Additive for improving purity and melt index of plastics in plastic recycling method and method using same

Abstract

The present invention relates to: an additive for improving the purity and melt index of plastics in a plastic recycling method; and a method using same. Specifically, the present invention relates to: an additive for improving the purity and melt index of plastics in a plastic recycling process, the additive being characterized by comprising a thickener-based viscosity agent; and a method for recycling plastics using same.

Description

Additives for improving the purity and melting index of plastics in plastic recycling methods and methods for using the same

[0001] The present invention relates to plastic recycling, and more particularly, to an additive for simultaneously improving the purity and melt index of plastic in a plastic recycling method, and a method for using the same.

[0002] Plastics are widely used in modern society because they are easy to process and their physical and chemical properties can be easily modified. Landfilling and incineration are widely used to dispose of waste plastics after use. However, because plastics are difficult to decompose naturally, landfilling can cause environmental problems, such as water and soil contamination, while incineration can cause air pollution.

[0003] To address these environmental issues, much research has been conducted to process, refine, or transform waste plastics for recycling, and some recycling methods are already being used.

[0004] There are three main technologies for recycling waste plastics quickly and easily: mechanical recycling, chemical recycling, and thermal recycling. Among them, mechanical recycling technology reshapes waste plastic into products by crushing, melting, and extruding, and its general process is illustrated in Figure 1. Specifically, this plastic recycling technology includes collecting plastic waste, sorting it by type, washing contaminants, crushing, melting, and extrusion, and pelletizing and manufacturing products. In the collection stage, plastic waste is collected. In the sorting stage, the collected plastic is sorted by type (e.g., PET, HDPE, PVC, LDPE, PP, PS, etc.). In the washing stage, the sorted plastic is washed to remove contaminants (food waste, oil, dust, etc.). In the crushing stage, the washed plastic is crushed into small pieces. In the melting and extrusion stage, the crushed plastic is melted and extruded (formed into a specific shape). In this stage, the plastic is converted into pellets, and these pellets become small granular plastic raw materials. Finally, in the pelletization and product manufacturing stage, new plastic products are manufactured using pellets made through the melting and extrusion process.

[0005] This mechanical waste plastic recycling technology has the advantage of being simple in process, allowing for entry into the business by introducing re-molding equipment, and having low manufacturing variable costs and initial investment. However, it has the disadvantage of having a narrow range of raw materials to use because it must use only high-quality colorless / transparent flakes, not being usable on food contact surfaces due to safety concerns (domestic standards), and ultimately requiring disposal due to quality deterioration issues.

[0006] To address these shortcomings, additives with various functions have been used. These additives primarily include plasticizers and viscosity modifiers to improve viscosity, and antioxidants and heat stabilizers to enhance thermal stability. However, these additives can only improve individual properties, limiting their ability to simultaneously improve two or more properties. Furthermore, mixing multiple types of additives can lead to interaction problems and increased costs.

[0007] Meanwhile, research is being conducted to increase the purity and melt index of waste plastics for recycling, thereby making them easier to process and reducing impurities, thus maintaining their original chemical and physical properties.

[0008] Purity is a concept that indicates the amount and type of impurities contained in a plastic material. High-purity plastics have fewer impurities and can well maintain the original chemical and physical properties of the material. To improve this purity, the use of additives such as accurate classification through infrared spectroscopy and thorough washing, high-efficiency crushing using microorganisms, and impurity removal and prevention, increased flexibility, and improved dispersibility are commonly considered in the waste plastic recycling process. Among these, antioxidants (e.g., phenol antioxidants), stabilizers (e.g., stearates), and dispersants (e.g., organic phosphoric acid esters) have been used as additives to improve purity.

[0009] In addition, the melt index is one of the methods for measuring the characteristics of the resin, and it is a value that evaluates the flowability of the resin in a molten state. If the melt index is high, the plastic flows easily, so the processability is good, and conversely, if the melt index value is low, the viscosity in the molten state is high, which may be difficult to process. To improve this, it is usually considered to use additives such as fluidity improvers and plasticizers, perform mechanical treatments such as ultrasonic treatment and high-shear mixing, or perform chemical treatments such as peroxide treatment and oxidizing agents. Among these, plasticizers (e.g., phthalates, plasticizing esters), lubricants (e.g., stearates, paraffin wax), and adhesion promoters (e.g., styrene-ethylene-butylene-styrene (SEBS)) have been used as additives to improve the melt index.

[0010] However, the use of these additives can only improve individual properties, limiting their ability to simultaneously improve two or more properties. Furthermore, mixing multiple types of additives can lead to interaction problems and increased costs.

[0011] The purpose of the present invention is to solve the above-mentioned problems, and to provide an additive capable of simultaneously improving the mechanical strength, thermal stability and melting index of plastic in a plastic recycling process by using one additive, and a method of recycling plastic using the same.

[0012] One aspect of the present invention provides an additive for improving the purity and melt index of plastic in a plastic recycling process, wherein the additive comprises a thickener-based viscosity agent.

[0013] In one aspect of the present invention, it is preferred that the thickener-based viscosity agent includes at least one of a polymer viscosity agent, an organic viscosity agent, and an inorganic viscosity agent.

[0014] In one aspect of the present invention, it is preferred that the polymeric viscosifier comprises at least one of polyethylene glycol (PEG) and ethylene-propylene rubber (EPR), the organic viscosifier comprises at least one of polyvinyl alcohol (PVA) and a cellulose-based viscosifier, and the inorganic viscosifier comprises at least one of nanoclay and carbon nanotube (CNT).

[0015] Another aspect of the present invention provides a method for recycling plastic, characterized in that the additive of claim 1 is added and mixed in a plastic recycling process.

[0016] In another aspect of the present invention, it is preferred to add and mix the additive of the present invention into a plastic matrix during the melting and extrusion steps of a plastic recycling process including collection of plastic waste, sorting by type, washing of contaminants, crushing, melting and extrusion, and pelletizing and product manufacturing.

[0017] In another aspect of the present invention, it is preferable to uniformly disperse the additive within the plastic matrix using a high-speed mixer or a twin-screw extruder.

[0018] In another aspect of the present invention, it is preferable that the additive is added in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the plastic matrix in the plastic recycling process.

[0019] In another aspect of the present invention, it is preferable that the addition and mixing of the base additive is performed under process conditions of a temperature of 60 to 80°C, a pressure of normal pressure to 100 bar, and a mixing time of 1 minute to 10 hours.

[0020] In another aspect of the present invention, it is preferable that the additive improves the mechanical strength, thermal stability and melting index of the plastic.

[0021] According to the present invention, by using a single additive, the mechanical strength, thermal stability, and melt index of a plastic can be simultaneously improved in a plastic recycling process. Specifically, the present invention can improve the thermal stability of a plastic in a plastic recycling process. The thickener-based viscosifier included in the additive of the present invention has high thermal properties, and thus can significantly improve the thermal stability of the plastic, thereby enhancing the durability of the recycled plastic product and its performance in high-temperature environments. In addition, the present invention can improve the melt index in a plastic recycling process. The thickener-based viscosifier included in the additive of the present invention can be uniformly dispersed within the plastic matrix to effectively control the viscosity, thereby improving the processability and fluidity of the plastic and increasing the efficiency of the plastic recycling process. In addition, the present invention can improve two or more physical properties as described above with a single additive, thereby reducing the cost of using the additive. In addition, due to the uniform dispersion of the additive within the plastic matrix, the physical properties of the final plastic product can be maintained uniformly, thereby improving the overall quality.

[0022] Figure 1 illustrates a general process of mechanical recycling technology.

[0023] FIG. 2 is a schematic diagram of the structure of a thickener-based viscosity agent of the present invention, wherein (a) is a schematic diagram of the thickener-based viscosity agent, and (b) illustrates the connection between the thickener-based viscosity agent and plastic particles.

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily practice the present invention. However, the description of the present invention is merely an embodiment for structural and functional explanation, and therefore the scope of the present invention should not be construed as being limited by the embodiments described in the text. That is, since the embodiments can be modified in various ways and can have various forms, the scope of the present invention should be understood to include equivalents that can realize the technical idea. In addition, the purposes or effects presented in the present invention do not mean that a specific embodiment must include all of them or only such effects, and therefore the scope of the present invention should not be construed as being limited thereby.

[0025] Singular expressions should be understood to include plural expressions unless the context clearly indicates otherwise, and terms such as "comprises" or "has" should be understood to specify the presence of stated features, numbers, steps, operations, components, parts, or combinations thereof, but not to exclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0026] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted to be consistent with their meaning within the context of the relevant technology, and should not be interpreted as having ideal or overly formal meanings unless explicitly defined herein.

[0027] The present invention is described in more detail below.

[0028] One aspect of the present invention provides an additive for improving the purity and melt index of plastic in a plastic recycling process, wherein the additive comprises a thickener-based viscosity agent.

[0029] The additive of the present invention comprises a thickener-based viscosity agent, and is characterized in that by using one such additive in a plastic recycling process, the mechanical strength, thermal stability and melt index of the plastic can be simultaneously improved in the plastic recycling process.

[0030] In the present invention, the thickener-based viscosity agent may include at least one of a polymer viscosity agent, an organic viscosity agent, and an inorganic viscosity agent. As illustrated in Fig. 2(a), the thickener-based viscosity agent has hydrophilic and hydrophobic groups and is a chemical used to control the viscosity and melting properties of plastics in a plastic recycling process. The thickener-based viscosity agent increases intermolecular interactions within the plastic matrix to increase viscosity, uniformly disperses impurities or foreign substances within the plastic to improve overall quality, and controls the fluidity of the plastic to improve processability.

[0031] The polymer viscosifier comprises at least one of polyethylene glycol (PEG) and ethylene-propylene rubber (EPR). Polyethylene glycol improves the melt flowability of the plastic and enables uniform dispersion, while ethylene-propylene rubber imparts flexibility and increases the melt index, thereby improving processability.

[0032] The organic viscosifier comprises at least one of polyvinyl alcohol (PVA) and a cellulose-based viscosifier. The polyvinyl alcohol reduces water absorption and increases the viscosity of the plastic, thereby controlling the melt index. The cellulose-based viscosifier is mixed into the plastic matrix to control viscosity and improve mechanical properties. The cellulose-based viscosifier preferably comprises at least one of carboxymethylcellulose (CMC), hydroxypropylmethylcellulose (HPMC), methylcellulose (MC) and ethylcellulose (EC), wherein carboxymethylcellulose is highly soluble in water, has excellent viscosity-increasing ability, and has excellent heat stability and film-forming ability, so that it can be used in various applications; hydroxypropylmethylcellulose is soluble in both water and organic solvents, is effective in viscosity control and stabilization, and has excellent heat stability and chemical resistance; methylcellulose is soluble in water and is viscous, has excellent thermoplasticity and film-forming ability, and has excellent stability and compatibility, so that it can be well combined with various polymers; and ethylcellulose is insoluble in water, but is soluble in many organic solvents, has excellent viscosity-controlling ability and film-forming ability, and has excellent moisture resistance and chemical resistance.

[0033] The above inorganic viscosity agent comprises at least one of nanoclay and carbon nanotubes (CNT). Nanoclay improves the viscosity and thermal stability of plastics at the same time, and is preferably selected from the group consisting of montmorillonite, smectite, bentonite, hectorite, saponite, beidelite, nontronite, swelling mica, vermicullite, synthetic mica, kanemite, magadite, kenyaite, kaolinite, illite, chlorite, muscovite, pyrophyllite, antigorite, glauconite, vermiculite, sepiolite, imogolite, sobockite, Materials that can be used include nacrite, anauxite, sericite, ledikite, chrysotile, and antigorite, which can be used alone or in combination. Carbon nanotubes can also increase viscosity and provide additional electrical properties.

[0034] Another aspect of the present invention provides a method for recycling plastic, characterized in that the additive of the present invention is added and mixed in a plastic recycling process.

[0035] The plastic recycling process typically includes collecting plastic waste, sorting by type, cleaning contaminants, crushing, melting and extrusion, and pelletizing and manufacturing products, and the additive of the present invention can be added and mixed into the plastic matrix during the melting and extrusion stages of the plastic recycling process.

[0036] It is important to use a high-efficiency mixing technique for adding and mixing the additive of the present invention to uniformly disperse the additive into the plastic matrix, and in the present invention, it is preferable to perform the addition and mixing in a high-speed mixer or a twin-screw extruder.

[0037] The additive is preferably added in an amount of 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the plastic matrix in the plastic recycling process. If the amount is less than the above range, the effects of improving mechanical strength, thermal stability, and melt index may be minimal due to a lack of the additive, and if the amount exceeds the above range, the physical properties may deteriorate, and problems may arise that lower the performance of the produced plastic product.

[0038] The addition and mixing of the additive is preferably performed under process conditions of a temperature of 60 to 80°C, a pressure of atmospheric pressure to 100 bar, and a mixing time of 1 minute to 10 hours. These conditions are optimized to maximize the melt index and purity improvement effect of the recycled plastic to which the additive of the present invention has been added. If these conditions are exceeded, the problem of not being able to enhance the above-described effects occurs.

[0039] By adding and mixing the additive of the present invention in this method, the mechanical strength, thermal stability, and melt index of the plastic can be improved. Specifically, the present invention can improve the thermal stability of the plastic in the plastic recycling process. The thickener-based viscosifier included in the additive of the present invention has high thermal properties, and thus can significantly improve the thermal stability of the plastic, thereby increasing the durability of the recycled plastic product and its performance in high-temperature environments. In addition, the present invention can improve the melt index in the plastic recycling process. The thickener-based viscosifier included in the additive of the present invention can be uniformly dispersed within the plastic matrix to effectively control the viscosity, thereby improving the processability and fluidity of the plastic and increasing the efficiency of the plastic recycling process. In addition, the present invention can improve two or more physical properties as described above with a single additive, thereby reducing the cost of using the additive. In addition, due to the uniform dispersion of the additive within the plastic matrix, the physical properties of the final plastic product can be maintained uniformly, thereby improving the overall quality.

[0040] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present invention, and the scope of the present invention is not limited to these examples alone.

[0041] <Example 1> Process 1 for recycling plastic

[0042] Waste PO resin recovered from agricultural mulching films is crushed and classified, and large foreign substances are separated and removed in the process, then crushed to obtain an average particle size (D 50) was prepared as a PO base resin in the form of pellets with a diameter of 4 mm. 100 kg of the PO base resin and 800 g of polyethylene glycol or ethylene-propylene rubber were supplied and mixed into a mixer to prepare an extrusion feed, which was supplied to an extruder through the extruder feed port.

[0043] As the above extruder, a double screw extruder was used, which included a cylinder with an inner diameter of 25 mm and a screw length of 800 mm.

[0044] The internal temperature of the extruder was sequentially increased from 150°C in the hopper to 190°C in the die, and melting and kneading of the PO base resin was performed within the extruder while simultaneously removing odor generated from the PO base resin.

[0045] At this time, the screw rotation speed was controlled to 300 rpm and the residence time was controlled to 120 seconds, and after the reaction extrusion, the extruded composition was discharged through the discharge port of the extruder. The extruded composition was supplied to a pelletizer to produce a PO recycled resin having an average diameter of 2 mm.

[0046] <Example 2> Process for recycling plastic 2

[0047] The same procedure as in Example 1 was followed except that 1 kg of polyvinyl alcohol or cellulose-based viscosifier was added instead of polyethylene glycol or ethylene-propylene rubber.

[0048] <Example 3> Process 3 for recycling plastic

[0049] The same procedure as in Example 1 was followed, except that 1 kg of montmorillonite or carbon nanotubes was added as nanoclay instead of polyethylene glycol or ethylene-propylene rubber.

[0050] <Experimental Example 1> Measurement of physical properties of recycled plastic products

[0051] Physical properties, thermal stability and melting index were performed in the following manner.

[0052] physical properties

[0053] Tensile strength and tensile elongation at break were measured at 2 in / min according to ASTM D638, and Shore A hardness of unaged samples was measured according to ASTM D2240. Modulus was also measured using an Instron UTM (4206-001) universal testing machine.

[0054] Thermal stability

[0055] The mass change was measured while heating from 40 to 400 °C at a rate of 10 °C / min while flowing air at a rate of 200 ml / min using a gravimetric analyzer (TA Instruments SDT-Q600). The temperature at which the decomposition rate reached 70% was defined as the thermal decomposition temperature.

[0056] Melting index

[0057] The melting index was measured using a 1.2 kg weight at 300°C using a Toyoseki MFR device according to the ASTM D1238-94A / ISO 1133 method.

[0058] The results are shown in Table 1 below.

[0059] Here, Comparative Example 1 is a sample without an additive added, Comparative Example 2 is a sample with 0.1 part by weight of nanoclay added as an additive, and Comparative Example 3 is a sample with 20 parts by weight of nanoclay added as an additive.

[0060] Tensile strength (MPa) Tensile elongation (%) Shore hardness (D) Modulus (GPa) Thermal stability (℃) Melt index (g / 10 min) Example 115.01 250 ± 746.0 ± 0.5 6.130 0 52 Example 215.50 255 ± 646.7 ± 0.36 330 254 Example 315.63 252 ± 447.1 ± 0.46 330 150 Comparative example 116.03 260 ± 548.0 ± 0.5 6.42 40 37 Comparative example 215.07 258 ± 346.5 ± 0.36 024 139 Comparative example 314.02 240 ± 439.9 ± 0.6 4.9 26 134

[0061] As shown in Table 1 above, it can be seen that the samples manufactured using the waste polyvinyl chloride compound composition according to the present invention have excellent thermal stability and melt index while securing physical properties. Specifically, it can be seen that Examples 1 to 3, which are samples including the additive of the present invention, have excellent thermal stability and melt index compared to Comparative Example 1 in which no additive was added, and that compared to Comparative Examples 2 and 3 in which the additive was added in an amount outside the range of the present invention, not only the physical properties but also the thermal stability and melt index were improved.

[0062] The above description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that modifications to other specific forms can be made without altering the technical aspects or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, components described as single may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0063] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0064] The present invention can simultaneously improve the mechanical strength, thermal stability, and melt index of plastics in a plastic recycling process by using a single additive. Specifically, the present invention can improve the thermal stability of plastics in a plastic recycling process. The thickener-based viscosifier included in the additive of the present invention has high thermal properties, which can significantly improve the thermal stability of plastics, thereby enhancing the durability of recycled plastic products and their performance in high-temperature environments. Furthermore, the present invention can improve the melt index in a plastic recycling process. The thickener-based viscosifier included in the additive of the present invention can be uniformly dispersed within the plastic matrix to effectively control viscosity, thereby improving the processability and fluidity of plastics and enhancing the efficiency of the plastic recycling process. Furthermore, the present invention can improve two or more physical properties as described above with a single additive, thereby reducing the cost of using the additive. Furthermore, the present invention has the advantage of maintaining the physical properties of the final plastic product uniformly due to the uniform dispersion of the additive within the plastic matrix, thereby improving the overall quality, and thus has industrial applicability.

Claims

1. As an additive to improve the purity and melt index of plastic in the plastic recycling process. An additive characterized in that the additive comprises a thickener-based viscosity agent.

2. An additive according to claim 1, characterized in that the thickener-based viscosity agent comprises at least one of a polymer viscosity agent, an organic viscosity agent, and an inorganic viscosity agent.

3. In the second paragraph, the polymer viscous agent comprises at least one of polyethylene glycol (PEG) and ethylene-propylene rubber (EPR), wherein the organic viscosifier comprises at least one of polyvinyl alcohol (PVA) and a cellulose-based viscosifier; An additive characterized in that the above inorganic viscosity agent comprises at least one of nanoclay and carbon nanotubes (CNT).

4. An additive according to claim 3, characterized in that the cellulose-based viscosity agent comprises at least one of carboxymethylcellulose (CMC), hydroxypropylmethylcellulose (HPMC), methylcellulose (MC), and ethylcellulose (EC).

5. A method for recycling plastic, characterized in that the additive of the first clause is added and mixed in the plastic recycling process.

6. A method for recycling plastic, characterized in that the additive of paragraph 1 is added and mixed into the plastic matrix during the melting and extrusion stages of the plastic recycling process, which includes collecting plastic waste, sorting by type, washing contaminants, crushing, melting and extruding, and pelletizing and manufacturing the product in paragraph 5.

7. A method for recycling plastic, characterized in that the additive is uniformly dispersed in a plastic matrix using a high-speed mixer or a twin-screw extruder according to claim 5 or 6.

8. A method for recycling plastic, characterized in that the additive is added in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the plastic matrix in the plastic recycling process according to claim 5 or 6.

9. A method for recycling plastic, characterized in that the addition and mixing of the additive in the fifth or sixth paragraph is performed under process conditions of a temperature of 60 to 80°C, a pressure of normal pressure to 100 bar, and a mixing time of 1 minute to 10 hours.

10. A method for recycling plastic according to claim 5 or 6, characterized in that the additive improves the mechanical strength, thermal stability and melting index of the plastic.

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