Manufacturing Method for Eco-Friendly Lightweight Composite Wood Made from Recycled Waste Plastics

Abstract

The present invention relates to a technology for manufacturing eco-friendly lightweight synthetic wood by recycling waste plastic, and more specifically, to a method for manufacturing eco-friendly lightweight synthetic wood by recycling waste plastic by selecting, collecting, washing, and crushing waste plastic, and then extruding and foaming a synthetic wood composition mixed with wood flour, etc., in a certain ratio to produce lightweight synthetic wood, wherein the method comprises: (a) a step of selecting waste plastic of PVC components from collected waste plastic; (b) a step of drying the selected waste plastic to a moisture content of 8% or less; (c) a step of crushing the dried waste plastic to form a powder; (d) a step of mixing fibrous wood flour and additives with the waste plastic powder in a certain mixing ratio to form a synthetic wood composition; and (e) a step of heating the synthetic wood composition to a certain temperature and extruding and foaming the synthetic wood to form an extrusion mold.

Description

Technology Field

[0001] The present invention relates to a technology for manufacturing eco-friendly lightweight synthetic wood by recycling waste plastic, and more specifically, to a method for manufacturing eco-friendly lightweight synthetic wood by recycling waste plastic, wherein waste plastic is sorted, collected, washed, and crushed, and then mixed with wood powder, etc., in a certain ratio to form a synthetic wood composition, which is then extruded and foam-molded to produce lightweight synthetic wood. Background Technology

[0002] Waste plastic is the primary cause of environmental pollution among synthetic resins, and research is being conducted on ways to process the waste plastic that accumulates every year. Solutions for processing waste plastic include improving recycling technologies, developing biodegradable plastics, changing consumer behavior patterns to avoid using single-use plastics, and strengthening global regulations.

[0003] While developing biodegradable plastics offers the advantage of making non-biodegradable plastics degradable, such development can be costly. Additionally, although methods to reduce single-use plastics by changing consumer patterns have been proposed, consumers are not easily changing their habits due to the convenience and ease of use. For these reasons, recycling is currently being presented internationally as the best solution for reducing environmental pollution.

[0004] Waste plastic is a petrochemical product manufactured from fossil fuels, and it emits significant amounts of greenhouse gases during its production and disposal processes. These greenhouse gases are having a considerable impact on global warming and climate change. As is well known, plastic does not biodegrade in nature or can take hundreds of years to break down, causing it to accumulate in the natural environment over long periods. Furthermore, during the decomposition process, it breaks down into microplastics, infiltrating ecosystems while polluting soil, water, and air. Microplastics can enter crops via rivers, and once they enter the ocean, they are absorbed by fish along with plankton; consequently, these microplastics eventually return to humans through fish and other aquatic life.

[0005] In addition, plastics often contain harmful chemicals such as plasticizers, flame retardants, and stabilizers, and when released into the natural environment, they can be toxic to living organisms and humans. Furthermore, harmful substances such as dioxins and furans are generated during incineration, and these harmful substances can cause air pollution and problems for human health.

[0006] Therefore, in order to reduce environmental pollution from these waste plastic products and minimize harm to humans caused by microplastics, toxins, or heavy metals contained in the plastic, it is most desirable for them to be recycled.

[0007] As recycling methods for waste plastics, options include incorporating waste plastics into synthetic wood for joint use or producing synthetic wood products containing waste plastics; recently, methods for manufacturing synthetic wood utilizing waste plastics are being proposed.

[0008] As a means of utilizing such waste plastics, it is a time when there is an urgent need for technological proposals that can recycle them in an eco-friendly way and better protect the environment, rather than simply selling or incinerating them. Prior art literature

[0009] Registered Patent No. 10-2566271 (Registered Aug. 8, 2023) Registered Patent No. 10-2552574 (Registered July 3, 2023) Registered Patent No. 10-2517438 (Registered March 29, 2023) Registered Patent No. 10-2016880 (Registered Aug. 26, 2019) The problem to be solved

[0010] The present invention was devised to solve the above-mentioned problems and aims to provide a method for manufacturing eco-friendly lightweight synthetic wood by recycling waste plastic, which enables the production of eco-friendly lightweight synthetic wood by recycling waste plastic. means of solving the problem

[0011] To achieve the above objective, the present invention provides a method for manufacturing eco-friendly lightweight synthetic wood recycled from waste plastic, characterized by comprising: (a) a step of separating waste plastic of PVC components from collected waste plastic; (b) a step of drying the separating waste plastic to a moisture content of 8% or less; (c) a step of crushing the dried waste plastic to form a powder; (d) a step of mixing fibrous wood powder and an additive in a certain mixing ratio to form a synthetic wood composition; and (e) a step of extruding the synthetic wood composition at a certain temperature and extruding and foaming the synthetic wood.

[0012] Step (a) of the present invention is characterized by comprising: (a-1) a step of separating only PVC from waste plastic using an optical separator; and (a-2) a metal removal step of separating metal from the waste plastic separated in the first step.

[0013] Step (b) of the present invention is characterized by comprising: (b-1) a step of washing the selected waste plastic; and (b-2) a step of drying the washed waste plastic by feeding it into a stirrer and rotating it at a constant speed to a moisture content of 8% or less.

[0014] Step (c) of the present invention is characterized by comprising: (c-1) a step of feeding dried waste plastic into a crusher and crushing it to 100 mesh or less; and (c-2) a step of cooling the crusher while crushing the waste plastic so that the internal temperature of the crusher is maintained at 15℃ to 20℃.

[0015] In step (d) of the present invention, the synthetic wood composition is characterized by being composed of 45 to 47 weight% waste plastic powder, 50 to 51 weight% fibrous wood powder, and 3 to 4 weight% additives.

[0016] The additive of the present invention is characterized by comprising 20 to 30 weight% of a dispersant, 60 to 65 weight% of a modifier, and 5 to 20 weight% of a foaming agent.

[0017] In the present invention, the waste plastic acts as a crosslinking agent during extrusion molding, and the foaming agent is characterized as being a closed-cell foaming agent.

[0018] In the present invention, the synthetic wood is characterized by being extruded such that a cavity is formed inside during extrusion molding, and a foaming agent is injected into the cavity to foam and extrude the synthetic wood. Effects of the invention

[0019] According to the method for manufacturing eco-friendly lightweight synthetic wood using waste plastic according to the present invention, since synthetic wood is manufactured by recycling waste plastic that is generally discarded, it has advantageous benefits when considering the cost-saving effect of waste disposal, even if social costs are incurred due to the disposal of waste plastic.

[0020] In addition, the method for manufacturing eco-friendly lightweight synthetic wood using recycled waste plastic according to the present invention has the effect of reducing carbon emissions and contributing to environmental protection because the produced waste plastic is recycled.

[0021] In addition, the method for manufacturing synthetic wood using recycled waste plastic according to the present invention has the effect of preventing environmental pollution and contributing to reducing climate change by recycling waste plastic, which was previously disposed of as waste, for new uses.

[0022] In addition, the method for manufacturing synthetic wood using recycled waste plastic according to the present invention has an advantageous effect in terms of manufacturing cost of synthetic wood because the processing additives contained in the waste plastic can be used as is.

[0023] In addition, the method for manufacturing synthetic wood using recycled waste plastic according to the present invention has the advantage of reducing the overall costs incurred during the manufacturing of synthetic wood because the processing additive is reused.

[0024] In addition, the method for manufacturing synthetic wood using recycled waste plastic according to the present invention has the advantage of being able to produce a product in which the specific gravity of the manufactured synthetic wood is less than 1.0. Brief explanation of the drawing

[0025] FIG. 1 is a flowchart of a method for manufacturing synthetic wood recycled from waste plastic according to the present invention. FIG. 2 is a flowchart relating to the process of recycling waste plastic and molding it into synthetic wood according to the present invention. Specific details for implementing the invention

[0026] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the embodiments described below are merely intended to provide a detailed description sufficient for a person skilled in the art to easily practice the invention, and do not imply that the scope of protection of the present invention is limited thereby. Furthermore, in describing various embodiments of the present invention, the same reference numerals will be used for components having the same technical features.

[0027] FIG. 1 is a flowchart of a method for manufacturing synthetic wood recycled from waste plastic according to the present invention, and FIG. 2 is a flowchart of a process for molding synthetic wood by recycling waste plastic according to the present invention.

[0028] As illustrated in FIG. 1, the method for manufacturing eco-friendly lightweight synthetic wood recycled from waste plastic according to the present invention comprises: (a) a step of sorting waste plastic of PVC components from collected waste plastic (S1); (b) a step of drying the sorted waste plastic to a moisture content of 8% or less (S2); (c) a step of crushing the dried waste plastic to form a powder (S3); (d) a step of mixing fibrous wood powder and an additive in a certain mixing ratio to form a synthetic wood composition (S4); and (e) a step of heating the synthetic wood composition to a certain temperature and extruding and foaming the synthetic wood to form an extrusion mold (S5), and each step is to be described in detail below.

[0030] 1. Sorting stage of waste plastic (S1):

[0031] First, waste plastic is sorted using a sorter. The waste plastic sorter can sort plastics by type or based on criteria such as weight. An optical sorter can be used as the sorter. The sorting step (S1) of waste plastic can be further subdivided into a step (S11) of sorting only PVC using an optical sorter and a metal removal step (S12) of separating metal from the waste plastic sorted in the first step. An optical sorter can be used to sort only PVC of the same type (S11), and the optical sorter detects the material and color of the plastic using near-infrared and visible light, thereby sorting various types of plastic. In the present invention, only PVC is sorted. Once the sorting of PVC is completed, a step (S12) of removing metal contained in the PVC is performed. The step of removing metal contained in the PVC can be performed by crushing the PVC into small particles and separating the metal and plastic using magnetic force or eddy current. Additionally, separation can be performed on a gravity table using the density difference between the metal and the PVC.

[0033] 2. Drying step of waste plastic (S2):

[0034] Next, the waste plastic undergoes a drying step. The waste plastic is dried to a moisture content of 8%. This process consists of a washing step (S21) for the sorted waste plastic and a drying step (S22) in which the washed waste plastic is fed into a stirrer and rotated at a constant speed to reduce the moisture content to 8% or less. First, the sorted waste plastic is washed (S21). Waste plastic sorted to contain only PVC is washed to remove impurities remaining in the waste plastic. Once the removal of impurities is complete, the washed waste plastic is dried while being stirred through a stirrer to achieve a constant moisture content of 8% or less (S22). A stirrer capable of heating to a certain temperature may be used to adjust the moisture content to 8% or less. The stirring speed of the stirrer is adjusted to 1000 rpm at low speed and to 3000 to 5000 rpm at high speed to control the moisture content of the waste plastic to 8%. Since the agitator may be heated to a high temperature while stirring to adjust the moisture content, problems such as carbonization of the waste plastic inside may occur. Therefore, to prevent carbonization of the waste plastic, a temperature sensor and a humidity sensor may be installed inside the agitator, and a controller may be provided to adjust the rotation speed and operating time by receiving signals from the temperature and humidity sensors.

[0036] 3. Waste plastic crushing step (S3):

[0037] Next, the waste plastic undergoes a step of crushing to form powder. The dried waste plastic is fed into a crusher and crushed to produce powder, at which time the powder is pulverized to have a particle size of 100 mesh or less. Specifically, this can be subdivided into a step (S31) of feeding the dried waste plastic into a crusher and crushing it to 100 mesh or less, and a step (S32) of cooling the crusher during the crushing of the waste plastic so that the internal temperature of the crusher is maintained at 15℃ to 20℃.

[0038] Prior to the crushing step, the crushed product containing heavy metals impregnated in the waste plastic can be separated by passing it through a secondary separator, which is a heavy metal separator, and then the crushing step can be performed.

[0039] Next, waste plastic is fed into a crusher and crushed to a size of 100 mesh or less (S31). When crushing waste plastic to pulverize it, if the temperature rises, the powder may form lumps due to the influence of additives during the first molding process. To prevent this, it is desirable to cool the crusher so that its temperature is maintained below room temperature. The crusher is cooled by using cooling water or air cooling on the outer surface of the crusher to maintain a constant temperature of 20°C to 30°C. More preferably, the waste plastic is crushed while being cooled to maintain a temperature of 15°C to 20°C during crushing (S32).

[0041] 4. Synthetic wood composition formation step (S4):

[0042] Next, a step is taken to form a synthetic wood composition by mixing certain components with finely pulverized waste plastic powder. The mixing ratio of the certain components consists of 45 to 47 weight% of waste plastic powder, 50 to 51 weight% of fibrous wood powder, and 2 to 5 weight% of additives.

[0043] Dispersants, modifiers, and foaming agents may be further added as additives. When the total additives make up 100%, the additives consist of 20 to 30 weight% of dispersant, 60 to 65 weight% of modifier, and 5 to 20 weight% of foaming agent.

[0044] The purpose of adding a dispersant is to improve the melt flowability of water, thereby allowing the extruded material to form a pattern similar to natural wood during molding into artificial wood. At this time, it is preferable to add 20 to 30 weight percent of the dispersant relative to the total weight of the additives; if the amount of dispersant is excessive, there is a problem with difficulty in mixing. The dispersant is not particularly limited, but a carboxyl-based dispersant is preferred.

[0045] It is preferable to add a modifier in an amount of 60 to 65 weight percent relative to the total weight of the additives. At this time, if the amount of the modifier among the additives is less than 60 weight percent, there is a disadvantage that the modification effect is insufficient, and if it exceeds 65 weight percent, there is a disadvantage that the modification effect is not further improved and only the cost burden becomes significant. Although not specifically limited, it is preferable to use maleic anhydride as the modifier.

[0046] It is preferable to add a foaming agent in an amount of 5 to 20 weight percent relative to the total weight of the additives. At this time, if the amount of foaming agent among the additives is less than 5 weight percent, there is a disadvantage that the foaming effect is insufficient, and if it exceeds 20 weight percent, there is a disadvantage that the physical properties are degraded.

[0048] Foaming and extrusion molding step (S5):

[0049] Next, the synthetic wood is extruded while foaming and extruding the synthetic wood mixture. The step of extruding the synthetic wood includes, as illustrated in FIG. 2, a step of mixing a composition of 45 to 47 weight% of waste plastic powder, 50 to 51 weight% of fibrous wood powder, and 2 to 5 weight% of additives by feeding it into a high-speed mixer (S51); a step of extruding the mixture mixed in the mixer while heating the first heater of the molding machine to 250°C (S52); a step of extruding the mixture that has passed through the first heater while heating it to 220°C in the second heater (S53); a step of extruding the mixture that has passed through the second heater while heating it to 200°C in the third heater (S54); and a step of foaming and extruding the mixture that has passed through the third heater of the molding machine while maintaining the fourth heater, fifth heater, and sixth heater at 150°C to 180°C (S55). In the extrusion process, a synthetic wood composition is heated and melted to a certain temperature to form internal cavities, and during the extrusion process, a foaming agent is injected into these cavities to foam and produce extruded synthetic wood. Since foaming occurs as the foaming agent is injected into the internal cavities, the foamed internal space becomes lighter than the extruded outer surface, thereby reducing the overall specific gravity of the synthetic wood.

[0050] As the mixture passes through each of the above heaters, the heating temperature is sequentially reduced and the mixture is extruded. As the mixture passes through each heater, it is foamed and extruded, and the mixture that has passed through the molding machine is downsized and extruded as it passes through a die (S56). Afterwards, the extruded synthetic wood is cooled (S57) to complete the final product (S58).

[0051] According to the present invention, since a foaming agent is used, lightweight synthetic wood with a specific gravity of less than 1 can be produced due to the foaming of individual internal closed-cell foaming agents. That is, when waste plastic is extruded as powder, it acts as a crosslinking agent and reacts with a closed-cell foaming agent to form a number of closed pores. Consequently, the specific gravity of the synthetic wood becomes less than 0.9 to 1.0 due to the foaming of the foaming agent in the internal space of the synthetic wood, thereby producing synthetic wood. Accordingly, it is possible to manufacture synthetic wood that is lighter than general synthetic wood and has lower water expansion, as the foam cells suppress the water expansion of the product according to temperature, while having high strength performance greater than the average strength of synthetic wood and, in particular, a specific gravity of less than 1, which is significantly lighter than the average specific gravity of synthetic wood (1.25).

[0052] In addition, according to the present invention, there are advantages such as reducing environmental carbon emissions by recycling waste plastics, solving difficult problems, and reducing social problems by manufacturing synthetic wood with eco-friendly effects.

[0054] Although embodiments of the present invention have been described above, it is understood that those skilled in the art can make various modifications without departing from the scope of the claims of the present invention. Explanation of the symbols

[0055] S1: Waste plastic sorting stage S2: Step of drying to a moisture content of 8% or less S3: Step of crushing waste plastic into a certain size S4: Step of forming a synthetic wood composition S5: Step of extruding synthetic wood

Claims

Claim 1 (a) a step of first sorting only the waste plastics containing PVC components from the collected waste plastics and then removing metal through magnetic separation; (b) a step of washing the sorted waste plastics, then feeding them into a stirrer and drying them to a moisture content of 8% or less while rotating; (c) a step of feeding the dried waste plastics into a crusher and crushing them to 100 mesh or less, while cooling the crusher to maintain the internal temperature of the crusher at 15℃ to 20℃ to form waste plastic powder; (d) a step of mixing 45 to 47 weight% of the waste plastic powder, 50 to 51 weight% of fibrous wood flour, and 2 to 5 weight% of additives, wherein the additives consist of 20 to 30 weight% of a dispersant, 60 to 65 weight% of a modifier, and 5 to 20 weight% of a foaming agent, and wherein the foaming agent is a closed-cell foaming agent to form a synthetic wood composition; and (e) a step of heating and extruding the synthetic wood composition, wherein a cavity is formed inside the synthetic wood during extrusion molding, and extruding while foaming by introducing the foaming agent into the cavity; wherein the waste plastic acts as a crosslinking agent during extrusion molding, characterized in that the waste plastic is recycled from waste plastic. Claim 2 A method for manufacturing eco-friendly lightweight synthetic wood recycled from waste plastic according to claim 1, wherein in step (b), the stirrer is dried while rotating at a speed of 1,000 to 5,000 rpm. Claim 3 A method for manufacturing eco-friendly lightweight synthetic wood recycled from waste plastic, characterized in that, in claim 1, the modifier is maleic anhydride. Claim 4 A method for manufacturing eco-friendly lightweight synthetic wood recycled from waste plastic according to claim 1, wherein step (e) is characterized by extruding through six stages of temperature control, in which the first heater is heated to 250°C, then sequentially lowered to 220°C and 200°C, and finally lowered to 150°C to 180°C. Claim 5 A method for manufacturing eco-friendly lightweight synthetic wood recycled from waste plastic, characterized in that, in claim 1, the specific gravity of the manufactured synthetic wood is less than 0.9 to 1.

0. Claim 6 delete Claim 7 delete Claim 8 delete

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