JP6810420B2 - Undercoat material and coating film forming method using this - Google Patents

Description

The present invention relates to an undercoat material to be applied to the surface of a hold and a coating film forming method using the same.

The surface of the hold of a cargo carrier is covered with epoxy resin paint, but it receives strong impact from both the cargo itself such as coal and ore and heavy machinery such as bulldozers used for loading and unloading, so it rusts and wears due to corrosion. The deterioration of the coating film due to such factors is remarkable. Although efforts have been made to extend the useful life of the coating film by mixing epoxy resin-based paint with highly hard alumina particles, etc., a coating film having a sufficient useful life commensurate with the cost has not yet been developed. Therefore, the surface of the hold is repainted every 1 to 3 years. However, in the case of epoxy resin-based paint, there is a problem that the number of processes is large and the wages are high because it is necessary to remove rust on the surface of the hold by sandblasting or the like.

On the other hand, as one of the rust preventive methods for iron, a method for keeping the surface of iron alkaline and passivating it is known. In general, iron is said to be in a stable state by forming a passivation layer of Fe ₂ O ₃ in the pH range of 9 to 12.5. For example, Patent Document 1 describes a mortar spraying method characterized in that a mortar obtained by mixing polymer cement, aggregate, water, and lithium nitrite solution is sprayed onto a predetermined portion of a concrete structure via a mortar spraying nozzle. The invention is disclosed. In the present invention, the passivation film destroyed by chlorine ions on the surface of the iron material embedded in concrete is regenerated by lithium nitrite to prevent rust formation.

Further, Patent Document 2 discloses an invention of an aqueous coating material obtained by mixing and stirring lithium silicate in a zinc powder-containing slurry prepared by mixing sodium silicate and zinc powder. The zinc powder-containing slurry has excellent stability in water because the zinc powder is covered with a dense film of silica, and the quality does not change even if it is left for a long time. Therefore, by adjusting the water-based coating material using the zinc powder-containing slurry, the water-based coating material has excellent rust prevention properties such as strong adhesion when applied to metal, sufficient hardness of the coating film, and salt spray resistance. A coating material can be obtained.

JP-A-2007-177567 Japanese Unexamined Patent Publication No. 2004-2637

The mortar described in Patent Document 1 is said to have excellent long-term rust prevention properties, but when applied to the surface of a hold, the coating thickness needs to be about 700 μm to 800 μm, and conventional epoxy is used. The cost is 3 to 4 times higher than that of resin paint.
Further, the zinc powder-containing slurry and the water-based coating material described in Patent Document 2 basically provide a water-based zinc rich paint at a lower cost. Zinc rich paint protects steel by acting as a cathode and zinc powder as an anode when a coating film defect that exposes the substrate occurs (sacrificial anticorrosion action). Therefore, there is a problem that the effect of zinc powder cannot be obtained unless the surface of the steel material is completely cleaned.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an undercoat material capable of increasing the strength of a coating film and reducing the base treatment to reduce costs, and a coating film forming method using the same. To do.

In order to achieve the above object, the first invention is an undercoat material to be applied to the surface of a hold.
6-12% by mass of lithium silicate, 3-6% by mass of acrylic copolymer emulsion or acrylic / styrene copolymer emulsion, 2-4% by mass of pigment, 0.2-0.4% by mass of dispersant It is characterized by being composed of a containing aqueous solution.

In the present invention, a strong coating film having rust particles as a skeleton is formed by infiltrating the undercoat material between the rust particles generated on the surface of the hold.
Lithium silicate exists in an aqueous solution as a polysilicate in which chain molecules surround a lithium atom. In the polysilicate structure, after penetrating into the rust layer, a solid continuous coating having a thickness on the order of nanometers is formed on the surface of the rust particles, and the entire rust layer has a strong structure.
However, since it was found that a large number of cracks were generated on the surface of the coating film when the aqueous solution of lithium silicate was cured, in the present invention, an acrylic copolymer emulsion or an acrylic / styrene copolymer emulsion was added to the aqueous solution of lithium silicate. Prevent cracks.
Since the lithium silicate aqueous solution is colorless and transparent, a pigment is added to the lithium silicate aqueous solution to improve the hiding rate (the degree to which the coating film covers the underlying color). At the same time, a dispersant is added to prevent agglomeration of pigment particles.

The second invention is a method of forming a coating film on the surface of a hold.
The process of applying a base treatment to the surface of the hold to make it as clean as 4 types of keren,
A step of applying the undercoat material according to the first invention to form an undercoat layer on the surface of the hold that has been subjected to the base treatment, and
It is characterized by including a step of applying an epoxy resin paint on the undercoat layer to form an overcoat layer.

In the present invention, since the rust layer is used as a film on the surface of the hold, the cleanliness equivalent to that of 4 types of keren is sufficient without the need for the conventional careful surface treatment. An epoxy resin paint with high deformation ability and excellent water resistance is used for the topcoat layer, which requires base followability and a certain level of water resistance.

Further, in the coating film forming method according to the second invention, it is preferable that the epoxy resin coating material contains a metal powder. This improves the wear resistance of the topcoat layer.

In the present invention, by infiltrating the undercoat material between the rust particles generated on the surface of the hold, a strong coating film having the rust particles as a skeleton is formed, so that a high-strength coating film can be realized. In addition, since the conventional careful surface treatment is not required, the cost can be reduced.

It is a schematic diagram for demonstrating the action of the undercoat material which concerns on this invention. This is an elemental mapping of a cross section of a test piece in which an undercoat material is infiltrated into a rust layer remaining on the surface of a steel material. (A) shows Fe, (B) shows O, and (C) shows Si distribution.

Subsequently, an embodiment embodying the present invention will be described with reference to the attached drawings, and the present invention will be understood.

[Technical Idea of the Present Invention]
In the present invention, the undercoat material 12 is infiltrated between the rust particles 11 generated on the surface of the steel material 10 constituting the hold to form a strong coating film having the rust particles 11 as a skeleton (see FIG. 1). Specifically, floating rust and the like in the rust layer are removed, and the undercoat material 12 containing lithium silicate is impregnated into the rust layer remaining on the surface of the steel material 10 to form an undercoat layer integrated with the rust layer.
Lithium silicate contained in the undercoat material 12 penetrates into the rust layer composed of rust particles 11 and then forms a solid continuous film having a thickness on the order of nanometers on the surface of the rust particles to make the entire rust layer a strong structure. ..

FIG. 2 shows an elemental mapping of a cross section of a test piece in which an undercoat material containing lithium silicate is impregnated into a rust layer remaining on the surface of a steel material. For example, in the case of an electron probe microanalyzer (EPMA), constituent elements can be analyzed from the wavelength and intensity of characteristic X-rays generated by irradiating a sample with an electron beam.
2 (A) shows Fe, FIG. 2 (B) shows O, and FIG. 2 (C) shows Si. It can be interpreted that Fe indicates the distribution of steel, which is the base material, O indicates iron oxide, which is rust, and Si indicates the distribution of lithium silicate, and it is shown that lithium silicate has penetrated deep into the rust layer. You can see from 2.

[Undercoat material]
The undercoat material according to the present invention is an undercoat material to be applied to the surface of the ship's warehouse, and contains 6 to 12% by mass of lithium silicate, 3 to 6% by mass of an acrylic copolymer emulsion or an acrylic / styrene copolymer emulsion, and a pigment. It is composed of an aqueous solution containing 2 to 4% by mass and 0.2 to 0.4% by mass of a dispersant.

If the amount of lithium silicate exceeds 12% by mass, not only the slurry concentration increases and the penetrating power into the rust layer decreases, but also cracks occur in the cured coating film. On the other hand, if the amount of lithium silicate is less than 6% by mass, the penetrating action into the rust layer becomes insufficient.

If the amount of the acrylic copolymer emulsion or the acrylic / styrene copolymer emulsion exceeds 6% by mass, the penetrating power into the rust layer decreases. On the other hand, if the acrylic copolymer emulsion or the acrylic / styrene copolymer emulsion is less than 3% by mass, the predetermined flexibility and adhesion strength cannot be ensured.
The mass ratio of lithium silicate to the acrylic copolymer emulsion or the acrylic / styrene copolymer emulsion is preferably about 2: 1.

As the pigment, titanium oxide, aluminum paste, or the like can be used.
If the amount of the pigment exceeds 4% by mass, the penetration of lithium silicate into the rust layer is inhibited. On the other hand, if the pigment content is less than 2% by mass, the hiding rate decreases.

As the dispersant, a wet dispersant, a nonionic surfactant, or the like can be used.
If the dispersant is more than 0.4% by mass, the predetermined adhesion strength cannot be obtained. On the other hand, if the dispersant is less than 0.2% by mass, the pigment particles agglomerate.

[Topcoat material]
As the topcoat material, an epoxy resin paint containing 10 to 15% by mass of metal powder is used.
Alumina or the like can be used as the metal powder.

[Coating film forming method]
The procedure for forming the coating film is shown below.
(STEP-1)
The surface of the hold is subjected to a base treatment that is as clean as 4 types of keren.
Class 4 keren is a base treatment that removes powders and dirt. For example, high-pressure water having a water pressure of about 15 MPa to 25 MPa may be sprayed from a nozzle toward the hold surface to perform a base treatment on the hold surface.

(STEP-2)
The above-mentioned undercoat material is applied to the surface of the hold that has been subjected to the base treatment to form an undercoat layer.
The thickness of the undercoat layer is about 20 μm to 40 μm (a coating amount of about 100 g / m ² ).
The standard drying time is about one day, but it varies depending on the condition of the rust layer.

(STEP-3)
The epoxy resin paint described above is applied onto the undercoat layer to form the overcoat layer.
The thickness of the overcoat layer is about ^{30μm~60μm (160g / m 2 ~320g /} m 2 about the coating amount).
The standard drying time is about one day.

Although one embodiment of the present invention has been described above, the present invention is not limited to the configuration described in the above-described embodiment, and is within the scope of the matters described in the claims. It also includes other possible embodiments and variations.

The verification test carried out for verifying the effect of the present invention will be described.
Table 1 shows the composition of the undercoat material used in the test. An acrylic copolymer emulsion was used as the emulsion, an aluminum paste was used as the pigment, and a wet dispersant was used as the dispersant.

Table 2 shows a list of coating film performance test results performed using the undercoat material shown in Table 1.
There are two types of steel sheets used: untreated naturally exposed rust steel sheet (150 mm x 70 mm x 3.2 mm) and 4 types of Keren naturally exposed rust steel sheet (150 mm x 70 mm x 3.2 mm), and epoxy resin paint is used as the topcoat material. did. Coating method and brushing, coating amount of the undercoat material 100 g / ^{m 2,} and a top coat material 160 g / ^{m 2.} The test piece was cured by air drying in the test room.
The adhesive strength test was carried out according to JIS K5600-5-7 "General paint test method-Part 5: Mechanical properties of coating film-Section 7: Adhesiveness (pull-off method)".

Since the adhesive strength of CASE 1, 5 and 6 was less than 1.0 N / mm ² , the evaluation was set to x (impossible). CASE2 had an adhesion strength of 1.0 N / mm ² or more, but cracks were observed on the surface of the coating film, so the evaluation was set to Δ (OK).
On the other hand, CASE 3 and 4 had an adhesion strength of 1.0 N / mm ² or more, and no cracks were observed on the coating film surface. In particular, CASE4 had an adhesion strength of 1.5 N / mm ² or more. Therefore, the evaluation of CASE3 was evaluated as ◯ (good), and the evaluation of CASE4 was evaluated as ⊚ (excellent).

10: Steel material, 11: Rust particles, 12: Undercoat material

Claims (3)

An undercoat material that is applied to the surface of the hold.
6-12% by mass of lithium silicate, 3-6% by mass of acrylic copolymer emulsion or acrylic / styrene copolymer emulsion, 2-4% by mass of pigment, 0.2-0.4% by mass of dispersant An undercoat material comprising an aqueous solution containing the mixture. It is a method of forming a coating film on the surface of the hold.
The process of applying a base treatment to the surface of the hold to make it as clean as 4 types of keren,
A step of applying the undercoat material according to claim 1 to the surface of the hold that has been subjected to the base treatment to form an undercoat layer, and
A coating film forming method comprising a step of applying an epoxy resin paint on the undercoat layer to form an overcoat layer. The method for forming a coating film on the surface of a hold according to claim 2, wherein the epoxy resin coating material contains a metal powder.