JPH06370B2 - Method for producing polyetheretherketone film - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a biaxially stretched polyether ether ketone film having excellent mechanical strength in the machine direction and the transverse direction.

[Prior art and problems]

Films made of polyetheretherketone (hereinafter abbreviated as PEEK) have excellent properties such as heat resistance, chemical resistance, and moisture absorption resistance, so they can be used for various applications such as magnetic tapes and electrical insulation tapes. Is expected to be used.

Such PEEK film is generally biaxially stretched for the purpose of improving mechanical strength such as tensile elastic modulus and tensile strength.

Conventionally, the production of a biaxially stretched PEEK film is performed by converting a substantially amorphous PEEK film into a temperature range from a second-order transition temperature (hereinafter also referred to as Tg) of PEEK to about 200 ° C.
It is carried out by simultaneous or sequential biaxial stretching.

However, when the PEEK film is stretched by simultaneous biaxial stretching, the stretching ratio can be increased, but this has little effect of improving the mechanical strength, and the resulting film has uneven thickness, resulting in a commercial value. Has a problem of significantly decreasing On the other hand, when the PEEK film is sequentially stretched by biaxial stretching, it is extremely difficult to increase the stretching ratio in both the machine direction and the transverse direction, though the mechanical strength is improved by the stretching. That is, if the uniaxial longitudinal stretching ratio is increased, the molecular axis orientation coefficient of the PEEK film increases and crystallization proceeds, so that the film breaks during transverse stretching, and even if it is possible to stretch, the transverse thickness The unevenness increases, the mechanical strength of the obtained film in the transverse direction decreases, and vertical cracking of the film easily occurs. On the contrary, if the stretching ratio in the transverse direction of the film is increased and the mechanical strength in that direction is increased, the stretching ratio in the longitudinal direction must be lowered.

Therefore, in the successive biaxial stretching of the PEEK film described above, it is difficult to obtain a film having excellent mechanical strength in the machine direction and the transverse direction.
The use of the obtained biaxially stretched PEEK film was limited to the fields where mechanical strength was not required so much.

[Means for solving problems]

The inventors of the present invention have conducted earnest studies on a manufacturing method for producing a PEEK biaxially stretched film, which has excellent mechanical strength in the machine direction and the transverse direction and can be easily biaxially stretched.

As a result, the amorphous PEEK film was stretched to have a specific molecular axis orientation coefficient and crystallization heat dissipation amount, then stretched in the transverse direction, and then further stretched in the longitudinal direction. It was found that a biaxially stretched PEEK film having excellent mechanical strength in the machine direction and the transverse direction and having a good balance can be obtained, and the present invention has been completed.

That is, in the present invention, a film made of substantially amorphous PEEK is stretched in the machine direction in the range of Tg to crystallization temperature (hereinafter abbreviated as Tc) of the PEEK to obtain a molecular axis orientation coefficient (hereinafter abbreviated as fe). ) Is 0.15 to 0.30 and the amount of crystallization heat release (hereinafter abbreviated as ΔHc) is 2.5 to 4.0 cal / gr, and the film is then added in the range of Tg to Tc of PEEK of 1.5. ~ 4.0 times in the transverse direction, then PE
It is a method for producing a PEEK film, which comprises stretching 1.2 to 1.8 times in the machine direction in the range of Tg to Tc of EK.

In the present invention, “substantially amorphous” means a state in which diffraction peaks due to crystal parts are not observed in the X-ray diffraction pattern, and fe is (11) of PEEK film due to X-rays.
The intensity distribution around the stretching axis of (0) and (200) is determined by Wilchin
It was obtained according to the handling of sky. Also, T
g, Tc and ΔHc are measured by a differential calorimeter (DSC) during the temperature rising process. Further, in the present invention, the “film” does not have a strict meaning regarding the thickness, but the “sheet” is also a generic term.

In the present invention, PEEK is a general formula What is shown by (however, n is a positive integer) is used without particular limitation. Among them, those having a melt viscosity at 380 ° C. of 1,000 to 200,000 poise at a shear rate of 200 sec ⁻¹ are particularly preferably used. Further, another resin may be added within a range that does not impair the heat resistance and moisture absorption resistance of PEEK. Examples of such other resins include polysulfone-based resins, poly-pphenylene sulfide, polyarylate, and polycarbonate.

In the present invention, it is necessary for the PEEK film before stretching to be substantially amorphous in order to perform stretching under each stretching condition described below.

The method for producing such a substantially amorphous PEEK film is not particularly limited. As a typical method, PEEK is melt-extruded at a temperature of 360 ° C. to 430 ° C. with a slit-shaped die, for example, a T-die, and then 120 ° C.
Examples of a method of casting on a cooling drum kept at the following temperature and a method of further promoting the quenching effect include an electrostatic casting method in which static electricity is applied to the extruded film to bring it into close contact with the surface of the cooling drum. In this case, it is preferable that the space between the die and the cooling surface (air gap) is small,
It is particularly preferably 100 mm or less.

In the present invention, a substantially amorphous PEKK film is first prepared in the temperature range of Tg to Tc of PEEK and fe of 0.1 or less.
5 to 0.30, preferably 0.18 to 0.28, and Δ
Hc is 2.5 to 4.0 cal / gr, preferably 2.8 to 3.8
It is important to stretch in the transverse direction so that cal / gr. That is, the present inventors have conducted extensive research on biaxial stretching of PEEK films, and as a result, found that the fc and ΔHc of the film after longitudinal stretching are extremely important for the difficulty of stretching in subsequent transverse stretching and longitudinal stretching. It was. If the above-mentioned fc is less than 0.15 or ΔHc is more than 4.0 cal / gr, it is easy to stretch in the transverse direction in the next step. It is difficult to increase the draw ratio and the mechanical properties in that direction cannot be sufficiently improved. If the stretching ratio in the machine direction is forcibly increased, the film will be broken. On the other hand, the above ΔHc is 2.5ca
When it is smaller than 1 / gr, the film is highly crystallized and oriented to be crystallized, so that it becomes extremely difficult to stretch in the lateral direction in the next step, and the film is broken. Also, f
If you try to make c larger than 0.30, you will inevitably get ΔHc
Deviates from the above range, causing film breakage.

When the stretching temperature is lower than Tg or higher than Tc, the film is broken and cannot be stretched.

In the present invention, fc and ΔHc of the PEEK film after being stretched in the transverse direction are the draw ratio at a predetermined stretching temperature,
It is preferable to adjust the stretching speed or the like to be within the above range. Generally, the draw ratio is 1.5 to 3 times,
Preferably 1.8 to 2.5 times, stretching speed is 200 to 8000
% / Min, preferably in the range of 500 to 6000% / min, and conditions for fc and ΔHc to be in the above ranges may be appropriately selected.

In the present invention, the above-described PEEK film after stretched in the machine direction is then stretched in the transverse direction in the temperature range of Tg to Tc to 1.
Stretching is performed at a stretch ratio of 5 to 4 times, preferably 2 to 3.5 times. When the stretching ratio is less than 1.5 times, the mechanical strength of the obtained biaxially stretched PEEK film in the transverse direction is not sufficiently improved, and only the one having large thickness unevenness can be obtained. Further, in a place where the draw ratio is larger than 4 times, the biaxially-stretched PE excellent in mechanical strength in the machine direction cannot be drawn in the next machine direction by the desired draw ratio.
Unable to get EK film. Further, when the stretching temperature is out of the range of Tg to Tc, it is impossible to perform stretching at the above stretching ratio.

In the present invention, the PEEK film may be stretched 1.2 to 1.8 times, preferably 1.3 to 1.5 times in the machine direction after the above-mentioned transverse stretching. In combination with the stretching conditions in the machine direction, it is extremely important for improving the mechanical strength in the machine direction of the obtained biaxially stretched PEEK film. That is, the draw ratio is 1.2
If the stretching ratio is higher than 1.8 times, the effect of improving the mechanical strength of the obtained biaxially stretched PEEK film in the machine direction is low, and if the stretching ratio is higher than 1.8 times, the film tends to break. When the temperature is out of the range of Tg to Tc, it is impossible to perform the above stretching.

In the present invention, the stretching means for the PEEK film is not particularly limited, and known stretching means can be adopted without limitation. For example, the stretching in the longitudinal direction is generally performed by stretching between two sets of nip rolls having different peripheral speeds, and the stretching in the lateral direction is generally performed by a tenter. Further, the stretching temperature may be maintained at a predetermined temperature during each stretching, and the temperature may be lowered between the longitudinal stretching and the lateral stretching, or between the lateral stretching and the longitudinal stretching, You don't have to lower it.

In the present invention, in order to improve the dimensional stability and heat resistance of the biaxially stretched film, it is a preferred embodiment that the film in the temperature range of 200 ° C to the melting point is subjected to heat treatment under tension or under limited shrinkage.

〔effect〕

As can be understood from the above description, according to the method of the present invention, by stretching the PEEK film under specific conditions, the stretching ratios in the transverse direction and the longitudinal direction can be sufficiently increased. It is possible to obtain a biaxially stretched PEEK film having extremely excellent mechanical strength.

The biaxially stretched PEEK film obtained by the method of the present invention is extremely useful for applications such as electrical insulating films, magnetic tape films, flexible print substrate films, etc., which require strength as well as heat resistance and moisture absorption resistance. Is.

〔Example〕

Examples will be shown below for illustrating the present invention more specifically, but the present invention is not limited to these examples.

In addition, various tests in Examples and Comparative Examples were performed by the following methods.

(1) Measurement of Tg, Tc, and ΔHc Measurement was performed by DSC at a scan speed of 20 ° C / min.

The Tg and Tc of PEEK were 150 ° C and 18 ° C.
It was 0 ° C.

(2) Tensile Modulus, Tensile Strength, Tensile Strength Measured according to ASTM-882.

Examples 1 to 5 and Comparative Examples 1 to 6 PEEK (380G manufactured by I.C.I.) was melt extruded at a temperature of 400 ° C. using a T-die, and an air gap of 40 mm was obtained.
Cast on a cooling drum at 100 ° C at 0.1
A 5 mm non-oriented film was obtained.

The obtained PEEK film was stretched by changing the conditions of longitudinal stretching, transverse stretching and longitudinal stretching as shown in Table 1.
The mechanical strengths (tensile modulus and tensile strength) of the obtained biaxially stretched PEEK film are also shown in Table 1.

The longitudinal stretching was performed by two sets of nip rolls having different peripheral speeds, and the transverse stretching was performed by using a tenter.

Claims (1)

[Claims] 1. A film made of substantially amorphous polyether ether ketone is stretched in the longitudinal direction in the range of the second-order transition temperature to the crystallization temperature of the polyether ether ketone so that the molecular axis orientation coefficient is 0. .15 to 0.30 and a crystallization heat release amount of 2.5 to 4.0 cal / gr was obtained, and the film was then added in the range of the second order transition temperature of polyetheretherketone to the crystallization temperature of 1.5. -Polyetheretherketone stretched in the transverse direction by a stretch ratio of 4.0 to 4.0 times, and then stretched in the longitudinal direction by a stretch ratio of 1.2 to 1.8 times in the range of the secondary transition temperature to the crystallization temperature of the polyetheretherketone. Film manufacturing method.