JPS6113869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the painting process (during painting and setting) and baking process of non-aqueous dispersion-type paints (hereinafter sometimes simply referred to as "non-aqueous paints"). The present invention relates to a method for maximizing the capture of organic solvents and preventing the release of polluting substances into the atmosphere. Non-aqueous paints use significantly fewer photochemically active solvents than conventional organic solvent-based paints, and are low-pollution paints in terms of the types of solvents and the total amount of emitted solvents. Most of the various vapors such as organic solvents generated during the process are released into the atmosphere without any removal treatment. However, even when using low-pollution paints, a coating system that releases as little solvent as possible is required from the viewpoint of preventing pollution caused by atmospheric contamination. The present invention has been completed to solve the above requirements. That is, in the present invention, a resin soluble in an organic solvent is used as a dispersion stabilizer, and a vinyl monomer is dissolved in the presence of the stabilizer, but a polymer formed from the monomer is not dissolved. When applying a non-aqueous dispersion type paint whose vehicle component is a non-aqueous polymer dispersion obtained by polymerizing the vinyl monomer in an organic solvent, the water-soluble organic solvent has a vapor pressure at 20°C. consists of a water-soluble solvent with a pressure of 90 mmHg or less, and the sum of the partial pressures of each solvent is 35 mm
A coating method in which a non-aqueous paint whose main component is a solvent composition that is less than Hg is applied and the paint film is baked, and the vapor generated by evaporation or volatilization during the coating and baking process is vapor-liquid contact method. removed by
This coating method is characterized by preventing the vapor from dispersing into the atmosphere and purifying it. As the non-aqueous paint used in the present invention, a well-known non-aqueous paint is used, but the non-aqueous paint currently used contains an aliphatic hydrocarbon in the solvent. Although this aliphatic hydrocarbon cannot be treated by the coating method of the present invention, most of the remaining solvent components can be treated by the coating method of the present invention. Also, it has become possible to almost prevent air pollution caused by vapors such as solvents generated during the baking process, so it is of high practical value industrially. For non-aqueous paints, aliphatic hydrocarbons are used as the main solvent during the production of dispersion polymers, and the amount of aliphatic hydrocarbons is determined at the stage when the non-aqueous paint is adjusted to the solid state (usually 30% to 50%) at the time of painting. However, in the present invention, the remaining solvent components are water-soluble organic solvents as described below. That is, the temperature of the water-soluble organic solvent used in the non-aqueous paint of the present invention at 20°C.
If the vapor pressure is greater than 90 mmHg, the vapor pressure is high and the absorption efficiency into liquid is significantly poor, making it unsuitable. Therefore, in the present invention, suitable solvents for use in non-aqueous paints have a vapor pressure of 90 mmHg or less at 20°C. In addition, the water solubility of the organic solvent in the present invention refers to the solubility in water at 20°C.
It is 0.5% by weight or more. In the present invention, water-soluble solvents with a vapor pressure of 90 mmHg or less at 20°C include ethanol,
n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, secondary butanol, tertiary butanol, n-amyl alcohol, isoamyl alcohol, secondary amyl alcohol, tertiary amyl alcohol, cyclohexanol,
Alcohol solvents such as ethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,
Glycol ether solvents such as diethylene glycol monobutyl ether, ether solvents such as dioxane and dimethyl dioxane, ethyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, secondary butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl acetate, acetic acid Ester solvents such as ethylene monobutyl ether, ethylene monobutyl acetate, and diethylene glycol monoethyl acetate are suitable. In order to use the above-mentioned solvents in accordance with the gist of the present invention, it is appropriate to use a combination in which the sum of the partial pressures of each solvent is 35 mmHg or less. If the sum of the partial pressures is greater than 35 mmHg, the amount of air discharged from the coating booth during spray painting is usually extremely large in the case of the gas-liquid contact method, which uses a liquid material mainly composed of water, so the amount of air absorbed by the liquid in the gas-liquid contact method is Efficiency becomes extremely poor. The non-aqueous paint in the present invention has resin, the water-soluble organic solvent mentioned above, and an aliphatic hydrocarbon solvent as main components, and the smaller the amount of the aliphatic hydrocarbon, the better. Further, unless the amount of the water-soluble solvent is 70% by weight or more, preferably 80% by weight or more, the effect of using the gas-liquid contact method using a liquid material mainly composed of water in the present invention cannot be exhibited. Suitable gas-liquid contact methods that can be used in the present invention include a scrubber method, a packed column method, a spray column method, a rotating disk method, a multistage column method, and a bubble stirring method. In either case, water or water combined with an appropriate drug can be used as the liquid material. Using water as a liquid material is inexpensive and advantageous in terms of wastewater treatment in the present invention. This gas-liquid contact method absorbs and removes the vapors generated during the painting process and the baking process, but the process may be such that the vapors from each of the above processes are treated together or separately. Furthermore, after absorbing various vapors such as solvents by the gas-liquid contact method, the vapor substances contained therein can be removed by, for example, an activated sludge method, an activated carbon adsorption method, a distillation method, etc. The treated water thus treated (purified) can be reused in the gas-liquid contact method, or if necessary, treated by a conventional method and then drained. Reference examples and examples are shown below. Reference Example Coating Conditions Conventional conventional coating methods (eg, spraying, electrostatic coating, dipping) can be applied to the non-aqueous paint according to the present invention. In order to confirm that the vapor generated during painting and baking can be treated by contacting gas and liquid, the inventor generated the vapor under the following coating and baking conditions. (1) Painting conditions A commonly used no-pump booth (manufactured by Taikisha Co., Ltd.) was used for the paint spray, and air spray painting was performed. The total length of the painting booth at this time was 7 m, and the total exhaust air volume was 640 Nm ³ /min.
The line speed was 3 m/min, and the setting room was 20 m. (In addition, the exhaust in the setting room is 50Nm ³ /
The vapor or volatilized vapor here is connected to the coating booth exhaust air through a duct, and the total exhaust air volume in the coating booth is 640 Nm ³ /min (including this vapor). (2) Baking conditions The baking furnace was a commonly used direct fire type, and city gas was used as fuel. The total length of the furnace was 60 m, the temperature inside the furnace was 160°C, and the exhaust air volume was 70 Nm ³ /min. (In addition, the temperature of the exhaust gas from the baking furnace was 80℃ after passing through heat exchange to reuse the heat.) Example 1 (1) Using a non-aqueous dispersion polymer and a methylated melamine resin produced in a conventional manner, the application material was dispersed and diluted in a conventional dispersion method so as to have the following composition to obtain a one-coat metallic non-metallic resin. Manufactures water-based paints. Non-aqueous dispersion polymer 22.9 parts Melamine resin 9.8 parts Aluminum paste 1.0 parts Other coloring pigments 2.5 parts Triethylamine 0.8 parts Ethylene glycol monoisopropyl ether 15 parts n-Butyl alcohol 5 parts Ethylene glycol monoethyl ether acetate
10 parts Diethylene glycol monoethyl ether acetate 15 parts Solvent naphtha 18 parts Here, the inventor applied and baked the above paint according to the method of the reference example. (At this time, the above paint was sprayed at 600g per minute using an air spray gun.) The vapor discharged from the painting and baking process was absorbed and purified by a gas-liquid contact method in the following manner. (2) Treatment of various types of steam discharged from the painting process Of the 640Nm ³ /min discharged from the painting process,
50Nm ³ /min is passed through a gas-liquid contact packed tower with a diameter of 0.8m and a height of 6m from the bottom to the top.
(manufactured by Toyo Rubber Co., Ltd.) was filled to 3.5 m. The liquid material for gas-liquid contact is a 3-ton tank of tap water that is used every minute.
The flow is adjusted with a flow meter so that the weight is 200Kg, and it flows down from the top. A gas syringe (2 ml) is used from the air outlet and exhaust port to the absorption tower, and the absorption liquid is placed in a glass bottle (100ml).
The solvent was quantitatively analyzed using a gas chromatograph on the air containing the vapor sampled from the circulating water (ml) and the treated liquid that had absorbed the vapor substance. The vapor contained in the exhaust air from the coating process is absorbed into the water (liquid material) by water-soluble organic solvents other than solvent naphtha due to gas-liquid contact, but they are absorbed during the exhaust air from the exhaust port of the packed tower. Due to the vapor-liquid equilibrium relationship of the vapor substance, the amount of the vapor substance in the water increases, and therefore the amount of the vapor substance in the exhaust air increases.
Therefore, based on the total qualitative and quantitative analysis (ppm) of various types of steam by gas chromatography, it was found that the amount of vapor substance at the exhaust port was 20 (80 The gas-liquid contact operation was continued until % absorption efficiency was reached. As a result of operating in this manner, the time required for the air outlet 100 to become the air outlet 20 and the amount of the vapor substance in the circulating water at this time were as shown in Table 1. (3) Treatment of various types of steam discharged from the baking process Of the 70Nm ³ /min exhausted from the baking process
50Nm ³ /min was measured by absorbing each vapor in the exhaust air by contacting the gas with tap water in the same manner as in (2). The results are shown in Table 1. Example 2 (1) Various types of steam discharged from the painting process and baking process are mixed and processed all at once. Painting and baking were carried out in the same manner as in Example 1, and various vapor substances discharged from the painting process and the baking process were mixed in the proportion of the exhaust air volume of each process, and Example 1 (2) was prepared.
Similarly, 50Nm ³ /min was fed into the packed column. That is, 45 Nm ³ /min from the exhaust air from the painting process and 5 Nm ³ /min from the exhaust air from the baking process were mixed, and various vapors were absorbed by tap water and analyzed by bringing the gas into liquid contact in a packed tower. The results are shown in Table 1. Table 1 Due to gas-liquid contact in the packed tower, the vapor flows through the air outlet.
100, the time required to reach the exhaust port 20, the vapor concentration at the ventilation port, the vapor concentration in the circulating water, and the concentration of the vapor substance in the circulating water. 【table】

Claims (1)

[Claims] 1 Using a resin soluble in an organic solvent as a dispersion stabilizer, the vinyl monomer dissolves in the presence of the stabilizer, but the polymer formed from the monomer does not dissolve in the organic solvent. When applying a non-aqueous dispersion type paint whose vehicle component is a non-aqueous polymer dispersion obtained by polymerizing the vinyl monomer, the water-soluble organic solvent must have a vapor pressure of 90 mmHg or less at 20°C. A coating method in which a non-aqueous dispersion-type paint is applied, the main component of which is a water-soluble solvent and whose solvent composition is such that the sum of the partial pressures of each solvent is 35 mmHg or less, and the paint film is baked, The vapor generated by evaporation or volatilization during the coating and baking process is removed by a gas-liquid contact method,
A coating method characterized by preventing the vapor from dispersing into the atmosphere and purifying it.