JPS6344051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an isotropically oriented film made of polyetheretherketone. Isotropy here means that properties such as mechanical strength are not impaired due to differences in direction within the plane of the film. Polyetheretherketone is a thermoplastic resin having the following structural units repeatedly, and is the most thermally stable resin among thermoplastic resins. In particular, because it does not structurally contain any elements other than carbon, hydrogen, and oxygen, it does not generate harmful gases even when burned, and is suitable for conventional heat-resistant resins such as polyimides, polysulfones, and polyphenylene sulfides. Various studies have been conducted as alternative, superior heat-resistant insulating materials. In particular, this film made of polyetheretherketone is used as a heat-resistant insulating film for winding tapes such as electric wires and magnet wires, hot water-resistant insulation coating tape, insulating tape for nuclear reactors, heat-resistant flexible printed circuit substrates, electrical Applications are expected for resistive surface heating element substrates, etc. We also use vacuum evaporation, sputtering, ion plating, etc. for metals, metal compounds, semiconductors, etc.
Attempts have been made to create electronic and optical devices by depositing thin films on synthetic resin films using methods such as plasma CVD, but when creating thin films, the synthetic resin film that serves as the base material is exposed to high temperatures and deforms. In addition, it is often desirable to heat the synthetic resin film that serves as the base material in view of the functional characteristics of the thin film material to be deposited.For these reasons, a synthetic resin film with high heat resistance is desired. However, the heat distortion temperature of polyetheretherketone film formed by ordinary melt extrusion method is
The temperature is low at 130-140℃, and the mechanical strength is not sufficient. It is known that such defects can be improved by stretching many thermoplastic resins. The present inventors also stretched a polyetheretherketone film obtained by melt extrusion molding and conducted studies to improve its properties, but in the usual method, the distortion caused by stretching causes heat setting. remains,
Only oriented films with extremely poor dimensional stability at high temperatures could be obtained. Therefore, the present inventors investigated the stretching conditions in order to improve the dimensional stability at high temperatures, and found that the orientation coefficients in two directions perpendicular to each other in the stretched film before heat setting were substantially the same. It was discovered that very effective heat setting is possible when the film is heated, and as a result of intensive study on a method for obtaining such a stretched film before heat setting, the present invention was arrived at. That is, the present invention has a specific gravity smaller than 1.276,
A film whose orientation coefficients are all in the range of 0.3 to 0.4 in the thickness direction of the film and in two directions perpendicular to the plane is stretched 1.5 to 4 times in one direction at a temperature of 140 to 180°C as primary stretching. After that, the first
The difference between the orientation coefficient in the first stretching direction and the orientation coefficient in the second stretching direction is 0.1 or less as the second stretching in the direction perpendicular to the next stretching direction in the range of 150 to 200 ° C.
Isotropic orientation characterized by stretching so that the sum of The present invention relates to a method for producing a polyetheretherketone film. In the present invention, a film having a specific gravity smaller than 1.276 and having orientation coefficients in the range of 0.3 to 0.4 in the film thickness direction and in two directions perpendicular to each other in the film can be easily obtained by the casting method. In order to make a film thick enough to be used, it is desirable to make it by melt extrusion.
The above-mentioned unstretched film produced by the melt extrusion method is produced by melt extruding polyetheretherketone at a temperature of 380°C or higher and 450°C or lower, and then pulling it using a cooling roll with a surface temperature of 140°C or lower and located within 20 cm from the die lip. It can be obtained by rapidly cooling while taking off so that the amount of netukuin obtained by taking off does not exceed 20% of the die lip width. In this case, the machine direction and the width direction of the extruded film can be selected as two directions that are perpendicular to each other in the plane. The orientation coefficient in the machine direction is cos ² φx,
If the orientation coefficient in the width direction is cos ² φy and the orientation coefficient in the thickness direction is cos ² φz, then cos ² φx + cos ² φy + cos ² φz
The relationship =1 holds true. Completely unoriented state
cos ² φx=cos ² φy=cos ² φz=1/3. The unstretched film obtained by the above melt extrusion method has all orientation coefficients within the range of 0.3 to 0.4, and is treated as substantially unoriented. If this range is shown in Desper's equilateral triangular diagram, it becomes the shaded area in Figure 1. Outside this region, the yield stress increases and stretching becomes difficult. Furthermore, if the gap between the die lip and the cooling roll is 20 cm or more, the pressed film moves through the air and slowly cools, resulting in a partially crystallized, patchy film. If it is further removed for more than 40 cm, the entire film will crystallize and become a grayish-yellow film. A similar phenomenon is observed when the cooling roll temperature is higher than 140°C. A highly crystallized film has a large yield stress;
Not only does the elongation decrease, making it unsuitable for stretching, but the transparency also decreases, which is a fatal drawback in some applications. The degree of crystallization can be judged by transparency, but specific gravity can be used to accurately measure the degree of crystallization. "The specific gravity of the amorphous part of polyetheretherketone is
1.265, and the specific gravity of the crystal part is 1.320. A film with a low crystallinity and a specific gravity of 1.276 or less, more preferably 1.272 or less, can be stretched by the same operation as a substantially amorphous film.
According to the above extrusion film forming method, the specific gravity is 1.270.
The following unstretched film is obtained. The unstretched film thus obtained is first stretched in one direction at a temperature of 140 to 180°C.
It is stretched 1.5 to 4 times. This direction may be the machine direction of the film when the unstretched film is made by extrusion molding, or
Although it may be the width direction, generally in sequential biaxial stretching, the machine direction is the primary stretching direction. When the first stretching ratio is less than 1.5, sufficient improvement is not observed in the mechanical strength of the film obtained after the second stretching. In this case, the sum of orientation coefficients in two directions within the film plane is smaller than 0.7. In addition, when stretching 4 times or more in the first stretching,
During the second stretching process, the film tends to break,
Unable to produce stably. Stretching temperature is 140
If the temperature is lower than ℃, uniform stretching will not be possible, resulting in a film with extremely poor thickness accuracy. If the stretching temperature is higher than 180° C., crystallization proceeds faster than stretching, resulting in a higher yield point stress, which not only makes stretching difficult but also causes opacity due to the formation of spherulites, which is undesirable. In the second stretching performed after the first stretching, the film is stretched in a direction perpendicular to the direction of the first stretching. In a rolled film in which the first stretching is performed in the machine direction, the direction of the second stretching is the width direction. The difference in orientation coefficient in each stretching direction in the present invention is
In order to achieve a value within 0.1, a method is used in which the film after the second stretching is directly irradiated with polarized light, the difference in orientation coefficient is calculated from the phase difference due to birefringence, and the stretching ratio is adjusted. As a simple method, there is a method in which the orientation coefficients are calculated from a film that has been stretched in advance with a combination of several types of stretching ratios, and stretching conditions are determined such that the sum of each is 0.7 or more and the difference is 0.1 or less, but the manufacturing method according to the present invention Since this is of extremely high order, it is necessary to obtain a large amount of data for determining the conditions, which is not very desirable. In the first stretching, a substantially non-oriented film is stretched, but in the second stretching, the oriented film is stretched in a direction perpendicular to the orientation direction. Even if stretching is performed under the same conditions, the orientation will not be isotropic. Since molecular chains become difficult to move due to orientation, it is preferable to perform the second stretching at a slightly higher temperature than the first stretching. Although the secondary stretching ratio that provides isotropic orientation varies depending on the stretching temperature, an isotropically oriented film can be easily obtained by controlling the orientation coefficient according to the present invention. In both the first stretching and the second stretching, unless the stretching speed is 300%/min or more, an effective change in the orientation coefficient cannot be obtained. In particular, 1000%/min or more is desirable. The isotropically oriented film thus obtained is heat set to improve its dimensional stability. Heat setting is carried out by heating the film for 1 to 60 seconds at a temperature above 200° C. and below the melting point under tension that allows limited shrinkage within 20%. If the sum of the orientation coefficients in the two stretching directions is less than 0.7, spherulites will be generated by heat setting and opacity will be observed, but if it is 0.7 or more, the transparency will hardly change. When the orientation coefficient of the heat-set isotropically oriented polyetheretherketone film is shown in an equilateral triangular diagram, it is included in the shaded area in FIG. In other words, the present invention is based on the idea that by monitoring the orientation coefficient, an unstretched film given specific physical properties is stretched and converted into a state exhibiting different specific physical properties. The isotropically oriented polyetheretherketone film obtained by the present invention has significantly better mechanical strength, heat resistance, and chemical resistance than an unstretched film. Furthermore, the anisotropically oriented polyetheretherketone film not according to the present invention has poor dimensional stability under heat, which is a serious drawback in electronics applications. The isotropically oriented polyetheretherketone film obtained by the present invention may be a film consisting only of polyetheretherketone, or may be a composite composition containing polyetheretherketone as a main component. good. Other components of the composite composition include lubricants, reinforcing agents, fillers, pigments,
It may be one or a combination of two or more selected from heat stabilizers, ultraviolet absorbers, antistatic agents, slipperiness improvers, nucleating agents, and the like. Examples 1 to 3, Comparative Examples 1 and 2 Amorphous films having a thickness of 0.2 mm were prepared from polyether ether ketone by melt extrusion. Film density is 1.270, orientation coefficient is cos ² φx=0.355,
cos ² φy=0.337, cos ² φz=0.308. This film was first stretched twice in the machine direction using a roll-type longitudinal stretching machine. The stretching roll temperature was 160°C and the stretching speed was 2300%/min. The density of the film after longitudinal stretching is 1.275, the orientation coefficient is cos ² φx = 0.489,
cos ² φy=0.265, cos ² φz=0.246. This longitudinally stretched film was stretched in the width direction using a tenter type horizontal stretching machine. The stretching ratio was determined by measuring the orientation coefficient of the film after stretching to determine the value at which cos ² φx and cos ² φy were equal. Although the stretching temperature and stretching speed were varied as shown in Table 1, an isotropically oriented film was easily obtained in each case. Table 1 also shows anisotropically oriented films not according to the present invention as comparative examples. In all cases, heat fixation was carried out at 270°C for a fixed length of 20 seconds. 【table】

[Brief explanation of the drawing]

FIG. 1 is an equilateral triangular diagram showing the range of orientation coefficients of the unstretched film used in the present invention, and FIG. 2 is an equilateral triangular diagram showing the range of orientation coefficients of the isotropically oriented polyetheretherketone film obtained by the present invention. It is.

Claims (1)

[Claims] 1 Polyether ether ketone having a specific gravity smaller than 1.276 and an orientation coefficient of 0.3 to 0.4 in the film thickness direction and in two directions perpendicular to the film plane is heated at 140 to 180°C in one in-plane direction.
After primary stretching 1.5 to 4 times at After secondary stretching by controlling the orientation coefficient, heat setting is carried out for 1 to 60 seconds under tension that allows limited shrinkage within 20% in an atmosphere at a temperature of 200°C or higher and lower than the melting point. A method for producing a sexually oriented polyetheretherketone film.