JPH08187779A - Stretched polystyrenic film and production thereof - Google Patents

Abstract

PURPOSE: To provide a stretched SPS film excellent in slip properties, reduced in surface damage and not containing an antiblocking agent or reduced in the addition amt. thereof in order to enable the reutilization of a scrap material without lowering dielectric breakdown voltage. CONSTITUTION: A polystyrenic stretched film is composed of a styrenic resin compsn. containing 70-100wt.% of a styrenic polymer having a high degree of syndiotactic configuration and has projections with a diameter of 0.2-5.0μm composed of a styrenic polymer on at least one surface thereof. This stretched polystyrenic film is produced by biaxially stretching a preformed object composed of the styrenic resin compsn. and characterized in that an average crystallinity is 25% or less and spherical crystals are present and by heat- treating the stretched film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polystyrene stretched film and a method for producing the same, and more particularly to a capacitor, an FPC film for electrical insulation, a photographic film, a plate-making film, an optical film such as OHP, a packaging film and the like. The present invention relates to a polystyrene-based stretched film that is preferably used.

[0002]

BACKGROUND OF THE INVENTION Styrene-based polymers having a syndiotactic structure (hereinafter referred to as
It may be abbreviated as "SPS". ) Is the mechanical strength,
Since it has excellent heat resistance, appearance, solvent resistance, etc., it is expected to be used for various purposes. In particular, various film, sheet or fiber extrusion techniques, molded products, applications, etc. have been proposed. In addition, many proposals have been made so far regarding a method for producing a stretched film, a stretched film having various physical properties, and its use. Among these, in the field of capacitor films, SPS stretched films, which are excellent in heat resistance, dielectric properties, and moisture resistance, are promising as materials, and the development of ultrathin films with good slipperiness is desired. For an ultrathin film having good slipperiness, a method of adding specific inorganic fine particles or organic fine particles is disclosed in JP-A-1-1823.
46, JP 3-74437 A, JP 6-A
57013, JP-A-6-57014, JP-A-6-57015, JP-A-6-57016, JP-A-6-57017, and JP-A-6-6403.
6, JP-A-6-64037, JP-A-6-6
5399, JP 6-65400 A, JP 6-65401 A, JP 6-65402 A,
JP-A-6-80793, JP-A-6-91748, JP-A-6-91749, and JP-A-6-114.
It is disclosed in Japanese Patent Laid-Open No. 924 and Japanese Patent Laid-Open No. 6-114925. However, when imparting slipperiness to the ultra-thin SPS film by adding inorganic particles or organic particles, the adhesiveness between the fine particles and SPS itself is not sufficient, and therefore, breakage during stretching or heat treatment, or microvoids in the film may occur. Occurrence, deterioration of slipperiness due to falling of fine particles in the subsequent step, scratches on the film surface, reduction of dielectric breakdown voltage, poor secondary processing suitability, etc., and it does not necessarily have sufficient performance as a film. I could not say.
Further, conventionally, in order to satisfy the required physical properties such as slipperiness, it is necessary to adjust the type and addition amount of inorganic particles or organic particles depending on the thickness of the film. There was a problem that it was difficult to do.

The present invention has been made in view of the above situation, and the present inventors have conducted extensive studies to solve the above problems such as slipperiness and surface scratches. Among them, SP
It was found that when S was crystallized statically, fine spherulites were formed. Then, when further study was conducted focusing on this minute spherulite, a method of forming spherulite on a part of the preform, the spherulite size and concentration can be achieved by controlling the thermal history after melting. I found that. Further, as a result of studying stretch-molded articles using various raw materials, it was found that specific projections formed by spherulites formed by stretching are effective in solving the above problems.
Based on such knowledge, the present invention is excellent in slipperiness, reduces surface scratches, and does not lower the dielectric breakdown voltage, on the other hand, an antiblocking agent is not added or added in order to enable reuse of scrap materials. It has been completed to provide an SPS stretched film having excellent properties such as a small amount.

[0004]

That is, the present invention relates to a stretched film comprising a styrene resin composition containing 70 to 100% by weight of a styrene polymer having a high syndiotactic structure, at least one of which is a stretched film. The present invention provides a polystyrene-based stretched film, characterized in that it has projections of 0.2 to 5.0 μm in diameter made of the styrene-based polymer on the surface of. The polystyrene-based stretched film preferably has 10 or more protrusions per 10,000 μm ² and a dynamic friction coefficient of 0.7 or less. Further, the present invention comprises a styrene resin composition containing 70 to 100% by weight of a styrene polymer having a high syndiotactic structure, and has an average crystallinity of 2
Biaxially stretching a preform containing 5% or less and having spherulites,
It also provides a method for producing a stretched polystyrene film, which is characterized by heat treatment. Hereinafter, the present invention will be described in more detail.

First, the material of the stretched polystyrene film of the present invention will be described. The syndiotactic styrene-based polymer in the present invention means that the stereochemical structure is a syndiotactic structure, that is, a phenyl group or a substituted phenyl group, which is a side chain, alternates with respect to the main chain formed from carbon-carbon bonds. The tacticity is determined by the nuclear magnetic resonance method ( ¹³ C-NMR method) using isotope carbon. ¹³ C-
The tacticity measured by the NMR method can be indicated by the abundance ratio of a plurality of continuous constitutional units, for example, diad in the case of 2, triad in the case of 3, and pentad in the case of 5. The styrene-based polymer having a high syndiotactic structure referred to in the invention is usually 75% or more, preferably 85% or more in racemic dyad, or 30% or more in racemic pentad,
Preferably, polystyrene having a syndiotacticity of 50% or more, poly (alkylstyrene), poly (halogenated styrene), poly (alkoxystyrene), poly (
Vinyl benzoate), hydrogenated polymers thereof and mixtures thereof, or copolymers containing these structural units. Here, as poly (alkylstyrene), poly (methylstyrene), poly (ethylstyrene), poly (propylstyrene), poly (butylstyrene), poly (phenylstyrene), poly (vinylnaphthalene), poly ( Vinyl styrene), poly (acenaphthylene), etc.
(Chlorostyrene), poly (bromostyrene), poly (fluorostyrene), etc. Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene). Of these, particularly preferred styrene-based polymers are copolymers of styrene and p-methylstyrene, polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), poly (p-tertiarybutylstyrene). ), Poly (p-chlorostyrene),
Examples thereof include poly (m-chlorostyrene) and poly (p-fluorostyrene) (JP-A-62-187708).
Issue).

Further, as the comonomer in the styrene-based copolymer, in addition to the above-mentioned styrene-based polymer monomers, olefin monomers such as ethylene, propylene, butene, hexene and octene, diene monomers such as butadiene and isoprene, and cyclic compounds. Examples thereof include diene monomers, polar vinyl monomers such as methyl methacrylate, maleic anhydride and acrylonitrile. In particular, a styrene-based polymer having a styrene repeating unit of 80 to 100 mol% and a p-methylstyrene repeating unit of 0 to 20 mol% is preferably used. The molecular weight of the styrene-based polymer is not particularly limited, but those having a weight average molecular weight of 10,000 or more and 3,000,000 or less are preferable, and those of 50,000 or more and 1,500,000 or less are more preferable. If the weight average molecular weight is less than 10,000, stretching may not be performed sufficiently. Further, the molecular weight distribution is not limited in its width and various kinds can be applied, but it is preferable that the weight average molecular weight (Mw) / number average molecular weight (Mn) is 1.5 or more and 8 or less. . The styrene-based polymer having the syndiotactic structure is remarkably excellent in heat resistance as compared with the conventional styrene-based polymer having the atactic structure. The styrene polymer having a high syndiotactic structure is contained in the stretched polystyrene film of the present invention in an amount of 70 to 100% by weight, preferably 80 to 100% by weight.

The polystyrene stretched film of the present invention contains a lubricant, another thermoplastic resin, an antioxidant, an inorganic filler, a rubber, a compatibilizer, a colorant, a cross-linking agent, and a cross-linking aid within a range that does not impair its purpose. Agents, nucleating agents, plasticizers, etc. can also be added. As the lubricant, for example, inorganic fine particles can be used. Here, the inorganic fine particles mean group IA, IIA
Tribe, IVA, VIA, VIIA, VIII, IB, IIB
Group, Group IIIB, Group IVB oxides, hydroxides, sulfides, nitrides, halides, carbonates, sulfates, acetates, phosphates, phosphites, organic carboxylates, silicates, Titanate, borate and their hydrous compounds, their complex compounds, and natural mineral particles are shown.

Specifically, Group IA element compounds such as lithium fluoride and borax (sodium borate hydrous salt), magnesium carbonate, magnesium phosphate, magnesium oxide (magnesia), magnesium chloride, magnesium acetate, magnesium fluoride, titanic acid Magnesium, magnesium silicate, magnesium silicate hydrous salt (talc), calcium carbonate, calcium phosphate, calcium phosphite, calcium sulfate (gypsum), calcium acetate, calcium terephthalate, calcium hydroxide, calcium silicate, calcium fluoride, calcium titanate , Strontium titanate, barium carbonate, barium phosphate, barium sulfate, barium phosphite, etc.
IIA group element compounds, titanium dioxide (titania), titanium monoxide, titanium nitride, zirconium dioxide (zirconia),
Group IVA element compounds such as zirconium monoxide, group VIA element compounds such as molybdenum dioxide, molybdenum trioxide and molybdenum sulfide, group VIIA element compounds such as manganese chloride and manganese acetate, group VIII element compounds such as cobalt chloride and cobalt acetate , Group IB element compounds such as cuprous iodide, Group IIB element compounds such as zinc oxide and zinc acetate, aluminum oxide
(Alumina), aluminum hydroxide, aluminum fluoride,
Group IIIB element compounds such as aluminosilicate (alumina silicate, kaolin, kaolinite), silicon oxide (silica,
Group IVB element compounds such as silica gel), graphite, carbon, graphite, glass, carnal stone, kainite, mica (
Particles of natural minerals such as mica, quinnemo) and birose ore are included. The average particle size of the inorganic fine particles used here is
There is no particular limitation, but it is preferably 0.001 to 3 μm, and the content in the molded product is 0.001 to 5% by weight, preferably 0.0
It is from 05 to 3% by weight. The inorganic fine particles are contained in the final molded article, but the method of containing them is not limited. For example, a method of adding or precipitating in an arbitrary process during polymerization, a method of adding in an arbitrary process of melt extrusion can be mentioned.

In the present invention, there are various kinds of other thermoplastic resins which can be added to the above-mentioned styrene-based polymer. For example, a styrene-based polymer having an atactic structure, a styrene-based polymer having an isotactic structure, Examples thereof include polyphenylene ether. These resins are easily compatible with the styrene-based polymer having the syndiotactic structure described above, are effective in controlling crystallization when creating a preform for stretching, and are improved in the stretchability after that, and the stretching condition A film that is easy to control and has excellent mechanical properties can be obtained. Among these, in the case of containing a styrene-based polymer having an atactic structure and / or an isotactic structure, those containing the same monomer as the styrene-based polymer having a syndiotactic structure are preferable. The content ratio of these compatible resin components is 1 to 70% by weight, especially 2 to 5%.
It may be 0% by weight. When the content of the compatible resin component exceeds 70% by weight, the heat resistance, which is an advantage of the styrene polymer having a syndiotactic structure, may be impaired, which is not preferable.

Other resins which can be added to the above-mentioned styrene polymer used in the present invention and which are incompatible resins include, for example, polyolefins such as polyethylene, polypropylene, polybutene and polypentene, polyethylene terephthalate, Polyester such as polybutylene terephthalate, polyethylene naphthalate, nylon-
Polyamide such as 6 or nylon 6,6, polythioether such as polyphenylene sulfide, polycarbonate, polyarylate, polysulfone, polyetheretherketone, polyethersulfone, polyimide, vinyl halide polymer such as Teflon, polymethylmethacrylate, etc. Examples of the acrylic polymer, polyvinyl alcohol, etc. other than the above compatible resins include cross-linking resins containing the above compatible resins. These resins are
Since it is incompatible with the styrene-based polymer having a syndiotactic structure used in the present invention, when contained in a small amount, it can be dispersed like islands in the styrene-based polymer having a syndiotactic structure, and after stretching. It is effective for giving moderate gloss and improving the surface slipperiness. The content ratio of these incompatible resin components is 2 to 50% by weight for the purpose of gloss, and 0 for the purpose of controlling the surface property.
001-5 weight% is preferable. Further, when the temperature used as a product is high, it is preferable to use an incompatible resin having relatively high heat resistance.

As the antioxidant, a phosphorus-based antioxidant, a phenol-based antioxidant and a sulfur-based antioxidant can be used. By using such an antioxidant,
A polystyrene resin composition having good heat stability can be obtained.
Here, various types of phosphorus-based antioxidants may be used, and they may be monophosphite, diphosphite, or the like. As monophosphite, tris (2,4-
Di-t-butylphenyl) phosphite; tris (mono- and di-nonylphenyl) phosphite and the like. The diphosphite has the general formula

[0012]

Embedded image

[In the formula, R ¹ and R ² may be the same or different and each is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms or 6 to 2 carbon atoms.
The aryl group of 0 is shown. ] A phosphite represented by the following formula is used, and specific examples thereof include distearyl pentaerythritol diphosphite; dioctyl pentaerythritol diphosphite; diphenyl pentaerythritol diphosphite; bis (2,4-di-t-butylphenyl) Pentaerythritol diphosphite; bis (2
6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite; dicyclohexyl pentaerythritol diphosphite; tris (2,4-di-t
-Butylphenyl) phosphite; tetrakis (2,4
-Di-t-butylphenyl) -4,4'-biphenylene phosphonite and the like. Among these, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite; bis (2,6-di-t-butyl-
4-methylphenyl) pentaerythritol diphosphite; tris (2,4-di-t-butylphenyl) phosphite; tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphonite Is preferably used.

Various kinds of phenolic antioxidants can be used, and specifically, dialkylphenol, trialkylphenol, diphenylmonoalkoxyphenol, tetraalkylphenol and the like are used. As dialkylphenol,
2,2'-methylenebis (6-t-butyl-4-methylphenol); 1,1-bis (5-t-butyl-4-hydroxy-2-methylphenyl) butane; 2,2'-methylenebis (4 -Methyl-6-cyclohexylphenol); 4,4'-thiobis (6-t-butyl-3-methylphenol); 2,2-bis (5-t-butyl-4-)
Hydroxy-2-methylphenyl) -4-n-dodecylmercapto-butane and the like can be mentioned. Examples of the trialkylphenol include 2,6-di-t-butyl-4-methylphenol; 2,2'-methylenebis (6-t-butyl-4-ethylphenol); 2,2'-methylenebis [4-methyl- 6- (α-methylcyclohexyl) phenol]; 2,2′-methylenebis (4-methyl-6-
Nonylphenol); 1,1,3-tris- (5-t-
Butyl-4-hydroxy-2-methylphenyl) butane; ethylene glycol-bis [3,3-bis (3-t
-Butyl-4-hydroxyphenyl) butyrate]; 1
-1-bis (3,5-dimethyl-2-hydroxyphenyl) -3- (n-dodecylthio) -butane; 1,3,5
-Tris (3,5-di-t-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene; 2,2-
Bis (3,5-di-t-butyl-4-hydroxybenzyl) malonic acid dioctadecyl ester; n-octadecyl-3- (4-hydroxy-3,5-di-t-butylphenyl) propionate; tetrakis [methylene (3,
5-di-t-butyl-4-hydroxyhydrocinnamate)] methane; 3,9-bis [1,1-dimethyl-2
-(Β- (3-t-Butyl-4-hydroxy-5-methylphenyl) propionyloxy) ethyl-2,4
8,10-Tetraoxaspiro [5,5] undecane;
Tris- (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate and the like can be mentioned. Examples of diphenylmonoalkoxyphenol include 2,6-diphenyl-4-methoxyphenol, and examples of tetraalkylphenol include tris- (4-t-butyl-2,6-di-methyl-3-hydroxybenzyl)-. Isocyanurate and the like can be mentioned.

Further, the sulfur type antioxidant is preferably a thioether type one, specifically, dilauryl-3,
3'-thiodipropionate; dimyristyl-3,3 '
-Thiodipropionate; distearyl-3,3'-thiodipropionate; pentaerythritol-tetrakis- (β-lauryl-thiopropionate); bis [2
-Methyl-4- (3-n-alkylthiopropionyloxy) -5-t-butylphenyl] sulfide; 2-mercaptobayzoimidazole and the like. Among these, especially pentaerythritol-tetrakis- (β-
Lauryl-thiopropionate) is preferred.

In the stretched polystyrene-based film of the present invention, if necessary, it has a --NH-- group and has a pH of 10,0.
Contains organic compounds having a molecular weight of less than 00. As such an organic compound, a compound in which an electron-withdrawing group is adjacent to an -NH- group is preferable, and examples of such an electron-withdrawing group include a benzene ring, a naphthalene ring, an anthracene ring, a pyridine ring, a triazine ring and an indenyl ring. And an aromatic ring or carbonyl structure such as a derivative thereof. The organic compound has a thermal decomposition temperature of 26
Those of 0 ° C. or higher are particularly preferable. Specifically, the following compounds, for example, 2,4-bis- (n-octylthio) -6
-(4-Hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-
Hydrocinnamide), N, N'-bis [3- (3,5-
Di-t-butyl-hydroxyphenyl) propionyl]
Hydrazine, 3- (N-salicyloyl) amino-1,
2,4-triazole, decamethylenedicarboxylic acid disalicyloyl hydrazide, isophthalic acid (2-phenoxypropionyl hydrazide), 2,2-oxazamide-bis [ethyl-3- (3,5-di-t-butyl-4] -Hydroxyphenyl) propionate], oxalyl-bis (benzylidene-hydrazide), N-formyl-N'-
Salicyloylhydrazine, 2-mercaptobenzimidazole, N, N'-di-2-naphthyl-p-phenylenediamine, 4,4'-bis (α, α-dimethylbenzyl) diphenylamine, 2-mercaptomethylbenzimidazole, Styrenated diphenylamine, octylated diphenylamine, N-phenyl-1-naphthylamine, poly (2,2,4-trimethyl-1,2-dihydroquinoline), 6-ethoxy-1,2-dihydro-2,
2,4-trimethylquinoline, N, N'-diphenyl-
p-phenylenediamine, N-phenyl-N '-(1,
3-dimethylbutyl) -p-phenylenediamine, N-
Phenyl-N '-(3-methacryloxy-2-hydroxypropyl) -p-phenylenediamine, thiodiphenylamine, p-aminodiphenylamine, N-salicyloyl-N'-aldehyde hydrazine, N-salicyloyl-N'-acetylhydrazine, N, N'-diphenyl-oxamide, N, N'-di (2-hydroxyphenyl) oxamide, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, N-phenyl-N'-
Isopropyl-p-phenylenediamine and the like can be mentioned. The above-mentioned organic compound having a -NH- group and having a molecular weight of less than 10,000 is optionally contained in the polystyrene stretched film of the present invention in an amount of less than 30% by weight.

The stretched polystyrene film according to the present invention is a stretched film made of a styrene resin composition containing 70 to 100% by weight of a styrene polymer having a high syndiotactic structure, and having at least one surface thereof. With a diameter of 0.2 to 5.0 μm comprising the styrene polymer
m, preferably 0.2 to 4.0 μm in diameter. A stretched film having no protrusions is not preferable because it causes surface scratches on the film and also causes defective insulation breakdown.
Further, if the protrusions are smaller than 0.2 μm, the slipperiness is insufficient, and if the protrusions are larger than 5.0 μm, they may break during stretching, which is not preferable. In addition, the polystyrene-based stretched film according to the present invention has 1000 protrusions.
In 0 μm ² , preferably 10 or more, more preferably 5
It is 0 or more, and the dynamic friction coefficient is preferably 0.7 or less, more preferably 0.6 or less. The protrusion is 10,000μ
When it is less than 10 in m ² , the slipperiness is insufficient, which is not preferable. Even when the coefficient of dynamic friction is more than 0.7, the slidability is insufficient, which is not preferable. Further, if the polystyrene-based stretched film of the present invention does not have the above physical properties, the suitability for secondary processing such as vapor deposition and lamination becomes insufficient, film surface scratches occur, or dielectric breakdown becomes insufficient, which is not preferable. . The above physical properties of the stretched film can be measured, for example, by the following evaluations. That is, the presence or absence of surface scratches and the protrusions are observed on the surface of the stretched film with a scanning electron microscope or the like. The material of the portion corresponding to the protrusion on the film surface can be confirmed by measuring the melting point of the protrusion by observing the polarized portion while raising the temperature with a polarization microscope equipped with a heating device. The polystyrene stretched film according to the present invention having such physical properties has excellent properties such as excellent slidability, reduced surface scratches, and no reduction in dielectric breakdown voltage.

Next, the method for producing the polystyrene stretched film of the present invention will be described. The polystyrene-based stretched film according to the present invention can be produced by various methods, but in order to obtain a stretched film having excellent slidability and suitable for secondary processing, etc. Is preferred. The styrenic resin composition used in the present invention can be produced by an arbitrary method, that is, various methods used for conventional thermoplastic resins, for example, (A)
A method in which the styrene polymer component and the component (B) other than the styrene polymer are mixed and melt-kneaded by an extruder or the like;
Method of adding component (B) at any stage of component extrusion process, method of adding component (B) at any stage of manufacturing process of component (A), component (A) and component (B) A method of melt-kneading the material mixed with the component (A) and the like can be applied. When the stretched film of the present invention is produced using such a styrene resin composition, the method is not particularly limited, but for example, by heating these materials after melting and / or heating after cooling. It can be manufactured by molding a preformed body, followed by biaxial stretching and heat treatment.

The operation from the heating and melting to the heat setting will be described below with reference to a specific example. First, the styrene polymer obtained as described above is used as a molding material, and this is usually extruded to obtain a preform. In this molding, it is common to mold the heat-melted molding material into a predetermined shape with an extruder, but do not heat the molding material and mold it in a softened state. Good. The extruder used here may be either a single-screw extruder or a twin-screw extruder, and may or may not have a vent. It should be noted that if an appropriate filter is used for the extruder, it is possible to remove impurities and foreign substances. Further, the shape of the filter can be appropriately selected and used such as a flat plate shape or a cylindrical shape. The extrusion conditions here are not particularly limited and may be appropriately selected according to various situations.
Preferably, the temperature is 50 ° C from the melting point of the molding material to the decomposition temperature.
Select in the high temperature range and set the shear stress to 5 × 10 ⁶ dyne /
and cm ² or less. The die used may be a T-die, an annular die or the like.

In order to obtain the film having the surface state of the present invention, it is preferable to generate spherulites in the preform for stretching, and various spherulites may be appropriately selected depending on the crystallization rate of the material, the thickness of the preform, and the cooling method. You can select the method. For example,
Examples include a method in which the molten styrene-based resin composition is cooled and then heated to generate spherulites, and a method in which the molten styrene-based resin composition is cooled to generate spherulites. When the molten styrenic resin composition is cooled and solidified, the temperature is usually in the range of 0 ° C to 30 ° C higher than the glass transition temperature of the material, preferably 70 ° C lower than the glass transition temperature to glass transition temperature. Is. The temperature for heating after cooling can be appropriately selected in the range of 120 ° C to 250 ° C, but is preferably in the range of 130 ° C to 240 ° C. In the method of producing spherulites in the cooling process,
It is possible to form spherulites only in the vicinity of the anti-quenched surface by quenching only one surface, and it is also possible to obtain a film having protrusions on one surface after stretching and the other surface being smooth. As the cooling and heating medium, a temperature-controlled gas, liquid, metal / ceramic roll, or the like can be used. When a metal roll is used, it is possible to control the heat transfer efficiency by using electrostatic pinning, an air knife, an air chamber, a touch roll, and the like, and prevent uneven thickness and waviness. The average crystallinity of the preform for stretching obtained here is preferably 25% or less,
Further, it is preferable that the presence of spherulites can be confirmed with a high-magnification polarizing microscope. Here, if the average crystallinity exceeds 25%, it is difficult to obtain a film having a surface state of the present invention, or breaking during stretching. If the preform for stretching has no spherulites, projections may not be formed by spherulites on the surface of the film after stretching.

In the case of biaxial stretching, the cooled and solidified preforming sheet for stretching may be simultaneously stretched in the machine direction and the transverse direction, but may be sequentially stretched in any order. The stretching may be performed in one stage or in multiple stages. The draw ratio is 2 times or more, preferably 3 times or more in terms of area ratio. When the stretching ratio is within this range, a stretched film having favorable physical properties can be obtained. As the stretching method, various methods such as a tenter method, a method of stretching between rolls, a method of bubbling utilizing gas pressure, and a method of rolling can be used, and if these are appropriately selected or combined and applied. Good. The stretching temperature is typically may be set between the glass transition temperature (Tg) and cold crystallization temperature of the preform (T _CC). When the stretching temperature exceeds the cold crystallization temperature, it becomes difficult to obtain a stretched film having a good surface condition. The stretching rate is usually 1 × 10 to 1 × 10 ⁵ % / min, preferably 1 × 10 ³ to 1 × 10 ⁵ % / min. When the stretched film obtained by stretching under the above-mentioned conditions is required to have dimensional stability at high temperature, heat resistance, and strength balance in the plane of the film, it is preferable to further perform heat setting. The heat setting can be carried out by a commonly used method, but the stretched film is subjected to a tensioned state, a relaxed state or a restricted shrinking state, from the glass transition temperature to the melting point of the film, preferably 100 ° C. lower than the melting point. It may be carried out by maintaining the temperature in the temperature range from the temperature to immediately before the melting point for 0.5 to 120 seconds. The heat setting can be performed twice or more by changing the conditions within the above range. Also,
This heat setting may be performed in an atmosphere of an inert gas such as argon gas or nitrogen gas. According to such a manufacturing method, it is possible to efficiently and reliably manufacture the stretched polystyrene film according to the present invention, which has excellent slipperiness and the like and is suitable for secondary processing and the like.

[0023]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Reference Example 1 17 g of copper sulfate pentahydrate (Cu SO ₄ .5H ₂ O) was placed in a glass container having an inner volume of 500 ml replaced with argon.
(71 mmol), 200 ml of toluene and 24 ml (250 mmol) of trimethylaluminum were added, and the mixture was reacted at 40 ° C. for 8 hours. Then, the solid portion was removed to obtain 6.7 g of a contact product. The molecular weight of this product was 610 as measured by the freezing point depression method.

Production Example 1 Production of Styrenic Polymer Having Syndiotactic Structure In a reaction vessel having an internal volume of 2 liters, the contact product obtained in Reference Example 1 above was 7.5 mmol as an aluminum atom,
Triisobutylaluminum 7.5 mmol, pentamethylcyclopentadienyl titanium trimethoxide
0.038 mmol and 1 liter of purified styrene were taken and a polymerization reaction was carried out at 90 ° C. for 5 hours. After completion of the reaction, after decomposing the catalyst component with a methanol solution of sodium hydroxide,
The product was washed repeatedly with methanol and dried to give a polymer.
466g was obtained. The weight average molecular weight of the obtained polymer was 1,
When measured by gel permeation chromatography at 130 ° C. using 2,4-trichlorobenzene as a solvent, it was 290000, and the weight average molecular weight / number average molecular weight was 2.72. Further melting point and ¹³ C-NMR
It was confirmed that the obtained polymer was polystyrene having a syndiotactic structure.

Example 1 A styrene-based polymer having a syndiotactic structure obtained as in Production Example 1 was melt extruded at 300 ° C., and then pelletized. The pellets thus obtained were melt-extruded by an extruder equipped with a melting filter having a filtration accuracy of 5 μm and brought into close contact with a cooling roll at 50 ° C. by the electrostatic pinning method to be rapidly cooled to a thickness of 1
A 00 μm amorphous preformed sheet was prepared. This amorphous preformed sheet was heat-treated at 170 ° C. for 30 seconds to obtain a preformed sheet for stretching. The presence or absence of crystals of these sheets before and after heating was observed with a 400 × polarizing microscope. As a result of the observation, crystals were present in the preformed sheet for stretching after heating, and the crystallinity measured by a differential scanning calorimeter (DSC) was 20%. This heat-treated stretched preformed sheet is continuously and longitudinally tripled at 110 ° C.,
Stretched in the transverse direction 3 times at 125 ℃, 240 ℃
Was heat treated to obtain a stretched film having a thickness of about 7 μm.
In order to judge the appropriateness of secondary processing of the obtained stretched film, a rubber roll was attached immediately before winding, and a load of 5 was applied.
It was wound up at kgf and the generation of white powder was observed. The surface of the obtained stretched film was observed with a scanning electron microscope for the presence of surface scratches and projections. In addition, the dynamic friction coefficient is determined by the ASTM D-1984 method,
The dielectric breakdown voltage was measured according to JIS C-2318 method. The results are shown in Table 1. Moreover, the surface photograph of the stretched film by a scanning electron microscope is shown in FIG. The obtained film was observed under polarized light with a polarizing microscope with a heating device while raising the temperature, and it was melted at around 270 ° C., which is the melting point of SPS.

Example 2 Similar to Example 1 except that an amorphous preformed sheet having a thickness of 40 μm was prepared and heat-treated at 160 ° C. for 30 seconds to obtain a stretched preformed sheet. To obtain a stretched film. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1. A surface photograph of the stretched film by a scanning electron microscope is shown in FIG.

Example 3 The same as Example 1 except that an amorphous preformed sheet having a thickness of 300 μm was prepared and heat-treated at 180 ° C. for 20 seconds to obtain a preformed sheet for stretching. To obtain a stretched film. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1. Moreover, the surface photograph of the stretched film by a scanning electron microscope is shown in FIG.

Comparative Example 1 A stretched film was obtained in the same manner as in Example 1 except that the amorphous preformed sheet was stretched and heat-treated after stretching without heat treatment. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1. Also,
Figure 4 shows a photograph of the surface of the stretched film with a scanning electron microscope.
Shown in

Comparative Example 2 Stretching was carried out in the same manner as in Comparative Example 1 except that 0.15% by weight of spherical silica having a diameter of 0.8 μm was added to the styrene polymer obtained in Production Example. I got a film. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1.

[0029]

[Table 1]

[0030]

Industrial Applicability As described in detail above, the stretched polystyrene film according to the present invention is excellent in slipperiness, reduces surface scratches, and does not lower the dielectric breakdown voltage. In order to make it possible, the anti-blocking agent has excellent properties such as no addition or a small addition amount. Such a stretched polystyrene film of the present invention can be suitably used as a capacitor, an FPC film for electrical insulation, a film for photography, a film for plate making, an optical film such as OHP, a film for packaging, etc., and has industrial utility value. Is extremely large.

[Brief description of drawings]

FIG. 1 is a surface photograph (1000 times) of a stretched film obtained in Example 1 by a scanning electron microscope.

FIG. 2 is a scanning electron micrograph (1000 ×) of the obtained stretched film in Example 2.

FIG. 3 is a scanning electron microscope surface photograph (1000 ×) of the obtained stretched film in Example 3.

FIG. 4 is a scanning electron microscope surface photograph (1000 ×) of the obtained stretched film in Comparative Example 1.

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Claims (4)

[Claims] 1. A stretched film comprising a styrene resin composition containing 70 to 100% by weight of a styrene polymer having a high syndiotactic structure, the stretch film comprising at least one surface of the styrene polymer. Diameter 0.2
A polystyrene-based stretched film having protrusions of up to 5.0 μm. 2. The polystyrene stretched film according to claim 1, wherein the number of the protrusions is 10 or more in 10000 μm ² . 3. The stretched polystyrene film according to claim 1, which has a dynamic friction coefficient of 0.7 or less. 4. A preform comprising a styrene-based resin composition containing 70 to 100% by weight of a styrene-based polymer having a high syndiotactic structure, having an average crystallinity of 25% or less and having spherulites. Is biaxially stretched and heat-treated, a method for producing a polystyrene-based stretched film.