JP5313483B2 - Worm gear oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a worm gear oil composition having excellent transmission efficiency and having little adverse influence to rubbers and coatings used in oil seal and the like. <P>SOLUTION: The worm gear oil composition for worm gear units consisting of a high tensile brass wheel and a steel worm comprises (A) at least one species base oil selected from (a) polyolefin-based base oils, (b) mineral oils and (c) alkyl group-substituted aromatic base oils and (B) a partial ester compound comprising a fatty acid and an aliphatic polyhydric alcohol having a 6-30C hydrocarbon group, wherein the content of the component (A) is 60-94 mass% and the content of the component (B) is 6-40 mass% based on the total weight of the composition. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a worm gear oil composition, and more particularly to a worm gear oil composition having high transmission efficiency and less adverse effects on rubber and paint.

  A worm gear unit (in this specification, “worm gear unit” refers to a power transmission device including a wheel and a worm. “Worm gear oil composition” refers to a lubricating oil composition used in the worm gear unit). Since it has a special structure and a power transmission mechanism and is characterized by a large reduction ratio and a small noise generation, it is widely used in industrial machines. However, since the transmission efficiency (transmission efficiency = output work / input work × 100) has been conventionally lower than the transmission efficiency of other transmission devices, improvement thereof has been desired. As a method for improving the transmission efficiency, the improvement of the worm gear unit itself such as the design, the material, and the rotation speed, and the development of a high-performance lubricating oil composition can be mentioned.

  By the way, in the worm gear unit, since the sliding speed is high and the contact pressure is also high, the lubrication conditions are severe, and the desired performance is often not obtained even if the normal gear oil composition is applied as it is. Therefore, it is necessary to specially develop the lubricating oil composition in consideration of the structure and frictional characteristics of the worm gear unit.

  So far, lubricating oil compositions based on polyalkylene glycol (hereinafter sometimes abbreviated as PAG) are known as lubricating oil compositions with high transmission efficiency for worm gear units. However, it has an effect on organic materials such as rubber used in oil seals and the like, and in particular, since the paint responsible for rust prevention of the machine is peeled off, there is a problem of causing rust and failure.

  Therefore, a worm gear oil composition that avoids this problem by using a base oil other than PAG has been developed. Patent Document 1 describes a worm gear oil composition in which a poly-α-olefin and an alkyl group-substituted aromatic compound are used as a base oil and an organic molybdenum compound is blended. It is mentioned that the efficiency is also good. Furthermore, the above document points out the compatibility between the lubricant and the worm and wheel materials, and aims to provide a worm gear oil composition suitable for a worm gear unit of a specific material (a copper-based alloy containing aluminum, silicon, and manganese). It is said.

  However, the worm gear oil composition containing the poly α-olefin, the alkyl group-substituted aromatic compound and the organomolybdenum compound is composed of a high-strength brass wheel and a steel worm as compared with a lubricating oil based on PAG. Since the worm gear unit is still inferior in transmission efficiency, there is a need for a worm gear oil composition that can achieve high transmission efficiency even in this worm gear unit. Further, since molybdenum is a rare metal and also a PRTR target substance, the development of a new worm gear oil composition is important from the viewpoint of the development of alternatives.

JP 9-316476 A

  The present invention has been made under such circumstances, and has an excellent transmission efficiency without using an organic molybdenum compound as an essential component, and has a low adverse effect on rubbers and paints used in oil seals and the like. The purpose is to provide goods.

  The present inventors diligently studied to achieve the above object, and paid attention to the special structure and friction state of the worm gear unit. In other words, because of the special structure and power transmission mechanism of the worm gear unit, the friction state is a complicated state where boundary lubrication and fluid lubrication are mixed, and the temperature can be as high as 180 ° C. or more depending on the oil agent selection and load conditions. . Under this high temperature condition, it is considered that a further load is applied to the tooth surface due to thermal expansion of the worm and the wheel, and adsorption, desorption, reaction film formation, etc. of the additive are also considered to be affected by the temperature.

  Conventionally, the reduction of the friction coefficient has been proposed as a means for improving the transmission efficiency of the worm gear unit, and the inventors of the present invention do not necessarily reduce the friction coefficient under the special conditions as described above. In addition, the present inventors have found that a worm gear oil composition containing a specific ester compound is effective in improving the transmission efficiency of the worm gear unit. The present invention has been completed based on such findings. That is, the present invention comprises (A) (a) a polyolefin base oil, (b) a mineral oil, and (c) at least one base oil selected from alkyl group-substituted aromatic base oils, and (B) the number of carbon atoms. A partial ester compound comprising a fatty acid having 6 to 30 hydrocarbon groups and an aliphatic polyhydric alcohol is included, the content of the component (A) is 60 to 94% by mass relative to the total amount of the composition, The present invention provides a worm gear oil composition for a worm gear unit comprising a high-strength brass wheel and a steel worm characterized by being 6 to 40% by mass.

  ADVANTAGE OF THE INVENTION According to this invention, the worm gear oil composition which has the outstanding transmission efficiency and has few bad influences on the rubber | gum and coating material which are used by an oil seal etc. is provided.

  The worm gear oil composition of the present invention comprises (A) a specific base oil and (B) a specific ester compound, and is used for a worm gear unit having a high-strength brass wheel and a steel worm.

  The (A) base oil used in the present invention comprises one or more base oils selected from (a) a polyolefin base oil, (b) a mineral oil, and (c) an alkyl group-substituted aromatic base oil.

The (A) base oil used in the present invention preferably has a viscosity index of 90 or more, more preferably 140 or more, from the viewpoint of oil film thickness during operation at high temperature, that is, oil film strength. A base oil having a viscosity index of 90 or more has a small viscosity change due to a temperature change, and a stable performance can be obtained even when used in a worm gear unit having a large temperature change. (A) As for the viscosity of a base oil, kinematic viscosity in 40 degreeC becomes like this. Preferably it is 20-50000 mm < ² > / s, Most preferably, it is 40-10000 mm < ² > / s. When the viscosity is less than 20 mm ² / s, the oil film thickness becomes too small, and when it exceeds 50000 mm ² / s, the viscosity of the composition becomes too high, and the viscosity may decrease due to mechanical or thermal shearing. is there. (A) The aniline point of the base oil is preferably 100 ° C or higher. If an aniline point is 100 degreeC or more, corrosion of organic materials, such as a coating material and rubber | gum, will be suppressed.

  Examples of the (a) polyolefin base oil used in the present invention include α-olefin homopolymers or copolymers, polybutenes or hydrides thereof, and carbons such as decene oligomers in terms of high viscosity index. Preferred are α-olefin oligomers of several 6 to 14, ethylene α-olefin copolymers such as ethylene-propylene copolymer, polybutene or hydrides thereof. These (a) polyolefin base oils may be used individually by 1 type, and may be used in combination of 2 or more type. In view of improving the viscosity index, the content of the component (a) with respect to the component (A) is preferably 50% by mass or more, more preferably 60% by mass or more.

  As the mineral oil (b) used in the present invention, for example, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil is subjected to solvent removal, solvent extraction, and hydrogenation. Mineral oil refined by carrying out one or more treatments such as decomposition, solvent dewaxing, catalytic dewaxing, hydrorefining, etc., or mineral oil produced by isomerizing wax, GTL WAX, and the like. These (b) mineral oils may be used individually by 1 type, and may be used in combination of 2 or more types.

Examples of the (c) alkyl group-substituted aromatic base oil used in the present invention include alkylbenzene and alkylnaphthalene. The addition of the component (c) has the effect of improving oxidation stability and preventing sludge generation. As the component (c), those having a viscosity index of 100 or less from the viewpoint of sludge solubility and the like are preferably used. Moreover, the thing whose viscosity in 40 degreeC is 20-200 mm < ² > / s can also be used preferably. When the viscosity is less than 20 mm ² / s, the oil film strength at high temperature operation is insufficient or the evaporation loss increases, and when it exceeds 200 mm ² / s, the solubility of sludge generated by oxidative degradation is reduced. There is. For these reasons, the above range is more preferably ²⁰ to 100 mm ² / s. These (c) alkyl group-substituted aromatic base oils may be used alone or in combination of two or more.

  As the alkylbenzene, an alkylbenzene substituted with a branched alkyl group can be preferably used. Examples of such branched alkyl groups include olefin groups obtained by polymerizing ethylene, propylene, and butylene. As the alkyl group of the alkylbenzene, those having 8 to 30, preferably 10 to 20 carbon atoms can be used. When this value is smaller than the above range, the viscosity becomes low and the oil film strength is insufficient, and when it is larger than the above range, the solubility of sludge generated by oxidative deterioration may be insufficient.

  As the alkyl naphthalene, a reaction product of an α-olefin and naphthalene can be preferably used. Here, as the α-olefin, those having 10 to 30 carbon atoms, specifically, tetradecene, hexadecene, octadecene, eicosene and the like can be used.

  The fatty acid partial ester compound (B) of the present invention is a partial ester obtained by a reaction between a fatty acid having a hydrocarbon group having 6 to 30 carbon atoms and an aliphatic polyhydric alcohol. The hydrocarbon group preferably has 8 to 28 carbon atoms, particularly preferably 16 to 24 carbon atoms.

  The hydrocarbon group having 6 to 30 carbon atoms includes a linear or branched hydrocarbon group, for example, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group. Group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, penticosyl group, docosyl group, tricosyl group, tetracosyl group, pentacosyl group, hexacosyl group, heptacosyl group, octacosyl group, nonacosyl group and Alkyl groups such as triacontyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, nonadecenyl group Two or more alkenyl groups, such as a ru group, an icosenyl group, a henicosenyl group, a dococenyl group, a tricocenyl group, a tetracocenyl group, a pentacocenyl group, a hexacocenyl group, a heptacocenyl group, an octacocenyl group, a nonacosenyl group, and a triaconenyl group. The hydrocarbon group etc. which it has can be mentioned. In addition, the hydrocarbon group having two or more alkyl groups, alkenyl groups, and double bonds includes all possible linear structures and branched structures, and includes two alkenyl groups and two double bonds. The position of the double bond in the hydrocarbon group having the above is arbitrary.

  Examples of the fatty acid having a hydrocarbon group having 6 to 30 carbon atoms include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, arachidic acid, behenic acid, and lignoceric acid And saturated fatty acids such as myristoleic acid, palmitoleic acid, oleic acid, and linolenic acid. From the viewpoint of transmission efficiency, it is preferable to use a fatty acid having 18 carbon atoms such as oleic acid or isostearic acid, and from the viewpoint of oxidation stability, it is preferable to use isostearic acid alone. In the reaction between the fatty acid having a hydrocarbon group having 6 to 30 carbon atoms and the aliphatic polyhydric alcohol, one kind may be used alone, or two or more kinds may be used in combination.

  Specific examples of the aliphatic polyhydric alcohol include ethylene glycol, glycerin, glycerin condensates (glycerin 2-6 mer, such as diglycerin, triglycerin, tetraglycerin), trimethylol alkane (for example, trimethylol). Ethane, trimethylolpropane, trimethylolbutane) and their dimer to tetramer, pentaerythritol, dipentaerythritol, 1,2,4-butanetriol, 1,3,5-butanetriol, 1,2,6- Polyhydric alcohols such as hexanetriol, 1,2,3,4-butanetetraol, sorbitol, sorbitan, sorbitol glycerin condensate, adonitol, arabitol, xylitol, dulcitol, allitol; xylose, arabinose, ribose, rhamnose, Glucose, may be mentioned fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sugars such as sucrose. Among the above, glycerin, glycerin condensate, sorbitan, trimethylolpropane, and pentaerythritol are preferable.

  The hydroxyl value of the fatty acid partial ester compound (B) of the present invention is preferably 7.5 to 500 mgKOH / g, more preferably 10 to 300 mgKOH / g. If the hydroxyl value of the fatty acid partial ester compound (B) is less than 7.5 mg, the transmission efficiency tends to decrease, and if it exceeds 500 mg, it tends to be a problem in terms of solubility in the base oil.

  Examples of fatty acid partial ester compounds (B) include glycerin isostearate, glycerin diisostearate and the like, partial esters of trimethylolpropane and isostearic acid, partial esters of trimethylolpropane and oleic acid, trimethylolpropane and isostearic acid, and olein Examples include partial esters of acids, partial esters of pentaerythritol and oleic acid.

  The fatty acid partial ester compound (B) of the present invention may be used alone or in combination of two or more. By using two or more fatty acid partial ester compounds in combination, it is possible to balance the transmission efficiency and the solubility. The fatty acid partial ester compound (B) is contained in an amount of 6 to 40% by mass, preferably 8 to 30% by mass, based on the total amount of the composition. When it is less than 6% by mass, sufficient transmission efficiency cannot be obtained, and when it exceeds 40% by mass, rubber compatibility is deteriorated.

  The hydroxyl value of the worm gear oil composition of the present invention is preferably 3 to 30 mgKOH / g, more preferably 3.5 to 27 mgKOH / g. When the hydroxyl value is less than 3 mgKOH / g, the transmission efficiency is deteriorated. When the hydroxyl value is more than 30 mgKOH / g, the solubility of the fatty acid partial ester compound (B) is generally low, so that the blending adjustment becomes difficult.

  In the lubricating oil composition of the present invention, other additives such as a viscosity index improver, a pour point depressant, a metal detergent, and an ashless dispersion are added as necessary, as long as the object of the present invention is not impaired. Agents, antioxidants, antiwear agents or extreme pressure agents, other friction reducing agents, rust inhibitors, surfactants or demulsifiers, metal deactivators, antifoaming agents, colorants, and the like can be appropriately blended. .

As the viscosity index improver, for example, polymethacrylate, dispersed polymethacrylate, olefin copolymer (for example, ethylene-propylene copolymer), dispersed olefin copolymer, styrene copolymer (for example, Styrene-diene copolymer, styrene-isoprene copolymer, etc.).
The blending amount of these viscosity index improvers is usually about 0.1 to 15% by mass, preferably 1 to 10% by mass based on the total amount of the worm gear oil composition from the viewpoint of the blending effect.

  Examples of the pour point depressant include polymethacrylate having a weight average molecular weight of about 5000 to 50,000.

  As the metallic detergent, any alkaline earth metal detergent used in lubricating oils can be used, for example, alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates, and the like. And a mixture of two or more selected from the above. Alkaline earth metal sulfonates include alkaline earth metal salts of alkyl aromatic sulfonic acids obtained by sulfonated alkyl aromatic compounds having a molecular weight of 300 to 1,500, preferably 400 to 700, particularly magnesium salts and / or Or a calcium salt etc. are mentioned, A calcium salt is used preferably especially. Alkaline earth metal phenates include alkylphenols, alkylphenol sulfides, alkaline earth metal salts of Mannich reactants of alkylphenols, especially magnesium salts and / or calcium salts, among which calcium salts are particularly preferred. Examples of the alkaline earth metal salicylate include alkaline earth metal salts of alkyl salicylic acid, particularly magnesium salts and / or calcium salts, among which calcium salts are preferably used. The alkyl group constituting the alkaline earth metal detergent is preferably an alkyl group having 4 to 30 carbon atoms, more preferably a linear or branched alkyl group having 6 to 18 carbon atoms, which are linear or branched. But you can. These may also be primary alkyl groups, secondary alkyl groups or tertiary alkyl groups. Further, as the alkaline earth metal sulfonate, alkaline earth metal phenate and alkaline earth metal salicylate, the above alkyl aromatic sulfonic acid, alkylphenol, alkylphenol sulfide, Mannich reaction product of alkylphenol, alkylsalicylic acid, etc. are directly used as magnesium and / or Or it reacts with alkaline earth metal bases such as calcium alkaline earth metal oxides and hydroxides, or once is converted to an alkali metal salt such as sodium salt or potassium salt and then substituted with alkaline earth metal salt, etc. As well as neutral alkaline earth metal sulfonates, neutral alkaline earth metal phenates and neutral alkaline earth metal salicylates, neutral alkaline earth metal sulfonates, neutral alkaline earth metal phenates and neutral Basic alkaline earth metal sulfonates, basic alkaline earth metal phenates and basic alkalis obtained by heating potash earth metal salicylates and excess alkaline earth metal salts or alkaline earth metal bases in the presence of water Earth metal salicylate or neutral alkaline earth metal sulfonate, neutral alkaline earth metal phenate and neutral alkaline earth metal salicylate in the presence of carbon dioxide react with carbonate or borate of alkaline earth metal Also included are overbased alkaline earth metal sulfonates, overbased alkaline earth metal phenates and overbased alkaline earth metal salicylates obtained by this.

  In the present invention, the content of the metallic detergent is usually 1% by mass or less, preferably 0.5% by mass or less in terms of metal element, and further 1.0% by mass of sulfated ash in the composition. In order to reduce it below, it is preferable to set it as 0.3 mass% or less. Further, the content of the metallic detergent is 0.005% by mass or more, preferably 0.01% by mass or more, in terms of metal element, and it has better oxidation stability, base number maintenance, and high temperature cleanability. In order to increase the amount, it is more preferably 0.05% by mass or more, and in particular, 0.1% by mass or more can provide a composition capable of maintaining the base number and the high temperature cleanliness for a long period of time. preferable. The sulfated ash referred to here is JIS K 2272 5. The value measured by the method prescribed in “Method for testing sulfated ash” is mainly due to the metal-containing additive.

  Examples of the antioxidant include phenolic antioxidants and amine antioxidants. Examples of the phenolic antioxidant include 4,4′-methylenebis (2,6-di-t-butylphenol); 4,4′-bis (2,6-di-t-butylphenol); 4,4′- Bis (2-methyl-6-tert-butylphenol); 2,2′-methylenebis (4-ethyl-6-tert-butylphenol); 2,2′-methylenebis (4-methyl-6-tert-butylphenol); 4 4,4′-butylidenebis (3-methyl-6-tert-butylphenol); 4,4′-isopropylidenebis (2,6-di-tert-butylphenol); 2,2′-methylenebis (4-methyl-6- Nonylphenol); 2,2′-isobutylidenebis (4,6-dimethylphenol); 2,2′-methylenebis (4-methyl-6-cyclohexylphenol); 2,6-di t-butyl-4-methylphenol; 2,6-di-t-butyl-4-ethylphenol; 2,4-dimethyl-6-t-butylphenol; 2,6-di-t-amyl-p-cresol; 2,6-di-t-butyl-4- (N, N′-dimethylaminomethylphenol); 4,4′-thiobis (2-methyl-6-tert-butylphenol); 4,4′-thiobis (3 -Methyl-6-t-butylphenol); 2,2'-thiobis (4-methyl-6-t-butylphenol); bis (3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide; bis (3 , 5-di-t-butyl-4-hydroxybenzyl) sulfide; n-octadecyl-3- (4-hydroxy-3,5-di-t-butylphenyl) propionate; 2,2′-thio [diethyl] - bis-3- (3,5-di -t- butyl-4-hydroxyphenyl) propionate] and the like. Among these, bisphenol-based and ester group-containing phenol-based ones are particularly preferable.

  Examples of the amine antioxidant include monooctyl diphenylamine; monoalkyl diphenylamines such as monononyl diphenylamine; 4,4′-dibutyldiphenylamine; 4,4′-dipentyldiphenylamine; 4,4′-dihexyldiphenylamine; 4,4′-diheptyldiphenylamine; 4,4′-dioctyldiphenylamine; dialkyldiphenylamines such as 4,4′-dinonyldiphenylamine; tetrabutyldiphenylamine; tetrahexyldiphenylamine; tetraoctyldiphenylamine; polyalkyldiphenylamine such as tetranonyldiphenylamine And naphthylamine-based, specifically α-naphthylamine; phenyl-α-naphthylamine; further butylphenyl-α- Fuchiruamin; pentylphenyl -α- naphthylamine; hexylphenyl -α- naphthylamine; heptylphenyl -α- naphthylamine; octylphenyl -α- naphthylamine; and alkyl-substituted phenyl -α- naphthylamine, such as nonylphenyl -α- naphthylamine. Of these, dialkyldiphenylamine type and naphthylamine type are preferable.

  Antiwear or extreme pressure agents include: organic molybdenum compounds such as zinc dithiophosphate, zinc dithiocarbamate, molybdenum dithiophosphate, disulfides, sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, thiocarbamates Sulfur-containing compounds such as phosphites; phosphorous esters, phosphate esters, phosphonate esters, and phosphorus-containing compounds such as amine salts or metal salts thereof; thiophosphite esters, thiophosphate esters, thiophosphonic acid Examples include esters and sulfur and phosphorus containing antiwear agents such as amine salts or metal salts thereof.

  As the friction reducing agent other than the fatty acid partial ester compound (B), any compound usually used as a friction reducing agent for lubricating oil can be used. For example, ester compounds other than the fatty acid partial ester compound (B) And ashless friction reducing agents such as fatty acids, aliphatic alcohols, aliphatic ethers and aliphatic amines having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms in the molecule.

  Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, barium sulfonate, dinonylnaphthalene sulfonate, alkenyl succinate, polyhydric alcohol ester and the like. The blending amount of these rust preventives is usually about 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, based on the total amount of the worm gear oil composition, from the viewpoint of the blending effect.

Examples of the surfactant or demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether and polyoxyethylene alkyl naphthyl ether.
Examples of the metal deactivator include 1,2,3-benzotriazole, N-alkylated benzotriazole, 1- [N, N-bis (2- (ethylhexyl) aminomethyl] methylbenzotriazole, N, N Examples include '-disalicylidene-1,2-propanediamine.

Examples of the antifoaming agent include silicone oil, fluorosilicone oil, fluoroalkyl ether, and polyacrylate. From the viewpoint of balance between the antifoaming effect and economy, 0.0001 to 0 based on the total amount of the worm gear oil composition. About 2% by mass is preferable.
Examples of the colorant include azobenzel-4-azo-2-naphthol, 1,4-di (isopropylamino) anthraquinone, 2,5-bis (5′-t-butylbenzoxalyl-2 ′) thiophene, and the like. It is done.

  The worm gear oil composition of the present invention is used for a worm gear unit having a high-strength brass wheel and a steel worm. Further, it is suitably used in a worm gear unit having a cylindrical worm, having a reduction ratio of 1/10 to 1/60 and a torque of 5 to 6000 N · m. The worm gear unit is suitably used in various industrial machines, escalators, moving walkways, unloading cranes, sail driving devices, and the like.

  Examples The present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. The base oil and additives used for the synthesis of the worm gear oil composition are shown below.

(Base oil)
Base oil 1: Lucant HC-600 [Mitsui Petrochemical Co., Ltd. ethylene α-olefin copolymer, 40 ° C. kinematic viscosity 9850 mm ² / s]
Base oil 2: 1-decene polymer hydrogenated [Idemitsu Kosan Co., Ltd., 40 ° C. kinematic viscosity 46.00 mm ² / s]

(Fatty acid ester)
Fatty acid esters 1 to 4 were synthesized using the fatty acids and polyhydric alcohols shown in Table 1. Their properties are shown in Table 2. Each test was performed based on the following test method.
Acid value: JIS K2501
Saponification value: JIS K2503
Hydroxyl value: JIS K0070
Iodine value: JIS K0070
40 ° C kinematic viscosity: JIS K2283

Commercially available ester compounds used in addition to the esters 1 to 4 are shown below.
Ester 5: Leodol MO-50 [Oleic acid monoglyceride manufactured by Kao Corporation; hydroxyl value 222 mgKOH / g, acid value 0.07 mgKOH / g, saponification value 170 mgKOH / g]
Ester 6: Decaglyn 5-ISV [Decaglyceryl pentaisostearate manufactured by Nikko Chemicals; hydroxyl value 177 mgKOH / g, acid value 2.43 mgKOH / g, saponification value 134 mgKOH / g]

(Other additives)
Extreme pressure agent 1: 0,0,0-triphenyl phosphorothioate Extreme pressure agent 2: Molybdenum dialkyldithiophosphate ester antioxidant 1: Monobutylphenyl monooctylphenylamine antioxidant 2: N- (p-tert-octylphenyl) ) -1-Naphtylamine metal deactivator: N-alkylated benzotriazole rust inhibitor: oxyalkylcarboxylate defoamer: dimethylpolysiloxane

  Using the above base oils and additives, worm gear oil compositions of Examples 1 to 9 and Comparative Examples 1 and 2 were prepared with the compositions and blending amounts shown in Table 3. In addition, the compounding quantity was represented by the mass part.

A commercially available lubricating oil composition used in addition to the above worm gear oil composition is shown below.
Comparative Example 3: Commercial product 1 (polyalkylene glycol-based lubricant)
Comparative Example 4: Commercially available product 2 (poly α-olefin-based lubricating oil)
Comparative Example 5: Commercial product 3 (poly α-olefin + alkylbenzene + organic molybdenum (Mo: 1900 ppm) -containing lubricating oil)

  The following tests and measurements were performed using the above lubricating oil composition. The results are shown in Table 4.

(Measurement method of actual machine transmission efficiency)
As shown below, EW100B30R (manufactured by Tsubaki Emerson, having a high-strength brass wheel and a steel worm) was used, and the actual machine transmission efficiency was measured in an environmental test chamber at a temperature of 25 ° C. ± 3 ° C.
After performing the familiar operation using the designated oil (hereinafter referred to as recommended oil) (Mobile SHC632) in the instruction manual, the recommended oil is replaced with the lubricating oil (1.5 L) for the above-mentioned examples and comparative examples. Flushing operation was performed twice. Thereafter, 1.5 L of lubricating oil having the same composition was filled, and measurement was performed after operating for about 6 hours until stabilization. During the familiar operation with the recommended oil, the cooling air is adjusted so that the oil temperature is constant at 120 ± 3 ° C under the same conditions as the measurement conditions of the following test. After that, the air volume and direction are not changed. The measurement of Examples or Comparative Examples was performed.
Measurement conditions The motor was rotated at 1740 rpm, the worm gear (reduction ratio 30: 1) was driven, and this was further driven by a hydraulic pump via a speed increaser. At this time, the input torque (Ti) and output torque (To) of the worm gear were measured with a torque meter, and the energy transfer efficiency was calculated by the following equation.
Energy transfer efficiency (%) = 3.3333 To / Ti

(Friction test)
Using a Bauden testing machine (manufactured by Maruhishi Engineering), SUJ-2 specular sphere for shell EP test on the sphere, CGM-3 manganese silicide high strength brass with mirror finish on the plate side, load 1500gf, oil temperature 110 ° C, The friction coefficient was measured at a rotational speed of 30.0 mm / sec, a reciprocation distance of 50 mm, and a reciprocation count of 100.

(Rubber compatibility test)
A No. 3 dumbbell test piece was taken from a sheet of A727 (nitrile rubber manufactured by NOK Corporation) or T303 (acrylic rubber manufactured by NOK Corporation), and after measuring the hardness of each dumbbell, it was immersed in each lubricating oil for 720 hours. (A727 is 100 ° C., T303 is 130 ° C.). The hardness after immersion was measured, and the change within ± 10 was defined as O, and the others were represented as x.

(Coating compatibility)
Polish the surface of an iron plate with a thickness of 1 cm × length 10 cm × width 5 cm with sandpaper, degrease it with hexane, and then apply it with a lacquer primer 111 lacquer primer red rust color (nitrified cotton paint manufactured by Kansai Paint Co., Ltd.), then click It was painted with 1000 2.5G6 / 3 (nitrified cotton paint manufactured by Kansai Paint Co., Ltd.). Each lubricating oil was applied to the coated iron plate, and a cycle consisting of 25 ° C. × 24 hours and 90 ° C. × 100 hours was repeated 20 times. The application of the lubricating oil was repeated every time the temperature reached 25 ° C. After completion of the cycle, the coating state was evaluated visually.
○ No change × Paint is peeled off.

  In the table, the viscosity grade value “320” is based on JIS K2001-1993, and “260” is based on the auxiliary viscosity grade in the annex of JIS K2001 established in 1978.

  As shown in Table 4, the worm gear oil compositions of Examples 1 to 9 are polyalkylene glycol-based lubricating oils (comparative example 3), The performance is equivalent to or better than that of an α-olefin-based lubricating oil (Comparative Example 4) and a lubricating oil containing poly α-olefin + alkylbenzene + organic molybdenum (Comparative Example 5). In particular, the worm gear oil composition of the present invention not only exceeds the performance related to the actual machine transmission efficiency, but also rubber and paint compared to the polyalkylene glycol-based lubricating oil, which is considered to be superior in terms of transmission efficiency. It will not invade. Further, in the present invention, unlike the conventional lubricating oil containing poly α-olefin + alkylbenzene + organic molybdenum, high transmission efficiency is achieved without using an organic molybdenum compound as an essential component.

  Since the worm gear oil composition of the present invention has properties of high transmission efficiency and less adverse effects on rubber and paint, it is suitably used in worm gear units and the like used in industrial machines and the like, thereby achieving energy saving. It becomes possible.

Claims (2)

(A) a base oil comprising an oligomer of an α-olefin having 6 to 14 carbon atoms or a hydride thereof, an ethylene / α-olefin copolymer or a hydride thereof, and (B) a partial ester compound of trimethylolpropane and isostearic acid. Or a partial ester compound of trimethylolpropane and isostearic acid and oleic acid,
The content of the component (A) is 60 to 94% by mass relative to the total amount of the composition, the content of the component (B) is 6 to 40% by mass, and the hydroxyl value of the worm gear oil composition is 3 to 30 mgKOH / g. A worm gear oil composition for a worm gear unit comprising a high-strength brass wheel and a steel worm.   The worm gear oil composition according to claim 1, wherein the oligomer having 6 to 14 carbon atoms or the hydride thereof is a hydrogenated 1-decene polymer.