KR101005854B1 - Alkaline degreasing agent composition for plating pretreatment and degreasing method using the same - Google Patents

Abstract

The present invention relates to an alkali degreasing agent composition for plating pretreatment and a degreasing method using the same, sodium hydroxide (NaOH) 20 ~ 35 g / L, sodium lauryl sulfate 2 ~ 6 g / l, sodium silicate (Na ₂ Alkali-based degreasing agent composition for plating pretreatment consisting of 0.2 to 3 g / l of SiO ₃ ), 20 to 50 g / l of sodium carbonate (Na ₂ CO ₃ ) and 10 to 40 g / l of ethylenediaminetetraacetic acid (EDTA) and the substrate By providing a degreasing method in the plating pretreatment step, the plating material is immersed in the composition of the, it is possible to minimize the defect of the plating process products.

Description

Alkaline degreasing agent composition for plating pretreatment and degreasing method using same {A alkaline degreasing agent for electroplating pretreatment process and electroplating method using the same}

The present invention relates to an alkaline degreasing agent composition for plating pretreatment and a degreasing method using the same.

The plating process is a process of coating a thin layer of another metal to improve the surface state of a metal or nonmetallic material, and is generally divided into a degreasing process, an activation process, a plating process, and a post-treatment process. The degreasing process is a very important part of the plating process and aims to remove contaminants such as oxides, hydroxides, metal salts and fats and oils attached to the metal surface, and degreasing alkalis, organic solvents and emulsions depending on the contaminants. Classified as

Organic solvent-based degreasing for the removal of mineral oils (rust preventive oil, grease, etc.) among organic substances, organic solvents such as alcohols, ketones, ethers, limonene and petroleum, and 1,1,1-trichlorethylene (TCE) and Chlorine-based solvents such as Freon are used, but the chlorine-based solvents are regulated due to the ozone layer destruction and the harmfulness to the human body.

In the case of emulsion degreasing, it is mainly used for the removal of organic-inorganic mixed contaminants generated in the polishing process, and is mainly used by mixing kerosine, crawling solvent, surfactant and water.

In the case of alkaline degreasing, water-soluble degreasing is used to remove animal and vegetable fats and oils. In the case of lipophilic contaminants, surfactants are added to improve degreasing ability.

Alkaline degreasing agents sold in Korea are prepared by adding several alkali salts and one or more surfactants. For example, sodium hydride (NaOH) enters to neutralize acidic dirt, and sodium triphosphate (Na ₃ PO ₄ ) is added to bridge the dirt, and to remove mineral fats and oils. Sodium pyrophosphate (Na ₄ P ₂ O ₇ ) is used. In addition, due to hard water, organic surfactants are also used by adding anionic, cationic, and nonionic compounds. Finally, in order to maintain alkalinity, sodium carbonate (Na2CO3) is added, and the surfactant is replaced with a cheap chemical agent. I use it. In the case of aluminum, sodium hydroxide is not added, and the amount of sodium metasilicate (Na ₂ SiO ₃ ) is increased, and even silicic acid-containing silicic acid is added to suppress corrosion. Use sodium pyrophosphate instead of sodium triphosphate and reduce the pH by reducing sodium carbonate to a minimum. In addition, surfactants are often used by adding soap and nonionics.

Such alkali-based degreasing agents are most widely used for the removal and removal of rust-preventive oils, cutting oils, press oils, etc. because of the advantages of low cost and no working bottles in the degreasing process, and a simple device.

The composition and performance of the alkali degreasing agent generally used are shown in Table 1 below.

However, the degreasing process of the metal surface is not just to achieve a degreasing effect but to perform saponification, emulsification, infiltration, dispersion and mechanical peeling. The saponification action refers to the separation of soap and glycerin by heating impurities in fats and oils in alkaline aqueous solution. However, in the case of mineral oils that do not saponify, they are dissolved by an organic solvent or removed by emulsification to atomize oils and disperse them. Penetration, also known as wetting, penetrates into oil and destroys oil molecules. Mechanical exfoliation is the process of removing oil from metal surfaces by mechanical forces, such as air agitation or ultrasonic cleaning.

Thus, the alkaline degreasing process is mainly a saponification reaction to heat the animal and vegetable fats and oils and react with an aqueous alkali solution to form a water-soluble soap, as shown in the following equation 1. Saponifiable fats and fats are fatty acid glycerin esters, which react with aqueous alkali solutions to break down sodium and glycerin. Since the soap produced in this reaction has emulsifying and dispersing power as a surfactant, the soap and the dispersing action are also performed by the aqueous alkali solution.

[Equation 1]

However, when the degreasing process is insufficient, poor adhesion of the plating layer, poor gloss, flaws of the plating surface, swelling, etc., brittleness and corrosion of the plating may occur. Surface contaminants in metal products depend on the material, shape, manufacturing process, and manufacturing environment, and it is very difficult to remove the contaminants completely.

Therefore, in the present invention, it was intended to develop a customized alkali degreasing agent that can be used in the degreasing process during the pretreatment of the plating process.

Accordingly, an object of the present invention is to provide a customized alkali degreasing agent that can be used in the degreasing step of the pretreatment of the plating process.

In addition, another object of the present invention is to provide a method for degreasing by immersing the plated body in the degreasing agent in the degreasing step during the pretreatment of the plating process.

In order to achieve the above object, the present invention is sodium hydroxide (NaOH) 20 ~ 35 g / L, sodium lauryl sulfate 2 ~ 6 g / L, sodium silicate (Na ₂ SiO ₃ ) 0.2 ~ 3 g An alkali-based degreasing agent composition for plating pretreatment consisting of / l, 20-50 g / l sodium carbonate (Na ₂ CO ₃ ) and 10-40 g / l ethylenediaminetetraacetic acid (EDTA) is provided.

In addition, in order to achieve another object, the present invention provides a degreasing method in the plating pretreatment process, characterized in that the plated body is immersed in the composition of the substrate.

Hereinafter, the present invention will be described in detail.

At this time, if there is no other definition in the technical terms and scientific terms used, it has a meaning commonly understood by those of ordinary skill in the art.

Repeated descriptions of the same technical constitution and operation as those of the conventional art will be omitted.

The present invention has been developed an alkali-based degreasing agent composition for plating pre-treatment that can be used to predict the service life is very excellent degreasing performance to minimize the defect of the plating process products.

Specifically, the present invention is sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), sodium silicate (Na ₂ SiO ₃ ), sodium lauryl sulfate and ethylene in the degreasing agent component used in the degreasing step of the conventional plating pretreatment process It is prepared by combining specific components of diamine tetraacetic acid (hereinafter referred to as EDTA) and adding these components at a certain ratio to double the cycle of use while improving the degreasing performance by synergistic effects.

In the alkali-based degreasing agent composition for plating pretreatment according to the present invention, sodium hydroxide is an alkali component that provides a degreasing effect through a saponification action, and 0.2 to 3 g / l of sodium silicate (Na ₂ SiO ₃ ) and sodium carbonate (based on 1 L of the total composition). Na ₂ CO ₃ ) It is preferable to use 20 to 35 g in the presence of 20 to 50 g / ℓ, more preferably 30 g, which is less than 20 g if the water to the surface of the plated body after the degreasing process This is because the suppression and degreasing effect is reduced, and when it exceeds 35 g, the water squeeze suppression and degreasing effect is insignificant in proportion to the excess amount.

In addition, sodium carbonate is used to improve the degreasing performance of sodium hydroxide. It is preferable to use 20-50 g in the presence of 20-35 g / l sodium hydroxide and 0.2-3 g / l sodium silicate based on 1 l of the total composition. And more preferably 40 g, since the use within the range of use is the most effective in improving the degreasing performance.

In addition, sodium silicate in the degreasing agent composition of the present invention is used to improve the degreasing performance of sodium hydroxide and sodium carbonate, because it is relatively expensive, in order to show the best degreasing performance with a minimum amount of use, the hydroxide on the basis of 1L total composition It is preferable to use 0.2-3 g in the presence of 20-35 g / l sodium and 20-50 g / l sodium carbonate, and more preferably 2 g. When using less than 0.2 g, the effect of improving degreasing performance is reduced. This is because if it is insignificant and exceeds 3g, the degreasing performance is insignificant in proportion to the excess amount and the production cost is increased.

In the present invention, sodium lauryl sulfate (hereinafter referred to as SLS) is a degreasing efficiency as a surfactant, but is known as a carcinogen, so 10 to 40 g of ethylenediaminetetraacetic acid based on 1 l of the total composition to show the best degreasing effect with a minimum amount of use. 2 to 6 g in the presence of / l, preferably 2 g is used, which is less than 2 g degreasing rate, when used in excess of 6 g, does not meet the purpose of the present invention in preparation for excess usage Degreasing effect is also minimal.

In addition, in the present invention, ethylenediaminetetraacetic acid alone does not show a degreasing effect of 90% or more as an anionic surfactant, but sodium hydroxide (NaOH) 20-35 g / l, sodium silicate with a minimum amount of SLS 2-4 g / l. (Na ₂ SiO ₃ ) in the presence of 0.2 to 3 g / l and 20 to 50 g / l sodium carbonate (Na ₂ CO ₃ ) in the use range of 10 to 40 g on the basis of 1 l of the total composition, preferably 25 g on average A degreasing rate of more than 95% is maintained even after 9 repetitions. Therefore, when the use of less than 10g in the present invention, the above-mentioned effect is insignificant, and when it is used in excess of 40g, the degreasing rate effect is insignificant compared to the excess amount used, it is preferable to use within the above-mentioned use range.

Thus, the most preferred optimum degreasing agent composition according to the present invention preferably consists of 30 g / l sodium hydroxide, 2 g / l SLS, 2 g / l sodium silicate, 40 g / l sodium carbonate and 25 g / l EDTA.

Meanwhile, the alkali degreasing agent composition for plating pretreatment according to the present invention provides a method of using the immersion type degreasing agent of the plated body, and preferably, the plated body is immersed for 25-40 minutes at the degreasing agent composition of 40 to 55 ° C. It is preferable to carry out degreasing. This is because the optimum degreasing effect appears in the optimum conditions of the degreasing process described above. More preferably, degreasing by plating the plated body for 35 minutes at 50-55 ° C. shows the best degreasing effect in terms of time and cost.

In addition, the immersion type degreasing agent composition according to the present invention is to prove at least nine times the service life of the degreasing efficiency of 95% or more, thereby minimizing the defective rate of the process product through accurate service life. Thus, the degreasing agent composition according to the present invention can be used repeatedly at least 9 times in the immersion type degreasing process.

In addition, the alkali-based degreasing agent prepared according to the present invention can be generally used in the degreasing step of the pretreatment process of the plating process, for example, the pretreatment process of the nickel plating process of the wheel nut of the automobile (nut), more specifically nickel-chromium It is preferable to use a customized alkali degreasing agent that can be used in the degreasing process of the copper plating pretreatment process, which is a plating process of the base plating.

As described above, the immersion type alkali-based degreasing agent of the present invention can predict the service life with excellent degreasing performance through suppression of water droplet formation and Hull-cell plating analysis on the plated body from which contaminants have been removed, thereby minimizing defects in the plating process products. Can be reduced.

Figure 1 shows the degreasing performance of each concentration of sodium hydroxide according to an embodiment of the present invention as a result of the degreasing rate and water droplets.
Figure 2 shows the degreasing performance of each concentration of SLS according to an embodiment of the present invention as a result of the degreasing rate and water droplets.
Figure 3 shows the degreasing performance of each concentration of sodium silicate according to an embodiment of the present invention as a result of the degreasing rate and water droplets.
Figure 4 shows the degreasing performance of each concentration of sodium carbonate according to an embodiment of the present invention as a result of the degreasing rate and water droplets.
Figure 5 shows the degreasing performance of each concentration of sodium carbonate according to another embodiment of the present invention as a result of the degreasing rate and water droplets.
Figure 6 shows the degreasing performance for each concentration of LAS according to an embodiment of the present invention.
Figure 7 shows the degreasing performance by concentration of EDTA according to an embodiment of the present invention.
8 shows degreasing performance for each concentration of EDTA according to another embodiment of the present invention.
Figure 9 shows the degreasing rate for each temperature according to the degreasing time of the alkaline degreasing agent in the present invention.
Figure 10 shows the degreasing rate according to the temperature of the alkaline degreasing agent in the present invention.
Figure 11 shows the results of water droplet condensation experiment of the plated body of the alkali degreasing agent according to the present invention.
Figure 12 shows the degreasing rate according to the number of repeated use of the alkaline degreasing agent according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples, and it will be apparent to those skilled in the art that various changes or modifications can be made within the spirit and scope of the present invention.

[ Experimental Example ]

1. Degreasing performance evaluation

There are two methods for evaluating degreasing performance: simple and overhaul. Simple inspection methods include water droplet condensation inspection, visual inspection, weight inspection, test pen (ink) inspection, ultraviolet irradiation method, contact angle inspection, etc., and detailed inspection methods include device analysis methods such as ESCA and SEM, and Hull for checking plating characteristics. -cell plating analysis. In this study, water drop lumping test and Hull-cell plating analysis were performed to evaluate the degreasing performance of the prepared degreasing agent. The dripping test is a method of indirectly checking the cleanliness of a surface by dropping water droplets on the surface of the material or by observing the spreading phenomenon using a spray. In the Hull-cell plating analysis, a 267 mL Hull having a different distance between a cathode and an anode is used. It is an analysis method that can observe the surface characteristics of plated specimens by the method of observing the plating surface with various current densities at the time of one plating using -cell group. In the Hull-cell plating analysis method, the total current was set to 2A at a temperature of 50 ° C. and plated for 5 minutes. It is a test method to observe the surface characteristics of plating by checking uniform plating characteristics from left (high current density) to right (low current density) in the Hull-cell plating pattern after plating.

[ Example ] Alkali system  Preparation of Degreasing Agent

Iron specimens used in this example (6.5 × 2cm) were used after washing with ultrasonic waves at 55 minutes for 10 minutes. After applying the vegetable oil used in the machine oil and the press process to dry iron specimens and drying it, put it in 500 mL of the alkali-based degreasing solution, and soak it for 30 to 40 minutes at a temperature of 40-50 ℃ to perform the degreasing process. Degreasing performance was evaluated. Alkaline immersion degreasers include sodium hydroxide (NaOH, 20 to 35 g / L), sodium carbonate (Na ₂ CO ₃ , 0.2 to 3.0 g / L), sodium silicate (Na ₂ SiO ₃ , 20 to 50 g / L), triphosphate Sodium (Na ₃ PO ₄ , 10 ~ 30g / L) was used, and as anionic surfactant, SLS (sodium lauric sulfate, 2 ~ 8g / L), EDTA (ethylene diamine tetra acetic acid, 10 ~ 40g / L), LAS (linear alkylbenzene sulfonic acid, 2.5 ~ 10g / L) was selected and prepared by variable mixing in a constant concentration in water.

(One) NaOH Effect of concentration on

In order to investigate the corrosiveness of the metal to NaOH, which is the base of the alkaline degreasing agent solution, the surface state was observed after immersing the iron specimen coated with fat or oil in 20 ~ 35g / L NaOH aqueous solution. The degreasing temperature was set at 50 ° C., and the degreasing performance was confirmed by a degreasing ratio and water droplet test after 40 minutes of degreasing. In this invention, the degreasing ratio was computed like Formula (2).

[Equation 2]

As a result, as shown in FIG. 1, the concentration of NaOH was set in the range of 20 to 35 g / L, the degreasing rate calculation result was found to be 56.8 to 61.2%, and water droplets were formed under all conditions.

Therefore, NaOH alone could not be used as a degreasing agent, and it is thought that the addition of surfactant and other alkali reagents should be made.

(2) SLS Influence of concentration

In order to investigate the effect of SLS, a surfactant, in degreasing agent composition, NaOH concentration was fixed at 30g / L at 50 ° C, and SLS concentration was changed to 2-8g / L for 40 minutes of degreasing performance.

As a result, as shown in FIG. 2, the degreasing rate increased as the concentration of SLS was increased, but the degreasing rate did not change at a concentration of 6.0 g / L or more. In addition, when the SLS of 6.0g / L or more was added as a result of water droplet formation, no water droplets formed on the surface, and in the Hull-cell plating analysis, when the SLS or more was added to 4.0g / L, no plating was observed in the high current part. . Therefore, the concentration of SLS could be recommended 6.0g / L.

(3) Sodium Silicate  Effect of Sodium Carbonate

After setting the basic composition of the alkaline degreasing agent to 30g / L sodium hydroxide, SLS 6.0g / L through the previous embodiment, and other such as sodium silicate (Na ₂ SiO ₃ ) and sodium carbonate (Na ₂ CO ₃ ) for 40 minutes at 50 ℃ Alkaline degreasing reagent was added and the degreasing performance was examined according to the ratio.

The concentration range of sodium silicate was 0.2 to 3.0 g / L, and the concentration range of sodium carbonate was varied to 20 to 50 g / L, and the results of experiments are shown in FIGS. 3 and 4, respectively.

As shown in Figures 3 and 4, both concentrations of sodium silicate and sodium carbonate increased the degreasing rate, it was confirmed that the addition of sodium silicate showed a better degreasing rate than sodium carbonate.

In addition, the result of water droplet condensation experiment and Hull-cell plating showed excellent degreasing performance in the composition of sodium silicate of 2.0g / L or more, and of sodium carbonate in the composition of 40g / L or more.

On the other hand, since the price of sodium silicate is higher than that of sodium carbonate, the experiment was performed by adjusting the addition ratio to high concentration of sodium carbonate and low concentration of sodium silicate.

Degreasing performance according to Na ₂ CO ₃ concentration was determined by NaOH concentration of 30g / L, SLS 6.0g / L, Na ₂ SiO ₃ 2.0g / L as the basic degreasing composition. At this time, the concentration range of sodium carbonate was set to 20 ~ 50g / L, degreasing conditions were fixed at 50 ℃, 40 minutes.

As a result, as shown in Figure 5, the degreasing performance increased as the concentration of sodium carbonate increased, but the change in the degreasing performance did not appear significantly when the concentration of sodium carbonate was added more than 40g. In addition, water droplet condensation experiments and Hull-cell plating analysis showed that water droplet condensation and low current and high current portions of carbonized and unplated phenomena were not observed when more than 30 g of sodium carbonate was added.

Thus, through this embodiment it was found that the optimal concentration of sodium carbonate is 40g based on the total composition 1ℓ.

Therefore, through the results of the above examples, it could be suggested that the optimal composition of the degreasing agent according to the present invention is sodium hydroxide 30g / L, sodium silicate 2.0g / L, sodium carbonate 40g / L and SLS 6.0g / L.

(4) Influence of Anionic Surfactants

In this example, the degreasing performance was confirmed by selecting EDTA and LAS as an anionic surfactant that can replace SLS classified as a carcinogen. LAS is the most widely used surfactant for metal cleaning, and EDTA is known to act as a water softener that makes hard water soft by making complexes with metal ions. At this time, the composition of the alkaline degreasing agent of the present invention is added to EDTA and LAS on the basis of sodium hydroxide 30g / ℓ, sodium silicate 2.0g / ℓ, sodium carbonate 40g / ℓ and compare the degreasing performance at 40 ℃ degreasing conditions for 40 minutes Analyzed.

As shown in Figure 6, the result of performing a degreasing experiment by varying the concentration range of the LAS anionic surfactant to 2.5 ~ 10g / L, as a result of evaluating the degreasing performance using LAS instead of SLS, the degreasing rate is more than 85% However, it was confirmed that degreasing performance was deteriorated by water droplet condensation experiment and Hull-cell plating analysis.

As shown in FIG. 7, the concentration range of EDTA was 10 to 40 g / L, and the result of the degreasing experiment showed that the range of addition amount was larger than that of other anionic surfactants in order to obtain a degreasing ratio of 90% or more. , EDTA alone could not be expected to excellent degreasing performance.

On the other hand, the basic composition of the degreasing agent according to the present invention to determine the SLS reduction effect of EDTA is sodium hydroxide 30g / L, sodium silicate 2.0g / L, sodium carbonate 40g / L and SLS (2.0g / L), the concentration range of EDTA As a result of confirming the degreasing performance by varying 20 to 35 g / l, as shown in FIG. 8, the degreasing ratio was excellent compared to the case of using only EDTA, and the result of water droplet formation and Hull-cell plating analysis showed very good degreasing performance. The addition of 25 g / ℓ showed the best degreasing performance.

Therefore, the optimal composition of the immersed alkaline degreasing agent according to the present invention can be presented as 30 g / L sodium hydroxide, 2 g / L SLS, 2 g / L sodium silicate, 40 g / L sodium carbonate and 25 g / L EDTA. .

(5) Alkali system  Determination of Degreasing Conditions

NaOH 30g / L, Na ₂ SiO ₃ 2.0g / L, Na ₂ CO ₃ 40g / L, SLS 6.0g / L, EDTA 25g / L with custom alkaline degreasing agent The optimization experiment of the degreasing process was performed. At this time, the degreasing temperature was kept constant in the range of 40 ~ 55 ℃, degreasing time was set to 25 to 40 minutes.

As a result, as shown in Figure 9 and Figure 10, in the case of degreasing time degreasing rate tended to increase as time increases, but the change in degreasing rate could not be observed at the time more than 35 minutes. The degreasing rate also increased with increasing degreasing temperature, but no change in degreasing rate was observed at temperatures above 50 ℃.

Also, the water droplet condensation experiment and the Hull-cell plating analysis according to the degreasing temperature and the degreasing time are shown in FIG. 11. At this time, the Hull-cell plating analysis was plated for 5 minutes with a total current (2A) at a temperature of 50 ℃ and was performed to observe the uniform plating characteristics of the right (low current density) portion from the left (high current density).

As shown in FIG. 11, in the case of the water droplet condensation test, when degreased for more than 35 minutes at a degreasing temperature of 50 ° C. or higher, excellent degreasing performance was observed. When degreased for 30 minutes or more, it was confirmed that the degreasing effect was excellent due to uniform plating characteristics from low current density to high current density.

Thus, in this embodiment, the optimum degreasing temperature and the degreasing time were set to 50 ° C. and 35 minutes, respectively.

(6) Service life

In the present embodiment, the degreasing agent composition of the present invention performs the same experiment every 35 minutes at the optimum degreasing temperature and the degreasing time at 50 ° C. and through the repeated degreasing experiment of the same degreasing agent to maintain a service life of 95% or more. The purpose of this study was to predict the replacement cycle of alkaline degreasing agent in the actual process.

As a result, as shown in Figure 12, the degreasing rate tended to decrease as the number of repetitions increased, but the degreasing rate was 95% or more until 9 repetitions.

Claims (6)

Sodium hydroxide (NaOH) 20-35 g / l, Sodium lauryl sulfate 2-6 g / l, Sodium silicate (Na ₂ SiO ₃ ) 0.2-3 g / l, Sodium carbonate (Na ₂ CO ₃ ) 20- An alkali degreasing agent composition for plating pretreatment consisting of 50 g / l and 10-40 g / l of ethylenediaminetetraacetic acid (EDTA). The method of claim 1,
30 g / l sodium hydroxide (NaOH), 2 g / l sodium lauryl sulfate, 2 g / l sodium silicate (Na ₂ SiO ₃ ), 40 g / l sodium carbonate (Na ₂ CO ₃ ) and ethylenediamine Alkaline degreaser composition for plating pretreatment, characterized in that it consists of 25 g / l of tetraacetic acid (EDTA). The degreasing method in a plating pretreatment process characterized by immersing the plated body in the composition according to claim 1. The method of claim 3, wherein
A degreasing method in a plating pretreatment process, characterized in that the composition is immersed for 25 to 40 minutes at a temperature of 40 to 55 ° C. The method of claim 4, wherein
A degreasing method in a plating pretreatment step, characterized in that the composition is immersed for 35 minutes at a temperature of 50 ° C. The method of claim 3, wherein
The composition is a degreasing method in the plating pre-treatment process, characterized in that the service life can be used repeatedly in the degreasing process at least nine times.

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