CN103302013A - Spraying technology for low covering power coating - Google Patents

Abstract

The invention discloses a spraying technology for low covering power coating, which is used for solving the problems that the low covering power coating is too thick in a sprayed paint film, consumes more paint material and is poor in appearance quality. The spraying technology adopts the technical scheme that the technology comprises the steps of polishing, the first time of colored paint spraying, the first time of colored paint flashing off, the second time of colored paint spraying, the second time of colored paint flashing off and the like; the spraying technology is characterized in that in the step of the first time of colored paint spraying, the low covering power colored paint and neutral color coating are mixed and sprayed; the ratio of the neutral color coating to the colored paint is 1:4 to 3:1. The technology is used for the low covering power coating spraying, can reduce the thickness of the sprayed film, save 10-30 percent of the colored paint, reduce apparent defects, such as sagging, pinholes and the like, improve the sprayed appearance quality of the colored paint, and meanwhile reduce the VOC (volatile organic compounds) emission of the paint.

Description

A spraying process for coatings with low hiding power

technical field

The invention relates to a spraying method, in particular to a spraying process for spraying low-hiding paint on metal surfaces. the

Background technique

The metal body shell of automobiles needs to be painted. The purpose of painting is to improve the protection and decoration of the car body, enhance the anti-corrosion ability of the car body, and improve the appearance of the car body. Paint spraying is an important link in the painting process, it can give the car colorful colors and bright appearance. In order to improve the decorative appearance of the topcoat, such as fullness and vividness, and reduce defects such as sagging and pinholes caused by too thick a paint film in one pass, the color paint spraying in the coating process is usually designed as two-pass spraying , that is: the second coat of paint after the first coat of paint flashes dry. However, for some low-hiding paints (such as yellow, red, etc.) with a minimum film thickness ≥ 25 μm required for some base paints or a minimum film thickness ≥ 35 μm for natural topcoats, even if the two-pass spraying process is used, there will still be The film thickness of the base paint is too thick due to insufficient hiding power, resulting in paint film defects such as sagging and pinholes, which seriously affect the appearance of the top coat. At the same time, because the paint film to be sprayed is too thick, too much paint needs to be consumed, which increases the corresponding material cost and VOC emissions (emissions of volatile organic compounds).

Contents of the invention

The present invention is used to solve the defects of the above-mentioned prior art, and provides a spraying process for low-hiding paints that can reduce the sprayed film thickness of colored paints and improve the sprayed appearance quality.

The said problem of the present invention is solved by the following technical solutions:

A spraying process for low-hiding paints, which includes the steps of grinding, first-pass color paint spraying, first-pass color paint flash-off, second-pass color paint spraying, and second-pass color paint flash-off steps. The feature is: in the first pass of the color paint spraying step, the color paint with low hiding power is mixed with the neutral color paint and then sprayed, and the ratio of the color paint and the neutral color mixture is neutral color: color paint=1: 4～3:1.

In the above spraying process for low hiding power paints, the color of the neutral color paint is between gray and white, and the lightness of the neutral color paint is greater than 50.

In the above spraying process for low hiding power paints, the film thickness of the first color paint spraying is controlled at 20-25 μm, and the film thickness of the second color paint spraying is controlled at 20-25 μm.

In the above spraying process for low hiding power paints, the color paint and the neutral color paint adopt the same system paint.

In the above spraying process for low hiding power paints, the flash-off time of the first color paint is 60 s to 180 s, and the flash-off time of the second color paint is 8 to 12 minutes.

The present invention improves the problems of too thick sprayed paint film of low hiding power paint, consumption of paint materials and poor appearance quality: for the low hiding power color paint and the neutral color of the same system in a certain proportion when spraying for the first time Spray after mixing to improve the hiding power of the color paint and reduce the film thickness; use the color paint without mixing for the second time of spraying. Since the first spraying is mixed with a neutral color, it is equivalent to diluting the color. At this time, the hue of the two-sprayed color paint does not change, and the cover will not change significantly when the second color paint is sprayed. The film thickness of the second spraying will not increase, so as to achieve the purpose of reducing the film thickness of the color paint spraying and reducing material consumption. The invention is used for the spraying of paints with low hiding power, which can reduce the spraying film thickness, save 10-30% of colored paints, reduce appearance defects such as sagging and pinholes, improve the appearance quality of colored paints sprayed, and can also reduce paint VOC emissions.

Detailed ways

The traditional automobile painting process is as follows: Primer (substrate) - intermediate coating spraying - intermediate coating flash-drying - intermediate coating drying - grinding - the first color paint spraying - the first color paint flash-drying - the second time Paint spraying - second paint flash-drying - varnish spraying - varnish flash-drying - paint drying. The present invention aims at the problem that the film thickness of the color paint is too thick and seriously affects the appearance quality due to insufficient hiding power in the coating process of the paint with low hiding power. Steps such as drying, second color paint spraying, and second color paint flash-drying have been improved (flash-drying refers to the drying of paint, for solvent-based paints, flash-drying is done by the natural volatilization of solvents, and for water-based paints, pre-baking is required. The hot air in the drying room will take away the moisture and solvent for flash drying), the main points of improvement are reflected in the first color paint spraying step, the specific method is as follows: After using low hiding power paint (such as yellow, red) When spraying, the first color paint spraying step is to mix the neutral color with the color paint and then spray. Neutral colors refer to various shades of gray series composed of black, white, and black and white. They are called achromatic systems, also known as neutral colors. The color of the neutral color is usually very soft, the color is not bright and dazzling, it is a color between the three major colors red, yellow, and blue, and it is neither a cool nor a warm color. The neutral color in the present invention refers to a neutral color paint between gray and white, the lightness of the neutral color is greater than 50, the mixing ratio of the neutral color and the color paint is, neutral color: color paint=1 :4～3:1. Color paint and neutral color should use the same system (referring to the same resin system) paint. In the first spraying, the color paint and the neutral color of the same system are mixed according to a certain proportion and then sprayed. Since the hiding power of the neutral color is better than that of the low hiding power color paint to be sprayed, adding the neutral color can improve the color of the color paint. The covering power can be reduced, and the film thickness can be controlled at 20-25μm; the second spraying is carried out without mixing, and the film thickness can also be controlled at 20-25μm. Since the first coat is mixed with a neutral color, it is equivalent to diluting the color. At this time, the hue of the color paint sprayed twice does not change, the cover will not change significantly when the color paint is sprayed for the second time, and the film thickness of the second time spraying will not increase. In order to achieve the purpose of reducing the thickness of the paint spraying film, improving the spraying quality and reducing material consumption.

After the first coat of color paint is sprayed, the first coat of paint flash-dry is carried out, and the flash-dry time of the first coat of paint is 60 s to 180 s to avoid bleeding between the two coats. Then carry out the second time color paint spraying, the coating that the second time color paint spraying is original color paint. After the second color paint is sprayed, the second color paint is flash-dried, and the second color paint flash-dry time is 8 to 12 minutes. Afterwards, the finish paint is sprayed. After the finish paint flashes dry, it enters the steps of color paint drying and strong cooling.

The spraying process of the present invention includes the first pass of color paint spraying, the first pass of color paint flashing, the second pass of color paint spraying, the second pass of flash drying and the like. Several specific examples of the above-mentioned steps are given below:

Embodiment 1: the low hiding power color paint that is sprayed is engineering yellow, and the hiding power of engineering yellow is 40 μ m (the actual spraying film thickness is about 45 μ m. The spraying hiding power of color paint is the minimum film thickness required to cover the base color, for To ensure that the base color can be covered, the actual spray film thickness must be greater than the film thickness required by the covering power). In the first color paint spraying step, the neutral color Haoyue White paint of the same system is mixed with the color paint, and the mixing ratio of Haoyue White: Engineering Yellow is 3:1. The film thickness of the first color paint spraying is 20 μm. The flash drying time of the first coat of color paint is 60 s. The coating used for the second pass of color paint spraying is engineering yellow paint, and the film thickness of the second time color paint spraying is 20 μm. The second coat of paint flashed dry for 8 minutes.

Example 2: The low hiding power paint sprayed is classic yellow, and the hiding power of classic yellow is 55 μm (the actual sprayed film thickness is about 65 μm). In the first color paint spraying step, the neutral color Haoyue White paint of the same system is mixed with the base paint, and the mixing ratio of Haoyue White: Classic Yellow is 1:4. The film thickness of the first color paint spraying is 25 μm. The flash drying time of the first coat of color paint is 180s. The coating used for the second color paint spraying is a classic yellow paint, and the film thickness of the second color paint spraying is 25 μm. The second coat of paint was flash-dried for 12 minutes.

Example 3: The low hiding power paint sprayed is maple leaf red, and the hiding power of maple leaf red is 45 μm (the actual sprayed film thickness is about 50 μm). In the first color paint spraying step, mix the neutral color Galaxy White paint with the color paint of the same system, and the mixing ratio Galaxy White: Maple Leaf Red is 1:1. The film thickness of the first color paint spraying is 23 μm. The flash drying time of the first coat of paint is 90 s. The paint used for the second pass of color paint spraying is low hiding power color paint maple leaf red, and the film thickness of the second time color paint spraying is 22 μm. The second coat of paint was flash-dried for 10 minutes.

The color paint and neutral color can be mixed before spraying, and the color paint and neutral color can be pre-mixed and put into the paint system, or a method similar to two-component varnish can be added in front of the spraying equipment. The color paints are mixed directly before spraying.

Claims (5)

1. spraying coating process that is used for low covering power coating, it comprise the spraying of reconditioning, first pass colored paint, first pass colored paint dodge do, second time colored paint spraying, second time colored paint dodge and the step such as do, it is characterized in that: in the described first pass colored paint spraying step, the colored paint of low covering power is mixed rear spraying with muted color coating, the ratio that colored paint mixes with muted color is muted color: colored paint=1:4～3:1.

2. the spraying coating process for low covering power coating according to claim 1 is characterized in that, the color of described muted color coating is between grey and white, and the lightness of neutral colored paint is greater than 50.

3. the spraying coating process for low covering power coating according to claim 2 is characterized in that, described first pass colored paint spraying thickness is controlled at 20-25 μ m, and second time colored paint spraying thickness is controlled at 20-25 μ m.

4. the spraying coating process for low covering power coating according to claim 3 is characterized in that, described colored paint and muted color coating adopt with system coating.

5. the spraying coating process for low covering power coating according to claim 4 is characterized in that, described first pass colored paint flash-off time is 60 s～180 s, and second time colored paint flash-off time is 8～12min.