JPS61114846A - Coated metallic plate having excellent weather resistance and workability and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a coated metal plate with excellent weather resistance and workability that is suitable for uses such as roofing materials, side wall materials, tank inner wall materials, parts for automobiles and bicycles, and parts for home appliances, and a method for manufacturing the same. be. [Conventional technology]

Traditionally, coated metal sheets used for exterior building materials and interior materials use cold-rolled steel sheets, galvanized steel sheets, stainless steel sheets, aluminum sheets, aluminum aluminum alloy sheets, and other metal sheets as the base metal plate. Generally used is a board coated with a thermosetting resin paint such as a polyester resin paint, a silicone-modified polyester resin paint, or a silicone-modified acrylic resin paint and then baked. Although coated metal sheets have good weather resistance, they are poor in workability, and if they are used in areas that require severe forming processes such as tight bending, the coating will There have been problems in that cracks occur in the film, which in turn causes the paint film to peel off, and even if the paint film does not peel off, the corrosion resistance deteriorates significantly.

Problem 1 to be Solved by the Invention The present inventors have conducted intensive research to eliminate the problems with conventional coated metal plates, and have developed a coating material with vinylidene fluoride resin as the main component that has excellent weather resistance and processability. However, since vinylidene fluoride resin is a crystalline resin, a chemical conversion treatment layer and an undercoat layer are formed on the surface. It was discovered that when a vinylidene fluoride resin paint is applied and baked on the surface of a metal plate, the resin crystallizes excessively during the process, making it impossible to obtain the desired properties. [Means for Solving the Problems] Therefore, the inventors of the present invention have devised a method for controlling the temperature and cooling conditions to control the temperature and cooling conditions when applying and baking vinylidene fluoride resin paint. The degree of crystallization is 1
They completed the present invention by discovering that the desired characteristics could be obtained by suppressing the content to 8% or less. That is, the present invention provides a metal plate having a crystallinity of 18% or less and a vinylidene fluoride resin content of 70% by weight or more on the top surface of a metal plate on which a chemical conversion treatment layer and an undercoat layer are formed on the surface. A coated metal plate with excellent weather resistance and workability, characterized in that a vinylidene fluoride resin-based top coat 1 is formed, and a method for producing the coated metal plate with excellent weather resistance and workability. After applying a chemical conversion treatment to the surface of the metal plate, and then applying and baking an undercoat, a non-recurring amount of vinylidene fluoride resin was applied on top of it.
Applying 0% by weight or more of vinylidene fluoride resin paint, 2
Weather resistance characterized by baking at a temperature of 30 to 270 degrees Celsius and rapidly cooling at a cooling rate gradient of 160 degrees Celsius or more to a temperature of 10 degrees Celsius or less while the paint temperature is higher than the recrystallization temperature of the resin. The present invention also provides a method for producing a coated metal plate with excellent workability. DESCRIPTION OF THE PREFERRED EMBODIMENTS A coated metal plate with excellent weather resistance and workability and a method for manufacturing the same according to the present invention will be explained in detail with reference to the drawings. Figure 1 is a cross-sectional view showing the structure of the coated metal plate with excellent weather resistance and workability according to the present invention, and Figure 2 shows a cooling rate of 10°C.
FIG. 3 is a graph showing an example of recrystallization characteristics of a vinylidene fluoride resin-based paint in the case of 1/min. FIG. 3 is a diagram showing a method of calculating crystallinity by X-ray diffraction. In the drawings, reference numeral 1 denotes a metal plate as a base material, and cold-rolled steel plates, galvanized steel plates, stainless steel plates, aluminum plates, aluminum alloy plates, etc. are used depending on the purpose of the coated metal plate to be manufactured. 2 is a chemical conversion treatment layer applied to the surface of the metal plate 1, and this chemical conversion treatment layer 2 has good adhesion to the undercoat film 1 formed thereon and improves the corrosion resistance of the metal plate 1. If so, it is not particularly limited, but a chemical conversion treatment layer formed by phosphate treatment or chromate treatment, which is similar to the chemical conversion treatment applied to ordinary painted metal plates, is preferable. 3 is an undercoat film layer formed by coating and baking on chemical conversion treatment (3) 2;
This undercoat IIJ so-called 3 is preferably an undercoat layer formed of an epoxy resin paint that has good adhesion to the chemical conversion treatment @2 of the lower layer and the vinylidene fluoride resin topcoat layer above it. The thickness is preferably about 4 to 6 microns. 4 is a vinylidene fluoride resin-based top coat layer having a crystallinity of 18% or less and a vinylidene fluoride resin content of 70% by weight or more, which is formed by coating and baking on the undercoat layer 3; Its thickness is preferably 18-22μ. The reason why the amount of vinylidene fluoride resin in the vinylidene fluoride resin-based top coat layer 4 must be 70% by weight or more is that if the vinylidene fluoride resin phase is less than 70% by weight, the weight of the vinylidene fluoride resin will be reduced. This is because the excellent properties of weatherability and processability are impaired by additives such as resin. In addition, the crystallinity of the vinylidene fluoride resin topcoat S layer 4 must be 18% or less, because as shown in the examples below, if the crystallinity exceeds f18%, the weather resistance as a topcoat film layer will deteriorate. This is because not only the properties but also the processability such as elongation properties and impact strength are rapidly reduced. As described above, the coated metal plate with excellent weather resistance and workability according to the present invention has the surface of the metal plate 10 subjected to chemical conversion treatment 1!2 from the metal plate 1 side. Undercoat 11113. It is characterized by the fact that layers are formed in the order of vinylidene fluoride resin topcoat 511m@4, but the difference from conventional coated metal sheets is that the top layer of vinylidene fluoride The resin-based top coat 114 is a coating layer formed of a vinylidene fluoride resin paint having a crystallinity of 18% or less and a vinylidene fluoride resin content of 70% by weight or more. In this way, in order to reduce the crystallinity of a vinylidene fluoride resin paint having a vinylidene fluoride resin group of 70% or more by weight to 18% or less, first, a chemical conversion treatment is applied to the surface of the metal plate 1 to form a chemical conversion treatment layer 2. After forming the undercoat [1113] by applying and baking an undercoat on the chemical conversion treatment layer 2,
A vinylidene fluoride resin paint containing 70% by weight or more of vinylidene fluoride resin in non-volatile content is applied onto the undercoat film layer 3, and then baked at a temperature of 230 to 270°C so that the paint temperature is the recrystallization temperature of the resin. While the temperature is still higher, the cooling rate gradient may be 160° C./sec or higher until the temperature reaches 70° C. or lower. This is because if the baking temperature of vinylidene fluoride resin paint is below 230°C, the vinylidene fluoride resin will not melt sufficiently and pinholes will occur, resulting in decreased weather resistance and processability. This is because when the temperature exceeds 270°C, the resin deteriorates and the strength of the coating film decreases. In addition, after coating and baking the vinylidene fluoride resin paint, while the paint temperature is higher than the recrystallization temperature of the resin, the cooling rate gradient is quenched at 160°C/sec or more until the temperature reaches 70°C or less. This is because if the cooling rate gradient of the resin is less than 7 seconds at 160°C or if the start of rapid cooling of the resin is lower than the recrystallization temperature of the resin, the recrystallization of the vinylidene fluoride resin will progress significantly and spherulites will form. However, the elongation properties and impact strength are reduced, and the excellent properties of weather resistance and processability, which are the objectives of the present invention, are achieved with a top coat.
! This is because it becomes impossible to obtain JIII, and the reason why the resin temperature is rapidly cooled to below 10°C is that if the temperature at the end of rapid cooling is 70°C or higher, molecular movement of crystal defects in the vinylidene fluoride resin paint will occur. As a result, crystallization progresses due to molecular rearrangement and the degree of crystallinity exceeds 18%, which deteriorates the elongation properties and impact strength of vinylidene fluoride resin paints. This is because it becomes impossible to obtain a top coat layer with excellent properties in terms of properties and processability. In this way, in the present invention, the top coat Il! It is a very important requirement that the crystallinity of the vinylidene fluoride resin top coat is 18% or less. An X-ray diffraction intensity test is performed on the top coat layer, and the diffraction area Xc of the crystalline portion and the diffraction area χa of the amorphous portion are determined and calculated using the following formula % formula % (). This X-ray diffraction intensity test method uses, for example, a copper target as an apparatus, a concentrated X-ray beam with a tube voltage of 40 V and a tube current of 80 mA, a nickel filter, and a divergence end slit. 1 degree as a receiving slit and 0.0 degree as a receiving slit to receive diffracted X-rays.
The diffraction intensity can be measured using a scintillation counter using a 3 mm one under measurement conditions such as a time constant of 1 second and a goniometer scanning speed of 1 degree/minute.

[Example 1] Hereinafter, an example of the present invention will be described. Austenitic stainless steel SUS 304 and ferritic stainless steel (19Cr -0,5Cu -0
,5Nb: Manufactured by Nisshin Steel, product name NSS 442M3
) A pre-degreased copper plate with a surface finish of 2D, plate thickness o, and 3mm was treated with a zinc phosphate treatment agent (manufactured by Nippon Pain Me@,
Pre-painting treatment with product name: Granogin #9100)
On top of that, an epoxy resin paint (manufactured by Nippon Paint ■, product name: changed to UNIFLON) was applied as an undercoat to a dry film thickness of 5μ using the roll coating method, and the plate was heated in a conveyor oven to reach a maximum board temperature of 200°C. , bake for 40 seconds, and apply a primer coat to each steel plate! Formed a blasphemy. After that, this coating 1'! As a top coat on the J decoy, vinylidene fluoride resin paint (manufactured by Nippon Paint ■, trade name: UNIFLON K) having the recrystallization properties shown in Figure 2 was applied by roll coating to a dry film thickness of 20 μm. After painting and baking again in a conveyor oven, it was rapidly cooled with a large amount of water to form a top coat layer. The combinations of baking conditions and cooling conditions are shown in Table 1. On the other hand, as a comparative example (1' to 4'), undercoat 11J
The same top coat as above was applied to the same Sυ5304 stainless steel plate on which II was formed to a dry film thickness of 20 μm.
A top coat layer was formed using the combination of baking conditions and cooling conditions shown in Table 1. In addition, as a comparative example (5'), an epoxy resin paint (manufactured by Nippon Paint V7J, product name: 1) rF was applied to a SUS 304 stainless steel copper plate similar to the above which had been subjected to chemical conversion treatment as a paint for forming an undercoat layer. P 1551 was used, and a silicone-modified polyester resin paint (manufactured by Nippon Paint ■, product name 20IF S~) was used as the paint for forming the top coat layer.
30) and according to the baking conditions shown in Table 1, undercoat each! @, a top coat layer was formed. Thereafter, a performance test of the obtained coated steel plate was conducted in the following manner. (1) Workability test (a) Bending test In accordance with "JIS G 332Or painted stainless steel plate", the inner interval of bending was set using a scissor plate (0) of the same thickness as the test plate (
Ol: close contact bending), 1 piece (1t). After bending two sheets (2t) 180°, a part of the corner was examined under a microscope (
X40) and evaluated based on the following criteria. ◎ mark: No abnormality O mark: Cracks of 10% or less occurred ・Mark: Cracks of more than 10% and 30% or less occurred Δ mark:
Cracks of more than 30% and less than 70% occur x India 0%
Cracks occur exceeding
82 kg x 1 m), bending radius 2II
Observe part of the corner of IIllR with a microscope (X40),
Evaluation was made using the same criteria as above. (2) Adhesion test For samples under normal conditions and after immersion in boiling water for 2 hours, J
In accordance with IS G 3320 r Painted Stainless Steel Plate, the inner spacing of the bending was made using zero scissor plates (of the same thickness as the test plate).
Ot: close bending), 2 pieces (2t: 1.4 pieces (4t) in 1
After bending 80 degrees, press cellophane tape on part of the corner.
It was forcibly peeled off and evaluated according to the following criteria. ◎ mark: No abnormality at all O mark: Very slightly peeled paint film - Mark: Slightly peeled paint film △ mark: Significantly peeled paint film × mark: Significantly peeled paint film (3) A 5,000-hour irradiation test was conducted using an ultraviolet carbon arc accelerated weathering test I (manufactured by Suga Test Instruments) specified in "Weather Resistance Test JIS 87752 r Ultraviolet Carbon Arc Lamp Weathering Tester". After the test, the 60 degree specular gloss of the test piece was measured using a gloss meter manufactured by Murakami Color Research Institute ■, and the gloss retention rate relative to the initial gloss was determined and evaluated. Second. Third. Table 4 shows the results of the performance evaluation test. Table 2 with blank spaces below Workability test results Table 3 Adhesion test results Table 4 Weatherability test results In the workability tests in Table 2,
) shows good performance with no abnormalities in the coating film at some corners in bending tests (○t, 1t, 2t) and impact tests. On the other hand, in the comparative examples (&1' to 4'), cracks occurred at some corners of the bending test at Ot and 1t, and in the comparative example (&5'), cracks also occurred at the 2nd corner. In the impact test, cracks occurred in some corners of the comparative examples (&1' to 5') in a range of 10 to 10%. In addition, a 16-roll molding machine was used to simulate actual molding. Although no cracks were observed in the closely bent parts of the examples (1 to 6) according to the present invention, the comparative examples (Nt1
' to 5'), cracks occurred in the closely bent portions. Cracks that occur during the molding process become a factor in the peeling of the coating film due to the intrusion of rainwater in the actual usage environment. In the coating film adhesion test shown in Table 3, (Na
1 to 6), Ot, 1t, and 2 were all in good condition with no peeling of the coating in the normal state and after immersion in boiling water for 2 hours. On the other hand, in the comparative examples (1' to 5'), peeling of the coating was observed after immersion in boiling water for 2 hours, and it is considered that the adhesion tends to deteriorate over time. In the weather resistance test shown in Table 3, the gloss retention rate of the present invention (lft 1 to 6) was 96 to 100%, and almost the initial gloss was retained even after 5000 hours, indicating good performance. On the other hand, in the comparative example (lk5'), the gloss retention rate decreased to 62%. This is because the paint film has deteriorated and chalking has occurred. [Effects] As detailed above, the coated metal sheet according to the present invention does not cause cracks or peeling of the coating even when subjected to severe forming processes such as automobile parts and home appliance parts, so the range of application is extremely wide compared to conventional materials. It is something. In addition, it has extremely good weather resistance even when used outdoors.
It has great industrial value because it hardly deteriorates over time and can be used without maintenance.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the structure of the coated metal plate with excellent weather resistance and workability according to the present invention, and Figure 2 shows a cooling rate of 10°C.
FIG. 3 is a graph showing an example of recrystallization characteristics of a vinylidene fluoride resin paint in the case of /1n. FIG. 3 is a diagram showing a method of calculating the degree of crystallinity by X-ray diffraction. 1...Metal plate 2...Chemical conversion treatment layer 3...Undercoat film layer 4...vinylidene fluoride resin-based topcoat film layer 1st factor 2nd figure 31!1 0 cuts angle (2θ)

Claims (1)

[Scope of Claims] 1. On the top surface of a metal plate on which a chemical conversion treatment layer and an undercoat layer are formed on the surface, the crystallinity is 18% or less and the amount of vinylidene fluoride resin is 70% by weight. % or more of a vinylidene fluoride resin topcoat layer, which has excellent weather resistance and workability. 2. The coated metal plate with excellent weather resistance and processability according to claim 1, wherein the undercoat layer is an epoxy resin undercoat layer. 3. The coated metal plate with excellent weather resistance and workability according to claim 2, wherein the undercoat film layer has a thickness of 4 to 6 μm. 4 The thickness of the vinylidene fluoride resin top coat layer is 18~
A coated metal plate with excellent weather resistance and workability according to any one of claims 1 to 3, which has a diameter of 22μ. 5 After applying chemical conversion treatment to the surface of the metal plate, then applying and baking an undercoat paint, and then applying a vinylidene fluoride resin paint containing 70% by weight or more of vinylidene fluoride resin in non-volatile content, 230 Weather resistance characterized by baking at a temperature of ~270°C and rapidly cooling while the paint temperature is higher than the recrystallization temperature of the resin at a cooling rate gradient of 160°C/sec or more until the temperature reaches 70°C or less. A method for manufacturing coated metal sheets with excellent workability.