JP2006001290A - Thickness control method of biaxially drawn film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thickness control method of a biaxially drawn film capable of reliably and properly monitoring and adjusting accuracy in thickness control and widthwise drawing ratio by correctly setting positions on the film corresponding to die bolts. <P>SOLUTION: The control method comprises the step of executing feedback control of the die bolts through an automatic T die control system 16 by measuring the thickness of the film at the positions Bf(i) corresponding the die bolts when a sheet S extruded from an automatic T die 10 having a plurality of the die bolts is biaxially drawn, into a film F within a twin screw extruder 14. The positions Bf(i) on the film corresponding to the die bolts are set by using a partial widthwise draw ratio Ff(i) calculated in conjunction with the positions Bs(i) on the sheet S corresponding to the die bolts set separately by arranging thickness gages 18a and 18b respectively on the sheet and the film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for controlling the thickness of a biaxially stretched film by an automatic T-die, and in particular, by accurately setting the bolt-corresponding position on the film of the T-die bolt required in the thickness control method, The present invention relates to a method for controlling the thickness of a biaxially stretched film that can reliably achieve and monitor the control.

  In general, the method for controlling the thickness of a biaxially stretched film is basically that a sheet of plastic material (raw material) extruded from an automatic T-die having a plurality of die bolts with adjustable opening gaps is a cast roll unit. Measure the thickness of the film itself when it is cooled and solidified and stretched by a biaxial stretching machine that consists of a longitudinal stretching machine and a transverse stretching machine equipped with a hot air device. By doing so, the T-die is controlled.

  That is, in more detail, by continuously measuring the thickness distribution at each position in the width direction on the sheet with a scanning thickness meter, the measured value has a deviation of a predetermined value or more from the reference thickness. The adjustment amount of the bolt at a position corresponding to the position is feedback-controlled.

  Therefore, according to such a thickness control method, it becomes possible to continuously form a film having a uniform thickness in the width direction.

  However, the conventional method for controlling the thickness of the biaxially stretched film has the following problems.

  That is, as described above, the conventional control method is configured to feedback-control a bolt at a position corresponding to a position in the width direction on the sheet where the measured value of the sheet thickness has a deviation of a predetermined value or more. Has been. However, in the conventional control method, the setting (assignment) of the position of the die bolt at the position corresponding to the position in the width direction on the sheet, in other words, the position on the film corresponding to the die bolt (the position corresponding to the die bolt on the film). However, in practice, it has not been achieved accurately, and thus the accuracy and monitoring of the control have not been sufficiently achieved.

  This will be explained here in a conclusion. In the conventional control method, the setting of the bolt-corresponding position on the film assumes that the stretching ratio in the transverse direction (lateral stretching ratio) on the film is constant. This is due to the fact that it was performed in a hurry. However, the transverse stretch ratio will be apparent from the description of the present invention described later, but is considerably different in the width direction of the film. Incidentally, such a difference in the partial transverse stretching ratio on the film not only caused the unevenness of the film thickness as described above, but also caused the unevenness of the tensile strength at the same time, thereby further reducing the film quality.

  Therefore, an object of the present invention is to provide a biaxially stretched film that can reliably achieve the accuracy of film thickness control and the monitoring and adjustment of the transverse stretch ratio by accurately setting the bolt-corresponding position on the film. It is to provide a thickness control method.

  In order to achieve the above object, a method for generating a partial transverse stretch amount or partial transverse stretch ratio according to the present invention is to form a sheet of plastic material supplied from an automatic T die as a film by biaxial stretching. A step of continuously measuring the thickness in the sheet width direction, a step of continuously measuring the thickness of the film in the film width direction, and a step of assigning the length in the sheet width direction to a plurality of first intervals Identifying the sheet material mass passing through a predetermined time through one of the first intervals on the assigned sheet by the measured data, and the sheet material mass passing through the first interval In order to specify the second interval in the film width direction of the film portion formed by the step, the one end side position in the film width direction of the second interval is the first interval. The second end position of the second interval is determined in association with the position in the sheet width direction, and the film portion sheet existing between the one end side position and the other end side position during the time corresponding to the predetermined time. Determining whether the material mass is equal to the sheet material mass that has passed through the first interval, and then determining the second interval of the film portion as a partial lateral stretch amount relative to the first interval of the sheet Alternatively, the ratio of the second interval to the first interval is defined as a partial lateral stretch ratio of the second interval to the first interval.

  Thus, in the present invention, the position corresponding to the die bolt on the film is fixed as in the past through the partial transverse stretching ratio calculated together with the position corresponding to the die bolt on the sheet set in advance on the sheet before stretching. It can set without going through a certain constant transverse stretch ratio. Therefore, it is obvious that the position corresponding to the die bolt can be set accurately. In the present invention, since the partial transverse stretch ratio is continuously calculated, the required monitoring and adjustment can be properly achieved.

  Therefore, according to the present invention, it is possible to reliably achieve monitoring and adjustment of film thickness control accuracy and transverse stretch ratio.

  According to the first aspect of the present invention, there is provided a method for generating a partial transverse stretching amount or a partial transverse stretching ratio according to the present invention. In forming a sheet of plastic material supplied from an automatic T-die as a film by biaxial stretching, the thickness of the sheet is set to the sheet Continuously measuring in the width direction, further measuring the thickness of the film continuously in the film width direction, assigning the sheet width direction length to a plurality of first intervals, The sheet material mass that passes through the first interval on the assigned sheet at a predetermined time is specified by the measured data, and the sheet material mass that has passed the first interval is formed. In order to specify the second interval in the film width direction of the film portion, the one end side position in the film width direction of the second interval is defined as the sheet width direction of the first interval. And the other end side position of the second interval is determined by the sheet material mass of the film portion existing between the one end side position and the other end side position during the time corresponding to the predetermined time. Determining the position equal to the sheet material mass that has passed through the first interval, and then determining the second interval of the film portion as a partial lateral stretch amount with respect to the first interval of the sheet, or Since the ratio of the second interval to the first interval is defined as the partial transverse stretch ratio of the second interval to the first interval, the sheet of the sheet extruded from the automatic T-die It is possible to accurately correspond to the film portions formed by the respective sheet portions allocated in the width direction.

  Moreover, according to this invention, since the said partial lateral stretch ratio is calculated continuously, the required monitoring and adjustment regarding film thickness control including the said partial lateral stretch ratio can also be achieved appropriately.

  Next, an embodiment of a method for controlling the thickness of a biaxially stretched film according to the present invention will be described in detail with reference to the accompanying drawings in relation to an apparatus for carrying out this method.

  First, in FIG. 1 comprising a sequential biaxial stretching machine or the like that stretches the machine direction and the transverse direction in separate steps, the thickness control method of the biaxially stretched film of the present invention basically adjusts the extrusion port gap. A sheet S as a raw material of a plastic material extruded from an automatic T die 10 having a plurality of possible die bolts (not shown) is cooled and solidified by a cast roll unit 12, and from a longitudinal stretching machine 14a and a lateral stretching machine 14b. The resulting biaxial stretching machine 14 is biaxially stretched in the longitudinal and lateral directions and formed into a film F as a product. In this case, a position corresponding to the die bolt on the film F is set, and a film thickness at the corresponding position is measured to detect a deviation from the reference thickness, and based on this deviation, an automatic T-die The control system 16 is configured to feedback control the adjustment length of the bolt.

  Further, hot air is supplied to the blower 15a and the duct 15b in the transverse stretching machine 14b. This is controlled by a hot air device control system (not shown).

  However, the automatic T-die control system 16 includes scanning thickness meters 18a and 18b for measuring the thicknesses of the sheet S and the film F before and after the stretching process by the biaxial stretching machine 14, respectively. The measurement data from both thickness gauges 18a and 18b are input via the thickness gauge controller 20, and the CPU 22 calculates the partial lateral stretch ratio on the film F, which will be described later, and sets the corresponding position of the die bolt. Then, the CPU 22 generates measured thickness distribution data at the corresponding positions of the respective die bolts, and designates the die bolts corresponding to positions having a deviation of a predetermined value or more from the reference thickness in these data. These die bolts are adjusted through the automatic T-die controller 24 so as to obtain appropriate lip gaps. Configured to perform a feedback control for. In FIG. 1, reference numeral 26 indicates a display device that can display various data obtained by arithmetic processing in the CPU 22.

  Therefore, in the present invention, as shown in FIGS. 2A and 2B, particularly in the feedback control, the die bolt corresponding position Bf (i) on the film F is the same as the corresponding position Bf (i). Separately, it is set via a partial lateral stretching ratio Ff (i) calculated together with the bolt corresponding position Bs (i) on the sheet, which is preset on the sheet S before the stretching process corresponding to the die bolt. . The setting of the die bolt corresponding position Bs (i) on the sheet S shown in FIG. 2A is an allocation method (for example, prior to the present applicant) in consideration of the neck-in phenomenon of the plastic material in the automatic T die 10. Japanese Patent Publication No. 5-76413 related to the application can be suitably applied.

  Therefore, first, the partial transverse stretch ratio Ff (i) on the film F after the stretching treatment is successively continued from the reference die bolt corresponding position Bf (0) on the film F as shown in FIG. Bf (1)... Bf (i), Bf (n) and Bf (-1)... Bf (-i)... Bf (-n). (Represented by (i) and the same shall apply to other definition items). The plastic material mass Mf (i) in the film F within each die bolt pitch corresponding width Wf (i) Plastic material mass Ms (i) in the sheet S within each die bolt pitch corresponding width Ws (i) between each die bolt corresponding position Bs (i) sequentially arranged from the reference die bolt corresponding position Bs (0). Are compared.

  Next, calculation processing when the present invention is carried out will be described with reference to FIGS.

（但し、Ｔｓ(i)、Ｔｆ(i)は、それぞれシートおよびフィルムのダイボルトピッチ対応幅Ｗｓ(i)、Ｗｆ(i)内における平均厚さであり、またＶｓ、Ｖｆは、それぞれシートおよびフィルムの移動速度を示す。）を演算することにより、その比即ち、部分横延伸倍率を、Ｗｆ(i)／Ｗｓ(i)＝Ｆｆ(i)として算定することができる。なお、前記式（１）には、シートおよびフィルムの間に密度変化がある際は、これを補償する密度項を加入することができる。 That is, since the plastic material masses Mf (i) and Ws (i) should not change, the following formula (1)

(However, Ts (i) and Tf (i) are average thicknesses in the die bolt pitch corresponding widths Ws (i) and Wf (i) of the sheet and film, respectively, and Vs and Vf are respectively the sheet and film By calculating (moving speed of the film), the ratio, that is, the partial transverse stretch ratio can be calculated as Wf (i) / Ws (i) = Ff (i). In addition, when there is a density change between the sheet and the film, a density term that compensates for this can be added to the formula (1).

  In the above formula (1), the left side means the amount of sheet material that passes through each die bolt pitch-corresponding width Ws (i) on the assigned sheet in a predetermined time. Corresponds to the die bolt pitch-corresponding width Wf (i) in the film width direction of the film portion on the film formed (biaxially stretched) by the sheet material mass that has passed the width Ws (i), corresponding to the predetermined time. It means the amount of film material that passes over time, and equation (1) defines that they are equal. The term “during the time corresponding to the predetermined time” means a time delayed by the time required for biaxial stretching until the sheet is formed into a film with respect to the predetermined time. Means that the measurement timing of the film part is delayed from the measurement timing of the sheet. Each die bolt pitch corresponding width Ws (i) on the sheet corresponds to the first interval in the present invention, and the die bolt pitch corresponding width Wf (in the film width direction of the film portion on the film). i) corresponds to the second interval in the present invention. The width Wf (i) corresponds to the amount of partial lateral stretching in the present invention.

  Next, the die bolt-corresponding position Bf (i) on the film F can be calculated in reverse calculation when calculating the partial lateral stretch ratio Ff (i).

から算定されるフィルムＦ上の前記ダイボルトピッチ対応幅Ｗｆ(i)を、基準ダイボルト対応位置Ｂｆ(O)から順次加算する。 That is, the following equation (2) obtained by converting the equation (1):

The die bolt pitch corresponding width Wf (i) on the film F calculated from the above is sequentially added from the reference die bolt corresponding position Bf (O).

を演算することにより、順次設定することができる。 That is, the following equation (3)

Can be set sequentially.

に変換することもできる。 The above formula (2) is obtained by using Ts (i) and Tf (i) as the thickness ratios TsR and TfR with respect to the average values, and using the overall transverse stretch ratio ESR.

Can also be converted.

  In the present invention, the partial transverse stretch ratio and the like on the film F can be continuously calculated or measured in this way, so that necessary monitoring and adjustment can be appropriately achieved as necessary. it can.

  FIG. 3 shows an embodiment of a control circuit (profile control system in the sheet width direction) including these monitoring or adjustment functions. That is, in FIG. 3, reference numeral 30 is a forming step of the sheet S, and 32 is a forming step of the film F. The profile processing unit 34 calculates profile distribution data of the sheet and the film, respectively, based on the data measured via the above. These profile distribution data can be displayed by the display means 36 and confirmed.

  Data relating to the sheet and film obtained in the profile processing unit 34 is compared and calculated with the sheet target profile 42 and the film target profile 44 in calculators 38 and 40, respectively. In this way, the result of the comparison calculation is transferred to the profile control calculation unit 48 via the control mode switch 46.

  The profile control calculation unit 48 calculates the set temperature of the automatic T-die, compares the calculated value with the set value in the calculator 50, and requires the heating means via the temperature controller 52 and the heating control output unit 54. The control signal is output. In temperature control in this case, feedback control is appropriately performed. Furthermore, control for adjusting the die bolts so as to have appropriate lip gaps is performed on the automatic T die via the die bolt controller 56.

  Next, the arithmetic processing step of the present invention will be described with reference to FIG.

  First, the die bolt corresponding position Bs (i) [and the die bolt pitch corresponding width Ws (i)] on the sheet S is assigned in consideration of the neck-in phenomenon of the T die 10 (step 1).

  Next, a reference die bolt corresponding position Bf (0) [and Bs (0)] on the film F (and the sheet S) is substituted for the above formula (2), in this case, a value ½ of the film width As a result, the film is set at the center of the film (step 2). In addition, this reference | standard die bolt corresponding position can also be set not to the said center part but to a sheet | seat edge part.

  Thereafter, with respect to the right half of the film F and the sheet S, the average thicknesses Tf (i) and Ts (i) and the moving speeds Vf and Vs of the film and the sheet are measured, and the die bolt pitch of the film is determined based on the measured data. Corresponding width Wf (i) and partial lateral stretch ratio Ff (i) are calculated (step 3). That is, according to (a) and (b) of FIG. 5, a calculation is performed based on the thickness tf at the measurement point X of the film thickness meter 18b of FIG. It is obtained when (i) exceeds Ms (i). At the same time, each die bolt corresponding position Bf (i) is also obtained.

  Next, in the same manner as in step 3, the same measurement and calculation are performed for the left half (step 4).

  Also, if necessary, necessary monitoring, for example, a graph display of the partial transverse stretching ratio or an alarm for the abnormal alarm and adjustment thereof, that is, adjustment of hot air conditions (hot air temperature, air volume, and wind speed) in the biaxial stretching machine. (Step 5).

  When it is determined that the measured thickness at each die bolt corresponding position Bf (i) has a deviation of a predetermined value or more from the reference value (step 6), the automatic T die 10 corresponding to this corresponding position. The operation amount of the die bolt is calculated (step 7) and an operation command is generated (step 8).

  In other words, in the present invention, the position corresponding to the die bolt on the film is set through the partial lateral stretch ratio calculated together with the position corresponding to the die bolt on the sheet set in advance on the sheet before stretching. That is, in the present invention, the position corresponding to the die bolt on the film is set without using a fixed constant transverse stretch ratio as in the prior art.

  Therefore, in the present invention, it is clear that the position corresponding to the die bolt can be accurately set. In the present invention, since the partial transverse stretch ratio can be calculated continuously, the required monitoring and adjustment can also be properly achieved. Thus, according to the present invention, it is possible to reliably achieve the accuracy of film thickness control and the monitoring and adjustment of the transverse draw ratio.

  Incidentally, the numerical data of one embodiment of the present invention having such a configuration will be described below. In this embodiment, the automatic T die 10 is configured to have a total width of 900 mm, a die bolt pitch width of 20 mm, and a number of die bolts of 45. And the width | variety and speed | rate of a sheet | seat and a film are set to 820 mm and 2870 mm (namely, constant transverse draw ratio 2870/820 = 3.5) and 50 m / min and 200 m / min, respectively.

  That is, in (a) and (b) of FIG. 5, the average thickness of the sheet [(a) of FIG. 5] and the film [(b) of FIG. 5] is set to 285 μm and 20 μm, respectively. The former (sheet) is quite different.

  In FIGS. 6 and 7, the die bolt pitch-corresponding width Wf (i) and the partial transverse stretch ratio on the film according to the present invention are in a considerable range (for example, in the case of the magnification) with respect to the conventional constant transverse stretch ratio. 3.34 to 3.75 times).

  In FIG. 8, it is understood that these differences are numerically displayed (for example, about 5 mm for the die bolt pitch-corresponding width Wf (i) on the film according to the present invention).

  Thus, in the said Example, it has shown that the width | variety corresponding to the die volt | bolt pitch on a film makes the transverse draw ratio partially differ. Therefore, in this type of film thickness control method, it has been proved that measures against the partial transverse stretch ratio are indispensable.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and many design changes can be made without departing from the spirit of the present invention.

It is a system block diagram which shows one Example of the apparatus which enforces the thickness control method of the biaxially stretched film which concerns on this invention. (A) is explanatory drawing which shows the calculation or calculation method of the die bolt corresponding position etc. on the sheet | seat in the thickness control apparatus in FIG. 1, (b) is the die bolt corresponding position etc. on the film in the thickness control apparatus in FIG. It is explanatory drawing which shows the calculation thru | or calculation method. It is a block diagram which shows the control circuit containing the monitoring and adjustment function in the thickness control apparatus in FIG. It is a flowchart figure which shows the control process with the thickness control apparatus in FIG. (A) is a profile characteristic diagram showing the sheet thickness in the thickness control device in FIG. 1, and (b) is a profile characteristic diagram showing the film thickness in the thickness control device in FIG. It is a profile characteristic diagram which shows the die bolt pitch corresponding | compatible width | variety on the film in the thickness control apparatus in FIG. It is a profile characteristic diagram which shows the partial lateral stretch ratio on the film in the thickness control apparatus in FIG. It is a list which shows the various numerical data in the thickness control apparatus in FIG.

Explanation of symbols

10 automatic T die 12 cast roll unit 14 biaxial stretching machine 14a longitudinal stretching machine 14b transverse stretching machine 15a blower 15b duct 16 control system 18a sheet thickness meter 18b film thickness meter 20 thickness meter controller 22 CPU
24 automatic T-die controller 26 display device 30 sheet forming step 32 film forming step 34 profile processing unit 36 display means 38, 40 calculator 42 sheet target profile 44 film target profile 46 control mode switching unit 48 profile control calculating unit 50 calculator 52 Temperature Controller 54 Heating Control Output Device 56 Die Bolt Controller

Claims (1)

When forming a sheet of plastic material supplied from an automatic T-die as a film by biaxial stretching, the thickness of the sheet is continuously measured in the sheet width direction, and the thickness of the film is continuously measured in the film width direction. Measuring automatically,
Allocating the sheet width direction length to a plurality of first intervals;
Identifying, by means of the measured data, a sheet material mass that passes in a predetermined time through one of the first intervals on the assigned sheet;
In order to specify the second interval in the film width direction of the film portion formed by the sheet material mass that has passed through the first interval, the one end side position in the film width direction of the second interval is defined as the first interval. And the other end side position of the second interval is a film portion existing between the one end side position and the other end side position during a time corresponding to the predetermined time. Determining the position where the sheet material mass is equal to the sheet material mass that has passed through the first interval;
Thereafter, the second interval of the film portion is determined as a partial lateral stretch amount with respect to the first interval of the sheet, or the ratio of the second interval to the first interval is set to the second interval. A method for generating a partial transverse stretching amount or a partial transverse stretching ratio, comprising the step of determining a partial transverse stretching ratio for the first interval.

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