Grease composition for electrical contacts

Abstract

Provided is a grease composition for electrical contacts that is heat resistant at high temperatures such as 130°C or higher and can suppress the occurrence of chattering at low temperatures such as -35°C or lower. The grease composition for electrical contacts of the present invention contains 5 to 18 mass % of a thickener containing a lithium complex soap, and has a kinematic viscosity at 40°C of 9 to 40 mmHg. 2 The composition is characterized in that it contains 82 to 92 mass % of a base oil containing poly-α-olefin of 1 / s.

Description

[Technical Field]

[0001] The present invention relates to a grease composition for electrical contacts that suppresses chattering in copper or silver contacts at low temperatures. [Background technology]

[0002] Grease is often applied to sliding electrical contacts in electrical products, on-board electrical components, etc. to prevent wear. In recent years, the market for electric vehicles has expanded, and the temperatures at the sliding electrical contacts of on-board electrical components of electric vehicles have risen, creating a demand for the development of a grease composition that does not deteriorate in performance even at high temperatures.

[0003] Lithium soap is often used as a thickener in greases used on electrical contacts, but the maximum temperature at which lithium soap grease can be used is around 130°C, and use at temperatures higher than this becomes difficult. Also, urea grease is an example of a grease that can be used at temperatures above 130°C, but when used for electrical contacts, it tends to form an insulating film on the contacts, which can hinder electrical conduction, and so there are few examples of practical use of this type.

[0004] On the other hand, grease applied to electrical contacts of automotive electrical components may be exposed to low temperatures outdoors, such as below freezing, which can cause the grease to thicken and harden, impairing electrical conductivity and resulting in voltage drops (chattering). To prevent chattering in such low temperature ranges, for example, a base oil with a kinematic viscosity of 9 to 40 mm at 40°C is used. 2 A grease composition for electrical contacts has been developed that contains a synthetic hydrocarbon oil containing 1,2-dichloro-1,3-dimethyl-2,4-trimethylsilyl-1 ... In addition, as another example, a grease composition for electrical contacts containing a thickener, a base oil, and an additive, which contains a quaternary ammonium salt of hectorite as an additive, has also been developed (see Patent Document 2 below). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-186609 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-204547 Summary of the Invention [Problem to be solved by the invention]

[0006] Electrical contacts of automotive electrical components, particularly those of electric vehicles, are exposed to a wide range of temperatures, from high temperatures (e.g., 130°C or higher) to low temperatures (e.g., -35°C or lower). Therefore, there is a need for the development of a grease composition that can be used at high temperatures and is effective in preventing chattering at low temperatures.

[0007] As a result of extensive research, the inventors discovered that by using a lithium complex soap as a thickener for a grease composition, heat resistance can be achieved in the high temperature range and chattering can be suppressed in the low temperature range, thereby achieving the present invention.

[0008] Therefore, an object of the present invention is to provide a grease composition for electrical contacts that has heat resistance in high temperature ranges such as 130°C or higher and can suppress the occurrence of chattering in low temperature ranges such as -35°C or lower. [Means for solving the problem]

[0009] The grease composition for electrical contacts according to one embodiment of the present invention contains 5 to 18 mass % of a thickener containing a lithium complex soap, and has a kinematic viscosity at 40°C of 9 to 40 mm 2 The composition is characterized in that it contains 82 to 92 mass % of a base oil containing poly-α-olefin of 1 / s.

[0010] In the grease composition for electrical contacts of one aspect described above, the lithium complex soap is preferably formed from 12-hydroxystearic acid and azelaic acid, and more preferably the lithium complex soap is represented by the following formula 1:

[0011] TIFF0007772980000001.tif31170

[0012] The grease composition for electrical contacts of the above-mentioned one embodiment preferably has a dropping point of 230° C. or higher.

[0013] The present invention also provides a thickener containing 5 to 18 mass % of a lithium complex soap, and a kinematic viscosity at 40°C of 9 to 40 mm 2 The present invention also covers a method for suppressing chattering at temperatures below -35°C, which involves applying to electrical contacts a grease composition containing 82 to 92 mass% of a base oil containing poly-α-olefin of 1 / s. [Effects of the Invention]

[0014] A grease composition for electrical contacts according to one embodiment of the present invention contains a predetermined amount of lithium complex soap as a thickener, and thereby has heat resistance at high temperatures such as 130°C or higher, and can suppress the occurrence of chattering at low temperatures such as -35°C. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a diagram showing the results of XRD analysis of the isohexane extraction residue of the grease composition of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described below based on one embodiment, but the present invention is not limited to this embodiment.

[0017] <Grease composition> A grease composition for electrical contacts according to one embodiment of the present invention (hereinafter also referred to as the present grease composition) contains 5 to 18 mass % of a thickener containing a lithium complex soap, and has a kinematic viscosity at 40°C of 9 to 40 mm 2 The base oil contains 82 to 92 mass % of a poly-α-olefin.

[0018] (thickener) The thickener of the present grease composition contains a lithium complex soap, and the thickener preferably contains 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. The lithium complex soap can be formed from a lithium aliphatic carboxylate and a lithium dibasic acid salt. Examples of the aliphatic lithium carboxylate include lithium 12-hydroxystearate and lithium stearate, and among these, lithium 12-hydroxystearate is preferred. Examples of dibasic acids include azelaic acid, succinic acid, malonic acid, adipic acid, pimelic acid, and sebacic acid, with azelaic acid being preferred.

[0019] More specifically, the lithium complex soap is particularly preferably one represented by the following formula 1:

[0020] TIFF0007772980000002.tif31170

[0021] The thickener may contain other components than the lithium complex soap, such as lithium 12-hydroxystearate. The mass proportion of the lithium complex soap in the thickener can be measured, for example, by XRD diffraction.

[0022] The thickener may be contained in the present grease composition in an amount of 5 to 18 mass %, preferably 10 to 16 mass %, and more preferably 12 to 14 mass %.

[0023] The thickener can be produced in the base oil, for example, by mixing an aliphatic carboxylic acid, a dibasic acid, lithium hydroxide, etc. with the base oil and heating the mixture, but the production method is not limited thereto.

[0024] (base oil) The base oil of the present grease composition may be a hydrocarbon synthetic oil, and examples of the hydrocarbon synthetic oil include poly-α-olefin (PAO) oil. A more specific example is PAO4 (kinematic viscosity at 100°C of about 4 mmHg). 2 / s) or PAO6 (kinematic viscosity at 100°C is approximately 6 mm 2 Examples of commercially available PAO6 products include those under the trade name "Synfluid PAO6" (manufactured by Chevron Phillips Chemical Company) and those under the trade name "SpectraSyn Plus6" (manufactured by Exxon Mobil Corporation), and examples of commercially available PAO4 products include those under the trade name "Synfluid PAO4" (manufactured by Chevron Phillips Chemical Company), those under the trade name "SpectraSyn 4" (manufactured by Exxon Mobil Corporation), and those under the trade name "SpectraSyn MaX3.5" (manufactured by Exxon Mobil Corporation).

[0025] The base oil may be used alone or in combination of two or more. For example, two or more types of base oil with different viscosities may be used in combination. However, it is preferable that the base oil does not contain a polymer such as polyisobutylene (trade name "Oppanol B15N" (manufactured by BASF)). The base oil preferably contains 98% by mass or more, more preferably 99% by mass or more, and particularly preferably 99.9% by mass or more (including 100% by mass) of a hydrocarbon synthetic oil.

[0026] The kinematic viscosity of the base oil at 40°C is 9 to 40 mm 2 / s is preferable, 11 to 35 mm 2 / s is more preferable, 14 to 32 mm 2 / s is particularly preferred.

[0027] The kinematic viscosity of the base oil at 100°C is not particularly limited, but is preferably 1 to 10 mm 2 / s is preferable, 2 to 8 mm 2 / s is more preferable, 3.5 to 6.5 mm 2 / s is particularly preferred.

[0028] The viscosity index of the base oil is preferably 130 or higher, the pour point of the base oil is preferably -60°C or lower, and the flash point of the base oil is preferably 230°C or higher.

[0029] The base oil may be contained in the present grease composition in an amount of 82 to 92 mass %, preferably 85 to 91 mass %, and more preferably 86 to 88 mass %.

[0030] (additives) The present grease composition may contain additives as components other than those described above. Examples of additives include antioxidants (e.g., amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, and alkylated-α-naphthylamine; phenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and 4,4'-methylenebis(2,6-di-t-butylphenol)); extreme pressure additives (e.g., phosphorus-based extreme pressure agents such as phosphate esters, acid phosphate esters, phosphites, acid phosphites, and amine salts thereof; sulfurized oils and fats; thiadiazole-based compounds; dialkyldisals; sulfur-based extreme pressure agents such as zinc dithiophosphate, zinc dithiocarbamate, and organometallic compounds such as nickel dithiocarbamate), rust inhibitors (for example, metal sulfonates, lanolin derivatives, sodium nitrite, succinic acid esters, zinc fatty acids, amines, and sorbitan monooleate), structural stabilizers, metal deactivators (for example, benzotriazole), wear reducers (for example, phosphate esters and dithiocarbamic acid esters), and metal oxides (for example, zinc oxide). The additive may be contained in one kind or in two or more kinds. When an additive is contained in the present grease composition, the additive is preferably contained in the present grease composition in an amount of 0.5 to 2 mass %.

[0031] (Manufacturing method) The present grease composition can be produced by blending the base oil, the thickener, and, if necessary, the above-mentioned additives in the above-mentioned proportions, followed by milling. Milling may be performed while heating. The milling can be carried out using a milling dispersion processing device such as a three-roll mill, a homogenizer, or a colloid mill, although the milling is not particularly limited.

[0032] (Physical properties of this grease composition) The grease composition preferably has a worked penetration in the range of 230 to 340, more preferably in the range of 250 to 280. The worked penetration can be measured in accordance with JIS K2220.

[0033] The grease composition preferably has a dropping point of 230° C. or higher, more preferably 250° C. or higher. The dropping point can be measured in accordance with JIS K2220.

[0034] This grease composition has a kinematic viscosity of 35mm at 40°C. 2 / s or less is preferable, and 31 mm 2 / s or less is more preferable, and 20 mm 2 The kinematic viscosity at 40°C can be measured in accordance with JIS K2283.

[0035] The grease composition preferably has a weight loss of at least -4.8% by mass, more preferably at least -4% by mass, and particularly preferably at least -2.5% by mass. The weight loss can be measured by the method shown in the Examples below.

[0036] The grease composition preferably exhibits a consistency change at 130°C in the range of +30 to +80, more preferably +40 to +70, and particularly preferably +45 to +65. The consistency change at -40°C is preferably in the range of -100 to -40, more preferably -90 to -50, and particularly preferably -80 to -60. The consistency at 130°C and -40°C is measured in the same manner as in the consistency measurement method of JIS K2220, and the amount of change can be determined based on the consistency at 25°C.

[0037] (Application) The present grease composition is suitable for use in sliding electrical contacts, particularly copper or silver contacts, and is particularly suitable for copper contacts. It is particularly suitable for automotive electrical components, particularly for electric vehicles, because it has heat resistance at high temperatures such as 130°C or higher and can suppress chattering at low temperatures such as -35°C. The on-vehicle electrical components include, for example, inhibitor switches. In addition to in-vehicle electrical components, examples of applications include vibration motors for mobile phones. [Example]

[0038] The present invention will be described below based on an example, but the present invention is not limited to this example.

[0039] The following Examples 1 to 4 and Comparative Examples 1 to 3 were prepared.

[0040] Example 1 In a 300 mL stainless steel cup, PAO6 (Synfluid PAO6 manufactured by Chevron Phillips Chemical Co., Ltd.; kinematic viscosity (40°C) 30.7 mm) was used as a base oil. 2 111.88 g of 12-hydroxystearic acid (manufactured by NOF Corporation under the trade name "Castor Hydrogenated Fatty Acid") was added to the mixture, which was then heated with stirring. At 80°C, 3.92 g of azelaic acid (manufactured by Emery Oleochemicals under the trade name "EMEROX1144") was added, and at 100°C, 21.08 g of 12-hydroxystearic acid (manufactured by NOF Corporation under the trade name "Castor Hydrogenated Fatty Acid") was added, and it was confirmed that the azelaic acid and 12-hydroxystearic acid had dispersed and melted into droplets.

[0041] After confirming melting, the temperature was lowered to 90-95°C, and then 7.46 g of anhydrous lithium hydroxide dispersion (Lubrizol 5280GR manufactured by Lubrizol Corporation) was added dropwise over 30-60 minutes. The temperature was then raised to 100-110°C and maintained at this temperature for 30-60 minutes to remove moisture. The mixture was then heated to 180°C at a rate of 2°C / min and held for 5 to 10 minutes, after which 55.66 g of the PAO6 was added as cooling oil. The mixture was cooled to room temperature with continued stirring, and then milled with a three-roll mill to produce the grease composition of Example 1.

[0042] To confirm whether the thickener in the grease composition of Example 1 had been converted into a lithium complex, the resulting grease composition was extracted with isohexane and the residue was subjected to XRD diffraction measurement, confirming that the grease composition of Example 1 contained 50 mass % or more of the lithium complex soap represented by the above formula 1, as shown in Figure 1, and thus confirming that the grease composition of Example 1 was a lithium complex grease. Note that in Figure 1, α represents the lithium complex soap represented by the above formula 1, and β represents lithium 12-hydroxystearate.

[0043] Example 2 The grease composition of Example 2 was prepared in the same manner as Example 1, except that the blending ratio of each raw material in Example 1 was changed as shown in Table 1 below. As a result of XRD diffraction analysis similar to that described above, it was confirmed that the grease composition of Example 2 was a lithium complex grease.

[0044] Example 3 In Example 1, PAO6 was used as the base oil, and PAO4 ("Synfluid PAO4" manufactured by Chevron Phillips Chemical Co., Ltd.; kinematic viscosity (40°C) 17.4 mmHg) was used. 2 The grease composition of Example 3 was prepared in the same manner as in Example 1, except that the mixing ratio of each raw material was changed to " / s") and the blending ratio of each raw material was changed as shown in Table 1 below. As a result of the same XRD diffraction analysis as above, it was confirmed that the grease composition of Example 3 was a lithium complex grease.

[0045] Example 4 In Example 1, PAO6 was used as the base oil, and PAO4 ("SpectraSyn Max 3.5" manufactured by Exxon Mobil Corporation; kinematic viscosity (40°C) 14.3 mmHg) was used. 2 The grease composition of Example 4 was prepared in the same manner as in Example 1, except that the mixing ratio of each raw material was changed to " / s") and the blending ratio of each raw material was changed as shown in Table 1 below. As a result of the same XRD diffraction analysis as above, it was confirmed that the grease composition of Example 4 was a lithium complex grease.

[0046] (Comparative Example 1) In a 300 mL stainless steel cup, PAO6 (Synfluid PAO6 manufactured by Chevron Phillips Chemical Co., Ltd.; kinematic viscosity (40°C) 30.7 mm) was used as a base oil. 2 185.1 g of styrene-isoprene block copolymer (manufactured by Infinium under the trade name of "Infineum SV-150") as a polymer was added, and 14.0 g of 12-lithium stearate (manufactured by Katsuta Chemical Industry under the trade name of "Li-OH-St") was added as a thickener. The mixture was heated to 240°C and subjected to a three-roll milling treatment to produce the grease composition of Comparative Example 1.

[0047] (Comparative Example 2) In Comparative Example 1, the base oil was PAO6 ("Synfluid PAO6" manufactured by Chevron Phillips Chemical Company; kinematic viscosity (40°C) 30.7 mm 2 The grease composition of Comparative Example 2 was produced in the same manner as in Comparative Example 1, except that only 186.0 g of sucrose / s was used.

[0048] (Comparative Example 3) In a 300 mL stainless steel cup A, PAO6 (Synfluid PAO6 manufactured by Chevron Phillips Chemical Co., Ltd.; kinematic viscosity (40°C) 30.7 mm) was added as a base oil. 261.7 g of methylparaben (PAO6) (61.7 g of methylparaben / s) and 7.0 g of MDI (diphenylmethane diisocyanate) (Millionate MT, manufactured by Tosoh Corporation) were added, heated to 60°C, and dissolved by stirring. 23.3 g of PAO6 and 8.0 g of p-toluidine (p-Toluidine, manufactured by Lanxess) were added to a 300 mL stainless steel cup B, and heated to 60°C to dissolve the mixture. This solution was added to stainless steel cup A, and the temperature was raised to 100°C while stirring and maintained for a certain period of time. Thereafter, the temperature was raised to 165°C while continuing stirring, and the mixture was allowed to cool while maintaining the temperature. The mixture was then milled using a three-roll mill to produce the grease composition of Comparative Example 3.

[0049] [Table 1]

[0050] (test) The following tests were carried out on the grease compositions of Examples 1 to 4 and Comparative Examples 1 to 3. The results of these tests are shown in Table 1 above.

[0051] <Unmixed / mixed consistency> The unmixed / worked penetration was measured in accordance with JIS K2220.

[0052] <Dripping point> The dropping point was measured in accordance with JIS K2220.

[0053] <Kinematic viscosity> The kinematic viscosity at 40°C was measured in accordance with JIS K2283.

[0054] <Oil separation degree> The oil separation rate was measured in accordance with JIS K2220 under conditions of 130°C and 24 hours.

[0055] <Change in consistency> The change in consistency was measured at 130°C or -40°C in the same manner as in the consistency measurement method of JIS K2220, and the difference was calculated using the consistency at 25°C as the standard.

[0056] <Grease thin film oxidation test> Each grease composition was applied to a 2 mm thick SPCC plate (cold-rolled steel plate) (120 mm long x 50 mm wide) and left to stand in a constant temperature bath at 150°C for 24 hours. After this, the change in consistency and weight loss of each grease composition before and after the test were confirmed. The weight loss was measured using an electronic balance. Grease compositions with a weight loss of 5.0 mass% or more due to softening / hardening of the consistency caused by high-temperature oxidation were deemed unsuitable for use in high-temperature environments and were therefore deemed to have failed the test.

[0057] <Chattering test> Each grease composition was applied to a thickness of 0.4 mm to a chattering test plate made by joining half a copper plate and half a POM (polyoxymethylene) resin plate. The copper rivet and the chattering test plate were then set in a reciprocating sliding tester ("Tribogear" manufactured by Shinto Chemical Co., Ltd.), and the specified load, voltage, and current were applied, with the plate sliding 10 times at 25°C for break-in. After leaving the plate to stand for 30 minutes at the specified temperature, the plate was subjected to 10 reciprocating sliding motions, during which the presence or absence of chattering was confirmed. Grease compositions that did not cause irregular voltage drops were rated as passing. (Measurement conditions) Load: 200g Sliding speed: 25mm / s Sliding width: 20mm (copper part 10mm, POM part 10mm) Voltage: 5V Current: 50mA Test temperature: -20℃, -40℃

[0058] <Base oil diffusion prevention test> Each grease composition was applied to a surface of frosted glass (100 mm long x 100 mm wide) conforming to JIS R3202, measuring 10 mm in diameter and 1.2 mm thick, and left to stand for 24 hours in a hot air circulating thermostatic chamber heated to 80°C. After standing, the size of oil bleeding from the edge of the applied grease composition was checked, and those that had oil bleeding of 2 mm or less were deemed to have passed. In addition, Examples 2 and 3 and Comparative Example 3 were not tested because they were expected to pass the test based on the results of Examples 1 and 4, which used the same or lower viscosity PAO as the base oil.

[0059] (result) The grease compositions of Examples 1 to 4, which contained poly-α-olefin in the base oil and lithium complex soap as a thickener, showed little change in consistency and little weight loss due to high-temperature oxidation, and did not experience discontinuous voltage drop (chattering) at -40°C. Furthermore, it was confirmed that the grease composition of Example 1 showed little oil bleeding and had a high ability to prevent the base oil from spreading. In contrast, the grease composition of Comparative Example 1, which contained a polymer in the base oil, showed softening due to high-temperature oxidation, and irregular voltage drops (chattering) occurred at -40°C, confirming that the base oil was diffusing. In Comparative Example 2, which contained lithium soap as a thickener, hardening of the grease composition due to high-temperature oxidation was observed, and it was confirmed that diffusion of the base oil occurred. In Comparative Example 3, which contained urea as a thickener, the occurrence of irregular voltage drops (chattering) at -20°C was confirmed.

[0060] The grease composition for electrical contacts of the present invention exhibits base oil diffusion prevention properties, can be used at temperatures of 130°C or higher, and has excellent chattering resistance at temperatures of -35°C or lower.

Claims

1. A thickener containing a lithium complex soap and 82 to 92% by mass of the total composition having a kinematic viscosity at 40°C of 9 to 40 mm ２ A grease composition for electrical contacts consisting solely of a base oil containing PAO4 or PAO6.

2. 2. The grease composition for electrical contacts according to claim 1, wherein the lithium complex soap is formed from 12-hydroxystearic acid and azelaic acid.

3. 3. The grease composition for electrical contacts according to claim 2, wherein the lithium complex soap is represented by the following formula 1:

4. 2. The grease composition for electrical contacts according to claim 1, wherein the dropping point of the grease composition is 230° C. or higher.

5. A thickener containing a lithium complex soap and 82 to 92% by mass of the total composition having a kinematic viscosity at 40°C of 9 to 40 mm ２ A method for suppressing chattering at temperatures below -35°C, comprising applying to an electrical contact a grease composition consisting solely of a base oil containing PAO4 or PAO6 with a viscosity of 1000 psi / s.

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