JP2008174819A - Coating film formation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating film formation method which is desirable for coating a substrate having an edge part and accomplishes excellent rust-preventive properties and coating appearance. <P>SOLUTION: The coating film formation method comprises: a chemical conversion step; an electrocrystallization step of immersing the chemically converted substrate in an aqueous solution containing at least one metal selected from the group of consisting of magnesium, manganese, lanthanum, praseodymium, and neodymium or at least one compound thereof and applying a voltage to the substrate to electrically crystallize an electrocrystallized film on its surface; and an electrodeposition film formation step of electrodepositing a cationic electrodeposition coating material on the substrate to form an electrodeposited film on the electrocrystallized coating film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coating film forming method comprising an electrodeposition coating film and an electrodeposition coating film, which is suitable for coating an object having an edge portion.

  A plurality of coating films having various roles are formed on the surface of an object to be coated such as a metal substrate to protect the object to be coated and at the same time give a beautiful appearance. In general, an electrodeposition coating film formed by electrodeposition coating is widely used as a coating film that imparts anticorrosion properties to an object to be coated. Electrodeposition coating can be applied to the details even if the object has a complicated shape, and can be applied automatically and continuously, especially in large and complex shapes such as automobile bodies. It has been widely put into practical use as an undercoating method for articles to be coated.

  The coating film is required to have good surface condition in addition to being required to impart corrosion resistance to the object to be coated. As a means for improving the surface state of the coating film, there is a method for improving the leveling property of the coating film when forming the coating film. For example, the surface state of the coating film can be improved by leveling the coating film by heat flow during curing such as heating. On the other hand, when the article to be coated has an edge portion, the coating of the edge portion is difficult even when electrodeposition coating is used. Furthermore, this leveling action and heat flow may cause the coating film to flow from the edge portion during heat curing, which results in poor rust prevention. Therefore, means for improving the rust prevention property of the edge portion is required in the coating of the object having the edge portion.

  As a method of improving the rust prevention property of the edge part, for example, by suppressing the flow of the electrodeposition coating film due to the heat flow at the time of electrodeposition coating heat curing, the film thickness of the edge part is secured, thereby preventing rust. The method of improving is mentioned. And in order to suppress the flow of the coating film by the heat flow at the time of heat curing, a thickener can also be added in a coating composition. However, by adding a thickener to the electrodeposition coating composition, the leveling property of the coating film is inferior, and the surface state of the flat part other than the edge part is inferior. For this reason, it is difficult to achieve both the improvement of the rust prevention property of the edge portion of the object to be coated and the improvement of the surface state of the coating film (the improvement of the coating film smoothness).

  In JP-A-4-325572 (Patent Document 1), at least one or more selected from metals, metal compounds, and salts thereof, which are dissolved in water at a pH of less than 7.0, as the first step, in the article to be coated. Cationic electrodeposition paint film characterized in that an acidic aqueous liquid containing metals is electrodeposited to deposit the metals, and then, as a second stage, a cationic electrodeposition paint is applied and applied repeatedly, and then heated. A forming method is described (claim 2). An object of the present invention is to obtain a coating film excellent in performance such as adhesion and rust prevention even on a metal base that has not been surface-treated. As the metals contained in the aqueous liquid used in this method, various metals are listed in the paragraph 0027. On the other hand, in the Examples, only examples using lead monoxide are described. Since lead used in this method has an adverse effect on the environment, it is a metal that has been required to reduce its use in recent years. For this reason, this method is not desirable from the viewpoint of environmental protection. Moreover, the invention described in this patent document 1 aims at providing the coating-film formation method with respect to the to-be-coated article which has not performed chemical conversion treatment as above-mentioned.

  Japanese Patent Application Laid-Open No. 2006-28551 (Patent Document 2) discloses a hot dip galvanized layer, a zinc phosphate chemical conversion treatment layer formed on the hot dip galvanization layer, and a surface of the zinc phosphate chemical conversion treatment layer. A treated galvannealed steel sheet having an electrically deposited metal oxide is described (claim 1). Examples of the electrically deposited metal oxide include zinc, silicon, titanium, aluminum, zirconium, tin, iron, barium, thallium and niobium (Claim 2 etc.). These metals are all different from the metals used in the present invention. The invention described in this document is different from the present invention in that an electrodeposition solution in which a metal oxide is dispersed in an organic solvent is used. Furthermore, this invention is an invention relating to a treatment for suppressing gas pin defects during cationic electrodeposition coating of an alloyed hot-dip galvanized steel sheet, and differs from the present invention in the configuration and solution of the invention.

Japanese Patent No. 2997562 JP 2006-28551 A

  The present invention solves the above-described conventional problems, and its object is to form a coating film that is suitable for coating an object having an edge and achieves excellent rust prevention and coating film appearance. It is to provide a method.

The present invention
Chemical conversion process,
The coating is carried out by immersing the chemical conversion treatment in an aqueous solution containing at least one metal or metal compound selected from the group consisting of magnesium, manganese, lanthanum, praseodymium and neodymium, and applying a voltage. Electrodeposition coating process for depositing the electrodeposited film on the surface of the object, and the electrodeposition coating of the cationic electrodeposition coating composition on the object to be coated. Forming, electrodeposition coating film forming step,
A method for forming a coating film including the above-mentioned object is achieved.

  As the aqueous solution, an aqueous solution containing at least one metal or metal compound selected from the group consisting of magnesium, praseodymium and neodymium is preferably used.

  Moreover, it is preferable that content of the metal or metal compound contained in the said aqueous solution is 2-500 mmol / L.

  The present invention also provides a coated product having a coating film obtained by the coating film forming method.

The present invention also provides
Chemical conversion process,
A voltage is applied by immersing the chemical conversion-treated object having an edge in an aqueous solution containing at least one metal or metal compound selected from the group consisting of magnesium, manganese, lanthanum, praseodymium and neodymium. An electrodeposition film forming step for electrically depositing an electrodeposition film on the surface of the object to be coated, and an electrodeposition coating of a cationic electrodeposition coating composition on the object to be coated Forming an electrodeposition coating film, an electrodeposition coating film forming step,
A method for improving the rust prevention property of the edge part in coating film formation is also provided.

  By the coating film forming method of the present invention, it is possible to improve both the rust prevention of the edge portion of the object to be coated and the smoothness of the coating film. In the coating film forming method of the present invention, by forming an electrodeposition film on the surface of an object to be coated before electrodeposition coating, it is difficult to form an electrodeposition coating film having a sufficient film thickness. It has the effect of improving rust prevention. The method for forming a coating film according to the present invention is particularly suitable for coating an object having a complicated shape such as an edge portion and requiring high rust prevention and surface smoothness.

The method of the present invention comprises:
Chemical conversion process,
An electrodeposited film that deposits an electrodeposited film on the surface of the object by immersing the chemical-treated object in an aqueous solution containing a specific metal or metal compound and applying a voltage. An electrodeposition coating film forming step for forming an electrodeposition coating film on the electrodeposited film by electrodeposition-coating a cationic electrodeposition coating composition on an object to be coated;
It is a method including. Details will be sequentially described below.

In the present invention, various substrates that can be energized, such as steel, can be used as the object to be coated. Examples of steel materials that can be used as coated materials include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel, electrogalvanized steel sheets, hot-dip galvanized steel sheets, zinc-aluminum alloy-based steel sheets, zinc-iron alloy-based steel sheets, zinc-magnesium alloys. Steel, zinc-aluminum-magnesium alloy-plated steel, aluminum-plated steel, aluminum-silicon alloy-plated steel, tin-plated steel, lead-tin alloy-plated steel, chromium-plated steel, etc. Steel materials obtained by subjecting steel plates to chemical conversion treatment, and the like.

  The method of the present invention is suitable for coating an object having an edge. Here, the “edge portion” means a corner portion of a base material that is an object to be coated. Examples of the object to be coated suitable for the method of the present invention include an automobile body and parts thereof having a complicated shape such as an edge portion and requiring high rust prevention and surface smoothness. Examples of other objects to be coated include home appliances and building materials such as sashes.

Chemical conversion treatment step In the coating film forming method of the present invention, first, a chemical conversion treatment is performed on the article to be coated using a chemical conversion treatment agent (chemical conversion treatment step). Generally, foreign materials that adversely affect the coating such as rust preventive oil and processing oil adhere to the steel material to be coated. These rust preventive oil and processing oil are removed by performing alkaline degreasing before coating. However, when these rust preventive oil and processing oil are removed, rust is likely to be generated. Therefore, it is necessary to first subject the coating object to chemical conversion treatment using a chemical conversion treatment agent after immersing the coating object in an alkaline degreasing solution to remove rust preventive oil and the like. And by performing a chemical conversion treatment, generation | occurrence | production of the rust produced in a short period can be prevented, and also the adhesiveness of a to-be-coated article and a coating film can be improved.

  As the chemical conversion treatment agent used in the chemical conversion treatment step, a zinc phosphate chemical conversion treatment agent is generally used. As such a zinc phosphate chemical conversion treatment agent, a commercially available product may be used, and examples thereof include SD-5350 manufactured by Nippon Paint Co., Ltd.

  In the present invention, a chemical conversion treatment agent that does not contain phosphate ions can also be used. Examples of such a chemical conversion treatment agent include a zirconium-based chemical conversion treatment agent.

Formation of Electrodeposition Film In the present invention, a chemical conversion-treated object is immersed in an aqueous solution containing a specific metal or metal compound (in the present specification, these may be collectively referred to as metals). By applying a voltage, an electrodeposited film is electrically deposited on the surface of the object to be coated.

  The metals contained in the aqueous solution used for forming the electrodeposition film are at least one metal or metal compound selected from the group consisting of magnesium, manganese, lanthanum, praseodymium and neodymium. Here, examples of the metal compound include organic acid salts, inorganic acid salts, hydroxides, and oxides of the above metals. However, it is a condition that these metal compounds have the property of being soluble in water. Examples of the metal organic acid salt include acetic acid, tartaric acid, citric acid, lactic acid, malic acid, dimethylolpropionic acid, formic acid, and the like. Examples of the metal inorganic acid salts include nitric acid, sulfuric acid, hydrochloric acid, sulfamic acid salts, and the like. As the metals contained in the aqueous solution, nitrates, acetates and lactates of the above metals are preferable.

  In the present invention, it is possible to form a coating film having excellent rust prevention and excellent surface smoothness by forming an electrodeposition film on an object to be coated using an aqueous solution containing the above metals. It was. The metal contained in the aqueous solution is more preferably praseodymium, neodymium, or a metal compound thereof. By using these metals, more excellent rust prevention and surface smoothness can be achieved.

  The content of metals contained in the aqueous solution is preferably 2 to 500 mmol / L. When content of metals is 2 mmol / L, there exists a possibility that sufficient antirust effect cannot be acquired. On the other hand, when the content of metals exceeds 500 mmol / L, the electrodeposition coating film appearance may be adversely affected.

  By immersing the object to be coated as a cathode in an aqueous solution containing the above metals and applying a voltage, an electrodeposited film is deposited on the surface of the object to be coated. A general processing temperature can be adopted as a processing temperature for depositing the electrodeposited film, and can be appropriately selected within a range of 10 to 70 ° C., for example.

  The electrodeposition film can be formed, for example, with an applied voltage of 10 to 200 V and an applied time of 5 to 180 seconds. When the applied voltage is less than 10 V, it may be difficult to obtain a uniform electrodeposited film. Moreover, when it exceeds 50V, there exists a possibility that the external appearance of the coating film obtained may deteriorate. If the application time is less than 5 seconds, it may be difficult to obtain a uniform electrodeposited film. Moreover, when application time exceeds 180 second, there exists a possibility of having a bad influence on the external appearance of an electrodeposition coating film.

  In addition, these applied voltages and application time can be suitably changed according to the kind of metals contained in aqueous solution. When the metal contained in the aqueous solution is, for example, magnesium, it is preferable that the applied voltage is 20 to 200 V and the applied time is 5 to 180 seconds. When the metal contained in the aqueous solution is, for example, praseodymium, neodymium, manganese, or lanthanum, it is preferable to carry out with an applied voltage of 10 to 50 V and an applied time of 5 to 50 seconds. By performing each metal with the applied voltage and the application time within the above ranges, it is possible to achieve better rust prevention and surface smoothness.

  In this way, metals (metal, metal hydroxide, metal oxide, etc.) are deposited on the object to be coated, and an electrodeposited film is formed. The object to be coated on which the electrodeposited film is formed may be washed with water as necessary before the electrodeposition film is formed.

Electrodeposition Coating Formation In the present invention, an electrodeposition coating is further formed on the electrodeposition coating thus formed. In the formation of this electrodeposition coating film, a cationic electrodeposition coating composition is used. The cationic electrodeposition coating composition used in the present invention comprises an aqueous solvent, a binder resin containing a cationic epoxy resin and a blocked isocyanate curing agent dispersed or dissolved in the aqueous solvent, a neutralizing acid, an organic solvent, and a pigment. Etc. are included.

Cationic Epoxy Resin Cationic epoxy resins include amine-modified epoxy resins. Cationic epoxy resins typically open all of the epoxy rings of a bisphenol-type epoxy resin with an active hydrogen compound capable of introducing a cationic group, or some epoxy rings with other active hydrogen compounds. It is produced by opening the ring and opening the remaining epoxy ring with an active hydrogen compound capable of introducing a cationic group.

  A typical example of the bisphenol type epoxy resin is a bisphenol A type or bisphenol F type epoxy resin. As the former commercial product, there are Epicoat 828 (manufactured by Yuka Shell Epoxy Co., Epoxy Equivalent 180-190), Epicoat 1001 (Same, Epoxy Equivalent 450-500), Epicoat 1010 (Same, Epoxy Equivalent 3000-4000), etc. As the latter commercial product, there is Epicoat 807 (same as above, epoxy equivalent 170).

  These epoxy resins may be modified with suitable resins such as polyester polyols, polyether polyols, and monofunctional alkylphenols. In addition, the epoxy resin can be chain-extended using a reaction between an epoxy group and a diol or dicarboxylic acid.

  These epoxy resins are ring-opened with an active hydrogen compound so that an amine equivalent of 0.3 to 4.0 meq / g is obtained after ring opening, and more preferably 5 to 50% of them are occupied by primary amino groups. It is desirable to do.

  Active hydrogen compounds that can introduce a cationic group include primary amines, secondary amines, tertiary amine acid salts, sulfides and acid mixtures. When an amine is used as the active hydrogen compound, an amine-modified epoxy resin having a tertiary amino group can be obtained by reacting an epoxy resin with a secondary amine. Moreover, when an epoxy resin and a primary amine are reacted, an amine-modified epoxy resin having a secondary amino group is obtained. Furthermore, an amine-modified epoxy resin having a primary amino group can be prepared by using a compound having a primary amino group and a secondary amino group. Here, when preparing an amine-modified epoxy resin having a primary amino group using a compound having a primary amino group and a secondary amino group, the primary amino group of the compound is changed before reacting with the epoxy resin. It can be prepared by blocking with a ketone to form a ketimine, which is introduced into an epoxy resin and then deblocked.

  Specific examples of primary amine, secondary amine and ketimine include, for example, butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N- Examples include dimethylethanolamine acetate and diethyl disulfide / acetic acid mixture. In addition, there are secondary amines with blocked primary amines such as aminoethylethanolamine ketimine, diethylenetriamine diketimine. Two or more of these amines may be used in combination.

Blocked isocyanate curing agent Polyisocyanate is used for the preparation of the blocked isocyanate curing agent. This polyisocyanate refers to a compound having two or more isocyanate groups in one molecule. The polyisocyanate may be any of aliphatic, alicyclic, aromatic and aromatic-aliphatic, for example.

  Specific examples of polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI), 2,2,4- C3-C12 aliphatic diisocyanates such as trimethylhexane diisocyanate and lysine diisocyanate; 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI) , Methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, and 1,3-diisocyanatomethylcyclo Carbon such as xane (hydrogenated XDI), hydrogenated TDI, 2,5- or 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (also referred to as norbornane diisocyanate). Aliphatic diisocyanates having a number of 5 to 18; aliphatic diisocyanates having an aromatic ring such as xylylene diisocyanate (XDI) and tetramethyl xylylene diisocyanate (TMXDI); Uretdione, uretonimine, burette and / or isocyanurate modified product); These may be used alone or in combination of two or more.

  Adducts or prepolymers obtained by reacting polyisocyanates with polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylolpropane and hexanetriol at an NCO / OH ratio of 2 or more may also be used as the block isocyanate curing agent.

  The blocking agent is added to a polyisocyanate group and is stable at ordinary temperature, but can regenerate a free isocyanate group when heated to a temperature higher than the dissociation temperature.

Pigment The cationic electrodeposition coating composition used in the method of the present invention may contain a commonly used pigment. Examples of pigments that can be used include commonly used inorganic pigments, for example colored pigments such as titanium white, carbon black and bengara; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; Zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate and aluminum phosphomolybdate, phosphomolybdic acid Examples include rust preventive pigments such as aluminum zinc. When the pigment is contained in the electrodeposition coating composition, the amount of the pigment is preferably 1 to 30% by weight with respect to the solid content of the cationic electrodeposition coating composition.

  When a pigment is used as a component of an electrodeposition paint, generally, the pigment is dispersed in advance in an aqueous solvent at a high concentration to form a paste (pigment dispersion paste). This is because the pigment is in a powder form, and it is difficult to disperse in a single step in a low concentration uniform state used in the electrodeposition coating composition. Such a paste is generally called a pigment dispersion paste.

  The pigment dispersion paste is prepared by dispersing a pigment together with a pigment dispersion resin in an aqueous solvent. As the pigment dispersion resin, a cationic polymer such as a cationic or nonionic low molecular weight surfactant or a modified epoxy resin having a quaternary ammonium group and / or a tertiary sulfonium group is generally used. As the aqueous solvent, ion-exchanged water or water containing a small amount of alcohol is used. In general, the pigment dispersion resin is used in an amount of 20 to 100 parts by mass with respect to 100 parts by mass of the pigment. After the pigment dispersion resin and the pigment are mixed, the pigment is dispersed using a normal dispersing device such as a ball mill or a sand grind mill until the pigment in the mixture has a predetermined uniform particle size. A paste can be obtained.

Other components When the cationic electrodeposition coating composition contains a dissociation catalyst for dissociating the blocking agent of the blocked isocyanate curing agent in addition to the above components, dibutyltin laurate, dibutyltin oxide, dioctyltin oxide, etc. Organic tin compounds, amines such as N-methylmorpholine, and metal salts such as strontium, cobalt and copper can be used. The concentration of the dissociation catalyst is preferably 0.1 to 6 parts by mass with respect to 100 parts by mass of the total of the cationic epoxy resin and the blocked isocyanate curing agent in the cationic electrodeposition coating composition.

Preparation of cationic electrodeposition coating composition The cationic electrodeposition coating composition used in the present invention is prepared by dispersing the above-described cationic epoxy resin, blocked isocyanate curing agent, and pigment dispersion paste in an aqueous solvent. The Further, the aqueous solvent usually contains a neutralizing acid in order to neutralize the cationic epoxy resin and improve the dispersibility of the binder resin emulsion. The neutralizing acid is an inorganic or organic acid such as hydrochloric acid, nitric acid, phosphoric acid, formic acid, acetic acid, lactic acid.

  The amount of the neutralizing acid used is preferably in the range of 10 to 25 mg equivalent to 100 g of the binder resin solid content including the cationic epoxy resin and the blocked isocyanate curing agent. The lower limit is more preferably 15 mg equivalent, and the upper limit is more preferably 20 mg equivalent. If the amount of the neutralizing acid is less than 10 mg equivalent, the affinity for water is not sufficient and the dispersion in water cannot be performed or the stability is extremely poor. If the amount exceeds 25 mg equivalent, the amount of electricity required for precipitation increases. , The precipitation of the solid content of the paint is lowered and the throwing power is inferior.

  The amount of the blocked isocyanate curing agent is sufficient to react with active hydrogen-containing functional groups such as primary, secondary amino groups, hydroxyl groups, etc. in the cationic epoxy resin during curing to give a good cured coating film. Needed. The amount of the blocked isocyanate curing agent is preferably 90/10 to 50/50, more preferably 80/20, expressed as a weight ratio of the cationic epoxy resin to the blocked isocyanate curing agent (cationic epoxy resin / curing agent). It is in the range of ~ 65/35. By adjusting the solid content ratio between the cationic epoxy resin and the blocked isocyanate curing agent, the fluidity and curing speed of the coating film (deposition film) during film formation are improved, and the smoothness of the coating film is improved.

  Examples of the organic solvent usually contained in the cationic electrodeposition coating composition include ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethyl hexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and propylene glycol monophenyl ether. Can be mentioned.

  In addition to the above, the cationic electrodeposition coating composition may contain conventional coating additives such as a plasticizer, a surfactant, an antioxidant, and an ultraviolet absorber. An amino group-containing acrylic resin, an amino group-containing polyester resin, and the like may be included.

Electrodeposition Electrodeposition is usually performed by applying a voltage of 50 to 450 V between the object to be coated as a cathode and the anode. If the applied voltage is less than 50V, electrodeposition may be insufficient, and if it exceeds 450V, the coating film may be destroyed and an abnormal appearance may be obtained. At the time of electrodeposition coating, the bath temperature of the coating composition is usually adjusted to 10 to 45 ° C.

  The electrodeposition coating process is composed of a process of immersing an object to be coated in a cationic electrodeposition paint composition, and a process of applying a voltage between the object to be coated as a cathode and an anode to deposit a film. . Moreover, although the time which applies a voltage changes with electrodeposition conditions, generally it can be made into 2 to 4 minutes.

  The film thickness of the electrodeposition coating film is preferably 5 to 40 μm, more preferably 10 to 25 μm. When the film thickness is less than 5 μm, the antirust property is insufficient, and when it exceeds 40 μm, the paint is wasted.

  The electrodeposition coating film obtained as described above is baked and cured by baking it at 120 to 260 ° C., preferably 140 to 220 ° C. for 10 to 30 minutes after completion of the electrodeposition process or after washing with water. An electrodeposition coating film is formed.

  By the coating film forming method of the present invention, it is possible to form a coating film excellent in rust prevention. The electrodeposition coating film itself is a coating film excellent in rust prevention. However, when the object to be coated has an edge part, it is difficult to ensure the film thickness of the electrodeposition coating film at the edge part due to the leveling action of the electrodeposition coating composition. It is possible to add a thickener to improve the rust prevention property of the electrodeposited coating film at the edge portion, but there is a problem that the surface state of the flat portion other than the edge portion is inferior.

  The coating film formed by the coating film forming method of the present invention has an electrodeposition coating film and an electrodeposition coating film. Among these, the electrodeposition film formed on the surface of the object to be coated itself has almost no melt fluidity when heated, so that a sufficient film thickness can be secured even at the edge portion. Thereby, the coating film excellent in rust prevention property is obtained also in an edge part. In the coating film forming method of the present invention, by forming an electrodeposited film on the surface of an object to be coated before electrodeposition coating, it is difficult to form an electrodeposited film having a sufficient film thickness. It is possible to improve rust prevention. The coating film forming method of the present invention can be used in combination with an electrodeposition coating composition having excellent rust prevention properties. By selecting an electrodeposition coating composition to be used in this way, a coating having further excellent rust prevention properties can be used. It is also possible to provide a membrane.

  The coating film forming method of the present invention is suitable for coating an object having an edge portion, and particularly has an intricate shape such as an edge portion and is required to have high rust prevention and surface smoothness. Suitable for painting.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on weight unless otherwise specified.

Production Example 1 Production of blocked isocyanate curing agent 199 parts of hexamethylene diisocyanate trimer (Coronate HX: manufactured by Nippon Polyurethane Co., Ltd.) and methyl in a flask equipped with a stirrer, cooler, nitrogen injection tube, thermometer and dropping funnel 32 parts of isobutyl ketone and 0.03 part of dibutyltin dilaurate were weighed out, and 87.0 parts of methyl ethyl ketoxime was added dropwise from the dropping funnel over 1 hour while stirring and bubbling nitrogen. The temperature was increased from 50 ° C. to 70 ° C. Thereafter, the reaction was continued for 1 hour, and the reaction was continued until the absorption of the NCO group disappeared with an infrared spectrometer. Thereafter, 0.74 parts of n-butanol and 39.93 parts of methyl isobutyl ketone were added to obtain a nonvolatile content of 80%.

Production Example 2 Production of amine-modified epoxy resin emulsion In a flask equipped with a stirrer, a cooler, a nitrogen injection tube and a dropping funnel, 71.34 parts of 2,4 / 2,6-tolylene diisocyanate (80/20 wt%), Methyl isobutyl ketone (111.98 parts) and dibutyltin dilaurate (0.02 parts) were weighed out and 14.24 parts of methanol was added dropwise from a dropping funnel over 30 minutes while stirring and nitrogen bubbling. The temperature was raised from room temperature to 60 ° C. due to heat generation. Thereafter, the reaction was continued for 30 minutes, and then 46.98 parts of ethylene glycol mono-2-ethylhexyl ether was added dropwise from the dropping funnel over 30 minutes. The temperature was raised to 70 to 75 ° C. due to heat generation. After continuing the reaction for 30 minutes, 41.25 parts of bisphenol A propylene oxide (5 mol) adduct (BP-5P manufactured by Sanyo Chemical Industries, Ltd.) was added, the temperature was raised to 90 ° C., and the IR spectrum was measured. The reaction was continued until the NCO group disappeared.

  Subsequently, 475.0 parts of a bisphenol A type epoxy resin having an epoxy equivalent of 475 (YD-7011R manufactured by Toto Kasei Co., Ltd.) was added and dissolved uniformly, then the temperature was raised from 130 ° C. to 142 ° C., and azeotrope with MIBK To remove water from the reaction system. After cooling to 125 ° C., 1.107 parts of benzyldimethylamine was added to carry out an oxazolidone ring formation reaction by a demethanol reaction. The reaction was continued until an epoxy equivalent of 1140.

  Thereafter, the mixture was cooled to 100 ° C., 24.56 parts of N-methylethanolamine, 11.46 parts of diethanolamine and 26.08 parts of aminoethylethanolamine ketimine (78.8% methyl isobutyl ketone solution) were added, and the mixture was heated at 110 ° C. for 2 hours. Reacted. Thereafter, 20.74 parts of ethylene glycol mono-2-ethylhexyl ether and 12.85 parts of methyl isobutyl ketone were added to dilute to adjust to 82% non-volatile matter. The number average molecular weight (GPC method) was 1380, and the amine equivalent was 94.5 meq / 100 g.

  In another container, 145.11 parts of ion-exchanged water and 5.04 parts of acetic acid were weighed, and 320.11 parts of the amine-modified epoxy resin heated to 70 ° C. (75.0 parts as a solid content) and Production Example 1 A mixture of 190.38 parts of a blocked isocyanate curing agent (25.0 parts as a solid content) was gradually added dropwise and stirred to disperse uniformly. Thereafter, ion exchange water was added to adjust the solid content to 36%.

Production Example 3 Production of Pigment Dispersion Resin A flask equipped with a stirrer, a cooler, a nitrogen injection tube, a thermometer and a dropping funnel, and 382.20 parts of bisphenol A type epoxy resin (trade name DER-331J) having an epoxy equivalent of 188, 111.98 parts of bisphenol A was weighed out, heated to 80 ° C., and dissolved uniformly. Then, 1.53 parts of a 1% 2-ethyl-4-methylimidazole solution was added and reacted at 170 ° C. for 2 hours. After cooling to 140 ° C., 196.50 parts of 2-ethylhexanol half-blocked isophorone diisocyanate (non-volatile content: 90%) was added thereto and reacted until the NCO group disappeared. To this was added 205.00 parts of dipropylene glycol monobutyl ether, followed by 408.00 parts of 1- (2-hydroxyethylthio) -2-propanol and 134.00 parts of dimethylolpropionic acid. 0.000 part was added and it was made to react at 70 degreeC. The reaction was continued until the acid value was 5 or less. The obtained pigment dispersion resin was diluted to 35% non-volatile content with 1150.50 parts of ion exchange.

Production Example 4 Preparation of Electrodeposition Coating Composition 120 parts of the pigment-dispersed resin dispersion obtained in Production Example 3 in a sand grind mill, 2.0 parts of carbon black, 50 parts by weight of calcined kaolin, and 50.0 parts of silicate compound Then, 80.0 parts of titanium dioxide, 18.0 parts of aluminum phosphomolybdate and 221.7 parts of ion-exchanged water were added and dispersed until the particle size became 10 μm or less to obtain a pigment paste (solid content 48%).

  To 100 parts of the cationic epoxy resin emulsion obtained in Production Example 2, 23 parts of the pigment dispersion paste was added and mixed. Furthermore, 0.6 parts of dibutyltin oxide and 122 parts of ion-exchanged water were added to obtain a cationic electrodeposition coating composition.

Production Example 5 Preparation of Electrodeposition Aqueous Solution (1) Praseodymium acetate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (1).

Production Example 6 Preparation of Electrodeposition Aqueous Solution (2) Neodymium acetate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (2).

Production Example 7 Preparation of Electrodeposition Aqueous Solution (3) Lanthanum acetate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (3).

Production Example 8 Preparation of Electrodeposition Aqueous Solution (4) Magnesium acetate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (4).

Production Example 9 Preparation of Electrodeposition Aqueous Solution (5) Manganese acetate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (5).

Production Example 10 Preparation of Electrodeposition Aqueous Solution (6) Praseodymium acetate (20 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (6).

Production Example 11 Preparation of Electrodeposition Aqueous Solution (7) Praseodymium acetate (50 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (7).

Comparative Production Example 1 Preparation of Electrodeposition Aqueous Solution (6) Cobalt nitrate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (8).

Comparative Production Example 2 Preparation of Electrodeposition Aqueous Solution (7) Nickel nitrate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (9).

Comparative Production Example 3 Preparation of Electrodeposition Aqueous Solution (8) Copper nitrate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (10).

Comparative Production Example 4 Preparation of Electrodeposition Aqueous Solution (9) Zinc acetate (10 mmol) was dissolved in 1 L of ion-exchanged water to prepare an electrodeposition aqueous solution (11).

Example 1
As an object to be coated, a commercially available olfa cutter spare blade LB-10 subjected to zinc phosphate chemical conversion treatment (SD-5350 manufactured by Nippon Paint Co., Ltd.) was used. This coating object was immersed in the electrodeposition aqueous solution (1) obtained from Production Example 5, and electrodeposition was performed at an applied voltage of 10 V and an applied time of 30 seconds. Next, after washing with ion-exchanged water, the cationic electrodeposition coating composition obtained from Production Example 4 was electrodeposited so that the film thickness of the dried coating film was 25 μm, and baked at 160 ° C. for 25 minutes. Cured to form a coating film. The cured coating film thus obtained was evaluated as follows.

Salt spray test A salt spray test based on JIS Z 2371 was performed for 168 hours on the obtained coating. The number of rust produced on the cutting edge by this test was counted. The results are shown in Table 1. The smaller the number of rust produced, the better the rust prevention.

Arithmetic mean roughness of roughness curve (Ra)
The cured coating film of the flat part of the obtained coated product (painted spare blade) was used for evaluation of the finished appearance. The arithmetic average roughness (Ra) of the roughness curve of this portion was measured using a surface roughness meter (SJ-201P manufactured by Mitutoyo Corporation; cut-off value = 0.25 mm). The evaluation results are shown in Table 1. The arithmetic mean roughness (Ra) of the roughness curve is a parameter defined in JIS B 0601-2001. When this Ra value is 0.25 μm or less, it can be evaluated that the coating film surface is smooth.

Examples 2-16
A coating film was formed in the same manner as in Example 1 except that the type of electrodeposition aqueous solution and the electrodeposition voltage were changed as shown in Table 1 or 2. The obtained coating film was evaluated in the same manner as in Example 1.

Comparative Example 1
A coating film was formed in the same manner as in Example 1 except that the electrodeposition coating film was formed without forming an electrodeposition coating film. The obtained coating film was evaluated in the same manner as in Example 1.

Comparative Examples 2-9
A coating film was formed in the same manner as in Example 1 except that the type of the aqueous solution for electrodeposition and the electrodeposition voltage were changed as shown in Table 3 or 4. The obtained coating film was evaluated in the same manner as in Example 1.

  As shown in Tables 1 to 4 above, the coating films obtained by the examples are excellent in the rust prevention property of the edge part, and the Ra value of the coating film in the flat part is low and the coating film surface is smooth. Recognize. On the other hand, when the coating is performed without forming the electrodeposited film as in Comparative Example 1, the rust prevention property of the edge portion is clearly inferior. Further, as in Comparative Examples 2 to 9, when an electrodeposited film was formed using other metals, although the rust prevention property of the edge portion was improved, there was a problem that the coating film surface deteriorated. It was.

  By the coating film forming method of the present invention, it is possible to improve both the rust prevention of the edge portion of the object to be coated and the smoothness of the coating film. The coating film forming method of the present invention is suitable for coating an object having an edge portion, and particularly has an intricate shape such as an edge portion and is required to have high rust prevention and surface smoothness. Suitable for painting.

Claims (5)

Chemical conversion process,
The coating is carried out by immersing the chemical conversion treatment in an aqueous solution containing at least one metal or metal compound selected from the group consisting of magnesium, manganese, lanthanum, praseodymium and neodymium, and applying a voltage. Electrodeposition coating process for depositing the electrodeposited film on the surface of the object, and the electrodeposition coating of the cationic electrodeposition coating composition on the object to be coated. Forming, electrodeposition coating film forming step,
A method for forming a coating film.   The coating film forming method according to claim 1, wherein an aqueous solution containing at least one metal or metal compound selected from the group consisting of magnesium, praseodymium and neodymium is used as the aqueous solution.   The coating-film formation method of Claim 1 or 2 whose content of the metal or metal compound contained in the said aqueous solution is 2-500 mmol / L.   A coated article having a coating film obtained by the coating film forming method according to claim 1. Chemical conversion process,
A voltage is applied by immersing the chemical conversion-treated object having an edge in an aqueous solution containing at least one metal or metal compound selected from the group consisting of magnesium, manganese, lanthanum, praseodymium and neodymium. An electrodeposition film forming step for electrically depositing an electrodeposition film on the surface of the object to be coated, and an electrodeposition coating of a cationic electrodeposition coating composition on the object to be coated Forming an electrodeposition coating film, an electrodeposition coating film forming step,
A method for improving the rust prevention property of the edge portion in coating film formation.