KR0137329B1 - Manufacturing method of polyester film - Google Patents

Abstract

The present invention relates to a method for producing a polyester film. In the method for producing a polyester film comprising the step of stretching and heat-treating the unstretched polyester sheet, the unstretched polyester sheet is composed of at least three polymer layers, the internal haze of the middle layer polymer of the three layers Is 0.001-0.05 / µm, the outer layer polymer has a surface haze of 0.03-1 and an inner haze of 0.01-0.5 / µm, and thus, the polyester film of the present invention has excellent transparency and excellent running performance. It can be easily used for photography, printing, and graphics that require color reproduction.

Description

Manufacturing method of polyester film

The present invention relates to a method for producing a polyester film, and more particularly, to a method for producing a polyester film having excellent transparency and active activity by coextrusion of a polymer having limited haze.

Polyester films represented by polyethylene terephthalate have excellent mechanical properties, heat resistance, weather resistance, electrical insulation, and chemical resistance, and thus are used in a wide range of fields such as packaging, photography, electrical, magnetic tape, and the like.

Among the various applications, the polyester film used in particular for photography, printing and graphics and graphics is required to have high color reproduction, and therefore excellent optical properties, inter alia, excellent transparency.

Polyester without additives is very transparent in the pure amorphous state, even at a thickness of about 50 μm in excess of 98% of light transmission.

However, in the polyester film produced without the addition of additives, there is a problem in that production and processing efficiency are extremely lowered because the so-called blocking phenomenon, which is attached to the processing rolls or films, is caused because the contact energy of the surface is large.

Therefore, in order to improve such a phenomenon by adding a lubricant as an additive to produce a polyester film having a stable running property.

However, as the amount of lubricant is increased, the running performance is improved, but since the film itself has more impurities, the transparency is further lowered. Thus, in order to produce a high-transparent film, the affinity between the lubricant and the polymer or a lubricant having a refractive index similar to that of the polymer is used. Research is underway to develop and a method of coating the lubricant only on the surface before the film is drawn, but the effect is still insignificant.

It is an object of the present invention to provide a method for producing a polyester film that is excellent in transparency and excellent in running performance and does not generate scratches in view of the above-mentioned problems.

In order to achieve the above object, in the present invention, in the method for producing a polyester film comprising the step of stretching and heat-treating the unstretched polyester sheet, the unstretched polyester sheet is composed of at least three polymer layers, The inner haze of the middle layer polymer of the two layers is 0.001-0.05 / 탆, the surface haze of the outer layer plymer is 0.03-1 and the inner haze is 0.01-0.5 / ㎛ provides a method for producing a polyester film do.

That is, the present invention intends to produce a polyester film having satisfactory transparency and runability by coextruding and stretching a polymer having limited haze.

The surface haze refers to haze caused by diffuse reflection of light due to protrusions present on the surface of the film, and the internal haze refers to haze that increases in proportion to the thickness of the film.

That is, all the haze is a value obtained by following Formula.

Total Haze = Surface Haze + Internal Haze × Film Thickness (μm) --- (1)

The total haze is measured using a Haze Mater, and it is possible to measure the surface and internal haze of each polymer by a simple calculation by measuring two polymers of different thicknesses.

The unstretched sheet introduced in the present invention consists of at least three polymer layers, of which the internal haze of the middle middle layer polymer is 0.001-0.05 / µm.

This is because a polymer having a lower internal haze of less than 0.001 / μm in the middle layer has to suppress the use of a catalyst at the time of manufacture, and the reaction productivity is poor. When the internal haze is larger than 0.05 / μm, the transparency of the entire film is inferior. to be.

Preferably the internal haze is 0.001-0.03 / μm.

Among the three layers, the outer layer polymer has a surface haze of 0.03-1 and an inner haze of 0.01-5 / μm, which means that if the surface haze is smaller than 0.03 and the inner haze is smaller than 0.01 / μm, This is because the runability is poor and scratches are generated during the processing, and if the surface haze is larger than 1 and the inner haze is larger than 0.5 / µm, the transparency of the film is excessively reduced.

Preferably the surface haze is 0.05-0.5 and the internal haze is 0.05-0.4 / μm.

The polymer constituting the middle layer and the outer layer may be homogeneous or heterogeneous as long as the haze value of the above range is satisfied.

In the final film obtained after extending | stretching, it is preferable to make it the sum total of the outer layer thickness to be 0.1-30 / micrometer.

This is because if the sum of the thickness of the outer layer after stretching is thinner than 0.1 / µm, the effect of the present invention is weak, and if the thickness is thicker than 30 µm, the haze becomes too large and undesirable.

More preferably, it is 0.5-20 micrometers.

In addition, in order to obtain an excellent effect, it is preferable to manufacture so that the haze of the final film is 2 or less

This is because a film with high transparency can be produced.

The haze value of the final film can be adjusted by predicting the haze value according to the above formula (1) and adjusting the thickness of each layer.

The method for preparing each layered polymer of the unstretched sheet is not particularly limited and is prepared by applying the conventional polyester polymerization method, but insoluble inorganic particles or organic particles are appropriately selected and added to the polyester to control haze.

Inorganic particles insoluble in polyester may be any known ones such as calcium carbonate, dolomite, glass spare, fiberglass, talc, kaolin, mica, silica, barium sulfate, aluminum silicate, alumina, and the like. It is not recommended to use particles with strong shielding as much as possible.

Organic particles insoluble in polyester include a copolymer of a monovinyl compound having one aliphatic unsaturated bond in a molecule and a compound having two or more aliphatic unsaturated bonds in a molecule with a crosslinking agent, a thermosetting phenol resin, a thermosetting epoxy resin, and a thermosetting compound. Fine powders of urea resin, benzoguanamine resin and fluorine resin can be used.

There is no particular limitation on the type and amount of the organic particles to be added, but in the case of repeated experiments, an excellent effect can be obtained when 0.01-3 wt% of particles having an average particle diameter of 0.001-5 μm are added.

In addition, it was found that more excellent effects can be obtained when using two or more of the particles.

The manufacturing method of the polyester sheet which has three or more layers is not specifically limited, A conventionally well-known coextrusion method can be utilized.

For example, a continuous sheet may be prepared by supplying molten polymer to a multi-manifold die or feedblock die to fix the judge's molten polymer to a rotating cooling drum.

The sheet thus produced is continuously subjected to the longitudinal stretching process, but any one of the single stage and the multiple stage stretching methods may be used.

Between longitudinal stretching and transverse stretching, in-line coating may be performed to improve the adhesiveness, antistatic property, etc. of the film within the range of the surface haze range defined in the claims of the present invention. Corona treatment may be used.

Hereinafter, the present invention will be described in detail through preferred embodiments.

Each characteristic is measured as follows.

1) layer thickness

The cross section of the film was cut with a microtome and observed with an electron microscope.

2) haze

It was measured under white light using Gardner's XL-211 haze meter.

3) light transmittance

It was measured by Murakami Color Co., Ltd. Clarilarita T.M-1D.

4) Average particle size

The scanning electron microscope was used to photograph 50 times the particles 50 times, measured by an image analysis device and the arithmetic average of the particle size of each part.

5) Scratch

The film was visually observed in the polarization field and judged as the number of scratches per 10 cm in width.

0: ◎

1-3: ○

3-10: △

10 or more: ×

Example 1

100 parts by weight of dimethyl terephthalate, 70 parts by weight of ethylene glycol and 0,05 parts by weight of calcium acetate were placed in a reactor and subjected to transesterification.

After 4 hours, 0.3 parts by weight of calcium carbonate particles having an average particle diameter of 0.5 μm were added to the system in which the transesterification reaction was completed, and then 0.06 parts by weight of trimethyl phosphate and 0.04 parts by weight of antimony trioxide were added. To prepare a polyester a.

After drying the said polyester, the film of thickness 100micrometer and 50micrometer was manufactured according to the conventional polyester film manufacturing method, and the surface haze was 0.5 and internal haze was 0.2 / micrometer.

On the other hand, except for the addition of calcium carbonate particles in the production of the polyester, polyester b was produced in the same manner.

Internal haze was 0.005 / micrometer.

After drying each polyester, the polyester a is brought to the outer layer (A, C layer) and the polyester b is brought to the middle layer (B layer), and fed to a die provided with a feed block at 290 ° C. to have a three-layer structure. An amorphous sheet was prepared.

Subsequently, the film was stretched 3.5 times at 90 ° C. in the longitudinal direction and 4.3 times at 110 ° C. in the transverse direction, and heat-treated at 210 ° C. for 3 seconds to produce films having thicknesses of 3, 44, and 3 μm, respectively.

At this time, haze and light transmittance were 1.7 and 94%, and there was no scratch and transparency was good.

The results are shown in Table 1.

Example 2

In the same manner as in the preparation of polyester a in Example 1, 0,1 part by weight of spherical silica having an average particle diameter of 0.5 µm and 0.2 part by weight of alumina having an average particle diameter of 0.01 µm were added instead of calcium carbonate particles having an average particle diameter of 0.5 µm. Polyester c was prepared having a surface haze of 0.4 and an internal haze of 0.1 / μm.

Polyester b was prepared according to the same method as in Example 1.

After drying each polyester, the polyester c to the outside (layers A and C), the polyester b to the center (layer B) and the thickness of each layer was 2, 46, respectively, according to the same method as in Example 1. And a film having a three-layer structure of 2㎛.

Haze and the light transmittance of the obtained film were 1.1 and 96%, and transparency was favorable without a scratch.

Example 3

Polyester d was prepared by the same method as in Example 2, but further adding 0.3 part by weight of calcium carbonate particles having an average particle diameter of 0.5 μm.

Surface haze and internal haze were 0.6 and 0.3 / μm, respectively.

Polyester b was prepared according to the same method as in Example 1.

After drying each polyester, the polyester d to the outside (layers A and C), the polyester b to the center (layer B) and the thickness of each layer is 2, 10, respectively, according to the same method as in Example 1 And a film having a three-layer structure of 2㎛.

Haze and light transmittance of the obtained film were good as 1.8 and 93%.

Example 4

In Example 1, 0.3 parts by weight of a thermosetting epoxy resin having an average particle diameter of 0.8 μm was added instead of calcium carbonate particles having an average particle size of 0.5 μm, so that the surface haze was 0.1 and the internal haze was 0.08 / Polyester e, which is μm, was prepared.

Polyester b was prepared according to the same method as in Example 1.

After drying each polyester, the polyester c (layer C) and polyester e (layer A) in Example 2 were placed outward and the polyester b was placed in the middle (layer B), and the die was installed in a multi-manifold. In the same manner as in Example 1 to obtain a film having a three-layer structure of 4, 38 and 8㎛ thickness of each layer, respectively.

Haze and light transmittance of the obtained film were good as 1.6 and 94%.

Comparative Example 1

Using a polyester b prepared in Example 1 alone, a film having a thickness of 50 μm was prepared.

The haze and light transmittance of the film were good as 0.5 and 98%, but there were many scratches on the film and the blocking phenomenon was severe, so there were many problems in actual use as in secondary processing.

Comparative Example 2

In the same manner as in Example 2, the amount of polyester c supplied to the outer layer (A, C layer) is increased by 8 times and the amount of polyester b supplied to the middle layer (layer B) is reduced to 1/2 Films having a three-layer structure in which the thickness of each layer were 16, 23, and 16 mu m, respectively were prepared.

Haze and light transmittance of the obtained film were poor as 3.8 and 86%.

Table 1 shows the thickness, surface and internal haze and total film properties of each layer in the films prepared according to the above Examples and Comparative Examples.

It can be seen from Table 1 that the film produced by coextrusion of the polymer with limited haze according to the method of the present invention has excellent film properties.

As described above, the polyester film produced according to the method of the present invention has excellent transparency and excellent running performance and hardly scratches, and thus can be easily used for photography, graphics, OHP, etc. You may use it for a dragon.

Claims (1)

Supplying a polymer prepared by a conventional polymerization method to a multi-minifold die or a feed block die and co-extruding to prepare an unstretched sheet, stretching the unstretched sheet in one or multiple stages, and performing heat treatment. In the method for producing a polyester comprising, the step of producing the unstretched sheet is a surface layer of 0.03 to 1 / 탆, respectively formed on both sides of the polymer layer and the polymer layer having an internal haze of 0.001 to 0.05 / μm Coextrusion of a three-layered polymer comprising an outer polymer layer having an inner haze of 0.01 to 0.5 / μm, and stretching and heat treatment of the unstretched sheet are the sum of the thicknesses of the outer layers of the final film that have been stretched and heat treated. The polyester is characterized in that the 0.1 to 30㎛, and the haze of the final film is 2 or less. Law.