JP4505954B2 - Lubricating grease composition - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lubricating grease composition. More specifically, the present invention relates to a relatively inexpensive lubricating grease composition that has improved wear resistance, leakage resistance, cleanability, and the like with respect to a counterpart material.
[0002]
[Prior art]
Conventional fluorine-based greases are composed of perfluoropolyether as a base oil, polytetrafluoroethylene and a tetrafluoroethylene copolymer as a thickener, and a small amount of other additives such as a rust preventive. Such a fluorine-based grease is excellent in durability at high temperatures, oxidation stability, chemical resistance, and the like, and thus can be used under extremely severe conditions.
[0003]
However, this grease is not only expensive because the base oil and the thickener are both fluorine-based, but it is not well-suited with metal, resin, rubber, etc., which are lubricating materials, and under conditions such as high load, An oil film necessary for lubrication was not formed, and noise or the like due to wear or sliding could be caused. In addition, these greases have low compatibility with hydrocarbon oils and cannot be mixed with them. Depending on the sealing conditions, grease leakage or poor lubrication may occur from bearings or gearboxes. Therefore, when using the fluorine-based grease, it is necessary to carefully remove the rust preventive agent previously applied to the bearing or the like with a solvent or the like.
[0004]
In addition, since fluorine-based grease has excellent solvent resistance, for example, CFC-113, HCFC-141b, HCFC-225, PFC can be used to clean bearings and other parts or machinery using fluorine-based grease. It is necessary to use chlorofluorocarbon solvents such as -5060. However, these chlorofluorocarbon solvents are said to have an effect on the destruction of the ozone layer and global warming, and some of them can no longer be used, and some of them will be restricted in the future.
[0005]
In order to avoid these problems, greases using vinylidene fluoride-hexafluoroisobutylene copolymer as a thickener (JP-A-4-246498) and fluorine-based greases using hexagonal lattice boron nitride as a thickener (same as above) No. 7-102274) has been proposed. However, these greases are inferior to conventional hydrocarbon greases in any one of price, compatibility with hydrocarbon oil, and detergency with a solvent.
[0006]
Furthermore, it has been proposed to use a fluorine-containing oil having a molecular terminal functional group (No. 1-272696), thereby imparting high corrosion resistance to the metal surface and greatly expanding the range of thickener selection. However, in this case as well, the price, wear resistance against the mating material, and cleaning properties are not sufficient. In addition, by adding fluorine-containing oil to hydrocarbon-based greases, it has been proposed that it is cheaper than conventional fluorine-based greases and has excellent wear resistance against the mating material (7-268370). In this case, the amount of fluorine-containing oil added is limited from the viewpoint of compatibility, and as a result, it is inevitable that the heat resistance is inferior to that of conventional fluorine-based grease.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a fluorine-based grease that is excellent in wear resistance, leakage resistance, cleanability, and the like with respect to a counterpart material, and that is satisfactory in cost.
[0008]
[Means for Solving the Problems]
An object of the present invention is to provide a lubricating grease composition in which at least one of an aliphatic dicarboxylic acid metal salt, a monoamide monocarboxylic acid metal salt, or a monoester carboxylic acid metal salt is added as a thickener to a perfluoropolyether base oil. Achieved by:
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The perfluoropolyether used as the base oil has a general formula
RfO (CF ₂ O) p (C ₂ F ₄ O) q (C ₃ F ₆ O) rRf
More specifically, for example, those represented by the following general formulas (1) to (4) are used, and those represented by the following general formula (5) are also used. Rf is a perfluoro lower alkyl group such as a perfluoromethyl group or a perfluoroethyl group.
(1) RfO (CF ₂ CF ₂ O) m (CF ₂ O) nRf
Here, m + n = 3 to 200 and m: n = 10 to 90:90 to 10 to 10 are randomly bonded, and this completely fluorinates the precursor produced by photo-oxidative polymerization of tetrafluoroethylene. Can be obtained.
(2) RfO [CF (CF ₃ ) CF ₂ O] m (CF ₂ O) nRf
Here, m + n = 3 to 200 and m: n = 10 : 90 are randomly bonded, and this is obtained by completely fluorinating a precursor produced by photo-oxidative polymerization of hexafluoropropene. .
(3) RfO [CF (CF ₃ ) CF ₂ O] l (CF ₂ CF ₂ O) m (CF ₂ O) nRf
Here, l + m + n = 3 to 200, l: m = 1 to 199: 199 to 1, and (l + m): n = 10 to 90:90 to 10 are randomly combined. It can be obtained by completely fluorinating a precursor produced by photo-oxidative polymerization of tetrafluoroethylene and hexafluoropropene.
(4) RfO (CFXCF ₂ O) _{3 to 50} CF ₂ X
Here, X is a CF ₃ group or an F atom, which is an acid fluoride compound having a terminal-CFXCOF group obtained by anionic polymerization of hexafluoropropylene oxide or tetrafluoroethylene oxide in the presence of a cesium fluoride catalyst. Can be obtained by treating with fluorine gas.
(5) F (CF ₂ CF ₂ CF ₂ O) _{2 to 100} CF ₂ CF ₃
This is because 2,2,3,3-tetrafluorooxetane is anionically polymerized in the presence of a cesium fluoride catalyst, and the resulting fluorinated polyether (CH ₂ CF ₂ CF ₂ O) n is subjected to about UV irradiation. It is obtained by treating with fluorine gas at 160 to 300 ° C.
[0010]
These perfluoropolyether base oils can be used alone or mixed, but when used as a lubricating oil, the viscosity (40 ° C.) is about 5 to 1500 cSt, preferably about 10 to 1000 cSt. It is desirable to be. Those with about 5 cSt or less have a large amount of evaporation, and the condition of evaporation (1.5% or less) stipulated in Class 3 of JIS rolling bearing grease, which is a heat-resistant grease rule, is not met. On the other hand, about 1500 cSt or more, the pour point (JIS K-2283) is 10 ° C or higher, and the bearing does not rotate at low temperature start in the normal method, and it is necessary to heat to make it usable, As a general grease, use qualification is lacking.
[0011]
In such a perfluoropolyether base oil, at least one of an aliphatic dicarboxylic acid metal salt, a monoamide monocarboxylic acid metal salt or a monoester carboxylic acid metal salt is used as a thickener in the lubricating grease composition. It is added in a proportion of 50% by weight, preferably about 3 to 35% by weight. If the addition ratio is higher or lower, the desired object of the present invention cannot be achieved.
[0012]
As the aliphatic dicarboxylic acid metal salt, a metal salt of a saturated or unsaturated dicarboxylic acid having 6 to 20 carbon atoms or 2 to 5 carbon atoms as described below is used. As the metal salt, lithium, sodium, potassium, calcium, barium, magnesium, copper, iron, cobalt, zinc, aluminum and the like are used alone or in admixture of two or more.
[0013]
Examples of saturated dicarboxylic acids forming such metal salts include oxalic acid, malonic acid, succinic acid, methyl succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonamethylene dicarboxylic acid, decamethylene. Examples include dicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, tridecanedicarboxylic acid, tetradecanedicarboxylic acid, pentadecanedicarboxylic acid, hexadecanedicarboxylic acid, heptadecanedicarboxylic acid, and octadecanedicarboxylic acid, and preferably adipic acid, pimelic acid, and suberin. Acid, azelaic acid, sebacic acid, nonamethylene dicarboxylic acid, decamethylene dicarboxylic acid, undecane dicarboxylic acid, dodecanedicarboxylic acid, tridecanedicarboxylic acid, tetradecanedicarboxylic acid, pentadecane Njikarubon acid, hexadecandioyl acid, hepta-decane dicarboxylic acid, octadecane dicarboxylic acid, or the like is used. Examples of the unsaturated dicarboxylic acid include maleic acid, fumaric acid, 2-methylene succinic acid, 2-ethylene succinic acid, alkenyl succinic acid such as 2-methylene glutaric acid, and the like. These saturated or unsaturated dicarboxylic acids are used alone or in combination of two or more.
[0014]
The monoamide monocarboxylic acid metal salt is one in which the dicarboxyl group of the dicarboxylic acid is amidated and metallized, and the above-mentioned metal salts are used.
[0015]
Examples of the amidated amine include aliphatic primary such as butylamine, amylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, laurylamine, myristylamine, palmitylamine, stearylamine, and behenylamine. Aliphatic secondary amines such as amine, dipropylamine, diisopropylamine, dibutylamine, diamylamine, dilaurylamine, monomethyllaurylamine, distearylamine, monomethylstearylamine, dimyristylamine, dipalmitylamine, allylamine, diallylamine Aliphatic unsaturated amines such as oleylamine and dioleylamine, cycloaliphatic amines such as cyclopropylamine, cyclobutylamine, cyclopentylamine and cyclohexylamine, Aromatic amines such as niline, methylaniline, ethylaniline, benzylamine, dibenzylamine, diphenylamine, α-naphthylamine and the like are preferable, preferably hexylamine, heptylamine, octylamine, nonylamine, decylamine, laurylamine, myristylamine Palmitylamine, stearylamine, behenylamine, dibutylamine, diamylamine, monomethyllaurylamine, monomethylstearylamine, oleylamine and the like are used.
[0016]
The monoester carboxylic acid metal salt is obtained by esterification and metal chloride of the dicarboxyl group of the dicarboxylic acid, and the above-mentioned metal salts are used.
[0017]
Examples of the alcohol to be esterified include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, capryl alcohol, nonyl alcohol, decyl. Aliphatic saturated alcohols such as alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and behenyl alcohol, aliphatic unsaturated alcohols such as allyl alcohol, crotyl alcohol, propargyl alcohol, oleyl alcohol, cyclopentanol, cyclohexanol, etc. Aromatic alcohols such as alicyclic alcohol, benzyl alcohol, cinnamyl alcohol, etc. Examples include heterocyclic alcohols such as ryl alcohol, preferably hexyl alcohol, heptyl alcohol, octyl alcohol, capryl alcohol, nonyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, behenyl alcohol, etc. Is used.
[0018]
In the composition containing the above components as essential components, powdered silica or fluororesin can be further added in an amount of about 50% by weight or less, preferably about 3 to 35% by weight in the lubricating grease composition. As a result, the wear resistance against the mating material can be further improved.
[0019]
Silica includes natural silica, silicon or its hydride produced by drying, pulverizing, and classifying wet silica cake produced from naturally occurring silica and oxidizing it with an oxide such as oxygen or water, A commonly used silica such as synthetic silica obtained by hydrolyzing a functional compound or hydrolyzing silicon tetrachloride in an oxyhydrogen flame at high temperature can be used depending on the application. These silicas generally have an average particle size of about 50 μm or less, preferably about 0.001 to 30 μm.
[0020]
As the fluororesin, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropene copolymer, perfluoroalkylene resin and the like conventionally used as a lubricant are used. Polytetrafluoroethylene produces polytetrafluoroethylene with a number average molecular weight Mn of about 1000 to 100000 by methods such as emulsion polymerization, suspension polymerization, and solution polymerization of tetrafluoroethylene. What was processed by methods, such as irradiation decomposition and physical crushing, is used. Also, the copolymerization reaction of tetrafluoroethylene and hexafluoropropene and the molecular weight reduction treatment are performed in the same manner as in the case of polytetrafluoroethylene, and those having a number average molecular weight of about 1000 to 600000 are used. The molecular weight can also be controlled by using a chain transfer agent during the copolymerization reaction. The obtained powdery fluororesin generally has an average primary particle size of about 500 μm or less, preferably about 0.1 to 30 μm.
[0021]
The composition further contains additives that have been added to conventional lubricants such as other thickeners, antioxidants, rust inhibitors, corrosion inhibitors, extreme pressure agents, oil agents, and other solid lubricants. It can be added as necessary.
[0022]
Examples of other thickeners include clay, graphite, zinc oxide, urea compound, polyethylene, polypropylene, polyamide, soap, and organic pigment.
[0023]
Examples of the antioxidant include 2,6-di-tert-butyl-4-methylphenol, 4,4'-methylenebis (2, 6-di-tert-butylphenol) phenol-based antioxidants such as alkyl diphenylamines (alkyl Group having 4 to 20 carbon atoms), amine-based antioxidants such as triphenylamine, phenyl-α-naphthylamine, phenothiazine, alkylated phenyl-α-naphthylamine, phenothiazine, and alkylated phenothiazine.
[0024]
Examples of the rust preventive agent include fatty acids, fatty acid soaps, fatty acid amines, alkyl sulfonates, paraffin oxides, polyoxyalkyl ethers, and the like, and examples of the corrosion inhibitor include benzotriazole, benzimidazole, thiadiazole, and the like. It is done.
[0025]
Examples of extreme pressure agents include phosphorus compounds such as phosphate esters, phosphites and phosphate ester amine salts, sulfur compounds such as sulfides and disulfides, and chlorine compounds such as chlorinated paraffin and chlorinated diphenyl. And sulfur compound metal salts such as zinc dialkyldithiophosphate and molybdenum dialkyldithiocarbamate.
[0026]
Examples of the oily agent include fatty acids or esters thereof, higher alcohols, polyhydric alcohols or esters thereof, aliphatic amines, fatty acid monoglycerides and the like. Examples of other solid lubricants include molybdenum disulfide, graphite, boron nitride, and silane nitride.
[0027]
Preparation of the composition is either (a) a method in which a predetermined amount of a pre-synthesized thickener and other necessary additives are added to a perfluoropolyether base oil and kneaded with a three-roll or high-pressure homogenizer, or (b) In a reaction vessel capable of heating and stirring, a perfluoropolyether base oil and an aliphatic dicarboxylic acid are added and dissolved by heating, and a predetermined amount of metal hydroxide (and amine or alcohol) is added to the metal chloride reaction ( And amidation reaction or esterification reaction), cooling, and then kneading with a three-roll or high-pressure homogenizer.
[0028]
【The invention's effect】
As a thickener for grease, metal soap, urea compound, silica, clay, graphite, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropene copolymer, etc. have been conventionally known. It was believed that the thickeners that could be used practically in greases were limited to polytetrafluoroethylene or tetrafluoroethylene-hexafluoropropene copolymers.
[0029]
However, the present inventors have found that aliphatic dicarboxylic acid metal salts, monoamide monocarboxylic acid metal salts or monoester monocarboxylic acid metal salts do not use fluorine-containing oils or fluorine-based surfactants having molecular terminal functional groups. It has been found here that it is mixed with the perfluoropolyether base oil in any proportion.
[0030]
Such new knowledge makes it possible to use an aliphatic dicarboxylic acid metal salt, a monoamide monocarboxylic acid metal salt or a monoester monocarboxylic acid metal salt as a thickener for a perfluoropolyether base oil. The lubricating grease composition as an essential component can improve the wear resistance, leakage resistance, cleanability, etc. of the counterpart material without substantially impairing the heat resistance of conventional fluorinated grease. There is also an advantage in terms of cost.
[0031]
The lubricating grease composition of the present invention having such characteristics is used for sliding bearings, sliding bearings, gears, valves, cocks, oil seals, electrical contacts, etc. used under severe conditions such as high temperature, high speed, and high load. It can be effectively applied to moving parts.
[0032]
【Example】
Next, the present invention will be described with reference to examples.
[0033]
Examples 1-18, Comparative Examples 1-6
[Base oil]
A: RfO [CF (CF ₃ ) CF ₂ O] nRf, viscosity (40 ° C.) 100 cSt
B: RfO [CF (CF ₃ ) CF ₂ O] nRf, viscosity (40 ° C.) 400 cSt
C: Rf O [CF (CF 3) CF 2] m (CF 2 O) nRf, viscosity (40 ℃) 85cSt
_{D: Rf O (CF 2 CF} 2 O) m (CF 2 O) nRf, viscosity (40 ° C.) 160 cSt
E: Rf O (CF ₂ CF ₂ O) mRf, viscosity (40 ° C) 65cSt
[Thickener]
A: Dilithium azelate
B: Disodium sebacate
C: Dipotassium octadecanedicarboxylate
D: Dicalcium dodecanedicarboxylate
E: Calcium adipate
F: Azelaic acid monostearylamide sodium salt
G: Sebacic acid monooctylamide potassium salt
H: Nonamethylene dicarboxylic acid monohexyl ester lithium salt
[Additive]
A: Emulsion polymerization method polytetrafluoroethylene (molecular weight about 100-200,000, average primary particle size 0.2 μm)
B: Solution polymerization method tetrafluoroethylene-hexafluoropropene copolymer (molecular weight: about 50,000 to 150,000, average primary particle size: 0.2 μm)
C: Natural silica (average particle size about 12μm)
[0034]
A lubricating grease composition was prepared by combining the above base oil, thickener and additives, and the performance of the composition was evaluated by the following various test methods.
[Abrasion resistance evaluation test for mating material]
Using a shell four-ball tester, test piece: SUJ2 (1/2 inch), 20 grade, rotation speed: 20 times / second, load: 392.3N (40Kgf), temperature: room temperature, time: wear for 60 minutes Test and measure wear scar diameter after test
[Bearing grease leakage test]
The bearing 6204ZZ (with metal seal) coated with synthetic hydrocarbon rust preventive oil is filled with 3.0g of grease, and at room temperature, condition 1: rotational speed 0.17s ^-1 -radial load 2750Kg
Condition 2: Rotational speed 2.87s ^-1 -Radial load 2750Kg
Condition 3: Rotation speed 50s ^-1 -Radial load 490Kg
Condition 4: Rotational speed 166.67s ^-1 -Radial load 490Kg
Rotate the bearing continuously for 2 hours under each of the above conditions, measure the amount of grease that leaked after the test was completed. Evaluation
[Detergency test (oil solubility test)]
Fill bearing 6204ZZ (without metal seal) with 3.0 g of grease, soak the grease-filled bearing in petroleum ether, ultrasonically wash for 10 minutes, and then measure the weight of grease degreased from the bearing. Evaluated as ◯ for degreased grease, △ for some remaining grease, and x for no change.
The above test results are shown in the following Tables 1 and 2 together with the base oil, thickener and additive combinations used.

Claims (3)

A lubricating grease composition obtained 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. The lubricating grease composition according to claim 1, wherein a perfluoropolyether having a viscosity of 5 to 1500 cSt (40 ° C) is used. The lubricating grease composition according to claim 1, further comprising powdery silica or a fluororesin.