Antifriction coating and method for producing the same - Patents.com

Abstract

1. A method of making an anti-friction coating composition, comprising: (A) combining (i) a solid lubricant, (ii) a solvent, (iii) a binder, and (iv) optionally an additive; and (B) milling (i) solid lubricant in the solvent (ii) using a basket mill, wherein the milling is for a time sufficient to form a dispersion of milled (i) solid lubricant in the (ii) solvent, wherein the binder (iii) and optional additives (iv) are each independently combined with the solid lubricant (i) and solvent (ii) before, during, after, or a combination of two or more of before, during, and after (B).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS none.

[0002] The present invention relates broadly to the technical field of anti-friction coating compositions comprising a binder, a solid lubricant, a solvent, and optionally other auxiliary additives, to a method for producing the anti-friction coating composition, to anti-friction coatings produced from the anti-friction coating composition, and to parts coated with the anti-friction coating. [Background technology]

[0003] Antifriction coatings (AFCs), also known as bonded lubricants, are used to reduce friction, wear, and noise in many applications. AFCs are typically produced by applying an AFC composition to a substrate and then subjecting the AFC composition to a curing process to form the AFC. The AFC composition is typically a dispersion of a binder, usually a polymeric resin, a solid lubricant, a solvent, and other additives. Antifriction coating compositions are applied to substrates by conventional application techniques. For example, AFC compositions can be applied by brushing, dipping, dip spinning, and spraying. Typical coating thicknesses are 5-20 μm.

[0004] The performance of anti-friction coatings can be determined by microscopic observation to determine coating coverage, and by measuring load capacity and product life using a linear oscillatory friction test in which the load is increased or held constant until the coating fails.

[0005] To achieve a coating thickness of 5-20 μm and to be usable in spray application, one manufacturing step requires grinding of the solids in the AFC composition. Grinding is typically performed using bead mills that can be used to process ultra-fine solids in liquids with particle sizes ranging from up to about 500 μm down to the submicron (nanometer) range. Depending on the product characteristics, various types of agitator bead mills with different grinding systems can be used. The grinding step using bead mills is the most expensive manufacturing step in AFC production.

[0006] The bead mill grinding process is expensive because the machine is technically demanding and difficult to clean, as well as the peripheral equipment such as pumps, hoses, and stirrers. Because of the difficulty in cleaning, the bead mill grinder must be limited to use with a single AFC product or a group of AFC products. Additional costs associated with the bead mill grinding process include the need for two vessels to prepare the AFC composition (one to pre-disperse the solids and the other to receive the ground product from the bead mill), and the abrasive wear on the bead mill chamber due to the low viscosity of the ground AFC composition, which requires frequent equipment replacement. Finally, bead mills used to produce AFC compositions are generally inefficient because multiple passes of the bead mill are required to achieve the desired particle size, and the particle size and distribution are difficult to control.

[0007] There is a need for a more efficient process for producing AFC compositions that reduces production time and uses equipment that is easier to clean, disperses and grinds solids in the same container, can be used across multiple products or product lines, and uses equipment that requires less frequent replacement due to wear.In addition, there is a need for a process for producing AFC compositions that allows for better control over the particle size and particle size distribution of the ground solids.Finally, there is a need for AFCs that have improved performance in terms of load capacity and product life. Summary of the Invention [Means for solving the problem]

[0008] The present invention relates to a process for making an anti-friction coating composition comprising the steps of: (A) combining (i) a solid lubricant, (ii) a solvent, (iii) a binder, and (iv) optionally, an additive; and (B) milling the solid lubricant (i) in the solvent (ii) using a basket mill, wherein the milling is for a time sufficient to form a dispersion of the milled (i) solid lubricant in the (ii) solvent, wherein the binder (iii) and optional additives (iv) are each independently combined with the solid lubricant (i) and the solvent (ii) before, during, after, or a combination of two or more of before, during, and after (B).

[0009] The present invention further relates to an anti-friction coating composition comprising a dispersion of (i) a solid lubricant, (ii) a solvent, (iii) a binder, and (iv) optionally additives, wherein the binder and the solid lubricant have a particle size (d90) of up to 50 μm and (d50) of up to 25 μm.

[0010] The process of the present invention provides a more efficient process for making AFC compositions that reduces production time, uses equipment that is easier to clean, disperses and grinds solids in the same vessel, can be used across multiple products or product lines, and requires less frequent replacement due to wear. Additionally, the process allows for greater control over the particle size of the ground solids in the AFC composition, and results in AFC compositions with improved performance in terms of load capacity and product life. [Brief description of the drawings]

[0011] [Figure 1] 1 shows a cross-sectional view of a basket mill used in accordance with the present invention. [Diagram 2] 2 shows the basket mill of FIG. 1 with the grinding device in a lowered position. [Diagram 3] 2 shows an enlarged scale cross-section of the basket mill of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] As used herein, the term "AFC composition" refers to an uncured composition that includes a solvent.

[0013] As used herein, the term "AFC" refers to a coating that results from applying an AFC composition to a substrate, removing solvent from the AFC composition on the substrate, and / or curing the AFC composition on the substrate.

[0014] As used herein, the articles "a" and "an" are open-ended and when describing elements of the invention, they are to be interpreted as including one or more.

[0015] 1. A method of making an anti-friction coating composition comprising the steps of: (A) (i) a solid lubricant; and (ii) a solvent; (iii) a binder; and (iv) optionally with an additive; (B) milling (i) the solid lubricant in the solvent (ii) using a basket mill, the milling being for a time sufficient to form a dispersion of the milled (i) solid lubricant in the (ii) solvent; The process wherein a binder (iii) and optional additives (iv) are each independently combined with the solid lubricant (i) and solvent (ii) before, during, after, or a combination of two or more of before, during, and after (B).

[0016] The solid lubricant (i), the solvent (ii), the binder (iii), and optionally the additives are combined. The solid lubricant may be any solid lubricant or mixture of solid lubricants known for use in AFCs. Examples of solid lubricants include, but are not limited to, graphite, MoS2, polytetrafluoroethylene (PTFE), silicone, zinc sulfide, tricalcium phosphate, wax, solid hydrocarbon wax, such as polyolefin wax (polypropylene wax, polyethylene wax, polyamide wax), or a mixture of two or more of PTFE, polyolefin wax, molybdenum disulfide, graphite, zinc sulfide, or tricalcium phosphate. A person skilled in the art will know which solid lubricants are suitable for the AFC composition and how to select a solid lubricant. Solid lubricants are commercially available.

[0017] The solvent may be any solvent or mixture of solvents commonly used in AFC compositions, and is typically selected to be a solvent for the binder. The solid lubricant, pigment, and any other components may not be, and typically are not, soluble in the solvent. Examples of solvents include, but are not limited to, water, alcohols (e.g., methanol, ethanol, propanol, butanol), ketones (e.g., acetone, methyl ethyl ketone, methyl butyl ketone, cyclohexanone), esters (e.g., butyl acetate), aliphatic hydrocarbons, heterocyclic (e.g., N-methylpyrrolidone), and non-heterocyclic aromatic solvents (e.g., toluene, xylene), including mixtures of two or more thereof. Alternatively, the solvent is a mixture of alcohol and ester with an alcohol:ester ratio of 10:90 to 50:50 (w / w). Alternatively, the solvent is any suitable combination of alcohol, ester, and ketone, or a mixture of butyl acetate, ethanol, and methyl ethyl ketone. One skilled in the art would know how to select solvents to combine in an AFC. Suitable solvents are commercially available.

[0018] The binder may be any binder or mixture of binders suitable for use in AFCs. Examples of binders include, but are not limited to, resins such as phenolic resins, epoxy resins, polyvinyl butyral, styrene-maleic anhydride (SMA) copolymers, polyvinyl acetate, polymeric butyl titanate, urea formaldehyde resins, polyamideimide, and silicone resins, or mixtures of two or more of phenolic resins, epoxy resins, polyvinyl butyral, styrene-maleic anhydride (SMA) copolymers, polyvinyl acetate, polymeric butyl titanate, urea formaldehyde resins, polyamideimide, and silicone resins. A person skilled in the art would know how to select a binder for an anti-friction coating. Suitable binders are commercially available.

[0019] The optional additive may be one or more additives, and the optional additive includes any other material that is commonly used in AFC but is not essential to AFC. Examples of optional additives include, but are not limited to, catalysts, pigments, surface tension additives, coupling agents, and thickeners. Any suitable catalyst that is commonly used in AFC may be included in the AFC. Examples of suitable catalysts include, but are not limited to, catalysts for this purpose, including phosphoric acid and phenolsulfonic acid. The catalyst will affect the cure speed of the AFC composition to form the AFC. Those skilled in the art will know how to select a suitable catalyst for the materials of the AFC composition. Suitable catalysts are commercially available.

[0020] Any pigment suitable for use with the components of the AFC may be combined. Examples of suitable pigments include, but are not limited to, calcium fluoride (CaF2), carbon black, aluminum trioxide (Al2O3), silicon carbide (SiC), antimony trioxide, silicon nitride (SiN4), titanium carbide (TiC), titanium oxide (TiO2), silicon oxide (SiO2), talc, and other suitable inorganic powders, and mixtures thereof. Other pigments that may be used include melamine cyanurate (alone or mixed with micronized amide wax, polyamide 12 polymer, polyether ether ketone polymer, and mixtures thereof, as well as the inorganic materials listed above). Those skilled in the art will know how to select a suitable pigment or mixture of pigments. Pigments suitable for use in the AFC are commercially available.

[0021] Any suitable surface tension additive for use with the components of the AFC may be combined. Surface tension additives are typically added to improve wetting of the coated parts. Examples of suitable surface tension additives include, but are not limited to, silicone glycols, polyester modified polydimethylsiloxanes. Those skilled in the art will know how to select a suitable surface tension additive. Suitable surface tension additives for use in AFCs are commercially available.

[0022] Any coupling agent suitable for use with the components of the AFC may be combined. The coupling agent additive is added to improve the adhesion between the AFC and the substrate and the cohesion between the binder and the solid lubricant. Examples of suitable coupling agents include, but are not limited to, silanes such as methyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, (ethylenediaminepropyl)trimethoxysilane, and (3-glycidoxypropyl)triethoxysilane. Those skilled in the art will know how to select a suitable coupling agent. Coupling agents suitable for use in the AFC are commercially available.

[0023] Any thickener or mixture of thickeners suitable for use with the components of the AFC may be combined as an optional additive. The thickener is added to modify the viscosity of the AFC composition to allow proper application of the AFC composition to the substrate and to provide the desired thickness of the AFC. Examples of suitable thickeners include, but are not limited to, polyamides, metal soaps, silica, bentonite, and urea-based materials. Those skilled in the art will know how to select a suitable thickener for use in the AFC. Suitable thickeners are commercially available.

[0024] The solid lubricant (i) and the solvent (ii) are combined in any order before and / or during the grinding in (B) below, or before the grinding in (B), or during the grinding in (B). The solid lubricant (i) and the solvent (ii) can be combined in any order in either the same or a different vessel as that used for grinding in (B), or (i) and (ii) are combined in any order in the same vessel as that used for the grinding step (B), or (i) and (ii) are combined by first adding (ii) to the vessel followed by adding (i) to the vessel while mixing and / or grinding, or by adding (i) to the vessel followed by adding (ii) while mixing and / or grinding. If (i) and (ii) are combined before grinding in (B), they may or may not be premixed before (B).

[0025] The combination of binder (iii) and optional additive (iv) can vary, each independently, combined together or separately with (i) and (ii) in any order and in any manner known in the art, either before, during, or after milling in (B); alternatively, solvent (ii) is combined in portions in the AFC composition, and a portion is combined with solid lubricant (i) before and / or during (B), and a portion of (ii) is separately combined with (iii) to form a mixture of (ii) and (iii), which mixture of (ii) and (iii) typically forms a solution, and subsequently, after milling the combination of (i) and (ii) in step (B), the mixture of (ii) and (iii) is combined with the combination of (i) and (ii). When (ii) is combined portion-wise, the mixture formed from the combination of (ii) and (iii) may be combined with the combination of (i) and (ii) either before, during, or after (B), or after (B), or before (B), or during (B).

[0026] Methods known in the art, such as using a dissolver disk or paddle mixer, may be used to mix (i), (ii), (iii) and (iv). A person skilled in the art would know how to select a suitable mixer. Many suitable mixers are commercially available.

[0027] In one embodiment, the method further comprises combining a binder (iii) with a second solvent (v) to form a mixture before, during, or after (i) and (ii) are milled in (B), or afterwards, and combining the mixture with a solid lubricant (i) and solvent (ii).

[0028] The second solvent (v) is as described above for solvent (ii). Solvent (ii) and second solvent (v) may be the same or different, or (ii) and (v) may be the same, or (ii) and (v) may be different. The binder and solid lubricant are as described above.

[0029] The binder (iii) and the second solvent (v) may be combined by methods known in the art. In one embodiment, (iii) and (v) are combined by mixing. Any mixing method known in the art may be used. A person skilled in the art will know how to combine (iii) and (v) and the equipment to use to mix (iii) and (v).

[0030] The basket mill of the present invention will be described with reference to Figures 1-3. The basket mill described herein should be considered as a preferred embodiment that has been found to work well. Those skilled in the art will appreciate that many changes can be made to the specific embodiment of the basket mill to obtain the same or similar results without departing from the spirit and scope of the present invention. The basket mill of the present invention comprises a substantially cylindrical double-layered vessel 10 that can be closed with a lid, a dissolver 20, and an agitator basket mill 30. A cleaning device, not shown in detail here, can also be placed in the vessel.

[0031] Dissolver 20 comprises a cylindrical shaft 21 having at its lower end a dissolver disc 22. Dissolver disc 22 has a plurality of alternating curved teeth 23 on its outer periphery on a circular surface. Shaft 21 has a central portion 24 of a first outer diameter which merges at its lower end into a lower portion 25 whose outer diameter is greater than that of the central portion.

[0032] The shaft 21 is fixed to the machine top 60 by a cylindrical bearing flange 26, which surrounds the bearing flange in a box-like manner. To ensure the necessary stability, the bearing flange 26 preferably extends over 1 / 3 of the total shaft length. In an embodiment of the invention, the height of the agitator basket mill 30 can be adjusted by a pneumatic cylinder 62, the piston rod 64 of which is attached to the middle plate 66. A number of hollow rods 33 extend from the lower surface of the middle plate 66 to the upper end of the agitator basket 30. Thanks to this configuration, the arrangement of the agitator basket 30 can be displaced up and down using the pneumatic cylinder 62, and furthermore, a coolant can be circulated in the agitator basket 30 via the hollow rods. Instead of a pneumatic cylinder, other adjustment means can also be used, such as, for example, a hydraulic cylinder or a worm drive.

[0033] The shaft 21 is supported by rotational bearings in a bearing flange 26, in which a needle or roller bearing 27 is provided at the lower end of the bearing flange 26 and a double self-aligning bearing 28 is provided at the upper end. The shaft 21 is driven in a known manner by a belt pulley 29. To reinforce the bearing flange 26, a number of reinforcing ribs 32 are provided at its upper end in a circumferentially displaced relationship with one another. The ribs 32 extend from approximately the center of the bearing flange 26 in a continuous inclination up to the horizontal flange, which is the upper flange in the installed position. These reinforcing ribs 32 give the bearing flange 26 a significantly higher level of stability compared to the bearing flanges known in the state of the art, in order to prevent unwanted deflections of the shaft 21, particularly in the pre-dispersing operation.

[0034] The agitator basket 30 is fixed to the underside of the machine top 60 via a plurality of cylindrical hollow bars 33 spaced circumferentially relative to one another and via a mid-plate 66, so that the height of the agitator basket 30 can be adjusted by the machine top 60 using a pneumatic cylinder 62. Instead of a pneumatic cylinder, other adjustment means such as, for example, a hydraulic cylinder or a worm drive, can also be used.

[0035] The agitator basket 30 itself comprises a housing 34, which is like a perforated sieve in which grinding balls and / or beads (not shown) are held. At its upper end, the housing 34 comprises a funnel having an opening 35 at its base through which the shaft 21 passes. The housing 34 may be of single-wall construction, double-wall construction, or another suitable construction. The housing 34 defines an annular passage with a central bore 35. A bead and / or ball agitator 36 is disposed within the annular passage extending coaxially therewith.

[0036] At its upper end, the bead and / or ball agitator 36 is connected by a ring disc 37 to a bearing block generally identified by the reference number 39. The bearing block includes a cylindrical bush 40 which is arranged around the lower shaft portion 25 in the lowered position and has an outwardly expanding step 41 at its lower end. A double rolling bearing 42 is supported on the step 41, the bearings being spaced apart from each other by an external spacer ring 43. A conveyor screw 44 is arranged radially inward from the spacer ring 43 between the bearings of the double rolling bearing 42. The double rolling bearing 42 is supported at its upper surface against the lower surface of the ring disc 37 by a further spacer ring 45. A bladed impeller 46 is arranged on the radially outer step of the ring disc 37 in order to increase the flow rate of the product from the vessel to the housing 34 during the assembly operation and at the same time to prevent the grinding balls from unnecessarily going outside the agitator basket mill. At the lower end of the bearing block 39, directly below the step 41 of the bush 40, there is provided an internal tooth arrangement 47 of an arcuate tooth coupling which represents a first coupling element for transmitting torque from the shaft 21 to the ring disc 36. Between the internal tooth arrangement 47 and the step 41 of the bush 40, a plurality of suction holes 48 are arranged in circumferentially spaced relation to one another. Radially outwardly, the double rolling bearing arrangement 42 is supported against the interior of a hollow truncated cone 49 which tapers continuously from its lower cylindrical part to its upper end and which is also supported on the internal step of the upper bearing of the double rolling bearing 42.

[0037] Above the upper bearing, between the inside of the upper end of the hollow cone 49, there is a gap of about 0.3 mm between the hollow cone 49 and the second spacer ring 45. During operation, a product stream can pass through this gap to cool the bearings and prevent them from drying out. This arrangement prevents the ingress of beads or grinding balls and thus the feared "bead breakage". The product stream flows continuously through the bearings, providing a self-cooling effect due to the conveyor screw 44 and the suction holes 48.

[0038] The hollow truncated cone is screwed to an inner ring element of a circular disc portion 51 by a plurality of circumferentially disposed screws 50. The disc portion 51 forms the bottom of the agitator basket mill 30 and houses a sieve 52 which extends radially outward from the inner ring element to the outer ring element of the disc portion 51. During the fine dispersion operation, media flows through the sieve 52 to separate the milled material from the beads.

[0039] Above the dissolver disc 22 and below the lower shaft portion 25 is an external tooth arrangement 53 forming a second coupling element. As the agitator basket mill 30 moves downward from the pre-dispersion position shown in Figure 1 to the fine dispersion position shown in Figure 2, the bushing 40 is displaced on the lower shaft portion 25 until the internal tooth arrangement 47 engages the external tooth arrangement 53. The arcuate tooth coupling now transmits shaft torque to the bead and / or ball agitator 36 to perform the fine dispersion operation.

[0040] The configuration of the upper shaft portion 24 has a smaller outer diameter than the lower shaft portion 25, ensuring that there is sufficient clearance between the shaft 21 and the agitator basket 30 in the pre-dispersion position to prevent undesirable damage to the bushing 40 due to lateral flexing movement of the shaft 21 during the pre-dispersion operation.

[0041] The arrangement of the coupling at the lower end of the agitator basket makes it possible to dispense with the hollow shaft found in the state of the art and at the same time furthermore combine the pre-dispersing device and the fine-dispersing device in one unit, where the change between the process steps can be achieved simply by lowering the agitator basket mill in the vessel, without the need to open it. It will be understood that instead of a positively locking coupling, it is also possible to use couplings with force-locking or quick-connect relationships, such as plate couplings. Finally, instead of the rolling bearings in the bearing blocks, it is also possible to use plain bearings.

[0042] Basket mills are commercially available. In one embodiment, the basket mill is from VMA-Getzmann. Basket mills suitable for use in the present invention are described in U.S. Patent Nos. 7,641,137 and 6,565,024, the descriptions of which are incorporated herein by reference.

[0043] The grinding balls and / or beads held by the agitator may comprise a variety of materials. Examples of materials contained in the beads include, but are not limited to, ZrO2, metal, glass, or a combination of ZrO2, metal, and glass. During (B), the beads are agitated by the bead agitator, and the movement of the beads pulverizes the solid lubricant (i).

[0044] The grinding balls and / or beads are substantially spherical. The diameter of the beads may vary, alternatively the diameter of the beads is up to 5 mm, alternatively 0.5-4 mm, alternatively 0.6-2.5 mm, alternatively 1.0-2.5 mm. The diameter of the grinding beads influences the particle size distribution of the solid lubricant. The particle size distribution of the solid lubricant may affect the performance of the AFC in terms of load capacity and product life.

[0045] Milling of (B) forms a dispersion of solid lubricant (i) in solvent (ii). The viscosity of the dispersion may vary, alternatively the viscosity is up to 5,000 mPa·s, alternatively the viscosity of the dispersion is 5 to 5,000, alternatively 20 mPa·s to 2500 mPa·s. The viscosity of the dispersion is measured using a Brookfield viscometer according to ASTM D1084 Method B.

[0046] A pre-dispersion of solid lubricant (i) and solvent (ii) may be made before grinding in (B), or (i) and (ii) may be combined and then ground in (B) without making a pre-dispersion. The pre-dispersion may be made in the same vessel as the grinding in (B) or in a separate vessel. After the pre-dispersion is made in the dissolver 10, the agitator basket 30 may be lowered into the pre-dispersion and the dispersion may be ground in the same vessel in (B), or the agitator basket 30 may be used to grind the combination of (i) and (ii) without pre-dispersing (i) in (ii). The pre-dispersion may be made using a separate dissolver disk, which is replaced by the basket mill by using a quick connector, where the dissolver disk is disconnected from the motor at the quick connect connector and the basket mill is connected using the quick connect connector. Those skilled in the art will know how to use a quick connector to exchange the dissolver disc and the basket mill and use the dissolver disc 10 of the basket mill to make a dispersion of the solid lubricant (i) and the solvent (ii), or how to make a dispersion in a separate vessel and then grind (B) in the basket mill (pre-dispersion using a separate dispersion device and the basket mill followed by grinding of the solid lubricant (i) in the solvent (ii)).

[0047] The particle size and particle size distribution of the solid lubricant can be controlled by controlling the milling time and tip speed of the bead agitator. A person skilled in the art will know how to change the tip speed and time of the bead agitator to change the particle size and particle size distribution. The time that milling (B) can be carried out can vary, or milling (B) is carried out for up to 20 hours, or from 5 minutes to 10 hours, or from 5 minutes to 5 hours.

[0048] The rotation speed of the bead agitator can be varied to alter the particle size and / or particle size distribution, or the rotation speed of the bead agitator can be up to 15,000 revolutions per minute (rpm), or alternatively between 100 rpm and 6000 rpm, or alternatively between 200 and 2000 rpm. One of ordinary skill in the art would know how to alter the rotation speed of the bead agitator.

[0049] The temperature of the process may vary, in one embodiment the process is carried out at ambient temperature, alternatively between 0°C and 80°C, alternatively between 10°C and 60°C, alternatively between 10°C and 40°C.

[0050] The size of the dissolver disc may vary depending on the size of the instrument, in one embodiment the dissolver disc has a diameter of up to 600mm, alternatively between 150mm and 450mm, alternatively between 30mm and 400mm.

[0051] The solid lubricant in the dispersion after milling (B) has a particle size (d90) of up to 75 μm and a particle size (d50) of up to 25 μm, or a particle size (d90) of 15 μm to 35 μm and a particle size (d50) of 5 μm to 15 μm. As used herein, particle size (d90) is the particle size value below which the fraction of particles has a diameter of 90% and particle size distribution (d50) is the particle size value below which the fraction of particles has a diameter of 50%. A person skilled in the art will know how to measure the particle size of the solids in the dispersion. Particle size is measured using a Horiba LA-950 laser diffraction particle size distribution analyzer.

[0052] A tribological coating composition prepared by the method of making a tribological coating composition described above. The AFC composition may be applied to a surface for any reason that an AFC composition is applied to a surface, such as to reduce friction, wear, and noise in many applications.

[0053] A tribological coating, wherein the tribological coating is prepared by forming a film of the tribological coating composition described above on a substrate and exposing the tribological coating composition to conditions to remove the solvent and form the tribological coating or to conditions to cure the AFC composition and form an AFC.

[0054] (i) a solid lubricant; and (ii) a solvent; (iii) a binder; and (iv) Optionally, additives 1. An anti-friction coating composition comprising a dispersion of 1. An anti-friction coating composition, wherein said solid lubricant has a particle size (d90) of up to 50 μm and (d50) of up to 25 μm.

[0055] The solid lubricant (i), the solvent (ii), the binder (iii), and the optional additives (iv) are as described above.

[0056] The particle size of the solid lubricant in the AFC is as described above. That is, the solid lubricant has a particle size (d90) of up to 50 μm and a particle size (d50) of up to 25 μm, or a particle size distribution (d90) of 15 μm to 35 μm and a particle size (d50) of 5 μm to 15 μm. The particle size and the method for measuring it are as described above with respect to the method for preparing the AFC composition.

[0057] The AFC composition is prepared by the method for preparing an AFC composition described above.

[0058] A method of making a tribological coating comprising the steps of applying to a substrate a tribological coating composition prepared as in the above method, and exposing the applied tribological coating composition to conditions to remove the solvent or to conditions to cure the AFC composition to form an AFC.

[0059] The AFC composition can be applied to a substrate by any method known in the art. Examples of methods that can apply the AFC composition include, but are not limited to, spraying, spin coating, brushing, dipping, and dip spin. Those skilled in the art will know how to apply the AFC composition to a substrate.

[0060] The AFC composition is exposed to conditions sufficient to drive off the solvent and / or cure the AFC composition, or the AFC is exposed to elevated temperatures, or temperatures between 10°C and 280°C, or temperatures between 30°C and 230°C to drive off the solvent and / or cure the AFC composition to form an AFC. Those skilled in the art will know how to cure the AFC composition to form an AFC. Alternatively, the AFC composition may include materials that use different curing mechanisms, such as moisture, ultraviolet (UV), or infrared (IR). Those skilled in the art will know how to expose the AFC composition to elevated temperatures, moisture, UV, or IR depending on the cure system used for the AFC. The AFC composition may be exposed to subatmospheric pressure to drive off the solvent. Those skilled in the art will know how to expose the AFC composition to subatmospheric pressure now.

[0061] The anti-friction coating thickness may vary, or the AFC thickness may be from 2 μm to 50 μm, or from 5 μm to 20 μm. A person skilled in the art will know how to coat a part to achieve these AFC thicknesses, and will know how to measure the coating thickness.

[0062] A component comprising a sliding member coated with an anti-friction coating composition prepared by the above method.

[0063] A part comprising a sliding member coated with an anti-friction coating composition prepared by the above method, wherein the AFC composition has been cured.

[0064] The AFC composition is cured on the component by exposing the coated component to conditions sufficient to cure the AFC composition, which are as described above with respect to the method of preparing the anti-friction coating.

[0065] The present invention is useful in providing an efficient process for making AFC compositions that reduces production time by using equipment that is easier to clean, disperses and grinds solids in the same container, can be used across multiple products or product lines, and requires less frequent replacement due to wear. Additionally, the present invention is useful in providing better control over the particle size distribution of ground solids in the AFC composition, resulting in AFC compositions with improved performance in terms of load capacity and product life. The AFC compositions are useful for coating parts to reduce friction, wear, and noise. EXAMPLES

[0066] The following examples are included to illustrate preferred embodiments of the invention, but they should not be considered as limiting the invention detailed in the appended claims. Those skilled in the art will appreciate that the techniques disclosed in the following examples represent techniques found by the inventors to work well in the practice of the invention, and therefore may be considered to constitute preferred modes for its practice. However, those skilled in the art will appreciate, in light of this disclosure, that many changes can be made to the specific embodiments disclosed and still obtain the same or similar results without departing from the spirit and scope of the invention. Unless otherwise stated, all percentages are by weight. The following table explains the abbreviations used in the examples.

[0067] [Table 1]

[0068] Table 2 then lists the formulations used in the examples to prepare the anti-friction coating compositions.

[0069] [Table 2]

[0070] For Examples 1-1, 1-2, and 1-3, a pre-dispersion was made by mixing the slurry samples with a 90 mm dissolver disk at 700 rpm for 10 minutes and 600 rpm for an additional 10 minutes. The pre-dispersion was bead milled for the time periods. The bead size range, basket fill volume, bead fill level, and bead agitator speed are as specified in Table 3 below. The basket mill used was from VMA-Getzmann TML5 with a 5 L vessel and used 1.0-1.2 mm ZrO2 beads.

[0071] In Examples 2-1, 2-2, 2-3, 3-1, 3-2, and 3-3, 320 kg of slurry was stirred at 400 rpm for 30 minutes using a 250 mm dissolver disk. The stirred slurry was then charged into a 500 L double-walled vessel and ground using a basket mill. The basket mills used in Examples 2-1, 2-2, and 2-3 were different from those used in Examples 3-1, 3-2, and 3-3. A model TML250 basket mill manufactured by VMA-Getzmann was used in Examples 2-1, 2-2, and 2-3, and a model TML500 manufactured by VMA-Getzmann was used for Examples 3-1, 3-2, and 3-3. Both basket mills used 1.2-1.7 mm ZrO2 beads.

[0072] The particle size results of the milling of the pre-dispersions are listed below in Table 4. Samples were taken at various times and particle size was measured using a Horiba LA-950 Laser Diffraction Particle Size Distribution Analyzer. The coatings were cast of the AFC composition and durability / life testing was performed according to ASTM D5707 in the SRV EL-4 test to determine the durability time of the product.

[0073] All Examples 1-X to 3-X (X is 1, 2, or 3) were milled with the parameters in Table 3. Samples were taken from each basket mill run after specific times (Table 3). All experiments were cooled by vessel and basket cooling during the milling process. The Comparative Example (320 kg) was milled in one pass using a conventional horizontal bead mill with a 15 L milling chamber and 2.0 mm steel beads. Only the milling chamber was cooled.

[0074] [Table 3]

[0075] [Table 4]

[0076] SRV EL-4 testing was performed according to ASTM D5707, with a constant load of 15N (EL-4) to demonstrate the durability of the product. A frequency of 20Hz and a stroke length of 1mm were used.

[0077] [Table 5]

[0078] The SRV LCC-4 200N (load capacity) test was performed according to procedure B of ASTM D5706. In the load capacity (LCC) test, the load is increased at a rate of 1 N / min up to 200 N after an initial hold of 15 N for 10 minutes at a temperature of 50° C. A frequency of 20 Hz and a stroke length of 1 mm were used.

Claims

1. 1. A method of making a friction-reducing coating composition, comprising: (A) (i) a solid lubricant; (ii) a solvent; and (iii) a binder; and (iv) Optionally, additives and combining the (B) milling the (i) solid lubricant in the solvent (ii) using a basket mill for a sufficient time such that the milling forms a dispersion of the milled (i) solid lubricant in the (ii) solvent; The method of claim 1, wherein the binder (iii) and the optional additive (iv) are each independently combined with the solid lubricant (i) and solvent (ii) before, during, after, or a combination of two or more of before, during, and after (B).

2. 10. The method of claim 1, wherein the binder (iii) is combined with the solid lubricant (i) and the solvent (ii) before or during (B).

3. 10. The method of claim 1, wherein the binder (iii) is combined with the solid lubricant (i) and the solvent (ii) after grinding the combination of (i) and (ii) in B.

4. 4. The method of claim 2 or 3, further comprising combining the binder (iii) with a second solvent (v) to form a mixture, and combining the mixture with the solid lubricant (i) and the solvent (ii).

5. 10. The method of claim 1, further comprising: (C) forming a pre-dispersion of the binder, the solid lubricant, the solvent, and the optional additives using a dissolver disk; and thereafter (D) carrying out the grinding of the pre-dispersion (B) in the same vessel in which the pre-dispersion was formed.

6. 6. The method of claim 5, wherein the basket mill comprises a container and an agitator basket, the agitator basket comprising beads and a bead agitator, a dissolver disc, and a drive shaft, the bead agitator and the dissolver disc being engaged with the drive shaft.

7. The method of claim 1 further comprising varying the grinding time to vary the average particle size and particle size distribution of the solid lubricant.

8. The method of claim 1 , wherein the binder is a phenolic resin, an epoxy resin, a silicone resin, or a mixture of two or more of a phenolic resin, an epoxy resin, and a silicone resin.

9. The solid lubricant is graphite, MoS 2 , PTFE, silicone, wax, solid hydrocarbon wax, or graphite, MoS 2 , PTFE, silicone, wax, and a mixture of two or more of a solid hydrocarbon wax.

10. 10. The method of claim 1, wherein the solvent is water, an alcohol containing 1 to 4 carbon atoms, a ketone containing 3 to 6 carbon atoms, an ester, a heterocyclic, aliphatic, or aromatic compound.

11. (i) a solid lubricant; (ii) a solvent; and (iii) a binder; and (iv) Optionally, additives 1. A friction-reducing coating composition comprising a dispersion of 1. An anti-friction coating composition, wherein said solid lubricant has a particle size (d90) of at most 75 μm and a (d50) of at most 50 μm.

12. A component comprising a sliding member coated with the anti-friction coating composition of claim 11.

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