JP2016155391A - Method for producing thermoplastic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a thermoplastic resin film having no appearance defects caused by thickness unevenness called gauge bands occurring on a roll film, and further to provide a method for producing a thermoplastic resin film which is reduced in variations in the film width and in variations in the thickness in the film flow direction while preventing gauge bands.SOLUTION: In a method for producing a thermoplastic resin film, when films are continuously produced by a fusion film forming method, an edge pinning is performed within the range of 5 mm or more and 180 mm or less from an end in the width direction of a film 2 on a cast roll 3.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a thermoplastic resin film based on a melt extrusion method.

  A melt film forming method is known as a method for forming a thermoplastic resin film. In the roll film wound up in this method, an appearance defect occurs when a film having thickness unevenness in the width direction called a gauge band is wound up.

  In order to solve the gauge band generated in the roll film, conventionally, a process of forming minute irregularities called knurling on the side edge of the film has been performed. Examples of the knurling include a method in which a film is sandwiched between a pair of embossing rolls having an uneven surface and pressed (Patent Documents 1 and 2 below).

  However, the method using an embossing roll has a problem that the film breaks during knurling when the thickness of the film is thin (for example, 20 to 55 μm) or the film is brittle depending on the material. In addition, when the film is bent even after the knurling, there is a problem that the knurled portion is easily broken.

JP 2007-91784 A Japanese Patent Laid-Open No. 2002- 211803

  This invention is made | formed in view of the said problem, The objective is to provide the manufacturing method of the thermoplastic resin film without the external appearance defect resulting from the thickness nonuniformity called the gauge band which generate | occur | produces in a roll film.

  Furthermore, another object of the present invention is to provide a method for producing a thermoplastic resin film which prevents a gauge band and at the same time suppresses film width fluctuation and thickness fluctuation in the film flow direction.

  The present inventor studied a manufacturing method in order to solve the above-described problems of the prior art. As a result, it has been found that in the melt film forming method, the above problem can be solved by setting the edge pinning, which is an electrostatic adhesion method, to a specific range on the inner side from the film end.

  In the melt film forming method, the molten resin discharged in the form of a film may be pressed against a cast roll by electrostatic pinning, but the present invention is particularly useful when a film is continuously produced by the melt film forming method. The present invention relates to a method for producing a thermoplastic resin film, characterized in that edge pinning is performed within a range of 5 mm or more and 180 mm or less from the end in the width direction of the film on a roll. By arranging edge pinning in the range of 5 mm or more and 180 mm or less from the end of the film in this way, the shrinkage of the end of the film occurs up to the edge pinning arrangement position, and the thickness of the edge pinning can be arbitrarily controlled. Therefore, by winding it as a roll film as it is, the effect is obtained that a gauge band is not generated even if the film end portion thickened similarly to the knurling process is restrained and the film central portion has uneven thickness.

  In the method for producing a thermoplastic resin film according to the present invention, it is possible to reduce the appearance defect caused by thickness unevenness called a gauge band generated in a roll film, and the use of a film for use in which the appearance of an optical film or the like is likely to be a problem. It can utilize suitably for manufacture.

  Further, while preventing the gauge band, it is possible to simultaneously suppress fluctuations in the film width and thickness fluctuations in the film flow direction, thereby further simplifying the manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an embodiment of the present invention, and is a schematic side view of a thermoplastic resin film manufacturing apparatus as viewed from a direction perpendicular to a film flow direction. 1 shows an embodiment of the present invention and is a schematic side view of a thermoplastic resin film production apparatus as viewed from the left side in FIG. 1.

  The present invention provides a thermoplastic resin film characterized by performing edge pinning within a range of 5 mm or more and 180 mm or less from the widthwise end of the film when continuously producing a film by a melt film-forming method. It is about the method. In the melt film-forming method of the film, the molten resin discharged in the form of a film may be produced by pressing the cast roll against the cast roll by electrostatic pinning, but in the present invention, edge pinning is used as electrostatic pinning, In particular, it is characterized by being arranged within a range of 5 mm or more and 180 mm or less from the width direction end of the film. Here, the melt film-forming method means using an extruder or the like to heat and knead the resin to melt and plasticize it, for example, to obtain a molten film by being discharged from a die hole on a slit. The molten film is cooled and solidified by bringing it into contact with a roll or the like (temperature-controlled) to obtain a film.

  Hereinafter, each process and resin will be described.

[Extrusion process]
In the present invention, an extruder can be suitably used to form a molten resin discharged in the form of a film. Examples of the type include a single-screw extruder, a co-directional meshing twin-screw extruder, Various extruders such as a meshing type twin screw extruder, a different direction non-meshing type twin screw extruder, and a multi-screw extruder can be used. Among them, the single-screw extruder is preferable because the resin staying portion in the extruder is small, so that it is possible to prevent thermal deterioration of the resin during extrusion and the equipment cost is low. Moreover, it is preferable to use an extruder having a vent mechanism in order to remove residual volatile components in the resin and heating products in the extruder.

  Moreover, as a form of the raw material of the thermoplastic resin thrown into an extruder, it is preferable to use solid resin, preferably about 3 mm square pellet shape. The pellet-shaped resin is generally supplied into the extruder through a hopper attached to the raw material supply port of the extruder.

  Furthermore, the resin supplied to the extruder is preferably heated and dried in advance so as not to cause hydrolysis or oxidative degradation of the resin. The amount of water in the resin is preferably 200 ppm or less, and the drying condition is preferably 3 hours or more at 100 ° C. although it depends on the resin. In drying, oxygen in the atmosphere to be dried is preferably removed to remove oxygen in the resin, and an inert gas atmosphere such as nitrogen is preferable. In addition, in view of necessary drying time and resin consumption time, drying uses a hopper type dryer in which a drying mechanism is provided in a hopper that supplies pellets to the extruder, or a dryer before supplying resin to the hopper. A method of drying and supplying the hopper so as not to absorb moisture, or a method using both of them can be suitably used. Among these, the method using a hopper type dryer is preferable because the moisture content can be reliably suppressed until just before the resin is supplied to the extruder, and further, the dryer before the hopper is used by using the dryer before the hopper. It is more preferable to use a dehumidifying atmosphere that dries quickly at a high temperature and does not allow moisture to enter in a hopper-type dryer because moisture does not enter even at a low temperature. Incidentally, it is preferable to avoid high temperatures in the hopper because blocking problems and fluctuations in the extruder supply section occur. Specifically, after drying at 120 ° C. for 3 hours or more with a dryer before the hopper, the inside of the hopper dryer is set to 40 to 100 ° C., so that the moisture content can be suppressed and the extrusion stability can be compatible.

  On the other hand, as a screw used in a single screw extruder or the like, a general full-flight configuration having a vent ratio or a compression ratio of about 2-3 for an extruder can be used, but there is no unmelted material. Thus, a special kneading mechanism such as a barrier flight may be provided.

  In the present invention, the extrusion conditions when using an extruder as the melting means need to be adjusted according to the thermoplastic resin used. For example, when using a polycarbonate resin having a viscosity average molecular weight of 12,000 to 20,000, The temperature of each cylinder part is preferably set so that the resin temperature at the exit of the extruder is 220 to 280 ° C, more preferably 240 to 270 ° C. If the resin temperature is lower than 220 ° C, the melt viscosity becomes very large, and it may become difficult to torque over the extruder or form a film. There is a possibility that. On the other hand, the temperature of the cylinder part of the extruder is a difference of 20 ° C. or less, preferably a difference of 10 ° C. or less, more preferably a difference of 5 ° C. or less with respect to the resin temperature at the time of die discharge described later. It is preferable to do. When these differences are larger than 20 ° C., it is difficult to uniformly change the temperature of the entire fluidized resin when it is changed in the line to the desired resin temperature after passing through the extruder, which is not preferable ( In particular, if the temperature becomes non-uniform when discharging into a film, the uniformity of the film will be reduced.

  Moreover, it is preferable to supply the molten resin obtained by melting means such as an extruder to a die using a gear pump. By using a gear pump, the discharge amount fluctuation in the extruder is absorbed, the supply quantitative property is remarkably improved, and the stability of the film thickness over time is effective. The molten resin quantitatively supplied from the gear pump or directly supplied from the extruder is supplied to the die through, for example, a tubular flow path, and discharged from the die into a film.

  Further, it is preferable to provide a foreign substance removing device in the resin flow path from the gear pump to the die or in the resin flow path from the melting means to the die when no gear pump or the like is used. Thereby, the foreign material contained in the raw material resin or the foreign material generated by the extruder or the gear pump can be trapped, and foreign material defects in the film can be reduced. As the foreign matter removing device, a screen mesh, a pleated filter, a leaf disk filter, or the like can be used. Among these, a leaf disk type filter is preferable from the relationship between filtration accuracy, filtration area, pressure resistance, and time until filter clogging due to foreign matter. The filter medium used can be a sintered non-woven fabric of metal fibers, and the filter filtration accuracy is preferably 1-20 μm cut, preferably 3-10 μm cut for optical applications. In addition, the number and size of the filter elements are determined. In order to shorten the residence time, it is preferable to reduce the number of the filter elements as small as possible with respect to the pressure resistance. Moreover, it is preferable to design a flow path such as each gap in the filter so as to eliminate stagnation of each part.

  In the present invention, dies having various structures can be used to form a molten resin discharged in the form of a film, but a T die is preferable, and for example, a general coat hanger die can be used. In particular, a mechanism capable of adjusting a gap in an arbitrary portion in the width direction of the lip by pressing a bolt or the like is preferable as a thickness adjusting mechanism in the width direction. Furthermore, it is possible to measure the thickness of the film online and adjust the thickness profile automatically using, for example, a thermally actuated bolt. Such a change is preferable because the thickness can be adjusted with high accuracy without involving a human hand.

[Film forming process]
The molten resin discharged in the form of a film is generally cooled and solidified after landing on the cast roll. In the present invention, the edge is within the range of 5 mm or more and 180 mm or less from the width direction end of the film on the cast roll. It is characterized by performing pinning. Furthermore, it is preferable to perform edge pinning within a range of 10 mm or more and 130 mm or less, particularly 15 mm or more and 100 mm or less from the end in the width direction of the film. If the edge pinning installation position is 5 mm or less from the film end, the effect of the thickness of the end due to film shrinkage is small, and it is difficult to obtain the same effect as knurling. Moreover, when the installation position of edge pinning is 180 mm or more from the end of the film, unevenness occurs in the shrinkage of the film, and thickness variation occurs.

  Moreover, the installation position in the flow direction of the film of edge pinning is preferably until the molten resin discharged in the form of a film lands on the cast roll, more preferably the T-die resin discharge port and the film land on the cast roll. From the midpoint of the point to the point where the film landed on the cast roll. If edge pinning is installed before the midpoint between the point where the T-die resin discharge port and the film land on the cast roll, spark discharge will occur to the T-die when voltage is applied, and the effect of edge pinning will not be obtained. And the T-die is not preferable because it is damaged by spark discharge. Also, if edge pinning is installed after the film landing point, it is not possible to suppress the film width variation that occurs up to the point where the T-die resin discharge port and the film land on the cast roll, and the film thickness variation in the flow direction also occurs. Absent.

  Also, the distance from the film surface to the edge pinning installation position is preferably from 1 mm to 10 mm. If the edge pinning installation position from the film surface is 1 mm or less, the film will come into contact with the edge pinning due to the shaking of the film during production. 10 mm or more is not preferable because edge pinning is too far away and the effect of electrostatic adhesion is reduced.

  The applied voltage for edge pinning depends on the distance from the film surface to the edge pinning installation position, but may be at least the voltage at which the film can be confirmed to adhere to the cast roll and less than the voltage at which spark discharge occurs. The voltage at which it can be confirmed that the film is in close contact with the cast roll is a voltage at which the charge applied by the discharge does not continue to accumulate, and is a situation in which electrostatic adhesion occurs between the film and the cast roll. On the other hand, as the applied voltage is increased, more charge is present on the film, and spark discharge occurs when charge cannot be stored in the film. This means that the film cannot be brought into close contact by electrical contact. Further, since the spark discharge is generated toward the roll side, it is preferable that the voltage be lower than the voltage at which the roll is broken and the spark discharge is generated.

  The surface temperature of the cast roll is preferably (Tg-50) ° C. ≦ T ≦ (Tg + 20) ° C. (Tg is a glass transition temperature). When the surface temperature of the cast roll is higher than Tg + 20, a peeling pattern is generated when the film is peeled off from the cast roll, which is not preferable. It is not preferable because of poor adhesion and fluctuations in thickness.

[resin]
In the present invention, various resins can be used as the thermoplastic resin. For example, norbornene resin, polycarbonate resin, polysulfone resin, polyethersulfone resin, polymethyl methacrylate resin, polyarylate resin, polystyrene Examples thereof include resins and polyvinyl chloride resins. Among these, it is preferable to use a polycarbonate resin that is particularly excellent in transparency and processability.

  In addition, when used as a light transmission layer of an optical recording medium, the light transmission layer and the substrate on which the light transmission layer is laminated are the same material in order to prevent the occurrence of warpage or distortion due to the difference in dimensional change rate with the substrate. Therefore, polycarbonate which is widely used as a substrate material for optical recording media is preferred. Among them, an aromatic polycarbonate which is produced and inexpensive and whose main constituent component is a repeating unit composed of 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is preferable. The main component here refers to a repeating component composed of a compound occupying 50 mol% or more of the dihydroxy compound which is a raw material of polycarbonate. Therefore, even if 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is used alone, another dihydroxy compound is added and copolymerized or mixed within a range not exceeding 50 mol%. be able to. Although it does not specifically limit as a dihydroxy compound used by copolymerizing or mixing, For example, 2, 2-bis (4-hydroxy-3-methylphenyl) propane, 1, 1-bis (4-hydroxy-3-t-butyl) Phenyl) propane, 2,2-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-hydroxy-) Bis (hydroxyaryl) alkanes such as 3,5-dibromophenyl) propane, 1,1-bis (4-hydroxyphenyl) ethylbenzene, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis Bis (hydroxylaryl) cyclohexane such as (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane Suns, fluorenes such as 9,9-bis (4-hydroxyphenyl) fluorene, dihydroxyaryl ethers such as 4,4′-dihydroxyphenyl ether, 4,4′-dihydroxy-3,3′-dimethylphenyl ether 4,4′-dihydroxyphenyl sulfide, dihydroxyaryl sulfides such as 4,4′-dihydroxy-3,3′-dimethylphenyl sulfide, 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxy-3, Examples include dihydroxyaryl sulfoxides such as 3′-dimethylphenyl sulfoxide, and compounds derived from the above compounds. These dihydroxy compounds may be used alone or in combination of two or more with respect to the main component of the repeating unit composed of bisphenol A as long as the transparency is not impaired. However, since bisphenol A is a cheap and readily available raw material, the more bisphenol A component is used, the cheaper the film becomes easier to industrially supply, and the repeating unit of bisphenol A is preferably 80 mol% or more, more preferably. Is preferably 90 mol% or more, particularly preferably 100 mol%.

  In addition, as the polymethyl methacrylate resin, those having various structures can be used. In particular, from the viewpoint of heat resistance, a polymethyl methacrylate resin having a ring structure in the main chain can be preferably used. . Examples of polymethyl methacrylate resins having a ring structure in the main chain include maleimide polymers, polyglutarimide polymers, polyglutaric acid polymers, maleic anhydride polymers, and lactone ring-containing polymers. be able to.

[Use of thermoplastic resin film]
The method of using the thermoplastic resin film of the present invention is not particularly limited. For example, the interior and exterior of automobiles, members of mobile phones, members of AV equipment, members of personal computer equipment, furniture products, various displays, lenses, It can be used for various applications that require external design such as window glass, accessories and sundries.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited to these specific Examples. In addition, the measuring method of each physical property measured in the following Examples and Comparative Examples is as follows.

(Glass-transition temperature)
10 mg of the resin was measured using a differential scanning calorimetry system (DSC, DSC-50 manufactured by Shimadzu Corporation) under a nitrogen atmosphere and a temperature increase rate of 20 ° C./min. Subsequently, the glass transition temperature was determined based on the measurement result by the midpoint method.

(Film thickness)
The thickness of the film edge was measured using a continuous thickness meter (Anritsu KB601B).

(Roll film appearance)
The appearance of the molded film was visually evaluated. If the formed film did not have a gauge band or winding deviation, it was indicated as “◯”, if it was generated, “X”, and if it was slight, “Δ”.

Example 1
A polycarbonate resin (Iupilon H-4000 manufactured by Mitsubishi Gas Chemical Co., Ltd., glass transition temperature 148 ° C.) was used as the thermoplastic resin, dried at 100 ° C. for 4 hours with a drying hopper, and supplied to a φ65 mm single screw extruder. The resin was heated and melted with an extruder to a resin temperature of 280 ° C., and the molten resin was extruded through a gear pump into a leaf disk filter having a diameter of 5 inches and a filtration accuracy of 5 μm cut, and a T-die. At this time, each member is connected from the extruder to the die by arranging piping having connecting portions at both ends between the members. A T-die having a width of 1500 mm was used, and after landing on a cast roll whose temperature was adjusted to resin Tg-20 ° C., the T-die was rapidly cooled and solidified by cooling on the cast roll.

  Further, edge pinning was performed as electrostatic pinning on the cast roll. For edge pinning, an electrostatic pinning device manufactured by Kasuga Electric Co., Ltd. was used. The position of edge pinning was a point where the film landed on a cast roll with respect to the flow direction of the film, and was 50 mm from the end in the width direction of the film with respect to the width direction of the film. The distance from the film surface to the edge pinning installation position was 2 mm.

  The film cooled and solidified on the cast roll was taken up at 10 m / min with a take-up roll and wound on the core (raw roll film). The film thus produced had a thickness of 70 μm at the center in the width direction of the film and 150 μm at the end. The appearance of the obtained roll film was good with no gauge band or winding shift.

(Example 2)
A roll film was prepared in the same manner as in Example 1 except that the edge pinning position with respect to the width direction of the film was set to 5 mm from the end portion in the width direction of the film. The thickness of the acquired width direction center part of the film was 70 micrometers, and the thickness of the edge part was 100 micrometers. The appearance of the obtained roll film was good with no winding deviation, although a slight gauge band was generated.

(Example 3)
A roll film was prepared in the same manner as in Example 1 except that the edge pinning position with respect to the width direction of the film was set to 150 mm from the end in the width direction of the film. The thickness of the central part of the obtained film was 70 μm, and the thickness of the end part was 200 μm. The appearance of the obtained roll film was good with no gauge band or winding shift.

(Comparative Example 1)
A film was prepared in the same manner as in Example 1 except that the edge pinning position with respect to the width direction of the film was set to 200 mm from the end in the width direction of the film. Although the thickness of the center part of the produced film was 70 micrometers and the thickness of the edge part was 250 micrometers, winding gap generate | occur | produced during film winding and acquisition of a roll film was not able to be performed.

(Comparative Example 2)
A roll film was prepared in the same manner as in Example 1 except that the edge pinning position with respect to the width direction of the film was set to the end in the width direction of the film. The thickness of the central part of the produced film was 70 μm, and the thickness of the end part was 80 μm. Although the obtained roll film had no winding deviation, a gauge band was generated.

1. T-die 2. 2. Thermoplastic resin Cast roll 4. 4. Cooling roll Freeroll 6. Edge pinning Distance from film edge to edge pinning

Claims (3)

  Production of a thermoplastic resin film characterized by performing edge pinning within a range of 5 mm or more and 180 mm or less from a width direction end of a film on a cast roll when continuously producing a film by a melt film-forming method Method.   The method for producing a thermoplastic resin film according to claim 1, wherein the edge pinned portion on the film is wound up without slitting.   3. The method for producing a thermoplastic resin film according to claim 1, wherein the thermoplastic resin is at least one resin selected from a polycarbonate resin and an acrylic resin.

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