JPH10175254A - Manufacture of biaxially oriented film and tenter unit used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tenter unit for maintaining a line speed at a set line sped even when a chain is elongated in a transverse orienting step using a tenter system for transverse orienting, and a method for manufacturing a film of stable quality (particularly heat shrink characteristics in a longitudinal direction) with stable steps by using the unit. SOLUTION: In the method for manufacturing a biaxially oriented film comprising the step of transverse orienting by the tenter unit 2 to control a line speed by a rotating speed of sprockets 23 for driving a chain 21, it corrects to cancel a speed difference of the line speed generated due to elongation of the chain 21 of the unit 2. As the unit 2 usable for the method, a line speed setter 26, an elongation measuring unit 27 for the chain, and a speed correcting unit 26 for correcting to cancel the speed difference due to the elongation of the chain based on an elongation amount measured by the unit 27 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a film and a tenter device using the same. More particularly, the process is stable even if the chain of the tenter device is stretched, and the heat shrinkage ratio of the stretched film. The present invention relates to a method for producing a film having a stable quality and a tenter device which can be used for the method.

[0002]

2. Description of the Related Art For example, a thermoplastic resin film such as a biaxially oriented polyester film is usually prepared by first extruding a thermoplastic resin into a sheet and quenching it to produce an amorphous sheet. , Longitudinally stretched by a tentering device, heat-treated, manufactured by slitting the ears, wound up on a product roll, and shipped.

At this time, the speed of the sheet or film is set as a line speed for each processing step. Then, the line speed in the tenter device is usually set to the same speed as the exit speed in the longitudinal stretching step in the preceding step.

[0004] A tenter device is constituted by mounting a large number of clips for gripping both ends of a film on a chain. The number of the clips depends on the length of the line, but is generally several hundred. In the chain, roller links including rollers are sequentially connected in a closed curve by pin link plates and pins to form an endless circulation path between the drive sprocket on the film exit side and the free sprocket on the inlet side, and the teeth of the drive sprocket are connected to the rollers. It is driven by a biting method.

[0005] Such a chain is extended as a whole due to wear of a bush constituting a pin or a roller link due to long-term use and extension of each link plate, and the pitch interval between clips mounted on the chain is reduced. become longer. For this reason, in the case of a chain, pins and bushes are usually replaced due to the above-mentioned abrasion condition, and when the amount of elongation becomes larger than a certain extent, the chain itself is replaced. When the elongation of the chain occurs, the slack is usually always tightened by moving the position of the shaft fixing base of the free sprocket on the inlet side away by a spring, a load tension or an air cylinder.

[0006] At the film manufacturing site, there are cases where a problem occurs in the heat shrinkage of the film and the running condition of the film in the tenter lug processing step is poor. The present inventor has investigated the situation of such a trouble and found that the cause was a line speed (set line speed) at which the running speed (line speed) of the clip was set by the elongation of the chain.
I found that it was faster.

[0007] The line speed in the tenter device process is:
Refers to the running speed of the chain, which speed is controlled by the rotation speed of the sprocket. The rotation speed is determined based on the chain length and the set line speed at the time when the elongation does not occur. Therefore, when the length of each pitch between the rollers of the chain elongates, that is,
It is presumed that the actual line speed in the case where the length of the chain is extended becomes faster than the set line speed by the ratio of the length of the extension. Conventionally, no correction has been taken for the correction of the chain speed corresponding to these elongations.

As described above, the line speed in the transverse stretching step and the heat treatment step in the tenter device when the chain elongates occurs is substantially equal to the set line speed in spite of the fact that it is set equal to the longitudinal stretching step exit speed. , A relative speed is generated between the set line speed in the longitudinal stretching process. As a result, it was found that the film was strongly tensioned between the two steps and contained a large strain inside, and was affected by the longitudinal shrinkage characteristics of the film after stretching.

The film stretched and heat-treated by the tenter device is usually subsequently taken up by a take-up roll, and in this step, the end portions at both ends are slit and wound up. At this time, the take-up roll speed is driven at the set line speed, and a speed difference is generated between the take-up roll speed and the exit speed of the tenter device. Therefore, in the above-described ear processing step, the film is loosened, and the film running tends to be unstable. Therefore, it is necessary to always pay attention to the slack of the film, and if the slack occurs, adjust the speed manually.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a film stretching apparatus in which a tenter device is used for transverse stretching. Is to provide a method of manufacturing a film having a stable process and quality (particularly, heat shrinkage characteristics in the longitudinal direction) while maintaining a set line speed, and a tenter apparatus that can be used for the method.

[0011]

That is, the first aspect of the present invention is as follows.
The gist of the invention is that in a method of manufacturing a biaxially stretched film including a transverse stretching by a tenter device in which a line speed is controlled by a rotation speed of a sprocket for driving a chain, a speed difference of a line speed caused by elongation of the chain of the tenter device is offset. And a method for producing a biaxially stretched film.

A second gist of the present invention is to provide a tenter device for use in transverse stretching of a film whose line speed is controlled by the rotation speed of a sprocket for driving a chain. The tenter device comprises a device and a speed correction device capable of correcting the speed difference due to the elongation of the chain based on the amount of elongation measured by the elongation measuring device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing a film of the present invention and an apparatus that can be used for the method will be described in detail with reference to the accompanying drawings.
It is not limited to the example of the following drawings. FIG. 1 is a schematic explanatory diagram of the features of the configuration of a tenter device that can be used in the film manufacturing method of the present invention and the arrangement relationship between the front and rear facilities.

The method for producing a film according to the present invention is directed to a biaxially stretched film including a transverse stretching by a tenter device (2) whose line speed is controlled by the rotation speed of a sprocket (22 or 23) for driving a chain (21). The manufacturing method is characterized in that a correction is made so as to cancel out a speed difference in line speed caused by elongation of the chain (21) of the tenter device (2).

The film produced by stretching in the present invention is not particularly limited as long as it is a biaxially stretched film using a thermoplastic resin. The thermoplastic resin is not particularly limited, for example, polyester represented by polyethylene terephthalate, polyolefin represented by polyethylene and polypropylene, and
Polyamides.

The above-mentioned biaxially stretched film is usually melt-kneaded with the above thermoplastic resin, extruded into a sheet form, quenched to form a substantially amorphous sheet, and then roll-rolled (1) and a tenter. It is manufactured by longitudinal stretching and transverse stretching, respectively, using the device (2). The thickness of the stretched film obtained by stretching in this manner is usually 100 μm or less.

When the biaxially stretched film is a biaxially stretched polyethylene terephthalate film, usually, the polyethylene terephthalate resin is melt-kneaded at 280 to 320 ° C., extruded into a sheet, quenched, and then substantially amorphous. Make a sheet. And the obtained amorphous sheet,
First, the film is stretched 2 to 6 times in the machine direction at 70 to 150 ° C. using a roll stretching machine (1), and then 2 to 6 times in the stretching zone of the tenter device (2) at 80 to 180 ° C. To 150-2 in the heat treatment zone if necessary.
Heat set at 50 ° C. for 1 to 300 seconds. At the time of the heat setting treatment, a condition for relaxing the film by 0.1 to 20% is preferably used together.

The sheet or film speed in the film manufacturing method of the present invention is set as a line speed for each processing step. The line speed in the tenter device (2) is normally set to be equal to the speed after the end of the longitudinal stretching process (1) in the preceding process. Then, the running speed of the film in the tenter device, that is, the actual line speed is corrected so as to be equal to the set line speed even if the chain (21) of the tenter device (2) elongates.

The tenter device (2) for correcting the actual line speed to be equal to the set line speed even when the chain (21) is elongated is not particularly limited.
One example is described below. Such a tenter device (2)
The line speed is controlled by the rotation speed of a sprocket (22 or 23) driving a chain (21), and a line speed setting device (25), a chain elongation measuring device (27), and the elongation measuring device (27) A) a speed compensator capable of compensating for a speed difference due to the elongation of the chain based on the amount of elongation measured in step (26).
And

As the main body of the tenter device (2), a known main body can be used. The basic structure of the tenter device (2) is a sprocket (2) installed at an inlet and an outlet on both left and right sides of the device.
Chains (21) are circulated and arranged on the left and right between 2 and 23).

At least one of the inlet and outlet sprockets (22 or 23) of the tenter device (2), usually the outlet sprocket (23), is driven to rotate by a sprocket driving device (24), and the chain (2) is rotated.
Chain (2) by biting into each roller of 1)
1) is driven. In the following description, it is assumed that the outlet sprocket (23) is driven to rotate and the inlet sprocket (22) is freely rotating.

The slack in the case where the chain (21) is elongated is tightened by moving the position of the shaft fixing base of the inlet sprocket (22) at the inlet portion by the load tension. The tenter device (2) can divide the entire length into a plurality of blocks as needed, and adjust the ambient temperature of each block as needed.

Also, on each chain (21) on both sides,
A large number of clips for film gripping are mounted at equal intervals, and the chain (21) itself advances while the distance between the chains on both sides is mechanically widened in the horizontal stretching section,
The film held by the clip mounted thereon is widened.

The line speed in the step of the tenter device (2) is calculated based on the line speed set by the line speed setting device (25).
Is determined by the rotation speed of. The calculation of the rotation speed is
The product of the rotational speed of the outlet sprocket (23), the number of teeth of the sprocket, and the pitch length between the rollers of the newly installed chain (21) that does not stretch due to use is determined to be equal to the line speed. Known methods can be used for the method of setting the line speed setting device (25) and the method of controlling the rotation of the outlet sprocket (23).

The elongation measuring device (27) is a device for measuring the amount of elongation of the chain (21). The method of measuring the amount of elongation is not particularly limited, but includes, for example, a method of detecting a displacement of the position of the inlet sprocket (22) from the initial position of the chain (21) at the shaft fixing base position. .

The method for detecting the above-mentioned displacement is not particularly limited. For example, a method of mechanically displaying the displacement on a scale,
An optical type or an electromagnetic type may be used. As a specific example, a method of connecting a differential transformer to the above-mentioned inlet sprocket (22) shaft fixing base as the elongation measuring device (27) can be mentioned. In this case, the magnitude of the displacement can be output as an electromotive force, and can be converted into the elongation of the chain by the elongation measuring device (27).

The speed correcting device (26) calculates a line speed difference from the amount of elongation of the chain (21) fed back from the elongation measuring device (27) based on the following equation, and according to the speed difference, The rotational speed of the outlet sprocket (23) is corrected so as to be reduced and canceled out. As a result, the line speed is maintained at the set value. A known mechanism can be used as the mechanism of the speed correction device (26).

[0028]

ΔV = V × (ΔL / L)

Here, ΔV is a line speed difference due to elongation, V
Is the set line speed, ΔL is the elongation of the chain (21), and L is the initial length of the chain (21).

As a result, in the present invention, since there is no speed difference between the line speed at the outlet of the longitudinal stretching step (1) and the line speed of the tenter device (2), stretching in this section does not occur, and Stretched film has no internal distortion,
The film is stretched to the longitudinal stretching ratio and the transverse stretching ratio according to the set conditions.

[0031]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

Example 1 A polyethylene terephthalate having 0.2% by weight of amorphous silica having an average particle diameter of 1.3 μm was melt-extruded at 285 ° C., cast on a cooling drum at 30 ° C., and rapidly cooled to a thickness of 173 μm. An amorphous sheet was obtained. The obtained amorphous sheet was first stretched in the longitudinal direction using a roll stretching machine (1), and then a biaxially stretched polyester film was manufactured using a tenter device (2).

The stretching in the longitudinal direction is performed by setting the line speed to 81 m / min and the pulling speed to 300 m / min with a line speed setting device (25) at 105 ° C. at a stretching ratio of 3.70 times in the longitudinal direction. went.

The initial length of each chain (21) on both sides of the used tenter device (2) is 35
m, and 280 clips are mounted on the chain at a pitch of 125 mm. Then, as a result of running for a total of 170,000 km, the length of the chain at the time of this extension was determined according to the display scale of the elongation measuring device (27) using a differential transformer connected to the inlet sprocket (22) shaft fixing base. , Had grown 120mm since the beginning of the new construction.

The stretching in the transverse direction was performed at 140 ° C. in the transverse direction at a stretching ratio of 3.90. At that time, the line speed was set to 300 m / min by the line speed setting device (25) of the tenter device (2), and the elongation measuring device (2) was used.
7) and the speed correction device (26) were operated to correct the line speed. The stretched film is subsequently heat-treated at 220 ° C. for 2 seconds, wound up by a winding device (4) while slitting both ends through a take-up roll (3), and a polyethylene terephthalate biaxially stretched film roll having a thickness of 12 μm is formed. Obtained.

According to actual measurements, the line speed during the above-mentioned stretching in the transverse direction was 300 m / min as set despite the elongation of the chain (21) as described above. The heat shrinkage in the longitudinal direction of the obtained film measured at 180 ° C. for 3 minutes was 1.9%, which was within the control limit of 2.2% as a product.

Comparative Example 1 Biaxial stretching was performed in the same manner as in Example 1 except that the elongation measuring device (27) and the speed compensating device (26) of the tenter device (2) were not operated. . When the line speed during the stretching in the transverse direction was measured, it was 301 m / m.
in, there was a speed difference of 1 m / min between the film speed at the exit of the roll stretching machine (1) and the film speed at the entrance of the tenter device (2) stretching process. The heat shrinkage in the longitudinal direction of the obtained film measured at 180 ° C. for 3 minutes was as large as 2.3% despite the speed difference of only 1 m / min. It was over 2%.

[0038]

As described above, according to the present invention, in a film stretching process using a tenter method, a tenter apparatus capable of maintaining a film traveling speed, that is, a line speed, at a set line speed even when a chain elongates. It is possible to provide a method for producing a film having a stable quality (especially, heat shrinkage property in the longitudinal direction) using the film, and as a result, the quality of the film can be maintained at a high level. The industrial value of the present invention is extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of the features of the configuration of a tenter device that can be used in the film manufacturing method of the present invention and the positional relationship between front and rear facilities.

[Explanation of symbols]

 1: longitudinal stretching process (roll stretching machine) 2: tenter device 21: chain 22: inlet sprocket 23: outlet sprocket 24: sprocket drive device 25: line speed setting device 26: speed correction device 27: elongation measuring device 3: take-up roll 4: Winding device

Claims (2)

[Claims] In a method for manufacturing a biaxially stretched film including a transverse stretching by a tenter device in which a line speed is controlled by a rotation speed of a sprocket for driving a chain, a speed difference of a line speed caused by elongation of a chain of the tenter device is determined. A method for producing a biaxially stretched film, wherein the film is corrected so as to cancel each other. 2. A tenter device for use in a transverse stretching of a film whose line speed is controlled by the rotation speed of a sprocket for driving a chain, wherein the line speed setting device, the chain elongation measuring device, and the tenter device are measured by the elongation measuring device. A speed correction device capable of correcting so as to cancel a speed difference caused by chain elongation based on the amount of elongation.