Grease for vacuum actuator

Abstract

The present invention relates to a kind of grease for vacuum actuator, it includes following component (a) and component (b): (a) perfluoropolyether, as base oil, the kinematic viscosity at 40 ℃ is 100 mm 2 / s above and less than 200 mm 2 / s, and the vapor pressure at 20 ℃ is 1.0 × 10 ‑ 7 Pa below;(b) polytetrafluoroethylene, as thickening agent, wherein, the shear viscosity of the grease for vacuum actuator at 25 ℃ is 4500 mPas below.

Description

Technical Field

[0001] This invention relates to lubricating grease for vacuum actuators. Background Technology

[0002] Vacuum chambers are used in the manufacture of flat panel displays such as liquid crystal displays and organic EL displays, or in the manufacture of semiconductor devices, to move substrates and the like towards the processing section of the device for various processes. In this case, a vacuum actuator, such as a rotary guide machine, is used to introduce driving force from a drive source located outside the vacuum chamber into the vacuum chamber.

[0003] In such vacuum actuators, it is required to maintain a tight seal for sustaining the vacuum and to transmit the driving force from the outside to the inside of the vacuum chamber. Therefore, it is essential for the vacuum actuator to have a tight seal at the sliding surface under vacuum conditions.

[0004] As a means of ensuring sealing on sliding surfaces under vacuum conditions, sealing devices having annular sealing portions formed of elastic materials are known. For example, Patent Document 1 describes a sealing device that can stably maintain sealing performance and suppress lubricant consumption.

[0005] However, in vacuum actuators, grease is sometimes used to lubricate the sliding surfaces. Grease helps prevent continuous wear on the sliding surfaces and reduces sealing performance under vacuum. However, even with grease in vacuum actuators, maintaining good lubrication over a long period is difficult, requiring a grease that can achieve this level of lubrication.

[0006] Existing technical documents Patent documents Patent document 1: Japanese Patent Application Publication No. 2019-090479. Summary of the Invention

[0007] The problem that the invention aims to solve The present invention provides a grease for vacuum actuators that can maintain good lubrication in vacuum actuators for a long time.

[0008] Methods for solving problems The embodiments of the present invention are as follows: A grease for a vacuum actuator, comprising the following components (a) and (b): (a) Perfluoropolyether, as a base oil, has a kinematic viscosity of 100 mm at 40°C. 2 / s or higher and less than 200mm 2 The vapor pressure at 20°C is 1.0 × 10⁻⁶ / s. -7 Below Pa; (b) Polytetrafluoroethylene, as a thickener, The grease used in the vacuum actuator has a shear viscosity of 4500 mPa at 25°C. Below s.

[0009] Invention Effects According to the present invention, a grease for vacuum actuators can be provided that can maintain a good lubrication state for a long time in a vacuum actuator. Detailed Implementation

[0010] The vacuum actuator grease described in this embodiment has a shear viscosity of 4500 mPa at 25°C. Below s, and containing: (a) perfluoropolyether as a base oil, with a kinematic viscosity of 100 mm at 40°C. 2 / s or higher and less than 200mm 2 The vapor pressure at 20°C is 1.0 × 10⁻⁶ / s. -7 (a) Pa or less; (b) polytetrafluoroethylene, as a thickener. The following provides a detailed description of the components contained in the grease for vacuum actuators, as well as the composition and properties of the grease.

[0011] <Base Oil> The grease used in vacuum actuators contains perfluoropolyether as a base oil. The kinematic viscosity of perfluoropolyether at 40°C is 100 mm³ / s. 2 / s or higher and less than 200mm 2 / s, with its upper limit preferably being 190mm. 2 / s or less, preferably 180mm 2 Below / s, further preferably 170mm 2 Below / s. Furthermore, the lower limit of the kinematic viscosity of perfluoropolyether at 40°C is preferably 110 mm⁻¹. 2 / s or higher, preferably 120mm 2 / s or higher, further preferably 130mm 2 / s or higher. By controlling the kinematic viscosity of the perfluoropolyether at 40°C, the shear viscosity of the grease at 25°C can be easily controlled within an appropriate range, and good lubrication can be easily maintained for a long time in vacuum actuators using the grease. The kinematic viscosity of the perfluoropolyether at 40°C was determined according to JISK 2220:2023. Such a base oil can be used alone or in combination with two or more.

[0012] In addition, the vapor pressure of perfluoropolyether at 20°C is 1.0 × 10⁻⁶. -7 Below Pa, the lower limit is not particularly limited, but is preferably 1.0 × 10⁻⁶. -13 Pa or higher, more preferably 1.0 × 10 Pa -12Pa or higher, more preferably 1.0 × 10 Pa -11 Pa or higher, particularly preferably 1.0 × 10 Pa -10 Pa or higher. Furthermore, the upper limit of the vapor pressure of perfluoropolyether at 20°C is preferably 1.0 × 10⁻⁶ Pa. -8 Pa or less, more preferably 1.0 × 10 Pa. -9 Below Pa. By controlling the vapor pressure of perfluoropolyether at 20°C, the evaporation rate of perfluoropolyether under reduced pressure is suppressed, easily preventing contamination within the vacuum chamber. The vapor pressure of perfluoropolyether at 20°C is determined by the Knudsen effusion method.

[0013] The grease for vacuum actuators preferably contains 70% to 99% perfluoropolyether by mass relative to the total mass of the grease, more preferably 75% to 95% perfluoropolyether, and even more preferably 80% to 90% perfluoropolyether.

[0014] Thickener The grease for vacuum actuators contains polytetrafluoroethylene (PTFE) as a thickener, preferably PTFE particles. The primary particle size of the PTFE particles is not particularly limited, but is preferably 0.01 μm or more and 0.50 μm or less, more preferably 0.03 μm or more and 0.30 μm or less, and even more preferably 0.05 μm or more and 0.15 μm or less. By controlling the primary particle size of the PTFE particles, the shear viscosity of the grease at 25°C can be easily controlled within an appropriate range, and good lubrication can be easily maintained for a long time in vacuum actuators using the grease. The primary particle size of the PTFE particles is determined by image analysis of photographs taken using a scanning electron microscope (SEM). Such a thickener can be used alone or in combination of two or more.

[0015] The grease for vacuum actuators preferably contains 1% or more and 30% or less polytetrafluoroethylene (PTFE) relative to the total mass of the grease, more preferably 5% or more and 25% or less PTFE, and even more preferably 10% or more and 20% or less PTFE.

[0016] Composition and properties of grease for vacuum actuators The shear viscosity of the grease used in vacuum actuators at 25°C is 4500 mPa. Below s. The lower limit of the shear viscosity at 25°C is not particularly limited, but is preferably 500 mPa. s or higher, more preferably 1000 mPa s or higher, more preferably 1500 mPa Above s. Furthermore, the upper limit of the shear viscosity of the grease for vacuum actuators at 25°C is preferably 3700 mPa. Below s, more preferably 3500 mPa Below s, more preferably 3000 mPa Below s, especially preferably 2500 mPa Below s. The shear viscosity of the vacuum actuator grease at 25°C can be controlled, for example, by the content of components (a) and (b), the kinematic viscosity of perfluoropolyether (component (a)) at 40°C, and the primary particle size of polytetrafluoroethylene (component (b)). By controlling the shear viscosity of the vacuum actuator grease at 25°C, for example, the resistance of the sliding surface in the vacuum actuator is reduced, stick-slip is less likely to occur, and wear is suppressed. Therefore, it is easy to maintain a good lubrication state for a long time in vacuum actuators using grease. The shear viscosity of the vacuum actuator grease at 25°C is as follows: as described in the examples described later, for example, using a cone-plate type rotational viscometer, the shear rate is increased from 0 s in 180 seconds at 25°C. -1 Rise to 360s -1 The shearing speed is 300s. -1 The measured shear viscosity value.

[0017] In addition, the working cone penetration (mixing degree) of the grease for vacuum actuators, as measured according to JISK 2220:2023, is preferably 100 or more and 500 or less, more preferably 200 or more and 400 or less, even more preferably 250 or more and 350 or less, and particularly preferably 280 or more and 330 or less.

[0018] Furthermore, the evaporation loss of the grease for vacuum actuators, as measured according to JISK 2220:2023 (test temperature 99°C, 22 hours), is preferably 0.01% by mass or more and 0.5% by mass or less, more preferably 0.05% by mass or more and 0.2% by mass or less.

[0019] The grease for vacuum actuators is preferably free of materials other than perfluoropolyether and polytetrafluoroethylene (PTFE). This means that the grease for vacuum actuators consists only of perfluoropolyether and PTFE, or only of perfluoropolyether, PTFE, and unavoidable impurities (impurities that inevitably mix in during the manufacturing of the grease). This makes it easier to prevent contamination within the vacuum chamber.

[0020] The grease for vacuum actuators is preferably composed of components (a) and (b). In this case, the grease for vacuum actuators refers to a grease composed only of components (a) and (b) or a grease composed only of components (a), components (b), and unavoidable impurities.

[0021] The mass ratio of component (a) to component (b) in the grease for vacuum actuators is preferably 3:1 to 5:1, more preferably 4:1 to 5:1.

[0022] The vacuum actuator grease described in this embodiment can be used, for example, in a vacuum actuator having: a partition wall that separates a vacuum-side space from an atmospheric-side space; a shaft member that passes through the partition wall and transmits driving force; and a sealing member disposed on the partition wall and sliding relative to a sliding surface formed on the outer periphery of the shaft member to seal the vacuum-side space from the atmospheric-side space. Furthermore, the vacuum actuator grease described in this embodiment can be applied to various uses, such as a vacuum actuator lubricant composition equipped with a lip-type vacuum seal.

[0023] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and includes the concept of the present invention and all the ways contained in the claims, and various changes can be made within the scope of the present invention.

[0024] Based on the above implementation methods, the present invention relates to the following [1] to [6].

[0025] [1] A grease for a vacuum actuator, characterized in that it comprises the following components (a) and (b): (a) Perfluoropolyether, as a base oil, has a kinematic viscosity of 100 mm at 40°C. 2 / s or higher and less than 200mm 2 The vapor pressure at 20°C is 1.0 × 10⁻⁶ / s. -7 Below Pa; (b) Polytetrafluoroethylene, as a thickener, The grease used in the vacuum actuator has a shear viscosity of 4500 mPa at 25°C. Below s.

[0026] [2] According to the vacuum actuator grease described in [1] above, wherein the kinematic viscosity of the perfluoropolyether at 40°C is 180 mm. 2 / s or less.

[0027] [3] The vacuum actuator grease according to [1] or [2] above, wherein, relative to the total mass of the vacuum actuator grease, it comprises 80% by mass and 99% by mass of the perfluoropolyether and 1% by mass and 20% by mass of the polytetrafluoroethylene.

[0028] [4] The vacuum actuator grease according to any one of [1] to [3] above, wherein the vacuum actuator grease comprises polytetrafluoroethylene particles with a primary particle size of 0.05 μm or more and 0.15 μm or less.

[0029] [5] The vacuum actuator grease according to any one of [1] to [4] above, wherein the shear viscosity at 25°C is 3700 mPa. Below s.

[0030] [6] The vacuum actuator grease according to any one of [1] to [5] above, wherein the vacuum actuator grease is composed of the component (a) and the component (b).

[0031] Example The present invention will be further described in detail below by way of examples, etc., but the present invention is not limited by these examples, etc.

[0032] <Preparation of Lubricating Grease> (Examples 1-4, Comparative Examples 1-4) The base oil (perfluoropolyether, PFPE) and thickener (polytetrafluoroethylene, PTFE) listed in Table 1 below are mixed at the proportions listed in Table 1 to obtain a homogeneous grease.

[0033] <Kinetic viscosity> Kinematic viscosity of PFPE at 40°C (mm) 2 The vapor pressure (Pa) of PFPE at 20°C was determined according to JISK 2220:2023. The vapor pressure (Pa) of PFPE at 20°C was determined by the Knudsen exudation method. The primary particle size (μm) of PTFE was determined by image analysis of SEM images of PTFE particles. The results are shown in Table 1.

[0034] <Shear viscosity> The shear viscosity (mPa) of the lubricating grease at 25°C was measured. For the time s), a cone-plate type rotational viscometer (manufactured by Anton Paar) was used, with a cone plate of 25 mm diameter and a cone angle of 1°. Measurements were performed at 25°C, with the shear rate decreasing from 0 s⁻¹ to 180 s⁻¹. -1 Rise to 360s -1 The shearing speed is 300s. -1 The shear viscosity at 25°C is taken as the shear viscosity of the grease. The results are shown in Table 1.

[0035] <Working cone penetration, evaporation loss> The working cone penetration of the grease was determined according to JISK 2220:2023, and the evaporation loss (mass%) of the grease was determined according to JISK 2220:2023 (test temperature 99℃, 22 hours). The results are shown in Table 1.

[0036] (Evaluation of grease) The obtained grease was subjected to the following durability test.

[0037] <Durability Testing> The obtained grease was used in the sealing sliding part of the vacuum actuator installed in the vacuum chamber. Using this vacuum actuator, a test was conducted under the following test conditions, in which the actuator rotated 180 degrees forward and then 180 degrees backward to return to the origin, repeating the cycle up to a maximum of 3 million times. In this test, the number of cycles (endurance cycles) until the vacuum conditions described below could no longer be maintained was measured. The results are shown in Table 1. Furthermore, the test was terminated at the point when the vacuum conditions described below could no longer be maintained.

[0038] (Experimental conditions) Rotational speed: The rotational speed at which the maximum circumferential speed of the sealed sliding part of the vacuum actuator is set is 0.3 m / sec.

[0039] Load conditions: The torque load is no load, and the torque load is only the load based on the sliding resistance of the seal.

[0040] Vacuum conditions: The vacuum level inside the vacuum chamber is 1.0 × 10⁻⁶. -5 Below Pa.

[0041] If the sealing sliding parts of the vacuum actuator cannot be adequately lubricated, stick-slip and other issues will occur, leading to vacuum leakage and making it impossible to maintain the aforementioned vacuum conditions. In this case, it is determined that the vacuum actuator can no longer be used, and the durability test is terminated even if 3 million cycles have not been reached.

[0042] [Table 1] The formulations of each component in Table 1 above are as follows.

[0043] PFPE A: FM30 (Made by Solvay SA, "FOMBLIN (registered trademark) M30") PFPE B: DS 200 (manufactured by Daikin Industries, Ltd., "DEMNUM (registered trademark) S-200") PFPE C: FM60 (Made by Solvay SA, "FOMBLIN (registered trademark) M60") PFPE D:B400V (Manufactured by NOK KLUEBER, "BARRIERTA J 400V") As shown in Table 1, the grease has a strength of 4500 mPa. Shear viscosity below s (25°C) and containing PFPE as a base oil (PFPE has a kinematic viscosity of 100 mmHg at 40°C). 2 / s or higher and less than 200mm 2 The vapor pressure at 20°C is 1.0 × 10⁻⁶ / s. -7 Using PTFE as a thickener (with a viscosity below 1000 mPa), a vacuum actuator grease that can maintain good lubrication for a long time was obtained (Examples 1-4). In particular, the shear viscosity at 25°C is 3700 mPa. In the greases of Examples 1 to 3 below, the durability test reached 3 million cycles, and the durability was even better.

[0044] On the other hand, a kinematic viscosity of 200 mm at 40°C was used. 2 The perfluoropolyether greases of Comparative Examples 1 to 4, with a shear viscosity of over / s, all had a shear viscosity exceeding 4500 mPa at 25°C. Additionally, the durability test only lasted 300,000 cycles, indicating poor durability.

Claims

1. A lubricating grease for a vacuum actuator, characterized in that, It contains the following ingredients (a) and (b): (a) Perfluoropolyether, as a base oil, has a kinematic viscosity of 100 mm at 40°C. 2 / s or higher and less than 200mm 2 The vapor pressure at 20°C is 1.0 × 10⁻⁶ / s. -7 Below Pa; (b) Polytetrafluoroethylene, as a thickener, The grease used in the vacuum actuator has a shear viscosity of 4500 mPa at 25°C. Below s.

2. The grease for vacuum actuators according to claim 1, wherein, The kinematic viscosity of the perfluoropolyether at 40°C is 180 mmHg. 2 / s or less.

3. The grease for vacuum actuators according to claim 1, wherein, The grease for the vacuum actuator comprises, relative to the total mass of the grease, 80% to 99% by mass of the perfluoropolyether and 1% to 20% by mass of the polytetrafluoroethylene.

4. The grease for vacuum actuators according to claim 1, wherein, The grease for the vacuum actuator contains polytetrafluoroethylene particles with a primary particle size of 0.05 μm or more and 0.15 μm or less.

5. The grease for vacuum actuators according to claim 1, wherein, The shear viscosity at 25°C is 3700 mPa. Below s.

6. The grease for vacuum actuators according to any one of claims 1 to 5, wherein, The grease for the vacuum actuator is composed of component (a) and component (b).

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