JP2003053257A - Method for manufacturing gas cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating method capable of applying powder coating to a gas cylinder having a valve part being a thermally fragile place using a general powder paint. SOLUTION: In applying baking/curing treatment to the gas cylinder, an infrared heating furnace is used to irradiate the gas cylinder with infrared rays so as to avoid the valve part weak to heat or the gas cylinder is irradiated with infrared rays in such a state that the valve part weak to heat is shielded from infrared rays to apply the baking/curing treatment to a powder coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating method and a gas cylinder manufacturing method, and more particularly to a gas cylinder manufacturing method including a step of performing powder coating on a gas cylinder equipped with a valve which is a weak point to heat.

[0002]

2. Description of the Related Art When manufacturing a gas cylinder such as an LP gas container, it is general that the valve is first attached to the main body of the gas cylinder, the gas cylinder is painted, and then the baking treatment is performed.

Here, as a typical coating method applied to the gas cylinder, solvent type coating and powder coating can be mentioned, but recently, the coating film strength after baking is high, and moreover, From the viewpoint of the effect on the global environment, powder coating, which is preferable, has been adopted more often.

[0004]

However, in powder coating, the temperature at which the applied coating film is baked and cured is high, and when the baking process is carried out by a general hot air circulation furnace, However, there is a problem that the valve portion attached to the gas cylinder body is deteriorated and deteriorated by heat.

That is, in a gas cylinder, the valve portion is thermally fragile and cannot withstand the temperature required for bake-hardening treatment of a general powder coating material, so that powder coating cannot be performed according to an ordinary procedure. It's extremely difficult.

In this regard, it is conceivable to coat the cylinder with a powder coating material which is thermoset at a relatively low temperature.
Considering the price and versatility, it is preferable to use a general powder coating that cures at a high temperature around 160 ° C.

The present invention has been made in view of the above problems, and an object thereof is to provide a new powder coating method for a gas cylinder equipped with a valve, thereby providing a new gas cylinder manufacturing method. To do.

[0008]

In order to achieve the above-mentioned objects, in the present invention, when performing the baking and hardening treatment of a gas cylinder using an infrared heating furnace, infrared rays should be avoided so as to avoid the portion of the bulb that is weak against heat. It is characterized in that the powder coating film is baked and cured by irradiation or by irradiation with infrared rays in a state where the bulb portion which is weak against heat is shielded from infrared rays.

More specifically, the present invention provides the following.

(1) A method of manufacturing a gas cylinder, comprising the steps of attaching a valve to a gas cylinder body, performing powder coating, and then baking and curing the powder coating film. A method for producing a gas cylinder, comprising irradiating infrared rays in a direction other than the bulb portion in an infrared heating furnace.

(2) A method of manufacturing a gas cylinder, comprising the steps of attaching a valve to a gas cylinder body, performing powder coating, and then subjecting the powder coating film to bake hardening treatment, wherein the bake hardening treatment comprises A method for producing a gas cylinder, comprising irradiating infrared rays in an infrared heating furnace with the bulb portion shielded from infrared rays.

(3) The method for producing a gas cylinder according to (1) or (2), wherein in the baking-hardening treatment, the infrared irradiation is performed while rotating the gas cylinder.

In the present invention, the "bake hardening treatment" as described above is intended to exclude a baking treatment which is carried out at about 60 ° C. to 90 ° C. and is not accompanied by hardening of the powder coating film.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION [Powder coating] Powder coating means that a powdery coating material having a nonvolatile content of 95% or more is distributed on a surface to be coated, and this is baked and melted at a temperature higher than the melting point of the powder. A method of forming a continuous coating film by spreading and curing. With powder coating, you can expect high coating performance and strong anticorrosion properties. Examples of the powder coating include a fluidized dipping method, an electrostatic powder coating method, an electrostatic fluidized dipping method and the like, and any of them may be used in the present invention.

In the fluidized dipping method, powder is put in the upper stage of a tank having a porous shelf, and when air is blown from below, the powder is suspended in the air. This is a method in which a coating material is put, powder is fused or electrostatically attached to the surface, and this is baked.

The electrostatic powder spray method is, in principle, the same as the electrostatic coating of liquid paint. It means that the powder electrostatically adheres to the object to be coated until it is heated and melted. It helps to keep a stable attachment.

In electrostatic coating, an object to be coated is an anode and a paint spraying device is a cathode, and a high voltage of several tens of KV is applied between them to form an electrostatic field. If the paint particles are negatively charged and sprayed, they are adsorbed to the object by electrostatic attraction. Then, the adhered resin powder is heated and melted to form a continuous coating film, but this electrostatic coating is superior in coating efficiency as compared with the air spray method. For electrostatic coating equipment,
For example, there are an electrostatic fogged type and a gun type.

The powder electrostatic coating device comprises, for example, a powder spray gun, a paint supply tank, a high voltage generator, and an alternating current of 10
0V is the operating voltage, and there are high voltage generators, for example, a DC voltage of -50 to -140V, which is brought to the spray gun by a high voltage cable, and a high voltage inside the gun.

The powder used for electrostatic coating has a particle size of 1
The thickness is preferably 00 μm or less, more preferably 50 μm or less.

<Powder Coating Material> There is no limitation on the coating material used for powder coating, and a known powder coating material can be appropriately selected and used. The resin used for powder coating is
It may be a thermosetting resin or a thermoplastic resin. Examples thereof include epoxy resin type, polyester resin type, acrylic resin type,
Examples of commercially available products include POWDAX P200 (trade name), POWDAX P250 (trade name), and Virucia 2000 (trade name) manufactured by Nippon Paint Co., Ltd.

The thermosetting powder coating composition contains, for example, a thermosetting resin as a coating film forming component and a curing agent as main components, and further comprises a pigment, a surface conditioner and other additives. Powder paints containing these components include powder solid color paints and powder clear paints.

The thermosetting resin suitable for the powder coating used in the present invention is preferably a thermosetting resin which is solid at room temperature, and examples thereof include acrylic resin, polyester resin and epoxy resin. One type or two or more types of the thermosetting resin are preferably selected depending on the use of the coating film to be formed. For example, when it is necessary to form a coating film with good weather resistance, an acrylic resin is used.When it is necessary to form a coating film with excellent coating properties such as impact resistance, a polyester resin is used. Epoxy resins are suitable when it is necessary to obtain excellent coating films.

The powder coating material may optionally contain a mixture of two or more of the above thermosetting resins.

Typical examples of acrylic resins include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, teracrylate.
Examples thereof include those obtained by polymerizing acrylic monomers such as t-butyl, glycidyl acrylate, glycidyl methacrylate, and 2-methylglycidyl methacrylate by a usual method, and copolymers of them and styrene are also included.

Typical examples of polyester resins include:
Polyhydric alcohols such as ethylene glycol, propanediol, pentanediol, hexanediol, neopentyl glycol, trimethylolpropane and pentaerythritol, and terephthalic acid, isophthalic acid, phthalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid,
Examples thereof include those obtained by reacting carboxylic acids such as ε-oxypropionic acid with a conventional method, and alkyd resins.

A typical example of the epoxy resin is a compound having two or more oxiranes in the molecule, for example, a glycidyl ether resin represented by a condensation reaction product of bisphenol A and epichlorohydrin, Examples thereof include alicyclic epoxy resin, cotton-like aliphatic epoxy resin, and novolac type epoxy resin.

The curing agent suitable for the powder coating used in the present invention can be appropriately selected depending on the functional group species of the thermosetting resin, and examples thereof include aliphatic isocyanate such as blocked isocyanate and sebacic acid, and amino. Examples thereof include blast resin, aliphatic acid anhydride, triglycidyl isocyanate, amine curing agent, dicyandiamide, phenol resin, epoxy resin, alkylmethylmelamine resin, and benzoguanamine resin.

Pigments suitable for the powder coating used in the present invention include, for example, titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, carbazole violet, anthrapyridine, azo orange, yellow, flavanslon yellow and isoindoline yellow. Coloring pigments such as 1, azo yellow, induslon blue, dibrom anthurone red, perylene red, azo red, anthraquinone red, quinacridone red, violet; barita powder, precipitated barium sulfate, barium carbonate, gypsum, clay, silica, white Carbon, diatomaceous earth, talc, magnesium carbonate, alumina white,
Examples include extender pigments such as gloss white and satin white, and bright pigments such as aluminum flakes and mica powder. The above pigments can be used alone, but may be used in combination of two or more kinds.

Additives that can be included in the powder coating include
A curing catalyst such as dodecylbenzene sulfonic acid, a surface modifier such as silicone or acrylic oligomer (typically dimethyl silicone, methyl silicone, etc.), an antioxidant such as benzophenone, a plasticizer, an ultraviolet absorber, benzoins, and a sauce. A stopping agent, a thickener, etc. are mentioned.

[Baking process] In the baking process,
A far-infrared furnace, a mid-infrared furnace, a near-infrared furnace, and other heat-ray radiation furnaces can be preferably used. It is preferable that the gas cylinder body is locally heated and the valve is not heated. The hot-air stove is not preferable because the temperature inside the stove becomes uniform.

<Infrared Irradiation> In the present invention, the object to be coated is heated by irradiating it with infrared rays. The infrared rays to be applied may be near infrared rays, mid-infrared rays or far infrared rays. Light rays having a wavelength in the range of 0.75 μm to 1000 μm, preferably 0.8 μm to 30 μm are used.

The heating by infrared irradiation can be carried out by using an infrared heating device, and various infrared heating devices can be used up to a surface temperature of the infrared heating device of about 300 ° C. to 700 ° C. . Examples of the infrared heating device include ceramic heaters PLC-322 and PLC-3 manufactured by Noritake Company Limited.
23, the same PLC-324, the same PLC-326, the same PLC
-328, the same PLC-222, the same PLC-223, the same P
LC-224, a far infrared ray drying furnace manufactured by Katsura Seiki Seisakusho, Ltd., and the like can be mentioned.

In the present invention, when the substrate is irradiated with infrared rays, the infrared rays are absorbed at the places where the infrared rays are irradiated, and the temperature at those places rises. Therefore, it is necessary to irradiate the coated surface with infrared rays. It should be noted that the heating by the irradiation of infrared rays does not depend on the heat conduction like the heating by hot air but can raise the temperature of the object to be coated in a short time, so that there is also an advantage that the heating step can be shortened.

When heating by infrared irradiation, as a method of adjusting the infrared irradiation amount, in addition to turning on / off the infrared irradiation device, adjusting the current value and the voltage value, and outputting the infrared ray from the infrared irradiation device. An infrared blocking element such as a shutter that can be opened and closed is installed in the infrared irradiation area, and adjustment is performed by opening and closing the infrared blocking element. Examples of the infrared ray blocking element include a shutter such as a stainless plate, a louver, a punching plate made of stainless steel, and a mesh plate. The method using the infrared ray blocking element has an advantage that the opening / closing degree can be instantly adjusted and the infrared ray irradiation amount can be finely adjusted.

<Baking Condition> In the present invention, the valve is kept at 160 ° C. or lower in this baking process. This makes it possible to prevent deterioration of thermally fragile parts in the valve. It is preferred that the valve be kept below 140 ° C. In this regard, for the valve of the cylinder, a thermally fragile thermoplastic resin such as nylon 6,6, neoisoprene-butadiene rubber or the like is used for the packing, Kelep sheet, and O-ring. In this case, it is possible to prevent these materials from being deteriorated or deformed.

As for the baking processing condition, a part other than the valve, for example, the baking temperature of the gas cylinder body is 15
8 ° C. to 193 ° C. is preferable, and the baking time means the time of irradiating infrared rays in the infrared heating furnace, and 1
Minutes to 26 minutes is preferable, and is adjusted according to the baking temperature of the gas cylinder body.

The baking temperature and the baking time are as shown in FIG.
Is preferable, and when the baking temperature is too low or the baking time is too short, the adhesion is insufficient and the coating film performance is deteriorated. On the other hand, when the baking temperature is too high or the baking time is too long, the adhesiveness is sufficient, but discoloration or unevenness may occur.

In the baking process, the valve of the gas cylinder may be covered with a member that shields it from infrared rays.
For example, the bulb may be surrounded by an infrared shielding member such as an aluminum plate. Alternatively, the radiant heat to the valve may be reduced by covering the valve with an aluminum foil, an aluminum plate or the like. A metal material such as aluminum can be used as the infrared shielding member. However, the material is not limited as long as it can shield infrared rays, and the material is not limited to a metal material, and may be a material such as ceramics, or
It may be a coating of infrared shielding paint on ceramic or metal.

<Manufacture of Gas Cylinder> In manufacturing the gas cylinder, as shown in FIG. 5, the gas cylinder main body is constructed by assembling the parts of the gas cylinder such as the neck and the body of the cylinder (S101) and assembled. After various tests such as an expansion test and a pressure test are performed on the gas cylinder body (S102), the valve is attached (S10).
3).

Then, powder coating is applied with the valve attached (S104). Powder coating is performed using the powder coating material and powder coating method as described above. Further, powder coating is generally adopted for top coating of gas cylinders.

After the powder coating is applied, the coating is baked and cured using an infrared heating furnace (S105),
As a result, the coating film on the surface of the gas cylinder is thermoset. As described above, the heating in the infrared heating furnace is performed by irradiating infrared rays directionally while avoiding the bulb portion, or by covering the bulb portion with an infrared shield such as aluminum foil. By irradiating infrared rays.
In addition, the infrared heating furnace used, the type of infrared light to be irradiated, etc. will be the same as those already explained in the column of "infrared irradiation", but a proper form among them is manufactured. It will be appropriately selected depending on the type and size of the gas cylinder to be used. In the baking oven, it is preferable to rotate the cylinder body.

After the baking and hardening treatment is performed, a final test such as a completion inspection is carried out (S106), and the manufactured gas cylinder is shipped (S107).

[0043]

Example Using the powder coating material shown in Table 1 below, powder coating was performed under the coating conditions shown in Table 1.

Next, in Examples 1 to 4,
In the far-infrared heating furnace, the gas cylinder was irradiated with far-infrared rays toward the central portion of the side surface of the gas cylinder (“middle” in FIG. 6) to perform directional heating, thereby performing the bake hardening treatment. On the other hand, in the comparative example, bake hardening treatment was performed in a hot air circulating furnace. The gas cylinder was appropriately rotated during the baking process.

With respect to the far-infrared heating in the far-infrared heating furnaces according to Examples 1 to 4, the baking treatment conditions were such that the central portion of the side surface of the gas cylinder was 160 at about 13 to 16 minutes after the infrared irradiation. The temperature was set to be in the range of ℃ to 200 ℃, and then allowed to cool. on the other hand,
Regarding hot air heating in the hot air circulation furnace according to the comparative example, heating is performed such that the central portion of the side surface of the gas cylinder is 160 ° C. to 170 ° C. within about 15 to 16 minutes after hot air ventilation, and then allowed to cool. I decided to do it.

Further, in Example 4, as shown in FIG. 7, far-infrared irradiation was performed in a state where the bulb was surrounded by an aluminum cover.

[0047]

[Table 1]

As a result of performing the bake-hardening treatment under the conditions as shown in Table 1 above, as for Examples 1 to 3,
Regardless of the type of powder coating used and the conditions of powder coating, the central part of the side of the gas cylinder (“middle” in Figure 6)
The same changes were found in the temperature changes over time, the temperature changes of the shoulder part of the gas cylinder (“upper” in FIG. 6), and the temperature changes of the valve part of the gas cylinder (“valve” in FIG. 6). The result was as shown in Figure 2.

As shown in FIG. 2, in Examples 1 to 3, the temperature rise in the valve portion rises more slowly than in the other portions, and the peak of the maximum temperature also deviates later. It is thought that this is because the valve part is heated by the residual heat of other parts, but in any case, when comparing the maximum temperatures, that of the valve part is higher than that of the central part on the side of the gas cylinder. It is about 10% lower in degrees Celsius.

FIG. 3 shows the temperature change with time in Example 4. As is clear from FIG. 3, the temperature change of Example 4 follows the same trajectory as that of Examples 1 to 3, but the maximum temperature is that of Examples 1 to 3. The temperature of the valve portion is about 20% lower than that of the central portion of the side surface of the gas cylinder in 20 degrees Celsius.

In the comparative example, as shown in FIG. 4, the central portion of the side surface of the gas cylinder (“middle” in FIG. 6) is also
The shoulder portion of the gas cylinder (“upper” in FIG. 6) and the valve portion of the gas cylinder (“valve” in FIG. 6) are to be similarly lifted.

The time axes in FIGS. 2 to 4 have the same ratio, but as is clear from comparison between FIGS. 2 and 3 and FIG. Since the coating material is directly heated, the temperature rises quickly and the heating time is shortened.

In Table 2 below, the central part of the side of the gas cylinder (“middle” in FIG. 6), the shoulder part of the gas cylinder (“upper” in FIG. 6), and the valve part of the gas cylinder (“valve in FIG. 6” ") Shows the maximum temperature and the state of the valve after bake hardening treatment.

The numerical values showing the respective maximum temperatures are shown in Example 1.
7 shows respective relative values when the maximum temperature (Tw) of the central portion (“middle” in FIG. 6) of the side surface of the gas cylinder is set to 100.

[0055]

[Table 2] Tw: Maximum temperature of the central part of the side of the gas cylinder (“middle” in FIG. 6) Tx: Maximum temperature of the shoulder part of the gas cylinder (“upper” in FIG. 6) Ty: Valve part of the gas cylinder ( Each value of the maximum temperature * Tw, Tx, and Ty of the “valve” in FIG. 6 is a relative value when Tw of Example 1 is 100. <Valve condition> ◎ ・ ・ ・ Same as before heating ○ ・ ・ ・ Same as before heating △ ・ ・ ・ Valve is damaged × ・ ・ ・ Valve pain is severe

[0056]

As described above, according to the present invention,
It becomes possible to apply powder coating using a general powder coating to a gas cylinder having a valve portion which is a thermally fragile portion.

That is, according to the present invention, it is possible to prevent the deterioration of the valve (particularly the resin component in the valve) even when the gas cylinder is baked and cured using a general powder coating. The yield rate of manufactured gas cylinders is improved. Further, since powder coating can be performed, coating film performance such as coating film strength is improved.

Further, according to the present invention, not only the thermally vulnerable portion such as the valve of the gas cylinder is heated but also the heating time is short, so that the thermally vulnerable portion has a high temperature. Since the time to be exposed to
Deterioration and deterioration of thermally vulnerable parts such as valves will be synergistically prevented. In addition, since the time required for the entire bake-hardening process is shortened, the gas cylinder manufacturing efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a correlation between a preferable baking time and a preferable baking temperature when performing a baking and hardening treatment by infrared directional heating according to the present invention.

FIG. 2 is a center portion (“middle” in FIG. 6) of a side surface of a gas cylinder when baked in a far infrared furnace in Examples 1 to 3, a shoulder portion (“upper” in FIG. 6) of the gas cylinder, and FIG. 7 is a diagram showing a temperature change with time of a valve portion (“valve” in FIG. 6) of the gas cylinder.

[FIG. 3] In Example 4, the central portion of the side surface of the gas cylinder (“middle” in FIG. 6) and the shoulder portion of the gas cylinder when baked in a far-infrared furnace with the valve portion surrounded by the aluminum cover. It is a figure which shows the time-dependent temperature change of the valve part ("valve" in FIG. 6) ("upper" in FIG. 6) and the gas cylinder.

FIG. 4 is a central portion (“middle” in FIG. 6) of the side surface of the gas cylinder when directly burned in a hot-air stove, a shoulder portion (“upper” in FIG. 6) of the gas cylinder, and a valve portion of the gas cylinder (FIG. It is a figure which shows the time-dependent temperature change of the "valve" in FIG.

FIG. 5 is a flowchart showing a manufacturing process of the gas cylinder according to the embodiment of the present invention.

FIG. 6 is a diagram for explaining a location where temperature is measured when directional heating with infrared rays is performed on a gas cylinder, and is a diagram showing an appearance of a general gas cylinder.

FIG. 7 is a diagram for explaining a location where a temperature is measured when a gas cylinder is directionally heated by infrared rays in a state where a valve portion is surrounded by an aluminum cover. ) Is an external view and a partial cross-sectional view in which a portion of the aluminum cover in FIG.

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Claims (3)

[Claims] 1. A method of manufacturing a gas cylinder, comprising the steps of: attaching a valve to a gas cylinder main body, then performing powder coating, and then subjecting the powder coating film to baking and hardening treatment, wherein the baking and hardening treatment comprises: A method for producing a gas cylinder, comprising irradiating infrared rays in a direction other than the bulb portion in an infrared heating furnace. 2. A method of manufacturing a gas cylinder, comprising the steps of attaching a valve to a gas cylinder body, performing powder coating, and then subjecting the powder coating film to baking and hardening treatment, wherein the baking and hardening treatment comprises: A method for producing a gas cylinder, which comprises irradiating infrared rays in an infrared heating furnace with the bulb portion shielded from infrared rays. 3. The method for producing a gas cylinder according to claim 1, wherein in the baking-hardening treatment, the infrared irradiation is performed while rotating the gas cylinder.