JP2015199803A - Primer composition for prepainted metal, coated film, method of forming coated film, prepainted steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a primer composition for a prepainted metal, which contains substantially no chromium and is excellent in corrosion resistance, adhesibility, moisture resistance and scratch resistance and in particular, provides a worked portion with excellent corrosion resistance even when blocking property of a top coating is inefficient.SOLUTION: The primer composition for a prepainted metal is provided which contains an organic resin (A), a curing agent (B), calcium vanadate (C), silica (D), silicate (E) and tripolyphosphate metal salt (F) and substantially no chromium and in which the solid content mass of the calcium vanadate (C) is 20 to 65 pts.mass based on 100 pts,mass of the total solid content of the organic resin (A) and the curing agent (B), the solid content mass of the silica (D) is 3 to 12 pts.mass based on 100 pts.mass of the total solid content of the (A) and (B) components, the solid content mass of the silicate (E) is 5 to 15 pts.mass in total based on 100 pts.mass of the total solid content of the (A) and (B) components, the tripolyphosphate metal salt (F) is a metal salt containing at least one element selected from aluminum and zinc, having electric conductivity of its 1 mass% solution of 5 to 50 μS/cm and its solid content mass is 4 to 25 pts.mass in total based on 100 pts.mass of the total solid content of the (A) and (B) components.

Description

The present invention relates to a precoat metal primer coating composition, a coating film, a method for forming a coating film, and a precoated steel sheet.

  Coated steel sheets coated with cold-rolled steel sheets or plated steel sheets as base materials are also called pre-coated metals, and are used in various applications such as air conditioner outdoor units, home appliance exteriors for water heaters, exterior building materials such as roofs and walls. It is used.

  In order to improve corrosion resistance and prevent rusting, the surface of a coated steel sheet including a galvanized steel sheet is usually coated on its surface. Conventionally, it has been common to use a chromium-based paint as a rust preventive paint. By forming the chromium-containing coating film, a chromium film is formed, and the generation of rust can be suppressed. However, the use of chromium has been restricted due to concerns about adverse environmental effects.

  Thus, various paints containing rust preventives other than chromium compounds have been proposed so far, but it is difficult to impart corrosion resistance equivalent to that of chrome paints. It has been difficult to apply the coated steel sheet to outdoor products such as roofing materials, wall materials, and air conditioner outdoor units. That is, when a coated steel sheet coated with a conventional non-chromium rust preventive paint is applied to outdoor-use products, significant rust is generated, resulting in poor appearance and poor adhesion of the coating film. There was a problem that occurred. In particular, when a coated steel sheet is applied to the above roofing material, wall material, etc., a flat steel sheet provided with a rust-preventive coating obtained by coating a rust-proof paint on the flat steel sheet is bent to obtain a formed body. Since the pre-coating method is adopted, it is required not only to have the above rust prevention property, but also to have folding workability, work adhesion, scratch resistance, etc., such that the coating film does not peel at the same time. In addition, the corrosion resistance of the cracked portion of the coating film generated in the processed part is also required.

  For example, in Patent Documents 1 and 2, it is proposed to use a rust preventive pigment that combines a compound that releases phosphate ions and a compound that releases vanadate ions as a non-chromium rust preventive pigment. The coating film formed from the said chromium-free rust preventive pigment has problems, such as that corrosion resistance is not enough with respect to the application to an outdoor use.

  Patent Documents 3 and 4 contain, as non-chromium-based rust preventive pigments, (1) vanadic acid compounds, (2) metal silicates, and (3) rust preventive pigments made of phosphate metal salts. An antirust coating composition is disclosed. However, these rust-preventive coating compositions also have room for improvement, as in Patent Documents 1 and 2, where the corrosion resistance is not sufficient for application to outdoor applications.

  Therefore, in order to further improve the corrosion resistance, Patent Document 5 describes a coating composition containing an organic resin (A), a curing agent (B), and calcium vanadate (C) from the viewpoint of further improving the corrosion resistance and moisture resistance. The calcium vanadate (C) has a 1% by mass aqueous solution having an electric conductivity of 200 to 2000 μS / cm, and the content of the calcium vanadate (C) is the organic resin (A). And the coating composition which is 50-150 mass parts with respect to 100 mass parts of total solid content of the said hardening | curing agent (B) is proposed.

Patent Document 6 discloses a coating composition containing (A) a hydroxyl group-containing film-forming resin, (B) a cross-linking agent, and (C) a rust preventive pigment mixture, the rust preventive pigment mixture (C). However, the amount of the vanadium compound (1) is 3 to 50 parts by mass and the oil absorption is 30 to 200 ml / 100 g with respect to 100 parts by mass of the total solid content of the resin (A) and the curing agent (B). The amount of (2) is 3 to 50 parts by mass, and the amount of metal salt (cobalt or nickel metal salt) (3) of metal phosphate, metal hydrogen phosphate and metal tripolyphosphate (1) is 1 to 50 The coating composition which is a mass part and whose quantity of this rust preventive pigment mixture (C) is 10-150 mass parts is proposed.
Further, Patent Document 7 discloses a coating composition containing (A) a hydroxyl group-containing film-forming resin, (B) a crosslinking agent, and (C) a rust-preventive pigment mixture, wherein the rust-preventive pigment mixture (C) (1) at least one vanadium compound of vanadium pentoxide, calcium vanadate and ammonium metavanadate, (2) at least one of cobalt and nickel, phosphoric acid, phosphorous acid, tripolyphosphorus There has been proposed a coating composition comprising a phosphoric acid-based metal salt which is at least one salt of acids, and (3) a metal silicate which is at least one of cobalt salts, nickel salts and calcium salts. Yes.
However, in accordance with the demand for further anticorrosion properties, these coating compositions also have insufficient corrosion resistance at the end portions and processed portions for application to outdoor applications, as in the case of the above-mentioned Patent Documents 1 to 4. There was room for improvement.

Japanese Patent Publication No. 5-50444 Japanese Patent No. 3461741 Japanese Patent No. 4323530 JP 2009-227748 A JP 2011-184624 A JP 2011-32425 A JP 2012-131907 A

  The use of a highly soluble rust preventive pigment can promote the formation of a protective coating on the end face and improve the corrosion resistance of the end portion. There was a problem that the moisture tends to be high, the moisture resistance and chemical resistance are lowered, and blistering occurs. Further, when the amount of elution is large, the amount of protective coating formed increases, and this protective coating appears as so-called white rust. In recent years, suppression of the occurrence of white rust has been strongly demanded as a higher demand. However, in the case of a coating film with insufficient barrier properties to the top coat, leaching of anticorrosive pigments from the undercoat tends to increase, There was a problem that rust was likely to occur.

 As a result of the rust preventive pigments described in Patent Documents 1 to 4 comprising a plurality of types of rust preventive components, when blended with a paint, the blending amount of the highly soluble vanadate compound tends to be kept relatively low. is there. As a result, although the resulting coating film can have relatively good moisture resistance, it has recently been required to have higher corrosion resistance, especially for the corrosion resistance of processed parts (insufficient rust suppression) when the coating of the top coating film is insufficient. It was still insufficient. Accordingly, the present situation is that no rust-preventing undercoating composition satisfying both the corrosion resistance and moisture resistance of the end face and the processed part according to higher requirements has been found.

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is excellent in corrosion resistance, adhesion, moisture resistance and scratch resistance, and even if the barrier property of the top coat film is insufficient, the end face Another object of the present invention is to provide a coating composition for precoat metal that is excellent in corrosion resistance of the processed portion and does not contain chromium, a coating film using the same, a method for forming the coating film, and a precoated steel sheet.

As a result of intensive studies to solve the conventional problems described above, the present inventors have used a tripolyphosphate metal salt comprising a specific metal salt, and a 1% by mass aqueous solution of the tripolyphosphate metal salt has a specific range. Further, an organic resin (A), a curing agent (B), calcium vanadate (C), silica (D), silicate (E), and tripolyphosphate metal salt (F) Even if the coating composition contained at a specific content does not contain chromium, it has excellent corrosion resistance, adhesion, moisture resistance, and scratch resistance, and even if the coating film has insufficient barrier properties, it can be processed. It was found that the corrosion resistance of the portion was excellent, and the present invention was completed.
The present invention has been completed based on such findings.

That is, the present invention is as follows.
[1] An organic resin (A), a curing agent (B), calcium vanadate (C), silica (D), silicate (E), and tripolyphosphate metal salt (F), and substantially chromium The coating composition for precoat metal which does not contain the solid content mass of the calcium vanadate (C) is 20 to 65 with respect to 100 mass parts of the total solid content of the organic resin (A) and the curing agent (B). The solid content mass of the silica (D) is 3 to 12 parts by mass with respect to 100 mass parts of the total solid content of the organic resin (A) and the curing agent (B), and the silicate ( The solid content mass of E) is 5 to 15 mass parts in total with respect to 100 mass parts of the total solid content of the organic resin (A) and the curing agent (B), and the tripolyphosphate metal salt (F) contains aluminum and At least one element selected from zinc And the electrical conductivity of a 1% by mass aqueous solution of the tripolyphosphate metal salt (F) is 5 to 50 μS / cm, and the solid content mass of the tripolyphosphate metal salt (F) is an organic resin. The undercoat paint composition for precoat metal which is a total of 4-25 mass parts with respect to 100 mass parts of total solid content of (A) and a hardening | curing agent (B).
[2] The undercoat paint composition according to [1], wherein the silicate (E) is a salt of at least one metal selected from aluminum, potassium, and sodium.
[3] The organic resin (A) contains a bisphenol type epoxy resin, and the curing agent (B) contains a blocked isocyanate and / or a melamine resin, according to [1] or [2] Undercoat paint composition.
[4] A coating film formed using the coating composition according to any one of [1] to [3].
[5] After applying the precoat metal coating composition according to [1] to [3] to the steel sheet, the coating is performed by heating until the temperature of the steel sheet is within a range of 120 to 300 ° C. Method for forming a film.
[6] The method for forming a coating film according to [5], wherein the baking heating time is 3 to 90 seconds.
[7] A precoated steel sheet having the coating film according to [4].

  According to the present invention, it is excellent in corrosion resistance, adhesion, moisture resistance and scratch resistance, and even if the coating film has insufficient barrier properties, it has excellent corrosion resistance in the processed part. A coating composition, a coating film using the coating composition, a method for forming the coating film, and a precoated steel sheet can be provided.

It is a schematic diagram which shows the outline of the coated steel plate test piece used for the corrosion resistance test. It is a schematic diagram which shows the crosscut part and 4T bending process part which were provided in the coated steel plate test piece used for the corrosion resistance test.

[Precoat metal undercoating composition]
The undercoat coating composition for precoat metal of the present invention (hereinafter also referred to as “coating composition”) comprises an organic resin (A), a curing agent (B), calcium vanadate (C), silica (D), silicate ( E), and a coating composition for a precoat metal containing a tripolyphosphate metal salt (F) and substantially free of chromium, wherein the solid content mass of the calcium vanadate (C) is an organic resin (A). And 20 to 65 parts by mass relative to 100 parts by mass of the total solid content of the curing agent (B), and the solid content mass of the silica (D) is the total solid content of the organic resin (A) and the curing agent (B). It is 3-12 mass parts with respect to 100 mass parts, and the solid content mass of the said silicate (E) is a total of 5 with respect to 100 mass parts of total solid content of an organic resin (A) and a hardening | curing agent (B). ~ 15 parts by mass, the gold tripolyphosphate The salt (F) is a metal salt containing at least one element selected from aluminum and zinc, and the electrical conductivity of a 1% by mass aqueous solution of the tripolyphosphate metal salt (F) is 5 to 50 μS / cm. The solid content mass of the tripolyphosphate metal salt (F) is 4 to 25 parts by mass in total with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B).

Here, in this specification, “substantially no chromium” means that the chromium content is 0.005 parts by mass or less with respect to 100 parts by mass of the solid content of the coating composition. .
In the present specification, “improves moisture resistance” means that even when the object is placed in a high-humidity environment, the coating film is less likely to cause swelling or peeling. Specifically, it is improved by increasing the moisture permeation suppressing performance of the coating film. However, if the moisture permeation suppression performance of the coating film is improved too much, the elution properties of calcium vanadate (C) and tripolyphosphate metal salt (F), which are rust preventive pigments, are reduced, and the corrosion resistance of the coating film is reduced. . Therefore, in order to achieve both the moisture resistance and the corrosion resistance of the end face and the processed part at a higher level than conventional, the moisture permeability suppressing performance is not excessively high, although the moisture permeability suppressing performance is higher than the conventional one. It is important to provide appropriate moisture permeability.

  The coating composition in the present invention uses a tripolyphosphate metal salt composed of a specific metal salt, and a 1% by mass aqueous solution of the tripolyphosphate metal salt has a specific range of electrical conductivity, and further includes an organic resin (A ), Curing agent (B), calcium vanadate (C), silica (D), silicate (E), and tripolyphosphate metal salt (F) are contained in specific contents, respectively. While interacting to form a dense coating, effective amounts of these components are retained in the coating. As a result, although it does not contain chromium, it is presumed that it is excellent in corrosion resistance, adhesion, moisture resistance and scratch resistance, and is excellent in corrosion resistance of the processed part even if the barrier property of the top coat film is insufficient.

[Organic resin (A)]
The organic resin (A) used in the coating composition of the present invention is not particularly limited as long as it is a resin having a functional group capable of reacting with the curing agent (B) described later and having a film-forming ability, For example, epoxy resins and modified products thereof (acrylic modified epoxy resins, etc.); polyester resins and modified products thereof (urethane modified polyester resins, epoxy modified polyester resins, etc.); acrylic resins and modified products thereof (urethane modified acrylic resins, etc.); urethane Resins and modified products thereof (epoxy modified urethane resins, etc.); phenol resins and modified products thereof (acrylic modified phenol resins, epoxy modified phenol resins, etc.); phenoxy resins; alkyd resins and modified products thereof (urethane modified alkyd resins, acrylic modified alkyds) Resin). These resins may be used alone or in combination of two or more.

  Examples of the epoxy resin include a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of a catalyst such as an alkali catalyst as necessary; bisphenol type epoxy resins such as bisphenol A type and bisphenol F type; and novolak Type epoxy resin.

  Examples of the modified epoxy resin include modified epoxy resins such as acrylic-modified epoxy resins, urethane-modified epoxy resins, and amine-modified epoxy resins. For example, taking an acrylic modified epoxy resin as an example, this may be prepared by reacting a polymerizable unsaturated monomer component containing acrylic acid or methacrylic acid with the bisphenol type epoxy resin or the novolac type epoxy resin. it can. For example, a urethane-modified epoxy resin can be prepared by reacting the bisphenol type epoxy resin or the novolac type epoxy resin with a polyisocyanate compound.

  The polyester resin is obtained by polycondensation of a polyhydric alcohol and a polybasic acid. Specific examples of the polyhydric alcohol include, for example, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 2, 3-butanediol or 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, hydrogenated bisphenol A, hydroxyalkylated bisphenol A, 1,4-cyclohexanedimethanol, 2,2-dimethyl -3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate (BASHPN), N, N-bis- (2-hydroxyethyl) dimethylhydantoin, polycaprolactone polyol, glycerin, sono And the like (hydroxyethyl) isocyanate - Bitoru, An'nitoru, trimethylol ethane, trimethylol propane, trimethylol butane, hexanetriol, pentaerythritol, dipentaerythritol, tris. As the polyhydric alcohol, only one kind may be used alone, or two or more kinds may be used in combination.

  Specific examples of the polybasic acid include, for example, phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetraphthalic acid, methyltetrahydrophthalic anhydride , Hymic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid , Succinic acid, succinic anhydride, lactic acid, dodecenyl succinic acid, dodecenyl succinic anhydride, cyclohexane-1,4-dicarboxylic acid, and endo acid anhydride. A polybasic acid may be used individually by 1 type, and may use 2 or more types together.

  Examples of the modified polyester resin include modified polyester resins such as urethane-modified polyester resin, epoxy-modified polyester resin, and acrylic-modified polyester resin. For example, taking a urethane-modified polyester resin as an example, it can be prepared by reacting the polyester resin with a polyisocyanate compound.

  Examples of the acrylic resin include hydroxyl groups such as hydroxymethyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxylpropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and N-methylolacrylamide. One or more monomers selected from (meth) acrylic monomers and lactone adducts thereof; (meth) acrylic acid; (meth) acrylic esters such as alkyl (meth) acrylate; (meth) acrylonitrile An acrylic resin made of In addition to the structural units derived from the above monomers, acrylic resins can be used for other monomers (for example, carboxyl group-containing ethylenic monomers such as crotonic acid, itaconic acid, fumaric acid and maleic acid, and vinyl monomers such as styrene). The derived structural unit may be included.

  Examples of the modified acrylic resin include modified acrylic resins such as urethane-modified acrylic resins. For example, taking a urethane-modified acrylic resin as an example, it can be prepared by reacting an acrylic resin with a polyisocyanate compound as described above.

  Among the above, as the organic resin (A), epoxy resin, polyester resin, acrylic resin can be used from the viewpoint of the balance of processing adhesion of the obtained coating film, scratch resistance and moisture resistance, corrosion resistance, and weather resistance of the obtained coating film. A thermosetting resin (A1) such as a resin or a modified product thereof can be used, and one or more selected from an epoxy resin, a polyester resin, and a modified product thereof can be used. Preferably, as the thermosetting resin (A1), at least one selected from a hydroxyl group-containing epoxy resin, a hydroxyl group-containing polyester resin, and a modified product containing a hydroxyl group is used. When the epoxy resin, the polyester resin and these modified products have a hydroxyl group, various melamine resins and various isocyanate compounds can be selected as the curing agent (B). As a result, it is particularly preferable because various physical properties can be imparted to the coating film by selecting the curing agent (B) having desired properties from among the various curing agents (B).

  Examples of the hydroxyl group-containing epoxy resin (including modified hydroxyl group-containing epoxy resin) include jER1004, jER1007, E1255HX30, YX8100BH30 manufactured by Mitsubishi Chemical Corporation. Examples of the hydroxyl group-containing polyester resin (including hydroxyl group-modified polyester resin modified products) include, for example, Beckolite 47-335 manufactured by DIC, Byron 220 manufactured by Toyobo, Byron BR3300, Byron GK130, Byron GK330, and the like. Can do.

  The number average molecular weight (Mn) of the hydroxyl group-containing epoxy resin (including the hydroxyl group-containing epoxy resin modified product) is preferably 2000 to 10000, more preferably 3000 to 8000, and the glass transition temperature (Tg) is 60. It is preferable that it is -120 degreeC, More preferably, it is 60-100 degreeC. The number average molecular weight (Mn) of the hydroxyl group-containing polyester resin (including the modified hydroxyl group-containing polyester resin) is preferably 2000 to 30000, more preferably 10,000 to 20000, and the glass transition temperature (Tg). Is preferably 0 to 80 ° C, more preferably 10 to 40 ° C. When the number average molecular weight (Mn) of the hydroxyl group-containing epoxy resin and / or hydroxyl group-containing polyester resin to be used is in the above range, the crosslinking reaction with the curing agent (B) described later proceeds sufficiently, and the moisture resistance of the coating film In addition, since the viscosity of the resulting coating composition is moderate, handling becomes easy, and the moisture permeability of the coating film is kept moderate. Thereby, elution of calcium vanadate contained in the coating film is not inhibited, and the corrosion resistance is improved. Moreover, the elongation rate of the coating film obtained is maintained by a moderate crosslinking density, and sufficient bending workability is obtained. In addition, the glass transition temperature (Tg) of the hydroxyl group-containing epoxy resin and / or hydroxyl group-containing polyester resin to be used is in the above range, so that the moisture permeability of the coating film is appropriately maintained and the moisture resistance of the coating film is maintained or improved. To do.

In the present specification, the number average molecular weight (Mn) is a value calculated based on the molecular weight of standard polystyrene from a chromatogram measured by gel permeation chromatography (GPC). In the present specification, the glass transition temperature (Tg) is a value measured using a thermal analyzer (“TMA100 / SSC5020” manufactured by Seiko Instruments Inc.). “Elongation rate” (unit:%) indicates how much the coating film stretches before it breaks when a tensile test is conducted on a single coating film (free film). Using the length (L) of the coating film at break and the length (L ₀ ) of the initial coating film, “elongation” = 100 × (L−L ₀ ) / L ₀ (%) .

 Content of the organic resin (A) in the coating composition of this invention is 20-80 mass% normally in the total solid of a coating composition, and it is preferable that it is 30-50 mass%. When the content of the organic resin (A) is within the above range, bending workability, coating workability, and coating film strength are maintained, and corrosion resistance is also obtained.

  In addition to the organic resin (A) described above, a thermoplastic resin (h1) and / or a self-crosslinking resin (h2) can also be used as the organic resin (A). Examples of the thermoplastic resin (h1) include a homopolymer or copolymer having methyl methacrylate, butyl methacrylate or the like as a monomer component; a cellulose resin; an acetal resin; an alkyd resin. Examples of the self-crosslinkable resin (h2) include urethane-modified polyester resins and acrylic-modified epoxy resins. As the thermoplastic resin (h1) and the self-crosslinking resin (h2), only one kind may be used alone, or two or more kinds may be used in combination. By further using the thermoplastic resin (h1) and / or the self-crosslinking resin (h2) as the organic resin (A), the physical properties of the coating film can be adjusted to desired properties.

[Curing agent (B)]
Examples of the curing agent (B) include a polyisocyanate compound; a blocked polyisocyanate compound in which an isocyanate group of the polyisocyanate compound is blocked with an active hydrogen-containing compound (e); an amino resin; a phenol resin and the like. It is preferable to use one or more selected from polyisocyanate compound (e) and amino resin.

  It does not restrict | limit especially as a polyisocyanate compound which comprises the said polyisocyanate compound and the said block polyisocyanate compound (e), A conventionally well-known thing can be used. Specific examples include 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, cyclohexane-1,3-diisocyanate or cyclohexane-1,4-diisocyanate, 1- Isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane (also known as isophorone diisocyanate; IPDI), dicyclohexylmethane-4,4′-diisocyanate (also known as hydrogenated MDI), 2-isocyanatocyclohexyl-2′- Isocyanatocyclohexylmethane or 4-isocyanatocyclohexyl-2'-isocyanatocyclohexylmethane, 1,3-bis- (isocyanatomethyl) -cyclohexane or 1,4-bis- (isocyana Methyl) -cyclohexane, bis- (4-isocyanato-3-methylcyclohexyl) methane, 1,3-α, α, α'α'-tetramethylxylylene diisocyanate or 1,4-α, α, α'α ' -Tetramethylxylylene diisocyanate, 2,4-diisocyanatotoluene or 2,6-diisocyanatotoluene, 2,2'-diisocyanatodiphenylmethane (MDI), 2,4'-diisocyanatodiphenylmethane (MDI) 4,4′-diisocyanatodiphenylmethane (MDI), 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, xylene diisocyanate, diphenyl-4,4′-diisocyanate, and the like. Moreover, you may use the cyclized polymer (isocyanurate type) of each diisocyanate, Furthermore, an isocyanate biuret body (biuret type) and an adduct type. A polyisocyanate compound may be used individually by 1 type, and may use 2 or more types together. The isocyanurate type polyisocyanate compound is one of those preferably used in the present invention.

  Among the above, it is preferable to use an aromatic polyisocyanate compound containing one or more aromatic functional groups in the molecule as the polyisocyanate compound. By using an aromatic polyisocyanate compound, the moisture resistance of the coating film can be improved and the coating film strength can be improved. As aromatic polyisocyanate compounds preferably used, 2,4-diisocyanatotoluene (TDI) or 2,6-diisocyanatotoluene (TDI), 2,2′-diisocyanatodiphenylmethane (MDI), 2, Examples include 4'-diisocyanatodiphenylmethane (MDI) or 4,4'-diisocyanatodiphenylmethane (MDI), xylene diisocyanate (XDI), naphthalene diisocyanate (NDI), and the like.

  The isocyanate group content measured according to JIS K 7301-1995 of the polyisocyanate compound constituting the block polyisocyanate compound (e) is usually 3 to 20% by mass in the solid content of the polyisocyanate compound, Preferably it is 5-15 mass%. If the isocyanate group content falls below the lower limit of the above preferable range, the curability of the coating film may be insufficient, which is not preferable. On the other hand, when the isocyanate group content exceeds the upper limit of the above preferred range, the resulting coating film may have an excessively high crosslinking density, which is not preferable.

The active hydrogen-containing compound (blocking agent) used in the block polyisocyanate compound (e) is not particularly limited, and is —OH group (alcohols, phenols, etc.), = N—OH group (oximes, etc.), Examples thereof include compounds having a ═N—H group (amines, amides, imides, lactams, etc.), compounds having a —CH ₂ — group (active methylene group), and azoles. Specific examples include, for example, phenol, cresol, xylenol, ε-caprolactam, σ-valerolactam, γ-butyrolactam, methanol, ethanol, n-, i-, or t-butyl alcohol, ethylene glycol monoethyl ether, ethylene Glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol, formamide oxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime, dimethyl malonate, dimethyl acetoacetate, acetylacetone , Pyrazole and the like. Only one type of active hydrogen-containing compound may be used alone, or two or more types may be used in combination.

  The heat dissociation temperature of the block polyisocyanate compound (e) depends on the type of polyisocyanate compound and active hydrogen-containing compound constituting the block polyisocyanate compound (e), the presence or absence of a catalyst, and the amount thereof. A block polyisocyanate compound (e) having an uncatalyzed state) of 120 to 180 ° C. is preferably used. By using the block polyisocyanate compound (e) exhibiting a dissociation temperature within this range, the stability of the coating can be improved, and since the cross-linking reactivity with the organic resin (A) is excellent, A coating film having good performance such as scratch resistance and moisture resistance can be obtained. Examples of the block polyisocyanate compound (e) having a dissociation temperature of 120 to 180 ° C. include Desmodule BL3175, Desmotherm 2170 manufactured by Sumika Bayer Urethane Co., Ltd.

As said amino resin, a melamine resin, a urea resin, etc. can be mentioned, Especially, a melamine resin is used preferably. The “melamine resin” generally means a thermosetting resin synthesized from melamine and an aldehyde, and has three reactive functional groups —NX ¹ X ² in one molecule of the triazine nucleus. As the melamine resin, a fully functional alkyl group including —N— (CH ₂ OR) ₂ [R is an alkyl group, the same shall apply hereinafter] as a reactive functional group; —N— (CH ₂ OR) (CH ₂ as a reactive functional group) OH) containing methylol group type; reactive functional group containing —N— (CH ₂ OR) (H); reactive functional group containing —N— (CH ₂ OR) (CH ₂ OH) Four types of methylol / imino group types containing —N— (CH ₂ OR) (H) or containing —N— (CH ₂ OH) (H) can be exemplified.

  In the present invention, among the melamine resins, a melamine resin (hereinafter referred to as amino resin (f)) having one or more methylol groups or imino groups on average in one molecule, that is, methylol group type, imino group It is preferable to use a mold or a methylol / imino group type melamine resin or a mixture thereof. The amino resin (f) is excellent in crosslinking reactivity with the organic resin (A) even in the absence of a catalyst, and a coating film having good scratch resistance and moisture resistance can be obtained.

  The content of the curing agent (B) in the coating composition of the present invention is preferably 10 to 80 parts by mass, more preferably 20 to 100 parts by mass of the solid content of the organic resin (A). -70 mass parts. When the content of the curing agent (B) (in terms of solid content) is included in the above range with respect to 100 parts by mass of the solid content of the organic resin (A), the crosslinking reaction with the organic resin (A) proceeds sufficiently. In addition to improved performance such as scratch properties, the moisture permeability of the coating film is moderately increased, the moisture resistance of the coating film is improved, and the elution of the anticorrosive pigment in the coating film is not hindered, and the corrosion resistance is improved. improves.

[Calcium vanadate (C)]
Calcium vanadate (C), which is a rust preventive pigment used in the coating composition of the present invention, has a specific electrical conductivity. Specifically, the electrical conductivity of its 1% by mass aqueous solution is 200- 2000 μS / cm. By using a predetermined amount of calcium vanadate (C) having an electric conductivity within this range, a coating film with improved corrosion resistance and moisture resistance can be obtained. In addition, calcium vanadate (C) having an electric conductivity within this range exhibits appropriate solubility, and thus effectively corrodes not only the painted surface of the article to be coated (such as a steel plate) but also the end surface portion. Can be prevented. The electric conductivity of a 1% by mass aqueous solution of calcium vanadate (C) is preferably 200 to 1000 μS / cm.

  In this specification, “1% by mass aqueous solution” refers to a solution obtained by adding 1 g of a sample (calcium vanadate) to 99 g of ion-exchanged water and stirring at room temperature for 4 hours. However, all the added samples may not be dissolved in the ion exchange water. The electric conductivity is a value obtained by measuring the electric conductivity of this 1% by mass aqueous solution using an electric conductivity meter (conductivity meter “CM-30ET” manufactured by Toa Denpa Kogyo Co., Ltd.).

  In this invention, content of the said calcium vanadate (C) is 20-65 mass parts with respect to 100 mass parts of total solids of an organic resin (A) and a hardening | curing agent (B), and 30-60 mass parts Is preferable, and 35-55 mass parts is more preferable. When the content of calcium vanadate (C) is within the above range with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B), an object to be coated (such as a steel plate) is applied. Calcium vanadate is eluted in the proper amount. As a result, the corrosion resistance is improved, the moisture permeability of the coating film is moderately high (water penetration into the coating film is moderate), and the moisture resistance of the coating film. As a result, the corrosion resistance is improved.

  As for the said calcium vanadate (C), it is preferable that the pH of the 1 mass% aqueous solution is 6.5-11.0, and it is more preferable that it is 7.0-10.0. When the pH is within this range, a coating film exhibiting high corrosion resistance can be obtained even when the article to be coated is a plated steel sheet containing zinc or aluminum. When the pH of a 1% by mass aqueous solution of calcium vanadate (C) is out of the above range, corrosion of zinc or aluminum may easily occur.

  In addition, "1 mass% aqueous solution" here has the same meaning as the above, The said pH is when pH of 1 mass% aqueous solution is measured using a pH meter (Horiba Seisakusho "F-54"). Value.

  The method for preparing calcium vanadate (C) used in the present invention is not particularly limited, and any method may be used. For example, it is obtained by mixing and reacting a calcium salt and a vanadium salt in water. Can do. The solid obtained by the reaction (usually a white solid) may be subjected to treatments such as washing with water, dehydration, drying, and pulverization as necessary.

  Examples of calcium salts for preparing calcium vanadate (C) include calcium carbonate, calcium hydroxide, calcium oxide, calcium chloride, calcium nitrate, calcium acetate and calcium sulfate. Furthermore, calcium salts of organic acids such as calcium formate are also preferably used. Examples of vanadium salts include, but are not limited to, vanadium pentoxide, potassium vanadate, sodium vanadate, and ammonium vanadate.

  In the case of preparing calcium vanadate (C) by reacting calcium salt with vanadium salt, calcium vanadate exhibiting a desired electrical conductivity and pH by adjusting the ratio of use of calcium salt and vanadium salt. Can be obtained. In order to adjust the electrical conductivity and / or pH within the above range, two or more kinds of calcium vanadate having different electrical conductivities and / or pH may be mixed uniformly.

[Silica (D)]
The silica used in the coating composition of the present invention is not particularly limited, and examples thereof include silica fine particles whose surface is untreated, silica fine particles whose surface is treated with an organic substance, and organic solvent-dispersible colloidal silica. .

Examples of the silica fine particles whose surface is not treated or treated with an organic substance include silica fine particles having an average particle diameter of 0.5 to 15 μm, preferably 1 to 10 μm, and organic solvent-dispersible colloidal silica. As the silica fine particles, those having an oil absorption of 30 to 350 ml / 100 g, preferably 30 to 150 ml / 100 g can be suitably used, and commercially available products include Silicia 710, Silicia 740, Silicia 550, and Aerosil. R972 (all of which are manufactured by Fuji Silysia Chemical Co., Ltd.), Mizukacil P-73 (manufactured by Mizusawa Chemical Industry Co., Ltd.), Gasil 200DF (manufactured by Crossfield Co., Ltd.) and the like.
The organic solvent-dispersible colloidal silica is also called an organosilica sol, in which silica fine particles having a particle size of about 5 to 120 nm are stably dispersed in an organic solvent such as alcohols, glycols, and ethers. Examples of commercially available products include OSCAL series (manufactured by JGC Catalysts & Chemicals), organosol (manufactured by Nissan Chemical Co., Ltd.), and the like.
The average particle diameter refers to a weight average particle diameter obtained by a normal measuring instrument using a laser scattering method, a diffraction method, or the like. For example, a laser diffraction particle size distribution measuring device “SALD” manufactured by Shimadzu Corporation is used. -2000 ".

  In this invention, content of the said silica (D) is 3-12 mass parts with respect to 100 mass parts of total solids of an organic resin (A) and a hardening | curing agent (B), and 4-8 mass parts is more. preferable. When the content of the silica (D) is within the above range with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B), the moisture resistance is improved.

[Silicate (E)]
The silicate (E) used in the coating composition of the present invention is a salt composed of silicon dioxide and a metal oxide, and may be any of orthosilicate, polysilicate and the like. Silicate (E) is a salt of at least one metal selected from aluminum, potassium, and sodium.
Examples of the silicate (E) include aluminum silicate, potassium silicate, sodium silicate, sodium aluminum silicate, orthosilicate, potassium orthosilicate, sodium orthosilicate, metametasilicate, potassium metasilicate, and metasilicate. Sodium etc. can be mentioned.
Among them, silicate (E) is preferably aluminum silicate, potassium silicate, or sodium silicate, and more preferably aluminum silicate.

  In this invention, content of the said silicate (E) is 5-15 mass parts with respect to 100 mass parts of total solids of an organic resin (A) and a hardening | curing agent (B), and 8-12 mass parts. Is more preferable. The content of the silicate (E) is within the above range with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B). Generation is suppressed, and a rust prevention effect is obtained.

[Tripolyphosphate metal salt (F)]
The tripolyphosphate metal salt (F), which is a rust preventive pigment used in the coating composition of the present invention, has a specific electrical conductivity. Specifically, the electrical conductivity of an aqueous solution of 1% by mass is 5%. ~ 50 μS / cm. By using a predetermined amount of the tripolyphosphate metal salt (F) having an electric conductivity within this range, generation of white rust in the processed part is suppressed, and an antirust effect is obtained.

  In this specification, “1% by mass aqueous solution” means that 1 g of a sample (a metal salt of tripolyphosphate (F) such as aluminum tripolyphosphate or zinc tripolyphosphate) is added to 99 g of ion-exchanged water for 4 hours at room temperature. A solution obtained by stirring. However, all the added samples may not be dissolved in the ion exchange water. The electric conductivity is a value obtained by measuring the electric conductivity of this 1% by mass aqueous solution using an electric conductivity meter (conductivity meter “CM-30ET” manufactured by Toa Denpa Kogyo Co., Ltd.).

Examples of the tripolyphosphate metal salt (F) used in the coating composition of the present invention include aluminum tripolyphosphate, zinc tripolyphosphate, and aluminum dihydrogen tripolyphosphate. Among these, it is preferable to use aluminum tripolyphosphate.
In this invention, content of the said tripolyphosphate metal salt (F) is 4-25 mass parts with respect to 100 mass parts of total solids of an organic resin (A) and a hardening | curing agent (B), and 8-22 masses. Part is preferable, and 12 to 20 parts by mass is more preferable. When the content of the tripolyphosphate metal salt (F) is within the above range with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B), generation of white rust in the processed part is suppressed. And an antirust effect is obtained.

  The coating composition of the present invention uses a tripolyphosphate metal salt composed of a specific metal salt, and a 1% by mass aqueous solution of the tripolyphosphate metal salt has a specific range of electrical conductivity, and further contains an organic resin (A ), Curing agent (B), calcium vanadate (C), silica (D), silicate (E), and tripolyphosphate metal salt (F) by adjusting their respective contents to an appropriate range, Despite not containing chromium, it has excellent corrosion resistance, adhesion, moisture resistance and scratch resistance, and even when the top coat film has insufficient barrier properties, it has excellent corrosion resistance at the processed part.

[Other additives]
The coating composition of this invention may contain other additives other than the above as needed. Examples of other additives include rust preventive pigments other than calcium vanadate (C); extender pigments other than silica (D); colorants such as color pigments and dyes; solvents; ultraviolet absorbers (benzophenone-based ultraviolet rays) Absorbers, etc.); antioxidants (phenolic, sulphoid, hindered amine antioxidants, etc.); plasticizers; surface conditioners (organic polymers, etc.); sagging agents; thickeners; waxes and other lubricants; pigments Dispersants; pigment wetting agents; leveling agents; anti-coloring agents; suspending agents; antifoaming agents; antiseptics; antifreezing agents; emulsifiers; antifungal agents; These additives may be used alone or in combination of two or more.

  Rust preventive pigments other than the above calcium vanadate (C) and the above tripolyphosphate metal salt (F) as long as they do not impair the moisture resistance, rust prevention, folding workability, etc. of the coating film obtained by the coating composition of the present invention. As these anti-corrosion pigments, non-chromium anti-corrosion pigments can be used. For example, molybdate pigments (zinc molybdate, strontium molybdate, etc.), phosphomolybdate pigments (phosphorus) Non-chromium rust preventive pigments such as aluminum molybdate pigments, calcium silica pigments, phosphate rust preventive pigments, silicate rust preventive pigments, and the like. These may be used alone or in combination of two or more. Since the coating composition of the present invention contains a predetermined amount of calcium vanadate (C) having a predetermined electrical conductivity and a metal tripolyphosphate (F) having a predetermined electrical conductivity, the coating composition exhibits sufficiently high corrosion resistance. However, rust preventive pigments other than calcium vanadate (C) and tripolyphosphate metal salt (F) as described above may be used as necessary.

 As other pigments other than the silica (D), alumina, bentonite, and the like can be added within a range that does not impair the moisture resistance, rust resistance, folding workability, and the like of the obtained coating film. These may be used alone or in combination of two or more.

  Examples of the colored pigment include colored inorganic pigments such as titanium dioxide, carbon black, graphite, iron oxide, and coal dust; phthalocyanine blue, phthalocyanine green, quinacridone, perylene, anthrapyrimidine, carbazole violet, anthrapyridine, azo orange, and flavan Examples thereof include colored organic pigments such as throne yellow, isoindoline yellow, azo yellow, indanthrone blue, dibromoanthanthrone red, perylene red, azo red, and anthraquinone red. These may be used alone or in combination of two or more.

  Examples of the solvent include water; ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether. Glycol organic solvents such as dipropylene glycol monoethyl ether and propylene glycol monomethyl ether acetate; alcohol organic solvents such as methanol, ethanol and isopropyl alcohol; ether organic solvents such as dioxane and tetrahydrofuran; 3-methoxybutyl acetate and acetic acid Ester organic such as ethyl, isopropyl acetate, butyl acetate Medium; ketone organic solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, isophorone; and N-methyl-2-pyrrolidone, toluene, pentane, iso-pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, mineral Spirit, Solvesso 100, Solvesso 150 (all are aromatic hydrocarbon solvents, manufactured by Shell Chemical Co., Ltd.) and the like. These may be used alone or in combination of two or more. The paint composition of the present invention may be a water-based paint or an organic solvent-based paint.

《Curing catalyst》
When the block polyisocyanate compound (e) and / or the polyisocyanate compound is used as the curing agent (B), the coating composition of the present invention may contain a curing catalyst. Examples of the curing catalyst include a tin catalyst, an amine catalyst, and a lead catalyst. Among them, an organic tin compound is preferably used. As the organic tin compound, for example, dibutyltin dilaurate (DBTL), dibutyltin oxide, tetra-n-butyl-1,3-diacetoxystanoxane and the like can be used. The content of the curing catalyst is usually 0.1 to 10 parts by mass and 0.1 to 1 part by mass with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B). Is preferred. When the content of the curing catalyst is within the above range, the storage stability of the coating composition is maintained.

  Moreover, also when using an amino resin as a hardening | curing agent (B), the coating composition of this invention may contain a curing catalyst. Examples of the curing catalyst in this case include acid catalysts such as carboxylic acid and sulfonic acid. Among them, dodecylbenzenesulfonic acid, paratoluenesulfonic acid and the like are preferably used. The content of the curing catalyst is usually 0.1 to 10 parts by mass and 0.1 to 1 part by mass with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B). Is preferred. When the content of the curing catalyst is within the above range, the storage stability of the coating composition is maintained.

  The coating composition of the present invention includes, for example, an organic resin (A), a curing agent (B), calcium vanadate (C), silica (D), silicate (E), and tripolyphosphate metal salt (F) and Other additives can be prepared by mixing using a mixer such as a roller mill, a ball mill, a bead mill, a pebble mill, a sand grind mill, a pot mill, a paint shaker, and a disper. Alternatively, the coating composition of the present invention comprises an organic resin (A) calcium vanadate (C), silica (D), silicate (E) and tripolyphosphate metal salt (F), and a curing agent ( It may be a two-component paint comprising a crosslinking agent component containing B).

  The coating composition of the present invention is applied as an undercoat paint also called a primer. The top coating and intermediate coating other than the coating composition of the present invention may be conventionally known. Examples of the top coating and intermediate coating include polyester resin-based paints and fluororesin-based paints.

[Coating film, its production method and pre-coated steel sheet]
The coating film of this invention is formed using the above-mentioned coating composition. Since the coating film of the present invention is formed using the coating composition described above, it is excellent in corrosion resistance, adhesion, moisture resistance and scratch resistance, and even if the coating film has insufficient barrier properties. Excellent corrosion resistance of end faces and processed parts.

  The object to be coated on which the coating film is formed by the coating composition of the present invention is not particularly limited as long as corrosion resistance is required, but a typical example is a steel sheet to be a base material such as a pre-coated metal (painted steel sheet). be able to. Examples of the steel plate include a galvanized steel plate, a cold-rolled steel plate, a stainless steel plate, and an aluminum plate. As galvanized steel sheet, galvanized steel sheet that utilizes sacrificial corrosion protection of zinc, specifically, hot dip galvanized steel sheet, electrogalvanized steel sheet, galvannealed steel sheet, aluminum-galvanized steel sheet, nickel-zinc plated Examples include steel plates, magnesium-aluminum-galvanized steel plates, magnesium-aluminum-silica-galvanized steel plates, and the like. It is preferable that the steel plate has been subjected to a surface treatment with a chemical conversion treatment agent before coating. Although it can select suitably as said surface treatment according to the steel plate to be used, the treatment which does not contain a heavy metal is preferable.

This coating film is preferably formed on a steel plate. As the steel sheet, for example, a galvanized steel sheet, an alloyed galvanized steel sheet, a hot dip zinc-aluminum alloy plated steel sheet, an aluminum alloy plated steel sheet, a hot dip zinc-aluminum-magnesium alloy plated steel sheet, a stainless steel sheet, a cold rolled steel sheet, or the like may be used. it can.
The steel sheet may be subjected to a surface treatment such as zinc phosphate treatment, chromium-free treatment such as Surf Coat EC2200 manufactured by Nippon Paint Co., Ltd., and coating type chromate.

Although the dry film thickness of the coating film of this invention is not restrict | limited in particular, From the same viewpoint as the above, Preferably they are 2 micrometers or more and 10 micrometers or less, Preferably they are 3 micrometers or more and 7 micrometers or less.
The dry film thickness of the coating film is calculated from an average value obtained by measuring 10 arbitrarily selected locations using an electromagnetic film thickness meter (manufactured by Fischer).

The coating film of the present invention can be produced by applying the above-mentioned precoat metal coating composition to a steel sheet, followed by heating and baking.
The coating method is not particularly limited, and a conventionally known method such as a roll coater, airless spray, electrostatic spray, curtain flow coater, etc. can be employed.

The baking temperature (that is, the temperature of the steel sheet) in the baking treatment is preferably 120 to 300 ° C., more preferably 150 to 280 ° C., and still more preferably from the viewpoint of preventing decomposition of the resin component and obtaining a uniform coating film. It is 180-260 degreeC, More preferably, it is 200-250 degreeC.
The baking time in the baking treatment is not particularly limited, and is preferably 3 to 90 seconds, more preferably 10 to 80 seconds, and still more preferably 30 to 60 seconds from the same viewpoint as described above.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “part” means “part by mass” unless otherwise specified, and “%” means “% by mass” unless otherwise specified.

[Raw materials]
In the following examples and comparative examples, the following raw materials were used.
(1) Epoxy resin BPA 1007 type “jER1007”: manufactured by Mitsubishi Chemical Corporation, hydroxyl group-containing epoxy resin (nonvolatile content: 30% (concentration was adjusted by adding cyclohexane so that the nonvolatile content was 30%), Mn: 2900 ]
(2) Epoxy resin BPA 1009 type “jER1009”: manufactured by Mitsubishi Chemical Corporation, hydroxyl group-containing epoxy resin (nonvolatile content: 30% (concentration was adjusted by adding cyclohexane so that the nonvolatile content was 30%), number average molecular weight (Mn): 3800]
(3) Aromatic blocked isocyanate “Desmotherm 2170”: manufactured by Sumika Bayer Urethane Co., Ltd., diphenylmethane diisocyanate (isocyanurate type, blocking agent: active methylene group-containing compound), thermal dissociation temperature (non-catalytic state): 120 ° C., isocyanate Group content: 5.7%, nonvolatile content: 70%].
(4) Aliphatic blocked isocyanate "Desmodule BL317": manufactured by Sumika Bayer Urethane Co., Ltd., hexamethylene diisocyanate (isocyanurate type, blocking agent: methyl ethyl ketone oxime), heat dissociation temperature (non-catalytic state): 160 ° C, isocyanate group Content: 14.9%, non-volatile content: 75%].
(5) Melamine resin “Mycoal 715”: manufactured by Nippon Cytec Industries, Ltd., imino group type melamine resin (nonvolatile content: 80%)
(6) Calcium vanadate: The preparation method will be described later.
(7) Ammonium vanadate manufactured by Taiyo Mining Co., Ltd.

(8) Aluminum tripolyphosphate and zinc tripolyphosphate: The preparation method will be described later.
(9) Aluminum dipolyphosphate aluminum “K White # 105”: manufactured by Teika Co., Ltd., calcium-treated product of aluminum dipolyphosphate (10) Aluminum silicate and calcium silicate: Commercial reagents (11) Silica “Nipseal E-200 ": Manufactured by Tosoh Silica Co., untreated silica, silicon dioxide (12) DBTL
“TVS Tin Lau” manufactured by Nitto Kasei Co., Ltd. [dibutyltin dilaurate, nonvolatile content: 100%].
(13) DBSA
“NACURE 5076” manufactured by Enomoto Kasei Co., Ltd. [dodecylbenzenesulfonic acid, nonvolatile content: 70%].
(14) Solvesso 150
Aromatic solvent manufactured by ExxonMobil

[Preparation of calcium vanadate]
549 g of calcium hydroxide (Ca (OH) ₂ ) and 451 g of vanadium pentoxide (V ₂ O ₅ ) were added to 10 L of water, heated to 60 ° C., and stirred at the same temperature for 2 hours. The obtained reaction product (white solid) was washed with water, dehydrated, dried at 100 ° C., and then pulverized to obtain calcium vanadate.
The electrical conductivity and pH of the obtained 1% by mass aqueous solution of calcium vanadate are as follows. Here, the preparation of the 1 mass% aqueous solution and the method for measuring the electrical conductivity and pH are as described above.

<Measurement of electrical conductivity>
The electrical conductivity of the preparation of the 1% by weight aqueous solution is as described above, and details are also described here.
(Measurement procedure of electrical conductivity)
(I) 99 g of ion-exchanged water and 1 g of a sample are added to a polyethylene narrow mouth bottle washed with ion-exchanged water.
(Ii) A stirrer chip washed with ion-exchanged water is added and stirred at room temperature for 4 hours. (Iii) After stirring, the electrical conductivity at a temperature of 25 ° C. is measured using an electrical conductivity meter (conductivity meter “CM-30ET” manufactured by Toa Denpa Kogyo Co., Ltd.).

[Preparation of aluminum tripolyphosphate]
367 g of sodium tripolyphosphate (Na ₅ (P ₃ O ₁₀ )) and 402 g of aluminum chloride hexahydrate (AlCl ₃ .6H ₂ O) were added to 10 L of water, heated to 60 ° C. and then at the same temperature for 2 hours. The obtained reaction product (white solid) was washed with water, dehydrated, dried at 100 ° C., and then pulverized to obtain aluminum tripolyphosphate.

[Preparation of zinc tripolyphosphate]
367 g of sodium tripolyphosphate (Na ₅ (P ₃ O ₁₀ )) and 227 g of zinc chloride hexahydrate (ZnCl ₂ ) were added to 10 L of water, heated to 60 ° C., and stirred at the same temperature for 2 hours. The obtained reaction product (white solid) was washed with water, dehydrated, dried at 100 ° C., and then pulverized to obtain zinc tripolyphosphate.

  The electrical conductivity of the obtained 1% by mass aqueous solution of aluminum tripolyphosphate, zinc tripolyphosphate and aluminum dihydrogen tripolyphosphate is as follows. Here, the preparation of the 1% by mass aqueous solution and the method for measuring the electrical conductivity are as described above.

Aluminum silicate and calcium silicate use commercially available reagents, and their water content is shown in Table 3. Here, the water content conforms to JIS K5101-16.2.
(I) A sample is accurately weighed in units of 0.01 g and 18 to 20 g (m ₀ ), placed in a beaker, 200 ml of room temperature ion-exchanged water, and continuously stirred at room temperature for 1 hour.
(Ii) Transfer the mixed solution to a 250 ml volumetric flask and dilute to the scale with ion-exchanged water. Then, it mixes so that it may become uniform and obtains a completely transparent filtrate (or centrifuge) by filtration or centrifugation.
(Iii) 100 ml of a completely clear filtrate (or centrifuge) is pipetted into a previously dried and weighed evaporating dish and evaporated on a water bath.
(Iv) The residue in the evaporating dish is dried with a dryer at 105 ° C. ± 2 ° C., placed in a desiccator, cooled and weighed in units of 1 mg. (M ₁ )
(V) The water content M is calculated by the following formula.
M = ((m ₁ × 2.5) / m ₀ ) × 100

<Preparation of coating composition A for steel plate back surface>
80 parts of titanium oxide is mixed with a mixture of 222 parts of “jER1007” which is the organic resin (A), 30 parts of cyclohexanone and 30 parts of “Solvesso 150”, and a dispersing machine (desktop SG mill 1500W type manufactured by Ohira System Co., Ltd.) Then, the obtained mixture and 332 parts of glass beads were added, and pigment dispersion was carried out until the particle diameter of the titanium oxide coarse particles became 15 μm or less to prepare a pigment dispersion paint. Thereafter, 45 parts of “Desmodur BL3175” which is a block polyisocyanate compound (e), 0.5 part of dibutyltin dilaurate (DBTL) (“TVS Tin Lau”), 45 parts of cyclohexanone and 45 parts of Solvesso 150 are added to this pigment dispersion paint. Was added and mixed uniformly to obtain a coating composition A.

<Preparation of coated steel plate>
After an aluminum galvanized steel sheet having a thickness of 0.4 mm was alkali degreased, a non-chromium chemical conversion treatment was performed by applying a phosphoric acid treatment agent “Surf Coat EC2310” manufactured by Nippon Paint on the front and back surfaces of the steel sheet, and dried. Next, the coating composition A obtained above is applied to the back surface of the obtained steel sheet so that the dry coating film has a thickness of 7 μm, and baked for 30 seconds at a maximum temperature of 180 ° C. Formed. Next, the coating composition of any of Examples 1 to 16 and Comparative Examples 1 to 9 is applied to the surface of the steel sheet so that the dry coating film has a thickness of 5 μm, and baked at a maximum temperature of 200 ° C. for 30 seconds. The surface undercoat film was formed. Furthermore, a polyester-based topcoat “NSC300HQ” made by Nippon Paint was applied onto the undercoat film so that the dry film thickness was 10 μm, and baked for 40 seconds at a maximum temperature of 210 ° C. A film was formed to obtain a coated steel sheet.

<< Evaluation of coating film performance >>
The following items <1> to <8> were subjected to a coating performance evaluation test. The results are shown in Tables 5-6.

<1> Boiling water resistance test Each coated steel sheet obtained above (the surface undercoat film is made of the coating composition of Examples 1 to 16 and Comparative Examples 1 to 9, respectively) is cut into 5 cm × 10 cm, The obtained test piece was immersed in boiling water at about 100 ° C. for 2 hours, and then pulled up to evaluate the coating appearance on the surface side in accordance with ASTM D714-56 (flat part swelling evaluation). ASTM D714-56 evaluates the size (average diameter) and density of each blister in comparison with a standard judgment photograph, and indicates a grade symbol. The size is 8 (diameter approx. 1 mm), 6 (diameter approx. 2 mm), 4 (diameter approx. 3 mm) and 2 (diameter approx. 5 mm) in this order, and the density is F, FM, M, MD from the smallest. , D is classified into 5 stages, and if there is no blister, it is set to 10. A score of 8FM or higher was evaluated as good. The score of evaluation is as shown below.

  Moreover, the cross-cut tape adhesion test (cross-cut adhesion test) was performed and evaluated about the coated steel plate test piece after being immersed in boiling water of about 100 ° C. for 2 hours. The cross-cut tape adhesion test is performed in accordance with JIS K-5400 8.5.2 (1990) cross-cut tape method with a gap spacing of 1 mm and 100 cross-cuts, and cellophane adhesive tape is adhered to the surface. The number of grids remaining on the painted surface when the film was peeled off rapidly was examined.

<2> Moisture resistance test Each coated steel sheet obtained above was cut into 5 cm x 10 cm, and the obtained test piece was left for 500 hours under conditions of 50 ° C x 98 RH% with pure water, and then boiled. In the same manner as in the aqueous test, the blistering of the flat portion was evaluated according to ASTM D714-56. A score of 8FM or higher was evaluated as good.

<3> Corrosion resistance test Each coated steel sheet obtained above was cut to 5 cm × 15 cm. At this time, cutting was alternately performed from the front surface and the back surface, and test pieces were prepared so that the cross section of each test piece had both an upper burr (cut from the back surface) and a lower burr (cut from the surface). Next, a cross cut with a narrow angle of 30 degrees and a cut width of 0.5 mm reaching the substrate at the center of the surface side is inserted with a cutter knife, the upper edge of the coated steel sheet is sealed with anticorrosive paint, and the bottom end is bent by 4T Processed part (Folded with the surface of the painted plate facing outside, sandwiching 4 plates of the same thickness as the painted plate inside, and bending the painted plate 180 degrees in a vise. 4 plates after processing Is removed.) The schematic diagram of the coated steel plate test piece obtained as described above is shown in FIG. FIG. 1 is a diagram schematically showing a cross section of an upper burr and a lower burr of the obtained coated steel plate test piece, and FIG. 2 shows a cross cut portion and a 4T bending processing portion of the obtained coated steel plate test piece. It is a figure shown typically.

  About each obtained coated steel plate test piece, the composite cycle corrosion test (CCT) was done according to JIS K5600-7-9A JASO M609. (Cycle 5% saline spray at 35 ° C. for 2 hours)-(Dry at 60 ° C. for 4 hours)-(Standing in a humidity resistance tester at RH 95% or higher at 50 ° C. for 2 hours) Time). The state of the edge part of the coated steel plate test piece after this test, the cross cut part, and the 4T bending process part was evaluated based on the following evaluation method and evaluation criteria. All evaluated 4 points or more as favorable.

(4T bending process part)
The areas where white rust and blisters were generated in the 4T bent portion were determined and evaluated according to the following criteria.
5: Generation area of white rust and swelling is less than 5%,
4: The generation area of white rust and swelling is 5% or more and less than 20%,
3: The generation area of white rust and swelling is 20% or more and less than 50%,
2: The generation area of white rust and swelling is 50% or more and less than 75%,
1: The generation area of white rust and swelling is 75% or more.

(Edge part)
The average value of the edge creep width (width of the bulge) of the surface of the left and right long sides (namely, the long side having the upper burr and the long side having the lower burr) of the coated steel sheet test piece was determined and evaluated according to the following criteria.
5: The swelling width is less than 5 mm,
4: The swelling width is 5 mm or more and less than 10 mm,
3: The swelling width is 10 mm or more and less than 15 mm,
2: The swelling width is 15 mm or more and less than 20 mm,
1: The swelling width is 20 mm or more.

(Cross cut part)
The length of occurrence of white rust at the crosscut portion was determined and evaluated according to the following criteria.
5: Generation length of white rust is less than 5%,
4: The generation length of white rust is 5% or more and less than 20%,
3: The generation length of white rust is 20% or more and less than 50%,
2: The generation length of white rust is 50% or more and less than 75%,
1: The generation length of white rust is 75% or more.

<4> Alkali resistance test Each coated steel plate obtained above was cut into 5 cm × 10 cm, and the obtained test piece was immersed in a 5% aqueous sodium hydroxide solution at 23 ° C. for 48 hours, then taken out, washed, and room temperature. Dried. About this coated steel plate test piece, the blister evaluation of the plane part was performed according to ASTM D714-56 similarly to the boiling water resistance test. A score of 8FM or higher was evaluated as good.

<5> Acid resistance test Each coated steel sheet obtained above was cut into 5 cm × 10 cm, and the obtained test piece was immersed in a 5% sulfuric acid aqueous solution at 23 ° C. for 48 hours, then taken out, washed, and at room temperature. Dried. About this coated steel plate test piece, the blister evaluation of the plane part was performed according to ASTM D714-56 similarly to the boiling water resistance test. A score of 8FM or higher was evaluated as good.

<6> Processed part adhesion Under a temperature condition of 23 ° C., one coated metal sheet (thickness 0.5 mm) of the same galvanized steel sheet as the coated steel sheet was applied to the coated steel sheets obtained in the examples and comparative examples. With this as a fulcrum, the coated steel plate was bent 180 °. After the polyester tape was brought into close contact with the bent portion and the tape was peeled off at an angle of 45 °, the area of the coating film peeled from the substrate was evaluated according to the following criteria.
1: No peeling of coating film
2: Coating film peeling is 5% or less,
3: More than 5% to 10% or less of coating film peeling,
4: Coating film peeling is more than 10% to 30% or less,
5: Coating film peeling exceeds 30%.

<7> Scratch resistance test Each coated steel plate obtained above was cut into 5 cm x 10 cm to obtain test pieces. At a room temperature of 23 ° C., using a coin scratch tester, hold the edge of the 10-yen copper coin at a 45 degree angle on the coating surface of each coated steel plate test piece while applying a 1 kg weight and pressing the 10-yen copper coin. Five scratches were made on the coated surface by pulling 50 mm at a speed of 10 mm / second. The degree of metal substrate exposure relative to the entire area of the wound was evaluated according to the following criteria. A score of 4 or more was evaluated as good.
5: No metal substrate is found on the scratched part,
4: A metal substrate is recognized in 10% or more and less than 25% of the area of the scratched part,
3: A metal substrate is recognized in 25% or more and less than 50% of the area of the scratched part,
2: A metal substrate is recognized in 50% or more and less than 75% of the area of the scratched part,
1: Almost no coating film is left on the scratched part, and a metal base is observed.

  From the results of Tables 5 to 6, a tripolyphosphate metal salt composed of a specific metal salt was used, and a 1 mass% aqueous solution of the tripolyphosphate metal salt had a specific range of electrical conductivity, and an organic resin (A ), Curing agent (B), calcium vanadate (C), silica (D), silicate (E), and tripolyphosphoric acid metal salt (F) are each contained in a specific content. And the coating film produced using the coating composition of Examples 1-16 compared with the coating film produced using the coating composition of Comparative Examples 1-9, corrosion resistance, adhesiveness, moisture resistance, and scratch resistance. The corrosion resistance of the processed part was excellent.

Claims (7)

Contains organic resin (A), curing agent (B), calcium vanadate (C), silica (D), silicate (E), and tripolyphosphate metal salt (F), substantially free of chromium An undercoat paint composition for precoat metal,
The solid content mass of the calcium vanadate (C) is 20 to 65 parts by mass with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B),
The solid content mass of the silica (D) is 3 to 12 parts by mass with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B),
The solid content mass of the silicate (E) is 5 to 15 parts by mass in total with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B),
The tripolyphosphate metal salt (F) is a metal salt containing at least one element selected from aluminum and zinc, and the electrical conductivity of a 1 mass% aqueous solution of the tripolyphosphate metal salt (F) is 5 to 50 μS. The solid content mass of the tripolyphosphate metal salt (F) is 4 to 25 parts by mass in total with respect to 100 parts by mass of the total solid content of the organic resin (A) and the curing agent (B). An undercoat paint composition for precoat metal, which is characterized.   The undercoat paint composition according to claim 1, wherein the silicate (E) is a salt of at least one metal selected from aluminum, potassium, and sodium. The organic resin (A) contains a bisphenol type epoxy resin,
The undercoat paint composition according to claim 1 or 2, wherein the curing agent (B) contains a blocked isocyanate and / or a melamine resin.   The coating film formed using the coating composition in any one of Claims 1-3.   A method of forming a coating film, wherein the precoating metal coating composition according to claim 1 is applied to a steel sheet, and then baking is performed until the temperature of the steel sheet is within a range of 120 to 300 ° C.   The method for forming a coating film according to claim 5, wherein the baking heating time is 3 to 90 seconds.   A precoated steel sheet having the coating film according to claim 4.

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