KR20220158616A - Extruder and strand die - Google Patents

Abstract

Provide are an extrusion device and a strand die capable of improving the quality of strands. The extrusion device (1) according to one embodiment includes: a tubular cylinder (20) extending in one direction and having a flow path (26) through which a raw material (60) of a strand (61) flows; a strand die (40) disposed on one end side of the cylinder (20) and having an inlet (44) through which the raw material (60) extruded from the cylinder (20) flows in, an outlet (45) through which the raw material (60) is discharged as the strand (61), and a flow path (46) through which the raw material (60) flows from the inlet (44) to the outlet (45); and a screw (30) which extrudes the raw material (60) toward the outlet (45) by rotating about a rotation shaft extending in one direction. If the cross-sectional area of the flow paths (26, 46) perpendicular to one direction is considered as a flow path cross-sectional area, the flow path cross-sectional area on the outlet (45) side of the strand die (40), compared to the tip of the screw (30) in the flow path (46), is smaller than the flow path cross-sectional area of the flow path (46) in the cylinder (20). The present invention can suppress the retention of the raw material (60) on a wall surface.

Description

Extruder and strand die {EXTRUDER AND STRAND DIE}

The present invention relates to an extruder and a strand die.

Patent Literature 1 describes an extruder equipped with a strand die that extrudes molten resin as strands. In the extrusion device of Patent Literature 1, the resin flow path has a reverse taper shape that expands toward the discharge port.

Japanese Unexamined Patent Publication No. 2012-232432

The strand die mounted at the tip of the extruder may be equipped with a breaker plate comprising a fine mesh to filter foreign matter. In this case, in order to secure the filtration area, the area of the breaker plate is widened. As a result, the resin passage has a portion whose diameter extends toward the discharge port.

Normally, when the diameter of the passage is enlarged, the flow rate (shear rate) decreases. A resin with strong non-Newtonian properties tends to remain on the wall surface due to extremely low fluidity when the shear rate is low. Then, the amount of heat (thermal energy) from the heater increases, causing thermal deterioration such as molecular weight reduction, and the quality of the strand deteriorates.

Other problems and new features will become apparent from the description of this specification and the accompanying drawings.

Extrusion apparatus according to one embodiment, a cylindrical cylinder extending in one direction having a flow path through which the raw material of the strand flows, disposed on one end side of the cylinder, an inlet through which the raw material extruded from the cylinder flows in , A strand die having a discharge port for discharging the raw material as a strand, and a flow path through which the raw material flows from the inlet to the discharge port, and a screw for extruding the raw material toward the discharge port by rotating about a rotating shaft extending in one direction, . smaller than

Strand die according to one embodiment is disposed on one end side of a cylindrical cylinder extending in one direction having a flow path through which the raw material of the strand flows, by a screw rotating around a rotating shaft extending in the one direction, from the cylinder A strand die having an inlet through which the extruded raw material flows, a discharge port through which the raw material is discharged as a strand, and a flow path through which the raw material flows from the inlet to the discharge port, and when the cross-sectional area of the flow path orthogonal to the one direction is the flow channel cross-sectional area , The cross-sectional area of the passage on the discharge port side is smaller than the cross-sectional area of the passage at the inlet port than the tip of the screw in the passage of the strand die.

According to the above one embodiment, it is possible to provide an extrusion device and a strand die capable of improving the quality of a strand. The above and other objects, features and advantages of the present disclosure will be more fully understood from the detailed description and drawings given below. The detailed description and drawings given below are provided for purposes of illustration and should not be considered as limiting the present disclosure.

1 is a side view illustrating the configuration of an extrusion device according to Embodiment 1;
2 is a cross-sectional view illustrating a cylinder of the twin-screw extrusion device according to Embodiment 1;
3 is a diagram illustrating a passage cross-sectional area of a cylinder according to Embodiment 1;
4 is a perspective view illustrating a strand die according to Embodiment 1;
5 is a partial cross-sectional perspective view illustrating a strand die according to Embodiment 1;
Fig. 6 is a cross-sectional view illustrating a strand die according to Embodiment 1, and shows a cross section of VI-VI in Fig. 4;
Fig. 7 is a cross-sectional view illustrating a strand die according to Embodiment 1, showing a cross section VII-VII in Fig. 4;
8 is a partial cross-sectional perspective view illustrating a strand die according to a comparative example;
9 is a cross-sectional view illustrating a strand die according to a comparative example;
10 is a cross-sectional view illustrating a strand die according to a comparative example;
11 is a diagram illustrating the shear rate in the flow path of the strand die according to the comparative example,
12 is a diagram illustrating the shear rate in the passage of the strand die according to the first embodiment.

For clarity of explanation, the following descriptions and drawings are appropriately omitted and simplified. In addition, in each figure, the same code|symbol is attached|subjected to the same element, and overlapping description is abbreviate|omitted as needed.

(Embodiment 1)

An extrusion device according to Embodiment 1 will be described. 1 is a side view illustrating the configuration of an extrusion device according to Embodiment 1. FIG. A part of FIG. 1 is shown in cross section. As shown in FIG. 1, the extrusion device 1 includes a drive unit 10, a reducer 11, a feeder 12, a liquid addition pump 13, a vacuum pump 14, a heater 15, A cylinder 20, a vent hole 23, a screw 30, and a strand die 40 are provided. In addition, the extrusion device 1 is equipped with a thermometer and a pressure gauge for measuring the temperature and pressure of the cylinder 20 and the strand die 40 at predetermined positions. The extruding device 1 may further include a strand bus 50 and a strand cutter 51 . The extrusion apparatus 1 extrudes the raw material 60 in which resin etc. melt|melted from the strand die 40, and forms the strand 61. The formed strand 61 is cooled by the strand bus 50 . After that, the strand 61 is cut by the strand cutter 51 to become a pellet 62 .

At this time, for convenience of description of the extrusion device 1, an XYZ Cartesian coordinate axis system is introduced. For example, one direction in which the cylinder 20 extends is the X-axis direction, and two directions orthogonal to the X-axis direction are the Y-axis direction and the Z-axis direction. For example, the Z-axis direction is a vertical direction, and the XY plane is a horizontal plane. In addition, the +Z-axis direction is upward. The end of the cylinder 20 on the +X-axis direction side is called one end, and the end of the cylinder 20 on the -X-axis direction side is called the other end. The direction in which the raw material 60 melted in the extrusion device 1 is extruded is the +X-axis direction. In the following, each configuration is described.

<Drive unit, reducer>

The drive unit 10 is disposed on the other end side of the cylinder 20, that is, on the -X axis direction side of the cylinder 20. The drive unit 10 rotates the screw 30 . When the extrusion device 1 is a twin-screw extrusion device, the driving unit 10 rotates the screws 31 and 32 . In addition, the extrusion device 1 is not limited to a twin-screw extrusion device, and may be a multi-screw extrusion device or a single-screw extrusion device. In addition, the screws 31 and 32 are generically called the screw 30.

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

＜Feeder＞

The feeder 12 is disposed above the cylinder 20 on the -X axis direction side. The feeder 12 throws in the raw material 60 of the pellet 62 into the inside of the cylinder 20, for example. The raw material 60 of the pellet 62 is resin etc., for example. In addition, the raw material 60 is not limited to a single resin, and may be a resin containing fibers such as glass fibers or a resin containing a pigment. A passage through which the raw material 60 flows inside the cylinder 20 is called a flow path 26 . The raw material 60 supplied from the feeder 12 to the flow path 26 is extruded in a direction from the root of the rotating screw 30 to the opposite tip, that is, in the +X-axis direction. The raw material 60 is melted inside the cylinder 20 by heat from the heater 15 installed in the cylinder 20 and the action accompanying the rotation of the screw 30, and turns into the melted raw material 60. It changes. The molten raw material 60 is sent to the strand die 40 through the opening of the cylinder 20 on the +X-axis direction side.

<Aqueduct pump, vacuum pump, heater>

The liquid addition pump 13 adds additives 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 so as to melt it.

＜Cylinder＞

The cylinder 20 is a tubular member extending in the X-axis direction. The cylinder 20 has a flow path 26 in which the raw material 60 of the strand flows. A screw 30 is accommodated in the passage 26 of the cylinder 20 . When the extrusion device 1 is a twin screw extrusion device, the cylinder 20 includes two cylinders 21 and a cylinder 22 . The two cylinders 21 and 22 have a shape in which side surfaces partially connected.

Fig. 2 is a cross-sectional view illustrating the cylinder 20 of the twin-screw extrusion device according to the first embodiment. In FIG. 2, the screw 31 and the screw 32 seen from the X-axis direction, and one screw 30 separated from the cylinder 20 are shown. As shown in FIGS. 1 and 2 , when the extrusion device 1 is a twin-screw extrusion device, the cylinder 20 includes two cylinders 21 and a cylinder 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 opposing side surfaces are partially removed and combined. A cross section orthogonal to the X-axis direction of the cylinder 20 is shaped like a spectacle, and specifically has a shape of the letter "8" tilted sideways. However, the sides on which the cylinders 21 and 22 are opposed are removed. Therefore, the flow path 26 of the cylinder 21 and the flow path 26 of the cylinder 22 are integrated.

Let D be the inner diameter of the cylinder 21 and the cylinder 22. Also, the central axes of the cylinder 21 and the cylinder 22 are C1 and C2. Let W be the distance between the central axis C1 and the central axis C2. Since the cylinder 21 and the cylinder 22 are united by partially removing the opposing side surfaces, the distance W < the inner diameter D is satisfied. The side surface of the cylinder 21 and the side surface of the cylinder 22 are connected by intersection L1 (intersection P1 in the cross-sectional view) on the +Z-axis direction side and intersection L2 (intersection P2 in the cross-sectional view) on the -Z-axis direction side. Let H be the height between the intersection line L1 and the intersection line L2. The height H is the height of the cylinder at the midpoint between the central axis C1 and the central axis C2.

<Screw>

The screw 30 rotates around a rotation axis extending in the X-axis direction. With this, the screw 30 pushes the molten raw material 60 toward the +X-axis direction. The screw 30 is disposed in a flow passage 26 formed inside the cylinder 20 . When the extrusion device 1 is a twin-screw extrusion device, two screws 31 and a screw 32 are arranged. The screw 31 is disposed in the flow passage 26 of the cylinder 21 . The screw 32 is disposed in the flow passage 26 of the cylinder 22 . The screw 32 rotates around 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 axis of rotation of the screw 31 is located on the central axis C1 of the cylinder 21 . The axis of rotation of the screw 32 is located on the central axis C2 of the cylinder 22. When the screw 31 and the screw 32 are viewed in the X-axis direction, they have an elongated shape having a length and a width. 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 d. A case in which the longitudinal direction of the screw 30 is directed toward the Z-axis direction is referred to as a vertical position. A case in which the width direction of the screw 30 is directed toward the Z-axis direction is referred to as a horizontal position. Then, the screw 31 in FIG. 2 is in a horizontal position, and the screw 32 is in a vertical position. Since the length of the screw 30 is equal to the length D of each of the cylinders 21 and 22, when the screw 31 is in a transverse position, the screw 32 assumes a longitudinal position. That is, the rotational phase of the screw 31 and the rotational phase of the screw 32 are shifted by 90°. In addition, the width d and the shape of the screw 31 and the screw 32 are set to be rotated in the passage 26 of the cylinders 21 and 22 with a phase shifted by 90°. Specifically, for example, α is defined as D/d, and the groove depth ratio of the screw 30 is defined. In this case, the distance W and the height H satisfy the following expressions (1) and (2).

[Equation 1]

[Equation 2]

FIG. 3 is a diagram illustrating a passage cross-sectional area of the cylinder 20 according to Embodiment 1. As shown in FIG. As shown in Fig. 3, when the cross-sectional area of the flow passage 26 orthogonal to the X-axis direction is denoted as the flow passage cross-sectional area S, the flow passage cross-sectional area S is obtained by the following equation (3).

[Equation 3]

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

[Equation 4]

[Equation 5]

<Vent hole, pressure/thermometer>

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

The pressure/thermometer is attached to a predetermined position such as the cylinder 20 and the strand die 40. The pressure/thermometer measures the pressure and temperature of the raw material 60, the molten raw material 60, the strand 61, and the like. The pressure/thermometer may measure the pressure and temperature of gas or the like generated by kneading of the raw material 60 .

<Strand die>

As shown in FIG. 1, the strand die 40 is arrange|positioned at one end side of the cylinder 20, ie, the +X-axis direction side of the cylinder 20. Strand die 40 is rectangular parallelepiped shape, for example. The strand 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 surface 48 is connected to one end of the cylinder 20. An inlet 44 is formed on the rear surface 48 . A discharge port 45 is formed on the front surface 47 . Therefore, the strand die 40 has an inlet 44 into which the molten raw material 60 extruded from the cylinder 20 flows in, an outlet 45 for discharging the molten raw material 60 as a strand 61, and , and a flow path 46 through which the molten raw material 60 flows from the inlet 44 to the discharge port 45.

At this time, the cross-sectional area of the channel 46 orthogonal to the X-axis direction is referred to as the channel cross-sectional area S0. Then, the passage cross-sectional area S0 on the discharge port 45 side is smaller than the tip of the screw 30 in the passage 46 of the strand die 40 than the passage cross-sectional area S in the passage 26 of the cylinder 20 . That is, the following formula (6) is satisfied.

[Equation 6]

4 is a perspective view illustrating the strand die 40 according to the first embodiment. 5 is a partially sectional perspective view illustrating the strand die 40 according to the first embodiment. FIG. 6 is a cross-sectional view illustrating the strand die 40 according to Embodiment 1, and shows a cross-section of VI-VI in FIG. 4 . Fig. 7 is a cross-sectional view illustrating the strand die 40 according to Embodiment 1, and shows a cross-section of VII-VII in Fig. 4 . As shown in Figs. 4 to 7, the strand die 40 includes a die holder 41, a die head 42, and a die 43. Further, between the die holder 41 and the die head 42, a breaker plate or straight ring may be disposed.

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

The die holder 41 has an inlet 44 through which the molten raw material 60 flows. In addition, the die holder 41 has a part of the flow path 46 . The inlet 44 of the die holder 41 is connected to one end of the cylinder 20 . Therefore, the molten raw material 60 extruded from the cylinder 20 flows into the inlet 44 . The raw material 60 flowing in from the inlet 44 moves through the flow path 46 .

The distal end of the screw 30 may be disposed in the passage 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 channel 46 of the die holder 41 in the X-axis direction. In this case, the passage cross-sectional area S41 of the inlet 44 may be the same as the passage cross-sectional area S of the cylinder 20 . Further, the shape of the passage cross-sectional area S41 of the inlet 44 may be a figure 8 shape similarly to the shape of the passage 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 raw material 60 can be suppressed. Further, by positioning the tip of the screw 30 closer to the cylinder 20 than the midpoint of the flow path 46 of the die holder 41, the flow rate of the raw material 60 is suppressed and at the same time, the die holder 41 It is possible to smooth out the change in the flow passage cross-sectional area S0 from the discharge port 45 to the discharge port 45.

It is preferable that the passage cross-sectional area S41 on the discharge port 45 side is smaller than the distal end of the screw 30 in the flow passage of the die holder 41 toward the discharge port 25 side (in the +X-axis direction side). That is, it is preferable that the passage cross-sectional area S41 gradually decreases toward the discharge port 45 side. In this way, a decrease in the shear rate on the wall surface of the flow path 46 can be suppressed. Further, in the die holder 41, the channel cross-sectional area S41 may have a smaller portion or a portion that does not change as it moves toward the +X-axis direction. That is, the flow passage cross-sectional area A1 at the position X1 on the X axis in the flow passage 46 of the die holder 41 and the flow passage cross-sectional area A2 at the position X2 on the +X-axis direction side of the position X1 are It is good, and there may be a part of A1=A2. However, there is no part where A1 > A2.

In the die holder 41, the shape of the cross section of the flow path 46 may gradually change from a figure 8 shape to an elliptical shape toward the discharge port 45 side.

The die head 42 is disposed on the discharge port 35 side rather than the die holder 41 . Die head 42 has a portion of flow path 46 . The molten raw material 60 moves along the flow path 46 in the +X-axis direction. The horizontal width of the flow path 46 of the die head 42 is larger toward the discharge port 45 (+X-axis direction side). That is, the horizontal width of the flow path 46 of the die head 42 gradually widens toward the +X-axis direction side. Further, at the connection point between the die holder 41 and the die head 42, the horizontal width of the flow path 46 of the die head 42 is the width of the flow path 46 of the die holder 41. equal to the width in the horizontal direction.

On the other hand, the width in the vertical direction of the flow path 46 of the die head 42 is smaller toward the discharge port 45 side (+X-axis direction side). That is, the width in the vertical direction of the flow path 46 of the die head 42 becomes narrower toward the +X-axis direction side. Further, at the connection point between the die holder 41 and the die head 42, the width in the vertical direction of the flow path 46 of the die head 42 is It is equal to the width in the vertical direction.

It is preferable that the channel cross-sectional area S42 of the die head 42 is constant in the X-axis direction. The flow path 46 of the die head 42 widens in the horizontal direction and narrows in the vertical direction, but if the flow path cross-sectional area S42 is constant, the decrease in shear rate on the wall surface of the flow path 46 can be suppressed. . The passage cross-sectional area S42 of the die head 42 is equal to or smaller than the passage cross-sectional area S41 of the die holder 41 . Specifically, at the connection point between the die holder 41 and the die head 42, the cross-sectional area of the passage S42 of the die head 42 is equal to the cross-sectional area of the passage of the die holder 41. On the +X-axis direction side of the connection point, the cross-sectional area of the passage S42 of the die head 42 may be smaller than the cross-sectional area of the passage of the die holder 41 .

The die 43 is disposed on the discharge port 45 side rather than the die head 42 . The die 43 has a discharge port 45 through which the molten raw material 60 is discharged as strands 61 . Die 43 has a portion of flow path 46 . A plurality of discharge ports 45 are arranged horizontally on the front surface 47 . The passage cross-sectional area S43 of the die 43 is equal to or smaller than the passage cross-sectional area S42 of the die head 42 . Specifically, at the connection point between the die head 42 and the die 43, the cross-sectional area of the passage S43 of the die 43 is equal to the cross-sectional area of the passage of the die head 42. However, the channel cross-sectional area S43 of the die 43 on the +X-axis direction side of the connection point may be smaller than the channel cross-sectional area S42 of the die head 42 .

<Comparison example>

Next, before explaining the effects of the present embodiment, a comparative example will be described. After that, the effect of the present embodiment will be described by contrasting with a comparative example. 8 is a partial cross-sectional perspective view illustrating a strand die 140 according to a comparative example. 9 is a cross-sectional view illustrating a strand die 140 according to a comparative example. 10 is a cross-sectional view illustrating a strand die 140 according to a comparative example. As shown in FIGS. 8-10, the strand die 140 includes the die holder 141, the die head 142, and the die|dye 143. A breaker plate 149 may be disposed between the die holder 141 and the die head 142 .

The inlet 144, the discharge port 145, the flow path 146, the front surface 147, and the rear surface 148 in the strand die 140 of the comparative example are the inlet ports in the strand die 40 of Embodiment 1 ( 44), the discharge port 45, the flow path 46, the front surface 47 and the rear surface 48.

In the comparative example, the passage cross-sectional area S140 on the discharge port 145 side is greater than the tip of the screw 30 in the passage 146 of the strand die 140 is larger than the passage cross-sectional area S in the passage of the cylinder 20 there is a part For example, the passage sectional area S141 of a portion of the passage 146 of the die holder 141 is larger than the passage sectional area S of the cylinder 20 . In addition, the passage cross-sectional area S142 of a portion of the passage 146 of the die head 142 is larger than the passage cross-sectional area S of the cylinder 20 .

Specifically, for example, a breaker plate 149 is disposed between the die holder 141 and the die head 142 in order to filter foreign matter mixed into the molten raw material 60 . The breaker plate 149 includes a fine mesh. In the comparative example, in order to secure the filtration area by the breaker plate 149, the breaker plate 149 and the passage cross-sectional areas S141 and S142 in front and behind the breaker plate 149 are increased. Therefore, the channel cross-sectional area S140 of the strand die 140 has a larger portion than the channel cross-sectional area S of the cylinder 20 .

When the channel cross-sectional area S140 of the strand die 140 is larger than the channel cross-sectional area S of the cylinder 20, the flow rate (shear rate) in the channel 146 of the strand die 140 decreases. As a result, the fluidity of the raw material 60 is extremely reduced, and it stays on the wall surface of the flow path 146 . Then, thermal deterioration of the raw material 60 is caused, and quality deterioration of the strand 61 occurs.

Next, effects of this embodiment will be described. In general, in the extrusion apparatus 1 composed of the cylinder 20 and the screw 30, the screw 30 rotates to convey the raw material 60 in which resin or the like is melted in the axial direction. In the cylinder 20, the raw material 60 hardly stays due to the high shear rate generated by the rotation of the screw 30, and thermal deterioration of the resin is relatively less likely to occur.

On the other hand, the strand die 40 is attached to the tip of the cylinder 20 and the screw 30. Therefore, the action of the high shear rate by the rotation of the screw 30 does not arise in the part ahead of the tip of the screw 30 in the strand die 40. Therefore, only the pressure flow flowing in the axial direction is generated in the strand die 40 . Therefore, as in the comparative example, the shear rate decreases as the channel cross-sectional area S140 of the strand die 140 increases. The resin fluid exhibiting low fluidity tends to stay on the wall surface of the flow path 146 and absorbs thermal energy by the heater mounted on the strand die 140, thereby preventing thermal degradation (quality degradation due to molecular weight reduction, discoloration, etc.) cause

On the other hand, in the present embodiment, the channel cross-sectional area S0 on the side of the discharge port 45 rather than the tip of the screw 30 in the channel 46 of the strand die 40 is in the channel 26 of the cylinder 20 is smaller than the passage cross-sectional area S of That is, the passage cross-sectional area S0 on the discharge port 45 side is smaller than the flow passage cross-sectional area S at any position relative to the tip of the screw 30 . Therefore, the flow rate (shear rate) of the raw material 60 in the flow path 46 does not decrease. In this way, in this embodiment, the shear rate in the flow path 46 of the strand die 40 can be raised. Therefore, it is possible to suppress the raw material 60 from being stagnant on the wall surface of the flow path 46 . Thereby, thermal deterioration of the raw material 60 can be suppressed and the quality of the strand 61 can be improved. Also, in this case, the filtration area of the breaker plate may be narrowed and the pressure loss may increase. However, adopting a straight ring and not using a breaker plate including a mesh is also an option by sufficiently managing contamination of the raw material 60 and the like.

Driving time [min] 60 120 180 240 300 YI of Comparative Example 2.6 3.3 6.1 8.5 12.6 YI of Embodiment 1 2.2 3.4 3.2 4.0 3.9

Table 1 is a table exemplifying the yellowing (Yellow Index, YI) of the resin at the time of forming the strand 61 using the strand dies 140 and 40 according to the comparative example and the first embodiment. For example, the strand dies 140 and 40 shown in Comparative Example and Embodiment 1 are attached to one end of a twin-screw extruder having a diameter D = 69 [mm] of the cylinder 20, and poly A test was conducted in which amide (6) was extruded at 300 [kg/h]. The temperature of the discharged strand 61 was about 280 [°C], and the temperature setting by the heater 15 of the strand dies 140 and 40 was 280 [°C]. Further, in order to accelerate the oxidative degradation of the resin, the raw material 60 for the resin was supplied into the twin-screw extrusion device and oxygen was simultaneously blown into the twin-screw extrusion device to increase the oxygen concentration in the twin-screw extrusion device.

As shown in Table 1, when the strand 61 is formed using the strand die 140 of the comparative example, when the operating time is 60, 120, 180, 240 and 300 [min], YI is, 2.6, 3.3, 6.1, 8.5 and 12.6, respectively. In the strand die 140 of the comparative example, resin that is transparent and does not show contamination of foreign matter is discharged at the beginning of extrusion. However, yellowing is observed over time. As a result of analyzing YI, the value rises after 3 hours and then gradually increases. In this way, in the case of the comparative example, YI increases as the driving time increases. As a result of disassembling the strand die 140 after the end of the experiment, it was confirmed that resin discolored to yellowish brown was deposited on the wide wall surface of the channel 146.

On the other hand, in the case where the strand 61 is formed using the strand die 40 of Embodiment 1, when the operating times are 60, 120, 180, 240 and 300 [min], YI is 2.2 and 3.4, respectively , 3.2, 4.0 and 3.9. In the strand die 40 of Embodiment 1, ejection of yellowed resin was not recognized in 5 hours from the start of the experiment to the end. Thus, in the case of Embodiment 1, YI hardly changes even if the driving time is long. When the flow path 46 was confirmed by disassembling the strand die 40 after the end of the experiment, it was confirmed that the yellowed resin was not deposited and that the resin flowed smoothly also in the strand die 40.

Next, the results of flow analysis using the strand dies 140 and 40 according to Comparative Example and Embodiment 1 will be described. 11 is a diagram illustrating the shear rate in the flow path 146 of the strand die 140 according to the comparative example. FIG. 12 is a diagram illustrating the shear rate in the flow path 46 of the strand die 40 according to the first embodiment. 11 and 12, the darker the color, the smaller the shear rate.

As shown in FIG. 11, in the result of performing a three-dimensional flow analysis in the flow path 146 under the extrusion condition of 300 [kg / h] using the strand die 140 of the comparative example, in the breaker plate 149 Since the flow path is widened to obtain a filtration area, a portion where the shear rate of the wall surface of the flow path 146 becomes 1 [1/sec] or less is visible. This suggests that even if an analysis in which the breaker plate 149 is changed to a straight ring is performed, the same wall shear rate is shown, and as a result, it is easy for the resin to linger in the portion of the enlarged flow path 46.

On the other hand, as shown in FIG. 12, in the result of performing a three-dimensional flow analysis in the passage 46 under the same extrusion conditions as in the comparative example using the strand die of Embodiment 1, the shear rate of the wall surface of the passage 46 secures more than 5 [1/sec] in the entire area. Therefore, retention of the raw material 60 on the wall surface can be suppressed, and deterioration of the resin due to application of an excessive amount of heat can be suppressed.

It goes without saying that this invention is not limited to the said embodiment, and various changes are possible in the range which does not deviate from the summary. Such changes should not be regarded as a departure from the scope of the technical idea of the present disclosure, and all modifications that would be apparent to those skilled in the art are intended to be included within the scope of the following claims.

Claims (10)

A cylindrical cylinder extending in one direction having a flow path through which the raw material of the strand flows;
A strand die disposed on one end side of the cylinder and having an inlet through which the raw material extruded from the cylinder flows in, a discharge hole through which the raw material is discharged as a strand, and a flow path through which the raw material flows from the inlet to the discharge port. ,
A screw for extruding the raw material toward the discharge port as it rotates around the rotating shaft extending in the one direction,
If the cross-sectional area of the flow path orthogonal to the one direction is the flow path cross-sectional area,
The extrusion apparatus, wherein a cross-sectional area of the passage on the discharge port side is smaller than the cross-sectional area of the passage in the passage of the cylinder than the tip of the screw in the passage of the strand die.
According to claim 1,
The strand die,
a die holder having the inlet;
a die head disposed on the discharge port side of the die holder;
a die arranged closer to the discharge port than the die head and having the discharge port;
The passage cross-sectional area of the die is less than or equal to the passage cross-sectional area of the die head,
The cross-sectional area of the passage of the die head is less than or equal to the cross-sectional area of the passage of the die holder.
According to claim 2,
The discharge ports are arranged in plurality in a horizontal direction orthogonal to the one direction,
The horizontal width of the flow path of the die head is larger toward the discharge port;
A width in the vertical direction of the flow path of the die head is smaller toward the discharge port;
The cross-sectional area of the passage of the die head is constant in the one direction.
According to claim 2 or 3,
The extrusion apparatus, wherein a cross-sectional area of the passage on the discharge port side is smaller than the tip of the screw in the flow passage of the die holder on the discharge port side.
According to claim 2 or 3,
The extrusion apparatus, wherein the tip of the screw is located closer to the cylinder than the midpoint of the flow path of the die holder in the one direction.
An inlet through which the raw material extruded from the cylinder is disposed on one end side of a tubular cylinder extending in one direction having a passage through which the raw material of the strand flows, and rotated around a rotating shaft extending in the one direction, A strand die having a discharge port for discharging the raw material as a strand, and a flow path through which the raw material flows from the inlet to the discharge port,
If the cross-sectional area of the flow path orthogonal to the one direction is the flow path cross-sectional area,
The cross-sectional area of the passage on the discharge port side is smaller than the tip of the screw in the passage of the strand die is smaller than the cross-sectional area of the passage in the inlet.
According to claim 6,
a die holder having the inlet;
a die head disposed on the discharge port side of the die holder;
a die arranged closer to the discharge port than the die head and having the discharge port;
The passage cross-sectional area of the die is less than or equal to the passage cross-sectional area of the die head,
The cross-sectional area of the passage of the die head is less than or equal to the cross-sectional area of the passage of the die holder.
According to claim 7,
The discharge ports are arranged in plurality in a horizontal direction orthogonal to the one direction,
The horizontal width of the flow path of the die head is larger toward the discharge port;
A width in the vertical direction of the flow path of the die head is smaller toward the discharge port;
The cross-sectional area of the passage of the die head is constant in the one direction.
According to claim 7 or 8,
Strand die, wherein a cross-sectional area of the passage on the discharge port side is smaller than the tip of the screw in the flow passage of the die holder toward the discharge port.
According to claim 7 or 8,
The strand die, wherein the tip of the screw is located closer to the cylinder than the midpoint of the flow path of the die holder in the one direction.

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