JP6848578B2 - How to make a plastic bottle - Google Patents

Description

The present application discloses a technique for forming a DLC film as a gas barrier film on the inner surface of a large volume gas barrier plastic bottle having a mouth, shoulders, body, and bottom.

Stainless steel containers are widely used as server containers for beverages such as beer. However, since the server container has a large volume of 20 liters or more, the container itself is heavy if it is made of stainless steel, and it takes a lot of cost and labor to transport and clean the container for reuse.

As an alternative to stainless steel containers, plastic containers have become widespread in recent years, mainly in Europe. However, in the conventional European products, in order to impart gas barrier properties to plastic bottles, polyethylene terephthalate resin (PET), which is the main raw material, contains scavengers using oxygen barrier resins and metal compounds. It does not comply with the recycling law.

In order to achieve both recyclability and gas barrier properties of the plastic bottle, it is effective to provide a gas barrier film on the inner surface of the plastic bottle without using the above-mentioned scavenger. For example, a bottle in which a diamond-like carbon (DLC) having a thickness of several tens of nm is formed on the inner surface of a plastic bottle having a mouth, shoulder, body, and bottom by a chemical vapor deposition (CVD). Is widespread. However, the mouth portion, which has a smaller diameter than the body portion, becomes dark brown with respect to the body portion due to the DLC film formation, and the entire bottle tends to have uneven color.

There are the following disclosure techniques for lightening the color of the mouth and alleviating color unevenness, but none of them can be applied to a large plastic bottle having a volume of 5 liters or more. For example, even if the technique disclosed in Patent Document 1 is used, it is difficult to eliminate the dark brown color of the mouth. Further, in the technique disclosed in Patent Document 2, a step of installing a tubular member after loading the bottle into a CVD chamber (deposition chamber) is required, and the tubular member is removed from the inside of the mouth after DLC film formation. Therefore, there is a problem that foreign matter is easily generated. Further, in the technique disclosed in Patent Document 3, while a general CVD film forming apparatus provides an exhaust port on a part of the wall surface of the chamber to perform exhaust, an exhaust method in which an exhaust pipe is newly prepared and installed. It has to be changed to, which requires investment and reduces production efficiency. Further, in the technique disclosed in Patent Document 4, since the DLC film is not formed on the mouth portion, the mouth portion is not colored, but on the other hand, the gas barrier property of the entire bottle is insufficient.

Japanese Unexamined Patent Publication No. 2003-237754 Japanese Unexamined Patent Publication No. 2008-050050 Japanese Unexamined Patent Publication No. 2006-160269 JP-A-2002-053119

In view of the above background technology, in the present application, in a method for manufacturing a plastic bottle including a step of forming a DLC film on the inner surface of a large volume plastic bottle of 5 liters or more, a sufficient gas barrier property is ensured and a mouth portion is provided. And a method that makes it possible to reduce the color unevenness of the body.

The present application provides one of the means for solving the above problems.
A method for manufacturing a plastic bottle, which comprises a step of forming a DLC film on the inner surface of the undeposited plastic bottle by a chemical vapor deposition method. The undeposited plastic bottle has a mouth, a shoulder, a body, and a bottom. , volume is less 35L least 5L, the ratio of the mouth inside diameter _{(D 1)} and the barrel inner diameter _{(D 2) (D 1 /} D 2) is 0.1 to 0.3, the chemical vapor deposition Disclosed is a manufacturing method in which a high frequency power of 3000 W or more and 5000 W or less is adopted in the film formation of the DLC film by the method.

In the manufacturing method of the present disclosure, it is preferable that the thickness of the DLC film on the inner surface of the body portion is 15 nm or more and 50 nm or less, and the thickness of the DLC film on the inner surface of the mouth portion is 500 nm or more and 1000 nm or less.

In the production method of the present disclosure, the DLC film on the inner surface of the body preferably has a binding composition in which I (D) / I (G) in Raman spectroscopy is 0.16 or more.

In the production method of the present disclosure, it is preferable that the DLC film on the inner surface of the body portion has a binding composition in which I (S) / I (N) in Raman spectroscopy is 1.0 or more.

In the production method of the present disclosure, it is preferable that the oxygen permeability of the plastic bottle is 0.10 cc / m ² / day or less.

In the production method of the present disclosure, it is preferable that the oxygen permeability of the plastic bottle is 0.06 cc / pkg / day or less.

In the manufacturing method of the present disclosure, it is preferable to obtain the undeposited plastic bottle by blow molding.

In the manufacturing method of the present disclosure, it is preferable that the plastic bottle is filled with a beverage containing carbonic acid.

According to the manufacturing method of the present disclosure, it is possible to manufacture a large-volume plastic bottle in which sufficient gas barrier properties are ensured and color unevenness due to a DLC film is reduced between the mouth and the body. Since the plastic bottle manufactured by the manufacturing method of the present disclosure is a plastic bottle that does not use an oxygen barrier resin or a scavenger of a metal compound in the resin layer, it can be recycled, effectively utilizing plastic resources, and protecting the environment. In addition, it is possible to suppress oxidation and putrefaction due to permeation of atmospheric water vapor and oxygen gas into the bottle, and to suppress carbon dioxide loss and flavor deterioration due to permeation of carbon dioxide gas and flavor components into the bottle.

It is a schematic diagram for demonstrating an example of the shape of the plastic bottle 10 manufactured by the manufacturing method of this disclosure. It is a figure which shows an example of the spectrum derived from the DLC film which can be confirmed in Raman spectroscopic analysis. It is a figure which shows schematicly the CVD apparatus used in an Example.

1. 1. Method for Manufacturing a Plastic Bottle The method for manufacturing a plastic bottle of the present disclosure includes a step of forming a DLC film on the inner surface of a non-deposited plastic bottle by a chemical vapor deposition method. As shown in FIG. 1, the undeposited plastic bottle used in the manufacturing method of the present disclosure has a mouth portion 1, a shoulder portion 2, a body portion 3 and a bottom portion 4, and has a volume of 5 L or more and 35 L or less, and a mouth portion. inside diameter _{(D 1)} and the ratio of the barrel inner diameter _{(D 2) (D 1 /} D 2) of 0.1 to 0.3. One of the features of the manufacturing method of the present disclosure is that a high frequency power of 3000 W or more and 5000 W or less is adopted in the film formation of the DLC film 5 by the chemical vapor deposition method.

An undeposited plastic bottle without a DLC film can be easily manufactured by, for example, a blow molding method in which a bottomed cylindrical parison (preform) is heated and blow-stretched in a mold. The shape of the parison, its manufacturing method, and the blow stretching conditions may be appropriately determined according to the volume and shape of the bottle.

The plastic bottle 10 can be manufactured by providing a DLC film on the inner surface of the undeposited bottle after blow molding using a general-purpose CVD device. For example, a non-deposited plastic container is housed inside an external electrode that matches the size of the plastic container, and after the internal electrode is placed at a predetermined position inside or outside the container opening, chemical vapor deposition (plasma chemical vapor deposition) is performed. ) Can form a gas barrier film in the container. The plasma chemical vapor deposition method is a method in which a raw material gas is dissociated and ionized by plasma generated under reduced pressure to generate a film-forming species, which is deposited and deposited on an adherend. For example, it is possible to use an apparatus as disclosed in Japanese Patent Application Laid-Open No. 2003-237754 and a spacer made of a dielectric material around the mouth and shoulder of the container. In this case, it is preferable to dispose the internal electrode having a gas supply pipe function at a position inside the bottle, which is 1/5 (20%) to 4/5 (80%) of the bottle height. Positions of 1/4 (25%) to 3/4 (75%) are more preferred.

Examples of the raw material gas for the DLC film include unsaturated hydrocarbon compounds such as acetylene, ethylene and propylene; saturated hydrocarbon compounds such as methane, ethane, propane and cyclohexane; and aromatic hydrocarbon compounds such as benzene, toluene and xylene. .. These may be used alone or in combination of two or more. Above all, it is preferable to use ethylene or acetylene gas alone.

A small amount of hydrogen and an organic compound may be mixed in the above-mentioned raw material gas. Further, the raw material gas may be diluted with a rare gas such as argon or helium.

When a DLC film is formed by the plasma chemical vapor deposition method, vacuum exhaust (decompression) and gas introduction are performed, and when the inside reaches a predetermined pressure (vacuum degree), the raw material gas is turned into plasma to form a film. The internal pressure at the time of film formation is preferably 1 Pa or more and 50 Pa or less in consideration of good film quality and physical properties and the time required for film formation. The raw material gas may be introduced through the internal electrode or directly into the chamber. In particular, by using both the gas introduction pipe and the internal electrode, the number of parts can be reduced, and it is possible to prevent the film-forming component from adhering to and falling on the parts and mixing foreign matter into the container film formation.

The inside of the chamber is set to a predetermined degree of vacuum, the raw material gas is supplied, and a voltage is applied between the external electrode and the internal electrode of the ground potential to generate plasma inside the container housed in the external electrode. As a result, a gas barrier film can be formed on the inner surface of the container. For example, when a high-frequency power source is used as the power source, the frequency may be, for example, several MHz or more and several 100 MHz or less, preferably 6 MHz or 13.56 MHz from the viewpoint of versatility. Further, as will be described later, it is important that the electric power (output) is 3000 W or more and 5000 W or less from the viewpoint of ensuring sufficient gas barrier property and reducing color unevenness between the body portion and the mouth portion. The film formation time can be, for example, 0.2 to 20 seconds, preferably 1.0 to 10 seconds.

According to the findings of the present inventor, only by scaling up the film forming conditions of the gas barrier film in the conventional small plastic bottle (for example, JP-A-8-053116) according to the shape of the large plastic bottle, the gas barrier property is of good quality. No film (particularly DLC film) can be obtained. The reason is as follows.

As described above, in general, in the DLC film formation of a container in which the inner diameter of the mouth (D _{1 ) is smaller than the inner diameter of the body (D 2} ), the DLC film thickness of the mouth 1 is larger than that of the body 3, resulting in a darker color. Become. Further, a large container of 5 liters or more is formed under general film forming conditions of a container of several hundred milliliters to 3 liters, for example, a high frequency output of about 100 to 1000 W, and a sufficient gas barrier property of the body 3 is obtained. Attempt, the dark color of the mouth becomes remarkable and the opacity becomes stronger.

In contrast, volume 5 liters or more, if the ratio _(D 1 / D ₂₎ is 0.1 or more and 0.3 or less relative to the barrel inner diameter of the mouth portion inner diameter _{(D 1) (D 2)} , the high-frequency power 3000W more By using the above conditions, the coloring of the mouth is reduced and a good appearance can be obtained. It is considered that the cause of this phenomenon is that when the film formation output is increased, plasma decomposition of the raw material gas proceeds, and the balance between the film formation on the container body and the film formation on the opening side changes. .. In DLC film formation on a container, the film formation conditions are extremely important because they affect the film quality. Above all, the film formation output has a great influence on the plasma decomposition of the raw material gas, so the film quality and physical properties of the DLC film. It is a requirement that has a great influence on. As described above, by setting the high frequency power to 3000 W or more, a tubular member can be loaded inside the mouth as in the past, a gas exhaust pipe can be placed inside the bottle, or a masking member can be attached to the mouth. Therefore, the gas barrier property of the bottle, the suppression of darkening of the mouth portion, and the transparency can be combined without performing the DLC film formation. The high frequency power is more preferably 4000 W or more. On the other hand, from the viewpoint of suppressing heat generation and abnormal discharge, the upper limit of high frequency power is preferably 5000 W or less.

When the output of high-frequency power is large, abnormal discharge is likely to occur if the pressure during film formation is high, and the possibility of damaging not only the film itself and the resin container but also the film forming apparatus increases. Efficient exhausting of the inside of the container is effective in suppressing abnormal discharge. In this regard, if the bottle diameter / body diameter ratio (D ₁ / D ₂ ) is 0.1 or more, preferably 0.15 or more, more preferably 0.2 or more, arrange a gas exhaust pipe inside the container. Even if the exhaust port is installed on the wall surface of the film forming chamber away from the container loading position, the inside of the container can be efficiently exhausted under the conventional equipment conditions.

In general, at high output, relatively thin resin-thick parts such as the shoulder of the container are susceptible to thermal deformation due to the heat generated, but the body diameter is 130 mm or more, more preferably 180 mm or more, and the resin thickness is 0.2 mm or more. More preferably, if it is 0.3 mm or more, thermal deformation due to heat is unlikely to occur. Since the resin thickness is inevitably designed to be thick from the viewpoint of the bottle strength of the large volume container, a special resin thickness design is not required due to the high frequency power condition when manufacturing the plastic bottle 10 of the present disclosure. Is.

Further, according to the findings of the present inventor, as the film formation output increases, the I (S) / I (N) of Raman spectrum analysis of the DLC film tends to increase, and the ratio of the inorganic component to the organic component tends to increase. .. Further, the larger the ratio of the inorganic components, that is, the larger I (S) / I (N), the more the hardness of the DLC film tends to increase and the more the refractive index tends to increase. This is a manifestation of the correlation that the higher the inorganic component ratio of the DLC film, the denser the film (increased density), and generally the hardness and refractive index of the film increase, which in turn increases the gas barrier property of the container. It is considered that the effect of becoming (reducing the oxygen permeability) can be obtained. From the above, by adopting high frequency power of 3000 W or more and 5000 W or less at the time of chemical vapor deposition of the DLC film, it is possible to obtain a container having both good appearance and high gas barrier property by suppressing coloration of the mouth portion.

2. Plastic Bottle 10 The plastic bottle 10 manufactured by the manufacturing method of the present disclosure will be described. As shown in FIG. 1, the plastic bottle 10 is formed by providing a DLC film 5 on the inner surface of a non-deposited plastic bottle made of a thermoplastic resin as a main raw material. Ungrown plastic bottles, the mouth portion 1, the shoulder portion 2 has a body portion 3 and a bottom 4, the volume is less 35L least 5L, mouth inside diameter (D ₁₎ and the barrel inner diameter (D ₂₎ and the The ratio (D ₁ / D ₂ ) is 0.1 or more and 0.3 or less.

2.1. Raw material Non-deposited plastic bottles use thermoplastic resin as the main raw material. The “main raw material” means that 90% by mass or more of the raw materials constituting the plastic bottle excluding the gas barrier film 5 is a thermoplastic resin. Preferably, 95% by mass or more, more preferably 98% by mass or more of the raw material is used as the thermoplastic resin. Specific examples of the thermoplastic resin include polyethylene terephthalate (PET) resin, polyethylene naphthalate (PEN) resin, polycarbonate (PC) resin and the like. In particular, PET resin is preferable because the above-mentioned blow molding becomes easier. Further, a nylon resin may be mixed in order to improve the heat resistance. On the other hand, needless to say, the plastic bottle 10 does not contain a metal compound scavenger as a raw material. If a scavenger is included, recycling becomes difficult and the above problems cannot be solved.

2.2. Shape As shown in FIG. 1, the plastic bottle 10 has a mouth portion 1, a shoulder portion 2, a body portion 3, and a bottom portion 4. The shapes of the mouth portion 1, the shoulder portion 2, the body portion 3 and the bottom portion 4 are not particularly limited. In particular, as shown in FIG. 1, it is preferable that the mouth portion 1, the shoulder portion 2 and the body portion 3 have a circular horizontal cross-sectional shape. This is because the gas barrier film 5 described later can be more uniformly provided on the inner surface of the bottle.

Plastic bottle 10 needs the ratio of the mouth inside diameter _{(D 1)} and the barrel inner diameter _{(D 2) (D 1 /} D 2) of 0.1 to 0.3. As described above, in the DLC film formation of a container having a diameter (D _{1 ) smaller than that of the body diameter (D 2} ), the DLC film thickness of the mouth portion is increased as compared with the body portion, and the color becomes darker. Further, when an attempt is made to obtain a sufficient gas barrier property of the body portion under general gas barrier film forming conditions, the dark color of the mouth portion 1 becomes very remarkable and the opacity becomes stronger. In the case of more volume 5L 35L or less, if the ratio of the mouth inside diameter _{(D 1)} and the barrel inner diameter _{(D 2) (D 1 /} D 2) of 0.1 to 0.3, in a chemical vapor deposition By adopting high-frequency power of 3000 W or more and 5000 W or less, it is possible to combine the gas barrier property of the bottle with the suppression of darkening of the mouth and the transparency. In this case, DLC film formation can be easily performed without loading a tubular member inside the mouth portion 1, arranging a gas exhaust pipe inside the bottle, or attaching a masking member to the mouth portion 1. ..

The plastic bottle 10 has, for example, an inner diameter (D ₁ ) of 30 mm or more and 100 mm or less, an inner diameter (D ₂ ) of the body portion of 150 mm or more and 350 mm or less, an overall height (H ₁ ) of 250 mm or more and 700 mm or less, and a mouth portion. The height (H ₂ ) is 20 mm or more and 80 mm or less, and the body height (H ₃ ) is 100 mm or more and 600 mm or less.

The thickness of the mouth 1, shoulder 2, body 3, and bottom 4 of the plastic bottle 10 (excluding the thickness of the gas barrier film 5) is not particularly limited. For example, as described above, when the DLC film 5 is provided on the inner surface of the bottle by chemical vapor deposition, the shoulder portion 2 and the body portion 3 preferably have a thickness of 0.2 mm or more from the viewpoint of suppressing thermal deformation of the bottle. , 0.3 mm or more is more preferable.

The volume of the plastic bottle 10 is 5 L or more and 35 L or less. The lower limit is preferably 10 L or more from the viewpoint of good transportation efficiency as a container for a beverage server. Conventionally, it has not been assumed that a gas barrier film is provided for such a large-volume plastic bottle.

2.3. DLC film The plastic bottle 10 is provided with the DLC film 5 on the inner surface by chemical vapor deposition. Regarding the threshold condition for recyclability of plastic bottles (for example, PET bottles) on which a DLC film is formed, the recyclability is determined by evaluation based on the voluntary standards of the PET Bottle Recycling Promotion Council. In this respect, the thickness of the DLC film in the body portion 3 is preferably 15 nm or more and 50 nm or less, and more preferably 20 nm or more from the viewpoint of gas barrier stability. With such a thickness, it is possible to obtain a plastic bottle having excellent recyclability and an even lower oxygen permeability. On the other hand, the thickness of the DLC film in the mouth portion 1 is usually larger than the thickness of the DLC film in the body portion 3. In this case, the thickness of the DLC film at the mouth 1 is preferably 500 nm or more and 1000 nm or less. The lower limit is more preferably 600 nm or more, and the upper limit is more preferably 750 nm or less. If the thickness of the DLC film of the mouth portion 1 is too large, the dark color of the mouth portion 1 becomes remarkable and the opacity becomes stronger.

Further, in this case, the DLC film on the inner surface of the body portion 3 preferably has a binding composition in which I (D) / I (G) in Raman spectroscopy is 0.16 or more. On the other hand, the upper limit of I (D) / I (G) is not particularly limited, but is preferably 0.22 or less. I (D) / I (G ) is a peak attributed to the end of the six-membered ring network of the DLC film, the intensity ratio of the peak due to the graphite structure from sp ² bond, if the range of the For example, it is easy to combine the transparency, strength, and gas barrier property of the film.

Further, in this case, the DLC film on the inner surface of the body portion 3 preferably has a binding composition in which I (S) / I (N) in Raman spectroscopy is 1.0 or more. A large I (S) / I (N) means that the ratio of the inorganic component to the organic component is high, and there is a correlation with the increase in the hardness of the film and the increase in the refractive index due to the densification of the DLC film. Yes, they work to improve gas barrier properties and reduce the oxygen permeability of the bottle. In this respect, the upper limit of I (S) / I (N) is not particularly limited, but is usually 15 or less, preferably 13 or less, and more preferably 10 or less.

2.4. Oxygen permeability The plastic bottle 10 preferably has an oxygen permeability of 0.10 cc / m ² / day or less. More preferably, it is 0.09 cc / m ² / day or less. Further, the plastic bottle 10 preferably has an oxygen permeability of 0.06 cc / pkg / day or less. More preferably, it is 0.05 cc / pkg / day or less. With such an oxygen permeability, it can be used, for example, as a server container filled with a beverage containing carbonic acid.

2.5. Uses The use of the plastic bottle 10 is not particularly limited, but it is preferable that the inside is filled with a liquid. The type of liquid is not particularly limited, and examples thereof include various beverages including carbonated beverages such as juice and beer, various oils such as cooking oil and industrial oil, and seasonings such as soy sauce to prevent carbon dioxide and flavor from coming off. It is effective in preventing oxidation due to oxygen permeation in the atmosphere. In particular, as described above, since the plastic bottle 10 of the present disclosure is excellent in gas barrier property, it can also be used as a server container for beverages containing carbonic acid.

Hereinafter, the plastic bottles of the present disclosure will be described in more detail based on Examples.

1. 1. Evaluation method of gas barrier film (DLC film) <Film thickness (nm)>
The film thickness of the mouth was set at a position 10 mm downward from the top surface of the mouth.
The film thickness of the body was set at a height half of the total height of the container.
For film thickness measurement, a line is drawn on the inner surface of the container with black magic ink, masking is performed to form a DLC film, and then the masking is removed with ethanol. Was measured using.

<Refractive index>
Ellipsometer J. A. Using a Woollam M-2000X machine, two values of amplitude reflectance Psi (Ψ) and phase difference Delta (Δ), which represent the polarization state, were measured under the conditions of an incident angle of 45 to 75 degrees and a measurement wavelength of 380 to 780 nm. The obtained spectrum was analyzed by an optical model based on optical theory such as Fresnel's reflectance coefficient and Snell's law, and the refractive index was obtained.
The refractive index is related to the density of the film, and in general, the higher the density, the higher the refractive index. It is considered that if the density is high, the film becomes dense and the barrier property is improved.

<Three-dimensional surface roughness Sa (nm)>
A part of the container at a height half of the total height of the container was cut out and measured using a Brooker white interference microscope Contour GTX machine under the conditions of a measurement range of 720 μm square, an eyepiece magnification of 1.0 times, and an objective lens magnification of 10 times. Three-dimensional surface roughness was analyzed.
If the film surface shape is too rough, the state of the film is poor, and if the three-dimensional surface roughness Sa is about 10 nm or less, generally good gas barrier properties tend to be easily obtained.

<Nanoindentation method hardness (N / m ² )>
A silicon wafer 20 mm square was attached to the inner surface of the container body at a height of half the total height of the container to form a DLC film, which was used for measurement.
Using a nanoindentation tester ENT-2100 manufactured by Elionix Co., Ltd. and a triangular pyramid (Berkovich type) indenter, the average value measured three times was calculated. In the measurement, the hardness of the DLC film is measured by setting the indenter pushing depth to a depth equivalent to 1/5 to 1/10 of the film thickness from the surface of the DLC film so that the influence of the base material (silicon wafer) does not appear. Analyzed.

<Raman spectroscopic analysis>
A 20 mm square silicon wafer was attached to the inner surface of the container body at a height of half the total height of the container to form a DLC film, which was used for analysis.
The measurement was performed using a Nicolet Almega XR machine manufactured by Thermo Fisher Scientific, with an excitation wavelength of 532 nm, a resolution of about 10 cm ^-1 , an irradiation diameter of 1 μφm (objective lens 100 times, peen hole diameter 25 μm), and an excitation output of 1% (0.1 mW at the sample position). The following was performed under the conditions of an exposure time of 30 seconds and an integration number of 6 times, and the following spectral analysis was performed.

<Raman spectroscopic analysis I (S) / I (N)>
The spectrum derived from the DLC film ^{appears at a peak in the range of approximately 1800 cm -1} to 1000 cm ^-1 (see, for example, FIG. 2) and is proportional to the amount of hydrogen element derived from the DLC raw material contained in the DLC film. The fluorescence intensity is increased, and the baseline intensity of the Raman spectrum is increased.
Peak intensity I (t) at the peak top wavenumber position of about 1500 cm ^-1 of the above peak, baseline intensity I (N), I (t) at that position minus baseline intensity I (N). From (S), I (S) / I (N) was calculated.
For I (S) / I (N), the relative ratio of the carbon-carbon bond amount and the carbon-hydrogen bond amount appears, and the higher this value, the harder the DLC film, and the better the gas barrier property tends to be. Be done.

<Raman spectroscopic analysis I (D) / I (G)>
For peaks in the range of approximately 1800 ^{cm -1} to 1000 cm ^{-1, the peak top of approximately 1500 cm -1} (D-band), which is believed to belong to the end of the 6-membered ring network of the DLC, ^{and sp 2 using the Voigt function.} A peak separation analysis was performed on three peaks, a peak with a peak top of about 1330 cm ^-1 attributed to the bonded graphite structure (G-band) and a peak with an unknown peak top of about 1200 cm ^{-1, and D-band and G were performed.} I (D) / I (G) was calculated from the ratio of each peak top intensity I (D) and I (G) of −band.
The higher the I (D) / I (G) value, the better the gas barrier property tends to be.

<Measurement of oxygen permeability>
Using an OX-TRAN2 / 61 machine manufactured by MOCON, the adapter head for the above device was attached to the bottle opening, and the oxygen permeability per bottle under the condition of measurement 23 ° C. and 50 RH% (cc / pkg / 24h · air). Was measured. Further, using the bottle surface area values were calculated oxygen permeability per unit area ^{(cc / m 2/24 ·} air).

<Coloring of the mouth>
The bottle was erected and visually observed, and evaluated according to the following criteria.
◎ Extremely light tan ○ Light tan △ Slightly dark tan × Dark tan

2. Preparation of plastic bottles 2.1. Blow molding <Examples 1 to 4, Comparative Examples 1 to 3 (volume 20 L)>
It was obtained by a two-step blow molding method (cold parison method) using a bottomed cylindrical parison made of polyethylene terephthalate resin and a bottle-shaped mold as a non-deposited plastic bottle for forming a gas barrier film. I prepared a bottle. Volume of the bottle was 20L, barrel inner diameter _{(D 2)} is 235 mm, the ratio of the mouth inside diameter _{(D 1)} and the barrel inner diameter _{(D 2) (D 1 /} D 2) is 0.2.

<Comparative Example 4 (volume 15L)>
A plastic bottle for forming a gas barrier film was obtained in the same manner as in Example 1 except that the shape of the parison and the shape of the mold were changed. The volume of bottle 15L, barrel inner diameter _{(D 2)} is 235 mm, the ratio of the mouth inside diameter _{(D 1)} and the barrel inner diameter _{(D 2) (D 1 /} D 2) was 0.2.

<Reference example 1 (volume 1L)>
A plastic bottle for forming a gas barrier film was obtained in the same manner as in Example 1 except that the shape of the parison and the shape of the mold were changed. Volume of the bottle was 1L, barrel inner diameter _{(D 2)} is 106 mm, the ratio of the mouth inside diameter _{(D 1)} and the barrel inner diameter _{(D 2) (D 1 /} D 2) is 0.2.

<Reference example 2 (volume 0.5L)>
A plastic bottle for forming a gas barrier film was obtained in the same manner as in Example 1 except that the shape of the parison and the shape of the mold were changed. Volume of the bottle is 0.5 L, barrel inner diameter _{(D 2)} is 70.5 mm, the ratio of the mouth inside diameter _{(D 1)} and the barrel inner diameter _{(D 2) (D 1 /} D 2) is 0.3 and did.

2.2. Deposition of DLC film As shown schematically in FIG. 3, a blow-molded undeposited bottle is housed in a CVD device having an external electrode suitable for the size of the bottle and an exhaust port on the chamber wall above the container mouth. An internal electrode of φ10 mm, which also serves as a gas supply pipe with pores at the tip, is placed at the position of 1/2 (50%) of the total height of the bottle inside the bottle to perform vacuum exhaust, and the ultimate pressure inside the container. After reaching 15 Pa, high-purity acetylene gas was introduced at a predetermined flow rate, and a DLC film was formed on the inner surface of the bottle by plasma chemical vapor deposition at a predetermined high-frequency power source, output (power), and time. The film forming conditions and the properties of the formed DLC film are shown in Table 1 below.

As shown in Table 1, among the film forming conditions of the DLC film, by setting the high frequency output to 3000 W or more and 5000 W or less, a plastic bottle having excellent gas barrier properties and reduced color unevenness between the body and the mouth can be obtained. Obtained (Examples 1 to 4).
On the other hand, when the high frequency output was reduced to 2000 W, although the gas barrier property was excellent, the color unevenness between the body and the mouth was remarkable (Comparative Example 1).
Further, when the high frequency output was reduced to 1000 W, the oxygen permeability increased to 0.13 cc / m ² / day (Comparative Example 2). When the properties of the DLC film on the body were confirmed, the DLC film was softer than in Examples 1 to 4 and Comparative Example 1, and the influence of the substrate (Si wafer) appeared in the hardness measurement. Further, I (D) / I (G) and I (S) / I (N) (ratio of the inorganic component to the organic component) are smaller than those of Examples 1 to 5, and are compared with Examples 1 to 4. The film was brittle as compared to Example 1.
Furthermore, in the absence of the gas barrier membrane, the oxygen permeability could not be made sufficiently small, as a matter of course (Comparative Examples 3 and 4).
When Examples 1 to 4 are compared with Reference Examples 1 and 2, it can be seen that the oxygen permeability in Examples 1 to 4 is comparable to that in Reference Examples 1 and 2. That is, it was found that by providing the DLC film on the inner surface of the bottle under the above-mentioned film forming conditions, it is possible to manufacture a plastic bottle having excellent gas barrier properties even when the bottle volume is large.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to manufacture a plastic bottle having a large volume of 5 liters or more, which ensures sufficient gas barrier properties and reduces color unevenness due to a DLC film between the mouth and the body. By manufacturing a large-volume gas-barrier plastic bottle, for example, the weight of beer server containers can be reduced, and the return process is not required, so that the labor for transporting and storing them can be significantly reduced. Furthermore, since there is little coloring of the container mouth and uneven color with the body, the transparency of the entire container is good, and it does not give the user a feeling of strangeness or anxiety, and it has a gas barrier property especially for beverage applications. Effective for market development of large plastic containers.

1 Mouth 2 Shoulder 3 Body 4 Bottom 5 Gas barrier membrane 10 Plastic bottle

Claims (8)

A method for manufacturing a plastic bottle, which comprises a step of forming a DLC film on the inner surface of a non-deposited plastic bottle by a chemical vapor deposition method.
The undeposited plastic bottle has a mouth, shoulders, body and bottom, has a volume of 5 L or more and 35 L or less, and has a ratio (D) _{of the inner diameter of the mouth (D 1} ) and the inner diameter of the body (D _{2). 1} / D ₂ ) is 0.1 or more and 0.3 or less,
In the film formation of the DLC film by the chemical vapor deposition method, high frequency power of 3000 W or more and 5000 W or less is adopted .
The film formation time of the DLC film is set to 6 seconds or less, and the thickness of the DLC film on the inner surface of the body is set to 15 nm or more and 50 nm or less.
Production method. Or less before Symbol mouth 1000nm the DLC film thickness of 500nm or more on the inner surface of the process according to claim 1. The DLC film on the inner surface of the body has a binding composition in which I (D) / I (G) in Raman spectroscopy is 0.16 or more.
The manufacturing method according to claim 1 or 2. The DLC film on the inner surface of the body has a binding composition in which I (S) / I (N) in Raman spectroscopy is 1.0 or more.
The manufacturing method according to any one of claims 1 to 3. The oxygen permeability of the plastic bottle is 0.10 cc / m ² / day or less.
The manufacturing method according to any one of claims 1 to 4. The oxygen permeability of the plastic bottle is 0.06 cc / pkg / day or less.
The manufacturing method according to any one of claims 1 to 5. The undeposited plastic bottle is obtained by blow molding.
The manufacturing method according to any one of claims 1 to 6. The plastic bottle is filled with a beverage containing carbonic acid.
The manufacturing method according to any one of claims 1 to 7.

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