PI ultrafine powder as lubricant additive

Abstract

The present invention relates to PI particles as lubricant additives.

Description

[0001] This invention relates to the use of PI particles as a lubricant additive, particularly a grease additive.

[0002] Lubricants, especially greases and lubricating oils, are known and widely used. Greases, sometimes also called "lubricating oils," are solid to semi-liquid substances formed by dispersing a thickener (thickener) in a liquid lubricant (base fluid). Other additives may be present to impart specific properties. In this context, see, for example, publication DE 10 2012 215145.

[0003] The basic consistency of a grease is determined by the combination of its base fluid and thickener. The base fluid is typically a base oil commonly used in the lubricant industry, such as mineral oil, synthetic oil, or vegetable oil.

[0004] Thickeners used include, for example, alkali metal or alkaline earth metal soaps. Non-soap-based thickeners, such as bentonite (clay-based) or polyurea, are also known.

[0005] Lubricants, especially greases and oils, can be produced by batch or continuous methods.

[0006] Lubricants and their production methods are known from the prior art and are available in a variety of compositions.

[0007] Lubrication of mechanical components (such as gears or bearings) presents particular challenges in terms of wear and friction. For this reason, lubricating oils and greases employ different additives to specifically improve or meet the requirements of these two primary properties. Tribological contact is also influenced by its mating components. This can be inorganic (e.g., steel / steel), organic (e.g., plastic / plastic), or hybrid (e.g., steel / plastic) contact. Therefore, the additives used must be matched to this tribological pairing. In other words, different tribological pairs (metal / metal, metal / plastic, plastic / plastic, etc.) require different lubricant properties. Optimized lubricants have not yet been suitable for all pairings.

[0008] CN 10649765 discloses PTFE powder as a thickener. Commercially available products are Algoflon® and “Xeon” PTFE wax.

[0009] Publications GB 2192896 B, US 4,787,993, and JP S63 / 172794 disclose PEEK or PI powder as additives for lubricants. However, only the effects on metal / metal friction pairings were investigated. Commercially available products are unknown.

[0010] PTFE contains fluorine and is used in lubricants in relatively large quantities (15-40%). The high temperatures generated by friction may potentially form toxic fluorinated compounds. In addition, PFOA (perfluorooctanoic acid) and other now-banned PFAS (perfluorinated and polyfluorinated alkyl compounds) are minor components present in small amounts in PTFE. PFOA-free PTFE is now available, but the prohibition of PTFE is also discussed in the EU (Bund für Umwelt und Naturschutz Deutschland eV, “Praktisch, langlebigund giftig” [Practical, long-lasting and toxic]; https: / / www.bmuv.de / faq / welche-pfas-wurden-bislang-verboten; https: / / echa.europa.eu / restrictions-under-consideration / - / substance-rev / 72301 / term; https: / / echa.europa.eu / documents / 10162 / f605d4b5-7c17-7414-8823-b49b9fd43aea). No information is available regarding the tribological behavior in metal / plastic or plastic / plastic friction pairings.

[0011] Therefore, known lubricants are unsatisfactory. Therefore, the object of the present invention is to provide a lubricant that has advantages over known lubricants.

[0012] This objective is achieved through the subject matter of the claims:

[0013] Contains particles with a diameter of up to 15 μm D 50 Lubricant containing PI particles, wherein the particle size D 50 The particle size distribution is determined by laser diffraction, preferably according to ISO 13320:2020, wherein the lubricant contains a thickener, preferably a soap thickener, preferably selected from lithium soap, lithium complex soap, aluminum soap, aluminum complex soap, calcium soap, calcium complex soap and combinations thereof.

[0014] Surprisingly, it was found that PI powder with a specific particle size (approximately 5 μm), i.e., polyimide powder, enables a significant reduction in the wear coefficient and / or friction coefficient of the aforementioned contact pairing.

[0015] Examples of suitable PI powders are known to those skilled in the art, for example from publication DE 10 2005 034969 A1.

[0016] Preferably, the PI powder is a polyimide-polyimide block copolymer composed of the following structural units or contains a polyimide-polyimide block copolymer composed of the following structural units: Where n and m are each between 2 and 20, preferably between 8 and 15. And x = 1 to 300, preferably 75 to 200, more preferably 100 to 175. And in addition: R1 and R3 are defined separately as follows: Furthermore, R2 and R4 are each defined separately as follows: Where n = 1 to 12, preferably 4 to 9.

[0017] In another preferred embodiment, the PI powder comprises a polyimide having terminal dicarboxylic anhydride groups as a block for producing a block copolymer having the following structure: Wherein: functional groups R1 and R2 are as defined in paragraph 15 above, and n=2-20, preferably 5 to 15, more preferably 8 to 12.

[0018] In another preferred embodiment, the PI powder comprises a polyimide-polyamide-carboxylic acid block copolymer having the following structure: Where n and m are each 2 to 20, preferably 8 to 15, and more preferably 9 to 12. And x = 1 to 300, preferably 75 to 200, more preferably 100 to 175. R1, R2, R3, and R4 are defined as in paragraph 15 above.

[0019] Surprisingly, it was found that the tribological properties of lubricants / greases could be improved by adding small amounts, more specifically, 0.5-2% by weight of PI ultrafine powder with an average particle size of about 5 μm.

[0020] Surprisingly, lubricants containing PI particles (approximately 5 μm) have been found to have advantages over conventional lubricant formulations in plastic / metal systems at both room temperature (RT) and high temperatures of 100°C.

[0021] The PI-modified lubricant according to the present invention can be used in a variety of applications. Its main applications can be seen in the automotive industry. Another application area is the lubrication of mechanical components (e.g., gears or bearings) in various branches of industry.

[0022] PI ultrafine powder is formed directly during precipitation imidization. The PI ultrafine powder thus produced is then dispersed in grease / lubricant, for example, using commercially available dispersing equipment (e.g., a planetary mixer).

[0023] PI is a very thermally stable polymer and exhibits significantly lower creep behavior than PTFE. Surprisingly, although PI is found to be spherically stable under pressure and therefore not adaptable to friction geometry, wear on lubricated surfaces is reduced compared to unfilled greases. Furthermore, it can be inferred that PTFE undergoes "grinding" over time under high-pressure loads and loses its effectiveness. Therefore, a longer service life can be achieved according to the present invention.

[0024] Figure 1 The particle size distribution in the first PI powder, as measured by laser diffraction particle size analysis, is shown. 10 The value is 1.3 μm, D 50 The value is 4.3 μm, D 90 The value is 9.8 μm, D 100 The value is 23.0 μm.

[0025] Figure 2 An apparatus for performing the HFRR process is shown.

[0026] Figure 3a and 3b The results of the HFRR (High Frequency Reciprocating Rig) process are shown for each.

[0027] In a first aspect, the present invention relates to a lubricant, preferably a grease, containing a particle size D formulated for lubricating at least two surfaces. 50 PI particles (i.e., PI powder or PI ultrafine powder) with a maximum size of 15 μm.

[0028] In the context of this invention, grease may be referred to as lubricant, lubricating substance, or lubricating material. These terms may be used synonymously.

[0029] In the context of this invention, grease is a specific embodiment of a lubricant. In a preferred embodiment, the lubricant according to the invention is grease.

[0030] In a preferred embodiment, the lubricant or grease according to the invention is not to be understood as lubricating oil.

[0031] In a preferred embodiment, the polyimide (PI) further includes polyetherimide (PEI) and / or polyamideimide (PAI).

[0032] In a preferred embodiment, at least two surfaces, more preferably all surfaces, are adjacent to each other, i.e., they have a common contact surface.

[0033] In a preferred embodiment, at least one surface is non-metallic.

[0034] In the context of this invention, "non-metallic" is preferably understood to mean that the corresponding surface contains at most 5% by weight of metal based on the total weight of the surface, and more preferably contains 0% by weight of metal based on the total weight of the surface.

[0035] Preferred metals are steel, aluminum, zinc, copper, gold, silver, platinum, and alloys containing said metals.

[0036] In a preferred embodiment, at least one non-metallic surface comprises or is composed of plastic, and at least one other surface comprises or is composed of metal; or at least two non-metallic surfaces comprise or are composed of plastic, and at least two other surfaces comprise or are composed of metal; or all non-metallic surfaces comprise or are composed of plastic, and all other surfaces comprise or are composed of metal; or exactly two surfaces exist, one of which comprises or is composed of plastic, and the other of which comprises or is composed of metal.

[0037] Suitable plastics include, for example, thermoplastics, thermosetting plastics, and elastomers known to those skilled in the art. Preferably, at least one non-metallic surface contains or is composed of polyetheretherketone (PEEK) and / or contains polyoxymethylene (POM) and / or contains UHMWPE (ultra-high molecular weight polyethylene, preferably having a molecular weight of 3.5 to 7.5 megag / mol) and / or contains PA66 and / or contains PA6G (cast polyamide 6) and / or contains PA12G (cast polyamide 12) and / or contains PPA. PPA is a nylon-type "semi-aromatic" polyamide, i.e., an aromatic diamine or aromatic diacid.

[0038] In another preferred embodiment, the particle size D is determined by laser diffraction particle size analysis. 50 Particle size D 50 The determination is preferably performed according to ISO 13320:2020. This is used to determine the particle size D. 50 One possible system is "LD (laser diffraction) wettable system with dispersant, ultrasonic, Malvern Mastersizer 3000".

[0039] The lubricants used according to the present invention typically contain a base oil, which is preferably selected from mineral oils, synthetic oils, vegetable oils, and any desired combination of two or more of the aforementioned oils.

[0040] In a preferred embodiment, the lubricant contains approximately 65% ​​to approximately 90% by weight of base oil, based on the total weight of the lubricant.

[0041] In the context of this invention, the terms "base oil" and "base oil" may be used synonymously.

[0042] Suitable base oils are known to those skilled in the art and are commercially available.

[0043] The base oils that can be used include all materials known for this purpose and commonly used in the production of lubricants. Examples include mineral oils, lubricants of vegetable or animal origin, or synthetic oils. The latter particularly include hydrocarbon oils, including halogenated hydrocarbon oils, and non-hydrocarbon oils such as polyalkylene glycols, polyether oils, ester oils, such as phosphate-based oils, and silicone oils. Also usable base oils are complex oils, such as mixtures of mineral and synthetic oils. Mixtures of different base oils may also be used.

[0044] Examples of base oils include lubricants derived from mineral oils, synthetic oils, and natural oils. Mineral lubricants include mineral oils that have been purified by a suitable combination of purification operations such as vacuum distillation, solvent deasphalting, solvent extraction, hydrogenolysis, solvent dewaxing, sulfuric acid treatment, clay treatment, and / or hydrorefining.

[0045] Other examples of base oils include synthetic lubricants. These include hydrocarbon oils, aromatic oils, ester oils, and ether oils. Hydrocarbon oils include polyalphaolefins, such as n-alkanes, isoalkanes, polybutene, polyisobutylene, 1-decene oligomers, 1-decene / ethylene co-oligomers, and their hydrogenated products. Aromatic oils include alkylbenzenes, such as monoalkylbenzenes, dialkylbenzenes, or polyalkylbenzenes; and alkylnaphthalenes, such as monoalkylnaphthalenes, dialkylnaphthalenes, or polyalkylnaphthalenes. Ester oils include diesters, triesters, or tetraesters of carboxylic acids, such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyladipate, ditridecyladipate, methyl acetyl ricinoleate, trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellitate; or they include polyol esters of carboxylic acids, such as trimethylolpropane octanoate, trimethylolpropane nonanoate, pentaerythritol 2-ethylhexanoate, and pentaerythritol nonanoate; or they include complex esters, which are low polyesters between polyhydroxy alcohols and a mixture of mono- or di-fatty acids. Ether oils include polyglycols, such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether; and phenyl ethers, such as alkylated diphenyl ethers, triphenyl ethers, and polyphenyl ethers with varying degrees of alkylation, or dialkyl ethers. Phosphate esters, such as tricresyl phosphate, silicone oils, and perfluoroalkyl ether oils (fluorinated oils), can also be used as synthetic oils.

[0046] The base oil used in this invention is not subject to any particular limitation, and any desired base oil can be used, such as base oils commonly used in lubricating oils and greases. The base oil typically has a viscosity of 1 to 4000 mm at 40°C. 2 kinematic viscosity per s (measured using a glass capillary viscometer).

[0047] The base oils used according to the present invention can be used alone or in mixtures thereof. Typically, the kinematic viscosity of the base oil to be used is adjusted to the preferred range described above.

[0048] Typical viscosity indices for base oils are 90-110 for mineral oils, 120-200 for synthetic hydrocarbon oils, 150-300 for polyalkylene glycols, 100-180 for ester oils, 190-500 for silicone oils, and 50-400 for perfluoroalkyl ether oils (PFPE oils).

[0049] It is preferred to use crude oil fractions containing alkanes, cycloalkanes and / or aromatics.

[0050] Synthetic oils are also preferred, especially polyalphaolefins, polyalkylene glycols, polyalkylene glycol ethers, dialkyl ethers, acetals, natural ester oils, perfluoropolyether oils, and silicone oils.

[0051] To achieve extended lubrication service life, it is particularly preferred to use at least 10% by weight of ester oil (especially polyol ester oil) based on the weight of the base oil.

[0052] In a further preferred embodiment, the base oil contains at least one substance belonging to at least one of Groups I to V according to the American Petroleum Institute (API) 1993 classification:

[0053] Group I: “Base substances containing less than 90% saturated compounds and / or more than 0.03% sulfur and with a viscosity index of at least 80 and at most 120.”

[0054] Group II: "Base material containing at least 90% saturated compounds and at most 0.03% sulfur and with a viscosity index of at least 80 and less than 120".

[0055] Group III: “Base material containing at least 90% saturated compounds and at most 0.03% sulfur and having a viscosity index of at least 120.”

[0056] Group IV: Synthetic oils produced from polyalphaolefins (PAO) with a viscosity index in the range of 125 to 200.

[0057] Group V: Any other type of base oil, such as naphthenic oils and esters.

[0058] The lubricants used according to the present invention typically contain thickeners, particularly soap thickeners.

[0059] In the context of this invention, the terms "thickener" and "thickening agent" may be used synonymously. Soap thickener is a specific form of thickener / thickening agent.

[0060] Suitable thickeners are known to those skilled in the art and are commercially available.

[0061] Examples of suitable thickeners include urea compounds, amide compounds, imide compounds, condensed aromatics such as indanthrene dyes, fluoropolymers, polyolefins, metal soaps, metal complex soaps, and inorganic substances such as silica gel, bentonite, carbon black, graphite, or silica aerogels.

[0062] Preferred thickeners are metal soaps or metal complex soaps derived from carboxylic acids, sulfonic acids, phosphoric acids and monovalent or polyvalent metal cations, particularly with aluminum, alkali metals (preferably lithium), alkaline earth metals, titanium and / or zirconium cations, or finely broken organic polymeric compounds, such as polytetrafluoroethylene, polyethylene or waxes.

[0063] Further preferred soap thickeners include lithium 12-hydroxystearate, lithium soap, lithium complex soap, aluminum soap, aluminum complex soap, calcium soap, and calcium complex soap.

[0064] Particularly preferred is that the soap thickener is lithium soap or lithium complex soap.

[0065] The lubricant according to the invention preferably contains about 2% to about 20% by weight of a thickener or a mixture of thickeners, based on the total weight of the lubricant in each case.

[0066] In each case, based on the total weight of the lubricant, the lubricant according to the invention particularly preferably contains about 2% to about 20% by weight of lithium soap or lithium complex soap or a combination thereof.

[0067] In another preferred embodiment, the lubricant comprises a thickener, particularly a soap thickener selected from the following: lithium soap, lithium complex soap, aluminum soap, aluminum complex soap, calcium soap, calcium complex soap, and any desired combination thereof.

[0068] In a particularly preferred embodiment, the lubricant comprises a soap thickener containing lithium soap or lithium complex soap or composed of lithium soap or lithium complex soap.

[0069] The lubricants used according to the present invention typically contain additives particularly selected from antioxidants, metal passivators, corrosion inhibitors, extreme pressure additives, anti-wear additives, solid lubricants, adhesive additives, dyes, and any desired combinations thereof.

[0070] In another preferred embodiment, the lubricant contains an amount of additive greater than 0% by weight to about 15% by weight, based on the total weight of the lubricant.

[0071] The lubricant according to the invention may contain one or more other optional additives.

[0072] Other suitable optional additives are known to those skilled in the art and are commercially available.

[0073] Suitable additives include antioxidants such as amines, phenols, sulfur compounds, and zinc dithiophosphate; rust inhibitors such as petroleum sulfonates, dinonylnaphthalene sulfonates, and sorbitol esters; lubricating additives such as fatty acids and vegetable oils; metal passivators such as benzotriazole and sodium sulfite; extreme pressure additives such as chlorine-, sulfur-, or phosphorus-containing inorganic compounds, zinc dithiophosphate, and organomolybdenum compounds; viscosity index improvers such as polymethyl methacrylate, polyisobutylene, and polystyrene; and solid lubricants such as polytetrafluoroethylene (PTFE), bentonite, tungsten disulfide, molybdenum disulfide, or other phosphates, oxides, sulfides, and sulfates with a layered structure.

[0074] The lubricant according to the invention preferably contains up to about 15% by weight of one or more additives, in each case based on the total weight of the lubricant.

[0075] In another preferred embodiment, the lubricant contains PI particles in an amount greater than 0% to about 15% by weight based on the total weight of the lubricant and / or the PI particles have a particle size D of up to 7 μm. 50 .

[0076] In another preferred embodiment, - The lubricant contains PI particles in an amount from greater than 0% by weight, or from about 0.25% by weight, in each case about 14% by weight, or about 13% by weight, or about 12% by weight, or about 11% by weight, or about 10% by weight, or about 9% by weight, or about 8% by weight, or about 7% by weight, or about 6% by weight, or about 5% by weight, or about 4% by weight, or about 3% by weight, in each case based on the total weight of the lubricant; and / or - The PI particles have a particle size D of at most 14 μm, at most 13 μm, at most 12 μm, at most 11 μm, at most 10 μm, at most 9 μm, at most 8 μm, at most 7 μm, at most 6 μm, at most 5.5 μm, or at most 5.25 μm. 50 ; and / or - Particle size D of PI particles 50 The size is at least 0.1 μm, at least 0.5 μm, at least 1.0 μm, at least 1.5 μm, at least 2.0 μm, at least 2.5 μm, or at least 3.0 μm.

[0077] In another preferred embodiment, - The PI particles have a particle size D of up to 7 μm. 50 And based on the total weight of the lubricant, the lubricant contains an amount of the PI particles from greater than 0% by weight to about 1% by weight; or - The PI particles have a particle size D of up to 12 μm. 50 Furthermore, based on the total weight of the lubricant, the lubricant contains PI particles in an amount ranging from more than about 1% by weight to about 3% by weight.

[0078] In another preferred embodiment, the lubricant contains PI particles in an amount ranging from greater than 0.8% to 1.2% by weight, based on the total weight of the lubricant.

[0079] In another preferred embodiment, the PI particles have a particle size D of up to 3.0 μm. 10 and / or a particle size D of up to 6.0 μm 50 and / or a particle size D of up to 13.0 μm 90and / or a particle size D of up to 47.0 μm 100 .

[0080] In another preferred embodiment, the particle size D 10 D 50 D 90 and / or D 100 In each case, the particle size is determined by laser diffraction analysis.

[0081] In another preferred embodiment, the particle size D 10 D 50 D 90 and / or D 100 In each case, it shall be determined in accordance with ISO 13320:2020.

[0082] In another preferred embodiment, the lubricant contains tetrafluoroethylene and / or polytetrafluoroethylene (PTFE) in an amount of up to about 1.0 wt% based on the total weight of the lubricant in each case, more preferably in an amount of 0 wt% based on the total weight of the lubricant in each case.

[0083] In another preferred embodiment, the lubricant contains a compound that releases toxic fluorine compounds formed by friction at high temperatures in an amount of up to about 1.0% by weight, more preferably 0% by weight, based on the total weight of the lubricant. Whether a temperature is considered high depends on the specific application of the lubricant and can be determined by those skilled in the art.

[0084] In another preferred embodiment, the coefficient of friction is determined by an MTM tribometer, preferably according to the experimental section of this application.

[0085] Appropriate procedures are known to those skilled in the art, for example from publications DE 10 2012 215145 and WO2012 / 123192 A1.

[0086] In another preferred embodiment, the wear / wear coefficient is determined by HFRR testing, preferably according to the experimental section of this application.

[0087] Suitable procedures are known to those skilled in the art, for example from publication WO 2012 / 123192 A1.

[0088] In another aspect, the present invention relates to the use of a lubricant according to the invention for lubrication between at least two surfaces, wherein at least one surface is non-metallic and is located in or on a vehicle and / or in or on a mechanical component.

[0089] In a preferred embodiment, the vehicle is an automobile and / or the mechanical component is a gear or bearing.

[0090] In another aspect, the present invention relates to a particle size D having a maximum of 15 μm or a maximum of 8 μm. 50 The PI particles are used to improve the tribological properties of the lubricant according to the invention (especially in terms of the coefficient of friction, wear and / or required lubrication between surfaces that interact and move relative to each other), the lubricant according to the invention being used for lubrication between at least two surfaces (where at least one surface is nonmetallic).

[0091] In a preferred embodiment, the number of (required) PI particles is determined by their proportion in the lubricant, preferably by their proportion in the lubricant as a percentage of the total weight of the lubricant.

[0092] The lubricant according to the invention can be used in a variety of applications. For example, the lubricant according to the invention can be a roller bearing grease, a high-temperature grease, a sliding bearing grease, a lubricant for food applications, a valve grease, an assembly grease, a contact lubricant, a semi-fluid grease (especially for transmissions), a high-speed grease, a high-pressure grease, a grease for plastic lubrication, or a long-life grease.

[0093] The lubricant according to the invention is particularly suitable for use in vehicles, gears, bearings, constant velocity joint shafts, roller bearings and transmissions. Experimental data The following examples are used to illustrate the present invention, but should not be considered as limiting.

[0094] To produce the lubricant of this invention, lithium grease (manufacturer: AXEL Christiernsson) was mixed with a corresponding proportion of PI particles at 2000 rpm for 5 minutes, without any additional additives. The lubricant was then discharged and used for testing.

[0095] Figure 3a and 3b In particular, it is shown that PI particles have roughly the same effect on the coefficient of friction as PTFE particles (5 μm), but do not exhibit the negative properties of the latter described in paragraph

[0010] . Figure 3a and 3b It also specifically demonstrates the reduction in the coefficient of wear caused by PI particles compared to grease without particles. like Figure 3a and 3b The results of the HFRR procedure shown are used according to Figure 2The equipment was determined using the following parameters: temperature: 80°C; contact pressure (GPa): 0.9; stroke (mm): 15; frequency (Hz): 15; test cylinder: AISI 52100; and test disc: AISI 52100.

Claims

1. Contains particles with a diameter of up to 15 μm D 50 Lubricant containing PI particles, Where the particle size D 50 Particle size was determined by laser diffraction particle size analysis, preferably according to ISO 13320:2020. The lubricant contains a thickener, preferably a soap thickener, and more preferably selected from lithium soap, lithium complex soap, aluminum soap, aluminum complex soap, calcium soap, calcium complex soap, and combinations thereof.

2. The lubricant according to claim 1, wherein the lubricant comprises a soap thickener containing lithium soap or lithium complex soap or composed of lithium soap or lithium complex soap.

3. The lubricant according to claim 1 or 2, wherein, Based on the total weight of the lubricant, the lubricant contains a thickener in an amount from about 2% to about 20% by weight, preferably a soap thickener.

4. The lubricant according to one or more of the preceding claims, wherein the lubricant comprises a base oil, preferably selected from mineral oils, synthetic oils, vegetable oils, and combinations thereof.

5. The lubricant of claim 4, wherein, based on the total weight of the lubricant, the lubricant contains an amount of the base oil from about 65% to about 90% by weight.

6. The lubricant according to one or more of the preceding claims, wherein the lubricant comprises an additive, the additive preferably selected from antioxidants, metal passivators, corrosion inhibitors, extreme pressure additives, anti-wear additives, solid lubricants, adhesive additives, dyes, and combinations thereof.

7. The lubricant of claim 6, wherein, based on the total weight of the lubricant, the lubricant contains an amount of the additive from greater than 0% to about 15% by weight.

8. The lubricant according to one or more of the preceding claims, wherein - Particle size D of PI particles 50 The values ​​are 5±4μm, 5±3μm, 5±2μm, or 5±1μm; or - The lubricant contains PI particles in an amount greater than 0% to about 15% by weight based on the total weight of the lubricant and / or the PI particles have a particle size D of up to 12 μm. 50 ; or - The lubricant contains PI particles in an amount greater than 0% to about 7% by weight based on the total weight of the lubricant and / or the PI particles have a particle size D of 2 μm to 8 μm. 50 ; or - The lubricant contains approximately 0.25% to approximately 3.5% by weight of PI particles based on the total weight of the lubricant, and / or the PI particles have a particle size D of 3 μm to 6 μm. 50 ; or - The lubricant is a grease, which preferably contains a soap thickener, the soap thickener being lithium soap or a lithium complex soap or composed of lithium soap or a lithium complex soap, and / or the grease contains PI particles, the amount of which is preferably from about 0.25% by weight to about 3.0% by weight based on the total weight of the grease, and / or the PI particles preferably have a particle size D of 3 μm to 5.5 μm. 50 .

9. The use of a lubricant as defined in one or more of the preceding claims for lubrication between at least two surfaces, preferably located in or on a vehicle and / or in or on a mechanical component.

10. The use according to claim 9, wherein, The vehicle is an automobile and / or the mechanical component is a gear or bearing.

11. The use according to claim 9 or 10, wherein - At least one surface is non-metallic; or - All surfaces contain metal or are composed of metal; or - All surfaces contain or are composed of plastic; or - All surfaces are non-metallic and contain or are composed of plastic; or - All surfaces contain or are composed of metal and do not contain plastic; or - At least one of the surfaces is non-metallic and contains or is composed of plastic, and at least one of the other surfaces contains or is composed of metal and does not contain plastic; or - At least two of the surfaces are non-metallic and contain or are composed of plastic, and at least two of the other surfaces contain or are composed of metal and do not contain plastic; or - There are exactly two surfaces, one of which contains plastic or is made of plastic, and the other of which contains metal or is made of metal.

12. The use according to claim 11, wherein the plastic in each case contains or is composed of polyetheretherketone (PEEK) and / or contains polyoxymethylene (POM) and / or is composed of UHMWPE and / or is composed of PA66 and / or is composed of PA66 and / or contains PA6G (cast polyamide 6) and / or is composed of PA6G and / or contains PA12G (cast polyamide 12) and / or is composed of PA12G and / or contains PPA or is composed of PPA.

13. Having a particle size D of up to 15 μm, preferably up to 8 μm or up to 6 μm. 50 PI particles are used to improve the tribological properties of a lubricant as defined in one or more of claims 1 to 8, and for lubrication between at least two surfaces as defined in one or more of claims 9 to 12.

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