JPH10294237A - Film for capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a film for a capacitor having excellent operability and enabling increase in capacitance of the capacitor, by using polyethylene-2,6- naphthalate to which calcium carbonate and plate-like aluminum silicate having specified grain sizes are mixed. SOLUTION: A film for a capacitor is produced, the film being made of polyethylene-2,6-naphthalate which contains calcium carbonate having average grain size of 0.5 to 5 μm, at 0.1 to 2 wt.%, and plate-like aluminum silicate having an average grain size of 0.1 to 2 μm, at 0.1 to 1 wt.%. The film has a base factor of 1 to 19%, and the density of protrusions with a height of not smaller than 1.5 μm on the film surface is 300 to 700/cm<2> . The polyethylene-2,6- naphthalate is a polyethylene-2,6-naphthalate copolymer in which not only the repeat structure units are substantially those of ethylene-2,6-naphthalate but also not less than 10% of the number of repeat structure units are those of other components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyethylene-2,6-naphthalate film used for a condenser.

[0002]

2. Description of the Related Art Polyethylene-2,6-naphthalate film is used as a film for capacitors because of its excellent mechanical properties, thermal properties and heat resistance.

With the recent demand for miniaturization of electric or electronic circuits, quality requirements for capacitors have been reduced in size and increased in capacity, and a thin film, which is a dielectric material serving as the base, must be formed. Is being promoted. The reason that the film that is a dielectric film in a film capacitor is made thinner is that (a) the capacitance of the capacitor is proportional to the area of the dielectric electrode of the dielectric material, and (b) it is inversely proportional to the film thickness. Since the capacitance per unit volume of the dielectric is inversely proportional to the square of the film thickness and proportional to the dielectric constant, as long as a dielectric material having the same dielectric constant is used, it is possible to reduce the size or increase the capacitance of the capacitor. This is because it is indispensable to reduce the thickness of the film if it is attempted.

[0004] Although there is a need to make such a film thinner, simply reducing the thickness of a conventional stretched film has the following problems. For example, as the film becomes thinner, there is a problem that workability in the process of depositing an electrode on the film, slitting, winding of the element, and the like is deteriorated.

This workability is related to the slipperiness of the film, and in order to improve the slipperiness, it is generally known that a thermoplastic resin film is provided with fine irregularities on the film surface. . As an example of such a method,
Inert inorganic fine particles may be added during or after the polymerization of the thermoplastic polymer as a raw material of the film (external particle addition method), or a part or all of the catalyst or the like used during the polymerization of the thermoplastic polymer may be reacted. A technique for precipitating in a polymer (internal particle precipitation method) is known.

However, in the method for producing an ultra-thin film, when the polymer to which the inert inorganic fine particles are added at the same concentration is thinned, the number of the inert inorganic fine particles per unit area decreases, and the fine particles on the film surface are reduced. , The film surface tends to be flat, and the slipperiness tends to decrease. Therefore, to compensate for the decrease in slipperiness due to thinning,
As the film thickness becomes smaller, it is necessary to increase the concentration of the added inert inorganic fine particles or to increase the particle size.

[0007] In this case, voids are formed at the interface, that is, the inert inorganic fine particles due to poor affinity between the inert inorganic fine particles and the thermoplastic polymer particularly during melt extrusion or stretching at a high draft ratio. As a result of the occurrence of voids, not only the mechanical properties (e.g., rupture strength, rupture elongation) of the obtained film are reduced, but also the rupture is likely to occur when manufacturing the film, There have been problems with reduced productivity and lack of stability in manufacturing conditions.

A thin thermoplastic film having a thickness of 4 μm or less, which solves such a problem and has excellent workability (handling property) and excellent film forming property, has been proposed previously (Japanese Patent Laid-Open No. Hei 1-1-1).
266145). However, when the thermoplastic film is a polyethylene-2,6-naphthalate film, there is no decrease in mechanical properties and the workability and the film-forming property are excellent. However, there is a problem that a film for a capacitor is not sufficient because an air layer generated when superimposed on each other becomes thick and the capacity of the capacitor per volume decreases.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a film for a capacitor which is excellent in workability and can increase the capacity of the capacitor.

[0010]

Means for Solving the Problems The present inventors have found that by using calcium carbonate and plate-like aluminum silicate having a specific particle size, it is possible to increase the capacity of a capacitor if the space factor is small even if the film surface is rough. Is possible,
Furthermore, they found that when the number of protrusions having a height of 1.5 μm or more was in a specific range, a film excellent in workability was obtained while maintaining the space factor, and the present invention was reached.

That is, according to the present invention, the average particle diameter is 0.5 to
Capacitor made of polyethylene-2,6-naphthalate containing 0.1 to 2% by weight of calcium carbonate having a thickness of 5 μm and 0.1 to 1% by weight of aluminum silicate having an average particle diameter of 0.1 to 2 μm. Film for
The space factor of the film is 1 to 19%, and the protrusions having a height of 1.5 μm or more on the film surface are 300 to 70%.
It is a film for capacitors, characterized in that the number is 0 / cm ² .

The polyethylene-2,6-naphthalate constituting the film for a capacitor of the present invention has a repeating structural unit of substantially not only ethylene-2,6-naphthalate but also 10% or less of the number of repeating structural units. Preferably no more than 5% contains the other components polyethylene-2,6-naphthalate copolymer and polymer mixture.

In general, polyethylene-2,6-naphthalate is obtained by polymerizing naphthalene-2,6-dicarboxylic acid or a functional derivative thereof, and ethylene glycol or a functional derivative thereof in the presence of a catalyst under appropriate reaction conditions. Before the completion of the polymerization of polyethylene-2,6-naphthalate, one or more third components (modifiers) are added to the polyethylene-2,6-naphthalate according to the present invention. Copolymerized or mixed polyethylene-2,6-naphthalate may be used. Preferred third components are compounds having a divalent ester-forming functional group, such as oxalic acid, adipic acid, phthalic acid, isophthalic acid,
Dicarboxylic acids such as terephthalic acid, naphthalene-2,7-dicarboxylic acid, succinic acid, diphenyl ether dicarboxylic acid and the like, or lower alkyl esters thereof; oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid; or Examples thereof include lower alkyl esters thereof and compounds such as dihydric alcohols such as propylene glycol and trimethylene glycol. Polyethylene-2,6-naphthalate or a modified polymer thereof is obtained by blocking a terminal hydroxyl group and / or a carboxyl group with a monofunctional compound such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, or methoxypolyalkylene glycol. Or a compound modified with a very small amount of a trifunctional or tetrafunctional ester-forming compound such as glycerin or pentaerythritol in a range where a substantially linear copolymer can be obtained.

The polyethylene-2,6-naphthalate is obtained by subjecting an ester-forming derivative of the above-mentioned acid component, for example, di-lower alkyl-2,6-naphthalate and ethylene glycol to a transesterification reaction by a known method, followed by polycondensation. In the transesterification reaction, a di-lower alkyl ester of 2,6-naphthalenedicarboxylic acid and ethylene glycol are reacted in the presence of a transesterification catalyst.

As the transesterification catalyst, a manganese compound is preferably used.
Oxides, chlorides, carbonates, carboxylates and the like can be mentioned. Of these, acetate is particularly preferably used.

It is preferable to add a phosphorus compound at the time when the transesterification reaction is substantially completed to deactivate the transesterification catalyst. As the phosphorus compound, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate and orthophosphoric acid can be preferably used. Of these, trimethyl phosphate is particularly preferred.

As the polycondensation catalyst, an antimony compound is preferably used, and as the antimony compound, antimony trioxide is particularly preferably used.

In the polyethylene-2,6-naphthalate of the present invention, the catalyst is polyethylene-2,6-naphthalate.
In 6-naphthalate, the following formulas (1), (2) and (3)
Is preferably contained.

[0019]

## EQU4 ## 30 ≦ Mn ≦ 100 (1)

[0020]

[Equation 5] 150 ≦ Sb ≦ 450 (2)

[0021]

P / Mn ≧ 1 (3) wherein Mn is a manganese element polyethylene-2,6-
The amount (ppm) in naphthalate, Sb is the amount of antimony element in polyethylene-2,6-naphthalate (pp
m) and P represent the amount (ppm) of the elemental phosphorus in polyethylene-2,6-naphthalate. ]

When the content of the manganese element is polyethylene-
If it is less than 30 ppm in 2,6-naphthalate, the transesterification reaction will be insufficient, while if it exceeds 100 ppm, the CR value of the film will decrease, and it may not be suitable as a film for capacitors. In addition, when the content of the antimony element is less than 150 ppm, the polycondensation reactivity is reduced and the productivity is deteriorated. Sometimes. Further, when P / Mn is less than 1, the intrinsic viscosity may be reduced.

The alkali metal content is 10 ppm
The following is preferred. 1 alkali metal content
If it exceeds 0 ppm, the CR value of the film may decrease, and the film may not be suitable as a capacitor film.

The film for a capacitor of the present invention has many fine projections on the film surface. Those numerous fine projections are, according to the invention, polyethylene-
It is derived from a large number of calcium carbonate and plate-like aluminum silicate dispersed and contained in 2,6-naphthalate.

In the present invention, the calcium carbonate contained in polyethylene-2,6-naphthalate has an average particle size of 0.5 to 5 μm, preferably 0.5 to 3 μm.

Here, the "average particle size" means the "equivalent spherical diameter" of the particles at a point of 50% by weight of the total particles measured. "Equivalent spherical diameter" means the diameter of an imaginary sphere (ideal sphere) having the same volume as a particle, and can be calculated from an electron micrograph of the particle or measurement by a normal sedimentation method.

If the average particle size of the calcium carbonate is less than 0.5 μm, wrinkles are likely to occur because the air squeezing property is poor (the entrapped air is difficult to escape) when the film is wound on a master roll or a product roll. Unsatisfactory, the workability in the processing step is reduced, which is not preferable. On the other hand, if the average particle size exceeds 5 μm, the film surface becomes too rough, the space factor increases, and furthermore, the dielectric breakdown voltage is reduced, and the number of insulation defects is increased. The average particle size of the calcium carbonate may be larger than the film thickness.

In the present invention, the added amount of calcium carbonate is 0.1 to 0.1 in polyethylene-2,6-naphthalate.
It must be 2% by weight, preferably 0.1 to 1% by weight. If the added amount of calcium carbonate is less than 0.1% by weight, the air squeezing property at the time of winding the film becomes poor. On the other hand, if it exceeds 2% by weight, the film surface becomes too rough and the dielectric breakdown voltage is lowered. Not preferred.

As the calcium carbonate used in the present invention,
Any material can be used, and calcite crystals such as precipitated limestone, chalk, and precipitated calcium carbonate generated from limestone by a chemical method, and lime milk are obtained by reacting carbon dioxide at high temperature. Argonite crystals, paterite crystals, and combinations thereof. Heavy calcium carbonate (calcite crystal) obtained by mechanically grinding limestone can also be used.

In the present invention, the plate-like aluminum silicate contained in polyethylene-2,6-naphthalate is
Its average particle size is 0.1-2 μm, preferably 0.3-
1.2 μm, the content of which is 0.1 to
1% by weight.

The average particle size of the plate-like aluminum silicate is 0.
When the thickness is less than 1 μm, the slipperiness of the film is impaired and the workability is deteriorated, which is not preferable. On the other hand, when it exceeds 2 μm, the film surface is too rough and the space factor increases, which is not preferred.

When the content of the plate-like aluminum silicate is less than 0.1% by weight, the air squeezing property at the time of winding the film becomes poor. On the other hand, when the content exceeds 1% by weight, the film surface becomes too rough and the space factor is reduced. It is not preferable because it increases.

In the present invention, the plate-like aluminum silicate refers to an aluminosilicate, and any one of them can be used, and examples thereof include kaolin clay made of a naturally occurring kaolin mineral. Further, the kaolin clay may have been subjected to a purification treatment such as washing with water.

In the present invention, polyethylene-2,6
Naphthalate contains calcium carbonate having an average particle size of 0.5 to 5 μm and plate-like aluminum silicate having an average particle size of 0.1 to 2 μm. If the workability of the film is to be ensured only with calcium carbonate, the space factor of the film is undesirably too large. On the other hand, only plate-like aluminum silicate cannot form large projections, and thus cannot achieve both workability and space factor.

The calcium carbonate and plate-like aluminum silicate to be added to the polyethylene-2,6-naphthalate of the present invention may be added before the polymerization of the polymer, during the polymerization reaction, or at the time of pelletizing after the polymerization. The mixture may be kneaded in the melt, or may be added during melt extrusion into a sheet, and may be dispersed and extruded in an extruder, but is preferably added before polymerization.

In order to add calcium carbonate and plate-like aluminum silicate to polyethylene-2,6-naphthalate, any known method may be employed. For example, the addition may be made before the polymerization of polyethylene-2,6-naphthalate. In this case, it is preferable that calcium carbonate and plate-like aluminum silicate are added to ethylene glycol, and the mixture is dispersed in a polymer by ultrasonic vibration or the like.

The space factor of the film for a capacitor of the present invention must be 1 to 19%.

The space factor is defined as the weight w (g) of the sample film 100 cm ² and the density d (cm ³ /
When the thickness by gravimetric method obtained from g) is t ₁ (μm), and ten sample films of 10 cm square are stacked and the thickness of one sample film obtained by using a micrometer is t ₂ (μm), This is a value calculated from the equation.

[0039]

## EQU7 ## Space factor F (%) = 100−t ₁ /
t ₂ × 100

If this space factor is less than 1%,
The slipperiness and workability (handling property) of the film are insufficient. On the other hand, if it exceeds 19%, the capacity of the capacitor per volume is low, which is not suitable for reducing the size and the capacity of the capacitor.

The surface of the capacitor film of the present invention has a large number of projections derived from the above-mentioned calcium carbonate and plate-like aluminum silicate.
Those having a height of 5 μm or more need to be 300 to 700 pieces / cm ² or less. 3 protrusions with a height of 1.5 μm or more
If the number is less than 00 / cm ² , the interval between the projections is widened, the film surface is flattened, and the slipperiness is reduced. On the other hand, if it exceeds 700 / cm ² , the film surface becomes too rough and the space factor becomes too large, which is not preferable.

The polymer for use in the capacitor film of the present invention preferably has an intrinsic viscosity of 0.40 or more, more preferably 0.40 to 0.80.
If the intrinsic viscosity is less than 0.40, process cutting may occur frequently.

The thickness of the capacitor film is 1 to
It is preferably 20 μm, more preferably 1 to 15 μm.
If the thickness is less than 1 μm, it is difficult to form a film.
If it exceeds, it may be difficult to reduce the size of the capacitor.

The heat shrinkage of the film for a capacitor of the present invention is preferably 3% or less. If it exceeds 3%, the film shrinks in the vapor deposition step during the production of the capacitor, and wrinkles may occur.

Further, from the viewpoint of being an electrically insulating material, the breakdown voltage (BDV) is preferably 260 V / μm or more.

The number of pinholes in the capacitor film of the present invention is preferably 0.1 / cm ² or less.

Furthermore, the CR value (insulation resistance) of the capacitor film of the present invention is preferably 10,000ΩF or more. If the CR value is less than 10,000 ΩF, the insulation resistance of the film becomes insufficient, and the film may be unsuitable as an electrical insulating material.

The number of protrusions having a height of 1.5 μm or more, the intrinsic viscosity of the polymer, the thickness of the film, the heat shrinkage, the breakdown voltage (BDV), the pinhole, and the CR value were measured by the methods described later. .

The capacitor film of the present invention is a biaxially oriented polyethylene-2,6-naphthalate film. The film is biaxial (eg, longitudinal and transverse)
It is preferable that each is stretched at a stretching ratio of 2 or more.
The stretching ratio in the biaxial direction may or may not be equal. The film may be a single film or a laminated film.

The polyethylene-2,6-naphthalate film of the present invention has an intrinsic viscosity of 0.40 at a normal extrusion temperature, that is, at a temperature not lower than the melting point (hereinafter referred to as Tm) and not higher than (Tm + 70 ° C.). The unstretched film having a thickness of 0.80 to 0.82 or more is used as the secondary transition point (hereinafter referred to as Tg) of polyethylene-2,6-naphthalate (Tg + 70 ° C.)
The film is stretched at a stretching ratio of 2.5 to 5.0 times in the longitudinal or transverse direction at the following temperature, and then in a direction perpendicular to the stretching direction (horizontal direction if the stretching direction is the longitudinal direction) Tg or more (T
g + 70 ° C.) or less at a stretching ratio of 2.5 to 5.0 times (stretching may be such a sequential biaxial stretching or a simultaneous biaxial stretching). The method is not particularly limited). The biaxially oriented film thus obtained is preferably heat-set at a temperature of (Tg + 70 ° C.) or more and Tm or less for 1 to 100 seconds.

[0051]

The present invention will be described in more detail with reference to the following examples. In the examples, various characteristic values were measured and evaluated by the following methods.

1. Particle size of particles (1-1) Particle size of powder Shimadzu CP-50 Centrifugal Particle Size Analyzer
yser). From the cumulative curve of particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve,
The particle size corresponding to 50 mass percent was read and this value was taken as the average particle size. (See “Granularity measurement technology”, published by Nikkan Kogyo Shimbun, 1975, p.242-247)

(1-2) Particle Size of Particles in Film A small piece of the sample film was fixed on a sample stage for a scanning electron microscope, and a sputtering device manufactured by JEOL Ltd. (JIS-1100) was used.
0.25 kV, 1.25 under a vacuum of 1 × 10 ⁻³ torr using a film type ion sputtering device.
An ion etching treatment was performed for 10 minutes under the condition of mA. Further, gold sputtering was performed by the same apparatus, observed at 10,000 to 30,000 times with a scanning electron microscope, and at least 100 times with Luzex 500 manufactured by Nippon Regulator Co., Ltd.
The major axis (Dli), minor axis (Dsi) and area equivalent particle diameter (Di) of each particle were determined. The number average value of the area equivalent particle diameter (Di) represented by the following formula was defined as the average particle diameter (D).

[0054]

(Equation 8)

2. Space factor (F) Film weight w (g) of sample 100 cm ² and density d
T ₁ (μm), the gravimetric thickness determined from (cm ³ / g)
Ten sample films of 0 cm square are stacked, and the thickness of one sample film determined using a micrometer is defined as t ₂ (μ
m) was calculated from the following equation.

[0056]

## EQU9 ## Space factor F (%) = 100−t ₁ /
t ₂ × 100

3. Surface protrusions (3-1) Number of protrusions with a height of 1.5 μm or more NIKON two-beam microscope OPTIPHOT (wavelength λ = 5)
46 nm) using interference fringes using it is lambda / 2, calculate a projection height, present per 1 cm ² 1.5
Protrusions of μm or more were counted.

(3-2) Surface roughness Non-contact type three-dimensional roughness meter (ET-30H, manufactured by Kosaka Laboratory)
K) using a semiconductor laser with a wavelength of 780 nm, a measuring length (Lx) of 1 mm with a light probe having a beam diameter of 1.6 μm, a sampling pitch of 2 μm, a cutoff of 0.25 mm, a vertical magnification of 10,000 times, and a horizontal magnification Magnification 200 times, number of scanning lines 100 (accordingly, measurement length Ly in Y direction = 0.2 mm)
The protrusion profile on the film surface was measured under the following conditions. When the roughness surface is represented by Z = f (x, y),
The value (Ra, nm) obtained by the following equation was defined as the surface roughness of the film.

[0059]

(Equation 10)

4. Intrinsic viscosity (IV) It measured at 25 degreeC using o-chlorophenol as a solvent. The unit is 100 cc / g.

5. Film forming property of the film The film forming property was represented by the number of times the film was broken when the biaxial stretching film forming was continuously operated for 8 hours. The unit is times / 8 hours.
Although the ultra-thin film is liable to break the film, it is usually preferable that this value be 2 times / 8 hours or less from the viewpoint of practical use.

6. Dielectric breakdown voltage (BDV) Measured according to the method shown in JIS C 2318, and n = 1
The average value of 00 was taken as the breakdown voltage (BDV).

7. CR value After the sample film was conditioned at 23 ° C. and 50% RH for 16 hours, the sample film was placed under an atmosphere of 23 ° C. and 50% RH.
It was measured according to the method shown in JIS C 2319.

8. A solution obtained by diluting the pinhole magic ink 10 times with reagent grade ethanol is dropped on the sample film adhered to the thermal paper, spread with an air brush, and counted the number of pinholes transferred to the thermal paper side. The number per 3000 cm ² was calculated.

9. Film thickness When the width of the sample film is W (cm), the length is 1 (cm), the weight is G (g), and the density is d (g / cm ³ ), the film thickness t (μm) is expressed by the following formula. Calculated.

[0066]

T = G / (W × 1 × d) × 10000

10. Heat shrinkage Mark lines were placed on the sample film at intervals of 30 cm, and heat treatment was performed for a certain period of time (150 ° C,
It was determined from the change in sample length after 30 minutes) according to the following equation.

[0068]

[Expression 12] Heat shrinkage (%) = (length before heat treatment−length after heat treatment) / length before heat treatment × 100

11. Amount of catalyst and amount of alkali metal in the film A sample film was washed and dried twice or more with distilled acetone, and then 0.200 g was collected. Next, it is wet-decomposed with reagent grade sulfuric acid, nitric acid, etc., and 20 ml of ion exchange distilled water is added.
A sample solution was used. This sample solution was applied to a high-frequency plasma emission spectrometer (Jarrel Ash, Atomu Comp Siries 80
The metal qualitative and quantitative analysis was performed in 0).

Examples 1-4 and Comparative Examples 1-2 After transesterification of dimethyl naphthalene-2,6-dicarboxylate and ethylene glycol in the presence of manganese acetate by a conventional method, trimethyl phosphate was added. did. Next, antimony trioxide, aluminum carbonate having a particle size shown in Table 1, and plate-like aluminum silicate are added in the amounts shown in Table 1, and polycondensed by a conventional method to obtain a polyethylene-2,6-naphthalate polymer. Obtained. After drying the polymer at 170 ° C. for 6 hours, it is fed to an extruder and melted at a melting temperature of 290 to 310 ° C.
mm slit die, surface finish 0.3S,
It was extruded on a rotating drum having a surface temperature of 50 ° C. to obtain an unstretched film.

The unstretched film obtained in this way was
The film was stretched 3.6 times in the machine direction at 140 ° C., then stretched 4.0 times in the transverse direction at 140 ° C., and heat-set at 220 ° C. for 5 seconds to obtain a 2-μm-thick biaxially oriented polyethylene-2,6- A naphthalate film was obtained. Table 1 shows the properties of these films.

[0072]

[Table 1]

[0073]

The present invention has the following excellent effects and is suitably used as a film for a capacitor requiring an extremely thin film. (1) There is no breakage during film formation, it is useful for forming ultra-thin films, and the space factor is small, so that the capacity of the capacitor can be increased. (2) The film surface is appropriately roughened, the film has good slipperiness, and is excellent in workability during film formation and processing. (3) A suitable amount of catalyst and metal, high insulation resistance, and excellent CR characteristics.

Claims (3)

[Claims] 1. A calcium carbonate having an average particle size of 0.5 to 5 μm, 0.1 to 2% by weight, and an average particle size of 0.1 to 2%.
A capacitor film comprising polyethylene-2,6-naphthalate containing 0.1 to 1% by weight of a plate-like aluminum silicate having a thickness of 1 μm, wherein the space factor of the film is 1 to 19% and the surface of the film is 1. 5μ
A film for a capacitor, wherein the number of protrusions having a height of at least m is 300 to 700 / cm ² . 2. The polyethylene-2,6-naphthalate has an intrinsic viscosity of 0.40 or more and a film thickness of 1-2.
0 μm, heat shrinkage of 3% or less, dielectric breakdown voltage of 260 V
^{2. The} film for a capacitor according to claim 1, wherein the film thickness is not less than / μm and the number of pinholes is not more than 0.1 / cm ² . 3. A manganese compound, an antimony compound as a polymerization catalyst for polyethylene-2,6-naphthalate, and a phosphorus compound as a heat stabilizer in an amount satisfying the following formulas (1), (2) and (3): Content of 10
ppm or less, and the CR value of the film is 10,000
3. The film for a capacitor according to claim 1, which has an ΩF or more. [Equation 1] 30 ≦ Mn ≦ 100 (1) [Equation 2] 150 ≦ Sb ≦ 450 (2) P / Mn ≧ 1 (3) Is polyethylene-2,6-
The amount (ppm) in naphthalate, Sb is the amount of antimony element in polyethylene-2,6-naphthalate (pp
m) and P represent the amount (ppm) of the elemental phosphorus in polyethylene-2,6-naphthalate. ]