JP7030065B2 - Lubricating fluid - Google Patents

Description

The present invention relates to a lubricating fluid suitably used as a shock absorber fluid. The present invention further relates to the use of a lubricating fluid in a shock absorber.

A shock absorber (sometimes also called a damper) is a mechanical device designed to smooth or dampen sudden impact impulses and dissipate kinetic energy. Shock absorbers are an important part of suspensions for automobiles, bikes or bicycles, aircraft landing gear, train suspensions, and supports for many industrial machines. Large shock absorbers are also used in construction and civil engineering to reduce the susceptibility of structures to seismic damage and resonance.

Shock absorbers convert kinetic energy into heat energy that can be subsequently dissipated. The hydraulic shock absorber is composed of a cylinder having a sliding piston inside. The cylinder is filled with shock absorber fluid. This fluid-filled piston / cylinder combination is also referred to as a dashpot. In vehicles, wheel suspensions typically include several shock absorbers, usually in combination with pressure elastic means such as coil springs, leaf springs, or torsion bars. These springs are not shock absorbers because they only store energy and do not dissipate or absorb it. When you move the wheel horizontally, the spring absorbs the vertical force and converts it into heat. The shock absorber, for example, with hysteresis in the tire of the wheel, suppresses the up and down movement of the unsprung weight, thereby effectively dampening the wheel bounce. This is achieved by converting kinetic energy into heat by fluid friction due to the flow of shock absorber fluid through a narrow orifice such as an internal valve.

WO201063752 discloses a fluid that can be used as a shock absorber fluid with high biodegradability and high compatibility with viscosity improvers, especially at low temperatures. The fluid contains a base oil composition and a viscosity index improver. The base oil composition comprises an ester of a GTL base oil and a polyhydroxy compound.

The present inventor has provided a lubricating fluid suitable for use as a shock absorber fluid having advantageous properties, eg, better long-term shear stability and / or better low temperature viscosity properties than commercially available shock absorber fluids. I've been trying to provide it.

The present invention has found that a lubricating fluid suitable for use as a shock absorber fluid can be prepared from an advantageous combination of GTL base oil, alkylbenzene or alkylnaphthalene, and a viscosity modifier. Such a combination exhibits good shear stability and good low temperature viscosity.

Therefore, the present invention is a lubricating fluid.
(A) Based on the weight of the lubricating fluid, at least 40% by weight of GTL base oil and
(B) 5 to 25% by weight of alkylbenzene or alkylnaphthalene based on the weight of the lubricating fluid.
(C) Includes a viscosity index improver of 0.1 to 20% by weight based on the weight of the lubricating fluid.
Lubricating fluids provide a lubricating fluid having a viscosity index in the range of 50-1000 and a pour point below −30 ° C.

Lubricating fluids are suitable for use as shock absorber fluids, but can also be used as fork oils or as working fluids or industrial lubricants such as bearings and circulating oils.

The invention further provides the use of the lubricating fluid according to the invention in shock absorbers.

The invention further provides a vehicle comprising the lubricating fluid according to the invention.

The lubricating fluid contains at least 40% by weight of GTL base oil relative to the weight of the lubricating fluid. The lubricating fluid preferably comprises a GTL base oil in the range of 50-90% by weight, more preferably 60-85% by weight, based on the weight of the lubricating fluid.

The term "GTL base oil" is used to describe the base oil synthesized by the Fisher-Tropsch method, which converts natural gas into liquid fuel. They have a very low sulfur content and aromatic content compared to mineral oil base oil refined from crude oil and have a very high paraffin composition ratio. The GTL base oil can be a mixture of several different GTL base oils with different viscosities. Preferably, the kinematic viscosity of the GTL base oil at 100 ° C. is in the range of 2 to 10 mm ² / s, more preferably in the range of 2.5 to 7 mm ² / s. The kinematic viscosity is suitably determined by ASTM D445. Suitable base oils known as "GTL4" and "GTL3" are available from Shell.

The lubricating fluid contains 5-25% by weight of alkylbenzene or alkylnaphthalene relative to the weight of the lubricating fluid. Preferably, the alkylbenzene or alkylnaphthalene is a mixture of different alkylbenzene molecules and / or alkylnaphthalene molecules. Alkylbenzene and / or alkylnaphthalene may be mono- or poly-substituted, but preferably mono- or di-substituted. In a preferred embodiment, the lubricating fluid comprises a mixture of 5-25% by weight alkylbenzene mono- or di-substituted with linear and / or branched alkyl groups, wherein the alkyl group is a C ₆ -C ₂₀ alkyl group. It is preferably a C ₉ to C ₁₅ alkyl group. The kinematic viscosity of alkylbenzene or alkylnaphthalene at 40 ° C. (suitably measured by ASTM D445) is preferably 3 to 400 mm ² / s, preferably 3 to 50 mm ² / s, more preferably 3 to 10 mm ² / s. s. The average relative molecular weight is preferably 180 to 300, preferably 200 to 280, and more preferably 230 to 260.

The lubricating fluid contains a viscosity index improver of 0.1 to 20% by weight based on the weight of the lubricating fluid. The lubricating fluid preferably contains 1-18% by weight, more preferably 3-10% by weight of the viscosity index improver.

Viscosity index improvers (also known as VI improvers, viscosity modifiers, or viscosity improvers) provide lubricants with high and low temperature operability. These additives impart shear stability and acceptable viscosity at elevated and low temperatures. Suitable viscosity index improvers include both low molecular weight and high molecular weight hydrocarbons, polyesters, and viscosity index improvers and dispersants that can function as both viscosity index improvers and dispersants. Typical molecular weights of these polymers range from about 10,000 to 1,000,000, more typically from about 20,000 to 500,000, and even more typically from about 50,000 to 200,000. be. Examples of suitable viscosity index improvers are polymers and copolymers of methacrylates, butadienes, olefins, or alkylated styrenes.

）である。 Preferably, the viscosity index improver is polymethylmethacrylate (also also referred to as PMMA), a copolymer of methyl and alkylmethacrylates of various chain lengths. A particularly preferred PMMA viscosity index improver is a commercially available Viscoplex viscosity improver.

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The lubricating fluid preferably further comprises one or more additives typically used for shock absorber fluids. These additives can be added in the form of an additive package. Typical additive packages include antioxidants and abrasion resistant agents, such as dispersants, detergents, corrosion and rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, flow points. Depressants, wax modifiers, encapsulation adaptors, friction modifiers, lubricants, anti-staining agents, pigments, anti-foaming agents, and de-embroidery agents may also be included.

The lubricating fluid preferably contains an antiwear additive. Suitable wear resistant additives include metal-containing and metal-free alkylthiophosphates such as zinc dialkyldithiophosphates typically used in an amount of about 0.4% by weight to about 1.4% by weight of the lubricating fluid. Is done.

The lubricating fluid preferably contains an anti-foaming agent. Silicones and organic polymers are typical anti-foaming agents. Preferably, the anti-foaming agent is a low silicon or non-silicon anti-foaming agent such as an acrylic copolymer or a fatty amine ethoxylate. The amount of the anti-foaming agent is preferably less than 1% by weight, preferably less than 0.1% by weight, more preferably less than 0.05% by weight, based on the weight of the lubricating fluid.

Lubricating fluids have a viscosity index in the range of 50-1000, preferably in the range of 100-600. Preferably, the viscosity index is determined according to ASTM D2272. If the viscosity index is too low, the lubricating fluid is likely to be too viscous at low temperatures, too low at high temperatures, and then the lubricating fluid will not function effectively in the shock absorber.

The lubricating fluid has a pour point of less than −30 ° C., preferably less than −45 ° C. Preferably, the pour point is determined according to ASTM D97. If the lubricating fluid has a higher pour point, then the fluid will not flow under cold ambient conditions and the shock absorber containing the fluid will not function.

The lubricating fluid preferably has a kinematic viscosity of at least 7 mm ² / s, preferably at least 10 mm ² / s, more preferably at least 12 mm ² / s at 40 ° C. Preferably, the kinematic viscosity at 40 ° C. is measured according to ASTM D445. Having such a viscosity is important if the lubricating fluid should function effectively in the shock absorber.

The lubricating fluid preferably has a Brookfield viscosity of less than 2000 cP, more preferably less than 1500 cP, most preferably less than 1250 cP at −40 ° C. Preferably, the Brookfield viscosity at −40 ° C. is determined by ASTM D2983. Having such a viscosity is important if the lubricating fluid should function effectively in the shock absorber.

The lubricating fluid preferably has a shear stability of less than 10%, more preferably less than 5%, most preferably less than 3% at 40 ° C. as measured according to CEC L-45-99. When used in shock absorbers, the lubricating fluid has the highest possible shear stability (and the lowest under test conditions) so that the lubricating fluid has the correct viscosity range for efficient operation over the longest possible period. It is important to have a possible loss of shear stability). If the lubricating composition has inadequate shear stability, it will be sheared over time and the viscosity will soon be out of the required range.

The present invention will be described below with reference to the following examples, but it is not intended to limit the scope of the present invention.

A shock absorber fluid (Example 1) having the formulations shown in Table 1 was prepared.

Both GTL base oils are available from Shell. The GTL4 base oil had a viscosity of 3.80-4.20 cSt (measured by ASTM D445) at 100 ° C. The GTL3 base oil had a viscosity of 2.8 cSt (measured by ASTM D445) at 100 ° C. Alkylbenzene was a mixture of monosubstituted alkylbenzenes having a kinematic viscosity of 3-5 mm ² / s at 40 ° C. The fluid was prepared by mixing and heating all of the ingredients until a homogeneous mixture was formed.

Test The shock absorber fluid of Example 1 and two types of commercial shock absorber fluids (Comparative Example 1 and Comparative Example 2) were tested. Table 2 shows the properties tested, the test methods used, and the results of Example 1, Comparative Example 1, and Comparative Example 2.

The results showed that all three shock absorber fluids had similar densities, viscosities at 40 ° C and 100 ° C, and viscosity indexes. The shock absorber fluid of the present invention (Example 1) has improved Brookfield viscosity as compared with commercial shock absorber fluids (Comparative Example 1 and Comparative Example 2), and also has better shear stability. It was.

Claims (4)

Lubricating fluid for shock absorbers
(A) Based on the weight of the lubricating fluid, at least 40% by weight of GTL base oil and
(B) A mixture of mono- or di-substituted alkylbenzenes having 5-25% by weight of linear and / or branched alkyl groups based on the weight of the lubricating fluid, wherein the alkyl groups are C6 to C6. A mixture of alkylbenzenes, which are C20 alkyl groups, and
(C) Includes a viscosity index improver selected from 0.1-20% by weight of methacrylate, butadiene, olefin, or alkylated styrene polymers and copolymers relative to the weight of the lubricating fluid.
A lubricating fluid in which the lubricating fluid has a viscosity index in the range of 50 to 1000 and a pour point of less than −30 ° C. The lubricating fluid according to claim 1, which comprises a GTL base oil in the range of 50 to 90% by weight. The lubricating fluid according to claim 1 or 2, which comprises a metal-containing or metal-free alkylthiophosphate in an amount of 0.4% by weight to 1.4% by weight of the lubricating fluid. The lubricating fluid according to any one of claims 1 to 3, which contains an acrylic copolymer or an aliphatic amine ethoxylate in an amount of less than 0.1% by weight based on the weight of the lubricating fluid.