JP4082671B2 - Biaxially oriented polyester film - Google Patents

Description

【００４９】
【表２】

【００５０】
実施例１および２は、本発明の要件を満たしているため、ゲル化ブツによる核なし異物が大幅に低減し、生産性、特に連続製膜性、フィルターライフが大幅に向上されるものであった。これに対して、比較例１〜１０は、本発明の要件を満たしていないフィルムでゲル化ブツによる核なし異物の低減、フィルム生産性に劣るものであった。
【００５１】
【発明の効果】
以上、詳述したように、本発明のフィルムは、ゲル化ブツによる核なし異物を低減し、生産性、特に連続製膜性、フィルターライフに優れるものであり、その工業的価値は高い。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biaxially oriented polyester film. More specifically, the present invention relates to a biaxially oriented polyester film excellent in productivity, in particular, continuous film-forming property and filter life, in which core-free foreign matters due to gelled particles are greatly reduced.
[0002]
[Prior art]
Biaxially oriented polyester films represented by polyethylene terephthalate are chemically stable, have high physical and mechanical strength, and are excellent in heat resistance, durability, chemical resistance, and electrical insulation. Widely used in capacitors, electrical insulating materials, packaging materials and industrial molded products.
Usually, in order to improve the handling property and winding workability of the polyester film, inorganic or organic inert fine particles are contained in the film (see, for example, Patent Document 1). A so-called gelled surface, which is a high-melting-point PET having a structure, is generated and becomes a core-free foreign substance, which is present in the film, resulting in a deterioration in the quality of the film.
[0003]
Especially in electrical and electronic equipment and optical applications, among the properties of the film, there are demands for improving heat resistance, reducing low molecular weight substances deposited on the film surface, and reducing foreign matter in the film. In recent years, the required properties for films have become more severe. Various proposals have been made for improving heat resistance and reducing low molecular weight substances deposited on the film surface (see, for example, Patent Document 2).
Although improvement of heat resistance and reduction of low molecular weight substances deposited on the film surface have been achieved to some extent, the present situation is that reduction of foreign substances, particularly foreign substances without nuclei due to gelling, has not been achieved. Therefore, attempts have been made to reinforce the melt line filter as a means of reducing foreign particles without gelation, but the filter life has been shortened due to the filter strengthening, and the filter must be replaced frequently. Will be invited. If the filter is mild in order to lengthen the filter life, there will be more nucleation-free foreign matter in the film due to gelled particles, which will cause adverse effects such as film quality degradation and frequent film breakage during the stretching process. .
[0004]
[Patent Document 1]
JP 7-18163 A [Patent Document 2]
Japanese Patent Laid-Open No. 6-200000
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and its solution is to greatly reduce the core-free foreign matter caused by gelling, improve productivity, particularly continuous film formation, filter life, and film. The object is to provide a biaxially stretched polyester film with greatly improved quality.
[0006]
[Means for Solving the Invention]
As a result of intensive studies in view of the above problems, the present inventor has found that these improvements can be effectively achieved by simultaneously containing a specific silica particle and an antioxidant, thereby completing the present invention. It came to do.
[0007]
That is, the gist of the present invention is that 0.01 to 1.0 weight of wet-process silica particles having a pore volume of 0.5 to 2.0 ml / g and an average particle diameter of 0.1 to 5.0 μm. %, And 0.01 to 0.5% by weight of an antioxidant, and the number of foreign particles without nuclei due to gelling is 10 pieces / m ² or less. It exists in an axially oriented polyester film.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The polyester constituting the film of the present invention is a polyester obtained using aromatic dicarboxylic acid or its ester and glycol as main starting materials, and 80% or more of the repeating structural units are ethylene terephthalate units or ethylene-2,6- Polyesters having naphthalate units or 1,4-cyclohexanedimethylene terephthalate units are preferred. In addition, the polyester may be copolymerized with other third component. As an aromatic dicarboxylic acid component, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid, etc.) can be used. As a glycol component, 1 type, or 2 or more types, such as diethylene glycol, triethylene glycol, propylene glycol, butanediol, neopentyl glycol other than ethylene glycol and 1, 4- cyclohexane dimethanol, can be used, for example. In any case, the polyester of the present invention refers to a polyester in which 80% or more of the repeating units have an ethylene terephthalate unit or an ethylene-2,6-naphthalene unit.
[0009]
The intrinsic viscosity of such a polyester is usually 0.45 or more, preferably 0.50 to 1.0, more preferably 0.52 to 0.80. When the intrinsic viscosity is less than 0.45, there arises a problem that the productivity at the time of film production is lowered or the mechanical strength of the film is lowered. On the other hand, from the viewpoint of the melt extrusion stability of the polymer, the intrinsic viscosity is preferably not more than 1.0.
[0010]
The polyester film of the present invention refers to a biaxially oriented polyester film using such a polyester as a starting material, and a known method can be used as a production method thereof. For example, it is usually melt-extruded into a sheet form at 270 to 330 ° C., then cooled and solidified at 40 to 80 ° C. to form an amorphous sheet, and then the area magnification is 4 to 20 times in the vertical and horizontal directions at 80 to 130 ° C. A method of sequential biaxial stretching or simultaneous biaxial stretching and heat treatment at 160 to 250 ° C. (for example, a method described in Japanese Patent Publication No. 30-5639) can be used. Stretching in the longitudinal and transverse directions may be performed in one step, and if necessary, stretching may be performed in multiple stages, or a heat treatment section may be provided for relaxation of orientation during the multistage stretching. Further, after biaxial stretching, the film may be stretched again before being subjected to the heat treatment step of the next step. This re-stretching can be performed in either the vertical or horizontal direction, or in both directions.
[0011]
The greatest feature of the present invention is that the specific silica particles and the antioxidant to be blended in the polyester film are contained at the same time. That is, by simultaneously containing specific amounts of wet method silica particles and antioxidants having a pore volume of 0.5 to 2.0 ml / g and an average particle size of 0.1 to 5.0 μm. Thus, it is possible to significantly reduce the core-free foreign matter caused by gelling, and to reduce film breakage during film production due to the core-free foreign matter.
[0012]
The wet-process silica particles used in the present invention have a form in which primary particles form a three-dimensional matrix structure by siloxane bonds, the surface is made porous, and the internal surface area is very large. Silica particles produced by such a wet method have a large surface area due to the porous surface, and a wide contact area with the resin and the antioxidant contained at the same time. Generation of high melting point PET having a stitch structure, that is, so-called gelled particles, can be suppressed, and coreless foreign matters can be reduced.
[0013]
The average particle size of the wet method silica particles used in the present invention is in the range of 0.1 to 5.0 μm. Since the diameter is small, the winding workability of the film is inferior, which is not preferable. On the other hand, when the thickness exceeds 5.0 μm, the number of foreign particles with nuclei is much larger than the foreign particles without nuclei due to gelation, which leads to deterioration of the film quality in optical applications.
[0014]
Furthermore, the pore volume of the wet process silica particles in the present invention is preferably in the range of 0.5 to 2.0 ml / g, preferably 0.6 to 1.8 ml / g. When the pore volume is less than 0.5 ml / g, the particles are not made porous, and the effect of reducing the non-nuclear foreign matter by the gelled powder tends to be lost. On the other hand, when it exceeds 2.0 ml / g, crushing and agglomeration are likely to occur, making it difficult to adjust the particle diameter and increasing the number of foreign particles with nuclei.
[0015]
The content of the wet process silica particles in the polyester film is in the range of 0.01 to 1.0% by weight. If it is less than 0.01% by weight, the slipperiness of the film is insufficient, and if it exceeds 1.0% by weight, the transparency is lowered.
[0016]
The method of blending the wet method silica particles used in the present invention with the polyester as the film forming raw material is not particularly limited, and a known method can be adopted. For example, particles and polyester chips can be directly blended, but in particular in any stage of the polyester production process as an ethylene glycol slurry dispersed in ethylene glycol as a raw material for polyester, preferably after completion of esterification or transesterification The polycondensation reaction is preferably carried out before the polycondensation reaction is started.
[0017]
The dispersion slurry of wet method silica particles used in the present invention can be prepared by a known method. For example, the dispersion can be adjusted using a high-speed stirrer, homomixer, ultrasonic disperser or the like having a plurality of shear blades in which particles and ethylene glycol are arranged in parallel with the rotation direction of the stirring blades. The dispersed slurry is desirably filtered with a filter of 1000 mesh or more for the purpose of removing coarse particles and undispersed aggregated particles in the slurry.
[0018]
In the polyester film of the present invention, the antioxidant contained simultaneously with the wet process silica particles is derived from, for example, phenolic, phosphorous, thioether, and mixtures thereof. The addition concentration of the antioxidant contained in the polyester film is in the range of 0.01 to 0.5% by weight, and preferably in the range of 0.05 to 0.3% by weight. When the content of the antioxidant is less than 0.01% by weight, it is difficult to reduce the coreless foreign matter by gelling. On the other hand, when it exceeds 0.5% by weight, there is an effect of reducing the foreign material without nuclei due to gelling, but the amount of the antioxidant present on the film surface is increased, and the adhesiveness of ink or the like is inferior. . Moreover, you may use the mixture of a 1 or more type of antioxidant, and it is preferable that the total density | concentration is in the said range in that case.
[0019]
Examples of phenolic antioxidants include tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 3,9-bis [1,1-dimethyl-2- {β- (3- t-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane, tetrakis [methylene-3- (3 ', 5'- Di-t-butyl-4′-hydroxyphenyl) propionate] methane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′-butylidenebis (6- t-butyl-3-methylphenol), octadecyl 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate, triethylene glycol-bis [3- (3-t- Til-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis [ 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2′-thiodiethylene-bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) Proponate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butyranyl) -1,3,5-triazine, N, N′-hexamethylene (3 , 5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxy-benzylphosphonic acid diethyl ester, 1,3,5- Trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, bis (3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid ethyl) calcium and the like Can be mentioned.
[0020]
Examples of phosphorus antioxidants include phosphoric acid, phosphorous acid, methyl phosphate, ethyl phosphate, triethyl phosphate, phenyl phosphate and the like and esters thereof. Specifically, phosphorus-cyclic neopentanetetrayl-bis (2,6-di-t-butyl-4-methylphenyl) ester, cyclic neopentanetetrayl-bis (octadecyl-phosphite), bis (2, 4-di-t-butylphenyl) pentaerythritol diphosphite, tris (2,4-di-t-butylphenyl) phosphite, 4,4'-butylidene-bis (3-methyl-6-t- Butylphenyl-di-tridecyl) phosphite, 1,1,3-tris (2-methyl-4-ditridecyl-phosphite-5-t-butylphenyl) butane, diphenyl-isooctyl-phosphite, dimethyl-isodecyl-phos Phyto, tris-nonylphenyl-phosphite, tri (mono + dinonylphenyl) phosphite, 4,4′-isopropyl Down - diphenol - alkyl _(C 12 _{-C 15)} such as phosphite.
[0021]
Examples of thioether antioxidants include ditridecyl-thio-di-propionate, tetrakis [methylene-3- (lauryl-thio) propionate] methane, bis [2-methyl-4- {3-n-alkyl (C ₁₂ or _{C 14)} thio - propionyloxy} -5-t-butylphenyl] such as sulfide and the like.
[0022]
The method for adding the antioxidant is not particularly limited, but is performed at an arbitrary stage until the polymer finishes passing through the extruder. For example, (1) a method of adding as an antioxidant slurry in the same manner as the wet method silica particle slurry at the time of polymerization of the raw material polyester, and (2) until the polymer finishes passing through the extruder at the time of forming the polyester film. Add at any stage. For example, there may be mentioned a method in which an addition port is provided in the extruder and an antioxidant is added to the molten or partially molten polyester.
[0023]
In the present invention, when an antioxidant is added in the extrusion step, the antioxidant may be added as a powder or may be added as a slurry dispersed in a suitable solvent. When the dispersion is added in a solvent, water or an organic solvent having a boiling point of 200 ° C. or lower is preferable as the solvent, and ethylene glycol is particularly preferable as the organic solvent. In this case, the extruder is preferably a twin-screw extruder, and the twin-screw extruder preferably has one or more vent ports, and at least one of them has a reduced pressure. That is, it is preferable to remove the solvent in the extrusion process.
[0024]
In the polyester film of the present invention, the number of coreless foreign matters due to gelling is 10 pieces / m ² or less, preferably 5 pieces / m ² or less, more preferably 3 pieces / m ² or less. If there are more than 10 cores / m ² of non-nucleated foreign matter due to gelling, the film will be broken frequently and the filter life will be shortened during the production of the polyester film, resulting in frequent filter replacement and reduced productivity. There is a problem that it is difficult to use to deteriorate film quality.
[0025]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by a following example, unless the summary is exceeded. In addition, the measurement methods and definitions of various physical properties and characteristics in the present invention are as follows. In the examples and comparative examples, “parts” means “parts by weight”.
[0026]
(1) Average particle diameter of particles The average spherical particle diameter was defined as the equivalent spherical diameter of the particles at 50% by weight of the total particles determined by the laser diffraction scattering method (LA-910, manufactured by Horiba, Ltd.).
[0027]
(2) Measured by pore volume nitrogen adsorption / desorption method and calculated by BET equation.
[0028]
(3) 1 g of intrinsic viscosity polymer was dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane (50/50 (weight ratio)) and measured at 30 ° C. using an Ubbelohde viscometer.
[0029]
(4) Filter life (initial pressure loss)
Using a sintered metal filtration filter that cuts foreign matter of 20 μm or more, melt extrusion was performed so that the extruded amount of the molten polymer was 10 g / cm ² · Hr per unit area of the filter, and the filter differential pressure ΔP (72 hours later) The filter life (initial pressure loss) was defined as the difference between the inlet and outlet pressures of the filter.
[0030]
(5) When two polarizing plates with no nuclei are in a crossed Nicol state and a polyester film is placed between the polarizing plates, the bright spot is marked visually, and the marking part is observed with a microscope to check for the presence of nuclei. Confirmed and counted. The measurement area was 1 m ² .
[0031]
(6) Film breakability at the time of film formation The situation in which the film breaks at the time of transverse stretching and heat setting was determined and evaluated by the following three ranks.
○: Almost no film breakage and good productivity Δ: Occasionally film breakage and slightly inferior productivity ×: Frequent film breakage and inferior productivity [0032]
(7) Handling workability The film was divided into the following three ranks regarding the winding work during film production and the film handling workability.
○: Good handleability and smooth work △: Handleability is generally good, but it is slightly smooth ×: Films are easily blocked and wrinkled, and handleability is poor [0033]
(8) Printing ink adhesion Toyo Ink Manufacture Co., Ltd. made using cello-color printing ink CCST39 indigo, applied to the film surface so that the coating thickness after drying is 1.5 μm, and at 80 ° C. for 1 minute. Dry with hot air to obtain a film for evaluation. The film for evaluation was conditioned at room temperature 23 ° C. and humidity 50% RH for 24 hours, and Neroban Co., Ltd. cellotape (registered trademark) (18 mm width) was kept from entering air bubbles on the ink coating surface of the film. It is pasted to a length of 7 cm, and a constant load is given thereon by a 3 kg manual load roll. The film is fixed, one end of the cellophane tape is connected to a 500 g weight, and a distance of 45 cm is evaluated by a method in which a peel test in a 180 ° direction is started after a natural fall. Adhesiveness was determined and evaluated in the following three stages.
○: The printing ink does not peel at all on the cellophane tape surface. Δ: 10 to 50% of the printing ink peels off to the cello tape (registered trademark) side. ×: The printing ink of 60% or more portion of the cellophane tape (registered trademark) side. [0034]
Example 1
[Slurry adjustment]
10 parts of wet-process silica particles having a pore volume of 1.60 ml / g and an average particle diameter of 2.4 μm were dispersed in 90 parts of ethylene glycol. Next, the mixture was dispersed at 10,000 rpm for 60 minutes with a homomixer (TK homomixer manufactured by Tokki Kako) and filtered through a 1000 mesh wire mesh filter to obtain an ethylene glycol slurry.
[0035]
[Production of polyester A]
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are heated and heated, and methanol is distilled off to carry out a transesterification reaction. After 4 hours from the start of the reaction, the temperature rises to 230 ° C. Warm to substantially complete the transesterification reaction. Next, 3 parts of the slurry was added, 0.04 part of ethyl acid phosphate was added, 0.04 part of antimony trioxide was further added, and a polycondensation reaction was carried out for 5 hours to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65. Yeah.
[0036]
[Production of polyester film]
The resulting polyester A and powdered antioxidant (pentaerythritol-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]) are taken in separate hoppers and vented biaxial Supplied to a screw extruder (added amount of antioxidant was 0.1% by weight in the film with a quantitative feeder). Melt-kneaded at 280 ° C. and −100 KPa vented vacuum. The sheet is extruded from a slit die onto a rotary cooling roll at 20 ° C. and rapidly cooled by a rotary cooling roll using an electrostatic application cooling method to obtain an amorphous sheet. The film was stretched 3.5 times at 90 ° C. and 3.7 times in the transverse direction at 110 ° C., and heat treated at 210 ° C. for 3 seconds to obtain a polyester film having a thickness of 12 μm. The characteristics were satisfactory as shown in Table 1 below.
[0037]
Example 2
In Example 1, the wet viscosity silica particle slurry and the antioxidant slurry (the amount of the antioxidant added so as to be 0.1% by weight in the film) were added at the same time when the polyester A was produced, and the intrinsic viscosity was increased. A polyester B of 0.66 was obtained. Only the obtained polyester was supplied to a twin screw extruder with a vent to obtain a polyester film having a thickness of 12 μm. The characteristics were satisfactory as shown in Table 1.
[0038]
Comparative Example 1
In Example 1, only polyester A was supplied to the extruder of a biaxial screw, and it carried out similarly to Example 1, and obtained the 12-micrometer-thick polyester film.
[0039]
Comparative Example 2
A polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1 except that dry silica particles having an average particle diameter of 2.1 μm were used in Example 1.
[0040]
Comparative Example 3
A polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1 except that wet method silica particles having a pore volume of 0.40 ml / g and an average particle size of 2.2 μm were used.
[0041]
Comparative Example 4
A polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1, except that wet method silica particles having a pore volume of 2.10 ml / g and an average particle size of 2.3 μm were used.
[0042]
Comparative Example 5
A polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1 except that wet method silica particles having a pore volume of 1.50 ml / g and an average particle size of 0.08 μm were used.
[0043]
Comparative Example 6
A polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1 except that wet method silica particles having a pore volume of 1.50 ml / g and an average particle size of 5.1 μm were used.
[0044]
Comparative Example 7
In Example 1, a polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1 except that the amount of antioxidant supplied was reduced (added so as to be 0.009 wt% in the film).
[0045]
Comparative Example 8
In Example 1, a polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1 except that the amount of antioxidant supplied was increased (added so as to be 0.6% by weight in the film).
[0046]
Comparative Example 9
In Example 1, a polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1 except that the amount of the wet process silica particles added was 0.009% by weight.
[0047]
Comparative Example 10
In Example 1, a polyester film having a thickness of 12 μm was obtained in the same manner as in Example 1 except that the amount of the wet process silica particles added was 1.1% by weight.
The physical properties and productivity of the films obtained in Examples and Comparative Examples are summarized in Tables 1 and 2 below.
[0048]
[Table 1]

[0049]
[Table 2]

[0050]
Since Examples 1 and 2 satisfy the requirements of the present invention, the core-free foreign matter due to gelation is greatly reduced, and productivity, particularly continuous film-forming properties and filter life are greatly improved. It was. On the other hand, Comparative Examples 1 to 10 were films that did not satisfy the requirements of the present invention, and were inferior in reducing core-free foreign matter and film productivity due to gelling.
[0051]
【The invention's effect】
As described above in detail, the film of the present invention reduces coreless foreign matters due to gelation and is excellent in productivity, particularly continuous film-forming properties and filter life, and has high industrial value.

Claims (1)

Wet silica particles having a pore volume of 0.5 to 2.0 ml / g and an average particle size of 0.1 to 5.0 μm are 0.01 to 1.0% by weight, and an antioxidant is 0%. A biaxially oriented polyester film containing 0.01 to 0.5% by weight, wherein the number of non-nucleated foreign matter due to gelling is 10 / m ² or less.