JPH09150446A - Extrusion molding method and feeding device of raw material to extruder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a continuous production of a film or a sheet by a method wherein the extrusion amount of the molten resin of an extruder, the change with the lapse of time of which has been premised, is made constant at all times. SOLUTION: In the extrusion molding method, in which stock resin 2 is charged to an extruder 7 and, after being melted with the extruder 7, extruded through a die 10 so as to be taken off in the form of film or sheet, the stock resin 2 is gravity fed to the extruder 7 under the condition that the amount of its gravity feed is made controllable and the screw 9 of the extruder 7 is rotated at a constant speed for molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion molding method for producing a film or a sheet and a raw material supply device for an extruder.

[0002]

2. Description of the Related Art Generally, in an extrusion molding method, a raw material resin such as a thermoplastic resin is melted by an extruder and then discharged with a die having an annular discharge port or a die having a straight discharge port. To produce films and sheets.

In the extrusion molding method such as the inflation molding method, adjustment is performed so that the width and thickness of the produced film or sheet are always maintained at the set values.

In order to carry out this adjustment manually, long-term skill and experience were required.

Therefore, in order to rationalize this problem, an automatic adjustment control system for automatically performing the adjustment has been proposed in recent years (see Japanese Patent Application Laid-Open Nos. 1-24721 and 1-26424, etc.).

This automatic adjustment control system will be further described with reference to FIG. 5, in which the raw material resin 2 charged into the raw material hopper 1 is
An extruder 7 is passed through a raw material shutter 3, which is opened and closed by a raw material opening and closing cylinder 4, a weight measuring device 5, and a weighing pot 6 in order.
Is supplied into the heating cylinder 8. After that, raw resin 2
Is melted while being transferred in the heating cylinder 8 by the rotation of the screw 9, discharged from the annular discharge port of the die 10, and then blown by the air supplied into the bubble 11 to form a thin film, It is taken up by the pinch roller 12.

Actually, the raw material resin 2 is fed by the screw 9 to consume the raw material resin 2 in the measuring kettle 6, and when the lower limit set value is measured by the lower limit set value sensor 14, When the raw material shutter 3 is turned on, the raw material resin 2 is dropped from the raw material hopper 1 to the weighing vessel 6, and when the upper limit setting sensor 13 measures the upper limit set value, the raw material resin 2 is turned off and the raw material from the raw material hopper 1 is turned on. It is designed to stop the resin 2 from falling.

At this time, after the upper limit set value sensor 13 detects the upper limit set value, the raw material resin 2 is consumed, and the upper limit set value sensor 13 does not detect the upper limit set value and is turned off. The raw material resin 2 is consumed, the lower limit set value sensor 14 detects the lower limit set value, and the weight of the raw material consumed per unit time until the moment when the sensor is turned on is measured to calculate the extrusion amount. Further, the take-up speed is calculated from the value of the cross-sectional area and the specific gravity of the product obtained by the calculated extrusion amount and the preset width and thickness of the film or sheet, and the pinch roller is generated by the signal from the automatic take-up speed control board 15. The rotation speed of 12 is controlled.

In addition to the control of the rotation speed of the pinch roller 12, it has also been proposed to variably control the rotation speed of the screw 9 of the extruder 7.

[0010]

However, in the conventional control methods described in the above publications, it is premised that the extrusion amount of the molten resin extruded from the extruder 7, that is, the weight consumption of the raw material changes. As a pinch roller 12
Since it variably controls the rotation speed of the screw, the rotation speed of the screw 9 of the extruder 7, etc., the object to be controlled constantly changes, and it is very difficult to perform appropriate control, and the control system becomes complicated. However, the cost is very high, and the produced films and sheets have drawbacks such as uneven thickness.

These drawbacks will be further explained below.

Disadvantage 1 In the conventional method, even if the raw material consumption weight is measured, the raw material consumption weight itself is not controlled, so that the extrusion amount cannot be quantified. Therefore, in order to bring the width and thickness of the film or sheet close to the set values, the take-up speed is constantly changed according to the change of the extrusion rate. And the following 1) to 5)
It causes an adverse effect as shown in. 1) The cooling effect of the air ring is different between when the take-up speed is high and when the take-up speed is small, which causes uneven cooling of the resulting film. 2) Since the take-up speed changes, the resistance to the bubbles 11 in the stabilizer 16 part may change, which may cause wrinkles in the product film. 3) Since the take-up speed is changed, the followability with the winder for winding the film is deteriorated, and the film cannot be wound to a certain extent, and the film may suffer from deafening or wrinkles. 4) When moving a printing machine etc. in-line, the pitch speed of printing is induced because the take-up speed changes. 5) Therefore, it may not be used for the production of high quality sheets and films with strict quality conditions.

Disadvantage 2 In the above-mentioned conventional method which employs the method of measuring the time for consuming the unit weight of the raw material resin 2, the measuring kettle 6
This causes a problem that the raw material consumption weight fluctuates when measuring the raw material consumed weight.

Disadvantage 3 Since the consumed weight of the raw material is not controlled, it is impossible to prevent extrusion unevenness (surging) of the extruder 7 caused by various causes.

Defect 4 Raw material resin 2 between the upper limit setting value and the lower limit setting value of the raw material kettle 6
When the extrusion amount is extremely small, it takes too much time to reach from the upper limit to the lower limit, resulting in poor control, and the pinch roller 1 as a take-up device is used.
It may not be possible to link with 2.

Disadvantage 5 Since the raw material shutter 3 is opened and closed by the raw material opening / closing cylinder 4, the raw material shutter 2 becomes clogged with the raw material resin 2 and becomes inoperable, or the raw material resin clogged the previous day when the raw material shutter 3 is changed to a different type of raw material resin. It came in and got in, causing problems such as color change.

Disadvantage 6 Since the upper limit setting value and the lower limit setting value of the raw material kettle 6 are provided and the measurement is carried out in units of small lots, the drop of the raw material resin 2 (time from the upper limit setting value until the raw material opening / closing cylinder 4 is closed) During that time, the amount of raw material resin that enters the raw material pot 6 becomes a time delay.

Disadvantage 7 The time from the upper limit set value to the lower limit set value is measured, but conversely, the time from the lower limit set value to the upper limit set value is not measured. Therefore, the measurable region and the non-measurable region are repeated over time, which causes a time delay and deteriorates the resolution.

Disadvantage 8 Since the raw material shutter 3 and the raw material opening / closing cylinder 4 are generally near the working environment, there is a risk of injury.

Disadvantage 9 Since the material shutter 3 and the material opening / closing cylinder 4 need to be installed, the machine cost becomes high.

Disadvantage 10 Since the measuring kettle 6 is generally small, the amount of raw material resin 2 biting into the extruder 7 is different between the vicinity of the upper limit setting value and the vicinity of the lower limit setting value, so that the extrusion amount varies. Resulting in.

Disadvantage 11 Since the capacity of a small lot measured between the upper limit set value and the lower limit set value is the unit of measurement, it is impossible to measure in a cycle shorter than the time measured during this period. As a result, the control performance deteriorates.

As described above, the extrusion molding method on the premise that the controlled object changes with the passage of time has a serious problem.

The present invention has been made in view of the above points, and the amount of molten resin extruded from an extruder, which is conventionally assumed to change with the passage of time, is always kept constant to continuously form a film or sheet. Production can be carried out, in other words, while the screw of the extruder is rotated at a constant speed to make the extrusion amount of the molten resin a constant value, while maintaining the supply amount of the raw material resin to the screw portion at an appropriate value. High-quality films and sheets can be continuously produced by continuous operation, eliminating the need for conventional material shutters and material opening / closing cylinders, simplifying the structure, and reducing the cost of extrusion molding methods and raw materials for extruders. An object is to provide a supply device.

[0025]

In order to achieve the above object, the extrusion molding method of the present invention according to claim 1 supplies a raw material resin to an extruder and melts the raw material resin by the extruder. In an extrusion molding method of extruding from a die and then taking the raw material resin in a film or sheet form, the raw material resin is fed to the extruder by gravity dropping and the amount of the natural dropping is adjustable. It is characterized in that the screw of the extruder is rotated at a constant speed for molding.

The raw material supply device for the extruder according to the second aspect of the present invention is formed so as to supply the raw material resin to the extruder by natural dropping and with the amount of natural falling adjustable. It is characterized by

The raw material supply device for the extruder is formed so that the size of the opening area of the raw material supply port through which the raw material resin falls naturally can be varied.

According to the present invention, when an extruder having a raw material feeding device for the extruder of the present invention is used for extrusion molding according to the method of the present invention, the raw material resin is naturally dropped from the raw material feeding device, and the natural dropping is performed. The screw of the extruder is rotated at a constant speed while the amount is adjustable and is supplied to the extruder, the raw material resin is melted by the extruder and extruded from the die in fixed amounts, and then the raw material resin is formed into a film or sheet. It can be take-off molded. According to the present invention, since the screw rotates at a constant speed and the amount of the raw material resin consumed by the rotational speed is supplied from the raw material supply device by free fall, the extrusion amount of the molten resin becomes constant, and the film or sheet The width and thickness of the film are automatically maintained at the set values, and continuous production of films and sheets without variations can be performed as products.

[0029]

FIG. 1 is a block diagram showing an embodiment of the present invention.
4 to FIG.

FIG. 1 shows an embodiment of an extrusion molding apparatus for carrying out the extrusion molding method according to the present invention using an extruder equipped with an embodiment of a raw material supply apparatus for an extruder according to the present invention. The same parts as those in the conventional example of FIG. 5 are designated by the same reference numerals, and FIGS. 2 to 4 show the raw material supply device.

In the embodiment of the present invention shown in FIG. 1, a raw material feeding cylinder of an extruder 7 which is a means for extruding a raw material resin 2 from a raw material hopper 1 through a raw material supply device 20 in place of the conventional measuring kettle 6. 7a. The raw material supply device 20 is formed so as to supply the raw material resin 2 to the extruder 7 by natural fall and with the amount of natural fall adjustable, and in the present embodiment, as shown in FIGS. As shown, the opening 33 through which the raw material resin 2 naturally falls
The size of the opening area of “a” can be freely changed to freely adjust the amount of natural fall. The raw material hopper 1 is fixed to a hopper support base 21 fixed to the outside of the raw material feeding cylinder 7a of the extruder 7 via a raw material weight measuring device 22 such as a strain gauge. The raw material weight measuring device 22 constantly measures the total weight of the raw material hopper 1, the raw material supply device 20, and the raw material resin 2, and outputs the measured weight to the raw material supply weight calculating section 23. This raw material supply weight calculation unit 23 is a raw material weight measuring device
From the amount of change in the total weight of the raw material hopper 1, the raw material supply device 20, and the raw material resin 2 sent from, the supply weight of only the raw material resin 2 is constantly calculated, and the calculation result is obtained. It is designed to output to. The raw material supply amount controller 24 controls the opening amount of the opening 33a of the raw material supply device 20 to control the supply amount of the raw material resin 2.
A raw material supply weight setting unit 25 for setting an appropriate raw material supply weight corresponding to the rotation speed of the screw 9 of the extruder 7 is provided inside.
And the set value of the raw material supply weight and the actual measured value of the actual raw material supply weight sent from the raw material supply weight calculation unit 23 are compared to each other so that the actual measured value always matches the set value. An opening degree calculation unit 26 that outputs a command for controlling the opening degree of the opening 33a to a drive motor 37 of the raw material supply device 20 described later is provided. Further, the raw material resin 2 is supplied into the raw material hopper 1 through a raw material feeding cylinder 27 which is suspended above and installed in the raw material hopper 1.

The raw material supply device 20 is provided in the middle of the supply cylinder 1a extending downward from the raw material hopper 1, and is formed as shown in FIGS. 2 to 4. That is,
As shown in FIG. 2, the supply cylinder 1a is divided into an upper supply cylinder 1au and a lower supply cylinder 1ad on the way, and an upper flange 28u and an upper flange 28u fixed to the outer peripheral surfaces of the upper supply cylinder 1au and the lower supply cylinder 1ad, respectively. Lower flange 28d
By connecting and with a plurality of connecting stays 29, an annular gap 30 is formed between the upper supply cylinder 1au and the lower supply cylinder 1ad. On the upper surface of the lower flange 28d, a plurality of rectangular grooves 31 which are oriented in the radial direction and which are rectangular in shape when viewed from above are engraved, and each of the rectangular grooves 31 has an outer end portion 32a directed upward. L-shaped slide rod 32
The horizontal part of is fitted slidably. Each slide rod 3
A horizontal iris plate 33 having an arc shape and semicircular shape at both ends is fixed to the upper surface of the inner end portion of the horizontal portion 2. Each iris plate 33 overlaps with the adjacent iris plate 33 at both ends, and is formed into a ring shape as a whole so as to form an opening 33a through which the raw material resin 2 passes, and through the gap 30 into the supply cylinder 1a. The opening / closing of the opening 33a through which the raw material resin 2 passes is variably adjusted. A roller 34 is rotatably attached to the upper end of the outer end portion 32a of the slide rod 32. An annular cam body 35 is rotatably mounted above the slide rod 32 between the flanges 28u and 28d. The lower surface of the cam body 35 has a width that allows the roller 34 to be slidably and rotatably sandwiched, and a plurality of arcuate cams that intersect the inner peripheral surface of the cam body 35 at a predetermined angle. The groove 35a is formed. A worm wheel 36 is formed on the outer peripheral surface of the cam body 35, and the worm 38 fixed to the output shaft of the drive motor 37 fixed on the lower flange 28d is meshed with the worm wheel 36. There is. This drive motor 37
Is rotated in the forward and reverse directions in response to a command from the opening degree calculation unit 26 of the raw material supply amount controller 24, and rotates the cam body 35 by a predetermined amount into the supply cylinder 1a of each iris plate 33. Is formed so that the opening length of the opening 33a is adjusted.

The rotating force of the drive motor 39 is transmitted to the screw 9 of the extruder 7 via the belt 40 and the speed reducer 41. Further, the controller 42 is provided with a screw rotation speed controller 43 that issues a command for controlling the rotation speed of the drive motor 39 to control the rotation speed of the screw 9. The screw rotation speed controller 43 also outputs a command of the screw rotation speed to the raw material supply weight setting unit 25 of the raw material supply amount controller 24. Further, the controller 42 is provided with the take-up speed controller 44 for controlling the rotation speed of the pinch roll 12 for taking the film.

Next, the operation of the present embodiment will be described.

First, the operating conditions are set as follows.

That is, the material of the raw material resin 2 is set according to the material, width, thickness, etc. of the film to be produced, and the optimum screw rotational speed is determined when the film is produced using the set raw material resin 2. Then, the screw rotation speed is input to the screw rotation speed controller 43 of the controller 42. The screw rotation speed is output to the drive motor 39 and also to the raw material supply weight setting unit 25 of the raw material supply amount controller 24.

The raw material supply weight setting unit 25 finds the weight of the raw material resin 2 conveyed by the screw 7 when the screw 7 rotates at the input screw rotation speed, sets the weight as the raw material supply weight, and opens it. It is output to the opening degree calculation unit 26. The opening degree calculation unit 26
The raw material resin 2 of the set raw material supply weight is used for each iris plate
The opening opening supplied to the raw material feeding cylinder 7a of the extruder 7 by natural fall from the opening 33a formed by 3 is calculated, and a command for rotating the cam body 35 to a predetermined position is output to the drive motor 37. Drive motor 37 that received this command
Rotates by a rotation amount according to the command, and rotates the cam body 35 to a predetermined position via the worm 38 and the worm wheel 36. With the rotation of the cam body 35, the roller 34 engaged with the cam groove 35a is moved along with the slide rod 32 along the square groove 31 in the radial direction of the supply cylinder 1a. As a result, the iris plate 33 fixed to each slide rod 32 is connected to the upper supply cylinder 1au and the lower supply cylinder 1ad.
Projecting into the supply cylinder 1a for a predetermined length from the gap 30 between
The opening of the opening 33a formed by each iris plate 33 is set to a size corresponding to the set raw material supply weight.

At the same time, the set values of the width and thickness of the film are input to the take-up speed controller 44 of the controller 2.

Next, the operation of the extrusion molding apparatus of this embodiment is started.

First, the operation of the extrusion molding apparatus is started up, and the operation of the extrusion molding apparatus is stabilized in such a manner that the above-mentioned set values are reached.

Explaining further, the screw 9 of the extruder 7
Is rotated at a constant speed with a set rotation speed, while the raw material resin 2 charged into the raw material hopper 1 from the raw material charging cylinder 27 has the opening of the raw material supply device 20 adjusted as described above. A fixed amount is supplied from the opening 33a in a natural falling state. In this way, the raw material charging cylinder 7
The raw material resin 2 supplied to a is conveyed toward the front end portion of the screw 7 by the screw 7 which is rotating immediately without stopping at the spot. The raw material resin 2 is melted while being transferred in the heating cylinder 8 by the rotation of the screw 9, is discharged from the annular discharge port of the die 10, and is blown by the air supplied into the bubble 11 to be a thin film. And is taken by the pinch roller 12. At this time, the opening of the opening 33a formed by each iris plate 33 is changed or the rotational speed of the screw 9 and the opening of the opening 33 are adjusted so that the produced film has a desired width and thickness. Change both and make fine adjustments. Further, in addition to this fine adjustment, the take-up speed of the pinch roller 12 is changed, and if necessary, the supply amount and temperature of the cooling air for cooling the bubble 11 from the outside are changed.

After the operation of the extrusion molding apparatus becomes stable in this way, the film production is continued while the rotation speed of the screw 9 of the extruder 7 is kept constant. At this time, in the present embodiment, the raw material weight measuring device 22 constantly measures the total weight of the raw material hopper 1, the raw material resin 2, and the raw material supply device 20, and outputs the measured weight to the raw material supply weight calculating section 23. To do. The raw material supply weight calculation unit 23 constantly calculates the supply weight of only the raw material resin 2 from the total weight of the raw material hopper 1, the raw material resin 2 and the raw material supply device 20 sent from the raw material weight measuring device 22, The calculation result is output to the raw material supply amount controller 24.

In the raw material supply amount controller 24, the opening degree calculation unit 26 actually sends the set value of the raw material supply weight set by the raw material supply weight setting unit 25 and the raw material supply weight calculation unit 23. And outputs a command for controlling the opening degree of the opening 33a to the drive motor 37 so that the measured value of the raw material supply weight is always matched with the set value. The drive motor 37 rotates by a rotation angle corresponding to the command, and finely adjusts the opening degree of the opening 33a formed by each iris plate 33 in the same manner as described above. As a result, extrusion molding is performed in which the actual raw material supply weight always matches the set value.

When extrusion molding is performed in this manner, the raw material resin 2 is naturally dropped from the raw material supply device 20, and
The screw 9 of the extruder 7 is rotated at a constant speed while the amount of the natural fall is adjusted to be supplied to the extruder 7, and the raw material resin 2 is melted by the extruder 7 and the die 1
It is possible to extrude a predetermined amount from 0, and then form the raw material resin 2 into a film or sheet shape and perform take-molding. Then, according to the present embodiment, the screw 9 rotates at a constant speed, and the amount of the raw material resin 2 consumed by the rotational speed is supplied from the raw material supply device 20 by free fall. Becomes constant, the width and thickness of the film or sheet are automatically maintained at the set values, and continuous production of the film or sheet without variation as a product can be performed.

To explain further, the present invention has the following advantages.

Advantage 1 In the conventional method shown in FIG. 5, the raw material resin 2 is supplied between the heating cylinder 8 of the extruder 7 and the measuring kettle 6 in a state where the raw material resin 2 is fully filled. Therefore, the blind of the rotating screw 9 pushes or lowers the raw material resin 2 clogged between the heating cylinder 8 and the measuring kettle 6, and the supply pressure of the raw material resin 2 into the heating cylinder 8 is increased. Change, and uneven extrusion occurs.

On the other hand, according to the present invention, in order to supply the raw material resin 2 in an amount consumed by the rotation speed of the screw 9 from the raw material supply device 20 by free fall, the supplied raw material resin 2 is charged into the raw material. It is conveyed toward the tip of the screw 7 by the screw 7 which is rotating immediately without staying in the cylinder 7a. Therefore, the raw material resin 2 is not clogged between the screw 7 and the raw material supply device 20, and the conventional raw material resin 2 is neither pushed up nor lowered, and the molten resin by the extruder 7 is prevented. The extrusion amount is controlled to a constant value, and the film or the like as a product has a completely uniform width and thickness.

Advantage 2 Since the screw 9 is rotated at a constant speed, the amount and state of the resin conveyed in the heating cylinder 8 are also constant.
Therefore, the amount of heat received by the resin conveyed in the heating cylinder 8 and the shearing force are always constant, and a uniform product such as a film or sheet can be produced.

Advantage 3 Since the product such as the film becomes uniform, the pinch roller 1
The necessity of changing the take-up speed, etc. by 2 is greatly reduced, the molding conditions are almost constant, and the reliability is greatly improved.

Advantage 4 In recent years, the trend is to improve the added value of products, mix raw materials resins, mix fillers, etc. for classification with other products.
Mixing of additives and, in some cases, foaming agents have been performed, and it has become difficult to perform uniform quantitative extrusion in the conventional hopper shape.

On the other hand, in the present invention, when molding is performed using a plurality of types of raw materials, a plurality of raw material feeding cylinders 7a are provided in the heating cylinder 8 of the extruder 7, and each raw material feeding cylinder 7a is provided with a drawing. By installing the raw material hopper 1, the feed cylinder 1a, and the raw material feeding device 20 shown in FIGS. 1 to 4, each raw material is fed to the extruder 7 in an appropriate amount, and these are uniformly mixed in the heating cylinder 8. By extruding a fixed amount at a time, a product having desired characteristics can be uniformly produced.

Advantage 5 It is possible to prevent uneven extrusion (generally referred to as surging) which is caused by various causes because the feed weight of the raw material is controlled.

Advantage 6 There is no trouble that the raw material shutter 2 of the conventional method is clogged with the raw material resin 2 and that when the raw material resin 2 of a different type is replaced, the raw material resin 2 clogged on the previous day is taken in and entered. Become.

Advantage 7 Since the raw material opening / closing cylinder 4 and the like are not required, it is not necessary to process the head difference of the raw material resin 2, so that there is no time delay.

Advantage 8 Machine cost is low because there is no raw material opening / closing cylinder 4 or the like.

Advantage 9 Since there is no raw material opening / closing cylinder 4 etc., there is no risk of injury due to it.

In the above embodiment, the case where the molten resin is extruded into a tube shape to produce a film has been described, but the present invention is similarly applied to the case where a sheet is produced using a T die. be able to.

Further, the present invention is not limited to the above-mentioned embodiment, but various modifications can be made if necessary. For example, the drive motor 37 and the worm 38
Instead of the worm wheel 36, a lever or the like may be attached to the cam body 5 and the cam body 35 may be manually rotated.

[0059]

As described above, since the extrusion molding method and the raw material supply device for the extruder according to the present invention are configured and functioning, it is assumed that the conventional method changes with the passage of time. The amount of molten resin extruded from the extruder can be made constant at all times for continuous production of films and sheets. In other words, the screw of the extruder can be rotated at a constant speed to keep the amount of molten resin extruded to a constant value. At the same time, it is possible to perform continuous production of high-quality films and sheets while maintaining the supply amount of the raw material resin to the screw portion at an appropriate value, eliminating the need for conventional raw material shutters and raw material opening / closing cylinders. The structure is simple, and the cost is low.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of an extrusion molding apparatus in which an embodiment of a raw material supply apparatus for an extruder of the present invention is installed.

FIG. 2 is a longitudinal sectional view showing an embodiment of a raw material supply apparatus for an extruder of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

4 is a partially cutaway plan view of FIG.

FIG. 5 is a schematic view showing an example of a conventional extrusion molding apparatus.

[Explanation of symbols]

 2 Raw material resin 7 Extruder 9 Screw 10 Die 20 Raw material supply device 33 Iris plate 33a Opening

Claims (4)

[Claims] 1. An extrusion molding method in which a raw material resin is supplied to an extruder, the raw material resin is melted by the extruder and extruded from a die, and then the raw material resin is taken into a film or sheet form and taken up. An extrusion-molding method, characterized in that the resin is supplied to the extruder by gravity fall and the amount of the natural fall is adjustable, and the screw of the extruder is rotated at a constant speed for molding. 2. A raw material supply device for an extruder, characterized in that it is formed so as to supply the raw material resin to the extruder by natural fall and with the amount of natural fall adjustable. 3. The raw material supply device for an extruder according to claim 2, wherein the size of the opening area of the raw material supply port through which the raw material resin naturally falls is variable. 4. The screw according to claim 2, wherein the screw of the extruder is rotated at a constant speed.
The raw material supply device for the extruder according to.