WO2012104313A1 - Method for forming a thickened lubricant and thickened lubricant formed thereby - Google Patents

Abstract

A method for forming a thickened lubricant, such as a grease, comprises forming polymer fibres having a diameter between 50 nanometres and 10 microns, more preferably between 100 nanometres and 1 micron, and depositing the polymer fibres into a lubricating fluid. The polymer fibres may be immediately deposited into the lubricating fluid upon being formed, such that the polymer fibres remain un-adhered to each other and the lubricating fluid rapidly cools the polymer fibres. A thickened lubricant formed according to this method is also disclosed.

Description

METHOD FOR FORMING A THICKENED LUBRICANT AND

THICKENED LUBRICANT FORMED THEREBY

CROSS-REFERENCES

The present application claims priority to U.S. patent application no. 61/438,462 filed on 1 February 2011 and U.S. patent application no. 61/487,343 filed on 18 May 2011, the contents of which are fully incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method for making thickened lubricants, e.g., greases, and thickened lubricants or greases formed thereby.

BACKGROUND

US 6,482,780 discloses a grease composition for a roller bearing comprising a metal soap- based thickening agent containing a long fibre-like material having a major axis length of at least 3 microns incorporated in a base oil comprising a lubricant having a polar group in its molecular structure and a non-polar lubricant blended in combination.

US 5,415,791 discloses a lubricating composition for solid lubricant-embedded sliding members comprising 5 to 78% by weight of a solid lubricant powder material, 5 to 30% by weight of a lubricating oil which is in a liquid or paste form at ordinary temperatures, 1 to 15%) by weight of a carrier for absorbing and retaining said lubricating oil, and 15 to 50% by weight of a thermosetting synthetic resin binder. The carrier may be an oleophilic fibre, such as cellulose fibre and polypropylene fibre.

US 4,370, 114 discloses a spinneret assembly for use in making "island-in-the-sea" materials, which comprise fibres (islands or cores) disposed or embedded in a polymer matrix (sea or sheath). Polymeric non-woven mats or fabrics are typically produced from a hot polymer melt according to well-known melt-blowing or electro-spinning techniques. In this case, the resulting fibres generally form a non-woven mat at relatively high temperatures, because the fibres partially melt to form bonds between them, thereby adhering the fibres. SUMMARY OF THE INVENTION

However, in order to make a thickened lubricant or grease using such polymeric non- woven mats, it would be necessary to destroy many of these bonds, which is a destructive process. That is, by breaking (chopping) up the mat structure, small (e.g., about 1-10 microns) networks of fibres will result, in which one fibre only ever belongs to one small 'particle-like' fibrous globular network. Consequently, using such a technique, it would not be possible to form an integral (continuous) three-dimensional structure, such as an integral structure typically found in conventional soap-based greases or the existing polymer grease technology.

On the other hand, the handling of dry, loose fibres having lengths less than 10 microns can lead to airborne particles (dusts) that are dangerous to the respiratory system. It is one object of the present disclosure to solve one or more problems of the known art.

This object is achieved by the method of claim 1, the lubricant of claim 14 and the method of claim 18. Further developments of the invention(s) are recited in the dependent claims. In one preferred embodiment of the present teachings, methods are taught for producing polymer fibres having a diameter less than 10 microns, and preferably greater than 50 nanometres, and immediately depositing the just-formed polymer fibres in a lubricating fluid to form a thickened lubricant. This method eliminates the need to extensively handle dry (loose) polymeric fibrous materials to prepare thickened lubricants or greases and hence provide a safer material to work with.

In another aspect of the present teachings, a thickened lubricant, such as a grease or a solid oil, may be prepared by dispersing such fibres or fibrous network in an oil or other lubricating fluid so that the resulting lubricant will have a structured three-dimensional network, which is able to retain and also release the lubricating fluid, e.g., an oil. This structure can be created by using nano- and/or micro-polymer fibres that are produced prior to the formation of the lubricant or grease. As a result, the polymer fibres thicken the oil or lubricating fluid, and/or increase the viscosity thereof, and form advantageous three- dimensional networks within the oil or lubricating fluid.

Since the polymer fibres according to the present teachings can be produced from a wide range of materials, the present teachings advantageously enable a wide flexibility or choice in the selection of the structuring (fibre or fibrous) material. The material can be selected to satisfy very specific operating conditions and/or to impart the lubricant or grease with advantageous properties, such as temperature stability, particular oil bleeding characteristics, etc. Thus, according to this aspect of the present teachings, refinements are possible in the physics and chemical tuning of the performance (lubrication, bleeding, fibre reinforcing, etc) as well as the particular processes for making and delivering this lubricant into the systems in need of lubrication.

Further objects, advantages and utilities of the present teachings will become apparent from the description of the detailed embodiments and the claims.

DETAILED DESCRIPTION OF THE INVENTION

The polymer fibres according to the present teachings are preferably "oleophilic". As utilized in the present teachings, the term "oleophilic" means that the surface of a flat piece of the material (i.e. the material that will be used to form the oleophilic fibres or fibrous material) will be readily covered (wetted) by oil or another lubricating fluid, because that will reduce the total surface energy of the system. A porous structure of an oleophilic material will absorb oil, like a sponge, through capillary action. The more oleophilic the material is, the smaller the "contact angle" of the drop of oil on a flat smooth surface of such material will be, which makes the contact angle a suitable measure of the degree of oleophilicity in accordance with the present teachings. In principle, if a small drop of oil exhibits an inner contact angle that is less 90 degrees when dropped onto a material, such material can be considered oleophilic. A higher degree of oleophilicity of the fibrous materials according to the present teachings (i.e. a smaller contact angle) may be more advantageous in certain embodiments.

Polymeric and/or oleophilic fibres according to the present teachings may be manufactured from one or more of the following polymer materials: polypropylene (PP), polyamide (PA), nylon 6,6, polyamide-6,6 (PA-6,6), polyamide-4,6 (PA-4,6), polyurethanes (PU), polybenzimidazole (PBI), polycarbonate (PC), polyacrylinitrile (PAN), acrylonitrile rubber (NBR), polyvinylalcohol (PVA), polylactic acid (PLA), polyethylene-co-vinyl-acetate (PEVA), PEVA, polymethacryate (PMMA), tetrahydroperfluorooctylacrylate (TAN), polyethylene oxide (PEO), collagen-PEO, polyaniline (PANI), polystyrene (PS), silk-like polymer with fibronectin functionality, polyninylcarbazole, polyethylene terephtalate (PET), polyacrylic acid (PAA), polypyrene methanol (PM), polyvinylphenol (PVP), polyvinylchloride (PVC), cellulose acetate (CA), polyacrylamide (PAAm), PLGA, collagen, polycaprolactone (PCL), poly(2-hydroxyethyl methacrylate) (HEMA), poly(vinylidene fluoride) (PVDF), poly ether imide (PEI), polyethylene glycol (PEG), poly(ferrocenyldimethylsilane) (PFDMS), poly(ethylene-co- vinyl alcohol), polyvinyl pyrrolidone (PVP), polymetha-phenylene isophthalamide, polyethylene naphthalate (PEN), Teflon®, polytetrafluorethene (PTFE), waxes, waxy polymers, polyolefins, polyesters, and/or polysulfones.

PP and PA are particularly preferred.

Other suitable polymer materials include biopolymers, especially for the production of biodegradable greases. Examples of suitable biopolymers are polysaccharides, such as cellulose, starch, chitin, chitosan, proteins, (poly)peptides, and gelatin.

Mixtures or blends of these polymers are suitable as well.

Suitable diameters of the fibres (the 'islands' or 'cores' in some embodiments of the present teachings) are between 50 nanometres and 10 microns. More preferably, the fibres have diameters between 100 nanometres and 1 micron, which is the range of diameters usually found in metallic-soap thickened greases.

Further, the fibres preferably have a length that is at least 5-10 times the diameter thereof. That is, the fibres preferably have an aspect ratio of at least 5 to 10. The length of the fibres can be suitably modified to effect desirable changes to the structural properties of the grease, its mechanical stability, and its bulk rheological properties. Thus, the fibre length can be optimized for particular application (usage) conditions. In addition, the base material for the fibres can be formulated, tuned or adapted for a specific application.

The fibres may be provided in a loose form or in a non-woven mat form, as will be further described below. Loose fibres and non-woven fibre mats can be made by melt blowing the polymer material according to well-known techniques in the art, in order to form micron or sub-micron diameter fibres. In the alternative, other techniques can be used as well, such as electro-spinning or nanotubing. The fibre material may also be obtained in the form of non-woven mats or cloths or "island-in-the-sea" materials from commercially available sources, as will be further discussed below.

In some embodiments of the present teachings, a solid fibrous material can also be sent to a final user as is, i.e. as a polymer-encapsulated fibrous network or as a fibre-embedded polymer material. In this case, the final user would only need to add oil or other lubricating fluid (and perform a simple mixing procedure) to produce the thickened lubricant or grease. This aspect of the present teachings provides a great degree of flexibility, because the solid fibrous material can be shipped worldwide relatively inexpensively due to its low weight (i.e. unlike oil or greases, which are relatively heavy). In another aspect of the present teachings, a small fraction (e.g., 0.1-5%) of fibres of one type can be added to grease that primarily contains a second type of fibre so as to impart special properties to the grease. For example, the fibres can be designed to melt at elevated temperatures to form a lubricant. In addition or in the alternative, the fibres can provide a structural function in the lubricant or grease.

Mixtures of two types of fibres A and B in a ratio A:B between 10:90 and 50:50 can be utilized to impart unique properties to the lubricant or grease. Naturally, more than two types of different fibres also may be combined into a single solid fibrous material and/or used to thicken a lubricating fluid, and the present teachings are not particularly limited in this regard.

The present fibres may be utilized with a wide variety of fluids having lubricating properties at the operating temperatures appropriate for various applications. Particularly suitable lubricants include, but are not limited to, mineral oils obtained from crude oil, group I, II and III lubricants, group IV lubricants (polyalphaolefins "PAO") and group V lubricants (all others). The aforementioned lubricant groups are the groups as designated by the American Petroleum Institute.

A more particular, but non-limiting, list of lubricating oils includes mineral oils, synthetic esters, and plant-based oils and their derivatives, such as oils derived from rapeseed, canola, sunflower, canola and palm. Animal -based oils, their derivatives and synthetic lubricants also may be suitably used in certain aspects of the present teachings, including but not limited to polyglycols (PG), polyalkylene glycol (PAG), white oils, silicone oils, very-high viscosity index oils (VHVI), water, glycerol and waxes. Particularly preferred oils are mineral oils, synthetic esters, PAOs and synthetic hydrocarbons.

The viscosity of the lubricant can range from very low (below lcSt at 40°C) to very high (several 1000 cSt at 40°C). The most suitable viscosity depends on the application temperature, speed, etc., and the present teachings provide for a wide variety of possible lubricating properties. However, oil types (as mentioned above) having a viscosity between 10 and 300 cSt at 40 degrees C are particularly preferred.

The optimal fibre density in the oil or other lubricating fluid (as described above) will depend on the required viscosity and consistency of the lubricant or grease for the particular application, as well as on the length and diameters of the fibres. Preferred fibre weight densities (based on the total lubricant weight) for a fibre-thickened lubricant according to the present teachings are between 0.1 and 20%. Preferred fibre densities for a fibre-thickened 'grease' are 2-15%, more preferably between 5 and 12%. However, if the fibres are used in conjunction with other thickeners, the fibre content may be reduced accordingly. The polymer fibres, the solid fibrous material (or polymer-encapsulated fibrous networks), the lubricating fluid/oil and/or the thickened lubricant (e.g., grease) according to the present teachings may include one or more known additives that are commonly used in the lubricant field. Suitable additives include additives that are typically used in the lubrication field to impart additional properties to the lubricant. These additives may give the lubricant special functionality with regard to aging of the lubricant (anti -oxidants), friction reducers, anti-wear, extreme pressure properties, etc.

In addition or in the alternative, additives can be added to give the grease a stronger structure by linking the fibres, such as by connecting the fibres using suitable polymers, waxes or the like. Other fibres can be used as additives as well.

Other suitable additives are ceramic particulates (silica, alumina, zirconia, etc), metallic particles, etc.

The additive(s) can be added to the polymer bulk base before the fibres are produced, but can be added also to the dry fibres or to the solid fibrous network (e.g., to the polymer material that coats, suspends, embeds and/or encapsulates the fibres). The additive(s) can also be added to the oil which is then mixed and homogenized with the fibres or solid fibrous material.

Another aspect of the present teachings relates to improved lubrication systems, e.g., for bearings, linear actuators, gears and any other mechanical raceway, track or sliding surface, which are lubricated using any of the thickened lubricants or greases disclosed herein.

In another aspect of the present teachings, lubricants are provided in the form thickened oils and/or greases. More specifically, lubricating fluids or oils are thickened with fibres according to the present teachings. While the most appropriate consistency is often determined by the application or usage of the thickened lubricant, the LGI grade or consistency (the standard set or determined by the National Lubricating Grease Institute) is preferably equal to or greater than 00. More preferably, lubricants according to the present teachings have a consistency or LGI grade between 1 and 3, e.g., 2. Such thickened greases are particularly suitable for usage in bearings.

Particularly preferred, but non-limiting embodiments of the present teachings are described in the following.

EMBODIMENT 1

In a first preferred embodiment of the present teachings, polymer fibres are preferably disposed, embedded and/or encapsulated in a "sea" of supporting polymeric material having a different composition and/or physical properties (e.g., different melting temperature and/or solubility) than the composition and/or physical properties of the polymer fibre material. For example, "islands-in-the-sea" (INS) bi-component materials may be utilized in this aspect of the present teachings, wherein a large number of fibres ('islands') can be disposed substantially in parallel within a larger-diameter 'sea' material. Such INS bi-component materials are available, e.g., from Hills Inc. of W. Melbourne, Florida, U.S.A. and include, e.g., sub-micron polypropylene fibres disposed in a polyvinyl acetate sea.

If the fibre 'island' material has a higher melting temperature than the sea material, it is possible to melt the sea material off or to dissolve it when added to a heated solvent, for example, a lubricating oil. In this case, the fibres or fibrous network, which were/was encapsulated in the polymer sea material, will become suspended in the lubricating fluid and will form advantageous three-dimensional structures, thereby imparting advantageous properties to the lubricating fluid, as was discussed above.

However, the sea material need not necessarily have a lower melting temperature than the island (fibre) material. Instead, in another embodiment, the sea material may be a material that dissolves naturally in the lubricating fluid (i.e. it is readily or at least substantially completely soluble in the lubricating fluid, which will be thickened by the fibres or fibrous network), without heating of the lubricating fluid, thereby releasing the fibres or fibrous networks (islands) from the encapsulating (sea) material and suspending the fibres or fibrous networks in the lubricating fluid. Therefore, according to the present embodiment, it is merely preferred the sea material can be dissolved or melted in oil, optionally by heating, to release the fibres or fibrous networks into the oil. As a non-limiting example, polypropylene (PP) having a relatively high melting temperature, e.g., between 160 and 175 °C, may be spun into fibres having a diameter less than 10 microns, but greater than 50 nanometres. The loose fibres may be utilized as is in the following steps, or may first be heated to form a non -woven mat material (i.e. a fibrous network), thereby bonding or adhering individual fibres together.

These fibres or fibrous networks are then coated, suspended, embedded and/or encapsulated in a sea material, which preferably has a lower melting temperature than the PP fibres and/or is highly soluble in the lubricating fluid, in which the solid fibrous material will be dispersed. Various known techniques may be utilized to suspend, embed or encapsulate the fibres or fibrous networks in the polymer sea material, including filament melt extrusion.

As non-limiting examples, the polymer encapsulating (sea) material may be comprised at least substantially of:

a lower molecular weight PP (for isotactic PP, MW<30,000, more preferably

MW<10,000),

co-polymers such as PP-PE (PE = polyethylene),

syndiotactic PP,

low melt-temperature PE and/or

waxes.

Waxes, in particular, provide the advantage that they can impart supplemental lubricating properties to the lubricating fluid. Preferred waxes include polymers having a molecular weight less than lx the molecular weight of the polymer with the same monomer unit between polymer entanglements, and include waxes, such as e.g., natural waxes, such as bees wax, or high molecular weight hydrocarbons, such as paraffin waxes. A low molecular weight polymer is defined as less than 3x molecular weight between entanglements. A high molecular weight polymer is defined as having at least 3x molecular weight between entanglements.

The below examples of the sea material, in conjunction with the high melting-temperature PP, provide additional specific, but non-limiting examples of the present teachings. In each example, the fibres having a diameter less than 10 microns are comprised at least substantially of polypropylene (PP) having a relatively high melting temperature, e.g., between 160 and 175 °C. Example A

The sea material is a 'wax' having a melting temperature of 90 - 100 °C, e.g., PP Licocene PP 1302 GR TP obtainable from Clariant International Ltd. of Muttenz Switzerland (hereinafter simply "Clariant"). Example B

The sea material is a 'wax' having a melting temperature of 120 - 130 °C, e.g., TP Licocene PP 4202 or Licowax PE 520 obtainable from Clariant.

Example C

The sea material is a polyether (PE), e.g., Licowax PE 190P obtainable from Clariant. Example D

The sea material is a wax consisting of a copolymer having polar and non-polar properties, e.g., Licowax OMFL obtainable from Clariant.

Example E

The sea material is an oil, e.g., a polyalphaolefin (PAO) having a base viscosity of 48 cSt. Example F

The sea material is obtained by degrading the same polymer as used for the fibres by subjecting the material to flash heating. Of course, all of these examples are also applicable to, or usable with, fibre polymers ('islands' or 'cores') other than PP.

After producing the island-in-the-sea solid fibrous material (i.e. the polymer-encapsulated fibrous network), it can be dispersed in, and the sea material can be directly dissolved into, the oil or lubricating fluid at a temperature that melts and dissolves the sea material. If necessary, heating may be applied to the dispersion (mixture) to expedite the dissolving of the sea material. Continuous stirring also should be applied to the dispersion in order to ensure proper entanglement of the fibres and the creation of a continuous three- dimensional network within the oil or lubricant fluid. Cooling of the mixture, if necessary, then finalises the lubricant-thickening (e.g., grease-forming) process.

In any of the above-noted examples, the INS fibres may be cut to an appropriate length before melting and/or dissolving the INS fibres in the oil or lubricating fluid, as will be discussed below. If pre-cut, the fibres may dissolve into the oil more quickly, but whilst still producing a suitable three-dimensional structure.

EMBODIMENT 2

In a second preferred embodiment of the present teachings, it is possible to directly deposit polymer fibres having a diameter less than 10 microns into the oil or lubricating fluid.

For example, any of the above-described known fibre-producing methods, e.g., melt- blowing, electro-spinning, force spinning, nanotubing or any similar method, may be utilized to make the fibres. However, such methods are modified by immediately depositing the just-formed fibres in the oil or lubricating fluid.

Such an embodiment enables fast cooling and/or quenching of the fibres, because the fibres are contacted and covered or coated by the oil or lubricating fluid before the fibres form a mat. This ensures that the fibres can be separated by the oil again and prevents the formation of 'non-continuous' networks, which would occur if a non-woven mat is broken into pieces. EMBODIMENT 3

Embodiment 3 is a modification of Embodiment 2, wherein polymer fibres having a diameter less than 10 microns are produced from a molten polymer base, such as by melt- blowing, electro-spinning or another known fibre-forming technique as described above or below, but the fibres are first cooled to well below their melting point before suspending in oil or lubricating fluid. This ensures the formation of a loosely structured fibrous network that can be easily dissolved into oil. It further enables the formation of a continuous three-dimensional network, which can be achieved by setting the air flow applied to the fibres at an appropriate temperature and flow rate.

EMBODIMENT 4

In a fourth embodiment of the present teachings, polymeric fibrous networks (e.g., non- woven mats) are first formed according to any of the fibre-forming techniques described above. However, prior to suspending/dissolving the fibrous networks in oil or lubricating fluid, the fibrous networks are processed (cut) to a suitable length, e.g., in the form of a solid fibrous material.

The method of the fourth embodiment enables fine control over the determination of the fibre length(s). In addition, this method for processing the fibres or fibrous networks has the advantageous effect of significantly reducing the amount of loose (dry) fibres that may be inhaled during handling to prepare the thickened lubricant and/or grease, thereby reducing potential health concerns of dangerous airborne materials. In the fourth embodiment, a dry fibrous network or non-woven fibre mat (formed according to any above-described method) is preferably soaked in a wax or wax-like material at a temperature above the melting temperature of the wax, but at a temperature below the melting temperature of the fibres contained in the dry fibrous network or non- woven fibre mat.

In principle, any material having a melting temperature lower than the polymer composition of the polymer fibres can be used as the encapsulating material in the present embodiment. Such a relatively low-melting temperature encapsulating material enables the fibres or fibrous networks to soak and embed into the encapsulating material when in a melted or liquid state.

After the fibres or fibrous networks have been soaked in the encapsulating material for a sufficient amount of time, the mixture may be cooled and thus solidified, thereby embedding the fibres in a solid matrix.

Thereafter, the solidified matrix can be cut, e.g., at room temperature or lower. The matrix can be processed using a variety methods known in the art to produce fibres cut to different length distributions that are suitable for the desired thickening properties. However, a preferred cutting method is to use a sharp cutting tool to slice clearly defined pieces of the solidified matrix under fine control and thus produce a narrow range of length distributions of the fibres. One suitable example of such tool, which can be scaled up easily in size and in number, is an automated microtome adapted to cut slices of the solid fibrous material into a thickness between 1 and 100s of microns, e.g. between about 1-400 microns, more preferably 1-50 microns. As a particularly preferred example, a sled microtome may be utilized by the placing a sample of the solid matrix (solid fibrous material) into a shuttle. The shuttle is then moved back and forth across a knife to form micron-thin slices. Such a method enables an extremely fine control of the fibre length distribution. Any scaled up version of such a cutting device in size of cutting length as well as number of cutters may be utilized with the present teachings.

Waxes are particularly well suited for use as the encapsulating or embedding material in this embodiment, because they are generally solid at room temperature. Any of the above- described waxes may be utilized in this embodiment of the present teachings.

By embedding the fibres in the encapsulating (e.g., wax or wax-like) material, there is significantly reduced chance that the fibres will become airborne during post-processing (e.g., during formation of the thickened-lubricant and/or grease) and form a fine dust. This will significantly improve the working environment for making the thickened-lubricants and/or grease.

If the fibres are randomly oriented in the fibrous network, such as in non-woven, melt- blown nano-fibres, this will result in a rather broad fibre length distribution. On the other hand, if the fibres are aligned in the fibrous network, the length distribution can be extremely narrow.

After cutting the slices, the wax (having the fibres or fibrous networks embedded therein) of the sliced solidified matrix can be dissolved in an oil or lubricating fluid, which may be heated if necessary, thereby immediately forming a fibre-thickened lubricant or grease that can be used as a lubricant.

If required, suitable lubricant additives can be added at any points in the manufacturing process. Any of the above-noted lubricant additives may be utilized, as necessary and/or desired.

In a further embodiment, it is preferred that the wax is suitably selected based upon the lubricating properties that it will impart to the oil or lubricating fluid after being dissolved therein. Non-limiting examples are natural waxes and commercially-available waxes marketed as having lubricating properties, such as the ones described above.

In addition or in the alternative, the wax may exhibit structure-enhancing properties, e.g., by depositing itself or precipitating onto the three-dimensional fibre structure upon cooling of the oil-wax -fibre mixture.

Suitable ratios, by weight or by volume, of wax to fibres are between l-to-10 and 10-to-l, more suitable are between 3 : 1 and 1 :3. Most suitable is around 1-to-l .

Representative, non-limiting examples of the present invention were described in detail above. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above or in the claims below may be utilized separately or in conjunction with other features and teachings to provide improved fibres, fibrous materials, solid fibrous materials or polymer-encapsulated fibrous materials, thickened- lubricants and greases, as well as methods for making and using the same.

Moreover, the combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

Claims

A method for forming a thickened lubricant, e.g., a grease, comprising:

forming polymer fibres having a diameter between 50 nanometres and 10 microns, more preferably between 100 nanometres and 1 micron, and

depositing the polymer fibres into a lubricating fluid, thereby forming the thickened lubricant.

The method according to claim 1, wherein the polymer fibres are immediately deposited into the lubricating fluid upon being formed, such that the polymer fibres remain unadhered to each other and the lubricating fluid rapidly cools the polymer fibres.

The method according to claim 1, wherein the polymer fibres are allowed to adhere to each other and at least partially cool, thereby forming a fibrous network, prior to depositing the polymer fibres into the lubricating fluid.

The method according to any preceding claim, wherein the polymer fibres are formed by melt-blowing, electro-spinning, force spinning or nanotubing.

The method according to any preceding claim, wherein the polymer fibres are oleophilic, at least substantially insoluble in the lubricating fluid at a normal operating temperature of the lubricating fluid and capable of increasing the viscosity of the lubricating fluid.

The method according to any preceding claim, wherein the polymer fibres have an aspect ratio of between 5 and 10.

The method according to any preceding claim, wherein the polymer fibres at least substantially comprise one or more of polypropylene (PP), polyamide (PA), nylon 6,6, polyamide-6,6 (PA-6,6), polyamide-4,6 (PA-4,6), polyurethane (PU), polybenzimidazole (PBI), polycarbonate (PC), polyacrylinitrile (PAN), acrylonitrile rubber (NBR), polyvinylalcohol (PVA), polylactic acid (PLA), polyethylene-co- vinyl-acetate (PEVA), PEVA, polymethacryate (PMMA), tetrahydroperfluorooctylacrylate (TAN), polyethylene oxide (PEO), collagen-PEO, polyaniline (PANI), polystyrene (PS), silk-like polymer with fibronectin functionality, polyninylcarbazole, polyethylene terephtalate (PET), polyacrylic acid (PAA), polypyrene methanol (PM), polyvinylphenol (PVP), polyvinylchloride (PVC), cellulose acetate (CA), polyacrylamide (PAAm), PLGA, collagen, polycaprolactone (PCL), poly(2-hydroxyethyl methacrylate) (HEMA), poly(vinylidene fluoride) (PVDF), polyether imide (PEI), polyethylene glycol (PEG), poly(ferrocenyldimethylsilane) (PFDMS), poly(ethylene-co-vinyl alcohol), polyvinyl pyrrolidone (PVP), polymetha-phenylene isophthalamide, polyethylene naphthalate (PEN), Teflon®, polytetrafluorethene (PTFE), wax, waxy polymer, polyolefin, polyester, and polysulfone.

The method according to any one of claims 1-7, wherein the polymer fibres at least substantially comprises polypropylene or polyamide, more preferably a polypropylene having a melting temperature of at least 160°C and optionally less than 175 °C.

The method according to any preceding claim, further comprising admixing one or more additives that impart a special functionality to the polymer fibres and/or to the lubricating fluid, such as anti-oxidants, friction reducers, anti-wear agents, and/or pressure-withstanding agents.

The method according to any preceding claim, wherein the lubricating fluid comprises one or more of:

mineral oil obtained from crude oil,

group I, II and III lubricants,

group IV lubricants and

group V lubricants.

The method according to any one of claims 1-9, wherein the lubricating fluid comprises one or more of mineral oil, synthetic ester, and plant-based oil and their derivatives, such as oils derived from rapeseed, canola, sunflower, canola and palm, more preferably one or more of mineral oils, synthetic esters, PAOs and synthetic hydrocarbons.

12. The method according to any one of claims 1-9, wherein the lubricating fluid comprises one or more of a mineral oil, a synthetic ester, a PAO and a synthetic hydrocarbon.

13. The method according to any one of claims 1-9, wherein the lubricating fluid is polyalphaolefin, the fibres are comprised of polypropylene fibres having an average fibre diameter of 350-450 nm, and the fibre density is 5-10%.

14. A thickened lubricant produced according to the method of any preceding claim.

15. The thickened lubricant according to claim 14, wherein the thickened lubricant has a LGI grade equal to or greater than 00, more preferably between 1 and 3, e.g., 2.

16. The thickened lubricant according to claim 14 or 15, wherein the fibre weight density based on the total lubricant weight is between 0.1 and 20%, more preferably between 2-15%, even more preferably between 5-12%.

17. The thickened lubricant according to claim 14, 15 or 16, wherein the lubricating fluid has a viscosity that is between 1-lOOOcSt at 40°C prior to the polymer fibres being deposited therein, more preferably between 10 and 300 cSt at 40°C.

18. A method for lubricating a bearing, comprising:

applying the thickened lubricant of any one of claims 14-17 to at least one portion of the bearing in need of lubrication during operation of the bearing.