JP2006328148A - Grease additive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a carbonate-containing grease composition from lowering in its lubricity for lowered abrasion resistance when the carbonate absorbs moisture. <P>SOLUTION: This grease additive contains a metal sulfonate and a carbonate and the grease composition is used the additive. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an additive for a grease composition that can effectively reduce wear in the presence of moisture.

  Grease is used as a lubricant to provide wear resistance, extreme pressure, low friction, and the like to sliding parts such as automobile drive systems and chassis parts. Grease basically consists of a base oil and a thickener. And in order to improve various above-mentioned performances more, improvement of these compositions, addition of various additives, etc. are proposed (refer patent documents 1-5).

  For the purpose of preventing direct contact between metals on the sliding surface, additives such as molybdenum disulfide and SP (sulfur-phosphorus) additives are blended in the grease. These additives receive a chemical reaction due to frictional heat, and form a film of glassy phosphate, sulfide, molybdenum disulfide or the like on the sliding surface to prevent direct contact between the sliding surfaces.

  However, the contact pressure may be very high in a point contact sliding form such as a sphere and a flat surface. Depending on the part, there may be a part having an extremely high surface pressure (3 GPa or more), and it may be difficult to maintain the wear resistance with a normal additive used for grease. Therefore, for the purpose of further improving the wear resistance of the reaction product film, a carbonate such as sodium carbonate is blended.

JP 2004-269551 A JP 2004-217702 A JP 2003-301190 A JP-A-10-280175 JP-A-9-276922

  However, the above method of blending a carbonate such as sodium carbonate with grease has the following problems. Carbonate has an action of absorbing moisture when left in a high temperature and humidity atmosphere for a long period of time. For example, in a sliding part using a porous resin cover, moisture penetrates into grease and binds to carbonate, and a film containing moisture is formed on the surface of the sliding part, thereby inhibiting the reaction of the additive on the sliding surface. . As a result, there is a problem that the sliding portions are in direct contact with each other and wear increases. Since there is no suitable additive for grease under ultra-high surface pressure other than carbonate, there is a strong demand to solve the above problems.

  The inventor has surprisingly found that the increase in wear due to moisture absorption can be suppressed by blending metal sulfonate with carbonate, and has completed the present invention.

The present invention includes the following inventions.
(1) An additive for grease comprising a metal sulfonate and a carbonate (except when the metal sulfonate is calcium sulfonate and the carbonate is calcium carbonate).
(2) The additive according to (1), wherein the metal sulfonate is calcium sulfonate.
(3) The additive according to (1) or (2), wherein the carbonate is at least one selected from the group consisting of sodium carbonate, potassium carbonate and calcium carbonate.
(4) A grease composition containing the additive according to any one of (1) to (3).

  The wear resistance of the sliding portion in the presence of moisture is improved by applying the grease composition containing the additive of the present invention to the sliding portion.

  Examples of the metal sulfonate used in the present invention include a metal salt of petroleum sulfonic acid obtained by sulfonation of an aromatic hydrocarbon component in a lubricating oil fraction, an alkyl aromatic such as dinonylnaphthalene sulfonic acid and alkylbenzene sulfonic acid. Synthetic sulfonic acid metal salts such as aromatic sulfonic acids, oxidized wax metal salts, petroleum sulfonic acid overbased metal salts, alkyl aromatic sulfonic acid overbased metal salts, and oxidized wax overbased metal salts At least one selected from the group consisting of: Particularly preferred are a metal salt of dinonylnaphthalene sulfonic acid and a metal salt of alkyl aromatic sulfonic acid. Examples of the metal ions constituting these metal sulfonates include divalent or trivalent metal ions such as calcium ions and magnesium ions. Particularly preferred is calcium ion.

  Examples of the carbonate used in the present invention include sodium carbonate, potassium carbonate, and calcium carbonate. Particularly preferred is sodium carbonate.

  In the present invention, a combination using calcium sulfonate as the metal sulfonate and sodium carbonate as the carbonate is particularly preferable.

  Although the compounding ratio of the metal sulfonate and carbonate can be selected as appropriate, the range of metal sulfonate: carbonate = 6: 4 to 9: 1 (molar ratio) is preferable.

  The mechanism by which the wear resistance of the sliding portion is improved by the combination of metal sulfonate and carbonate is considered as follows. When a metal sulfonate is present in a grease composition containing carbonate, the polar portion of the metal sulfonate adheres to the surface of the carbonate particles and a micelle-like structure is formed, so that moisture absorption into the carbonate is suppressed. It is thought that. As a result, moisture and hydrate are difficult to approach the carbonate in the grease composition, so that the tribo film formation is not hindered on the sliding surface to which the grease composition containing the additive of the present invention is applied. This improves the intervening property and improves the wear resistance. Further, the carbonate and water are isolated from each other, so that the sliding portion is prevented from being corroded.

  The grease additive of the present invention constitutes a grease composition in combination with ordinary base oils and thickeners and, if necessary, ordinary additives such as antioxidants, rust inhibitors and extreme pressure agents. Can do. Although the compounding quantity of the additive of this invention in a grease composition can be selected suitably, it is preferable that it is the range of 0.1 to 5.0 weight%.

  As the base oil, those used in ordinary grease can be used. For example, synthetic hydrocarbon base oils such as poly α-olefin and polybutene synthetic squalane, dibasic acid diesters, polyol ester base oils such as neopentyl polyol ester, phosphate ester bases such as alkyl phosphate esters and allyl phosphate esters 1 type from base oil, polyglycol base oil such as polyethylene glycol, polypropylene glycol, polyethylene glycol ester, polyethylene glycol ether, or mineral base oil such as naphthenic mineral oil, paraffin mineral oil, aromatic mineral oil, highly produced mineral oil, etc. Alternatively, a plurality of types can be selected and used.

  Thickeners include soaps such as sodium soap, lithium soap, calcium soap, calcium complex soap, aluminum complex soap, lithium complex soap, organic bentonite, ultrafine silica, sodium terephthalate, urea compound, polytetrafluoro Non-soap thickeners such as ethylene are exemplified, but not limited thereto. The grease additive of the present invention is considered to function also as a thickener, but the combined use with other thickeners as listed here is not hindered.

  As a preferable example of the grease composition using the additive for grease of the present invention, base oil (paraffinic mineral oil, synthetic oil (poly α-olefin), etc.): 80 to 90% by weight, S—P additive: 0. 1 to 0.3% by weight, Mo-based additive (solid): 0.2 to 0.8% by weight, Mo-based additive (liquid): 0.2 to 0.8, Additive for grease of the present invention: The composition which consists of 0.1 to 5 weight% can be mentioned. In this example, the viscosity of the base oil is preferably 100 to 300 mm / sec (40 ° C.) and 10 to 50 mm / sec (100 ° C.).

  The present invention will be specifically described below based on examples, but the present invention is not limited by these descriptions.

  Grease compositions (Examples and Comparative Examples) shown in Table 1 below were prepared.

  Using these grease compositions (Examples and Comparative Examples) to which moisture (0.2, 0.5, 1.0% by weight) was added, a sliding test was conducted. The test conditions are as follows.

  The appearance of the plate after the end of the sliding test using 1.0 wt% water added grease is shown in FIG. In the examples, wear was suppressed compared to the comparative example.

  FIG. 2 shows the relationship between the amount of added water and the maximum wear depth of the plate. In the comparative example, the wear depth increased as the amount of water added increased, but in the examples, the increase in wear due to the addition of water was hardly observed.

The appearance of the plate after the completion of the sliding test using 1.0 wt% water added grease is shown. The relationship between the amount of added water and the maximum wear depth of the plate is shown.

Claims (4)

  An additive for grease comprising a metal sulfonate and a carbonate (except when the metal sulfonate is calcium sulfonate and the carbonate is calcium carbonate).   The additive of claim 1, wherein the metal sulfonate is calcium sulfonate.   The additive according to claim 1 or 2, wherein the carbonate is at least one selected from the group consisting of sodium carbonate, potassium carbonate and calcium carbonate.   The grease composition containing the additive in any one of Claims 1-3.

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