JP2006290400A - Package filled with ion-containing contents, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic container excellent in barrier properties and transparency and hard to degrade in the barrier properties due to a direct contact with contents. <P>SOLUTION: An inorganic oxide film is formed at least on the internal surface of the plastic container by a plasma CVD method. The inorganic oxide film is subjected to hydrogen plasma treatment with an electron density of 1×10<SP>14</SP>m<SP>-3</SP>to 1×10<SP>18</SP>m<SP>-3</SP>, thereby obtaining a package capable of keeping high barrier properties for a long time even if filled with ion-containing contents. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a coating process of a silicon oxide film on a plastic container such as a PET bottle.

Plastic containers such as PET bottles are widely used in various fields because of their various characteristics such as easy molding, light weight, and low cost.

However, plastic containers have the property of permeating low-molecular gases such as oxygen, carbon dioxide, and water vapor, which often causes problems.

As means for solving such a problem, there is a technique for improving the gas barrier property of a plastic container by forming an inorganic oxide film such as a carbon film or a silicon oxide film on the inner surface or outer surface of the plastic container. When a film is formed on the inner surface of a plastic container, a gas barrier property of about 10 to 20 times that of an untreated container is obtained.

On the other hand, the gas barrier property when the film is formed on the outer surface of the plastic container is only about 2 to 5 times that of the untreated container, and the inner surface film formation is generally used as a film forming process for a PET bottle or the like. It has been.

As a method for forming a film on a plastic container, a plasma CVD method, a vacuum deposition method and a sputtering method have been put into practical use. When forming a film on the inner surface of the container, it is difficult to use a vacuum evaporation method or a sputtering method, and a plasma CVD method is used.

As a film forming method using the plasma CVD method, for example, as shown in Patent Document 1, a hollow external electrode substantially similar to the outer shape of the container and an internal electrode substantially similar to the container are disposed. There is a method in which a container is installed, high frequency power is applied to an external electrode to generate capacitively coupled plasma, and a thin film having a gas barrier property is formed on the inner surface of the container.

An inorganic oxide film has an advantage that a high barrier property can be obtained and the transparency is excellent.

As a process for forming an inorganic oxide film on the inner surface of a plastic container, a method of forming a silicon oxide film using an organic silane material by a plasma CVD method has been put into practical use.

The plastic container formed with the inorganic oxide film manufactured by such a technique has a problem that the film deteriorates and the barrier property decreases when the contents directly touch the surface of the inorganic oxide film.

In the sample in which the barrier property was lowered, the film thickness was gradually lowered, and finally the film was peeled off from the base material. For example, it has been found that when contents such as tap water, mineral water, tea, and saline are filled, the barrier property is reduced to the level of an untreated bottle within a few days.

Nonpolar oil etc. are mentioned as a content in which barrier property does not change easily.

A characteristic of the content in which the barrier lowering occurs is that it is an aqueous solution containing various ions. Therefore, there is a high possibility that the ions in the contents have some effect on the silicon oxide film and the barrier property is lowered.

In addition, dangling bonds that do not contribute to the bonding of the film, so-called dangling bonds, are generated on the surface of the silicon oxide film formed by the plasma CVD method.

Since dangling bonds are highly active, impurities are likely to be adsorbed and reacted on the surface.

The reaction between ions in the contents and dangling bonds may be a starting point for deterioration of the film.
JP-A-8-53117

An object of the present invention is to provide a plastic container that is excellent in barrier properties and transparency and is less likely to be deteriorated by direct contact of contents.

The invention according to claim 1 is characterized in that an inorganic oxide film is formed at least on the inner surface of a plastic container, and the inorganic oxide film is subjected to hydrogen plasma treatment, and contains an ion-containing content. A package to be filled.

The invention according to claim 2 is the package for filling the content containing ions according to claim 1, wherein the plastic container is a plastic bottle.

The invention according to claim 3 is a package body filled with the content containing ions according to claim 1 or 2, wherein the inorganic oxide film is a silicon oxide film. .

The invention according to claim 4 is characterized in that the inorganic oxide film is formed by a plasma CVD method, and the package is filled with the content containing ions according to any one of claims 1 to 3. It is a manufacturing method of a body.

The invention according to claim 5 is characterized in that the electron density in the hydrogen plasma treatment is 1 × 10 ¹⁴ m ⁻³ to 1 × 10 ¹⁸ m ^−3. It is a manufacturing method of the package body filled with the content containing the described ion.

When the inorganic oxide film on the inner surface of a plastic container is treated with hydrogen plasma, the contents of barriers of the package over time are filled even when the contents containing various ions such as tap water, mineral water, tea, and saline are filled. Deterioration can be prevented.

First, an inorganic oxide film is formed on the inner surface of a plastic container.

As a material of the plastic container, PET (polyethylene terephthalate), polyethylene, or the like can be used.

As a method for forming the inorganic oxide film, a vacuum vapor deposition method, a plasma CVD method, or a sputtering method can be used, but the plasma CVD method is most effective when a film forming process is performed on the inner surface of the container.

When a silicon oxide film is used as the inorganic oxide film, organic silane-based hexamethyldisiloxane, tetraethoxysilane, tetramethylsilane, or tetramethoxysilane can be used as a film forming material.

Next, hydrogen plasma treatment is performed on the inorganic oxide film.

As the hydrogen plasma condition of the inorganic oxide film, an electron density of 1 × 10 ¹⁴ m ⁻³ to 1 × 10 ¹⁸ m ⁻³ can be used.

When hydrogen plasma treatment is performed on the surface of an inorganic oxide film formed on the inner surface of a plastic container, the number of dangling bonds decreases due to hydrogen bonding to the dangling bonds on the surface of the film, thereby lowering the barrier of the plastic container. It is thought that it can be suppressed.

When hydrogen plasma treatment is performed, the plasma tends to become unstable as compared with the case where plasma is generated with oxygen gas or argon gas. Specifically, the plasma may be localized only in a part of the plastic container, and the plasma may not be uniformly generated in the plastic container.

In such a case, the hydrogen plasma treatment is not uniformly performed on the inorganic oxide film, which causes a problem.

In order to avoid this, the high frequency power applied is adjusted so that the plasma has an electron density of 1 × 10 ¹⁴ m ⁻³ to 1 × 10 ¹⁸ m ⁻³ . By doing so, the plasma is stabilized and the entire film surface can be uniformly treated.

As a plastic container, a PET (polyethylene terephthalate) bottle having a thickness of 350 μm and a capacity of 500 ml was used.

First, the PET bottle was placed in a vacuum chamber, and evacuation was performed until the inside of the vacuum chamber reached 0.1 Pa.

Next, 2 sccm of hexamethyldisiloxane and 50 sccm of oxygen gas, which are raw material gases for the silicon oxide film, were supplied into the PET bottle. At this time, the pressure in the vacuum chamber was 5.5 Pa.

Next, high frequency power of 13.56 MHz and 200 W was applied to generate plasma inside the bottle, and a silicon oxide film was formed on the inner surface of the PET bottle for 10 seconds.

Next, 50 sccm of hydrogen gas was supplied into the bottle. At this time, the pressure in the vacuum chamber was 3.0 Pa.

Finally, plasma is generated inside the bottle by applying high-frequency power of 13.56 MHz and 200 W, and a hydrogen plasma treatment is performed on the surface of the silicon oxide film for 2 seconds to obtain a package filled with contents containing ions. It was. At this time, when the electron density of the plasma was measured by the probe method, it was 2 × 10 ¹⁶ m ⁻³ .

In order to examine the gas barrier properties of the PET bottles thus produced, the oxygen permeation amount of the PET bottles was examined.

The oxygen permeation amount of the PET bottle not subjected to the silicon oxide film formation process was 0.250 fmol / (pg · s · Pa), whereas after the silicon oxide film formation process was performed, hydrogen plasma was applied to the silicon oxide film. The oxygen permeation amount of the treated PET bottle was 0.020 fmol / (pg · s · Pa).

That is, the treated PET bottle had an oxygen barrier property about 10 times that of the untreated PET bottle.

PET bottles that have been subjected to hydrogen plasma treatment after silicon oxide film formation treatment are filled with 500 ml of 1% NaCl aqueous solution and stored in a 40 ° C. environment for 30 days. The oxygen transmission rate of PET bottles is 0.020 fmol / (pg · s -Pa).
<Comparative Example 1>

As a plastic container, a PET (polyethylene terephthalate) bottle having a thickness of 350 μm and a capacity of 500 ml was used.

First, the PET bottle was placed in a vacuum chamber, and evacuation was performed until the inside of the vacuum chamber reached 0.1 Pa.

Next, 2 sccm of hexamethyldisiloxane and 50 sccm of oxygen gas, which are raw material gases for the silicon oxide film, were supplied into the PET bottle. At this time, the pressure in the vacuum chamber was 5.5 Pa.

Next, high frequency power of 13.56 MHz and 200 W was applied to generate plasma inside the bottle, and a silicon oxide film was formed on the inner surface of the PET bottle for 10 seconds.

In order to examine the gas barrier properties of the PET bottles thus produced, the oxygen permeation amount of the PET bottles was examined.

The oxygen permeation amount of the PET bottle not subjected to the silicon oxide film forming treatment was 0.250 fmol / (pg · s · Pa), whereas the oxygen permeation amount of the PET bottle subjected to the silicon oxide film forming treatment was 0. It was 0.020 fmol / (pg · s · Pa).

That is, the treated PET bottle had an oxygen barrier property about 10 times that of the untreated PET bottle.

A PET bottle subjected to silicon oxide film formation treatment was filled with 500 ml of a 1% NaCl aqueous solution and stored in a 40 ° C. environment for 30 days. The oxygen permeation amount of the PET bottle was 0.250 fmol / (pg · s · Pa). .
<Comparative example 2>

As a plastic container, a PET (polyethylene terephthalate) bottle having a thickness of 350 μm and a capacity of 500 ml was used.

First, the PET bottle was placed in a vacuum chamber, and evacuation was performed until the inside of the vacuum chamber reached 0.1 Pa.

Next, 2 sccm of hexamethyldisiloxane and 50 sccm of oxygen gas, which are raw material gases for the silicon oxide film, were supplied into the PET bottle. At this time, the pressure in the vacuum chamber was 5.5 Pa.

Next, high frequency power of 13.56 MHz and 200 W was applied to generate plasma inside the bottle, and a silicon oxide film was formed on the inner surface of the PET bottle for 10 seconds.

Next, 50 sccm of hydrogen gas was supplied into the bottle. At this time, the pressure in the vacuum chamber was 3.0 Pa.

Finally, plasma is generated inside the bottle by applying high frequency power of 13.56 MHz and 10 W, and a hydrogen plasma treatment is performed on the surface of the silicon oxide film for 2 seconds to obtain a package filled with contents containing ions. It was.

At this time, when the electron density of the plasma was measured by the probe method, it was 5 × 10 ¹³ m ⁻³ . When plasma was observed, plasma was emitted near the bottom of the bottle, but no plasma emission could be confirmed in other parts.

In order to examine the gas barrier properties of the PET bottles thus produced, the oxygen permeation amount of the PET bottles was examined.

The oxygen permeation amount of the PET bottle not subjected to the silicon oxide film formation process was 0.250 fmol / (pg · s · Pa), whereas after the silicon oxide film formation process was performed, hydrogen plasma was applied to the silicon oxide film. The oxygen permeation amount of the treated PET bottle was 0.020 fmol / (pg · s · Pa).

That is, the treated PET bottle had an oxygen barrier property about 10 times that of the untreated PET bottle.

PET bottles that have been subjected to hydrogen plasma treatment after silicon oxide film formation treatment are filled with 500 ml of 1% NaCl aqueous solution and stored in a 40 ° C. environment for 30 days, the oxygen permeation rate of the PET bottle is 0.240 fmol / (pk · s -Pa).

Since the container produced according to the present invention has a high oxygen barrier property, the contents are not oxidized even if the storage period is longer than that of a normal plastic container.

It can also be used for contents that are difficult to apply due to deterioration of the silicon oxide film, such as aqueous solutions containing various ions such as tap water, mineral water, tea, and saline.

Claims (5)

At least an inorganic oxide film is formed on the inner surface of a plastic container, and the inorganic oxide film is subjected to a hydrogen plasma treatment. The package for filling contents containing ions according to claim 1, wherein the plastic container is a plastic bottle. The package body filled with contents containing ions according to claim 1, wherein the inorganic oxide film is a silicon oxide film. The said inorganic oxide film was formed by plasma CVD method, The manufacturing method of the package body with which the content containing the ion in any one of Claim 1 thru | or 3 is filled. 5. The content containing ions according to claim 1, wherein an electron density in the hydrogen plasma treatment is 1 × 10 ¹⁴ m ⁻³ to 1 × 10 ¹⁸ m ^−3. A manufacturing method for a package.