JP2020104303A - Method of producing film - Google Patents

Abstract

To provide a method of producing film capable of reducing splitting of non-oriented film in a process of obtaining the non-oriented film through cooling and solidification on a cooling drum.SOLUTION: A method of producing film of this invention includes a cast step of extruding a molten thermoplastic resin composition in a sheet from a die and cooling and solidifying the composition by a cooling drum to obtain non-oriented film. In a range from a point horizontal to a rotation axis of the cooling drum to a base of the cooling drum on a surface of the non-oriented film, if a circle having a diameter of 150 mm is an area A; an area with a centroid thereof being positioned on a center of the area A, with a diameter thereof being 50 mm or more and less than 150 mm, and occupying part of the area A is an area B; an area being a remainder obtained by subtracting the area B from the area A is an area C; an average temperature of the area B is b (°C); and an average temperature of the area C is c (°C), then (c-b) is constantly 5 (°C) or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for producing a film having excellent film-forming stability.

A film obtained by molding a thermoplastic resin into a thin film is, due to its excellent mechanical properties, electrical properties, etc., thermal transfer applications, thermal stencil applications, photographic applications, graphic applications, adhesive tapes, packaging materials, It is preferably used as various industrial materials such as materials for automobiles, building materials, flexible printed boards, membrane switches, sheet heating elements, electric insulating materials such as flat cables, magnetic recording materials, and materials for capacitors.

The film is manufactured through a process of extruding a molten thermoplastic resin into a sheet form from a die, cooling and solidifying the sheet on a rotating cooling drum to form a sheet. Usually, it is required for the film to have few surface irregularity defects, and as a means for reducing the surface irregularity defects, for example, a method of forming a water film on a cooling drum is adopted. In this method, water vapor is continuously applied to the widthwise surface of the rotating cooling drum to form a water film, and the molten thermoplastic resin is extruded to the water film forming part, and is cooled and solidified while applying electrostatic force. By peeling the obtained sheet, it is possible to reduce the occurrence of uneven defects at this stage. It is also known to provide a water film removing unit for removing the remaining water film in order to form a uniform water film on the surface of the cooling drum again after peeling the sheet (Patent Documents 1 and 2). ).

By interposing a water film between the molten thermoplastic resin and the surface of the cooling drum in this way, it is possible to eliminate air that accompanies the thermoplastic resin. As a result, the generation of fine bubbles on the surface of the non-oriented film obtained by forming a sheet is suppressed, and the generation of uneven defects due to the fine bubbles is reduced.

Further, in recent years, in order to improve productivity, the film production rate itself has been increased. When the film production rate is increased, the rotation speed of the cooling drum also usually increases, so that more air is trapped between the molten thermoplastic resin and the surface of the cooling drum. In view of this tendency, there is a growing need for a technique for reducing surface irregularity defects.

JP-A-1-241413 JP-A-2014-193597

However, although the methods of Patent Documents 1 and 2 can improve the adhesion between the cooling drum and the thermoplastic resin and the flatness of the non-oriented film, a sufficient study has been made on the problem that the non-oriented film cracks during cooling and solidification. Was not done. Further, in Patent Document 2, it was considered that the problem of the non-oriented film cracking on the cooling drum having the water film formed was that the variation in the strength of electrostatic application due to the unevenness of the thickness of the water film was a major factor. Therefore, attempts have been made to deal with this problem by making the water film thicker or uniform, but the effect of suppressing cracking of the non-oriented film is not sufficient.

In view of the background of the related art, the present invention provides a method for producing a film capable of reducing cracks in a non-oriented film in a step of cooling and solidifying on a cooling drum to obtain a non-oriented film. And

In order to solve the above problems, the present invention has the following configurations.

That is, the present invention can be achieved by the following.
(1) A method for producing a film, which comprises a step of extruding a molten thermoplastic resin composition into a sheet form from a die, and cooling and solidifying the same by a cooling drum to obtain an unoriented film, which is a location horizontal to a rotation axis of the cooling drum. On the surface of the non-oriented film in the range from to the bottom of the cooling drum, a circle having a diameter of 150 mm is a region A, the center of gravity is on the center of the region A, the maximum diameter is 50 mm or more and less than 150 mm, and a region occupying a part of the region A. Is a region B, a region obtained by subtracting the region B from the region A is a region C, an average temperature of the region B is b (° C.), and an average temperature of the region C is c (° C.), (c−b) is always It is 5 (degrees C) or less, The manufacturing method of the film characterized by the above-mentioned.
(2) The method for producing a film according to (1), wherein the thickness of the non-oriented film is 10 μm or more and 150 μm or less.
(3) The method for producing a film according to (1) or (2), wherein the rotation speed of the cooling drum is 20 m/min or more and 120 m/min or less.
(4) The method for producing a film according to any one of (1) to (3), wherein a water film having a thickness of 0.5 μm or more and 5.0 μm or less is formed on the surface of the cooling drum.
(5) The method for producing a film according to any one of (1) to (4), wherein the thermoplastic resin composition contains a polyester resin as a main component.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the film which can reduce the crack of a non-oriented film in the process of cooling and solidifying on a cooling drum and obtaining a non-oriented film can be provided.

It is a schematic diagram showing a schematic diagram of a casting process. It is a schematic diagram showing a non-oriented film and areas A to C on a cooling drum.

The present invention is a method for producing a film having a casting step in which a molten thermoplastic resin composition is extruded from a die in a sheet shape and cooled and solidified in a cooling drum to obtain a non-oriented film, which is horizontal to the rotation axis of the cooling drum. On the surface of the non-oriented film in the range from the location to the bottom of the cooling drum, a circle having a diameter of 150 mm is in the region A, the center of gravity is on the center of the region A, and the maximum diameter is 50 mm or more and less than 150 mm and occupies a part of the region A. When the region is the region B, the region A is the region B minus the region C, the average temperature of the region B is b (° C.), and the average temperature of the region C is c (° C.), (c−b) is The feature is that the temperature is always 5 (° C.) or less. Here, the non-oriented film refers to a film obtained by extruding a molten thermoplastic resin into a sheet shape and cooling and solidifying the extruded sheet. In addition, the film, in general, a thermoplastic resin molded into a sheet, in addition to non-oriented film, uniaxially oriented film having molecular orientation in one direction, biaxially oriented film having molecular orientation in two directions. Including.

The method for producing a film of the present invention has a casting step in which a molten thermoplastic resin composition is extruded from a die into a sheet shape and cooled and solidified by a cooling drum to obtain a non-oriented film. Here, the molten thermoplastic resin composition refers to a composition containing a thermoplastic resin as a main component and the thermoplastic resin in a molten state. The term "main component" as used herein refers to a component that is contained in an amount of more than 50% by mass and 100% by mass or less based on all components constituting the thermoplastic resin composition, and hereinafter, the main component can be similarly interpreted. .. By adopting such an embodiment, the extruded molten thermoplastic resin composition can be molded into a sheet, and a non-oriented film can be easily obtained. The non-oriented film obtained in the casting step may be then peeled off from the cooling drum and wound, or may be further stretched in a uniaxial or biaxial direction to give a uniaxially oriented film or a biaxially oriented film.

The thermoplastic resin constituting the molten thermoplastic resin composition in the method for producing a film of the present invention is not particularly limited as long as it does not impair the effects of the present invention, for example, polyethylene, polypropylene, polyolefin resins such as polymethylpentene, nylon. 6, polyamide resin such as nylon 66, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN), polybutylene naphthalate (PBN), polytrimethylene terephthalate (PPT), polyethylene Polyester resins such as -p-oxybenzoate and poly-1,4-cyclohexylene dimethylene terephthalate (PCT), and polycarbonate resins can be used alone or in combination. Among them, from the viewpoint of mechanical strength, heat resistance, chemical resistance, durability, and versatility of the obtained film, it is preferable that the thermoplastic resin composition contains a polyester resin as a main component, and PET or PEN is mainly used. More preferably, it is used as a component. When the molten thermoplastic resin composition contains a plurality of thermoplastic resins, the content of the thermoplastic resin is calculated by adding all the thermoplastic resins.

In the method for producing a film of the present invention, the polyester resin refers to a resin having a molecular structure in which diol units and dicarboxylic acid units are alternately repeated. For example, dicarboxylic acid or its ester-forming derivative (hereinafter, these are collectively referred to as these. Dicarboxylic acid and the like) and diol or derivatives thereof (hereinafter, these may be collectively referred to as diol and the like). Examples of the diol and the like include ethylene glycol, diethylene glycol, neopentyl glycol, polyalkylene glycol and the like, and examples of the dicarboxylic acid and the like include terephthalic acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid. Acid etc. are mentioned.

Further, the thermoplastic resin in the present invention may be a copolymer containing a copolymerized unit in the molecular chain as long as the effect of the present invention is not impaired. Examples of such a copolymer include a diol unit other than the diol unit most contained in the molecular chain, and a polyester containing dicarboxylic acid units other than the dicarboxylic acid unit most contained in the molecular chain in the molecular chain. In addition to resins, polyacetal resins, polyphenylene sulfide resins, etc. may be mentioned.

Further, the molten thermoplastic resin composition is a known additive, for example, a stabilizer, a viscosity modifier, an antioxidant, a filler, a slip agent, an antistatic agent, an antiblocking agent, as long as the effects of the present invention are not impaired. A release agent, a release agent, and the like can also be included.

The manufacturing method of the film of the present invention, from the viewpoint of reducing the crack of the non-oriented film at the time of peeling from the cooling drum, in the non-oriented film surface in the range from the rotation axis of the cooling drum to the cooling drum bottom side, which is horizontal, A circle with a diameter of 150 mm is the region A, the center of gravity is on the center of the region A, the maximum diameter is 50 mm or more and less than 150 mm, the region occupying a part of the region A is the region B, and the region obtained by subtracting the region B from the region A is When the average temperature of the regions C and B is b (° C.) and the average temperature of the region C is c (° C.), it is important that (c−b) is always 5 (° C.) or less.

With such a mode, it is possible to suppress the occurrence of local temperature decrease occupying a certain area on the non-oriented film that is in close contact with the cooling drum. Therefore, the cooling effect in the cooling drum is made uniform over the entire non-oriented film, and cracks in the non-oriented film that occur mainly when peeled from the cooling drum can be reduced. From the above viewpoint, (c-b) is preferably 3°C or lower, and more preferably 1°C or lower. From the above viewpoint, the more uniform the temperature of the non-oriented film is, the more preferable. Therefore, the lower limit of (c-b) is 0°C.

Hereinafter, a method of measuring each region and temperature will be specifically described with reference to the drawings. 1 is a schematic view showing a schematic view of a casting process (a schematic view when observed in parallel with a rotation axis), and FIG. 2 is a schematic view showing a non-oriented film and regions A to C on a cooling drum ( It is a schematic view when observed perpendicularly to the axis of rotation. As shown in FIG. 1, in the casting step, the molten thermoplastic resin composition is extruded from the die 3 in a sheet shape onto the cylindrical cooling drum 2 which rotates about the rotating shaft 1 in the direction of the arrow to be cooled and solidified. Thereby, the non-oriented film 4 can be obtained.

In the present invention, "a range from a location horizontal to the rotation axis of the cooling drum to the bottom of the cooling drum" means a line where the horizontal plane including the center line of the rotation axis 1 and the non-oriented film 4 intersect, and the bottom of the cooling drum. Section, that is, the range indicated by reference numeral 5 in FIGS. Region A (reference numeral 6 in FIG. 2) is a circle having a diameter of 150 mm drawn on the curved surface of the non-oriented film in the range indicated by reference numeral 5. A region B (reference numeral 7 in FIG. 2) is a region that occupies a part of the region A6, the center of gravity is on the center of the region A, and the maximum diameter is 50 mm or more and less than 150 mm. Here, the maximum diameter means a distance between two points on the outer circumference of the area B7 so that the distance becomes maximum. Although the region B is illustrated as a circle in FIG. 2, the shape of the region B7 is not particularly limited as long as the above requirements are satisfied. The area C (reference numeral 8 in FIG. 2) is the remaining area excluding the area B7 from the area A6. “When the average temperature of the region B is b (° C.) and the average temperature of the region C is c (° C.), (c−b) is always 5 (° C.) or less” means a region satisfying the above requirements. It means that (c−b) is always 5° C. or lower, regardless of how B and region C are set. To be more simple, it means that there is no region in the range of reference numeral 5 that is locally lower than the surrounding average temperature by 5 degrees or more.

Whether or not (c-b) is always 5 (° C.) or less can be determined by the following procedure. First, the temperature of the non-oriented film in a range from a position horizontal to the rotation axis of the cooling drum to the bottom of the cooling drum is displayed as an image by thermography, and the maximum diameter is 50 mm or more and less than 150 mm when analyzed or visually observed. Specify the part where the temperature difference from the surroundings is the largest (the part where the temperature is extremely lower than the surroundings). Next, after setting the region A centering on the center of the part, regions B and C are set inside the region A using an image analyzer or the like so that the average temperature difference becomes maximum, and the average temperature of the region B is set. b(° C.) and the average temperature c(° C.) of the region C are calculated, and (c−b) is calculated. If the value of (c-b) thus obtained is 5° C. or lower, it can be determined that (c-b) is always 5 (° C.) or lower.

Thermography is a device that analyzes infrared rays radiated from an object and displays an image that represents the heat distribution as a diagram.In the image obtained by thermography, normally, from the lowest temperature, blue, light blue, green, Yellow and red colors are distributed. The upper detection limit and the lower detection limit of thermography can be appropriately adjusted according to the specifications of the apparatus, cooling conditions, etc., but from the viewpoint of efficiently detecting a difference of 5° C., the temperature between the upper detection limit and the lower detection limit is 10° C. The detection lower limit can be set to 45° C. and the detection upper limit can be set to 55° C., for example. An image obtained by thermography exhibits blue when the temperature reaches the lower detection limit and red when the temperature reaches the upper detection limit, but the color does not change depending on the temperature change below the lower detection limit or above the upper detection limit.

In the local cooling part where the value of (c−b) exceeds 5° C., since the region B adheres to the cooling drum more firmly than the region C, a difference in crystallization occurs between the regions B and C, and peeling occurs. It is believed that the non-oriented film sometimes cracks. Further, the cooling drum plays a role of cooling the molten thermoplastic resin to a glass transition temperature or lower and solidifying it, but at the same time, since crystallization of the thermoplastic resin is suppressed, in the region B where the temperature is low, the peripheral region C The crystallization of the thermoplastic resin is not promoted as compared with. When the non-oriented film is peeled from the cooling drum by applying force in such a state that the crystallinity is non-uniform, even if the relatively high crystallinity part is peeled, the relatively low crystallinity part It is considered that one of the reasons why the crack of the non-oriented film occurs at the time of peeling is that it cannot follow sufficiently. Conventionally, when solidifying on a cooling drum, a method has been adopted in which static electricity is applied to improve the adhesion between the non-oriented film and the cooling drum. Although it was considered to be unevenness, as a result of examination by the present inventor, it was found that it was due to the local cooling portion as described above.

If the area where the local temperature drop is observed is excessively large, the imbalance in crystallinity is alleviated. Further, when the area where the local temperature decrease is observed is excessively small, the area of the portion where the adhesion to the cooling drum becomes high can be suppressed. Therefore, even if there is a locally low temperature such that the maximum diameter is less than 50 mm or 150 mm or more, the non-oriented film is unlikely to crack when peeled from the cooling drum. Considering this point, the maximum diameter of the region B is preferably 60 mm or more and 140 mm or less, and more preferably 70 mm or more and 130 mm or less.

On the surface of the non-oriented film in the range from the position parallel to the rotation axis of the cooling drum to the bottom of the cooling drum, a circle having a diameter of 150 mm is located in the area A, the center of gravity is located on the center of the area A, and the maximum diameter is 50 mm or more and less than 150 mm. When a region occupying a part of the region A is a region B, a region obtained by subtracting the region B from the region A is a region C, an average temperature of the region B is b (°C), and an average temperature of the region C is c (°C). In addition, the method for keeping (c-b) always 5 (° C.) or less or the above preferable range is not particularly limited as long as the effects of the present invention are not impaired, but the temperature of the surface of the cooling drum is controlled more uniformly. There is a method.

A specific example of a method for controlling the surface temperature of the cooling drum more uniformly will be described below in view of the mechanism that the surface temperature of the cooling drum becomes uneven. The cooling drum is usually provided with pipes in parallel with the width direction or in a spiral shape. The surface temperature of the cooling drum can be controlled by inflowing the cooling medium whose temperature is controlled from one end of this pipe and letting it flow out from the other end. Industrial water is generally used as the cooling medium, but since this industrial water contains metallic components such as iron and manganese, as well as foreign substances such as evaporation residues, the cooling drum is used for a long period of time. If the industrial water is continuously flowed into the pipe, the foreign matter may adhere to the inner side surface of the cooling drum and partially deposit, or the foreign matter may react with the metal on the side surface of the pipe to form an aggregate. Since the temperature unevenness on the surface of the cooling drum locally occurs due to the generation and fall of these deposits and agglomerates, such deposits and agglomerates can be quickly removed by regularly cleaning the piping. By removing it, the surface temperature of the cooling drum can be controlled more uniformly.

The cleaning agent used for cleaning the pipe can be appropriately selected from known ones within a range that does not impair the effects of the present invention, but it is preferable to use a cleaning agent containing hydrogen peroxide from the viewpoint of the cleaning effect. .. As the cleaning agent containing hydrogen peroxide, a slime removing agent (“Thai slime” (registered trademark) DS manufactured by Ichinen Chemicals Co., Ltd.) and the like can be preferably used. The concentration of the cleaning agent can be appropriately determined depending on the composition, the material of the pipe, the amount of deposits and aggregates in the pipe, and the like. When the slime remover is used, 100% by volume of the entire aqueous solution is used. At this time, it is preferable to make the aqueous solution containing the slime removing agent in an amount of 1% by volume or more and 15% by volume or less, and more preferably 5% by volume or more and 10% by volume. When the concentration of the slime removing agent is 1% by mass or more, a sufficient cleaning effect can be obtained, and when it is 15% by volume or less, damage to the pipe can be reduced.

In the film production method of the present invention, the thickness of the non-oriented film is preferably 10 μm or more and 150 μm or less from the viewpoint of maximizing the effects of the present invention. By adopting such a mode, it is possible to reduce the occurrence of thickness unevenness and reduce cracking of the non-oriented film when peeled from the cooling drum. When the thickness of the non-oriented film is 150 μm or less, the thermal effect (cooling effect) of the cooling drum spreads in the entire thickness direction of the film, and the temperature unevenness of the cooling drum propagates to the entire non-oriented film, so that cracks easily occur. .. Therefore, the advantage of using the film production method of the present invention becomes greater when the thickness of the non-oriented film is 150 μm or less. Further, by setting the thickness of the non-oriented film to 10 μm or more, it becomes easy to suppress the occurrence of thickness unevenness when the molten thermoplastic resin is extruded into the cooling drum and molded.

In the method for producing a film of the present invention, the rotation speed of the cooling drum is preferably 20 m/min or more and 120 m/min or less from the viewpoint of maximizing its advantages and suppressing the occurrence of thickness unevenness. By setting the rotation speed of the cooling drum in the above range, cracking of the non-oriented film at the time of peeling from the cooling drum can be easily suppressed even when the thickness of the solidified by cooling is 10 μm or more and 150 μm or less. When the rotation speed of the cooling drum is 20 m/min or more, the time required for solidification by cooling (the time during which the non-oriented film is in close contact with the cooling drum) becomes short, so that the cooling must be performed rapidly, and therefore local cooling is required. Parts are likely to occur. Therefore, the advantage of using the method for producing a film of the present invention is great. On the other hand, when the rotation speed of the cooling drum is 120 m/min or less, the entrainment of air due to the increase in the rotation speed of the cooling drum is suppressed, and as a result, the occurrence of uneven thickness of the non-oriented film is reduced.

In the film manufacturing method of the present invention, it is preferable to form a water film on the surface of the cooling drum. As a means for forming a water film, air containing water vapor is sprayed on the surface of the cooling drum kept below its dew point to cause dew condensation (condensation method), or a method of spraying water vapor having an electrostatic charge, a roller. There are methods such as bleeding or transfer coating. The water film may be film-like at the time of application, or may be dot-like like water droplets due to dew condensation or water vapor, as long as the film is film-like at the time of grounding.

Further, when a water film is formed on the surface of the cooling drum, the water remaining on the surface of the cooling drum after peeling the non-oriented film from the surface of the cooling drum may cause thickness unevenness in the width direction and the longitudinal direction. Since the amount of water is large, it is preferable to remove water by an air blow vacuum method, a suction roll or the like between the peeling of the non-oriented film and the formation of a new water film.

In the method for producing a film of the present invention, it is preferable to form a water film having a thickness of 0.5 μm or more and 5.0 μm or less on the surface of the cooling drum from the viewpoint of reducing the thickness unevenness of the non-oriented film. By setting the thickness of the water film to be 5.0 μm or less, the air existing between the molten polyester resin and the cooling drum is pushed out, while the aggregation due to the surface tension of the water film on the cooling drum is suppressed and the water film component is used. By reducing the formation of the wavy shape, it is possible to reduce the unevenness in the thickness of the water film. Since the thickness unevenness of the water film directly affects the thickness unevenness of the non-oriented film after cooling and solidification, even if the thickness of the water film is set in consideration of further suppressing the formation of the wave shape due to the water film component. Good. Considering this point, the thickness of the water film is more preferably 3.0 μm or less, further preferably 2.0 μm or less. Further, the lower limit of the thickness of the water film is 0.5 μm in order to reduce the formation of uneven defects on the surface of the non-oriented film due to the entrained airflow being caught between the molten thermoplastic resin composition and the cooling drum. Become.

When the film to be produced is a biaxially oriented film having a thickness of 1 μm or more and 5 μm or less, the non-oriented film is stretched in the running direction (longitudinal direction) of the film or in the direction (width direction) orthogonal to the longitudinal direction in the plane. Although it is general to provide a step to make the film thin, if the film is stretched at an excessively high stretching ratio, the film often breaks. Therefore, the stretching ratio has an upper limit. Therefore, in manufacturing such a biaxially oriented film having a small thickness, a method of forming a non-oriented film into a thin film so as to have a thickness in the above range is adopted. When the thickness of the non-oriented film is small as described above, the uneven thickness of the water film is likely to be directly reflected on the non-oriented film. Furthermore, since the thickness of the finally obtained biaxially oriented film is thin, the unevenness of the thickness of the non-oriented film also has a large effect on the surface defects and the unevenness of thickness of the stretched biaxially oriented film. From this point of view, there is an advantage that the unevenness of the thickness of the water film can be suppressed.

When forming a water film on the surface of the cooling drum in the method for producing a film of the present invention, from the viewpoint of preventing the water film from drying, in a gas atmosphere until the polyester resin is peeled off after being cooled and solidified from the water film forming portion. It is also preferable to control the water content in the range of 10 g/m ³ or more and 20 g/m ³ or less.

In the method for producing a film of the present invention, when the thermoplastic resin constituting the molten thermoplastic resin composition contains a polyester resin, the polyester resin may contain a copolyester resin. Here, the copolymerized polyester resin means a polyester resin in which at least one of a dicarboxylic acid unit and a diol unit, which are repeating units, is composed of a plurality of types of constitutional units. The proportion of copolymerized units in the polyester resin is not particularly limited as long as it does not impair the effects of the present invention, from the viewpoint of reducing unevenness defects and thickness unevenness of the surface while maintaining film-forming stability, molten thermoplastic resin composition When the total dicarboxylic acid units and total diol units of the polyester resin therein are 100 mol %, 10 mol% or more is preferable, 12 mol% or more is more preferable, and 15 mol% or more is further preferable. By adopting such a mode, it is possible to suppress crystallization when the melted thermoplastic resin on the water film formed on the cooling drum is solidified, and therefore cracks in the film can be reduced. Further, the adjustment of the proportion of copolymerized units in the polyester resin, it is possible to use only a copolymerized polyester resin having a low proportion of copolymerized units, but to prepare a copolymerized polyester resin master having a high proportion of copolymerized units, May be mixed with a homopolyester consisting only of the main dicarboxylic acid units and diol units of the copolyester resin.

Suitable applications for the film obtained by containing the copolyester resin in the molten thermoplastic resin composition include, for example, twist packaging applications in which the twist shape is required to be maintained when the film is twisted. .. Other examples include heat sensitive stencil applications to which a technique of melting a film by perforation heat is applied.

As described above, when the molten thermoplastic resin composition contains the copolyester, the temperature after cooling and solidification is 80° C. or more and 110° C. or less, though it depends on how heat is applied in the film manufacturing process. By controlling the crystallization of the non-oriented film itself at a low temperature, it is possible to obtain a film with a low degree of crystallinity. Such a film having a low crystallinity has a property that the shape after twisting is easily maintained and that the film is easily perforated because the film is melted by the heat of perforation.

Furthermore, in the method for producing a film of the present invention, uneven defects, film cracking, and thickness unevenness are reduced, and the crystallinity of the film-forming stability polyester resin measured by differential scanning calorimetry (DSC) is 30%. It is preferably not less than 60% and not more than 60%. As described above, when the polyester resin contains 10 mol% or more of copolymerized units as described above, the crystallinity tends to be low when the film is formed. Therefore, when using a relatively low crystallinity polyester resin having a crystallinity in the above range as a raw material, by adopting the method for producing a polyester film of the present invention, mitigating cracks during the production process, And a high quality film can be obtained.

On the other hand, even if the molten thermoplastic resin composition does not contain the copolyester as described above, it is possible to reduce the crystallinity of the non-oriented film by lowering the temperature of the cooling drum. However, the lower limit of the surface temperature of the cooling drum is preferably 10° C. from the viewpoint of reducing film cracks caused by uneven cooling due to dew condensation on the cooling drum.

Hereinafter, the film manufacturing method of the present invention will be specifically described by taking a uniaxially oriented film and a biaxially oriented film as examples, but the present invention is not limited to the following embodiments.

First, the resin pellets are supplied to the raw material charging section of the extruder to heat and melt the resin. After that, the amount of extrusion is made uniform by a gear pump or the like, and the melted resin is extruded, and foreign matters and gelled substances are removed through a filter. At this time, the number of extruders may be one or more. When using a plurality of extruders, the thermoplastic resin that has passed through the filter is fed to the laminating apparatus. A multi-manifold die, a feed block, a static mixer, or the like can be used as the laminating device, and these may be combined arbitrarily.

The molten thermoplastic resin composition thus obtained is discharged from the die as a sheet-like melt and cooled and solidified by a cooling drum to obtain a non-oriented film. In this step, it is preferable to enhance the adhesion with the cooling drum by the electrostatic application method. The electrostatic application method is, for example, as shown in Japanese Patent Publication No. 48-29311, applying a high voltage of direct current or alternating current to a molten thermoplastic resin composition, a die, a cooling drum, or the like, and applying an electrostatic force. This is a method of bringing the molten thermoplastic resin composition into close contact with a cooling drum. This method can reduce the trapping of air and the uneven thickness of the non-oriented film.

In this step, a circle having a diameter of 150 mm is located in the area A, the center of gravity is located on the center of the area A, and the maximum diameter is 50 mm on the surface of the non-oriented film in the range from a position horizontal to the rotation axis of the cooling drum to the bottom of the cooling drum. An area that is not less than 150 mm and occupies a part of the area A is an area B, an area obtained by subtracting the area B from the area A is an area C, an average temperature of the area B is b (° C.), and an average temperature of the area C is c( (C) is always 5 (C) or less. As a method for providing such an aspect, for example, it is possible to periodically clean the pipes inside the cooling drum and remove the deposits and agglomerates that affect the surface temperature of the cooling drum at an early stage.

The cleaning agent used for cleaning the pipe can be appropriately selected from known ones within a range that does not impair the effects of the present invention, but it is preferable to use a cleaning agent containing hydrogen peroxide from the viewpoint of the cleaning effect. .. As the cleaning agent containing hydrogen peroxide, a slime removing agent (“Thai slime” (registered trademark) DS manufactured by Ichinen Chemicals Co., Ltd.) and the like can be preferably used. When the slime remover is used, it is preferably diluted with water to 1 volume% or more and 15 volume% or less, more preferably 5 volume% or more and 10 volume% or less from the viewpoint of cleaning effect and damage to piping. Is.

Next, the non-oriented film obtained by cooling and solidifying the molten thermoplastic resin composition may be subjected to uniaxial stretching for stretching in the longitudinal direction or width direction or biaxial stretching for stretching in the longitudinal direction and width direction. .. The biaxial stretching may be carried out by simultaneous biaxial stretching in which two directions are simultaneously stretched, or sequential biaxial stretching in which the uniaxially oriented film obtained by previously stretching in one direction is further stretched in another direction. it can. Stretching in the longitudinal direction in the successive biaxial stretching can be performed by, for example, the difference in the rotation speed of the roll, and simultaneous biaxial stretching and widthwise stretching in the sequential biaxial stretching can be performed by, for example, a tenter device. You can

The draw ratio and the thickness of the film can be appropriately set according to the composition of the film, the use, etc., but generally, the higher the draw ratio, the thinner the film can be made. For example, when a biaxially oriented film is obtained by simultaneous biaxial stretching or sequential biaxial stretching using a non-oriented film having a thickness of 10 μm or more and 150 μm or less, by stretching at an area ratio of 10 times or more and 30 times or less, In particular, a thin biaxially oriented film having a thickness of about 1 to 5 μm can be obtained. When a biaxially oriented film of such a thin film is obtained, usually, since the rotation speed of the cooling drum increases and air entrapment tends to increase, the method for producing a film of the present invention that can reduce thickness unevenness is used. Greater benefits.

The uniaxially oriented film or the biaxially oriented film thus obtained is cooled in a subsequent conveying step, and once wound into a wide roll by a wide winder. After that, the uniaxially oriented film or the biaxially oriented film is unwound from the wide roll, and if necessary, it is cut into a required width and length by a slitter and rewound to obtain a film roll.

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 measuring methods and the like for each item in the examples and comparative examples are as follows.
〔Measuring method〕
(1) Evaluation of (c-b) (° C.) As a measuring device, a thermography (manufactured by FLUKE Co., Ti29 industrial/commercial thermography, measurable temperature range −20° C. to 600° C., lower temperature in display image) From which blue, light blue, green, yellow, and red colors are distributed in this order). In each example and each comparative example, the minimum measurement temperature of thermography was set to 45° C. and the maximum measurement temperature was set to 55° C. (that is, in the display image, when the temperature is 45° C. or lower, blue, and when it is 55° C. or higher). Is set to display red.)

It is obtained by photographing the range (5 in FIGS. 1 and 2) from the side surface in the direction of rotation of the rotating cooling drum to the bottom of the cooling drum (the reference numeral 5 in FIG. 1), which is horizontal to the axis of rotation of the cooling drum, for four sections (one rotation of the cooling drum). In the image, the presence or absence of a locally low temperature portion was visually checked, and when there was no such portion, (c-b) was 5°C or lower. On the other hand, when such a part was observed, it evaluated by the following procedures.

First, the scale ratio of the thermographic image was obtained from the size of the photographed image and the size of the cooling drum, and a transparent film (OPP film) having a size corresponding to a circle having a diameter of 150 mm was cut out on the thermographic image. After that, the cut OPP film is superposed on the image of the thermography, and it is confirmed whether or not there is a portion where the blue thermography is observed only in the OPP film. If there is no such portion, (c-b) is 5°C. The following is assumed. On the other hand, when such a part was observed, it was evaluated by the following procedure.

After that, two points were taken on the outer circumference of the region where blue was observed on the thermographic image so that the straight line distance was the maximum, and the length of the straight line as the actual size of the cooling drum was 50 mm or more and 150 mm from the scale ratio. In the case where the tint of green to red is visually confirmed in the thermographic image in the area below and the area where blue is observed is subtracted from the OPP film area, the area where blue is observed is area B, the OPP film. If the region where the blue color was observed was subtracted from the region, the region C was determined to have a temperature difference of 5° C. or more, and (c−b) was determined to be 5° C. or more.

(2) Water Film Thickness A regular reflection infrared film thickness meter/moisture meter RX200 manufactured by Kurashiki Spinning Co., Ltd. was used to measure the thickness of the water film on the most convex surface from the front of the cooling drum. Specifically, the measurement position was fixed at a position 25 mm away from the surface of the film being solidified on the most convex surface from the front surface of the cooling drum, the continuous measurement time was set to 30 seconds, and the water film was measured in units of 0.1 seconds. The thickness of the After that, the average value of the extracted film thickness was obtained, and the obtained value was defined as the water film thickness (μm).

[Comparative Example 1]
As a thermoplastic resin, polyethylene terephthalate pellets having an intrinsic viscosity of 0.65 produced by a conventional method were dried under reduced pressure at 180° C. for 3 hours, supplied to an extruder, and melted at 280° C. Then, it is supplied to a molding die through a filter, and static electricity is applied so that the thickness of the film after cooling and solidification is 30 μm, while the rotation speed is 50 m/min and the surface temperature is 25° C. on a cooling drum. After cooling and solidifying, a non-oriented film was obtained (the cooling drum used here is one in which the pipes have not been washed for a long period of time). Then, the non-oriented film was stretched in the longitudinal direction and the width direction so as to have an area ratio of 15 times to obtain a biaxially oriented film having a thickness of 2 μm. When the film formation by this step was tried continuously for 8 hours, two breaks occurred and the film formation stability was poor. When the non-oriented film on the side surface of the cooling drum was confirmed by thermography, one place where (c−b) was 5° C. or lower was confirmed.

[Comparative Example 2]
A biaxially stretched film having a thickness of 2 μm was obtained in the same manner as in Comparative Example 1 except that a water film having a thickness of 2.5 μm was formed on the cooling drum of Comparative Example 1. Similarly, the film formation was tried continuously for 8 hours, but the film formation stability was poor because the film was fractured twice. When the non-oriented film on the side surface of the cooling drum was confirmed by thermography, one place where (c−b) was 5° C. or lower was confirmed.

[Comparative Example 3]
A biaxially stretched film having a thickness of 2 μm was obtained in the same manner as in Comparative Example 1 except that a water film having a thickness of 0.5 μm was formed on the cooling drum of Comparative Example 1. Similarly, the film formation was tried continuously for 8 hours, but the film formation stability was poor because the film was fractured three times. When the non-oriented film on the side surface of the cooling drum was confirmed by thermography, one place where (c−b) was 5° C. or lower was confirmed.

[Example 1]
A slime remover (“Thai slime” (registered trademark) DS manufactured by Ichinen Chemicals Co., Ltd.) was diluted in water to a concentration of 5% by volume, and then circulated in a pipe in a cooling drum for 2 hours to wash the pipe. After that, when film formation was tried continuously for 8 hours in the same manner as in Comparative Example 1, there was no breakage and the film formation stability was good. When the non-oriented film on the side surface of the cooling drum was confirmed by thermography, no part where (c-b) was 5° C. or lower was confirmed.

[Example 2]
After cleaning the pipes in the cooling drum by the same method as in Example 1, the film formation was tried continuously for 8 hours in the same manner as in Comparative Example 3, and there was no breakage and the film formation stability was good. .. When the non-oriented film on the side surface of the cooling drum was confirmed by thermography, no part where (c-b) was 5° C. or lower was confirmed.

According to the present invention, it is possible to provide a film production method capable of reducing cracks in a non-oriented film in the step of cooling and solidifying on a cooling drum to obtain a non-oriented film. By using the present invention, it is possible to improve the film-forming stability without impairing the quality, the film obtained by the method for producing a film of the present invention, heat transfer applications, heat sensitive stencil applications, photographic applications, graphic applications of Also suitable as various industrial materials such as adhesive tapes, packaging materials, automotive materials, building materials, flexible printed boards, membrane switches, sheet heating elements, electrical insulating materials such as flat cables, magnetic recording materials, and materials for capacitors. Can be used for.

1 rotating shaft 2 cooling drum 3 die 4 non-oriented film 5 range from a position horizontal to the rotating shaft of the cooling drum to the bottom of the cooling drum 6 area A
7 Area B
8 Area C

Claims (5)

A method for producing a film having a cast step of extruding a molten thermoplastic resin composition into a sheet from a die and cooling and solidifying with a cooling drum,
On the surface of the non-oriented film in the range from the position parallel to the rotation axis of the cooling drum to the bottom of the cooling drum, a circle having a diameter of 150 mm is located in the area A, the center of gravity is located on the center of the area A, and the maximum diameter is 50 mm or more and less than 150 mm. When a region occupying a part of the region A is a region B, a region obtained by subtracting the region B from the region A is a region C, an average temperature of the region B is b (°C), and an average temperature of the region C is c (°C). In addition, (c-b) is always 5 (°C) or less, a method for producing a film. The method for producing a film according to claim 1, wherein the thickness of the non-oriented film is 10 μm or more and 150 μm or less. The rotation speed of the said cooling drum is 20 m/min or more and 120 m/min or less, The manufacturing method of the film of Claim 1 or 2 characterized by the above-mentioned. The method for producing a film according to claim 1, wherein a water film having a thickness of 0.5 μm or more and 5.0 μm or less is formed on the surface of the cooling drum. The said thermoplastic resin composition has a polyester resin as a main component, The manufacturing method of the film in any one of Claims 1-4 characterized by the above-mentioned.

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