KR950015144B1 - White-colored polyester film - Google Patents

Abstract

Polyester film is prepd. by ; surface-treating inorganic particles with a coupling agent; and coating them with polyolefin; then mixing 2-50 wt.% of that and polyester and bi-axial drawing. The inorganic particles are one more selected from calcium carbonate, barium sulfonate, titanium dioxide, talc, magnesium oxide or magnesium carbonate, and their ave. particle size is 0.2-10 micrometer. The coupling agent is selected in one or more than two of titanate type, silane type or zirconate type coupling agent. The obtd. film has improved film properties eg. white colorness, light-transparency and appearance density.

Description

White polyester film and its manufacturing method

The present invention relates to a polyester film having excellent whiteness used as a substrate of a paper substitute and a method of manufacturing the same, and more specifically, by adding inorganic particles coated with a polyolefin by surface treatment with a coupling agent, whiteness, light transmittance and apparent density, etc. The polyester film which improved the film characteristic of this, and its manufacturing method are related.

Polyester films such as polyethylene terephthalate and polyethylene naphthalate are widely used in various industrial products because of excellent mechanical, electrical, chemical resistance, heat resistance and weather resistance. Especially, biaxially oriented polyethylene terephthalate film has dimensional stability Because of its excellent flatness and elastic modulus, it is attracting much attention in magnetic tapes, graphic arts, stamping foils and packaging.

In addition, plastic film, unlike paper, can be stored for a long time without debris, so it is a substitute for paper, namely cards, labels, paper for printers, paper for barcode printers, posters, maps, dust-free paper, display boards, white boards, and photo papers. Increasingly, it is used as a base material for copy paper. In particular, printed materials used outdoors are difficult to withstand the weather using paper, so conventionally, a resin or plastic film has been used, and since the paper is torn when peeling after adhesion on labels or adhesive paper, the plastic film Should be used.

However, there are some problems in using a polyester film simply as the use of the paper substitute. In other words, these polyester films are too stiff or too soft to have a texture different from that of paper, and they do not give a paper-like feel due to the difference in transparency or reflection of light.

Therefore, various methods have been developed to give paper-like properties while utilizing the excellent properties of the polyester film. Japanese Laid-Open Patent Publication No. 62-243120 and the like add inorganic particles to a polyester substrate, and Japanese Laid-Open Patent Publication No. 63-64310 and the like disclose a method of adding inorganic particles to a polyolefin base to impart whiteness and concealability to a film. Japanese Patent Publication No. 58-50625 seeks to reduce the weight of the film and reduce the manufacturing cost while providing concealment by scattering the permeation amount by bubbles generated by adding and chemically decomposing bubbles to generate bubbles. . In addition, Japanese Patent Laid-Open No. 63-168441 combines and stretches a polyolefin to polyester to form fine bubbles on the surface and inside of the film to impart writing properties to the surface. In Japanese Patent Laid-Open No. 2-284929, The polyolefin was added together with the inorganic particles to reduce the amount of the inorganic particles, thereby simultaneously seeking the surface characteristics and the weight reduction of the film.

However, when manufacturing a film by such a conventional method has the following problems.

1) When inorganic particles are added to a polyester base material, specific gravity is high and manufacturing cost becomes high.

2) Films with a polyolefin substrate have no heat resistance, poor numerical stability, and low mechanical strength.

3) In the case of lowering the apparent density by forming microbubbles inside the film to reduce the manufacturing cost per film area, the surface is easy to be destroyed, and there is a problem that the density is increased by removing the microbubbles inside to prevent the surface destruction phenomenon.

4) When polyolefin is mixed with polyester to form micro bubbles, dispersion stains of the polyolefin resin tend to occur, and heat resistance, numerical stability, and optical properties of the film are poor.

5) In the case of manufacturing the film by adding the inorganic particles, the dispersibility of the inorganic particles is poor, die-line is likely to occur, and a lot of breakage occurs, so the productivity is easily deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a white polyester film and a method of manufacturing the same, which can improve productivity while solving the above problems and having film properties such as whiteness, light transmittance and apparent density suitable for use as a substrate for paper substitutes. It is.

Method for producing a polyester film of the present invention for achieving the above object is characterized in that the biaxially stretched 2 to 50% by weight of the polyester surface-treated with a coupling agent and coated with a polyolefin to the polyester.

The polyester of the present invention corresponds to any one that forms a film. For example, polyethylene terephthalate (hereinafter, abbreviated as PET). Polytetramethylene terephthalate, polyethylene-P-oxybenzoate, poly-1.4-cyclohexylene dimethylene terephthalate, polyethylene-2.6-naphthalene dicarboxylate, and the like. This excellent PET is preferred. These polyesters may be homopolyesters or copolyesters. As a copolymerization component, for example, diol components, such as ethylene glycol, neopentylene glycol, polyalkylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2.6-naphthalene dicarboxylic acid, 5-sodium sulfo isophthalic acid, etc. Dicarboxylic acid components are included.

Inorganic particles of the present invention include talc, magnesium oxide, magnesium carbonate, calcium carbonate, barium sulfate, titanium dioxide, and the like. Particularly, calcium carbonate, barium sulfate, titanium dioxide, and the like are preferable, and may be used alone or in combination. Moreover, in order to raise the whiteness of a film, you may add a fluorescent brightener. These inorganic particles use those having an average particle diameter of 0.2 to 10 µm, and preferably 0.3 to 8 µm. When the average particle diameter is smaller than 0.2 μm, agglomeration between inorganic particles is likely to occur, and it is difficult to impart surface characteristics to the film. When the average particle diameter is larger than 10 μm, breakage occurs a lot when the film is manufactured, and the filter pressure rapidly increases.

Coupling agents used to surface-treat inorganic particles in the present invention include titanate-based, silane-based, and zirconate-based coupling agents, which are organic polymer oxides of tetravalent elements such as titanium, silicon, and zirconium. The coupling agent has the advantage of low cost and wide application range, and when the color of the film is important, it is preferable to use a zirconate coupling agent.

Examples of titanate-based coupling agents include neopentyl (diallyl) oxytri (dioctyl) pyrophosphate titanate of the following structural formula (I) and neopentyl (diallyl) oxytree (N) of the following structural formula (II). Ethylenediamine) ethyl titanate and the like.

Examples of the zirconate-based coupling agent include cyclo (dioctyl) pyrophosphate dioctyl zirconate of the following structural formula (III) and neopentyl (diallyl) oxy tri (dioctyl) fatigue of the following structural formula (IV). Phosphate zirconate and the like.

The silane coupling agent includes, for example, a vinyl-based compound such as vinyltriethoxysilane of the following structural formula (V) and a methacryl-based coupling agent such as methacryloxypropyl trimethoxysilane of the following structural formula (VI).

The usage-amount of these coupling agents is 0.05-1 weight% based on the weight of an inorganic particle, and 0.1-1 weight% is preferable. If the amount is less than 0.05% by weight, the coating effect of the polyolefin resin is not good because the effect as a coupling agent is not good, and when the amount is more than 1% by weight, aggregation between the inorganic particles occurs, resulting in poor dispersion of the inorganic particles during film formation. There is this.

The surface treatment of the inorganic particles with a coupling agent includes a dilution solution of the coupling agent using a solvent to deposit the inorganic particles therein, and after the inorganic particles are scattered for a while, the dilution solution of the coupling agent is blown. Although a method etc. are mentioned, it is not limited to these.

In the present invention, the polyolefin coating the inorganic particles surface-treated with the coupling agent may be any compound that can be mixed with polyester to form a film. For example, low density polyethylene, high density polyethylene, polypropylene, polybutene, polymethyl Pentenes are included. These polyolefins are not limited only to homopolymers, but these copolymers may be sufficient. In particular, polyolefins having a low critical surface tension are preferred, and polypropylene and polymethylpentene are more preferred. Polymethylpentene is most preferred because it has good peelability with polyester and easy generation of microbubbles during stretching. The polyolefin is used in an amount of 0.5 to 50% by weight based on the weight of the inorganic particles. If the amount is less than 0.5% by weight, the coating effect of the inorganic particles is poor. When it is larger than 50% by weight, the heat resistance and numerical stability of the film are poor.

Examples of the method for coating the inorganic particles with the polyolefin include a method of depositing the inorganic particles surface-treated with the coupling agent in a dilute solution of the polyolefin, but is not limited thereto.

The timing of adding the inorganic particles surface-treated with the coupling agent and coated with the polyolefin to the polyester may be immediately after polymerization of the polyester or during melt extrusion. The addition amount of the coated inorganic particles should be 2 to 50% by weight based on the weight of the polyester, preferably 5 to 40% by weight. If the added amount is less than 2% by weight, it is difficult to obtain the desired whiteness, and when it is more than 50% by weight, film forming elongation is not good.

Polyolefin-coated inorganic particles are mixed with polyester at 2 to 50% by weight and then extruded through a T-Die in an extruder heated to 285 ° C. The unstretched sheet cooled and solidified in a cooling drum having a surface temperature of 10 to 60 ° C. was longitudinally stretched through a roll heated to 80 to 120 ° C., and then cooled in a roll group of 20 to 30 ° C., followed by a stenter of 90 to 140 ° C. Transverse stretching through

The polyester film of this invention needs to be biaxially oriented. The draw ratio is 2 to 5 times each in the longitudinal and transverse directions, and the area magnification thereof (the longitudinal draw ratio × transverse draw ratio) is 4 to 25 times. If the area magnification is less than 4 times, the resulting film is not good in whiteness, glossiness, cushioning properties, and easily cutability, and thus it is difficult to use as a white film. There is this.

The biaxially stretched film as described above is heat-fixed in a tenter at 150 to 235 ° C for uniformity and numerical stability, uniformly slow cooled, and then wound at room temperature to obtain a white polyester film of the present invention.

The white polyester film of the present invention has an apparent density of 0.6 g / cm 3 to 1.1 g / cm 3, preferably 0.6 g / cm 3 to 0.95 g / cm 3, and more preferably 0.7 g / cm 3 to 0.9 g / cm 3. If the apparent density is less than 0.6 g / cm 3, the surface strength is not low because there are too many microbubbles inside, and if it exceeds 1.1 g / cm 3, the manufacturing cost becomes expensive and it is not competitive with paper.

Moreover, the light transmittance of the white polyester film of this invention is 0.5%-2.0%, and 0.8%-1.6% is preferable. If the light transmittance is smaller than 0.5%, the amount of the microbubbles must be contained, so that the strength of the film is lowered, and if it is higher than 2.0%, the concealability of the film is small, so that the backside is visible, which is not good.

Moreover, the whiteness of the white polyester film of this invention is 80%-110, and 85%-105% are preferable. If the whiteness is less than 80%, the film will have a yellowish color, resulting in a less luxurious print. If it exceeds 110%, the film will have a blue color.

As described above, the polyester film of the present invention can obtain the following effects even when a large amount of inorganic particles are added by mixing the inorganic particles coated with a polyolefin by surface treatment with a coupling agent to the polyester.

1) Since a die line does not arise in a film and the film forming property of a film is excellent, productivity can be improved.

2) Dropping of inorganic particles does not occur on the surface of the film.

3) Since the dispersion of the inorganic particles in the polyester becomes uniform, no stain occurs on the film.

4) Sufficient glossiness can be obtained.

The invention is explained in more detail through the following examples. However, the following examples are only examples of the present invention and the present invention is not limited thereto.

The method used to measure the physical properties of the polyester film of the present invention is as follows.

[How to measure]

1) apparent density

A density gradient tube consisting of carbon tetrachloride and xylene was maintained at 25 ° C. and measured by ups and downs.

2) light transmitting heat

According to ASTM D1003 it was measured with a diameter of 25mm, scattering angle of 2.5 degrees.

3) whiteness

When reflectance B% of wavelength 450nm and reflectance G% of 550nm are based on JIS-L-1015,

ㆍ Whiteness = 4B-3G

4) glossiness

According to ASTM D523, the reference diameter was measured as the black diameter, and the measurement angle was measured at 60 degrees.

5) elongation

It judged as follows from the extending | stretching state of a film forming.

○; When a homogeneous film is obtained with no breaks and no stretching stains

△; When a homogeneous film can be obtained with slight breakage and no stretching stains

×; If there are many breaks and there are stretch stains even when stretched

6) particle diameter

The particle diameter of the fine particles was measured by observing the particles with an electron microscope. At this time, ten or more particles were observed to obtain an average particle diameter.

[Examples 1-4] and [Comparative Examples 1, 2]

Titanium dioxide inorganic particles having an average particle diameter of 0.45 µm were surface-treated with the titanate coupling agent in the amounts shown in Table 1, coated with 20.0% by weight of polymethylpentene, and mixed with polyethylene terephthalate in 10.0% by weight of titanium dioxide. Vacuum dried at 180 ° C. for 3 hours and then extruded through a tee-die in an extruder heated to 285 ° C. FIG. The unstretched sheet cooled and solidified in a cooling drum at a surface temperature of 10 to 60 ° C. was longitudinally stretched through a roll heated to 80 to 120 ° C., and then cooled in a roll group of 20 to 30 ° C., followed by a stainless steel at 90 to 140 ° C. Transverse stretching through the site. The biaxially stretched film was heat-set in a tenter at 150 to 235 ° C., uniformly slow cooled, and wound up at room temperature to prepare a white polyethylene film having a thickness of 100 μm.

The physical properties of the film prepared as described above are measured and shown in Table 1 below.

[Examples 5-8] and [Comparative Examples 3, 4]

The same procedure as in Example 1-4 was carried out, except that the average particle diameter of the inorganic particles was 0.45 μm, the amount of the coupling agent was 0.50%, and only the addition amount of the coated inorganic particles was changed as shown in Table 2 below. , Heat setting and winding were performed to prepare a white polyester film having a thickness of 100 μm.

The physical properties of the film prepared as described above are measured and shown in Table 2 below.

[Examples 9-12] and [Comparative Examples 5 and 6]

The same method as in Example 1-4, except that the amount of the coupling agent used was 0.50%, the amount of the coated inorganic particles was added at 10.0% by weight, and only the average particle diameter of the inorganic particles was changed as shown in Table 3 below. Biaxial stretching, heat setting, and winding were performed to prepare a white polyester film having a thickness of 100 µm.

The physical properties of the film prepared as described above are measured and shown in Table 3 below.

As shown in Table 1, when the amount of the coupling agent used exceeds 1% by weight of the inorganic particles, agglomeration of the inorganic particles occurs, resulting in poor film elongation and deterioration in optical properties of the film. In addition, when the content is less than 0.05% by weight, the effect of the coupling agent cannot be expected, so that voids are not formed in the film, and the apparent density exceeds 1.1 g / cm 3 and the optical properties of the surface are also reduced. When the amount of the coupling agent is 0.05 to 1.0% by weight of the inorganic particles, it can be seen that the apparent density is appropriately lowered and the optical properties are also improved.

As shown in Table 2, when the mixed amount of the coated inorganic particles is less than 2.0% by weight of polyester, in particular, the optical properties of the film such as light transmittance and white light are lowered, and when it exceeds 50% by weight, the apparent density becomes high and film forming elongation is poor. It turns out that productivity falls. It can be seen that the apparent density is the lowest and the optical properties of the film are excellent when the mixed amount of the coated inorganic particles is around 10% by weight of the polyester.

As shown in Table 3, the larger the average particle diameter of the inorganic particles, the apparent density increases, and it can be seen that the glossiness, especially among the optical properties of the film, is greatly reduced. When the average particle diameter of the inorganic particles is smaller than 0.2 μm or larger than 10 μm, the apparent density exceeds 1.1 g / cm 3 and optical properties such as light transmittance decrease, whereas the apparent density is appropriate in the 0.2 to 10 μm range and the optical properties are excellent. Can be done.

As described above, the white polyester film of the present invention which is biaxially stretched by mixing an inorganic particle with a coupling agent and coated with a polyolefin in polyester is not only excellent in optical properties such as whiteness, light transmittance, Its excellent ductility allows for improved productivity and is particularly suitable for use as a substrate for paper substitutes.

TABLE 1

TABLE 2

TABLE 3

Claims (8)

A method for producing a polyester film characterized in that the inorganic particles are surface-treated with a coupling agent and coated with polyolefin to 2 to 50 weight of polyester and biaxially stretched. The method of claim 1, wherein the inorganic particles are at least one selected from calcium carbonate, barium sulfate, titanium dioxide, talc, magnesium oxide, and magnesium carbonate. The method for producing a polyester film according to claim 1 or 2, wherein the inorganic particles have an average particle diameter of 0.2 to 10 µm. The method of claim 1, wherein the coupling agent is at least one selected from titanate-based, silane-based and zirconate-based coupling agents. The method for producing a polyester film according to claim 1 or 4, wherein the coupling agent is surface treated using 0.05 to 1% by weight of the inorganic particles. The method according to claim 1, wherein the polyolefin is coated by using 0.5 to 50% by weight of the inorganic particles. The method for producing a polyester film according to claim 1, wherein an area magnification of the biaxial stretching is 4 to 25 times. A polyester film prepared according to claim 1, characterized by an apparent density of 0.6 to 1.1 g / cm 3, a light transmittance of 0.5 to 2.0% and a whiteness of 80 to 110%.