JP6754223B2 - Film manufacturing equipment and film manufacturing method - Google Patents

Description

The present invention relates to a film manufacturing apparatus and a film manufacturing method. More specifically, the present invention relates to a film manufacturing apparatus that carries out a melt extrusion method to manufacture a resin film. The present invention also relates to a film manufacturing method for manufacturing a resin film by a melt extrusion method.

As a method for producing a high-quality thermoplastic resin film for optical applications, the T-die method by melt extrusion is known. This method is generally referred to as a melt extrusion method.
The film manufacturing apparatus that carries out the melt extrusion method is roughly divided into the apparatus and equipment on the extruder side and a roll group downstream of the apparatus and equipment. The melt extrusion method has a step of extruding a resin into a sheet from a T-die mounted on the extruder side, cooling the resin with a group of rolls downstream, stretching the resin as necessary, and then winding the resin.
In the melt extrusion method, in order to make the characteristics of the obtained product (resin film) uniform, the characteristics of the resin film after molding are measured, the operation amount of each process is calculated based on the variation in the characteristics, and the operation amount of each process is calculated. Feedback is given to the operation.
Patent Document 1 proposes a method and an apparatus for measuring the characteristics of a resin film formed by a melt extrusion method and controlling the screw rotation speed of the extruder and the temperatures of the extruder and the gear pump according to the measured film characteristics. Has been done.
Patent Document 1 describes that it is important to improve the kneadability of the extruder and stabilize the discharge accuracy of the gear pump in order to make the variation in film characteristics after molding uniform.

Patent Document 2 discloses a technique in which a heating means is provided in a pipe so that the fluctuation of the molten resin temperature at the end of the pipe on the extruder side is within a certain range, and the temperature of the heating means is controlled by PI control or PID control. ing.
Further, in Patent Document 2, the parameter (proportional band) of proportional control (P control) in PID control is set to 2 or more, and the parameter (integration time) of integral control (I control) is set to 200 or more.
In Patent Document 2, by setting the P value (proportional control parameter) and the I value (integral control parameter) in the above range, the temperature of the molten resin flowing in the pipe does not change suddenly, and the T-die is used. It is described that the temperature of the supplied molten resin is always kept constant and the fluctuation of the discharge pressure discharged from the T-die is stable, so that the thickness unevenness in the flow direction of the resin film can be suppressed.

Japanese Unexamined Patent Publication No. 2014-193604 JP-A-2007-144883

As described above, the resin film used for optical applications has high required quality. Therefore, when manufacturing a resin film used for optical applications, it is desirable that the temperature of the path through which the resin passes is precisely controlled.
Therefore, in melt extrusion of a resin film, the temperature of each part of the device and equipment on the extruder side that melts the raw material resin and extrudes it from the T-die into a sheet is controlled by ON / OFF control, proportional control, PID control, and the like. ..
When manufacturing a film used for optical applications, PID control, which has high accuracy of temperature control, is often used for temperature control of devices and equipment on the extruder side.

Here, in order to perform PID control, it is necessary to set a P value which is a parameter of proportional control, an I value which is a parameter of integral control, and a D value which is a parameter of differential control. However, in PID control, the actions of each parameter are correlated, and experience and knowledge are required to obtain the optimum value of the PID parameter according to the characteristics of the controlled object.
Therefore, commercially available temperature controllers are often equipped with an auto-tuning function for PID parameters. Even in the temperature control of the film manufacturing apparatus, when the temperature of each part is PID controlled, the PID parameter is often set by using the auto-tuning function mounted on the temperature controller.

However, in temperature control of a film manufacturing apparatus that manufactures a film used for optical applications, the PID parameter set by the auto-tuning function is not always the optimum value in many cases.
Since the quality of resin films used for optical applications is high, the room where the film manufacturing equipment is installed is often air-conditioned and the temperature inside the room is kept within a certain range. That is, an air conditioner is provided at the place where the device for manufacturing the resin film is installed, and the temperature is controlled so that the place where the device is installed maintains a constant environment. Therefore, the surrounding environment of the film manufacturing apparatus is often more stable than that of the ordinary manufacturing equipment.

On the other hand, the film manufacturing apparatus itself is a large heat source, and it may be difficult to keep the indoor temperature constant.
For example, the indoor air may flow due to the updraft generated by the high temperature of the extruder body, and the temperature variation in the room may fluctuate to change the temperature of the environment surrounding the flow path through which the molten resin passes. .. In addition, the ambient temperature in the immediate vicinity of the extruder may be irregularly disturbed due to the influence of the on / off timing of the air conditioner and the blower provided as peripheral equipment.

For this reason, the ambient temperature near the extruder may be irregularly disturbed and the resin temperature may fluctuate. Here, if the PID parameter is appropriate, the temperature fluctuation of the resin converges at an early stage, and the influence on the resin film as a product is small.
However, if the PID parameter set by the auto-tuning function is not the optimum value, the temperature fluctuation of the resin is out of the permissible range, and the resin film as a product is adversely affected. In particular, when the temperature is controlled by PID control while the ambient temperature fluctuates, the ambient temperature changes even during the full-scale production of the resin film, so the temperature of each part of the device and equipment on the extruder side is stable. Instead, an unexpected temperature distribution occurs in the resin in the resin flow path, which adversely affects the resin film as a product.

Specifically, each part of the device and equipment on the extruder side constituting the extruder to the T-die is controlled to a desired temperature by a heating means such as a heater. However, among the devices and equipment on the extruder side, the connecting pipe connecting the extruder, gear pump, and T-die is the distance from the resin flow part to the outer surface, that is, the wall thickness of the pipe wall is thin and passes through the inside. The molten resin to be extruded may be affected by changes in the environment around the process and changes in temperature.
If there is a temperature difference between the molten resin near the center and the wall surface in the resin flow path, the viscosity characteristics in the width direction of the film discharged from the T-die become non-uniform, and as a result, for example, the low viscosity region is thick and the high viscosity region. It becomes a non-uniform thickness profile shape such that the thickness becomes thin.

In addition, it is difficult to obtain the optimum PID parameters by auto-tuning performed while the ambient temperature fluctuates and there are not a few temperature fluctuations in each part of the melt extrusion equipment. In actual manufacturing, the thickness profile shape Also causes a fluctuating phenomenon.
Furthermore, if the thickness unevenness in the flow direction or width direction of the film exists under the condition that the temperature and temperature distribution of the molten resin are not stable, the lip spacing of the T-die is adjusted to eliminate the thickness unevenness. When various adjustments such as the above are performed, adjustments other than the main cause are performed while the thickness profile shape fluctuates due to temperature changes, and the thickness of the film is rather disturbed.

Therefore, if the ambient temperature fluctuates and there are temperature fluctuations in each part of the melt extrusion facility, it should be suspected that the PID parameters are inappropriate and the PID parameters should be corrected immediately.

On the other hand, in the method described in Patent Document 1, the screw rotation speed in the extruder and the temperature setting values of the extruder and the gear pump are changed and adjusted for the variation in the characteristics of the film, but the PID parameter is corrected. Therefore, it is difficult to adjust the control amount for the fluctuation of the resin temperature inside the connecting pipe due to the influence of the atmospheric temperature fluctuation. In addition, the connecting pipes and the like that are most susceptible to changes in atmospheric temperature are not subject to adjustment, and fluctuations in film characteristics cannot be eliminated only by adjusting the extruder or gear pump as described in Patent Document 1.

Further, as a method for setting the optimum PID parameter in PID control, there is a method described in Patent Document 2, but in the method described in Patent Document 2, the wind flow and the atmospheric temperature around the film manufacturing apparatus are stable. In the environment, it exerts the effect of suppressing temperature fluctuations of the molten resin flowing in the piping, but it is difficult to immediately respond to changes in the atmospheric temperature that occur irregularly during production and the accompanying changes in the thickness profile. is there.
That is, if the P value is stronger than the optimum PID parameter, hunting occurs, while if the P value is weakened to suppress hunting, it takes time to stabilize at the target temperature.

However, in the prior art, it is difficult to know whether or not the PID parameter set by the auto-tuning function is appropriate. Therefore, the temperature of each part is controlled based on an inappropriate PID parameter, and full-scale production of the film is performed in a state where the film characteristics are not stable.
That is, when producing a resin film, the resin film is first molded on a trial basis, and then the resin film is produced in earnest. As described above, in the prior art, it is difficult to know whether or not the PID parameter set by the auto-tuning function is appropriate. Therefore, the PID parameter is unsuitable at the stage of experimentally molding the resin film. Is difficult to understand, and there are cases where full-scale production is started with the PID parameters remaining inappropriate. Then, during full-scale production, it is discovered that there are variations in the thickness of the film, and the PID parameters are corrected, but the production is interrupted and the workability is poor. In addition, the resin film produced up to that point may be wasted.

In particular, in an environment where the ambient temperature of the controlled object fluctuates greatly, it is not possible to immediately determine whether or not the PID parameter is the optimum parameter even if it is obtained by auto-tuning.
If the PID parameter obtained by auto-tuning is not an appropriate PID parameter, the heater or the like will hunt and the profile shape of the resin film will be disturbed. That is, if the PID parameter obtained by auto-tuning is not an appropriate PID parameter, the quality of the thickness of the manufactured resin film deteriorates.

In addition, the change in profile shape is not short-term, but takes a long time such as one cycle in units of tens of minutes, so the production manager may not notice it, and if it is not noticed, it will be low for a long time. We will continue to make quality resin films.
In addition, the ambient temperature of the controlled object may fluctuate significantly after the start of production. For example, the environment around the controlled object was stable at the start of production, but the surrounding environment may be disturbed some time after the start of production. As a result, the initially set PID parameters become incompatible, and the heater or the like may hunt during production. Even in this case, since the change in profile shape takes a long time such as one cycle in units of tens of minutes, the production manager may not notice it, and if it does not notice it, a low quality resin film will be used for a long period of time. I will continue to make it.

It is an object of the present invention to pay attention to the above-mentioned problems of the prior art and to develop a film manufacturing apparatus having a function of determining whether or not the control parameters of the heating means are appropriate. An object of the present invention is to develop a film manufacturing apparatus having a function of determining whether or not a PID parameter is appropriate. Another object of the present invention is to provide a method for producing a film capable of producing a film having less unevenness in thickness.

An embodiment for solving the above-mentioned problems is a film manufacturing apparatus having an extruder for extruding a molten resin and a die mounted on the extruder, and extruding the resin into a sheet from the die to form a resin film. In the above, there is a heating means for adjusting the temperature of the resin in the path through which the resin passes, and the heating means is controlled based on at least one of proportional control, differential control, and integral control, and is in the width direction of the resin film. The thickness measuring means for measuring the thickness of each part in the above, the contour curve determining means for determining the rough contour curve of the resin film based on the measured values of the thickness measuring means, and the determined contour curve satisfy a predetermined condition. It is a film manufacturing apparatus characterized by having a notification means for performing a predetermined notification in some cases.

It is desirable that the contour curve determining means approximates the rough contour curve of the resin film to a predetermined constant function having a coefficient as a variable.

In another aspect, in a film manufacturing apparatus having an extruder for extruding a molten resin and a die mounted on the extruder and extruding the resin into a sheet from the die to form a resin film, the resin is used. There is a heating means for adjusting the temperature of the resin in the passing path, and the heating means is controlled based on at least one of proportional control, differential control, and integral control, and the thickness of each part in the width direction of the resin film. A thickness measuring means for measuring the thickness, and a contour curve determining means for approximating a change in the thickness of the resin film in the width direction to a predetermined constant function with a coefficient as a variable, based on the measured values of the thickness measuring means. The film manufacturing apparatus is characterized by having a notification means for performing a predetermined notification when the coefficient satisfies a predetermined condition.

Further, the contour curve determining means approximates a rough contour curve of the thickness of the resin film or a change in the thickness of the resin film in the width direction to a quadratic function having a coefficient as a variable, and is a quadratic term coefficient. It is desirable that the notification means perform a predetermined notification on condition that the absolute value exceeds a certain value.

The recommended film manufacturing method is a film manufacturing method characterized by using the above-mentioned film manufacturing apparatus, modifying the control parameters of the heating means after notification by the notification means, and molding a resin film. ..

According to the film manufacturing apparatus of the present invention, it is possible to determine whether or not the set PID parameter is appropriate.
Further, according to the film manufacturing method of the present invention, it is possible to manufacture a film having less uneven thickness.
Further, according to the present invention, by approximating the contour curve to a quadratic curve, it is possible to quantify the change in profile shape due to hunting of temperature changes. As a result, fluctuations in the profile shape can be detected in a timely manner, measures such as re-correcting the parameters can be taken, and the formation of a low-quality resin film can be minimized.

It is a block diagram which shows an example of the film manufacturing apparatus which concerns on embodiment of this invention. It is a block diagram of the control device of the film manufacturing apparatus of FIG. It is a flowchart which shows the operation of the film manufacturing apparatus of FIG. It is explanatory drawing explaining the contour curve, (a) shows the case which assumed the film with a thick central part, and (b) shows the case where the film with a thin central part is assumed. It is a graph explaining the quadratic curve approximation method of the thickness profile in the film width direction of the film extruded from the extruder of the film manufacturing apparatus of FIG. 1, (a) is the thickness of the extruded resin film on the X axis. It is a graph with the Y-axis taken, and (b) is a graph in which the product effective part of the graph (a) is extracted and the scale of the Y-axis is enlarged. It is a figure which shows the time-dependent change and the threshold value of the quadratic term of the thickness profile approximation curve which concerns on embodiment of this invention, (a) shows the state before the control parameter is corrected, (b) is after the control parameter is corrected. Indicates the state of.

Prior to the detailed description, an outline of the embodiment of the present invention will be described.
The film manufacturing apparatus 1 of the present embodiment has an extruder 2 for extruding a molten resin and a T-die 13 mounted on the extruder 2. The film manufacturing apparatus 1 is an apparatus for forming the resin film 37 by extruding the resin into a sheet from the T-die 13 described above, similarly to the known one.
The path through which the resin of the film manufacturing apparatus 1 passes includes electric heaters 22, 23, 25 to 33, which are heating means for adjusting the temperature of the resin, and the heating means may be at least one of proportional control, differential control, and integral control. It is controlled based on. In this embodiment, proportional control, differential control, and integral control are used together.
Further, the film manufacturing apparatus 1 has a thickness gauge 5 as a thickness measuring means for measuring the thickness of each portion in the width direction of the resin film 37. The contour curve determining means for determining the rough contour curve of the resin film 37 based on the measured value of the thickness measuring means is configured by a CPU or a memory (not shown). Further, it has a notification unit such as a display unit and a speaker that performs a predetermined notification when the determined contour curve satisfies a predetermined condition.

The heating means does not necessarily have to be the electric heaters 22, 23, 25 to 33, and may use other heat sources such as steam. The contour curve determining means does not have to have a CPU or a memory. The notification means is not limited to the display screen and the speaker.

The contour curve of the resin film 37 may be a curve representing the contour of the resin film 37 when the resin film 37 is placed in a zero gravity state, as in the case where the resin film 37 is placed on a flat place. It may be a contour curve focusing only on the thickness. In the present specification, the contour focusing only on the latter thickness is referred to as a thickness profile.

The rough contour curve is a curve obtained by macroscopically observing the profile of the resin film 37, ignoring minute irregularities on the surface.
The film manufacturing apparatus 1 of the present embodiment has a heating means for adjusting the temperature of the resin in the path through which the resin passes, and the heating means is controlled based on at least one of proportional control, differential control, and integral control. Is. Therefore, it is necessary to set at least one of the P value, which is a parameter for proportional control, the I value, which is a parameter for integral control, and the D value, which is a parameter for differential control. As described above, in the specific embodiment described below, the P value, the I value, and the D value are all set.

In the film manufacturing apparatus 1 of the present embodiment, a thickness measuring means for measuring the thickness of each part in the width direction of the resin film 37 and a rough contour curve of the thickness of the resin film 37 based on the measured values of the thickness measuring means are obtained. It has a contour curve determining means for determining. Then, it is determined whether or not the parameters such as proportional control are appropriate based on the contour curve.
When the resin temperature happens to be stable with respect to the set temperature while the control parameters of the heating means are inadequate, or due to the influence of disturbance, etc., the resin temperature is not stable with respect to the set temperature. In this case, as described above, a temperature difference occurs in the molten resin between the center and the vicinity of the wall surface in the resin flow path, and the viscosity characteristics in the width direction of the resin film 37 discharged from the die become non-uniform, resulting in, for example, a region having a low viscosity. It has a non-uniform thickness profile shape such that the thick and highly viscous region becomes thin.

In the film manufacturing apparatus of the present embodiment, the contour curve determining means determines a rough contour curve of the thickness of the resin film 37, and determines whether or not parameters such as proportional control are appropriate based on the contour curve. , It is possible to determine whether or not each parameter is appropriate in consideration of the influence of disturbance and the like.

In the film manufacturing apparatus of the present embodiment, the change in the thickness of the resin film 37 in the width direction is approximated to a predetermined constant function having a coefficient as a variable, and the parameter of proportional control is appropriate based on the coefficient of the function. It is determined whether or not it is. Therefore, it is possible to determine whether or not each parameter is appropriate after considering the influence of disturbance and the like.

The contour curve determining means of the film manufacturing apparatus of the present embodiment approximates the rough contour curve of the thickness of the resin film 37 or the change in the thickness of the resin film 37 in the width direction to a quadratic function having a coefficient as a variable. The notification means performs a predetermined notification on condition that the absolute value of the coefficient of the quadratic term exceeds a certain value.

As is well known, the quadratic function is a function expressed by "Y = aX ² + bX + c", and is a function that draws a diagram that is convex upward or convex downward. That is, if the coefficient "a" of the quadratic term (sometimes simply referred to as the quadratic term a) is positive, it becomes convex downward, and if "a" is negative, it becomes convex upward.
When the temperature of the resin is not stable with respect to the set temperature, the viscosity characteristics in the width direction of the resin film 37 discharged from the T-die become non-uniform, and as a result, for example, a region having a low viscosity is thick and a region having a high viscosity becomes thick. It has a non-uniform profile shape that makes it thinner. Therefore, the rough contour curve of the thickness of the resin film 37 draws a figure that is convex upward or convex downward, and can be applied to a quadratic function.

Similarly, the change in the thickness of the resin film 37 in the width direction draws a figure that is convex upward or convex downward, and can be applied to a quadratic function.
When the amount of unevenness of the resin film 37 (difference in thickness between the thick part and the thin part) is large, the coefficient "a" of the quadratic term of the approximated quadratic function becomes large, and when the amount of unevenness of the resin film 37 is small, the approximation The coefficient "a" of the quadratic term of the quadratic function is small.
Therefore, the amount of unevenness of the resin film 37 can be known by paying attention only to the absolute value of the coefficient of the quadratic term, and it is possible to know whether or not the parameter is appropriate.
The absolute value of the coefficient of the quadratic term may be the same or different when the coefficient "a" is positive and when it is negative.

Hereinafter, specific embodiments of the film manufacturing apparatus 1 will be described. FIG. 1 shows a film manufacturing apparatus 1 according to an embodiment of the present invention. The film manufacturing apparatus 1 is a series of equipment composed of a plurality of apparatus, and includes an apparatus and equipment on the extruder 2 side, a roll group 3 for passing the extruded resin film 37, and a thickness gauge (thickness measuring means). Has 5. The film manufacturing apparatus 1 further includes a stretching apparatus, a winding apparatus, and the like (not shown). In the present embodiment, the extruded resin film 37 is cooled by the roll group 3 to become the original resin film 35.
Further, the film manufacturing apparatus 1 has a control device 20.

The extruder 2 is a known one, and a screw shaft (not shown) is built in the cylinder 6. The extruder 2 melts the resin charged into the cylinder 6 from the hopper 7, advances the resin with a screw (not shown), and extrudes the molten resin from the discharge portion 16 at the tip. In addition to the extruder 2, the devices and equipment on the extruder 2 side include a connecting pipe 10, a gear pump 11, a connecting pipe group 12, and a T-die 13.
A gear pump 11 is connected to the discharge section 16 of the extruder 2 via a connecting pipe 10. Further, there is a connecting pipe group 12 on the discharge side of the gear pump 11, and a T die 13 is provided at the tip of the connecting pipe group 12. There are filters 17a, 17b, 17c in a part of the connecting pipe group 12. The gear pump 11, the connecting pipe group 12, the filters 17a, 17b, 17c, etc. are not essential constituents of the present invention.
In this way, the T-die 13 is connected to the extruder 2 via the connecting pipe 10, the gear pump 11, and the connecting pipe group 12. Then, the resin discharged from the extruder 2 enters the T die 13 via the connecting pipe 10, the gear pump 11, and the connecting pipe group 12, and is extruded from the T die 13 to the roll group 3.
In the present embodiment, the cylinder 6, the connecting pipe 10, the gear pump 11, the connecting pipe group 12, and the T die 13 of the extruder 2 are paths through which the resin passes.

In the present embodiment, the paths through which the resin passes are partitioned into a plurality of paths and the temperature is individually controlled. That is, in the present embodiment, all the devices and equipment on the extruder 2 side are temperature-controlled. The cylinder 6 of the extruder 2 is divided into a plurality of sections, and an electric heater (not shown) is provided in each section. Further, a heat medium for cooling may be circulated in each section of the cylinder 6. An electric heater 22 is attached to the connecting pipe 10. An electric heater 23 is also attached to the gear pump 11.
In the present embodiment, the connecting pipe group 12 is composed of eight pipes. That is, the connecting pipe group 12 is divided into eight sections from the 12a section to the 12h section, and electric heaters 25 to 32 are individually attached to each section.

An electric heater 33 is also attached to the T-die 13.
In the present embodiment, the temperature control of each section of the cylinder 6, the electric heater 22 of the connecting pipe 10, the electric heater 23 of the gear pump 11, the electric heaters 22 to 32 of each section 12a to 12h of the connecting pipe group 12, and T. The electric heater 33 of the die 13 is individually PID-controlled.
That is, temperature sensors 21a to 21m are attached to each section of the apparatus and equipment on the extruder 2 side. Then, each of the temperature sensors 21a to 21m is connected to the control device 20.

There is a roll group 3 on the downstream side of the apparatus and the equipment on the extruder 2 side. In FIG. 1, five rolls 25a to 25e are shown in the roll group 3, but the number of rolls is arbitrary. In this embodiment, the rolls 25a to 25d are cooling rolls. The roll 25e is a guide roll.
The roll group 3 is in the vicinity of the T die 13 and cools the resin extruded from the T die 13.
Further, a touch roll (not shown) may be additionally installed facing the roll 25a, and the film 37 may be sandwiched between the touch roll and the roll 25a.
The temperature of each of the cooling rolls (rolls 25a to 25d) is controlled by PID control. Specifically, the coolant is circulated in the cooling rolls (rolls 25a to 25d), and the temperature or circulation amount of the coolant is PID controlled.
When the touch roll is provided, it is desirable to circulate the coolant for the touch roll and control the temperature by PID control.

The thickness gauge (thickness measuring means) 5 is a device that measures the thickness of each part of the resin film 35 after cooling in the width direction. The thickness gauge 5 measures the thickness of the resin film 35 by irradiating it with radiation. The thickness gauge 5 includes a scanning device (not shown), and can move the radiation source or the light receiving portion in the width direction of the resin film 35. The thickness gauge 5 can measure the thickness of each part while moving the radiation source or the like, and can measure the distribution of the thickness in the width direction. The thickness gauge 5 is not limited to one that uses radiation, and may be one that uses another light beam such as a laser beam, or one that uses another physical phenomenon.
In the present embodiment, the thickness gauge 5 is installed on the downstream side of the roll group 3 and measures the thickness of each part of the resin film 35 after cooling.

As shown in FIG. 2, the control device 20 has a PID control unit, a parameter storage unit, a temperature history storage unit, a contour curve determining means, and a comparison unit.
Here, the PID control unit is an arrangement of a plurality of PID control devices. A plurality of PID control devices constituting the PID control unit are commercially available. The parameter storage unit is attached to each PID control device.

The temperature history storage unit, the contour curve determining means, and the comparison unit are composed of a CPU and a memory (not shown). The specific operation is realized by the software stored in the memory.
The temperature history storage unit stores the temperature of each unit detected by each temperature sensor.
The temperature of each unit stored in the temperature history storage unit can be graphed and displayed on the display unit as needed.
The contour curve determining means has a contour shape calculation function for calculating a rough contour curve of the thickness of the resin film 35 based on the data detected by the thickness gauge 5. It also has a function to approximate the calculated contour curve to a quadratic function.

The comparison unit has a function of monitoring the coefficient of the quadratic term of the quadratic function and comparing the coefficient of the quadratic term with the threshold value.
The specific functions of the temperature history storage unit and the comparison unit will be described later.

In the film manufacturing apparatus 1 of the present embodiment, as described above, the temperature control of each section of the cylinder 6, the electric heater 22 of the connecting tube 10, the electric heater 23 of the gear pump 11, and each section 12a to 12h of the connecting tube group 12 The electric heaters 25 to 32 and the electric heater 33 of the T-die 13 are individually PID-controlled.
As described above, the PID control unit of the control device 20 has a large number of commercially available PID control devices built-in, and the signals of the temperature sensors 21a to 21m for detecting the temperature of each section are built in the control device 20. It is input to the PID control device in charge of each of the divided sections. The electric heaters 22 to 33 in each section and the heaters (not shown) for heating the heat medium are controlled based on the output of the PID controller in charge of each section.

Further, the detected value of the temperature sensor in each section is input to the temperature history storage unit in the control device 20. The measurement data of the thickness gauge 5 is input to the contour curve determining means of the control device 20.

In the film manufacturing apparatus 1 of the present embodiment, the resin melted and kneaded in the extruder 2 passes through a series of resin flow paths including the gear pump 11 and the filters 17a, 17b, 17c to reach the T-die 13. Then, the resin is extruded from the T die 13 into a sheet shape, and the resin is cooled by the roll group 3 to become a raw film 35 (hereinafter, simply referred to as a resin film 35).
The molded resin film 35 is conveyed in the direction of arrow X in FIG. 1, and the thickness of each part in the width direction is sequentially measured by the thickness gauge 5.
The measured thickness data in the width direction is taken into the contour curve determining means of the control device 20. Then, the overall shape of the thickness profile is analyzed, and the presence or absence of an abnormality in the thickness profile is determined.

Here, the thickness profile of the resin film 35 will be added. Ideally, the thickness of each part of the cooled resin film 35 in the width direction is the same, but the central part is bulging as shown in FIG. 4A or the central part is formed as shown in FIG. 4B. It may be dented. Assuming that the resin film 35 is placed in a weightless state, the cross-sectional shape is as shown on the upper side of FIGS. 4A and 4B. Note that FIGS. 4A and 4B show the cross-sectional shape of the effective use range of the resin film 35, which is the cross-sectional shape of only the central portion of the resin film 35 extruded from the T-die 13, and is shown in FIG. 5A. ) In the graph, it is the area described as "product width".
The thickness profile is the thickness data of each point of the resin film 35 measured by the thickness gauge 5 at regular intervals while traversing in the width direction of the resin film. That is, it is a distribution curve showing the thickness distribution in the width direction in which the thickness of each point of the resin film 35 is plotted each time the resin film 35 is traversed.

Hereinafter, the contents of analysis and determination of thickness profile abnormality will be described with reference to FIGS. 5 and 6.

FIG. 5A is a graph of the thickness data captured by the thickness gauge 5 by scanning in the width direction as it is. That is, all the data measured by the thickness gauge 5. Although the aspect ratio is not accurate, the curve drawn by the graph in FIG. 5A is a contour curve focusing only on the thickness of the resin film 35, and is a thickness profile of the resin film 35.
In the graph of FIG. 5A, if the resin film 35 is in the entire scanning region of the thickness gauge 5, the thickness is plotted as the value on the Y axis.
The thickness profile of the resin film 35 has minute irregularities.

In the molded resin film 35, both edge portions are cut off, and only the central portion is utilized. In the graph of FIG. 5A, the region described as "product width" is the central portion where both edge portions are cut off and remains.
The graph drawn by the solid line in FIG. 5 (b) is the thickness data obtained by extracting the range corresponding to the product part from the graph in FIG. 5 (a) and enlarging the scale in the thickness direction. The solid line in FIG. 5A is the thickness profile of the resin film 35, and has minute irregularities.
It can be said that the portion drawn by the solid line in the graph of FIG. 5B accurately represents the change in the thickness of the film.

In the present embodiment, the contour curve determining means of the control device 20 calculates a rough contour of the thickness of the resin film 35. That is, as shown in the graph drawn by the broken line in FIG. 5B, minute irregularities are ignored and a rough tendency of the change in thickness is calculated.
More specifically, the width of the resin film 35 is taken on the X-axis, the thickness of the resin film 35 is taken on the Y-axis, and the graph drawn by the solid line in FIG. 5B is applied to the curve of the quadratic function. In other words, the curve representing the exact outline drawn by the solid line in FIG. 5B is approximated to a quadratic function having a coefficient as a variable.
Here, the quadratic function is a function expressed by "Y = aX ² + bX + c", and is a function that is convex upward or convex downward.
Further, as a rule of thumb, the thickness of the resin film 35 may be thicker or thinner at the center in the width direction, and when the thickness is graphed, it becomes convex upward or convex downward. Therefore, if the minute unevenness of the resin film 35 is ignored and the rough tendency of the change in thickness is reviewed, it can be approximated to some quadratic function.

As described above, in the present embodiment, the thickness data is curve-approximated by a quadratic function with the horizontal axis representing the position in the width direction and the vertical axis representing the thickness as shown by the broken line in FIG.
Here, the coefficient a of the quadratic term of the quadratic function represents an approximated quadratic curve, that is, the direction and opening degree of the parabola. When the coefficient a has a positive sign, the quadratic curve has a concave shape having a minimum value, and when the coefficient a has a negative sign, the quadratic curve has a convex shape having a maximum value. Further, the closer the absolute value of the coefficient a is to 0, the larger the opening of the quadratic curve is, the smaller the difference in thickness between the center and the end of the quadratic curve is, and the farther the absolute value of the coefficient a is from 0, the larger the opening of the quadratic curve. The opening becomes narrower and the difference in thickness between the central portion and the end portion of the quadratic curve becomes large.
Therefore, if the coefficient a of the quadratic term of the quadratic function is used as a variable, the coefficient a of the quadratic function approximated to the thickness profile can be specified.

Further, in the present embodiment, the coefficient a of the quadratic term of the quadratic function described above is continuously calculated, and whether or not this value exceeds a certain threshold value is monitored. That is, the comparison unit of the control device 20 monitors the coefficient a of the quadratic term of the quadratic function, compares the coefficient a of the quadratic term with the threshold value, and monitors whether or not the threshold value is exceeded. Then, in the present embodiment, when the threshold value is exceeded a certain number of times within a certain time, a predetermined notification is performed. Specifically, an alarm is displayed on a display unit which is one of the notification means. In addition, an alarm sound is emitted from a speaker (not shown) or the like to notify that an abnormality has occurred. In the present embodiment, when the coefficient a of the quadratic term of the quadratic function exceeds the threshold value twice within a certain time, an alarm is displayed on the display unit and an alarm sound is emitted from the speaker or the like.

Specifically, in the present embodiment, the wave shape of the time-dependent fluctuation of the coefficient a is monitored, and when the coefficient a exceeds the threshold values set in advance for both positive and negative, the thickness profile in the width direction is generally convex or Since it indicates that the shape is concave, it is determined that the thickness profile is abnormal at least when such a peak and / or valley shape is detected twice or more.
FIG. 6A is a wave shape when it is determined that the thickness profile is abnormal, and FIG. 6B is an example of a wave shape which is determined to be normal.
That is, the temperature of each part is PID controlled as described above, but the temperature of each part pulsates to some extent. As a result, the thickness of the resin film 35 partially changes, and the thickness profile changes unevenly with time. That is, as a rule of thumb, the thickness of the resin film 35 repeats increasing and decreasing in the central portion in the width direction.

Therefore, if the uneven shape exceeding the threshold value is repeated, it is expected that the unevenness change exceeding the threshold value will occur after that.
Therefore, in the present embodiment, the wave shape of the time-dependent fluctuation of the coefficient a is monitored, and when the state in which the absolute value of the coefficient a exceeds the threshold value is repeated, an alarm is displayed on the display unit and an alarm sound is emitted from the speaker or the like. did.

Further, the thickness profile is composed of minute irregularities appearing when the thickness meter 5 detects minute irregularities on the surface and overall irregularities felt when the whole is viewed macroscopically. Here, the change in the thickness profile that occurs when the temperature control of each section is not appropriate appears as an overall unevenness that is felt when viewed macroscopically. Conversely, the causal relationship between the appropriateness of temperature control in each section and the minute unevenness is smaller than that of the macroscopic unevenness.
In the present embodiment, since the thickness profile is approximated to a quadratic function, minute irregularities are substantially ignored, and overall irregularities having a deep causal relationship with the temperature control of each section are emphasized.
Therefore, it is possible to accurately detect that the temperature control is inappropriate, more specifically, that the PID parameter is inappropriate.

The operation of the film manufacturing apparatus 1 of the present embodiment is represented by a flowchart as shown in FIG.
The process shown in the flowchart is carried out when the resin film is extruded on a trial basis prior to full-scale production.
According to the flowchart, step 1 starts timing the timer. This timer is determined in consideration of the interval at which the change in thickness appears. Specifically, the time is sufficiently long with respect to the interval at which the change in thickness known from the rule of thumb appears, and it is desirable that the time is 5 times or more of the interval. On the other hand, if the time is excessively long, the significance of the test production is lost. Therefore, it is desirable that the interval of the thickness change is 20 times or less, which is known as a rule of thumb.

In the following step 2, it is determined whether or not the absolute value of the coefficient a exceeds the threshold value. If the threshold is exceeded, the process proceeds to step 3 and 1 is added to the counter. Then, the process proceeds to step 4, and it is determined whether or not the current number of counters is 2 or more.
If the absolute value of the coefficient a does not exceed the threshold value in step 2, step 3 is skipped and the process proceeds to step 4, and it is determined whether or not the current number of counters is 2 or more.

If the number of counters is 2 or more, it means that the phenomenon of exceeding the threshold value is repeated. Therefore, the process proceeds to step 6 to perform a predetermined notification. In this embodiment, an alarm or the like is issued. If the number of counters is less than 2, the process proceeds to step 5, and the time of the timer that started the time in step 1 is confirmed. If the time has passed, the series of controls is terminated. If the time has not passed, the process returns to step 2.

In the present embodiment, when an abnormality occurs, the control parameters of each heating means (electric heater) are modified.

The abnormality referred to here means that the overall thickness profile shape within the product width is significantly deviated from the flat shape allowed for the quality of the product. When the thickness profile shape deviates from the flat shape, various adjustments such as adjusting the lip spacing of the T-die 13 to eliminate minute thickness unevenness of the resin film 35 are performed before the adjustment effect appears. The thickness profile shape also fluctuates to offset the effect of the adjustment, or the thickness is disturbed by adjusting more than necessary.

The threshold value for the time-dependent fluctuation of the quadratic term of the quadratic curve described above is appropriately determined depending on the thickness of the target resin film 35 and the required quality. As a preferred embodiment, the value having the maximum absolute value in the quadratic term such that the quadratic curve within the product width falls within the range of thickness unevenness allowed for the quality of the product is used as the threshold value for each of the positive and negative values. If the threshold value is too small, even a slight change in the thickness profile shape is immediately determined to be abnormal, and the adjustment of the PID parameter is repeated more than necessary. On the other hand, if the threshold value is too large, various thickness adjustments such as adjustment of the lip spacing of the T-die 13 are performed while the thickness profile shape is fluctuating, which causes a factor of disturbing the thickness.
The absolute values of the positive and negative thresholds may be the same or different.

Here, in the film manufacturing method of the present embodiment, the film manufacturing apparatus 1 described above is used, and after the notification by the notification means (display unit and speaker), the control parameters of the heating means are modified to form the resin film. It is a feature.
Hereinafter, the features of the film manufacturing method of the present embodiment will be described.

If an abnormality in the thickness profile shape is detected after the process from raw material supply to sheet winding has stabilized, it is caused by environmental disturbance, that is, hunting of temperature control of the extruder 2 due to a sudden change in atmospheric temperature. there's a possibility that. Temperature control hunting is because the PID parameters (P, I, D values) of PID control that control temperature control are not set to the optimum values under the environment, or they do not correspond to disturbances such as atmospheric temperature fluctuations. It often occurs.
Therefore, in the present embodiment, when an abnormality due to a change in the unevenness of the thickness profile shape is detected, the fluctuation analysis of the temperature data of each process from the cylinder 6 to the T die 13 of the extruder 2 of the apparatus and equipment on the extruder 2 side is analyzed. Then, the PID parameter of the temperature control is corrected for the process having a large correlation with the fluctuation of the quadratic term or the process having a clearly large range of the temperature fluctuation as compared with the time of quality stabilization.

That is, the control device 20 used in the present embodiment has a temperature history storage unit, and stores the temperature of each unit detected by each temperature sensor.
When an abnormality in the thickness profile shape is detected, the record in the temperature history storage unit can be read out, and if necessary, it can be graphed and displayed on the display unit.
Further, as described above, an alarm is displayed on the display unit which is one of the notification means, and an alarm sound for notifying that an abnormality has occurred is emitted from a speaker or the like (not shown).
In the film manufacturing method of the present embodiment, the control parameter of the heating means is modified after the notification, and the resin film is molded.
Specifically, when an abnormality in the thickness profile shape is detected, the notification means notifies the user of the fact. The user examines the temperature change of each section and selects a section suspected to be the cause of the abnormality in the thickness profile shape. Then, the PID parameter of the PID controller in charge of the section is modified.

The content of the modification of the PID parameter of the temperature control in the present embodiment is to increase the P value which is the proportional gain or the I value which is the integral gain, for the purpose of suppressing the temperature fluctuation of a specific part. adjust. The amount of adjustment cannot be uniquely defined because multiple factors such as resin characteristics, equipment specifications, and operating conditions are intertwined, and adjustments are made while comparing with the suppression status of temperature fluctuations at the target site.
Both the auto-tuning function and the manual adjustment can be selected for the correction of the PID parameter of the temperature control, but the manual adjustment is more preferable in that the fine adjustment can be made while confirming the effect of the PID parameter correction on the thickness profile abnormality. ..

As described above, the step of collecting the width direction thickness profile data of the film formed by extruding the resin from the T die 13 into a sheet by the melt extrusion method and the thickness of the product width range in the width direction thickness profile data. A quadratic function that approximates the profile to a curve is obtained, the temporal fluctuation of the coefficient of the quadratic term in the obtained quadratic function is monitored, and peaks and / or valleys exceeding the preset threshold as the wave shape of the fluctuation appear at least twice. A film manufacturing method is used that includes a step of detecting a change over time and a step of readjusting the PID parameters of each part constituting between the cylinder 6 of the extruder 2 and the T-die 13 in response to the detection. As a result, temperature fluctuations that affect the thickness profile can be suppressed in a timely manner, and as a result, thickness unevenness and gauge bands are less likely to occur, and a high-quality film can be stably obtained over a long period of time.

Therefore, as shown in FIG. 6 (a), by modifying the PID parameter from the state where the quadratic term of the approximate curve of the thickness profile fluctuates greatly with time as shown in FIG. The secondary term is stable, the variation in the thickness profile is small, and a high-quality film can be stably obtained for a long period of time.

In the embodiment described above, the thickness profile is approximated to a quadratic function and the quadratic term is monitored, but the thickness profile may be approximated to another function. For example, the thickness profile may be approximated to a circular function, a trigonometric function, a cycloid function, or an elliptic function.
Further, it may be determined whether or not the PID parameter is appropriate based on the area of the region drawn by the curve of the thickness profile.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
[Example 1]
A resin film 35 having a length of 1000 m as one roll was molded by using a film manufacturing apparatus 1 that melts an acrylic thermoplastic resin and extrudes it from a T-die 13 into a sheet. Each process temperature (temperature of each section) of the film manufacturing apparatus 1 is appropriately set according to the characteristics of the resin, and the PID parameter of the temperature controller that keeps the temperature of each process constant is automatically set after the resin supply amount is stabilized. Automatically set by tuning. The thickness profile in the width direction of the molded resin film 35 is sequentially measured in-line, and the thickness profile data for each scan is measured by the vertical axis (Y) for the thickness and the horizontal axis (X) for the thickness meter 5. It was plotted as a non-dimensional number divided by the maximum measurement width and approximated to a quadratic curve. Assuming that the thickness unevenness allowed for the product is ± 0.6% of the standard thickness, the value of the coefficient a of the quadratic term for the quadratic curve representing the thickness profile within the product width to be within the standard thickness of ± 0.6% is It was ± 5. Therefore, the threshold value is set to ± 5 for the wave shape data of the quadratic term a in the quadratic curve.

When the film was wound about 300 m from the start of winding, the value of the coefficient a in the quadratic term exceeded the threshold value for the second time. Therefore, the temperature data of each process of the film manufacturing apparatus 1 was analyzed, and due to the influence of the surrounding air flow. The PID parameters were manually adjusted for the sections where the temperature fluctuation range was large. After that, the temperature fluctuation range of the target section is reduced to the same level as other processes, the secondary term a does not exceed the threshold value again by the end of winding, and the wound shape of the wound film is misaligned, gauge band, etc. It was in good condition.
[Comparative Example 1]

When film molding was performed under the same apparatus configuration and initial conditions as in Example 1 and the film was wound 1000 m without monitoring the thickness profile shape and readjusting the PID parameters of the extrusion equipment, the appearance of the film roll was 3 The gauge band of the book was observed, and the winding appearance deteriorated.
[Reference example]

The film was formed by setting the threshold value of the coefficient a of the quadratic term of the quadratic curve to ± 2 under the same apparatus configuration and conditions as in Comparative Example 1. As a result, since the secondary term a exceeded the threshold value every several tens of meters and the PID parameter was adjusted each time, the temperature was not stable at the set temperature, the gauge band remained, and a good winding shape could not be obtained. From this result, it can be seen that it is not preferable that the threshold value is excessively small.

1 Film manufacturing equipment 2 Extruder 3 Roll group 5 Thickness gauge (thickness measuring means)
10 Connecting pipe 11 Gear pump 12 Connecting pipe group 13 T-die 20 Control device 21a to 21m Temperature sensor 22,23 Electric heater 25 to 33 Electric heater

Claims (6)

In a film manufacturing apparatus having an extruder for extruding a molten resin and a die mounted on the extruder, the resin is extruded into a sheet from the die to form a resin film.
A heating means that adjusts the temperature of the resin in the path through which the resin passes ,
A thickness measuring means for measuring the thickness of each part in the width direction of the resin film, and
A contour curve determining means that determines a rough contour curve of the resin film based on the measured value of the thickness measuring means, and
Determined contour curve have a notification unit for performing a predetermined notification when a predetermined condition is satisfied,
The contour curve determining means approximates the rough contour curve of the thickness of the resin film to a quadratic function having a coefficient as a variable.
A film characterized in that the notification means performs a predetermined notification on condition that the coefficient of the quadratic term of the quadratic function is monitored with time and the coefficient of the quadratic term of the quadratic function exceeds a threshold value. manufacturing device. In a film manufacturing apparatus having an extruder for extruding a molten resin and a die mounted on the extruder, the resin is extruded into a sheet from the die to form a resin film.
A heating means that adjusts the temperature of the resin in the path through which the resin passes ,
A thickness measuring means for measuring the thickness of each part in the width direction of the resin film, and
It has a contour curve determining means that approximates a change in the thickness of the resin film in the width direction to a quadratic function with a coefficient as a variable based on the measured value of the thickness measuring means.
Have a notification means for said coefficients performs a predetermined notification when a predetermined condition is satisfied,
A film characterized in that the notification means performs a predetermined notification on condition that the coefficient of the quadratic term of the quadratic function is monitored with time and the coefficient of the quadratic term of the quadratic function exceeds a threshold value. manufacturing device. Claim 1 or claim 1 , wherein the notification means performs the predetermined notification on condition that the coefficient of the quadratic term of the quadratic function exceeds the threshold value two or more times within a certain time. 2. The film manufacturing apparatus according to 2. The heating means is controlled based on at least one of proportional control, differential control, and integral control.
One of claims 1 to 3 , wherein the control parameter of the heating means is modified on condition that the coefficient of the quadratic term of the quadratic function exceeds the threshold value a certain number of times within a certain time. The film manufacturing apparatus described. A film manufacturing apparatus having an extruder for extruding a molten resin and a die mounted on the extruder, and extruding the resin into a sheet from the die to form a resin film .
There is a heating means for adjusting the temperature of the resin in the path through which the resin passes, and the heating means is controlled based on at least one of proportional control, differential control, and integral control.
A thickness measuring means for measuring the thickness of each part in the width direction of the resin film, and
Based on the measured value of the thickness measuring means have a contour curve determination means for determining a rough contour curve of the resin film, the contour curve determination means a rough contour curve of the thickness of the resin film, the coefficient of variable A film manufacturing method that uses a film manufacturing device that approximates a quadratic function.
The control parameter of the heating means is set on the condition that the coefficient of the quadratic term of the quadratic function is monitored with time and the coefficient of the quadratic term of the quadratic function exceeds the threshold number a certain number of times within a certain time. A method for producing a film, which comprises modifying and molding a resin film. Has a extruder for extruding a molten resin, the die attached to the extruder, the resin from the die a film manufacturing apparatus for forming a resin film extruded into a sheet,
There is a heating means for adjusting the temperature of the resin in the path through which the resin passes, and the heating means is controlled based on at least one of proportional control, differential control, and integral control.
A thickness measuring means for measuring the thickness of each part in the width direction of the resin film, and
Based on the measured value of the thickness measuring means, the change in thickness in the width direction of the resin film, have a contour curve determination means for approximating a constant function predetermined for the coefficient variable, the contour curve determining means Is a film manufacturing method using a film manufacturing apparatus that approximates the change in thickness of the resin film in the width direction to a quadratic function with a coefficient as a variable.
The control parameter of the heating means is set on the condition that the coefficient of the quadratic term of the quadratic function is monitored with time and the coefficient of the quadratic term of the quadratic function exceeds the threshold number a certain number of times within a certain time. A method for producing a film, which comprises modifying and molding a resin film.

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