JPH0566418B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a rust-preventive coating composition, and more specifically, an inorganic zinc primer (hereinafter abbreviated as "IZP") that is applied to the steel surface of a steel structure or the surface of a primary rust-preventive coating. ) relates to a rust-preventive coating composition that improves defects such as cracking and peeling. Conventional technology Conventionally, steel materials for steel structures such as ships, bridges, tanks, plants, and offshore structures have a dry film thickness of 80 to 160 μm after blasting or after applying a primary rust-preventing paint after blasting. It is applied to a certain extent,
Suppresses and prevents corrosion of steel materials. In general, IZP, which is mainly composed of a silicate ester condensate and zinc powder, suppresses or prevents corrosion of steel due to the electrochemical action of the zinc powder.
It contains more than % by weight of zinc powder.
As described above, IZP contains a much higher amount of pigment than ordinary organic resin-based paints, and the color vehicle whose main component is a silicate ester condensate is used only as a color vehicle, unlike ordinary organic resins. Since IZP has almost no film-forming property, its film-forming properties are weak. Therefore, when IZP becomes a thick film of 120μ or more, cracks occur in the paint film due to distortion caused by the shrinkage stress of the paint film during the drying process, and the adhesion with the steel material decreases, resulting in peeling of the paint film, etc. Defects occur. Furthermore, since the reactivity with pigments and the like is extremely low during the drying process, the varnish tends to float to the surface, resulting in increased cracking and peeling of the paint film. In addition, the above phenomenon is particularly noticeable on primary rust preventive paint, so there are restrictions such as applying a thin layer of IZP or leaving it outdoors for more than a week after applying the primary rust preventive paint. Rust paint can be applied at any time after painting.
There is a strong need for something that can consistently and consistently coat a sufficiently thick film of 150μ under IZP and any environmental conditions. Conventionally, in order to prevent such cracking, methods have been used to physically prevent cracking, for example by using scaly and large pigments such as mica or glass flakes, or by uniformly mixing them with silicate esters. A method is used in which cracking is prevented by using an organic resin that can be used in combination to take advantage of the film-forming properties of the organic resin. However, when scaly pigments with large particle sizes are used together, problems such as clogging of the nozzle of the painting equipment are likely to occur during painting, and the workability of the painting is greatly reduced, reducing its practicality as a paint. become scarce. Furthermore, if the pigment is of a size that does not pose a problem in painting workability, it cannot be said that the thick coating property is sufficient. on the other hand,
When an organic resin is used in combination, the paint workability and appearance of the paint film are good, but since the organic resin coats and insulates the zinc dust, the contact rate between the zinc dusts decreases and the corrosion protection of the paint film deteriorates. Sexuality becomes worse. Thus, no effective method has been available to prevent cracking in thick IZP films. Problems to be Solved by the Invention The present invention aims to solve the problems of IZP described above, such as cracking and peeling in thick films. Means for Solving the Problems In view of the above points, the present inventors have conducted extensive research and have completed the present invention. That is, the present invention relates to a rust-preventing coating composition that contains as main components a color vehicle containing a silicate ester condensate, zinc powder, and calcium metasilicate. The silicate ester condensate used in the present invention has the general formula (R is an alkyl group having 1 to 8 carbon atoms, n is an integer of 0 or 1 or more, preferably an integer of 1 to 12). The starting materials are monomers and partial condensates such as , ethyl silicate, propyl silicate, isopropyl silicate, butyl silicate, and isobutyl silicate. In this,
Ethyl silicate partial condensates are preferred from the viewpoint of drying properties, adhesion properties, liquid storage stability, etc. As an ethyl silicate partial condensate, ethyl silicate 40
(manufactured by Colcoat Co., Ltd.), ethyl silicate 40 (manufactured by Tama Chemical Co., Ltd.), Silbond 40 (manufactured by Stauffer Chemical Co., Ltd.).
(manufactured by Union Carbide Co), Efhyl Silicate 40 (manufactured by Union Carbide Co)
These raw materials are usually dissolved in a solvent,
It is hydrolyzed under an acid catalyst. As the zinc powder used in the present invention, any conventionally known zinc powder can be used as long as it dissolves Zn and has a sacrificial anode effect. The particle size of the zinc powder used is usually within the range of 1 to 100 microns, but is optimally within the range of 3 to 15 microns. When particles within this optimum particle size range are used, workability during coating becomes good and a coating film having a uniform appearance can be obtained. The amount of zinc dust to be blended into the paint of the present invention is not particularly limited, but is usually 30 to 95% by weight, preferably 50 to 92% by weight in the total blended solid components. It is best to mix zinc powder so that Furthermore, the calcium metasilicate used in the present invention has the chemical formula _CaSiO3 as a main component,
And 100 mesh passes are 99% or more acicular or long columnar fibrous crystalline substances. Typical examples of calcium metasilicate include:
Kemoritz ASB-1, Kemoritz ASB-2, Kemoritz ASB-3, Kemoritz ASB-4, Kemoritz ASB-5 (manufactured by Wolkem),
NYAD400, NYAD325, NYAD1250 (or more)
NYCO A Division of Processed Minerals
Inc.) etc. The calcium metasilicate is blended in a proportion of 1 to 30% by weight in the total solid components of the anticorrosive coating composition. If the above compounding amount is less than 1% by weight, there will be no effect at all in preventing cracking of a thick coating, and on the contrary,
When mixed in an amount exceeding 30% by weight, the effect of preventing cracking of a thick coating film is observed, but since the calcium metasilicate acts as a reaction accelerator for the silicate ester condensate, the color vehicle and zinc Finally, the pot life of the paint after mixing calcium metasilicate is shortened, making it less practical as a paint. A particularly preferable range for the above blending amount is 2
~20% by weight. Effect In the present invention, calcium metasilicate is
What prevents cracking of the IZP paint film is that calcium metasilicate and silicate ester condensate react quickly during the drying process of the paint film. It is estimated that it promotes molecularization, alleviates the distortion caused by shrinkage stress that occurs during the drying process of the IZP coating, and prevents cracking. Furthermore, since calcium metasilicate reacts with the silicate ester condensate, it cannot be used by pre-dispersing it in a color vehicle. Therefore, the form of the paint consists of a liquid component whose main component is a vehicle,
It is a one-liquid, one-powder type with powder components mainly consisting of zinc dust and calcium metasilicate, and these are mixed together at the time of use. Various commonly used coloring pigments and extender pigments can also be added to the composition of the present invention. Furthermore, organic resins such as vinyl butyral, tetraalkyl titanates, trialkyl borates, etc., which are commonly used as additives, can also be added. Furthermore, in order to modify the viscosity of the coating liquid, various thickeners, anti-settling agents, etc. can be added. The anticorrosive coating composition of the present invention as described above is applied onto a steel plate by a conventional method, and a coating film is formed by drying at room temperature or forced drying. Examples Hereinafter, the present invention will be explained by examples. Unless otherwise specified, "parts" or "%" are "parts by weight"
Or "% by weight". Ethyl silicate hydrolyzate solutions shown in the heavy examples and comparative examples were prepared with the following composition. Ethyl silicate-40 (manufactured by Colcoat Co., Ltd.) 100 parts Ethyl alcohol 135 parts Deionized water 10 parts 2% hydrochloric acid 5 parts Total 250 parts The above composition was stirred with a stirrer for 1 hour and reacted, resulting in ethyl silicate hydrolysis. A solution was prepared. Moreover, the nonvolatile content of this hydrolyte solution is 30%. Example 1 Ethylsilicate hydrolyzate solution 100 parts Zinc powder 325 parts Calcium metasilicate (1% in nonvolatile content) Example 2 Ethylsilicate hydrolyzate solution 100 parts Zinc powder 325 parts Calcium metasilicate (in nonvolatile content) 22.7 parts Example 3 Ethylsilicate hydrolyzate solution 100 parts Zinc powder 325 parts Calcium metasilicate (30% in non-volatile matter) 152.1 parts Comparative Example 1 Ethylsilicate hydrolyzate solution 100 parts Zinc Comparative example 2 Ethyl silicate hydrolyzate solution 100 parts Zinc powder 325 parts Calcium metasilicate (proportion in non-volatile matter: 0.5%) 1.8 parts Comparative example 3 Ethyl silicate hydrolyzate solution 100 parts Zinc powder 325 parts Calcium metasilicate Silicate (50% of non-volatile content) 355 parts Comparative example 4 Ethyl silicate hydrolyzate solution 100 parts Zinc powder 325 parts Mica (6% of non-volatile content)
22.7 parts Comparative Example 5 Ethyl silicate hydrolyzate solution 100 parts Zinc powder 325 parts Vinyl butyral resin (34% of non-volatile content) 12.5 parts
Paint on a 90 x 300 mm sandblasted steel plate using an airless coating machine with a sloped film thickness so that the dry film thickness ranges from 30 to 300μ, then place the coated plate in an atmosphere of 20℃ and 75% RH. After being left for 15 days, the film thickness at which cracks began to appear on the coated plate was measured. In addition, SD zinc primer is used as a primary anti-corrosion paint on a 3.2 x 90 x 300 mm sandblasted steel plate.
ZENo.1000HA (manufactured by Kansai Paint Co., Ltd.) was applied using an airless coating machine to a dry film thickness of approximately 20μ, and after drying this coated plate for one day in an atmosphere of 20℃ and 75%RH, the above The compositions of Examples and Comparative Examples were applied onto the primary anti-corrosion coating using an airless coating machine to determine the dry film thickness.
The film thickness was applied with a gradient in the range of 30 to 300μ, and the coated board was then placed in an atmosphere of 20℃ and 75% RH for 15 days, and the film thickness at which cracks began to appear on the coated board was measured. . Furthermore, each composition of the above Examples and Comparative Examples,
A 3.2 x 70 x 150 mm sandblasted steel plate was coated on both sides of the steel plate with an airless coating machine to a dry film thickness in the range of 70 to 80μ, and the coated plate was dried in an atmosphere of 20℃ and 75% RH for 7 days. , investigate the appearance of the paint film,
Thereafter, it was subjected to a salt spray test to test its corrosion resistance. The test results are shown in Table 1.

[Table] Effects As is clear from Table 1 above, the rust-preventive coating composition of the present invention has improved coating film appearance, corrosion resistance, painting workability,
200~300μ without hindering performance such as pot life etc.
It has excellent coating performance that does not cause cracking even in very thick films.

Claims (1)

[Scope of Claims] 1. A rust-preventing coating composition containing a silicate ester condensate, zinc powder, and calcium metasilicate as main components. 2 Calcium metasilicate (CaSiO ₃ ) is
2. The anticorrosive coating composition according to claim 1, wherein 100 mesh passes are 99% or more of acicular or long columnar fibrous crystals. 3. The anticorrosive coating composition according to claim 1, wherein calcium metasilicate is blended in an amount of 1 to 30% by weight in the solid component of the composition.