Abstract:
A lubricant for metal working comprising a dicarboxylic acid represented by the following general formula (I) or its amine salt or its alkali metal salt and a sulfur extreme pressure agent: ##STR1## wherein R 1  stands for COOH or H; and R 2  stands for H when R 1  is COOH and COOH when R 1  is H.

Description:
This application is a continuation of application Ser. No. 07/820,989, filed Jan. 15, 1992, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Industrial Application 
     The present invention relates to a lubricant for metallurgy (metal working). More particularly, the present invention is concerned with a lubricant for use in metal working such as cutting, grinding, drawing and wire drawing, which comprises a particular dicarboxylic acid or its amine salt or its alkali metal salt and a sulfur extreme-pressure agent. 
     2. Description of the Prior Art 
     In lubricants used for metal working, such as cutting, grinding, drawing, wire drawing, pressing, etc., an oiliness improver, an extreme pressure agent, a rust preventive, a surfactant, a preservative, an antioxidant, etc., are added to a vegetable or animal oil or fat, a mineral oil, a synthetic oil or a mixture thereof or water, and the mixture is used as such or in the form of a 1 to 30% emulsion or an aqueous solution. In recent years, with an increase in the size of various working machines, an increase in the precision and the hardness of metal materials, an increase in the speed and pressure in working conditions, an increase in the precision of a finished surface, etc., the working conditions have become more and more severe, so that the conventional lubricants for metallurgy have become impossible to cope with the use under severe conditions. For this reason, the addition of chlorine- and sulfur-containing extreme-pressure agents has become indispensable. 
     In recent years, however, a fear for the toxicity and carcinogenicity of the organochlorine compounds has remarkably increased. Further, a non-chlorinated lubricant has become thought to be desired also from the viewpoint of a rise in the environmental pollution problem. 
     Since, however, non-chlorinated lubricants which have been developed and are currently in the market (for example, JIS W No. 1, first class and JIS W No. 2, second class) are free from an extreme-pressure agent, they are unsatisfactory for use in plastic working such as high-speed and heavy cutting and drawing. Japanese Patent Laid-Open No. 181896/1986 discloses a water-soluble cutting oil containing polysulfide, and Japanese Patent Laid-Open Nos. 149997/1983 and 139791/1985 disclose a water-soluble cutting oil containing an amine salt or an alkali metal salt of a monoester, such as an adduct of a dicarboxylic acid represented by the following general formula (I) with polyoxypropylene glycol, polyoxyethylene glycol, polyoxypropylene or the like. ##STR2## wherein R 1  stands for COOH or H; and R 2  stands for H when R 1  is COOH, and COOH when R 1  is H. These water-soluble cutting oils, however, are not yet satisfactory for use in high-speed and heavy cutting from the viewpoint of the precision and service life of the tool. 
     Examples of the non-chlorinated lubricating additive known in the art include a product of a reaction of an organic amine with an organic phosphoric ester or an organic phosphorous ester (see U.S. Pat. No. 3,553,131) and a product of a reaction of a dihydrocarbyl phosphite having 1 to 6 carbon atoms with an alkoxyamine or a vicinal diol or a product of a reaction of the dihydrocarbyl phosphite with a boron compound (diboron trioxide, boric acid, metaborate, alkyl borate or the like) (see U.S. Pat. Nos. 4,529,528, 4,557,845, 4,555,353, 4,532,057, and 4,522,629). They, however, lack in the extreme-pressure property for use as an additive of a lubricant for metallurgy. Japanese Patent Laid-Open No. 308495/1989 discloses a product of a reaction of an alkoxylated amine with an organic phosphite, a product of a reaction of an alkoxylated amine with an organic phosphite and a boron-containing compound (diboron trioxide, metaborate or an organic boron compound), etc. These reaction products, however, are not yet satisfactory in the improvement of the effect, and a further improvement has been desired in the art. 
     SUMMARY OF THE INVENTION 
     Under the above-described circumstances, the present inventors have made extensive and intensive studies with a view to providing a lubricant for metal working which is excellent in the cutting property, grinding property and plastic working property as well as in the putrefaction resistance, deterioration resistance and anti-foaming property and, as a result, have found that a lubricant for metal working comprising a dicarboxylic acid represented by the following general formula (I) or its amine salt or its alkali metal salt and a sulfur extreme pressure agent can attain the above-described object: ##STR3## wherein R 1  stands for COOH or H; and R 2  stands for H when R 1  is COOH, and COOH when R 1  is H. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The dicarboxylic acid represented by the general formula (I) or its alkali metal salt or its amine salt can be added to a mineral oil or/and a synthetic oil together with a sulfur extreme-pressure agent, an oiliness improver, a rust preventive, etc., and the resultant mixture can be used as a water-insoluble lubricant for metal working. Alternatively, it can be added to water or a mineral oil or/and a synthetic oil together with a sulfur extreme-pressure agent, a surfactant, a rust preventive, a preservative, etc., and a lubricant composition for metal working of an emulsion type or a soluble type is prepared from the resultant mixture by the conventional means. In this case, a useful proportion of addition of the compound is properly selected according to the kind of the additives used in combination with the compound, the purpose of use of the lubricant and the condition of use of the lubricant. 
     Examples of the alkali metal in the alkali metal salt or amine salt of the dicarboxylic acid represented by the general formula (I) include lithium, sodium and potassium, and sodium or potassium is preferred from the practical viewpoint. Various amine compounds which have been used as an amine salt in a water-soluble cutting lubricant can be used as an amine for forming the amine salt. Examples of the amine compound include alkylamines such as tributylamine, 2-ethylhexylamine, stearylamine, dimethylstearylamine, ethylene oxide adducts of these alkylamines, alkanolamines such as diethanolamine, triethanolamine and diisopropanolamine, dicyclohexylamine, morpholine and N-aminopropylmorpholine, and alkanolamines are particularly useful. 
     The alkali metal salt or amine salt of the dicarboxylic acid represented by the general formula (I) can be easily produced by adding to the dicarboxylic acid an alkali metal hydroxide or an amine in slight excess of the neutralization equivalent and is preferred also from the viewpoint of the rust preventing property and deterioration resistance. 
     The amount of incorporation of the dicarboxylic acid represented by the general formula (I) or its alkali metal salt or its amine salt is preferably 1 to 40% by weight, still preferably 3 to 35% by weight. 
     Examples of the sulfur extreme-pressure agent used in the present invention include vulcanized oils and fats (vulcanized rapeseed oil, vulcanized lard, vulcanized synthetic sperm oil, etc.), polysulfides (an ester of dibenzyl monosulfide, dibenzyl disulfide, dibenzyl octasulfide, di-tert-dodecyl polysulfide, di-tert-nonyl polysulfide, dihexadecyl polysulfide or diethanol disulfide with a fatty acid, etc.) and thiocarbonates (a glycol ester of xanthogen disulfide, xanthogen tetrasulfide or xanthic acid), and polysulfides, that is, di-tert-dodecyl polysulfide, di-tert-nonyl polysulfide, etc., are preferred. 
     The amount of incorporation of the above-described sulfur extreme pressure agent is preferably 1 to 30% by weight, still preferably 5 to 20% by weight. 
     Examples of the mineral oil used in the present invention include refined mineral oils, such as machine oil and turbine oil, and examples of the synthetic oil include synthetic hydrocarbon oils such as poly-α-olefin oil and polypentadiene oil, ester oils such as a fatty acid pentaerythritol ester and dioctyl sebacate and polyether polyol. 
     Examples of the rust preventive used in the present invention include a calcium salt of a petroleum sulfonic acid, a barium salt of a petroleum sulfonic acid, a sodium salt of a petroleum sulfonic acid, sorbitan monooleate, lanolin, a calcium salt of oxidized wax, a barium salt of oxidized wax, a sodium salt of oxidized wax, an alkoxyphenylamine, dicyclohexylamine, pentaerythritol monoester, an alkanolamine, an alkylimidazoline, oleylsarcosine, and oleylamine oleate. 
     Examples of the surfactant used in the present invention include a potassium soap of a petroleum sulfonic acid, a sodium soap of a petroleum sulfonic acid, an alkylsulfamide carboxylate, octylphenol ethoxylate, nonylphenol ethoxylate, a C 12-18  alcohol ethoxylate and 2:1 diethanolamine fatty acid amide. 
    
    
     The present invention will now be described in more detail with reference to the following Examples and Comparative Examples. It, however, is not limited to these Examples only. 
     EXAMPLE 1 
     Water-insoluble cutting oils respectively having compositions specified in the following Table 1 were prepared and subjected to a load wear index (LWI) (ASTM D-2783) test through the use of a shell type high-speed four-ball tester. The results are given in Table 1. 
     The amount of addition in the table is part by weight unless otherwise specified. 
     
                       TABLE 1______________________________________        Comp. Ex.  Ex.        1-1  1-2    1-3    1-1  1-2  1-3______________________________________mineral oil    90     90     90   90   90   90rapeseed oil   3      3      3    3    3    3TEA salt of DA-1550 *1       7    3    3    3chlorinated paraffin          7      3(Cl: 45%)di-tert-nonyl trisulfide                 4           4di-tert-dodecyl trisulfide             4di-tert-dodecyl tetrasulfide                4pressure resistance (lb)          22.0   23.0   18.5 26.5 26.0 26.5______________________________________ Note) ##STR4## manufactured by Harima Chemicals, Inc. 
    
     EXAMPLE 2 
     Emulsion type grinding and cutting oils respectively having compositions specified in the following Tables 3 (a), (b) and (c) were produced and subjected to measurement of the coefficient of friction at 25° C. through the use of a Model N2 Soda pendulum oiliness tester, and a putrid smell after standing for 7 days. Further, a rust preventive property was measured by a method which comprises immersing a dry cutting chip of a casting in emulsion type cutting oils respectively having compositions specified in Tables 3 (a), (b) and (c) for 24 hr, removing the cutting oils, placing the chip in a Petri dish and observing the state of occurrence of rust 72 hr after the placement. A cutting test was conducted by measuring the number of holes necessary for the torque value to become 10 kw in a drill press. The cutting conditions are specified in Table 2, and the test results are given in Tables 3 (a), (b) and (c). 
     
                       TABLE 2______________________________________machine       HDP-500tool          carbide drill (16 mmφ)material of workpiece         SS41plate thickness         35 mmcutting speed number of revolutions:                          850 rpm         feed:            0.28______________________________________ 
    
     
                       TABLE 3(a)______________________________________              Comp. Ex.              2-1   2-2     2-3______________________________________mineral oil          67.5    67.5    70.5Na petroleum sulfonate                5       5       5nonylphenol surfactant                8       8       8preservative         0.5     0.5     0.5triethanolamine      6       6       6oleic acid           3       3DA-1550                              10Na salt of DA-1550chlorinated-paraffin (Cl: 45%)                        5product of reaction of amine                10with phosphiteand boric acid*.sup.1vulcanized synthetic sperm oil                        5di-tert-nonyl trisulfidedi-tert-nonyl tetrasulfidedi-tert-dodecyl trisulfidedi-tert-dodecyl pentasulfide10% emulsion of the above compositioncoefficient of friction (μ)                0.14    0.13    0.12putrid smell after 7 days                slight  slight  freerust preventive property                Δ x       ∘surface tension (dyne/cm)                40      40      37tool life (number of holes)                70      90      60______________________________________ Note) *.sup.1 a product of a reaction of equimolar amounts of bis(2hydroxypropyl)tallowamine, di(2ethylhexyl)phosphite and boric acid. 
    
     
                       TABLE 3(b)______________________________________              Ex.              2-1   2-2     2-3______________________________________mineral oil          70.5    70.5    70.5Na petroleum sulfonate                5       5       5nonylphenol surfactant                8       8       8preservative         0.5     0.5     0.5triethanolamine      6       6       6oleic acidDA-1550              5       5       5Na salt of DA-1550chlorinated paraffin (Cl: 45%)product of reaction of aminewith phosphite and boric acid*.sup.1vulcanized synthetic sperm oil                5di-tert-nonyl trisulfide     5di-tert-nonyl tetrasulfide           5di-tert-dodecyl trisulfidedi-tert-dodecyl pentasulfide10% emulsion of the above compositioncoefficient of friction (μ)                0.12    0.12    0.12putrid smell after 7 days                free    free    freerust preventive property                ∘                        ∘                                ∘surface tension (dyne/cm)                39      40      39tool life (number of holes)                300 or  300 or  300 or                more    more    more______________________________________ Note) *.sup.1 a product of a reaction of equimolar amounts of bis(2hydroxypropyl)tallowamine, di(2ethylhexyl)phosphite and boric acid. 
    
     
                       TABLE 3(c)______________________________________          Ex.          2-4   2-5     2-6     2-7______________________________________mineral oil      70.5    70.5    70.5  70.5Na petroleum sulfonate            5       5       5     5nonylphenol surfactant            8       8       8     8preservative     0.5     0.5     0.5   0.5triethanolamine  6       6       6     6oleic acidDA-1550          5       5Na salt of DA-1550               5     5chlorinated paraffin (Cl: 45%)product of reaction of aminewith phosphite and boric acid*.sup.1vulcanized synthetic sperm oil   5di-tert-nonyl trisulfidedi-tert-nonyl tetrasulfidedi-tert-dodecyl trisulfide            5                     5di-tert-dodecyl pentasulfide                    510% emulsion of theabove compositioncoefficient of friction (μ)            0.12    0.12    0.12  0.12putrid smell after 7 days            free    free    free  freerust preventive property            ∘                    ∘                            ∘                                  ∘surface tension (dyne/cm)            40      40      38    38tool life (number of holes)            300 or  300 or  300 or                                  300 or            more    more    more  more______________________________________ Note) *.sup.1 a product of a reaction of equimolar amounts of bis(2hydroxypropyl)tallowamine, di(2ethylhexyl)phosphite and boric acid. 
    
     EXAMPLE 3 
     Soluble type cutting oils respectively having compositions specified in the following Tables 4 were produced and subjected to measurement of the coefficient of friction at 25° C. through the use of a Model N2 Soda pendulum oiliness tester and a cutting test in the same manner as that of the Example 2. The results are given in Table 4. 
     In Table 4, DIPA salt represents a diisopropanolamine salt, and TEA salt represents a triethanolamine salt. 
     
                       TABLE 4______________________________________     Comp. Ex.  Ex.     3-1  3-2    3-3    3-1   3-2   3-3______________________________________Na petroleum       5      5      5    5     5     5sulfonateTEA salt of 30            30ricinolic acidTEA salt of        30polyoxypropyleneglycol monoesterof DA-1550nonylphenolsurfactantNa salt of DA-1550             30DIPA salt of                         30DA-1550TEA salt of                                30DA-1550chlorinated paraffin       10     10(Cl: 45%)di-tert-nonyl                  10    10    10trisulfidedi-tert-nonyltetrasulfideproduct of reaction       10of amine withphosphiteand boric acidcaprylic acid       4.5    4.5    4.5  4.5   4.5   4.5preservative       0.5    0.5    0.5  0.5   0.5   0.5water       50     50     50   50    50    5010% emulsion of theabove compositioncoefficient of       0.15   0.18   0.13 0.12  0.12  0.12friction (μ)tool life   70     80     90   150   180   170(number of holes)______________________________________ 
    
     As exemplified above, it is possible to provide a non-chlorinated lubricant for metal working having an excellent cutting property, no odor and excellent putrefaction and deterioration resistances through the use of a dicarboxylic acid or its amine salt or its alkali metal salt and a sulfur extreme-pressure agent.