JP3503519B2 - Corrosion inhibitor / discoloration inhibitor for copper-based materials - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a corrosion inhibitor / discoloration inhibitor for copper-based materials (copper and copper alloys), a copper-based material containing the same, and a treatment liquid for corrosion inhibition / discoloration prevention of copper-based material products. Processing lubricants. The present invention also relates to a copper product treated with the above corrosion inhibitor / discoloration inhibitor, and a packaging material for a copper-based material containing the same.

The corrosion inhibitor / discoloration inhibitor according to the present invention can suppress the ant nest-like corrosion found in copper pipes for heat exchangers such as refrigerators and air conditioners, and also discolor the copper surface. It can be prevented for a long period of time.

[0003]

2. Description of the Related Art Since copper has high thermal conductivity, is easy to process, and has relatively high corrosion resistance, copper pipes and copper alloy pipes are particularly used for various pipes for heat exchange. The surfaces of copper and copper alloys are covered with an oxide film, which serves as a protective film and shows high corrosion resistance because copper itself is a noble metal.

For example, pipes of copper alloy such as special brass and cupro-nickel are used for heat exchangers (eg, condensers) of thermal and nuclear power plants, chemical plants, ships and the like. Since highly corrosive seawater, river seawater, etc. are often used as cooling water for such heat exchangers, various anticorrosion measures have been taken. For example, injecting a small amount of iron ions into the cooling water is effective in suppressing corrosion such as pitting and erosion, but since iron adheres to the inside of the pipe and heat transfer efficiency decreases, the inner surface is coated to form an organic coating. The method of application has become common. Regarding this inner surface coating, for example, Japanese Patent Publication Sho 59
-50269, JP-A-62-77600, 63-118598,
63-233299, 63-233300, Japanese Examined Patent Publication 3-35548,
No. 4-81116, JP-A-6-42892, and JP-A-6-193792. Japanese Unexamined Patent Publication (Kokai) No. 63-145788 describes an aqueous solution of ferrous sulfate in which carboxylate ions coexist as an anticorrosive agent for such copper pipes.

Even in copper-based pipes for flowing tap water or ground water, pitting corrosion may occur due to residual chlorine in tap water or other factors, and countermeasures have been considered. The most common method is to add an organic inhibitor to water. It is known that benzotriazoles are particularly effective as organic inhibitors for copper-based materials. Other anticorrosion additives are described in JP-A-6-88262 and JP-A-6-287776.

JP-A-59-74283 discloses that an aqueous solution of a compound that forms a stable chelate with copper (eg, citric acid, tartaric acid, phytic acid, or their salts) is circulated in a copper tube, It has been proposed to attach an anticorrosion coating to the surface.

As mentioned above, the surfaces of copper and copper alloys are
It is covered with an oxide film made of cuprous oxide, but the color looks different depending on the thickness of this oxide film. For example, in the case of pure copper, if the thickness of the oxide film increases, dark brown, reddish brown, purple,
The color changes in the order of blue, green, yellow, orange, and red, and appears as a discoloration. When clean pure copper is placed in a dry atmosphere, the oxide film grows rapidly up to 30-40 Å and then stops growing and discoloration hardly occurs. However, when the humidity is high or the atmosphere contains an acidic gas such as sulfuric acid or hydrogen sulfide, the oxidation is further promoted, the oxide film becomes thick, and the above-mentioned discoloration occurs.

It is known that treatment with organic inhibitors, especially benzotriazoles, is effective in preventing this discoloration. For example, a tarnish inhibitor having a composition of benzotriazole 4 to 6%, hexylene glycol 25 to 30%, amine compound 5 to 6%, nonionic surfactant 1 to 3%, and the balance being water is commercially available in weight%. Copper products such as plates and strips are treated with such a discoloration-preventing agent before shipment before they are used by the user to prevent discoloration.

Copper pipes are also used in piping for heat exchangers such as refrigerators and air conditioners (eg, home room air conditioners). In recent years, a copper pipe used for this purpose has been leaking due to unexplained penetration, which has become a problem. Penetration of the copper pipe occurs due to a completely different aspect of corrosion from normal pitting and erosion. That is, this corrosion is such that the surface opening of the corrosion hole is, for example, 10 μm or less, which is too small to be detected by the naked eye, while the inside of the corrosion hole is intricate in an indeterminate direction and is connected in a tunnel shape to form a cave in some places. It is generally called "ant's nest-like" corrosion because it has a characteristic that it is filled with corrosion products mainly composed of cuprous oxide, and the corrosion form looks like an ant's nest. In the vicinity of the surface opening of the corrosion pit, discoloration to adzuki bean or reddish brown is observed, which is different from the normal pitting which causes discoloration of green-blue.

This ant nest corrosion is not found in the inspection at the time of assembling the air conditioner or the like, but is often found in the product inspection at the time of shipment after the product is stored or at the beginning of use by the user. That is, the ant nest corrosion progresses within a short period of time after the product is assembled and leads to penetration. For example, there were cases in which a 0.35 mm thick copper tube caused a penetration accident within 3 months. Although ant nest corrosion is small in number, it leads to an early penetration accident and significantly impairs the reliability of the product. Therefore, countermeasures against it are urgent.

The inventors of the present invention have conducted extensive studies on ant nest corrosion and found that the cause is the component in the lubricating oil used for copper pipe processing. As a corrosive medium for ant nest corrosion (corrosion-causing substance), it was initially pointed out that decomposition products of chlorine-based organic solvents used for degreasing and cleaning after processing are possible. It was also confirmed that the corrosion could be reproduced. However, even if the chlorine-based organic solvent reacts with water, formic acid is not generated, and since copper-based pipes that have not been degreased and washed with this solvent also have ant nest-like corrosion, corrosion media other than chlorine-based organic solvents result of pursuing the oxygen-containing organic compound contained in the lubricating oil (e.g., ester, higher alcohol, ether) degradation products of low molecular weight produced by the hydrolysis of, in particular C ₁ -C ₂ alcohol, aldehyde, carboxylic acid It was found that aldehyde, which is a causative substance of ant nest corrosion, exhibits particularly strong corrosiveness.

On the basis of this finding, the present inventors searched for a substance effective in preventing this corrosion, and as a result, disclosed in JP-A-6-10164.
U.S. Pat. Nos. 6-10165, 6-10166, and 6-10167, urea-based, thiourea-based, imidazole-based, benzothiazole-based, phenothiazine-based,
And that thiocarbamic acid-based organic compounds are effective as corrosion inhibitors for ant nest corrosion of copper-based materials, and this corrosion inhibitor should be added to the lubricating oil used for copper pipe processing. It was also found that the above can prevent the ant nest corrosion caused by the above-mentioned lubricating oil.

[0013]

The above corrosion inhibitors proposed by the present inventors are merely attached to the surface of the copper-based material. Further, since these corrosion inhibitors are soluble to some extent in both water and organic solvents, they will be removed in the washing step during the production of water and copper pipes that condense on the surface of the copper-based material during use, It has been difficult to maintain stable corrosion-inhibiting hardening over a long period of time.

An object of the present invention is to provide a corrosion inhibitor / discoloration inhibitor which forms a strong film on the surface of a copper-based material. As a result, the corrosion inhibitor / discoloration inhibitor is stably present on the surface of the copper-based material, and the ant nest-like corrosion of the copper-based material can be effectively suppressed for a long period of time.

[0015]

The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, some silane coupling agents suppress long-term inhibition of ant nest corrosion of copper-based materials. The present invention has been completed, and the present invention has been reached. It was also found that this silane coupling agent can prevent discoloration of the copper-based material for a long period of time in addition to ant nest corrosion.

In the present invention, silane coupling containing one or more elements selected from N, O and S, and further having a functional group or a hydrophobic group capable of adsorbing a carboxyl group at the molecular end thereof. It is a corrosion-inhibiting / discoloration-preventing agent for copper-based materials, which is characterized by comprising an agent.

The functional group capable of adsorbing the carboxyl group can be selected from primary and secondary amino groups and epoxy group, and the hydrophobic group is -NR ¹ R ² (R ¹ and R ² are alkyl groups or aryl groups). Group), -NHR ³ (R ³ is an alkyl group or aryl group having 2 or more carbon atoms), -NHCOR ¹ (R ¹ is the same as above), an alkyl group having 4 or more carbon atoms and a fluorine-containing alkyl group, and an aryl group You can choose from.

According to the present invention, further, a treatment liquid for a copper-based material and a copper-based material product, which comprises a solution containing the above corrosion-inhibiting / discoloring-preventing agent in an organic solvent; Lubricating oil for processing copper-based materials containing tarnish inhibitor;
A copper-based material product, in particular a copper tube for a heat exchanger, characterized in that the hydrolysis product of the above corrosion inhibitor / discoloration inhibitor is bound to the surface; and the above corrosion inhibitor / discoloration inhibitor inside or on the surface thereof. A packaging material for the copper-based material product containing the same is also provided.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION First, the mechanism of ant nest corrosion of a copper-based material, which has been investigated by the present inventors, will be described. The following mainly describes corrosion of copper, but the same applies to the case of copper alloys.

Copper pipes for heat exchangers such as refrigerators and air conditioners are shipped to heat exchanger processing makers through pipe making by bright drawing at copper pipe manufacturers, bright annealing or washing processes. At this stage, the lubricating oil used during processing hardly remains on the surface of the copper pipe due to volatilization and washing with a solvent. Manufacturers of heat exchangers perform the secondary processing of copper pipes, such as cutting, bending, expanding the mouthpiece and fixing the fins, using lubricating oil.

After the heat exchanger is assembled and processed, it is washed with a chlorine-based organic solvent before shipment. However, recently, from the viewpoint of environmental pollution, there is a tendency to avoid using chlorine-based organic solvents, and volatile lubricants have been used in place of conventional non-volatile lubricants, and products have not been washed. .

The present inventors have found that a large number of lubricating oils (7 companies, 20
Species) was investigated for corrosiveness of copper pipes. As a result, it was found that 17 kinds of lubricating oil caused ant nest corrosion. Corrosiveness tended to be greater with volatile lubricants than with non-volatile lubricants. Further, it was confirmed by ion chromatography that the lubricating oil that caused ant nest corrosion produced formic acid and / or acetic acid when reacted with water. Further, all of these lubricating oils contain oxygen-containing organic compounds such as esters, ethers and higher alcohols as common components. When these compounds react with water to cause hydrolysis, they are low molecular weight alcohols,
It was suspected that they were the caustic media for the ant nest corrosion of copper-based materials as they produced aldehydes or carboxylic acids.

Then, as such a low molecular weight hydrolysis product, C _{1 of} methanol, formaldehyde and formic acid is used.
Compounds, and of ethanol, acetaldehyde, acetic acid
Focusing on C ₂ compounds and investigating their corrosiveness to copper-based materials, they all caused ant nest corrosion.
However, the form of corrosion in the case of acetic acid was close to pitting corrosion. The corrosiveness was in the order of formaldehyde> formic acid>methanol≈acetaldehyde>ethanol> acetic acid.

From the above, the main corrosive medium for ant nest-like corrosion peculiar to copper-based materials is a low molecular weight (C ₁ , C ₂ ) oxygen-containing organic compound such as aldehyde, carboxylic acid, alcohol, and C ₂ It was found that the C ₁ compound was more corrosive, and the aldehyde showed the strongest corrosive property among the types of compounds. In addition, the ant nest-like corrosion of the copper-based material occurs in the lubricating oil because the above-mentioned low molecular weight compound that serves as a corrosion medium is generated by the hydrolysis of components such as ester, ether, and higher alcohol in the lubricating oil. Conceivable.

It is known that alcohols are easily oxidized to aldehydes using copper as a catalyst. When aldehyde is oxidized, it becomes a carboxylic acid, but according to the experiments by the present inventors, in the presence of copper, aldehyde (formaldehyde)
To carboxylic acid (formic acid) easily occurs. It can be inferred that this oxidative reaction of aldehyde to carboxylic acid involving copper is a reaction which becomes the formula (5) through the following formulas (1) to (4).

[0026] _{RCHO + Cu 2 0 → RCOOH +} 2Cu + (1) Cu → Cu + + e - (2) 1/2 O 2 + H 2 O + 2e - → 2OH - (3) 2Cu + 2OH - → Cu 2 0 + H 2 O (4 ) RCHO + 1/2 O ₂ → RCOOH (5) From the above, it is speculated that the causative agent of ant nest corrosion of copper-based materials is carboxylic acid generated from alcohol or aldehyde, especially formic acid. Regarding the corrosion mechanism of ant nest corrosion, the following reaction formula has already been shown in a study by Japan Copper Center, etc., and carboxylic acid, especially formic acid, is also used as the corrosion medium. Although it does not appear in this reaction equation, the oxidation of Cu to Cu ₂ 0 proceeds due to the presence of water and the dissolved oxygen in water.

3Cu + 2RCOOH + O ₂ → Cu ₂ O + Cu (RCOO) ₂ + H ₂ O (6) This reaction formula is shown more accurately in consideration of the findings of the present inventors.

[0028]

[Chemical 1] It is considered that ant nest corrosion progresses according to this reaction formula, but this reaction formula cannot explain that formaldehyde is more corrosive than formic acid. Considering the finding found by the present inventors that the oxidation of formaldehyde to formic acid is likely to occur in the presence of copper, the aldehyde is adsorbed on the surface of copper, and thus the adsorbed aldehyde is converted into a carboxylic acid on the copper surface. It is speculated that the carboxylic acid that was oxidized and formed on the copper surface would immediately induce ant nest corrosion. Oxidation of an aldehyde to a carboxylic acid on the copper surface is accompanied by dissolution of copper as seen from the above equations (1) to (4), so it is thought to promote the formation of copper oxide near the copper surface.

Further, since the tip of the corrosion hole is in a state where the active point is always maintained due to the decrease in pH caused by the copper dissolution reaction and the carboxylic acid formation reaction and the formation of a local battery, It is speculated that erosion may proceed only in the direction, resulting in ant nest corrosion. It is considered that the reason why aldehyde is more corrosive than carboxylic acid is that the amount of copper eluted is large and the pH is maintained at the corrosion tip where corrosion easily proceeds.

According to the present invention, N having a lone pair of electrons,
A silane coupling agent containing one or more elements selected from O and S and further having a functional group capable of adsorbing a carboxyl group or a hydrophobic group is used as a corrosion inhibitor / discoloration inhibitor for copper-based materials. To use as.

Generally, the silane coupling agent is X ₃ -Si.
- (CH ₂₎ represented by the n-Y becomes the general formula. 3 X is the 2
One or more, preferably all three, are hydrolyzable groups (alkoxy groups are common, but may be halogen) and the rest are lower alkyl groups (eg methyl, ethyl). n
Is generally in the range of 0 to 4, preferably 2 to 3. Y is a functional group moiety, and examples of the functional group generally include halogen, vinyl, acryloxy or methacryloxy, amino, mercapto, ureido, epoxy-containing groups (eg, epoxycyclohexyl group, glycidoxy group) and the like.

The silane coupling agent was developed to improve the adhesion between the inorganic material and the polymer when the inorganic material such as glass fiber and inorganic filler (eg calcium carbonate) is blended with the polymer. And is generally inorganic-
The adhesion between organics can be improved. This is because the hydrolyzable group (X) of the silane coupling agent hydrolyzes and binds to the inorganic material, while its-(CH ₂ ) n-Y moiety has a high affinity (in some cases, reactivity) with the organic material. ) Is shown.

The silane coupling agent can also be used for surface treatment for making the surface of the inorganic material substrate hydrophobic or adhesive to the organic material. The bonding process of the silane coupling agent to the substrate in that case is shown in FIG. The bonding process is basically the same even if the substrate is glass fiber or filler as described above.

As shown in FIG. 1, the substrate (material in the figure) of the inorganic material has hydroxyl groups (OH groups) on the surface, and the OH groups generated by hydrolysis of the silane coupling agent and the OH groups on the surface of the substrate are of
The silane coupling agent is firmly bonded to the surface of the substrate due to the condensation reaction between the OH groups. In addition, OH generated by hydrolysis
Of the groups, the remaining OH groups which are not used for the reaction with the substrate are condensed by the silane coupling agents and polymerized through a siloxane bond (-Si-O-) to form a crosslinked structure of polysiloxane. . Thus, the surface of the substrate is covered with the polysiloxane film. This coating has excellent durability due to its crosslinked structure.

Although not shown, the-(CH ₂ ) n-Y portion of the silane coupling agent is not hydrolyzable and remains after the above reaction, so that the surface of the formed polysiloxane film is This organic group portion is present, and thereby the adhesiveness with the organic material and the hydrophobicity are imparted to the substrate surface.

When the substrate of the inorganic material is a metal such as aluminum, iron or zinc, the hydroxide of which can exist stably, innumerable OH groups are present on the metal surface. Therefore, in the process shown in FIG. 1, the silane coupling agent can be firmly bonded to the surface of the substrate by the chemical bond. However, since copper is not a metal in which hydroxide can stably exist, OH groups do not exist on the surface. Therefore,
Bonding to the substrate by the condensation reaction of OH groups as shown in FIG. 1 is impossible.

Therefore, in the present invention, the silane coupling agent contains an element having a lone electron pair, that is, one of N, O and S.
One kind or two or more kinds are contained. N can be introduced into the silane coupling agent in the form of, for example, an amino group or an imino group. The amino group may be any of primary, secondary and tertiary amino groups. O may be in the form of oxy (ether), ketone and the like. S may be in the form of mercapto, thio (thioether).

By containing the element having a lone electron pair in this way, as shown in the case of N in FIG. A coupling agent can be attached to the copper surface. Also in this case, as shown in FIG. 2, the hydrolyzable group of the silane coupling agent (a methoxy group in the figure) is first hydrolyzed to an OH group, and the OH group is generated between the adjacent silane coupling agent molecules. The condensation reaction between the two forms a crosslinked structure of polysiloxane, and the substrate surface is covered with the polysiloxane film.

When the copper surface is covered with the polysiloxane film having a dense cross-linking structure as described above, even if the aldehyde adheres to the copper surface, it is difficult to contact the copper necessary for its oxidation, so that the aldehyde (eg, formaldehyde) ) Is a carboxylic acid
It becomes difficult to be oxidized (for example, formic acid). Similarly, with respect to alcohol, since copper serves as a catalyst for oxidation to aldehyde, oxidation to aldehyde is less likely to occur. Therefore, a carboxylic acid such as formic acid mainly acts as a corrosion medium.

In order to suppress the corrosion due to carboxylic acid, the silane coupling agent used in the present invention contains, in addition to the above-mentioned element having a lone electron pair, a molecular terminal (X ₃ -Si- (CH ₂ ) n-
A functional group capable of adsorbing a carboxyl group or a hydrophobic group is contained at the end of the Y portion of the general formula Y. Therefore, such functional groups or hydrophobic groups are present in the polysiloxane film.

When the polysiloxane film has a functional group capable of adsorbing a carboxyl group (hereinafter referred to as an adsorbing group), as shown in FIG.
Since (eg, formic acid) is adsorbed by this adsorption group, it cannot act as a corrosion medium. Therefore, this is particularly effective in suppressing corrosion by carboxylic acids such as formic acid.

On the other hand, when a hydrophobic group having water repellency is present in the polysiloxane film, as shown in FIG. 3 (b), water and all the corrosive media (alcohol, aldehyde, carboxylic acid) are used.
Becomes hard to come close to the surface of copper. As mentioned above, water is
In particular, it is involved in the corrosion mechanism by aldehyde. Therefore, in this case, although it is effective in suppressing the corrosion caused by the carboxylic acid, it is particularly effective in suppressing the corrosion caused by the aldehyde such as formaldehyde.

As described above, since there are some differences in the mechanism of suppressing corrosion, the above two kinds of silane coupling agents, that is, those having a group that adsorbs a carboxyl group and those having a hydrophobic group are used. You may use together.

As the carboxyl group-adsorbing group, a basic amino group, particularly a primary amino group and a secondary amino group, and an epoxy group reactive with the carboxyl group are mentioned because the carboxyl group is acidic. To be The amino group also acts as an adsorption group for the carboxyl group at the same time as the above-mentioned lone electron pair is imparted. The silane coupling agent is
For example, two or more amino groups such as a primary amino group and a secondary amino group may be contained in the molecule.

Examples of the hydrophobic group include the following: -NR ¹ R ² (R ¹ and R ² are alkyl groups or aryl groups; for example, methyl, ethyl, propyl, butyl, hexyl, octyl, phenyl. ), A di (alkyl or aryl) amino group, —NHR ³ (R ³ is an alkyl group or aryl group having 2 or more carbon atoms; for example, ethyl, propyl, butyl, hexyl,
Octyl, decyl, phenyl) monoalkyl or aryl) amino group, -NHCOR ¹ (R ¹ is the same as above) represented by a carbonamido group (e.g., -NHCOCH ₃ , -NHCOC ₄ H ₉ ), carbon number 4 or more alkyl groups and fluorine-containing alkyl groups (eg, butyl, hexyl, octyl, decyl, perfluorohexyl, perfluorooctyl), aryl groups (eg, phenyl, biphenyl, naphthyl)
.

Specific examples of the silane coupling agent that can be used in the present invention are shown below: Silane coupling agent having an adsorption group

[0047]

[Chemical 2]

Silane coupling agent having a hydrophobic group

[0049]

[Chemical 3]

The above-mentioned silane coupling agent is effective in suppressing the ant nest corrosion of the copper-based material as described above, but in addition to that, it is also effective in preventing discoloration of the copper-based material. did. As described above, the discoloration of the copper-based material is caused by the increase in the thickness of the cuprous oxide layer on the copper surface caused by the oxidation of the copper on the surface. This oxidation occurs due to the reaction with oxygen in the air, but since copper once dissolves and precipitates as cuprous oxide, it is necessary to interpose water. As described above, the silane coupling agent used in the present invention forms a polysiloxane film on the copper surface to protect the copper, so that it becomes difficult for water to approach the copper surface. Therefore, it is considered that oxidation of the copper surface is suppressed and discoloration due to this oxidation is prevented.
Since water is present in the discoloration, the silane coupling agent having a hydrophobic group has a large discoloration preventing effect.

The method of using the silane coupling agent-based corrosion inhibitor / discoloration inhibitor according to the present invention will be described below.

The corrosion inhibitor / discoloration inhibitor may be prepared by dissolving a solution of the agent in a suitable organic solvent, and subjecting a product made of a copper-based material (eg, copper tube) to surface treatment with this solution. The organic solvent is not particularly limited, and polar solvents such as alcohols, ketones and esters, and hydrocarbon solvents such as hexane and benzene can be used, but in the sense that the solvent does not become a corrosion medium, the hydrocarbon solvent is preferable. The solution concentration is not particularly limited, but is usually 0.01 to 0.3.
A wt% range is preferred.

The copper-based material product to be treated is preferably cleaned in advance by degreasing or the like according to a conventional method. In the case of copper products, any type of copper is acceptable. Phosphorus deoxidized copper is particularly susceptible to ant nest corrosion, which is effective for this material, but can be applied to other materials. The treatment method may be appropriately selected depending on the shape of the product, such as dipping, spraying or coating. After the treatment, the silane coupling agent is hydrolyzed by moisture in the air to form a polysiloxane film even if it is left alone after the treatment, but it may be heated to accelerate the hydrolysis if desired. The polysiloxane film formed in this manner is chemically stable, and remains after it is subjected to cleaning treatment with an organic solvent or degreasing with an alkaline aqueous solution, for example, so that the corrosion inhibition / discoloration prevention effect continues.

However, when the surface treatment with the solution of the corrosion inhibitor / discoloration preventing agent is carried out as described above, the number of treatment steps is increased, so that the manufacturing cost is increased. As a countermeasure, in the present invention, the desired effect can be obtained also by adding a corrosion inhibitor / discoloration inhibitor to the volatile lubricating oil used during plastic working. Lubricating oil, whether used during plastic working of copper-based material products (e.g., drawing process for copper pipes, rolling process for copper plates)
(For example, in the case of a copper pipe, pipe expanding or hairpin processing, and in the case of a copper plate, punching or bending may be used.)

The corrosion inhibitor / discoloration inhibitor of the present invention becomes strong when a polysiloxane film is formed, but it is removed by a washing step before forming the film, and it is difficult to obtain the desired effect. Therefore, the lubricating oil to which the corrosion inhibitor / discoloration inhibitor of the present invention is added is a volatile lubricating oil. As a result, when the lubricating oil volatilizes, the corrosion inhibitor / discoloration inhibitor remains on the surface of the copper-based material to form a polysiloxane film. As described above, ant nest corrosion is more likely to occur when a volatile lubricant is used than when a non-volatile lubricant is used.
According to the present invention, ant nest corrosion that is likely to occur in volatile lubricating oil can be suppressed, so that it becomes possible to use a volatile lubricating oil that does not require labor while suppressing ant nest corrosion.

Examples of the volatile lubricating oil that can be used include ether type, ester type, hydrocarbon type, paraffin type and the like. The lubricating oil may contain various additives. The amount of the corrosion inhibitor / discoloration inhibitor added to the lubricating oil may be in the range that does not impair the lubricating properties of the lubricating oil, and is preferably in the range of 1 to 20 g / L.

Generally, at the time of plastic working, a lubricating oil is used in each step to prevent seizure between the tool and the material and suppress the temperature rise. When plastic working is performed using a volatile lubricating oil containing the corrosion inhibitor / discoloration inhibitor of the present invention, the residual corrosion inhibitor / discoloration inhibitor remains on the surface of the copper-based material due to the coordinate bond after volatilization of the lubricating oil. The surface is coated with a polysiloxane coating that binds and has carboxylic groups and / or hydrophobic groups. This film is chemically stable because it bonds to the surface of the copper-based material of the base material through a coordination bond and is chemically stable, and remains without being removed even if degreasing or washing is performed after plastic working. Therefore, just by adding this corrosion inhibitor / discoloration inhibitor to the lubricating oil during plastic working, the surface of the copper-based material is protected from ant-like corrosion and discoloration for a long period of time from the subsequent processing to use. be able to.

Furthermore, the corrosion inhibitor / discoloration inhibitor of the present invention is used as a packaging material for copper-based material products (eg, paper, cloth, non-woven fabric,
Even if it is contained inside or on the surface of (packaging material such as wood, plastic film, etc.) by impregnation, mixing, coating, etc., it absorbs carboxylic acid which is a corrosive medium for ant nest corrosion, and copper-based material products It is possible to prevent the corrosion medium from adhering to the surface of, and to suppress corrosion / prevent discoloration.

[0059]

[Example] As a corrosive liquid, an aqueous formic acid solution and an aqueous formaldehyde solution each having a concentration of 0.1 vol% were prepared using a reagent grade.

The following silane coupling agents and comparative treatment agents were prepared as corrosion inhibitors / discoloration inhibitors. All of these are commercial products. Among silane coupling agents, A, B and D have a carboxyl group-adsorbing group, C, E and H have both an adsorbing group and a hydrophobic group, and F and G have a hydrophobic group. Is.

Silane coupling agent A: (CH ₃ O) ₃ Si (CH ₂ ) ₃ NH (CH ₂ ) ₂ NH ₂ B: (CH ₃ O) ₃ Si (CH ₂ ) ₃ NH ₂ C: (CH ₃ O) ₃ Si (CH ₂ ) ₃ NH-Ph (Ph = phenyl) D: (CH ₃ O) ₃ Si (CH ₂ ) ₃ NH (CH ₂ ) ₂ NH (CH ₂ ) ₂ NH ₂ E: (CH ₃ O) ₃ Si (CH ₂ ) ₃ NHC ₆ H ₁₃ F: (C ₂ H ₅ O) ₃ Si (CH ₂ ) ₃ N (C ₂ H ₅ ) ₂ G: (C ₂ H ₅ O) ₃ Si (CH ₂ ) ₃ NHCOCH ₃ H: (CH ₃ O) ₃ Si (CH ₂ ) ₃ NHCH ₂ CH ₂ C ₆ F ₁₃ Comparative treatment agent X: Benzotriazole Y: Ph-CO-NH-CO-Ph (diphenylurea) Z: (CH ₃ O) ₃ Si (CH ₂ ) ₃ SH Preparation of Treatment Solution The silane coupling agent and the comparative treatment agent were mixed with 0.1
The solution was dissolved in hexane to a concentration of wt% and this solution was used for the treatment.

Treatment Method A copper tube (outer diameter 9.52 mm, wall thickness 0.35 mm) is cut into a length of 300 mm, and then swarf is blown off. Then, the copper tube is degreased and washed with acetone immediately before the treatment, and well dried to completely remove the residual acetone. 1L of this copper tube
After immersing in the processing liquid placed in the measuring cylinder for 10 seconds,
It was dipped in the same manner as the treatment liquid using hexane to remove the excess corrosion inhibitor / discoloration inhibitor.

Corrosion Test Five copper tubes treated as described above with each corrosion inhibitor / discoloration inhibitor were prepared for each condition, one end of each copper tube was covered with a silicon stopper, and the copper tube was placed in the copper tube. Inject 1 mL of an aqueous solution of 0.1 vol% concentration of formic acid or formaldehyde. Then, after sealing the other end of the copper tube with a silicon stopper, a constant temperature bath set to a temperature cycle of 25 ° C for 12 hours and -40 ° C for 12 hours was used.
Use the test tubes to line up the copper tubes and keep them in the thermostat for a predetermined period (1 month or 3 months). For comparison, the untreated copper pipe and the copper pipe treated with the comparative treatment material solution are treated in the same manner.

After the corrosion test period, each test condition
15 test pieces were cut out, embedded with an epoxy resin and polished. Since ant nest corrosion often occurs under the reddish brown spot-like discolored part on the surface of the test piece, the test piece was cut out at this part. When no discoloration was observed, 15 test pieces were cut out centering on the upper part of the copper tube where corrosion is likely to occur.

The corrosion was evaluated by observing the cross section of the copper pipe with an optical microscope and measuring the erosion depth. Table 1 shows the maximum measured erosion depth and the number (test frequency) of test pieces in which 15 ant nest corrosion occurred.

[0066]

[Table 1]

As can be seen from Table 1, ant nest-like corrosion occurred in all 15 test pieces with both the formic acid and formaldehyde corrosive solutions without treatment, and even at a low concentration of 0.1 vol%,
It can be seen that these become corrosive media. From the maximum erosion depth, formaldehyde was more corrosive than formic acid.

When treated with a specific silane coupling agent according to the present invention, a remarkable corrosion inhibiting effect is exerted, the occurrence frequency is remarkably reduced, the maximum erosion depth is remarkably reduced, or the occurrence frequency is 0 in some cases. Became.

On the other hand, even if a silane coupling agent is used,
The effect of inhibiting corrosion was small for Z, which has neither an adsorptive group for the carboxyl group nor a hydrophobic group. Also,
Conventional corrosion inhibitors such as benzotriazole and diphenylurea have no corrosion inhibitory effect because the moisture that adheres to the surface of the copper pipe removes the corrosion inhibitor during the test.

Discoloration Test On the other hand, in order to confirm the discoloration prevention effect, the steel pipe treated in the same manner as in the above-mentioned corrosion test was left in the indoor atmosphere and the degree of discoloration on the outer surface was confirmed by visual observation. The test (leave) period is 1 month and 3 months. The appearance observation results were evaluated by a relative five-level evaluation using the untreated product as a standard (the discoloration of the untreated product was 5, and the case without discoloration was 1). The test results are shown in Table 2.

[0071]

[Table 2]

In the case of the silane coupling agent of the present invention, the evaluation value of discoloration was 1 or 2, and it was confirmed that it has an effect of preventing discoloration. It is presumed that this is because the hydrophobic group prevents direct contact with copper or the dense film formation of the silane coupling agent.

[0073]

INDUSTRIAL APPLICABILITY The corrosion-inhibiting / discoloration-preventing agent of the present invention can maintain the corrosion-inhibiting / discoloring-preventing effect for a long period of time by forming a film which is chemically stable and has excellent durability. Also, by adding a small amount of a corrosion inhibitor / discoloration inhibitor to the volatile lubricating oil during plastic working, a strong protective film can be formed on the surface of the copper pipe, and no special treatment is required, It is possible to suppress ant nest corrosion and discoloration of the copper-based material. As a result, the quality and reliability of the copper-based material product are improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a bonding mode of a silane coupling agent to a material having a hydroxyl group on the surface.

FIG. 2 is an explanatory diagram showing a bonding mode of a silane coupling agent to a copper material having no hydroxyl group on the surface.

FIG. 3 (a) is a silane coupling agent having an adsorptive group, and FIG. 3 (b) is a silane coupling agent having a hydrophobic group.
FIG. 3 is an explanatory view showing a corrosion inhibition mechanism of each of the above.

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23F 11/10 C10M 139/06 C10N 30:12 C10N 40:20

Claims (7)

(57) [Claims] 1. 1 or 2 selected from N, O and S
A corrosion inhibitor / discoloration inhibitor for a copper-based material, which comprises a silane coupling agent containing the above elements and further having a functional group capable of adsorbing a carboxyl group at the molecular end or a hydrophobic group. 2. The functional group capable of adsorbing the carboxyl group is selected from primary and secondary amino groups and epoxy group, and the hydrophobic group is —NR ¹ R ² (R ¹ and R ² are alkyl groups or aryl groups). Group), -NHR ³ (R ³ is an alkyl group or aryl group having 2 or more carbon atoms), -NHCOR ¹ (R ¹ is the same as above), an alkyl group having 4 or more carbon atoms and a fluorine-containing alkyl group, and an aryl group The corrosion inhibitor / discoloration inhibitor for a copper-based material according to claim 1, which is selected from the group consisting of: 3. A treatment liquid for copper-based materials and copper-based material products, which comprises a solution containing the corrosion inhibitor / discoloration inhibitor according to claim 1 or 2 in an organic solvent. 4. A volatile lubricating oil containing the corrosion inhibitor / discoloration inhibitor according to claim 1 or 2.
Lubricating oil for processing copper materials. 5. A copper-based material product, wherein the hydrolysis product of the corrosion inhibitor / discoloration inhibitor according to claim 1 or 2 is bound to the surface. 6. A copper tube for a heat exchanger, wherein the hydrolysis product of the corrosion inhibitor / discoloration inhibitor according to claim 1 or 2 is bonded to the surface. 7. A packaging material for a copper-based material product, which contains the corrosion inhibitor / discoloration inhibitor according to claim 1 or 2 inside or on the surface thereof.