JP2875134B2 - Method for producing thermoplastic resin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermoplastic resin film, and more particularly to a method for laminating a plurality of thermoplastic resin films and stretching them at least in the transverse direction, and then separating them into respective stretched films. And a method for simultaneously producing a stretched film.

[0002]

2. Description of the Related Art In recent years, the size and weight of electric devices such as condensers, thermal transfer printing machines, stencil printing machines, audio decks, video decks, etc. have been increasingly reduced, and as a result, thinner films have been used. Is required.

[0003] The problem in producing such a thin film is that the production is not increased because the film is thin, and the productivity due to frequent breakage of the film during film formation due to the thin film. It is a drop. As a solution to such a problem, it has been proposed to double the production amount by superposing and stretching a plurality of films and separating the obtained superimposed films respectively (for example,
JP-A-50-22069, JP-A-51-27678
No., JP-A-51-31775, etc.).

[0004]

However, in this method, the films adhere to each other at the time of stretching and heat setting, making it impossible to peel them off, or because the films are thin, the films are easily broken when peeling each layer after stretching. Even when not performed, there is a problem that surface delamination, pinholes, and the like are generated and cannot be supplied as a product.

To solve these problems, a method has been proposed in which a spacer is fed between films to be superposed (Japanese Patent Application Laid-Open No. 53-86686). However, this method requires a new spacer. Further, it is expected that the film may be scratched or broken frequently due to the rubbing between the spacer and the film.

An object of the present invention is to solve these problems and to provide a method for dramatically improving the productivity of a stretched thin film.

[0007]

The present invention has the following arrangement to attain the object.

A method for simultaneously producing a plurality of (n) stretched films by laminating a plurality of (n) films made of a thermoplastic resin and stretching the films at least in the lateral direction, and then separating the laminated films respectively. A thermoplastic resin film characterized in that the end portions of the films (1) to (n-1) are continuously folded in the longitudinal direction, and another film is overlapped on one side of the folded end portion and stretched in the transverse direction. Manufacturing method.

The thermoplastic resin in the present invention may be any thermoplastic resin as long as the film has the property of being stretchable. Representative examples include polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, high-density polyethylene, polypropylene, nylon 6, nylon 66, and the like.

In the present invention, the film to be subjected to the transverse stretching may be an unstretched film that has not been stretched at all, or a film that has been stretched uniaxially in the longitudinal direction.
It is not regulated at all by the film properties such as refractive index, haze and surface roughness.

In the present invention, the form in which the film ends are successively folded in the longitudinal direction (longitudinal direction) is not particularly limited as long as the tenter clip (grip) can grip the folded portion sufficiently. When another film is superimposed on one side of the folded portion and provided to the tenter, the folded portion of one film and the end of the other film must be completely gripped by the tenter clip.
If the clip does not bite properly enough, the film may come off the clip during preheating and stretching. Further, the holding position in the film width direction by the tenter clip needs to be within the range of the folded portion. Thus, when the inside is gripped, there is no space between the stacked films, and stickiness occurs due to the surface properties of the film, and there is a concern that the film may be broken in the tenter by gripping a thinner portion than the film center. Outside of this, the film cannot be gripped by the tenter clip.

Hereinafter, some of the film folding and gripping modes using a tenter clip will be described with reference to the drawings.

FIG. 1 is a view showing the state of gripping the film of the tenter clip as viewed from the upstream side of the film formation. The edge (12) of the upper film is folded in a double downward direction, and the tenter clip (1) is overlapped with the edge (13) of the lower film.
This is the case where the user bites in 1).

FIG. 2 is a diagram showing variations of a method of folding a film edge and a method of overlapping a film with another film. Fig. 2-a shows the lower film folded up twice.
This is the case where the other film is stacked. Figure 2-b is a
This is a case where three films are overlaid in the same manner as in the above. FIG. 2C shows a case where the lower film is folded three times upward and the other film is stacked.

Various methods can be used for folding the film edge. For example, FIG. 3 is a view showing a state in which a film edge is double-folded upward with an edge folding tool (U-shaped channel plate) obtained by bending a flat plate. FIG. 4 is a view showing a state in which a film edge is double-folded upward by a rotatable disk having a U-shaped groove (a U-shaped grooved disk). FIG. 5 is a diagram showing a state in which the film edge is folded three times upward by two flat plates which are installed at shifted positions. FIG. 6 shows the case where the position is shifted.
FIG. 11 is a diagram showing a state in which a film edge is folded three times upward by a rotatable disk. FIG. 7 is a view showing a state in which the film edge is double-folded upward by an edge folding tool in which a partition plate is installed in a bent plate. These details are described in Japanese Patent Application Laid-Open No. 4-267127, and this description is incorporated by reference.

In the present invention, a plurality (n), preferably 2 to 5, more preferably 2 to 3 films of a thermoplastic resin are superposed, and 1 to (n-1), preferably (n-1). As described above, the end of the film is folded, and another film is overlapped on one side of the folded end to perform the transverse stretching. The transverse stretching device may be a normal clip type tenter, and may be a device that performs only transverse stretching or a simultaneous biaxial stretching machine. The stretching in the transverse stretching apparatus may be only transverse stretching, or may be simultaneous longitudinal and transverse biaxial stretching.
As the stretching conditions, conventionally known conditions can be used. Film thickness after stretching is 0.5 ~ 15μ
m, more preferably 3 to 10 μm.

[0017]

The present invention will be further described below with reference to examples.

[0018]

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 was melted at 280 ° C., extruded from a die onto a casting roll at 40 ° C., and immediately cooled to obtain an unstretched film. This was stretched 3.6 times in the machine direction at 80 ° C. using rolls having different speeds to obtain a uniaxially stretched film. Next, a cutter was placed at a position shifted by 20 mm from the center in the width direction of the film, and the film was divided in the flow direction. Using a U-shaped grooved disk, both edges of the wider film
Fold it up twice so that the fold width is 20 mm on one side, shift the other film in the width direction using inclined rolls, overlap the film with the edge folded from the top, and supply it to the tenter in that state Then, transverse stretching was performed. The superposed films after the transverse stretching had no adhesion between the films, the films were separated, the ends were slit-removed, and each was wound on another roll. Table 1 shows the film forming characteristics.

[0019]

[Comparative Example 1] A uniaxially stretched film obtained in the same manner as in Example 1 was cut into a flow direction by inserting a cutter at the center in the width direction, and one of the films was shifted in the width direction using an inclined roll, and the other was shifted. (Without folding the edges) and feed it to the tenter as it is.
Lateral stretching was performed in the same manner as in Example 1. Adhesion was observed between the films in the superposed films after the transverse stretching. Table 1 shows the film forming characteristics.

[0020]

[Table 1]

[0021]

Example 2 An unstretched film obtained in the same process as in Example 1 was put in a position shifted by 40 mm from the center in the width direction, and divided in the flow direction. Next, the two edges of the wider film are folded three times upward using two rotatable disks placed at different positions so that the folding width is 20 mm on each side. One film is shifted in the width direction by using an inclined roll, superimposed on the film whose edge is folded from the top, and supplied to the tenter in that state,
Lateral stretching was performed. The superposed films after the transverse stretching had no adhesion between the films, the films were separated, the ends were slit-removed, and each was wound on another roll. Table 2 shows the film forming characteristics.

[0022]

COMPARATIVE EXAMPLE 2 An unstretched film obtained in the same manner as in Example 2 was divided in the flow direction by inserting a cutter at the center in the width direction, and one of the films was shifted in the width direction by using an inclined roll. The film was overlaid (overlapping without folding the edges), and the film was laterally stretched as it was in Example 2 using a tenter. Adhesion was observed between the films in the superposed films after the transverse stretching. Table 2 shows the film forming characteristics.

[0023]

[Table 2]

The determination of adhesion in Examples 1 and 2 and Comparative Examples 1 and 2 was such that when the two films were separated after the transverse stretching, there was no resistance at all, there were no scratches or adhesion marks on the overlapping surface, In the surface micrograph observation of the surface, the state where there was no damage or scraping of the projections was defined as no sticking after transverse stretching. When two films were locally and completely adhered to each other and were to be peeled, the film was torn because the film was thin, or a state where an adhesive mark remained on the surface when the film was peeled was regarded as sticky.

From the above results, the film end is continuously folded in the longitudinal direction, another film is overlapped on the side where the folded end is located, and the film is stretched in the lateral direction. It can be seen that it can be prevented.

[0026]

According to the present invention, when a plurality of thermoplastic films are superimposed and stretched at least in the transverse direction and then separated into respective stretched films to produce a plurality of stretched films simultaneously, Can be prevented, and the productivity of a stretched thin film can be dramatically improved.

The thermoplastic resin film formed by the method of the present invention is suitable for use in condensers, thermal transfer ink ribbons, stencil printing, audio tapes, video tapes and the like.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a state of gripping a film of a tenter clip as viewed from an upstream side of a film formation.

FIG. 2 is a view showing a method of folding a film edge and a method of overlapping with another film.

FIG. 3 is a view showing a state in which a film edge is double-folded upward by an edge folding tool obtained by bending a flat plate;

FIG. 4 is a diagram showing a state in which a film edge is double-folded upward by a rotatable disk having a U-shaped groove.

FIG. 5 is a diagram showing a state in which a film edge is folded three times upward by two flat plates which are installed at shifted positions.

FIG. 6 is a view showing a state in which the film edge is folded three times upward by two rotatable disks which are set at shifted positions.

FIG. 7 is a view showing a state in which a film edge is double-folded upward by an edge folding tool in which a partition plate is installed in a bent plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Tenter clip 12 Film (upper side) 13 Film (lower side) 31 Edge folding tool (U-shaped grooved plate) 32 Film 41 Edge folding tool (U-shaped grooved disk) 42 Film 43 Bearing 44 Edge folding tool rotating shaft 51 Edge folding tool a 52 Edge folding tool b 53 Film 61 Rotating disc edge folding tool a 62 Rotating disc edge folding tool b 63 Film 64 Rotating disc edge folding tool a Rotating axis 65 Rotating disc edge folding tool b Rotating axis 71 Edge folding tool (bending plate) 72 Edge folding tool (partition plate) 73 Film arrow Film flow direction

Continuation of the front page (56) References JP-A-61-158423 (JP, A) JP-A-54-97676 (JP, A) JP-A-4-267127 (JP, A) JP-A-63-92434 (JP, A) , A) (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 55/02-55/28

Claims (1)

(57) [Claims] A method for simultaneously producing a plurality of (n) stretched films by laminating a plurality of (n) films made of a thermoplastic resin and stretching them at least in the lateral direction, and then separating the laminated films respectively. Wherein the end of the film of 1 to (n-1) is continuously folded in the longitudinal direction, another film is overlapped on one side of the folded end, and the film is stretched in the lateral direction. A method for producing a plastic resin film.