Method for starting resin pellet manufacturing apparatus, method for manufacturing resin pellet, and resin pellet manufacturing apparatus

Abstract

To reduce an amount of pellet cooling water wasted.SOLUTION: A method for starting a pellet manufacturing apparatus 1 includes a water supply step in which, before starting production of resin pellets, pellet cooling transport water PCW stored in a water tank 50 is supplied to a water chamber 30 by a pump 60 to fill the water chamber 30, and then the supply of the pellet cooling transport water is stopped so that the water level of the pellet cooling transport water reaches a target water level TL set at a position lower than an upper end 163 of a return line 200.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a start-up method for a resin pellet manufacturing apparatus, a method for manufacturing resin pellets, and a resin pellet manufacturing apparatus. [Background technology]

[0002] Conventionally, a pellet manufacturing apparatus for manufacturing resin pellets is known. For example, Patent Document 1 discloses a pelletizing apparatus (pellet manufacturing apparatus) including a PCW (PELLET COOLING / TRANSPORT WATER) tank (water tank), an outward path, a circulation box (water chamber), and a return path. In this technology, a circulation flow path is formed in which pellet cooling transport water (pellet cooling water) that flows from the PCW tank to the circulation box through the outward path flows from the circulation box to the PCW tank through the return path. The return path connects the circulation box and the PCW via above the circulation box. The pelletizing apparatus further includes a die (die plate) having a die hole (die hole) arranged facing the water chamber, and a cutter blade (cutter) arranged in the circulation box for cutting the molten resin discharged from the die hole to manufacture resin pellets.

[0003] In this pelletizing device, before starting the production of resin pellets, a heat medium is passed through the inside of the die to heat the die. In this state, the pellet cooling transport water is circulated in the circulation flow path, and then the circulation is stopped, the pellet cooling transport water is discharged from the circulation box, and a predetermined amount of the pellet cooling transport water is stored in the circulation box. Then, the pellet cooling transport water stored in the circulation box is heat exchanged with the die to warm the pellet cooling transport water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-240494 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in Patent Document 1, the pellet cooling transport water is discharged from the circulation box to the outside of the circulation flow path in order to lower the water level of the pellet cooling transport water, which is not economical. In detail, in the above-mentioned pelletizing device, the pellet cooling transport water is circulated and then stopped to fill the circulation box with the pellet cooling transport water, but at the time of stopping the circulation, the pellet cooling transport water accumulates up to the upper end of the forward path, and the water level of the pellet cooling transport water is high. Due to this high water level, excessive water pressure acts inside the circulation box, which may push back the resin present inside the die hole and cause the pellet cooling transport water to enter the inside of the die hole. For this reason, in the above-mentioned pelletizing device, the pellet cooling transport water is discharged from the circulation box to the outside of the circulation flow path to lower the water level. However, since the pellet cooling transport water discharged outside the circulation flow path is generally discarded, discharging the pellet cooling transport water outside the circulation flow path in order to lower the water level leads to an increase in the amount of waste, which is not economical.

[0006] The present invention has been made in consideration of the above problems, and has an object to reduce the amount of pellet cooling water discarded. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a start-up method for a resin pellet manufacturing apparatus comprising: a circulation flow path having an outward path through which pellet cooling water discharged by a pump from a water tank reaches a water chamber; and a return path through which the pellet cooling water passes above the water chamber and returns from the water chamber to the water tank; a die plate having a plurality of die holes and arranged facing the water chamber; and a cutter arranged in the water chamber for cutting the molten resin discharged from the plurality of die holes to granulate resin pellets, the start-up method comprising: a start-up step of: before starting the production of the resin pellets, supplying the pellet cooling water stored in the water tank to the water chamber by the pump to fill the water chamber, and then stopping the supply of the pellet cooling water so that the water level of the pellet cooling water reaches a target water level set at a position lower than the upper end of the return path.

[0008] According to this configuration, in the water supplying step, the supply of the pellet cooling water is stopped in response to the target water level, so that the amount of pellet cooling water to be discarded can be reduced compared to the case where the pellet cooling water is circulated in the circulation flow path and then discharged so that the water level of the pellet cooling water is set to the target water level.

[0009] In the above configuration, in the water supplying step, water may be supplied to the water chamber while returning a portion of the pellet cooling water discharged from the water tank by the pump to the water tank.

[0010] According to this configuration, in the water supply process, a part of the pellet cooling water is returned to the water tank, while the remaining pellet cooling water is supplied to the water chamber. This makes it possible to reduce the flow rate of the pellet cooling water flowing into the water chamber, compared to a case in which a part of the pellet cooling water is not returned to the water tank. As a result, the rate at which the pellet cooling water accumulates in the water chamber becomes relatively slow, making it easy to stop the water supply when the water level of the pellet cooling water corresponds to the target water level.

[0011] In the above configuration, in the water supplying process, the pellet cooling water may be supplied to the water chamber through an auxiliary flow path having an inner diameter smaller than an inner diameter of the outward path and arranged in parallel with at least a portion of the outward path.

[0012] According to this configuration, in the water supplying step, the pellet cooling water is supplied to the water chamber through the auxiliary flow path having an inner diameter smaller than that of the forward flow path, so the flow rate of the pellet cooling water flowing into the water chamber can be reduced compared to when the water is supplied exclusively through the forward flow path. As a result, the rate at which the pellet cooling water accumulates in the water chamber becomes relatively slow, so that it becomes easy to stop the water supply when the water level of the pellet cooling water corresponds to the target water level.

[0013] In the above configuration, the present invention further includes a rotation step that is performed at least after the water supply step, and rotates the cutter while the cutter is in contact with the die plate, and in the rotation step, the cutter may be rotated while the pellet cooling water is supplied to the water chamber through the auxiliary flow path.

[0014] In the rotation process, the temperature of the die plate may be excessively increased due to frictional heat generated by the rotation of the cutter in contact with the die plate. In response to this, according to the above-mentioned configuration, the pellet cooling water is supplied from the auxiliary flow path, so that the temperature of the die plate can be controlled.

[0015] In the above configuration, in the rotating step, the pellet cooling water may be discharged through a discharge flow passage communicating the water chamber with an outside of the water chamber while the pellet cooling water is being supplied to the water chamber.

[0016] According to this configuration, the pellet cooling water in the water chamber can be agitated by the cutter rotating in the water chamber while replacing the pellet cooling water in the water chamber. This makes it possible to prevent localized boiling in the water chamber. As a result, the temperature of the surface of the die plate facing the water chamber is kept uniform.

[0017] Furthermore, according to the above-described configuration, the resin that drips out of the die holes of the die plate and is scooped up by the cutter can be discharged to the outside of the water chamber together with the pellet cooling water discharged from the water chamber.

[0018] In the above configuration, in the rotating process, the amount of the pellet cooling water discharged through the discharge flow path may be adjusted so that the water surface position of the pellet cooling water in the water chamber is maintained at the target water level.

[0019] According to this configuration, during the rotation process, the water level of the pellet cooling water can be prevented from being positioned at a water level that deviates from the target water level.

[0020] In the above configuration, in the water supply process, a flow path switching mechanism that is arranged downstream of the pump on the forward path and is switchable between a first state in which both the water chamber and the water tank are destinations for the pellet cooling water, a second state in which one of the water chamber and the water tank is destination for the pellet cooling water, and a third state in which the other of the water chamber and the water tank is destination for the pellet cooling water may be set to the first state, thereby supplying the pellet cooling water to the water chamber.

[0021] According to this configuration, in the water supply process, the flow path switching mechanism is in the first state, so that a portion of the pellet cooling water is returned to the water tank while the remaining pellet cooling water is supplied to the water chamber. This makes it possible to reduce the flow rate of the pellet cooling water flowing into the water chamber, compared to a case in which a portion of the pellet cooling water is not returned to the water tank. Furthermore, when it becomes necessary to circulate the pellet cooling water, the flow path switching mechanism can be switched to the second state to set the destination of the pellet cooling water to the water chamber. Furthermore, when it becomes necessary to switch the destination of the pellet cooling water to the water tank, the flow path switching mechanism can be set to the third state. In this way, by providing the flow path switching mechanism, it becomes easy to switch the destination of the pellet cooling water according to the purpose.

[0022] In the above configuration, the return path has an upper connecting flow path connected to the upper part of the water chamber and extending upward, and an inclined flow path that includes a lower end connected to the upper connecting flow path and slopes upward from the lower end to the upper end of the return path, and during the water supply process, the target water level may be set at a position lower than the lower end.

[0023] According to this configuration, since the target water level is set at a position lower than the lower end of the inclined flow channel, the water pressure acting in the water chamber can be suppressed compared to the case where the target water level is set at a position higher than the lower end, so that the pellet cooling water can be efficiently prevented from pushing back the resin present in the die holes of the die plate and entering the die holes.

[0024] Furthermore, since there is no need to discharge the pellet cooling water in the inclined flow passage, the amount of pellet cooling water to be disposed of can be reduced.

[0025] A method for producing resin pellets according to another aspect of the present invention is a method for producing resin pellets in a resin pellet production apparatus equipped with a circulation flow path having an outward path where pellet cooling water discharged by a pump from a water tank reaches a water chamber and a return path where the pellet cooling water passes above the water chamber and returns from the water chamber to the water tank, the method including a water supplying step of supplying the pellet cooling water stored in the water tank to the water chamber before starting production of the resin pellets, a rotation step of rotating a cutter placed in the water chamber while bringing the cutter into contact with a die plate having a plurality of die holes facing the water chamber, a heating step of heating the die plate to melt resin present inside the plurality of die holes, and a resin material The method includes a material supplying process for supplying material to the die plate from upstream, a manufacturing process for cutting the molten resin discharged from a plurality of die holes of the die plate with the cutter in the water chamber to granulate the resin pellets, and manufacturing the resin pellets by cooling the resin pellets with the pellet cooling water while transporting them from the water chamber, and an operation shut-down process for stopping heating of the die plate when molten resin is present inside the plurality of die holes and stopping operation of the resin pellet manufacturing apparatus, and in the water supplying process, after filling the water chamber with the pellet cooling water, the supply of the pellet cooling water is stopped so that the water level of the pellet cooling water reaches a target water level set at a position lower than the upper end of the return path.

[0026] According to this configuration, in the water supplying step, the supply of the pellet cooling water is stopped in response to the target water level, so that the amount of pellet cooling water to be discarded can be reduced compared to the case where the pellet cooling water is circulated in the circulation flow path and then discharged so that the water level of the pellet cooling water is set to the target water level.

[0027] In the above configuration, in the rotating step, the water level of the pellet-cooling water may be maintained at the target water level, and the rotation speed of the cutter may be set to be smaller than the rotation speed of the cutter in the manufacturing step.

[0028] When the level of the pellet cooling water is maintained at the target level, the water pressure acting in the water chamber is suppressed, but there is a possibility that cavitation may occur as the cutter rotates. In contrast, with this configuration, the cutter rotation speed is set to be smaller than the cutter rotation speed during the manufacturing process, so the occurrence of cavitation can be suppressed compared to when the cutter rotation speed is set to be the same as or larger than the cutter rotation speed during the manufacturing process.

[0029] A resin pellet manufacturing apparatus according to another aspect of the present invention includes a water tank for storing pellet cooling water, a water chamber for receiving the pellet cooling water from the water tank, an outward path connecting the water tank and the water chamber, a return path connecting the water chamber and the water tank via above the water chamber, a water supply section for supplying the pellet cooling water from the water tank to the water chamber through the outward path, a die plate having a plurality of die holes facing the water chamber, and a cutter disposed in the water chamber for granulating resin pellets by cutting molten resin discharged from the plurality of die holes of the die plate within the water chamber, and the water supply section stops supplying the pellet cooling water when the water level of the pellet cooling water reaches a target water level set at a position lower than the upper end of the return path before starting production of the resin pellets.

[0030] According to this configuration, the pump stops discharging the pellet cooling water in accordance with the target water level, so that the amount of pellet cooling water discarded can be reduced compared to when the water level of the pellet cooling water is set to the target water level by circulating the pellet cooling water in the circulation flow path and then discharging the pellet cooling water.

[0031] In the above configuration, the device further includes a first auxiliary flow path having an inner diameter smaller than the inner diameter of the outward path and supplying the pellet cooling water flowing out from the water tank to the water chamber, a return flow path branching off from the outward path and connecting the outward path and the water tank, and a flow path switching mechanism switching the destination of the pellet cooling water, wherein the first auxiliary flow path starts from a region of the outward path between the water tank and the flow path switching mechanism or a predetermined region of the return flow path and ends in a region of the outward path between the flow path switching mechanism and the water chamber or the water chamber, and may be opened when the pellet cooling water is supplied to the water chamber before the production of the resin pellets begins.

[0032] According to this configuration, water can be supplied to the water chamber through the first auxiliary flow path, which has an inner diameter smaller than that of the forward flow path. This allows the flow rate of pellet cooling water flowing into the water chamber to be reduced compared to when water is supplied exclusively through the forward flow path. This allows the pellet cooling water to accumulate in the water chamber at a relatively slow pace, making it easier to stop the water supply when the water level of the pellet cooling water corresponds to the target water level. As a result, the amount of pellet cooling water discarded can be reduced.

[0033] In the above configuration, the device may further include a second auxiliary flow path having an inner diameter smaller than the inner diameter of the forward path and different from the first auxiliary flow path, and the second auxiliary flow path may be connected to the water chamber, starting from a region of the forward path between the water tank and the flow path switching mechanism, or a predetermined region of the return flow path, and ending at the tip of the rotation shaft of the cutter.

[0034] The resin pellets cut by the cutter and granulated are normally transported to the outside of the water chamber by the pellet cooling water. However, the resin pellets may be affected by the water flow generated in the water chamber by the rotation of the cutter and may remain near the tip of the rotation shaft of the cutter. In contrast, according to the present configuration, the tip of the rotation shaft of the cutter is set at the end point of the second auxiliary flow path, so that the pellet cooling water can be discharged from the tip to move the resin pellets remaining around the tip. This makes it possible to transport the remaining resin pellets as usual.

[0035] In the above configuration, the pellet cooling water may further include a discharge flow passage for discharging the pellet cooling water from the water chamber to an outside of the water chamber. Effect of the Invention

[0036] According to this configuration, it is possible to reduce the amount of pellet cooling water that is discarded. [Brief description of the drawings]

[0037] [Figure 1] 1 is a diagram showing a schematic configuration of a pellet manufacturing apparatus according to an embodiment of the present invention. [Diagram 2] 2 is an enlarged cross-sectional view of a die plate provided in the pellet manufacturing apparatus of FIG. 1. [Diagram 3] 1 is a flowchart showing a method for producing resin pellets according to an embodiment of the present invention. [Figure 4] 2 is a diagram showing the flow of pellet-cooling water when water is supplied using a water storage flow path provided in the pellet production apparatus of FIG. 1. FIG. [Diagram 5] 2 is a diagram showing the flow of pellet cooling water when water is supplied using an axis-passing passage provided in the pellet production apparatus of FIG. 1. FIG. [Figure 6] FIG. 4 is a diagram showing a schematic configuration of a flow path switching mechanism according to a first modified embodiment of the present invention. [Figure 7] FIG. 13 is a diagram showing a schematic configuration of a pellet manufacturing apparatus according to a second modified embodiment of the present invention. [Figure 8]8A to 8C are schematic diagrams showing the configuration of a flow path switching mechanism provided in the pellet manufacturing apparatus of FIG. 7, where (a) shows the flow path switching mechanism in a first state, (b) shows the flow path switching mechanism in a second state, and (c) shows the flow path switching mechanism in a third state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] <Pellet manufacturing equipment configuration> A pellet manufacturing apparatus 1 (resin pellet manufacturing apparatus) according to one embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing a schematic configuration of the pellet manufacturing apparatus 1 according to one embodiment of the present invention. Fig. 2 is an enlarged cross-sectional view of a die plate 20, which will be described later. In the following, the +Y direction in each drawing is referred to as the upward direction, and the -Y direction is referred to as the downward direction.

[0039] The pellet manufacturing apparatus 1 manufactures resin pellets. As shown in Fig. 1, the pellet manufacturing apparatus 1 includes a feeder 2, a mixer 4, a gear pump 6, a screen changer 8, a die holder 10, a die plate 20, a water chamber 30, a pelletizer 40, a water tank 50, a pump 60, a cooling device 70, a flow path switching mechanism 80, a dryer 90, an outward path 100, a return path 110, a water storage path 120 (first auxiliary path), a shaft passing path 130 (second auxiliary path), a discharge path 140, and a return path 200.

[0040] The feeder 2 supplies a resin material such as polypropylene or polyethylene to the mixer 4 .

[0041] The mixer 4 is driven by a motor (not shown) and kneads the resin material supplied from the feeder 2. The mixer 4 supplies the kneaded resin material to a diverter valve (not shown). The diverter valve switches the destination of the resin kneaded by the mixer 4. In detail, the diverter valve switches between setting the destination of the resin to the gear pump 6 or setting the destination of the resin to outside the pellet manufacturing apparatus 1.

[0042] The gear pump 6 applies pressure to the resin material supplied from the diverter valve, and sends the resin material toward the die plate 20. The resin pressurized by the gear pump 6 passes through a screen changer 8 and a die holder 10, and reaches the die plate 20.

[0043] The screen changer 8 removes foreign matter contained in the resin supplied from the gear pump 6. The resin that has passed through the screen changer 8 passes through the die holder 10 and heads toward the die plate 20.

[0044] The die holder 10 holds a die plate 20. Inside the die holder 10, a die holder passage (not shown) is formed through which the resin material that has passed through the screen changer 8 flows.

[0045] The die plate 20 is held by the die holder 10 and is disposed opposite the water chamber 30. The die plate 20 has a plurality of die holes 20H (FIG. 2) facing the water chamber 30, a heat transfer medium flow path 21 (FIG. 2), and a temperature transmitter 22 (FIG. 1). The die holes 20H communicate the die holder passage with the inside of the water chamber 30, and guide the resin material that has passed through the die holder passage into the inside of the water chamber 30. That is, the resin material that has passed through the die holder passage and reached the die holes 20H is discharged into the water chamber 30 through the die holes 20H. Each die hole 20H is formed with a small diameter, and thus the resin material discharged from each die hole 20H is formed into an elongated shape. The heat transfer medium flow path 21 is a flow path through which a heat transfer medium that heats the die plate 20 flows. For example, steam or hot oil is used as the heat transfer medium. The temperature transmitter 22 measures the temperature of the die plate 20. The temperature measured by the temperature transmitter 22 is transmitted to a control device (not shown).

[0046] Returning to Fig. 1, the water chamber 30 is a container that receives pellet cooling transport water PCW (pellet cooling water) from the water tank 50 and stores the pellet cooling transport water PCW. The pellet cooling transport water PCW is a liquid that cools the resin pellets produced in the pellet production apparatus 1 and transports the resin pellets.

[0047] The pelletizer 40 cuts the resin material discharged from the die plate 20 to produce resin pellets. In detail, the pelletizer 40 has a pelletizer motor 42, a rotating shaft 44, a cutter holder 46, and a plurality of cutters 48.

[0048] The pelletizer motor 42 is a drive source that rotates a plurality of cutters 48 .

[0049] The rotating shaft 44 has one end connected to the pelletizer motor 42 and the other end 47 (tip) disposed in the water chamber 30 to which the cutter holder 46 is attached, and transmits the rotational force generated by the pelletizer motor 42 to the cutter holder 46. The rotating shaft 44 is formed in a cylindrical shape, and the space on the radial inner side of the rotating shaft 44 communicates with the inside of the water chamber 30. The rotating shaft 44 is also connected to a hydraulic unit or a pneumatic unit (not shown), and can move forward and backward in the axial direction. That is, the rotating shaft 44 can move the cutter holder 46 toward and away from the die plate 20.

[0050] The cutter holder 46 is attached to the rotating shaft 44 in a state in which it circumferentially surrounds the other end 47 of the rotating shaft 44. A plurality of cutters 48 are fixed to the cutter holder 46. In detail, the plurality of cutters 48 are arranged on the radial end face of the cutter holder 46 at equal or unequal intervals along the circumferential direction.

[0051] The multiple cutters 48 extend in the radial direction starting from an end surface in the radial direction of the cutter holder 46. As the rotating shaft 44 advances in the axial direction, the multiple cutters 48 come into contact with the surface of the die plate 20. As the pelletizer motor 42 is driven to rotate the cutter holder 46, the multiple cutters 48 rotate in the circumferential direction of the cutter holder 46 with the rotating shaft 44 as the center of rotation.

[0052] The water tank 50 is a container that stores the pellet cooling transport water PCW. The water tank 50 has a heating device 52. The heating device 52 heats the pellet cooling transport water PCW stored in the water tank 50.

[0053] The pump 60 discharges the pellet cooling transport water PCW stored in the water tank 50 toward the water chamber 30. Note that, although the pump 60 according to this embodiment does not have a function of adjusting the flow rate of the pellet cooling transport water PCW, in other embodiments, the pump 60 may have this function.

[0054] The cooling device 70 is disposed downstream of the pump 60 and cools the pellet cooling transport water PCW flowing from the water tank 50 toward the water chamber 30 .

[0055] The flow path switching mechanism 80 is a three-way valve disposed downstream of the pump 60 in the forward path 100, and has a first port connected to a first forward path portion 100a described later, a second port connected to a second forward path portion 100b described later, and a third port connected to a return path 110. The flow path switching mechanism 80 according to this embodiment can switch between a first state and a second state. The first state is a state in which the forward path first portion 100a and the forward path second portion 100b are connected, and the forward path first portion 100a and the return path 110 are prevented from being connected. The first state can be rephrased as a state in which the pellet cooling transport water PCW flowing out of the water tank 50 is sent to the water chamber 30 by the water flow generated by the pump 60. The second state is a state in which the forward path first portion 100a and the return path 110 are connected, and the forward path first portion 100a and the forward path second portion 100b are prevented from being connected. The second state can be rephrased as a state in which the pellet cooling transport water PCW flowing out of the water tank 50 is sent exclusively to the water tank 50 .

[0056] The dryer 90 is disposed above the water chamber 30 and dries the resin pellets. The dryer 90 has a separation device (not shown) that separates the resin pellets from foreign matter.

[0057] The outgoing path 100 constitutes a part of the circulation flow path 300, and connects the water tank 50 and the lower part of the water chamber 30. The inner diameter of the outgoing path 100 is set to about 12 inches to 14 inches. The outgoing path 100 has an outgoing path first portion 100a disposed between the water tank 50 and the flow path switching mechanism 80, and an outgoing path second portion 100b disposed between the flow path switching mechanism 80 and the water chamber 30. As shown in FIG. 1, the outgoing path second portion 100b is provided with a water level gauge 102 that measures the water level of the pellet cooling transport water PCW.

[0058] The return flow path 110 branches off from the outward flow path 100 and connects the outward flow path 100 to the water tank 50 .

[0059] The water storage flow path 120 is arranged in parallel with at least a part of the forward path 100. The water storage flow path 120 has an inner diameter smaller than that of the forward path 100. Specifically, the inner diameter of the water storage flow path 120 is set to about 2 inches to 3 inches. As shown in FIG. 1, the water storage flow path 120 according to this embodiment starts from a predetermined area of ​​the forward path first portion 100a and ends at a predetermined area of ​​the forward path second portion 100b. That is, the water storage flow path 120 has a structure in which it branches from the forward path first portion 100a to the forward path second portion 100b. The water storage flow path 120 is provided with a water storage flow path valve 122. The water storage flow path valve 122 is an opening / closing valve that can be switched between an open state in which the water storage flow path 120 is open and a closed state in which the water storage flow path 120 is closed. In this embodiment, the water storage passage valve 122 functions as a water supply unit that supplies the pellet cooling transport water PCW from the water tank 50 through the outward path 100 to the water chamber 30 .

[0060] The shaft passing passage 130 is disposed in parallel with at least a part of the forward passage 100. The shaft passing passage 130 has an inner diameter smaller than that of the forward passage 100. Specifically, the inner diameter of the shaft passing passage 130 is set to about 2 inches to 3 inches. The shaft passing passage 130 according to this embodiment starts from a predetermined region of the forward passage first portion 100a, passes through the inside of the rotating shaft 44, and ends at the other end 47 of the rotating shaft 44, and communicates with the water chamber 30. The shaft passing passage 130 is provided with a shaft passing passage valve 132. The shaft passing passage valve 132 is an opening / closing valve that switches between an open state in which the shaft passing passage 130 is open and a closed state in which the shaft passing passage 130 is closed.

[0061] The discharge flow passage 140 connects the bottom of the water chamber 30 to a discharge tank (not shown) provided in the pellet manufacturing apparatus 1. The discharge flow passage 140 is provided with a discharge flow passage valve 142 whose opening degree can be adjusted. When the discharge flow passage valve 142 is opened, the pellet cooling transport water PCW stored in the water chamber 30 flows into the discharge tank.

[0062] The return path 200 extends above the water chamber 30 and connects the water chamber 30 to the water tank 50. In detail, the return path 200 has an upper connecting flow path 150, an upward inclined flow path 160 (inclined flow path), a dryer connecting flow path 170, and a water tank connecting flow path 180.

[0063] The upper connecting flow passage 150 is connected to the upper end of the water chamber 30 and extends upward from the upper end.

[0064] The upward inclined flow passage 160 is inclined upward toward the dryer 90. The upward inclined flow passage 160 has a base end portion 162 (lower end portion) connected to the upper connecting flow passage 150, and an upper end portion 163 (upper end portion) connected to the dryer connecting flow passage 170. As shown in FIG. 1, the upper end portion 163 is located at the uppermost portion (highest position) of the return passage 200. Specifically, the upper end portion 163 is located about 20 m above the upper end of the water chamber 30.

[0065] The dryer connecting passage 170 connects the upper end portion 163 of the upwardly inclined passage 160 and the dryer 90 .

[0066] The water tank connecting passage 180 extends downward from the dryer 90 and connects the dryer 90 and the water tank 50 .

[0067] The water chamber 30, the water tank 50, the forward path 100, and the return path 200 described above constitute a circulation flow path 300. In the circulation flow path 300, the pellet cooling transport water PCW discharged from the water tank 50 by the pump 60 reaches the water chamber 30 through the forward path 100, and the pellet cooling transport water PCW flowing out from the water chamber 30 reaches the water tank 50 through the return path 200 (the upper connection flow path 150, the upward inclined flow path 160, the dryer connection flow path 170, and the water tank connection flow path 180) above the water chamber 30.

[0068] <Method of manufacturing resin pellets in resin pellet manufacturing equipment> Next, a method for producing resin pellets in the pellet production apparatus 1 according to this embodiment will be described. Fig. 3 is a flow chart showing the method for producing resin pellets. Fig. 4 is a diagram showing the flow of pellet cooling water when water is supplied to the water chamber 30 using the water storage passage 120. Fig. 5 is a diagram showing the flow of pellet cooling transport water PCW when water is supplied to the water chamber 30 using the shaft passing passage 130. Note that, in the following, it is assumed that the inside of the die hole 20H of the die plate 20 is clogged with solidified resin after the previous production process (described later).

[0069] 3, first, a water supply process is performed in which the pellet cooling transport water PCW stored in the water tank 50 is supplied to the empty water chamber 30 (step S1). In the water supply process, the pellet cooling transport water PCW is sent to the water chamber 30 using the water storage flow path 120. In detail, the flow path switching mechanism 80 is switched to the second state (a state in which the outward path first portion 100a and the return flow path 110 are connected) and the water storage flow path valve 122 is switched to an open state to open the water storage flow path 120. When the pump 60 is started in this state, as shown in FIG. 4, a part of the pellet cooling transport water PCW discharged by the pump 60 from the water tank 50 flows through the return flow path 110 to the water tank 50, and the remaining pellet cooling transport water PCW flows through the water storage flow path 120 to the water chamber 30.

[0070] In the water supply process, the water chamber 30 is filled with the pellet cooling transport water PCW supplied to the water chamber 30 through the water storage passage 120. Then, referring to the measurement value of the water level gauge 102, when the water level (water surface) of the pellet cooling transport water PCW reaches a target water level TL ( FIG. 1 ) that is a water level lower than the upper end 163 of the upward inclined passage 160, the water storage passage valve 122 is switched to a closed state to stop the supply of the pellet cooling transport water PCW.

[0071] The target water level TL is a water level lower than the water level of the pellet cooling transport water PCW when the circulation of the pellet cooling transport water PCW is stopped after the circulation. The target water level TL is preferably set at a position (height) that suppresses excessive water pressure from acting on the water chamber 30. In detail, the target water level TL is preferably set at a position (height) that can suppress the generation of water pressure that pushes back the resin material present in the multiple die holes 20H of the die plate 20 and causes the pellet cooling transport water PCW to enter the multiple die holes 20H. As shown in FIG. 1, the target water level TL according to this embodiment is set at a position higher than the upper part of the water chamber 30 and lower than the base end 162 of the upward inclined flow path 160. That is, the target water level TL is set in an arbitrary region of the upper connection flow path 150.

[0072] Next, a rotation process is performed in which the cutters 48 are rotated while being in contact with the die plate 20 (step S2). First, in the rotation process, the pellet cooling transport water PCW is supplied to the water chamber 30 through the shaft passing passage 130. In detail, the passage switching mechanism 80 is set to the second state (a state in which the forward passage first portion 100a and the return passage 110 are connected), and the shaft passing passage valve 132 is opened to open the shaft passing passage 130. In this way, as shown in FIG. 5, a part of the pellet cooling transport water PCW flowing out from the water tank 50 flows through the return passage 110 to the water tank 50, and the remaining pellet cooling transport water PCW flows through the shaft passing passage 130 to the water chamber 30.

[0073] In the rotation process according to this embodiment, while the pellet cooling transport water PCW is supplied to the water chamber 30, a part of the pellet cooling transport water PCW is discharged through the discharge passage 140. In detail, the pellet cooling transport water PCW is discharged while adjusting the flow rate of the pellet cooling transport water PCW discharged from the water chamber 30 by adjusting the opening of the discharge passage valve 142. This makes it possible to maintain the water surface position of the pellet cooling transport water PCW at the target water level TL.

[0074] Then, while the pellet cooling transport water PCW is being supplied and discharged, the rotating shaft 44 is advanced in the axial direction to bring the multiple cutters 48 into contact with the die plate 20, and the pelletizer motor 42 is started to rotate the multiple cutters 48. Note that the rotation of the multiple cutters 48 may be started at a point prior to the rotation process, for example, at the point of the water supply process.

[0075] In addition, in the rotating process according to this embodiment, the output of the pelletizer motor 42 is adjusted so that the rotation speed of the multiple cutters 48 is smaller than the rotation speed of the multiple cutters 48 during the manufacturing process described below.

[0076] Next, a heating step is performed (step S3) in which a heat medium is caused to flow through the heat medium passage 21 (FIG. 2) of the die plate 20 to heat the die plate 20. In the heating step according to this embodiment, the pellet cooling transport water PCW is supplied through the water storage passage 120 or the shaft passing passage 130, and the pellet cooling transport water PCW is discharged through the discharge passage 140. At this time, the multiple cutters 48 continue to rotate.

[0077] Next, a waiting step is performed to wait until the die plate 20 reaches a predetermined temperature (the temperature at which the resin material in the die holes 20H melts) (step S4). As described above, the temperature of the die plate 20 is measured by the temperature transmitter 22, so whether or not the predetermined temperature has been reached is understood based on the measurement value of the temperature transmitter 22.

[0078] Next, when the die plate 20 reaches a predetermined temperature, a circulation process is performed to circulate the pellet cooling transport water PCW (step S5). In the circulation process, the flow path switching mechanism 80 is switched to a first state (a state in which the outward first portion 100a and the outward second portion 100b are connected) to circulate the pellet cooling transport water PCW through the circulation flow path 300.

[0079] Next, a start-up step is performed to start up the mixer 4, the feeder 2, and the gear pump 6 (step S6). In the start-up step, the resin material is newly supplied from the feeder 2, kneaded by the mixer 4, and pressurized by the gear pump 6 to reach the die holes 20H, which extrudes the molten resin present in the die holes 20H into the water chamber 30. In other words, the start-up step is a step (material supply step) of supplying the resin material from upstream (upstream in the transport direction of the resin material) to the die plate 20.

[0080] The above-described steps S1 to S6 correspond to the start-up method of the pellet manufacturing apparatus 1.

[0081] Next, a manufacturing process for manufacturing resin pellets is performed (step S7). First, in the manufacturing process, the molten resin discharged into the inside of the water chamber 30 is cut by the multiple cutters 48 to granulate the resin pellets. At this time, the pellet cooling transport water PCW is supplied from the shaft passage 130 so that the resin pellets do not remain near the rotation center of the cutters 48 (near the other end 47) due to the water flow generated in the water chamber 30 by the rotation of the multiple cutters 48. Next, while cooling the resin pellets with the pellet cooling transport water PCW stored in the water chamber 30, the resin pellets are transported to the dryer 90 by the pellet cooling transport water PCW flowing out of the water chamber 30. Then, after drying the resin pellets with the dryer 90, the dried resin pellets are discharged to the outside of the pellet manufacturing device 1. In this way, the resin pellets are manufactured.

[0082] In addition, since the resin pellets produced immediately after the start of the production process may not meet the quality requirements for the product, these resin pellets may be discarded. In this case, the process up to the point where the resin pellets are discarded may be considered to correspond to the start-up method of the pellet production apparatus 1.

[0083] Next, when a predetermined number of resin pellets are produced in the production process, an operation stop step is performed to stop the operation of the pellet production apparatus 1 (step S8). In the operation stop step, the operation of the mixer 4, the feeder 2, and the gear pump 6 is stopped to stop the supply of the resin material, and heating of the die plate 20 is stopped in a state where the molten resin is present inside the die holes 20H. Then, the pellet cooling transport water PCW is circulated in the circulation flow path 300 and the apparatus waits until the resin material clogged in the die holes 20H reaches a predetermined temperature (the temperature at which the molten material clogged in the die holes 20H solidifies). As a result, the resin material clogged in the die holes 20H exchanges heat with the circulating pellet cooling transport water PCW and solidifies inside the die holes 20H. In this way, the pellet production apparatus 1 can be resumed for the next operation from the above-mentioned "situation where the solidified resin is clogged inside the die holes 20H of the die plate 20". That is, the next operation can be resumed from the state of step S1. Then, the operation of the pellet production apparatus 1 is stopped.

[0084] As described above, in the water supply process according to this embodiment, the supply of the pellet cooling transport water PCW is stopped in response to the target water level TL. Therefore, the amount of the pellet cooling transport water PCW to be discarded can be reduced compared to the case where the water level of the pellet cooling transport water PCW is set to the target water level TL by discharging the pellet cooling transport water PCW after circulating the pellet cooling transport water PCW in the circulation flow path 300.

[0085] Moreover, in the water supply process according to the above embodiment, a portion of the pellet cooling transport water PCW is returned to the water tank 50, while the remaining pellet cooling transport water PCW is supplied to the water chamber 30. This makes it possible to reduce the flow rate of the pellet cooling transport water PCW flowing into the water chamber 30, compared to a case in which a portion of the pellet cooling transport water PCW is not returned to the water tank 50. As a result, the rate at which the pellet cooling transport water PCW accumulates in the water chamber 30 becomes relatively slow, making it easy to stop the water supply when the water level of the pellet cooling transport water PCW corresponds to the target water level TL.

[0086] In addition, in the water supply process according to the above embodiment, the pellet cooling transport water PCW is supplied to the water chamber 30 through the water storage flow path 120 having an inner diameter smaller than the inner diameter of the forward path 100, so that it is easy to stop the water supply when the target water level TL is reached. In detail, as described above, the inner diameter of the forward path 100 (the forward path second portion 100b) is set to about 12 inches to 14 inches, so when the water supply is performed exclusively using the forward path second portion 100b, the pellet cooling transport water PCW quickly accumulates in the water chamber 30. Therefore, in this case, it is difficult to stop the water supply by aiming at the target water level TL. In contrast, if the pellet cooling transport water PCW is supplied through the water storage flow path 120 having an inner diameter smaller than the inner diameter of the forward path 100 as in this embodiment, the flow rate of the pellet cooling transport water PCW flowing into the water chamber 30 can be reduced compared to the case of supplying water exclusively through the forward path second portion 100b. As a result, the rate at which the pellet cooling transport water PCW accumulates in the water chamber 30 becomes relatively slow, making it easy to stop the water supply during the water supply process when the water level of the pellet cooling transport water PCW corresponds to the target water level TL.

[0087] In order to reduce the flow rate of the pellet cooling transport water PCW flowing into the water chamber 30, it is also possible to provide the pellet manufacturing apparatus 1 with a pump having a flow rate adjustment function instead of the pump 60 according to this embodiment. However, pumps having the above-mentioned function are generally expensive, and such a measure may increase the manufacturing cost of the pellet manufacturing apparatus 1. In contrast, in this embodiment, the flow rate of the pellet cooling transport water PCW can be reduced without using the above-mentioned expensive pump, and therefore an increase in manufacturing costs can be suppressed.

[0088] In addition, in the rotation process according to the above embodiment, the pellet cooling transport water PCW is supplied through the shaft passing passage 130, so that the temperature of the die plate 20 can be controlled. In detail, in the rotation process, the temperature of the die plate 20 may be excessively increased due to frictional heat generated by the rotation of the multiple cutters 48 in contact with the die plate 20. In contrast, according to the above configuration, the temperature of the die plate 20 can be controlled by the pellet cooling transport water PCW supplied from the shaft passing passage 130. In other words, the temperature of the die plate 20 can be prevented from excessively increasing.

[0089] Particularly, in the rotation process according to the above embodiment, the pellet cooling transport water PCW is supplied through the shaft passing passage 130, not through the water storage passage 120. That is, the pellet cooling transport water PCW can be supplied through the shaft passing passage 130, the end point of which is the other end 47 located in the vicinity of the die plate 20. This allows the pellet cooling transport water PCW to be supplied in the vicinity of the die plate 20, so that the temperature of the die plate 20 can be more reliably prevented from rising excessively.

[0090] In addition, in the rotation process according to the above embodiment, the pellet cooling transport water PCW is supplied and discharged while rotating the multiple cutters 48. That is, the pellet cooling transport water PCW in the water chamber 30 can be agitated by the multiple cutters 48 rotating in the water chamber 30 while replacing the pellet cooling transport water PCW in the water chamber 30. This makes it possible to suppress localized boiling in the water chamber 30. As a result, the temperature of the surface of the die plate 20 facing the water chamber 30 is kept uniform.

[0091] Furthermore, according to the above configuration, the resin that drips out of the die hole 20H of the die plate 20 and is scooped up by the multiple cutters 48 can be discharged outside the water chamber 30 together with the pellet cooling transport water PCW discharged from the water chamber 30.

[0092] In addition, in the rotation process according to the above embodiment, the flow rate of the pellet cooling transport water PCW discharged from the discharge passage 140 is adjusted so that the water surface position of the pellet cooling transport water PCW is kept at the target water level TL. This makes it possible to prevent the water surface of the pellet cooling transport water PCW from being positioned at a water level deviating from the target water level TL.

[0093] Moreover, in the water supplying process according to the above embodiment, since the target water level TL is set at a position lower than the base end 162 of the upwardly inclined flow path 160, the water pressure acting in the water chamber 30 can be suppressed compared to the case where the target water level TL is set at a position higher than the base end 162. This makes it possible to efficiently suppress the pellet cooling transport water PCW from pushing back the resin material present inside the multiple die holes 20H of the die plate 20 and entering the insides of the die holes 20H.

[0094] Furthermore, in the water supply process according to the above embodiment, since it is not necessary to discharge the pellet cooling transport water PCW in the upward inclined flow path 160, the amount of waste of the pellet cooling transport water PCW can be reduced. In detail, when a method is adopted in which the pellet cooling transport water PCW is supplied to the upper end 163 of the upward inclined flow path 160 by circulating the pellet cooling transport water PCW, and then the pellet cooling transport water PCW is discharged to set the water level of the pellet cooling transport water PCW to the target water level TL, the pellet cooling transport water PCW accumulated in the submerged area AR shown in FIG. 1 is discharged. In contrast, in the water supply process according to the present embodiment, after the water chamber 30 is filled with the pellet cooling transport water PCW, the supply of the pellet cooling transport water PCW is stopped at the point when the water level of the pellet cooling transport water PCW corresponds to the target water level TL. In this way, water does not accumulate in the submerged area AR, so there is no need to discharge the pellet cooling transport water PCW. As a result, the amount of waste of the pellet cooling transport water PCW is reduced.

[0095] In addition, in the rotation process according to the above embodiment, the output of the pelletizer motor 42 is adjusted so that the rotation speed of the multiple cutters 48 is smaller than the rotation speed of the multiple cutters 48 during the manufacturing process, so that the occurrence of cavitation in the water chamber 30 is suppressed. As described above, in the stage where the rotation process is being performed, the water level of the pellet cooling transport water PCW is maintained at the target water level TL, and the water pressure acting in the water chamber 30 is suppressed. For this reason, if the rotation speed of the multiple cutters 48 during the rotation process is set to be the same as or larger than the rotation speed of the multiple cutters 48 during the manufacturing process, cavitation may occur. In contrast, in this embodiment, the output of the pelletizer motor 42 is adjusted so that the rotation speed of the multiple cutters 48 during the rotation process is smaller than the rotation speed of the multiple cutters 48 during the manufacturing process, so that the occurrence of cavitation can be suppressed.

[0096] In addition, in the pellet manufacturing apparatus 1 of the above embodiment, the pump 60 stops discharging the pellet cooling transport water PCW in accordance with the target water level TL, so that the amount of pellet cooling transport water PCW discarded can be reduced compared to the case where the water level of the pellet cooling transport water PCW is set to the target water level TL by circulating the pellet cooling transport water PCW in the circulation flow path 300 and then discharging the pellet cooling transport water PCW.

[0097] Furthermore, in the pellet manufacturing apparatus 1 according to the above embodiment, water can be supplied to the water chamber 30 through the water storage passage 120 having an inner diameter smaller than the inner diameter of the outward passage 100. This allows the flow rate of the pellet cooling transport water PCW flowing into the water chamber 30 to be reduced compared to when water is supplied exclusively through the outward passage 100. Therefore, the rate at which the pellet cooling transport water PCW accumulates in the water chamber 30 becomes relatively slow, making it easy to stop the water supply when the water level of the pellet cooling water corresponds to the target water level TL. As a result, the amount of pellet cooling transport water PCW discarded can be reduced.

[0098] In addition, in the pellet manufacturing apparatus 1 according to the above embodiment, the end point of the shaft passage 130 is set to the other end 47, i.e., the tip of the rotating shaft 44, so that the resin pellets remaining near the other end 47 can be transported as usual. In detail, the resin pellets cut and granulated by the multiple cutters 48 are normally transported to the outside of the water chamber 30 by the pellet cooling transport water PCW. However, the resin pellets may remain near the other end 47 due to the influence of the water flow generated in the water chamber 30 by the rotation of the multiple cutters 48. In contrast, according to the present configuration, the end point of the shaft passage 130 is set to the other end 47, so that the pellet cooling water can be discharged from the other end 47 to move the resin pellets remaining around the other end 47. This makes it possible to transport the resin pellets remaining near the other end 47 as usual.

[0099] Furthermore, since the pellet manufacturing apparatus 1 according to the above embodiment includes the discharge flow passage 140, it is possible to discharge the pellet cooling transport water PCW.

[0100] Furthermore, in the heating process according to this embodiment, the pellet cooling transport water PCW is supplied through the water storage passage 120 or the shaft passing passage 130, and the pellet cooling transport water PCW is discharged through the discharge passage 140. That is, the pellet cooling transport water PCW in the water chamber 30 is appropriately replaced. According to this configuration, it is possible to suppress the water temperature of the pellet cooling transport water PCW in the water chamber 30 from rising excessively.

[0101] Furthermore, in the heating step according to the present embodiment, the plurality of cutters 48 rotate. According to this configuration, the pellet cooling transport water PCW stored in the water chamber 30 is stirred by the rotation of the plurality of cutters 48, and the water temperature in the water chamber 30 is made uniform. Therefore, it becomes possible to heat the die plate 20 uniformly.

[0102] Furthermore, in the start-up method of the pellet manufacturing apparatus 1 according to the above embodiment, unlike the case where the water level of the pellet cooling transport water PCW is set to the target water level TL by discharging the pellet cooling transport water PCW after circulating the pellet cooling transport water PCW in the circulation flow path 300, there is no need to discharge the pellet cooling transport water PCW. Therefore, the pellet manufacturing apparatus 1 can be started up relatively quickly.

[0103] The pellet manufacturing apparatus 1 according to one embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment. The following modified embodiments are possible in the present invention.

[0104] (1) In the previous embodiment, the flow path switching mechanism 80 is described as being composed of a three-way valve. Alternatively, the flow path switching mechanism may be composed of two on-off valves. FIG. 6 is a diagram showing a schematic configuration of a flow path switching mechanism 80A according to this modified embodiment. As shown in FIG. 6, the flow path switching mechanism 80A according to this modified embodiment has a first on-off valve 81A and a second on-off valve 82A. The first on-off valve 81A is an on-off valve that switches between an open state in which the first forward path portion 100a and the second forward path portion 100b are in communication with each other and a closed state in which both portions 100a and 100b are blocked. The second on-off valve 82A is an on-off valve that switches between an open state in which the return flow path 110 is open and a closed state in which the return flow path 110 is blocked. For example, by opening the first on-off valve 81A and closing the second on-off valve 82A, a water flow similar to that in the first state according to the flow path switching mechanism 80 of the previous embodiment can be realized. Moreover, by closing the first on-off valve 81A and opening the second on-off valve 82A, it is possible to realize a water flow similar to that in the second state of the flow path switching mechanism 80 according to the previous embodiment. Moreover, by opening the first on-off valve 81A and opening the second on-off valve 82A, it is possible to designate both the water chamber 30 and the water tank 50 as destinations for the pellet cooling transport water PCW.

[0105] (2) In the above embodiment, the pellet manufacturing apparatus 1 is provided with the water storage passage 120, but the water storage passage 120 is not essential. This will be described in detail below.

[0106] Fig. 7 is a development view of a pellet manufacturing apparatus 1B according to this modified embodiment. Fig. 8 is a schematic diagram showing the configuration of a flow path switching mechanism 80B according to this modified embodiment. Fig. 8(a) shows the flow path switching mechanism 80B in a first state, Fig. 8(b) shows the flow path switching mechanism 80B in a second state, and Fig. 8(c) shows the flow path switching mechanism 80B in a third state. Note that in this modified embodiment, differences from the above embodiment will be mainly described, and descriptions of commonalities will be omitted.

[0107] 7, unlike the pellet manufacturing apparatus 1 according to the previous embodiment, the pellet manufacturing apparatus 1B does not include a water storage flow path 120. Moreover, the pellet manufacturing apparatus 1B includes a flow path switching mechanism 80B instead of the flow path switching mechanism 80 according to the previous embodiment.

[0108] The flow path switching mechanism 80B is a three-way valve disposed on the downstream side of the pump 60 in the forward path 100, and has a first port connected to the forward path first portion 100a, a second port connected to the forward path second portion 100b, and a third port connected to the return path 110. As shown in (a) to (c) of FIG. 8, the flow path switching mechanism 80B can switch between a first state, a second state, and a third state. The first state (FIG. 8(a)) according to this modified embodiment is a state in which the forward path first portion 100a is connected to both the forward path second portion 100b and the return path 110. The first state can be rephrased as a state in which both the water chamber 30 and the water tank 50 are destinations of the pellet cooling transport water PCW. The second state (FIG. 8(b)) according to this modified embodiment is a state in which the outward path first portion 100a and the outward path second portion 100b are connected while preventing the outward path first portion 100a from connecting with the return flow path 110. The second state can be rephrased as a state in which the water chamber 30 is the destination of the pellet cooling transport water PCW. The third state (FIG. 8(c)) according to this modified embodiment is a state in which the outward path first portion 100a and the return flow path 110 are connected while preventing the outward path first portion 100a and the outward path second portion 100b from connecting. The third state can be rephrased as a state in which the pellet cooling transport water PCW is exclusively sent to the water tank 50.

[0109] In the water supply process of the pellet manufacturing apparatus 1B, the pellet cooling transport water PCW is supplied to the water chamber 30 by closing the shaft passing passage valve 132 while keeping the passage switching mechanism 80B in the first state.

[0110] In addition, during the rotation process of this pellet manufacturing apparatus 1B, the flow path switching mechanism 80B is set to the third state, and the shaft passing flow path valve 132 is opened to open the shaft passing flow path 130, thereby supplying pellet cooling transport water PCW to the water chamber 30 through the shaft passing flow path 130.

[0111] 7, the first forward path portion 100a of the pellet manufacturing apparatus 1B is provided with a flow rate control valve 105B, which is a valve whose opening degree can be adjusted. By reducing the opening degree of the flow rate control valve 105B, the flow rate of the pellet cooling transport water PCW flowing into the water chamber 30 can be reduced.

[0112] As described above, in the water supply process of the pellet manufacturing apparatus 1B according to this modified embodiment, the flow path switching mechanism 80B is set to the first state (a state in which the first forward path portion 100a is connected to both the second forward path portion 100b and the return flow path 110), so that a part of the pellet cooling transport water PCW is returned to the water tank 50, while the remaining pellet cooling transport water PCW is supplied to the water chamber 30. This makes it possible to reduce the flow rate of the pellet cooling transport water PCW flowing into the water chamber 30, compared with the case in which a part of the pellet cooling transport water PCW is not returned to the water tank 50. As a result, the pace at which the pellet cooling transport water PCW accumulates in the water chamber 30 becomes relatively slow, making it easy to stop the water supply in response to the target water level TL. That is, in the water supply process, it is possible to achieve the same effect as when the pellet cooling transport water PCW is supplied to the water chamber 30 using the water storage flow path 120 or the shaft passing flow path 130 according to the previous embodiment, without using the water storage flow path 120 or the shaft passing flow path 130 according to the previous embodiment.

[0113] In addition, when it becomes necessary to circulate the pellet cooling transport water PCW during a circulation process or the like, the flow path switching mechanism 80B can be switched to the second state (a state in which the outbound first portion 100a and the outbound second portion 100b are connected) and the destination of the pellet cooling transport water PCW can be set to the water chamber 30.

[0114] In addition, when it is necessary to switch the destination of the pellet cooling transport water PCW to the water tank 50, for example, when supplying water through the axis passing passage 130, the passage switching mechanism 80B can be set to the third state (a state in which the first outbound portion 100a and the return passage 110 are connected).

[0115] In this way, the pellet manufacturing apparatus 1B of this modified embodiment is equipped with a flow path switching mechanism 80B instead of the flow path switching mechanism 80 of the previous embodiment, so that the destination of the pellet cooling transport water PCW can be easily switched depending on the purpose.

[0116] Furthermore, the pellet manufacturing apparatus 1B according to this modified embodiment includes a flow rate control valve 105B, which is a valve whose opening degree can be adjusted. For this reason, for example, when the flow path switching mechanism 80B is set to the first state, the flow rate of the pellet cooling transport water PCW supplied to the water chamber 30 can be further reduced by setting the opening degree of the flow rate control valve 105B to a small value. As a result, the rate at which the pellet cooling transport water PCW accumulates in the water chamber 30 becomes even slower, making it even easier to stop the water supply when the water level of the pellet cooling water corresponds to the target water level TL.

[0117] (3) In the previous embodiment, an example was described in which the pellet cooling transport water PCW was supplied to the water chamber 30 through the water storage passage 120 in the water supplying step. Instead of this, the pellet cooling transport water PCW may be supplied through the shaft passing passage 130. In other words, the shaft passing passage valve 132 of the shaft passing passage 130 may function as the water supply unit according to the present invention. Alternatively, in the water supplying step, the pellet cooling transport water PCW may be supplied to the water chamber 30 by using both the water storage passage 120 and the shaft passing passage 130. In other words, the water storage passage valve 122 of the water storage passage 120 and the shaft passing passage valve 132 of the shaft passing passage 130 may function as the water supply unit according to the present invention.

[0118] (4) In the previous embodiment, the water storage flow path 120 is described as starting from a predetermined area in the first forward path portion 100a and ending at a predetermined area in the second forward path portion 100b, but the starting and ending points of the water storage flow path 120 are not limited to this. Although not shown in the figures, the water storage flow path 120 may start from a predetermined area in the return flow path 110. Also, although not shown in the figures, the water chamber 30 may be the ending point.

[0119] (5) In the above embodiment, the shaft-passing passage 130 has a start point in a predetermined region of the outward passage first portion 100a and an end point in the other end 47 of the rotating shaft 44. However, the start point of the shaft-passing passage 130 is not limited to this. Although not shown in the drawings, the shaft-passing passage 130 may start from any region of the return passage 110.

[0120] (6) The pellet manufacturing apparatus 1 according to the previous embodiment may further include a water volume adjustment flow path that starts at the upper part of the water chamber 30 or at a region of the upper connecting flow path 150 that is lower than the target water level TL, and ends at a discharge tank not shown.

[0121] (7) In the above embodiment, an example has been described in which the water storage passage valve 122 functions as the water supply unit according to the present invention, but instead, the pump 60 may function as the water supply unit. In this case, the water supply in the water supplying process may be stopped by stopping the operation of the pump 60. Note that the operation of the pump 60 may be stopped manually, or the operation may be automatically stopped by a control device (not shown) provided in the pellet manufacturing apparatus 1. [Explanation of symbols]

[0122] 1, 1B: Pellet manufacturing equipment 20: Die plate 20H: Die hole 30: Water room 44: Rotation axis 47: Other end (tip of rotating shaft) 48: Cutter 50: Water tank 60: Pump 80, 80A, 80B: Flow path switching mechanism 100: Outbound 110: Return flow path 120: Water storage channel (first auxiliary channel) 122: Water storage flow path valve (water supply section) 130: Axis passage (second auxiliary passage) 140: Discharge flow path 150: Upper connecting channel 160: Upward sloping channel (sloping channel) 162: Base end (lower end) 163: Upper end 200:Return 300: Circulation flow path PCW: Pellet cooling transport water (pellet cooling water) TL:Target water level

Claims

1. A method for starting up a resin pellet manufacturing apparatus comprising: a circulation flow path having an outward path through which pellet cooling water discharged from a water tank by a pump reaches a water chamber, and a return path through which the pellet cooling water passes above the water chamber and returns from the water chamber to the water tank; a die plate having a plurality of die holes and disposed facing the water chamber; and a cutter disposed in the water chamber for cutting molten resin discharged from the plurality of die holes to form resin pellets, the method comprising the steps of: transporting the formed resin pellets from the water chamber while cooling them with the pellet cooling water flowing through the circulation flow path, a water supplying step of, before starting the production of the resin pellets, supplying the pellet cooling water stored in the water tank to the water chamber by the pump to fill the water chamber, and then stopping the supply of the pellet cooling water so that the water level of the pellet cooling water reaches a target water level set at a position lower than the upper end of the return path; How to start up a resin pellet manufacturing equipment.

2. In the water supplying step, water is supplied to the water chamber while returning a part of the pellet cooling water discharged from the water tank by the pump to the water tank. A method for starting up the resin pellet manufacturing apparatus according to claim 1.

3. In the water supplying step, the pellet cooling water is supplied to the water chamber through an auxiliary flow path having an inner diameter smaller than an inner diameter of the outward flow path and arranged in parallel with at least a part of the outward flow path. A method for starting up the resin pellet manufacturing apparatus according to claim 1 or 2.

4. The method further includes a rotating step, which is performed at least after the water supplying step, of rotating the cutter in a state in which the cutter is in contact with the die plate, In the rotating step, the cutter is rotated while the pellet cooling water is supplied to the water chamber through the auxiliary flow path. A method for starting up the resin pellet manufacturing apparatus according to claim 3.

5. In the rotating step, the pellet cooling water is discharged through a discharge flow path that communicates the water chamber with an outside of the water chamber while the pellet cooling water is being supplied to the water chamber. A method for starting up the resin pellet manufacturing apparatus according to claim 4.

6. In the rotating step, the amount of the pellet cooling water discharged through the discharge flow path is adjusted so that the water surface position of the pellet cooling water in the water chamber is maintained at the target water level. A method for starting up the resin pellet manufacturing apparatus according to claim 5.

7. In the water supply process, a flow path switching mechanism is disposed on the forward path downstream of the pump and is switchable between a first state in which both the water chamber and the water tank are destinations of the pellet cooling water, a second state in which one of the water chamber and the water tank is destination of the pellet cooling water, and a third state in which the other of the water chamber and the water tank is destination of the pellet cooling water, by setting the flow path switching mechanism to the first state. A method for starting up the resin pellet manufacturing apparatus according to claim 2.

8. The return path has an upper connecting flow path that is connected to an upper portion of the water chamber and extends upward, and an inclined flow path that includes a lower end that is connected to the upper connecting flow path and is inclined upward from the lower end to the upper end of the return path, In the water supplying step, the target water level is set to a position lower than the lower end portion. A method for starting up the resin pellet manufacturing apparatus according to claim 7.

9. A method for producing resin pellets in a resin pellet production apparatus having a circulation flow path including an outward path through which pellet cooling water discharged by a pump from a water tank reaches a water chamber, and a return path through which the pellet cooling water passes above the water chamber and returns to the water tank from the water chamber, comprising: a water supplying step of supplying the pellet cooling water stored in the water tank to the water chamber before starting the production of the resin pellets; a rotating step of rotating a cutter disposed in the water chamber while the cutter is in contact with a die plate having a plurality of die holes facing the water chamber; a heating step of heating the die plate to melt the resin present inside the plurality of die holes; a material supplying step of supplying a resin material from an upstream side to the die plate; a manufacturing process in which the molten resin discharged from the plurality of die holes of the die plate is cut by the cutter in the water chamber to form the resin pellets, and the resin pellets are cooled by the pellet cooling water while being transported from the water chamber to manufacture the resin pellets; and a stop operation step of stopping heating of the die plate while the molten resin is present inside the plurality of die holes, and stopping operation of the resin pellet manufacturing apparatus, In the water supplying step, after the water chamber is filled with the pellet cooling water, the supply of the pellet cooling water is stopped so that the water level of the pellet cooling water reaches a target water level set at a position lower than the upper end of the return path. A method for producing resin pellets.

10. In the rotating step, the water level of the pellet cooling water is maintained at the target water level, and a rotation speed of the cutter is set to be smaller than a rotation speed of the cutter during the manufacturing step. The method for producing the resin pellets according to claim 9.

11. A resin pellet manufacturing apparatus, A water tank for storing pellet cooling water; a water chamber for receiving the pellet cooling water from the water tank; an outward path connecting the water tank and the water chamber; a return path that connects the water chamber and the water tank via an upper portion of the water chamber; a water supply unit that supplies the pellet cooling water from the water tank through the outward path to the water chamber; a die plate having a plurality of die holes facing the water chamber; a cutter that is disposed in the water chamber and cuts the molten resin discharged from the plurality of die holes of the die plate in the water chamber to produce resin pellets, the water supply unit stops supplying the pellet cooling water when a water level of the pellet cooling water reaches a target water level set at a position lower than an upper end of the return path before starting production of the resin pellets. Resin pellet manufacturing equipment.

12. a first auxiliary flow passage having an inner diameter smaller than an inner diameter of the outward flow passage and supplying the pellet cooling water flowing out of the water tank to the water chamber; a return flow path branching from the outward flow path and connecting the outward flow path and the water tank; A flow path switching mechanism for switching the destination of the pellet cooling water is further provided, The first auxiliary flow path starts from a region of the outward path between the water tank and the flow path switching mechanism or a predetermined region of the return flow path, and ends in a region of the outward path between the flow path switching mechanism and the water chamber or the water chamber, and is opened when the pellet cooling water is supplied to the water chamber before the start of production of the resin pellets. The resin pellet manufacturing apparatus according to claim 11.

13. a second auxiliary flow path having an inner diameter smaller than an inner diameter of the outward flow path and different from the first auxiliary flow path; the second auxiliary flow path starts from a region of the outward flow path between the water tank and the flow path switching mechanism or a predetermined region of the return flow path, and ends at a tip of the rotation shaft of the cutter, and communicates with the inside of the water chamber. The resin pellet manufacturing apparatus according to claim 12.

14. Further, a discharge flow path is provided for discharging the pellet cooling water from the water chamber to the outside of the water chamber. The resin pellet manufacturing apparatus according to any one of claims 11 to 13.

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