JPS62244476A - Improved method for anticorrosion painting of metal cast and forged product - Google Patents

Abstract

PURPOSE:To obtain a film having good corrosion resistance by curing at relatively low temp., by a method wherein the under-coating of a specific wash primer is applied to a metal cast and forged product and urethane resin paint is subsequently applied thereto to cure the formed film in an amine atmosphere. CONSTITUTION:A wash primer used as under-coat consists of a base material based on a butyral resin and zinc chromate and a curing agent based on phosphate. This under coat is applied to the surface of a metal cast and forged product such as an iron cast article or an aluminum die cast product and urethane resin paint such as two pack type polyurethane product is subsequently applied thereto to be cured in an evaporated amine atmosphere or the urethane paint may be subjected to atomizing painting by air containing evaporated amine. Because curing can be performed at ambient temp. or at low temp. of 100 deg.C or less in both cases, a corrosion resistant film having no transparent part due to heat flow is obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to castings of ferrous materials and ferrous metal materials, etc.
This invention relates to an improved anti-rust coating method for forged products, that is, various metal casting and forging products.

[Conventional technology]

Conventional anti-rust coating methods for various metal castings and forgings, such as iron castings and aluminum die-casting products, include coating with quick-drying alkyd resin paint or lacquer-type paint and drying the coating at room temperature, or drying the paint film at room temperature. Hori Te El Q n0ρ
~ 1 ward n0ρkadankoφ drying method is used. The corrosion resistance of coatings on metal castings and forgings obtained by such conventional coating methods is only about 72 to 120 hours using the Tsuruto spray method. Therefore, in order to obtain coatings with even better corrosion resistance, A method of baking the painted film using an alkyd-melamine baking-curing paint is used.

[Problem that the invention seeks to solve]

However, in the painting method using the above-mentioned bake-hardening paint, the metal castings and forgings to be coated generally have a large specific heat and are usually thick, so the heat added by baking increases. This method requires a very large amount of heat, and also has the disadvantage that the temperature of the object to be coated increases slowly and baking takes time. Additionally, there may be differences in temperature distribution on the surface of metal castings and forgings, which prevents the coating from curing uniformly, making it difficult to obtain sufficient performance, especially in areas where the coating is insufficiently cured. It also had drawbacks.

In addition, metal rust F2 products generally have a high surface roughness, so the heat flow during heat curing causes the coating film to become thinner at the protruding parts, resulting in so-called see-through, resulting in a decrease in corrosion resistance due to insufficient coating film. It will be done.

Therefore, an object of the present invention is to provide a coating method for forming a coating film having excellent corrosion resistance on metal castings and forgings, which generally have a large surface roughness, without requiring high-temperature baking heat. Use paint at room temperature or 100°
By curing at a low temperature below C, the problem of see-through due to heat flow is solved, and by applying a so-called wash primer as an undercoat, corrosion resistance is further improved.

[Means for solving problems]

The present invention involves painting metal castings and forgings with a two-component wash primer, followed by (A) painting with a urethane resin paint, and curing the paint film in a vaporized amine atmosphere, or (B)
) The urethane paint is atomized with air containing vaporized amine, and when applying rust-preventive coating to metal rust forgings, first apply a wash primer consisting of butyral resin, zinc chromate, and phosphoric acid, and then A coating method characterized by coating with a urethane resin paint and curing the urethane resin paint film in an amine atmosphere in a gaseous state, and when applying anti-corrosion coating to metal castings and forgings, first apply butyral resin. This coating method is characterized by applying a wash primer consisting of , zinc chromate, and phosphoric acid, and then atomizing the urethane resin paint with air containing vaporized amine.

Metal castings and forgings that can be coated using the method of the present invention include castings and forgings made of various iron-based materials, aluminum die-casting products, iron,
There are non-ferrous metal castings and forgings.

The wash primer used in the present invention may be any commonly known two-component wash primer consisting of a base material mainly composed of butyral resin and zinc chromate and a curing agent mainly composed of phosphoric acid.

The urethane resin paint that can be used in the present invention may be any paint that contains a compound or resin having an incyanate group in the vehicle, but two-component polyurethane paints are particularly preferred.

A two-component polyurethane paint consists of a paint component (base material) containing a resin having two or more hydroxyl groups in the molecule, and a compound or monomer or prepolymer (hardening agent) having two or more isocyanate groups in the molecule. ) is a paint that is used by mixing a predetermined amount with before painting.

In the method of the present invention, as the base polyol component of the two-component polyurethane paint, 20 to 95% by weight of an acrylic resin polyol, an alkyd resin polyol, or a polyester resin polyol having a hydroxyl value of 10 or more and an epoxy resin having an epoxy value of 300 to 4,000 are used. Preferably, it consists of 5 to 80% by weight of the resin polyol.

The curing agent components of the two-component polyurethane paint used in the present invention include tolylene diisocyanate and xylene diisocyanate. −, hexamethylene diisocyanate,
3 to 3 of diisocyanate compounds such as isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, lysine diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated inphorone diisocyanate.
Pentamer, furthermore, an adduct obtained by reacting an excess molar amount of the above diisocyanate compound with a dihydric alcohol such as ethylene glycol or propylene glycol or a trihydric alcohol such as glycerin or trimethylolpropane, and furthermore, a polymer thereof. can be used.

The curing agent is used by mixing in a ratio of 0.8 to 1.2 moles of isocyanate groups per mole of hydroxyl groups in the base polyol component.

The above-mentioned base polyol component that can be used in the present invention may optionally contain other resins such as cellulose derivatives, polyvinyl chloride, polyvinyl acetate, and vinyl chloride for the purpose of improving the drying properties, physical properties, and appearance of the coating film. , vinyl acetate copolymer, etc. may be mixed, and pigment solvents and various additives may also be added.

Pigments include colored pigments such as carbon black, iron oxide, titanium oxide, inorganic pigments such as yellow lead, cyanine green, cyanine blue and other organic pigments, and anti-rust pigments such as strontium chrome-1-, lead white, and calcium leadate. ,
Basic lead sulfate, red lead, zinc chromate, barium chromate: Extender pigments such as calcium carbonate, talc,
Clay, barium sulfate, silica powder, etc. can be used. Any solvent can be used as long as it does not react with the curing agent, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, cellosolve acetate, toluene, xylene, and the like.

As various additives, a suspending agent, an antioxidant, a viscosity modifier, a surface modifier, etc. can be used.

The base polyol component of the two-component polyurethane paint used in the present invention has a hydroxyl value of 10 or more, preferably from -0 to 300. If the hydroxyl value is less than 10, the number of urethane bonds generated by the reaction with the incyanate compound will be too small, and the resulting coating will not have sufficient corrosion resistance.If the hydroxyl value exceeds 300, as will be described later, According to the present invention, when exposed to an amine atmosphere, curing at room temperature takes a long time, which is not preferable. In addition, the epoxy resin used in combination has an epoxy value of 300 to 40.
A value of 0.00 is preferable; if it is less than 300, the coating film formed will be insufficiently cured, and if it exceeds 4000, the viscosity of the paint may become too high, making it difficult to coat, and may also cause a decrease in the thickness of the coating film. Therefore, the urethane resin paint used in the unsophisticated method of the present invention contains 20 to 95% by weight of a polyol component with a hydroxyl value of 10 or more, and an epoxy value of 3.
5 to 80% by weight of 00 to 4000 epoxy resin
If the epoxy resin component is less than 5% by weight, the corrosion resistance of the coating film formed will decrease, and if it exceeds 80% by weight, the coating film may be exposed to the amine atmosphere described below. This is not preferred because it takes a long time to cure.

To carry out the method of the present invention, first, the base material of the wash primer described above and a curing agent are mixed at a fixed ratio,
Apply to obtain a film thickness of μ. Next (A> The above-mentioned base polyol component and hardening agent polyisocyanate are mixed and applied to a metal cast and forged product. Furthermore, it may be hardened by exposing it to an amine atmosphere.

Alternatively, instead of (A), (B) the urethane resin paint may be atomized and applied using air containing vaporized amine.

The amines that can be used at this time are preferably tertiary amines, such as aliphatic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, triamylamine, and tetramethylethylenediamine;
Aromatic amines such as diethylaniline, diethylaniline, tribenzylamine, N-methylmorpholine, N-ethylmorboline, or methyljetanolamine,
There are alkanolamines such as dimethylethanolamine, diethylethanolamine, dibutylethanolamine, di(2-ethylhexyl)ethanolamine, ethylenediethanolamine, and dibdelisopropanolamine, among which dimethylethanolamine and tetramethylethylenediamine are preferred.

The amine concentration in the above amine atmosphere or atomizing air is about 10 to 3000 ppm, preferably about 600 to 2
000 ppm, and the ambient temperature is preferably room temperature, but a temperature of 0 to -00°C, preferably 10 to 50°C may be used. It should be noted that the amine atmosphere has a 0.0.
It is preferable to circulate at a wind speed of 5 to 2.0 m/sec.

The time of exposure to the amine atmosphere, that is, the time required to cure the coating film, varies depending on the thickness of the coating film, but is generally 1.
~10 minutes, preferably 2-3 minutes is sufficient. Generally, after processing in an amine atmosphere, it is preferable to blow amine-free air at room temperature to accelerate drying and curing. At this time, room temperature is sufficient as the air temperature, but in some cases, a temperature of 100°C or less, preferably 25 to 50°C may be used.

[For production]

According to the method of the present invention, it is not necessary to heat the coating film or the metal casting and forgings as in the conventional coating method after overcoating the metal castings and forgings using the above-mentioned wash primer and urethane resin paint. As mentioned above, the coating can be cured by brief exposure to an amine atmosphere. As a result, there is no reduction in film thickness due to heat flow as in conventional methods, and there is no variation in film performance due to localized or uneven heating, and as shown in the examples below, corrosion resistance in salt spray tests has been confirmed. An excellent coating film can also be obtained.

〔Example〕

The present invention will be explained below with reference to Examples.

In the text, parts are parts by weight.

Example 1 After polishing a cast iron casting by shot blasting, 7μ of a two-component wash primer (trade name: Wash Primer #20, manufactured by Shinto Toyo Co., Ltd.; base/hardener: 80/20) was applied.
I applied it to make it look like this.

Soto I-way old, l-1-shitadai-yu 2 ito /7'
The paint was applied so that the dry coating film was 30μ.

Base component (acrylic polyol/epoxy resin-60/
40) Carbon black 3.0 parts Sl-rotium romate 5.0 parts Talc
10.0 parts clay
15.0 parts polyacrylic polyol (
Hydroxyl value 25, manufactured by Dainippon Ink Co., Ltd., non-volatile content 50%) 35.0 parts Epicoat 1001 (Epoxy resin with an epoxy value 4 50-500, manufactured by Yuka Shell Epoxy Co., Ltd. > 12.0 parts Thinner 20.0 parts total
100.0 parts Curing agent component: SUMIDULE L-75 (2) (renediisocyanate, manufactured by Sumitomo Bayer Urethane) 14.5 parts After painting, leave to stand at room temperature for 2 minutes, then blow in an atmosphere containing 800 ppm of dimethylethanolamine at a wind speed of 1.2 m/min. The coating was exposed in seconds. Thereafter, it was dried and cured by blowing room temperature air for another 10 minutes.

After another day, cross-cut the paint film with a knife,
After placing it in a salt spray tester for 480 hours, it was taken out, washed with water, and dried. Cellophane tape was pressed onto the cross-cut area, and the tape was peeled off to measure the peeling width of the coating film from the cross-cut area. Within 3 degrees, good corrosion resistance was obtained. In addition, there were no straight chains in the protrusions of the molded product, and the appearance was good.

Example 2 In the same manner as in Example], add 7μ of wash primer.
I applied it to make it look like this.

Next, immediately a two-component urethane resin paint similar to that in Example 1 was atomized with air containing vaporized amine, and coated to a thickness of 30 μm.

The amine used was triethylamine, and its concentration in the air was 6.
It was 00 ppm.

The coating film performance was tested in the same manner as in Example 1.

After being placed in a chloride spray tester for 360 hours, it was taken out, washed with water, and dried. When the peeling of the coating film from the cross-cut portion was measured, it was within 3 degrees at Katayama, indicating good corrosion resistance.

In addition, the straight chain of the mold crystal protrusion is 2 to 2 per 10c+++2.
It was 3 points.

[Comparative Example 1] The coating film was cured at 120°C for 2 hours in an amine-free atmosphere.
Painting was carried out in the same manner as in Example 1, except that baking was performed for 0 minutes.

After 240 hours of the salt spray test, the cellophane tape at the cross-cut portion was peeled off, and although the peeling width was within 3 degrees, many straight chains were generated from the convex portions, resulting in poor appearance.

〔Effect of the invention〕

According to the method of the present invention, it can be dried at room temperature in a short time, and it can be dried at room temperature, which saves energy. It is suitable as a coating method for metal castings and forgings because it eliminates defects such as corrosion-resistant paper coating.

Claims (1)

[Claims] 1. When applying anti-corrosion coating to metal castings and forgings, first apply a wash primer consisting of butyral resin, zinc chromate, and phosphoric acid, then apply urethane resin paint, and leave it in a gas phase. A coating method characterized by curing a urethane resin paint film in an amine atmosphere. 2. When applying anti-rust coating to metal castings and forgings, first apply a wash primer consisting of butyral resin, zinc chromate, and phosphoric acid, and then atomize the urethane resin paint with air containing amine. A painting method characterized by: 3. The coating method according to claims 1 and 2, wherein the urethane resin paint is a two-component polyurethane paint. 4. The base polyol component of the two-component polyurethane paint is an acrylic resin polyol, an alkyd resin polyol, or a polyester resin polyol with a hydroxyl value of 10 or more from 20 to 20.
4. The coating method according to claim 3, comprising 95% by weight of an epoxy resin polyol and 5 to 80% by weight of an epoxy resin polyol having an epoxy value of 300 to 4000, and the curing agent component comprising a polyisocyanate compound.