Method for manufacturing oil gel capsules and method for manufacturing vehicle contact parts containing oil gel capsules

Abstract

To provide an overlay material which responds to the temperature environment, and provide a method for manufacturing oil gel capsules and a method for manufacturing a contact part for vehicles, including oil gel capsules.SOLUTION: An oil gel capsule includes an oil gel including an oil and a gelator, and at least one surfactant bonded to the oil gel. Preferably, the oil gel is in a gel state at a temperature less than a phase transition temperature and is in a liquid state at a temperature greater than a phase transition temperature. The oil gel has a phase transition temperature of about 60°C to about 70°C inclusive.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing an oil gel capsule and a method for manufacturing a vehicle contact part including an oil gel capsule, and more particularly to a material for an overlay layer formed on the surface of a vehicle contact part such as a bearing alloy. [Background technology]

[0002] A bearing is a mechanical element that limits relative motion to a desired movement and reduces friction between moving parts. Bearings are susceptible to fatigue failure when loaded with a stiff chain or ball, so alloy-based bearings (hereinafter referred to as bearing alloys) that have excellent abrasion resistance, corrosion resistance, and thermal conductivity and have vibration absorption capabilities are mainly used. However, bearing alloys are also subject to wear due to continuous friction, which can lead to a rapid decline in their seizure resistance. Therefore, various coating materials, i.e. overlay materials, have been developed to protect bearing alloys from wear, and polyamideimide and lubricants are commonly used as overlay materials. When developing an overlay material, it is necessary to take into consideration that the wear resistance of bearings deteriorates significantly in the early stages of vehicle operation, and it is therefore necessary to extend the life of the composite material (bearing alloy and overlay material) by preventing additional wear in the early stages of vehicle operation, i.e., the initial wear stage of the bearings. Therefore, it is necessary to develop an overlay material that can retain its anti-seizure properties even after wear has occurred in the composite material.

[0003] Patent Document 1 discloses microcapsules as one of the overlay materials. The microcapsules contain a liquid phase lubricant in a hard plastic skin, and the liquid phase lubricant is released to the outside when the plastic skin is physically damaged. It can be said that the release of the liquid phase lubricant is not related to the temperature environment of the composite material. In addition, the damaged plastic skin aggregates, which not only induces defects in the engine, but also reduces the engine efficiency. Patent Document 2 discloses a lubricant composition that is sensitive to temperature changes. Patent Document 2 relates to a method of infiltrating a lubricant composition composed of a lubricant and a gelator into pores inside a bearing, which is a sintered material. However, the high viscosity of the lubricant composition and the size of the pores inside the bearing limit its application. Furthermore, since the lubricant composition is not disclosed as an overlay material for bearings, there is a limit to its use as a method for extending the life of composite materials. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent Publication No. 9,982,715 [Patent Document 2] Japanese Patent Publication No. 2013-113371 [Patent Document 3] Korean Patent Publication No. 10-0454659 Summary of the Invention [Problem to be solved by the invention]

[0005] One object of the present invention is to develop an overlay material that is sensitive to the temperature environment. Another object of the present invention is to develop an overlay material that does not cause agglomeration even after oil is released. [Means for solving the problem]

[0006] The oil gel capsule of the present invention is characterized by comprising an oil gel containing an oil and a gelator, and at least one surfactant combined with the oil gel.

[0007] The oil gel is preferably in a gel state at temperatures below the phase transition temperature and in a liquid state at temperatures above the phase transition temperature. The oil gel preferably has a phase transition temperature of about 60°C or higher and about 70°C or lower. The oil gel capsules can have a size of 0.1 to less than 10 μm, preferably 0.1 to 1 μm.

[0008] The oil is engine oil and the gelator is 12-Hydroxyoctadecanoic acid ( 12-Hydroxyoctadecanoic acid ) and the 12- Hydroxyoctadecanoic acid The content of is preferably 1 to 10 wt % based on the total weight of the engine oil. The surfactant may be PVA (Polyvinyl alcohol).

[0009] The oil powder of the present invention is characterized in that it contains at least two of the oil gel capsules, and the oil gel capsules are aggregated. The vehicle contact part of the present invention is characterized in that an overlay layer containing the oil gel capsules is formed. The overlay layer preferably has a thickness of 10 to 30 μm.

[0010] The manufacturing method of the vehicle contact part of the present invention is characterized by including a step of coating the surface of the vehicle contact part with an organic solution containing the oil gel capsules or the oil powder, and a step of drying the vehicle part.

[0011] The method for producing a vehicle contact part of the present invention includes the steps of: (a) mixing oil and a gelator to produce an oil gel; (b) mixing the oil gel and an aqueous surfactant solution to form at least one of the oil gel capsules; (c) drying the aqueous solution to recover the oil powder; (d) redispersing the oil powder in an organic solvent to prepare a first organic solution containing 2 to 10 wt % of the oil gel capsules; (e) preparing an overlay mixture solution by mixing the first organic solution and a second organic solution containing 30 to 50 wt % of polyamideimide and additives in a weight ratio of 1:0.5 to 1:2; and (f) drying the vehicle contact part after coating the overlay mixture solution on the surface of the vehicle contact part. Effect of the Invention

[0012] According to the present invention, it is possible to provide an overlay material that is sensitive to the temperature environment and has improved abrasion resistance and seizure resistance. According to the present invention, the gelator and surfactant aggregation phenomena do not occur even after the oil is released. [Brief description of the drawings]

[0013] [Figure 1] 1 shows a bearing containing oil gel capsules of the present invention. [Diagram 2] (a) to (c) are confocal fluorescence images of oil gel capsules contained in a bearing. [Diagram 3] FIG. 1 is a diagram showing a method for producing an oil gel capsule, showing steps (a) and (b). [Figure 4] 1 is a graph showing the results of DSC measurements of (a) heat flow and (b) change in first phase transition temperature of an oil gel depending on the weight ratio of 12-HSA. [Diagram 5] The photographs were taken at 25°C after engine oil and 2 wt% 12-HSA were mixed to form an oil gel with a phase transition temperature of about 62°C. (a) is the oil gel without added dye, and (b) is the oil gel with added dye. The dye was added to show the state of the oil gel more clearly. [Figure 6] (a) and (b) are photographs taken of the oil gels in Fig. 5 (a) and (b) after heating at 90°C. [Figure 7](a) and (b) are photographs taken after adding 2 wt% PVA aqueous solution to the oil gel in Figure 6 (a) and (b) and mixing. [Figure 8] FIG. 7(b) is a confocal fluorescence image of the oil gel capsule in the aqueous solution. [Figure 9] FIG. 7(b) is a confocal fluorescence image of the oil gel capsule in the aqueous solution. [Figure 10] FIG. 7(b) is a confocal fluorescence image of the oil gel capsule in the aqueous solution. [Figure 11] 8 shows a size distribution graph of the oil gel capsules in the aqueous solution of FIG. 7(a) measured by Dynamic Light Scattering. [Figure 12] (a) and (b) are photographs taken after the aqueous solutions of (a) and (b) in FIG. 7 were freeze-dried. [Figure 13] 12(a) and (b) are photographs taken after the oil powders of FIG. 12(a) and (b) were redispersed in the organic solvent NMP to prepare a first organic solution containing 10 wt % of oil gel capsules. [Figure 14] 13(a) and (b) are photographs taken after the first organic solution of FIG. 13(a) and (b) and the second organic solution containing 50 wt % of polyamideimide and additives were mixed in a weight ratio of 1:1. [Figure 15] 14(a) and (b) are photographs taken after the overlay mixed solution of FIG. 14(a) and (b) was coated on the surface of the bearing alloy. [Figure 16] The results of reciprocating friction tests of steel disk specimens of Examples 1 to 3 and Comparative Example 1 are shown. [Figure 17] The results of reciprocating friction tests of steel disk specimens of Examples 1 to 3 and Comparative Example 1 are shown. [Figure 18] (a) to (c) show the action process of the oil gel capsule. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will now be described in detail, without, however, being restricted or limited by the illustrative examples. FIG 1 shows a bearing including the oil gel capsule of the present invention. FIG 2(a)-(c) are confocal fluorescent images of the oil gel capsule included in the bearing. As shown in FIG 1 and FIG 2, the bearing 10 can include a back steel 100, a bearing alloy 200, and an overlay layer 300, and the overlay layer 300 can include at least one oil gel capsule 310. The oil gel capsule 310 refers to a particle including an oil gel 311 and a surfactant 312 surrounding the oil gel 311, and more specifically, refers to a particle including an oil gel 311 and at least one surfactant combined with the oil gel 311. The oil gel 311 refers to an oil including a gelator 311B, and may include an oil 311A ​​and a gelator 311B.

[0015] Fig. 3 shows a method for producing oil gel capsules. As shown in Fig. 3, the method for producing oil gel capsules includes a step of (a) mixing oil and a gelator to form an oil gel, and a step of (b) mixing the oil gel and a surfactant aqueous solution to produce at least one oil gel capsule. Steps (a) and (b) will be described in detail below with reference to Figs. 4 to 11.

[0016] (a) Step: An oil gel can be formed by mixing oil and a gelator. A gelator can be added to the oil. However, since the object and the direction of addition do not need to be specified as described above, the oil may be added to the gelator. For more uniform mixing, it is preferable to mix the oil and the gelator using an ultrasonic grinder. The formed oil gel is in a gel state. The weight ratio of the gelator when mixing the oil and gelator (the weight of the gelator relative to the total weight of the oil) is preferably a weight ratio effective for gelling the entire oil being mixed. In addition, since the phase transition temperature of the oil gel changes depending on the weight ratio of the gelator, the weight ratio of the gelator is preferably a weight ratio effective for the oil gel to maintain a gel state at room temperature, and is preferably a weight ratio effective for maintaining a gel state in all temperature environments (maximum temperature is approximately 60°C) that a bearing containing oil gel will experience before being installed in a vehicle.

[0017] The phase transition temperature of an oil gel refers to the temperature at which an oil gel in a gel state liquefies into a liquid state, or at which an oil gel in a liquid state gels into an oil gel state. An oil gel maintains a gel state at temperatures below the phase transition temperature, and maintains a liquid state at temperatures above the phase transition temperature.

[0018] According to an embodiment of the present invention, the oil may be engine oil and the gelator may be 12-Hydroxyoctadecanoic acid (hereinafter, 12-HSA). The weight ratio of 12-HSA is preferably 1-10 wt% based on the total weight of the engine oil, and the oil gel may have a phase transition temperature of about 60°C to about 70°C. If less than 1 wt% of 12-HSA is mixed with the engine oil, the reticular fiber structure of 12-HSA is not formed in the engine oil, and therefore the oil gel is not formed. If more than 10 wt% of 12-HSA is mixed with the engine oil, a saturation state is reached in which the increase in the phase transition temperature of the oil gel decreases according to the increase in the weight ratio of 12-HSA, and the weight of the engine oil relative to the weight of the gelator becomes smaller, so that the lubricating properties of the oil gel or oil gel capsules are reduced. Therefore, 12-HSA is preferably added in an amount of 1-10 wt% based on the total weight of the engine oil. However, the type of gelator and the weight ratio of the gelator are not limited thereto.

[0019] Figures 4(a) and (b) are graphs showing the results of measuring the phase transition temperature of oil gels according to the weight ratio of 12-HSA by DSC. As shown in Figures 4(a) and (b), it can be seen that when 1.5 wt% or more of 12-HSA is added, an oil gel having a phase transition temperature exceeding about 61°C can be formed. FIG. 5 shows pictures taken at 25° C. after engine oil and 2 wt % 12-HSA were mixed to form an oil gel with a phase transition temperature of about 62° C. FIG. 5(a) shows an oil gel without added dye, and FIG. 5(b) shows an oil gel with added dye. The dye was added to more clearly show the state of the oil gel. As shown in FIG. 5(a) and (b), the oil gel exists in a gel state without fluidity in a temperature environment below the phase transition temperature of about 62° C. The absence of fluidity can be seen from the fact that the surface of the oil gel is not parallel to the ground. More specifically, the gel state of the oil gel refers to a state in which the oil is trapped and held in the network fibrous structure of the gelator.

[0020] Figures 6 (a) and (b) are photographs taken after the oil gels of Figures 5 (a) and (b) were heated to 90°C. As shown in Figures 6 (a) and (b), the oil gel regains its fluidity and exists in a liquid state in a temperature environment higher than the phase transition temperature of about 62°C. The existence of fluidity can be seen from the fact that the surface of the oil gel is roughly parallel to the ground. More specifically, the liquid state of the oil gel refers to the state in which the reticular fibrous structure of the gelator is broken down and the gelator exists in a dispersed state in the oil. Comparing Figures 6(a) and (b) with Figures 5(a) and (b), it can be seen that the oil gel in the liquid state is more transparent than the oil gel in the gel state. When the oil gels in Figures 6(a) and (b) are cooled to 25°C, they can be restored to the state of the oil gels in Figures 5(a) and (b).

[0021] (b) Step: At least one or more oil gel capsules can be produced by mixing the oil gel and the surfactant aqueous solution. The oil gel capsules are produced when the oil gel is surrounded by each of the surfactant molecules in the surfactant aqueous solution. Meanwhile, the oil gel can be seen as being encapsulated by the surfactant. More specifically, since the oil gel is fat-soluble (hydrophobic) and the surfactant aqueous solution is hydrophilic, an interface is formed between the surface of the oil gel and the aqueous solution, and the fat-soluble part of the surfactant moves toward the oil gel, while the hydrophilic part of the surfactant moves toward the aqueous solution, producing the oil gel capsules.

[0022] Preferably, the oil gel in a liquid state can be mixed with the surfactant aqueous solution to produce the oil gel capsules. The oil gel in a gel state can be liquefied in advance and mixed with the surfactant aqueous solution, and the oil gel in a gel state can be added to the surfactant aqueous solution or the surfactant aqueous solution can be added to the oil gel in a gel state, and then mixed with an ultrasonic grinder, while the oil gel in a gel state can be liquefied using the heat energy coming out of the ultrasonic grinder. In either case, it is preferable to use an ultrasonic grinder for more uniform mixing. The surfactant can refine the oil gel, so that fine oil gel capsules can be produced. By finely refining the oil gel, the oil gel capsules can be uniformly dispersed in the overlay layer. The oil gel capsules are formed smaller than 10 μm, which is the average thickness of the overlay layer, and their size is 0.1 to less than 10 μm. The size of the oil gel capsules is preferably 1 to 5 μm, and more preferably 1 μm or less.

[0023] The surfactant can prevent aggregation between finely divided oil gel particles when the oil gel capsules aggregated as oil powder are redispersed in an organic solvent. According to one embodiment of the present invention, the surfactant may be PVA (Polyvinyl alcohol), and 1-10 wt% of PVA aqueous solution is mixed with the oil gel. Here, 1-10 wt% refers to the ratio of the weight of PVA to the weight of the PVA aqueous solution. If less than 1 wt% of PVA aqueous solution is mixed with the oil gel, when the oil gel capsules aggregated as oil powder are redispersed in an organic solvent, the aggregation phenomenon between the oil gel capsules may occur strongly, and the aggregated oil gel capsules may not be redispersed. If more than 10 wt% of PVA aqueous solution is mixed with the oil gel, the content of oil in the oil gel capsules may relatively decrease, and the lubricating properties of the oil gel or the oil gel capsules may decrease. The role of the surfactant is to make the oil gel finer, to uniformly disperse the oil gel capsules in the overlay layer, and to prevent aggregation between the oil gels, and the type and content of the surfactant are not limited thereto. The surfactant may be selected from an anionic surfactant, a cationic surfactant, an amphoteric surfactant, or a nonionic surfactant. On the other hand, the weight ratio of the oil gel and the surfactant aqueous solution when mixed is 1:2 to 1:10.

[0024] Figures 7(a) and (b) are photographs taken after adding 2 wt% PVA aqueous solution to the oil gels of Figures 6(a) and (b), respectively, and mixing them. As shown in Figures 7(a) and (b), it can be seen that the oil gel, which was transparent as a liquid before mixing, turned white like milk. This means that an emulsion of fine particles in an aqueous solution was formed, and the fine particles here refer to oil gel capsules.

[0025] 8 to 10 are confocal fluorescence images of the oil gel capsules in the aqueous solution of FIG. 7(b). FIG. 11 shows a size distribution graph of the oil gel capsules in the aqueous solution of FIG. 7(a) measured by dynamic light scattering. As shown in FIG. 8 to FIG. 11, it can be confirmed that the oil gel capsules may not have a spherical shape and their size is 1 μm or less. More specifically, the size of the oil gel capsules is 0.1 μm (= 100 μm) to 1 μm (= 1000 nm).

[0026] (c) Step: The method for producing oil gel capsules may further include a step (c) of drying the aqueous solution containing at least one or more oil gel capsules. By drying the aqueous solution containing the oil gel capsules, the distance between the oil gel capsules is reduced, and the oil gel capsules may aggregate. The aggregation of oil gel capsules does not mean that at least two or more oil gel capsules are combined into one oil gel capsule, but means that the surfactants of each oil gel capsule are in physical contact with each other. The aggregated oil gel capsules are viscous like clay, have a powder form, and have a soft touch like powder. Hereinafter, the aggregation of at least two or more oil gel capsules is referred to as oil powder. The oil powder can be added to an organic solvent, and the aggregated oil gel capsules can be dispersed again. The drying step (c) is preferably performed using a freeze dryer.

[0027] Figures 12 (a) and (b) are photographs taken after freeze-drying the aqueous solutions of Figures 7 (a) and (b). As shown in Figures 12 (a) and (b), oil powder can be confirmed, and the oil gel capsules can be recovered in powder form. In Figures 12 (a) and (b), each powder has a size that can be identified by the naked eye, but the oil gel capsules generated through step (b) have a micron or sub-micron size, so each powder is formed by the aggregation of multiple oil gel capsules.

[0028] The process of adding the oil gel capsules prepared through steps (a) to (c) to the overlay layer of the bearing will be described in detail below. Each step described below will be referred to as step (d), step (e), and step (f). (d) Step: The oil powder can be added to the organic solvent to redisperse the aggregated oil gel capsules. The aggregated oil gel capsules can be dispersed as shown in Figs. 8 to 10. However, unlike Figs. 8 to 10, the oil gel and the organic solvent, for example, NMP (N-Methyl-2-pyrrolidone), are also lipophilic, so that no interface is formed on the surface of the oil gel, and some of the surfactants bound to the oil gel are dispersed in the organic solvent. The organic solution containing 2 to 10 wt% of the oil powder is referred to as the first organic solution, and the first organic solution can be said to be an organic solution containing 2 to 10 wt% of the oil gel capsules. Here, wt% means the ratio of the weight of the oil gel capsules to the total weight of the first organic solution.

[0029] Figures 13(a) and (b) are photographs taken after the oil powders of Figures 12(a) and (b) were redispersed in the organic solvent NMP to produce a first organic solution containing 10 wt% of oil gel capsules. As shown in Figures 13(a) and (b), the fact that the aggregation between the oil gel capsules has been eliminated can be seen from the translucent color of the first organic solution.

[0030] (e) Step: The overlay mixed solution can be prepared by mixing the first organic solution and the second organic solution containing 30-50 wt% polyamideimide and additives at a weight ratio of 1:0.5-1:2. Here, wt% means the weight ratio of the solid content to the total weight of the second organic solution. The solvent of the second organic solution may be NMP. (a) and (b) of FIG. 14 are photographs taken after mixing the first organic solution of (a) and (b) of FIG. 13 with the second organic solution containing 50 wt% polyamideimide and additives at a weight ratio of 1:1.

[0031] (f) Step: After the overlay mixed solution is coated on the surface of the bearing alloy, the bearing can be dried. (a) and (b) of FIG. 15 are photographs taken after the overlay mixed solution of (a) and (b) of FIG. 14 is coated on the surface of the bearing alloy. The drying of the bearing can be performed in one step, or in two steps for preserving the oil gel capsule. The bearing after drying can have an overlay layer of 10 to 30 μm in thickness.

[0032] Examples and comparative examples of the present invention will be described below. Manufacturing process of oil gel capsules 0.3030g (approximately 2wt%) of gelator 12-HSA was added to 15g of engine oil and mixed using an ultrasonic grinder to produce an oil gel with a phase transition temperature of approximately 62°C. 5g of oil gel was liquefied, and 75ml of 2wt% PVA aqueous solution was added and mixed using an ultrasonic grinder to produce oil gel capsules. Water was removed from the aqueous solution containing the oil gel capsules using a freeze dryer, and oil powder was collected.

[0033] Overlay layer manufacturing process Example 1 10g of oil powder was added to 90g of NMP solvent to prepare an NMP solution (first organic solution) containing 10wt% oil gel capsules. When preparing the first organic solution, the oil gel capsules were uniformly redispersed in the NMP solvent using a stirrer. After preparing an NMP solution (second organic solution) containing 50wt% polyamideimide and additives (including lubricants), 50g of the first organic solution and 50g of the second organic solution were mixed to prepare an overlay mixed solution. The overlay mixed solution was coated on the surface of the bearing alloy, dried at 150-200°C for 30 minutes, and then dried at 210-240°C for 15 minutes to prepare an overlay layer with a thickness of about 10μm (Example 1 is represented by Sample 1 in Figures 16 and 17). Example 2 The overlay mixture solution of Example 1 was coated twice to produce a coating layer with a thickness of about 20 μm (Example 2 is represented as Sample 2 in FIGS. 16 and 17). Example 3 The overlay mixture solution of Example 1 was coated three times to produce a coating layer with a thickness of about 30 μm (Example 3 is represented as Sample 3 in FIGS. 16 and 17).

[0034] Comparative Example 1 Only the prototype DLA02, which did not contain oil gel capsules, produced an overlay layer of about 10 μm (Comparative Example 1 is represented by DLA02 in FIGS. 16 and 17). 16 and 17 show the results of reciprocating dynamic friction tests of steel disk specimens of Examples 1 to 3 and Comparative Example 1. The test conditions were dry condition, 10 minutes, 50N load, 5Hz reciprocating speed, and 10mm stroke. Referring to FIGS. 16 and 17, in the case of Comparative Example 1, which does not contain oil gel capsules, a continuous increase in the friction coefficient and a decrease in contact voltage were observed through repeated friction tests, whereas in the cases of Examples 1 to 3, the initial friction coefficient and contact voltage were maintained even after 10 minutes. In other words, it can be confirmed that the oil gel capsules improved the low friction and anti-seizure properties of the bearings. FIG. 18 (a) to (c) show the action process of the oil gel capsule. At the beginning of vehicle operation, friction occurring in the bearing causes wear or cracks in the overlay layer and the bearing alloy along with a local temperature rise. The local temperature rise can transform the oil gel in a gel state into an oil gel in a liquid state, and the oil gel in a liquid state can form a lubricating film at the worn or cracked area. As a result, additional friction and wear on the bearing can be suppressed at the early wear stage of vehicle operation, and the life of the bearing can be extended. In addition, the gelator is diluted in an excessive amount of engine oil, and at low concentrations the gelator does not form a reticular fiber structure, so the gelator does not coagulate after the oil is released. The surfactant is also diluted in the engine oil, so no coagulation occurs.

[0035] The oil gel capsules can be added to the lubricant to further improve the lubricating properties of the lubricant, and can also be applied to the next generation of environmentally friendly vehicles, such as hybrid vehicle engines, electric vehicles and hydrogen fuel cell vehicles operating in non-lubricated environments, where the harsh engine friction and wear environment is becoming more and more severe due to the rising need to develop high-efficiency engines.

[0036] Although the present invention has been described in detail above through representative embodiments, those skilled in the art will understand that various modifications can be made to the above-described embodiments without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by not only the claims below, but also all modifications or modified forms derived from the concepts equivalent to the claims. [Explanation of symbols]

[0037] 10. Bearings 100 ···Backsteel 200 ···Bearing alloy 300 Overlay Layer 310 ···Oil gel capsule 311 Oil Gel 311A ···Oil 311B Gelator 312 Surfactants

Claims

1. An oil gel comprising engine oil and a gelator; and The oil gel capsule includes at least one surfactant combined with the oil gel, The gelator is 12-hydroxyoctadecanoic acid, The content of the 12-hydroxyoctadecanoic acid is 1 to 10 wt % based on the total weight of the engine oil, The oil gel has a phase transition temperature of 60° C. or more and 70° C. or less, The oil gel capsules are characterized in that they have a size of 0.1 μm or more and 1 μm or less.

2. The oil gel capsule according to claim 1, wherein the oil gel is in a gel state at a temperature below the phase transition temperature.

3. 2. The oil gel capsule according to claim 1, wherein the oil gel is in a liquid state at a temperature exceeding the phase transition temperature.

4. 2. The oil gel capsule according to claim 1, wherein the surfactant is PVA (Polyvinyl alcohol).

5. 2. An oil powder comprising at least two oil gel capsules according to claim 1, the oil gel capsules being agglomerated.

6. A contact part for a vehicle, comprising an overlay layer formed on a surface thereof, the overlay layer containing the oil gel capsule according to any one of claims 1 to 4.

7. The vehicle contact part according to claim 6, wherein the overlay layer has a thickness of 10 to 30 μm.

8. A step of coating an organic solution containing the oil gel capsule according to any one of claims 1 to 4 or the oil powder according to claim 5 on a surface of a contact part for a vehicle; and A method for manufacturing a vehicle contact part, comprising the step of drying the vehicle contact part.

9. (a) mixing engine oil and a gelator to produce an oil gel; (b) mixing the oil gel and an aqueous solution of a surfactant to produce at least one or more oil gel capsules according to any one of claims 1 to 4; (c) drying the aqueous solution to recover the oil powder according to claim 5; (d) redispersing the oil powder in an organic solvent to prepare a first organic solution containing 2 to 10 wt % of the oil gel capsules; (e) preparing an overlay mixture solution by mixing the first organic solution and a second organic solution containing 30 to 50 wt % of polyamideimide and additives in a weight ratio of 1:0.5 to 1:2; and (f) a step of coating the overlay mixture solution on a surface of the vehicle contact part and then drying the vehicle contact part.

Images