JP2018159115A - Method for producing plastic bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a plastic bottle that includes the step for depositing a DLC film on the inner surface of a plastic bottle with a large volume of 5 liters or more, where, sufficient gas barrier properties are secured, and color irregularities in a mouth and a trunk are suppressed.SOLUTION: A method for producing a plastic bottle includes the step for depositing a DLC film on the inner surface of an undeposited plastic bottle by chemical vapor deposition. The undeposited plastic bottle has a mouth 1, a shoulder 2, a trunk 3 and a bottom 4, has a volume of 5-35 L, with the ratio between the mouth inner diameter (D) and the trunk inner diameter (D)(D/D) of 0.1-0.3, where, in depositing of the DLC film 5 by the chemical vapor deposition, high frequency power of 3000-5000 W is employed. In the method, the thickness of the DLC film 5 in the trunk 3 is 15-50 nm, and the thickness of the DLC film 5 in the mouth 1 is 500-1000 nm.SELECTED DRAWING: Figure 1

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, a shoulder, a body, and a 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 and the like, the container itself is heavy when it is made of stainless steel, and much cost and labor are required for transporting and cleaning the container for reuse.

  As an alternative to stainless steel containers, plastic containers have recently become widespread mainly in Europe. However, conventional European products contain scavengers that use oxygen barrier resin and metal compounds in the main raw material polyethylene terephthalate resin (PET) to give gas barrier properties to plastic bottles. It becomes incompatible with the recycling law.

  In order to achieve both the recyclability of the plastic bottle and the gas barrier property, 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 diamond like carbon (DLC) having a thickness of several tens of nanometers is formed on the inner surface of a plastic bottle having a mouth portion, a shoulder portion, a body portion, and a bottom portion by a chemical vapor deposition (CVD) method. Is popular. However, the mouth portion having a diameter smaller than that of the body portion becomes dark brown with respect to the body portion due to DLC film formation, and the entire bottle tends to be uneven in color.

  Although there are the following disclosed techniques for lightening the mouth and reducing color unevenness, 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, the dark brown color of the mouth is difficult to be eliminated. The technique disclosed in Patent Document 2 requires a step of installing the cylindrical member after the bottle is loaded into the CVD chamber (deposition chamber), and the cylindrical member is removed from the inside of the mouth after the DLC film formation. Therefore, there is a problem in that film formation foreign matter is likely to occur. Further, in the technique disclosed in Patent Document 3, a general CVD film forming apparatus performs exhaust by providing an exhaust port on a part of the wall surface of the chamber, whereas an exhaust method in which a new exhaust pipe is produced and installed. It must be changed to an investment, which requires investment and reduces production efficiency. Furthermore, 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 becomes insufficient.

JP 2003-237754 A JP 2008-050050 A JP 2006-160269 A JP 2002-053119 A

  In view of the above-described background art, in the present application, in the plastic bottle manufacturing method including the step of forming a DLC film on the inner surface of a large-capacity plastic bottle of 5 liters or more, a sufficient gas barrier property is secured, and the mouth portion And a method that makes it possible to reduce uneven color of the body.

This application is one of the means for solving the above-described problems.
A method of manufacturing a plastic bottle comprising a step of forming a DLC film on the inner surface of an undeposited plastic bottle by chemical vapor deposition, wherein the undeposited plastic bottle has a mouth, a shoulder, a trunk 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 A manufacturing method is disclosed in which high-frequency power of 3000 W or more and 5000 W or less is employed in the 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 to 50 nm and the thickness of the DLC film on the inner surface of the mouth portion is 500 nm to 1000 nm.

  In the manufacturing method of the present disclosure, it is preferable that the DLC film on the inner surface of the body portion has a bond composition in which I (D) / I (G) in Raman spectroscopic analysis is 0.16 or more.

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

In the manufacturing method of this indication, it is preferable that the oxygen permeability of the said plastic bottle is 0.10 cc / m < ² > / day or less.

  In the manufacturing method of this indication, it is preferable that the oxygen permeability of the said plastic bottle is 0.06 cc / pg / 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, the plastic bottle is preferably filled with a beverage containing carbonic acid.

  According to the manufacturing method of the present disclosure, it is possible to manufacture a large-capacity plastic bottle in which sufficient gas barrier properties are ensured and color unevenness due to the 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 metal compound scavenger in the resin layer, it can be recycled, and the plastic resources can be effectively used and the environment can be protected. Further, oxidation and decay due to permeation of atmospheric water vapor and oxygen gas into the bottle can be suppressed, and carbonation loss and flavor reduction due to permeation of carbon dioxide gas and flavor components inside the bottle to the outside of the bottle can be suppressed.

It is the schematic for demonstrating an example of the shape of the plastic bottle 10 manufactured with the manufacturing method of this indication. It is a figure which shows an example of the spectrum originating in the DLC film which can be confirmed in a Raman spectroscopic analysis. It is a figure which shows schematically the CVD apparatus used in the Example.

1. Method for Producing Plastic Bottle The method for producing a plastic bottle of the present disclosure includes a step of forming a DLC film on the inner surface of an undeposited plastic bottle by chemical vapor deposition. As shown in FIG. 1, the non-film-form plastic bottle used for the manufacturing method of this indication has the mouth part 1, the shoulder part 2, the trunk | drum 3, and the bottom part 4, and is 5L or more and 35L or less in volume, inside diameter _{(D 1)} and the ratio of the barrel inner diameter _{(D 2) (D 1 /} D 2) of 0.1 to 0.3. The manufacturing method of the present disclosure has one feature in that high-frequency power of 3000 W or more and 5000 W or less is employed in the formation of the DLC film 5 by chemical vapor deposition.

  An undeposited plastic bottle not provided with a DLC film can be easily manufactured by, for example, a blow molding method in which a bottomed cylindrical parison (preform) is heated and blown and stretched in a mold. What is necessary is just to determine a parison shape, its manufacturing method, and blow drawing conditions suitably according to the volume and shape of a bottle.

  The plastic bottle 10 can be manufactured by providing a DLC film on the inner surface of the non-deposited bottle after blow molding using a general-purpose CVD apparatus. For example, a non-deposited plastic container is accommodated inside an external electrode that matches the size of the plastic container, and chemical vapor deposition (plasma chemical vapor deposition) is performed after the internal electrode is placed at a predetermined position inside or outside the container opening. ) Can form a gas barrier film in the container. The plasma chemical vapor deposition method is a method in which a source gas is dissociated and ionized by plasma generated under reduced pressure to generate a film-forming species, and is deposited and formed 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, the internal electrode having a gas supply pipe function is preferably disposed at a position inside the bottle and 1/5 (20%) to 4/5 (80%) of the bottle height, A position of 1/4 (25%) to 3/4 (75%) is more preferable.

  Examples of the source 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; aromatic hydrocarbon compounds such as benzene, toluene and xylene. . These may be used alone or in admixture of two or more. Among these, it is preferable to use ethylene or acetylene gas alone.

  A small amount of hydrogen or an organic compound may be mixed in the source gas. Further, the source gas may be diluted with a rare gas such as argon or helium.

  When a DLC film is formed by plasma chemical vapor deposition, evacuation (reduced pressure) and gas introduction are performed, and when the inside reaches a predetermined pressure (degree of vacuum), the source gas is turned into plasma and formed. The internal pressure at the time of film formation is preferably 1 Pa or more and 50 Pa or less in view of good film quality and physical properties and the required film formation time. The source 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 film formation components can be prevented from adhering to and falling from the parts and mixing foreign substances into the container film formation.

  The inside of the chamber is set to a predetermined degree of vacuum, source gas is supplied, and a voltage is applied between the external electrode and the internal electrode at the ground potential to generate plasma inside the container accommodated in the external electrode. Thus, 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 can be, for example, several MHz to several hundred MHz, and preferably 6 MHz or 13.56 MHz from the viewpoint of versatility. Further, as will be described later, it is important that the power (output) is 3000 W or more and 5000 W or less from the viewpoint of ensuring sufficient gas barrier properties 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 knowledge of the present inventor, high-quality gas barrier properties can be obtained only by scaling up the film-forming conditions (for example, JP-A-8-053116) of a gas barrier film in a conventional small plastic bottle in accordance with the shape of a large plastic bottle. A film (particularly a DLC film) cannot be obtained. The reason is as follows.

As described above, in general, in DLC film formation of a container having a smaller inner diameter (D ₁ ) than the inner diameter (D ₂ ) of the body, the DLC film thickness of the mouth 1 is larger than that of the body 3, and Become. Furthermore, a large container of 5 liters or more is formed under a general film formation condition 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. If it tries to do so, the dark color of the mouth becomes conspicuous and the opacity increases.

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 these conditions, the coloring of the mouth is reduced and a good appearance is obtained. The cause of this phenomenon is thought to be that the plasma decomposition of the source gas progresses when the film formation output is increased, and the balance between the film formation on the container body and the film formation on the opening side changes. . In the DLC film formation on the container, the film formation conditions are extremely important because they affect the film quality, and among them, the film formation output greatly affects the plasma decomposition of the source gas. It is a requirement that greatly affects As described above, by setting the high-frequency power to 3000 W or more, a cylindrical member is loaded inside the mouth as in the past, a gas exhaust pipe is placed inside the bottle, or a masking member is attached to the mouth. Even without performing DLC film formation, it is possible to combine the gas barrier properties of the bottle with the suppression of darkening of the mouth and transparency. 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 the high frequency power is preferably 5000 W or less.

When the output of the high-frequency power is large, if the pressure during film formation is high, abnormal discharge is likely to occur, and the possibility of damaging not only the film itself and the resin container but also the film forming apparatus increases. In order to suppress abnormal discharge, it is effective to exhaust the inside of the container efficiently. In this respect, 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, a gas exhaust pipe is disposed inside the container. At least, the inside of the container can be efficiently evacuated under the conventional equipment conditions in which the exhaust port is installed on the wall surface of the film forming chamber away from the container loading position.

  Further, generally, at a high output, due to the heat generation, a relatively thin resin thickness portion such as a shoulder portion of the container is easily subjected to thermal deformation, but a trunk diameter of 130 mm or more, more preferably 180 mm or more, a resin thickness of 0.2 mm or more, More preferably, if it is 0.3 mm or more, thermal deformation due to heat is unlikely to occur. In addition, since the resin thickness is inevitably designed from the viewpoint of the bottle strength of the large-capacity container, no special resin thickness design is required for the high-frequency power condition in manufacturing the plastic bottle 10 of the present disclosure. It is.

  Further, according to the inventor's knowledge, as the deposition output increases, I (S) / I (N) in the Raman spectrum analysis of the DLC film increases, and the ratio of the inorganic component to the organic component tends to increase. . Further, as the ratio of the inorganic component is larger, that is, as I (S) / I (N) is larger, the tendency of increasing the hardness of the DLC film and increasing the refractive index is obtained. This is a manifestation of the correlation that the higher the inorganic component ratio of the DLC film, the denser the film (density increases), and generally the hardness and refractive index of the film increase. As a result, the gas barrier property of the container increases. It is considered that the effect (being reduced oxygen permeability) is 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 coloring of the mouth.

2. Plastic Bottle 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 obtained by providing a DLC film 5 on the inner surface of an undeposited plastic bottle made mainly of a thermoplastic resin. The undeposited plastic bottle has a mouth part 1, a shoulder part 2, a body part 3 and a bottom part 4, has a volume of 5L or more and 35L or less, and has a mouth inner diameter (D ₁ ) and a body inner diameter (D ₂ ). The ratio (D ₁ / D ₂ ) is 0.1 or more and 0.3 or less.

2.1. Raw material Non-deposited plastic bottles are mainly made of thermoplastic resin. The “main raw material” means that 90% by mass or more of the raw material 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 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-described blow molding becomes easier. Further, a nylon resin may be mixed in order to improve heat resistance. On the other hand, needless to say, the plastic bottle 10 does not contain a metal compound scavenger as a raw material. When a scavenger is included, recycling becomes difficult and the above problem 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 trunk portion 3, and a bottom portion 4. The shapes of the mouth part 1, the shoulder part 2, the trunk part 3 and the bottom part 4 are not particularly limited. In particular, as shown in FIG. 1, it is preferable that the horizontal cross-sectional shapes of the mouth part 1, the shoulder part 2 and the body part 3 are circular. This is because the gas barrier film 5 described later can be provided uniformly 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, when a DLC film is formed in a container having a smaller diameter (D ₁ ) than the body diameter (D ₂ ), the DLC film thickness at the mouth increases compared to the body, resulting in a dark color. Furthermore, when it is attempted to obtain a sufficient gas barrier property of the body portion by general gas barrier film forming conditions, the deep color of the mouth portion 1 becomes very remarkable and the opacity is increased. 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 transparency. In this case, DLC film formation can be easily performed without loading a cylindrical member inside the mouth portion 1, disposing 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 the mouth part of 30 mm to 100 mm, an inner diameter (D ₂ ) of the body part of 150 mm to 350 mm, and an overall height (H ₁ ) of 250 mm to 700 mm. 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 (except for the thickness of the gas barrier film 5) at the mouth portion 1, the shoulder portion 2, the body portion 3 and the bottom portion 4 of the plastic bottle 10 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, it is preferable that the shoulder portion 2 and the trunk portion 3 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 5L or more and 35L or less. The lower limit is preferably 10 L or more from the viewpoint of good transport efficiency as a beverage server container. Conventionally, it has not been assumed that a gas barrier film is provided on 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 of whether or not a plastic bottle (for example, PET bottle) on which a DLC film is formed can be recycled, whether or not recycling is possible is determined by evaluation based on a voluntary standard 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. By setting it as such thickness, while being excellent in recyclability, it can be set as a plastic bottle with a still lower oxygen permeability. On the other hand, the thickness of the DLC film at the mouth 1 is usually larger than the thickness of the DLC film at the body 3. In this case, it is preferable that the thickness of the DLC film in the mouth portion 1 is not less than 500 nm and not more than 1000 nm. 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 at the mouth 1 is too large, the dark color of the mouth 1 becomes noticeable and the opacity increases.

In this case, it is preferable that the DLC film on the inner surface of the body portion 3 has a bond composition in which I (D) / I (G) in Raman spectroscopic analysis 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 the intensity ratio of the peak attributed to the end of the six-membered ring network of the DLC film and the peak attributed to the graphite structure derived from the sp ² bond, and is within the above range. For example, the transparency, strength, and gas barrier properties of the film are easily combined.

  Furthermore, in this case, it is preferable that the DLC film on the inner surface of the body portion 3 has a bond composition in which I (S) / I (N) in Raman spectroscopic analysis 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 an increase in the hardness of the film due to the densification of the DLC film and an increase in the refractive index. Yes, they work to improve the gas barrier properties, and the oxygen permeability of the bottle is reduced. 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, 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. The plastic bottle 10 preferably has an oxygen permeability of 0.06 cc / pg / day or less. More preferably, it is 0.05 cc / pg / day or less. With such oxygen permeability, for example, it can be used as a server container filled with a beverage containing carbonic acid.

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

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

1. About evaluation method of gas barrier film (DLC film) <film thickness (nm)>
The film thickness at the mouth was 10 mm downward from the top of the mouth.
The film thickness of the trunk portion was a film thickness at a height position that was half of the total height of the container.
Film thickness measurement is done by writing a line with black magic ink on the inner surface of the container to perform DLC film formation, and then removing the masking with ethanol. The location is a high-precision fine shape measuring instrument ET4000A manufactured by Kosaka Laboratory Ltd. It measured using.

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

<Three-dimensional surface roughness Sa (nm)>
A part of the container at half the height of the container is cut out and measured using a Bruker white interference microscope Contour GTX machine under the conditions of a measuring 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 film state 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 hardness (N / m ² )>
A DLC film was formed by attaching a 20 mm square silicon wafer to the inner surface of the container barrel at half the height of the entire container, and used for measurement.
The average value measured 3 times was calculated using a nanoindentation tester ENT-2100 manufactured by Erio Nix Co., Ltd. and a triangular pyramid (Berkovic type) indenter. In the measurement, the indenter indentation depth is set to a depth corresponding to 1/5 to 1/10 of the film thickness from the surface of the DLC film so that the influence of the substrate (silicon wafer) does not appear, and the hardness of the DLC film is measured. Analyzed.

<Raman spectroscopy>
A DLC film was formed by attaching a 20 mm square silicon wafer to the inner surface of the container body at half the height of the entire container, and was subjected to analysis.
Measurement was performed using a Nicolet Almega XR machine manufactured by Thermo Fisher Scientific, an excitation wavelength of 532 nm, a resolution of about 10 cm ⁻¹ , an irradiation diameter of ¹ μφm (objective lens 100 times, a pein hole diameter of 25 μm), and an excitation output of 1% (0.1 mW at the sample position). The following spectrum analysis was performed under the conditions of an exposure time of 30 seconds and an integration count of 6 times.

<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. As a result, the fluorescence intensity increases and the baseline intensity of the Raman spectrum increases.
The peak intensity I (t) at the peak top wavenumber position of about 1500 cm ⁻¹ of the above peak, the baseline intensity I (N) at that position, and the peak intensity I obtained by subtracting the baseline intensity I (N) from I (t). From (S), I (S) / I (N) was calculated.
I (S) / I (N) shows the relative ratio of the amount of carbon-carbon bonds and the amount of carbon-hydrogen bonds, and the higher this value, the harder the DLC film, and the better the gas barrier properties generally. It is done.

<Raman spectroscopy I (D) / I (G)>
For a peak in the range of approximately 1800 cm ⁻¹ to 1000 cm ⁻¹ , a peak (D-band) of about 1500 cm ⁻¹ considered to be attributed to the end of the DLC six-membered ring network using a Forked function, sp ² Peak separation analysis is performed on three peaks, a peak (G-band) having a peak top of about 1330 cm ⁻¹ attributed to the graphite structure of the bond and a peak having an unidentified peak top of about 1200 cm ⁻¹ , and D-band and G I (D) / I (G) was calculated from the ratio of each -band peak top intensity I (D), I (G).
Generally, the higher the I (D) / I (G) value, the better the gas barrier property.

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

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

2. Production of plastic bottle 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 an undeposited plastic bottle for depositing a gas barrier film. A bottle was prepared. 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 parison shape and mold shape 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 parison shape and mold shape 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 0.5 L)>
A plastic bottle for forming a gas barrier film was obtained in the same manner as in Example 1 except that the parison shape and mold shape 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. Film formation of DLC film As shown schematically in FIG. 3, a blow-molded non-film forming bottle is accommodated in a CVD apparatus having an external electrode matched to the size of the bottle and an exhaust port on the chamber wall above the container opening. Then, an internal electrode of φ10mm that also serves as a gas supply pipe with a fine hole at the tip is arranged at a position where the total bottle height in the bottle is ½ (50%), and evacuation is performed. After the pressure reached 15 Pa, a 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 formation conditions and the properties of the formed DLC film are shown in Table 1 below.

As shown in Table 1, among the conditions for forming the DLC film, by setting the high-frequency output to 3000 W or more and 5000 W or less, the plastic bottle has excellent gas barrier properties and reduced color unevenness between the body and the mouth. 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 trunk portion and the mouth portion 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 property of the DLC film of the trunk portion was confirmed, the DLC film was softer than those of Examples 1 to 4 and Comparative Example 1, and the influence of the base (Si wafer) appeared in the hardness measurement. Moreover, I (D) / I (G) and I (S) / I (N) (ratio of the inorganic component to the organic component) are smaller than those in Examples 1 to 5, and Examples 1 to 4 and Comparison Compared to Example 1, the membrane was brittle.
Furthermore, when the gas barrier film was not provided, it was obvious that the oxygen permeability could not be made sufficiently small (Comparative Examples 3 and 4).
In addition, when Examples 1-4 and Reference Examples 1 and 2 are compared, it turns out that the oxygen permeability in Examples 1-4 is comparable with Reference Examples 1 and 2. That is, it was found that by providing a DLC film on the inner surface of the bottle under the film forming conditions described above, a plastic bottle having excellent gas barrier properties can be manufactured even when the bottle volume is increased.

  According to the present invention, it is possible to manufacture a plastic bottle having a large capacity of 5 liters or more in which sufficient gas barrier properties are secured and color unevenness due to the DLC film is reduced between the mouth and the body. By manufacturing a large-capacity gas barrier plastic bottle, for example, it is possible to reduce the weight of a server container for beer and the like, and since a return process becomes unnecessary, the labor for transporting and storing them can be greatly reduced. Furthermore, since there is little coloring of the container mouth and color unevenness with the body, the transparency of the entire container is improved, and it does not give the user a different texture or anxiety. It is effective for the market development of large plastic containers.

1 mouth part 2 shoulder part 3 trunk part 4 bottom part 5 gas barrier film 10 plastic bottle

Claims (8)

A method for producing a plastic bottle comprising a step of forming a DLC film on the inner surface of an undeposited plastic bottle by chemical vapor deposition,
The undeposited plastic bottle has a mouth, a shoulder, a body, and a bottom, has a volume of 5L to 35L, and a ratio of a mouth inner diameter (D ₁ ) to a body inner diameter (D ₂ ) (D ₁ / D ₂ ) is 0.1 or more and 0.3 or less,
Adopting a high frequency power of 3000 W or more and 5000 W or less in the formation of the DLC film by the chemical vapor deposition method,
Production method. The thickness of the DLC film on the inner surface of the trunk is 15 nm or more and 50 nm or less,
The thickness of the DLC film on the inner surface of the mouth is 500 nm or more and 1000 nm or less,
The manufacturing method according to claim 1. The DLC film on the inner surface of the trunk portion has a bond composition in which I (D) / I (G) in Raman spectroscopic analysis is 0.16 or more.
The manufacturing method of Claim 1 or 2. The DLC film on the inner surface of the body portion has a bond composition in which I (S) / I (N) in Raman spectroscopic analysis is 1.0 or more.
The manufacturing method of any one of Claims 1-3. The oxygen permeability of the plastic bottle is 0.10 cc / m ² / day or less,
The manufacturing method of any one of Claims 1-4. The oxygen permeability of the plastic bottle is 0.06 cc / pg / day or less,
The manufacturing method of any one of Claims 1-5. Obtaining the undeposited plastic bottle by blow molding,
The manufacturing method of any one of Claims 1-6. The plastic bottle is filled with a beverage containing carbonic acid,
The manufacturing method of any one of Claims 1-7.