JP2001341199A - Method for manufacturing sequentially biaxially stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a sequentially biaxially stretched film in an industrially stable manner by preventing the breakage of a film in the lateral stretching process of a sequential biaxial stretching method. SOLUTION: In a method for manufacturing the biaxially stretched film by stretching a film longitudinally and subsequently stretching the longitudinally stretched film laterally by a flat type lateral stretching machine, the rotational speeds of a plurality of roll groups provided in the preheating part, stretching part and cooling part in the longitudinal stretching process are set so that the fluctuation ratios of the respective zones are set to 0.2% or less.

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 biaxially stretched film by longitudinally stretching and then transversely stretching it with a flat type transverse stretching machine, which relates to a method for preventing film breakage in a transverse stretching step. It is.

[0002]

2. Description of the Related Art As a method for producing a biaxially stretched film using a thermoplastic resin such as polyamide or polyester as a raw material, a biaxially stretched film is stretched in a roll longitudinally and then transversely stretched by a flat type transverse stretching machine. A sequential biaxial stretching method for manufacturing and a simultaneous biaxial stretching method for simultaneously stretching vertically and horizontally in a tenter are used. In the sequential biaxial stretching method, the stretching ratio in the longitudinal and transverse directions can be freely changed, and since the productivity is excellent,
Particularly, it is the most general method for producing a biaxially stretched polyester film. However, the sequential biaxial stretching method has a problem in that oriented crystallization proceeds after longitudinal stretching in a roll, and the film often breaks in the next transverse stretching step.

[0003]

DISCLOSURE OF THE INVENTION The present invention is to prevent a film from being broken in a transverse stretching step in the sequential biaxial stretching method as described above, and industrially stably produce a sequentially biaxially stretched film. To provide a way to do so.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a plurality of roll groups provided in each zone of a preheating section, a stretching section, and a cooling section in a longitudinal stretching step. It has been found that the above problem can be solved by adjusting the fluctuation rate of the rotation speed of the motor within a certain range, and the present invention has been achieved.

That is, the gist of the present invention is to provide a method for producing a biaxially stretched film by longitudinally stretching and then transversely stretching with a flat type transverse stretching machine.
A sequential biaxially stretched film is characterized in that the rotational speed of a plurality of rolls provided in each of a stretching section and a cooling section zone is controlled so that the fluctuation rate in each zone is 0.2% or less.

Hereinafter, the present invention will be described in detail. FIG. 1 is a process chart of a general method for producing a biaxially stretched film. First, the molten polymer is extruded into a sheet shape from a T-die 1, cooled and solidified by a cooling roll 2 to form an unstretched film, longitudinally stretched in a longitudinal direction of the film by a longitudinal stretching roll 3, and then stretched in a width direction by a transverse stretching machine 4. And wound up as a product 5.

FIG. 2 is a side view of rolls in a general vertical stretching machine. The unstretched film 6 is stretched by cutting the tension of a preheating roll 7 and a stretching roll 8 of a nip roll 9 with a speed gradient. Is done. The vertically stretched film is cooled by a cooling roll 10.

In the present invention, the rate of change of the rotation speed of the plurality of rolls provided in each zone of the preheating section, the stretching section and the cooling section in the longitudinal stretching step is 0.2% in each zone.
It is necessary to: When the fluctuation rate of the rotation speed in any of the zones exceeds 0.2%, the frequency of breakage of the film in the horizontal stretching machine in the next step increases.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically by way of examples.

[0010]

EXAMPLES Example 1 A polyethylene terephthalate resin (intrinsic viscosity 0.67, manufactured by Unitika) was melt-extruded into a sheet form from a T-die having a width of 630 mm and brought into contact with a cooling roll rotating at a diameter of 600 mm and a peripheral speed of 50 m / min. And cool to 150μ thickness
m of unstretched film was formed. The unstretched film was heated at a pre-heating unit roll rotation speed of 50 m / min, a stretching unit roll rotation speed and a cooling unit roll rotation speed of 150 m / min.
The stretching was performed at a stretching ratio of 3.0 times within the range of 0.2% or less of the rotating speed of each zone. Next, the film was transversely stretched at a temperature of 80 ° C. at a stretch ratio of 3.5 times. In this case, the number of times the film was broken in the transverse stretching step was as good as 0 times / 24 hours.

Comparative Example 1 A biaxially stretched polyethylene terephthalate film was produced under the same conditions as in Example 1 except that the rate of change in the rotation speed of the stretching section roll was 0.4% of the stretching section roll speed. In this case, the number of times the film was broken in the transverse stretching step was 5 times / 24 hours.

[0012]

According to the present invention, there is provided a method for industrially stably producing a sequentially biaxially stretched film in which the film is prevented from being broken in the transverse stretching step in the sequential biaxial stretching method. .

[Brief description of the drawings]

FIG. 1 is a schematic view of a process of producing a biaxially stretched film by a sequential biaxial stretching method.

FIG. 2 is a schematic view showing roll groups of a preheating section, a stretching section, and a cooling section in a longitudinal stretching step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 T-die 2 Cooling roll 3 Roll of preheating part, drawing part, cooling part of longitudinal drawing process 4 Horizontal drawing machine 5 Film product 6 Unstretched film 7 Preheating part roll 8 Drawing part roll 9 Nip roll 10 Cooling part roll

Claims (1)

[Claims] 1. A method for producing a biaxially stretched film by longitudinally stretching and then transversely stretching with a flat type transverse stretching machine, wherein a plurality of zones provided in each of a preheating section, a stretching section, and a cooling section in a longitudinal stretching step. A method for manufacturing a sequentially biaxially stretched film, wherein the rotational speed of a roll group is set to 0.2% or less in each zone.