JP2005139484A - Magnesium alloy base material, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dramatically enhance corrosion resistance of magnesium alloy having high activity, and to ensure conductivity on the surface thereof. <P>SOLUTION: Magnesium alloy base material having conductivity and corrosion resistance has: a film formed of a surface treating agent containing (A) at least one kind of organosilicon comound having three carbonyl groups and alkoxysily groups by a weight ratio of 5 to 15 when the total of elements (A) to (D) is taken as 100, (B) at least one kind of epoxy resin modified by alkanolamines by a weight ratio of 10 to 30, (C) at least one kind of blocked polyisocyanate by a weight ratio of 50 to 70, and (D) at least one kind of amino resin by a weight ratio of 5 to 15; an electroless plating pretreatment film obtained by mixing or reacting silane coupling agent having a functional group with metal capturing capability in one molecule thereon and a noble metal compound; and an electroless plating film thereon. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface treatment of a magnesium alloy substrate. More specifically, it relates to improving the corrosion resistance of the magnesium alloy base material and imparting conductivity.

Magnesium alloys are lightest in practical alloy materials and have the characteristics of high strength, and are used for the purpose of weight reduction in various directions. However, since magnesium alloys are rich in activity, the problem of poor corrosion resistance is a major problem. As a countermeasure against this, it is conceivable to plate a magnesium alloy, but there is a circumstance that it is difficult to plate because an oxide film is formed on the magnesium surface. In addition to this, since magnesium is the most basic metal among practical metals, there is a problem that a battery is formed and magnesium is corroded at an accelerated rate if there are minute scratches such as pinholes in the plating film. .
For these reasons, plating is usually not an effective measure for improving the corrosion resistance of magnesium alloy materials.

By the way, in order to improve the corrosion resistance by coating a metal surface such as aluminum and also improve the adhesion to the paint, the present applicant has already proposed a surface treatment agent containing a tricarbonyl organosilicon compound ( Patent Document 1).
This patent document 1 discloses that the present invention can also be applied to a magnesium alloy. Certainly, the surface treatment agent is also effective for a magnesium alloy and can improve the corrosion resistance. However, since magnesium is rich in activity, it cannot be said that the improvement in the corrosion resistance is sufficiently satisfactory. In addition, the coating by this surface treatment insulates the magnesium alloy and makes its metalization more difficult.

On the other hand, as a pretreatment method of electroless nickel for copper or copper alloy, Patent Document 2 proposes a pretreatment liquid that effectively applies a catalyst for electroless plating to an object to be plated.
JP2002-161372 JP2003-13241

  An object of the present invention is to drastically improve the corrosion resistance of a magnesium alloy rich in activity, and at the same time to ensure the conductivity of the surface. An object of the present invention is to provide a magnesium alloy base material that can also ensure conductivity.

  As a result of intensive studies, the present inventor has found that the specific surface treatment and further electroless plating on the magnesium alloy base material ensure the conductivity of the magnesium alloy material and at the same time the corrosion resistance is remarkable. The inventors have found that it contributes to improvement, and have reached the present invention.

［ただし、該化合物には互変異性体であるエノール型も含む。一般式（１）において、Ｒ¹、Ｒ³は炭素数１〜５のアルキル基、Ｒ²、Ｒ⁴は炭素数２〜１０のアルキレン基、ｘ、ｙ、ｚはそれぞれ０又は１を示す。］
（４）一分子中に金属捕捉能を持つ官能基を有するシランカップリング剤がアゾール系化合物とエポキシシラン系化合物との反応により得られたシランカップリング剤であることを特徴とする前記（２）又は（３）記載のマグネシウム合金基材の製造方法。
（５） 金属捕捉能を持つ官能基がイミダゾール基であることを特徴とする前記（２）〜（４）のいずれか１項に記載のマグネシウム合金基材の製造方法。
（６） 貴金属化合物がパラジウム化合物であることを特徴とする前記（２）〜（５）のいずれか１項に記載のマグネシウム合金基材の製造方法に関する。 That is, the present invention
(1) (A) at least one of organosilicon compounds having three carbonyl groups and alkoxysilyl groups, 5 to 15 in a weight ratio based on (A) to (D) as a whole, (B) alkanol At least one epoxy resin modified with amines, 10-30, (C) at least one blocked polyisocyanate, 50-70, (D) at least one amino resin, Electroless plating pretreatment obtained by mixing or reacting a coating with a surface treatment agent contained in 5 to 15 above, a silane coupling agent having a functional group having a metal capturing ability in one molecule and a noble metal compound A conductive and corrosion-resistant magnesium alloy substrate characterized by comprising a coating and an electroless plating coating thereon.
(2) The magnesium alloy material surface has a weight ratio of 5 to 5 with (A) at least one organosilicon compound having three carbonyl groups and alkoxysilyl groups, with (A) to (D) as a whole. 15, (B) at least one epoxy resin modified with alkanolamines, 10-30, (C) at least one polyisocyanate blocked, 50-70, (D) amino resin Is treated with a surface treating agent containing 5 to 15 in the same manner, and then a silane coupling agent having a functional group having a metal capturing ability in one molecule and a noble metal compound are mixed in advance in a weight ratio shown below. Alternatively, the magnesium alloy substrate according to claim 1, wherein the magnesium alloy base material is treated with a pretreatment liquid for electroless plating, and further electrolessly plated. Production method.
1/10 <silane coupling agent / noble metal compound <10/1
(3) (A) The method for producing a magnesium alloy substrate according to (2), wherein the organosilicon compound having three carbonyl groups and alkoxysilyl groups is represented by the following general formula (1): .

[However, the compound includes an enol form which is a tautomer. In the general formula ^{(1), R 1, R} 3 is an alkyl group having 1 to 5 carbon atoms, R ^2, R ⁴ represents an alkylene group, x, y, z are each 0 or 1 2 to 10 carbon atoms. ]
(4) The above-mentioned (2), wherein the silane coupling agent having a functional group having a metal scavenging ability in one molecule is a silane coupling agent obtained by a reaction between an azole compound and an epoxy silane compound. Or the method for producing a magnesium alloy substrate according to (3).
(5) The method for producing a magnesium alloy substrate according to any one of (2) to (4), wherein the functional group having a metal capturing ability is an imidazole group.
(6) The method for producing a magnesium alloy substrate according to any one of (2) to (5), wherein the noble metal compound is a palladium compound.

  According to the present invention, it is possible to improve the corrosion resistance of the Mg alloy base material, which has been difficult in the past, and sufficiently maintain the conductivity of the Mg alloy surface without impairing the conductivity of the Mg alloy surface. For this reason, the Mg alloy of the present invention has electromagnetic wave shielding properties and is useful as a rear cover for video equipment such as a television.

  An organosilicon compound having three carbonyl groups and an alkoxyl group (hereinafter abbreviated as tricarbonyl compound) used in the surface treatment method of the present invention is disclosed in Japanese Patent Application Laid-Open Nos. 9-3076 and 3077. Further, the disclosed compounds can be preferably used.

  In the epoxy resin modified with (B) alkanolamines used in the present invention (hereinafter abbreviated as a modified epoxy resin), the alkanolamines include primary or secondary amino groups that can undergo an addition reaction with the epoxy group of the epoxy resin. The alkanolamine which has, Especially preferably, diethanolamine is mentioned.

  Examples of the epoxy resin in the epoxy resin modified with alkanolamines used in the present invention include bisphenol A based on bisphenol A and F type epoxy resin. Others include brominated epoxy resins in which hydrogen on the benzene ring of bisphenol A type epoxy resins is partially substituted with bromine, dimer acid glycidyl ester epoxy resins, phenoxy resins, glycidyl amine type epoxy resins, novolac type epoxy resins, glycidyl esters Type epoxy resin, biphenyl type epoxy resin, cycloaliphatic type epoxy resin and the like.

The (C) blocked polyisocyanate (hereinafter abbreviated as blocked isocyanate) used in the present invention includes tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanate methyl. Caproate, 4,4'-methylenebis (cyclohexyl isocyanate), methylcyclohexane 2,4 (2,6) diisocyanate, 1,3- (isocyanatomethyl) cyclohexane, isophorone diisocyanate, trimethylhexane diisocyanate, dimer acid diisocyanate , Phenol-based, lactam-based, active methylene-based, acid amide-based, imide-based, amine-based, imidazole-based, urea-based, imine-based, and oxime-based blocking agents obtained by ordinary methods It is possible. Preferable blocking agents are phenol-based, lactam-based, acid amide-based, active methylene-based, and oxime-based, with oxime-based being particularly preferable. Examples of the oxime blocking agent include formaldoxime, acetoaldoxime, methyl ethyl ketone oxime, and cyclohexanone oxime.
What is especially shown by a following formula is preferable.

[However, in general formula (2), (3), R < ⁷ >, R < ⁸ > shows a C1-C5 alkyl group. ]

  Examples of the (D) amino resin used in the present invention include butylated urea resins, butylated melamine resins, methylated melamine resins, butylated benzoguanamine resins, and the like. Particularly preferred are methylated melamine resins. be able to.

The composition composition weight ratio of the present invention is that the total components (A) to (D) are 100, the tricarbonyl compound (A) is 5 to 15, the modified epoxy resin (B) is 10 to 30, and the component (C). The blocked isocyanate is preferably 50 to 70, and the amino resin of component (D) is preferably 5 to 15. When the weight ratio of the tricarbonyl compound is smaller than 5, the corrosion resistance and flexibility of the film formed by the surface treatment agent are lowered.
If it exceeds 15, flexibility and acid resistance will decrease. When the weight ratio of the modified epoxy resin is out of the range of 10 to 30, the corrosion resistance, coating film adhesion, flexibility, and acid resistance of the coating are greatly reduced. When the weight ratio of the blocked isocyanate is out of the range of 50 to 70, the corrosion resistance, coating film adhesion, flexibility, and acid resistance of the coating are lowered. In particular, the decrease in flexibility is great. When the weight ratio of the amino resin is outside the range of 5 to 15, the flexibility and acid resistance of the film are lowered.

  In the present invention, it is preferable to use an organic solvent in order to uniformly apply the composition to an adherend. Organic solvents include aromatics such as toluene and xylene, cellsolves such as methoxyethanol and ethoxyethanol, glycol ethers such as methylpropylene glycol and propylpropyleneglycol, ketones such as acetone and methylethylketone, and esters such as ethyl acetate. And alcohols such as methanol and isopropyl alcohol. Moreover, you may add a viscosity modifier, an antifoamer, a ultraviolet absorber, surfactant, etc. as needed.

  The metal surface treating agent of the present invention is applied to a magnesium alloy substrate. As this alloy base material, an alloy of magnesium and, for example, aluminum and / or zinc is preferable. The metal surface treatment agent of the present invention is preferably used in a diluted state in which the organic solvent is 50 to 99% by weight with respect to the total solid content of the components (A) to (D). As a coating method, known coating methods such as spray coating, dip coating, brush coating, and roll coating can be applied.

  In order to sufficiently bring out the effects of the present invention, it is preferable to heat-dry the coating after coating. Heat drying is preferably performed at 100 to 300 ° C. for 5 seconds to 60 minutes. A uniform coating film is formed by removing the solvent and carrying out a curing reaction under the heating conditions after coating, thereby achieving the object of the present invention. The thickness of the coating film is preferably 0.1 to 100 μm. More preferably, it is 0.3-3 micrometers. If it is less than 0.1 μm, sufficient rust preventive property cannot be imparted, and if it exceeds 100 μm, it is not preferable from the viewpoint of economy.

Next, in the surface treatment method of the present invention, after the treatment with the surface treatment agent comprising (A) to (D) is performed, electroless plating is performed. The pretreatment liquid for that purpose consists of a liquid obtained by previously mixing or reacting a silane coupling agent having a functional group having a metal scavenging ability in one molecule and a noble metal compound in the weight ratio shown below.
1/10 <silane coupling agent / noble metal compound <10/1

In the electroless plating of the present invention, it is important to use the specific silane coupling agent as a pretreatment liquid. In other words, the presence of a functional group having a metal-capturing ability in the molecule makes it possible to take an electronic state and orientation that effectively expresses the activity of the plating catalyst. By being a silane coupling agent, the material to be plated It becomes possible to express the adhesiveness.
The electroless plating of the present invention is preferably nickel alloy plating or chromium alloy plating.

The silane coupling agent having a functional group having a metal capturing ability used in the pretreatment agent of the present invention is not limited to these, but includes an amino group, a carboxyl group, an azole group, a hydroxyl group, a mercapto group, and the like. The silane coupling agent which has is mentioned. Among these, those having an azole group are preferable. Further, as the azole group, imidazole, oxazole, thiazole, selenazole, pyrazole, isoxazole, isothiazole, triazole, oxadiazole, thiadiazole, tetrazole, oxatriazole, thiatriazole, bendazole, indazole, benzimidazole, benzotriazole, etc. Can be mentioned. Of these, an imidazole group is particularly preferable. Also, the a silane coupling agent, in addition to the noble metal ion capturing group, a compound having a -SiX ₁ X ₂ X _{3 group, X 1, X 2, X} 3 is an alkyl group, such as halogen or alkoxy group And any functional group that can be fixed to an object to be plated. X ₁ , X ₂ and X ₃ may be the same or different.

  Such silane coupling agents are known per se. For example, JP-A-6-256358 discloses a silane coupling agent obtained by a reaction of an azole compound and an epoxy silane compound. In addition, as an epoxy group-containing silane compound to be reacted with such a nitrogen-containing heterocyclic azole compound,

(Wherein R ¹ and R ² are hydrogen or an alkyl group having 1 to 3 carbon atoms, and n is 1 to 3). The reaction between the azole compound and the epoxy group-containing silane compound can be performed under the conditions described in JP-A-6-256358. For example, 0.1 to 10 mol of an epoxy group-containing silane compound is dropped at 80 to 200 ° C. with respect to 1 mol of the azole compound, and the reaction is performed for 5 minutes to 2 hours. At that time, a solvent is not particularly required, but an organic solvent such as chloroform, dioxanemethanol or ethanol may be used. Other examples of the silane coupling agent having a metal scavenging ability used in the present invention include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-β (aminoethyl) γ-aminopropyltrimethoxysilane. N-β (aminoethyl) γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane and the like.

  In addition, the noble metal compound includes palladium, silver, platinum, gold and other chlorides, hydroxides, oxides, sulfates that exhibit a catalytic effect when nickel is deposited on the surface of copper or a copper alloy from an electroless plating solution. And ammine complexes such as ammonium salts, among which palladium compounds, particularly palladium chloride, are preferred. The noble metal compound is preferably used as an aqueous solution, and the concentration in the solution to be treated is preferably 5 to 100 mg / L.

  When the surface of the substrate to be electrolessly plated is treated with a pretreatment liquid in which a silane coupling agent having a functional group having a metal capturing ability in one molecule as described above and a precious metal ion are mixed or reacted in advance, this liquid is suitable. It can be used in a solution obtained by dissolving in a suitable solvent such as water, methyl alcohol, ethyl alcohol, 2-propanol, acetone, toluene, ethylene glycol, polyethylene glycol, dimethylformamide, dimethyl sulfoxide, dioxane, or a mixture thereof. . When water is used, it is necessary to optimize the pH of the solution depending on the surface to be plated and the plating conditions. For copper or copper alloys, the method of volatilizing the solvent after surface coating by dipping is common, but this is not a limitation, and it is a method of uniformly attaching a silane coupling agent to the surface. I just need it. Depending on the state of adhesion, there may be a case where the drying step can be omitted only by washing with water. The concentration of the silane coupling agent having a functional group having a metal capturing ability in one molecule in the pretreatment solution is not limited to this, but 0.001 to 10% by weight is easy to use. If it is less than 0.001% by weight, the amount of the compound adhering to the surface of the substrate tends to be low, and the effect is difficult to obtain. On the other hand, if the amount exceeds 10% by weight, the amount of adhesion is too large to be dried. In order to volatilize the solvent used after the surface treatment, it is sufficient to dry the surface by heating above the volatilization temperature of the solvent. When water is used as a solvent, it is possible to omit the drying step and perform plating only by washing with water after the surface treatment. However, in this case, it is necessary to perform sufficient washing with water in order to prevent the catalyst from being brought into the plating solution from the surface of the object to be plated.

A pretreatment solution for electroless nickel plating on copper or a copper alloy, in which a silane coupling agent having a functional group having a metal-capturing ability in one molecule and a noble metal compound are mixed or reacted in advance at a weight ratio shown below. When used, electroless plating can be performed by pretreatment at room temperature (10 to 30 ° C.).
1/10 <silane coupling agent / noble metal compound <10/1

  When the weight ratio is less than 1/10, the ratio of the silane coupling agent is too small, and sufficient adhesion with the substrate cannot be obtained. Moreover, when said weight ratio exceeds 10/1, the catalytic activity ability of a noble metal compound falls and sufficient plating film is not obtained.

As a matter of course, the surface to be plated may be cleaned (such as dilute sulfuric acid cleaning) before the plating pretreatment.
Hereinafter, examples and comparative examples of the present invention will be shown to describe the present invention more specifically.
Comparative Example 1

In Comparative Example 1, a case where only the metal surface treatment agent disclosed in JP-A-2002-161372 is applied to the magnesium alloy substrate will be described.
(1) Synthesis of Tricarbonyl Compound A tricarbonyl compound (in formula 1, R ¹ is a methyl group, R ² is an n-propyl group, R ³ is a methyl group, and R ⁴ is n-undecyl group, x is 0, y is 1z is 0).

(2) Synthesis of modified epoxy resin 150 g of bisphenol A type epoxy resin (Japan Epoxy Resin Epicoat 1007 (molecular weight of about 2900)) and 150 g of propylene glycol were put into a three-necked flask to obtain a uniform solution at 150 ° C. in a nitrogen atmosphere. . A solution obtained by dissolving 10,8 g of diethanolamine in 10.8 g of propylene glycol was dropped into this solution over 30 minutes. After completion of the dropping, the reaction was continued at 150 ° C. for 1 hour to obtain a diethanolamine-modified epoxy resin. Completion of the reaction was confirmed by GPC (gel permeation chromatography).

(3) Synthesis of blocked isocyanate resin Tolylene diisocyanate (a mixture of 2,6- and 2,4-isomers) and methyl ethyl ketone oxime were reacted in a conventional manner to synthesize blocked isocyanate. Completion of the reaction was confirmed by FTIR.
With respect to 100 parts of the epoxy resin, 280 parts of a blocked isocyanate resin, 55 parts of a tricarbonyl compound, and 50 parts of an amino resin (Sumitomo Chemical Industries Summar M-40ST) are weighed to a solid content of 10%. A solution obtained by diluting and dissolving in methylpropylene glycol was used as a metal surface treatment agent.

  This metal surface treating agent was applied onto a magnesium alloy substrate (AZ31B, 55 mm × 55 mm × 0.6 mm) by spin coating. Then, it heat-processed for 10 minutes at 220 degreeC with the hot-air circulation type dryer, and the surface treatment board | substrate 1 was created. When the film thickness of the surface-treated film after drying was measured with an eddy current film thickness meter, it was about 1 μm.

In Example 1, an example in which electroless nickel plating is further applied to the surface-treated substrate 1 prepared in Comparative Example 1 will be described.
The surface-treated magnesium alloy substrate 1 prepared in Comparative Example 1 was immersed in a 100 mg / L aqueous solution of equimolar reaction product of imidazole containing 20 mg / L of palladium and γ-glycidoxypropyltrimethoxysilane at 60 ° C. for 5 minutes. Thereafter, it was washed with water, immersed in an electroless nickel bath having the composition shown in Table 1 at 55 ° C. for 5 minutes, and nickel-plated to prepare a nickel-plated substrate 2. The film thickness of nickel was measured to be 1 μm by fluorescent X-ray.

The end surfaces of the surface-treated substrate 1 prepared in Comparative Example 1 and the nickel-plated substrate 2 prepared in Example 1 were sealed with water-resistant tape so that the exposed portion was 45 mm × 45 mm, and a salt spray test described in JIS Z 2371 was performed. It was. The test time was 96 hours.
Comparative Example 2

With respect to 100 parts of the modified epoxy resin described in Comparative Example 1, 280 parts of a blocked isocyanate resin and 50 parts of an amino resin (Summar M-40ST manufactured by Sumitomo Chemical Industries) are weighed so that the solid content becomes 10%. A solution obtained by diluting and dissolving with methylpropylene glycol was used as the metal surface treating agent (composition excluding the tricarbonyl compound from Comparative Example 1).
This metal surface treating agent was applied onto a magnesium alloy substrate (AZ31B, 55 mm × 55 mm × 0.6 mm) by spin coating. Then, it heat-processed for 10 minutes at 220 degreeC with the hot-air circulation type dryer, and the surface treatment board | substrate 2 was created. When the film thickness of the surface-treated film after drying was measured with an eddy current film thickness meter, it was about 1 μm.
The end surfaces of the surface-treated substrate 2 (Comparative Example 2) and the untreated magnesium alloy substrate (AZ31B, 55 mm × 55 mm × 0.6 mm, Comparative Example 3) are sealed with water-resistant tape so that the exposed portion is 45 mm × 45 mm. The salt spray test described in JIS Z 2371 was conducted. The test time was 96 hours.
The results are also shown in Table 2.

Claims (6)

(A) At least one organic silicon compound having three carbonyl groups and an alkoxysilyl group is used at a weight ratio of 5 to 15 with (A) to (D) as a whole, and (B) alkanolamines. At least one modified epoxy resin, 10-30, (C) at least one blocked polyisocyanate, 50-70, (D) at least one amino resin, A pretreatment film obtained by mixing or reacting a noble metal compound with a silane coupling agent and a silane coupling agent having a functional group having a metal capturing ability in one molecule thereon, A conductive and corrosion-resistant magnesium alloy base material, further comprising an electroless plating film thereon. The magnesium alloy material surface has (A) at least one organic silicon compound having three carbonyl groups and alkoxysilyl groups in a weight ratio of 5 to 15 in terms of a weight ratio of (A) to (D) as a whole. B) At least one of epoxy resins modified with alkanolamines, 10-30, (C) At least one of blocked polyisocyanates, 50-70, (D) At least one of amino resins The seed is treated with a surface treating agent containing 5 to 15 and then a silane coupling agent having a functional group having a metal capturing ability in one molecule and a noble metal compound are mixed or reacted in advance at a weight ratio shown below. A method for producing a magnesium alloy substrate according to claim 1, wherein the magnesium alloy substrate is treated with a pretreatment liquid for electroless plating, and further electrolessly plated. .
1/10 <silane coupling agent / noble metal compound <10/1 (A) The method for producing a magnesium alloy substrate according to claim 2, wherein the organosilicon compound having three carbonyl groups and alkoxysilyl groups is represented by the following general formula (1).

[However, the compound includes an enol form which is a tautomer. In the general formula ^{(1), R 1, R} 3 is an alkyl group having 1 to 5 carbon atoms, R ^2, R ⁴ represents an alkylene group, x, y, z are each 0 or 1 2 to 10 carbon atoms. ]
3. The magnesium according to claim 2, wherein the silane coupling agent having a functional group having a metal capturing ability in one molecule is a silane coupling agent obtained by a reaction between an azole compound and an epoxy silane compound. A method for producing an alloy substrate. The method for producing a magnesium alloy substrate according to any one of claims 2 to 4, wherein the functional group having a metal scavenging ability is an imidazole group. The method for producing a magnesium alloy substrate according to any one of claims 2 to 5, wherein the noble metal compound is a palladium compound.