JP2020044837A - Manufacturing method of film - Google Patents

Abstract

To provide a manufacturing method of a film capable of decomposing sublimable organic compounds and volatile organic compounds generated from the film and a coating material, etc., for an extended period and also capable of reducing contamination of a tenter apparatus and defect occurrence in the film by deposition of melamine analogs which are sublimable organic compounds.SOLUTION: The manufacturing method of a film includes a drawing step of drawing a sheet at least in one direction by using a tenter apparatus equipped with a preheating zone and a drawing zone from its upstream in order, wherein the manufacturing method of a film is characterized by that the preheating zone is equipped with a gas phase circulation path, the gas phase circulation path includes in its inside a platinum catalyst and a heating mechanism, and the temperature of the platinum catalyst is controlled to be at 250°C or over and 400°C or under.SELECTED DRAWING: Figure 1

Description

  The present invention decomposes a sublimable organic compound or a volatile organic compound generated from a film or a coating material for a long period of time, and further adheres a melamine or the like, which is a sublimable organic compound, thereby contaminating a tenter device and causing a defect of the film. The present invention relates to a method for producing a film capable of reducing generation thereof.

  The film can be manufactured by stretching the sheet in at least one direction using a tenter device or the like. This tenter device is generally divided into a plurality of zones in which the temperature can be individually controlled from an inlet to an outlet, and a plurality of zones having different temperatures and different clip widths are formed until a sheet is stretched into a film. pass. As one of the temperature control methods of each zone in the tenter device, a method of providing a gas circulation path in a room constituting the zone, and performing a supply / exhaust or heating of a gas circulating in the room to raise and lower the temperature. Is used.

  If the gas circulation path has a structure in which the gas sprayed on the film circulates near both ends in the width direction of the room, the gas near both ends in the width direction circulates to both ends in the width direction, but near the center in the width direction. Cannot flow to both ends in the width direction, and may flow in the film transport direction. This tendency increases in proportion to the length of the film in the width direction and the transport speed.

Further, when the raw material of the film or the coating agent applied to the surface of the film contains ethylene glycol mono-normal butyl ether (butyl cellosolve), aldehydes such as acetaldehyde and formaldehyde, derivatives thereof, and decomposition products thereof, Alternatively, when the raw materials and the components of the coating material cause a chemical reaction in the film manufacturing process to generate the above-mentioned compound, the gas in the tenter device contains the above-mentioned compound, and if these are discharged, the environment is adversely affected. May have an effect. As a method for removing the compound from the gas, a method using a hydrophobic zeolite as an adsorbent (Patent Document 1), or a method in which a platinum group element is coated on a ceramic honeycomb body by coating γ · Al ₂ O ₃ on a substrate. There is known a method of using a catalyst in which one or more lanthanoid-based metal oxides are added to a catalyst carrying more than one kind (Patent Document 2).

  In each zone, a film material or a coating material applied to the film surface is coated with melamine, melamine-formaldehyde, a derivative thereof, or a nitrogen-containing compound generated by decomposition thereof (hereinafter, these components are collectively referred to as “these components”). Melamines), the melamines may sublime or volatilize, and the gas in the preheating zone or the stretching zone particularly contains a large amount of melamines. When the gas in the preheating zone or the stretching zone flows in the direction of transport of the film and reaches the lower temperature zone, the saturation amount of the melamines decreases with a decrease in the temperature of the gas, and the melamine eventually precipitates. The melamines thus precipitated cause contamination in the tenter device and adhesion of foreign substances to the film.

  As a measure for reducing the precipitation of melamines, a measure for increasing the supply / exhaust volume of each zone can be considered. However, as the amount of gas taken in from the outside increases, enormous energy is required for heating the gas. Therefore, there is a limit in increasing the supply / exhaust amount of each zone. There is little prior art literature on contamination in the tenter device due to melamines, but it is well known about contamination in the tenter device due to oligomers volatilizing from the film surface mainly in the zone where heat setting is performed by a similar mechanism. . As a countermeasure, a method of reducing the oligomer concentration in the gas by providing a platinum catalyst in the gas circulation path has been used (Patent Documents 3 and 4).

JP-A-7-80248 JP-A-6-126173 JP 2017-177534 A WO2009 / 125829

  The methods described in Patent Documents 1 and 2 are used for purifying exhaust gas of a factory or an engine, respectively, and a sufficient effect can be expected in these applications. However, the gas circulating in the tenter device is generally hot and contains a greater amount of the compound. Therefore, in order to apply these methods to purify the gas in the tenter, it is necessary to replace the adsorbent and the catalyst frequently in order to compensate for the lack of trapping capacity and resolution. There was a challenge in having to stop. Further, although the methods described in Patent Documents 3 and 4 have an effect of lowering the oligomer concentration in a gas, they are effective for sublimable organic compounds other than oligomers such as melamines and volatile organic compounds such as aldehydes. It has not been sufficiently examined whether or not they have the same effect.

  The present invention solves the drawbacks of the related art, decomposes sublimable organic compounds and volatile organic compounds generated from films and coating materials over a long period of time, further precipitates melamines in a tenter device, and melts melamine. It is an object of the present invention to provide a method for producing a film that can reduce the occurrence of defects due to adhesion of kinds.

In order to solve the above problems, the present invention has the following configurations.
(1) A method for producing a film having a stretching step of stretching a sheet in at least one direction by a tenter device having a preheating zone and a stretching zone in order from an upstream side, wherein the preheating zone includes a gas circulation path, A method for producing a film, characterized in that the gas circulation path has a platinum catalyst and a heating mechanism inside, and the temperature of the platinum catalyst is controlled at 250 ° C to 400 ° C.
(2) The method for producing a film according to (1), wherein the preheating zone includes means for suppressing gas flow in a longitudinal direction.
(3) The method for producing a film according to (1) or (2), wherein a heat setting zone is provided downstream of the stretching zone.
(4) The heat fixing zone has a gas circulation path, the gas circulation path has a platinum catalyst and a heating mechanism inside, and controls the temperature of the platinum catalyst to be more than 210 ° C. and 400 ° C. or less. The method for producing a film according to (3), wherein
(5) Any one of (1) to (4), further comprising a step of applying a coating agent containing at least one of a sublimable organic compound and a volatile organic compound before the stretching step. 3. The method for producing a film according to item 1.
(6) The method for producing a film according to (5), wherein the sublimable organic compound contains a melamine.
(7) The method for producing a film according to (5) or (6), wherein the volatile organic compound contains at least one of butyl cellosolve, acetaldehyde, and formaldehyde.

  According to the present invention, a sublimable organic compound or a volatile organic compound generated from a film or a coating material is decomposed over a long period of time, and furthermore, precipitation of melamines in a tenter device and occurrence of defects due to adhesion of the melamines are reduced. A method for producing a film.

FIG. 3 is a schematic cross-sectional view when a room on a downstream side of a preheating zone in a tenter device used in an example is cut along a film surface and a surface perpendicular to a longitudinal direction.

  The method for producing a film of the present invention is a method for producing a film having a stretching step of stretching a sheet in at least one direction by a tenter device having a preheating zone and a stretching zone in order from the upstream side, wherein the preheating zone is a gas. A circulation path is provided, wherein the gas circulation path has a platinum catalyst and a heating mechanism therein, and controls the temperature of the platinum catalyst to be 250 ° C. or more and 400 ° C. or less.

  The film manufacturing method of the present invention includes a stretching step of stretching a sheet in at least one direction with a tenter device including a preheating zone and a stretching zone. By adopting such an embodiment, preheating and stretching of the sheet can be easily performed in a series of steps. Here, the preheating zone refers to a section where the temperature of the sheet entered from the entrance is raised to the stretching temperature, and the stretching zone refers to a section where the preheated sheet is stretched in at least one direction. Note that a sheet refers to a planar resin molded product in a stage before completion of stretching in a tenter device, and a film refers to a sheet obtained by stretching a sheet in at least one direction by a tenter device.

  The pre-heating zone and the stretching zone may be composed of one room or may be composed of a plurality of rooms as long as the effects of the present invention are not impaired, and when there are a plurality of rooms, the temperature can be controlled for each room. It is good also as a mode. Here, the room refers to a space in the tenter device that is divided by a wall having a gap through which a sheet or a film passes.

  The stretching direction and the magnification in the stretching zone can be adjusted by, for example, the spread of the clip in the width direction, or the difference in running speed between the preceding clip and the succeeding clip (hereinafter, sometimes referred to as the difference in the speed of the clip). it can. More specifically, stretching in the longitudinal direction is enabled by the difference in speed of the clip, and stretching in the width direction is enabled by the spread of the clip in the width direction. By increasing the speed difference of the clips and the spread of the clips in the width direction, the stretching ratio in each direction can be increased. Note that the longitudinal direction refers to a direction in which a sheet or a film travels, and the width direction refers to a direction perpendicular to the longitudinal direction in a sheet surface or a film surface.

  The method for producing a film of the present invention preferably includes a step of applying a coating material containing at least one of a sublimable organic compound and a volatile organic compound before the stretching step. Here, a sublimable organic compound is defined as the temperature at the triple point when a diagram (phase diagram) showing whether a substance is in a gas, liquid, or solid state under a certain pressure and temperature condition is drawn. Is higher than 25 ° C. and the pressure indicated by the triple point is higher than 1 atm. A volatile organic compound is an organic compound defined by the World Health Organization (WHO) as a highly volatile organic compound (VVOC) or a volatile organic compound (VOC), and is not a sublimable organic compound. Say. The term “coating agent containing a sublimable organic compound” includes not only a coating agent containing a sublimable organic compound itself but also a coating material that generates a sublimable organic compound by heating in a tenter device. This point is the same for the “coating agent containing a volatile organic compound”, and the same applies to the components contained in the coating agent.

  When a sheet coated with a coating material containing a sublimable organic compound is conveyed to a tenter device, evaporation of the solvent component and sublimation of the sublimable organic compound occur as the temperature rises, and the sublimate becomes a foreign substance in the film or inside the tenter device. May cause contamination. In addition, when a sheet coated with a coating agent containing a volatile organic compound is conveyed to a tenter device, the volatile organic compound is volatilized with an increase in temperature, and a gas containing the volatile substance is discharged to the outside. The load on the system increases. Therefore, the method for producing a film of the present invention includes a step of applying a coating agent containing at least one of a sublimable organic compound and a volatile organic compound before the stretching step. The generation of foreign substances and environmental load can be reduced.

  The sublimable organic compound contained in the coating agent is not particularly limited, but specific examples include naphthalene, oxalic acid, and melamines. Among them, melamines are used as a hardening agent in coatings, and their sublimates are likely to cause foreign substances. Therefore, from the viewpoint of increasing the advantages of the present invention, the sublimable organic compound preferably contains melamines. The melamines refer to melamine, melamine-formaldehyde, derivatives thereof, and components that generate these compounds by decomposition. In the production of a film having a step of applying a coating agent containing melamines, the precipitation risk of the melamines is higher than usual, so the advantage of using the present invention in terms of reducing the generation of foreign substances due to this is large. Become.

  The volatile organic compound contained in the coating agent is not particularly limited, but specific examples include toluene, xylene, ethyl acetate, butyl cellosolve, acetaldehyde, formaldehyde, and the like. Above all, butyl cellosolve used as an organic solvent and a surfactant, and acetaldehyde and formaldehyde used as a curing agent in a coating material are easily volatilized by increasing the temperature, and when discharged, have a great adverse effect on the environment. Therefore, it is preferable that the volatile organic compound contains at least one of butyl cellosolve, acetaldehyde, and formaldehyde from the viewpoint of reducing the influence of the exhaust from the tenter device on the environment. In the production of a film having a step of applying a coating agent containing these components, the risk of precipitation of these components is higher than usual, and the present invention is intended to reduce the environmental impact due to these components. The advantage of using is greater.

  In the film manufacturing method of the present invention, it is important that the preheating zone has a gas circulation path. With such an embodiment, the heated gas circulates in the preheating zone, so that the temperature in the preheating zone can be easily controlled with a small amount of energy.

  The gas circulation path refers to a path through which the gas in the zone can circulate. As long as the gas circulation path has a structure capable of circulating the gas in the room, an air supply line that takes in outside air and an exhaust that discharges gas in the zone to the outside as long as the effects of the present invention are not impaired. A line may be provided. The same applies to a heat fixing zone described later. When there are a plurality of rooms constituting the preheating zone, if at least one of the rooms has a gas circulation path, the preheating zone has a gas circulation path. This also applies to a heat setting zone described later.

  In the method for producing a film of the present invention, it is important that the gas circulation path in the preheating zone has a platinum catalyst and a heating mechanism inside. By adopting such an aspect, it is possible to decompose the melamines and oligomers sublimated into the gas from the sheet in the process of preheating, and the volatile organic compound described above, and the tenter device in the tenter device caused by the melamines and oligomers It is possible to reduce the influence on the environment due to contamination, adhesion of foreign substances to the film, and exhausting a gas containing a volatile organic compound.

  For example, melamine, which is an example of a sublimable organic compound, or a coating material containing a component that produces melamine by a reaction such as decomposition often contains a large amount of water, and is usually around a stretching temperature in a preheating zone. It is dried when heated. Then, as the melamine having volatility evaporates together with the moisture as the coating material dries, the gas in the preheating zone contains abundant melamine. On the other hand, the melting point of melamines is usually higher than the preheating temperature (for example, the melting point of melamine is around 280 ° C.), and thus melamines precipitate (sublimate) after volatilization. By such a mechanism, precipitation of melamines becomes remarkable in the preheating zone. Therefore, providing a platinum catalyst and a heating mechanism inside the gas circulation path in the preheating zone is particularly advantageous in terms of reducing the precipitation of sublimable organic compounds such as melamines.

  Melamines are often used as a coating agent, particularly as a curing agent. When a sheet coated with an aqueous coating material containing melamines by in-line coating or the like is conveyed to a tenter device, the temperature of the coating material is raised in a preheating zone, and moisture in the coating material evaporates. At that time, some of the melamines also sublimate in the oven, and may eventually precipitate on the wall of the gas circulation path in the course of circulation.

  Although melamines are suitably used as components of a coating composition, the source of melamines to be decomposed according to the present invention is not limited to coating compositions. The same applies to the source of butyl cellosolve, which is often used as an organic solvent or a surfactant in a coating agent, and the source of acetaldehyde or formaldehyde, which is often used as a curing agent.

  Oligomers are low molecular compounds that sublime into a gas from a sheet or a film in the process of obtaining a film by heating and stretching a sheet in a tenter device, and are derived from a monomer of a resin component constituting the sheet or the film. Good, oligomers in gas will precipitate when their concentration reaches saturation. Specific examples of the oligomer include linear oligomers (terephthalic acid, monohydroxyethyl terephthalic acid, bis-β-hydroxyethyl terephthalic acid) when the film is a polyethylene terephthalate (hereinafter sometimes referred to as PET) film. And the like, and cyclic oligomers (cyclic trimers and cyclic dimers of the linear oligomers).

  The platinum catalyst is a catalyst capable of burning the above-mentioned volatile organic compound in addition to sublimable organic compounds such as oligomers and melamines at a high temperature, and a gas circulation path unless the effects of the present invention are impaired. It may be arranged at any position within. The heating mechanism refers to a mechanism that can raise the temperature of the platinum catalyst. The heating mechanism can be freely selected within a range that does not impair the effects of the present invention, and for example, an electric heater or a burner can be used. In addition, the arrangement is not particularly limited as long as the platinum catalyst can be heated without impairing the effects of the present invention. For example, it can be arranged to face the platinum catalyst or can be arranged inside the platinum catalyst. It is.

  In addition, the platinum catalyst may be disposed at one place of the gas circulation path or at a plurality of places as long as the effect of the present invention is not impaired, but a sublimable organic compound such as melamine, an oligomer, From the viewpoint of improving the effect of reducing the content of these components in the gas by burning the volatile organic compound or the like in multiple stages, it is preferable to dispose them at a plurality of locations. When a platinum catalyst is arranged at a plurality of locations, a plurality of heating mechanisms can be arranged accordingly.

  The configuration of the tenter device in the film manufacturing method of the present invention is not particularly limited as long as it includes a preheating zone and a stretching zone as long as the effects of the present invention are not impaired. Preferably, a heat setting zone is provided downstream of the zone. The heat setting zone refers to a section in which the film obtained by stretching is processed at a temperature higher than the stretching temperature (hereinafter, this process may be referred to as heat setting), and the heat dimensional stability of the film due to the heat setting. improves. Note that, similarly to the preheating zone and the stretching zone, the heat fixing zone may be configured with one room or may be configured with a plurality of rooms as long as the effects of the present invention are not impaired. May be a mode in which the temperature can be controlled for each room.

  If the tenter device has a heat setting zone, the film manufacturing method of the present invention may be configured such that the heat setting zone has a gas circulation path, and the gas circulation path has a platinum catalyst and a heating mechanism inside. Is preferred. Usually, the heat setting zone is the section where the temperature is the highest and the sublimation of the oligomer is the most remarkable among the zones in the tenter apparatus. Therefore, by adopting such an embodiment, the concentration of the oligomer in the gas in the heat fixing zone can be reduced, so that the contamination of the apparatus and the deterioration of the quality of the film due to the oligomer can be reduced, and the supply / exhaust amount can be reduced. It becomes easier to reduce the energy for heating the gas by reducing the energy.

  Furthermore, in order to reduce the energy required for adjusting the temperature of each zone, a gas circulation path is provided not only for the preheating zone and the heat fixing zone, but also for the stretching zone and a cooling zone described below, and the gas circulation path has a platinum catalyst inside. It is also preferable to adopt an embodiment having a heating mechanism.

  In the film production method of the present invention, it is important to control the temperature of the platinum catalyst in the gas circulation path of the preheating zone to 250 ° C. or more and 400 ° C. or less from the viewpoint of achieving both film quality and productivity. The temperature of the platinum catalyst refers to a surface temperature measured by a contact thermometer. The contact-type thermometer used for the temperature of the platinum catalyst can be arbitrarily selected from those capable of measuring, and for example, HPD-1100 type E (manufactured by Anritsu Keiki Co., Ltd.) or the like can be suitably used.

  If the temperature of the platinum catalyst in the gas circulation path of the preheating zone is 250 ° C. or lower, the resolution of the sublimable organic compound (melamines are exemplified in this paragraph as a specific example) by the platinum catalyst is not sufficiently exhibited, and the melamines Is easily precipitated as a solid, so that impurities such as undecomposed melamine and dust accumulate on the surface of the platinum catalyst with use, and the melamine decomposition effect of the platinum catalyst is further reduced. As a result, melamines tend to accumulate in the preheating zone and its gas circulation path, and the contamination of the tenter device by the melamines and the deterioration of film quality are accelerated. On the other hand, if the temperature of the platinum catalyst is higher than 400 ° C., a sufficient effect of decomposing melamines can be obtained, but the catalyst surface is deteriorated by heat, so that the period until catalyst activity disappears becomes short. As a result, the frequency of exchanging the platinum catalyst by stopping the production of the film increases, which leads to a decrease in productivity and an increase in production cost. From the viewpoint of achieving both film quality and productivity, the temperature of the platinum catalyst in the gas circulation path of the preheating zone is preferably controlled to 290 ° C to 360 ° C, more preferably to 290 ° C to 340 ° C. preferable. In addition, by controlling the temperature of the platinum catalyst to 250 ° C. or more and 400 ° C. or less, or the above preferable range, the resolution of volatile organic compounds such as butyl cellosolve, formaldehyde, and acetaldehyde can be sufficiently ensured.

  When the heat fixing zone of the tenter device has a gas circulation path and the gas circulation path has a platinum catalyst and a heating mechanism inside, from the viewpoint of achieving both film quality and productivity, the heat fixing zone gas It is preferable to control the temperature of the platinum catalyst in the circulation path to more than 210 ° C. and 400 ° C. or less.

  When the temperature of the platinum catalyst in the gas circulation path of the heat setting zone is 210 ° C. or lower, the catalytic activity of the platinum catalyst decreases. Therefore, impurities such as undecomposed oligomers and dust accumulate on the surface of the platinum catalyst with use, and the oligomer decomposition effect of the platinum catalyst is significantly reduced. As a result, since the surface of the platinum catalyst is covered with the oligomer, the effect of decomposing the oligomer is significantly reduced. On the other hand, if the temperature of the platinum catalyst is higher than 400 ° C., a sufficient oligomer decomposition effect can be obtained, but the period until catalyst activity disappears due to the deterioration of the catalyst surface due to heat is shortened. As a result, the frequency of exchanging the platinum catalyst by stopping the production of the film increases, which leads to a decrease in productivity and an increase in production cost.

  In the method for producing a film of the present invention, the temperature of the gas circulating in the preheating zone can be appropriately set according to the type of the resin component constituting the film to be produced. The method of adjusting the temperature of the gas circulating in the preheating zone is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected. For example, separately from the heating mechanism of the platinum catalyst, a method of arranging and controlling a temperature control device such as a heater, a heat exchanger, or a cooler in the gas circulation path, or providing an air supply line and an exhaust line in the gas circulation path A method of adjusting the supply / exhaust amount can be used. Specifically, the temperature of the gas circulating in the preheating zone is increased by heating the gas with a heating device such as a heater, or by reducing the amount of supply and exhaust when the temperature in the preheating zone is higher than the temperature of the outside air. Can be raised.

  The method for producing a film of the present invention is intended to reduce the contamination of the apparatus due to the precipitation of sublimable organic compounds such as melamines and the generation of foreign matters in the film, and a tenter apparatus for volatile organic compounds such as butyl cellosolve, acetaldehyde, and formaldehyde. From the viewpoint of preventing discharge to the outside, it is preferable that the preheating zone includes a means for suppressing the flow of gas in the longitudinal direction. Means for suppressing the flow of gas in the longitudinal direction may exist anywhere in the preheating zone as long as the effects of the present invention are not impaired, but sublimable organic compounds such as melamines generated in the preheating zone, and volatile organic compounds. From the viewpoint of reducing the outflow of the compound to another zone or the downstream side, the compound is preferably present immediately before the stretching zone.

  In the method for producing a film of the present invention, a means for suppressing gas flow in the longitudinal direction may be provided in addition to the preheating zone, as long as the effects of the present invention are not impaired. For example, in the case of using a tenter apparatus having a cooling zone downstream of the heat setting zone, in order to reduce the precipitation of not only melamines but also oligomers sublimed from the film due to heating, the longitudinal direction immediately before the cooling zone is reduced. It is also preferable to provide a means for suppressing gas flow.

  The means for suppressing the flow of gas in the longitudinal direction is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected. For example, in addition to using a hole nozzle as an air blowing nozzle in a tenter device, physical means such as an air curtain can also be employed. These may be used in combination as long as the effects of the present invention are not impaired.

  Next, with respect to the method for producing a film of the present invention, the production of a PET film by a sequential biaxial stretching method using a tenter device having a preheating zone, a stretching zone, a heat setting zone, and a cooling zone in this order will be described below as an example. Will be described.

  First, resin pellets are supplied to a raw material input section of an extruder, and the resin is heated and melted. Thereafter, the resin extruded amount is made uniform by a gear pump or the like, the resin melted by heating is extruded, and foreign matter and gelled substances are removed through a filter or the like. At this time, the number of extruders may be one or more. When a plurality of extruders are used, the thermoplastic resin that has passed through the filter is sent to the laminating apparatus. As the laminating apparatus, a multi-manifold die, a feed block, a static mixer, or the like can be used, and these may be arbitrarily combined.

  The resin melt thus obtained is discharged as a sheet-like melt from a die, extruded onto a cooling body such as a casting drum, and solidified by cooling to obtain a non-oriented sheet. As a specific method of obtaining a non-oriented sheet from a sheet-like melt, using a wire-like, tape-like, needle-like or knife-like electrode, the sheet-like melt is electrostatically applied to a cooling body such as a casting drum. It is preferable to use a method in which the solidification and the rapid solidification are performed. Other methods include blowing air from a slit-shaped, spot-shaped or planar-shaped device to bring the sheet-like molten material into close contact with a cooling body such as a casting drum to rapidly cool and solidify, or cooling the sheet-like molten material with a nip roll A method in which the material is brought into close contact with the body and solidified by rapid cooling is also preferable.

  Next, the obtained non-oriented sheet is stretched in the longitudinal direction (longitudinal stretching) to obtain a uniaxially oriented sheet. Longitudinal stretching can be performed in one stage using one or a plurality of stretching rolls having the same peripheral speed, or can be performed in multiple stages using a plurality of stretching rolls having different peripheral speeds, The magnification is preferably 2 to 7 times. In the longitudinal stretching, after the non-oriented sheet is heated by the preheating roll, the non-oriented sheet can be further heated by an infrared heater or the like.

  Further, after the longitudinal stretching, a step of applying a coating agent for forming a functional layer such as an easily adhesive layer on both surfaces or one surface of the obtained uniaxially oriented sheet may be provided. The method for applying the coating agent is not particularly limited, and for example, a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a wire bar coating method, a die coating method, a spray coating method, and the like can be used.

  Thereafter, the uniaxially oriented sheet obtained by longitudinal stretching is guided to a tenter device, and is stretched (transversely stretched) in the width direction to obtain a biaxially oriented film. The preheating zone of the tenter device used for performing the horizontal stretching includes a gas circulation path having a platinum catalyst and a heating mechanism inside. Then, the temperature of the platinum catalyst is controlled at 250 ° C. or more and less than 400 ° C. By adopting such an embodiment, it is possible to reduce the contamination of the apparatus and the generation of foreign matter due to the precipitation of melamines, and to reduce the frequency of replacement of the platinum catalyst. From the above viewpoint, the temperature of the platinum catalyst in the gas circulation path of the preheating zone is preferably controlled at 290 ° C to 360 ° C, more preferably at 290 ° C to 340 ° C.

  In the tenter device, the heat fixing zone may further include a gas circulation path having a platinum catalyst and a heating mechanism therein. By adopting such an embodiment, it is possible to reduce the contamination of the apparatus and the generation of foreign substances due to the precipitation of the oligomer that sublimes mainly in the heat fixing zone, and to reduce the exchange frequency of the platinum catalyst. From the above viewpoint, the temperature of the platinum catalyst in the gas circulation path of the heat setting zone is preferably controlled to be higher than 210 ° C. and equal to or lower than 400 ° C.

  The tenter device grips both ends in the width direction of the uniaxially oriented sheet with clips running inside the tenter device, and runs the preheating zone, the stretching zone, the heat fixing zone, and the cooling zone in this order, thereby bringing the uniaxially oriented sheet to the stretching temperature. The film is heated and stretched in the horizontal direction, and then heat-set and cooled. Thus, a biaxially oriented film can be obtained. Each zone in the tenter device may be configured with only one room, or may be configured with a plurality of rooms that can change the temperature setting for each zone.

  The temperature of the preheating zone and the stretching zone is preferably from 80 to 160 ° C, more preferably from 85 to 130 ° C, and more preferably from 90 to 120 ° C, depending on the thickness of the finally obtained film, the stretching speed, and the presence or absence of in-line coating. Is more preferred. By setting the temperature of the preheating zone and the stretching zone to 80 ° C. or higher, film breakage is reduced, and by setting the temperature to 160 ° C. or lower, a film having sufficient strength can be obtained.

  The magnification of the transverse stretching depends on the thickness of the finally obtained film, the stretching speed, the presence or absence of in-line coating, and the like, but from the viewpoint of preventing stretching unevenness and film breakage, is preferably 2.5 to 6.0 times, 3.0-5.5 times are more preferable, and 3.5-5.0 times are still more preferable.

  When the platinum catalyst is also introduced into the heat setting zone, the temperature of the heat setting zone may be 210 ° C. or more and 300 ° C. or less from the viewpoint of stabilizing the structure of PET by crystallization and activating the platinum catalyst. Preferably, it is 220 ° C. or higher and 300 ° C. or lower, more preferably 230 ° C. or higher and 300 ° C. or lower.

  In the method for producing a film of the present invention, after the transverse stretching step, in order to reduce the occurrence of scratches and the like caused by friction of the film surface when winding as an intermediate roll described later, a knurl is formed near both ends in the width direction. Embossing may be performed. The embossed portion can be cut and removed in the process of forming a final product, similarly to the edge portion having a large film thickness.

  The biaxially oriented film thus obtained is cooled in the subsequent transporting step, and once wound up as an intermediate roll by a wide winding machine, then cut by a slitter to a required width and length, and the final product is formed. Become.

  The film obtained by the present invention has few defects caused by melamines and oligomers, and can be used as various optical films. Specifically, it can be suitably used as a base film for a prism sheet, a base film for a hard coat, a base film for an anti-reflection (AR) film, a base film for light diffusion, a transparent conductive film, and the like.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples. The tenter devices used in the examples and comparative examples, the measuring methods for each item, and the like are as follows.

[Tenter device]
In the tenter apparatus, the preheating zone, the stretching zone, the heat setting zone, and the cooling zone are located in this order, and the preheating zone is divided into two rooms, the stretching zone is divided into four rooms, and the heat fixing zone is divided into four rooms. Was used. The temperature is made uniform in all the rooms in each zone, and when a platinum catalyst (trade name: NM-12, manufactured by JGC Universal Co., Ltd.) is placed, it is placed in the gas circulation path of the preheating zone and heated by an electric heater (seeds heater). To control the temperature (Examples 1 to 6 and Comparative Examples 1 and 2 described later). In addition, the platinum catalyst in the preheating zone is located in the circulation path of the room closer to the stretching zone among the two rooms in the preheating zone, and the platinum catalyst in the heat fixing zone is located in the third room counting from the stretching zone side. Each was provided in the circulation path. As a nozzle for blowing air onto the film, a hole nozzle (H: 170 mm, B: 13 mm, Examples 1 to 5 and Comparative Examples 1 to 3, which will be described later), or a slit nozzle (H: 170 mm, B: 2,700 mm) Example 6) was used. Here, H is the distance between the ejection hole of the nozzle and the film, and B is the major diameter of the ejection hole.

  Hereinafter, a more specific description will be given with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a room on the downstream side of a preheating zone in a tenter device used in Example 1 when cut along a film surface and a surface perpendicular to a longitudinal direction. In the room 2 of the preheating zone in the tenter device 1, a gas whose temperature is controlled is blown from nozzles 4a and 4b disposed above and below the sheet 3 traveling inside the room. The ejected gas is circulated in the gas circulation path 5 by a circulation fan 6 driven by a motor (indicated by M in FIG. 1), temperature-controlled by a steam heater 7, and ejected again from the nozzles 4a and 4b. Is done. A platinum catalyst 9 is provided on the upstream side of the filter 8 in the gas circulation path 5 (upstream of the steam heater 7), and an electric heater 10 (seeds heater: 1.7 kW × 10) is provided so as to face the platinum catalyst 9. Is arranged. With this electric heater 10, the platinum catalyst 9 can be heated to a desired temperature.

[Pollution risk by melamines]
The amount of melamines deposited in the rooms constituting each zone was measured according to the following procedures (1) to (4), and the risk of melamine contamination was evaluated according to the following evaluation criteria. The risk of contamination by melamine was highest in S, and S to C were considered acceptable.

(Measurement of melamine precipitation amount)
(1) Six platinum catalysts (size: 300 mm x 400 mm x 10 mm) are attached to a SUS304 frame, and the cross-sectional shape when cut to minimize the area is a rectangle of 1600 mm x 2,100 mm. It was installed in the gas circulation path. Then, a SUS metal piece (100 mm × 100 mm × 2 mm) whose mass was measured in advance was fixed at a position 10 mm away from the leeward surface of the platinum catalyst. Thereafter, as described in each of the following Examples and Comparative Examples, a film was manufactured over a period of one year to one year and 15 days. In a place where the platinum catalyst is not placed, a metal piece is placed at a position where the distance to the frame is equal, and in the stretching zone, the metal piece is placed in the gas circulation path of the first room counted from the preheating zone side. Pieces were placed.
(2) The metal piece attached in (1) was removed, the mass was measured, and the mass of the attached piece was determined by subtracting the previously measured mass of the metal piece.
(3) Part of the deposit was sublimated again at 250 ° C., and the sublimate was collected with 25 mL of ethanol. The collected sublimate was introduced into a trace nitrogen analyzer (ND-100, manufactured by Mitsubishi Chemical Corporation), pyrolyzed and oxidized, and the generated nitric oxide was measured by a chemiluminescence method. For the quantification, the concentration was automatically calculated from a calibration curve prepared using a pyridine standard solution in advance. The measurement conditions were as follows: the thermal decomposition portion was 800 ° C., and the oxygen flow rate was 300 ml / min. From the obtained nitrogen-containing concentration, the mass ratio of the nitrogen-containing substance to the entire attached matter was determined.
(4) The mass of the deposit obtained in (2) is multiplied by the mass ratio of the amount of the nitrogen-containing substance obtained in (3) to calculate the amount of deposit of the nitrogen-containing material. And

(Evaluation criteria)
S: The amount of melamines precipitated was 0.90 g or less in the preheating zone, 0.20 g or less in the stretching zone, and 0.50 g or less in the heat fixing zone.
A: The amount of melamines precipitated was more than 0.90 g in the preheating zone and 1.00 g or less, 0.20 g or less in the stretching zone, and 0.50 g or less in the heat fixing zone.
B: Melamine precipitation amount was 1.00 g or less in the preheating zone and 0.20 g or less in the stretching zone, but exceeded 0.50 g in the heat fixing zone.
C: Melamine precipitation amount was 1.00 g or less in the preheating zone, but exceeded 0.20 g in the stretching zone.
D: Not applicable to any of SC.

[Risk of formaldehyde leakage]
Using "INTERLIGENT AIR DETECTOR WP6930S" (manufactured by Shenzhen City Amami Science & Technology Co., Ltd.), which was previously performed in the formaldehyde-free air, the formaldehyde concentration (ppm) in the air was measured at intervals of 1 second over 60 seconds. The average of the obtained values was taken as the formaldehyde concentration in air (ppm). At this time, the measurement point is the entrance of the tenter device in the longitudinal direction, the center of the film to be conveyed in the width direction, and the position of the film in the height direction (direction perpendicular to the film surface). The point was a point 100 mm away from the side surface. Based on the obtained formaldehyde concentration in the air (ppm), the formaldehyde leakage risk was evaluated according to the following evaluation criteria, and only ○ was regarded as acceptable.
：: The formaldehyde concentration in the air was 0.1 ppm or less.
X: The formaldehyde concentration in the air exceeded 0.1 ppm.

(Example 1)
Polyethylene terephthalate having an intrinsic viscosity of 0.6 was melt-extruded at 285 ° C. by an extruder, and discharged from a die in a sheet shape. The obtained sheet-like material is cooled and solidified by a cooling drum having a surface temperature of 30 ° C. to form a non-oriented film, and is subjected to a longitudinal stretching at a temperature of 90 ° C. and a magnification of 3.5 times using a longitudinal stretching machine having a plurality of rolls. Stretched. On the obtained uniaxially oriented sheet having a width of 1.0 m, a coating agent containing 1 wt% of melamine and containing formaldehyde is applied inline by a bar coating method so as to have a thickness of 6 μm, and then a preheating zone is formed. It was introduced into a tenter device in which a platinum catalyst was arranged in the gas circulation path of the downstream room of the two chambers, and preheating was performed under the condition that the temperature of the gas ejected from the hole nozzle was controlled at 110 ° C. Subsequently, the film was stretched in the width direction at a temperature of 115 ° C. and a magnification of 3.5, and then subjected to a heat fixing process in an environment in which the temperature of the gas ejected from the hole nozzle in the heat fixing zone was controlled at 230 ° C. The heat setting zone also had a gas circulation path, and a platinum catalyst was arranged in the gas circulation path in the third room from the upstream side. Thereafter, the biaxially oriented film was cooled to 70 ° C. or lower and wound up at a speed of 75 m / min by a winder to obtain a biaxially oriented film roll having a thickness of 40 μm. The average film transport speed in the tenter was controlled at 22 m / min. After a period of 1 year to 1 year and 15 days has elapsed since the operation of the tenter apparatus, the amount of melamines deposited in each zone was measured by the above-described method, and the risk of contamination by melamines was evaluated. The evaluation of the formaldehyde leakage risk was performed within 10 days from the start of the operation of the tenter device. Table 1 shows the evaluation results.

(Examples 2 to 6 Comparative Examples 1 to 3)
Production of a film and evaluation of each item were performed in the same manner as in Example 1 except that the presence or absence of the platinum catalyst in the preheating zone and the heat fixing zone, the temperature, and the nozzle in the preheating zone were as shown in Table 1. Table 1 shows the evaluation results.

  According to the present invention, a sublimable organic compound or a volatile organic compound generated from a film, a coating material, or the like is decomposed over a long period of time. It is possible to provide a film manufacturing method capable of reducing the occurrence.

DESCRIPTION OF SYMBOLS 1 Tenter apparatus 2 Room 3 of preheating zone Sheet 4a, 4b Nozzle 5 Gas circulation path 6 Circulation fan 7 Steam heater 8 Filter 9 Platinum catalyst 10 Electric heater

Claims (7)

A film manufacturing method having a stretching step of stretching a sheet in at least one direction with a tenter device including a preheating zone and a stretching zone in order from the upstream side,
The preheating zone includes a gas circulation path, the gas circulation path includes a platinum catalyst and a heating mechanism inside, and controls the temperature of the platinum catalyst to be 250 ° C. or more and 400 ° C. or less. Manufacturing method.   The method for producing a film according to claim 1, wherein the preheating zone includes means for suppressing gas flow in a longitudinal direction.   The method for producing a film according to claim 1, further comprising a heat setting zone downstream of the stretching zone.   The heat fixing zone includes a gas circulation path, the gas circulation path has a platinum catalyst and a heating mechanism inside, and controls the temperature of the platinum catalyst to be more than 210 ° C. and 400 ° C. or less. The method for producing a film according to claim 3.   The film according to any one of claims 1 to 4, further comprising, before the stretching step, a step of applying a coating material containing at least one of a sublimable organic compound and a volatile organic compound. Production method.   The method according to claim 5, wherein the sublimable organic compound contains melamines. The method according to claim 5, wherein the volatile organic compound includes at least one of butyl cellosolve, acetaldehyde, and formaldehyde.

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