Abstract:
A general-purpose organic rust initiator which can effectively prevent corrosion of metals comprising a compound of formula (1): ##STR1## wherein R 1  is a perfluoroalkyl group having 1 to 6 carbon atoms; R 2  is a hydrogen atom or a group defined for R 1  ; R 4  is an acid group selected from --OH, --COOH, --SH, --SO 2  OH, --PO(OH) 2 , --SCH 2  COOH, --SO 2  NHCH 2  COOH or a salt thereof; R 3  is a hydrogen atom or a group defined for R 4  ; or R 3  and R 4  together form an acid group selected from --N═N--NH--, --CH═N--N--, --SO 2  --NH--CO--, --S--C(SH)═N-- or a salt thereof.

Description:
This application is a continuation of application Ser. No. 08/046,305, filed Apr. 15, 1993, now abandoned. 
    
    
     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. 
     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 aromatic compounds having specific fluorine-containing alkyl groups represented by the general formula (1): ##STR2## (wherein, in the above general formula, R 1  represents a fluorine-substituted alkyl group; R 2  is a hydrogen atom or a group defined for R 1  or an organic residue; R 3  and R 4  are hydrogen or an ionizable group at least for either of the two or an ionizable group in which R 3  and R 4  are connected to each other). 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The fluorine-substituted alkyl group represented by R 1  in general formula (1) used in the present invention includes, for example, alkyl groups containing not more than 20 carbon atoms substituted by at least one fluorine atom, with the alkyl group being optionally substituted 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, imiadazole, pyrazole, iminodicarbonyl, iminodisulfonyl, iminocarbonyl sulfonyl, and the like, 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) of the present invention are as follows: 
     No. 1 Sodium 3,4-bis(trifluoromethyl)benzenesulfonate 
     No. 2 Calcium 3-pentafluoroethyl-6-hydroxybenzoate 
     No. 3 Triethanol amine salt of p-tertiarynonafluorobutylbenzenesulfonate 
     No. 4 Sodium p-trifluoromethylbenzenesulfonyl aminoacetate 
     No. 5 Sodium p-pentafluoroethylphenyl 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) of the present invention 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 of 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 of 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 (SS41,50×50×2 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 
     
                       TABLE 1______________________________________               Brine      Wetting               Spray Test TestRust Inhibotor      (24 hrs.)  (400 hrs.)______________________________________ExampleNos.2-1     Compound No. 2  No rusting No rusting2-2     Compound No. 3  No rusting No rusting2-3     Compound No. 4  No rusting No rusting2-4     Compound No. 5  No rusting No rustingControlExampleNos.2-1     Ca-Petroleum Sulfonate                   Extensive  Rusting                   rusting2-2     Sodium Lauroyl Amino                   Rusting    Slight   Acetate                    rusting2-3     Sodium Stearoyl Thio                   Rusting    No rusting   Acetate______________________________________ 
    
     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 50×25 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 100 ml/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. 
     
                       TABLE 2______________________________________           Alumi-Rust Inhibitor  num      Brast  Solder Copper______________________________________ExampleNos.3-1    Compound No. 6               0.10     0.04 0.09   0.023-2    Compound No. 7               0.05     0.06 0.06   0.04ControlExampleNos.3-1    Benzotriazole               0.52     0.14 0.42   0.093-2    Benzothiazole               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 (50×50×2 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 hours 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 
     0.5 g of compound No. 9 (Example 5-1) or compound No. 10 (Example 5-2) was dissolved in 100 ml 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, 50×50×2 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.