JPH0939088A - Manufacture of polystyrene film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and continuously produce a film high in transparency by performing the lateral stretching and thermal fixing treatment of polystyrene having a syndiotactic structure. SOLUTION: A preheated polystyrene sheet 6 having a syndiotactic structure is fed to a heating zone 2 performing lateral stretching and the interval of the clips 8 attached to both ends of the polystyrene sheet is gradually increased to laterally stretch the polystyrene sheet. In the lateral stretching zone 2, temp. (Ttd deg.C) is adjusted within a range from the glass transition temp. (Tg deg.C) of polystyrene used in the sheet to (Tg+20) deg.C. The sheet laterally stretched in the lateral stretching zone 2 is fed to a thermal fixing zone 3 in order to be thermally fixed and the interval between the clips 8 provided to both ends of the sheet and widened for lateral stretching in a high temp. atmosphere is kept. The temp. (Tha deg.C) of the thermal fixing zone is adjusted to temp. higher than the temp. (Ttd deg.C) of the lateral stretching zone by 60-120 deg.C.

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 polystyrene resin film having a syndiotactic structure which is excellent in transparency and can be used as a support for photographic films.

[0002]

2. Description of the Related Art Polystyrene resins are used in various molded products and packaging materials because they are difficult to absorb moisture and have excellent transparency and gloss. Also, since it has good electric properties such as dielectric constant and insulating property, it is also used as an electric insulating material for capacitors, high frequency cables and the like. However, polystyrene-based resins generally do not have a satisfactory level of heat resistance, impact resistance, etc., and when the polystyrene-based resins are used for the above-mentioned applications, polystyrene-based resins are used in addition to other types of resins, rubbers, and inorganic filler materials. A blended product containing the above is used. That is, since the styrene resin polymer used conventionally has an atactic structure and is amorphous, it is not sufficiently high in mechanical strength such as impact resistance as described above. I can't say.
Further, since the polystyrene-based resin is non-crystalline as described above, improvement in physical properties due to stretching treatment (promotion of oriented crystallization) could not be expected.

Also, the blended resin of the above polystyrene resin and other resins cannot be said to be at a sufficiently satisfactory level in heat resistance, impact resistance and the like. On the other hand, other general thermoplastic resins such as polyethylene, polypropylene, polyethylene terephthalate, and polyamide are not satisfactory in heat resistance and chemical resistance, and few are not easily affected by water vapor. There is also a problem that raw materials are expensive and disadvantageous in manufacturing. On the other hand, recently developed syndiotactic polystyrene (also referred to as SPS, for example, JP-A-62-10481).
No. 8) shows crystallinity and has a melting point of 160 ° C. to 330 ° C.
It has a high temperature of ℃, excellent heat resistance, chemical resistance, and humidity stability. Furthermore, it is considered to be used for various purposes because the raw material is inexpensive and advantageous in production because it uses a styrene monomer. For example, JP-A-3-131843 discloses use of a photographic film as a support, and JP-A-2-673.
Japanese Patent Publication No. 28 describes use as a packaging material.

On the other hand, recently developed syndiotactic polystyrene (also referred to as SPS, for example, JP-A-62-104818) has crystallinity, a high melting point of 160 ° C. to 330 ° C., and heat resistance. Since it is excellent in chemical resistance and humidity stability, and the raw material is inexpensive and advantageous in manufacturing because it uses a styrene monomer, it is considered to be used for various purposes. For example, JP-A-3-13184
No. 3 discloses use of a photographic film as a support, and JP-A No. 2-67328 describes use as a packaging material.

In order to prepare a stretched film using the SPS resin having such excellent performance, the resin may be first melt-extruded to prepare an unstretched sheet (raw sheet) and then stretched in the longitudinal and transverse directions. However, stretching alone is not sufficient for improving the physical properties of the sheet by promoting oriented crystallization, particularly reducing the heat shrinkage rate, and heat resistance. To compensate for this, it is common to perform heat setting. Has been done in.
(For example, JP-A-2-67328 and JP-A-6-
No. 57014)

Generally, heat setting of a thermoplastic film is performed in a temperature range higher than the glass transition temperature and lower than the melting point, but in the case of syndiotactic polystyrene, the heat setting effect cannot be obtained if the temperature is too low. However, if it is too high, there is a problem that the sheet becomes white due to crystallization, and it cannot be said that the optimum heat setting conditions have been clarified. For example, Japanese Unexamined Patent Publication No. 2-67328 described above describes that stretching is carried out at a temperature of 120 ° C. in the lengthwise and transverse directions of 3 times at the same time, and heat setting is performed at 250 ° C.
No. 4, gazette describes performing transverse stretching 3.3 times at 120 ° C. and heat setting at 260 ° C.
These are heat set at a relatively high temperature. However, heat setting at such a high temperature, when the stretching treatment and heat setting are performed continuously (that is, in the case of actual production),
There is a problem that a stretched film cannot be stably and continuously produced. That is, in order to fully exert the heat setting effect, it is preferable to raise the heat setting temperature as much as possible, but for example, when heat setting is performed by heating in the heat setting zone, if the heating temperature is too high, The sheet that has been excessively softened by the above may be torn and ruptured in the tensile direction of the transverse stretching clip attached from the transverse stretching zone that is the adjacent zone, and therefore, the stretched sheet is stable. There is a problem that it cannot be manufactured continuously.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a polystyrene film capable of stably and continuously producing a film of a polystyrene resin having a syndiotactic structure having high transparency. It is in.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventor has found that the production of a polystyrene resin film having a syndiotactic structure according to the following method causes almost no film breakage. It was found that the transverse stretching and the heat setting can be continuously and stably performed without performing the above. In the present invention, an unstretched sheet obtained by extruding polystyrene having a syndiotactic structure after heating and melting is stretched in the machine direction under heating, and then the sheet is transversely stretched in a heated zone and then heated. The method for producing a polystyrene film by continuously performing heat setting treatment in another heated zone adjacent to the heated zone, wherein the transverse stretching and heat setting treatment are carried out by the following formula (1) and (2): 60 ≦ Ths−Ttd ≦ 120 (1) Tg ≦ Ttd ≦ Tg + 20 (2) [where Ttd is the temperature of the heated zone in which the transverse stretching is performed (unit: ° C. Is the temperature of the heated zone (unit is ° C) in which the heat setting treatment is performed, and Tg is the glass transition temperature of polystyrene having the syndiotactic structure. It is a numerical value of (the unit is ℃). ] The manufacturing method of the polystyrene film characterized by performing on the conditions satisfy | filled.

The preferred embodiment of the method for producing a polystyrene film of the present invention is as follows. 1) The temperature change of the sheet when moving from the heated zone for transverse stretching to the heating zone for heat setting treatment is 40 ° C / sec or less (preferably 20-40 ° C / sec).
Seconds). 2) The time for passing through the heating zone for transverse stretching of the sheet is 3 to 60 seconds, and the time for passing through the heating zone for performing the heat setting treatment is 3 to 45 seconds. 3) The polystyrene film comprises polystyrene having a syndiotactic structure and inorganic fine particles contained in the polystyrene in a proportion of 0.001 to 0.1% by weight based on the polystyrene. 4) The inorganic fine particles of 3) above are silica. 5) The primary particles of the inorganic fine particles of 3) above are 5 to 45 m ²
/ G specific surface area, 0.001-0.1 ml / g pore volume and 0.05-5.0 μm average particle size. 6) The inorganic fine particles of 3) above are pulverized products of quartz glass or natural quartz. 7) The thickness of the polystyrene film is 25 to 300
μm (preferably 50 to 200 μm). 8) The polystyrene film is for a support for a photographic light-sensitive material such as a photographic film.

In the method for producing a polystyrene film of the present invention, basically, an unstretched sheet obtained by heat-melting and extruding polystyrene having a syndiotactic structure,
After stretching in the machine direction under heating, the sheet is transversely stretched in a heated zone, and then continuously heat-set in another heated zone adjacent to the heated zone. The process consists of

The manufacturing method of the present invention will be described in detail step by step. In (1), an unstretched sheet (raw fabric) is prepared, and in (2), a biaxially stretched film is prepared. (1) A polystyrene pellet having a syndiotactic structure is heated and dried at 150 to 200 ° C. to crystallize the polystyrene. The obtained polystyrene was charged into a single-screw or twin-screw extruder having a die at the tip, and 280 to 3
It is heated and melted at 20 ° C., and the heated polystyrene is discharged in a sheet form from a die of an extruder. When the inorganic fine particles and the like are contained in polystyrene, the dried pellets (master pellets) and the mother pellets containing the inorganic fine particles and the like are put into a single-screw or twin-screw extruder having a die at the tip, and the temperature is adjusted to 280 to 320 ° C. The heat-melted and heated polystyrene is discharged in a sheet form from the die of the extruder. As the extruder, it is preferable to use a twin-screw extruder so that the master pellets and the mother pellets can be efficiently mixed. An extruder having no vent may be used, but it is preferable to use an extruder having a vent in order to prevent bubbles from being generated in the film due to the generated gas. Further, it is preferable to use a gear pump (a metering pump) in order to stably discharge from the extruder and to send out the molten resin. Before discharging the molten resin from the die into a sheet, filtration may be performed with a filter. As a material for the filter, a metal filter medium such as a sintered fiber of stainless steel or a sintered wire mesh is preferable.
The filtration accuracy of the filter is generally in the range of 5 to 20 μm.

The molten polystyrene discharged in a sheet form as described above is cooled on a cooling drum (casting drum) to form an unstretched sheet. The thickness of the unstretched sheet obtained is generally in the range of 0.8 to 2 mm. The temperature of the surface of the cooling drum is preferably 55 to 85 ° C. 55 ° C
When it is less than the above range, the central part of the sheet is rapidly cooled, so that a warp appears strongly at the end part, so that a trouble is likely to occur in the subsequent stretching step. If the temperature exceeds 85 ° C, the sheet sticks to the cooling drum, making it difficult to form an unstretched film. The sheet is cooled at an average rate of 60 to 200 ° C./minute from when the molten resin discharged from the die comes into contact with the cooling drum to the glass transition temperature, and then the sheet is cooled to 30 ° C.
It is preferable that the temperature is averagely cooled in the range of 40 to 100 ° C./minute until the temperature reaches 0 ° C. If the cooling rate after reaching the glass transition temperature is low, the haze of the finally obtained stretched film will be high.

Improvement of the smoothness of the surface of the unstretched sheet formed from the molten resin discharged, improvement of the smoothness of the surface,
Suppression of increase in sheet thickness at the edge, uniform sheet thickness,
In order to prevent crystallization of the sheet and the like, it is common to perform heating of the cooling drum, electrostatic application, edge pinning, cooling air blowing, air suction and water application, or combined use of calender rolls. . These can be performed alone or in combination. For the same purpose, it is preferable to reduce the backlash of the gears of the variable speed reducer such as the cooling drum, the eccentricity of the pulley, and the deviation of the roller interval of the drive chain. It is also important to take measures against vibration such as the die head for extrusion

(2) The polystyrene film of the present invention can be obtained by biaxially stretching the raw fabric (unstretched sheet) obtained above. The stretching method is a sequential biaxial stretching method. The obtained unstretched sheet is stretched in the longitudinal direction (extrusion direction or longitudinal direction) by a heated roll or the like. The longitudinally stretched sheet is then laterally stretched and heat-set by the transverse stretching device (tenter) shown in FIG. FIG. 1 is a plan view of a transverse stretching device.

The sheet 6 stretched in the longitudinal direction (extrusion direction or longitudinal direction) under heating is clamped at both ends by the clips 8 sent out by the clip-conveying endless belt 7, conveyed to the preheating zone 1 and preheated. Subsequently, the sheet 6 is conveyed to a heated zone (horizontal stretching zone) 2 in which lateral stretching is performed, and the interval between the clips 8 at both ends is gradually increased, and lateral stretching is performed. In the present invention, in the transverse stretching zone 2, from the glass transition temperature (Tg ° C.) of the polystyrene used for the sheet to (Tg + 20)
Temperature (Ttd ° C) is adjusted in the range of ℃ (Tg ≦ Ttd ≦
Tg + 20). The transverse stretching zone generally passes in 3-60 seconds. Preferably, it is 5 to 45 seconds. The sheet laterally stretched in the lateral stretching zone 2 is subsequently conveyed to a heated zone (heat fixing zone) 3 for heat setting, and spreads for the above horizontal stretching under an atmosphere of higher temperature. The distance between the clips 8 at both ends is maintained. In the present invention, the temperature of the heat setting zone (Ths ° C) is adjusted to be 60 to 120 ° C higher than the temperature of the transverse stretching zone (Ttd ° C) (60≤Ths-Ttd≤120). As a result, the sheet is hardly torn and broken in the clip direction before and after the heat setting zone 3, and the sheet is hardly broken in the transverse stretching zone. Further, there is no whitening phenomenon of the sheet that occurs when the heat setting temperature is increased. The heat setting zone generally passes in 3 to 45 seconds. It is preferably 5 to 30 seconds. The heat-fixed sheet is then conveyed to a heating zone (heat relaxation zone) 4 for heat relaxation, where the distance between the clips 8 at both ends is gradually reduced to perform relaxation. The thermal relaxation amount is generally 1 to 10%. Then, it is cooled in the cooling zone 5 to obtain the sequentially biaxially stretched polystyrene film 6'of the present invention.
The thermal relaxation zone generally passes in 10 to 50 seconds. It is preferably 15 to 25 seconds. Furthermore, the temperature change of the sheet when moving from the transverse stretching zone to the heat setting zone is 40 ° C./sec or less (preferably 10 to 40 ° C. /
Second), it is preferable to adjust the heating energy (by changing the conveying speed, etc.) or the thickness of the sheet to perform stretching and heat setting.

In the transverse stretching method of the present invention, if the stretching ratio is too low, the sheet cannot be oriented sufficiently, the sheet becomes brittle, the haze becomes high, and uniform stretching becomes difficult. On the other hand, if the magnification is too high, the sheet is likely to tear in the lateral direction, which is not preferable because the sheet may tear in the tenter. The stretching ratio is generally 2 in both length and width.
It is preferably 6 times, and particularly preferably 3 to 5 times. The transverse stretching speed is preferably about 5 to 250% / sec from the viewpoint of making the amount of heat applied to the sheet uniform, controlling the orientation, and easiness of handling. The biaxially stretched sheet that has been transversely stretched is
As described above, it is conveyed to the heat setting treatment zone while being held by the clip. Here, the heat resistance, the dimensional stability, and the heat resistance of the stretched film obtained by subjecting the stretched film to a temperature of not less than the glass transition temperature and not more than the melting point and within the range satisfying the above conditions while applying tension (heat fixing treatment) while applying tension. Properties such as chemical resistance and gas permeability can be improved. Further, the stretched sheet may be cut at both ends (so-called ears) through a heat relaxation zone and a cooling zone and wound, or may be continuously conveyed to a coating step. In the cooling zone, cooling is performed by blowing air at room temperature or lower.

Polystyrene having a syndiotactic structure used in the present invention (hereinafter sometimes referred to as SPS)
Is a polystyrene resin whose stereoregularity is a syndiotactic structure, in which phenyl groups or substituted phenyl groups, which are side chains with respect to the main chain formed from carbon-carbon bonds, are mainly located in opposite directions. It has a three-dimensional structure. The stereoregularity (tacticity) can be quantified by a nuclear magnetic resonance method (NMR method).
The stereoregularity measured by this nuclear magnetic resonance method can be indicated by the existence ratio of a plurality of continuous constitutional units, for example, a diad in the case of 2 units, a trad in the case of 3 units, and a pen dadd in the case of 5 units. However, the syndiotactic polystyrene-based resin (SPS-based resin) referred to in the present invention means that the stereoregularity (tacticity) is 75% or more in racemic dieat or 30% or more in racemic pentad.
It has. Further, those having a syndiotactic structure of 85% or more in diat or 50% or more in pentad are preferable.

Examples of polystyrene-based resins that can be used in the present invention include polystyrene and various substituted polystyrenes such as polyalkylstyrene and polyhalogenated styrene. Examples of substituted polystyrenes are poly (o-, m- or p-methylstyrene), poly (2,4-, 2,5-3,4- or 5-
Poly (alkylstyrene) such as dimethylstyrene) and poly (pt-butylstyrene); poly (o-, m-
Or p-chlorostyrene), poly (o-, m- or p-bromostyrene), poly (o-, m- or p)
-Fluorostyrene) and poly (o-methyl-p-fluorostyrene) such as poly (halogenated styrene); poly (o-, m- or p-chloromethylstyrene) such as poly (halogen-substituted alkylstyrene); poly (O-,
m- or p-methoxystyrene) and poly (o-, m
-Or p-ethoxystyrene) or other poly (alkoxystyrene); poly (o-, m- or p-carboxymethylstyrene) or other poly (carboxyalkylstyrene); poly (p-vinylbenzylpropyl ether) or other poly (Alkyl ether styrene); poly (p-trimethylsilyl styrene) and other poly (alkyl silyl styrene); and poly (vinyl benzene dimethoxy phosphate). Further, as an example of the polystyrene-based resin, a copolymer of the above-mentioned substituted styrene and unsubstituted styrene (for example, a copolymer of styrene and p-methylstyrene) is of course preferable.

In the present invention, polystyrene is particularly preferable among the examples of the polystyrene resin. Further, the polystyrene resin 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, an isotactic structure or a polystyrene resin having an atactic structure is used. It may be a mixture thereof with or incorporated into the copolymer chain.

The polystyrene resin having the syndiotactic structure can be produced by a known method.
For example, the method is described in Japanese Patent Laid-Open No. 3-74437. With respect to the molecular weight of the polystyrene resin having the syndiotactic structure, its weight average molecular weight is preferably in the range of 10,000 to 3,000,000, and particularly preferably in the range of 50,000 to 15,000,000.

The polystyrene film obtained by the present invention preferably contains inorganic fine particles.
Examples of such inorganic fine particles include silica, talc, calcium carbonate, calcium sulfate, mica, kaolin, kaolinite and the like. Of these, silica is preferred.

Preferable examples of the silica include crushed quartz glass and crushed natural quartz. In the present invention, the silica may not be surface-treated, but surface-treated silica is preferable in order to improve the affinity with the resin and suppress the generation of voids during stretching. The surface treatment can be performed using a known surface treatment agent such as a silane coupling agent. Examples of silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxysilane), N- (2-aminoethyl)-.
3-aminopropylmethyldimethoxysilane, N- (2
-Aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-
Epoxycyclohexyl) ethyltrimethoxysilane,
Mention may be made of 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-mercaptopropyltrimethoxysilane.

The average particle diameter of the primary particles of the above-mentioned inorganic fine particles (preferably silica) is preferably in the range of 0.1 to 5.0 μm, particularly preferably in the range of 0.2 to 2.0 μm. The specific surface area is preferably 5 to 45 m ² / g. The pore volume is preferably in the range of 0.001 to 0.1 ml / g.
With silica having a specific surface area of more than 45 m ² / g, the silica particles are likely to aggregate with each other to form secondary particles or coarse particles of higher order, which reduces the slipperiness of the resulting film. On the other hand, silica having a specific surface area of less than 5 m ² / g has a low affinity with the polymer, so that voids generated when biaxially stretched become large and the transparency of the film decreases. In the case of silica having a pore volume of more than 0.1 ml / g, silica particles tend to aggregate with each other to form secondary particles or higher coarse particles, so that the slipperiness of the obtained film is deteriorated. In addition, the quality may not be stable. On the other hand, silica having a pore volume of less than 0.001 ml / g has a low affinity with the polymer, so that the voids generated when biaxially stretched become large and the transparency of the film decreases.

Furthermore, the average particle size of the primary particles of the above-mentioned inorganic fine particles (preferably silica) is 0.05 to 5.0 μm.
m is generally, 0.1 to 3.0 μm is preferable, and 0.1 to 2.0 μm is more preferable. Average particle size is 0.05
Silica of less than μm has a small effect of imparting slipperiness,
The film containing such silica does not have sufficient lubricity, or the transparency of the film decreases when silica is contained to the extent that sufficient lubricity is obtained. Further, silica having an average particle size of more than 5.0 μm has a great effect from the viewpoint of imparting slipperiness, but when a particle having such a large particle size is used, a large void is likely to occur around the particle in a biaxially stretched film. As a result, a film having high haze and low transparency is obtained. Further, when such silica having a large particle size is aggregated and present in the film, it becomes a serious defect.

In order to balance the slipperiness and transparency of the film on a high level, the amount of silica having the above-described shape, specific surface area, pore volume and average particle diameter is adjusted to the thickness of the film to be produced. It is preferable to optimize accordingly. For example, the optimum addition amount of the silica of the present invention to a film having a thickness of 25 to 300 μm is 0.001 to 0.1% by weight, and 0.005 to 0.1% by weight is preferable. If the amount added is less than 0.001% by weight, generally required slipperiness cannot be secured, and if the amount added exceeds 0.1% by weight, transparency is generally lowered. The film thickness is 50-200.
μm is preferred.

Further, the SPS used in the present invention may contain other resins in order to improve electrostatic adhesion, slipperiness, stretchability, processing suitability, etc., and to obtain roughening and weight reduction. Or rubber (in an amount of 10% by weight or less of SPS), a nucleating agent, a fluorescent agent,
An antioxidant, a plasticizer, a colorant, an antistatic agent or the like may be added at the time of absorbing ultraviolet rays.

[0027]

【Example】

[Example 1] As syndiotactic polystyrene, a copolymer of styrene having a syndiotactic structure and p-methylstyrene (copolymerization ratio: styrene / p-methylstyrene = 89/11 (molar ratio); Syndiotactic City (Diat): 85%; Melt Flow Index: 10; Glass Transition Temperature: 97 ° C (D
SC-50 was used in nitrogen (by temperature increase of 10 ° C./min). The resin pellets were put into a full flight type single screw extruder (diameter = 40 mm, L / D = 26) and the width was 23 cm.
A coat hanger type die was attached and melt extrusion was performed at a die lip temperature of about 310 ° C., and the mixture was cooled and solidified on a casting drum to prepare an unstretched sheet having a thickness of about 1.2 mm.

The unstretched sheet was longitudinally stretched 3.5 times under heating and conveyed to a preheating zone (1 in FIG. 1) heated to 100 ° C. The sheet temperature also reached 100 ° C. in this zone.
The sheet that has reached the predetermined temperature is then sent to the transverse stretching zone (2 in FIG. 1) heated to 105 ° C., and the sheet is subjected to about 10% s.
It was transversely stretched 4 times at a stretching speed of ec (passing time of the transverse stretching zone was 30 seconds). The stretched sheet is then 210
It was transferred to a heat setting zone (3 in FIG. 1) heated to 0 ° C. The temperature change of the sheet at this time is ΔT = 35 (° C / sec)
Met. This measurement was performed by embedding a thermocouple in the sheet. The sheet that passed the heat setting zone (passing time of the heat setting zone was 15 seconds) was subjected to 7% heat relaxation in the heat relaxation zone (4 in FIG. 1) heated to 210 ° C., and then in the cooling zone (in FIG. 1). After cooling with cold air at 15 ° C. in 5), both ends (ears) were cut and wound up. In the above steps, the sheet was hardly torn or cut, and the stretched sheet could be stably and continuously produced. Further, the obtained film had high transparency, and no whitening phenomenon was observed.

Example 2 A polystyrene film was produced in the same manner as in Example 1 except that the transverse draw ratio was changed to 4.4. As in the case of Example 1, a stretched sheet could be stably and continuously produced. Further, the obtained film had high transparency, and no whitening phenomenon was observed.

Example 3 A polystyrene film was produced in the same manner as in Example 2 except that 0.02% by weight of silica was added to the resin pellet to prepare an unstretched sheet. As in the case of Example 1, a stretched sheet could be stably and continuously produced. Further, the obtained film had high transparency, and no whitening phenomenon was observed.

Comparative Example 1 An attempt was made to manufacture a polystyrene film in the same manner as in Example 1 except that the temperature of the heat setting heating zone was changed from 210 ° C. to 260 ° C. In the above conditions, the sheet vertically splits near the inlet of the heat setting heating zone, which propagates to the transverse stretching zone and becomes unable to undergo transverse stretching, and at the exit of the tenter, the `` contracted galvanized sheet plate remains held in the clip. The corrugated sheet ”was ejected. Under these conditions, there was no recovery after that.

Comparative Example 2 Example 1 was repeated except that the temperature in the transverse stretching heating zone was changed from 105 ° C. to 110 ° C. and the temperature in the heat setting heating zone was changed from 210 ° C. to 255 ° C. An attempt was made to manufacture a polystyrene film in the same manner as in. Under the above conditions, the sheet was vertically torn near the entrance of the heat setting zone, and production became impossible.

Table 1 shows the above manufacturing conditions.

[0035]

[Table 1] Table 1 ──────────────────────────────────── Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 ───────────────────────────────────── Vertical stretching ratio (times) 3.5 3.5 3.5 3.5 3.5 Horizontal stretching ratio (times) 4.0 4.4 4.4 4.0 4.4 Preheating zone (℃) 100 100 100 100 100 Horizontal stretching zone (℃) 105 105 105 105 110 Heat setting zone (℃) 210 210 210 260 255 Thermal relaxation zone (℃) 210 210 210 210 210 Thermal relaxation amount (%) 7 7 7 7 7 Ths-Ttd (℃) 105 105 105 155 145 △ T (℃ / sec) 35 35 35 35 35 Others − − Silica content − − ─ ───────────────────────────────────

[0036]

By utilizing the production method of the present invention, a biaxially stretched film made of an SPS resin can be continuously and stably produced. Therefore, according to the present invention,
It is possible to easily obtain a polystyrene film having high heat resistance, chemical resistance, and humidity stability, which are properties derived from the syndiotactic structure, and having excellent mechanical strength. Further, such a film can be advantageously used as a photographic material such as a photographic film support, a packaging material such as a packaging film, a plate-making material such as a plate-making support and an electric material.

[Brief description of drawings]

FIG. 1 is a plan view showing an outline of a transverse stretching device that can be used in the present invention.

[Explanation of symbols]

 1 Preheating Zone 2 Horizontal Stretching Heating Zone 3 Heat Fixing Heating Zone 4 Thermal Relaxation Zone 5 Cooling Zone 6 Sheets Stretched in Longitudinal Direction 6'Sequentially Biaxially Stretched Sheet 7 Clip Endless Belt for Transport 8 Clip

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Ogura No. 200 Onakazato, Fujinomiya City, Shizuoka Prefecture Fuji Photo Film Co., Ltd.

Claims (3)

[Claims] 1. An unstretched sheet obtained by heat-melting and extruding polystyrene having a syndiotactic structure,
After stretching in the machine direction under heating, the sheet is transversely stretched in a heated zone and then continuously heat-set in another heated zone adjacent to the heated zone. A method for producing a polystyrene film, wherein the transverse stretching and the heat setting treatment are carried out by the following formulas (1) and (2): 60 ≦ Ths−Ttd ≦ 120 (1) Tg ≦ Ttd ≦ Tg + 20. (2) [where Ttd represents the value of the temperature (unit: ° C) of the heated zone in which the transverse stretching is performed, and Ths is the temperature (unit: in the heated zone of the heat setting treatment). C.) and the Tg is the glass transition temperature (in ° C) of polystyrene having the syndiotactic structure. ] The manufacturing method of the polystyrene film characterized by performing on the conditions satisfy | filled. 2. The production of a polystyrene film according to claim 1, wherein the temperature change of the sheet when moving from the heated zone for transverse stretching to the heating zone for heat setting treatment is 40 ° C./sec or less. Method. 3. The time for passing through the heating zone for transversely stretching the sheet is 3 to 60 seconds, and the time for passing through the heating zone for performing the heat setting treatment is 3 to 45 seconds. The method for producing a polystyrene film according to 1.