JP7610421B2 - Grease composition - Google Patents

Description

This invention relates to a grease composition.

Grease compositions with excellent wear resistance have been developed. Patent Document 1 (JP Patent No. 4505954) discloses a lubricating grease composition with excellent wear resistance, leakage resistance, cleanability, etc., by adding at least one of an aliphatic dicarboxylic acid metal salt, a monoamide monocarboxylic acid metal salt, or a monoester carboxylic acid metal salt as a thickener to a perfluoropolyether base oil. Patent Document 2 (JP Patent No. 4810842) discloses a lubricant composition for bearings of automobile accessories, which has excellent wear resistance and rust prevention properties by containing a perfluoropolyether base oil, a powdered fluororesin thickener, and a Ca salt or Na salt of an aromatic sulfonic acid or a saturated aliphatic dicarboxylic acid as a rust prevention additive. Patent Document 3 (Patent Publication No. 6055746) discloses a grease that uses a fluorine-based synthetic oil as a base oil, contains one or more inorganic acids selected from phosphates, tungstates, sulfates, and sulfites, and the inorganic acid salt is an alkali metal salt, and has excellent wear resistance and low environmental impact.

The grease compositions disclosed in Patent Documents 1 to 3 have excellent wear resistance at low temperatures, but there is a demand for even better wear resistance at high temperatures.

Patent No. 4505954 Patent No. 4810842 Patent No. 6055746

The present invention was made in consideration of the above circumstances, and provides a grease composition that has excellent wear resistance even at high temperatures.

The present invention relates to a grease composition containing pyrophosphoric acid and sodium sebacate,
The total content of pyrophosphate and sodium sebacate in the grease composition is 2 to 15 mass %,
The grease composition has a mass ratio of pyrophosphoric acid to the total mass of pyrophosphoric acid and sodium sebacate, that is, (pyrophosphoric acid)/(pyrophosphoric acid+sodium sebacate), of 0.01 to 0.15.
The present invention further provides a grease composition containing a perfluoropolyether as a base oil.
The present invention further provides a grease composition containing fluororesin particles as a thickener.

It is possible to provide a grease composition that has excellent wear resistance even at high temperatures.

The grease composition of the present invention contains pyrophosphoric acid (diphosphoric acid, H ₄ P ₂ O ₇ ) and sodium sebacate (C ₈ H ₁₆ (COONa) ₂ ), and the total content of pyrophosphoric acid and sodium sebacate in the grease composition is 2 to 15 mass %. Also, in the grease composition, the mass ratio of pyrophosphoric acid to the total mass of pyrophosphoric acid and sodium sebacate, (pyrophosphoric acid)/(pyrophosphoric acid + sodium sebacate), is 0.01 to 0.15. By containing pyrophosphoric acid and sodium sebacate such that the total content of pyrophosphoric acid and sodium sebacate is 2 to 15 mass % and (pyrophosphoric acid)/(pyrophosphoric acid + sodium sebacate) is 0.01 to 0.15, it is believed that a reaction film containing phosphate and sodium salts of components derived from the base oil is formed on the surface of a material to which the grease composition is applied. As a result, excellent wear resistance can be exhibited even at high temperatures, for example, of 200° C. or higher.

Each component contained in the grease composition of one embodiment will be described in detail below.
(Base oil)
The grease composition of one embodiment further contains a base oil. The type of base oil is not particularly limited, and examples thereof include synthetic oils and mineral oils. The synthetic oils and mineral oils may be used alone or in combination. Examples of synthetic oils include hydrocarbon oils such as polyα-olefins, ethylene-α-olefin copolymers, polybutene (polyisobutylene), alkylbenzenes, and alkylnaphthalenes; ester oils such as diesters (esters of dicarboxylic acids and monoalcohols), polyol esters, and aromatic esters; and ether oils such as perfluoropolyethers and alkyldiphenyl ethers. These synthetic oils may be used alone or in combination of two or more. Examples of aromatic esters include phthalic acid esters, isophthalic acid esters, trimellitic acid esters, and pyromellitic acid esters. Examples of polyol esters include esters of polyhydric alcohols and monocarboxylic acids. Examples of polyhydric alcohols include trimethylolpropane, ditrimethylolpropane, trimethylolethane, ditrimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, neopentyl glycol, etc. Examples of monocarboxylic acids include monovalent fatty acids having 4 to 16 carbon atoms, such as butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, etc.

Examples of perfluoropolyether base oils include those represented by the following general formulas (1) to (5).
(1) RfO(CF ₂ CF ₂ O) _m (CF ₂ O) _n Rf
Here, Rf is a perfluoro lower alkyl group such as a perfluoromethyl group or a perfluoroethyl group, m+n=3-200, m:n=10-90:90-10.
(2) RfO[CF(CF ₃ )CF ₂ O] _m (CF ₂ O) _n Rf
Here, Rf is a perfluoro lower alkyl group such as a perfluoromethyl group or a perfluoroethyl group, m+n=3 to 200, and m:n=10:90.
(3) RfO[CF(CF ₃ )CF ₂ O] _l (CF ₂ CF ₂ O) _m (CF ₂ O) _n Rf
Here, Rf is a perfluoro lower alkyl group such as a perfluoromethyl group or a perfluoroethyl group, l+m+n=3-200, l:m=1-199:199-1, (l+m):n=10-90:90-10.
(4) RfO (CFXCF ₂ O) _{3 to 50} CF ₂
Here, Rf is a perfluoro lower alkyl group such as a perfluoromethyl group or a perfluoroethyl group, and X is a _CF3 group or an F atom.
(5) F(CF ₂ CF ₂ CF ₂ O) _2-100 CF ₂ CF ₃

(Pyrophosphate, Sodium Sebacate)
The total content of pyrophosphoric acid and sodium sebacate in the grease composition is 2 to 15 mass%, and the mass ratio of pyrophosphoric acid to the total mass of pyrophosphoric acid and sodium sebacate, (pyrophosphoric acid)/(pyrophosphoric acid + sodium sebacate), is 0.01 to 0.15. By having the total content of pyrophosphoric acid and sodium sebacate and the mass ratio (pyrophosphoric acid)/(pyrophosphoric acid + sodium sebacate) within the above ranges, the grease composition can have excellent wear resistance even when used in a high temperature environment. The total content of pyrophosphoric acid and sodium sebacate in the grease composition is preferably 2 to 10 mass%, more preferably 2 to 7 mass%, and even more preferably 3 to 5 mass%. The mass ratio of pyrophosphoric acid to the total mass of pyrophosphoric acid and sodium sebacate, (pyrophosphoric acid)/(pyrophosphoric acid + sodium sebacate), is preferably 0.03 to 0.15, more preferably 0.03 to 0.12, and even more preferably 0.05 to 0.1. By having the total content and mass ratio of pyrophosphoric acid and sodium sebacate within the above ranges, the grease composition can have even better wear resistance at high temperatures.

(Other additives)
The grease composition may contain a thickener, an antioxidant, an extreme pressure agent, a viscosity index improver, etc., as long as the object of the present invention is not impaired. Examples of the thickener include metal soap, metal complex soap, carbon black, aerosil, bentone, terephthalamate, urea, phthalocyanine, fluororesin, and melamine cyanurate. Preferably, the thickener is a fluororesin particle, and the fluororesin particle may be polytetrafluoroethylene particles. Examples of the antioxidant include a phenol-based antioxidant, an amine-based antioxidant, a phosphoric acid-based antioxidant, and a sulfur-based antioxidant. Examples of the extreme pressure agent include phosphorus-based compounds such as phosphate esters, phosphites, and phosphate ester amine salts, sulfur compounds such as sulfides and disulfides, sulfur-based metal salts such as dialkyldithiophosphate metal salts and dialkyldithiocarbamate metal salts, and chlorine compounds such as chlorinated paraffin and chlorinated diphenyl. Examples of the viscosity index improver include polymethacrylate, ethylene-propylene copolymer, polyisobutylene, polyalkylstyrene, and hydrogenated styrene-isoprene copolymer.

The grease composition of the present invention can be preferably used by being applied to materials to be used in high-temperature environments. For example, the grease composition can be used to exert a lubricating effect in bearings such as rolling bearings and sliding bearings, devices inside automobiles such as electric radiator fan motors and fan couplings, resin manufacturing devices such as film tenders and film laminators, and papermaking devices such as corrugating machines. The temperature of the material to which the grease composition of the present invention is applied and used is not particularly limited as long as it is high, and examples of the temperature include temperatures of 200°C or higher and temperatures of 150 to 200°C.

The following provides a detailed explanation of preferred embodiments of the present invention based on examples and comparative examples, but the present invention is not limited to these examples.

(Examples 1 to 4, Comparative Examples 1 to 9)
Grease compositions having the compositions shown in Tables 1 and 2 below were prepared. The grease compositions prepared in each example were applied between a ball of φ10 mm made of SUJ2 material and a disk of 24 mm diameter and 7.9 mm thickness made of SUJ2 material. Next, using an SRV tester (Type 5), the ball was slid on the disk under the conditions of a temperature of 200° C., a frequency of 50 Hz, a test time of 1 hour, an amplitude of 1 mm, and a load of 20 N. The diameter of the wear mark on the ball after the test was measured and was taken as the wear amount (μm) of the ball. The measurement results of the wear amount are shown in Tables 1 and 2 below. The smaller the wear amount of the ball, the better the wear resistance of the grease composition at high temperatures. In Comparative Example 7, the test was terminated midway because an excessive load was applied to the SRV tester during the test. In addition, the grease composition prepared in Comparative Example 8 became hard and could not be applied between the ball and the disk. For this reason, it was not possible to evaluate the wear resistance at high temperatures for the grease compositions prepared in Comparative Examples 7 and 8.

The names of the materials used in Tables 1 and 2 are as follows:
Lubron L-2 (trade name) (manufactured by Daikin Industries, Ltd.): (PTFE) polytetrafluoroethylene particles, thickener BARRIERTA J 400 FLUID (trade name) (manufactured by NOK Kluber): perfluoropolyether base oil Irgacore DSSG (trade name) (manufactured by BASF Japan Ltd.): sodium sebacate sodium pyrophosphate reagent (trade name) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.): sodium pyrophosphate pyrophosphate reagent (trade name) (manufactured by Kanto Chemical Co., Ltd.): pyrophosphate

From the results in Tables 1 and 2, it was confirmed that a grease composition having a total content of pyrophosphoric acid and sodium sebacate of 2 to 15 mass % and a mass ratio of pyrophosphoric acid to the total mass of pyrophosphoric acid and sodium sebacate, (pyrophosphoric acid)/(pyrophosphoric acid + sodium sebacate), of 0.01 to 0.15, has excellent wear resistance even at a high temperature of 200°C.

Claims (1)

A grease composition containing pyrophosphate and sodium sebacate,
The total content of pyrophosphate and sodium sebacate in the grease composition is 2 to 15 mass %,
the mass ratio of pyrophosphoric acid to the total mass of pyrophosphoric acid and sodium sebacate, (pyrophosphoric acid)/(pyrophosphoric acid+sodium sebacate) , is 0.01 to 0.15;
Contains perfluoropolyether as base oil,
A grease composition comprising fluororesin particles as a thickener .