KR20180032622A - Use of polyglycerol esters as friction modifiers in lubricant formulations - Google Patents

Abstract

The present invention relates to lubricating oil compositions comprising polyfunctional carboxylic acids and saturated or unsaturated, linear or branched fatty acids and / or polyglycerol partial esters of poly (hydroxystearic acid) and their use for lubricating engines and reducing friction will be.

Description

Use of polyglycerol esters as friction modifiers in lubricant formulations

The present invention relates to lubricating oil compositions comprising polyfunctional carboxylic acids and saturated or unsaturated, linear or branched fatty acids and / or polyglycerol partial esters of poly (hydroxystearic acid) and their use for lubricating engines and reducing friction will be.

Energy loss due to friction in the lubricated contacts can be reduced by adding a friction modifier to the lubricant formulation. Friction modifiers are used in gear and engine oil formulations to which lower viscosity formulations are applied, in particular to save energy. While reducing energy loss in the fluid, low viscosity lubricants require a friction modifier to struggle to keep the sliding surface completely separate from each other and to maintain the lubricant film on the surface.

The friction modifier acts by forming an adsorption layer on the metal surface. They are very important in mixed lubrication conditions where the sliding surface is not always separated by a lubricant film of sufficient thickness. Such conditions can be simulated with a miniature traction machine (MTM) that can measure the coefficient of friction over a wide range of conditions.

The friction reducing additives that have been used to improve fuel economy belong to three main chemically defined categories: organic, metal organic and oil insoluble. The organic friction modifier additives themselves form four major categories: (i) carboxylic acids or their derivatives such as partial esters, (ii) nitrogen-containing compounds such as amides, imides, amines and their derivatives, (iii) Or phosphonic acid derivatives and (iv) organic polymers.

Examples of friction reducing additives in current commercial practice are glycerol monooleate and oleyl amide (both derived from unsaturated fatty acids), or molybdenum dialkyldithiocarbamates. Also used are copolymers with blocks of polyethylene glycols (WO 2011/107739 and WO 2015/065801) or other alkoxide polymers (WO 2014/139935). It is also known that polyglycerols solubilized by long alkyl chains attached via ether functional groups (US 7,803,745) or ester functional groups (WO 2015/044639) can be used as friction modifiers.

It has now been found to the present invention that polyglycerol partial esters of polyfunctional carboxylic acids and saturated or unsaturated, linear or branched fatty acids and / or poly (hydroxystearic acid) exhibit excellent performance as friction modifiers for lubricants. Excellence means a greater reduction in friction coefficient and / or a more efficient friction reduction due to a lower throughput rate and / or a better combination of oil compatibility and friction reduction performance.

In a first embodiment, the present invention relates to a lubricating oil composition comprising a lubricating base oil and a polyglycerol moiety ester, wherein the polyglycerol moiety ester comprises a polyglycerol mixture

(i) a polyfunctional carboxylic acid and

(ii) a saturated or unsaturated, linear or branched fatty acid and / or

(ii) poly (hydroxystearic acid)

To obtain an esterified product.

Polyglycerol esters have been found to be particularly effective in non-polar formulations containing primarily the American Petroleum Association (API) Groups II, III and / or IV as lubricant basestocks.

The American Petroleum Institute (API) currently defines five groups of lubricant base stocks (API Publication 1509). Groups I, II and Ill are mineral oils classified by their saturate and sulfur content and by their viscosity index. The table below shows these API classes for Groups I, II and Ill.

Group I base stocks are solvent refined mineral oils, the cheapest base stocks to produce and currently account for most of the base stock sales. They provide satisfactory oxidative stability, volatility, low temperature performance and traction characteristics and have very good solubility for additives and contaminants.

The Group II base stock solution is an almost hydrogenated mineral oil and provides generally improved volatility and oxidation stability compared to Group I base stock solutions.

Group Ill base stocks are strictly hydrotreated mineral oils or they can be produced via wax or paraffin isomerization. They are known to have better oxidative stability and volatility than the Group I and II base concentrates, but have a limited range of commercially available viscosities.

The Group IV base stocks are different from Groups I, II and III in that they are synthetic base stocks, for example, polyalphaolefins (PAO). PAO has good oxidation stability, volatility, and low pour point. Disadvantages include moderate solubility of the polar additive, e. G., An antiwear additive.

Although Group II, II, and IV oils are known for their exceptional stability to oxidation and high temperatures, they provide only limited solubility for polar additives such as friction modifiers. For this reason, the lubricating oil composition according to the present invention may contain up to 10% of the ester base oil according to API Group V as a solubilizing agent.

Group V base undecided amounts are all base undecided amounts that are not included in another group. Examples include alkyl naphthalene, alkyl aromatics, vegetable oils, esters (e.g., polyol esters, diesters and monoesters), polycarbonates, silicone oils and polyalkylene glycols.

The performance of the friction modifier of the polyglycerol partial esters according to the invention can be achieved in formulations with or without additional ester base stock solutions.

In a preferred embodiment, the lubricating oil composition according to the invention is characterized in that they are based on the total weight of the lubricating oil composition

(a) 90 to 100% by weight of a nonpolar oil selected from the group consisting of the American Petroleum Association (API) Groups II, III and IV and / or mixtures thereof and

(b) a polar ester oil of group V according to the definition of the American Petroleum Institute (API) 0-10%

And a control unit.

Polyglycerol partial esters of poly (hydroxystearic acid) and polyfunctional carboxylic acids are known as adjuvants to disperse inorganic micro pigment in cosmetic and pharmaceutical formulations as W / O emulsifiers and in oil dispersions (EP 1 500 427 B1 And EP 1 683 781 B1). For best performance as a friction modifier, the parameter surface activity or polarity and oil solubility should be balanced and adjusted to the polarity of the representative oil mixture used as the base stock solution. The balance of the polar and non-polar moieties in the polymer is described by the calculated HLB value. This can be done by selection of polyglycerol to be characterized with a certain degree of polymerization and by selection of carboxylic acid and polycarboxylic acid. In particular, the amount of polycarboxylic acid has a major influence on the molecular weight of the resulting component (measured in SEC). The ratio of acid and alcohol functionality is important because it determines the degree of esterification and hence the amount of OH-functional groups that have not been worked up (OH-determined by titration). The free acid functional group is undesired and should be kept at a minimum level (described by acid value determined by titration).

The superior performance over other friction modifiers is due to the high polarity of the polyglycerol moiety, the free OH-functionality due to partial esterification, and the polymeric nature of the material that provides multiple inter-bonding sites between the surface and the friction-reducing component. The polymeric properties of the described friction modifiers are particularly important for the solubility of the components because highly polar moieties in the molecule must be retained in the solution.

These polyglycerol partial esters of polyfunctional carboxylic acids and saturated or unsaturated, linear or branched fatty acids and / or poly (hydroxystearic acid) are obtained by reacting the polyglycerol mixture with from 8 to 22 carbon atoms, preferably from 12 to 18 carbon atoms Saturated and unsaturated, linear or branched fatty acids having from 4 to 54 carbon atoms, preferably from 6 to 36 carbon atoms, more preferably from 6 to 18 carbon atoms and even more preferably from 6 to 12 carbon atoms With a polyfunctional carboxylic acid having an average functionality of 2 to 4, preferably 2 to 3, and more preferably 2 to 2.5, with carbon atoms, and the degree of esterification of the polyglycerol mixture is from 30 to < RTI ID = 0.0 > 75%.

The average functionality of the multifunctional carboxylic acid mixture can be determined using the following equation:

Particularly suitable linear or branched saturated fatty acid components are caprylic, capric, lauric, tridecanoic, myristic, palmitic, margaric, stearic, isostearic, arachidic, ≪ / RTI > and mixtures thereof. Suitable saturated fatty acids are also 12-hydroxystearic acid. Natural mixtures include, for example, coconut fatty acids which contain lauric acid as a major constituent and which also contain saturated C14 - to C18-fatty acids and may contain small amounts of saturated C8 - to C18-fatty acids and unsaturated fatty acids, and Lt; / RTI > fatty acid which is essentially a mixture of palmitic acid and stearic acid.

Suitable unsaturated fatty acid components include monoolefinically unsaturated acids such as hexadecenoic acid, octadecenoic acid such as oleic acid (cis-9-octadecenoic acid) or elaidic acid (trans-9-octadecenoic acid) (Cis-13-docosenoic acid) or brassidic acid (trans-13-docosenoic acid), polyunsaturated fatty acids such as octadecadienic acid and octadecatrienoic acid Such as linoleic acid and linolenic acid, ricinoleic acid, and mixtures thereof.

Liquid fatty acids containing from 18 to 22 carbon atoms, so-called oleic acid, ricinoleic acid, erucic acid and isostearic acid are particularly suitable. Due to the branching, the solidification temperature is less than 35 ° C. It is also possible to use fatty acid mixtures which may also contain wax-like components such as hydrogenated ricinoleic acid.

The poly (hydroxystearic acid) co-used in accordance with the present invention may, for example, be selected from the group consisting of hydroxystearic acid, preferably 12-hydroxystearic acid, obtained by curing of ricinoleic acid or industrial castor oil fatty acid, Lt; / RTI > can be prepared in a manner known per se. They have an average degree of polymerization of from 1 to 10 units, preferably from 2 to 8 units and especially from 2 to 5 units.

The polyfunctional carboxylic acid may be a dicarboxylic acid, a tricarboxylic acid or a polycarboxylic acid. The polyfunctional carboxylic acid may be unsubstituted or optionally substituted by one, two or three hydroxy groups, preferably by one hydroxy group.

The aliphatic dicarboxylic acid used for the esterification should have a chain length of 3 to 18 carbon atoms. They include, for example, malonic acid, succinic acid, fumaric acid, maleic acid, dimethylglutaric acid, adipic acid, trimethyladipic acid, azelaic acid, sebacic acid, dodecanedioic acid, octadecanedioic acid, octadecanedioic acid, It can be linear or branched as well.

The dicarboxylic acid used may also be a dimeric fatty acid. As is known, these are mixtures of acyclic and cyclic dicarboxylic acids obtained by catalytic dimerization of unsaturated fatty acids having 12 to 22 carbon atoms.

The preparation and use of dimer acids and their physical and chemical properties are described in " The Dimer Acids: The chemical and physical properties, reactions and applications ", Ed. E. C. Leonard; Humko Sheffield Chemical, 1975, Memphis, Tenn.

The dicarboxylic acid may also contain, to a lesser extent, trifunctional and multifunctional carboxylic acids. The functionality of the mixture should not exceed a value of 2 to 2.5 mol average.

Further, phthalic acid, trimellitic acid and pyromellitic acid may be used as the polyfunctional carboxylic acid.

The term "polyglycerol" according to the present invention encompasses glycerol-containing polyglycerols. Therefore, the glycerol content should be considered to calculate the amount, mass, and so on. The term glycerol oligomer or polyglycerol (s) encompasses linear as well as cyclic structures.

Suitable polyglycerols are, in particular, those having an average degree of condensation > 2, preferably 3 to 6. These are industrial polyglycerol mixtures obtained, for example, by the alkali catalytic condensation of glycerol at elevated temperatures, and the classifications having the desired degree of condensation therefrom can be obtained by distillation methods as the case may be. Also suitable are polyglycerols obtained, for example, from epichlorohydrin or glycidol by other methods. Commercial polyglycerols are available from companies such as Solvay, Spiga Nord, Daicel or Lonza.

In the polyglycerol partial esters according to the invention, from 30 to 75%, preferably from 50 to 65%, of the hydroxyl groups of the polyglycerol are esterified. They are initially esterified with 25-60%, preferably 35-50% using fatty acids and in the second stage with dicarboxylic acid to a total esterification degree of 30-75%, preferably 50-65% ≪ / RTI > Through appropriate selection of hydrophilic and lipophilic molecular moieties, an HLB value of 3 to 7 is targeted to obtain the desired product.

The HLB value is a measure of the degree of hydrophilicity or affinity of a molecule and is determined by calculating the value for a different region of the molecule. For purposes of the present invention, the HLB values of the polyglycerol partial esters are calculated as follows:

HLB = (mp / (mp + ma)) * 20,

Where mp is the mass of the polyglycerol and ma is the mass of the mono-, di-, and polycarboxylic acid as well as the carboxylic acid mixture comprising the polyhydroxy fatty acid used in the synthesis of the polyglycerol ester. For example, esterification of 100 g polyglycerol with 90 g mono-carboxylic acid and 10 g dicarboxylic acid results in an HLB of 100 g / m < 2 > independently of the degree of polymerization of the polyglycerol and the type of carboxylic acid used, (90 g + 10 g + 100 g)) * 20 = 10.

In the case of the present invention, it is essential that the polyglycerol main skeleton of the polyglycerol partial ester contains an average degree of polymerization of 2 to 8, preferably 2.5 to 6, particularly preferably 3 to 4.5. Suitable methods for determining oligomer distribution of polyglycerol in a given polyglycerol partial ester include hydrolysis or alcoholysis of the partial ester, separation of the polyglycerol formed from the formed carboxylic acid compound, and analysis by gas chromatography after derivatization .

The polyglycerol partial esters according to the invention can be prepared according to methods known per se by heating the reaction components and removing the resulting water of the reaction by distillation. The reaction may be accelerated by an acidic catalyst such as a sulfonic acid, phosphoric acid or phosphorous acid or an alkaline or alkaline earth metal oxide or a basic catalyst such as hydroxide, alcoholate or salt, or a Lewis acid such as tin salt. However, the addition of the catalyst is not absolutely necessary. The polyglycerol partial esters are preferably prepared in a two step process, which is carried out in a manner known per se again. In the first step, polyglycerols are esterified using monofunctional fatty acids or some fatty acids. After most or all fatty acids have reacted, the multifunctional carboxylic acid is then added and the esterification reaction is continued. The progress of the reaction can be monitored, for example, by measuring the acid number through the removed water of the reaction, or by infrared spectroscopy. Generally, the acid value in the final product is desired to be < 20, preferably < 10. Products with an acid value < 5 are particularly preferred. Acid value is measured according to DIN EN ISO 2114.

The weight average molecular weight M _w of the claimed polyglycerol partial esters determined via SEC for the polymethylmethacrylate (PMMA) standard ranges from 2,000 to 15,000 g / mol, preferably from 4,000 to 10,000 g / mol, The index is 1.5 to 5, preferably 2 to 4.

The OH-number (OH-number) of the polyglycerol partial esters according to the invention ranges from 50 to 180 mg KOH / g, preferably from 80 to 170 mg KOH / g and most preferably from 110 to 150 mg KOH / g to be. OH- is measured according to DIN 53 240-2.

In the case of engine oils, the organic polymeric friction reducing additive is present in the vehicle engine oil in an amount of from 0.2 to 5% by weight, preferably from 0.3 to 3% by weight, and even more preferably from 0.5 to 2% by weight, based on the total weight of the lubricating oil composition Lt; / RTI &gt;

Thus, in a preferred embodiment of the present invention,

(a) from 0.2 to 5% by weight, preferably from 0.3 to 3% by weight, even more preferably from 0.5 to 2% by weight, based on the total weight of the lubricating oil composition, of a polyglycerol partial ester,

(API) Groups II, III and IV, based on the total weight of the lubricating oil composition, (b) 85 to 99.8 wt%, preferably 87 to 99.7 wt%, and even more preferably 88 to 99.5 wt% And / or a mixture thereof, and

(c) 0 to 10% by weight, based on the total weight of the lubricating oil composition, of a polar ester oil of group V according to the definition of American Petroleum Institute (API)

&Lt; / RTI &gt;

In a preferred embodiment, up to 100% by weight of (a), (b) and (c) are added.

In addition to the polyglycerol partial esters according to the invention, the lubricating oil compositions described herein may also comprise one or more additional additive (s). These additives include dispersant inhibitor (DI) additives selected from the group consisting of viscosity index (VI) improvers, pour point depressants and dispersants, detergents, defoamers, corrosion inhibitors, antioxidants, antiwear and extreme pressure additives and additional friction modifiers.

Suitable viscosity index improvers are, for example, polyalkyl (meth) acrylate polymers, ethylene-propylene copolymers, styrene-isoprene copolymers, hydrogenated styrene-isoprene copolymers, polyisobutylene, and dispersant type viscosity index improvers .

Suitable pour point depressants are, for example, polyalkyl (meth) acrylate polymers.

Suitable dispersing agents include, for example, alkenyl succinimides, alkenyl succinate esters, alkenyl succinimides modified with other organic compounds, alkenyl succin modified by post treatment with ethylene carbonate or boric acid A dispersant of an alkali metal borate, a dispersion of an alkali metal borate, a polyamide ashless dispersant, or the like, or a mixture of such a dispersant / RTI &gt;

Suitable detergents include, for example, water-soluble neutral and overbased sulfonates of metals, especially alkali or alkaline earth metals such as barium, sodium, potassium, lithium, calcium and magnesium, phenates, Phosphonates, salicylates, and naphthenates and other oil-soluble carboxylates. The most commonly used metals are calcium and magnesium, both of which may be present in detergents used in lubricants, and mixtures of calcium and / or magnesium and sodium. Particularly convenient metal detergents are neutral and overbased calcium sulfonates having a TBN of 20 to 450, neutral and overbased calcium carbonate phenates having TBN of 50 to 450 and sulfurized phenates and TBN of 20 to 450, Magnesium or calcium salicylate. Combinations of overbased or neutral or both detergents may also be used.

Suitable defoamers are, for example, selected from the group consisting of alkyl (meth) acrylate polymers, silicone oils and dimethyl silicone polymers.

Suitable corrosion inhibitors are, in many cases, divided into rust preventive additives and metal passivating / deactivating agents. The rust preventive additives used are, inter alia, sulfonates such as petroleum sulfonate or (in many cases overbased) synthetic alkylbenzene sulfonates such as dinonylnaphthenesulfonate; Carboxylic acid derivatives such as lanolin (wool), paraffin oxide, zinc naphthenate, alkylated succinic acid, 4-nonylphenoxy-acetic acid, amides and imides (N-acyl sarcosine, imidazoline derivatives); Amine-neutralized mono- and dialkyl phosphates; Morpholine, dicyclohexylamine or diethanolamine. Metal passivating / deactivating agents include benzotriazole, tolyltriazole, tolutriazole (e.g., Vanlube 887 or 887E), 2-mercaptobenzothiazole, dialkyl-2,5-dimers Mercapto-1,3,4-thiadiazole; N, N'-dissalicylideneethylenediamine, N, N'-disalicylidenepropylenediamine; Zinc dialkyl dithiophosphates and dialkyl dithiocarbamates.

Suitable antioxidants include, for example, phenolic (phenolic) oxidation inhibitors such as 4,4'-methylene-bis (2,6-di-tert- butylphenol), 4,4'- bis Butylphenol), 4,4'-bis (2-methyl-6-tert-butylphenol), 2,2'-methylene- ), 4,4'-butylidene-bis (3-methyl-6-tert-butylphenol), 4,4'-isopropylidene- -Methylene-bis (4-methyl-6-nonylphenol), 2,2'-isobutylidene-bis (4,6-dimethylphenol), 2,2'- Butylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6- Di- tert -butyl-phenol, 2,6-di-tert-1-dimethylamino-p-cresol, 2,6- Methyl-6-tert-butylphenol), 2,2'-thiobis (4-methyl- butyl-benzyl) -sulfide, and bis (3,5-di-tert-butyl- Is benzyl). Other types of antioxidants include alkylated diphenylamines (e.g., lrganox L-57 from BASF), metal dithiocarbamates (e.g., zinc dithiocarbamate) and methylene bis Butyl dithiocarbamate).

Suitable antiwear additives are, for example, phosphates, phosphites, carbamates, esters, sulfur-containing compounds and molybdenum complexes.

Suitable extreme pressure additives include, for example, zinc dialkyldithiophosphates (primary alkyl, secondary alkyl, and aryl types), sulfurized oils, diphenylsulfide, methyltrichlorostearate, chlorinated naphthalenes, fluoroalkylpolysiloxanes, Lead naphthenate.

A second embodiment of the present invention is directed to an engine oil comprising the lubricating oil composition described above.

A third embodiment of the present invention is directed to a method of lubricating an engine using the lubricating oil composition described above.

A fourth embodiment of the invention relates to a method of applying / adding the lubricating oil composition described above to reduce friction in the engine.

The invention is illustrated by the following non-limiting examples.

Example

Example 1 : Polycarboxylic acid ester prepared from polyglycerol, isostearic acid, sebacic acid and poly (hydroxystearic acid) according to Synthesis Example 2 of EP 1 500 427 B1.

A mixture of isostearic acid (91.1 g, 0.320 mol) and poly (hydroxystearic acid) (141.7 g, 0.120 mol, acid value of 47 mg KOH / g) was passed through nitrogen with polyglycerol (61.9 g, 0.121 mol, and a hydroxyl value of 950 mg KOH / g). After 2 hours at this temperature, the acid value of the reaction mixture was < 10. The mixture was then cooled to 130 DEG C and sebaceous acid (20.2 g, 0.100 mol) was added and the mixture was again heated to 240 <0> C. After 3 hours at this temperature, an acid value &lt; 5 and a viscous product was obtained.

Comparative Example 1 : Polycarboxylate ester prepared from ethoxylated soybean oil, oleic acid and dimer acid

6.3% of the oxirane - [O] epoxidized soybean oil (300 g, 0.302 mol), oleic acid (331 g, 1.18 mol) and the dimer acid (57.5 g having a content; 0.101 mol, from about 2% monobasic acid, About 96% dimer acid and about 2% trimeric acid and high polyacid) was heated to 240 DEG C until the acid value was < 10 mg KOH / g.

The structure of this polymer is different from the polyglycerol partial esters according to the present invention and therefore is not included in the present invention.

Comparative Example 2 : Polycarboxylate ester prepared from polyglycerol, isostearic acid and sebacic acid

A mixture of 72 g of isostearic acid and 11 g of sebacic acid was esterified with 17 g of polyglycerol (average degree of polymerization = 3) at 240 占 폚 while passing through nitrogen. The reaction was then cooled when the acid value reached 12.

The OH-value of this polymer is much lower than the preferred range according to the invention.

Comparative Example 3 :

Polymeric friction modifier Perfad ™ 3006 (available from Croda Inc., US 2013/0079536, WO 2011/107739 Al and for physical properties, Lube Magazine No. 120, April 2014, page 27]).

The structure of this polymer is different from the polyglycerol partial esters according to the present invention and therefore is not included in the present invention.

Comparative Example 4 :

For polymeric friction modifier FERPAD ™ 3057 (structure US 2013/0079536, WO 2011/107739 A1 diluted from FERPAD ™ 3050, available from Croda Sucursal Colombia, Lube Magazine No. 120, April 2014, page 27).

The structure of this polymer is different from the polyglycerol partial esters according to the present invention and therefore is not included in the present invention.

Table 1: Physical data of Examples and Comparative Examples

M _n and M _w are measured by GPC using PMMA (polymethylmethacrylate) as a standard

^*) The value provided for Furfad ™ 3050; Furfad ™ 3057 is a dilute form of Furfad ™ 3050

All polymers were diluted in a Group III Nexbase 3043 according to the American Petroleum Institute (API). The final blend has a similar kinematic viscosity (KV ₁₀₀ ) of about 4.45 cSt at 100 ° C.

For Comparative Examples 3 and 4, a processing rate of 0.5% is recommended by the manufacturer.

Table 1: The viscosity value of the blend tested

(KV ₁₀₀ = kinematic viscosity at 100 ° C)

Determination of friction-reducing action:

The measurement of the coefficient of friction at 100 占 폚 was carried out on a mini traction machine (MTM) of PCS Instruments. The test consisted of evaluating the level of friction occurring at the lubricated contacts formed by steel balls and steel discs. The speed of the ball and the disk are run independently. The ball is loaded and rubbed against the steel disk in a rolling slip condition, and the contact is completely contained in the oil.

For each sample, a two-step test was performed:

1) Run In step

For this step, the conditions described in Table 2 below were applied, and SRR refers to the sliding roll ratio. This parameter was kept constant during the 2 hour test and is defined as:

(여기서 U _볼 - U _디스크 는 미끄럼 속도를 U는 동반흐름(entrainment) 속도를 나타내고 U=(U _볼 +U _디스크 )/2로 주어진다)

(Where U _ball - U _disk, a sliding speed U denotes the accompanying currents (entrainment) speed given by U = (U + U _{ball disc)} / 2)

Table 2: Test parameters for the run-in step

2) Stribeck curve evaluation

Then, the friction coefficient was measured under the conditions shown in Table 3 to obtain Strybeck.

Table 3: Conditions for the Stryvek curve evaluation

The Stryvek curve is plotted in Fig. Curve NB3043-Ref refers to a formulation containing 100% Group III oil named Nexbase 3043.

Figure 1: Measure the Stryvek curve after 2 hours of run-in phase

In order to denote the% reduction in friction obtained by Example 1, the quantifiable result, which can be expressed as a number, is obtained as follows:

Integration of friction value curves in the range of 0.005-2.5 m / s with sliding velocity using quadrilateral rule. The area corresponds to the "total friction" over the entire velocity range studied. The smaller the area, the greater the friction-reduction effect of the irradiated polymer.

The percentage of friction reduction calculated therefrom for the reference oil is given in Table 4 below.

Table 4: Quantitative evaluation of friction reduction

The data in Table 4 and Figure 1 clearly show that the inventive polymers have a far better effect on reducing friction than the corresponding comparative polymers of the prior art using different chemistries. As shown in Table 5 below, the effect is much more pronounced in low-speed situations.

Table 5 shows the integration data of the friction value curves within the sliding speeds in the range of 0.005 to 0.090 m / s, since the low speed for the use of the lubricant composition according to the present invention is of particular economic interest.

The percentage reduction in friction calculated from the determined area and the reference oil is shown in Table 5 in a manner similar to that of Table 4.

Table 5: Quantitative evaluation of friction reduction at low frequencies (0.005 to 0.090 m / s)

The data in Table 5 again clearly show that the polymers of the present invention have a far better effect with respect to the reduction of friction than the corresponding comparative polymers of the prior art.

Compared to the results shown in Table 4, it can be seen that the friction-increasing action of the lubricant compositions for use in accordance with the present invention is very apparent, especially within the range of low sliding speeds.

Claims (14)

(a) a polyglycerol mixture
(i) a polyfunctional carboxylic acid and
(ii) a saturated or unsaturated, linear or branched fatty acid and / or
(ii) poly (hydroxystearic acid)
, Wherein the degree of esterification of the polyglycerol mixture is from 30 to 75% of the OH groups,
From 0.2 to 5% by weight, based on the total weight of the lubricating oil composition, of a polyglycerol partial ester;
(b) 85 to 99.8% by weight, based on the total weight of the lubricating oil composition, of a non-polar basis stock solution selected from the group consisting of the United States Petroleum Association (API) Groups II, III and IV and / or mixtures thereof; And
(c) 0 to 10% by weight, based on the total weight of the lubricating oil composition, of a polar ester oil of group V according to the definition of American Petroleum Institute (API)
&Lt; / RTI &gt; The lubricating oil composition according to claim 1, wherein the polyglycerol has an average degree of condensation of 3 to 6. 3. Lubricant composition according to claim 1 or 2, characterized in that the fatty acid is saturated or unsaturated, linear or branched with 8 to 22 carbon atoms, preferably 12 to 18 carbon atoms. 4. The composition according to any one of claims 1 to 3, wherein the saturated fatty acid is selected from the group consisting of caprylic acid, capric acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, margaric acid, stearic acid, Wherein the lubricating oil composition is selected from the group consisting of acetic acid, arachidic acid, behenic acid, 12-hydroxystearic acid, and mixtures thereof. 5. The composition according to any one of claims 1 to 4, wherein the unsaturated fatty acid is selected from the group consisting of hexadecenoic acid, octadecenoic acid, eicosanoic acid, docosenoic acid, octadecadienoic acid, octadecatrienoic acid, ricinoleic acid, Lt; RTI ID = 0.0 &gt; 1, &lt; / RTI &gt; 6. Lubricating oil according to any one of claims 1 to 5, characterized in that the polyfunctional carboxylic acid has from 4 to 54 carbon atoms, preferably from 6 to 12 carbon atoms, and from 2 to 2.5 average functionality Composition. 7. The composition of any one of claims 1 to 6 wherein the polyfunctional carboxylic acid is selected from the group consisting of malonic acid, succinic acid, fumaric acid, maleic acid, dimethylglutaric acid, adipic acid, trimethyladipic acid, azelaic acid, sebacic acid, Wherein the aliphatic dicarboxylic acid is an aliphatic dicarboxylic acid selected from the group consisting of diacids and their anhydrides. 8. The lubricating oil composition according to any one of claims 1 to 7, wherein the polyglycerol partial esters have an HLB value of from 3 to 7. 9. The lubricating oil composition according to any one of claims 1 to 8, wherein the polyglycerol partial ester has an OH-number (OH-number) in the range of 50 to 180 mg KOH / g. 10. The lubricating oil composition according to any one of claims 1 to 9, further comprising at least one further additive (s). 11. The composition of claim 10 wherein at least one additional additive (s) is selected from the group consisting of viscosity index (VI) improvers, pour point depressants, dispersants, detergents, defoamers, corrosion inhibitors, antioxidants, antiwear and extreme pressure additives, and friction modifiers &Lt; / RTI &gt; 12. Lubricant composition according to any one of claims 1 to 11, characterized in that the polyglycerol partial esters have a weight average molecular weight of from 2,000 to 15,000 g / mol, preferably from 4,000 to 10,000 g / mol. A method for lubricating an engine using the lubricating oil composition according to any one of claims 1 to 12. 13. A method for reducing friction in an engine by applying the lubricating oil composition according to any one of claims 1 to 12.

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