Biodegradable resin composition for extrusion coating

Abstract

The present invention relates to a biodegradable resin composition for extrusion coating. The biodegradable resin composition for extrusion coating according to one embodiment of the present invention contains 5% to 95% by weight of PHA (polyhydroxyalkanoate), has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min at 190°C and 2.16 kg according to ASTM D1238, and the weight-average molecular weight of the PHA is in the range of 30,000 g / mol to 1,200,000 g / mol, and therefore has excellent mechanical properties such as processability and thermal adhesive strength even at low temperatures.

Description

[Technical Field]

[0001] The present disclosure relates to a biodegradable resin composition for extrusion coating that has excellent mechanical properties such as thermal adhesive strength and processability even at low temperatures. [Background technology]

[0002] In recent years, growing concerns about environmental issues have led to active research into the treatment and recycling of various household waste materials. Specifically, inexpensive and highly processable polymeric materials widely used in the manufacture of various products, such as paper, film, textiles, packaging materials, bottles, and containers, can emit harmful substances when incinerated at the end of their lifespan. Furthermore, some types of materials can take hundreds of years to decompose naturally.

[0003] Therefore, research is ongoing into biodegradable polymers that can decompose in a short period of time, making them environmentally friendly, while also improving their mechanical properties and processability, extending the life of the product itself, reducing waste, and increasing recyclability.

[0004] Polyhydroxyalkanoates (PHAs) are biodegradable resins composed of several hydroxycarboxylic acids produced by many microorganisms and used as intracellular storage materials. Polyhydroxyalkanoates have similar physical properties to conventional petroleum-derived synthetic resins such as polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate terephthalate (PBST), and polybutylene succinate adipate (PBSA), and are completely biodegradable and highly biocompatible.

[0005] Meanwhile, resins such as polyethylene (PE) and ethylene vinyl acetate (EVA), which have excellent processability due to the presence or absence of long-chain branching and high or low melt strength, have traditionally been used as resins for extrusion coating. However, PE and EVA have the disadvantage of low heat resistance, so research is underway to improve their heat resistance. Polypropylene (PP) is also used, but due to its low processability and melt strength, its use is limited to instant ramen containers and HMR food containers.

[0006] Furthermore, because PE, EVA, and PP are petrochemical resins made from petroleum, they are not biodegradable in soil or the ocean, causing environmental pollution and becoming an environmental problem in recent years. To solve these problems, extrusion coating resins using biodegradable resins such as PLA (polylactic acid), PBS, and PBAT have been developed. However, many of these resins have the disadvantage that they only decompose under specific conditions and are not easily biodegradable in the ocean.

[0007] Furthermore, these biodegradable resins have inferior mechanical properties, such as thermal adhesive strength, and are prone to thermal decomposition, making them difficult to process because the extrusion coating process is often performed at higher temperatures than film processing. While petroleum-based plastics improve processability when processed at temperatures above 300°C, many biodegradable resins thermally decompose at temperatures above 300°C, reducing their melt strength and making it difficult to operate the process properly. Prolonged heating can also cause thermal decomposition at temperatures above 260°C. During extrusion coating, the molten resin layer is not properly formed, resulting in uneven thickness and making high-speed operation difficult. For this reason, many biodegradable resin manufacturers have yet to produce a suitable biodegradable resin for extrusion coating. Therefore, biodegradable resin compositions that are environmentally friendly due to their excellent biodegradability and biocompatibility, and that also have excellent mechanical properties, such as thermal adhesive strength and processability, even at low temperatures, making them suitable for extrusion coating processes, are being investigated. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 2021-0008466 Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, an object of the present disclosure is to provide a biodegradable resin composition that is environmentally friendly due to its excellent biodegradability and biocompatibility, and that is suitable for extrusion coating processes due to its excellent mechanical properties, such as thermal adhesive strength and processability, even at low temperatures. [Means for solving the problem]

[0010] A biodegradable resin composition for extrusion coating according to one embodiment of the present disclosure contains 5% by weight to 95% by weight of polyhydroxyalkanoate (PHA), and has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, and the weight average molecular weight of the PHA is 30,000 g / mol to 1,200,000 g / mol.

[0011] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating has a viscosity reduction rate (S) according to the following formula 1 of 25% to 99%. S=((S 100 -S1) / S1)×100 (Formula 1)

[0012] In Equation 1, when the viscosity of the biodegradable resin composition for extrusion coating is measured at 210°C and a shear rate (1 / s) of 1 to 100, S1 is the viscosity (Pa s) measured at a shear rate of 1, and S 100 is the viscosity (Pa·s) measured at a shear rate of 100.

[0013] According to one embodiment of the present disclosure, S1 is 50 Pa·s to 1,200 Pa·s, and S 100 can be between 30 Pa·s and 300 Pa·s.

[0014] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating has a repulp value (P, %) according to the following formula 2 of 40% or more. P=((24-R) / 24)×100 (Formula 2)

[0015] In Equation 2, a paper substrate (basis weight: 30 g / m) was coated with the biodegradable resin composition for extrusion coating. 2 ~500g / m 2 When a biodegradable coating layer is formed on a biodegradable laminate, 24 g of the dried sample is dissociated in 1.2% water (dissociation energy consumption: 20 kWh / t) to obtain a slurry, and this slurry is circulated through a 0.15 mm slit screen at 10 L / min for 15 minutes. The dry mass (g) of the residue after circulating is defined as R.

[0016] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating may have a biocarbon content based on radioactive carbon isotope content of 25% or more as determined by ASTM D 6866-20 Method B (AMS).

[0017] According to one embodiment of the present disclosure, the PHA may comprise 4-hydroxybutyric acid (4-HB) repeat units in an amount of 0.1% to 50% by weight.

[0018] According to one embodiment of the present disclosure, the PHA may have a melt flow index (MI) of 0.5 g / 10 min to 60 g / 10 min when measured at 190° C. and 2.16 kg according to ASTM D1238.

[0019] According to one embodiment of the present disclosure, the PHA may include at least one repeat unit selected from the group consisting of 3-hydroxybutyric acid (3-HB), 3-hydroxypropionic acid (3-HP), 3-hydroxyhexanoic acid (3-HH), 3-hydroxyvaleric acid (3-HV), 4-hydroxyvaleric acid (4-HV), 4-hydroxybutyric acid (4-HB), 5-hydroxyvaleric acid (5-HV), and 6-hydroxyhexanoic acid (6-HH).

[0020] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating may further contain at least one selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), thermoplastic starch (TPS), polyvinyl alcohol (PVA), polycaprolactone (PCL), bio-based polyethylene, and bio-based polypropylene.

[0021] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating further contains polylactic acid (PLA), and the PLA may have a melt flow index (MI) of 3 g / 10 min to 40 g / 10 min when measured at 190°C and 2.16 kg according to ASTM D1238, or a melt flow index (MI) of 25 g / 10 min to 80 g / 10 min when measured at 210°C and 2.16 kg according to ASTM D1238, and a glass transition temperature (Tg) of 45°C to 65°C.

[0022] According to one embodiment of the present disclosure, the weight ratio of PHA to PLA can be 5:95 to 95:5.

[0023] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating may further include at least one additive selected from the group consisting of a slip agent, a plasticizer, an antioxidant, a nucleating agent, a lubricant, a melt strength enhancer, and a chain extender.

[0024] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating may contain additives in an amount of 0.05 phr to 20 phr.

[0025] According to one embodiment of the present disclosure, the plasticizer may include at least one selected from the group consisting of ethyl acetate, polyethylene glycol (PEG), triethyl citrate (TEC), erucamide, oleamide, stearamide, epoxidized soybean oil, dibutyl phthalate (DBP), sorbitol, carnauba wax, glycerin monostearate (GMS), polyvinyl acetate polymer, and vinyl acetate copolymer.

[0026] According to one embodiment of the present disclosure, the chain extender may include at least one selected from the group consisting of 2,5-dimethyl-2,5-(di-(tert-butylperoxy)hexane) (DTBPH), pyromellitic dianhydride (PMDA), hexamethylene diisocyanate (HMDI), dicumyl peroxide (DCP), polycarbodiimide (PCDI), di-(tert-butylperoxyisopropyl)benzene (DTBPIB), epoxy, polyamide, and oxazoline.

[0027] A biodegradable laminate according to another embodiment of the present disclosure includes a substrate layer and a biodegradable coating layer on at least one side of the substrate layer, wherein the biodegradable coating layer is formed from a biodegradable resin composition for extrusion coating, which contains 5% to 95% by weight of polyhydroxyalkanoate (PHA) and has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, and the weight average molecular weight of the PHA is 30,000 g / mol to 1,200,000 g / mol.

[0028] A method for producing a biodegradable laminate according to another embodiment of the present disclosure includes the steps of preparing a biodegradable resin composition for extrusion coating and extrusion coating the biodegradable resin composition for extrusion coating onto at least one side of a substrate to form a biodegradable coating layer, wherein the biodegradable resin composition for extrusion coating contains 5% to 95% by weight of polyhydroxyalkanoate (PHA), has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, and the weight average molecular weight of the PHA is 30,000 g / mol to 1,200,000 g / mol. [Effects of the Invention]

[0029] A biodegradable resin composition for extrusion coating according to one embodiment of the present disclosure contains 5% by mass to 95% by mass of polyhydroxyalkanoate (PHA), has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min at 190°C and 2.16 kg according to ASTM D1238, and the weight average molecular weight of the PHA is in the range of 30,000 g / mol to 1,200,000 g / mol, and therefore has excellent processability even at low temperatures and excellent mechanical properties such as thermal adhesive strength.

[0030] Specifically, the biodegradable resin composition for extrusion coating contains a polyhydroxyalkanoate (PHA) resin, which provides excellent biodegradability and biocompatibility, allowing it to biodegrade in soil and the ocean, making it environmentally friendly. Furthermore, the biodegradable resin composition for extrusion coating contains PHA and PLA with controlled fluidity, thereby controlling the melt flow index (MI) to 5 g / 10 min to 60 g / 10 min when measured at 190 °C and 2.16 kg according to ASTM D1238. As a result, the extrusion coating process can be carried out smoothly at temperatures of 150 to 260 °C, which is lower than the 300 °C required for conventional extrusion coating processes, and mechanical properties such as thermal adhesive strength are also excellent.

[0031] In particular, the extrusion coating process can be carried out at a lower temperature than in conventional extrusion coating processes, and at a temperature at which biodegradable thermal decomposition does not occur. More specifically, even at a temperature lower than the 300°C processing condition for PE and PP resins, which are conventionally used as extrusion coating resins, the same fluidity as PE and PP resins can be ensured, resulting in extremely excellent processability.

[0032] Therefore, the biodegradable resin composition for extrusion coating is biodegradable in soil and the ocean and is suitable for the extrusion coating process, making it environmentally friendly. It can be used effectively as a packaging material for food or masks, and as a material for paper cartons such as milk cartons that require airtightness and oxygen and moisture barrier properties. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a photograph showing the evaluation results of processability according to Evaluation Example 2-1 of Example 2-1 and Comparative Example 2-5. [Figure 2] 1 is a photograph showing that no coating layer was formed in the extrusion coating step of Comparative Example 2-1. [Figure 3] 1 is a photograph of an extrusion-coated product produced using a biodegradable resin composition for extrusion coating according to one embodiment of the present disclosure. [Figure 4] 1 shows the results of rheology measurements of a biodegradable resin composition for extrusion coating according to an embodiment of the present disclosure and PLA, PE, and PP, which are conventionally used as extrusion coating resins. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present disclosure will be described in detail below. However, the present disclosure is not limited to the following disclosure, and various modifications are possible within the scope of the gist of the present invention, as in the case of the following disclosure.

[0035] In this specification, when a part is described as "comprising" an element, it does not mean that the part excludes other elements, but that the part may include other elements, unless otherwise specified.

[0036] Numerical values ​​and expressions relating to amounts of components, reaction conditions, etc. used herein can be understood even if modified by the word "approximately," unless otherwise specified.

[0037] In this specification, when an element is said to be formed on or under another element, this includes not only the case where the element is formed directly on or under the element, but also the case where the element is formed indirectly on or under the element through intervening elements.

[0038] In this specification, terms such as "first," "second," etc. are used in describing various components. However, these components should not be bound by these terms. These terms are used simply to distinguish one component from another.

[0039] Biodegradable resin composition for extrusion coating A biodegradable resin composition for extrusion coating according to one embodiment of the present disclosure contains 5% by weight to 95% by weight of polyhydroxyalkanoate (PHA), and has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, and the weight average molecular weight of the PHA is 30,000 g / mol to 1,200,000 g / mol.

[0040] The biodegradable resin composition for extrusion coating can be processed smoothly in the extrusion coating process even at temperatures of 260°C or less, where thermal decomposition does not occur. More specifically, it has excellent extrusion coating performance even at low temperatures such as 230°C or less.

[0041] The biodegradable resin composition for extrusion coating can be processed at a temperature of 260°C, which is lower than the 300°C processing condition for PE and PP resins that have traditionally been used as extrusion coating resins, and can maintain the same fluidity as PE and PP resins extrusion coated at 300°C, demonstrating extremely excellent processability.

[0042] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating contains a PHA.

[0043] PHA is a natural thermoplastic polyester polymer that accumulates within microbial cells. It is a biodegradable material that can be composted and ultimately decomposed into carbon dioxide, water, and organic waste without producing hazardous waste.

[0044] Specifically, PHA is a natural thermoplastic polyester polymer that accumulates within microbial cells. When a bacterium is supplied with nutrients (nitrogen sources, phosphorus, etc.) unevenly, it accumulates PHA within the cell and stores carbon and energy.

[0045] Furthermore, PHA has similar physical properties to conventional petroleum-derived synthetic polymers such as polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate terephthalate (PBST), and polybutylene succinate adipate (PBSA), and is completely biodegradable and has excellent biocompatibility.

[0046] In particular, unlike other environmentally friendly plastic materials such as PBS, PLA, and PTT, PHA can be synthesized from over 150 types of monomers, and depending on the type of monomer, hundreds of different types of PHA can be prepared. Depending on the type of monomer, there are hundreds of different types of PHA, each with completely different structures and properties.

[0047] PHAs may be composed of a single monomer repeating unit in living cells, or may be formed by polymerizing one or more types of monomer repeating units. Specifically, PHAs may be homopolyhydroxyalkanoates (hereinafter referred to as HOMO PHAs) or polyhydroxyalkanoate copolymers (hereinafter referred to as PHA copolymers), i.e., copolymers in which different repeating units are regularly or randomly distributed in the polymer chain.

[0048] Examples of repeating units that PHA may have include 2-hydroxybutyric acid, lactic acid, glycolic acid, 3-hydroxybutyric acid (hereinafter referred to as 3-HB), 3-hydroxypropionic acid (hereinafter referred to as 3-HP), 3-hydroxyvaleric acid (hereinafter referred to as 3-HV), 3-hydroxyhexanoic acid (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-hydroxydodecanoate (hereinafter referred to as 3-HDd), 4-hydroxybutyric acid (hereinafter referred to as 4-HB), 4-hydroxyvaleric acid (hereinafter referred to as 4-HV), 5-hydroxyvaleric acid (hereinafter referred to as 5-HV), and 6-hydroxyhexanoic acid (hereinafter referred to as 6-HH). The PHA may contain one or more repeating units selected from the above.

[0049] Specifically, the PHA may contain one or more repeating units selected from the group consisting of 3-HB, 4-HB, 3-HP, 3-HH, 3-HV, 4-HV, 5-HV, and 6-HH.

[0050] More specifically, the PHA may contain 4-HB repeat units in an amount of 0.1 to 50% by weight, for example, 0.1 to 48%, 0.1 to 46%, 0.5 to 50%, 10 to 50%, 20 to 50%, 25 to 50%, 0.1 to 40%, 0.5 to 40%, 1 to 35%, or 5 to 30% by weight of 4-HB repeat units.

[0051] By ensuring that the content of 4-HB repeating units satisfies the above range, processability suitable for extrusion coating can be ensured. Specifically, by ensuring that the content of 4-HB repeating units satisfies the above range, excellent extrusion coating performance can be achieved, allowing processing at temperatures of 260°C or less, where thermal decomposition does not occur, more specifically, at temperatures of 150 to 260°C, 150 to 230°C, or 160 to 210°C. Furthermore, if the content of 4-HB repeating units is less than 0.1% by weight, the crystallinity will be too high, placing a strain on the extruder and making processing difficult. If the content exceeds 50% by weight, the crystallinity will be too low, making it difficult to ensure sufficient strength in the molten resin layer and preventing smooth processing.

[0052] The PHA may also be a PHA copolymer that contains 4-HB repeating units and one additional repeating unit different from the 4-HB repeating unit, such as two, three, four, five, six, or more additional repeating units. For example, the PHA may be poly-3-hydroxybutyrate-co-4-hydroxybutyrate (hereinafter referred to as 3HB-co-4HB).

[0053] Furthermore, PHA may contain isomers. For example, PHA may contain structural isomers, enantiomers, or geometric isomers. Specifically, PHA may contain structural isomers.

[0054] Alternatively, the PHA may be a PHA copolymer with controlled crystallinity. For example, the PHA may contain at least one type of 4-HB repeating unit, and the crystallinity of the PHA resin may be adjusted by controlling the content of the 4-HB repeating unit.

[0055] For example, the PHA may be a PHA copolymer containing at least one repeating unit selected from the group consisting of 3-hydroxybutyric acid (3-HB), 4-hydroxybutyric acid (4-HB), 3-hydroxypropionic acid (3-HP), 3-hydroxyhexanoic acid (3-HH), 3-hydroxyvaleric acid (3-HV), 4-hydroxyvaleric acid (4-HV), 5-hydroxyvaleric acid (5-HV), and 6-hydroxyhexanoic acid (6-HH).

[0056] Specifically, the copolymer PHA contains 4-HB repeating units and may further contain one or more repeating units selected from the group consisting of 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 copolymer may have 4-HB repeating units and 3-HB repeating units.

[0057] Alternatively, the PHA may be a PHA copolymer comprising 4-HB repeat units and 3-HB repeat units, with the PHA comprising 20% ​​or more by weight of 3-HB repeat units. For example, the PHA may contain 3-HB repeat units in an amount of 35% or more, 40% or more, 50% or more, 60% or more, 70% or more, or 75% or more to 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 by weight.

[0058] The crystallinity-adjusted PHA may be one in which the degree of crystallinity and amorphousness are adjusted as the degree of disorder in the molecular structure increases, specifically by adjusting the type or proportion of monomers or the type or content of isomers.

[0059] According to one embodiment of the present disclosure, the PHA may contain two or more PHAs with different crystallinity. Specifically, two or more PHAs with different crystallinity may be mixed together to adjust the content of 4-HB repeating units within the above-mentioned specific range.

[0060] Specifically, the PHA may include a first PHA that is a semi-crystalline PHA and a second PHA that is an amorphous PHA. More specifically, the first PHA may be a crystallinity-controlled semi-crystalline PHA, and the second PHA may be a crystallinity-controlled amorphous PHA. The PHA used in one embodiment of the present disclosure may be a semi-crystalline PHA or an amorphous PHA. Furthermore, the PHA used in one embodiment of the present disclosure may be a mixture of a semi-crystalline PHA and an amorphous PHA.

[0061] The glass transition temperature (Tg) of the PHA may be -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.

[0062] The crystallization temperature (Tc) of PHA may not be measured, but is often 60°C to 120°C, 60°C to 110°C, 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.

[0063] The melting point (Tm) of the PHA may not be measured, but may be 100°C to 170°C, 105°C to 170°C, 105°C to 165°C, 110°C to 160°C, 115°C to 155°C, 110°C to 150°C, 120°C to 150°C, or 120°C to 140°C.

[0064] The PHA may also have a weight-average molecular weight of 30,000 g / mol to 1,200,000 g / mol. For example, the weight-average molecular weight of the PHA may be 50,000 g / mol to 1,200,000 g / mol, 100,000 g / mol to 1,200,000 g / mol, 200,000 g / mol to 1,200,000 g / mol, 350,000 g / mol to 1,200,000 g / mol, 400,000 g / mol to 1,200,000 g / mol, 600,000 g / mol to 1,200,000 g / mol, 100,000 g / mol to 1,000,000 g / mol, or 200,000 g / mol to 900,000 g / mol.

[0065] If the weight-average molecular weight of the PHA is less than 30,000 g / mol, the melt strength will be too low, making it difficult to form a molten resin layer, i.e., a coating layer, by the extrusion coating process.If the weight-average molecular weight of the PHA is more than 1,200,000 g / mol, the load inside the extruder may make processing difficult.

[0066] The PHA may have a melt flow index (MI) of 0.5 g / 10 min to 60 g / 10 min when measured at 190°C and 2.16 kg in accordance with ASTM D1238. For example, the melt flow index (MI) of the PHA measured at 190°C and 2.16 kg in accordance with ASTM D1238 may be 0.5 g / 10 min to 40 g / 10 min, 0.7 g / 10 min to 35 g / 10 min, 0.9 g / 10 min to 35 g / 10 min, 1 g / 10 min to 35 g / 10 min, 1.5 g / 10 min to 30 g / 10 min, 3 g / 10 min to The melt flow index of the PHA may be 30g / 10 min, 0.7g / 10 min to 15g / 10 min, 0.8g / 10 min to 10g / 10 min, 1g / 10 min to 8g / 10 min, 1g / 10 min to 5g / 10 min, 20g / 10 min to 60g / 10 min, 0.5g / 10 min to 5g / 10 min, 0.5g / 10 min to 3g / 10 min, or 2g / 10 min to 15g / 10 min. When the melt flow index of the PHA satisfies the above range, it can be made to have excellent extrusion coatability, allowing it to be processed at temperatures of 260°C or less, more specifically 150 to 260°C, where thermal decomposition does not occur.

[0067] The PHA may have a crystallinity of 90% or less as measured by DSC (Differential Scanning Calorimeter). For example, the crystallinity of the PHA resin can be measured by differential scanning calorimetry and may be 90% or less, 85% or less, 80% or less, 75% or less, or 70% or less.

[0068] The PHA can have a polydispersity index (PDI) of less than 3. For example, the PHA may have a polydispersity index of 2.5 or less, 2.1 or less, or 2.0 or less.

[0069] PHAs may be obtained by cell disruption using non-mechanical or chemical methods. Specifically, PHAs are natural thermoplastic polyester polymers that accumulate within microbial cells. Because PHAs have a relatively large average particle size, they may be obtained through a disruption process to more effectively control the yield of the desired substance and improve process efficiency.

[0070] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating contains 5 to 95% by weight of the PHA. For example, the PHA content may be 5 to 90% by weight, 10 to 95% by weight, 10 to 90% by weight, 5 to 80% by weight, or 10 to 80% by weight, based on the total weight of the biodegradable resin composition for extrusion coating.

[0071] Specifically, satisfying the above content range ensures processability suitable for the extrusion coating process. More specifically, if the PHA content is less than 5 wt%, the melt flowability and biodegradation rate may decrease, and cracking at low temperatures may not be prevented. Furthermore, if the PHA content exceeds 95 wt%, the crystallization rate of the PHA is low, making it difficult to form an appropriate coating layer on the substrate.

[0072] The biodegradable resin composition for extrusion coating may further contain at least one selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), thermoplastic starch (TPS), polyvinyl alcohol (PVA), polycaprolactone (PCL), bio-based polyethylene, and bio-based polypropylene.

[0073] PHA can accelerate the decomposition rate of commonly used biodegradable resins. By using PHA together with at least one selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), thermoplastic starch (TPS), polyvinyl alcohol (PVA), polycaprolactone (PCL), bio-based polyethylene, and bio-based polypropylene, the oxygen and moisture barrier effect can be controlled, and the oxygen and moisture barrier properties can be further improved.

[0074] Specifically, the biodegradable resin composition for extrusion coating may further contain polylactic acid (PLA). More specifically, the biodegradable resin composition for extrusion coating may contain PHA and PLA. By using PLA with controlled flowability in combination with PHA, biodegradability and extrusion processability can be further improved.

[0075] The PLA may have a melt flow index (MI) of 3 g / 10 min to 40 g / 10 min when measured at 190°C and 2.16 kg in accordance with ASTM D1238. For example, the melt flow index (MI) of the PLA measured in accordance with ASTM D1238 at 190°C and 2.16 kg may be 5 g / 10 min to 40 g / 10 min, 10 g / 10 min to 40 g / 10 min, 8 g / 10 min to 35 g / 10 min, 10 g / 10 min to 25 g / 10 min, or 15 g / 10 min to 24 g / 10 min.

[0076] The PLA may have a melt flow index (MI) of 25 g / 10 min to 80 g / 10 min when measured at 210°C and 2.16 kg in accordance with ASTM D1238. For example, the melt flow index (MI) of the PLA at 210°C and 2.16 kg measured in accordance with ASTM D1238 may be 26 g / 10 min to 65 g / 10 min, 30 g / 10 min to 62 g / 10 min, 35 g / 10 min to 80 g / 10 min, or 40 g / 10 min to 60 g / 10 min.

[0077] The PLA may have a glass transition temperature (Tg) of 45 to 65°C. For example, the glass transition temperature (Tg) of the PLA may be 45 to 60°C, 50 to 65°C, or 55 to 60°C.

[0078] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating may contain 5 to 95% by weight of PLA. For example, the PLA content may be 10 to 95% by weight, 20 to 95% by weight, 30 to 95% by weight, 10 to 90% by weight, 30 to 90% by weight, 5 to 80% by weight, or 10 to 80% by weight, based on the total weight of the biodegradable resin composition for extrusion coating.

[0079] The weight ratio of PHA to PLA may be 5:95 to 95:5. For example, the weight ratio of PHA to PLA may be 5:95 to 90:10, 10:90 to 80:20, 20:80 to 70:30, 50:50 to 70:30, or 5:95 to 50:50.

[0080] When the melt flow index and glass transition temperature of PLA satisfy the above ranges, processability suitable for extrusion coating can be ensured. Furthermore, when the PLA content and weight ratio to PHA satisfy the above ranges, processability suitable for extrusion coating can be further improved.

[0081] According to one embodiment of the present disclosure, the biodegradable resin composition for extrusion coating may further include at least one additive selected from the group consisting of a slip agent, a plasticizer, an antioxidant, a nucleating agent, a lubricant, a melt strength enhancer, and a chain extender.

[0082] The biodegradable resin composition for extrusion coating may contain additives in an amount of 0.05 to 20 phr. For example, the additive content may be 0.05 to 15 phr, 0.1 to 10 phr, 0.15 to 8 phr, 0.2 to 6 phr, or 0.5 to 3 phr. Here, phr (per hundred resin) refers to the unit of input amount of material added to 100 parts by weight of polymer (1 phr: 1 g input amount per 100 g of polymer).

[0083] The slip agent may contain at least one selected from the group consisting of fatty acids or their salts, waxes, and amide compounds. For example, the slip agent may contain at least one selected from the group consisting of stearic acid and its monomers, oleic acid and its monomers, palmitic acid and its monomers, silicone, fatty acid alcohols, oleamide, erucamide, stearamide, calcium stearate, zinc stearate, magnesium stearate, aluminum stearate, potassium oleate, zinc oleate, magnesium oleate, aluminum oleate, calcium palmitate, zinc palmitate, magnesium palmitate, aluminum palmitate, ethylene bis(stearamide) (EBS), beeswax, carnauba wax, and candelilla wax.

[0084] The biodegradable resin composition for extrusion coating may contain the slip agent in an amount of 0.1 to 5 phr, for example, 0.1 to 3 phr, 0.2 to 2.5 phr, 0.3 to 1.5 phr, or 0.5 to 1.2 phr.

[0085] The plasticizer may include at least one selected from the group consisting of ethyl acetate, polyethylene glycol (PEG), triethyl citrate (TEC), erucamide, oleamide, stearamide, epoxidized soybean oil, dibutyl phthalate (DBP), carnauba wax, glycerin monostearate (GMS), sorbitol, polyvinyl acetate polymer, and vinyl acetate copolymer.

[0086] The biodegradable resin composition for extrusion coating may contain a plasticizer in an amount of 0.05 to 10 phr. For example, the content of the plasticizer may be 0.1 to 8 phr, 0.1 to 5 phr, 0.2 to 2 phr, or 0.5 to 1.5 phr.

[0087] The antioxidant is an additive for preventing decomposition by ozone or oxygen, preventing oxidation during storage, or preventing deterioration of physical properties. Conventional antioxidants may be used as long as they do not impair the effects of the present disclosure.

[0088] Specifically, the antioxidant may include at least one selected from the group consisting of hindered phenol-based antioxidants and phosphite (phosphorus-based) antioxidants.

[0089] The hindered phenol-based antioxidant may include, for example, at least one selected from the group consisting of 4,4'-methylenebis(2,6-di-t-butylphenol), octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[3-(3,5-di-t-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.

[0090] The phosphite (phosphorus) antioxidant may include at least one selected from the group consisting of, for example, tris-(2,4-di-t-butylphenyl)phosphite, bis-(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis-(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, distearyl-pentaerythritol diphosphite, [bis(2,4-di-t-butyl-5-methylphenoxy)phosphino]biphenyl, and N,N-bis[2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxyphosphepin-6-yl]oxy]-ethyl]ethanamine.

[0091] The biodegradable resin composition for extrusion coating may contain an antioxidant in an amount of 0.05 phr to 10 phr. For example, the content of the antioxidant may be 0.1 phr to 3 phr, 0.2 phr to 2.5 phr, 0.3 phr to 1.5 phr, or 0.5 phr to 1.2 phr.

[0092] The nucleating agent may be one that more effectively controls the crystallinity of the biodegradable resin composition for extrusion coating. When the same preparation process is used, processability, such as processing speed, can be further improved. For example, the nucleating agent may contain carbonates, silicates, etc. Examples of nucleating agents include, but are not limited to, calcium carbonate, silica, talc, boron nitride, cellulose, and sorbitol derivatives.

[0093] The biodegradable resin composition for extrusion coating may contain the nucleating agent in an amount of 0.1 to 20 phr. For example, the content of the nucleating agent may be 1 to 20 phr, 3 to 18 phr, 5 to 15 phr, or 6 to 10 phr.

[0094] Lubricants are components added to strengthen the binding or affinity between resins, reduce frictional heat generated during extrusion to prevent thermal decomposition, and ensure a smooth extrusion process. They can provide good workability while maintaining mechanical properties similar to those of the base material. For example, the lubricant may be one or a mixture of two or more environmentally friendly natural products selected from the group consisting of stearates, palmitates, and laurates, or sorbitol, but are not limited thereto.

[0095] The biodegradable resin composition for extrusion coating may contain the lubricant in an amount of 0.05 to 10 phr, for example, 0.05 to 5 phr, 0.1 to 3.5 phr, 0.2 to 3 phr, 0.5 to 2.5 phr, or 1 to 2 phr.

[0096] The chain extender may include at least one selected from the group consisting of 2,5-dimethyl-2,5-(di-(tert-butylperoxy)hexane) (DTBPH), pyromellitic dianhydride (PMDA), hexamethylene diisocyanate (HMDI), dicumyl peroxide (DCP), polycarbodiimide (PCDI), di-(tert-butylperoxyisopropyl)benzene (DTBPIB), epoxy, polyamide, and oxazoline.

[0097] The biodegradable resin composition for extrusion coating may contain the chain extender in an amount of 0.05 to 5 phr. For example, the content of the chain extender may be 0.05 to 4 phr, 0.1 to 3 phr, 0.15 to 2 phr, 0.2 to 1.5 phr, or 0.2 to 1 phr.

[0098] According to one embodiment of the present disclosure, the melt flow index (MI) of the biodegradable resin composition for extrusion coating, measured in accordance with ASTM D1238 at 190°C and 2.16 kg, is 5 g / 10 min to 60 g / 10 min, 5 g / 10 min to 50 g / 10 min, 5 g / 10 min to 42 g / 10 min, 7 g / 10 min to 45 g / 10 min, 7 g / 10 min to 30 g / 10 min, 7 g / 10 min to 75 g / 10 min, 7 g / 10 min to 80 g / 10 min, 7 g / 10 min to 90 g / 10 min, 7 g / 10 min to 95 g / 10 min, 7 g / 10 min to 100 g / 10 min, 7 g / 10 min to 120 g / 10 min, 7 g / 10 min to 140 g / 10 min, 7 g / 10 min to 160 g / 10 min, 7 g / 10 min to 18 ... g / 10 min to 25g / 10 min, 8g / 10 min to 60g / 10 min, 10g / 10 min to 60g / 10 min, 14g / 10 min to 60g / 10 min, 15g / 10 min to 60g / 10 min, 20g / 10 min to 60g / 10 min, 8g / 10 min to 40g / 10 min, 10g / 10 min to 40g / 10 min, or 10g / 10 min to 35g / 10 min.

[0099] A melt flow index within the above range ensures processability suitable for extrusion coating. More specifically, if the melt flow index is less than 5 g / 10 min, surface crystallization and solidification proceed rapidly during film extrusion, making it difficult to ensure sufficient adhesion to the substrate. Therefore, to ensure sufficient bonding to substrates such as paper or nonwoven fabrics, which are commonly used, the processing temperature must be increased to 260°C or higher.

[0100] However, at temperatures above 260°C, the melt strength of many biodegradable resins decreases, making high-speed processing impossible, thermal decomposition occurs, or fluidity becomes unstable, making processing difficult. Furthermore, if the melt flow index exceeds 60 g / 10 min, the melt strength of the resin decreases, making it difficult to form a coating layer, i.e., a molten resin layer. Even if a molten resin layer is formed, increasing the processing speed will cause the thickness to increase unstably in weak parts of the molten resin layer, resulting in very poor thickness uniformity.

[0101] Furthermore, the biodegradable resin composition for extrusion coating may have a viscosity reduction rate (S) according to the following formula 1 of 25 to 99%. S=((S 100 -S1) / S1)×100 (Formula 1)

[0102] In Equation 1, when the viscosity of the biodegradable resin composition for extrusion coating is measured at 210°C and a shear rate (1 / s) of 1 to 100, S1 is the viscosity (Pa s) measured at a shear rate of 1, and S 100 is the viscosity (Pa·s) measured at a shear rate of 100.

[0103] For example, the viscosity reduction rate (S) according to the above formula 1 may be 25 to 98%, 30 to 97%, 40 to 95%, 42 to 98%, 42 to 95%, 40 to 90%, 50 to 87%, or 55 to 85%.

[0104] When the viscosity reduction rate (S) according to the above formula 1 in the biodegradable resin composition for extrusion coating according to one embodiment of the present disclosure satisfies the above range, fluidity suitable for the extrusion process can be ensured even at an extrusion process temperature of 210°C, which is lower than conventional temperatures.

[0105] The shear rate may be measured using, but is not limited to, a rotational rheometer.

[0106] S1 may be 50 Pa·s to 1,200 Pa·s, and S 100 For example, S1 may be 50 Pa·s to 1000 Pa·s, 50 Pa·s to 900 Pa·s, 50 Pa·s to 850 Pa·s, 50 Pa·s to 750 Pa·s, 50 Pa·s to 500 Pa·s, 100 Pa·s to 600 Pa·s, 120 Pa·s to 550 Pa·s, or 150 Pa·s to 400 Pa·s, and S 100 The viscosity may be 45 Pa·s to 200 Pa·s, 50 Pa·s to 150 Pa·s, 60 Pa·s to 100 Pa·s, or 70 Pa·s to 90 Pa·s.

[0107] The biodegradable resin composition for extrusion coating has a viscosity (S 10 ) may be 40 Pa·s to 800 Pa·s, 50 Pa·s to 650 Pa·s, 55 Pa·s to 500 Pa·s, 60 Pa·s to 400 Pa·s, or 70 Pa·s to 350 Pa·s.

[0108] S1, S 10 , and S 100 When the above range is satisfied, the processability suitable for the extrusion coating process can be further improved.

[0109] FIG. 4 shows the results of rheology measurements of the biodegradable resin composition for extrusion coating according to an embodiment of the present disclosure and PLA, PE, and PP, which are conventionally used as resins for extrusion coating.

[0110] Specifically, the viscosities of the biodegradable resin composition for extrusion coating containing PHA, and PLA, PE, and PP were measured using a rotational rheometer at shear rates (1 / s) of 1 to 100. In this case, the measurement temperature was 210°C for the biodegradable resin composition for extrusion coating, 240°C for PLA, and 300°C for PE and PP.

[0111] 4, the viscosity reduction rate at shear rates of 1 to 100 indicates that the biodegradable resin composition for extrusion coating according to the present disclosure has a fluidity similar to that of PE, despite being processed at a lower temperature than PE. Therefore, the biodegradable resin composition for extrusion coating according to an embodiment of the present disclosure can have a fluidity similar to that of PE, which has traditionally been used as an extrusion coating resin. It also has excellent extrusion coating performance, allowing it to be processed at temperatures of 260°C or lower, more specifically, 210°C, at which thermal decomposition does not occur.

[0112] The biodegradable resin composition for extrusion coating may have a repulp value (P, %) of 40% or more according to the following formula 2: P=((24-R) / 24)×100 (Formula 2)

[0113] In Equation 2, a paper substrate (basis weight: 30 g / m) was coated with the biodegradable resin composition for extrusion coating. 2 ~500g / m 2 When a biodegradable coating layer is formed on a biodegradable laminate, 24 g of the dried sample is dissociated in 1.2% water (dissociation energy consumption: 20 kWh / t) to obtain a slurry, and this slurry is circulated through a 0.15 mm slit screen at 10 L / min for 15 minutes. The dry mass (g) of the residue after circulating is defined as R.

[0114] For example, the repulp value according to the above formula 2 may be 42% or more, 45% or more, 50% or more, 60% or more, 70% or more, 75% or more, or 80% or more. When the repulp value according to the above formula 2 satisfies the above range, excellent biodegradability can be achieved, and recyclability can be further improved.

[0115] More specifically, the repulp value may vary depending on the basis weight of the paper substrate used.

[0116] biodegradable laminate A biodegradable laminate according to another embodiment of the present disclosure includes a substrate layer and a biodegradable coating layer on at least one side of the substrate layer, the biodegradable coating layer being formed from a biodegradable resin composition for extrusion coating containing 5% to 95% by weight of polyhydroxyalkanoate (PHA), and the biodegradable resin composition has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, and the weight average molecular weight of the PHA is 30,000 g / mol to 1,200,000 g / mol.

[0117] Since the biodegradable laminate has a biodegradable coating layer formed from the biodegradable resin composition for extrusion coating, it is biodegradable in soil and the ocean and can be used as a packaging material applicable to food, industry, cosmetics, etc.

[0118] For example, the above-mentioned biodegradable laminate can be applied to environmentally friendly packaging materials for packaging products, and can be used as packaging materials for foods such as coffee, cup rice, cup ramen, dried fish, etc., as packaging materials for masks, medicines, etc., and can be applied to secondary packaging materials for protecting primary packaged products, but is not limited to these.

[0119] Furthermore, the biodegradable laminate can exhibit excellent effects when used as a paper pack such as a milk pack that requires oxygen and moisture barrier properties or airtightness, and packaging materials manufactured using the biodegradable laminate can be in the form of a pouch, paper container, sheet, etc., but are not limited to these.

[0120] Furthermore, packaging materials containing the above-mentioned biodegradable laminates can be biodegraded in soil and the ocean, and therefore when discarded in nature, particularly when discarded in the ocean, they can be decomposed by microorganisms without requiring special conditions for biodegradation.

[0121] From the viewpoint of improving coating properties, it may be preferable that the substrate layer is a substrate made of a single material. The substrate may be, for example, paper, kraft paper, cloth, nonwoven fabric, etc., or may be, but is not limited to, polyolefin film, PET film, nylon film, cotton, metal foil, wood, etc. Furthermore, when the substrate comprises paper or kraft paper, it has better biodegradability than other plastic materials, which may be advantageous in providing an environmentally friendly packaging material.

[0122] The substrate layer may have a thickness of 15 μm or more. For example, the thickness of the substrate layer may be 15 μm or more, 20 μm or more, 50 μm or more, 70 μm or more, 100 μm or more, 130 μm or more, 150 μm or more, 200 μm or more, 300 μm or more, or 500 μm or more.

[0123] The base weight of the base layer is 30 g / m 2 ~500g / m 2 The substrate layer may be, for example, paper, kraft paper, woven fabric, knitted fabric, or nonwoven fabric, and the basis weight of the substrate may be 30 g / m 2 ~500g / m 2 , 30g / m 2 ~350g / m 2 , 30g / m 2 ~200g / m 2 , 50g / m 2 ~200g / m 2 , 80g / m 2 ~200g / m 2 , 100g / m 2 ~200g / m 2 , 130g / m 2 ~190g / m 2 , 150g / m 2 ~185g / m 2 , or 120 g / m 2 ~320g / m 2 It can be.

[0124] On the other hand, a barrier layer may be disposed on at least one side of the substrate layer. An environmentally friendly blocking layer may be applied to the surface of the substrate layer to provide moisture and / or oxygen barrier properties, and a functional coating layer having antistatic properties or adhesive properties may also be formed. The functional coating layer may include a primer coating layer and an adhesive coating layer, and may have commonly used materials and physical properties as long as the desired effects of the present disclosure are not impaired.

[0125] The thickness of the biodegradable coating layer can be 5 μm to 70 μm, 5 μm to 50 μm, 5 μm to 40 μm, or 6 μm to 30 μm.

[0126] The biodegradable coating layer may have a thermal adhesive strength (sealing strength) of 500 gf or more. For example, the thermal adhesive strength (sealing strength) of the biodegradable coating layer may be 600 gf or more, 800 gf or more, 1000 gf or more, or 1200 gf or more. If the thermal adhesive strength of the biodegradable coating layer obtained by the extrusion coating process is less than 500 gf, it may not be applicable as a packaging material and may be limited to lightweight packaging materials.

[0127] The biodegradable coating layer may have a peel strength of 200 gf or more. For example, the peel strength of the biodegradable coating layer may be 300 gf or more, 350 gf or more, 400 gf or more, or 500 gf or more.

[0128] Method for producing biodegradable laminate A method for producing a biodegradable laminate according to another embodiment of the present disclosure includes the steps of preparing a biodegradable resin composition for extrusion coating and extrusion coating the biodegradable resin composition for extrusion coating onto at least one side of a substrate to form a biodegradable coating layer, wherein the biodegradable resin composition for extrusion coating contains 5% to 95% by weight of polyhydroxyalkanoate (PHA), has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, and the weight average molecular weight of the PHA is 30,000 g / mol to 1,200,000 g / mol.

[0129] The details of the biodegradable resin composition for extrusion coating are as already explained.

[0130] The amount of the biodegradable resin composition for extrusion coating applied to at least one side of the substrate is 6 g / m 2 ~120g / m 2 , 6g / m 2 ~100g / m 2 , 8g / m 2 ~80g / m 2 , 9g / m 2 ~70g / m 2 , 10g / m 2 ~60g / m 2 , 12g / m 2 ~60g / m 2 , or 13 g / m 2 ~45g / m 2 When the coating amount satisfies the above range, coating properties, productivity, and processability can be further improved.

[0131] The coating step may be carried out at 150 to 260° C. For example, the coating step is an extrusion coating step, and may be carried out at 150 to 250° C., 150 to 240° C., or 160 to 210° C. The coating step, specifically the extrusion coating step, can be carried out at a temperature lower than the conventional temperature of 300° C., while ensuring sufficient thermal adhesive strength and fluidity.

[0132] In extrusion coating, a low coating amount is required for high-speed processing, so if the melt strength is low, high-speed processing becomes difficult, and it may be difficult to form a thin coating layer. However, the biodegradable resin composition for extrusion coating according to one embodiment of the present disclosure can ensure sufficient physical properties, more specifically, fluidity such as melt viscosity, even at low temperatures, so that a thin coating layer can be formed.

[0133] Mode of Invention The present disclosure will be described in more detail below with reference to examples. However, the following examples are for the purpose of illustrating the present disclosure and are not intended to limit the scope of the present disclosure to these examples alone. [Example]

[0134] Preparation of biodegradable resin compositions for extrusion coating Example 1-1 Polylactic acid resin (PLA, manufacturer: TotalEnergies Corbion, weight average molecular weight (Mw): 120,000 g / mol to 250,000 g / mol, melt flow index (MI) at 190 °C and 2.16 kg per ASTM D1238: 10 g / 10 min to 40 g / 10 min) and polyhydroxyalkanoate (PHA; poly(3-hydroxybutyrate-co-4-hydroxybutyrate), 4-hydroxybutyrate (4-HB) content: 0.1 wt%, weight average molecular weight (Mw): 600,000 g / mol, ASTM A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 25 g / 10 min) was produced by mixing two resins (based on D1238, melt flow index at 190°C, 2.16 kg: 2 g / 10 min to 15 g / 10 min) in a weight ratio of 95:5, adding 1 phr of an epoxy chain extender and 2 phr of a sorbitol lubricant. Here, phr (per hundred resin) refers to the unit of input amount of material added per 100 parts by weight of polymer (1 phr: 1 g input amount per 100 g of polymer).

[0135] Example 1-2 A biodegradable resin composition for extrusion coating (melt flow index at 190°C and 2.16 kg: 24 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C and 2.16 kg according to ASTM D1238: 1 g / 10 min to 5 g / 10 min) was used.

[0136] Examples 1-3 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 17 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C, 2.16 kg: 1 g / 10 min to 5 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 80:20.

[0137] Examples 1-4 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 42 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 120,000 g / mol, melt flow index at 190°C, 2.16 kg: 20 g / 10 min to 60 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 50:50.

[0138] Examples 1-5 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 14 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C, 2.16 kg: 1 g / 10 min to 5 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 50:50.

[0139] Examples 1-6 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 7 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 1,200,000 g / mol, melt flow index at 190°C, 2.16 kg: 0.5 g / 10 min to 3 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 50:50.

[0140] Examples 1-7 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 10 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C, 2.16 kg: 1 g / 10 min to 5 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 30:70.

[0141] Examples 1-8 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 5 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 0.1 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C, 2.16 kg: 2 g / 10 min to 15 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 5:95.

[0142] Examples 1-9 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 5 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C, 2.16 kg: 1 g / 10 min to 5 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 5:95.

[0143] Comparative Example 1-1 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 24 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 0.1 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C, 2.16 kg: 1 g / 10 min to 5 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 97:3.

[0144] Comparative Example 1-2 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 22 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C, 2.16 kg: 1 g / 10 min to 5 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 97:3.

[0145] Comparative Examples 1-3 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 42 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 25,000 g / mol, melt flow index at 190°C, 2.16 kg: 30 g / 10 min to 90 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 80:20.

[0146] Comparative Examples 1-4 A biodegradable resin composition for extrusion coating (melt flow index at 190°C and 2.16 kg: 13 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 0.05 wt %, weight average molecular weight (Mw): 600,000 g / mol) was mixed with PLA in a weight ratio of 50:50.

[0147] Comparative Examples 1-5 A biodegradable resin composition for extrusion coating (melt flow index at 190°C and 2.16 kg: 11 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 64 wt %, weight average molecular weight (Mw): 600,000 g / mol) was mixed with PLA in a weight ratio of 50:50.

[0148] Comparative Examples 1-6 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 5 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 1,400,000 g / mol, melt flow index at 190°C, 2.16 kg: 0.5 g / 10 min to 2 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 50:50.

[0149] Comparative Examples 1-7 A biodegradable resin composition for extrusion coating (melt flow index at 190°C and 2.16 kg: 8 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 0.05 wt %, weight average molecular weight (Mw): 600,000 g / mol) was mixed with PLA in a weight ratio of 30:70.

[0150] Comparative Examples 1-8 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 68 g / 10 min) was produced in the same manner as in Example 1-1, except that polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 25,000 g / mol, melt flow index at 190°C, 2.16 kg: 30 g / 10 min to 90 g / 10 min according to ASTM D1238) was mixed with PLA in a weight ratio of 5:95.

[0151] Comparative Examples 1-9 A biodegradable resin composition for extrusion coating (melt flow index at 190°C, 2.16 kg: 3 g / 10 min) was produced in the same manner as in Example 1-1, except that 100 parts by weight of polyhydroxyalkanoate (PHA; 4-hydroxybutyric acid (4-HB) content: 46 wt %, weight average molecular weight (Mw): 600,000 g / mol, melt flow index at 190°C, 2.16 kg: 1 g / 10 min to 5 g / 10 min according to ASTM D1238) was used without being mixed with PLA.

[0152] Evaluation example 1-1: Melt flow index The melt flow index (MI) of the biodegradable resin compositions for extrusion coating prepared in Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-9 was measured at 190°C and 2.16 kg in accordance with ASTM D1238.

[0153] Evaluation example 1-2: Flow analysis The biodegradable resin compositions for extrusion coating prepared in Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-9 were subjected to rheological analysis using a rotational rheometer (trade name: MCR102e, manufacturer: Anton Paar).

[0154] Specifically, the viscosity of each biodegradable resin composition for extrusion coating was measured at 210°C at a shear rate (1 / s) of 1 to 100 using a rotational rheometer (product name: MCR102e, manufacturer: Anton Paar). At this time, the viscosity reduction rate (S) was calculated using the following formula 1 to evaluate the rheology, i.e., fluidity, of the biodegradable resin composition for extrusion coating. S=((S 100 -S1) / S1)×100 (Formula 1)

[0155] In Equation 1, the viscosity of the biodegradable resin composition for extrusion coating is the viscosity (Pa·s) when measured at 210°C and at a shear rate (1 / s) of 1 to 100, where S1 is the viscosity measured at a shear rate of 1, S2 is the viscosity measured at a shear rate of 100, and S3 is the viscosity measured at a shear rate of 100.100 )

[0156] [Table 1]

[0157] From Table 1 above, it can be seen that the biodegradable resin compositions for extrusion coating of Examples 1-1 to 1-9 have melt flow indexes and viscosity reduction rates at 190°C and 2.16 kg according to ASTM D1238 that both satisfy the desired ranges, and therefore have flow properties, including fluidity, that are suitable for the extrusion coating process. In particular, they can be processed at temperatures of 260°C or less, and have excellent extrusion coating performance at 210°C, a temperature at which thermal decomposition does not occur.

[0158] Preparation of biodegradable laminate Example 2-1 The biodegradable resin composition for extrusion coating of Example 1-1 was applied to a paper substrate (manufacturer: Hankook Paper, basis weight: 280 g / m) using a 120Φ extruder (1600 mm wide die), which is an extrusion coating facility for producing paper packaging materials. 2 A biodegradable laminate with a biodegradable coating layer (thickness: 0.045 mm) was produced by extrusion coating on one side of a sheet of paper (width: 1,000 mm, thickness: 0.352 mm) at a processing temperature of 210°C, a cooling roll temperature of 23°C, and a processing speed starting from 10 m / min and increasing to 90 m / min.

[0159] Examples 2-2 to 2-9 and Comparative Examples 2-1 to 2-9 Biodegradable laminates were produced in the same manner as in Example 2-1, except that the biodegradable coating compositions for extrusion coating prepared in Examples 1-2 to 1-9 and Comparative Examples 1-1 to 1-9 were used, respectively. However, in Comparative Examples 2-1 to 2-4 and 2-6 to 2-8, it was not possible to form a coating layer under the above process conditions.

[0160] Figure 2 is a photograph showing that a coating layer was not formed in the extrusion coating process of Comparative Example 2-1. As can be seen from Figure 2, Comparative Example 2-1 had low fusion strength, holes were formed in the molten resin layer, i.e., the coating layer, and fluidity was uneven, so an appropriate coating layer was not formed.

[0161] Evaluation example 2-1: Workability The coating processability of the biodegradable laminates of Examples 2-1 to 2-9 and Comparative Examples 2-1 to 2-9 was evaluated.

[0162] Specifically, using a 120Φ extruder (1600 mm wide die), which is extrusion coating equipment for producing paper packaging materials, extrusion coating was performed at a processing speed starting from 10 m / min and gradually increasing to 90 m / min, and the condition of the formed coated surface was visually observed, and the speed just before the coated surface became disordered, such as the generation of bubbles, was measured. In such cases, if the processing speed at which an uneven coated surface was observed was 60 m / min or higher, a circle was marked. Note that if the processing speed at which an uneven coated surface was observed was less than 60 m / min, a cross was marked.

[0163] 1 is a photograph showing the evaluation results of processability for Evaluation Example 2-1 of Example 2-1 and Comparative Example 2-1. As can be seen from Fig. 1, the coated surface of Example 2-1 was uniform, whereas the coated surface of Comparative Example 2-1 was uneven.

[0164] Evaluation example 2-2: Peel strength The biodegradable laminates of Examples 2-1 to 2-9 and Comparative Examples 2-5 and 2-9 were each cut to a width of 15 mm and a length of 30 mm to prepare samples, and the peel strength between the substrate and the biodegradable coating layer was measured at a speed of 200 mm / min using a universal testing machine (product name: 34SC-1, manufacturer: Instron).

[0165] Evaluation example 2-3: Thermal adhesive strength The biodegradable laminates of Examples 2-1 to 2-9 and Comparative Examples 2-5 and 2-9 were each cut to a width of 15 mm and a length of 30 mm to prepare samples, and the thermal adhesive strength (sealing strength) between the substrate and the biodegradable coating layer was measured at a speed of 200 mm / min using a universal testing machine (product name: 34SC-1, manufacturer: Instron). The sealing between the substrate and the biodegradable coating layer was performed at a temperature of 140°C for 1 second.

[0166] Evaluation Example 2-4: Renewability The biodegradable laminates of Examples 2-1 to 2-9 and Comparative Examples 2-1 to 2-9 were evaluated for recyclability as paper products using the UL2485 Environmental Claim Verification Procedure (ECVP).

[0167] Specifically, each biodegradable laminate was dried at room temperature for 24 hours, and then 24g samples were prepared. The samples were adjusted to a 1.2% concentration using a standard disintegrator equipped with a power measurement device and disintegrated until the disintegration energy consumption reached 20kWh / t. The disintegrated slurry samples were sent to a screen classifier, where they were subjected to a bonding process while circulating a total of 30 liters of water at a flow rate of 10 L / min for 15 minutes. In this case, the material that passed through the 0.15mm screen in the screen classifier was further subjected to a junction process using a 200-mesh sieve to prevent it from being mixed with the circulating water.

[0168] The material remaining on the 200-mesh sieve was placed in a circulation tank containing fine particles that had passed through the 200-mesh sieve and thoroughly stirred. Three liters of the suspension were collected. The collected suspension was filtered through a filter device using filter paper of known dry weight, dried in accordance with Section 8 of KS M ISO 638, and weighed. The repulp value (P,%) was calculated using the following formula 2 to evaluate recyclability. P=((24-R) / 24)×100 (Formula 2)

[0169] In Equation 2, a paper substrate (basis weight: 280 g / m) was coated with the biodegradable resin composition for extrusion coating. 2 When a biodegradable laminate was obtained by forming a 0.045 mm thick biodegradable coating layer on a 1000 mm x 1,000 mm wide x 0.352 mm thick sheet, 24 g of the dried sample was dissociated in 1.2% water (dissociation energy consumption: 20 kWh / t) to obtain a slurry, which was then passed through a 0.15 mm slit screen and circulated at 10 L / min for 15 minutes. The dry mass (g) of the residue was defined as R.

[0170] [Table 2]

[0171] *If no measurement was performed because a biodegradable coating layer was not formed, this is indicated by "-".

[0172] From Table 2 above, it can be seen that the biodegradable laminates of Examples 2-1 to 2-9 were excellent in all of processability, peel strength, sealing strength, and recyclability. Specifically, the biodegradable laminates of Examples 2-1 to 2-9 each had a biodegradable coating layer formed using the biodegradable resin composition of Examples 1-1 to 1-9, and were able to form a uniform coating layer on the coating surface at a lower processing temperature of 210°C than conventional ones and at a processing speed of 60 m / min or more, and had excellent peel strength and sealing strength from the substrate, a high repulp value, and excellent recyclability.

[0173] In contrast, the biodegradable laminates of Comparative Examples 2-1 to 2-3 and 2-8 used the biodegradable resin compositions of Comparative Examples 1-1 to 1-3 and 1-8, respectively, which had low fluidity, and therefore it was impossible to form a coating layer under the above process conditions. In Comparative Examples 2-4, 2-6, and 2-7, the load on the extruder was too great, making coating impossible. Furthermore, in Comparative Examples 2-5 and 2-9, although a coating layer could be formed, the coated surface was uneven, and processability and quality were inferior compared to Examples 2-1 to 2-9, even at a very low processing speed. In particular, Comparative Example 2-9 had significantly lower peel strength and sealing strength than Examples 2-1 to 2-9.

Claims

1. A biodegradable resin composition for extrusion coating, comprising 5% by weight to 95% by weight of a polyhydroxyalkanoate (PHA), having a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, and the weight average molecular weight of the PHA is 30,000 g / mol to 1,200,000 g / mol.

2. The biodegradable resin composition for extrusion coating according to claim 1, having a viscosity reduction rate (S) of 25% to 99% according to the following formula 1: S = ((S) １００ -S １ ) / S １ ) × 100 (Formula 1) In Equation 1, when the viscosity of the biodegradable resin composition for extrusion coating is measured at 210°C and a shear rate of 1 to 100 (1 / s), S １ is the viscosity (Pa s) measured at a shear rate of 1, and S １００ is the viscosity (Pa·s) measured at a shear rate of 100.

3. The S １ is 50 Pa·s to 1,200 Pa·s, and １００ 3. The biodegradable resin composition for extrusion coating according to claim 2, wherein the viscosity is 30 Pa·s to 300 Pa·s.

4. The biodegradable resin composition for extrusion coating according to claim 1, having a repulp value (P, %) of 40% or more according to the following formula 2: P=((24-R) / 24)×100 (Formula 2) In Equation 2, a paper substrate (basis weight: 30 g / m) was coated with the biodegradable resin composition for extrusion coating. ２ ~500g / m ２ When a biodegradable coating layer was formed on a biodegradable laminate, 24 g of the dried sample was dissociated in 1.2% water (dissociation energy consumption: 20 kWh / t) to obtain a slurry, and this slurry was circulated through a 0.15 mm slit screen at 10 L / min for 15 minutes. The dry mass (g) of the residue was defined as R.

5. 2. The biodegradable resin composition for extrusion coating according to claim 1, wherein the biocarbon content based on the radioactive carbon isotope content according to ASTM D 6866-20 Method B (AMS) is 25% or more.

6. 2. The biodegradable resin composition for extrusion coating according to claim 1, wherein the polyhydroxyalkanoate (PHA) contains 0.1% by weight to 50% by weight of 4-hydroxybutyric acid (4-HB) repeating units.

7. 2. The biodegradable resin composition for extrusion coating according to claim 1, wherein the PHA has a melt flow index (MI) of 0.5 g / 10 min to 60 g / 10 min when measured at 190°C and 2.16 kg in accordance with ASTM D1238.

8. 2. The biodegradable resin composition for extrusion coating according to claim 1, wherein the PHA contains at least one repeating unit selected from the group consisting of 3-hydroxybutyric acid (3-HB), 3-hydroxypropionic acid (3-HP), 3-hydroxyhexanoic acid (3-HH), 3-hydroxyvaleric acid (3-HV), 4-hydroxyvaleric acid (4-HV), 4-hydroxybutyric acid (4-HB), 5-hydroxyvaleric acid (5-HV), and 6-hydroxyhexanoic acid (6-HH).

9. 2. The biodegradable resin composition for extrusion coating according to claim 1, further comprising at least one selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), thermoplastic starch (TPS), polyvinyl alcohol (PVA), polycaprolactone (PCL), bio-based polyethylene, and bio-based polypropylene.

10. 2. The biodegradable resin composition for extrusion coating according to claim 1, further comprising polylactic acid (PLA), wherein the PLA has a melt flow index (MI) of 3 g / 10 min to 40 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, a melt flow index (MI) of 25 g / 10 min to 80 g / 10 min when measured in accordance with ASTM D1238 at 210°C and 2.16 kg, and a glass transition temperature (Tg) of 45°C to 65°C.

11. 11. The biodegradable resin composition for extrusion coating according to claim 10, wherein the weight ratio of the PHA to the PLA is 5:95 to 95:

5.

12. The biodegradable resin composition for extrusion coating according to claim 1, further comprising at least one additive selected from the group consisting of slip agents, plasticizers, antioxidants, nucleating agents, lubricants, melt strength enhancers, and chain extenders.

13. The biodegradable resin composition for extrusion coating according to claim 12, comprising the additive in an amount of 0.05 phr to 20 phr.

14. 13. The biodegradable resin composition for extrusion coating according to claim 12, wherein the plasticizer comprises at least one selected from the group consisting of ethyl acetate, polyethylene glycol (PEG), triethyl citrate (TEC), erucamide, oleamide, stearamide, epoxidized soybean oil, dibutyl phthalate (DBP), carnauba wax, glycerin monostearate (GMS), sorbitol, polyvinyl acetate polymer, and vinyl acetate copolymer.

15. 13. The biodegradable resin composition for extrusion coating according to claim 12, wherein the chain extender comprises at least one selected from the group consisting of 2,5-dimethyl-2,5-(di-(tert-butylperoxy)hexane) (DTBPH), pyromellitic dianhydride (PMDA), hexamethylene diisocyanate (HMDI), dicumyl peroxide (DCP), polycarbodiimide (PCDI), di-(tert-butylperoxyisopropyl)benzene (DTBPIB), epoxy, polyamide, and oxazoline.

16. A method for producing a biodegradable laminate, comprising preparing a biodegradable resin composition for extrusion coating, and extrusion coating the biodegradable resin composition for extrusion coating on at least one side of a substrate to form a biodegradable coating layer, The biodegradable resin composition for extrusion coating contains 5% by weight to 95% by weight of polyhydroxyalkanoate (PHA), has a melt flow index (MI) of 5 g / 10 min to 60 g / 10 min when measured in accordance with ASTM D1238 at 190°C and 2.16 kg, and the weight average molecular weight of the PHA is 30,000 g / mol to 1,200,000 g / mol.

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