JPH0553828B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating paint slag generated in a factory painting process. In the painting process of mass-producing factories for automobiles, electrical equipment, building materials, etc., thermosetting resin paint is often sprayed, and paint slag is generated during this process. For example, in spray painting of automobile bodies, where a large amount of paint scum is generated, the mist of paint (often baked paint for topcoat) that does not adhere to the car body due to overspray and is suspended in the air in the paint booth is captured by a water film. The paint slag is collected and sent to a separation pit, where some of it floats and some of it settles down to a sticky mud with a moisture content of 30 to 50%. Although there have been various proposals for effectively utilizing paint slag collected in this way (for example, Japanese Patent Publication No. 52-35373), it is difficult to handle due to its high viscosity and strong adhesion, so it is not actually used effectively. The reality is that waste is disposed of by incineration or landfill. However, because the properties of slag are as described above, it takes a lot of effort to handle it for incineration or landfilling.In particular, when incinerating slag, it may soften and flow due to heat, causing abnormal combustion, or Combustion is extremely difficult to manage as it decomposes and releases harmful gases, requiring a special combustion furnace. The present invention provides a method for treating paint slag that turns such paint slag into spongy particles that are not sticky and do not soften or flow when heated, and the purpose is to make the paint slag into a form that is easy to handle. By doing so, it is possible to smoothly and economically collect and utilize the resources as effective resources. The term "sponge-like particles" as used in the present invention does not refer to particles having a sponge-like structure, but rather particles having a sponge-like feel.
The particles are individually irregular in shape, the particle size is not necessarily constant, and includes particles of aggregates of small particles, and the color is not specified. In order to make effective use of paint slag, it is necessary to make it easier to handle it, and as a result of experimenting to reduce the stickiness, we found that the stickiness easily disappears when alkali or acid is added and heated. There was found. It is thought that the loss of tackiness is due to the resin component of the paint slag being changed by the alkali or acid and curing is accelerated, but the reaction mechanism is not clear. When an alkali is added and heated and stirred, the paint slag generally becomes paste-like and does not harden significantly, although it varies depending on the type of paint slag, but when an acid is added, it changes to a sponge-like state containing coexisting water. However, although the particle size changes depending on the stirring conditions, the particles have approximately the same particle size. These particles have no stickiness or heat softening properties that paint slag has, so they can be easily transported and
It is easy to store, and can be used as a filler by drying and pulverizing, or can be processed by combustion without any problems. Therefore, it becomes possible to collect the paint slag and to utilize it smoothly and economically. As the strong acid, either mineral acid or organic acid can be used, but strong acids such as hydrochloric acid, sulfuric acid, and para-toluenesulfonic acid are suitable, with sulfuric acid being the most suitable in terms of availability, ease of handling, and price. . This acid can be used at a concentration that is generally commercially available, or in some cases, the waste acid that maintains strong acidity can be used as it is.
Or dilute with water and use. If the acid is diluted and added, it will contain more water and have better fluidity, making it easier to stir throughout the process. The amount of acid added is 1% or more based on the paint slag, but it is diluted by the 30 to 50% water content of the paint slag, so if the acid is diluted and added, the final acid concentration is 3%. It is desirable to adjust it so that it is more than that. If the temperature is below 50°C, curing will be slow, and if the temperature is above 90°C, the resin component will decompose and harmful gases such as formaldehyde and acrolein will be violently generated, so heating and stirring is preferably from 50 to 80°C. As the curing reaction progresses, the adhesive becomes sponge-like particles containing water and loses its stickiness. The size of the particles changes depending on the strength of stirring, and if stirring is performed such as applying a large shearing force or mixing and stirring such as grinding is performed, the particles become fine. If a small amount of surfactant is added during this curing reaction and the mixture is heated and stirred to cause slight foaming, the fluidity of the reactant increases and the stirring and mixing state becomes better. The surfactant may be anionic, cationic, or nonionic, but for example, dodecyltrimethylammonium chloride is added in an amount of 0.05 to 1% based on the paint slag. Stirring that causes significant foaming or excessive addition of surfactant is unfavorable in terms of operation since reactants overflow from the tank. The acid remaining in the acid-treated paint slag may be neutralized with an alkali such as sodium hydroxide, or it may be removed by washing with water. Since the coarse particles obtained by the treatment of the present invention as described above are non-adhesive particles, it is extremely easy to dispose of them as they are, and since they themselves contain considerable calories and valuable inorganic substances, By incineration, valuable materials can be recovered and used as a heat source. Therefore, the effects of the present invention are extremely large. Example 1 Paint slag (pigment 12%, thermosetting resin 48%, solvent 9
%, water 31%), 5 g of the acid shown in Table 1 and 25 g of water were added to 50 g, and the mixture was heated and stirred at 70 to 80°C. The results are shown in Table 1.

【table】

[Table] Example 2 Paint slag (8% pigment, 42% thermosetting resin, 5% solvent, 5% water) was placed in a 15 volume crutcher-type stirring tank, sulfuric acid and water were added, and the mixture was heated and stirred. The results are shown in Table 2.

[Table] Example 3 A surfactant was added under the same conditions as in Experiment No. 3 of Example 2. The results are shown in Table 3.

【table】

[Table] Example 4 Paint slag (Example 1
(same as above) was charged, 90g of 98% sulfuric acid was added, and the mixture was heated and stirred. Temperature 65-70℃, stirring speed 78r.p.
m. for 15 minutes and neutralized using 200 g of 40% sodium hydroxide. 3.2 kg of particles with a particle size of 0.2-0.5 mm were obtained.

Claims (1)

[Claims] 1 A strong acid is added to viscous spray painting waste containing water and having a solid content of 50% or more, and the waste is then stirred. A method for treating painting waste, characterized by converting it into non-adhesive coarse particles. 2. The treatment method according to claim 1, wherein the strong acid is sulfuric acid, hydrochloric acid, nitric acid, para-toluenesulfonic acid, or a used strong acidic waste acid such as these. 3 The amount of acid used is 1 to 15% of the painted waste to be treated.
% by weight. The treatment method according to claim 1. 4. The treatment method according to claim 1, wherein the strong acid is used diluted. 5. The treatment method according to claim 1, wherein the stirring treatment is carried out in the presence of a surfactant. 6. The treatment method according to claim 1, wherein the stirring treatment is performed under heating at 50 to 90°C. 7. The treatment method according to claim 1, wherein the coarse grains are mainly aggregates that are irregularly shaped and have spongy elasticity.