JPS62289275A - Painted metallic sheet having excellent workability and lubricity and its production - Google Patents

Abstract

PURPOSE:To produce a painted metallic sheet having excellent workability and lubricity by coating the metallic sheet with a thermosetting resin coated film on the surface of which fluoroplastic powder is exposed. CONSTITUTION:The fluoroplastic powder of a polytetrafluoroethylene or the like having the m.p. higher than the crosslink curing temp. of the thermosetting resin of a thermosetting resin paint is compounded with said paint consisting of a thermosetting polyester resin or the like at 0.1-20pts.wt. per 100pts.wt. powder paint. After the paint is coated on the metallic sheet, the coating is baked to the temp. above the m.p. of the thermosetting resin and below the crosslink curing temp. thereof and is then further baked by increasing the temp. to the temp. above the crosslink curing temp. of the thermosetting resin and below the m.p. of the fluoroplastic. As a result, the coated film has excellent workability and lubricity and has resistance to grazing even if the coated metal lic sheet is subjected to working involving ironing.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention is a method of applying fluororesin powder to the surface of a coating film mainly composed of a high-molecular-weight thermosetting resin with excellent processability. Painted metal plate exposed and provided with lubricity by fluororesin powder, and part 5! Regarding the method of sending.

(Prior art) For rationalization, the method of manufacturing outer panels of home appliances, etc. has traditionally been to use painted metal plates (hereinafter referred to as pre-coated metal plates), which are pre-painted metal plates such as steel plates and aluminum. However, as the types of parts manufactured using this method have expanded in recent years, application to parts that undergo increasingly severe processing is also being considered. For this reason, there is an increasing demand for pre-coated metal plates with coatings that can withstand severe processing.

Generally, in order to improve the processability of a pre-coated metal sheet, if the coating is made of a high-molecular weight resin coating, the tensile strength will be higher, and the limit elongation before cracking will be larger, resulting in severe conditions such as tight bending. It will also withstand processing. However, when a solvent-based paint is prepared using a high-molecular-weight resin, the viscosity increases significantly, making it difficult to apply using normal painting methods.On the other hand, lowering the viscosity to make it possible to paint can reduce the film thickness by 1.
7. For this reason, attempts have been made to use pre-coated metal plates coated with a thermosetting high molecular weight resin powder coating for applications that require severe processing.

However, this pre-coated metal plate also has disadvantages in that if the processing is a process that involves hardening such as press molding, scratches are likely to occur on the coating film and the lubricity of the coating film is poor.

(Problems to be Solved by the Invention) Therefore, the present invention provides a pre-coated metal plate with excellent workability and lubricity that prevents scratches on the coating film even when subjected to processing that involves ironing, and a pre-coated metal plate with excellent lubricity. A manufacturing method is provided.

(Means for solving problem (1)) The present inventors have conducted various studies to develop a pre-coated metal plate with excellent coating film workability and lubricity. It was discovered that by exposing fluorocarbon resin powder on the surface of a greasy coating, the friction coefficient of the coating can be reduced and the scratch resistance against processing that involves ironing can be greatly improved. In order to expose the fluorocarbon resin powder on the surface, a high molecular weight thermosetting resin powder coating is blended with a 7-strand resin powder whose melting point is higher than the crosslinking temperature of the thermosetting resin of the coating. When baking after painting on a board, the temperature is first kept at a melting temperature that does not cause a cross-linking hardening reaction (for thermosetting + 11't). It has been found that the two-stage baking method for fixing the fat powder on the surface of the fiber (7) can be carried out by raising the temperature to a temperature above which a crosslinking and curing reaction occurs.

The present invention was made based on this knowledge, and the present invention is based on a thermosetting method in which the fluororesin powder is not exposed on the surface and has excellent workability and lubricity. After mixing a pre-coated metal plate and a thermosetting resin powder coating with a fluororesin powder having a melting point higher than the crosslinking temperature of 114 degrees of the thermosetting TH resin in the coating, and coating the metal plate,
Baking at a temperature higher than the melting point of the thermosetting resin and lower than the crosslinking and curing temperature, and then further baking at a temperature higher than the crosslinking and curing temperature of the thermosetting resin and lower than the melting point of the fluorine-based U(). The present invention provides a method for producing the above-mentioned pre-coated metal plate, which is characterized by excellent workability and lubricity.

In the precoated metal plate of the present invention, the fluororesin powder containing one thermosetting five-finger coating has a melting point of thermosetting (
(The temperature should be higher than the crosslinking and curing temperature of the fat.

This is when forming a coating film on a metal plate. 7) Is the cable resin powder thermosetting? This is because if it becomes compatible with the Jf fat, the lubricity characteristic of the 7-wire type fat will disappear, and it will not be possible to impart lubricity to the coating film. Therefore, polytetrafluoroethylene (&, e+, 327
(°C, hereinafter referred to as PTFE) Powder powder with a high melting point is used. This I'TFE powder may be of low molecular weight or high molecular weight. The average particle size of the powder is 1~・t()μ
It is preferable to use a material with an I11 or so, and to have 9 to 17+ut, Ta5'2: in the coating film.

Thermosetting properties of the coating film (3) (As the resin, thermosetting polyester resin with a crosslinking curing temperature of 160 to 260°C, which is used in conventional powder coatings, acrylic resin, A4 resin, or epoxy resin) etc. is sufficient.

The pre-coated metal plate of the present invention is produced by blending a high molecular weight thermosetting 4111f powder coating with a thermosetting resin (a 7.7-strand rubber whose melting point is higher than the crosslinking and curing temperature of the sealant) (fat powder). Qllr is temporarily coated using a known powder coating method such as an electrostatic powder coating method or a fluidized dipping method, and then baked. Cross-linking and curing (maintaining the temperature below 1 degree) will cause the thermosetting resin powder to melt, but since the fluorine 8I resin powder will not melt, the 7J, MjH resin powder will bleed onto the coating surface. Then, in this state, the baking temperature is set to 27.
NOx (raise the temperature to below the melting point of the fat. This rise 1
Since the thermosetting resin is hardened, the fluororesin powder is exposed on the surface of the coating film. If the temperature is raised higher than the crosslinking and curing temperature of direct thermosetting resin during baking, the fluororesin powder will not bleed sufficiently to the surface layer, so fluorine 1? However, the lubricating effect of the coating film made with TJF fat rice powder cannot be obtained.

The thermosetting resin powder for the thermosetting resin powder coating has a melting point of about 80 to 150°C and a crosslinking curing temperature of 160 to 2.
Those used in conventional thermosetting resin powder coatings with a temperature of about 60°C and an average particle size of about 1 to 100 μm may be used.
Further, as the fluororesin powder, a powder having a temperature of 9 points higher than the crosslinking and curing temperature of the thermosetting resin powder, for example, l'TFE powder as described above may be used. The amount of fluororesin powder added to the thermosetting resin powder coating is 0.1 to 20 parts by weight per 100 resin of the powder coating. This is because if the amount of the 7-strand resin powder blended is less than this range, the lubricating effect of the coating film will be reduced, and if it is too large, the adhesion between the coating film and the metal plate will be reduced. The formulation may be done by mixing a thermosetting resin powder coating with a fluororesin powder,
Alternatively, a heptad resin powder may be dispersed in a molten thermosetting resin, cooled and then powdered, and a powder coating may be prepared using this powder. It is preferable to use a heptadium-based (31 fat) powder with an average particle diameter of about 1 to 4 μI11.

Note that if a metal plate is coated with a solvent-based paint in which fluororesin powder is dispersed, the fluororesin powder will be coated with the thermosetting resin, and a pre-coated metal plate with the fluororesin powder exposed on the surface of the coating will not be obtained.

The metal plate to be coated is not particularly limited, and cold rolled steel plates, galvanized steel plates, aluminum plated steel plates, stainless steel plates, aluminum plates, etc. can be used. Further, when painting, it is also possible to perform phosphate treatment or chrome treatment to improve paint film adhesion and corrosion resistance.

Next, the present invention will be explained with reference to Examples.

(Example) A 170.5 II 1 m hot-dip galvanized steel plate was degreased and subjected to surface treatment using zinc phosphate, and then heated using a mixture of low molecular weight PTFE powder with an average particle size of 7 μm as shown in Table 1. A curable polyester resin powder coating was applied using an electrostatic powder coating method. Further, as a comparative example, a thermosetting polyester resin powder coating (polyester resin crosslinking and curing temperature: 170 to 180° C.) containing no low molecular weight PTFE powder was applied in the same manner as described above.

Thereafter, these coated steel plates were baked in a near-infrared heating furnace under condition A in Figure 1 or under condition I3t' in Figure 2 to form a coating film of 1735.
A μmo pre-coated steel plate was used.

The following performance tests were conducted on the prepainted steel sheet manufactured in this manner.

(1) Bending workability JIS G 331HJ color galvanized iron plate], 0 scissors plates with the same thickness as the test plate are placed on the inside of the bend.
After applying one sheet (IL) and two sheets (2t) and bending it 180 degrees, the outer bent portion coating film was observed with a 40x microscope.
Evaluation was made based on the following criteria.

○; No abnormality △; Cracks occur at 1096 or less ×; Cracks occur at 1()% or more (2) Intoxication I? JIS K 7204r wear wheel test for plastics 1
? The amount of wear was measured in accordance with the "Wear test method".

(3) After applying stain-resistant marker ink and leaving it for 24 hours at a temperature of 20°C, wipe off the marker ink with methyl alcohol and check the color difference (ΔE) between the area coated with marker ink and the area not coated with marker ink. It was measured.

(4) Rectangular cylinder drawing property fjS3 After performing the rectangular cylinder drawing process as shown in Fig. 3, the state of paint film scratches on some corners was observed with a 10x magnifying glass, and evaluated by the following master.

○: No abnormality in the coating film Δ: Less than 50% scratches were observed on the coating film ×: 50% or more scratches were observed on the coating film As shown in Table 1, thermosetting υ (By incorporating 117 FE powder into the thin coating film,
The precoated steel sheet of the present invention in which the PTFE powder is exposed on the surface of the coating film has better wear resistance, stain resistance, and rectangular tube drawability than the steel sheet that does not contain the PTFE powder in the coating film. Further, even when the coating film contains r'TFE powder, no decrease in bendability is observed.

In addition, if a pre-coated plate containing PTFI: powder is produced by the method of the present invention, a pre-coated steel plate with excellent wear resistance, stain resistance and rectangular tube drawability can be obtained. It can be seen that it is exposed on the surface of the paint film.

(Effects of the Invention) As described above, the pre-coated steel sheet of the present invention has excellent lubricity, so even if it is used in applications that require ironing such as press forming, there will be no frosting on the coating film. becomes less.

1. Simple on page 1 of L-I? 11. Figures 1 and 2 show the baking conditions for the powder paint-coated steel plate in the example, and Figure 3 shows the baking conditions for the steel sheet coated with powder paint in the example. It is a perspective view showing the rectangular cylinder drawing shape of the drawing test.

patent issuer Nisshin Steel Co., Ltd. representative person Mitsuru Susumu Fuji Figure 1 Figure 2

Claims (3)

[Claims] (1) A coated metal plate with excellent workability and lubricity, characterized in that the metal plate is coated with a thermosetting resin coating film in which fluororesin powder is exposed on the surface. (2) A thermosetting resin powder coating is mixed with a fluorine-based resin powder whose melting point is higher than the crosslinking temperature of the thermosetting resin in the coating, and after being applied to a metal plate, the coating is crosslinked at a temperature higher than the melting point of the thermosetting resin. Coated metal with excellent workability and lubricity, which is characterized by baking at a temperature below the curing temperature, then raising the temperature to a temperature above the crosslinking curing temperature of the thermosetting resin and below the melting point of the fluororesin, and then baking again. Method of manufacturing the board. (3) Processing according to claim 2, characterized in that 0.1 to 20 parts by weight of fluororesin powder is blended into the thermosetting resin powder coating per 100 parts by weight of the powder coating. A method for producing a coated metal plate with excellent properties and lubricity.