JPH0733060B2 - Manufacturing method of polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polyester film having improved slitability.

[Background technology]

The polyester film is generally produced as follows. First, the raw material is supplied to an extruder, melt-extruded, and formed into a sheet by a die. Then, this is cooled and solidified to form an unstretched sheet. This unstretched sheet is stretched in the longitudinal direction and further stretched in the width direction to obtain a biaxially stretched polyester film. This polyester film is passed through a slit, and both side edges are cut to have a desired width.

However, the polyester film obtained by the conventional production method has a problem that the slit property is poor because a lot of beard is formed at the cut end during slitting. Polyester films are used in a wide range of fields such as magnetic tapes and general industrial applications. However, when magnetic tapes are manufactured using conventional polyester films, the slitting properties of conventional polyester films are Since it was bad, the performance of the product might be problematic.

[Object of the Invention]

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing a polyester film capable of obtaining a polyester film having a good slit property.

[Disclosure of Invention]

The inventors have conducted extensive research in order to achieve the above-mentioned object. In the process, it was thought that there was some correlation between the parameters relating to the properties of the polyester film and the slittability, and this was investigated for many parameters. As a result, among these parameters, the particle size Sc of the polyester crystal, the crystalline plane orientation index xi of the polyester and Δn [Δn = (n _MD −n _TD ) × 10 ³ ]
It was found that the above object can be achieved by defining the person by a predetermined formula, and the present invention was completed here.

That is, the present invention is a method for producing a biaxially stretched polyester film, wherein the particle size Sc of the polyester crystals of the obtained film, the crystalline plane orientation index xi and Δ of the polyester.
A method for producing a polyester film is characterized in that these parameters Sc, xi, Δn are adjusted so that n satisfies the following expression (a), and a film is produced.

5 ≦ −6.36−0.284xi + 0.254Sc−0.026Δn ...
(A) However, Sc: grain size (Å) xi (crystal plane orientation index) of polyester crystal = [I (10) / I (100)] × 10 ² (b) where I: wide-angle X-ray Diffraction intensity Δn = (n _MD −n _TD ) × 10 ³ (c) Note that n _MD : longitudinal refractive index n _TD : lateral refractive index The present invention will be described in detail below.

The crystalline plane orientation index xi of polyester is a value obtained by the above equation (b), and becomes smaller as the plane orientation advances. As described above, I in the formula (b) is the intensity by wide-angle X-ray diffraction, and I (10) is the diffraction intensity at 26.0 ° corresponding to the diffraction angle of the (10) plane of the polyester crystal. , I (100) is the diffraction intensity at 22.5 ° corresponding to the diffraction angle of the (100) plane of the polyester crystal.

The diffraction intensity was set by stacking a polyester film with a thickness of 50 μm on a sample holder of an X-ray diffractometer (such as Geigerflex manufactured by Rigaku Denki Co., Ltd.) and setting the X-ray irradiation angle in the plane perpendicular to the longitudinal direction of the film. It can be changed and measured by the reflection method. The measurement conditions are as follows.

Time constant -2 seconds Traction speed -1 degree / minute Divergency Slit-1.5mmφ Scattering Slit -1 degree X-ray-Cu-Cu a-cathode Cu-Kα ray (35kV, 5mA, Ni filter) Crystalline orientation index xi is It can be lowered by increasing the area ratio during stretching, and conversely can be increased by lowering. This does not concern only the draw ratio in the machine direction or the draw ratio in the transverse direction. Further, the crystalline plane orientation index can be lowered by performing stretching at a low temperature and can be increased by performing stretching at a high temperature when compared at the same area magnification. The three parameters Sc, xi, Δn are related to each other, and
Although satisfying the equation, if attention is paid only to the parameter xi, in the equation (a), the crystalline plane orientation index xi may be lowered to satisfy this equation.

The particle size (crystal size) Sc (Å) of the polyester crystal is a value defined by the following equation (d).

Sc = λ / [(B−b) cos θ] (d) where B: half-value width of diffraction peak b = 0.12 λ: wavelength of Kα ray of Cu (1.5418Å) θ: diffraction angle of peak The particle size Sc of the polyester crystal is calculated as follows. That is, using an X-ray diffractometer, the diffraction peak was observed by the reflection method while changing the angle between the film width direction and the X-ray incident direction. The particle size Sc in the diffraction crystal direction is calculated.

The particle size Sc of the polyester crystal generally increases as the crystallization by plane orientation or heat progresses. Therefore,
The crystal grain size Sc can be increased by increasing the area ratio during stretching to promote the plane orientation, and conversely by decreasing the area ratio, the crystal grain size Sc can be decreased. Further, when compared at the same area magnification, the crystal grain size Sc can be increased by stretching at a low temperature, and conversely, the crystal grain size Sc can be reduced by stretching at a high temperature. Further, the crystal grain size Sc can be increased as the crystallization temperature is increased by increasing the temperature of the heat treatment during manufacturing, and conversely, the crystal grain size Sc can be reduced by decreasing the heat treatment temperature. Focusing only on the parameter Sc, it can be seen that in the formula (a), the grain size of the polyester crystal may be increased to satisfy this formula.

The parameter Δn can be calculated according to JIS K 7105-1981 by measuring n _MD and n _TD using an Abbe refractometer and putting these measured values in the above formula (c). The setting direction of the film with respect to the incident light and the angle of the deflecting plate set on the telescope are as shown in FIG. 1 in the measurement of n _TD and shown in FIG. 2 in the measurement of n _MD . To be In FIGS. 1 and 2, 3 indicates a film, 4 indicates a deflector, arrow B indicates incident light, and arrow C indicates the longitudinal direction of the film.

Δn can be increased by increasing n _MD and decreasing n _TD, and decreased by reversing it. n _MD can be raised by increasing the stretching ratio in the machine direction, and can be lowered by lowering it. n _TD can be lowered by lowering the stretching ratio in the transverse direction, and can be raised by raising it in the opposite direction. Further, n _MD can be raised by lowering the longitudinal stretching temperature, and conversely, it can be lowered. n _TD can be lowered by increasing the transverse stretching temperature and conversely can be raised by lowering it. Focusing only on the parameter Δn, it can be seen that in the above equation (a), Δn should be lowered in order to satisfy this equation.

The method for producing a polyester film according to the present invention is such that the particle size Sc of the polyester crystals, the crystalline plane orientation index xi and Δn of the polyester satisfy the above formula (a),
Since the parameters Sc, xi and Δn are adjusted, the slit property is improved.

To confirm this, polyester films of Samples 1-7 were made. Then, the grain size S of the polyester crystal
c, the crystalline plane orientation indices xi and Δn of the polyester were measured, and these measured values were put into the following formula (e) to calculate the estimated slit property. Here, the expression (e) is the same as the expression (a) except that the left side 5 is changed to and ≦ is changed to =. If this is 5 or more, the parameters Sc, xi, Δn of the film are If the formula (a) is satisfied and less than 5, it means that the film parameters Sc, xi, Δn do not satisfy the formula (a).

= -6.36-0.284xi + 0.254Sc-0.026Δn
(E) On the other hand, with respect to Samples 1 to 7, the number of whiskers on the cut end face was measured. The number of mustaches on the cut end surface is 2 after slitting each sample.
The sheets were laminated, and the number of whiskers on the cut end surface (one side) was counted by observing a field of view of a length of 2.0 mm with a 50 × optical microscope. Here, the slit used was a shear cutter type manufactured by Nishimura Seisakusho, and the slit speed was 50 m / min.

Then, according to Table 1, this whisker number was made to correspond to the actually measured value of the slit property y, and the slit property was determined. However, ⊚ is very excellent, ◯ is good, Δ is normal, and x is bad.

The polyester films of Samples 1 to 7 were prepared as follows.

(Sample 1) To dimethyl terephthalate and ethylene glycol, add 0.08% by weight of calcium acetate, 0.15% by weight of lithium acetate, 0.04% by weight of antimony oxide, 0.15% by weight of trimethyl phosphate and 0.03% by weight of calcium carbonate having an average particle size of 1.1 μm. Polycondensation was carried out by a conventional method to obtain a polyester having an intrinsic viscosity of 0.62.

This polyester is dried and extruded by a conventional method to give an unstretched sheet, which is passed through a group of rolls 11 to 19, 11 ', 16'17'19' shown in FIG. Was stretched. In the figure, 5 indicates a polyester film stretched in the machine direction. The temperature of the roll is 11,12 78 ℃, 1
3,14 was 120 ° C, 15 was 125 ° C, 16 was 125 ° C, and 17 was 114 ° C. Then, the rolls 15 to 16 were stretched at a draw ratio of 1.1, the rolls 16 to 17 were stretched to be 1.21 times, and the rolls 17 to 18 were stretched to be 2.4 times. Next, 110 ℃ in the first tenter
Was stretched 3.7 times in the transverse direction under hot air. After this, the film was introduced into the second tenter, and 3.3% in hot air at 205 ° C.
While relaxing, heat setting was performed at 205 ° C. to obtain a polyester film.

(Sample 2) The temperatures of rolls 15, 16 and 17 were set to 128 ° C and 128, respectively.
A polyester film was obtained in the same manner as in Sample 1, except that the temperature was 115 ° C. and 115 ° C., and the film was stretched in the transverse direction by 1.15 times in the second tenter.

(Sample 3) Using 0.035% by weight of calcium carbonate, roll 1
Temperatures 3-14, 15 and 16 are 115 ° C, 120 ° C and 120 ° C, respectively.
℃, 1.50 times between rolls 16-17, between rolls 17-18 2.
A polyester film was obtained in the same manner as in Sample 1, except that the polyester film was stretched to 50 times and heat-set at 210 ° C.

(Sample 4) Using 0.04% by weight of calcium carbonate, roll 17
A polyester film was obtained in the same manner as in Sample 1 except that it was stretched 2.0 times in the range of -18.

(Sample 5) A polyester film was obtained in the same manner as in Sample 1, except that the rolls 13 and 14 were set to 123 ° C. and the rolls 17 to 18 were stretched 2.0 times.

(Sample 6) A polyester film was obtained in the same manner as in Sample 1 except that the film was stretched 1.05 times in the transverse direction in the second tenter.

(Sample 7) Use 0.15% by weight of calcium carbonate and roll 17
A polyester film was obtained in the same manner as in Sample 1, except that it was stretched 2.0 times in the range from -18 to 1.05 times in the second tenter in the transverse direction.

Table 2 shows the particle size Sc of the polyester crystals of each sample, the crystalline plane orientation index xi of the polyester, Δn, the estimated slit property and the actually measured slit property y.

From Table 2, estimated slit property and measured slit property y
It can be seen that it is possible to estimate the measured slit property y from the estimated slit property, and if is 5 or more, the measured slit property is ○.
As described above, it can be seen that the excellent slit property is exhibited.

〔The invention's effect〕

The method for producing a polyester film according to the present invention is such that the particle size Sc of the polyester crystals of the obtained film, the crystalline plane orientation index xi and Δn of the polyester are represented by the following formula (a):
Since the parameters Sc, xi, and Δn are adjusted so as to satisfy the above condition, a film having a very small number of beards and an excellent slit property can be stably obtained.

[Brief description of drawings]

Figure 1 is an explanatory diagram of the n _TD measurement method using the Abbe refractometer,
Figure 2 is an illustration of the method for measuring n _{MD with} the Abbe refractometer,
FIG. 3 is an explanatory diagram of manufacturing the sample. 3 ... Polyester film

Continuation of the front page (56) Reference JP-A-58-23323 (JP, A) JP-A-59-121625 (JP, A) JP-A-55-64635 (JP, A) JP-A-61-154924 (JP , A) JP-A-61-237623 (JP, A) JP-A-61-254328 (JP, A)

Claims (1)

[Claims] 1. A method for producing a biaxially stretched polyester film, comprising a polyester crystal grain size Sc,
The crystalline plane orientation indices xi and Δn of the polyester are set so that these parameters Sc, xi,
A method for producing a polyester film, which comprises adjusting Δn to make a film. 5 ≦ −6.36−0.284xi + 0.254Sc−0.026Δn ...
(A) However, Sc: grain size of the polyester crystal (Å) xi (crystalline plane orientation index) = [I (10) / I (100)] x 10 ² I: intensity by wide-angle X-ray diffraction Δn = ( n _MD −n _TD ) × 10 ³ where n _MD : vertical refractive index n _TD : horizontal refractive index