JPH11268737A - Steel drum having internal face coated with resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel drum having an internal face coated with a resin which prevents the coating layer from cracking or peeling. SOLUTION: In a steel drum in which a coating layer of resin is hermetically formed on the entire internal surface of a can body, out of a lower wedge- shaped gap made annularly in a connection part between a cylindrical tube part 1 forming the drum body and a base plate part 2 and an upper wedge- shaped gap made annularly in a connection part between the cylindrical tube part 1 and a top plate part, at least the lower wedge-shaped gap is filled with a metal layer 4. The metal layer 4 is made of a material having strength equal to or greater than that of the matrix of the drum body, and also connected with the matrix of the drum body. And the coating layer 6 is formed of one or more layers of polyethylene resin or polypropylene resin. The coating layer 6 is connected to the matrix of the drum body, via an adhesive layer 5, at least in the part of the surface of the metal layer 4, and the adhesive layer 5 has strength equal to or greater than that of the coating layer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel drum having an inner surface coated with a resin.

[0002]

2. Description of the Related Art Conventionally, an inner resin-coated steel drum can is generally degreased or phosphated on the inner surface of the can body and then spray-coated with a liquid paint diluted with a solvent and reduced in viscosity, or solid powder. A body paint is electrostatically applied and heated and baked to form a coating.

[0003] First, in the case of forming a coating with a solvent-containing paint, in order to prevent foaming inside the coating due to evaporation of the solvent at the time of heating baking after coating, one baking of the coating requires a thick film of 20 to 30 µm or more. Difficult to paint. Also, when thick film coating is performed by repeating coating baking a plurality of times, if the thickness is 30 μm or more, distortion due to curing shrinkage of the coating film increases, the adhesion of the coating film significantly decreases, and a new problem that the coating film is easily peeled off. Is generally 30
Painted with a thick film of μm or less.

[0004] In the composition of such a solvent-containing coating, an epoxy resin, a phenol resin, or a coating mainly containing an epoxy phenol resin is used. In any of these cases, the material itself is resistant to some non-aqueous chemicals, but the coating is basically a thin film, so the barrier properties against various chemicals are insufficient, and the chemicals are severely corrosive. In particular, when an aqueous chemical solution containing electrolyte ions is filled and used, peeling of the coating film and rusting of the coating base occur in a short period of time. For this reason, it can be said that an inner surface coating drum using a solvent-containing paint is not suitable for filling with a highly corrosive chemical solution.

[0005] On the other hand, in the case of electrostatic coating of a solid powder coating, compared to the case of spray coating of a solvent dilution coating,
Since there is no foaming due to evaporation of the solvent during baking, a thick film coating of generally 50 μm or more and 200 to 2000 μm is also possible.

For the composition of such a powder coating, a coating mainly composed of an epoxy resin, a polyester resin, a polyethylene resin, a polypropylene resin or the like is used. Of these, when a paint containing polyethylene resin or polypropylene resin as the main component is used, the material itself is resistant to a wider range of chemicals, exhibits anticorrosive barrier properties, and is inexpensive, so it is filled with highly corrosive chemicals. It can be said that it is optimal to coat the inner surface (heavy and anticorrosion coating) of the drum with a thick coating with a paint mainly composed of polyethylene resin or polypropylene resin. For this reason, a steel drum can coated with a polyethylene resin or a polypropylene resin on the inner surface has been partially used as a container for filling a highly corrosive chemical.

[0007]

However, in the conventional drums made of steel coated with a polyethylene resin or a polypropylene resin as described above, the durability test of the present inventors using the actual coated drums using actual coated drums was carried out. According to the results, some chemicals such as surfactants (eg, sodium alkyl allyl sulfonate (Sodium A
lkyl Aryl Sulfonate) and sodium lauryl sulfate (So
dium Lauryl Sulfate) or an amino acid-based surfactant, etc.) is used as the content, and the coating on the boundary between the main plate of the drum and the tubular body and its surroundings will crack in a short period of time. It has been found that there is a problem that the coating is peeled off from the part and the base is corroded. This is considered to be one of the causes due to the stress acting on the boundary portion under the pressure of the content, particularly when the content is the surfactant.

The present invention has a problem with the above-mentioned conventional steel drum having an inner surface coated with a polyethylene resin or a polypropylene resin, that is, a problem that the coating is liable to crack when the content is a chemical such as a surfactant. To eliminate
It is an object of the present invention to provide an inner resin-coated steel drum having more excellent chemical resistance and corrosion resistance.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to prevent the cracking of the coating, and as a result, have found that the composition of the coating material to be used and the vicinity of the boundary between the main plate and the tubular body in the drum can body. It has been found that by specifying and manufacturing conditions and coating conditions, a coated can having desired performance can be obtained, and the present invention has been achieved.

[0010] In the steel drum according to the present invention, a resin coating layer is formed on the entire inner surface of the can body.

In the steel drum can, according to the present invention, a lower wedge-shaped gap formed annularly at a joint between the body tube and the base plate forming the can body, and a joint between the body tube and the top plate are formed. At least the lower wedge-shaped gap of the annularly formed upper wedge-shaped gap is closed by the metal layer. The metal layer is formed of a material having a strength equal to or higher than that of the can base material and is bonded to the can base material. The coating layer is formed of one or more polyethylene resin or polypropylene resin. The coating layer is bonded to the base body of the can via an adhesive layer at least at a surface portion of the metal layer, and the adhesive layer has a strength equal to or higher than that of the above-mentioned coating layer.

In the present invention, the adhesive layer is desirably a thermoset resin having a glass transition temperature of 50 ° C. or higher.

[0013] The resin constituting the layer may be a resin mainly composed of at least one of an epoxy resin, an epoxy phenol, a phenol, a melamine resin, a polyester resin, a urethane resin and an amino resin. Also,
The adhesive layer can be formed with a thickness of 1 to 50 μm.

The coating layer is a modified polyethylene resin obtained by grafting 0.01 to 1% by weight of at least one unsaturated carboxylic acid selected from maleic acid, maleic anhydride, phthalic acid and acrylic acid. Alternatively, it contains one or more modified polypropylene resins and has a density of 0.91 to 0.
96, and can be formed of a resin having a melt flow rate of 1 to 10 g / min. In that case, the coating layer has a thickness of 50 to 20.
It is 00 μm, and the thickness step at the portion corresponding to the outer edge of the metal layer can be 500 μm or less per 1 mm length.

According to the drum can of the present invention, the wedge-shaped gap forming the boundary between the body tube portion of the can body and the base plate portion or the top plate portion is connected by a metal layer having a strength equal to or higher than that of the can body base material. When the container is filled with chemicals and other contents and used in a sealed condition, the internal pressure of the container due to the weight of the contents or the increase in the internal pressure due to evaporation of the chemical, the load due to vertical stacking during storage, and handling When subjected to an external impact force or the like, there is no deformation that widens the wedge-shaped gap. That is,
Since there is no significant deformation at the gap interval in the case of the conventional drum can, there is no local excessive distortion in the coating of the upper layer such as polyethylene resin or polypropylene resin, and therefore no cracking or peeling occurs.

The adhesive layer is a heat-hardened resin having a glass transition temperature of 50 ° C. or higher, for example, having a higher strength than a coating layer such as an upper polyethylene resin or a polypropylene resin. Due to the strong restraint, when the can is filled with the chemical solution, even if it receives the above-mentioned pressure or the like, its deformation is restrained by the adhesive layer and does not cause excessive distortion.

Further, at the outer edge of the region of the metal layer, a step is apt to be formed on the surface thereof.
When it is formed to a thickness of up to 2000 μm, it is desirable that the step is 500 μm or less per 1 mm length. This is because the local concentration of distortion caused by shrinkage of the coating layer during heating / cooling molding in forming the coating layer and deformation of the can during practical use of the drum can is avoided.

[0018]

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

FIG. 1 is a cross-sectional view showing a joint portion formed by tightening a body tube portion and a base plate portion of a steel drum can and its vicinity.
The lower end portion of the body tube portion 1 and the outer peripheral edge portion of the main plate portion 2 are fastened to each other to form a joint portion 3. This winding is not limited to double as shown, but may be triple.

An annular wedge-shaped gap is formed at the joint start portion of the joint portion 3 at the time of joining. In this embodiment, the metal layer 4 is formed so as to close the wedge-shaped gap. The metal layer 4 is formed of a metal having a strength equal to or higher than that of the base material of the can body, that is, the base material of the body tube portion 1 and the base plate portion 2, and is bonded to the can body base material. The thickness of the metal layer 4 (throat thickness in the case of welding) is preferably equal to or greater than the base material of the body tube portion 1 and the base plate portion 2. Usually, this metal layer 4 is formed by welding.

On the metal layer 4, an adhesive layer 5 is formed. In the present embodiment, the adhesive layer 5 is provided so as to slightly extend from the region of the metal layer 4 to the body tube portion 1 and the main plate portion 2. And further above, that is,
In the area of the adhesive layer 5, the covering layer 6 is formed so as to be in direct contact with the body tube 1 and the base plate 2 on the adhesive layer 5 and otherwise.
Are formed.

The coating layer 6 is formed of one or more polyethylene resin or polypropylene resin. More specifically, the coating layer 6 is formed by grafting at least one or more unsaturated carboxylic acids selected from maleic acid, maleic anhydride, phthalic acid, and acrylic acid at 0.01 to 1% by weight. Contains at least one polyethylene resin or modified polypropylene resin, and has a density of 0.91 to 0.9
6. The resin may have a melt flow rate of 1 to 10 g / min. Such a coating layer 6
Is formed to have a thickness of 50 to 2000 μm. In a portion corresponding to the outer edge of the metal layer 4, there may be a slight difference in level with the adhesive layer. In this case, the coating layer 6 formed here Thickness difference of 500 μm per 1 mm length
The following is preferred.

The adhesive layer 5 has a strength equal to or higher than that of the coating layer 6. In this case, the adhesive layer 5 is preferably made of a thermoset resin having a glass transition temperature of 50 ° C. or more. .

The resin forming the adhesive layer 5 is epoxy resin, epoxy phenol, phenol, melamine resin,
At least one of polyester resin, urethane resin and amino resin can be a main component, and the film thickness is 1 to 5
It is preferably 0 μm.

As described above, the structure including the metal layer 4, the adhesive layer 5, and the coating layer 6 may be provided not only in the above-described body tube portion and the base plate portion but also in the body tube portion and the top plate portion. it can.

When the contents such as a chemical solution are filled in the inner resin-coated steel drum of the present embodiment, an inner pressure by the contents acts on the body tube portion 1 and the base plate portion 2. In addition, the internal pressure of the can increases due to evaporation of some chemicals. Further, even before the filling of the contents, various loads such as a load due to the vertical stacking and storage of the drums and an impact force at the time of transportation and handling are applied, and the load between the body tube portion 1 and the main plate portion 2 is increased. Try to spread. However, in the present embodiment, the metal layer 4 having a strength equal to or higher than that of the can body base material is bonded thereto, and the deformation here is prevented. Therefore, cracks and peeling are prevented in the upper layer film, that is, the adhesive layer 5 and the coating layer 6. Further, even if the coating layer 6 attempts to be deformed by the above-mentioned force or the action of the chemical solution, the adhesive layer 5 holds the coating layer 6 with a strength equal to or higher than that of the coating layer 6, so that the coating layer 6 is prevented from cracking and peeling. You.

The present invention can be implemented not only in the embodiment shown in FIG. 1 but also in a modified embodiment. For example, FIG.
As described above, the range of the adhesive layer 5 is not limited to the portion of the metal layer 6,
It can also be provided over the entire area where the coating layer 6 is formed.

<Examples> Examples of the present embodiment will be described below along with test results shown in Table 3. Note that the comparative example is an example of a drum can not according to the present invention. 1. Production of drum can made of resin coated steel on the inner surface Production of drum can Drum can 200
(Liter) steel drum can, a wedge-shaped gap between the body tubular member and the base plate member on the inner surface side of the can was cornered using a welding rod (MG-2) manufactured by Kobe Steel Ltd. (wire diameter: 1 mm). The body member and the main plate member were connected to each other with metal without any gap. The thickness (throat thickness) of this metal layer is 1.
It was 2 mm or more. In addition, as a result of performing a tensile test by cutting out a test piece for a connection portion between the body member and the base plate member, there was no breakage at the connection portion of the metal due to fillet welding, and the break was at the body member or base plate member serving as a base material of the can. occured. That is, the metal layer had strength higher than that of the can base material.

The chemical composition and mechanical properties of the deposited metal for the above welding rod are as shown in Tables 1 and 2.

[0030]

Table 1 Chemical composition of deposited metal (%, shielding gas: CO
₂ )

[0031]

[Table 2] Mechanical properties of deposited metal (Shielding gas: C
O ₂ ) Formation of an adhesive layer After the inner surface of the drum can is polished with a grinder, sandpaper, blast, or the like, or degreased with an alkali or an organic solvent, or treated with a phosphate such as zinc phosphate or iron phosphate, or subjected to chromate treatment, The adhesive layer material was applied (coated) with a spray, a brush, a roll, or the like so as to have a dry film thickness of 1 to 50 μm, and the solvent was sufficiently dried in a heating furnace.

Next, a polyethylene resin or polyethylene resin powder having the following physical properties is coated on the surface of the adhesive layer in the range of 50 to 2000 μm by electrostatic powder coating, and then heated in a heating furnace at 230 ° C. Heating was performed for 15 minutes to sufficiently cure the adhesive layer and simultaneously completely melt the polyethylene resin powder or the polypropylene resin powder to form a smooth and uniform continuous film.
The coating layer thus formed was firmly adhered to the can base material over the entire inner surface of the drum including the fillet weld.

The strength of the adhesive layer was compared with that of the coating layer by a tensile test in accordance with ASTM D638 for a single test piece of the adhesive layer material and a single test piece of the coating material which were cured and formed under the same conditions as the above-mentioned coating. By
The tensile strength was compared.

The measurement of the glass transition temperature of the adhesive layer is as follows.
The adhesive layer material cured under the same conditions as the coating production conditions was measured using a thermomechanical tester (TMA). 2. Evaluation of Drum Can Made In regard to the chemical resistance and corrosion resistance tests, the drum made of the resin coated on the inner surface prepared above was used as a test can, and the content of the drum was 50% of a surfactant made of sodium alkyl allyl sulfonate. % (NaCl) and an aqueous solution of 3% amino acid were filled in 200 (Leter), placed in a thermostat at 30 ° C. with the base plate face down, and left for 3 months.
After the lapse of three months, the inner solution was discharged, and the degree of color contamination of the inner solution by the corrosion product of the drum can body, cracking, peeling of the resin coating on the inner surface of the can, and corrosion of the base were examined.

[0035]

[Table 3]

[0036]

As described above, according to the present invention, a metal layer is formed in an annular wedge-shaped gap formed between a body tube portion and a base plate portion, and the metal layer has a strength equal to or greater than that of a can base material. Shall also
After forming an adhesive layer at least in the area of the metal layer, a coating layer of polyethylene resin or polypropylene resin was formed, and the adhesive layer had a strength equal to or higher than that of the coating layer. As a result, the deformation in the metal layer can be suppressed as much as possible by the stress received during storage and handling of the metal layer, and as a result, there is an effect that cracking and peeling of the coating layer can be prevented with almost no deformation of the coating layer.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a steel drum as one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a main part of a steel drum as another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body pipe part 2 Main plate part 4 Metal layer 5 Adhesive layer 6 Coating layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toyofumi Fuga 8--11-11 Ginza, Chuo-ku, Tokyo Inside Steel Pipe Drum Co., Ltd. (72) Inventor Tetsuhiro Koike 8-11-11 Ginza, Chuo-ku, Tokyo Steel Pipe Drum Co., Ltd.

Claims (6)

[Claims] 1. A wedge-shaped lower gap formed in an annular shape at a joining portion between a body tube portion and a base plate portion of a steel drum in which a resin coating layer is formed in close contact with the entire inner surface of the can body. And, of the upper wedge-shaped gap annularly formed at the joint between the body tube part and the top plate part, at least the lower wedge-shaped gap is closed with a metal layer, and the metal layer is equal to or larger than the can base material. The cover layer is formed of a material having strength and bonded to the base body of the can, and the cover layer is formed of one or more polyethylene resin or polypropylene resin, and the cover layer is formed at least at a surface portion of the metal layer via an adhesive layer. An inner resin-coated steel drum can bonded to a can base material, wherein the adhesive layer has a strength equal to or higher than that of the coating layer. 2. The inner resin-coated steel drum according to claim 1, wherein the adhesive layer is a thermosetting resin having a glass transition temperature of 50 ° C. or higher. 3. The inner resin according to claim 2, wherein the resin forming the adhesive layer is mainly composed of at least one of epoxy resin, epoxy phenol, phenol, melamine resin, polyester resin, urethane resin and amino resin. Coated steel drum. 4. The inner resin-coated steel drum according to claim 2, wherein the adhesive layer has a thickness of 1 to 50 μm. 5. A modified polyethylene resin obtained by grafting 0.01 to 1% by weight of at least one unsaturated carboxylic acid selected from maleic acid, maleic anhydride, phthalic acid and acrylic acid. Or containing at least one modified polypropylene resin, the density is 0.91 to 0.9
6. The inner resin-coated steel drum according to claim 1, wherein the resin has a melt flow rate of 1 to 10 g / min. 6. The coating layer according to claim 1, wherein the coating layer has a thickness of 50 to 2000 μm, and a step of the thickness at a portion corresponding to the outer edge of the metal layer is 500 μm or less per 1 mm length. 6. A drum made of steel coated with an inner surface resin according to 5.