CN107434996A - Lubricating fluid - Google Patents

Abstract

Disclose a kind of lubricating fluid for being suitable as cushioning fluid.The lubricating fluid includes at least 40wt% GTL base oils on the basis of its weight, and viscosity index (VI) is 50 1000 and pour point is less than 30 DEG C.

Description

lubricating fluid

technical field

The present invention relates to lubricating fluids suitable for use as shock absorbing fluids. The invention also relates to the use of said lubricating fluid in shock absorbers.

Background technique

Shock absorbers (sometimes called dampers) are mechanical devices designed to dampen or dampen sudden shock pulses and dissipate kinetic energy. Shock absorbers are an important component in the shock absorption of automobiles, motorcycles or bicycles, aircraft landing gear, train shock absorption and the support of many industrial machines. Large shock absorbers are also used in construction and civil engineering to reduce the susceptibility of structures to earthquakes and resonance.

Shock absorbers convert kinetic energy into heat, which can then be dissipated. Hydraulic shock absorbers consist of a cylinder with a sliding piston inside. The cylinder is filled with damping fluid. This fluid-filled piston/cylinder combination is also known as a damper. In vehicles, the damping of the wheels usually consists of several shock absorbers, mainly in combination with pressure-elastic devices such as coil springs, leaf springs or torsion bars. These springs are not shock absorbers because the springs only store energy but do not dissipate or absorb it. If the wheel is placed in a horizontal motion, the springs absorb the upward and downward forces and convert them into heat. Together with the hysteresis of, for example, a wheel tire, the shock absorber dampens the up and down motion of the unsprung weight, effectively dampening wheel bounce. This is accomplished by converting the kinetic energy of the shock fluid into heat due to fluid friction caused by the flow of the damping fluid through narrow orifices such as internal valves.

WO 201063752 discloses fluids useful as shock absorbing fluids which have high biodegradability and high compatibility with viscosity modifiers, especially at low temperatures. The fluid comprises a base oil composition and a viscosity index improver. The base oil composition comprises a GTL base oil and an ester of a polyol.

The present inventors sought to provide lubricating fluids suitable for use as damping fluids having advantageous properties such as better long-term shear stability and/or better low temperature viscosity properties than commercially available damping fluids.

Contents of the invention

The present inventors have discovered that lubricating fluids suitable for use as shock absorbing fluids can be prepared from an advantageous combination of GTL base oils, alkylbenzenes or alkylnaphthalenes, and viscosity modifiers. This combination exhibits good shear stability and good low temperature viscosity.

Accordingly, the present invention provides a lubricating fluid comprising, by weight thereof:

(a) at least 40% by weight of GTL base oil;

(b) 5-25% by weight of alkylbenzene or alkylnaphthalene; and

(c) 0.1-20wt% viscosity index improver;

Wherein the lubricating fluid has a viscosity index of 50-1000 and a pour point below -30°C.

The lubricating fluid is suitable as a shock absorbing fluid, but can also be used as a fork oil or as an industrial lubricant such as hydraulic fluid or bearing oil and circulating oil.

The present invention also provides the use of a lubricating fluid according to the invention in a shock absorber.

The invention also provides a vehicle comprising the lubricating fluid of the invention.

detailed description

The lubricating fluid contains at least 40 wt% GTL base oil based on its weight. The lubricating fluid preferably comprises 50-90 wt%, based on its weight, of the GTL base oil, more preferably 60-85 wt%.

The term "GTL base oil" is used to describe base oils synthesized by the Fischer-Tropsch process of converting natural gas into liquid fuels. They have a very low sulfur and aromatics content and a very high paraffinic fraction compared to mineral oil base oils refined from crude oil. The GTL base oil can be a mixture of several different GTL base oils with different viscosities. The kinematic viscosity of the GTL base oil at 100°C is preferably 2-10 mm ² /s, more preferably 2.5-7 mm ² /s. The kinematic viscosity is suitably determined according to ASTM D445. Suitable base oils such as known as "GTL 4" and "GTL 3" are available from Shell.

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

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

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

Preferably, the viscosity index improver is polymethylmethacrylate (also known as PMMA), a copolymer of methyl and alkyl methacrylates of various chain lengths. A particularly preferred PMMA viscosity index improver is the commercially available Viscoplex viscosity improver (Viscoplex is GmbH&CO.KG, trade name of Darmstadt Germany).

The lubricating fluid suitably also contains one or more additives commonly employed in shock absorbing fluids. These additives can be added in the form of additive packages. Typical additive packages include antioxidants and anti-wear agents, but can also include dispersants, detergents, corrosion and rust inhibitors, metal passivators, extreme pressure additives, anti-seize agents, pour point depressants, wax conditioners , seal compatibilizer, friction modifier, lubricity agent, antifouling agent, color developer, defoamer and demulsifier.

The lubricating fluid preferably contains anti-wear additives. Suitable anti-wear additives include metal-containing and metal-free alkylthiophosphates, such as zinc dialkyldithiophosphates, typically in an amount of about 0.4-1.4% by weight of the lubricating fluid.

The lubricating fluid preferably contains a defoamer. Silicones and organic polymers are typical defoamers. The defoamer is preferably a low-silicon or no-silicon defoamer, such as an acrylic copolymer or an aliphatic amine ethoxylate. The amount of antifoaming agent is suitably less than 1 wt%, preferably less than 0.1 wt% and more preferably less than 0.05 wt%, based on the weight of the lubricating fluid.

The lubricating fluid has a viscosity index of 50-1000, preferably 100-600. Viscosity Index is suitably determined according to ASTM D2272. If the viscosity index is too low, the lubricating fluid may be too viscous at low temperatures and too thin at high temperatures, whereby the lubricating fluid may not function effectively in the shock absorber.

The pour point of the lubricating fluid is below -30°C, preferably below -45°C. Pour point is suitably determined according to ASTM D97. If the lubricating fluid has a high pour point, the fluid may not flow under cold ambient conditions and a shock absorber containing the fluid may not function.

The kinematic viscosity of the lubricating fluid at 40°C is suitably at least 7 mm ² /s, preferably at least 10 mm ² /s and more preferably at least 12 mm ² /s. The kinematic viscosity at 40°C is suitably determined according to ASTM D445. Having this viscosity is important if the lubricating fluid is to function effectively in the shock absorber.

The Brookfield viscosity of the lubricating fluid at -40°C is suitably less than 2000 cP, more preferably less than 1500 cP and most preferably less than 1250 cP. Brookfield viscosity at -40°C is suitably determined according to ASTM D2983. Having this viscosity is important if the lubricating fluid is to function effectively in the shock absorber.

The shear stability of the lubricating fluid at 40°C (measured according to CEC L-45-99) is suitably less than 10%, more preferably less than 5% and most preferably less than 3%. It is important that the lubricating fluid has the highest possible shear stability (and the lowest possible loss of shear stability under the test conditions) so that when used in a shock absorber, the lubricating fluid has effective operation for the longest possible period of time for the correct viscosity. If the lubricating composition has poor shear stability, it will drop in shear over time and the viscosity will quickly be outside the desired range.

The invention is described below with reference to the following examples, which do not limit the scope of the invention in any way.

Example

A shock absorbing fluid (Example 1) was prepared having the formulation shown in Table 1 below:

Table 1

Both GTL base oils were obtained from Shell. GTL 4 base oils have a viscosity at 100°C (measured by ASTM D445) of 3.80-4.20 cSt. The GTL 3 base oil has a viscosity at 100°C (measured by ASTM D445) of 2.8 cSt. Alkylbenzenes are mixtures of mono-substituted alkylbenzenes having a kinematic viscosity of 3-5 mm ² /s at 40°C. The fluid is prepared by mixing and heating all components until a homogeneous mixture is obtained.

test

The shock absorbing fluid of Example 1 and two commercially available shock absorbing fluids (Comparative Example 1 and Comparative Example 2) were tested. Table 2 presents the tested properties, the applied test methods and the results of Example 1, Comparative Example 1 and Comparative Example 2.

Table 2

performance Test Methods Example 1 Comparative example 1 Comparative example 2 Density at 15°C (g/cm ³ ) ASTM D4052 0.8247 0.8611 0.836 Viscosity at 40°C (cSt) ASTM D445 13.086 14.18 14.5018 Viscosity at 100°C (cSt) ASTM D445 3.8561 4.0547 4.0913 viscosity index ASTM D2272 210.7 206.4 202.3 Brookfield Viscosity at -40°C (cP) ASTM D2983 1020 2369 1800 Pour point (℃) ASTM D97 -60 <-45 <-45 Shear Stability (% Viscosity Loss) at 40°C CEC L-45-99 2.70 13.50 6.02

The results show that the density, viscosity and viscosity index at 40°C and 100°C are similar for all three damping fluids. The shock absorbing fluid of the present invention (Example 1) has improved Brookfield viscosity and also has better shear stability compared to commercially available shock absorbing fluids (Comparative Example 1 and Comparative Example 2).

Claims (8)

1. A lubricating fluid comprising, by weight thereof: (a) at least 40% by weight of GTL base oil; (b) 5-25% by weight of alkylbenzene or alkylnaphthalene; and (c) 0.1-20wt% viscosity index improver; Wherein the lubricating fluid has a viscosity index of 50-1000 and a pour point below -30°C. 2. The lubricating fluid of claim 1, comprising 50-90 wt% of the GTL base oil. 3. Lubricating fluid according to claim 1 or 2, comprising 5-25% by weight of a mixture of alkylbenzenes mono- or di-substituted by linear and/or branched chain alkyl groups, wherein said alkyl groups are _C6 -C ₂₀ alkyl. 4. The lubricating fluid of any one of the preceding claims, wherein the viscosity index improver is selected from polymers and copolymers of methacrylates, butadiene, olefins or alkylated styrenes. 5. The lubricating fluid of any one of the preceding claims, comprising a metal-containing or metal-free alkylthiophosphate in an amount of about 0.4 to 1.4% by weight of the lubricating fluid. 6. A lubricating fluid according to any one of the preceding claims, comprising an acrylic acid copolymer or fatty amine ethoxylate in an amount of less than 0.1 wt% based on the weight of the lubricating fluid. 7. Use of a lubricating fluid according to any one of the preceding claims in a shock absorber. 8. A vehicle comprising the shock absorber of claim 7.