JP3923913B2 - Wash water reuse method and reuse system - Google Patents

Description

【００３１】
表１の結果より、再利用される洗浄水のＴＯＣ濃度が１０ｍｇ／Ｌ以下で、且つシリコン含有量が５ｍｇ／Ｌ以下である場合に、塗装膜の表面状態が良好であることが確認された。
【図面の簡単な説明】
【図１】 本発明に係る洗浄水の再利用システムの好適な一態様を示す説明図。
【符号の説明】
１・・・洗浄タンク群、１−１・・・主洗浄タンク、１−２・・・副洗浄タンク、１−３・・・ミスト洗浄タンク、２・・・ポンプ、３，１４・・・活性炭塔、４，１５・・・混床樹脂塔、５・・・水質測定器、６・・・高純水タンク、７〜１３・・・バルブ、ａ〜ｄ・・・流路[0001]
[Field of the Invention]
The present invention relates to a reuse method and a reuse system of cleaning water discharged when a chemical conversion coating applied to an alloy workpiece containing at least magnesium and / or aluminum is washed.
[0002]
[Prior art]
When coating an alloy product containing at least magnesium and / or aluminum, for example, a vehicle wheel, the surface of the alloy is subjected to chromate treatment as a pretreatment to improve the coating adhesion between the main paint and the alloy, and a chemical conversion coating Has been given.
[0003]
In the water cleaning of the chemical conversion film, the used cleaning water has been conventionally reused. As a means for reusing used washing water, the used washing water is purified using an ion exchange resin member and reused. The used washing water is separated from the washing section and the ion exchange resin member. The purified wash water was reused by circulating between them (see, for example, Patent Document 1).
[0004]
However, the used cleaning water recycling means described above simply circulates and reuses the cleaning water passing through the ion exchange resin member without considering the purity of the cleaning water. Inadequate paint adhesion due to contamination of used washing water due to exceeding the limit, and waste due to replacement below the exchange capacity of the ion exchange resin occurred.
[0005]
[Patent Document 1]
JP-A-55-54597
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and in reusing the cleaning water discharged in the water washing step after the chemical conversion treatment of the alloy object, the paint adhesion due to the dirt of the used washing water To provide a reuse method and a reuse system of washing water that can suppress the occurrence of defects and reduce the cost of reuse of washing water by efficiently using an ion exchange resin. With the goal.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have focused on the components of used washing water purified by the ion exchange resin member and have completed the present invention.
[0008]
That is, the present invention relates to a method for reusing cleaning water, and reuse of used cleaning water discharged from a step of cleaning a chemical conversion coating applied to an alloy article to be coated containing at least magnesium and / or aluminum. A method of passing the used washing water through an activated carbon tower filled with activated carbon, and filling the used washing water passed through the activated carbon tower in the step with a cation exchange resin and an anion exchange resin. The TOC concentration and silicon content of the used washing water purified through the two steps, and the TOC concentration and the silicon content are less than a predetermined value, respectively. In some cases, the method further comprises a step of reusing the used cleaning water as cleaning water for the chemical conversion coating.
[0009]
The present invention also relates to a system for reusing cleaning water, and reuse of used cleaning water discharged from a process of cleaning a chemical conversion coating applied to an alloy article to be coated containing at least magnesium and / or aluminum. An activated carbon tower filled with activated carbon, a mixed bed resin tower filled with a cation exchange resin and an anion exchange resin, and used washing water purified through the activated carbon tower and the mixed bed resin tower. Means for measuring the TOC concentration and silicon content of the resin, and when the TOC concentration and the silicon content measured by the means are less than a predetermined value, the used cleaning water is reused as cleaning water for the chemical conversion coating. And a control means.
[0010]
In the present invention, the predetermined value of the TOC concentration is preferably 10 mg / L, and the predetermined value of the silicon content is preferably 5 mg / L.
[0011]
Here, the “TOC concentration” is an abbreviation for the total organic carbon (Total Organic Carbon) and indicates the content of organic components in the waste water (used washing water).
[0012]
Until now, the relationship between the degree of purification of cleaning water and poor coating adhesion has not been studied in detail with regard to the reuse of cleaning water, but the relationship between the two is clearly defined for the first time by the present invention. It became possible to improve the paint adhesion of the object to be cleaned in the reuse of the film cleaning water.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The present invention relates to the reuse of cleaning water used for cleaning a chemical conversion coating applied to an alloy coating, and has been developed with a focus on the purity of the cleaning water to be reused. It was completed on the basis of the extremely important knowledge that the TOC concentration in water and the silicon content have a very important influence on the coating adhesion of an object to be coated.
[0014]
That is, the cleaning water recycling method according to the present invention is used cleaning water discharged from the step of cleaning the chemical conversion coating applied to the alloy object, and is passed through the activated carbon tower and the mixed bed resin tower. Measures the TOC concentration and silicon content of the clarified and purified cleaning water, and reuses the used cleaning water as cleaning water for the conversion coating when the TOC concentration and the silicon content are less than the predetermined values, respectively. It is characterized by doing.
[0015]
In addition, the cleaning water reuse system according to the present invention includes an activated carbon tower and a mixed bed resin tower for purifying used cleaning water discharged from the process of cleaning the chemical conversion coating applied to the alloy object. And a means for measuring the TOC concentration and silicon content of the used washing water that has been passed through the activated carbon tower and the mixed bed resin tower and purified, and the TOC concentration and silicon content measured by the means And a control means for reusing the used cleaning water as cleaning water for the chemical conversion coating when each of the above is below a predetermined value.
[0016]
The surface of the alloy before chemical conversion treatment has oxide film, hydroxide film, and oil film that are produced in the manufacturing process, and if the dirt on the surface of the alloy is not washed beforehand, the defective rate will increase in the painting process. In order to remove these stains, a treating agent containing a chlorinated solvent, a petroleum solvent, a surfactant or the like is used. Therefore, the used cleaning water after the chemical conversion film cleaning contains contaminants such as an oxide film, a hydroxide film, an oil film, a chlorinated solvent, a petroleum solvent, and a surfactant.
[0017]
Such used washing water is purified by passing it through an activated carbon tower and a mixed bed resin tower. In the present invention, the degree of purification of the used washing water that can be reused as the washing water for the conversion coating is as follows. As described above, the standard is the TOC concentration and the silicon content in the washing water, and preferably the TOC concentration is 10 mg / L or less and the silicon content is 5 mg / L or less. As long as the TOC concentration and silicon content of the used cleaning water purified through the activated carbon tower and the mixed bed resin tower are within the above ranges, the occurrence of poor paint adhesion can be suppressed even if reused as cleaning water. On the other hand, since the activated carbon tower and the mixed bed resin tower can continue to be used until the above range is exceeded, waste due to replacement below the replacement capacity can be prevented and the cost can be reduced.
[0018]
The activated carbon used in the present invention in order to remove the organic component contained in the used washing water is not particularly limited, and those having any shape such as granular, powdery, and fibrous can be used. From the viewpoint of low cost and less pressure loss, granular activated carbon can be preferably used.
[0019]
Further, the mixed bed resin tower used in the present invention is not particularly limited, and can be properly used depending on the waste water pollutant or the degree of contamination thereof. As a mixed bed resin tower,
1) Combination of strong acidic cation exchange resin and strong basic anion exchange resin 2) Combination of strong acidic cation exchange resin and weak basic anion exchange resin 3) Weak acidic cation exchange resin and strong basicity Combinations with anion exchange resins 4) Combinations of weakly acidic cation exchange resins and weakly basic anion exchange resins. The mixed bed resin tower of 1) is most preferable when high purity water is obtained. In the mixed bed resin tower of 2), after passing through the strongly acidic cation exchange resin, water having a high degree of purification can be obtained as compared with the double bed type beneficial to the weakly basic inion exchange resin. In the mixed bed resin tower of 3), after passing through the weakly acidic ion exchange resin, water having a higher degree of purification can be obtained as compared with the double bed system in which the liquid is passed through the strongly basic anion exchange resin. The mixed bed resin tower of 4) has some desalting ability, and in the case of wastewater containing salt, highly purified water is obtained. In the present invention, these mixed bed towers can be properly used according to the waste water pollutant or its contamination degree as described above.
[0020]
Hereinafter, the present invention will be described in more detail with reference to the drawings showing preferred embodiments of the present invention.
In FIG. 1, 1 represents a cleaning tank group, and the cleaning tank group 1 is arranged in the order of a main cleaning tank 1-1, a sub-cleaning tank 1-2, and a mist cleaning tank 1-3. The alloy to which the chemical conversion film after the chemical conversion treatment is adhered is washed in this order and moves to the next coating step.
[0021]
Wash water circulates in the flow path in the direction of the arrow. The cleaning liquid discharged from the main cleaning tank 1-1 passes through the flow path a, passes through the pump 2, passes through the flow path b, and passes through the activated carbon tower 3 filled with activated carbon. In the activated carbon tower 3, organic substances contained in the cleaning liquid are collected. Next, the washing liquid passes through the channel c and is passed through the mixed bed resin tower 4 filled with the cation exchange resin and the anion exchange resin. Here, the cation and the anion contained in the washing water are adsorbed and removed. . Thereafter, the cleaning water passes through the flow path d, passes through the flow path e under water quality monitoring by the water quality measuring device 5, and is reused as cleaning water in the mist cleaning section 1-3.
[0022]
In the water quality measuring instrument 5, the TOC concentration and the silicon content are constantly measured, and the purity of the washing water that has passed through the activated carbon tower 3 and the mixed bed resin tower 4 is monitored. When the water quality measuring device 5 measures a value exceeding the allowable value for either the TOC concentration or the silicon content in the wash water, the valves 7 and 8 are opened, the valve 9 is closed, and the wastewater treatment outside the system is performed. Drain cleaning water to the facility. Thereafter, the valves 8, 9 and 10 are closed, the valve 7 is opened, a prescribed amount of high-pure water prepared in the high-pure water tank 6 is introduced into the system, and the washing water is replaced. After replacement of the washing water, the valve 7 is closed, the valves 9, 12 and 13 are opened, and the washing water is guided to the flow path h, thereby switching to the activated carbon tower 14 and the mixed bed resin tower 15 prepared in different systems. To do.
[0023]
【Example】
Detailed studies were made on the relationship between the adhesion of the object to be cleaned, the TOC concentration of the cleaning water to be reused, and the silicon content. Table 1 shows the results of evaluating the coating film surface state of the alloy that was subjected to the main coating after cleaning with different TOC concentrations and silicon contents of the cleaning water.
[0024]
[Evaluation of paint film surface condition]
The evaluation of the surface condition is the result of carrying out JIS K5400 (coating general test method: water resistance test) and JIS K5400 (coating general test method: moisture resistance test), and the symbols in the table indicate the following evaluation criteria.
[0025]
A: No change was observed in any of the two evaluation methods.
[0026]
○: There was almost no change in either evaluation method.
[0027]
X: Whitening / peeling was observed in either or both evaluation methods.
[0028]
Water resistance test: A test piece is immersed in water at room temperature for 200 hours, scratched on the substrate, and subjected to a taping test.
[0029]
Moisture resistance test: A test piece is held in an environment of 90% humidity and a temperature of 45 to 50 ° C. for 200 hours, after which the base mesh is scratched and a taping test is performed.
[0030]
[Table 1]

[0031]
From the results of Table 1, it was confirmed that the surface state of the coating film was good when the TOC concentration of the reused cleaning water was 10 mg / L or less and the silicon content was 5 mg / L or less. .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a preferred embodiment of a cleaning water reuse system according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Washing tank group, 1-1 ... Main washing tank, 1-2 ... Sub washing tank, 1-3 ... Mist washing tank, 2 ... Pump, 3,14 ... Activated carbon tower, 4, 15 ... Mixed bed resin tower, 5 ... Water quality measuring device, 6 ... High pure water tank, 7-13 ... Valve, ad ... Flow path

Claims (2)

A method for reusing used cleaning water discharged from a step of cleaning a chemical conversion coating applied to an alloy-coated object containing at least magnesium and / or aluminum, wherein the used cleaning water is filled with activated carbon. A step of passing through the activated carbon tower, a step of passing the used washing water passed through the activated carbon tower in the step into a mixed bed resin tower filled with a cation exchange resin and an anion exchange resin, and the two steps. The TOC concentration and the silicon content of the used cleaning water purified through the above are measured, and the used cleaning water when the TOC concentration is 10 mg / L or less and the silicon content is 5 mg / L or less . A method for reusing cleaning water as a cleaning water for chemical conversion coatings. A system for reusing spent cleaning water discharged from a step of cleaning a chemical conversion coating applied to an alloy workpiece containing at least magnesium and / or aluminum, comprising an activated carbon tower filled with activated carbon, and a cation A mixed bed resin tower packed with an exchange resin and an anion exchange resin, means for measuring the TOC concentration and silicon content of used washing water purified through the activated carbon tower and the mixed bed resin tower, Control means for reusing the used cleaning water as cleaning water for the chemical conversion coating when the TOC concentration measured by the means is 10 mg / L or less and the silicon content is 5 mg / L or less . Wash water reuse system.

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