Biaxially oriented films, laminates, and environmentally friendly packaging materials containing the films

Abstract

The present invention relates to a biaxially stretched film containing polylactic acid (PLA) and polyhydroxyalkanoate (PHA), a laminate, and an environmentally friendly packaging material containing the film. Specifically, the biaxially stretched film of the present invention contains a specific content range of PHA, and the film's composite flexible noise index (LSN) satisfies a specific range, thereby having excellent strength and flexibility at the same time, improving optical properties and thermal properties, and reducing noise levels. In addition, the laminate of the present invention includes a first layer and a second layer having a specific composition, thereby improving the above properties, and since the first layer and the second layer have good interlayer compatibility, it can maintain excellent interlayer adhesion properties. Therefore, the biaxially stretched film and laminate can be used as packaging materials in various fields and provide high-quality packaging materials.

Description

[Technical Field]

[0001] The present invention relates to biaxially oriented films, laminates, and environmentally friendly packaging materials containing the films. [Background technology]

[0002] recently, So-called untact (un-contact) Due to factors such as consumer culture and hygiene, the use of disposable products is increasing, and the use of food packaging materials in particular is showing a significant increase.

[0003] Currently, the general-purpose plastic films used for packaging include petroleum-derived polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP). However, PVC film is subject to numerous restrictions due to the release of hazardous substances such as dioxins when incinerated, while polyethylene film has poor dimensional stability and poor mechanical properties, limiting its use to low-grade packaging paper. Polypropylene film, which has a relatively stable molecular structure and good mechanical properties, is almost always disposed of in landfills after packaging. This poses serious environmental problems as it causes soil pollution due to the chemical and biological stability of plastic film, which accumulates without decomposing.

[0004] Recently, much research has been conducted on polylactic acid (PLA), an aliphatic polyester with a highly biodegradable resin. However, the use of PLA film for packaging is limited due to its insufficient flexibility and high noise level.

[0005] Therefore, research is also being conducted into films that use polylactic acid mixed with other resins.

[0006] For example, Patent Document 1 discloses a film made by mixing polylactic acid and polybutylene adipate terephthalate (PBAT). However, in this case, the compatibility between the two materials is insufficient, resulting in reduced transparency, reduced thermal properties, and difficulty in simultaneously achieving satisfactory flexibility and strength.

[0007] Research has also been conducted on multilayer films in which a resin layer containing polylactic acid is laminated with another resin layer, such as polyethylene terephthalate (PTT). However, in this case, it is difficult to achieve a satisfactory noise reduction effect or flexibility, and the compatibility between the resin layers may decrease, resulting in poor interlayer adhesion or separation, which may adversely affect processability and productivity. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 2014-0106882 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been devised to solve the above-mentioned problems of the prior art. An object of the present invention is to provide a biaxially stretched film which simultaneously has excellent strength and flexibility, has excellent compatibility between resins, has excellent transparency, and has improved noise and thermal properties.

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

[0011] It is still another object of the present invention to provide a method for producing a laminate that is economical and efficient, and that is excellent in processability and productivity while achieving the above-mentioned properties.

[0012] A further object of the present invention is to provide a high-quality, environmentally friendly packaging material that is biodegradable and environmentally friendly 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 stretched film that contains polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and that contains more than 0% by weight and less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the biaxially stretched film, and that has a flexibility noise composite index (LSN) represented by the following formula 1-1 of 20 or less when the film has a thickness of 19 to 21 μm.

[0014] <Formula 1-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the formula 1-1, N AVG is the average sound level (dB) calculated by measuring the maximum sound level five times when a class 2 sound level meter specified in KS C IEC61672-1 is aimed at the noise source and a biaxially stretched film test piece with a width of 21 cm and a length of 29.5 cm is swung at a speed of 120 times per minute from the ground at a height of 1.2 m to 1.5 m. The unit is omitted. The LS is a unit-free value that indicates the loop stiffness (gf) measured by fixing a loop-shaped biaxially stretched film specimen having a width of 1.5 cm and a length of 18 cm to a loop stiffness tester according to ASTM D747, and measuring the load at the center of the loop.

[0015] The present invention also provides a laminate comprising a first layer containing a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA), and a second layer disposed on one side of the first layer and containing a second polylactic acid (PLA), wherein the first layer contains more than 0 wt % and less than 30 wt % of polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

[0016] The present invention also provides a method for producing a laminate, comprising the steps of: preparing a first resin containing a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA), and a second resin containing a 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 the first polylactic acid (PLA) and the polyhydroxyalkanoate (PHA), and a second layer disposed on one side of the first layer and containing the second polylactic acid (PLA), and the first layer contains more than 0 wt% and less than 30 wt% of the polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

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

[0018] The biaxially stretched film according to the present invention contains polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and contains PHA in a specific content range. The film's composite flexibility noise index (LSN) satisfies a specific range, thereby providing excellent strength and flexibility, low noise levels, and improved optical and thermal properties.

[0019] Furthermore, the laminate according to the present invention includes a first layer and a second layer having a specific composition, and therefore has excellent strength and flexibility at the same time, low noise level, and improved optical and thermal properties. Furthermore, since the first and second layers have good interlayer compatibility, excellent interlayer adhesion properties can be maintained.

[0020] Furthermore, the method for producing a laminate according to the present invention is economical and efficient, and can further improve processability and productivity.

[0021] Furthermore, the biaxially oriented film and the laminate are biodegradable and completely decompose when disposed of in a landfill, making them environmentally friendly. Therefore, they can be used in a variety of fields as packaging materials, thereby providing high-quality packaging materials. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram of a stack according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of a stack according to another embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram of a stack according to yet another embodiment of the present invention. [Figure 4] FIG. 4 shows a schematic diagram of a method for manufacturing a laminate according to one implementation of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in detail below with reference to examples. The implementation examples are not limited to the contents disclosed below, and may be modified in various forms as long as the gist of the invention is not changed.

[0024] In this specification, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless specifically stated to the contrary.

[0025] In this specification, unless otherwise specified, the singular expression "a," "an," or "an" is to be construed as including the singular or plural as the context requires.

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

[0027] Meanwhile, in this specification, terms such as first layer, second layer, first, and second are used to describe various components, and the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0028] In addition, the criteria for "one side" / "hitting surface" or "top" / "bottom" of each component will be explained based on the drawings, and these terms are only used to distinguish the components and may be interchangeable in actual application.

[0029] In this specification, when one component is described as being formed above or below another component, this includes all cases where one component is formed directly above or below the other component, or indirectly via yet another component.

[0030] In addition, the size of each component in the drawings may be exaggerated for illustrative purposes and does not represent the actual size. The same reference numerals refer to the same components throughout the specification.

[0031] [Biaxially oriented film] In one embodiment, a biaxially stretched film is provided, which contains polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and contains more than 0% by weight and less than 30% by weight of polyhydroxyalkanoate (PHA) based on the total weight of the biaxially stretched film, 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 formula 1-1, N AVG is the average sound level (dB) calculated by measuring the maximum sound level five times when a class 2 sound level meter specified in KS C IEC61672-1 is aimed at the noise source and a biaxially stretched film test piece with a width of 21 cm and a length of 29.5 cm is swung at a speed of 120 times per minute from the ground at a height of 1.2 m to 1.5 m. The unit is omitted. The LS is a unit-free value that indicates the loop stiffness (gf) measured by fixing a loop-shaped biaxially stretched film specimen having a width of 1.5 cm and a length of 18 cm to a loop stiffness tester according to ASTM D747, and measuring the load at the center of the loop.

[0033] In one embodiment, the inclusion of polylactic acid (PLA) and polyhydroxyalkanoate (PHA) can improve flexibility and reduce noise. In particular, the inclusion of polyhydroxyalkanoate (PHA) in an amount greater than 0 wt% and less than 30 wt% based on the total weight of the biaxially stretched film can improve flexibility while maintaining appropriate strength, further improving optical properties, and providing a film with low heat shrinkage at high temperatures of 100°C or higher and minimal thickness variation. Furthermore, by controlling the composite flexibility noise index (LSN) expressed by Equation 1-1 to 20 or less, strength, flexibility, and noise can be further improved. Furthermore, by providing the film as a biaxially stretched film that is stretched in both directions, the physical properties and formability of the film can be further improved, resulting in the realization of high-quality packaging materials, which is of technical significance.

[0034] The biaxially stretched film according to the embodiment will be described in more detail below. A biaxially oriented film according to one implementation includes polylactic acid (PLA) and polyhydroxyalkanoate (PHA).

[0035] Unlike petroleum-based resins, polylactic acid (PLA) is biomass-based, making it possible to utilize renewable resources. It also emits less carbon dioxide, the main cause of global warming, during production compared to existing resins, and is environmentally friendly as it is biodegradable by water and microorganisms when landfilled.

[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) may be measured by gel permeation chromatography (GPC). If the weight-average molecular weight (Mw) of the polylactic acid (PLA) is outside the above range, the mechanical strength and heat resistance of the film may be reduced compared to when the weight-average molecular weight (Mw) is within the above 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 content of the L-lactic acid 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 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 comprise more than 70 wt%, 75 wt% or more, 80 wt% or more, 85 wt% or more, 88 wt% or more, 90 wt% or more, 93 wt% or more, or 95 wt% or more, based on the total weight of the biaxially stretched film, or less than 100 wt%, 99 wt% or less, 98 wt% or less, 97 wt% or less, or 95 wt% or less, based on the total weight of the biaxially stretched film.

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

[0042] If the content of polylactic acid (PLA) is too low, the tensile strength may decrease, the heat shrinkage rate may increase, and optical properties such as transparency and light transmittance may decrease.On the other hand, if the content of polylactic acid (PLA) is too high, the brittleness may increase, the flexibility may decrease, and the product may be prone to cracking or breaking, and may be noisy.

[0043] In particular, polylactic acid (PLA) is highly brittle, and when the temperature range for use is below 20°C, the film tends to harden, making it prone to cracking or breaking when subjected to impact in winter. When the temperature range for use is above 35°C, the film tends to lose elasticity and become soft, making it noisy, limiting its use.

[0044] Therefore, in the embodiment, polyhydroxyalkanoate (PHA), which has excellent flexibility and low noise level, is mixed with the polylactic acid (PLA).

[0045] In particular, in the biaxially stretched film according to the embodiment, the content of polyhydroxyalkanoate (PHA) contained in the biaxially stretched film is important in order to achieve excellent strength, flexibility, improved optical properties, thermal properties, and improved noise level.

[0046] Biaxially stretched films according to implementations can include greater than 0 wt % and less than 30 wt % polyhydroxyalkanoate (PHA), based on the total weight of the biaxially stretched film.

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

[0048] If the content of polyhydroxyalkanoate (PHA) is too high, the tensile strength may decrease, the heat shrinkage rate may increase, the extrusion processability may decrease, and the optical properties may deteriorate. On the other hand, if the content of polyhydroxyalkanoate (PHA) is too low, the brittleness may increase, the flexibility may decrease, and the film may be prone to cracking or breakage, and the noise level may increase.

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

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

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

[0052] For example, the polyhydroxyalkanoate (PHA) may be a copolymerized polyhydroxyalkanoate (PHA) with controlled crystallinity, including a copolymerized polyhydroxyalkanoate containing at least one unit of the following formula 1 and at least one unit of the following formula 2: [Chemical formula 1] JPEG0007749026000001.jpg2455In the above Chemical Formula 1, R1 is a substituted C1-C8 alkylene, m is an integer of 1 or greater.

[0053] [Chemical formula 2] JPEG0007749026000002.jpg2454In the above Chemical Formula 2, R2 is a substituted or unsubstituted C1 to C8 alkylene, n is an integer of 1 or greater.

[0054] In this regard, in the above Chemical Formulas 1 and 2, unless otherwise specified, the term "substituted" may include a substituted or unsubstituted alkyl group, specifically a substituted or unsubstituted C1 to C8 alkyl group.

[0055] The polyhydroxyalkanoate (PHA) may be a polyester containing only the units of Chemical Formula 1 and the units of Chemical Formula 2 as polymerized units, or may contain not only the units of Chemical Formula 1 and the units of Chemical Formula 2 as polymerized units, but also different polymerized units other than those mentioned above. Furthermore, the units of Chemical Formula 2 may be repeated randomly.

[0056] In some embodiments, in Formula 1, R1 may be, for example, a substituted C2-C8 alkylene, a substituted C3-C8 alkylene, or a substituted C3-C6 alkylene, and m may be 1-12,000.

[0057] In Chemical Formula 2, R2 can be, for example, a substituted or unsubstituted C2 to C8 alkylene, a substituted or unsubstituted C3 to C8 alkylene, or a substituted or unsubstituted C4 to C8 alkylene. For example, in Chemical Formula 2, R2 can include an unsubstituted alkylene. Furthermore, n can be 1 to 12,000.

[0058] In addition, in the above Chemical Formulas 1 and 2, the substituents may each include C1 to C8 alkyl, C1 to C6 alkyl, or C1 to C4 alkyl.

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

[0060] [Chemical formula 1-1] JPEG0007749026000003.jpg3354In the above chemical formula 1-1, R3 is methyl, ethyl, or propyl; m is an integer of 1 or greater.

[0061] [Chemical formula 2-1] JPEG0007749026000004.jpg2958In the above chemical formula 2-1, n is an integer of 1 or greater.

[0062] Specifically, in the above Chemical Formula 1-1, R3 may be methyl and m may be 1 to 12,000.

[0063] In the above Chemical Formula 2-1, n can be 1 to 12,000.

[0064] The crystallinity-controlled polyhydroxyalkanoate (PHA) may be one whose crystallinity and amorphousness are controlled by increasing the disorder in its molecular structure, and specifically, the type of monomer, the ratio of monomers, or the type and / or content of isomers may be controlled.

[0065] According to an embodiment, the polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing units of the Chemical Formula 1 and units of the Chemical Formula 2, and the content of the units of the Chemical Formula 2 may be 1 wt % or more, 3 wt % or more, 5 wt % or more, 10 wt % or more, and 60 wt % or less, 55 wt % or less, or 50 wt % or less, based on the total weight of the copolymerized polyhydroxyalkanoate.

[0066] For example, the polyhydroxyalkanoate (PHA) may be a copolymerized polyhydroxyalkanoate (PHA) containing units of Chemical Formula 1 and units of Chemical Formula 2, and the content of units of Chemical Formula 2 may be 1 to 60 wt%, 5 to 50 wt%, 10 to 60 wt%, 10 to 50 wt%, 15 to 60 wt%, 15 to 50 wt%, 20 to 60 wt%, 20 to 50 wt%, 25 to 60 wt%, 25 to 50 wt%, 30 to 60 wt%, 30 to 50 wt%, 35 to 60 wt%, 35 to 50 wt%, 40 to 60 wt%, 40 to 50 wt%, 45 to 60 wt%, 45 to 50 wt%, or 46 to 50 wt%.

[0067] According to an embodiment, 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 a realization example, the copolymerized polyhydroxyalkanoate (PHA) can be an amorphous polyhydroxyalkanoate (PHA).

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

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

[0071] In the polyhydroxyalkanoate (PHA), the amorphousness can increase as the content of the unit of Chemical Formula 2 increases. Therefore, in the biaxially stretched film according to the embodiment, the content of the unit of Chemical Formula 2 in the amorphous polyhydroxyalkanoate (PHA) can be important.

[0072] For example, the amorphous polyhydroxyalkanoate (PHA) may contain the unit of Chemical Formula 2 in an amount of 15 to 60 wt %, 15 to 50 wt %, 20 to 60 wt %, 20 to 50 wt %, 25 to 60 wt %, 25 to 50 wt %, 30 to 60 wt %, 30 to 50 wt %, 35 to 60 wt %, 35 to 50 wt %, 40 to 60 wt %, 40 to 50 wt %, 45 to 60 wt %, 45 to 50 wt %, or 46 to 50 wt %, based on the total weight of the polyhydroxyalkanoate (PHA).

[0073] The biaxially stretched film according to the embodiment contains the unit of Chemical Formula 2 in the above range, which has the advantage that when polyhydroxyalkanoate (PHA) is mixed with polylactic acid (PLA), there is compatibility between the resins and excellent optical properties, which can further improve the optical properties of the film. If the unit of Chemical Formula 2 in polyhydroxyalkanoate (PHA) is less than 15 wt%, compatibility between the resins may be poor, which can reduce transparency and light transmittance.

[0074] According to an embodiment, 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 contained in an amount of 15% by weight to 60% by weight based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0075] In the polyhydroxyalkanoate (PHA), the amorphousness increases as the content of the 4-hydroxybutyrate (4-HB) unit increases. Therefore, in the biaxially stretched film according to the embodiment, the content of the 4-hydroxybutyrate (4-HB) unit in the amorphous polyhydroxyalkanoate (PHA) may be important.

[0076] For example, the 4-hydroxybutyrate (4-HB) units may be contained in an amount of, for example, 20 to 60 wt %, for example, 25 to 60 wt %, for example, 25 to 50 wt %, for example, 30 to 60 wt %, for example, 30 to 50 wt %, for example, 35 to 60 wt %, for example, 35 to 50 wt %, for example, 40 to 60 wt %, for example, 40 to 50 wt %, for example, 45 to 60 wt %, for example, 45 to 50 wt %, for example, 46 to 60 wt %, or for example, 46 to 50 wt %, based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0077] The biaxially stretched film according to the embodiment contains 4-hydroxybutyrate (4-HB) units in the above range, which has the advantage that when polyhydroxyalkanoate (PHA) is mixed with polylactic acid (PLA), compatibility between the resins is improved, thereby further improving the optical properties of the film. If the 4-hydroxybutyrate (4-HB) units are less than 15 wt%, compatibility between the resins may be poor, resulting in reduced optical properties.

[0078] The polyhydroxyalkanoate (PHA) contains 3-hydroxybutyrate as a polymer unit. (3-HB) units and polyesters containing only 4-hydroxybutyrate (4-HB) units (i.e., the polymerized units are 3-hydroxybutyrate (3-HB) units and 4-hydroxybutyrate (4-HB) units or 3-hydroxybutyrate as a polymerized unit (3-HB) units and 4-hydroxybutyrate (4-HB) units, and may further contain different polymerized units other than those described above. The 4-hydroxybutyrate (4-HB) units may also be randomly repeated.

[0079] Examples of the different polymerized units include lactate (LA), glycolate (GA), 3-hydroxypropionate (3HP), 3-hydroxyvalerate (3HV), 5-hydroxyvalerate (5HV), 5-hydroxyhexanoate (5HH), 6-hydroxyhexanoate (6HH), 3-hydroxyhexanoate (3HH), and 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) may 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. If the weight average molecular weight (Mw) and glass transition temperature (Tg) of the amorphous polyhydroxyalkanoate (PHA) satisfy the above ranges, optical properties such as transparency and light transmittance are improved, which may be more advantageous in achieving the desired noise reduction effect and flexibility improvement effect.

[0082] According to one implementation, the biaxially stretched film may further comprise 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 hard acrylate, polystyrene, nylon, and soft 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] By including the filler, the biaxially stretched film can have excellent slip properties and improved processability, and can provide excellent quality.

[0087] The particle size of the filler may be 0.1 μm to 6.0 μm, for example, 1.0 μm to 5.5 μm or 2.0 μm to 5.2 μm.

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

[0089] According to one embodiment, the biaxially stretched film may have a soft noise composite index (LSN) represented by the formula 1-1 of 20 or less when the thickness of the film is 19 μm to 21 μm.

[0090] The LSN (Flexibility Noise Composite Index) expressed by the formula 1-1 is the product of the average noise intensity and the loop stiffness of the biaxially stretched film, and is an index showing the degree of the composite properties of flexibility and noise intensity of the biaxially stretched film. Therefore, the LSN (Flexibility Noise Composite Index) can be a measure of the quality of packaging materials containing the biaxially stretched film.

[0091] The soft noise composite index (LSN) is the average noise intensity (N AVG ) is lower, average Noise level (N AVG The lower the loop stiffness (LS), the lower the flexible noise composite index (LSN) may be, and the higher the loop stiffness (LS), the higher the flexible noise composite index (LSN).

[0092] When the composite flexible noise index (LSN) having such properties satisfies the above-mentioned specific range, the biaxially stretched film has excellent mechanical properties, optical properties, and thermal properties, and can reduce noise levels.

[0093] Specifically, the flexible noise composite index (LSN) of the biaxially stretched 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 composite index (LSN) of the biaxially stretched film exceeds 20, the flexibility may decrease, the brittleness may increase, and the noise may increase, which may result in a deterioration in quality when used as a packaging material.

[0094] The composite flexible noise index (LSN) of the biaxially stretched film may be the same or different depending on the machine direction (MD) and transverse direction (TD) of the biaxially stretched film, where the machine direction (MD) of the biaxially stretched film refers to the length direction or machine direction, and the transverse direction (TD) of the biaxially stretched film refers to the width direction, which is perpendicular to the machine direction (MD).

[0095] Specifically, the flexible noise composite index (LSN) of the biaxially stretched film in the machine direction (MD) MD ) 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 transverse direction (TD) flexibility noise composite index (LSN) of the biaxially stretched film TD ) 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 is LSN MD May only satisfy or LSN TD May only satisfy or LSN MD and LSN TD In this case, the biaxially stretched film according to the embodiment can improve flexibility while maintaining appropriate tensile strength and can reduce noise, which is more advantageous in achieving 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 intensity (N AVGThe noise intensity was measured by swinging a single biaxially stretched film at a constant speed for one minute at a height of 1.2 to 1.5 m from the ground using a sound level meter of Class 2 or higher as specified in KS C IEC 61672-1, facing the direction of the noise source. The maximum sound level was recorded, and this process was repeated five times to calculate the average of the maximum sound levels for each run, which was defined as the average sound level. The sound level can be measured at a height of 1.2 to 1.5 m above the ground. If there is an obstacle over 1.5 m high at the measurement point, the measurement can be performed at a point approximately 1.0 to 3.5 m away from the obstacle in the direction of the noise source.

[0099] The biaxially stretched film has an average noise intensity (N AVG ) is preferably controlled in order to provide a high-quality packaging material.

[0100] Specifically, the average noise intensity (N AVG ) may 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 intensity (N AVG ) is 86 dB or less, it is advantageous in controlling the soft noise composite index (LSN) of the above formula 1-1 to 20 or less, and it is possible to improve noise and provide a high-quality packaging material.

[0102] In addition, in the formula 1-1, the loop stiffness (LS) of the biaxially stretched film is measured based on ASTM D747 by fixing a loop-shaped biaxially stretched film specimen having a width of 1.5 cm and a length of 18 cm to a loop stiffness tester (manufactured by Toyo Seiki Seisakusho) and measuring the load at the center of the loop, and is an index showing the degree of flexibility of the biaxially stretched film.

[0103] The biaxially stretched film may have a loop stiffness (LS) of 0.23 gf or less, 0.22 gf or less, 0.21 gf or less, or 0.20 gf or less. Specifically, the loop stiffness (LS) of the biaxially stretched film may be, for example, 0.10 to 0.23 gf, for example, 0.10 to 0.22 gf, for example, 0.10 to 0.21 gf, or for example, 0.10 to 0.20 gf.

[0104] The lower the loop stiffness (LS) of the biaxially stretched film, the greater the flexibility, and the higher the loop stiffness (LS) of the biaxially stretched film, the less flexibility there may be.

[0105] Furthermore, the loop stiffness (LS) of the biaxially stretched film may be the same or different in the machine direction (MD) and the transverse direction (TD) of the biaxially stretched film.

[0106] Specifically, the loop stiffness (LS) of the biaxially stretched film in the machine direction (MD) MD ) may be, for example, 0.10 to 0.23 gf, for example, 0.10 to 0.22 gf, for example, 0.12 to 0.22 gf, for example, 0.12 to 0.21 gf, for example, 0.15 to 0.21 gf.

[0107] The transverse direction (TD) loop stiffness (LS TD ) can be, for example, 0.10 to 0.23 gf, for example, 0.10 to 0.22 gf, for example, 0.12 to 0.22 gf, or for example, 0.14 to 0.22 gf.

[0108] The biaxially stretched film is LS MD Only satisfied well, or LS TD May only satisfy or LS MD and L.S. TD In this case, the biaxially stretched film according to the embodiment is more effective in controlling the soft noise composite index (LSN) expressed by the formula 1-1 within the above range, which is more advantageous in achieving the desired effect and can provide an environmentally friendly packaging material with excellent quality.

[0109] On the other hand, the biaxially stretched film has a thermal shrinkage rate (S 100 ) may be 15% or less.

[0110] <Formula 1-2> Heat shrinkage rate (S 100 )={(L 25 -L 100 ) / L 25}×100 In the formula 1-2, L 25 is the initial length (mm) of the biaxially stretched film specimen at 25°C, L 100 is the length (mm) of the biaxially stretched film specimen measured immediately after being held in a hot air blower at 100°C for 5 minutes.

[0111] The thermal shrinkage rate (S 100 ) is a value obtained by converting the degree of thermal shrinkage of a biaxially stretched film test piece into a percentage at a hot air temperature of 100°C, and is a value calculated as a percentage of the change in length of the biaxially stretched film test piece measured immediately after being retained in a hot air blower for 5 minutes relative to the initial length of the biaxially stretched film test piece.

[0112] The heat shrinkage rate (S 100 ) can be calculated by cutting a biaxially stretched film into a length of 150 mm and a width of 2 cm, regardless of the direction, to prepare a test piece, and then measuring the initial length at room temperature and the length of the biaxially stretched film test piece after it has been left in a hot air oven at 100°C for 5 minutes.

[0113] The heat shrinkage rate (S 100 ) can 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 heat shrinkage rate (S 100 ) satisfies the above range or less, the degree of thermal shrinkage at high hot air temperatures of 100°C or higher is small, and therefore the thermal properties are improved, and printability and moldability can be further improved.

[0115] The heat shrinkage rate (S 100 ) can be the same or different in the machine direction (MD) and transverse direction (TD) of the biaxially stretched film.

[0116] Specifically, the thermal shrinkage rate (S MD100 ) can 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 heat shrinkage rate (S TD100 ) can 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 ratios of the biaxially stretched film in the machine direction (MD) and the transverse direction (TD) exceed the above ranges, problems will arise in printing due to severe shrinkage in the machine direction and the transverse direction caused by hot air during printing and lamination, and the film will curl severely after printing, causing it to be rolled up, which is undesirable.

[0119] Meanwhile, the biaxially stretched film according to the embodiment may have a forming index (FI) represented by the following formula 1-3 of 65 or more.

[0120] <Formula 1-3> Forming index (FI)=TS / LS In the formula 1-3, TS is measured based on ASTM D882 by cutting a specimen to a length of approximately 100 mm and a width of 15 mm, then attaching the specimen so that the distance between chucks is 50 mm. The tensile strength (kgf / mm 2 ) where LS is as defined above.

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

[0122] That is, according to the embodiment, one of the main features of the biaxially stretched film is that it has increased flexibility and soft properties while maintaining an appropriate range of strength, for example, tensile strength. In this case, the biaxially stretched film has excellent formability and can be advantageous for expanding various applications.

[0123] The forming index (FI) of the biaxially stretched film may be, for example, 65 or more, 68 or more, 70 or more, 75 or more, 80 or more, 85 or more, 90 or more, 95 or more, or 100 or more. Specifically, the forming index (FI) of the biaxially stretched film may be, for example, 65 to 120, for example, 65 to 110, or for example, 65 to 105. If the forming index (FI) of the biaxially stretched film is less than 65, the flexibility may be reduced and the film may easily break, or the strength may be reduced and various problems may occur during processing or molding, limiting the applicability to various uses, and molded products such as packaging materials using the biaxially stretched film may suffer from reduced quality or defects.

[0124] The forming index (FI) of the biaxially stretched film can be the same or different in the machine direction (MD) and transverse direction (TD) of the biaxially stretched film.

[0125] Specifically, the forming index (FI) of the biaxially stretched film in the machine direction (MD) MD ) can be, for example, 65 to 90, for example, 70 to 90, or for example, 70 to 80.

[0126] The forming index (FI) of the biaxially stretched film in the transverse direction (TD) TD ) can be, for example, 80 to 110, for example, 85 to 110, or for example, 90 to 110.

[0127] The biaxially stretched film is FI MD Only satisfied well, or FI TD May only satisfy or FI MD and F.I. TDIn this case, the biaxially stretched film according to the embodiment can improve flexibility while maintaining appropriate tensile strength, and can provide an environmentally friendly packaging material with excellent quality.

[0128] In addition, in the formula 1-3, the loop stiffness (LS) of the biaxially stretched film is as defined above.

[0129] In addition, the tensile strength of the biaxially stretched film can be measured by preparing a biaxially stretched film test piece in accordance with ASTM D882, cutting it to a length of 100 mm and a width of 15 mm, and mounting it so that the distance between chucks is 50 mm. The test piece is then subjected to an experiment using an Instron Universal Testing Machine (UTM, model 5966) at a tensile speed of 200 mm / min at room temperature of 25°C, and then measuring the tensile strength using a program built into the machine.

[0130] The tensile strength is, for example, 9 to 25 kgf / mm 2 , for example, 9.5 to 22 kgf / mm 2 , for example, 10 to 22 kgf / mm 2 , for example, 12 to 20 kgf / mm 2 , or, for example, 13 to 20 kgf / mm 2 It could be.

[0131] When the tensile strength satisfies the above range, the productivity, processability and formability of the biaxially stretched film can be improved at the same time.

[0132] In addition, the tensile strength (TS) of the biaxially stretched film may be the same or different depending on the machine direction (MD) and the transverse direction (TD) of the biaxially stretched film.

[0133] Specifically, the tensile strength (TS) of the biaxially stretched film in the machine direction (MD) MD ) is, for example, 9 to 25 kgf / mm 2 , for example 9.5~22kgf / mm 2 , for example, 10 to 22 kgf / mm 2 , for example, 12 to 20 kgf / mm 2, or, for example, 13 to 18 kgf / mm 2 It could be.

[0134] The tensile strength (TS) of the biaxially stretched film in the transverse direction (TD) TD ) is, for example, 9 to 25 kgf / mm 2 , 10~25kgf / mm 2 , for example, 11 to 23 kgf / mm 2 , for example, 12 to 23 kgf / mm 2 , or, for example, 15 to 20 kgmm 2 It could be.

[0135] The biaxially stretched film is MD Only satisfied well or TS TD Only satisfied or TS MD and T.S. TD In this case, the biaxially stretched film according to the embodiment can control the forming index (FI) represented by the above formula 1-3 within the above range, and can simultaneously improve productivity, processability, and formability, thereby providing an environmentally friendly packaging material with excellent quality.

[0136] On the other hand, the biaxially stretched film has a strain-stress curve of 200 kgf / mm 2 ~380kgf / mm 2 , 200kgf / mm 2 ~360kgf / mm 2 , 200kgf / mm 2 ~350kgf / mm 2 , 250kgf / mm 2 ~350kgf / mm 2 , or 260 kgf / mm 2 ~350kgf / mm 2 The modulus is 200 kgf / mm 2 If the modulus is less than 380 kgf / mm, the resistance to mechanical tension during processing such as printing or lamination will be insufficient, which is undesirable because wrinkles will occur in the running direction, causing problems in printing, or breakage during running. 2If the modulus exceeds 100%, the stiffness of the film increases and the film may be easily broken or cracked by external impact. Also, the lower the modulus within the above range, the better the flexibility.

[0137] Meanwhile, the biaxially stretched film may have a thickness deviation of 10 μm or less across the entire width of the film. Specifically, the biaxially stretched 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 across the entire width of the film.

[0138] When the biaxially stretched film according to the embodiment contains amorphous polyhydroxyalkanoate (PHA), it has excellent stretching uniformity, and therefore it is possible to provide a biaxially stretched film with little thickness deviation.

[0139] On the other hand, the biaxially stretched film can have excellent optical properties. Specifically, the biaxially stretched 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 above range, the transparency of the film may be significantly reduced, which may limit its use in packaging applications where the contents of the contents can be seen.

[0140] When the biaxially stretched film according to the embodiment contains a specific content of amorphous polyhydroxyalkanoate (PHA), the biaxially stretched film can provide a transparent biaxially stretched film due to low haze.

[0141] The biaxially stretched film may have a light transmittance of 90% or more, 92% or more, or 93% or more.

[0142] Furthermore, the biaxially stretched film has a biodegradability of 90% or more, measured by the amount of carbon dioxide generated according to 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 if its biodegradability is 90% or more of the standard substance.

[0143] The above-described structural and physical property characteristics of the biaxially stretched film according to the embodiment can be efficiently achieved by manufacturing the biaxially stretched film according to the embodiment. The method for producing the biaxially stretched film will now be described in detail.

[0144] [Manufacturing method of biaxially stretched film] A method for producing a biaxially stretched 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 stretched 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 contents or mixing weight ratios of the polylactic acid (PLA) and polyhydroxyalkanoate (PHA) are as described above.

[0147] During the mixing, a filler may be added to improve lubricity and quality. The type, content, particle size, etc. 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, the sheet can be obtained by contacting it with a cooling roll cooled to about 10°C to 30°C.

[0149] The second step may involve 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 at 40°C to 100°C in the machine direction (MD) by 2 to 4 times its original size.

[0151] For example, the melt-extruded sheet can be preheated to 50°C to 80°C, and then passed through rolls in a stretching zone at 70°C to 100°C to be longitudinally stretched 2 to 4 times.

[0152] The stretched film can be stretched transversely at 50°C to 110°C by 3 to 5 times its original size in the transverse direction (MD).

[0153] For example, the stretched film may have a first section with an average temperature of 80°C to 105°C in the initial 30% section and a second section with an average temperature of 80°C to 110°C in the final 70% section. No. 2 The film can be transversely stretched 3 to 5 times within the section of the tenter, which is divided into zones.

[0154] In some implementations, by providing the film as a biaxial film that is stretched in both directions, the physical properties and formability of the film can be further improved, making it possible to realize high-quality packaging materials.

[0155] If a uniaxial film is stretched in one of the machine and cross directions, the thickness of the film will vary greatly, and the strength of the other direction, which is not stretched, will be significantly reduced, and the thermal properties may also be reduced.

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

[0157] The heat setting step can 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] Producing the biaxially stretched film by the manufacturing method of the embodiment may be more effective in producing a biaxially stretched film having the desired structure and properties.

[0159] [Laminate] In one embodiment, a laminate is provided, comprising a first layer comprising a first polylactic acid (PLA) and a 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 more than 0 wt% and less than 30 wt% of polyhydroxyalkanoate (PHA), based on the total weight of the first layer.

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

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

[0162] Furthermore, the laminate is biodegradable and completely decomposes when buried, making it environmentally friendly. This makes it possible to utilize it in a wider range of fields and demonstrate excellent properties, which is of technical significance.

[0163] Referring to FIG. 1, a laminate 1 according to an embodiment of the present invention includes a first layer 12 and a second layer 11 disposed on one side 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 side of the first layer, and a corona layer, a coating layer, or both disposed on the other side of the first layer.

[0165] 2, the laminate 1 may include a first layer 12, a second layer 11 disposed on an upper surface of the first layer 12, and a corona layer 13 disposed on a lower surface of the first layer 12. In this case, a coating layer may be disposed instead of the corona layer disposed on the lower surface of the first layer 12.

[0166] Also, referring to FIG. 3, the laminate 1 may include a first layer 12, a second layer 11 disposed on the upper surface of the first layer 12, a corona layer 13 disposed on the lower surface of the first layer 12, and a coating layer 14 disposed on the lower surface of the corona layer 13. Each layer of the laminate according to the embodiment will now be described in detail.

[0167] -First layer- According to one implementation, the first layer includes a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA).

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

[0169] The first layer contains the first polylactic acid (PLA) and polyhydroxyalkanoate (PHA), which not only improves flexibility and reduces noise, but also has good interlayer compatibility with the second layer containing the second polylactic acid (PLA), maintaining excellent interlayer adhesion properties and further improving processability and productivity.

[0170] If the first layer contains only one of the resins polylactic acid (PLA) and polyhydroxyalkanoate (PHA), or neither, it is difficult to achieve a satisfactory noise reduction effect or flexibility. Furthermore, the compatibility between the first and second layers in the laminate may decrease, resulting in poor interlayer adhesion or separation between the layers, which may adversely affect 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) may be measured by gel permeation chromatography (GPC). When the weight-average molecular weight (Mw) of the first polylactic acid (PLA) is outside the above range, the mechanical strength and heat resistance of the laminate may be further improved.

[0172] The first polylactic acid (PLA) may include 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 content of the L-lactic acid 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 comprise, based on the total weight of the first layer, more than 70 wt%, 75 wt% or more, 80 wt% or more, 85 wt% or more, 88 wt% or more, 90 wt% or more, 93 wt% or more, or 95 wt% or more, and may comprise, based on the total weight of the first layer, less than 100 wt%, 99 wt% or less, 98 wt% or less, 97 wt% or less, or 95 wt% or less.

[0176] Specifically, the first polylactic acid (PLA) may be contained in an amount of more than 70 wt% to less than 100 wt%, more than 70 wt% to 99 wt%, 75 wt% to 99 wt%, 75 wt% to 98 wt%, 75 wt% to 97 wt%, 80 wt% to 97 wt%, 85 wt% to 97 wt%, 90 wt% to 97 wt%, 95 wt% to less than 100 wt%, 95 wt% to 97 wt%, or 90 wt% to 95 wt%, 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, the heat shrinkage rate may increase, and optical properties such as transparency and light transmittance may decrease. On the other hand, if the content of the first polylactic acid (PLA) is too high, the brittleness may increase, the flexibility may decrease, and the laminate may be prone to breaking or cracking, and there may be problems with loud noise.

[0178] In particular, the first polylactic acid (PLA) has a high brittleness, so when the temperature range for use is below 20°C, the film tends to harden and crack easily when it is subjected to impact in winter. When the temperature range for use is above 35°C, the film tends to lose elasticity and become soft, and is noisy, so its use is limited.

[0179] Therefore, in the embodiment, the first polylactic acid (PLA) is mixed with polyhydroxyalkanoate (PHA), which has excellent flexibility and low noise.

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

[0181] According to an implementation, the first layer may include more than 0 wt % and less than 30 wt % polyhydroxyalkanoate (PHA), based on the total weight of the first layer.

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

[0183] If the content of polyhydroxyalkanoate (PHA) is too high, the tensile strength may decrease, the heat shrinkage rate and thickness deviation may increase, the extrusion processability may decrease, and the optical properties may deteriorate.On the other hand, if the content of polyhydroxyalkanoate (PHA) is too low, the brittleness may increase, the flexibility may decrease, making it more susceptible to cracking or breaking, and the noise level may increase.

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

[0185] According to a realization example, the polyhydroxyalkanoate (PHA) can be the same as the polyhydroxyalkanoate (PHA) mentioned in the biaxially stretched film.

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

[0187] For example, the copolymerized polyhydroxyalkanoate (PHA) may be a copolymerized polyhydroxyalkanoate (PHA) with controlled crystallinity, including 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 polymerized units, or may contain the units of Chemical Formula 1 and the units of Chemical Formula 2 as polymerized units, and may further contain different polymerized units other than the above. Furthermore, the units of Chemical Formula 2 may be repeated randomly.

[0189] The crystallinity-controlled polyhydroxyalkanoate (PHA) may be one whose crystallinity and amorphousness are controlled by increasing the irregularity in its molecular structure, and specifically, the type of monomer, the ratio of monomers, or the type and / or content of isomers may be controlled.

[0190] According to an embodiment, the polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing units of the Chemical Formula 1 and units of the Chemical Formula 2, and the content of the units of the Chemical Formula 2 may be 1 wt % or more, 3 wt % or more, 5 wt % or more, 10 wt % or more, and 60 wt % or less, 55 wt % or less, or 50 wt % or less, based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0191] For example, the polyhydroxyalkanoate (PHA) may be a copolymerized polyhydroxyalkanoate (PHA) containing units of Chemical Formula 1 and units of Chemical Formula 2, and the content of units of Chemical Formula 2 may be 1 to 60 wt%, 5 to 50 wt%, 10 to 60 wt%, 10 to 50 wt%, 15 to 60 wt%, 15 to 50 wt%, 20 to 60 wt%, 20 to 50 wt%, 25 to 60 wt%, 25 to 50 wt%, 30 to 60 wt%, 30 to 50 wt%, 35 to 60 wt%, 35 to 50 wt%, 40 to 60 wt%, 40 to 50 wt%, 45 to 60 wt%, 45 to 50 wt%, or 46 to 50 wt%.

[0192] According to an embodiment, 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 a realization example, the copolymerized polyhydroxyalkanoate (PHA) can be an amorphous polyhydroxyalkanoate (PHA).

[0194] When the copolymerized polyhydroxyalkanoate (PHA) is an amorphous polyhydroxyalkanoate (PHA), the optical properties of the laminate can be improved compared to when a 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 an amorphous polyhydroxyalkanoate (PHA), the amorphous polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA) containing units of Chemical Formula 1 and units of Chemical Formula 2, and may contain 15 to 60 wt % of units of Chemical Formula 2 based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0196] In the polyhydroxyalkanoate (PHA), the amorphousness can increase as the content of the unit of Chemical Formula 2 increases. Therefore, in the first layer according to the embodiment, the content of the unit of Chemical Formula 2 in the amorphous polyhydroxyalkanoate (PHA) can be important.

[0197] For example, the amorphous polyhydroxyalkanoate (PHA) may contain the unit of Chemical Formula 2 in an amount of 15 to 55 wt%, 15 to 50 wt%, 20 to 60 wt%, 20 to 50 wt%, 25 to 60 wt%, 25 to 50 wt%, 30 to 60 wt%, 30 to 50 wt%, 35 to 60 wt%, 35 to 50 wt%, 40 to 60 wt%, 40 to 50 wt%, 45 to 60 wt%, 45 to 50 wt%, or 46 to 50 wt%, based on the total weight of the polyhydroxyalkanoate (PHA).

[0198] The first layer contains the units of Formula 2 in the above range, which has the advantage of improving the optical properties of the laminate due to the compatibility between the resins when polyhydroxyalkanoate (PHA) is mixed with first polylactic acid (PLA). If the units of Formula 2 in the polyhydroxyalkanoate (PHA) are less than 15 wt %, the compatibility between the resins will be poor, resulting in reduced transparency and light transmittance of the laminate, as well as reduced modulus and noise level.

[0199] According to an embodiment, 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 contained in an amount of 15 to 60 wt % based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

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

[0201] For example, the 4-hydroxybutyrate (4-HB) units may be contained in an amount of, for example, 20 to 60 wt %, for example, 25 to 60 wt %, for example, 25 to 50 wt %, for example, 30 to 60 wt %, for example, 30 to 50 wt %, for example, 35 to 60 wt %, for example, 35 to 50 wt %, for example, 40 to 60 wt %, for example, 40 to 50 wt %, for example, 45 to 60 wt %, for example, 45 to 50 wt %, for example, 46 to 60 wt %, or for example, 46 to 50 wt %, based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

[0202] The first layer contains 4-hydroxybutyrate (4-HB) units in the above range, which has the advantage that when polyhydroxyalkanoate (PHA) is mixed with the first polylactic acid (PLA), compatibility between the resins is ensured, further improving the optical properties of the laminate. If the 4-hydroxybutyrate (4-HB) units are less than 15 wt%, compatibility between the resins may be poor, resulting in a deterioration in the optical properties of the laminate.

[0203] The polyhydroxyalkanoate (PHA) may be a polyester containing only 3-hydroxybutyrate (3-HB) and 4-hydroxybutyrate (4-HB) units as polymerized units (i.e., the polymerized units consist only of 3-hydroxybutyrate (3-HB) and 4-hydroxybutyrate (4-HB) units), or it may contain 3-hydroxybutyrate (3-HB) and 4-hydroxybutyrate (4-HB) units as polymerized units, and may further contain different polymerized units other than those mentioned above. In addition, the 4-hydroxybutyrate (4-HB) units may be repeated randomly.

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

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

[0206] According to one implementation, the first layer may further include 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 hard acrylate, polystyrene, nylon, and soft 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] By including the filler, the first layer can have excellent slip properties and improve processability, thereby providing excellent quality.

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

[0211] The first layer may contain the filler in an amount of 0.01 to 3 wt %, 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 wt %, 0.01 to 2 wt %, 0.01 to 1.5 wt %, 0.01 to 1 wt %, 0.01 to 0.5 wt %, or 0.01 to 0.2 wt %, 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 implementation, the second layer is disposed on one side of the first layer and includes a second polylactic acid (PLA).

[0214] Since the second layer contains the second polylactic acid (PLA), it has good compatibility with the first layer containing the first polylactic acid (PLA) and polyhydroxyalkanoate (PHA), and therefore can maintain excellent interlayer adhesion properties, thereby further 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 layer and the second layer will be poor, resulting in poor interlayer adhesion properties or separation between the layers, which may have a negative impact on processability and productivity.

[0216] The second layer may include an isomer of the second polylactic acid. The second layer can include the L-isomer, D-isomer, DL-isomer, or a mixture thereof of the second polylactic acid (PLA). For example, the second polylactic acid (PLA) can be a random copolymer of L-lactic acid and D-lactic acid.

[0217] Specifically, the second polylactic acid may include L-isomer and D-isomer stereoisomers having opposite configurations, and these stereoisomers may be identical in chemical structure and physical properties, but may be mirror images of each other in configuration.

[0218] When the second layer contains a mixture of the L-isomer and D-isomer of the second polylactic acid, the transparency of the film is improved and the film has thermal adhesive properties, making it suitable for thermal adhesive applications.

[0219] According to an embodiment, the second layer may contain 5 wt% to 30 wt% of the D-isomer, based on the total weight of the second polylactic acid. If the D-isomer content is too high, the thickness variation and heat shrinkage of the laminate may increase, and physical properties of the laminate, such as tensile strength, may decrease. Furthermore, in the production and processing process, poor winding may occur during the roll pass, resulting in reduced processability and productivity. On the other hand, if the D-isomer content is too low, a large amount of heat may be required during the thermal bonding process, and the laminate may become deformed, such as undulating, when being formed into a film.

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

[0221] For example, the second layer may contain poly-L-lactic acid (L-PLA) and poly-D-lactic acid (D-PLA), with the weight ratio of L-PLA to D-PLA (L-PLA:D-PLA) being 70-95:5-30, for example 72-95:5-28, for example 74-93:7-26, or for example 75-93:7-25.

[0222] When the weight ratio of the L-isomer to the D-isomer satisfies the above range, the optical properties and thermal adhesion performance of the film can be improved, and the thickness variation and thermal shrinkage of the laminate can be reduced, and physical properties such as tensile strength and modulus can be improved, thereby improving processability and productivity.

[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, or for example, 50,000 to 300,000 g / mol. The weight-average molecular weight (Mw) may be measured by gel permeation chromatography (GPC). When the weight-average molecular weight (Mw) of the second polylactic acid (PLA) is outside the above range, the mechanical strength and heat resistance of the laminate may 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. 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 comprise a filler to improve the slip characteristics.

[0227] The filler may be the same as or different from the type and content of the filler in the first layer. specifically, The aforementioned The particle size of the filler contained in the second layer may be 0.1 μm to 6.0 μm. 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 slipperiness is improved in the process, and 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] Meanwhile, 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] -Corona layer- According to one embodiment, the laminate 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, it is possible to remove oil and other contaminants from the laminate surface, create a surface that is compatible with the adhesive site, increase adhesive strength, and chemically and physically modify the surface, thereby further improving hydrophilicity, adhesiveness, printability, coating properties, deposition properties, etc.

[0233] Specifically, the first layer of the laminate has very little polarity and high crystallinity due to the absence of polar groups, which may result in low affinity for inks and adhesives. To achieve this, 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 surface energy.

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

[0235] The first layer may have a surface tension of 38 dyn / cm or more relative to the corona-treated surface, for example, 38 to 70 dyn / cm, for example, 38 to 68 dyn / cm, or for example, 38 to 66 dyn / cm. When the surface tension of the first layer relative to the corona-treated surface satisfies this range, the adhesion, printability, coating properties, deposition properties, etc. of the laminate may be further improved.

[0236] The thickness of the corona layer can be adjusted appropriately depending on the use and purpose of the laminate, and specifically can be, for example, 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 may further include a coating layer disposed on the other side of the first layer.

[0238] The coating layer may include a primer coating layer, which may improve antistatic properties.

[0239] The primer coating layer may be on the other side of the first layer, or if the laminate includes the corona layer, the corona layer may be on the other side of the first layer and the primer coating layer may be on the other side (lower side) of the corona layer.

[0240] Specifically, a primer coating layer may be formed on the other surface of the first layer by applying a primer treatment to the other surface of the corona layer disposed on the other surface of the first layer. other side The lower surface may be treated with a primer to form a primer coating layer.

[0241] The primer coating layer may contain at least one selected from the group consisting of ammonium compounds, phosphoric acid compounds, and polymers such as acrylic resins and urethane resins, all of which have antistatic properties.

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

[0243] The surface resistance is measured by evaluating the antistatic performance using a surface resistance measuring device at room temperature (22±2° C.) and relative humidity (60%±10%).

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

[0245] The stack of implementations of the present invention may include a multi-layer structure of two or more layers, such as three or more layers, for example four or more layers.

[0246] -Physical properties of laminates- According to one embodiment, when the thickness of the laminate is 19 to 22 μm, the laminate may have a soft noise composite index (LSN) represented by the following formula 2-1 of 18 or less.

[0247] <Formula 2-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the formula 2-1, N AVG is the average sound level (dB) calculated by measuring the maximum sound level five times when a class 2 sound level meter specified in KS C IEC61672-1 is pointed in the direction of the noise source and a laminated test piece with a width of 21 cm and a length of 29.5 cm is repeatedly crumpled and unfolded for 10 seconds at a height of 1.2 m to 1.5 m from the ground. The value is the unit-free value. The LS is a unit-free numerical value that indicates the loop stiffness (gf) measured based on ASTM D747 by fixing a loop-shaped laminate specimen having 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.

[0248] The composite flexibility noise index (LSN) expressed by the formula 2-1 is the product of the average noise intensity of the laminate and the loop stiffness, and is an index showing the composite characteristics of flexibility and noise intensity of the laminate. Therefore, the composite flexibility noise index (LSN) can be a measure of the quality of molded products such as packaging materials containing the laminate.

[0249] The soft noise composite index (LSN) is the average noise intensity of the first layer (N AVG ) is lower, the noise level (N AVG The lower the loop stiffness (LS), the lower the flexible noise composite index (LSN) may be, and the higher the loop stiffness (LS), the higher the flexible noise composite index (LSN).

[0250] When the soft noise composite index (LSN) having such characteristics satisfies the above-mentioned specific range, the laminate has excellent mechanical properties, optical properties and thermal properties, and can reduce noise levels.

[0251] Specifically, the Flexibility 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 Flexibility Noise Composite Index (LSN) of the laminate exceeds 18, flexibility may decrease and brittleness may increase, and noise may increase, which may result in a decrease in quality when applied to packaging materials.

[0252] The laminate's composite flexible noise index (LSN) may be the same or different depending on the machine direction (MD) and transverse direction (TD) of the laminate, where the machine direction (MD) of the laminate refers to the length direction or machine direction, and the transverse direction (TD) of the laminate refers to the width direction as the direction perpendicular to the machine direction (MD).

[0253] Specifically, the composite flexible noise index (LSN) of the laminate in the machine direction (MD) MD ) can be, for example, 4 to 18, 5 to 18, 5 to 17, 6 to 17, 8 to 17, or 8 to 16.

[0254] The laminate's transverse direction (TD) flexibility noise composite index (LSN TD ) can be, for example, 4 to 18, 5 to 17, 5 to 16, 6 to 16, 8 to 15, or 9 to 15.

[0255] The stacked body is MD Only satisfied well or LSN TD May only satisfy or LSN MD and LSN TDIn this case, the laminate according to the embodiment can improve flexibility while maintaining appropriate tensile strength, and can reduce noise, which is more advantageous in achieving the intended effects, and can provide an environmentally friendly packaging material with excellent quality.

[0256] On the other hand, in the formula 2-1, the average noise intensity (N AVG The noise intensity was measured using a Class 2 sound level meter or higher specified in KS C IEC 61672-1, facing the direction of the noise source, at a height of 1.2 to 1.5 m from the ground. The laminate was repeatedly crumpled and unfolded at a constant speed 10 times for 10 seconds, and the maximum sound level was recorded. This process was repeated five times, and the average of the maximum sound levels for each cycle was calculated and defined as the average sound level. The sound level can be measured at a height of 1.2 to 1.5 m from the ground. If there is an obstacle over 1.5 m high at the measurement point, the measurement can be performed at a distance of approximately 1.0 to 3.5 m from the obstacle toward the noise source.

[0257] The laminate has an average noise intensity (N AVG ) is preferable in terms of providing high-quality packaging materials.

[0258] Specifically, the average noise intensity (N AVG ) may 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 intensity (N AVG ) is 86 dB or less, it is advantageous in controlling the soft noise composite index (LSN) of the above formula 2-1 to 18 or less, and it is possible to improve noise and provide a high-quality packaging material.

[0260] In addition, in the formula 2-1, the loop stiffness (LS) of the laminate is measured based on ASTM D747 by fixing a loop-shaped laminate test piece having a width of 1.5 cm and a length of 18 cm to a loop stiffness tester (manufactured by Toyo Seiki Seisakusho) and measuring the load at the center of the loop, and is an index showing the degree of flexibility of the laminate.

[0261] The loop stiffness (LS) of the laminate may be 0.20 gf or less, or 0.19 gf or less. Specifically, the loop stiffness (LS) of the laminate may be, for example, 0.10 to 0.20 gf, for example, 0.10 to 0.19 gf, for example, 0.10 to 0.18 gf, or for example, 0.10 to 0.17 gf.

[0262] A lower loop stiffness (LS) of the laminate may increase flexibility, and a higher loop stiffness (LS) of the laminate may decrease flexibility.

[0263] Additionally, the loop stiffness (LS) of the laminate may be the same or different in the machine direction (MD) and transverse direction (TD) of the laminate.

[0264] Specifically, the loop stiffness (LS) of the laminate in the machine direction (MD) MD ) can be, for example, 0.10 to 0.20 gf, for example, 0.10 to 0.19 gf, for example, 0.11 to 0.19 gf, for example, 0.11 to 0.18 gf, or for example, 0.11 to 0.15 gf.

[0265] The transverse direction (TD) loop stiffness (LS TD ) can be, for example, 0.10 to 0.20 gf, for example, 0.10 to 0.18 gf, for example, 0.10 to 0.17 gf, or for example, 0.12 to 0.16 gf.

[0266] The laminate is MD Only satisfied well, or LS TD May only satisfy or LS MD and L.S. TDIn this case, the laminate according to the embodiment is more effective in controlling the soft noise composite index (LSN) expressed by the above formula 2-1 within the above range, and is therefore more advantageous in achieving the intended effect, so that an environmentally friendly packaging material with excellent quality can be provided.

[0267] On the other hand, the laminate has a thermal shrinkage rate (S 100 ) may be 15% or less.

[0268] <Formula 2-2> Heat shrinkage rate (S 100 )(%)={(L 25 -L 100 ) / L 25}×100 In the formula 2-2, L 25 is the initial length (mm) of the laminate test piece at 25°C, L 100 is the length (mm) of the laminate test piece measured immediately after being left in a hot air blower at 100°C for 5 minutes.

[0269] The thermal shrinkage ratio (S 100 ) is a value obtained by converting the degree of thermal shrinkage of a laminate test piece into a percentage when exposed to hot air at a temperature of 100°C, and is a value calculated as a percentage of the change in length of the laminate test piece measured immediately after being left in the hot air blower for 5 minutes relative to the initial length of the laminate test piece.

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

[0271] The heat shrinkage rate (S 100 ) can 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 heat shrinkage rate (S100 ) satisfies the above range or less, the degree of thermal shrinkage at high hot air temperatures of 100°C or more is small, and therefore the thermal properties are improved, and the printability and moldability can be further improved.

[0273] The thermal shrinkage rate (S 100 ) can be the same or different in the machine direction (MD) and transverse direction (TD) of the laminate.

[0274] Specifically, the thermal shrinkage rate (S MD100 ) can 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 rate (S TD100 ) can 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 machine direction (MD) and the cross direction (TD) of the laminate exceed the above ranges, problems will arise in printing due to severe shrinkage in the machine direction and the cross direction caused by hot air during printing and lamination, and curling will occur severely after printing, resulting in a phenomenon of rolling up, which is not preferable.

[0277] Meanwhile, the laminate according to the embodiment may have a forming index (FI) represented by the following formula 2-3 of 65 or more.

[0278] <Formula 2-3> Forming index (FI)=TS / LS In the formula 2-3, TS was measured by cutting a specimen into a length of approximately 100 mm and a width of 15 mm according to ASTM D882, and then attaching the specimen so that the distance between chucks was 50 mm. The tensile strength (kgf / mm 2 ) where LS is as defined above.

[0279] The forming index (FI) of the laminate is the ratio of the tensile strength to the loop stiffness of the laminate and can provide a measure of whether the tensile strength and flexibility are adequate.

[0280] That is, according to the embodiment, one of the main features of the laminate is that it can maintain an appropriate range of strength, for example, tensile strength, while having increased flexibility and soft properties. In this case, the laminate has excellent formability and can be advantageous for various expanded applications.

[0281] The forming index (FI) of the laminate may be, for example, 65 or more, 68 or more, 70 or more, 73 or more, 75 or more, 80 or more, 85 or more, 88 or more, 90 or more, 95 or more, or 100 or more. Specifically, the forming 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 forming index (FI) of the laminate is less than 65, the flexibility may be reduced and the laminate may easily break, or the strength may be reduced and various problems may occur during processing or molding, limiting the applicability to various applications, and the quality of molded products such as packaging materials using the laminate may be reduced or defects may occur.

[0282] The forming index (FI) of the laminate may be the same or different in the machine direction (MD) and transverse direction (TD) of the laminate.

[0283] Specifically, the forming index (FI) of the laminate in the machine direction (MD) MD ) is, for example, 65 to 120, for example, 65 to 100, for example It can be 65-90, or for example 70-90.

[0284] The forming index (FI) of the laminate in the transverse direction (TD) TD ) can be, for example, 70 to 120, for example, 72 to 110, for example, 80 to 110, for example, 90 to 110, or for example, 90 to 105.

[0285] The laminate is MD Only satisfied well, or FI TDMay only satisfy or FI MD and FI TD In this case, the laminate according to the embodiment can improve flexibility while maintaining appropriate tensile strength, and can provide an environmentally friendly packaging material with excellent quality.

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

[0287] In addition, the tensile strength of the laminate can be measured by preparing a laminate test piece in accordance with ASTM D882, cutting it to a length of 100 mm and a width of 15 mm, and attaching it so that the chuck distance is 50 mm. The tensile strength can be measured using an Instron universal testing machine (UTM, model 5966) at a tensile speed of 200 mm / min at room temperature of 25°C, followed by a program installed in the machine.

[0288] The tensile strength is, for example, 7 to 20 kgf / mm 2 , for example, 8 to 20 kgf / mm 2 , for example, 8 to 18 kgf / mm 2 , for example, 9 to 17 kgf / mm 2 , or, for example, 10 to 17 kgf / mm 2 It could be.

[0289] When the tensile strength satisfies the above range, the productivity, processability and moldability of the laminate can be improved at the same time.

[0290] Additionally, the tensile strength (TS) of the laminate may be the same or different in the machine direction (MD) and transverse direction (TD) of the laminate.

[0291] Specifically, the tensile strength (TS) of the laminate in the machine direction (MD) MD ) is, for example, 7 to 14 kgf / mm 2 , for example 8~14kgf / mm 2 , for example, 9 to 14 kgf / mm 2 , for example, 10 to 14 kgf / mm 2 , or, for example, 11 to 14 kgf / mm2 It could be.

[0292] The tensile strength (TS) of the laminate in the transverse direction (TD) TD ) is, for example, 8 to 20 kgf / mm 2 , for example 10-20kgf / mm 2 , for example, 11 to 20 kgf / mm 2 , for example, 12 to 18 kgf / mm 2 , or, for example, 13 to 17 kgf / mm 2 It could be.

[0293] The laminate is MD Only satisfied well or TS TD Only satisfied or TS MD and T.S. TD In this case, the laminate according to the embodiment can control the forming index (FI) represented by the above formula 2-3 within the above range, so that the productivity, processability, 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 stress-strain curve of 200 kgf / mm 2 ~380kgf / mm 2 , 230kgf / mm 2 ~380kgf / mm 2 , 250kgf / mm 2 ~350kgf / mm 2 , 280kgf / mm 2 ~350kgf / mm 2 , or 290 kgf / mm 2 ~350kgf / mm 2 The modulus is 200 kgf / mm 2 If the modulus is less than 380 kgf / mm, the resistance to mechanical tension during processing such as printing or lamination will be insufficient, and wrinkles will occur in the running direction, causing problems in printing, or the film will break during running, which is undesirable. 2If the modulus exceeds 100%, the stiffness of the laminate increases and the laminate may easily break or crack due to an external impact. Also, the lower the modulus within the above range, the more excellent the flexibility.

[0295] Additionally, the modulus of the laminate may be the same or different in the machine direction (MD) and the transverse direction (TD) of the laminate.

[0296] Specifically, the modulus (M MD ) is 200kgf / mm 2 ~380kgf / mm 2 , 250kgf / mm 2 ~380kgf / mm 2 , 260kgf / mm 2 ~350kgf / mm 2 , 290kgf / mm 2 ~350kgf / mm 2 , or 295kgf / mm 2 ~345kgf / mm 2 It could be.

[0297] The transverse direction (TD) modulus (M TD ) is, for example, 200 kgf / mm 2 ~380kgf / mm 2 , 260kgf / mm 2 ~380kgf / mm 2 , 270kgf / mm 2 ~350kgf / mm 2 , 280kgf / mm 2 ~350kgf / mm 2 , or 300 kgf / mm 2 ~350kgf / mm 2 It could be.

[0298] Furthermore, the modulus (M TD ) is the machine direction (MD) modulus (M MD ) can be larger than

[0299] Meanwhile, the thickness deviation of the laminate relative to the thickness across the entire width of the laminate may be 10 μm or less. Specifically, the thickness deviation of the laminate relative to the thickness across 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 adhesive strength of the first layer and the second layer is 0.7 to 2.0 kgf / mm 2 Specifically, the thermal adhesive strength of the first layer and the second layer may be 0.7 to 1.8 kgf / mm 2 , 0.9~1.8kgf / mm 2 or 0.9 to 1.7 kgf / mm 2 It could be.

[0302] If the thermal adhesive strength of the first layer and the second layer is satisfied within the above range, the interlayer adhesive properties are excellent, separation of the layers can be prevented, and processability and productivity can be further improved.

[0303] The thermal adhesive strength was measured by preparing a laminate test piece according to ASTM D882, cutting it to a length of about 100 mm and a width of about 15 mm, and thermally laminating the opposing first and second layers using a heat seal tester (Tester Sangyo Co., Ltd., TP-701-B). The laminate test piece was then mounted on an Instron Universal Testing Machine (UTM, Model 5966) so that the thermally laminated portion of the laminate test piece was in the center and the chuck distance was 50 mm. The first and second layers of the laminate test piece were then peeled at a 180° angle at a tensile speed of about 200 mm / min at room temperature of about 25°C, and the peel strength was measured using a program built into the tensile testing machine.

[0304] On the other hand, the laminate can 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 may be significantly reduced, which may limit its use in packaging applications where the contents of the contents can be seen.

[0305] The laminate according to the embodiment can provide a transparent laminate due to low haze when it contains a specific content of amorphous polyhydroxyalkanoate (PHA).

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

[0307] Furthermore, the laminate has a biodegradability of 90% or more, measured based on the amount of carbon dioxide generated according to 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 if its biodegradability is 90% or more of the standard substance.

[0308] The above-described structural and physical property characteristics of the laminate according to the implementation can be efficiently achieved by manufacturing the laminate according to the implementation.

[0309] The method for producing the laminate will now be described in detail.

[0310] [Method of manufacturing laminate] In one embodiment, a method for producing a laminate is provided, the method comprising the steps of: preparing a first resin including a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA) and a second resin including a 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), the laminate comprising a first layer including the first polylactic acid (PLA) and the polyhydroxyalkanoate (PHA) and a second layer disposed on one side of the first layer and including the second polylactic acid (PLA), the first layer comprising more than 0 wt % and less than 30 wt % of the polyhydroxyalkanoate (PHA) based on the total weight of the first layer.

[0311] A method for manufacturing 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, thereby further improving processability and productivity and achieving the physical property effects desired in the present invention in an economical and efficient manner.

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

[0313] Specifically, the first resin includes a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA), and the contents or mixing weight ratios thereof are as described above.

[0314] In addition, when the first polylactic acid (PLA) and the polyhydroxyalkanoate (PHA) are mixed, a filler may be further added to improve slipperiness and quality. The type, content, particle size, etc. of the filler are as described above.

[0315] Meanwhile, the second resin includes a second polylactic acid (PLA), which is as described above.

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

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

[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 the melt extrusion, the resin may be brought into close contact with a cooling roll cooled to about 10° C. to 40° C. to obtain a two-layer laminated sheet.

[0320] Meanwhile, depending on the implementation, the method may further include a step of drying the first resin and the second resin before the melt co-extrusion.

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

[0322] For example, when the extruder is a single extruder, the drying step may be followed by melt co-extrusion, which may be carried out at a temperature of 40°C to 130°C for 4 hours to 24 hours.

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

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

[0325] By biaxially stretching the laminated sheets in both directions, the physical properties and formability of the laminate can be further improved, and a high-quality packaging material can be realized.

[0326] If the laminate is uniaxially stretched in only one of the machine and cross directions, the thickness deviation of the laminate will be large, and the strength of the other side that is not stretched will decrease, and the thermal properties may also decrease.

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

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

[0329] Specifically, a corona layer may be formed by corona treating the first layer.

[0330] In the corona treatment, a corona discharge occurs when a high frequency-high voltage output is applied between a discharge electrode and a treatment roll, and the corona treatment can be carried out by passing the desired surface at this time.

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

[0332] Also, a coating layer may 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 formed by primer treating the other surface of the first layer with a primer composition containing at least one selected from the group consisting of ammonium-based compounds, phosphate-based compounds, and polymers such as acrylic resins and urethane-based resins to form surface roughness and further improve adhesion properties.

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

[0334] The primer composition may also contain a curing agent, more specifically, 4,4'-diaminodiphenylmethane (DDM), aromatic diamines, and mixtures thereof. In this case, the curing agent may be added in an amount of 0.1 to 50 wt % based on the total weight of the primer composition.

[0335] The primer treatment may be performed by a method commonly used in the art, such as spraying, brushing, rolling, etc. Specifically, the primer composition may be sprayed onto the surface of the first layer using an airless spray under the conditions of an induction time of 1 to 30 minutes, a spray pressure of 5 to 500 MPa, a nozzle diameter of 0.46 to 0.58 mm, and a spray angle of 40° to 80°.

[0336] Additionally, in order to improve the adhesiveness of the laminate, surface treatments such as plasma treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment may be carried out as appropriate.

[0337] Producing the laminate by the manufacturing method of the embodiment may be 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 stretched film, the biaxially stretched film comprising polylactic acid (PLA) and polyhydroxyalkanoate (PHA), the biaxially stretched film comprising more than 0 wt% and less than 30 wt% of polyhydroxyalkanoate (PHA) based on the total weight of the biaxially stretched film, and when the thickness of the film is 19 μm to 21 μm, the flexible noise composite index (LSN) represented by the above formula 1-1 is 20 or less.

[0339] In another embodiment, an environmentally friendly packaging material may 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 side of the first layer and comprising a second polylactic acid (PLA), the first layer comprising more than 0% by weight and 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, for example, as a general disposable packaging material or food packaging material, or in the form of a fiber that can be used as a woven fabric, knitted fabric, nonwoven fabric, rope, etc., or in the form of a container that can be used as a food packaging container such as a bento box.

[0341] The environmentally friendly packaging material has excellent strength and flexibility, as well as excellent optical properties such as transparency, thermal properties, and low noise level, and thus can provide excellent physical properties and quality. Furthermore, the packaging material is biodegradable and completely decomposes when landfilled, making it environmentally friendly. Therefore, the packaging material can be used in various fields and can demonstrate excellent properties.

[0342] (Example) The present invention will be described in more detail with reference to the following examples, which are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0343] [Manufacturing biaxially stretched film] (Example 1-1) A mixed resin was prepared by blending polylactic acid (PLA) resin (NatureWorks, USA), a random copolymer of L-lactic acid and D-lactic acid (L-lactic acid content: 98 wt%), with 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, with amorphous polyhydroxyalkanoate (PHA) resin (CJ, Korea), with a glass transition temperature (Tg) of -30°C, and silica (Fuji Silysia Chemical, 3.9 μm). The polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA) were blended 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. The silica content was 0.1 wt% based on the total weight of the biaxially stretched film.

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

[0345] The sheet thus obtained was immediately preheated to 55°C and then stretched 3 times in the machine direction (MD) by passing it through rolls in a stretching zone at 70°C. The stretched film was then stretched 4 times in the transverse direction (TD) in the stretching zone of a tenter divided into two zones: an average temperature of 85°C in the initial 30% zone and an average temperature of 100°C in the final 70% zone.

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

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

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

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

[0350] (Examples 1-5) A biaxially stretched film was produced in the same manner as in Example 1-3, except that crystalline polyhydroxyalkanoate (PHA) resin (CJ Co., Korea) was used instead of amorphous polyhydroxyalkanoate (PHA).

[0351] (Comparative Example 1-1) As shown in Table 1 below, a biaxially stretched film was produced 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 stretched 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 stretched 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 a temperature of 220°C, and then brought into close contact with a cooling roll cooled to 20°C to obtain a sheet. The sheet was then stretched three times in the machine direction (MD), and the stretched sheet was heat-set at 150°C in the heat treatment section of a tenter to produce a uniaxially stretched film.

[0354] [Table 1]

[0355] [Laminate manufacturing] Example 2-1 -Step 1: Preparing the first resin and the second resin- <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 wt%), 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, an amorphous polyhydroxyalkanoate (PHA) resin (CJ Corporation, Korea) with a glass transition temperature (Tg) of approximately -30°C, and silica (Fuji Silysia Chemical Co., Ltd., 3.9 μm). In this case, the first polylactic acid (PLA) and the amorphous polyhydroxyalkanoate (PHA) were mixed so that the weight ratio of the first polylactic acid (PLA) and the 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. 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: Melt co-extrusion to obtain a two-layer laminated sheet- The result obtained in step 1 The aforementionedThe first resin and the second resin were each dried in a dehumidifying dryer at about 50°C for about 5 hours to remove moisture, and then melt-extruded through a single extruder to obtain a two-layer laminated sheet. At this time, the extrusion temperature of the first resin was about 210°C. The aforementioned The extrusion temperature of the second resin was about 220°C.

[0358] -Step 3: Biaxially stretching and heat setting to obtain a laminate- The laminated sheet obtained in step 2 was stretched about 3 times in the machine direction (MD) at about 75°C, stretched about 3.8 times in the transverse direction (TD) at about 85°C, heat-set at about 140°C, and then relaxed by about 2% to produce a laminate having a thickness of about 19.98 μm.

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

[0360] (Examples 2-5) As shown in Table 2 below, a 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 Co., 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 the first polylactic acid (PLA) resin was used as the component of the first layer.

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

[0363] (Comparative Example 2-3) As shown in Table 2 below, a laminate was produced 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 the random copolymer of L-lactic acid and D-lactic acid.

[0364] [Table 2]

[0365] (Evaluation example) (Evaluation Example 1: Thickness and Standard Deviation) The thickness of each of the films and laminates produced in the examples and comparative examples was measured across the entire width, and the thickness deviation was calculated.

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

[0367] Meanwhile, 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, Fine Rufu Co., Ltd.), and the thickness deviation was calculated using the following equation 3.

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

[0369] (Evaluation example 2: tensile strength) Film and laminate test pieces were prepared according to ASTM D882, then cut to a length of 100 mm and a width of 15 mm, and attached so that the distance between chucks was 50 mm. The test pieces were evaluated according to ASTM D882 using an Instron universal testing machine (UTM, model 5966) at a tension speed of 200 mm / min at room temperature of 25°C, and then measured using a program built into the machine.

[0370] TS MD is the tensile strength in the machine direction of the biaxially stretched film or laminate specimen, and TS TD is the transverse tensile strength of the biaxially oriented film or laminate specimen.

[0371] (Evaluation example 3: Modulus) Based on ASTM D882, biaxially stretched film test pieces and laminate test pieces manufactured in the examples and comparative examples were prepared, and then cut to a length of 100 mm and a width of 15 mm. The test pieces were attached so that the distance between the chucks was 50 mm. Tests were then conducted using an Instron universal testing machine (UTM, model 5966) at a tensile speed of 200 mm / min, and the modulus (kgf / mm) was calculated using a program built into the machine. 2 ) value was obtained.

[0372] The modulus in the machine direction (MD) and the modulus in the transverse direction (TD) of the biaxially stretched film specimen or laminate specimen were measured.

[0373] (Evaluation Example 4: Heat shrinkage rate) Each of the films and laminates prepared in the examples and comparative examples was cut into a length of 150 mm and a width of 1.5 cm, regardless of the direction, to prepare test specimens. The initial length at room temperature and the length of the biaxially stretched film test specimen or laminate test specimen immediately after being retained in a hot air oven at 100°C for 5 minutes were measured, and the heat shrinkage was evaluated using the following formulas 1-2 and 2-2.

[0374] <Formula 1-2> Heat shrinkage rate (S 100)={(L 25 -L 100 ) / L 25}×100 In the formula 1-2, L 25 is the initial length (mm) of the biaxially stretched film specimen at 25°C, L 100 is the length (mm) of the biaxially stretched film specimen measured immediately after being held in a hot air blower at 100°C for 5 minutes.

[0375] <Formula 2-2> Heat shrinkage rate (S 100 )={(L 25 -L 100 ) / L 25}×100 In the formula 2-2, L 25 is the initial length (mm) of the laminate test piece at 25°C, L 100 is the length (mm) of the laminate test piece measured immediately after being left in a hot air blower at 100°C for 5 minutes.

[0376] S MD100 is the thermal shrinkage in the machine direction of the biaxially stretched film or laminate specimen, and S TD100 is the thermal shrinkage in the transverse direction of the biaxially stretched film or laminate specimen.

[0377] (Evaluation Example 5: Haze and Light Transmittance) The biaxially stretched films and laminates produced in the examples and comparative examples were each measured using a haze meter (Haze Meter) according to ASTM D1003. Guard i, BYK-Gardner The haze and light transmittance were analyzed using a FTIR spectrometer (Fuji Electric Co., Ltd.).

[0378] (Evaluation example 6: Noise level) For biaxially stretched film, a Class 2 sound level meter or higher (A-weighting circuit: A-weighting, dynamic response: fast mode) specified in KS C IEC61672-1 was aimed toward the noise source, and the maximum sound level was measured once when a 21 cm wide and 29.5 cm long biaxially stretched film specimen was swung at a speed of 120 r / min. at a point 1.2 m to 1.5 m above the ground (if there was an obstacle over 1.5 m high at the measurement point, the point was 1.0 m to 3.5 m away from the obstacle toward the noise source). The same method was used to measure the sound level five times, and the average sound level (dB) was calculated.

[0379] For the laminate, a Class 2 sound level meter or higher (A-weighting circuit, fast dynamic response) specified in KS C IEC61672-1 or higher was used, pointed toward the noise source, and a 21 cm wide and 29.5 cm long laminate test piece was crumpled and unfolded 10 times for 10 seconds at a point 1.2 to 1.5 m above the ground (if there was an obstacle over 1.5 m high at the measurement point, the test piece was 1.0 to 3.5 m away from the obstacle toward the noise source). The maximum sound level was measured once. The same method was used to measure the sound level five times each, and the average sound level (dB) was calculated.

[0380] (Evaluation example 7: Loop stiffness) The loop stiffness was measured based on ASTM D747 by fixing a 1.5 cm wide and 18 cm long loop-shaped biaxially stretched film test piece and a 18 cm long laminate test piece to a loop measuring device (Loop Stiffness Tester, Toyo Seiki Seisakusho) and measuring the load at the center of the loop.

[0381] LS MD is the longitudinal loop stiffness of the biaxially stretched film or laminate specimen, and LS TD is the transverse loop stiffness of the biaxially oriented film or laminate specimen.

[0382] (Evaluation Example 8: Flexible Noise Composite Index (LSN)) Using the noise levels and loop stiffnesses of Evaluation Examples 6 and 7, the flexible noise composite index (LSN) of the biaxially stretched film was calculated, as represented by the following formula 1-1.

[0383] <Formula 1-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the formula 1-1, N AVG is the average sound level (dB) calculated by measuring the maximum sound level five times when a class 2 sound level meter specified in KS C IEC61672-1 is aimed at the noise source and a biaxially stretched film test piece with a width of 21 cm and a length of 29.5 cm is swung at a speed of 120 times per minute from the ground at a height of 1.2 m to 1.5 m. The unit is omitted. The LS is a unit-free value that indicates the loop stiffness (gf) measured based on ASTM D747 by fixing a loop-shaped biaxially stretched film specimen having 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.

[0384] LSN MD is the longitudinal flexibility noise composite index of biaxially stretched film, and LSN TD is the transverse flexibility noise composite index of biaxially stretched film.

[0385] On the other hand, the noise intensity and loop stiffness of the evaluation examples 6 and 7 were used to determine the composite flexibility noise index (LSN) of the laminate, which is represented by the following formula 2-1.

[0386] <Formula 2-1> Flexible Noise Composite Index (LSN) = N AVG ×LS In the formula 2-1, N AVGis the average sound level (dB) calculated by measuring the maximum sound level five times when a class 2 sound level meter specified in KS C IEC61672-1 is aimed at the noise source and a laminated test piece with a width of 21 cm and a length of 29.5 cm is repeatedly crumpled and unfolded for 10 seconds at a height of 1.2 m to 1.5 m from the ground. The value is a unit-free value. The LS is a unit-free numerical value that indicates the loop stiffness (gf) measured based on ASTM D747 by fixing a loop-shaped laminate specimen having 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.

[0387] LSN MD is the longitudinal flexibility noise composite index of the laminate, and LSN TD is the laminate's transverse flexibility noise composite index.

[0388] (Evaluation Example 9: Forming Index) Using the tensile strength and loop rigidity of Evaluation Examples 2 and 7, the forming index (FI) of the biaxially stretched film and laminate, respectively, was calculated, as represented by the following formula 1-3 and formula 2-3.

[0389] <Formula 1-3> Forming index (FI)=TS / LS In the formula 1-3, TS is the tensile strength (kgf / mm²) without units, measured by cutting a biaxially stretched film specimen into a length of 100 mm and a width of 15 mm according to ASTM D882, and attaching the specimen to a chuck with a distance of 50 mm between chucks using a universal testing machine (UTM). LS is as defined above.

[0390] <Formula 2-3> Forming index (FI)=TS / LS In the formula 2-3, TS was measured by cutting a laminate test piece into a length of approximately 100 mm and a width of 15 mm according to ASTM D882, and then attaching the test piece so that the distance between chucks was 50 mm. The tensile strength (kgf / mm 2 ) where LS is as defined above.

[0391] FI MD is the forming index in the machine direction of the biaxially stretched film or laminate specimen, and FI TD is the forming index in the transverse direction of the biaxially stretched film or laminate specimen.

[0392] [Table 3]

[0393] As can be seen from Table 3, the biaxially stretched films of the examples containing polylactic acid (PLA) and polyhydroxyalkanoate (PHA) in a specific content range and having a composite flexibility noise index (LSN) of 20 or less had excellent strength and flexibility, as well as excellent thermal properties and improved noise levels.

[0394] Specifically, the biaxially stretched films of Examples 1-1 to 1-5 have a tensile strength of 9 to 25 kgf / mm 2 The loop stiffness is in the appropriate range of 0.1 to 0.23 gf, and it has excellent flexibility. In addition, the noise level is low at 86 dB or less, and the thermal shrinkage rate is extremely low at 15% or less even at a high temperature of 100°C, so both the mechanical properties and thermal characteristics are excellent.

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

[0396] On the other hand, in the case of the biaxially stretched film of Comparative Example 1-2, which contained an excess amount of polyhydroxyalkanoate (PHA) of 30% by weight or more, the tensile strength was about 4 to 6 kgf / mm 2 At a high temperature of 100°C, the heat shrinkage rate increased significantly to 17-20%. In addition, the haze increased to over 14% and the light transmittance was approximately 85%, significantly reducing the optical properties.

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

[0398] On the other hand, the biaxially stretched films of Examples 1-1 to 1-4 containing amorphous polyhydroxyalkanoate (PHA) had a low haze of 6.8% or less and excellent light transmittance of 90% or more, whereas the biaxially stretched film of Example 1-5 using crystalline polyhydroxyalkanoate (PHA) had increased haze and decreased light transmittance, resulting in poor optical properties, compared to the biaxially stretched film of Example 1-3 containing the same amount of polyhydroxyalkanoate (PHA).

[0399] [Table 4]

[0400] As can be seen from Table 4, the laminate of the example, which includes a first layer containing a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA) within a specific content range and a second layer containing a second polylactic acid (PLA), has excellent strength and flexibility, as well as excellent thermal properties and improved noise levels. Furthermore, the interlayer compatibility between the first and second layers is good, so the interlayer adhesion properties are also excellent.

[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 0.1 to 0.2 gf, and excellent flexibility. MD ) is 7 to 14 kgf / mm 2 When the temperature is within the appropriate range, the heat shrinkage rate is very low at 15% or less even at a high temperature of 100°C, the haze is 10% or less, and the light transmittance is 90% or more, and the mechanical, thermal, and optical properties are all excellent.

[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, 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 has the same composition of the second layer.

[0403] On the other hand, in the case of the laminate of Comparative Example 2-2, in which the first layer contained an excessive amount of polyhydroxyalkanoate (PHA) of 30% by weight or more, the thickness deviation of the laminate increased, and the longitudinal tensile strength (TS MD ) and transverse tensile strength (TS TD ) are approximately 6.4kgf / mm 2 and 7.8 kgf / mm 2 At a high temperature of 100°C, the heat shrinkage rate increased significantly to 15.3 to 16.8%, and the optical properties also deteriorated.

[0404] Furthermore, in the case of the laminate of Comparative Example 2-3, in which polytriethylene terephthalate (PTT) was used instead of the second polylactic acid in the second layer, the compatibility between the first and second layers was insufficient during stretching, resulting in insufficient interlayer adhesion properties, and delamination made it impossible to produce a stretched film (film formation).

[0405] In contrast, the laminating agents of Examples 2-1 to 2-6 are composed of a first layer containing a first polylactic acid (PLA) and a polyhydroxyalkanoate (PHA) and a second layer placed on one side of the first layer and containing a second polylactic acid (PLA), and therefore have good compatibility, resulting in excellent adhesive properties for the first and second layers even after stretching.

[0406] On the other hand, in the case of the laminate of Example 2-5, which used crystalline polyhydroxyalkanoate (PHA), the thermal shrinkage rate was significantly reduced compared to the laminates of Comparative Examples 2-1 to 2-3, and although it had the advantages of being easy to dry for extrusion processing and generating less bubbles during extrusion processing, 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, flexibility, etc. were improved compared to the laminates of Comparative Examples 2-1 to 2-3, but the thickness deviation of the laminate and the heat shrinkage rate were relatively increased compared to the laminate of Example 2-3, which had the same composition of the first layer.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: Corona layer 14: Coating layer

Claims

1. Contains polylactic acid (PLA) and amorphous polyhydroxyalkanoate (PHA), Contains greater than 0 wt% and less than 30 wt% polyhydroxyalkanoate (PHA), based on the total weight of the biaxially stretched film; A biaxially stretched film having a flexible noise composite index (LSN) represented by the following formula 1-1 of 20 or less when the thickness of the biaxially stretched film is 19 μm to 21 μm: <Formula 1-1> Flexible Noise Composite Index (LSN) = N ＡＶＧ ×LS In the formula 1-1, The N ＡＶＧ is the average noise intensity (dB) calculated by measuring the maximum noise intensity five times when a class 2 sound level meter specified in KS C IEC 61672-1 is aimed toward the noise source and a biaxially stretched film test piece with a width of 21 cm and a length of 29.5 cm is swung at a speed of 120 times per minute from the ground at a height of 1.2 m to 1.5 m, and the value is a unit-free value. The LS is a unit-free value that indicates the loop stiffness (gf) measured based on ASTM D747 by fixing a loop-shaped biaxially stretched film specimen having 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.

2. The N ＡＶＧ is 86 dB or less, The biaxially stretched film according to claim 1, wherein the LS is 0.10 to 0.23 gf.

3. The biaxially stretched film according to claim 1, wherein the forming index (FI) represented by the following formula 1-3 is 65 or more: <Formula 1-3> Forming index (FI) = TS / LS In the formula 1-3, TS is a tensile strength (kgf) / mm measured at room temperature using a universal testing machine (UTM). ２ ) is a numerical value without units, The LS is a unit-free value that indicates the loop stiffness (gf) measured by fixing a loop-shaped biaxially stretched film specimen having a width of 1.5 cm and a length of 18 cm to a loop stiffness tester according to ASTM D747 and measuring the load at the center of the loop.

4. 4. The biaxially stretched film of claim 3, which satisfies at least one property selected from the following properties: Longitudinal (MD) Flexible Noise Composite Index (LSN) ＭＤ ) 5 to 20, Lateral (TD) Flexible Noise Composite Index (LSN) ＴＤ ) 5 to 20, Forming index (FI) in machine direction (MD) ＭＤ ) 65-90, Transverse direction (TD) forming index (FI ＴＤ ) 80-110, Tensile strength in machine direction (MD) (TS ＭＤ )9~25kgf / mm ２ , Transverse (TD) tensile strength (TS ＴＤ )9~25kgf / mm ２ , the thickness deviation of the biaxially stretched film relative to the thickness across the width is 10 μm or less; Haze 10% or less, and The thermal shrinkage rate (S １００ ) 15% or less: <Formula 1-2> Heat shrinkage rate (S １００ ) = {(L ２５ -L １００ ) / L ２５ } x 100 In the formula 1-2, L ２５ is the initial length (mm) of the biaxially stretched film specimen at 25°C, L １００ is the length (mm) of the biaxially stretched film specimen measured immediately after being held in a hot air blower at 100°C for 5 minutes.

5. The polyhydroxyalkanoate (PHA) is a copolymerized polyhydroxyalkanoate (PHA), The biaxially stretched film according to claim 1, wherein the copolymerized polyhydroxyalkanoate (PHA) contains at least one unit of the following Chemical Formula 1 and at least one unit of the following Chemical Formula 2: [Chemical formula 1] In the above Chemical Formula 1, The R １ is the substituted C １ ~C ８ is an alkylene of the formula m is an integer of 1 or greater, [Chemical formula 2] In the above Chemical Formula 2, The R ２ is a substituted or unsubstituted C １ ~C ８ is an alkylene of the formula n is an integer of 1 or more.

6. 6. The biaxially stretched film according to claim 5, wherein the copolymerized polyhydroxyalkanoate (PHA) contains the unit of Chemical Formula 2 in an amount of 1 wt % to 60 wt % based on the total weight of the copolymerized polyhydroxyalkanoate (PHA).

7. An environmentally friendly packaging material comprising the biaxially stretched film according to claim 1.

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