JPH0691750A - Syndiotactic polystyrene biaxially drawn film - Google Patents

Abstract

PURPOSE:To provide a syndiotactic polystyrene biaxially drawn film which is superior in flatness and thickness mottling. CONSTITUTION:The title film is a biaxially drawn film which consists of a styrene polymer with a syndiotactic structure, of which the orientation ratio obtained by the formula shown below is 0.4-2.0, and at the same time, of which the distribution in the azimuth direction of a crystal element, which is evaluated using a crystal diffraction peak which is at 20.6 deg. in the wide angle X-ray diffraction, is not divided around the maximal value and has only one peak. (Orientation ratio: Ax/Ay, Ax: 1222cm<-1> band strength when the polarization direction of infrared beams meets the width direction of the film, Ay: 1222cm<-1> band strength when the polarization direction of infrared beams meets the longitudinal direction of the film.)

Description

Detailed Description of the Invention

[0001]

The present invention relates to a biaxially stretched syndiotactic polystyrene film excellent in flatness and thickness unevenness,
More specifically, the present invention relates to a biaxially stretched syndiotactic polystyrene film having good flatness and thickness unevenness when used for magnetic tape, photo / plate making, condenser, and packaging.

[0002]

2. Description of the Related Art Syndiotactic polystyrene biaxially stretched films have been developed that have excellent heat resistance, electrical properties, transparency, etc. (Japanese Patent Laid-Open Nos. 1-110122 and 1-11).
68709, 1-182346, 2-2797.
No. 31, No. 3-74437, No. 3-109453,
3-99828, 3-124427, 3-1
31644), magnetic tapes, capacitors,
It is expected to be applied to various film applications such as packaging.
In recent years, in particular, there has been a strong demand in recent years for thin films having excellent flatness and thickness unevenness. However, in the conventional syndiotactic polystyrene biaxially stretched film, when stretched to a high ratio to make it thin,
Since the syndiotactic polystyrene-based biaxially stretched film is brittle, breakage occurs during stretching and the stretchability deteriorates.
Therefore, when the draw ratio was lowered, the flatness and thickness unevenness were not satisfactory, so that only a limited number of applications were developed.

[0003]

Since the syndiotactic polystyrene biaxially stretched film is fragile, it is apt to break during stretching of the film. For this reason, the draw ratio may be set lower, but at this time, problems arise in terms of flatness and thickness unevenness. An object of the present invention is to provide a syndiotactic polystyrene biaxially stretched film excellent in flatness and thickness unevenness.

[0004]

Means for Solving the Problems Under the stretching conditions in which breakage is unlikely to occur during stretching, the present inventors have earnestly studied to satisfy both the flatness and the thickness unevenness, and as a result, the alignment and crystal of the syndiotactic polystyrene molecular chain The inventors have found that it is possible to satisfy both flatness and thickness unevenness by controlling the orientation of the child within a certain range, and have reached the present invention. That is, the present invention has an orientation ratio of 0.4 to 2.0 determined by the following formula and has a wide angle X-ray diffraction of 20.6.
Syndiotactic polystyrene excellent in flatness and thickness unevenness, characterized in that the distribution of crystallites in the azimuth direction evaluated using the crystal diffraction peak at ゜ does not split near the maximum value and has only one peak Biaxially stretched film.
The polystyrene polymer with stereoregularity having a syndiotactic structure used in the present invention has a tacticity of diad (two constitutional units) in which a side chain phenyl group or substituted phenyl group is quantified by a nuclear magnetic resonance method. At 85%
As described above, it is desirable that the pentad (5 units) has a syndiotactic structure of 50% or more. Examples of the polystyrene-based polymer include polystyrene, poly (p-, m- or o-methylstyrene), poly (2,4-, 2,5-, 3,4- or 3,
5- (dimethylstyrene), poly (p-tertiarybutylstyrene) and other poly (alkylstyrenes), poly (p-,
m- or o-chlorostyrene), poly (p-, m- or o-bromostyrene), poly (p-, m- or o-fluorostyrene),
Poly (halogenated styrene) such as poly (o-methyl-p-fluorostyrene), poly (halogen-substituted alkylstyrene) such as poly (p-, m- or o-chloromethylstyrene), poly (p-, m -Or o-methoxystyrene), poly (p-, m- or o-ethoxystyrene) and other poly (alkoxystyrene), poly (p-, m- or o-carboxymethylstyrene) and other poly (carboxyalkylstyrene) )
Examples thereof include poly (alkyl ether styrene) such as poly (p-vinylbenzylpropyl), poly (alkylsilylstyrene) such as poly (p-trimethylsilylstyrene), and poly (vinylbenzyldimethoxyphosphide).

In the present invention, polystyrene is particularly preferable among the polystyrene polymers. Also,
The polystyrene-based polymer having a syndiotactic structure used in the present invention is not necessarily a single compound, and if the syndiotacticity is within the above range, a polystyrene-based polymer having an atactic structure or an isotactic structure is used. It may be a mixture of, a copolymer and a mixture thereof. The biaxially stretched syndiotactic polystyrene of the present invention is obtained by melt-extruding the syndiotactic polystyrene by a conventional method, then sequentially or simultaneously biaxially stretched, and further stretched in the longitudinal direction or the transverse direction as needed, and then 150- 280
It is obtained by heat-setting at a temperature of ° C, and the most important feature is that the molecular orientation and crystal orientation of the film are within a certain range. The molecular orientation obtained by the infrared absorption method is a parameter for evaluating how much the main chains of syndiotactic polystyrene molecular chains are aligned by transconformation as a whole system including a crystal part and an amorphous part. As this value approaches 1, the molecular chains are isotropic, and as it approaches 0, TD
It is oriented in the direction, and as it becomes larger than 1, it is oriented in the MD direction. The inventors have found that the molecular orientation determined by this infrared absorption method has a very strong correlation with the stretchability, and when this value is outside the claimed range, the breakage during stretching or heat setting increases rapidly, A good film cannot be obtained.

Next, in the syndiotactic polystyrene film of the present invention, the distribution curve in the azimuth direction of the crystallite evaluated using the crystal diffraction peak at 20.6 ° in wide-angle X-ray diffraction did not split near the maximum value. It is necessary to give only one peak. This crystal orientation represents the degree of orientation of the syndiotactic polystyrene crystallite, and the distribution curve in the azimuth direction does not split near the maximum value and
Giving only one peak indicates that the crystallites are extremely oriented in that direction. The inventors have found that the orientation of this crystallite has a close correlation with the flatness / thickness variation of the film, and further, by making the orientation distribution curve not split near the maximum value but only one peak, We found that such flatness and thickness unevenness can be improved.

[0007]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation method of the film is shown below. (1) Molecular Orientation The molecular orientation of syndiotactic polystyrene molecular chains was measured according to the report that the infrared absorption band at 1222 cm ⁻¹ was due to transconformation. Using a Perkin Elmer infrared spectrophotometer, the inclination of the sample with respect to polarized infrared was changed and the absorption intensity was measured. 1222 cm ^-1 of light,
The absorption intensity when the electric vector of the incident light coincided with the width direction of the film was standardized in the 1182 cm ^-1 band as Ax, and the absorption intensity when it coincided with the longitudinal direction of the film was normalized in the 1182 cm ^-1 band. If the value is Ay, the molecular orientation is defined by Ax / Ay.

(2) Crystal orientation distribution A biaxially stretched film was laminated so as to have a thickness of about 500 mm to prepare a sample for X-ray diffraction, which was a sample of an X-ray diffractometer (Rotaflex, manufactured by Rigaku Denki Co., Ltd.). Install in the holder. When the X-ray is incident perpendicularly to the film surface, θ = 0 °, and when the detector is on the extension line of the incident X-ray, 2θ = 0 °. First, the sample is set so that the scanning surface and the width direction of the film are parallel to each other, and this state is set to an azimuth angle χ = 0 °. In this state, scan 2θ and fix the detector at the maximum position of the crystal diffraction peak seen near 2θ = 20.6 °. In this state, θ is further scanned and θ is fixed when the intensity of the diffraction peak has a maximum value. In this way, after so-called crystal plane alignment, the azimuth angle is scanned, and the azimuth angle dependence of the crystal diffraction peak intensity at this time is recorded, which is called a crystal orientation distribution curve.

(3) Flatness A film having a width of 50 cm was unwound from a roll for a length of 200 cm, and the flatness of the film was observed and evaluated in five steps, and the results were expressed by the following rankings. 1st grade; there is a wavy surface even with strong tension 2nd grade; there is some wavy even with strong tension 3rd grade; no waviness when strong tension is applied 4th grade; no waviness when weak tension is applied 5th grade; tension No waviness without applying

(4) Thickness unevenness The widthwise central portion of the biaxially stretched film was measured along the longitudinal direction with a continuous film thickness measuring instrument manufactured by Micron Instruments Co., Ltd. and calculated by the following formula. Thickness group = (maximum thickness-minimum thickness) / average thickness x 100% Grade 1: Thickness group 10% or more Grade 2: Thickness group 8-10% Grade 3: Thickness group 6-8% Grade 4: Thickness group 4-6% Grade 5: Thickness group 4% or less

EXAMPLE As a lubricant, 2.0% by weight of calcium carbonate having an average particle size of 0.8 μm, a degree of variation of 20% and an area shape factor of 75% was added to 100% by weight of syndiotactic polystyrene (weight average molecular weight 300000). Chips and polymer chips to which a lubricant was not added were mixed at a weight ratio of 1: 9, dried, melt-extruded at 295 ° C., cooled and solidified to obtain an amorphous sheet. The amorphous sheet was first stretched 1.6 times in the machine direction at 110 ℃ using multiple infrared heaters, and then stretched in the machine direction using a roll heated to 140 ℃.
Stretch 2.0 times. Then in a tenter, laterally at 110 ° C 1.
After stretching 6 times, it is stretched 2.0 times in the transverse direction at 140 ° C. This film was heat-set at 240 ° C. and then relaxed at 230 ° C. in the width direction by 3%. The resulting film has a molecular orientation
At 0.9, the crystal orientation distribution curve gave only one peak without splitting near the maximum value as shown in FIG. The flatness of this film was grade 5, and the thickness group was grade 5.

Comparative Example The amorphous sheet used in the examples is stretched 2.8 times in the machine direction using a roll heated to 135 ° C. Then, it was stretched 3.0 times in the transverse direction at 120 ° C with a tenter and heat set at 250 ° C.
It was relaxed at 0 ° C in the width direction by 3%. The obtained film had a molecular orientation of 0.8, and the crystal orientation distribution curve was split into two near the maximum value as shown in FIG. The flatness of this film was grade 2, and the thickness group was grade 2.

[0013]

As described above, the present invention is a syndiotactic polystyrene biaxially stretched film which is extremely excellent in flatness and thickness unevenness by adopting the constitution as described in the claims. Can be said to be.

[Brief description of drawings]

FIG. 1 is a crystal orientation distribution curve of a film obtained in an example.

FIG. 2 is a crystal orientation distribution curve of a film obtained in a comparative example.

[Explanation of symbols]

 Azimuthal angle: Film azimuth Intensity: Crystal diffraction intensity

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B29K 105: 32 B29L 7:00 4F (72) Inventor Tadashi Okuhira 2-1-1 Katata, Otsu City, Shiga Prefecture No. 1 Toyobo Co., Ltd.

Claims (1)

[Claims] 1. A crystal diffraction peak composed of a styrene-based polymer having a substantially syndiotactic structure, having an orientation ratio of 0.4 to 2.0 determined by the following formula and having a wide-angle X-ray diffraction at 20.6 ° is used. A biaxially stretched syndiotactic polystyrene film, characterized in that the distribution of crystallites evaluated in the azimuth direction does not split around the maximum value and has only one peak. Orientation ratio = Ax / Ay Ax: infrared light polarization direction 1222Cm ^-1 band intensity Ay when matched with the width direction of the film: the infrared light polarization direction when matched with the longitudinal direction of the film 1222Cm ^-1 Band strength