JPH0811204A - Stretching device for plastic film - Google Patents

Abstract

PURPOSE:To provide a stretching device of a plastic film which is capable of performing stretching at stabilized and high magnification. CONSTITUTION:In a stretching device of a plastic film stretching in a receiving direction of the film by discriminating between speeds by a low speed roll 3 and high speed roll 4, the stretching device of the plastic film is comprised by providing two pinch rolls 31 for stabilized running of the film on the low speed roll 3, an upstream side pinch roll 311 out of the pinch rolls 31 for the stabilized running is provided on a common osculating line between the pinch roll and low speed roll 3 and a position where the film is inserted and a downstream side pinch roll 312 is provided on a position between a separating point of a film from the low speed roll 3 and within 200mm from the separating point. Therefore, stretching of a stabilized and high magnification plastic film becomes possible without generating creases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretching device for plastic films, and more particularly to a stretching device capable of stable and high-magnification stretching.

[0002]

2. Description of the Related Art As a stretching device for stretching a film in a take-up direction, a low speed roll 3 and a high speed roll 4 are provided as shown in the schematic sectional view of FIG. An apparatus for drawing in the film taking direction is known. As for the overall configuration of this apparatus, the preheating roll 2 and the low speed side nip roll 1 are arranged in front of the low speed roll 3, and the cooling roll 5 and the high speed side nip roll 6 are arranged behind the high speed roll 4. There is.

In the above apparatus, the running stability of the film 7 in and around the low speed roll 3 becomes unstable, and the film surface condition after drawing is poor. Therefore, it is difficult to increase the overall draw ratio. there were. Therefore,
As a means for improving the running stability of the film on a low speed roll, the roll temperature and the roughness of the roll surface are changed, but the effect on the running stability is small. Further, a method is known in which a pinch roll is provided for each of the low speed roll and the high speed roll, but there is a problem that the arrangement of the rolls is complicated and the entire apparatus is complicated.

[0004]

DISCLOSURE OF THE INVENTION The present invention has found a stretching device capable of solving the above-mentioned problems, and its gist is to provide a film drawing by providing a speed difference between a low speed roll 3 and a high speed roll 4. In a plastic film stretching device that stretches in the taking direction, two pinch rolls 31 for stable traveling of the film are provided on the low speed roll 3.
Among the stable traveling pinch rolls 31, the upstream pinch roll 311 is provided at a position where the film enters on the common contact line of the pinch roll and the low speed roll 3, and the downstream pinch roll 312 is provided from the low speed roll 3 of the film. A plastic film stretching apparatus is characterized in that it is provided at a separation point or a position within 200 mm from the separation point.

The present invention will be described below with reference to the drawings. An example of the device of the present invention is shown in the schematic sectional view of FIG. 1. Most of the structure of the device is the same as that of the conventional device of FIG. 3, and a stable traveling pinch roll 31 of the film is provided on the low speed roll 3. Two
The difference is that they are provided individually. This stable traveling pinch roll 31 needs to be provided at a specific position. The upstream pinch roll 311 is provided at a position where the film enters the common contact line of the pinch roll and the low speed roll 3, and the downstream pinch roll 312 is provided at the film. The distance from the low speed roll 3 or the position within 200 mm from the distance.

By providing two stable traveling pinch rolls 31 at such positions, the contact force between the traveling film 7 and the low speed roll 3 is improved by the contact pressure of the pinch rolls, and the pinch rolls are in contact with each other. Air entrapment between the film and roll at the non-existing portion is reduced, and slippage between the film and roll is eliminated.

The stable traveling pinch roll 31 is required to generate a uniform linear pressure over the entire width of the film. As shown in the schematic sectional view of FIG. It is preferable to use a so-called crown roll, which is larger than the above, and a synthetic rubber such as nitrile butadiene rubber can be preferably used as the material of the roll, and the crown amount can be appropriately determined depending on the film thickness, width and the like.

Further, it is preferable to provide a groove portion in the circumferential direction on the surface of the pinch roll 31 so as to prevent the entrainment of air between the film and the film. As the shape of the groove portion, various cross-sectional shapes can be provided. For example, as shown in the schematic sectional view of FIG. Rectangular cross section, b. Trapezoidal cross section, c. Triangular section, d. An example is a semicircular cross section,
A groove having a width of 1 to 2 mm, preferably 0.5 to 1 mm, and a depth of 0.5 to 1 mm is suitable. If the depth is too large, the film tends to be scratched.

When a film is stretched using the apparatus of the present invention having the above-mentioned structure, the high speed roll 4 is used, although the take-up speed of each roll varies depending on the thickness of the film, the draw ratio and the like.
It is preferable that the film tension of the stretching by does not affect the film on the low speed roll 3.
It would be good if the effect could be eliminated with 1, but it is difficult to eliminate it completely. Therefore, it is preferable to set the speeds such that the take-up speeds of the low speed nip roll 1, the preheating roll 2 and the low speed roll 3 are sequentially increased. The increase ratio may be increased by about 0.5 to 2% between the rolls. Hereinafter, the present invention will be described with reference to examples.

[0010]

EXAMPLE A vinyl chloride resin film was stretched to form a film by using the roll shown in FIG. Low speed roll 3 ... Hard chrome plated roll (250mm
φ) Stable running pinch roll 31 ... Made of nitrile butadiene rubber roll, central part 100 mmφ, both ends 96 mm
A groove portion (width 11 mm, depth 0.5 mm) having a rectangular cross section is engraved on the φ crown roll and the roll surface.

Of the stable running pinch rolls 31, the upstream pinch roll 311 is provided at a position where the film enters the common contact line of the pinch roll and the low speed roll 3, and the downstream pinch roll 312 is used as the low speed roll of the film. It is provided at a point away from 3. In addition, the low speed nip roll 1, the preheating roll 2 and the low speed roll 3 shown in FIG.
The speed ratio of each is increased by 2% and high speed roll 4
When the film was stretched by, the film could be formed with no problem in quality up to a stretching ratio of 3 times.

On the other hand, when the same stretching as described above was carried out by an apparatus which does not use the above-mentioned stable running pinch roll 31, when the stretching ratio exceeds 2.3, wrinkles and the like are generated in the film. There was a quality problem.

[0013]

As described above, according to the device of the present invention,
There is an advantage that the plastic film can be stably stretched at a high magnification without wrinkling or the like.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a stretching device of the present invention.

FIG. 2 is a schematic cross-sectional view of a stable traveling pinch roll (A) used in the stretching device of the present invention and a groove portion thereof.

FIG. 3 is a schematic sectional view showing an example of a conventional stretching device.

[Explanation of symbols]

 1 Low speed nip roll 2 Preheating roll 3 Low speed roll 31 Stable running pinch roll 311 Upstream side pinch roll 312 Downstream side pinch roll 4 High speed roll

Claims (2)

[Claims] 1. A plastic film stretching apparatus for stretching a film in a film-drawing direction with a speed difference between the low-speed roll (3) and the high-speed roll (4), whereby the film is stably run on the low-speed roll (3). Two pinch rolls (31) for driving are provided, and among the pinch rolls (31) for stable running, the upstream pinch roll (311) is placed on the common contact line of the pinch roll and the low speed roll (3). The pinch roll (3
12) is provided at a distance from the low speed roll (3) of the film or at a position within 200 mm from the distance from the low speed roll (3). 2. The plastic film stretching apparatus according to claim 1, wherein the pinch roll (31) is a crown roll, and a groove (7) is provided on the surface in the circumferential direction.