JP2016011344A - Stretch film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretch film excellent in particle dispersibility, excellent in handleability such as winding property, scraping resistance and dielectric breakdown property, especially suitable for a film capacitor.SOLUTION: There is provided a stretch film consisting of a resin composition containing a polystyrene resin having a syndiotactic structure and a porous silica particle having an average particle diameter A of 0.5 to 5 μm and DBA value of 200 millimolar/kg or less with the content of the porous silica particle of 0.01 to 3 mass% based on the mass of the resin composition.

Description

  The present invention relates to a stretched film comprising a resin composition with improved dispersibility of porous silica particles. More specifically, handling properties such as winding property, abrasion resistance, and dielectric breakdown characteristics made of a resin composition with improved dispersibility of porous silica particles in a polystyrene resin having a syndiotactic structure have been improved. In particular, the present invention relates to a stretched film suitable for a film capacitor and a resin composition used therefor.

  Conventionally, a film capacitor is manufactured by a method in which a film such as a biaxially oriented polyethylene terephthalate film or a biaxially oriented polypropylene film and a metal thin film such as an aluminum foil are overlapped and wound or laminated. In recent years, with the demand for miniaturization of electric or electronic circuits, film capacitors have also been miniaturized and mounted, and further heat resistance has been demanded in addition to electrical characteristics. In automotive applications, the range of use extends not only in the cab, but also in the engine room. In addition to electrical characteristics, film capacitors that are suitable for environments with higher temperatures and higher humidity are required. Yes.

  In response to this requirement, Japanese Patent Application Laid-Open No. 2000-173855 uses a polyethylene-2,6-naphthalenedicarboxylate film having better heat resistance than a polyethylene terephthalate film or polypropylene film, its crystal state, intrinsic viscosity, etc. There has been proposed a method for improving electric characteristics by controlling the above. However, since polyethylene-2,6-naphthalenedicarboxylate is a polar polymer, there is a limit to the improvement of electrical characteristics.

  On the other hand, Japanese Patent Application Laid-Open Nos. Hei 2-143851, Hei 3-124750, and Hei 5-200858 propose a method using a syndiotactic polystyrene film excellent in heat resistance and electrical characteristics. . However, since it is difficult to form a film as compared with a conventionally used polyester film and the film is easily torn, an improvement in handling at the time of producing a capacitor is also demanded. As a method for improving the film forming property and handling property, JP 2009-1664 A and JP 2009-62456 A propose a method of blending a powder filler. However, since voids are likely to occur between the syndiotactic polystyrene resin and the powder filler during film formation, it is necessary to achieve both handleability such as winding of the resulting film, and dielectric breakdown characteristics and abrasion resistance. Was difficult.

JP 2000-173855 A Japanese Patent Laid-Open No. 2-143851 Japanese Patent Laid-Open No. 3-124750 Japanese Patent Laid-Open No. 5-200858 JP 2009-1664 A JP 2009-62456 A

  The present invention has been made in view of the background art described above, and its purpose is excellent in particle dispersibility in a polystyrene resin having a syndiotactic structure, handling properties such as winding property, abrasion resistance, and dielectric breakdown. Stretched film excellent in characteristics (breakdown voltage, variation thereof), and particularly suitable for use as a film capacitor, and a resin used for diluting with a base resin or the like as needed to form the stretched film It is to provide a composition.

  As a result of intensive studies to achieve the above object, the present inventors have found that a resin composition in which porous silica particles having specific surface characteristics are blended in a polystyrene resin having a syndiotactic structure is obtained by dispersing the particles. Stretched film that has excellent properties, has small voids when diluted with a base resin as required, and is formed into a stretched film, and has good handling, dielectric breakdown characteristics, and abrasion resistance for film capacitors. The present invention has been found.

Thus, according to the present invention,
“1. A stretched film comprising a resin composition comprising a polystyrene-based resin having a syndiotactic structure and porous silica particles having an average particle diameter A of 0.5 to 5 μm and a DBA value of 200 mmol / kg or less. A stretched film in which the content of the porous silica particles is 0.01 to 3% by mass based on the amount of the resin composition material.
2. 2. The stretched film according to 1 above, wherein the resin composition further contains a thermoplastic amorphous resin.
3. 3. The stretched film as described in 2 above, wherein the thermoplastic amorphous resin is polyphenylene ether.
4). 4. The stretched film according to 2 or 3 above, which contains 5 to 48% by mass of a thermoplastic amorphous resin based on the mass of the resin composition.
5). 5. The stretched film according to any one of 1 to 4 above, wherein the refractive index in the thickness direction is 1.575 to 1.635.
6). 6. The stretched film according to any one of 1 to 5 above, containing 0.1 to 5% by mass of an antioxidant based on the mass of the resin composition.
7). 7. The stretched film according to 6 above, wherein the antioxidant has a thermal decomposition temperature of 250 ° C. or higher.
8). The stretched film according to any one of 1 to 7 above, wherein the compression rate of the porous silica particles is 20 to 90%.
9. Furthermore, the stretched film in any one of said 1-8 which contains 0.01-3 mass% of particle | grains whose average particle diameter A is 0.01 micrometer or more and less than 0.5 micrometer on the basis of film mass.
10. 20. The stretched film according to any one of 1 to 19, wherein the number of coarse particles having a maximum length of 25 μm or more contained in the film is 10 / m ² or less.
11. The stretched film according to any one of 1 to 10 above, wherein a void ratio represented by the following formula (1) of voids generated around the porous silica particles contained in the film is 50% or less.
(1) Void ratio = ((void diameter around particle−particle diameter) / void diameter around particle) × 100
12 A resin composition comprising a resin material containing a syndiotactic polystyrene resin mixed with porous silica particles having an average particle size B of 0.5 to 5 μm and a DBA value of 200 mmol / kg or less. The resin composition whose content of this porous silica particle is 0.01-10 mass% on the basis of the mass of a resin composition.
13. 13. The resin composition as described in 12 above, wherein the resin composition further contains a thermoplastic amorphous resin.
14 14. The resin composition as described in 12 or 13 above, wherein the compression rate of the porous silica particles is 20 to 90%. "
Is provided.

  Since the stretched film of the present invention contains a specific amount of porous silica particles having a specific particle size and a specific surface property in a polystyrene resin having a syndiotactic structure excellent in heat resistance and electrical properties, The dispersibility is extremely good, and the void generated due to the particles is small, and the handleability, dielectric breakdown characteristics, and abrasion resistance are excellent, and it is particularly suitable for a film capacitor.

<Stretched film>
The stretched film of the present invention is a resin composition comprising a syndiotactic polystyrene resin (hereinafter sometimes referred to as SPS) and porous silica particles having an average particle diameter A of 0.5 to 5.0 μm. Consists of.

The syndiotactic polystyrene resin used here has a three-dimensional structure in which phenyl groups and substituted phenyl groups, which are side chains, are alternately positioned in opposite directions with respect to the main chain formed from carbon-carbon bonds. It is. In general, tacticity is quantified by nuclear magnetic resonance ( ¹³ C-NMR) with isotope carbon, and the abundance ratio of a plurality of consecutive constitutional units, for example, dyad in the case of two, triad in the case of three, In the case of five, it can be indicated by a pentad or the like. In the present invention, the polystyrene-based resin having a syndiotactic structure is polystyrene, poly (alkyl) having a syndiotacticity of 75% or more, preferably 85% or more, or 30% or more, preferably 50% or more, of pentad. Styrene), poly (halogenated styrene), poly (alkoxystyrene), poly (vinyl benzoate), polymers in which a part of these benzene rings are hydrogenated, mixtures thereof, or structural units thereof. The copolymer containing is designated. Here, poly (alkyl styrene) includes poly (methyl styrene), poly (ethyl styrene), poly (propyl styrene), poly (butyl styrene), poly (phenyl styrene), and the like. ) Include poly (chlorostyrene), poly (bromostyrene), poly (fluorostyrene) and the like. Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene). Among these, preferable polystyrene resins include polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), poly (p-tertiarybutylstyrene), poly (p-chlorostyrene), and poly (m- Chlorostyrene), poly (p-fluorostyrene), and a copolymer of styrene and p-methylstyrene. Among them, polystyrene is preferable.

  Further, in the case where the polystyrene resin in the present invention is used as a copolymer containing a copolymer component, as its comonomer, in addition to the above-mentioned polystyrene resin monomer, ethylene, propylene, butene, hexene, octene. Olefin monomers such as diene monomers such as butadiene and isoprene, cyclic diene monomers, polar vinyl monomers such as methyl methacrylate, maleic anhydride, and acrylonitrile.

The weight-average molecular weight of the syndiotactic polystyrene resin is preferably 1.0 × 10 ^{4 to} 3.0 × 10 ⁶ , and more preferably 5.0 × 10 ^{4 to} 1.5 × 10 6. ⁶ and particularly preferably 1.1 × 10 ^{5 to} 8.0 × 10 ⁵ . By setting the weight average molecular weight to 1.0 × 10 ⁴ or more, preferably 5.0 × 10 ⁴ or more, and particularly preferably 1.1 × 10 ⁵ or more, the strength and elongation characteristics are excellent and the heat resistance is further improved. A molded product such as a film can be obtained. Further, when the weight average molecular weight is 3.0 × 10 ⁶ or less, preferably 1.5 × 10 ⁶ or less, particularly preferably 8.0 × 10 ⁵ or less, the stretching tension is in a suitable range, and at the time of film formation, etc. Breakage and the like are less likely to occur.

  The porous silica particles contained in the stretched film of the present invention must have an average particle size A of 0.5 to 5 μm, preferably 0.8 to 2.5 μm. When this average particle diameter is less than 0.5 μm, the slipping property of the film is insufficient, and the winding property and handling property become insufficient. On the other hand, when it exceeds 5 μm, the diameter of voids formed around the particles by stretching or the like becomes large, which is not preferable. The content of the particles is 0.01 to 3% by mass, more preferably 0.02 to 1% by mass, particularly preferably 0.05 to 0.5% by mass based on the amount of the resin composition substance. There is a need to. If this content is less than the lower limit, the slipping property is insufficient and the winding property becomes poor. On the other hand, if the upper limit is exceeded, the abrasion resistance becomes insufficient, and the dielectric breakdown characteristics and film-forming stretchability are impaired.

  The porous silica particles used in the present invention are required to have a DBA value (di-n-butylamine adsorption amount) of 200 mmol / kg or less, preferably 100 mmol / kg or less. When the DBA value exceeds 200 mmol / kg, not only the dispersion of the porous silica particles in the resin composition is deteriorated, but also voids are easily generated between the resin and the particles when formed into a stretched film. This is not preferable. The DBA value here is the amount of di-n-butylamine adsorbed when the porous silica particles are treated with a toluene solution of di-n-butylamine (the amount of adsorbed di-n-butylamine per milligram of particles (mmol)). It is.

  The production method of the porous silica particles is not particularly limited, and the surface of the porous silica particles produced by a conventionally known method such as a sol-gel method or a precipitation method is treated with, for example, an alkylalkoxysilane compound or a silazane compound. Thus, it can be easily obtained by modifying the silanol group on the particle surface. When there are many silanol groups on the particle surface, the affinity with the polystyrene-based resin having a syndiotactic structure is lowered and the dispersibility of the particles in the resin composition is lowered. Not only does voids easily occur between the resin and the particles, but the activity of the particle surface is increased, and adverse effects such as re-aggregation of particles tend to occur when blended in the resin material.

  The porous silica particles used in the present invention further have a compressibility (at 0.2 gf load: measured with a micro compression test MCTM-200 manufactured by Shimadzu Corporation) in the range of 20 to 90%, particularly 50 to 85%. Is preferred. When the compression ratio is in this range, it is considered that the diameter of voids formed around the particles is reduced by moderately deforming the particles due to stress during processing into a stretched film or the like.

  The porous silica particles are preferably aggregated particles obtained by agglomerating primary particles, and more preferably, the primary particle diameter is 0.01 to 0.1 μm and the pore volume is 0.5 to 2. It is preferably in the range of 0 ml / g, and the average pore diameter is preferably in the range of 5 to 25 nm. By satisfying such requirements, it is considered that the diameter of voids formed around the particles is reduced by moderately deforming the particles due to stress during processing into a stretched film or the like.

  The stretched film of the present invention described above contains particles having an average particle size A of 0.01 μm or more and less than 0.5 μm (hereinafter sometimes referred to as inactive particles) in addition to the porous silica particles described above. It is preferable to do. By containing such inert particles, the slipperiness of the film can be improved while maintaining a high dielectric breakdown voltage, and a stretched film having excellent winding properties can be obtained. When the average particle diameter A of the inert particles is too small, the effect of improving the slipping property tends to be lowered, and the effect of improving the winding property is also lowered. On the other hand, if it is too large, the height of the low protrusions on the film surface becomes too high, thereby making the slipping property too high, and the winding property such as end face misalignment during winding is reduced. In addition, voids in the film tend to increase, resulting in low abrasion resistance and dielectric breakdown voltage. From such a viewpoint, the average particle diameter A of the inert particles is preferably 0.05 μm or more and less than 0.5 μm, more preferably 0.1 μm or more and less than 0.5 μm, particularly preferably 0.2 to 0.4 μm. is there. The average particle diameter of the inert particles is preferably smaller than the average particle diameter A of the porous silica particles, and the difference is preferably 0.2 μm or more.

  Such inert particles are preferably spherical particles having a particle size ratio (major axis / minor axis) of 1.0 to 1.3. The particle size ratio is more preferably 1.0 to 1.2, and particularly preferably 1.0 to 1.1. When the particle size ratio is in the above numerical range, the effect of improving the winding property and the effect of improving the dielectric breakdown voltage can be further increased.

  Such inert particles may be either organic particles or inorganic particles. Examples of the organic particles include polymer resin particles such as polystyrene resin particles, silicone resin particles, acrylic resin particles, styrene-acrylic resin particles, divinylbenzene-acrylic resin particles, polyester resin particles, polyimide resin particles, and melamine resin particles. Can be mentioned. Among these, silicone resin particles and polystyrene resin particles are preferable from the viewpoint of excellent slipperiness and abrasion resistance, and spherical silicone resin particles and spherical polystyrene resin particles are particularly preferable as described above. Examples of inorganic particles include (1) silicon dioxide (including hydrates, silica sand, quartz, etc.); (2) alumina in various crystal forms; (3) silicic acid containing 30% by mass or more of SiO 2 component. Salts (eg, amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), warm asbestos, zircon, fly ash, etc.); (4) oxides of Mg, Zn, Zr, and Ti (5) sulfates of Ca and Ba; (6) phosphates of Li, Ba, and Ca (including monohydrogen and dihydrogen salts); (7) benzoates of Li, Na, and K; (8) terephthalate of Ca, Ba, Zn, and Mn; (9) titanate of Mg, Ca, Ba, Zn, Cd, Pb, Sr, Mn, Fe, Co, and Ni; Ba and Pb chromate; (11) carbon (eg potassium Carbon black, graphite, etc.); (12) glass (e.g., glass powder, glass beads, etc.); (13) Ca, and Mg carbonates; (14) fluorite; (15) spinel type oxides. Of these, calcium carbonate particles and silica particles are preferable, and silica particles are particularly preferable from the viewpoint of excellent slipperiness and abrasion resistance. Such inorganic particles are preferably spherical as described above, and spherical silica particles are particularly preferred.

Most preferable as the inert particles are spherical silicone resin particles. When spherical silicone resin particles are used as the inert particles, the heat resistance becomes particularly high due to a synergistic effect when polyphenylene ether is used in combination as a thermoplastic amorphous resin described later.
The content of the inert particles is preferably 0.01 to 3% by mass, more preferably 0.05 to 2% by mass, and further preferably 0.1 to 0.5% by mass in 100% by mass of the resin composition. Particularly preferably, it is 0.1 to 0.3% by mass or less. By containing such inert particles in the above range, the handleability of the film can be improved while maintaining a high dielectric breakdown voltage.
In addition, when melt-molding a resin composition containing no inert particles into a film, the inert particles are added as they are or as master chips so that the content of the inert particles in the resulting film is in the above range. It doesn't matter.

  The stretched film of the present invention preferably further contains a thermoplastic amorphous resin. The thermoplastic amorphous resin here is a thermoplastic amorphous resin having a Tg (glass transition temperature) determined by DSC (differential scanning calorimeter) higher than that of SPS. When such a thermoplastic amorphous resin is blended with SPS, not only the glass transition temperature as a mixture increases, but also the heat resistance improves and the dielectric breakdown voltage at high temperatures increases. Moreover, the thermal dimensional stability of the stretched film is improved, and the stretchability can also be improved. From such a viewpoint, the glass transition temperature of the thermoplastic amorphous resin is preferably 150 ° C. or higher, more preferably 180 ° C. or higher, and particularly preferably 200 ° C. or higher. The higher the glass transition temperature of the thermoplastic amorphous resin to be blended, the greater the effect of improving the above effects such as thermal dimensional stability. However, in consideration of melt extrusion and the like, the substantial upper limit is preferably 350 ° C., more preferably Is 300 ° C.

  Preferred examples of such thermoplastic amorphous resin include aromatic polyethers such as polyphenylene ether and polyetherimide, polycarbonate, polyarylate, polysulfone, polyethersulfone, and polyimide. Among these, it is easy to improve stretchability, and because it has a synergistic effect when combined with an antioxidant, not only heat resistance and dimensional stability, but also dielectric breakdown voltage is further improved. Particularly preferred. Examples of the polyphenylene ether resin used here include conventionally known resins such as poly (2,3-dimethyl-6-ethyl-1,4-phenylene ether) and poly (2-methyl-6-chloromethyl-1). , 4-phenylene ether), poly (2-methyl-6-hydroxyethyl-1,4-phenylene ether), poly (2-methyl-6-n-butyl-1,4-phenylene ether), poly (2-ethyl-6-isopropyl-1,4-phenylene ether), poly (2-ethyl-6-n-propyl-1,4-phenylene ether), poly (2,3,6-trimethyl-1) , 4-phenylene ether), poly (2- (4′-methylphenyl) -1,4-phenylene ether), poly (2-bromo-6-phenyl-1,4-phenylene ether), poly 2-methyl-6-phenyl-1,4-phenylene ether), poly (2-phenyl-1,4-phenylene ether), poly (2-chloro-1,4-phenylene ether), poly (2 -Methyl-1,4-phenylene ether), poly (2-chloro-6-ethyl-1,4-phenylene ether), poly (2-chloro-6-bromo-1,4-phenylene ether), Poly (2,6-di-n-propyl-1,4-phenylene ether), poly (2-methyl-6-isopropyl-1,4-phenylene ether), poly (2-chloro-6-methyl-) 1,4-phenylene ether), poly (2-methyl-6-ethyl-1,4-phenylene ether), poly (2,6-dibromo-1,4-phenylene ether), poly (2,6 -Dichloro-1,4-phenyle Ethers), poly (2,6-diethyl-1,4-phenylene ether), poly (2,6-dimethyl-1,4-phenylene ether) and the like, and copolymers thereof Can be mentioned. Further, those modified with a modifying agent such as maleic anhydride or fumaric acid are also preferably used. Furthermore, a copolymer obtained by graft copolymerization or block copolymerization of a vinyl aromatic compound such as styrene with the polyphenylene ether is also used. Of these, poly (2,6-dimethyl-1,4-phenylene ether) is particularly preferred.

  The intrinsic viscosity (measured in chloroform at 30 ° C.) of the polyphenylene ether resin is preferably in the range of 0.2 to 0.8 dl / g, more preferably in the range of 0.3 to 0.6 dl / g. When the intrinsic viscosity is less than 0.2 dl / g, the mechanical strength of the resulting resin composition may be lowered. On the other hand, when it exceeds 0.8 dl / g, the fluidity of the resulting resin composition is lowered, and the processing at the time of melt molding into a film or the like tends to be difficult. Two or more types of polyphenylene ether resins may be used in combination, and in this case, those having different intrinsic viscosities may be mixed to obtain a desired intrinsic viscosity.

The content ratio of thermoplastic amorphous resin such as polyphenylene ether resin is preferably higher from the viewpoint of electrical characteristics for film capacitors, and is preferably a polystyrene resin. From the viewpoint of heat resistance during film formation, it is preferable that the amount of polyphenylene ether resin is large. Therefore, the content of the thermoplastic amorphous resin is preferably 48% by mass or less, more preferably in the range of 5 to 48% by mass, based on the mass of the resin composition. By containing the thermoplastic amorphous resin in an amount within the above range, a stretched film having excellent heat resistance and a high dielectric breakdown voltage, that is, an improved dielectric breakdown voltage at high temperatures can be obtained. When the content is too small, the heat resistance improving effect tends to be low, the dielectric breakdown voltage improving effect tends to be low, and the stretchability improving effect is poor. From such a viewpoint, the content of the thermoplastic amorphous resin is more preferably 8% by mass or more, further preferably 11% by mass or more, and particularly preferably 20% by mass or more. Moreover, when there is too much content, it exists in the tendency for the crystallinity of SPS to fall easily, and it exists in the tendency for the heat resistance of a film to fall. From such a viewpoint, the content of the thermoplastic amorphous resin is more preferably 45% by mass or less, further preferably 40% by mass or less, and particularly preferably 35% by mass or less.
In the stretched film of the present invention, other resins may be used in combination with the SPS and the thermoplastic amorphous resin as long as the object of the present invention is not impaired.

  The stretched film of the present invention preferably further contains an antioxidant. The antioxidant may be either a primary antioxidant that captures the generated radicals to prevent oxidation, or a secondary antioxidant that decomposes the generated peroxides to prevent oxidation. Examples of the primary antioxidant include phenol-based antioxidants and amine-based antioxidants, and examples of the secondary antioxidant include phosphorus-based antioxidants and sulfur-based antioxidants. Of these, primary antioxidants are preferred, and phenolic antioxidants are particularly preferred.

  The antioxidant preferably has a thermal decomposition temperature of 250 ° C. or higher. When the thermal decomposition temperature is high, the effect of improving the dielectric breakdown voltage at a high temperature becomes high. When the thermal decomposition temperature is too low, the antioxidant itself is thermally decomposed during melt extrusion, which tends to cause problems such as contamination of the process and yellowing of the polymer. From such a viewpoint, the thermal decomposition temperature of the antioxidant is more preferably 280 ° C. or higher, further preferably 300 ° C. or higher, and particularly preferably 320 ° C. or higher. The antioxidant in the present invention is preferably less susceptible to thermal decomposition and preferably has a higher thermal decomposition temperature, but in reality, the upper limit is about 500 ° C.

  Moreover, it is preferable that melting | fusing point of antioxidant is 90 degreeC or more. If the melting point is too low, the antioxidant melts faster than the resin material during melt extrusion, and the polymer tends to slip at the screw supply portion of the extruder. This causes problems such as unstable polymer supply. From such a viewpoint, the melting point of the antioxidant is more preferably 120 ° C. or higher, further preferably 150 ° C. or higher, and particularly preferably 200 ° C. or higher. On the other hand, when the melting point of the antioxidant is too high, the antioxidant is difficult to melt during melt extrusion, and the dispersion in the resin material tends to be poor. Thereby, problems such as the effect of adding the antioxidant appear only locally. From such a viewpoint, the melting point of the antioxidant is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, further preferably 220 ° C. or lower, and particularly preferably 170 ° C. or lower.

  A commercial item can also be used as it is as the above antioxidant. Examples of commercially available products include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1010), N, N′- Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1024), N, N′-hexane-1,6-diylbis [ 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1098) is preferred. These antioxidants may be used alone or in combination of two or more.

The content of the antioxidant is preferably 0.1 to 5% by mass based on the mass of the resin composition. By containing the antioxidant in a content within the above numerical range, the effect of improving the dielectric breakdown voltage can be increased. When the content of the antioxidant is too small, the effect of adding the antioxidant is not sufficient, and the effect of improving the dielectric breakdown voltage tends to be low. From such a viewpoint, the content of the antioxidant is more preferably 0.2% by mass or more, further preferably 0.5% by mass or more, and particularly preferably 1% by mass or more. On the other hand, when the content is too large, the antioxidant tends to aggregate in the stretched film, and the defects due to the antioxidant tend to increase. Lower. From such a viewpoint, the content of the antioxidant is more preferably 3% by mass or less, and particularly preferably 2% by mass or less.
In addition, when melt-molding a resin composition containing no antioxidant into a film, the antioxidant is added as it is or as a master chip so that the antioxidant content in the resulting film is in the above range. It doesn't matter.

  The stretched film of the present invention contains other resin components different from the thermoplastic amorphous resin, for example, in order to further improve film forming properties, mechanical properties, surface properties, etc., within a range not impairing the object of the present invention. Or additives such as antistatic agents, colorants, weathering agents and the like can be added. Further, inert particles other than the above-mentioned particles may be used in a small amount as long as the object of the present invention is not impaired.

  The stretched film of the present invention preferably has a refractive index in the thickness direction of 1.575 to 1.635. By setting the refractive index in the thickness direction within the above numerical range, the dielectric breakdown voltage can be further increased. In addition, the frequency of film breakage in the film manufacturing process is reduced, and productivity is easily improved. From such a viewpoint, the refractive index in the thickness direction is preferably 1.620 or less, more preferably 1.615 or less, and particularly preferably 1.610 or less. On the other hand, when the refractive index in the thickness direction is too low, the dielectric breakdown voltage tends to be low. Further, the frequency of film breakage in the capacitor manufacturing process increases, and the productivity of the capacitor tends to decrease. Furthermore, the thickness unevenness of the film tends to deteriorate, and it becomes difficult to obtain a capacitor with stable quality. From such a viewpoint, the refractive index in the thickness direction is more preferably 1.590 or more, further preferably 1.595 or more, and particularly preferably 1.600 or more. The refractive index in the thickness direction can be easily adjusted depending on the film forming conditions.

In the stretched film of the present invention, the number of coarse agglomerated particles having a maximum length of 25 μm or more present in the film is 10 or less per 1 m ² , further 5 / m ² or less, particularly 3 / m ² or less. preferable. When the number of coarse agglomerated particles is larger than the upper limit, uneven projections are generated on the film surface, and when the film is made into a wound film, winding deviation may be deteriorated and workability may be lowered. Moreover, it becomes a starting point of a fracture | rupture in a film forming extending | stretching process, and stretchability may become unstable.

  The stretched film of the present invention preferably has substantially no void around the porous silica particles. Here, “substantially free of voids” means that there may be no voids, voids that do not cause dropout of particles, or voids that do not decrease dielectric breakdown voltage, and will be described later. When the void ratio is measured by the method, the void ratio calculated as a ratio of (void diameter around particle−particle diameter) and void diameter around the particle is 50% or less, and particularly preferably 30% or less. means. If the void ratio exceeds 50%, particles fall off during processing, and not only process contamination but also the surface roughness changes, resulting in poor handling of the film roll. In addition, the dielectric breakdown voltage decreases and the variation tends to increase (dielectric breakdown characteristics tend to deteriorate).

  Although the thickness in particular of the stretched film of this invention is not restrict | limited, Since the effect of this invention comes out easily, so that it becomes thin, it is especially preferable that it is 0.4-6.5 micrometers. More preferably, it is 0.4-6.0 micrometers, Most preferably, it is 0.5-3.5 micrometers. By using such a film thickness, a capacitor having a high capacitance can be obtained.

The stretched film of the present invention preferably further has a dielectric breakdown voltage (BDV) at 120 ° C. of 450 V / μm or more. The fact that the breakdown voltage satisfies such a requirement means that the breakdown voltage is excellent even at a high temperature. The breakdown voltage is more preferably 500 V / μm or more, and further preferably 520 V / μm or more.
The standard deviation of the dielectric breakdown voltage is preferably 40 V / μm or less, more preferably 30 V / μm or less, and still more preferably 20 V / μm or less. If this standard deviation satisfies this requirement, it means that the local breakdown voltage drop is small (variation is small), and it increases the reliability of the material when used as an electrical insulation material such as a capacitor. Can do.

  The stretched film of the present invention preferably has a center line average surface roughness Ra of 7 to 89 nm on at least one side. When the center line average surface roughness Ra is within this range, the effect of improving the winding property can be increased. Moreover, blocking resistance improves and the external appearance of a roll can be made favorable. When the center line average surface roughness Ra is too low, the slipping property tends to be too low, and the effect of improving the winding property is lowered. On the other hand, if it is too high, the slipping property tends to be too high, and the effect of improving the winding property, such as end face misalignment at the time of winding, becomes low. From such a viewpoint, the lower limit of the centerline average surface roughness Ra is more preferably 11 nm or more, further preferably 21 nm or more, and particularly preferably 31 nm or more. The upper limit of the center line average surface roughness Ra is more preferably 79 nm or less, still more preferably 69 nm or less, and particularly preferably 59 nm or less.

  Moreover, it is preferable that the 10-point average roughness Rz of the at least single side | surface of the stretched film of this invention is 200-3000 nm. When the 10-point average roughness Rz is within this range, the effect of improving the winding property can be increased. When the 10-point average roughness Rz is too low, the air release property tends to be low when the film is wound as a roll, and the effect of improving the winding property such that the film is liable to skid is reduced. In particular, when the film thickness is thin, the film loses its elasticity, so that the air release property tends to be further lowered, and the effect of improving the winding property is further reduced. On the other hand, when the 10-point average roughness Rz is too high, the number of coarse protrusions tends to increase, and the effect of improving the dielectric breakdown voltage is reduced. From such a viewpoint, the lower limit of the 10-point average roughness Rz is more preferably 600 nm or more, further preferably 1000 nm or more, and particularly preferably 1250 nm or more. Further, the upper limit of the 10-point average roughness Rz is more preferably 2600 nm or less, further preferably 2250 nm or less, and particularly preferably 1950 nm or less.

<Film production method>
The stretched film of the present invention described above can basically be obtained by a conventionally known method or a method accumulated in the industry. Hereinafter, the production method for obtaining the stretched film of the present invention will be described in detail. The stretched film of the present invention may be a uniaxially oriented film or a biaxially oriented film, but is preferably a biaxially stretched film from the viewpoint of the balance between productivity and physical properties. Hereinafter, a biaxially stretched film will be described as an example.

  First, a predetermined amount of SPS and porous silica particles are mixed and melted with the above-described thermoplastic amorphous resin, inert particles, additives such as an oxidizing agent, and the like as necessary to prepare an unstretched sheet. . Specifically, the resin material is heated and melted at a temperature not lower than the melting point (Tm, unit: ° C.) and not higher than (Tm + 50 ° C.), extruded into a sheet, cooled and solidified to obtain an unstretched sheet. At this time, it is preferable to use a resin composition in which SPS, porous silica particles, thermoplastic amorphous resin, inert particles, an oxidizing agent, and the like are mixed in advance, and a resin composition having a large content thereof is used as a master chip. And may be diluted with a base resin during film formation. Furthermore, for example, a plurality of master chips containing, for example, porous silica particles, thermoplastic amorphous resin, inert particles, or an oxidizing agent are prepared in advance, and these master chips and base resin are formed with a predetermined content during film formation. It may be mixed and melted to form a film.

The obtained unstretched sheet is biaxially stretched. Stretching may be performed simultaneously in the machine direction (machine axis direction) and the transverse direction (direction perpendicular to the machine axis direction and the thickness direction), or may be sequentially performed in any order. For example, in the case of sequential stretching, first, it is 3.2 to 5.8 times, preferably 3 in the uniaxial direction at a temperature of (glass transition temperature of resin composition (Tg, unit: ° C) -10 ° C) to (Tg + 70 ° C). .3 to 5.4 times, more preferably 3.4 to 5.0 times, and then 3.8 to 5.9 at a temperature of Tg to (Tg + 80 ° C.) in a direction perpendicular to the uniaxial direction. The film is stretched at a magnification of 1.0, preferably 4.0 to 5.5, more preferably 4.1 to 5.1, and still more preferably 4.2 to 4.9. Furthermore, the area stretch ratio (= longitudinal stretch ratio × lateral stretch ratio) is preferably 12.0 times or more in order to obtain a film having a refractive index in the thickness direction described above. When the area stretch ratio decreases, the heat resistance tends to decrease. Therefore, the area stretch ratio is more preferably 13.0 times or more, further preferably 13.5 times or more, and particularly preferably 14.0 times or more. Further, if the area stretch ratio is too high, breakage is likely to occur during film formation and stretching. From such a viewpoint, the area stretch ratio is preferably 22 times or less, more preferably 20 times or less, still more preferably 18 times or less, and particularly preferably 17 times or less.
In the present invention, a coating layer is formed by applying a coating solution for forming a coating layer on an unstretched sheet or a uniaxially stretched film that is preferably uniaxially stretched in the longitudinal direction. May be.

  Next, heat setting is performed at a temperature of (Tg + 70 ° C.) to Tm. The heat setting temperature is 200 to 260 ° C, preferably 225 to 255 ° C, more preferably 235 to 250 ° C. When the heat setting temperature is too high, film breakage is likely to occur particularly when a film having a thin film thickness is produced, and the thickness unevenness is deteriorated. If the relaxation treatment is performed at a temperature lower by 20 ° C. to 90 ° C. than the heat setting temperature as necessary after the heat setting, the dimensional stability is improved.

<Resin composition>
The resin composition preferably used for production of the stretched film of the present invention is obtained by melting and mixing porous silica particles with the above-mentioned syndiotactic polystyrene resin.
The average particle diameter B of the porous silica particles used here is preferably 0.5 to 5 μm, particularly preferably 0.8 to 3.0 μm. When this average particle size is less than 0.5 μm, the average particle size A of the porous silica particles in the film when melt-formed into a film or the like becomes small and the slipping property is insufficient, so that the winding property and handling property are insufficient. Tends to be insufficient. On the other hand, when the thickness exceeds 5 μm, the diameter of voids formed around the particles by stretching or the like tends to increase when melt-molding into a film or the like. The content of the particles is 0.01 to 10% by mass, preferably 0.5 to 5.0% by mass based on the amount of the resin composition material. If the content is less than 0.01% by mass, the slidability of the molded product after being formed into a film or the like is insufficient, and the handleability becomes insufficient. On the other hand, when it exceeds 10% by mass, the dispersion of the particles in the resin composition is deteriorated, which is not preferable. In addition, when the resin composition is melt-molded as it is and formed into a film or the like, the content of the particles is 0.01 to 3% by mass, as described above, further 0.02 to 1% by mass, particularly 0.05. It is preferable to set it as the range of -0.5 mass%. On the other hand, when diluting with a base resin or the like to form a melt film, a resin composition having a high content, for example, 0.5 to 10% by mass, is formed into a film or the like (in the film) What is necessary is just to dilute so that content of may become said range.

  Further, the DBA value of the porous silica particles needs to be 200 mmol / kg or less, preferably 100 mmol / kg or less as described above. When the DBA value exceeds 200 mmol / kg, not only the dispersion of the porous silica particles in the resin composition is deteriorated, but also voids are easily generated between the resin and the particles when formed into a stretched film. This is not preferable.

  The compressibility of the porous silica particles is preferably in the range of 20 to 90%, particularly 50 to 85% as described above. When the compression ratio is within this range, it is considered that the diameter of the void formed around the particles is reduced by moderately deforming the particles due to the stress at the time of processing into a stretched film.

  As described above, such a resin composition preferably contains a thermoplastic amorphous resin, particularly a polyphenylene ether resin. The content ratio of the thermoplastic amorphous resin is 48 mass% or less based on the mass of the resin composition, and more preferably in the range of 5 to 48 mass% when the resin composition is melt-molded as it is to be molded into a film or the like. It is preferable that By doing so, it is possible to obtain a stretched film having excellent heat resistance and a high breakdown voltage, that is, an improved breakdown voltage at a high temperature. When the content is too small, the heat resistance improving effect tends to be low, the dielectric breakdown voltage improving effect tends to be low, and the stretchability improving effect is poor. From such a viewpoint, the content of the thermoplastic amorphous resin is more preferably 8% by mass or more, further preferably 11% by mass or more, and particularly preferably 20% by mass or more. Moreover, when there is too much content, it exists in the tendency for the crystallinity of SPS to fall easily, and it exists in the tendency for the heat resistance of a film to fall. From such a viewpoint, the content of the thermoplastic amorphous resin is more preferably 45% by mass or less, further preferably 40% by mass or less, and particularly preferably 35% by mass or less. On the other hand, the resin composition is used as a masterbatch and does not contain porous silica particles, for example, a base resin such as a syndiotactic polystyrene resin or a masterbatch containing other additives is melt-kneaded and diluted. When using, a resin composition having a high polyphenylene ether resin content, for example, a resin composition having a content of 20 to 80% by mass, is diluted so that the content in the resin composition molded into a film is within the above range. do it.

  The mixing method of the porous silica particles and the resin material is not particularly limited, and may be added at the polymerization stage of the resin material, or may be added by a method of melt-kneading the resin material obtained by polymerization. May be. For example, the particle powder and the resin material may be supplied from the same supply port of the melt kneader and melt kneaded, or the resin material is first put into a melt kneader such as a biaxial kneading extruder with a vent. Alternatively, a method of adding the particles to the portion where the resin material is melted may be used. Of these, a method is preferable in which the particles and resin pellets or resin powder are mixed in advance and then fed into a vented twin-screw kneading extruder. According to such a method, since the particles are attached to the surface of the resin pellets or resin powder, when the crushing progresses inside the kneader, the contact distance between the particles and the resin is extremely small, so that the dispersibility is high. It is estimated that it will further improve.

  As a twin screw kneading extruder with a vent, a particle addition port is provided in a full flight part of a screw arranged inside a vented twin screw kneading extruder, and a feed blade and a return blade for kneading and dispersing particles are provided. It is preferable to use a device in which at least one rotor segment having at least one rotor segment is provided downstream from the addition port in the axial direction of the screw. Here, the vent line is for removal of by-products from the resin. Further, the vented twin-screw kneading extruder preferably has 1 to 3 rotor segments. If there is no rotor segment, the kneading dispersibility of the particles will be reduced, and if the rotor segment exceeds three locations, the propulsive force of the resin will be reduced and venting will be likely to occur. Moreover, it is preferable to have a kneading disk for supplementing the kneading dispersion of the porous particles.

<Condenser>
The stretched film of the present invention described above can obtain a capacitor by, for example, laminating a metal layer on at least one side. The material of the metal layer is not particularly limited, and examples thereof include aluminum, zinc, nickel, chromium, tin, copper, and alloys thereof. Further, these metal layers may be slightly oxidized. Moreover, since a metal layer can be formed easily, it is preferable that a metal layer is a vapor deposition type metal layer formed by the vapor deposition method. In addition, when laminating the metal layer, by providing a coating layer in advance, the stretched film layer (base material layer) and the metal layer can have an appropriate adhesive force, and processing such as winding in the production of film capacitors. In the case of applying, the metal layer is not peeled off and the function as a capacitor is exhibited. Furthermore, at the same time, the coating layer and the metal layer have moderate adhesion, and even if a discharge occurs, the coating layer with a small surface energy is peeled off from the film first, and only the metal layer and the coating layer are destroyed. It is not destroyed, thereby not being short-circuited, and the effect of improving the dielectric breakdown voltage can be increased.

  Hereinafter, the present invention will be further described by examples. Each characteristic value was measured by the following method.

(1) Average particle diameter Average particle diameter A
The surface of the film was treated with a plasma reactor to expose the particles, and a gold thin film deposition layer was formed on the surface with a thickness of 200 to 300 mm by a gold sputtering apparatus. Next, using a scanning electron microscope, the image is observed at a magnification of 15,000 times, and the shape (outline) of the measurement object is set to be a binarized image with a Luzex 500 manufactured by Japan Regulator Co., Ltd. The area equivalent particle diameter (Di) was determined for each of the particles, and the number average was calculated by removing 5 particles from the maximum value and the minimum value, respectively, to obtain the average particle diameter A of the particles.
Average particle size B
Ethanol was used as a dispersion medium, and the average particle diameter B was determined on the basis of volume distribution using a laser diffraction particle size distribution analyzer SALD-2000J manufactured by Shimadzu Corporation.

(2) DBA value of porous silica particles (adsorption amount of di-n-butylamine)
A sample of 250 mg dried at 105 ° C. for 2 hours is precisely weighed, 50 ml of 1/500 N-DBA solution (petroleum benzine solvent) is added thereto, and the mixture is allowed to stand at 20 ° C. for 2 hours. To 25 ml of this supernatant, add 5 ml of chloroform and 2-3 drops of crystal violet indicator, and titrate with a 1/100 N-perchloric acid solution (acetic anhydride solvent) until the purple color turns blue. To do. Separately, it was blanked to obtain Bml, and the DBA value was calculated by the following formula.
DBA value (mmol / kg) = 80 (A−B) f
Where f is the titer of 1 / 100N-perchloric acid solution (see R. Meyer; Kautschuku. Gummi., 7 [8], 180-182 (1954))

(3) Compression rate Using a small compression test MCTM-200 manufactured by Shimadzu Corporation, load is performed under the condition of a load load rate of 0.0725 gf / sec, and the compression rate at 0.2 gf load is obtained. Five particles having the same particle size as the average particle size were selected and measured, and the average value was calculated as the particle compression ratio.

(4) Film-forming stretchable film raw materials were supplied to an extruder, and the occurrence of volatile components when melt-extruding through a die and the film-forming property in the film-drawing film-forming process were evaluated according to the following criteria.
◎: There is no coarse agglomerate at the time of polymer melt extrusion, and the film forming process can be produced without breaking. ○: Coarse agglomerate can be seen at the time of polymer melt extrusion, but it can be produced without breaking. Some things are seen and breakage sometimes occurs and stable production cannot be achieved ×: Coarse aggregates are remarkable during polymer melt extrusion, or breakage occurs frequently and cannot be produced

(5) Filter pressurization When the film raw material is converted by discharge amount (kg) / filter area (cm ² ) with H-250 (sintered (grain) type filter having an opening of 25 μm) manufactured by Japan PALL, extrusion The filter pressure difference (ΔP) increased from the initial pressure when 100 kg was filtered at a temperature of 300 ° C. and 5 kg / cm ² was evaluated and evaluated according to the following criteria.
◎: There is no pressure increase of the filter at the time of melt extrusion, and it can be stably extruded ○: Pressure increase of the filter temporarily occurs at the time of melt extrusion, but it can be stably extruded △: The pressure of the filter is moderate at the time of melt extrusion However, it cannot be stably extruded for a long time. X: The pressure of the filter suddenly increased during melt extrusion, and it could not be extruded in a short time.

(6) Content of porous silica particles, other particles, thermoplastic amorphous resin, antioxidant in the film Porous silica particles and other particles: Select a solvent that dissolves the resin but does not dissolve the particles. Then, after dissolving the sample, the particles were centrifuged from the resin, and the ratio of the particles to the sample weight (wt%) was used as the particle content. Moreover, when other particles were contained, each content rate was calculated from the content ratio of the particles.
Thermoplastic Amorphous Resin: The components of the thermoplastic amorphous resin and the amount of each component were specified by ¹ H-NMR measurement and ¹³ C-NMR measurement.
Antioxidant: The component of the antioxidant and the amount of each component were specified by ¹ H-NMR measurement and ¹³ C-NMR measurement. In the case of N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide] (registered trademark Irg1098), tert-butyl-4- The peak intensity due to hydrogen due to the hydrocarbon chain between the hydroxyphenyl and the amide bond was measured. Based on the NMR measurement results, when the stabilizer reacted with the resin, the content converted to the original stabilizer was determined. In addition, if a polymer and an unreacted stabilizer are mixed with a stabilizer that has reacted with a polymer and a plurality of peak positions are detected even when focusing on the same hydrocarbon chain, the content is calculated from the total value of them. Asked.

(7) Refractive index in the thickness direction The refractive index (Nz) in the thickness direction was measured at 23 ° C. and 65% RH using an Abbe refractometer using sodium D line (589 nm) as a light source. A higher refractive index in the thickness direction means that molecular chains are oriented in the plane direction of the film.

(8) Number of coarse particles Using a universal projector, the film sample was magnified 20 times by transmitted illumination, and the number of particles having a maximum length (major axis) contained in 1 m ² area of 25 μm or more was counted.

(9) Void ratio The film was cut with a microtome along the thickness direction and the width direction, and the cut surface was 20,000 times with Hitachi Scanning Electron Microscope S-4700, and the porosity in the film on the cut surface The silica particles and the voids around them were observed, the diameter of the cross section of each particle and the void cross section around each particle was determined for 10 particles, and the void ratio of each particle was calculated by the following formula.
Void ratio = ((void diameter around particle−particle diameter) / void diameter around particle) × 100
The average of the void ratio was calculated for 10 particles to obtain the average void ratio, and it was evaluated whether or not the void was substantially present in the film.
◯: There is substantially no void (average void ratio is 30% or less)
Δ: substantially free of voids (average void ratio is more than 30%, 50% or less)
X: Void is substantially present (average void ratio exceeds 50%)

(10) Surface roughness (Ra and Rz)
Measurement length (Lx) 1 mm, sampling pitch 2 μm, cut-off using a non-contact type three-dimensional roughness meter (Kosaka Laboratories, ET-30HK) with a semiconductor laser with a wavelength of 780 nm and an optical stylus with a beam diameter of 1.6 μm The protrusion profile on the film surface was measured under the conditions of 0.25 mm, thickness direction magnification 10,000 times, lateral direction magnification 200 times, and the number of scanning lines 100 (thus, the measurement length Ly in the Y direction was 0.2 mm). . When the roughness curved surface was represented by Z = f (x, y), the value obtained by the following formula was defined as the center line average surface roughness (Ra, unit: nm) of the film.

  Further, in the projection profile of the film surface obtained by the Ra, 5 points from the highest peak (Hp) and 5 points from the lower valley (Hv) are taken, and the value obtained by the following equation is 10 of the film. The point average roughness (Rz, unit: nm) was used.

(11) Winding property In the film production process, the film was wound up into a roll having a width of 550 mm and a width of 6000 m at a speed of 100 m / min.
A: The surface roughness is uniform over the entire film surface, and the roll has a good winding shape. B: Due to the influence of coarse aggregate particles in the film, 1 to less than 5 pimples (protruding bulges) are seen on the surface of the roll. Although almost good C: Many coarse aggregates in the film, 5 or more pimples (protruding bulges) are seen on the surface of the roll, poor appearance D: film end face misalignment of the roll occurs, winding shape is poor

(12) Dielectric breakdown voltage (BDV) and variation The stretched film sample is 0.1 kV using ITS-6003 manufactured by Tokyo Seiden Co., Ltd. based on the plate electrode method in the DC test described in JIS standard C2151. The voltage at the time of breakdown was measured as the dielectric breakdown voltage. The measurement was performed at n = 50, the average value was the breakdown voltage, and the standard deviation was the variation in breakdown voltage. The measurement was performed at room temperature of 25 ° C.

(13) Scratch resistance A film cut to 1/2 inch in width and 400 mm in length is run on a stainless guide pin (surface roughness: Ra of 40 nm) using a film running tester, The travel speed was 20 mm / second and the distance of 200 mm was reciprocated twice (winding angle 90 °, outlet tension 50 g). After running, the film contact portion of the guide pin and the guide pin contact surface of the film were observed with a scanning electron microscope S-4700 manufactured by Hitachi at a magnification of 100, and the determination was made according to the following criteria. The smaller the accumulation width of the shaved particles, the better the shaving.
○: Less than 0.20 mm Δ: 0.20 mm or more and less than 0.50 mm x: 0.50 mm or more

(14) Blocking resistance Films cut into 100 mm squares are stacked so that the total thickness is 20 μm or more (one film with a thickness of 20 μm or more is used as one sheet), aluminum of the same size A laminated body was produced by sandwiching one sheet at the top and bottom with foil. The laminate was subjected to thermocompression bonding with a hot press. The pressing conditions were a press temperature of 125 ° C., a press pressure of 5 MPa, and a press time of 30 minutes. After crimping, the laminate was heat treated in an oven at 150 ° C. for 30 minutes, and the peel strength between the cooled laminate film and aluminum foil was measured. The peel force was measured using a tensile tester under the conditions of a tensile speed of 300 mm / min, and the blocking property was determined from the measurement results according to the following criteria.
◯: Peeling almost naturally or having an average peeling force of 1.0 mN / mm or less Δ: Partially blocking, but the average peeling force is exceeding 1.0 mN / mm, 3.0 mN / mm or less X: Blocking as a whole, and average peel force exceeds 3.0 mN / mm

[Synthesis Example 1]
A 22 wt% sodium silicate aqueous solution and a 37 wt% sulfuric acid aqueous solution were reacted using a mixing nozzle to obtain a silica hydrosol. The silica hydrosol gelled in about 7 minutes to obtain a silica hydrogel. This silica hydrogel was roughly crushed to a diameter of about 10 mm, hydrothermally treated at 90 ° C. and pH 9.0 for 5 hours, and then washed with water. Next, the silica hydrogel washed with water is subjected to a first step of drying for 60 minutes using a vibration fluidized bed (trade name “vibration fluid phase device VUA-15 type” manufactured by Chuo Kako Co., Ltd.), and then dried to a moisture content of 7%. Got. Thereafter, a second step of adding water to the dried silica is performed to obtain a silica adjusted to a water content of 37%, and then a third step of drying for 2 hours in the vibrating fluidized bed is performed again. A gel silica having a water content of 1% was obtained. This dried silica is pulverized using a jet mill, and 100 parts of the obtained silica is charged into a vibrating fluidized bed, and 12 parts of n-octyltriethoxysilane is sprayed while being vibrated and flowed with dehumidified air, and flows for 30 minutes. Mixed. Then, it was immediately put into a constant temperature and humidity chamber maintained at a temperature of 25 ° C. and a humidity of 90%, and a surface-treated silica powder was obtained by maintaining for 72 hours. Again, it was pulverized using a jet mill for silica dispersion. Table 1 shows the characteristic values of the obtained silica powder 1 (porous silica particles 1).

[Synthesis Examples 2, 3, 5]
The same treatment as in Synthesis Example 1 was performed except that the average particle size was adjusted by changing the jet mill conditions. Table 1 shows the characteristic values of the silica powders 2, 3, and 5 obtained.

[Synthesis Example 4]
The same treatment as in Synthesis Example 1 was performed except that the amount of n-octyltriethoxysilane to be added was changed. The characteristic values of the obtained silica powder 4 are shown in Table 1.

[Synthesis Example 6]
To make the particle size small, the same as Synthesis Example 1 except that after the first jet mill treatment, silica is made into 10% slurry with distilled water and a wet grinding step of a sand grinder (dyno mill, capacity 5 L) is added. Was done. The characteristic values of the obtained silica powder 6 are shown in Table 1. Since this silica powder had an average particle size of too small as 0.3 μm, the compression rate could not be measured.

[Synthesis Example 7]
The same treatment as in Synthesis Example 1 was performed, except that the surface treatment with n-octyltriethoxysilane was not performed. The characteristic values of the obtained silica powder 7 are shown in Table 1.

[Example 1]
Two feed blades and two return blades for the rotor disk are installed in the ventilated twin-screw kneading extruder KTX-46 made by Kobe Steel with a vacuum vent at the resin inlet and at two locations, and further downstream of the rotor segment. A kneading disk is arranged on the side, and a polyphenylene ether resin (hereinafter abbreviated as PPE) is introduced from the resin inlet using equipment in which a resistance part with a reverse feed full flight screw is arranged immediately downstream of the kneading disk. Mitsubishi Engineering Plastics Iupiace PX-100L (Tg 210 ° C.) is 40 parts by mass, Syndiotactic polystyrene resin (hereinafter sometimes abbreviated as SPS), and Idemitsu Kosan Zarek 60ZC is 55.8 parts by mass. As an antioxidant, Ciba Specialty Chemicals Inc. The Ganokkusu 1010 was 0.2 part by weight mixture turned.
Further, 4 parts by mass of the silica powder 1 described above as porous silica particles was added from the middle part of the twin-screw kneading extruder (downstream part of the kneading disk) and mixed and dispersed. At this time, the mixture feed amount was 35 parts by mass / Hr, the barrel temperature was 270 ° C., and the screw rotation speed was 250 rpm. Thereafter, the resin was cooled with a cooling bath, and then cut with a letterer to obtain a resin composition chip having a major axis of about 4 mm, a minor axis of about 4 mm, and a length of about 3 mm. The obtained resin composition chip is shown in Table 1.

[Examples 2 to 5, Comparative Examples 1 to 3]
A resin composition chip was obtained in the same manner as in Example 1 except that the usage ratio of the porous silica particles, PPE, and SPS used was as shown in Table 1. They are also shown in Table 1.

[Example 6]
In addition to the porous silica particles, 4 parts by mass of spherical silicone resin particles having an average particle size B of 0.3 μm were used, and the use rate of SPS was as described in Table 1, and was the same as in Example 1. A resin composition chip was obtained. They are also shown in Table 1.

[Comparative Example 4]
A resin composition chip was obtained in the same manner as in Example 1 except that spherical silica particles (non-porous) having an average particle size B of 2.0 μm were used instead of the porous silica particles to be used. They are also shown in Table 1.

[Example 11]
Resin composition chip obtained in Example 1 (master chip A), polyphenylene ether resin (Mitsubishi Engineering Plastics Iupiace PX-100L), syndiotactic polystyrene resin (Dareko Kosan Zalek 60ZC), polyphenylene aerel After drying a master chip containing 5% by weight of Ciba Specialty Chemicals Irganox 1010 as an antioxidant in a resin (Iupiace PX-100L manufactured by Mitsubishi Engineering Plastics), a film having the composition shown in Table 2 was obtained. These were mixed at a ratio and supplied to an extruder, melted at 300 ° C., extruded from a die slit, and cooled and solidified on a casting drum cooled to 50 ° C. to prepare an unstretched sheet. In addition, since antioxidant was partly scattered in the film forming process of the film, the antioxidant content in the mixture of raw materials was increased so that the content in the film was 1% by weight.
This unstretched sheet was stretched 3.5 times in the longitudinal direction (machine axis direction) at 140 ° C., and subsequently led to a tenter, and then 4.5 times in the lateral direction (direction perpendicular to the machine axis direction and the thickness direction). The film was stretched twice. At that time, the transverse stretching speed was 5000% / min, the transverse stretching temperature was divided into four equal parts, the first stage temperature was 126 ° C., and the final stage temperature was 145 ° C. Thereafter, the film was heat-fixed at 250 ° C. for 9 seconds, and further subjected to a 2% relaxation treatment in the transverse direction while cooling to 180 ° C. to obtain a biaxially stretched film having a thickness of 2.5 μm and wound into a roll. The properties of the obtained film are shown in Table 2.

[Examples 12-14, 16, 19, 20, 23-27, Comparative Examples 11-13, 15, 16]
Using a master chip as shown in Table 2 or 3, the composition of the resulting film is as shown in Table 2 or 3, so that polyphenylene ether resin, polycarbonate resin, syndiotactic polystyrene resin and antioxidant The same operation as in Example 11 was repeated except that the contained master chip was used in combination. The evaluation results of the obtained stretched film are shown in Tables 2 and 3. In Examples 25 and 26, a syndiotactic polystyrene resin (Idemitsu Kosan Zarek 60ZC) containing 5% by weight of Irganox 1010 was used as an antioxidant-containing master chip.

[Examples 15, 17, 18, 21, 22, Comparative Example 14]
First, a polyphenylene ether resin, a polystyrene resin having a syndiotactic structure, porous silica particles and an antioxidant were mixed in the same manner as in Example 1 so that the composition of the obtained film was as described in Table 2 or 3. A resin composition chip was obtained. The obtained resin composition was dried and formed into a film in the same manner as in Example 11 to obtain a biaxially stretched film. The evaluation results of the obtained stretched film are shown in Tables 2 and 3.

PC in Table 2 is a bisphenol A type polycarbonate (Idemitsu Petrochemical A300, glass transition temperature: 145 ° C.).
In Tables 2 and 3, Irg1010 represents pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1010). Irg1098 is N, N′-bis-3- (3′5′di-t-butyl-4′-hydroxyphenyl) propionylhexamethylenediamine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1098), and Irg565 is 2,4. -Bis (n-octylthio) -6- (4'-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX565).

  The stretched film of the present invention is excellent in particle dispersibility and has a small diameter of voids caused by the particles, so that it is excellent in abrasion resistance, handleability, and dielectric breakdown characteristics (dielectric breakdown voltage and variations thereof). It can be suitably used for a film capacitor.

Claims (14)

  A stretched film comprising a polystyrene-based resin having a syndiotactic structure and a porous silica particle having an average particle size A of 0.5 to 5 μm and a DBA value of 200 mmol / kg or less, Stretched film in which the content of porous silica particles is 0.01 to 3 mass% based on the amount of the resin composition material.   The stretched film according to claim 1, wherein the resin composition further contains a thermoplastic amorphous resin.   The stretched film according to claim 2, wherein the thermoplastic amorphous resin is polyphenylene ether.   The stretched film of Claim 2 or 3 which contains 5-48 mass% of thermoplastic amorphous resins on the basis of the mass of a resin composition.   The stretched film according to any one of claims 1 to 4, wherein the refractive index in the thickness direction is 1.575 to 1.635.   The stretched film according to any one of claims 1 to 5, which contains 0.1 to 5% by mass of an antioxidant based on the mass of the resin composition.   The stretched film according to claim 6, wherein the thermal decomposition temperature of the antioxidant is 250 ° C. or higher.   The stretched film according to any one of claims 1 to 7, wherein the compression rate of the porous silica particles is 20 to 90%.   Furthermore, the stretched film in any one of Claims 1-8 which contains 0.01-3 mass% of particles with an average particle diameter A of 0.01 micrometer or more and less than 0.5 micrometer on the basis of the mass of a resin composition. The stretched film according to claim 1, wherein the number of coarse particles having a maximum length of 25 μm or more contained in the film is 10 / m ² or less. The stretched film according to any one of claims 1 to 10, wherein a void ratio represented by the following formula (1) of voids generated around the porous silica particles contained in the film is 50% or less.
(1) Void ratio = ((void diameter around particle−particle diameter) / void diameter around particle) × 100   A resin composition comprising a resin material containing a syndiotactic polystyrene resin mixed with porous silica particles having an average particle size B of 0.5 to 5 μm and a DBA value of 200 mmol / kg or less. The resin composition whose content of this porous silica particle is 0.01-10 mass% on the basis of the mass of a resin composition.   The resin composition according to claim 12, wherein the resin composition further contains a thermoplastic amorphous resin.   The resin composition according to claim 12 or 13, wherein the compression rate of the porous silica particles is 20 to 90%.