JP2006089073A - Internally coated plastic container and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a internally coated plastic container which is colorless and transparent and can hold an excellent gas barrier properties even by heating, and a method for manufacturing it. <P>SOLUTION: The plastic container is equipped with a gas barrier coating layer 4 composed of a coating layer 2 and a coating layer 3 on its inner face side. The coating layer 2 is a silicon-containing film including a plasma polymer of an organosilicon compound formed on the inner surface of the container 1 by a plasma CVD from a starting raw material containing the organosilicon compound, and has a thickness of 50-700 Å and an atomic ratio of silicon to oxygen of 1/1.5-1/2.3. The coating layer 3 is an amorphous carbon film formed on the coating layer 2 by a plasma CVD from a starting raw material containing a carbon compound, and has a thickness of 10-300 Å and a surface tension of ≤55×10<SP>-3</SP>N/m. Change in colored transparency before and after forming the gas barrier coating layer 4 on the body part of the container 1 is ≤2.5 by a ΔE<SP>*</SP>value calculated by an L<SP>*</SP>a<SP>*</SP>b<SP>*</SP>color system. A barrier properties index value is ≥5.0. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inner surface-coated plastic container having a gas barrier coating layer on the inner surface side, and a method for manufacturing the same.

  Conventionally, various plastic containers represented by polyester containers, polyolefin containers and the like have been used as containers for beverages, foods, aerosols, cosmetics and the like. The plastic container has a problem that the gas barrier property is inferior to a metal container or a glass container. Therefore, in order to improve the gas barrier property, in recent years, it has been proposed to provide a gas barrier coating layer made of either a carbon film or a silicon-containing film on the inner surface side of the plastic container by a plasma CVD method. .

  The plastic container provided with the carbon coating as the gas barrier coating layer includes, for example, an untreated plastic container in which no coating is formed in a plasma CVD processing apparatus, and at least the inner surface of the container is decompressed to a predetermined degree of vacuum. Thereafter, it can be produced by introducing a starting material such as acetylene in the form of gas into the inner surface of the container and applying a microwave or a high-frequency voltage to generate plasma in the container (see, for example, Patent Document 1). . The plastic container provided with the carbon coating can obtain excellent gas barrier properties by thickening the carbon coating.

  However, when the film thickness of the carbon coating is increased, there are disadvantages that the processing adhesion to the plastic container is lowered and the coloring becomes conspicuous. The coloring by the carbon film may give an unpleasant impression to consumers depending on the contents, and may become an obstacle when the plastic container on which the carbon film is formed is collected and reused. In a plastic container provided with the carbon coating, the coloration can be avoided by reducing the thickness of the carbon coating, but when this is done, sufficient gas barrier properties cannot be obtained.

  On the other hand, a plastic container provided with the silicon-containing film as the gas barrier coating layer is formed by using, for example, an organic silicon compound or the like instead of a starting material such as acetylene for forming the carbon film as a starting material. It can be manufactured in the same manner as the plastic container provided (see, for example, Patent Document 2). The plastic container provided with the silicon-containing coating is not colored and has excellent gas barrier properties at room temperature.

  However, the plastic container provided with the silicon-containing film has a disadvantage that the gas barrier property is remarkably lowered when heated after filling the contents. For example, when a so-called hot pack in which a beverage container is provided with a beverage containing the silicon-containing coating is heated to a temperature of 75 ° C. or higher, particularly 85 ° C. or higher, the gas barrier property of the container is lowered. The tendency of the gas barrier property to decrease due to the hot pack is high in the case of a low acid beverage having a pH of 5 or higher, such as tea, coffee, and sports drink. The gas barrier property of the container can also be used when the container is aseptically filled into a plastic container having a silicon-containing film at room temperature and then stored for a long time in a warming atmosphere of 50 ° C. or higher by a warming bender or the like. Decreases with time.

In the plastic container provided with the silicon-containing coating, if the film thickness of the silicon-containing coating is increased, the gas barrier property deterioration due to heating during the hot pack or warm storage can be improved to some extent, but this is not sufficient. The silicon-containing film cannot obtain flexibility suitable for coating a plastic container, and the work adhesion is lowered.
JP-A-8-53116 JP-A-3-223342

  The present invention eliminates such inconveniences and is colorless and transparent, and is capable of maintaining an excellent gas barrier property even when subjected to heating such as warm storage in a hot pack or a warming bender at room temperature. The object is to provide a plastic container.

  Another object of the present invention is to provide a method for producing the inner surface-coated plastic container.

In order to achieve such an object, the present invention provides an inner surface-coated plastic container having a gas barrier coating layer formed on the inner surface side by plasma CVD, wherein the gas barrier coating layer is plasma generated from a first starting material containing an organosilicon compound. A silicon-containing film containing a plasma polymer of an organosilicon compound formed on the inner surface of the container by CVD, the first coating layer having a thickness in the range of 50 to 700 angstroms, and a first coating layer containing a carbon compound An amorphous carbon film formed on the first coating layer by plasma CVD from two starting materials, having a thickness in the range of 10 to 300 Å and a surface tension in the range of 55 × 10 ⁻³ N / m or less. A transparent colored layer before and after the formation of the gas barrier coating layer in a relatively flat portion of the barrel portion of the container. The change in the degree is characterized in that the ΔE ^* value calculated by the L ^* a ^* b ^* color system is 2.5 or less.

  The inner surface-coated plastic container of the present invention has a gas barrier comprising, on the inner surface side, a first coating layer made of a silicon-containing coating and a second coating layer made of an amorphous carbon coating laminated on the first coating layer. By providing the coating layer, it is less colored and highly transparent, and excellent gas barrier properties can be maintained even when heated in a warm storage state with a hot pack or a warming bender.

  The silicon-containing film as the first coating layer is directly formed on the inner surface of the container by plasma CVD from a first starting material containing an organosilicon compound. The silicon-containing coating is 50 to 700 angstroms, preferably, in order to obtain the gas barrier coating layer having a low coloration and high transparency and excellent gas barrier properties when the amorphous carbon coating is laminated thereon. It has a thickness in the range of 100-500 Angstroms. When the thickness of the silicon-containing coating is less than 50 angstroms, the gas barrier coating layer cannot have sufficient gas barrier properties even when the amorphous carbon coating is laminated, and when the thickness exceeds 700 angstroms. When the amorphous carbon coating is laminated, the work adhesion and transparency of the gas barrier coating layer are lowered.

  Further, in order to obtain the gas barrier coating layer having an excellent gas barrier property, the silicon-containing film needs to contain a plasma polymer of an organosilicon compound, and the atomic ratio between silicon and oxygen in the film It is suitable that (Si / O) is in the range of 1 / 1.5-1 to 2.3, more preferably in the range of 1 / 1.7 to 1 / 2.2. When the atomic ratio between silicon and oxygen is not within the above range, even if the amorphous carbon film is laminated, the gas barrier property of the gas barrier coating layer cannot be made sufficient. In addition, the silicon-containing film may have good adhesion with the inner surface of the plastic container and adhesion with the amorphous carbon film when the atomic ratio of silicon and oxygen is in the above range. it can.

  The silicon-containing film may contain other elements such as hydrogen, carbon, and nitrogen as long as the atomic ratio of silicon and oxygen is within the above range. The silicon-containing film may have a single layer configuration or a multilayer configuration of two or more layers.

  Next, an amorphous carbon film as the second coating layer is formed on the first coating layer by plasma CVD from a second starting material containing a carbon compound. In order to obtain the gas barrier coating layer having a low coloration and high transparency and excellent gas barrier properties when laminated on the silicon-containing coating, the amorphous carbon coating is 10 to 300 angstroms, preferably 30 to 30 angstroms. With a thickness in the range of 150 Angstroms. If the amorphous carbon film has a thickness of less than 10 angstroms, even if it is laminated on the silicon-containing film, the gas barrier coating layer cannot have sufficient gas barrier properties, and the thickness exceeds 300 angstroms. And the gas barrier coating layer has low colorability and transparency when laminated on the silicon-containing film.

The amorphous carbon film has a surface tension in the range of 55 × 10 ⁻³ N / m or less. The surface tension is an index of hydrophobicity of the gas barrier coating layer, and as the surface tension increases, the hydrophobicity of the gas barrier coating layer decreases. According to the study by the present inventors, it has been found that the gas barrier coating layer with lower hydrophobicity has a lower gas barrier property due to heating. Thus, the amorphous carbon coating has a surface tension in the above range, so that the gas barrier coating layer can be prevented from being deteriorated in gas barrier properties even when heated in a warm storage state in a hot pack or a heating bender. And excellent gas barrier properties can be maintained.

  The amorphous carbon film has a so-called diamond-like structure composed of hydrogen and carbon, but may contain oxygen and other elements in addition to hydrogen and carbon.

The colorability and transparency of the plastic container of the present invention can be evaluated by the change in the color transparency before and after the gas barrier coating layer is formed using the ΔE ^* value calculated by the L ^* a ^* b ^* color system as an index. it can. And the plastic container of this invention can obtain the outstanding colorless transparency because (DELTA ⁾ E ^* value calculated by L ^* a ^* b ^* color system is 2.5 or less. As a result, the plastic container of the present invention can give a favorable impression to consumers regardless of the contents, and can be reused without any problem even after collection.

  Further, the plastic container of the present invention has a ratio A / B between the oxygen barrier property A before forming the gas barrier coating layer and the oxygen barrier property B after forming the gas barrier coating layer and heating and filling the contents. The barrier property index value indicated by is characterized by being 5.0 or more. The gas barrier property after heating of the plastic container of the present invention includes the oxygen barrier property A before forming the gas barrier coating layer of the container and the oxygen barrier property after forming the gas barrier coating layer and heating and filling the contents. It can be evaluated by a barrier property index value indicated by a ratio A / B with B. And the plastic container of this invention can hold | maintain the gas barrier property which was excellent after a heating because the said barrier property index value is 5.0 or more, the contents can be hot-packed, or the contents can be kept at room temperature. After filling with, it can be used without any problem for the purpose of long-term storage in a heating bender.

  According to the plastic container of the present invention, when the gas barrier coating layer composed of the first coating layer and the second coating layer is subjected to heating such as a warm storage state in a hot pack or a warming bender, It has a gas barrier property that is superior to the effects of each of the first coating layer and the second coating layer, and further superior to the sum of both effects.

  In the plastic container of the present invention, the plastic container is accommodated in the plasma processing apparatus, and at least the inner surface of the container is depressurized to a predetermined degree of vacuum, and then the first starting material containing the organosilicon compound is introduced into the inner surface of the container. Forming a first coating layer, which is a silicon-containing coating containing a plasma polymer of an organosilicon compound, on the inner surface of the container by plasma CVD, and subsequently forming the inner surface of the container after the first coating layer is formed. And a step of introducing a second starting material containing a carbon compound on the side and forming a second coating layer which is an amorphous carbon coating on the first coating layer by plasma CVD. be able to. According to the manufacturing method, since the first and second coating layers can be formed by the same plasma processing apparatus, the inner surface-coated plastic container can be manufactured efficiently. According to the manufacturing method, the hybrid layer having a structure in which the structure of the first coating layer and the structure of the second coating layer are mixed is formed at the boundary between the first coating layer and the second coating layer. It can be formed, and the mixed layer can improve the interlayer adhesion between the first coating layer and the second coating layer.

  In the plastic container of the present invention, the plastic container is accommodated in the first plasma processing apparatus, and at least the inner surface of the container is depressurized to a predetermined degree of vacuum, and then the first container containing the organosilicon compound on the inner surface of the container. And a step of forming a first coating layer, which is a silicon-containing coating containing a plasma polymer of an organosilicon compound, on the inner surface of the container by plasma CVD, and after the formation of the first coating layer The container is taken out from the first plasma processing apparatus and accommodated in the second plasma processing apparatus, and at least the inner surface of the container is depressurized to a predetermined degree of vacuum, and the inner surface of the container contains a carbon compound. And a method of introducing a second starting material and forming a second coating layer, which is an amorphous carbon coating, on the first coating layer by plasma CVD. . According to the manufacturing method, since two plasma processing apparatuses are used and the first coating layer and the second coating layer are separately formed in each plasma processing apparatus, they are formed in the same plasma processing apparatus. Since there is no need to switch the starting material according to the coating layer to be used, and the plastic container on which the first coating layer is formed can be temporarily stored as an intermediate, the inner surface-coated plastic container can be produced efficiently. Can do.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory cross-sectional view showing the configuration of the plastic container of the present embodiment, and FIG. 2 is an explanatory cross-sectional view showing an apparatus used for manufacturing the plastic container of the present embodiment.

  The plastic container of the present embodiment is a low-acid beverage such as teas, coffees, sports drinks and milk drinks that are sold after being heated and stored in a heating bender after hot filling (hot pack) or normal temperature aseptic filling. It is used as various containers such as containers, containers for beverages such as carbonated drinks, sparkling liquor and beer, containers for foods such as sauces and soy sauce, containers for aerosol contents and the like. Examples of the plastic constituting the plastic container include polyester resins obtained by polycondensation of polyhydric alcohols such as polyethylene terephthalate and polyethylene naphthalate and polyvalent carboxylic acids, polyolefin resins such as polyethylene and polypropylene, polyallyl resins, and polyether series. Examples thereof include resins and acrylic resins, but polyester resins or polyolefin resins are suitable, and polyethylene terephthalate is particularly suitable. When the plastic container is used in a container for low acid beverages that is sold after being hot-packed or stored at a warming bender etc. after hot filling or aseptic filling at room temperature, it increases the crystallinity of the resin and is heat resistant. It is preferable to impart properties.

  As shown in a part of FIG. 1, the plastic container 1 of the present embodiment includes a first coating layer 2 formed on the inner surface and a second coating layer formed on the first coating layer 2. A gas barrier coating layer 4 composed of the coating layer 3 is provided.

  The first coating layer 2 is a silicon-containing film containing a plasma polymer of an organosilicon compound formed by plasma CVD from a starting material containing an organosilicon compound, and ranges from 50 to 700 angstroms, preferably from 100 to 500 angstroms. With a thickness of. The first coating layer 2 preferably has an atomic ratio (Si / O) between silicon and oxygen in the silicon-containing coating in the range of 1 / 1.5-1 to 2.3. It is preferably in the range of 1.5 to 1 / 2.2.

On the other hand, the second coating layer 3 is an amorphous carbon film that is formed by plasma CVD from a starting material containing carbon atoms, and in which carbon and hydrogen form a so-called diamond-like structure, and is 10 to 300 angstroms, preferably It has a thickness in the range of 30 to 150 angstroms. Further, the second coating layer 3 has a surface tension as a hydrophobic index of 55 × 10 ⁻³ N / m or less.

The colorless transparency of the plastic container 1 is determined using the ΔE ^* value calculated by the L ^* a ^* b ^* color system (JIS Z 8729) standardized by the International Lighting Commission (CIE) as an index. It can be evaluated by a change in coloring transparency before and after the formation of the gas barrier coating layer 4 in the body portion of the film.

The ΔE ^* value is the L ^* value of the L ^* a ^* b ^* color system when a relatively flat portion of the body of the plastic container 1 is cut out and light is vertically passed through this portion by a color difference meter. , A ^* value, b ^* value are compared before and after the formation of the gas barrier coating layer 4, and ΔL ^* value and Δa ^* value calculated as the difference between the value before and after the formation of the gas barrier coating layer 4. , Δb ^* value is calculated by the following equation (1).

ΔE ^* = (ΔL ^{* 2} + Δa ^{* 2} + Δb ^{* 2} ) ^1/2 (1)
In the plastic container 1, by appropriately setting the coating composition of the coating layers 2 and 3, the change in the colored transparency is 2.5 or less in the ΔE ^* value, and the gas barrier coating layer 4 having excellent colorless transparency. Can be provided.

  The gas barrier property after heating of the plastic container 1 includes the oxygen barrier property A before forming the gas barrier coating layer of the container, and the oxygen barrier property after forming the gas barrier coating layer and heating and filling the contents. The barrier property index value BIF (Barrier Improvement Factor) indicated by the ratio A / B with B can be evaluated. The oxygen barrier properties A and B are expressed by the oxygen permeation amount (ml / day / tube) per plastic container 1 per day. The oxygen permeation amount can be measured based on JIS K 7126 using a gas permeability measuring device such as OX-TRAN (trade name) manufactured by Mocon.

  By providing the gas barrier coating layer 4 composed of the coating layers 2 and 3 in the plastic container 1, the gas barrier property after heating is 5.0 or more in terms of the barrier property index value BIF, and excellent gas barrier property even when heated. Can be held.

  Next, a method for manufacturing the plastic container 1 will be described.

  In the present embodiment, the plastic container 1 is manufactured by the plasma CVD apparatus 11 shown in FIG. The plasma CVD apparatus 11 includes a processing chamber 14 defined by a side wall 12 formed of Pyrex (registered trademark) glass and a bottom plate 13 that can be moved up and down, and includes a microwave generator 15 at a position facing the side wall 12. ing. An exhaust chamber 18 defined by a side wall 16 and an upper wall 17 is provided above the processing chamber 14, and a partition wall 19 is provided between the processing chamber 14.

  The bottom plate 13 accommodates the plastic container 1 in the processing chamber 14 by placing the untreated plastic container 1 and moving upward. The plastic container 1 housed in this manner is arranged so that the inside of the container communicates with the exhaust hole 21 provided in the partition wall 19 via the mouth holder 20. In the mouth holder 20, the upper projecting portion 22 is closely inserted into the exhaust hole 21, and the mouth holder 23 is inserted into the mouth of the plastic container 1 with a predetermined interval.

  The processing chamber 14 and the exhaust chamber 18 communicate with each other through a valve 25 of a vent 24 provided in the partition wall 19, and an opening 26 formed in the side wall 16 of the exhaust chamber 18 is connected to a vacuum device (not shown). Yes. A gas introduction pipe 28 for supplying a gaseous starting material (hereinafter abbreviated as source gas) is supported on the upper wall 17 of the exhaust chamber 18 via a seal 27, and the gas introduction pipe 28 has one end. The portion passes through the upper wall 17 and the mouth holder 20 and is inserted into the plastic container 1, and the other end is connected to first and second source gas sources (not shown). The first and second source gas sources can be switched with respect to the gas introduction pipe 28. There is a gap between the gas introduction pipe 28 and the inner peripheral surface of the mouth holder 20.

  In the manufacturing method of this embodiment, first, the first coating layer 2 is formed inside the untreated plastic container 1 using the plasma CVD apparatus 11. The coating layer 2 may be formed according to a method known per se, for example, as follows.

The coating layer 2 is formed by first moving up the bottom plate 13 on which the plastic container 1 is placed, housing the plastic container 1 in the processing chamber 14, and then operating a vacuum device (not shown) to evacuate the chamber 18. The inside of the processing chamber 14 is depressurized through the vent 24 by exhausting the inside. At the same time, the inside of the plastic container 1 is depressurized to a degree of vacuum of 10 ⁻¹ to 10 ² Pa through a gap between the gas introduction pipe 28 inserted into the exhaust hole 21 and the inner peripheral surface of the mouth holder 20. When the degree of vacuum is less than 10 ⁻¹ Pa, it takes a long time to form the coating layer 2, and when it exceeds 10 ² Pa, the adhesion of the coating layer 2 to the plastic container 1, workability, and gas barrier properties deteriorate.

  Next, the first source gas is supplied into the plastic container 1 from the first source gas source (not shown) through the gas introduction pipe 28. In the plasma CVD apparatus 11, the first source gas is continuously supplied and continuously exhausted by the vacuum apparatus, so that the inside of the processing chamber 14 and the plastic container 1 is maintained at the vacuum level. The supply amount of the first source gas is set to an appropriate amount according to the surface area of the target plastic container 1 and the thickness of the coating film to be formed.

  Examples of the first source gas include silanes such as silane, alkylsilane, dialkylsilane, and trialkylsilane, alkoxysilanes such as monoalkoxysilane, dialkoxysilane, and trialkoxysilane, tetraalkyldisiloxane, and hexaalkyldisilane. In addition to siloxanes such as siloxane, silazanes such as hexamethyldisilazane, and the like, known organic silicon compound gases can be used. As the first source gas, the organic silicon compound gas can be used alone or in combination of two or more, and oxygen gas is preferably mixed and used in an appropriate ratio. When an organic silicon compound having a high carbon content is used as the first source gas, it is preferable to increase the mixing ratio of oxygen gas in order to remove carbon as carbon dioxide. The first source gas may be diluted with a rare gas such as argon or helium.

  When other gas such as oxygen gas or rare gas is used as the first source gas together with the organosilicon compound gas, the gas is introduced by mixing the organosilicon compound gas with another gas in advance. The gas may be introduced from the pipe 28, or two gas introduction pipes 28 may be provided, and the gas of the organosilicon compound may be introduced from one of them, and another gas may be introduced from the other one. Alternatively, the gas introduction pipes 28 may be provided in an inner and outer double so that the organic silicon compound gas is introduced from one of the inner and outer sides and the other gas is introduced from the other side. However, when two gas introduction pipes 28 are provided, or when the gas introduction pipes 28 are provided in an inner and outer double, care must be taken that the organosilicon compound and other gases are sufficiently mixed. .

  Then, while the first source gas is being supplied, the microwave generator 15 is operated to irradiate a predetermined microwave for a predetermined time, thereby electromagnetically exciting the source gas into the plastic container 1. Plasma is generated to form a silicon-containing film as the first coating layer 2 on the inner surface of the plastic container 1.

As a result, it has a thickness in the range of 50 to 700 angstroms, preferably 100 to 500 angstroms, includes a plasma polymer of an organosilicon compound, and preferably has an atomic ratio (Si / O) of silicon to oxygen of 1/1. A coating layer 2 in the range of .5 to 1 / 2.2 is obtained. In addition, the coating layer 2 alone has a ΔE ^* value of preferably 1.5 or less, and more preferably 1.0 or less.

  In the manufacturing method of the present embodiment, if the first coating layer 2 is formed as described above, the second plasma is continuously formed on the coating layer 2 in the same plasma CVD apparatus 11 without taking out the plastic container 1. The covering layer 3 is formed. The coating layer 3 may be formed according to a method known per se, for example, as follows.

  The coating layer 3 is formed by reducing the pressure inside the processing chamber 14 by the vacuum device while the plastic container 1 having the coating layer 2 formed in the processing chamber 14 is housed, and at the same time, the inside of the plastic container 1 is 1-50 Pa. Depressurize to the degree of vacuum. If the degree of vacuum is less than 1 Pa, it takes a long time to form the coating layer 3, and if it exceeds 50 Pa, the adhesion of the coating layer 3 to the coating layer 2, workability, and gas barrier properties deteriorate.

  Next, a second source gas is supplied from a second source gas source (not shown) into the plastic container 1 through the gas introduction pipe 28. In the plasma CVD apparatus 11, the second source gas is continuously supplied and continuously exhausted by the vacuum apparatus, so that the inside of the processing chamber 14 and the plastic container 1 is maintained at the degree of vacuum. The supply amount of the second source gas is set to an appropriate amount according to the surface area of the target plastic container 1 and the thickness of the coating film to be formed.

  Examples of the second source gas include aliphatic unsaturated hydrocarbon compounds such as acetylene, ethylene and propylene, aliphatic saturated hydrocarbon compounds such as methane, ethane and propane, and aromatic hydrocarbon compounds such as benzene, toluene and xylene. A carbon compound gas such as acetylene or ethylene, which is an aliphatic unsaturated hydrocarbon compound, is preferable. The second source gas may be used alone or as a mixture of two or more as required. A small amount of hydrogen, oxygen, an organosilicon compound, or other film-forming organic as a film modifier. You may use a compound together. The second source gas may be diluted with a rare gas such as argon or helium.

  When other gas such as the film modifier or rare gas is used as the second source gas together with the carbon compound gas, the carbon compound gas is mixed with the other gas in advance. The gas may be introduced from the introduction pipe 28, or two gas introduction pipes 28 may be provided, and the carbon compound gas may be introduced from one of them, and another gas may be introduced from the other one. Alternatively, the gas introduction pipes 28 may be provided in an inner and outer double so that the carbon compound gas is introduced from one of the inner and outer sides and the other gas is introduced from the other side. However, when two gas introduction pipes 28 are provided, or when the gas introduction pipes 28 are provided in an inner and outer double, care must be taken that the carbon compound gas and other gases are sufficiently mixed. is there.

  Then, while the second source gas is being supplied, the microwave generator 5 is operated to irradiate a predetermined microwave for a predetermined time, thereby electromagnetically exciting the second source gas to a plastic container. Plasma is generated in 1 to form an amorphous carbon film as the second coating layer 3 on the coating layer 2.

As a result, a coating having a thickness in the range of 10 to 300 angstroms, preferably 30 to 150 angstroms, substantially consisting of carbon and having a surface tension as a hydrophobic index of 55 × 10 ⁻³ N / m or less. Layer 3 is obtained.

The coating layer 3 is made of the amorphous carbon coating and generally exhibits a transparent light brown color in the thick film. In this embodiment, the coating layer 3 is formed within the above range, and the coating layer 3 is formed under appropriate conditions. Therefore, the ΔE ^* value of the coating layer 3 alone is preferably 2.0 or less, and more preferably 1.5 or less.

The ΔE ^* value of the coating layer 2 alone is 1.5 or less, more preferably 1.0 or less, and the ΔE ^* value of the coating layer 3 alone is 2.0 or less, more preferably 1.5 or less. The ΔE ^* value of the gas barrier coating layer 4 composed of the coating layers 2 and 3 can be 2.5 or less.

  Next, when the coating layer 3 is formed, the operation of the vacuum apparatus is stopped, the inside of the processing chamber 14 and the plastic container 1 is returned to normal pressure, and then the gas barrier coating layer comprising the coating layers 2 and 3 is formed. The plastic container 1 in which 4 is formed is taken out from the plasma CVD apparatus 11.

  In the apparatus of this embodiment, the formation of the coating layer 2 and the formation of the coating layer 3 are performed by a single plasma CVD apparatus 11, but two plasma CVD apparatuses 11 are used and one plasma CVD apparatus 11 is used. After the formation of the coating layer 2 in the step, the plastic container 1 on which the coating layer 2 is formed is taken out from the plasma CVD apparatus 11, and then the plastic container 1 is accommodated in the other plasma CVD apparatus 11. May be formed. By using the two plasma CVD apparatuses 11, it is not necessary to switch between the source gas for forming the coating layer 2 and the source gas for forming the coating layer 3.

  In the present embodiment, the first and second source gases are electromagnetically excited to generate plasma by irradiating the microwave from the microwave generator 15, but the inner and outer surfaces of the plastic container 1 are used. An electrode may be disposed on the electrode, and plasma may be generated by applying a high-frequency current to the electrode. However, in order to form the coatings 2 and 3 having excellent adhesion, workability, and gas barrier properties on the inner surface side of the plastic container 1, a method of generating plasma by irradiating microwaves is more suitable.

  Next, Examples, Reference Examples and Comparative Examples of the present invention will be shown.

  In this embodiment, a polyethylene terephthalate resin bottle (hereinafter abbreviated as a PET bottle) having an internal volume of 280 ml obtained by biaxial stretch blow molding of a polyethylene terephthalate resin preform is used as the plastic container 1. The gas barrier coating layer 4 composed of the coating layers 2 and 3 was formed on the inner surface side of the PET bottle by the plasma CVD apparatus 11 shown in FIG. Note that hexamethyldisiloxane and oxygen were used as the first source gas for forming the coating layer 2, and acetylene was used as the second source gas for forming the coating layer 3.

  The thickness of the coating layer 2 that is a silicon-containing coating, the thickness of the coating layer 3 that is an amorphous carbon coating, the surface tension as an index of hydrophobicity, and the total thickness of the coating layers 2 and 3 of the gas barrier coating layer 4 Table 1 shows the thickness. In addition, in the coating layer 2 which is a silicon-containing film, the atomic ratio of silicon to oxygen in the plasma polymer of the organosilicon compound was 1 / 2.0.

Next, from the PET bottle before the formation of the gas barrier coating layer 4 and the PET bottle on which the gas barrier coating layer 4 is formed, each flat portion of the body is cut out, and light is allowed to pass vertically by a color difference meter. The L ^* value, a ^* value, and b ^* value of the ^* a ^* b ^* color system were measured, and the ΔL ^* value, Δa ^* value, and Δb ^* value were calculated as the difference between them. The ΔE ^* value was calculated from the ΔL ^* value, Δa ^* value, and Δb ^* value according to the above equation (1). Table 1 shows Δb ^* values as the degree of container coloring and ΔE ^* values as the degree of container transparency.

  Next, with respect to the PET bottle before the formation of the gas barrier coating layer 4, the oxygen permeability per day of the PET bottle was measured to obtain an oxygen barrier property A. Further, with respect to the PET bottle after the gas barrier coating layer 4 was formed, the oxygen transmission rate per one PET bottle per day was measured to obtain an oxygen barrier property A ′. Further, after the gas barrier coating layer 4 was formed, the contents were filled under model hot pack conditions (hereinafter abbreviated as model hot pack conditions).

  The model hot pack conditions are as follows. First, about 90 ° C. warm water (pH 7) is filled into a PET bottle, capped, then laid down for 30 seconds and held for 3 minutes. Next, the plastic bottle is immersed in warm water of 75 ° C. for 3 minutes, then taken out and cooled with water for 15 minutes. After the water cooling, the contents are discarded and the obtained plastic bottle is used as a test sample.

  Next, with respect to the PET bottle obtained by processing under the model hot pack conditions, the oxygen permeability per day for each PET bottle was measured to obtain the oxygen barrier property B.

  Then, the gas barrier property index value BIF is calculated as a ratio A / B between the oxygen barrier property A before the formation of the gas barrier coating layer 4 and the oxygen barrier property B after the gas barrier coating layer 4 is formed and the contents are heated and filled. did. Table 1 shows the oxygen barrier properties A, A ', B and the gas barrier property index value BIF.

  Next, after aseptically filling a green bottle (pH 6.4) with a green tea beverage (pH 6.4) into the PET bottle on which the gas barrier coating layer 4 is formed, the green tea beverage is immediately taken out from the PET bottle, and the L value of the Lab Hunter color system, a Value and b value were measured. Next, the green tea beverage is aseptically filled at room temperature into the PET bottle after the gas barrier coating layer 4 is formed, and stored in a heated atmosphere at 60 ° C. for 4 weeks. Then, the green tea beverage is taken out from the PET bottle, and Lab Hunter The L value, a value, and b value of the color system were measured. Then, ΔL value, Δa value, and Δb value are calculated as the difference between the L value, a value, and b value immediately after the aseptic filling at room temperature and the L value, a value, and b value after storage, and ΔL The ΔE value of the Lab Hunter color system was calculated from the value, Δa value, and Δb value according to the following equation (2). The results are shown in Table 1.

ΔE = (ΔL ² + Δa ² + Δb ² ) ^1/2 (2)
The ΔE value of the Lab Hunter color system includes the color of the green tea beverage immediately after aseptic filling at room temperature, and the color of the green tea beverage after aseptic filling at room temperature and further stored in a heated atmosphere at 60 ° C. for 4 weeks. The greater the ΔE value, the more the green tea beverage is oxidized and deteriorated, in other words, the lower the gas barrier property of the PET bottle.
[Reference example]
In this reference example, for the same PET bottle as used in Example 1, the oxygen permeability per day was measured for each PET bottle without forming the gas barrier coating layer 4 at all. The oxygen permeability corresponds to the oxygen barrier property A of the PET bottle before the gas barrier coating layer 4 is formed.

  Next, after processing the said PET bottle in which the gas barrier coating layer 4 was not formed at all by the said model hot pack conditions, the oxygen permeation rate per one said PET bottle was measured, and it was set as oxygen barrier property B. Then, the gas barrier property index value BIF was calculated in exactly the same manner as in Example 1. Table 1 shows the oxygen barrier properties A and B and the gas barrier property index value BIF.

Next, with respect to the PET bottle in which the gas barrier coating layer 4 was not formed at all, the ΔE value of the Lab Hunter color system as the green tea beverage color change was calculated in the same manner as in Example 1. The results are shown in Table 1.
[Comparative Example 1]
In this comparative example, the same PET bottle as used in Example 1 was used, and the gas barrier coating layer 4 consisting only of the coating layer 3 was formed on the inner surface side of the PET bottle by the plasma CVD apparatus 11 shown in FIG. Note that acetylene was used as the second source gas for forming the coating layer 3.

  Table 1 shows the thickness of the coating layer 3 that is an amorphous carbon coating, the surface tension as an index of hydrophobicity, and the thickness of the gas barrier coating layer 4.

Next, Δb ^* values and ΔE ^* values of the L ^* a ^* b ^* color system were calculated in exactly the same manner as in Example 1. Table 1 shows Δb ^* values as the degree of container coloring and ΔE ^* values as the degree of container transparency.

  Next, in exactly the same manner as in Example 1, the oxygen barrier properties A, A ′, and B were obtained, and the gas barrier property index value BIF was calculated. Table 1 shows the oxygen barrier properties A, A ', B and the gas barrier property index value BIF.

Next, in exactly the same manner as in Example 1, the ΔE value of the Lab Hunter color system as the green tea beverage color change degree was calculated. The results are shown in Table 1.
[Comparative Example 2]
In this comparative example, the same PET bottle as used in Example 1 was used, and the gas barrier coating layer 4 consisting only of the coating layer 2 was formed on the inner surface side of the PET bottle by the plasma CVD apparatus 11 shown in FIG. The covering layer 2 is a silicon-containing film containing a plasma polymer of an organosilicon compound formed using hexamethyldisiloxane and oxygen as the first source gas, and the silicon of the plasma polymer of the organosilicon compound The atomic ratio with oxygen was 1 / 2.0. Table 1 shows the thickness of the coating layer 2 and the thickness of the gas barrier coating layer 4.

Next, Δb ^* values and ΔE ^* values of the L ^* a ^* b ^* color system were calculated in exactly the same manner as in Example 1. Table 1 shows Δb ^* values as the degree of container coloring and ΔE ^* values as the degree of container transparency.

  Next, in exactly the same manner as in Example 1, the oxygen barrier properties A, A ′, and B were obtained, and the gas barrier property index value BIF was calculated. Table 1 shows the oxygen barrier properties A, A ', B and the gas barrier property index value BIF.

Next, in exactly the same manner as in Example 1, the ΔE value of the Lab Hunter color system as the green tea beverage color change degree was calculated. The results are shown in Table 1.
[Comparative Example 3]
In this comparative example, the gas barrier coating layer 4 consisting only of the coating layer 3 was formed on the inner surface side of the same PET bottle used in Example 1 in the same manner as in the comparative example 1 except that the film thickness was changed.

  Table 1 shows the thickness of the coating layer 3 that is an amorphous carbon coating, the surface tension as an index of hydrophobicity, and the thickness of the gas barrier coating layer 4.

Next, Δb ^* values and ΔE ^* values of the L ^* a ^* b ^* color system were calculated in exactly the same manner as in Example 1. Table 1 shows Δb ^* values as the degree of container coloring and ΔE ^* values as the degree of container transparency.

  Next, in exactly the same manner as in Example 1, the oxygen barrier properties A, A ′, and B were obtained, and the gas barrier property index value BIF was calculated. Table 1 shows the oxygen barrier properties A, A ', B and the gas barrier property index value BIF.

  Next, in exactly the same manner as in Example 1, the ΔE value of the Lab Hunter color system as the green tea beverage color change degree was calculated. The results are shown in Table 1.

  From Table 1, the following is clear.

  First, in the PET bottle in which the gas barrier coating layer 4 of the reference example is not formed at all, the gas barrier property of the PET bottle is low as apparent from the oxygen barrier properties A and B. Is big.

Next, in the PET bottle including only the coating layer 3 made of an amorphous carbon coating as the gas barrier coating layer 4 of Comparative Example 1, the thickness of the coating layer 3 is set to 146 angstroms, whereby the container coloring degree Δb ^* value and the container transparency are obtained. The ΔE ^* value becomes smaller. However, it is clear that the oxygen barrier property A ′ after the formation of the gas barrier coating layer 4 and the oxygen barrier property B after heating and filling are low, and a sufficient gas barrier property cannot be obtained.

In the PET bottle having only the coating layer 3 made of an amorphous carbon coating as the gas barrier coating layer 4, the oxygen after formation of the gas barrier coating layer 4 can be obtained by setting the thickness of the coating layer 3 to 453 Å as in Comparative Example 3. The barrier property A ′ and the oxygen barrier property B after heat filling can be improved, and an excellent gas barrier property can be obtained. However, when the amorphous carbon film has the thickness, it is clear that the container coloring degree Δb ^* value and the container transparency ΔE ^* value become large, and sufficient colorless transparency cannot be obtained.

Next, in the PET bottle provided with only the coating layer 2 made of a silicon-containing coating as the gas barrier coating layer 4 of Comparative Example 2, the container coloring degree Δb ^* value and the container transparency ΔE ^* value are small, and after the gas barrier coating layer 4 is formed. The oxygen barrier property A ′ is high, and it has excellent gas barrier properties. However, in the PET bottle, the oxygen barrier property B after the gas barrier coating layer 4 is formed and heated and filled is the same as the oxygen barrier property A before the gas barrier coating layer 4 is formed. It is clear that the gas barrier properties are greatly reduced.

The pet of Example 1 provided with the coating layer 2 made of a silicon-containing coating as the gas barrier coating layer 4 and the coating layer 3 made of an amorphous carbon coating laminated on the coating layer 2 for the reference example and each comparative example. It is apparent that the bottle has excellent colorless transparency with a small container coloring degree Δb ^* value and container transparency degree ΔE ^* value. Further, the PET bottle of Example 1 has a high oxygen barrier property A ′ after the formation of the gas barrier coating layer 4, an excellent gas barrier property at room temperature, and a high oxygen barrier property B after heating and filling. It is clear that excellent gas barrier properties are maintained later.

  Furthermore, according to the PET bottle of Example 1, the green tea beverage discoloration is much lower than the PET bottles of the reference example and comparative examples 1 and 2 by maintaining excellent gas barrier properties even after heating. It is clear that it has excellent content preservation.

  Therefore, the PET bottle of Example 1 has the same thickness of the coating layer 2 as the PET bottle of Comparative Example 2, and the thickness of the coating layer 3 is the same as the PET bottle of Comparative Example 1, It is clear that an effect more than the sum of the effects obtained by the PET bottles of Comparative Examples 1 and 2 can be achieved.

  In Examples 2 to 4, except that the thickness of the coating layer 3 that is an amorphous carbon coating was changed, the gas barrier coating layer 4 composed of the coating layers 2 and 3 on the inner surface side of the PET bottle was exactly the same as in Example 1. Formed. In the PET bottles of Examples 2 to 4, the atomic ratio between silicon and oxygen in the silicon-containing coating forming the coating layer 2 was in the range of 1 / 1.8 to 1 / 2.2.

  Next, the thickness of the coating layer 2 that is a silicon-containing coating of each PET bottle of Examples 2 to 4, the thickness of the coating layer 3 that is an amorphous carbon coating, the surface tension as a hydrophobic index, Table 2 shows the thickness of the gas barrier coating layer 4 as the total of the three thicknesses.

Next, Δb ^* values and ΔE ^* values of the L ^* a ^* b ^* color system were calculated for each of the PET bottles of Examples 2 to 4 exactly as in Example 1. Table 2 shows the Δb ^* value as the container coloring degree of each PET bottle and the ΔE ^* value as the container transparency.

  Next, for each of the PET bottles of Examples 2 to 4, the oxygen barrier properties A, A ′, and B were determined in exactly the same manner as in Example 1, and the gas barrier property index value BIF was calculated. Table 2 shows the oxygen barrier properties A, A ′, and B and the gas barrier property index value BIF of each PET bottle.

  Next, for each of the PET bottles of Examples 2 to 4, the ΔE value of the Lab Hunter color system as the green tea beverage color change degree was calculated exactly as in Example 1. The results are shown in Table 2.

  Table 2 also shows the data of Example 1.

From Table 2, the PET bottles of Examples 2 to 4 in which the thickness of the coating layer 2 made of an amorphous carbon coating is in the range of 31 to 205 angstroms are similar to the plastic bottles of Example 1 in the degree of container coloration Δb ^*. It is clear that the value, container transparency ΔE ^* value is small and has excellent colorless transparency. Further, each of the PET bottles of Examples 2 to 4 has a high oxygen barrier property A ′ after the formation of the gas barrier coating layer 4 as in the PET bottle of Example 1, and has an excellent gas barrier property at room temperature. It is clear that the oxygen barrier property B after heating and filling is high, and the excellent gas barrier property is maintained even after heating.

  In Examples 1 to 4, the barrier index value when using warm water having a pH of 7.0 is evaluated. According to the PET bottles of Examples 1 to 4, a green tea beverage having a pH of 6.4, pH 6.7. As for the mineral water and black coffee having a pH of 5.5, the barrier index value is 5.0 or more, and an excellent gas barrier property can be obtained.

Explanatory sectional drawing which shows the structure of the plastic container of this invention. Explanatory sectional drawing which shows the example of 1 structure of the apparatus used for manufacture of the plastic container of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Plastic container, 2 ... 1st coating layer, 3 ... 2nd coating layer, 4 ... Gas barrier coating layer.

Claims (4)

In the inner surface-coated plastic container having a gas barrier coating layer formed by plasma CVD on the inner surface side,
The gas barrier coating layer is a silicon-containing coating containing a plasma polymer of an organosilicon compound formed on the inner surface of the container by plasma CVD from a first starting material containing an organosilicon compound, and having a thickness of 50 to 700 angstroms. A first coating layer having a thickness in the range, and an amorphous carbon coating formed on the first coating layer by plasma CVD from a second starting material comprising a carbon compound, in the range of 10-300 angstroms. A second coating layer having a thickness and a surface tension in the range of 55 × 10 ⁻³ N / m or less,
Inner surface-coated plastic characterized in that a change in coloring transparency before and after formation of the gas barrier coating layer in the body portion of the container is 2.5 or less in a ΔE ^* value calculated by the L ^* a ^* b ^* color system container.   The ratio A / B of the oxygen barrier property A before forming the gas barrier coating layer of the inner surface coated plastic container and the oxygen barrier property B after forming the gas barrier coating layer and heating and filling the contents is indicated by A / B. 2. The inner surface-coated plastic container according to claim 1, wherein the barrier property index value is 5.0 or more. A plastic container is accommodated in a plasma processing apparatus, and at least the inner surface of the container is depressurized to a predetermined degree of vacuum, and then a first starting material containing an organosilicon compound is introduced into the inner surface of the container, and the container is subjected to plasma CVD. Forming a first coating layer which is a silicon-containing coating containing a plasma polymer of an organosilicon compound on the inner surface of
After the formation of the first coating layer, a second starting material containing a carbon compound is subsequently introduced into the inner surface of the container, and a second coating layer that is an amorphous carbon coating is formed on the first coating layer by plasma CVD. Forming the inner surface-coated plastic container. A plastic container is accommodated in the first plasma processing apparatus, and at least the inner surface of the container is depressurized to a predetermined degree of vacuum, and then a first starting material containing an organosilicon compound is introduced into the inner surface of the container, and plasma CVD is performed. Forming a first coating layer, which is a silicon-containing coating containing a plasma polymer of an organosilicon compound, on the inner surface of the container,
After the formation of the first coating layer, the container is taken out of the first plasma processing apparatus and accommodated in the second plasma processing apparatus, and at least the inner surface of the container is depressurized to a predetermined vacuum level, And a step of introducing a second starting material containing a carbon compound on the inner surface of the container and forming a second coating layer, which is an amorphous carbon film, on the first coating layer by plasma CVD. Manufacturing method of inner surface-coated plastic container.

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