JP3518170B2 - Metal drying method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drying method for preventing drying unevenness / stain in the field of aqueous metal surface treatment and metal cleaning. More specifically, the present invention relates to a method of treating with an aqueous solution containing a pretreatment agent for drying and then drying without washing with water.

[0002]

2. Description of the Related Art Conventionally, in the fields of water-based metal surface treatment and metal cleaning, in order to prevent unevenness and stains on the surface of the metal, a water drainage replacement method using a solvent, a centrifugal dehydration method and the like have been used. However, the centrifugal dehydration method sometimes deforms the product depending on the type and shape of the metal, and at the same time, it causes complete drying unevenness.
Difficult to prevent stains. Therefore, the water-drainage substitution method using a solvent is generally industrially adopted.

[0003] In many cases, drying with water adhering causes discoloration due to unevenness in drying and stains, which lowers the product value. The water drainage replacement method with a solvent is a method of rinsing (final finishing) and then treating with a chlorofluorocarbon or chlorine-based solvent to replace water on the metal surface.

However, the use of CFCs and chlorine-based solvents, which are the solvents used in the drainage substitution method described above, causes environmental damage, and therefore their use has been regulated worldwide, and a technique to replace them is strongly demanded. Has been. The use of low-toxicity solvents such as isopropyl alcohol has been proposed as an alternative technology, but these solvents are flammable (flammable).
Therefore, there is a problem in safety as compared with CFCs or chlorine-based solvents, and there is a drawback that equipment costs are high.

Drying using drainage substitution with a solvent is an ideal drying method in which uneven drying and stains do not occur.
Due to environmental damage and safety, various alternative technologies are being investigated. At present, various alternative techniques have been proposed, but it is hard to say that a satisfactory technique has been completed with regard to the occurrence of uneven drying and stains.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the need for a draining and replacing step with a solvent that causes environmental damage, to prevent the generation of spots and stains even when dried with water adhering, and at the same time to clean the surface. Another object of the present invention is to provide a method for drying a metal to obtain a smooth metal surface.

[0007]

MEANS FOR SOLVING THE PROBLEMS The inventors of the present invention passed an aqueous solution containing a dry pretreatment agent through an ion exchange resin to circulate the solution, and maintained the electric conductivity at 50 μS / cm or less with the aqueous solution. It was found that, after the treatment, the product was not washed with water and dried without causing unevenness in drying or stains.

That is, according to the present invention, after treatment with a dry pretreatment agent consisting of an aqueous solution containing at least one of the compounds represented by the formulas (1) and (2), without washing with water,
In the method for drying a metal, which is characterized by drying, the aqueous solution is passed through an ion exchange resin and circulated, and the electric conductivity is maintained at 50 μS / cm or less to suppress the occurrence of drying unevenness / stains, It relates to a drying method for obtaining a clean metal surface.

[0009]

[Chemical 3] (Wherein R 1, R 2, and R 3 are hydrogen, an alkyl group, an alkenyl group, a cycloalkyl group, or a phenyl group,
These groups may have a substituent. )

[0010]

[Chemical 4] (Wherein R 1, R 2, R 3, and R 4 are hydrogen, an alkyl group,
It is an alkenyl group, a cycloalkyl group, or a phenyl group, and these groups may have a substituent. )

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous metal surface treatment process used in the present invention includes electroless plating, electroplating, anodizing, pickling, alkaline washing, chemical polishing, electrolytic polishing, mechanical polishing, metal coloring treatment, etching. , Chemical conversion treatment, etc., and the water-based metal cleaning process includes degreasing,
Examples include processes such as acid cleaning, alkali cleaning, and electrolytic cleaning.

In these various metal surface treatments and metal washing processes, after rinsing with water and prior to drying, the metal is treated with a drying pretreatment agent that maintains an electric conductivity of 50 μS / cm or less, and then the metal is dried. As a result, it is possible to suppress the occurrence of drying unevenness / staining and obtain a clean metal having a good appearance.

Drying unevenness and stains can be roughly classified into those caused by water quality and those caused by metal oxidation. Drying unevenness / spots due to metal oxidation are treated with a dry pretreatment agent of the present invention, that is, an aqueous solution containing a compound represented by the formula (1) or (2), and dried without washing with water. By the action of the compound of the formula (1) or the formula (2), it is possible to prevent uneven drying and stains due to metal oxidation.

On the other hand, the unevenness or stains caused by the water quality are caused by the non-evaporated components contained in the water used in the bath for preparing the dry pretreatment agent or the dry pretreatment agent itself. If it exceeds the limit, evaporation residue on the metal surface after drying becomes remarkable, and it appears as unevenness or stains. or,
Even if the concentration of non-evaporable components contained in the water used for the construction bath and the pre-drying treatment is below the limit, depending on the water quality of the washing process immediately before the pre-drying treatment, non-evaporation that is attached to the metal and brought in from the washing process When the components accumulate in the pre-drying treatment step and the concentration exceeds the limit, evaporation residue causes drying unevenness / spots.

Generally, in various metal surface treatments and metal washing processes, various mineral acids, organic acids, alkali metal salts, or metal salts are used in large amounts in the preceding step of the rinse water washing step. In many cases, these non-evaporated components adhere to the metal and are brought into the rinse water washing step, and the water quality in the rinse water washing step becomes unsuitable for use of the dry pretreatment agent in the present invention. Therefore, in order to satisfy the water quality in the rinse water washing step, it is necessary to use a large amount of clean water containing a small amount of non-evaporated components and dilute the non-evaporated components.

In addition, as a cause of non-evaporated components accumulating in the drying pretreatment step of the present invention, the drying pretreatment agent in use, that is, the compound represented by the formula (1) or the formula (2) is used. A chemical reaction such as decomposition from the above is considered, which may cause non-evaporated components, which may cause unevenness or stains.

If a large amount of clean water is used in the water washing step, it is possible to suppress the carry-in of non-evaporated components from the water washing step to the pre-drying treatment step. However, since it is impossible to remove the non-evaporated components generated by the chemical reaction such as decomposition of the pre-drying treatment agent, the non-evaporated components are accumulated in the pre-drying treatment step. Occurs,
It becomes uneconomical because the bath in the pre-drying process needs to be renewed. In addition, it is not desirable to use a large amount of clean water in the washing step, because the load on the water treatment facility and the wastewater treatment facility increases.

By circulating the aqueous solution containing the pre-drying agent of the present invention through the ion exchange resin and circulating it, it is possible to prevent the accumulation of non-evaporated components in the pre-drying treatment step, and to prevent the occurrence of drying unevenness and stains. Can be suppressed. As process control in the process, it is useful to control the electric conductivity of the treatment liquid within a predetermined range. As a management standard,
Although it depends on the concentration and type of the pretreatment agent for drying, it is preferable to maintain the electrical conductivity of the aqueous solution at 50 μS / cm or less by passing through the ion exchange resin, and usually at 30 μS / cm or less. Is best.

The dry pretreatment agent of the present invention, that is, the compound represented by the formula (1) or (2) reacts with water to form a cation, and its aqueous solution shows basicity. Considering hydroxylamine as an example of the compound of formula (1) and hydrazine as an example of the compound of formula (2), the equilibrium formula between each compound and water is represented by formula a) and formula b). . NH ₂ OH + H ₂ O → NH ₃ OH ⁺⁺ OH ^- a) N ₂ H ₄ + H ₂ O → N ₂ H ₅ ⁺ + OH ^- b)

Since NH ₃ OH ⁺ and N ₂ H ₅ ⁺ are cations, they can be trapped by a cation exchange resin. But,
These ions are trapped only immediately after the cation exchange resin is regenerated, that is, when the cation exchange resin is in the H type, and these ions are Na ⁺ , K ⁺ , Ca ²⁺ , M
Compared with cations that are generally present in the process of metal surface treatment or metal cleaning such as g ²⁺ , Fe ³⁺ , Cu ²⁺ , Ni ²⁺ , Ag ^+, etc., binding to a cation exchange resin The force is weak, and therefore, when cations such as Na ⁺ are present in the aqueous solution, they are easily exchanged with these ions on the exchange resin and eluted into the aqueous solution as NH ₃ OH ⁺ or N ₂ H ₅ ^+. . It is considered that these phenomena occur not only for hydroxylamine and hydrazine, but also for these substitution products, that is, the entire compound represented by formula (1) or formula (2).

That is, when an aqueous solution containing the dry pretreatment agent of the present invention is passed through the cation exchange resin immediately after regeneration, the treatment agent component represented by the formula (1) or (2) is cation exchanged as an ion. It is captured by the resin, and the concentration of the treating agent in the pre-drying treatment step is reduced. However, after all the H ⁺ in the cation exchange resin has been exchanged and desorbed, the reduction in the concentration of the treating agent stops. Therefore, while the treatment agent component is captured by the ion exchange resin and the treatment agent concentration is decreasing, it is necessary to supplement the treatment agent and maintain the treatment agent concentration in the pre-drying treatment step at a predetermined concentration.

However, the treatment agent component trapped in the ion-exchange resin is Na ⁺ as an impurity in the pre-drying treatment step,
K ⁺ , Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Cu ²⁺ , Ni ²⁺ , Ag
^When cations such as ⁺ are brought in, they are exchanged with these ions on the ion-exchange resin and eluted again in the pre-drying treatment solution, so the aqueous solution containing the pre-drying agent is passed through the ion-exchange resin. The processing agent component is not lost by the liquid. Further, even when the treatment agent component represented by the formula (1) or the formula (2) is being passed through the ion exchange resin or while being captured by the ion exchange resin, there is no change due to a chemical reaction such as decomposition. It rarely happens, and it exists stably.

Therefore, by passing the aqueous solution containing the pre-drying agent through the ion exchange resin, the ionic non-evaporated components brought in from the washing step and the pre-drying agent itself can be introduced without losing the components of the pretreatment agent. The ionic non-evaporated components generated by the reaction such as decomposition can be efficiently removed, and the bath renewal in the drying pretreatment step due to the accumulation of these non-evaporated components can be eliminated.

In the present invention, the type of ion exchange resin used is not particularly limited, and it is a strong acid cation exchange resin, a weak acid cation exchange resin, a strong basic anion exchange resin, a weak basic anion exchange resin, Examples thereof include chelate resins. Further, a synthetic adsorbent or the like can be used depending on the kind of the component dissolved in water.

The strongly acidic cation exchange resin is a styrene-based cation exchange resin having a sulfonic acid group or a crosslinked polystyrene-based cation exchange resin. The weakly acidic cation exchange resin is a methacrylic cation exchange resin having a carboxylic acid group or an acrylic cation exchange resin. The strongly basic anion exchange resin is a styrene-based anion exchange resin having a quaternary ammonium group. Examples of the weakly basic anion exchange resin include a styrene-based ion exchange resin having an amino group, a methacrylic-based ion exchange resin, and an acrylic-based ion exchange resin.

The chelate resin is a crosslinked polystyrene chelate resin having an iminodiacetic acid group or a crosslinked polystyrene chelate resin having a polyamine group. As the synthetic adsorbent, styrene-divinylbenzene-based synthetic adsorbent,
Examples thereof include methacrylic synthetic adsorbents.

There is no particular restriction on the treatment method of the aqueous solution containing the pre-drying treatment agent of the present invention, single bed single tower system, two bed two tower system, two bed three tower system, multi-layer bed system, mixed bed system. Etc. may be used, and there is no particular restriction on the reproducing method.

The hydroxylamines represented by the formula (1) and the hydrazines represented by the formula (2) used in the present invention have different boiling points or decomposition temperatures depending on the drying conditions.
The temperature is preferably not higher than 0 ° C, and usually, the optimum temperature is not higher than 150 ° C. A compound having a boiling point or a decomposition temperature of more than 250 ° C has a high effect of preventing metal oxidation, but the components of the dry pretreatment agent adhere to the dried metal surface, resulting in uneven drying.
It causes stains and at the same time makes it difficult to obtain a clean metal surface. This defect can be prevented by increasing the drying temperature, but it is not preferable from the viewpoint of handleability and economy.
A compound having a boiling point or a decomposition temperature of 150 ° C. or lower has a high effect of preventing metal oxidation, can obtain a good appearance without drying unevenness and stains, can secure a clean metal surface, and is optimal in terms of handling. .

With respect to the hydroxylamine compound represented by the formula (1), preferred compounds are specifically exemplified as follows.
Hydroxylamine, O-methylhydroxylamine,
O-ethylhydroxylamine, N-methylhydroxylamine, N, N-dimethylhydroxylamine, N,
O-dimethylhydroxylamine, N-ethylhydroxylamine, N, N-diethylhydroxylamine,
N, O-diethylhydroxylamine, O, N, N-trimethylhydroxylamine, N- (2-methoxyethyl) hydroxylamine, N-allylhydroxylamine, N, O-diallylhydroxylamine, O-cyclohexyl-N, N -Dimethylhydroxylamine, N-
Examples thereof include phenylhydroxylamine. Of these, hydroxylamine and N, N-diethylhydroxylamine are most suitable.

With respect to the hydrazine compound represented by the formula (2), specific examples of preferable compounds include 1,1-
Diethylhydrazine, 1,2-diethylhydrazine, methylhydrazine, ethylhydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, 1,2-diisopropylhydrazine, hydrazine, cyclohexylhydrazine, phenylhydrazine, 1-methyl-2 -Phenylhydrazine, allylhydrazine, isopropylhydrazine and the like. Among these, particularly, hydrazine, methylhydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, ethylhydrazine,
1,1-diethylhydrazine, 1,2-diethylhydrazine and the like are most suitable.

In the practice of the present invention, the concentration of the treatment agent component represented by the formula (1) or (2) in the aqueous solution is generally at least 1 ppm. 1 ppm
If the amount is less than the above, the effect is obtained, but depending on the type of metal, shape, water quality, drying method, etc., uneven drying or stain may occur. In addition, although there is no particular upper limit for the unevenness in drying and stains, it is generally 5 in consideration of handleability and economy.
It is unsuitable to use at a concentration over 0000 ppm. Practically, considering the handling property, the economical efficiency, and the type, shape, water quality, and drying method of the metal to be treated, it is usually 20 ppm or more, preferably 50 to 10,000 p.
It is preferred to hold at pm.

The treatment method with the aqueous solution containing the compound represented by the formula (1) or (2) is by means of dipping, stirring, shaking, spraying, ultrasonic irradiation or the like. When the treatment process has multiple stages, the concentration of the treatment agent component should be at least 1p in the final treatment tank.
If it is pm, the concentration of the other treatment tanks is not particularly limited and is arbitrary.

The treatment time varies depending on the type, shape, treatment method, etc. of the metal and is not particularly limited. But practically 1
0 to 600 seconds is preferable. If it is less than 10 seconds, the product may have uneven drying or stains, and if it exceeds 600 seconds, there is no problem in the treatment effect itself, but it is unsuitable from the viewpoint of productivity and economy. . The treatment temperature is also not particularly limited, but it is preferably room temperature or higher. 8 to improve drying efficiency
There is no problem in the treatment effect even if it is washed with hot water at 0 ° C. or higher, and there is an advantage that a metal having an excellent appearance can be obtained.

The metal used in the present invention is iron,
Copper, nickel, chromium, cobalt, lead, zinc, aluminum, titanium, tin, gold, silver, etc., and alloys thereof.
Further, the invention can be applied to a product which is metallized on the surface of resin, glass, ceramics or the like by means of adhesion, pressure bonding, plating, vapor deposition, ion plating or the like.

[0035]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the invention is not limited to the following Examples.

Example 1 A bearing part (made of SS400) is chemically polished, deburred and brightened, and then washed with water. Next, a 100 ppm hydroxylamine aqueous solution prepared using ion-exchanged water is subjected to a dipping treatment at room temperature for 120 seconds, and dried in a blast dryer at 100 ° C. These series of treatments were performed 200 times. During this period, an aqueous solution containing 100 ppm hydroxylamine was mixed with the ion-exchange resin tower (Mitsubishi Kagaku Co., Ltd. Diaion SK102 and Diaion SA10A mixed bed 1).
(Column type), and the electric conductivity of the aqueous solution is 10 to 15 μm.
Maintained at S / cm.

Example 2 Instead of the bearing part and the 100 ppm hydroxylamine aqueous solution in Example 1, a test piece (iron-
Nickel alloy: 42 alloy) and 500 ppm hydrazine aqueous solution, and the electrical conductivity of the aqueous solution is 30 μS / c
The same procedure as in Example 1 was carried out except that the temperature was maintained at m.

Example 3 Instead of the 500 ppm hydrazine aqueous solution of Example 2,
The same procedure as in Example 2 was repeated except that a 1,000 ppm N, N-diethylhydroxylamine aqueous solution was used.

Example 4 A liquid crystal polymer containing an inorganic filler (Vectra C-820 manufactured by Polyplastics Co., Ltd.) was used to obtain a molded substrate having a component mounting recess by injection molding. Electroless plating is applied to the entire surface of this molded product. Next, a plating resist pattern was formed using an electrodeposition type photoresist. A circuit pattern was formed on the thus-obtained substrate with bright nickel plating of 20 μm, and gold strike plating was further performed, and then gold plating for wire bonding was 0.3 μm. After that, the plating resist and the electroless copper plating of the non-circuit portion were removed from the substrate. Finally, a pre-drying treatment was carried out by performing ultrasonic cleaning for 30 seconds at room temperature with an aqueous solution of 5,000 ppm 1,1-dimethylhydrazine prepared using ion-exchanged water. Then, it was dried in a hot air dryer at 80 ° C. These series of treatments were performed 200 times. During this period, a mixed bed 1 using 5,000 ppm 1,1-dimethylhydrazine aqueous solution was prepared by using an ion exchange resin tower (manufactured by Mitsubishi Chemical Corporation, Diaion WK40 and Diaion SA11A).
(Column type) and the electric conductivity of the aqueous solution is 20 μS / cm
Maintained at.

Comparative Example 1 The procedure of Example 1 was repeated, except that the 100 ppm hydroxylamine aqueous solution was not passed through the ion exchange resin tower.

Comparative Example 2 The procedure of Example 2 was repeated, except that the 500 ppm hydrazine aqueous solution was not passed through the ion exchange resin tower.

Comparative Example 3 The procedure of Example 3 was repeated, except that the 1,000 ppm N, N-diethylhydroxylamine aqueous solution was not passed through the ion exchange resin column.

Comparative Example 4 The procedure of Example 4 was repeated, except that the 5,000 ppm 1,1-dimethylhydrazine aqueous solution was not passed through the ion exchange resin tower.

The metal product after each of the above treatments was visually observed, and the appearance of drying unevenness, stains, etc. was evaluated in four levels according to the following criteria. ⊚: Very good with no appearance defects such as drying unevenness / stains ○: Almost no appearance defects such as drying unevenness / staining △: Excellent appearance defects such as drying unevenness / staining Inferior ×: Inferior in appearance defects such as uneven drying and stains

The above results are shown in Table 1. Table 1   Number of treatments 1 to 50 51 to 100 101 to 150 151 to 200   Example 1 ◎ ◎ ◎ ◎   Example 2 ◎ ◎ ◎ ◎   Example 3 ◎ ◎ ◎ ◎   Example 4 ◎ ◎ ◎ ◎   Comparative Example 1 ◎ ○ to △ × ×   Comparative Example 2 ◎ ○ to △ × ×   Comparative Example 3 ◎ ○ to △ × ×   Comparative Example 4 ◎ ○ to △ × ×

[0046]

Industrial Applicability According to the method of the present invention, the metal surface is clean, and a good appearance without drying unevenness or stains can be obtained, and further, the ionic non-evaporating component can be efficiently removed from the aqueous solution of the drying pretreatment agent, and the drying can be performed. The bath renewal in the pretreatment process can be eliminated for a long period of time.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23G 5/036

Claims (5)

(57) [Claims] 1. In a metal pre-drying treatment step, an aqueous solution containing a pre-drying agent is passed through an ion exchange resin for circulation, and treated with an aqueous solution whose electric conductivity is maintained at 50 μS / cm or less, A method for drying a metal, which comprises drying without washing with water. 2. The method according to claim 1, wherein the pre-drying treatment agent has the following formula (1). [Chemical 1] (In the formula, R 1, R 2, and R 3 are hydrogen, an alkyl group, an alkenyl group, a cycloalkyl group, or a phenyl group, and these groups may have a substituent.) 3. The method according to claim 1, wherein the pre-drying treatment agent has the following formula (2). [Chemical 2] (Wherein R 1, R 2, R 3, and R 4 are hydrogen, an alkyl group,
It is an alkenyl group, a cycloalkyl group, or a phenyl group, and these groups may have a substituent. ) 4. The method according to claim 2, wherein the compound represented by the formula (1) is hydroxylamine, N, N-diethylhydroxylamine. 5. The compound represented by the formula (2) is hydrazine, methylhydrazine, ethylhydrazine, 1,1- or 1,2-dimethylhydrazine, 1,1- or 1,
The method according to claim 3, which is 2-diethylhydrazine.