JP2015214349A - Inner surface-coated metal drum and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inner surface-coated metal drum with no air bubble and blow hole by a simple method.SOLUTION: [1] An inner surface of a metal drum is coated at a thickness of 0.001-10 mm with a thermoplastic resin with a melt flow rate of 10 g/10 min or more. [2] The thermoplastic resin is a resin selected from among polyolefin, polyester, polyamide and fluorine-based resins. [3] The inner surface of the metal drum is brought into fluid contact at a speed of 4000 cm^2/min or more in the state of melting the thermoplastic resin.

Description

The present invention relates to a drum can whose inner surface is coated with a thermoplastic resin.

Drum cans filled with various contents such as food, beverages, chemical raw materials, monomers, surfactants, paints, edible oils, mineral oils, resins, strong acidic substances, strong alkaline substances, etc. In order to prevent the elution of contaminants from the drum can container to the contents during the long-term storage, and the corrosion of the drum can by the contents, a method of coating the inner surface of the drum can with a resin is known.

For example, the polyethylene coating method is known in which the fuselage and base plate or top plate are wound and processed into an open drum shape (cup shape), and then a polyethylene powder coating is electrostatically coated on the inner surface of the container and melted in a heating furnace. It has been. In addition, polyethylene powder paint is electrostatically applied to the fuselage and the base plate or the top plate in advance, and after tightening with a material that has been heated and melted in a heating furnace to form a polyethylene coating film, the winding portion is fused. In order to do this, a method of heating and melting again is also known. Further, there is a method in which a body and a base plate or a top plate are formed by using a steel plate laminated with a polyethylene film in advance, and then heated and melted in order to fuse the tightened portion after being tightened.

However, in the above-described prior art, a heat melting treatment is performed in order to make the polyethylene powder or the laminate film adhere to the tightening portion. Bubbles may be generated. This was taken in between the film and the inner surface of the drum can when a small amount of gas present between the particles of the polyethylene powder coating applied to the tightening portion or the laminate film was fused to cover the tightening portion. Air. Moreover, when such a gas bursts, a blow hole opened to the outside is formed. The presence of bubbles and blowholes in the drum inner surface coating is known to cause a decrease in the mechanical strength and barrier properties of the coating, and it is desirable to suppress the generation of bubbles and blowholes.

Patent No. 3726039

As a method for solving the above problem, in Japanese Patent No. 3726039 (Patent Document 1), after the heating and melting step of the electrostatically coated resin powder coating, a hole is formed in a portion where the gas inside the resin coating exists. A method for removing bubbles is disclosed. However, it is not easy to completely remove the fine gas taken into the resin, and there is a concern that the barrier property of the coating film is lowered by the holes opened to remove the bubbles. Therefore, there has been a demand for a method for producing an inner surface-coated drum can that is free of bubbles and blowholes by a simpler method.

As a result of intensive studies to solve the above problems, the present inventors have coated the inner surface with a thermoplastic resin having a melt flow rate of 10 [g / 10 minutes] or more in a thickness of 0.001 to 10 [mm]. The present invention has been completed by finding out that the above-described problems of the prior art can be solved by using the drum can.

That is, the present invention is as follows.
[1]
A drum can characterized in that an inner surface is coated with a thermoplastic resin having a melt flow rate of 10 [g / 10 min] or more to a thickness of 0.001 to 10 [mm].
[2]
The drum can according to claim 1, wherein the thermoplastic resin according to claim 1 is any one of polyolefin, polyester, polyamide, and fluorine resin.
[3]
The manufacturing method of the drum can according to claim 1, further comprising a step of coating the inner surface of the drum can by fluid contact at a speed of 4000 [cm 2 / min] or more while the thermoplastic resin is melted. Method.

ADVANTAGE OF THE INVENTION According to this invention, the drum can by which inner surface coating was carried out with the thermoplastic resin layer without a bubble and a blowhole is provided.

Apparatus for manufacturing inner surface coated drum as one embodiment of the present invention Apparatus for manufacturing inner surface coated drum as one embodiment of the present invention

Hereinafter, modes for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described. However, the present invention is not limited to the modes shown below, and various modifications can be made within the scope of the gist. Can be implemented.

〔Drum〕
The drum can in the present embodiment is a metallic cylindrical container of 18 liters or more and 400 liters or less. If the said characteristic is satisfy | filled, the shape will not be specifically limited, A conventionally well-known shape, for example, an open type and a tight head type drum can, is also contained. Further, the body may be subjected to various processes such as beads and corrugates, and the top plate and the base plate may be embossed, and such processing can be performed after the inner surface coating treatment of the present invention is performed.

The material of the metal used for the drum can in this embodiment is not particularly limited, and various metal species such as steel, tinplate, tin-free steel, stainless steel, aluminum, copper, titanium, and alloys thereof can be used. .

The drum can in the present embodiment may be subjected to a conventionally known chemical conversion treatment or base coating on the inner and outer surfaces before coating with a resin. Such treatment is preferable because the durability of the drum can and the adhesion of the resin can be improved, but the chemical conversion treatment and the base coating treatment are not necessarily required.

〔Thermoplastic resin〕
In the present embodiment, the thermoplastic resin covering the inner surface of the drum can has a melt flow rate of 10 [g / 10 min] or more. The melt flow rate is measured in accordance with JIS K 7210, and the measurement condition is that the melting point of the thermoplastic resin is less than 200 [° C.] measured at 230 [° C.] and the melting point is 200 [° C.] or more. With respect to, the melting point of the thermoplastic resin +30 [° C.] was used as the measurement temperature, and the load was 49 [N] for each load. When a plurality of thermoplastic resins are mixed and used, the determination is made based on the melt flow rate under the above measurement conditions based on the thermoplastic resin having the highest melting point. As for the melt flow rate measured on the said conditions, the weight per 10 minutes is 10-500 [g], 20-400 [g] is still more preferable, 30-300 [g] is still more preferable. By setting the melt flow rate within the above range, it is preferable because bubbles and blowholes in the thermoplastic resin layer can be reduced and corrosion of the drum can and contamination of the contents can be suppressed.

In this embodiment, the thickness of the inner surface coating layer made of the thermoplastic resin is 0.001 to 10 [mm]. The thickness of the coating layer is preferably 0.005 to 5 [mm], more preferably 0.01 to 1 [mm], and still more preferably 0.02 to 0.5 [mm]. By setting the thickness of the thermoplastic resin layer within the above range, it is preferable because bubbles and blowholes can be reduced and corrosion of the drum can and contamination of the contents can be suppressed.

In this embodiment, by setting the melt flow rate of the thermoplastic resin and the thickness of the coating film in the above ranges, it is possible to form a film on the inner surface of the drum can in a short time and to improve productivity, which is preferable. The film formation speed using the thermoplastic resin is not particularly limited, but coating at a speed of 4000 [cm ^ 2 / min] or more by using a thermoplastic resin having a melt flow rate of 10 [g / 10 minutes] or more. Layer formation is possible. From the viewpoint of productivity, it is preferably 4000 [cm ^ 2 / min] or more, more preferably 10,000 [cm ^ 2 / min] or more, and still more preferably 20000 [cm ^ 2 / min] or more. The formation rate of the coating layer with the thermoplastic resin can be calculated from the time taken for the coating treatment and the coating area.

In the present embodiment, the type of thermoplastic resin that coats the inner surface of the drum can is not particularly limited, and polyolefin resins such as polyethylene, polypropylene, polybutylene, and ethylene / α-olefin copolymers, polyvinyl chloride, polyvinyl acetate, Polyvinyl resins such as polyvinylidene chloride, polyvinyl alcohol and polyvinyl acetal, polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polystyrene, styrene / acrylonitrile copolymer Styrene resins such as styrene / acrylonitrile / butadiene copolymer, nylon-6, nylon-11, nylon-12, nylon-6,6, nylon-6,1 , Nylon-6,12, Nylon-6T, Nylon-6I, Nylon-9T, Nylon-M5T, polyamide resins such as polyamide / polyether elastomer, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE) ), Polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer ( ETFE), fluororesin such as ethylene / chlorotrifluoroethylene copolymer (ECTFE), polycarbonate, polyacetal, polyphenylene ether, polyarylate, polysulfone, polyethersulfone, polyphenylenesulfide, Polyether ether ketone, polyimide, polyether imide, and thermoplastic elastomer materials such as styrene, olefin, vinyl chloride, urethane, ester, and amide can be used alone or in combination. Among the thermoplastic resins, polyolefin-based, polyester-based, polyamide-based, and fluorine-based resins are preferable from the viewpoint of corrosion resistance and content contamination resistance of the drum can.

In the present embodiment, the adhesive strength of the thermoplastic resin layer to the inner surface of the drum can is not particularly limited, but is preferably 0.1 [kg / 25 mm] or more in a T-shaped peel test in accordance with JIS K6854. kg / 25 mm] or more is more preferable, and 2 [kg / 25 mm] or more is more preferable. It is preferable that the adhesive strength of the thermoplastic resin layer be within the above range because the corrosion resistance of the drum can is improved and further, the peeling of the thermoplastic resin layer coated on the inner surface of the drum can be suppressed.

In the present embodiment, when a resin having poor adhesion to a metal such as polyethylene, polypropylene, or fluororesin is used as the thermoplastic resin, a conventionally known adhesion improving technique can be used. Examples of the adhesive improvement technique include corona treatment, flame treatment, plasma treatment, excimer laser treatment, ultraviolet irradiation treatment, and primer treatment. Such treatment for improving adhesiveness may be performed on either one of the thermoplastic resin and the inner surface of the drum, or both. It is preferable to perform such a treatment because the adhesive force between the thermoplastic resin and the drum can inner surface can be improved. As the primer treatment, a general solvent type adhesive, an anchor coating agent, or a solventless type such as a hot melt adhesive can also be used. In addition to the above-mentioned adhesive improvement technology, thermoplastic resins having a polar functional group such as acid-modified polyolefin and thermoplastic resins having high adhesion to metals such as ionomer resins. It is also preferable to use, since the adhesion to the drum can can be improved. In the present embodiment, the thermoplastic resin may contain conventionally known additives (such as an antioxidant, a stabilizer, a flame retardant, a pigment, an inorganic filler, and a softening agent).

[Production method of resin-coated drum]
In the present embodiment, the method for producing a drum can whose inner surface is coated with a thermoplastic resin is not particularly limited, and a conventionally known method for producing a resin-coated drum can can be used, and a steel plate laminated with a thermoplastic resin film is used. Although it is possible to use the drum can to process it, among others, the method of covering the inner surface by fluidly contacting the drum can in a state where the thermoplastic resin is melted is less likely to generate bubbles and blowholes in the thermoplastic resin layer In view of productivity, the processing speed is also high.

Hereinafter, although the manufacturing method of the drum can of this embodiment is illustrated, this invention is not limited to the following.
<Production Example 1>
After setting the container that has been processed into a cup shape by tightening the body and the base plate into a device that can rotate the drum can in the biaxial direction shown in FIG. 1, the heated and melted thermoplastic resin is put into the container The coating layer is formed by rotating the drum can with the above-described apparatus in a temperature atmosphere equal to or higher than the melting point of the resin to bring the molten resin inside into fluid contact with the inner surface of the container. Thereafter, the opening is inclined downward, the molten resin surplus inside is discharged, and then the inner surface coating of the drum can is completed by cooling. The thickness of the coating layer can be controlled by adjusting the input amount of the thermoplastic resin and the discharge amount of the excess resin.

<Production Example 2>
A drum body having a tight head structure is formed by winding a body, a base plate, and a top plate having a base portion, and set in a device similar to that shown in FIG. The thermoplastic resin pellets are put into the container from the base part, the apparatus is operated, the drum can is rotated, and heat treatment is performed with a burner from the outside of the drum can, so that the thermoplastic resin pellet inside is dissolved and the drum can at the same time. Cover the inner surface with resin. When the resin is surplus, the opening is inclined downward, the molten resin inside is discharged from the base portion, and then cooled, thereby completing the resin coating on the inner surface of the drum can.

<Production Example 3>
The resin melted by heating above the melting point is poured into the container processed into a cup shape by winding the body and the base plate, and the diameter is slightly smaller than the inner diameter of the drum can using an apparatus as shown in FIG. By lowering the mold whose surface has been released from the mold, the inside of the drum can be pressure-bonded, and the gap between the drum can and the mold is filled using the fluidity of the molten thermoplastic resin. Cover the inner surface of the drum.

<Production Example 4>
A drum can is formed using a laminated steel plate obtained by laminating a thermoplastic film on a steel plate by a conventionally known method, and heat treatment is performed to fuse the film at the winding portion, thereby obtaining an inner surface-coated drum can. It is done.

Examples of the present invention and comparative examples will be described below.
<Example 1>
Using the method of Production Example 1, the inner surface of the drum can was coated with polyethylene having MFR = 30 [g / 10 min]. The coating speed calculated from the coating processing time was 2,000 [cm ^ 2 / min]. When the obtained inner surface coated drum was confirmed, the thickness of the coating layer was 0.002 [mm], there were no uncoated portions, and no bubbles or blowholes were confirmed.

<Example 2>
Using the method of Production Example 2, the inner surface of the drum can was coated with maleic anhydride-modified polypropylene having MFR = 15 [g / 10 min]. The coating speed calculated from the coating treatment time was 2,000 [cm ^ 2 / min], and the thickness of the coating layer was 0.03 [mm]. Thereafter, polypropylene having MFR = 120 [g / 10 min] was further poured to coat the polypropylene layer on the maleic anhydride-modified polypropylene layer. The coating speed calculated from the coating treatment time was 2,000 [cm ^ 2 / min], and the thickness of the coating layer was 0.05 [mm]. When the finally obtained inner surface coated drum was confirmed, there was no uncoated portion, and no bubbles or blowholes were confirmed.

<Example 3>
Using the method of Production Example 3, the inner surface of the drum can was coated with polyethylene terephthalate having MFR = 20 [g / 10 min]. The coating speed calculated from the coating processing time was 2,000 [cm ^ 2 / min]. When the obtained inner surface coated drum was confirmed, the thickness of the coating layer was 0.03 [mm], there were no uncoated portions, and no bubbles or blowholes were confirmed.

<Example 4>
Using the method of Production Example 4, an inner surface coated drum using 6-nylon with MFR = 25 [g / 10 min] was produced. The thickness of the coating layer was 0.03 [mm], there were no uncoated portions, and no bubbles or blowholes were confirmed.

<Example 5>
Using the method of Production Example 1, the inner surface of the drum can was coated with ETFE having MFR = 15 [g / 10 min]. The coating speed calculated from the coating processing time was 4,000 [cm ^ 2 / min]. When the obtained inner surface coated drum was confirmed, the thickness of the coating layer was 0.02 [mm], there were no uncoated portions, and no bubbles or blowholes were confirmed.

<Example 6>
Using the method of Production Example 2, the inner surface of the drum can was coated with polyethylene having MFR = 30 [g / 10 min]. The coating speed calculated from the coating processing time was 12,000 [cm ^ 2 / min]. When the obtained inner surface coated drum was confirmed, the thickness of the coating layer was 0.5 [mm], there were no uncoated portions, and no bubbles or blowholes were confirmed.

<Example 7>
Using the method of Production Example 3, the inner surface of the drum can was coated with polyethylene terephthalate having MFR = 20 [g / 10 min]. The coating speed calculated from the coating processing time was 20,000 [cm ^ 2 / min]. When the obtained inner surface coated drum was confirmed, the thickness of the coating layer was 0.1 [mm], there were no uncoated portions, and no bubbles or blowholes were confirmed.

<Example 8>
Using the method of Production Example 4, maleic anhydride polypropylene (thickness = 20 [μm], MFR = 15 [g / 10 min]) and polypropylene (thickness = 50 [μm], MFR = 120 [g / 10 min]) An inner-coated drum can was manufactured using a two-layer film. There were no uncoated areas, and no bubbles or blowholes were observed.

<Example 9>
Using the method of Production Example 1, 6-nylon with MFR = 25 [g / 10 min] was coated on the inner surface of the drum. The coating speed calculated from the coating processing time was 2,000 [cm ^ 2 / min]. When the obtained inner surface coated drum was confirmed, the thickness of the coating layer was 0.8 [mm], there were no uncoated portions, and no bubbles or blowholes were confirmed.

<Example 10>
Using the method of Production Example 1, the inner surface of the drum can was coated with ETFE having MFR = 15 [g / 10 min]. The coating speed calculated from the coating processing time was 5,000 [cm ^ 2 / min]. When the obtained inner surface coated drum was confirmed, the thickness of the coating layer was 0.8 [mm], there were no uncoated portions, and no bubbles or blowholes were confirmed.

<Comparative Example 1>
Using the method of Production Example 1, the inner surface of the drum can was coated with polyethylene of MFR = 5 [g / 10 min]. Although the coating process was performed for the same processing time as in Example 6, uncoated portions remained on the inner surface of the drum, the coating process was not completed, and bubbles and blowholes were also confirmed.

<Comparative Example 2>
Using the method of Production Example 2, 6-nylon with MFR = 6 [g / 10 min] was coated on the inner surface of the drum. Although the coating process was performed for the same processing time as in Example 9, uncoated portions remained on the inner surface of the drum, the coating process was not completed, and bubbles and blowholes were also confirmed.

<Comparative Example 3>
Using the method of Production Example 3, the inner surface of the drum can was coated with polyethylene terephthalate having MFR = 6 [g / 10 min]. Although the coating process was performed for the same processing time as in Example 9, uncoated portions remained on the inner surface of the drum, the coating process was not completed, and bubbles and blowholes were also confirmed.

<Comparative Example 4>
Using the method of Production Example 4, an inner surface-coated drum can using 6-nylon with MFR = 5 [g / 10 min] was produced. Air bubbles and blowholes were also found on the inner surface of the drum.

The drum can of the present invention has a resin inner surface coating layer free from bubbles and blowholes, and has industrial potential as a container having excellent corrosion resistance.

1 Drum 2 Horizontal axis 3 Vertical axis 4 Drum 5 Mold

Claims (3)

A drum can characterized in that an inner surface is coated with a thermoplastic resin having a melt flow rate of 10 [g / 10 min] or more to a thickness of 0.001 to 10 [mm]. The drum can according to claim 1, wherein the thermoplastic resin according to claim 1 is any one of polyolefin, polyester, polyamide, and fluorine resin. The manufacturing method of the drum can according to claim 1, further comprising a step of coating the inner surface of the drum can by fluid contact at a speed of 4000 [cm 2 / min] or more while the thermoplastic resin is melted. Method.

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