JPS6280022A - Lateral stretching equipment for plastic film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stretching device for stretching a plastic film in the transverse direction.

[Prior Art] Conventionally, as a device for stretching a plastic film in the lateral direction, there is generally a one-type device for stretching a flat film in the lateral direction, in which both sides of a flat film are held with clips and stretched in the lateral direction while being fed in the longitudinal direction. However, since the equipment is very large-scale, it requires a large space and the equipment cost is extremely high.

For this reason, in recent years, a type of stretching method different from the one-type clip tenter method described above has been developed, which uses a pair of stretching pulleys that rotate in opposite directions in substantially the same plane and a pair of belts that engage with the pulleys. Apparatus for stretching plastic films has been invented. (For example, JP-A-15-15-
126427) However, although this method has a simpler structure than the conventional clip tenter one-way method, it is not possible to obtain a high-quality plastic stretched film suitable for practical use.

That is, when a plastic film is stretched in the transverse direction using the above-mentioned apparatus, the ends of the film gripped by the pulley and belt are stretched in the transverse direction without shrinking in the longitudinal direction, whereas they are stretched in the free state. The central part of a certain film is stretched in the horizontal direction while extremely shrinking in the vertical direction, and as a result, the stretched film obtained not only has non-uniform physical properties at the edges and the central part, but also has a significant "ear drooping" phenomenon in the width direction. ”
exhibits.

This "ear drooping phenomenon" is due to the phenomenon that the edges of the film are longer than the center in the longitudinal direction of the film. If the base film droops, pitch deviations may occur during printing, and lamination problems may occur. This is not preferable because it causes wrinkles during the process and has a significant negative impact on the production rate, yield, etc. during secondary processing.

For the above-mentioned reasons, the flatness of the stretched film is one of the essential quality items that is extremely important, like the thickness unevenness and strength of the film.

[Problems to be Solved by the Present Invention] The purpose of the present invention has been made in view of the above-mentioned problems of the conventional device. The objective is to properly stretch a plastic film in the transverse direction.

That is, the present invention provides a new type of stretching device that uses a pair of film gripping mechanisms and a backup roll to stretch a film over the entire width direction while regulating shrinkage in the longitudinal direction that occurs due to stretching in the lateral direction. ,
The object of the present invention is to obtain a high-quality plastic stretched film that is particularly suitable for secondary processing by preventing the "ear drooping phenomenon" in the width direction of the film.

[Means for Solving the Problems] As a result of intensive research to solve the problems of conventional apparatuses for stretching plastic films in the transverse direction, the present inventors have developed a book based on film behavior during stretching. This led to the invention of an inventive device.

That is, the present invention provides an apparatus for gripping both ends of a plastic film with a pair of film gripping mechanisms and stretching it in the lateral direction, in which the pair of film gripping mechanisms are spread out at symmetrical positions at a spread angle of within 45 degrees. It is provided,
By rotating this film gripping mechanism in the same direction, each of them forms an almost vertical circular arc trajectory.Furthermore, along the circular arc trajectory formed by this film gripping mechanism, there are multiple The present invention provides a new type of plastic film stacking and stretching apparatus characterized in that two backup rolls are disposed between the pair of film gripping mechanisms.

The present invention will be explained below with reference to the drawings.

Figures 1 and 2 schematically show an embodiment of the device of the present invention, with Figure 1 being a front view, and Figure 2 being the arrow x in Figure 1.
It is a figure seen from -x' direction.

In the figure, reference numerals 1 and 1-1 denote a pair of film gripping mechanisms, which are disposed in symmetrical positions with a spread angle θ of 45 degrees or less, and are each held in an almost vertical arc by a drive bag M (not shown). They form an orbit and rotate in the same direction (direction A in the figure) at the same speed.

As this pair of film gripping mechanisms 1.1-1, a conventionally known gripping method is used, for example, as shown in FIG. 4, a pulley 2
A method in which the end of the plastic film is held at the joint portion of the plastic film 1 and the belt 22, or a clip method using a push spring 23 as shown in FIG. 5 can be applied.

2 is a backup roll, which is separated from the pair of film gripping mechanisms 1.1-1 between the pair of film gripping mechanisms 1.1-1;
A plurality of them are arranged in a positional relationship that maintains contact with the plastic film along the arcuate trajectory formed by the plastic film.

This backup roll 2 rotates while always maintaining a convexly curved state as shown in FIG. 3, and the degree of curvature can be arbitrarily adjusted.

[Operation] Next, the operation of the apparatus of the present invention will be explained. The plastic film 3, which is an original film, is fed into a pair of film gripping mechanisms 1.1-1 through the pinch roll 4 and the guide roll 5, and the gripping start point A is While heating in the heating chamber 6, the plastic film 3 is moved in the longitudinal direction by the backup roll 2 along a circular arc trajectory that widens toward the end and is formed as the pair of film gripping mechanisms 1.1-1 rotate. The PlusDeck film is stretched uniformly in the transverse direction until it reaches a grasping end position approximately within a semicircumference.

In the above stretching process, for example, if there is no backup roll 2, the plastic film 3 is fed without shrinking in the vertical direction because both ends in the width direction are fully gripped by the film gripping mechanism 1.1-1. On the other hand, the central portion of the film in the width direction is not restrained in any way, and therefore, as it is stretched in the horizontal direction, it is transported while shrinking in the vertical direction. That is, the pair of film gripping mechanisms 1.1-1
The radius of the circular arc orbit formed by R is R, and the length in the longitudinal direction of the plastic stretched film obtained when the stretching process is performed on a semicircle is πR at the end of the film in the radial direction.
On the other hand, in the central part, πRcosθ/2 (θ:
The end divergence angle formed by the pair of film gripping mechanisms) is long at the edges in the film's radial direction and short at the center, resulting in the resulting stretched plastic film exhibiting an "ear drooping phenomenon" in the width direction.

However, in the present invention, as described above, the shrinkage of the plastic film 3 is restrained by the convexly curved backup roll 2, and the degree of curvature of the backup roll 2 is determined by the pair of film gripping mechanisms 1.1-1. By appropriately adjusting the divergence angle θ, the shrinkage in the longitudinal direction that occurs due to stretching in the transverse direction is suppressed throughout the width of the film, without causing any difference in length in the longitudinal direction. That is, it is possible to stretch the plastic film without exhibiting the "ear droop phenomenon".

The thus stretched plastic film is longitudinally cut at both #11 parts gripped by a pair of cutters 7.7-1 near the gripping end point B, passes through a guide roll 8, is taken up by a nip roll 9, and is annealed. The film is wound up after the internal strain generated during stretching is removed by the rolls 10.

On the other hand, both end portions that have been completely gripped by the pair of film gripping mechanisms 1.1-1 can be taken out as appropriate in the form of a band while remaining in an unstretched state.

The stretching ratio of the plastic film is determined by the ratio of the length at the gripping end point B to the actual length between the left and right gripping parts at the gripping start point A of the plastic film that is fed in, and the length of the plastic film at the gripping end point B is It can be arbitrarily selected depending on the diameter of the arcuate trajectory formed by -1, the divergent angle θ, the gripping start position, and the gripping end position. However, if the divergent angle θ formed by the pair of film gripping mechanisms becomes larger than 45 degrees, the shrinkage in the longitudinal direction at the center of the film that occurs as the film is stretched in the lateral direction becomes extremely large. Even if the backup roll 2 is provided, a significant "ear drooping phenomenon" will result, so the divergence angle θ needs to be selected within 45 degrees.

Note that liquid heating, steam heating, hot air heating, or radiant heating can be employed as the heating means in the pJ% chamber 6. Furthermore, preheating the plastic film before stretching allows for more uniform stretching. It is effective in doing so.

[Effects] As described above, the plastic film transverse stretching device of the present invention has a configuration based on the behavior of the plastic film during stretching, so it can uniformly and easily transversely stretch the plastic film, and the stretching ratio and thickness can be adjusted. It not only makes the physical properties of plastic films uniform, such as plastic films, but also produces stretched products with high commercial value that do not sag in the width direction and have excellent suitability for secondary processing. This is an extremely practical transverse stretching device for plastic film, which can greatly simplify the structure of the device, and can also be configured compactly and significantly reduce the initial cost and running cost of the equipment.

[Brief explanation of drawings]

1 and 2 show an embodiment of the transverse stretching apparatus for plastic film of the present invention, and FIG. 1 is a front view;
FIG. 2 is a view seen from the direction of the arrow xx" in FIG. 1. FIG. 3 is a partially enlarged view showing the configuration of the backup roll seen from the direction of the arrow Y-Y' in FIG. , FIGS. 4 and 5 are partial cross-sectional views showing an example of the film gripping mechanism. 1.1-1 Film gripping mechanism No. 2 Backup roll 3 Plastic film 41 Pinch roll 5 ...Guide roll 6...Heating chamber 7.7-1φ battle・Cutter 8・ΦΦ guide roll 9Φ1 pinch roll 10...Annealing roll

Claims (1)

[Claims] In an apparatus that grips both ends of a plastic film with a pair of film gripping mechanisms and stretches it in the lateral direction, the pair of film gripping mechanisms are provided at symmetrical positions in a shape that spreads out at an angle of within 45 degrees, and the film By rotating in the same direction, the gripping mechanisms each form a nearly vertical circular arc trajectory, and the film gripping mechanism also has a plurality of backup mechanisms whose degree of curvature can be adjusted along the circular arc trajectory formed by the film gripping mechanism. A plastic film transverse stretching device, characterized in that a roll is disposed between the pair of film gripping mechanisms.