Rust inhibitor

Abstract: A general-purpose organic rust inhibitor which can effectively prevent corrosion of metals, and which comprising a compound represented by the general formula (1): wherein, in the above general formula (1), R₁ represents a fluorine-substituted alkyl group; R₂ is a hydrogen atom or a group defined for R₁ or an organic residue; R₃ and R₄ are hydrogen or an ionizable group at least for either of the two, or an ionizable group in which R₃ and R₄ are connected to each other.

Description: BACKGROUND OF THE INVENTION The present invention relates to a rust inhibitor, specifically to a rust inhibitor comprising a specific fluorine-substituted alkyl benzene derivative which is brought into contact with a metal surface, thereby inhibiting rust formation on the metal. There have, heretofore, been many methods for inhibiting rust formation on the surface of metal materials, for which purposes numerous rust inhibitors have been proposed and used in practice. For example, inorganic materials, such as sodium polyphosphate and nitrite salts are well known. Problems of environmental destruction including marine pollution have lately focused attention on organic materials. Typical organic rust inhibitors heretofore known include vegetable oils, certain fatty acids, sulfonated hydrocarbon oils, benzotriazoles, dicyclohexylamine salts, and the like, which are effective for specific metals. However, these organic materials are unsatisfactory as excellent general-purpose rust inhibitors. US-A-4278791 discloses as an anti-corrosion agent a benzimidazolyl-2-alkane-phosphonic acid of the formula wherein R 1 and R 2 may be identical or different and may inter alia represent hydrogen or a trifluoromethyl group; the substituent R 3 represents hydrogen, lower alkyl, phenyl or optionally substituted benzyl; and the bridging group -A- denotes a bivalent C 1-15 hydrocarbon radical. SUMMARY OF THE INVENTION Thus, an object of the present invention is to provide excellent general-purpose organic rust inhibitors which can effectively prevent corrosion of metals, such as steel, copper, chromium, manganese, nickel, and aluminum, as well as alloys based on these components, or noble metals, such as gold, silver, and alloys containing these metals. The present inventor has made intensive investigation on anticorrosion mechanisms of the known organic rust inhibitors, and has discovered that the strong bonding of the inhibitors to the metal surface is important to protect the surface so as to retain excellent rust inhibition. The above object of the present invention is met by the use of a compound represented by the general formula (1) as a rust inhibitor: wherein R 1 represents a fluorine-substituted C 1-20 alkyl group; R 2 is a hydrogen atom, a group as defined for R 1 or an organic residue containing not more than 6 carbon atoms; and R 3 and R 4 are independently hydrogen or an ionizable group, with the proviso that at least one of R 3 and R 4 is an ionizable group or R 3 and R 4 may be connected to each other to form a heterocyclic ring including an ionizable group, the heterocyclic ring being triazole, thiazole, pyrazole, iminodicarbonyl, iminodisulfonyl or iminocarbonyl sulfonyl. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The fluorine-substituted C 1-20 alkyl group represented by R 1 in general formula (1) used in the present invention includes, for example, alkyl groups substituted by at least one fluorine atom, with the alkyl group being optionally substitued by residues other than hydrogen atoms, such as chlorine, hydroxyl, and acetyl, such as monofluoromethyl, difluoromethyl, trifluoromethyl, monofluorodichloromethyl, difluorochloro-methyl, pentafluoroethyl, isoheptafluoropropyl, normalheptafluoropropyl, isononafluorobutyl, tertiary nonafluorobutyl, normalnonafluorobutyl, and the like. R 2 represents a hydrogen atoms, a group defined by R 1 or a group selected from organic residues where the organic residue includes organic residues containing not more than 6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertiary butyl, methoxy, ethoxy, acetoxy, aryl groups, and the like. R 3 and R 4 are selected independently from hydrogen atoms and ionizable groups, where at least either R 3 or R 4 is an ionizable group, the ionizable groups being for example, sulfino, sulfonic, carbomethoxy, carboxymethylthio, carboxymethyl sulfonyl, N-(carboxymethyl)-aminosulfonyl, N-(carboxymethyl)carbamoyl, 2-carboxyethylthio, 2-carboxyethyl sulfonyl, N-(2-carboxyethyl)aminosulfonyl, N-(2-carboxyethyl)carbamoyl, 3-carboxypropylthio, 3-carboxypropyl sulfonyl, 3-carboxypropyl aminosulfonyl, N-(3-carboxypropyl)carbamoyl, carbamoyl, aminosulfonyl, N-hydroxycarbamoyl, N-hydroxyaminosulfonyl, phosphono, phosphonoxy, phosphino, hydroxy, carboxy, and mercapto. In addition, R 3 and R 4 are groups which may be bonded together to generate triazole, thiazole, pyrazole, iminodicarbonyl, iminodisulfonyl, iminocarbonyl sulfonyl, so as to be able to dissociate hydrogen ions; or the dissociable hydrogen ions of these groups may be substituted by metal atom ions or partially substituted by metal atom ion, such as alkali metals, such as lithium, sodium, potassium, and rubidium, alkaline earth metals, such as beryllium, magnesium, calcium, strontium, and barium, titanium, yttrium, zirconium, iron, aluminum, nickel, zinc, tin, lead, and cadmium, or groups which formed organic amine salts with amines, trimethyl amine, monoethanol amine, dectanol amine, triethanol amine, morpholine, dicyclohexylamine, pyridine, tripropanol amine, polyethylene imine, vinyl pyridine, polyvinyl pyridine, and the like. Preferred examples of the compound represented by the above general formula (1) for use in the present invention are as follows: No. 1 Sodium 3,4-bis(trifluoromethyl)benzenesulfonate No. 2 Calcium 3-heptafluoroethyl-6-hydroxybenzoate No. 3 Triethanol amine salt of p-tertiarynonafluorobutylbenzenesulfonate No. 4 Sodium p-trifluoromethylbenzenesulfonyl aminoacetate No. 5 Sodium p-heptafluoroethylphenyl thioacetate No. 6 Pottasium m-trifluoromethylbenzotriazole salt No. 7 m-trifluoromethyl benzotriazole No. 8 Dicyclohexylamine p-trifluoromethylphenylsulfonate salt No. 9 Potassium m-tertiarynonafluorobutyl saccharine salt No. 10 Sodium p-trifluoromethylbenzoate These compounds represented by the above general formula (1) can be synthesized by known methods; in particular, the fluoroalkyl groups are readily obtained by fluorine substitutions of chloro or bromo alkyl groups. In general, an alkyl group of an alkyl benzene is chlorinated or brominated followed by replacing it with fluorine or the like, to give a fluoroalkyl aromatic group, and then introducing an ionizable group, or else the alkyl group of the goal compound is fluorinated to prepare these compounds. Specifically, compound No. 1 is prepared by side chain chlorination of 3,4-dimethylbenzene sulfonic acid, thereby resulting is 3,4-bis(trichloromethyl) benzenesulfonic acid. Then, in alkaline water, the compound is subjected to substitution with potassium fluoride to obtain the goal compound No. 1. However, the present invention is in no way restricted by the method of manufacture of these compounds. The rust inhibitor compound for use in the present invention, which is either a compound represented by the above general formula (1) alone or a plurality of compounds thereof in combination, is brought into contact with the metal material to be protected against corrosion, thereby showing its effectiveness, wherein optionally it is used by incorporating, dispersing or dissolving in water, organic solvents, detergents, lubricating oils, cotton oil, rubber, a resin coating, such as an alkyd resin, or a synthetic resin to give a composition, which is then brought into contact with the metal material, or else the composition is then brought into contact with the metal followed by vaporizing off the water, solvent, or the like, thereby exhibiting its effectiveness. Either application can be used in conjunction with a known rust inhibitor where its rust inhibitory effect can be further enhanced by incorporating one or a plurality of a surface active agent, a dispersant, a dye, a pigment, a flavor, an antiweathering agent, an antioxidant, sodium silicate, a filler, or the like additive. The rust inhibitor compound for use in the present invention is in no way restricted by specifying a combination with these materials or its use or the application to specific metals. Metals which the present invention targets for corrosion inhibition are metals such as iron, copper, choromium, manganese, nickel, aluminum, titanium, tantalum, molybdenum, and tin, as well as alloys based on these components, or reinforced alloys obtained by adding small amounts of other metals, carbon, boron, silicon, or the like, or noble metals, such as gold and silver and alloys containing these metals. These metals or alloys are used in a variety of applications including sundries, architectual materials, vehicle steel, tools, machines, and their parts, aircraft materials, marine materials, electronic materials and their parts, electronic device materials, communication materials, and the like. EXAMPLES The present invention is further described in detail by the following examples. However, in no way will the present invention be limited by the following examples. EXAMPLE 1 AND CONTROL EXAMPLE 1 0.5 g of compound No. 1 was dissolved in 100 mℓ of 5% by weight brine and placed in a dish (Example 1). A similar solution was prepared except for using p-tertiary butyl benzoic acid as a control example (Control Example 1). In these dishes were placed sandpaper, a toluene-degreased steel coupon (SS41,50x50x2 mm), followed by placing a lid on top and allowing it to stand for 24 hours at 40°C. These two coupons after standing were removed and subjected to observation which indicated no change on the surface of the steel coupon of Example 1 with the solution remaining colorless and transparent; on the other hand, the surface of the steel coupon of Control Example 1 was yellow with the solution remaining having changed to a light brown color. EXAMPLE 2 Test steel coupons (SPCC B) were subjected to a brine spray test (JIS Z 2371) and wetting test (JIS K 2246.) The following composition was prepared and coated onto test pieces, followed by drying for six hours at room temperature and submitting to tests, to give the results shown in Table 1. Microwax 30% by weight Lanolin 10 Mixed Xylene 59 Triisopropanol Amine 0.5 Rust Inhibitor 0.5 Rust Inhibotor Brine Spray Test (24 hrs.) Wetting Test (400hrs.) Example Nos.2-1 Compound No. 2 No rusting No rusting 2-2 Compound No. 3 No rusting No rusting 2-3 Compound No. 4 No rusting No rusting 2-4 Compound No. 5 No rusting No rusting Control Example Nos.2-1 Ca-Petroleum Sulfonate Extensive rusting Rusting 2-2 Sodium Lauroyl Amino Acetate Rusting Slight rusting 2-3 Sodium Stearoyl Thio Acetate Rusting No rusting EXAMPLE 3 An antifreeze (ethylene-glycol-based, JIS Specification PT Grade) containing 1% by weight of a rust inhibitor of the present invention was prepared and subjected to a rust inhibition evaluation as an antifreeze according to JIS K 2234. Each of these antifreeze samples containing each rust inhibitor was diluted to 30% by volume with synthetic water solutions prepared by the aforementioned test method, to permit immersing in the solution, according to the specified method, a test piece which had been subjected to the specified treatment (a 50x25 mm piece with a 6.5 mm diameter hole drilled through the center; the aluminum and the solder were about 3 mm thick, and the copper and brass were 1.6 mm thick), followed by introducing dry air from an air inlet tube at a rate of 100mℓ/min while they were held at 88± 2 °C for 336 hours. On completing the test, the test pieces were, according to the specified procedure weighed accurately to 0.1 mg to compute the weight reduction, expressed in units of mg/cm 2 , with the results given in Table 2. Rust Inhibitor Aluminum Brast Solder Copper Example Nos.3-1 Compound No. 6 0.10 0.04 0.09 0.02 3-2 Compound No. 7 0.05 0.06 0.06 0.04 Control Example Nos.3-1 Benzotriazole 0.52 0.14 0.42 0.09 3-2 Benzotiazole 0.46 0.20 0.53 0.15 Table 2 clearly shows that the rust inhibitors of the present invention gave considerably low numerical values indicating an appreciable inhibition of corrosion of these metal materials. EXAMPLE 4 AND CONTROL EXAMPLE 4 Super-mild steel test pieces (50x50x2 mm) were evenly sprayed with an ethanol solution of 1% by weight of compound No. 8 (Exampel 4) or with dicyclohexyl ammonium nitrite (Control Example 4) as the control example and were left standing for 50 horus at 40 °C and at a humidity of 90%. Example 4 revealed no change at all, but Control Example 4 showed brown-colored rust formation. EXAMPLE 5 AND CONTROL EXAMPLE 5 0.5g of compound No. 9 (Example 5-1) or compound No. 10 (Example 5-2) was dissolved in 100mℓ of city water and placed in a dish; a similar solution was prepared (Control Example 5) except for using sodium p-tertiary butyl benzoate. In these dishes were immersed sandpapered, toluene-degreased steel coupons (SS41, 50x50x2 mm), followed by standing at 25°C for 240 hours. After standing, each coupon was taken out for observation which indicated no changes on the surface of steel coupons in Examples 5-1 and 5-2, giving colorless and transparent remaining solutions, but the surface of the steel coupon of Control Example 5 was discolored and brown giving a red-brown colored turbid remaining solution. The rust inhibitor of the present invention, clearly demonstrated in these examples, exhibits superior rust inhibitory effects compared to the known rust inhibitors and, thus, can be used singly or in combinations with other materials in a multi-purpose rust inhibitory application.

Claims: The use of a compound represented by the general formula (1) as a rust inhibitor: wherein R 1 represents a fluorine-substituted C 1-20 alkyl group; R 2 is a hydrogen atom, a group as defined for R 1 or an organic residue containing not more than 6 carbon atoms; and R 3 and R 4 are independently hydrogen or an ionizable group, with the proviso that at least one of R 3 and R 4 is an ionizable group or R 3 and R 4 may be connected to each other to form a heterocyclic ring including an ionizable group, the heterocyclic ring being triazole, thiazole, pyrazole, iminodicarbonyl, iminodisulfonyl or iminocarbonyl sulfonyl. The use according to claim 1, wherein the compound represented by the general formula (1) is sodium 3,4-bis(trifluoromethyl)benzenesulfonate. The use according to claim 1, wherein the compound represented by the general formula (1) is calcium 3-pentafluoroethyl-6-hydroxybenzoate. The use according to claim 1, wherein the compound represented by the general formula (1) is triethanol amine salt of p-tertiarynonafluorobutylbenzenesulfonate. The use according to claim 1, wherein the compound represented by the general formula (1) is sodium p-trifluoromethylbenzenesulfonyl aminoacetate. The use according to claim 1, wherein the compound represented by the general formula (1) is sodium-p-pentafluoroethylphenyl thioacetate. The use according to claim 1, wherein the compound represented by the general formula (1) is potassium m-trifluoromethylbenzotriazole salt. The use according to claim 1, wherein the compound represented by the general formula (1) is m-trifluoromethyl benzotriazole. The use according to claim 1, wherein the compound represented by the general formula (1) is dicyclohexylamine p-trifluoromethylphenylsulfonate salt. The use according to claim 1, wherein the compound represented by the general formula (1) is potassium m-tertiarynonafluorobutyl saccharine salt. The use according to claim 1, wherein the compound represented by the general formula (1) is sodium p-trifluoromethylbenzoate.

Inventors: OTOMO SHIGERU, OTOMO, SHIGERU
Applicants: UNION CHEMICAL CO LTD, UNION CHEMICAL CO., LTD.
Application year: 1993
Main classification: C23F11
IPC codes: C23F11