CN115384029A

CN115384029A - Extrusion device and wire-drawing die

Info

Publication number: CN115384029A
Application number: CN202210570218.5A
Authority: CN
Inventors: 富山秀树
Original assignee: Japan Steel Works Ltd
Current assignee: Japan Steel Works Ltd
Priority date: 2021-05-24
Filing date: 2022-05-24
Publication date: 2022-11-25
Also published as: TW202311007A; KR20220158616A; JP2022179930A

Abstract

The invention provides an extrusion device and a wire-drawing die capable of improving the quality of a material bar. An extrusion apparatus (1) of one embodiment includes: a cylindrical cylinder (20) extending in one direction and having a flow path (26) through which a raw material (60) of a material bar (61) flows; a wire-drawing die (40) having an inlet (44) disposed on one end side of the cylinder and into which the raw material extruded from the cylinder flows, a discharge port (45) through which the raw material is discharged as a strand (61), and a flow path (46) through which the raw material flows from the inlet (44) to the discharge port (45); and a screw (30) that extrudes the raw material toward the discharge port (45) by rotating about a rotating shaft extending in one direction, wherein, when the cross-sectional area of the flow path (26) and the cross-sectional area of the screw orthogonal to the one direction are taken as the flow path cross-sectional area, the flow path cross-sectional area of the flow path of the die (40) located closer to the discharge port (45) than the tip of the screw (30) is smaller than the flow path cross-sectional area of the flow path of the cylinder.

Description

Extrusion device and wire-drawing die

Technical Field

The present invention relates to an extrusion device and a wire-drawing die.

Background

Patent document 1 describes an extrusion device including a die for extruding a molten resin as a strand. In the extrusion device of patent document 1, the flow path of the resin is formed in an inverted conical shape having a diameter expanding toward the discharge port.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open No. 2012-232432

Disclosure of Invention

Problems to be solved by the invention

A wire-drawing die attached to the tip of the extrusion device may be provided with a perforated plate (breaker plate) having a small mesh for filtering foreign matter. In such a case, the area of the porous plate is increased to secure the filtration area. As a result, the flow path of the resin has a portion whose diameter is increased toward the discharge port.

Generally, when the flow path is expanded in diameter, the flow velocity (shear velocity) decreases. A resin having a strong non-newtonian property has very low fluidity at a low shear rate and is likely to be retained on a wall surface. This increases the amount of heat (thermal energy) from the heater, and causes thermal degradation such as a decrease in molecular weight, thereby degrading the quality of the strand.

Other objects and novel features will be apparent from the description of the specification and the drawings.

An extrusion apparatus of an embodiment includes: a cylindrical cylinder extending in one direction and having a flow path through which a raw material of the bar flows; a wire-drawing die having an inlet port disposed on one end side of the cylinder and into which the raw material extruded from the cylinder flows, an outlet port from which the raw material is discharged as a strand, and a flow path from the inlet port to the outlet port through which the raw material flows; and a screw that rotates about a rotation shaft extending in the one direction to extrude the raw material toward a discharge port, wherein a cross-sectional area of the flow path orthogonal to the one direction is defined as a flow path cross-sectional area, and the flow path cross-sectional area of the flow path of the die on the discharge port side relative to a tip of the screw is smaller than the flow path cross-sectional area of the flow path of the cylinder.

A screw of a die according to an embodiment is disposed on one end side of a cylindrical cylinder extending in one direction and having a flow path through which a material of a strand flows, the screw rotating around a rotation shaft extending in the one direction, the die including: an inflow port into which the raw material extruded from the cylinder by the screw flows; an outlet for discharging the raw material as a strand; and a flow path through which the raw material flows from the inlet to the outlet, wherein if a cross-sectional area of the flow path orthogonal to the one direction is defined as a flow path cross-sectional area, the flow path cross-sectional area of the flow path on the outlet side relative to a tip of the screw is smaller than the flow path cross-sectional area on the inlet.

According to the above-described embodiment, the extrusion device and the die capable of improving the quality of the strand can be provided. The above objects, features and advantages, and other objects, features and advantages of the present disclosure will be more fully understood from the detailed description given below and the accompanying drawings. The detailed description and drawings set forth below are illustrative in nature and are not intended to limit the disclosure.

Drawings

Fig. 1 is a side view illustrating the configuration of an extrusion apparatus according to embodiment 1.

Fig. 2 is a sectional view illustrating a cylinder of the biaxial extrusion device of embodiment 1.

Fig. 3 is a diagram illustrating a flow passage cross-sectional area of the cylinder in embodiment 1.

Fig. 4 is a perspective view illustrating a wire-drawing die of embodiment 1.

Fig. 5 is a partially cut-away perspective view illustrating a wire-drawing die according to embodiment 1.

Fig. 6 is a sectional view illustrating the wire-drawing die of embodiment 1, showing a section VI-VI of fig. 4.

Fig. 7 is a sectional view illustrating a wire-drawing die of embodiment 1, showing a section VII-VII of fig. 4.

Fig. 8 is a partially cut-away perspective view illustrating a wire-drawing die of a comparative example.

Fig. 9 is a sectional view illustrating a wire-drawing die of a comparative example.

Fig. 10 is a sectional view illustrating a wire-drawing die of a comparative example.

Fig. 11 is a graph illustrating the shear rate in the flow path of the wire-drawing die of the comparative example.

Fig. 12 is a diagram illustrating the shear rate in the flow path of the wire-drawing die of embodiment 1.

Detailed Description

For the sake of clarity, the following description and drawings are appropriately omitted and simplified. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary.

(embodiment mode 1)

The extrusion apparatus of embodiment 1 will be explained. Fig. 1 is a side view illustrating the structure of an extrusion apparatus according to embodiment 1. The part of fig. 1 shows a cross section. As shown in fig. 1, the extrusion apparatus 1 includes a driving unit 10, a speed reducer 11, a feeder 12, a charge pump 13, a vacuum pump 14, a heater 15, a cylinder 20, a vent 23, a screw 30, and a die 40. The extrusion device 1 further includes a thermometer and a pressure gauge at predetermined positions, which measure the temperature and pressure of the cylinder 20 and the die 40. The extrusion apparatus 1 may further include a strand bath 50 and a strand cutter 51. The extrusion apparatus 1 extrudes a raw material 60 obtained by melting a resin or the like from a wire-drawing die 40 to form a strand 61. The formed strand 61 is cooled in the strand bath 50. Thereafter, the strand 61 is cut into pellets 62 by the strand cutter 51.

Here, an XYZ rectangular coordinate system is introduced for convenience of explanation of the extrusion apparatus 1. For example, one direction in which the cylinder 20 extends is referred to as an X-axis direction, and two directions orthogonal to the X-axis direction are referred to as a Y-axis direction and a Z-axis direction. For example, the Z-axis direction is a vertical direction, and the XY plane is a horizontal plane. The + Z-axis direction is upward. The end of the cylinder 20 on the + X axis direction side is referred to as one end, and the end of the cylinder 20 on the-X axis direction side is referred to as the other end. The direction in which the raw material 60 melted in the extrusion apparatus 1 is extruded is set as the + X-axis direction. The respective configurations are explained below.

< driving part, speed reducer >

The drive unit 10 is disposed on the other end side of the cylinder 20, i.e., on the-X axis direction side of the cylinder 20. The drive unit 10 rotates the screw 30. In the case where the extrusion apparatus 1 is a twin-screw extrusion apparatus, the driving section 10 rotates the

screws

31 and 32. The extrusion apparatus 1 is not limited to a biaxial extrusion apparatus, and may be a multi-axis extrusion apparatus or a uniaxial extrusion apparatus.

Screws

31 and 32 are collectively referred to as screw 30.

The driving unit 10 is, for example, a motor. The speed reducer 11 is disposed between the drive unit 10 and the screw 30. The speed reducer 11 adjusts the rotation of the driving unit 10 and transmits the adjusted rotation to the screw 30. Thereby, the screw 30 is rotated by the power source of the driving unit 10 adjusted by the speed reducer 11.

< feeder >

The feeder 12 is disposed above the cylinder 20 in the-X axis direction. The feeder 12, for example, feeds a raw material 60 of particles 62 into the interior of the cylinder 20. The raw material 60 of the particles 62 is, for example, a resin or the like. The raw material 60 is not limited to the resin monomer, and may be a resin containing fibers such as glass fibers or a resin containing a pigment. The path through which the raw material 60 flows inside the cylinder 20 is referred to as a flow path 26. The raw material 60 supplied from the feeder 12 to the flow path 26 is extruded from the root of the rotating screw 30 in the direction toward the opposite tip, i.e., in the + X-axis direction. The raw material 60 is melted in the cylinder 20 by heat from the heater 15 attached to the cylinder 20 and by the action of the rotation of the screw 30, and becomes the melted raw material 60. The melted raw material 60 is fed to the die 40 through the opening on the + X axis direction side of the cylinder 20.

< charging pump, vacuum pump, heater >

The charge pump 13 adds an additive to the raw material 60. The vacuum pump 14 adjusts the flow path inside the cylinder 20 to a predetermined pressure. The heater 15 heats the raw material 60 to melt.

< cylinder body >

The cylinder block 20 is a cylindrical member extending in the X-axis direction. The cylinder 20 has a flow path 26 for flowing a raw material 60 of a bar inside. The screw 30 is accommodated in the flow path 26 of the cylinder 20. In the case where the extrusion apparatus 1 is a twin-screw extrusion apparatus, the cylinder 20 includes two

cylinders

21 and 22. The two

cylinders

21 and 22 are partially connected at their side surfaces.

Fig. 2 is a sectional view illustrating a cylinder 20 of the biaxial extrusion device according to embodiment 1. Fig. 2 shows the

screws

31 and 32 and 1 screw 30 removed from the cylinder 20 when viewed in the X-axis direction. As shown in fig. 1 and 2, in the case where the extrusion apparatus 1 is a twin-screw extrusion apparatus, the cylinder 20 includes two

cylinders

21 and 22 extending in the X-axis direction. The cylinder 21 and the cylinder 22 are arranged side by side in the Y axis direction, and the opposite side surfaces are partially removed to be combined. The cylinder 20 has a cross section orthogonal to the X-axis direction in a shape of glasses, specifically, a horizontal "8". The opposite side surfaces of the cylinder 21 and the cylinder 22 are removed. Thereby, the flow passage 26 of the cylinder 21 is integrated with the flow passage 26 of the cylinder 22.

The inner diameters of the cylinder 21 and the cylinder 22 are D. The central axes of the cylinder 21 and the cylinder 22 are denoted by C1 and C2. The distance between the central axis C1 and the central axis C2 is W. The cylinder 21 and the cylinder 22 have their opposite side surfaces partially removed and are combined, and therefore the distance W < the inner diameter D. The side surface of the cylinder 21 and the side surface of the cylinder 22 are connected to each other by an intersection L1 on the + Z-axis direction side (intersection P1 in the sectional view) and an intersection L2 on the-Z-axis direction side (intersection P2 in the sectional view). The height between the intersecting lines L1 and L2 is H. The height H is a height of the cylinder at a midpoint between the center axes C1 and C2.

< screw rod >

The screw 30 rotates about a rotation axis extending in the X-axis direction. Thereby, the screw 30 extrudes the molten material 60 in the + X axis direction. The screw 30 is disposed in the flow path 26 formed inside the cylinder 20. When the extrusion apparatus 1 is a twin-screw extrusion apparatus, two

screws

31 and 32 are arranged. The screw 31 is disposed in the flow path 26 of the cylinder 21. The screw 32 is disposed in the flow path 26 of the cylinder 22. The screw 32 rotates about a rotation axis extending in the X-axis direction at a position adjacent to the screw 31 in the Y-axis direction. For example, the screw 32 is disposed on the + Y axis direction side of the screw 31.

The rotation axis of the screw 31 is located on the central axis C1 of the cylinder 21. The rotation axis of the screw 32 is located at the central axis C2 of the cylinder 22. The

screws

31 and 32 have an elongated shape having a length and a width when viewed from the X-axis direction. The length of the screw 30 is D equal to the inner diameter of each

cylinder

21 and 22. The width of the screw 30 is denoted by d. The case where the longitudinal direction of the screw 30 is oriented in the Z-axis direction is referred to as a longitudinal direction position. The case where the width direction of the screw 30 is directed in the Z-axis direction is referred to as a lateral position. Thus, the screw 31 in fig. 2 is in the horizontal position, and the screw 32 is in the vertical position. Since the length of the screw 30 is the same as the length D of each of the

cylinders

21 and 22, the screw 32 is in the vertical position when the screw 31 is in the horizontal position. That is, the rotational phase of the screw 31 is shifted by 90 ° from the rotational phase of the screw 32. The width d, the shape of the screw 31, and the shape of the screw 32 are set so as to be rotatable in the flow path 26 of each of the

cylinders

21 and 22 with a phase shifted by 90 °. Specifically, for example, α is defined as D/D, and is set as the groove depth ratio of the screw 30. In this case, the distance W and the height H satisfy the following expressions (1) and (2).

[ number 1 ]

Number 2

Fig. 3 is a diagram illustrating a flow passage cross-sectional area of the cylinder 20 according to embodiment 1. As shown in fig. 3, when the cross-sectional area of the flow channel 26 perpendicular to the X-axis direction is defined as a flow channel cross-sectional area S, the flow channel cross-sectional area S is obtained by the following formula (3).

[ number 3 ]

S＝S1+S2 (3)

Here, the area S1 is the sum of the area of the sector from the intersection point P1 to the intersection point P2 with the central axis C1 as the center and the area of the sector from the intersection point P1 to the intersection point P2 with the central axis C2 as the center. The area S2 is an area of a rectangle surrounded by the central axis C1, the intersection P1, the central axis C2, and the intersection P2. Thus, the area S1 and the area S2 are respectively the following expression (4) and expression (5).

[ number 4 ]

[ number 5 ]

< Vent hole, pressure/thermometer >

The vent 23 discharges volatile substances, moisture, and the like generated from the raw material 60 kneaded by the rotation of the screw 30 to the outside of the cylinder 20.

The pressure/temperature gauge is attached to a predetermined position of the cylinder block 20, the wire-drawing die 40, and the like. The pressure/temperature gauge measures the pressure and temperature of the raw material 60, the melted raw material 60, the bar 61, and the like. The pressure/temperature gauge may measure the pressure and temperature of the gas or the like generated by kneading the raw material 60.

< wire-drawing die >

As shown in fig. 1, the wire-drawing die 40 is disposed on one end side of the cylinder 20, that is, on the + X axis direction side of the cylinder 20. The wire-drawing die 40 has a rectangular parallelepiped shape, for example. The die 40 has a front surface 47 on the + X-axis direction side and a rear surface 48 on the-X-axis direction side. The rear face 48 is connected to one end of the cylinder 20. An inlet 44 is formed in the rear face 48. A discharge port 45 is formed in the front face 47. Thus, the wire-drawing die 40 has: an inlet 44 into which the molten material 60 extruded from the cylinder 20 flows; a discharge port 45 for discharging the molten raw material 60 as a strand 61; and a flow path 46 through which the molten material 60 flows from the inlet 44 to the outlet 45.

Here, the cross-sectional area of the flow channel 46 perpendicular to the X-axis direction is set to the flow channel cross-sectional area S0. Thus, the flow passage cross-sectional area S0 of the flow passage 46 of the die 40 on the discharge port 45 side with respect to the tip of the screw 30 is smaller than the flow passage cross-sectional area S of the flow passage 26 of the cylinder 20. That is, the following formula (6) is satisfied.

[ number 6 ]

S0＜S (6)

Fig. 4 is a perspective view illustrating a wire-drawing die 40 according to embodiment 1. Fig. 5 is a partially cut-away perspective view illustrating a wire-drawing die 40 according to embodiment 1. Fig. 6 is a sectional view showing the wire-drawing die 40 of embodiment 1, showing a section VI-VI of fig. 4. Fig. 7 is a sectional view showing the wire-drawing die 40 of embodiment 1, showing a section VII-VII of fig. 4. As shown in fig. 4 to 7, the wire-drawing die 40 includes a die holder 41, a die head 42, and a die 43. A porous plate or a rectifying portion may be disposed between the die holder 41 and the die head 42.

As described above, the flow passage cross-sectional area S0 of the flow passage 46 of the wire-drawing die 40 is collectively referred to as the flow passage cross-sectional area S0. The cross-sectional areas of the flow paths in the die holder 41, the die head 42, and the die 43 are referred to as a flow-path cross-sectional area S41, a flow-path cross-sectional area S42, and a flow-path cross-sectional area S43, respectively.

The die holder 41 has an inlet 44 into which the melted material 60 flows. Further, the die holder 41 has a part of the flow path 46. An inflow port 44 of the die holder 41 is connected to one end of the cylinder 20. Thereby, the molten material 60 extruded from the cylinder 20 flows into the inlet 44. The raw material 60 flowing in from the inlet 44 moves in the flow path 46.

The tip portion of the screw 30 may be disposed in the flow path 46 of the die holder 41. For example, the tip of the screw 30 may be positioned closer to the cylinder 20 than the midpoint of the flow path 46 of the die holder 41 in the X-axis direction. In this case, the flow path cross-sectional area S41 of the inlet 44 may be the same as the flow path cross-sectional area S of the cylinder 20. The shape of the flow path cross-sectional area S41 of the inlet 44 may be 8-shaped, similar to the shape of the flow path cross-sectional area S of the cylinder 20. By positioning the tip of the screw 30 in the flow path 46 of the die holder 41, a decrease in the flow rate of the molten material 60 can be suppressed. Further, by positioning the tip of the screw 30 on the cylinder 20 side of the midpoint of the flow path 46 of the die holder 41, it is possible to reduce the change in the flow path cross-sectional area S0 from the die holder 41 to the discharge port 45 while suppressing the decrease in the flow rate of the raw material 60.

Preferably, the flow path cross-sectional area S41 of the die holder 41 on the discharge port 45 side is smaller on the discharge port 25 side (+ X axis direction side) than on the front end of the screw 30. That is, the flow path sectional area S41 is preferably gradually reduced toward the discharge port 45 side. This can suppress a decrease in the shear rate at the wall surface of the flow path 46. In the die holder 41, the flow path cross-sectional area S41 may be smaller toward the + X axis direction side or may be unchanged. That is, the flow path cross-sectional area A1 at the position X1 on the X axis and the flow path cross-sectional area A2 at the position X2 on the + X axis direction side of the position X1 in the flow path 46 of the die holder 41 may have a portion A1 < A2 or a portion A1= A2. But there are no portions where A1 > A2.

In the die holder 41, the cross-sectional shape of the flow path 46 may gradually change from a 8-shape to an elliptical shape as it goes toward the discharge port 45.

The die head 42 is disposed on the side of the discharge port 35 with respect to the die holder 41. Die 42 has a portion of a flow path 46. The molten raw material 60 moves in the + X-axis direction in the flow path 46. The width in the horizontal direction in the flow path 46 of the die 42 is larger toward the discharge port 45 side (+ X-axis direction side). That is, the width in the horizontal direction in the flow path 46 of the die 42 gradually increases toward the + X axis direction side. At the connection point between the die holder 41 and the die 42, the horizontal width of the flow path 46 of the die 42 is the same as the horizontal width of the flow path 46 of the die holder 41.

On the other hand, the width in the vertical direction in the flow path 46 of the die 42 decreases toward the discharge port 45 (+ X axis direction side). That is, the width in the vertical direction in the flow path 46 of the die 42 becomes narrower toward the + X axis direction side. At the connection point between the die holder 41 and the die 42, the width in the vertical direction in the flow path 46 of the die 42 is the same as the width in the vertical direction in the flow path 46 of the die holder 41.

It is preferable that the flow path sectional area S42 of the die 42 is constant in the X-axis direction. The flow path 46 of the die 42 is horizontally widened and vertically narrowed, and when the flow path cross-sectional area S42 is constant, a decrease in the shear rate can be suppressed at the wall surface of the flow path 46. The flow path cross-sectional area S42 of the die 42 is equal to or smaller than the flow path cross-sectional area S41 of the die holder 41. Specifically, at the connection point of the die holder 41 and the die 42, the flow path sectional area S42 of the die 42 is the same as the flow path sectional area of the die holder 41. The cross-sectional area S42 of the die 42 may be smaller than the cross-sectional area of the die holder 41 on the + X axis direction side of the connecting point.

The die 43 is disposed on the side of the discharge port 45 with respect to the die head 42. The die 43 has a discharge port 45 for discharging the molten material 60 as a strand 61. The die 43 has a portion of the flow path 46. The discharge port 45 is provided in plurality in parallel in the horizontal direction on the front surface 47. The flow path cross-sectional area S43 of the mold 43 is equal to or less than the flow path cross-sectional area S42 of the die 42. Specifically, at the connecting point of the die 42 and the die 43, the flow path sectional area S43 of the die 43 is the same as the flow path sectional area of the die 42. However, the flow path cross-sectional area S43 of the mold 43 may be smaller than the flow path cross-sectional area S42 of the die 42 on the + X axis direction side from the connecting point.

< comparative example >

Next, a comparative example will be described before the effects of the present embodiment are described. Next, the effects of the present embodiment will be described in comparison with comparative examples. Fig. 8 is a partially cut-away perspective view illustrating a wire-drawing die 140 of a comparative example. Fig. 9 is a sectional view illustrating a wire-drawing die 140 of a comparative example. Fig. 10 is a sectional view illustrating a wire-drawing die 140 of a comparative example. As shown in fig. 8 to 10, the wire-drawing die 140 includes a die holder 141, a die head 142, and a die 143. A porous plate 149 may be disposed between the die holder 141 and the die head 142.

The inlet 144, the outlet 145, the flow path 146, the front face 147 and the rear face 148 in the drawing die 140 of the comparative example correspond to the inlet 44, the outlet 45, the flow path 46, the front face 47 and the rear face 48 in the drawing die 40 of embodiment 1.

In the comparative example, there is a portion in the flow path 146 of the die 140, which is located closer to the discharge port 145 than the tip of the screw 30, and which has a larger flow path sectional area S140 than the flow path of the cylinder 20. For example, a flow path sectional area S141 of a part of the flow path 146 of the die holder 141 is larger than the flow path sectional area S of the cylinder 20. Further, a flow path sectional area S142 of a part of the flow path 146 of the die head 142 is larger than the flow path sectional area S of the cylinder 20.

Specifically, for example, a porous plate 149 is disposed between the die holder 141 and the die head 142 to filter foreign matters mixed in the molten raw material 60. The perforated plate 149 comprises a mesh of small holes. In the comparative example, in order to secure the filtration area by the porous plate 149, the porous plate 149 and the flow path cross-sectional areas S141 and S142 before and after the porous plate 149 were increased. Therefore, the flow path sectional area S140 of the wire-drawing die 140 has a portion larger than the flow path sectional area S of the cylinder 20.

When the flow passage sectional area S140 of the wire-drawing die 140 is larger than the flow passage sectional area S of the cylinder 20, the flow velocity (shear velocity) in the flow passage 146 of the wire-drawing die 140 decreases. This causes the material 60 to have very low fluidity and to be retained on the wall surface of the flow path 146. This causes thermal degradation of the raw material 60, resulting in deterioration of the quality of the strand 61.

Next, the effects of the present embodiment will be described. In the extrusion apparatus 1 including the cylinder 20 and the screw 30, the screw 30 is rotated to convey a raw material 60 in which a resin or the like is melted in an axial direction. In the cylinder 20, the raw material 60 hardly remains due to the high shear velocity caused by the rotation of the screw 30, and thermal degradation of the resin is less likely to occur.

On the other hand, the die 40 is attached to the front ends of the cylinder 20 and the screw 30. Therefore, the portion of the die 40 that is forward of the tip of the screw 30 does not have a high shear velocity caused by the rotation of the screw 30. The die 40 thus produces only a pressure flow which flows purely in the axial direction. Therefore, as in the comparative example, the larger the flow passage cross-sectional area S140 of the wire-drawing die 140, the lower the shear rate. The resin fluid exhibiting low fluidity easily stays on the wall surface of the flow path 146, absorbs heat energy generated by the heater attached to the drawing die 140, and causes thermal degradation (degradation in quality due to a decrease in molecular weight, discoloration, and the like).

In contrast, in the present embodiment, the flow passage cross-sectional area S0 of the flow passage 46 of the die 40 on the discharge port 45 side with respect to the tip of the screw 30 is smaller than the flow passage cross-sectional area S of the flow passage 26 of the cylinder 20. That is, the flow path sectional area S0 located closer to the discharge port 45 than the tip of the screw 30 is smaller than the flow path sectional area S at any position. This prevents the flow velocity (shear velocity) of the raw material 60 in the flow path 46 from decreasing. As described above, in the present embodiment, the shear rate in the flow path 46 of the die 40 can be increased. Therefore, the stagnation of the raw material 60 on the wall surface of the flow path 46 can be suppressed. This can suppress thermal deterioration of the raw material 60 and improve the quality of the strand 61. In this case, the pressure loss may be increased due to a decrease in the filtration area of the porous plate. Alternatively, however, the flow regulating portion may be used without using a porous plate including meshes by sufficiently performing the foreign matter mixing management of the raw material 60.

[ TABLE 1 ]

Table 1 shows examples of yellowing (Yellow Index, YI) of the resin when strands 61 were formed using the dies 140 and 40 of comparative example and embodiment 1. For example, the drawing dies 140 and 40 shown in comparative example and embodiment 1 were attached to one end of the biaxial extrusion device having a diameter D =69 2 [ mm ] of the cylinder 20, and a test of extruding polyamide 6 at 300[ kg/h ] was performed as the raw material 60. The temperature of the discharged bar 61 was set to about 280 c, and the temperature of the wire-drawing dies 140 and 40 by the heater 15 was set to 280 c. In order to particularly promote the oxidative deterioration of the resin, it is assumed that the raw material 60 of the resin is supplied to the biaxial extrusion device and oxygen is blown into the biaxial extrusion device so as to increase the oxygen concentration in the biaxial extrusion device.

As shown in Table 1, in the case of forming the bar 61 using the drawing die 140 of the comparative example, YI was 2.6, 3.3, 6.1, 8.5 and 12.6 at running times of 60, 120, 180, 240 and 300[ min ], respectively. In the die 140 of the comparative example, at the beginning of the start of extrusion, the resin which was transparent and in which no foreign matter was mixed was discharged. However, yellowing was observed with the lapse of time. The value rose after 3 hours by YI analysis and then gradually increased. As described above, in the case of the comparative example, YI is larger as the operation time is longer. After the experiment, the die 140 was disassembled, and a resin deposit discolored to a tan color was observed on the wide wall surface of the flow path 146.

On the other hand, in the case of forming the strand 61 using the die 40 of embodiment 1, YI is 2.2, 3.4, 3.2, 4.0 and 3.9 at running times of 60, 120, 180, 240 and 300[ min ], respectively. In the wire-drawing die 40 according to embodiment 1, no yellowing resin was discharged in 5 hours from the start to the end of the experiment. As described above, in embodiment 1, YI is almost unchanged even if the operating time increases. After the completion of the experiment, the die 40 was disassembled to check the flow path 46, and it was confirmed that no yellowing resin was accumulated and that smooth resin flow was also achieved in the die 40.

Next, the results of flow analysis using the wire-drawing dies 140 and 40 of comparative example and embodiment 1 will be described. Fig. 11 is a diagram illustrating the shear rate in the flow path 146 of the wire-drawing die 140 of the comparative example. Fig. 12 is a diagram illustrating the shear rate in the flow path 46 of the wire-drawing die 40 according to embodiment 1. In fig. 11 and 12, darker indicates a smaller shear rate.

As shown in FIG. 11, the three-dimensional flow analysis in the channel 146 was performed under the extrusion condition of 300[ 2 ], [ kg/h ] using the drawing die 140 of the comparative example, and as a result, the channel was widened by taking the filtration area of the porous plate 149 into account, and a portion where the shear rate of the wall surface of the channel 146 became 1[1/sec ] or less was observed. This indicates that the analysis performed by changing the porous plate 149 to the rectifying portion also shows the same wall shear rate, and as a result, the resin is likely to accumulate in the enlarged flow path 46.

On the other hand, as shown in fig. 12, the three-dimensional flow analysis in the flow channel 46 was performed under the same extrusion conditions as in the comparative example using the wire-drawing die of embodiment 1, and as a result, the shear rate of the wall surface of the flow channel 46 was secured over the entire range of 5[1/sec ] or more. Therefore, the retention of the wall surface raw material 60 can be suppressed, and the deterioration of the resin due to the application of excessive heat can be suppressed.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. Such variations are not to be regarded as a departure from the scope of the technical spirit of the disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

1. An extrusion apparatus, comprising:

a cylindrical cylinder extending in one direction and having a flow path through which a raw material of the bar flows;

a wire-drawing die having an inlet port disposed on one end side of the cylinder and into which the raw material extruded from the cylinder flows, an outlet port from which the raw material is discharged as a strand, and a flow path from the inlet port to the outlet port through which the raw material flows; and

a screw that rotates about a rotation axis extending in the one direction to extrude the raw material toward a discharge port,

if the cross-sectional area of the flow path orthogonal to the one direction is defined as a flow path cross-sectional area,

the flow path sectional area in the flow path of the wire-drawing die on the discharge port side compared with the leading end of the screw is smaller than the flow path sectional area in the flow path of the cylinder.

2. Extrusion apparatus according to claim 1,

the wire-drawing die comprises:

a die holder having the inflow port;

a die head disposed on the discharge port side of the die holder; and

a die having the discharge port and disposed on the discharge port side of the die head,

the flow path cross-sectional area of the mold is equal to or less than the flow path cross-sectional area of the die head,

the flow path cross-sectional area of the die head is equal to or less than the flow path cross-sectional area of the die holder.

3. Extrusion apparatus according to claim 2,

a plurality of the discharge ports are arranged side by side in a horizontal direction orthogonal to the one direction,

the width in the horizontal direction in the flow path of the die is larger closer to the discharge port side,

the width in the vertical direction in the flow path of the die is smaller toward the discharge port,

the flow path sectional area of the die is constant in the one direction.

4. Extrusion apparatus according to claim 2 or 3,

the flow path cross-sectional area of the flow path of the die holder on the discharge port side relative to the tip of the screw is smaller toward the discharge port side.

5. Extrusion apparatus according to claim 2 or 3,

the front end of the screw is located on the cylinder side with respect to a midpoint in the one direction of the flow path of the die holder.

6. A die for wire drawing, characterized in that a screw is disposed on one end side of a cylindrical cylinder, wherein the cylinder extends in one direction and has a flow path through which a material for a strand flows, and the screw rotates about a rotation shaft extending in the one direction, the die comprising: an inflow port into which the raw material extruded from the cylinder by the screw flows; an outlet for discharging the raw material as a strand; and a flow path through which the raw material flows from the inlet to the outlet,

the flow path sectional area at the discharge port side in the flow path of the die, which is located in comparison with the leading end of the screw, is smaller than the flow path sectional area at the flow inlet.

7. The wire-drawing die of claim 6, comprising:

a die holder having the inflow port;

a die head disposed on the discharge port side of the die holder;

8. Die according to claim 7,

the flow path sectional area of the die is constant in the one direction.

9. Die according to claim 7 or 8,

the cross-sectional area of the flow path on the discharge port side in the flow path of the die holder is smaller as it is closer to the discharge port side than the tip of the screw.

10. Die according to claim 7 or 8,