JPH0366766A - Rust proof coating material and coating using the same - Google Patents

Abstract

PURPOSE:To obtain the subject rust proof coating material showing quick drying properties especially at the edge part, excellent in rust proof effect and capable of reducing complicated processes such as blasting and polishing by blending an epoxy polymer resin with a vapor phase rust preventive and a specified mixed solvent. CONSTITUTION:With (A) an epoxy polymer resin (preferably urethane-modified epoxy resin), (B) a vapor phase rust preventive (e.g. alkylcarboxylic acid salt or benzotriazole) and (C) a mixed solvent (preferably one composed of 25-55wt.% solvent having <90 deg.C boiling point, 35-60wt.% solvent having 90-120 deg.C boiling point and 20-35wt.% solvent having)120 deg.C boiling point) containing a solvent having <=90 deg.C boiling point in an amount of 10-60wt.% are blended, thus obtaining the objective coating material.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a rust-preventing paint and a coating method using the same. The present invention relates to a rust-preventive paint that can exhibit rust-preventive performance, and a coating method using the rust-preventive paint as an undercoat in powder coating.

[Problems to be solved by conventional techniques and inventions] Conventionally,
For the purpose of preventing rust on metals, PI! is applied to the surface of metal materials such as steel using air spray methods, airless spray methods, electrostatic coating methods, etc. Forming a film (hereinafter referred to as "antirust coating") is widely practiced. In such antirust coating, it is preferable for rust prevention that a coating film of sufficient thickness be formed on the entire surface of the metal.

However, in the past, as shown in Figure 2,
Steel plate with an edge (E) projecting at an acute angle (
In the case of S), there was a problem in that a coating film was less likely to be formed on the end portion (E) than on the center portion (C).

For this reason, we applied blasting to the edges or ground the edges using sandpaper to give them a rounded shape, and after applying the electrostatic coating method, we applied the coating around the edges (covering). Efforts have been made to prevent thinning of the film or breakage of the film at the ends, such as by applying powder coating.

However, this method requires a great deal of labor and time for blasting, grinding, etc., resulting in high coating costs.

In addition, attempts have been made to improve the rust prevention effect at the edges by intensively painting the edges where the coating film is difficult to form, but this has hardly produced any significant effect.

Figure 3 shows a powder coating film (RF) applied to the steel plate (S) using zinc-rich paint as an undercoat anti-corrosion paint, concentrated on the edge (B). This is an enlarged view of the vicinity of the end (the part surrounded by the broken line in Fig. 2) when the PF) is applied by the painting method. 1 roll of steel (S) with Paris (B)
This is an enlarged view of the vicinity of the end when the rust-preventing undercoat 11J (RF) and powder coating (PF) are similarly applied using the electrostatic coating method.

As is clear from both figures, the powder coating melts during baking and drying, and the coating film spreads from the edge (E) or the edge (B) (hereinafter referred to as the "edge, etc.") to the center (C). Since the film is pulled in the direction of , formation of an I film or film breakage occurs at those parts.

As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved by using a specific anticorrosive paint according to the present invention.

That is, although it is not currently clear why the following phenomenon occurs, it is unclear at present even to the inventors of the present invention, but regarding a rust preventive paint containing a polymeric epoxy resin and a volatile rust preventive agent, a solvent with a viscosity of 111 sections specific boiling point IIl as
If you use Kai's mixed solvent, the paint will flow from the center to the edges (a so-called rising phenomenon), and it will be possible to apply a sufficiently thick anti-corrosion coating to edges, etc., where it was difficult to form a coating film in the past. They obtained the surprising finding that membranes can be transformed.

The present invention has been made based on this knowledge, and its purpose is to provide a sufficient thickness even in areas where the anti-corrosive coating is generally not intended to be applied, such as edges. It is an object of the present invention to provide a rust-preventive paint that exhibits excellent rust-preventive performance that can form a coating film of 100% or less, and a coating method that uses the rust-preventive paint as an undercoat for powder coating.

[Means to solve the problem]

The rust-preventive paint according to the present invention (hereinafter referred to as the "paint of the present invention") for achieving the purpose listed in E is a polymeric epoxy resin,
10% of a volatile rust inhibitor and a solvent whose boiling point does not exceed 90"C.
~60% by weight of a mixed solvent.

The above-mentioned polymeric epoxy resins include epoxy-organic polyamines, modified epoxy-isocyanates, epoxy-phenols, which have been conventionally commonly used for paints.
Thermosetting materials such as urea and melamine can be used, but it is preferable to use materials that have excellent drying properties, chemical resistance, and water resistance.Also, quick-drying materials with excellent solvent evaporation properties are preferred. #In order to obtain a paint, it is preferable to use a urethane-modified polymeric epoxy resin.

Commercially available polymer epoxy resins include EVOKEY 5TOSP (product code, manufactured by Mitsui Toatsu Co., Ltd., urethane-modified epoxy resin), PKHH resin (product name, manufactured by Union Carbide), and Arakido KA.
1500 (product code, manufactured by Arayo Kagaku Co., Ltd.) is exemplified.

Note that, normally, those having a weight average molecular weight of about 10,000 to 30,000 can be used.

The above-mentioned volatile rust preventives include alkyl carboxylates, organic amine carboxylates, complexes containing amino salts of polymeric carboxylic acids, mineral-based low-viscosity lubricating oils, benzotriazole, cyclohexyl ammonium cyclohexyl, etc. Preferred examples include carbamate (CMC), diisopropylamine nitrite (D I PAN) and cyclohexylamine nitrite (DrCHAN).

The polymer epoxy resin and the volatile rust preventive agent have a ratio of 4 to 99% of the polymer epoxy resin to the total solid content in the paint.
It is preferable to mix 9% by weight of the volatile rust preventive agent and 0.1 to 5% by weight of the volatile rust preventive agent.

If the amount of polymeric epoxy resin blended is less than 4% by weight, it may be difficult to form a coating, the coating may become sloppy, or it may have poor adhesion to the base material, while if it exceeds 99.9% by weight. If this happens, the rust prevention performance at the edges etc. will decrease.

In addition, if the amount of the volatile rust preventive is 0.1 parts by weight without grooves, the rust prevention performance at the edges etc. will decrease, and if it exceeds 5 parts by weight, the volatile rust preventive will be dissolved. This requires a large amount of alcoholic solvent, and the use of a large amount of alcoholic solvent makes it difficult to dissolve the polymeric epoxy resin and increases manufacturing costs.

As the above-mentioned solvent, those commonly used as paint solvents such as ethers, alcohols, xylene, toluene, and benzene can be used. It is necessary to use a mixed solvent containing within the range of % by weight. This is because, by using a solvent having such a boiling point composition, the above-mentioned swelling phenomenon can be significantly exhibited.

A mixed solvent having such a boiling point composition has a boiling point of 90
An example is one consisting of 10 to 1% of a solvent having a boiling point of less than 120°C, 20 to 80% by weight of a solvent having a boiling point of 90 to 120°C, and 10 to 40% by weight of a solvent having a boiling point of more than 120°C. 25-55% by weight of a solvent with a boiling point of less than 90°C, a boiling point of 90-12
A mixed solvent consisting of 35 to 60% by weight of a solvent at 0°C and 20 to 35% by weight of a solvent whose boiling point exceeds 120°C is more preferred.

In addition, if necessary, one or more types of various pigments such as rust preventive pigments, extender pigments, colored pigments, or metal powder pigments may be added to improve the rust preventive performance, or a new material may be added separately. Functions may be imparted to the paint.

The above pigment is 1 to 9% of the total solid content in the anticorrosive paint.
The content is preferably in the range of 6% by weight.

The paint of the present invention can be applied using various conventionally known painting methods such as air spraying, airless spraying, and electrostatic painting. It goes without saying that it is particularly suitable for use.

In addition, in the case of spray painting, etc., the paint of the present invention can be further diluted with a volatile solvent of the same type as the solvent contained therein to adjust the viscosity to an appropriate value.

Next, a coating method (hereinafter referred to as "method of the present invention") in which the above-mentioned paint of the present invention is used as an undercoat anticorrosive paint for powder coating will be explained.

The gist of the method of the present invention is to first undercoat the object to be coated with the paint of the present invention, dry it, and then topcoat it with a powder coating and bake dry it.

There are two types of powder coatings: thermoplastic powder coatings, which melt when heated and form a coating as they are, and thermosetting powder coatings, which melt when heated and then undergo a crosslinking reaction to harden.Which one should you use? You can also do that.

Examples of thermoplastic powder coatings include vinyl chloride resin powder coatings and thermoplastic polyester powder coatings, and examples of thermosetting powder coatings include epoxy resin powder coatings and thermosetting polyester powder coatings. Examples include body paints and acrylic resin powder paints.

In addition, when using thermoplastic powder coatings, vinyl chloride resin, boria-based resin, polyolefin, polyester, etc.
In addition, when using thermosetting powder coating, epoxy resin,
Polyester, acrylic resin, etc. may be used as the binder.

The method of applying the powder coating is not particularly limited in the method of the present invention, and various conventionally known methods can be used, such as a spray method, a fluidized dipping method, and an electrostatic coating method.

As mentioned above, since the paint of the present invention is a quick-drying paint that contains a predetermined amount of a low-boiling point solvent and is a paint that dries at room temperature, it is usually sufficient to dry it for about 5 minutes at room temperature. In addition, the baking drying may be carried out at an appropriate temperature and time depending on the type of powder coating used. [Examples] The present invention will be explained in more detail based on Examples below. The present invention is not limited to the following examples, and can be modified as appropriate without changing the gist thereof.

(Examples 1 to 4) Anti-T'S paints for undercoat having various weight compositions were kneaded and prepared using a paint charter. Table 1 shows the weight compositions. In Table 1, additive No. 5 is a type of surfactant for improving the dispersibility of solids in the paint. Note that isopropyl alcohol (82.24°C) and methyl ethyl ketone (79.53°C) were used as solvents whose boiling points did not exceed 90°C. In addition, Table 2 shows the resins used for preparing the anti-corrosion paints for undercoating shown in Table 1 (■ to ■ in Table 1).
Indicates the product name, type of polymer, solid content lid, solvent & I precept, and manufacturer.

Each of the above-mentioned undercoat terms wI paints was diluted with a solvent of the same strength as the solvent contained therein, and then spray-painted onto the steel sample Fi having sharp edges, mainly at the edges.

After the above spray coating, the coating film was left to stand at room temperature for 5 minutes to dry and harden. At the edges, the solvent begins to evaporate immediately after spray painting, and the paint begins to harden as soon as it adheres.
A coating film of sufficient thickness was formed at the edges. In Example 1, in which a urethane-modified polymeric epoxy resin was used, the solvent evaporated faster than the others, and drying and curing was completed in about 2 to 3 minutes. Next, a powder coating (manufactured by Kubo Takashi Paint Co., Ltd., trade name "Thiodenyl DMJ") was applied onto the above coating film and baked and dried for 20 minutes at a turbidity of 180°C.During this baking drying, the melted undercoat coating was removed. However, as shown in Figure 1, a sufficient thickness of undercoat with a thickness of about 5μ for rust prevention was applied not only to the center but also to the edges. A coating was formed.

Note that f! due to melting of the powder coating during baking. ! Almost no film displacement occurred. This seems to be because the contact angle of the powder coating with the coating film is smaller than the contact angle (wetting angle) of the powder coating with the steel plate when the powder coating is applied directly to the steel plate, improving adhesion. .

Next, regarding the antirust coating films obtained in Examples 1 to 4 of E, J
An accelerated test using salt water spray was conducted for 120 hours in accordance with IS Z 2371, and the presence or absence of occurrence of corrosion was determined visually to evaluate the anti-corrosion and rust-preventing performance of each anti-M paint.

As a result, no surface defects such as mackerel or corrosion were observed on the edges of any of the rust-preventing coatings formed in Examples 1 to 4.
It was found that the antirust paint obtained in step 4 exhibited excellent antirust performance.

(Comparative Examples 1 to 4) As shown in Table I, a rust-proofing paint for undercoat that does not contain a volatile rust inhibitor (Comparative Example 1 in Table 1) and a rust-proof paint for undercoat that does not contain a polymeric epoxy resin ( In Table 1, Comparative Example 2.
3 and 4) were prepared, and the anticorrosive performance of each anticorrosive paint was evaluated in the same manner as in Examples 1 to 4.

As a result, in Comparative Example 1, some rust was observed. In addition, in Comparative Examples 2 to 4, occurrence of corrosion and corrosion was significantly observed.

Note that the No. 4 dryer used in Comparative Examples 2 to 4 is a desiccant prepared by mixing a lead dryer, a cobalt dryer, and the like.

From the above corrosion and rust prevention performance test results, it is understood that the paint of the present invention has excellent corrosion and rust prevention performance.

(Hereinafter, blank space) [Effects of the Invention] As explained above in detail, according to the paint of the present invention, the paint dries particularly quickly at the edges, etc., so that it is easy to dry the edges, etc., where coating film breakage is likely to occur. Even in this case, a coating film of sufficient thickness is formed, making it possible to obtain a practically satisfactory rust prevention effect. Therefore, the blasting treatment that was previously required,
Complicated processes such as grinding can be reduced.

Furthermore, according to the method of the present invention, the undercoat paint used has excellent adhesion to the object to be coated and dries quickly, so that the powder paint can be topcoated and baked dry in a short time after the undercoat is applied. Therefore, the workability of painting is improved.

Furthermore, according to the method of the present invention, the paint of the present invention used is quick-drying and has a sufficient ability to form a rust-preventing film not only on flat areas but also on edges, so baking drying is performed once after forming the powder coating. It is sufficient to simply carry out this process, and the powder coating process can be simplified.

Furthermore, if the method of the present invention is applied to paint a member that has many pinholes, cracks, etc. that are prone to corrosion, the vaporizable anti-corrosion agent contained in the two paints will remove the pinholes, cracks, etc. It evaporates in the holes and stays there, protecting those parts from rusting.

As described above, the present invention has excellent and unique effects.

[Brief explanation of drawings]

Figure 1 is a partial cross-sectional view of the vicinity of the end of a steel plate that has been powder-coated after being undercoated with the anti-rust paint according to the present invention, Figure 2 is a cross-sectional view of the switch cover, Figures 3 and 4. is a partially enlarged cross-sectional view of the vicinity of the end of a steel plate that has been undercoated with a conventional rust-preventive paint and then powder-coated.

Claims (1)

[Claims] 1. A polymeric epoxy resin, a volatile rust preventive agent, and a boiling point of 9
A rust-preventing paint characterized by containing a mixed solvent containing 10 to 60% by weight of a solvent whose temperature does not exceed 0°C. 2. The anticorrosive paint according to claim 1, wherein the polymeric epoxy resin is a urethane-modified epoxy resin. 3. The amount of the polymer epoxy resin in the solid content is 4 to 99%.
9% by weight and 0.1 to 5 parts by weight of the volatile rust preventive agent.
The anticorrosive paint according to claim 1 or 2, comprising: 4. The anticorrosive paint according to any one of claims 1 to 3, which contains at least one kind of pigment selected from antirust pigments, extender pigments, colored pigments, and metal powder pigments. 5. A coating method comprising undercoating an object to be coated with the rust-preventing paint according to any one of claims 1 to 4 and drying it, then overcoating with a powder coating and baking-drying.