JPS6359856B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a film thickness control method. In film manufacturing equipment that manufactures biaxially stretched film from molten thermoplastic resin, when the die is disassembled and assembled, when the gap between the resin passages in the lip is adjusted to change the thickness of the product, or when the extrusion rate per width of the die is When changing the amount, it is normal to have to start from a state where the thickness deviation accuracy is quite poor, and the thickness deviation must be adjusted after the start, but this thickness deviation adjustment operation is delicate, There was a limit to the accuracy of adjusting the uneven thickness even when performed by an experienced person. Also, the working environment is bad.
If it was done manually, there was a risk of harm to health. On the other hand, when adjusting the uneven thickness using an automatic thickness unevenness adjustment device, it is easier to adjust the uneven thickness than manually.
It must be possible to adjust the uneven thickness in a short time, and the final adjustment accuracy must be excellent.Determine the correspondence between the location where uneven thickness occurs on the film and the position of the die operating bolt. This has not been put to practical use because there is no satisfactory way to do so. The present invention addresses the above-mentioned problems by determining in advance the correspondence between the width direction positions of the sheet before transverse stretching and the film after transverse stretching and the position of the die operating bolt, and After converging the profile to an acceptable range for the set profile,
The thickness deviation of the film after horizontal stretching is measured, and if it is out of the tolerance range, the profile before horizontal stretching is corrected, and the die operating bolt is set so that the profile before horizontal stretching converges to the tolerance range with respect to the modified profile. The present invention relates to a film thickness control method characterized in that the thickness of the film or sheet is adjusted by returning to the operation of measuring the thickness deviation of the film after the transverse stretching. The purpose of this invention is to provide an improved film thickness control method that can adjust the thickness unevenness in a short time and improve the accuracy of the final thickness unevenness adjustment. Next, the film thickness control method of the present invention will be explained with reference to an embodiment shown in Figs. 1 to 4. In Figs. The automatic adjustment device 3 is a die operating bolt, and the bolt 3 is rotated by the automatic bolt adjustment device 2 to deform the die adjustment lip 1a, thereby adjusting the amount of extrusion from the slit. Reference numeral 4 denotes a cooling and solidifying device for forming the molten thermoplastic resin extruded from the slit of the die 1 into a sheet 5, which is composed of a group of rolls. Further, numeral 6 denotes a longitudinal stretching device for longitudinally stretching the sheet 5 in the direction in which the sheet travels, and is composed of a group of rolls. 8 is a longitudinally stretched sheet 7
As shown in FIG. 3, both sides of the sheet 7 are held by clips 18a and 18b, and the sheet 7 is laterally stretched in the above direction while being heated. Then, it is formed into a film 9. At this time, edges 10a and 10b which are not laterally stretched are formed in the ranges x ₁ and x ₂ on both sides of the film 9. The width of the ears 10a, 10b is determined by the ear width detection device 11a,
11b. Since it is difficult to make the stretched film near the edges uniform in thickness, only the slit portions 12a and 12b (widths l ₁ and l ₂ ) are cut. 15 is a product film cut in the range l ₁ and l ₂ ; 16 is a winder for winding the product film 15; 14 is a thickness measuring device for measuring the thickness distribution of the product film 15 in the width direction; 19; 19 is a thickness measuring device for measuring the thickness distribution in the width direction of the sheet 5 coming out of the cooling and solidifying device 4 and the sheet 7 coming out of the longitudinal stretching device 6; 17 is an arithmetic and control device; Each of the above thickness measuring devices 14, 19, 1
When receiving the measurement results in step 9, the calculations described later are carried out, and the results are transmitted to the bolt automatic adjustment device 2, the die operation bolt 3 is rotated by the bolt automatic adjustment device 2, and the die adjustment lip 1a is deformed. The amount of extrusion from the slit is adjusted. Next, the operation of the automatic thickness unevenness adjustment device will be explained.
Each die operating bolt 3 has an evenly spaced pitch on the die 1.
The molten thermoplastic resin extruded from the die 1 is formed into a sheet 5 by the cooling and solidifying device 4 so as to be reduced in the width direction (netching), and the width Wb is set at the base of the die 1. is smaller than the width Wa. In addition, the widths of the strip-shaped sheets 5 corresponding to each die operation bolt 3 are Wb ₁ , Wb ₂ , Wb ₃ ......
Wbi differs in the width direction and becomes smaller as it approaches both sides, but the relationship between the equidistant pitch Wai of each die operating bolt 3 and the strip width Wbi is reproducible once the forming conditions are determined, and it can be determined through experiments in advance. Also, since the width Wb of the sheet 5 and the strip width Wbi are correlated, it is convenient for thickness control to find the correlation formula. Since the netting phenomenon also occurs in the longitudinal stretching device 6, the above is not applicable to the cooling and solidifying device 4.
It can also be applied between the
The relationship between Wbi and Wci is determined in advance through experiments. As described above, the correspondence relationship between the width direction position of the sheet 7 before lateral stretching and each die operating bolt 3 is obtained. Focusing on the fact that the time for adjusting the thickness of the film 9 after horizontal stretching can be shortened by converging the profile of the sheet 7 before horizontal stretching to a certain degree, first, the profile of the sheet 7 before horizontal stretching, that is, The original fabric profile is converged to a certain tolerance range with respect to the set profile. That is, before horizontal stretching (after longitudinal stretching) by the thickness measuring device 19.
The widthwise thickness of the sheet 7 is measured, and the result is transmitted to the arithmetic and control device 17, which calculates the thickness deviation for each die operating bolt 3 with respect to the set profile. The operating amount of each die-operated bolt 3 is calculated using a predetermined method, the result is transmitted to the bolt automatic adjustment device 2, and the bolt automatic adjustment device uses the same bolt 3.
is rotated by a predetermined amount, and as a result, the die adjustment lip 1a
The desired sheet width direction profile is obtained by repeatedly deforming the bolts 3, correcting the uneven thickness by adjusting the extrusion amount corresponding to each bolt 3, and measuring the result with the thickness measuring device 19. Finally converge to an acceptable range. The degree of convergence may be determined based on the standard deviation value, variance value, or maximum deviation value for the set profile for each die operating bolt 3. Experience has shown that the standard deviation value σ for the set profile, i.e.

[Formula] (Pi is the setting profile corresponding to the i-th die operating bolt, Poi is the measurement profile corresponding to the i-th die operating bolt) is converged to 05%, then the deviation of film 15 after horizontal stretching is ±3 to ±5
%to go into. The setting profile may be set by measuring the profile of the sheet 7 before being laterally stretched when the product film 15 after being laterally stretched is within the permissible range. However, even if the profile of the sheet 7 before transverse stretching is strictly converged to the desired profile, the film 15 after transverse stretching may not necessarily fall within the allowable range as a product due to slight differences in the stretching conditions; Film 1 after horizontal stretching
5, it is necessary to make fine adjustments. Fine adjustment of the film 15 after this horizontal stretching is performed by the following method. As shown in FIG.
a and 10b are formed, but their widths x ₁ and x ₂ depend on the conditions of lateral stretching or the width of the sheet 7 near the edges 10a and 10b.
It varies depending on the thickness. The ear portion widths x ₁ and x ₂ are measured by the ear width measuring devices 11a and 11b, but since the ear portions 10a and 10b are not laterally stretched, the positions of the ear portions 10a and 10b are the same as those of the sheet 7 before the width stretching. It will be the same width as the ear. Further, the widths l ₁ and l ₂ of the slit portions 12a and 12b to be cut may be automatically measured, but since they are generally fixed values, they can be given as data for calculation. The relationship between the width Wα and the position in the width direction of the product film 15 and the thickness is measured by the thickness measuring device 14, and the results are transmitted to the arithmetic and control unit 17. 12a,1
2b), that is, Z=Wα+(l ₁ −x ₁ )+(l ₂ −x ₂ )/Wc−x ₁ −x ₂ is calculated. Generally, the average transverse stretching ratio is 8 to 10 times for polypropylene, and about 3 to 4 times for polyethylene terephthalate, polystyrene, nylon, etc. The correspondence between the widthwise position of the product film 15 and the position of the die operating bolt 3 can be estimated by the following method. Point P on the side edge of the product film 15 corresponds to a point (x ₁ +l ₁ -x ₁ /Z) from the side edge Q on the sheet 7 before lateral stretching. Therefore, the relative position between point P on the side edge of the product film 15 and the die operating bolt 3 is determined from the relationship between the strip width Wci of the sheet 7 before horizontal stretching and the die operating bolt 3. It can be calculated that the section y from point P corresponds to the i-th die operating bolt 3. That is, it can be calculated that the section ( _y2 - _y1 ) from point P corresponds to (i+1) of the die operating bolt 3. Similarly, the correspondence relationship between the product film 15 and each die operating bolt 3 is calculated, and from the relationship between the widthwise position of the product film 15 measured by the thickness measuring device 14 and the thickness deviation, each die operating bolt 3 is calculated.
Calculate _the standard _deviation →Product deviation (X)
Repeat the operation. If, on the other _hand , After a predetermined time has elapsed by operating the die operation bolt, the original fabric profile of the sheet 7 before lateral stretching is measured. If the measured value (Y) is outside the allowable value (V ₂ ) and Y>V ₂ , then
Recalculate the bolt operation amount to bring it within the allowable range. On the other hand, if the measured value (Y) is within the allowable value (V ₂ ), Y≦V ₂ , the product film 15 after horizontal stretching is measured again, and the operations after the product film measurement are repeated. Note that all of the arithmetic and control operations are performed by the arithmetic and control device 17.
The product film 15 obtained by the above thickness control method is wound up by a winding machine 16. If the ear widths x ₁ and x ₂ are stable and there is no need to measure them using the ear width measuring devices 11a and 11b, they may be measured manually and input to the arithmetic and control unit 17. Furthermore, if the lateral stretching ratio of a specific portion differs due to the characteristics of the lateral stretching device 8, etc., the lateral stretching ratio of that portion may be corrected. Furthermore, the profile control of the sheet 7 before horizontal stretching may be performed by measuring the thickness in the width direction of the sheet 5 before longitudinal stretching, instead of measuring the thickness in the width direction of the sheet 7 before horizontal stretching. As described above, the film thickness control method of the present invention associates the location where uneven thickness of the film or sheet occurs with the position of the operating bolt, and after converging the profile of the sheet for horizontal stretching to an allowable range, If the subsequent product film has a thickness deviation exceeding the allowable value, the thickness is adjusted by correcting the profile before lateral stretching, so that the thickness deviation can be adjusted in a short time. Moreover, the final thickness unevenness accuracy can be improved. Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the film thickness control method according to the present invention, FIG. 2 is a vertical side view showing a die and bolt automatic adjustment device, and FIG.
FIG. 4 is a longitudinal sectional front view taken along the line shown in the figure, and FIG. 4 is a control block diagram. 1...Die, 2...Bolt automatic adjustment device, 3...
...Die operating bolt, 7... Sheet before horizontal stretching, 1
5...Film after horizontal stretching.

Claims (1)

[Claims] 1. Obtain in advance the correspondence between the widthwise position of the sheet before horizontal stretching and the film after horizontal stretching and the position of the die operating bolt, and make the profile of the sheet before horizontal stretching converge to an allowable range with respect to the set profile. After that, the thickness deviation of the film after horizontal stretching is measured, and if it is out of the tolerance range, the profile before horizontal stretching is corrected, and the profile before horizontal stretching is converged to the tolerance range with respect to the corrected profile. A method for controlling the thickness of a film, comprising adjusting the thickness of the film or sheet by operating a die operating bolt and then returning to the operation of measuring the thickness deviation of the film after the transverse stretching.