JPH0687158A - Production of syndiotactic polystyrene biaxially-oriented film - Google Patents

Abstract

PURPOSE:To obtain a method for producing a syndiotactic polystyrene biaxially- oriented film superior in heat resistance, mechanical characteristics, thickness uniformity, and flatness with a high productivity. CONSTITUTION:A syndiotactic polystyrene biaxially-oriented film production method includes an orienting process for orienting an unoriented syndiotactic polystyrene polymer sheet longitudinally and, thereafter, orienting it crosswise and a thermally fixing process for tensing and thermally fixing the oriented sheet in a tenter. The sheet is oriented longitudinally in a temperature range from a 10 deg.C higher than the glass transition temperature of the unoriented sheet to the cold crystallization temperature thereof. The sheet is oriented crosswise in two or more temperature zones. The final temperature zone in a crosswise orientation is determined to be from 70 deg.C lower than the maximum thermally fixing temperature up to the maximum temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a biaxially stretched syndiotactic polystyrene film, and more specifically, it is a syndiotactic polystyrene resin having excellent heat resistance, mechanical properties, thickness uniformity and flatness. The present invention relates to a method for producing an axially stretched film with high productivity.

[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. As a method for producing a syndiotactic polystyrene-based film, a substantially amorphous film is stretched in a temperature range of a glass transition temperature or higher and a cold crystallization temperature or lower, and heat-treated in a temperature range of a cold crystallization temperature or higher under tension and a melting point or lower. Method (Japanese Patent Laid-Open No. 1-
110122), a method of stretching a syndiotactic polystyrene polymer having a weight average molecular weight of 100,000 or more in a uniaxial direction at a draw ratio of 2 times or more or in a biaxial direction at a draw ratio of 1.5 times or more, and at a temperature of 120 to 250 ° C. Production method of heat treatment (JP-A-1-316246), density of syndiotactic polystyrene polymer or its derivative 1.07 g / cm
³ below, crystals excessive 5 heated to 30 percent of the preliminary molded product for stretching, the absolute value of the birefringence of the film is 3 × 10 ^-3 ~70 × 10 ^-3
There is known a method (Japanese Patent Laid-Open No. 3-99828) in which the film is stretched in the machine direction so as to be in the range of 1, and then successively stretched in the transverse direction and then heat-treated.

[0003]

However, in the above-mentioned conventional production method, the syndiotactic polystyrene polymer cannot be stretched at a high ratio because it is likely to be broken during stretching, and the syndiotactic polystyrene polymer is stretched at a low ratio. It was found that in such a case, the film forming speed was low, the productivity was poor, and the uneven thickness and the flatness were poor. Further, in the above conventional method, heat treatment requires a long time in order to improve heat resistance, the flatness of the obtained biaxially stretched film is likely to be poor, and sufficient heat resistance may be obtained depending on the heat treatment temperature. It turns out that there are cases where you cannot get it. The present invention has been made in view of such circumstances, and has heat resistance,
An object of the present invention is to provide a manufacturing method for obtaining a syndiotactic polystyrene biaxially stretched film having excellent mechanical properties, thickness uniformity, and flatness with high productivity.

[0004]

[Means for Solving the Problems] The present invention is to perform longitudinal stretching in a stretching step on a non-stretched sheet in a temperature range of 10 ° C. or more higher than its glass transition temperature to a cold crystallization temperature or less, and transverse stretching. In two or more temperature zones,
The temperature of the final zone of transverse stretching is 70 ℃ above the maximum temperature of heat setting
Whether it is performed in the temperature range of low temperature to maximum temperature, the maximum temperature of this heat setting is from 220 ℃ to less than the melting point, or after the completion of tension heat setting, the temperature is kept below the maximum temperature of heat setting. 0.5 to 6% relaxation treatment, or after completion of tension heat fixation or after transverse relaxation treatment, at a temperature higher than the glass transition temperature by 10 ° C or more and at a temperature not higher than the maximum heat fixation temperature by 0.1 in the longitudinal direction.
Provided is a production method for obtaining a syndiotactic polystyrene biaxially stretched film having excellent heat resistance, mechanical properties, thickness uniformity, and flatness, which is characterized by being subjected to a relaxation treatment of 3% by high productivity. It is a thing. Further, when the properties of the syndiotactic polystyrene biaxially stretched film obtained in the present invention were evaluated, it became clear that the difference in the physical properties in the width direction was small, and uniform physical properties could be obtained in almost the entire width direction of the film. It has become possible and has proved to be a very good manufacturing method. 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 phenyl group or a substituted phenyl group which is a side chain is quantified by a nuclear magnetic resonance method. It is desirable that the syndiotactic structure is 85% or more, and pentad (5 constitutional units) is 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 (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. Further, the polystyrene polymer having a syndiotactic structure used in the present invention does not necessarily have to be a single compound, and if the syndiotacticity is within the above range, the polystyrene polymer having an atactic structure or an isotactic structure is used. It may be a mixture with a combination, a copolymer and a mixture thereof. The polystyrene-based polymer used in the present invention has a weight average molecular weight of 10,000 or more, more preferably 50,000 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. The upper limit of the weight average molecular weight is not particularly limited, but 150
If it is more than 000, breakage may occur due to an increase in stretching tension, which is not preferable. The polystyrene-based polymer used in the present invention may contain, if necessary, known lubricant fine particles, an antioxidant, an antistatic agent, and the like in appropriate amounts. 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 easily occurs during stretching, resulting in poor production stability, which is not preferable.

The type and amount of the lubricant fine particles are not particularly limited, but silica, titanium dioxide, talc,
Examples are particles that are inert to syndiotactic polystyrene-based polymers, such as metal oxides such as kaolinite, salts of metals such as calcium carbonate, calcium phosphate, and barium sulfate, or particles consisting of organic polymers. Any one of these lubricants may be used alone, or two or more thereof may be used in combination, but in order to obtain a film having good slipperiness, the average particle system of the lubricant used is
0.01 μm or more and 2.0 μm or less, especially 0.05 μm or more and 1.5 μm
The following is preferred, and the degree of variation in particle size (ratio between standard deviation and average particle size) is preferably 25% or less, and the addition amount is 0.005% by weight or more and 2.0% by weight or less based on 100% by weight of syndiotactic polystyrene polymer. It is preferable that the content be 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 (%) The addition method of these fine particles is not particularly limited, but is added in any step of the polymerization step of the styrene-based monomer. how to,
A method of kneading as a masterbatch after polymerization or a method of directly adding and adding during melt extrusion can be mentioned.

In the present invention, the unstretched sheet is stretched in the machine direction in the machine direction by 10 ° C. from its glass transition temperature.
It is necessary to carry out in the temperature range from the higher temperature to the cold crystallization temperature or lower. 20 ° C above the glass transition temperature
From the high temperature to the cold crystallization temperature or higher. If the stretching temperature in the machine direction is less than 10 ° C higher than the glass transition temperature, the stretching may be cold stretching and the film may be whitened. Also, when stretched to a high ratio, breakage easily occurs,
Further, the thermal dimensional stability of the final film becomes poor, and a film having excellent heat resistance cannot be obtained. Further, at a temperature higher than the cold crystallization temperature, crystallization of the film progresses, and subsequent transverse stretching becomes difficult. The optimum stretching ratio in the machine direction cannot be limited because it depends on the stretching speed, but in the process of increasing the stretching ratio, the stretching ratio at which the stretching tension rises or the ratio at which the orientation begins to change greatly, The following is good. As a guideline for these magnifications, 3.0 to 4.
It is about 5 times. The stretching speed in the machine direction is 10,000% / min or more,
Preferably 15000% / min or more, more preferably 20000% / min
That is all. If it is less than 10000% / min, mechanical strength and flatness tend to be poor. Further, the stretching in the machine direction may be one step, or may be two or more steps. When the film is longitudinally stretched in two or more steps, it is preferable that the film is stretched at a temperature of 20 ° C. or more higher than the glass transition temperature until the final stretching in the longitudinal direction so that the thickness uniformity of the film is maintained and a low orientation is obtained. In the final longitudinal stretching, from the draw ratio at which the draw tension rises or the ratio at which the orientation begins to change significantly, 0.5
It is preferable to stretch at a draw ratio equal to or less than twice as high. Further, it is necessary to cool the film after the stretching in the machine direction is completed.
It is considered that the film in longitudinal stretching is because crystallization proceeds due to stretching heat even if the stretching temperature is set to a cold crystallization temperature or lower, but if cooling is not performed, breakage easily occurs in the subsequent transverse stretching. Become. Cooling is preferably performed by a roll on the high speed side of the roll that has been longitudinally stretched. Further, this cooling temperature is preferably lower than about 40 ° C. In the case of stretching in multiple stages, if the stretching performed in the latter stage is continuously performed and the temperature is lower than the cold crystallization temperature, it is not always necessary to cool each stretching to about 40 ° C.

In the present invention, the transverse stretching in the stretching step is carried out in two or more temperature zones, and the temperature in the final zone of the transverse stretching is 70 ° C. lower than the maximum heat setting temperature to the maximum temperature range. There is a need. This makes it possible to obtain a syndiotactic polystyrene biaxially stretched film having excellent heat resistance, mechanical properties, thickness uniformity, and flatness with high productivity. When the stretching in the transverse direction is carried out in one zone, under conditions where the stretching temperature is relatively low, that is, at a temperature 10 to 30 ° C. higher than the glass transition temperature, it is difficult to stretch at a high ratio, resulting in poor thickness uniformity and productivity. When the stretching temperature is relatively high, that is, when the stretching temperature is higher than the glass transition temperature by 30 ° C. or more, the stretching ratio can be increased, but mechanical properties tend to be poor, and flatness and thickness uniformity are also obtained. Becomes difficult. If the temperature in the final zone of transverse stretching is lower than the maximum temperature for heat setting by 70 ° C. or more, breakage easily occurs during heat setting, and it is difficult to improve heat resistance and thickness uniformity. At a temperature higher than the maximum temperature for heat setting, breakage easily occurs during stretching, and flatness is likely to be poor.

The stretching temperature in the transverse direction is preferably gradually increased from the initial stretching temperature to the final stretching temperature, and the initial stretching temperature in the transverse direction is 10 ° C. above the glass transition temperature.
Temperatures up to -50 ° C are preferred. The temperature difference between adjacent zones is preferably 100 ° C or lower, more preferably 70 ° C or lower, and particularly preferably 50 ° C or lower. Here, the transverse stretching may be performed continuously, or a constant length zone or a relaxation zone may be provided in the middle of the transverse stretching. Also in these cases, lowering the temperature of each zone during the transverse stretching step to be lower than the temperature of the previous zone is not preferable because it causes breakage.

In the present invention, the maximum temperature for tension heat fixation is
It is preferable that the temperature is from 220 ° C to below the melting point. More preferably, the temperature is 230 ° C. or higher and 10 ° C. or more lower than the melting point.
If the maximum temperature of heat setting is 220 ° C or less, it is necessary to heat-fix for a long time or to obtain sufficient heat resistance in order to obtain good heat resistance. It cannot be produced at a temperature higher than the melting point because it melts. The time required for heat setting varies depending on the temperature of heat setting and the required heat resistance, but it does not exceed 30 seconds, and usually 10 seconds or less is sufficient. In the present invention, after completion of the tension heat setting, a relaxation treatment of 0.5 to 6% in the lateral direction is performed at a temperature not higher than the maximum temperature of heat setting. This further improves the lateral heat shrinkage. The relaxation treatment temperature is determined by the temperature required for heat resistance and the shrinkage ratio at that temperature, but usually 10 ° C to the temperature required for heat resistance
A temperature as high as 30 ° C is good. In the present invention, after the tension heat fixation is completed or after the transverse relaxation treatment, the glass transition temperature is 10 ° C.
At the above-mentioned high temperature, a relaxation treatment of 0.1 to 3% is carried out in the longitudinal direction at a temperature not higher than the maximum heat setting temperature. This further improves the heat shrinkage in the vertical direction. The relaxation treatment temperature is determined by the temperature at which heat resistance is required and the shrinkage ratio at that temperature, but usually a temperature higher by about 10 to 30 ° C. than the temperature at which heat resistance is required.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement / evaluation methods used in the present invention are shown below. (1) Heat shrinkage rate at 200 ° C. (HS200) The shrinkage rate of the film in a tension-free state at 200 ° C. for 30 minutes was determined. (2) Modulus of elasticity Attach the film at a width of 10 mm and a length interval of 100 mm to a tensile tester (Autograph made by Shimadzu Corp.), temperature 23 ℃,
In an environment with a humidity of 65% RH, the tensile strength at a speed of 200 mm / min was measured, and the strength against rising elongation was determined in kg / mm ² units.

(3) Thickness uniformity Using a film thickness measuring machine (manufactured by Micron Measuring Instruments Co., Ltd.)
The thickness was measured for 5 m, and the uniformity of thickness was evaluated in 5 steps, and the following ranking was used. Grade 1; thickness unevenness 10% or more Grade 2; thickness unevenness 8 to 10% Grade 3; thickness unevenness 6 to 8% Grade 4; thickness unevenness 4 to 6% Grade 5; thickness unevenness less than 4% Was calculated. Thickness unevenness = [(maximum film thickness-minimum film thickness) / average film thickness] x 100 (%) (4) Flatness A film with a width of 50 cm is unrolled for a length of 200 cm from a roll and the flatness of the film is observed. It was evaluated 5 times and expressed in the following ranking. 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

Example 1 As a lubricant, 3.0% by weight of calcium carbonate having an average particle size of 1.0 μm, a degree of variation of 20% and an area shape factor of 80% was added to 100% by weight of syndiotactic polystyrene (weight average molecular weight 300000). Polymer chips and non-lubricated polymer chips were mixed at a weight ratio of 1: 9, dried, melted at 295 ° C, extruded from T die with 200 μm lip gap, and cooled at 40 ° C. It adhered to the roll by the electrostatic loading method and was cooled and solidified to obtain an 82 μm amorphous sheet. The amorphous sheet is first preheated to 95 ° C. by a roll, four infrared heaters having a surface temperature of 700 ° C. are used, and further heated to a film temperature of 135 ° C. in a longitudinal direction of 3.8.
It was stretched twice. Here, the rise of stretching tension is 3.7
It was double. The film was cooled to 35 ° C. by the roll on the high speed side of the two rolls stretched in the machine direction. After that, the film was preheated to 120 ° C. with a tenter, the initial transverse stretching temperature was 120 ° C., 2.5 times, then 170 ° C., 1.2 times, and 200 ° C., 1.2 times. Then 10 at 260 ° C
Tension heat fixation treatment was performed for a second.

Example 2 The film obtained in Example 1 was further subjected to 3% transverse relaxation treatment at 220 ° C. Example 3 The film obtained in Example 2 was further subjected to 2% longitudinal relaxation treatment at 220 ° C.

Comparative Example 1 In Example 1, the transverse stretching and deformation rate were the same,
The same method was used except that the temperature was kept constant at 120 ° C.
When the transverse draw ratio was set to 3.6, which is the same as the total draw ratio in Example 1, frequent breakage occurred and stable production could not be performed. Comparative Example 2 The same procedure as in Comparative Example 1 was repeated except that the thickness of the amorphous sheet was set to 75 μm and the transverse stretching ratio was set to 3.3 times. Comparative Example 3 The procedure of Comparative Example 1 was repeated except that the transverse stretching temperature was 150 ° C.

[0016]

As described above, the longitudinal stretching in the stretching step is performed on the unstretched sheet in the temperature range of 10 ° C. or more higher than the glass transition temperature to the cold crystallization temperature or less, and the transverse stretching is performed 2 The temperature in the final zone of transverse stretching is 70 ° C lower than the maximum temperature of heat setting to the maximum temperature, or the maximum temperature of heat setting is 220 ° C. If the temperature is less than the melting point, or after the heat-setting of tension is finished, 0.5-6% relaxation treatment in the transverse direction is performed at a temperature not higher than the maximum temperature of heat-setting, or after completion of heat-setting of tension or after transverse relaxation, the glass transition temperature is 10 ° C. Higher than the above, at a temperature below the maximum heat setting temperature, 0.1 to 0.1
By performing 3% relaxation treatment, it becomes possible to obtain a syndiotactic polystyrene biaxially stretched film having excellent heat resistance, mechanical properties, thickness uniformity, and flatness with uniform physical properties in almost the entire width direction. It is possible to obtain a syndiotactic polystyrene biaxially stretched film having excellent characteristics at high speed and in high yield in the width direction, and therefore the industrial value of the present invention is great.

[0017]

[Table 1]

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

Claims (4)

[Claims] 1. A stretching step of stretching an unstretched sheet of a syndiotactic polystyrene-based polymer in a longitudinal direction and then a transverse direction, and a heat-setting treatment step of performing tension heat-setting in a tenter after this stretching step. In the method for producing a syndiotactic polystyrene-based biaxially stretched film, stretching in the longitudinal direction is performed at a temperature of 10 ° C or higher than the glass transition temperature of the unstretched sheet.
The temperature is from the higher temperature to the cold crystallization temperature or less, the transverse stretching is performed in two or more temperature zones, and the temperature of the final zone of the transverse stretching is 70 ° C lower than the maximum temperature of heat setting to the maximum temperature. A method for producing a syndiotactic polystyrene-based biaxially stretched film, characterized by being in the range. 2. The method for producing a syndiotactic polystyrene biaxially stretched film according to claim 1, wherein the maximum temperature for heat setting is from 220 ° C. to less than the melting point. 3. The method for producing a syndiotactic polystyrene biaxially stretched film according to claim 1, wherein after the tension heat setting is completed, a relaxation treatment of 0.5 to 6% in the transverse direction is performed at a temperature not higher than the maximum temperature of heat setting. 4. After completion of tension heat fixation or after lateral relaxation treatment,
4. The method for producing a syndiotactic polystyrene biaxially stretched film according to claim 1, wherein 0.1% to 3% relaxation treatment in the machine direction is performed at a temperature higher than the glass transition temperature by 10 ° C. or higher and at a temperature not higher than the maximum temperature for heat setting.