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 cooler (16) capable of cooling the cylinder (12).

Description

Technical Field

[0001] The present invention relates to a resin decomposition treatment method and a resin decomposition treatment device. 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, one of the objects of the present invention is to provide a resin decomposition treatment method and a resin decomposition treatment apparatus capable of efficiently performing resin decomposition treatment to promote the above-mentioned resin recycling.

[0012] Other issues and new features can be learned from the description and drawings of this specification.

[0013] Means for solving problems

[0014] According to one embodiment disclosed in the present application, a resin decomposition treatment method has 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 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 unit provided at the front end of the cylinder.

[0015] Here, in this decomposition treatment method, the cylinder is cooled by cooling water between the resin supply part and the fluid supply part.

[0016] According to one embodiment disclosed in the present application, a resin decomposition processing device comprises: a cylinder; a resin supply portion, which supplies a thermoplastic resin as a target of decomposition processing to the cylinder; a screw, which transports the supplied thermoplastic resin and the molten plasticized thermoplastic resin in the cylinder; a fluid supply portion, 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; an extrusion portion, which is arranged at the front end of the cylinder and extrude the decomposition product of the thermoplastic resin to the outside of the cylinder; and a cooling mechanism, which is arranged between the resin supply portion and the fluid supply portion and can cool the cylinder.

[0017] Effects of the Invention

[0018] According to one embodiment disclosed in the present application, it is possible to provide a method and apparatus for efficiently performing a resin decomposition treatment. 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 describe the configuration in Figure 1 A diagram showing a side view of a screw in a cylinder of a decomposition treatment device.

[0021] Figure 3 It is used to illustrate Figure 1 A diagram showing the state of backflow occurring in a decomposition treatment device.

[0022] Figure 4 It is used to illustrate Figure 1 A diagram showing the state of backflow occurring in a 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 This is a perspective view showing a schematic structure of a safety hopper that can be attached to a resin supply unit.

[0025] Figure 7 It is a diagram for explaining the size relationship between the lower end opening and the cover portion at a horizontal cross-section of the lower end opening. DETAILED DESCRIPTION

[0026] 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.

[0027] <Research Process>

[0028] First, the research process of the present invention will be described.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] <Implementation Method>

[0036] [Resin decomposition treatment device]

[0037] Figure 1 It is a diagram showing a configuration example of a resin decomposition treatment device according to the present 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.

[0038] Figure 1 The resin decomposition treatment device 10 shown is a device for exposing a resin to be decomposed to a fluid in a subcritical state or a supercritical state to perform a decomposition treatment.

[0039]

[42] The resin decomposition processing device 10 has 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 cooling mechanism 16.

[0040] 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.

[0041] 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 body 12 also shows a fluid supply hole 12 b configured for the fluid supply part 13 .

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The fluid supply unit 13 supplies heated and pressurized fluid into 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.

[0048] 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.

[0049] In the above-mentioned manner, the fluid is added to the molten plasticized thermoplastic resin. At this time, since the cylinder 12 is heated and pressurized, the fluid supplied here is supplied into the cylinder 12 against the pressure. That is, the fluid is pressurized to have a pressure greater than the pressure in the cylinder 12 provided with the fluid supply part 13, and is supplied into the cylinder 12 from the fluid supply part 13.

[0050] 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 .

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] In the present embodiment, the cooling mechanism 16 cools a predetermined region of the cylinder 12. The cooling mechanism 16 is provided on the outer periphery of the cylinder 12 to cool a region between the resin supply unit 11 and the fluid supply unit 13.

[0057] As the cooling mechanism 16, any cooling mechanism that can cool the outer peripheral surface of the cylinder body 12 can be applied, and a known cooling mechanism can be applied, for example, a cooling jacket can be provided on the outer periphery of the cylinder body 12. The cooling jacket is connected to a cooler (cooling water circulation device), and a structure that always circulates cooling water of a predetermined temperature to the cooling jacket so that the cylinder body 12 can be cooled to a predetermined temperature can be cited.

[0058] By providing the cooling mechanism 16, the outer periphery of the cylinder 12 on the resin supply portion 11 side can be cooled, so that the supplied thermoplastic resin and the molten plasticized thermoplastic resin can be cooled on the resin supply portion 11 side, thereby reducing the pressure inside the cylinder 12. Therefore, in the cylinder 12, the backflow of the molten plasticized thermoplastic resin ejected from the resin supply portion 11 can be suppressed.

[0059] [Resin decomposition treatment method]

[0060] 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.

[0061] 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.

[0062] It should be noted that the resin product to be decomposed provided here is not particularly limited, and may be made of a thermoplastic resin, and examples of the resin include polyamide (PA) resin, polycarbonate (PC) resin, polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, etc. Nylon resin is preferred.

[0063] 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.

[0064] Here, the temperature is gradually increased by a heater provided on the outer periphery of the cylinder 12 while being conveyed, and is gradually pressurized by a pressure pump capable of pressurizing the inside of the cylinder 12 while being conveyed. By heating and pressurizing in this way, the thermoplastic resin can be easily conveyed by the screw 12a in a molten and plasticized state.

[0065] Depending on the type of resin used, it is preferred that the resin temperature be heated and pressurized to a condition of, for example, 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 nylon resin, for example, it is preferred that the resin temperature be 300 to 350° C. and the resin pressure be 15 to 18 MPa.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] Next, the cooling step which is a characteristic of this embodiment will be described.

[0076] 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 .

[0077] 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.

[0078] In this embodiment, in order to suppress such backflow, Figure 1 As shown, a cooling mechanism 16 is provided on the outer periphery of the cylinder 12. The cooling mechanism 16 is provided on the outer periphery of the cylinder 12 between the resin supply unit 11 and the fluid supply unit 13, thereby preventing the internal temperature of the cylinder 12 from being excessively high.

[0079] At this time, it is preferable that the cylinder 12 be cooled to 3 to 130° C. or the resin temperature in the cylinder 12 be cooled to 20 to 200° C. by the cooling mechanism 16 . By setting such a temperature, the backflow can be effectively suppressed.

[0080] It should be noted that at this time, Figure 3 In the cylinder 12 shown, at least one measuring sensor selected from a resin thermometer, a resin pressure gauge, and a cylinder thermometer may be provided on the cylinder block from the resin supply section 11 to the fluid supply section 13. In this case, even if the cooling mechanism 16 is not activated at the beginning of the operation of the decomposition treatment device, the cooling mechanism 16 can be activated when a sign of backflow is detected to effectively suppress the backflow.

[0081] It should be noted that the cylinder block provided with the measuring sensor is preferably set as the cylinder block on the side of the resin supply unit 11, which is mostly composed of particles. In this way, when the value measured by the measuring sensor 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 based on cooling can be started.

[0082] For example, Figure 3 The decomposition process continues in the state shown in the figure. The pressure on the molten resin 51 side becomes high and the molten resin begins to Figure 4 When the molten resin 51 flows back toward the resin supply unit 11 as shown, the measured value change of the measuring sensor is detected. When it is determined that the backflow occurs by detecting the change, the control unit connected to the measuring sensor operates the cooling mechanism 16 to cool the cylinder 12. As a result, the pressure of the molten resin in the cylinder 12 is reduced, and the molten resin 51 can be prevented from flowing back and being ejected together with the pellets 50 toward the resin supply unit 11.

[0083] It should be noted that, as the measured value of the measuring sensor, in order to use its control unit to control the operation of the cooling mechanism 16, a threshold value based on the measured value can be set, or a threshold value based on the changed value can be set by monitoring its change over time. The threshold value can be appropriately set according to the resin, fluid, decomposition treatment conditions, etc. used.

[0084] In the case of a decomposition treatment in which polyamide is used as the thermoplastic resin to be decomposed and water is used as the 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%.

[0085] [Operation of the decomposition processing device]

[0086] 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.

[0087] First, the resin decomposition treatment device 10 is started and operation is started (S1). The cylinder 12 is heated to a predetermined temperature by the start of operation, and the drive of the screw 12a is started. Next, the cooling mechanism 16 starts cooling the cylinder 12 (S2).

[0088] The pellets 50 are used as the resin to be decomposed and are started to be supplied to the resin supply unit 11 (S3), and after confirming that the resin is sufficiently melted and plasticized and transported in the cylinder 12, the supply of heated and pressurized fluid from the fluid supply unit 13 is started (S4).

[0089] Then, the pressure is increased to set the pressure in the cylinder 12 to a predetermined pressure (S5). Then, it is confirmed that the pressure reaches the predetermined pressure (S6), and the resin decomposition process is started. After the decomposition process is started, it is confirmed whether there is a sign of backflow (S7), and if there is no sign, the operation is continued (S8). Here, if there is a sign of backflow, the cooling temperature of the cylinder 12 is reduced by the cooling mechanism 16, and the process is repeated until the sign disappears (S9).

[0090] Since the cylinder 12 is always cooled by the cooling mechanism 16, the pressure on the resin supply unit 11 side does not drop excessively, and thus the backflow can be suppressed (prevented). 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.

[0091] [Safety Hopper]

[0092] It should be noted that the above-mentioned resin decomposition treatment device 10 is assumed to be further provided with a safety hopper in order to suppress the influence on the surrounding personnel and the like when the backflow occurs. As the safety hopper, for example, Figure 6 The safety hopper 21 is shown.

[0093] The safety hopper 21 is constructed to include: a resin inlet 22; a connecting structure 23 for connecting to the resin supply part 11; and a cover part 24, which arranges the lower end opening part 22a of the resin inlet 22 inside, covers the surrounding of the lower end opening part 22a of the resin inlet 22 from the connecting structure 23, and has an opening at a position different from the upper end opening part 22b of the resin inlet 22.

[0094] The resin inlet 22 is a member for guiding the resin fed into the resin supply unit 11 when the resin is fed. For example, when the resin such as pellets is fed from the upper opening 22b of the resin inlet 22, it moves downward due to the action of gravity, passes through the lower opening 22a, and further moves downward by falling, so that the resin is fed to the resin supply unit 11. At this time, the lower opening 22a is preferably configured to be located vertically above the opening of the resin supply unit 11 for supplying the resin.

[0095] The resin supply unit 11 and the safety hopper 21 are connected and fixed to each other, and the connection structure 23 is fixed around the opening of the resin supply unit 11. The connection structure 23 is also provided with a hole in the opening of the resin supply unit 11, so that the resin injected from the resin injection port 22 can be reliably supplied to the resin supply unit 11.

[0096] As described above, the cover 24 covers the periphery of the lower end opening 22 a of the resin inlet 22 from the connection structure 23 and has an opening 24 a at a position different from the upper end opening 22 b of the resin inlet 22 .

[0097] The lower end opening 22a of the resin input port 22 is arranged inside the cover 24, but the upper end opening 22b is not arranged. That is, in the safety hopper, the upper end opening 22b is exposed to the outside, and the lower end opening 22a is not exposed to the outside. Thus, the resin can be easily input from the upper end opening 22b, and the input resin can be reliably supplied to the resin supply part 11 through the inside of the cover 24.

[0098] The cover portion 24 can suppress the injected resin from overflowing to the outside and can supply all of it to the resin supply portion 11 , thereby suppressing the loss of the resin to be processed.

[0099] Furthermore, the safety hopper 21 is provided so that even when the molten resin 51 flows back from the resin decomposition treatment device 10 , the backflow can be prevented from causing an impact or damage to personnel or the like.

[0100] In the case where the molten resin 51 is ejected from the resin decomposition treatment device 10 in reverse flow, the molten resin 51 ejects violently from the opening of the resin supply part 11 while pushing the particles 50 back to the resin supply part 11. At this time, if the safety hopper 21 is not provided, the molten resin 51 ejects upward from the opening of the resin supply part 11. Since a feeder for supplying resin is usually arranged above it, such ejection will affect the resin supply operation. In addition, it is also conceivable that if there are people around, the molten resin ejected upward spreads around the resin supply part 11 and causes damage such as burns.

[0101] On the other hand, if the safety hopper 21 is provided, even when the molten resin 51 is ejected, the molten resin 51 can be ejected in the opening direction of the opening 24a by the cover 24. That is, the ejection direction of the molten resin 51 can be controlled to any direction.

[0102] Furthermore, the opening 24a of the cover portion 24 is preferably arranged so that its opening direction faces a direction different from the resin inlet 22, such as a horizontal direction or downward. Thus, the opening direction can be directed toward a space without personnel or a splash-proof plate or enclosure can be provided in the opening direction to suppress the influence of the molten resin 51 on the outside from being ejected. At this time, the resin inlet 22 and the opening 24a are preferably arranged in a direction orthogonal to the opening direction.

[0103] It should be noted that in order to further suppress the influence of the molten resin 51 spraying out, it is preferred to set the area of ​​the cover part 24 (excluding the area of ​​the lower end opening part 22a) larger than the area of ​​the lower end opening part 22a on the horizontal plane of the lower end opening part 22 of the resin inlet 22.

[0104] Figure 7 It is a diagram for explaining the relationship between the size of the lower end opening 22a and the cover 24 on the horizontal cross-sectional plane of the lower end opening 22a. Here, the area of ​​the cover 24 (excluding the area of ​​the lower end opening 22a) is preferably 3 times or more, more preferably 4 times or more, further preferably 8 times or more, and particularly preferably 16 times or more of the area of ​​the lower end opening 22a.

[0105] By setting the area of ​​the lower end opening 22 a and the area of ​​the cover 24 to a predetermined relationship as described above, even when the molten resin 51 is ejected in reverse flow, the molten resin 51 can be guided and ejected from the resin input port 22 by the cover 24 , which is preferable.

[0106] 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.

[0107] Description of Reference Numerals

[0108] 10 Resin decomposition treatment device

[0109] 11 Resin supply unit

[0110] 12 Cylinder

[0111] 12a Screw

[0112] 12b Fluid supply port

[0113] 13 Fluid supply unit

[0114] 14 Extrusion Department

[0115] 15 Rotation drive mechanism

[0116] 16 Cooling mechanism

Claims

1. A method for decomposing a resin, characterized in that: The process includes the following steps: (a) heating and pressurizing the thermoplastic resin in a cylinder to melt and plasticize it; (b) after the step (a), mixing a heated and pressurized fluid with the thermoplastic resin; (c) after the step (b), decomposing the thermoplastic resin by exposing it to a subcritical state or a supercritical state using the fluid; and (d) While cooling the cylinder with cooling water, the decomposition product of the thermoplastic resin obtained in the step (c) is extruded from an extrusion portion of the cylinder.

2. The method for decomposing resin according to claim 1, characterized in that: In the step (b), the heated and pressurized fluid is supplied to the cylinder in a subcritical state or a supercritical state.

3. The method for decomposing resin according to claim 1, characterized in that: The cooling of the cooling water is started simultaneously with the step (a) or before the step (a).

4. The method for decomposing resin according to claim 1, characterized in that: In the step (a), 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 cooling of the cooling water is started according to the measured value.

5. The method for decomposing resin according to claim 1, characterized in that: The temperature of the cylinder is set to 150° C. or less by the cooling.

6. The method for decomposing resin according to claim 1, characterized in that: The temperature of the cooling water is 0.5-50°C.

7. The method for decomposing resin according to claim 6, characterized in that: The cooling water is circulated and supplied to the outer periphery of the cylinder.

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

9. A resin decomposition treatment device, characterized in that: include: Cylinder body; A screw, which is disposed in the cylinder and is capable of mixing and conveying the thermoplastic resin; an extrusion unit provided in the cylinder body and configured to extrude the decomposition product of the thermoplastic resin to the outside of the cylinder body; and A cooling mechanism is used to cool the cylinder body.

10. The resin decomposition treatment device according to claim 9, characterized in that: The cooling mechanism is configured to circulate cooling water around the outer periphery of the cylinder.

11. The resin decomposition treatment device according to claim 9, characterized in that: A control unit is provided, wherein the control unit includes at least one selected from a resin thermometer for measuring the temperature of the thermoplastic resin, a resin pressure gauge for measuring the pressure of the thermoplastic resin, and a cylinder thermometer for measuring the temperature of the cylinder, in the cylinder provided between the resin supply unit and the fluid supply unit, and starts cooling of the cooling mechanism in accordance with a change in the measured value.

12. A resin decomposition treatment device, characterized in that: include: a cylinder having a resin supply portion for supplying a thermoplastic resin; A screw, which is disposed in the cylinder and can mix and transport the thermoplastic resin; an extrusion unit provided in the cylinder body and configured to extrude the decomposition product of the thermoplastic resin to the outside of the cylinder body; and a hopper disposed above the resin supply unit, The hopper comprises: a cover portion having an opening and arranged to cover the resin supply portion; and A resin inlet is provided at the upper portion of the cover portion, The opening and the resin inlet are located in different directions.

13. The decomposition processing device according to claim 12, characterized in that: The opening of the hopper and the resin input port are located in a direction perpendicular to an opening direction.

14. The decomposition processing device according to claim 12, characterized in that: The resin input port of the hopper is located vertically above the resin supply unit.

15. The resin decomposition treatment device according to claim 12, characterized in that: On a horizontal plane where the lower end opening of the resin inlet is provided, an area of ​​the cover portion excluding the lower end opening is three times or more the area of ​​the lower end opening.

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