JPS591577B2 - Nijikuen Shin Film no Atsumi Murano - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and an apparatus for correcting thickness unevenness of a tubular film after stretching, particularly during the production of a tubular biaxially stretched film.

In the tubular biaxially stretched film manufacturing method using the tubular method, generally an upper nip roller 1 is used as shown in FIG.
A tube-shaped film (hereinafter referred to as a raw material tube) 3 before stretching is guided between two sets of nip rollers and a lower nip roller 2 which has a faster speed, and a gas-filled nozzle and a gas filling nozzle are introduced into the raw material tube. Gas is press-injected by a gas filling device 4 made up of the same roller, etc., and heated by a heating device 5 to raise the temperature of the film. When the film reaches the stretching temperature, the film is radially At the same time, due to the speed difference between the upper and lower nip rollers, it is also stretched in the axial direction.

The stretched film is guided into a flat shape by a cooling stabilizer 6, folded by a lower nip roller 2, and further wound to form a product. The most important thing in this production method is that the produced stretched film has the required thickness and that the thickness is uniform in all directions.

However, the raw fabric tube itself often has thickness unevenness and cooling unevenness that makes the structure of the raw fabric tube non-uniform, and it is very difficult to obtain a raw fabric tube without these. The raw tube is heated for stretching as described above, but if the thickness of the raw tube is uneven, stretching in the circumferential direction of the raw tube does not start at the same time when it is heated. The tension in each part becomes unbalanced, causing the film to sway during stretching.

This wobbling further increases the rate of thickness unevenness of the stretched film during stretching. Therefore, if the temperature of only the thickest part is made higher than the other parts before stretching, a product with very little thickness unevenness can be obtained after stretching.

The present invention relates to a method and apparatus for easily correcting thickness unevenness of a stretched film.

That is, the first invention is based on a method for manufacturing a biaxially stretched film by the tubular method, and a heated element is built into a large part of the thickness of the raw material tube that comes out from the upper two rollers and advances downward. In addition, the gap portion of a slit heater made of a cylindrical body having a gap extending in the axial direction of the raw fabric tube is brought close to each other to generate a high temperature that allows a thicker portion of the raw fabric tube to flow out from the gap of the slit heater. The second invention is a method of heating the original film tube to a higher temperature than other parts by radiant heat from the air and gaps, and preventing uneven thickness of the original film tube from remaining on the film after stretching. A device for carrying out the invention, wherein the cylindrical body has a built-in heating element and has a gap extending in the axial direction of the raw fabric tube, the gap being larger than the thickness of the raw fabric tube. This invention relates to a device for correcting thickness unevenness of a biaxially stretched film using the tubular method, which is arranged so as to be able to appropriately face different parts. Next, the present invention will be explained based on one embodiment of FIGS. 2 and 3.

FIG. 2 is an elevational view showing the relationship between the raw fabric tube 11 coming out from the upper two rollers (not shown) and the slit heater 12, and FIG. 3 is a cross section taken along line I in FIG. It is a diagram.

As shown in the figure, the slit heater 12 has a cylindrical body 13 whose top and bottom are closed and has a gap 14 extending in the axial direction of the raw material tube on the side surface thereof, and a heating element such as a far-infrared heater 15 is installed in the cylindrical body. It has a built-in structure, and as shown in FIG. 1, upstream of the stretching self-heating device 5,
When the rough heating device 7 is used together, it is installed in the preheating device 51 between the two devices 5.7 or above the stretching temperature heating device so that the raw fabric tube is irradiated 5 from the gap 14. It has a rhyme.

It is possible to know at which position on the circumference of the original film tube how thick the film is compared to a predetermined thickness by measuring the film tube after stretching.

Therefore, the thickness distribution of the original fabric tube is measured in advance, and the position where heating is required where the thickness is larger is confirmed. Then, one or more of the slit heaters 12 are arranged on the support so that the position can be changed around the raw fabric tube, and the slit heater 1 is placed so that the gap 14 faces the position of the raw fabric tube where heating is required. Heating is performed by energizing only the slit heater, which is moved and fixed on a support and whose gap is directed toward the position where heating is required. If the number of slit heaters arranged for a position requiring heating is insufficient, the insufficient number of slit heaters are additionally arranged on the support. Of course, it is also possible to arrange a large number of slit heaters in close proximity to each other around the raw fabric tube and to fix the slit heaters to the support body, and to energize only the slit heaters whose gaps 14 are directed to the position where heating is required. .

In either case, it is desirable that the direction in which the gap 14 of the slit heater faces can be adjusted by, for example, turning the cylindrical body. When the required slit heaters are energized in this way, the air heated by the far-infrared heater 15 becomes an upward airflow and is discharged from above the narrow gap 14, as shown in FIG. 2, and is partially concentrated on the film. It is sprayed and diffused.

In this case, air is supplied into the cylinder from below. In FIG. 4, the width of the gap 14 is 2T1:ITL with the slit heater as shown in FIGS. A raw tube made of polypropylene with a thickness of ▲0.720Tr1rL is inserted from the gap between the above cylinders.
FIG. 6 is a diagram showing the temperature distribution at the gap outlet of the slit heater 1 while descending at a speed of 3.0 m/Sec from a position of 0 Tr1 m. According to this figure, the temperature at the bottom of the slit heater is normal, but the temperature rises rapidly toward the top. In this example, the temperature at the top is approximately 1
The temperature is 80° C., and hot air at this temperature is blown locally onto the surface of the raw fabric tube. If this rising air current is not generated, heating will be performed only by radiant heat from the built-in slit heater, and in order to obtain the above-mentioned temperature of 180° C., it is necessary to increase the voltage considerably. That is, the main feature of the present invention is that such a slit heater can locally apply high temperature to the raw fabric tube with little power consumption. In addition, the required temperature varies depending on the type of southern fat that makes up the raw fabric tube, the speed at which the raw fabric moves, and the degree of uneven thickness, but these temperatures can be easily achieved by applying voltage. Needless to say, if the slit heater 1 is movably provided around the raw fabric tube, the purpose can be sufficiently achieved by using one or a small number of slit heaters 1.

Example: A raw fabric tube with an average thickness of 0.720Tf1m was preheated while being lowered, and stretched to the stretching temperature with air forced into the polypropylene (trade name: Sho Aroma SG5lO). Between the drawing process and the stretching temperature heating process, the width is 2TIUn and the length is 500mm.
Using a slit heater with a gap of Tr$L and a built-in far-infrared heater, the distance between the gap between the raw fabric tube and the slit heater was set to 10TIn, and a particularly thick part of the raw fabric tube was irradiated. The outlet temperature was as shown in Figure 4, and the difference between the thick part of the tube after stretching and the particularly thin part of the tube after stretching was 0.1101H1n when the slit heater 1 was not used. There was a significant decrease of 0.0401WL, indicating that the slit heater had a great effect.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of the stretching device, Fig. 2 is a schematic enlarged longitudinal sectional side view showing the positional relationship between the raw material tube being formed and the slit heater, which is an embodiment of the present invention, and Fig. 3 is the same as above. FIG. 4, which is a partial cross-sectional view along a line, is a graph showing the relationship between the height of the slit heater 1 and the temperature at the gap outlet of the slit heater 1. In the figure, 3 and 11 are the raw fabric tubes,
12 is a slit heater, 13 is its cylindrical body, 14 is a gap, 15 is a heating element, 16 is a support, 17
Reference numerals a and 17b designate brackets which close each end of the cylindrical body so as to be rotatable and on which the slit heater is mounted so as to be movable along the support.

Claims (1)

[Claims] 1. In a method for producing a biaxially stretched film using the tubular method, a portion of the raw material tube that comes out from an upper nip roller and moves downward, where the thickness is uneven, is covered with a slit heater having a gap in the axial direction of the raw material tube. A method for correcting thickness unevenness in a biaxially stretched film, the method comprising heating with high temperature air flowing out from gaps and radiant heat from the gaps. 2. A slit heater that has a built-in heating element and has a gap that extends in the axial direction of the raw fabric tube can be appropriately positioned so that the gap part faces a part of the raw fabric tube that is being stretched and has uneven thickness. A device for correcting thickness unevenness of a biaxially stretched film using the tubular method, characterized in that the device is arranged as follows.