JP3203210B2 - Anticorrosion coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion coating method, and more particularly to a back surface (a ceiling surface of a ballast tank) of a cargo tank of a carrier for transporting animal and vegetable oils having a high pour point such as heavy C oil and palm oil having a high viscosity. The present invention relates to an anticorrosion coating method for providing a long-term anticorrosion property to a place where the temperature becomes high as in the above) and for forming a coating layer having excellent adhesion.

[0002]

2. Description of the Related Art Conventionally, tar epoxy resin coating JIS is usually provided on a ceiling surface of a ballast tank which is a back surface of a bottom portion of a cargo tank of a carrier ship for transporting animal and vegetable oil having a high pour point.
Two or one equivalents are coated with a dry film thickness of 200 to 250 μm. Also, recently, the modified epoxy resin paint is often applied with a dry film thickness of 250 to 300 μm.

[0003] Heavy fuel oil or palm oil has a high viscosity at room temperature and has poor fluidity. Therefore, when loading and unloading, it is necessary to heat the luggage to lower the viscosity and improve workability. Is normal. The heating temperature is often about 50 to 70 ° C, but may be 80 ° C or more. When such a high-temperature object is loaded, the temperature of the ceiling surface of the ballast tank (the back surface at the bottom of the cargo tank) also rises to the same level as the load. After unloading, seawater is injected into the ballast tank, but the seawater in winter is cold and may be 5 ° C or less. By injecting seawater into the ballast tank, the tank is rapidly cooled.

[0004] As described above, the loading, unloading and repeated pouring of water into the ballast tank cause the ceiling surface of the ballast tank to fall within the range of 80 to 5 ° C, sometimes from 80 ° C to 5 ° C.
Due to the instantaneous temperature change to below ℃, the coating film is exposed to an environment in which the expansion and contraction of the coating film is severe. For this reason, there is a problem in that a coating film obtained by using a normal ballast tank coating material causes coating film defects such as peeling and cracking at an early stage, and corrosion and rust easily occur.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, that is, when exposed to an environment in which the coating film expands and contracts sharply due to temperature changes, coating defects such as peeling and cracking occur early. It is intended to solve the problem that corrosion, rust easily occurs, and the problem that rust, blisters, peeling, etc. occur due to permeation of corrosive substances. It is another object of the present invention to provide an anticorrosion coating method capable of exhibiting anticorrosion and rust prevention effects over a long period of time and forming a coating film layer having excellent adhesion.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and have found that after applying an organic or inorganic shop primer, a flexible epoxy resin is blended in a specific amount. It has been found that the above object can be achieved by applying the above paint, and the present invention has been achieved. That is, the anticorrosion coating method of the present invention includes: (i) a step of applying a shop primer on an object to be coated and drying at room temperature; and (ii) a flexible epoxy resin (solid content) on the generated shop primer coating. Occupies 1 to 30% by weight of the total resin solids, and the glass transition temperature Tg of the coating film after coating (hereinafter, referred to as
(Hereinafter simply referred to as Tg) and a step of applying an anticorrosive coating composition having a coating film elongation of 10% or more and drying at room temperature.

[0007]

Embodiments of the present invention will be described below in detail. Examples of the shop primer that can be used in the anticorrosion coating method of the present invention include a wash primer, a zinc-rich primer, and a non-zinc primer, and a zinc-rich primer is particularly preferable.

Examples of the vehicle of the organic zinc-rich primer include a combination of an epoxy resin and a polyamide resin, a chlorinated rubber, a polystyrene resin, and a silicone resin. Examples of the inorganic zinc-rich primer vehicle include ethyl silicate, lithium silicate, sodium silicate, potassium silicate, ammonium silicate, and the like. Lithium silicate.

In the anticorrosion coating composition which can be used as a top coat in the anticorrosion coating method of the present invention, the flexible epoxy resin (solid content) accounts for 1 to 30% by weight of the total resin solids. This is an anticorrosion coating composition in which the Tg of the subsequent coating film is 50 ° C. or more, and the elongation percentage of the coating film is 10% or more. As the flexible epoxy resin, polyethylene glycol glycidyl ether type, polypropylene glycol glycidyl ether type, glycidyl ether type of bisphenol A alkylene oxide adduct, glycidyl ether type of bisphenol A polymerized fatty acid adduct,
Representative examples include, but are not limited to, various epoxy resins of the dimer acid diglycidyl ester type, and mixtures of two or more of these.

[0010] The anticorrosion coating composition which can be used in the anticorrosion coating method of the present invention contains the above-mentioned flexible epoxy resin as an essential component. The components are contained in the same mixing ratio.
That is, the anticorrosion coating composition that can be used in the anticorrosion coating method of the present invention includes, in addition to the above flexible epoxy resin, an amine-cured epoxy resin, an isocyanate-cured polyol resin, a chlorinated resin, a cumarone indene resin, and a chloride. Vinyl resins, xylene resins, ketone resins, petroleum resins, bitumens such as coal tar pitch and swollen charcoal, or binders such as mixtures of two or more thereof, xylenes, aromatic hydrocarbons such as toluene, alcohols, It can contain organic solvents such as ketones, and if necessary, coloring pigments such as titanium oxide, iron oxide, and carbon black; extenders such as talc, calcium carbonate, barium sulfate, and mica; and other precipitation inhibitors And various additives such as a flow stopper, a repelling inhibitor and the like.

In the above anticorrosion coating composition, the flexible epoxy resin (solid content) is 1 to 30% by weight, preferably 3 to 25% by weight of the total resin solids including the flexible epoxy resin.
Accounts for% by weight. When the content of the flexible epoxy resin (solid content) is less than 1% by weight of the total resin solid content, the effects intended in the present invention become insufficient, which is not preferable.
Conversely, if the content exceeds 30% by weight, the coating film does not have sufficient physical strength, and the tendency to cause coating film defects is undesirably increased.

The above anticorrosion coating composition has a Tg of a coated film of 50 ° C. or more, preferably 70 ° C. or more, and an elongation of the coated film of 10% or more, preferably 12% or more. It is. If the Tg of the coating film after coating is less than 50 ° C., the coating film tends to deteriorate quickly in a high-temperature environment, which is not preferable. Further, when the elongation percentage of the coating film is less than 10%, it is not preferable because the coating film tends to have difficulty in relaxing the stretching stress due to an instantaneous temperature change.

In the anticorrosion coating method of the present invention, first, the shop primer is applied by spraying, brushing or the like to the steel surface which has been sufficiently rusted off by sand blasting or shot blasting. In the anticorrosion coating method of the present invention, the dry thickness of the shop primer is 10 to 30 μm, preferably 10 to 20 μm.
It is. When the film thickness is less than 10 μm, it is difficult to obtain the desired anticorrosion property. Conversely, when the film thickness exceeds 30 μm, cohesive failure easily occurs inside the dry coating layer of the shop primer. It is not preferable because the coating film layer is easily peeled off due to slight impact, mechanical stress or thermal shock. On the shop primer coating film obtained by drying the shop primer at room temperature, brush the anticorrosion coating composition, spray coating machine,
The thickness of the dried coating film is 200-500μ by a roller etc.
m, preferably 250 to 300 μm, and dried at room temperature to finish.

[0014]

The present invention will be described below in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the examples and comparative examples, "parts" is "parts by weight". First, each shop primer and each anticorrosion paint composition having the following composition were prepared. Preparation of zinc rich primer:

[Formulation 1] Zinc powder 30 parts Rust preventive pigment 5 parts Heat resistant pigment 13 parts Precipitation inhibitor 3 parts Isobutanol 13 parts Isopropanol 13 parts Toluene 13 parts Ethyl silicate solution 10 parts (Ethyl silicate solution was mixed at the time of use) .

[Formulation 2] Zinc powder 70 parts Ethyl silicate solution 10 parts Toluene 10 parts Cellosolve solvent 10 parts (Zinc powder was mixed at the time of use).

[Formulation 3] Epoxy resin 6 parts Zinc powder 75 parts Precipitating inhibitor 2 parts Xylene 10 parts MIBK 5 parts Modified polyamine resin 2 parts (Modified polyamine resin was mixed at the time of use).

In Formulas 1 to 3, the solid content concentration of Colcoat 40 (trade name, manufactured by Nippon Colcoat Co., Ltd., a chain or branched condensate of tetraethylorthosilicate having an average degree of condensation of about 4 to 5) in Formulations 1 to 3 was used. 40
% Alcohol solution), an epoxy resin having an epoxy equivalent of 450 to 500 was used as the epoxy resin, and a modified polyamine resin having an amine value of 80 to 120 was used as the modified polyamine resin.

Preparation of anticorrosion coating composition: Of the components shown in Table 1 below, all components other than the polyamine resin and the polyamide resin component which are curing agents are the amounts shown in Table 1 (parts by weight).
Each mixture was kneaded at a ratio in a sand mill for 2 hours to prepare each formulation. Immediately before coating, a polyamine resin or a polyamide resin component was mixed with the blended components in the amounts (parts by weight) shown in Table 1 to prepare an anticorrosive coating composition.

Examples 1 to 6 and Comparative Examples 1 to 6 Shot blasted steel (JIS G 3101, 70 ×
(150 × 3.2 mm) was degreased with xylene and dried. Next, a shop primer having a formulation number shown in Table 2 was applied by air spray so that the dry film thickness became 15 ± 5 μm, and dried at 20 ° C. and 75% RH for 7 days to obtain a shop primer coating film. . Then, a dry film thickness of 250 to 30 was applied to the anticorrosive paint composition having the composition number shown in Table 2 on the shop primer coating film by air spray.
It was applied to a thickness of 0 μm and dried at 20 ° C. and 75% RH for 7 days. The obtained coated plate was subjected to a heat cycle test and a 90 ° C. salt water immersion test by the following methods.

<Heat cycle test>
The mixture was heated to 0 ° C. and then immersed in 5 ° C. ice water. After repeating this operation 10 times, the test plate was immersed in a container filled with a 3% by weight saline solution, kept at 60 ° C., and allowed to stand for one week. This operation was defined as one cycle, and the operation was performed for 15 cycles. <90 ° C. Salt Water Immersion Test> The test plate was immersed in a container filled with a 3% by weight saline solution, kept at 90 ° C., and allowed to stand for 4 months.

After the heat cycle test and the 90 ° C. salt water immersion test, the adhesion of the coating film was measured, and the appearance of the coating film was observed. Further, the rate of decrease in the adhesion of the coating film was determined from the adhesion of the coating film before the test and the adhesion of the coating film after the test. These were evaluated based on the evaluation criteria of Table 3 below. The results were as shown in Table 4 below. Further, the elongation percentage and Tg of each isolated coating film were measured, and the relationship with the coating film performance was grasped.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

As is clear from the evaluation results shown in Table 4, the coating films obtained by the methods of Examples 1 to 6, which are the anticorrosion coating methods of the present invention, have excellent anticorrosion properties and durability. Was. On the other hand, in the case of Comparative Example 1 in which the blending amount of the flexible epoxy resin exceeds 30% by weight of the total resin solids, the physical strength of the coating film was insufficient, and the heat cycle test was conducted. It could not withstand the 90 ° C. salt water immersion test. In the case of Comparative Examples 2, 5, and 6 using a coating composition in which the elongation percentage of the coating film after coating was less than 10%, the heat cycle resistance was poor, and the elongation percentage of the coating film after coating was 10%. %, The heat cycle resistance and the 90 ° C. salt water immersion were both poor in the case of Comparative Example 3 using a coating composition in which the Tg of the coating film was less than 50 ° C. and the Tg of the coating film after coating was 50 ° C. In the case of Comparative Example 4 using a coating composition of less than 90 ° C., the salt water immersion property at 90 ° C. was poor, which was not preferable.

[0028]

The anticorrosion coating method according to the present invention is an anticorrosion coating method capable of forming a coating film capable of relaxing expansion stress due to temperature change and maintaining the anticorrosion property for a long period of time. Suitable for painting places subject to temperature changes.

Continuation of the front page (56) References JP-A-6-71223 (JP, A) JP-A-3-42078 (JP, A) JP-A-59-222275 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) B05D 7/24 302 B05D 7/14 C09D 5/08 C09D 163/00

Claims (1)

(57) [Claims] (1) a step of applying a shop primer on an object to be coated and drying at room temperature; and (ii) a step of applying a flexible epoxy resin (solid content) to the total resin solid content on the generated shop primer coating film. And the glass transition temperature Tg of the coated film after coating is 50 ° C.
A method for applying an anticorrosive coating composition having an elongation percentage of 10% or more and drying at room temperature.