JP2006314671A - Plasma treatment method of plastic container and plasma treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment method for simultaneously sterilizing the inner and outer surfaces of a plastic container by plasma. <P>SOLUTION: The plastic container 5 surrounded by a high frequency induction coil 21 is held within a plasma treatment chamber 1, a gas supply pipe 13 is inserted in the plastic container 5 held within the chamber 1 and the chamber 1 is evacuated while supplying a gas into the chamber 1 from the gas supply pipe 13 to hold the interior of the chamber 1 to a predetermined degree of vacuum while allowing the gas to flow along the outer surface of the container 5 from the inner surface thereof. Subsequently, high frequency is applied to the high frequency induction coil 21 to introduce a high frequency electric field into the chamber 1 and the plasma of the gas is formed in the vicinity of the inner and outer surfaces of the container 5 by the high frequency electric field to sterilize the inner and outer surfaces of the container 5 at the same time by plasma. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma processing method and apparatus for plastic containers such as plastic bottles, and more particularly to a plasma processing method and apparatus capable of plasma sterilization of an inner surface and an outer surface of a plastic container at the same time. It is.

  Conventionally, in order to improve the characteristics of various substrates, a deposited film is formed on the surface by a plasma CVD method. For example, in the field of packaging materials, it is known to improve the gas barrier property by forming a vapor deposition film by a plasma CVD method on a plastic substrate such as a container, and the inner surface or outer surface of a plastic container by plasma. Techniques for sterilizing potato are also known.

  For example, Patent Document 1 discloses a method in which an electrode is placed in a container placed in a vacuum container and a high frequency is applied to the electrode to sterilize the inside of the container.

  Patent Document 2 discloses a plastic container processing method, in which plasma processing is performed indoors so that plasma contacts the container wall surface, and vacuum is used to manufacture, process, and sterilize the plastic container. A method is disclosed for disinfecting the inner and outer surfaces of a plastic container.

Also known is a technique for performing sterilization by plasma and formation of a deposited film at the same time. For example, in Patent Document 3, a sterilization surface by plasma treatment is provided on the entire inner surface of a plastic container body. A plastic container is disclosed in which a gas barrier thin film is provided on the entire surface including the surface.
JP-A-7-184618 Special table 2003-506276 gazette JP 2003-95273 A

  However, none of the conventionally known plasma processing methods disclosed in the above-mentioned patent documents etc. sterilize the inner surface and the outer surface of the plastic container at the same time. For example, in the techniques of Patent Documents 1 and 3, only the inner surface of the plastic container is plasma sterilized, and the outer surface is not plasma sterilized. Further, in Patent Document 2, sterilization is performed on the inner surface and the outer surface of the plastic container, but after the inner surface sterilization, the gas introduction is switched to the outer surface to perform the outer surface sterilization, and the inner and outer surfaces are sterilized at the same time. Therefore, it is difficult to sterilize in a short time.

  Thus, even if the formation of a deposited film using plasma is taken into consideration, there is no known technique for plasma processing the inner surface and the outer surface of a plastic container at the same time.

Accordingly, an object of the present invention is to provide a plasma processing method and apparatus for simultaneously sterilizing the inner and outer surfaces of a plastic container.
Another object of the present invention is to provide a plasma processing method and apparatus capable of simultaneously sterilizing plasma on the inner and outer surfaces of a plastic container and simultaneously forming a deposited film by plasma on the inner and outer surfaces of the plastic container.

According to the present invention, the plastic container is held in the plasma processing chamber so as to be surrounded by the high frequency induction coil,
Holding a predetermined degree of vacuum in the chamber while flowing plasma gas along the inner and outer surfaces of the plastic container held in the chamber;
Next, a high frequency electric field is applied to the high frequency induction coil to introduce a high frequency electric field into the chamber, and the plasma of the gas is formed in the vicinity of the inner surface and the outer surface of the plastic container by the high frequency electric field. Are simultaneously plasma sterilized, and a plasma processing method is provided.

According to the present invention, for a plastic container held in a chamber having an exhaust port, gas is supplied while the inside of the chamber is held at a predetermined degree of vacuum, and plasma of the gas is generated. In a plasma processing apparatus that performs plasma processing of a plastic container,
A gas supply pipe for supplying the gas, and a high-frequency induction coil for generating plasma of the gas by a high-frequency electric field,
The high-frequency induction coil is disposed in the chamber so as to surround the plastic container held in the chamber,
The gas supply pipe is provided so as to penetrate the wall of the chamber from the outside and enter the plastic container held in the chamber,
A plasma processing apparatus is provided in which the plastic container is held in the chamber so that an internal space and an external space of the container communicate with each other.

  In the plasma processing method and apparatus of the present invention, since a high frequency electric field that causes glow discharge is introduced using a high frequency induction coil arranged so as to surround the plastic container, the glow treatment is performed in the region near the outer surface and the inner surface of the container. In order to introduce the high-frequency electric field as described above while the gas flows continuously from the inner surface to the outer surface of the container, gas plasma is generated by glow discharge near the inner surface and the outer surface of the container. The inner surface and the outer surface can be plasma sterilized at the same time, and the sterilization time can be greatly shortened.

  In the present invention, by selecting the type of gas, a vapor deposition film by plasma CVD can be simultaneously formed on the inner surface and the outer surface of the container at the same time as sterilization, and the gas barrier property of the container can be improved.

  In the present invention, the plasma gas for plasma treatment is flowed into the chamber from a gas supply pipe penetrating the inner surface of the container, and an exhaust port formed in the chamber is provided in the chamber. By arranging it at a position facing the bottom of the plastic container to be held, the gas can flow smoothly along the outer surface from the inner surface of the container, and it is efficient to sterilize the inner surface and outer surface of the container and to form a deposited film. It can be performed uniformly.

The present invention will be described below based on specific examples shown in the accompanying drawings.
FIG. 1 is a side sectional view showing a schematic structure of a plasma processing apparatus for suitably carrying out the plasma processing method of the present invention.

  In FIG. 1, this processing apparatus is provided with a chamber denoted by 1 as a whole, and a plasma processing chamber 3 is formed in the chamber 1, and the processing chamber 3 is in an inverted state as shown in the figure. Bottle 5 is held.

  Although not shown in FIG. 1, the opening of the plastic bottle 5 is held on a base having an appropriate shape so that the internal space and the external space of the bottle 5 communicate with each other. Yes.

  Furthermore, the chamber 1 is divided into an upper chamber 1a and a lower chamber 1b. For example, by moving the upper chamber 1a, the processing chamber 3 is opened, the plastic bottle 5 is introduced into the processing chamber 3, and The bottle 3 after the plasma treatment is taken out.

  An exhaust port 7 is formed in the upper wall of the upper chamber 1a, and a vacuum pump 11 is connected to the exhaust port 7 via a valve 9 so that the inside of the processing chamber 3 can be evacuated. It has become. As shown in the figure, the exhaust port 7 is positioned so as to face the bottom of the bottle 5 so that a gas for plasma processing, which will be described later, flows from the inner surface of the bottle 5 along the outer surface and is exhausted. is doing.

  A gas supply pipe 13 extending from the outside through the bottom wall of the lower chamber 1b enters the inside of the bottle 5 held in the processing chamber 3. The gas supply pipe 13 is connected to a gas supply source 17 and a sterilized air supply source 19 via a switching valve 15, and supplies a gas for plasma processing from the gas supply source 17, or is sterilized from an inorganic air source 19. Air can be supplied.

  Such a gas supply pipe 13 is usually pipe-shaped, and gas is blown out from the tip thereof. Further, a large number of openings are also formed on the side surface of the tip portion entering the bottle 5. The gas is blown out from the side surface.

  Further, as is apparent from FIG. 1, a high frequency induction coil 21 is disposed so as to surround the entire bottle 5 held in the processing chamber 3, and this high frequency induction coil 21 is used for matching for impedance matching. A high frequency oscillator 25 provided outside the processing chamber 3 is connected via the box 23, and a high frequency of 13.56 MHz, for example, is applied to the induction coil 21 to generate a high frequency electric field.

  Plasma sterilization using the plasma processing apparatus as described above is performed as follows.

First, the valve 9 is opened and the vacuum pump 11 is operated to evacuate, and the degree of vacuum at which glow discharge can occur in the processing chamber 3, for example, a vacuum of several Torr or less, particularly about 10 ^{−1 to} 10 ⁻⁴ Torr. Depressurize every time. While maintaining such a degree of vacuum by this exhaust, a gas for plasma processing is caused to flow from the gas supply source 17 side via the switching valve 15, and the gas is supplied from the gas supply pipe 13 to the inside of the bottle 5. Thereby, as shown in FIG. 1, the gas supplied into the bottle 5 flows out of the bottle 5 along the inner surface of the bottle 5 and is exhausted from the exhaust port 7 along the outer surface of the bottle 5. It becomes. That is, when the exhaust port 7 is arranged so as to face the bottom of the bottle 5, the gas supplied into the bottle 5 is exhausted while flowing smoothly along the inner surface and the outer surface of the bottle 5. It becomes.

  Next, the high frequency oscillator 25 is operated, and a high frequency is applied to the induction coil 21 with an output of about 50 to 2000 W. Thereby, a high frequency electric field is introduced into the region including the wall of the bottle 5. However, since the inside of the processing chamber 3 is maintained at a predetermined degree of vacuum and the gas flows along the inner surface and the outer surface of the bottle 5, glow discharge occurs near the inner surface and the outer surface of the bottle 5 due to the high-frequency electric field, A gas plasma is formed. Accordingly, the inner surface and the outer surface of the bottle 5 can be plasma sterilized at the same time. The plasma sterilization time varies depending on the volume of the bottle 5 and the like, but is usually about 1 to 20 seconds when the volume is 2 liters.

  After the plasma sterilization process described above is completed, the supply of the plasma processing gas from the supply source 17 is stopped, the plasma processing gas in the processing chamber 3 is exhausted, the valve 9 is closed, the vacuum pump 11 and the high frequency oscillation are performed. After the operation of the machine 25 is stopped, the switching valve 15 is switched to the sterilized air supply source 19 side, sterilized air is supplied from the gas supply pipe 13, the inside of the processing chamber 3 is returned to atmospheric pressure, and the sterilized bottle 5 is taken out from the inside of the processing chamber 3, and the sterilization process is thereby completed. The sterilized bottle 5 is filled with the contents under aseptic conditions, for example.

  The gas used for the plasma sterilization described above is not particularly limited, and any gas can be used. However, when this treatment is performed only for sterilization, it is preferable to use an inert gas such as helium gas or argon gas in order to avoid denaturation such as oxidation of the bottle 5.

  Furthermore, in the present invention, simultaneously with the sterilization described above, a vapor deposition film can be formed simultaneously on the inner and outer surfaces of the bottle 5 by plasma CVD. That is, since the plasma of an arbitrary gas exhibits a sterilizing effect, even when a reactive gas for forming a deposited film is supplied from the gas supply source 17, it is possible to perform sterilization simultaneously with the formation of the deposited film. is there.

  Plasma CVD is a method for growing a thin film using gas plasma. Basically, a gas containing a raw material gas is discharged under a low electric field by a high electric field, activated and generated under reduced pressure. It consists of a process in which a substance is deposited on a substrate in the gas phase or through a chemical reaction on the substrate. That is, in the present invention, a plasma of a reactive gas is formed by glow discharge by a high frequency electric field, and a plasma reactant is simultaneously formed on the inner surface and the outer surface of the bottle 5 described above as a vapor deposition film.

Typical examples of such a vapor deposition film formed by plasma CVD include a carbon film, a metal oxide film, a metal nitride film, and a metal carbide film, and the type of reactive gas (plasma gas) depends on the vapor deposition film to be formed. It is selected according to the type. For example, when forming the carbon film by using a hydrocarbon gas, organic film using an organometallic compound gas when forming the metal oxide film organometallic compound and oxidizing gas when forming the metal When forming a nitride film, an organometallic compound and a nitriding gas are used as reaction gases, and when forming a metal carbide film, an organometallic compound and a hydrocarbon gas are used as reaction gases. That is, by using such a reactive gas, a vapor deposition film containing carbon, metal oxide, metal nitride, and metal carbide is formed on the inner surface and the outer surface of the bottle 5, and the gas barrier property of the bottle 5 is improved. Is possible.

  As the hydrocarbon, methane, ethane, ethylene, propylene, acetylene, benzene and the like are used, and acetylene and benzene having a particularly high carbon content are preferably used.

As the organometallic compound, an organosilicon compound is preferably used. However, the organosilicon compound is not limited to the organosilicon compound as long as it reacts with an oxidizing gas to form a metal oxide. Various things, such as organic aluminum compounds, such as aluminum, and others, an organic titanium compound, can be used. Examples of organosilicon compounds include hexamethyldisilane, vinyltrimethylsilane, methylsilane, dimethylsilane, trimethylsilane, diethylsilane, propylsilane, phenylsilane, methyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, Organic silane compounds such as tetraethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, etc., organic such as octamethylcyclotetrasiloxane, 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane A siloxane compound or the like is used. In addition to these materials, aminosilane, silazane, and the like can also be used. These organometallic compounds can be used alone or in combination of two or more. Moreover, silane (SiH ₄ ) or silicon tetrachloride can be used in combination with the above-described organosilicon compound.

Examples of the oxidizing gas used when forming the oxide film include oxygen and NO _x, and examples of the nitriding gas used when forming the nitride film include nitrogen and ammonia Is used. In the case of forming a carbide film, acetylene, benzene or the like having a large carbon content in the hydrocarbon is used.

  Further, an inert gas such as Ar or He can be used in combination with the above reactive gas (plasma gas) as a plasma auxiliary or carrier gas.

  In addition, when the plasma sterilization and the formation of the deposited film are performed using the reactive gas containing the organometallic compound and the oxidizing gas as described above, the formed deposited film has many inorganic bonds. It is known that the film has a higher gas barrier property, but has a lower adhesion to the plastic and has a drawback that peeling or cracking is likely to occur due to, for example, expansion of the bottle 5. Further, the smaller the inorganic bonds and the more organic bonds, the lower the gas barrier property, but the higher the adhesion to plastic. Therefore, when forming a deposited film simultaneously with sterilization by plasma treatment using the above-described reactive gas, first a film containing a lot of organic bonds (film with high adhesion) is formed, and then In addition, it is preferable to form a film rich in gas barrier properties containing a lot of inorganic bonds.

  The composition of the deposited film as described above can be adjusted by adjusting the composition of the reactive gas and the output of glow discharge.

  For example, when the supply amount of the oxidizing gas is small as compared with the organometallic compound, the level of the oxidation reaction of the organometallic compound is low, and a polymer containing a lot of organic bonds is formed. As a result, a highly adhesive film can be formed. Further, by increasing the supply amount of the oxidizing gas as compared with the organometallic compound, the oxidation reaction of the organometallic compound proceeds to a high level, so that almost complete metal oxide is formed. That is, it is possible to form a film with few organic bonds and high oxidation degree and excellent gas barrier properties. Therefore, at the initial stage of the reaction, the supply amount of the oxidizing gas may be reduced, and the supply amount of the oxidizing gas may be increased when the reaction proceeds to some extent and a deposited film having a certain thickness is formed.

  In addition, when the glow discharge output is low, the progress of the plasma reaction is suppressed, a film having high adhesion with a low degree of oxidation and containing many organic bonds is formed, and the glow discharge output is high. Since the plasma reaction proceeds rapidly and the oxidation reaction of the organometallic compound proceeds to a high level, a film having a high gas barrier property is formed. Therefore, at the initial stage of the reaction, within the range where glow discharge occurs, film formation is performed by applying a high frequency with low output, and when the reaction proceeds to some extent and a deposited film having a certain thickness is formed, A deposited film having the above composition distribution can also be formed by applying a high frequency to form a film.

  The plasma treatment time (film formation time) when using the reactive gas as described above and forming the deposited film simultaneously with the plasma sterilization is the inner surface area of the bottle to be processed, the thickness of the thin film to be formed, and the processing time. Although it differs depending on the type of gas, etc., it cannot be specified in general, but for a 2 liter plastic bottle, one second or more is required for the stability of plasma processing, and a reduction in time is required from the viewpoint of cost. However, it can be on the order of minutes if necessary.

  In the above-described example, a bottle is shown as a container used for processing. However, the bottle is not limited to a bottle, and the processing described above can be applied to, for example, a wide-mouthed cup-shaped container. Furthermore, the material for forming the container is not limited, and the present invention can be applied to a plastic container formed of any thermoplastic resin.

  The excellent effects of the present invention will be described in the following experimental examples.

[Production of plasma processing bottle]
The processing apparatus shown in FIG. 1 (frequency of a high-frequency oscillator; 13.56 MHz) is used, and a plastic bottle (PET bottle, internal volume: 500 ml) as a subject is shown in FIG. Arranged to be.

Next, the valve 15 was closed, the valve 9 was opened, the vacuum pump 11 was operated, and the degree of vacuum in the processing chamber 3 was reduced to 10 ⁻⁵ Torr. Further, the switching valve 15 is connected to the gas supply source 17 side while the valve 9 is open, and the ratio (volume ratio) of hexamethyldisiloxane (HMDSO) / oxygen (O ₂ ) as the reactive gas is 1:10. Was supplied from the gas supply pipe 13 until the degree of vacuum in the processing chamber 3 reached 10 ⁻³ Torr. Next, the high frequency oscillator 25 is operated, a high frequency electric field is introduced into the processing chamber 3 from the high frequency induction coil 21 through the matching box 23, plasma is formed inside and outside the bottle, and SiOx films are formed on the inside and outside surfaces of the bottle. The bottle inner and outer surfaces were sterilized by reactive gas plasma (treatment time: 10 seconds).

  After completion of the film formation and sterilization, the valve 9 is closed, the switching valve 15 is connected to the aseptic air side, and aseptic air is introduced into the processing chamber 3 until the inside of the processing chamber 3 is at atmospheric pressure, Removed aseptically.

[Production of spore-attached plastic bottles]
Bacillus subtilis (IFO 13721) was cultured as a test bacterium on soybean-casein digest agar medium (trade name: SCD agar medium (Nippon Pharmaceutical)) at 37 ° C for 3 weeks to form mature spores. is, the cells were concentrated by centrifugation, 85 ° C., and heat-treated at 15 minutes, to prepare a spore solution of 10 ⁹ (spores / ml). A predetermined amount of this spore solution was sprayed onto a plastic bottle with a sprayer, and 10 ⁶ spores were attached to each bottle and dried for 12 hours to obtain a spore attachment bottle. By spraying the spore solution, Group A with spores attached to the inner surface of the bottle, Group B with spores attached to the outer surface of the bottle, and Group C with spores attached to the inner and outer surfaces of the bottle were prepared. A test was conducted. About each bottle, the number of living spore was counted with the following method, and the bactericidal effect was evaluated.

<Evaluation test 1>
Sterilized water of 1/3 bottle capacity is injected into the A group bottle after plasma treatment, sealed with a sterilized plastic cap, and spore adhered to the inner surface of the bottle by shaking vigorously 50 times. The extract was released into water, and the entire amount of the extract was filtered through a membrane filter (pore size: 0.45 μm). The same operation was performed three times in total, and living residual spores were collected by filtration on the same membrane filter. This filter was placed on a Petri dish pad pre-soaked with soybean-casein digest medium (trade name: SCD medium (Nippon Pharmaceutical Co., Ltd.), cultured at 37 ° C. for 2 days, colonies were counted, and live spore was obtained. I asked for a number. The results are shown in Table 1.

<Evaluation Test 2>
Put a sterilized silicone stopper on the group B bottle after plasma treatment, put it in a sterilized large retort pouch, inject 500 ml of sterilized water, heat seal and then shake vigorously 50 times to release spores on the outer surface of the bottle into the sterilized water. The total amount of this extract was collected by filtration through a membrane filter (pore size 0.45 μm). Again, 500 ml of sterilized water was injected, the above operation was repeated, and the cells were collected by filtration on the same filter.

<Evaluation Test 3>
A C group bottle after the plasma treatment was sterilized with a silicone stopper, placed in a sterilized large retort pouch, and subjected to the same operation as in <Evaluation Test 2> to obtain a filtered and collected filter C_out. Remove the bottle from the large retort pouch, remove the silicone stopper, inject sterilized water in an amount of 1/3 of the bottle capacity into the bottle, and seal with a sterilized plastic cap. Thus, filter C_in collected by filtration was obtained. These were counted in the same manner as in <Evaluation Test 1>, and the colonies of filter C_out and filter C_in were summed to determine the number of surviving spores. The results are shown in Table 1.

<Comparative evaluation test 1>
Using an untreated A group bottle without plasma treatment, the same operation as in <Evaluation Test 1> was performed once to release spores adhering to the inner surface of the bottle into sterile water. Take a certain amount of this extract, make a solution diluted appropriately with sterilized water, filter the solution at each dilution stage with a membrane filter (pore size 0.45 μm), and count the number of surviving spores as in <Evaluation Test 1>. The results are shown in Table 1.

<Comparative evaluation test 2>
Using the untreated B group bottle without plasma treatment, the same operation as in <Evaluation Test 2> is performed once to release spores on the outer surface of the bottle into sterile water, and in the same manner as in <Comparative Evaluation Test 1>. The number of surviving spores was determined and the results are shown in Table 1.

  Using a non-treated C group bottle that is not subjected to plasma treatment, the number of live residual spores on the outer surface of the bottle is obtained in the same manner as in <Comparative Evaluation Test 2>, and the bottle is taken out from a large retort pouch. >, The number of living inner spores was determined in the same manner as in <Evaluation Test 3>, and the number of living residual spores was determined in the same manner as in <Evaluation Test 3>.

  From the results of the above evaluation tests, it is understood that according to the present invention, the inner and outer surfaces of the container are effectively sterilized simultaneously.

1 is a side sectional view showing a schematic structure of a plasma processing apparatus for favorably implementing a plasma processing method of the present invention.

Explanation of symbols

1: Chamber 3: Plasma processing chamber (inside chamber)
5: Plastic bottle 7: Exhaust port 11: Vacuum pump 13: Gas supply pipe 17: Gas supply source for plasma processing 21: High frequency induction coil 25: High frequency oscillator

Claims (6)

Hold the plastic container in the plasma processing chamber so as to be surrounded by the high frequency induction coil,
Holding a predetermined degree of vacuum inside the chamber while flowing a plasma gas along the inner and outer surfaces of the plastic container held in the chamber;
Next, a high frequency electric field is applied to the high frequency induction coil to introduce a high frequency electric field into the chamber, and the plasma of the gas is formed in the vicinity of the inner surface and the outer surface of the plastic container by the high frequency electric field. A plasma processing method characterized in that plasma sterilization is performed simultaneously.   A gas supply pipe is inserted into the plastic container held in the chamber, and the plasma gas is exhausted from the chamber while supplying the plasma gas from the gas supply pipe. The plasma processing method according to claim 1, wherein the plasma treatment method flows along an inner surface and an outer surface.   Plasma sterilization treatment using a hydrocarbon gas or an organometallic compound gas or a mixed gas containing at least one of an organometallic compound gas and at least one of an oxidizing gas, a nitriding gas and a hydrocarbon gas as the plasma gas The plasma processing method according to claim 1, wherein a vapor deposition film is formed on the inner surface and the outer surface of the plastic container at the same time.   The plasma processing method according to claim 3, wherein an organic silicon compound is used as the organometallic compound, and a vapor deposition film containing a silicon oxide component is formed on the inner surface and the outer surface of the plastic container simultaneously with the plasma sterilization treatment. For a plastic container held in a chamber having an exhaust port, a plasma is supplied to the plastic container by generating a plasma of the gas while supplying the gas while maintaining the inside of the chamber at a predetermined degree of vacuum. In plasma processing equipment,
A gas supply pipe for supplying the gas, and a high-frequency induction coil for generating plasma of the gas by a high-frequency electric field,
The high-frequency induction coil is disposed in the chamber so as to surround the plastic container held in the chamber,
The gas supply pipe is provided so as to penetrate the wall of the chamber from the outside and enter the plastic container held in the chamber,
The plasma processing apparatus, wherein the plastic container is held in the chamber so that an internal space and an external space of the container communicate with each other.   The plasma processing apparatus according to claim 4, wherein the exhaust port is disposed so as to face a bottom portion of a plastic container held in the chamber.

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