JPS6221840B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to fluid compositions for vehicle central hydraulic systems. A vehicle centralized hydraulic system is a system in which hydraulic equipment is mounted inside the vehicle, and uses a single hydraulic source and type of oil to control power steering, brakes, automatic transmissions, shock absorbers, wind seal wipers, and seat actuators. Alternatively, it is a system that operates a window actuator, etc., and the fluid used in this system is the fluid for the central hydraulic system (Central Hydraulic System Fluid).
This is called system fluid. The properties required for fluids for vehicle central hydraulic systems are the SAE71R1 standard (mineral oil-based) in the United States.
It has been established as the SAE71R2 standard (synthetic oil type). These standards have been established based on the properties required for both power steering fluid and brake fluid, and the specific required properties are as follows. 1. Excellent fluidity at low temperatures. 2. Excellent shear stability. 3. Capable of operating over a wide temperature range. 4. Must have a high boiling point and flash point. 5. Do not form precipitates or condensates at low temperatures. 6. Low foaming. 7. Excellent lubricity and oxidation stability. 8. Do not corrode the metal parts of the hydraulic system or allow the rubber parts to swell excessively. As described above, the required properties are diverse and strict, but the inventors of this application have selected (A) polybutene, (B) C ₂ as liquids that pass the SAE71R1 standard.
~ _C12 α-olefin homopolymer or copolymer and (C) at least one hydrocarbon base oil selected from the group consisting of highly aromatic hydrocarbon nuclear hydride; (1) polymethacrylate and ( 2) We have previously applied for a hydraulic oil composition containing at least one viscosity index improver selected from the group consisting of polyolefins as essential components (Japanese Patent Application Laid-Open No. 151903/1983). For the fluid used,
From a safety standpoint, and with the rise in temperature in the engine room due to exhaust gas countermeasures, performance at high temperatures, such as high flash point, high initial boiling point, and low evaporation loss, has become necessary.
Furthermore, compatibility with the rubber materials used in centralized hydraulic systems, especially nitrile rubber, has become more important than ever, and in addition to the SAE standards mentioned above, the aniline point of the fluid used is now within a desirable range. Certain things have become required of us. The new required properties for fluids for vehicle central hydraulic systems, including these, are as follows.

[Table] However, the SAE standard itself is extremely strict, and the fluids that pass it are also
Since almost no hydraulic oil composition other than the one disclosed in No. 151903 is known, it has been extremely difficult to provide a fluid that also satisfies the various required properties described above. An object of the present invention is to provide a vehicle centralized hydraulic system that satisfies the SEA standards and also satisfies performance under high temperatures such as flash point, initial boiling point, and evaporation loss as listed in the table above, as well as compatibility with rubber materials. An object of the present invention is to provide a fluid composition for a system. The present invention contains 70-95% by weight of a hydrocarbon base oil (1) and 5-30% by weight of a viscosity index improver (2);
The hydrocarbon base oil (1) is (A) 40 to 99% by weight based on the hydrocarbon base oil;
(a) a polybutene having an average molecular weight of 100 to 500;
and (b) 2 to 12 carbon atoms with an average molecular weight of 100 to 600.
at least one component selected from the group consisting of at least one homopolymer or copolymer of α-olefin (excluding butene); and (B) 1 to 6 based on the hydrocarbon base oil. weight%
lower alkyl biphenyl, and the viscosity index improver (2) has 1 to 1 carbon atoms.
The present invention relates to a fluid composition for a vehicle central hydraulic system, which is a polymethacrylate having a viscosity average molecular weight of 10,000 to 700,000 obtained by polymerizing at least one ester of 18 saturated monohydric aliphatic alcohols and methacrylic acid. Hereinafter, the fluid composition for a vehicle central hydraulic system according to the present invention will be explained in more detail. The fluid compositions of the present invention include (1) 70-95% by weight hydrocarbon base oil and (2) 5-30% by weight viscosity index improver. In addition, in the present invention, (3)
Additives of 0.1 to 10% by weight can also be blended. (1) Hydrocarbon base oil The hydrocarbon base oil (1) referred to in the present invention includes (A) (a) polybutene having an average molecular weight of 100 to 500, and (b) polyα-polybutene having an average molecular weight of 100 to 600. It contains at least one component selected from the group consisting of olefins (excluding polybutene) and (B) lower alkyl phenyl. In addition, (C) a petroleum-based lubricating oil fraction can be blended as needed. (1-A-a) Polybutene has an average molecular weight of 100~
500, preferably 150-300 can be used. If the average molecular weight is smaller than this range, the flash point will be low, and if it is larger than this range, the viscosity will be too high, which is not preferable. The viscosity of these polybutenes is less than 6.0 _cSt7 (40℃) and less than 2.0cSt (100℃), and if the viscosity does not exceed this range, some amount of heavier polybutene or hydrogenated polybutene may also be mixed. can do. The method for producing polybutene is well known to those skilled in the art. For example, a butane-butene fraction produced by decomposition of petroleum fraction is used as a raw material, and so-called Friedel, such as aluminum chloride, magnesium chloride, boron fluoride, or titanium tetrachloride, is used as a raw material. -Crafts Catalyst,
Alternatively, a method can be adopted in which the polymerization is carried out at -30 to 30°C using a complex compound thereof as a catalyst and, if necessary, a co-catalyst such as an organic halide or hydrochloric acid. (1-A-b) The poly-α-olefin is a homopolymer or copolymer of at least one α-olefin having 2 to 12 carbon atoms (excluding butene), preferably α-olefin having 6 to 10 carbon atoms. Those obtained by polymerization and having an average molecular weight of 100 to 600, preferably 250 to 450 can be used. If the average molecular weight is smaller than this range, the flash point will be low, and if it is larger than this range, the viscosity will be too high, which is not preferable. The viscosity of these polyα-olefins is 20.0 cSt or less (40℃)
and 4.0cSt or less (100℃). The method for producing polyα-olefin is well known to those skilled in the art, and for example, using the above α-olefin as a raw material, aluminum chloride/aluminum bromide catalyst, aluminum bromide/hydrogen bromide catalyst, boron fluoride/alcohol It can be produced by cationic polymerization using an aluminum chloride-based catalyst or an aluminum chloride ester catalyst, radical polymerization using heat or peroxide, or polymerization using a Ziegler-based catalyst. In the present invention, the amount of component (1-A),
That is, the amount of (1-A-a) polybutene and/or (1-A-b) polyα-olefin is 40 to 99% by weight, particularly 60 to 80% by weight, based on the hydrocarbon base oil (1). It is preferable that Further, when both (1-A-a) polybutene and (1-A-b) poly-α-olefin are used together, the blending ratio of the former is 10 to 70% by weight, preferably 25 to 55% by weight.
Based on the weight percentage, the latter is 30 to 90% by weight, preferably 45 to 75% by weight. (1-B) Lower alkylbiphenyl includes monomethylbiphenyl, dimethylbiphenyl, monoethylbiphenyl, diethylbiphenyl,
At least one compound selected from the group consisting of triethylbiphenyl, monoisopropylbiphenyl, diisopropylbiphenyl, and isomer mixtures of the lower alkylbiphenyl can be used. These lower alkyl biphenyls have a boiling point of 260°C or higher, a viscosity of 30 cP or lower (at 20°C), and a pour point of 0°C or lower. The method for producing lower alkyl biphenyl is well known to those skilled in the art, and is disclosed, for example, in Japanese Patent Publication No. 17506/1982 or Japanese Patent Publication No. 30096/1983. Specifically, typical examples include alkylation of biphenyl with a lower olefin or transalkylation of polyalkylbenzene with biphenyl. The amount of lower alkyl biphenyl is 1 to 60% by weight, preferably 5 to 40% by weight, based on the hydrocarbon base oil (1). If the amount of lower alkyl biphenyl is less than this range,
If the aniline point becomes high, the rubber material used in the hydraulic system will shrink, and the low-temperature viscosity will increase, which is undesirable.If it exceeds this range, the aniline point will decrease, causing the rubber material to expand in volume. This is undesirable because it lowers the properties of the rubber material, such as tensile strength and elongation. In addition, in the hydrocarbon base oil (1) of the fluid composition according to the present invention, if necessary, the petroleum lubricating oil fraction (1-C) is added to 55% by weight or less, preferably 55% by weight or less based on the hydrocarbon base oil. It can also be blended with a limit of 45% by weight or less. The petroleum lubricating oil fraction referred to herein is one with a viscosity of 15.0 cSt or less (40°C) and 4.0 cSt or less (100°C), a viscosity index of 70 or more, and a pour point of -10°C or less. (2) Viscosity index improver The viscosity index improver (2) in the present invention is a viscosity index improver obtained by polymerizing at least one ester of a saturated monohydric aliphatic alcohol having 1 to 18 carbon atoms and methacrylic acid. It is a polymethacrylate having an average molecular weight of 10,000 to 700,000, preferably 50,000 to 200,000. If the viscosity average molecular weight of polymethacrylate is smaller than this range, adding the amount necessary to obtain sufficient viscosity in the high temperature range is not preferable because the viscosity in the low temperature range will become too high. is not preferable because it does not have sufficient shear stability and the viscosity of the composition decreases in a high temperature range. The amount of viscosity index improver is from 5 to 30% by weight, preferably from 7 to 20% by weight based on the fluid composition. If the amount of the viscosity index improver is less than this range, the viscosity of the fluid composition at high temperatures will not be sufficient, and the low-temperature properties of the lower alkyl biphenyl-containing oil will deteriorate. Moreover, if it exceeds this range, the viscosity in the low temperature range becomes too large, which is not preferable. (3) Additives In the fluid composition according to the present invention, in addition to the essential components hydrocarbon base oil (1) and viscosity index improver (2), antioxidants, oiliness agents, At least one of an anti-wear agent, a detergent-dispersing agent, an antifoaming agent, a metal deactivator, etc. can be added. Details of the various additives are introduced, for example, in "Petroleum Product Additives" (Saiwai Shobo) edited by Toshio Sakurai, but preferred embodiments are as follows. As the antioxidant, alkylphenols, aromatic amines, and dithiophosphorus metal salts can be used, and specifically, 2,6-di-tert.-
Butylparacresol, 2,6-di-tert.-
Examples include butylphenol, phenyl-α-naphthylamine, and zinc dialkyldiophosphate. The amount added is based on the fluid composition.
0.1 to 3.0 weight is preferred. As the oily agent, higher fatty acids such as oleic acid, stearic acid, higher alcohols such as oleyl alcohol, esters of higher fatty acids, alkylamines, oils and fats, and sulfurized oils and fats can be used. The amount added is preferably 0.05 to 6.0% by weight based on the fluid composition. As the anti-wear agent, dithiophosphate metal salts, phosphate esters, etc. can be used. The amount added is preferably 0.1 to 5% by weight based on the fluid composition. As detergents and dispersants, neutral, basic or ultrabasic metal sulfonates, phenates,
Phosphonates and ashless types such as alkenylsuccinimides, benzylamines, etc. can be used. The amount added is preferably 0.1 to 40% by weight based on the liquid composition. As the antifoaming agent, silicones and esters such as polymethacrylate can be used, and the amount added is preferably 0.002 to 0.5% by weight based on the fluid composition. As the metal deactivator, benzotriazole or the like can be used, and the amount added is preferably 0.005 to 0.5% by weight based on the fluid composition. Among the various additives mentioned above, preferred are antioxidants, oily agents, anti-wear agents, and antifoaming agents. When these various additives are used together, the total amount thereof is 0.1 to 0.1 to 0.1 based on the fluid composition. Preferably it is 10% by weight. The fluid composition for a vehicle central hydraulic system according to the present invention is a fluid that satisfies the above-mentioned SAE standards and has performance at high temperatures and compatibility with rubber materials that are superior to fluids that pass these standards. Not only can it be used as a fluid for centralized hydraulic systems, but also for other uses, such as brake fluid,
It can also be used as power steering fluid, shock absorber fluid, and automatic transmission fluid. Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. The compositions of Examples 1 to 8 in Table 1 are fluid compositions for vehicle central hydraulic systems according to the present invention, and the compositions of Comparative Examples 1 to 9 in Table 2 are compositions for comparison. In the table, (1-A) to (1-
C) Components are weight% based on hydrocarbon base oil (1)
Components (2) and (3) are expressed as weight % based on the fluid composition. The oil types and additives used are as follows. (1) Hydrocarbon base oil (1-A-a) polybutene; A has an average molecular weight of 250. (1-A-b) Poly α-olefin; B is poly α-olefin mainly composed of 1-decel trimer, and average molecular weight 440 C is poly α-olefin mainly composed of 1-decene dimer. - Olefin, average molecular weight
280. (1-B) Lower alkylbiphenyl; D is lower alkylbiphenyl mainly consisting of ethylbiphenyl. E is lower alkylbiphenyl mainly consisting of a mixture of ethylbiphenyl and propylbiphenyl. (1‐C) Petroleum lubricating oil fraction; F has a viscosity of 1.658 cSt
(100℃) lubricating oil fraction. (2) Viscosity index improver; Polymethacrylate G is
Polymerization of ester of methacrylic acid and a mixture of saturated monohydric aliphatic alcohols having 1 to 18 carbon atoms containing 30% by weight of n-butyl alcohol, 17% by weight of n-decyl alcohol and 27% by weight or more of n-hexadecyl alcohol. It is a polymethacrylate obtained by the following methods, and has a viscosity average molecular weight of 631,000. Polymethacrylate H is a polymethacrylate obtained by polymerizing an ester of methacrylic acid and a saturated monohydric aliphatic alcohol mixture having 1 to 18 carbon atoms containing 60% by weight or more of n-dodecyl alcohol, and has a viscosity average molecular weight of 143000. (3) Additive; Antioxidant I is 2,6-di-tert.
-Butyl para-cresol Oil-based agent J is oil. Anti-wear agent K is zinc dialkyldithiophosphate. Antifoaming agent L is silicone. Various performance tests were conducted on the compositions of Examples 1 to 8 and the compositions of Comparative Examples 1 to 9, and the results are shown in Tables 1 and 2, respectively. The test method is as follows. 1 Viscosity: Measured at 100°C according to ASTM D445.
It is preferable that it is 6.3 cSt or more. 2 Low temperature viscosity: −40 by Bruckfield method
Measured at °C. It is preferably 2000cSt or less. 3 Flash point: Measured according to ASTM D92. The temperature is preferably 107°C or higher, particularly 140°C or higher. 4 Initial boiling point: Measured according to ASTM D158. The temperature is preferably 204°C or higher, particularly 240°C or higher. 5 Aniline point; measured according to JISK2256. 80~100
It is preferable that it is ℃. 6 Evaporation loss: Measured after 48 hours at 100℃ in accordance with JISK2233. It is preferably 15% by weight or less. Comparative Examples 1 to 5 Comparative Examples 1, 2 to 3, and 4 to 5 are (1-A-a) polybutene, (1-
These are test results for A-b) polyα-olefin and (1-B) lower alkyl biphenyl. The viscosity at 100℃ is insufficient for each component alone, especially lower alkyl biphenyl alone has an insufficient viscosity at -40℃.
Because it solidifies at ℃ and has an extremely low aniline point, it cannot be put to practical use. Examples 1 to 3 In Example 1, both polybutene and polyα-olefin were used together as the component (1-A), and lower alkyl biphenyl [component (1-B)] and polymethacrylate [component (2)] were used together. ], and Examples 2 to 3 are compositions further containing various additives [component (3)]. All of them passed various tests and were found to be excellent fluid compositions for vehicle central hydraulic systems. Examples 4 to 6 In Examples 4 to 6, polyα was used as the component (1-A).
- It is a composition that uses only olefin and further contains lower alkyl biphenyl [component (1-B)], polymethacrylate [component (2)] and various additives [component (3)]. It passed the test and was found to be an excellent fluid composition for vehicle central hydraulic systems. Examples 7 to 8 Examples 7 to 8 are compositions in which the fluid composition according to the present invention is further blended with a petroleum lubricating oil fraction [component (1-C)] and various additives [component (3)]. All of them passed various tests and were found to be excellent fluid compositions for vehicle central hydraulic systems. Comparative Examples 6 to 9 Comparative Example 6 is a poly-α-olefin [(1-A-
b) component] and lower alkyl biphenyl [(1
The composition uses component -B] as a base oil and does not contain polymethacrylate [component (2)], but it is not suitable for use in vehicle central hydraulic systems because its viscosity at 100°C is insufficient and it solidifies at -40°C. cannot be used. That is, in the present invention, polymethacrylate is an essential component that not only increases the high-temperature viscosity but also improves the low-temperature properties of the lower alkyl biphenyl-containing oil. In Comparative Examples 7 to 9, polyα-olefin [(1-A-b) component] alone or polybutene [(1-A-a) component] was used as the base oil, and polymethacrylate was added to this base oil. It is a composition containing [component (2)] and does not contain lower alkyl biphenyl [component (1-B)]. The compositions of Comparative Examples 7 and 8 have too high a viscosity at -40°C and too high an aniline point, so they cannot be preferably used in vehicle central hydraulic systems from the viewpoint of compatibility with rubber materials. On the other hand, although the composition of Comparative Example 9 was adjusted to have a low-temperature viscosity of 2000 cSt or less, it cannot be used for the purpose of the present invention because its flash point is low and its evaporation loss is large.

【table】

【table】

【table】

Claims (1)

[Scope of Claims] 1 70-95% by weight hydrocarbon base oil (1) and 5-95% by weight of hydrocarbon base oil (1)
30% by weight of a viscosity index improver (2); the hydrocarbon base oil (1) contains (A) 40-99% by weight based on the hydrocarbon base oil;
(a) a polybutene having an average molecular weight of 100 to 500;
and (b) 2 to 12 carbon atoms with an average molecular weight of 100 to 600.
at least one component selected from the group consisting of at least one homopolymer or copolymer of α-olefin (butene excluded); and (B) 1 to 60% based on the hydrocarbon base oil. weight%
lower alkyl biphenyl, and the viscosity index improver (2) has 1 to 1 carbon atoms.
1. A fluid composition for a central vehicle hydraulic system, which is a polymethacrylate having a viscosity average molecular weight of 10,000 to 700,000 obtained by polymerizing at least one ester of 18 saturated monohydric aliphatic alcohols and methacrylic acid.