JPH0563509B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a hydraulic fluid composition that can be used over a wide temperature range and exhibits a relatively high flash point. More specifically, the fluid of this invention consists essentially of a dimethylsiloxane/alkylmethylsiloxane copolymer loaded with a synthetic hydrogenated poly-alpha-olefin. The invention further relates to the use of the above composition in hydraulic systems. [Prior Art and Problems to be Solved by the Invention] Certain silicone fluids are known to have excellent resistance to shear, thermal degradation, and oxidative degradation. Furthermore, unlike typical hydrocarbon lubricating oils or hydraulic fluids, they maintain a relatively flat viscosity-temperature profile. On the other hand, these silicones generally do not have a high degree of lubricity in steel-to-steel contacts, as exemplified by hydrocarbons such as mineral oil, a property that is extremely important in many hydraulic applications. This problem is caused by silicone "base fluid"
This problem can be solved to some extent by incorporating certain lubricity additives into the mixture. In an effort to take advantage of the fundamental advantages of both of these liquid types at the same time, some researchers have combined them in various lubricant compositions. For example, in British Patent No. 1224885, Mackenzie
A composition is disclosed comprising a mineral oil and a homopolymeric diorganopolysiloxane as a viscosity index improver therefor, the organic groups being predominantly methyl groups. In the siloxane polymers of these compositions, the remaining organic groups are alkyl, alkaryl, or aralkyl groups having 6 to 30 carbon atoms in sufficient amount to render them soluble in mineral oil. You can choose from more. In U.S. Pat. No. 4,059,534, Morro et al.
~1000000cS of polydimethylsiloxane
A lubricating oil composition comprising ~50% by weight, the remainder of the composition comprising alkenes, isoparaffins,
and naphthenes. −65
It teaches a hydrocarbon oil with a viscosity of less than 40,000 cS at (-54°C). The major contribution to the art claimed by this disclosure is a lubricating composition that has improved viscosity-temperature characteristics by dissolving high viscosity polydimethylsiloxane in a hydrocarbon oil, and that the composition has better siloxane properties at low temperatures. The purpose is to provide a product whose components do not separate. European Patent Application No. published on April 16, 1986
No. 0177825A1 discloses that the organic group has 1 to 7 carbon atoms.
an organomethylsiloxane unit selected from an alkyl group or a phenyl group;
The preparation of a lubricating oil comprising a silicone copolymer containing alkylmethylsiloxane units which can have 16 carbon atoms is described. These copolymers must have pour points below -15°C and must be miscible with mineral oils, synthetic lubricating oils, and lubricity additives commonly used in such oils. There are further limitations. More recently, the need for fire-resistant military aircraft hydraulic fluids with a wide operating temperature range has been recognized by Gschwender et al., Lubrication Engineering, Vol. 42, No. 485-490.
(1986). On the one hand, mineral oil-based hydraulic fluids (MIL-H-5606) are used extensively in military aircraft and are
Although it is considered possible to operate down to a low temperature, this fluid has two major drawbacks. The relatively low flash point of approximately 100-110°C makes this fluid dangerously easy to ignite and propagate at a high rate once combustion begins.
Furthermore, the shear stability of this fluid is less than desired, especially given the design trend toward higher operating pressures (and associated large shear rates) in modern Air Force aircraft. On the other hand, experience with synthetic hydrogenated polyalpha-olefin fluids indicates that these fluids have high flash points (>205°C).
It was also good in that it was relatively stable against shearing. Unfortunately, such polyα
- Hydraulic fluids based on olefins either have too high a viscosity at low temperatures or have too low a flash point (i.e. when using low molecular weight poly-alpha-olefins) for use in very cold operations. Therefore, Guschewender et al. lists target properties for so-called "low-temperature MIL-H-83282" fluids that combine aspects of both MIL specifications and include viscosity limits as shown below. Present what you want. Temperature (°C) Viscosity (eS) -54 2500 (max) -40 500 (max) 100 3.5 (min) 135 1.5 (min) The high flash point of the MIL-H-83282 liquid mentioned above is It is further recognized that they are incompatible, and that at least 163°C and 191°C
Analysis targets in °C were set for flash point and combustion point respectively. Moreover, a key requirement for a successful candidate fluid is that the fluid be compatible with existing military fluids (i.e. MIL
-H-5606 and MIL-H-83282). None of the technical disclosures of the above-mentioned patent specifications -
A dimethylsiloxane/alkylmethylsiloxane copolymer that forms a base fluid composition that combines the required viscosity-temperature profile and flash point of a suitable candidate for use in fire-resistant hydraulic fluids from 54°C to 135°C. and poly-alpha-olefins. The low-temperature viscosities described above are derived from hydrogenated polyalpha-
It has been discovered that this can be achieved by mixing olefins. Unexpectedly, this, as well as other desirable characteristics of both dimethylsiloxane/alkylmethylsiloxane copolymer fluids and polyalpha-olefin fluids for use in hydraulic applications,
can be achieved while still maintaining the flash point of
Additionally, the compositions thus formed are compatible with existing military fluids (i.e. MIL-H-5606 and MIL-H-
83282), making it possible to perform "drain-fill" replacement in current hydraulic systems. [Means and effects for solving the problem] Therefore, the present invention provides (A) dimethylsiloxane/
an alkylmethylsiloxane copolymer,
The average formula below, i.e. (In this formula, Me represents a methyl group,
R' is independently selected from alkyl groups having from 1 to 10 carbon atoms, R represents an alkyl group having from 4 to 10 carbon atoms, x has an average value from 5 to 15, and the value of y is 0.5 to 4 and the ratio of y/x is 0.3 or less) 40 to 90
Parts by weight, and (B) the following formula, i.e. Synthetic hydrogenated polyα-olefin 10~
A homogeneous hydraulic fluid composition consisting essentially of 60 parts by weight, having a total of 100 parts by weight of components (A) and (B) as described above. This invention further provides that component (B) has the following formula: Regarding a similar composition represented by The invention further provides that component (B) is selected from a dimer, trimer, or tetramer of decene-1, and the viscosity of the homogeneous hydraulic fluid is 2500 cS or less at -54°C and at 100°C. and an open flash point of at least 163°C. The present invention also relates to improvements in methods of transmitting force in hydraulic systems, including the use of the compositions described above as the hydraulic fluid in such systems. The present invention comprises (A) dimethylsiloxane/alkylmethylsiloxane copolymer and (B) synthetic hydrogenated polyα
- Relating to a hydraulic fluid composition consisting essentially of a homogeneous mixture with an olefin. Component (A) of the present invention has the following average formula: In this formula, Me represents a methyl group and R is a straight or specialized alkyl group having 4 to 10 carbon atoms, such as n-pentyl group, isopentyl group, n-hexyl group, n-
heptyl group, n-octyl group, diisobutyl group,
Copolymers such as n-nonyl or n-decyl groups. Straight chain alkyl groups are more preferred than branched structures. R is n-hexyl group or n
-octyl group is more preferred. The R′ group for the terminal silicon atom is 1 to
identical or separate short-chain alkyl groups having 10 carbon atoms, such as methyl, ethyl, propyl,
Such as butyl, hexyl, octyl, or decyl, with methyl being preferred. The value of x in the above formula may range from 5 to 15, preferably from 6 to 12. The value of y may correspondingly range from 0.5 to 4, preferably from 0.5 to 3. However, the value of y is limited so that the ratio of y/x is 0.3 or less. In the above general formula, x and y are preferably chosen such that the viscosity of the copolymer liquid is in the range of about 5 to 50 centistokes (cS) at 25°C. Preferably, this viscosity is about
It is 10-20cS. A highly preferred embodiment of the invention is that R is n-hexyl, R' is methyl,
This is obtained when x is about 6 and y is about 1, or when R is n-octyl and R' is methyl, x is about 8 and y is 0.5. The above copolymers of the invention may be prepared by methods well known in the art. For example, they can be synthesized by cohydrolysis and subsequent condensation of appropriate diorganodialkoxysilanes or diorganodichlorosilanes. In this approach, a desired amount of end-capping reactant (R′) ₃ SiZ is included in the reaction mixture to control the molecular weight of the product (i.e., more end-capping reactant produces a lower molecular weight product). occur).
The R′ group of this end-capping reactant is the component (A)
This is the same as shown above. The Z group is
Halogens (e.g. chlorine, fluorine, or bromine)
or a hydrolyzable species such as an alkoxy group (eg, methoxy group, ethoxy group). Another method that can be applied to synthesize the copolymers is the acid- or base-catalyzed equilibrium reaction of diorganocyclosiloxanes in the presence of the aforementioned end-capping reactants. Yet another preferred method is based on the following general formula: (wherein Me represents a methyl group and R' is as defined above). These intermediates are well known to those skilled in the art and may be prepared by acid equilibration of commercially available polymethylhydrogensiloxanes and cyclic dimethylsiloxanes in various proportions. The molecular weight of this intermediate may be adjusted by adding an appropriate amount of an end capping monomer such as hexamethyldisiloxane. The SiH functional intermediate is then reacted with approximately 25% excess of the desired alkene to chemically add the latter to the former SiH group. This addition reaction is catalyzed by platinum complexes known in the art. Component (B) of the present invention is at least one synthetic hydrogenated poly-α-olefin selected from dimer, trimer, or tetramer of decene-1, and can be represented by the following formula: . (dimer) (trimer) (Tetramer) In a preferred embodiment of the present invention, component (B) is a poly-α-olefin trimer. However, component (A) contains the above dimers, trimers, and tetramers to provide the high flash point and viscosity-temperature profile necessary to meet the target requirements of low temperature MIL-H-83282. This can be achieved by mixing the mixture, and this can be determined by routine experimentation. Poly alpha-olefin fluids are well known in the art and can be prepared from monomeric decene-1 by catalytic polymerization and hydrogenation. If you are interested, see, for example, the October 1981 US government report AFWAL-TR- by Cupples et al.
81-4109 (Wright-Patterson)
Reference is made to the method outlined by the Air Force Wright Aeronautical Research Laboratory, Materials Laboratory, Patterson Air Force Base. These fluids are manufactured by Gulf Oil Chemicals in Hyeuston, Texas.
Chemicals Co., Ltd. under the trade name SYNFLUID. The compositions of the invention may be prepared by simply mixing components (A) and (B) to form a homogeneous mixture thereof. The mixing method is not particularly important;
Any of the commonly used methods known in the art may be used. The mixture so made is typically a "base fluid" in that the lubricity additives and other adjuvants described below are combined with it to create a fully formulated hydraulic fluid.
It is called. When component (B) is a decene trimer, 40 to 90 parts by weight of component (A) are mixed with 60 to 10 parts of component (B) to make 100 parts of the composition of the invention. However, it is preferred to mix 40 to 60 parts by weight of component (A) with 60 to 40 parts of decene trimer. Most preferably, equal weights of decene trimer and component (A) dimethylsiloxane/alkylmethylsiloxane copolymer liquid are used;
The dimethylsiloxane/alkylmethylsiloxane copolymer component in this case is delineated by the preferred ranges set forth above. When component (B) is a decene tetramer, 80 to 90 parts by weight of component (A) are mixed with 20 to 10 parts of component (B) to make 100 parts of the composition of the invention. Apart from this, the composition of the present invention can be used in low temperature MIL
- May be defined by the basic physical properties required by the goals of H-83282. In this case, 100 parts by weight of the composition comprises 10 to 90 parts by weight of component (A) and at least one synthetic hydrogenated polyamide selected from dimers, trimers, or tetramers of decene-14. α−
90 to 10 parts by weight of olefin, the viscosity at -54°C is 2500 cS or less, the viscosity at 100°C is at least 3.5 cS, and the open flash point is at least 163°C. Preferably,
40-60 parts by weight of component (A) are mixed with 60-40 parts of component (B). These properties will be readily available to those skilled in the art through routine experimentation in light of the above disclosure. As previously stated, various additives are generally incorporated into the base fluid of this invention to prepare a fully formulated hydraulic fluid. Antiwear or lubricity additives, such as tricresyl phosphate, dibutyl chlorendate, and antimony dialkyl dithiocarbamates, are preferably incorporated at about 1 to 10 weight percent. Rubber swell additives such as di(2-ethylhexyl) sebacate or tributyl phosphate may contain from about 1 to
It will be incorporated at 5% by weight. These are typically used with polydimethylsiloxanes as these base fluids tend to shrink the rubber components by leaching plasticizers from the rubber components. Generally, the alkyl content or alkyl group size of component (A) is increased, or component (B) is increased.
As more and more are utilized, the need for swelling additives becomes less. p,p'- at a concentration of about 0.1 to 0.5 weight percent
Antioxidants such as dioctyl diphenylamine and butylated hydroxytoluene are generally required to protect alkyl groups from oxidation at high service temperatures. Dyes can also be added at low concentrations, primarily for identification purposes. Other non-essential additives, e.g. flame retardants,
Defoamers, corrosion inhibitors, and the like may also find utility in combination with the base fluids of the present invention. Increasing the alkylmethylsiloxane content of component (A) to approach 100% allows the resulting base solution to be formulated to meet the target viscosity requirements of low temperature MIL-H-83282. The result was a polymer that was unsatisfactory in that it could not be used. Moreover, as the alkyl content increased, the swelling of any Gol component in the hydraulic system also increased, leading to undesirable results in some systems. It will be appreciated by those skilled in the art that some of the target requirements of low temperature MIL-H-83282 can be met by varying the molecular weight of the base fluid composition and/or by incorporating various additives. Although it is possible to do so, it will be recognized that the important properties presented above are not usually modulated by such operations. Thus, for example, if the base fluid (i.e., the composition of the siloxane copolymer and polyalpha-olefin of the present invention) does not simultaneously exhibit the required viscosity-temperature profile and a sufficiently high flash point; Combining base fluids into a fully formulated hydraulic fluid for testing generally does not meet the target properties of low temperature MIL-H-83282. Therefore, base fluid compositions that do not pass these critical property requirements are
It was determined that the target did not meet MIL-H-83282. The invention also relates to an improved method for transmitting actuating force (pressure) in a hydraulic system, where the actuating fluid is essentially of a composition of a siloxane copolymer and a polyalpha-olefin as described. Consists of one. In this improved method, the fluid-containing portion of the hydraulic system component is filled with the composition of the invention as previously disclosed. Examples of hydraulic system components contemplated herein include pumps, fluid coupling devices such as diaphragms, hydraulic line means, valves, and hydraulic actuation means such as hydraulic motors, pistons, and servo valves. Hydraulic systems that would benefit most from the use of the working base fluid of this invention are those that are required to operate between temperature extremes of -54°C and 135°C, and that simultaneously use mineral oil as the hydraulic fluid. This is a hydraulic system that requires improved fire resistance. The method of the invention is therefore most suitably used in connection with military aircraft hydraulic systems. Other hydraulic systems in which the method of the invention may be advantageously used include civil aircraft, land and sea military transport and combat vehicles, spacecraft, and systems for use in boreal regions or other cold environments. Includes machinery. EXAMPLES The following examples are provided to further illustrate the compositions of this invention and should not be construed as limiting the invention. The invention is set out in the claims. All parts and percentages in the examples below are by weight unless indicated to the contrary. Example 1 Into a flask equipped with a stirrer, thermometer, condenser, addition funnel, and means for purging with dry nitrogen gas, 316 g of hexene-1 is charged with a dimethylvinylsiloxy group terminated to give 0.7 weight percent platinum. 0.1 ml of a chloroplatinic acid complex of divinyltetramethyldisiloxane (prepared according to Example 1 of Willing, US Pat. No. 3,419,593) diluted with blocked polydimethylsiloxane was added. To this mixture, 800 g of a siloxane copolymer of the following average composition: Me ₃ SiO (MeHSiO) _4.4 (Me ₂ SiO) _9.8 SiMe ₃ (in which Me represents a methyl group) were added over a period of 2 hours. The reaction was exothermic and the contents were cooled to maintain the temperature between 25°C and 50°C. The calculated average structural formula of the resulting copolymer was as shown below. Example 2 400 g of copolymer prepared in Example 1 above, 500 g of siloxane with average formula Me ₃ SiO (Me ₂ SiO) _4.7 SiMe ₃ and dimethylcyclosiloxane with 3, 4 and 5 dimethylsiloxane units. 100g of a mixture of and 1g of potassium hydroxide (KOH)
Stir the mixture with under nitrogen atmosphere and approx.
Heated to 160°C. Approximately 20 ml of volatile products were removed by distillation. The remaining mixture was further reacted at 160°C for 4 hours and then cooled to room temperature. 1 g of trimethylchlorosilane was added and the resulting mixture was stirred for an additional 30 minutes. The product was pressure filtered to remove potassium chloride (KCl) generated during neutralization of the base catalyst. Finally, add the product to 20mm
Pot temperature of 250℃ with Hg (steam temperature 208℃)
Stripped up to. The residue weighs 579
g, specific gravity was 0.927, viscosity at 25°C was 11.55 cS, and the calculated average structural formula was as follows. Example 3 A homogeneous composition was prepared by mixing equal parts of the solution prepared in Example 2 and 4cS Synfluid (Gulf Oil Chemicals, Inc., Hyuston, Texas). The latter fluid has the following formula, namely: It is described as a trimer of decene with . For this composition, the viscosity at various temperatures,
The open flash point and combustion point were also measured.
The results are reported in Table 1 below. Example 4 Following the above method described in Example 1, the following average structural formula, i.e. A siloxane copolymer was prepared with This fluid was mixed with an equal volume of 4 cS of synfluid as in Example 3, and the viscosity and flash and fire points of the composition were measured. These results are also the first
Shown in the table. Example 5 Comparative Example A solution of 538 g of octene-1 and 0.05 ml of a 0.1 molar isopropyl alcohol solution of chloroplatinic acid was
Heated to 120°C under nitrogen atmosphere. In this mixture,
480 g of a siloxane polymer having the following average composition: Me ₃ SiO (MeHSiO) _1.3 SiMe ₃ (in which Me represents a methyl group) were added over 40 minutes. The reaction generates heat up to approximately 130°C,
This temperature was maintained for 80 minutes to complete the reaction. The product was stripped at 10 mm Hg to a vessel temperature of 240°C (steam temperature 191°C) and then pressure filtered. This homopolymer had a viscosity of 14.1 cS at 25°C, and its calculated structural formula was as follows. To this fluid was mixed an equal volume of the decene trimer described above in Example 3 (4 cS synfluid). Viscosity and flash point test results for this composition are also reported in Table 1. As can be seen from Table 1, only the compositions of the present invention simultaneously meet the target viscosity and flash point requirements of Air Force Low Temperature MIL-H-83282.

[Table] *Products from Gulf Oil Chemicals of Hyeuston, Texas

Claims (1)

[Claims] 1 (A) The following average formula, that is, (In this formula, Me represents a methyl group,
R' is independently selected from alkyl groups having from 1 to 10 carbon atoms, R represents an alkyl group having from 4 to 10 carbon atoms, x is from 5 to 15, y is from 0.5 to 4, and y /x ratio is less than 0.3)
40 to 90 parts by weight of a siloxane copolymer represented by, and (B) the following formula, i.e. Synthetic hydrogenated polyα-olefin represented by
60 to 10 parts by weight, consisting essentially of the above ingredients (A) and (B) in total
A composition having 100 parts by weight. 2 60 to 40 parts by weight of component (A) in 40 to 60 parts by weight
The composition according to claim 1, wherein (B) is mixed. 3 (A) The following average formula, i.e. (In this formula, Me represents a methyl group,
R' is independently selected from alkyl groups having from 1 to 10 carbon atoms, R represents an alkyl group having from 4 to 10 carbon atoms, x is from 5 to 15, y is from 0.5 to 4, and y /x ratio is less than 0.3)
80 to 90 parts by weight of dimethylsiloxane/alkylmethylsiloxane copolymer represented by, and (B) the following formula, i.e. Synthetic hydrogenated polyα-olefin represented by
20 to 10 parts by weight, consisting essentially of the above components (A) and (B) in total
A composition having 100 parts by weight. 4 (A) The following average formula, i.e. (In this formula, Me represents a methyl group,
R' is independently selected from alkyl groups having from 1 to 10 carbon atoms, R represents an alkyl group having from 4 to 10 carbon atoms, x is from 5 to 15, y is from 0.5 to 4, and y /x ratio is less than 0.3)
10 to 90 parts by weight of a siloxane copolymer represented by (B) at least one synthetic hydrogenated polyα selected from a dimer, trimer, or tetramer of decene-1;
- 90 to 10 parts by weight of olefin, consisting essentially of the above components (A) and (B) in total;
Contains 100 parts by weight, and has a viscosity at -54℃
2500cS or less, viscosity at 100℃ is at least
3.5cS and an open flash point of at least 163°C. 5. A method for transmitting force in a hydraulic system, comprising using the composition according to claim 1 as a hydraulic fluid. 6. A method for transmitting force in a hydraulic system, comprising using the composition according to claim 3 as a hydraulic fluid. 7. A method for transmitting force in a hydraulic system, comprising using the composition according to claim 4 as a hydraulic fluid.