Corrosion-preventive coating composition

Abstract

The present invention provides a corrosion-preventive coating composition that allows each step in the corrosion prevention process to be carried out in fewer steps, reduces the risk of re-corrosion, and, when applied to a corroded structure, restores the surface to its pre-corrosion state. [Solution] A corrosion-resistant coating film is used, formed from a corrosion-resistant coating composition (Y) which contains an ionic liquid (X) consisting of a thiocyanate anion and a cation (B) and has a pH of 5 to 9 at 25°C, preferably having a halogen content of 20 ppm or less.

Description

Technical Field

[0001] The present invention relates to an anticorrosive coating composition.

Background Art

[0002] Antirust paint compositions are often applied at the site where structures and the like are manufactured. By applying these paint compositions, a paint film is formed on the surface of the structure, and the erosion of red rust can be prevented by blocking air and water, which are the causes of red rust, a corrosion factor. Generally, in order to improve the barrier properties against air and water, methods such as adding inorganic fillers such as calcium hydroxide and magnesium hydroxide to the antirust paint (Patent Document 1), and adding a surfactant having a hydrophobic group such as α-olefin oxide to the antirust paint (Patent Document 2) have been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] However, in either of the methods of Patent Documents 1 and 2, the function of blocking air and water has not reached a satisfactory level. Also, when red rust occurs on the surface of the structure, the attack of corrosion of the structure cannot be suppressed, and there is a problem that after a certain period has elapsed since painting, it is necessary to remove the red rust generated on the surface of the structure and repaint. The object of the present invention is to provide a coating composition having excellent anticorrosion properties.

Means for Solving the Problems

[0005] As a result of intensive studies to solve the above problems, the present inventors have arrived at the present invention. In other words, the present invention relates to a corrosion-preventive coating composition (Y) comprising an ionic liquid (X) consisting of a thiocyanate anion and a cation (B) having a pH of 5 to 9 at 25°C, and a corrosion-preventive coating film formed from the corrosion-preventive coating composition (Y). [Effects of the Invention]

[0006] The corrosion-preventive coating composition (Y) of the present invention provides the following effects. (1) Excellent appearance of the coating film. (2) Excellent corrosion resistance. (3) Excellent resistance to moisture and heat. (4) Excellent rust resistance. [Modes for carrying out the invention]

[0007] The present invention will be described in detail below.

[0008] The corrosion-preventive coating composition (Y) of the present invention is a corrosion-preventive coating composition comprising an ionic liquid (X) consisting of a thiocyanate anion and a cation (B), having a pH of 5 to 9 at 25°C.

[0009] The cation (B) is not particularly limited, and any known cation that can form an ionic liquid when combined with a thiocyanate anion can be used. Examples of known cations include ammonium cations, primary ammonium cations, secondary ammonium cations, tertiary ammonium cations, quaternary ammonium cations, and amidinium cations. In this invention, an ionic liquid refers to an ionic compound consisting of anions and cations that are in a liquid state at temperatures below 100°C.

[0010] Examples of ammonium cations include unsubstituted ammonium ions.

[0011] Examples of the primary ammonium cation include cations such as methylammonium, ethylammonium, propylammonium, and isopropylammonium.

[0012] Examples of the secondary ammonium cation include cations such as dimethylammonium, diethylammonium, methylethylammonium, methylpropylammonium, and methylisopropylammonium.

[0013] Examples of the tertiary ammonium cation include cations such as trimethylammonium, triethylammonium, dimethylethylammonium, dimethylpropylammonium, methylmorpholinium, and dimethylisopropylammonium.

[0014] Examples of the quaternary ammonium cation include acyclic quaternary ammonium cations (cations represented by the following general formula (1)) and cyclic quaternary ammonium cations (N,N-dimethylmorpholinium cation, N-ethyl-N-methylmorpholinium cation), etc.

[0015] [Chemical formula] [In general formula (1), R1 to R4 each independently represent a linear or branched alkyl group having 1 to 10 carbon atoms.]

[0016] Examples of the amidinium cation include cations represented by the following general formula (2), cations represented by the following general formula (3), etc., and the cation represented by the following general formula (2) is preferred.

[0017] [Chemical formula] [In general formula (②), R5 and R7 each independently represent a linear or branched alkyl group having 1 to 10 carbon atoms, and R6, R8, and R9 represent a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms.]

[0018] [Chemical formula] [In General Formula (3), R 10 , R 12 are each independently a linear or branched alkyl group having 1 to 10 carbon atoms, R 11 is a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, R 13 , R 14 are each independently a linear or branched alkyl group having 1 to 10 carbon atoms. Further, some or all of R 10 to R 14 may combine with each other to form a divalent to tetravalent group and form a heterocyclic ring together with a nitrogen atom.]

[0019] Examples of the cations represented by the above General Formula (2) and General Formula (3) include cations such as 1,2,3,4-tetramethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2,4-diethylimidazolinium, 1,2-dimethyl-3,4-diethylimidazolinium, 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, and 1,2,3-trimethylimidazolium.

[0020] From the viewpoint of corrosion protection, the cation (B) is preferably at least one cation selected from the group consisting of amidinium cations and quaternary ammonium cations, more preferably at least one cation selected from the group consisting of the cation represented by General Formula (1) and the cation represented by General Formula (2), still more preferably the cation represented by General Formula (2), and particularly preferably 1-ethyl-3-methylimidazolium.

[0021] The ionic liquid (X) may contain an inorganic salt such as a pH adjuster, nitrate, or phosphate as a component other than the salt of the thiocyanate anion and the cation (B).

[0022] The ionic liquid (X) has a pH of 5 to 9 at 25°C, preferably 5.5 to 7.5, and more preferably 6.5 to 7.3, from the viewpoint of corrosion protection. The pH of the ionic liquid (X) is particularly important from the viewpoint of corrosion protection for metals; if the pH is less than 5.0, it will cause the metal surface to penetrate, and if the pH is greater than 9.0, the chemical polishing power of the thiocyanate anion will decrease. If the pH is outside the range of 5.0 to 9.0, the composition ratio of acid and amine is either too acidic or too amine-heavy, so the pH can be adjusted by measuring the acid value or amine value of the ionic liquid (X) and adding a basic component or acid component corresponding to the obtained value.

[0023] The pH of the ionic liquid (X) is measured by the glass electrode method in accordance with the method described in JIS Z8802, using an aqueous solution of the ionic liquid (X) adjusted to a concentration of 1% by weight.

[0024] From the viewpoint of corrosion prevention, the halogen content of the ionic liquid (X) is preferably 20 ppm or less, and more preferably 10 ppm or less. Within this halogen content range, metal corrosion caused by halogens can be better prevented. Unless intentionally added, halogens are mainly present in the raw materials used when synthesizing anions, and when halogenated salts are used as cations (B). If the halogen content is higher than 20 ppm, the halogen content can be reduced by dissolving it in acetone or the like and then passing it through a column packed with alumina, for example.

[0025] The halogen content of an ionic liquid (X) can be determined by diluting the ionic liquid (X) 100 to 10 times with ultrapure water, performing ion chromatography under the following conditions to determine the content of various halogens, and then calculating the sum of the obtained halogen content. Equipment: Ion chromatograph (Thermo SCIENTIFIC: Dionex ICS-5000+DC) Column: IonPack AS-22 + IonPack AG-22 Suppressor: ARES 4mm Solvent: Mixed solution of 4.5 mM sodium carbonate and 1 mM sodium bicarbonate. Standard sample: Anion mixed standard solution IV (Kanto Chemical) Measurement temperature: 35℃ Flow rate: 1.2mL / min

[0026] From the viewpoint of corrosion resistance, it is preferable that the total amine value of the ionic liquid (X) is 2 mg KOH / g or less. If the total amine value is greater than 2 mg KOH / g, the amine value can be reduced by adding an acid component equal to the acid value corresponding to the value.

[0027] The total amine number of the ionic liquid (X) was measured according to the method of ASTM D2074.

[0028] From the viewpoint of corrosion prevention, the acid value of the ionic liquid (X) is preferably 30 mg KOH / g or less. A value of 30 mg KOH / g or less suppresses the reduction in corrosion resistance due to metal corrosion caused by the acid. If the acid value exceeds 30 mg KOH / g, the acid value can be lowered by adding an amine or basic component equal to the amine value corresponding to the value.

[0029] The acid value of ionic liquid (X) can be adjusted by adding a basic compound. The acid value of ionic liquid (X) is measured by methods such as JIS K 0070.

[0030] The ionic liquid (X) may contain water, but from the viewpoint of corrosion resistance, the water content relative to the ionic liquid (X) is preferably 2.0% by weight or less, and more preferably 1.0% by weight or less. If the water content exceeds 2.0% by weight, the water may adhere to the metal surface to be protected, causing hydroxide formation and potentially reducing corrosion resistance.

[0031] The water content can be evaluated using the Karl Fischer titration method. The measurement is performed by volumetric method, and methanol can be used as the solvent. Approximately 50 ml of methanol is placed in the titrator, and the methanol is made anhydrous with Karl Fischer titration solution. Then, the sample to be measured is quickly added to the titrator using the reduction method, and the amount of titration required to make it anhydrous again with Karl Fischer titration solution, the mass of the sample to be measured, and the titer of the Karl Fischer titration solution are used to calculate the water content using the following formula. Water content (%)=(A×f) / (B×10) A: Volume (ml) of Karl Fischer titration solution used for titrating the sample. f: Titer of Karl Fischer titration solution (mgH2O / ml) B: Sample mass (g)

[0032] In this invention, the ionic liquid (X) is a liquid at 25°C. Because the ionic liquid (X) is a liquid, dilution with water or organic solvents, and drying with water or other substances after rust prevention / corrosion prevention treatment are unnecessary. The fact that it is a liquid at 25°C can be confirmed by visually observing its fluidity.

[0033] In the present invention, the method for producing the ionic liquid (X) is not particularly limited, but examples include the method described in J.Am.Chem.Soc., 69, 2269 (1947), U.S. Patent No. 4,892,944, etc. (a method of quaternizing a tertiary amine with a carbonate ester and then exchanging the salt). A preferred manufacturing method when cation (A) is a quaternary ammonium cation is exemplified below.

[0034] Manufacturing method A tertiary amine (the tertiary amine before the formation of a quaternary ammonium cation) is reacted with an equivalent or greater amount (e.g., 1.1 to 5.0 equivalents) of a dialkyl carbonate ester (e.g., dimethyl carbonate, diethyl carbonate) in or without a solvent (e.g., methanol) at a reaction temperature of 80 to 200°C, preferably 100 to 150°C, to form a quaternary ammonium salt. Then, an acid that forms the aforementioned anion is added (0.9 to 1.0 equivalents based on the equivalent amount of quaternary ammonium), and the mixture is stirred at 10 to 50°C for 1 hour to exchange the salt. The solvent is removed by distillation under reduced pressure at 80 to 120°C to obtain the desired quaternary ammonium salt. Here, as a tertiary amine, if the target quaternary ammonium cation is the amidinium cation mentioned above, examples include 1,2-dimethylimidazole, 1-methylimidazole, and 1-ethylimidazole.

[0035] From the viewpoint of moisture and heat resistance, the corrosion-resistant coating composition (Y) preferably contains at least one resin (E) selected from urethane resin, acrylic resin, and epoxy resin as a component other than the ionic liquid (X).

[0036] Examples of urethane resins include polymers consisting of a polyol-derived portion and a polyisocyanate-derived portion, that is, polymers obtained by polymerizing a polyol and a polyisocyanate.

[0037] The urethane resin may consist of one type of urethane resin, or it may be a mixture of two or more types of urethane resins.

[0038] Examples of the polyol include one or more polyols selected from the group consisting of polyoxyalkylenediols, polyester diols, and polycarbonate diols.

[0039] The polyol may consist of one type of polyol, or it may be a mixture of two or more types of polyols.

[0040] The polyoxyalkylenediol is preferably a polyether diol having an oxyalkylene group with 2 to 4 carbon atoms, and more preferably one or more selected from the group consisting of polyoxyethylene diol, polyoxypropylene diol, propylene oxide-ethylene oxide copolymer diol (random and / or block copolymer), and polytetramethylene ether glycol.

[0041] The number-average molecular weight of the polyoxyalkylenediol is preferably 500 to 20,000, more preferably 1,000 to 15,000, and even more preferably 2,000 to 10,000.

[0042] Examples of the polyester diol include polyester diols obtained by condensing a diol selected from the group consisting of aliphatic diols and aromatic diols having 2 to 10 carbon atoms with a dicarboxylic acid selected from the group consisting of aliphatic dicarboxylic acids having 2 to 10 carbon atoms and aromatic dicarboxylic acids having 8 to 12 carbon atoms.

[0043] Examples of the aliphatic diols having 2 to 10 carbon atoms include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,7-heptanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

[0044] Examples of the aromatic diols include 1,4-benzenedimethanol and 1,4-benzenediethanol.

[0045] Examples of the aliphatic dicarboxylic acids having 2 to 10 carbon atoms include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, and fumaric acid.

[0046] Furthermore, the aliphatic dicarboxylic acid having 2 to 10 carbon atoms may also have a ring structure. Examples of aliphatic dicarboxylic acids having the aforementioned ring structure and having 2 to 10 carbon atoms include 1,1-cyclopropanedicarboxylic acid, 1,1-cyclobutanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and bicyclo[2.2.2]octane-1,4-dicarboxylic acid.

[0047] Examples of the aforementioned aromatic dicarboxylic acids having 8 to 12 carbon atoms include terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid.

[0048] The number-average molecular weight of the polyester diol is preferably 1,000 to 20,000, more preferably 1,500 to 15,000, and even more preferably 2,000 to 10,000.

[0049] Examples of the polycarbonate diol include a polycarbonate diol produced by condensing one or more diols selected from the group consisting of aliphatic diols having 2 to 10 carbon atoms and aromatic diols with a low molecular weight carbonate compound [for example, a dialkyl carbonate with an alkyl group having 1 to 6 carbon atoms, an alkylene carbonate having an alkylene group having 2 to 6 carbon atoms, and a diaryl carbonate having an aryl group having 6 to 9 carbon atoms, etc.] while undergoing a de-alcoholization reaction. Two or more diols and low molecular weight carbonate compounds may be used in combination.

[0050] Specific examples of polycarbonate diols include polyhexamethylene carbonate diol, polypentamethylene carbonate diol, polytetramethylene carbonate diol, and poly(pentamethylene / hexamethylene) carbonate diol [for example, a diol obtained by condensing 1,5-pentanediol and 1,6-hexanediol with a dialkyl carbonate while de-alcoholizing them].

[0051] Examples of the polyisocyanates include aromatic polyisocyanates having 8 to 16 carbon atoms, linear aliphatic polyisocyanates having 5 to 12 carbon atoms, and alicyclic polyisocyanates having 9 to 15 carbon atoms. These polyisocyanates may have 2 to 3 or more isocyanate groups.

[0052] The polyisocyanate may consist of one type of polyisocyanate, or it may be a mixture of two or more types of polyisocyanates.

[0053] Examples of the aforementioned aromatic polyisocyanates having 8 to 16 carbon atoms include 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, crude tolylenediisocyanate, 4,4'-diphenylmethanediisocyanate, 2,4'-diphenylmethanediisocyanate, crude diphenylmethanediisocyanate, m-xylylenediisocyanate, 4,4'-diisocyanatobiphenyl, 4,4'-diisocyanato-3,3'-dimethylbiphenyl, and 1,5-diisocyanatonaphthalene.

[0054] Examples of the chain-like aliphatic polyisocyanates having 5 to 12 carbon atoms include pentamethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate (a mixture of 2,2,4- and 2,4,4-). From the viewpoint of resistance to moisture and heat, hexamethylene diisocyanate is preferred.

[0055] Examples of the alicyclic polyisocyanates having 9 to 15 carbon atoms include isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, and norbornane diisocyanate.

[0056] Examples of acrylic resins include polymers obtained by homopolymerizing or copolymerizing monomers having polymerizable double bonds. Examples of monomers having polymerizable double bonds include unsaturated monocarboxylic acids having 3 to 30 carbon atoms [e.g., (meth)acrylic acid (representing acrylic acid and / or methacrylic acid; the same applies hereinafter), isocrotonic acid crotonic acid, cinnamic acid, etc. and their esters, etc.], unsaturated dicarboxylic acids (anhydrides) having 3 to 30 carbon atoms [e.g., (anhydride) maleic acid, fumaric acid, itaconic acid, (anhydride) citraconic acid and mesaconic acid, etc.], and monoalkyl (1 to 24 carbon atoms) esters of unsaturated dicarboxylic acids having 3 to 30 carbon atoms [e.g., monomethyl maleate, monooctadecyl maleate, monoethyl fumarate, monobutyl itaconic acid, glycol itaconic acid monoether and monoeicosyl citraconic acid, etc.].

[0057] Examples of epoxy resins include phenol novolac type epoxy resins, naphthol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, naphthylene ether type epoxy resins, glycidyl ester type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, anthracene type epoxy resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiroring-containing epoxy resins, cyclohexanedimethanol type epoxy resins, trimethylol type epoxy resins, and tetraphenylethane type epoxy resins. The above epoxy resin (A) may be used alone or in combination of two or more types.

[0058] The content of the ionic liquid (X) in the corrosion-preventive coating composition (Y) of the present invention is preferably 5 to 45% by weight, and more preferably 10 to 30% by weight.

[0059] The content of resin (E) in the corrosion-resistant coating composition (Y) of the present invention is preferably 55 to 95% by weight, and more preferably 70 to 90% by weight.

[0060] The corrosion-preventive coating composition (Y) of the present invention may also include an ionic liquid other than the ionic liquid (X), which is an ionic liquid consisting of an anion other than the thiocyanate anion and the cation (B).

[0061] Other than thiocyanate anions, known anions can be used, such as inorganic strong acids (a1), halogen atom-substituted alkyl group-containing strong acids (a2), halogen atom-containing sulfonylimides (a3), halogen atom-containing sulfonylmethides (a4), halogen atom-containing carboxylic acid amides (a5), nitrile group-containing imides (a6), nitrile-containing methides (a7), and halogen atom-containing alkylamines (a8), from which hydrogen atoms have been removed. The anions may also be a mixture of two or more types.

[0062] Examples of inorganic strong acids (a1) include hydrofluoric acid, hydrochloric acid, sulfuric acid, phosphoric acid, HClO4, HBF4, HPF6, HAsF6, HSbF6, and fluorosulfonic acid.

[0063] Examples of halogen atom-substituted alkyl group-containing strong acids (a2) include trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid, trichloromethanesulfonic acid, pentachloropropanesulfonic acid, heptachlorobutanesulfonic acid, trifluoroacetic acid, pentafluoropropionic acid, pentafluorobutanoic acid, trichloroacetic acid, pentachloropropionic acid, and heptachlorobutanoic acid.

[0064] Examples of halogen atom-containing sulfonylimides (a3) ​​include bis(fluoromethylsulfonyl)imide, bis(trifluoromethylsulfonyl)imide, and bis(fluorosulfonyl)imide.

[0065] Examples of halogen atom-containing sulfonylmethides (a4) include tris(trifluoromethylsulfonyl)methide.

[0066] Examples of halogen atom-containing carboxylic acid amides (a5) include bis(trifluoroacet)amide.

[0067] Examples of nitrile group-containing imides (a6) include HN(CN)2.

[0068] Examples of nitrile-containing methides (a7) include HC(CN)3.

[0069] Examples of halogen atom-containing alkylamines (a8) include HN(CF3)2.

[0070] The halogen content of the corrosion-preventive coating composition (Y) of the present invention is preferably 20 ppm or less from the viewpoint of corrosion prevention, and more preferably 10 ppm or less. If the halogen content is within this range, metal corrosion due to halogens can be prevented. Unless intentionally added, halogens are mainly present in the raw materials used when synthesizing anions in ionic liquids (X), and when halogenated salts are used as cations (B). If the halogen content is higher than 20 ppm, the halogen content can be reduced by dissolving it in acetone or the like and then passing it through a column packed with alumina, for example.

[0071] The halogen content of the corrosion-preventive coating composition (Y) can be measured in the same manner as that of the ionic liquid (X).

[0072] The corrosion-preventive coating composition (Y) of the present invention can be obtained by melt-mixing or solution-mixing the ionic liquid (X), resin (E), and optionally additives of the present invention. As a melt-mixing method, generally, each component, in pellet form, powder form, or liquid form, can be mixed in a suitable mixer (such as a Henschel mixer), and then mixed in an extruder to form pellets. As a solution-mixing method, one or both of (X) and (E) can be mixed in the form of a solution in a solvent. Examples of solvents used in solution mixing include alcohols [e.g., monoalcohols such as methanol, ethanol, and isopropanol, diols such as ethylene glycol and propylene glycol], ethers [e.g., diethylene glycol, tetrahydrofuran, and 1,4-dioxane], ketones [e.g., acetone, methyl ethyl ketone, methyl isopropyl ketone, and methyl isobutyl ketone], and esters [ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, and butyl cellosolve acetate]. This includes amides [e.g., dimethylformamide, diethylformamide, dimethylacetamide, and N-methylpyrrolidone], aromatic hydrocarbons [e.g., benzene, toluene, xylene, ethylbenzene, triethylbenzene, amylbenzene, diamylbenzene, amyltoluene, diphenylethane, and tetralin], aliphatic hydrocarbons [e.g., hexane, heptane, octane, and decane], alicyclic hydrocarbons [e.g., cyclohexane, cyclohexene, methylcyclohexane, and decalin], and other solvents, as well as mixtures of two or more of these.

[0073] The corrosion-resistant coating of the present invention is a corrosion-resistant coating formed from the above-mentioned corrosion-resistant coating composition (Y). Similar to the case in which conventional corrosion-resistant paints are formed from conventional corrosion-resistant coating compositions, the corrosion-resistant coating of the present invention is formed by uniformly applying the corrosion-resistant coating composition of the present invention to an object.

[0074] The thickness of the anticorrosive coating of the present invention is not particularly limited and can be set to an appropriate range depending on the characteristics of the anticorrosive coating of the present invention (e.g., coating wear rate) and application (type of substrate, period of use, etc.). However, for example, a thickness of 30 to 10,000 μm is preferred immediately after formation. [Examples]

[0075] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. In the following, "parts" refers to parts by weight.

[0076] <Manufacturing Example 1> A solution of 135 parts (1.5 moles) of dimethyl carbonate dissolved in 192 parts of methanol was added to a stirred autoclave, and 96 parts (1.0 mole) of 1-ethylimidazole was added dropwise using a dropper funnel. The mixture was then stirred at 130°C for 40 hours to obtain 1-ethyl-3-methylimidazolium methyl carbonate salt. Next, a solution of 76 parts (1.0 mole) of ammonium thiocyanate dissolved in 76 parts of deionized water was added. After removing the precipitated ammonium carbonate by filtration, the mixture was heated to 110°C under a reduced pressure of 1.0 kPa while passing nitrogen gas at a rate of 0.1 mL / min to remove the solvents dimethyl carbonate, methanol, and deionized water, obtaining an ionic liquid (X-1) consisting of a thiocyanate anion and a 1-ethyl-3-methylimidazolium cation.

[0077] <Manufacturing Example 2> 311 parts (1.0 mol) of didecylmethylamine, 90 parts (1.0 mol) of dimethyl carbonate, and 64 parts of methanol as a solvent were charged into a stirred autoclave and reacted at 110°C for 12 hours to obtain didecyldimethylammonium methyl carbonate salt. Next, a solution of 76 parts (1.0 mol) of ammonium thiocyanate dissolved in 152 parts of methanol was added. The mixture was then stirred at 90°C for 4 hours to decompose and remove ammonium carbonate. Next, the mixture was heated to 110°C under a reduced pressure of 1.0 kPa while passing nitrogen gas at a rate of 0.1 mL / min to remove the methanol solvent and deionized water, obtaining an ionic liquid (X-2) consisting of thiocyanate anions and didecyldimethylammonium cations.

[0078] <Manufacturing Example 3> 98 parts (1.0 mol) of 2,4-dimethylimidazoline, 180 parts (2.0 mol) of dimethyl carbonate, and 57 parts of methanol as a solvent were charged into a stirred autoclave and reacted at 120°C for 12 hours to obtain 1,2,3,4-tetramethylimidazolinium methyl carbonate salt. Next, a solution of 76 parts (1.0 mol) of ammonium thiocyanate dissolved in 152 parts of methanol was added. The mixture was then stirred at 90°C for 4 hours to decompose and remove ammonium carbonate. Next, the mixture was heated to 110°C under a reduced pressure of 1.0 kPa while passing nitrogen gas at a rate of 0.1 mL / min to remove the dimethyl carbonate, methanol, and deionized water, obtaining an ionic liquid (X-3) consisting of a thiocyanate anion and a 1,2,3,4-tetramethylimidazolinium cation.

[0079] <Manufacturing Example 4> 311 parts (1.0 mol) of dioctylmethylamine, 90 parts (1.0 mol) of dimethyl carbonate, and 64 parts of methanol as a solvent were charged into a stirred autoclave and reacted at 110°C for 12 hours to obtain dioctyldimethylammonium methyl carbonate salt. Next, a solution of 74.5 parts (0.98 mol) of ammonium thiocyanate dissolved in 150 parts of methanol was added. The mixture was then stirred at 90°C for 4 hours to decompose and remove ammonium carbonate. Next, the mixture was heated to 110°C under a reduced pressure of 1.0 kPa while passing nitrogen gas at a rate of 0.1 mL / min to remove the methanol solvent and obtain an ionic liquid (X-4) consisting of a thiocyanate anion and a dioctyldimethylammonium cation.

[0080] <Comparative Manufacturing Example 1> 92 parts (1.0 mol) of thioglycolic acid were diluted with 29 parts of deionized water, and 61 parts of 28% by weight aqueous ammonia were added to obtain a 60% by weight aqueous solution (ratio X-1) of a salt consisting of thioglycolic acid anion and ammonium cation by a neutralization reaction.

[0081] <Comparative Manufacturing Example 2> A solution of 135 parts (1.5 mol) of dimethyl carbonate dissolved in 192 parts of methanol was added to a stirred autoclave, and 96 parts (1.0 mol) of 1-ethylimidazole was added dropwise using a dropper funnel. The mixture was then stirred at 130°C for 40 hours to obtain 1-ethyl-3-methylimidazolium methyl carbonate salt. Next, 182 parts of a 60 wt% aqueous solution of ammonium thioglycolate, prepared by the same synthesis method as in Comparative Example 1, were added. The mixture was then stirred at 90°C for 4 hours to decompose and remove ammonium carbonate. The mixture was then heated to 110°C under a reduced pressure of 1.0 kPa while passing nitrogen gas at a rate of 0.1 mL / min to remove the solvent dimethyl carbonate, methanol, and ion-exchanged water, obtaining an ionic liquid (ratio X-2) consisting of thioglycolate anion and 1-ethyl-3-methylimidazolium cation.

[0082] <Comparative Manufacturing Example 3> 76 parts of ammonium thiocyanate were dissolved in 76 parts of deionized water to obtain a 50% by weight aqueous solution (ratio X-3) of a salt consisting of a thiocyanate anion and an ammonium cation.

[0083] <Comparative Manufacturing Example 4> An ionic liquid (ratio X-4) consisting of a thiocyanate anion and a 1-ethyl-3-methylimidazolium cation was obtained by the same method as in Production Example 1, except that the amount of ammonium thiocyanate was changed to 73 parts (0.96 molar parts).

[0084] <Comparative Manufacturing Example 5> For comparison, we used alkenyl succinic acid [DSA, manufactured by Sanyo Chemical Industries, Ltd.], a commercially available rust inhibitor component, as is, and designated it as (Ratio X-5).

[0085] The water content, pH, and halogen content were measured for the ionic liquid (X) of Production Examples 1-4 and Comparative Production Examples 1-5. The results are shown in Table 1.

[0086] [Table 1]

[0087] The anions and cations (B) shown in Table 1 are as follows: SCN: Thiocyanate ion TGA: Thioglycolate ion EMI: 1-ethyl-3-methylimidazolium ion DDA: Didecyldimethylammonium ion TMIm: 1,2,3,4-Tetramethylimidazolinium ion DOA: Dioctyldimethylammonium ion NH4: Ammonium ion

[0088] <Examples 1-11, Comparative Examples 1-8> According to the raw materials used (parts) in Table 2, each raw material was used to prepare a corrosion-preventive coating composition (Y) containing an ionic liquid (X). The appearance of the coating film, corrosion resistance, heat and humidity resistance, and rust prevention were evaluated using the following test methods. The results are shown in Table 2.

[0089] [Table 2]

[0090] The resins (E) shown in Table 2 are as follows: (E-1): Commercially available acrylic resin [Sanyo Chemical Industries, Ltd., "Polysic 310S"] (E-2): Commercially available urethane resin [Sanyo Chemical Industries, Ltd., "Sunprene LQ3190"] (E-3): Commercially available epoxy resin [DIC Corporation, "EPICLON EXA-192"]

[0091] (1) Evaluation of the appearance of the coating film A stainless steel plate (material: SUS304, 1mm thick x 60mm long x 80mm wide) was immersed in 10% hydrochloric acid in a PP tray for 1 minute. After wiping the surface with paper, it was left to stand for 1 week in a constant temperature and humidity chamber at 40°C and 85% humidity to create a test piece with red rust. The prepared test specimens were coated with the anticorrosive coating compositions described in Examples 1-11 and Comparative Examples 1-8 using a squeegee to achieve a coating thickness of 190-210 μm, and then dried overnight. The appearance of the coating after drying was visually evaluated with ○ and × according to the following criteria. ○: No exposure of the test specimen or localized thickness variations are observed in the coating. ×: The coating shows exposure of the test specimen and localized unevenness in thickness.

[0092] (2) Corrosion resistance test A stainless steel plate (material: SUS304, 1mm thick x 60mm long x 80mm wide) was immersed in 10% hydrochloric acid in a PP tray for 1 minute. After wiping the surface with paper, it was left to stand for 1 week in a constant temperature and humidity chamber at 40°C and 85% humidity to create a test piece with red rust. After applying the corrosion-preventive coating compositions described in Examples 1-11 and Comparative Examples 1-8 to the prepared test specimens, they were left to stand for one month in a constant temperature and humidity chamber at 30°C and 50% humidity. The coated surface was then removed with acetone solvent, and the degree of red rust removal was visually evaluated on the following four scales. ◎: Red rust can be restored to black rust and / or iron at a rate of 95% or more relative to the area. ○: Red rust has a recovery rate of 80% or more but less than 95% of the area to black rust and / or iron. △: Red rust has a recovery rate of 60% or more but less than 80% of the area to black rust and / or iron. ×: Red rust has a recovery rate of less than 60% of the area to black rust and / or iron. The area was measured using an Olympus DSX500 digital microscope, and the restoration rate was calculated as (area of ​​rust before testing - area of ​​rust after testing) / (area of ​​rust before testing) × 100 (%).

[0093] (3) Corrosion resistance test after moisture and heat resistance test A stainless steel plate (material: SUS304, 1mm thick x 60mm long x 80mm wide) was immersed in 10% hydrochloric acid in a PP tray for 1 minute. After wiping the surface with paper, it was left to stand for 1 week in a constant temperature and humidity chamber at 40°C and 85% humidity to create a test piece with red rust. After applying the corrosion-preventive coating compositions described in Examples 1-11 and Comparative Examples 1-8 to the prepared test specimens, they were left to stand for 1 day in a constant temperature and humidity chamber at 30°C and 50% humidity, and then left to stand for 1000 hours in a constant temperature and humidity chamber at 50°C and 85% humidity. The coated surface was then removed with acetone solvent, and the degree of red rust removal was visually evaluated on the following four scales. ◎: Red rust can be restored to black rust and / or iron at a rate of 95% or more relative to the area. ○: Red rust has a recovery rate of 80% or more but less than 95% of the area to black rust and / or iron. △: Red rust has a recovery rate of 60% or more but less than 80% of the area to black rust and / or iron. ×: Red rust has a recovery rate of less than 60% of the area to black rust and / or iron.

[0094] (4) Rust prevention test A stainless steel plate (material: SUS304, 1mm thick x 60mm long x 80mm wide) was polished in accordance with JIS K2246:2018 to create a test specimen. After applying the corrosion-preventive coating compositions described in Examples 1-11 and Comparative Examples 1-8 to the prepared test specimens, they were left to stand for one month in a constant temperature and humidity chamber at 30°C and 50% humidity. The coated surface was then removed with acetone solvent, and the degree of red rust formation was visually evaluated on the following four scales. ◎: Red rust is less than 5% of the area. ○: Red rust covers 5% or more but less than 20% of the area. △: Red rust covers 20% to less than 40% of the area. ×: Red rust covers more than 40% of the area.

[0095] The results in Table 2 show that the composition of the present invention exhibits both a corrosion-preventive effect on SUS plates that have developed red rust and an effect as a rust inhibitor. [Industrial applicability]

[0096] The corrosion-resistant coating composition of the present invention functions not only as a corrosion-resistant paint but also as a rust-preventive paint. Furthermore, because it contains an ionic liquid, it has high conductivity and can be used not only as a chemical polishing agent but also as an electrolytic polishing agent. It is also useful as a rust inhibitor and as a primer after various polishing processes.

Claims

1. A corrosion-preventive coating composition (Y) comprising an ionic liquid (X) consisting of a thiocyanate anion and a cation (B), having a pH of 5 to 9 at 25°C.

2. The corrosion-preventive coating composition (Y) according to claim 1, wherein the halogen content of the ionic liquid (X) is 20 ppm or less.

3. The corrosion-preventive coating composition (Y) according to claim 1, wherein the cation (B) is at least one cation selected from the group consisting of amidinium cations and quaternary ammonium cations.

4. The corrosion-preventive coating composition (Y) according to claim 1, wherein the cation (B) is 1-ethyl-3-methylimidazolium.

5. The corrosion-resistant coating composition (Y) according to claim 1, comprising at least one resin (E) selected from urethane resin, acrylic resin, and epoxy resin.

6. A corrosion-resistant coating film formed from the corrosion-resistant coating composition (Y) according to any one of claims 1 to 5.

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