JP2002166463A - Extruder and extrusion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extruder capable of manufacturing a molded article of high quality without suppressing extrusion quantity even when a high viscosity resin is extruded. SOLUTION: The extruder is equipped with a cylindrical cylinder and a screw 51 arranged in the cylinder along the longitudinal direction of the cylinder. Especially, the screw 51 is divided into a plurality of individual zones Z1, Z2, Z3 and Z4 and is equipped with a plurality of temperature measuring means 11a, 11b, 11c and 11d for respectively measuring the temperatures of the individual zones Z1-Z4 and temperature regulating means 12a, 12b, 12c and 12d for regulating the temperature of the screw 51 on the basis of the measuring results of the temperature measuring means 11a-11d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruder for melting and pressurizing a thermoplastic resin (hereinafter abbreviated as "resin") and supplying it to a molding machine, and a method for extruding a resin using the extruder. About.

[0002]

2. Description of the Related Art FIG. 3 shows an example of the structure of a conventional extruder.
In the figure, reference numeral 1 denotes a cylinder, which has a cylindrical shape extending horizontally, and has a cylinder 1 at one end (the left end in the figure).
A hopper 2 for supplying resin from above to a space S formed therein is attached. The space S is reduced in diameter at the other end of the cylinder 1 and bent downward, and is connected to a die (molding machine) 4 via an adapter 3.

A screw 5 has a cylindrical shaft portion 5 which is coaxially inserted into the space S from one end and gradually increases in diameter toward the tip end (the other end of the cylinder 1).
a and a blade 5b spirally formed around the shaft portion 5a and having substantially the same diameter as the space S. Shaft 5a
Is located near the other end of the space S, and the shaft 5
a coupling 6 for closing the space S from one end side
The shaft portion 5a is provided with a coupling 6 and a speed reducer 7.
Through a drive source (not shown). Reference numeral 8 denotes a temperature controller that controls the temperature of the cylinder 1. The temperature controller 8 includes a heater 8 a that covers the periphery of the cylinder 1 along the circumferential direction of the cylinder 1 and extends along the longitudinal direction of the cylinder 1. It is schematically configured by arranging a plurality of them in parallel.

The resin supplied to the space S via the hopper 2 is guided by the blades 5b with the rotation of the screw 5 driven by the driving source, and is conveyed through the space S to the other end. It is heated from the surroundings via the cylinder 1 by the temperature controller 8 and melted. Further, since the diameter of the shaft portion 5a gradually increases toward the other end, the volume of the space S gradually decreases toward the other end, and as a result, the resin melted in the space S moves toward the other end. The pressure is gradually increased with the transport of Space S
The resin melted and pressurized in the inside is supplied to the die 4 via the adapter 3 and formed into a predetermined shape (for example, a film shape) according to the outlet shape of the die 4.

[0005]

When the resin is extruded, the resin generates heat due to stress generated between the molten resin and the surface of the screw 5 due to sliding between the resin and the screw 5. As a result, the surface of the screw 5 is extruded. In the vicinity, the resin tends to locally become hot. This tendency is, for example, LLDPE and EVA
This is remarkable when extruding a high-viscosity resin such as Therefore, particularly when extruding a high-viscosity resin, the locally heated resin is discharged mainly from the center in the width direction of the T-die when the die 4 is a T-die, for example. The resulting film gradually becomes thicker at the center in the width direction with the passage of time, causing a problem that the thickness of the film becomes non-uniform. Also, the locally heated resin is screw 5
There is also a problem in that carbonization occurs near the surface of the alloy and it is mixed as foreign matter into the molded product.

On the other hand, in the case where a screen or the like for collecting foreign matter is interposed in the space S from the cylinder 1 to the adapter 3 for the purpose of preventing foreign matter from being mixed into the molded product, the molten resin in the space S Is prevented by the screen, the back pressure applied to the molten resin increases, and the resin easily generates heat. As a result, the finer the mesh of the screen in order to improve the quality of the molded product, the more easily the above-mentioned problem due to the heat generation of the resin is likely to occur.

However, in the above-mentioned conventional extruder, since the temperature of the resin is adjusted by the temperature controller 8 provided in the cylinder 1, the screw 5 located at a position opposed to the cylinder 1 with the space S interposed therebetween. The temperature of the resin in the vicinity cannot be sufficiently controlled. Therefore, in the above-described conventional extruder, when extruding a high-viscosity resin, it is necessary to cope by suppressing the amount of resin extruded to such an extent that the temperature of the resin in the vicinity of the screw 5 does not excessively increase. There has been a new problem that the production of molded products is reduced. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an extruder capable of producing a high-quality molded product without suppressing the resin extrusion amount even when extruding a high-viscosity resin. And

[0008]

According to the present invention, there is provided a cylinder having a cylindrical shape, and a thermoplastic resin provided in the cylinder along a longitudinal direction of the cylinder and supplied into the cylinder from one end side. An extruder provided with a screw for feeding to the other end side, in particular, a plurality of temperature measuring means for dividing the screw into a plurality of zones along the longitudinal direction and measuring the temperature of each zone; and And a temperature adjusting means for adjusting the temperature of the screw based on the measurement result of the temperature measuring means.

In this case, the temperature adjusting means is disposed in the screw for each of the zones, and adjusts the temperature of the screw for each of the zones based on the measurement results of the individual temperature measuring means. Is desirable.

[0010] The temperature adjusting means includes, for example, a flow path formed in the screw and for adjusting the temperature of the screw by changing the temperature of a fluid passing through the screw. In this case, it is desirable that the flow path is formed spirally around the axis of the screw.

[0011] The present invention also relates to a method for extruding a thermoplastic resin using the above extruder. In particular, the temperature control means controls the screw to be rotated immediately after the rotation speed of the screw becomes a steady rotation speed. It is characterized by the strongest cooling, followed by a weaker cooling.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In addition, since the present invention has a feature in the structure of the screw among the extruders, the same reference numerals as those shown in FIG. 3 are used for the configuration other than the screw, and the description is omitted. .

FIGS. 1 and 2 show examples of the structure of a screw according to the extruder of the present invention. The screw 51 includes a shaft 5a and a blade 5b having the same shape as the conventional screw 5 described above. Furthermore, in this screw 51, a plurality (4 in the figure)
Temperature sensors (temperature measuring means) 11a, 11b, 1
1c and 11d are embedded at equal intervals along the longitudinal direction of the screw 51 on the surface of the shaft portion 5a. These temperature sensors 11a to 11d include a plurality of (four in the figure) zones Z ₁ , Z ₂ , Z ₃ , and Z ₄ corresponding to the number of temperature sensors 11a to 11d assumed along the longitudinal direction of the screw 51. located in the central part, the screw 5 in each zone Z ₁ to Z ₄
1 were measured.

Each zone Z ₁ is provided inside the shaft 5a.
At a position corresponding to the to Z _4, a flow path (temperature adjusting means) for adjusting the temperature of the screw 51 12a, 12b, 12
c and 12d are respectively formed so as to form a spiral around the axis of the screw 51. Further, the individual flow paths 12a to
From both ends of 12d, flow paths 13a, 13b, 13c, 13d, 14a, 14 along the longitudinal direction of the screw 51 are formed.
b, 14c and 14d are respectively extended toward the base end side of the screw 51 (the one end side of the extruder) inside the shaft portion 5a (only the flow paths 13a to 13d are shown in FIG. 1). There).

Although omitted in the figure, for example,
The channels 12a to 12d are formed by providing spiral grooves on the surface of the shaft portion 5a at equal intervals, and winding a pipe constituting the channels 12a to 12d around these grooves. In addition, the flow paths 12a to 12d and the flow paths 13a to 13d and 14a
To 14d are the channels 13a to 13d, 14a to 14
d is formed, and the flow path 13a to 13d, 14a
-14d are inserted into the hollow shaft portion 5a from the base end side so that the distal ends thereof communicate with both ends of the flow paths 12a-12d, respectively.

The flow paths 13a to 13d and 14a to 14d
Pipes 16a, 16b, 16c, 16d, 17 provided at the base end of the rotary joint 15 via a rotary joint 15 rotatably supporting the screw 51.
a, 17b, 17c, and 17d. The coupling 6 and the speed reducer 7 are mounted on the rotary joint 15.

Next, the extrusion of the resin by the extruder equipped with the screw 51 having the above-described configuration will be described below.
The resin supplied to the space S via the hopper 2 is guided by the blades 5b with the rotation of the screw 51 driven from the drive source via the speed reducer 7 and the rotary joint 15, and flows through the space S into the extruder. While being conveyed to the other end side, it is heated from the surroundings via the cylinder 1 by the temperature controller 8 and melted. The melted resin is gradually pressurized while being conveyed to the other end side, supplied to the die 4 via the adapter 3, and formed into a predetermined shape according to the exit shape of the die 4.

During the extrusion operation, the temperature of the resin near the surface of the screw 51 is measured by the temperature sensors 11a to 11a.
The d, is measured for each zone Z ₁ to Z _4. These measurements (not shown.) The control means extruder provided to be transmitted, the control means of each said measurement zone Z ₁ to Z ₄
Is compared with the target temperature (the temperature for maintaining the resin temperature in the space S at the target value) in the pipes 16a to 16a.
The fluid is transmitted to a fluid supply means (not shown) for supplying a fluid having an arbitrary temperature to 16d. Then, the fluid at a predetermined temperature based on the above result is supplied to the conduits 16a to 16d and the flow paths 13a to 1d.
Is supplied to the flow path 12a~12d through 3d, these fluids, the surface temperature of the screw 51, the zones Z ₁ ~
It is adjusted every Z _4. The fluid that has passed through the flow paths 12a to 12d is recovered by the fluid supply means through the flow paths 14a to 14d and the pipes 17a to 17d.

In this extruder, the temperature of the resin in the space S is controlled not only by the temperature control from the cylinder 1 side by the temperature controller 8 but also by the temperature control from the screw 51 side by the flow paths 12a to 12d. . Therefore, the temperature of the resin can be more efficiently and accurately controlled as compared with the conventional extruder in which only the temperature control by the temperature controller 8 is performed.

[0020] In particular, by adjusting, based on the surface temperature of the screw 51 in each zone Z ₁ to Z ₄ measured by the temperature sensor 11 a to 11 d, the temperature of the fluid passing through the flow channel 12 a to 12 d, in the extrusion Screw 51
Surface temperature is directly controlled. Therefore, for example, even when the resin generates heat due to the stress generated between the molten resin and the surface of the screw 51, the surface of the screw 51 passes through the flow path 1.
By cooling through 2a to 12d, the screw 5
1 prevents the temperature of the resin from rising near the surface.

As a result, even when a high-viscosity resin such as LLDPE or EVA is extruded from a T-die connected to the extruder, a change in the thickness of the film over time due to a local temperature rise of the resin is prevented. As a result, a film having a uniform thickness is always obtained. Therefore, according to the present invention, even when extruding a high-viscosity resin, it is not necessary to suppress the resin extrusion amount to prevent the temperature rise of the resin in the vicinity of the screw 51 as in the conventional extruder described above. It is possible to efficiently produce quality molded products. In addition, the high-temperature resin is not carbonized near the surface of the screw 51 and does not enter the molded product as foreign matter.

Further, the screw 51 is connected to a plurality of zones Z ₁ to Z ₁ .
Divided into Z _4, by adjusting the basis of the measurement result of the temperature sensor 11a~11d respectively provided in these zones Z ₁ to Z _4, the temperature of the fluid passing through the plurality of flow paths 12a~12d respectively, middle extrusion in the surface temperature of the screw 51, since the respectively adjusted for each individual zones Z ₁ to Z _4, thereby enabling more fine-grained temperature control. Therefore, the surface temperature of the screw 51 in the individual zones Z ₁ to Z _4, can be accurately maintained to a more desirable range.

Further, since the flow paths 12a to 12d are arranged so as to form a spiral around the axis of the screw 51,
The surface temperature of the screw 51, over the entire area of each zone Z ₁ to Z _4, also an effect that can be adjusted quickly and uniformly is.

The specific shape of each member constituting the extruder, particularly the screw 51, or the number of zones Z _{1 to} Z ₄ , temperature sensors 11a to 11d, and channels 12a to 12d, depends on the resin to be extruded, Needless to say, it can be arbitrarily changed according to the type of the die 4 or the use environment of the extruder without departing from the spirit of the present invention.

In controlling the temperature of the screw 51 using the flow paths 12a to 12d, in addition to the control based on the measurement results of the temperature sensors 11a to 11d, a predetermined program previously input to the control means is used. Based control can also be implemented. For example, in general, the amount of heat generated by the resin is highest immediately after the rotation speed of the screw 51 reaches the steady rotation speed, so that the screw 51 is cooled most strongly immediately after the rotation speed of the screw 51 becomes the steady rotation speed. Thereafter, it is also possible to gradually change the temperature of the fluid passing through the flow paths 12a to 12d so as to gradually cool the fluid thereafter. Further, the temperature control based on such a predetermined program and the temperature sensor 11
The temperature control based on the measurement results of the temperature sensors 11a to 11d is continuously performed with time, and the temperature control is basically performed based on a predetermined program. It is also possible to modify the range.

The temperature during the extrusion varies depending on the type of the resin to be extruded while exhibiting various heat generation or heat absorption patterns such as a temperature rising with the elapse of the processing time or a temperature falling below the temperature at the time of the extrusion. . Therefore, in controlling the temperature of the screw 51, the control means individually sets a control constant according to the type of the resin, and sets a normal ON / OFF control.
In addition to the off control, temperature control (P operation) based on P operation (proportional operation), I operation (integration operation), D operation (differential operation), etc.
ID control). For example, for cooling the screw 51, a control constant in the PID control is set in advance in accordance with a pattern in which the surface temperature of the screw 51 rises,
On the basis of these control constants, the screw 51 is cooled such that an optimal temperature change pattern is always maintained.

[0027]

As described above, according to the present invention, the screw of the extruder is divided into a plurality of zones along the longitudinal direction, and the temperature of each of these zones is measured based on the measurement results of the plurality of temperature measuring means. , Because the temperature adjusting means provided in the screw adjusts the temperature of the screw,
For example, the following effects can be obtained.

(1) The temperature of the resin in the extruder is controlled not only by the temperature controller from the cylinder side but also by the temperature controller from the screw side. Therefore, it becomes possible to more efficiently and accurately control the temperature of the resin as compared with a conventional extruder in which only the temperature control by the temperature controller is performed.

(2) Since the temperature adjusting means directly controls the screw temperature based on the screw surface temperature in each zone, for example, even when the resin generates heat due to stress generated between the molten resin and the screw surface. By cooling the surface of the screw with the temperature control means, a rise in the temperature of the resin near the surface of the screw is prevented. As a result, for example, a high-viscosity resin such as LLDPE or EVA
Even when extruding from a T-die connected to this extruder,
A temporal change in the thickness of the film due to a local rise in the temperature of the resin is prevented, and a film having a uniform thickness is always obtained. Therefore, even when extruding a high-viscosity resin, unlike a conventional extruder, it is not necessary to suppress the resin extrusion amount to prevent the temperature of the resin near the screw from rising, and to efficiently produce a high-quality molded product. It becomes possible to produce. Also,
The hot resin is carbonized in the vicinity of the screw surface and does not enter the molded product as foreign matter.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an example of the structure of a screw used in an extruder of the present invention.

FIG. 2 is a sectional view of the screw shown in FIG. 1 taken along the line II-II in FIG.

FIG. 3 is a sectional view showing an example of the structure of an extruder to which the present invention is applied.

[Explanation of symbols]

1 cylinder 11a, 11b, 11c, 11d temperature sensor (temperature measuring means) 12a, 12b, 12c, 12d flow path (temperature adjusting means) 51 screw _{Z 1, Z 2, Z 3} , Z 4 Zone

Claims (5)

[Claims] 1. A cylinder having a cylindrical shape, and a screw disposed in the cylinder along a longitudinal direction of the cylinder and feeding a thermoplastic resin supplied into the cylinder from one end to the other end. An extruder comprising: a plurality of temperature measuring means for dividing the screw into a plurality of zones along the longitudinal direction, each of which measures a temperature of each zone; and a plurality of temperature measuring means provided in the screw. An extruder comprising: a temperature adjusting unit that adjusts the temperature of the screw based on a measurement result. 2. The apparatus according to claim 1, wherein said temperature adjusting means is provided in said screw for each of said zones, and adjusts the temperature of said screw for each of said zones based on the measurement results of said individual temperature measuring means. The extruder according to claim 1, characterized in that: 3. The temperature control device according to claim 1, wherein the temperature control means includes a flow passage formed in the screw and configured to control the temperature of the screw by changing the temperature of a fluid passing through the screw. Or the extruder according to 2. 4. The extruder according to claim 3, wherein the flow path is formed helically around the axis of the screw. 5. A method for extruding a thermoplastic resin using the extruder according to claim 1, wherein said temperature control means controls the rotational speed of said screw to be a steady rotational speed. Immediately after cooling, the screw is cooled most strongly, and then gradually weakened.