JP4873037B2 - Non-pressure resistant plastic container - Google Patents

Description

The present invention relates to a non-pressure-resistant plastic container that easily deforms due to an internal / external pressure difference .

  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, while supplying a reaction gas into a plastic container maintained at a predetermined degree of vacuum, plasma is generated by glow discharge in the container to react with the reaction gas, thereby vapor deposition on the inner surface of the container. A film forming method for forming a film is known, and it is known to improve gas barrier properties by forming such a deposited film. In the film forming method as described above, glow discharge for realizing a plasma state is typically generated using microwaves or high frequencies. In particular, when microwaves are used, glow discharge can be generated with a relatively low degree of vacuum compared to when using high frequencies, and the intended vacuum can be achieved without using a special vacuum pump. There are advantages such as achieving the degree.

  By the way, the film forming method for forming a vapor deposition film on the inner surface of a plastic container by the plasma CVD method as described above is used for a non-pressure-resistant plastic container (for example, mayonnaise) in which the container is easily deformed by a difference in internal and external pressure. In case of squeeze bottles etc.) there is a problem. That is, since it is necessary to keep the inside of the plastic container in a vacuum state in which glow discharge is generated, the container itself is greatly deformed due to the difference between the internal and external pressures, so that film formation becomes virtually impossible.

  As a film forming method in which the above problems are solved, for example, an enclosure made of a microwave permeable material is arranged in a microwave introduction chamber, and a plastic container is accommodated in the enclosure, and the enclosure and the plastic container are accommodated. A vapor deposition film is formed on the inner surface of the plastic container by introducing a reaction gas into the plastic container and introducing a microwave into the chamber while maintaining a predetermined degree of vacuum so that there is no pressure difference between the two. Has been proposed (see Patent Document 1).

Japanese translation of PCT publication No. 2002-509845 (Claim 18, FIG. 4)

  The film forming method proposed in Patent Document 1 generates glow discharge due to microwaves, and is considered not to cause a difference in internal and external pressures of the container. Therefore, it is also applicable to non-pressure-resistant plastic containers. can do. However, this film formation method has a problem that it is difficult to form a vapor deposition film on the inner surface of the bottom wall of the plastic container, and a uniform vapor deposition film cannot be formed over the entire inner surface of the plastic container.

Accordingly, an object of the present invention is to provide a non-pressure-resistant plastic container that easily deforms due to an internal / external pressure difference, and in which a deposited film is formed over substantially the entire inner surface including the bottom. There is.

According to the invention, the following formula:
[(V ₀ −V ₁ ) / V ₀ ] × 100
Where
V ₀ indicates the volume in the container when the pressure difference between the inside and outside of the container wall is 0,
V ₁ indicates the volume in the container when the pressure difference between the inside and the outside of the container wall is 2 kPa.
A non-pressure-resistant plastic container having a vapor deposition film on substantially the entire inner surface of the container wall of the container having a volume deformation rate defined by is 5% or more at 22 ° C. is provided.
The non-pressure-resistant plastic container has a microwave plasma by placing a non-pressure-resistant plastic container in a microwave introduction chamber and introducing a microwave into the chamber while introducing a reaction gas into the plastic container. Manufactured by forming a deposited film on the inner surface of a plastic container by the CVD method.
(A) A substantially whole outer surface of the plastic container disposed in the chamber is covered with a partition made of a microwave permeable material, and in this state, a space between the partition and the plastic container and / or inside the plastic container By maintaining the space at a degree of vacuum at which glow discharge occurs and supplying the reaction gas into the plastic container while supplying the microwave introduced into the chamber through the partition wall into the plastic container, Forming a deposited film by a microwave plasma CVD method on the inner surface of a plastic container;
(B) The supply of the microwave is performed in a state where the pressure difference between the space between the partition wall and the plastic container and the space in the plastic container is maintained at ± 2 kPa or less,
The method is adopted.

In the non-pressure resistant plastic container of the present invention,
1. The deposited film is formed by microwave plasma CVD and has a thickness of 30 nm or less at the body portion;
2. Being a squeeze bottle,
Is preferred.

When the non-pressure-resistant plastic container of the present invention is manufactured by film formation by microwave plasma CVD, the outer surface of the plastic container disposed in the microwave introduction chamber is substantially completely transmitted including the bottom. It is an important feature to form a film on the inner surface of the container by supplying a microwave while covered with a conductive partition.

  In other words, since the plastic container is covered with the partition wall, the space between the partition wall and the plastic container and the space inside the plastic container are maintained at a degree of vacuum to the extent that glow discharge occurs. A glow discharge can be generated without causing a pressure difference therebetween, and a vapor-deposited film can be formed on the inner surface of a non-pressure-resistant container that easily deforms due to an internal / external pressure difference.

  Moreover, in the present invention, the partition wall is disposed so as to cover the bottom portion of the plastic container, so that it is possible to effectively form a vapor deposition film on the inner surface of the bottom portion. That is, the film forming method of Patent Document 1 described above is to cover the plastic container in the chamber with a microwave transmissive enclosure. However, when forming a film on the inner surface of the container, the enclosure is kept at a predetermined degree of vacuum. In order to hold, the enclosure has a cylindrical shape with openings at both ends, and the bottom of the container is not covered with the enclosure. Therefore, when the inside of the container and the inside of the enclosure are held at a predetermined degree of vacuum and a microwave is introduced to cause glow discharge, a large discharge space is formed on the outer surface side in the vicinity of the bottom of the container. Glow discharge occurs preferentially on the outer surface side, and almost no glow discharge occurs inside the bottom (inside the container). As a result, it is considered that film formation is not effectively performed on the inner surface of the bottom of the container. However, in the present invention, since the bottom of the container is also covered with the partition, the discharge space between the partition and the bottom of the container is extremely small, and as a result, film formation is also effectively performed on the inner surface of the bottom of the container. .

Thus, according to the present invention, for the non-pressure-resistant plastic container easily deformed by internal and external pressure difference occurs, it is possible to bottom be included to form a uniform deposited film over the entire inner surface, formation of the deposited film Thus, characteristics such as gas barrier properties can be improved.

The figure which shows an example of the structure of the film-forming apparatus for manufacturing the non-pressure-resistant plastic container of this invention .

In FIG. 1 showing an example of a film forming apparatus for producing a plastic container according to the present invention , a plasma processing chamber generally indicated by 10 includes an annular base 12, a cylindrical side wall 14, and an upper part of the cylindrical side wall 14. These members are each formed of a conductor such as metal, so as to cut off the microwave and prevent leakage of the microwave to the outside of the chamber 10. It has become.

An exhaust hole 20 is formed in the center portion of the annular base 12, and the upper end of the neck portion of the inverted plastic container 1 (non-pressure-resistant plastic container) is formed above the exhaust hole 20 of the base 12. The gripping holders 22 are provided at appropriate intervals, and the exhaust holes 20 communicate with both the inner space and the outer space of the inverted container 1. A gas supply pipe 24 is inserted from the exhaust hole 20 into the container 1 held in an inverted state.

  Further, a partition wall 26 is provided on the upper side of the annular base 12 so as to cover the entire outer surface of the plastic container 1 held in an inverted state. The ceiling portion 26 a of the partition wall 26 is detachably provided so that the plastic container 1 can be accommodated in the partition wall 26. The partition wall 26 is made of a microwave permeable material, and can be made of various dielectric materials such as an organic material such as a resin or an inorganic material such as a ceramic as long as it has an appropriate strength (pressure resistance). It may be formed.

  A microwave inlet 30 is provided in the cylindrical side wall 14 forming the chamber 10, and a microwave transmission member 32 such as a waveguide or a coaxial cable is connected to the microwave inlet 30. That is, a microwave is introduced into the plasma processing chamber 10 from a predetermined microwave oscillator through the microwave transmission member 32. Further, the microwave inlet may be provided in the canopy 16 and / or the base 12 instead of the cylindrical side wall.

  In film formation, first, the plastic container 1 is held in an inverted state on the annular base 12 and accommodated in the partition wall 26. In this state, the annular base 12 is raised by an appropriate lifting device, As shown in FIG. 1, the plastic container 1 is placed in a plasma processing chamber 10 made of a microwave blocking material.

Next, the gas supply pipe 24 is inserted into the container 1 from the exhaust hole 20 and the vacuum pump is driven to exhaust the exhaust hole 20 between the interior of the plastic container 1 and the partition wall 26 and the plastic container 1. Maintain the space in a vacuum. That is, due to such pressure reduction, there is almost no pressure difference between the internal pressure and the external pressure of the plastic container 1 (the pressure in the space between the partition wall 26 and the plastic container 1), specifically ± 2 kPa or less, in particular substantially Therefore , even though a non-pressure-resistant plastic container is used as the container 1, no deformation occurs during film formation, and it is possible to effectively form a film inside the container. Become.

  The gas supply pipe 24 for supplying the reaction gas to the inside of the container 1 may be formed of any material as long as the reaction gas can be supplied uniformly and stably. Preferably there is. That is, when a metal supply tube is used, this tube acts as an antenna, and plasma is generated by glow discharge stably in a very short time due to electron emission, so that the processing time can be shortened. Because. Further, the gas supply pipe 24 is preferably a porous pipe in that the reaction gas is uniformly supplied to the inner surface of the container 1. For example, the opening defined by the nominal filtration accuracy is in the range of 1 to 300 μm. Are suitable. The nominal filtration accuracy is one of the characteristic values used when a porous material is used as a filter. For example, the nominal filtration accuracy of 130 μm is the above particle size when this porous material is used for a filter. It means that foreign objects can be captured. Therefore, in the present invention, it is most preferable to use a metal porous tube as the gas supply tube 24. For example, the gas supply tube 24 is made of a porous metal such as bronze powder or stainless steel powder. Use what you have.

  The degree of pressure reduction by exhaust from the exhaust hole 20 is such that the inside of the plastic container 1 is maintained at a degree of vacuum such that reaction gas is introduced from the gas supply pipe 24 and microwaves are introduced to generate glow discharge. For example, the inside of the plastic container 1 should be in the range of 10 to 500 Pa, particularly preferably 20 to 200 Pa. Therefore, the space between the partition wall 26 and the plastic container 1 is also at a similar vacuum level. Kept in a state.

After evacuation as described above, the reaction gas is introduced into the plastic container 1 through the gas supply pipe 26, and the microwave is introduced into the plasma processing chamber 10 through the microwave transmission member 32. This microwave is introduced into the plastic container 1 via the partition wall 26, and plasma due to glow discharge is generated in the space between the partition wall 26 and the container 1 and inside the container 1. The electron temperature in this plasma is several tens of thousands K, and the temperature of the gas particles is about two orders of magnitude higher than that of several hundred K, and is in a thermally non-equilibrium state. In contrast, the plasma treatment can be effectively performed, and a dense and homogeneous vapor deposition film is formed on the inner surface of the non-pressure-resistant plastic container 1 by the reaction of the reactive gas supplied into the container 1.

  By the way, in the present invention, as shown in FIG. 1, the partition wall 26 is formed along the outer surface of the plastic container 1, except for the upper end portion of the neck portion held by the holder 22. Is substantially covered with a partition wall 26, and the distance between the partition wall 26 and the outer surface of the container 1 is preferably set to at least 15 mm or less, particularly 10 mm or less. That is, in the present invention, the space between the partition wall 26 and the container 1 is also evacuated to a pressure-reduced state at which glow discharge can occur. Glow discharge is preferentially generated between them, and glow discharge is not effectively generated inside the container 1. Therefore, it is difficult to form a vapor deposition film on the inner wall of the container 1. .

  The plasma treatment time differs depending on the inner surface area of the container to be treated, the thickness of the thin film to be formed, and the type of reaction gas used for the treatment. One second or more is necessary from the viewpoint of the stability of the plasma treatment, and a reduction in time is required from the viewpoint of cost.

  After forming the deposited film, the supply of the reaction gas is stopped, and if necessary, a cooling gas such as air or nitrogen gas is introduced between the partition wall 26 and the container 1 and inside the container 1 to bring the plastic container 1 to room temperature. After cooling and returning the inside of the container 1 and the like to atmospheric pressure, the container 1 is taken out from the plasma processing chamber 10 and the annular base 12, and the film forming operation is completed.

(Plastic container to be processed 1)
In the present invention, as the non-pressure-resistant plastic container 1 on which the vapor deposition film is to be formed, those made of various plastics can be used. For example, as such plastics, thermoplastic resins known per se, specifically, low density polyethylene, high density polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene or ethylene, propylene, Random or block copolymers of α-olefins such as 1-butene and 4-methyl-1-pentene, cyclic olefin copolymers, ethylene / vinyl acetate copolymers, ethylene / vinyl alcohol copolymers, ethylene / Ethylene / vinyl compound copolymer such as vinyl chloride copolymer, polystyrene, styrene resin such as acrylonitrile / styrene copolymer, ABS, α-methylstyrene / styrene copolymer, polyvinyl chloride, polyvinylidene chloride, chloride Vinyl / vinylidene chloride copolymer, poly Polyvinyl compounds such as methyl acrylate and polymethyl methacrylate, polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11 and nylon 12, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate , Polycarbonate, polyphenylene oxide, polylactic acid, or the like, biodegradable polymers, or a mixture thereof.

In the present invention, the non-pressure-resistant plastic container 1 has the following formula :
[(V ₀ −V ₁ ) / V ₀ ] × 100
Where
V ₀ indicates the volume in the container when the pressure difference between the inside and outside of the container wall is 0,
V ₁ indicates the volume in the container when the pressure difference between the inside and the outside of the container wall is 2 kPa.
A volume deformation rate defined by is used at a temperature of 22 ° C. of 5% or more, particularly 10% or more . That is, a viscous substance such as mayonnaise is filled in a container such as a squeeze bottle and squeezed out from the bottle. Such a squeeze bottle is a typical non-pressure-resistant container, and the volume deformation rate is remarkably large. In the conventional film formation method using microwave plasma processing, when forming a vapor deposition film on the inner surface of such a non-pressure-resistant container, there arises a disadvantage that the container is deformed due to the reduced pressure for generating the plasma. However, in the present invention, when the vapor deposition film is formed, the generation of the internal and external pressure difference of the container is effectively suppressed. Therefore, such a non-pressure-resistant container is also effectively vapor-deposited on the inner surface thereof. A film can be formed. Of course, in addition to the squeeze bottle, a vapor-deposited film can be effectively formed even in a non-pressure-resistant container having a thin wall and a high volume deformation rate as described above.

(Reactive gas)
As the reaction gas supplied from the gas supply pipe 24, various known gases are used depending on the purpose of the plasma treatment.
For example, a compound containing atoms, molecules or ions constituting the thin film in a gas phase state and placed on an appropriate carrier gas is used.
The raw material compound must be highly volatile, and hydrocarbons such as methane, ethane, ethylene, and acetylene are used to form the carbon film and the carbide film. For forming the silicon film, silicon tetrachloride, silane, an organic silane compound, an organic siloxane compound, or the like is used. Halides (chlorides) such as titanium, zirconium, tin, aluminum, yttrium, molybdenum, tungsten, gallium, tantalum, niobium, iron, nickel, chromium, and boron, and organometallic compounds are used.
Further, oxygen gas is used for forming the oxide film, and nitrogen gas or ammonia gas is used for forming the nitride film.
These source gases can be used in appropriate combination of two or more kinds depending on the chemical composition of the thin film to be formed.
On the other hand, argon, neon, helium, xenon, hydrogen and the like are suitable as the carrier gas.

  In the present invention, a combination of an organic siloxane compound such as hexamethyldisiloxane and oxygen gas is most preferable in terms of improving the gas barrier property of the plastic container. A silicon oxide film having excellent barrier properties can be formed.

  The amount of reaction gas to be introduced varies depending on the surface area of the container to be treated and the type of gas. As an example, in the surface treatment on a 2-liter plastic bottle, 1 to 500 cc / in a standard state per bottle. It is desirable to supply at a flow rate of min, particularly 2 to 200 cc / min.

  When thin film formation is performed by reaction of a plurality of source gases, one source gas can be supplied excessively. For example, in the case of forming a silicon oxide film, it is preferable to supply an excess of oxygen gas compared to the silicon source gas, and in the case of forming a nitride, an excess of nitrogen or ammonia is supplied compared to the metal source gas. can do.

(Microwave)
As the microwave that generates glow discharge, it is preferable to use a microwave whose frequency is allowed to be used industrially 2.45 GHz, 5.8 GHz, 22.125 GHz.

  Microwave output varies depending on the surface area of the substrate to be treated and the type of raw material gas, but in the surface treatment of a 2-liter plastic bottle, power of 50 to 1500 W, particularly 100 to 1000 W, per bottle. It is desirable to supply so that it becomes.

(Processing container)
The processing container formed as described above, that is, the non-pressure-resistant plastic container of the present invention has a uniform and dense vapor deposition film on its inner surface . For example, it is possible to form a thin film deposition film having substantially the same thickness from the inner surface of the bottom portion of the plastic container to the inner surface of the trunk portion.
Moreover, in connection with forming such a vapor deposition film using the glow discharge by a microwave,
Glow discharge by microwaves has high energy and forms a dense film. As a result, even a very thin film of 30 nm or less has characteristics of high gas barrier properties and high film flexibility due to its very thin film. On the other hand, a similar film can be obtained by using a high frequency glow discharge, but the film density is low and a film thickness of 70 nm or more is necessary to obtain gas barrier properties. Flexibility is reduced and the above properties are not obtained.

  The following experimental examples further illustrate the present invention, but the present invention is in no way limited to the following examples.

(Thickness measurement method)
(Fluorescent X-ray method) Using a fluorescent X-ray (ZSX100e) manufactured by Rigaku Denki Kogyo Co., Ltd., the amount of silicon in the film was quantified, and the amount of silicon was converted to SiO ₂ to obtain the SiOx film thickness.

  (Masking method) A bottle masked with an aqueous resin was coated with an SiOx film, the aqueous resin was dissolved by washing with water, a step in the SiOx film was created, and the step was measured by AFM to obtain a film thickness.

(Water contact angle measurement method)
The bottle coated with SiOx was cut out, and the water contact angle of the membrane was measured at 22 ° C. using a FACE automatic contact angle meter CA-Z type manufactured by Kyowa Interface Science Co., Ltd. A film made by this method has a smaller water contact angle as a SiOx film having a sufficient reaction, and a silicon compound film containing an organic substance that has a poor reaction has a large water contact angle and a poor gas barrier property.

(Measurement of oxygen transmission rate)
The oxygen permeation amount of the bottle was measured in an environment of 37 ° C. and 100% RH with an oxygen permeation measuring device (Oxtran) manufactured by Modern Control.

(Film density measurement method)
Using a X'Pert MRD manufactured by Philips, the film density was measured by the X-ray total reflection method.

(Experimental example 1): Example of the present invention A microwave power source having a frequency of 2.45 GHz and a maximum output of 1.2 KW, a metal cylindrical plasma processing chamber having a diameter of 90 mm and a height of 500 mm, and an oil rotary vacuum pump for evacuating the processing chamber An apparatus having a rectangular waveguide for introducing microwaves from an oscillator into a plasma processing chamber was used.

Further, as the gas supply pipe, a sintered stainless steel gas supply pipe having a porous structure with an outer diameter of 10 mm and a length of 150 mm is used. A cylindrical polyethylene bottle (PE bottle) with a thickness of 180 mm (under the neck of 165 mm) is used, and an acrylic resin bottomed cylindrical partition wall having an inner diameter of 70 mm and a height of 185 mm is installed on the outside of the bottle ( distance from the partition wall). : 14.0 mm), the degree of vacuum in the partition wall and in the bottle is 10 Pa, 3 sccm of hexamethyldisiloxane (hereinafter referred to as HMDSO) and 30 sccm of oxygen are introduced, and then a microwave of 360 W is transmitted from the microwave oscillator to transmit the partition wall. And plasma is generated in the PE bottle and plasma treatment (5.0 seconds) is performed to form a deposited film inside the PE bottle It was.
The distance between the partition wall and the bottle is indicated by the distance between the inner surface of the partition wall and the outer surface of the bottle body, but the same applies to the following experimental examples.

The film thickness, deposition rate, and water contact angle of the film were measured, and the results are shown in Table 1.
The film thickness was measured for the central part of the body part and the center part of the bottom part by the fluorescent X-ray method, and is shown in Table 1 as the body part thickness (average value) and the bottom part thickness. Further, the deposition rate of the film was calculated from the body thickness (average value) and the plasma treatment time.

(Experimental example 2): Example of the present invention A vapor deposition film was formed and evaluated in the same manner as in Experimental example 1 except that a PE bottle with a body diameter of 50 mm was used and the distance from the partition wall was 10.0 mm. The results are shown in Table 1.

(Experimental Example 3): Invention Example A vapor deposition film was formed in the same manner as in Experimental Example 1 except that a PE bottle having a body diameter of 70 mm was used and the distance from the partition wall was set to 0 mm. Are shown in Table 1.

(Experimental Example 4): Invention Example A vapor deposition film was formed and evaluated in the same manner as in Experimental Example 1 except that a PE bottle having a body diameter of 36 mm was used and the distance from the partition wall was set to 17.0 mm. The results are shown in Table 1.

  In each of Experimental Examples 1 to 4 in which the vapor deposition film was formed using a predetermined partition wall, the bottle was not crushed and the vapor deposition film could be formed over the entire inner surface of the bottle including the bottom. However, in the experimental example in which the distance between the partition wall and the bottle is set to be larger than 15 mm, the deposition rate of the film is slow, the productivity is lowered, the contact angle of the obtained film with water is large, and the gas barrier property is also Lower than that of other experimental examples. Therefore, the interval between the partition wall and the bottle is set to 15 mm or less, which is effective in securing a high deposition rate, allowing the reaction to proceed quickly and sufficiently, and obtaining a vapor deposition film having a sufficient thickness for gas barrier properties. I understand that.

(Experimental example 5): Comparative experimental example A vapor deposition film was formed on the inner side of the PE bottle in the same manner as in Example 1 except that a PE bottle having a body diameter of 70 mm was used without using an acrylic resin partition wall. As a result, in the process of setting the inside of the bottle to 10 Pa, the bottle was crushed, plasma was not generated, and film formation was impossible.

(Experimental example 6): Example of the present invention A cylindrical bulkhead with a bottom made of acrylic resin having an inner diameter of 70 mm and a height of 205 mm on the outside of a polyethylene terephthalate (PET) bottle having a body portion of 65 mm, a height of 200 mm, and a diameter of 28 mm. The PET bottle before forming the vapor deposition film was formed by forming a vapor deposition film inside the PET bottle as in Example 1 and measuring the oxygen permeation amount of this vapor deposition film-coated PET bottle, except that the distance from the bottle was 5 mm). The oxygen permeation amount was compared. The oxygen permeation amount of the vapor-deposited film-coated bottle was 1/30 that was uncoated, indicating a very excellent oxygen barrier property.

In addition, using a PET bottle of the same shape as above, a 10 mm square silicon wafer is attached to the inner surface of the barrel at a position 105 mm from the bottom of the bottle, and the deposited film is coated in the same manner. It was measured by the total reflection method. As a result, the density of the film was as high as 2.0 g / cm ² . Moreover, about this bottle, the film thickness was measured from the level | step difference using the masking method. As a result, the film thickness was very thin at 25 nm.

  From the results of this experimental example, it is understood that in the present invention, a high-density deposited film is formed, and the gas barrier property can be remarkably improved even though the film thickness is small.

Claims (3)

Following formula:
[(V ₀ −V ₁ ) / V ₀ ] × 100
Where
V ₀ indicates the volume in the container when the pressure difference between the inside and outside of the container wall is 0,
V ₁ indicates the volume in the container when the pressure difference between the inside and the outside of the container wall is 2 kPa.
A non-pressure-resistant plastic container having a vapor deposition film on substantially the entire inner wall surface of the container whose volume deformation rate defined by the above is 5% or more at 22 ° C. 2. The non-pressure-resistant plastic container according to claim 1 , wherein the vapor deposition film is formed by microwave plasma CVD and has a thickness at a body portion of 30 nm or less. The non-pressure-resistant plastic container according to claim 1 or 2, which is a squeeze bottle.

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