JP5923424B2 - Method for producing thermoplastic resin film - Google Patents

Description

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

  In the melt film forming method, a method is known in which a sheet-like molten resin extruded from a die is brought into close contact with a cast roll by an electrostatic contact method and cooled. The electrostatic contact method is referred to as electrostatic pinning, and includes edge pinning that electrostatically contacts the film end and wire pinning that electrostatically contacts the entire width of the film (for example, Patent Documents 1 and 2).

  Edge pinning has the effect of suppressing film width variation and film thickness variation in the flow direction by electrostatically adhering the film edge, but according to the study of the present inventor, volatile content in the resin can be obtained. If there is, there is a problem that the cast roll at the center of the film with low film adhesion becomes dirty with time and the dirt is transferred to the film.

  In addition, wire pinning that electrostatically adheres to the entire width of the film does not cause problems such as edge pinning because it adheres to the entire width of the film. There is a problem that is likely to occur.

JP 2009-166325 A JP-A-62-048522

  The present invention has been made in view of the above problems, and the object of the present invention is to prevent the cast roll from becoming dirty with time even if the resin has a volatile content in the melt film forming method. An object of the present invention is to provide a method for producing a thermoplastic resin film characterized in that contamination is reduced.

  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 the above problem can be solved by performing edge pinning and wire pinning simultaneously.

  That is, the present invention is a method for producing a thermoplastic resin film in which a molten resin discharged in the form of a film is pressed against a cast roll by electrostatic pinning, and edge pinning and wire pinning are performed from the upstream side as electrostatic pinning. Arranged in order, including the position where the resin temperature on the cast roll is the glass transition temperature (hereinafter, Tg (° C.)), the wire pinning is downstream from this position and upstream from the position where the wire pinning is peeled off from the cast roll. The wire tension of the wire pinning is 5% or more and 99% or less of the wire breaking tension, and relates to a method for producing a thermoplastic resin film. According to this, it is possible to prevent film surface defects such as pinning bubbles and stripes in the film width direction and to reduce film contamination caused by contamination of the cast roll.

  In the method for producing a thermoplastic resin film according to the present invention, even if the resin has a volatile component in the melt film-forming method, the stain on the cast roll does not easily progress over time, and as a result, the cast roll becomes dirty on the film. It becomes difficult to be transferred and produces an effect that a film having a beautiful appearance can be produced.

1 is a schematic side view of a thermoplastic resin film production apparatus according to an embodiment of the present invention.

  A method for producing a thermoplastic resin film according to the present invention is a method for producing a thermoplastic resin film in which a molten resin discharged in a film shape is pressed against a cast roll by electrostatic pinning, and edge pinning and wire are used as electrostatic pinning. The pinning is arranged in this order from the upstream side, and the wire pinning is located downstream of the cast roll including the position where the resin temperature on the cast roll becomes the glass transition temperature (hereinafter, Tg (° C.)). The wire tension of the wire pinning is 5% or more and 99% or less of the wire breaking tension. Here, the molten resin discharged in the form of a film can be obtained by, for example, using an extruder or the like, melting and plasticizing by heating and kneading the resin, and being discharged from a die hole on the slit, In particular, in the present invention, the molten resin discharged in the form of a film is cooled and solidified by bringing it into contact with a cast roll (preferably temperature-controlled) to obtain a film.

  Hereinafter, the present invention will be described from the viewpoint of each step and resin.

[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 the foreign material defect 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 formation 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, edge pinning and wire pinning are performed on the cast roll at that time. The positional relationship of each pinning includes edge pinning and wire pinning in this order from the upstream side, and includes the position where the resin temperature on the cast roll becomes the glass transition temperature (hereinafter, Tg (° C.)). It is characterized in that it is arranged on the downstream side from this position and on the upstream side from the position where it is peeled off from the cast roll.

  In particular, the position of edge pinning is preferably set before the molten resin discharged in the form of a film lands on the cast roll, more preferably the point where the T-die resin discharge port and the film land on the cast roll. From the midpoint to the point where the film reaches 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.

  In addition, the position of edge pinning with respect to the film width direction may be within the film in the film width direction, but it is preferable to install it at the end of the film as much as possible in consideration of the product width. Furthermore, 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 less than 1 mm, the film will come into contact with the edge pinning due to the shaking of the film during production. If it is larger than 10 mm, the edge pinning is too far away and the effect of electrostatic adhesion is reduced, which is not preferable.

  The applied voltage for edge pinning depends on the distance from the film surface to the edge pinning installation position, but it may be at least the voltage at which the film can be confirmed to be in close contact with 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, a large amount of charge is present on the film, and the spark discharge occurs when the charge cannot be stored on the film. This means that the film cannot be brought into close contact by electrical contact. In addition, since the spark discharge is generated toward the roll side, it is preferable that the voltage be equal to or lower than a voltage at which the roll is broken and the spark discharge is generated.

  On the other hand, the installation position of the wire pinning is downstream from this, including the position where the molten resin discharged in the form of a film lands on the cast roll and the resin temperature on the cast roll becomes Tg (usually Since the temperature of the discharged molten resin is higher than Tg, the position where Tg is reached is the position where the resin temperature has dropped to Tg.), Installed upstream from the position where the film peels from the cast roll It is preferable to do. When wire pinning is placed at a position where the film-like thermoplastic resin is at a temperature higher than Tg, it is difficult to adjust the wire pinning conditions, and film surface defects such as pinning bubbles and stripes in the film width direction occur. It becomes easy and it is not preferable. On the other hand, even if the wire pinning is arranged downstream from the position where the film peels off from the cast roll, the film does not adhere to the cast roll, and if the resin has a volatile content, dirt accumulates on the cast roll. Is not preferable because it is transferred to a film.

  Also, the distance from the film surface to the wire pinning installation position is preferably from 1 mm to 10 mm, and it is difficult to adjust the wire pinning installation position from the film surface to less than 1 mm, and the wire may come into contact with the film. If it is larger than 10 mm, the wire pinning is too far away and the effect of electrostatic adhesion is reduced, which is not preferable.

  In addition, the applied voltage of wire pinning also depends on the distance from the film surface to the wire pinning installation position, as with edge pinning, but it is more than 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. If it is good. 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, a large amount of charge is present on the film, and the spark discharge occurs when the charge cannot be stored on the film. This means that the film cannot be brought into close contact by electrical contact. In addition, since the spark discharge is generated toward the roll side, it is preferable that the voltage be equal to or lower than a voltage at which the roll is broken and the spark discharge is generated.

  Moreover, it is preferable that the tension | tensile_strength of a wire is 5 to 99% of the breaking tension of the wire to be used. More preferably, they are 30% or more and 95% or less, More preferably, they are 50% or more and 90% or less. When the wire tension is 5% or less of the breaking tension of the wire, the wire is loosened, and the adhesion of the film to the cast roll becomes non-uniform, resulting in undesirably cast roll contamination. Further, when the wire tension is 99% or less of the breaking tension of the wire, the wire may be broken.

  The surface temperature of the cast roll is preferably (Tg-50) ° C. ≦ T ≦ Tg ° C. (Tg is the glass transition temperature). More preferably, (Tg−40) ° C. ≦ T ≦ (Tg−5) ° C., and further preferably (Tg−30) ° C. ≦ T ≦ (Tg−10) ° C. When the cast roll temperature is higher than Tg, the film does not fall below Tg on the cast roll, which is not preferable. When the cast roll temperature is lower than (Tg-50) ° C., if the resin has a volatile component, the volatile component is rapidly cooled. It is not preferable because it tends to accumulate on the cast roll and may reduce the effect of using wire pinning together.

[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 bonded are made of the same material in order to prevent warpage or distortion due to the difference in dimensional change with the substrate. For this reason, 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. Moreover, it can be used as various optical films, such as a phase difference film used for a liquid crystal display.

  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 temperature)
The film temperature on the cast roll was measured with a non-contact thermometer (TMZ53-350F3 manufactured by Japan Sensor Co., Ltd.).

(Film appearance)
The appearance of the molded film was visually evaluated. If the molded film did not have dirt or horizontal streaks, it was indicated as “◯”, if it was generated, “X”, and if it occurred, it was indicated as “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 so as to have a resin temperature of 280 ° C. with an extruder, and the molten resin was extruded through a gear pump to a 5-inch, 5-μm cut leaf disk filter 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. 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.

  In addition, edge pinning and wire pinning were arranged in this order from the upstream side as electrostatic pinning (note that edge pinning and wire pinning were manufactured by Kasuga Electric Co., Ltd.).

  The arrangement of edge pinning is the position where the film lands on the cast roll with respect to the flow direction of the film-like molten resin (hereinafter sometimes simply referred to as film), and the end portion with respect to the width direction of the film. did. Furthermore, the distance from the film surface to edge pinning was 2 mm.

  On the other hand, the arrangement of the wire pinning is a position where the resin temperature becomes Tg (° C.) with respect to the flow direction of the film (upstream side from the position where the film peels from the cast roll), and the distance from the film surface to the wire pinning is 2 mm. It was.

  Moreover, as a wire for wire pinning, a tungsten wire φ0.15 (wire breaking tension: 35 N) was used, and the wire was set up with a tension of 90% of the wire breaking tension. The wire tension was measured with a digital force gauge AD4932A-50N manufactured by A & D Corporation.

  On the other hand, the film cooled and solidified on the cast roll was taken up by a take-up roll at 10 m / min, and a film original having a film thickness of 70 μm was obtained from the take-up core. The appearance of the obtained film was good with no dirt and horizontal stripes.

(Example 2)
The wire pinning wire is installed with a tension of 5% of the wire breaking tension, and the wire pinning position is set at a position where the resin temperature becomes Tg-20 (° C) with respect to the film flow direction (the film is a cast roll). A film was produced in the same manner as in Example 1 except that the film was formed on the upstream side from the position where the film was peeled off. The appearance of the obtained film was good with no dirt and horizontal stripes.

(Example 3)
A film was prepared in the same manner as in Example 1 except that the wire pinning wire was installed with a tension of 99% of the wire breaking tension, and the cast roll temperature was Tg (° C.). The appearance of the obtained film was good with no dirt and horizontal stripes.

Example 4
A film was prepared in the same manner as in Example 1 except that the wire pinning wire was installed with a tension of 99% of the wire breaking tension, and the cast roll temperature was Tg-50 (° C). Although the appearance of the obtained film was slightly dirty, it was not at a problematic level.

(Example 5)
A film was produced in the same manner as in Example 1 except that the wire pinning wire was installed with a tension of 5% of the wire breaking tension, and the cast roll temperature was resin Tg (° C.). Although the appearance of the obtained film was slightly dirty, it was not at a problematic level.

(Comparative Example 1)
As electrostatic pinning, edge pinning is not used, only wire pinning is used, and the position of wire pinning is the position where the resin temperature becomes Tg + 130 (° C) with respect to the film flow direction (position where the film contacts the cast roll) A film was produced in the same manner as in Example 1 except that. The appearance of the obtained film had horizontal streaks.

(Comparative Example 2)
A film was produced in the same manner as in Example 1 except that wire pinning was not used as electrostatic pinning and only edge pinning was used. The appearance of the obtained film was soiled.

(Comparative Example 3)
A film was produced in the same manner as in Example 1 except that the position of the wire pinning was changed to a position where the resin temperature was Tg + 5 (° C.) with respect to the film flow direction. The appearance of the obtained film had horizontal streaks.

(Comparative Example 4)
The cast roll temperature is Tg + 10 (° C.), and the wire pinning arrangement is the position where the resin temperature is Tg + 10 (° C.) relative to the film flow direction (upstream side from the position where the film peels from the cast roll). A film was produced in the same manner as in Example 1. The appearance of the obtained film had horizontal streaks.

(Comparative Example 5)
A film was produced in the same manner as in Example 1 except that the wire pinning wire was installed with a tension of 2% of the wire breaking tension. The appearance of the obtained film was soiled.

1. T-die 2. 2. Thermoplastic resin Cast roll 4. 4. Cooling roll Freeroll 6. Edge pinning Wire pinning 8. Wire pinning installation range

Claims (3)

A method for producing a thermoplastic resin film in which a molten resin discharged in a film form is pressed against a cast roll by electrostatic pinning, and edge pinning and wire pinning are arranged in this order from the upstream side as electrostatic pinning,
Including the position where the resin temperature on the cast roll is the glass transition temperature (hereinafter referred to as Tg (° C.)), the wire pinning is arranged on the downstream side from this position and on the upstream side from the position where it is peeled off from the cast roll,
A method for producing a thermoplastic resin film, wherein the wire tension of wire pinning is 5% or more and 99% or less of the wire breaking tension. The surface temperature T (° C.) of the cast roll is
(Tg-50) ≦ T ≦ Tg
The method for producing a thermoplastic resin film according to claim 1, wherein:   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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