JP2022179930A - Extrusion apparatus and strand die - Google Patents

Abstract

To provide an extrusion apparatus and a strand die that can improve quality of a strand.SOLUTION: An extrusion apparatus 1 in one embodiment includes: a cylindrical cylinder 20 extending in one direction with a flow path 26 through which a raw material 60 of a strand 61 flows; a strand die 40 disposed at one end of the cylinder 20 and having an inlet 44 through which the raw material 60 extruded from the cylinder 20 flows, a discharge port 45 through which the raw material 60 is discharged as the strands 61, and a flow path 46 through which the raw material 60 flows from the inlet 44 to the discharge port 45; and a screw 30 that pushes the raw material 60 toward the discharge port 45 by rotating around a rotary shaft extending in one direction. If the cross-sectional areas of the flow paths 26 and 46 orthogonal to the one direction are defined as flow-path cross-sectional areas, the flow-path cross-sectional area in the flow path 46 of the strand die 40 to the discharge port 45 side from a tip of the screw 30 is smaller than the flow-path cross-sectional area in the flow path 46 of the cylinder 20.SELECTED DRAWING: Figure 6

Description

The present invention relates to extrusion equipment and strand dies.

Patent Literature 1 describes an extruder equipped with a strand die for extruding a molten resin as a strand. In the extrusion device of Patent Document 1, the resin flow path has a reverse tapered shape that expands in diameter toward the discharge port.

JP 2012-232432 A

A strand die attached to the tip of an extrusion device may be equipped with a breaker plate containing a fine mesh to filter out foreign matter. In such a case, the area of the breaker plate is increased in order to secure the filtration area. As a result, the resin flow path has a portion whose diameter increases toward the ejection port.

In general, when the diameter of the channel increases, the flow velocity (shear velocity) decreases. Resins with strong non-Newtonian properties have extremely low fluidity when the shear rate is low, and tend to stay on the wall surface. As a result, the amount of heat (thermal energy) from the heater increases, causing thermal deterioration such as a decrease in molecular weight, thereby deteriorating the quality of the strand.

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

An extrusion device according to one embodiment includes a cylindrical cylinder extending in one direction and having a flow path through which a raw material of a strand flows, and a flow path arranged at one end of the cylinder into which the raw material extruded from the cylinder flows. By rotating a strand die having an inlet, 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 rotating shaft extending in one direction, and a screw for pushing out the raw material to the discharge port side, and if the cross-sectional area of the flow path perpendicular to the one direction is defined as the cross-sectional area of the flow path, the flow path of the strand die may be positioned above the tip of the screw in the flow path. The channel cross-sectional area on the outlet side is smaller than the channel cross-sectional area in the channel of the cylinder.

The strand die according to one embodiment is arranged on one end side of a cylindrical cylinder extending in one direction and having a flow path through which the raw material of the strand flows. A strand die having an inlet into which the raw material extruded from the cylinder flows, an outlet 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 outlet, wherein the one When the cross-sectional area of the flow path perpendicular to the direction is defined as the cross-sectional area of the flow path, the cross-sectional area of the flow path on the discharge port side of the tip of the screw in the flow path of the strand die is equal to the flow path cross-sectional area at the inlet. Smaller than the cross-sectional area of the road.

According to the embodiment, it is possible to provide an extrusion device and a strand die capable of improving the quality of strands.

1 is a side view illustrating the configuration of an extrusion device according to Embodiment 1. FIG. 2 is a cross-sectional view illustrating a cylinder of the twin-screw extruder according to Embodiment 1. FIG. FIG. 4 is a diagram exemplifying a flow passage cross-sectional area of a cylinder according to Embodiment 1; 1 is a perspective view illustrating a strand die according to Embodiment 1. FIG. 1 is a partially cross-sectional perspective view illustrating a strand die according to Embodiment 1. FIG. FIG. 5 is a cross-sectional view illustrating the strand die according to Embodiment 1, showing a cross section taken along line VI-VI of FIG. 4; FIG. 5 is a cross-sectional view illustrating the strand die according to Embodiment 1, showing a cross section taken along line VII-VII in FIG. 4; It is a partial cross-sectional perspective view which illustrated the strand die which concerns on a comparative example. FIG. 3 is a cross-sectional view illustrating a strand die according to a comparative example; FIG. 3 is a cross-sectional view illustrating a strand die according to a comparative example; It is the figure which illustrated the shear rate in the flow path of the strand die which concerns on a comparative example. 4 is a diagram exemplifying the shear rate in the flow channel of the strand die according to Embodiment 1. FIG.

For clarity of explanation, the following descriptions and drawings are omitted and simplified as appropriate. Moreover, in each drawing, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary.

(Embodiment 1)
An extrusion device according to Embodiment 1 will be described. FIG. 1 is a side view illustrating the configuration of an extrusion device according to Embodiment 1. FIG. Part of FIG. 1 is shown in cross section. As shown in FIG. 1, the extrusion device 1 includes a drive unit 10, a speed 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. ing. Further, the extruder 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 extrusion device 1 may further include a strand bath 50 and a strand cutter 51 . The extruder 1 extrudes a raw material 60 in which resin or the like is melted from a strand die 40 to form a strand 61 . The formed strands 61 are cooled in the strand bath 50 . After that, the strand 61 is cut by the strand cutter 51 into pellets 62 .

Here, for convenience of explanation of the extrusion device 1, an XYZ orthogonal coordinate axis system is introduced. For example, one direction in which the cylinder 20 extends is defined as the X-axis direction, and two directions orthogonal to the X-axis direction are defined as the Y-axis direction and the Z-axis direction. For example, the Z-axis direction is the vertical direction, and the XY plane is the horizontal plane. The +Z-axis direction is upward. The end of the cylinder 20 on the +X-axis direction is called one end, and the end of the cylinder 20 on the -X-axis direction is called the other end. The direction in which the molten raw material 60 is extruded in the extruder 1 is defined as the +X-axis direction. Each configuration will be described below.

<Drive unit, reducer>
The drive unit 10 is arranged on the other end side of the cylinder 20, that is, on the -X-axis direction side of the cylinder 20. As shown in FIG. The drive unit 10 rotates the screw 30 . When the extruder 1 is a twin-screw extruder, the driving section 10 rotates the screws 31 and 32 . The extruder 1 is not limited to a twin-screw extruder, and may be a multi-screw extruder or a single-screw extruder. Moreover, the screws 31 and 32 are collectively called the screw 30 .

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

<Feeder>
The feeder 12 is arranged above the cylinder 20 on the −X axis side. The feeder 12 feeds the raw material 60 of the pellets 62 into the cylinder 20, for example. The raw material 60 of the pellets 62 is, for example, resin or the like. Note that 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 the direction from the root of the rotating screw 30 toward the tip on the opposite side, that is, in the +X-axis direction. The raw material 60 is melted inside the cylinder 20 by the heat from the heater 15 attached to the cylinder 20 and the action accompanying the rotation of the screw 30 , and changes into the molten raw material 60 . The melted raw material 60 is sent to the strand die 40 through the +X-axis direction side opening of the cylinder 20 .

<Liquid addition pump, vacuum pump, heater>
The liquid addition pump 13 adds an additive to the raw material 60 . Vacuum pump 14 adjusts the flow path inside 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 channel 26 in which the strand raw material 60 flows. A screw 30 is accommodated in the flow path 26 of the cylinder 20 . The cylinder 20 includes two cylinders 21 and 22 when the extruder 1 is a twin-screw extruder. The two cylinders 21 and 22 have a shape in which side surfaces are partially connected.

FIG. 2 is a cross-sectional view illustrating the cylinder 20 of the twin-screw extruder according to the first embodiment. FIG. 2 shows the screws 31 and 32 viewed from the X-axis direction and one screw 30 removed from the cylinder 20 . As shown in FIGS. 1 and 2, when the extruder 1 is a twin-screw extruder, 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 opposed side surfaces are partially removed and combined. A cross section of the cylinder 20 orthogonal to the X-axis direction is eyeglass-shaped, specifically, a "8" shape laid down sideways. However, the opposite sides of cylinder 21 and cylinder 22 have been 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 cylinders 21 and 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<inner diameter D is satisfied. The side surface of the cylinder 21 and the side surface of the cylinder 22 are connected by an intersection line L1 (intersection point P1 in the sectional view) on the +Z-axis direction and an intersection line L2 (intersection point P2 in the sectional view) on the −Z-axis direction side. Let H be the height between the line of intersection L1 and the line of intersection L2. Height H is the height of the cylinder at the midpoint between central axis C1 and central axis C2.

<Screw>
The screw 30 rotates around a rotation axis extending in the X-axis direction. Thereby, the screw 30 pushes out the melted raw material 60 in the +X-axis direction. The screw 30 is arranged in a channel 26 formed inside the cylinder 20 . When the extruder 1 is a twin-screw extruder, two screws 31 and 32 are arranged. The screw 31 is arranged in the flow path 26 of the cylinder 21 . The screw 32 is arranged in the flow path 26 of the cylinder 22 . The screw 32 is adjacent to the screw 31 in the Y-axis direction and rotates around a rotation axis extending in the X-axis direction. For example, the screw 32 is arranged 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. As shown in FIG. The rotation axis of the screw 32 is located on the central axis C2 of the cylinder 22. As shown in FIG. When viewed from the X-axis direction, the screws 31 and 32 have an elongated shape with a length and a width. The length of the screw 30 is D, which is the same as the inner diameter of each cylinder 21 and 22 . Let d be the width of the screw 30 . When the length direction of the screw 30 faces the Z-axis direction, it is called a vertical position. A position in which the width direction of the screw 30 faces the Z-axis direction is called a lateral position. The screw 31 in FIG. 2 is then in the horizontal position and the screw 32 in the vertical position. Since the length of the screw 30 is the same as the length D of each cylinder 21 and 22, when the screw 31 is in the lateral position the screw 32 assumes the longitudinal position. That is, the phase of rotation of the screw 31 and the phase of rotation of the screw 32 are out of phase by 90°. Also, the width d and the shape of the screws 31 and 32 are made to be rotatable in the flow passages 26 of the cylinders 21 and 22 out of phase by 90°. Specifically, for example, α is defined as D/d to be the groove depth ratio of the screw 30 . In that case, the distance W and the height H should satisfy the following formulas (1) and (2).

FIG. 3 is a diagram illustrating the channel cross-sectional area of the cylinder 20 according to the first embodiment. As shown in FIG. 3, when the cross-sectional area of the flow path 26 perpendicular to the X-axis direction is defined as a cross-sectional area S, the cross-sectional area S of the flow path can be obtained by the following equation (3).

Here, the area S1 is the sum of the area of the sector from the intersection point P1 to the intersection point P2 centered on the central axis C1 and the area of the sector from the intersection point P1 to the intersection point P2 centered on the central axis C2. 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, the area S1 and the area S2 are given by the following equations (4) and (5), respectively.

<Vent hole, pressure/thermometer>
The vent hole 23 discharges volatile substances and moisture generated from the raw material 60 kneaded by the rotation of the screw 30 to the outside of the cylinder 20 .

Pressure/thermometers are attached to predetermined positions of the cylinder 20, the strand die 40, and the like. The pressure/thermometer measures the pressure and temperature of the raw material 60, molten raw material 60, strand 61, and the like. The pressure/thermometer may measure the pressure and temperature of gas or the like generated by kneading the raw material 60 .

<Strand die>
As shown in FIG. 1 , the strand die 40 is arranged on one end side of the cylinder 20 , that is, on the +X-axis direction side of the cylinder 20 . The strand die 40 has, for example, a rectangular parallelepiped shape. The strand die 40 has a front surface 47 on the +X-axis direction and a rear surface 48 on the −X-axis direction. Rear surface 48 is connected to one end of cylinder 20 . An inlet 44 is formed in the rear surface 48 . A discharge port 45 is formed in the front surface 47 . Therefore, the strand die 40 has an inlet 44 into which the melted raw material 60 extruded from the cylinder 20 flows, an outlet 45 through which the melted raw material 60 is discharged as a strand 61, and a melt from the inlet 44 to the outlet 45. It has a channel 46 through which the raw material 60 flows.

Here, let the cross-sectional area of the flow path 46 perpendicular to the X-axis direction be the flow-path cross-sectional area S0. Then, the cross-sectional area S0 of the flow path 46 of the strand die 40 on the discharge port 45 side of the tip of the screw 30 is smaller than the cross-sectional area S of the flow path 26 of the cylinder 20 . That is, the following formula (6) is satisfied.

FIG. 4 is a perspective view illustrating a strand die 40 according to Embodiment 1. FIG. FIG. 5 is a partially cross-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 the first embodiment, showing a cross section taken along line VI-VI in FIG. FIG. 7 is a cross-sectional view illustrating the strand die 40 according to Embodiment 1, showing a cross section taken along line VII-VII in FIG. As shown in FIGS. 4-7, strand die 40 includes die holder 41 , die head 42 and die 43 . A breaker plate or straight ring may be arranged between the die holder 41 and the die head 42 .

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

The die holder 41 has an inlet 44 into which the molten raw material 60 flows. Also, the die holder 41 has a part of the flow path 46 . An 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 that has flowed in from the inlet 44 moves through the channel 46 .

A tip portion of the screw 30 may be arranged in the flow path 46 of the die holder 41 . For example, the tip of the screw 30 may be located 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 channel cross-sectional area S41 of the inlet 44 may be the same as the channel cross-sectional area S of the cylinder 20. FIG. Also, the shape of the cross-sectional area S41 of the flow path of the inlet 44 may be a figure 8 like the shape of the cross-sectional area S of the flow path of the cylinder 20 . By locating the tip of the screw 30 in the flow path 46 of the die holder 41 , it is possible to suppress a decrease in the flow velocity of the molten raw material 60 . Furthermore, since the tip of the screw 30 is positioned closer to the cylinder 20 than the midpoint of the flow path 46 of the die holder 41, the flow velocity of the raw material 60 is suppressed, and the cross-sectional area S0 of the flow path from the die holder 41 to the discharge port 45 is increased. can slow down the change in .

A cross-sectional area S41 of the flow path of the die holder 41 on the discharge port 45 side of the tip of the screw 30 is preferably smaller toward the discharge port 25 side (+X-axis direction side). In other words, it is preferable that the flow passage cross-sectional area S41 gradually decreases toward the ejection port 45 side. As a result, it is possible to suppress a decrease in the shear rate on the wall surface of the channel 46 . In the die holder 41, the channel cross-sectional area S41 may have a portion that is smaller toward the +X-axis direction side, or may have a portion that does not change. In other words, the cross-sectional area A1 at the position X1 on the X-axis in the flow path 46 of the die holder 41 and the cross-sectional area A2 at the position X2 on the +X-axis direction side of the position X1 have a portion where A1<A2. or there may be a portion where A1=A2. However, there is no portion where A1>A2.

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

The die head 42 is arranged closer to the ejection port 35 than the die holder 41 is. Die head 42 has a portion of channel 46 . The melted raw material 60 moves in the +X-axis direction in the channel 46 . The width of the flow path 46 of the die head 42 in the horizontal direction increases toward the discharge port 45 side (+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. 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 same as the horizontal width of the flow path 46 of the die holder 41 .

On the other hand, the vertical width of the flow channel 46 of the die head 42 is smaller toward the discharge port 45 side (+X-axis direction side). At the connection point between the die holder 41 and the die head 42 , the vertical width of the flow path 46 of the die head 42 is the same as the vertical width of the flow path 46 of the die holder 41 .

It is preferable that the flow passage cross-sectional area S42 of the die head 42 is constant in the X-axis direction. The flow channel 46 of the die head 42 expands in the horizontal direction and narrows in the vertical direction, but if the flow channel cross-sectional area S42 is constant, it is possible to suppress a decrease in the shear rate on the wall surface of the flow channel 46. . The flow channel cross-sectional area S42 of the die head 42 is equal to or smaller than the flow channel 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 channel cross-sectional area S<b>42 of the die head 42 is the same as the channel cross-sectional area of the die holder 41 . The channel cross-sectional area S42 of the die head 42 may be smaller than the channel cross-sectional area of the die holder 41 on the +X-axis direction side of the connection point.

The die 43 is arranged closer to the ejection port 45 than the die head 42 is. The die 43 has a discharge port 45 for discharging the melted raw material 60 as a strand 61 . Die 43 has a portion of channel 46 . A plurality of discharge ports 45 are horizontally arranged on the front surface 47 . The flow channel cross-sectional area S43 of the die 43 is equal to or smaller than the flow channel cross-sectional area S42 of the die head 42 . Specifically, at the connection point between the die head 42 and the die 43 , the channel cross-sectional area S<b>43 of the die 43 is the same as the channel cross-sectional area of the die head 42 . However, the channel cross-sectional area S43 of the die 43 may be smaller than the channel cross-sectional area S42 of the die head 42 on the +X-axis direction side of the connection point.

<Comparative example>
Next, before describing the effects of this embodiment, a comparative example will be described. After that, the effect of the present embodiment will be described in comparison with a comparative example. FIG. 8 is a partially cross-sectional perspective view illustrating a strand die 140 according to a comparative example. FIG. 9 is a cross-sectional view illustrating a strand die 140 according to a comparative example. FIG. 10 is a cross-sectional view illustrating a strand die 140 according to a comparative example. The strand die 140 includes a die holder 141, a die head 142 and a die 143, as shown in FIGS. A breaker plate 149 may be positioned between the die holder 141 and the die head 142 .

The inlet 144, the outlet 145, the flow path 146, the front surface 147 and the rear surface 148 of the strand die 140 of the comparative example are the same as the inlet 44, the outlet 45, the flow path 46, the front surface 47 and the rear surface of the strand die 40 of the first embodiment. 48.

In the comparative example, the channel cross-sectional area S140 on the discharge port 145 side of the tip of the screw 30 in the channel 146 of the strand die 140 is larger than the channel cross-sectional area S in the channel of the cylinder 20 in some parts. For example, a flow channel cross-sectional area S<b>141 of the flow channel 146 of the die holder 141 is larger than the flow channel cross-sectional area S of the cylinder 20 . Further, a flow channel cross-sectional area S142 of a portion of the flow channel 146 of the die head 142 is larger than the flow channel cross-sectional area S of the cylinder 20. As shown in FIG.

Specifically, for example, a breaker plate 149 is arranged between the die holder 141 and the die head 142 in order to filter foreign substances mixed in the molten raw material 60 . Breaker plate 149 includes a fine mesh. In the comparative example, the breaker plate 149 and the channel cross-sectional areas S141 and S142 before and after the breaker plate 149 are increased in order to secure the filtering area of the breaker plate 149 . Therefore, the flow channel cross-sectional area S140 of the strand die 140 has a portion larger than the flow channel cross-sectional area S of the cylinder 20 .

When the flow channel cross-sectional area S140 of the strand die 140 is larger than the flow channel cross-sectional area S of the cylinder 20, the flow velocity (shear velocity) in the flow channel 146 of the strand die 140 decreases. As a result, the fluidity of the raw material 60 is extremely lowered, and the raw material 60 stays on the wall surface of the flow path 146 . As a result, the raw material 60 is deteriorated by heat, and the quality of the strand 61 is deteriorated.

Next, the effects of this embodiment will be described. Generally, in the extruder 1 configured by the cylinder 20 and the screw 30, the screw 30 rotates to axially transport the molten raw material 60 such as resin. 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 unlikely 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 portion of the strand die 40 beyond the tip of the screw 30 is not affected by the high shear rate due to the rotation of the screw 30 . Thus, the strand die 40 experiences only purely axial pressure flow. Therefore, as in the comparative example, the shear rate decreases as the cross-sectional area S140 of the strand die 140 increases. A resin fluid exhibiting low fluidity tends to stay on the wall surface of the flow path 146, absorbs thermal energy from the heater attached to the strand die 140, and causes thermal deterioration (molecular weight reduction, quality deterioration due to discoloration, etc.).

On the other hand, in the present embodiment, the cross-sectional area S0 of the flow path 46 of the strand die 40 on the discharge port 45 side of the tip of the screw 30 is larger than the cross-sectional area S of the flow path 26 of the cylinder 20. small. That is, the channel cross-sectional area S0 on the discharge port 45 side of the tip of the screw 30 is smaller than the channel cross-sectional area S at any position. Therefore, the flow velocity (shear velocity) of the raw material 60 in the flow path 46 does not decrease. Thus, in this embodiment, the shear rate in the flow path 46 of the strand die 40 can be increased. Therefore, it is possible to prevent the raw material 60 from stagnating on the wall surface of the channel 46 . Thereby, thermal deterioration of the raw material 60 can be suppressed, and the quality of the strand 61 can be improved. In this case, pressure loss may increase due to the narrow filtering area of the breaker plate. However, it is also possible to adopt a straight ring and not use a breaker plate including a mesh by sufficiently controlling contamination of the raw material 60 and the like.

Table 1 is a table exemplifying the yellowing (Yellow Index, YI) of the resin when the strand 61 is formed 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 the comparative example and the first embodiment are attached to one end of the twin-screw extruder having a diameter D of the cylinder 20 of 69 [mm], and 300 [kg/ h] extrusion tests were carried out. The temperature of the extruded strand 61 was about 280[° C.], and the temperature setting by the heaters 15 of the strand dies 140 and 40 was set at 280[° C.]. Further, in order to intentionally accelerate the oxidative deterioration of the resin, the conditions were set such that oxygen was blown into the twin-screw extruder at the same time as supplying the raw material 60 of the resin to raise the oxygen concentration in the twin-screw extruder.

As shown in Table 1, when the strand die 140 of the comparative example is used to form the strand 61, when the operation time is 60, 120, 180, 240 and 300 [min], YI is 2.0 min. 6, 3.3, 6.1, 8.5 and 12.6. In the strand die 140 of the comparative example, at the beginning of extrusion, a resin that is transparent and free from foreign matter is discharged. However, yellowing is confirmed with the lapse of time. Analysis of YI revealed that the value increased after 3 hours and then gradually increased. Thus, in the case of the comparative example, the longer the operating time, the larger the YI. When the strand die 140 was disassembled after the experiment was completed, deposition of yellowish brown resin was confirmed on the wide wall surface of the flow path 146 .

On the other hand, when the strand die 40 of Embodiment 1 is used to form the strand 61, when the operation time is 60, 120, 180, 240 and 300 [min], YI is 2.2, 3.0 min, respectively. 4, 3.2, 4.0 and 3.9. In the strand die 40 of Embodiment 1, no yellowing resin was discharged in 5 hours from the start to the end of the experiment. As described above, in the case of Embodiment 1, YI hardly changes even if the operating time is long. After the experiment was completed, the strand die 40 was disassembled and the flow path 46 was checked.

Next, results of flow analysis using the strand dies 140 and 40 according to the comparative example and the first embodiment will be described. FIG. 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. In FIGS. 11 and 12, the darker the color, the lower the shear rate.

As shown in FIG. 11, using the strand die 140 of the comparative example, under the extrusion condition of 300 [kg / h], the result of performing a three-dimensional flow analysis in the flow path 146 shows that the filtration area at the breaker plate 149 Since the channel is widened in order to increase the shear rate of the wall surface of the channel 146, there is a portion where the shear rate is 1 [1/sec] or less. This indicates that the same wall shear rate is obtained even when the breaker plate 149 is changed to a straight ring, and as a result, the resin tends to stay in the enlarged flow path 46 portion.

On the other hand, as shown in FIG. 12, the strand die of Embodiment 1 was used to perform three-dimensional flow analysis in the flow path 46 under the same extrusion conditions as in the comparative example. Secure a speed of 5 [1/sec] or more in the entire area. Therefore, it is possible to suppress the retention of the raw material 60 on the wall surface, and it is possible to suppress the deterioration of the resin due to the application of an excessive amount of heat.

It goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications can be made without departing from the spirit of the present invention.

1 Extruder 10 Drive Unit 11 Reducer 12 Feeder 13 Liquid Addition Pump 14 Vacuum Pump 15 Heaters 20, 21, 22 Cylinder 23 Vent Hole 26 Flow Paths 30, 31, 32 Screw 40 Strand Die 41 Die Holder 42 Die Head 43 Die 44 Inlet 45 Discharge port 46 Flow path 47 Front surface 48 Rear surface 50 Strand bus 51 Strand cutter 60 Raw material 61 Strand 62 Pellets 140 Strand die 141 Die holder 142 Die head 143 Die 144 Inlet 145 Discharge port 146 Flow path 147 Front surface 148 Rear surface 149 Breaker plate

Claims (10)

a cylindrical cylinder extending in one direction and having a channel through which the raw material of the strand flows;
An inlet that is arranged at one end of the cylinder and into which the raw material extruded from the cylinder flows, a discharge port that discharges the raw material as a strand, and a flow path through which the raw material flows from the inlet to the discharge port. a strand die comprising;
a screw that pushes the raw material toward the outlet by rotating around the rotating shaft extending in one direction;
with
Assuming that the cross-sectional area of the flow path perpendicular to the one direction is the cross-sectional area of the flow path,
The cross-sectional area of the flow path on the discharge port side of the tip of the screw in the flow path of the strand die is smaller than the cross-sectional area of the flow path in the flow path of the cylinder,
Extrusion equipment. The strand die is
a die holder having the inlet;
a die head arranged closer to the ejection port than the die holder;
a die disposed closer to the ejection port than the die head and having the ejection port;
including
The cross-sectional area of the flow path of the die is equal to or less than the cross-sectional area of the flow path of the die head,
The flow channel cross-sectional area of the die head is equal to or less than the flow channel cross-sectional area of the die holder,
2. The extrusion apparatus of claim 1. a plurality of the ejection ports are arranged in a horizontal direction orthogonal to the one direction;
the width in the horizontal direction of the flow path of the die head is larger toward the ejection port side;
the width in the vertical direction of the flow path of the die head is smaller toward the discharge port side,
The cross-sectional area of the flow path of the die head is constant in the one direction,
3. An extrusion apparatus according to claim 2. The cross-sectional area of the flow path on the discharge port side of the tip of the screw in the flow path of the die holder is smaller toward the discharge port.
4. An extrusion device according to claim 2 or 3. 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;
The extrusion device according to any one of claims 2-4. The raw material extruded from the cylinder by a screw arranged at one end of a cylindrical cylinder extending in one direction and having a flow path through which the raw material of the strand flows, and rotating about the rotating shaft extending in the one direction. A strand die having an inlet for inflow, an outlet for discharging the raw material as a strand, and a flow path for the raw material to flow from the inlet to the outlet,
Assuming that the cross-sectional area of the flow path perpendicular to the one direction is the cross-sectional area of the flow path,
The cross-sectional area of the flow path on the discharge port side of the tip of the screw in the flow path of the strand die is smaller than the cross-sectional area of the flow path at the inlet,
Strand die. a die holder having the inlet;
a die head arranged closer to the ejection port than the die holder;
a die disposed closer to the ejection port than the die head and having the ejection port;
including
The cross-sectional area of the flow path of the die is equal to or less than the cross-sectional area of the flow path of the die head,
The flow channel cross-sectional area of the die head is equal to or less than the flow channel cross-sectional area of the die holder,
A strand die according to claim 6. a plurality of the ejection ports are arranged in a horizontal direction orthogonal to the one direction;
the width in the horizontal direction of the flow path of the die head is larger toward the ejection port side;
the width in the vertical direction of the flow path of the die head is smaller toward the discharge port side,
The cross-sectional area of the flow path of the die head is constant in the one direction,
A strand die according to claim 7. The cross-sectional area of the flow path on the discharge port side of the tip of the screw in the flow path of the die holder is smaller toward the discharge port.
Strand die according to claim 7 or 8. 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;
Strand die according to any one of claims 7-9.

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