JPS6213387B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improving the adhesion of a coating film to a coated object such as a zinc plate, a galvanized iron plate, or a zinc-based (including coating material) wire, bar, pipe, or molded material such as a cast or forged product. It is something. When applying paint to a surface to be coated, such as a zinc plate or galvanized iron plate, the adhesion will be extremely poor if applied to a smooth, untreated surface, so sandblasting or other methods may be used to create unevenness. Alternatively, coating is usually applied after chemical conversion treatment with phosphoric acid or the like. However, this requires extra steps and time, and has the disadvantage of a large loss in construction costs. The present inventors believe that if it is possible to give the paint a similar effect to that of chemical conversion treatment by improving the composition of the paint, then applying the paint after chemical conversion treatment is a common practice. As a result of intensive research based on the concept that this process can be performed in one operation, simplifying the work process and shortening the work time, it will be possible to reduce costs. When acid aluminum salt and fast-acting corrosive salt are contained, zinc plate,
The present invention was completed based on the finding that the adhesion of coating films to galvanized iron plates and the like is improved. That is, the present invention consists in the combined use of a condensed aluminum phosphate salt and a fast-acting corrosive salt for zinc in the paint. To explain the invention more specifically,
The condensed aluminum phosphate salts used in the present invention include aluminum salts of polyphosphoric acid (tripolyphosphoric acid, etc.) and metaphosphoric acid (trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, etc.). In addition, the condensed aluminum phosphate salt used in the present invention has a water soluble content of 0.01 to 0.01 by the method of JIS K-5101.
It is necessary that the water-soluble content is in the range of 5%, preferably in the range of 0.5 to 2%. If the water-soluble content is less than the above range, the adhesion of the coating film to the metal coating will not be improved sufficiently. Furthermore, if the water-soluble content is greater than the above range, no improvement in the adhesion of the coating film can be expected and the performance of the coating film will also deteriorate. The mechanism of why condensed aluminum phosphate salts with the above properties improve the adhesion of paint films to metal coatings is not clear, although aluminum orthophosphates do not sufficiently improve adhesion. Although no clear explanation can be given, it can be considered as follows. In other words, some condensed phosphate ions are liberated by the small amount of water present in the paint, and when this paint is applied to a metal object, the partially liberated condensed phosphate ions cause the surface of the coated plate to This is because the same effect as a chemically treated board is achieved by being treated with phosphate. Furthermore, the phosphate treatment effect of condensed phosphate ions on the coated plate is due to moisture from outside the coating film (e.g. moisture in the air, rainwater, etc.) entering the coating film, resulting in the release of condensed phosphate ions. It is also carried out continuously by condensed phosphate ions. Considering that it is generally accepted that condensed phosphate ions have greater reactivity toward zinc than orthophosphate ions, it is confirmed that condensed aluminum phosphate salts are effective. Furthermore, the reason why the water-soluble content is required to be in the range of 0.01 to 5% is that if a substance with this level of solubility is added to the coating film, it will not cause a decrease in coating performance, and the metal coating will not deteriorate. This is because the reactivity of condensed phosphate ions with respect to substances is optimal. The above mechanism is more understandable than the fact that when condensed phosphates (particularly aluminum dihydrogen tripolyphosphate) are added to inorganic zinc paints, they have the effect of suppressing the formation of white rust due to zinc dust. Furthermore, it has been found that the adhesion of the coating film can be further improved by using a condensed aluminum phosphate salt and a fast-acting corrosive salt against zinc in an amount of 2% or less (in the coating film). That is,
As the fast-acting corrosive salt, manganous monophosphate, tribasic lead sulfate, stannous oxalate, zinc sulfate, magnesium silicofluoride, and calcium silicofluoride can be used. It is possible to use one type or a mixture of two or more of these fast-acting corrosive salts, but if the amount used exceeds 2%, the performance of the coating will decrease, and blistering will especially occur. Undesirable. In addition, since these corrosive salts are fast-acting, they attack the metal coating in a short period of time, facilitating the reaction between condensed phosphate ions and the metal ions, and forming a phosphoric acid coating on the metal coating. The mechanism of facilitating formation promotes the effect of improving the adhesion of coating films to zinc plates, galvanized iron plates, etc. The amount or type of these corrosive salts must be selected depending on the type of condensed aluminum phosphate salt and the type of vehicle. Example The paint composition was as shown in Table 1 below.

[Table] The samples specifically used in this paint formulation are as follows. Titanium oxide: manufactured by Teikoku Kako Co., Ltd., trade name JR-602 Varnish solid content resin: manufactured by Dainippon Ink Co., Ltd., trade name Betsukosol J524
(Coconut oil modified short oil alkyd resin, non-volatile content 60
%) and Dainippon Ink Co., Ltd., trade name Supervetsucomin J-820 (n-butyl etherified melamine resin, non-volatile content 60%), in a solid content of 70% of the former and 30% of the latter. Condensed phosphate: Aluminum dihydrogen tripolyphosphate (Teikoku Kako)
K-Bond Co., Ltd.) Instant-acting corrosive salt: As the instant-acting corrosive salt, the following special grade reagents were pulverized and used. Manganese monophosphate Tribasic lead sulfate Stannous oxalate Zinc sulfate Magnesium silicofluoride Calcium silicofluoride Dispersion conditions were as follows: Dispersion for 30 minutes using a paint conditioner (manufactured by Igarashi Kikai), with particles of 10 μm or less (JIS K5400A law). The paint obtained as described above was coated on the following coated plate using a bar coater and dried at room temperature for one week to form a coating layer with a thickness of 30 to 34 .mu.m. Coated plate: Galvanized steel plate (JIS G3303) The coated plate thus obtained was tested according to the test items listed below, and the results of the evaluation of adhesion are shown in Table 2 below. It is. First test: 1 week at room temperature, 2nd: 48 hours at 40°C, 30 minutes drying.

[Table] That is, according to the results in Table 2, it is clear that a preferable improvement in adhesion can be obtained by adding an appropriate amount of corrosive salt according to the present invention. According to the present invention as explained above, by incorporating a condensed aluminum phosphate salt and a fast-acting corrosive salt into the paint, the adhesion of the paint film to the zinc-based metal coating is improved, and special surface roughening is achieved. It can form a stable coating film with little loss in terms of time and construction costs without requiring any treatment, and it also has the effect of effectively preventing blistering and rust. This invention has great industrial effects.

Claims (1)

[Claims] 1. In the paint used for zinc-based metal coatings,
Condensed aluminum phosphate salt and 2% on coating base
Any one or two of the following manganese monophosphate, tribasic lead sulfate, stannous oxalate, zinc sulfate, magnesium silicofluoride, and calcium silicofluoride.
A coating composition containing at least one species. 2. The coating composition according to claim 1, which uses aluminum dihydrogen tripolyphosphate or aluminum metaphosphate as the condensed phosphate.