RU2742037C2 - Lubricant fluid - Google Patents

Abstract

FIELD: lubricants.

SUBSTANCE: present invention discloses lubricating liquids suitable for use as shock-absorbing liquids which can be obtained from a favorable combination of GTL base oil, having kinematic viscosity at 100 °C in range of 2 to 10 mm²/s; mixtures of alkylbenzenes which are mono- or di-substituted with linear and/or branched alkyl groups, where the alkyl groups are C₆-C₂₀ alkyl groups; and a viscosity modifier selected from polymers or copolymers of methacrylate, butadiene, olefins or alkylated styrenes. Shock-absorbing fluid contains from 50 to 90 wt % of lubricating oil of base oil GTL, has viscosity index in range from 100 to 600 and setting point is below −30 °C.

EFFECT: such combination demonstrates good shear resistance and good viscosity at low temperature.

3 cl, 2 tbl

Description

Scope of invention

This invention relates to a lubricating fluid that is suitably used as a shock absorber fluid. This invention further relates to the use of a lubricating fluid in a shock absorber.

State of the art

A shock absorber (sometimes referred to as a damper) is a mechanical device designed to dampen or damp a sudden shock and dissipate kinetic energy. Shock absorbers are an important part of automotive, motorcycle or bicycle suspensions, aircraft chassis, train suspensions, and supports for many production plants. Large shock absorbers are also used in architecture and construction to reduce the susceptibility of structures to earthquakes and resonance.

Shock absorbers convert kinetic energy into thermal energy, which is then dissipated. The hydraulic shock absorbers consist of a cylinder with a sliding piston inside. The cylinder is filled with shock absorber fluid. This fluid-filled piston / cylinder combination is also referred to as a damper. In a vehicle, the wheel suspension usually contains several shock absorbers, mainly in combination with elastic pressure devices, namely cylindrical springs, leaf springs or torsion shafts. These springs are not shock absorbers, as the springs only store and do not dissipate or absorb energy. If the wheel is driven on a horizontal plane, the spring will absorb up and down force and convert this into heat. The shock absorber, together with hysteresis, for example in wheel tires, dampens the up and down movement of the unsprung parts, thereby effectively reducing wheel bouncing. This is achieved by converting kinetic energy into heat through friction of the fluid due to the flow of the shock absorber fluid through a narrow opening, namely the inner valve.

WO201063752 discloses fluids that can be used as damping fluids that are highly biodegradable and highly compatible with a viscosity improver, especially at low temperatures. The fluids contain a composition based on a base oil and an additive that improves the viscosity index. The base oil composition includes a GTL base oil and a polyhydroxy ester.

The inventors of the present invention have sought to provide lubricating fluids suitable for use as shock absorber fluids having beneficial properties, for example, better long-term shear resistance and / or better viscosity properties at low temperatures than commercially available shock absorber fluids.

The essence of the invention

The inventors have found that lubricating fluids suitable for use as damping fluids can be prepared from a favorable combination of GTL base oil, alkylbenzene or alkylnaphthalene and a viscosity modifier. This combination exhibits good shear resistance and good low temperature toughness.

Accordingly, this invention provides a lubricating fluid comprising:

a) at least 40% wt. from the mass of the lubricating fluid of the GTL base oil;

b) from 5 to 25% wt. from lubricating liquid alkylbenzene or alkylnaphthalene; and

c) from 0.1 to 20% wt. from lubricating fluid additives that improve the viscosity index;

moreover, the lubricating fluid has a viscosity index in the range from 50 to 1000 and a pour point below -30 ^o C.

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

This invention further provides the use of a lubricating fluid of the invention in a shock absorber.

The present invention further further provides a vehicle containing the lubricating fluid of the invention.

Detailed description of the invention

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

The term "GTL base oil" is used to describe base oils that are synthesized by the Fischer-Tropsch method by converting natural gas to liquid fuel. They have a very low sulfur and aromatics content compared to mineral base oils obtained from crude oil refining and have a very high paraffin content. GTL base oil is a blend of several 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. Kinematic viscosity is appropriately determined according to ASTM D445. Suitable base oils known as "GTL 4" and "GTL 3" are available from Shell.

The lubricating fluid contains from 5 to 25% wt. from the mass of the lubricating fluid of alkylbenzene or alkylnaphthalene. Accordingly, alkylbenzene or alkylnaphthalene is a mixture of different alkylbenzene and / or alkylnaphthalene molecules. Alkylbenzenes and / or alkylnaphthalenes are mono- or polysubstituted, but are preferably mono- or disubstituted. In a preferred embodiment of the invention, the lubricating fluid contains from 5 to 25% wt. mixtures of alkylbenzenes which are mono- or disubstituted with linear and / or branched alkyl groups, the alkyl groups being C ₆ -C ₂₀ alkyl groups, preferably C ₉ -C ₁₅ alkyl groups. The kinematic viscosity at 40 ^° C of alkylbenzene or alkylnaphthalene (suitably determined according to ASTM D445) is suitably 3 to 400 mm ² / s, preferably 3 to 50 mm ² / s, and more preferably 3 to 10 mm ² / s. The average relative molecular weight is suitably from 180 to 300, preferably from 200 to 280 and more preferably from 230 to 260.

The lubricating fluid contains from 0.1 to 20% wt. from the mass of the lubricating fluid of the viscosity index improver. The lubricating fluid preferably contains from 1 to 18% wt. additives that improve the viscosity index, preferably from 3 to 10% wt.

Viscosity index improvers (also known as VI improvers, viscosity modifiers, or viscosity improvers) provide lubricants with high and low temperature performance. These additives provide shear resistance and acceptable viscosity at elevated temperatures and at low temperatures. Suitable viscosity index improvers include both low molecular weight and high molecular weight hydrocarbons, polyesters and dispersing viscosity index improvers, which can function as a viscosity index improver and dispersant. Typical molecular weights for these polymers are from about 10,000 to 1,000,000, more specifically from about 20,000 to 500,000, and even more specifically from about 50,000 to 200,000. Examples of suitable viscosity index improvers are polymers and copolymers of methacrylate, butadiene, olefins or alkylated styrenes.

Preferably, the viscosity index improver is polymethyl methacrylate (hereinafter referred to as PMMA), that is, a copolymer of methyl and alkyl methacrylates with different chain lengths. Particularly preferred PMMA viscosity index improvers are the commercially available Viscoplex viscosity improvers (Viscoplex is a trademark of Röhm GmbH & CO. KG, Darmstadt, Germany).

The lubricating fluid accordingly additionally contains one or more additives, which are usually used in shock absorber fluids. These additives are introduced as an additive package. A typical additive package includes antioxidants and antiwear additives, but may also include dispersants, detergents, corrosion and rust inhibitors, metal deactivators, ultra-high pressure additives, extreme pressure additives, depressants, paraffinic oil pour point depressants, additives that improve compatibility with sealant, anti-friction lubricants, lubricating additives, additives that improve non-staining, chromophore agents, antifoams and demulsifiers.

The lubricating fluid preferably contains an antiwear additive. Suitable antiwear additives include metal-containing and metal-free alkyl thiophosphates, namely zinc dialkyldithiophosphates, typically used in amounts from about 0.4 wt. up to about 1.4% wt. from the lubricating fluid.

The lubricating fluid preferably contains an antifoam agent. Typical defoamers are silicones and organic polymers. Preferably, the defoamer is a low silicon or no silicon defoamer, namely an acrylic copolymer or fatty amine ethoxylate. The amount of antifoam is preferably less than 1% by weight. from the mass of the lubricating fluid, preferably less than 0.1% wt. and more preferably less than 0.05% wt.

The lubricating fluid has a viscosity index in the range of 50 to 1000, preferably in the range of 100 to 600. Accordingly, the viscosity index is determined according to ASTM D2272. If the viscosity index is too low, the lubricant is likely to be too viscous at low temperatures and too thin at higher temperatures, and the lubricant will not function effectively in the shock.

The lubricating fluid has a pour point below -30 ^° C, preferably below -45 ^° C. Accordingly, the pour point is determined according to ASTM D97. If the lubricating fluid has a higher pour point, then the fluid will not flow in cold environments and the shock absorber containing fluid will not function.

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

The lubricating fluid suitably has a Brookfield viscosity at -40 ^° C of less than 2000 cps, more preferably less than 1500 cps, and most preferably less than 1250 cps. Accordingly, the Brookfield viscosity at -40 ^° C is determined according to ASTM D2983. This type of viscosity is important if the lubricating fluid is to function effectively in the shock absorber.

The lubricating fluid suitably has a shear resistance at 40 ^° C, measured according to CEC L-45-99, of less than 10%, more preferably less than 5%, most preferably less than 3%. It is important that the lubricating fluid has the highest possible shear strength (and the least possible loss of shear strength under test conditions) so that when used in a shock absorber, the lubricating fluid has the correct viscosity range for efficient operation over the longest possible time. If the lubricating composition has low shear strength, it will drip down over time and the viscosity will soon fall outside the desired range.

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

Example

Was obtained shock absorber fluid (Example 1), having the composition shown in table 1:

Table 1

Component Amount (% wt.) Base oil GTL 4 10,00 Base oil GTL 3 68.18 Alkylbenzene 15.00 Enhancer VI 6.00 Additive package for shock absorber fluid (contains dispersants, detergents, antiwear additives, antioxidants) 0.75 Ashless antiwear additive 0.05 Low Silicon Defoamer 0.02

Both GTL base oils are manufactured by Shell. The GTL 4 base oil has a viscosity at 100 ^° C (measured according to ASTM D445) from 3.80 to 4.20 cSt. The GTL 3 base oil has a viscosity at 100 ^° C (measured according to ASTM D445) 2.8 cSt. Alkylbenzene was a mixture of monosubstituted alkylbenzenes with a kinematic viscosity at 40 ^o C from 3 to 5 mm ² / s. The liquid was prepared by mixing and heating all components until a homogeneous mixture was obtained.

Test

The shock absorber fluid of Example 1 and two 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 for Example 1, Comparative example 1 and Comparative example 2.

table 2

Property Test method Example 1 Comparative example 1 Comparative example 2 Density at 15 ^o C (g / cm ³ ) ASTM D4052 0.8247 0.8611 0.836 Viscosity at 40 ^o C (cSt) ASTM D445 13,086 14.18 14.5018 Viscosity at 100 ^o C (cSt) ASTM D445 3.8561 4.0547 4.0913 Viscosity index ASTM D2272 210.7 206.4 202.3 Brookfield Viscosity @ -40 ^o C (cP) ASTM D2983 1020 2369 1800 Pour point ( ^o С) ASTM D97 -60 <-45 <-45 Shear Resistance at 40 ^o C (% Viscosity Loss) CEC L-45-99 2.70 13.50 6.02

The results show that all three shock absorber fluids had similar density, viscosity at 40 ^° C and 100 ^° C, and viscosity index. The shock absorber fluid of the invention (Example 1) had improved Brookfield viscosity compared to commercial shock absorber fluids (Comparative Example 1 and Comparative Example 2) and also had better shear strength.

Claims (7)

1. Shock absorbing fluid containing: a) from 50 to 90 wt% based on the mass of the shock absorber fluid, GTL base oil having a kinematic viscosity at 100 ° C in the range from 2 to 10 mm ² / s; b) from 5 to 25% wt. based on the weight of the shock absorber fluid, a mixture of alkylbenzenes that are mono- or disubstituted linear and / or branched alkyl groups, where the alkyl groups are C ₆ -C ₂₀ alkyl groups; and c) from 0.1 to 20% wt. based on the weight of the shock absorber fluid, viscosity index improvers selected from polymers or copolymers of methacrylate, butadiene, olefins or alkylated styrenes; characterized in that the shock absorber fluid has a viscosity index in the range from 100 to 600 and a pour point below -30 ^o C. 2. The shock absorber fluid according to claim 1, containing metal-containing or metal-free alkyl thiophosphate in an amount of 0.4 to 1.4 wt%. based on the mass of the shock absorber fluid. 3. The shock absorber fluid according to claim 1 or 2, containing acrylic copolymer or fatty amine ethoxylate in an amount of less than 0.1% wt. based on the mass of the shock absorber fluid.