Resin decomposition treatment method and decomposition treatment device

Abstract

The invention provides a resin decomposition processing method and a resin decomposition processing device which can safely and efficiently perform resin decomposition processing. A resin decomposition processing device (10) is provided with: a cylinder (12); a resin supply unit (11) that supplies a thermoplastic resin to the cylinder (12); a screw (12a) that conveys the supplied thermoplastic resin and the thermoplastic resin that has been melted and plasticized; a fluid supply unit (13) that supplies a fluid in a heated and pressurized state into the cylinder so as to decompose the molten and plasticized thermoplastic resin in a subcritical state or a supercritical state; an extrusion section (14) that is provided at the tip of the cylinder (12) and that discharges a decomposed product of the thermoplastic resin to the outside of the cylinder; a rotation drive mechanism (15) that rotationally drives the screw (12a); and a reverse flow suppression mechanism (16) that suppresses the reverse flow of the molten and plasticized thermoplastic resin in the cylinder (12).

Description

Technical Field

[0001] The present invention relates to a resin decomposition treatment method and a decomposition treatment device, and in particular to a resin decomposition treatment method and a decomposition treatment device that avoids the generation of a backflow to the resin supply part side when the resin is decomposed under high temperature and high pressure. Background Art

[0002] At present, plastic products are used in a wide range of fields and their usage is huge. On the other hand, the disposal of plastic products is costly, and the impact on the environment is also a problem because plastic products are left in the natural environment and their components flow into rivers, seas, etc. or pass through them.

[0003] Therefore, various studies have been conducted on recycling various resins to effectively utilize resources. For example, a method of recycling and reusing a monomer obtained by thermally decomposing an acrylic resin using a twin-screw extruder is known (for example, see Patent Document 1).

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

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 11-106427 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, 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. Usually, since high temperature and high pressure conditions are obtained, the structure of the decomposition treatment device used for this purpose, such as the sealing structure, has been studied.

[0010] On the other hand, if a decomposition treatment apparatus capable of withstanding the critical state and the supercritical state is prepared, for example, a dedicated apparatus must be manufactured, which increases the initial cost and the total treatment cost.

[0011] Therefore, in order to promote the above-mentioned resin recycling, the present invention aims to provide a resin decomposition treatment method and a resin decomposition treatment device capable of safely and continuously performing resin decomposition treatment.

[0012] Means for solving problems

[0013] The resin decomposition treatment method disclosed in the present application has the following steps: (a) supplying a thermoplastic resin from a resin supply section to a cylinder; (b) heating and pressurizing the supplied thermoplastic resin in the cylinder to melt and plasticize it; (c) supplying a heated and pressurized fluid from a fluid supply section to the melted and plasticized thermoplastic resin and mixing them; (d) exposing the melted and plasticized thermoplastic resin to a subcritical state or a supercritical state using the supplied fluid to decompose it; and (e) extruding the decomposition product of the thermoplastic resin obtained in step (d) from an extrusion section provided at the front end of the cylinder.

[0014] Here, in the decomposition treatment method, 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 of suppressing the backflow of the molten plasticized thermoplastic resin is started based on the measured value.

[0015] The resin decomposition treatment device disclosed in the present application includes: a cylinder; a resin supply part, which supplies a supplied thermoplastic resin as a decomposition treatment object to the cylinder; a screw, which transports the supplied thermoplastic resin and the molten plasticized thermoplastic resin in the cylinder; a fluid supply part, which supplies a heated and pressurized fluid into the cylinder to decompose the molten plasticized thermoplastic resin in a subcritical state or a supercritical state; and an extrusion part, which is arranged at the front end of the cylinder and discharges the decomposition product of the thermoplastic resin to the outside of the cylinder.

[0016] In addition, the decomposition treatment device has a backflow suppression mechanism, which has 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 meter for measuring the energy consumption or driving torque of the rotation driving mechanism that drives the screw in a cylinder body arranged between the resin supply part and the fluid supply part, and suppresses the backflow of the molten 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 meter.

[0017] Effects of the Invention

[0018] According to the resin decomposition treatment method and the decomposition treatment device disclosed in the present application, it is possible to provide a resin decomposition treatment method and the decomposition treatment device that can be performed safely and continuously. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a side view showing a schematic configuration of the resin decomposition treatment device according to the first embodiment.

[0020] Figure 2 It is used to illustrate Figure 1A side view of a screw arranged in a cylinder of a decomposition processing device.

[0021] Figure 3 is used to explain in more detail Figure 1 Diagram of the backflow suppression mechanism in the decomposition treatment device.

[0022] Figure 4 is used to explain in more detail Figure 1 Diagram of the backflow suppression mechanism in the decomposition treatment device.

[0023] Figure 5 This is a flowchart for explaining the operation of the resin decomposition treatment device according to the first embodiment.

[0024] Figure 6 It is a side view showing the schematic structure of the resin decomposition treatment device according to the second embodiment.

[0025] Figure 7 This is a flowchart for explaining the operation of the resin decomposition treatment device according to the second embodiment.

[0026] Figure 8 It is a side view showing the schematic structure of the resin decomposition treatment device according to the third embodiment.

[0027] Fig. 9 This is a flowchart for explaining the operation of the resin decomposition treatment device according to the third embodiment. DETAILED DESCRIPTION

[0028] The following describes the embodiments in detail based on the examples and drawings. It should be noted that in all the drawings used to describe the embodiments, components having the same functions are denoted by the same or related reference numerals, and their repeated descriptions are omitted.

[0029] <Research Process>

[0030] First, the research process of the present invention will be described.

[0031] As described above, when a resin is decomposed (depolymerized) using a fluid in a subcritical state or a supercritical state, a closed processing container that can withstand the processing conditions is usually prepared. However, the inventors of the present application have studied the possibility of using a resin extruder used when forming a resin material for the decomposition of the resin.

[0032] That is, the inventors of the present application considered whether it is possible to use such a resin extrusion device without preparing a special processing device for resin decomposition processing, and directly or slightly modify the existing extrusion device to be suitable for decomposition processing to continuously and efficiently perform resin decomposition processing.

[0033] The 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 uses a screw to transport the molten plasticized resin. In addition, the molten plasticized resin is fully kneaded during transportation in the cylinder, and is extruded from a mold provided at the front end of the cylinder as a uniformly mixed resin material. The cylinder is heated and pressurized, so it is assumed that the decomposition process of the above-mentioned resin can also be carried out by directly using the device and mixing a subcritical state or supercritical state fluid with the resin in the cylinder.

[0034] In fact, the inventors of the present application attempted a resin decomposition process under such conditions and confirmed that a subcritical state could be maintained in the cylinder and that the resin decomposition process could be performed.

[0035] However, when the decomposition treatment is continued, the molten plasticized resin and the pre-molten resin may be ejected from the resin supply portion of the extruder in reverse flow. This is considered to be because the resin supply portion of the extruder is usually not sealed but is open to the atmosphere, and the pressure of the molten plasticized resin in the cylinder is greater than the pressure of the pre-molten resin on the resin supply portion side.

[0036] Therefore, in order to provide a decomposition treatment device that can safely continue to perform resin decomposition treatment without backflow when the molten plasticized resin is subjected to resin decomposition treatment based on a subcritical state using an extruder, various studies have been conducted, and a resin decomposition treatment method and a decomposition treatment device that can suppress backflow have been discovered. The resin decomposition treatment device and the decomposition treatment method in this embodiment are described in detail below.

[0037] <Implementation method 1>

[0038] [Resin decomposition treatment device]

[0039] Figure 1 This is a diagram showing a configuration example of a resin decomposition treatment device according to the first embodiment. Figure 2 It is used to describe the configuration in Figure 1 The diagram of the screw in the cylinder of the resin decomposition treatment device shown is a side view.

[0040] Figure 1 The resin decomposition treatment device 10 shown is a device for performing a decomposition treatment by exposing a resin to be decomposed to a fluid in a subcritical state or a supercritical state.

[0041] The resin decomposition treatment device 10 includes a resin supply unit 11 , a cylinder 12 having a screw, a fluid supply unit 13 for supplying fluid to the cylinder 12 , an extrusion unit 14 , a rotation drive mechanism 15 for driving the screw of the cylinder 12 , and a backflow suppression mechanism 16 .

[0042] The resin supply unit 11 is a component that 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. As the supplied thermoplastic resin, various forms of materials such as pellets, powders, and flakes can be used, and for example, the resin is fed from the top into the resin supply unit 11 having a hopper by a feeder or the like and supplied into the cylinder 12. The following description takes the case where the supplied thermoplastic resin is pellets as an example.

[0043] The cylinder 12 has a screw 12 a inside. Figure 2 A cross-sectional view of the cylinder block 12 is shown to understand Figure 1 The internal structure of the cylinder 12 of the resin decomposition treatment device 10. It should be noted that Figure 2 The cylinder 12 also includes a fluid supply hole 12 b for configuring the fluid supply portion 13 and an overflow hole 12 c for discharging the molten plasticized thermoplastic resin from the cylinder 12 to the outside.

[0044] By rotating the screw 12a, the supplied resin is gradually transported to the extrusion section 14 side (downstream side) inside the cylinder 12. When a twin-shaft screw having two screws is used as the screw 12a, a twin-shaft extruder can be formed. The twin-shaft extruder has the flexibility that the operating conditions such as the rotation speed of the screw and the set temperature of the barrel can be freely changed, and has various advantages such as high transportability and continuous processing.

[0045] The cylinder 12 is composed of, for example, a plurality of cylinder blocks connected together, each of which is provided with a space capable of conveying thermoplastic resin therein. A screw 12a is provided in the space, and the screw 12a is connected to a rotation drive mechanism 15. The screw 12a is rotated by the rotation drive mechanism 15, so that the resin to be decomposed can be conveyed in the cylinder 12.

[0046] In addition, the cylinder 12 is provided with a heater so that its temperature can be adjusted. The thermoplastic resin to be decomposed is conveyed from the resin supply unit 11 toward the extrusion unit 14 side, and is gradually heated by the heater at this time, so that the molten plasticized thermoplastic resin can be easily obtained. In addition, the molten plasticized thermoplastic resin obtained in the above manner can be easily conveyed in the cylinder 12 and further conveyed to the downstream side.

[0047] The molten resin in the cylinder 12 and the fluid supplied from the fluid supply unit 13 are pressurized by the screw 12 a and reach a subcritical state or a supercritical state.

[0048] When the fluid is supplied by the fluid supply unit 13 described later, the melted and plasticized thermoplastic resin is mixed with the fluid. At this time, the temperature and pressure in the cylinder 12 are adjusted to a predetermined level by the heater and the screw provided in the cylinder 12 as described above, and the cylinder 12 becomes a subcritical state or a supercritical state. Then, while the thermoplastic resin is further conveyed in the cylinder 12 while maintaining the subcritical state or the supercritical state, the thermoplastic resin is decomposed.

[0049] The fluid supply unit 13 supplies heated and pressurized fluid to the melted and plasticized thermoplastic resin in the cylinder 12. The fluid supply unit 13 is configured to supply the fluid into the cylinder 12 after the thermoplastic resin is melted and plasticized in the cylinder 12.

[0050] On the downstream side of the fluid supply section 13, the melted plasticized thermoplastic resin is exposed to the fluid in the subcritical state or supercritical state due to the fluid supplied from the fluid supply section 13 and decomposes. It should be noted that the fluid supplied from the fluid supply section 13 only needs to be in the subcritical state or supercritical state in the cylinder 12, and it may not be in the subcritical state or supercritical state before being supplied to the cylinder 12. It should be noted that if the supplied fluid is in the subcritical state or supercritical state before being supplied to the cylinder 12, and is supplied to the cylinder 12 while maintaining this state, the melted plasticized thermoplastic resin starts to decompose immediately after the fluid is supplied, which is preferred.

[0051] The fluid is added to the molten plasticized thermoplastic resin in the above manner. At this time, since the cylinder 12 is heated and pressurized, the fluid supplied here is supplied into the cylinder 12 against the pressure.

[0052] After the fluid is supplied as described above, it is in a subcritical state or a supercritical state. Therefore, the temperature of the supplied fluid is preferably the same as or higher than the temperature of the melted and plasticized thermoplastic resin in the fluid supply unit 13 .

[0053] Therefore, it is preferable that the fluid supply unit 13 is provided with a heating mechanism capable of setting the supplied fluid to a predetermined heated state. Figure 1 1 shows a diagram of the fluid supply unit 13 connected to the heated water manufacturing device 13a. In this way, the heated water manufacturing device 13a is used to prepare a fluid in a predetermined heated state, and the obtained fluid is passed through a pipe through a pump such as a plunger pump, and can be supplied from the fluid supply unit 13 to the cylinder 12.

[0054] The extrusion unit 14 is a member for discharging the decomposition product of the thermoplastic resin conveyed in the cylinder 12 to the outside of the decomposition treatment device 10, and has a throttle portion of an extrusion hole or an extrusion port. The extrusion unit 14 can be configured to discharge the decomposition product to the outside while maintaining the pressure in the device.

[0055] It should be noted that the extrusion unit 14 may be connected to a container for recovering raw materials, or may be connected to a different processing device to further perform a predetermined treatment on the decomposition product of the extruded thermoplastic resin.

[0056] The rotation drive mechanism 15 is a device for rotating a screw 12a provided in the cylinder 12. The thermoplastic resin to be decomposed is conveyed in the cylinder 12 by the screw rotated by the rotation drive mechanism 15.

[0057] It should be noted that it can be a double-shaft extruder with two screws in the cylinder body 12, or it can be a single-shaft extruder with one screw. In the case of a double-shaft extruder, the two screws are arranged parallel to each other and rotate. The two shafts can be configured to mesh with each other or not. When the number of screws is set to two, due to the high efficiency of conveying raw materials and high mixing performance, when the screw diameter is the same, the extrusion amount of the double-shaft with two screws can be increased compared with the single-shaft with one screw, so it is preferred. In addition, the extension direction of the cylinder body 12 is the same as the extension direction of the screw in the cylinder body 12.

[0058] The backflow suppression mechanism 16 is a mechanism for suppressing the backflow of the supplied thermoplastic resin or the melt-plasticized thermoplastic resin from being ejected from the resin supply unit 11 side in the cylinder 12 .

[0059] In the present 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 for controlling the operation of the relief valve 16b based on the measurement value obtained by the measuring sensor 16a. Here, as the measuring sensor 16a, a screw measuring meter (not shown) for measuring the energy consumption of the rotary drive mechanism 15 driving the screw and / or the rotary torque of the rotary drive mechanism 15 may be provided.

[0060] 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 gauge. The measuring sensor 16a may be one of the resin thermometer, the resin pressure gauge, the cylinder thermometer, and the screw measuring gauge, or may be a combination of multiple sensors. Figure 1 In the example in which one measuring sensor 16a is provided, a plurality of measuring sensors of the same kind may be provided. In the case where a plurality of measuring sensors are provided, it is preferred that they are respectively provided in different cylinder blocks in the cylinder block constituting the cylinder 12. It should be noted that when a screw measuring meter is provided as the measuring sensor 16a, it does not need to be provided in the cylinder block, but is provided so as to be able to measure its energy consumption and / or rotational torque in the rotation drive mechanism 15.

[0061] The overflow valve 16b is an on-off valve that can open and close the overflow hole 12c connecting the inside of the cylinder 12 with the outside atmosphere at any time. The overflow valve 16b can be opened and closed manually or automatically. By opening the overflow valve 16b, the pressure in the cylinder 12 can be reduced, and the backflow can be effectively suppressed. It should be noted that Figure 1 , an example of a structure in which a control unit 16c is provided and can be automatically opened and closed is shown. If such a structure is adopted, when a predetermined measurement value is detected, the relief valve 16b can be immediately opened, and the backflow suppression operation can be performed without delay.

[0062] The overflow valve 16b is configured to be arranged in the cylinder 12 after the thermoplastic resin in the cylinder 12 is melted and plasticized. Preferably, its configuration position is closer to the extrusion section 14 side (downstream side) than the fluid supply section 13, more preferably between the fluid supply section 13 and the extrusion section 14, close to the extrusion section 14, and particularly preferably in the cylinder block adjacent to the extrusion section 14.

[0063] The control unit 16c is connected to the measuring sensor 16a and the overflow valve 16b, and always monitors the temperature or pressure measured by the measuring sensor 16a. When the measured value exceeds a specified threshold or the rate of change of its measured value exceeds a specified value, the overflow valve 16b is automatically opened to discharge the molten plasticized resin in the cylinder 12 to the outside of the device.

[0064] The backflow suppression mechanism 16 may monitor the measured value of the measuring sensor 16a, issue a warning when a predetermined measured value is detected, and manually open the relief valve 16b when the warning is issued. In this case, the control unit 16c may not be provided.

[0065] <Resin decomposition treatment method>

[0066] Next, regarding the decomposition treatment method of the resin of this embodiment, using the above-mentioned Figure 1 Each step will be described by taking the case of the resin decomposition treatment device 10 as an example.

[0067] First, a thermoplastic resin is supplied from the resin supply unit 11 to the cylinder 12 (step (a); resin supply step). In this step, the thermoplastic resin to be decomposed is supplied to the inside of the cylinder 12 which is the main body of the decomposition treatment device.

[0068] It should be noted that the resin product to be decomposed provided here is not particularly limited, and it can be made of thermoplastic resin and undergo hydrolysis. Examples of the resin include polyamide (PA) resin, polycarbonate (PC) resin, polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, etc. In this embodiment, an example of the hydrolysis of polyamide (PA) resin is introduced.

[0069] Next, the supplied thermoplastic resin is heated and pressurized in the cylinder 12 to be melt-plasticized (step (b); melt-plasticizing step). Here, the supplied thermoplastic resin in the resin supply step is heated and pressurized while being conveyed in the cylinder 12 toward the extrusion unit 15 by the screw 12a.

[0070] Here, the temperature is gradually increased by the heater provided on the outer periphery of the cylinder 12 while being conveyed, and the pressure is gradually increased while being conveyed by the screw inside the cylinder 12. By heating and pressurizing in this way, the thermoplastic resin can be easily conveyed by the screw 12a in a molten and plasticized state.

[0071] Depending on the type of resin used, it is preferred that the resin temperature be heated and pressurized, for example, to a resin temperature of 250 to 400° C. and a resin pressure of 15 to 22 MPa, before the fluid supply process described below. It should be noted that it is preferred to set the temperature to 150 to 250° C. and 15 to 20 MPa before the fluid supply process. More specifically, when the resin to be decomposed includes a polyamide (PA) resin, for example, it is preferred that the resin temperature be 300 to 350° C. and the resin pressure be 15 to 18 MPa.

[0072] 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 (step (c): fluid supply step). The supplied fluid is mixed with the molten and plasticized thermoplastic resin.

[0073] In order to decompose the molten plasticized resin, the fluid supplied at this time can be a fluid that can be set to a subcritical state or a supercritical state, such as water, alcohols such as methanol, and preferably water. The supercritical state refers to a state in which the liquid has an activity that is an intermediate state between a liquid and a gas in a region exceeding its liquid critical point, and the subcritical state refers to a liquid phase state in a region slightly lower than the supercritical state.

[0074] The conditions of the subcritical state and the supercritical state vary depending on the fluid used. In the case of water, the subcritical state can be, for example, set to 150-350°C and the pressure can be above the saturation pressure (for example, the saturation pressure at 300°C is 8.59 MPa, and the saturation pressure at 350°C is 16.54 MPa), and the supercritical state can be, for example, set to above 374°C and above 22 MPa.

[0075] Here, the subcritical state or supercritical state can be set before or after the supply of the molten plasticized thermoplastic resin, and the heating and pressurizing state can be adjusted in the fluid supply process so that the supplied fluid becomes the desired condition. It should be noted that it is preferably set to a subcritical state or a supercritical state before supply, and the fluid is supplied into the cylinder 12. Thus, 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 while mixing.

[0076] Then, after the above-mentioned fluid is supplied, the thermoplastic resin melted and plasticized in the cylinder 12 is mixed with the fluid in a subcritical state or a supercritical state to be decomposed ((d) step; decomposition step). It is preferred that the decomposition step be performed for a time period sufficient for the thermoplastic resin to be fully decomposed, and the mixing time with the fluid in a subcritical state or a supercritical state can be adjusted by the length of the cylinder 12 and the conveying speed based on the rotation of the screw 12a.

[0077] The time for the decomposition treatment is, for example, preferably 2 to 5 minutes, more preferably 5 to 10 minutes, and further preferably 10 to 15 minutes.

[0078] The thermoplastic resin exposed to the subcritical state or supercritical state in this way has its bonds cut and decomposed (depolymerized) into resin decomposition products in which monomers serving as raw materials are obtained.

[0079] Then, the decomposed product of the thermoplastic resin obtained in the decomposition step is extruded from the extrusion unit 14 provided at the front end of the cylinder 12 (step (e); extrusion step). The extruded decomposed product of the resin is recovered and can be reused as a raw material in the production of the resin.

[0080] It should be noted that, when reusing, impurities contained in the decomposed product are preferably removed, and an impurity removal step may be performed during recovery.

[0081] Next, the backflow suppression step which is a feature of this embodiment will be described.

[0082] When performing the above steps (a) to (e), the thermoplastic resin introduced into the cylinder 12 is, for example, in the form of granules and is easy to handle. After introduction, it is heated and pressurized in the above manner to be melted and plasticized. Figure 3 As shown, solid pellets 50 supplied from the resin supply unit 11 are semi-molten while being conveyed to the downstream side, and then become completely molten molten resin 51 .

[0083] At this time, when the pressure on the pellet 50 side is balanced with the pressure on the molten resin 51 side, continuous operation can be achieved and efficient decomposition treatment can be performed. However, when the balance is broken and the pressure on the molten resin 51 side is higher than the pressure on the pellet 50 side, the molten resin 51 pushes the pellet 50 back to the resin supply unit 11 side and flows back, and the molten resin 51 and the pellet 50 are sometimes finally ejected from the resin supply unit 11 to the outside in a mixed state.

[0084] In this embodiment, in order to suppress such backflow, Figure 1 As shown, the cylinder 12 has a measuring sensor 16a. Figure 3 The example in which the measuring sensor 16a includes a resin thermometer 16a-1, a resin pressure gauge 16a-2, and a cylinder temperature gauge 16a-3 is shown, but as mentioned above, the measuring sensor 16a may be one, two, or three. In addition, the measuring sensor 16a may be independent of the screw measuring gauge (in this case, the screw measuring gauge is provided in the rotation drive device 15), or the screw measuring gauge may be combined with at least one of the resin thermometer 16a-1, the resin pressure gauge 16a-2, and the cylinder temperature gauge 16a-3. The following refers to the case where the measuring sensor 16a is provided in the cylinder block. Figure 3 to explain.

[0085] Here, in Figure 3 , an example is shown in which the resin temperature meter 16a-1, the resin pressure meter 16a-2, and the cylinder temperature meter 16a-3 are arranged in the cylinder block from the resin supply part 11 to the fluid supply part 13 in the cylinder 12, but the measuring sensors can also be arranged on one cylinder block.

[0086] Even when the measuring sensor 16a is provided in one cylinder block, there is no problem because the above-mentioned pressure balance disruption can be detected. In addition, when the measuring sensor 16a is provided in a plurality of cylinder blocks, the above-mentioned pressure balance disruption can be detected more accurately, which is preferable.

[0087] It should be noted that the cylinder block provided with the measuring sensor 16a is preferably set as the cylinder block on the side of the resin supply unit 11 where most of the particles are formed. In this way, when the value measured by the measuring sensor 16a in the cylinder block on the side of the resin supply unit 11 changes, the occurrence of backflow can be accurately detected, and the suppression action described later can be started.

[0088] For example, in Figure 3 The decomposition process is continued in the state shown, and the pressure on the molten resin 51 side becomes high. Figure 4When the molten resin starts to flow back toward the resin supply unit 11, the control unit 16c detects a change in at least one of the measured values ​​of the resin thermometer 16a-1, the resin pressure gauge 16a-2, and the cylinder temperature gauge 16a-3. When it is determined that the backflow has occurred, the control unit 16c opens the relief valve 16b to discharge the molten resin 51 from the cylinder 12 through the opening to the outside. As a result, the pressure of the molten resin in the cylinder 12 is reduced, and the molten resin 51 can be suppressed from flowing back toward the resin supply unit 11 together with the particles 50. As a specific example, the relief valve 16b is opened when the temperature of the resin thermometer 16a-1 rises by 10%, for example, from 240°C to 265°C.

[0089] It should be noted that, as the measurement value of the measurement sensor 16a, in order to control the operation of the relief valve 16b by the control unit 16c, a threshold value based on the measurement value may be set, or a threshold value based on the change value may be set by monitoring the change over time. The threshold value may be appropriately set according to the cylinder body where the measurement sensor 16a is installed, the resin and fluid used, the conditions of the decomposition process, etc.

[0090] In the case of a decomposition process in which a polyamide resin is used as a thermoplastic resin to be decomposed and water is used as a supplied fluid, the threshold value based on the measured value may be, for example, a case where the resin temperature is set to 50 to 225° C., the resin pressure is set to 1 to 8 MPa, and the cylinder temperature is set to 25 to 250° C. Also, as the threshold value based on the change value, for example, a case where the resin temperature is set to 5 to 30%, the resin pressure is set to 5 to 30%, and the cylinder pressure is set to 5 to 30%.

[0091] <Operation of the decomposition processing device>

[0092] As described above, the resin decomposition treatment device and the resin decomposition treatment method of this embodiment refer to Figure 5 A series of operations of the resin decomposition treatment device 10 will be described with reference to the flowchart.

[0093] First, the resin decomposition device 10 is started, 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 decomposition device 10 starts to operate (S1-3). By starting the operation, the cylinder 12 is heated to a predetermined temperature, and the drive of the screw 12a is started.

[0094] As for the resin to be decomposed, pellets 50 are started to be supplied to the resin supply unit 11 (S1-4), and after confirming that the resin is fully melted and plasticized and transported in the cylinder 12, heated and pressurized fluid is started to be supplied from the fluid supply unit 13 (S1-5).

[0095] In addition, the pressure in the cylinder 12 is increased to a predetermined pressure (S1-6). When the pressure is increased, the presence or absence of a backflow sign is determined based on the measured value of the measuring sensor 16a (S1-7). If there is no backflow sign, the operation is continued (S1-8).

[0096] Then, confirm that the pressure reaches the specified pressure (S1-9), and again determine whether there is a backflow sign based on the measured value of the measuring sensor 16a (S1-10). If there is no backflow sign at this time, continue to operate and continue to decompose the resin (S1-11).

[0097] On the other hand, when the presence or absence of the above-mentioned backflow sign is confirmed (S1-7, S1-10), if there is a backflow sign, the relief valve 16b is released (S1-12, S1-13). By releasing the relief valve 16b, the pressure in the cylinder 12 can be quickly reduced, and the backflow can be suppressed (prevented). In addition, the presence or absence of the backflow sign is always carried out after the operation is continued (S1-11), thereby reliably suppressing (preventing) the backflow.

[0098] When restarting the operation after releasing the relief valve 16b, the relief valve 16b is closed (S1-14), and the pressure is increased again (S1-6), and the operation is performed while confirming whether there is a sign of backflow (S1-7 to S1-14). It should be noted that after the relief valve is released and opened, if there is a cause of backflow, it is preferably eliminated and then restarted.

[0099] If there are no problems, the operation is continued until the decomposition treatment of the resin is completely completed, and the decomposition treatment device is stopped when it is completely completed.

[0100] (Implementation Method 2)

[0101] <Production equipment for resin composite materials>

[0102] The second embodiment is an embodiment in which the backflow is suppressed by changing the amount of resin supplied from the resin supply unit as the backflow suppression mechanism, and the other configurations can be the same as those of the first embodiment. Figure 6 This is a diagram showing a configuration example of a resin decomposition treatment device according to a second embodiment.

[0103] Figure 6 The resin decomposition treatment device 20 shown includes a resin supply unit 11 , a cylinder 12 having a screw, a fluid supply unit 13 for supplying fluid to the cylinder 12 , an extrusion unit 14 , a rotation drive mechanism 15 for driving the screw of the cylinder 12 , and a backflow suppression mechanism 26 .

[0104] Here, the resin supply unit 11, the cylinder 12, the fluid supply unit 13, the extrusion unit 14, and the rotation drive mechanism 15 are the same as those described in the first embodiment, and thus the description thereof is omitted. The second embodiment is characterized in that the backflow is suppressed by changing the resin supply amount from the resin supply unit 11 as described above, and a backflow suppression mechanism 26 is provided. The backflow suppression mechanism 26 will be described in detail below.

[0105] In this embodiment, the backflow suppression mechanism 26 is constructed to include at least one measuring sensor 26a selected from a resin thermometer, a resin pressure gauge and a cylinder thermometer, a feeder 26b capable of adjusting the amount of resin supplied to the resin supply unit 11, and a control unit 16c for controlling the operation of the feeder 26b based on the measurement value obtained by the measuring sensor 26a.

[0106] The measurement sensor 26a can be configured similarly to the measurement sensor 16a described in the first embodiment, and therefore description thereof will be omitted here.

[0107] The feeder 26b can use a known feeder and is a device for supplying the resin to be decomposed to the resin supply unit 11. The feeder 26b used in this embodiment has a function of adjusting its supply amount and is connected to the control unit 26c described below to change the amount of resin supplied according to the situation.

[0108] The control unit 26c is connected to the measuring sensor 26a and the feeder 26b, and always monitors the temperature or pressure measured by the measuring sensor 26a. When the measured value exceeds a specified threshold or the rate of change of its measured value exceeds a specified value, it takes action to increase the amount of resin supplied from the feeder 26b to the resin supply unit 11.

[0109] The backflow suppression mechanism 26 may monitor the measurement value of the measurement sensor 26a and issue a warning when a predetermined measurement value is detected, and manually increase the resin supply amount from the feeder when the warning is issued. In this case, the control unit 26c may not be provided.

[0110] <Resin decomposition treatment method>

[0111] Next, regarding the decomposition treatment method of the resin of this embodiment, using the above-mentioned Figure 6 Each step will be described by taking the case of the resin decomposition treatment device 20 as an example.

[0112] It should be noted that steps (a) to (e) of the resin decomposition treatment method in this embodiment are common to the resin decomposition treatment method described in the first embodiment, and therefore their description is omitted. In this embodiment, the backflow suppression step is a feature, and since it is different from the first embodiment, the following mainly describes the difference.

[0113] When the above-mentioned steps (a) to (e) are performed, as in the first embodiment and Figure 3 As described above, the solid pellets 50 supplied from the resin supply unit 11 are transported to the downstream side while being semi-molten, and then become completely molten molten resin 51. When the pressure balance between the pellets 50 and the molten resin 51 is broken, the molten resin 51 sometimes pushes the pellets 50 back to the resin supply unit 11 and flows backward, and finally the molten resin 51 and the pellets 50 are mixed and ejected from the resin supply unit 11 to the outside.

[0114] In this embodiment, in order to suppress such backflow, Figure 6 As shown in FIG. 1 , the cylinder 12 includes at least one measuring sensor 26a selected from a resin thermometer, a resin pressure gauge, and a cylinder thermometer. The measuring sensor 26a can be configured similarly to the measuring sensor 16a of the first embodiment.

[0115] In this embodiment, Figure 3 The decomposition process continues in the state shown in the figure, and the pressure on the molten resin 51 side becomes high and the molten resin is as Figure 4 When the resin starts to flow back toward the resin supply unit 11, the control unit 26c detects the change of at least one of the measured values ​​of the resin thermometer 16a-1, the resin pressure gauge 16a-2, and the cylinder temperature gauge 16a-3. When it is determined that the backflow has occurred, the control unit 26c increases the resin supply amount in the feeder 26b, thereby increasing the pressure on the pellet 50 side. In this way, the pressure balance of the pellet 50 and the molten resin 51 in the cylinder 12 can be adjusted, and the molten resin 51 can be suppressed from flowing back and ejecting together with the pellet 50 toward the resin supply unit 11.

[0116] At this time, the threshold value and the change value described in the first embodiment may be set as the measurement value of the measurement sensor 26 a and the sensor may be operated.

[0117] It should be noted that the increase in the amount of resin may be an amount sufficient to suppress the ejection caused by the backflow, and is preferably 1.5 to 2.5 times the amount of resin originally supplied, for example.

[0118] In addition, after the amount of resin is increased, the measured value of the measuring sensor 26a may be checked again to check whether the backflow is suppressed. If the backflow is not suppressed, the amount of resin may be further increased and repeated until the backflow is suppressed. In this case, the increase in the amount of resin may be increased in stages by about 1.1 to 1.5 times the amount of resin originally supplied.

[0119] <Operation of the decomposition processing device>

[0120] The resin decomposition treatment device and the decomposition treatment method of the present embodiment are as described above. Figure 7 A series of operations of the resin decomposition treatment device 20 will be described with reference to the flowchart of FIG.

[0121] First, the resin decomposition device 20 is started, and the measurement sensor 26a displays the measured value (temperature, pressure) (S2-1). Next, the operation of the decomposition device 20 is started (S2-2). When the operation starts, the cylinder 12 is heated to a predetermined temperature, and the drive of the screw 12a is also started.

[0122] As for the resin to be decomposed, the pellets 50 are started to be supplied to the resin supply unit 11 (S2-3), and after confirming that the resin is fully melted and plasticized and transported in the cylinder 12, the supply of heated and pressurized fluid is started from the fluid supply unit 13 (S2-4).

[0123] In addition, the pressure in the cylinder 12 is increased to a predetermined pressure (S2-5). When the pressure increase is started, the presence or absence of a backflow sign is determined based on the measured value of the measuring sensor 26a (S2-6). If there is no backflow sign, the operation is continued (S2-7).

[0124] Then, confirm that the pressure has reached the specified pressure (S2-8), and again determine whether there is a backflow sign based on the measured value of the measuring sensor 26a (S2-9). If there is no backflow sign at this time, continue to operate and continue the decomposition process of the resin (S2-10).

[0125] On the other hand, when confirming the presence or absence of the above-mentioned backflow signs (S2-6, S2-9), if there are backflow signs, the amount of resin supplied from the feeder 26b is increased (S2-11, S2-12). After increasing the amount of supplied resin, confirm the measured value of the measuring sensor 26a to confirm whether the sign disappears (S2-13). If the sign disappears, continue to operate and continue the decomposition process (S2-9). If the sign does not disappear, increase the supply of resin again (S2-11, S2-12), and repeat until the sign disappears. By increasing the amount of supplied resin, the pressure balance between the particles 50 and the molten resin 51 can be adjusted in the cylinder 12, thereby suppressing (preventing) backflow. In addition, the presence or absence of backflow signs is always carried out after continuing the operation (S2-10), thereby reliably suppressing (preventing) backflow.

[0126] If there are no problems, the operation is continued until the decomposition treatment of the resin is completely completed, and the decomposition treatment device is stopped when it is completely completed.

[0127] (Implementation method 3)

[0128] The third embodiment is an embodiment in which the backflow is suppressed by stopping the supply of fluid from the fluid supply unit as the backflow suppression mechanism, and the other configurations can be the same as those of the first embodiment. Figure 8 This is a diagram showing a configuration example of a resin decomposition treatment device according to a third embodiment.

[0129] Figure 8 The resin decomposition treatment device 30 shown includes a resin supply unit 11 , a cylinder 12 having a screw, a fluid supply unit 13 for supplying fluid to the cylinder 12 , an extrusion unit 14 , a rotation drive mechanism 15 for driving the screw of the cylinder 12 , and a backflow suppression mechanism 36 .

[0130] Here, the resin supply unit 11, the cylinder 12, the fluid supply unit 13, the extrusion unit 14, and the rotation drive mechanism 15 are the same as those described in the first embodiment, and thus the description thereof is omitted. The third embodiment is characterized in that the fluid supply from the fluid supply unit 13 is stopped in the above-mentioned manner to suppress the backflow and a backflow suppression mechanism 36 is provided. The backflow suppression mechanism 36 is described in detail below.

[0131] In the present 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 on a pipe for supplying the fluid, and a control unit 36c capable of controlling the opening and closing of the valve 36b based on a measurement value obtained by the measuring sensor 36a.

[0132] The measurement sensor 36a can be configured similarly to the measurement sensor 16a described in the first embodiment, and therefore description thereof will be omitted here.

[0133] The valve 36b can be a well-known valve, and is provided in a pipe connected to supply the fluid from the fluid supply unit 13 to the cylinder 12. By opening and closing the valve 36b, it is possible to control whether the fluid can be supplied to the cylinder 12 and the supply amount.

[0134] The control unit 36c is connected to the measuring sensor 36a and the valve 36b, and always monitors the temperature or pressure measured by the measuring sensor 36a. When the measured value exceeds a specified threshold or the rate of change of its measured value exceeds a specified value, it takes action to close the valve 36b and stop supplying fluid to the cylinder 12.

[0135] The backflow suppression mechanism 36 may monitor the measurement value of the measurement sensor 36a and issue a warning when a predetermined measurement value is detected, and when the warning is issued, the fluid supply from the fluid supply unit 13 is manually stopped. In this case, the control unit 36c may not be provided.

[0136] <Resin decomposition treatment method>

[0137] Next, regarding the decomposition treatment method of the resin of this embodiment, using the above-mentioned Figure 8 Each step will be described by taking the case of the resin decomposition treatment device 30 as an example.

[0138] It should be noted that steps (a) to (e) of the resin decomposition method in this embodiment are common to the resin decomposition method described in the first embodiment, and therefore their description is omitted. This embodiment is characterized by a backflow suppression step, and since it is different from the first embodiment, the following mainly describes the difference.

[0139] When the above-mentioned steps (a) to (e) are performed, as in the first embodiment and Figure 3 As described above, the solid pellets 50 supplied from the resin supply unit 11 are transported to the downstream side while being semi-molten, and then become completely molten molten resin 51. When the pressure balance between the pellets 50 and the molten resin 51 is broken, the molten resin 51 pushes the pellets 50 back to the resin supply unit 11 and flows backward, and the molten resin 51 and the pellets 50 are sometimes finally ejected from the resin supply unit 11 to the outside in a mixed state.

[0140] In this embodiment, in order to suppress such backflow, Figure 8 As shown in FIG. 1 , the cylinder 12 includes at least one measuring sensor 36a selected from a resin thermometer, a resin pressure gauge, and a cylinder thermometer. The measuring sensor 36a can be configured similarly to the measuring sensor 16a of the first embodiment.

[0141] In this embodiment, Figure 3 As the decomposition process continues in the state shown in FIG. 1 , the pressure on the molten resin 51 side becomes high and the molten resin begins to flow toward Figure 4 In the case of backflow on the resin supply unit 11 side, the control unit 36c detects a change in at least one of the measured values ​​of the resin thermometer 16a-1, the resin pressure gauge 16a-2, and the cylinder temperature gauge 16a-3. When it is determined that backflow has occurred, the control unit 36c closes the valve 36b to stop the fluid supply to the cylinder 12. In this way, the pressure balance between the pellets 50 and the molten resin 51 in the cylinder 12 can be adjusted, and the molten resin 51 can be prevented from backflowing and ejecting together with the pellets 50 to the resin supply unit 11 side.

[0142] In this case, the threshold value and the change value described in the first embodiment may be set as the measurement value of the measurement sensor 36 a and the sensor may be operated.

[0143] <Operation of the decomposition processing device>

[0144] As described above, the resin decomposition treatment device and the resin decomposition treatment method of this embodiment refer to Fig. 9 A series of operations of the resin decomposition treatment device 30 will be described with reference to the flowchart.

[0145] First, the resin decomposition device 30 is started, and the measurement sensor 36a displays the measured values ​​(temperature, pressure) (S3-1). Next, the operation of the decomposition device 30 is started (S3-2). The cylinder 12 is heated to a predetermined temperature by the start of the operation, and the drive of the screw 12a is also started.

[0146] As for the resin to be decomposed, pellets 50 are started to be supplied to the resin supply unit 11 (S3-3), and after confirming that the resin is sufficiently melted and plasticized and transported in the cylinder 12, supply of heated and pressurized fluid is started from the fluid supply unit 13 (S3-4).

[0147] In addition, the pressure in the cylinder 12 is increased to a predetermined pressure (S3-5). When the pressure increase is started, the presence or absence of a backflow sign is determined based on the measured value of the measuring sensor 36a (S3-6). If there is no backflow sign, the operation is continued (S3-7).

[0148] Then, confirm that the pressure reaches the specified pressure (S3-8), and again determine whether there is a backflow sign based on the measured value of the measuring sensor 36a (S3-9). If there is no backflow sign at this time, continue to operate and continue the decomposition process of the resin (S3-10).

[0149] On the other hand, when the presence or absence of the above-mentioned backflow sign is confirmed (S3-6, S3-9), if there is a backflow sign, the valve 36b is closed to stop the fluid supply 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 changed here can be conditions that can suppress the backflow, for example, the resin supply amount, the fluid supply amount, the screw speed, the cylinder temperature, etc.

[0150] After the operating conditions are changed, the valve 36b is opened to restart the fluid supply (S3-4). By stopping the fluid supply, the pressure balance between the pellets 50 and the molten resin 51 can be adjusted in the cylinder 12, thereby suppressing (preventing) the backflow. In addition, the presence or absence of backflow signs is always performed even after the operation is continued (S3-10), thereby reliably suppressing (preventing) the backflow.

[0151] If there are no problems, the operation is continued until the decomposition treatment of the resin is completely completed, and the decomposition treatment device is stopped when it is completely completed.

[0152] As mentioned above, although embodiment and Example of this invention were demonstrated more concretely, this invention is not limited to the said embodiment and Example, Of course, various changes can be made in the range which does not deviate from the summary.

[0153] Description of Reference Numerals

[0154] 10, 20, 30 resin decomposition treatment device

[0155] 11 Resin supply unit

[0156] 12 Cylinder

[0157] 12a Screw

[0158] 12b Fluid supply port

[0159] 12c Overflow hole

[0160] 13 Fluid supply unit

[0161] 14 Extrusion Department

[0162] 15 Rotation drive mechanism

[0163] 16, 26, 36 Backflow suppression mechanism

[0164] 16a, 26a, 36a measuring sensor

[0165] 16c, 26c, 36c control unit

[0166] 16b Relief valve

[0167] 26b feeder

[0168] 36c Valve

Claims

1. A method for decomposing a resin, characterized in that: The process includes the following steps: (a) supplying a thermoplastic resin from a resin supply unit to a cylinder; (b) heating and pressurizing the supplied thermoplastic resin in the cylinder to melt and plasticize it; (c) supplying a heated and pressurized fluid from a fluid supply unit to the molten and plasticized thermoplastic resin to mix the mixture; (d) exposing the melt-plasticized thermoplastic resin to a subcritical state or a supercritical state by using the supplied fluid to decompose the thermoplastic resin; and (e) extruding the decomposition product of the thermoplastic resin obtained in the step (d) from an extrusion portion provided at the front end of the cylinder, In the 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 of suppressing backflow of the molten plasticized thermoplastic resin is started based on the measured value.

2. The method for decomposing resin according to claim 1, characterized in that: The backflow suppression step is a step of discharging the molten and plasticized thermoplastic resin from the cylinder to the outside in the cylinder on the downstream side of the fluid supply portion.

3. The method for decomposing resin according to claim 2, characterized in that: The molten resin is discharged to the outside from an overflow hole provided in the cylinder adjacent to the extrusion portion.

4. The method for decomposing resin according to claim 1, characterized in that: The backflow suppression step is a step of increasing the supply amount of the thermoplastic resin in the step (a).

5. The method for decomposing resin according to claim 4, characterized in that: The supply amount of the thermoplastic resin is increased by 1.5 to 2.5 times.

6. The method for decomposing resin according to claim 1, characterized in that: The backflow suppression step is a step of stopping the supply of the fluid in the step (c).

7. The method for decomposing resin according to claim 1, characterized in that: The thermoplastic resin is a polyamide resin.

8. A resin decomposition treatment device, characterized in that: include: Cylinder body; a resin supply unit that supplies a thermoplastic resin to be subjected to a decomposition treatment to the cylinder; a screw that conveys the supplied thermoplastic resin and the melt-plasticized thermoplastic resin in the cylinder; A fluid supply unit that supplies a heated and pressurized fluid into the cylinder to decompose the molten plasticized thermoplastic resin in a subcritical state or a supercritical state; An extrusion unit, which is disposed at the front end of the cylinder body and extrudes the decomposition product of the thermoplastic resin to the outside of the cylinder body; as well as A backflow suppression mechanism, which has 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 meter for measuring the energy consumption or driving torque of a rotation driving mechanism driving the screw, in the cylinder body arranged between the resin supply part and the fluid supply part, and can suppress the backflow of the molten plasticized thermoplastic resin based on at least one of the measured values ​​of the resin thermometer, the resin pressure gauge, the cylinder thermometer and the screw meter.

9. The resin decomposition treatment device according to claim 8, characterized in that: The backflow suppression mechanism includes: an overflow valve configured to open and close an overflow hole that connects the interior of the cylinder to the external atmosphere in the cylinder on the downstream side of the fluid supply unit; and a control unit that controls the opening and closing of the overflow valve based on the measured value.

10. The resin decomposition treatment device according to claim 9, characterized in that: The relief valve is provided on the cylinder adjacent to the extrusion portion.

11. The resin decomposition treatment device according to claim 8, characterized in that: The backflow suppression mechanism includes: 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 based on the measured value.

12. The resin decomposition treatment device according to claim 8, characterized in that: The backflow suppression mechanism includes: a valve provided in a pipe connected to the fluid supply unit and used to supply the fluid; and a control unit capable of controlling opening and closing of the valve based on the measured value.

Images