JPH03107458A - Method for forming film on inside surface of plastic container - Google Patents

Abstract

PURPOSE:To form the plasma-polymerized film having fluid impermeability and gas barrier property from a gaseous monomer on the inside surface of a plastic tank by subjecting the inside surface of the plastic tank to an ion bombardment pretreatment, then supplying the gaseous monomer and generating a plasma discharge between the electrodes in the tank. CONSTITUTION:The electrodes 601, 602 are disposed to face each other in the plastic tank 10 consisting of polyethylene, polypropylene, etc., and the inside of the tank is evacuated to a reduced pressure. An inert gas, such as He or Ar is supplied from a cylinder 607 into the tank and a high-frequency voltage is impressed to the two electrodes 601, 602 by a electric power source 608 to generate the glow discharge and to generate the plasma by the inert gas, by which the ion bombardment treatment is executed and the wettability and adhesiveness of the inside surface of the tank are improved. The atmosphere in the tank is then replaced with the gaseous monomer 611, such as tetrafluoroethylene and the plasma is generated in the same manner as mentioned above. The plasma-polymerized film from this gaseous monomer is thus formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a coating on the inner surface of a resin container.

[Conventional technology]

For forming a barrier layer on the inner surface of a resin container (for example, a motorcycle fuel tank), Japanese Patent Application Laid-Open No. 56-81344
A technique related to the publication No. 1 has been proposed.

In this technique, the inner surface of a resin container is subjected to plasma treatment, thereby activating the polar groups of the resin constituting the container. An epoxy resin is then applied as a barrier layer to the inner surface of the container, which has improved adhesiveness due to this activation.

[Problem to be solved by the invention]

The barrier layer made of the epoxy resin has poor flexibility and impact resistance. This causes the disadvantage that cracks occur in the barrier layer and the barrier effect is impaired.

SUMMARY OF THE INVENTION In view of the problems of the prior art, an object of the present invention is to provide a method capable of forming a coating having excellent flexibility and impact resistance inside a hollow resin container.

[Means to solve the problem]

In the present invention, a step of sealing a monomer gas or a mixed gas thereof in a resin container, and a step of forming a polymer film of the gas on the inner surface of the container by plasma polymerization are carried out.

[Effect]

According to the film forming method according to the present invention, a plasma polymerized film is formed on the inner surface of a hollow resin container.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross section of a motorcycle fuel tank 10 formed by a so-called blow molding method. The fuel tank 10 is made of single-layer high-density polyethylene, which is economical and has excellent impact resistance. This tank 10 has an average thickness of 4 m+m and an internal capacity of 10 liters.

When forming the tank 10 by the blow molding method, first, as shown in FIG. Pinch the top and bottom of the parison 30 in such a way as to pinch the parison 30.

Next, by blowing air through the air blowing port 50, the parison 30 is inflated within the mold 40 as shown in FIG. As a result, the parison 30 is pressed against the inner surface of the mold 40, and as a result, the tank 10 is molded.

The plasma polymerization apparatus 60 shown in FIG. 1 is used to form a plasma polymerization coating on the inner surface of the tank 10 that has been blow-molded as described above.

In this plasma polymerization apparatus 60, the tips of the gas distribution piping group are located within the air blowing port 50, and the discharge electrodes 601 and 602 are located within the tank 10.

This pipe group and electrodes 601 and 602 are connected to the air blowing port 5.
0 is supported on a support (not shown) that seals the
Therefore, by inserting this support into the air blowing port 50, the sealing of the tank 10 and the positioning of the piping group etc. are performed at the same time.

When forming a plasma polymerized film on the inner surface of the tank 10 using this plasma polymerization apparatus 60, first, the exhaust control valve 603 is opened and the pressure inside the tank 10 is reduced to 10-8 Torr using the pump 604.

Note that the pressure inside the tank 10 is monitored by a vacuum gauge 605.

After the pressure inside the tank 10 is reduced, the control valve 606 is opened to introduce inert gas for pretreatment into the tank 10 from the cylinder 607, and at the same time, the high frequency power source 608 is activated. Note that at this time, the pressure inside the tank 10 is
10" Torrl: maintained by adjustment of 6.

For example, the high frequency power supply 608 has an output of 100W.
, an output frequency of 13.56 MHz is used. The high frequency output from this high frequency power supply 608 is applied between the electrodes 601 and 602 via a matching box 609, and the accompanying glow discharge between the electrodes 601 and 602 causes the inert gas to be discharged into the tank 10. Plasma is generated.

As a result, the inner surface of the base material of the tank 10 is subjected to so-called ion birding in the plasma of the inert gas for pretreatment, thereby improving the wettability and adhesion of the inner surface of the base material. By forming a plasma polymerized film, which will be described later, after such pretreatment, the adhesion of the film to the inner surface of the tank can be strengthened.

In this example, the pretreatment with the inert gas was performed for 50 minutes.
It's been going for a minute.

Further, as the inert gas, one of helium, argon, oxygen, nitrogen, etc., or a mixture of two or more thereof is used.

When the above pretreatment is completed, the control valve 606 is closed and the power supply 608 is turned off, and then,
The pressure inside the tank 10 is reduced by a pump 604. Then, when the pressure drops to 10-8 Torr, the control valve 610 is opened, and monomer gas (for example, tetrafluoroethylene gas) is introduced into the tank 10 from the cylinder 611. At this time, the flow rate of the monomer gas is For example, 500C:C(
STP)/min.

In this state, the power supply 608 is activated, thereby generating plasma within the tank 10. This plasma activates the monomer gas, and as a result, a barrier plasma polymerized film of the monomer gas is formed on the inner surface of the tank 10.

When the process of forming the polymeric film continues for about 10 minutes, the power supply 608 is turned off and the valve 610 is closed. Thereafter, the pressure inside the tank 10 is reduced by the pump 604.
The pressure is gradually reduced by 10 = To
The control valve 612 is opened when the pressure is lowered to rr. Along with this, an inert gas for after-treatment is introduced into the tank 10 from the cylinder 613, and at that time, the tank 1
The pressure within 0 is adjusted to 10-ITo by adjusting the valve 612.
It is held in rr.

Power supply 608 is now activated, thereby placing the plasma polymerized coating in an inert gas plasma. As a result, the polymeric coating is crosslinked, making it stronger and more stable.

In addition, as the inert gas for the above-mentioned post-processing, one type of hydrogen, rare gas, etc., or a mixture of two or more of them is used.

After the post-treatment with the inert gas is carried out for about 5 minutes, the power supply 60g is turned off and the valve 612 is closed. Thereafter, the pressure inside the tank 10 is reduced, and when the pressure drops to 1.0 Torr, the pump 604 is stopped to return the inside of the tank 10 to atmospheric pressure.

Then, by opening the mold, it is possible to obtain a resin tank 10 having a plasma polymerized coating having liquid, impermeability and gas barrier properties formed on the inner surface.

Note that unreacted monomer gas and inert gas in the film forming process are completely recovered and reused through the vacuum pump 604.

In the above embodiment, the film forming process is performed on the tank 10 inside the mold 4, but if the tank 10 is highly airtight, the film forming process is performed after the tank 10 is taken out from the mold 40. You can.

The material of the resin constituting the base of the tank 10 is not particularly limited, and general organic polymer compounds often used in blow molding, such as polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, polystyrene, etc., can be used. can. Also, JP-A-50-2
It is also possible to use the multilayered resin shown in No. 20738 as the tank base material.

On the other hand, the plasma polymerizable monomer (organic compound) used in the present invention is not limited to the tetrafluoroethylene shown in the examples, but any monomer that can form a film by plasma polymerization can be used. and,
Even if the monomer contains metal atoms or atoms other than carbon such as fluorine, silicon, phosphorus, sulfur, etc., no disadvantages arise. The monomers may be used alone or in combination of two or more.

If a fluorinated monomer or an organosilicon compound is used as the monomer, high liquid impermeability and gas barrier properties can be imparted to the tank 10, and the monomer may also contain an organosilicon compound and an acceptor molecule such as iodine or bromine or a metal atom. By using a monomer, it is also possible to impart an antistatic effect to the tank 10.

In addition, examples of the above-mentioned fluorinated monomers include monofluoromethane, difluoromethane, trifluoroethane,
Tetrafluoromethane, monofluorodichloromethane,
Monofluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, hexafluoroethane, difluorodichloroethane, trifluorotrichloroethane, monofluoropropane, trifluoropropane, pentafluoropropane, perfluoropropane, difluorodichloropropane, tetrafluorodichloroethane Chloropropane, monofluoro-n-butane, trifluoro-n
-butane, tetrafluoro n-butane, octafluoro n-butane, difluoro n-butane, monofluoroisobutane, difluoroisobutane, pentafluoroisobutane, monofluorodichloro n-butane, difluorodichloroisobutane, tetrafluorodichloroisobutane, etc. I can do it.

Examples of organosilicon compounds include tetrachlorosilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, and trimethylmethoxysilane. Silane, phenyltrimethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, allylsilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-chloropropyltrichlorosilane, etc. I can do it.

In the above example, a plasma polymerized coating with a single layer structure is formed, but two or more layers can be formed as necessary. For example, in the case of two layers, the first layer is applied to the inner surface of the tank. After forming the plasma polymerized film, a second layer is formed using one or a mixture of two or more monomers different from those used in the first layer.
A layered plasma polymerized film is formed. As a preferred specific example, a hydrophilic plasma polymerized film is first formed using a monomer containing a nitrogen atom or an oxygen atom such as allylamine, vinyl pyridine, propargyl alcohol, or methyl methacrylate, and then a hydrophilic plasma polymerized film is formed using a monomer containing a nitrogen atom or an oxygen atom such as allylamine, vinyl pyridine, propargyl alcohol, or methyl methacrylate. A plasma polymerized film is formed using a fluorinated monomer.

The conditions for plasma polymerization when carrying out the present invention may be almost the same as those for ordinary plasma polymerization.

That is, the electron temperature in the reactant zone during the plasma polymerization reaction is preferably 10,000 to 28,000 OO, and the degree of vacuum may be IXlo-3 to I Torr. Furthermore, the flow rate of the gas containing monomer flowing into the tank is, for example, the internal volume 1
For a 0 liter tank, 0. 1-20c
c (STP) /min may be sufficient. Note that the above gas can be introduced into the tank after being mixed with an inert gas such as argon, helium, xenon, neon, etc. as a carrier gas.

There are no particular restrictions on the temperature of the tank 10 during plasma polymerization, but it is preferably 0° C. or higher and lower than the melting point of the tank base material. Note that 1. The thickness of the plasma polymerized film is determined by the liquid impermeability and gas barrier performance of the tank, but is usually 0.1 to
It is about 10 μm.

The plasma polymerization apparatus used in the present invention may be a known one and only needs to be modified to the extent that it can be attached to a blow molding machine. Known polymerization apparatuses include an internal electrode capacitive type, an external electrode capacitive type, an external electrode induction type, etc., but it is preferable to apply an internal electrode capacitive type as shown in the Examples to the present invention.

Further, the discharge method of the polymerization apparatus may be any one of high frequency discharge, microwave discharge, low frequency discharge, etc., and is not particularly limited. In the case of high frequency discharge, the output frequency is 13.56
For the old 1z, a power supply with an output power of about 10 to 200W, and an output frequency of 2450MHz in the case of microwave discharge,
In the case of a power supply with an output power of about 100 to 5000 layers, and even lower frequency discharge, an output frequency of 0.1 to 20 KHz,
A power source with an output power of about 10 to 200 W is applied. Note that in order to form a uniform film, it is preferable to use high frequency discharge as shown in the examples.

2 Figure 4 shows the amount of gasoline permeated in a fuel tank with a plasma polymerized film of tetrafluoroethylene (monomer) formed on its inner surface according to the present invention, a fuel tank with a fluorine-treated inner surface, and a fuel tank with an untreated inner surface. It shows.

The above test tanks had an average thickness of 4 m+m and an internal capacity of 10 liters. The amount of permeation shown in the same figure is measured from the amount of decrease in 5 liters of gasoline placed in the tank, and is a relative value when the amount of permeation after 30 days in an untreated tank is taken as 1oO. It is represented.

As is clear from the figure, the amount of gasoline permeated in the plasma-polymerized tank is significantly smaller than that of other tanks, and its gasoline impermeability is particularly excellent.

(Effects of the Invention) Since the film forming method according to the present invention uses plasma polymerization as a film forming means, it is chemically stable, chemically stable, cross-linked with high density, and has barrier resistance, chemical resistance, and heat resistance. Also, a coating with excellent mechanical strength can be adhered to the inner surface of the tank.

Note that the present invention can be applied not only to fuel tanks but also to all types of resin containers.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram illustrating the configuration of a plasma polymerization apparatus applied to the film forming method according to the present invention, and FIGS.
The figure is a conceptual diagram showing the procedure for forming a tank according to the blow molding method, and FIG. 4 is a graph showing test results regarding the amount of gasoline permeation. DESCRIPTION OF SYMBOLS 10... Tank, 30... Parison, 40... Mold, 50... Air blowing port, 60... Plasma polymerization apparatus. JP-A-3 107458 (6) Light baking time (Sun)

Claims (1)

[Claims] The method is characterized by comprising the steps of: sealing a monomer gas or a mixed gas thereof in a resin container; and forming a polymerized film of the gas on the inner surface of the resin container using a plasma polymerization method. A method of forming a film on the inner surface of a resin container.