Method of manufacturing film

Abstract

To provide a method of manufacturing a film by use of simultaneous biaxial stretching, capable of detecting clip abnormality from a shape of a vestige of a clip gripping body to enable portent of film breakage due to the clip abnormality.SOLUTION: A method of manufacturing a film has a step of performing simultaneous biaxial stretching while gripping widthwise directional both end portions of the film with clips (a simultaneous biaxial stretching step). After the simultaneous biaxial stretching step, the method has a step of measuring shapes of widthwise directional end portions of the film (a film widthwise directional end portion shape measuring step), and performs the film widthwise directional end portion shape measuring continuously.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a film.

Background Art

[0002] In the production of biaxially stretched polyester films, a method of producing by a simultaneous biaxial stretching method has been conventionally known. For example, Patent Document 1 describes a method of stretching a film by gripping the end of the film with a clip in a method of producing a film by a simultaneous biaxial stretching method.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the method described in Patent Document 1, there is a problem that film breakage occurs in the stretching step of stretching the film while gripping the end of the film with a clip.

[0005] As a result of intensive studies on the above problems, the present inventors have found that film breakage occurring during film stretching is affected by the wear state of the clip that grips the film during film stretching. An object of the present invention is to provide a method for manufacturing a film capable of detecting at an early stage a clip in which wear leading to film breakage in the stretching step has progressed and predicting film breakage.

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention is characterized by the following. (1) A method for manufacturing a film having a step of simultaneously biaxially stretching while gripping both end portions in the width direction of the film with clips (simultaneous biaxial stretching step), the method comprising a step of measuring the shape of the end portion in the width direction of the film after the simultaneous biaxial stretching step (film width direction end portion shape measuring step), and a film manufacturing method for continuously performing the film width direction end portion shape measurement. (2) The method for manufacturing a film according to (1), wherein an abnormality is detected by measuring the shape of the end portion in the width direction of the film. (3) In the measurement of the shape of the end portion in the width direction of the film, when the interval between portions where the shape of the end portion in the width direction of the film is convex from the center in the width direction toward the end portion in the width direction is ±30% or more from the average value of all clip intervals in the simultaneous biaxial stretching step, it is detected as an abnormality. The method for manufacturing a film according to (1). (4) The method for manufacturing a film according to any one of (1) to (3), wherein the stretching ratio of the film in the simultaneous biaxial stretching step is such that the total stretching ratio of the longitudinal (film flow direction) ratio and the lateral (film width direction) ratio is 10.0 times or more and 25.0 times or less. (5) The method for manufacturing a film according to any one of (1) to (4), wherein the film forming speed of the film is 50 m / min or more and 400 m / min or less. (6) The method for manufacturing a film according to any one of (1) to (5), wherein the film is a film mainly composed of polyethylene terephthalate.

Advantages of the Invention

[0007] According to the present invention, by continuously measuring the shape of the end portion in the width direction of the film, it becomes possible to detect the wear state of the clips that grip the end portion in the width direction of the film in the stretching step, and by quickly replacing the corresponding clips, film breakage can be prevented.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0009] Hereinafter, the method for manufacturing the film of the present invention will be specifically described. The present invention relates to a method for manufacturing a film having a step of performing simultaneous biaxial stretching (simultaneous biaxial stretching step) while gripping both end portions in the width direction of the film with clips, and having a step of measuring the shape of the end portion in the width direction of the film (film width direction end portion shape measuring step) after the simultaneous biaxial stretching step. The method of performing simultaneous biaxial stretching while gripping both end portions in the width direction of the film with clips is not particularly limited, but the stenter simultaneous biaxial stretching method driven by a linear motor system is preferably used. Generally, a stenter is provided in a heating oven and is used to perform stretching treatment, relaxation, or heat treatment at a fixed length while running on a pair of left and right rails while gripping both end portions in the width direction of the film.

[0010] In the case of a stentor using a linear motor system, when there are two individually drivable clips each traveling at linear velocities V0 and V1, fixed heat treatment is possible when the clips are made to travel at the same speed with V0 = V1. Alternatively, when the linear velocity is set such that V0 > V1 and the clips decelerate as they move forward, relaxation heat treatment can be performed. Or, when the linear velocity is set such that V0 < V1 and the clips accelerate as they move forward, it can be stretched in the longitudinal direction. Also, it is a stretching machine that can accelerate as the clip moves forward with V0 < V1 and can simultaneously stretch in both the width direction and the longitudinal direction by widening the stentor rail width. When stretching treatment is performed with such a stretching machine, both end portions in the width direction of the film gripped by the clip are formed into a shape that is curved in a concave and convex pattern at regular intervals according to the stretching ratio and stretching temperature conditions, with the traces of the clip grip. As a result of the inventors' intensive studies, it was found that if the clip used during this stretching wears over time and cannot securely grip the film, resulting in slippage or the like, the concave and convex shape formed at regular intervals at the film end portion, that is, the grip marks, will no longer be at regular intervals. If such a worn abnormal clip that cannot securely grip the film is left unattended, it will reach a state of so-called slipping through where it cannot grip the film completely, which can cause problems such as film breakage. Therefore, it has a step of measuring the shape of the film end portion in the width direction after the simultaneous biaxial stretching step (film width direction end portion shape measurement step). By continuously performing the measurement of the film width direction end portion shape, it becomes possible to detect the wear state of the clip at an early stage, and by quickly replacing the corresponding clip, film breakage can be prevented. In particular, it is preferable to detect an abnormality by measuring the shape of the film end portion in the width direction.

[0011] As a method for measuring the shapes of both end portions in the film width direction, although not particularly limited, using a laser displacement meter as an end portion measurement sensor can be mentioned. In particular, when a laser displacement meter as shown in FIG. 2 is installed after the stentor for measurement, it is preferable because it becomes possible to accurately measure the shape of the film end portion in the width direction after stretching.

[0012] Here, when continuously measuring the end shape in the film width direction and detecting an abnormality by such measurement, if the interval between portions where the end shape in the film width direction is convex from the center in the width direction toward the end in the width direction has a change of ±30% or more with respect to the average value of the total clip intervals in the simultaneous biaxial stretching process, it is preferably detected as an abnormality. By detecting an abnormality when there is a change within such a range, it becomes possible to accurately suppress film breakage while appropriately maintaining the clip replacement frequency. When slippage, which is an abnormal gripping of the clip, occurs, the film cannot be gripped firmly, so the unevenness of the gripping marks disappears.

[0013] In the method for producing a film of the present invention, a thermoplastic resin is preferably used as the resin for forming the film. Examples of the thermoplastic resin include polyesters, polyamides, and polyolefins, among which polyesters are preferably used. A polyester is a polyester mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol. Here, as the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-biphenyletherdicarboxylic acid, 4,4'-biphenylsulfonedicarboxylic acid, etc. can be used. Among them, terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid are preferably used. As the aliphatic dicarboxylic acid, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, etc. can be used. These acid components may be used alone or in combination of two or more, and further, oxyacids such as hydroxybenzoic acid may be partially copolymerized.

[0014] Specific examples of the polyester used in the polyester film of the present invention include, for example, polyethylene terephthalate, a copolymer of ethylene terephthalate and ethylene isophthalate, a copolymer of ethylene terephthalate and ethylene naphthalate, a copolymer of hexamethylene terephthalate and cyclohexanedimethylene terephthalate, a blend of polyethylene terephthalate and polybutylene terephthalate, and a blend of polyethylene terephthalate and polyetherimide. From the viewpoint of stretchability, polyethylene terephthalate and polyethylene naphthalate are particularly preferably used.

[0015] Hereinafter, the manufacturing method of the film of the present invention will be described by taking a polyester film as an example, but the present invention is not limited to such an example. First, the polyester is extruded onto a casting drum by a die (T-die) extrusion method to obtain an unstretched film, and then it is subjected to a stenter to be stretched simultaneously in the film longitudinal direction and the film width direction. The stretching temperature is, for example, 80 to 160 ° C, preferably 85 to 130 ° C, more preferably 90 to 110 ° C for simultaneous stretching. By setting the stretching temperature to be equal to or higher than the above-mentioned temperature, breakage of the film can be suppressed, and by setting the stretching temperature to be equal to or lower than the above-mentioned temperature, sufficient strength can be obtained. The stretching ratio is not particularly limited and is appropriately selected according to the type of polymer used. From the viewpoint of preventing stretching unevenness, the total stretching ratio in the longitudinal direction and the width direction is, for example, 8.0 to 30.0 times, preferably 9.0 to 25.0 times, more preferably 10.0 to 25.0 times, and particularly preferably 10.0 to 20.0 times.

[0016] After the simultaneous biaxial stretching process, if necessary, preferably at a temperature of 140 to 210°C, more preferably 160 to 200°C, preferably 1.05 to 1.8 times, more preferably 1.2 to 1.6 times, it is preferable to perform stretching again in the longitudinal and / or width directions (re-stretching process). By setting the stretching ratio in the re-stretching process within the above-mentioned range or more, a sufficient increase in strength can be obtained, and by setting the stretching ratio in the re-stretching process within the above-mentioned range or less, film breakage can be suppressed. Thereafter, heat setting is performed, for example, at 180 to 235°C, preferably 190 to 220°C, for example, for 0.5 to 20 seconds, preferably 1 to 15 seconds. By setting the heat setting temperature within the above-mentioned range or less, the crystallization of the film can proceed favorably and the structure becomes easy to stabilize. On the other hand, by setting the heat setting temperature within the above-mentioned range, it is possible to suppress excessive relaxation of the amorphous chain portion of the polyester, suppress a decrease in Young's modulus, and obtain sufficient strength. Thereafter, it is preferable to perform a relaxation treatment of 0.5 to 7.0% in the longitudinal direction and / or width direction.

[0017] The measurement of the film width direction end shape can be continuously performed at any stage after the simultaneous biaxial stretching process. However, it is preferable to perform the measurement after cooling the film temperature to 50°C or less after the heat setting process and before performing edge trimming, because the film width direction end shape can be accurately measured. Thereafter, edge trimming and cutting are performed by a known method to obtain a wound polyester film roll having a predetermined width and length.

Examples

[0018] Examples are shown below [Measurement and Evaluation Methods] (1) Regarding the measurement of the film width direction end shape A laser sensor (IG-028 manufactured by KEYENCE) was installed in a process after the stenter (after simultaneous biaxial stretching and before the heat setting process) and before edge trimming. Also, the sensor position was adjusted to a position where the film end could be detected by the sensor, and the film end shape was captured during film production.

[0019] (2) Regarding the judgment of the measured values For all the clips, the intervals between the convex end shapes were tabulated, and the simple average was calculated. If the deviation of an individual convex interval was greater than 30% compared to the previously calculated average value, it was determined as abnormal.

[0020] (3) Manufacture of the film It was carried out by a method for manufacturing a film for magnetic materials. Using two extruders E1 and E2, to the extruder E1 heated to 280 °C, as the raw material A layer for the smooth surface that becomes the magnetic surface, a dry polyester chip containing 0.20 mass% of one type of additive particle made of colloidal silica was supplied. To the extruder E2 also heated to 280 °C, as the raw material B layer for the rough surface that becomes the running surface, polyester chips in a kneaded and dried state of 10 / 90 parts by mass each of polyester A / B were supplied respectively. These were merged in the die so that the A layer side was on the side of the cast drum surface, and while applying an electrostatic charge to the cast drum with a surface temperature of 25 °C, they were closely cooled and solidified to produce a laminated unstretched film. This laminated unstretched film was preheated at 96 °C in a simultaneous biaxial stretching machine, and then during the stretching temperature of 96 °C and stretching time of 6 seconds, it was simultaneously stretched 3.51 times in the longitudinal direction (MD stretching 1) and 3.45 times in the width direction (TD stretching 1) respectively. Subsequently, during the temperature of 190 °C and stretching time of 6 seconds, it was stretched 1.15 times in the flow direction (MD stretching 2) and 1.41 times in the width direction (TD stretching 2). Subsequently, after stopping heating for 0.5 seconds, in the heat treatment zone in the stenter, heat treatment was carried out at a temperature of 220 °C for 2 seconds, then at a temperature of 230 °C for 2 seconds, then at a temperature of 235 °C for 2 seconds, and further at a temperature of 130 °C for treatment. The shape of the film end after the stretching treatment in the stenter was measured with a sensor. Then, after uniformly cooling to 25 °C, the film ends were removed to obtain a biaxially oriented polyester film with a width of 5 m and a total film thickness of 4.5 μm, and then it was wound up on a core.

Industrial Applicability

[0021] According to the present invention, by using the method for detecting deformation of the end of the film of the present invention in the film manufacturing process, it is possible to discover wear of the clip at an early stage and take necessary measures, and to efficiently eliminate defective clips. Therefore, by using the film manufacturing method of the present invention Thus, the film can be produced stably and efficiently.

Explanation of Signs

[0022] 1 Die (T-die) 2 Casting drum 3 Stenter (performing simultaneous biaxial stretching and heat treatment) 4 End shape measurement sensor 5 Edge trimming cutter 6 Trimming edge 7 Take-up device 8 Film 9 End measurement sensor

Claims

1. A method for manufacturing a film, comprising a step of performing simultaneous biaxial stretching while gripping both end portions in the width direction of the film with clips (simultaneous biaxial stretching step), and having a step of measuring the shape of the end portions in the width direction of the film after the simultaneous biaxial stretching step (film width direction end portion shape measurement step), and the film manufacturing method for continuously performing the film width direction end portion shape measurement.

2. The method for manufacturing a film according to claim 1, wherein an abnormality is detected by the measurement of the shape of the end portions in the width direction of the film.

3. In the measurement of the shape of the end portions in the width direction of the film, when the interval between locations where the shape of the end portions in the width direction of the film is convex from the center in the width direction toward the end portions in the width direction is ±30% or more from the average value of all clip intervals in the simultaneous biaxial stretching step, it is detected as an abnormality. The method for manufacturing a film according to claim 1.

4. The method for manufacturing a film according to claim 1 or 2, wherein the total stretching ratio of the film in the simultaneous biaxial stretching step, which is the sum of the longitudinal (film flow direction) ratio and the transverse (film width direction) ratio, is 10.0 times or more and 25.0 times or less.

5. The method for manufacturing a film according to claim 1 or 2, wherein the film is a film mainly composed of polyethylene terephthalate.

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