JPH0664036A - Biaxially drawn film of syndiotactic polystyrene - Google Patents

Abstract

PURPOSE:To obtain a biaxially drawn film of syndiotactic polystyrene with excellent smoothness of the surface of the film, good handling characteristics regardless of film thickness and good scraping resistance of the film surface. CONSTITUTION:The title film consists of a styrene polymer having substantially syndiotactic structure and has at most 10/mm<2> projections of at least 1mum at least on one face, at most 200/mm<2> projections of smaller than 1mum and at least 0.54mum, a three dimensional surface roughness SRa of at least 0.01mum and at most 0.O5mum, an SDELTAa of at least 0.01 and at most 0.04 and an air escaping speed of at most 500sec.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a syndiotactic polystyrene biaxially stretched film, and more specifically, it has excellent smoothness of the film surface and good handling characteristics regardless of the film thickness. The present invention relates to a biaxially stretched syndiotactic polystyrene film having good abrasion resistance.

[0002]

2. Description of the Related Art Biaxially stretched syndiotactic polystyrene films are excellent in heat resistance, electrical characteristics, transparency, etc.
It is expected to be applied to various film applications such as magnetic tapes, photo / plate making, capacitors, and packaging. When used for these films, the handling property and the abrasion resistance property are major factors that determine the workability of the film processing process and the product quality. On the other hand, in these applications, smoothing and thinning of the film surface are also required. However, in the syndiotactic polystyrene biaxially stretched film, if the surface is simply smoothed and further thinned, the handling characteristics at the time of production and processing of the film become poor, and further, when the film is running, it becomes a guide roll. Due to such contact, scratches on the film surface due to poor abrasion resistance and adhesion of white powder to the roll occur.

As a film having good slipperiness, a film in which inorganic particles are added, the surface roughness Ra is within a specific range, and the coefficient of static friction is limited is known (Japanese Patent Laid-Open No. 3-74437).
issue).

[0004]

However, although the above-mentioned conventional films having good slipperiness can provide good handling characteristics at low speed work, there arises a problem that the handling characteristics rapidly deteriorate at high speed work. There was an occasion. Further, in the syndiotactic polystyrene biaxially stretched film, the handling property tends to deteriorate particularly when the thickness of the film becomes thin, and the above inorganic particles are added to the film to define the range of the surface roughness Ra and the coefficient of static friction. Also has the same tendency, and therefore, even if good handling characteristics are obtained,
When the thickness was changed, desired handling characteristics could not be obtained. Further, since the syndiotactic polystyrene biaxially stretched film is brittle at room temperature, there are problems such as scratches on the film and adhesion of white powder to the roll due to contact with the roll during production and processing of the film.

The present invention has excellent film surface smoothness,
And excellent handling properties regardless of the thickness of the film, further provides a good syndiotactic polystyrene-based biaxially stretched film with good abrasion resistance that does not cause scratches on the film surface during running or white powder on the roll. The purpose is to

[0006]

According to the present invention, the number of protrusions of 1 μ or more is 10 pieces / mm ² or less on at least one side and less than 1 μm 0.54 μ.
200 protrusions / m ² or less, 3D surface roughness SRa
Excellent in smoothness of film surface and related to film thickness, characterized by 0.01 μm or more and 0.05 μm or less, S Δa of 0.01 μm or more and 0.04 μm or less, and air bleeding speed of 500 seconds or less The present invention provides a syndiotactic polystyrene type biaxially stretched film which is excellent in handling property and has excellent abrasion resistance on the film surface.

The polystyrene polymer having stereoregularity of syndiotactic structure used in the present invention has a tacticity of diad (constituent unit is a phenyl group or a substituted phenyl group which is a side chain) quantified by a nuclear magnetic resonance method. 85% or more for two) and 50 for pentad (5 units)
It is desirable that the structure has a syndiotactic structure of not less than%.

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 (alkylstyrene) such as poly (p-tertiarybutylstyrene), poly (p-, m- or o-chlorostyrene),
Poly (halogenated styrene) such as poly (p-, m- or o-bromostyrene), poly (p-, m- or o-fluorostyrene), poly (o-methyl-p-fluorostyrene), poly ( p-, m- or o-chloromethylstyrene) and other poly (halogen-substituted alkylstyrenes), poly (p-, m- or o-methoxystyrene), poly (p-, m- or o-ethoxystyrene), etc. Poly (alkoxystyrene), poly (p-, m-
Or, poly (carboxyalkylstyrene) such as o-carboxymethylstyrene), poly (alkyletherstyrene) such as poly (p-vinylbenzylpropyl), poly (alkylsilylstyrene) such as poly (p-trimethylsilylstyrene), and Examples thereof include 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 polystyrene polymer used in the present invention has a weight average molecular weight of 10,000 or more, more preferably 50,0.
00 or more. When the weight average molecular weight is less than 10,000, it is not possible to obtain a biaxially stretched film having excellent strength and elongation characteristics and heat resistance. For the upper limit of the weight average molecular weight,
Although not particularly limited, if it is 1500,000 or more, breakage occurs due to an increase in the drawing tension, so that it is not preferable.

Further, the syndiotactic polystyrene biaxially stretched film of the present invention can be produced by a known method, for example, a sequential biaxial stretching method in which longitudinal stretching and transverse stretching are carried out in order,
Stretching methods such as transverse / longitudinal / longitudinal stretching method, longitudinal / horizontal / longitudinal stretching method, longitudinal / longitudinal / horizontal stretching method can be adopted, and selected according to various characteristics such as required strength and dimensional stability. To be done. In addition, you may perform a heat setting process, a longitudinal relaxation process, a lateral relaxation process etc. as needed. The relationship between the height of protrusions and the number of protrusions, the three-dimensional surface roughness SRa and SΔa, and the air bleeding speed are adjusted by the film forming conditions of the film and the lubricant particles. The type and amount of the lubricant particles are not particularly limited as long as the relationship between the protrusion height and the number of protrusions, the three-dimensional surface roughness SRa and S Δa, and the air bleeding speed fall within a predetermined range, silica, Examples of the particles include metal oxides such as titanium dioxide, talc, and kaolinite, salts of metals such as calcium carbonate, calcium phosphate, and barium sulfate, or particles inert to syndiotactic polystyrene-based polymers such as particles made of organic polymers. Any one of these lubricants may be used alone, or two or more thereof may be used in combination, but the average particle size of the lubricant used is 0.01
μm or more and 2.0 μm or less, particularly 0.05 μm or more and 1.5 μm or less, the degree of variation in particle size (the ratio of standard deviation to average particle size) is preferably 25% or less, and the addition amount is 100 parts by weight of syndiotactic polystyrene polymer. 0 for%.
The content is preferably 005% by weight or more and 2.0% by weight or less, and particularly preferably 0.1% by weight or more and 1.0% by weight or less. In addition, it is preferable that the shape of the lubricant particles includes at least one kind having a surface shape factor of 60% or more. This area shape factor is calculated by the following equation. Area shape factor = (projected cross-sectional area of particle / area of circle circumscribing particle) × 100 (%) In the polystyrene-based polymer used in the present invention, known antioxidants, antistatic agents, etc. may be added as necessary. It is possible to use a mixture containing a suitable amount of. The blending amount is preferably 10% by weight or less with respect to 100% by weight of the polystyrene polymer. If it exceeds 10% by weight, breakage tends to occur during stretching, resulting in poor production stability. The syndiotactic polystyrene biaxially stretched film of the present invention may have protrusions on at least one side of 10 μm / mm ² or less for 1 μm or more and 200 protrusions / mm ^{2 for} less than 1 μm and 0.54 μm or more. preferable. If the number of protrusions having a size of 1 μm or more exceeds 10 / mm ² , scratches and white powder are likely to occur due to the protrusions falling off from the film during running, resulting in poor abrasion resistance. Further, when the number of protrusions of less than 1 μm and 0.54 μm or more exceeds 200 / mm ² , the protrusions fall off, resulting in poor abrasion resistance. The protrusions of less than 0.54μ are not particularly limited, but 100 protrusions / mm ² or more of protrusions of less than 0.54μ and 0.27μ or more are required to prevent deterioration of abrasion resistance due to scratches and deterioration of handling properties. Is desirable.

Further, the syndiotactic polystyrene biaxially stretched film of the present invention needs to have a three-dimensional surface roughness SRa of at least one surface of 0.01 μm or more and 0.05 μm or less. If SRa is less than 0.01 μm, handling properties and abrasion resistance will be poor, and if it exceeds 0.05 μm, electromagnetic conversion properties will be poor in, for example, magnetic tape applications, and transparency will be reduced in photoengraving applications. Problems such as deterioration of withstand voltage characteristics occur in capacitor applications. Further, S Δa needs to be 0.01 or more and 0.04 or less. When S Δa is less than 0.01, the handling characteristics are poor, and when S Δa is more than 0.04, the electromagnetic conversion characteristics are poor in, for example, magnetic tape applications, and transparency is reduced in photography and plate making applications, which is not preferable, and film capacitors are used. In use, problems such as deterioration of withstand voltage characteristics occur.

Further, the air bleeding speed of at least one surface of the syndiotactic polystyrene type biaxially stretched film of the present invention must be 500 seconds or less. By setting the time to 500 seconds or less, a syndiotactic polystyrene type biaxially stretched film having good handling characteristics can be obtained regardless of the thickness and strength of the film even during high-speed work.
On the other hand, if the air bleed speed exceeds 500 seconds, the handling characteristics during high-speed work will be poor, and for example, when winding the film into a roll at high speed, air will be entrapped between the film and the take-up roll. Wrinkles are liable to occur, the winding shape becomes poor, and the film is meandered in the width direction due to the lubricating effect of the air layer in which the film is wound, resulting in uneven roll end surfaces.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition,
The evaluation method of the film is shown below.

(1) Three-dimensional surface roughness SRa, S Δa Using a stylus-type three-dimensional surface roughness meter (SE-3AK, Kosaka Laboratory Ltd.) on the film surface, the radius of the needle is 2 μm and the load is
Cutoff value of 0 in the longitudinal direction of the film under the condition of 30 mg.
25 mm, measuring length 1 mm, 2 μm pitch
It is divided into 500 points and the height of each point is calculated by 3D roughness analyzer (SP
A-11). The same operation as above was continuously performed 150 times in the width direction of the film at intervals of 2 μm, that is, over 0.3 mm in the width direction of the film, and the data was taken into the analyzer. Next, using an analyzer, SRa, SΔa
I asked. (2) Air release rate The measurement device shown in FIG. 1 is prepared. That is, a circular hole 1a is provided on the upper surface of the base 1, a glass plate 2 having a diameter of 70 mm is fixed in the hole 1a, and the glass plate 2 is fixed between the outer periphery of the glass plate 2 and the hole wall 1b. A groove is formed, and a ring-shaped groove 1c surrounding the hole 1b is opened, the groove 1c is communicated with the groove on the outer periphery of the glass flat plate 2, and the vacuum pump 4 is inserted through the pipe 3 into the groove 1c. Connect the suction port of. Then, a film sample 5 having a size that covers the glass flat plate 2 is placed on the upper surface of the base 1, and the outer periphery of the film sample 5 is hermetically fixed to the base 1 with an adhesive tape 6, and the vacuum pump 4 is driven to drive the glass flat plate. The time (seconds) from the appearance of the interference fringes on the outer peripheral portion of 2 to the spread of the interference fringes on the entire surface of the glass flat plate 2 and the movement thereof is measured, and this time (second) is defined as the air bleeding speed.

(3) Number of protrusions on the film surface After thinly and uniformly depositing aluminum on the film surface,
1m at 400x magnification using Nache two-beam interference microscope
The area of m ² was observed, and the projections having the interference fringes corresponding to the projection height were counted. (4) Film handling characteristics When slitting a wide slit roll at a high speed and rewinding it into a small roll, whether there is no problem with roll misalignment at the end of the roll, wrinkles, valves, etc.
It was graded and evaluated according to the following ranking. 1st grade: It is extremely difficult to obtain a problem-free slit roll 2nd grade: A low-problem slit roll can be obtained 3rd grade: A medium-speed slit roll can be obtained 4th grade: A high-speed nonproblem slit Roll is obtained

(5) Scratch resistance of film When the tape roll having a narrow slit in the film is rubbed against a metal guide roll to run, the amount of scratches generated after rubbing the guide roll against a constant supply tension And the amount of white powder adhered to the roll are evaluated on a scale of 5 and represented by the following rankings. When the evaluation results for scratches and white powder are different, the worse result of the two is adopted. 1st grade: Many scratches, white powder is very much generated 2nd grade: Many scratches, white powder is often generated 3rd class: Scratches are slightly present, white powder is slightly present 4th class: Almost no scratches, white powder is almost 5th grade; No scratches, no white powder

(6) Average particle size Lubricant particles are observed by a scanning electron microscope S-510 manufactured by Hitachi, Ltd., and photographed ones are magnified and copied to trace the external shape of the lubricant and optionally to 200 The individual particles were painted black. This image was measured for the Feret diameter in the horizontal direction of each particle using a Luzex 500 type image analyzer manufactured by Nikole Co., Ltd., and the average value was taken as the average particle diameter. Also,
The degree of variation in particle size was calculated by the following formula. Variability = (standard deviation of particle size / average particle size) x 100
(%) (7) Area shape factor 20 particles are arbitrarily selected from the trace image used to measure the average particle diameter, and the projected cross-sectional area of each particle is measured using the image analysis device used in (6). did. Further, the area of the circle circumscribing these particles was calculated and calculated by the following formula. Area shape factor = (projected cross-sectional area of particle / area of circle circumscribing particle) x 100 (%)

Example As a lubricant, silica having an average particle size of 1.2 μm, a degree of variation of 20% and an area shape factor of 75% was used with respect to 100% by weight of syndiotactic polystyrene (weight average molecular weight 300000).
After mixing the polymer chip added with the weight% and the polymer chip not added with the lubricant in a weight ratio of 1: 9, dried, melted at 295 ° C., and extruded from a T die with a 200 μm lip gap, A 71 μm amorphous sheet was obtained by adhering to a chill roll at 40 ° C by electrostatic loading and then solidifying by cooling. The amorphous sheet is first preheated to 95 ° C by a roll,
Using three infrared heaters with a surface temperature of 850 ℃, further heating, and stretching at a film temperature of 138 ℃ 3.6 times in the machine direction, then preheat the film to 120 ℃ with a tenter, and stretching temperature 120 ℃ in the transverse direction. The film was stretched 3.3 times at 260 ° C. and heat set at 260 ° C. The thickness of the obtained film was 6 μm. The measurement results of the obtained film are shown in the table.

Comparative Example The same operation as in Example was carried out except that the degree of silica dispersion of the lubricant particles was set to 40%. The evaluation results of the obtained film are shown in the table.

[0021]

[Table 1]

[0022]

As described above, according to the present invention, by adopting the constitution as described in the claims, the surface of the film is smooth and the handling property is good regardless of the thickness of the film. Further, a syndiotactic polystyrene biaxially stretched film having excellent abrasion resistance on the film surface is provided, and therefore the industrial value of the present invention is great.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an apparatus for measuring an air escape rate according to the present invention.

[Explanation of symbols]

 1: Platform 2: Glass flat plate 3: Suction pipe 4: Vacuum pump 5: Film sample 6: Adhesive tape

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Okuhira 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd.

Claims (1)

[Claims] 1. A styrene-based polymer having a substantially syndiotactic structure, and at least one projection having a size of 1 μ or more is 10 pieces / mm ² or less and a projection having a size of less than 1 μm and 0.54 μm or more is 200 pieces / mm ² or less. The three-dimensional surface roughness SRa is 0.01 μm or more and 0.05 μm or less, the S Δa is 0.01 or more and 0.04 or less, and the air bleeding speed is 500 seconds or less. Axial stretched film.