JPH09227808A - Water-base metallic coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-base metallic coating material which hardly causes sagging even when applied by spray coating and of which the metallic pigment is uniformly oriented almost parallel to a coated surface, by using an organic solvent mixture comprising a water-soluble low-boiling solvent and a high-boiling solvent different in boiling point by at least a specified temperature. SOLUTION: The water-soluble low-boiling solvent (A) has such solubility in water that at least 20g thereof dissolves in 100g of water at 20 deg.C, and a boiling point of 100 deg.C or lower. Examples of the solvent A used include methanol and ethanol. The high-boiling solvent (B) is water-soluble or water-insoluble and preferably has a boiling point of 160 deg.C or higher. Examples of the solvent B used include diethylene glycol monobutyl ether and n-octyl alcohol. It is desirable that the difference in boiling point between these two solvents is at least 80 deg.C, especially 100-170 deg.C. It is suitable that the solvents A and B respectively account for 10-90wt.% and 90-10wt.% of the total weight of the mixture. The concentration of these two solvents when applied by spray coating is preferably 5-50wt.% based on solids. The suitable humidity in a coating atmosphere is 50-90%, and the suitable film thickness is 10-30μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based metallic paint having a coating film with excellent metallic feeling and smoothness.

[0002]

2. Description of the Related Art A water-based metallic paint is mainly composed of a vehicle component, a metallic pigment and water. In particular, when spray coating under high humidity by electrostatic method or spray method, since the volatility of water is slow, the coating film is liable to sag, and the metallic orientation is not sufficient.

[0003]

DISCLOSURE OF THE INVENTION The present invention aims to eliminate the above-mentioned defects in an aqueous metallic paint, and by using a water-soluble low-boiling solvent having a boiling point difference of 80 ° C. or more and a high-boiling solvent in combination, It has been found that even if spray coating is performed below, the coating does not easily sag, and the metallic pigment is uniformly oriented almost parallel to the coated surface.

[0004]

Means for Solving the Problems That is, the present invention is an aqueous metallic paint obtained by adding an organic solvent, wherein the organic solvent comprises a water-soluble low boiling point solvent and a high boiling point solvent,
Moreover, the present invention relates to a water-based metallic coating material in which the boiling point difference between the both solvents is 80 ° C. or more.

The aqueous metallic coating material of the present invention is a coating material containing a vehicle component, a metallic pigment, a water-soluble low-boiling point solvent, a high-boiling point solvent and water as main components.

The vehicle component is composed of a base resin and a cross-linking agent. The base resin is a cross-linking agent such as an acrylic resin, a urethane resin, a polyester resin and an alkyd resin having a cross-linkable functional group such as a hydroxyl group, a carboxyl group and an epoxy group. Examples thereof include blocked polyisocyanates capable of reacting with these functional groups, melamine resins, and carboxyl group-containing compounds.

Metallic pigments include aluminum, mica,
Flake pigments such as colored mica and micaceous iron oxide are preferred. 3 to 50 parts by weight of these metallic pigments are suitable for 100 parts by weight (solid content) of the vehicle component. Furthermore, organic pigments, inorganic pigments, and the like can be blended as necessary.

In addition to these, it is essential that the water-based metallic coating material of the present invention contains an organic solvent composed of a water-soluble low boiling point solvent and a high boiling point solvent.

That is, when a water-based metallic paint containing such an organic solvent is spray-coated under high humidity, most or all of the water-soluble low-boiling point solvent evaporates by the time the spray-paint particles adhere to the object to be coated. The solid content concentration of the coating film increased and its viscosity also increased, the coating film was less likely to sag, and the metallic pigments were easily oriented in parallel. Moreover, since a high-boiling solvent is also present, even if the solid content concentration of the coating film increases, its viscosity does not rise sharply and the finished appearance does not deteriorate.

In the water-soluble low boiling point solvent, "water-soluble" means that the solubility in 100 g of water is 20 g or more at 20 ° C.,
It is particularly preferably 100 g or more. Although the boiling point is not particularly limited, it is preferably 100 ° C. or lower, particularly 85 ° C. or lower, and specifically, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, dioxolane and the like are particularly preferable.

The high boiling point solvent may be either water-soluble or water-insoluble, but the latter is preferred. Here, “water-soluble” means that the solubility in 100 g of water is about 20 g or more at 20 ° C., and less than that is water-insoluble. The boiling point is not particularly limited, but is preferably 160 ° C. or higher, particularly 180 ° C. or higher, and specifically, diethylene glycol monobutyl ether (water-soluble), 2-ethyl-1-hexanol (water-insoluble), diisobutyl ketone (water-insoluble). Sex), ethyl acetoacetate (water-insoluble), ethyl benzoate (water-insoluble), N-methylpyrrolidone (water-soluble), triethylbenzene (water-insoluble), 2-ethylhexyl acetate (water-insoluble), diethylene glycol acetate Examples thereof include monobutyl ether (water-insoluble), ethylene glycol dibutyl ether (water-insoluble), and n-octyl alcohol (water-insoluble).

In the present invention, the difference in boiling point between the water-soluble low-boiling solvent and the high-boiling solvent is 80 ° C. or more, and particularly 100 to 170.
C. is preferred. If this difference is less than 80 ° C and the amount of low boiling point solvent is large, the amount of volatilization during coating is large, while if the amount of high boiling point solvent is large, the residual rate in the coating film is large. It is not preferable because it is difficult to control the properties and viscosity and the object of the present invention cannot be achieved.

The mixing ratio of the water-soluble low boiling point solvent is 10 to 90%, especially 30 to 7 based on the total weight of the both solvents.
0%, the high boiling point solvent is 90 to 10%, particularly 70 to 30%.

The ratio of the both solvents in the water-based metallic paint of the present invention is 5 to 5 per solid content in the paint during spray coating.
50% by weight, especially 10 to 30% by weight is preferred.

The method for coating the aqueous metallic paint of the present invention is, for example, using a vehicle component, a metallic pigment and both organic solvents, and further adding water to give a viscosity of 15 to 65 seconds /
It is suitable to adjust the temperature of the Ford cup # 4/20 ° C. and perform this with an atomizing type such as an automatic air atomizing coater, an electrostatic centrifugal atomizing type bell coater, or a manual air atomizing coater. The humidity of the coating atmosphere is preferably 50 to 90%, and the coating film thickness is preferably 10 to 30 μm based on the cured coating film. The heat curing temperature of the coating film is preferably 120 to 160 ° C.

Coating the aqueous metallic coating composition of the present invention and curing the coating film, or without curing it, and further coating the coating surface with a clear coating composition and heat curing to form a top coating film. Is preferred.

As the clear paint, for example, a hydroxyl group,
Main component is a base resin such as acrylic resin, urethane resin, polyester resin and alkyd resin having a crosslinkable functional group such as carboxyl group and epoxy group, and a crosslinking agent such as block polyisocyanate, melamine resin and carboxyl group-containing compound. Thermosetting compositions are suitable and form transparent coatings. Heat curing temperature is 120-1
60 ° C. is preferred.

[0018]

Since the water-based metallic coating material of the present invention uses a water-soluble low-boiling point solvent having a boiling point difference of 80 ° C. or more and a high-boiling point solvent in combination, it does not easily sag even when spray-painted under high humidity. A metallic coating film is obtained in which the metallic pigment is oriented substantially parallel to the coated surface. The water-soluble low boiling point solvent has a high effect of diluting the vehicle component and lowers the viscosity, so that the solid content concentration can be increased and the solid content concentration in the coating film applied to the object to be coated becomes high. The high boiling point solvent swells the vehicle component and increases the viscosity of the applied coating film. The evaporation rate of these organic solvents is almost unaffected by high and low ambient humidity. Therefore, it is possible to increase the solid content concentration when the viscosity of the coating is kept constant by adding a water-soluble low-boiling solvent to the conventional water-based metallic coating, and because it has a low boiling point, it is necessary to coat the material to be coated. Most of it evaporates, the solid content concentration and viscosity of the coating film increase, and the solvent remains in the coating film by using a high boiling point solvent in combination,
When spray coating has good dust compatibility and is insoluble in water, it swells the vehicle component to increase the viscosity of the coating film, improves the orientation of the metallic pigment, and prevents sagging.

[0019]

【Example】

Example 1 Hydroxyl group-containing aqueous acrylic resin 70 parts by weight, methylated melamine resin 30 parts by weight, aluminum pigment 10 parts by weight, water-soluble low boiling point solvent (boiling point 64 ° C., methyl alcohol) 10
By weight, 15 parts by weight of a high-boiling solvent (boiling point 183 ° C, 2-ethylhexanol, water-insoluble) and water were mixed to obtain an aqueous metallic paint having a viscosity of 40 seconds / Ford cup # 4/20 ° C. .

Using a manual air atomization coating machine in an atmosphere with a humidity of 70%, the coating film thickness was set to 2 based on the cured coating film.
Paint to 0μ and leave at room temperature for 7 minutes, then 1
It was heated at 40 ° C. for 30 minutes to be cured. When the coated surface was visually evaluated, there was no sagging after all, and a metallic coating film in which the metallic pigment was uniformly oriented parallel to the coated surface was obtained.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the high boiling point solvent was not used among the organic solvents in Example 1 above. as a result,
When the coated surface was visually evaluated, sagging was clearly observed, and the orientation of the metallic pigment was also non-uniform.

[0022]

Claims (1)

[Claims] 1. A water-based metallic paint obtained by adding an organic solvent, wherein the organic solvent comprises a water-soluble low-boiling solvent and a high-boiling solvent, and the boiling point difference between the both solvents is 80 ° C. or more. Water-based metallic paint characterized by.