JP3489605B2 - 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 uneven drying and stains in the field of aqueous metal surface treatment and metal cleaning. More specifically, it relates to a method of treating with a metal surface treating agent, or after washing with a metal detergent, treating with a treating agent comprising an aqueous solution containing a compound represented by the formula (1), and then drying. .

[0002]

2. Description of the Related Art Conventionally, in the field of water-based metal surface treatment and metal cleaning, as a method for preventing metal oxidation in a drying process for preventing unevenness in drying and stains, a drainage substitution method with a solvent, a vacuum drying method, nitrogen Examples include drying in an atmosphere. However, the vacuum drying method increases the equipment cost,
Work efficiency is also low. In addition, the equipment cost for drying in a nitrogen atmosphere is also high, and the cost is high due to the use of a large amount of nitrogen, and these drying methods are applied to special products, and water draining with a solvent is generally used. The substitution method is industrially adopted.

[0003] In many cases, when water is attached and dried,
Discoloration due to oxidation of the metal surface occurs and the product value drops.
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 or chlorine-based solvents, which are the solvents used in the above-mentioned drainage substitution method, causes environmental destruction, and therefore their use has been regulated worldwide, and alternative techniques to replace them are strongly suggested. It has been demanded. As an alternative technology, the use of low-toxicity solvents such as isopropyl alcohol has been proposed, but these solvents are flammable (combustible), have a safety problem compared to CFCs or chlorine-based solvents, and are expensive to install. There is a drawback that becomes.

When metal oxidation in the water washing step poses a problem, a method of using a deoxidizer for removing dissolved oxygen, a corrosion inhibitor, a passivation film forming agent, etc. in the water washing step is a method for preventing metal oxidation. Are known.

Oxidation in the water washing step is caused by oxygen dissolved in water. Therefore, by removing dissolved oxygen in water as much as possible, metal oxidation in water can be prevented. Generally, reducing agents such as hydrazine, hydroxylamine, sodium sulfite and sodium bisulfite are used as the oxygen scavenger.

As the corrosion inhibitor, amine compounds are generally used. The function of the corrosion inhibitor is to prevent the metal oxidation by uniformly adsorbing and coating the surface of the metal and cutting the contact between the metal and oxygen. As a passivation film forming agent,
By using an oxidizing agent such as dichromate, chromate, nitrite, etc., a corrosion-resistant passivation film is formed on the metal surface to prevent further oxidation.

On the other hand, as a technique for preventing metal oxidation in the drying step, a drainage replacement method using a solvent has been mainly used.
The drainage replacement method using a solvent does not have the ability to reduce or wash the metal, and is to prevent metal oxidation after the washing step, that is, in the drying step.

Usually, the drying step is carried out in the air, and it is an atmosphere in which oxygen is constantly present. It is difficult to remove existing oxygen with a deoxidizer or the like to prevent metal oxidation, and to prevent oxidation in water. It is impossible to apply a means for removing dissolved oxygen for the purpose. Therefore, by performing drainage replacement with a solvent to remove water, it is possible to perform drying that prevents the occurrence of uneven drying and stains even when sufficient oxygen is supplied.

In the drying step, the rate of metal oxidation is low in the initial stage of drying when water adhering to the metal surface forms a water film. However, as the drying progresses, the water film on the metal surface is destroyed, the metal surface is exposed directly, and in the latter stage of drying in a moist atmosphere, oxygen in the atmosphere is continuously supplied in sufficient quantity, Since the surface temperature is also high, the oxidation of metal rapidly progresses.

In a general metal surface treatment process to which a drying method by drainage replacement using a solvent is applied, metal oxidation in the water washing process is extremely small, and in many cases, even if no special means is adopted, the water washing process is performed. The amount of metal oxidation generated does not lead to phenomena such as discoloration of the final product. However, the amount of metal oxidation in the drying step is large, and if the metal is dried without performing drainage replacement with a solvent as described above, discoloration occurs in the prior art, resulting in a defective product.

As described above, it is not only difficult to prevent metal oxidation in the drying step by using an oxygen scavenger, but the oxygen scavenger component may be removed by drying with washing water containing the oxygen scavenger attached. It deposits (evaporates to dryness) on the metal surface, causing uneven drying and stains. Further, since the deposited oxygen scavenger component adversely affects the next step, it was indispensable to keep the rinse water as clean as possible.

When a corrosion inhibitor is used, even if it is possible to prevent metal oxidation in the drying process, a corrosion inhibitor is present on the metal surface, and it is impossible to obtain a clean metal surface without uneven drying or stains. Is. Therefore, in a later step,
The adsorbed corrosion inhibitor may be adversely affected, and it becomes necessary to remove the corrosion inhibitor before the treatment of the next step. or,
Although the use of a passivation film-forming agent can produce a product with a good appearance without drying unevenness or spots, the metal surface is covered with a uniform oxide film (passive film), which is different from the case of a corrosion inhibitor. Similarly, it is impossible to obtain a clean metal surface.
Therefore, the uniform oxide film is adversely affected in the subsequent process, and it becomes necessary to remove the oxide film (passive film) before the next process.

On the other hand, in the case of the drying using the drainage substitution method, the oxidation of the metal is prevented by removing the water content, and the solvent used is evaporated and scattered in the drying step and does not remain on the metal surface. Therefore, the metal is an ideal drying method in which a clean surface can be obtained at the same time that a good appearance free from uneven drying and stains is obtained.

However, the use of these solvents is environmentally destructive and there is a strong demand for alternative techniques. As an alternative technique, it is difficult to carry out a satisfactory drying of the metal having various defects as described above, even if the technique of preventing metal oxidation in water is directly used.

[0016]

DISCLOSURE OF THE INVENTION The present invention does not require a draining and replacing step with solvents that cause environmental damage, prevents unevenness and spots even when dried with water adhered, and at the same time provides a clean metal surface. To provide a method for drying a metal.

[0017]

[Means for Solving the Problems] There is a strong demand for an alternative technique of the drying method by draining and replacing using CFCs and chlorine-based solvents which cause environmental damage. Therefore, the present inventors have found that a dry pretreatment agent using an aqueous solution containing a compound represented by the formula (1) can effectively prevent metal oxidation and, at the same time, remove the dry pretreatment agent on a dried metal surface. It has been found that a clean metal surface is obtained, without the components sticking.

In various processes used for surface treatment of water-based metals and cleaning of water-based metals, if water is dried with water adhering to the metal, in many cases, discoloration due to metal oxidation occurs, resulting in uneven drying and stains. However, in the present invention, after treatment with a metal surface treatment agent or a metal detergent, prior to the drying step, water is attached by treating the metal with an aqueous solution containing a compound represented by the formula (1). The present invention relates to a drying method for preventing a metal oxidation in a drying step even if it is dried as it is, suppressing the occurrence of drying unevenness and spots and obtaining a clean metal surface. That is, the present invention, after treating with a treating agent consisting of an aqueous solution containing a compound represented by the formula (1),
The present invention relates to a drying method characterized by drying without washing with water.

[0019]

[Chemical 2]

(In the formula, R 1, R 2, R 3 and R 4 are hydrogen or an alkyl group having 1 to 5 carbon atoms and an alkenyl group having 2 to 4 carbon atoms, and these groups may have a substituent. , These groups may be the same or different, and in the formula, X is a hydroxyl group, or a carbonate group or a bicarbonate group, and n is 1
Or 2. )

[0021]

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, the metal is treated with an aqueous solution containing the compound represented by the formula (1) or dried with rinsing water. The aqueous solution containing the compound represented by (1) is added to the aqueous solution, and then the metal is dried. As a result, it is possible to suppress the occurrence of uneven drying and stains, and to obtain a metal having a good appearance and a clean appearance.

The boiling point or decomposition temperature of the compound represented by the formula (1) used in the present invention varies depending on the drying conditions, but it is 180 ° C.
The following compounds are optimal. Boiling point or decomposition temperature is 180
A compound exceeding ℃ has a high effect of preventing metal oxidation, but the components of the dry pretreatment agent adhere to the dried metal surface, which causes uneven drying and stains, and it is 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 180 ° C. or lower has a high effect of preventing metal oxidation, and a good appearance without drying unevenness and stains can be obtained, and at the same time, a clean metal surface can be secured, which is optimal in terms of handling.

With respect to the compound represented by the formula (1), specific examples of optimum compounds include ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, Choline, Neuline, Ethyltrimethylammonium, Diethyldimethylammonium, Triethylmethylammonium, Trimethylisopropylammonium hydroxide, tert-Butyl-trimethylammonium hydroxide, Allyltrimethylammonium hydroxide, Ammonium carbonate, Tetramethylammonium carbonate, Tetraethylammonium carbonate, Carbonate Trimethyl hydroxyethyl ammonium, ammonium bicarbonate, tetra bicarbonate Chill ammonium bicarbonate tetraethylammonium bicarbonate trimethyl hydroxyethyl ammonium, and the like.

In carrying out the present invention, the concentration of the compound represented by the formula (1) in the aqueous solution is not particularly limited,
At least the pH of the treatment liquid is preferably kept at 8.5 or higher. If the pH is less than 8.5, it is effective, but the kind of metal,
Depending on the shape, water quality, and drying method, uneven drying and stains may occur. Regarding the upper limit concentration of uneven drying and stains, it is generally inappropriate that the pH of the treatment liquid exceeds 11 in consideration of handleability, economy and the like.

The treatment method with the aqueous solution containing the compound represented by the formula (1) is by dipping, spraying or the like. When the treatment process has multiple stages, if the pH of the treatment liquid containing the compound represented by the formula (1) is kept at least 8.5 or more in the final washing tank, the pH of other washing tanks is not particularly limited and may be arbitrary. is there.

The treatment time varies depending on the type, shape, treatment method, etc. of the metal and is not particularly limited. However, practically 10
~ 600 seconds are preferred. If it is less than 10 seconds, uneven drying and stains may occur on the product. Even if it exceeds 600 seconds, there is no problem in the treatment effect itself, but it is inappropriate from the viewpoint of productivity and economy. The treatment temperature of the aqueous solution containing the compound represented by formula (1) is not particularly limited, but is preferably room temperature or higher. In order to improve the drying efficiency, there is no problem in the treatment effect even if it is washed with hot water at 80 ° 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,
Adhesion, pressure bonding, plating, vapor deposition on the surfaces of copper, nickel, chromium, cobalt, lead, zinc, aluminum, titanium, tin, gold, silver and / or their alloys and / or resin, glass, ceramics, etc. It can be applied to products metallized by means such as ion plating.

In the method of the present invention, the mechanism of preventing metal oxidation itself in the drying step of the compound represented by the formula (1) has not been elucidated, but it is presumed to exhibit the following behavior.

That is, the compound represented by the formula (1) is adsorbed on the metal surface to form a uniform coating film, and prevents contact between the metal and oxygen. Compared to water and non-adsorbed components, the components adsorbed on the metal are less likely to evaporate and scatter, forming a uniform coating film until the final stage of the drying process.

After the water and the non-adsorbed components are evaporated and scattered, the components adsorbed on the metal are also scattered and scattered. However, since the atmosphere in which the metal is placed is dry at this stage, as in the case of the draining replacement by the solvent, Even if the metal and oxygen come into contact with each other, oxidation of the metal does not occur so much as to cause a problem in practice, and it is possible to obtain a dried product having good appearance by preventing uneven drying and stains.

Further, even when the compound used in the present invention has self-decomposability even when it is strongly adsorbed to a metal and evaporation and scattering hardly occur, it is finally decomposed and scattered to obtain a clean metal surface. You can The compound represented by the formula (1) is a substance capable of evaporating and scattering not only by itself but also by oxidation products with oxygen and self-decomposition products in the drying step. Minutes do not occur.

[0033]

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. In the examples,% is by weight unless otherwise specified.

Example 1 A bearing part (made of SS400) is chemically polished, deburred and brightened, and then washed with water. Then, an aqueous solution containing 30 ppm of ammonium hydroxide was added to obtain PH9.5.
Immersion treatment is performed at room temperature for 120 seconds using the aqueous solution adjusted to 1, the liquid is drained by a centrifugal dehydrator, and dried in a box dryer at 80 ° C.

Example 2 The same as Example 1 except that 200 ppm of tetramethylammonium hydroxide was added and an aqueous solution adjusted to PH 10.3 was used instead of adding the ammonium hydroxide solution used in Example 1. went.

Example 3 A copper-clad laminate is surface-adjusted, a water-soluble dry film is pressure-bonded thereto, and a pattern film is overlaid and exposed. Then, it is developed with a 1% aqueous solution of sodium carbonate on a continuous conveyor line to dissolve and remove the dry film in the uncured portion to expose the metallic copper in the unnecessary portion. Then, with a copper chloride etching solution,
After the exposed metallic copper is dissolved and removed, the dry film in the hardened portion is dissolved and removed with a 3% caustic soda aqueous solution. Then
An aqueous solution containing 10 ppm of choline is added, and the aqueous solution adjusted to pH 8.8 is spray-washed with a spray-washer at room temperature for 20 seconds. Then, after squeezing with a squeezing roll and an air knife, it is dried with a conveyor hot air dryer. In this way, a printed wiring circuit board was manufactured.

Example 4 A test piece (iron-nickel alloy) is chemically polished, deburred and brightened. Then, at room temperature, an aqueous solution containing 100 ppm of ammonium hydroxide was added, and PH1
It is washed with an aqueous solution adjusted to 0.8 for 10 seconds. This is drained by air blow and then dried in a box dryer at 80 ° C.

Example 5 The hot work tool steel with lubricating oil adhered thereto is washed with alkali and then washed with water. Then, an aqueous solution containing 50 ppm of tetramethylammonium hydroxide is added and immersed in an aqueous solution adjusted to pH 9.0 at 80 ° C. for 30 seconds. This is 10
Dry with a centrifugal dehydrator kept at 0 ° C.

Example 6 Using a liquid crystal polymer containing an inorganic filler (Vectra C-820 manufactured by Polyplastix Co., Ltd.), a molded substrate having a recess for mounting a component was obtained 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. Bright nickel plating on the substrate thus obtained is 10-30μ
After forming a circuit pattern with a wire and then performing gold strike plating, gold plating for wire bonding is performed.
3 μm was applied. After that, the plating resist and the electroless copper plating of the non-circuit portion were removed from the substrate. Finally, 5 ppm of ammonium hydroxide was added, and ultrasonic cleaning was performed at room temperature for 30 seconds with an aqueous solution adjusted to pH 8.8.
After air-blowing, it was dried in a hot air dryer at 80 ° C.

Example 7 A test piece (brass) was plated with silver of 3 μm, washed with water, and added with 500 ppm of ammonium carbonate to adjust the pH to 1
It was immersed in an aqueous solution adjusted to 0.2 for 60 seconds. After this,
It was dried with a hot air dryer at 80 ° C.

Example 8 The procedure of Example 4 was repeated except that 1000 ppm of ammonium bicarbonate was added and an aqueous solution adjusted to PH 10.3 was used instead of the ammonium hydroxide used in Example 4.

Comparative Example 1 The procedure of Example 1 was repeated, except that the pre-drying treatment was not performed using the aqueous ammonium hydroxide solution adjusted to pH 9.5 of Example 1.

Comparative Example 2 Example 3 was repeated except that the choline solution was not added to the washing water of Example 3.

Comparative Example 3 The procedure of Example 4 was repeated, except that the ammonium hydroxide solution was not added to the wash water of Example 4.

Comparative Example 4 The procedure of Example 5 was repeated, except that the pre-drying treatment with the tetramethylammonium hydroxide aqueous solution adjusted to pH 9.0 of Example 5 was not performed.

Comparative Example 5 The procedure of Example 6 was repeated, except that the pre-drying treatment with the aqueous ammonium hydroxide solution adjusted to pH 8.8 of Example 6 was not performed.

Comparative Example 6 Example 7 was repeated except that the pre-drying treatment with the ammonium carbonate solution adjusted to PH 10.2 of Example 7 was not carried out.
I went the same way.

After visually observing the metal products after the above various treatments,
The appearance of dry unevenness, stains, etc. was evaluated in four levels according to the following criteria. ◎ Very good with no appearance defects such as drying unevenness and stains. ○ Very few appearance defects such as drying unevenness and spots, and excellent △ Some minor defects in appearance such as drying unevenness and stains occur. × Inferior appearance defects such as uneven drying and stains

The above results are shown in Table 1. Table 1 Example No. 1 2 3 4 5 6 7 8 Evaluation results ◎ ○ ○ ○ ◎ ○ ○ ◎ Comparative Example No. 1 2 3 4 5 6 Evaluation result × × △ △ × ×

[0050]

EFFECTS OF THE INVENTION The dried metal product obtained by the method of the present invention has a clean metal surface and has a good appearance free from uneven drying and spots, like the dried product obtained by the drainage substitution method using a flon or chlorine solvent. To be Therefore, it is possible to eliminate the use of CFCs or chlorine-based solvents that damage the environment.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23G 5/036 F26B 19/00 F26B 21/14

Claims (4)

(57) [Claims] 1. After being treated with a metal surface treating agent or a metal cleaning agent, and then with a treating agent comprising an aqueous solution containing a compound represented by the following formula (1), drying without washing with water. A method for drying a metal, comprising: [Chemical 1] (In the formula, R1, R2, R3, and R4 are hydrogen or 1 to 5 carbon atoms.
And an alkenyl group having 2 to 4 carbon atoms, and these groups may have a substituent, and these groups may be the same or different. Further, in the formula, X is a hydroxyl group, or a carbonate group or a bicarbonate group, and n is 1 or 2. ) 2. The drying method according to claim 1, wherein the compound represented by the formula (1) is selected from the group consisting of ammonium hydroxide, ammonium carbonate, and ammonium bicarbonate. 3. The drying method according to claim 1, wherein the compound represented by the formula (1) is selected from the group consisting of tetramethylammonium hydroxide, choline and neuline. 4. The drying method according to claim 1, which comprises treating with a treating agent containing a compound represented by the formula (1) and having a concentration adjusted to maintain pH of 8.5 or more.