JPH08143727A - Biaxially oriented polystyrene film - Google Patents

Abstract

PURPOSE: To prepare a biaxially oriented polystyrene film having few coarse protrusions on the surface and being excellent in transparency, slip, withstand voltage properties and abrasion resistance by mixing a specified surface- irregularity-forming agent with a surface modifier. CONSTITUTION: This film is the one made from a syndiotactic polystyrene resin and containing inorganic and/or organic surface-irregularity-forming agents and a polystyrene-based surface modifier. It is desirable that the polystyrene resin has a syndiotactic structure of a diad fraction of 85% or above and a pentad fraction of 50% or above. It is desirable that the surface-irregularity- forming agent has a mean particle diameter of 0.01-2.0μm and that it is used in an amount of 0.005-0.2wt.% or above. An example of the surface modifier used is the one having a polystyrene skeleton which has an average molecular weight of 5000 or above and is modified with an iminium ion at one molecular end, and it is desirably used in an amount of 0.1-10wt.% based on the surface- irregularity-forming agent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a syndiotactic polystyrene biaxially stretched film, and more particularly, it is suitable as a base film for packaging, capacitors, magnetic tapes, etc., and has transparency, slipperiness, withstand voltage characteristics and abrasion resistance. The present invention relates to a syndiotactic polystyrene-based biaxially stretched film having excellent properties.

[0002]

2. Description of the Related Art Syndiotactic polystyrene biaxially stretched films have excellent heat resistance, electrical properties, transparency, etc. and can be applied to various film applications such as magnetic tapes, photo / plate making, capacitors, and packaging. Is expected. When used for these purposes, its slipperiness and abrasion resistance are major factors that affect the workability of the film manufacturing process and processing process. On the other hand, in these applications, it is strongly required that the film surface is smooth and has good transparency or thinness. However, in the syndiotactic polystyrene biaxially stretched film, if the surface is simply smoothed, and the film is made transparent or thin, the handling property during manufacturing and processing of the film is poor,
Also, due to poor slipperiness due to contact with a guide roll or the like when the film is running, abrasion resistance is poor in that white powder or the like is generated due to scratches or abrasion. In addition, the syndiotactic polystyrene biaxially stretched film is brittle,
Voids are easily generated around the lubricant added for imparting lubricity, and the transparency is reduced. The generation of the voids makes it easier for the lubricant to fall off, and increases the abrasion during the running of the film.

As a film having good slipperiness, it is known that an inorganic lubricant is added, the surface roughness Ra is in a specific range, and the coefficient of static friction is limited. (JP-A-3-74
No. 437)

[0004]

However, even with the above-mentioned conventional films having good slipperiness, good handling characteristics can be obtained at low speed work, but the handling characteristics sharply deteriorate at high speed work. was there. Further, in the syndiotactic polystyrene biaxially stretched film, the handling property tends to deteriorate particularly when the film thickness becomes thin, and the above-mentioned inorganic particles were added to define the range of the surface roughness Ra and the static friction coefficient. The film has the same tendency, and therefore, even if good handling characteristics were obtained, desired handling characteristics could not be obtained if the thickness was changed. Furthermore, it has been found that the syndiotactic polystyrene biaxially stretched film is brittle, and scratches and white powder are easily generated on the film surface due to friction with rolls during the production and processing of the film, resulting in poor abrasion resistance. It was In addition, due to the brittleness of the syndiotactic polystyrene biaxially stretched film, voids are easily generated around the lubricant added to improve the lubricity, resulting in a decrease in transparency and an increase in abrasion. Was likely to cause problems. Also, aggregation of the added lubricants occurs,
The obtained film had a large number of coarse projections, and the particles thereof were likely to fall off, which was a cause of poor abrasion resistance.

The present invention suppresses the agglomeration of lubricant particles in the film and suppresses the generation of coarse particles, so that the interface between the inorganic and / or organic lubricant and the syndiotactic polystyrene polymer is suppressed. An object of the present invention is to provide a syndiotactic polystyrene biaxially stretched film that suppresses peeling, has no coarse protrusions, and has excellent transparency, slipperiness, withstand voltage characteristics and abrasion resistance.

[0006]

The syndiotactic polystyrene biaxially stretched film of the present invention is an inorganic and / or organic surface irregularity forming agent (hereinafter referred to as a lubricant).
And a film obtained by forming a film containing a polystyrene-based surface modifier, which has few coarse protrusions on the film surface and is excellent in transparency, slipperiness, withstand voltage characteristics and abrasion resistance.

The polystyrene polymer having stereoregularity of syndiotactic structure used in the present invention has a tacticity in which a phenyl group or a substituted phenyl group, which is a side chain, is quantified by a nuclear magnetic resonance method and has a diad (constituent unit). 85% or more, pentad (5 units)
It is desirable to have a syndiotactic structure of 50% or more.

Examples of the polystyrene-based polymer include polystyrene, poly (p-, m- or o-methylstyrene),
(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 (o-methyl-p-fluorostyrene)
Such as poly (halogenated styrene), poly (p-, m-
Or poly (halogen-substituted alkylstyrene) such as o-chloromethylstyrene), poly (p-, m- or o)
-Methoxystyrene), poly (p-, m- or ethoxystyrene), etc. poly (alkoxystyrene), poly (p-, m- or o-carboxymethylstyrene), etc. poly (carboxyalkylstyrene), poly Examples thereof include poly (alkyl ether styrene) such as (p-vinylbenzylpropyl), poly (p-trimethylsilylstyrene), and poly (vinylbenzyldimethoxyphosphide).

In the present invention, polystyrene is particularly preferable among the polystyrene polymers. Further, the polystyrene-based polymer having a syndiotactic structure used in the present invention does not necessarily have to be a single compound, and if the syndiotactic city is within the above range, an atactic structure or an isotactic polystyrene-based polystyrene is used. It may be a mixture with a polymer, a copolymer or 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. If 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 1,500,000 or more, it is not so preferable because breakage occurs due to an increase in stretching tension.

Examples of the inorganic and / or organic lubricants used in the present invention include silica, titanium dioxide,
Inorganic inorganic compound particles such as talc, kaolinite, silicon dioxide, alumina, calcium carbonate, calcium phosphate, barium sulfate, and calcium fluoride, organic compound particles such as crosslinked polystyrene, crosslinked polymethacrylic acid ester, and crosslinked polyacrylic acid ester are exemplified. To be done. Further, non-crosslinked polymers such as polyester, polyamide, polyolefin and polyphenylene sapphide are also included.
These lubricants may be used alone,
Moreover, you may use together 2 or more types.

In the present invention, the average particle size of the inorganic and / or organic lubricant added to the syndiotactic polystyrene polymer is 0.01 μm or more and 2.0 μm or less,
In particular, it is preferably 0.05 μm or more and 1.5 μm or less, and the addition amount is preferably 0.005 to 2% by weight based on 100% by weight of the syndiotactic polystyrene polymer, and particularly 0.1
~ 0.8 wt% is preferred. If the average particle size is less than 0.01 μm or the addition amount is 0.005% by weight or less, the slipperiness of the film becomes insufficient, which is not preferable. Also, the average particle size is 2μ
If m or the added amount exceeds 2% by weight, voids are generated on the film surface, coarse protrusions are generated, the transparency of the film is deteriorated, white powder is generated due to abrasion during running, and withstand voltage characteristics are deteriorated. Not preferable.

In the present invention, the polystyrene-based surface modifier added to the above-mentioned lubricant has, for example, a polystyrene skeleton having an average molecular weight of 5,000 or more, and one molecule end thereof is modified with an iminium ion. Zeofine BV manufactured by K.K. The introduction of iminium ions at the molecular ends causes a chemical reaction between the surface of the fine particles of the lubricant and the iminium ions to prevent the lubricants from aggregating and improving the dispersion. Since the matrix resin of the surface modifier is a syndiotactic polystyrene polymer, a modifier having a polystyrene skeleton is particularly effective, and the average molecular weight of the skeleton is preferably 5,000 or more.
If the average molecular weight is less than 5,000, the strength and elongation characteristics and heat resistance of the film may be impaired, which is not preferable. The amount of the modifier added is preferably 0.1 to 10% by weight with respect to the lubricant,
Particularly, 0.5 to 5% by weight is preferable. If it is 0.1% by weight or less, the desired effect cannot be expected, and if it is 10% by weight or more, the effect is not increased.

The syndiotactic polystyrene-based polymer used in the present invention may contain, if necessary, an appropriate amount of a known antioxidant, antistatic agent or the like. The blending amount is preferably 10% by weight or less with respect to 100% by weight of the syndiotactic polystyrene polymer. If it exceeds 10 parts by weight, breakage is likely to occur during stretching, resulting in poor production stability.

Furthermore, 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 performed in order, as well as lateral / longitudinal / longitudinal stretching methods and longitudinal stretching methods. -A stretching method such as a transverse / longitudinal stretching method or a longitudinal / longitudinal / transverse stretching method can be adopted and is selected according to various properties such as required strength and dimensional stability. Further, heat setting treatment, longitudinal relaxation treatment, lateral relaxation treatment, etc. can be performed.

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 obtained syndiotactic polystyrene type | system | group biaxially stretched film is shown below. (1) Surface smoothness Using a Surfcom 300A surface roughness meter (Tokyo Seimitsu Co., Ltd.), needle diameter 1 μm, load 0.07 g, measurement reference length 0.8 mm, cutoff 0.
The center line average roughness (Ra, μm) measured under the condition of 08 mm was used.

(2) Number of coarse protrusions on the film surface After thinly depositing aluminum on the film, the number of coarse protrusions with four or more interference fringes (number per 1 mm ^{2 of} measurement area) is counted using a two-beam interference microscope. Then, ranking was performed according to the number of coarse projections. 1st grade; 16 pieces / mm ² or more 2nd grade; 12 to 15 pieces / mm ² 3rd grade; 8 to 11 pieces / mm ² 4th grade; 4 to 7 pieces / mm ² 5th grade; 0 to 3 pieces / mm ²

(3) Film processability The film is slit into a tape shape and rubbed on a metal guide roll to run at high speed for a long time, and the tape tension after rubbing the guide roll is large or small. The amount of white powder generated on the surface of the guide roll and the amount of white powder generated on the surface of the guide roll were evaluated and ranked according to the following 5 grades. (A) Slidability 1st class; high tension (many scratches) 2nd class: slightly high tension (very many scratches) 3rd class; tension medium (slightly scratches exist) 4th class: tension slightly small (almost no scratches) 5th class; tension Small (No scratches) (B) Abrasion resistance 1st class: White powder is very much generated 2nd class: White powder is frequently generated 3rd class: White powder is slightly generated 4th class: White powder is almost not generated 5th class: White powder is generated None

(4) Durability Running Durability was measured using the apparatus shown in FIG. FIG.
Referring to, a load 9 is attached to one end of the tape, the tape passes through the free roll 8, the tension inspection device 7, and the free roll 6, and contacts the commercial VTR guide pin 5,
Free roll 4, tension inspection device 3 and free roll 2
Then, the crank 1 was rotated to bring the tape into contact with a commercially available guide pin, and the durability running property was measured. The measurement conditions are
It was performed in an atmosphere of a temperature of 23 ° C. and a relative humidity of 65%. The film was brought into contact with a commercially available VTR guide pin at an angle of 3 / 4π (unit radian), a constant load of 50 g was applied, the crank was rotated at 8.0 rpm, and the dynamic friction coefficient and static friction coefficient when the film was reciprocated 100 times. Increments (Δμkd
And Δμks) were evaluated and ranked. A commercially available VTR guide pin having a maximum protrusion height of 0.15 μm and a center line average roughness of 0.008 μm measured by a stylus type surface roughness meter was used. 1st grade; increment of friction coefficient 0.2 or more 2nd grade; 0.15 to 0.20 3rd grade; 0.10 to 0.15 4th grade; 0.05 to 0.105 5th grade; less than 0.05

(5) Light Transmittance According to JIS-K6714, using a Poic integrating sphere type HTR meter SEP-H2D manufactured by Nippon Seimitsu Optical Co., Ltd.,
The light transmittance of the film was determined. (6) Withstand voltage It was measured according to JIS-C2318. Using a 10 KV DC withstanding voltage tester, the voltage when the film was broken and short-circuited was read at a pressure rising rate of 100 kv / sec in an atmosphere of 23 ° C. and 50% RH.

Examples 1 and 2 As a lubricant, 1.1 μm spherical silica (Example-1),
Using 1.1 μm of cross-linked polystyrene (Example-2) consisting of styrene, divinylbenzene and methacrylic acid, 2% by weight of surface modifier (Zeofine BV, type 02, molecular weight 17 × 10 ³ , relative to these lubricants, Nippon Zeon Co., Ltd.) was added. The weight average molecular weight of the syndiotactic polystyrene used was 30 × 10.
^{At 4} , the syndiotactic structure was almost perfect. This polymer is dried, melted at 295 ° C, extruded from the T-die, and adhered to a 40 ° C cooling roll by the electrostatic loading method.
It was cooled and solidified to obtain a 120 μm amorphous sheet. This amorphous sheet is first preheated to 100 ° C. by a roll and further heated by using three infrared heaters having a surface temperature of 800 ° C., a film temperature of 135 ° C. is stretched 3.6 times in the longitudinal direction, and then a tenter Preheat the film to 120 ° C,
Stretching 3.3 times in the transverse direction at a stretching temperature of 120 ° C and 260 ° C
It was heat set in. The thickness of the obtained film was 10 μm.

Comparative Example 1 1.1 μm spherical silica was used as a lubricant, and a film was prepared in the same manner as in Example 1 without adding a surface modifier. It is shown below together with Examples.

[0023]

As described above, according to the present invention, by adopting the constitution as set forth in the claims, the lubricant particles in the film are less aggregated, the film surface is less likely to have coarse projections, and the transparency is improved. A syndiotactic polystyrene biaxially stretched film having excellent slipperiness and abrasion resistance is provided, and therefore the industrial value of the present invention is great.

[0024]

[Table 1]

[Brief description of drawings]

FIG. 1 is a device for measuring durability running.

[Explanation of symbols] 1; cranks 2, 4, 6, 8; free rolls 3, 7; tension inspection device 9; load

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Claims (3)

[Claims] 1. A biaxially stretched film made of a syndiotactic polystyrene resin, characterized by containing an inorganic and / or organic surface irregularity forming agent and a polystyrene surface modifier. Biaxially stretched film. 2. A polystyrene-based biaxially stretched film according to claim 1, wherein the polystyrene-based surface modifier according to claim 1 is modified with iminium ions at the molecular terminals. 3. The polystyrene-based biaxially stretched film according to claim 1, wherein the content of the polystyrene-based surface modifying agent according to claim 1 is 0.1 to 10% by weight with respect to the surface unevenness forming agent. .