060] Specifically, PHA resin is a natural thermoplastic polyester polymer that accumulates in microbial cells. As it is a biodegradable material, it can be composted and eventually decomposes into carbon dioxide, water, and organic waste without producing toxic waste. In particular, PHA resin is biodegradable in soil and ocean. Therefore, when a biodegradable resin layer contains PHA resin, it is biodegradable under any environmental conditions (e.g., soil and ocean) and possesses environmentally friendly properties. Thus, when a multilayer film includes a biodegradable resin layer (containing PHA resin), it offers significant advantages because it can be used as an environmentally friendly packaging material in various fields.

[0061] PHA resins can be formed by the enzymatic polymerization of one or more monomer repeating units in living cells.

[0062] PHA resin can be a polyhydroxyalkanoate copolymer resin (hereinafter referred to as PHA copolymer), specifically, a copolymer containing two or more different repeating units (wherein the different repeating units are randomly distributed in the polymer chain).

[0063] Examples of repeating units that may be included in PHA include 2-hydroxybutyrate, lactic acid, glycolic acid, 3-hydroxybutyrate (hereinafter referred to as 3-HB), 3-hydroxypropionate (hereinafter referred to as 3-HP), 3-hydroxyvalerate (hereinafter referred to as 3-HV), 3-hydroxyhexanoate (hereinafter referred to as 3-HH), 3-hydroxyheptanoate (hereinafter referred to as 3-HHep), 3-hydroxyoctanoate (hereinafter referred to as 3-HO), 3-hydroxynonanoate (hereinafter referred to as 3-HN), 3-hydroxydecanoate (hereinafter referred to as 3-HD), 3-hydroxydodecanate (hereinafter referred to as 3-HDd), 4-hydroxybutyrate (hereinafter referred to as 4-HB), 4-hydroxyvalerate (hereinafter referred to as 4-HV), 5-hydroxyvalerate (hereinafter referred to as 5-HV), and 6-hydroxyhexanoate (hereinafter referred to as 6-HH). PHA resin may contain one or more repeating units selected from the repeating units described above.

[0064] Specifically, the PHA resin may contain one or more repeating units selected from 3-HB, 4-HB, 3-HP, 3-HH, 3-HV, 4-HV, 5-HV, and 6-HH.

[0065] More specifically, the PHA resin may contain 4-HB repeating units. That is, the PHA resin may be a PHA copolymer containing 4-HB repeating units.

[0066] Furthermore, PHA resins may contain isomers. For example, PHA resins may contain structural isomers, enantiomers, or geometric isomers. Specifically, PHA resins may contain structural isomers.

[0067] In addition, the PHA resin can be a PHA copolymer containing 4-HB repeating units and also containing a repeating unit different from the 4-HB repeating units, or containing two, three, four, five, six or more repeating units that are different from each other.

[0068] According to an embodiment of the present invention, the PHA resin may comprise a polyhydroxyalkanoate copolymer resin, wherein the polyhydroxyalkanoate copolymer resin comprises at least one repeating unit selected from 3-HB, 3-HP, 3-HH, 3-HV, 4-HV, 5-HV, and 6-HH and 4-HB repeating units.

[0069] Specifically, the PHA copolymer may contain 4-HB repeating units, and further contain one or more repeating units selected from 3-HB repeating units, 3-HP repeating units, 3-HH repeating units, 3-HV repeating units, 4-HV repeating units, 5-HV repeating units, and 6-HH repeating units. More specifically, the PHA resin may be a polyhydroxyalkanoate copolymer resin containing 3-HB repeating units and 4-HB repeating units.

[0070] For example, PHA resin can be poly-3-hydroxybutyrate-co-4-hydroxybutyrate (hereinafter referred to as 3HB-co-4HB).

[0071] According to an embodiment of the present invention, it is important to adjust the content of 4-HB repeating units in the PHA copolymer.

[0072] In other words, in order to obtain the physical properties desired by the present invention, particularly to improve biodegradability in soil and ocean and to obtain excellent physical properties (e.g., improved optical, thermal and mechanical properties), the content of 4-HB repeating units in the PHA copolymer may be important.

[0073] More specifically, based on the total weight of the PHA copolymer, the PHA copolymer may contain 0.1 wt% to 60 wt% of 4-HB repeating units. For example, based on the total weight of the PHA copolymer, the content of 4-HB repeating units may be 0.1 wt% to 55 wt%, 0.5 wt% to 60 wt%, 0.5 wt% to 55 wt%, 1 wt% to 60 wt%, 1 wt% to 55 wt%, 1 wt% to 50 wt%, 2 wt% to 55 wt%, 3 wt% to 55 wt%, 3 wt% to 50 wt%, 5 wt% to 55 wt%, 5 wt% to 50 wt%, 10 wt% to 55 wt%, 10 wt% to 50 wt%, 1 wt% to 40 wt%, 1 wt% to 30 wt%, 1 wt% to 29 ...30 wt%, 1 wt% to 40 wt%, 1 % to 25% by weight, 1% to 24% by weight, 2% to 20% by weight, 2% to 23% by weight, 3% to 20% by weight, 3% to 15% by weight, 4% to 18% by weight, 5% to 15% by weight, 8% to 12% by weight, 9% to 12% by weight, 15% to 55% by weight, 15% to 50% by weight, 20% to 55% by weight, 20% to 50% by weight, 25% to 55% by weight, 25% to 50% by weight, 35% to 60% by weight, 40% to 55% by weight or 45% to 55% by weight.

[0074] If the content of 4-HB repeating units meets the above range, it can improve biodegradability in soil and ocean, maintain excellent optical properties, improve the thermal properties of the material, and further improve mechanical properties (e.g., flexibility and strength).

[0075] Furthermore, the PHA resin contains at least one or more 4-HB repeating units, and the content of the 4-HB repeating units can be controlled to adjust the crystallinity of the PHA resin. In other words, the PHA resin can be a PHA copolymer with controlled crystallinity.

[0076] PHA resins with adjustable crystallinity are those in which the crystallinity and amorphous state are adjusted as the irregularity in their molecular structure increases. Specifically, the type and ratio of monomers or the type and / or content of isomers can be adjusted.

[0077] PHA resin can contain a combination of two or more PHA resins with different crystallinities. That is, the PHA resin can be adjusted by mixing two or more types of PHA resins with different crystallinities to make the content of 4-HB repeating units within a specific range.

[0078] For example, the PHA resin comprises a mixture of a first PHA resin and a second PHA resin with different contents of 4-HB repeating units, and the PHA resin can be adjusted such that the content of 4-HB repeating units is from 0.1% by weight to 60% by weight based on the total weight of the PHA resin. The specific characteristics of the first PHA resin and the second PHA resin are described below.

[0079] Meanwhile, based on the total weight of the PHA copolymer, the PHA copolymer may contain, for example, 20% or more, 35% or more, 40% or more, 50% or more, 60% or more, 70% or more, or 75% or more and 99% or less, 98% or less, 97% or less, 96% or less, 95% or less, 93% or less, 91% or less, 90% or less, 80% or less, 70% or less, 60% or less, or 55% or less of 3-HB repeating units.

[0080] Meanwhile, the glass transition temperature (Tg) of the PHA resin can be, for example, -45°C to 80°C, -35°C to 80°C, -30°C to 80°C, -25°C to 75°C, -20°C to 70°C, -35°C to 5°C, -25°C to 5°C, -35°C to 0°C, -25°C to 0°C, -30°C to -10°C, -35°C to -15°C, -35°C to -20°C, -20°C to 0°C, -15°C to 0°C, or -15°C to -5°C.

[0081] For example, the crystallization temperature (Tc) of the PHA resin may not be measured, or may be, for example, 70°C to 120°C, 75°C to 120°C, 75°C to 115°C, 75°C to 110°C, or 90°C to 110°C.

[0082] For example, the melting temperature (Tm) of the PHA resin may not be measured, or it may be, for example, 100°C to 170°C, 110°C to 150°C, or 120°C to 140°C.

[0083] The weight-average molecular weight (Mw) of PHA resin can be, for example, from 10,000 g / mol to 1,200,000 g / mol. For example, the weight-average molecular weight of PHA resin can be 50,000 g / mol to 1,200,000 g / mol, 100,000 g / mol to 1,200,000 g / mol, 50,000 g / mol to 1,000,000 g / mol, 100,000 g / mol to 1,000,000 g / mol, 200,000 g / mol to 1,200,000 g / mol, 250,000 g / mol to 1,150,000 g / mol, 300,000 g / mol to 1,100,000 g / mol, 350,000 g / mol to 1,000,000 g / mol, 350,000 g / mol to 950,000 g / mol, 100,000 g / mol to 900,000 g / mol, 20 0000g / mol to 800000g / mol, 200000g / mol to 700000g / mol, 250000g / mol to 650000g / mol, 200000g / mol to 400000g / mol, 300000g / mol to 800000g / mol, 300000g / mol to 600000g / mol, 500000g / mol to 1200000g / mol, 500000g / mol to 1000000g / mol, 550000g / mol to 1050000g / mol, 550000g / mol to 900000g / mol or 600000g / mol to 900000g / mol.

[0084] Meanwhile, the biodegradable resin layer can be a single layer, or it can include two or more biodegradable resin layers.

[0085] When a biodegradable resin layer has two or more layers, it may include a first resin layer and a second resin layer.

[0086] When the biodegradable resin layer is a single layer, the thickness of the biodegradable resin layer can be from 10 μm to 200 μm, for example, from 15 μm to 150 μm, from 20 μm to 100 μm, or from 25 μm to 50 μm. When the biodegradable resin layer has two or more layers, the thickness of the first resin layer and the second resin layer can each be from 5 μm to 100 μm, for example, from 7 μm to 80 μm, from 10 μm to 50 μm, or from 12 μm to 25 μm.

[0087] The first resin layer and the second resin layer may each contain a first PHA resin and a second PHA resin. The first PHA resin and the second PHA resin can be distinguished based on the content of 4-HB repeating units, the glass transition temperature (Tg), the crystallization temperature (Tc), and the melting temperature (Tm).

[0088] Specifically, the first resin layer comprises a first PHA resin. Based on the total weight of the first PHA resin, the first PHA resin may contain, for example, 15% to 60% by weight, 15% to 55% by weight, 20% to 55% by weight, 25% to 55% by weight, 30% to 55% by weight, 35% to 55% by weight, 20% to 50% by weight, 25% to 50% by weight, 30% to 50% by weight, 35% to 50% by weight, or 20% to 40% by weight of 4-HB repeating units.

[0089] The glass transition temperature (Tg) of the first PHA resin can be -45°C to -10°C, -35°C to -10°C, -35°C to -15°C, -35°C to -20°C, or -30°C to -20°C.

[0090] For example, the crystallization temperature (Tc) of the first PHA resin may not be measured, or may be, for example, 60°C to 120°C, 60°C to 110°C, 70°C to 120°C, or 75°C to 115°C.

[0091] For example, the melting temperature (Tm) of the first PHA resin may not be measured, or may be, for example, 100°C to 170°C, 100°C to 160°C, 110°C to 160°C, or 120°C to 150°C.

[0092] The weight-average molecular weight (Mw) of the first PHA resin can be, for example, 10,000 g / mol to 1,200,000 g / mol, 10,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 1,200,000 g / mol, for example, 70,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 10 00000 g / mol, 200000 g / mol to 1200000 g / mol, 300000 g / mol to 1000000 g / mol, 100000 g / mol to 900000 g / mol, 500000 g / mol to 900000 g / mol, 200000 g / mol to 800000 g / mol or 200000 g / mol to 400000 g / mol.

[0093] Simultaneously, the second resin layer comprises a second PHA resin. Based on the total weight of the second PHA resin, the second PHA resin may contain 0.1 wt% to 30 wt% of 4-HB repeating units. The second PHA resin may contain, for example, 0.1 wt% to 30 wt%, 0.5 wt% to 30 wt%, 1 wt% to 30 wt%, 3 wt% to 30 wt%, 1 wt% to 28 wt%, 1 wt% to 25 wt%, 1 wt% to 24 wt%, 1 wt% to 20 wt%, 1 wt% to 15 wt%, 2 wt% to 25 wt%, 3 wt% to 25 wt%, 3 wt% to 24 wt%, 5 wt% to 24 wt%, 5 wt% to 20 wt%, greater than 5 wt% to less than 20 wt%, 7 wt% to 20 wt%, 10 wt% to 20 wt%, 15 wt% to 25 wt%, or 15 wt% to 24 wt% of 4-HB repeating units.

[0094] The first and second PHA resins can differ from each other in the content of 4-HB repeating units.

[0095] The glass transition temperature (Tg) of the second PHA resin can be, for example, -30°C to 80°C, -30°C to 10°C, -25°C to 5°C, -25°C to 0°C, -20°C to 0°C, or -15°C to 0°C.

[0096] The glass transition temperature (Tg) of the first PHA resin and the glass transition temperature (Tg) of the second PHA resin can be different from each other.

[0097] The crystallization temperature (Tc) of the second PHA resin can be, for example, 70°C to 120°C, for example, 75°C to 115°C, or for example, it may not be measured.

[0098] The melting temperature (Tm) of the second PHA resin can be, for example, 100°C to 170°C, for example, 105°C to 165°C, for example, 110°C to 160°C, for example, 100°C to 150°C, for example, 115°C to 155°C, or for example, 120°C to 150°C.

[0099] The weight-average molecular weight (Mw) of the second PHA resin can be 10,000 g / mol to 1,200,000 g / mol, 50,000 g / mol to 1,200,000 g / mol, 70,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 1,100,000 g / mol, 100,000 g / mol to 1,000,000 g / mol, 300,000 g / mol to 1,000,000 g / mol, 100,000 g / mol to 900,000 g / mol, 200,000 g / mol to 800,000 g / mol, 200,000 g / mol to 600,000 g / mol, 200,000 g / mol to 400,000 g / mol, or 400,000 g / mol to 700,000 g / mol.

[0100] Specifically, the first PHA resin has a glass transition temperature (Tg) of -35°C to -15°C, and the second PHA resin satisfies at least one characteristic selected from a glass transition temperature (Tg) of -15°C to 0°C, a crystallization temperature (Tc) of 80°C to 110°C, and a melting temperature (Tm) of 120°C to 160°C. Furthermore, the glass transition temperatures (Tg) of the first and second PHA resins can be different from each other. Additionally, the crystallization temperature (Tc) and melting temperature (Tm) of the first PHA resin may not be measured.

[0101] If the first PHA resin and the second PHA resin each satisfy at least one of the following within the range of 4-HB repeating unit content, glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm), it may be more advantageous to obtain the desired effect of the present invention.

[0102] Furthermore, the first PHA resin and the second PHA resin can each be a PHA resin with adjustable crystallinity.

[0103] For example, the first PHA resin may comprise an amorphous PHA resin (hereinafter referred to as aPHA resin), and the second PHA resin may comprise a semi-crystalline PHA resin (hereinafter referred to as scPHA resin).

[0104] aPHA resin and scPHA resin can be distinguished based on the content of 4-HB repeating units, glass transition temperature (Tg), crystallization temperature (Tc), melting temperature (Tm), etc.

[0105] Based on the total weight of the PHA resin, the aPHA resin may contain, for example, 25% to 50% by weight of 4-HB repeating units.

[0106] The glass transition temperature (Tg) of aPHA resin can be, for example, -35°C to -20°C.

[0107] The crystallization temperature (Tc) of aPHA resin does not need to be measured.

[0108] The melting temperature (Tm) of aPHA resin does not need to be measured.

[0109] Based on the total weight of the PHA resin, the scPHA resin may contain, for example, 1% to less than 25% by weight of 4-HB repeating units.

[0110] The glass transition temperature (Tg) of scPHA resin can range from -20℃ to 0℃.

[0111] The crystallization temperature (Tc) of scPHA resin can range from 75°C to 115°C.

[0112] The melting temperature (Tm) of scPHA resin can range from 110°C to 160°C.

[0113] If the biodegradable multilayer film according to an embodiment of the invention comprises two or more layers including a first resin layer and a second resin layer, it may be more advantageous to provide a variety of properties compared to a single layer.

[0114] Specifically, the first resin layer containing the first PHA resin may be beneficial for improving interlayer adhesion, and the second resin layer containing the second PHA resin may be more beneficial for improving printability.

[0115] Furthermore, the first resin layer and the second resin layer can be distinguished based on the content of 4-HB repeating units contained in the PHA, the glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm) of the PHA.

[0116] Furthermore, the content of 4-HB repeating units in the PHA of the first resin layer can be greater or less than the content of 4-HB repeating units in the PHA of the second resin layer. Preferably, the content of 4-HB repeating units in the PHA of the first resin layer can be greater than the content of 4-HB repeating units in the PHA of the second resin layer.

[0117] Additionally, the biodegradable resin layer may also contain at least one biodegradable resin selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene succinate-adipate (PBSA), polybutylene terephthalate-adipate (PBST), polyhydroxybutyrate-valerate (PHBV), polycaprolactone (PCL), polybutylene terephthalate-adipate (PBSAT), and thermoplastic starch (TPS).

[0118] In addition, the biodegradable resin layer may also contain at least one additive selected from slip agents, antioxidants, crosslinking agents, nucleating agents, fillers, stabilizers, and compatibilizers. For example, the additive may be used in amounts from 0.5% to 30% by weight, based on the total weight of the biodegradable resin layer.

[0119] Slip agents are additives used to improve slip properties (slippery properties) during the extrusion process and to prevent film surfaces from adhering to each other.

[0120] Any commonly used slip agent can be used as the slip agent, as long as it does not impair the effect of the invention. For example, the slip agent can be at least one selected from erucamide, oleamide, and stearamide.

[0121] Based on the total weight of the biodegradable resin layer, the slip agent can be used in amounts such as 0.01 wt% to 20 wt%, 0.01 wt% to 15 wt%, 0.01 wt% to 12 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 8 wt%, 0.01 wt% to 5 wt%, 0.2 wt% to 4.5 wt%, 0.2 wt% to 4 wt%, or 0.5 wt% to 3 wt%.

[0122] If the content of the slip agent meets the above range, processability, productivity and formability can be further improved, and this may be more conducive to achieving the desired effects of the present invention.

[0123] Antioxidants are additives used to prevent decomposition by ozone or oxygen, to prevent oxidation during storage, and to prevent the deterioration of the physical properties of films.

[0124] Any commonly used antioxidant can be used as an antioxidant, as long as it does not impair the effectiveness of the invention.

[0125] Specifically, antioxidants may include at least one selected from hindered phenolic antioxidants and phosphite (phosphorus) antioxidants.

[0126] Hindered phenolic antioxidants may include, for example, at least one selected from 4,4'-methylene-bis(2,6-di-tert-butylphenol), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane.

[0127] Phosphite antioxidants may include, for example, at least one selected from tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol-diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol-diphosphite, pentaerythritol distearate diphosphite, [bis(2,4-di-tert-butyl-5-methylphenoxy)phosphino]biphenyl, and N,N-bis[2-[[2,4,8,10-tetra(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphazenecycloheptane-6-yl]oxy]ethyl]ethylamine.

[0128] Based on the total weight of the biodegradable resin layer, the antioxidant can be used in amounts such as 0.01 wt% to 20 wt%, 0.01 wt% to 15 wt%, 0.01 wt% to 12 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 8 wt%, 0.01 wt% to 5 wt%, 0.2 wt% to 4.5 wt%, 0.2 wt% to 4 wt%, or 0.5 wt% to 3 wt%.

[0129] If the content of antioxidants meets the above range, the physical properties of the film can be improved, and this may be more conducive to achieving the desired effects of the present invention.

[0130] A crosslinking agent is an additive used to modify the properties of PHA and increase the molecular weight of the resin. Conventional crosslinking agents can be used as long as they do not impair the effects of this invention.

[0131] For example, the crosslinking agent may be at least one selected from fatty acid esters, natural oils containing epoxy groups (epoxidation), diallyl phthalate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, diethylene glycol dimethacrylate, and bis(2-methacryloyloxyethyl) phosphate.

[0132] Based on the total weight of the biodegradable resin layer, the crosslinking agent can be used in amounts such as 0.01 wt% to 20 wt%, 0.01 wt% to 15 wt%, 0.01 wt% to 12 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 8 wt%, 0.01 wt% to 5 wt%, 0.2 wt% to 4.5 wt%, 0.2 wt% to 4 wt%, or 0.5 wt% to 3 wt%.

[0133] If the content of the crosslinking agent meets the above range, the physical properties of the film can be improved, and this may be more conducive to obtaining the desired effect of the present invention.

[0134] Nucleating agents are additives used to supplement or alter the crystalline morphology of polymers and to increase the crystallization (curing) rate as the polymer melt cools. In particular, because the PHA resin used in this invention has a low crystallization rate, the process can be difficult due to prolonged viscosity. If a nucleating agent is used to address this problem, the crystallization rate can be increased to further improve processability, moldability, and productivity, and the desired physical properties can be effectively obtained.

[0135] Any commonly used nucleating agent can be used as a nucleating agent, as long as it does not impair the effects of the present invention.

[0136] Specifically, nucleating agents can be elemental substances (pure substances), metal compounds containing complex oxides (such as carbon black, calcium carbonate, synthetic silica and its salts, silicon dioxide, zinc white, clay, kaolin, basic magnesium carbonate, mica, talc, quartz powder, diatomaceous earth, dolomite powder, titanium dioxide, zinc oxide, antimony oxide, barium sulfate, calcium sulfate, aluminum oxide, calcium silicate, metal salts of organophosphorus compounds, and boron nitride), and low molecular weight organic compounds with metal carboxylic acid ester groups (such as octanoic acid, benzoic acid, heptanoic acid, nonanoic acid, and lauric acid). Myristic acid, palmitic acid, stearic acid, behenic acid, waxy acid, lignite acid, beeswax acid, benzoic acid, p-tert-butylbenzoic acid, terephthalic acid, monomethyl terephthalate, isophthalic acid and metal salts of monomethyl isophthalate), and polymeric organic compounds having metal carboxylic acid ester groups (e.g., carboxyl-containing polyethylene obtained by oxidation of polyethylene, carboxyl-containing polypropylene obtained by oxidation of polypropylene, copolymers of acrylic acid or methacrylic acid with olefins (e.g., ethylene, propylene and 1-butene), acrylic acid or methacrylic acid... Copolymers of olefins and styrene, copolymers of olefins and maleic anhydride, and salts of copolymers of styrene and maleic anhydride; polymeric organic compounds (e.g., α-olefins branching to a carbon atom at position 3 and having 5 or more carbon atoms, such as 3,3-dimethyl-1-butene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-methyl-1-hexene, and 3,5,5-trimethyl-1-hexene); vinylcycloalkane polymers (e.g., vinylcyclopentane, vinylcyclohexane, etc.). Nucleating agents include vinylnorborneol, polyolefin alcohols (e.g., polyethylene glycol and polypropylene glycol), poly(glycolic acid), cellulose, cellulose esters, and cellulose ethers, phosphoric acid or phosphorous acid and their metal salts (e.g., metal salts of diphenyl phosphate, diphenyl phosphite, bis(4-tert-butylphenyl) phosphate, and methylene bis(2,4-tert-butylphenyl) phosphate), sorbitol derivatives (e.g., bis(p-methylbenzyl)sorbitol and bis(p-ethylbenzyl)sorbitol), as well as thioacetic anhydride, p-toluenesulfonic acid, and their metal salts. Nucleating agents can be used alone or in combination.

[0137] Based on the total weight of the biodegradable resin layer, the nucleating agent can be used in amounts such as 0.01 wt% to 20 wt%, 0.01 wt% to 15 wt%, 0.01 wt% to 12 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 8 wt%, 0.01 wt% to 5 wt%, 0.2 wt% to 4.5 wt%, 0.2 wt% to 4 wt%, or 0.5 wt% to 3 wt%.

[0138] If the nucleating agent content meets the above range, the crystallization rate can be increased to improve formability, and the productivity and processability of the film can be further improved.

[0139] A filler is an additive that improves moldability by increasing the crystallization rate during the molding process. Any commonly used filler can be used as a filler, as long as it does not impair the effects of the invention. The filler may include at least one selected from calcium carbonate (e.g., light or heavy calcium carbonate), silica, talc, kaolin, barium sulfate, clay, calcium oxide, magnesium hydroxide, titanium dioxide, carbon black, and glass fiber.

[0140] The average particle size of the filler (particularly inorganic fillers) can be from 0.5 μm to 5 μm. If the average particle size of the inorganic filler is less than 0.5 μm, it is difficult to disperse the particles. If it exceeds 5 μm, the particle size becomes too large, which may impair the effectiveness of the invention. Based on the total weight of the biodegradable resin layer, the filler can be used in amounts such as 0.01 wt% to 20 wt%, 0.01 wt% to 15 wt%, 0.01 wt% to 12 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 8 wt%, 0.01 wt% to 5 wt%, 0.2 wt% to 4.5 wt%, 0.2 wt% to 4 wt%, or 0.5 wt% to 3 wt%.

[0141] If the content of the filler meets the above range, it may be more conducive to obtaining the desired effect of the present invention.

[0142] A stabilizer is an additive used to protect against oxidation and heating and to prevent color changes. Any commonly used stabilizer can be used as a stabilizer, as long as it does not impair the effectiveness of the invention.

[0143] Specifically, the stabilizer can be selected from trimethyl phosphate, triphenyl phosphate, trimethylphosphine, phosphoric acid, and phosphorous acid.

[0144] Based on the total weight of the biodegradable resin layer, the stabilizer can be used in amounts such as 0.01 wt% to 20 wt%, 0.01 wt% to 15 wt%, 0.01 wt% to 12 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 8 wt%, 0.01 wt% to 5 wt%, 0.2 wt% to 4.5 wt%, 0.2 wt% to 4 wt%, or 0.5 wt% to 3 wt%.

[0145] If the content of the stabilizer meets the above range, it may be more conducive to obtaining the desired effect of the present invention.

[0146] In addition, compatibilizers are additives that impart compatibility by removing non-uniformity between resins.

[0147] Any commonly used compatibilizer can be used as a compatibilizer, as long as it does not impair the effectiveness of the invention.

[0148] Specifically, the compatibilizer may include at least one selected from polyvinyl acetate (PVAc), isocyanate, polypropylene carbonate, glycidyl methacrylate, ethylene-vinyl alcohol, polyvinyl alcohol (PVA), ethylene vinyl acetate, and maleic anhydride.

[0149] Based on the total weight of the biodegradable resin layer, the compatibilizer may be used in amounts such as 0.01 wt% to 20 wt%, 0.01 wt% to 15 wt%, 0.01 wt% to 12 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 8 wt%, 0.01 wt% to 5 wt%, 0.2 wt% to 4.5 wt%, 0.2 wt% to 4 wt%, or 0.5 wt% to 3 wt%.

[0150] If the content of the compatibilizer meets the above range, the physical properties of the film can be improved by increasing the compatibility between the resins used, and this may be more conducive to obtaining the desired effect of the present invention.

[0151] Barrier layer

[0152] The biodegradable multilayer film of the present invention may include a barrier layer to block moisture and oxygen.

[0153] In addition, barrier layers can impart advantages to the substrate of a product, such as reduced permeability to moisture and oxygen, good oil resistance, and rigidity.

[0154] The barrier layer may contain ethylene vinyl alcohol (hereinafter referred to as EVOH) resin. EVOH resin may be an ethylene vinyl alcohol copolymer resin.

[0155] Because the barrier layer contains EVOH resin, it can form a layer that blocks moisture and oxygen, and this may be more conducive to achieving a 3g / m³ biodegradable multilayer film. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 • atm • day or less oxygen transfer rate.

[0156] In particular, embodiments of the present invention are characterized in that the barrier layer does not contain aluminum or nylon materials; instead, it uses EVOH resin as an environmentally friendly material to provide excellent barrier properties against moisture and oxygen.

[0157] Furthermore, because EVOH resin contains hydroxyl (OH) functional groups, it exhibits excellent compatibility with biodegradable resin layers containing PHA resin, which contains OH functional groups. This minimizes delamination between the barrier layer and the biodegradable resin layer and improves adhesion. Additionally, the barrier layer containing EVOH resin and the biodegradable resin layer containing PHA resin can be easily co-extruded in the process, further improving processability and productivity.

[0158] Meanwhile, since the content of vinyl groups and the molecular weight of EVOH resin can be controlled, EVOH resin can further improve the physical properties of biodegradable multilayer films.

[0159] The content of vinyl groups in EVOH resin can be, for example, from 10% to 70% by weight, from 20% to 60% by weight, or from 25% to 50% by weight. When the content of vinyl groups in EVOH resin meets the above range, the barrier properties against moisture and oxygen can be improved.

[0160] The barrier layer can be located on the base layer.

[0161] In addition, the barrier layer may be located on at least one side of the biodegradable resin layer.

[0162] Based on the total weight of the biodegradable multilayer film, the barrier layer can be 10% by weight or less. The barrier layer exhibits excellent barrier properties against moisture and oxygen, even at low weight (content).

[0163] The thickness of the barrier layer can range from 5 μm to 50 μm. For example, the thickness can be 5 μm to 40 μm, 5 μm to 35 μm, or 5 μm to 30 μm. Because the thickness of the barrier layer meets these ranges, the barrier properties against moisture and oxygen, as well as productivity, can be further improved. If the thickness of the barrier layer is less than the above range, it is difficult to achieve sufficient barrier properties. If the thickness is greater than the above range, there may be problems with high processing costs and low productivity.

[0164] The barrier layer and the biodegradable resin layer can be formed by co-extrusion on the base layer or by lamination on the base layer.

[0165] Adhesive layer

[0166] The biodegradable multilayer film of the present invention may also include an adhesive layer.

[0167] According to an embodiment of the present invention, when the barrier layer and the biodegradable resin layer are formed by laminating on the base layer, an adhesive layer can be inserted between the base layer, the biodegradable resin layer and the barrier layer.

[0168] For example, refer to Figure 4 The biodegradable multilayer film (1) includes a substrate layer (13), a barrier layer (12) disposed on the substrate layer, and a biodegradable resin layer (11) disposed on the barrier layer (12). It may include a first adhesive layer (16) between the substrate layer (13) and the barrier layer (12) and a second adhesive layer (17) between the barrier layer (12) and the biodegradable resin layer (11).

[0169] Furthermore, the biodegradable multilayer film includes a substrate layer, a biodegradable resin layer disposed on the substrate layer, and a barrier layer disposed on the biodegradable resin layer, and may include a first adhesive layer and a second adhesive layer respectively inserted therebetween.

[0170] Furthermore, when the biodegradable multilayer film includes a first resin layer and a second resin layer as biodegradable resin layers and the first resin layer and the second resin layer are formed by lamination on a substrate layer, an adhesive layer may also be formed on at least one side of each of the first resin layer and the second resin layer.

[0171] The adhesive layer has excellent adhesive strength and can be selected in various ways without impairing the effects of the invention. For example, the adhesive layer may contain at least one selected from polyhydroxyalkanoates (PHA), polysiloxane compounds, polyvinyl alcohol (PVA), ethylene vinyl acetate (EVA), acrylic resins, and urethane resins.

[0172] The thickness of the adhesive layer can be 5μm to 20μm, 5μm to 15μm, or 5μm to 10μm.

[0173] polymer resin layer

[0174] The biodegradable multilayer film of the present invention may also include a polymer resin layer.

[0175] The biodegradable multilayer film may further include at least one polymer resin layer comprising at least one selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene succinate-adipate (PBSA), polybutylene terephthalate-adipate (PBST), polyhydroxybutyrate-valerate (PHBV), polycaprolactone (PCL), polybutylene terephthalate-adipate (PBSAT), thermoplastic starch (TPS), polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE).

[0176] Specifically, the biodegradable multilayer film may further include at least one polymer resin layer, the polymer resin layer comprising at least one selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), thermoplastic starch (TPS), polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE).

[0177] The polymer resin layer can be formed on the barrier layer, on the biodegradable resin layer, or on both.

[0178] For example, a polymer resin layer can be formed on the barrier layer, and the polymer resin layer can be selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), thermoplastic starch (TPS), and polypropylene (PP). Specifically, the polymer resin layer can be selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), and polypropylene (PP). Furthermore, from the viewpoint of biodegradability, the polymer resin layer can be selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), and thermoplastic starch (TPS).

[0179] Furthermore, when the biodegradable multilayer film includes a first resin layer and a second resin layer as biodegradable resin layers, a polymer resin layer can be formed on at least one side of each of the first resin layer and the second resin layer.

[0180] The thickness of the polymer resin layer can be from 5 μm to 50 μm. For example, the thickness of the polymer resin layer can be from 5 μm to 40 μm, 5 μm to 35 μm, or 5 μm to 30 μm.

[0181] Various structures of biodegradable multilayer thin films

[0182] Figures 1 to 4 Cross-sectional views of various structures of biodegradable multilayer films according to embodiments of the present invention are shown.

[0183] First, the biodegradable multilayer film (1) according to an embodiment of the present invention may include a substrate layer (13) and a biodegradable resin layer (11) disposed on the substrate layer (13).

[0184] In addition, the biodegradable multilayer film (1) may also include a barrier layer (12).

[0185] Specifically, the barrier layer (12) can be disposed on the base layer (13), for example, inserted between the base layer (13) and the biodegradable resin layer (11).

[0186] In addition, the barrier layer (12) can be arranged on the biodegradable resin layer (11).

[0187] refer to Figure 1 According to an embodiment of the present invention, the biodegradable multilayer film (1) may include a substrate layer (13), a barrier layer (12) disposed on the substrate layer (13) and a biodegradable resin layer (11) disposed on the barrier layer (12).

[0188] According to another embodiment, a biodegradable multilayer film may include a substrate layer, a biodegradable resin layer disposed on the substrate layer, and a barrier layer disposed on the biodegradable resin layer.

[0189] The barrier layer (12) and the biodegradable resin layer (11) can be formed by co-extrusion on the base layer (13) or by lamination on the base layer (13).

[0190] According to the implementation plan, when the barrier layer (12) and the biodegradable resin layer (11) are formed by lamination on the base layer (13), refer again to Figure 4 The biodegradable multilayer film (1) includes a substrate layer (13), a barrier layer (12) disposed on the substrate layer, and a biodegradable resin layer (11) disposed on the barrier layer (12). It may include a first adhesive layer (16) between the substrate layer (13) and the barrier layer (12) and a second adhesive layer (17) between the barrier layer (12) and the biodegradable resin layer (11).

[0191] According to another embodiment, the biodegradable multilayer film includes a substrate layer, a biodegradable resin layer disposed on the substrate layer, and a barrier layer disposed on the biodegradable resin layer, and may include a first adhesive layer and a second adhesive layer respectively inserted therebetween.

[0192] In addition, refer to Figure 2 When the biodegradable multilayer film (1) includes a biodegradable resin layer (11) having a first resin layer and a second resin layer, the biodegradable multilayer film (1) may include a substrate layer (13), a barrier layer (12) disposed on the substrate layer, a first resin layer (14) disposed on the barrier layer (12) and a second resin layer (15) disposed on the first resin layer (14).

[0193] For example, a biodegradable multilayer film can have the following structure: substrate / barrier layer / first resin layer / second resin layer, substrate / barrier layer / second resin layer / first resin layer, substrate / first resin layer / barrier layer / second resin layer, substrate / second resin layer / barrier layer / first resin layer, substrate / first resin layer / second resin layer / barrier layer / first resin layer, substrate / first resin layer / second resin layer / barrier layer, or substrate / second resin layer / first resin layer / barrier layer.

[0194] More specifically, see reference Figure 3 The base layer (13) includes paper, and the biodegradable multilayer film may have the following structure: base layer (13) / first resin layer (14) / barrier layer (12) / second resin layer (15) or base layer / second resin layer / barrier layer / first resin layer.

[0195] Biodegradable multilayer films may include, for example, three or more layers (e.g., 3 to 11 layers) and have a total thickness of 30 μm to 350 μm, for example, 30 μm to 150 μm.

[0196] The barrier layer can account for 10% or less of the thickness of a biodegradable multilayer film.

[0197] The ratio of the total thickness of the biodegradable resin layer and the base layer to the thickness of the barrier layer can be from 90:10 to 99:1.

[0198] The thickness ratio of the biodegradable resin layer to the barrier layer can be from 1:0.1 to 1:0.5.

[0199] In addition, the thickness ratio of the paper layer and the biodegradable resin layer to the barrier layer can be from 1:0.01 to 1:0.1.

[0200] The thickness of the biodegradable resin layer can range from 10 μm to 100 μm.

[0201] Meanwhile, the thickness ratio of the first resin layer to the second resin layer can be from 1:0.5 to 1:1.5. When the thickness ratio of the first resin layer to the second resin layer meets the above range, it may be beneficial to control the adhesive strength and film strength.

[0202] Physical properties of biodegradable multilayer films

[0203] The multilayer film according to embodiments of the present invention can be biodegraded by any of microorganisms, moisture, oxygen, light and heat, and is characterized by low water vapor transfer rate and oxygen transfer rate as well as excellent adhesive properties.

[0204] Specifically, the water vapor transfer rate (WVTR) of the biodegradable multilayer film can be, for example, 3 g / m³. 2 • atm • days or less, 2.5g / m2 ·atm·day or less, 2g / m 2 ·atm·day or less, 1g / m 2 • atm • day or less, 0.8g / m 2 • atm • day or less, 0.7g / m 2 • atm • day or less, 0.6 g / m 2 • atm • day or less or 0.5 g / m 2 • atm • day or less.

[0205] Water vapor transfer rate can be measured, for example, using a Mocon Permatran-w3 / 33 water vapor transfer rate meter at 38°C ± 0.5°C and 90% ± 2% relative humidity.

[0206] Furthermore, the oxygen transfer rate (OTR) of biodegradable multilayer films can be, for example, 10 cc / m 2 ·atm·day or less, 5cc / m 2 ·atm·day or less, 3cc / m 2 ·atm·day or less, 2cc / m 2 ·atm·day or less, 1cc / m 2 • atm • day or less, 0.5cc / m 2 • atm • day or less, 0.4cc / m 2 ·atm·day or less, 0.3cc / m 2 • atm • day or less or 0.2cc / m 2 • atm • day or less.

[0207] Oxygen transfer rate (OTR) can be measured using a Labthink OX2 / 230 oxygen transfer rate meter at 23°C ± 0.5°C.

[0208] In addition, the tensile strength of the biodegradable multilayer film can be, for example, 10 MPa to 50 MPa, or, for example, 20 MPa to 40 MPa.

[0209] The biodegradable multilayer film was cut into samples 100 mm in length and 15 mm in width, and mounted onto an INSTRON Universal Testing Machine (UTM, model 5966) with a chuck spacing of 50 mm according to ASTM-D882. Testing was conducted at a tensile speed of 200 mm / min at room temperature (25°C), and tensile strength was measured using the program installed in the equipment.

[0210] If the tensile strength meets the above range, the productivity, processability, and formability of biodegradable multilayer films can be improved simultaneously.

[0211] Meanwhile, the heat-sealing strength of the biodegradable resin layer can be 0.5 kgf / 15 mm to 15 kgf / 15 mm, 1 kgf / 15 mm to 10 kgf / 15 mm, 3 kgf / 15 mm to 10 kgf / 15 mm, or 4 kgf / 15 mm to 8 kgf / 15 mm.

[0212] When the biodegradable resin layer comprises a first resin layer and a second resin layer, the heat-sealing strength of the first resin layer can be 1 kgf / 15 mm to 15 kgf / 15 mm, 3 kgf / 15 mm to 10 kgf / 15 mm, 3 kgf / 15 mm to 8 kgf / 15 mm, or 4 kgf / 15 mm to 8 kgf / 15 mm. Furthermore, the heat-sealing strength of the second resin layer can be 1 kgf / 15 mm to 12 kgf / 15 mm, 1 kgf / 15 mm to 10 kgf / 15 mm, 3 kgf / 15 mm to 10 kgf / 15 mm, or 3 kgf / 15 mm to 7 kgf / 15 mm.

[0213] In addition, the heat-sealing strength of the barrier layer can be 0.5 kgf / 15 mm to 10 kgf / 15 mm, 0.8 kgf / 15 mm to 8 kgf / 15 mm, 1 kgf / 15 mm to 8 kgf / 15 mm, or 1 kgf / 15 mm to 5 kgf / 15 mm.

[0214] Heat seal strength can be measured, for example, using LLOYD's LD5 universal tensile tester with a clamping gap of 50 mm, a speed of 100 mm / min, and a sample width of 15 mm.

[0215] When the heat-sealing strength of the biodegradable resin layer and the heat-sealing strength of the barrier layer each meet the above ranges, the interlayer adhesion properties are excellent, thereby preventing delamination of each layer and further improving processability and productivity.

[0216] Meanwhile, biodegradable multilayer films can possess excellent optical properties.

[0217] Specifically, the haze of the biodegradable multilayer film can be 20% or less, 15% or less, 10% or less, 7% or less, 6% or less, or 5% or less. If the haze exceeds the above ranges, the haze of the biodegradable multilayer film is significantly reduced, which may limit its use for packaging purposes (e.g., where the contents within the packaging material are visible).

[0218] In addition, the transmittance of biodegradable multilayer films can be 85% or higher, 88% or higher, or 90% or higher.

[0219] Furthermore, biodegradable multilayer films are characterized by a biodegradability of 90% or higher in soil and ocean. Biodegradability refers to the rate of decomposition compared to standard materials (e.g., cellulose) over the same period. The Korean Ministry of Environment defines a biodegradable material with a biodegradability of 90% or higher after 180 days, or 60% or higher after 45 days, compared to standard materials. Specifically, it is based on biodegradability measured according to composting conditions (ISO 14855-1).

[0220] [Method for preparing biodegradable multilayer thin films]

[0221] A method for preparing a biodegradable multilayer film according to an embodiment of the present invention includes melt extrusion of polyhydroxyalkanoate (PHA) resin to form a biodegradable resin layer on a substrate, wherein the heat-sealing strength of the biodegradable resin layer is from 0.5 kgf / 15 mm to 15 kgf / 15 mm, and the biodegradable multilayer film has a strength of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 • atm • day or less oxygen transfer rate.

[0222] In addition, methods for preparing biodegradable multilayer films also include melt extrusion of ethylene vinyl alcohol (EVOH) resin to form a barrier layer, wherein the biodegradable resin layer and the barrier layer can be formed by melt co-extrusion of polyhydroxy fatty acid ester (PHA) and ethylene vinyl alcohol (EVOH) resin on a substrate layer, or by melt extrusion of each and lamination on a substrate layer.

[0223] Specifically, methods for preparing biodegradable multilayer films may include melt co-extrusion of polyhydroxyalkanoate (PHA) resin and ethylene vinyl alcohol (EVOH) resin to form a biodegradable resin layer and a barrier layer on a substrate layer.

[0224] According to another embodiment of the present invention, a method for preparing a biodegradable multilayer film may include melt extruding polyhydroxyalkanoate (PHA) resin and ethylene vinyl alcohol (EVOH) resin, respectively, and laminating them on a substrate layer to form a biodegradable resin layer and a barrier layer.

[0225] Methods for preparing biodegradable multilayer films can be designed with various structures by effectively combining the structure of the multilayer film and materials with different functions, depending on the intended purpose. In particular, when using the co-extrusion method according to embodiments of the invention, this is more advantageous for preparing multilayer films by extruding a single material or simultaneously extruding different materials to combine materials with different functions. Therefore, processability and productivity can be further improved in an effective manner.

[0226] The method for preparing biodegradable multilayer films will be described in detail below.

[0227] Methods for preparing biodegradable multilayer films may include melt extrusion of PHA resin to form a biodegradable resin layer on a substrate layer.

[0228] In addition, methods for preparing biodegradable multilayer films may include melt co-extrusion of PHA resin and EVOH resin to form a biodegradable resin layer and a barrier layer on a substrate layer.

[0229] PHA resin and EVOH resin are as described above.

[0230] PHA resin and EVOH resin can each be in powder, granule, or pellet form. Specifically, PHA resin and EVOH resin can each be in pellet form.

[0231] When PHA resin and EVOH resin are each in pellet form, each resin can be cooled, for example, to 75°C or lower, 30°C or lower, or 5°C or lower, and then the cooled resin can be cut to produce pellets.

[0232] The cutting step can be performed using a pellet cutter without limitation, as long as it is commonly used in the art, and the pellets can have various shapes.

[0233] In addition, a drying step can be performed on the pellets. Drying can be carried out at 30°C to 100°C for 2 to 12 hours. Specifically, drying can be carried out at 35°C to 95°C, 40°C to 90°C, or 45°C to 85°C for 3 to 12 hours or 4 to 10 hours. Since the drying conditions of the pellets meet the above ranges, the quality can be further improved.

[0234] During melt co-extrusion, the extrusion temperatures of PHA resin and EVOH resin can be controlled independently. Melt co-extrusion can be carried out at temperatures ranging from 120°C to 250°C.

[0235] Specifically, the extrusion temperature of PHA resin and EVOH resin can be the same or different.

[0236] The extrusion temperature of PHA resin can be, for example, 120°C to 250°C, 120°C to 200°C, 140°C to 200°C, 140°C to 190°C, 140°C to 180°C, or 140°C to 170°C.

[0237] The extrusion temperature of EVOH resin can be, for example, 120°C to 250°C, 140°C to 250°C, 140°C to 240°C, 140°C to 230°C, or 140°C to 220°C.

[0238] When the extrusion temperatures of PHA resin and EVOH resin are different from each other, the difference in extrusion temperatures can be 50°C or less, 40°C or less, or 30°C or less.

[0239] Furthermore, according to embodiments of the invention, when the base layer comprises paper and a biodegradable resin layer and a barrier layer are formed on the base layer, careful temperature control may be required during melt co-extrusion to enable extrusion bonding in the lowest melting temperature region. Otherwise, the objectives of the invention may be difficult to achieve due to deformation and partial burning of the paper (which is the base layer).

[0240] Furthermore, after melt co-extrusion, stretching, heat treatment (heat setting), and / or drying can be performed. Process conditions used in the art can be used for these steps, provided they do not impair the desired effects of the invention.

[0241] Furthermore, according to an embodiment of the present invention, the PHA resin may comprise a first PHA resin and a second PHA resin. In this case, the first PHA resin, the second PHA resin, and the EVOH resin can be melt co-extruded. That is, these three types of resins can be melt co-extruded to form a first resin layer, a second resin layer, and an EVOH resin layer on a substrate layer. In this case, the arrangement and sequence of each resin layer can be designed in various ways according to the desired purpose.

[0242] The types and specific characteristics of the first and second PHA resins are as described above.

[0243] Furthermore, at least one polymeric resin selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene succinate-adipate (PBSA), polybutylene terephthalate-adipate (PBST), polyhydroxybutyrate-valerate (PHBV), polycaprolactone (PCL), polybutylene terephthalate-adipate (PBSAT), thermoplastic starch (TPS), polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE) can be used for melt co-extrusion with a first PHA resin, a second PHA resin, and an EVOH resin to form a first resin layer, a second resin layer, an EVOH resin layer, and a polymeric resin layer on a substrate layer. In this case, the arrangement and sequence of each resin layer can be designed in various ways according to the desired purpose.

[0244] In addition, the biodegradable resin layer, polymer resin layer, and / or EVOH resin layer may also contain at least one additive selected from slip agents, antioxidants, crosslinking agents, nucleating agents, fillers, stabilizers, and compatibilizers. The specific types and amounts of the additives are as described above.

[0245] In methods for preparing biodegradable multilayer films, when a biodegradable resin layer and a barrier layer are formed by melt co-extrusion, the weight (content) of the barrier layer relative to the biodegradable multilayer film can be minimized, while obtaining excellent barrier properties against moisture and oxygen. In particular, when paper is used as a substrate layer and a biodegradable resin layer and a barrier layer are melt co-extruded onto the paper, an effective biodegradable multilayer film can be provided, which has optimized barrier properties (blocking effect) against moisture and oxygen and is biodegradable in soil or ocean.

[0246] Meanwhile, according to another embodiment of the present invention, a method for preparing a biodegradable multilayer film may include melt extruding PHA resin and EVOH resin respectively to prepare PHA film and EVOH film respectively, and laminating them on a substrate layer to form a biodegradable resin layer and a barrier layer.

[0247] In the method, PHA resin and EVOH resin are melt-extruded separately to prepare PHA film and EVOH film respectively, and then laminated on a substrate to form a biodegradable resin layer and a barrier layer, wherein the lamination can be formed by forming an adhesive layer between the substrate, the biodegradable resin layer and the barrier layer.

[0248] The type, thickness, and arrangement of the adhesive layer are as described above.

[0249] During melt extrusion, the extrusion temperatures of PHA resin and EVOH resin can be controlled separately.

[0250] Specifically, the extrusion temperature of PHA resin and EVOH resin can be the same or different.

[0251] The extrusion temperature of PHA resin can be, for example, 120°C to 250°C, for example, 120°C to 200°C, for example, 140°C to 200°C, for example, 140°C to 190°C, for example, 140°C to 180°C, or for example, 140°C to 170°C.

[0252] The extrusion temperature of EVOH resin can be, for example, 120°C to 250°C, for example, 140°C to 250°C, for example, 140°C to 240°C, for example, 140°C to 230°C, or for example, 140°C to 220°C.

[0253] When the extrusion temperatures of PHA resin and EVOH resin are different from each other, the difference in extrusion temperature can be 50°C or less, 40°C or less, or 30°C or less.

[0254] Afterward, PHA resin and EVOH resin can be extruded separately, and then an adhesive layer can be used to bond them together for lamination.

[0255] Environmentally friendly packaging materials

[0256] According to an embodiment of the present invention, an environmentally friendly packaging material is provided, the environmentally friendly packaging material comprising the above-mentioned biodegradable multilayer film.

[0257] Specifically, according to embodiments of the present invention, environmentally friendly packaging materials may include biodegradable multilayer films, wherein the biodegradable multilayer film comprises a base layer and a biodegradable resin layer, the biodegradable resin layer comprising polyhydroxyalkanoate (PHA) resin, the biodegradable resin layer having a heat-sealing strength of 0.5 kgf / 15 mm to 15 kgf / 15 mm, and the biodegradable multilayer film having a density of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 • atm • day or less oxygen transfer rate.

[0258] According to another embodiment of the present invention, the environmentally friendly packaging material may include a biodegradable multilayer film, wherein the biodegradable multilayer film comprises a base layer, a barrier layer, and a biodegradable resin layer, the biodegradable resin layer comprising polyhydroxyalkanoate (PHA) resin, the biodegradable resin layer having a heat-sealing strength of 0.5 kgf / 15 mm to 15 kgf / 15 mm, the barrier layer comprising ethylene vinyl alcohol (EVOH) resin, and the biodegradable multilayer film having a heat-sealing strength of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 • atm • day or less oxygen transfer rate.

[0259] Environmentally friendly packaging materials can be in the form of films, and can be used, for example, as multi-purpose single-use packaging materials and food packaging materials. Environmentally friendly packaging materials can include air caps.

[0260] In addition, environmentally friendly packaging materials can be used in a variety of ways, including pet food packaging, seaweed packaging, nut packaging, dried food packaging, face mask packaging, feed packaging, and coffee bags.

[0261] Environmentally friendly packaging materials can be prepared by further processing a biodegradable multilayer film into a desired shape for a desired application. Processing can be carried out by any method known in the art (e.g., extrusion, injection molding, compression molding, pressure molding, blow molding or blow forming (e.g., blown film, blown foam), calendering, rotational molding, casting (e.g., cast sheets, cast films), or thermoforming).

[0262] Environmentally friendly packaging materials can be landfilled; therefore, even when used in large quantities, the risk of environmental pollution is very low compared to conventional packaging materials. They possess excellent formability and flexibility, enabling the provision of high-quality, biodegradable, environmentally friendly packaging materials with superior physical properties and quality.

[0263] The mode of the present invention

[0264] The present invention will now be described in detail with reference to embodiments. However, the following embodiments are intended to illustrate the invention, and the scope of the invention is not limited thereto.

[0265] <Example>

[0266] Example 1: A multilayer film having a structure of paper / second resin layer (scPHA) / first resin layer (aPHA) / barrier layer (EVOH)

[0267] Step 1: Preparation of PHA resin and EVOH resin

[0268] As polyhydroxyalkanoate (PHA) resins, a first PHA resin (3-HB-co-4-HB, aPHA) (manufacturer: CJ, South Korea) and a second PHA resin (3-HB-co-4-HB, scPHA) (manufacturer: CJ, South Korea) were prepared as shown in Table 1 below. As EVOH resins, ethylene vinyl alcohol (EVOH) resin (H171B, manufacturer: Kuraray) with a vinyl group content of 38 mol% in pellet form was prepared.

[0269] [Table 1]

[0270]

[0271] Step 2: Form a biodegradable resin layer (second resin layer and first resin layer) and a barrier layer on the substrate layer by melt co-extrusion.

[0272] Using a T-die three-layer co-extrusion laminator, the EVOH resin, the first PHA resin (aPHA), and the second PHA resin (scPHA) prepared in step 1 are sequentially loaded into each of extruders A, B, and C. Paper (manufacturer: Moorim) is used as the base layer. The EVOH resin, the first PHA resin (aPHA), and the second PHA resin (scPHA) are melt co-extruded (three-layer extruded) such that the second resin layer containing the second PHA resin (scPHA) is in contact with the base layer. The melt co-extrusion temperatures for the EVOH resin, the first PHA resin (aPHA), and the second PHA resin (scPHA) are set to 240°C, 160°C, and 160°C, respectively.

[0273] The biodegradable multilayer film has a structure of paper (83 μm) / second resin layer (scPHA) (15 μm) / first resin layer (aPHA) (15 μm) / barrier layer (EVOH) (8 μm) and a total thickness of 121 μm.

[0274] Example 2: A multilayer film having a structure of paper / first resin layer (aPHA) / second resin layer (scPHA) / barrier layer (EVOH)

[0275] A multilayer film with a structure of paper (83 μm) / first resin layer (aPHA) (15 μm) / second resin layer (scPHA) (15 μm) / barrier layer (EVOH) (8 μm) and a total thickness of 121 μm was obtained in the same manner as in Example 1. The difference is that in step 2 of Example 1, EVOH resin, second PHA resin (scPHA) and first PHA resin (aPHA) were sequentially loaded into extruders A, B and C and melt co-extrusion was performed so that the first resin layer containing the first PHA resin (aPHA) was in contact with the substrate layer.

[0276] Example 3: A multilayer film having a structure of paper / barrier layer (EVOH) / first resin layer (aPHA) / second resin layer (scPHA)

[0277] A multilayer film with a structure of paper (83 μm) / barrier layer (EVOH) (8 μm) / first resin layer (aPHA) (15 μm) / second resin layer (scPHA) (15 μm) and a total thickness of 121 μm was obtained in the same manner as in Example 1. The difference is that in step 2 of Example 1, the second PHA resin (scPHA), the first PHA resin (aPHA) and the EVOH resin were sequentially loaded into extruders A, B and C and melt co-extruded to make the barrier layer containing the EVOH resin contact the substrate layer.

[0278] Example 4: A multilayer film having a structure of paper / first resin layer (aPHA) / barrier layer (EVOH) / second resin layer (scPHA)

[0279] A multilayer film with a structure of paper (83 μm) / first resin layer (aPHA) (15 μm) / barrier layer (EVOH) (8 μm) / second resin layer (scPHA) (15 μm) and a total thickness of 121 μm was obtained in the same manner as in Example 1. The difference is that in step 2 of Example 1, the second PHA resin (scPHA), EVOH resin and the first PHA resin (aPHA) were sequentially loaded into extruders A, B and C and melt co-extrusion was performed so that the first resin layer containing the first PHA resin (aPHA) was in contact with the substrate layer.

[0280] Example 5: Paper / EVOH / Second Resin Layer (scPHA)

[0281] A multilayer film with a structure of paper (83 μm) / barrier layer (EVOH) (8 μm) / second resin layer (scPHA) (15 μm) and a total thickness of 106 μm was obtained in the same manner as in Example 1, except that in step 2 of Example 1, the second PHA resin (scPHA) and EVOH resin were sequentially loaded into extruders A and B and melt co-extruded so that the barrier layer containing EVOH resin was in contact with the substrate layer.

[0282] Example 6: A multilayer film (laminated film) having a structure of paper / first resin layer (aPHA) / barrier layer (EVOH) / second resin layer (scPHA)

[0283] In step 2 of Example 1, EVOH resin is melt-extruded in an extruder at 240°C to form a barrier film (barrier layer), a second PHA resin (scPHA) is melt-extruded at 160°C to form a second resin film (second resin layer), and a first PHA resin (aPHA) is melt-extruded at 160°C to form a first resin film (first resin layer).

[0284] Paper (manufacturer: Moorim) was used as the substrate layer. The individual films prepared above were laminated onto the substrate layer to form a structure having paper / first resin layer (aPHA) / barrier layer (EVOH) / second resin layer (scPHA). In this case, an adhesive solution was used to bond each layer. Therefore, a multilayer film with a structure of paper (83 μm) / first resin layer (aPHA) (15 μm) / barrier layer (EVOH) (8 μm) / second resin layer (scPHA) (15 μm) was obtained.

[0285] Example 7: A multilayer film (laminated) having a structure of paper / barrier layer (EVOH) / first resin layer (aPHA) / second resin layer (scPHA)

[0286] A multilayer film was obtained in the same manner as in Example 6, except that the lamination order in Example 6 was changed to have a structure of paper (83 μm) / barrier layer (EVOH) (8 μm) / first resin layer (aPHA) (15 μm) / second resin layer (scPHA) (15 μm).

[0287] Comparative Example 1: A multilayer film (laminated film) with a structure of polyethylene terephthalate (PET) / thin aluminum layer / nylon layer / cast polypropylene (CPP) layer.

[0288] A multilayer film was obtained in the same manner as in Example 6, except that the multilayer film was formed with a structure having a polyethylene terephthalate (PET) / thin aluminum layer / nylon layer / cast polypropylene (CPP) layer.

[0289] Comparative Example 2: Multilayer thin film with a substrate / CPP layer structure

[0290] A multilayer film was obtained in the same manner as in Example 1, except that the multilayer film was formed as a structure having a base layer and a cast polypropylene (CPP) layer using CPP resin.

[0291] Comparative Example 3: Multilayer thin film with a substrate / LDPE layer structure

[0292] A multilayer film was obtained in the same manner as in Comparative Example 2, except that the multilayer film was formed as a structure having a base layer and a low-density polyethylene (LDPE) layer using LDPE resin instead of cast polypropylene (CPP) resin.

[0293] Comparative Example 4: Multilayer thin film with a substrate / LLDPE layer structure

[0294] A multilayer film was obtained in the same manner as in Comparative Example 2, except that the multilayer film was formed as a structure having a base layer and a linear low-density polyethylene (LLDPE) layer using LLDPE resin instead of cast polypropylene (CPP) resin.

[0295] Comparative Example 5: Multilayer film with a paper / EVOH / PBAT layer structure

[0296] In Example 5, PBAT resin (Ankor Bioplastics) was used instead of the second PHA resin (scPHA) to obtain a multilayer film with a structure of paper (83 μm) / barrier layer (EVOH) (8 μm) / polybutylene terephthalate (PBAT) layer (15 μm) in the same manner as in Example 5.

[0297] Evaluation of Implementation Examples

[0298] Evaluation of Example 1

[0299] To examine the thermal adhesion of the multilayer films obtained in the examples and comparative examples, a heat-sealing method was used. The heat-sealing strength was measured to evaluate the peeling of the thermally bonded areas.

[0300] The heat seal strength was measured using a LLOYD LD5 universal tensile tester with a clamping gap of 50 mm, a speed of 100 mm / min, and a sample width of 15 mm. The results are shown in Table 2 below.

[0301] [Table 2]

[0302] Heat seal strength (kgf / 15mm) First resin layer (aPHA layer) 6.5 Second resin layer (scPHA layer) 5.5 EVOH 2.2

[0303] As shown in Table 2 above, the heat-sealing strength of the first resin layer (aPHA layer) and the second resin layer (scPHA layer) are approximately 6.5 kgf / 15 mm and 5.5 kgf / 15 mm, respectively, and the heat-sealing strength of the EVOH layer is approximately 2.2 kgf / 15 mm. The heat-sealing strength of each layer is excellent.

[0304] Evaluation of Example 2

[0305] The water vapor transfer rate and oxygen transfer rate of the multilayer films obtained in the examples and comparative examples were measured under the following conditions.

[0306] Water vapor transfer rate (WVTR) was measured using a Mocon Permatran-w3 / 33 water vapor transfer rate meter at 38°C ± 0.5°C and 90% ± 2% relative humidity.

[0307] Oxygen transfer rate (OTR) was measured at 23°C ± 0.5°C using a Mocon OX2-TRAN 2 / 12 oxygen transfer rate meter.

[0308] The water vapor transfer rate, oxygen transfer rate, and biodegradability of the multilayer films obtained in the examples and comparative examples are summarized in Table 3 below.

[0309] [Table 3]

[0310]

[0311] As can be seen from Table 3 above, unlike the multilayer films of Comparative Examples 1 to 5, the multilayer films of Examples 1 to 7 are biodegradable in soil and ocean, and their water vapor transfer rate and oxygen transfer rate are significantly reduced.

[0312] Specifically, the multilayer films of Examples 1 to 7 have a density of 0.38 g / m³. 2 ·atm·day up to 2.55g / m 2 The water vapor transfer rate per day is 0.17 cc / m³. 2 ·atm·day up to 0.39cc / m 2 The oxygen transfer rate per day (atm).

[0313] In comparison, the multilayer films of Comparative Examples 2 to 4 have a density of 4.5 g / m³. 2 • atm • day or greater water vapor transfer rate and 1000 cc / m 2 • atm·day or greater oxygen transfer rate. Compared with the multilayer films of Examples 1 to 7, the water vapor transfer rate and oxygen transfer rate are significantly increased.

[0314] Furthermore, the water vapor transfer rate and oxygen transfer rate of the multilayer thin film in Comparative Example 1 were 0.09 g / m³. 2 ·atm· Tianhe 0.10cc / m 2 ·atm·day, which is non-biodegradable in both soil and ocean.

[0315] Furthermore, in the multilayer film of Comparative Example 5, the biodegradable resin layer contains only PBAT resin and not PHA resin. Therefore, the water vapor transfer rate is 4.5 g / m³. 2 The vapor transfer rate is ·atm·day, which is increased compared to the water vapor transfer rate of the multilayer films in Examples 1 to 7. It is non-biodegradable in both soil and ocean.

[0316] Furthermore, it was confirmed that the water vapor transfer rate and oxygen transfer rate of the multilayer films in Examples 1 to 7 varied significantly according to the lamination sequence.

[0317] Specifically, the multilayer film of Example 4, having a structure of paper / first resin layer (aPHA layer) / barrier layer (EVOH layer) / second resin layer (scPHA layer), has a density of 0.38 g / m³. 2 The water vapor transfer rate per day is 0.17 cc / m³. 2 Oxygen transfer rate per atm per day. Compared with the multilayer films of Comparative Examples 2 to 5, the water vapor transfer rate and oxygen transfer rate are significantly reduced, and it is biodegradable in both soil and ocean.

[0318] [Explanation of reference numerals in the attached figures]

[0319] 1: Biodegradable multilayer thin films

[0320] 11: Biodegradable resin layer

[0321] 12: Barrier layer

[0322] 13: Basal layer

[0323] 14: First resin layer

[0324] 15: Second resin layer

[0325] 16: First adhesive layer

[0326] 17: Second adhesive layer.

Claims

1. A biodegradable multilayer film, the biodegradable multilayer film comprising a substrate layer and a biodegradable resin layer, wherein, The biodegradable resin layer comprises polyhydroxyalkanoate (PHA) resin, the heat-sealing strength of the biodegradable resin layer is 0.5 kgf / 15 mm to 15 kgf / 15 mm, and the biodegradable multilayer film has a strength of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 The oxygen transfer rate is atm or less, and the polyhydroxyalkanoate (PHA) resin comprises a first PHA resin and a second PHA resin, wherein the glass transition temperature (Tg) of the first PHA resin is -35°C to -20°C, the glass transition temperature (Tg) of the second PHA resin is -20°C to 0°C, and the glass transition temperatures (Tg) of the first PHA resin and the second PHA resin are different from each other.

2. The biodegradable multilayer film according to claim 1, wherein, The biodegradable multilayer film also includes a barrier layer, and the barrier layer contains ethylene vinyl alcohol (EVOH) resin.

3. The biodegradable multilayer film according to claim 1, wherein, The polyhydroxy fatty acid ester (PHA) resin is a polyhydroxy fatty acid ester copolymer resin containing repeating units of 4-hydroxybutyrate (4-HB), and the polyhydroxy fatty acid ester copolymer resin contains 0.1% to 60% by weight of repeating units of 4-hydroxybutyrate (4-HB) based on the total weight of the polyhydroxy fatty acid ester copolymer resin.

4. The biodegradable multilayer film according to claim 2, wherein, The biodegradable resin layer includes a first resin layer and a second resin layer. The first resin layer comprises a first PHA resin, the first PHA resin comprising 15% to 60% by weight of a repeating 4-hydroxybutyrate (4-HB) unit. The second resin layer comprises a second PHA resin, the second PHA resin comprising 0.1% to 30% by weight of a repeating unit of 4-hydroxybutyrate (4-HB), and The first and second PHA resins differ from each other in the content of 4-HB repeating units.

5. The biodegradable multilayer film according to claim 4, wherein, The second PHA resin satisfies at least one property selected from a glass transition temperature (Tg) of -20°C to 0°C, a crystallization temperature (Tc) of 70°C to 120°C, and a melting temperature (Tm) of 100°C to 170°C.

6. The biodegradable multilayer film according to claim 2, wherein, The barrier layer and the biodegradable resin layer are formed by co-extrusion on the substrate layer or by lamination on the substrate layer.

7. The biodegradable multilayer film according to claim 4, wherein, Biodegradable multilayer films include the following structures: Base layer / barrier layer / first resin layer / second resin layer; Base layer / barrier layer / second resin layer / first resin layer; Base layer / first resin layer / barrier layer / second resin layer; Base layer / second resin layer / barrier layer / first resin layer; Base layer / first resin layer / second resin layer / barrier layer; or Base layer / Second resin layer / First resin layer / Barrier layer.

8. The biodegradable multilayer film according to claim 7, wherein, The substrate layer includes at least one selected from paper, polyethylene terephthalate (PET) film, polyimide (PI) film, polypropylene (PP) film, and polyethylene (PE) film.

9. The biodegradable multilayer film according to claim 8, wherein, The substrate layer includes paper, and the biodegradable multilayer film has the following structure: substrate layer / first resin layer / barrier layer / second resin layer or substrate layer / second resin layer / barrier layer / first resin layer.

10. The biodegradable multilayer film according to claim 1, wherein, The biodegradable multilayer film also includes an adhesive layer, and the adhesive layer comprises at least one selected from polyhydroxyalkanoates (PHA), polysiloxane compounds, polyvinyl alcohol (PVA), ethylene vinyl acetate (EVA), acrylic resins, and urethane resins.

11. The biodegradable multilayer film according to claim 1, wherein, The biodegradable multilayer film further includes at least one polymer resin layer comprising at least one selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene succinate-adipate (PBSA), polybutylene terephthalate-adipate (PBST), polyhydroxybutyrate-valerate (PHBV), polycaprolactone (PCL), polybutylene terephthalate-adipate (PBSAT), thermoplastic starch (TPS), polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE).

12. The biodegradable multilayer film according to claim 1, wherein, The biodegradable resin layer also contains at least one additive selected from slip agents, antioxidants, crosslinking agents, nucleating agents, fillers, stabilizers, and compatibilizers.

13. The biodegradable multilayer film according to claim 1, wherein, The biodegradable resin layer further comprises at least one biodegradable resin selected from polybutylene terephthalate (PBAT), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene succinate-adipate (PBSA), polybutylene terephthalate-adipate (PBST), polyhydroxybutyrate-valerate (PHBV), polycaprolactone (PCL), polybutylene terephthalate-adipate (PBSAT), and thermoplastic starch (TPS).

14. The biodegradable multilayer film according to claim 2, wherein, The biodegradable multilayer film has a thickness of 30 μm to 350 μm, the barrier layer accounts for 10% or less of the thickness of the biodegradable multilayer film, and the thickness ratio of the biodegradable resin layer to the barrier layer is 1:0.1 to 1:0.

5.

15. The biodegradable multilayer film according to claim 4, wherein, The thickness ratio of the first resin layer to the second resin layer is 1:0.5 to 1:1.

5.

16. The biodegradable multilayer film according to claim 4, wherein, The heat-sealing strength of the barrier layer is 0.5 kgf / 15 mm to 10 kgf / 15 mm, the heat-sealing strength of the first resin layer is 1 kgf / 15 mm to 15 kgf / 15 mm, and the heat-sealing strength of the second resin layer is 1 kgf / 15 mm to 12 kgf / 15 mm.

17. A method for preparing a biodegradable multilayer thin film, the method comprising: The polyhydroxyalkanoate (PHA) resin is melt-extruded to form a biodegradable resin layer on the substrate. The biodegradable resin layer has a heat-sealing strength of 0.5 kgf / 15 mm to 15 kgf / 15 mm, and The biodegradable multilayer film has a concentration of 3 g / m³. 2 • atm • day or less water vapor transfer rate and 10 cc / m 2 Oxygen transfer rate of atm per day or less, The polyhydroxyalkanoate (PHA) resin comprises a first PHA resin and a second PHA resin, wherein the glass transition temperature (Tg) of the first PHA resin is -35°C to -20°C, and the glass transition temperature (Tg) of the second PHA resin is -20°C to 0°C, and the glass transition temperatures (Tg) of the first PHA resin and the second PHA resin are different from each other.

18. The method for preparing biodegradable multilayer films according to claim 17, wherein, The method further includes melt extrusion of ethylene vinyl alcohol (EVOH) resin to form a barrier layer, and The biodegradable resin layer and barrier layer are formed by melt co-extrusion of polyhydroxyalkanoate (PHA) resin and ethylene vinyl alcohol (EVOH) resin on a substrate layer, or by melt extrusion of each and lamination on a substrate layer.

19. The method for preparing a biodegradable multilayer thin film according to claim 18, wherein, A biodegradable resin layer and a barrier layer are formed on a base layer by melt co-extrusion, and the melt co-extrusion is carried out at a temperature of 120°C to 250°C.

20. The method for preparing a biodegradable multilayer thin film according to claim 18, wherein, The biodegradable resin layer and the barrier layer are laminated onto the base layer, and the lamination is performed by forming an adhesive layer between the base layer, the biodegradable resin layer and the barrier layer.

21. The method for preparing biodegradable multilayer films according to claim 17, wherein, Based on the total weight of the first PHA resin, the first PHA contains 15% to 60% by weight of a repeating unit of 4-hydroxybutyrate (4-HB). Based on the total weight of the second PHA resin, the second PHA contains 0.1% to 30% by weight of 4-hydroxybutyrate (4-HB) repeating units, and The first and second PHA resins differ from each other in the content of 4-HB repeating units.

22. An environmentally friendly packaging material, said environmentally friendly packaging material comprising a biodegradable multilayer film according to any one of claims 1 to 16.

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