KR20230048731A - Method of plastic degradation - Google Patents

Abstract

The present invention provides: a method for promoting the decomposition of plastic, comprising a step of treating plastic with plasma; and the plastic decomposed by the method. By confirming that the peaks corresponding to a carbonyl group peak and an ether peak increase through plasma treatment through the method of the present invention, it is confirmed that plasma can be used as a pretreatment method to promote decomposition of waste vinyl.

Description

Method of plastic degradation {Method of plastic degradation}

The present invention relates to a method for accelerating decomposition of plastics, comprising the step of treating plastics with plasma; and plastics decomposed by the method.

Agricultural films are used to cover soil or greenhouses or to protect pastures and hay, but their usage is increasing as the level of agriculture improves. The global agricultural film market is expected to increase at an average annual growth rate of 7.18% from $7.82 billion in 2016 and reach $11.06 billion in 2021. It is expected to increase and reach $ 98.4 million in 2022 (agricultural film market, research and development special zone technology global market trend report 2018). Among these agricultural films, more than 10% is used as a mulching film for covering soil, and non-degradable polyethylene is the main material. As the mulching film takes a lot of effort to remove the used film once its role is finished, research on promoting the decomposition of waste vinyl has been actively conducted recently, but carbonyl with stable structure, high molecular weight, and oxidation and hydrolysis Biodegradation by microorganisms is difficult due to various reasons such as lack of group-like bonds and high hydrophobicity.

In order to solve these problems, physical and chemical pretreatments such as UV, heat, and strong acid are essential. In general, the biodegradation mechanism of polyethylene is initiated by the generation of a carbonyl group in a polymer chain, that is, a carbonyl group degradable by a microbial enzyme must be formed in the polymer. When a carbonyl group is generated, it is converted to an alcohol group by monooxygenase and finally oxidized to an aldehyde group.

However, agricultural waste vinyl that is illegally landfilled without being collected is hardly decomposed, blocks the flow of moisture and air, and blocks the flow of microorganisms in the soil, further devastation of the soil. In addition, illegal incineration causes air pollution by emitting dioxin, chlorine and hydrogen chloride gas, in addition to the risk of forest fire. It is causing damage to the rural environment.

Meanwhile, in Korea, related ministries jointly put forward a strategy to revitalize the white bio industry in 2020. This is an industry in which biotechnology is grafted onto the plastics industry, using renewable resources such as plants or using microorganisms, enzymes, and catalysts to replace materials in the existing plastics industry with bio-based ones. White bio products emit relatively little carbon dioxide in the production process and contribute to carbon neutrality by absorbing carbon dioxide in the process of growing biomass, such as raw materials such as plants, so global interest is increasing as an alternative solution to environmental pollution. For agricultural use, biodegradable mulching film is representative, and recently it has been used as an essential agricultural material. However, this biodegradable mulching film is not properly distributed to farms due to early decomposition, low reliability due to weak strength, and high price. Therefore, apart from technology development of biodegradable mulching films, research on surface modification to biodegradability of existing mulching films is required.

Under this background, the present inventors have made efforts to decompose eco-friendly agricultural waste vinyl, and as a result, the carbonyl group of agricultural waste vinyl treated with plasma, which is also applied in the field of environmental improvement such as the purification of polluted air, water, and soil, increases. As a result of confirming that degradation by microbial enzymes is possible, the present invention was completed by confirming that plasma treatment can be used as a pretreatment method for promoting decomposition of waste vinyl.

One object of the present invention is to provide a method for accelerating decomposition of plastics comprising the step of treating plastics with plasma.

Another object of the present invention is to provide a plastic degraded by the above method.

A detailed description of this is as follows. Meanwhile, each description and embodiment disclosed in the present invention may also be applied to each other description and embodiment. That is, all combinations of the various elements disclosed herein fall within the scope of the present invention. In addition, it cannot be seen that the scope of the present invention is limited by the specific descriptions described below.

One aspect of the present invention for achieving the above object provides a plastic decomposition acceleration method comprising the step of treating plastic with plasma.

As used herein, the term "plastic" refers to organic-based polymeric materials and mixtures thereof that can be molded by heat or pressure, and is widely used in daily life, such as films, synthetic fibers, bottles, tubes, toys, high heat resistance, It is used for various purposes ranging from high-strength materials. In the present invention, the plastic may refer to waste plastic, which is Low Density PolyEthylene (LPDE) used as agricultural vinyl, and more specifically, may refer to a post-use agricultural mulching film.

The term "mulching" refers to covering the surface of cultivated soil when cultivating crops. In the past, rice straw, barley straw, grass, etc. were used, but today polyethylene film is used. The polyethylene film is also referred to as a mulching film or mulching vinyl, and can be used not only for growing crops in the open field, but also for horticultural facilities such as houses. In the present invention, the mulching film may mean a mulching film for open fields, but is not limited thereto.

As used herein, the term "plasma" is a form of material known as the fourth state of matter other than solid, liquid, and gas, and may mean low-temperature plasma (or non-equilibrium plasma). In the present invention, the plasma is by a dielectric barrier discharge (DBD) method, and specifically, it is possible to use the electrical property of generating plasma ions by passing electricity through electrodes on both sides of the dielectric. The DBD method is widely used in industry because it can be discharged at atmospheric pressure (normal pressure) and room temperature, and in the case of material surface treatment, almost all treatments can be performed through the DBD method.

As used herein, the term "plastic decomposition" specifically refers to waste plastic decomposition, and more specifically refers to decomposition of agricultural mulching films, but is not limited thereto. For the purpose of the present invention, the plastic decomposition method may mean increasing biodegradability through surface modification of plastic by plasma treatment.

In one embodiment of the present invention, as a result of confirming whether carbonyl groups are generated by plasma discharge water treatment for agricultural mulching films, 1,750 cm ^-1 in the film after treatment compared to before the discharge water treatment (C = O carbonyl peak) And it was confirmed that the absorbance increased around 1,100 cm ^-1 (CO, ether peak) (FIG. 3).

In addition, in one embodiment of the present invention, as a result of confirming whether or not carbonyl groups are generated by direct plasma treatment for agricultural mulching films, similarly, compared to before the direct plasma treatment, the film after treatment has a time-dependent close to 1,750 cm ^-1 (C = O carbonyl peak) and around 1,100 cm ^-1 (CO, ether peak), it was confirmed that the absorbance increased (FIG. 4).

Through this, it was confirmed that the surface of the agricultural mulching film (waste plastic) was modified to be advantageous for microbial biodegradation after use by plasma treatment.

Another aspect of the present invention for achieving the above object provides a plastic degraded by a method for accelerating plastic decomposition, which includes treating the plastic with plasma.

At this time, the "plastic", "plasma" and "plastic decomposition" are as described above.

It was confirmed that decomposition by microbial enzymes becomes possible as the carbonyl group of agricultural waste vinyl treated by the method of the present invention increases, and surface dielectric barrier discharge plasma can be usefully used as a pretreatment method to promote decomposition of waste vinyl. .

1 is a graph showing the results of analyzing plasma operating conditions and active species characteristics of a plasma device.
Figure 2 is a graph showing the results of FT-IR analysis before and after using the untreated mulching film.
3A is a graph showing the results of FT-IR analysis of mulching films stored in plasma discharge water (pH 3.4) and acidic water (pH 3.0).
4 is a graph showing the results of FT-IR analysis of mulching films by direct plasma treatment over time.
5 is a graph comparing and analyzing the carbonyl index (Ico) by non-treatment, plasma discharge water treatment, and plasma direct treatment.

Hereinafter, the present invention will be described in more detail through examples. These examples are intended to explain the present invention in more detail, and the scope of the present invention is not limited by these examples.

Experimental Example 1. Preparation of Plasma Discharge Water

First, plasma treated discharge water using surface dielectric barrier discharge (SDBD) was prepared.

Specifically, plasma discharge water prepared by discharging for 20 minutes on the water surface with SDBD atmospheric pressure plasma was diluted and prepared to pH 3.4, and mulching films were stored in each plasma discharge water for 6 days before and after use. At this time, an acidic solution of pH 3.0 was used as a comparative example of plasma discharge water, and similarly, mulching films before and after use were stored in each acidic solution for 6 days and compared. The mulching film was used by mulching in the field for 5 months for sesame and soybeans in actual farms. Detailed test materials and sample names are shown in Table 1 below.

number film type Vinyl thickness (mm) acid water treatment Plasma discharge water treatment One Sesame 0.018 A1 D1 2 corner 0.039 A2 D2 3 bean 0.033 A3 D3 4 bean 0.035 A4 D4 5 Sesame - after use 0.018 A5 D5 6 corn - after 0.039 A6 D6 7 Beans - After 0.035 A7 D7

Experimental Example 2. Plasma direct treatment

Plasma direct treatment was performed on the surface of the mulching film for 20, 40, and 60 minutes at atmospheric pressure and room temperature at 110 W using SDBD atmospheric pressure plasma as described above.

Specifically, the plasma device was treated under an operating condition of discharging for 20 minutes, a 10-minute period was set for each sample, and the operation was performed immediately after 10 minutes.

The functional group change on the surface of the mulching film by direct plasma treatment was confirmed through FT-IR analysis, and the analysis was repeated 5 times. Plasma direct treatment was performed on sample Nos. 1, 5, and 7 in Table 1, and was treated for 20, 40, and 60 minutes, respectively. Detailed sample names are shown in Table 2 below.

number Plasma treatment time (minutes) 20 40 60 One P20-1 P40-1 P60-1 5 P20-5 P40-5 P60-5 7 P20-7 P40-7 P60-7

In addition, the carbonyl index (Ico) was analyzed through absorbance measurement at 1,740 cm ^-1 and 1,835 cm ^-1 of FT-IR, and its formula is as follows.

Ico = [A(1740)-A(1835)]/(0.008*t)

A: absorbance, t: time

Experimental Example 3. Chemical Characteristics Analysis of Mulching Film

In order to examine the chemical properties of the mulching film used in the present invention, the results of peak analysis for FT-IR and carbonyl are shown in Table 3 below.

Wavenumbers (cm ^-1 ) peak 1,740 and 1,835 Carbonyl index (Ico) 1470.46 _CH2 bending peak 1234.22 C-O group 909 and 2020 vinyl index (IV)

Experimental Example 4. Analysis of Active Species Characteristics of Plasma Device

Active species in the vicinity of plasma generation were investigated by sampling gas through a gas port installed in the chamber using a gas analyzer, and the concentration of active species was expressed according to the plasma exposure time.

As a result, as shown in FIG. 1, ozone (O ₃ ), nitrogen monoxide (NO), and nitrogen dioxide (NO ₂ ) were detected. At this time, the O ₃ and NOx were detected using CO physics CLD60 and Anseros Ozomat GM professional, respectively. was measured. Their maximum concentrations were 465 ppm, 486 ppm and 407 ppm, respectively, but it was confirmed that O ₃ was quickly decomposed due to its short half-life.

Example 1. FT-IR analysis of untreated film

C1, C2, C4, C5, C6 and C7 to determine whether carbonyl groups degradable by microbial enzymes are generated in the polymer through comparative FT-IR analysis before and after use of the control film without any treatment. The absorbance of was confirmed.

As a result, as shown in FIG. 2, it was confirmed that the absorbance increased at around 1,750 cm ^-1 (C=O carbonyl peak) and around 1,100 cm ^-1 (CO, ether peak) in the film after use compared to before use.

Therefore, it was confirmed that surface modification favorable to microbial biodegradation occurred due to physical/chemical changes during actual use of the film.

Example 2. FT-IR analysis of plasma discharge water treatment (acid treatment) film

D1, D2, D4 before and after use of the mulching film stored in the plasma discharge water (pH 3.4) prepared in Experimental Example 1 for 6 days in order to check whether carbonyl groups are generated by the plasma discharge water treatment used as an acid treatment means. , FT-IR analysis of D5, D6 and D7 was performed. In addition, as a comparative example, FT-IR analysis of A1, A2, A4, A5, A6 and A7 stored in acidic water (pH 3.0) for 6 days was performed and compared.

As a result, as shown in FIGS. 3A and 3B, absorbance at around 1,750 cm ^-1 (C = O carbonyl peak) and around 1,100 cm ^-1 (CO, ether peak) after using the mulching film compared to before using it. It was confirmed that was increased, and a difference in carbonyl group generation for acidic water/discharge water treatment was confirmed depending on the sample.

Therefore, it was confirmed that surface modification favorable to microbial biodegradation occurred through plasma discharge water treatment.

Example 3. FT-IR analysis of plasma direct treated films

In order to confirm whether or not carbonyl groups were generated by direct plasma treatment, FT-IR analysis was performed after direct surface treatment of the mulching film at 110 W at normal pressure and room temperature for 20, 40, and 60 minutes using SDBD atmospheric pressure plasma.

As a result, as shown in FIG. 4, it was confirmed that the absorbance increased at around 1,750 cm ^-1 (C=O carbonyl peak) and around 1,100 cm ^-1 (CO, ether peak) in a time-dependent manner for each sample.

Therefore, it was confirmed that surface modification favorable to microbial biodegradation occurred through direct plasma treatment.

In addition, the carbonyl index (Ico) was comparatively analyzed using the absorbances at 1,740 cm ^-1 and 1,835 cm ^-1 of FT-IR confirmed in Examples 1 to 3.

As a result, as shown in FIG. 5, the carbonyl index before using the mulching film was the highest in the plasma treated discharge water, 7 times more than untreated, 5 times more than acidic water, in preparation for direct plasma treatment for 60 minutes. It was also confirmed that it was significantly better than 2 times. After using the mulching film, the carbonyl index was confirmed to be high in direct plasma treatment.

In summary, it was confirmed that the peaks corresponding to the carbonyl group peak and the ether peak increased through plasma treatment, and thus it was confirmed that plasma can be used as a pretreatment method to promote decomposition of waste vinyl.

From the above description, those skilled in the art to which the present invention pertains will be able to understand that the present invention may be embodied in other specific forms without changing its technical spirit or essential features. In this regard, it should be understood that the embodiments described above are illustrative in all respects and not limiting. The scope of the present invention should be construed as including all changes or modifications derived from the meaning and scope of the claims to be described later and equivalent concepts rather than the detailed description above are included in the scope of the present invention.

Claims (9)

A method for accelerating decomposition of plastics, comprising subjecting plastics to plasma. The method of claim 1, wherein the plastic is agricultural waste plastic. The method of claim 1, wherein the plasma treatment is a surface dielectric barrier discharge method. The method according to claim 1, wherein the plasma treatment is a plasma discharge water treatment or a direct plasma treatment. The method according to claim 4, wherein the plasma discharge water treatment is stored for 6 to 180 days. The method of claim 4, wherein the plasma direct treatment is performed directly on the surface for 20 minutes to 60 minutes. The method of claim 4, wherein the plasma discharge water has a pH of 3.4. The method of claim 1, wherein the plasma treatment generates carbonyl groups to modify the surface to be hydrophilic. A plastic degraded by the method of claims 1 to 8.

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