JP3070823B2 - Method for producing thermoplastic resin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thermoplastic resin film. More specifically, the thickness unevenness of the film can be reduced during extrusion molding, and
The present invention relates to a method for producing a thermoplastic resin film capable of suppressing the occurrence of die streaks, which are defects on the film surface, and capable of obtaining a highly rigid film having a high Young's modulus.

[0002]

2. Description of the Related Art In producing a thermoplastic resin film, thickness uniformity is an important basic quality. For example, when polyester is taken as an example of a thermoplastic resin, the polyester film has excellent properties, and therefore, it is used for base insulation for magnetic recording media, electrical insulation for capacitors, OA for printer ribbons, and heat-perforated printing. It is used in various applications such as heat-sensitive stencil paper, and in these applications, high dimensional accuracy is required for the film thickness year by year. When the thickness unevenness worsens, the physical properties resulting from the film thickness become uneven, which leads to deterioration of the quality of the product. Further, even if the quality of the product is not directly related to the quality of the processed product, the trouble in processing the film into the product, the deterioration of the winding shape, and the deterioration of the quality of the processed product are caused.

By the way, a method of forming a thermoplastic resin into a film generally involves melting the resin with an extruder, removing foreign matter through a filter or the like, and then forming a slit in accordance with the shape of the film to be formed. It is discharged from a die (die) and continuously formed on a rotating roll (casting drum) through which a cooling medium is passed. At this time, an electrostatic force is often applied to bring the resin film into close contact with the casting drum. further,
In order to increase the strength of the film, the obtained film is generally stretched in a longitudinal direction (longitudinal direction) or a width direction (lateral direction).

[0004] Here, the causes of uneven thickness of the unstretched film before stretching are caused by fluctuations in the discharge amount when melt-extruded and extruded into a sheet on a casting drum, and between the die and the casting drum (LDD). And (3) film vibration of the resin film in a still molten state, uneven rotation of the casting drum, and the like. Therefore, various methods have conventionally been proposed for improving thickness unevenness. For example, a method of suppressing the rotation unevenness of a casting drum that cools and solidifies a molten resin (Japanese Patent Laid-Open No. 55-93420), and a method of applying a molten resin to a casting drum with an electrostatic force so as to easily receive the electrostatic force. (Japanese Unexamined Patent Publication No. Sho 59)
-91121) has been proposed, but the effect is not yet sufficient.

Further, in order to suppress film vibration between L and D, a method has been proposed in which the extrusion temperature of a thermoplastic resin is lowered to increase the melt viscosity of the resin (Japanese Patent Application No. 6-70789). In addition, except for the purpose of reducing uneven thickness,
Similarly, a method has been proposed in which a thermoplastic resin is once heated to a melting temperature or higher, then cooled to a temperature lower than the melting temperature or higher than a recrystallization temperature and extruded (Japanese Patent Laid-Open No. 4-347617). However, according to the study of the present inventors, these methods are effective when the discharge amount of the resin is small, but when applied to a high discharge amount such as an actual production line, heat conduction in the resin becomes rate-limiting. It became clear that the resin could not be cooled sufficiently. In the latter (Japanese Patent Laid-Open No. 4-347617), there is a description that a plurality of resins are laminated, but it is for laminating different resins in order to impart functionality, and a plurality of extruders are used. Is required. Further, the present inventors have found that there is a problem that lowering the extrusion temperature of the resin tends to cause die streaks on the sheet surface, which significantly deteriorates the quality of the film.

Further, generally, a method of extruding a thermoplastic resin at a temperature lower than the melting point is described in, for example, Japanese Patent Publication No. Sho 53-1198.
No. 0, Japanese Patent Publication No. 53-19625, Japanese Patent Publication No.
No. 55087 can be mentioned. However, these methods use a circular die, and in the case of a circular die, since it is discharged in a cylindrical shape, there is no end and it is difficult to disturb the flow even if it is cooled below the melting point, but when a flat die is used However, there is a problem that the end is easily solidified first and the flow is easily disturbed. Further, the methods disclosed in these publications adopt a configuration in which the resin is cooled below the melting point before the land portion of the die, and the cooled resin is supplied to the land portion. More specifically, the resin is cooled to the melting point or lower inside the die to solidify the resin, and then supplied to the land to extrude while applying shear. Therefore, a very high extrusion pressure is required, extrusion is difficult with a normal extruder, a special extruder for high pressure is required, and extrusion stability is poor. Further, the load on the die body and the die is large, which causes deformation and reduced durability. In addition, it is extremely difficult to widen such a solidified resin, and even if the resin can be widened, the flow becomes uneven due to uneven flow.

[0007]

As described above, there is a strong demand for improving the film thickness unevenness, and various improvement methods have been proposed for that purpose, but the effect is still insufficient.

[0008] The present invention particularly relates to a method for extruding a resin by cooling it in a die, which compensates for a shortage of cooling capacity when the discharge amount is large, suppresses the generation of a problematic die streak, and allows the resin to be formed on a casting drum. It is an object of the present invention to provide a method for producing a film having high dimensional accuracy and small thickness unevenness by reducing unevenness in thickness of a formed film.

[0009]

According to the present invention, there is provided a method for producing a thermoplastic resin film, which comprises melting and extruding a thermoplastic resin from a die and forming the film on a cooling roll to obtain a film. , A) the flow of the thermoplastic resin melted by the extruder is divided into two or more flow paths, and b) the temperature (Tex) at which at least one of the flow paths extrudes the thermoplastic resin from the extruder. ) And the temperature at which the thermoplastic resin starts to cool down and crystallize (Tc
b) After cooling to the above temperature (Td), c) Laminate the thermoplastic resin sent from each channel in the thickness direction and extrude it as one sheet from the die, and d) Form into a sheet on a cooling roll The method comprises the steps of:

Hereinafter, the present invention will be described in detail. As the thermoplastic resin in the present invention, polyethylene, polypropylene, polyolefin resin such as polymethylpentene, nylon 6, polyamide resin such as nylon 66,
Polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, poly-
A polyester resin such as 1,4-cyclohexane dimethylene terephthalate, a polyacetal resin, a polyphenylene sulfide resin, and the like can be used. Further, these resins may be homo resins, or may be copolymers or blends. In addition, various known additives such as an antioxidant, an antistatic agent, a crystal nucleating agent, and inorganic particles may be added to these resins.

The method of melt extrusion in the present invention includes:
Using a commercially available extruder, the thermoplastic resin was supplied to the supply unit, and the rotation of the screw in the heated extruder melted the resin, and the molten resin fed from the extruder was heated. It leads to the base through the inside of the flow channel (polymer tube). If necessary, a gear pump may be provided to remove foreign matter and denatured polymer through a filter and to improve the quantitative supply. The polymer thus guided is widened to a required width inside the die, discharged from the die, and cooled and solidified in a sheet shape on a casting drum.

Here, a known single-screw or twin-screw extruder can be used as the extruder. The shape of the screw of the extruder may be optimal depending on the properties of the thermoplastic resin to be applied. The heating temperature of the thermoplastic resin in the extruder is higher than the melting point when the thermoplastic resin shows crystallinity, so that no unmelted material remains. The melting point of the thermoplastic resin can be easily measured by a known method using a differential scanning calorimeter (DSC). Generally, in the case of a polymer material, the melting point is not observed as one point,
Observed as a broad-tailed peak. Here, the melting point that determines the heating temperature of the extruder is not necessarily the peak temperature, but the temperature at the end of the foot (melting end temperature: Tm
It is preferable to employ e). Most of the resin is melted at the peak temperature, but there is a possibility that the resin in the expanded portion of the foot does not melt but remains unmelted, and it is preferable to heat to Tme or more. As the die, a cylindrical die (circular die) or a parallel die (flat die) can be used. In the present invention, a flat die is preferably used. From the viewpoint of uneven thickness and the like, a higher quality film can be obtained by using a flat die. The flat die is not particularly limited. For example, as described in “Plastic extrusion molding and its application” by Keiji Sawada (Seibundo Shinkosha Co., Ltd.), a cylindrical groove ( It may be any of a manifold die (also referred to as a T-die) having a (manifold), a fish tail die shaped like a fish tail, and a coat hanger die shaped between them. A flat die is a part called a die hopper that usually spreads the molten resin in the width direction, and a land that is a final part that shapes the resin into a desired shape after spreading the resin in the width direction, and is a parallel part having a certain slit gap. It is composed of parts called parts.

Here, in the present invention, it is necessary to divide the flow of the molten resin sent from the extruder into two or more flow paths inside a polymer tube or a base. In the present invention, as will be described later, it is necessary to cool the thermoplastic resin, but as a result of extensive studies by the present inventors, if the cooling time of the resin is short, the time required for heat conduction of the thermoplastic resin is reduced. Therefore, although the surface of the thermoplastic resin sheet is cooled, the inside of the sheet is not sufficiently cooled. Here, if the cooling temperature is lowered in order to increase the cooling efficiency, the temperature of the surface of the thermoplastic sheet becomes too low, solidification starts, and extrusion becomes impossible. On the other hand, in order to lengthen the cooling time, it is necessary to lengthen the flow path of the cooling portion, and there is a disadvantage that the apparatus becomes large. Therefore,
The present inventors have as a result of diligent study, divided the flow of the molten resin into a plurality of flow paths, and by cooling the thermoplastic resin in necessary flow paths among them, it is possible to cool the inside of the sheet. I found According to this method, it is possible to make the cooling device compact by properly designing the cooling device. That is, the present method increases the cooling surface area per volume of the molten resin, that is, without increasing the flow path length of the molten resin by increasing the cooling specific surface area, and also sets the cooling temperature to the surface of the thermoplastic resin. Can be maintained at a temperature that does not solidify.

In the present invention, it is preferable that the thermoplastic resin melted by one extruder is divided into two or more flow paths inside the die. By dividing the thermoplastic resin guided from one extruder through a polymer tube into a plurality of flow paths in the base, it is possible to realize only by remodeling the base without major remodeling of existing equipment. . It should be noted that another or the same type of thermoplastic resin derived from another extruder may be laminated and co-extruded for the purpose of modifying the surface of the film.

In the present invention, the thermoplastic resin divided into two or more flow paths as described above is supplied to at least one of the flow paths at a temperature (T
It is necessary to cool to a temperature (Td) lower than ex). By cooling the molten resin, the melt viscosity of the molten resin film discharged from the die is increased, and it becomes stable against external airflow between the die and the casting drum (between L and D) and disturbance such as air vibration, The film vibration of the resin film between L and D is suppressed, and a film with small thickness unevenness can be obtained. In general, in order to increase the viscosity of a thermoplastic resin, a method of increasing the molecular weight or a method of adding a thickener can be considered, but these methods are not preferable because they modify the resin. By the way, when the molten sheet obtained by cooling in this manner is taken at a high draft ratio, and then subjected to a known biaxial stretching, it is surprising that a highly rigid film having a high Young's modulus can be obtained. all right. here,
The draft ratio for obtaining a highly rigid film is preferably 15 or more. More preferably, it is 20 or more. Here, the draft ratio is a ratio of the linear discharge speed of the die to the linear drawing speed of the casting drum, and is defined as (linear drawing speed /
Discharge linear velocity).

In the present invention, it is necessary that the temperature (Td) of the cooled thermoplastic resin is equal to or higher than the temperature at which the thermoplastic resin starts to cool down and crystallize (Tcb). In the case of a polymer resin, even if the resin in a molten state is cooled below the melting end temperature (Tme) of the thermoplastic resin, it does not solidify in a short time,
The so-called supercooled liquid phase state can be maintained.
If the temperature is lower than this, the resin starts to crystallize, and the surface of the extruded film becomes rough, extrusion abnormality, uneven flow occurs, or solidifies with time, and it becomes impossible to extrude with an ordinary extruder. In the present invention, the thermoplastic resin is cooled, and at that time, it is important that the resin is never solidified. It is important to use a supercooled state of a polymer and extrude it in a liquid phase even at a temperature below the melting point.

In the present invention, the temperature (Td) of the cooled thermoplastic resin is preferably lower than the melting end temperature (Tme) of the thermoplastic resin. When Td exceeds Tme, the effect of cooling in the present invention is small, and it is difficult to obtain a film having good thickness unevenness.
Further, it is difficult to achieve high rigidity even if the material is taken up at a high draft ratio and biaxially stretched.

In the present invention, after cooling the thermoplastic resin in at least one flow path, the thermoplastic resin sent from each flow path must be laminated in the thickness direction and extruded as one sheet from the die. . An object of the present invention is to solve the disadvantage that the inside of the sheet cannot be cooled when the cooling is performed without dividing the flow path. If the sheet is not extruded as one sheet, the meaning of the present invention is lost. Also, 1
As a method of forming a single sheet, a method of arranging the resin from each channel in the width direction is also conceivable. However, in that case, there is a problem that unevenness in the width direction occurs due to unevenness of cooling in each flow path. By laminating in the thickness direction as in the present invention,
It is possible to make the unevenness between the flow paths uniform.

Further, in the present invention, it is preferable to cool the thermoplastic resin in all the channels divided into a plurality of channels. In order to suppress thickness unevenness accompanying film vibration between L and D, it is advantageous that the melt viscosity as a whole of the molten sheet between L and D is high. It is preferable that the sheets are cooled as uniformly as possible from the surface to the inside. However, as shown in FIG. 1, the temperature unevenness in the thickness direction of the film becomes smaller but not completely eliminated as compared with the case where the flow path is not divided. In FIG. 1, 1 indicates the temperature distribution in the film thickness direction according to the conventional method, and 2 indicates the temperature distribution in the film thickness direction according to the method (three flow paths) of the present invention.

As a method for cooling the molten resin, it is preferable that each resin is expanded to a width of a sheet discharged from a die and then cooled. In consideration of the cooling efficiency of the molten resin, the larger the specific surface area of cooling, the higher the cooling efficiency. Therefore, if the width of each resin is increased to the width of the sheet to be discharged, the thickness of the molten resin in each flow path can be reduced, and the efficiency of cooling increases. Furthermore, since the molten resin after cooling has a high melt viscosity, it is difficult to uniformly widen the width. Therefore, in each of the flow paths, cooling is performed after the sheet is widened to the width of the sheet discharged from the die, and the sheet is stacked in the thickness direction while maintaining the width, thereby making it possible to uniformly widen the sheet. It is easier to perform such widening and cooling in the base than in a flow path such as a polymer tube. There is a method of performing a process of providing a cooling medium flow path that can be cooled in a known multilayer die, and providing a cooling adapter in a manifold portion in the die. Although there is no particular limitation on the cooling means, for example, there is a method in which a hole for cooling is provided and a coolant is passed through the hole. As the refrigerant, various liquid refrigerants such as air or water can be used, and a desired temperature can be set by controlling the temperature and flow rate of the refrigerant. After widening and cooling in the die, it is also preferable to provide a pool of molten resin with the widened width and then to overlap in the thickness direction. By providing the reservoir, a difference in discharge pressure between the flow paths is absorbed, uniform superposition is possible, and thickness uniformity is improved.

In the present invention, when cooling the resin, it is preferable that the resin is discharged in a transient state of cooling. Due to the transitional state, the vicinity of the thick edge is left at a relatively high temperature, and the solidification from the edge can be suppressed.

As a result of the study by the present inventors, it is clear that when the molten resin thus uniformly cooled is discharged from the die, a new problem arises in that die streaks are easily generated on the sheet surface. became. Cap streaks are those in which convex or concave streaks are generated on the surface of the discharge sheet from the cap, and those that continue to occur at fixed positions in the cap width direction, or where the position is not fixed, random Some may occur. It is not clear why the die streaks are likely to occur in the discharge of the cooled molten resin, but it is considered that fine crystal solidified precipitates on the surface of the die upon cooling, causing the die streaks.

Therefore, in the present invention, the flow of the thermoplastic resin is divided into three or more flow paths, and when the cooling temperature of the thermoplastic resin in each flow path is finally laminated in the thickness direction, It is preferable that the temperatures in the two flow paths through which the thermoplastic resin flowing on both surfaces of the sheet flows be higher than the temperatures in the other flow paths. That is, when discharged from the die as one sheet, the temperature of the surface of the sheet is high,
The inside of the sheet is configured to be sufficiently cooled, and the thickness of the cooled layer is reduced to reduce unevenness in thickness. In addition,
It is also preferable that the sheet is discharged at the temperature extruded from the extruder without providing a cooling means in the flow path of the thermoplastic resin on both surfaces of the sheet. Also, the thickness of both surface layers is not required to be thick because the purpose is to prevent the occurrence of die streaks. Rather, the thinner the possible, the thicker the internally cooled layer becomes, resulting in uneven thickness. This is preferable because the effect of reducing the amount of the carbon dioxide increases. However, if it is too thin, the temperature will drop to the same temperature as that of the internal cooling layer due to heat conduction between the time when it is laminated with the internal cooling layer and is discharged from the die, and the effect of preventing die streaks will be lost. A preferred thickness configuration is about 1% to 20% of the thickness of the entire sheet.

Even when the degree of cooling is not changed by the flow path, it is preferable to provide a heating means at the tip of the die where the resin is discharged, and to heat the surface of the discharged thermoplastic resin sheet. When the sheet is uniformly cooled from the surface to the inside and discharged, the heating means instantaneously heats only the sheet surface to prevent the die streaks. Of course, it is also preferable to use together with the above-described method of changing the degree of cooling by the flow path.

The single molten sheet thus obtained needs to be formed into a sheet on a cooling roll (casting drum). An object of the present invention is to suppress film vibration in a sheet in a molten state before sheet formation on a casting drum, and to suppress thickness unevenness.

Although the thickness of the film to which the present invention is applied is not particularly limited, the thickness of the unstretched film is preferably from 10 μm to 300 μm. For thicker films, the film itself is thicker,
The effect of the present invention is small because it is hardly affected by disturbance.
For films thinner than this, without splitting the flow path,
It is possible to cool the inside of the molten sheet, and the effect of the present invention is small. More preferably, 30 μm to 20 μm
0 μm.

The molded film having excellent thickness uniformity obtained by the present invention may be used as it is as an unstretched film, or may be subjected to uniaxial or biaxial stretching and heat treatment to be oriented and crystallized to improve the properties. Is also preferably performed. As a method for imparting orientation, a sequential biaxial stretching method in which stretching is performed in the longitudinal direction between rolls having a difference in peripheral speed, followed by transverse stretching in a tenter, and heat treatment, biaxial stretching in the tenter simultaneously in the longitudinal and transverse directions, heat treatment A known method such as a simultaneous biaxial stretching method can be used. According to the present invention, it is possible to obtain a film having excellent thickness uniformity even after stretching. Here, when the draft ratio of the drawing by the casting drum is drawn at a high ratio of 15 or more, a highly rigid film having a high Young's modulus can be obtained by subjecting the film to normal biaxial stretching. Conventionally, in order to obtain a highly rigid film, a method of performing uniaxial or biaxial stretching again after biaxial stretching, a method of performing each stretching of biaxial stretching in multiple stages, and the like have been applied. According to the method, it is possible to obtain a highly rigid film without such equipment modification. Of course, by adjusting the cooling temperature and the draft ratio, it is also possible to obtain a normal rigid film.

[Evaluation Method of Physical Properties] (1) Thermal Characteristics A robot DSC “RDC220” manufactured by Seiko Electronics Industry Co., Ltd. was used as a differential scanning calorimeter, and a disk station “SSC / 520” manufactured by the company was used as a data analyzer.
Using “0”, about 5 mg of a sample was melted and held at 300 ° C. for 5 minutes on an aluminum tray, quenched and solidified with liquid nitrogen, and then heated from room temperature at a heating rate of 20 ° C./min. The start temperature of the endothermic peak of melting observed at this time was Tmb, the peak temperature was Tm, and the end temperature of the peak was Tme. Also 30
After the temperature was raised to 0 ° C, it was melted and held for 5 minutes, and the temperature was lowered at a rate of 20 ° C /
The temperature dropped in minutes. At this time, the start temperature of the exothermic peak of the cooling crystallization observed was Tcb, the peak temperature was Tc, and the end temperature of the peak was Tce. Here, in the range from room temperature to 300 ° C,
When the endothermic peak of melting and the exothermic peak of cooling crystallization were not observed, Tme was regarded as 300 ° C. and Tcb was regarded as room temperature.

(2) Unevenness of Film Thickness Using a film thick nest tester KG601A manufactured by Anritsu Corporation and an electronic micrometer K306C, three
The thickness of a film sampled at a width of 0 mm and a length of 10 m is continuously measured. Thickness maximum value Tmax at 10m length
(Μm) and the minimum value Tmin (μm), R = Tmax−Tmin was calculated, and from R and the average thickness Tave (μm) having a length of 10 m, the thickness unevenness (%) = R / Tave × 100.

(3) Temperature The temperature Tex at which the thermoplastic resin was extruded from the extruder was measured by providing a hole in the polymer tube at the outlet of the extruder, inserting a thermocouple, and applying a seal to prevent leakage of the resin. The temperature (Td) of the thermoplastic resin cooled in the flow path was measured by providing a hole at the outlet of the cooling section in the flow path, inserting a thermocouple, and applying a seal to prevent leakage of the resin. The wall surface temperature of the base and the like was measured by providing a hole in the member to the vicinity of the wall surface and inserting a thermocouple. Further, the temperature of the resin discharged from the base was measured after a thermocouple was inserted into the discharged resin and the temperature was stabilized.

(4) Draft ratio The weight of the molten resin discharged for one minute is measured, and the discharge amount Q
(Kg / min). Cross-sectional area S of resin flow path at die outlet
(Cm ² ) and the specific gravity d of the molten resin, the discharge linear velocity Vex
= Q / d / S x 10 (m / min) is calculated. When the resin was polyethylene terephthalate, the specific gravity was 1.2. This Vex and the peripheral speed Vcd (m
/ Min), the draft ratio = Vcd / Vex.

(5) Cap streak After the cap tip was cleaned with a copper plate, film formation was continued under constant conditions for 3 hours. Three hours later, the molten resin sheet discharged from the mouthpiece is observed for 1 minute. If no streaks are observed, “○”, if less than three streaks are observed, “△”, and three or more streaks are observed. Indicates “×”.

(6) Young's modulus Automatic film strength / elongation measuring device manufactured by Orientec Co., Ltd .:
10m width using Tensilon AMF / RTA-100
m, the test length was 100 mm, and the tensile speed was 300 mm / min.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Example 1 As a thermoplastic resin, polyethylene terephthalate having an intrinsic viscosity of 0.65 was used. When thermal characteristics were measured using DSC, Tmb: 240 ° C., Tm: 255 ° C., Tme:
268 ° C, Tcb: 203 ° C, Tc: 188 ° C, Tce: 1
74 ° C. The polyethylene terephthalate pellets were vacuum-dried at 180 ° C. for 3 hours, supplied to an extruder, melted at 290 ° C., and supplied to a molding die via a filter. The die used had a shape which was divided into three layers inside the die and laminated after widening. The resin is divided into three channels at the inlet of the base, and each channel has a manifold.
The resin was widened to a width of 00 mm, a plurality of holes having a diameter of 7 mm were provided in the vicinity of the flow path after each widening, and cooling was performed by passing air therethrough. After cooling, the resin is laminated again in the thickness direction, and finally, the lip gap is 1 mm and the width is 400 m.
m, and passed through a land portion having a length of 10 mm. The division into three layers (A / B / C layers),
A: B: C = 1: 1: 1 was equally divided. 2 in the cooling section
A cooling air of 5 ° C. is supplied to each of the three flow paths at a flow rate of 0.10.
Cooling was performed at a flow rate of m ³ / minute. The temperature (Tex) extruded from the extruder was 290 ° C. The temperature at the mouth of the die after passing through the polymer tube was also 290 ° C. The resin temperatures of the A, B, and C layers immediately after the flow path division and the widening were all 288 ° C., and the resin temperature at the cooling unit outlet was 250 ° C. for each layer. The film extruded from the die was rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25 ° C. while applying static electricity, and was wound. At this time, the distance (between L and D) between the die and the casting drum was 30 mm. The thickness of the obtained film was 100 μm. The draft ratio was 10. The thickness unevenness in the longitudinal direction of the obtained film is as follows.
5%, and a film having good thickness unevenness was obtained.

Example 2 In the same manner as in Example 1, a polyethylene terephthalate resin was extruded from a die and formed into a film on a casting drum. At this time, the flow rate of the resin cooling air flowing through the die was set to 0.15 m ³ / min for each of the three flow paths. At this time, Tex was 290 ° C., the resin temperature at the mouth of the mouthpiece was 290 ° C., the resin temperature of the A, B, and C layers immediately after widening was 287 ° C., and the resin temperature at the outlet of the cooling unit was 220 ° C.
Met. The thickness of the obtained film was 100 μm. The draft ratio was 10. The thickness unevenness in the longitudinal direction of the obtained film was 1.2%, and a film having good thickness unevenness was obtained.

Comparative Example 1 In the same manner as in Example 1, a polyethylene terephthalate resin was extruded from a die and formed into a film on a casting drum. At this time, the flow rate of resin cooling air flowing through the die was set to 0.23 m ³ / min for each of the three flow paths. At this time, Tex was 290 ° C., the resin temperature at the mouth of the die was 290 ° C., the resin temperature of the A, B, and C layers immediately after widening was 284 ° C., and the resin temperature at the outlet of the cooling unit was 190 ° C.
Met. However, the resin discharged from the die began to solidify with the passage of time, and finally became impossible to extrude.

Example 3 In the same manner as in Example 1, a polyethylene terephthalate resin was extruded from a die and formed into a film on a casting drum. At this time, the flow rate of the resin cooling air flowing through the die was set to 0.06 m ³ / min for each of the three flow paths. At this time, Tex was 290 ° C., the resin temperature at the mouth of the mouthpiece was 290 ° C., the resin temperature of the A, B, and C layers immediately after widening was 289 ° C., and the resin temperature at the outlet of the cooling unit was 269 ° C.
Met. The thickness of the obtained film was 100 μm. The draft ratio was 10. The thickness unevenness in the longitudinal direction of the obtained film was 3.6%, and although the thickness unevenness was good, a film slightly inferior to Example 1 was obtained.

Example 4 In the same manner as in Example 1, a polyethylene terephthalate resin was extruded from a die and formed into a film on a casting drum. At this time, division of three layers (A / B / C layer),
The lamination thickness ratio is A: B: C = 1: 3: 1, and the outer layer portions are made thinner.
A flow rate of 0.15 m ³ / min.
No air was flowed through the layers. At this time, Tex is 290 ° C,
The resin temperature at the inlet of the die is also 290 ° C, the resin temperatures of the A and C layers immediately after widening are all 289 ° C, the B layer is 287 ° C, the resin temperature at the cooling unit outlet is A, the C layer is 281 ° C, and the B layer is 235
° C. The thickness of the obtained film was 100 μm. The draft ratio was 10. The thickness unevenness in the longitudinal direction of the obtained film was 1.6%, and a film having good thickness unevenness was obtained. Further, a film having a very small amount of die streaks on the film surface was able to be obtained.

Example 5 In the same manner as in Example 1, a polyethylene terephthalate resin was extruded from a die and formed into a film on a casting drum. At this time, division of three layers (A / B / C layer),
The lamination thickness ratio is A: B: C = 1: 3: 1, and the outer layer portions are made thinner.
A flow rate of 0.15 m ³ / min.
The layers each had a flow rate of 0.03 m ³ / min. At this time, Tex was 290 ° C., and the resin temperature at the inlet of the die was 290 ° C.
℃, resin temperature of A, C layer immediately after widening is 288 ℃,
The B layer had a resin temperature of 287 ° C., the resin temperature at the outlet of the cooling section was A, the C layer had a temperature of 263 ° C., and the B layer had a resin temperature of 235 ° C. The thickness of the obtained film was 100 μm. The draft ratio was 10. 1.2% thickness unevenness in the longitudinal direction of the obtained film
And a film having good thickness unevenness is obtained.
It was possible to obtain a film having a very small number of die streaks on the film surface.

Example 6 In exactly the same manner as in Example 1, a polyethylene terephthalate resin was extruded from a die and formed into a film on a casting drum. However, a small electric heater was attached to the end of the lip from which the resin of the base was discharged, and only the front end of the base was heated. The thickness of the obtained film is 100 μm
Met. The draft ratio was 10. The thickness unevenness in the longitudinal direction of the obtained film was 1.4%, a film having good thickness unevenness was obtained, and a film having a very small amount of die streaks on the film surface was able to be obtained.

Comparative Example 2 In the same manner as in Example 1, a polyethylene terephthalate resin was extruded from a die and formed into a film on a casting drum. At this time, a single-layered ordinary die without dividing the flow path was used. Cooling was performed at a flow rate of 25 ° C./min at a flow rate of 0.50 m ³ / minute near the flow path after the resin was widened. At this time, Tex was 290 ° C., the resin temperature at the mouth of the mouthpiece was 290 ° C., and the resin temperature immediately after widening was 288 ° C.
The resin temperature at the outlet of the cooling section was 270 ° C. The thickness of the obtained film was 100 μm. Draft ratio is 1
It was 0. The thickness unevenness in the longitudinal direction of the obtained film was 5.6%, and the thickness unevenness was poor.

Comparative Example 3 The same as in Example 1, except that the polyethylene terephthalate resin was extruded from a die with a reduced discharge rate, and a film was formed on a casting drum. At this time, a single-layered ordinary die without dividing the flow path was used. Cooling air of 25 ° C. is flowed in the vicinity of the flow path after resin widening at a flow rate of 0.50 m.
Cooling was performed at a flow rate of ³ / min. At this time, Tex is 290 ° C,
The resin temperature at the inlet of the die was 290 ° C., the resin temperature immediately after widening was 287 ° C., and the resin temperature at the outlet of the cooling unit was 258 ° C. The thickness of the obtained film was 25 μm. The draft ratio was 10. The thickness unevenness in the longitudinal direction of the obtained film was 2.6%, and the thickness unevenness was relatively good.

Example 7 In exactly the same manner as in Example 1, a polyethylene terephthalate resin was extruded from a die and formed into a film on a casting drum. The thickness of the obtained film is 100 μ
m. The draft ratio was 10. The thickness unevenness in the longitudinal direction of the obtained film was 1.4%, and a film having good thickness unevenness was obtained. Further, after heating the film with a group of rolls heated to 80 ° C., the film was stretched longitudinally 3.3 times, guided to a tenter while holding both ends of the film with clips, and preheated in a hot air atmosphere of 85 ° C. , And heat-treated at 210 ° C., pulled out from a tenter while gradually cooling, and wound up the film. The thickness of the obtained film was 8 μm, and the Young's modulus in the longitudinal direction of the film was 450 kg / mm ² . The thickness unevenness was relatively good at 3.4%.

Example 8 In exactly the same manner as in Example 7, a polyethylene terephthalate resin was extruded from a die, and a film was formed on a casting drum at a draft ratio of 20. The thickness of the obtained film was 50 μm. . The thickness unevenness in the longitudinal direction of the obtained film was 1.6%, and a film having good thickness unevenness was obtained. Further, the film is heated to 80 ° C.
After the film is heated by the roll group heated in the above, the film is stretched 3.3 times longitudinally, guided to a tenter while gripping both ends of the film with clips, preheated in a hot air atmosphere at 85 ° C., and horizontally stretched 3.6 times at 90 ° C. Then, a heat treatment was performed at 210 ° C., and the film was taken out from the tenter while being gradually cooled, and the film was wound. The thickness of the obtained film was 4 μm, and the Young's modulus in the longitudinal direction of the film was 550 kg / mm ^2, and a high-strength film could be obtained. The thickness unevenness was relatively good at 3.9%.

Example 9 In exactly the same manner as in Example 7, a polyethylene terephthalate resin was extruded from a die, and a film was formed on a casting drum at a draft ratio of 40. The thickness of the obtained film was 25 μm. . The thickness unevenness in the longitudinal direction of the obtained film was 2.2%, and a film having good thickness unevenness was obtained. Further, the film is heated to 80 ° C.
After the film is heated by the roll group heated in the above, the film is stretched 3.3 times longitudinally, guided to a tenter while gripping both ends of the film with clips, preheated in a hot air atmosphere at 85 ° C., and horizontally stretched 3.6 times at 90 ° C. Then, a heat treatment was performed at 210 ° C., and the film was taken out from the tenter while being gradually cooled, and the film was wound up. The thickness of the obtained film was 2 μm, and the Young's modulus in the longitudinal direction of the film was 630 kg / mm ^2, and a high-strength film could be obtained. The thickness unevenness was relatively good at 4.2%.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

As described in detail above, according to the method of the present invention, a film having a small thickness unevenness, a suppressed generation of die streaks, and a high Young's modulus can be efficiently produced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature distribution in a film thickness direction according to a conventional method and a method according to the present invention.

[Explanation of symbols]

1 Temperature distribution in the film thickness direction by the conventional method 2 Temperature distribution in the film thickness direction by the method (3 channels) in the present invention

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // B29K 101: 12 B29L 9:00 (56) References JP-A-3-213324 (JP, A) JP-A-53-137265 (JP, A) JP-B 47-1698 (JP, B1) JP-B 51-5070 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 47/00-47 / 96

Claims (9)

(57) [Claims] 1. A thermoplastic resin is melt-extruded from a die,
A method of forming a film on a cooling roll to obtain a film, comprising: a) dividing a flow of a thermoplastic resin melted by an extruder into two or more flow paths; and b) separating at least one of the flow paths. After cooling the thermoplastic resin to a temperature (Td) lower than the temperature (Tex) at which the thermoplastic resin was extruded from the extruder and equal to or higher than the temperature-lowering crystallization starting temperature (Tcb) of the thermoplastic resin, c) The thermoplastic resin sent from is laminated in the thickness direction and extruded as one sheet from the die,
d) A method for producing a thermoplastic resin film, which is formed into a sheet on a cooling roll. 2. The thermoplastic resin film according to claim 1, wherein a temperature (Td) of the thermoplastic resin cooled in the at least one flow path is lower than a melting end temperature (Tme) of the thermoplastic resin. Manufacturing method. 3. A flow of the thermoplastic resin melted by one extruder is divided into two or more flow paths inside the die.
A method for producing the thermoplastic resin film according to claim 1. 4. A flow of the thermoplastic resin is divided into a plurality of three or more flow paths, and the cooling temperature (Td) of the thermoplastic resin in each flow path is determined when the thermoplastic resin is finally laminated in the thickness direction. ,
The method for producing a thermoplastic resin film according to any one of claims 1 to 3, wherein the temperatures in the two flow paths through which the thermoplastic resin flowing on both surfaces of the sheet flows are higher than the temperatures in the other flow paths. 5. The flow of the thermoplastic resin is divided into a plurality of flow paths of three or more, and when the thermoplastic resin is finally laminated in the thickness direction, the two flows through which the thermoplastic resin flows on both surfaces of the sheet. Without providing a cooling means in the path, cooling the thermoplastic resin by providing a cooling means by a cooling medium in other flow paths,
A method for producing the thermoplastic resin film according to any one of claims 1 to 4. 6. A two or more thermoplastic resins into a plurality of flow paths, cooling in all flow paths which are divided, method for producing a thermoplastic resin film according to any one of claims 1 to 4 . 7. The cooling method according to claim 1, wherein when cooling the thermoplastic resin, the resin is expanded in each channel to a width of a sheet discharged from a die, and then cooled in each channel. A method for producing a thermoplastic resin film according to any one of the above. 8. The thermoplastic resin film according to claim 1, wherein a heating means is provided at a tip of the die from which the resin is discharged to heat the surface of the thermoplastic resin sheet to be discharged. Manufacturing method. 9. The thermoplastic resin film according to claim 1, wherein the thickness of the unstretched film discharged from the die and formed on a sheet on a cooling roll is 10 μm or more and 300 μm or less. Production method.