Biaxially oriented film, laminate, and environmentally friendly packaging materials containing the film.

Abstract

To provide a laminate that simultaneously has excellent strength and flexibility, exhibits improved noise level and thermal properties, and possesses excellent interlayer adhesion characteristics owing to good interlayer compatibility between a first layer and a second layer, as well as a method for producing the same.SOLUTION: Provided is a laminate which comprises: a first layer comprising a first polylactic acid (PLA) and polyhydroxyalkanoate (PHA); and a second layer disposed on one side of the first layer and comprising a second polylactic acid (PLA), wherein the first layer comprises greater than 0 wt.% to less than 30 wt.% of the polyhydroxyalkanoate (PHA) based on the total weight of the first layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a biaxially oriented film, a laminate, and an environmentally friendly packaging material including the film. [Background technology]

[0002] Recently, the use of disposable products has been increasing due to the so-called "un-contact" consumer culture and hygiene concerns, with a particularly significant increase in the use of food packaging materials.

[0003] Currently, common plastic films used in packaging materials include petroleum-derived polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP). However, PVC film is subject to many restrictions on use because it generates harmful substances such as dioxins when incinerated, and polyethylene film has poor dimensional stability and low mechanical properties, limiting its use to low-grade packaging paper. Polypropylene film has a relatively stable molecular structure and good mechanical properties, but after use in packaging, it is mostly disposed of in landfills. Due to the characteristics of plastic films that accumulate without decomposing much due to their chemical and biological stability, this causes serious environmental problems as a cause of soil pollution.

[0004] Furthermore, much research has recently been conducted on polylactic acid (PLA), an aliphatic polyester resin with high biodegradability. However, the aforementioned polylactic acid film lacks flexibility and generates significant noise, limiting its use in packaging.

[0005] Therefore, research is also underway on films that use polylactic acid mixed with other resins.

[0006] For example, Patent Document 1 discloses a film using a mixture of polylactic acid and polybutylene adipate terephthalate (PBAT). However, in this case, there may be problems such as insufficient compatibility between the two materials, resulting in reduced transparency, decreased thermal properties, and difficulty in simultaneously achieving satisfactory flexibility and strength.

[0007] Furthermore, research has been conducted on multilayer films in which the resin layer containing polylactic acid is laminated with other resin layers, such as polytriethylene terephthalate (PTT). However, in this case, it is not only difficult to achieve a satisfactory noise reduction effect or flexibility, but there is also the potential problem that the compatibility between the resin layers decreases, leading to poor interlayer adhesion characteristics or delamination, which negatively affects processability and productivity. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Korean Published Patent No. 2014-0106882 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] This invention was devised to solve the problems of the prior art described above. The object of the present invention is to provide a biaxially oriented film that simultaneously possesses excellent strength and flexibility, has excellent transparency due to the compatibility of the resins, and has improved noise levels and thermal properties.

[0010] Another object of the present invention is to provide a laminate that simultaneously possesses excellent strength and flexibility, has improved noise levels and thermal properties, and exhibits excellent interlayer adhesion properties due to good interlayer compatibility between the first and second layers.

[0011] Another object of the present invention is to provide a method for manufacturing a laminate that achieves the aforementioned properties while being economical and efficient, and while being excellent in processability and productivity.

[0012] Another object of the present invention is to provide a biodegradable, environmentally friendly, and high-quality environmentally conscious packaging material by using a biaxially oriented film or laminate having the above-mentioned properties. [Means for solving the problem]

[0013] The present invention provides a biaxially oriented film comprising polylactic acid (PLA) and polyhydroxyalkanoate (PHA), wherein the PHA content is greater than 0% to less than 30% by weight, based on the total weight of the biaxially oriented film, and the flexible noise composite index (LSN) represented by the following formula 1-1 is 20 or less when the film thickness is 19 to 21 μm.

[0014] <Formula 1-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the above formula 1-1, The aforementioned N AVG This is the average noise level (dB) calculated by measuring the maximum noise level five times each when a Class 2 sound level meter, as defined in KS C IEC61672-1, was pointed towards the noise source and shaken a biaxially oriented film test piece measuring 21 cm wide and 29.5 cm long at a speed of 120 times per minute at a height of 1.2 m to 1.5 m above the ground. The unit is omitted. The aforementioned LS is measured by fixing a loop-shaped biaxially oriented film test specimen with a width of 1.5 cm and a length of 18 cm to a loop stiffness tester and measuring the load at the center of the loop, in accordance with ASTM D747. mN ) and the numerical value excluding the unit The value obtained by dividing by 9.8 That is the case.

[0015] Furthermore, the present invention provides a laminate comprising a first layer containing a primary polylactic acid (PLA) and a polyhydroxyalkanoate (PHA), and a second layer disposed on one surface of the first layer and containing a secondary polylactic acid (PLA), wherein the first layer contains more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

[0016] Furthermore, the present invention provides a method for producing a laminate comprising the steps of: preparing a first resin containing first polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and a second resin containing second polylactic acid (PLA) (Step 1); melt co-extruding the first resin and the second resin to obtain a two-layer laminated sheet (Step 2); and biaxially stretching and heat-setting the laminated sheet to obtain a laminate (Step 3), wherein the laminate comprises a first layer containing first polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and a second layer disposed on one surface of the first layer and containing second polylactic acid (PLA), and the first layer containing more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

[0017] Furthermore, the present invention provides an environmentally friendly packaging material that includes the biaxially oriented film or laminate. [Effects of the Invention]

[0018] The biaxially oriented film according to the present invention contains polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and contains PHA within a specific content range, and the flexible noise composite index (LSN) of the film satisfies a specific range, thereby simultaneously possessing excellent strength and flexibility, as well as low noise levels and improved optical and thermal properties.

[0019] Furthermore, the laminate according to the present invention, by including a first layer and a second layer having a specific composition, simultaneously possesses excellent strength and flexibility, low noise levels, improved optical and thermal properties, and maintains excellent interlayer adhesion properties due to the good interlayer compatibility of the first and second layers.

[0020] Furthermore, the method for manufacturing laminates according to the present invention can further improve processability and productivity through an economical and efficient method.

[0021] Furthermore, the biaxially oriented film and the laminate are biodegradable and completely decompose when disposed of in landfills, possessing environmentally friendly properties. Therefore, they can be used in various fields as packaging materials, thus providing high-quality packaging materials. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 is a schematic diagram of a laminate according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of a laminate according to another embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram of a laminate according to another embodiment of the present invention. [Figure 4] Figure 4 schematically shows a method for manufacturing a laminate according to one embodiment of the present invention. [Modes for carrying out the invention]

[0023] The invention will be described in detail below with reference to examples. The examples disclosed below are not limited to those disclosed below and can be modified in various forms as long as the gist of the invention is not altered.

[0024] In this specification, when a part is said to "include" a component, it means, unless otherwise stated, that it may include other components rather than excluding them.

[0025] In this specification, singular expressions are to be interpreted as including singular or plural, as interpreted in the context, unless otherwise specified.

[0026] Furthermore, all numerical ranges indicating the physical properties, dimensions, reaction conditions, etc., of the components described herein should be understood to be modified by the term "approximately" in all cases, unless otherwise specified.

[0027] On the other hand, in this specification, terms such as Layer 1, Layer 2, or 1st, 2nd, etc., are used to describe various components, and such components are not limited by such terms. The terms are used solely for the purpose of distinguishing one component from another.

[0028] Furthermore, the criteria for "one side" / "striking surface" or "top" / "bottom" of each component are explained based on the drawings, and these terms are merely for distinguishing components and may be interchangeable in actual application.

[0029] In this specification, when one component is described as being formed on or below another component, this includes all instances where one component is formed directly on or below another component, or indirectly through yet another component.

[0030] Furthermore, the dimensions of each component in the drawings may be exaggerated for illustrative purposes and do not represent the actual dimensions in which they are applied. Also, the same reference number throughout the specification refers to the same component.

[0031] [Biaxially oriented film] In one example, a biaxially oriented film is provided that contains polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and, based on the total weight of the biaxially oriented film, contains more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA), and when the thickness of the film is 19 μm to 21 μm, the flexible noise composite index (LSN) represented by the following formula 1-1 is 20 or less.

[0032] <Formula 1-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the above formula 1-1, The aforementioned N AVG This is the average noise level (dB) calculated by measuring the maximum noise level five times each when a Class 2 sound level meter, as defined in KS C IEC61672-1, was pointed towards the noise source and shaken a biaxially oriented film test piece measuring 21 cm wide and 29.5 cm long at a speed of 120 times per minute at a height of 1.2 m to 1.5 m above the ground. The unit is omitted. The aforementioned LS is the loop stiffness (mN) measured by fixing a loop-shaped biaxially oriented film test specimen with a width of 1.5 cm and a length of 18 cm to a loop stiffness tester, and loading the load at the center of the loop, based on ASTM D747. The value obtained by removing the units and dividing it by 9.8.

[0033] In one implementation example, by including polylactic acid (PLA) and polyhydroxyalkanoate (PHA), flexibility can be improved and noise levels can be reduced. In particular, by including polyhydroxyalkanoate (PHA) in an amount of more than 0% to less than 30% by weight based on the total weight of the biaxially oriented film, it is possible to maintain appropriate strength while improving flexibility, further improving optical properties, and providing a film with low thermal shrinkage at high temperatures above 100°C and minimal thickness deviation. Furthermore, by controlling the flexible noise composite index (LSN) represented by formula 1-1 to 20 or less, strength, flexibility, and noise levels can be further improved. Consequently, by providing the film as a biaxially oriented film stretched in both directions, the physical properties and moldability of the film can be further improved, which has technical significance in realizing a high-quality packaging material.

[0034] The following provides a more detailed explanation of biaxially oriented films based on real-world examples. One example of a biaxially oriented film contains polylactic acid (PLA) and polyhydroxyalkanoate (PHA).

[0035] Unlike petroleum-based resins, polylactic acid (PLA) is biomass-based, allowing for the use of recycled resources. Furthermore, it is environmentally friendly, as its production emits less carbon dioxide (a major contributor to global warming) compared to existing resins, and it is biodegradable by moisture and microorganisms when disposed of in landfills.

[0036] The polylactic acid (PLA) may have a weight-average molecular weight (Mw) of 100,000 to 1,000,000 g / mol, for example, 100,000 to 800,000 g / mol, 100,000 to 500,000 g / mol, or 100,000 to 300,000 g / mol. The weight-average molecular weight (Mw) can be measured by gel permeation chromatography (GPC). If the weight-average molecular weight (Mw) of the polylactic acid (PLA) falls outside the range, the mechanical strength and heat resistance of the film may decrease compared to when it is within the range.

[0037] The polylactic acid (PLA) may contain L-lactic acid, D-lactic acid, DL-lactic acid, or a combination thereof. Specifically, the polylactic acid (PLA) may be a random copolymer of L-lactic acid and D-lactic acid. In this case, the L-lactic acid content may be 80% to 99% by weight, 83% to 99% by weight, or 85% to 99% by weight, based on the total weight of the polylactic acid.

[0038] The polylactic acid (PLA) may have a melting temperature (Tm) of 100°C to 250°C, 110°C to 220°C, or 120°C to 200°C.

[0039] The aforementioned polylactic acid (PLA) may have a glass transition temperature (Tg) of 30°C to 80°C, 40°C to 80°C, 40°C to 70°C, or 45°C to 65°C.

[0040] The polylactic acid (PLA) may contain more than 70% by weight, 75% or more by weight, 80% or more by weight, 85% or more by weight, 88% or more by weight, 90% or more by weight, 93% or more by weight, or 95% or more by weight, based on the total weight of the biaxially oriented film. Furthermore, the polylactic acid (PLA) may contain less than 100% by weight, 99% or less by weight, 98% or less by weight, 97% or less by weight, or 95% or less by weight, based on the total weight of the biaxially oriented film.

[0041] Specifically, the polylactic acid (PLA) may be included in amounts of more than 70% to less than 100% by weight, more than 70% to 99% by weight or less, 75% to 99% by weight or less, 75% to 98% by weight or less, 75% to 97% by weight or less, 80% to 97% by weight or less, 85% to 97% by weight or less, 90% to 97% by weight or less, 95% to less than 100% by weight, 95% to 97% by weight or less, or 90% to 95% by weight or less, based on the total weight of the biaxially oriented film.

[0042] If the polylactic acid (PLA) content is too low, the tensile strength may decrease and the thermal shrinkage rate may increase, potentially leading to a decrease in optical properties such as transparency and light transmittance. On the other hand, if the polylactic acid (PLA) content is too high, brittleness may increase, flexibility may decrease, making the material prone to crumbling or breaking, and noise may be a problem.

[0043] In particular, polylactic acid (PLA) has a high degree of brittleness, and when used at temperatures below 20°C, the film hardens. Therefore, in winter, the film tends to crack or break easily when subjected to impact. When used at temperatures above 35°C, the film tends to lose its elasticity and become flimsy, and its use is limited due to the high level of noise it generates.

[0044] Therefore, the examples are characterized by using a mixture of polylactic acid (PLA) and polyhydroxyalkanoate (PHA), which has excellent flexibility and low noise levels.

[0045] In particular, in the biaxially oriented film as demonstrated in the examples, the content of polyhydroxyalkanoate (PHA) in the biaxially oriented film is important in order to achieve excellent strength, flexibility, improved optical properties, thermal properties, and reduced noise levels.

[0046] The biaxially oriented film in the example may contain more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the biaxially oriented film.

[0047] Specifically, the biaxially oriented film may contain the polyhydroxyalkanoate (PHA) in amounts of more than 0% to less than 30% by weight, 1% or more to less than 30% by weight, 1% or more to 25% by weight or less, 2% or more to 25% by weight or less, 3% or more to 25% by weight or less, 3% or more to 20% by weight or less, 3% or more to 15% by weight or less, 3% or more to 10% by weight or less, more than 0% to 5%, 3% to 5%, or 5% to 10% by weight, based on the total weight of the biaxially oriented film.

[0048] If the polyhydroxyalkanoate (PHA) content is too high, the tensile strength may decrease, the thermal shrinkage rate may increase, extrusion processability may decrease, and optical properties may deteriorate. On the other hand, if the polyhydroxyalkanoate (PHA) content is too low, brittleness may increase, flexibility may decrease, making it prone to crumbling and cracking, and noise levels may increase.

[0049] According to the implementation example, the mixed weight ratio of polylactic acid (PLA) and polyhydroxyalkanoate (PHA) may be greater than 70 to less than 100: greater than 0 to less than 30, for example 80 to 97:3 to 20, for example 80 to 95:5 to 20, for example 90 to 97:3 to 10, for example 90 to 95:5 to 10, or for example 95 to 97:3 to 5. When the mixed weight ratio of polylactic acid (PLA) and polyhydroxyalkanoate (PHA) satisfies the above range, it is possible to improve flexibility while having appropriate strength, improve optical and thermal properties, and reduce noise levels.

[0050] According to the implementation example, the polyhydroxyalkanoate (PHA) may be a copolymerized polyhydroxyalkanoate (PHA).

[0051] Specifically, the copolymerized polyhydroxyalkanoate (PHA) may be a polyhydroxyalkanoate (PHA) with controlled crystallinity.

[0052] For example, the polyhydroxyalkanoate (PHA) may be a copolymerized polyhydroxyalkanoate (PHA) with controlled crystallinity, comprising a copolymerized polyhydroxyalkanoate containing at least one unit of the following chemical formula 1 and at least one unit of the following chemical formula 2. [Chemical formula 1] JPEG0007898492000001.jpg2252 In the above chemical formula 1, The aforementioned R1 is a substituted C1-C8 alkylene, m is an integer greater than or equal to 1.

[0053] [Chemical formula 2] JPEG0007898492000002.jpg2251 In the above chemical formula 2, The aforementioned R2 is a substituted or unsubstituted C1-C8 alkylene. n is an integer greater than or equal to 1.

[0054] In this context, the term "substituted" in chemical formulas 1 and 2 may include substituted or unsubstituted alkyl groups, specifically substituted or unsubstituted C1-C8 alkyl groups, unless otherwise specified.

[0055] The polyhydroxyalkanoate (PHA) may be a polyester containing only the units of chemical formula 1 and the units of chemical formula 2 as polymerization units, and may also contain other different polymerization units. Furthermore, the units of chemical formula 2 may be repeated randomly.

[0056] According to the implementation example, in the chemical formula 1, R1 may be, for example, a substituted C2-C8 alkylene, a substituted C3-C8 alkylene, or a substituted C3-C6 alkylene. Also, m may be between 1 and 12000.

[0057] In the aforementioned chemical formula 2, R2 may be, for example, a substituted or unsubstituted C2-C8 alkylene, a substituted or unsubstituted C3-C8 alkylene, or a substituted or unsubstituted C4-C8 alkylene. For example, in the aforementioned chemical formula 2, R2 may include an unsubstituted alkylene. Also, n may be between 1 and 12000.

[0058] Furthermore, in chemical formulas 1 and 2, the substituents may each include C1-C8 alkyl, C1-C6 alkyl, or C1-C4 alkyl.

[0059] Specifically, the polyhydroxyalkanoate (PHA) may contain at least one unit of the following chemical formula 1-1 and at least one unit of the following chemical formula 2-1.

[0060] [Chemical formula 1-1] JPEG0007898492000003.jpg3250 In the above chemical formula 1-1, The aforementioned R3 is methyl, ethyl, or propyl. m is an integer greater than or equal to 1.

[0061] [Chemical formula 2-1] JPEG0007898492000004.jpg2955 In the above chemical formula 2-1, n is an integer greater than or equal to 1.

[0062] Specifically, in the above chemical formula 1-1, R3 is methyl, and m can be 1 to 12000.

[0063] In the above chemical formula 2-1, n can be between 1 and 12000.

[0064] The aforementioned polyhydroxyalkanoate (PHA) with adjusted crystallinity may be one in which crystallinity and amorphousness are adjusted by increasing irregularity in the molecular structure, and specifically, this may involve adjusting the type of monomer, the ratio of monomers, or the type and / or content of isomers.

[0065] According to the implementation example, the polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing the unit of chemical formula 1 and the unit of chemical formula 2, and the content of the unit of chemical formula 2 is 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, 60% by weight or less, 55% by weight or less, and 50% by weight or less, based on the total weight of the copolymerized polyhydroxyalkanoate.

[0066] For example, the polyhydroxyalkanoate (PHA) is a copolymer polyhydroxyalkanoate (PHA) containing the unit of chemical formula 1 and the unit of chemical formula 2, and the content of the unit of chemical formula 2 may be 1-60% by weight, 5-50% by weight, 10-60% by weight, 10-50% by weight, 15-60% by weight, 15-50% by weight, 20-60% by weight, 20-50% by weight, 25-60% by weight, 25-50% by weight, 30-60% by weight, 30-50% by weight, 35-60% by weight, 35-50% by weight, 40-60% by weight, 40-50% by weight, 45-60% by weight, 45-50% by weight, or 46-50% by weight.

[0067] According to the implementation example, the polyhydroxyalkanoate (PHA) may include isomers. For example, the polyhydroxyalkanoate (PHA) may include structural isomers, enantiomers, or geometric isomers. Specifically, the polyhydroxyalkanoate (PHA) may include structural isomers.

[0068] According to the implementation example, the copolymerized polyhydroxyalkanoate (PHA) may be amorphous polyhydroxyalkanoate (PHA).

[0069] When the copolymerized polyhydroxyalkanoate (PHA) is amorphous polyhydroxyalkanoate (PHA), compared to when crystalline polyhydroxyalkanoate (PHA) is used as the polyhydroxyalkanoate (PHA) and mixed with polylactic acid (PLA) to produce a film, the compatibility between the resins is improved, which may result in improved optical properties.

[0070] When the copolymerized polyhydroxyalkanoate (PHA) is amorphous polyhydroxyalkanoate (PHA), the amorphous polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing the units of chemical formula 1 and the units of chemical formula 2, and may contain the units of chemical formula 2 in an amount of 15% to 60% by weight based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0071] In the polyhydroxyalkanoate (PHA), the amorphousness may increase as the content of the unit of chemical formula 2 increases. Therefore, in the biaxially oriented film according to the realization example, the content of the unit of chemical formula 2 in the amorphous polyhydroxyalkanoate (PHA) may be important.

[0072] For example, the amorphous polyhydroxyalkanoate (PHA) may contain the unit of chemical formula 2 in amounts of 15-60% by weight, 15-50% by weight, 20-60% by weight, 20-50% by weight, 25-60% by weight, 25-50% by weight, 30-60% by weight, 30-50% by weight, 35-60% by weight, 35-50% by weight, 40-60% by weight, 40-50% by weight, 45-60% by weight, 45-50% by weight, or 46-50% by weight, based on the total weight of the polyhydroxyalkanoate (PHA).

[0073] The biaxially oriented film, as demonstrated in this example, contains the units of chemical formula 2 within the specified range. This provides excellent compatibility between the resins and superior optical properties when used in combination with polylactic acid (PLA), thus offering the advantage of further improving the optical properties of the film. If the units of chemical formula 2 in the polyhydroxyalkanoate (PHA) are less than 15% by weight, the compatibility between the resins will deteriorate, potentially reducing transparency and light transmittance.

[0074] According to an example, the amorphous polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing 3-hydroxybutyrate (3-HB) units and 4-hydroxybutyrate (4-HB) units, and the 4-hydroxybutyrate (4-HB) units may be present in an amount of 15% to 60% by weight based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0075] In the polyhydroxyalkanoate (PHA), the amorphous nature increases as the content of the 4-hydroxybutyrate (4-HB) units increases. Therefore, in the biaxially oriented film according to the realization example, the content of the 4-hydroxybutyrate (4-HB) units in the amorphous polyhydroxyalkanoate (PHA) may be important.

[0076] For example, the 4-hydroxybutyrate (4-HB) units may be included in amounts such as 20-60% by weight, 25-60% by weight, 25-50% by weight, 30-60% by weight, 30-50% by weight, 35-60% by weight, 35-50% by weight, 40-60% by weight, 40-50% by weight, 45-60% by weight, 45-50% by weight, 46-60% by weight, or 46-50% by weight, based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0077] The biaxially oriented film, as demonstrated in the example, contains 4-hydroxybutyrate (4-HB) units within the specified range. This provides compatibility between the resins when used in combination with polyhydroxyalkanoate (PHA) and polylactic acid (PLA), thus offering the advantage of potentially improving the optical properties of the film. If the 4-hydroxybutyrate (4-HB) units are less than 15% by weight, the compatibility between the resins will deteriorate, potentially reducing the optical properties.

[0078] The polyhydroxyalkanoate (PHA) may be a polyester containing only 3-hydroxybutyrate (3-HB) units and 4-hydroxybutyrate (4-HB) units as polymerization units (i.e., the polymerization units consist only of 3-hydroxybutyrate (3-HB) units and 4-hydroxybutyrate (4-HB) units), or it may contain 3-hydroxybutyrate (3-HB) units and 4-hydroxybutyrate (4-HB) units as polymerization units, and further may contain other different polymerization units. In addition, the 4-hydroxybutyrate (4-HB) units may be repeated randomly.

[0079] Examples of the aforementioned different polymerization units include lactate (LA), glycolate (GA), 3-hydroxypropionate (3HP), 3-hydroxyvalerate (3HV), 5-hydroxyvalerate (5HV), 5-hydroxyhexanoate (5HH), 6-hydroxyhexanoate (6HH), or 3-hydroxyhexanoate (3HH), or hydroxyalkanoates having 7 or more carbon atoms.

[0080] The polyhydroxyalkanoate (PHA) may have a weight-average molecular weight (Mw) of 100,000 g / mol to 1,000,000 g / mol, 100,000 g / mol to 900,000 g / mol, 120,000 g / mol to 850,000 g / mol, or 150,000 g / mol to 800,000 g / mol. The weight-average molecular weight (Mw) can be measured by gel permeation chromatography (GPC).

[0081] The polyhydroxyalkanoate (PHA) may have a glass transition temperature (Tg) of -5°C to -50°C, -15°C to -40°C, or -20°C to -40°C. When the weight-average molecular weight (Mw) and glass transition temperature (Tg) of the amorphous polyhydroxyalkanoate (PHA) satisfy the above range, optical properties such as transparency and light transmittance are improved, which may be even more advantageous in achieving the desired noise reduction and flexibility improvement effects.

[0082] According to one example, the biaxially oriented film may further contain a filler. The filler may include an organic filler, an inorganic filler, or a mixture thereof.

[0083] The organic filler may include an organic filler containing a material selected from rigid acrylate, polystyrene, nylon, and flexible acrylate.

[0084] The inorganic filler may be one or more selected from the group consisting of barium sulfate, silica, and calcium carbonate.

[0085] The filler may be an inorganic filler, and may include, for example, silica.

[0086] The biaxially oriented film, by containing the filler, can have excellent slipperiness and improved processability, and can provide superior quality.

[0087] Furthermore, the particle size of the filler may range from 0.1 μm to 6.0 μm. For example, the particle size of the filler may range from 1.0 μm to 5.5 μm or from 2.0 μm to 5.2 μm.

[0088] The biaxially oriented film may contain the filler in an amount of 0.01 to 3% by weight, based on the total weight of the biaxially oriented film. For example, the biaxially oriented film may contain the filler in an amount of 0.05 to 2.5% by weight, 0.1 to 2% by weight, 0.2 to 1.7% by weight, or 0.5 to 1.5% by weight, based on the total weight of the biaxially oriented film.

[0089] In one example, a biaxially oriented film may have a flexible noise composite index (LSN) of 20 or less, expressed by formula 1-1, when the film thickness is 19 μm to 21 μm.

[0090] The Flexible Noise Synchronization Index (LSN), expressed by Equation 1-1, is the product of the average noise level and loop stiffness of the biaxially oriented film, and is an index indicating the degree of the combined characteristics of flexibility and noise level of the biaxially oriented film. Therefore, the Flexible Noise Synchronization Index (LSN) can serve as a measure of the quality of packaging materials including the biaxially oriented film.

[0091] The aforementioned flexible noise composite index (LSN) is the average noise level (N) of the biaxially oriented film. AVG The lower the ) the lower the average noise level (N AVG The higher the loop stiffness (LS), the higher the flexible noise composite index (LSN) can be. Also, the flexible noise composite index (LSN) can be lower as the loop stiffness (LS) decreases, and higher as the loop stiffness (LS) increases.

[0092] When the flexible noise composite index (LSN) having these characteristics satisfies the specified range, the biaxially oriented film exhibits excellent mechanical properties, optical properties, and thermal properties, and can reduce noise levels.

[0093] Specifically, the flexible noise index (LSN) of the biaxially oriented film may be, for example, 20 or less, 19 or less, 18 or less, 17 or less, 16 or less, or 15 or less. If the flexible noise index (LSN) of the biaxially oriented film exceeds 20, flexibility may decrease, brittleness may increase, and noise may increase, which may lead to a decrease in quality when applied to packaging materials.

[0094] The flexible noise composite index (LSN) of the biaxially oriented film may be the same or different depending on the longitudinal (MD) and transverse (TD) directions of the biaxially oriented film. In this case, the longitudinal (MD) direction of the biaxially oriented film refers to the length direction or the machine direction, and the transverse (TD) direction of the biaxially oriented film is a direction perpendicular to the longitudinal (MD) direction and may refer to the width direction.

[0095] Specifically, the flexible noise composite index (LSN MD ) in the machine direction (MD) of the biaxially stretched film can be, for example, 5 to 20, 5 to 19, 5 to 18, 10 to 18, 14 to 18, or 15 to 18.

[0096] The flexible noise composite index (LSN TD ) in the transverse direction (TD) of the biaxially stretched film can be, for example, 5 to 20, 5 to 19, 8 to 19, 10 to 19, 12 to 19, or 13 to 19.

[0097] The biaxially stretched film may satisfy only LSN MD , or may satisfy only LSN TD , or may satisfy both LSN MD and LSN[[ID=2']] TD In this case, the biaxially stretched film according to the embodiment can improve flexibility while maintaining appropriate tensile strength and can reduce noise, so it is more advantageous in realizing the intended effect and can provide an environmentally friendly packaging material with excellent quality.

[0098] On the other hand, in the formula 1-1, the average noise level (N AVG ) of the biaxially stretched film is measured using a class 2 noise meter or higher specified in KS C IEC61672-1. The film is oriented towards the noise source direction, and at a point 1.2 m to 1.5 m above the ground, the noise level generated by shaking a single biaxially stretched film at a constant speed for 1 minute is measured, and the maximum noise level is recorded. This is repeated 5 times for each, and the average value of the maximum noise levels for each time is obtained and defined as the average noise level. The noise level can be measured at a height of 1.2 m to 1.5 m above the ground. If there is an obstacle exceeding 1.5 m in height at the measurement point, it can be measured at a point about 1.0 m to 3.5 m away from the obstacle in the noise source direction.

[0099] Controlling the average noise level (N AVG ) of the biaxially stretched film below a specific range is preferable in terms of providing a high-quality packaging material.

[0100] Specifically, the average noise level (N) of the biaxially oriented film. AVG ) could be, for example, 86 dB or less, for example, 85 dB or less, for example, 84 dB or less, for example, 83 dB or less, or for example, 82.5 dB or less.

[0101] The average noise level (N) of the biaxially oriented film AVG If the noise level is 86 dB or less, it is advantageous in controlling the flexible noise composite index (LSN) of equation 1-1 to 20 or less, and it is possible to improve noise and provide high-quality packaging materials.

[0102] Furthermore, in Equation 1-1, the loop stiffness (LS) of the biaxially oriented film is determined based on ASTM D747 by fixing a loop-shaped biaxially oriented film test piece with a width of 1.5 cm and a length of 18 cm to a loop measuring device (Loop Stiffness Tester, Toyo Seiki Seisakusho) and measuring the load at the center of the loop. It is an index indicating the degree of flexibility of the biaxially oriented film.

[0103] The loop stiffness (LS) of the aforementioned biaxially oriented film is: 2.25 mN below, 2.16 mN below, 2.06 mN The following, or 1.96 mN The following is possible. Specifically, the loop stiffness (LS) of the biaxially oriented film is, for example, 0.98~2.25mN ,for example 0.98~2.16mN ,for example, 0.98~2.06mN , or for example It could be between 0.98 and 1.96 mN.

[0104] The lower the loop stiffness (LS) of the biaxially oriented film, the greater its flexibility; and the higher the loop stiffness (LS) of the biaxially oriented film, the greater its flexibility.

[0105] Furthermore, the loop stiffness (LS) of the biaxially oriented film may be the same or different depending on the longitudinal (MD) and transverse (TD) directions of the biaxially oriented film.

[0106] Specifically, the longitudinal (MD) loop stiffness (LS) of the biaxially oriented film. MD ) is, for example 0.98~2.25mN ,for example 0.98~2.16mN ,for example 1.18~2.16mN ,for example 1.18~2.06 mN ,for example 1.47~2.06 mN It is possible.

[0107] The lateral (TD) loop stiffness (LS) of the biaxially oriented film TD ) is, for example 0.98~2.25mN ,for example 0.98~2.16mN ,for example 1.18~2.16mN , or for example 1.37~2.16mN It is possible.

[0108] The aforementioned biaxially oriented film is LS MD It is sufficient to satisfy only, or LS TD It may be sufficient to satisfy only, or LS MD and LS TD All of these conditions can be satisfied. In this case, the biaxially oriented film according to the example is more effective in controlling the flexible noise composite index (LSN) represented by formula 1-1 within the range, and is therefore more advantageous in achieving the desired effect, and can provide a high-quality, environmentally friendly packaging material.

[0109] On the other hand, the biaxially oriented film has a thermal shrinkage rate (S) expressed by the following formula 1-2. 100 ) may be 15% or less.

[0110] <Formula 1-2> Thermal shrinkage coefficient (S 100 )={(L 25 -L 100 ) / L 25}×100 In the above formula 1-2, L 25 This is the initial length (mm) of the biaxially oriented film test specimen at 25°C. L 100 This is the length (mm) of the biaxially oriented film test specimen measured immediately after being exposed to a 100°C hot air blower for 5 minutes.

[0111] The thermal shrinkage coefficient (S) expressed by the above formula 1-2 100This value represents the degree of thermal shrinkage of a biaxially oriented film test specimen at a hot air temperature of 100°C, converted to a percentage. It is calculated as a percentage of the initial length of the biaxially oriented film test specimen relative to its initial length, and the change in length of the biaxially oriented film test specimen measured immediately after being left in a hot air machine for 5 minutes.

[0112] The aforementioned thermal shrinkage rate (S 100 The length can be calculated by cutting a biaxially oriented film into test specimens of 150 mm in length and 2 cm in width, regardless of direction, and then measuring the initial length at room temperature and the length of the biaxially oriented film test specimens after being left in a 100°C hot air oven for 5 minutes.

[0113] The aforementioned thermal shrinkage rate (S 100 ) may be 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, or 4.5% or less.

[0114] The aforementioned thermal shrinkage rate (S 100 If the above range is satisfied, the degree of thermal shrinkage at hot air temperatures of 100°C or higher is small, which improves thermal properties and can further improve printability and moldability.

[0115] Furthermore, the thermal shrinkage rate (S) of the biaxially oriented film. 100 ) may be the same or different depending on the longitudinal (MD) and transverse (TD) directions of the biaxially oriented film.

[0116] Specifically, the thermal shrinkage rate (S) in the longitudinal direction (MD) of the biaxially oriented film. MD100 ) may be 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4.5% or less, or 4% or less.

[0117] The thermal shrinkage rate (S) in the transverse direction (TD) of the biaxially oriented film TD100 ) could be, for example, 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, or 4.5% or less.

[0118] If the thermal shrinkage rates in the longitudinal (MD) and transverse (TD) directions of the biaxially oriented film exceed the aforementioned range, printing problems occur due to the severe shrinkage in the longitudinal and transverse directions caused by hot air during printing and lamination, and curling occurs severely after printing, which is undesirable.

[0119] On the other hand, the biaxially oriented film used in the realization example may have a molding index (FI) of 65 or higher, as expressed by the following formulas 1-3.

[0120] <Formula 1-3> Forming index (FI)=TS / LS In the above formula 1-3, TS is a test specimen prepared by cutting a piece approximately 100 mm long and 15 mm wide according to ASTM D882, then mounting it so that the distance between the chucks is 50 mm, and measuring the tensile strength of the test specimen at room temperature using a universal testing machine (UTM). MPa ) is a numerical value with units removed, and LS is as defined above.

[0121] The forming index (FI) of the biaxially oriented film is the ratio of the tensile strength to the loop stiffness of the biaxially oriented film, and can serve as a measure of whether the tensile strength and flexibility are appropriate.

[0122] In other words, according to the implementation example, one of the main features of the biaxially oriented film may be that it can maintain an appropriate range of strength, such as tensile strength, while having increased flexibility and soft properties. In this case, the biaxially oriented film may have excellent moldability and be advantageous for expanding its applications in various ways.

[0123] The molding index (FI) of the biaxially oriented film may be, for example, 65 or higher, 68 or higher, 70 or higher, 75 or higher, 80 or higher, 85 or higher, 90 or higher, 95 or higher, or 100 or higher. Specifically, the molding index (FI) of the biaxially oriented film may be, for example, 65 to 120, for example, 65 to 110, or for example, 65 to 105. If the molding index (FI) of the biaxially oriented film is less than 65, the flexibility will decrease and it will easily break, or the strength will decrease and various problems will occur during processing or molding, and there will be limitations on its application to various uses, and molded products such as packaging materials to which the biaxially oriented film is applied may experience a decrease in quality or defects.

[0124] The forming index (FI) of the biaxially oriented film may be the same or different depending on the longitudinal (MD) and transverse (TD) directions of the biaxially oriented film.

[0125] Specifically, the molding index (FI) in the longitudinal direction (MD) of the biaxially oriented film. MD ) could be, for example, 65-90, for example, 70-90, or for example, 70-80.

[0126] The molding index (FI) in the transverse direction (TD) of the biaxially oriented film. TD ) could be, for example, 80-110, for example, 85-110, or for example, 90-110.

[0127] The aforementioned biaxially oriented film is FI MD It is sufficient to satisfy only, or FI TD It may be sufficient to satisfy only, or FI MD and FI TD All of these conditions can be satisfied. In this case, the biaxially oriented film used in the example can improve flexibility while maintaining appropriate tensile strength, and can provide a high-quality, environmentally friendly packaging material.

[0128] Furthermore, in equations 1-3, the loop stiffness (LS) of the biaxially oriented film is as defined above.

[0129] Furthermore, the tensile strength of the biaxially oriented film can be measured by preparing a biaxially oriented film test specimen in accordance with ASTM D882, cutting it to a length of 100 mm and a width of 15 mm, mounting it so that the distance between the chucks is 50 mm, and then conducting an experiment at a tensile speed of 200 mm / min at room temperature of 25°C using an Instron universal testing machine (UTM, model name 5966), and then measuring it using a program built into the equipment.

[0130] The aforementioned tensile strength is, for example, 88.2~245.0 MPa ,for example 93.1~215.6MPa ,for example 98.0~215.6MPa ,for example 117.6~196.0 MPa , or for example 127.4~196.0 MPa It is possible.

[0131] When the tensile strength satisfies the aforementioned range, the productivity, processability, and moldability of the biaxially oriented film can be improved simultaneously.

[0132] Furthermore, the tensile strength (TS) of the biaxially oriented film may be the same or different depending on the longitudinal (MD) and transverse (TD) directions of the biaxially oriented film.

[0133] Specifically, the tensile strength (TS) in the longitudinal direction (MD) of the biaxially oriented film. MD ) is, for example 88.2~245.0 MPa ,for example 93.1~215.6MPa ,for example 98.0~215.6MPa ,for example 117.6~196.0 MPa , or for example 127.4~176.4 MPa It is possible.

[0134] The tensile strength (TS) in the transverse direction (TD) of the biaxially oriented film. TD ) is, for example, 88.2~245.0 MPa , 98.0~245.0 MPa ,for example 107.8~225.4 MPa ,for example 117.6~225.4 MPa , or for example 147.0~196.0 MPa It is possible.

[0135] The biaxially oriented film is the TS MD It is sufficient to satisfy only, or TS TD It may be sufficient to satisfy only, or TS MDand TS TD All of these conditions can be satisfied. In this case, the biaxially oriented film according to the example can control the molding index (FI) represented by formula 1-3 within the range, thereby simultaneously improving productivity, processability, and moldability, and providing a high-quality, environmentally friendly packaging material.

[0136] On the other hand, the biaxially oriented film has a strain-stress curve. 1960~3724MPa , 1960~3528MPa, 1960~3430MPa, 2450~3430MPa ,or 2548~3430MPa It has the modulus of the modulus. 1960MPa If the modulus is less than the specified value, the resistance to mechanical tension during processing such as printing or lamination will be insufficient, which is undesirable as it may cause wrinkles in the direction of travel, resulting in printing problems or breakage during travel. On the other hand, if the modulus is 3724 MPa Beyond a certain range, the stiffness of the film increases, making it easily ruptured or cracked by external impacts. Furthermore, within the aforementioned range, a lower modulus generally indicates greater flexibility.

[0137] On the other hand, the biaxially oriented film may have a thickness deviation of 10 μm or less relative to the total thickness of the film width. Specifically, the biaxially oriented film may have a thickness deviation of 9 μm or less, 8.5 μm or less, 8 μm or less, 7 μm or less, 6.5 μm or less, or 5 μm or less relative to the total thickness of the film width.

[0138] In the example, the biaxially oriented film, when containing amorphous polyhydroxyalkanoate (PHA), exhibits excellent stretch uniformity, thus providing a biaxially oriented film with minimal thickness deviation.

[0139] On the other hand, the biaxially oriented film may have excellent optical properties. Specifically, the biaxially oriented film may have a haze of 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less. If the haze exceeds the aforementioned range, the transparency of the film will be significantly reduced, which may limit its use in packaging applications where the contents are visible.

[0140] The biaxially oriented film, as demonstrated in the example, may provide a transparent biaxially oriented film with low haze when it contains amorphous polyhydroxyalkanoate (PHA) in a specific amount.

[0141] Furthermore, the biaxially oriented film may have a light transmittance of 90% or more, 92% or more, or 93% or more.

[0142] Furthermore, the biaxially oriented film is characterized by having a biodegradability of 90% or more, as measured by the amount of carbon dioxide emitted based on KS M3100-1. Biodegradability indicates the ratio of decomposition to a standard substance (e.g., cellulose) over the same period, and the Ministry of Environment of the Republic of Korea defines a substance as biodegradable when its biodegradability is 90% or more compared to a standard substance.

[0143] The structural and physical properties of the biaxially oriented film according to the realization example can be efficiently achieved by manufacturing it using the manufacturing method for the biaxially oriented film according to the realization example. The method for manufacturing the biaxially oriented film will be described in detail below.

[0144] [Method for manufacturing biaxially oriented film] A method for producing a biaxially oriented film may include: a first step of mixing polylactic acid (PLA) and polyhydroxyalkanoate (PHA) and then melt-extruding the mixture to produce a sheet; a second step of biaxially stretching the melt-extruded sheet to produce a film; and a third step of heat-setting the biaxially oriented film.

[0145] Specifically, the first step may include mixing polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and then melt-extruding the mixture to produce a sheet.

[0146] The content or mixed weight ratio of polylactic acid (PLA) and polyhydroxyalkanoate (PHA) is as described above.

[0147] Furthermore, fillers may be added during the mixing process to improve lubricity and quality. The type, content, and particle size of the filler are as described above.

[0148] The melt extrusion is carried out at 180°C to 250°C, and after the melt extrusion, a sheet can be obtained by bringing it into close contact with a cooling roll cooled to approximately 10°C to 30°C.

[0149] The second step may include the step of biaxially stretching the melt-extruded sheet to produce a film.

[0150] The melt-extruded sheet can be preheated to 50°C to 80°C, and then stretched longitudinally (MD) by 2 to 4 times at 40°C to 100°C.

[0151] For example, the melt-extruded sheet can be preheated to 50°C to 80°C, then passed through a stretching section of 70°C to 100°C to be stretched longitudinally to 2 to 4 times its original size.

[0152] The stretched film can be stretched transversely (MD) by 3 to 5 times at 50°C to 110°C.

[0153] For example, the stretched film can be stretched 3 to 5 times laterally within a tenter section that is divided into a first section where the average temperature of the initial 30% section is 80°C to 105°C, and a second section where the average temperature of the later 70% section is 80°C to 110°C.

[0154] As demonstrated in the implementation example, by providing a biaxially stretchable film, the physical properties and moldability of the film can be further improved, thereby enabling the creation of high-quality packaging materials.

[0155] If a uniaxial film is stretched in either the longitudinal or transverse direction, the thickness deviation of the film can be significant, leading to a substantial decrease in the strength of the unstretched side and potentially degrading its thermal properties.

[0156] The third step may include a step of heat-setting the biaxially stretched film.

[0157] The heat setting step may be carried out at 50°C to 150°C, 70°C to 150°C, 100°C to 150°C, or 120°C to 150°C.

[0158] Manufacturing the biaxially oriented film using the manufacturing method described in the example may be even more effective in producing a biaxially oriented film having the desired structure and physical properties.

[0159] [Laminated structure] In one embodiment, the present invention provides a laminate comprising a first layer containing a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA), and a second layer disposed on one surface of the first layer and containing a second polylactic acid (PLA), wherein the first layer contains more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

[0160] In one implementation example, by including a first layer and a second layer having the specified composition, specifically a first layer containing primary polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and a second layer containing secondary polylactic acid (PLA) on one side of the first layer, not only can flexibility be improved and noise levels reduced, but the good interlayer compatibility between the first and second layers can improve interlayer adhesion characteristics, thereby further improving processability and productivity.

[0161] In particular, by having the first layer contain more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the first layer, it is possible to maintain appropriate strength while improving flexibility, further improve optical properties, and provide a laminate with low thermal shrinkage at high temperatures of 100°C or higher and small thickness deviation.

[0162] Furthermore, the aforementioned laminate is biodegradable and completely decomposes when disposed of in a landfill, possessing environmentally friendly properties. Therefore, it has technical significance in that it can be utilized in a wider range of fields and exhibit superior characteristics.

[0163] Referring to Figure 1, the laminate 1 according to an embodiment of the present invention includes a first layer 12 and a second layer 11 disposed on one surface of the first layer 12.

[0164] A laminate according to another embodiment of the present invention may include a first layer, a second layer disposed on one surface of the first layer, and a corona layer, a coating layer, or both disposed on the other surface of the first layer.

[0165] Specifically, referring to Figure 2, the laminate 1 may include a first layer 12, a second layer 11 positioned on the upper surface of the first layer 12, and a corona layer 13 positioned on the lower surface of the first layer 12. In this case, a coating layer may be placed instead of the corona layer positioned on the lower surface of the first layer 12.

[0166] Referring to Figure 3, the laminate 1 may include a first layer 12, a second layer 11 positioned on the upper surface of the first layer 12, a corona layer 13 positioned on the lower surface of the first layer 12, and a coating layer 14 positioned on the lower surface of the corona layer 13. The following provides a detailed explanation of each layer of the laminate based on an example of its implementation.

[0167] -1st layer- According to one example, the first layer contains primary polylactic acid (PLA) and polyhydroxyalkanoate (PHA).

[0168] The first polylactic acid (PLA) may be the same as the polylactic acid (PLA) mentioned in the description of the biaxially oriented film.

[0169] By including primary polylactic acid (PLA) and polyhydroxyalkanoate (PHA) in the first layer, not only can flexibility be improved and noise levels reduced, but good interlayer compatibility with the second layer containing secondary polylactic acid (PLA) can be maintained, thus enabling superior interlayer adhesion and further improving processability and productivity.

[0170] If the first layer contains only one of the resins, primary polylactic acid (PLA) and polyhydroxyalkanoate (PHA), or neither, it may be difficult to achieve a satisfactory noise reduction effect or flexibility. Furthermore, the interlayer compatibility between the first and second layers in the laminate may decrease, resulting in poor interlayer adhesion or even delamination, which could negatively impact processability and productivity.

[0171] The first polylactic acid (PLA) may have a weight-average molecular weight (Mw) of 100,000 to 1,000,000 g / mol, for example, 100,000 to 800,000 g / mol, 100,000 to 500,000 g / mol, or 100,000 to 300,000 g / mol. The weight-average molecular weight (Mw) can be measured by gel permeation chromatography (GPC). If the weight-average molecular weight (Mw) of the first polylactic acid (PLA) falls outside this range, the mechanical strength and heat resistance of the laminate can be further improved.

[0172] The first polylactic acid (PLA) may contain L-lactic acid, D-lactic acid, DL-lactic acid, or a combination thereof. Specifically, the first polylactic acid (PLA) may be a random copolymer of L-lactic acid and D-lactic acid. In this case, the L-lactic acid content may be 80% to 99% by weight, 83% to 99% by weight, or 85% to 99% by weight, based on the total weight of the first polylactic acid.

[0173] The first polylactic acid (PLA) may have a melting temperature (Tm) of 100°C to 250°C, 110°C to 220°C, or 120°C to 200°C.

[0174] The first polylactic acid (PLA) may have a glass transition temperature (Tg) of 30°C to 80°C, 40°C to 80°C, 40°C to 70°C, or 45°C to 65°C.

[0175] The first polylactic acid (PLA) may contain more than 70% by weight, 75% or more by weight, 80% or more by weight, 85% or more by weight, 88% or more by weight, 90% or more by weight, 93% or more by weight, or 95% or more by weight, based on the total weight of the first layer. Furthermore, the first polylactic acid (PLA) may contain less than 100% by weight, 99% or less by weight, 98% or less by weight, 97% or less by weight, or 95% or less by weight, based on the total weight of the first layer.

[0176] Specifically, the first polylactic acid (PLA) may be included in amounts of more than 70% to less than 100% by weight, more than 70% to 99% by weight or less, 75% to 99% by weight or more, 75% to 98% by weight or less, 75% to 97% by weight or more, 80% to 97% by weight or less, 85% to 97% by weight or more, 90% to 97% by weight or less, 95% to less than 100% by weight, 95% to 97% by weight or more, or 90% to 95% by weight or less, based on the total weight of the first layer.

[0177] If the content of the first polylactic acid (PLA) is too low, the tensile strength of the laminate may decrease and the thermal shrinkage rate may increase, potentially leading to a decrease in optical properties such as transparency and light transmittance. On the other hand, if the content of the first polylactic acid (PLA) is too high, brittleness increases, flexibility decreases, making it prone to crumbling and cracking, and potentially causing significant noise problems.

[0178] In particular, the first polylactic acid (PLA) has a high degree of brittleness, causing the film to harden when used at temperatures below 20°C. In winter, the film tends to crack or break easily when subjected to impact. When used at temperatures above 35°C, the film tends to lose its elasticity and become flimsy, and its use is limited due to the high level of noise it generates.

[0179] Therefore, in the implementation example, the first polylactic acid (PLA) is used in combination with polyhydroxyalkanoate (PHA), which has excellent flexibility and low noise levels.

[0180] In particular, the content of polyhydroxyalkanoate (PHA) in the first layer is important in order to achieve the excellent strength, flexibility, improved optical properties, thermal properties, and reduced noise level of the laminate.

[0181] According to the implementation example, the first layer may contain more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

[0182] Specifically, the first layer may contain the polyhydroxyalkanoate (PHA) in amounts of more than 0% to less than 30% by weight, more than 0% to less than 25% by weight, more than 0% to less than 20% by weight, 1% or more to less than 30% by weight, 1% or more to 25% by weight or less, 2% or more to 25% by weight or less, 2% or more to 20% by weight or less, 3% or more to 25% by weight or less, 3% or more to 20% by weight or less, 3% or more to 15% by weight or less, 3% or more to 10% by weight or less, more than 0% to 5%, 3% to 5%, or 5% to 10% by weight, based on the total weight of the first layer.

[0183] If the polyhydroxyalkanoate (PHA) content is too high, the tensile strength may decrease, the thermal shrinkage rate and thickness deviation may increase, extrudeability may decrease, and optical properties may deteriorate. On the other hand, if the polyhydroxyalkanoate (PHA) content is too low, brittleness may increase, flexibility may decrease, making it prone to crumbling and cracking, and noise levels may increase.

[0184] According to the implementation example, the mixed weight ratio of the first polylactic acid (PLA) and the polyhydroxyalkanoate (PHA) may be greater than 70 to less than 100: greater than 0 to less than 30, for example 80 to 97:3 to 20, for example 80 to 95:5 to 20, for example 90 to 97:3 to 10, for example 90 to 95:5 to 10, or for example 95 to 97:3 to 5. When the mixed weight ratio of the first polylactic acid (PLA) and the polyhydroxyalkanoate (PHA) satisfies the above range, it is possible to improve flexibility while having appropriate strength, improve optical and thermal properties, and reduce noise levels.

[0185] According to the implementation example, the polyhydroxyalkanoate (PHA) may be the same as the polyhydroxyalkanoate (PHA) mentioned in the biaxially oriented film.

[0186] Specifically, the copolymerized polyhydroxyalkanoate (PHA) may be a polyhydroxyalkanoate (PHA) with controlled crystallinity.

[0187] For example, the copolymerized polyhydroxyalkanoate (PHA) may be a copolymerized polyhydroxyalkanoate (PHA) in which the crystallinity is controlled, comprising a copolymerized polyhydroxyalkanoate containing at least one unit of chemical formula 1 and at least one unit of chemical formula 2.

[0188] The polyhydroxyalkanoate (PHA) may be a polyester containing only the units of chemical formula 1 and the units of chemical formula 2 as polymerization units, or it may contain the units of chemical formula 1 and the units of chemical formula 2 as polymerization units, and further may contain other different polymerization units. In addition, the units of chemical formula 2 may be repeated randomly.

[0189] The aforementioned polyhydroxyalkanoate (PHA) with adjusted crystallinity may be one in which crystallinity and amorphousness are adjusted by increasing the irregularity of the molecular structure, and specifically, this may involve adjusting the type of monomer, the ratio of monomers, or the type and / or content of isomers.

[0190] According to the implementation example, the polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing the unit of chemical formula 1 and the unit of chemical formula 2, and the content of the unit of chemical formula 2 is 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, 60% by weight or less, 55% by weight or less, and 50% by weight or less, based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0191] For example, the polyhydroxyalkanoate (PHA) is a copolymer polyhydroxyalkanoate (PHA) containing the unit of chemical formula 1 and the unit of chemical formula 2, and the content of the unit of chemical formula 2 may be 1-60% by weight, 5-50% by weight, 10-60% by weight, 10-50% by weight, 15-60% by weight, 15-50% by weight, 20-60% by weight, 20-50% by weight, 25-60% by weight, 25-50% by weight, 30-60% by weight, 30-50% by weight, 35-60% by weight, 35-50% by weight, 40-60% by weight, 40-50% by weight, 45-60% by weight, 45-50% by weight, or 46-50% by weight.

[0192] According to the implementation example, the polyhydroxyalkanoate (PHA) may include isomers. For example, the polyhydroxyalkanoate (PHA) may include structural isomers, enantiomers, or geometric isomers. Specifically, the polyhydroxyalkanoate (PHA) may include structural isomers.

[0193] According to the implementation example, the copolymerized polyhydroxyalkanoate (PHA) may be amorphous polyhydroxyalkanoate (PHA).

[0194] When the copolymerized polyhydroxyalkanoate (PHA) is amorphous polyhydroxyalkanoate (PHA), the optical properties of the laminate may be improved compared to when crystalline polyhydroxyalkanoate (PHA) is used as the polyhydroxyalkanoate (PHA) and mixed with the first polylactic acid (PLA) to form the first layer.

[0195] When the copolymerized polyhydroxyalkanoate (PHA) is amorphous polyhydroxyalkanoate (PHA), the amorphous polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing the units of chemical formula 1 and the units of chemical formula 2, and may contain 15 to 60% by weight of the units of chemical formula 2 based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0196] In the polyhydroxyalkanoate (PHA), the amorphousness may increase as the content of the unit of chemical formula 2 increases. Therefore, in the first layer of the realized example, the content of the unit of chemical formula 2 in the amorphous polyhydroxyalkanoate (PHA) may be important.

[0197] For example, the amorphous polyhydroxyalkanoate (PHA) may contain the unit of chemical formula 2 in amounts of 15-55% by weight, 15-50% by weight, 20-60% by weight, 20-50% by weight, 25-60% by weight, 25-50% by weight, 30-60% by weight, 30-50% by weight, 35-60% by weight, 35-50% by weight, 40-60% by weight, 40-50% by weight, 45-60% by weight, 45-50% by weight, or 46-50% by weight, based on the total weight of the polyhydroxyalkanoate (PHA).

[0198] The first layer contains the units of chemical formula 2 within the specified range, which has the advantage of improving the optical properties of the laminate when polyhydroxyalkanoate (PHA) is mixed with primary polylactic acid (PLA) due to the compatibility between the resins. If the units of chemical formula 2 in the polyhydroxyalkanoate (PHA) are less than 15% by weight, the compatibility between the resins will deteriorate, reducing the transparency and light transmittance of the laminate, and potentially decreasing the modulus and noise level.

[0199] According to an example, the amorphous polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing 3-hydroxybutyrate (3-HB) units and 4-hydroxybutyrate (4-HB) units, and the 4-hydroxybutyrate (4-HB) units may be present in an amount of 15 to 60% by weight based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0200] In the polyhydroxyalkanoate (PHA), the amorphousness increases as the content of the 4-hydroxybutyrate (4-HB) units increases. Therefore, in the first layer of the realized example, the content of the 4-hydroxybutyrate (4-HB) units in the amorphous polyhydroxyalkanoate (PHA) may be important.

[0201] For example, the 4-hydroxybutyrate (4-HB) units may be included in amounts such as 20-60% by weight, 25-60% by weight, 25-50% by weight, 30-60% by weight, 30-50% by weight, 35-60% by weight, 35-50% by weight, 40-60% by weight, 40-50% by weight, 45-60% by weight, 45-50% by weight, 46-60% by weight, or 46-50% by weight, based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0202] The first layer contains 4-hydroxybutyrate (4-HB) units within the specified range, which has the advantage of further improving the optical properties of the laminate when polyhydroxyalkanoate (PHA) is mixed with the first polylactic acid (PLA) due to the compatibility between the resins. If the amount of 4-hydroxybutyrate (4-HB) units is less than 15% by weight, the compatibility between the resins will deteriorate, and the optical properties of the laminate may decrease.

[0203] The polyhydroxyalkanoate (PHA) may be a polyester containing only 3-hydroxybutyrate units (3-HB) and 4-hydroxybutyrate (4-HB) units as polymerization units (i.e., the polymerization units consist only of 3-hydroxybutyrate units (3-HB) and 4-hydroxybutyrate units (4-HB), or it may contain 3-hydroxybutyrate units (3-HB) and 4-hydroxybutyrate (4-HB) units as polymerization units, and may also contain other different polymerization units. Furthermore, the 4-hydroxybutyrate (4-HB) units may be repeated randomly.

[0204] Examples of the aforementioned different polymerization units include lactate (LA), glycolate (GA), 3-hydroxypropionate (3HP), 3-hydroxyvalerate (3HV), 5-hydroxyvalerate (5HV), 5-hydroxyhexanoate (5HH), 6-hydroxyhexanoate (6HH), or 3-hydroxyhexanoate (3HH), or hydroxyalkanoates having 7 or more carbon atoms.

[0205] The weight-average molecular weight (Mw) and glass transition temperature (Tg) of the polyhydroxyalkanoate (PHA) are as described above.

[0206] According to one implementation example, the first layer may further contain a filler. The filler may include an organic filler, an inorganic filler, or a mixture thereof.

[0207] The organic filler may include an organic filler containing a material selected from rigid acrylate, polystyrene, nylon, and flexible acrylate.

[0208] The inorganic filler may be one or more selected from the group consisting of barium sulfate, silica, and calcium carbonate. The filler may be an inorganic filler, and may include, for example, silica.

[0209] The first layer, by including the filler, can have excellent lubricity and improved processability, thereby providing superior quality.

[0210] Furthermore, the particle size of the filler may range from 0.1 μm to 6.0 μm. For example, the particle size of the filler may range from 1.0 μm to 5.5 μm or from 2.0 μm to 5.2 μm.

[0211] The first layer may contain the filler in an amount of 0.01 to 3% by weight, based on the total weight of the first layer. For example, the first layer may contain the filler in an amount of 0.01 to 2.5% by weight, 0.01 to 2% by weight, 0.01 to 1.5% by weight, 0.01 to 1% by weight, 0.01 to 0.5% by weight, or 0.01 to 0.2% by weight, based on the total weight of the first layer.

[0212] The thickness of the first layer may be, for example, 1 μm to 20 μm, for example, 2 μm to 19 μm, or for example, 3 μm to 17 μm.

[0213] -Second layer- According to one example, the second layer is arranged on one surface of the first layer and contains secondary polylactic acid (PLA).

[0214] Because the second layer contains secondary polylactic acid (PLA), it has good compatibility with the first layer containing primary polylactic acid (PLA) and polyhydroxyalkanoate (PHA), thus maintaining excellent interlayer adhesion properties and potentially improving processability and productivity.

[0215] If the second layer does not contain the second polylactic acid (PLA) but contains another resin such as polytriethylene terephthalate (PTT), the interlayer compatibility between the first and second layers will be poor, which may result in poor interlayer adhesion or separation between the layers, negatively impacting processability and productivity.

[0216] The second layer may contain isomers of the second polylactic acid. The second layer may contain L-isomers, D-isomers, DL-isomers, or mixtures thereof of the second polylactic acid. For example, the second polylactic acid (PLA) may be a random copolymer of L-lactic acid and D-lactic acid.

[0217] Specifically, the second polylactic acid can include stereoisomers of L-isomers and D-isomers having opposite configurations to each other. Such stereoisomers have the same chemical structure and physical properties, but only the configurations can be symmetric to each other as mirror images.

[0218] When the second layer includes a mixture of L-isomers and D-isomers of the second polylactic acid, the transparency of the film is improved and it has thermal adhesion performance, so it can be utilized for thermal adhesion applications.

[0219] According to an implementation example, the second layer can include 5 wt% to 30 wt% of D-isomers based on the total weight of the second polylactic acid. If the content of the D-isomers is too high, the thickness deviation and thermal shrinkage rate of the laminate may increase, and the physical properties of the laminate such as tensile strength may decrease. In the process, there may be insufficient winding property during production and processing, resulting in problems in roll pass, and the processability and productivity may decrease. On the other hand, if the content of the D-isomers is too low, a large amount of heat is required during thermal adhesion processing, and the shape of the laminate may be deformed, such as the film being wavy when the laminate is formed into a film.

[0220] According to an implementation example, the second layer includes a mixture of L-isomers and D-isomers of the second polylactic acid, and the weight ratio of the L-isomers and D-isomers can be 70 to 95:5 to 30.

[0221] For example, the second layer can include poly-L-lactic acid (L-PLA) and poly-D-lactic acid (D-PLA). At this time, the weight ratio of L-PLA and D-PLA (L-PLA:D-PLA) can be 70 to 95:5 to 30, for example 72 to 95:5 to 28, for example 74 to 93:7 to 26, or for example 75 to 93:7 to 25.

[0222] When the weight ratio of the L-isomer and the D-isomer satisfies the above range, the optical properties of the film are improved, and the thermal adhesion performance can be further improved. In addition, the thickness deviation and the thermal shrinkage rate of the laminate can be reduced, and physical properties such as tensile strength and modulus can be improved, and the processability and productivity can be further improved.

[0223] The second polylactic acid (PLA) may have a weight average molecular weight (Mw) of, for example, 50,000 to 1,000,000 g / mol, for example, 50,000 to 800,000 g / mol, for example, 50,000 to 500,000 g / mol, for example, 50,000 to 300,000 g / mol. The weight average molecular weight (Mw) can be measured by gel permeation chromatography (GPC). When the weight average molecular weight (Mw) of the second polylactic acid (PLA) is out of the above range, the mechanical strength and heat resistance of the laminate can be further improved.

[0224] The second polylactic acid (PLA) may have a melting temperature (Tm) of, for example, 100°C to 250°C, 110°C to 220°C, or 120°C to 200°C. Also, the second polylactic acid (PLA) may not have a melting temperature (Tm).

[0225] The second polylactic acid (PLA) may have a glass transition temperature (Tg) of 20°C to 80°C, 25°C to 80°C, 30°C to 75°C, or 35°C to 70°C.

[0226] On the other hand, the second layer may further contain a filler to improve the sliding property.

[0227] The filler may be the same as or different from the type and content of the filler in the first layer. Specifically, the particle size of the filler contained in the second layer may be 0.1 μm to 6.0 μm. Also, the second layer may contain the filler in an amount of 0.01 to 3% by weight based on the total weight of the second layer.

[0228] When the second layer contains a filler, the sliding property is improved in the process, and the processing can be made easier.

[0229] The thickness of the second layer may be, for example, 0.1 μm to 20 μm, for example, 0.1 μm to 18 μm, or for example, 0.1 μm to 16 μm.

[0230] On the other hand, the thickness ratio of the first layer to the second layer may be, for example, 1:0.1 to 1, for example, 1:0.1 to 0.9, or for example, 1:0.1 to 0.8.

[0231] -COVID-19 group- The laminate according to one embodiment may further include a corona layer disposed on the other surface of the first layer. Specifically, the corona layer may be formed directly on the other surface of the first layer.

[0232] By further including a corona layer in the laminate, contaminants such as oil on the surface of the laminate can be removed, creating a surface that is compatible with the bonding site and increasing the adhesive strength. This results in chemical and physical surface modification, which can further improve hydrophilicity, adhesion, printability, coating properties, and vapor deposition properties.

[0233] Specifically, the first layer of the laminate has very little polarity and high crystallinity because it lacks polar groups, which may result in poor affinity for inks and adhesives. Therefore, high frequency and high voltage can be applied to the surface of the first layer to cause dielectric breakdown of molecular bonds on the surface, generating polar groups on the surface and increasing the surface energy.

[0234] The corona layer is formed by corona treatment of the first layer and may contain polar functional groups selected from the group consisting of -CO, -COOH, and -OH.

[0235] In the first layer, the surface tension with respect to the corona-treated surface is 38 mN / m That's all. For example, 38-70 mN / m For example, 38-68 mN / m , or for example, 38-66 mN / mThis is possible. In the first layer, when the surface tension with respect to the corona-treated surface satisfies the above range, the adhesiveness, printability, coating properties, vapor deposition properties, etc. of the laminate can be further improved.

[0236] The thickness of the corona layer can be appropriately adjusted according to the use and purpose of the laminate. Specifically, for example, it can be 0.1 nm to 1000 nm, for example, 0.2 nm to 900 nm, or, for example, 0.1 nm to 800 nm, but is not limited thereto.

[0237] -Coating layer- The laminate according to one implementation example may further include a coating layer disposed on the other surface of the first layer.

[0238] The coating layer can include a primer coating layer, and if so, the antistatic performance can be improved.

[0239] The primer coating layer can be included on the other surface of the first layer, or when the laminate includes the corona layer, the primer coating layer can be included on the other surface (lower surface) of the corona layer included on the other surface of the first layer.

[0240] Specifically, a primer treatment can be performed on the other surface of the first layer to form a primer coating layer. Or, a primer treatment can be performed on the other surface (lower surface) of the corona layer disposed on the other surface of the first layer to form a primer coating layer.

[0241] The primer coating layer can include one or more selected from the group consisting of ammonium-based compounds, phosphate-based compounds having antistatic performance, and polymers such as acrylic resins and urethane resins.

[0242] The surface resistance of the primer coating layer can be 0.1 to 30 Ω / sq, 0.2 to 28 Ω / sq, 0.3 to 26 Ω / sq, 0.4 to 24 Ω / sq, or 1 to 20 Ω / sq.

[0243] The aforementioned surface resistance was evaluated using a surface resistance meter to assess the antistatic performance, for example, at room temperature (22±2℃) and relative humidity (60%±10%).

[0244] The thickness of the coating layer can be appropriately adjusted depending on the application and purpose of the laminate, and may be, but is not limited to, 15nm to 50nm, 20nm to 45nm, 25nm to 40nm, or 30nm to 35nm.

[0245] The laminates in the embodiment of the present invention may include a multilayer structure of two or more layers, for example, three or more layers, or for example, four or more layers.

[0246] -Physical properties of laminated materials- In one example, when the thickness of the laminate is 19 to 22 μm, the flexible noise composite index (LSN) expressed by the following formula 2-1 may be 18 or less.

[0247] <Formula 2-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the above equation 2-1, The aforementioned N AVG This is the average noise level (dB) calculated by measuring the maximum noise level five times for each test, using a Class 2 sound level meter as defined in KS C IEC61672-1, pointed towards the noise source, at a height of 1.2m to 1.5m above the ground, while repeatedly crumpling and unfolding a laminated test piece measuring 21cm wide and 29.5cm long for 10 seconds each time. The unit is omitted. The aforementioned LS is measured by fixing a loop-shaped laminate test specimen with a width of 1.5 cm and a length of 18 cm to a loop stiffness tester and measuring the load at the center of the loop, in accordance with ASTM D747. mN ) and the numerical value excluding the unit The value obtained by dividing by 9.8 That is the case.

[0248] The flexible noise composite index (LSN), represented by Equation 2-1, is expressed as the product of the average noise level of the laminate and the loop stiffness, and is an index that indicates the degree of the combined characteristics of the flexibility and noise level of the laminate. Therefore, the flexible noise composite index (LSN) can serve as a measure of the quality of molded products such as packaging materials that include the laminate.

[0249] The aforementioned flexible noise composite index (LSN) is calculated using the average noise level (N) of the first layer. AVG The lower the ) the lower the noise level (N AVG The higher the loop stiffness (LS), the higher the flexible noise composite index (LSN) can be. Also, the flexible noise composite index (LSN) can be lower as the loop stiffness (LS) decreases, and higher as the loop stiffness (LS) increases.

[0250] When the flexible noise composite index (LSN) having such characteristics satisfies the specified range, the laminate exhibits excellent mechanical properties, optical properties, and thermal properties, and can reduce noise levels.

[0251] Specifically, the flexible noise composite index (LSN) of the laminate may be, for example, 18 or less, 17 or less, 16 or less, or 15 or less. If the flexible noise composite index (LSN) of the laminate exceeds 18, flexibility may decrease and brittleness may increase, potentially leading to increased noise, and thus, if applied to packaging material, quality may deteriorate.

[0252] The flexible noise composite index (LSN) of the laminate may be the same or different depending on the longitudinal (MD) and transverse (TD) directions of the laminate. In this case, the longitudinal (MD) direction of the laminate may refer to the length direction or the mechanical direction, and the transverse (TD) direction of the laminate may refer to the width direction as the direction perpendicular to the longitudinal (MD) direction.

[0253] Specifically, the flexible noise composite index (LSN) in the longitudinal direction (MD) of the laminated material. MD ) could be, for example, 4-18, 5-18, 5-17, 6-17, 8-17, or 8-16.

[0254] The composite flexible noise index (LSN) in the lateral direction (TD) of the laminated material. TD) could be, for example, 4-18, 5-17, 5-16, 6-16, 8-15, or 9-15.

[0255] The laminate is the LSN MD It is sufficient to satisfy only, or LSN TD It may be sufficient to satisfy only, or LSN MD and LSN TD Both conditions can be satisfied. In this case, the laminate according to the implementation example can improve flexibility while maintaining appropriate tensile strength and can reduce noise, thus being more advantageous in achieving the desired effect and providing a high-quality, environmentally friendly packaging material.

[0256] On the other hand, in formula 2-1, the average noise level of the laminate (N AVG The noise level was measured using a Class 2 sound level meter or higher as defined in KS C IEC61672-1, pointed towards the noise source, at a height of 1.2m to 1.5m above the ground, while repeatedly crumpling and unfolding the laminated material at a constant speed for 10 seconds. The maximum noise level was recorded, and this was repeated 5 times for each cycle. The average value of the maximum noise level for each cycle was calculated and defined as the average noise level. The noise level can be measured at a height of 1.2m to 1.5m above the ground. If there is an obstacle higher than 1.5m at the measurement point, the measurement can be taken at a point approximately 1.0m to 3.5m away from the obstacle in the direction of the noise source.

[0257] The laminated body has an average noise level (N) below a certain range. AVG Controlling ) can be preferable in terms of providing high-quality packaging materials.

[0258] Specifically, the average noise level (N) of the laminate AVG ) could be, for example, 86 dB or less, for example, 85 dB or less, for example, 84.8 dB or less, or for example, 84 dB or less.

[0259] The average noise level (N) of the laminated material AVGIf the noise level is 86 dB or less, it is advantageous in controlling the flexible noise composite index (LSN) of equation 2-1 to 18 or less, and it is possible to improve noise and provide high-quality packaging materials.

[0260] Furthermore, in Equation 2-1, the loop stiffness (LS) of the laminate is determined based on ASTM D747 by fixing a loop-shaped laminate test specimen with a width of 1.5 cm and a length of 18 cm to a loop stiffness tester (Toyo Seiki Seisakusho) and measuring the load at the center of the loop. It is an index indicating the degree of flexibility of the laminate.

[0261] The loop stiffness (LS) of the laminate is, 1.96 mN The following, or 1.86 mN The following may be true. Specifically, the loop stiffness (LS) of the laminate is, for example, 0.98~1.96 mN ,for example 0.98~1.86mN ,for example 0.98~1.76mN , or for example 0.98~1.67mN It is possible.

[0262] The lower the loop stiffness (LS) of the laminate, the greater the flexibility; and the higher the loop stiffness (LS) of the laminate, the greater the flexibility.

[0263] Furthermore, the loop stiffness (LS) of the laminate may be the same or different depending on the longitudinal direction (MD) and the transverse direction (TD) of the laminate.

[0264] Specifically, the longitudinal (MD) loop stiffness (LS) of the laminate MD ) is, for example 0.98~1.96 mN ,for example 0.98~1.86mN ,for example 1.08~1.86 mN ,for example 1.08~1.76mN , or for example 1.08~1.47mN It is possible.

[0265] The lateral (TD) loop stiffness (LS) of the laminate TD ) is, for example 0.98~1.96 mN ,for example 0.98~1.76mN ,for example 0.98~1.67mN , or for example 1.18~1.57mN It is possible.

[0266] The laminate, The LS MD It is sufficient to satisfy only, or LS TD It may be sufficient to satisfy only, or LS MD and LS TD Both conditions can be satisfied. In this case, the laminate according to the implementation example is more effective in controlling the flexible noise composite index (LSN) represented by formula 2-1 within the range, and is therefore more advantageous in achieving the desired effect, thus providing a high-quality, environmentally friendly packaging material.

[0267] On the other hand, the laminate has a thermal shrinkage coefficient (S) represented by the following formula 2-2. 100 ) may be 15% or less.

[0268] <Formula 2-2> Thermal shrinkage coefficient (S 100 )(%)={(L 25 -L 100 ) / L 25}×100 In the above equation 2-2, L 25 This is the initial length (mm) of the laminated test specimen at 25℃. L 100 This is the length (mm) of the laminated test specimen measured immediately after being exposed to a 100°C hot air blower for 5 minutes.

[0269] The thermal shrinkage coefficient (S) expressed by the above formula 2-2 100 This value represents the degree of thermal shrinkage of the laminated test specimen at a hot air temperature of 100°C, converted to a percentage. It is calculated as a percentage of the change in length of the laminated test specimen measured immediately after being left in a hot air machine for 5 minutes, relative to the initial length of the laminated test specimen.

[0270] The aforementioned thermal shrinkage rate (S 100 The length can be calculated by cutting the laminate into 150 mm long and 2 cm wide pieces regardless of direction to create test specimens, and then measuring the initial length at room temperature and the length of the laminate test specimens after being left in a 100°C hot air oven for 5 minutes.

[0271] The aforementioned thermal shrinkage rate (S100 ) may be 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, or 4.5% or less.

[0272] The aforementioned thermal shrinkage rate (S 100 If the above range is satisfied, the degree of thermal shrinkage at hot air temperatures of 100°C or higher is small, so the thermal properties are improved and printability and moldability can be further improved.

[0273] Furthermore, the thermal shrinkage rate (S) of the laminate 100 ) may be the same or different depending on the longitudinal (MD) and transverse (TD) directions of the laminate.

[0274] Specifically, the thermal shrinkage rate (S) in the longitudinal direction (MD) of the laminate. MD100 ) may be 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4.7% or less, or 4.5% or less.

[0275] The thermal shrinkage coefficient (S) in the lateral direction (TD) of the laminate TD100 ) could be, for example, 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5.5% or less, or 5.0% or less.

[0276] If the thermal shrinkage rates in the longitudinal (MD) and transverse (TD) directions of the laminate exceed the aforementioned range, the shrinkage in the longitudinal and transverse directions due to hot air during printing or lamination will be severe, causing printing problems, and severe curling will occur after printing, resulting in a curling phenomenon, which is undesirable.

[0277] On the other hand, the laminates in the real-world examples may have a molding index (FI) of 65 or higher, as expressed by the following formula 2-3.

[0278] <Formula 2-3> Forming index (FI)=TS / LS In the above equation 2-3, TS prepares test specimens by cutting them to a length of approximately 100 mm and a width of 15 mm according to ASTM D882, then mounts them so that the distance between the chucks is 50 mm, and measures the tensile strength of the test specimens at room temperature using a universal testing machine (UTM). MPa ) is a numerical value with units removed, and LS is as defined above.

[0279] The molding index (FI) of the laminate is the ratio of the tensile strength to the loop stiffness of the laminate, and can serve as a measure of whether the tensile strength and flexibility are appropriate.

[0280] In other words, according to the implementation example, one of the main features of the laminate may be that it can maintain an appropriate range of strength, such as tensile strength, while having increased flexibility and soft properties. In this case, the laminate has excellent moldability and may be advantageous for expanding its applications in various ways.

[0281] The molding index (FI) of the laminate may be, for example, 65 or higher, 68 or higher, 70 or higher, 73 or higher, 75 or higher, 80 or higher, 85 or higher, 88 or higher, 90 or higher, 95 or higher, or 100 or higher. Specifically, the molding index (FI) of the laminate may be, for example, 65 to 120, for example, 65 to 110, or for example, 65 to 105. If the molding index (FI) of the laminate is less than 65, the flexibility may decrease and it may easily break, the strength may decrease and various problems may occur during processing or molding, there may be limitations on its application to various uses, the quality of molded products such as packaging materials to which the laminate is applied may decrease, or defects may occur.

[0282] The molding index (FI) of the laminate may be the same or different depending on the longitudinal (MD) and transverse (TD) directions of the laminate.

[0283] Specifically, the molding index (FI) in the longitudinal direction (MD) of the laminate. MD ) could be, for example, 65-120, for example, 65-100, for example, 65-90, or for example, 70-90.

[0284] The molding index (FI) in the lateral direction (TD) of the laminate.TD ) could be, for example, 70-120, for example, 72-110, for example, 80-110, for example, 90-110, or for example, 90-105.

[0285] The laminate, The FI MD It is sufficient to satisfy only, or FI TD It may be sufficient to satisfy only, or FI MD and FI TD Both conditions can be satisfied. In this case, the laminate according to the implementation example can improve flexibility while maintaining appropriate tensile strength, and can provide a high-quality, environmentally friendly packaging material.

[0286] Furthermore, in equation 2-3, the loop stiffness (LS) of the laminate is as defined above.

[0287] Furthermore, the tensile strength of the laminate can be measured by preparing a laminate test specimen in accordance with ASTM D882, cutting it to a length of 100 mm and a width of 15 mm, mounting it so that the distance between the chucks is 50 mm, and then conducting an experiment at a tensile speed of 200 mm / min at room temperature of 25°C using an Instron universal testing machine (UTM, model name 5966), and then measuring it using a program built into the equipment.

[0288] The aforementioned tensile strength is, for example, 68.6~196.0MPa ,for example 78.4~196.0 MPa ,for example 78.4~176.4MPa ,for example 88.2~166.6MPa , or for example 98.0~166.6MPa It is possible.

[0289] When the tensile strength satisfies the aforementioned range, the productivity, processability, and moldability of the laminate can be improved simultaneously.

[0290] Furthermore, the tensile strength (TS) of the laminate may be the same or different depending on whether it is in the longitudinal (MD) or transverse (TD) direction of the laminate.

[0291] Specifically, the tensile strength (TS) in the longitudinal direction (MD) of the laminate. MD ) is, for example 68.6~137.2 MPa ,for example 78.4~137.2 MPa , for example 88.2~137.2 MPa , for example 98.0~137.2MPa , or, for example 107.8~137.2 MPa may be

[0292] The tensile strength (TS TD ) in the transverse direction (TD) of the laminate is, for example 78.4~196.0 MPa , for example 98.0~196.0 MPa , for example 107.8~196.0 MPa , for example 117.6~176.4 MPa , or, for example 127.4~166.6 MPa may be

[0293] The laminate may satisfy only the TS MD , or may satisfy only the TS TD , or may satisfy both the TS MD and the TS TD . In this case, since the laminate according to the embodiment can control the formability index (FI) represented by the formula 2-3 within the above range, productivity, workability, and formability can be improved simultaneously, and an environmentally friendly packaging material with excellent quality can be provided

[0294] On the other hand, the laminate has a modulus on the stress-strain curve 1960~3724MPa, 2254~3724MPa, 2450~3430MPa, 2744~3430MPa , or 2842~3430MPa . If the modulus is less than 1960MPa , the resistance to mechanical tension in processing steps such as printing or laminating is insufficient, so wrinkles occur in the running direction and printing problems occur, or breakage occurs during running, which is not preferable. On the other hand, if the modulus exceeds 3724 MPa , the rigidity of the laminate increases, and it can be easily broken or cracked by an external impact. Also, the lower the modulus within the above range, the more excellent the flexibility can be

[0295] Also, the modulus of the laminate may be the same or different depending on the machine direction (MD) and the transverse direction (TD) of the laminate

[0296] Specifically, the modulus (M<( MD ) in the machine direction (MD) of the laminate is 1960~3724MPa, 2450~3724MPa, 2548~3430MPa, 2842~3430MPa , or2891~3381MPa It may be.

[0297] The modulus (M TD ) in the transverse direction (TD) of the laminate is, for example, 1960~3724MPa, 2548~3724MPa, 2646~3430MPa, 2744~3430MPa or 2940~3430MPa It may be.

[0298] Also, the modulus (M TD ) in the transverse direction (TD) of the laminate may be greater than the modulus (M MD ) in the longitudinal direction (MD).

[0299] On the other hand, the thickness deviation of the laminate with respect to the thickness over the entire width of the laminate may be 10 μm or less. Specifically, the thickness deviation of the laminate with respect to the thickness over the entire width of the laminate may be 9 μm or less, 8.5 μm or less, 8 μm or less, 7 μm or less, 6.5 μm or less, 5 μm or less, or 4.7 μm or less.

[0300] On the other hand, the laminate has excellent interlayer adhesion properties between the first layer and the second layer.

[0301] Specifically, the thermal adhesion strength between the first layer and the second layer may be 6.9~19.6MPa It may be. Specifically, the thermal adhesion strength between the first layer and the second layer may be 6.9~17.6MPa, 8.8~17.6MPa or 8.8~16.7MPa It may be.

[0302] When the thermal adhesion strength between the first layer and the second layer satisfies the above range, the interlayer adhesion properties are excellent, the occurrence of separation of each layer can be prevented, and the workability and productivity can be further improved.

[0303] The heat-bonding strength was determined by, for example, preparing a laminate test specimen based on ASTM D882, cutting it to a length of approximately 100 mm and a width of approximately 15 mm, heat-bonding the opposing first and second layers using a Heat Seal Tester (Tester Industries Co., Ltd., TP-701-B), and then mounting the laminate test specimen using an Instron UTM (Universal Test Machine, Model 5966) so that the heat-bonded portion of the laminate test specimen was in the center and the distance between the chucks was 50 mm. The strength of peeling the first and second layers of the laminate test specimen at a 180° angle at a tensile speed of approximately 200 mm / min at room temperature of approximately 25°C was evaluated, and then measured using a program built into the tensile equipment.

[0304] On the other hand, the laminate may have excellent optical properties. Specifically, the laminate may have a haze of 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less. If the haze exceeds the above range, the transparency of the laminate decreases significantly, which may limit its use in packaging applications where the contents are visible.

[0305] The laminates shown in the examples, when containing amorphous polyhydroxyalkanoates (PHAs) in specific amounts, may provide transparent laminates due to their low haze.

[0306] Furthermore, the laminate may have a light transmittance of 90% or more, 92% or more, or 93% or more.

[0307] Furthermore, the laminate is characterized by having a biodegradability of 90% or more, as measured by the amount of carbon dioxide generated based on KS M3100-1. Biodegradability indicates the ratio of decomposition to a standard substance (e.g., cellulose) over the same period, and the Ministry of Environment of the Republic of Korea defines a substance as biodegradable when its biodegradability is 90% or more compared to a standard substance.

[0308] The structural and physical properties of the laminate according to the realization example can be efficiently achieved by manufacturing it using the manufacturing method of the laminate according to the realization example.

[0309] The method for manufacturing the laminate is described in detail below.

[0310] [Method for manufacturing laminates] One embodiment provides a method for manufacturing a laminate, comprising the steps of: preparing a first resin containing first polylactic acid (PLA) and polyhydroxyalkanoate (PHA) and a second resin containing second polylactic acid (PLA) (Step 1); melt co-extruding the first resin and the second resin to obtain a two-layer laminated sheet (Step 2); and biaxially stretching and heat-setting the laminated sheet to obtain a laminate (Step 3), wherein the laminate comprises a first layer containing first polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and a second layer disposed on one surface of the first layer and containing second polylactic acid (PLA), and the first layer contains more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

[0311] The manufacturing method for a laminate according to an embodiment of the present invention involves melt co-extruding a first resin and a second resin having specific compositions to obtain a two-layer laminated sheet, which is then biaxially stretched and heat-set. This method improves processability and productivity, and achieves the desired physical properties in the present invention in an economical and efficient manner.

[0312] Referring to Figure 1, the method for producing the laminate (S100) may include the step (S110) of preparing a first resin containing first polylactic acid (PLA) and polyhydroxyalkanoate (PHA) and a second resin containing second polylactic acid (PLA).

[0313] Specifically, the first resin comprises primary polylactic acid (PLA) and polyhydroxyalkanoate (PHA), with their content or mixed weight ratio being as described above.

[0314] Furthermore, when mixing the first polylactic acid (PLA) and polyhydroxyalkanoate (PHA), fillers may be added to improve lubricity and quality. The type, content, and particle size of the filler are as described above.

[0315] On the other hand, the second resin contains a second polylactic acid (PLA). The second polylactic acid (PLA) is as described above.

[0316] The method for manufacturing the laminate (S100) may include the step (S120) of melt-co-extruding the first resin and the second resin to obtain a two-layer laminated sheet.

[0317] During the melt co-extrusion process, the extrusion temperatures of the first resin and the second resin can be adjusted.

[0318] Specifically, the extrusion temperature of the first resin and the extrusion temperature of the second resin may be the same or different, and the difference between the extrusion temperature of the first resin and the extrusion temperature of the second resin may be 80°C or less. Specifically, the difference between the extrusion temperature of the first resin and the extrusion temperature of the second resin may be 60°C or less, 50°C or less, or 40°C or less.

[0319] For example, the extrusion temperature of the first resin may be, for example, 180°C to 250°C, and the extrusion temperature of the second resin may be, for example, 180°C to 270°C. After melt extrusion, a two-layer laminated sheet can be obtained by bringing it into close contact with a cooling roll cooled to approximately 10°C to 40°C.

[0320] On the other hand, some realization examples may further include a step of drying the first resin and the second resin before the melt co-extrusion.

[0321] The aforementioned drying step may or may not be necessary, depending on the type of extruder.

[0322] For example, if the extruder is a single extruder, melt co-extrusion may be performed after the drying step. The drying step may be performed, for example, at 40°C to 130°C for 4 to 24 hours.

[0323] The method for manufacturing the laminate (S100) may include the step (S130) of biaxially stretching and heat-fixing the laminated sheets to obtain the laminate.

[0324] Specifically, the two-layer laminated sheet can be biaxially stretched, and the biaxial stretching step may include, for example, a step of preheating to 50°C to 80°C, then stretching longitudinally (MD) by 2 to 4 times at 40°C to 100°C, and a step of stretching transversely (MD) by 3 to 5 times at 50°C to 110°C.

[0325] By performing biaxial stretching of the aforementioned laminated sheet in both directions, the physical properties and moldability of the laminate can be further improved, thereby enabling the realization of high-quality packaging material.

[0326] If uniaxial stretching is performed in only one direction, either the longitudinal or transverse direction, the thickness deviation of the laminate will be significant, the strength of the other unstretched portion will decrease, and the thermal properties may also deteriorate.

[0327] Furthermore, the heat setting step may be carried out at 50°C to 150°C, 70°C to 150°C, 100°C to 150°C, or 120°C to 150°C.

[0328] On the other hand, the manufacturing method of the laminate (S100) may further form a corona layer, a coating layer, or both on the other surface of the first layer.

[0329] Specifically, a corona layer can be formed by corona treatment of the first layer.

[0330] In the aforementioned corona treatment, corona discharge occurs when a high-frequency, high-voltage output is applied between the discharge electrode and the processing roll. By passing the discharge through a desired surface, corona treatment can be performed.

[0331] Specifically, the intensity of the corona discharge can be, for example, 3kW to 20kW. If the intensity of the corona discharge is below this range, the corona discharge treatment effect will be minimal, and conversely, if the intensity of the corona discharge exceeds this range, excessive surface modification may cause surface damage. The composition and properties of the corona layer are as described above.

[0332] Furthermore, a coating layer can be formed on the other surface of the first layer. The coating layer may include a primer coating layer, and the primer coating layer may be primer-treated on the other surface of the first layer with a primer composition containing one or more selected from the group consisting of ammonium compounds, phosphate compounds, and polymers such as acrylic resins and urethane resins to form a surface roughness and further improve adhesive properties.

[0333] The primer coating layer may form a corona layer on the other surface of the first layer, or, if the laminate includes the corona layer, on the other surface of the first layer, and the primer coating layer may be formed on the other surface of the corona layer.

[0334] Furthermore, the primer composition may contain a curing agent component, more specifically, which may be 4,4'-diaminodiphenylmethane (DDM), aromatic diamines, or mixtures thereof. In this case, the amount of curing agent component added may be 0.1 to 50% by weight based on the total weight of the primer composition.

[0335] The aforementioned primer treatment method can be a conventional method used in this industry, such as a spray injection method, brushing, or rolling. Specifically, an airless spray can be used with a saturation time of 1 to 30 minutes and a spray pressure of 5 to 500. MPa The primer composition can be sprayed onto the surface of the first layer under the conditions of a nozzle diameter of 0.46 to 0.58 mm and a spray angle of 40° to 80°.

[0336] In addition, surface treatments such as plasma treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment may be performed as appropriate to enhance the adhesion of the laminate.

[0337] Manufacturing the laminate using the manufacturing method of the example may be even more effective in producing a laminate having the desired structure and physical properties.

[0338] [Environmentally friendly packaging materials] In one embodiment, an environmentally friendly packaging material can be provided that includes a biaxially oriented film, the biaxially oriented film contains polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and the polyhydroxyalkanoate (PHA) is present in an amount of more than 0% to less than 30% by weight based on the total weight of the biaxially oriented film, and when the thickness of the film is 19 μm to 21 μm, the flexible noise composite index (LSN) represented by formula 1-1 is 20 or less.

[0339] In another embodiment, an environmentally friendly packaging material can be provided, comprising a laminate, the laminate comprising a first layer comprising a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA), and a second layer disposed on one surface of the first layer and comprising a second polylactic acid (PLA), wherein the first layer contains more than 0% to less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

[0340] The environmentally friendly packaging material may be in the form of a film that can be used as a general disposable packaging material and food packaging material, or it may be in the form of a fiber that can be used as a woven fabric, knitted fabric, nonwoven fabric, rope, etc., or it may be in the form of a container that can be used as a food packaging container such as a bento box.

[0341] The aforementioned environmentally friendly packaging material possesses both excellent strength and flexibility, as well as superior optical properties such as transparency and thermal properties, and includes a laminate with low noise levels, thereby providing excellent physical properties and quality. Furthermore, it is biodegradable, completely decomposes when disposed of in landfills, and offers environmentally friendly properties, making it suitable for use in various fields as a packaging material and allowing it to exhibit its excellent characteristics.

[0342] (Examples) The present invention will be described in more detail by the following examples. The following examples are illustrative only, and the scope of the present invention is not limited thereto.

[0343] [Manufacturing of biaxially oriented film] (Example 1-1) A mixed resin was produced by mixing a polylactic acid (PLA) resin (NatureWorks, USA), which is a random copolymer of L-lactic acid and D-lactic acid (L-lactic acid content: 98% by weight), has a weight-average molecular weight of 150,000 g / mol, a melting temperature (Tm) of 170°C, and a glass transition temperature (Tg) of 58°C; an amorphous polyhydroxyalkanoate (PHA) resin (CJ, South Korea), which has a glass transition temperature (Tg) of -30°C; and silica (Fuji Silysia Chemical Co., Ltd., 3.9 μm). In this process, the polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA) were mixed so that the weight ratio of polylactic acid (PLA) to amorphous polyhydroxyalkanoate (PHA) in the final film was 97:3, as shown in Table 1 below, and the silica content was 0.1% by weight based on the total weight of the biaxially oriented film.

[0344] The mixed resin was melt-extruded through an extruder at a temperature of 220°C, and then pressed against a cooling roll cooled to 20°C to obtain a sheet.

[0345] The sheet obtained in this way was immediately preheated to 55°C, and then passed through a stretching section at 70°C to be stretched three times in the longitudinal direction (MD). The stretched film was then stretched four times in the transverse direction (TD) within a stretching section of a tenter that was divided into two zones: an initial 30% zone with an average temperature of 85°C and a later 70% zone with an average temperature of 100°C.

[0346] Next, the stretched sheet was heat-set at 150°C in the heat treatment section of a tenter to produce a biaxially oriented film with a thickness of 19.98 μm.

[0347] (Examples 1-2) As shown in Table 1 below, a biaxially oriented film was produced in the same manner as in Example 1-1, except that the weight ratio of polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA) in the final biaxially oriented film was mixed to 95:5.

[0348] (Examples 1-3) As shown in Table 1 below, a biaxially oriented film was produced in the same manner as in Example 1-1, except that the weight ratio of polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA) in the final biaxially oriented film was mixed to 90:10.

[0349] (Examples 1-4) As shown in Table 1 below, a biaxially oriented film was produced in the same manner as in Example 1-1, except that the weight ratio of polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA) in the final biaxially oriented film was 80:20.

[0350] (Examples 1-5) A biaxially oriented film was produced using the same method as in Examples 1-3, except that a crystalline polyhydroxyalkanoate (PHA) resin (CJ Corporation, South Korea) was used instead of amorphous polyhydroxyalkanoate (PHA).

[0351] (Comparative Example 1-1) As shown in Table 1 below, a biaxially oriented film was manufactured in the same manner as in Example 1-1, except that only polylactic acid (PLA) resin was used.

[0352] (Comparative Example 1-2) As shown in Table 1 below, a biaxially oriented film was produced in the same manner as in Example 1-1, except that the weight ratio of polylactic acid (PLA) resin and amorphous polyhydroxyalkanoate (PHA) resin in the biaxially oriented film was 70:30.

[0353] (Comparative Examples 1-3) A mixed resin of polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA), similar to that used in Examples 1-3, was melt-extruded through an extruder at 220°C. After obtaining a sheet by adhering it to a cooling roll cooled to 20°C, it was stretched three times in the longitudinal (MD) direction. Finally, the stretched sheet was heat-set at 150°C in the heat treatment section of a tenter to produce a uniaxially oriented film.

[0354] [Table 1]

[0355] [Manufacturing of laminates] (Example 2-1) -Step 1: Preparation of the first and second resins- <First Resin> A mixed resin was prepared by mixing a first polylactic acid (PLA) resin (NatureWorks LLC, 4032D), which is a random copolymer of L-lactic acid and D-lactic acid (L-lactic acid content: 98% by weight), has a weight-average molecular weight of approximately 190,000 g / mol, a melting temperature (Tm) of approximately 160°C, and a glass transition temperature (Tg) of approximately 58°C, with an amorphous polyhydroxyalkanoate (PHA) resin (CJ Corporation, South Korea), which has a glass transition temperature (Tg) of approximately -30°C, and silica (Fuji Silysia Chemical Co., Ltd., 3.9 μm). In this process, the mixing of the first polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA) was carried out so that the weight ratio of the first polylactic acid (PLA) to amorphous polyhydroxyalkanoate (PHA) in the final first layer was approximately 97:3, as shown in Table 2 below, and the silica content was approximately 500 ppm based on the total weight of the first layer.

[0356] <Second resin> A second polylactic acid (PLA) resin (NatureWorks LLC, 4060D) was prepared, which is a random copolymer of L-lactic acid and D-lactic acid and has a glass transition temperature (Tg) of approximately 52°C. In this process, the L-lactic acid and D-lactic acid were mixed so that the weight ratio of poly-L-lactic acid (L-PLA) to poly-D-lactic acid (D-PLA) in the final second layer was approximately 90:10, as shown in Table 2 below.

[0357] -Step 2: A step to obtain a two-layer laminated sheet by melt co-extrusion- The first resin and the second resin obtained in step 1 were dried using a dehumidifying dryer at approximately 50°C for approximately 5 hours to remove moisture, and then melt-co-extruded through a single extruder to obtain a two-layer laminated sheet. At this time, the extrusion temperature of the first resin was approximately 210°C, and the extrusion temperature of the second resin was approximately 220°C.

[0358] -Stage 3: Biaxial stretching and heat fixing to obtain a laminate- The laminated sheets obtained in step 2 were stretched approximately 3 times in the longitudinal direction (MD) at approximately 75°C, then stretched approximately 3.8 times in the transverse direction (TD) at approximately 85°C, then heat-set at approximately 140°C, and finally relaxed by approximately 2% to produce a laminate with a thickness of approximately 19.98 μm.

[0359] (Examples 2-2 to 2-4 and 2-6) As shown in Table 2 below, the laminate was manufactured in the same manner as in Example 2-1, except that the composition of the final first and second layers was different in step 1 of Example 2-1.

[0360] (Examples 2-5) As shown in Table 2 below, the laminate was manufactured in the same manner as in Example 2-3, except that in step 1 of Example 2-3, crystalline polyhydroxyalkanoate (PHA) resin (CJ Corporation, South Korea) was used instead of amorphous polyhydroxyalkanoate (PHA), and the composition of the final second layer was different.

[0361] (Comparative Example 2-1) As shown in Table 2 below, a laminate was manufactured in the same manner as in Example 2-1, except that in step 1 of Example 2-1, only polylactic acid (PLA) resin was used as the component of the first layer.

[0362] (Comparative Example 2-2) As shown in Table 2 below, the laminate was manufactured in the same manner as in Example 2-1, except that the composition of the final first and second layers was different in step 1 of Example 2-1.

[0363] (Comparative Example 2-3) As shown in Table 2 below, the laminate was manufactured in the same manner as in Example 2-3, except that in step 1 of Example 2-1, polytriethylene terephthalate (PTT) was used for the second layer instead of a random copolymer of L-lactic acid and D-lactic acid.

[0364] [Table 2]

[0365] (Example of evaluation) (Evaluation example 1: Thickness and standard deviation) The thickness of the films and laminates produced in the examples and comparative examples was measured relative to their total width, and the thickness deviation was determined.

[0366] For the biaxially oriented films produced in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-3, the film thickness d (nm) was measured at 5 cm intervals in the width direction using an electric micrometer (Millitron 1245D, FineLewf Co., Ltd.), and the thickness deviation was calculated using the following formula 3.

[0367] On the other hand, for the laminates manufactured in Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3, the thickness d (nm) of the laminate was measured at 5 cm intervals in the width direction using an electric micrometer (Millitron 1245D, FineLewf Co., Ltd.), and the thickness deviation was calculated using the following formula 3.

[0368] <Expression 3> Thickness deviation = Maximum thickness in the width direction - Minimum thickness in the width direction

[0369] (Evaluation Example 2: Tensile Strength) After preparing film and laminate test specimens according to ASTM D882, they are cut to a length of 100 mm and a width of 15 mm, mounted with a chuck distance of 50 mm, and evaluated at a tensile speed of 200 mm / min at room temperature of 25°C using an Instron universal testing machine (UTM, model name 5966) according to ASTM D882. The results can then be measured using a program built into the equipment.

[0370] TS MD TS is the longitudinal tensile strength of a biaxially oriented film test specimen or laminate test specimen. TD This is the lateral tensile strength of a biaxially oriented film test specimen or laminate test specimen.

[0371] (Evaluation example 3: Modulus) Based on ASTM D882, biaxially oriented film test specimens and laminate test specimens manufactured in the examples and comparative examples were prepared, cut to a length of 100 mm and a width of 15 mm, mounted with a chuck distance of 50 mm, and tested at a tensile speed of 200 mm / min using an Instron universal testing machine (UTM, model name 5966). The modulus was then calculated by the program built into the equipment. MPa The value was obtained.

[0372] Furthermore, the modulus in the longitudinal direction (MD) and the modulus in the transverse direction (TD) of the biaxially oriented film test specimen or laminate test specimen were measured, respectively.

[0373] (Evaluation example 4: Thermal shrinkage rate) After cutting the films and laminates produced in the examples and comparative examples to test specimens with a length of 150 mm and a width of 1.5 cm, regardless of direction, the initial length at room temperature and the length of the biaxially oriented film or laminate test specimens immediately after being left in a 100°C hot air oven for 5 minutes were measured, and the thermal shrinkage rate was evaluated using the following formulas 1-2 and 2-2.

[0374] <Formula 1-2> Thermal shrinkage coefficient (S 100 )={(L 25 -L 100 ) / L 25}×100 In the above formula 1-2, L 25 This is the initial length (mm) of the biaxially oriented film test specimen at 25°C. L 100 This is the length (mm) of the biaxially oriented film test specimen measured immediately after being exposed to a 100°C hot air blower for 5 minutes.

[0375] <Formula 2-2> Thermal shrinkage coefficient (S 100 )={(L 25 -L 100 ) / L 25}×100 In the above equation 2-2, L 25 This is the initial length (mm) of the laminated test specimen at 25℃. L 100 This is the length (mm) of the laminated test specimen measured immediately after being exposed to a 100°C hot air blower for 5 minutes.

[0376] S MD100 S is the longitudinal thermal shrinkage coefficient of a biaxially oriented film test specimen or laminate test specimen. TD100 This is the lateral thermal shrinkage rate of a biaxially oriented film test specimen or laminate test specimen.

[0377] (Evaluation Example 5: Haze and Light Transmittance) For each of the biaxially oriented films and laminates produced in the above examples and comparative examples, the haze and light transmittance were analyzed using a haze meter (Haze Guard i, BYK-Gardner) according to ASTM D1003.

[0378] (Evaluation example 6: Noise level) For biaxially oriented films, a Class 2 sound level meter or higher (auditory weighting circuit: A-weighting, dynamic characteristics: fast mode) as defined in KS C IEC61672-1 was pointed towards the noise source. The maximum noise level was measured once at a height of 1.2m to 1.5m above the ground (or 1.0m to 3.5m away from the noise source if there was an obstacle taller than 1.5m at the measurement point) while a biaxially oriented film test piece measuring 21cm wide and 29.5cm long was shaken at a speed of 120 times per minute. The noise level was measured five times using the same method, and the average noise level (dB) was determined.

[0379] On the other hand, in the case of laminates, a Class 2 sound level meter or higher (auditory weighting circuit: A-weighting, dynamic characteristics: fast mode) as defined in KS C IEC61672-1 was pointed towards the noise source, and the maximum noise level was measured once by crumpling and unfolding a laminate test piece measuring 21 cm wide and 29.5 cm long 10 times for 10 seconds at a height of 1.2 m to 1.5 m above the ground (or 1.0 m to 3.5 m away from the obstacle in the direction of the noise source if there was an obstacle taller than 1.5 m at the measurement point). The noise level was measured 5 times using the same method, and the average noise level (dB) was determined.

[0380] (Evaluation example 7: Loop stiffness) Loop stiffness was determined according to ASTM D747 by fixing loop-shaped biaxially oriented film specimens and laminate specimens, each 1.5 cm wide and 18 cm long, to a Loop Stiffness Tester (Toyo Seiki Seisakusho) and measuring the load at the center of the loop.

[0381] LS MDThis is the longitudinal loop stiffness of a biaxially oriented film specimen or laminate specimen, LS TD This is the lateral loop stiffness of a biaxially oriented film specimen or laminate specimen.

[0382] (Evaluation Example 8: Flexible Noise Composite Index (LSN)) Using the noise levels and loop stiffness from evaluation examples 6 and 7, the flexible noise composite index (LSN) of the biaxially oriented film, expressed by the following equation 1-1, was determined.

[0383] <Formula 1-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the above formula 1-1, The aforementioned N AVG This is the average noise level (dB) calculated by measuring the maximum noise level five times each when a Class 2 sound level meter, as defined in KS C IEC61672-1, was pointed towards the noise source and shaken a biaxially oriented film test piece measuring 21 cm wide and 29.5 cm long at a speed of 120 times per minute at a height of 1.2 m to 1.5 m above the ground. The unit is omitted. The aforementioned LS is the loop stiffness (mN) measured by fixing a loop-shaped biaxially oriented film test specimen with a width of 1.5 cm and a length of 18 cm to a loop stiffness tester and measuring the load at the center of the loop, based on ASTM D747. The value obtained by removing the units and dividing it by 9.8.

[0384] LSN MD LSN is the longitudinal flexible noise composite index of a biaxially oriented film. TD This is the lateral flexibility noise composite index of a biaxially oriented film.

[0385] On the other hand, using the noise levels and loop stiffness of the evaluation examples 6 and 7, the flexible noise composite index (LSN) of the laminate, expressed by the following equation 2-1, was determined.

[0386] <Formula 2-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the above equation 2-1, The aforementioned N AVG This is the average noise level (dB) calculated by measuring the maximum noise level five times each while a Class 2 sound level meter, as defined in KS C IEC61672-1, is pointed towards the noise source and a laminated test piece measuring 21 cm wide and 29.5 cm long is crumpled and unfolded 10 times for 10 seconds at a height of 1.2 m to 1.5 m from the ground. The unit is omitted. The aforementioned LS is measured by fixing a loop-shaped laminate test specimen with a width of 1.5 cm and a length of 18 cm to a loop stiffness tester and measuring the load at the center of the loop, in accordance with ASTM D747. mN ) and the numerical value excluding the unit The value obtained by dividing by 9.8 That is the case.

[0387] LSN MD LSN is the LSN (Longitudinal Sound Noise Index), which is the LSN of the flexible noise composite index in the longitudinal direction of the laminate. TD This is the composite index of flexible noise in the lateral direction of the laminated material.

[0388] (Evaluation Example 9: Molding Index) Using the tensile strength and loop stiffness from evaluation examples 2 and 7, the molding index (FI) of the biaxially oriented film and laminate, respectively, was determined using the following equations 1-3 and 2-3.

[0389] <Formula 1-3> Forming index (FI)=TS / LS In the above formula 1-3, TS prepares biaxially oriented film test specimens according to ASTM D882, cuts them to a length of 100 mm and a width of 15 mm, mounts them so that the distance between chucks is 50 mm, and measures the tensile strength of the test specimens using a universal testing machine (UTM). MPa ) is a numerical value with units removed, and LS is as defined above.

[0390] <Formula 2-3> Forming index (FI)=TS / LS In the above equation 2-3, TS prepares a laminated test specimen by cutting it to a length of approximately 100 mm and a width of 15 mm according to ASTM D882, then mounts it so that the distance between the chucks is 50 mm, and measures the tensile strength of the test specimen at room temperature using a universal testing machine (UTM). MPa ) is a numerical value with units removed, and LS is as defined above.

[0391] FI MD FI is the longitudinal molding index of a biaxially oriented film test specimen or laminate test specimen. TD This is the lateral molding index of a biaxially oriented film test specimen or laminate test specimen.

[0392] [Table 3]

[0393] As can be seen from Table 3 above, in the case of the biaxially oriented film of the example, which contains polylactic acid (PLA) and polyhydroxyalkanoate (PHA) within a specific content range and has a flexible noise composite index (LSN) of 20 or less, it exhibits excellent strength and flexibility simultaneously, while also having excellent thermal properties and improved noise levels.

[0394] Specifically, the biaxially oriented films of Examples 1-1 to 1-5 have a tensile strength of 88.2~245.0 MPa It has an appropriate range, and the loop rigidity is 0.98~2.25mN It is highly flexible. Furthermore, it has a low noise level of 86 dB or less, and a very low thermal shrinkage rate of 15% or less even at high temperatures of 100°C, indicating excellent mechanical and thermal properties.

[0395] On the other hand, in the case of the biaxially oriented film of Comparative Example 1-1, which does not contain polyhydroxyalkanoate (PHA), the flexible noise composite index exceeded 20, indicating an increase in the loop stiffness of the film, a decrease in flexibility, and an increase in noise level. In particular, it was confirmed that the loop stiffness increased by more than 60% and the noise level increased by more than 10% compared to the biaxially oriented film of Example 1-4.

[0396] On the other hand, in the case of the biaxially oriented films of Comparative Examples 1-2, which contain an excess of 30% by weight or more of polyhydroxyalkanoate (PHA), the tensile strength is approximately 39.2~58.8MPa The thermal shrinkage rate decreased significantly, and at a high temperature of 100°C, it increased dramatically to 17-20%. In addition, the haze increased to over 14%, and the light transmittance also decreased significantly to approximately 85%, resulting in a substantial decline in optical properties.

[0397] Furthermore, in the case of the uniaxially oriented film of Comparative Examples 1-3, the thickness deviation increased by more than 250% to 11.3 μm compared to the biaxially oriented film of Examples 1-3 containing the same amount of amorphous polyhydroxyalkanoate (PHA), the strength in the unoriented transverse direction (TD) was significantly reduced, and the heat shrinkage rate also increased by more than 40%.

[0398] On the other hand, the biaxially oriented films of Examples 1-1 to 1-4, which contained amorphous polyhydroxyalkanoate (PHA), had low haze of 6.8% or less and excellent light transmittance of 90% or more. In contrast, the biaxially oriented film of Example 1-5, which used crystalline polyhydroxyalkanoate (PHA), showed increased haze and decreased light transmittance compared to the biaxially oriented film of Example 1-3, which contained the same amount of polyhydroxyalkanoate (PHA), resulting in degraded optical properties.

[0399] [Table 4]

[0400] As can be seen from Table 4, in the case of the laminate of the example, which includes a first layer containing polyhydroxyalkanoate (PHA) within a specific content range and a second layer containing polylactic acid (PLA), it simultaneously possesses excellent strength and flexibility, excellent thermal properties, improved noise levels, and good interlayer compatibility between the first and second layers, resulting in excellent interlayer adhesion properties.

[0401] Specifically, the laminates of Examples 2-1 to 2-6 have a low noise level of 86 dB or less, a loop stiffness of 0.98 to 1.96 mN, and excellent flexibility. In addition, the tensile strength in the longitudinal direction (MD) (TS) is also high. MD When the pressure is within the appropriate range of 68.6 to 137.2 MPa, the thermal shrinkage rate is very low at 15% or less even at high temperatures of 100°C, the haze is 10% or less, and the light transmittance is 90% or more, indicating excellent mechanical, thermal, and optical properties.

[0402] On the other hand, in the case of the laminate of Comparative Example 2-1, which does not contain polyhydroxyalkanoate (PHA) in the first layer, the loop rigidity of the laminate increased and the flexibility decreased, and the noise level increased. In particular, it was confirmed that the loop rigidity and noise level increased compared to the laminate of Example 2-1, which had the same composition as the second layer.

[0403] On the other hand, in the case of the laminate of Comparative Example 2-2, in which the first layer excessively contained 30% or more of polyhydroxyalkanoate (PHA), the thickness deviation of the laminate increased, and the tensile strength in the longitudinal direction (TS) decreased. MD ) and tensile strength in the lateral direction (TS TD ) are approximately 62.7 MPa and 76.4 MPa The thermal shrinkage rate decreased significantly at high temperatures of 100°C, reaching 15.3-16.8%, and the optical properties also deteriorated.

[0404] Furthermore, in the case of the laminates of Comparative Examples 2-3, in which polytriethylene terephthalate (PTT) was used instead of polylactic acid in the second layer, the interlayer adhesion characteristics were insufficient due to inadequate compatibility between the first and second layers during stretching, making it impossible to produce a stretched film (film) due to delamination.

[0405] In contrast, the laminating agents of Examples 2-1 to 2-6 are composed of a first layer containing primary polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and a second layer containing secondary polylactic acid (PLA) arranged on one surface of the first layer. Because of their good compatibility, the adhesive properties of the first and second layers remain excellent even after stretching.

[0406] On the other hand, in the case of the laminates of Example 2-5 using crystalline polyhydroxyalkanoate (PHA), the thermal shrinkage rate was significantly reduced compared to the laminates of Comparative Examples 2-1 to 2-3. Although there were advantages such as easier drying for extrusion processing and less bubble generation during extrusion, the modulus and noise level were slightly increased compared to the laminates of Examples 2-1 to 2-4 which contained amorphous polyhydroxyalkanoate (PHA) in the first layer.

[0407] Furthermore, in the case of the laminate of Example 2-6, in which the weight ratio of L-PLA to D-PLA in the second layer was increased to 62:38, the mechanical properties, thermal properties, optical properties, noise level, and flexibility were improved compared to the laminates of Comparative Examples 2-1 to 2-3. However, compared to the laminate of Example 2-3, which had the same composition as the first layer, the thickness deviation of the laminate increased relatively, and the thermal shrinkage rate increased. In addition, it was confirmed that the processability and productivity were somewhat reduced due to insufficient winding properties during film production and processing. [Explanation of Symbols]

[0408] 1: Laminate 11:Second layer 12: 1st layer 13: Coronavirus layer 14: Coating layer

Claims

1. A first layer comprising primary polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA), The first layer comprises a second layer disposed on one surface of the first layer and containing a second polylactic acid (PLA), The first layer is a laminate containing more than 0% to less than 30% by weight of amorphous polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

2. The amorphous polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA), The copolymerized polyhydroxyalkanoate (PHA) comprises at least one unit of the following chemical formula 1 and at least one unit of the following chemical formula 2, according to claim 1: [Chemical formula 1] In the aforementioned chemical formula 1, The aforementioned R １ is the substituted C １ ~C ８ It is an alkylene, m is an integer greater than or equal to 1, [Chemical formula 2] In the aforementioned chemical formula 2, The aforementioned R ２ C is either substituted or non-substituted. １ ~C ８ It is an alkylene, n is an integer greater than or equal to 1.

3. The laminate according to claim 2, wherein the copolymerized polyhydroxyalkanoate (PHA) contains the unit of chemical formula 2 in an amount of 1% to 60% by weight based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

4. The second layer comprises a mixture of the L-isomer and D-isomer of the second polylactic acid, The laminate according to claim 1, wherein the second layer contains 5% to 30% by weight of D-isomers based on the total weight of the second polylactic acid.

5. The first layer further includes a corona layer, a coating layer, or both, disposed on the other surface of the first layer. The corona layer is formed by corona treatment of the first layer and contains polar functional groups selected from the group consisting of -CO, -COOH, and -OH. In the first layer, the surface tension with respect to the corona-treated surface is 38 mN / m or more. The coating layer includes a primer coating layer, The laminate according to claim 1, wherein the primer coating layer is formed on the other surface of the first layer or the other surface of the corona layer by priming treatment and has a surface resistance of 0.1 to 30 Ω / □.

6. The tensile strength (TS) in the longitudinal direction (MD) of the laminate. ＭＤ The tensile strength (TS) in the transverse direction (TD) is 68.6 to 137.2 MPa. ＴＤ The pressure ranges from 78.4 to 196.0 MPa. The laminate according to claim 1, wherein the thermal bonding strength of the first and second layers is 6.9 to 19.6 MPa.

7. Step 1 involves preparing a first resin containing primary polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA), and a second resin containing secondary polylactic acid (PLA). Step 2: Melt co-extrude the first resin and the second resin to obtain a two-layer laminated sheet. The step (step 3) includes the step of biaxially stretching and heat-fixing the laminated sheets to obtain a laminate, The laminate comprises a first layer containing primary polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA), The first layer comprises a second layer disposed on one surface of the first layer and containing a second polylactic acid (PLA), A method for producing a laminate, wherein the first layer contains amorphous polyhydroxyalkanoate (PHA) in an amount of more than 0% to less than 30% by weight, based on the total weight of the first layer.

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