Method and apparatus for decomposing resins

Abstract

To provide a resin decomposition treatment method and a decomposition treatment apparatus capable of conducting a resin decomposition treatment safely and efficiently.SOLUTION: A resin decomposition treatment apparatus 10 includes: a cylinder 12; a resin supply part 11 configured to supply a thermoplastic resin to the cylinder 12; a screw 12a configured to transport the supplied thermoplastic resin and the molten and plasticized thermoplastic resin; a fluid supply part 13 configured to supply a fluid in a heated and pressured state inside the cylinder so as to apply a decomposition treatment to the molten and plasticized thermoplastic resin in a subcritical state or a supercritical state; an extrusion part 14 disposed on a top edge of the cylinder 12 and configured to eject a decomposition product of the thermoplastic resin out of the cylinder; a rotary driving mechanism 15 configured to rotary-drive the screw 12a; and a counter flow restraint mechanism 16 configured to restrain a counter flow of the thermoplastic resin molten and plasticized inside the cylinder 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for decomposing resin, and more particularly to a method and an apparatus for decomposing resin that prevent backflow to the resin supply section side when performing the decomposition treatment of resin in a high-temperature and high-pressure state.

Background Art

[0002] Currently, plastic products are used in a very wide range of fields, and their usage amounts are enormous. On the other hand, the disposal of plastic products is costly, and there are also problems with the environmental impact caused by their components flowing into rivers, seas, etc. when they are left in the natural environment.

[0003] Therefore, various resins have been variously studied for effectively utilizing resources by recycling them. For example, a method of recovering and reusing monomers obtained by thermally decomposing acrylic resin using a twin-screw extruder is known (see, for example, Patent Document 1).

[0004] In recent years, as a method for decomposing resin, a method of obtaining monomers by exposing the resin to a fluid in a subcritical state or a supercritical state has also been studied.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, when using a subcritical state or a supercritical state, it is necessary to set a predetermined temperature and pressure according to the liquid (fluid) used, and usually, high-temperature and high-pressure conditions are required. Therefore, a decomposition treatment apparatus used for that purpose is considered to be sealed.

[0007] On the other hand, preparing a decomposition treatment device that can withstand such subcritical or supercritical conditions would require, for example, the manufacture of a dedicated device, resulting in high initial costs and consequently higher overall processing costs.

[0008] Therefore, the present invention aims to provide a resin decomposition method and decomposition apparatus that can safely and continuously perform resin decomposition processing in order to promote the recycling of resins as described above. [Means for solving the problem]

[0009] The resin decomposition method disclosed in this application comprises: (a) a step of supplying a thermoplastic resin from a resin supply unit to a cylinder; (b) a step of heating and pressurizing the supplied thermoplastic resin in the cylinder to melt and plasticize it; (c) a step of supplying a heated and pressurized fluid from a fluid supply unit to the melt and plasticized thermoplastic resin and mixing them; (d) a step of decomposing the melt and plasticized thermoplastic resin by exposing it to a subcritical or supercritical state with the supplied fluid; and (e) a step of extruding the decomposed product of the thermoplastic resin obtained in step (d) from an extrusion unit provided at the tip of the cylinder.

[0010] In this decomposition process, in step (b), at least one selected from the temperature of the thermoplastic resin, the pressure of the thermoplastic resin, and the temperature of the cylinder is measured, and a backflow suppression step is initiated to suppress the backflow of the molten and plasticized thermoplastic resin according to the measured value.

[0011] The resin decomposition apparatus disclosed herein comprises a cylinder; a resin supply unit for supplying a thermoplastic resin to be decomposed to the cylinder; a screw for transporting the supplied thermoplastic resin and the molten and plasticized thermoplastic resin within the cylinder; a fluid supply unit for supplying a heated and pressurized fluid into the cylinder in order to decompose the molten and plasticized thermoplastic resin in a subcritical or supercritical state; and an extrusion unit provided at the tip of the cylinder for discharging the decomposed thermoplastic resin to the outside of the cylinder.

[0012] Furthermore, the decomposition apparatus has a cylinder provided between the resin supply unit and the fluid supply unit, which includes at least one selected from a resin thermometer for measuring the temperature of the thermoplastic resin, a resin pressure gauge for measuring the pressure of the thermoplastic resin, a cylinder thermometer for measuring the temperature of the cylinder, and a screw measuring meter for measuring the energy consumption or driving torque of the rotary drive mechanism that drives the screw. The apparatus also has a backflow suppression mechanism that suppresses the backflow of the molten and plasticized thermoplastic resin in response to a change in at least one of the measured values ​​of the resin thermometer, the resin pressure gauge, the cylinder thermometer, and the screw measuring meter. [Effects of the Invention]

[0013] The resin decomposition method and decomposition apparatus disclosed in this application provide a safe and continuously operable resin decomposition method and apparatus. [Brief explanation of the drawing]

[0014] [Figure 1] This is a side view showing the schematic configuration of the resin decomposition apparatus according to Embodiment 1. [Figure 2] This is a side view illustrating the screw positioned inside the cylinder of the disassembly apparatus shown in Figure 1. [Figure 3] This figure provides a more detailed explanation of the backflow suppression mechanism in the decomposition apparatus shown in Figure 1. [Figure 4] This figure provides a more detailed explanation of the backflow suppression mechanism in the decomposition apparatus shown in Figure 1. [Figure 5] This is a flowchart illustrating the operation of the resin decomposition apparatus of Embodiment 1. [Figure 6] This is a side view showing the schematic configuration of the resin decomposition apparatus according to Embodiment 2. [Figure 7] This is a flowchart illustrating the operation of the resin decomposition apparatus of Embodiment 2. [Figure 8] This is a side view showing the schematic configuration of the resin decomposition apparatus according to Embodiment 3. [Figure 9] It is a flowchart for explaining the operation of the resin decomposition processing apparatus of Embodiment 3.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the embodiments will be described in detail based on examples and drawings. In all the drawings for explaining the embodiments, members having the same function are denoted by the same or related reference numerals, and repeated explanations thereof are omitted.

[0016] <Process of Consideration> First, the process of consideration of the present invention will be described. As described above, when decomposing (depolymerizing) resin with a fluid in a subcritical state or a supercritical state, usually, a sealed processing container capable of withstanding the processing conditions is often prepared. However, the present inventors considered whether a resin extruder used when forming a resin material could be used for this resin decomposition process.

[0017] That is, the present inventors thought that by using such a resin extruder, without preparing a special processing apparatus for the resin decomposition process, the existing extruder could be used as it is or with slight modification suitable for the decomposition process, and the resin decomposition process could be carried out continuously and efficiently.

[0018] An extruder usually supplies a thermoplastic resin as a raw material from one side of a cylindrical cylinder, gradually heats and kneads it in the cylinder, and conveys the melt-plasticized resin with a screw. Then, the melt-plasticized resin is sufficiently kneaded while being conveyed in the cylinder and is extruded from a die provided at the tip of the cylinder as a resin material that is uniformly mixed. Since the inside of this cylinder is under heated and pressurized conditions, it was assumed that in the above resin decomposition process, the apparatus could be used as it is and the decomposition process could be carried out by mixing a fluid in a subcritical state or a supercritical state and the resin in the cylinder. < /

[0019] [

[0019] In fact, the inventors of this invention tried decomposing resin under such conditions and confirmed that they could maintain a subcritical state in the cylinder and also perform the resin decomposition process.

[0020] However, when this disassembly process was continued, molten and plasticized resin and unmolten resin sometimes backflowed and ejected from the resin supply section of the extruder. This is thought to be because the resin supply section of the extruder is not normally sealed and is open to the atmosphere, causing the pressure of the molten resin that has been melted and plasticized in the cylinder to become greater than the pressure of the unmolten resin on the resin supply section side.

[0021] Therefore, in order to provide a resin decomposition apparatus that can continue and safely perform the resin decomposition process without backflow of the molten plasticized resin, even when using an extruder to decompose resin in a subcritical state, various studies were conducted, and a resin decomposition method and apparatus that can suppress backflow were found. The resin decomposition apparatus and decomposition method in this embodiment will be described in detail below.

[0022] <Embodiment 1> [Resin decomposition equipment] Figure 1 shows an example of the configuration of the resin decomposition apparatus according to Embodiment 1. Figure 2 is a diagram illustrating the screw arranged inside the cylinder of the resin decomposition apparatus shown in Figure 1, and is a side view.

[0023] The resin decomposition apparatus 10 shown in Figure 1 is a device used to decompose a resin to be decomposed by exposing it to a subcritical or supercritical fluid.

[0024] This resin decomposition processing apparatus 10 includes a resin supply unit 11, a cylinder 12 having a screw, a fluid supply unit 13 that supplies fluid to the cylinder 12, an extrusion unit 14, a rotary drive mechanism 15 that drives the screw of the cylinder 12, and a backflow suppression mechanism 16.

[0025] The resin supply unit 11 supplies the resin to be decomposed to the cylinder 12. In this embodiment, a thermoplastic resin is supplied as the resin to be decomposed. Various forms of thermoplastic resin are used as the supplied material, such as pellets, powder, and flakes. For example, the supplied material is introduced from above into the resin supply unit 11, which has a hopper, by a feeder or the like, and supplied into the cylinder 12. The following explanation will use the case where the supplied thermoplastic resin is pellets as an example.

[0026] The cylinder 12 has a screw 12a inside. Figure 2 shows a cross-sectional view of the cylinder 12 to show the internal structure of the resin decomposition apparatus 10 shown in Figure 1. Figure 2 also shows a fluid supply hole 12b where the fluid supply unit 13 is located, and a relief hole 12c that can discharge the molten and plasticized thermoplastic resin from inside the cylinder 12 to the outside.

[0027] By rotating this screw 12a, the supplied resin is gradually transported through the inside of the cylinder 12 toward the extrusion section 14 (downstream side). If a twin-screw system with two screws is used as this screw 12a, a twin-screw extruder can be constructed. A twin-screw extruder has the flexibility to freely change operating conditions such as the screw rotation speed and barrel temperature setting, and also has various advantages such as high transportability and continuous processing capability.

[0028] The cylinder 12 is composed of, for example, multiple cylinder blocks connected together, and each cylinder block has a space inside that can transport thermoplastic resin. A screw 12a is provided in this space, and the screw 12a is connected to a rotary drive mechanism 15. This rotary drive mechanism 15 rotates the screw 12a, allowing the resin to be disassembled to be transported in the cylinder 12.

[0029] Furthermore, the cylinder 12 is equipped with a heater to adjust its temperature. The thermoplastic resin to be decomposed is transported from the resin supply unit 11 toward the extrusion unit 14, and at that time, it is gradually heated by the heater, making it easy to obtain molten and plasticized thermoplastic resin. The molten and plasticized thermoplastic resin thus obtained can be easily transported within the cylinder 12 and further transported downstream.

[0030] Furthermore, the molten resin in the cylinder 12 and the fluid supplied from the fluid supply unit 13 are pressurized by the screw 12a and reach a subcritical or supercritical state.

[0031] During the process, when fluid is supplied by the fluid supply unit 13 (described later), the molten and plasticized thermoplastic resin and the fluid are mixed. At this time, the heater and screw provided in the cylinder 12 adjust the temperature and pressure inside the cylinder 12 to a predetermined level, resulting in a subcritical or supercritical state. While maintaining this subcritical or supercritical state, the decomposition process of the thermoplastic resin is continued as it is transported further inside the cylinder 12.

[0032] The fluid supply unit 13 supplies heated and pressurized fluid to the molten and plasticized thermoplastic resin in the cylinder 12. The fluid supply unit 13 is positioned so as to be supplied into the cylinder 12 after the thermoplastic resin has been molten and plasticized within the cylinder 12.

[0033] The fluid supplied from the fluid supply unit 13 exposes the molten and plasticized thermoplastic resin downstream to a subcritical or supercritical fluid, causing it to decompose. The fluid supplied from the fluid supply unit 13 only needs to be in a subcritical or supercritical state within the cylinder 12; it does not need to be in a subcritical or supercritical state immediately before being supplied to the cylinder 12. It is preferable to supply the fluid in a subcritical or supercritical state before supplying it to the cylinder 12 and maintaining that state, as this will initiate the decomposition of the molten and plasticized thermoplastic resin immediately after the fluid is supplied.

[0034] As described above, the fluid is added to the molten and plasticized thermoplastic resin, but at this time the inside of cylinder 12 is heated and pressurized, so the fluid supplied here is supplied to the inside of cylinder 12 against that pressure.

[0035] Furthermore, in order to achieve a subcritical or supercritical state after the fluid is supplied as described above, it is preferable that the supplied fluid be at a temperature equal to or higher than the temperature of the molten and plasticized thermoplastic resin in the fluid supply unit 13.

[0036] Therefore, it is preferable that the fluid supply unit 13 is equipped with a heating means capable of bringing the supplied fluid to a predetermined heating state. For example, Figure 1 shows a diagram in which the fluid supply unit 13 is connected to a heated water production device 13a. In this way, the heated water production device 13a produces a fluid that has reached a predetermined heating state, and the obtained fluid can be supplied from the fluid supply unit 13 to the cylinder 12 through piping using a pump such as a plunger pump.

[0037] The extrusion unit 14 is a component that discharges the decomposition products of the thermoplastic resin that have been conveyed inside the cylinder 12 to the outside of the decomposition processing device 10, and has an extrusion hole or a constricted extrusion port. The extrusion unit 14 should be configured to discharge the decomposition products to the outside while maintaining the pressure inside the device.

[0038] Furthermore, this extrusion unit 14 may be connected to a container for recovering raw materials, or it may be connected to a different processing device to further treat the decomposed products of the extruded thermoplastic resin.

[0039] The rotary drive mechanism 15 is a device for rotating the screw 12a located inside the cylinder 12. The screw, rotated by the rotary drive mechanism 15, transports the thermoplastic resin of the material to be disassembled inside the cylinder 12.

[0040] Furthermore, the extruder may be a twin-screw extruder with two screws in the cylinder 12, or a single-screw extruder with one screw. In the case of a twin-screw extruder, the two screws are arranged parallel to each other and rotate. The two shafts may be arranged to mesh with each other, or they may be arranged not to mesh with each other. When the number of screws is two, a twin-screw extruder with two screws is preferable to a single-screw extruder with one screw, for the same screw diameter, because it allows for a higher extrusion rate due to the higher raw material transport efficiency and higher mixing performance. Also, the direction of extension of the cylinder 12 is the same as the direction of extension of the screws inside the cylinder 12.

[0041] The backflow suppression mechanism 16 is a mechanism for suppressing backflow of the thermoplastic resin supplied or molten and plasticized thermoplastic resin from the resin supply section 11 side within the cylinder 12.

[0042] In this embodiment, the backflow suppression mechanism 16 is configured to include at least one measuring sensor 16a selected from a resin thermometer, a resin pressure gauge, and a cylinder thermometer, a relief valve 16b provided in the cylinder 12, and a control unit 16c that controls the operation of the relief valve 16b according to the measured value obtained from the measuring sensor 16a. Here, the measuring sensor 16a may include a screw measuring meter (not shown) that measures the energy consumption of the rotary drive mechanism 15 that drives the screw and / or the rotational torque of the rotary drive mechanism 15.

[0043] As described above, the measuring sensor 16a is at least one measuring sensor selected from a resin thermometer, a resin pressure gauge, a cylinder thermometer, and a screw measuring sensor. This measuring sensor 16a may be one of the resin thermometer, resin pressure gauge, cylinder thermometer, and screw measuring sensor, or a combination of several may be provided. Also, although Figure 1 shows an example in which one measuring sensor 16a is provided, multiple measuring sensors of the same type may be provided. When multiple sensors are provided, it is preferable to provide them in different cylinder blocks among the cylinder blocks that make up the cylinder 12. Note that if a screw measuring sensor is provided as the measuring sensor 16a, it does not need to be provided in the cylinder block, but is provided in the rotational drive mechanism 15 so that its energy consumption and / or rotational torque can be measured.

[0044] The relief valve 16b is an on-off valve that can open and close the relief hole 12c, which connects the inside of the cylinder 12 to the external atmosphere, at any desired timing. This relief valve 16b may be opened and closed manually or automatically. By opening this relief valve 16b, the pressure inside the cylinder 12 can be reduced, and backflow can be effectively suppressed. In Figure 1, an example configuration is shown in which a control unit 16c is provided to enable automatic opening and closing. With such a configuration, when a predetermined measurement value is detected, the relief valve 16b can be opened immediately, and the backflow suppression operation can be performed without delay.

[0045] The relief valve 16b is installed in the cylinder 12 after the thermoplastic resin has been melted and plasticized. It is preferably located on the side of the extrusion section 14 (downstream) from the fluid supply section 13, more preferably closer to the extrusion section 14 between the fluid supply section 13 and the extrusion section 14, and particularly preferably in a cylinder block adjacent to the extrusion section 14.

[0046] The control unit 16c is connected to the measuring sensor 16a and the relief valve 16b. The control unit 16c constantly monitors the temperature or pressure measured by the measuring sensor 16a, and when the measured value exceeds a predetermined threshold or the rate of change of the measured value exceeds a predetermined magnitude, it automatically opens the relief valve 16b to discharge the molten plasticized resin inside the cylinder 12 to the outside of the device.

[0047] The backflow suppression mechanism 16 may monitor the measured value of the measuring sensor 16a and issue a warning when a predetermined measured value is detected, and when the warning is issued, the relief valve 16b may be opened manually. In this case, the control unit 16c does not need to be provided.

[0048] <Method for decomposing resin> Next, the resin decomposition treatment method of this embodiment will be explained, using the resin decomposition treatment apparatus 10 shown in Figure 1 as an example.

[0049] First, thermoplastic resin is supplied from the resin supply unit 11 to the cylinder 12 ((a) step; resin supply step). This step supplies the thermoplastic resin to be decomposed into the cylinder 12, which is the main body of the decomposition processing device.

[0050] The resin products to be decomposed provided here are not particularly limited as long as they are made of thermoplastic resin and undergo hydrolysis. Examples of such resins include polyamide (PA) resin, polycarbonate (PC) resin, polyethylene terephthalate (PET) resin, and polybutylene terephthalate (PBT) resin. In this example, we will introduce an example of the hydrolysis of polyamide (PA) resin.

[0051] Next, the supplied thermoplastic resin is heated and pressurized within the cylinder 12 to melt and plasticize it (step (b); melt and plasticize step). Here, the thermoplastic resin supplied in the resin supply step is heated and pressurized while being transported by the screw 12a towards the extrusion section 15 within the cylinder 12.

[0052] Here, the thermoplastic resin is gradually heated to a high temperature by a heater located on the outer circumference of the cylinder 12 while being transported, and is also gradually pressurized by a screw inside the cylinder 12 while being transported. In this heated and pressurized state, the thermoplastic resin is molten and plasticized, and can be easily transported by the screw 12a.

[0053] Although it varies depending on the type of resin used, it is preferable to heat and pressurize the resin before the fluid supply process described below, for example, so that the resin temperature is 250 to 400°C and the resin pressure is 15 to 22 MPa. It is preferable to have the resin at 150 to 250°C and 15 to 20 MPa immediately before the fluid supply process. More specifically, if the resin to be decomposed includes polyamide (PA) resin, it is preferable to have the resin temperature at 300 to 350°C and the resin pressure at 15 to 18 MPa.

[0054] Next, the heated and pressurized fluid is supplied from the fluid supply unit 13 to the molten and plasticized thermoplastic resin in the cylinder 12 ((c) step: fluid supply step). The supplied fluid is then mixed with the molten and plasticized thermoplastic resin.

[0055] The fluid supplied at this time is a fluid that can be brought to a subcritical or supercritical state in order to decompose the molten plasticized resin, such as water or an alcohol such as methanol, with water being preferred. The supercritical state refers to a state that has activity in a region above the critical point of the liquid, becoming an intermediate state between liquid and gas, while the subcritical state refers to a liquid phase state that has activity in a region slightly lower than the supercritical state.

[0056] The conditions for subcritical and supercritical states differ depending on the fluid used. However, in the case of water, the subcritical state can be achieved by, for example, setting the pressure to be above the saturation pressure at 150-350°C (for example, the saturation pressure at 300°C is 8.59 MPa, and the saturation pressure at 350°C is 16.54 MPa), while the supercritical state can be achieved by, for example, setting the temperature to 374°C or higher and the pressure to 22 MPa or higher.

[0057] Here, the fluid may be brought to a subcritical or supercritical state before or after supplying it to the molten, plasticized thermoplastic resin. In this fluid supply process, the heating and pressurizing conditions are adjusted so that the supplied fluid meets the desired conditions. It is preferable to bring the fluid to a subcritical or supercritical state before supplying it and then supplying this fluid into the cylinder 12. In this way, when the fluid is supplied into the cylinder 12, the molten, plasticized thermoplastic resin is mixed with the fluid, and the decomposition process can be started simultaneously with the mixing.

[0058] Then, after the above-mentioned fluid is supplied, the thermoplastic resin melted and plasticized in the cylinder 12 is mixed with the subcritical or supercritical fluid and thereby decomposed (step (d); decomposition step). This decomposition step is preferably carried out for a time sufficient for the thermoplastic resin to decompose sufficiently, and this mixing time with the subcritical or supercritical fluid can be adjusted by the length of the cylinder 12 and the conveying speed due to the rotation of the screw 12a.

[0059] The time for the above decomposition process is preferably 2 to 5 minutes, more preferably 5 to 10 minutes, and even more preferably 10 to 15 minutes.

[0060] When thermoplastic resins are exposed to subcritical or supercritical conditions in this way, their bonds are broken, and they decompose (depolymerize) back into their original monomers, becoming decomposition products of the resin.

[0061] Then, the decomposed thermoplastic resin obtained in this decomposition process is extruded from the extrusion section 14 provided at the tip of the cylinder 12 ((e) step; extrusion process). The extruded decomposed resin is recovered. This decomposed resin can be reused as a raw material in resin manufacturing.

[0062] Furthermore, when reusing the material, it is preferable to remove impurities contained in the decomposition product, and an impurity removal process may be carried out during recovery.

[0063] Next, we will describe the backflow suppression process, which is characteristic of this embodiment. When steps (a) to (e) above are performed, the thermoplastic resin introduced into the cylinder 12 is, for example, in the form of granular pellets for easier handling, and after being introduced, it is heated and pressurized as described above to melt and plasticize. At this time, as shown in Figure 3, the solid pellets 50 supplied from the resin supply unit 11 are transported downstream and become semi-molten, and then become completely molten resin 51.

[0064] At this time, if the pressure on the pellet 50 side and the pressure on the molten resin 51 side are balanced, continuous operation is possible and the decomposition process can be carried out efficiently. However, if this balance is disrupted and the pressure on the molten resin 51 side becomes higher than the pressure on the pellet 50 side, the molten resin 51 will flow back, pushing the pellet 50 back towards the resin supply unit 11, and eventually, the molten resin 51 and pellet 50 may be ejected from the resin supply unit 11 to the outside in a mixed state.

[0065] In this embodiment, in order to suppress such backflow, the cylinder 12 is provided with a measuring sensor 16a, as shown in Figure 1. Figure 3 shows an example in which the measuring sensor 16a is provided with a resin thermometer 16a-1, a resin pressure gauge 16a-2, and a cylinder thermometer 16a-3. However, as mentioned above, there may be one, two, or three types of measuring sensors 16a. Furthermore, the measuring sensor 16a may be a screw measuring sensor alone (in this case, the screw measuring sensor is provided on the rotary drive device 15), or a screw measuring sensor may be combined with at least one of the resin thermometer 16a-1, resin pressure gauge 16a-2, and cylinder thermometer 16a-3. The following explanation will be given with reference to Figure 3, in which the measuring sensor 16a is provided on the cylinder block.

[0066] In Figure 3, an example is shown where the resin thermometer 16a-1, resin pressure gauge 16a-2, and cylinder thermometer 16a-3 are installed in the cylinder block of the cylinder 12 from the resin supply section 11 to the fluid supply section 13. However, the measuring sensors may be installed in a single cylinder block.

[0067] Even if installed in a single cylinder block, there is no problem as long as the measuring sensor 16a is provided, as it can detect when the pressure balance is disrupted. Furthermore, if installed in multiple cylinder blocks, it is preferable because it can more accurately detect when the pressure balance is disrupted.

[0068] It is preferable that the cylinder block on the resin supply unit 11 side, where the measurement sensor 16a is installed, is the one where the resin supply unit 11 side is mostly composed of pellets. In this way, if there is a change in the value measured by the measurement sensor 16a in the cylinder block on the resin supply unit 11 side, it is possible to accurately detect that backflow is occurring and initiate the suppression operation described later.

[0069] For example, if the decomposition process is continued in the state shown in Figure 3, but the pressure on the molten resin 51 side increases and the molten resin begins to flow back to the resin supply unit 11 side as shown in Figure 4, the control unit 16c detects a change in at least one of the measured values ​​of the resin thermometer 16a-1, resin pressure meter 16a-2, and cylinder thermometer 16a-3 and determines that backflow is occurring, then opens the relief valve 16b and discharges the molten resin 51 from inside the cylinder 12 to the outside through the opening. This reduces the pressure of the molten resin inside the cylinder 12, preventing the molten resin 51 from flowing back to the resin supply unit 11 side together with the pellets 50 and being ejected. A specific example is opening the relief valve 16b when the temperature of the resin thermometer 16a-1 rises by 10%, for example, from 240°C to 265°C.

[0070] Furthermore, the measurement value from the measuring sensor 16a may be used to set a threshold value for controlling the operation of the relief valve 16b by the control unit 16c, or the change over time may be monitored and a threshold value based on the fluctuation may be set. This threshold value should be set appropriately depending on the cylinder in which the measuring sensor 16a is installed, the resin and fluid used, the conditions of the disassembly process, etc.

[0071] In a decomposition process using polyamide resin as the thermoplastic resin to be decomposed and water as the supplied fluid, examples of threshold values ​​based on measured values ​​include setting the resin temperature to 50-225°C, the resin pressure to 1-8 MPa, and the cylinder temperature to 25-250°C. Examples of threshold values ​​based on fluctuations include setting the resin temperature to 5-30%, the resin pressure to 5-30%, and the cylinder pressure to 5-30%.

[0072] <Operation of the disassembly and processing device> The resin decomposition apparatus and decomposition method of this embodiment have been described above, but the series of operations of this resin decomposition apparatus 10 will now be explained with reference to the flowchart in Figure 5.

[0073] First, the resin decomposition processing device 10 is started up, and the measured values ​​(temperature, pressure) are displayed by the measuring sensor 16a (S1-1). Next, the relief valve 16b is closed (S1-2), and the operation of the decomposition processing device 10 is started (S1-3). Upon starting the operation, the cylinder 12 is heated to a predetermined temperature, and the screw 12a is also driven.

[0074] As the resin to be decomposed, pellets 50 are supplied to the resin supply unit 11 (S1-4). After confirming that the resin has been sufficiently melted and plasticized and is being transported through the cylinder 12, the supply of heated and pressurized fluid from the fluid supply unit 13 is started (S1-5).

[0075] Furthermore, the system starts increasing the pressure inside cylinder 12 to a predetermined pressure (S1-6). Simultaneously with the start of the pressure increase, the system determines whether there are any signs of backflow based on the measurement value of the measuring sensor 16a (S1-7). If there are no signs of backflow, the system continues operation (S1-8). After confirming that the pressure has reached the specified pressure (S1-9), the system checks again for any signs of backflow using the measurement of the measuring sensor 16a (S1-10). If there are no signs of backflow at this point, the system continues operation and the resin decomposition process continues (S1-11).

[0076] On the other hand, when checking for signs of backflow (S1-7, S1-10), if signs of backflow are found, the relief valve 16b is opened (S1-12, S1-13). By opening the relief valve 16b, the pressure inside the cylinder 12 can be quickly reduced, thereby suppressing (preventing) backflow. Furthermore, by continuously checking for signs of backflow even after continuing operation (S1-11), backflow can be reliably suppressed (prevented).

[0077] If operation is to be resumed after the relief valve 16b has been opened, the relief valve 16b should be closed (S1-14), the pressure should be increased again (S1-6), and the operation should be carried out while checking for any signs of backflow (S1-7 to S1-14). It is preferable that, after the relief valve has been opened, any cause of backflow should be removed before resuming operation.

[0078] If there are no problems, the operation will continue until the resin decomposition process is completely finished, at which point the decomposition apparatus will be stopped.

[0079] (Embodiment 2) <Manufacturing equipment for resin composite materials> This second embodiment is an embodiment in which backflow is suppressed by varying the amount of resin supplied from the resin supply unit as a backflow suppression mechanism, and the other configurations can be the same as those of the first embodiment. Figure 6 is a diagram showing an example of the configuration of the resin decomposition apparatus of the second embodiment.

[0080] The resin decomposition processing apparatus 20 shown in Figure 6 comprises a resin supply unit 11, a cylinder 12 having a screw, a fluid supply unit 13 that supplies fluid to the cylinder 12, an extrusion unit 14, a rotary drive mechanism 15 that drives the screw of the cylinder 12, and a backflow suppression mechanism 26.

[0081] Here, the resin supply unit 11, cylinder 12, fluid supply unit 13, extrusion unit 14, and rotary drive mechanism 15 are the same as those described in Embodiment 1, so their description will be omitted. In this Embodiment 2, backflow is suppressed by varying the amount of resin supplied from the resin supply unit 11 as described above, and is characterized by having a backflow suppression mechanism 26. The backflow suppression mechanism 26 will be described in detail below.

[0082] In this embodiment, the backflow suppression mechanism 26 is configured to include at least one measuring sensor 26a selected from a resin thermometer, a resin pressure gauge, and a cylinder thermometer; a feeder 26b that can adjust the amount of resin supplied to the resin supply unit 11; and a control unit 16c that controls the operation of the feeder 26b according to the measured value obtained from the measuring sensor 26a.

[0083] Since the measurement sensor 26a can have the same configuration as the measurement sensor 16a described in the first embodiment, its description is omitted here.

[0084] The feeder 26b can be a known feeder and is a device that supplies the resin to be disassembled to the resin supply unit 11. The feeder 26b used in this embodiment has a function to adjust the amount of resin supplied and is connected to the control unit 26c, which will be described next, so that the amount of resin supplied can be changed according to the situation.

[0085] The control unit 26c is connected to the measuring sensor 26a and the feeder 26b, and constantly monitors the temperature or pressure measured by the measuring sensor 26a. When the measured value exceeds a predetermined threshold or the rate of change of the measured value exceeds a predetermined magnitude, the control unit operates to increase the amount of resin supplied from the feeder 26b to the resin supply unit 11.

[0086] The backflow suppression mechanism 26 may monitor the measured value of the measuring sensor 26a and issue a warning when a predetermined measured value is detected. When the warning is issued, the amount of resin supplied from the feeder may be manually increased. In this case, the control unit 26c may not be necessary.

[0087] <Method for decomposing resin> Next, the resin decomposition treatment method of this embodiment will be explained step by step, using the resin decomposition treatment apparatus 20 shown in Figure 6 described above as an example.

[0088] The resin decomposition method in this embodiment is the same as the resin decomposition method described in the first embodiment, from steps (a) to (e), so its explanation will be omitted. This embodiment is characterized by a backflow suppression step, which differs from the first embodiment, so the differences will be explained below.

[0089] When steps (a) to (e) above are performed, as explained in the first embodiment and Figure 3, the solid pellets 50 supplied from the resin supply unit 11 are transported downstream and become semi-molten, and then completely molten into molten resin 51. When the balance between the pressure on the pellet 50 side and the pressure on the molten resin 51 side is disrupted, the molten resin 51 flows back, pushing the pellets 50 back towards the resin supply unit 11, and eventually, the molten resin 51 and pellets 50 may be ejected from the resin supply unit 11 to the outside in a mixed state.

[0090] In this embodiment, in order to suppress such backflow, the cylinder 12 is provided with at least one measuring sensor 26a selected from a resin thermometer, a resin pressure gauge, and a cylinder thermometer, as shown in Figure 6. This measuring sensor 26a can have the same configuration as the measuring sensor 16a in the first embodiment.

[0091] In this embodiment, the decomposition process was continued in the state shown in Figure 3, but when the pressure on the molten resin 51 side increased and the molten resin began to flow back to the resin supply unit 11 side as shown in Figure 4, the control unit 26c detects a change in at least one measurement value of the resin thermometer 16a-1, resin pressure meter 16a-2, and cylinder thermometer 16a-3 and determines that backflow is occurring, and increases the amount of resin supplied in the feeder 26b to increase the pressure on the pellet 50 side. This adjusts the balance between the pressure of the pellet 50 and the molten resin 51 in the cylinder 12, and prevents the molten resin 51 from flowing back to the resin supply unit 11 side together with the pellet 50 and being ejected.

[0092] In this case, the measurement values ​​of the measuring sensor 26a can be set to the threshold values ​​or fluctuation values ​​described in the first embodiment, and the system can be operated accordingly.

[0093] The increase in resin volume only needs to be sufficient to suppress the ejection caused by the backflow mentioned above. For example, it is preferable to increase the amount of resin to 1.5 to 2.5 times the amount originally supplied.

[0094] Furthermore, after increasing the amount of resin, the measurement value of the measuring sensor 26a may be checked again to confirm whether or not backflow has been suppressed. If backflow has not been suppressed, the amount of resin may be increased further, and this process may be repeated until backflow is suppressed. In this case, the amount of resin may be increased in stages, to about 1.1 to 1.5 times the amount of resin that was originally supplied.

[0095] <Operation of the disassembly and processing device> The resin decomposition apparatus and decomposition method of this embodiment have been described above, but the series of operations of this resin decomposition apparatus 20 will now be explained with reference to the flowchart in Figure 7.

[0096] First, the resin decomposition processing device 20 is started up, and the measured values ​​(temperature, pressure) are displayed by the measuring sensor 26a (S2-1). Next, the operation of the decomposition processing device 20 is started (S2-2). Upon starting operation, the cylinder 12 is heated to a predetermined temperature, and the screw 12a is also driven.

[0097] As the resin to be decomposed, pellets 50 are supplied to the resin supply unit 11 (S2-3). After confirming that the resin has been sufficiently melted and plasticized and is being transported through the cylinder 12, the supply of heated and pressurized fluid from the fluid supply unit 13 is started (S2-4).

[0098] Furthermore, the system starts increasing the pressure inside cylinder 12 to a predetermined pressure (S2-5). Simultaneously with the start of the pressure increase, the system determines whether there are any signs of backflow based on the measurement value of the measuring sensor 26a (S2-6). If there are no signs of backflow, the system continues operation (S2-7).

[0099] After confirming that the pressure has reached the specified pressure (S2-8), the system checks again for signs of backflow using the measurement of the measuring sensor 26a (S2-9). If there are no signs of backflow at this point, the system continues operation and the resin decomposition process continues (S2-10).

[0100] On the other hand, when checking for signs of backflow (S2-6, S2-9), if signs of backflow are found, the amount of resin supplied from feeder 26b is increased (S2-11, S2-12). After increasing the amount of supplied resin, the measurement value of the measuring sensor 26a is checked to confirm whether the signs of backflow have disappeared (S2-13). If the signs of backflow have disappeared, operation is continued and the decomposition process is continued (S2-9). If the signs of backflow have not disappeared, the supply of resin is increased again (S2-11, S2-12), and this is repeated until the signs of backflow disappear. By increasing the amount of supplied resin, the pressure balance between the pellets 50 and the molten resin 51 in the cylinder 12 can be adjusted, thereby suppressing (preventing) backflow. Furthermore, by constantly checking for signs of backflow even after continuing operation (S2-10), backflow can be reliably suppressed (prevented).

[0101] If there are no problems, the operation will continue until the resin decomposition process is completely finished, at which point the decomposition apparatus will be stopped.

[0102] (Embodiment 3) This third embodiment is an embodiment in which backflow is suppressed by stopping the supply of fluid from the fluid supply unit as a backflow suppression mechanism, and the other configurations can be the same as those of the first embodiment. Figure 8 is a diagram showing an example of the configuration of the resin decomposition apparatus of the third embodiment.

[0103] The resin decomposition apparatus 30 shown in Figure 8 comprises a resin supply unit 11, a cylinder 12 having a screw, a fluid supply unit 13 that supplies fluid to the cylinder 12, an extrusion unit 14, a rotary drive mechanism 15 that drives the screw of the cylinder 12, and a backflow suppression mechanism 36.

[0104] Here, the resin supply unit 11, cylinder 12, fluid supply unit 13, extrusion unit 14, and rotary drive mechanism 15 are the same as those described in Embodiment 1, so their description will be omitted. In this Embodiment 3, backflow is suppressed by stopping the supply of fluid from the fluid supply unit 13 as described above, and is characterized by having a backflow suppression mechanism 36. The backflow suppression mechanism 36 will be described in detail below.

[0105] In this embodiment, the backflow suppression mechanism 36 is configured to include at least one measuring sensor 36a selected from a resin thermometer, a resin pressure gauge, and a cylinder thermometer; a valve 36b connected to the fluid supply unit 13 and provided in the piping for supplying the fluid; and a control unit 36c capable of controlling the opening and closing of the valve 36b according to the measured value obtained by the measuring sensor 36a.

[0106] Since the measurement sensor 36a can have the same configuration as the measurement sensor 16a described in the first embodiment, its description is omitted here.

[0107] Valve 36b can be a known valve and is installed in the piping connected to supply fluid from the fluid supply unit 13 to the cylinder 12. By opening and closing this valve 36b, it is possible to control whether or not fluid is supplied to the cylinder 12 and the amount supplied.

[0108] The control unit 36c is connected to the measuring sensor 36a and the valve 36b, and constantly monitors the temperature or pressure measured by the measuring sensor 36a. When the measured value exceeds a predetermined threshold or the rate of change of the measured value exceeds a predetermined magnitude, the control unit closes the valve 36b to stop the fluid supplied to the cylinder 12.

[0109] The backflow suppression mechanism 36 may monitor the measured value of the measuring sensor 36a and issue a warning when a predetermined measured value is detected, allowing the fluid supply from the fluid supply unit 13 to be manually stopped when the warning is issued. In this case, the control unit 36c does not need to be provided.

[0110] <Method for decomposing resin> Next, the resin decomposition treatment method of this embodiment will be explained, using the resin decomposition treatment apparatus 30 shown in Figure 8 as an example.

[0111] The resin decomposition method in this embodiment is the same as the resin decomposition method described in the first embodiment, from steps (a) to (e), so its explanation will be omitted. This embodiment is characterized by a backflow suppression step, which differs from the first embodiment, so the differences will be explained below.

[0112] When steps (a) to (e) above are performed, as explained in the first embodiment and Figure 3, the solid pellets 50 supplied from the resin supply unit 11 are transported downstream and become semi-molten, and then completely molten into molten resin 51. When the balance between the pressure on the pellet 50 side and the pressure on the molten resin 51 side is disrupted, the molten resin 51 flows back, pushing the pellets 50 back towards the resin supply unit 11, and eventually, the molten resin 51 and pellets 50 may be ejected from the resin supply unit 11 to the outside in a mixed state.

[0113] In this embodiment, in order to suppress such backflow, the cylinder 12 is provided with at least one measuring sensor 36a selected from a resin thermometer, a resin pressure gauge, and a cylinder thermometer, as shown in Figure 8. This measuring sensor 36a can have the same configuration as the measuring sensor 16a in the first embodiment.

[0114] In this embodiment, the disassembly process was continued in the state shown in Figure 3. However, when the pressure on the molten resin 51 side increased and the molten resin began to flow back into the resin supply unit 11 side as shown in Figure 4, the control unit 36c detects a change in at least one of the measured values ​​of the resin thermometer 16a-1, resin pressure meter 16a-2, and cylinder thermometer 16a-3 and determines that backflow is occurring. In this case, the control unit 36c closes the valve 36b and stops the supply of fluid to the cylinder 12. This adjusts the balance between the pressure of the pellets 50 and the molten resin 51 in the cylinder 12, preventing the molten resin 51 from flowing back into the resin supply unit 11 side together with the pellets 50 and being ejected.

[0115] In this case, the measurement values ​​of the measuring sensor 36a can be set to the threshold values ​​or fluctuation values ​​described in the first embodiment, and the system can be operated accordingly.

[0116] <Operation of the disassembly and processing device> The resin decomposition apparatus and decomposition method of this embodiment have been described above, and now the series of operations of this resin decomposition apparatus 30 will be explained with reference to the flowchart in Figure 9.

[0117] First, the resin decomposition processing device 30 is started up, and the measured values ​​(temperature, pressure) are displayed by the measuring sensor 36a (S3-1). Next, the operation of the decomposition processing device 30 is started (S3-2). Upon starting operation, the cylinder 12 is heated to a predetermined temperature, and the screw 12a is also driven.

[0118] As the resin to be decomposed, pellets 50 are supplied to the resin supply unit 11 (S3-3). After confirming that the resin has been sufficiently melted and plasticized and is being transported through the cylinder 12, the supply of heated and pressurized fluid from the fluid supply unit 13 is started (S3-4).

[0119] Furthermore, the system starts increasing the pressure inside cylinder 12 to a predetermined pressure (S3-5). Simultaneously with the start of the pressure increase, the system determines whether there are any signs of backflow based on the measurement value of the measuring sensor 36a (S3-6). If there are no signs of backflow, the system continues operation (S3-7).

[0120] After confirming that the pressure has reached the specified pressure (S3-8), the system checks again for any signs of backflow using the measurement of the measuring sensor 36a (S3-9). If there are no signs of backflow at this point, the system continues operation and the resin decomposition process continues (S3-10).

[0121] On the other hand, when checking for signs of backflow (S3-6, S3-9), if signs of backflow are found, valve 36b is closed to stop the supply of fluid from the fluid supply unit 13 (S3-11, S3-12). After stopping the fluid supply, the operating conditions are changed (S3-13). The operating conditions to be changed here can be any conditions that can suppress backflow, such as resin supply amount, fluid supply amount, screw rotation speed, cylinder temperature, etc.

[0122] After the operating conditions are changed, valve 36b is opened to resume fluid supply (S3-4). By stopping the fluid supply, the pressure balance between the pellets 50 and the molten resin 51 in the cylinder 12 can be adjusted, thereby suppressing (preventing) backflow. Furthermore, by continuously checking for any signs of backflow even after continuing operation (S3-10), backflow can be reliably suppressed (prevented).

[0123] If there are no problems, the operation will continue until the resin decomposition process is completely finished, at which point the decomposition apparatus will be stopped.

[0124] Although the present invention has been specifically described above with reference to embodiments and examples, it goes without saying that the present invention is not limited to these embodiments and examples, and can be modified in various ways without departing from its essence. [Explanation of symbols]

[0125] 10, 20, 30 Resin decomposition apparatus 11 Resin supply unit 12 cylinders 12a Screw 12b Fluid supply hole 12c relief holes 13 Fluid supply section 14 Extrusion section 15 Rotary drive mechanism 16,26,36 Backflow suppression mechanism 16a, 26a, 36a measuring sensors 16c, 26c, 36c control unit 16b Relief valve 26b Feeder 36c valve

Claims

1. A resin decomposition method including the following steps: (a) A step of supplying thermoplastic resin from the resin supply unit to the cylinder; (b) A step of heating and pressurizing the supplied thermoplastic resin in the cylinder to melt and plasticize it; (c) A step of supplying a heated and pressurized fluid from a fluid supply unit to the molten and plasticized thermoplastic resin and mixing it; (d) A step of decomposing the molten and plasticized thermoplastic resin by exposing it to a subcritical or supercritical state with the supplied fluid; and (e) A step of extruding the decomposition product of the thermoplastic resin obtained in step (d) from an extrusion section provided at the tip of the cylinder. Here, in step (b), at least one selected from the temperature of the thermoplastic resin, the pressure of the thermoplastic resin, and the temperature of the cylinder is measured, and a backflow suppression step is started to suppress the backflow of the melt-plasticized thermoplastic resin according to the measured value.

2. In the resin decomposition treatment method according to claim 1, A resin decomposition method, wherein the backflow suppression step is a step of discharging the molten and plasticized thermoplastic resin from the cylinder downstream of the fluid supply unit to the outside.

3. In the resin decomposition treatment method according to claim 2, A method for decomposing a resin, wherein the melted and plasticized thermoplastic resin is discharged to the outside through a relief hole provided in the cylinder adjacent to the extrusion section.

4. In the resin decomposition treatment method according to claim 1, A resin decomposition treatment method wherein the backflow suppression step is a step of increasing the supply amount of the thermoplastic resin in step (a).

5. In the resin decomposition treatment method according to claim 4, A method for decomposing a resin, comprising increasing the supply amount of the thermoplastic resin by 1.5 to 2.5 times.

6. In the resin decomposition treatment method according to claim 1, A method for decomposing a resin, wherein the backflow suppression step is a step of stopping the supply of the fluid in step (c).

7. In the resin decomposition treatment method according to claim 1, A method for decomposing a resin, wherein the thermoplastic resin is a polyamide resin.

8. Resin decomposition apparatus, including the following: Cylinder; A resin supply unit that supplies the thermoplastic resin to be disassembled to the cylinder; In the cylinder, a screw for conveying the supplied thermoplastic resin and the melted and plasticized thermoplastic resin; A fluid supply unit that supplies a heated and pressurized fluid into the cylinder in order to decompose the molten and plasticized thermoplastic resin in a subcritical or supercritical state; An extrusion section provided at the tip of the cylinder for extruding the decomposed product of the thermoplastic resin to the outside of the cylinder; and A backflow suppression mechanism is provided in the cylinder between the resin supply unit and the fluid supply unit, and the cylinder has at least one selected from a resin thermometer for measuring the temperature of the thermoplastic resin, a resin pressure meter for measuring the pressure of the thermoplastic resin, a cylinder thermometer for measuring the temperature of the cylinder, and a screw measuring meter for measuring the energy consumption or driving torque of the rotary drive mechanism that drives the screw, and the backflow suppression mechanism can suppress the backflow of the molten and plasticized thermoplastic resin according to at least one of the measurements of the resin thermometer, the resin pressure meter, the cylinder thermometer, and the screw measuring meter.

9. In the resin decomposition apparatus according to claim 8, A resin decomposition apparatus comprising: a relief valve provided in the cylinder downstream of the fluid supply unit, capable of opening and closing a relief hole connecting the inside of the cylinder to the external atmosphere; and a control unit that controls the opening and closing of the relief valve according to the measured value.

10. In the resin decomposition apparatus according to claim 9, A disassembly apparatus in which the relief valve is provided in the cylinder adjacent to the extrusion section.

11. In the resin decomposition apparatus according to claim 8, A resin decomposition apparatus comprising: a backflow suppression mechanism having a feeder capable of adjusting the amount of resin supplied from the resin supply unit; and a control unit that increases the amount of resin supplied from the resin supply unit to the cylinder by the feeder according to the measured value.

12. In the resin decomposition apparatus according to claim 8, A resin decomposition apparatus comprising: a backflow suppression mechanism connected to the fluid supply unit and provided in a piping for supplying the fluid; and a control unit capable of controlling the opening and closing of the valve according to the measured value.

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