JP5345935B2 - Low phosphorus lubricating oil composition with lead corrosion inhibition - Google Patents

Description

  The present invention relates in part to lubricating oil compositions. In particular, the present invention is a lubricating oil composition using a mixture of zinc dithiophosphate, wherein the total phosphorus content of the lubricating oil composition is less than about 0.06% by weight based on the total weight of the lubricating oil composition. The present invention relates to a low phosphorus lubricating oil composition. The low phosphorus lubricating oil composition of the present invention is effective in suppressing lead corrosion when used as a lubricating oil composition in an internal combustion engine.

  Emissions from automobile exhaust have been a problem for decades, and as an effort to deal with this problem, the use of unleaded fuel (partially dealing with lead pollution from leaded fuel) , The use of oxygen-added fuel (which will reduce hydrocarbon emissions), the use of a catalytic converter (which will also reduce hydrocarbon emissions), and the like.

  Although catalytic converters are used today in gasoline vehicles without exception, the efficiency of these converters is directly related to the ability of the catalyst to convert unburned or partially burned hydrocarbons generated during combustion into carbon dioxide and water. Yes. One problem that arises with the use of such converters is catalyst poisoning, which results in reduced catalyst efficiency. Since catalytic converters are intended for long term use, catalytic poisoning will cause contaminants to be released from the internal combustion engine to the atmosphere at high levels over a long period of time.

  To minimize such poisoning, the industry has set standards for both fuel and lubricant contents. For example, fuel standards include lead poisoning of the catalyst and the use of unleaded gasoline to avoid lead release to the environment. For example, see Patent Document 1.

  As an additive system that has recently been treated as an industry standard for lubricants, phosphorus-containing additives such as zinc dithiophosphate antiwear agents used in lubricating oil compositions used to lubricate internal combustion engines There is an agent. That is, the phosphorus-containing additive reaches the catalytic converter, for example, through exhaust gas recirculation and / or blow-by processes and other methods known in the art. For example, see Non-Patent Document 1 and Non-Patent Document 2. In any event, it is known that phosphorus accumulates at active metal sites within the catalytic converter, thereby reducing catalyst efficiency and effectively harming the catalyst over time. As a result of the above, a new focus has been placed on reducing the phosphorus in lubricating oils. For example, the draft GF-4 specification for lubricating oil compositions proposes a phosphorus content that is significantly lower than the amount used so far.

  When the phosphorus level of a lubricating oil composition containing an oil-soluble phosphorus-containing wear-resistant compound is lowered, there is a problem that the wear resistance performance is significantly lowered due to the reduction of the phosphorus content. A well-known class of antiwear additives are metal alkyl phosphates, especially zinc dialkyldithiophosphates, which generally have phosphorus levels higher than 0.1% by weight when used for wear control. Used for lubricating oil. Below this level, it has been found that it is not an effective anti-wear additive. For example, as exemplified in Patent Document 2, when the phosphorus level due to the presence of the metal dithiophosphate additive in the lubricating oil composition is reduced by half from 0.095 wt% to 0.048 wt% The engine wear increases about 7 times.

  Zinc dithiophosphates have a dialkyl group or a diaryl group. The zinc dialkyldithiophosphates are further subdivided into primary alkyl dithiophosphate zinc and secondary alkyl dithiophosphate zinc. Pentan-1-ol and 3-methylbutan-2-ol are examples of primary and secondary alcohols used to produce primary and secondary zinc dithiophosphates. Various species of zinc dithiophosphate behave differently (see below).

Performance parameters of zinc dithiophosphate species
Primary alkyl Secondary alkyl aryl Thermal stability Medium Low High Anti-wear protection Medium High Low Hydrolytic stability Medium High Low

  Each type has important uses in recent additive packages. Therefore, in order to provide adequate wear resistance and at the same time keep the phosphorus level below 0.1% by weight in the presence of the metal dithiophosphate additive, any lubricating oil composition should have an appropriate mixture of zinc dithiophosphate. It is important to get. This is because phosphorus tends to deposit in the catalytic converter, thereby reducing catalyst efficiency and tending to harm the catalyst.

US Pat. No. 4,975,096 (Buckley III), “Long-Chain Aliphatic Hydrocarbon Amine Additives with Oxyalkylene Hydroxy Linking Groups,” issued December 4, 1990 US Pat. No. 6,696,393, issued February 24, 2004

Beck, et al., "Effect of oil-induced catalyst poisoning on FTP performance of LEV catalytic equipment", SAE Technical Paper, 972842, 1997. Darr, et al., "Effects of oil-induced contaminants on emissions from TWC-equipped vehicles", SAE, 2000-01-1881, 2000.

  Therefore, in order to provide adequate wear resistance and at the same time keep the phosphorus level below 0.1% by weight in the presence of the metal dithiophosphate additive, any lubricating oil composition should have an appropriate mixture of zinc dithiophosphate. It is important to get. That is, phosphorus accumulates in the catalytic converter, thereby reducing catalyst efficiency and showing a tendency to harm the catalyst.

  As noted above, the present invention relates in part to lubricating oil compositions. In particular, the present invention employs a mixture of zinc dithiophosphate in a fixed proportion, and the low phosphorus lubrication wherein the total phosphorus content of the lubricating oil composition is less than about 0.06% by weight based on the total weight of the lubricating oil composition. It relates to an oil composition. The low phosphorus lubricating oil composition of the present invention is effective in suppressing lead corrosion when used as a lubricating oil composition in an internal combustion engine.

Thus, in its broadest aspect, the present invention provides a lubricating oil comprising a major amount of a base oil of lubricating viscosity and a minor amount of a mixture of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate. A composition wherein the ratio of zinc primary dialkyldithiophosphate to zinc secondary dialkyldithiophosphate is from about 2: 1 to about 1: 2, based on phosphorus content, and the primary zinc dialkyldithiophosphate And the ratio of the zinc dialkyldithiophosphate mixture to the zinc diaryldithiophosphate is from about 6: 1 to about 1: 1 based on the phosphorus content and the total phosphorus content of the lubricating oil composition It relates to a lubricating oil composition that is less than about 0.06% by weight based on the total weight of the composition.

  A small amount of the mixture of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate used in the lubricating oil composition of the present invention, based on the total weight of the lubricating oil composition, is about 0. 1% to about 1.5% by weight, preferably about 0.3% to about 1.2% by weight, and more preferably about 0.5% to about 1.0% by weight. .

  The lubricating oil composition of the present invention comprises from about 0.05% to about 1.2% by weight primary zinc dialkyldithiophosphate, from about 0.05% to about 1%, based on the total weight of the lubricating oil composition. 2% by weight secondary zinc dialkyldithiophosphate and from about 0.02% to about 0.7% by weight zinc diaryldithiophosphate. Preferably, the lubricating oil composition of the present invention is from about 0.1 wt% to about 0.7 wt% primary zinc dialkyldithiophosphate, from about 0.1 wt% to about 0.7 wt%, based on the total weight of the lubricating oil composition. About 0.7% by weight secondary zinc dialkyldithiophosphate, and about 0.05% to about 0.5% by weight zinc diaryldithiophosphate. More preferably, the lubricating oil composition of the present invention is from about 0.2% to about 0.5% by weight primary zinc dialkyldithiophosphate, about 0.2% by weight, based on the total weight of the lubricating oil composition. To about 0.5% by weight of a secondary zinc dialkyldithiophosphate and about 0.1% to about 0.3% by weight of zinc diaryldithiophosphate.

The primary alkyl group of the primary zinc dialkyldithiophosphate has from about C _{1 to} about C ₁₃ carbon atoms, preferably from about C _{3 to} about C ₁₀ carbon atoms, more preferably from about C carbon atoms. C _{6 to} about C ₈ .

The secondary alkyl group of the zinc secondary dialkyldithiophosphate has from about C _{3 to} about C ₁₃ carbon atoms, preferably from about C _{3 to} about C ₈ carbon atoms, more preferably from about C carbon atoms. C _{3 to} about C ₆ .

The aryl group of the zinc diaryldithiophosphate has from about C _{6 to} about C ₃₀ carbon atoms, preferably from about C _{6 to} about C ₂₄ carbon atoms, more preferably from about C _{6 to} about C ₂₀ carbon atoms. It is.

  In a preferred embodiment, the ratio of primary zinc dialkyldithiophosphate to zinc secondary dialkyldithiophosphate is from about 3: 2 to about 2: 3 based on phosphorus content. More preferably, the ratio is about 1: 1.

  In a preferred embodiment, the ratio of the mixture of primary zinc dialkyldithiophosphate and zinc secondary dialkyldithiophosphate to zinc diaryldithiophosphate is from about 4: 1 to about 1: 1 based on phosphorus content. More preferably, the ratio is about 2: 1.

  In a particularly preferred embodiment, the ratio of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate in the mixture is 1: 1: 1 based on the phosphorus content.

  In another aspect, the total phosphorus content of the lubricating oil composition of the present invention is preferably less than about 0.05% by weight based on the total weight of the lubricating oil composition.

  In another aspect, the sulfur content of the lubricating oil composition of the present invention is less than about 0.5% by weight, preferably less than about 0.2% by weight, based on the total weight of the lubricating oil composition, and The total sulfated ash content of the lubricating oil composition of the present invention is less than about 1.2% by weight, preferably less than about 1.0% by weight, more preferably about 0.000, based on the total weight of the lubricating oil composition. It is less than 8% by mass.

As one of the methods of the present invention, the present invention further relates to a method for improving lead corrosion. The method of the present invention is a lubricating oil composition comprising a major amount of a base oil of lubricating viscosity and a minor amount of a mixture of zinc primary dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate, The ratio of primary zinc dialkyldithiophosphate to secondary zinc dialkyldithiophosphate is from about 2: 1 to about 1: 2, based on phosphorus content, primary zinc dialkyldithiophosphate and secondary dialkyldithiophosphorus. The ratio of the zinc acid mixture to zinc diaryldithiophosphate is from about 6: 1 to about 1: 1 based on the phosphorus content , and the total phosphorus content of the lubricating oil composition is the total mass of the lubricating oil composition. Operating the internal combustion engine with a lubricating oil composition that is less than about 0.06% by weight.

Among other factors, the present invention provides a low phosphorus lubricating oil composition comprising a proportion of a mixture of zinc dithiophosphates that can surprisingly lead to improved lead corrosion. The mixture of zinc dithiophosphates comprises primary zinc dialkyldithiophosphates, secondary zinc dialkyldithiophosphates and zinc diaryldithiophosphates. The ratio of primary zinc dialkyldithiophosphate to secondary zinc dialkyldithiophosphate is from about 2: 1 to about 1: 2, based on phosphorus content, primary zinc dialkyldithiophosphate and secondary dialkyldithiophosphorus. A synergistic combination of mixed zinc dithiophosphates wherein the ratio of the zinc acid mixture to the zinc diaryldithiophosphate is from about 6: 1 to about 1: 1, based on the phosphorus content, provides a total oil content in the lubricating oil composition. Even when used at less than about 0.06% by weight based on the total weight of the lubricating oil composition, lead corrosion can be greatly reduced when used to lubricate internal combustion engines.

The present invention relates in part to lubricating oil compositions. In particular, the present invention uses a mixture of zinc dithiophosphates, including primary zinc dialkyldithiophosphates, zinc secondary dialkyldithiophosphates and zinc diaryldithiophosphates, using primary dialkyldithiodiphosphates and secondary dialkyldithiophosphates. The ratio of zinc acid to zinc acid is from about 2: 1 to about 1: 2, based on phosphorus content, and the ratio of the mixture of primary dialkyl zinc dithiophosphate and secondary zinc dialkyl dithiophosphate to zinc diaryl dithiophosphate. Is about 6: 1 to about 1: 1, based on phosphorus content , and the total phosphorus content of the lubricating oil composition is less than about 0.06 wt% based on the total weight of the lubricating oil composition The present invention relates to a lubricating oil composition. The low phosphorus lubricating oil composition of the present invention is effective in suppressing lead corrosion when used as a lubricating oil in an internal combustion engine.

  In the following, each of these components of the claimed composition is described in detail. Prior to such description, the following terms are first defined.

  “Alkyl” means both straight and branched chain alkyl groups.

  “Aryl” means a substituted or unsubstituted aromatic group, such as a phenyl group, a tolyl group, a xylyl group, an ethylphenyl group, and a cumenyl group.

  “Low phosphorus” means the phosphorus content of the lubricating oil composition of the present invention. The phosphorus content is in the range of about 0.005% to about 0.06% by weight based on the total weight of the lubricating oil composition.

“Total phosphorus” is the residue that remains because phosphorus is present as part of the oil-soluble phosphorus-containing antiwear compound or the presence of P ₂ S ₅ used to produce the metal dihydrocarbon dithiophosphate. It means the total amount of such phosphorus in the lubricating oil composition, regardless of whether it is present in the lubricating oil composition as a contaminant, such as phosphorus. In any case, the amount of phosphorus that can be tolerated in the lubricating oil composition does not depend on the source. However, phosphorus is preferably a part of the lubricating oil additive.

  Unless otherwise specified, all percentages are weight percent.

[Zinc dithiophosphate compound]
In the lubricating oil composition of the present invention, a mixture of zinc dithiophosphate is used in part. Zinc dithiophosphates are independently characterized by Formula I.

  Each R is independently a group containing from about 1 to about 30 carbon atoms.

The R group of the dithiophosphate is independently about C _{1 to} about C ₁₃ primary alkyl, about C _{3 to} about C ₁₃ secondary alkyl, and about C _{6 to} about C ₃₀ aryl group, Good. Preferably, independently R groups dithiophosphate, primary alkyl of about C ₃ -C _10, secondary alkyl of about C ₃ -C _8, and about C ₆ - was at about C ₂₄ aryl group It's okay. More preferably, the R group of the dithiophosphate is independently about C _{6 to} about C ₈ primary alkyl, about C _{3 to} about C ₆ secondary alkyl, and about C _{6 to} about C ₂₀ aryl. It may be a group. The R group may be a substantial hydrocarbon group. By “substantially hydrocarbon” is meant a hydrocarbon containing substituents that do not substantially affect the hydrocarbon nature of the group, such as ether, ester, nitro or halogen.

  The R group of zinc dithiophosphate is, for example, a primary alcohol, specifically methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, dodecanol, octadecanol, propenol, butenol, 2 -Ethylhexanol; secondary alcohol, specifically isopropyl alcohol, secondary butyl alcohol, isobutanol, 3-methylbutan-2-ol, 2-pentanol, 4-methyl-2-pentanol, 2-hexanol , 3-hexanol, amyl alcohol; aryl alcohol, specifically phenol, substituted phenol (especially alkylphenol such as butylphenol, octylphenol, nonylphenol, dodecylphenol), It can be derived from a substituted phenol.

  The R group is preferably independently a primary alkyl, secondary alkyl or aryl group.

  For the purposes of the present invention, it is believed that a mixture of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate is present in the lubricating oil composition of the present invention in a phosphorus based ratio. It is done. The ratio of primary zinc dialkyldithiophosphate to zinc secondary dialkyldithiophosphate is from about 2: 1 to about 1: 2, and the ratio of zinc primary dialkyldithiophosphate to zinc secondary dialkyldithiophosphate. The ratio of mixture to zinc diaryldithiophosphate is from about 6: 1 to about 1: 1. Preferably, the ratio of primary zinc dialkyldithiophosphate to zinc secondary dialkyldithiophosphate is in the range of about 3: 2 to about 2: 3, more preferably about 1: 1, based on phosphorus content. . Preferably, the ratio of the mixture of primary zinc dialkyldithiophosphate and zinc secondary dialkyldithiophosphate to zinc diaryldithiophosphate is in the range of about 4: 1 to about 1: 1 based on phosphorus content, more preferably Is about 2: 1. Most preferably, the ratio of the mixture of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate is 1: 1: 1 based on phosphorus content.

  Many of the zinc dithiophosphates that can be used in the present invention are commercially available. However, zinc dithiophosphates are widely known in the art, and those skilled in the art can readily synthesize such compounds that meet the purpose of the present invention. In general, zinc dithiophosphates can be prepared by an initial reaction of phosphorus pentasulfide with alcohol or phenol or a mixture of alcohol and / or phenol, such as those exemplified above for the R group. The reaction requires 4 moles of alcohol or phenol per mole of phosphorus pentasulfide and can be conducted within a temperature range of about 50 ° C to about 200 ° C. Thus, the production of O, O-di-n-hexyl phosphorodithioic acid includes, for example, reacting phosphorus pentasulfide with 4 moles of n-hexyl alcohol at about 100 ° C. for about 2 hours. Hydrogen sulfide is released and the residue is phosphorodithioic acid. The production of the metal salt of this acid can be accomplished by reaction with zinc oxide or zinc hydroxide to yield zinc dithiophosphate. It is sufficient to simply mix and heat these two reactants to cause the reaction, and the resulting product is sufficiently pure for the purposes of the present invention.

  Patent documents describing the synthesis of such zinc dithiophosphates include the specifications of U.S. Pat. Nos. 2,680,123, 300,822, 3,151,575, 3,387,791, 4,377,527, 4,495,075, and 4,778,906. You can give a letter. Each of these patent documents is also referred to in this specification as reference content.

[Lubricating oil composition]
The zinc dithiophosphate mixture of the present invention is generally added to the base oil in an amount sufficient to provide lead corrosion inhibition to the internal combustion engine. Generally, the lubricating oil composition of the present invention contains a major amount of a base oil of lubricating viscosity and a minor amount of a mixture of the inventive zinc dithiophosphate.

(Base oil of lubricating viscosity)
Base oil, as used herein, is manufactured by each manufacturer to the same specifications (regardless of source or manufacturer's location), meets the same manufacturer's specifications, and has a unique formulation and manufacture. It is defined as a base oil or blend of base oils that is a lubricating oil component identified by an identification number or both. A variety of different methods can be used to produce the base stock, including but not limited to distillation, solvent refining, hydrotreating, oligomerization, esterification and rerefining. Rerefined base stock is substantially free of materials introduced by manufacturing, contamination, or previous use. The base oils of the present invention may be any natural or synthetic lube base oil fraction, particularly those having a kinematic viscosity of about 4 centistokes (cSt) to about 20 cSt at 100 degrees Celsius (° C). is there. Examples of hydrocarbon synthetic oils include oils produced by polymerization of ethylene, polyalphaolefins or PAOs, or oils produced by hydrocarbon synthesis methods using carbon monoxide gas and hydrogen gas, such as the Fischer-Tropsch process. Can be mentioned. Preferred base oils are those that have a small amount even when they contain a heavy fraction, for example an oil that has little viscosity, such as a lubricating oil fraction having a viscosity of about 20 ° C. or more at about 100 ° C. The oil used as the base oil is selected or blended depending on the desired end use and finished oil additive, and the desired grade of engine oil, such as SAE viscosity grade 0W, 0W-20, 0W. -30, 0W-40, 0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40 It becomes a lubricating oil composition of 10W-50, 15W, 15W-20, 15W-30 or 15W-40.

  Base oils can be obtained from natural lubricating oils, synthetic lubricating oils or mixtures thereof. Suitable base oils include base oils obtained by isomerization of synthetic and crude waxes, and hydrogen produced by hydrocracking (rather than solvent extraction) the aromatic and polar components of the crude feedstock. A chemical decomposition base oil can be mentioned. Suitable base oils include those contained in all API classes I, II, III, IV and V as defined in API Publication 1509, 14th edition, Appendix I, December 1998. Table 1 lists the saturation levels and viscosity indices of Group I, II and III base oils. Group IV base oils are polyalphaolefins (PAO). Group V base oils include all other base oils not included in Group I, II, III, or IV. Group III base oils are preferred.

Table 1 Saturation, sulfur content and viscosity index of Class I, II, III, IV and V base oils ───────────────────────── ────────────
Species saturation (ASTM viscosity index (ASTM D4294,
Determined by D2007) ASTM D4297 or
Sulfur content (determined by ASTM ASTM D3120)
D2270)
─────────────────────────────────────
I Saturation less than 90% and / or 80 or more, less than 120
Above 0.03% sulfur
II Saturation 90% or more and 80 or more, less than 120
Sulfur content 0.03% or less
III Saturation 90% or more and 120 or more
Sulfur content 0.03% or less
IV All polyalphaolefins (PAOs)
Everything else not included in VI, II, III or IV species ─────────────────────────────────── ──

  Natural lubricating oils can include animal oils, vegetable oils (eg, rapeseed oil, castor oil and lard oil), petroleum oils, mineral oils, and oils derived from coal or shale.

Synthetic oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and copolymerized olefins, alkylbenzenes, polyphenyls, alkylated diphenyl ethers, alkylated diphenyl sulfides, and derivatives thereof, and the like And homologues. Synthetic lubricating oils can also include alkylene oxide polymers, true copolymers, copolymers, and derivatives in which the terminal hydroxyl groups have been modified by esterification, etherification, or the like. Another suitable class of synthetic lubricating oils includes esters of dicarboxylic acids and various alcohols. Esters that can be used as synthetic oils also include those made from about C _{5 to} about C ₁₂ monocarboxylic acids and polyols and polyol ethers. Trialkyl phosphate ester oils such as those exemplified by tri-n-butyl phosphate and tri-iso-butyl phosphate are also suitable for use as the base oil.

  Silicon-based oils (eg, polyalkyl, polyaryl, polyalkoxy or polyaryloxy-siloxane oils and silicate oils) constitute another useful class of synthetic lubricating oils. Other synthetic lubricating oils include liquid esters of phosphorus-containing acids, high molecular weight tetrahydrofurans, and polyalphaolefins.

  Base oils may be derived from unrefined, refined, rerefined oils or mixtures thereof. Unrefined oils are obtained directly from natural or synthetic raw materials (eg, coal, shale or tar sand bitumen) without further purification or processing. Examples of unrefined oils include shale oil obtained directly by retorting, petroleum oil obtained directly by distillation, or ester oil obtained directly by an esterification method, each then used without further treatment can do. Refined oils are the same as unrefined oils except that they have been treated in one or more refining steps to improve one or more properties. Suitable purification techniques include distillation, hydrocracking, hydrotreating, dewaxing, solvent extraction, acid or base extraction, filtration, and percolate, all known to those skilled in the art. The rerefined oil is obtained by treating the used oil in the same manner as used to obtain the refined oil. These rerefined oils, also known as reclaimed or reprocessed oils, are often further processed by techniques aimed at removing used additives and oil breakdown products.

  Base oils derived from wax hydroisomerization can also be used alone or in combination with the natural and / or synthetic base oils.

  Such wax isomerate oils are produced by hydroisomerizing natural or synthetic waxes or mixtures thereof using a hydroisomerization catalyst.

  In the lubricating oil composition of the present invention, the base oil is preferably used in a major amount. The major amount of base oil, as defined herein, comprises about 40% by weight or more. A preferred amount of base oil comprises from about 40% to about 97% by weight of the lubricating oil composition, preferably greater than about 50% to about 97%, more preferably from about 60% to about 97% by weight. Most preferably from about 80% to about 95% by weight. (Mass%, as used herein, means mass% of lubricating oil unless otherwise specified.)

  The amount of the zinc dithiophosphate mixture used in the lubricating oil composition of the present invention is small compared to a base oil having a lubricating viscosity. Generally, the amount is from about 0.1% to about 1.5%, preferably from about 0.3% to about 1.2%, more preferably from about 0%, based on the total weight of the lubricating oil composition. 0.5 mass% to about 1.0 mass%.

  The lubricating oil composition of the present invention comprises primary zinc dialkyldithiophosphate in an amount of from about 0.05% to about 1.2% by weight, preferably about 0.1% by weight, based on the total weight of the lubricating oil composition. To about 0.7 mass%, more preferably about 0.2 mass% to about 0.5 mass%.

  The lubricating oil composition of the present invention comprises the secondary dialkyldithiodiphosphate zinc from about 0.05% to about 1.2% by weight, preferably about 0.1% by weight, based on the total weight of the lubricating oil composition. To about 0.7 mass%, more preferably about 0.2 mass% to about 0.5 mass%.

  The lubricating oil composition of the present invention contains primary zinc diaryldithiophosphate from about 0.02% to about 0.7% by weight, preferably about 0.05% by weight, based on the total weight of the lubricating oil composition. To about 0.5 wt%, more preferably about 0.1 wt% to about 0.3 wt%.

  In a preferred embodiment, the phosphorus content of the lubricating oil composition of the present invention is preferably less than about 0.05% by weight based on the total weight of the lubricating oil composition.

  In another aspect, the lubricating oil composition of the present invention further has a sulfur content of less than about 0.5 wt%, preferably less than about 0.2 wt%, based on the total weight of the lubricating oil composition; And the total sulfated ash content of the lubricating oil composition of the present invention is less than about 1.2 wt%, preferably less than about 1.0 wt%, more preferably about 1.0 wt%, based on the total weight of the lubricating oil composition. It is less than 0.8% by mass.

(Other additive components)
The following additive components are examples of components that can be preferably used in combination with the lubricating oil additive of the present invention. Examples of these additives are given to illustrate the invention and are not intended to limit the invention.

(A) A detergent is an additive designed to hold an acid neutralizing compound in oil in solution. Detergents are usually alkaline and react with strong acids (sulfuric acid and nitric acid) that are produced during the combustion of the fuel and leave the uncontrollable environment corroding the engine parts. Examples include carboxylates, sulfurized or unsulfurized alkyl or alkenyl phenates, alkyl or alkenyl aromatic sulfonates, sulfurized or unsulfurized metal salts of polyhydroxyalkyl or alkenyl aromatic compounds, alkyl or alkenyl hydroxy aromatic sulfonates. , Sulfurized or unsulfurized alkyl or alkenyl naphthenates, metal salts of alkanolic acids, metal salts of alkyl or alkenyl polyacids, and chemical and physical mixtures thereof.

(B) The dispersant is an additive that retains soot and combustion products in a suspended state in the oil body, thereby preventing deposits such as sludge and lacquer. In general, an ashless dispersant is a nitrogen-containing dispersant formed by reacting an alkenyl succinic anhydride with an amine. Examples include alkenyl succinimides, alkenyl succinimides modified with other organic compounds such as ethylene carbonate post-treatment, and alkenyl succinimides, polysuccinimides, alkenyl succinates modified with boric acid. There is.

(C) Antioxidant:
1) Phenol type (phenolic) antioxidant: 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert-butylphenol), 4, 4'-bis (2-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 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-tert-butyl-4-methylphenol 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-α-dimethylamino-p-cresol, 2,6 -Di-tert-4- (N, N'-dimethylaminomethylphenol), 4,4'-thiobis (2-methyl-6-tert-butylphenol), 2,2'-thiobis (4-methyl-6-) tert-butylphenol), bis (3-methyl-4-hydroxy-5-tert-butylbenzyl) -sulfide, and bis (3,5-di-tert-butyl-4-hydroxybenzyl).

  2) Diphenylamine type antioxidants: alkylated diphenylamine, phenyl-α-naphthylamine, and alkylated α-naphthylamine.

  3) Other types: metal dithiocarbamates (eg, zinc dithiocarbamate), and methylenebis (dibutyldithiocarbamate).

(D) Rust prevention additive (rust prevention agent):
1) Nonionic polyoxyethylene surfactant: polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl Ethers, polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol monooleate, and polyethylene glycol monooleate.

  2) Other compounds: stearic acid and other fatty acids, dicarboxylic acids, metal soaps, fatty acid amine salts, metal salts of heavy sulfonic acids, partial carboxylic acid esters of polyhydric alcohols, and phosphate esters.

(E) Demulsifier: adduct of alkylphenol and ethylene oxide, polyoxyethylene alkyl ether, and polyoxyethylene sorbitan ester.

(F) Extreme pressure agent (EP agent): sulfurized oil, diphenyl sulfide, methyltrichlorostearate, chlorinated naphthalene, benzyl iodide, fluoroalkylpolysiloxane, and lead naphthenate.

(G) Friction modifier: fatty alcohol, fatty acid, amine, borated ester, and other esters.

(H) Multifunctional additive: sulfurized oxymolybdenum dithiocarbamate, sulfurized oxymolybdenum organophosphorodithioate, oxymolybdenum monoglyceride, oxymolybdenum diethylate amide, amine-molybdenum complex compound, and sulfur-containing molybdenum complex compound.

(I) Viscosity index improver (VII): polymethacrylate type polymer, ethylene / propylene copolymer, styrene / isoprene copolymer, hydrogenated styrene / isoprene copolymer, hydrogenated star-branched polyisoprene, poly Isobutylene, hydrogenated star-branched styrene / isoprene copolymer, and dispersion type viscosity index improver.

(J) Pour point depressants: polymethyl methacrylates, alkyl methacrylates, and dialkyl fumarate / vinyl acetate copolymers.

(K) Antifoaming agent: alkyl methacrylate polymer and dimethyl silicone polymer.

  The invention is further illustrated by the following examples, which illustrate particularly advantageous process embodiments. This example is provided to illustrate the invention and is not intended to limit the invention.

[Example 1]
Bis (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc (0.24 mass%, primary) and bis (O, O′-di- (2-butyl / 4- 0 of zinc methyl-2-pentyl) dithiophosphate (0.15 wt%, secondary) and zinc bis (O, O′-di- (dodecylphenyl) dithiophosphate (0.39 wt%, aryl) A low phosphorus lubricating oil composition of the present invention was prepared by blending a .78 wt% mixture with a Class II base oil of lubricating viscosity.Bis (O, O'-di- (2-ethyl-1-hexyl) The ratio of zinc dithiophosphate to zinc bis (O, O'-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate was about 1: 1 based on phosphorus content. O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc and bis (O, O′-di- (2-butyrate) The ratio of the mixture of / 4-methyl-2-pentyl) zinc dithiophosphate to zinc bis (O, O'-di- (dodecylphenyl) dithiophosphate was about 2: 1 based on phosphorus content. (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc, bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate zinc, The ratio in the ternary mixture with (O, O′-di- (dodecylphenyl) dithiophosphate zinc was 1: 1: 1 based on the phosphorus content. Mass% of phosphorus in the produced lubricating oil composition Was less than about 0.06% by weight based on the total weight of the lubricating oil composition, and the sulfur content and sulfated ash content were 0.2% by weight and 0.02% based on the total weight of the lubricating oil composition, respectively. The lubricating oil composition% was an isobuty having a molecular weight (MW) of 1200. Bissuccinimide dispersant, MW2300 isobutylene bissuccinimide dispersant, neutral sulfonate detergent, overbased calcium phenate, molybdenum antioxidant, diphenylamine antioxidant, phenolic antioxidant, antifoaming agent, flow A 100 mass% lubricating oil composition containing a point depressant and a viscosity index improver was obtained.

[Comparative Example A]
Bis (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc and bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate zinc and bis ( Instead of a mixture with zinc O, O′-di- (dodecylphenyl) dithiophosphate, only about 1.16% by weight zinc arylbis (O, O′-di- (dodecylphenyl) dithiophosphate was added. Comparative Example A was prepared according to Example 1.

[Comparative Example B]
Bis (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc and bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate zinc and bis ( Instead of a mixture with zinc O, O′-di- (dodecylphenyl) dithiophosphate, about 0.46 zinc bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate Comparative Example B was prepared according to Example 1 except that only the mass% was added.

[Comparative Example C]
Bis (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc and bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate zinc and bis ( Instead of a mixture with zinc O, O′-di- (dodecylphenyl) dithiophosphate, only about 0.71% by weight of zinc bis (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate is used. Comparative Example C was prepared according to Example 1 except that it was added.

[Comparative Example D]
Bis (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc and bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate zinc and bis ( Instead of a mixture of zinc O, O′-di- (dodecylphenyl) dithiophosphate, zinc bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate and bis (O Comparative Example D was prepared according to Example 1 except that about 0.81% by weight of a mixture with, O′-di- (dodecylphenyl) dithiophosphate zinc was added in a ratio of about 1: 1.

[Comparative Example E]
Bis (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc and bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate zinc and bis ( Instead of a mixture of zinc O, O'-di- (dodecylphenyl) dithiophosphate, zinc bis (O, O'-di- (2-ethyl-1-hexyl) dithiophosphate and bis (O, O'- Comparative Example E was prepared according to Example 1 except that about 0.94% by weight of a mixture with zinc di- (dodecylphenyl) dithiophosphate was added in a ratio of about 1: 1.

[Comparative Example F]
Bis (O, O′-di- (2-ethyl-1-hexyl) dithiophosphate zinc and bis (O, O′-di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate zinc and bis ( Instead of a mixture of zinc O, O'-di- (dodecylphenyl) dithiophosphate, zinc bis (O, O'-di- (2-ethyl-1-hexyl) dithiophosphate and bis (O, O'- Comparative Example F was prepared according to Example 1 except that about 0.59% by weight of a mixture with zinc di- (2-butyl / 4-methyl-2-pentyl) dithiophosphate was added in a ratio of about 1: 1. Manufactured.

  For each formulation according to Example 1 and Comparative Examples A-F, using the high temperature corrosion bench test (HTCBT) (ASTM D6594), which is an industry standard bench test for measuring the corrosion performance of motor oil, A lead corrosion test was performed. Briefly, four metal specimens of copper, lead, tin and phosphor bronze are immersed in a measured amount of engine oil. Air is blown on the hot oil for a certain period of time. At the end of the test, the lead specimen and the fatigued oil are examined for corrosion and corrosion products, respectively. Reference oils were also tested with each test group to confirm the validity of the test.

  Table 2 summarizes the test results.

Table 2
HTCBT test results ─────────────────────────────────────
Example Comparative Example
1 ABCD EF
────────────────────────────────────
Lead (ppm) 48.4 113.4 93.4 305 64.6 87.3 99.4
────────────────────────────────────

  These results include a 1: 1: 1 ratio of a mixture of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate, and the lubricating oil composition has a phosphorus content of 0.1. The low phosphorus lubricating oil composition of the present invention (Example 1) having a content of less than 06% by mass provides superior lead corrosion inhibition performance as compared with a comparative example that does not contain a mixture of all three types of dithiophosphates. Show. The amount of lead corrosion can be significantly reduced by the lubricating oil composition of the present invention.

Claims (28)

A lubricating oil composition comprising a major amount of a base oil of lubricating viscosity, and a minor amount of a mixture of a primary zinc dialkyldithiophosphate, a secondary zinc dialkyldithiophosphate and a zinc diaryldithiophosphate, wherein the primary dialkyldithiophosphorus The ratio of zinc acid to secondary zinc dialkyldithiophosphate is 2: 1 to 1: 2, based on phosphorus content, and a mixture of zinc dialkyldithiophosphate and zinc secondary dialkyldithiophosphate and diaryl The ratio to zinc dithiophosphate is 6: 1 to 1: 1, based on the phosphorus content , and the total phosphorus content of the lubricating oil composition is less than 0.06% by weight based on the total weight of the lubricating oil composition A lubricating oil composition.   A small amount of a mixture of zinc primary dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate is 0.1% to 1.5% by weight based on the total weight of the lubricating oil composition. Item 4. The lubricating oil composition according to Item 1.   A small amount of a mixture of zinc primary dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate is 0.3% to 1.2% by weight based on the total weight of the lubricating oil composition. Item 4. The lubricating oil composition according to Item 1.   A small amount of a mixture of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate is 0.5% to 1.0% by weight based on the total weight of the lubricating oil composition. Item 4. The lubricating oil composition according to Item 1.   The mixture is 0.05% to 1.2% by weight primary dialkyldithiodiphosphate zinc, 0.05% to 1.2% by weight secondary dialkyl, based on the total weight of the lubricating oil composition. The lubricating oil composition of claim 1, comprising zinc dithiophosphate and 0.02 wt% to 0.7 wt% zinc diaryldithiophosphate.   The mixture is 0.1% to 0.7% by weight primary zinc dialkyldithiophosphate, 0.1% to 0.7% by weight secondary dialkyl, based on the total weight of the lubricating oil composition. The lubricating oil composition according to claim 5, comprising zinc dithiophosphate and 0.05% to 0.5% by weight zinc diaryldithiophosphate.   The mixture is 0.2% to 0.5% by weight primary dialkyl dithiodiphosphate zinc, 0.2% to 0.5% by weight secondary dialkyl, based on the total weight of the lubricating oil composition. The lubricating oil composition of claim 6 comprising zinc dithiophosphate and 0.1 to 0.3 wt% zinc diaryldithiophosphate. The lubricating oil composition according to claim 1, wherein the primary alkyl group of the primary zinc dialkyldithiophosphate has C _{1 to} C ₁₃ carbon atoms. The lubricating oil composition according to claim 8, wherein the primary alkyl group of the primary zinc dialkyldithiophosphate has C _{3 to} C ₁₀ carbon atoms. The lubricating oil composition according to claim 9, wherein the primary alkyl group of the primary zinc dialkyldithiophosphate has C _{6 to} C ₈ carbon atoms. The lubricating oil composition according to claim 1, wherein the secondary alkyl group of the secondary zinc dialkyldithiophosphate has C _{3 to} C ₁₃ carbon atoms. The lubricating oil composition according to claim 11, wherein the secondary alkyl group of the secondary zinc dialkyldithiophosphate has C _{3 to} C ₈ carbon atoms. The lubricating oil composition according to claim 12, wherein the secondary alkyl group of the zinc secondary dialkyldithiophosphate has C _{3 to} C ₆ carbon atoms. The lubricating oil composition according to claim 1, wherein the aryl group of zinc diaryldithiophosphate has C _{6 to} C ₃₀ carbon atoms. Aryl group of diaryl zinc dithiophosphate is, the lubricating oil composition of claim 14 which is the number of C ₆ to C ₂₄ carbon atoms. The lubricating oil composition according to claim 15, wherein the aryl group of zinc diaryldithiophosphate has C _{6 to} C ₂₀ carbon atoms.   The lubricating oil composition according to claim 1, wherein the ratio of primary zinc dialkyldithiophosphate to zinc secondary dialkyldithiophosphate is in the range of 3: 2 to 2: 3 based on the phosphorus content.   The lubricating oil composition according to claim 17, wherein the ratio of primary zinc dialkyldithiophosphate to secondary zinc dialkyldithiophosphate is 1: 1 based on phosphorus content.   The lubrication of claim 1, wherein the ratio of the mixture of zinc primary dialkyl dithiophosphate and zinc secondary dialkyl dithiophosphate to zinc diaryl dithiophosphate is in the range of 4: 1 to 1: 1 based on phosphorus content. Oil composition.   20. The lubricating oil composition of claim 19, wherein the ratio of the mixture of primary zinc dialkyldithiophosphate and zinc secondary dialkyldithiophosphate to zinc diaryldithiophosphate is 2: 1 based on phosphorus content.   The lubricating oil composition of claim 1, wherein the ratio of the mixture of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate is 1: 1: 1 based on phosphorus content.   The lubricating oil composition according to claim 1, wherein the total phosphorus content of the lubricating oil composition is less than 0.05 mass% based on the total mass of the lubricating oil composition.   The lubricating oil composition according to claim 1, wherein the total sulfur content of the lubricating oil composition is less than 0.5 mass% based on the total mass of the lubricating oil composition.   The lubricating oil composition according to claim 23, wherein the total sulfur content of the lubricating oil composition is less than 0.2 mass% based on the total mass of the lubricating oil composition.   The lubricating oil composition according to claim 1, wherein the total sulfated ash content of the lubricating oil composition is less than 1.2 mass% based on the total mass of the lubricating oil composition.   26. The lubricating oil composition of claim 25, wherein the total sulfated ash content of the lubricating oil composition is less than 1.0% by weight based on the total weight of the lubricating oil composition.   27. The lubricating oil composition of claim 26, wherein the total sulfated ash content of the lubricating oil composition is less than 0.8% by weight based on the total weight of the lubricating oil composition. Lubricating oil composition for improving lead corrosion, comprising a major amount of base oil of lubricating viscosity and a small amount of a mixture of primary zinc dialkyldithiophosphate, zinc secondary dialkyldithiophosphate and zinc diaryldithiophosphate Wherein the ratio of zinc primary dialkyldithiophosphate to zinc secondary dialkyldithiophosphate is from 2: 1 to 1: 2, based on phosphorus, and the primary dialkyldithiophosphate zinc and secondary dialkyldithiophosphate The ratio of the mixture of zinc dialkyldithiophosphate to zinc diaryldithiophosphate is 6: 1 to 1: 1 based on the phosphorus content , and the total phosphorus content of the lubricating oil composition is the total mass of the lubricating oil composition Operating an internal combustion engine with a lubricating oil composition that is less than 0.06% by weight.