Paek fine powder as lubricant additives

Abstract

The invention relates to PAEK particles as lubricant additives.

Description

[0001] The invention relates to the use of PAEK particles as lubricant additives, in particular lubricating grease additives.

[0002] The generic term polyaryletherketone (PAEK) refers to a family of high-performance polymers with distinct thermomechanical properties. These polymers contain aromatic rings connected by an oxygen atom (ether) and / or a carbonyl group (ketone). Their properties depend primarily on the ether / ketone ratio. In the abbreviations used to designate members of the PAEK family, the letter "E" denotes an ether function and the letter "K" denotes a ketone function. In the remainder of this description, these abbreviations will be used, where appropriate, instead of the usual names to designate the compounds to which they refer.

[0003] The PAEK family includes in particular polyether ketone (PEK), polyether ether ketone (PEEK), polyether ether ketone ketone (PEEKK), polyether ketone ketone (PEKK), poly-ether-ketone-ether-ketone-ketone (PEKEKK), poly-ether-ether-ketone-ether-ketone (PEEKEK), poly-ether-ether-ether-ketone (PEEEK) and Polyether diphenyl ether ketone (PEDEK).

[0004] PAEKs preferably comprise units of the following formulas: (-Ar-X-) and (-Ar 1 -Y-), where Ar and Ar 1 each denote a divalent aromatic radical; Ar and Ar 1 can preferably be selected from the group consisting of 1,3-phenylene, 1,4-phenylene, 4,4'-biphenylene, 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene; X denotes an electron-withdrawing group; it can preferably be selected from the carbonyl group and the sulfonyl group; Y denotes a group selected from an oxygen atom, a sulfur atom, an alkylene group (such as -CH 2 -) and isopropylidene.

[0005] In a preferred embodiment, at least 50%, preferably at least 70% and in particular at least 80% of the X groups are carbonyl groups and at least 50%, preferably at least 70% and in particular at least 80% of the Y groups are oxygen atoms.

[0006] According to a further preferred embodiment, 100% of the groups X represent a carbonyl group and 100% of the groups Y represent an oxygen atom.

[0007] In a preferred embodiment, the PAEK particles are PEKK particles and preferably contain structural units of the formulas Ia, Ib and / or mixtures thereof:

[0008] In a preferred embodiment, the PAEK particles are PEEK particles and preferably contain structural units of the formula IIa: The PEEK particles may contain para sequences of formula IIb: The sequence can be completely para, but it is also possible to introduce partial or complete meta sequences according to formulas (III) and / or (IV): or ortho sequences according to formula V

[0009] In a preferred embodiment, the PAEK particles are PEK particles and preferably contain structural units of the formula VI: The sequence can be completely para, but it is also possible to introduce partial or complete meta sequences (formulas VII and VIII):

[0010] In a preferred embodiment, the PAEK particles are PEEKK particles and preferably contain structural units of the formula IX:

[0011] In a preferred embodiment, the PAEK particles are PEEEK particles and preferably contain structural units of the formula X: It is possible to introduce metasequences into these structures at the ethers and ketones, but also biphenol sequences according to formula XI:

[0012] The indices "x", "y" and "n" are each preferably an integer of at least 50 or at least 100, preferably in the range of 150 to 950, particularly preferably in the range of 150 to 500.

[0013] The radical "*" is preferably -H; -C 1-10 -alkyl, branched or unbranched, unsubstituted; or -aryl, unsubstituted or mono- or disubstituted with -C 1-10 -alkyl or -OC 1-10 -alkyl, in each case branched or unbranched, unsubstituted.

[0014] PAEK powders are known to those skilled in the art and are commercially available.

[0015] Lubricants, especially greases and oils, are well-known and widely used. Lubricating greases, sometimes also referred to as "fats," are solid to semi-liquid substances created by dispersing a thickener in a liquid lubricant (base fluid). They may also contain other additives that impart special properties.

[0016] The basic consistency of a lubricating grease is determined by the combination of base fluid and thickener. The base fluid is usually a base oil commonly used in the lubricant industry, such as mineral oil, synthetic oil, or vegetable oil.

[0017] Alkali metal or alkaline earth metal soaps are used as thickeners. Non-soap-based thickeners, such as bentonite (clay-based) or polyurea, are also known.

[0018] Lubricants, especially greases and lubricating oils, can be produced in batch processes or by continuous processes.

[0019] Lubricants and their manufacturing processes are known from the state of the art and are commercially available in numerous compositions.

[0020] The lubrication of machine elements (e.g. gears or bearings) presents a particular challenge with regard to wear and friction. For this reason, various additives are used in lubricants, particularly lubricating greases and lubricating oils, to improve or meet these two main properties, among others. The tribological contact is also influenced by the friction partners. This can be an inorganic contact (e.g. steel / steel), an organic contact (e.g. plastic / plastic), or a mixed contact (e.g. steel / plastic). The additives used must therefore be tailored to this tribological pairing. In other words: different tribological pairings (metal / metal, metal / plastic, plastic / plastic, etc.) require different lubricant properties. To date, optimized lubricants are not available for all pairings.

[0021] Publication JP 2002 / 363589 discloses PTFE powder as a thickener in lubricants. Commercially available products include Algoflon® and "Xeon" PTFE waxes.

[0022] PTFE contains fluorine and is used in relatively large quantities in lubricants (15-40%). Toxic fluorine compounds may be formed at high temperatures caused by friction. Furthermore, PFOA (perfluorooctanoic acid) and other PFAS (per- and polyfluorinated alkyl compounds), which have since been banned, are minor components that are / were present in small quantities in PTFE. PFOA-free PTFE is now available, but a ban on PTFE is also being discussed in the EU (German Federation for the Environment and Nature Conservation, "Practical, durable, 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 on the tribological behavior in metal / plastic or plastic / plastic friction pairings.

[0023] Publications GB 2 192 896 B, US 4,787,993, and JPS 63-172794 disclose PEEK or PI (polyimide) powders as additives for lubricants. However, only the effect on metal-to-metal friction pairs was investigated. Commercially available products based on these additives are not known.

[0024] The current lubricants are therefore unsatisfactory. The challenge is therefore to provide lubricants that offer advantages over the current lubricants.

[0025] This problem is solved by the subject matter of the patent claims.

[0026] It was surprisingly found that with PAEK powders, i.e. polyaryletherketone powders, of a certain particle size for the aforementioned contact pairs, a significant reduction in the wear and / or friction coefficient can be achieved.

[0027] By adding small amounts, especially in the range of 0.5-2 wt.% of PAEK fine powder with an average particle size D 50 of up to 20 µm, the tribological properties of lubricants, especially lubricating greases, can be improved.

[0028] Based on MTM (Mini Traction Machine) values, it was shown that a lubricant containing PAEK particles of a certain size has advantages over a conventional lubricant preparation in the plastic / metal system both at room temperature (RT) and at elevated temperatures of 100°C.

[0029] Furthermore, it was surprisingly found that the ability of the lubricant to retain the base oil depends on the size of the PAEK particles.

[0030] PAEK-modified lubricants according to the invention can be used in a variety of applications. One primary application is the automotive sector. Another application is the lubrication of machine components (e.g., gears or bearings) in various industries.

[0031] PAEK fine powders are produced, for example, by cryogenic grinding of coarse powders. The resulting PAEK fine powders are then dispersed in lubricants, particularly lubricating greases, using commercially available dispersing equipment such as planetary mixers.

[0032] The PAEK polymer PEEK is a thermally very stable polymer and exhibits significantly lower creep behavior than PTFE.

[0033] Figure 1shows the particle size distribution in a first PEEK powder, measured by laser diffraction particle size analysis. The D 10 value is 2.0 µm, the D 50 value is 7.5 µm, the D 90 value is 15.5 µm, and the D 100 value is 97.5 µm.

[0034] Figure 2 shows the particle size distribution in a second PEEK powder, measured by laser diffraction particle size analysis. The D 10 value is 3.4 µm, the D 50 value is 10.1 µm, the D 90 value is 18.5 µm, and the D 100 value is 111.0 µm.

[0035] Figure 3 shows a comparison of the lubricating effect between a grease according to the invention and a comparison grease.

[0036] Figure 4 shows the dependence of the coefficient of friction (CoF) on the composition of the lubricating grease.

[0037] Figure 5 shows a device for performing an HFRR (high frequency reciprocating rig) method.

[0038] In a first aspect, the invention relates to the use of a lubricant, preferably a lubricating grease, which contains PAEK particles with a particle size D 50 of up to 20 µm (ie a PAEK powder or PAEK ultrafine powder), for lubricating between at least two surfaces, of which at least one surface is non-metallic.

[0039] The PAEK particles are preferably selected from the group consisting of PEK particles, PEEK particles, PEEKK particles, PEKK particles, PEKEKK particles, PEEKEK particles, PEEEK particles, PEDEK particles and optionally mixtures thereof.

[0040] The PAEK particles are particularly preferably selected from the group consisting of PEEK particles, PEK particles, PEKK particles and, if appropriate, mixtures thereof.

[0041] The PAEK particles are still particularly preferred PEEK particles.

[0042] In a further preferred embodiment, the PAEK particles are either PEK particles or PEKK particles.

[0043] For the purposes of the invention, a lubricating grease can be understood as a lubricant, lubricant, or lubricating material. These terms can be used synonymously.

[0044] In a preferred embodiment, the lubricant according to the invention is a lubricating grease.

[0045] In a preferred embodiment, the lubricant according to the invention is not to be regarded as a lubricating oil.

[0046] In a preferred embodiment, at least two surfaces, particularly preferably all surfaces of possible friction partners, border on one another, ie they have a common contact surface.

[0047] For the purposes of the invention, "non-metallic" preferably means that the corresponding surface contains at most 5 wt.% of metals, based on the total weight of the surface, and particularly preferably contains 0 wt.% of metals, based on the total weight of the surface.

[0048] If at least one of the surfaces is metallic or metal-based, the metal is preferably selected from the group consisting of aluminum, zinc, copper, gold, silver, and platinum. Compositions, especially alloys, based on the aforementioned metals are also possible.

[0049] In a preferred embodiment, at least one of the non-metallic surfaces contains or consists of plastic and at least one of the remaining surfaces contains or consists of metal, or exactly two surfaces are present, wherein one of the surfaces contains or consists of plastic and the other of the surfaces contains or consists of metal.

[0050] Suitable plastics include, for example, thermoplastics, thermosets, and elastomers known to those skilled in the art. Preferably, at least one of the non-metallic surfaces contains or consists of polyetheretherketone (PEEK), and / or polyoxymethylenes (POM), and / or UHMWPE (ultra-high molecular weight polyethylene with a molecular mass of preferably 3.5 to 7.5 million g / mol), and / or PA66, and / or PA6G (cast polyamide 6), and / or PA12G (cast polyamide 12), and / or PPAs. PPAs are "semi-aromatic" nylon-type polyamides, i.e., either aromatic diamine or aromatic diacid.

[0051] Preferably, the particle size D50 is determined using laser diffraction particle size analysis. The particle size D50 is preferably determined according to ISO 13320:2020. One possible system for determining the particle size D50 is laser diffraction in an aqueous system with a dispersant. A suitable measurement device is the Malvern Mastersizer 3000.

[0052] The lubricant used according to the invention usually contains a base oil which is preferably selected from the group consisting of mineral oils, synthetic oils, vegetable oils and any combination of two or more of these oils.

[0053] In a preferred embodiment, the lubricant contains the base oil in an amount of about 65 wt.% to about 90 wt.%, based on the total weight of the lubricant.

[0054] For the purposes of the present invention, the terms "base oil" and "base oil" can be used synonymously.

[0055] Suitable base oils are known to those skilled in the art and are commercially available.

[0056] Any known materials commonly used in the manufacture of lubricants can be used as base oils. Examples include mineral oils, lubricating oils of vegetable or animal origin, or synthetic oils. The latter include, in particular, hydrocarbon oils, including halogenated hydrocarbon oils, as well as non-hydrocarbon oils such as polyalkylene glycols, polyether oils, ester oils such as oils based on phosphoric acid esters, and silicone oils. Compound oils, such as mixtures of mineral oils and synthetic oils, can also be used as base oils. Mixtures of different base oils can also be used.

[0057] Examples of base oils include lubricating oils made from mineral oils, synthetic oils, and natural oils. Mineral lubricating oils include mineral oils that have been purified through 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.

[0058] Other examples of base oils are synthetic lubricating oils. These include hydrocarbon oils, aromatic oils, ester oils, and ether oils. Hydrocarbon oils include poly-alpha-olefins, such as n-paraffins, isoparaffins, polybutene, polyisobutylene, 1-decene oligomers, 1-decene / ethylene co-oligomers, and hydrogenation products thereof. Aromatic oils include alkylbenzenes, e.g., mono-, di-, or polyalkylbenzenes; and alkylnaphthalenes, such as mono-, di-, or polyalkylnaphthalenes.The ester oils include di-, tri-, or tetraesters of carboxylic acids, such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, methyl acetyllicinolate, trioctyl trimesitate, tridecyl trimesitate, and tetraoctyl pyrromelitate; or they include polyol esters of carboxylic acids, such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, and pentaerythritol pelargonate; or they include complex esters, which are oligoesters between a polyhydroxy alcohol and a mixed mono- or dibasic fatty acid. The ether oils include polyglycols, such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether. as well as phenyl ethers, such as alkylated diphenyl, triphenyl and polyphenyl ethers of varying degrees of alkylation, or dialkyl ethers.Furthermore, phosphoric acid esters such as tricresyl phosphate, silicone oils and perfluoroalkyl ether oils (fluorine oils) can be used as synthetic oils.

[0059] The base oils used in the invention are not subject to any specific restrictions, and any base oil commonly used in lubricating oils and greases can be used. Base oils typically have a kinematic viscosity of 1 to 4000 mm² / s at 40°C (determined using a glass capillary tube viscometer).

[0060] The base oils used in the present invention can be used either individually or in the form of a mixture thereof. The kinetic viscosity of the base oils to be used is usually adjusted to the preferred range specified above.

[0061] Typical viscosity indices of base oils are in the range of 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).

[0062] Petroleum fractions containing paraffinic, naphthenic and / or aromatic hydrocarbons are preferably used.

[0063] Synthetic oils, in particular poly-alphaolefins, polyalkylene glycols, polyalkylene glycol ethers, dialkyl ethers, acetals, natural ester oils, perfluoropolyether oils and silicone oils are also preferred.

[0064] To achieve an extended lubrication life, it is particularly preferred to use at least 10% by weight, based on the weight of the base oil, of an ester oil (in particular a polyol ester oil).

[0065] In a further preferred embodiment, the base oil contains at least one substance according to at least one of groups I to V according to the classification of American Petroleum Institute (API) from 1993: Group I: "Base stocks containing less than 90 percent saturates and / or more than 0.03 percent sulfur and a viscosity index of at least 80 and a maximum of 120." Group II: "Base stocks containing at least 90 percent saturates and a maximum of 0.03 percent sulfur, and a viscosity index of at least 80 and less than 120." Group III: "Base stocks containing at least 90 percent saturates and a maximum of 0.03 percent sulfur, and a viscosity index of at least 120." Group IV: Synthetic oils made from polyalphaolefins (PAO) with a viscosity index in the range of 125 to 200. Group V: Any other type of base oil, e.g., naphthenic oils and esters.

[0066] The lubricant used according to the invention usually contains a thickener, in particular a soap thickener.

[0067] For the purposes of the present invention, the terms "thickener" and "thickening agent" can be used synonymously. A soap thickener is a specific form of a thickener.

[0068] Suitable thickeners are known to the person skilled in the art and are commercially available.

[0069] Examples of suitable thickeners are urea compounds, amide compounds, imide compounds, condensed aromatic hydrocarbons such as indanthrene dyes, fluoropolymers, polyolefins, metal soaps, metal complex soaps, and inorganic substances such as silica gels, bentonites, carbon blacks, graphites or aerosils.

[0070] Preferred thickeners are metal soaps or metal complex soaps derived from carboxylic acids, sulfonic acids, phosphoric acids, with mono- or polyvalent metal cations, in particular with aluminum, alkali metal (preferably lithium), alkaline earth metal, titanium, and / or zirconium cations, or finely divided organic polymeric compounds, such as polytetrafluoroethylene, polyethylene or waxes.

[0071] Other preferred soap thickeners are lithium 12-hydroxystearate, lithium soaps, lithium complex soaps, aluminum soaps, aluminum complex soaps, calcium soaps and calcium complex soaps.

[0072] The soap thickener is particularly preferably a lithium soap or a lithium complex soap.

[0073] The lubricant according to the invention preferably contains about 2% by weight to about 20% by weight of a thickener or a mixture of thickeners, in each case based on the total weight of the lubricant.

[0074] The lubricant according to the invention particularly preferably contains about 2% to about 20% by weight of a lithium soap or a lithium complex soap or a combination thereof, in each case based on the total weight of the lubricant.

[0075] In a further preferred embodiment, the lubricant contains a thickener, in particular a soap thickener selected from the group consisting of lithium soaps, lithium complex soaps, aluminum soaps, aluminum complex soaps, calcium soaps, calcium complex soaps and any combinations thereof.

[0076] In a particularly preferred embodiment, the lubricant contains a soap thickener which contains or consists of a lithium soap or a lithium complex soap.

[0077] The lubricant used according to the invention usually contains an additive, in particular selected from the group consisting of antioxidants, metal deactivators, corrosion inhibitors, extreme pressure additives, wear protection additives, solid lubricants, adhesion additives, dyes and any combinations thereof.

[0078] In a further preferred embodiment, the lubricant contains the additive in an amount of more than 0 wt.% up to about 15 wt.%, based on the total weight of the lubricant.

[0079] The lubricant according to the invention may contain one or more further optional additives.

[0080] Suitable additional optional additives are known to the person skilled in the art and are commercially available.

[0081] Useful additives include antioxidants such as amines, phenols, sulfur compounds, and zinc dithiophosphate; rust inhibitors such as petroleum sulfonates, dinonyl naphthalene sulfonate, and sorbitan esters; lubricity-enhancing additives such as fatty acids and vegetable oils; metal deactivators 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 polymethacrylate, polyisobutylene, and polystyrene; and solid lubricants such as polytetrafluoroethylene ("PTFE"), bentonites, tungsten disulfide, molybdenum disulfide, or other layered phosphates, oxides, sulfides, and sulfates.

[0082] The lubricant according to the invention preferably contains up to about 15% by weight of one or more additives, each based on the total weight of the lubricant.

[0083] In a further preferred embodiment, the lubricant contains the PAEK particles in an amount of more than 0 wt.% up to about 15 wt.%, based on the total weight of the lubricant.

[0084] In a further preferred embodiment, the lubricant contains PAEK particles with a particle size D 50 of up to 12 µm, preferably up to 8 µm, particularly preferably up to 7 µm.

[0085] In a further preferred embodiment the lubricant contains the PAEK particles in an amount of more than 0 wt.% or of about 0.25 wt.%, up to about 14 wt.% or up to about 13 wt.% or up to about 12 wt.% or up to about 11 wt.% or up to about 10 wt.% or up to about 9 wt.% or up to about 8 wt.% or up to about 7 wt.% or up to about 6 wt.% or up to about 5 wt.% or up to about 4 wt.% or up to about 3 wt.-%, in each case based on the total weight of the lubricant; and / or the PAEK particles have a particle size D 50 of up to 17 µm or of up to 16 µm or of up to 15 µm or of up to 14 µm or of up to 13 µm or of up to 12 µm or of up to 11 µm or of up to 10 µm or of up to 9 µm or of up to 8 µm or of up to 7 µm or of up to 6 µm or of up to 5.5 µm; and / or the PAEK particles have a particle size D 50 of at least 0.1 µm or at least 0.5 µm or at least 1.0 µm or at least 1.5 µm or at least 2.0 µm or at least 2.5 µm or at least 3.0 µm.

[0086] In a further preferred embodiment the PAEK particles have a particle size D 50 of up to 7 µm and the lubricant contains the PAEK particles in an amount of more than 0 wt.% up to about 1 wt.%, based on the total weight of the lubricant; or the PAEK particles have a particle size D 50 of up to 12 µm and the lubricant contains the PAEK particles in an amount of more than about 1 wt.% up to about 3 wt.%, based on the total weight of the lubricant.

[0087] In a further preferred embodiment, the lubricant contains the PAEK particles in an amount of less than 0.8 wt.% and / or more than 1.2 wt.%, based on the total weight of the lubricant.

[0088] In a further preferred embodiment, the PAEK particles have a particle size D 10 of up to 3.0 µm, and / or a particle size D 50 of up to 6.0 µm, and / or a particle size D 90 of up to 13.0 µm and / or a particle size D 100 of up to 47.0 µm.

[0089] The definitions of paragraphs

[0088] to

[0093] are applicable accordingly if the PAEK particles are selected from the group consisting of PEK particles, PEEK particles, PEEKK particles, PEKK particles, PEKEKK particles, PEEKEK particles, PEEEK particles, PEDEK particles and / or mixtures thereof.

[0090] The particle size D 10 , D 50 , D 90 and / or D 100 is preferably determined by laser diffraction particle size analysis, preferably in accordance with ISO 13320:2020.

[0091] In a further preferred embodiment, the lubricant contains tetrafluoroethylene and / or polytetrafluoroethylene (PTFE) in an amount of at most about 1.0 wt.%, each based on the total weight of the lubricant. Particularly preferably, the lubricant does not contain tetrafluoroethylene and / or polytetrafluoroethylene (PTFE).

[0092] In a further preferred embodiment, the lubricant contains compounds that release toxic fluorine compounds at high temperatures generated by friction, in an amount of at most about 1.0 wt.%, based on the total weight of the lubricant. Particularly preferably, the lubricant contains no compounds that release toxic fluorine compounds at high temperatures generated by friction. When a temperature is considered high depends on the specific application of the lubricant and can be determined by a person skilled in the art.

[0093] In a further preferred embodiment, the coefficient of friction is determined by an MTM tribometer or an MTM (Mini Traction Machine), preferably carried out according to the experimental part of the present application.

[0094] Corresponding methods are known to the person skilled in the art, for example from the publications DE 10 2012 215145 and WO 2012 / 123192 A1.

[0095] In a further preferred embodiment, the wear or wear coefficient is determined via the HFRR test, preferably carried out according to the experimental part of the present application.

[0096] Corresponding methods are known to the person skilled in the art, for example from the publication WO 2012 / 123192 A1.

[0097] In a further aspect, the invention relates to a use of a lubricant according to the invention for lubricating between at least two surfaces, at least one of which is non-metallic, and which are located in or on a vehicle and / or in or on a machine element.

[0098] In a preferred embodiment, the vehicle is an automobile and / or the machine element is a gear or bearing.

[0099] In a further aspect, the invention relates to a use of PAEK particles having a particle size D 50 of up to 20 µm or up to 12 µm or up to 8 µm or up to 6 µm for improving tribological properties (in particular with regard to the coefficient of friction, the wear and / or the required lubrication between mutually interacting surfaces in relative motion) of a lubricant according to the invention for lubricating between at least two surfaces, of which at least one is non-metallic.

[0100] In a preferred embodiment, the number of (required) PAEK particles is determined via their proportion in the lubricant, preferably via their proportion in the lubricant in wt.%, based on the total weight of the lubricant.

[0101] The lubricants according to the invention can be used in a wide variety of applications. For example, the lubricant according to the invention can be a rolling bearing grease, high-temperature grease, plain bearing grease, lubricant for food applications, fitting grease, assembly grease, contact lubricant, fluid grease (especially for gears), high-speed grease, extreme pressure grease, grease for plastics lubrication, or long-life grease.

[0102] The lubricants according to the invention are particularly suitable for use in or for vehicles, gears, bearings, constant velocity joints, rolling bearings and transmissions. Experimental data

[0103] The following examples serve to illustrate the invention but are not to be construed as limiting.

[0104] Fretting and HFRR tests were conducted in steel contact. The HFRR test (lower pressures) demonstrated advantages for PEEK particles in wear and in the CoF. The following tests were conducted in an MTM experiment on two different greases containing PEEK powders (+ Fuchs reference grease): Medium: Special grease from Fuchs: 1.5 wt.% PEEK 10µm in Li-complex soap (manufacturer INS - Innovation Nanomaterials & Strategy); 0.5 wt.% PEEK 5µm in Li-complex soap (manufacturer INS). Disc material: VESTAKEEP ®< L 4000 G, Tarnoform 300M, steel 100Cr6. MTM-Stribeck curve (recording of the friction coefficient over the speed profile 5-2200 mm / s) Parameters: Force: 30N SRR (Sliding Roll Ratio): 25% Temperature: 25 and 100°C Medium: Grease A duplicate determination was carried out with 3 Stribeck curves each, and an average value was calculated from a total of 6 Stribeck curves. Result: Advantages of PEEK powders in grease compared to a fully formulated special grease from Fuchs are shown for a VESTAKEEP ®< L 4000 G(disk) / steel(100Cr6 ball) pairing.

[0105] Figure 3shows that a grease with PEEK particles (0.5 wt.% / 5 µm) shows advantages in terms of reducing the coefficient of friction (CoF) compared to a special grease from Fuchs (Fuchs grease Renolit MP as standard reference; standard EP multi-purpose grease) in an MTM measurement (coefficient of friction versus speed (so-called Stribeck curve), ball on disc) for a plastic (PEEK disc) / metal (100Cr6 ball) pairing.

[0106] Figure 4 shows the dependence of the coefficient of friction (CoF) on the underlying lubricating grease. The line illustrates the coefficient of friction. With PEEK grease, a reduction in the coefficient of friction and the wear coefficient (bar) occurs.

[0107] The PTFE additives only reduced the wear coefficient. This was surprising, as experts would expect a reduction in the friction coefficient for PTFE.

[0108] The determination of the results of the HFRR procedure according to Figure 4 was carried out using the device according to Figure 5 and at 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.

[0109] The following table shows further advantages, especially of PEEK powders (5 µm; 3 wt%) in Li-lubricating grease: Fat particles Oil separation Unworked NLGI Grade Drop Point (°C) (30 h, 100 °C) (wt%) Penetration (*0.1 mm) Li - 2.48 269 2 204 Li PEEK 5 µm (3 wt%) 0.53 265 2 204 Li PEEK 10 µm (3 wt%) 1.38 281 2 204 Li PTFE 5µm (1.5 wt%) 1.36 277 2 204 The smaller the value of "oil separation" under these conditions, the less oil is lost from the Li-grease matrix, i.e. the better oil is stored. The oil separation value for PEEK powders (5 µm; 3 wt%) is lower than for other PEEK powders (10 µm; 3%) and for PTFE powders (5 µm; 1.5 wt%). Therefore, the inventive PEEK powder (5 µm; 3 wt%) shows a better oil storage ability than other PEEK powders (10 µm; 3%) and PTFE powders (5 µm; 1.5 wt%).

Claims

1. Use of a lubricant containing PAEK particles with a particle size D 50 of up to 20 µm, for lubrication between at least two surfaces, at least one of which is non-metallic.

2. The use according to claim 1, wherein - at least one of the non-metallic surfaces contains or consists of plastic and at least one of the remaining surfaces contains or consists of metal; or - at least two of the non-metallic surfaces contain or consist of plastic and at least two of the remaining surfaces contain or consist of metal; or - all of the non-metallic surfaces contain or consist of plastic and all of the remaining surfaces contain or consist of metal; or - there are exactly two surfaces, one of the surfaces containing or consists of plastic and the other of the surfaces containing or consists of metal.

3. The use according to claim 2, wherein the plastic contains or consists of polyetheretherketone (PEEK), and / or contains or consists of polyoxymethylenes (POM), and / or contains or consists of UHMWPE (ultra-high molecular weight polyethylene), and / or contains or consists of PA66, and / or contains or consists of PA6G (cast polyamide 6), and / or contains or consists of PA12G (cast polyamide 12), and / or contains or consists of PPAs.

4. The use according to one or more of the preceding claims, wherein the particle size D 50 determined by laser diffraction particle size analysis, preferably according to ISO 13320:2020.

5. The use according to one or more of the preceding claims, wherein the lubricant contains a thickener, preferably a soap thickener, preferably selected from the group consisting of lithium soaps, lithium complex soaps, aluminum soaps, aluminum complex soaps, calcium soaps, calcium complex soaps and combinations thereof.

6. The use according to claim 5, wherein the lubricant contains a soap thickener which contains or consists of a lithium soap or a lithium complex soap.

7. The use according to claim 5 or 6, wherein the lubricant contains the thickener, preferably the soap thickener, in an amount of about 2% to about 20% by weight, based on the total weight of the lubricant.

8. The use according to one or more of the preceding claims, wherein the lubricant contains a base oil, preferably selected from the group consisting of mineral oils, synthetic oils, vegetable oils and combinations thereof.

9. The use according to claim 8, wherein the lubricant contains the base oil in an amount of about 65% to about 90% by weight, based on the total weight of the lubricant.

10. The use according to one or more of the preceding claims, wherein the lubricant contains an additive, preferably selected from the group consisting of antioxidants, metal deactivators, corrosion inhibitors, extreme pressure additives, anti-wear additives, solid lubricants, adhesion additives, dyes and combinations thereof.

11. The use according to claim 10, wherein the lubricant contains the additive in an amount of more than 0 wt.% up to about 15 wt.%, based on the total weight of the lubricant.

12. The use according to one or more of the preceding claims, wherein - the PAEK particles have a particle size D 50 of 5±4 µm, 5±3 µm, 5±2 µm, or 5±1 µm; or - the PAEK particles have a particle size D 50 of 10±4 µm, 10±3 µm, 10±2 µm, or 10±1 µm; or - the lubricant contains the PAEK particles in an amount of more than 0 wt.% up to about 15 wt.%, based on the total weight of the lubricant, and / or the PAEK particles have a particle size D 50 of up to 12 µm; or - the lubricant contains the PAEK particles in an amount of more than 0 wt.% up to about 7 wt.%, based on the total weight of the lubricant, and / or the PAEK particles have a particle size D 50from 2 µm to 12 µm, preferably from 2 µm to 8 µm; or - the lubricant contains the PAEK particles in an amount of about 0.25 wt.% to about 3.5 wt.%, based on the total weight of the lubricant, and / or the PAEK particles have a particle size D 50 from 3 µm to 12 µm, preferably from 4 µm to 11 µm, particularly preferably from 4 µm to 6 µm; or - the lubricant is a lubricating grease, which preferably contains a soap thickener which contains or consists of a lithium soap or a lithium complex soap, and / or the lubricating grease contains the PAEK particles preferably in an amount of about 0.25 wt.% to about 3.0 wt.%, based on the total weight of the lubricating grease, and / or the PAEK particles preferably have a particle size D 50 from 3 µm to 5.5 µm.

13. The use according to one or more of the preceding claims, wherein - the PAEK particles are selected from the group consisting of PEK particles, PEEK particles, PEEKK particles, PEKK particles, PEKEKK particles, PEEKEK particles, PEEEK particles, PEDEK particles, and mixtures thereof; preferably from the group consisting of PEEK particles, PEK particles, PEKK particles, and mixtures thereof; or - the PAEK particles are PEEK particles.

14. Use of a lubricant as defined in one or more of the preceding claims for lubricating between at least two surfaces as defined in one or more of the preceding claims and which are located in or on a vehicle and / or in or on a machine element, wherein the vehicle is preferably an automobile and / or the machine element is preferably a gear or bearing.

15. Use of PAEK particles with a particle size D 50of up to 20 µm, preferably up to 12 µm or up to 8 µm or up to 6 µm, for improving tribological properties of a lubricant, preferably with regard to the coefficient of friction, the wear and / or the required lubrication between mutually interacting surfaces in relative motion, as defined in one or more of claims 1 to 13, for the lubrication between at least two surfaces, as defined in one or more of claims 1 to 13.

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