JPS5844463B2 - Netsukaso Seiji Yushifilm Noatsusachiyouseihohou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adjusting the thickness of stretched thermoplastic films.

When stretching thermoplastic resin films, it is extremely important and difficult to make the thickness distribution of the film uniform, especially the thickness distribution in the width direction.For this reason, various thickness adjustment and control force methods have been proposed. has been done.

Conventional film thickness adjustment methods generally measure the thickness distribution of a stretched film, and based on the measurement results, the thickness distribution of the film before stretching is adjusted and made uniform.

To adjust the thickness distribution of the film before stretching, increase or decrease the amount of resin supplied per unit time of the film.

A specific means for this is to adjust the lip gap of the extrusion die for causing the molten resin to flow out in the form of a film.

However, in the conventional film thickness adjustment force method, the relationship between the film thickness variation rate before stretching and the film thickness variation rate after stretching is not constant, resulting in more thickness adjustment than necessary. However, there are disadvantages in that unrecoverable thickness fluctuations may occur, and it takes a long time to obtain a preferable thickness distribution.

Here, to explain the relationship between the film thickness variation rate (CVA and CVs) before and after stretching, if there is a thickness deviation of the film before stretching, the thinner part will be stretched more and the thicker part will be stretched more. Hard to get.

To explain this relationship using Figure 1, the average thickness of the film before stretching is tA, the deviation of the thick part is dA, the average thickness of the film after stretching is t8, the deviation of the thick part is ds, and the deviations dA, ds The same results can be obtained by using the standard deviations in the width direction σA and σ8 of the thickness of the film before and after stretching instead.

Therefore, t8 and d measured on the film after stretching.
If the thickness of the film before stretching is adjusted using s (or σS) as a guide, the adjustment will obviously be excessive.

a indicates the rate at which the film thickness variation rate is increased by stretching.

(Hereinafter, a is referred to as the amplification rate.

) However, the width increase rate a varies greatly depending on the film manufacturing conditions (type of resin raw material, amount of resin drawn, stretching ratio, stretching temperature, etc.), and even under the same manufacturing conditions, the thickness of the film before stretching It differs depending on the magnitude of the deflection deviation dA (or σA) and the position of deflection, and this
, making it difficult to adjust the thickness.

The present invention was achieved as a result of studies to improve these drawbacks of conventional methods, and its gist is (1) measuring the width direction thickness distribution of the film before and after stretching; (2) From the width direction thickness distribution of the film after stretching, detect the width direction position where the thickness deviation is large and its deviation 1, (3)-
force, elongation i in the vicinity of the width direction position detected in the previous section (2)? J
and the thickness variation rate in the width direction of the film after stretching to calculate the increase rate of the thickness variation rate due to stretching. (4) The thickness deviation of the film after stretching detected in the previous section 2 is (5) Substitute the corrected deviation into the relationship between the pre-required thickness adjustment operation amount and the film thickness change amount before stretching; (6) Then perform the necessary thickness adjustment operation. The present invention provides a method for adjusting the thickness of a thermoplastic resin film, which is characterized in that the thickness of the film is adjusted at the position where the thickness deviation is large by determining the amount of thickness deviation.

The present invention will be explained in detail below.

FIG. 2 is a film manufacturing process diagram illustrating an embodiment of the saw method of the present invention.

1 is an extrusion die for flowing out the molten resin in the form of a film, and is equipped with a large number of adjustment bolts 11.

The resin flowing out from the die 1 is cooled and solidified to obtain a film FA before stretching.

Next, this film FA is stretched by a length direction stretching device 2 and a width direction stretching device 3 to form a biaxially stretched film FS.
is obtained.

41 is a thickness measuring device for measuring the thickness distribution in the width direction of film FA before stretching, and 42 is a thickness measuring device for measuring the thickness distribution in the width direction of film F8 after stretching. .

For example, β-ray thickness measuring devices are used as these thickness measuring devices 41 and 42, and these devices scan in the width direction of the film to continuously measure the 1-IJ force direction thickness distribution of the film.

In this case, it is preferable that the Jiv width measuring device 42 do not scan all the way to the end of one film FS, but scan the film except for the ends of the film corresponding to two to three ends of the adjustment bolts 11.

This is because when the adjusting bolts at both ends of the die 1 are operated, the overall flow of the molten resin is likely to be disturbed, and the degree of necking and sinking when the resin flows out from the die 1 also changes, making it difficult to adjust the thickness.

Therefore, it is better to leave the bolts on both sides of the die 1 out of the 2-1 operation quadrant, obtain thickness measurement data excluding both ends of the film Fs, and perform post-U processing based on that data.

The thickness distribution in the width direction thus obtained is manually entered into a calculator 5 and recorded in a recorder 6.

The calculator 5 detects the positions where the deviations of the fills l and Fs after stretching are large and the deviations thereof, and calculates the increase rate of the variation rate of dryness due to stretching in the vicinity of the positions.

Then, by correcting the thickness deviation of the film Fs using the obtained width increase rate, the thickness deviation that needs to be adjusted in the film FA of the stretching stitch 1 is calculated.

At this time, even if there is a thickness deviation in the film FA before stretching, the thickness deviation does not necessarily remain at the corresponding position in the films 7- and Fs after stretching, and the thickness deviation in the films 1 and FS after stretching does not necessarily remain at the corresponding position. The shape of the deviation (the cross-sectional shape of the FIJ force-direction surface of the film at that part does not necessarily match that of the film FA, so the thickness adjustment is based on the thickness distribution of the film F8 rather than the thickness distribution of the film FA). Width increase rate a
It is necessary to correct it and use it.

Further, the calculator 5 stores the relationship between the thickness adjustment operation amount and the amount of change in the thickness of the fill 1 and FA before stretching, which has been determined experimentally in advance.

In this example, the thickness adjustment operation amount is, for example, the adjustment bolt 1.
It is a good idea to experimentally find out in advance how much the thickness of the reno oil t and FA will change if the adjustment port 1-11 is operated by a certain angle. In some cases, the thickness is adjusted by creating a temperature distribution in the width direction, but in this case, the thickness adjustment operation amount is the temperature change AT or the change in the heater power required to create the AT. You can take JE.

By substituting the thickness deviation of one film FS after the correction described in iiJ into this relationship, the thickness deviation will be converted into the thickness adjustment operation amount, and the adjustment bolt drive device 12 will adjust the adjustment bolt drive device 12 based on the data. The thickness is adjusted by operating 1-11 by the required amount.

Since the width increase rate a often differs depending on the position in the width direction of the film, the increase FIJ rate in the vicinity of each pole 1 is calculated, and the width increase rate for the bolt to be operated is used.

Since the present invention is a film thickness adjustment force method as clarified above, it has the following excellent features.

In other words, if the thickness distribution of the film Fs after stretching is measured and the thickness is adjusted directly using the result, it is possible to accurately determine the thickness adjustment operation amount for the deviation that requires adjustment for the reason stated at the beginning. I can't.

In addition, if the thickness is adjusted using the thickness distribution of the film A FA before stretching, the shape of the deviation of the film FA and the film F
Since the shape of the deviation of S does not necessarily match, the thickness adjustment becomes extremely inaccurate.

On the other hand, in the method of the present invention, when adjusting the thickness based on the thickness distribution of the film FS after stretching, the film F
Since the thickness deviation of S is corrected by the expansion rate a, the film manufacturing conditions, film j before stretching, FA
Regardless of the size of the thickness deviation of The value can be directly converted into the thickness adjustment manipulated variable Z.

Therefore, the method of the present invention can easily control the film thickness automatically, and is especially suitable for manufacturing films that require high quality such as polyester resin films (eg, polyethylene terephthalate films). Efficiency is maximized.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a film for explaining the amplification rate. FIG. 2 is a film manufacturing process diagram showing one embodiment of the present invention. FA...Film before stretching, Fs...
Film after stretching, 2... Length direction stretching device,
3... Neutral force stretching device, 41... Thickness measuring device for film FA before stretching, 42... Thickness measuring device for film FS after stretching.

Claims (1)

[Claims] 1. Measure the thickness distribution in the width direction of the film before and after stretching, and 2. From the thickness distribution in the width direction of the film after stretching, determine the position in the width direction where the thickness deviation is large and the deviation thereof. 3-Force, calculate the increase rate of the thickness variation rate due to stretching by comparing the widthwise thickness variation rate of the film before and after stretching in the vicinity of the width direction position detected in the previous section 2, The thickness deviation of the film after stretching detected in the previous section 2 is corrected by this width increase rate, and the corrected deviation is calculated by combining the predetermined thickness adjustment operation amount and the film thickness change amount before stretching. 6. A method for adjusting the thickness of a thermoplastic resin film, characterized in that the thickness of the film at the position where the thickness deviation is large is adjusted by substituting into the relationship: