JPH1177061A - Treating agent for spray booth circulating water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make spray mist caught in circulating water stable and non- adhesive and to highly disperse produced coating sludge in a circulating water. SOLUTION: A kind of sepiolite of the chemical formula Si12 Mg8 O30 (OH)4 (OH2 )4 .8H2 O is contained, Since the sepiolite is of low charge, is scarcely affected by other ions when added into circulating water, and is stable and it can be reacted with spray mist to make the mist non-adhesive. Partially flocculated coating sludge is dispersed in the circulating water as particles larger than those of alumina sol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic collection of paint sludge by making paint mist contained in circulating water of a wet-type painting booth non-adhesive, dispersing it in the circulating water, and performing solid-liquid separation by centrifugation. The present invention relates to a treating agent which enables the recovered dewatered paint sludge and is suitable for versatile recyclability.

[0002]

2. Description of the Related Art In a wet coating booth, paint mist that has not adhered to an object to be coated is collected by water, and after solid-liquid separation processing, the treated water is returned to the coating booth and circulated. The recovered paint sludge has been incinerated or discarded in the past, but in recent years, it has also been regenerated and recycled as a filler for underbody paints for automobiles and aqueous emulsion paints for fuel tanks.

[0003] By the way, paint mist contained in circulating water in the coating process of an automobile is composed of a bake-curable paint such as an acrylic-melamine resin paint, and has a high tackiness because it is in an uncured state. When the paint mist having high adhesiveness is collected in the circulating water, paint sludge generated by agglomeration adheres to a circulation pump or a pipe, and eventually causes a problem that circulation becomes difficult. Therefore, conventionally, various treatment agents have been added to the circulating water to make the collected paint mist non-adhesive.

[0004] For example, US Pat.
No. 4,504,395 discloses bentonite clay. U.S. Pat. No. 3,515,575 discloses talc, chalk and the like. However, in the clay mineral-based treating agent, for example, bentonite has a cation exchange capacity of 60 to 1.
Due to the high charge of 00meq / 100g, it is easily affected by electrolyte ions and easily aggregates, and the treatment agent not adsorbed by the paint mist precipitates in the circulation pit. As a result, the concentration of the treating agent in the treated water decreases, so that it is necessary to further add the treating agent and the consumption increases. In addition, the sediment at the bottom of the circulation pit increases, and periodic cleaning is required.

[0005] A large number of various organic treating agents are also commercially available, and the paint mist in the circulating water is aggregated and solid-liquid separated. However, since the circulating water circulates while being stirred,
There is a problem that foaming tends to occur particularly with organic treatment agents. Therefore, a large amount of antifoaming agent is used in combination.However, when regenerating and recycling paint sludge containing a large amount of antifoaming agent, the particle size increases due to powder agglomeration and the quality deteriorates. Become.

On the other hand, JP-A-2-18492 discloses that
A treating agent comprising alumina in pseudo-boehmite or boehmite form is disclosed. According to this treating agent, the paint mist in the circulating water can be made tack-free and coagulated and settled by adding a small amount thereof, so that solid-liquid separation can be easily performed. By the way, in order to collect the paint sludge separated from the solid and the liquid, it is desirable that the paint sludge is floated on the surface of the treated water and is continuously collected. Therefore, conventionally, a treatment agent that aggregates paint sludge as much as possible has been used, and a large amount of air has been entrapped in the venturi to increase buoyancy. However, in this method, the volume of the paint sludge is increased, and water is also entrained at the same time as air, so that the weight and the volume of the paint sludge are increased.

[0007] That is, the work of lifting heavy and bulky paint sludge from the circulation pit requires a manual operation, so that the man-hour is increased. When the paint sludge is settling, the man-hour is further increased. Further, even if the paint sludge can be recovered, there is a problem that a step of dehydrating the water contained in the recovered paint sludge is required for recycling.

On the other hand, in Japanese Patent Application Laid-Open No. 5-104008, a stirring device is arranged in a circulation pit, and paint sludge is uniformly dispersed in circulating water by forcibly stirring water mixed with paint sludge and centrifuged. There is disclosed a method of performing solid-liquid separation and dehydration at the same time by supplying the liquid to an apparatus or the like. According to this method, since the paint sludge is dispersed in the circulating water, pumping can be performed. Therefore, by supplying the circulating water to the centrifugal separator by the pump, the solid-liquid separation and the dehydration of the circulating water can be automated, and the paint sludge can be automatically recovered, so that the man-hour can be significantly reduced.

Therefore, by using the processing agent disclosed in JP-A-2-18492 and the method disclosed in JP-A-5-104058, the addition of a small amount of the processing agent makes the coating sludge non-tacky. The paint sludge can be dispersed in the circulating water, and the paint sludge can be easily collected by using a centrifugal separator or the like while preventing adhesion to the equipment.

[0010]

However, Japanese Patent Laid-Open No. 2-1
The alumina-based treating agent disclosed in Japanese Patent No. 8492 has a large amount of consumption because aluminum is an amphoteric metal, and the ionicity and solubility vary depending on the pH, and it is difficult to control the amount of addition depending on the type of paint. There is a problem that the processing becomes uneven. When the consumption of the treating agent is increased, the dispersibility of the paint sludge is improved, but abnormal foaming of the circulating water may occur.

The particle diameter of the paint sludge treated with the alumina-based treating agent is as fine as 10 μm or less.
There is a problem that the centrifugal separation efficiency is low because it is smaller than the appropriate particle size (15 to 30 μm) of the centrifuge. Therefore, in order to improve the paint sludge balance rate of the centrifugal separator, the control standard of the paint sludge concentration in the circulation pit must be increased.

However, in this case, when the paint line is stopped, such as on a holiday, the amount of settled paint sludge increases, and the amount of paint sludge deposited on a circulation path, a circulation pit, or the like may increase. In addition, since the precipitation of fine particles becomes a dense hard cake, it is often difficult to re-emerge and recover with a pump. Furthermore, when the paint sludge treated and recovered by the alumina-based treating agent is mixed with, for example, paint for an underbody of an automobile to be recycled, there is a problem that the initial viscosity becomes unstable and the paint becomes unsuitable for quality standards. Was.

The present invention has been made in view of such circumstances, and can stabilize a paint mist trapped in circulating water in a stable manner, and form a paint sludge with an appropriate particle diameter of a centrifugal separator. An object of the present invention is to provide a treatment agent that can be highly dispersed in circulating water. Another object of the present invention is to provide a treating agent which does not deteriorate the properties of the paint even if the recovered paint sludge is mixed with the paint.
The purpose is to improve recyclability.

[0014]

Means for Solving the Problems The characteristics of the coating booth circulating water treating agent of claim 1 for solving the above-mentioned problems, the formula _{Si 12 Mg 8 O 30 (OH} ) 4 (OH 2) 4 · 8H 2 O
Or sepiolite consisting of Claim 2
The feature of the treatment agent for circulating water in a painting booth described in claim 1 is claim 1.
In the treatment agent for circulating water in a coating booth described in (1), the treatment agent comprises a building bath agent and a replenishing agent, and sepiolite is contained at least in the building bath agent.

Further, a feature of the treatment agent for circulating water in a coating booth according to claim 3 is that, in the treatment agent for circulating water in a coating booth according to claim 2, 1 to 20% by weight of sepiolite and 1% of silica sol are used as supplements. -20% by weight (solid content of silica)
Containing 1 to 10% by weight of silicate and 1 to 3% of carbonate
30% by weight of an alkali auxiliary.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Sepiolite has a low cation exchange capacity of 10 to 15 meq / 100 g, so that it is stable against being affected by other ions when added to circulating water. As a result, it is possible to sufficiently react with the paint mist, and the paint mist is sufficiently made tack-free. Further, the paint sludge which has become tack-free and partially agglomerated becomes larger particles than in the case of the alumina-based treating agent and is highly dispersed in circulating water.

Therefore, the circulating water containing the paint sludge can be supplied to the centrifugal separator by the pump, and the automatic collection of the dewatered paint sludge becomes possible. In addition, even if the control standard for the paint sludge concentration in the circulation pit is lowered, the centrifugal separator can be operated with a high paint sludge balance, and the amount of paint sludge settled when the painting line is stopped can be reduced. . And, since the particle size of the paint sludge is large, even if it settles, it does not become a hard cake and can be easily redispersed, and can be collected when the coating line is restarted.

The dewatered paint sludge discharged from the centrifugal separator has reduced tackiness and curability, and has a low water content, so that it is light even at high density, so that the recovered dewatered paint sludge can be easily handled. This sepiolite is a mineral and is supplied in the form of powder or pellets made of a natural product or a refined product, with a pure content of 80 to 90% by weight, SiO 2
₂ 53-68% by weight, MgO 21-25% by weight, Al ₂
It has a composition of 0.1 to 4.0% by weight of O ₃ and has a three-layer structure in which an octahedral magnesium layer is arranged between two tetrahedral silica layers.

This sepiolite is initially added to the circulating water in powder form at least as a building bath agent. in this case,
The addition amount is about 0.05 to 0.3% by weight based on the circulating water, and the Mg hardness of the circulating water is 100 to 300 pp.
m and pH are desirably 7.5 to 8.5. This increases the magnesium hardness of the circulating water, improves the dispersibility of the tackified paint sludge, and suppresses foaming. If the amount of sepiolite is less than 0.05% by weight, the effect of the addition is not exhibited. If the amount exceeds 0.3% by weight, the effect is saturated and the excess sludge causes a decrease in the paint sludge balance. Failure may occur.

Sepiolite is circulated during processing by adsorption to paint mist, formation of floc by reaction with an electrolyte such as a pH adjuster, or separation of centrifugal separation of sepiolite particles of 10 μm or more, which are coarsened by aggregation. The concentration in water decreases. Therefore, during processing
Replenish the shortage of sepiolite in an appropriate amount,
It is desirable to maintain hardness. That is, it is desirable to add sepiolite as a supplement as needed in a form corresponding to the paint mist mixed into the circulating water.

The sepiolite as a replenisher is preferably added to the circulating water as a slurry. For example, water 8
0-99.5% by weight and sepiolite 0.5-20% by weight
, For example, a COWLES dissolver or SILV
The slurry is preferably formed using a high shear stirring device such as an ERSON mixer. When using sepiolite as a slurry, it is desirable to adjust the viscosity of the slurry using a viscosity modifier in order to prevent precipitation of sepiolite. As this viscosity modifier, 1 to 5% by weight of an acid composed of one or more of hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, butyric acid, propionic acid and lactic acid can be used. In this case, it is desirable to add an acid to a slurry containing sepiolite at a high concentration of 6 to 10% by weight and use it as a pregel.

As the viscosity modifier, 1 to 5% by weight of one or more of a carbonate such as sodium hydroxide, potassium hydroxide and sodium carbonate, a silicate such as sodium silicate and an amine salt can be used. However, care must be taken because excessive addition of electrolyte causes an extreme increase in viscosity. It is preferable to use sepiolite by adding it to circulating water together with silica sol. Sepiolite reacts with the carboxyl group, which is a functional group of paint mist, to generate hydrophobic soap, and charge neutralization by silica sol, the adsorptivity of sepiolite to paint mist increases synergistically. Usage can be reduced. The silanol group of the silica sol also has the effect of suppressing the generation of circulating water.

The silica sol includes acidic anion type (pH 2 to 4, silica solid content 20 to 30% by weight),
Basic anion type (pH 9-10.5, silica solid content 20-41% by weight), cation type (pH 4-5,
Examples thereof include silica solids of 20 to 22), and a cation type serving as a counter ion of a paint mist is preferable, and a cation type coated with alumina is particularly preferable.

The addition amount of the silica sol is desirably in the range of 0.4 to 1.6% by weight based on the paint mist mixed into the circulating water. If the amount is less than 0.4% by weight, the effect of the combined use with sepiolite is not exhibited. If the amount is more than 1.6% by weight, the dispersion tendency of the paint sludge may be increased. Since the concentration of silica sol in the circulating water also decreases during the treatment, it is desirable to replenish the silica sol in an appropriate amount during the treatment, and it is preferable to use an alkali agent as an auxiliary agent as a supplement added to the circulating water. As a result, the usage of sepiolite can be reduced. As the alkaline agent, sodium hydroxide, potassium hydroxide, or the like can be used. However, since it is highly basic and requires careful handling, and there is a concern that foaming may occur in circulating water, sodium carbonate, potassium carbonate, etc. It is desirable to use an acid salt such as a neutral salt of sodium hydrogen carbonate or potassium hydrogen carbonate. The addition amount of the neutral salt or the acid salt is 0.2 to
A range of 1.0% by weight is suitable, and most preferably 0.6% by weight.

It is also preferable to use a silicate as the alkaline agent. The silicate reacts with some of the sepiolite to form flocs, which are absorbed by the paint mist,
The particle size of the formed paint sludge is even larger. Therefore, the recovery efficiency of the paint sludge is improved, and the dewatering property of the paint sludge in the centrifugal separator is also improved. Examples of the silicate include sodium salts such as sodium orthosilicate, sodium sesquisilicate and sodium metasilicate, and potassium silicate. Molar ratio in the case of sodium salt (SiO ₂ / Na ₂ O) is desirably those of 2 to 4, in the case of potassium salts the molar ratio (SiO ₂ / K ₂ O) is 2
3.8 is desirable. The addition amount of these silicates
The range of 0.1 to 0.6% by weight relative to the paint mist is suitable, and most preferably 0.2% by weight. Also, since the concentration of the alkaline agent in the circulating water decreases during the treatment, it is desirable to supply an appropriate amount during the treatment.

As an alkaline agent, sodium carbonate,
It is preferable to use a silicate together with a neutral salt such as potassium carbonate or an acid salt such as sodium hydrogen carbonate or potassium hydrogen carbonate. Thereby, foaming can be further suppressed. That is, as a replenisher, sepiolite is 1 to 20% by weight, preferably 1 to 10% by weight, and silica sol is 1 to 20% by weight (silica solid content), preferably 1 to 10% by weight.
It is preferable to use a main agent consisting of 15% by weight and an alkali auxiliary containing 1 to 10% by weight of a silicate and 1 to 30% by weight of a carbonate.

As described above, the treatment agent for circulating water in the coating booth of the present invention can reduce the amount of treatment agent to be used by dividing the form into a building bath agent and a replenisher. In addition, from the viewpoint of cost reduction, the sepiolite used in the present invention, bentonite, hectorite, montmorillonite,
Smectite, talc, chalk, kaolin, alumina and the like can be used in combination within a range that does not impair the effects of the present invention.

[0028]

The present invention will be specifically described below with reference to examples and comparative examples. FIG. 1 is a configuration explanatory view of a treatment line for a coating booth circulating water using the treatment agent of the present embodiment. The circulation pit 1 is supplied with 2 tons of water, and the pit circulation pump 2 is driven to perform a booth operation with the coating booth 3 at a circulation water amount of 400 L / min.

The circulating water is supplied from the circulating pit 1 to the screw decanter type centrifugal separator 5 by driving the water supply pump 4, the dewatered paint sludge generated by the centrifugal separation is supplied to the container 6, and the water is returned to the circulating pit 1 by the return pipe 7. Returned to The circulating water is sprinkled on the surface of the circulating water of the circulation pit 1 from a sprinkling pipe 8 connected to a water pipe 40 of a water pump 4,
A riser pipe 9 is arranged at the bottom of the circulation pit 1 to stir the circulating water.

In this embodiment, the centrifugal separator 5 is of a screw decanter type. However, in some cases, a separator type (disk type) or a cylindrical type (basket type) may be used. The separation plate type is mainly used for emulsions and suspensions containing a small amount of solids, and the cylindrical type is mainly used for small volume simple separation operations containing particles which are relatively easily separated. In particular, a decanter type is suitable for treating circulating water in a painting booth of an automobile because the circulating pit has a large capacity.

Example 1 In the above processing line, first, sepiolite powder (manufactured by SPAIN / TOLSA, average particle size 3)
25 mesh) and the circulating water has a sepiolite concentration of 0.0
The solution was introduced into the circulating water of the circulation pit 1 so as to be 5% by weight as a building bath agent. Then, while the processing line was being driven, a spray gun was used to spray a total of 5 kg of an intermediate paint for automobile bodies (polyester-melamine baking paint) into the coating booth 3 at a discharge rate of 100 cc / min. At the same time, the replenisher was dropped from the auxiliary tank 11 into the circulating water of the circulation pit 1.

The supplement was 30% by weight of potassium carbonate and 10% by weight.
% By weight of sodium silicate (molar ratio SiO ₂ / Na ₂ O =
2) The total supply of potassium carbonate and sodium silicate in the paint spray is 10% by weight of the paint mist.
It dripped on average so that it might become. The supply amount of the replenisher corresponded to the amount of the paint mist, and the supply of the replenisher was stopped when the paint spraying was completed.

The operating conditions of the centrifugal separator 5 were such that the supply rate was 8 L / min, the centrifugal force was 2000 G, and the pool depth was fixed at a differential speed of 20 rpm in the second stage among the three stages. The centrifugal separator 5 was started to operate together with the water supply pump 4 at the same time as the end of the paint spraying, and then operated for one hour. (Example 2) Sepiolite powder was added as a construction bath agent so that the concentration of sepiolite in the circulating water was 0.1% by weight, and 10% by weight of sodium silicate (molar ratio SiO ₂ / Na ₂ ) was used as a supplement. It is the same as Example 1 except that an aqueous solution containing only O = 2) was used.

Example 3 A slurry containing 20% by weight of sepiolite from the main agent tank 10 was added to 8% by weight of the paint mist.
And 30% by weight of potassium carbonate and 10% by weight of sodium silicate (molar ratio S
An aqueous solution containing iO ₂ / Na ₂ O = 2) was mixed with potassium carbonate and sodium silicate so that the total supply amount was 2% by weight of the paint mist.
It dripped so that it might become. Other conditions are the same as in the first embodiment.

Example 4 15% by weight of sepiolite and 5% by weight of cationic silica sol from the base tank 10
The slurry containing the mixture was dropped so that the total amount of sepiolite and silica sol was 8% by weight of the coating mist, and 30% by weight of potassium carbonate and 10% by weight of sodium silicate (molar ratio SiO ₂ / Na ₂ O) were added from the auxiliary tank 11. = 2) was dropped so that the total supply amount of potassium carbonate and sodium silicate was 2% by weight of the paint mist. Other conditions are the same as in the first embodiment.

Example 5 A slurry containing 10% by weight of sepiolite and 10% by weight of cationic silica sol was dropped from the main agent tank 10 so that the total amount of sepiolite and silica sol was 8% by weight of the paint mist. An aqueous solution containing 30% by weight of potassium carbonate and 10% by weight of sodium silicate (molar ratio: SiO ₂ / Na ₂ O = 2) was supplied from the tank 11 to a tank in which the total supply amount of potassium carbonate and sodium silicate was 2% by weight of the paint mist. The solution was dropped. Other conditions are the same as in the first embodiment.

(Example 6) 5% by weight of sepiolite and 15% by weight of cationic silica sol from the main agent tank 10
The slurry containing the mixture was dropped so that the total amount of sepiolite and silica sol was 8% by weight of the coating mist, and 30% by weight of potassium carbonate and 10% by weight of sodium silicate (molar ratio SiO ₂ / Na ₂ O) were added from the auxiliary tank 11. = 2) was dropped so that the total supply amount of potassium carbonate and sodium silicate was 2% by weight of the paint mist. Other conditions are the same as in the first embodiment.

(Example 7) A slurry containing 20% by weight of cationic silica sol was dropped from the base material tank 10 so that the silica sol was 8% by weight of the paint mist. An aqueous solution containing sodium silicate in an amount of 2% by weight (molar ratio: SiO ₂ / Na ₂ O = 2) was added dropwise so that the total supply amount of potassium carbonate and sodium silicate was 2% by weight of the paint mist. Other conditions are the same as in the first embodiment.

(Example 8) A slurry containing 10% by weight of sepiolite and 10% by weight of alkali anionic silica sol was dropped from the main agent tank 10 so that the total amount of sepiolite and silica sol was 8% by weight of the paint mist.
From the auxiliary tank 11, 30% by weight of potassium carbonate and 10% by weight of sodium silicate (molar ratio SiO ₂ / Na ₂ O =
The aqueous solution containing 2) was dropped so that the total supply amount of potassium carbonate and sodium silicate was 2% by weight of the paint mist. Other conditions are the same as in the first embodiment.

(Example 9) 10% by weight of sepiolite and 10% of acidic anionic silica sol
The slurry containing 10% by weight of the slurry containing 30% by weight was dropped from the auxiliary tank 11 so that the total amount of the sepiolite and the silica sol was 8% by weight of the paint mist.
An aqueous solution containing sodium silicate (molar ratio: SiO ₂ / Na ₂ O = 2) was dropped so that the total supply amount of potassium carbonate and sodium silicate was 2% by weight of the paint mist. Other conditions are the same as in the first embodiment.

Example 10 A slurry containing 10% by weight of sepiolite and 10% by weight of cationic silica sol was dropped from the main agent tank 10 so that the total amount of sepiolite and silica sol was 8% by weight of the paint mist. An aqueous solution containing 30% by weight of potassium carbonate and 10% by weight of sodium silicate (molar ratio: SiO ₂ / Na ₂ O = 3) was supplied from the tank 11 to a tank in which the total supply amount of potassium carbonate and sodium silicate was 2% by weight of the paint mist. The solution was dropped. Other conditions are the same as in the first embodiment.

Example 11 A slurry containing 10% by weight of sepiolite and 10% by weight of cationic silica sol was dropped from the main agent tank 10 so that the total amount of sepiolite and silica sol was 8% by weight of the paint mist. An aqueous solution containing 30% by weight of potassium carbonate and 10% by weight of sodium silicate (molar ratio: SiO ₂ / Na ₂ O = 4) was supplied from the tank 11 to a total supply amount of potassium carbonate and sodium silicate of 2% by weight of the paint mist. The solution was dropped. Other conditions are the same as in the first embodiment.

(Comparative Example 1) In the above treatment line, first, bentonite powder ("Bentoni" Nippon Talc Co., Ltd.)
(Average particle size: 300 mesh) was put into the circulating water of the circulation pit 1 so that the bentonite concentration in the circulating water was 0.1% by weight. 30% by weight from auxiliary tank 11
An aqueous solution containing potassium carbonate and 10% by weight of sodium silicate (molar ratio SiO ₂ / Na ₂ O = 2) was added dropwise so that the total supply amount of potassium carbonate and sodium silicate was 10% by weight of the paint mist. Other conditions are the same as in the first embodiment.

Comparative Example 2 A slurry containing 20% by weight of bentonite was dropped from the main agent tank 10 so that the concentration of bentonite was 8% by weight of the paint mist. Other conditions are the same as in Comparative Example 1. (Comparative Example 3) A slurry containing 15% by weight of bentonite from the main agent tank 10 had a bentonite concentration of 8 of paint mist.
It was added dropwise so as to obtain a weight%. Other conditions are the same as in Comparative Example 1.

Comparative Example 4 A slurry containing 10% by weight of bentonite was dropped from the main agent tank 10 so that the concentration of bentonite was 8% by weight of the paint mist. Other conditions are the same as in Comparative Example 1. Comparative Example 5 A slurry containing 5% by weight of bentonite was dropped from the main agent tank 10 so that the concentration of bentonite was 8% by weight of the paint mist. Other conditions are the same as in Comparative Example 1.

(Comparative Example 6) In the above-mentioned processing line, first, an aqueous solution of alumina sol (alumina concentration: 20% by weight) was introduced into the circulating water of the circulation pit 1 so that the alumina concentration in the circulating water was 0.1% by weight. Main agent tank 1
0 to alumina sol aqueous solution (alumina concentration 20% by weight)
Was dropped so that the alumina was 8% by weight of the paint mist. Further, an aqueous solution of sodium hydroxide having a concentration of 30% by weight was dropped from the auxiliary tank 11 so that sodium hydroxide was 2% by weight of the paint mist. Other conditions are the same as in the first embodiment.

(Comparative Example 7) In the above processing line, first, an aqueous solution of alumina sol (alumina concentration: 20% by weight) was introduced into the circulating water of the circulating pit 1 so that the concentration of alumina in the circulating water became 1.0% by weight. Other conditions are the same as in Comparative Example 6. (Comparative Example 8) An aqueous solution of alumina sol (alumina concentration: 20% by weight) was dropped from the main agent tank 10 so that alumina became 16% by weight of the paint mist. Further auxiliary tank 1
An aqueous solution of sodium hydroxide having a concentration of 1 to 30% by weight was added dropwise so that the amount of sodium hydroxide was 4% by weight of the paint mist. Other conditions are the same as in Comparative Example 6.

(Test / Evaluation) In the above Examples and Comparative Examples, the following measurements were performed. (1) Paint sludge balance rate (%) The circulating water on the water supply side and the circulating water on the return side of the centrifugal separator 5 were collected, and each of them was suction-filtered with a 3 μm membrane filter to measure the amount of paint sludge. Then, the paint sludge balance rate was calculated by the following equation, and evaluated by Table 1.

Balance rate (%) = ｛(water supply-side discharge-side amount)
/ Water supply side x100

[0050]

[Table 1] (2) Water content (%) of paint sludge 10 g of dewatered paint sludge discharged from the centrifugal separator 5 into the container 6 was collected, dried at 105 ° C. for 1 hour, and weighed. Then, the water content of the paint sludge was calculated by the following equation, and evaluated by Table 2. Water content (%) = {(weight before drying−weight after drying) / weight before drying} × 100

[0051]

[Table 2] (3) Adhesiveness of dewatered paint sludge (g) 10 g of dewatered paint sludge discharged from the centrifugal separator 5 into the container 6 is collected, hardened into a spherical shape while wiping off the surface water, and placed in the viscometer shown in FIG. did. A weight of 100 g was applied to the spherical sample 13 using the balance 12 for 3 minutes, and after removing the load, water was slowly poured into the beaker 14 with a washing bottle, and water when the balance 12 was separated from the sample 13 was removed. Was measured as the tackiness. And it evaluated according to Table 3.

[0052]

[Table 3] (4) Non-adhesion state of paint sludge Paint sludge in the circulation pit 1 was sampled and evaluated based on Table 4 by finger touch.

[0053]

[Table 4] (5) Foaming property A 1-meter measure was placed in a place where the surface of the circulating water was stagnant in the circulation pit 1, and the maximum foaming height (cm) and the water level (cm) of the circulating water were recorded. The value calculated according to the following equation was defined as the foaming property, and evaluated according to Table 5.

Foamability (%) = ｛(maximum foaming height−water level)
/ Water level x100

[0055]

[Table 5] (6) Dispersibility The dispersibility of the paint sludge in the circulation pit 1 was calculated according to the following equation, and evaluated according to Table 6.

Dispersibility (%) = {(amount of paint sludge−non-volatile content of treating agent) / non-volatile content of spray paint} × 100

[0057]

[Table 6] (7) Dropping stability of the treating agent The dropping weight of the treating agent dropped from the main agent tank and the auxiliary agent tank per minute was measured ten times, and the difference between the maximum dripping weight and the minimum dripping weight was determined and evaluated according to Table 7. did.

[0058]

[Table 7] Table 8 summarizes the compositions of the treating agents of the above Examples and Comparative Examples, and Table 9 shows the results of the above evaluations.

[0059]

[Table 8]

[0060]

[Table 9]

From Table 9, it can be seen that the use of the treating agents of the respective examples makes the paint sludge non-adhesive,
High dispersibility inside. Also, foaming in the circulation pit 1 is reduced. The dewatered paint sludge discharged from the centrifugal separator 5 has low moisture content and low adhesiveness, and thus has excellent handling workability. Further, the treating agents of the respective examples have excellent dropping stability.

On the other hand, in the case of the conventional treatment agent as a comparative example, a defect was found in any of the above-mentioned evaluation items, and it is apparent that the treatment agent of this example has particularly excellent characteristics. (Evaluation of recyclability) The dewatered paint sludge recovered in Example 3 was dried at 150 ° C. for 12 hours, thermally cured, and pulverized to 100 μm or less. The obtained powder was added to each of the four types of underbody paints for automobiles at 10% by weight, and the paints were tested for adhesion, initial viscosity stability, and coating film properties.

A similar test was conducted on the dewatered paint sludge recovered in Comparative Example 7. Further, a melamine resin-based treatment agent and an aluminum hydroxide-based treatment agent were selected as conventional treatment agents, and the same test was performed on dewatered paint sludge obtained by treating in the same manner as in Example 1. Table 10 shows the results. In addition, since there was no difference in the physical properties of the coating films and no good results were obtained, the results are omitted, and only the results of the adhesiveness and the initial viscosity stability are shown.

[0064]

[Table 10] Notation of the result (left side: adhesive property right side: initial viscosity stability) (○: standard passed ×: standard failed) From Table 10, the dehydrated paint sludge obtained by the treating agent of the example is a paint for underbody of an automobile. It can be seen that there is no decrease in the characteristics even when the mixture is mixed, and that the recyclability is excellent.

[0065]

According to the treatment agent for circulating water of a coating booth of the present invention, paint sludge can be made stable and tack-free, so that adhesion of paint sludge to a circulation pump and piping can be prevented. Since the paint sludge has high dispersibility in the circulation pit, circulating water can be supplied to the centrifugal separator by using a pump, and the solid-liquid separation and dehydration can be efficiently performed by the centrifugal separator. Therefore, continuous automatic treatment of the circulating water becomes possible, and the number of steps can be significantly reduced.

Since the paint sludge balance is high, the control standard for the paint sludge concentration in the circulating water can be kept low. Therefore, the amount of paint sludge settled when the painting line is stopped is reduced. And, since the particle size of the paint sludge is large, it can be easily re-floated without forming a hard cake even if settled, and can be easily collected when the coating line is restarted.

The dewatered paint sludge discharged from the centrifugal separator has reduced tackiness and curability, and has a low moisture content, so that it is light even at high density, so that the recovered dewatered paint sludge can be easily handled. The dewatered paint sludge obtained by using the treatment agent for circulating water in the coating booth of the present invention has excellent recyclability without deterioration in properties even when mixed with the paint.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a treatment line for circulating water of a coating booth used in an embodiment of the present invention.

FIG. 2 is a front view of an apparatus for measuring the degree of adhesion of dewatered paint sludge in an embodiment of the present invention.

[Explanation of symbols]

1: Circulation pit 2: Circulation pump 3:
Painting booth 4: Water pump 5: Centrifuge 7:
Return pipe 10: Main agent tank 11: Auxiliary agent tank

Continued on the front page (72) Inventor Shoichi Sakano 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kenichi Tomotsu 1-15-1 Nihombashi, Chuo-ku, Tokyo Inside Japan Parkerizing Co., Ltd. ) Inventor Katsunori Urata 2-22-1, Nihombashi Ningyocho, Chuo-ku, Tokyo Inside Parker Corporation (72) Inventor Toru Sunaga 2-2-1 Nihonbashi Ningyocho, Chuo-ku, Tokyo Inside Parker Corporation

Claims (3)

[Claims] 1. The chemical formula of Si ₁₂ Mg ₈ O ₃₀ (OH) ₄ (O
H ₂₎ paint booth circulation water treating agent which comprises sepiolite consisting of ₄ · 8H ₂ O. 2. The treating agent for circulating water in a coating booth according to claim 1, wherein the treating agent comprises a building bath agent and a replenishing agent, and sepiolite is contained at least in the building bath agent. 3. A replenisher comprising a main agent containing 1 to 20% by weight of sepiolite and 1 to 20% by weight of silica sol (silica solid content), 1 to 10% by weight of silicate and 1 to 3% of carbonate.
The treatment agent for circulating water in a coating booth according to claim 2, comprising an alkali auxiliary containing 0% by weight.