JP4340764B2 - Method for manufacturing inner surface coated plastic container - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an inner surface-coated plastic container having a coating containing amorphous carbon on the inner surface side.
[0002]
[Prior art]
Conventionally, containers made of various plastics such as polyethylene terephthalate resin have been used as containers for fluid substances such as beverages, foods, aerosols, cosmetics, and pharmaceuticals. The plastic container is lighter than a metal container or a glass container, but has a problem that it is inferior in gas barrier properties.
[0003]
In recent years, in order to improve the gas barrier property, it has been proposed and put to practical use to provide a film containing amorphous carbon by the plasma CVD method on the inner surface side of the plastic container. In the plasma CVD method, for example, the plastic container is disposed in a hollow processing chamber, the inside of the processing chamber and the plastic container is evacuated and kept in a vacuum, and the inside of the plastic container is made of acetylene or the like from the mouth. The coating is formed on the inner surface of the plastic container by introducing the starting material in the form of gas and applying a high frequency or microwave voltage to generate plasma in the plastic container.
[0004]
A plastic container in which the coating film is formed on the inner surface side can exhibit excellent gas barrier properties by increasing the thickness of the coating film. However, when the film thickness is increased, the adhesion of the film to the plastic container is lowered and cannot follow the processing deformation, so that there is a problem that sufficient workability cannot be obtained. Further, when the film thickness is increased, there is a problem that coloring by the film becomes remarkable.
[0005]
The coloring by the film may not be preferred by consumers depending on the contents. In addition, when the coating film is colored, it may be an obstacle when a used container such as a polyethylene terephthalate resin container (hereinafter abbreviated as a plastic container) is collected and reused.
[0006]
Therefore, it is desired to develop a method for producing a plastic container having a thin coating film and excellent gas barrier properties.
[0007]
In view of the above circumstances, the present inventors have studied the gas barrier performance of the coating containing amorphous carbon formed on the inner surface side of the plastic container. As a result, it has been found that the gas barrier performance of the coating varies greatly depending on the proportion of atoms other than carbon, particularly nitrogen atoms or oxygen atoms, contained in the coating.
[0008]
The present inventors have further studied based on the above knowledge, and by suppressing the ratio of the number of nitrogen atoms or the number of oxygen atoms to the number of carbon atoms contained in the film within a predetermined range, the film thickness of the film It has been found that excellent gas barrier properties can be obtained even if the thickness is reduced.
[0009]
In the manufacturing method, the gas component supplied into the plastic container contains a nitrogen-containing compound such as dimethylformamide and air in addition to the gaseous starting material, and nitrogen atoms contained in the coating film. Alternatively, the oxygen atom is derived from the nitrogen-containing compound or air. The air is incompletely exhausted inside the processing chamber and the plastic container, or when the airtightness of the apparatus maintained at a predetermined degree of vacuum is insufficient, and air leakage occurs in the plastic container. It is mixed in the starting material.
[0010]
Therefore, in the manufacturing method, by controlling the amount of nitrogen gas or oxygen gas in the gas component supplied into the plastic container, the number of nitrogen atoms or the number of oxygen atoms relative to the number of carbon atoms contained in the film is reduced. The ratio can be kept within a predetermined range.
[0011]
However, in the conventional manufacturing method, once the manufacturing is started, even if the amount of nitrogen-containing compound or air mixed in the starting material changes and exceeds a predetermined range, it is detected and controlled. Therefore, the ratio of the number of nitrogen atoms or the number of oxygen atoms to the number of carbon atoms contained in the coating film cannot be suppressed within a predetermined range, and a plastic container having a predetermined gas barrier property cannot be obtained. There is a need for improvement in terms of manufacturing process control, product quality control, and product yield.
[0012]
[Problems to be solved by the invention]
The present invention eliminates such inconvenience, and manufactures a plastic container having a low gas barrier property when the amount of nitrogen-containing compound or air mixed in the gas component supplied into the plastic container exceeds a predetermined range. Another object of the present invention is to provide a method for producing an inner surface-coated plastic container that can prevent and further eliminate those having low gas barrier properties in the produced plastic container.
[0013]
[Means for Solving the Problems]
In order to achieve such an object, a method for producing an inner surface-coated plastic container according to the present invention includes storing a plastic container in a plasma CVD apparatus, maintaining the inside of the plasma CVD apparatus at a predetermined degree of vacuum, and placing carbon in the plastic container. Forming a film containing amorphous carbon on the inner surface of the plastic container by supplying a starting material containing atoms in a gaseous state and applying predetermined energy to the plasma CVD apparatus to generate plasma in the plastic container In the method of manufacturing an inner surface-coated plastic container, nitrogen is selectively detected by detecting light in a specific wavelength region in an emission spectrum of plasma generated by a gas component containing the starting material supplied into the plastic container. by detecting the emission intensity of the plasma, more than 20% by volume based on the total amount of said gas component When the nitrogen content of the is detected, by adjusting the concentration of the nitrogen-containing compound to be mixed into the gas component, nitrogen gas is characterized in that so as to be 20% by volume based on the total amount of the gas component .
[0014]
In the production method of the present invention, when the gas component supplied into the plastic container contains a nitrogen-containing compound or air in addition to the gaseous starting material, nitrogen derived from the nitrogen-containing compound or air. Contains ingredients.
[0015]
Therefore, in the manufacturing method of the present invention, a gas component containing the starting material is supplied into the plastic container, and a predetermined energy is applied to the plasma CVD apparatus, whereby an emission spectrum due to plasma generated in the plastic container. Is measured, and the light emission intensity by the plasma of the nitrogen component (hereinafter abbreviated as nitrogen plasma light emission intensity) is detected by selectively detecting light in a specific wavelength region in the emission spectrum. In this way, since the presence or absence of nitrogen in the gas component and the amount thereof can be known from the nitrogen plasma emission intensity, when the nitrogen plasma emission intensity exceeds a predetermined intensity, it is contained in the gas component. It is determined that the nitrogen component exceeds the predetermined range, and the cause is eliminated.
[0016]
In the production process of the present invention, as the elimination of the cause, specifically, it controls the concentration of nitrogen-containing compounds to be mixed into the gas component supplied into the plastic container. As a result, the nitrogen gas is suppressed to 20% by volume or less with respect to the total amount of the gas components.
[0017]
Therefore, according to the manufacturing method of the present invention, when a nitrogen component in an amount exceeding 20% by volume is detected with respect to the total amount of the gas component supplied into the plastic container, the manufacturing of the plastic container having a low gas barrier property is prevented. can do.
[0018]
The concentration of the control of the nitrogen-containing compound to be mixed into the gas component, for example, can be performed by the feedback control, if the nitrogen component in an amount exceeding 20% by volume based on the total amount of the gas component is detected immediately containing nitrogen By taking measures to suppress the amount of compound contamination, a predetermined gas barrier property can be secured for a plastic container produced thereafter. However, when performing the feedback control, a predetermined gas barrier property cannot be obtained for a plastic container manufactured when a nitrogen component in an amount exceeding 20% by volume is detected with respect to the total amount of the gas component .
[0019]
Therefore, in the production method of the present invention, when a nitrogen component in an amount exceeding 20% by volume is detected with respect to the total amount of the gas component, the plastic container on which the coating film is formed is excluded from the production process. To do. In this case, by removing the plastic container manufactured when the nitrogen component in an amount exceeding 20% by volume with respect to the total amount of the gas component is detected from the manufacturing process after the film formation, the gas barrier is removed. It is possible to prevent mixing of a low-quality plastic container into a good product.
[0020]
Nitrogen in the manufacturing method of the present invention, the amount of nitrogen components contained before SL gas component, for the intensity of the light quantity and the specific wavelength region of nitrogen components must have already created the calibration curve, which is detected The plasma emission intensity can be obtained by comparing with the calibration curve.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a system configuration diagram showing a configuration example of an apparatus used in the manufacturing method of the present embodiment, and FIG. 2 is generated when the gas component supplied into the plastic container is only the gaseous starting material. FIG. 3 shows an example of the spectrum of plasma generated when the gas component supplied into the plastic container contains a nitrogen component in addition to the gaseous starting material. FIG.
[0022]
In this embodiment, an inner surface-coated plastic container is manufactured using the apparatus shown in FIG.
[0023]
In the apparatus shown in FIG. 1, reference numeral 1 denotes a plasma CVD apparatus. The plasma CVD apparatus 1 includes a processing chamber 4 defined by a side wall 2 made of Pyrex (registered trademark) glass and a bottom plate 3 that can be raised and lowered. The microwave generator 5 is provided at a position facing the side wall 2. An exhaust chamber 8 defined by a side wall 6 and an upper wall 7 is provided above the processing chamber 4, and a partition wall 9 is provided between the processing chamber 4.
[0024]
The bottom plate 3 accommodates the plastic container 10 in the processing chamber 4 by placing the plastic container 10 and moving upward. The plastic container 10 housed in this manner is arranged so that the inside of the container communicates with the exhaust hole 12 provided in the partition wall 9 through the mouth holder 11. In the mouth holder 11, the upper protrusion 13 is closely inserted into the exhaust hole 12, and the mouth holder 14 is inserted into the mouth of the plastic container 10 with a predetermined interval.
[0025]
The processing chamber 4 and the exhaust chamber 8 communicate with each other through a valve 16 of a vent 15 provided in the partition wall 9, and an opening 17 formed in the side wall 6 of the exhaust chamber 8 is connected to a vacuum device (not shown). Yes. A gas introduction pipe 19 for supplying a gaseous starting material (hereinafter abbreviated as a raw material gas) is supported on the upper wall 7 of the exhaust chamber 8 via a seal 18, and the gas introduction pipe 19 is supported on the upper wall 7. And the mouth holder 11 are inserted into the plastic container 10. There is a gap between the gas introduction pipe 19 and the inner peripheral surface of the mouth holder 11.
[0026]
In addition, at a position facing the side wall 2 of the processing chamber 4 (a surface facing the microwave generator 5 in FIG. 1), a light receiving unit 20 that receives light emitted from the generation of plasma in the plastic container 10 is provided. . The light receiving unit 20 is connected to the plasma emission spectroscopic analyzer 22 by an optical fiber 21. The plasma emission spectrometer 22 includes a bandpass filter 23, a detection unit 24, and a main control unit 25, and the optical fiber 21 is connected to the bandpass filter 23. The main control unit 25, excluded from the manufacturing process and the gas component control means 26 for controlling the concentration of nitrogen-containing compound to be mixed in said gas component, the plastic container 10 which is not provided with a predetermined gas barrier properties as a defective container Connected to the defective container removing means 27.
[0027]
In the apparatus shown in FIG. 1, first, a plastic container 10 is placed on the bottom plate 3 of the plasma CVD apparatus 1. Then, the bottom plate 3 is moved up and the plastic container 10 is stored in the processing chamber 4.
[0028]
The plastic container 10 is used as a container for fluid substances such as beverages, foods, aerosols, cosmetics, pharmaceuticals, and the like. Polyester resins such as polyethylene terephthalate, polyolefin resins such as polyethylene and polypropylene, polyamide resins, poly It consists of ether resin, polyacrylic resin, and the like. When used as a beverage container, the plastic container 10 is suitably made of a polyester resin or a polyolefin resin.
[0029]
Next, a vacuum device (not shown) is operated to exhaust the inside of the exhaust chamber 7, and thereby the pressure inside the processing chamber 4 is reduced to a vacuum degree of 1 to 50 Pa through the vent 15. At the same time, the inside of the plastic container 10 is depressurized to a vacuum degree of 1 to 50 Pa through a gap between the gas introduction pipe 19 inserted into the exhaust hole 12 and the inner peripheral surface of the mouth holder 11.
[0030]
Next, a raw material gas having a predetermined composition is supplied from the gas introduction pipe 19 into the plastic container 10. In the plasma CVD apparatus 1, the raw material gas is continuously supplied and continuously exhausted by the vacuum apparatus, so that the inside of the processing chamber 4 and the plastic container 10 is maintained at the degree of vacuum. The supply amount of the source gas is set to an appropriate amount according to the surface area of the target plastic container 10 and the thickness of the coating film to be formed. The supply amount of the source gas is 0.1 to 0.8 sccm per surface area of the container in order to form the coating film having a thickness of 0.02 to 0.08 μm in the plastic container 10 having an internal volume of 200 to 2000 ml. A range of / cm ² is suitable.
[0031]
Examples of the source gas include aliphatic unsaturated hydrocarbons such as ethylene and acetylene, aliphatic saturated hydrocarbons such as methane, ethane and propane, aromatic hydrocarbons such as benzene, toluene and xylene, oxygen-containing hydrocarbons, Nitrogen hydrocarbons can be used. The source gas may be used alone or as a mixture of two or more as required. A small amount of hydrogen, an organosilicon compound, or other film-forming organic compound is used in combination as a film modifier. Also good. The source gas may be diluted with a rare gas such as argon or helium.
[0032]
However, in order to form a polymer thin film that is a coating with excellent gas barrier properties in a shorter time, it is suitable that 60% by volume or more, preferably 80% by volume or more of the raw material gas is acetylene, Preferably, the source gas is substantially acetylene. When the source gas is substantially composed of acetylene, the acetylene may contain inevitable impurities mixed in during the production process.
[0033]
And while the said source gas is supplied, the microwave generator 5 is operated, for example, 2.45 GHz, 150-600 W of microwaves are 0.2-2.0 second, Preferably it is 0.4- By irradiating for 1.5 seconds, the source gas is electromagnetically excited to generate plasma in the plastic container 10, thereby forming an amorphous carbon film (not shown) on the inner surface of the plastic container 10. At this time, as described above, the raw material gas is continuously supplied and continuously exhausted by the vacuum device, so that the interior of the processing chamber 4 and the plastic container 10 is maintained at the vacuum degree. The above-mentioned film can be formed. In addition, when the microwave irradiation time is less than 0.2 seconds, a desired film thickness may not be obtained in the coating film. When the microwave irradiation time exceeds 2.0 seconds, the film thickness of the coating film increases and coloring may occur. May become darker.
[0034]
Next, when the supply of the source gas is completed, the microwave generator 5 is stopped, the inside of the processing chamber 4 and the plastic container 10 is returned to atmospheric pressure, the bottom plate 3 is lowered, and the plastic container 10 is removed. The processing is terminated by taking out. The microwave generator 5 may be stopped at the same time as the supply of the source gas is completed, but may be irradiated for a short time. By doing in this way, the raw material gas component remaining in the container can be completely formed into a film, and the gas barrier property of the obtained plastic container 10 and the flavor resistance when the contents are filled are further improved. Can be made.
[0035]
In the manufacturing method of the present embodiment, when the microwave generator 5 is operated to generate plasma by the gas component supplied into the plastic container 10, the emission spectrum of the plasma is analyzed by the plasma emission spectrometer 22. Then, the nitrogen plasma emission intensity included in the emission spectrum is detected.
[0036]
According to the plasma emission spectroscopic analyzer 22, the light emitted by the plasma generated in the plastic container 10 is received by the light receiving unit 20 and sent to the bandpass filter 23 by the optical fiber 21.
[0037]
At this time, the emission spectrum of the plasma is as shown in FIG. 2 when the gas component supplied into the plastic container 10 is only the source gas. On the other hand, when the gas component supplied into the plastic container 10 contains a nitrogen component in addition to the source gas, the emission spectrum is as shown in FIG. In the spectrum shown in FIG. 3, it is considered that light in the wavelength region of 700 to 800 nm corresponds to light emission unique to nitrogen plasma, and is relatively difficult to overlap with light emission of other components.
[0038]
Therefore, the bandpass filter 23 selectively transmits light in the wavelength region of 700 to 800 nm, and the detecting means 24 detects the intensity of the light in the wavelength region as nitrogen plasma emission intensity. Next, the data of the nitrogen plasma emission intensity detected by the detection means 24 is sent to the main control means 25. The main control means 25 stores a calibration curve prepared in advance for the amount of nitrogen component contained in the gas component and the intensity of light in the wavelength region, and the nitrogen plasma emission intensity detected by the detection means 24 Is compared with the calibration curve to determine the amount of nitrogen component contained in the gas component.
[0039]
The plastic container 10 having the coating on the inner surface side has a ratio of the number of nitrogen atoms to the number of carbon atoms of 15 or less when the number of carbon atoms contained in the coating is 100, or an oxygen atom to the number of carbon atoms Excellent gas barrier properties can be obtained when the number ratio is 20 or less, or the ratio of the total number of nitrogen atoms and oxygen atoms to the number of carbon atoms is 27 or less. For example, when the plastic container 10 is a beverage container, the gas barrier property is preferably 0.02 ml / day or less, more preferably 0.015 ml / day or less, as an oxygen transmission rate per container. The ratio of the number of nitrogen atoms or the number of oxygen atoms to the number of carbon atoms in the film can be measured by, for example, an X-ray photoelectron spectrometer (ESCA).
[0040]
In the manufacturing method of the present embodiment, in order to keep nitrogen and oxygen contained in the coating within the above range, the gas component supplied into the plastic container 10 contains 20 nitrogen gas with respect to the total amount of the gas component. It is necessary that the oxygen gas is 10% by volume or less with respect to the total amount of the gas components, and the total of nitrogen gas and oxygen gas is 15% by volume or less.
[0041]
Therefore, the main control means 25 adjusts the concentration of the nitrogen-containing compound mixed in the gas component by the gas component control means 26 when an amount of nitrogen component exceeding 20% by volume is detected with respect to the total amount of the gas component. Then, the gas component supplied into the plastic container 10 is set so that the nitrogen gas is 20 volume% or less with respect to the total amount of the gas component .
[0042]
As a result, the subsequent plastic container 10, the nitrogen contained in said coating film formed can be suppressed within the range, it is possible to prevent the production of low plastic container 10 having gas barrier properties.
[0043]
Further, when a nitrogen component in an amount exceeding 20% by volume with respect to the total amount of the gas components is detected, the main control unit 25 sets the plastic container 10 taken out from the processing chamber 4 as a defective container, and rejects the defective container 27. To eliminate from the manufacturing process.
[0044]
In the present embodiment, light emitted from the plasma generated in the plastic container 10 is received by the light receiving unit 20 and then analyzed by the plasma emission spectroscopic analyzer 22 including the bandpass filter 23, the detection unit 24, and the control unit 25. However, the analysis can be performed without using the bandpass filter 23. Further, instead of the light receiving unit 20, a light sensor may be provided directly at a desired position on the side wall 2 for analysis.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a configuration example of an apparatus used in a manufacturing method of the present invention.
FIG. 2 is a diagram showing an example of an emission spectrum of plasma generated when a gas component supplied into a plastic container is only a gaseous starting material.
FIG. 3 is a diagram showing an example of an emission spectrum of plasma generated when a gas component supplied into a plastic container contains a nitrogen component in addition to a gaseous starting material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Plasma CVD apparatus, 22 ... Plasma emission spectroscopy analyzer, 26 ... Gas component control means, 27 ... Defective container exclusion means.

Claims (3)

A plastic container is accommodated in the plasma CVD apparatus, the inside of the plasma CVD apparatus is maintained at a predetermined degree of vacuum, a starting material containing carbon atoms is supplied in the form of a gas into the plastic container, and a predetermined amount is supplied into the plasma CVD apparatus. In the method for producing an inner surface-coated plastic container in which a film containing amorphous carbon is formed on the inner surface of the plastic container by applying energy and generating plasma in the plastic container
By selectively detecting light in a specific wavelength region in the emission spectrum of the plasma generated by the gas component containing the starting material supplied into the plastic container, the emission intensity of the nitrogen plasma is detected, When a nitrogen component in an amount exceeding 20% by volume is detected with respect to the total amount of the gas component, the concentration of the nitrogen-containing compound mixed in the gas component is adjusted so that the nitrogen gas is 20 % with respect to the total amount of the gas component. A method for producing an inner surface-coated plastic container, wherein the volume% or less is set . 2. The method for manufacturing an inner surface-coated plastic container according to claim 1, wherein when the emission intensity of the nitrogen plasma exceeds a predetermined intensity, the plastic container on which the film is formed is excluded from the manufacturing process. A plastic container is accommodated in the plasma CVD apparatus, the inside of the plasma CVD apparatus is maintained at a predetermined degree of vacuum, a starting material containing carbon atoms is supplied in the form of gas into the plastic container, and a predetermined amount is supplied into the plasma CVD apparatus. In the method for producing an inner surface-coated plastic container in which a film containing amorphous carbon is formed on the inner surface of the plastic container by applying energy and generating plasma in the plastic container,
By selectively detecting the light in a specific wavelength region in the emission spectrum of the plasma generated by the gas component containing the starting material supplied into the plastic container, the emission intensity of the nitrogen plasma is detected, A method for producing an inner surface-covered plastic container, characterized in that when a nitrogen component in an amount exceeding 20% by volume is detected with respect to the total amount of the gas component, the plastic container on which the coating is formed is excluded from the production process.

Images