DECOMPOSITION METHOD AND DECOMPOSITION DEVICE FOR RESIN

Abstract

Resin decomposition process comprising the following steps: (a) feeding a thermoplastic resin from a resin supply into a cylinder; (b) heating and pressurizing and then melt-plasticizing the supplied thermoplastic resin in the cylinder; (c) supplying a heated and pressurized fluid from a fluid supply to the melt-plasticized thermoplastic resin and mixing the fluid with the thermoplastic resin; (d) decomposing the melt-plasticized thermoplastic resin by subjecting the thermoplastic resin to a subcritical state or a supercritical state by the supplied fluid; and (e) extruding a decomposition product of the thermoplastic resin obtained in step (d) from an extruder provided at a tip of the cylinder, wherein in the step (b), a backflow suppression step is performed in which at least one selected from a temperature of the thermoplastic resin, a pressure of the thermoplastic resin and a temperature of the cylinder is measured, and then the backflow of the melt-plasticized thermoplastic resin is suppressed in accordance with the measured value.

Description

TECHNICAL FIELD

[0001] The present invention relates to a decomposition method and a decomposition apparatus for resin, and more particularly to a decomposition method and a decomposition apparatus for resin configured to prevent backflow to a resin supply side when the resin is decomposed under high temperature and high pressure conditions. STATE OF THE ART

[0002] Currently, plastic products are used in a wide variety of areas, and the amount of plastic products consumed is enormous. On the other hand, the disposal of plastic products is expensive, and there is a problem with their impact on the environment, as their components end up in rivers, oceans, and the like when they are left in nature, for example.

[0003] For this reason, effective utilization of various resins as resources by recycling in various ways has been the subject of research, and, for example, a method for collecting and reusing monomers obtained by thermal decomposition of acrylic resin using a twin-screw extruder is known (see, for example, Patent Document 1).

[0004] In recent years, a method for obtaining monomers by exposing such a resin to a liquid in a subcritical or supercritical state has also been investigated as a resin decomposition method. STATE OF THE ART DOCUMENT PATENT SPECIFICATION

[0005] Patent Document 1: Published Japanese Patent Application JP H11-106 427 A SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] Furthermore, when using the subcritical or supercritical state, a specific temperature and pressure must be set depending on the fluid to be used. Since the conditions are usually high temperature and high pressure, a sealed device or similar is considered a decomposition device for such applications.

[0007] On the other hand, making a decomposition device resistant to such a subcritical or supercritical state initially incurs high costs, as, for example, a corresponding device must first be manufactured, which increases the overall costs.

[0008] Accordingly, it is an object of the present invention to provide a decomposition method and a resin decomposition apparatus capable of safely and continuously decomposing a resin to promote the recycling of the resin as described above. MEANS TO SOLVE THE PROBLEMS

[0009] A resin decomposition method disclosed in the present application comprises: a step (a) of supplying a thermoplastic resin from a resin supply into a cylinder; a step (b) of heating and pressurizing and then melt-plasticizing the supplied thermoplastic resin in the cylinder; a step (c) of supplying a heated and pressurized fluid from a fluid supply to the melt-plasticized thermoplastic resin and mixing the fluid with the thermoplastic resin; a step (d) of decomposing the melt-plasticized thermoplastic resin by subjecting the melt-plasticized thermoplastic resin to a subcritical state or a supercritical state by the supplied fluid; and a step (e) of extruding a decomposed product of the thermoplastic resin obtained in step (d) from an extruder provided at a tip of the cylinder.

[0010] Here, in step (b) of this decomposition method, a backflow suppression step is performed, in which step at least one of a temperature of the thermoplastic resin, a pressure of the thermoplastic resin, and a temperature of the cylinder is measured, and then the backflow of the melt-plasticized thermoplastic resin is suppressed in accordance with the measured value.

[0011] A resin decomposition apparatus disclosed in the present disclosure comprises: a cylinder; a resin feeder that feeds a thermoplastic resin to be decomposed into the cylinder; a screw that transports the fed thermoplastic resin and a melt-plasticized thermoplastic resin in the cylinder; a fluid feeder that feeds a heated and pressurized fluid into the cylinder to decompose the melt-plasticized thermoplastic resin in a subcritical state or a supercritical state; and an extruder that is provided at a tip of the cylinder and extrudes a decomposition product of the thermoplastic resin to the outside of the cylinder. EFFECTS OF THE INVENTION

[0012] Furthermore, this decomposition device includes, in the cylinder provided between the resin supply and the fluid supply, at least one selected from the group consisting of a resin thermometer for measuring a temperature of the thermoplastic resin, a resin pressure gauge for measuring a pressure of the thermoplastic resin, a cylinder thermometer for measuring a temperature of the cylinder, and a screw gauge for measuring a power consumption or a drive torque of a rotary drive mechanism driving the screw, and further comprises a backflow suppression mechanism that suppresses the backflow of the melt-plasticized thermoplastic resin in accordance with the change of at least one of the measured values ​​of the resin thermometer, the resin pressure gauge, the cylinder thermometer, and the screw gauge.

[0013] According to a decomposition method and a decomposition apparatus for resin disclosed in the present specification, a resin decomposition method and a resin decomposition apparatus capable of decomposing the resin safely and continuously can be provided. SHORT DESCRIPTIONS OF THE DRAWINGS Fig. 1 is a side view showing a schematic configuration of a resin decomposition apparatus according to a first embodiment. Fig. Fig. 2 is a side view diagram for explaining a screw arranged in a cylinder of the decomposition apparatus of Fig. 1 is arranged. Fig. 3 is a diagram for explaining in more detail a backflow suppression mechanism of the decomposition device of Fig. 1. Fig. Fig. 4 is a diagram for explaining in more detail a backflow suppression mechanism of the decomposition device of Fig. 1. Fig. 5 is a flowchart for explaining the operation of the resin decomposition apparatus according to the first embodiment. Fig. 6 is a side view showing a schematic configuration of a resin decomposition apparatus according to a second embodiment. Fig. 7 is a flowchart for explaining the operation of the resin decomposition apparatus according to the second embodiment. Fig. 8 is a side view showing a schematic configuration of a resin decomposition apparatus according to a third embodiment. Fig. 9 is a flowchart for explaining the operation of the resin decomposition apparatus according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Embodiments will be described in detail below using examples and drawings. Note that components having the same function are denoted by the same or similar reference numerals throughout the drawings for describing the embodiments, and repetition of their descriptions is omitted. <Hintergrund der Untersuchung>

[0015] First, the background of the study of the present application will be explained. For the decomposition (depolymerization) of the resin by the fluid in the subcritical or supercritical state, as described above, a sealed process container resistant to the process conditions is generally prepared. However, for the decomposition of the resin, the present inventors investigated the possibility of using a resin extruder used for molding resin materials.

[0016] That is, the inventors of the present invention have considered a possibility that the resin can be continuously and efficiently decomposed by using such a resin extruder without manufacturing a special processing apparatus for the decomposition of resin but by using an already existing extruder suitable for the decomposition as it is or with slight modifications.

[0017] In the extruder, generally, the thermoplastic resin as raw material is fed from one end of a tubular cylinder and gradually heated and kneaded within the cylinder. Then, the melt-plasticized resin is conveyed or moved by a screw. Subsequently, the melt-plasticized resin is sufficiently kneaded while being conveyed within the cylinder and extruded as a uniformly mixed resin material from a nozzle provided at a tip of the cylinder. An internal state of the cylinder is a heated and pressurized state, and therefore, it has been considered that even in the case of resin decomposition, the decomposition can be performed using the same device by mixing the resin with the fluid in the subcritical state or the supercritical state within the cylinder.

[0018] As an actual result of the decomposition of resin under such conditions tested by the present inventors, it was confirmed that the subcritical state can be maintained in the cylinder and that the resin can also be decomposed.

[0019] However, the continuation of this decomposition frequently caused backflow and outflow of the melt-plasticized resin and the unmelted resin from the resin feed of the extruder. This is believed to be due to the fact that the resin feed side of the extruder is usually not closed and is exposed to the atmosphere, and therefore the pressure of the melt-plasticized molten resin in the cylinder becomes greater than the pressure of the unmelted resin on the resin feed side.

[0020] Accordingly, the present inventors conducted various studies to provide a decomposition device that can safely and continuously decompose the resin without causing backflow of the melt-plasticized resin, even when decomposing resin in a subcritical state using an extruder. The present inventors developed a decomposition method and resin decomposition device that can suppress the occurrence of backflow. The decomposition method and resin decomposition device according to the present embodiment will be explained in detail below. <Erste Ausführungsform> [Resin decomposition device]

[0021] Fig. 1 is a diagram showing a configuration example of a resin decomposition apparatus according to the first embodiment. Fig. 2 is a diagram in side view for explaining a screw which is inserted into a cylinder of the type shown in Fig. 1 shown resin decomposition device.

[0022] The Fig. The resin decomposition apparatus 10 shown in Figure 1 is an apparatus used for decomposing a resin to be decomposed by exposing the resin to a fluid in a subcritical or supercritical state.

[0023] The resin decomposition device 10 includes a resin supply 11, a cylinder 12 with a screw, a fluid supply 13 that supplies a fluid to the cylinder 12, an extruder 14, a rotary drive mechanism 15 that drives the screw of the cylinder 12, and a backflow suppression mechanism 16.

[0024] The resin feeder 11 supplies the resin to be decomposed to the cylinder 12. In the present embodiment, a thermoplastic resin is supplied as the resin to be decomposed. The thermoplastic resin to be used and supplied has a varying form, for example, as a pellet, powder, or flakes, and is supplied from the top of the resin feeder 11 via a hopper, for example, through a feeder or the like, and is guided into the cylinder 12. The case of the thermoplastic resin to be supplied as a pellet will be explained below by way of example.

[0025] The cylinder 12 contains a screw 12a inside. Fig. Fig. 2 is a diagram in a cross-sectional view of the cylinder 12 so that the internal structure of the cylinder 12 of the resin decomposition device 10 in Fig. 1. In the cylinder 12 in Fig. 2 also shows a fluid supply port 12b in which the fluid supply 13 is arranged, and a relief port 12c which can discharge the melt-plasticized thermoplastic resin from the interior of the cylinder 12 to the outside.

[0026] By rotating the screw 12a, the supplied resin is gradually transported within the barrel 12 toward the extruder 14 (downstream). A twin-screw extruder can be designed by using a twin-screw with two screws as the screw 12a. The twin-screw extruder has the flexibility to freely change the operating conditions, such as the screw speed and barrel setting temperature, and also has various advantages, such as high transportability and continuous processability.

[0027] The cylinder 12, for example, consists of a connection of several cylinder blocks, and each cylinder block contains a space through which the thermoplastic resin can be transported. The screw 12a is located in this space, and the screw 12a is connected to the rotary drive mechanism 15. The screw 12a is rotated by the rotary drive mechanism 15 to transport the resin to be decomposed into the cylinder 12.

[0028] Furthermore, the cylinder 12 is equipped with a heater so that its temperature can be adjusted. During the transport of the thermoplastic resin to be decomposed from the resin feeder 11 to the extruder 14, the thermoplastic resin is gradually heated by the above-described heater, thereby easily providing the melt-plasticized thermoplastic resin. Furthermore, the melt-plasticized thermoplastic resin provided as described above can be easily transported into the cylinder 12 and is further transported to the downstream side.

[0029] In addition, the molten resin in the cylinder 12 and the liquid supplied from the fluid supply 13 are pressurized by the screw 12a to reach the subcritical or supercritical state.

[0030] By supplying the fluid from the fluid supply 13 described below during processing, the melt-plasticized thermoplastic resin and the fluid are mixed. At this time, the interior of the cylinder 12 is heated to a predetermined temperature and pressure by the heater and screw provided in the cylinder 12 as described above, so that the subcritical state or the supercritical state is achieved. During further transportation in the cylinder 12 in the subcritical or supercritical state, the decomposition of the thermoplastic resin is then promoted.

[0031] The fluid supply 13 supplies the heated and pressurized liquid to the melt-plasticized thermoplastic resin in the cylinder 12. The fluid supply 13 is arranged so that the thermoplastic resin is melt-plasticized in the cylinder 12 and then fed into the cylinder 12.

[0032] By the fluid supplied from the fluid supply 13, the melt-plasticized thermoplastic resin on its downstream side is decomposed when exposed to the fluid in the subcritical or supercritical state. Note that the fluid supplied from the fluid supply 13 only needs to reach the subcritical state or supercritical state in the cylinder 12, and the fluid does not need to be in the subcritical state or supercritical state immediately before being supplied to the cylinder 12. However, if the fluid to be supplied is brought into the subcritical or supercritical state before being supplied to the cylinder 12 and then supplied into the cylinder 12 while maintaining this state, the decomposition of the melt-plasticized thermoplastic resin begins immediately after the fluid is supplied, and therefore this state is preferable.

[0033] The liquid is added to the melt-plasticized thermoplastic resin as described above. Since the interior of cylinder 12 is heated and pressurized at the time of addition, the liquid added at this time is forced into cylinder 12 against the pressure.

[0034] Since the fluid is brought into the subcritical or supercritical state after being supplied as described above, the temperature of the fluid to be supplied is preferably equal to or higher than the temperature of the melt-plasticized thermoplastic resin in the fluid supply 13.

[0035] Therefore, the fluid supply 13 is preferably equipped with a heating device that can bring the fluid to be supplied into a predetermined heated state. Fig. For example, Figure 1 shows a diagram in which the fluid supply 13 is connected to a hot water generating device 13a. It is sufficient to generate the fluid of the predetermined heated state by using the hot water generating device 13a as described above, and then supply the resulting fluid from the fluid supply 13 into the cylinder 12 through a pipe using a pump such as a plunger pump.

[0036] The extruder 14 is a member that discharges the decomposed thermoplastic resin, which is transported through the cylinder 12, to the outside of the decomposition device 10 and has an opening for extrusion or an extrusion orifice. The extruder 14 can be configured so that the decomposed product can be discharged to the outside while maintaining pressure within the device.

[0037] It should be noted that the extruder 14 may be connected to a container for collecting the raw material or to another processing device so that the extruded decomposition product of the thermoplastic resin is subjected to a further predetermined process.

[0038] The rotary drive mechanism 15 is a device for rotating the screw 12a located inside the cylinder 12. The thermoplastic resin to be decomposed is transported or moved through the cylinder 12 by the screw rotated by the rotary drive 15.

[0039] It should be noted that either a twin-screw extruder with two screws in the barrel 12 or a single-screw extruder with a single screw can be used. In the case of the twin-screw extruder, the two screws rotate parallel to each other. The two shafts can be arranged to mesh or not mesh with each other. When the number of screws is two, the twin-screw extruder with two screws is preferable to the single-screw extruder with a single screw for the same screw bore diameter, as it achieves a high extrusion rate due to the high conveying efficiency of the raw material and the high kneading performance. In addition, the extension direction of the barrel 12 is the same as the extension direction of the screw(s) inside the barrel 12.

[0040] The backflow suppression mechanism 16 is a mechanism for suppressing or preventing the backflow into the above-described cylinder 12, which is the spout member of the supplied thermoplastic resin or the melt-plasticized thermoplastic resin on the resin supply 11 side.

[0041] In the present embodiment, the backflow suppression mechanism 16 is configured to include: at least one measurement sensor 16a selected from the group consisting of a resin thermometer, a resin pressure gauge, and a cylinder thermometer; a relief valve 16b provided in the cylinder 12; and a controller 16c that controls the operation of the relief valve 16b in accordance with a measurement value provided by the measurement sensor 16a. Here, the measurement sensor 16a may include a screw gauge (not shown) that measures the power consumption of the screw-driving rotary drive mechanism 15 and / or the torque of the rotary drive mechanism 15.

[0042] As described above, the measuring sensor 16a is at least one measuring sensor selected from the group consisting of the resin thermometer, the resin pressure gauge, the cylinder thermometer, and the screw gauge. The measuring sensor 16a may be the resin thermometer, the resin pressure gauge, the cylinder thermometer, or the screw gauge, or may consist of a combination of several of these components. Even if Fig. 1 shows an example of a single measuring sensor 16a, multiple measuring sensors of the same type may be provided. When multiple measuring sensors are provided, it is preferable to provide each of them for a different cylinder block among the cylinder blocks that make up the cylinder 12. Note that when the screw measuring device is provided as the measuring sensor 16a, it does not necessarily have to be provided for the cylinder block and is provided so that the power consumption and / or torque of the rotary drive mechanism 15 can be measured.

[0043] The relief valve 16b is an opening / closing valve capable of opening / closing the relief port 12c connecting the interior of the cylinder 12 to the outside atmosphere at any time. The relief valve 16b can be opened and closed manually or automatically. By opening the relief valve 16b, the pressure in the cylinder 12 can be reduced and backflow can be effectively suppressed. Fig. Figure 1 shows a configuration example in which the control unit 16c is provided for automatically opening / closing the relief valve 16b. With such a configuration, the relief valve 16b can be opened immediately when a predetermined measured value is detected, and the backflow suppression process can be performed without delay.

[0044] The relief valve 16b is provided so as to be arranged in a region of the cylinder 12, the region being a subsequent region of a region in which the melt-plasticized thermoplastic resin is formed, and its arranged position is preferably closer to the side of the extruder 14 (downstream) than the fluid supply 13, and is preferably closer to the extruder 14 while being located between the fluid supply 13 and the extruder 14, and is more preferably provided on the cylinder block beside the extruder 14.

[0045] The control device 16c is connected to the measuring sensor 16a and the pressure relief valve 16b and continuously monitors the temperature or pressure measured by the measuring sensor 16a. When the measured value exceeds a predetermined threshold or when the rate of change of the measured value exceeds a predetermined value, the control device 16c automatically opens the pressure relief valve 16b to discharge the melt-plasticized resin in the cylinder 12 to the outside.

[0046] The backflow prevention mechanism 16 may be configured to monitor the measured value of the measuring sensor 16a and issue a warning when the predetermined measured value is detected, and then manually open the pressure relief valve 16b when the warning is issued. In this case, the control device 16c may be omitted. < Resin decomposition process>

[0047] Hereinafter, each step of the resin decomposition method according to the present embodiment will be described, taking the case of using the above-described resin decomposition device 10 in Fig. 1 serves as an example.

[0048] First, the thermoplastic resin is supplied from the resin supply 11 to the cylinder 12 (step (a): resin supply step). In this step, the thermoplastic resin to be decomposed is filled into the cylinder 12, which forms the housing of the decomposition device.

[0049] Note that the resin product to be decomposed and delivered here is not specifically limited, as long as it is made of thermoplastic resin and is hydrolyzed. Examples of resin types include polyamide (PA) resin, polycarbonate (PC) resin, polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, or the like. In this embodiment, an example of hydrolysis of polyamide (PA) resin will be discussed.

[0050] Subsequently, the supplied thermoplastic resin is heated and pressurized in the cylinder 12 and melt-plasticized (step (b): melt-plasticizing step). Here, the thermoplastic resin supplied in the above resin supply step is heated and pressurized while being transported in the cylinder 12 by the screw 12a to the extruder 15.

[0051] Here, the thermoplastic resin is gradually heated to a high temperature by the heater provided on the outer circumference of the cylinder 12 during transportation, and the thermoplastic resin is gradually pressurized by the screw in the cylinder 12 during transportation. The thermoplastic resin, which is melt-plasticized by the heating and pressurization as described above, can be easily transported by the screw 12a.

[0052] Although it depends on the type of resin to be used, it is preferable to heat and pressurize the thermoplastic resin before the fluid supply step described below, for example, at a resin temperature of 250°C to 400°C and a resin pressure of 15 to 22 MPa. Immediately before the fluid supply step, the conditions preferably reach 150 to 250°C and 15 to 20 MPa. More specifically, when the polyamide (PA) resin is included as the resin to be decomposed, the resin temperature preferably reaches 300°C to 350°C and the resin pressure preferably reaches 15 to 18 MPa.

[0053] Subsequently, the heated and pressurized fluid from the fluid supply 13 is supplied to the melt-plasticized thermoplastic resin in the cylinder 12 (step (c): fluid supply). The fluid supplied here is mixed with the melt-plasticized thermoplastic resin.

[0054] The fluid supplied at this time is a fluid such as water or an alcohol such as methanol, which can be brought into the subcritical or supercritical state to decompose the melt-plasticized resin, with water being preferred. The supercritical state refers to a state with an activity intermediate between liquid and gas in a range beyond the liquid critical point, while the subcritical state refers to a liquid phase state with an activity in a range slightly lower than that of the supercritical state.

[0055] The conditions for the subcritical and supercritical states vary depending on the fluid used. For example, when using water, a pressure equal to or higher than the saturation pressure at 150 to 350°C is sufficient for the subcritical state (e.g., a saturation pressure of 8.59 MPa at 300°C or a saturation pressure of 16.54 MPa at 350°C). For the supercritical state, for example, a temperature equal to or higher than 374°C and a pressure equal to or higher than 22 MPa are sufficient.

[0056] The fluid can also be brought into the subcritical or supercritical state before or after being fed to the melt-plasticized thermoplastic resin. In this fluid feeding step, the heating and pressure conditions are adjusted so that the fluid to be fed meets the desired conditions. Note that it is advantageous to bring the fluid into the subcritical or supercritical state before feeding it and then feed the fluid into the cylinder 12. In this way, by feeding the fluid into the cylinder 12, the melt-plasticized thermoplastic resin is mixed with the fluid, and decomposition can begin simultaneously with the mixing.

[0057] After the fluid is supplied, the melt-plasticized thermoplastic resin in the cylinder 12 is mixed with the fluid in the subcritical or supercritical state and thus decomposed (step (d): decomposition step). This decomposition step is preferably carried out for a period of time during which the thermoplastic resin is sufficiently decomposed, and the mixing time with the fluid in the subcritical state or supercritical state can be adjusted by the length of the cylinder 12 and the conveying speed caused by the rotation of the screw 12a or the like.

[0058] For example, the period of time for the above-mentioned decomposition is preferably 2 to 5 minutes, more preferably 5 to 10 minutes, and even more preferably 10 to 15 minutes.

[0059] The thermoplastic resin subjected to the subcritical or supercritical state as described above is severed at its bond and then becomes the decomposition product of the resin, which has been decomposed (depolymerized) into monomer, which is the raw material.

[0060] Then, the decomposed product of the thermoplastic resin obtained in the decomposition step is extruded from the extruder 14 at the tip of the cylinder 12 (step (e): extrusion step). The decomposed and extruded resin product is collected. This decomposition product can be reused as raw material for resin production.

[0061] It should be noted that during reuse it is advantageous to remove the impurities contained in the decomposition product and that a step to remove impurities can be carried out during collection.

[0062] Next, the backflow suppression step, which is a distinguishing feature of the present embodiment, will be explained. In the above-described steps (a) to (e), the thermoplastic resin introduced into the cylinder 12 is in the form of, for example, a granular pellet for easy handling, and is then heated and pressurized, and then melt-plasticized after feeding as described above. At this time, as shown in Fig. 3, a solid pellet 50 supplied from the resin supply 11 is semi-melted while being transported to the downstream side and then becomes the fully melted melt resin 51.

[0063] At this time, if the pressure on the pellet 50 side and the pressure on the melt resin 51 side are balanced, the process can continue and decomposition can be carried out efficiently. However, if this balance is lost and the pressure on the melt resin 51 side is higher than the pressure on the pellet 50 side, the melt resin 51 will flow backward while pushing the pellet 50 back toward the resin feeder 11, and eventually the melt resin 51 and the pellet 50 may splash out of the resin feeder 11 in a mixed state.

[0064] In the present embodiment, the cylinder 12 contains a measuring sensor 16a for suppressing such backflow, as shown in Fig. 1 is shown. Fig. 3 shows an example in which this measuring sensor 16a is a resin thermometer 16a-1, a resin pressure gauge 16a-2, and a cylinder thermometer 16a-3. However, as described above, the measuring sensor 16a may also consist of one, two, or three types. Alternatively, the measuring sensor 16a may consist of a single screw gauge (in this case, the screw gauge is provided on the rotary drive device 15) or a combination of the screw gauge with at least one type of the resin thermometer 16a-1, the resin pressure gauge 16a-2, and the cylinder thermometer 16a-3. The following explanation will be made with reference to Fig. 3, in which the measuring sensor 16a is provided on the cylinder block.

[0065] Fig. Figure 3 shows an example in which the cylinder blocks in the cylinder 12 between the resin supply 11 and the fluid supply 13 can be provided with the resin thermometer 16a-1, the resin pressure measuring device 16a-2, and the cylinder thermometer 16a-3. However, the measuring sensor can also be mounted on a single cylinder block.

[0066] Even if the gauge sensor is provided for a single cylinder block, pressure imbalance can be detected if the gauge sensor 16a is provided, and therefore, this does not pose a problem. Furthermore, if the gauge sensor is provided on a plurality of cylinder blocks, pressure imbalance can be detected more accurately, and therefore, this is preferable.

[0067] Regarding the cylinder block equipped with the measuring sensor 16a, it should be noted that the cylinder block on the resin supply 11 side, which mostly contains pellets, is preferably equipped with the same. In this way, when the cylinder block on the resin supply 11 side exhibits a change in the numerical value measured by the measuring sensor 16a, the occurrence of backflow can be accurately detected, and then a suppression process described later can be initiated.

[0068] For example, if the decomposition in the Fig. 3, but the pressure on the side of the melting resin 51 increases, so that the backflow of the molten resin to the side of the resin supply 11 begins, as shown in Fig. As shown in Figure 4, the change in the value measured by at least one of the resin thermometer 16a-1, the resin pressure gauge 16a-2, and the cylinder thermometer 16a-3 is detected. When the occurrence of backflow is confirmed, the control device 16c opens the relief valve 16b to discharge the molten resin 51 from the inside of the cylinder 12 to the outside through an orifice. This reduces the pressure of the molten resin inside the cylinder 12, thereby suppressing a situation of backflow and pouring of the molten resin 51 along with pellets 50 to the resin supply 11 side. As a concrete example, the relief valve 16b is opened when a temperature increase of 10% is observed, so that the resin thermometer 16a-1 indicates a temperature of, for example, 240°C to 265°C.

[0069] Note that for the value measured by the measuring sensor 16a, for controlling the operation of the relief valve 16b, the control device 16c may set a threshold value based on the measured value or a threshold value based on the changed value obtained by monitoring its change over time. This threshold value may be appropriately set depending on the cylinder equipped with the measuring sensor 16a, the resin or fluid to be used, the decomposition conditions, or the like.

[0070] In the case of decomposition using polyamide resin as the thermoplastic resin to be decomposed and water as the supply fluid, the threshold value can be set, for example, to 50 to 225°C for the resin temperature, 1 to 8 MPa for the resin pressure, and 25 to 250°C for the cylinder temperature based on the measured value to be illustrated. The threshold value based on the changed value can be set, for example, to 5 to 30% for the resin temperature, 5 to 30% for the resin pressure, and 5 to 30% for the cylinder pressure. <Betrieb der Zersetzungsvorrichtung>

[0071] The resin decomposition device and the resin decomposition method according to the present embodiment have been explained above. A series of operations of the resin decomposition device 10 will be described with reference to the flowchart in Fig. 5 explained.

[0072] First, the resin decomposition device 10 is activated, and the values ​​(temperature and pressure) measured by the measuring sensor 16a are displayed (S1-1). Then, the pressure relief valve 16b is closed (S1-2), and the operation of the decomposition device 10 is started (S1-3). Upon starting operation, the cylinder 12 is heated to a predetermined temperature, and the drive of the screw 12a is also started.

[0073] The feed of pellets 50 as resin to be decomposed to the resin feeder 11 is started (S1-4). After confirming sufficient melting / plasticization of the resin and its transport in the cylinder 12, the feed of the heated and pressurized fluid from the fluid feeder 13 is started (S1-5).

[0074] Furthermore, pressurization is started to adjust the pressure in cylinder 12 to a predetermined pressure (S1-6). Simultaneously with the start of pressurization, whether there is a backflow sign is determined based on the value measured by the measuring sensor 16a (S1-7). If there is no backflow sign, the process continues (S1-8). Then, it is confirmed that the pressure has reached the predetermined pressure (S1-9), and whether there is a backflow sign is confirmed again based on the value measured by the measuring sensor 16a (S1-10). If there is no backflow sign in this case, the process continues to continue resin decomposition (S1-11).

[0075] In contrast, if a backflow sign is present, the relief valve 16 is opened (S1-12, S1-13) when it is confirmed that there is a backflow sign as described above (S1-7, S1-10). By opening the relief valve 16, the pressure inside the cylinder 12 can be quickly reduced and the backflow can be suppressed (prevented). In particular, by continuously checking whether there is a backflow sign even after operation has resumed (S1-11), the backflow can be reliably suppressed (prevented).

[0076] If operation is to be resumed after opening the pressure relief valve 16, close the pressure relief valve 16 (S1-14), restart pressurization (S1-6), and continue operation while checking for backflow (S1-7 to S1-14). After opening the pressure relief valve 16, it is recommended that operation be resumed after any possible cause of backflow has been eliminated.

[0077] If there are no problems, the process continues until all resin decompositions are completed. When all decompositions are complete, the decomposition device stops. <Zweite Ausführungsform> [Device for producing resin composites]

[0078] The second embodiment is an embodiment for suppressing backflow by changing the amount of resin supplied from the resin supply as a backflow suppression mechanism, and the other configurations may be the same as those of the first embodiment. Fig. 6 is a diagram showing a configuration example of a resin decomposition apparatus according to the second embodiment.

[0079] The Fig. The resin decomposition apparatus 20 shown in Fig. 6 comprises the resin supply 11, the cylinder 12 with the screw, the fluid supply 13 which supplies the fluid to the cylinder 12, the extruder 14, the rotary drive mechanism 15 which drives the screw of the cylinder 12, and a backflow suppression mechanism 26.

[0080] Here, the resin feeder 11, the cylinder 12, the fluid feeder 13, the extruder 14, and the rotary drive mechanism 15 are identical to those described in the first embodiment, and therefore their description is omitted here. The second embodiment is configured to suppress backflow by changing the amount of resin supplied from the resin feeder 11 as described above, and differs in the backflow suppression mechanism 26. The backflow suppression mechanism 26 will be explained in more detail below.

[0081] In the present embodiment, the backflow suppression mechanism 26 is configured to include: at least one measurement sensor 26a selected from the group consisting of a resin thermometer, a resin pressure gauge, and a cylinder thermometer; a supply device 26b capable of adjusting the amount of resin supplied to the resin supply 11; and a controller 26c that controls the operation of the supply device 26b in accordance with the measurement value obtained from the measurement sensor 26a.

[0082] The configuration of the measuring sensor 26a may be identical to that of the measuring sensor 16a described in the first embodiment and will therefore not be described further here.

[0083] As the feeder 26b, a well-known feeder can be used, and the feeder 26b is a device that supplies the resin to be decomposed to the resin feeder 11. The feeder 26b used in this embodiment has a feed amount adjustment function and is connected to the control device 26c described below, and can change the amount of resin to be fed depending on the situation.

[0084] The control device 26c is connected to the measuring sensor 26a and the supply device 26b and continuously monitors the temperature or pressure measured by the measuring sensor 26a. If the measured value exceeds a predetermined threshold or if a rate of change of the measured value exceeds a predetermined value, the control device 26c operates to increase the amount of resin supplied from the supply device 26b to the resin supply 11.

[0085] Regarding the backflow suppression mechanism 26, it can be configured to monitor the value measured by the measuring sensor 26a, issue a warning when a predetermined measured value is detected, and manually increase the amount of resin delivered from the feeder when the warning is issued. In this case, the control device 26c can be omitted. < Resin decomposition process>

[0086] Hereinafter, each step of the resin decomposition method according to the present embodiment will be described, taking the case of using the above-described resin decomposition device 20 in Fig. 6 serves as an example.

[0087] Note that steps (a) to (e) of the resin decomposition method according to the present embodiment are the same as those of the resin decomposition method described in the first embodiment, and therefore their description will be omitted. Since the distinctive feature of the present embodiment is the backflow suppression step, which differs from that of the first embodiment, this difference will be mainly explained below.

[0088] In the steps (a) to (e) described above, as in the first embodiment and in Fig. 3, the solid pellet 50 supplied from the resin supply 11 is half-melted while being transported to the downstream side, and then becomes the fully melted melt resin 51. Then, when the balance between the pressure on the pellet 50 side and the pressure on the melt resin 51 side is lost, the melt resin 51 flows back while pushing the pellet 50 back toward the resin supply 11, and finally, the melt resin 51 and the pellet 50 may come out of the resin supply 11 in a mixed state.

[0089] In the present embodiment, in order to suppress such backflow, the cylinder 12 contains at least one measuring sensor 26a selected from the group consisting of a resin thermometer, a resin pressure measuring device and a cylinder thermometer, as shown in Fig. 6. This measuring sensor 26a can be configured to have the same configuration as the measuring sensor 16a of the first embodiment.

[0090] In the present embodiment, when the decomposition in the Fig. 3, but the pressure on the side of the melt resin 51 increases to start the backflow of the melt resin towards the side of the resin supply 11, as shown in Fig. 4, the change in the value measured by at least one of the resin thermometer 16a-1, the resin pressure measuring device 16a-2, and the cylinder thermometer 16a-3 is detected. If the occurrence of backflow is confirmed, the control device 26c increases the resin supply amount in the supply device 26b to increase the pressure on the molten resin 51 side. This adjusts the balance between the pressures of the pellet 50 and the molten resin 51 inside the cylinder 12, thereby suppressing a situation of backflow and outflow of the molten resin 51 along with the pellet 50 to the resin supply 11 side.

[0091] In this case, the threshold value explained in the first embodiment or the changed value can be set for the value measured by the measuring sensor 26a and the device can be operated.

[0092] It should be noted that the increased amount of resin is sufficient to suppress leakage due to backflow, and the amount is preferably, for example, 1.5 to 2.5 times the amount of resin originally supplied.

[0093] Even after increasing the resin amount, the value measured by the measuring sensor 26a is confirmed again to determine whether backflow has been suppressed. If backflow has not been suppressed, the resin amount can be further increased, and these steps can be repeated until backflow is suppressed. In this case, the resin amount can be gradually increased until it reaches approximately 1.1 to 1.5 times the originally supplied resin amount. <Betrieb der Zersetzungsvorrichtung>

[0094] The resin decomposition apparatus and the resin decomposition method according to the present embodiment have been explained above. A series of operations of the resin decomposition apparatus 20 will be described with reference to the flowchart in Fig. 7 explained.

[0095] First, the resin decomposition device 20 is activated, and the values ​​(temperature and pressure) measured by the measuring sensor 26a are displayed (S2-1). Subsequently, the operation of the decomposition device 20 is started (S2-2). Upon starting the operation, the cylinder 12 is heated to a predetermined temperature, and the drive of the screw 12a is also started.

[0096] The supply of pellets 50 as the resin to be decomposed to the resin supply 11 is started (S2-3). After confirming sufficient melting / plasticization of the resin and its transport in the cylinder 12, the supply of the heated and pressurized fluid from the fluid supply 13 is started (S2-4).

[0097] In addition, pressurization is started to adjust the pressure in cylinder 12 to a predetermined pressure (S2-5). Simultaneously with the start of pressurization, the value measured by the measuring sensor 26a is used to determine whether backflow is present (S2-6). If there is no backflow, the process continues (S2-7).

[0098] Then, it is confirmed that the pressure has reached the specified pressure (S2-8), and it is again confirmed whether there is a backflow indication based on the value measured by the measuring sensor 26a (S2-9). If there is no backflow indication in this case, the process continues to continue resin decomposition (S2-10).

[0099] Conversely, if it is confirmed that there is a backflow sign as described above (S2-6, S2-9), if a backflow sign is present, the amount of resin supplied by the supply device 26b is increased (S2-11, S2-12). After increasing the supplied resin amount, the value measured by the measuring sensor 26a is confirmed, and it is determined whether the sign has disappeared (S2-13). If the sign has disappeared, the process continues to continue resin decomposition (S2-10). If the sign has not disappeared, the amount of resin is increased again (S2-11, S2-12), and these steps are repeated until the sign disappears. By increasing the supplied resin amount, the balance between the pressures of the pellet 50 and the melt resin 51 inside the cylinder 12 is adjusted, thereby suppressing (preventing) backflow.If it is continuously confirmed that there is no sign of backflow even after the operation is continued (S2-10), the backflow can be reliably suppressed (prevented).

[0100] If there are no problems, the process continues until all resin decompositions are complete. When all decompositions are complete, the decomposition device stops. (Third embodiment)

[0101] The third embodiment is an embodiment for suppressing backflow by interrupting the fluid supply from the fluid supply as a backflow suppression mechanism, and the other configurations may be the same as those of the first embodiment. Fig. 8 is a diagram showing a configuration example of a resin decomposition apparatus according to the third embodiment.

[0102] The Fig. The resin decomposition apparatus 30 shown in Fig. 8 comprises the resin supply 11, the cylinder 12 with the screw, the fluid supply 13 that supplies the fluid to the cylinder 12, the extruder 14, the rotary drive mechanism 15 that drives the screw of the cylinder 12, and a backflow suppression mechanism 36.

[0103] Here, the resin feeder 11, the cylinder 12, the fluid feeder 13, the extruder 14, and the rotary drive mechanism 15 are identical to those described in the first embodiment, and therefore their description is omitted here. The third embodiment is configured to suppress backflow by stopping the fluid supply from the fluid feeder 13 as described above and differs in the backflow suppression mechanism 36. The backflow suppression mechanism 36 will be explained in more detail below.

[0104] In the present embodiment, the backflow suppression mechanism 36 is configured to include: at least one measurement sensor 36a selected from the group consisting of a resin thermometer, a resin pressure gauge, and a cylinder thermometer; a valve 36b connected to the fluid supply 13 and disposed on a line for supplying the fluid; and a control device 36c capable of controlling the opening / closing of the valve 36b in accordance with the measurement value obtained from the measurement sensor 36a.

[0105] The configuration of the measuring sensor 36a may be identical to that of the measuring sensor 16a described in the first embodiment and will therefore not be described further here.

[0106] A well-known valve can be used as the valve 36b, and the valve 36b is arranged in the line connected for supplying the fluid from the fluid supply 13 to the cylinder 12. By opening / closing the valve 36b, the decision of whether the fluid is supplied to the cylinder and the supply amount can be controlled.

[0107] The control device 36c is connected to the measuring sensor 36a and the valve 36b and continuously monitors the temperature or pressure measured by the measuring sensor 36a. If the measured value exceeds a predetermined threshold or if the rate of change of the measured value exceeds a predetermined value, the control device 36c closes the valve 36b, thereby stopping the fluid supply to the cylinder 12.

[0108] Regarding the backflow suppression mechanism 36, it can be configured to monitor the value measured by the measuring sensor 36a, issue a warning when a predetermined measured value is detected, and manually stop the fluid supply from the fluid supply 13 when the warning is issued. In this case, the control device 36c can be omitted. <harzzersetzungsverfahren>

[0109] Hereinafter, each step of the resin decomposition method according to the present embodiment will be described, taking the case of using the above-described resin decomposition device 30 in Fig. 8 serves as an example.

[0110] Note that steps (a) to (e) of the resin decomposition method according to the present embodiment are the same as those of the resin decomposition method described in the first embodiment, and therefore their description will be omitted. Since the distinctive feature of the present embodiment is the backflow suppression step, which differs from that of the first embodiment, this difference will be mainly explained below.

[0111] In the steps (a) to (e) described above, as in the first embodiment and in Fig. 3, the solid pellets 50 supplied from the resin feeder 11 are semi-melted while being transported to the downstream side, and then become the fully molten molten resin 51. Then, when the balance between the pressure on the pellet 50 side and the pressure on the molten resin 51 side is lost, the molten resin 51 flows back while pushing the pellets 50 back toward the resin feeder 11, and finally, the molten resin 51 and the pellets 50 may come out of the resin feeder 11 in a mixed state.

[0112] In the present embodiment, in order to suppress such backflow, the cylinder 12 contains at least one measuring sensor 36a selected from the group consisting of a resin thermometer, a resin pressure measuring device and a cylinder thermometer, as shown in Fig. 8. This measuring sensor 36a may be configured to have the same configuration as the measuring sensor 16a of the first embodiment.

[0113] In the present embodiment, if the decomposition in the Fig. 3, but the pressure on the side of the melt resin 51 increases to start the backflow of the melt resin towards the side of the resin supply 11, as shown in Fig. As shown in Figure 4, the change in the value measured by at least one of the resin thermometer 16a-1, the resin pressure gauge 16a-2, and the cylinder thermometer 16a-3 is detected. If the occurrence of backflow is confirmed, the control device 36c closes the valve 36b, thereby stopping the fluid supply to the cylinder 12. This adjusts the balance between the pressures of the pellets 50 and the melt resin 51 inside the cylinder 12, thereby suppressing a situation of backflow and outflow of the melt resin 51 along with the pellets 50 to the resin supply 11 side.

[0114] In this case, the threshold value or the changed value can be set for the value measured by the measuring sensor 36a as explained in the first embodiment, and the device can be operated. <Betrieb des Zersetzungsvorrichtung>

[0115] The resin decomposition device and the resin decomposition method according to the present embodiment have been explained above. A series of operations of the resin decomposition device 30 will be described with reference to the flowchart in Fig. 9 explained.

[0116] First, the resin decomposition device 30 is activated, and the values ​​(temperature and pressure) measured by the measuring sensor 36a are displayed (S3-1). Then, the operation of the decomposition device 30 is started (S3-2). Upon starting the operation, the cylinder 12 is heated to a predetermined temperature, and the drive of the screw 12a is also started.

[0117] The supply of pellets 50 as resin to be decomposed to the resin supply 11 is started (S3-3). After confirming sufficient melting / plasticization of the resin and its transport in the cylinder 12, the supply of the heated and pressurized fluid from the fluid supply 13 is started (S3-4).

[0118] In addition, pressurization is started to adjust the pressure in cylinder 12 to a predetermined pressure (S3-5). Simultaneously with the start of pressurization, a check is made for backflow based on the value measured by the measuring sensor 36a (S3-6). If there is no backflow, the process continues (S3-7).

[0119] Then, it is confirmed that the pressure has reached the specified pressure (S3-8), and it is again confirmed whether there is a backflow indication based on the value measured by the measuring sensor 36a (S3-9). If there is no backflow indication in this case, the process continues to continue resin decomposition (S3-10).

[0120] In contrast, if backflow is confirmed as described above (S3-6, S3-9), valve 36b is closed, stopping the fluid supply from fluid supply 13 (S3-11, S3-12). After the fluid supply is stopped, the operating conditions are changed (S3-13). The operating conditions to be changed in this case only need to be those capable of suppressing backflow, such as the resin supply amount, fluid supply amount, screw speed, barrel temperature, or the like.

[0121] After the operating conditions change, valve 36b is opened, resuming the fluid supply (S3-4). By interrupting the fluid supply, the pressure balance between the pellets 50 and the melt resin 51 inside the cylinder 12 is adjusted, thereby suppressing (preventing) backflow. If it is continuously confirmed that there are no signs of backflow even after resuming operation (S3-10), backflow can be reliably suppressed (prevented).

[0122] If there are no problems, the process continues until all resin decompositions are completed. When all decompositions are complete, the decomposition device stops.

[0123] In the foregoing, the present invention has been specifically described with reference to the embodiments and examples. However, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the present invention. EXPLANATION OF REFERENCE SYMBOLS 10, 20, 30 resin decomposition device 11 Resin supply 12 cylinders 12a snail 12b Fluid supply opening 12c Overpressure opening 13 Fluid supply 14 extruders 15 Rotary drive mechanism 16, 26, 36 Backflow suppression mechanism 16a, 26a, 36a measuring sensor 16c, 26c, 36c control device 16b Pressure relief valve 26b Supply / feed 36c valve< / harzzersetzungsverfahren>

Claims

[1] Resin decomposition process comprising the following steps: (a) feeding a thermoplastic resin from a resin supply into a cylinder; (b) heating and pressurizing and then melt-plasticizing the supplied thermoplastic resin in the cylinder; (c) supplying a heated and pressurized fluid from a fluid supply to the melt-plasticized thermoplastic resin and mixing the fluid with the thermoplastic resin; (d) decomposing the melt-plasticized thermoplastic resin by subjecting the thermoplastic resin to a subcritical state or a supercritical state by the supplied fluid; and (e) extruding a decomposition product of the thermoplastic resin obtained in step (d) from an extruder provided at a tip of the cylinder, wherein in the step (b), a backflow suppression step is performed in which at least one selected from a temperature of the thermoplastic resin, a pressure of the thermoplastic resin and a temperature of the cylinder is measured, and then the backflow of the melt-plasticized thermoplastic resin is suppressed in accordance with the measured value. [2] The resin decomposition method according to claim 1, wherein the backflow suppressing step is a step of discharging the melt-plasticized thermoplastic resin from the cylinder to the outside in the cylinder located closer to a downstream side than the fluid supply. [3] The resin decomposition method according to claim 2, wherein the molten resin is discharged to the outside through a relief port provided in the cylinder adjacent to the extruder. [4] The resin decomposition method according to claim 1, wherein the step of suppressing the backflow is a step of increasing the supply amount of the thermoplastic resin in step (a). [5] The resin decomposition method according to claim 4, wherein the supply amount of the thermoplastic resin increases by 1.5 to 2.5 times. [6] The resin decomposition method according to claim 1, wherein the step of suppressing the backflow is a step of interrupting the supply of the fluid in the step (c). [7] The resin decomposition method according to claim 1, wherein the thermoplastic resin is a polyamide resin. [8] Resin decomposition device comprising a cylinder; a resin feeder that supplies the cylinder with a thermoplastic resin to be decomposed; a screw that transports the supplied thermoplastic resin and the melt-plasticized thermoplastic resin in the cylinder; a fluid supply that supplies a heated and pressurized fluid into the cylinder to decompose the melt-plasticized thermoplastic resin in a subcritical state or a supercritical state; an extruder provided at a tip of the cylinder and extruding a decomposition product of the thermoplastic resin to the outside of the cylinder; and a backflow suppression mechanism including, in the cylinder provided between the resin supply and the fluid supply, at least one of the following elements: 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 gauge for measuring a power consumption or a drive torque of a rotary drive mechanism driving the screw, wherein the backflow suppression mechanism is capable of suppressing the backflow of the melt-plasticized thermoplastic resin in accordance with at least one of the measured values ​​of the resin thermometer, the resin pressure gauge, the cylinder thermometer, and the screw gauge. [9] The resin decomposition apparatus according to claim 8, wherein the backflow suppression mechanism in the cylinder located closer to a downstream side than the fluid supply comprises: a pressure relief valve for opening / closing a pressure relief port for communication between the interior of the cylinder and the outside atmosphere; and a control device that controls the opening / closing of the pressure relief valve depending on the measured value(s). [10] The resin decomposition apparatus according to claim 9, wherein the pressure relief valve is disposed in the cylinder adjacent to the extruder. [11] The resin decomposition device according to claim 8, wherein the backflow suppression mechanism comprises: a feed device capable of regulating the amount of resin delivered by the resin feed; and a control device that increases the amount of resin delivered from the resin supply to the cylinder according to the measured value(s). [12] The resin decomposition device according to claim 8, wherein the backflow suppression mechanism comprises: a valve connected to the fluid supply and provided in a conduit for supplying the fluid; and a control device capable of controlling the opening / closing of the valve depending on the measured value(s).

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