JP7437680B2 - Pellet manufacturing system, extruder and pellet manufacturing method - Google Patents

Description

The present invention relates to a pellet manufacturing system, an extruder, and a pellet manufacturing method.

The molten resin extruded from the extruder is discharged in the form of a string from the outlet hole formed in the die to generate a strand, and after the strand is cooled and solidified, the strand is cut into pellets of a certain length using a strand cutter. Pellet manufacturing technology is known.

In the production of pellets, molten resin extruded from an extruder is conveyed by a conveyor and then cut by a strand cutter to form pellets. At this time, the pellet diameter (that is, the strand diameter before cutting) is adjusted by taking the strand extruded from the extruder by a roller provided in a strand cutter (Patent Document 1).

Japanese Patent Application Publication No. 5-278027

However, due to environmental factors, such as fluctuations in the temperature of the molten resin extruded from the extruder, fluctuations in the raw materials supplied to the extruder, and blockage of the die hole, the diameter of the strand may deviate from the allowable range. . In this case, if pellet production continues as it is, the number of defective products will increase. Therefore, technology to prevent defective products is required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to detect abnormalities in strand diameter control based on strand diameter measurement results.

Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

A pellet manufacturing system that is one aspect of the present invention includes an extruder that discharges strands from a die, a feeder that supplies raw materials to the extruder, and a system that takes the strands, processes them, and measures the diameter of the taken strands. a strand cutter having a measuring means for guiding the strand discharged from the die to the strand cutter; and a strand guide device for guiding the strand discharged from the die to the strand cutter; and a control unit configured to generate an alarm when a new strand take-up speed instructed to the strand cutter based on the strand diameter measured by the measuring means is not within an allowable range. It is something to send out.

An extruder that is one aspect of the present invention includes a strand discharge mechanism that is supplied with raw materials from a feeder and discharges a strand from a die, and a strand that is discharged from the die and then guided through a strand guiding device for processing. and a control section that controls the strand take-up speed of a strand cutter having a measuring means for measuring the diameter of the taken-off strand, based on the strand diameter measured by the measuring means, the control section If the new strand take-up speed instructed to the strand cutter based on the strand diameter measured by the measuring means is not within a permissible range, an alarm is generated.

A method for producing pellets, which is one aspect of the present invention, includes supplying raw materials to an extruder equipped with a die, discharging a strand from the die, guiding the strand discharged from the die to a strand cutter, and discharging the strand from the die. The cutter takes the strand and processes it, measures the diameter of the taken strand, controls the taking speed of the strand of the strand cutter based on the measured strand diameter, and controls the strand taking speed of the strand cutter based on the measured strand diameter. If the new strand take-up speed instructed to the strand cutter is not within an allowable range, an alarm is sent.

According to the present invention, it is possible to detect an abnormality in strand diameter control based on the measurement result of the strand diameter.

1 is a side view schematically showing the overall configuration of a pellet manufacturing system according to a first embodiment. FIG. 2 is a perspective view showing details of the configuration of a die and a die holder. 3 is a sectional view taken along line III-III in FIG. 2. FIG. FIG. 3 is a diagram schematically showing the internal configuration of a strand cutter. 3 is a flowchart showing a control operation of the pellet manufacturing system according to the first embodiment. 7 is a flowchart showing a modification example of the control operation of the pellet manufacturing system according to the first embodiment. It is a figure which shows the switching of the switching valve of a strand cutter. FIG. 2 is a side view schematically showing the overall configuration of a pellet manufacturing system according to a second embodiment.

Hereinafter, specific embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings are appropriately simplified. In addition, the same elements are given the same reference numerals, and redundant explanations will be omitted.

In the following embodiments, when necessary for convenience, the explanation will be divided into multiple sections or embodiments, but unless otherwise specified, they are not unrelated to each other, and one does not differ from the other. This is related to variations, applications, detailed explanations, supplementary explanations, etc. of some or all of the above. In addition, in the following embodiments, when referring to the number of elements (including numbers, numerical values, amounts, ranges, etc.), we also refer to cases where it is specifically specified or where it is clearly limited to a specific number in principle. However, it is not limited to the specific number, and may be greater than or less than the specific number.

Furthermore, in the following embodiments, the constituent elements (including operational steps, etc.) are not necessarily essential, unless specifically stated or when it is considered to be clearly essential in principle. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of components, etc., the shape, positional relationship, etc. of components, etc. are referred to, unless specifically stated or when it is considered that it is clearly not possible in principle. This shall include things that approximate or are similar to, etc. This also applies to the above-mentioned numbers (including numbers, numerical values, amounts, ranges, etc.). Note that the right-handed xyz coordinates shown in the figures below are for convenience in explaining the positional relationships of the constituent elements. Usually, the xy plane is a horizontal plane, and the positive direction of the z-axis is vertically upward.

Embodiment 1
The overall configuration of a pellet manufacturing system including an extruder according to Embodiment 1 will be described. FIG. 1 is a side view schematically showing the overall configuration of a pellet manufacturing system 100. As shown in FIG. 1, a pellet manufacturing system 100 includes an extruder 10, a feeder 20, a strand cutter 30, and a strand guiding device 40 according to this embodiment.

The extruder 10 is a device that melts and kneads resin raw materials and extrudes them as string-like strands. The resin raw material includes various resins such as single resins to multi-component compounds, and other raw materials, such as polypropylene. The extruder 10 may be a single-screw extruder or a multi-screw extruder such as a twin-screw extruder. As shown in FIG. 1, the extruder 10 includes a cylinder 12 containing a screw 11, a motor 13 that rotationally drives the screw 11, a hopper 14 that is a socket for resin raw material, and a molten resin raw material (hereinafter referred to as molten resin). It has a die 15 for discharging a cord-like strand (referred to as a string). A die holder 16 that holds the die 15 is provided between the cylinder 12 and the die 15 of the extruder 10. Details of the configurations of the die 15 and the die holder 16 will be described later.

Thermometers 17 for monitoring and controlling the temperature of the cylinder 12 are installed at multiple locations in the cylinder 12. Furthermore, a thermometer 18 for monitoring the temperature of the molten resin and a pressure gauge 19 for monitoring the pressure of the molten resin are installed in the die holder 16.

The feeder 20 supplies a fixed amount of resin raw material to the hopper 14 of the extruder 10. The strand cutter 30 cuts the strand guided through the strand guiding device 40 to a desired length to produce pellets.

The strand guiding device 40 has a guiding path 41, such as a mesh belt conveyor, for guiding the strand to the strand cutter 30.

Next, details of the configuration of the die and die holder will be described. FIG. 2 is a perspective view showing details of the configuration of the die 15 and the die holder 16. As shown in FIG. 2, a plurality of outflow holes 15a are formed in the die 15 in a line in the Y-axis direction. A string-like strand is generated by discharging the molten resin from the outflow hole 15a.

The die holder 16 consists of an inflow part 16a into which the molten resin flows from the cylinder 12 of the extruder 10, and an outflow part 16b into which the molten resin flows out into the die 15. A cutting mechanism 51 may be attached to the die holder 16. The cutting mechanism 51 has a blade 51b attached to the tip of a direct-acting actuator 51a. The actuator 51a is driven to cut the strand discharged from the outflow hole 15a. Before cutting, the strand is guided to the off-product side by the resin receiving plate 42, and after cutting, as the resin receiving plate 42 moves or rotates, the strand rides on a conveyor and is automatically guided to the strand cutter.

FIG. 3 is a sectional view taken along line III-III in FIG. 2. As shown in FIG. 3, channels 16aA and 16bA communicating with the outlet hole 15a of the die 15 are formed inside the inlet portion 16a and the outlet portion 16b of the die holder 16, respectively. A filter 52 is arranged at the boundary between the flow path 16aA and the flow path 16bA. By installing the filter 52, it is possible to prevent foreign matter mixed into the molten resin and unmelted resin produced when kneading is insufficient from being mixed into the strand.

The pressure gauge 19 installed in the inflow portion 16a has a pressure detecting portion exposed to the flow path 16aA, and detects the pressure of the molten resin. That is, the pressure gauge 19 substantially detects the pressure at which the molten resin is discharged from the die 15 (hereinafter referred to as "molten resin discharge pressure"). The thermometer 18 installed in the outflow portion 16b has a temperature detecting portion exposed to the flow path 16bA, and detects the temperature of the molten resin. That is, the thermometer 18 substantially detects the temperature at which the molten resin is discharged from the die 15 (hereinafter referred to as "molten resin discharge temperature").

The strand cutter 30 will be explained. FIG. 4 schematically shows the internal configuration of the strand cutter 30. The strand cutter 30 has a take-off roller 31 and a cutter 35.

The take-up roller 31 adjusts the diameter of the strand to a desired diameter, and the drive roller 32 rotates around a horizontal fixed rotation axis 32A, and the drive roller 32 is vertically displaceable and rotates around a horizontal movable rotation axis 33A. It is composed of a rotating pinch roller 33. The strand is sandwiched between a drive roller 32 and a pinch roller 33.

The drive roller 32 is a rigid member made of metal or the like and has a cylindrical outer peripheral surface processed to prevent the strand from slipping, and is rotated by a motor. The pinch roller 33 is also a rigid member made of metal or the like and has a cylindrical outer peripheral surface processed to prevent the strand from slipping. The pinch roller 33 may be rotated by a motor, or may be driven in accordance with the rotation of the drive roller 32. When the pinch roller 33 is driven, the rotation speed of the pinch roller 33 can be adjusted by adjusting the rotation speed of the drive roller 32. When the pinch roller 33 rotates, it is desirable to synchronize the rotational speeds of the drive roller 32 and the pinch roller 33 at the contact portion of their outer peripheral surfaces by interlocking the drive roller 32 and the pinch roller 33 through gears, for example.

The cutter 35 includes a rotating blade 36 and a fixed blade 37. The rotary blade 36 is configured as a drum-shaped cutter that is rotatable around a horizontal rotary blade rotation axis 36A, and a plurality of rotary blade edges 36B are provided at regular intervals in the circumferential direction of the drum. The fixed blade 37 guides the strand pushed out from the take-off roller 31. When the rotary blade tip 36B of the rotary blade 36 hits the strand from directly above the strand, the strand is sandwiched between the rotary blade tip 36B and the fixed blade 37 and sheared. This cuts the strands and forms pellets.

The cut pellets are guided by the switching valve 39 and discharged to the product box B1 through the opening OP and the path P1. The switching valve 39 is rotatable around a switching valve rotating shaft 39A extending in the horizontal direction, and is configured to be able to switch the discharge destination of the pellets to the product box B1 or the defective product box B2.

The diameter of the strand cut by the cutter 35 is approximately the same as the diameter of the strand pushed out from the take-up roller 31 toward the cutter 35, and the diameter of the strand is measured as the distance between the outer peripheral surfaces of the drive roller 32 and the pinch roller 33. can. In this configuration, by indirectly measuring the amount of displacement of the movable rotating shaft 33A of the pinch roller 33 as the amount of displacement of the arm 33B that pivotally supports the movable rotating shaft 33A, the distance between the outer peripheral surfaces of the drive roller 32 and the pinch roller 33 is measured. is measuring the variation in distance. A displacement detection sensor 34 is provided at a position facing the end 33C of the arm 33B. As the displacement detection sensor 34, any sensor such as an optical non-contact sensor may be used.

Arm 33B is biased by spring 38. Thereby, the pinch roller 33 can contact the strand even if the strand diameter changes. Further, when the drive roller 32 and the pinch roller 33 do not sandwich the strand, the outer peripheral surfaces of the two come into contact with each other.

In order to optimize the diameter of the strand when it is extruded from the extruder 10 and reaches the strand cutter 30, the specific gravity of the resin material, the diameter, length and number of holes in the die, the rotation speed of the screw 11, the resin This is achieved through control based on parameters such as temperature. However, the diameter of the strand extruded from the die may vary due to environmental factors such as fluctuations in resin temperature, fluctuations in the raw material supplied to the extruder, and blockage of the die hole. The diameter of the arrived strands may also vary.

Therefore, the diameter of the strand that has reached the strand cutter 30 is detected by the displacement amount detection sensor 34, and the rotation speed of the drive roller 32 and the pinch roller 33 is feedback-controlled according to the detection result to adjust the take-up speed.

Next, an outline of the flow of pellet production will be explained with reference to FIG. First, resin raw material is supplied from the feeder 20 to the hopper 14 . The resin raw material supplied into the cylinder 12 from the hopper 14 is kneaded by the screw 11, and the resin raw material is melted by heat from a heater (not shown) and the action accompanying the rotation of the screw 11. Then, the molten resin is pushed out into the die 15 by rotation of the screw 11. Thereby, the molten resin is discharged from the die 15 as a strand. The strand cutter 30 cuts the fed strand into desired dimensions and shape. This produces pellets.

Next, details of the processing by the control unit 60 will be explained. In addition, in the following description, FIG. 1 will also be referred to as appropriate. FIG. 5 is a flowchart showing the control operation of the pellet manufacturing system 100.

The theoretical value of the strand diameter can be determined from related parameters. For example, the strand diameter is determined by the rotation speed of the screw, the amount of resin raw material supplied, the discharge pressure of the molten resin (die speed), the temperature of the molten resin, the specific gravity of the resin pellets, the number of die holes, the strand cutter take-off speed, etc. Used as a parameter. In other words, a desired strand diameter can be achieved by adjusting the strand take-up speed. Therefore, in this configuration, the strand diameter is continuously monitored by the displacement detection sensor 34 provided in the strand cutter 30, and the strand take-up speed is feedback-controlled.

Step S1
The control unit 60 starts the operations of the extruder 10, the feeder 20, the strand cutter 30, and the strand guiding device 40 in order to start the pellet manufacturing process. Thereby, the feeder 20 starts supplying raw materials to the extruder 10, and the molten resin is extruded from the extruder 10 to generate a strand. Strand guiding device 40 transports the strand to strand cutter 30 . At this time, manufacturing parameters such as the temperature of the molten resin, extrusion pressure (die speed), and strand cutter take-off speed are adjusted automatically or manually so that the strand diameter at the sensor position is within an allowable range.

Step S2
Thereafter, during pellet production, the control unit 60 continuously monitors the strand diameter RS through the displacement detection sensor 34 in order to feedback control the strand take-up speed based on the strand diameter monitoring information.

Step S3
The control unit 60 determines whether the measured strand diameter RS is within an allowable range.

Step S4
When the control unit 60 determines that the measured strand diameter RS is outside the allowable range, the strand take-up speed V is controlled to keep the strand diameter RS within the allowable range. Control of the strand take-up speed V is performed automatically or manually.

When automatically controlling the strand take-up speed V, the control unit 60 calculates the strand take-off speed V necessary to bring the strand diameter RS taken by the strand cutter 30 to a value within an allowable range. Then, the control unit 60 instructs the strand cutter 30 to calculate the new strand take-up speed V.

When automatically controlling the strand take-up speed V, for example, the user of the pellet manufacturing system 100 can set a new strand take-up speed by operating input means such as a knob, button, or touch panel provided on the control unit 60. V to the strand cutter 30.

Step S5
The control unit 60 determines whether the new strand take-up speed V is within a predetermined allowable range. In addition, when controlling the strand take-up speed V automatically, it is desirable that this determination be performed subsequent to calculation of a new strand take-up speed V.

Step S6
If the new strand take-off speed V is outside the allowable range, the control unit 60 determines that the new strand take-off speed V is an abnormal value and issues an alarm.

Step S7
If the new strand take-up speed V is within the allowable range, the control unit 60 monitors the strand diameter RS through the displacement detection sensor 34. Even if the strand take-up speed V is controlled in the process up to step S6, there is a risk that the strand diameter RS will fall out of the allowable range due to an abnormality in the extruder 10, for example. Therefore, here, such an abnormality is detected by monitoring the strand diameter RS.

Step S8
The control unit 60 determines whether the measured strand diameter RS is within an allowable range. If the measured strand diameter RS is within the allowable range, the process returns to continuous monitoring of the strand diameter RS (step S2).

Step S9
If the measured strand diameter RS is outside the allowable range, the control unit 60 determines that the measured strand diameter RS is an abnormal value and issues an alarm.

As described above, according to this configuration, when controlling the strand take-up speed based on the measurement results of the strand diameter, if the strand take-up speed and the strand diameter to be controlled deviate from the allowable range, an alarm is generated to detect an abnormality. Can be notified.

Thereby, the pellet manufacturing system 100 can quickly recognize the occurrence of an abnormality in the control state of the strand take-up speed and the strand diameter, and can take necessary measures.

Furthermore, further countermeasures may be taken after step S6 or step S9 or simultaneously with these steps. FIG. 6 is a flowchart showing a modification of the control operation of the pellet manufacturing system 100.

As shown in FIG. 6, the pellet discharge destination may be changed by operating the switching valve 39 of the strand cutter 30 (step S10 in FIG. 6). FIG. 7 shows switching of the switching valve 39 of the strand cutter 30. As shown in FIG. 7, the control unit 60 instructs the strand cutter 30 to operate the switching valve 39 to rotate the switching valve 39 and change the pellet discharge path from P1 to P2, thereby discharging the pellets. The destination is switched from the product box B1 to the defective product box B2. This can prevent defective pellets from being mixed into product pellets.

Further, in order to avoid mixing of defective products, the strand discharged from the outlet hole 15a of the die 15 shown in FIG. 2 may be cut by the cutting mechanism 51. In this case, the cut strands are discharged into a discharge box (not shown) by the resin receiving plate 42 shown in FIG. Thereby, it is possible to prevent a strand whose diameter is out of the permissible range from being conveyed to the strand cutter 30.

Further, the control unit 60 may stop the operation of each part of the pellet manufacturing system 100, that is, the extruder 10, the feeder 20, the strand cutter 30, and the strand guiding device 40 (step S11 in FIG. 6). Thereby, production of pellets can be stopped in a state where an abnormality occurs, and generation of defective products can be prevented.

Furthermore, by referring to the respective states of the extruder 10, feeder 20, strand cutter 30, and strand guiding device 40, if any of them is abnormal, it indicates that an abnormality has occurred in the display device, for example. The parts may also be displayed. Thereby, the user of the pellet manufacturing system 100 can easily understand where the abnormality is occurring and take necessary measures.

Embodiment 2
The overall configuration of the pellet manufacturing system according to the second embodiment will be described. FIG. 8 is a side view schematically showing the overall configuration of the pellet manufacturing system 200. As shown in FIG. 8, the pellet manufacturing system 200 has a configuration in which the strand guiding device 40 of the pellet manufacturing system 200 according to the first embodiment is replaced with a strand guiding device 70.

While the strand guiding device 40 has been described as having a guiding path 41 such as a mesh belt type conveyor, the strand guiding device 70 has a configuration that cools the strands with a cooling liquid.

The strand guiding device 70 has a water tank 71 supported by a pedestal 72, and the water tank 71 holds a cooling liquid 73 for cooling the strand ST. Guide rollers 74 and 75 are provided in the cooling liquid 73 to guide the strand ST. Guide roller 74 is provided on the extruder 10 side, and guide roller 75 is provided on the strand cutter 30 side. The strand ST discharged from the die 15 enters the cooling liquid 73 , is guided by a guide roller 74 and is conveyed toward the guide roller 75 , and is guided by the guide roller 75 and conveyed toward the strand cutter 30 . The strand ST reaches the strand cutter 30 after being cooled by passing through the cooling liquid 73.

Also in this configuration, the strand take-up speed can be controlled based on the measurement result of the strand diameter in the strand cutter 30, so even if the configuration of the strand guiding device is changed, the same system as the pellet manufacturing system 100 according to the first embodiment can be used. It is possible to perform an action.

In other words, the strand diameter is measured just before the strand is cut, and the strand diameter is controlled based on the measurement results, so it is not affected by fluctuations in the process before the strand cutter. It is possible to construct a pellet manufacturing system that can reduce the amount of waste.

Other Embodiments The present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit. The plurality of examples explained above can also be implemented in combination as appropriate. For example, steps S10 and S11 in FIG. 6 may be performed in reverse order or may be performed in parallel.

The control unit 60 may be provided separately from the extruder 10, feeder 20, strand cutter 30, and strand guiding device 40, or may be incorporated into any of these. For example, the control unit 60 may be incorporated into the extruder 10.

In the above embodiment, the monitored parameter is within the permissible range, which means that the monitored parameter is larger than the lower limit value and larger than the upper limit value with respect to the permissible range defined by the lower limit value and the upper limit value. also means small. Furthermore, the fact that the monitored parameter is outside the allowable range means that the monitored parameter is smaller than the lower limit value or larger than the upper limit value. Note that when the monitored parameter matches the lower limit value or the upper limit value, it may be determined that it is within the permissible range or outside the permissible range, as necessary.

10 Extruder 11 Screw 12 Cylinder 13 Motor 14 Hopper 15 Die 15a Outflow hole 16 Die holder 16a Inflow section 16aA, 16bA Channel 16b Outflow section 17, 18 Thermometer 19 Pressure gauge 20 Feeder 30 Strand cutter 31 Roller 32 Drive roller 32A Fixed rotation Shaft 33 Pinch roller 33A Movable rotating shaft 33B Arm 33C End 34 Displacement detection sensor 35 Cutter 36 Rotating blade 36A Rotating blade rotating shaft 36B Rotating blade tip 37 Fixed blade 38 Spring 39 Switching valve 39A Switching valve rotating shaft 40, 70 Strand guidance Device 41 Guide path 42 Resin receiving plate 51 Cutting mechanism 51a Actuator 51b Knife 52 Filter 60 Control part 71 Water tank 72 Frame 73 Coolant 74, 75 Guide rollers 100, 200 Pellet production system B1 Product box B2 Defective product box OP Opening P1, P2 Exhaust route ST Strand

Claims (4)

an extruder that discharges the strand from the die;
a feeder that supplies raw materials to the extruder;
a strand cutter having a measuring means for taking and processing the strand and measuring the diameter of the taken strand;
a strand guiding device that guides the strand discharged from the die to the strand cutter;
A control unit that controls a take-up speed of the strand of the strand cutter based on the strand diameter measured by the measuring means,
The control unit issues an alarm if a new strand take-up speed instructed to the strand cutter based on the strand diameter measured by the measuring means is not within an allowable range;
The control unit may control whether the strand diameter measured by the measuring means falls within an allowable range when a new strand take-up speed instructed to the strand cutter based on the strand diameter measured by the measuring means falls within an allowable range. If not, an alarm will be sent and
The strand cutter includes a switching valve that determines a discharge destination for the pellets obtained by cutting the taken-up strand,
The control unit operates the switching valve depending on the presence or absence of the alarm, and changes the discharge destination of the pellets.
Pellet production system. The control unit stops operation of the extruder, the feeder, the strand cutter, and the strand guiding device in a state in which the alarm is issued.
The pellet manufacturing system according to claim 1 . a strand discharge mechanism that is supplied with raw material from a feeder and discharges the strand from the die;
The strand is guided through a strand guiding device after being discharged from the die, and the strand is processed by the strand cutter. A control unit that controls based on the measured strand diameter,
The control unit issues an alarm if a new strand take-up speed instructed to the strand cutter based on the strand diameter measured by the measuring means is not within an allowable range;
The control unit may control whether the strand diameter measured by the measuring means falls within an allowable range when a new strand take-up speed instructed to the strand cutter based on the strand diameter measured by the measuring means falls within an allowable range. If not, an alarm will be sent and
The strand cutter includes a switching valve that determines a discharge destination for the pellets obtained by cutting the taken-up strand,
The control unit operates the switching valve depending on the presence or absence of the alarm, and changes the discharge destination of the pellets.
Extruder. Feed raw materials to an extruder equipped with a die,
Discharging the strand from the die;
guiding the strand discharged from the die to a strand cutter;
Taking and processing the strand with the strand cutter, and measuring the diameter of the taken strand,
controlling the take-up speed of the strand of the strand cutter based on the measured strand diameter;
If the new strand take-up speed instructed to the strand cutter based on the measured strand diameter is not within a permissible range, transmitting an alarm;
If a new strand take-up speed instructed to the strand cutter based on the measured strand diameter is within a permissible range, and the measured strand diameter is not within a permissible range, transmitting an alarm;
The strand cutter includes a switching valve that determines a discharge destination for the pellets obtained by cutting the taken-up strand,
operating the switching valve depending on the presence or absence of the alarm to change the discharge destination of the pellets;
Pellet manufacturing method.

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