JPH0334458B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a tubular simultaneously biaxially stretched polyether/ether/ketone film. In recent years, the uses of plastic film have expanded, and the performance required of plastic film has also increased accordingly. Above all, there is a strong need for heat resistance, especially for aerospace materials and high-grade electrical insulation materials. It is no exaggeration to say that polyimide film is currently the only film that satisfies these requirements. However, since polyimide film is made into a film by a solution method, industrial production requires large-scale and complicated equipment, resulting in very poor productivity, resulting in a high film price. In view of these circumstances, the present inventors developed a polyether/ether/ketone film that is inexpensive, heat resistant, has good optical properties, and has well-balanced longitudinal and horizontal mechanical properties using an extrusion method (tube-shaped simultaneous biaxial stretching method). ) to provide a more efficient production method. It is generally well known that a film with improved mechanical properties, optical properties, and heat resistance can be obtained by biaxially stretching thermoplastic resins, and the tenter method is the biaxially stretching method for this purpose. The tube method is known. The tenter method is generally a sequential two-stage stretching method in which an unstretched flat film is heated to the appropriate temperature for stretching, then stretched in the longitudinal direction using rolls, and then stretched in the transverse direction by chuck holding. Since the portion held by the chuck is definitely lost, it is inevitable that the production efficiency of the film will be reduced and that the physical properties of the resulting film will vary in length and width. On the other hand, in the tube method, an unstretched film is introduced between the delivery and take-up rolls, the film is reheated from the circumferential direction to the appropriate temperature for stretching, and expanded and stretched using internal pressure.The equipment is simple and compact, and the tenter method The production efficiency of the film is very high as there is no lost part that is retained in the chuck, and the physical properties of the film obtained are also well balanced in the length and width as it is simultaneously biaxially stretched in the length and width. By the way, polyether/ether/ketone resin is a crystalline resin, and when crystallization progresses and the degree of crystallinity becomes too high, it becomes hard and brittle, and becomes gray and opaque, making it unusable in the state of an unstretched film. Physical properties cannot be improved by stretching. For this reason, it is necessary for polyether/ether/ketone films to have a low degree of crystallinity and to improve physical properties such as film strength and optical properties by performing biaxial stretching processing. However, in the production method currently commonly used in the tube method, in which the molten resin extruded from an annular die is cooled using gas such as air, the film is hard and brittle, and breaks when introduced into the delivery roll, resulting in subsequent stretching. Processing becomes impossible. Therefore, it is no exaggeration to say that there are no examples of industrial production of simultaneously biaxially stretched polyether/ether/ketone films using the tube method. In view of these circumstances, the present inventors have developed a tube method, which uses a relatively small device compared to the tenter method and has good work efficiency and production efficiency, and which has high heat resistance and optical properties by simultaneous biaxial stretching. The technical challenge was to obtain a high-strength polyether/ether/ketone film with excellent physical properties and well-balanced length and width. As a result of intensive research into the conditions to make this possible, the method of the present invention was discovered. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing a polyether/ether/ketone film that is simultaneously biaxially stretched using a tube method. That is, the present invention is a tube-shaped unstretched polyether, which is melt-extruded from an annular die and rapidly cooled.
The crystallinity is maintained at 10% or less in a method in which a ketone film is continuously introduced between the delivery and take-off Nitzpro rolls, and during this time the film is reheated from the circumferential direction, expanded by internal pressure, and simultaneously biaxially stretched. 60~140 tube-shaped unstretched film
This is a method for producing a tubular simultaneously biaxially stretched polyether/ether/ketone film, which is characterized in that the film is reheated to a temperature of °C and then stretched to an area magnification of 4 to 36 times. It is known that the degree of crystallization of a crystalline film varies significantly depending on the cooling rate after melt extrusion, and that the faster the cooling rate, the lower the crystallinity degree. In the case of polyether/ether/ketone films, the more crystallized they become, the more they become gray and opaque, and become hard and brittle. However, as mentioned above, tube-like stretching is generally done by reheating between two sets of rolls, a delivery roll and a take-up roll. Because the film is stretched by internal pressure, crystallization progresses significantly and the film becomes hard and brittle. When it is introduced into the delivery roll, the film cracks, making it impossible to carry out further stretching. Table 1 shows the results of tests on the relationship between the cooling rate of polyether/ether/ketone resins, the degree of crystallinity and stretchability of the obtained films, and the appearance of the obtained films. The degree of crystallinity used in the present invention was determined by measuring the density by a method using a density gradient tube and by comparative calculation. The specific gravity of the amorphous portion of polyether, ether, and ketone is 1.265, and the specific gravity of the crystalline portion is 1.320. The density gradient tube used to determine the degree of crystallinity of the present invention measures density in a 25°C solution consisting of liquid paraffin/carbon tetrachloride.

[Table] From Table 1, simultaneous biaxial stretching in the vertical and horizontal directions is possible when the crystallinity of the film is at least 10% or less after cooling at a cooling rate of 24°C/sec or higher, and the resulting film has optical properties. A film with good balance of longitudinal and lateral mechanical properties was obtained, and in particular, when the degree of crystallinity was 6% or less, the optical properties of the obtained film such as light transmittance and gloss were extremely good. When the crystallinity exceeded 10%, the film became hard and could not be stably stretched. We investigated various methods to achieve such a low degree of crystallinity, and found that the polyether/ether/ketone film extruded from an annular die could not achieve the low crystallinity targeted by the present invention using the conventional air cooling method using gas. It has been found that it is extremely difficult to obtain a high temperature, so when carrying out the present invention, the film is rapidly cooled by a cooling method using a liquid such as water, or a cooling method using a combination of this and an air cooling method. It is preferable. Next, the drawing temperature, which is an important component of the present invention, will be explained. Generally speaking, the higher the degree of crystallinity, the higher the drawing temperature needs to be.
It has been found that simultaneous biaxial stretching is possible at very low temperatures in the case of the present invention, in which the degree of crystallinity is lowered by cooling the film at a cooling rate of .degree. C./second or higher. That is, in the present invention, the stretching temperature to enable simultaneous biaxial stretching is 60 to 140°C.
The optimal range is preferably 80 to 120°C; on the other hand, if the temperature is lower than 60°C, the film will break during stretching, making stable stretching impossible, and if the temperature exceeds 140°C. In some cases, crystallization of the unstretched film progressed during stretching, and the optical properties of the resulting film deteriorated. Stretching temperature is 80~120℃
Within this range, very stable stretching was carried out, and the optical properties of the resulting film, such as light transmittance and gloss, were also extremely good. Furthermore, to explain the stretching ratio, which is another component of the present invention, it is appropriate that the area ratio (longitudinal stretching ratio x lateral stretching ratio) is 4 to 36 times, especially in the area ratio of 9 to 25 times. Stable production of bubbles was achieved, and good film thickness unevenness was obtained. On the other hand, in practice, the area magnification is 4
When the area magnification is less than 36 times, stretching unevenness remains and the accuracy of film thickness unevenness is poor, and when the area magnification exceeds 36 times, bubbles often burst during stretching, making stable production impossible. Next, to explain the effect of the present invention, the film obtained by the method of the present invention has a high continuous use heat resistance temperature according to the UL standard (220 ° C was obtained in the experimental example).
It exhibits heat resistance that is almost equivalent to the heat resistance temperature of polyimide film (230℃), and the film has good transparency and gloss.Moreover, since it is simultaneously biaxially stretched vertically and horizontally, the strength of the vertical and horizontal film is significantly strengthened, and the strength is balanced in both vertical and horizontal directions. had. Table 2 shows the comparative physical properties of the simultaneously biaxially stretched polyether/ether/ketone film obtained according to the present invention and the polyimide film.

[Table] As shown in Table 2, polyimide film exhibits some hygroscopicity, so the physical properties of polyimide film deteriorate in a high temperature and humidity atmosphere, but the film produced by the method of the present invention is also characterized in that it is not affected by high temperature and humidity. have. The film obtained by the production method of the present invention takes advantage of these characteristics to be used in the fields of hot water-resistant insulating tape, microwave oven lining, capacitors, and liquid crystal display fields.
It can be used in the field of heat-resistant flexible printed circuit substrates, etc. Incidentally, when carrying out the method of the present invention, the inclusion of anti-blocking agents, lubricants, heat stabilizers, ultraviolet absorbers, and other additives used to improve the properties of the film can significantly impair the mechanical and optical properties of the film. It is possible as long as it does not cause any damage. EXAMPLES The present invention will be specifically explained below with reference to Examples, but these Examples are not intended to limit the present invention in any way. Example 1 Polyether-ether-ketone resin (manufactured by IMPERIAL CHEMICAL INDUSTRIES, hereinafter referred to as ICI) was extruded at a melting temperature of 400°C through a 50φ annular die, and immediately heated to a water temperature of 10°C.
A water cooling device that uses water at a temperature of 35 degrees
Rapidly cooled at °C/second, crystallinity 3%, width 82mm, thickness
A 135μ tubular unstretched film was produced.
This unstretched film is guided to a delivery roll, heated to a temperature of 100°C by a cylindrical heating device using an infrastein heater, and then air is introduced into the tube. Stretched to twice its original size, taken to a take-up roll, and then passed through a winding device to a thickness of 15 μm and a width.
I wound up a 246mm film. The obtained film had good transparency and gloss, and had improved mechanical properties with well-balanced longitudinal and lateral strength, and could be stably produced. Example 2 Polyether ether ketone resin (manufactured by ICI) was extruded through a 50φ annular die at a melting temperature of 400°C, and immediately cooled at a cooling rate of 24°C/sec using a water cooling device using water at a temperature of 10°C. Crystallinity
A tube-shaped unstretched film with a width of 82 mm and a thickness of 160 μm was produced. This unstretched film is guided to a delivery roll, heated to a temperature of 120°C by a cylindrical heating device using an infrastein heater, and then air is introduced into the tube.
Stretched to 4x in both length and width and 16x in area, then rolled to a thickness of 10μ and width using a winding device.
I wound up a 328mm film. Film production was carried out stably, and a film with well-balanced mechanical properties in the longitudinal and lateral directions and good optical properties was obtained. Comparative Example 1 Polyether ether ketone resin (manufactured by ICI) was extruded through a 50φ annular die at a melting temperature of 400°C, and cooled with a water cooling device at a cooling rate of 18°C/sec to obtain crystallinity of 47%, width 82mm, An unstretched film with a thickness of 150μ was produced. This unstretched film was led to a delivery roll, heated to various temperatures by a device using an installed infrastein heater, and then air was introduced into the tube to stretch the film. However, stable bubble stretching could not be performed, and the film was impossible to manufacture.

Claims (1)

[Claims] 1. A tubular unstretched polyether/ether/ketone film that has been melt-extruded from an annular die and rapidly cooled is continuously introduced between the feeding and taking-off rolls, and during this time the film is reheated from the circumferential direction and heated by internal pressure. In the method of expanding and simultaneously biaxially stretching, a tubular unstretched film with crystallinity kept below 10% is reheated to a temperature of 60 to 140°C, and then stretched to an area magnification of 4 to 36 times. A method for producing a tubular simultaneously biaxially stretched polyether/ether/ketone film.