Method and facility for manufacturing resin molding

Abstract

To provide a method and a facility for manufacturing a resin molding having high apparent density, which suppress generation of powder at the time of handling of the molding.SOLUTION: A method for manufacturing a resin molding includes: a molding step of extrusion molding synthetic resins mainly consisting of a thermoplastic resin in a heated state, and obtaining a compressed body; a cutting step of cutting the compressed body by a heated cutting blade, and obtaining a cut body; and a cooling step of cooling the cut body, and obtaining the resin molding. A facility for manufacturing the resin molding includes: an extrusion molding machine for extrusion molding the synthetic resins mainly consisting of the thermoplastic resin in the heated state, and obtaining the compressed body; a heating cutting machine for cutting the compressed body extrusion molded by the extrusion molding machine by the heated cutting blade, and obtaining the cut body; and a cooling facility for cooling the cut body cut by the heating cutting machine.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and equipment for producing resin molded articles by extrusion molding of synthetic resins. In this specification, "synthetic resins" includes not only used plastics that are general waste, commonly known as waste plastics, but also plastics that become industrial waste, such as scraps and defective synthetic resins generated during the manufacturing process, and used plastics. [Background technology]

[0002] In recent years, steelworks have begun to use carbon sources other than coal, such as LNG, as fuel and reducing agents due to societal demands for reducing carbon dioxide emissions and rising coking coal prices. However, to further reduce carbon dioxide emissions, there is a need to reduce dependence on fossil fuels such as LNG. Against this backdrop, efforts are being made to recycle waste plastics as a carbon source. Traditionally, much of the waste plastic has been incinerated. However, incineration has a significant environmental impact, including the generation of carbon dioxide, and also poses the problem of thermal damage to the incinerator. Therefore, recycling waste plastics as a carbon source in steelworks could solve these problems. One chemical recycling technology for waste plastics involves mixing the waste plastics with coal in the steelworks' coke ovens and dry-distilling them together.

[0003] When waste plastics are mixed with coal and dry-distilled in a coke oven, the waste plastics have the property of extracting hydrogen from the coal at the contact surface with the coal during the dry-distillation process. This hydrogen extraction reduces the melting point of the coal, resulting in a decrease in the strength of the coke after dry-distillation. Therefore, it is preferable that the contact surface between the coal and the waste plastics to be dry-distilled is small. If the apparent density of the waste plastics is low, the specific surface area of ​​the waste plastics increases, increasing the contact area with the coal. Therefore, increasing the apparent density of the waste plastics is important for preventing a decrease in coke strength.

[0004] Technologies for increasing the apparent density of waste plastics have been developed. For example, Patent Document 1 discloses a method for producing a plastic molded body by heating waste plastic to 180 to 260°C, compression-molding (extrusion-molding), cutting, and cooling (quenching) in a water-cooling device. Patent Document 2 discloses a method for heating waste plastic to 100 to 140°C, compression-molding (extrusion-molding), and then cooling by spraying water on a cooling conveyor. Patent Document 3 discloses a method for extrusion-molding plastic while heated to a temperature higher than 140°C but lower than 180°C, and then cooling the resulting plastic molded body with air to 40°C or lower. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-327189 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-103336 [Patent Document 3] Japanese Patent Publication No. 2023-007040 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional technology has the following problems. The method described in Patent Document 1 involves heating waste plastics to 180 to 260°C and compression molding them. The document states that when the temperature of waste plastics is below 180°C, the high viscosity of the plastic makes molding difficult, and gas trapped in the compressed plastic is difficult to escape, resulting in a low apparent density after molding. However, when the viscosity of plastics is reduced by heating them at high temperatures as in Patent Document 1, the fluidity of the plastics becomes too high, making it impossible to maintain a constant discharge (extrusion) rate from the compression molding machine, resulting in unstable productivity. Furthermore, the method described in Patent Document 1 requires rapid cooling of the molded body discharged (extruded) from the compression molding machine to maintain its shape due to the high fluidity of the plastics. However, according to experiments conducted by the inventors, rapid cooling forms a solidified phase on the surface of the plastic molded body, which in turn prevents the remaining gas from escaping. As a result, voids corresponding to the remaining gas remain within the plastic molded body.

[0007] On the other hand, the method described in Patent Document 2 involves heating waste plastics to 100 to 140°C and compression molding them. This document states that if molding is performed at a temperature above 140°C, the plastics will be in a molten or semi-molten state, which will cause excessive fluidity, hindering extrusion and reducing productivity. Unless the plastics are in a molten or semi-molten state, extrusion compression molding is not possible, and the apparent density cannot be made sufficiently high.

[0008] In addition, the method described in Patent Document 3 involves heating plastic to a temperature above 140°C but below 180°C, compression molding, and then air cooling. This method can increase the apparent density of plastic molded bodies to a certain extent. However, all of the methods described in Patent Documents 1 to 3 have the problem of generating powder after cutting the molded body, which reduces yield.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a method and equipment for producing resin molded bodies with high apparent density by suppressing the generation of powder during handling of the molded bodies. [Means for solving the problem]

[0010] The inventors have conducted extensive research into the manufacturing conditions for resin molded articles that can solve the above-mentioned problems, and as a result have developed the following novel manufacturing method and manufacturing equipment. That is, the gist of the present invention for solving the above-mentioned problems is as follows. [1] A molding process in which synthetic resins mainly composed of thermoplastic resins are extruded in a heated state to obtain a compressed body; a cutting step of cutting the compressed body with a heated cutting blade to obtain cut bodies; a cooling step of cooling the cut body to obtain a resin molded body; A method for producing a resin molded product, comprising: [2] The method for producing a resin molded product according to the above [1], wherein in the molding step, the synthetic resin is extrusion molded in a state where the synthetic resin is heated to a temperature higher than 140°C and lower than 180°C. [3] The method for producing a resin molded product according to the above [1] or [2], wherein the temperature of the cutting blade in the cutting step is set to a temperature in the range of not less than the heating temperature in the molding step and less than 260°C. [4] In any one of the above [1] to [3], the apparent density of the resin molded body obtained in the cooling step is 0.9 to 1.1 g / cm 3 The method for producing a resin molded body is as follows. [5] An extrusion molding machine for extruding synthetic resins, mainly thermoplastic resins, in a heated state to obtain a compressed body; a heating cutter for cutting the compressed body extruded by the extrusion molding machine with a heated cutting blade to obtain cut bodies; and a cooling facility for cooling the cut body cut by the heating cutter. [6] In the above [5], the heating cutter has a function of adjusting the temperature of the cutting blade so that it is equal to or higher than the temperature at which the extrusion molding machine heats the synthetic resins and is lower than 260°C. [Effects of the Invention]

[0011] According to the present invention, mainly in the production of resin molded products, the cutting blade is heated to a high temperature when cutting the resin molded product, so the cut surface remains molten for a while, and powdering of the cut surface of the resin molded product can be suppressed. This improves yield and suppresses the inclusion of powder in subsequent processes. Therefore, the present invention is particularly suitable as a method and equipment for producing resin molded products to be mixed with coal and dry-distilled in a coke oven. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an explanatory diagram schematically illustrating an embodiment of a method and equipment for producing a resin molded body according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following is a detailed description of embodiments of the present invention. The following embodiments are intended to exemplify equipment and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope defined in the claims.

[0014] A method for producing a resin molded product according to one embodiment of the present invention includes a molding step of extrusion-molding a synthetic resin in a heated state, a cutting step of cutting the compressed product with a heated cutting blade, and a cooling step. In the molding step, a compressed product is obtained by extrusion-molding a synthetic resin in a heated state at a temperature higher than 140°C and lower than 180°C. In the cutting step, the compressed product is cut with a heated cutting blade to obtain cut products. In the cooling step, the cut products are preferably air-cooled to form resin molded products at a temperature of 40°C or less.

[0015] (synthetic resins) In this embodiment, the synthetic resins, which are one of the raw materials for the resin molded body, are primarily thermoplastic resins. That is, the synthetic resins contain 50% by mass or more of thermoplastic resin. Preferably, the synthetic resins contain 80% by mass or more of thermoplastic resin. The synthetic resins include waste plastics, which may be pre-treated, as necessary, by crushing, air sorting, magnetic sorting, or the like. Examples of thermoplastic resins include polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride. The raw material is a synthetic resin primarily composed of a thermoplastic resin containing one or more of these. The difference in physical properties between synthetic resins and biomass, which will be described later, is important. Therefore, the average particle size, density, and mass are measured in advance. The average particle size of synthetic resins is the cumulative 50% passing diameter based on the equivalent sphere volume.

[0016] <Forming process> The type and format of the extrusion molding machine used in this embodiment are not particularly limited. Any machine can be used as long as it compresses, i.e., consolidates, synthetic resins, and heats them to a predetermined temperature before extruding them from a die, i.e., an extrusion nozzle, to obtain a compressed body. A typical example is a screw-type extrusion molding machine that compresses and extrudes synthetic resins using a screw, but is not limited to this. Furthermore, the method for heating the synthetic resins to a predetermined temperature is not limited. For example, a method in which a heating element such as an electric heater is attached to the outer periphery of the extrusion molding machine to heat the synthetic resins inside, or a method in which a heating mechanism is provided in the die portion of the extrusion molding machine and the synthetic resins are heated only in this die portion can be used.

[0017] In this embodiment, the heating temperature of the synthetic resins extruded in the extrusion molding machine, i.e., the extrusion molding temperature, is set to greater than 140°C and less than 180°C, thereby maintaining the synthetic resins in a molten or semi-molten state during extrusion molding. This facilitates extrusion molding of the synthetic resins in a consolidated state, and since the synthetic resins have a constant viscosity, productivity can be maintained at a constant level. If the heating temperature of the synthetic resins extruded in the extrusion molding machine is 140°C or lower, the synthetic resins do not reach a molten or semi-molten state and cannot be extruded in a sufficiently consolidated state. As a result, the apparent density of the resin molded product cannot be sufficiently high. On the other hand, if the heating temperature of the synthetic resins is 180°C or higher, the viscosity of the synthetic resins decreases and the flowability becomes too high. As a result, the extrusion speed from the extrusion molding machine cannot be maintained at a constant level, resulting in unstable productivity.

[0018] <Cutting process> In this embodiment, a cutter is installed at the outlet of the extrusion molding machine, and a heated cutting blade is used to cut the compressed body extruded from the extrusion molding machine into pieces of appropriate size. It is preferable to heat the cutting blade with a heater. For example, the heater may be an internal heating type, in which an electric heater is covered with a metal such as ceramic, and the shape of the heater does not interfere with cutting the compressed body of synthetic resins. In the cutting step, the compressed body obtained by extrusion molding is cut into pieces of 200 to 1000 cm3 in volume by the cutter. 3 It is preferable to cut the resin compact into a size of 1000 cm3 to produce a resin compact product. If the volume is above the lower limit, when such a resin compact is mixed with coal and dry-distilled in a coke oven, the contact area between the dry-distilled coal and the resin compact is small, and a decrease in the strength of the produced coke can be suppressed. On the other hand, there is no particular upper limit to the volume of the resin compact. When mixed with coal and dry-distilled in a coke oven, the volume of the resin compact is 1000 cm3. 3 If the volume exceeds 1000 cm, the voids after thermal decomposition of synthetic resins will become large, which may cause voids in the product coke and lead to a decrease in coke strength. Therefore, when resin compacts are mixed with coal and used for carbonization in a coke oven, the volume of the resin compact should be less than 1000 cm. 3 It is preferable to do the following:

[0019] In this embodiment, the temperature of the cutting blade is preferably set to a range between the heating temperature in the molding process and less than 260°C. If the heating temperature of the cutting blade is lower than the heating temperature in the molding process, the semi-molten compressed body near the cut surface is rapidly cooled by contact with the cutting blade, and a solidified phase is formed on the surface of the cut body. This may prevent the gas remaining in the cut body from escaping. As a result, voids corresponding to the remaining gas remain in the resin molded body, resulting in a decrease in apparent density. On the other hand, if the heating temperature of the cutting blade is set to 260°C or higher, the cut surface may melt excessively, causing burn-through at the molten surface and reducing yield. Furthermore, there is a risk of low-boiling-point plastics vaporizing, which may lead to the generation and leakage of toxic gases and reduced yield.

[0020] <Cooling process> In this embodiment, after the cutting process, the cut pieces are cooled in a cooling facility (air cooling) to form resin molded bodies. The gradual cooling effect of air cooling allows gas components to be appropriately released from the resin molded body, thereby improving the apparent density of the plastic molded body.

[0021] The average cooling rate when the cut pieces after the cutting step are cooled by air to 40°C or less is preferably less than 10°C / min. This allows the above-mentioned effects to be effectively achieved. Here, the average cooling rate refers to the cooling rate at the average temperature of the entire cross section of the resin molded product. The cut pieces after the cutting step are usually cut to an appropriate size and air-cooled to 40°C or less. Specific cooling methods include, for example, placing the cut pieces in a pit or container and allowing them to cool in the air, or slowly cooling them in a pit or container with a heat-insulating cover to control the cooling rate.

[0022] In this embodiment, the apparent density of the resin molding is the average value of the apparent densities of 10 resin moldings randomly selected.

[0023] In this embodiment, the resin molded body produced through the above-described steps has a small amount of gas components remaining in the resin molded body and an apparent density of 0.9 to 1.1 g / cm 3In this embodiment, the temperature of the cutting machine is higher than the temperature of the compressed body, so the compressed body does not rapidly cool. As a result, the vicinity of the cut surface of the cut body remains molten for a while, and the remaining gas inside the cut body naturally escapes. In addition, after the remaining gas escapes, the plastic molded body near the cut surface remains molten for a while, filling the voids caused by the remaining gas, further improving the apparent density. Furthermore, in conventional extrusion molding machines, the cut surface is not heated, so powder is generated from the cut surface. This leads to a decrease in yield. However, in this embodiment, the cut surface remains molten for a while, reducing the generation of powder and improving yield.

[0024] Figure 1 shows a schematic diagram of an example of manufacturing equipment suitable for use in the method for manufacturing a resin molded body according to this embodiment. 1 is an extrusion molding machine (compression molding machine) that extrudes a heated synthetic resin A. 3 is a cooling facility that air-cools the cut pieces extruded and cut from the extrusion molding machine 1. 6 is a cutting blade of a cutter that cuts the compressed body extruded and molded by the extrusion molding machine into cut pieces B of a predetermined size.

[0025] The extrusion molding machine 1 of this embodiment is a screw-type extrusion molding machine, and a screw shaft (not shown) is disposed inside a cylindrical casing 10 (machine body) along the longitudinal direction of the casing for pushing synthetic resins A. This screw shaft is driven to rotate by the power of a drive unit (not shown).

[0026] A supply port 12 for supplying synthetic resin A is disposed at one end of the casing 10. An extrusion die 13 is provided at the other end of the casing. A cutter 6 (cutting blade) is provided on the outside of the die 13 for cutting the extruded compressed body to an appropriate length. In addition, a heating element 14 such as an electric heater is provided on the outer periphery of the casing 10 so that the synthetic resin A inside the casing 10 can be heated.

[0027] In this embodiment, extrusion molding is performed at normal pressure. Note that a pressure reducing means (gas suction means) may be provided to suck out gas from inside the extrusion molding machine 1 and reduce the pressure inside the machine to below atmospheric pressure. For this purpose, an exhaust port is provided midway through the casing 10, and pressure reducing means such as a suction blower or vacuum pump is connected to this exhaust port via an exhaust pipe.

[0028] The cutting machine has a cutting blade 6 heated by a heater 7. For example, the heater may be an internal heating type in which the electric heater is covered with a metal such as ceramic, and the shape does not interfere with cutting plastic.

[0029] The cooling equipment 3 is composed of, for example, a pit or a container for storing the cut pieces extruded and cut from the extrusion molding machine 1. This cooling equipment 3 may simply store the cut pieces and allow them to cool in the atmosphere, or it may be equipped with a heat-insulating cover to control the cooling rate and allow the cut pieces to be cooled slowly.

[0030] In this embodiment, synthetic resin A, primarily composed of thermoplastic resin, is fed into extrusion molding machine 1 through supply port 12. The synthetic resin A is forced into casing 10 by the screw shaft, where it is heated while being compressed (consolidated). The primary heat source for heating is heating element 14, but frictional heat of synthetic resin A due to consolidation may also be a heat source. This heating results in a molten or semi-molten state, and the synthetic resin A is extruded through die 13 at a heating temperature (extrusion temperature) greater than 140°C and less than 180°C. Furthermore, extrusion molding of synthetic resin A is preferably performed while reducing the pressure inside extrusion molding machine 1 to less than atmospheric pressure by suctioning gas from inside extrusion molding machine 1 using a pressure reducing means. This allows for the removal of water vapor generated within extrusion molding machine 1 and prevents residual gas from being mixed into the resin molded body.

[0031] The synthetic resin A extruded from the die 13 is cut into an appropriate size by a heated cutting blade 6 at the die outlet, and cut pieces B are obtained. The cut surfaces of the cut pieces B are temporarily melted. The cut pieces are then air-cooled in the cooling equipment 3 to a temperature of 40°C or less, preferably at an average cooling rate of less than 10°C / min. This allows gas components to be appropriately released from the cut pieces, and a resin molded piece C with a high apparent density can be obtained. The resin molded piece C obtained in this manner has little gas components remaining inside and is sufficiently compacted. [Example]

[0032] As shown below, Example 1 of the invention and Comparative Example 1 were prepared and their physical properties were compared. (Example 1) Using the resin molding manufacturing equipment shown in Figure 1, resin moldings were manufactured using plastics primarily composed of thermoplastic resin as raw materials. The plastic was fed into an extrusion molding machine, compressed (consolidated) while being heated, and extrusion-molded at a heating temperature of 150°C (extrusion molding temperature) to obtain a compressed body. A cutting blade was heated to 180°C with a heater to cut the compressed body, obtaining cut bodies. The obtained cut bodies were air-cooled to below 40°C, and then the plastic molding product was obtained. The apparent density of 10 randomly selected plastic moldings was measured using the submerged weighing method, and the average of these measurements was used as the apparent density of the product. (Comparative Example 1) The plastic was extruded under the same conditions as in Example 1, except that the cutter was not heated. Other conditions were the same as in Example 1.

[0033] The following shows a comparison of the apparent density and dust generation rate of the plastic molded articles produced in Example 1 and Comparative Example 1. Here, the dust generation rate is defined as the mass of dust generated relative to the total mass of plastics used in molding. The apparent density of the plastic molded body (product) produced in Example 1 was 0.92 g / cm 3 In contrast, the apparent density of the plastic molded body (product) produced in Comparative Example 1 was 0.91 g / cm 3The rate of powder generation was 3.3%. This result shows that heating the cut surface is effective in increasing the apparent density and suppressing the amount of powder generation. From the above results, it was confirmed that the invention example can produce plastic molded products with higher apparent density and less powder generation than the method of comparative example 1. [Explanation of symbols]

[0034] 1. Extrusion molding machine 10 Casing 12 Supply port 13 Die 14 Heating element 3 Cooling equipment 6 Cutting machine (cutting blade) 7 Heater (heating machine) A. Plastics (synthetic resins) B cut body C Resin molded body

Claims

1. a molding step of extruding a synthetic resin, mainly a thermoplastic resin, in a heated state to obtain a compressed body; a cutting step of cutting the compressed body with a heated cutting blade to obtain cut bodies; a cooling step of cooling the cut body to obtain a resin molded body; A method for producing a resin molded product, comprising:

2. The method for producing a resin molded article according to claim 1, wherein the molding step comprises extrusion molding the synthetic resin in a state where the synthetic resin is heated to a temperature higher than 140°C and lower than 180°C.

3. The method for producing a resin molded article according to claim 1 or 2, wherein the temperature of the cutting blade in the cutting step is set to a temperature in the range of not less than the heating temperature in the molding step but less than 260°C.

4. The apparent density of the resin molded body obtained in the cooling step is 0.9 to 1.1 g / cm ３ The method for producing a resin molded article according to claim 1 or 2, wherein

5. an extrusion molding machine for extruding synthetic resins, mainly thermoplastic resins, in a heated state to obtain a compressed body; a heating cutter for cutting the compressed body extruded by the extrusion molding machine with a heated cutting blade to obtain cut bodies; and a cooling facility for cooling the cut body cut by the heating cutter.

6. 6. The resin molding production facility according to claim 5, wherein the heat cutter has a function of adjusting the temperature of the cutting blade so that the temperature is equal to or higher than the temperature at which the synthetic resin is heated by the extrusion molding machine and lower than 260°C.

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