KR100231760B1 - Polyester film - Google Patents

Abstract

According to the present invention, 0.04 to 0.25% by weight of spherical silica particles having an average particle size of 0.01 to 0.2 µm is added after esterification of carboxylic acid and glycol, and 0.008 to spherical organic polymer particles having an average particle diameter of 0.3 to 1.5 µm. By biaxially stretching the polyester resin condensation-polymerized by adding 0.08% by weight to 0.08% by weight, the surface roughness of the film is smoothed, thereby minimizing surface scattering of light, and using the organic polymer particles having excellent transparency and affinity with the polyester resin. Since the void which causes the transparency fall is removed, the biaxially-oriented polyester film excellent in transparency and glossiness can be obtained.

Description

Biaxially oriented polyester film with excellent transparency

The present invention relates to a biaxially oriented polyester film having excellent transparency and glossiness. More specifically, two or more small and small carboxylic acids and one or more glycols have different average particle diameters before and after condensation polymerization. The present invention relates to a high transparency and high gloss polyester film having excellent winding property used for packaging, laminating, graphic arts, etc. by adding inert spherical particles of.

Polyester films have excellent physical and chemical properties and are widely used as industrial base materials. In particular, the mechanical strength, thermal properties, electrical properties, chemical resistance, moisture resistance, water resistance, etc. is excellent, it is widely used for packaging, industrial use. Particularly, in order to improve the transparency of the film, a method of securing a certain level of transparency by minimizing the amount of inorganic inert particles added during the manufacture of a polyester film has been attempted. It became worse and caused a decrease in productivity.

That is, when the polyester film is wound, protrusions are formed by the close contact between the polyester films, resulting in poor appearance of the polyester film roll, and when the product is processed by exposure after coating a photosensitive material on the polyester film, the polyester film Abnormal refraction of exposure occurred due to the projections in, making normal products impossible.

In particular, in order to prevent projections in the process of cutting and winding the polyester film to a certain size, air is mixed between the polyester films, and the winding speed is slowed down because the winding is performed while suppressing the adhesion between the polyester films by the formed air layer. Hourly productivity decreases. In addition, the roll wound as described above has a problem such that it is difficult to use in post-processing due to the looseness of the cross section occurs at the center of the roll during the process of moving the product after the product is shipped.

In order to solve such a problem, conventionally, an external particle method of adding a single inorganic compound such as kaolin, silicon dioxide, calcium carbonate and the like during polyester polymerization is applied. In this case, it is difficult to simultaneously secure the diactivity and transparency of the polyester film.

In other words, if an inert inorganic compound is used to improve the activity, the haze of the transparency of the polyester film is increased due to the opposite phenomenon, so that the amount of the inorganic compound used in the field of use of the polyester film requiring high transparency is increased. It is inevitable.

Therefore, a method of improving the activity of a polyester film by using fine particles and coarse particles has been attempted. However, when using 0.1 to 0.5 μm of silica (EP-0486225A3) as the fine particles used, winding the polyester film with a roll The color of the exterior was milky, so the image of the product was not good.

Accordingly, an object of the present invention is to provide a polyester film having excellent winding properties, high transparency and high gloss, and having no appearance of milky roll after winding.

Detailed Description of the Invention The polyester is made from aromatic dicarboxylic acids such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, or esterification thereof and ethylene glycol as starting materials, but may contain another third component. . At this time, the dicarboxylic acid component as the starting material of the present invention includes isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, phthalic acid, adipic acid, sebacic acid. Such acid components may be used alone or in combination of two or more.

Another starting material, the glycol component includes, for example, ethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentylglycol, and the like, and may be used in one kind or two or more kinds.

In the present invention, it is possible to obtain a polyester film in which 80% or more of the repeating structural units are composed of ethylene terephthalate or ethylene 2,6-naphthalene structure.

The polyester in the present invention may include additives such as heat stabilizers, anti-broking agents, antioxidants, antistatic agents, ultraviolet absorbers and the like.

The greatest feature of the present invention is to provide a polyester film having excellent transparency and transparency as well as excellent productivity and winding property by mixing two spherical particles having different average particle diameters.

The present invention adds 0.04 to 0.25% by weight of spherical silica particles having an average particle size of 0.01 to 0.2 μm and esters of spherical organic polymer particles having an average particle size of 0.3 to 1.5 μm before esterification of carboxylic acid and glycol. To 0.08% by weight is added to cause a polycondensation reaction to obtain a polyester resin, from which a biaxially oriented polyester film having excellent transparency is obtained.

In the present invention, the spherical silica particles of the two large and small inert particles having different average particle diameters are more preferably in average particle size of 0.03 to 0.1 탆, and the addition amount is preferably 0.08 to 0.20% by weight, and the average of spherical organic polymer particles is average. The particle size is 0/5 to 0.1 mu m, and the amount of addition is preferably 0.01 to 0.04 wt%.

If the average particle diameter of the spherical silica particles is smaller than 0.01 mu m, the particle agglomeration is severe and the surface of the film becomes very rough, and if larger than 0.2 mu m, the transparency of the film is lowered. In addition, when the content of the spherical silica particles is less than 0.04% by weight, the coefficient of friction increases, the film winding property is worse, and when more than 0.25% by weight, the transparency is reduced.

Moreover, when the average particle diameter of spherical organic polymer particle | grains is smaller than 0.3 micrometer, the winding characteristic of a film will fall, and when larger than 1.5 micrometers, transparency of a film will fall. In addition, when the content of the spherical organic polymer particles is less than 0.008% by weight, the film winding property deteriorates, and when more than 0.08% by weight is used, the transparency decreases.

When the film production process is described, in the final process of transesterification, small and large particles are added and polycondensed to obtain a polyester resin. The polyester resin is sufficiently dried in a drier, a sheet is formed through an extruder, and the sheet is biaxially stretched again to obtain a polyester film having excellent winding properties and transparency.

The biggest feature of the present invention is that since the small particles are all spherically dispersed in a spherical shape, the film surface roughness is smooth, so that the surface scattering of light due to the roughness is minimized, thereby improving transparency. In addition, by using organic polymer particles having excellent affinity with the polyester resin, another feature is to remove voids that cause a decrease in transparency. Further, by using fine particles much smaller than the average wavelength of white light, the protrusions on the winding roll can be effectively suppressed without affecting the haze rise.

The polyester film produced by the present invention has a thickness of 9 to 188 µm, haze of 1.0% or less at a wavelength of 589 nm, a coefficient of kinetic friction of less than 0.48, and an appearance after winding with a roll. It has no winding and can be wound tightly without any protrusion due to its excellent winding property when slitting.

The following examples and comparative examples further illustrate the invention but do not limit the invention.

Example 1

100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, 0.09 parts of manganese acetate tetrahydrate, and 0.04 parts of thymonium trioxide were heated in a reactor and run out of methanol to effect transesterification. After transesterification of the reaction mixture over 4 hours, 0.06 parts of phosphoric acid was added to the reaction mixture, and 1.0 parts of spherical silica small particles having an average particle diameter of 0.05 µm and 0.2 parts of polystyrene organic particles having an average particle diameter of 0.5 µm were ethylene glycol slurry. It was added to the reaction product in the form and polycondensation was carried out for 4 hours to obtain polyether (A) having an intrinsic viscosity of 0.62.

Except not adding the particles, the same transesterification and polycondensation reaction as in the production of the polyester (A) were carried out to obtain a polyester (B) having an intrinsic viscosity of 0.61.

The polyester (A) (B) synthesized above was mixed at a weight ratio of 15:85, melt-extruded and cooled to solid at 290 ° C to form an amorphous unstretched film, which was 3.2 times in the longitudinal direction at 85 ° C and 125 ° C. Was stretched 4.0 times in the transverse direction and heat-treated at 220 ° C. for about 3 seconds to produce a biaxially stretched polyester film having a thickness of 25 μm.

Since then, various physical properties of the polyester film obtained here were evaluated.

Example 2

100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, 0.09 parts of manganese acetate tetrahydrate and 0.04 parts of thymonium trioxide were heated in a reactor to carry out transesterification with methanol. The reaction mixture was completed transesterification over 4 hours. After adding 0.06 parts of phosphoric acid to the reaction mixture, 1.0 parts of spherical silica small particles having an average particle diameter of 0.05 µm and 0.1 parts of polystyrene organic particles having an average particle diameter of 1.0 µm were added to the reaction product in the form of an ethylene glycol slurry and polycondensed for 4 hours. Was carried out to obtain polyester (C) having an intrinsic viscosity of 0.62.

After mixing polyester (C) and polyester (B) in a ratio of 15:85, a biaxially stretched polyester film having a thickness of 25 μm was prepared in the same manner as in Example 1.

Comparative Example 1

Using the fine particles of silica having an average particle diameter of 0.3 μm and the large particles of precipitated silica having an average particle size of 2 μm as large particles, a polyester was prepared by the method of Example 1 and mixed with the polyester (B) in a ratio of 15:85. Then, a biaxially stretched polyester film having a thickness of 25 μm was prepared in the same manner as in Example 1.

Comparative Example 2

0.1 parts of precipitated silica particles having an average particle diameter of 2 µm were added alone to the reaction product in the form of an ethylene glycol slurry to prepare a polyester, followed by mixing with a polyester (B) in a ratio of 15:85, followed by the same method as in Example 1. A biaxially stretched polyester film having a thickness of 25 μm was prepared.

In Table 1 below, the physical properties such as type, content, size, haze, and dynamic coefficient of friction for each of the examples and the comparative examples are shown. In addition, the physical property measurement of the biaxially oriented film was carried out according to the following method.

(1) Average particle size of particles

The average particle diameter of the particle slurry was measured using a particle size distribution analyzer ("Granulometer HR-850" manufactured by Silas, France), and the particle size on the film was measured by using an electron microscope. The point which is% was made into the average particle diameter of a particle | grain.

(2) runability

Static and dynamic coefficients of friction were measured by ASTM-B1894 using a coefficient of friction coefficient manufactured by Kang Shin.

(3) haze

The biaxially stretched film was measured with a haze meter (300A manufactured by Nippon Denshoku Co., Ltd.) to measure the turbidity of the film. The measuring method was based on JIS-Z8722.

(4) film color

Judging by the naked eye to judge milkiness

A: No milky color. B: There is a little milky color.

C: There is a lot of milk.

(5) film winding

After slitting, the film roll is visually discriminated to determine the grade.

A: Normal winding B: Can be used but projections exist.

C: Unusable, many projections exist.

The present invention adds two large and small spherical inert particles having different average particle diameters in the final process of transesterification and biaxially stretches a polyester resin subjected to condensation polymerization to smooth the surface of the film, thereby minimizing surface scattering of light, and thus transparency. By using the organic polymer particles having excellent affinity with the polyester resin and excellent in affinity, the voids causing the decrease in transparency can be removed, thereby improving the glossiness.

Claims (2)

In the final transesterification process, 0.04 to 0.25% by weight of spherical silica particles having an average particle diameter of 0.01 to 0.2 μm and 0.008 to 0.08% by weight of spherical organic polymer particles having an average particle diameter of 0.3 to 1.5 μm were subjected to a polycondensation reaction. A biaxially oriented polyester film excellent in transparency, which is obtained from an ester resin. The biaxially oriented polyester film having excellent transparency according to claim 1, wherein polystyrene particles are used as the organic polymer particles.