JP2004255695A - Method for producing thermoplastic resin sheet and device for detecting fault - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a thermoplastic resin sheet which can improve the yield and quality of the sheet and a device for detecting a fault. <P>SOLUTION: The thermoplastic resin sheet is produced by using an electrostatic application device having a cooling drum and electric discharge electrodes formed above the drum. In the method, when a fault is detected by the fault detecting device, a countermeasure means is instructed and monitored by the fault detecting device to adjust production conditions. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a thermoplastic resin sheet. More specifically, the present invention relates to a method for forming a thermoplastic resin sheet having excellent surface properties, improved yield, and stable quality by detecting the occurrence of defects and adjusting production conditions.
[0002]
[Prior art]
Conventionally, in a method of manufacturing a thermoplastic resin sheet by an electrostatic application cooling method mainly including a cooling drum and an electrode stretched over the cooling drum, a defect detector is provided in a film product part to improve quality. Stabilizing methods have been used.
[0003]
Since the position of the discharge electrode is important for obtaining a good molding state by the electrostatic application method, a method of automatically adjusting the electrode position based on a defect signal from a defect detector has been proposed (eg, Patent Document 1). As for the defect detector, there has been proposed a method of detecting the surface unevenness of an object to be inspected with high accuracy by using a periodic light and dark stripe pattern (for example, see Patent Document 2).
[0004]
[Patent Document 1]
JP-A-10-193441 (Page 1-2, FIG. 1, FIG. 2)
[0005]
[Patent Document 2]
JP-A-2002-116015 (pages 2-3)
[0006]
[Problems to be solved by the invention]
However, the cause that gives a defect to the thermoplastic resin sheet is not only the position of the discharge electrode. There may be defects before reaching the discharge electrode. When this defect is exposed at the upper part of the cast, it appears as a streak-like defect on the thermoplastic resin sheet, which causes a quality problem. Even if a discharge electrode is used for a sheet having no defect, if the discharge electrode is used for a long time on the upper part of the cast, a low molecular substance sublimated from the molten polymer adheres to the discharge electrode, so that the discharge electrode functions gradually. Fades away. For this reason, an application failure portion is generated, and a defect appears in the thermoplastic resin sheet, which may cause a quality problem.
[0007]
The present invention is intended to solve such a problem, and by discriminating the characteristics of the defects and taking measures on-time for each defect, a method for producing a thermoplastic resin sheet excellent in yield and quality and It is an object to provide a defect detection device.
[0008]
[Means for Solving the Problems]
To achieve this object, the present invention has the following configuration. That is, the present invention relates to a method for manufacturing a thermoplastic resin sheet using a cooling drum and an electrostatic application device having a discharge electrode stretched over the cooling drum, wherein a defect is detected by a defect detector. The main point is a method for producing a thermoplastic resin sheet, wherein the production conditions are adjusted by indicating and monitoring means by the defect detector.
[0009]
Further, the defect detection device of the present invention is a defect detection device for detecting a defect of a sheet obtained by quenching and solidifying a molten thermoplastic resin using an electrostatic application device. A defect detection device comprising means for determining the type of a defect based on a moving speed signal of a discharge electrode.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The thermoplastic resin in the present invention can generally include all resins that can be formed into a sheet. Typical thermoplastic resins include polyesters such as polyethylene terephthalate, and the effects of the present invention are remarkable. The thermoplastic resin may be a homopolymer, a copolymer or a polymer alloy. Further, additives and the like may be contained. Further, the sheet extruded from the die may be a multilayer or a single layer regardless of the same kind or different.
[0011]
Usually, when a discharge electrode is used in a method of manufacturing a thermoplastic resin sheet using an electrostatic application method, the discharge electrode is moved and used. This is because when the same electrode is used for a long time, the function as a discharge electrode gradually decreases because the low-molecular substance sublimated from the molten resin adheres to the discharge electrode. If a part of the moving discharge electrode has an electrode defect, for example, a burr, a chip, or a foreign substance adhered thereto, a defect appears on the thermoplastic resin sheet. It is known that as a feature of the defect, the electrode defect moves in the width direction together with the movement of the defect. As a disadvantage, there is a case where the thickness unevenness is not uniform and the surface shape has a defect.
[0012]
The manufacturing method of the present invention is a manufacturing method of a thermoplastic resin sheet using a cooling drum and an electrostatic application device having a discharge electrode stretched over the cooling drum, when a defect is detected by a defect detector, This is a method for producing a thermoplastic resin sheet, wherein production conditions are adjusted by instructing and monitoring countermeasures by the defect detector.
[0013]
Here, the method for detecting the defect is not particularly limited, and a known method can be used. For example, there is a method using a CCD camera. A known method can be used as a method of instructing a countermeasure for a defect. For example, there is a method of recognizing the type of a detected defect and electrically instructing a countermeasure for each defect type. In addition, a known method can be used for the monitoring method.
[0014]
Conventionally, there has been a method of automatically adjusting the electrode position based on a defect signal from a defect detector. However, since there was no monitoring function, the measures against the defect were insufficient.
[0015]
In the present invention, the position at which the defect detector is installed is not particularly limited. However, it is preferable that the defect detector be located on an unstretched sheet rather than on a stretched sheet since specific measures can be taken promptly after detecting a defect.
[0016]
In the present invention, the shape of the discharge electrode is not particularly limited. For example, the discharge electrode may be formed of a linear or tape-shaped conductive material. And the effect of the present invention is remarkable. .
[0017]
In the present invention, it is preferable that the defect detector performs defect type determination based on the defect position of the thermoplastic resin sheet and the moving speed signal of the discharge electrode from the electrostatic application device. By using this method, it is possible to determine whether the defect is caused by the electrostatic application device or not.
[0018]
In the manufacturing method of the present invention, it is preferable to change the moving speed of the discharge electrode provided in the electrostatic applying device based on the result of detecting the defect. For example, when the defect detector detects a defect moving in the width direction and a defect having the same electrode transition speed, the moving speed of the discharge electrode is increased to minimize the defects appearing in the product, thereby reducing product loss. . Further, when no defect is detected over time, the moving speed can be returned to a normal speed or reduced, so that the electrode is not wasted. In the present invention, it is also preferable to send a rewinding signal to the sheet winding device based on the detection result of the defect. Normally, in the sheet winding step, the product length or twice or three times the product length is wound using a sheet winding device. Therefore, when a defect occurs, unless it is dealt with promptly, the defect is mixed in the product, and a lot of loss is generated. Therefore, for example, if the defect detector detects a defect that moves in the width direction at the same speed as the electrode transfer speed, after the defect disappears, a rewind signal is sent to the sheet winding device and the defect is mixed in the next product. Avoiding it is effective. Furthermore, if a defect occurs within the winding length of 1/10, the method of changing the winding length of the winding device to the sum of the defect mixing portion length and the product length, and performing no rewinding is more suitable. It is preferably used.
[0019]
In the present invention, when the defect detector repeatedly detects a defect on the winding side of the discharge electrode, particles having a dust degree of 0.5 μm or more within 1 m around the discharge electrode are 1.8 × 10 ^{7 in} 1 m ^3. A method of reducing the number to less than the number is preferably used. Even if a discharge electrode having no defect is used, if the discharge electrode is used for a long time on the upper portion of the cast drum, the function as a discharge electrode gradually decreases because the low molecular substance sublimated from the molten polymer adheres to the discharge electrode. This is because the correlation with the degree of dust around the discharge electrode is large. The method for reducing the dust degree is not particularly limited, and a known method can be used. For example, an air curtain or an air filter is preferably used. Next, a defect detection apparatus according to the present invention will be described.
[0020]
The defect detection device of the present invention is a defect detection device for detecting a defect of a sheet obtained by rapidly cooling and solidifying a molten thermoplastic resin using an electrostatic application device, and a discharge electrode from the electrostatic application device. And a means for determining the type of a defect based on the moving speed signal of the defect.
[0021]
For example, in order to detect a defect of the sheet, a light emitting unit and a light receiving unit are disposed with the sheet interposed therebetween, and the light emitting unit is provided with a light-shielding pattern of light and dark stripes that is not orthogonal to the width direction of the sheet. If there is an irregular defect, the light-shielding pattern of light and dark stripes is distorted by the lens effect, and this is an apparatus for detecting this. With such an apparatus, it is possible to efficiently discriminate between the case where there is no irregularity-like defect in the film and the case where it is present.
[0022]
Next, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments without departing from the gist thereof.
[0023]
FIG. 1 is a schematic view illustrating a preferred apparatus for realizing the manufacturing method according to the present invention, and particularly illustrates a portion for forming a molten resin into a sheet.
[0024]
In FIG. 1, the manufacturing apparatus mainly includes a base 1, a casting drum 2, and a static electricity applying device 3. The cap 1 is preferably used to adjust a gap for extruding the molten resin polymer 6 by using a heat bolt and a manual bolt, and is disposed so as not to come into contact with the casting drum 2 from the rotation center upward. From the die 1, the molten resin 6 is supplied to the casting drum 2. The casting drum 2 may be of a type that controls the temperature of the casting drum 2 by passing water whose temperature and flow rate have been adjusted. The casting drum 2 preferably has a mirror-finished surface or a cracked or honeycomb-shaped surface.
[0025]
A tape system using a tape-shaped electrode was used for the electrostatic application device 3a. In addition, a wire system using a wire electrode can be used. Reference numeral 3b denotes an electrode transfer control device, which can change the transfer speed by a signal from a defect detector.
[0026]
The sheet 7 formed into a sheet using the apparatus shown in FIG. 1 is wound into a roll through a subsequent stretching step 5. In the stretching step, a sequential stretching method or a simultaneous biaxial stretching method can be used.
[0027]
Although the installation position of the defect detection device of the present invention is not particularly limited, it is preferably disposed between the casting drum 2 and the stretching step 5. By arranging at this position, before entering the stretching step 5, the film width for detecting the defect is narrow, so that not only the equipment cost can be suppressed, but also the defect can be detected quickly. It is preferable that the light projecting unit is provided with an inclined light-shielding pattern of light and dark stripes that is not orthogonal to the width direction of the film, as illustrated in FIG. With this pattern, if an uneven defect is present in the film, the inclined light-shielding pattern of bright and dark stripes is distorted as illustrated in FIG. 3 by the lens effect, and the presence or absence of the uneven defect in the film can be efficiently determined.
[0028]
【Example】
(Example 1)
The dried polyethylene terephthalate chip is melt-extruded at 280 ° C., discharged in a sheet form from a die, charged with a discharge electrode, adhered on a cooling rotary drum, and cooled and solidified. The defect detector of the present invention was operated in a state where a streak-like defect was generated on the sheet surface due to the cause. As a result, the defect detector detected a streak-like defect moving in the width direction on the unstretched sheet, and sent a fast-forward signal to the discharge electrode moving device to move at a speed 25 times the normal speed. As a result, the reject rate was reduced to 0.4% from 20% before the operation of the defect detector.
[0029]
(Example 2)
After Example 1, when the defect disappeared from the sheet, a rewind signal was automatically sent to the winding device to prevent the defect from being mixed into the next product. As a result, it is possible to accurately distinguish between a defective product and a good product.
[0030]
(Example 3)
In Example 2, it was 1/20 of the product length that the defect detector detected a streak-like defect on the unstretched sheet. Thereafter, when the defect disappeared from the sheet, it was automatically wound around the winding device for 1/20 minute of the product length to prevent the defect from being mixed into the next product, and then the product was taken out. Usually, a necessary core portion was replaced with a portion containing a defect, and as a result, the product loss was effectively reduced.
[0031]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the sheet which does not have a defect in an electrostatic application cooling method can be stably produced. Further, a thermoplastic resin sheet excellent in yield improvement and quality stability can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view illustrating a preferred apparatus for realizing a manufacturing method according to the present invention.
FIG. 2 is a diagram illustrating a relationship between inclined light-shielding patterns of the defect detection device according to one embodiment of the present invention.
FIG. 3 is a relation diagram of a defect detection result according to an embodiment of the present invention.
[Explanation of symbols]
1: Base 2: Casting drum 3a: Electrostatic application device 3b: Electrode transfer control device 4a: Sensor camera 4b: Light projecting device 4c: Inclined light shielding pattern 4d: Defect detection device 5: Stretching process 6: Molten resin 7: Unstretched Sheet 8: stretched sheet 9: winding control device A: defect

Claims (9)

In a method for manufacturing a thermoplastic resin sheet using a cooling drum and an electrostatic applicator having a discharge electrode stretched over the cooling drum, when a defect is detected by a defect detector, the defect detector measures the defect. The method for producing a thermoplastic resin sheet, wherein the production conditions are adjusted by instructing and monitoring the conditions. The method for producing a thermoplastic resin sheet according to claim 1, wherein the defect detector detects a defect on the unstretched sheet. 3. The method for producing a thermoplastic resin sheet according to claim 1, wherein a tape-shaped discharge electrode is used in the electrostatic application device. The thermoplastic resin according to any one of claims 1 to 3, wherein the defect detector performs defect type determination based on a defect position of the thermoplastic resin sheet and a moving speed signal of the discharge electrode from the electrostatic application device. A method for manufacturing a resin sheet. The method for producing a thermoplastic resin sheet according to any one of claims 1 to 4, wherein a moving speed of a discharge electrode provided in the electrostatic application device is changed based on a detection result of the defect. The method for producing a thermoplastic resin sheet according to any one of claims 1 to 5, wherein a rewind signal is sent to the sheet winding device based on a result of detecting the defect. When the defect detector repeatedly detects a defect on the winding side of the discharge electrode, particles having a dust degree of 0.5 μm or more within 1 m around the discharge electrode are reduced to 1.8 × 10 ⁷ or less in 1 m ^3. The method for producing a thermoplastic resin sheet according to any one of claims 1 to 6, wherein: The method for producing a thermoplastic resin sheet according to any one of claims 1 to 7, wherein a polyester is used as the thermoplastic resin. A defect detecting device for detecting a defect of a sheet obtained by rapidly cooling and solidifying a molten thermoplastic resin using an electrostatic application device, wherein a defect is detected based on a moving speed signal of a discharge electrode from the electrostatic application device. A defect detection device comprising means for determining the type of a defect.

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