Low-temperature hydraulic oil composition suitable for door closer and preparation method of low-temperature hydraulic oil composition

Abstract

The invention relates to the technical field of door closer hydraulic oil, and discloses a low-temperature hydraulic oil composition suitable for a door closer and a preparation method thereof, and the low-temperature hydraulic oil composition comprises the following raw materials: base oil, a viscosity index improver, a pour point depressant, a hydraulic oil complexing agent and an anti-foaming agent. The low-temperature hydraulic oil composition suitable for the door closer has excellent low-temperature performance, high viscosity index and wide-temperature-range viscosity stability, excellent wear resistance and extreme pressure protection, good anti-foaming performance and sealing adaptability, and can meet the use requirements of a certain door closer sold in the market.

Description

Technical Field

[0001] This application relates to the field of hydraulic oil technology for door closers, and mainly to a low-temperature hydraulic oil composition suitable for door closers and its preparation method. Background Technology

[0002] Door closer hydraulic oil has evolved from the initial general-purpose mechanical oil into a specialized and refined product segment.

[0003] In the early stages of door closer development, there was no specific definition for the internal oil used; common industrial machine oils or low-grade lubricants were generally employed. The core concept at this stage was "functional realization," not "performance optimization." These oils provided basic viscous damping at room temperature, allowing the door to close slowly. However, their simple composition and lack of targeted additives presented significant drawbacks: Extremely narrow temperature range: The viscosity is extremely sensitive to temperature. At slightly lower temperatures, it becomes as viscous as syrup, causing the door to close slowly or even fail; at slightly higher temperatures, it becomes as thin as water, losing its damping effect and causing the door to slam shut.

[0004] Rapid performance degradation: It is prone to oxidation, producing gum and carbon deposits, which clog the internal precision valve core, leading to regulation failure and oil leakage.

[0005] Poor sealing compatibility: This can easily lead to premature aging, swelling, or shrinkage of rubber seals, causing leakage.

[0006] At this point, the hydraulic oil of the door closer is regarded as a replaceable "black box" consumable, and its selection relies on experience rather than science, resulting in huge uncertainty in the overall performance and reliability of the door closer.

[0007] With the modernization of buildings and the upgrading of market demands, especially the emergence of high-rise buildings and large public venues, higher requirements have been placed on the reliability and environmental adaptability of door closers. The industry has begun to realize that the hydraulic oil for door closers is a core technological component that determines their performance, rather than a common consumable. This has led to the emergence and initial differentiation of specialized hydraulic oils. Specialized formulations emerge: Oil suppliers and door closer manufacturers are collaborating to develop hydraulic oils specifically for door closers. These oils use more refined mineral oils as their base and incorporate viscosity index improvers, antioxidants, and rust inhibitors, significantly improving temperature adaptability and service life.

[0008] Climate-driven initial segmentation: The market is, for the first time, functionally differentiating hydraulic fluids based on the most obvious environmental factor—temperature. Standard hydraulic fluid: suitable for normal indoor environments in temperate regions.

[0009] Low-temperature hydraulic oil: Contains pour point depressant, specially designed for cold regions to ensure normal operation in winter.

[0010] Wide-temperature / all-season hydraulic oils: Through optimized formulation, they strive to maintain stable performance over a wider temperature range, becoming a selling point for mid-to-high-end products.

[0011] Extreme segmentation of application scenarios: Regional customization: Formulas are optimized for special climates such as the extreme cold of Northern Europe, the extreme heat of the Middle East, and the high humidity of coastal areas.

[0012] Customized for specific functions and scenarios: such as a silent type for hospitals and laboratories; a heavy-duty and durable type for fire escape routes; and a low-VOC and environmentally friendly type for clean rooms.

[0013] Fire safety standards: This has led to the development of fire-resistant door closer fluids that meet specific building codes (although not traditional hydraulic oil, they represent the ultimate in functional specialization).

[0014] This stage marks the transformation of door closer hydraulic oil from an "industrial general-purpose product" to a "door control-specific product," thus ushering in a new era of refined development.

[0015] As the "blood" of a hydraulic door closer, the performance of the hydraulic fluid directly determines the door closer's damping stability, environmental adaptability, service life, and reliability. Currently, against the backdrop of rising building safety standards, frequent extreme weather events, and the growing awareness of sustainable development, the development of door closer hydraulic fluid is undergoing profound changes. The increasing complexity of building design and the deepening of global trade have amplified the differences in application scenarios. The refinement process of door closer hydraulic fluid has expanded from a single temperature dimension to a multi-faceted matrix encompassing materials, performance, geographical location, and special functions.

[0016] Co-design with sealing systems: The development of door closer hydraulic oil is no longer conducted in isolation, but rather involves rigorous compatibility testing with sealing materials such as nitrile rubber, EPDM rubber, and fluororubber. The goal is to achieve "molecular-level" matching, eliminating seal failures and leaks caused by oil-rubber incompatibility at the source.

[0017] Synthetic technology leads to a leap in performance: To meet the demands of extreme environments and long service life, synthetic base oils, represented by polyalphaolefins and esters, have been introduced. These have given rise to entirely new high-performance subcategories: Fully synthetic wide-temperature-range hydraulic fluid: can work stably in extreme temperature ranges from -40℃ to 80℃, suitable for any climate zone and high-standard projects worldwide.

[0018] Ultra-long life hydraulic fluid: It has excellent oxidation and shear stability, designed to match the building's life cycle and achieve "lifetime maintenance-free".

[0019] Therefore, existing technologies still need further development. Currently, for low-temperature environments, a low-temperature hydraulic oil composition suitable for door closers needs to be developed, and it also needs to be compatible with sealing materials. Summary of the Invention

[0020] In view of the shortcomings of the prior art, the purpose of this application is to provide a low-temperature hydraulic oil composition suitable for door closers and a method for preparing the same, aiming to provide a new low-temperature hydraulic oil composition suitable for door closers with excellent low-temperature performance and sealing adaptability.

[0021] The technical solution of this application is as follows: A low-temperature hydraulic oil composition suitable for door closers, wherein the raw materials include base oil, viscosity index improver, pour point depressant, hydraulic oil compounding agent, and antifoaming agent.

[0022] The low-temperature hydraulic oil composition of this application for door closers has excellent low-temperature performance, high viscosity index and wide temperature range viscosity stability, excellent anti-wear and extreme pressure protection, good anti-foaming properties and sealing adaptability, and can meet the usage requirements of a commercially available door closer.

[0023] The aforementioned cryogenic hydraulic oil composition for door closers, wherein, by weight percentage, comprises: The viscosity index improver is 4.0~15.0%; The pour point depressant is 0.5-1.0%; The hydraulic oil compound is 0.5~1.0%; The antifoaming agent is 0.02~0.05%; The base oil balance.

[0024] The low-temperature hydraulic oil composition suitable for door closers, wherein the base oil is one or a combination of two or more of the following: 10# white oil, 60N, 70N, 100N, 150N, Lu'an 3#, and transformer oil; The viscosity index improver is one or a combination of two or more of Jilin Chemical 0150, V1-300, V8-310, V1-248, 178A and SCR-602; The pour point depressant is selected from polymethyl methacrylate pour point depressants; The hydraulic oil compound is one of 3010A, 5003, ALRO L208, HRD7012, and H8035; The antifoaming agent is one or a combination of two or more of AC AMH2, T922, T921, V14-520 and 155.

[0025] The low-temperature hydraulic oil composition suitable for door closers, wherein the base oil is a combination of 1-10℃ transformer oil and 150N, wherein the 1-10℃ transformer oil and the 150N are compounded in a mass ratio of 1.9:1.

[0026] The low-temperature hydraulic oil composition suitable for door closers, wherein the viscosity index improver is a combination of Jilin Chemical 0150 and 178A, wherein Jilin Chemical 0150 and 178A are compounded in a mass ratio of 6.18:1.

[0027] The aforementioned low-temperature hydraulic oil composition suitable for door closers, wherein the pour point depressant is one of T602B, T602HB, and TC-602.

[0028] The aforementioned low-temperature hydraulic oil composition suitable for door closers, wherein the hydraulic oil compound is ALRO L208.

[0029] The low-temperature hydraulic oil composition suitable for door closers, wherein the antifoaming agent is a combination of AC AMH2 and V14-520, wherein AC AMH2 and V14-520 are compounded in a mass ratio of 1:8.

[0030] The aforementioned cryogenic hydraulic oil composition for door closers, wherein, by weight percentage, comprises: The base oil content was 84.495%. The viscosity index improver is 14.36%; The pour point depressant is 0.5%; The hydraulic oil compound is 0.6%; The antifoaming agent is 0.045%.

[0031] A method for preparing a cryogenic hydraulic oil composition suitable for door closers as described above, comprising the following steps: Add the base oil and mix well; Heat to 55±5℃, add viscosity index improver, stir evenly, then add hydraulic oil compound, pour point depressant and antifoaming agent in sequence, and stir evenly.

[0032] Beneficial effects: The low-temperature hydraulic oil composition of this application for door closers has excellent low-temperature performance, high viscosity index and wide temperature range viscosity stability, excellent anti-wear and extreme pressure protection, good anti-foaming properties and sealing adaptability, and can meet the usage requirements of a commercially available door closer. Detailed Implementation

[0033] This application provides a low-temperature hydraulic oil composition suitable for door closers and a method for preparing the same. To make the objectives, technical solutions, and effects of this application clearer and more explicit, the following provides a more detailed description. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0034] In this application, a low-temperature hydraulic oil composition suitable for door closers is provided, based on properties such as low-temperature performance, high viscosity index and wide temperature range viscosity stability, excellent anti-wear and extreme pressure protection, sealing compatibility and good anti-foaming properties.

[0035] The cryogenic hydraulic oil composition for door closers provided in this application comprises base oil, viscosity index improver, pour point depressant, hydraulic oil compounding agent, and antifoaming agent.

[0036] Base oil, as a liquid medium, transmits pressure and damping force. The viscosity of the base oil is the fundamental physical property that generates hydraulic damping. The low-temperature viscosity and pour point of the base oil directly determine the lowest temperature at which the oil can remain fluid. The chemical composition of the base oil determines its behavior at low temperatures. Paraffinic mineral oils easily crystallize at low temperatures, leading to solidification. In contrast, deeply hydrotreated hydroisomerized oils or synthetic hydrocarbons, with their regular molecular structure, few branches, and extremely low pour points (below -50°C), are the fundamental guarantee of low-temperature performance. The viscosity-temperature characteristics of the base oil itself are crucial. All functional additives (anti-wear agents, antioxidants, pour point depressants, etc.) must be uniformly and stably dissolved or dispersed in the base oil to function. The solubility and chemical stability of the base oil directly affect the effectiveness and durability of the additives. For example, some synthetic base oils (such as ester oils) are polar, which can enhance the adsorption of anti-wear agents and rust inhibitors on metal surfaces, creating a synergistic effect with the additives and achieving a "1+1>2" effect. The current mainstream economical choice uses a hydrogenation process to remove unstable components and waxes, resulting in a lower pour point, higher viscosity index, and good overall performance, meeting most conventional low-temperature requirements. In this application, the base oil can be one or a combination of two or more mineral oils, such as 10# white oil, 60N, 70N, 100N, 150N, Lu'an 3#, and transformer oil. Preferably, the base oil is a blend of 1-10℃ transformer oil and 150N. Further, the base oil is a blend of 1-10℃ transformer oil and 150N at a mass ratio of 1.9:1. Using this preferred base oil can meet the low-temperature performance requirements of low-temperature hydraulic oils, ensuring that various additives are uniformly and stably dispersed in the base oil and function effectively.

[0037] Viscosity index improvers are high-molecular polymers and are the most crucial and core additives for achieving "wide temperature range" performance. At low temperatures, their molecular chains coil, having little impact on the fluidity of the base oil; at high temperatures, the molecular chains extend and expand, increasing internal friction and thus "thickening" the oil. This significantly improves the viscosity index of the oil, ensuring it is neither excessively viscous at low temperatures (maintaining fluidity) nor excessively thin at high temperatures (maintaining sealing and lubrication capabilities), forming the basis for achieving "one oil for all seasons." For door closers, this directly determines the stability of the opening and closing force and speed in different seasons. In this application, the viscosity index improver can be one or a combination of two or more of Jilin Chemical 0150, V1-300, V8-310, V1-248, 178A, and SCR-602. Preferably, the viscosity index improver is a compound of Jilin Chemical 0150 and 178A. Further, the viscosity index improver is a compound of Jilin Chemical 0150 and 178A at a mass ratio of 6.18:1. Using this preferred viscosity index improver can meet the requirements of low-temperature performance, high viscosity index and wide temperature range viscosity stability of low-temperature hydraulic oil.

[0038] Pour point depressants are specifically designed to overcome low-temperature limits and are a direct guarantee of low-temperature performance. Base oils (especially mineral oils) precipitate microcrystalline wax at low temperatures, forming a network structure that causes them to solidify. Pour point depressants adsorb onto the surface of these wax crystals, preventing them from forming a large network, thus significantly lowering the oil's pour point and allowing it to remain fluid at even lower temperatures. This is a decisive factor in whether low-temperature hydraulic oils can function properly in extremely cold environments (such as below -30°C). Without efficient pour point depressants, door closers will completely fail in harsh winter outdoor environments or cold storage. In this application, polymethyl methacrylate (PMA) is selected as the pour point depressant. PMA has customizable molecular structure, an efficient mechanism of action, and multifunctionality (pour point depressant + viscosity increase). Compared to the limitations of alkylnaphthalenes and the insufficient temperature resistance of EVA (ethylene-vinyl acetate copolymer), PMA has a more comprehensive performance advantage in high-end lubricants and specialty oils, and is one of the most widely used and best-performing types of pour point depressants currently available. The pour point depressant can be one of T602B, T602HB, TC-602, etc. Preferably, the pour point depressant is T602B. Using this preferred pour point depressant can meet the low-temperature performance requirements of cryogenic hydraulic oils.

[0039] Anti-wear agents / extreme pressure agents protect the precision moving parts inside door closers (such as pistons, cylinders, and regulating valve cores) from wear and abrasion. By forming a robust adsorbed or chemically reacted film on the metal surface, sliding friction is converted into interlaminar shear, thereby reducing direct metal-to-metal contact and wear. Extreme pressure agents react to form a film under high temperature and pressure (such as instantaneous impact), preventing sintering. Although door closers are not heavily loaded, they operate frequently and have precise internal valves. Anti-wear agents ensure that the equipment maintains dimensional accuracy and damping stability during long-term, high-frequency operation, preventing internal leakage, reduced damping force, and regulation failure caused by wear.

[0040] Antioxidants delay the aging and deterioration of oils under the influence of heat and oxygen, extending the service life of both the oil and valve closers. They terminate the chain oxidation reaction by preferentially reacting with oxygen or by decomposing peroxides produced during oil oxidation. Valve closers operate in a sealed environment for extended periods (years or even decades). Oxidation leads to increased oil viscosity, higher acid values, and the formation of sludge and varnish. Sludge can clog delicate throttling orifices, and increased acid values ​​can corrode metal and seals. Antioxidants are crucial for ensuring long-term performance stability.

[0041] Rust inhibitors prevent the rust and corrosion of metal components (steel, copper, etc.) in a system. They work by forming a dense, protective film on the metal surface, blocking moisture and air. Some rust inhibitors have the ability to neutralize acidic substances. The internal environment of a door closer is not absolutely water-free. Temperature changes can cause condensation, and trace amounts of moisture from the air may seep in over long-term use. Rust inhibitors protect expensive metal components from jamming, accelerated wear, and eventual failure caused by corrosion.

[0042] Metal passivators prevent the catalytic oxidation of non-ferrous metals, especially copper and its alloys. They eliminate catalytic activity by forming an inert protective film on the metal surface or by binding with metal ions. Valve closers may contain copper components (such as bearings and valve parts). Copper is a strong oxidation catalyst. Metal passivators effectively inhibit the rapid oxidation of oils initiated by metal ions, complementing and enhancing antioxidant systems.

[0043] In this application, the hydraulic oil compound includes anti-wear agents / extreme pressure agents, antioxidants, rust inhibitors, and metal passivators. The hydraulic oil compound can be one of 3010A, 5003, ALRO L208, HRD7012, H8035, etc. Preferably, the hydraulic oil compound is ALRO L208. Using this preferred compound can satisfy the excellent anti-wear and extreme pressure protection performance of low-temperature hydraulic oil.

[0044] Antifoaming agents inhibit the formation of foam in hydraulic fluids and accelerate its elimination. They work by reducing the strength of the liquid film on the surface of bubbles, making them easier to break. Antifoaming agents are typically insoluble in oil and dispersed within it as extremely fine particles. During valve closing, hydraulic oil flows and shears at high speeds in valves and pipelines, easily introducing air and generating foam. Foam can lead to unstable damping (uneven closing speed), abnormal noise, and accelerate oil oxidation and lubrication failure. Antifoaming agents ensure the smoothness and quietness of hydraulic system operation. In this application, the antifoaming agent can be one or a combination of two or more of AC AMH2, T922, T921, V14-520, and 155. Preferably, the antifoaming agent is a combination of AC AMH2 and V14-520. Further, the antifoaming agent is a combination of AC AMH2 and V14-520 at a mass ratio of 1:8. Using this preferred antifoaming agent can meet the requirement of good antifoaming performance for low-temperature hydraulic oils.

[0045] Furthermore, the cryogenic hydraulic oil composition for door closers of this application comprises, by weight percentage, the following raw materials: Viscosity index improver: 4.0~15.0%; Pour point depressant 0.5~1.0%; Hydraulic oil compound agent 0.5~1.0%; Antifoaming agent 0.02~0.05%; Base oil balance.

[0046] Preferably, the cryogenic hydraulic oil composition for door closers of this application comprises, by weight percentage, the following raw materials: Base oil 84.495%; Viscosity index improver 14.36%; Pour point depressant 0.5%; Hydraulic oil compound agent 0.6%; Antifoaming agent 0.045%.

[0047] By using the above-preferred raw material ratios, with transformer oil as the base oil and 150N compounded at a mass ratio of 1.9:1, and Jilin Chemical 0150 and 178A compounded at a mass ratio of 6.18:1, the prepared oil can achieve a suitable viscosity, with a kinematic viscosity of 49.0-50.0 mm² / s at 40℃. It also exhibits excellent low-temperature performance, high viscosity index and wide temperature range viscosity stability, outstanding anti-wear and extreme pressure protection, good anti-foaming properties and sealing adaptability.

[0048] In this application, by selecting a suitable base oil, the solubility and performance of various additives in the base oil are optimized. By compounding different additives, the best additives and their compounding ratios are selected to maximize their performance, thereby achieving the best performance of the oil and better sealing compatibility.

[0049] The cryogenic hydraulic oil composition for door closers disclosed in this application has the following advantages: (1) Low-temperature performance pour point test can reach -48℃; (2) Excellent foam performance can meet the requirements of 0 / 0, 0 / 0, 0 / 0; (3) It meets the door closer test requirements and has good compatibility with the rubber ring.

[0050] This application also provides a method for preparing the above-mentioned low-temperature hydraulic oil composition suitable for door closers, comprising the following steps: Add the base oil and mix thoroughly; Heat to 55±5℃, add viscosity index improver, stir thoroughly, then add hydraulic oil compound, pour point depressant and antifoaming agent in sequence, stir evenly, and wait for the raw materials to dissolve evenly.

[0051] The present application will be further described below through specific embodiments.

[0052] 1. In the embodiments of this application, the sources of some raw materials are as follows: 10# White Oil: Maoming Petrochemical Co., Ltd.; 60N: CNOOC Huizhou Petrochemical Co., Ltd.; 70N: Tianjin Yitaicheng Chemical Technology Co., Ltd.; 100N: Panjin Northern Asphalt Co., Ltd.; 150N: CNOOC Huizhou Truth Co., Ltd.; Lu'an No. 3: Dongguan Hongli Chemical Co., Ltd. Transformer oil at 1-10℃: Maoming Petrochemical Co., Ltd.; Jilin Chemical 0150: Foshan Jinjian Lubricating Oil Co., Ltd.; V1-300: Evonik International Trading (Shanghai) Co., Ltd.; 178A: Shenyang Great Wall Lubricating Oil Manufacturing Co., Ltd.; SCR-602: Shenyang Great Wall Lubricating Oil Manufacturing Co., Ltd.; T602B: Guangzhou Ruishengyan Chemical Technology; T602HB: Guangzhou Ruishengyan Chemical Technology; TC-602: Guangzhou Ruishengyan Chemical Technology; 3010A: Guangzhou Ruicheng New Materials Co., Ltd.; 5003: Guangzhou Ruicheng New Materials Co., Ltd.; ALRO L208: Guangzhou Ruicheng New Materials Co., Ltd.; HRD7012: Guangzhou Ruishengyan Chemical Technology; H8035: Zibo Huihua Chemical Co., Ltd.; AC AMH2: BASF; T922: Dongguan Blue Whale Chemical Technology Co., Ltd. T921: Dongguan Blue Whale Chemical Technology Co., Ltd. V14-520: Evonik International Trading (Shanghai) Co., Ltd.; 155: Mengqingxin Additives Trading (Shanghai) Co., Ltd.

[0053] 2. In the embodiments of this application, the preparation method is as follows: First, add the base oil and stir thoroughly. Then heat to 55±5℃, add the viscosity index improver, stir thoroughly and evenly, and then add the compounding agent, pour point depressant and antifoaming agent in sequence. Once the sample is stirred and dissolved evenly, it is ready.

[0054] 3. In this embodiment of the application, the performance testing method is as follows: Test methods for kinematic viscosity, viscosity index, pour point, open flash point, foaming properties, abrasion resistance and sealing suitability: refer to GB / T 265, GB / T 2541, GB / T 3535, GB / T 3536, GB / T 12579, SH / T 0189 and SH / T0305.

[0055] Example 1 and Comparative Examples 1-1 to 1-15 each prepared a low-temperature hydraulic oil composition, the composition of which is shown in Table 1 and Table 2.

[0056] Table 1

[0057] Table 2

[0058] The kinematic viscosity, viscosity index, and pour point of the low-temperature hydraulic oil compositions prepared in Example 1 and Comparative Examples 1-1 to 1-15 were tested, and the test results are shown in Table 3.

[0059] Table 3

[0060] As can be seen from the data in Table 3, Example 1 uses base oil blended with 1-10℃ transformer oil and 150N at a mass ratio of 1.9:1, and base oil viscosity index improver blended with Jilin Chemical 0150 and 178A at a mass ratio of 6.18:1. This results in a low-temperature hydraulic oil composition with moderate viscosity and excellent low-temperature performance, which is superior to that of Comparative Examples 1-1 to 1-15. It is more suitable for use in door closers in low-temperature environments.

[0061] Comparative Example 1 and Examples 2-1 to 2-3 each prepared a low-temperature hydraulic oil composition, the composition of which is shown in Table 4.

[0062] Table 4

[0063] The low-temperature performance of the low-temperature hydraulic oil compositions prepared in Comparative Example 1 and Examples 2-1 to 2-3 was tested, and the results are shown in Table 5.

[0064] Table 5

[0065] As can be seen from Table 5, different pour point depressants and different amounts added will have a significant impact on its low-temperature performance. When pour point depressant T602B is used and the amount added is 0.5%, the low-temperature performance is better.

[0066] Comparative Examples 2 and Examples 3-1 to 3-4 each prepared a low-temperature hydraulic oil composition, the composition of which is shown in Table 6.

[0067] Table 6

[0068] The anti-wear properties of the low-temperature hydraulic oil compositions prepared in Examples 1, 2, and 3-1 to 3-4 were tested, and the results are shown in Table 7.

[0069] Table 7

[0070] As can be seen from Table 6, the addition of different proportions of different hydraulic oil additives has a significant impact on the anti-wear performance of the low-temperature hydraulic oil composition. When ALRO L208 is used and the addition amount is 0.6%, the anti-wear performance of the low-temperature hydraulic oil composition is the best.

[0071] Comparative Example 3 and Examples 4-1 to 4-4 each prepared a low-temperature hydraulic oil composition, the composition of which is shown in Table 8.

[0072] Table 8

[0073] The foaming properties of the low-temperature hydraulic oil compositions prepared in Examples 1, 3, and 4-1 to 4-4 were tested, and the results are shown in Table 9.

[0074] Table 9

[0075] As can be seen from Table 9, the foaming performance of low-temperature hydraulic oil compositions varies depending on the type of antifoaming agent added. The foaming performance of V14-520 and AC AMH2 in a ratio of 8:1 is better than that of other compounded antifoaming agents.

[0076] The technical specifications of the low-temperature hydraulic oil composition prepared in Example 1 are shown in Table 10.

[0077] Table 10

[0078] The low-temperature hydraulic oil composition prepared in Example 1 was used to conduct relevant tests on a commercially available door closer. The test results are as follows: 1. Full closing time: refers to the time required for the door closer to close the door from the maximum open position (e.g., 90°) to the fully closed position under standard test conditions (room temperature).

[0079] 2. Set speed: This refers to the target closing time preset by adjusting the door closer valve. The test is to verify whether the door closer can be accurately adjusted and stabilized at the set value.

[0080] 3. Test temperature and test time: This part simulates the environment. The door closer is placed in a set low temperature (-15℃) environment for a specified number of hours to test its internal seal and the stability of the hydraulic oil.

[0081] 4. Closing time after low temperature test / s (≤25s): After the door closer undergoes a low temperature test, the hydraulic oil inside will become viscous, resulting in a slower closing speed. Under low temperature conditions (-15℃), the closing time should not exceed 25 seconds, otherwise it will affect the use or even cause the door to fail to close.

[0082] 5. Door closing effect after high temperature test / s (≥3s): High temperature will thin the hydraulic oil, which may cause the door to close too quickly. Under high temperature (40℃) conditions, the closing time should not be less than 3 seconds to prevent excessive closing impact force, which may cause danger or damage.

[0083] Table 11

[0084] The test results are shown in Table 11. The low-temperature hydraulic oil composition of Example 1 of this application meets the requirements of a commercially available door closer and has passed the relevant tests of the door closer.

[0085] In this application, by screening and compatibility of base oils and additives, the low-temperature hydraulic oil composition achieves excellent low-temperature performance, high viscosity index and wide temperature range viscosity stability, excellent anti-wear and extreme pressure protection, good anti-foaming properties and sealing adaptability, which can meet the usage requirements of a commercially available door closer.

[0086] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of this application.

Claims

1. A low temperature hydraulic fluid composition suitable for use in a door closer, characterized in that, The raw materials include base oil, viscosity index improver, pour point depressant, hydraulic oil complex agent, antifoaming agent.

2. The low temperature hydraulic oil composition suitable for use in door closers according to claim 1, characterized in that, According to the weight percentage, it comprises: The viscosity index improver 4.0-15.0%; The pour point depressant 0.5-1.0%; The hydraulic oil complex agent 0.5-1.0%; The antifoaming agent 0.02-0.05%; The base oil is one of 10# white oil, 60N, 70N, 100N, 150N, Lu'an 3#, transformer oil or a combination of two or more above; 3. The low temperature hydraulic fluid composition suitable for use in door closers according to claim 1, characterized in that, The viscosity index improver is one of Jihua 0150, V1-300, V8-310, V1-248, 178A and SCR-602 or a combination of two or more above; The pour point depressant is selected from polymethyl acrylate pour point depressant; The hydraulic oil complex agent is one of 3010A, 5003, ALRO L208, HRD7012 and H8035; The antifoaming agent is one of AC AMH2, T922, T921, V14-520 and 155 or a combination of two or more above. The base oil is a combination of I-10℃ transformer oil and 150N, and the I-10℃ transformer oil and the 150N are compounded at a mass ratio of 1.9:

1.

4. The low temperature hydraulic fluid composition suitable for use in door closers according to claim 1, characterized in that, The viscosity index improver is a combination of Jihua 0150 and 178A, and the Jihua 0150 and the 178A are compounded at a mass ratio of 6.18:

1.

5. The low temperature hydraulic fluid composition suitable for use in door closers according to claim 1, characterized in that, The pour point depressant is one of T602B, T602HB and TC-602.

6. The low temperature hydraulic fluid composition suitable for use in door closers according to claim 1, characterized in that, The hydraulic oil complex agent is ALRO L208.

7. The low temperature hydraulic fluid composition suitable for use in door closers according to claim 1, characterized in that, The antifoaming agent is a combination of AC AMH2 and V14-520, and the AC AMH2 and the V14-520 are compounded at a mass ratio of 1:

8.

8. The low temperature hydraulic fluid composition suitable for use in door closers according to claim 1, characterized in that, According to the weight percentage, it comprises:

9. A low temperature hydraulic oil composition suitable for use in a door closer according to any of claims 1 to 8 characterised in that, The base oil 84.495%; The viscosity index improver 14.36%; The pour point depressant 0.5%; The hydraulic oil complex agent 0.6%; The antifoaming agent 0.045%. The method comprises the following steps:

10. A process for the preparation of a low temperature hydraulic fluid composition suitable for use in door closers as claimed in any one of claims 1 to 9, characterised in that, Add base oil and stir uniformly; Heat to 55±5℃, add viscosity index improver, stir uniformly, and then add hydraulic oil complex agent, pour point depressant and antifoaming agent in sequence and stir uniformly. ​

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