Method for improving biodegradation rate of biodegradable plastic

Abstract

The present invention relates to a method for improving the biodegradation rate of a biodegradable plastic. The method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention comprises: a step (S100) of preparing a depolymerization solution by mixing alcohol and hydroxide; and a step (S200) of applying the depolymerization solution to a biodegradable plastic.

Description

Method to increase the biodegradation rate of biodegradable plastics

[0001] The present invention relates to a method for improving the biodegradation rate of biodegradable plastics, and more specifically, to a method for increasing the biodegradation rate of biodegradable plastics through pretreatment.

[0002]

[0003] Plastics are widely used in various fields due to their economic advantages and excellent properties, such as physical strength and permeability, and their usage is increasing significantly every year. However, as environmental problems caused by waste plastics and microplastics have emerged globally, research has been conducted to replace or recycle conventional plastics. As a result, various types of biodegradable plastics have been developed. Biodegradable plastics are materials that can be completely decomposed into water, carbon dioxide, and humus by bacteria, algae, and fungi found in nature under specific conditions, and are manufactured from various raw materials (biomass or fossil fuel-based compounds). Examples of such biodegradable plastics include polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS). Furthermore, biodegradable plastics can be converted into eco-friendly energy through the biogas generated during fermentation.

[0004] However, even biodegradable plastics take months to years to decompose, and since the rate of decomposition is slower depending on the environment, there are still limitations to using biodegradable plastics for solving environmental problems and generating eco-friendly energy.

[0005] Accordingly, there is an urgent need for a method to solve the problem of the biodegradation rate of conventional biodegradable plastics.

[0006]

[0007] The present invention aims to solve the problems of the aforementioned prior art, and one aspect of the present invention is to provide a method for improving the biodegradation rate of biodegradable plastics through a base-catalyzed hydrolysis reaction and an ester exchange reaction.

[0008] In addition, another aspect of the present invention aims to provide a method for producing eco-friendly biogas by introducing a biodegradable plastic, which has been pretreated as a method to increase the biodegradation rate of the biodegradable plastic, into an anaerobic digestion process.

[0009]

[0010] A method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention comprises: (a) a step of preparing a depolymerization solution by mixing an alcohol and a hydroxide; and (b) a step of applying the depolymerization solution to the biodegradable plastic.

[0011] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, the alcohol may include a straight-chain C1-C4 alcohol.

[0012] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, the hydroxide may include one or more selected from the group consisting of alkali metal hydroxide, alkaline earth metal hydroxide, and ammonium hydroxide.

[0013] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, the alkali metal hydroxide may include one or more selected from the group consisting of potassium hydroxide and sodium hydroxide.

[0014] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, the concentration of the depolymerization solution may be 0.05M to 1M.

[0015] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, in step (b), the depolymerization solution and the biodegradable plastic may be mixed and heat-treated at a predetermined temperature.

[0016] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, (c) the biodegradable plastic coated with the depolymerization solution can be heat-treated at a predetermined temperature.

[0017] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, the predetermined temperature may be 40℃ to 90℃.

[0018] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, in step (b), the depolymerization solution and the biodegradable plastic can be mixed using a screw.

[0019] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, in step (c), the biodegradable plastic coated with the depolymerization solution can be introduced into a heating chamber capable of controlling the internal temperature and heat-treated.

[0020] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, the biodegradable plastic coated with the depolymerization solution can be heat-treated using a microwave.

[0021] In addition, in the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, the biodegradable plastic may be a biodegradable plastic having an ester functional group.

[0022] Meanwhile, a biogas production method according to an embodiment of the present invention includes the step of anaerobic digestion of the biodegradable plastic coated with the depolymerization solution.

[0023] In addition, in the biogas production method according to an embodiment of the present invention, prior to the anaerobic digestion step, the depolymerization solution and the biodegradable plastic may be mixed and heat-treated at a predetermined temperature.

[0024] In addition, the biogas production method according to an embodiment of the present invention may further include a step of heat-treating the biodegradable plastic coated with the depolymerization solution at a predetermined temperature prior to the anaerobic digestion step.

[0025]

[0026] The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

[0027] Prior to this, terms and words used in this specification and claims shall not be interpreted in their ordinary and dictionary meanings, but must be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor may appropriately define the concept of the terms to best describe his invention.

[0028]

[0029] According to the present invention, by pre-treating biodegradable plastics using a depolymerization solution, it is expected that the biodegradation efficiency of biodegradable plastics can be improved in actual usage environments. In addition, the problem of ecosystem pollution caused by microplastics can be solved, and volume-based food waste bags or garbage bags made of biodegradable plastics can be treated together with food or waste through anaerobic digestion without being separated.

[0030] Furthermore, biodegradable plastics pretreated with a depolymerization solution can be fed into an anaerobic digestion process to produce eco-friendly biogas.

[0031]

[0032] FIG. 1 is a flowchart of a method for improving the biodegradation rate of biodegradable plastics according to an embodiment of the present invention.

[0033] FIG. 2 is a schematic diagram illustrating an apparatus for performing a method to improve the biodegradation rate of biodegradable plastics according to an embodiment of the present invention.

[0034] Figure 3 is a drawing showing a stirring screw used in the depolymerization solution application step illustrated in Figure 1.

[0035] FIG. 4 is a flowchart of a method for improving the biodegradation rate of biodegradable plastics according to another embodiment of the present invention.

[0036] FIGS. 5 and 6 are flowcharts of a biogas production method according to an embodiment of the present invention.

[0037] FIG. 7 is a flowchart of a biogas production method according to another embodiment of the present invention.

[0038] Figure 8 shows the depolymerization effect on the PBAT film according to Experimental Example 1.

[0039] Figure 9 shows the depolymerization effect on the PBS film according to Experimental Example 1.

[0040] Figure 10 shows the depolymerization effect on PBAT films according to the number of pretreatments in Experimental Example 2.

[0041] Figure 11 shows the depolymerization effect on PBAT films according to the amount of depolymerization solution sprayed according to Experimental Example 3.

[0042] Figure 12 shows the depolymerization effect on various mulch films according to Experimental Example 4.

[0043] FIGS. 13 and 14 show the depolymerization effect on various mulch films according to Experimental Example 5.

[0044] Figures 15 to 18 show the biodegradation enhancement effect of the depolymerization pretreatment according to Experimental Example 6.

[0045]

[0046] The objects, specific advantages, and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings. In describing the present invention below, detailed descriptions of related prior art that could unnecessarily obscure the essence of the invention are omitted.

[0047] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0048]

[0049] FIG. 1 is a flowchart of a method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an apparatus for performing the method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention, and FIG. 3 is a diagram of a stirring screw used in the depolymerization solution application step shown in FIG. 1.

[0050] As illustrated in FIGS. 1 and 2, a method for improving the biodegradation rate of a biodegradable plastic according to an embodiment of the present invention includes the step of preparing a depolymerization solution by mixing an alcohol and a hydroxide (S100), and the step of applying the depolymerization solution to the biodegradable plastic (S200).

[0051]

[0052] The present invention relates to a method for increasing the biodegradation rate of biodegradable plastics through pretreatment. Although biodegradable plastics have been developed that can be completely decomposed into water, carbon dioxide, and humus by bacteria, algae, and fungi existing in nature under certain conditions, there is a problem in that it takes several months to several years for even biodegradable plastics to decompose. The present invention has been devised as a method to solve this problem.

[0053] Specifically, the method for improving the biodegradation rate of a biodegradable plastic according to the present invention includes a step of preparing a depolymerization solution (S100) and a step of applying a depolymerization solution (S200).

[0054]

[0055] The depolymerization solution preparation step (S100) is a process for preparing a depolymerization solution capable of thermochemically depolymerizing biodegradable plastics using a base-catalyzed hydrolysis reaction and an ester exchange reaction. The depolymerization solution can be prepared by mixing an alcohol and a hydroxide.

[0056] Here, the alcohol may be a straight-chain, branched-chain, cyclic alcohol, or a combination thereof, preferably a straight-chain C1-C4 alcohol. For example, at least one selected from the group consisting of methanol, ethanol, propanol, and butanol may be used.

[0057] Meanwhile, the hydroxide may include one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide. That is, the hydroxide may be selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide, ammonium hydroxide, tetraalkyl ammonium hydroxide, and combinations thereof. As an example, as an alkali metal hydroxide, it may include one or more selected from the group consisting of potassium hydroxide and sodium hydroxide.

[0058] These depolymerization solutions, mixed with alcohols and hydroxides, can destroy ester functional groups. Therefore, when the depolymerization solution is applied to biodegradable plastics containing ester functional groups, the biodegradable plastic is thermochemically depolymerized through base-catalyzed hydrolysis and ester exchange reactions. Here, the biodegradable plastic having an ester functional group may include one or more selected from the group consisting of polyethylene terephthalate (PET), polyglycolide or polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polyethylene adipate (PEA), polybutylene succinate (PBS), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene adipate terephthalate (PBAT), and Vectran. However, the biodegradable plastic is not necessarily limited to these, and there are no specific restrictions as long as it is a biodegradable plastic in which the ester functional group is destroyed by the depolymerization solution.

[0059] Meanwhile, the concentration of the depolymerization solution is an important factor affecting the biodegradation rate and can be 0.05M to 1M.

[0060]

[0061] The depolymerization solution application step (S200) is a process of applying the depolymerization solution to the biodegradable plastic. A spray application method may be used to apply the depolymerization solution. The spray may be a spray that has chemical resistance to the depolymerization solution, and a certain amount may be sprayed onto the biodegradable plastic through the spray. Additionally, a spray capable of controlling the spray amount may be used to adjust the spray amount according to the type of biodegradable plastic. Alternatively, the depolymerization solution may be applied by immersing the biodegradable plastic in the depolymerization solution.

[0062] Depolymerization pretreatment can be performed by leaving the biodegradable plastic coated with depolymerization at room temperature. However, depolymerization pretreatment does not necessarily have to be performed at room temperature, and heat treatment may also be performed at a predetermined temperature. This heat treatment may be performed simultaneously while mixing the depolymerization solution and the biodegradable plastic, or as a subsequent procedure after the depolymerization solution application step (S200).

[0063] For example, with reference to FIG. 3, a horizontal stirrer equipped with a heating means (see FIG. 3 (a)) or a vertical stirrer (see FIG. 3 (b)) can be used to rotate a screw to mix the depolymerization solution and the biodegradable plastic while heating the stirrer, thereby allowing the application of the depolymerization solution and heat treatment to be performed simultaneously. When using such a screw, the mixing speed, heat treatment temperature, and time can be controlled. Here, the heat treatment temperature may be 40°C to 90°C, and the heat treatment time may be 30 minutes or less.

[0064] The case in which a heat treatment process is performed as a subsequent procedure after the depolymerization solution application step (S200) will be described later.

[0065]

[0066] FIG. 4 is a flowchart of a method for improving the biodegradation rate of biodegradable plastics according to another embodiment of the present invention.

[0067] With reference to FIG. 4, a method for improving the biodegradation rate of a biodegradable plastic according to another embodiment of the invention may further include a heat treatment step (S300).

[0068] The heat treatment step (S300) is a process of heat-treating the biodegradable plastic coated with the depolymerization solution through the aforementioned depolymerization solution coating step (S200) at a predetermined temperature. Here, the heat treatment may be performed using a heating chamber or a microwave. Specifically, a heating chamber capable of controlling the internal temperature may be prepared, the biodegradable plastic coated with the depolymerization solution may be introduced into the heating chamber, and heat-treated at a predetermined temperature. When using such a heating chamber, the temperature and time may be controlled; the heat treatment temperature may be 40°C to 90°C, and the heat treatment time may be 30 minutes or less. In addition to a heating chamber, the biodegradable plastic coated with the depolymerization solution may also be pretreated using a microwave. In this case, the wavelength of the microwave and the treatment time may be controlled.

[0069]

[0070] This depolymerization pretreatment process can be performed on products such as mulch films, food or garbage bags, etc., made from biodegradable plastics, or on raw materials such as films before they are commercialized.

[0071]

[0072] In summary, according to the present invention, by pre-treating biodegradable plastics using a depolymerization solution, it is expected that the biodegradation efficiency of biodegradable plastics can be improved in actual usage environments. Furthermore, it can solve the problem of ecosystem pollution caused by microplastics, and allows volume-based food waste bags or garbage bags made of biodegradable plastics to be treated together with food or waste through anaerobic digestion without being separated.

[0073]

[0074] Biodegradable plastics pretreated with a depolymerization solution can also be utilized for natural biogas production, and this is explained below. As the depolymerization pretreatment process has been previously described, explanations for overlapping content are omitted or described only briefly.

[0075] FIGS. 5 and 6 are flowcharts of a biogas production method according to an embodiment of the present invention. As shown in FIGS. 5 and 6, the biogas production method according to an embodiment of the present invention includes a depolymerization solution application step (S100) and an anaerobic digestion step (S200).

[0076]

[0077] The depolymerization solution application step (S100) is a process of preparing a depolymerization solution and applying the depolymerization solution to a biodegradable plastic as described above. The depolymerization solution can be prepared by mixing an alcohol and a hydroxide. The alcohol may be a straight-chain, branched-chain, cyclic alcohol, or a combination thereof; for example, a straight-chain C1-C4 alcohol may be used. The hydroxide may include one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide; for example, one or more selected from the group consisting of potassium hydroxide and sodium hydroxide may be used. The concentration of the depolymerization solution may be 0.05 M to 1 M. Since this depolymerization solution thermochemically depolymerizes the biodegradable plastic through a base-catalyzed hydrolysis reaction and an ester exchange reaction, the biodegradable plastic to be depolymerized may be a biodegradable plastic having an ester functional group.

[0078] The application of the depolymerization solution can be performed by spraying or immersion. Additionally, the application of the depolymerization solution and heat treatment can be performed simultaneously by heating the stirrer while mixing the depolymerization solution and the biodegradable plastic using the screw of the stirrer. When using a screw, the mixing speed, heat treatment temperature, and time can be controlled, and the heat treatment temperature can be 40°C to 90°C, and the heat treatment time can be 30 minutes or less.

[0079]

[0080] The anaerobic digestion step (S200) is a process of anaerobic digesting biodegradable plastic coated with a depolymerization solution. Anaerobic digestion is a process in which biodegradable plastic is decomposed by microorganisms in an oxygen-free environment. This anaerobic digestion can be carried out by introducing biodegradable plastic coated with a depolymerization solution into an anaerobic digester where oxygen is blocked and microorganisms can proliferate. Here, the biodegradable plastic may be introduced into the anaerobic digester in a cut or crushed state. Since biogas is generated during this anaerobic digestion process, biogas can be produced by separating the biogas from the anaerobic digester. According to the present invention, since the biodegradation rate is accelerated due to the depolymerization solution, more biogas can be produced in the same amount of time.

[0081]

[0082] FIG. 7 is a flowchart of a biogas production method according to another embodiment of the present invention. With reference to FIG. 7, the biogas production method according to another embodiment of the present invention may further include a heat treatment step (S150) prior to the anaerobic digestion step (S200).

[0083] The heat treatment step (S150) is a process performed between the depolymerization solution application step (S100) and the anaerobic digestion step (S200), in which the biodegradable plastic coated with the depolymerization solution is heat-treated at a predetermined temperature. Here, a heating chamber or a microwave may be used for the heat treatment. For example, the biodegradable plastic coated with the depolymerization solution may be introduced into a heating chamber and heat-treated at a temperature of 40°C to 90°C for 30 minutes or less. Additionally, the biodegradable plastic coated with the depolymerization solution may be pre-treated by adjusting the wavelength of the microwave and the treatment time.

[0084]

[0085] The present invention will be explained in more detail below through experimental examples.

[0086] Experimental Example 1: Confirmation of Depolymerization Effect on PBAT / PBS Film

[0087] Depolymerization solutions were prepared by mixing various alcohols and hydroxides, and PBAT films and PBS films were pretreated with the depolymerization solutions to confirm the depolymerization effect, and the results are shown in Figures 8 and 9. Figure 8 shows the depolymerization effect on the PBAT film according to Experimental Example 1, and Figure 9 shows the depolymerization effect on the PBS film according to Experimental Example 1.

[0088] Here, a total of six types of depolymerization solutions (KOH+Methanol, KOH+Ethanol, KOH+Propanol, NaOH+Methanol, NaOH+Ethanol, NaOH+Propanol) were prepared by mixing alcohols such as methanol, ethanol, and propanol with hydroxides such as potassium hydroxide and calcium hydroxide. PBAT films and PBS films were each cut into 4 cm × 4 cm pieces, immersed in the depolymerization solution, and then subjected to heat treatment. The depolymerization effect was compared while varying the concentration of the depolymerization solution, the heat treatment temperature, and the time.

[0089] First, to check the depolymerization effect on PBAT films, referring to Figure 8(a), a total of six types of depolymerization solutions were set to a concentration of 0.125 M and tested at 60°C for 5 minutes, resulting in significant weight loss for all six types. In particular, the KOH+Propanol depolymerization solution exhibited the best depolymerization effect. For the KOH+Ethanol and KOH+Propanol depolymerization solutions, which showed relatively superior depolymerization effects, their concentrations were adjusted to 0.125 M and 0.25 M, respectively, and the depolymerization effects were compared by pre-treating at temperatures of 50°C, 60°C, and 70°C for 3 minutes and 7 minutes. As a result, the depolymerization effect was excellent when pretreated at 60°C and 70°C for 7 minutes with a concentration of 0.25 M, and when pretreated at 70°C for 3 minutes with a concentration of 0.125 M (see Fig. 8(b)). In addition, for KOH+Ethanol and KOH+Propanol depolymerization solutions, the concentration was adjusted from 0.038 M to 0.188 M by increasing it in increments of 0.005 M, and the depolymerization effect was compared by pretreating at temperatures of 60°C to 95°C for 5 to 10 minutes. As a result, a high depolymerization effect was confirmed under all conditions, and it was confirmed that there were differences in the depolymerization effect depending on the concentration of the depolymerization solution, the heat treatment temperature, and the time (see Fig. 8(c)). Based on these results, it can be seen that the biodegradation rate of biodegradable plastics can be controlled by adjusting the type, concentration, heat treatment temperature, and time of the depolymerization solution.

[0090] Next, when examining the depolymerization effect on PBS films, similar to PBAT films, when a total of six types of depolymerization solutions were prepared at a concentration of 0.125 M and pretreated at 60°C for 5 minutes, the KOH+Propanol depolymerization solution exhibited the best depolymerization effect (see Fig. 9(a)). For the KOH+Ethanol and KOH+Propanol depolymerization solutions, which showed excellent depolymerization effects, their concentrations were adjusted to 0.125 M and 0.25 M, respectively, and pretreated at temperatures of 50°C, 60°C, and 70°C for 3 and 7 minutes. Likewise, when pretreated at a concentration of 0.25 M at 60°C and 70°C for 7 minutes, and when pretreated at a concentration of 0.125 M at 70°C for 3 minutes, the depolymerization effect was excellent (see Fig. 9(b)). For KOH+Ethanol and KOH+Propanol depolymerization solutions, the concentration was adjusted from 0.038 M to 0.188 M in increments of 0.005 M, and the depolymerization effect was compared by pretreatment at a temperature of 60℃ to 90℃ for 5 to 6 minutes. As a result, a high depolymerization effect was confirmed under all conditions, and it was confirmed that the depolymerization effect varied depending on the concentration of the depolymerization solution, the heat treatment temperature, and the time (see Fig. 9(c)).

[0091]

[0092] Experimental Example 2: Depolymerization Effect According to Number of Depolymerization Pretreatments

[0093] The depolymerization effect according to the number of pretreatments was compared by spraying the 0.125 M concentration KOH+Propanol depolymerization solution prepared in Experimental Example 1 onto a PBAT film (4 cm × 4 cm) once and twice. Here, the spray amount was 1 ml / g, and the pretreatment was performed at 60°C for 5 minutes. Figure 10 shows the depolymerization effect on the PBAT film according to the number of pretreatments in Experimental Example 2.

[0094] Referring to Fig. 10(a), the weight loss increases as the number of pretreatments increases, indicating that the depolymerization effect is proportional to the number of pretreatments. Additionally, in the images of the PBAT film (Fig. 10(b)) and SEM images (Fig. 10(c)), changes occur on the surface of the film as the number of pretreatments increases, confirming that the biodegradability has improved.

[0095]

[0096] Experimental Example 3: Depolymerization effect according to the amount of depolymerization solution sprayed

[0097] The spray amount of the depolymerization solution was changed to 10 ml / g, and a single pretreatment was performed in the same manner as in Experimental Example 2, and the results are shown in Fig. 11. Fig. 11 shows the depolymerization effect on PBAT films according to the spray amount of the depolymerization solution according to Experimental Example 3.

[0098] Comparing Fig. 10 (a) and Fig. 11 (a), it can be seen that the depolymerization effect increases as the spray amount increases. In addition, the same effect can be confirmed in the image of the PBAT film (Fig. 11 (b)) and the SEM image (Fig. 11 (c)).

[0099]

[0100] Experimental Example 4: Depolymerization effect on various mulch films

[0101] For a total of five types of mulching films (4 cm × 4 cm) manufactured by Sejin Bio Co., Ltd., Ilshin Chemical Co., Ltd., Eco & Tayture Co., Ltd. (Eco &), Green Bio Co., Ltd., and Imwon Economic and Social Cooperative (Toto Saeng), the KOH+Ethanol and KOH+Propanol depolymerization solutions prepared in Example 1 were pretreated at room temperature for 30 minutes, and the depolymerization effect was confirmed. Figure 12 shows the depolymerization effect on various mulching films according to Experimental Example 4.

[0102] Figure 12 (a) shows the depolymerization effect after pretreatment by spraying 0.5 ml of a KOH+Propanol depolymerization solution with a concentration of 0.188 M. Although there are slight differences in the depolymerization effect depending on the manufacturer, it can be seen that a depolymerization effect occurs overall.

[0103] Figure 12(b) shows the depolymerization effect of pre-treating a mulching film of Ilshin Chemical Co., Ltd. by spraying 0.5 to 2.0 ml of 0.188 M KOH+Propanol and KOH+Ethanol depolymerization solutions. Based on this, there was a difference in weight loss depending on the amount of depolymerization solution sprayed.

[0104] To minimize microbial influence, ethanol was selected, and 1.5 ml of the KOH+Ethanol depolymerization solution was sprayed onto Ilshin Chemical Co., Ltd.'s mulching film while varying the concentration from 0.188 to 0.752 M for pretreatment. As a result, the best depolymerization effect was observed at a concentration of 0.564 M.

[0105]

[0106] Experimental Example 5: Depolymerization effect on various mulch films

[0107] 1.5 ml of a 0.564 M KOH+Ethanol depolymerization solution was sprayed onto the mulching film (5 types, 4 cm × 4 cm) of Experimental Example 4 and the LDPE mulching film (4 cm × 4 cm), and the depolymerization effect was compared by pre-treating at 30°C for 30 minutes. Figures 13 and 14 show the depolymerization effect on various mulching films according to Experimental Example 5.

[0108] Referring to Fig. 13, a weight change of more than 15% was observed in 3 out of 5 types of mulching films. In the SEM image of Fig. 14, surface changes occurred in all 5 types, indicating that biodegradability can be improved by treatment with a depolymerization solution.

[0109]

[0110] Experimental Example 6: Biodegradation-enhancing effect of depolymerization pretreatment

[0111] 1.5 ml and 3.0 ml of a 0.564 M KOH+Ethanol depolymerization solution were sprayed onto a mulching film (8 cm × 8 cm) from Ilshin Chemical Co., Ltd., and pretreatment was performed at 30°C for 30 minutes. Afterward, the film was washed with deionized water (DW) and a biodegradation test was performed. The biodegradation evaluation conditions are as shown in [Table 1] below.

[0112] Biodegradation Evaluation Conditions Standard Material: TLC-grade cellulose Test Material: Inoculum 1:50 Dry Solid Size / Form: 2 cm × 2 cm film Inoculum Mass / Type: 150 g Soil Size: 0.5 cm ~ 1 cm Mixing Frequency: Weekly Temperature: 30 ± 2 ℃ Moisture Content: 30 ~ 40% Evaluation: CO2 Content

[0113]

[0114] Figures 15 to 18 show the biodegradation enhancement effect of the depolymerization pretreatment according to Experimental Example 6.

[0115] Figures 15 and 16 show the decomposition effect of the mulching film up to the 60-day mark. The pre-treated mulching film showed a weight change of 7.9% compared to the untreated mulching film, and the biodegradation effect increased by approximately 1.8 times, with distinct changes in the surface (see Figure 15). In addition, the difference in biodegradability between the pre-treated and untreated mulching films became more significant as time passed (see Figure 16).

[0116] Figures 17 and 18 show the decomposition effect of the mulching film up to the 90-day mark. The pre-treated mulching film showed a weight change of 23.1% compared to the untreated mulching film, indicating a very high degree of pretreatment, and the biodegradation effect increased by more than twofold, confirming a greater improvement in biodegradability (see Figure 17). The difference in biodegradability between the pre-treated mulching film and the untreated mulching film widened significantly until 60 days, but after 60 days, the difference remained almost unchanged (see Figure 18).

[0117]

[0118] Although the present invention has been described in detail through specific embodiments and experimental examples, this is for the purpose of specifically explaining the invention, and the invention is not limited thereto. It is evident that modifications or improvements can be made by those skilled in the art within the technical scope of the invention.

[0119] All simple variations or modifications of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims.

[0120]

[0121] The present invention is recognized as having industrial applicability as a method for improving the biodegradation rate of biodegradable plastics through base-catalyzed hydrolysis and ester exchange reactions.

Claims

1. (a) a step of preparing a depolymerization solution by mixing an alcohol and a hydroxide; and (b) a step of applying the above depolymerization solution to the biodegradable plastic; a method for improving the biodegradation rate of a biodegradable plastic.

2. In Claim 1, The above alcohol is, Method for improving the biodegradation rate of biodegradable plastics containing straight-chain C1-C4 alcohols.

3. In Claim 1, The above hydroxide is, A method for improving the biodegradation rate of biodegradable plastics comprising one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide.

4. In Claim 3, The above alkali metal hydroxide is, A method for improving the biodegradation rate of biodegradable plastics comprising one or more selected from the group consisting of potassium hydroxide and sodium hydroxide.

5. In Claim 1, The concentration of the above depolymerization solution is, Method for improving the biodegradation rate of biodegradable plastics with a biodegradability of 0.05M to 1M.

6. In Claim 1, In step (b) above, A method for improving the biodegradation rate of biodegradable plastic by mixing the above depolymerization solution and the above biodegradable plastic and heat-treating at a predetermined temperature.

7. In Claim 1, (c) A method for improving the biodegradation rate of a biodegradable plastic by heat-treating the biodegradable plastic coated with the above depolymerization solution at a predetermined temperature.

8. In claim 6 or claim 7, The above predetermined temperature is, Method for improving the biodegradation rate of biodegradable plastics at 40℃ to 90℃.

9. In Claim 6, In step (b) above, A method for improving the biodegradation rate of biodegradable plastic by mixing the above depolymerization solution and the above biodegradable plastic using a screw.

10. In Claim 7, In step (c) above, A method for improving the biodegradation rate of a biodegradable plastic by introducing the biodegradable plastic coated with the depolymerization solution into a heating chamber capable of controlling the internal temperature and heat treating it.

11. In Claim 7, A method for improving the biodegradation rate of a biodegradable plastic by heat-treating the biodegradable plastic coated with the depolymerization solution using a microwave.

12. In Claim 1, The above-mentioned biodegradable plastic is, Method for improving the biodegradation rate of biodegradable plastics having ester functional groups.

13. A method for producing biogas comprising the step of anaerobically digesting the biodegradable plastic coated with the depolymerization solution according to Claim 1.

14. In Claim 13, Prior to the above anaerobic digestion step, A method for producing biogas by mixing the above depolymerization solution and the above biodegradable plastic and heat-treating at a predetermined temperature.

15. In Claim 13, Prior to the above anaerobic digestion step, A method for producing biogas further comprising the step of heat-treating the biodegradable plastic coated with the above depolymerization solution at a predetermined temperature.

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