JPH01314136A - Synthetic resin film, method and device for film thickness-control in film molding of melt-extruding type - Google Patents

Abstract

PURPOSE:To enable the film with desired thickness to be produced quickly and in high accuracy by a method in which the winding time of a completed film is measured, and while the completed film is wound up, the weight of the completed film having been wound up is measured, and further the feed rate of the film is automatically regulated. CONSTITUTION:In a wind-up machine 6, a start switch 10 is pushed in the wind-beginning of a film 3a, and a stop switch 11 is pushed in wind-finishing, whereby the film of arbitrary amount 3a is wound up. Then winding time T is measured by the stop watch in an arithmetic unit 7. The weight W of the film wound up by the wind-up machine, is measured by a weighing machine 12. The arithmetic unit 7 loads the winding time T from the stopwatch 7a and the weight W of the sample film 3b from the weighing machine 12. The arithmetic unit 7 gives the winding time T and the weight W, the thickness (t) and other prescribed value to the formula for obtaining the thickness of the film drawn out at a constant speed, thereby computing the drawn out speed of the film, and controlling a speed-regulating motor 5 by way of a motor- controlling part 9 so that the feed rate of a nip roll 4 is a required speed V.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a long synthetic resin film with high precision in thickness, and a method for controlling the thickness of the film as desired during the production of the film. Regarding the device.

[Conventional technology]

Conventionally, in order to control film thickness during melt extrusion film forming, the thickness of the finished film was actually measured, and based on the measured value, an appropriate film withdrawal speed was determined based on the experience and skill of the operating engineer. This is done by stipulating the following:

[Problem to be solved by the invention]

Long films, which are raw materials for packaging films, are required to have highly accurate thicknesses that are compatible with precise automatic packaging equipment, and long films with accurate thicknesses are desired.

The thickness of the finished film during melt extrusion film forming does not correspond uniquely to the drawing speed of the film in a one-to-one manner, but changes depending on parameters such as the amount of resin discharged from the extruder and the width of the film. do.

The discharge amount, film width, etc. are determined in advance according to the specifications of the film to be formed, and are adjusted to be constant.

However, in order to adjust the film thickness, the film specifications and the type of resin material must be considered empirically, and the feed speed must be adjusted by skilled technicians based on the measured film thickness value. There is.

Therefore, when changing the film specifications continuously without stopping the film manufacturing equipment, or when changing the production capacity by changing the resin discharge amount midway through even if the film specifications are the same, the change It is desirable to be able to adjust the film thickness quickly without requiring any skill.

In particular, when changing the production capacity of films with the same specifications, the amount of resin extruded in the extruder is changed by changing the rotation speed of the extrusion screw, and the film draw-out side is changed to keep the film thickness constant. The rotation speed of the nip roll is changed in proportion to the rotation speed of the extrusion screw.

However, the proportional relationship between the rotation speed of the extrusion screw and the rotation speed of the nip roll to keep the film thickness constant is not linear, and furthermore, this proportional relationship changes depending on the density of the resin and other parameters. Proportional control using simple proportional constants makes it difficult to change production capacity while keeping film thickness constant.

Furthermore, when changes are made to increase production capacity, if the film thickness changes and it takes time to adjust, a large number of defective products will be produced in a short period of time.

[Means to solve the problem]

According to the present invention, the above problem is solved as follows.

By extruding the molten resin and forming it into a film, we draw it out at a constant speed and measure the time from the start of one roll of the drawn film until the end of one roll.
The required amount of film is wound up, the weight of the wound film is measured, and the winding time, weight of the wound film, desired thickness, and other specified values are determined for the film that is drawn out at a constant speed. A synthetic resin film that is obtained by calculating the drawing speed of the film by feeding it into a calculation formula for calculating the thickness of the film, and then drawing the film while keeping the drawing speed determined in this manner constant.

There is a process of drawing out the molten resin at a constant speed to form it into a film, a process of winding up the film by measuring the winding time of the finished film that has been drawn out, a process of measuring the weight of the finished film that has been wound up, and a process of measuring the weight of the finished film that has been drawn out. By giving the film winding time, the weight of the film wound within this time, and the desired thickness to the relational expression between the speed of the film being pulled out and the thickness of the film obtained by the drawing speed, A film forming method for forming a film by a melt extrusion method, comprising a step of calculating a drawing speed of the film, and a step of correcting the drawing speed of the film based on the drawing speed of the film determined by the calculation process. How to control film thickness at different times.

A film forming means for forming a molten resin into a film, a film drawing means equipped with a feed roll for feeding the film at a constant speed, a means for winding up the film sent out from the film drawing means, and a film winding means for rolling the film. A winding time measuring means for measuring the time from the start of winding to the end of winding, a means for measuring the weight of the wound film, and a calculation formula for calculating the thickness of the film fed at a constant speed. Film feed speed calculation means for calculating the feed speed of the film drawing means by giving the weight to be taken, a desired thickness and other specified values;
1. A film thickness control device for melt extrusion film forming, comprising a feed roll drive control means for controlling the rotational speed of a feed roll of a film drawing means in accordance with a feed speed calculated by a calculation means.

[For production]

The film feed speed ( V) is automatically adjusted.

〔Example〕

FIG. 1 is a block diagram when the present invention is implemented using a blown film molding method.

(1) is an extruder, (1a) is a screw motor, (2) is a film forming die, (3) is a film pulled out from the die (2), (4) is a film that is folded into a flat shape, and a nip roll that is pulled out at a constant speed (5
) is a governor motor that drives the nip roll (4) at a required speed and at a constant speed; (6) is a governor motor that drives the nip roll (4) at a constant speed;
) is a winder that winds up the finished film sent out from the machine.

The screw motor (1a) rotates the extrusion screw of the extruder (1) to control the amount of resin discharged.

The nip roll (4) is controlled at a constant speed by a speed governor motor (5), which is controlled by a calculation device (7) so that the finished film (3a) has a desired thickness.
controlled by.

The arithmetic unit (7) includes a microcomputer-based arithmetic unit (8) and a motor control unit (5) that controls the speed governor motor (5).
9).

The computing device (7) is also provided with a stopwatch (7a) for measuring the time during which the winder (6) is winding the finished film (3a). This stopwatch (7
The start switch (10) and stop switch (11) for transmitting the start signal and stop signal in a) are pulled out from the computing device (7) and connected to the outside so that they can be operated near the winding machine (6). It is connected.

Furthermore, the calculation device (7) includes an electronic weighing scale (12).
is externally connected, and the measured value of this weight scale (12) is sent as an electrical signal to a calculation device! (7) is automatically imported.

Note that the arithmetic device (7) is substantially a computer, and includes a CRT monitor (13), a key input device (14), and a printer (15) as peripheral devices.

In the winder (6), the required sample film (3b
), the winding time (T) is measured.

That is, when starting to wind the sample film (3b) or cutting the first end of the wound film, press the start switch (10), and at the end of winding or cutting the end of the wound film, press the stop switch (11). is pressed to input the winding start and winding end points of the winder (6) into the arithmetic unit (7).

The amount of winding of the sample film (3b) is appropriate, but usually a fraction of the amount of the product is sufficient.

The wound sample film (3b) is weighed on a weight scale (1
2), the weight is measured, and the value is calculated by the calculation device (7).
is input.

In the calculation device (7), the weight of the winding shaft (16) is removed and the actual weight (W) of the sample film (3b) is taken in.

In the arithmetic device (7), the start switch (1
0) and when the stop switch (11) is operated is captured by the stopwatch (7a) as the winding time (T).

In addition, the arithmetic device (7) is provided with a key to calculate the desired thickness (1) of the finished film (3a) via the key human power device (14).
, and each constant value required for the calculations described below are input in advance.

In the blown film forming system configured as described above, before the synthetic resin film of the present invention is obtained and before the control according to the method of the present invention is performed, the screw motor (1a) of the extruder (1) is operated in an appropriate manner. It is assumed that the rotation speed is maintained at a constant speed. In other words, the state is set immediately after the production capacity is changed.

The amount of molten resin discharged from the extruder (1) at that time is unknown, but is kept constant per hour.

This molten resin is extruded from a die (2) to form a film (3), and is pulled out by a nip roll (4) while keeping the speed constant, and the finished film (3a) is sent to a winder (6).

In the winder (6), a start switch (10) is pressed at the beginning of winding the film (3a), and a stop switch (11) is pressed at the end of winding to wind up an arbitrary amount of film (3a). The winding time (T) at that time is
Measure with the stopwatch (7a) of the calculation device (7).

The film wound up by the winding machine (6) is measured as a sample film (3b) and its weight (W) is measured using a scale (12).
is measured.

The computing device (7) takes in the winding time (T) from the stopwatch (7a) and the weight (W) of the sample film (3b) from the weighing scale (12).

Note that the calculation device (7) has the required film thickness (1
), and physical property values determined in advance by the resin material.

Specified values such as constants determined in advance according to film specifications are input in advance.

The calculation device (7) adds one winding time (T) to a calculation formula (described later) for determining the thickness of the film that is drawn out at a constant speed.
By giving the weight (W), thickness (1), and other specified values, calculate the drawing speed (V) of the film, and set the feeding speed of the nip roll (4) to the calculated speed (V). The speed governor motor (5) is controlled via the motor control section (9) in this way.

In this way, the velocity (V
) is kept constant and the finished film (3a) is pulled out.
is a long piece with a desired thickness (1) that satisfies the high precision specifications of automatic packaging equipment and the like. This film is wound up by a winder (6) as a product film.

When winding this product film, the winding time (
By measuring T) and the weight (W) of the product film and adjusting the feed speed (V) based on those values, the thickness (1) can be kept constant over a long period of time. High quality film can be obtained.

Next, the winding time (T) of the completed film (3a).

Completed film (3a) wound within that time (T)
The calculation for determining the feeding speed (V) of the nip roll (4) in order to obtain the desired thickness (1) from the weight (W) of will be explained.

The feeding speed (V) is the length (L) of the finished film (3a) fed by the nip roll (4) within the winding time (T).
It corresponds to and is expressed by the following formula.

V=L/T ---1 --- (1) The length (L) fed by the nip roll (4) within the winding time (T) and the length (L) that is wound up within the same time (T). sample film (3
b) The lengths (L) are equal.

This length (L) is determined by the number of rotations (N) of the nip roll (4) during the winding time (T), the circumference of the nip roll (4), that is, the diameter (D) of the nip roll (4), and the ratio of pi. (π)
The correction coefficient (K
), it is expressed by the following formula.

L = −N・π・D ---1-(II) The weight 1 (W) of the wound sample film (3b) is the product of the volume and the specific gravity (ρ) of the material, and the volume is is the cross-sectional area in the direction perpendicular to the longitudinal direction of the sample film (3b), that is, the film width (b) multiplied by the film thickness (70), which is then multiplied by the film length (L). Therefore, the following equation is obtained.

W=b-t・L・ρ -----(m) In addition, the finished film obtained by infusion molding (3a)
is folded in two layers, so the desired thickness (1
) is 1/2 of the film thickness (tl) in equation (2), and the following equation is obtained.

w=b.2t-L.rho --- (mV) Expressing equation (2) in terms of length (L) and substituting it into equation 1, the following equation is obtained.

V = 1/(2t b ρ)・W/T ---(V) Desired thickness (1), - film width (b), density (ρ),
Since it is a known number determined in advance by the film specifications, 1
When /(2tbρ) is a constant (A), the following equation is obtained.

V=A-W/T----1---(VI)A=1/2
t bρ calculation device i! (7) calculates equation (VI) and calculates the speed signal (
V), and this signal (V) controls the speed governor motor (5).

The speed governor control of the speed governor motor (5) is mechanical speed governor control.

Alternatively, either electric speed governor control is possible.

For example, in the case of mechanical speed control, a speed control lever of a continuously variable transmission mechanism is driven by an appropriate electric actuator, and the position of the speed control lever corresponding to the adjustment speed is measured with a potentiometer. The position signal of this potentiometer is converted into the circumferential speed of the nip roll (4), that is, the feed speed (
V), electrical control is performed based on the speed signal (v) obtained from the calculation result of the equation (VI).

In the case of electrical speed governor control, the speed of the governor motor (5) whose speed is controlled by one-frequency synchronous control, pulse synchronous control, phase control, or other electrical speed control is controlled according to the control target value. The electric signal generated by the motor is controlled by a speed signal (v) calculated by a calculation device (7).

The weight of the sample film (3b) (
When the value of W) is input, Equation (VI) is calculated using the already input winding time (T) and six constant values (A) that are predetermined based on film specifications and the like.

The speed signal (V) obtained as a result is transmitted to the governor motor (5).
The rotational speed of the machine is quickly adjusted according to the feed rate (V).

On the other hand, the film width (b) in the constant (A) in equation (VI) is set as a specified value in advance by the key manual device (14).
This is one of the constant values input from .

This is because the bubble diameter is mechanically determined by a bubble guide (not shown), so the film width (b) is a constant value that is maintained at a preset required value.

However, in order to further improve the accuracy of the film thickness, it is desirable to give the film width (b) as an actual value as well.

(16) in FIG. 1 is a film width measuring device for this purpose. This film width measuring device! (16), the width of the completed film (3a) is constantly measured, and the signal of the obtained film width (b) is input to the arithmetic unit (7). In the calculation device (7), the average value of the film width (b) within the winding time (T) is used as the value of the film width (b) in the constant (A).

FIGS. 2 and 3 show an embodiment in which the method of the present invention is applied to a blown film forming apparatus.

(30) is a vertically long frame member, and a horizontally horizontal extruder (31) is installed at the bottom of this frame member (30), and above the resin discharge end (31a) of the extruder (31). is provided with a film forming die (32) having an annular die lip.

An air ring (34) is provided around the outer periphery of the die lip on the upper surface of the die (32) for cooling the molten film (33) that is discharged from the die lip and pulled upward. Above the center of the die (32) is provided an inside mandrel (36) that inflates the molten film (33) to form a bubble (35).

Above the inside mandrel (36) is a bubble guide (37), above that is a bubble folding guide (
38), but above it is a nip roll (39)
is provided.

The bubble folding guide (38) consists of two guide plates (38
a) The upper end is pivoted on a horizontal axis so that the narrowing angle of the bubble that opens downward can be adjusted. The upper end of the guide (38) is connected to the nip roll (39).
) is fixed to the bottom of the

Bubble folding guide (38) and nip roll (39)
is guided by the frame member (30) and the hoist (40)
It is attached to a carriage (41) which is suspended from the shaft and is movable up and down.

The length of the bubble (35) changes as the carriage (41) moves up and down. The length of the bubble (35) depends on the bubble diameter (corresponding to the folding width) and the drawing speed of the film.

properly adjusted.

The carriage (41) is provided with a governor motor (42) that drives the nip roll (39) at a constant speed.

The speed governor motor (42) is connected to the control box (43) housing the arithmetic unit (7) and is controlled as described above.

The bubble (35) is folded flat and the nip roll (
The finished film (44) is fed out at a constant speed from 39).
) is guided downward via a guide roll (45),
The finished film (44) is sent to an automatic winding machine (47) via a feed roll (46) that sends out the finished film (44) by applying appropriate tension.
sent to.

The automatic winder (47) takes the completed film (4) that is sent to it.
4) is wound onto the winding shaft (48), and when the amount of winding reaches a certain amount, the film (44) is automatically cut.

The take-up roll (49) is discharged.

Next, a new winding shaft (48) is automatically supplied and the cut end of the film (44) is automatically wound around it.

This is repeated one after another, and the film (44) is automatically wound up.

Note that the configuration of the automatic winder (47) is not the gist of the present invention, so a detailed explanation will be omitted;
(Japanese Unexamined Patent Application Publication No. 1983-1989).

The take-up roll (49) is guided by the guide rail (50) and sent out to the finished product take-out section (51). A weight scale (52) corresponding to the weight scale (12) is provided in the middle of this guide rail (50).

There is a section of the required length in the middle of the guide rail (50), and this section is used as the cradle (53) of the weighing scale (51).
It has become.

As a result, the finished film (
44) is a take-up roll (49), and the guide rail (5
0) and placed on a weighing scale (52), where the weight is measured.

Transfer the film from the take-up roll (49) to the sample film (3).
In case of b), automatic winding device! Depending on the operation of the film cutting device in (47), switches (not shown) similar to the start switch (10) and stop switch (11) are activated. The output signal of this switch is input to an arithmetic unit (7) to measure the winding time (T) for one turn.

Although the above embodiments relate to the case where the lip shape of the blown film is annular, it goes without saying that the present invention can also be applied to a T-die in which the film is molded into a sheet shape.

In the case of T-die, since the finished film is in the form of a sheet, equation (m) can be directly applied to calculate the thickness.

Incidentally, fine adjustment of the film thickness in a film manufacturing machine is generally performed by changing the rotational speed of the film draw-out side, that is, the nip roll.

However, the discharge amount of resin per unit time of the extruder (1) is also a parameter that changes the film thickness, so adjusting the rotation speed of the screw motor (1a) of the extruder (1) can also change the film thickness. The thickness can be adjusted.

Therefore, according to the present invention, the film thickness can also be controlled by keeping the rotational speed of the nip roll constant and controlling the rotational speed of the screw motor (1a).

〔Effect of the invention〕

In the method of the present invention, the film feeding speed is automatically adjusted by measuring the required sample film winding time and the weight of the sample film wound within that time, and the film of the desired thickness is quickly formed. Manufactured in
Moreover, a long film with high thickness accuracy is provided.

Further, in the apparatus of the present invention, the film thickness is automatically adjusted, so that no skill is required for the adjustment.

Furthermore, during normal film manufacturing, a finished product winding roll is designated as a sample and the winding time and film weight are measured to ensure a uniform film thickness at all times.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the method of the present invention, FIG. 2 is a side view of a blown film forming apparatus in which the method of the present invention is implemented, and FIG. 3 is a block diagram showing one embodiment of the method of the present invention. - ■ line arrow view. (1) Extruder (2) Film forming die (LA) screw motor (3) Film (3)
a) Finished film (3b) Sample film (4) Nip roll (5) Speed regulating motor (6)
Winder (7) Arithmetic unit (7a) Stopwatch (8) Arithmetic unit (9) Motor control unit
(10) Start switch (11) Stop switch (12) Weight scale (13) CRT monitor
(14) Key human powered device (15) Printer
(16) Film width measuring device (30) Frame member
(31) Extruder (31a) resin discharge end
(32) Film forming die (33) Melt film (34) Air ring (35) Bubble
(36) Inside mandrel (37) Bubble guide (38) Bubble folding guide (
39) Nip roll (40) Hoist (41
) Carriage (42) Governor motor (43)
Control box (44) Finished film (45)
Guide roll (46) Feed roll (47) Automatic winder (48) Winding shaft (49) Winding roll (5o) Guide rail (51) Take-out section
(52) Weight scale (53) pedestal Figure 3

Claims (12)

[Claims] (1) While extruding the molten resin and forming it into a film, draw it out at a constant speed, and then
By measuring the time from the start of winding to the end of winding, the required amount of film is wound, and the weight of the wound film is measured, and the winding time, weight of the wound film, and desired thickness are calculated. By feeding the thickness and other specified values into the formula for determining the thickness of a film drawn at a constant speed, the drawing speed of the film is determined, and the drawing speed thus determined is kept constant. A synthetic resin film that can be pulled out. (2) The process of drawing out the molten resin at a constant speed and forming it into a film, and the winding time of the drawn finished film are measured.
The process of winding the film, the process of measuring the weight of the completed film, the speed at which the film is pulled out, and the thickness of the film obtained by the speed at which it is pulled out are combined into the relationship between the film winding time and the film thickness. The weight of the film that can be wound within the time,
The method is characterized by comprising a step of calculating the film drawing speed by giving a desired thickness, and a step of correcting the film drawing speed based on the film drawing speed determined by the calculation process. A method for controlling film thickness during film forming by melt extrusion. (3) A film forming means for forming a molten resin into a film, a film drawing means provided with a feed roll for feeding the film at a constant speed, a means for winding up the film sent out from the film drawing means, and a film winding means There is a winding time measuring means for measuring the time from when the film starts winding to the end of winding, a means for measuring the weight of the wound film, and a calculation formula for calculating the thickness of the film fed at a constant speed. and a film feeding speed calculating means for calculating the feeding speed of the film drawing means by giving the winding weight, a desired thickness and other specified values; 1. A film thickness control device during melt extrusion film forming, comprising: a feed roll drive control means for controlling the rotational speed of the feed roll of the means. (4) The film thickness control device for melt extrusion film forming according to claim (3), wherein the film forming means is an inflation film forming device. (5) The film thickness control device for melt extrusion film forming according to claim (3), wherein the film forming means is a film forming device using a T-die. (6) The film winding device according to any one of claims (3) to (5), wherein the film winding means is an automatic winding device that outputs an electric signal for measuring the winding time at the beginning and end of winding. Film thickness control device during melt extrusion film forming. (7) The film thickness control device for melt extrusion film forming according to any one of claims (3) to (5), wherein the film winding time measuring means is an electronic stopwatch. (8) The film thickness control device for melt extrusion film forming according to claim (7), wherein the electronic stopwatch measures time by a computer constituting the film feed speed calculation means. (9) During melt extrusion film forming according to any one of claims (3) to (8), the means for measuring the weight of the film is an electronic weight scale connected to a computer constituting the film feed rate calculation means. Film thickness control device. (10) Melt extrusion film forming according to any one of claims (3) to (9), wherein the means for measuring the weight of the film is provided in the middle of the take-up roll take-out path in the automatic film take-up device. Film thickness control device. (11) The film thickness control device for melt extrusion film forming according to any one of claims (3) to (10), wherein the feed roll driving means is a mechanical speed regulating motor. (12) The film thickness control device for melt extrusion film forming according to any one of claims (3) to (10), wherein the feed roll driving means is an electronic speed regulating motor.