KR100439626B1 - Two-axially drawn polyester film - Google Patents

Abstract

The present invention relates to a biaxially stretched polyester film, wherein the polyester film of the present invention comprises at least 60 mol% of ethylene terephthalate repeating units and has a first viscosity of 0.4 to 0.9 dl / g, the first polyester resin 60 mol% or more of ethylene terephthalate repeating units are included on both surfaces of the first polymer resin layer formed of 3 to 10% by weight of inorganic particles and 3 to 10% by weight of polyolefin resin based on 1 polyester resin. A second polyester resin having an intrinsic viscosity of 0.4 to 0.9 dl / g and a second polymer resin layer formed of 0.04 to 0.1 wt% of a fluorescent brightener based on the second polyester resin are laminated. It is done. The biaxially stretched polyester film according to the present invention is excellent in hiding power, glossiness and whiteness, and has good stretching processability and coating property, and is useful for various labels, printing materials, decorations, and billboards.

Description

Two-axially drawn polyester film

The present invention relates to a biaxially stretched polyester film, and more particularly, has excellent hiding power, glossiness and whiteness, good drawing processability and coating property, and is useful for various labels, printing materials, decorations, and billboards. It is about a film.

Conventionally, various labels, advertisement boards, etc. were manufactured using polyvinyl chloride, paper, etc. as a raw material. Films made of polyvinyl chloride have a weak impact strength and heat resistance, and are easily broken by external impact, and the film is easily deformed due to heat generated during printing, and there is a problem in that environmental hormones such as dioxins are discharged during incineration. . In addition, in the case of paper, physical properties are worse in terms of water resistance, mechanical strength and durability.

In view of these problems, the amount of film produced using polyester as a raw material is gradually increasing.

Polyethylene terephthalate, a raw material of polyester film, is not only chemically and physically stable and high in mechanical strength, but also excellent in heat resistance, durability, chemical resistance and electrical insulation, and is suitable for magnetic recording media, capacitors, packaging paper, photographic films, and various moldings. It is widely used throughout the industry for applications such as processed products. In particular, the white polyester film used for labels, printing materials, decorations and billboards is imparted hiding power by adding a titanium compound or a barium compound as a pigment, but when the film is made thin, the hiding power is deteriorated. Therefore, in the case of a thin film, the amount of inorganic particles to be added or the particle size of the added particles should be increased to improve the hiding power. However, according to this method, the film is poor in elongation and the roughness is reduced, the gloss is reduced.

Another method of increasing the hiding power is to add a polyolefin resin in addition to the inorganic particles or to coat the polyolefin resin on the surface of the inorganic particles to be added. In this method, however, the olefine resin moves to the surface of the film to reduce the surface energy of the film, thereby deteriorating the coating suitability of the film and causing breakage in the stretching process during film production due to bubbles formed throughout the film. It is easy, and the mechanical property is bad, such as surface strength falling.

Accordingly, the technical problem to be solved by the present invention is to solve the above problems, excellent hiding power, gloss and whiteness, good stretching processability and coating properties, biaxially stretched polyester useful for various labels, printing materials, decorations and billboards, etc. To provide the film.

In order to achieve the above technical problem, the present invention, the first polyester resin containing an ethylene terephthalate repeating unit 60 mol% or more and the intrinsic viscosity of 0.4 to 0.9dl / g, 3 to 3 based on the first polyester resin 60 mol% or more of ethylene terephthalate repeating units are included on both surfaces of the first polymer resin layer including 10 wt% of inorganic particles and 3 to 10 wt% of polyolefin resin, and the ultimate viscosity is 0.4 to 0.9 dl / g. A biaxially stretched polyester film comprising a second polymer resin layer formed by laminating a phosphorus second polyester resin and a 0.02 to 0.1% by weight fluorescent brightener based on the second polyester resin to provide.

In the biaxially stretched polyester film according to the present invention, the average particle diameter of the inorganic particles added to the first polymer resin layer is preferably 0.1 to 3 µm, and such inorganic particles include titanium dioxide, barium sulfate and zinc sulfide. Any one or more selected from the group consisting of can be used.

In addition, polyethylene, polypropylene, and copolymers thereof may be used as the polyolefin resin mixed with the first polyester resin of the first polymer resin layer.

In the biaxially stretched polyester film according to the present invention, the fluorescent brightener added to the second polymer resin layer is preferably a bisbenzoazole-based fluorescent brightener.

Hereinafter, a biaxially stretched polyester film and a method of manufacturing the same according to the present invention will be described in detail.

The present invention, the first polyester resin containing at least 60 mol% ethylene terephthalate repeating unit and the intrinsic viscosity of 0.4 to 0.9dl / g, 3 to 10% by weight of inorganic particles based on the first polyester resin and A second polyester resin having an intrinsic viscosity of 0.4 to 0.9 dl / g and containing at least 60 mol% of ethylene terephthalate repeating units on both surfaces of the first polymer resin layer including 3 to 10 wt% of a polyolefin resin; It provides a biaxially stretched polyester film, characterized in that the second polymer resin layer formed by laminating 0.04 to 0.1% by weight of a fluorescent brightener based on the second polyester resin is laminated.

The 1st and 2nd polyester resin used for the polyester film of this invention contains 60 mol% or more of ethylene terephthalate repeating units. If the ethylene terephthalate repeating unit is less than 60 mol%, there is a problem that the thermal stability of the polyester film containing it is lowered. In addition to the ethylene terephthalate repeating unit, one or more other components consisting of aromatic dicarboxylic acid and diol may be copolymerized within 40 mol%. Such aromatic dicarboxylic acids include dimethyl terephthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclobutanedicarboxylic acid, cyclohexanedicarboxylic acid, 5-sulfoisophthalic acid and 5-sulfopropoxyiso Phthalic acid, difetyldicarboxylic acid, diphenoxyalkanedicarboxylic acid, adipic acid, sebacic acid, anthracenedicarboxylic acid, and the like. Examples of the diol component include ethylene glycol, trimethylene glycol and tetramethylene. Alkylene glycols such as glycol, pentamethylene glycol, hexamethylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and the like.

The first and second polyester resins used in the biaxially stretched polyester film of the present invention were dissolved in 25 ml of orthochlorophenol at a concentration of 0.3 g at 35 ° C., and the ultimate viscosity measured by the three-point method was 0.4 to 0.9 dl /. It is preferable that it is g, and it is more preferable that it is 0.5-0.8 dl / g. If the polyester resin having an intrinsic viscosity of less than 0.4 dl / g is used for the film, there is a fear that breakage occurs during stretching and the mechanical strength of the final product may be lowered. In addition, if the intrinsic viscosity of the polyester resin exceeds 0.9dl / g, there is a fear that the extrusion process is unstable due to the increase in shear stress as the melt viscosity rises.

In the biaxially stretched polyester film of the present invention, the content of the inorganic particles added to the first polymer resin layer is preferably 3 to 10% by weight based on the total amount of the first polyester resin, but less than 3% by weight of the film The hiding power improvement effect of is insignificant, and when it exceeds 10% by weight, physical properties such as stretchability of the film are lowered. It is preferable to use any one or more selected from the group consisting of titanium dioxide, barium sulfate and zinc sulfide as the inorganic particles.

In order to improve the concealability of the biaxially stretched polyester film of the present invention, the light scattering effect should be maximized. In particular, since the diffraction of light hardly occurs when the particle size of the inorganic particles is too large or small, the particle size of the inorganic particles is preferably 0.1 to 3 µm which is slightly smaller than 1/2 of the wavelength of the light to be scattered.

In the biaxially stretched polyester film of the present invention, the polyolefin resin mixed with the first polyester resin is preferably mixed with 3 to 10% by weight based on the first polyester resin component, within the range of Mechanical properties can be maintained while improving hiding power.

It is preferable to use any one selected from the group consisting of polyethylene, polypropylene, and copolymers thereof as the polyolefin resin.

In the biaxially stretched polyester film of the present invention, the second polymer resin layer contains a fluorescent brightener. Fluorescent brighteners emit light by absorbing light energy in the ultraviolet region and displacing the energy in the short wavelength region of visible light. Therefore, the short wavelength reflectance of visible light is supplemented when only inorganic materials are added. The fluorescent brightener preferably has a reflectance of 75% or more at 440 nm, which is a short wavelength region of visible light. The amount of the fluorescent brightener is preferably 0.04 to 0.1% by weight based on the total amount of the second polyester resin forming the second polymer resin layer. When the content is less than 0.04% by weight, the effect of increasing the reflectance is insignificant, and the content is greater than 0.1% by weight. The lower surface of the film not only becomes blue but also lowers the intrinsic viscosity of the polyester resin, thereby degrading the moldability and mechanical properties of the film.

As the optical brightener used in the biaxially stretched polyester film of the present invention, it is preferable to use a bisbenzoazole fluorescent brightener, and as such a bisbenzoazole fluorescent brightener, 2,2 '(1,2-ethenedyldi- 4,1phenylene) bisbenzoxazole (2,2 '(1,2-Ethenediyldi-4,1 Pheyl

ene) bisbenzoxazole).

In the biaxially stretched polyester film of the present invention, the second polymer resin layer is laminated on both surfaces of the first polymer resin layer containing polyolefin. Therefore, it is possible to prevent the polyolefin resin contained in the first polymer resin layer from moving to the surface of the film, thereby maintaining good coating suitability, stretchability and mechanical properties of the film.

The biaxially stretched polyester film of the present invention can be produced, for example, by the following method.

In the method for preparing the first and second polymer resins containing inorganic particles having a content according to the present invention and polyolefin resins or fluorescent brighteners, these additives are added to ethylene glycol to form a slurry, followed by direct esterification reaction. Or a process for producing a master batch chip in which a transesterification reaction is carried out, and a polyester polycondensate in which all or part of an additive is added at a high concentration is mixed with a polyester resin containing no additive in an extrusion process. Can be. In the latter case, it is easy to control the concentration of the masterbatch chip, which is advantageous for the small quantity multiplication. In particular, in order to improve the dispersion degree of an additive, the method of manufacturing the polyester master chip which has 60-80 weight part, and then mixing with resin which does not contain an additive is preferable.

In this way, after obtaining a resin containing the additive of the present invention, a film is prepared, for example, according to the commonly known tee-die method or inflation method. That is, after the resin containing the additive is mixed with the resin containing no additive and melted, the second polymer resin layer is laminated around the first polymer resin layer in the feed block. Subsequently, a three-layer sheet is formed by extruding through a coextrusion die, and then biaxially stretched to obtain a biaxially stretched polyester film. In this case, it is preferable that the total draw ratio of the sheet is 12 or more. In some cases, the film may be heat treated to impart dimensional stability.

The film thus obtained can be appropriately designed depending on the application, but is preferably 15 to 100 µm. In addition, the thickness ratio of the first polymer resin layer and the second polymer resin layer is also not particularly limited, but considering the properties of the film, the thickness of the second polymer resin layer is preferably 5/100 to 15/100 of the total film thickness. Do.

The surface of the biaxially stretched polyester film of the present invention may be corona discharge-treated or further coated with another resin, and other resin layers may be further laminated or laminated.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, it is a matter of course that the scope of the present invention is not limited to the following examples.

EXAMPLE

Example 1

Dimethyl terephthalate and ethylene glycol were mixed in an equivalent ratio of 1: 2, and then a transesterification catalyst was added thereto to prepare bis-hydroxyethylene terephthalate as a monomer of polyethylene terephthalate. Subsequently, a polycondensation catalyst was added to complete the polycondensation reaction to prepare a polyethylene terephthalate resin having an intrinsic viscosity of 0.64 dl / g.

Subsequently, using a compounder screw rpm 300 to prepare a master chip in which 70% by weight of polyethylene terephthalate resin, 20% by weight of titanium dioxide having an average particle diameter of 0.5 μm and 10% by weight of polypropylene were prepared at 285 ° C. A raw material resin of the first polymer resin layer was prepared by mixing 1: 1 with the polyethylene terephthalate resin not added.

In addition, bisbenzoazole-based fluorescent brightener (2,2 '(1,2-') in 99% by weight of polyethylene terephthalate resin at 285 ° C using a compounder screw rpm 300.

Ethentyldi-4,1phenylene) bisbenzoxazole (2,2 '(1,2-Ethenediyldi-4,1 Pheylene) bisbenzo

After preparing a master chip mixed with 1% by weight of xazole), a polyethylene terephthalate resin containing no additives and a master chip were mixed at a ratio of 95: 5 to prepare a raw material resin of the second polymer resin layer.

Subsequently, after melting each of the raw material resins prepared above, a second polymer resin layer was laminated around the first polymer resin layer in the feed block, and extruded through a coextrusion die to form a three-layer sheet. Subsequently, the sheet was stretched 3.5 times in the longitudinal and transverse directions, respectively, and heat-set at 200 ° C. to obtain a laminated white polyester film having a thickness of 30 μm. At this time, the thickness of each layer was 3/24/3 micrometer.

Example 2

A film was prepared in the same manner as in Example 1, except that barium sulfate was added instead of titanium dioxide added to the first polymer resin layer.

Example 3

A film was prepared in the same manner as in Example 1, except that 8 wt% of titanium dioxide and polypropylene were added to the first polymer resin layer based on the total weight of the first polymer resin layer.

Example 4

A film was prepared in the same manner as in Example 1 except that the draw ratios in the longitudinal and transverse directions were each set to 3.0.

Comparative Example 1

In the same manner as in Example 1, except that the bisbenzoazole-based fluorescent brightener added to the second polymer layer was added to 0.05% by weight to prepare a single layer film as a raw material of the second polymer resin layer. A film was prepared.

Comparative Example 2

A film was prepared in the same manner as in Comparative Example 1, except that the amount of titanium dioxide was added to 20 wt% instead of the bisbenzoazole-based fluorescent brightener.

Comparative Example 3

A film was manufactured in the same manner as in Example 1, except that 0.05 wt% of the bisbenzoazole-based fluorescent brightener added to the second polymer resin layer was added to the first polymer resin layer.

Various physical properties of the films produced according to the above Examples and Comparative Examples were measured by the following method, and the results are shown in Table 1.

(1) light transmittance

It measured according to ASTM D1003 (diameter 25MM, scattering angle 2.5 degree).

(2) glossiness

It measured according to ASTM D523 (reference diameter: black diameter, measuring angle: 60 degrees).

(3) whiteness

It measured using JIS L-1015.

Whiteness = 4B-3G

Wherein B is reflectance of 450 nm (%) and G is reflectance of 550 nm (%).

(4) roughness

It measured using JIS B 0601 (cut-off 0.25mm).

(5) surface tension

It was evaluated using Nuret reagent according to ASTM 2578.

(6) strength

It was measured according to ASTM D882.

(7) extensibility

The number of breaks during the 24 hour continuous production of the film was measured.

Light transmittance Surface tension Glossiness Whiteness Roughness burglar Fracture (%) (dyne / ㎠) (%) (%) (Μm) (kg / ㎡) (Time / 24 hours) Example 1 12 43 98 98 0.018 24 0 Example 2 13 43 95 97 0.015 23 0 Example 3 9 43 98 95 0.014 19 One Example 4 7 43 95 95 0.022 20 2 Comparative Example 1 8 34 80 97 0.162 18 5 Comparative Example 2 7 43 75 98 0.232 16 10 Comparative Example 3 12 43 99 90 0.18 24 0

Referring to Table 1, it can be seen that the laminated polyester biaxially oriented film according to the present invention has excellent glossiness, whiteness and excellent stretching processability.

On the other hand, the single-layer polyester film (Comparative Example 1 and Comparative Example 2) containing only the optical brightener and / or inorganic particles can be seen that the roughness and the gloss and stretching processability is poor due to the large amount of additives. In addition, it can be seen that when the fluorescent brightener is added to the first polymer resin layer (Comparative Example 3), the whiteness of the film is poor.

As described above, the biaxially stretched polyester film according to the present invention is excellent in hiding power, glossiness and whiteness, and has good drawing processability and coating property, and is useful for various labels, printing materials, decorations, and billboards.

Claims (9)

A first polyester resin containing at least 60 mol% of ethylene terephthalate repeating units and having an intrinsic viscosity of 0.4 to 0.9 dl / g, 3 to 10 weight% of inorganic particles and 3 to 10 weight based on the first polyester resin. A second polyester resin having an intrinsic viscosity of 0.4 to 0.9 dl / g and containing at least 60 mol% of ethylene terephthalate repeating units on both surfaces of the first polymer resin layer formed of% polyolefin resin; A biaxially stretched polyester film comprising a second polymer resin layer formed by laminating 0.04 to 0.1% by weight of an optical brightener based on an ester resin. The biaxially stretched polyester film according to claim 1, wherein the inorganic particles have an average particle diameter of 0.1 to 3 mu m. The biaxially stretched polyester film of claim 1, wherein the inorganic particles are any one or more selected from the group consisting of titanium dioxide, barium sulfate, and zinc sulfide. The biaxially stretched polyester film of claim 1, wherein the polyolefin resin is selected from the group consisting of polyethylene, polypropylene, and copolymers thereof. The biaxially stretched polyester film of claim 1, wherein the fluorescent brightener is a bisbenzoazole-based fluorescent brightener. The method of claim 5, wherein the bisbenzoazole-based optical brightener is 2,2 '(1,2-ethenedyldi-4,1 phenylene) bisbenzoxazole (2,2' (1,2-Ethenediyldi-4) , 1 Pheylene) bisbenzoxazole) biaxially oriented polyester film, characterized in that. The biaxially stretched polyester film according to claim 1, wherein the thickness is 15 to 100 µm. The biaxially stretched polyester film according to claim 1, wherein the second polymer resin layer has a thickness of 5/100 to 15/100 of the total film thickness. The biaxially stretched polyester film according to claim 1, wherein the total draw ratio is 12 or more.