KR19990065015A - Biaxially oriented polyester film with excellent transparency - Google Patents

Abstract

The present invention relates to a method for producing a highly transparent polyester film having excellent coiling properties, and more particularly, a polyester in which inert large and small particles are added before the polycondensation reaction after esterifying one or more carboxylic acids and one or more glycols. To produce a two-layer or more co-extruded film that differentiates the particle composition of each layer to provide a method for producing a polyester film excellent in winding properties and transparency used in packaging, product protection, construction materials, laminate, and graphic arts. On the upper surface of the biaxially oriented polyester film, a surface layer consisting of calcium phosphate having an average particle diameter of 0.5-8.0 μm and particles of glass beads and silica particles having an average particle diameter of 0.2 μm or less is formed. Co-extruded laminated film with layer structure or 3 layer structure Damaged biaxially oriented polyester film.

Description

Biaxially oriented polyester film with excellent transparency

The present invention relates to a method for producing a highly transparent polyester film having excellent coiling properties, and more particularly, a polyester in which inert large and small particles are added before the polycondensation reaction after esterifying one or more carboxylic acids and one or more glycols. To produce a two-layer or more co-extruded film that differentiates the particle composition of each layer to provide a method for producing a polyester film excellent in winding properties and transparency used in packaging, product protection, construction materials, laminate, and graphic arts. will be.

Currently, polyester film has excellent physical and chemical properties and is widely used as an industrial base material. In particular, mechanical strength, thermal properties, electrical properties, chemical resistance, moisture resistance, water resistance and transparency have been widely used in packaging, industrial, etc. In order to further secure the transparency of the film, a method of securing a certain level of transparency by minimizing the amount of inert particles added to the polyester film has been attempted. However, due to the opposite payment phenomenon, productivity is reduced due to poor processability of the polyester film. Caused.

That is, when the polyester film is wound, the protrusions are formed by the close contact between the polyester films, resulting in a poor appearance of the film roll, and after coating the photosensitive resin on the film, abnormal refraction of exposure is caused by the projections on the polyester film. This caused a number of problems, such as difficult to manufacture a normal product.

In particular, in order to prevent the occurrence of protrusions in the process of cutting and winding to a certain size after the manufacture of the polyester film, the winding speed is increased because the air layer formed by incorporating air between the polyester films while suppressing adhesion between the polyester films. It leads to a decrease of productivity per unit time. In addition, the roll wound by this method is loosely wound to cause a problem such that the cross-section omission phenomenon occurs at the center of the roll during the process from the product shipment to the post-processing, making it impossible to use in the post-processing.

In order to solve such a problem, a method of improving the activity of a polyester film by using fine particles and coarse particles has been attempted in the past, but after using a silica agent having a particle diameter of 0.1 to 0.5 μm as the fine particles to be used (EP- 0486225A3) After winding the polyester film, the color of the roll became milky, and the image of the product was not good, and there was a limit to simultaneously secure winding and transparency.

Accordingly, an object of the present invention is to provide a method for producing a polyester film having excellent winding and transparency by co-extrusion, and having a good winding state without the appearance of milky roll after winding. In more detail, in the case of the co-extruded two-layer laminated film, the purpose of the present invention is to differentiate the particle design on the back surface, reduce the amount of particles causing turbidity, and add particles only to the surface to improve the winding property. Meanwhile, in the case of the co-extrusion three layers, the coilability can be improved by using a particle-free polyester in the middle layer and particles in both surface layers, and a polyester is used per unit volume of the film by using a particle-free in the middle layer. By reducing the amount of particles significantly, transparency can be improved.

Hereinafter, the present invention will be described in detail, the polyester is made of an aromatic dicarboxylic acid such as terephthalic acid, 2,6-naphthalenedicarboxylic acid or the like and esterification thereof and ethylene glycol mainly as starting materials, but includes another third component. can do. At this time, the dicarboxylic acid component of the starting material of the present invention includes isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, phthalic acid, adipic acid, sebacic acid. These 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, polyester having 80% or more of the repeating structural units composed of ethylene terephthalate or ethylene 2,6-naphthalene structure was better.

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

A feature of the present invention is that the polyester resin used in the present invention uses calcium phosphate or glass beads having a similar refractive index and excellent affinity with the polyester resin as the large particles, and fine particles such as silica as the small particles. By producing a two- or three-layer coextrusion film composed of the surface layer surface to which the particles are added and the intermediate layer (or back layer) surface to which the particles are not added, not only the productivity and the winding property are excellent, but also the polyester having excellent transparency To provide a film.

In the final step of transesterification during polymerization, small and large particles are added and polycondensed to obtain a polyester resin. The polyester film and the resin which do not use particle | grains are fully dried in each dryer, and the laminated sheet is formed through the extruder and die which were designed to be co-extruded, and it is biaxially stretched again, and is excellent in winding property and transparency. Get

The average particle diameters of calcium phosphate and glass beads, which are large particles to be used, are 0.5 to 3.0 μm, more preferably 1 to 2 μm, and the content in the film is 0.001 to 0.3 wt%, preferably 0.004 to 0.2 wt%. . The average particle diameter of the fine particles is 0.2 μm or less, preferably 0.05 μm or less, which is smaller than the average wavelength of white light, and the content in the film is 0.001 to 0.3 wt%, preferably 0.004 to 0.2 wt%.

The biggest feature of the present invention is that coextrusion, which differentiates the particle design of the surface (inner surface), is used to secure winding and transparency at the same time. Another feature is that the particle diameter is 0.5 μm, which is an average wavelength of white light. In view of the fact that the haze shows the maximum value, the large particles of 0.5 µm or more and the fine particles of 0.5 µm or less are mixed.

The polyester film produced by the present invention has a thickness of 9 to 188 μm, has a low coefficient of haze at a coefficient of kinetic friction and a wavelength of 589 nm, and does not look milky after winding with a roll. It is excellent in brittleness and can be wound up tightly without generation of protrusions.

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 to carry out transesterification with methanol being discharged. The reaction mixture was completed transesterification over 4 hours. To the reaction mixture, 0.06 parts of phosphoric acid, 0.88 parts of silica fine particles having an average particle diameter of 0.05 μm, and 0.88 parts of calcium phosphate having an average particle diameter of 1.5 μm were added to the reaction product in the form of an ethylene glycol slurry, and polycondensation was carried out for 4 hours to give an extreme viscosity. Obtained polyester (A) of 0.62.

Except not adding the inorganic particles, the same transesterification reaction and polycondensation reaction as in the production of the polyester (A) were carried out to obtain a polyester (B) having an intrinsic viscosity of 0.62.

Each chip is melt-extruded and cooled and solidified at 290 ° C. so that the chips obtained by mixing the polyester (A) and (B) synthesized above in a weight ratio of 5:95 are used as both surface layers and the non-particle polyester (B) is used as an intermediate layer. To form an amorphous unstretched film laminated in three layers, and the surface layer had a thickness of 3.2 times in the longitudinal direction at 85 ° C. and 4.0 times in the transverse direction at 125 ° C., followed by heat treatment at 220 ° C. for about 3 seconds to obtain a thickness of 12. A biaxially stretched polyester film having a thickness was prepared.

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

Example 2

Example 5 After mixing the polyester particles (A) and the polyester (B) in the ratio of 5: 95 using silica particles having an average particle diameter of 0.05 μm as fine particles and glass beads having an average particle diameter of 1.5 μm as the large particles, In the same manner as in 1, a biaxially stretched polyester film having a thickness of 12 μm was laminated in three layers having no particles used in the intermediate layer.

Example 3

The surface layer was made of a chip containing a mixture of polyester (A) and polyester (B) in a 5:95 ratio using fine silica having an average particle diameter of 0.05 μm as fine particles and calcium phosphate large particles having an average particle diameter of 1.5 μm as a large particle. A biaxially stretched polyester film having a thickness of 12 μm was prepared in the same manner as in Example 1 except that a two-layer laminated film having particles as the back layer was made.

Comparative Example 1

It is a single layer using a chip containing a mixture of polyester (A) and polyester (B) in a ratio of 3: 97 using silica particles having an average particle diameter of 0.05 μm as fine particles and calcium phosphate having an average particle diameter of 1.5 μm as large particles. A biaxially stretched polyester film having a thickness of 12 μm was prepared.

Comparative Example 2

Silica having an average particle diameter of 0.05 μm as fine particles and calcium phosphate having an average particle diameter of 1.5 μm as a large particle was used as a single layer using a chip in which the polyester (A) and polyester (B) were mixed in a 5:95 ratio. To prepare a 12 탆 biaxially stretched polyester film.

Table 1 below summarizes the type, content, size and physical properties of the haze and dynamic friction coefficients of the particles used for the comparative examples.

(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),

The particle size of the film was measured using an electron microscope, and the average particle diameter of the particle was defined as a point of 50% of the volume fraction of the particle in terms of a sphere.

(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 by HAZE METER (300 A of NIPPON DENSHOKO, Inc.), and the turbidity of the film was measured. The measuring method was based on JIS-Z8722.

(4) Threshold

When the state of the roll after winding was visually evaluated, when there were more than three projections having a diameter of 5 mm or more on the surface of the roll, the evaluation was good when there were more than three and the diameter was less than 3 mm and less than three. Even if only one projection having a diameter of 3 mm or more occurred, it was evaluated as defective.

Table 1

The biaxially oriented polyester film according to the present invention not only has excellent winding properties but also significantly reduces the number of particles used per unit volume of the film by using particles free in the intermediate layer, thereby improving transparency.

Claims (2)

On the upper surface of the biaxially oriented polyester film, a surface layer consisting of calcium phosphate having an average particle diameter of 0.5-8.0 μm, particles of grass beads and silica particles having an average particle diameter of 0.2 μm or less is formed, and the intermediate layer or the back layer is a two layer without particles. A biaxially oriented polyester film having a co-extruded laminated film having a structure or a three-layer structure, which has improved winding and transparency. The method of claim 1, The particle size of calcium phosphate and glass beads is 0.001-0.3% by weight, and the content of silica particles is 0.001-0.3% by weight.