Extrusion device and method for manufacturing resin products

Abstract

To facilitate the management of quality of resin products that are manufactured by using resin extruded from an extrusion apparatus.SOLUTION: An extrusion apparatus has a cylinder 2, and a die 5 mounted to the cylinder 2. The die 5 includes: a resin flow channel part 22 in which molten resin is fed from the cylinder 2; and a hole part 21 which is continuous with the resin flow channel part 22 in order to discharge the molten resin. The extrusion apparatus additionally includes: a pressure measuring unit 31 for measuring the pressure of the molten resin in the cylinder 2 or in the die 5; and a calculation unit for calculating the viscosity of the molten resin on the basis of a measurement value of the pressure measuring unit 31.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an extrusion device and a method for producing a resin product. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2016-7819 (Patent Document 1) describes a technique related to a strand manufacturing device equipped with an extruder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-7819 A Summary of the Invention [Problem to be solved by the invention]

[0004] Resin products, such as resin pellets, can be manufactured using the resin extruded from the extrusion device. In order to control the quality of the manufactured resin pellets, it is necessary to periodically extract the manufactured resin pellets and measure the viscosity to confirm whether the quality is stable. However, periodically extracting the manufactured resin pellets and measuring the viscosity is time-consuming, which makes the quality control of the resin pellets difficult and also leads to an increase in the manufacturing cost of the resin pellets. For this reason, it is desired to make it easier to control the quality of the resin products manufactured using the resin extruded from the extrusion device.

[0005] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0006] According to one embodiment, the extrusion device has a cylinder, a die having a hole for ejecting molten resin, a pressure measuring unit that measures the pressure of the molten resin in the cylinder or in the die, and a calculation unit that calculates the viscosity of the molten resin based on the measurement value of the pressure measuring unit.

[0007] According to one embodiment, a method for producing a resin product includes the steps of (a) preparing an extrusion device having a cylinder and a die attached to the cylinder, (b) supplying a resin material into the cylinder to form a molten resin, and discharging the molten resin from a hole in the die, and (c) measuring a pressure of the molten resin in the cylinder or the die, and (d) calculating a viscosity of the molten resin based on the pressure of the molten resin measured in the step (c). Effect of the Invention

[0008] According to one embodiment, it becomes easier to control the quality of resin products manufactured using the resin extruded from the extrusion device. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing a configuration example of a pellet production system using an extrusion device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a front view of the extrusion device according to the embodiment. [Diagram 3] 1 is a cross-sectional view of a main part of an extrusion device according to an embodiment of the present invention; [Figure 4] FIG. 11 is a cross-sectional view of a main part of a modified example of the extrusion device according to the embodiment. [Diagram 5] 4 is a plan view showing a resin flow path portion and a plurality of holes formed in a flange portion of a cylinder and a die. FIG. [Figure 6] FIG. [Figure 7] 1 is a graph showing the correlation between shear rate and viscosity of a resin. [Figure 8]4 is an explanatory diagram showing the structure of the tip of the extrusion device and a graph showing the pressure of the molten resin at each position of the structure. FIG. [Figure 9] FIG. 13 is a plan view of a die used in a further modified example of the extrusion device of one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are used for the members having the same functions, and the repeated explanations are omitted. In the following embodiments, the explanations of the same or similar parts will not be repeated as a rule unless it is particularly necessary.

[0011] (Embodiment) <Examples of the configuration of an extrusion device and a pellet production system using the same> FIG. 1 is an explanatory diagram (side view) showing an example of the configuration of a pellet production system (pellet production device) 12 using an extrusion device (extrusion molding device) 1 of the present embodiment.

[0012] First, a schematic configuration of the extrusion device 1 will be described with reference to FIG. 1. The extrusion device 1 shown in FIG. 1 has a cylinder (barrel) 2, two screws 17 rotatably (freely) arranged in the cylinder 2, a rotary drive mechanism 3 for rotating the screws 17 in the cylinder 2, a hopper (resin input section) 4 arranged on the upstream side (rear end side) of the cylinder 2, a die (mold) 5 attached to the downstream end of the cylinder 2, and an operation panel (operation section, operation table) 6. The hopper 4 is connected to the upper surface of the cylinder 2, and resin can be supplied into the cylinder 2 through the hopper 4. The temperature of the cylinder 2 is controlled by a temperature adjustment means (temperature adjustment mechanism) such as a heater (not shown). The extrusion device 1 may further have a filler supply device (not shown) connected to the cylinder 2, in which case a desired filler can be supplied into the cylinder 2 from the filler supply device.

[0013] In addition, when referring to the "downstream side" and the "upstream side" in relation to the extrusion device 1, the "downstream side" means the downstream side of the resin flow in the extrusion device 1, and the "upstream side" means the upstream side of the resin flow in the extrusion device 1. Therefore, in the extrusion device 1, the side closer to a plurality of holes 21 of the die 5, which will be described later, is the downstream side, and the side farther from the plurality of holes 21 of the die 5, i.e., the side closer to the hopper 4, is the upstream side.

[0014] Two screws 17 are rotatably (freely rotatably) inserted and built into the cylinder 2. For this reason, the extrusion device 1 can also be considered as a twin-screw extrusion device (twin-screw extruder). In the cylinder 2, the two screws 17 are arranged to mesh with each other and rotate. The longitudinal direction (long side direction, axial direction, extension direction) of the cylinder 2 and the longitudinal direction (long side direction, axial direction, extension direction) of the screws in the cylinder 2 are the same.

[0015] In this embodiment, the case where the number of screws 17 in the cylinder 2 is two has been described, but as another embodiment, the number of screws 17 in the cylinder 2 can be one. However, when the number of screws 17 in the cylinder 2 is two, a larger spatial volume can be secured, so that for the same screw diameter, a twin-shaft (two screws 17) can provide a higher raw material supply capacity than a single-shaft (one screw 17).

[0016] The die 5 can function to mold the molten resin extruded from the cylinder 2 of the extrusion device 1 into a predetermined cross-sectional shape (here, a string shape) and discharge it. For this reason, the die 5 is a die (metal mold) for extrusion molding.

[0017] In this application, "melting" is not limited to melting by heat, but also includes melting by a solvent, etc. Therefore, not only melting a resin by heating, but also melting a resin by a solvent or by microwaves can be included in the "molten resin". Liquid resin can also be included in the "molten resin".

[0018] The operation panel 6 has a display unit 7 and an input unit 8. The input unit 8 is composed of, for example, an input keyboard, a switch, a dial, a button, a touch panel, etc. By inputting commands and data necessary for operating the extrusion device 1 into the input unit 8, the operation of the extrusion device 1 can be controlled. The display unit 7 can display, for example, information input into the input unit 8, information related to the operation and state of the extrusion device 1, etc.

[0019] The operation panel 6 includes a control unit 9 that controls the operation of the extrusion device 1. The control unit 9 controls the operation of the extrusion device 1 in response to commands and data input to the input unit 8. The control unit 9 can be configured, for example, by a computer including a semiconductor chip (semiconductor processor) for control and a semiconductor chip (memory chip) for storage.

[0020] The control unit 9 also includes a calculation unit 10 that calculates the viscosity of the molten resin based on a measurement value (a pressure value of the molten resin measured by the pressure measurement unit 31) of a pressure measurement unit 31 described later. The calculation unit 10 is configured by, for example, a semiconductor chip (semiconductor processor) for calculation. The viscosity calculated by the calculation unit 10 can be displayed on the display unit 7.

[0021] The control unit 9 also includes a storage unit 11. The viscosity calculated by the calculation unit 10 can also be stored (recorded) in the storage unit 11. The storage unit 11 is configured, for example, by a semiconductor chip for storage (memory chip) or the like.

[0022] Here, the case where the control unit 9 is built into the operation panel 6 is described, but in another embodiment, the control unit 9 (control computer) can be provided separately from the operation panel 6 (i.e., outside the operation panel 6). Here, the case where the calculation unit 10 and the storage unit 11 are included in the control unit 9 is described, but one or both of the calculation unit 10 and the storage unit 11 can be provided separately from the control unit 9 (control computer). Also, the display unit 7 can be provided separately from the operation panel 6 (i.e., outside the operation panel 6).

[0023] The pellet production system 12 shown in FIG. 1 further includes a cooling tank 13 and a cutting device 14 in addition to the extrusion device 1 .

[0024] Next, an outline of the operation of the pellet production system 12 including the extrusion device 1 shown in FIG. 1 will be described.

[0025] In the extrusion device 1, the resin material (thermoplastic resin) supplied from the hopper 4 into the cylinder 2 is melted (i.e., becomes molten resin) while being sent forward in the cylinder 2 by the rotation of the screw 17. When a filler is supplied from a filler supplying device (not shown) into the cylinder 2, the resin (molten resin) and the filler are kneaded in the cylinder 2 of the extrusion device 1 by the rotation of the screw 17, so that the molten resin in the cylinder 2 contains the filler. The extrusion device 1 is operated by inputting commands and data necessary for the operation of the extrusion device 1 into the input unit 8, and the operation of the extrusion device 1 is controlled by the control unit 9.

[0026] In the extrusion device 1, the molten resin sent forward inside the cylinder 2 by the rotation of the screw 17 is extruded (discharged) from a die 5 (more specifically, a plurality of holes 21 of the die 5, described below) attached to the tip of the cylinder 2. At this time, the molten resin is formed into a string shape by the die 5 and extruded from the die 5 as a strand (resin strand) 15. The strand 15 extruded from the die 5 of the extrusion device 1 is cooled and solidified (hardened) in a cooling tank 13. The solidified strand 15 is cut to a predetermined length by a cutting device 14. In this way, pellets (resin pellets) 16 are produced as a resin product. In the pellet production system 12, the extrusion device 1 can function as a strand production device.

[0027] For this reason, the process of producing a resin product (pellets 16 in this case) includes a step of preparing an extrusion device 1 having a cylinder 2 and a die 5 attached to the cylinder 2, a step of supplying a resin material into the cylinder 2 of the extrusion device 1 to form a molten resin, and a step of discharging the molten resin from a hole 21 of the die 5. The process of producing a resin product (pellets 16 in this case) further includes a step of measuring the pressure of the molten resin in the cylinder 2 or the die 5 of the extrusion device 1 by a pressure measuring unit 31 described later, and a step of calculating the viscosity of the molten resin by a calculation unit 10 based on the pressure of the molten resin measured by the pressure measuring unit 31. The measurement of the pressure of the molten resin by the pressure measuring unit 31 and the calculation of the viscosity of the molten resin by the calculation unit 10 will be described in more detail later.

[0028] <About the die configuration> Next, the configuration of the vicinity of the tip end of the extrusion device 1 of this embodiment, in particular the configuration of the die (metal mold) 5, will be described with reference to Figs. 2 to 6.

[0029] FIG. 2 is a front view of the extrusion device 1 of this embodiment, and shows a front view of the die 5 attached to the tip of the cylinder 2. FIG. 3 is a cross-sectional view of the main part of the extrusion device 1 of this embodiment. FIG. 3 corresponds to the cross-sectional view at the position of the A1-A1 line shown in FIG. 2. FIG. 4 is a cross-sectional view of the main part showing a modified example of the extrusion device 1 of this embodiment, and shows a cross section corresponding to FIG. 3. In addition, in FIG. 2 to FIG. 4, for simplification, the fixing members (screws, etc.) for fixing each member are omitted from the illustration. FIG. 5 is a plan view showing the opening 23, the resin flow path portion 22, and the multiple holes 21 formed in the flange portion 2a of the cylinder 2 and the die 5. In FIG. 5, the flow of the molten resin is typically shown by arrows. In addition, when the breaker plate 32 is provided as in FIG. 4, the breaker plate 32 is located at the position shown by the dotted line in FIG. 5. 3 and 4 correspond to the cross-sectional view taken along line A1-A1 in Fig. 2, but also correspond to the cross-sectional view taken along line A2-A2 in Fig. 5. Fig. 6 is a perspective view showing the breaker plate 32.

[0030] 2 to 5 show the X direction, the Y direction, and the Z direction. The X direction, the Y direction, and the Z direction are directions that intersect with each other, and more specifically, are directions that are perpendicular to each other. Therefore, the X direction and the Y direction are perpendicular to each other, and the Z direction is perpendicular to the X direction and the Y direction. The X direction and the Y direction correspond to the horizontal direction, and the Z direction corresponds to the up-down direction (height direction). The Y direction is the extension direction (longitudinal direction, axial direction) of the cylinder 2, and is also the direction in which the molten resin mainly flows inside the opening 23 and the resin flow path portion 22.

[0031] The die 5 has a plurality of holes (die holes, discharge ports, nozzles, openings) 21 for discharging the molten resin (here, strands 15 made of the molten resin), and a resin flow path section 22 for guiding the molten resin supplied (introduced) from the cylinder 2 to the plurality of holes 21. That is, the resin flow path section 22 and the plurality of holes 21 are formed in the die 5. The plurality of holes 21 are spatially connected to the resin flow path section 22. The resin flow path section 22 extends in a flow path direction (here, the Y direction) from an inlet through which the molten resin flows from the cylinder 2 to the plurality of holes 21. In the die 5, the plurality of holes 21 are aligned in the X direction and spaced apart from each other. FIG. 2 shows a case in which the plurality of holes 21 are arranged in a staggered arrangement, but as another embodiment, the plurality of holes 21 may be arranged in a single row. Also, since FIG. 2 and FIG. 5 are schematic diagrams, the number of holes 21 in FIG. 2 does not match the number of holes 21 in FIG. 5, but they actually match. The number of holes 21 formed in the die 5 may be, for example, about 3 to 100.

[0032] In addition, the extending direction of each of the multiple holes 21 provided in the die member 5a is preferably inclined downward from the Y direction. That is, each hole 21 preferably extends in an obliquely downward direction. This makes it easier to guide the strand 15 to the cooling tank 13 because the molten resin is discharged obliquely downward from the multiple holes 21.

[0033] The multiple holes 21 communicate (are spatially connected) with a common resin flow path section 22. The resin flow path section 22 and the multiple holes 21 are spaces in which the molten resin supplied (introduced) to the die 5 can flow (move). The resin flow path section 22 and the multiple holes 21 can also be considered as a flow path (resin flow path) formed in the die 5 for the passage of the molten resin. The resin flow path consisting of the resin flow path section 22 and the multiple holes 21 is surrounded by the metal material constituting the die 5.

[0034] The multiple holes 21 function to mold the cross-sectional shape of the molten resin (strand 15) extruded from the die 5 into a predetermined shape. That is, since the molten resin passes through the multiple holes 21 and is discharged to the outside of the die 5, the molten resin is molded into a predetermined cross-sectional shape by the holes 21 and discharged (extruded) from the holes 21 to the outside of the die 5. For example, when the cross-sectional shape of the holes 21 (a cross-sectional shape substantially perpendicular to the extension direction of the holes 21) is circular, the cross-sectional shape of the molten resin (strand 15) discharged from the holes 21 (a cross-sectional shape substantially perpendicular to the extension direction of the strand 15) is also circular. In addition, the diameter of the strand 15 can be controlled by the diameter of the holes 21. However, the diameter of the strand 15 also changes depending on the flow speed of the molten resin when it is discharged from the holes 21. The resin flow path section 22 functions as a flow path (resin flow path) for guiding the molten resin supplied from the cylinder 2 to the die 5 to the multiple holes 21.

[0035] The die 5 is composed of a die member (die main body) 5a and a die member (die holder, die holding portion) 5b. That is, the die 5 has the die member 5a and the die member 5b, and the die member 5b is attached to the flange portion 2a at the tip (downstream tip) of the cylinder 2 of the extrusion device 1, and the die member 5a is attached to the front side (opposite side to the side connected to the flange portion 2a of the cylinder 2) of the die member 5b. Therefore, the die member 5a is held by the flange portion 2a of the cylinder 2 via the die member 5b, and the die member 5b has the function of holding the die member 5a. The multiple holes 21 are formed in the die member 5a. The resin flow path portion 22 is formed across the die member 5a and the die member 5b, but is mainly formed in the die member 5b. Therefore, the die member 5b holds the die member 5a in which the multiple holes 21 are formed, and also has the function of defining (prescribing) the resin flow path portion 22 for guiding the molten resin from the cylinder 2 to the multiple holes 21.

[0036] The die 5 can be made of one integral member, but if the die 5 is made of multiple members (here, die members 5a and 5b), it becomes easier to form the multiple holes 21 and the resin flow path 22, and the die 5 can be easily processed. Since the cross-sectional shape of the strand 15 is determined by the holes 21 formed in the die member 5a, the die member 5a can be regarded as the die, and the die member 5b can be regarded as a die holder for holding the die (die member 5a). The die member 5b can also be made of multiple members (metal members, metal mold members), and in that case, the die member 5b can be constructed by fixing the multiple members with fixing members such as screws or bolts.

[0037] The die 5 is preferably made of a metal material, and therefore the die members 5a and 5b are preferably made of a metal material. The die member 5a is fixed to the die member 5b by a fixing member (not shown) such as a screw or a bolt. The die member 5b is attached and fixed to the flange portion 2a of the cylinder 2 by a fixing member (not shown) such as a screw or a bolt.

[0038] The extrusion device 1 of the present embodiment has a pressure measuring unit 31 that measures the pressure of the molten resin in the cylinder 2 or the die 5. The pressure measuring unit 31 includes, for example, a pressure sensor (pressure gauge). The pressure measuring unit 31 can be disposed in the cylinder 2 or the die 5.

[0039] However, it is desirable that the pressure measuring unit 31 measures the pressure of the molten resin at a position upstream of the hole 21 and as close as possible to the hole 21 in the flow path of the molten resin in the extrusion device 1. For this reason, it is preferable that the pressure measuring unit 31 is disposed in the die 5 rather than in the cylinder 2 to measure the pressure of the molten resin in the resin flow path portion 22 in the die 5 (the molten resin flowing through the resin flow path portion 22). It is more preferable that the pressure measuring unit 31 is disposed in the die member 5a to measure the pressure of the molten resin in the resin flow path portion 22 in the die member 5a (the molten resin flowing through the resin flow path portion 22), and this case is shown in Figs. 3 and 4.

[0040] Fig. 4 is a modified example of the structure in Fig. 3, and shows a case where a breaker plate 32 and a screen mesh 33 are used. As shown in Fig. 4, a breaker plate 32 can be interposed in the middle of the flow (flow path) of the molten resin, upstream of the plurality of holes 21. As can be seen from Figs. 4 and 6, the breaker plate 32 is a member in which a plurality of openings (holes) 32a through which the molten resin can pass are formed (arranged).

[0041] 4, not only the breaker plate 32 but also a screen mesh 33 can be interposed in the flow (flow path) of the molten resin upstream of the plurality of holes 21. The screen mesh 33 is a net-like member and has a plurality of openings (holes) through which the molten resin can pass.

[0042] The breaker plate 32 and the screen mesh 33 are disposed upstream of the hole 21, specifically, between the flange 2a of the cylinder 2 and the die 5 (hence, between the opening 23 of the flange 2a and the resin flow path 22 of the die 5). The number of screen meshes 33 may be one or more. It is preferable to use both the breaker plate 32 and the screen mesh 33, but there may be cases where one or the other is used.

[0043] In addition, since the size of the opening of the screen mesh 33 is smaller than the size of the opening 32a of the breaker plate 32, the opening of the screen mesh 33 is not shown in Fig. 4. However, since both the screen mesh 33 and the breaker plate 32 have a plurality of openings through which the molten resin can pass, the molten resin supplied from the cylinder 2 can pass through the screen mesh 33 (the plurality of openings) and the breaker plate 32 (the plurality of openings 32a) and flow into the resin flow path section 22 of the die 5. The screen mesh 33 and the breaker plate 32 have the function of filtering out foreign matter in the molten resin and the function of increasing the back pressure in the cylinder 2 to increase the effect of kneading the resin in the cylinder 2.

[0044] The die member 5b is attached to the flange portion 2a of the cylinder 2 so that the opening (outlet for the molten resin) 23 of the flange portion 2a at the tip of the cylinder 2 communicates (spatially connects) with the resin flow path portion 22 of the die 5. Therefore, the molten resin conveyed while being kneaded by the screw 17 inside the cylinder 2 is extruded from the opening 23 of the flange portion 2a at the tip of the cylinder 2, supplied to the resin flow path portion 22 of the die 5, flows through the resin flow path portion 22 into the multiple holes 21, and is discharged from the multiple holes 21 to the outside of the die 5. The molten resin discharged from the multiple holes 21 becomes the strand 15. In addition, when the breaker plate 32 and the screen mesh 33 are provided as shown in FIG. 4, the molten resin extruded from the opening 23 of the flange portion 2a at the tip of the cylinder 2 passes through the screen mesh 33 (the multiple openings) and the breaker plate 32 (the multiple openings 32a) and is supplied to the resin flow path portion 22 of the die 5.

[0045] <Main features and effects> The extrusion device 1 of the present embodiment has a pressure measuring unit 31 that measures the pressure of the molten resin in the cylinder 2 or in the die 5, and a calculation unit 10 that calculates the viscosity of the molten resin based on the measurement value of the pressure measuring unit 31 (the pressure value of the molten resin measured by the pressure measuring unit 31). Furthermore, the process of producing a resin product (pellets 16 in this case) using the extrusion device 1 of the present embodiment includes a step of measuring the pressure of the molten resin in the cylinder 2 or in the die 5 of the extrusion device 1 by the pressure measuring unit 31, and a step of calculating the viscosity of the molten resin by the calculation unit 10 based on the pressure of the molten resin measured by the pressure measuring unit 31.

[0046] The molten resin extruded from the cylinder 2 is supplied to the resin flow path 22 of the die 5, flows through the resin flow path 22 into the multiple holes 21, and is discharged (extruded) from the multiple holes 21 to the outside of the die 5. At this time, since the opening diameter of the holes 21 is quite small, a pressure loss occurs when the molten resin passes through the holes 21. The pressure loss when the molten resin passes through the holes 21 depends on the viscosity of the molten resin, and the higher the viscosity, the larger the pressure loss, and the lower the viscosity, the smaller the pressure loss. Therefore, if the pressure loss when the molten resin passes through the holes 21 is known, the viscosity of the molten resin passing through the holes 21 can be known (estimated). The pressure loss when the molten resin passes through the holes 21 is the difference between the pressure of the molten resin immediately before passing through the holes 21 and the pressure of the molten resin immediately after passing through the holes 21 and being discharged to the outside of the die 5, but the pressure of the molten resin immediately after being discharged to the outside of the die 5 is almost equal to atmospheric pressure. Therefore, by estimating the pressure of the molten resin immediately before passing through hole 21 using the measurement value of pressure measurement unit 31, it is possible to estimate the pressure loss that occurs when the molten resin passes through hole 21, and based on that, it is possible to calculate the viscosity of the molten resin passing through hole 21. Such calculation of the viscosity of the molten resin based on the measurement value of pressure measurement unit 31 can be performed by calculation unit 10. A specific example of a specific calculation method will be described in more detail later.

[0047] While the extrusion device 1 is operated to discharge strands 15 made of molten resin from the multiple holes 21 of the die 5, the pressure of the molten resin in the cylinder 2 or the die 5 is measured by the pressure measuring unit 31, and the viscosity of the molten resin can be calculated by the calculation unit 10 based on the measured value, so that the viscosity of the molten resin during the operation of the extrusion device 1 can be grasped in real time. In addition, the pressure of the molten resin is continuously monitored by the pressure measuring unit 31, so that the viscosity of the molten resin during the operation of the extrusion device 1 can be continuously monitored. The viscosity of the molten resin calculated by the calculation unit 10 can be displayed on the display unit 7, and can be always displayed on the display unit 7 using, for example, a numerical value or a graph. That is, the process of manufacturing a resin product (pellets 16 in this embodiment) using the extrusion device 1 of this embodiment further includes a process of displaying the viscosity of the molten resin calculated by the calculation unit 10 on the display unit 7. Therefore, by looking at the display unit 7, the real-time viscosity of the molten resin during the operation of the extrusion device 1 and the change over time of the viscosity can be easily and accurately grasped. The quality of a resin product (pellets 16 in this example) manufactured using the extrusion device 1 depends on the viscosity of the molten resin formed in the cylinder 2 and discharged from the multiple holes 21 of the die 5. For this reason, in order to properly manage the quality of a resin product (pellets 16 in this example) manufactured using the extrusion device 1, it is extremely useful to be able to grasp the real-time viscosity of the molten resin during the operation of the extrusion device 1 and the change over time of the viscosity of the molten resin when the extrusion device 1 is operated continuously for a long period of time. In this embodiment, this is possible because the extrusion device 1 has a pressure measurement unit 31 and a calculation unit 10, so that the quality of the resin product (pellets 16 in this example) manufactured using the extrusion device 1 can be easily managed. For this reason, the manufacturing cost of the resin product (pellets 16 in this example) manufactured using the extrusion device 1 can also be reduced. In addition, since the continuous change over time in the viscosity of the molten resin during the operation of the extrusion device 1 can be visually confirmed on the display unit 7, the kneading state (kneading index) of the resin in the extrusion device 1 and the stability of the quality of the molten resin (strands 15) discharged from the multiple holes 21 of the die 5 can be easily grasped.

[0048] The viscosity of the molten resin calculated by the calculation unit 10 can be stored (recorded) in the storage unit 11. When the viscosity of the molten resin changes due to some factor, the change can be grasped in real time by the display unit 7, and by storing (recording) the change over time of the molten resin in the storage unit 11, it is also possible to confirm after the fact that the viscosity of the molten resin has changed due to some factor.

[0049] Also, the pressure measuring unit 31 and the calculating unit 10 can obtain discontinuous (periodic) data on the viscosity of the molten resin (for example, viscosity measured at the same time every day), and this data can be used to monitor the stability of the quality of the resin product (pellets 16 in this case). The discontinuous (periodic) data and data on the stability of the quality of the resin product (pellets 16 in this case) determined based on this data can also be displayed on the display unit 7.

[0050] <First example of a method for calculating the viscosity of a molten resin> Next, a first example of a specific method for calculating the viscosity of the molten resin based on the pressure value of the molten resin measured by the pressure measuring unit 31 will be described.

[0051] Since the cross-sectional dimension of the hole 21 of the die 5 (the area of ​​the cross section approximately perpendicular to the direction in which the molten resin flows) is considerably smaller than the cross-sectional dimension of the resin flow path section 22 of the die 5 (the area of ​​the cross section approximately perpendicular to the direction in which the molten resin flows), the pressure loss of the molten resin as it flows through the resin flow path section 22 is not that large, whereas the pressure loss of the molten resin as it passes through the hole 21 is considerably large.

[0052] The shear rate γ when the molten resin passes through the hole 21 a is expressed by the following Equation 1.

[0053]

number

[0054] In this formula 1, D is the diameter of the hole 21, and Q in formula 1 is the flow rate of the molten resin passing through each hole 21. The flow rate Q is expressed as Q=Q0 / N, where Q0 is the flow rate of the molten resin supplied from the cylinder 2 to the resin flow path portion 22 of the die 5, and N is the number of holes 21. Q0 can be set as an extrusion flow rate setting value when operating the extrusion device 1.

[0055] Moreover, the shear stress σ when the molten resin passes through the hole 21 is expressed by the following formula 2.

[0056]

number

[0057] In this formula 2, ΔP is the pressure loss when the molten resin passes through the hole 21, and is expressed as ΔP=P1-P0. Here, P1 is the pressure of the molten resin immediately before passing through the hole 21, and the pressure of the molten resin measured by the pressure measuring unit 31 can be used as this pressure P1. P0 is the pressure of the molten resin immediately after passing through the hole 21 and being discharged to the outside of the die 5, and atmospheric pressure can be used as the value of this pressure P0. In formula 2, L is the length of the hole 21 (the length in the direction in which the resin flows).

[0058] Viscosity of molten resin η a is expressed by the following Equation 3 based on Equation 1 and Equation 2.

[0059]

number

[0060] In this formula 3, the diameter D of the hole 21 and the length L of the hole 21 are known values, and the flow rate Q (=Q0 / N) of the molten resin passing through each hole 21 is a value that can be controlled by the set value of the extrusion flow rate (Q0) when operating the extrusion device 1. Therefore, as can be seen from this formula 3, the viscosity η acan be calculated if the pressure loss ΔP when the molten resin passes through the hole 21 is known. As described above, ΔP=P1-P0, the atmospheric pressure is used as the value of the pressure P0, and the pressure of the molten resin measured by the pressure measuring unit 31 is used as the value of the pressure P1, and the viscosity η of the molten resin can be calculated from the formula 3. a can be calculated.

[0061] For example, the diameter D and length L of the holes 21 and the number N of the holes 21 may be input in advance into the viscosity calculation program of the calculation unit 10, and the flow rate Q may be automatically input when the extrusion flow rate (Q0) of the extrusion device 1 is set. Then, the pressure measurement unit 31 measures the pressure of the molten resin, and the viscosity η of the molten resin is calculated from the formula 3 based on the measured pressure. a The calculation unit 10 can calculate the above.

[0062] In addition, here, it is assumed that pressure loss occurs in the hole 21, and the viscosity of the molten resin is calculated based on this. For this reason, it is preferable that the pressure of the molten resin at the entrance of the hole 21 and the pressure of the molten resin measured by the pressure measurement unit 31 are as consistent as possible, and this can improve the accuracy of the viscosity of the molten resin calculated based on the measurement value of the pressure measurement unit 31. For this reason, it is preferable that the pressure loss caused by the movement of the molten resin from the pressure measurement position by the pressure measurement unit 31 to the entrance of the hole 21 is sufficiently low compared to the pressure loss caused by the molten resin passing through the hole 21, and in order to realize this, it is preferable that the pressure measurement position of the molten resin by the pressure measurement unit 31 is as close as possible to the entrance of the hole 21. However, the pressure measurement unit 31 measures the pressure of the molten resin before the hole 21 (upstream side of the hole 21), not the pressure of the molten resin inside the hole 21. From this viewpoint, it is preferable that the pressure measuring unit 31 is arranged in the die 5 rather than in the cylinder 2, and the pressure of the molten resin in the resin flow path portion 22 in the die 5 is measured by the pressure measuring unit 31, and it is even more preferable that the pressure measuring unit 31 is arranged in the die member 5a, and the pressure of the molten resin in the resin flow path portion 22 in the die member 5a is measured by the pressure measuring unit 31.

[0063] 7 is a graph showing the correlation between the shear rate and viscosity of a resin. The viscosity of the molten resin calculated from the measured value of the pressure measuring unit 31 according to the method of the first example above is plotted as a diamond. In addition, a viscosity fitting curve obtained by measuring the viscosity of the produced resin pellets using a capillary rheometer is shown as a solid line.

[0064] As can be seen from Fig. 7, the diamond plots and the solid viscosity fitting curve are almost identical. This also shows that if the viscosity of the molten resin is calculated from the measured value of the pressure measuring unit 31 according to the method of the first example above, the viscosity characteristics of the manufactured resin product (here, resin pellets) can be grasped, and the quality of the manufactured resin product (resin pellets) can be controlled.

[0065] <Second example of the method for calculating the viscosity of molten resin> Next, a second example of a specific method for calculating the viscosity of the molten resin based on the pressure value of the molten resin measured by the pressure measuring unit 31 will be described. This second example is premised on the case where the breaker plate 32 and the screen mesh 33 are used as in the structure shown in FIG.

[0066] 4, as described above, the pressure loss of the molten resin when it flows through the resin flow path 22 is not so large, whereas the pressure loss of the molten resin when it passes through the hole 21 is quite large. However, in the case of the structure in Fig. 4, the pressure loss of the molten resin when it passes through the openings of the screen mesh 33 and the openings 32a of the breaker plate 32 is also quite large.

[0067] Therefore, even in the case of the structure of FIG. 4, if the viscosity of the molten resin is measured by the pressure measuring unit 31 downstream of the screen mesh 33 and the breaker plate 32, the viscosity of the molten resin can be calculated using the method of the first example based on the measurement value of the pressure measuring unit 31 without considering the pressure loss when passing through the screen mesh 33 and the breaker plate 32. If the viscosity of the molten resin is measured by the pressure measuring unit 31 downstream of the screen mesh 33 and the breaker plate 32, even if the screen mesh 33 and the breaker plate 32 are clogged due to some factor, it is possible to prevent the clogging from affecting the measurement value of the pressure measuring unit 31, thereby improving the stability of the measurement value of the pressure measuring unit 31. Therefore, even in the case of the structure of FIG. 4, it is preferable to measure the viscosity of the molten resin by the pressure measuring unit 31 downstream of the screen mesh 33 and the breaker plate 32, and therefore the pressure measuring unit 31 is preferably disposed in the die 5, and more preferably disposed in the die member 5a.

[0068] However, in the case of the structure shown in Figure 4 above, even if the viscosity of the molten resin is measured by pressure measurement unit 31 upstream of screen mesh 33 and breaker plate 32 (i.e., when pressure measurement unit 31 is arranged in cylinder 2), the viscosity of the molten resin can be calculated based on the measurement value of pressure measurement unit 31 using the method of the second example described below.

[0069] Fig. 8 is an explanatory diagram showing the structure of the tip of the extrusion device 1 and a graph showing the pressure of the molten resin at each position of the structure. In Fig. 8, the pressure measuring unit 31 is not shown, but other than that, the structure is the same as that in Fig. 4 above.

[0070] 8, the pressure of the molten resin drops significantly when passing through the openings of the screen mesh 33 and the openings 32a of the breaker plate 32, and when passing through the holes 21, resulting in a pressure loss. In comparison, the pressure loss when passing through the resin flow path 22 is significantly smaller. For this reason, if the pressure measurement value when the viscosity of the molten resin is measured by the pressure measurement unit 31 upstream of the screen mesh 33 and the breaker plate 32 (i.e. when the pressure measurement unit 31 is disposed in the cylinder 2) is taken as Pa, the pressure measurement value Pa can be approximately expressed by the following Equation 4.

[0071]

number

[0072] Here, ΔP1 in the formula 4 is the pressure loss when the molten resin passes through the hole 21, and ΔP2 is the pressure loss when the molten resin passes through the opening of the screen mesh 33 and the opening 32a of the breaker plate 32. In addition, the viscosity η of the molten resin a is assumed to be constant.

[0073] By modifying the above formula 1, the following formula 5 is obtained.

[0074]

number

[0075] Here, D1 in Equation 5 is the diameter of the hole 21, and Q1 in Equation 5 is the flow rate of the molten resin passing through each hole 21. The flow rate Q1 is expressed as Q1=Q0 / N1, where Q0 is the flow rate of the molten resin supplied from the cylinder 2 to the resin flow path portion 22 of the die 5, and N1 is the number of holes 21. Q0 can be set as the extrusion flow rate setting value when operating the extrusion device 1. L1 in Equation 5 is the length of the hole 21 (the length in the direction in which the resin flows).

[0076] On the other hand, ΔP2 in Equation 5 is expressed by the following Equation 6.

[0077]

number

[0078] Here, ΔP2 in Equation 6 B is the pressure loss when passing through the opening 32a of the breaker plate 32, and ΔP2 in Equation 6 M is the pressure loss when passing through the screen mesh 33 (openings). As shown in Equation 6, ΔP2 is B and ΔP2 M It is expressed as the sum (total) of and.

[0079] Pressure loss ΔP2 when passing through the opening 32a of the breaker plate 32 B can be calculated in the same way as the pressure loss ΔP1 when passing through the hole 21, and is expressed by the following Equation 7.

[0080]

number

[0081] Here, D2 in Equation 7 is the diameter of the opening 32a of the breaker plate 32, and Q2 in Equation 7 is the flow rate of the molten resin passing through each opening 32a. The flow rate Q2 is expressed as Q2=Q0 / N2, ​​where Q0 is the flow rate of the molten resin supplied from the cylinder 2 to the resin flow path section 22 of the die 5, and N2 is the number of openings 32a. Q0 can be set as the extrusion flow rate setting value when operating the extrusion device 1. L2 in Equation 7 is the length of the opening 32a of the breaker plate 32 (the length in the direction in which the resin flows).

[0082] Pressure loss ΔP2 when passing through the screen mesh 33 M can be calculated using the following Equation 8.

[0083]

number

[0084] Here, in Equation 8, u is the flow velocity of the molten resin, α is the viscous resistance coefficient, β is the inertial resistance coefficient, and ρ is the density. The viscous resistance coefficient α and the inertial resistance coefficient β are values ​​specific to the screen mesh, and can be provided by the screen mesh manufacturer. In addition, when using a plurality of overlapping screen meshes 33, ΔP2 obtained by Equation 8 is multiplied by the number of overlapping sheets. M Just add them together.

[0085] By incorporating the above-mentioned formulas 5, 6, 7, and 8 into the above-mentioned formula 4, the following formula 9 is obtained.

[0086]

number

[0087] Here, the part A in the formula 9 is related to the pressure loss when passing through the breaker plate 32, the part C in the formula 9 is related to the pressure loss when passing through the hole 21, and the parts B and E in the formula are related to the pressure loss when passing through the screen mesh 33. Of these, the viscosity η a The contributions are from parts A, B, and C. Therefore, by transforming Equation 9, we obtain the following Equation 10.

[0088]

number

[0089] Here, A, B, C, and E in formula 10 are the parts indicated by A, B, C, and E in formula 9, respectively.

[0090] By transforming Equation 10, the following Equation 11 is obtained.

[0091]

number

[0092] From this formula 11, the viscosity of the molten resin is measured by the pressure measuring unit 31 on the upstream side of the screen mesh 33 and the breaker plate 32, and the viscosity η of the molten resin is calculated based on the pressure measurement value Pa. a can be calculated.

[0093] Therefore, in the case where a breaker plate 32 or a screen mesh 33 is used as shown in FIG. 4 above, even if the pressure measurement unit 31 is arranged on the cylinder 2 side and measures the viscosity of the molten resin upstream of the screen mesh 33 and the breaker plate 32, the calculation unit 10 can calculate the viscosity of the molten resin based on the pressure measurement value of the pressure measurement unit 31.

[0094] However, when the pressure measurement unit 31 is disposed on the cylinder 2 side and measures the viscosity of the molten resin by the pressure measurement unit 31 upstream of the screen mesh 33 and the breaker plate 32, clogging or the like caused by some factor in the screen mesh 33 and the breaker plate 32 will affect the measured value of the pressure measurement unit 31. This is undesirable because it leads to a discrepancy (error) between the calculated viscosity and the actual viscosity when the calculation unit 10 calculates the viscosity of the molten resin based on the measured value of the pressure measurement unit 31.

[0095] For this reason, when a member having a plurality of openings through which the molten resin passes, such as the breaker plate 32 or the screen mesh 33, is used, it is more preferable to measure the pressure of the molten resin using the pressure measuring unit 31 downstream of the member and upstream of the plurality of holes 21. In that case, the method of the first example above may be used to calculate the viscosity. This prevents clogging or the like due to some factor in a member having a plurality of openings through which the molten resin passes, such as the breaker plate 32 or the screen mesh 33, from affecting the measured value of the pressure measuring unit 31. This makes it possible to more accurately suppress or prevent a deviation (error) between the calculated viscosity and the actual viscosity when the calculation unit 10 calculates the viscosity of the molten resin based on the measured value of the pressure measuring unit 31.

[0096] <Modification> A further modified example of the extrusion device 1 of the present embodiment will be described with reference to Fig. 9. Fig. 9 is a plan view of a die 5 used in the further modified example of the extrusion device 1 of the present embodiment, and corresponds to Fig. 2 above.

[0097] In the case of FIG. 2, the number of holes (openings for discharging molten resin) 21 provided in the die 5 is multiple (two or more), but in the case of FIG. 9, the number of holes (openings for discharging molten resin) 21 provided in the die 5 is one. In addition, in the case of FIG. 9, the cross-sectional shape of the hole 21 (cross-sectional shape approximately perpendicular to the extension direction of the hole 21) is, for example, slit-shaped, and in this case, the molten resin discharged from the slit-shaped hole 21 is not strand-shaped but film-shaped. The film-shaped molten resin discharged (extruded) from the slit-shaped hole 21 shown in FIG. 9 is cooled by a cooling device such as a cooling roll and solidifies to become a resin film. Therefore, in the case of FIG. 9, the resin product manufactured is, for example, a resin film. The resin film is transported to a winding machine (not shown) and wound up. Even in such a case, as described above, the pressure of the molten resin in the cylinder 2 or die 5 of the extrusion device 1 can be measured by the pressure measuring unit 31, the calculation unit 10 can calculate the viscosity of the molten resin based on the measurement value of the pressure measuring unit 31, and the viscosity of the molten resin can be displayed on the display unit 7. This makes it possible to obtain the effects described above.

[0098] The invention made by the inventor has been specifically described above based on the embodiment thereof. However, it goes without saying that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. [Explanation of symbols]

[0099] 1. Extrusion equipment 2 Cylinder 3 Rotational drive mechanism 4 Hopper 5 Die 5a, 5b Die members 6 Control panel 7 Display section 8 Input section 9. Control Unit 10 Calculation section 11 Storage section 12 Pellet production system 13 Cooling tank 14 Cutting device 15 Strand 16 pellets 17 Screw 21 Hole 22 Resin flow path section 23 Opening 31 Pressure measurement section 32 Breaker Plate 33 Screen Mesh

Claims

1. Extrusion equipment including: Cylinder; a die attached to said cylinder; a resin flow path portion provided in the die and into which the molten resin is supplied from the cylinder; a plurality of holes provided in the die, connected to the resin flow path portion, and for discharging the molten resin; a pressure measuring unit for measuring the pressure of the molten resin in the die; and A calculation unit that calculates the viscosity of the molten resin based on the measurement value of the pressure measurement unit; Where: the die includes a die body portion in which the plurality of holes are formed, and a die holder portion attached to the cylinder and holding the die body portion, The resin flow path portion is formed across the die holder portion and the die main body portion, the pressure measuring unit is disposed in the die main body and measures a pressure of the molten resin flowing through the resin flow path in the die main body; Resin pellets are produced using the molten resin discharged from the plurality of holes.

2. 2. The extrusion device according to claim 1, The nozzle further includes a member having a plurality of openings through which the molten resin can pass, the member being located upstream of the plurality of holes, The pressure measuring unit measures the pressure of the molten resin downstream of the member and upstream of the hole.

3. 3. The extrusion device according to claim 2, The member is disposed between the cylinder and the die.

4. 3. The extrusion device according to claim 2, The member includes a breaker plate.

5. 3. The extrusion device according to claim 2, The extrusion apparatus, wherein the member comprises a screen mesh.

6. 2. The extrusion device according to claim 1, The extrusion device further comprises a display unit that displays the viscosity calculated by the calculation unit.

7. 7. The extrusion device according to claim 6, The extrusion device further comprises a storage unit that stores the viscosity calculated by the calculation unit.

8. 2. The extrusion device according to claim 1, The extrusion apparatus, wherein the pressure measuring unit includes a pressure sensor.

9. A method for producing a resin product, comprising the steps of: (a) preparing an extrusion apparatus having a cylinder, a die attached to the cylinder, a pressure measuring unit disposed within the die, and a calculation unit; (b) supplying a resin material into the cylinder to form a molten resin, and discharging the molten resin from a plurality of holes in the die; (c) producing resin pellets using the molten resin discharged from the plurality of holes; (d) measuring the pressure of the molten resin in the die by the pressure measuring unit; (e) calculating a viscosity of the molten resin by the calculation unit based on the pressure of the molten resin measured in the (d) process; Where: the die includes a die body portion in which the plurality of holes are formed, and a die holder portion attached to the cylinder and holding the die body portion, a resin flow path portion to which the molten resin is supplied from the cylinder is formed across the die holder portion and the die main body portion, The plurality of holes are connected to the resin flow path portion, The pressure measuring unit is disposed in the die body, In the step (d), the pressure measuring unit measures the pressure of the molten resin flowing through the resin flow path in the die main body.

10. The method for producing a resin product according to claim 9, (f) displaying the viscosity of the molten resin calculated in the step (e) on a display unit; The method for producing a resin product further comprises:

11. The method for producing a resin product according to claim 9, the extrusion device further includes a member having a plurality of openings through which the molten resin can pass, the member being located upstream of the plurality of holes; A method for manufacturing a resin product, wherein the pressure measuring section measures the pressure of the molten resin downstream of the member and upstream of the plurality of holes.

Images