JPS6334191B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a rust-preventing paint composition with excellent heat resistance. More specifically, the present invention relates to a primary rust-preventing paint composition that is effective as a primary rust-preventive paint for large steel structures, and which ensures sufficient rust-preventive properties even when heated for welding, strain relief, and the like. (Prior art) Many anti-rust paints containing various anti-rust pigments are known, but among them, zinc-rich paint containing zinc powder has excellent anti-rust properties and is used for large steel structures such as ships and bridges. It is widely used as a primary anti-rust coating. Zinc-rich paint is a paint that is generally obtained by mixing a large amount of zinc powder with an organic or inorganic binder, and is used to prevent sacrificial corrosion of zinc through electrochemical interaction between the zinc in the paint film and the steel surface. It has a rust-preventing effect due to its action and the blocking action of oxygen and moisture by the corrosion products of zinc. However, this zinc-rich paint also has the following drawbacks. First of all, increasing the zinc powder content in the paint film increases the sacrificial anticorrosion effect of zinc and improves the rust prevention performance. Sexuality decreases. On the other hand, if the zinc powder content is reduced, the sacrificial anticorrosive action of zinc is reduced, resulting in poor rust preventive performance and the purpose of preventing rust cannot be fully achieved. Second, for parts heated to high temperatures, such as the back side of welds and the back side of strain relief, the heat causes significant oxidation of zinc in the paint film, reducing the sacrificial corrosion protection effect, resulting in a decrease in rust prevention. The corrosion resistance also decreases, and the purpose of preventing rust is not achieved. Large steel structures have many welding points and strain relief points, and as a result, even though they are coated with primary anti-corrosion paint, it takes a lot of effort to remove the rust before applying the top coat. The current situation is that Therefore, there is a desire for a coating material that has a low zinc dust content and exhibits excellent antirust performance even in areas heated to high temperatures. In the conventional technology, in order to maintain anti-rust performance in parts with a small content of zinc dust and heated to high temperatures, for example, hydrolyzed initial condensates of tetraalkoxysilane and hydrolyzed initial condensates of alkyltrialkoxysilane are used. There are examples of using a combination of silica (Japanese Patent Application 158785-1985) or a combination of a hydrolyzed initial condensate of tetraalkoxysilane and solvent-type colloidal silica (Japanese Patent Application 1987-093540).
A satisfactory effect cannot be obtained by simply selecting the type of binder. In addition, there are also examples of using zinc powder in which the surface of zinc particles is coated with conductive particles to suppress oxidation of zinc (Japanese Patent Application No. 59-199205), or examples of using zinc alloy powder with a higher melting point than zinc. (Japanese Patent Application No. 59-093541), however, the manufacturing process of such a powder requires a great deal of labor, and the materials are less easily available and less economical. As a result of intensive research into the high-temperature oxidation of zinc powder in binders, the present inventors found that the temperature of the steel plate on the back side during welding or strain relief exceeds 600℃, and when heated to such high temperatures, They also discovered a new composition that maintains antirust performance and completed the present invention. (Structures and Effects of the Invention) That is, the gist of the present invention is to provide a coating composition containing a binder and zinc dust, in which the zinc dust is spherical and has an average volume-based particle diameter of 6 by the light transmission sedimentation method. ~10μ, and particles with a particle size of 2μ or more are present at 97% by volume or more based on the total amount of zinc dust, and the zinc powder content is 20~10% by volume in 100 parts by volume of the dry coating film.
60 parts by volume of a primary rust preventive paint composition having heat resistance of 600°C or higher. The primary rust-preventing paint composition of the present invention is a rust-preventing paint composition generally called a shot primer that is applied to a rust-removed steel plate with a dry film thickness of 10 to 30 μm. The zinc powder used in the composition of the present invention can be produced by any known suitable method, such as a spraying method. This zinc powder is spherical and has an average particle diameter of 6 to 10 μm as measured by a light transmission sedimentation method, and particles having a particle diameter of 2 μm or more account for 97% by volume or more based on the total amount of zinc dust.
Here, the particle size measurement method was limited to the light transmission sedimentation method, as described in "Pigments" (Vol. 27, No. 1, 1983, Japan Pigment Technology Association). This is because they are different. In addition, spherical shape is not limited to only true spheres, This means that the practical sphericity defined by is 0.8 or more.
Being spherical means that the specific surface area is small, and high-performance rust prevention can be maintained even when exposed to high temperatures during welding, strain relief, etc. If the average particle diameter is less than 6 μm, the heat resistance of the zinc powder will be poor and it will be easily oxidized when exposed to high temperatures.
If it exceeds 10μ, the zinc powder will settle quickly after adjusting the coating composition, the dispersion stability of the composition will decrease, and it will be difficult to obtain a uniform coating film. If the zinc powder is scaly, for example, or contains 3% by volume or more of particles with an average particle size of 6 μm or more and 2 μm or less, the antirust performance in areas heated to high temperatures will decrease. In the composition of the present invention, zinc powder is present in the dry coating film.
It is sufficient to mix it so that it becomes 20 to 60% by volume. If the amount is too small, good antirust performance will not be obtained, and if it is too much, the amount of white rust will increase and the adhesion to the top coat will decrease. The heat-resistant binder used in the present invention may be any binder used in primary rust-preventing paints, such as hydrated silicic acid esters (e.g., tetraethoxysilane methyltrimethoxysilane, etc.). Decomposition initial condensate, solvent-based colloidal silica (dispersion medium e.g. methanol, isopropyl alcohol), silicate (e.g. sodium silicate,
lithium silicate, potassium silicate, ammonium silicate). In particular, hydrolyzed initial condensates of silicate esters, solvent-based colloidal silica,
Alternatively, a combination of both is preferred. The combined use of a hydrolyzed initial condensate of silicate ester and solvent-based colloidal silica maintains good coating performance without cracking even if the amount of zinc dust is reduced. The primary antirust coating of the present invention is required to have heat resistance of 600°C or higher, preferably 800°C or higher. The inventors have discovered that the back side of the steel plate is 600 mm thick during welding and strain relief work.
It was found that temperatures exceed ℃, and in some cases exceed 800℃. Therefore, the primary anticorrosive paint is required to have heat resistance of at least 600°C as a critical temperature.
Heat resistance of 600°C or higher is imparted to paints by various factors, such as the selection of binders and additives. Their mixtures give extremely high heat resistance (over 800°C). In the composition of the present invention, in addition to the above-mentioned binder and zinc powder, various pigments, solvents,
Additives and the like may be added as necessary. Pigment components may be ordinary extender pigments, anti-rust pigments, colored pigments, and metal powder pigments, specifically talc, mica, barium sulfate, clay, calcium carbonate, zinc white, titanium white, Bengara, and zinc phosphate. , aluminum phosphate, barium metaborate, zinc molybdate, aluminum molybdate, calcium silicide, ferroalloy and the like. Solvent components include normal isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, butyl cellosolve, ethyl cellosolve, methyl ethyl ketone, methyl isobutyl ketone, xylol, triol, etc., and are designed to optimize painting workability and film drying properties. An appropriate amount may be added. As additive components, agents commonly used in anti-rust paints such as anti-sagging agents, wetting agents, reaction accelerators, adhesion agents, color separation inhibitors, and anti-settling agents are mixed in appropriate amounts depending on the purpose. good. The composition of the present invention can be prepared according to conventional methods. For example, a liquid component containing a binder and a system containing other powder components may be stored in separate containers, and the two may be mixed immediately before use. Alternatively, part or all of the powder components other than the part that reacts with the binder (for example, zinc dust) may be dispersed together with the liquid component containing the binder, and the mixture and the remaining components may be mixed immediately before use.
For dispersing the liquid component and the powder component, a conventional dispersing machine such as a disper, a homomixer, a roll mill, a sand grind mill, a ball mill, etc. may be used. In the composition thus obtained, the binder concentration may generally be 5 to 40% by weight, and the composition is applied to the steel structure by conventional means such as air spray, airless spray, roll coater, brush, etc.
It may be dried by natural drying or hot air drying. The composition of the present invention having the above-mentioned structure can fully exhibit its function as a primary rust-preventing paint,
Moreover, it is possible to maintain rust prevention even in heated parts such as the welded back surface and the strain relief back surface. (Examples and Comparative Examples) Next, the present invention will be specifically described with reference to Examples and Comparative Examples. The average particle diameter and particle size distribution of the zinc powder used in these Examples and Comparative Examples were measured using the Horiba centrifugal automatic particle size distribution analyzer CAPA, which is a type of light transmission sedimentation method analyzer.
-500 (manufactured by Horiba, Ltd.). As for the measurement conditions, a 50% by weight aqueous glycerin solution was used as the dispersion medium, and the rotation speed was 500 rpm. The results are shown in Table 1. Incidentally, the average particle diameter as used herein means an intermediate particle diameter. Further, the above-mentioned measuring device is described in detail in the above-mentioned document "Pigments".

【table】

[Table] *1 Zinc dust E Zinc dust A/C = 1/1 (weight ratio)
The compositions of Examples 1 to 8 and Comparative Examples 1 to 5 shown in Table 2 were sufficiently dispersed using the zinc powder shown in Table 1. The following tests were conducted on this composition. (1) Exposure test A sandblasted steel plate was used as a test piece, coated with air spray to a dry film thickness of 15±2μm, and heated at 20°C.
After being air-dried for 7 days at a relative humidity of 75%, or further heated in an electric furnace at 600°C or 800°C for 10 minutes and cooled, a rust prevention test was conducted. The test was conducted for three months in the coastal area (Naruto City), and the state of red rust was evaluated.
Judgment was made using ASTM (D610), and the state of occurrence of white rust was judged as (〇: Practical, ×: Not Practical). (2) Precipitation stability test After preparing the composition shown in Table 2, test it with a disper for 30 minutes.
Stir for a minute. Next, the stirring was stopped, and after leaving it for 10 minutes, the amount of sediment deposited on the bottom of the container was examined using a spatula (〇: The amount of sediment was small and there was no practical problem. ×: The amount of sediment was large and it was not practical). I judged it. The above test results are shown in Table 2. As is clear from the table, the composition of the present invention has less precipitation and white rust, and has excellent rust prevention properties after heating at 600°C or 800°C.

【table】

【table】

【table】

Claims (1)

[Claims] 1. Contains a heat-resistant binder and zinc powder, and
In a primary rust preventive paint composition for steel that has heat resistance of 600°C or higher, the zinc powder is spherical and has an average volume-based particle diameter of 6 to 6 by the light transmission sedimentation method.
10μ range, and particles with a particle size of 2μ or more are present at 97% by volume or more based on the total amount of zinc dust, and the zinc dust content is 20 to 60 parts by volume per 100 parts by volume of the dry coating film. composition. 2. The composition according to claim 1, wherein the heat-resistant binder is a hydrolyzed initial condensate of a silicate ester, a solvent-type colloidal silica, or a mixture of both.