Surface treatment agent, surface-treated metal, and surface treatment method

Abstract

To provide a surface treatment agent capable of improving adhesion to a coating film.SOLUTION: A surface treatment agent comprising at least one metal component (A) selected from the group consisting of zirconium, titanium, and hafnium, and an alkyldiallylamine polymer (C), wherein the content of the metal component (A) is 10 to 100,000 ppm by mass in terms of a metal element based on the total mass of the surface treatment agent, and the alkyldiallylamine polymer (C) has a segment having a heterocyclic structure represented by formula (1a) or (1b): SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a surface treatment agent, a surface-treated metal, and a surface treatment method. [Background technology]

[0002] Conventionally, when cathodic electrodeposition coating or powder coating is applied to the surface of a metal substrate, the surface of the metal substrate is subjected to a surface treatment in advance in order to improve corrosion resistance, coating adhesion, etc. In recent years, surface treatment (chemical conversion coating) using chromium-free zinc phosphate has become widespread.

[0003] Chemical conversion treatment using zinc phosphate has problems such as difficult wastewater treatment due to the high reactivity of the treatment agent, generation of sludge, and a large environmental load. To address this problem, a chemical conversion treatment agent comprising at least one selected from the group consisting of zirconium, titanium, and hafnium, fluorine, and a water-soluble resin has been proposed (see, for example, Patent Document 1).

[0004] The technology disclosed in Patent Document 1 can perform good chemical conversion treatment on metals such as iron, zinc, and aluminum. However, there is still room for improvement in the corrosion resistance obtained after coating with cationic electrodeposition coating, powder coating, etc. Therefore, a chemical conversion treatment agent with improved corrosion resistance has been proposed (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-218074 [Patent Document 2] Patent No. 7052137 Summary of the Invention [Problem to be solved by the invention]

[0006] With respect to the technology disclosed in Patent Document 2, there has been a demand for further improvement in adhesion to coating films.

[0007] The present disclosure has been made in view of the above, and has an object to provide a surface treatment agent that can improve adhesion to a coating film. [Means for solving the problem]

[0008] (1) The present disclosure relates to a surface treatment agent comprising: (A) at least one metal component selected from the group consisting of zirconium, titanium, and hafnium; and (C) an alkyldiallylamine polymer, wherein the content of the metal component (A) is 10 to 10,000 mass ppm in terms of metal element relative to the total mass of the surface treatment agent; and the alkyldiallylamine polymer (C) has a segment having a heterocyclic structure represented by the following formula (1a) or (1b):

[0009] [ka] (R in the above formulas (1a) and (1b) 1 represents an alkyl group or an aralkyl group.

[0010] (2) The surface treatment agent according to (1), wherein the weight-average molecular weight of the alkyldiallylamine polymer (C) is 500 to 500,000, and the content thereof is 25 to 5,000 mass ppm in terms of resin solids concentration relative to the total mass of the surface treatment agent.

[0011] (3) The surface treatment agent according to (1) or (2), further comprising at least one metal component selected from the group consisting of aluminum, copper, and zinc.

[0012] (4) The surface treatment agent according to any one of (1) to (3), which has a pH of 2.0 to 6.0.

[0013] (5) The surface treatment agent according to any one of (1) to (4), wherein the content of the segments having the heterocyclic structure represented by the formulas (1a) and (1b) in the alkyldiallylamine polymer (C) is 25 mol % or more and 100 mol % or less, based on all the segments contained in the alkyldiallylamine polymer (C).

[0014] (6) The surface treatment agent according to any one of (1) to (5), further comprising fluorine (B), and the concentration of the fluorine (B) is 10 to 12,500 ppm by mass in terms of elemental fluorine relative to the total mass of the surface treatment agent.

[0015] (7) A surface-treated metal having a surface treatment film formed on its surface by the surface treatment agent according to any one of (1) to (6).

[0016] (8) The content of the metal component (A) in the surface treatment film is 5 to 500 mg / m in terms of metal element. 2 The surface-treated metal according to (7),

[0017] (9) A surface treatment method comprising a surface treatment film forming step of forming a surface treatment film by treating the surface of an object to be coated with the surface treatment agent according to any one of (1) to (6).

[0018] (10) The surface treatment method according to (9), further comprising an electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating the substrate on which the surface treatment film has been formed. [Effects of the Invention]

[0019] According to the present disclosure, a surface treatment agent capable of improving adhesion to a coating film can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present disclosure will be described, but the present disclosure is not limited to the following embodiments.

[0021] <Surface treatment agent> The surface treatment agent according to this embodiment can form a surface treatment film on the surface of a metal substrate, which provides favorable corrosion resistance after painting. The metal substrate on which the surface treatment film has been formed and painted can be used for various purposes, including, but not limited to, automobile bodies and automobile parts. Examples of the painting method include cationic electrodeposition painting, powder painting, aqueous painting, and solvent painting.

[0022] The surface treatment agent according to the present embodiment contains at least one metal component (A) selected from the group consisting of zirconium, titanium, and hafnium, and an alkyldiallylamine polymer (C), and may further contain fluorine (B) as an optional component.

[0023] (Metal component (A)) The metal component (A) is a component for forming a surface treatment film. When a surface treatment film containing at least one metal component (A) selected from the group consisting of zirconium, titanium, and hafnium is formed on a metal substrate, the corrosion resistance and abrasion resistance of the metal substrate can be improved, and the adhesion to a coating film such as an electrodeposition coating film can be improved.

[0024] The zirconium source is not particularly limited, but examples thereof include alkali metal fluorozirconates such as KZrF, hydrofluoric zirconate (HZrF), ammonium hexafluorozirconate ((NH)ZrF), ammonium zirconium carbonate ((NH)ZrO(CO)), tetraalkylammonium-modified zirconium, zirconium fluoride, and zirconium oxide.

[0025] The titanium source is not particularly limited, but examples thereof include alkali metal fluorotitanates, fluorotitanates such as (NH4)2TiF6, soluble fluorotitanates such as fluorotitanate acids such as H2TiF6, titanium fluoride, and titanium oxide.

[0026] The source of the hafnium is not particularly limited, but examples thereof include fluorohafnate acids such as H2HfF6, and hafnium fluoride.

[0027] The content of the metal component (A) is 10 to 10,000 ppm by mass in terms of metal element relative to the total mass of the surface treatment agent (total mass including solid and volatile components of the surface treatment agent; the same applies below). If the content of the metal component (A) is less than 10 ppm, the resulting surface treatment film will not have sufficient performance. If the content of the metal component (A) exceeds 10,000 ppm by mass, no further effect will be obtained, which is economically disadvantageous. From the above viewpoints, the content of the metal component (A) is preferably 50 to 2,000 ppm by mass, more preferably 100 to 1,000 ppm by mass in terms of metal element.

[0028] (Fluorine (B)) Fluorine (B) has the function of etching the surface of a metal substrate. The fluorine source is not particularly limited, and examples thereof include fluorides such as hydrofluoric acid, ammonium fluoride, fluoroboric acid, ammonium hydrogen fluoride, sodium fluoride, and sodium hydrogen fluoride. Complex fluorides include, for example, hexafluorosilicates, and specific examples thereof include hydrofluorosilicic acid, zinc hydrofluorosilicate, manganese hydrofluorosilicate, magnesium hydrofluorosilicate, nickel hydrofluorosilicate, iron hydrofluorosilicate, and calcium hydrofluorosilicate. Fluorine-containing compounds such as alkali metal fluorozirconates, which are exemplified as sources of the metal component (A), can serve as sources of fluorine (B) as well as the metal component (A).

[0029] The concentration of fluorine (B) is preferably 10 to 12,500 ppm by mass in terms of elemental fluorine relative to the total mass of the surface treatment agent. If the concentration of fluorine (B) is less than 10 ppm by mass, etching will be insufficient and a good surface treatment film will not be obtained. If the concentration exceeds 12,500 ppm by mass, etching will be excessive and a satisfactory surface treatment film will not be formed. From the above viewpoints, the concentration of fluorine (B) is more preferably 125 to 1,250 ppm by mass. As a method for measuring the concentration of fluorine (B), for example, a method of measuring by quantitative analysis using ion chromatography can be mentioned.

[0030] (Alkyldiallylamine polymer (C)) The alkyldiallylamine polymer (C) is a polymer containing at least a segment derived from alkyldiallylamine (hereinafter, may be referred to as "alkyldiallylamine segment"). The alkyldiallylamine segment may be in a quaternized state. The alkyldiallylamine polymer (C) may have only alkyldiallylamine segments in its structure, or may contain segments other than alkyldiallylamine segments. Furthermore, each of the above segments may independently have a counter ion. The alkyldiallylamine polymer (C) may be a homopolymer or a copolymer.

[0031] [Alkyldiallylamine segment] The alkyldiallylamine segment has a heterocyclic structure represented by the following formula (1a) or (1b):

[0032] [ka]

[0033] R in the above formulas (1a) and (1b) 1 represents an alkyl group or an aralkyl group. Examples of the alkyl group include unsubstituted alkyl groups having from 1 to 10 carbon atoms, and more preferably unsubstituted alkyl groups having from 1 to 6 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. The aralkyl group is preferably an aralkyl group having from 7 to 11 carbon atoms. Examples of aralkyl groups having from 7 to 11 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a phenylbutyl group, and a naphthylmethyl group.

[0034] The alkyldiallylamine polymer (C) is preferably an acid addition salt having an anionic counter ion to an ammonium cation. The dissociation constant pKa of the acid forming the acid addition salt is preferably within the range of -3.7 to 4.8. In this specification, the dissociation constant pKa of the acid means the value when the solvent is water and the temperature is 25°C. Examples of the alkyldiallylamine segment constituting the alkyldiallylamine polymer (C) that is the acid addition salt are represented by the following general formulas (1c) and (1d).

[0035] [ka]

[0036] R in the above formulas (1c) and (1d) 2 represents an alkyl group or an aralkyl group, R 3 represents hydrogen, an alkyl group, or an aralkyl group; D - indicates a monovalent anion.

[0037] The anionic counter ion is not particularly limited, but examples thereof include monovalent anions, such as carboxylate ions such as formate ion, acetate ion, and benzoate ion, chloride ion, sulfate ion, sulfamate ion, and nitrate ion. Acids that form acid addition salts include organic acids such as formic acid, acetic acid, and benzoic acid, and inorganic acids such as hydrochloric acid, sulfuric acid, sulfamic acid, and nitric acid.

[0038] The content of the alkyldiallylamine segment is preferably 25 mol% or more and 100 mol% or less relative to all segments of the alkyldiallylamine polymer (C). By having the content of the alkyldiallylamine segment within the above content range, the adhesion of the formed surface treatment film to the coating film can be improved. From the above viewpoint, the content is more preferably 50 mol% or more and 100 mol% or less.

[0039] [Other segments] The segments other than the alkyldiallylamine segment contained in the alkyldiallylamine polymer (C) are not particularly limited, and examples thereof include segments derived from allylamine, segments derived from sulfur dioxide (sulfonyl groups), segments derived from unsaturated compounds having a hydroxy group such as 2-hydroxyethyl (meth)acrylate, segments derived from (meth)acrylic monomers having a primary amino group, segments derived from N,N-dialkylaminoalkyl (meth)acrylates and their salts or quaternized products, N,N-dialkylaminoalkyl (meth)acrylamides and their salts or quaternized products, vinylimidazole and its salts or quaternized products, vinylpyridine and its salts or quaternized products, N-alkylallylamine and its salts, N,N-dialkylallylamine and its salts, N-alkyldiallylamine and its salts or quaternized products, and segments derived from alkyl (meth)acrylate esters such as methyl (meth)acrylate and ethyl (meth)acrylate, vinyl carboxylates such as vinyl acetate and vinyl propionate, and unsaturated acids.

[0040] The allylamine-derived segment has, for example, a structure represented by the following formula (2).

[0041] [ka]

[0042] The allylamine-derived segment may have the same anionic counter ion as the alkyldiallylamine segment.

[0043] Examples of the (meth)acrylic monomer having the primary amino group include acrylamide, methacrylamide, aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, aminobutyl (meth)acrylate, aminopentyl (meth)acrylate, and aminohexyl (meth)acrylate.

[0044] The weight-average molecular weight of the alkyldiallylamine polymer (C) is preferably 500 to 500,000. If the weight-average molecular weight is less than 500, sufficient adhesion of the surface treatment film cannot be obtained. If the weight-average molecular weight exceeds 500,000, the formation of the surface treatment film may be inhibited. From the above viewpoints, the weight-average molecular weight of the alkyldiallylamine polymer (C) is preferably 5,000 to 100,000.

[0045] The weight-average molecular weight of alkyldiallylamine polymer (C) can be measured, for example, by gel permeation chromatography (GPC). The measurement equipment, for example, is a Hitachi L-6000 high-performance liquid chromatograph, with a Hitachi L-6000 eluent pump, a Shodex RI SE-61 differential refractive index detector, and a dual-column Asahi Pak aqueous gel filtration type GS-220HQ (molecular weight exclusion limit: 3,000) and GS-620HQ (molecular weight exclusion limit: 2,000,000). An example of the GPC measurement method is shown below. The sample is adjusted to a concentration of 0.5 g / 100 ml with the eluent, and 20 μl is used. The eluent is a 0.4 mol / L aqueous sodium chloride solution. The column temperature is 30°C, and the flow rate is 1.0 ml / min. A calibration curve is obtained using polyethylene glycols with molecular weights of 106, 194, 440, 600, 1470, 4100, 7100, 10300, 12600, and 23000 as standard samples. The weight average molecular weight (Mw) of the polymer is determined based on the calibration curve.

[0046] The content of the alkyldiallylamine polymer (C) is preferably 25 to 5,000 ppm by mass in terms of resin solids concentration relative to the total mass of the surface treatment agent. If the content is less than 25 ppm by mass, sufficient adhesion of the surface treatment film cannot be obtained. If the content exceeds 5,000 ppm by mass, the formation of the surface treatment film may be inhibited. From the above viewpoints, the content of the alkyldiallylamine polymer (C) is more preferably 50 to 2,500 ppm by mass, and even more preferably 50 to 600 ppm by mass, in terms of resin solids concentration.

[0047] The alkyldiallylamine polymer (C) may be modified within the scope of the present invention. For example, some of the amino groups of the alkyldiallylamine polymer (C) may be modified by a method such as acetylation, or the alkyldiallylamine polymer (C) may be crosslinked with a crosslinking agent to an extent that does not affect solubility.

[0048] The method for preparing the alkyldiallylamine polymer (C) is not particularly limited, but for example, a method of radically polymerizing a monomer mixture containing alkyldiallylamine and, if necessary, other components in a suitable solvent in the presence of a radical polymerization initiator can be mentioned. The polymerization conditions can be appropriately selected from those known to those skilled in the art.

[0049] (Other polymers) The surface treatment agent according to this embodiment may contain a polymer other than the alkyldiallylamine polymer (C). Examples of the polymer other than the alkyldiallylamine polymer (C) include polymer components such as diallylamine polymers other than the alkyldiallylamine polymer (C), polyallylamine resins, polyvinylamine resins, polydiallylamine resins, urethane resins, acrylic resins, polyester resins, and natural polymer derivatives such as chitin / chitosan derivatives and cellulose derivatives. When the surface treatment agent according to this embodiment contains a polymer other than the alkyldiallylamine polymer (C), the solid content by mass of the alkyldiallylamine polymer (C) relative to the total mass of the solid contents of all polymers is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0050] (Other ingredients) The surface treatment agent according to this embodiment preferably further contains a silane coupling agent. By including a silane coupling agent in the surface treatment agent, the coating film adhesion of the surface treatment film can be further improved. The silane coupling agent is not particularly limited, but is preferably one or more silane coupling agents selected from the group consisting of, for example, amino group-containing silane coupling agents, epoxy group-containing silane coupling agents, hydrolysates of amino group-containing silane coupling agents, hydrolysates of epoxy group-containing silane coupling agents, polymers of amino group-containing silane coupling agents, and polymers of epoxy group-containing silane coupling agents.

[0051] The amino group-containing silane coupling agent is not particularly limited, and examples thereof include known silane coupling agents such as N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N,N-bis[3-(trimethoxysilyl)propyl]ethylenediamine. Commercially available amino group-containing silane coupling agents such as KBM-602, KBM-603, KBE-603, KBM-903, KBE-9103, and KBM-573 (all manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used.

[0052] The hydrolyzate of the amino group-containing silane coupling agent can be produced by a conventionally known method, for example, by dissolving the amino group-containing silane coupling agent in ion-exchanged water and adjusting the acidity with an arbitrary acid. As the hydrolyzate of the amino group-containing silane coupling agent, a commercially available product such as KBP-90 (manufactured by Shin-Etsu Chemical Co., Ltd.: active ingredient 32%) can also be used.

[0053] The epoxy group-containing silane coupling agent is not particularly limited, and examples thereof include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldiethylethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 5,6-epoxyhexyltriethoxysilane, etc. Commercially available agents such as "KBM-403," "KBE-403," "KBE-402," and "KBM-303" (all manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used.

[0054] The surface treatment agent according to this embodiment may contain components other than those described above. For example, it is preferable that the surface treatment film-forming component further contains at least one metal component selected from the group consisting of aluminum, copper, and zinc. This can further improve the corrosion resistance of the metal substrate on which the surface treatment film is formed. The surface treatment film-forming component may also contain at least one metal component selected from the group consisting of magnesium, calcium, gallium, and indium. It may also contain metal components such as manganese, iron, cobalt, nickel, and chromium. The source of the film-forming component is not particularly limited, and examples include oxides, hydroxides, fluorides, chlorides, sulfates, nitrates, borates, carbonates, and organic acid salts of each metal. The metal components of the film-forming component may be incorporated into the surface treatment agent as components eluted from the metal substrate to be surface-treated in the surface treatment bath.

[0055] The surface treatment agent according to this embodiment may contain an oxidizing agent. For example, it is preferable that the surface treatment agent further contains at least one oxidizing agent selected from the group consisting of nitric acid and nitrous acid as a surface treatment film-forming component. This can promote the formation of the surface treatment film and improve the corrosion resistance of the metal substrate. Examples of the oxidizing agent include inorganic acids and salts thereof. It is believed that inorganic acids and salts thereof act as oxidizing agents to promote the reaction of forming the surface treatment film. Examples of inorganic acids include nitric acid, nitrous acid, hydrochloric acid, bromic acid, chloric acid, hydrogen peroxide, HMnO4, and HVO3. The surface treatment agent may also contain a sulfonic acid group-containing compound or a salt thereof as an oxidizing agent.

[0056] The surface treatment agent according to this embodiment preferably contains substantially no phosphate ions. In this specification, "substantially no phosphate ions" means that phosphate ions are not contained to an extent that they function as a component in the surface treatment agent. Since the surface treatment agent according to this embodiment contains substantially no phosphate ions, phosphorus, which causes environmental load, is not substantially used. Furthermore, the generation of sludge, such as iron phosphate or zinc phosphate, that occurs when using a zinc phosphate treatment agent can be suppressed.

[0057] (pH) The surface treatment agent preferably has a pH of 2.0 to 6.0. If the pH is less than 2.0, excessive etching occurs, making it impossible to form a satisfactory surface treatment film. If the pH is greater than 6.0, etching is insufficient, making it impossible to obtain a satisfactory surface treatment film. From the above viewpoints, the pH is more preferably 2.0 to 5.5, and even more preferably 3.0 to 4.5. To adjust the pH of the surface treatment agent, acidic compounds such as nitric acid and sulfuric acid, and basic compounds such as sodium hydroxide, potassium hydroxide and ammonia can be used.

[0058] <Surface-treated metal> The surface-treated metal has a surface treatment film formed by curing the surface treatment agent according to the present embodiment on the surface of a metal substrate, which is the substrate to be coated. The surface-treated metal according to the present embodiment not only exhibits excellent adhesion and corrosion resistance between the surface treatment film and the metal substrate, but also exhibits excellent adhesion and corrosion resistance between the coating and the surface treatment film when a coating such as an electrodeposition coating is further formed on the surface treatment film. Examples of the metal substrate include, but are not limited to, iron-based substrates, aluminum-based substrates, zinc-based substrates, and magnesium-based substrates. Here, the iron-based substrates, aluminum-based substrates, zinc-based substrates, and magnesium-based substrates refer to iron-based substrates made of iron and / or its alloys, aluminum substrates made of aluminum and / or its alloys, zinc-based substrates made of zinc and / or its alloys, and magnesium-based substrates made of magnesium and / or its alloys, respectively. The metal substrate may be composed of a plurality of iron-based substrates, aluminum-based substrates, and zinc-based substrates.

[0059] In the surface-treated metal according to this embodiment, the content of the metal component (A) in the surface treatment film formed by the surface treatment agent is 5 to 500 mg / m in terms of metal element. 2 It is preferable that the content of the metal component (A) is 5 mg / m 2 If the content of the metal component (A) is less than 500 mg / m, a uniform surface treatment film cannot be obtained. 2 If the content of the metal component (A) exceeds 5 to 200 mg / m, no further effect can be obtained, which is economically disadvantageous. 2 In addition, in the surface treatment film formed by the surface treatment agent, the ratio of the carbon content to the metal component (A) content, C / A, is preferably 7 to 25%.

[0060] The surface-treated metal having a surface treatment film formed by hardening the surface treatment agent of this embodiment is formed by a polymerization reaction or the like of each component contained in the surface treatment agent. As a result, the structure of the resulting polymer is complex, making it impossible or impractical to directly identify the surface treatment film by its structure. In other words, there are circumstances (impossible or impractical circumstances) in which it is impossible or impractical to directly identify the surface-treated metal of this embodiment by its structure or properties.

[0061] <Surface treatment method> The surface treatment method for treating the surface of a metal substrate using the surface treatment agent according to this embodiment may include a surface treatment film forming step and an electrodeposition coating film forming step.

[0062] (Surface treatment film formation process) The surface treatment film forming step is a step of forming a surface treatment film on the surface of the metal substrate to produce a surface-treated metal. The surface treatment film forming step is carried out by contacting the surface treatment agent with the surface of the metal substrate. The contacting method is not particularly limited, and examples thereof include immersion, spraying, and roll coating. The treatment temperature in the surface treatment film forming step can be in the range of 15 to 70°C, and preferably in the range of 30 to 50°C. The treatment time in the surface treatment film forming step can be in the range of 5 to 1200 seconds, and preferably in the range of 30 to 120 seconds.

[0063] (Electrodeposition coating formation process) The electrodeposition coating film forming step is a step in which the surface-treated metal produced in the surface treatment film forming step is electrodeposited to form an electrodeposition coating film on the surface. The electrodeposition coating is not particularly limited, but can be, for example, cationic electrodeposition coating. The cationic electrodeposition paint used in the cationic electrodeposition coating is not particularly limited, and conventionally known cationic electrodeposition paints made of aminated epoxy resins, aminated acrylic resins, sulfonated epoxy resins, etc. can be used. The electrodeposition coating method using the above electrodeposition paint is not particularly limited, and known electrodeposition coating methods can be applied.

[0064] (Other processes) The surface treatment method according to this embodiment may include a degreasing treatment step and a post-degreasing water-rinsing treatment step before the surface treatment film-forming step. Alternatively, another surface treatment step may be included after the post-degreasing water-rinsing treatment step and before the surface treatment film-forming step, or a post-surface treatment water-rinsing treatment step may be included after the surface treatment film-forming step and before the electrodeposition coating film-forming step.

[0065] The degreasing treatment step is carried out by immersing the workpiece in a degreasing agent such as a phosphorus-free, nitrogen-free degreasing cleaning solution for a few minutes at, for example, 30 to 55° C. A preliminary degreasing treatment may be carried out before the degreasing treatment step.

[0066] The post-degreasing water washing step is a step of washing off the degreasing agent after the degreasing step, and is carried out by spraying a large amount of washing water once or multiple times.

[0067] The post-surface-treatment water-rinsing step is carried out by spraying or immersing in water one or more times within a range that does not affect adhesion and corrosion resistance after painting. The final water-rinsing step is preferably carried out with ion-exchanged water or pure water. After the post-surface-treatment water-rinsing step, a step of drying the surface-treated metal may be carried out as needed.

[0068] In the above embodiment, the surface treatment method for treating the surface of a metal substrate has been described as including an electrodeposition coating film formation step. The surface treatment method of the present invention may include, instead of the electrodeposition coating film formation step, a step of performing any one of powder coating, aqueous coating, and solvent coating on the substrate on which the surface treatment film has been formed. The step of performing powder coating, aqueous coating, or solvent coating is not particularly limited, and a conventionally known method can be used. The surface treatment agent according to this embodiment can impart corrosion resistance equivalent to that imparted to an electrodeposition coating film to a coating film formed by powder coating, aqueous coating, or solvent coating. [Example]

[0069] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to the following examples.

[0070] Example 1 A commercially available cold-rolled steel plate (SPCC-SD, manufactured by Nippon Test Panel Co., Ltd., 70 mm x 150 mm x 0.8 mm) was used as the metal substrate, and surface treatment was performed under the following conditions.

[0071] The degreasing process involved immersion in 2% Surf Cleaner 53 (a degreasing agent manufactured by Nippon Paint Surf Chemicals) at 40°C for 2 minutes. The post-degreasing water rinse process involved spraying tap water for 30 seconds. The surface treatment process involved zirconia hydrofluoric acid, alkyl diallylamine polymer (alkyl diallylamine segment: 100 mol%, molecular weight 20,000, hydrochloric acid (pKa -3.7) salt), and zinc nitrate hexahydrate (Zn(NO3)2·6H2O). As shown in Table 1, the surface treatment agent was prepared so that the Zr content (metal element equivalent) was 100 ppm by mass, the fluorine concentration was 125 ppm by mass, the alkyl diallylamine polymer content was 150 ppm by mass in terms of resin solids, the Al content was 50 ppm by mass, and the Zn content was 500 ppm by mass. The pH was adjusted to 4.2 using sodium hydroxide. The temperature of the surface treatment agent was adjusted to 40°C, and the metal substrate was immersed in the agent for 120 seconds.

[0072] After the surface treatment, the specimen was rinsed with tap water for 30 seconds by spraying. The specimen was then further sprayed with ion-exchanged water for 30 seconds by spraying. The specimen was then dried at 80°C for 5 minutes in an electric drying oven. The content of Zr (mg / m), which is the metal component (A) in the surface treatment film, was measured using a "ZSX Primus II" (X-ray analyzer manufactured by Rigaku Corporation). 2 ) and C content (mg / m 2 ) were measured and are shown in Table 2. In Table 2, "Zr coating amount" indicates the content of zirconium as the metal component (A) in the surface treatment coating, and "C coating amount" indicates the content of carbon in the surface treatment coating.

[0073] For the electrodeposition coating film formation process, "Powernics 310" (cationic electrodeposition paint manufactured by Nippon Paint Automotive Coatings Co., Ltd.) was used to perform electrodeposition coating so that the dry film thickness was 20 μm, and after rinsing with water, the plate was heated and baked at 170°C for 20 minutes to prepare the test plate of Example 1.

[0074] (Other Examples and Comparative Examples) Test plates for other Examples and Comparative Examples were prepared in the same manner as in Example 1, except that the composition of the surface treatment agent used in the surface treatment process was as shown in Table 1, and the metal substrate or treatment temperature was as shown in Table 2. Aluminum nitrate nonahydrate was used as the aluminum component, zinc nitrate hexahydrate was used as the zinc (Zn) component, and copper nitrate trihydrate was used as the copper (Cu) component. The surface treatment agents were prepared so that the Al and Cu contents were at the concentrations shown in Table 1. In Examples 15 to 18, two types of resins (polymers) were used in combination. The two resins were mixed in the following combinations: PAS-M-1:PAA-D19HCl in Examples 15 to 17, with a 1:3 ratio in Example 15, a 1:1 ratio in Example 16, and a 3:1 ratio in Example 17 (all ppm by mass). Example 18 used the following combination of PAS-M-1:PAS-21CL (1:1 ppm by mass). In Example 19, PAS-M-1 and a silane coupling agent were used in combination, and in Example 20, surface treatment was carried out at a low temperature. The concentration (ppm by mass) of each component shown in Table 1 means the concentration relative to the total mass of the surface treatment agent. In Table 1, "alkyldiallylamine polymer (C)" is abbreviated as "polymer (C)." Details of the symbols (abbreviations) shown in Tables 1 and 2 are provided below.

[0075] (Alkyldiallylamine polymer (C)) Unless otherwise specified, all products listed below are manufactured by Nittobo Medical Co., Ltd. Mw means weight average molecular weight. PAS-M-1: Methyldiallylamine hydrochloride polymer (Mw: 20,000) PAS-M-1L: Methyldiallylamine hydrochloride polymer (Mw: 5,000) PAS-M-1A: Methyldiallylamine acetate polymer (Mw: 20,000) PAS-22SA-40: Methyldiallylamine amide sulfate polymer (Mw: 15,000) PAS-2201Cl: Methyldiallylamine hydrochloride-sulfur dioxide copolymer (Mw: 3,000)

[0076] (Other ingredients) PAA-D19HCl: Allylamine hydrochloride-diallylamine hydrochloride copolymer (Mw: 40,000, segment ratio: allylamine segment 5%, diallylamine segment (R of the above formula (1a)) 1 : Hydrogen atom) 95%) PAS-21CL: Diallylamine hydrochloride polymer (Mw: 20,000), R of the above formula (1a) 1 : Polymers containing diarylamine segments that are hydrogen atoms KBM-603: N-2(aminoethyl)3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. Al: Aluminum nitrate nonahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.) Zn: Zinc(II) nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.) Cu: Copper(II) nitrate trihydrate (Fujifilm Wako Pure Chemical Industries, Ltd.)

[0077] (base material) SPC: Cold-rolled steel plate (SPCC-SD, manufactured by Nippon Test Panel Co., Ltd., 70 mm x 150 mm x 0.8 mm) GA: Galvannealed steel sheet (SCGA270D, manufactured by Nippon Test Panel Co., Ltd., 70 mm x 150 mm x 0.8 mm) GI: Hot-dip galvanized steel sheet (GC090190AB, manufactured by Etalon, 70 mm x 150 mm x 0.8 mm) Al: Aluminum alloy (6K21, manufactured by Kobe Steel, 70mm x 150mm x 0.8mm)

[0078] The pKa of acetic acid, which is an acid that forms an acid addition salt, is 4.8, and the pKa of sulfamic acid is 1.0.

[0079] [Adhesion test 1] For the test panels of the Examples and Comparative Examples, 10 × 10 grid-like cuts were made with a width of 1 mm so as to reach the substrate. A Cellotape (registered trademark) peeling test was then conducted on the grid-cut surfaces of the electrodeposition coating film to measure the peeling rate of the coating film. Evaluation was performed according to the following criteria, with a score of 4 or higher being considered a pass. The results are shown in Table 2.

[0080] (Evaluation criteria) 5: Peeled squares are 0 / 100 4: Peeled mass is 1 / 100 to 5 / 100 3: Peeled mass is 6 / 100~10 / 100 2: Peeled mass is 11 / 100~50 / 100 1: Peeled mass is 50 / 100 to 100 / 100

[0081] [Adhesion test 2] The test plates of the examples and comparative examples were immersed in pure water at 40°C for 240 hours. Afterwards, excess water was wiped off the test plates with a cloth. Next, 10 x 10 grid-like cuts were made with a width of 1 mm so as to reach the substrate. A Cellotape (registered trademark) peel test was then conducted on the grid-cut surface of the electrodeposition coating film, and the peel rate of the coating film was measured. Evaluation was performed according to the same criteria as above, with a score of 4 or higher being considered a pass. The results are shown in Table 2.

[0082] [Table 1]

[0083] [Table 2]

[0084] From the results in Tables 1 and 2, it was confirmed that the surface treatment agents according to the examples provided preferable adhesion after coating compared to the surface treatment agents according to the comparative examples.

Claims

1. The present invention comprises at least one metal component (A) selected from the group consisting of zirconium, titanium, and hafnium, and an alkyldiallylamine polymer (C), The content of the metal component (A) is 10 to 10,000 mass ppm in terms of metal element relative to the total mass of the surface treatment agent, The alkyldiallylamine polymer (C) has a segment having a heterocyclic structure represented by the following formula (1a) or (1b): 【Chemistry 1】 (R in the above formulas (1a) and (1b) １ represents an alkyl group or an aralkyl group.

2. 2. The surface treatment agent according to claim 1, wherein the alkyldiallylamine polymer (C) has a weight average molecular weight of 500 to 500,000 and is contained in a resin solids concentration of 25 to 5,000 ppm by mass relative to the total mass of the surface treatment agent.

3. The surface treatment agent according to claim 1 , further comprising at least one metal component selected from the group consisting of aluminum, copper, and zinc.

4. The surface treatment agent according to claim 1, which has a pH of 2.0 to 6.

0.

5. 2. The surface treatment agent according to claim 1, wherein the content of the segments having a heterocyclic structure represented by the formulas (1a) and (1b) in the alkyldiallylamine polymer (C) is 25 mol % or more and 100 mol % or less, based on all segments contained in the alkyldiallylamine polymer (C).

6. 2. The surface treatment agent according to claim 1, wherein the surface treatment agent further contains fluorine (B), and the concentration of the fluorine (B) is 10 to 12,500 ppm by mass in terms of elemental fluorine, relative to the total mass of the surface treatment agent.

7. A surface-treated metal having a surface treatment film formed on its surface by the surface treatment agent according to any one of claims 1 to 6.

8. The content of the metal component (A) in the surface treatment film is 5 to 500 mg / m in terms of metal element. ２ The surface-treated metal according to claim 7, wherein

9. A surface treatment method comprising a surface treatment film forming step of forming a surface treatment film by treating the surface of an object to be coated with the surface treatment agent according to any one of claims 1 to 6.

10. The surface treatment method according to claim 9, further comprising an electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating the substrate on which the surface treatment film has been formed.

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