JPH09201873A - Production of syndiotactic polystyrene film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an SPS base film having excellent thermal, mechanical, physical, chemical and optical characteristics and dimensional stability and excellent in the balance of mechanical strength, Young's modulus and thermal properties such as a heat shrinkage factor or the like in both longitudinal and lateral directions. SOLUTION: A non-stretched amorphous film composed of an SPS base film is subjected to first stage stretching in one direction in a magnification of 2.7-5.0 times and subsequently subjected to second stage stretching in the direction right-angled to the first stage stretching direction in a magnification of 1.2-4.5 times. At that time, first stage stretching temp. is selected so that the refractive index in the direction right-angled to the stretching direction within the film plane after first stage stretching is 1.597 or more and second stage stretching temp. is set to 70-below 105V and the stretched film is thermally fixed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a syndiotactic polystyrene film. More specifically, the present invention relates to a method for stretching a syndiotactic polystyrene film, which has an excellent balance of mechanical strength in both longitudinal and transverse directions.

[0002]

2. Description of the Related Art Syndiotactic polystyrene (hereinafter abbreviated as "SPS") film has excellent thermal, mechanical, physical, chemical, and optical properties of PET film, and particularly, optical film. It has excellent characteristics (light transmittance, haze, etc.) and dimensional stability. Therefore, the SPS film is used for photographic light-sensitive materials (color,
X-rays, printing materials, magnetic recording applications (audio,
Suitable for video applications, floppy disks, etc.), electrical applications (capacitors, electrical insulating materials, etc.), vapor deposition applications, packaging applications, etc.

The SPS-based film is obtained by first stretching the SPS-based unstretched film in the longitudinal direction and then stretching it in the transverse direction in order, in addition to the longitudinal / transverse sequential stretching method. Later, the horizontal / longitudinal sequential stretching method for longitudinal stretching,
A longitudinal / longitudinal sequential stretching method, a longitudinal / transverse / longitudinal sequential stretching method, a longitudinal / longitudinal / transverse sequential stretching method, a simultaneous biaxial stretching method, or the like is adopted.

By the way, in the film forming process of a general-purpose polyester (polyethylene terephthalate, polyethylene-2,6-naphthalate, etc.) film, the film is first oriented in the longitudinal direction, oriented in the longitudinal direction, and then transversely oriented in the direction perpendicular thereto. A sequential biaxial stretching film forming method is generally used in which the film is oriented in the width direction and heat-set to secure mechanical strength (Young's modulus etc.) in both longitudinal and transverse directions, heat shrinkage ratio, etc. in a well-balanced manner.

The film production of SPS film on an industrial level is characterized by the successive biaxial stretching method, which is excellent in productivity (high film formation speed) and excellent quality (particularly good thickness unevenness, mechanical strength and heat). Vertical / horizontal balance etc.) and conventional production equipment (stenter biaxial stretching film formation equipment with tenter method)
You can't think of it without taking advantage of.

[0006] However, in the film formation of SPS type film by longitudinal / transverse or lateral / longitudinal sequential biaxial stretching, the SPS obtained is
The physical properties of the film such as strength in both the vertical and horizontal directions are
The same results as the film physical properties of the polyester support are not reproduced. That is, the SPS-based unstretched film is first longitudinally or transversely stretched to be oriented in the longitudinal or widthwise direction, and then transversely or longitudinally stretched at a right angle thereto to be oriented in the lateral or longitudinal direction. Then, the heat-fixed film becomes more predominant in the latter half of the successive stretching. That is, in the case of longitudinal / transverse sequential stretching or transverse / longitudinal sequential stretching,
It is a fact that the strength and Young's modulus in the transverse direction or the longitudinal direction are relatively retained, but conversely, the strength and Young's modulus in the transverse direction or the transverse direction are unexpectedly decreased. In the film forming method in which the SPS film is sequentially biaxially stretched and heat-set, the orientation in the first stretching is largely eliminated in the subsequent stretching, and the mechanical strength and Young's modulus in the first stretching direction are lowered, The mechanical strength in the stretching direction, Young's modulus, in other words, the orientation due to the latter half of stretching is dominant. Therefore, the sequential biaxially stretched film forming method of the SPS film has a problem in that the mechanical strength, the Young's modulus, the heat shrinkage ratio, etc. in the longitudinal and transverse directions are well balanced.

[0007]

Accordingly, the object of the present invention is to have excellent thermal, mechanical, physical, chemical and optical properties, high dimensional stability, and both longitudinal and transverse directions. An object of the present invention is to provide a method for producing an SPS-based film having an excellent balance of thermal properties such as mechanical strength, Young's modulus and heat shrinkage.

[0008]

[Means for Solving the Problems] An unstretched amorphous film made of an SPS type film is stretched in one direction in a first step at a specific ratio, and then in a direction perpendicular to the first step stretching direction. When stretching the second stage at a specific ratio, the first stage stretching temperature is selected so that the refractive index in the direction perpendicular to the stretching direction in the film plane after the first stage stretching is a specific value or more, It was achieved by a method for producing an SPS-based film, which comprises stretching at a second-stage stretching temperature and heat-setting.

That is, an unstretched amorphous film made of a syndiotactic polystyrene film is first stretched in one direction at a magnification of 2.7 to 5.0, and then in the first stretch direction. On the other hand, the magnification is 1.2 at right angles.
When the second stage is stretched at 4.5 times to 4.5 times, the first stage stretching temperature is selected so that the refractive index in the direction perpendicular to the stretching direction in the film plane after the first stage stretching is 1.597 or more,
This is achieved by a method for stretching a syndiotactic polystyrene film, which comprises stretching at a second stage stretching temperature of 70 ° C. or more and less than 105 ° C., and then heat setting.

Although the degree of orientation of the SPS film increases as the draw ratio increases, the structural characteristics of the SPS film show that the numerical value of the refractive index increases with increasing the draw ratio in the longitudinal and transverse directions. There is a feature that it is small in the direction and large in the thickness direction.

In the film formation of the SPS type film in the longitudinal / transverse sequential biaxial stretching, based on the findings of the film in the longitudinal / transverse sequential biaxial stretching of the polyester film, the stretching conditions in which the longitudinal / lateral strength and Young's modulus are almost the same. (Approximately same draw ratio, draw temperature, draw speed, etc.) are adopted. However, in the SPS film, the strength (Young's modulus) in the stretching direction of the first stretched film (uniaxially stretched film) is equivalent to the stretch ratio, and even after the first stretch, the first stretch is continued. When stretched and oriented in the direction perpendicular to the direction and heat set, the orientation in the first stretching direction is canceled, the mechanical strength and Young's modulus decrease, and the mechanical strength and Young's modulus in the perpendicular direction increase,
It is confirmed that the SPS-based film in which the mechanical strengths in the longitudinal and lateral directions and the Young's modulus are out of balance and which is oriented in the later second-stage stretching direction with a bias is formed. This tendency is weakly seen in polyester film, but
Compared with the polyester type, the degree is large, indicating that the strength in the first stage stretching direction after the second stage stretching, the Young's modulus, in other words, the orientation in the first stage stretching direction is largely eliminated. This means that the vertical and horizontal strengths and Young's modulus are almost the same,
Alternatively, the strength and Young's modulus in both the vertical and horizontal directions are well balanced, which is beyond the purpose of forming a large film.

The present invention will be described in more detail below. First, the syndiotactic polystyrene of the present invention will be described.

In the present invention, a film containing syndiotactic polystyrene (SPS) as a main component means that the stereoregular structure (tacticity) is mainly a syndiotactic structure, that is, a main chain formed from carbon-carbon bonds. On the other hand, a phenyl group or a substituted phenyl group, which is a side chain, has a steric structure in which they are alternately located in opposite directions, and the main chain of the main chain is a styrene polymer which is a racemo chain, or a composition containing the same. If it is a styrene homopolymer, it can be polymerized by the method described in JP-A No. 62-117708, and for other polymers, JP-A Nos. 1-46912 and 1-1785.
It can be obtained by polymerizing by the method described in No. 05 and the like.

The tacticity is quantified by a nuclear magnetic resonance method ( ¹³ C-NMR method) using isotope carbon. ^The tacticity measured by the ¹³ C-NMR method can be indicated by the abundance ratio of a plurality of continuous constitutional units, for example, diad in the case of 2 units, triad in the case of 3 units, and pentad in the case of 5 units. However, the styrene-based polymer mainly having a syndiotactic structure referred to in the present invention is usually a racemic diad of 75% or more,
Preferably 85% or more, or racemic triad 60
% Or more, preferably 75% or more, or racemic pentad 30% or more, preferably 50% or more.

Specific monomers of the polymer constituting the syndiotactic polystyrene-based composition include styrene, alkylstyrene such as methylstyrene, halogenated (alkyl) styrene such as chloromethylstyrene and chlorostyrene, alkoxystyrene, A single or a mixture containing vinyl benzoate as a main component.

The polystyrene-based resin having a syndiotactic structure of the present invention uses the above-mentioned raw material monomers as a catalyst for polymerization and is disclosed in JP-A-5-320448, p.
(A) Transition metal compound and (b) described on page 10
Those containing aluminoxane as a main component, or (b) (a)
It can be produced by polymerization using a compound containing, as a main component, a transition metal compound and a compound capable of reacting with the transition metal compound (c) to form an ionic complex.

To produce the styrenic polymer used in the film of the present invention, first, the styrenic monomer is sufficiently purified and then polymerized in the presence of any of the above catalysts. At this time, the polymerization method, polymerization conditions (polymerization temperature, polymerization time), solvent, etc. may be appropriately selected. Usually from -50
At a temperature of 200 ° C, preferably 30-100 ° C,
Polymerization is carried out for 1 second to 10 hours, preferably 1 minute to 6 hours. As the polymerization method, any of a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method and the like can be used, and either continuous polymerization or discontinuous polymerization may be used. Here, in the solution polymerization, as a solvent, for example, aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, and aliphatic hydrocarbons such as cyclopentane, hexane, heptane, and octane may be used alone or in combination. It can be used in combination. in this case,
The monomer / solvent (volume ratio) can be arbitrarily selected. The molecular weight and composition of the polymer may be controlled by a commonly used method. The molecular weight can be controlled by, for example, hydrogen, temperature, monomer concentration and the like.

It is necessary to pay close attention to the purification of the styrene-based monomer, catalyst, solvent, etc. used, washing of the polymerization kettle, etc., also from the viewpoint that no foreign matter is mixed in.

Polymerization catalyst (a) (a) transition metal compound and (b) aluminoxane as a main component, or (b) ionic by reacting with (a) transition metal compound and (c) transition metal compound A compound containing a compound capable of forming a complex as a main component is used, but each of the above (a) and (b) contains Ti, Zr, Cr, V, Nb, Ta, and Al metal. The amount of the catalyst is very small, and most of it is dissolved and does not precipitate as a metal, but rarely in the polymer, or in the film forming process, together with the metal of the polymer extrusion filter material, such as bronze. May be deposited as foreign matter.

When the polymer is polymerized in a batch system, when the molten polymer is extruded and cut into pellets, foreign matter (for example, dust) must be thoroughly excluded from the outside. In addition, foreign substances that cannot be avoided during polymer polymerization were removed by a process of cutting into pellets, using a mesh or a metal powder sintering type filter having a coarser mesh than a film forming filter. Better. It is considered that the polymer is removed by a filter during the film forming process, but it may not be completely removed. Therefore, it is preferable to remove it as much as possible in the process before the film forming. The same applies to continuous polymerization.

The molecular weight of the SPS film of the present invention is not limited as long as it is formed into a film, but the weight average molecular weight is preferably 10,000 to 3,000,000, and particularly 30,000. It is preferably from about 1,500,000. The molecular weight distribution (weight average molecular weight / number average molecular weight) at this time is preferably 1.5 to 8. This molecular weight distribution can be adjusted by mixing different molecular weights. In addition, other monomers copolymerizable with these may be copolymerized to the extent that the effects of the present invention are not impaired.

The SPS film of the present invention is preferably SPS made from styrene alone,
Further, as a film containing SPS, it is possible to control the crystallization rate by mixing SPS with a styrene polymer (IPS) having an isotactic structure in which the main chain is a meso chain, and to obtain a stronger film. It is possible to When mixing SPS and IPS,
The ratio depends on the stereoregularity of each other, but 3
0:70 to 99: 1, preferably 50:50 to 98: 2
It is.

The support may contain inorganic fine particles, an antioxidant, a UV absorber, an antistatic agent, a dye, a pigment, a dye, etc., in order to impart functionality, within a range not impeding the object of the present invention. Is also good.

The polymer used for forming the SPS film has a weight average molecular weight of 10,000 or more, more preferably 30,000.
0 or more. When the weight average molecular weight is less than 10,000, a film excellent in strength characteristics and heat resistance cannot be obtained. The upper limit of the weight average molecular weight is not particularly limited, but if the weight average molecular weight is 1,500,000 or more, rupture may occur due to an increase in stretching tension, which is not preferable. Furthermore, the SPS film of the present invention is SP
The S-based pellets are dried at 120 to 180 ° C. for 1 to 24 hours under vacuum or normal pressure under an atmosphere of inert gas such as air or nitrogen. The target moisture content is not particularly limited, but is 0.05% or less, preferably 0.01% or less, from the viewpoint of preventing reduction in mechanical strength and the like due to hydrolysis.
More preferably, it is 0.005% or less. However, these methods are not particularly limited as long as the purpose is achieved.

A known method can be applied to the extrusion during film formation, but it is preferable to extrude with a T-die, for example.
Melt and extrude SPS pellets at 280-350 ° C,
An unstretched film is produced by cooling and solidifying while applying static electricity on a casting roll.

Next, this unstretched film is biaxially stretched to obtain 2
Orient the axis. The manufacturing method of the SPS film of the present invention is
In addition to the sequential biaxial stretching method in which longitudinal stretching and transverse stretching are performed in order, the transverse / longitudinal sequential biaxial stretching method is preferably used. Needless to say, the present invention can be applied to the first sequential stretching such as the transverse / longitudinal / longitudinal stretching method and the longitudinal / transverse / longitudinal stretching method.

By the way, as a method for stretching the SPS-based unstretched film, 110 to 150 ° C. {(Tg + 1
0 to 0 ° C to (Tg + 50) ° C} and stretched 2.0 to 5.0 times, and then 115 to 160 ° C in the transverse direction {(Tg + 1
5) It is known that the film is stretched 2.0 to 5.0 times at a temperature of (Tg + 60) ° C.} and heat set at 170 to 270 ° C. for 3 to 100 seconds.

Here, Tg represents the glass transition temperature (° C.) of the SPS film, which is about 100 ° C.

Under these stretching conditions, however, the orientation structure formed by the first-stage stretching has a different degree depending on the stretching temperature and the stretching ratio. It is known that the film is broken a little and an oriented structure is newly formed by the second-stage stretching, so that the mechanical properties of the film in the second-stage stretching direction are stronger than those of the first-stage stretching direction in terms of physical properties of the film.

Polyesters (polyethylene terephthalate, polyethylene naphthalate, etc.) have a tendency to a considerable extent, but the oriented structure formed by the first-stage stretching is maintained, and the subsequent stretching in the perpendicular direction also results in the stretching direction. It is considered that since a new orientation structure is formed in, the mechanical strengths in the stretching directions of both the first stage and the second stage are maintained and balanced.

On the other hand, the reason for this is not clear, but SPS
In the case of the system film, the orientation structure formed by the first-stage stretching is destroyed by the subsequent stretching in the orthogonal direction, and a new orientation structure is formed in the direction orthogonal to the first-stage stretching direction, It is considered that the film loses the mechanical strength in the stretching direction of the stage and more strongly develops the mechanical strength in the stretching direction of the second stage, and as a result, a film in which the balance of mechanical properties is lost is obtained.

Therefore, it is possible to suppress the destruction of the orientational structure obtained in the former stage stretching, and in the subsequent latter stage stretching in the perpendicular direction,
It is conceivable that the orientation structure should be formed in the right-angle direction, or destruction should be avoided, and the orientation should be set high beforehand.

As a result of intensive studies to eliminate these drawbacks, the present inventor (1) stretched an unstretched amorphous film made of syndiotactic polystyrene film in the plane of the film after the first stage stretching. If the stretching temperature is selected so that the refractive index in the direction perpendicular to the direction becomes 1.597 or more and the first-stage stretching is performed, the orientation in the stretching direction is high and the orientation structure is strong because the stretching is performed at a low temperature. This is the same as increasing the substantial draw ratio as compared with the case where the drawing temperature is high (conventional method). Therefore, the second-stage stretching (performed in the direction perpendicular to the first-stage stretching direction), while slightly destroying the structure formed by the first-stage stretching, while maintaining the structure sufficiently, It is possible to produce a film with well-balanced mechanical strength in the vertical and horizontal directions and Young's modulus, since the oriented structure can be formed together.

The present invention has been completed by finding the above.

In addition to the above, in the above-described generally known stretching method for SPS-based unstretched film, the crystallization speed of the SPS-based film is extremely fast, although there is a degree of difference depending on the stretching temperature and the stretching ratio. In addition, it is known that the crystallization is greatly promoted by the first-stage stretching. Therefore, if the stretching method of the present invention is adopted, the first stage stretching is carried out at a low temperature, the crystallinity of the stretched film is suppressed, and the second stage stretching (performed in the direction perpendicular to the first stage stretching direction). Can be uniformly performed at a lower temperature than the conventional method, and the obtained biaxially oriented film has extremely few thickness unevenness.

Since the second-stage stretching is carried out at a low temperature, it is not necessary to make the second-stage stretching ratio larger than the first-stage stretching ratio, and it has been found that a film having an arbitrary degree of orientation in length and width can be easily obtained. did.

That is, in the present invention, a substantially unstretched amorphous film made of a syndiotactic polystyrene film is first stretched and stretched in one direction at a magnification of 2.7 to 5.0, and then stretched. When the second-stage stretching is performed in a direction perpendicular to the stretching direction at a draw ratio of 1.2 to 4.5, the first-stage stretching temperature is set to a direction perpendicular to the stretching direction in the film plane after the first-stage stretching. By a stretching method of a syndiotactic polystyrene film, the refractive index is selected to be 1.597 or more, the second stage stretching temperature is 70 ° C. or more and less than 105 ° C., and then heat setting is performed. It has been achieved.

In the present invention, the refractive index in the direction perpendicular to the stretching direction in the plane of the film after the first-stage stretching is measured at 25 ° C. using an Abbe refractometer with α-bromonaphthalene as an intermediate liquid. The value of Na for the D line is shown.
Although the refractive index often changes in the width direction of the film (the direction perpendicular to the first-stage stretching in the film plane), the value adopted in the present invention is the minimum value of the refractive index. SP
In the S-type film, the refractive index becomes smaller as the orientation in the longitudinal and transverse directions progresses, and the part where the refractive index is the smallest has the highest crystallization, and the part where the second stage drawing has the worst drawability. It doesn't come off.

In the present invention, an unstretched amorphous film made of the syndiotactic polystyrene film is used,
The first-stage stretching temperature is selected so that the refractive index in the direction perpendicular to the stretching direction in the film plane after the first-stage stretching is 1.597 or more, and the first-stage stretching ratio is 2.7 to 5.0. Stretch. As the stretching temperature becomes lower, the refractive index in the direction perpendicular to the stretching direction in the film plane after the first stage stretching tends to increase. Therefore, in order to make the refractive index 1.597 or more, It is better to stretch at the lowest temperature possible.
A suitable stretching temperature range is a temperature at which the lower limit of the refractive index is 1.597, and the lower limit is controlled by the low temperature stretching limit temperature. The upper limit of the refractive index is not particularly limited, but 1.625
It is a degree.

If the stretching temperature is too low, the film will not be smoothly stretched, and a film having a significantly large thickness and thin spots in which stretched portions and unstretched portions are mixed can be obtained. The low temperature stretching limit temperature at which stretching unevenness does not exist varies slightly depending on the polymer type and the stretching ratio, but the stretching temperature at which the refractive index becomes 1.597 or more is about 90 ° C, and the upper limit is less than 105 ° C. Is.

A uniaxially oriented SPS film having a refractive index of 1.597 or more in the direction perpendicular to the stretching direction in the plane of the film after the first-stage stretching, which has been stretched by the above-described method, is then applied to the stretching direction. A second stage drawing is carried out in a direction of a right angle at a drawing temperature of 70 ° C. or more and less than 105 ° C. and a draw ratio of 1.2 to 4.5 times.

The reason why such a low temperature is adopted as the second-stage stretching temperature is that the crystallinity of the uniaxially stretched film is extremely low, and the orientation structure by the first-stage stretching is not lost by the stretching at such a low temperature. In addition, since the oriented structure can be formed by the second-stage stretching, a film having well-balanced mechanical strength in the longitudinal and lateral directions and Young's modulus can be manufactured.
In addition, from the viewpoint of production in a factory, there are advantages that drawing is smoothly performed in continuous production, breakage does not occur, and thickness unevenness is extremely small. The other reason is that it is not necessary to make the second-stage draw ratio larger than the first-stage draw ratio, and a film having an arbitrary degree of orientation in the longitudinal and lateral directions can be easily obtained.

If the stretching temperature in the second stage is lower than 70 ° C., the film is cut, and if the stretching temperature is 105 ° C. or higher, the orientation in the stretching direction in the first stage is considerably lost, and the stretching in the second stage stretching direction is lost. Since the orientation cannot be obtained, the film has low mechanical strength in the vertical and horizontal directions and a low Young's modulus. At this time, the thickness unevenness in the width direction becomes large, which is not preferable.

The heat treatment temperature for heat treatment of the stretched film can be appropriately changed depending on the application. For shrink-wrapping applications requiring high shrinkage, 115 ° C or higher and 175 ° C or lower, photographic photosensitive applications requiring color stability (colors, X-rays, printing sensitive materials, etc.), magnetic recording applications (audio, Video, floppy, etc.), electrical applications (capacitors, electrical insulating materials, etc.), vapor deposition applications (stamping, metallizing, etc.), depending on the purpose.
A temperature of 0 ° C., preferably 220-270 ° C. is adopted. The heat treatment time is not particularly limited, but is usually 3 seconds to 1
About 00 seconds is adopted.

It goes without saying that longitudinal heat relaxation, horizontal heat relaxation treatment, etc. may be carried out as necessary.

In addition to the above film forming method, slipperiness, adhesiveness,
In order to impart various properties such as antistatic performance, an SP in which the above-described properties are imparted to at least one surface of the SPS film.
It is also possible to produce an SPS laminated film in which S-based films are laminated. The lamination method is such that the resin is melted in a laminar flow and then extruded from a die, or cooled and solidified SPS unstretched film or SPS uniaxially stretched film is extrusion-laminated with molten SPS, and then longitudinally It is obtained by stretching in both transverse directions or in a direction perpendicular to the uniaxial stretching direction and heat setting. Similarly, the manufacturing method of the present invention may be applied to the manufacturing method of the SPS-based laminated film.

In addition to the above, in order to impart various characteristics such as slipperiness, adhesiveness and antistatic performance, at least one surface of the SPS film is surface-coated (by applying vinylidene chloride to provide a gas barrier property, or by in-line coating). (Providing slipperiness, easy adhesion, etc.) may be performed.

The SPS-based biaxially oriented film obtained by the method of the present invention has a high mechanical strength in both longitudinal and transverse directions and a high Young's modulus and is well balanced. At the same time, the film has low crystallinity, excellent transparency, and extremely few thick and thin spots.

According to the method of the present invention, it is not always necessary to make the second-stage draw ratio larger than the first-stage draw ratio, and a film in which the orientation is arbitrarily changed in the longitudinal and lateral directions can be produced.

The SPS stretched film thus obtained can be usefully used in various applications.
Especially for photographic materials, magnetic recording, electrical applications,
It can be usefully used for vapor deposition applications, packaging applications and the like, and its thickness is not particularly limited, but it is useful for those having a thickness of 3 to 350 μm.

[0051]

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 (1) Polymerization of SPS Polymer SPS polymer pellets were prepared according to JP-A-3-131843. From the preparation of the catalyst to the polymerization reaction, all were carried out under a dry argon stream. Copper sulfate pentahydrate (CuSO ₄ · 5H ₂ O) 1 in a glass container with an internal volume of 500 ml
Add 7.8 g (71 mmol), 200 ml of purified benzene and 24 ml of trimethylaluminum, and add 8 at 40 ° C.
The catalyst was adjusted by stirring for a time. This was placed under an argon gas flow. After filtering through 3 glass filters, the filtrate was freeze-dried. This was taken out, put in a 2 liter stainless steel container, and tributylaluminum and pentacyclopentadiethyl titanium methoxide were further mixed therein, and mixed with 9
Heated to 0 ° C. In this, purified styrene and 4-
1 liter and 75 ml of methylstyrene were added, and the polymerization reaction was continued at this temperature for 8 hours. Thereafter, the mixture was cooled to room temperature, 1 liter of methylene chloride was added, and a methanol solution of sodium methylate was added with stirring to deactivate the catalyst. The content was gradually dropped into 20 liters of methanol, filtered through a glass filter, washed with methanol three times, and then dried. 1,
The weight average molecular weight of this polymer was 280,000, which was determined from the measurement results of GPC measured with standard polystyrene at 135 ° C. using 2,4-trichlorobenzene as a solvent. The melting point of this polymer was ¹³ C-NMR at 245 ° C.
It was confirmed that the polymer obtained also had a syndiotactic structure.

This was pelletized with an extruder to secure the required amount.

(2) Film formation of SPS-based film The obtained SPS-based polymer pellets were dried at 150 ° C. for 3 hours in a nitrogen atmosphere and melt-extruded into a film form from a T-die at 330 ° C. to obtain a sheet. Was rapidly cooled and solidified on a cooling drum at 25 ° C. by an electrostatic application method to prepare an unstretched film.

When this unstretched film was stretched by a known roll stretching machine at a stretching ratio of 4.4 times, uniform stretching was carried out at 90 ° C. or more and less than 105 ° C. and a high orientation was maintained at 90 ° C. or less. . It was found that when the temperature was less than 90 ° C, remarkable stretching unevenness was generated, and the low temperature stretching limit temperature was 90 ° C.

The SPS-based unstretched film was first stretched in the longitudinal direction under the conditions shown in Table 1, and then the film was stretched in the transverse direction at right angles to the first-stage stretching direction in the width direction. The results of stepwise stretching are as follows.

The film thickness after stretching was about 100 μm.

The refractive index is the refractive index in the width direction perpendicular to the stretching direction in the film plane after the first-stage stretching. Using an Abbe refractometer, α-bromonaphthalene as an intermediate liquid is used. The value with respect to the D line of Na measured at 25 ° C is shown. Although the refractive index often changes in the width direction of the film (the direction perpendicular to the first-stage stretching in the film plane), the value adopted in the present invention is the minimum value of the refractive index.

[0059]

[Table 1]

Experiment No. 2 to 7 and No. 15 to 1
The film of the present invention No. 7 was well stretched, and the film thickness unevenness after stretching was (± 2 to ± 4)% per 1 m width.

On the other hand, in Experiment No. In the comparative examples 12 to 14, the film was whitened and the thickness was 1 m.
The width was so bad (± 10% to ± 15%) that it could not be used. Experiment No. The film thickness of 8 and 9 are
It was very poor at ± 8% and ± 45% per 1 m width, and was unusable. Experiment No. 1,10
In Nos. 11 and 18, the film is cut or broken, or
Stretching is difficult and not practical.

Example 2 An SPS-based unstretched film obtained by polymerizing an SPS-based polymer in the same manner as described in Example 1 was prepared.
The results of the first stage stretching in the longitudinal direction under the conditions shown in Table 2 and the second stage stretching of the film in the width direction perpendicular to the first stage stretching direction in the film plane are as follows. . The film thickness after stretching was about 100 μm.

The method of displaying and measuring the refractive index is the same as in the first embodiment.

[0064]

[Table 2]

Experiment No. The films of the present invention Nos. 19 to 23 were well stretched, and the film thickness unevenness after stretching was (± 2 to ± 4)% per 1 m width.

As is clear from the above results shown in Tables 1 and 2, in the method for producing an SPS-based film of the present invention, the first stage of stretching is 90 ° C. or higher 105 with the glass transition temperature of the SPS-based film sandwiched. When it is stretched 2.7 to 5.0 times at a temperature of less than 0 ° C, the refractive index in the direction perpendicular to the stretching direction in the film plane after the first stage stretching is maintained at 1.597 or more,
Thereafter, the film was stretched at a temperature of 70 ° C. or more and less than 105 ° C. in a direction perpendicular to the first-stage stretching direction in the plane of the film.
It can be seen that when a second stage stretching of 2 to 4.5 times is carried out, a film with good thickness and thinness can be obtained.

Experiment No. Comparative Examples 12 to 14 are films formed under generally known stretching conditions,
In both cases, the refractive index in the direction perpendicular to the stretching direction within the film plane after the first-stage stretching is less than 1.597. This film and the experiment No. 2 to 5 films obtained by the present invention (all have a refractive index of 1.597 or more in the direction perpendicular to the stretching direction in the plane of the film after the first stage stretching)
Was heat-set at 255 ° C. for 30 seconds and 100 μm thick S
A PS film was obtained.

Table 3 shows the longitudinal and transverse mechanical properties (breaking strength, Young's modulus) of the obtained SPS film.

Tensileon RTA-1 manufactured by Orientec Co., Ltd. was used to measure the breaking strength and Young's modulus in the longitudinal and transverse directions.
Was measured at room temperature. Cut into a length of 1 cm and a length of 15 cm in the longitudinal direction and the width direction of the SPS support,
The film was gripped by a tensilon so that the film length was 10 cm and pulled at a speed of 100% / min to draw a stress-strain curve. The breaking strength was calculated by dividing the stress at break by the film cross-sectional area before pulling. Young's modulus was calculated from the tangent line of the rising portion of the stress-strain curve, and S
It is calculated by dividing the PS support thickness by the cross-sectional area, and both units are expressed in kgf / mm ² . The thickness of the SPS-based support was measured at 7 points using a micrometer, the maximum value and the minimum value were excluded, and the thickness of each measurement sample was averaged at 5 points in μm units. expressed.

[0070]

[Table 3]

From the results of Table 3, it is shown that the SPS film manufacturing method of the present invention can produce a film having excellent mechanical strength in both length and width and a well-balanced film. On the other hand, in the comparative example (conventional manufacturing method), although the strength at break and Young's modulus were impaired and the transverse draw ratio was equal to or less than the longitudinal draw ratio, although it was stretched in the longitudinal direction to some extent. It is understood that the film has increased breaking strength and Young's modulus.

From the above results, an unstretched amorphous film made of SPS type film was stretched in one direction at a magnification of 2.7 to 5.0, and then stretched in the first stage. When the second-stage drawing is performed at a draw ratio of 1.2 to 4.5 in the right-angled direction, the first-stage drawing temperature is set so that the refractive index in the direction perpendicular to the drawing direction in the film plane after the first-stage drawing is 1.5.
It is selected to be 97 or more, and the second stage drawing temperature is 70 ° C.
The SPS-based biaxially oriented film of the present invention, which is obtained by stretching at 105 ° C. or less and then heat setting, obtains a well-balanced film having high mechanical strength in both longitudinal and transverse directions and Young's modulus. be able to. At the same time, it is possible to produce a film having low film crystallinity, excellent transparency, and extremely small thickness unevenness.

[0073]

The SPS-based biaxially oriented film of the present invention has high mechanical strength in both longitudinal and transverse directions and a high Young's modulus.
And you can get a well-balanced film. At the same time, it is possible to produce a film having low film crystallinity, excellent transparency, and extremely small thickness unevenness.

Claims (1)

[Claims] 1. An unstretched amorphous film made of a syndiotactic polystyrene film is first stretched in one direction at a magnification of 2.7 to 5.0, and then in the first stretch direction. 1.2 to 4.5 magnification in the direction perpendicular to
At the time of the second-stage stretching, the first-stage stretching temperature is selected so that the refractive index in the direction perpendicular to the stretching direction in the film plane after the first-stage stretching is 1.597 or more, and the second-stage stretching is performed. A method for producing a syndiotactic polystyrene film, which comprises stretching at a temperature of 70 ° C. or higher and lower than 105 ° C., and then heat setting.