KR20060076799A - Polyester resin and biaxially oriented polyester film produced with the same - Google Patents

Abstract

Disclosed are polyester resins and biaxially stretched polyester films which are excellent in process passability and electrical durability, which are useful for producing dielectric films for capacitors. The polyester resin is prepared by mixing a dicarboxylic acid component and a glycol component to prepare a slurry, followed by esterification reaction and polycondensation, having an intrinsic viscosity of 0.50 to 0.75 dl / g, and an average particle diameter of 0.1 to 0.5 μm. 0.05 to 0.25 wt% of aluminum oxide and 0.05 to 0.25 wt% of inorganic particles having an average particle diameter of 0.05 to 0.2 μm selected from the group consisting of silica, calcium carbonate, kaolin, titanium oxide, and zeolite. The present invention also provides a biaxially stretched polyester film produced using the polyester resin.

Polyester film, capacitor, inorganic particle, aluminum oxide, winding property

Description

Polyester resin and biaxially stretched polyester film produced using the same {Polyester resin and biaxially oriented polyester film produced with the same}

The present invention relates to a polyester resin and a biaxially stretched polyester film prepared using the same. More particularly, the present invention relates to a polyester resin and a biaxially stretched polyester which are excellent in process permeability and electrical durability, and are useful for preparing a dielectric film of a capacitor. It is about a film.

In today's trend toward lighter and shorter electronics, parts used inside are also required to be smaller and higher in performance. Accordingly, capacitors used in a wide range of fields from general electrical appliances to precision electronics are also miniaturized and high in performance. Much research is being done for. A capacitor is an electric circuit element for the purpose of charge accumulation and consists of an electrode, a dielectric positioned between the electrodes, and an electrode lead-out terminal. As insulation and dielectric materials for capacitors, polyesters such as polyethylene terephthalate are widely used. The polyethylene terephthalate is more easily wound, slitting and mechanical than polyolefin, polystyrene or polyphenylene sulfide resins. This is because it is excellent in that it is possible to thin the film to a thickness of about 1㎛, and having a large dielectric constant value of about 3.1 has the advantage of compactly manufacturing a relatively large capacity capacitor.

Capacitance is a value that indicates how well charge can be accumulated, and the capacitance of the capacitor is proportional to the width of the electrode and inversely proportional to the distance between the electrodes. Therefore, in order to increase the capacitance per unit volume, an ultrathin dielectric having a thickness of 1 μm or less is used. However, when the dielectric film of the capacitor is ultra-thin, the process passability worsens and the polyester adheres to the roller surface. In order to solve this problem, a method of obtaining an ultra-thin film by laminating a polyester film and another thermoplastic resin film, followed by a casting and stretching process, and peeling has been proposed (JP-A 51-39777). Further problems such as additional burden of the silver equipment, deformation of the film upon peeling after lamination, and stretching irregularities caused by using resins having different thermal properties and wrinkle formation due to thermal deformation are generated.

As another method for improving process permeability, a method of forming internal particles by a reaction catalyst during polymerization or adding external particles to impart irregularities to the film surface has been proposed. However, the method of forming internal particles to impart irregularities on the surface of the film is excellent in affinity with the polymer, and has the advantage of reducing the voids around the particles that have a fatal effect on the insulation properties of the product after stretching, but the particle size It is difficult to control the process to control and the particle amount and size is limited, so it is difficult to achieve a good process passability when manufacturing a thin film, the method of adding external particles is somewhat easy to control the size and content of the particles, Due to the lack of affinity with the polymer, voids are formed around the particles after stretching, so that the film thickness around the particles becomes thin, and thus there is a disadvantage that they are destroyed when a high voltage is applied or a long voltage is applied.

Accordingly, it is an object of the present invention to provide a polyester resin and a biaxially stretched polyester film excellent in process passability and electrical durability.

Another object of the present invention is to provide a polyester resin and a biaxially stretched polyester film useful for producing a dielectric film of a capacitor.

In order to achieve the above object, the present invention is prepared by mixing the dicarboxylic acid component and the glycol component to prepare a slurry, and then produced by the esterification reaction and poly-condensation, the intrinsic viscosity is 0.50 to 0.75 dl / g, the average 0.05 to 0.25 wt% of aluminum oxide having a particle diameter of 0.1 to 0.5 μm and 0.05 to 0.25 wt% of inorganic particles having an average particle diameter of 0.05 to 0.2 μm selected from the group consisting of silica, calcium carbonate, kaolin, titanium oxide, and zeolite. It provides a polyester resin. The present invention also provides a biaxially stretched polyester film produced by using the polyester resin.

Hereinafter, the present invention will be described in more detail.

In the present invention, a dicarboxylic acid component and a glycol component are mixed to prepare a slurry, followed by esterification reaction and polycondensation, and have an intrinsic viscosity of 0.50 to 0.75 dl / g, with an average particle diameter of 0.1 to 0.5 μm. Provided is a polyester resin comprising 0.05 to 0.25 wt% of inorganic particles having an average particle size of 0.05 to 0.2 μm selected from the group consisting of 0.05 to 0.25 wt% aluminum and silica, calcium carbonate, kaolin, titanium oxide, and zeolite. Representative polyester resins used in the present invention is polyethylene terephthalate, for example, can be prepared by transesterification and polycondensation of dimethyl terephthalate or terephthalic acid and ethylene glycol, wherein the batch and continuous reactors Can be used. In addition, the polyester resin may be obtained by reacting various dicarboxylic acid components and glycol components. As the dicarboxylic acid components, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,5-naphthalene dicarboxylic acid Or an aliphatic dicarboxylic acid such as sebacic acid, and the glycol component may be an aliphatic glycol such as ethylene glycol, 1,4-butanediol, diethylene glycol, or other aromatic glycol. As for the melt specific resistance of the polyester resin superposed | polymerized as mentioned above, 1.0 * 10 <^6> cm <cm> or more is preferable, 1.0 * 10 <^7> cm <cm> or more is more preferable, It is preferable that intrinsic viscosity is 0.50-0.75dl / g. If the intrinsic viscosity of the polyester resin is less than 0.50dl / g, there is a problem in the mechanical properties of the film, if it exceeds 0.75dl / g has a high melt viscosity, there is a problem in the extrusion and film forming process due to excessive load.

The polyester film used as the dielectric for the capacitor has to go through the winding process of the device when manufacturing the capacitor. Therefore, the film must have a proper coefficient of friction and runability. It is preferable to add the inorganic particles at any stage before the polyester polymerization is terminated within the range to be maintained. However, when the external particles are excessively introduced into the film, as mentioned above, after stretching due to lack of affinity with the polymer, voids are formed around the particles, resulting in a thin film thickness around the particles to apply a high voltage or a long time voltage. It is best to add as little particle as possible, since it will break when added.

The inorganic particles used in the present invention are for imparting adhesion and affinity with aluminum used as electrodes, and include aluminum oxide having an average particle diameter of 0.1 to 0.5 µm and silica, calcium carbonate, kaolin, having an average particle diameter of 0.05 to 0.2 µm, One type of inorganic particles selected from the group consisting of titanium oxide and zeolite may be mixed and used, wherein when the particle size of the inorganic particles is less than 0.05 μm, the roughness of the film is lowered and adhesion occurs to the roller during the process pass. In addition, air flows in between the roller and the film, causing a problem that the film flows. When the particle diameter of the inorganic particles exceeds 0.5 µm, the projections on the surface are transferred to the film, which acts as a defect. The content of the inorganic particles is preferably 0.05 to 0.25% by weight based on the total polyester resin. When the content of the inorganic particles is less than 0.01% by weight, the roughness (roughness) of the film is lowered, the adhesion occurs on the roller during the process or the air flows between the roller and the film, there is a problem that the film flows, the content of the inorganic particles When it exceeds 0.25% by weight, the insulation property is decreased when high voltage is applied, and capacity control is not easy when manufacturing a capacitor device due to the difference in dielectric constant between inorganic particles and polymer, and the hardness of aluminum oxide causes defects in film cutting.

The present invention also provides a monoaxially or laminated biaxially stretched polyester film produced using the polyester resin. The biaxially stretched polyester film is melt extruding the polyester resin; Casting by electrostatic method; It is produced through the longitudinal stretching step. The melt extrusion of the polyester resin is performed at 265 to 305 ° C., and a sheet having a thickness of 30 to 60 μm by an electrostatic pinning technique which is quenched and solidified on a rotary cooling drum fixed at a surface temperature of 30 ° C. ) Is manufactured. The sheet thus prepared is first drawn in the longitudinal direction in the range of 80 to 120 ° C. in 3.0 to 6.0 times, and then recooled to be stretched in the transverse direction in the range of 100 to 140 ° C. and then stretched to 3.0 to 5.0 times. Heat treatment is performed at 3 ° C. for 15 seconds to prepare a film having a thickness of 3.5 μm to 8.0 μm.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples. The following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by the following examples.

[Examples 1 to 6 and Comparative Examples 1 to 4] Polyethylene terephthalate resin and biaxially stretched polyethylene terephthalate film production

Terephthalic acid and ethylene glycol were mixed at a ratio of 1: 1.2, to prepare a slurry, and esterification reaction was carried out to prepare a low molecular weight oligomer. Phosphoric acid was added as an antimony trioxide and a heat stabilizer as a catalyst, and a polycondensation reaction was carried out for 3 hours to prepare a polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g.

The prepared polyethylene terephthalate resin was melt-extruded at 290 ° C. to be formed into a sheet having a thickness of 80 μm, stretched 3.5 times in the longitudinal direction of the sheet at 90 ° C., and stretched 4.0 times in the transverse direction of the sheet at 140 ° C. After the heat treatment at 230 ℃ to prepare a biaxially stretched polyethylene terephthalate film having a thickness of 57 ㎛ 6㎛ crystallinity, the surface roughness, process permeability and device properties (capacity change, durability) of the film was measured and the results are shown in the table 1 is shown together.

[Property evaluation method]

1) Surface roughness: Measured according to JIS B0601-1976.

2) Process permeability: After passing the polyethylene terephthalate film through the roller at a speed of 200 m / min for 1 hour at room temperature, the degree of sticking to the meander and the roller was measured five times, and determined according to the following criteria.

-1st level: All 5 levels of roller barrel

-2nd level: 3 ~ 4 times good level

-3rd level: 1 ~ 2 times pass through roller

-Level 4: All rollers defective.

 3) Capacity change (△ C): After winding the polyethylene terephthalate film together with the electrode, the capacity before and after heat treatment at 110 ℃ is measured and the capacity change after heat treatment is good. If so, it was determined to be defective.

4) Durability of the condenser: The polyethylene terephthalate films produced in the above Examples and Comparative Examples were applied to 100 condensers each having a capacity of 1 kV, and were applied at 100 V, and were broken by performing 50,000 times of on / off at 2 second intervals. Or when the difference in capacity before and after the test is 0.5% or more.

Inorganic particles Surface Roughness (㎛) Fair passability Element property Silica Aluminum oxide Particle size (㎛) Content (% by weight) Particle size (㎛) Content (% by weight) △ C durability Example 1 0.1 0.05 0.3 0.10 0.04 1st grade Good Good Example 2 0.1 0.10 0.5 0.05 0.04 1st grade Good Good Example 3 0.05 0.15 0.3 0.05 0.04 1st grade Good Good Example 4 0.05 0.10 0.5 0.10 0.06 1st grade Good Good Example 5 0.1 0.10 0.1 0.10 0.04 1st grade Good Good Example 6 0.05 0.05 0.3 0.15 0.05 1st grade Good Good Comparative Example 1 0 0 0.7 0.15 0.04 1st grade Bad Bad Comparative Example 2 0.04 0.15 0 0 0.04 Level 3 Good Good Comparative Example 3 0.1 0.02 0.3 0.05 0.03 Level 3 Good Good Comparative Example 4 0.1 0.15 0.3 0.15 0.07 1st grade Bad Bad

From Table 1, it can be seen that the polyethylene terephthalate film prepared in Examples 1 to 6 of the present invention are all first-class passability, good capacity change and durability of the capacitor using the same. However, Comparative Examples 1 and 4 have good process passability, but have poor capacity change and durability, and Comparative Examples 2 and 3 have good capacity change and durability, but have poor process passability, making them unsuitable as dielectrics for capacitors. Can be.

As described above, the polyester resin and the biaxially stretched polyester film according to the present invention are excellent in process passability and electrical durability, and are useful for producing a dielectric film of a capacitor.

Claims (4)

The slurry was prepared by mixing the dicarboxylic acid component and the glycol component, and then prepared by esterification reaction and polycondensation, and having an intrinsic viscosity of 0.50 to 0.75 dl / g, and having an average particle diameter of 0.1 to 0.5 μm of 0.05 to aluminum oxide. A polyester resin comprising 0.25 wt% and 0.05 to 0.25 wt% of inorganic particles having an average particle diameter of 0.05 to 0.2 μm selected from the group consisting of silica, calcium carbonate, kaolin, titanium oxide, and zeolite. The polyester resin according to claim 1, wherein the dicarboxylic acid component is dimethyl terephthalate and the glycol component is ethylene glycol. The biaxially stretched polyester film of single layer or lamination manufactured using the polyester resin of Claim 1. The biaxially stretched polyester film of claim 3, wherein the biaxially stretched polyester film has a thickness of 3.5 to 8 μm.