KR102398825B1 - lubricant - Google Patents

Abstract

Lubricating oils suitable for use as buffer fluids are disclosed. The lubricating oil comprises at least 40% by weight of the GTL base oil, based on the weight of the lubricating oil, and has a viscosity index in the range of 50 to 1000, and a pour point of less than -30°C.

Description

lubricant

The present invention relates to a lubricant suitable for use as a shock absorber. The invention also relates to the use of lubricants in shock absorbers.

A shock absorber (also called a damper) is a mechanical device designed to damp or damp a sudden shock impulse and dissipate kinetic energy. Shock absorbers are an important part of the supports of automobiles, motorcycles or bicycles, aircraft landing gears, train suspensions, and many industrial machinery. Large buffers are also used in architectural and civil engineering to reduce the susceptibility of structures to earthquake damage and resonance.

Buffers can convert kinetic energy into thermal energy and dissipate it. Hydraulic shock absorbers consist of a cylinder with a sliding piston inside. The cylinder is filled with a buffer fluid. This fluid-filled piston/cylinder combination is also referred to as a dashpot. Wheel suspensions in vehicles usually include several shock absorbers together with pressure-elastic means such as coil springs, leaf springs or torsion bars. These springs are just springs that store and do not waste or absorb energy and are not shock absorbers. When you move the wheel horizontally, the spring will absorb the up-and-down force and convert it into heat. The shock absorber effectively dampens wheel bounce by slowing down the motion of the unspring weight up and down with hysteresis, for example the tire on the wheel. This is accomplished by converting kinetic energy into heat through fluid friction due to the flow of the buffer fluid through a narrow orifice, such as an internal valve.

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

The inventors have endeavored to provide lubricants suitable for use as buffer fluids that have advantageous properties, such as longer term shear stability and/or lower temperature viscosity properties than commercially available buffer fluids.

The inventors have discovered that lubricating oils suitable for use as buffer fluids can be prepared from advantageous combinations 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 oil comprising:

(a) at least 40% by weight of a GTL base oil, based on the weight of the lubricating oil;

(b) from 5 to 25% by weight of an alkylbenzene or alkylnaphthalene, based on the weight of the lubricating oil; and

(c) 0.1 to 20% by weight, based on the weight of the lubricating oil, of a viscosity index improver;

The lubricating oil has a viscosity index in the range of 50 to 1000, and a pour point of less than -30 °C.

Lubricants are suitable for use in shock absorbers, but can also be used as industrial lubricants such as fork or hydraulic oils, bearings and circulation oils.

The invention further provides for the use of a lubricant according to the invention in a shock absorber.

The invention further provides a vehicle comprising a lubricant according to the invention.

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

The term "GTL base oil" is used to describe a base oil synthesized by the Fischer-Tropsch method of converting natural gas into a liquid fuel. They have a very low sulfur content and aromatic content and a very high paraffin composition compared to mineral base oils refined from crude oil. The GTL base oil may be a mixture of several different GTL base oils with different viscosities. Preferably, the dynamic viscosity of the GTL base oil at 100° C. is in the range of 2 to 10 mm ² /sec, more preferably 2.5 to 7 mm ² /sec. The kinematic viscosity is suitably determined according to ASTM D445. Suitable base oils known as "GTL 4" and "GTL 3" are available from Shell.

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

The lubricating oil comprises 0.1 to 20% by weight of the viscosity index improver, based on the weight of the lubricating oil. The lubricating oil preferably comprises 1 to 18% by weight, more preferably 3 to 10% by weight of the viscosity index improver.

Viscosity index improvers (also called VI improvers, viscosity modifiers or viscosity modifiers) provide high and low temperature operability to lubricants. 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 improver dispersants that can function as both viscosity index improvers and dispersants. Typical molecular weights of these polymers are from about 10,000 to 1,000,000, more typically from about 20,000 to 500,000, and more typically from about 50,000 to 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 poly methyl methacrylate (further referred to as PMMA), ie 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 a trade name of Rohm GmbH & CO. (KG, Darmstadt, Germany)).

The lubricating oil suitably further comprises one or more additives typically used in buffer fluids. These additives may be added in the form of an additive package. Typical additive packages include antioxidants and anti-wear agents, but dispersants, detergents, rust inhibitors, metal deactivators, extreme pressure additives, foam inhibitors, pour point depressants, wax modifiers, sealants, friction modifiers, lubricants, anti-dye agents, It may contain a coloring agent, an antifoaming agent and an antidote.

The lubricating oil preferably comprises an anti-wear additive. Suitable antiwear additives include metal-containing and metal-free alkylthiophosphates, such as zinc dialkyldithiophosphates, typically used in amounts from about 0.4% to about 1.4% by weight of the lubricant.

The lubricating oil preferably includes an anti-foaming agent. Silicones and organic polymers are typical defoamers. Preferably, the anti-foaming agent is a low-silicone or silicone-free anti-foaming agent such as an acrylic copolymer or a fatty amine ethoxylate. The amount of anti-foaming agent is suitably 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 oil.

The lubricating oil has a viscosity index in the range from 50 to 1000, preferably in the range from 100 to 600. A suitable viscosity index is determined according to ASTM D2272. If the viscosity index is too low, the lubricant will be too viscous at low temperatures and too thin at high temperatures, and then the lubricant will not function effectively in the buffer.

The lubricating oil preferably has a pour point of less than -30°C, preferably less than -45°C. Suitably the pour point is determined according to ASTM D97. If the lubricant has a higher pour point, the fluid will not flow in cold ambient conditions and the buffer containing the fluid will not work.

The lubricant 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. Suitably the kinematic viscosity is determined according to ASTM D445 at 40°C. It is important for the lubricant to have this viscosity in order to work effectively in the shock absorber.

The lubricant suitably has a Brookfield viscosity at -40°C of less than 2000 cP, more preferably less than 1500 cP and most preferably less than 1250 cP. Suitably at -40°C, the Brookfield viscosity is determined by ASTM D2983. It is important for the lubricant to have this viscosity in order to work effectively in the shock absorber.

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

Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these.

Example

A buffer fluid (Example 1) with the composition shown in Table 1 was prepared:

Table 1

Two GTL base oils are purchased from Shell. GTL 4 base oil has a viscosity of 3.80 to 4.20 cSt at 100° C. (measured by ASTM D445). GTL 3 base oil has a viscosity of 2.8 cSt at 100° C. (measured by ASTM D445). The alkylbenzene was a mixture of mono-substituted alkylbenzenes having a kinematic viscosity of 3-5 mm ² /s at 40°C. A fluid was prepared by mixing and heating all the ingredients until a homogeneous mixture was produced.

Test

The buffer fluid of Example 1 and two commercial buffer fluids (Comparative Example 1 and Comparative Example 2) were tested. Table 2 shows the properties tested, the test method used and the results of Example 1, Comparative Example 1 and Comparative Example 2.

Table 2

The result is that the three buffer fluids have similar densities and viscosities at 40° C. to 100° C. and viscosity index. The buffer fluid of the present invention (Example 1) has improved Brookfield viscosity compared to commercial buffer fluids (Comparative Example 1 and Comparative Example 2), and also has good shear stability.

Claims (8)

As a lubricant used in shock absorbers,
(a) at least 40% by weight based on the weight of the lubricating oil, GTL base oil;
(b) 5 to 25% by weight, based on the weight of the lubricating oil, of a mixture of alkylbenzenes mono- or di-substituted with linear and/or branched C ₆ -C ₂₀ alkyl groups; and
(c) 0.1 to 20% by weight, based on the weight of the lubricating oil, of a viscosity index improver selected from polymers and copolymers of methacrylates, butadiene, olefins or alkylated styrenes;
wherein the lubricating oil has a viscosity index in the range of 50 to 1000 and a pour point of less than -30°C.
The lubricating oil of claim 1 comprising in the range of 50 to 90 wt % GTL base oil.
The lubricating oil of claim 1 comprising metal-free or metal-free alkylthiophosphates in an amount of from 0.4% to 1.4% by weight of the lubricating oil.
The lubricating oil of claim 1 comprising an acrylic copolymer or a fatty amine ethoxylate in an amount of less than 0.1% by weight, based on the weight of the lubricating oil. delete delete delete delete