Bioplastics with improved heat resistance and Manufacturing method thereof

Abstract

The present invention relates to a bioplastic with improved heat resistance and a method for manufacturing the same. By using an aqueous acetic acid solution and an aqueous citric acid solution, either individually or in combination, to dissolve starch for the production of starch-based plastics, the invention identifies novel combination effects resulting from chemical interactions, thereby providing a method for manufacturing bioplastics with improved water resistance, durability, and heat resistance. Furthermore, the present invention provides a bioplastic possessing both eco-friendly characteristics and excellent physical performance by optimizing the components of the starch plastic, the components of the coating solution, the number of coatings, and the amount of coating sprayed.

Description

Technology Field

[0001] The present invention relates to a bioplastic with improved heat resistance and a method for manufacturing the same, and more specifically, to a bioplastic characterized by being environmentally friendly while having improved water resistance, durability, and heat resistance, and a method for manufacturing the same. Background Technology

[0003] As many people become aware that plastic materials are a cause of environmental pollution, consumer demand for eco-friendly alternatives is increasing. In other words, unlike conventional plastics that require landfilling or incineration, biodegradable plastics are environmentally friendly and offer the advantage of sustainability.

[0004] However, conventional biodegradable plastics such as PLA (Poly-Lactic Acid) and PGA (Polyglycolic Acid), while possessing excellent biodegradability, have the disadvantage of weak physical properties such as water resistance, heat resistance, and impact resistance. Accordingly, as seen in prior art literature, technologies regarding environmentally friendly and functionally superior bioplastics have been researched, including bioplastics utilizing chitosan and bioplastics utilizing cuticle layers. In the case of these chitosan-based bioplastics, while water resistance is improved, there is still a possibility of performance degradation under extreme conditions (e.g., high humidity, immersion). Furthermore, cuticle components are sensitive to heat and solvents, raising concerns that mixing them with thermoplastics may be difficult or lead to performance degradation. As such, the practical application of bioplastics still entails many technical challenges, and the technical task remains to strike a balance across various aspects, including economic feasibility, physical performance, mass production efficiency, and durability.

[0005] To solve these problems, the present invention focuses on improving the water resistance, durability, and heat resistance of bioplastics. In particular, the present invention was completed by developing a technology for a method of manufacturing bioplastics that effectively maintains stable physical properties even in high-temperature environments, compared to existing biodegradable plastics (PLA, PBAT, PHA, PBS, etc.). Prior art literature

[0007] Korean Patent Publication No. 10-1996-0022569 (Published July 18, 1996) Method for separating and extracting chitin using crab shells

[0008] Bae So-hyun et al., Production and Application of Eco-friendly Water-Repellent Spray Using Cuticle Extract, 2021. The problem to be solved

[0009] The present invention relates to a bioplastic and a method for manufacturing the same, characterized by improved water resistance, durability, and heat resistance by identifying a new combination effect resulting from chemical interactions when using an aqueous acetic acid solution and an aqueous citric acid solution, respectively or in combination, to dissolve starch for the manufacture of starch-based plastic, as a solution to the problems described above.

[0010] In addition, the present invention aims to provide a bioplastic that simultaneously possesses eco-friendly characteristics and excellent physical performance by optimizing the components of the starch plastic, the components of the coating solution, the number of coatings, and the amount of coating sprayed. means of solving the problem

[0012] To solve the above problem, the present invention provides a method for manufacturing a bioplastic with improved heat resistance, characterized by comprising the steps of: (S100) preparing a starch-based mixture by mixing starch, glycerin, an aqueous solution of acetic acid or an aqueous solution of citric acid; (S200) manufacturing a starch plastic by heating and drying the starch-based mixture; and (S300) coating the starch plastic with a coating solution in which chitosan is dissolved.

[0013] The starch-based mixture may comprise 30 to 70 parts by weight of glycerin and 300 to 500 parts by weight of the aqueous acetic acid solution or aqueous citric acid solution, based on 100 parts by weight of the starch.

[0014] The above aqueous acetic acid solution or aqueous citric acid solution may each have a concentration of 3 to 7 wt.%.

[0015] The weight ratio of the aqueous acetic acid solution and the aqueous citric acid solution may be 1:0.5 to 2.0.

[0016] In the above coating step, the coating solution may be one in which the chitosan is dissolved in an aqueous acetic acid solution at a concentration of 0.9 to 1.1 wt.%.

[0017] In the above coating step, the number of times the coating solution is coated may be 1 to 6 times.

[0018] The spray amount of the coating solution is 0.01 to 0.1 mL / cm² relative to the starch plastic. 2 It could be.

[0019] To achieve the above objective, the present invention provides a bioplastic with improved heat resistance characterized by being manufactured by the above manufacturing method as a means of solving the problem. Effects of the invention

[0021] The present invention provides a method for manufacturing bioplastics with improved water resistance, durability, and heat resistance by identifying novel combination effects resulting from chemical interactions when using an aqueous acetic acid solution and an aqueous citric acid solution, respectively or in combination, to dissolve starch for the production of starch-based plastics.

[0022] In addition, the present invention has the effect of providing a bioplastic that simultaneously possesses eco-friendly characteristics and excellent physical performance by optimizing the components of the starch plastic, the components of the coating solution, the number of coatings, and the amount of coating sprayed.

[0023] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0025] FIG. 1 is a process block diagram illustrating a method for manufacturing a bioplastic with improved heat resistance according to a preferred embodiment of the present invention. FIG. 2 is an experimental photograph illustrating the steps of preparing a starch-based mixture and manufacturing a starch plastic according to a preferred embodiment of the present invention. Figure 3 is an experimental photograph illustrating the preparation of a coating solution in which the cuticle is dissolved according to a preferred embodiment of the present invention. Figure 4 is an experimental photograph illustrating the preparation of a coating solution in which chitosan is dissolved according to a preferred embodiment of the present invention. Figure 5 is a graph showing the tensile strength of a starch plastic manufactured according to a preferred embodiment of the present invention. Figure 6 is an image of a starch plastic manufactured according to a preferred embodiment of the present invention, taken using an optical microscope. FIG. 7 is a graph showing the results of Differential Scanning Calorimetry (DSC) measurements according to preferred embodiments 1 and 2 of the present invention. FIG. 8 is a graph showing the results of Differential Scanning Calorimetry (DSC) measurements according to preferred embodiments 1 and 2 of the present invention. Specific details for implementing the invention

[0026] The present invention will be described in detail below according to preferred embodiments with reference to the attached drawings, but specific descriptions of configurations and operations that are readily known to those skilled in the art will be omitted. Furthermore, it should be noted that the present invention is not necessarily limited by the following embodiments, and that those skilled in the art can make various modifications to the invention within the scope of the technical concept of the invention without departing from it.

[0028] The terms used in this specification have been selected based on currently widely used general terms whenever possible, taking into account their functions in the present invention; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, terms have been arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should be defined not merely by their names, but based on their meanings and the overall content of the invention.

[0030] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0032] Numerical ranges include the values ​​defined in the above ranges. All maximum numerical limits given throughout this specification include all lower numerical limits as clearly written. All minimum numerical limits given throughout this specification include all higher numerical limits as clearly written. All numerical limits given throughout this specification will include all better numerical ranges within a wider numerical range, as clearly written.

[0034] Hereinafter, a method for manufacturing a bioplastic with improved heat resistance according to a preferred embodiment of the present invention (hereinafter referred to as the "method for manufacturing a bioplastic") will be described with reference to the attached Drawing 1.

[0036] For reference, FIG. 1, which is attached to this specification, is a process block diagram for explaining a method for manufacturing a bioplastic with improved heat resistance according to a preferred embodiment of the present invention.

[0038] A method for manufacturing a bioplastic according to a preferred embodiment of the present invention may include: (S100) a step of preparing a starch-based mixture by mixing starch, glycerin, an aqueous solution of acetic acid or an aqueous solution of citric acid; (S200) a step of manufacturing a starch plastic by heating and drying the starch-based mixture; and (S300) a step of coating the starch plastic with a coating solution in which chitosan is dissolved.

[0040] For reference, FIG. 2, which is attached to this specification, is an experimental photograph illustrating the steps of preparing the starch-based mixture and manufacturing the starch plastic according to a preferred embodiment of the present invention.

[0042] First, the present invention may include the step (S100) of preparing a starch-based mixture by mixing starch, glycerin, an aqueous solution of acetic acid or an aqueous solution of citric acid.

[0043] This step involves preparing a mixture using starch, which is a biodegradable material. The starch may be selected from the group consisting of tapioca starch, corn starch, potato starch, sweet potato starch, rice starch, wheat starch, and mung bean starch.

[0044] Specifically, the starch-based mixture may comprise 30 to 70 parts by weight of glycerin and 300 to 500 parts by weight of the aqueous acetic acid solution or aqueous citric acid solution per 100 parts by weight of the starch. More preferably, it may comprise 40 to 60 parts by weight of glycerin and 300 to 500 parts by weight of the aqueous acetic acid solution or aqueous citric acid solution per 100 parts by weight of the starch.

[0045] The concentration of the above aqueous acetic acid solution may be 3 to 7 wt.%.

[0046] The concentration of the above aqueous citric acid solution may be 3 to 7 wt.%.

[0047] When the above starch-based mixture includes an aqueous acetic acid solution and an aqueous citric acid solution, the weight ratio of the aqueous acetic acid solution and the aqueous citric acid solution may be 1:0.5 to 2.0.

[0049] Meanwhile, the starch-based mixture according to the present invention is characterized by the technical feature of including the aqueous acetic acid solution or the aqueous citric acid solution.

[0050] The acetic acid mentioned above forms weak hydrogen bonds with the hydroxyl groups (-OH) of starch, thereby inhibiting direct bonding with water and consequently improving water resistance. Additionally, the carboxyl groups (-COOH) of citric acid inhibit the molecular mobility of starch by forming strong hydrogen bonds with the hydroxyl groups (-OH) of starch, which prevents decomposition by heat—in other words, improves thermal stability.

[0051] However, when an aqueous acetic acid solution and an aqueous citric acid solution are used together, as shown in Figure 2, a pattern of water droplet spreading can be observed regardless of the number of coatings, which means that water resistance is reduced. That is, when the aqueous acetic acid solution and the aqueous citric acid solution are used separately, the plastic has effects such as water resistance or heat resistance due to interaction with starch, whereas when the aqueous acetic acid solution and the aqueous citric acid solution are used together, the two components exhibit a new combination effect through chemical interaction, which may strengthen or weaken the effects such as water resistance and heat resistance.

[0052] As such, the present invention is characterized by the technical feature of optimizing the concentrations and mixing ratios of the aqueous acetic acid solution and the aqueous citric acid solution by identifying new combination effects resulting from chemical interactions when using the aqueous acetic acid solution and the aqueous citric acid solution separately or in combination to dissolve starch.

[0054] Next, (S200) may include the step of manufacturing starch plastic by heating and drying the starch-based mixture.

[0055] Specifically, the starch-based mixture may be heated at 180 to 220°C while stirring for 15 to 25 minutes. Subsequently, the heated mixture may be poured onto an acrylic plate, spread widely to a certain thickness, and then dried at 1 to 35°C for 40 to 56 hours to produce a starch plastic.

[0056] At this time, the above-mentioned constant thickness may vary depending on the concentration of the starch-based mixture, but is preferably 0.05 to 0.17 cm. However, it may be adjusted according to the intended use of the bioplastic to be finally manufactured.

[0058] Next, (S300) the step of coating the starch plastic with a coating solution in which chitosan is dissolved may be included.

[0059] The above chitosan may be obtained from chitin through a deacetylation process. Generally, chitin is a polymer abundant in the shells of crustaceans, insects, etc., and may be extracted by a known chemical treatment method. For example, the chemical treatment method may involve crushing the shells of crustaceans (e.g., crabs, lobsters, shrimp, etc.) to deash them (Step 1), followed by deproteinization (Step 2) and decolorization (Step 3) to extract chitin. Using such decolorized chitin has the effect of increasing the utility of the final bioplastic product. Subsequently, the decolorized chitin may be dissolved in an aqueous NaOH solution at a concentration of 5 to 15 g / L, stirred at 100 to 140°C for 1 to 3 hours, cooled at room temperature, and washed with distilled water to obtain a chitin residue. At this time, the concentration of the above NaOH aqueous solution may be 49 to 51 wt.%.

[0061] Meanwhile, the above-mentioned chitin possesses some hydrophilicity, whereas due to the hydrophobicity of the acetyl group, it has the characteristic of being almost insoluble in common solvents such as water, ethanol, and acetone. Accordingly, the present invention is characterized by using chitosan obtained through a deacetylation process from the above-mentioned chitin.

[0062] The coating solution according to the present invention may be prepared by dissolving the chitosan in an aqueous acetic acid solution at a concentration of 0.9 to 1.1 wt.%. At this time, the aqueous acetic acid solution may have a concentration of 1 to 3 wt.%. Through this, the amino group (-NH2) of the decolorized chitin becomes a cationic amino group (-NH3 + It is converted into ) and not only dissolves easily in aqueous solution, but these cationic properties also have the effect of strengthening the bonding force with the plastic surface.

[0063] The chitosan according to the present invention may be used in which the degree to which acetyl groups are removed from chitin, that is, the deacetylation ratio, is 50 to 85%, and more preferably in which it is 70 to 85%. Generally, it is known that the higher the deacetylation ratio, the greater the water solubility of chitosan and thus the greater the solubility in an aqueous solution. However, if chitosan deacetylated beyond the above range is used, the proportion of amino groups increases, which strengthens hydrogen bonding and intermolecular interactions, making it difficult to prepare a uniform coating solution.

[0064] The above dissolution may be performed by stirring at 110 to 130°C for 1 to 3 hours.

[0066] In this step, the number of coatings of the coating solution may be 1 to 6 times. More preferably, it may be 1 to 4 times, and most preferably 3 times.

[0067] The spray amount of the coating solution is 0.01 to 0.1 mL / cm² relative to the starch plastic. 2 It may be, and more preferably 0.03 to 0.05 mL / cm with respect to the starch plastic. 2 It may be, and most preferably 0.03 to 0.04 mL / cm² with respect to the starch plastic. 2 It could be.

[0069] The above-mentioned coated starch plastic may further include a step of drying at 50 to 70°C for 20 to 40 minutes.

[0070] If the above coating is repeated several times, the above drying step can also be performed repeatedly.

[0072] Through this, the present invention provides a bioplastic with improved heat resistance characterized by being manufactured by the above-described manufacturing method.

[0073] In one embodiment of the present invention, the bioplastic can be used as surgical sutures. Since the surgical sutures must maintain a sterile state through high-temperature sterilization (e.g., 121–134°C, autoclave), they require heat resistance, but at the same time, they need the characteristic of biodegrading after a certain period of time following surgery. Accordingly, the heat-resistant bioplastic of the present invention can be utilized.

[0074] In one embodiment of the present invention, when the bioplastic is used as a fertilizer packaging material, it is possible to prevent the deterioration of the fertilizer's quality in environments exposed to high temperatures (temperatures inside warehouses or transport vehicles in summer) during storage and transportation, and it has the effect of naturally decomposing after use.

[0075] In one embodiment of the present invention, the bioplastic is safe to hold hot food and does not deform, so it can be used as a food packaging material, and furthermore, it can be utilized in automotive parts, exterior materials for electronic products, etc., that require durability and heat resistance.

[0077] Hereinafter, the bioplastic according to the present invention and the method for manufacturing the same will be specifically described through the following embodiments, and the present invention is not necessarily limited only to the following embodiments.

[0079] 1. Preparation of coating solution

[0080] 1-1. Preparation of a coating solution in which the cuticle is dissolved

[0081] 75 parts by weight of cellulase and 5,000 parts by weight of 99.9% ethanol were added to 100 parts by weight of finely chopped camellia leaves in an Erlenmeyer flask and stirred on a hot plate at 25°C for 1 hour, then left at room temperature for 24 hours. 45 ml of the solution was placed into centrifuge tubes and centrifuged at 4,000 rpm for 30 minutes at 20°C. The supernatant of the centrifuged solution was separated to prepare a cuticle-dissolved coating solution. For reference, Figure 3 is an experimental photograph illustrating the preparation of the cuticle-dissolved coating solution.

[0083] 1-2. Preparation of coating solution containing dissolved chitosan

[0084] Crab shells were crushed and filtered through a 20 mesh sieve, then mixed with 1N HCl to a concentration of 66.6 g / L. The mixture was stirred for 30 minutes and then washed with distilled water to deash the residue (Step 1). After filtration, 5 wt.% NaOH was added to the dried residue to a concentration of 66.6 g / L, stirred at 65°C for 1 hour, and then subjected to the same washing process as the previous step, thereby deproteinizing the residue (Step 2). The residue from the previous step was treated with a 0.32 wt.% NaOCl solution for 3 minutes to a concentration of 100 g / L to extract the whitened chitin (Step 3). The extracted chitin was dissolved in a 50 wt.% NaOH aqueous solution to a concentration of 10 g / L, stirred at 120°C for 2 hours, cooled to room temperature, and washed with distilled water to obtain the chitin residue. The above chitin residue was dissolved in 2 wt.% acetic acid at a concentration of 1.0 wt.%. The dissolution was performed by stirring at 120°C for 2 hours. Through this, a coating solution containing dissolved chitosan was prepared. For reference, Figure 4 is an experimental photograph illustrating the preparation of the coating solution containing dissolved chitosan.

[0086] 2. Manufacture of starch plastic

[0087] 2-1. Starch plastic containing aqueous acetic acid solution

[0088] 400 parts by weight of a 5 wt.% aqueous acetic acid solution and glycerin (300, 400, 500, 600, 700 parts by weight) were added to 100 parts by weight of tapioca starch. A starch-based mixture was prepared by heating the mixture on a hot plate at 200°C for 20 minutes while stirring until viscosity was achieved. The starch-based mixture was poured onto an acrylic plate, spread to a thickness of 0.1 cm, and dried at room temperature for 48 hours to produce starch plastic.

[0090] 2-2. Starch plastic containing aqueous acetic acid solution and aqueous citric acid solution

[0091] The process was carried out in the same manner as described in '2-1. Preparation of coating solution using aqueous acetic acid solution' above, but 200 parts by weight of a 5 wt.% aqueous acetic acid solution, 200 parts by weight of a 5 wt.% aqueous citric acid solution, and 500 parts by weight of glycerin were added to 100 parts by weight of tapioca starch. A starch plastic was prepared by proceeding in the same manner otherwise.

[0093] 3. Manufacture of Coated Bioplastics

[0094] <Example 1.>

[0095] A starch plastic prepared by the method of '2-1. Starch plastic containing an aqueous acetic acid solution' above was used, wherein 400 parts by weight of a 5 wt.% aqueous acetic acid solution and 500 parts by weight of glycerin were added to 100 parts by weight of tapioca starch.

[0096] The above starch plastic was coated repeatedly 0 to 6 times with the above '1-2. Coating solution dissolved in chitosan'. At this time, 0.036 mL / cm² per application. 2 It was sprayed with a spray amount, and for each coating, the starch plastic was dried in a 60℃ oven for 30 minutes.

[0098] <Example 2.>

[0099] The procedure was carried out in the same manner as in Example 1 above, but a starch plastic prepared by the method of 'starch plastic containing an aqueous acetic acid solution and an aqueous citric acid solution' was used.

[0101] <Comparative Example 1.>

[0102] The procedure was carried out in the same manner as in Example 1 above, but the starch plastic was coated 0 to 6 times repeatedly with the '1-1. Coating solution in which cuticle is dissolved'.

[0104] 4. Evaluation of Starch Plastics

[0105] 4-1. Evaluation of Starch Plastics According to Glycerin Content

[0106] To measure the tensile strength of starch plastics according to glycerin content, the tensile strength of the above '2-1. Starch plastic containing acetic acid aqueous solution' was analyzed. Five commercially available samples of 10mm × 50mm size were extracted from each plastic, and the results were analyzed using the average Max Stress (MPa) value, using a UTM instrument.

[0107] As a result, as shown in Figure 5, it can be seen that the tensile strength decreases as the glycerin content increases. That is, it was confirmed that the tensile strength of the starch plastic containing 300 parts by weight of glycerin per 100 parts by weight of tapioca starch was the best. However, in the case of the starch plastic containing 300 to 400 parts by weight of glycerin per 100 parts by weight of tapioca starch, cracking of the material was observed during the drying process due to high hardness. Therefore, it was determined that the starch plastic containing 300 to 400 parts by weight of glycerin would be difficult to use for general purposes, and thus the mechanical properties of the starch plastic containing 500 parts by weight of glycerin were determined to be the best.

[0109] 4-2. Evaluation of Starch Plastics According to the Type of Coating Solution

[0110] In order to measure the water resistance of starch plastics according to the type of coating solution, the degree of improvement in water resistance according to the number of coatings was analyzed for Example 1 and Comparative Example 1, respectively. At this time, an optical microscope was used to confirm the uniformity of the coating, and a contact angle meter was used to analyze the degree of improvement in water resistance according to the number of coatings.

[0111] First, the coating solution for Example 1 and Comparative Example 1 was sprayed once, twice, and three times, respectively, and the uniformity of the coating was analyzed using an optical microscope. As shown in Figure 6, it was observed that white areas were evenly distributed when the coating solution was sprayed once, twice, and three times, respectively, for Example 1 and Comparative Example 1, which means that the coating solution particles are uniformly arranged. In addition, it was found that the proportion of white areas increased compared to black areas as the number of coatings increased. Based on this fact, it is believed that the coating effect can be enhanced by applying the coating multiple times.

[0112] In addition, as a result of analyzing the degree of improvement in water resistance according to the number of coatings using a contact angle measuring instrument, as shown in Table 1 below, the contact angles of Comparative Example 1 were 18.17, 23.93, and 36.92 for the first, second, and third coatings, respectively, and the contact angles of Example 1 were 23.3, 37.35, and 41.19. That is, since the contact angle increases as the number of coatings increases for both Example 1 and Comparative Example 1, it can be seen that water resistance is proportional to the number of coatings. However, when comparing the contact angle of the uncoated product (16.18) with the contact angle after a single coating, the contact angle of the cuticle-coated Comparative Example 1 does not show a significant difference, so it can be concluded that the starch plastic of Example 1 has better water resistance. Finally, it was concluded that the product with the best product quality was a starch plastic containing 500 parts by weight of glycerin per 100 parts by weight of tapioca starch, coated with a chitosan coating solution three times.

[0113] Comparative Example 1 Example 1 Number of coatings 0 coatings 1 coat 2 coats 3 coats 1 coat 2 coats 3 coats contact angle 16.18° 18.17° 23.93° 36.92° 23.30° 37.35° 41.19°

[0115] 4-3. Evaluation of Starch Plastics According to Type

[0116] To compare the heat resistance of the bioplastics of Example 1 and Example 2 above, bioplastics coated with the '1-2. Coating Solution Dissolved in Chitosan' 0, 3, and 6 times, respectively, were measured using Differential Scanning Calorimetry (DSC). As a result, as shown in Fig. 7, it was found that the bioplastic of Example 2 has a lower glass transition temperature (Tg) and a higher melting point (Tm). Through this, it was confirmed that the starch plastic containing acetic acid and citric acid of Example 2 has superior heat resistance compared to the starch plastic containing only acetic acid. For reference, Figs. 7 and 8 are graphs showing the results of Differential Scanning Calorimetry (DSC) measurements according to Example 2 of the present invention and Example 1, which is a counterpart thereof.

[0117] Furthermore, the tensile strength was measured using a UTM instrument to assess the durability of the starch plastics of Examples 1 and 2, and the results are shown in Table 2 below. It was determined that the tensile strength of the starch plastic treated with three coatings in Example 1 was the best, while it was found that there was no significant difference when compared to the results of Example 2. In other words, it was found that the mixing of the aqueous citric acid solution was unrelated to the improvement of durability.

[0118] Example 1 Example 2 Number of coatings 0 coatings 3 coats 6 coats 0 coatings 3 coats 6 coats tensile strength 0.0028 0.0133 0.0031 0.0017 0.0130 0.0034

[0120] Although a heat-resistant bioplastic and a method for manufacturing the same according to a preferred embodiment of the present invention have been described as above, this is merely for illustrative purposes, and those skilled in the art will understand that various changes and modifications are possible within the scope of the technical spirit of the present invention.

Claims

Claim 1 (S100) a step of preparing a starch-based mixture by mixing starch, glycerin, an aqueous solution of acetic acid or an aqueous solution of citric acid; (S200) a step of manufacturing a starch plastic by heating and drying the starch-based mixture; and (S300) a step of coating the starch plastic with a coating solution in which chitosan is dissolved, characterized by comprising a method for manufacturing a bioplastic with improved heat resistance. Claim 2 A method for manufacturing a heat-resistant bioplastic according to claim 1, wherein the starch-based mixture comprises 30 to 70 parts by weight of glycerin and 300 to 500 parts by weight of the aqueous acetic acid solution or aqueous citric acid solution, based on 100 parts by weight of the starch. Claim 3 A method for manufacturing a heat-resistant bioplastic according to claim 1, characterized in that the aqueous acetic acid solution or the aqueous citric acid solution each has a concentration of 3 to 7 wt.%. Claim 4 A method for manufacturing a heat-resistant bioplastic, characterized in that, in claim 1, the weight ratio of the aqueous acetic acid solution and the aqueous citric acid solution is 1:0.5 to 2.

0. Claim 5 A method for manufacturing a heat-resistant bioplastic according to claim 1, wherein, in the coating step, the coating solution is characterized in that the chitosan is dissolved in an aqueous acetic acid solution at a concentration of 0.9 to 1.1 wt.%. Claim 6 A method for manufacturing a heat-resistant bioplastic, characterized in that, in the coating step of claim 1, the number of coatings of the coating solution is 1 to 6 times. Claim 7 In claim 1, in the coating step, the spray amount of the coating solution is 0.01 to 0.1 mL / cm² relative to the starch plastic. 2 A method for manufacturing heat-resistant bioplastic characterized by Claim 8 A heat-resistant bioplastic characterized by being manufactured by the manufacturing method of claim 1

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