Coating composition and packaging material manufactured using same

Abstract

The present invention relates to a coating composition and a packaging material manufactured by using same. The coating composition comprises: polyhydroxyalkanoate (PHA); and two or more polylactic acids (PLA). The present invention can provide a packaging material having improved physical properties due to the coating composition.

Description

Coating composition and packaging material manufactured using the same

[0001] The present invention relates to a packaging material (paper-based packaging material) having excellent biodegradability and recyclability, and improved durability, water resistance, oil resistance, heat resistance, and contamination resistance, including a coating composition used in the manufacture of a packaging material and a coating layer manufactured from the coating composition.

[0002] Typically, paper has high breathability and low ductility, limiting its use as a packaging material for food products requiring barrier properties and formability. To improve the performance of paper packaging, various packaging materials have been developed, using paper as a base material and coated with various types of synthetic resins (e.g., polyolefin resins such as polyethylene and polypropylene).

[0003] However, unlike paper packaging materials that decompose naturally in the soil in a relatively short period of time, packaging materials coated with synthetic resin have a problem in that the synthetic resin coating layer remains after landfilling due to the difficulty in decomposition of the synthetic resin, which reduces the environmental friendliness of the packaging materials.

[0004] To address the above issues, a technology has been proposed for manufacturing packaging materials using biodegradable resins instead of synthetic resins. For example, packaging materials extruded with polylactic acid (PLA) are considered. PLA is obtained through the condensation reaction of lactic acid, and the monomers used for its production are produced during the fermentation process of plants such as corn, cassava, and sugarcane.

[0005] Polylactic acid (PLA) is known as a representative biodegradable resin, but to be precise, it is desirable to classify it as a compostable resin because it is biodegradable under industrial composting conditions. Therefore, packaging materials coated with polylactic acid (PLA) have various environmental restrictions on the disposal method after use, and when landfilled, it requires the same decomposition time as packaging materials coated with synthetic resin, raising concerns about greenwashing, which has recently emerged as a social issue. In addition, biodegradable resins such as polylactic acid (PLA) have lower melting temperature and heat resistance than synthetic resins, which limits their application to mass-produced packaging material manufacturing lines that are operated under high temperature and / or high pressure conditions.

[0006] Therefore, it is necessary to develop packaging materials that have excellent biodegradability and improved physical properties such as heat resistance, so that they can be applied to various fields.

[0007] In order to solve the above-mentioned conventional problems, the object of the present invention is to provide a coating composition capable of forming a coating layer having secured thermal stability and stretchability by including one or more specific polymer resins.

[0008] In addition, another object of the present invention is to provide a packaging material having excellent biodegradability and recyclability, and improved durability, water resistance, oil resistance, heat resistance, and contamination resistance, including a coating layer prepared from the above coating composition.

[0009] Another object of the present invention is to provide a method for manufacturing a packaging material capable of efficiently manufacturing the packaging material.

[0010] To achieve the above object, the present invention provides a coating composition comprising polyhydroxyalkanoate (PHA) and two or more types of polylactic acid (PLA).

[0011] According to one embodiment of the present invention, the polyhydroxyalkanoate may contain 0.1 to 60 wt% of repeating units derived from 4-hydroxybutyrate (4HB) based on the total weight of the polyhydroxyalkanoate.

[0012] According to another embodiment of the present invention, the polylactic acid (PLA) may include a first polylactic acid; and a second polylactic acid having a different melting index (MI) from the first polylactic acid.

[0013] According to another embodiment of the present invention, the melting index (MI) of the first polylactic acid may be 40 g / 10 min to 70 g / 10 min, and the melting index (MI) of the second polylactic acid may be 1 g / 10 min to 30 g / 10 min.

[0014] According to another embodiment of the present invention, based on the total weight of the mixed resin in which the polyhydroxyalkanoate and the polylactic acid are mixed, the content of the polyhydroxyalkanoate may be 5 wt% to 65 wt%, the content of the first polylactic acid may be 30 wt% to 75 wt%, and the content of the second polylactic acid may be 5 wt% to 20 wt%.

[0015] According to another embodiment of the present invention, based on the total weight of the mixed resin in which the polyhydroxyalkanoate and the polylactic acid are mixed, the content of the polyhydroxyalkanoate included in the coating composition may be 5 wt% to 65 wt%, and the content of the polylactic acid included in the coating composition may be 35 wt% to 95 wt%.

[0016] According to another embodiment of the present invention, the polyhydroxyalkanoate has a weight average molecular weight (Mw) of 100,000 g / mol to 1,000,000 g / mol and a melting temperature (T m ) is 120 ℃ to 200 ℃, and the heat distortion temperature (T d ) can be over 200 ℃.

[0017] According to another embodiment of the present invention, the coating composition may further comprise a chain extender.

[0018] Meanwhile, the present invention provides a packaging material comprising a substrate layer including paper; and a coating layer provided on the substrate layer, wherein the coating layer is formed from the coating composition.

[0019] According to one embodiment of the present invention, the packaging material may have a recovery rate of the substrate layer of 70% or more in a recyclability evaluation based on UL2485.

[0020] On the other hand, the present invention provides a method for manufacturing a packaging material, comprising the steps of preparing a substrate including paper; and melt-extruding the coating composition onto the substrate to form a substrate layer and a coating layer.

[0021] The coating composition according to the present invention can form a coating layer with secured thermal stability and stretchability by including polyhydroxyalkanoate and one or more types of polylactic acid. Therefore, even when the coating composition is coated on a base substrate such as paper using the extrusion method, which is a mass-production packaging material manufacturing method performed under high temperature and / or high pressure conditions, a stable coating is achieved, thereby improving the manufacturing efficiency of the packaging material.

[0022] In addition, since the packaging material manufactured using the coating composition according to the present invention has excellent biodegradability and recyclability, as well as improved durability, water resistance, oil resistance, heat resistance, and contamination resistance, it can be used not only for manufacturing disposable consumer goods such as beverage cups using various molding methods (e.g., hot air method, ultrasonic sealing method, paper press method, etc.), but also for manufacturing food containers for microwave cooking.

[0023] Figure 1 is a cross-sectional view showing a packaging material according to one embodiment of the present invention.

[0024] Figure 2 is a reference diagram for explaining Test Example 2.

[0025] Figure 3 is a reference diagram for explaining Test Example 3.

[0026] Figure 4 is a rejection image confirmed during the recyclability evaluation process of Test Example 4.

[0027] Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the contents disclosed below, and may be modified in various forms as long as the gist of the invention is not changed.

[0028] The word "comprising" or "including" in this specification is intended to specify particular features, regions, steps, processes, elements and / or components, and does not exclude the presence or addition of other features, regions, steps, processes, elements and / or components, unless specifically stated to the contrary.

[0029] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification are to be understood as being modified by the term “about” in all cases unless otherwise specified.

[0030]

[0031] The present invention provides a coating composition (coating composition for packaging material) comprising one or more specific polymer resins, a packaging material (paper-based packaging material) manufactured using the same, and a method for manufacturing the packaging material. Specifically, the coating composition may comprise three or more compostable polymer resins, and by coating the same on a paper substrate, a packaging material that is biodegradable under both industrial and household composting conditions is manufactured, which is described as follows.

[0032]

[0033] coating composition

[0034] The coating composition of the present invention comprises polyhydroxyalkanoate (PHA); and two or more types of polylactic acid (PLA). Since the coating composition comprises polyhydroxyalkanoate (PHA) with excellent biodegradability and two or more types of polylactic acid (PLA) with different melting properties, it is possible to secure extrusion stability when manufacturing a packaging material using a melt extrusion coating method, while providing a packaging material with excellent biodegradability (compostability).

[0035]

[0036] polyhydroxyalkanoate (PHA)

[0037] The polyhydroxyalkanoate (PHA) contained in the coating composition of the present invention is a natural polymer accumulated within microbial cells. This PHA not only biodegrades under household composting conditions, but also aerobically biodegrades in marine environments according to the test standards defined in ASTM D6691. It also possesses excellent ductility and impact resistance, making it highly competitive as a coating material for naturally biodegradable packaging materials.

[0038] The above PHA may be a homopolymer or a copolymer comprising repeating units derived from various monomers. Specifically, the PHA is at least one selected from the group consisting of 3-hydroxybutyrate (3HB), 3-hydroxyhexanoate (3HH), 3-hydroxypropionate (3HP), 3-hydroxyvalerate (3HV), 4-hydroxybutyrate (4HB), 4-hydroxyhexanoate (4HH), 4-hydroxypropionate (4HP), 4-hydroxyvalerate (4HV), 5-hydroxyvalerate (5HV), and 6-hydroxyhexanoate (6HH). It may contain repeating units derived from monomers.

[0039] For example, the PHA is poly 3-hydroxybutyrate-co-3-hydroxyhexanoate copolymer (P3HB-co-3HH), poly 3-hydroxybutyrate-co-3-hydroxyvalerate copolymer (P3HB-co-3HV), poly 3-hydroxybutyrate-co-3-hydroxypropionate copolymer (P3HB-co-3HP), poly 3-hydroxybutyrate-co-4-hydroxybutyrate copolymer (P3HB-co-4HB), poly 3-hydroxybutyrate-co-4-hydroxyhexanoate copolymer (P3HB-co-4HH), poly 3-hydroxybutyrate-co-4-hydroxyvalerate copolymer (P3HB-co-4HV) and poly It may include at least one selected from the group consisting of 3-hydroxybutyrate-co-4-hydroxypropionate copolymer (P3HB-co-4HP).

[0040] These PHAs can be classified into crystalline PHA (cPHA), semi-crystalline PHA (scPHA), or amorphous PHA (aPHA) depending on the type of monomer and the content of repeating units derived from the monomer. For example, the crystallinity of the PHA can be controlled depending on the content of repeating units derived from 4-hydroxybutyrate (4HB), and thus the PHA can be classified into cPHA, scPHA, or aPHA. Specifically, the PHA can be an amorphous PHA having a relatively high content of the 4HB repeating unit.

[0041] According to the present invention, the PHA may contain 0.1 wt% to 60 wt% of the repeating unit (4HB repeating unit) derived from 4-hydroxybutyrate (4HB) based on the total weight of the PHA. Specifically, the PHA may contain 0.1 wt% to 60 wt%, 1 wt% to 58 wt%, 5 wt% to 55 wt%, 10 wt% to 53 wt%, 15 wt% to 50 wt%, 20 wt% to 45 wt%, 25 wt% to 43 wt%, or 30 wt% to 40 wt% of the 4HB repeating unit based on the total weight of the PHA, but is not limited thereto. When the content of the 4HB repeating unit is within the above range, the softness and impact resistance of the packaging material can be increased.

[0042] For example, the PHA may be a poly 3-hydroxybutyrate-co-4-hydroxybutyrate copolymer (P3HB-co-4HB) comprising a repeating unit (3HB repeating unit) derived from the 3-hydroxybutyrate (3HB) and a repeating unit (4HB repeating unit) derived from the 4-hydroxybutyrate (4HB). Specifically, the PHA may be a P3HB-co-4HB comprising 40 wt% to 99.9 wt% of the 3HB repeating unit and 0.1 wt% to 60 wt% of the 4HB repeating unit, based on the total weight of the PHA. More specifically, the PHA may be an amorphous P3HB-co-4HB comprising 55 wt% to 75 wt% of the 3HB repeating unit and 25 wt% to 45 wt% of the 4HB repeating unit based on the total weight of the PHA.

[0043] The weight average molecular weight (Mw) of the above PHA is not particularly limited, but may be 100,000 g / mol to 1,000,000 g / mol, 200,000 g / mol to 900,000 g / mol, 300,000 g / mol to 800,000 g / mol, 400,000 g / mol to 700,000 g / mol, or 500,000 g / mol to 700,000 g / mol.

[0044] The above PHA has a melting temperature (T m ) may or may not be measured. Specifically, the PHA has a melting temperature (T m ) may not be measured, or may be 120 ℃ to 200 ℃, 140 ℃ to 190 ℃, or 160 ℃ to 180 ℃.

[0045] The above PHA has a heat distortion temperature (T d ) may be 200 ℃ or higher, 230 ℃ or higher, 250 ℃ or higher, 270 ℃ or higher, 290 ℃ or higher, or 310 ℃ or higher (e.g., 250 ℃ to 300 ℃). The heat distortion temperature (T d) can mean the temperature when an arbitrary amount of deformation (0.25 mm) occurs under a constant load (0.45 MPa / 1.8 MPa).

[0046] According to the present invention, the content of the PHA may be 5 wt% to 65 wt% based on the total weight of the mixed resin in which the PHA and the PLA are mixed. Specifically, the content of the PHA may be 5 wt% to 65 wt%, 10 wt% to 60 wt%, 15 wt% to 55 wt%, 20 wt% to 50 wt%, 25 wt% to 45 wt%, or 30 wt% to 40 wt% based on the total weight of the mixed resin, but is not limited thereto.

[0047]

[0048] polylactic acid (PLA)

[0049] The polylactic acid (PLA) included in the coating composition of the present invention has the characteristic of high rigidity. The polylactic acid (PLA) is included in two or more types in the coating composition. For example, the PLA may include a first polylactic acid (first PLA), a second polylactic acid (second PLA), or a combination thereof.

[0050] Specifically, the PLA may include a first polylactic acid (first PLA) and a second polylactic acid (second PLA) having a different melting index (MI) from the first polylactic acid (first PLA). As two types of PLAs having different melting indices (MI) are introduced into the coating composition, the flowability required in the melt extrusion coating method is secured, thereby preventing surging and the like from occurring while allowing the coating composition to sufficiently permeate the substrate when manufacturing a packaging material using the coating composition.

[0051] The first PLA may include L-lactic acid, D-lactic acid, D,L-lactic acid, or a combination thereof. The weight average molecular weight (Mw) of the first PLA is not particularly limited, but may be from 10,000 g / mol to 500,000 g / mol, from 5,000 g / mol to 300,000 g / mol, or from 100,000 g / mol to 200,000 g / mol.

[0052] The first PLA may have a melting index (MI) of greater than 30 g / 10 min, greater than 35 g / 10 min, greater than 40 g / 10 min, greater than 50 g / 10 min, greater than 60 g / 10 min, or greater than 70 g / 10 min, based on 210° C. and 2.16 kg. Specifically, the first PLA may have a melting index (MI) of, but not limited to, 40 g / 10 min to 70 g / 10 min, 45 g / 10 min to 70 g / 10 min, or 50 g / 10 min to 70 g / 10 min.

[0053] The second PLA may include L-lactic acid, D-lactic acid, D,L-lactic acid, or a combination thereof. The weight average molecular weight (Mw) of the second PLA is not particularly limited, but may be 10,000 g / mol to 500,000 g / mol, 5,000 g / mol to 300,000 g / mol, or 100,000 g / mol to 200,000 g / mol.

[0054] The second PLA may have a melting index (MI) of less than 35 g / 10 min, less than or equal to 30 g / 10 min, less than or equal to 28 g / 10 min, less than or equal to 25 g / 10 min, less than or equal to 20 g / 10 min, or less than or equal to 15 g / 10 min, based on 210° C. and 2.16 kg. Specifically, the second PLA may have a melting index (MI) of, but not limited to, 1 g / 10 min to 30 g / 10 min, 3 g / 10 min to 20 g / 10 min, or 5 g / 10 min to 10 g / 10 min.

[0055] According to the present invention, the content of the PLA may be 35 wt% to 95 wt% based on the total weight of the mixed resin in which the PHA and the PLA are mixed. Specifically, the content of the PLA may be 35 wt% to 95 wt%, 40 wt% to 90 wt%, 45 wt% to 85 wt%, 50 wt% to 80 wt%, 55 wt% to 75 wt%, or 60 wt% to 70 wt% based on the total weight of the mixed resin, but is not limited thereto.

[0056] For example, when the PLA includes the first PLA and the second PLA, the content of the first PLA may be 30 wt% to 75 wt%, and the content of the second PLA may be 5 wt% to 20 wt%, based on the total weight of the mixed resin. Specifically, the content of the first PLA may be 30 wt% to 75 wt%, 40 wt% to 70 wt%, 50 wt% to 65 wt%, or 55 wt% to 60 wt%, based on the total weight of the mixed resin, but is not limited thereto. In addition, the content of the second PLA may be 5 wt% to 20 wt%, 7 wt% to 18 wt%, 10 wt% to 15 wt%, or 10 wt% to 12 wt%, based on the total weight of the mixed resin, but is not limited thereto.

[0057]

[0058] Meanwhile, the coating composition of the present invention may further comprise a chain extender. By further including the chain extender, compatibility between PHA and PLA of different species can be enhanced, thereby improving melt strength. The chain extender is not particularly limited as long as it is a commonly known compound, and specific examples thereof include epoxide compounds, carbodiimide compounds, isocyanate compounds, acrylate compounds, or phosphate compounds.

[0059] The content of the chain extender is not particularly limited, but considering the properties of the coating composition, it may be 0 to 3.5 parts by weight, 0.1 to 2.5 parts by weight, or 0.2 to 1.5 parts by weight, based on 100 parts by weight of the mixed resin.

[0060] The coating composition of the present invention may further include commonly known additives (e.g., antioxidants, slip agents, dispersants, heat stabilizers, UV blockers, fillers, etc.) to improve processability and improve quality.

[0061]

[0062] packaging materials

[0063] In general, compostable polymer resins have lower melting temperatures and heat resistance than synthetic resins (e.g., polyolefin resins). Therefore, during thermal processing such as extrusion, a relatively low temperature range is required to prevent quality loss due to deterioration. Therefore, they have low manufacturing suitability for mass-production packaging material manufacturing lines that are mainly used in high-speed production environments. However, in the present invention, a coating composition in which heat-resistant polylactic acid (PLA) is mixed with amorphous polyhydroxyalkanoate (aPHA) with a relatively low glass transition temperature is applied to manufacture a packaging material, thereby ensuring improved heat stability and stretchability. In addition, the packaging material of the present invention is manufactured by coating the coating composition in a thin film using a melt extrusion method, thereby overcoming the limitations of biodegradable paper packaging materials that were previously limited to disposable consumer goods such as beverage cups used in franchises, and can exhibit stable durability and heat stability even when cooked in a microwave oven.

[0064] The packaging material of the present invention includes a substrate layer and a coating layer, which will be described with reference to FIG. 1 as follows.

[0065]

[0066] Substrate layer (10)

[0067] The substrate layer (10) included in the packaging material of the present invention includes paper. Specifically, the substrate layer (10) may be made of a paper substrate. The paper substrate is not particularly limited as long as it is commonly known, and specifically, it may include at least one selected from the group consisting of white paper (imitation paper), off-white paper, colored paper, rough paper, medium-quality paper, pile paper, art paper, snow paper, snow white paper, single-sided art paper, royal art paper, NCR paper, laser paper, laid paper, CCP paper, kraft paper, Manila ivory paper, royal ivory paper, tracing paper, tantalum paper, fancy paper, cotton paper, label paper, white cardboard, photographic paper, and cup paper.

[0068] The basis weight of the above paper substrate is not particularly limited, but considering the mechanical strength of the packaging material, it may be 50 gsm or more, 70 gsm or more, 90 gsm or more, 150 gsm or more, 210 gsm or more, 230 gsm or more, 260 gsm or more, or 280 gsm or more (e.g., 30 gsm to 350 gsm).

[0069] One side and / or the other side of the paper substrate may be primed to increase bonding strength with the coating layer (20), or may be subjected to printing processing to impart a design.

[0070]

[0071] Coating layer (20)

[0072] The coating layer (20) included in the packaging material of the present invention is formed from the above-described coating composition. Since the coating layer (20) is manufactured using the above-described coating composition, a packaging material with excellent durability, water resistance, oil resistance, heat resistance, and contamination resistance can be provided.

[0073] The thickness of the above coating layer (20) is not particularly limited, but considering the properties of the packaging material, it may be 20 ㎛ or more, 50 ㎛ or more, 70 ㎛ or more, or 100 ㎛ or more (e.g., 20 ㎛ to 200 ㎛).

[0074]

[0075] The packaging material of the present invention can be formed into a cup using a hot air method or an ultrasonic sealing method, or can be processed using a paper press method in a press mold. The cup forming using the hot air method can be performed at a temperature of 400°C to 600°C.

[0076] The packaging material of the present invention possesses excellent water and oil resistance, making it suitable as a packaging material for food and other products. In particular, the packaging material exhibits improved oil resistance compared to conventional packaging materials coated with a polyolefin resin, a nonpolar molecule. Consequently, the packaging material exhibits low absorption of oily foods and thus excellent contamination resistance.

[0077] Furthermore, the packaging material of the present invention exhibits excellent biodegradability and recyclability. Specifically, the packaging material may have a recovery rate of the substrate layer of 70% or higher (specifically, 75% to 99.9%, 85% to 99%, or 95% to 98%) in a recyclability evaluation based on UL2485.

[0078]

[0079] Method for manufacturing packaging materials

[0080] The present invention can secure processability in a mass-production packaging material manufacturing line by manufacturing a packaging material using the above-described coating composition.

[0081] Specifically, the method for manufacturing a packaging material of the present invention includes the steps of preparing a substrate including paper; and the step of melt-extruding the above-described coating composition onto the substrate to form a substrate layer and a coating layer (the step of manufacturing a packaging material including a substrate layer and a coating layer).

[0082] The substrate including the above paper may be the paper substrate described above, and its preparation may be performed by a commonly known process.

[0083] The above melt extrusion is performed to coat the above-described coating composition into a thin film on the above-described substrate. In particular, in the present invention, since a coating composition including PHA and two types of PLAs having different melt properties (e.g., melt index (MI) etc.) is used for the melt extrusion, a coating layer can be formed while preventing load and surging phenomena within the extruder and ensuring stable flowability. The formation of a coating layer through such melt extrusion is differentiated from a conventional coating method in which a coating layer is formed by applying, depositing, or transferring an emulsion or a fluidic coating material.

[0084] Meanwhile, PHA included in the above coating composition is prone to solidification by heat, which can affect the properties of the coating layer and packaging material. Therefore, in the melt extrusion coating process, it is important to maintain a constant flowability within the extruder. Unlike conventional melt extrusion coating of polyolefin resins, the range of processable conditions is not wide, and therefore, careful adjustment of the melt extrusion coating conditions is necessary.

[0085] For example, according to the present invention, melt extrusion of the coating composition can be performed at a temperature of 150°C to 220°C.

[0086] The present invention is described in more detail through the following examples. However, the scope of the present invention is not limited to these examples.

[0087]

[0088] 1. Preparation of coating composition

[0089] [Example 1]

[0090] A coating composition including a mixed resin in which 65 wt% of the first PLA, 5 wt% of the second PLA, and 30 wt% of PHA (P3HB-co-4HB) were mixed based on the total weight of the mixed resin was prepared by a conventional method.

[0091]

[0092] [Example 2]

[0093] A coating composition including a mixed resin in which 60 wt% of the first PLA, 10 wt% of the second PLA, and 30 wt% of PHA (P3HB-co-4HB) were mixed based on the total weight of the mixed resin was prepared by a conventional method.

[0094]

[0095] [Example 3]

[0096] A coating composition including a mixed resin in which 65 wt% of the first PLA, 5 wt% of the second PLA, and 30 wt% of PHA (P3HB-co-4HB) were mixed based on the total weight of the mixed resin was prepared by a conventional method.

[0097]

[0098] [Example 4]

[0099] A coating composition including a mixed resin in which 60 wt% of the first PLA, 10 wt% of the second PLA, and 30 wt% of PHA (P3HB-co-4HB) were mixed based on the total weight of the mixed resin was prepared by a conventional method.

[0100]

[0101] The properties of the first PLA and the second PLA used in Examples 1 to 4 are shown in Table 1 below. In this case, the melting index (MI) is a value measured under the conditions of 210°C and 2.16 kg.

[0102]

[0103] Example 1 Example 2 Example 3 Example 4 1st PLAMI (g / 10 min) 50 50 50 50 Mw (g / mol) 105,017 105,017 105,017 105,017 105,017 2nd PLAMI (g / 10 min) 824 188 Mw (g / mol) 194,647 150,969 163,154 194,647

[0104]

[0105] 2. Packaging material manufacturing

[0106] [Manufacturing Examples 1 to 4]

[0107] The coating compositions prepared in Examples 1 to 4 were melt-extruded at a temperature of 170 to 190°C at a speed of 60 m / min using a single-screw extruder (screw diameter Φ120 mm) on a paper substrate to produce packaging materials having a structure of a paper substrate layer (thickness: about 365 μm) / resin coating layer (thickness: 40 μm), respectively.

[0108]

[0109] [Comparative Manufacturing Example 1]

[0110] Packaging material made of paper was prepared.

[0111]

[0112] [Comparative Manufacturing Example 2]

[0113] A conventional packaging material having a structure of a paper substrate layer (thickness: approximately 365 ㎛) / resin coating layer (thickness: 30 ㎛) was prepared by coating a polyolefin resin (specifically, polypropylene) on a paper substrate.

[0114]

[0115] [Test Example 1] Evaluation of water resistance and oil resistance

[0116] Each of the packaging materials of Manufacturing Example 1 and Comparative Manufacturing Example 1 was cut to a size of 70 mm in width and 70 mm in length to prepare specimens, and the initial weights of the specimens were measured. Next, after fixing the specimens to a Cobb sizing tester (Gurley Cobb sizing tester), water resistance and oil resistance were evaluated, respectively, and the results are shown in Table 2 below. Specifically, for water resistance, distilled water was poured as a test liquid, and for oil resistance, a test liquid corresponding to the KIT12 grade was poured onto the specimens in an amount of 25 ml each. After the time specified in Table 2 below had elapsed, the test liquid was removed, and the final weight of the specimen was measured. In addition, the Cobb value and whether the specimens passed the KIT12 grade were confirmed by comparing them with the initial weight.

[0117]

[0118] Example 1 of manufacturing a coated paper (Paper) Example 1 of manufacturing a coated paper (Coated paper) Water resistance (g / m) 2 )(Cobb value)2 min 23.6< 110 min 50.0< 1 Oil resistance (KIT 12) 15 seconds Fail (KIT5) Pass

[0119] Referring to Table 2 above, it can be confirmed that the packaging material of Manufacturing Example 1 coated with the coating composition of Example 1 according to the present invention has excellent water resistance and oil resistance compared to the packaging material of Comparative Manufacturing Example 1 made only of a paper substrate.

[0120]

[0121] [Test Example 2] Durability and Cooking Stability Evaluation

[0122] A container manufactured using the packaging material of Manufacturing Example 1 coated with the coating composition of Example 1 according to the present invention was filled with hot water (approximately 90.5°C) and stored for 24 hours. Then, the exterior (inside and outside) of the container was visually observed to determine if there were any abnormalities, thereby evaluating durability. As a result of the observation, it was confirmed that no phenomena such as decomposition, peeling, or swelling of the resin coating layer provided inside the container occurred.

[0123] Meanwhile, commercially available noodle-type food (food containing animal fat or chili oil) and water were put into each container manufactured using the packaging materials of Manufacturing Example 1 and Comparative Manufacturing Example 2, and cooked in a microwave oven to evaluate cooking stability. Specifically, water was put into each container, and cooking was performed in a microwave oven with an output of 1000 W by performing standard cooking (cooking for about 2 minutes) and overcooking (cooking for about 5 minutes) for more than twice the standard cooking time as instructed in the cooking method, and the results are shown in Fig. 2. Referring to Fig. 2, it was confirmed that there was no leakage or deformation of appearance in the container manufactured using the packaging material of Manufacturing Example 1 according to the present invention.

[0124]

[0125] [Test Example 3] Pollution Resistance Evaluation

[0126] Containers were formed using the packaging material of Manufacturing Example 1 coated with the coating composition of Example 1 according to the present invention, and the packaging material of Comparative Manufacturing Example 2 coated with a conventional polyolefin resin, and their contamination resistance was evaluated assuming a food-eating situation. Specifically, food contained in each container was cooked in a microwave for 2 to 5 minutes and left at room temperature for 1 hour, after which the food was emptied and each container was lightly washed in running water. Then, the contamination level of each container was checked, and the results are shown in Fig. 3 (A: packaging material of Comparative Manufacturing Example 2, B: packaging material of Manufacturing Example 1).

[0127] Referring to Fig. 3, when the bottom part of each container was partially cut and checked through visual evaluation and YI measurement indicators, it was confirmed that the container manufactured using the packaging material of Manufacturing Example 1 according to the present invention showed little discoloration due to food and was cleanly washed, showing excellent contamination resistance.

[0128]

[0129] [Test Example 4] Recyclability Evaluation

[0130] In order to confirm that the packaging material of Manufacturing Example 1 coated with the coating composition of Example 1 according to the present invention is superior to the packaging material of Comparative Manufacturing Example 2 coated with a conventional polyolefin resin in terms of recyclability in addition to improved composting performance, recyclability was evaluated. Specifically, each packaging material was requested to a domestic paper recyclability testing agency to evaluate recyclability (reference standard: recyclability analysis method UL2485 / dissociation stage TAPPI205, screen stage TAPPI 275). As a result, the rejection rate was confirmed to be 24.15% for the packaging material (B) of Manufacturing Example 1 and 36.92% for the packaging material (A) of Comparative Manufacturing Example 2. In addition, the pulp recovery rate (base layer recovery rate) was confirmed to be about 98% for the packaging material (B) of Manufacturing Example 1 and about 67% for the packaging material (A) of Comparative Manufacturing Example 2 (see FIG. 4).

[0131]

[0132] [Test Example 5] Processability Evaluation

[0133] The processability of the coating compositions prepared in Examples 1 and 4 was evaluated by visually checking the apparent flowability of the coating compositions when melt-extruding them at a temperature of 170 to 190°C at a speed of 60 m / min using a single screw pilot extruder on a paper substrate, and the results are shown in Table 3 below.

[0134] Stability: When the coating composition flows evenly and coats the paper substrate without any bending.

[0135] Somewhat stable: When the coating composition flows and coats the paper substrate with a slight curve.

[0136] Instability: When the coating composition flows and coats the paper substrate in a severely curved state.

[0137]

[0138] Example 1 Example 4 2nd PLA MI (210 ℃ / 2.16 kg) 88 Processability Stability Stability

[0139] Referring to Table 3 above, it can be confirmed that the coating compositions of Examples 1 and 4 according to the present invention have excellent processability (coating properties).

[0140]

[0141] [Test Example 6] Thickness Deviation Measurement

[0142] The thickness deviation of the packaging materials manufactured in Manufacturing Examples 1 to 4 was measured using a measurement method using a thickness gauge for film (Mitutoyo) and a basis weight measurement method for paper packaging materials, and the results are shown in Table 4 below. In the basis weight measurement method, samples were cut into 100 mm length and width, and the weight was measured after pretreatment for more than 24 hours in an environment of 23°C and 50% RH.

[0143]

[0144] Manufacturing Example 1 (Example 1) Manufacturing Example 2 (Example 2) Manufacturing Example 3 (Example 3) Manufacturing Example 4 (Example 4) Thickness standard deviation (weight change) 1.42.01.32.1

[0145] Referring to Table 4 above, it can be confirmed that the coating compositions of Examples 1 to 4 according to the present invention have excellent processability (coating properties), and thus, packaging materials can be manufactured with almost no thickness deviation.

Claims

1. A coating composition comprising polyhydroxyalkanoate (PHA); and two or more types of polylactic acid (PLA).

2. In paragraph 1, A coating composition, wherein the polyhydroxyalkanoate comprises 0.1 to 60 wt% of a repeating unit derived from 4-hydroxybutyrate (4HB) based on the total weight of the polyhydroxyalkanoate.

3. In paragraph 1, A coating composition comprising the polylactic acid, a first polylactic acid, and a second polylactic acid having a different melting index (MI) from the first polylactic acid.

4. In paragraph 3, A coating composition wherein the melting index (MI) of the first polylactic acid is 40 g / 10 min to 70 g / 10 min, and the melting index (MI) of the second polylactic acid is 1 g / 10 min to 30 g / 10 min.

5. In paragraph 3, Based on the total weight of the mixed resin in which the above polyhydroxyalkanoate and the above polylactic acid are mixed, A coating composition wherein the content of the polyhydroxyalkanoate is 5 wt% to 65 wt%, the content of the first polylactic acid is 30 wt% to 75 wt%, and the content of the second polylactic acid is 5 wt% to 20 wt%.

6. In paragraph 1, Based on the total weight of the mixed resin in which the above polyhydroxyalkanoate and the above polylactic acid are mixed, A coating composition wherein the content of the polyhydroxyalkanoate is 5 wt% to 65 wt% and the content of the polylactic acid is 35 wt% to 95 wt%.

7. In paragraph 1, The above polyhydroxyalkanoate has a weight average molecular weight (Mw) of 100,000 g / mol to 1,000,000 g / mol and a melting temperature (T m ) is 120 ℃ to 200 ℃, and the heat distortion temperature (T d ) is 200 ℃ or higher, coating composition.

8. In paragraph 1, A coating composition further comprising a chain extender.

9. A substrate layer including paper; and Including a coating layer provided on the above substrate layer, A packaging material, wherein the coating layer is formed from a coating composition according to any one of claims 1 to 8.

10. In paragraph 9, The above packaging material is a packaging material having a recovery rate of 70% or more of the base layer in a recyclability evaluation based on UL2485.

11. Step of preparing a substrate including paper; and A method for manufacturing a packaging material, comprising a step of forming a substrate layer and a coating layer by melt-extruding a coating composition according to any one of claims 1 to 8 on the substrate.

Images