Grease composition for electrical contacts

Abstract

The present invention provides an electrical contact grease composition that has heat resistance in high-temperature ranges such as 130°C or above, and can suppress chattering in low-temperature ranges such as -35°C or below. [Solution] The electrical contact grease composition of the present invention contains 5 to 18% by mass of a thickener containing lithium complex soap, and has a kinematic viscosity of 9 to 40 mm at 40°C. 2 It is characterized by containing 82-92% by mass of a base oil containing poly-α-olefin of / s.

Description

[Technical Field]

[0001] The present invention relates to an electrical contact grease composition that suppresses chattering at copper or silver contacts in low-temperature ranges. [Background technology]

[0002] Sliding electrical contacts in electrical products and automotive electronic components are often coated with grease to prevent wear. In recent years, the electric vehicle market has expanded, and the temperature of sliding electrical contacts in electric vehicle electronic components has increased, creating a demand for the development of grease compositions that do not degrade in performance even at high temperatures.

[0003] Lithium soap is commonly used as a thickener in greases for electrical contacts, but the maximum temperature at which lithium soap grease can be used is around 130°C, making it difficult to use at temperatures higher than that. Another example of a grease that can be used at temperatures above 130°C is urea grease, but when used for electrical contacts, it tends to form an insulating film on the contacts, which may hinder electrical conductivity, and therefore there are very few examples of its practical application.

[0004] On the other hand, grease applied to electrical contacts in automotive electronic components can be exposed to freezing temperatures outdoors, which can cause it to thicken and harden, impairing conductivity and resulting in voltage drop (chattering). To prevent chattering at such low temperatures, for example, the base oil should have a kinematic viscosity of 9-40 mmHg at 40°C. 2 A grease composition for electrical contacts has been developed that contains a synthetic hydrocarbon oil of / s and includes at least one additive selected from the group consisting of organozinc compounds and thiadiazole compounds (see Patent Document 1 below). Furthermore, in another form, an electrical contact grease composition comprising a thickener, a base oil, and an additive has been developed, which includes a quaternary ammonium salt of hectorite as an additive (see Patent Document 2 below). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-186609 [Patent Document 2] Japanese Patent Publication No. 2006-204547 [Overview of the Initiative] [Problems that the invention aims to solve]

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

[0007] As a result of diligent research, the inventors of the present invention discovered that by using lithium complex soap as a thickener in a grease composition, it is possible to achieve heat resistance in high-temperature ranges and suppress chattering in low-temperature ranges, thereby realizing the present invention.

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

[0009] An electrical contact grease composition according to one aspect of the present invention contains 5 to 18% by mass of a thickener containing lithium complex soap, and has a kinematic viscosity of 9 to 40 mm at 40°C. 2 It is characterized by containing 82-92% by mass of a base oil containing poly-α-olefin of / s.

[0010] In the grease composition for electrical contacts according to the above aspect, 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] TIFF2026139106000001.tif31170

[0012] The grease composition for electrical contacts according to the above aspect preferably has a dropping point of 230°C or higher.

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

[0014] The grease composition for electrical contacts according to one aspect of the present invention, by containing a predetermined amount of lithium complex soap as a thickener, has heat resistance in a high temperature range such as 130°C or higher, and can suppress chattering occurrence in a low temperature range such as -35°C. Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a diagram showing the results of XRD diffraction of an isohexane extraction residue in the grease composition of Example 1. Mode for Carrying Out the Invention

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

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

[0018] (Thickener) The thickener in this grease composition contains lithium complex soap, preferably in an amount of 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. Lithium complex soaps can be formed from lithium aliphatic carboxylate and lithium dibasic acid. Examples of lithium aliphatic carboxylates include lithium 12-hydroxystearate and lithium stearate, with lithium 12-hydroxystearate being preferred. Examples of dibasic acids include azelaic acid, succinic acid, malonic acid, adipic acid, pimelic acid, and sebacic acid, with azelaic acid being the preferred choice.

[0019] More specifically, the lithium complex soap is particularly preferred if it is represented by the following formula 1.

[0020] TIFF2026139106000002.tif31170

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

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

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

[0024] (Base Oil) Examples of the base oil for the present grease composition include hydrocarbon synthetic oils, and examples of the hydrocarbon synthetic oils include poly-α-olefin (PAO) oils. More specific examples include PAO4 which is a hydrocarbon synthetic oil having a kinematic viscosity at 100°C of about 4 mm 2 / s) or PAO6 having a kinematic viscosity at 100°C of about 6 mm 2 / s). Examples of commercially available PAO6 include "Synfluid PAO6" (manufactured by Chevron Phillips Chemical Company LLC) and "SpectraSyn Plus6" (manufactured by Exxon Mobil). Examples of commercially available PAO4 include "Synfluid PAO4" (manufactured by Chevron Phillips Chemical Company LLC), "SpectraSyn 4" (manufactured by Exxon Mobil) and "SpectraSyn MaX3.5" (manufactured by Exxon Mobil).

[0025] As the base oil, one type may be used alone, or two or more types may be used in combination. For example, two or more types having different viscosities may be used in combination to constitute the base oil. 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 of a hydrocarbon synthetic oil, 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, more preferably 11 to 35 mm 2 / s, and particularly preferably 14 to 32 mm 2 / s.

[0027] The kinematic viscosity of the base oil at 100°C is not particularly limited, but is between 1 and 10 mm. 2 / s is preferred, 2-8 mm 2 / s is more preferable, 3.5~6.5mm 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 can be contained in this grease composition in an amount of 82-92% by mass, preferably 85-91% by mass, and more preferably 86-88% by mass.

[0030] (Additives) This grease composition may contain additives as other components besides those mentioned above. Examples of additives include antioxidants (e.g., amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, alkylated-α-naphthylamine, etc., phenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), etc.), extreme pressure additives (e.g., phosphorus-based extreme pressure agents such as phosphate esters, acidic phosphate esters, phosphite esters, acidic phosphite esters and their amine salts, sulfurized oils and fats, thiadiazole compounds, dialkyldisal Examples include sulfur-based extreme pressure agents such as phosphates and methylene bis-dialkyldithiocarbamates, organometallic compounds such as zinc dithiophosphate, zinc dithiocarbamate, and nickel dithiocarbamate, rust inhibitors (e.g., metal sulfonates, lanolin derivatives, sodium nitrite, succinic acid esters, zinc fatty acid esters, amines, sorbitan monooleate), structural stabilizers, metal deactivators (e.g., benzotriazole), wear reducers (e.g., phosphate esters, dithiocarbamate esters), and metal oxides (e.g., zinc oxide). The additive may include one type, or two or more types. If additives are included in this grease composition, it is preferable to include the additives in an amount of 0.5 to 2% by mass.

[0031] (Manufacturing method) This grease composition can be manufactured by blending a base oil, a thickener, and, if necessary, the above-mentioned additives in the above-mentioned proportions, and then milling the mixture. Milling may also be carried out while heating. Milling can be performed using milling and dispersion processing equipment such as a three-roll mill, homogenizer, or colloid mill, although this is not a specific limitation.

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

[0033] This grease composition preferably has a dropping point of 230°C or higher, and 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 35 mmHg at 40°C. 2 Preferably, it should be less than or equal to / s, and 31mm 2 It is more preferable to be less than or equal to / s, and 20mm 2 It is particularly preferable that the kinematic viscosity is less than or equal to / s. The kinematic viscosity at 40°C can be measured in accordance with JIS K2283.

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

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

[0037] (Application) This grease composition is suitable for use in sliding electrical contacts, and is suitable for copper or silver contacts, and particularly suitable for copper contacts. In particular, it has heat resistance in high temperature ranges such as 130°C or above, and can suppress chattering in low temperature ranges such as -35°C, making it suitable for automotive electrical components, especially those in electric vehicles. Examples of automotive electronic components include inhibitor switches. Other examples besides automotive electronic components include, for instance, vibration motors in mobile phones. [Examples]

[0038] The present invention will be described below based on one embodiment. However, the present invention is not limited to this embodiment.

[0039] Examples 1-4 and Comparative Examples 1-3 were prepared as follows.

[0040] (Example 1) In a 300mL stainless steel cup, use PAO6 (Chevron Phillips Chemicals "Synfluid PAO6"; kinematic viscosity (40℃) 30.7mm) as the base oil. 2 111.88g of ( / s) was added, and the mixture was heated while stirring. At 80°C, 3.92g of azelaic acid (EMEROX1144, manufactured by Emery Oleochemicals) was added, and at 100°C, 21.08g of 12-hydroxystearic acid (Hydrogenated Castor Fatty Acid, manufactured by NOF Corporation) was added. It was confirmed that the azelaic acid and 12-hydroxystearic acid had dispersed and melted in droplets.

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

[0042] To confirm whether the thickener in the grease composition of Example 1 had formed a lithium complex, isohexane extraction was performed on the obtained grease composition, and XRD diffraction was measured on the residue. As shown in Figure 1, it was confirmed that the grease composition of Example 1 contained 50% by mass or more of the lithium complex soap represented by Formula 1, thus confirming that the grease composition of Example 1 is a lithium complex grease. In Figure 1, α represents the lithium complex soap represented by Formula 1, and β represents lithium 12-hydroxystearate.

[0043] (Example 2) The grease composition of Example 2 was prepared in the same manner as in Example 1, except that the mixing ratio of each raw material was changed as shown in Table 1 below. XRD diffraction results, as described above, confirmed that the grease composition of Example 2 is a lithium complex grease.

[0044] (Example 3) In Example 1, PAO6 was used as the base oil instead of PAO4 (Synfluid PAO4 manufactured by Chevron Phillips Chemicals; kinematic viscosity (40℃) 17.4 mm²). 2 Except for changing the formula to " / s" and further changing the blending ratio of each raw material as shown in Table 1 below, the grease composition of Example 3 was prepared in the same manner as in Example 1. XRD diffraction results in the same manner as above confirmed that the grease composition of Example 3 is a lithium complex grease.

[0045] (Example 4) In Example 1, PAO6 was used as the base oil instead of PAO4 (ExxonMobil's "SpectraSyn Max 3.5; kinematic viscosity (40℃) 14.3 mm²) 2 Except for changing the formula to " / s" and further changing the blending ratio of each raw material as shown in Table 1 below, the grease composition of Example 4 was prepared in the same manner as in Example 1. XRD diffraction results in the same manner as above confirmed that the grease composition of Example 4 is a lithium complex grease.

[0046] (Comparative Example 1) In a 300mL stainless steel cup, use PAO6 (Synfluid PAO6 manufactured by Chevron Phillips Chemicals; kinematic viscosity (40℃) 30.7mm) as the base oil. 2 185.1g of ( / s) and 0.9g of styrene-isoprene block copolymer (Infineum SV-150, manufactured by Infinium Corporation) as a polymer were added, and then 14.0g of lithium 12-stearate (Katsuta Chemical Co., Ltd., product name Li-OH-St) was added as a thickener. The mixture was heated to 240°C and milled with a three-roll mill to produce the grease composition of Comparative Example 1.

[0047] (Comparative Example 2) In Comparative Example 1, the base oil used was PAO6 (Synfluid PAO6, manufactured by Chevron Phillips Chemicals; kinematic viscosity (40℃) 30.7 mm²). 2 The grease composition of Comparative Example 2 was prepared in the same manner as in Comparative Example 1, except that only 186.0g of / s was used.

[0048] (Comparative Example 3) In a 300mL stainless steel cup A, add PAO6 (Synfluid PAO6 manufactured by Chevron Phillips Chemicals; kinematic viscosity (40℃) 30.7mm) as the base oil. 261.7g of (s) and 7.0g of MDI (diphenylmethane diisocyanate) ("Millionate MT" manufactured by Tosoh Corporation) were added and heated at 60°C, stirring to dissolve. 23.3g of PAO6 and 8.0g of p-toluidine ("p-Toluidine" manufactured by Lanxess) were added to a 300mL stainless steel cup B and heated at 60°C to dissolve and prepare a solution. This solution was added to stainless steel cup A, and the temperature was raised to 100°C while stirring, and held for a certain period of time. After that, stirring was continued to raise the temperature to 165°C, and stirring was continued while maintaining that temperature, and the mixture was allowed to cool. Furthermore, the mixture was milled using a three-roll milling process to produce the grease composition of Comparative Example 3.

[0049] [Table 1]

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

[0051] <Implosion / Consistency of mixing> The non-mismatch / mismatch consistency 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 degree of oil separation was measured in accordance with JIS K2220 under conditions of 130°C for 24 hours.

[0055] <Consistency changes> Consistency changes were measured at 130°C or -40°C in the same manner as the consistency measurement method specified in JIS K2220, and the difference was calculated using the consistency at 25°C as the baseline.

[0056] <Grease Thin Film Oxidation Test> Each grease composition was applied to a 120mm x 50mm SPCC (cold-rolled steel sheet) to a thickness of 2mm and left to stand in a 150°C constant temperature bath for 24 hours. The consistency change and weight loss of each grease composition before and after testing were then checked. Weight loss was measured using an electronic balance. Grease compositions that showed a consistency softening / hardening due to high-temperature oxidation and a weight loss of 5.0 mass% or more were deemed unsuitable for use in high-temperature environments and were rejected.

[0057] <Chattering Test> A chattering test plate, formed by joining a copper plate and a POM (polyoxymethylene) resin plate in equal areas, was coated with each grease composition to a thickness of 0.4 mm. The copper rivet and the chattering test plate were then set in a reciprocating sliding test machine (Shinto Chemical Co., Ltd. "Tribogear"), and a specified load, voltage, and current were applied. The machine was slid 10 times at 25°C for a break-in period. After standing for 30 minutes at the specified temperature, the machine was slid 10 times back and forth, and the presence or absence of chattering was checked. Grease compositions that did not produce irregular voltage drops were deemed acceptable. (Measurement conditions) Load: 200g, Sliding speed: 25mm / s, Sliding width: 20mm (10mm copper section, 10mm POM section) Voltage: 5V Current: 50mA Test temperature: -20℃, -40℃

[0058] <Base oil diffusion prevention test> Each grease composition, with a diameter of 10 mm and a thickness of 1.2 mm, was applied to frosted glass (100 mm x 100 mm) conforming to JIS R3202, and left to stand for 24 hours in a hot air circulating constant temperature bath heated to 80°C. After standing, the size of oil seepage from the edges of the applied grease composition was checked, and those with oil seepage of 2 mm or less were deemed acceptable. Furthermore, since Examples 2 and 3 and Comparative Example 3 were expected to pass the tests based on the results of Examples 1 and 4, which use the same or lower viscosity PAO as the base oil, no further testing was conducted.

[0059] (result) The grease compositions of Examples 1 to 4, which contain poly-α-olefin as the base oil and lithium complex soap as a thickener, exhibited minimal consistency changes and weight loss due to high-temperature oxidation, and did not show discontinuous voltage drops (chattering) at -40°C. Furthermore, the grease composition of Example 1 was confirmed to have minimal oil seepage and high base oil diffusion prevention properties. In contrast, the grease composition of Comparative Example 1, which contains 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 diffused. 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, irregular voltage drops (chattering) were observed at -20°C.

[0060] The electrical contact grease composition of the present invention exhibits base oil diffusion prevention properties, can be used at temperatures above 130°C, and has excellent chattering properties at temperatures below -35°C.

Claims

1. It contains 5 to 18% by mass of a thickener including lithium complex soap, and has a kinematic viscosity of 9 to 40 mm at 40°C. ２ An electrical contact grease composition containing 82 to 92% by mass of a base oil containing poly-α-olefin of / s.

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

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

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

5. It contains 5 to 18% by mass of a thickener including lithium complex soap, and has a kinematic viscosity of 9 to 40 mm at 40°C. ２ A method for suppressing chattering at temperatures below -35°C, comprising applying a grease composition containing 82 to 92% by mass of a base oil containing poly-α-olefin of / s to electrical contacts.

Images