JPH0558381B2 - - Google Patents

Description

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

[Conventional technology]

Conventionally, to control the film thickness during melt-extrusion film forming, the thickness of the finished film is actually measured, and based on the measured value, the operating engineer's experience and skill determine the appropriate film drawer. This is done by determining the speed.

[Problem to be solved by the invention]

Long films that serve as 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 molding does not have a unique one-to-one correspondence with the film withdrawal speed, but changes depending on parameters such as the extruder's resin discharge rate and film width. 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 a constant value.

However, in order to adjust the film thickness,
The feed speed is adjusted by the skilled technicians based on the measured film thickness values, taking into account the film specifications and the type of resin material empirically.

Therefore, without stopping the film manufacturing equipment,
No skill is required to adjust the film thickness after the change when changing film specifications continuously, or when changing the production capacity by changing the resin discharge amount midway through even if the film specifications are the same. It is desirable that this can be done promptly.

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

However, the proportional relationship between the number of rotations of the extrusion screw and the number of rotations of Nitzprol, which is required 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. Therefore, with proportional control using a simple proportionality constant, it is difficult to change the production capacity while keeping the film thickness constant.

Further, 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.

While extruding molten resin and forming it into a film,
The film is pulled out at a constant speed, and the required amount of film is wound by measuring the time from the start of winding to the end of winding, and the weight of the film is measured. The time taken, the weight of the wound film, the desired thickness and other specified values,
Synthetic resin film obtained by calculating the drawing speed of the film by applying it to a calculation formula for calculating the thickness of the film drawn at a constant speed, and then drawing the film while keeping the drawing speed determined in this way constant. .

A process of drawing out molten resin at a constant speed and forming it into a film, a process of winding the film by measuring the winding time of the drawn out finished film, 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 is produced by a melt extrusion method, which comprises a process of calculating a film withdrawal speed, and a process of correcting the film withdrawal speed based on the film withdrawal speed determined by the calculation process. A method for controlling film thickness during film forming.

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 for winding 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. Take weight and
A film feed speed calculating means for calculating the feed speed of the film drawing means by giving a desired thickness and other prescribed values; 1. A film thickness control device during melt extrusion film forming, comprising: a feed roll drive control means for controlling rotation speed.

[Effect]

By measuring the winding time T of the completed film, winding the completed film, and measuring the weight W of the completed film, the film feed speed V is automatically adjusted to obtain the desired thickness. adjusted to.

〔Example〕

FIG. 1 is a block diagram when the present invention is carried out using an inflation film molding method.

1 is an extruder, 1a screw motor, 2 is a film forming die, 3 is a film drawn out from the die 2, 4 is a nip roll that folds the film 3 flat and draws it 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 the nip roll 4;
This 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, and the speed governor motor 5 is controlled by a calculation device 7 so that the thickness of the completed film 3a becomes desired.
controlled by.

The calculation device 7 includes a calculation section 8 using a microcomputer and a motor control section 9 that controls the speed governor motor 5 .

The computing device 7 is also provided with a stop watch 7a for measuring the time during which the winder 6 is winding the finished film 3a. The start switch 10 and stop switch 11 that transmit the start signal and stop signal of the stop watch 7a are
A computing device 7 is provided so that it can be operated near the winding machine 6.
It is pulled out and connected to the outside.

Furthermore, the calculation device 7 includes an electronic weighing scale 12.
is externally connected, and the measured value of this weighing scale 12 is automatically input into the arithmetic unit 7 as an electrical signal.

Note that the arithmetic device 7 is essentially 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 3 is
When winding b, 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, the start switch 10 is pressed, and when winding is finished,
Alternatively, when cutting the end of the wound film, the stop switch 11 is pressed to input the winding start and winding end points of the winder 6 to the arithmetic unit 7.

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

The wound sample film 3b is placed on a weight scale 12 and weighed, and the weight is input to the calculation device 7.

In the arithmetic unit 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 unit 7, the time during which the start switch 10 and the stop switch 11 are operated is taken in as the winding time T by the stop watch 7a.

Further, the arithmetic device 7 is provided with a desired thickness t of the completed film 3a via the key input device 14.
and each constant value required for the calculations described below are input in advance.

In the inflation 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 1 of the extruder 1
It is assumed that a is maintained at an appropriate constant rotational 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 completed 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 a desired amount of the film 3a. Winding time T
is measured by the stop watch 7a of the arithmetic unit 7.

The weight W of the film wound by the winder 6 is measured by a weighing scale 12 as a sample film 3b.

The computing device 7 takes in the winding time T from the sweep watch 7a and the weight W of the sample film 3b from the weight scale 12, respectively. In addition,
The arithmetic unit 7 is inputted in advance with prescribed values such as a required film thickness t, physical property values determined in advance based on the resin material, and constants determined in advance according to the film specifications.

The calculation device 7 calculates the thickness of the film by inputting the winding time T, the weight W, the thickness t, and other specified values to a calculation formula (described later) for calculating the thickness of the film that is drawn out at a constant speed. The drawing speed V is calculated, and the speed governor motor 5 is controlled via the motor control section 9 so that the feeding speed of the nip roll 4 becomes the calculated speed V.

In this way, the completed film 3 is pulled out while keeping the speed V determined by the calculation device 7 constant.
A is a long piece with a desired thickness t 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 the product film, if the winding time T and the weight W of the product film are measured and the feed speed V is corrected based on the measured values,
The thickness t is kept constant over a long period of time, resulting in a high quality film.

Next, the winding time T of the completed film 3a,
The calculation for determining the feed speed V of the nip roll 4 in order to obtain the desired thickness t from the weight W of the completed film 3a wound within the time T will be explained.

The feed speed V corresponds to the length L of the completed film 3a fed by the nip roll 4 within the winding time T, and is expressed by the following equation.

V=L/T (I) The length L fed by the nip roll 4 within the winding time T and the length L of the sample film 3b wound within the same time T are equal.

This length L is determined by the number of rotations N of the nip roll 4 within the winding time T, the circumferential length of the nip roll 4, that is, the diameter D of the nip roll 4 multiplied by pi, the slip rate of the nip roll 4, and It is expressed by the following equation using a correction coefficient K that takes into consideration the shrinkage rate of the completed film 3a.

L=K・N・π・D ...() Weight 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 the cross-sectional area in the direction perpendicular to the longitudinal direction of the sample film 3b, that is, the film width b and the film thickness t ₁
, and then multiplied by the length L of the film. Therefore, the following equation is obtained.

W=b・t ₁・L・ρ () Note that the completed film 3a obtained by inflation molding is folded into two layers, so the desired thickness t is determined by the formula Film thickness t ₁
is 1/2, and the following formula is obtained.

W=b・2t・L・ρ () Expressing the formula for the length L and substituting it into the formula, the following formula is obtained.

V=1/(2tbρ)・W/T... () Since the desired thickness t, film width b, and density ρ are known numbers determined in advance by the film specifications,
If 1/(2tbρ) is a constant A, the following equation is obtained.

V=A・W/T...() A=1/2tbρ The calculation device 7 calculates the formula and outputs a speed signal v corresponding to the feed speed V proportional to the constant A, and with 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, the speed control lever of the 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 using a potentiometer. death,
The position signal of this potentiometer is made to correspond to the circumferential speed of the nip roll 4, that is, the feed speed V, and is electrically controlled based on the speed signal v obtained from the calculation result of the above formula.

In the case of electric speed governor control, frequency synchronous control,
A speed-governing motor 5 whose speed is controlled by pulse synchronous control, phase control, or other electrical speed control.
On the other hand, an electric signal corresponding to the control target value is controlled by a speed signal v calculated by the calculation device 7.

The calculation device 7 inputs the weight W of the sample film 3b.
When the value of is input, the following equation is calculated using the winding time T that has already been input and the constant value A that is predetermined based on the film specifications and the like.

The speed signal v obtained as a result is the speed signal v of the governor motor 5.
The rotation speed of the feed speed V is quickly adjusted according to the feed speed V.

On the other hand, the film width b in the constant A in the formula is set as one of the constant values inputted in advance from the key input device 14 as a specified value.

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 predetermined 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.

16 in FIG. 1 is a film width measuring device for this purpose. The width of the completed film 3a is constantly measured by the film width measuring device 16, and the obtained film width b signal is inputted to the arithmetic unit 7. The arithmetic unit 7 uses the average value of the film width b within the winding time T as the value of the film width b for 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.

Reference numeral 30 denotes a vertically elongated frame member. A horizontally placed extruder 31 is installed at the bottom of this frame member 30, and a film molding die having an annular die lip is installed above the resin discharge end 31a of the extruder 31. 32 are provided.

At the outer periphery of the die lip on the upper surface of the die 32, there is an air ring 3 for cooling the molten film 33 discharged from the die lip and being pulled upward.
4 are provided. An inside mandrel 36 is provided above the center of the die 32 to inflate the molten film 33 to form a bubble 35.

A bubble guide 37 is provided above the inside mandrel 36, a bubble folding guide 38 is provided above the bubble guide 37, and a nip roll 39 is provided above the bubble guide 37.

The bubble folding guide 38 consists of two guide plates 3
The upper end of the bubble 8a 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 fixed to the lower part of the nip roll 39.

Bubble folding guide 38 and Nitsuprol 39
is guided by the frame member 30, suspended by a hoist 40, and attached to a carriage 41 that is vertically movable.

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

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 a control box 43 housing the arithmetic unit 7, and is controlled as described above.

The completed film 44, in which the bubble 35 is folded into a flat shape and is sent out at a constant speed from the nip roll 39, is guided downward via the guide roll 45 and is given an appropriate tension to form the completed film 44.
The film is sent to an automatic winder 47 via a feed roll 46 that sends out the film.

The automatic winder 47 winds the completed film 44 that is sent onto the winding shaft 48, and when the amount of winding reaches a certain amount, automatically cuts the film 44 and discharges the winding roll 49. do.

Next, a new winding shaft 48 is automatically supplied, and the cut end of the film 44 is automatically wound around it. Repeat this one after another until the film 44
is automatically wound up.

The configuration of the automatic winder 47 is not the gist of the present invention, so a detailed explanation will be omitted;
Please refer to No. 101801 (Japanese Unexamined Patent Publication No. 1983-1989).

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

There is a divided part of the required length in the middle of the guide rail 50, and this part is connected to the pedestal 5 of the weighing scale 51.
It's becoming 3.

As a result, the completed film 44 wound around the winding shaft 48 is turned into a winding roll 49, and the guide rail 5
0 and placed on the weighing scale 52, and the weight is measured.

When the film on the take-up roll 49 is to be used as the sample film 3b, switches (not shown) similar to the start switch 10 and stop switch 11 are operated in accordance with the operation of the film cutting device in the automatic winder 47. The output signal of this switch is input to the arithmetic unit 7, and the winding time T for one roll is measured.

Although the above embodiments relate to the case where the lip shape of the inflation 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, the completed film is in the form of a sheet, so the formula 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 drawing side, that is, the nip roll.

However, since the amount of resin discharged per unit time from the extruder 1 is also a parameter that changes the film thickness, it is possible to change the film thickness by adjusting the rotational speed of the screw motor 1a of the extruder 1. can be adjusted.

Therefore, according to the present invention, the film thickness can 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, so that the film of the desired thickness can be quickly produced. The present invention provides a long film that is manufactured with high accuracy in thickness and has a high thickness accuracy.

Further, in the apparatus of the present invention, since the film thickness is automatically adjusted, 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 drawings]

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 adapted to carry out the method of the present invention, and FIG. FIG. 1... Extruder, 2... Film forming die, 1
a...Screw motor, 3...Film, 3a
...Completed film, 3b...Sample film,
4...Nipprol, 5...Governing motor, 6...
Winding machine, 7... Arithmetic device, 7a... Stop watch, 8... Arithmetic unit, 9... Motor control unit, 10
... Start switch, 11 ... Stop switch, 12 ... Weight scale, 13 ... CRT monitor, 1
4...key input device, 15...printer, 16...
...Film width measuring device, 30...Frame member, 31...
...Extruder, 31a...Resin discharge end, 32...Film forming die, 33...Melted film, 34...
Air ring, 35...bubble, 36...inside mandrel, 37...bubble guide, 38...
... Bubble folding guide, 39 ... Nitzprol, 40 ... Hoist, 41 ... Carriage, 42
...Governing motor, 43...Control box, 44...
...Completed film, 45...Guide roll, 46...
Feed roll, 47... Automatic winding machine, 48... Winding shaft, 49... Winding roll, 50... Guide rail,
51... Removal section, 52... Weight scale, 53...
cradle.

Claims (1)

[Claims] 1. While extruding and forming a molten resin into a film, the required amount is determined by keeping the speed constant and pulling out the film, and by measuring the time from the start of winding to the end of winding of the pulled out film. At the same time as winding up the film, measure the weight of the wound film, and calculate the winding time, the weight of the wound film, the desired thickness and other specified values, and calculate the thickness of the film drawn out at a constant speed. Synthetic resin film obtained by calculating the drawing speed of the film by applying it to a calculation formula for calculating the film speed, and then drawing the film while keeping the drawing speed determined in this way constant. 2. A process of drawing out the molten resin at a constant speed and forming it into a film, a process of measuring the winding time of the drawn out finished film and winding the film, and a process of measuring the weight of the finished film that has been wound up. To give 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 drawn out and the thickness of the film obtained by the drawing speed. A melt extrusion method for producing a film, which is characterized by comprising a process of calculating the film withdrawal speed, and a process of correcting the film withdrawal speed based on the film withdrawal speed determined by the calculation process. A method for controlling film thickness during film forming. 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 for forming a 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, a calculation formula for calculating the thickness of the film fed at a constant speed, the winding time, a film feeding speed calculating means for calculating the feeding speed of the film drawing means by giving a winding weight, a desired thickness and other specified values; 1. A film thickness control device for melt extrusion film forming, comprising: 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. Melt extrusion film forming 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 winding time at the beginning and end of winding. Film thickness control device. 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 stop watch measures time by a computer constituting the film feed speed calculation means. 9. The film thickness control device for melt extrusion film forming according to any one of claims 3 to 8, wherein the means for measuring the weight of the film is an electronic weighing scale connected to a computer constituting the film feed speed calculation means. 10. The film thickness control device for 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 a take-up roll take-out passage in an automatic film winder. . 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 drive means is an electronic speed regulating motor.